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ABSTRACTObjectivesApple pomace, a waste byproduct of apple processing, is rich in nutrients (e.g. polyphenols and soluble fiber) with the potential to be neuroprotective. The aim of this study was to employ RNA-sequencing (RNASeq) technology to investigate diet-gene interactions in the hypothalamus of rats after feeding a Western diet calorically substituted with apple pomace.MethodsAdolescent (age 21–29 days) female Sprague–Dawley rats were randomly assigned (n = 8 rats/group) to consume either a purified standard diet, Western (WE) diet, or Western diet calorically substituted with 10% apple pomace (WE/AP) for 8 weeks. RNA-seq was performed (n = 5 rats/group) to determine global differentially expressed genes in the hypothalamus.ResultsRNA-seq results comparing rats fed WE to WE/AP revealed 15 differentially expressed genes in the hypothalamus. Caloric substitution of WE diet with 10% apple pomace downregulated (q < 0.06) five genes implicated in brain aging and neurodegenerative disorders: synuclein alpha, phospholipase D family member 5, NADH dehydrogenase Fe-S protein 6, choline O-acetyltransferase, and frizzled class receptor 6.DiscussionAltered gene expression of these five genes suggests that apple pomace ameliorated synthesis of the neurotransmitter, acetylcholine, in rats fed a WE diet. Apple pomace, a rich source of antioxidant polyphenols and soluble fiber, has been shown to reverse nonalcoholic fatty liver disease (NAFLD). Diet-induced NAFLD decreases hepatic de novosynthesis of choline, a precursor to acetylcholine. Based on preclinical evidence, apple pomace has the potential to be a sustainable functional food for maintaining brain function and for reducing the risk of neurodegeneration.

Mob grazing, which uses very high stocking densities for short durations followed by a relatively long rest period, was designed to mimic bison (Bison bison) grazing in western U.S. grassland. This project assessed the suitability of mob grazing for livestock production in the Northeast. Objectives were to compare the effects of mob and rotational grazing on dry matter (DM) mass, nutritive value, and botanical composition across four grazing seasons. Eight, 0.10‐ha paddocks were established in 2014 as a randomized complete block with four replications, and seeded with alfalfa (Medicago sativaL.), white clover (Trifolium repensL.), orchardgrass (Dactylis glomerataL.), narrowleaf plantain (Plantago lanceolataL.), and tall fescue [Schedonorus arundinaceus(Schreb.) Dumort]. Mob‐grazed (MOB) paddocks were grazed by yearling beef cattle twice each year, (70–90–day interval), and rotationally grazed (ROT) paddocks were grazed four to six times each year (when sward height reached 25 cm). Cumulative pre‐grazing forage biomass (PGFM) of ROT was greater than MOB in three of four years. At the final grazing, the PGFM of ROT exceeded MOB by 2,500 kg ha−1. Within year, PGFM of ROT was more consistent, varying by only 1,000–1,400 kg DM ha−1compared with 1,800–2,800 kg DM ha−1for MOB. Grazing strategy altered botanical composition; ROT favored grasses while MOB favored alfalfa. Forage fiber content was consistently lower in ROT than MOB paddocks, indicating superior nutritive value. Results suggest rotational grazing is likely suitable for more consistent forage production of greater nutritive value in temperate, cool‐season grass‐legume pastures of the northeastern United States.

Managing cropping systems to sequester soil organic C (SOC) improves soil health and resilience to changing climate. Perennial crops, no‐till planting, manure, and cover crops can add SOC; however, their impacts have not been well documented in the northeastern United States. Our objectives were (i) to monitor SOC from a bioenergy cropping study in Pennsylvania that included a corn (Zea maysL.)–soybean [Glycine max(L.) Merr.]–alfalfa (Medicago sativaL.) rotation, switchgrass (Panicum virgatumL.), and reed canarygrass (Phalaris arundinaceaL.); (ii) to use the CQESTR model to predict SOC sequestration in the bioenergy crops (with and without projected climate change); and (iii) to use CQESTR to simulate influence of tillage, manure, cover cropping, and corn stover removal in typical dairy forage (silage corn–alfalfa) or grain corn–soybean rotations. Over 8 yr, measured SOC increased 0.4, 1.1, and 0.8 Mg C ha−1yr−1in the bioenergy rotation, reed canarygrass, and switchgrass, respectively. Simulated and measured data were significantly correlated (p< 0.001) at all depths. Predicted sequestration (8–14 Mg C ha−1over 40 yr) in dairy forage rotations was much larger than with corn–soybean rotations (−4.0–0.6 Mg C ha−1over 40 yr), due to multiple years of perennial alfalfa. No‐till increased sequestration in the simulated dairy forage rotation and prevented a net loss of C in corn–soybean rotations. Simulations indicated limited impact of cover crops and manure on long‐term SOC sequestration. The low solids content of liquid dairy manure is the likely reason for the less‐than‐expected impact of manure. Overall, simulations suggest that inclusion of alfalfa provides the greatest potential for SOC sequestration with a typical Pennsylvania crop rotation. Bioenergy crops sequestered significant quantities of SOC.CQESTR accurately predicted SOC levels at the site.Inclusion of alfalfa in rotation was predicted to significantly increase SOC.No‐till was predicted to increase SOC in both dairy forage and corn–soybean rotations.Cover crops and manure had limited impact on simulated long‐term SOC accumulation.

Poor winter hardiness is one of the factors limiting the use of the palatable and productive cool‐season forage grass perennial ryegrass (Lolium perenneL) in the northeastern United States. We compared freeze tolerance among seedlings of 13 commercial cultivars of perennial ryegrass in a controlled environment chamber. After a 14‐d acclimation period, plants were chilled to −10, −15, or −20°C for 1 h, then gradually warmed. After 36 d, surviving plants were counted then harvested and weighed. Mortality rate varied significantly among cultivars (0–13% at −10°C, 47–100% at −20°C). The temperature at which 50% of plants would die (LT50) ranged from −12.9 to −20.8°C. Hardiness ratings provided by the breeder did not match well with LT50 except for the most hardy cultivars. Extreme minimum temperature predictions were extracted from regional climate forecasts for three 30‐yr periods: baseline (1960–1989), short‐term future (2015–2044), and long‐term future (2070–2099). During the baseline period, only 2 to 33% of the northeastern United States was warm enough for these cultivars to survive during at least 50% of winters. Potential tolerable area may increase to 57 to 88% by 2099. Although other factors such as snow cover and variability of winter temperatures affect winter survival in the field, breeding for freeze tolerance has increased the potential extent of perennial ryegrass. Further improvements and the changing climate may greatly increase the utility of perennial ryegrass as a forage in the northeastern United States.

Living in low-income countries often restricts the consumption of adequate protein and animal protein.

Younger children are considered to be more vulnerable to late effects (LE), which prompted us to study LE in patients after haematopoietic stem cell transplantation (HSCT) for a haematological malignancy before the age of 3. In this multicentre EBMT study, cumulative incidence (CI) and severity of endocrine LE, central nervous system complications and secondary malignancies at 5, 10, 15 and 20 years of follow-up were assessed. Risk factors (RF) like gender, diagnosis, age at and year of HSCT, TBI- or chemo-conditioning and GVHD were analysed. CI of any LE was 0.30, 0.52, 0.66 and 0.72 at 5, 10, 15 and 20 years after HSCT, respectively. In 25% of the patients, LE were severe at a median follow-up of 10.4 years. In multivariate analysis, only TBI was a RF for having any LE and for thyroid dysfunction and growth disturbance. Female gender was a RF for delayed pubertal development. Some more insight could be gained by descriptive analysis regarding the role of TBI and GVHD on the severity of LE. Although only five selected LE have been studied and median follow-up is relatively short, the incidence and severity of these LE are considerable but not different from what has been found in older children and TBI is the main RF.

Intrachromosomal amplification of chromosome 21 (iAMP21) identifies a high-risk subtype of acute lymphoblastic leukaemia (ALL), requiring intensive treatment to reduce their relapse risk. Improved understanding of the genomic landscape of iAMP21-ALL will ascertain whether these patients may benefit from targeted therapy. We performed whole-exome sequencing of eight iAMP21-ALL samples. The mutation rate was dramatically disparate between cases (average 24.9, range 5–51) and a large number of novel variants were identified, including frequent mutation of the RAS/MEK/ERK pathway. Targeted sequencing of a larger cohort revealed that 60% (25/42) of diagnostic iAMP21-ALL samples harboured 42 distinct RAS pathway mutations. High sequencing coverage demonstrated heterogeneity in the form of multiple RAS pathway mutations within the same sample and diverse variant allele frequencies (VAFs) (2–52%), similar to other subtypes of ALL. Constitutive RAS pathway activation was observed in iAMP21 samples that harboured mutations in the predominant clone (⩾35% VAF). Viable iAMP21 cells from primary xenografts showed reduced viability in response to the MEK1/2 inhibitor, selumetinib, in vitro. As clonal (⩾35% VAF) mutations were detected in 26% (11/42) of iAMP21-ALL, this evidence of response to RAS pathway inhibitors may offer the possibility to introduce targeted therapy to improve therapeutic efficacy in these high-risk patients.

Ecosystem C gain or loss from managed grasslands depends on management practices. However, limited information is available at the field scale on how the type of defoliation, specifically grazing vs. cutting, affects gross primary productivity (GPP) and ecosystem respiration (RE) immediately after defoliation and during the regrowth process. This study takes advantage of daily field‐scale micrometeorological measurements of GPP and REmade over a 9‐yr period on two pastures that were grazed or cut approximately five times per year to examine the relative effects of grazing and cutting on GPP and RE. The null hypotheses were that the initial reduction in GPP and REfollowing defoliation and the time required for recovery to pre‐defoliation levels did not differ in response to defoliation method. Overall, REwas greater in cut pastures than in grazed pastures. Regardless of defoliation method, REdid not change during the first week after defoliation, or during the 5 wk following. The initial reduction in GPP2000(GPP in full sunlight) was greater when pastures were cut (70%) than grazed (46%) and recovery to pre‐defoliation levels took 5 wk for cut pastures vs. 3 wk when grazed. This study suggests, all other management practices being similar, that grazed pastures should be stronger annual C sinks than cut pastures. However, cut and grazed pastures are rarely managed in the same way such that the realized balance between GPP and REwill depend on both physiological responses to defoliation and management intensity.

Increasing plant species richness is often associated with an increase in productivity and associated ecosystem services such as soil C sequestration. Here we report on a 9‐yr experiment to evaluate the forage production and C sequestration potential of grazed pastures sown to either a two‐species cool‐season grass‐legume mixture or a five‐species mixture of grasses, legumes, and a non‐legume forb. We hypothesized that forage production and soil C sequestration would be greater in the five‐species compared with the two‐species mixture. We also evaluated the effects of rainfall and temperature on the difference in forage production between mixtures. When averaged across years, the five‐species mixture produced 31% more forage biomass than the two‐species mixture, and the difference between mixtures tended to be greater in wet than in dry summers (R2= 0.42, P= 0.06). There was no relationship between growing season temperature and differences in biomass production. Soil C accumulation to 100 cm depth in the five‐species mixture was 1.80 vs. 0.50 Mg ha−1yr−1for the two‐species mixture (P= 0.15) with significant increases in the five‐species mixture occurring at the 10 to 20 cm (P= 0.06) and 20 to 30 cm (P= 0.03) depths. Increased productivity in the five‐species mixture persisted throughout the experiment despite changes in species composition that resulted in similar composition between the mixtures by the last 2 yr of the study. Increased soil C possibly had a positive feedback effect on forage production permitting the five‐species mixture to out‐yield the two‐species mixture even after differences in species composition had largely disappeared.

Many long-term childhood cancer survivors suffer from treatment-related late effects, which may occur in any organ and include a wide spectrum of conditions. Long-term follow-up (LTFU) is recommended to facilitate early diagnosis and to ensure better health outcomes. Due to the heterogeneity of these sequelae, different specialists work together in the diagnosis and treatment of these conditions. Experts from both pediatric and internal medicine are involved in age-appropriate care by providing a transition process. Hence, LTFU of childhood cancer survivors is a prototypic example of multidisciplinary care for patients with complex needs treated in a specialized setting. International collaborations of healthcare professionals and scientists involved in LTFU of childhood cancer survivors, such as the International Guideline Harmonization Group, compile surveillance recommendations that can be clinically adopted all over the world. These global networks of clinicians and researchers make a joint effort to address gaps in knowledge, increase visibility and awareness of cancer survivorship and provide an excellent example of how progress in clinical care and scientific research may be achieved by international and multidisciplinary collaboration.

Studies in the northeastern United States have shown that the improved cultivars of narrow‐leaf plantain (Plantago lanceolataL.) do not have sufficient winter hardiness to persist under wintertime conditions typical of that region. However, an experimental line, PG700, developed from productive plants collected from the southern, mid‐Atlantic, and midwestern United States had significantly greater survival after freezing than the commercially available cultivars. A field study was initiated in 2006 to select for additional freezing tolerance in PG700. Superior materials collected after two‐years of selection pressure were evaluated in growth chambers for survival after exposure to −11 and −14°C or after exposure to drought that was severe enough to kill all visible leaves. The cultivar Tonic was included as a freezing‐susceptible control. Survival of spaced plants of PG700 in the field was high, with mortality rates of 9% following the first winter after transplanting, 26% of the remaining plants after the following summer, and 11% after the second winter. Even with the low selection pressure, progeny of plants selected after the first winter had more than twice the survival rate of the original population when exposed to −14°C. No Tonic plants survived at −14°C. PG700 did not have greater drought resistance than Tonic, nor was its drought resistance improved by the selection process. Increased freezing tolerance will increase the suitability of plantain as a component of perennial pasture mixtures in temperate regions of the United States.

Net CO2exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site‐years of measurements were partitioned into gross photosynthesis and ecosystem respiration by using the nonrectangular hyperbolic light‐response function method. The analyses produced net CO2exchange data and new ecosystem‐scale ecophysiological parameter estimates for legume crops determined at diurnal and weekly time steps. Dynamics and annual totals of gross photosynthesis, ecosystem respiration, and net ecosystem production were calculated by gap filling with multivariate nonlinear regression. Comparison with the data from grain crops obtained with the same method demonstrated that CO2exchange rates and ecophysiological parameters of legumes were lower than those of maize (Zea maysL.) but higher than for wheat (Triticum aestivumL.) crops. Year‐round annual legume crops demonstrated a broad range of net ecosystem production, from sinks of 760 g CO2m−2yr−1to sources of –2100 g CO2m−2yr−1, with an average of –330 g CO2m−2yr−1, indicating overall moderate CO2–source activity related to a shorter period of photosynthetic uptake and metabolic costs of N2fixation. Perennial legumes (alfalfa, Medicago sativaL.) were strong sinks for atmospheric CO2, with an average net ecosystem production of 980 (range 550–1200) g CO2m−2yr−1.

Understanding the regulation of net ecosystem exchange and soil C sequestration within pasture systems requires knowledge of its component fluxes, including photosynthetic uptake and respiratory loss. However, little information is available on the partitioning of soil respiration (RS) between its heterotrophic respiration (RH) and rhizosphere respiration (RR) components for perennial cool‐season pasture species. The purpose of this study was to use stable C isotopes to examine the effects of regrowth after defoliation on the components of soil respiration for grassland plots planted as an orchardgrass (Dactylis glomerataL.)–white clover (Trifolium repensL.) mixture but dominated by orchardgrass (90 to 100% of harvested biomass). Respiration components were quantified during the first 3 wk following defoliation at the beginning of July in 2010 and 2011. In 2010, RS, RH, and RRwere all lowest 1 d after cutting (DAC). Both RSand RHsignificantly increased by 8 DAC but no further increase occurred over the next 2 wk. In contrast, RRcontinued to increase throughout the regrowth period. In 2011, RSdid not differ among harvests and averaged across dates was less than in 2010. During the 2011 regrowth period RHincreased slightly whereas RRdid not change significantly. The rhizosphere contribution (RC) to RSaveraged 0.49, increasing from 0.35 to 0.56 during regrowth in 2010 but decreasing from 0.62 to 0.43 in 2011. Differences among years in respiration responses during regrowth were possibly due to a combination of factors including resource limitations, soil moisture stress, and differences in soil temperature.

Abstract:Japanese knotweed (Fallopia japonica) is a highly invasive species that has become a serious problem in riparian zones and along road and railroad right-of-ways in North America and Europe. Once established, it forms solid colonies choking out other herbaceous vegetation, displacing native species, negatively affecting wildlife, and altering hydrological processes. We evaluated the ability of 6 native species mixtures to prevent recolonization by Japanese knotweed at a site receiving either 1 or 2 yr of glyphosate applications and mowing to suppress existing Japanese knotweed stands. One year of spraying and mowing was not sufficient to adequately suppress Japanese knotweed. By 37 months after sowing, only the multi-species riparian buffer mixture (RBM) had plant cover 20%, whereas cover for all other mixtures was <10%. Japanese knotweed had successfully reinvaded all plots with percent cover ranging from 72–96%. Two years of spraying and mowing reduced Japanese knotweed percent cover to an average of 12% (range 7–18%) during the first 2 yr after sowing and to 28–43% by 37 months. Only 2 species mixtures adequately established when sown following 2 yr of Japanese knotweed suppression, the RBM and a mixture of Virginia wildrye (Elymus virginicus) and prairie cordgrass (Spartina pectinata). Percent cover for both mixtures was 80% at 25 months after sowing and ≥50% after 37 months. Two years of Japanese knotweed suppression was necessary before native species mixtures could successfully compete against invasive recolonization.

Abstract:Japanese knotweed (Fallopia japonica) is a highly invasive species that has become a serious problem in riparian zones and along road and railroad right-of-ways in North America and Europe. Once established, it forms solid colonies choking out other herbaceous vegetation, displacing native species, negatively affecting wildlife, and altering hydrological processes. We evaluated the ability of 6 native species mixtures to prevent recolonization by Japanese knotweed at a site receiving either 1 or 2 yr of glyphosate applications and mowing to suppress existing Japanese knotweed stands. One year of spraying and mowing was not sufficient to adequately suppress Japanese knotweed. By 37 months after sowing, only the multi-species riparian buffer mixture (RBM) had plant cover 20%, whereas cover for all other mixtures was <10%. Japanese knotweed had successfully reinvaded all plots with percent cover ranging from 72–96%. Two years of spraying and mowing reduced Japanese knotweed percent cover to an average of 12% (range 7–18%) during the first 2 yr after sowing and to 28–43% by 37 months. Only 2 species mixtures adequately established when sown following 2 yr of Japanese knotweed suppression, the RBM and a mixture of Virginia wildrye (Elymus virginicus) and prairie cordgrass (Spartina pectinata). Percent cover for both mixtures was 80% at 25 months after sowing and ≥50% after 37 months. Two years of Japanese knotweed suppression was necessary before native species mixtures could successfully compete against invasive recolonization.

Understanding the regulation of ecosystem CO2flux from forage production systems requires knowledge of component fluxes, including photosynthetic uptake and respiratory loss. Experimental separation of soil respiration into heterotrophic and rhizosphere respiration has been difficult, complicating efforts to quantify management and environmental effects on grazing land C sequestration. This study takes advantage of differences in the natural abundance of 13C between C3and C4plant species to separate microbial respiration of C4–derived soil organic matter from root respiration by C3forage species. Respiratory flux and C isotope data were collected in May, July, and September 2008 and 2009 from plots containing either orchardgrass (Dactylis glomerataL.) or white clover (Trifolium repensL.). The site had been a big bluestem (Andropogon gerardiVitman) field for about 30 yr before grass and clover establishment. Thus, the soil organic C had a strong C4signature. At each sampling period, respiration measurements were made at the midpoint of the regrowth cycle, 2 wk following mowing. Rhizosphere respiration accounted for about 50% of soil respiration in July and September but only 40% in May. Rhizosphere respiration under orchardgrass averaged 50% of total soil respiration compared with 43% under white clover. Accurate quantification of the components of ecosystem respiration will aid in the development of realistic models to simulate ecosystem C flux.

Satellite‐based normalized difference vegetation index (NDVI) data have been extensively used for estimating gross primary productivity (GPP) and yield of grazing lands throughout the world. However, the usefulness of satellite‐based images for monitoring rotationally‐grazed pastures in the northeastern United States might be limited because paddock size is often smaller than the resolution limits of the satellite image. This research compared NDVI data from satellites with data obtained using a ground‐based system capable of fine‐scale (submeter) NDVI measurements. Gross primary productivity was measured by eddy covariance on two pastures in central Pennsylvania from 2003 to 2008. Weekly 250‐m resolution satellite NDVI estimates were also obtained for each pasture from the moderate resolution imaging spectroradiometer (MODIS) sensor. Ground‐based NDVI data were periodically collected in 2006, 2007, and 2008 from one of the two pastures. Multiple‐regression and regression‐tree estimates of GPP, based primarily on MODIS 7‐d NDVI and on‐site measurements of photosynthetically active radiation (PAR), were generally able to predict growing‐season GPP to within an average of 3% of measured values. The exception was drought years when estimated and measured GPP differed from each other by 11 to 13%. Ground‐based measurements improved the ability of vegetation indices to capture short‐term grazing management effects on GPP. However, the eMODIS product appeared to be adequate for regional GPP estimates where total growing‐season GPP across a wide area would be of greater interest than short‐term management‐induced changes in GPP at individual sites.

Root allocation and distribution patterns can influence forage yield during periods of moisture or nitrogen stress, as deep‐rooted species access water and nutrients found deeper in the soil profile. In a greenhouse study, we examined rooting characteristics to a depth of 50 cm for 21 cool‐season forage species (9 grasses, 6 legumes, and 6 forbs) exposed to drought and low N conditions. The goal of this research was to compare root distribution under uniform growing conditions for common grass, legume and non‐leguminous forb species found in humid‐temperate pastures of the northeast United States. Nitrogen or water stressed grasses generally had greater root biomass and a greater proportion of roots in the 30 to 40 cm soil layer than did stressed legumes or forbs. Low N significantly reduced root weight, but to a lesser extent than the decrease in shoot weight, resulting in an increase in root/shoot ratio. Drought stress reduced shoot weight but had no effect on root weight, also resulting in a greater root/shoot ratio. Drought stress also increased the proportion of deep roots compared with controls, whereas, N stress did not. Comparisons with previously published field studies suggested that information from container‐grown plants could provide insights into field results, and also suggested that inherent species differences in root distribution could explain some, but not all, rooting patterns observed in multi‐species forage mixtures.

Decades of plowing have depleted organic C stocks in many agricultural soils. Conversion of plowed fields to pasture has the potential to reverse this process, recapturing organic matter that was lost under more intensive cropping systems. Temperate pastures in the northeast USA are highly productive and could act as significant C sinks. However, such pastures have relatively high biomass removal as hay or through consumption by grazing animals. In addition, the ability to sequester C decreases over time as previously depleted stocks are replenished and the soil returns to equilibrium conditions. The objective of this research was to use eddy covariance systems to quantify CO2fluxes over two fields in central Pennsylvania that had been managed as pastures for at least 35 yr. Net ecosystem exchange measurements averaged over 8 site‐years suggested that the pastures were acting as small net C sinks of 19 g C m−2yr−1(positive values indicate uptake). However, when biomass removal and manure deposition were included to calculate net biome productivity, the pastures were a net source of −81 g C m−2yr−1(negative values indicate loss to the atmosphere). Manure generated from the hay that was consumed off site averaged 18 g C m−2yr−1Returning that manure to the pastures would have only partially replenished the lost C, and the pastures would have remained net C sources. Heavy use of the biomass produced on these mature pastures prevented them from acting as C sinks.

Although most pasture growth models simulate many above‐ and belowground components of the plant community, calibration and validation are usually based only on periodic measurements of aboveground forage yield. This research used daily measurements of gross primary productivity (GPP) to validate the photosynthesis subroutine of the Integrated Farm System Model (IFSM). The model was calibrated for a pasture grazed by beef cattle (Bos taurus) in 2003, then validated with data from 2004 through 2006. Predicted and observed annual yield differed by 14 ± 9%, whereas predicted GPP differed from observed GPP by only 7 ± 3%. Seasonal trends in GPP were also adequately simulated, although a slight overestimation in the spring and early‐summer and underestimation in the later half of the year occurred. Overestimation occurred when wintertime temperatures were above freezing or when N availability was high following fertilizer application. Late‐season underestimation was related to low soil N availability which resulted from excessive N uptake by plants earlier in the year. Only minor adjustments in model structure were needed to improve simulation of GPP. Most adjustments involved changes in parameter values, many of which are often difficult to find or lacking in the literature. Refinement of models to accurately simulate the seasonal distribution of physiological parameters such as GPP will help ensure that model structures correctly represent the true dynamics of C assimilation and pasture growth.

Chicory (Cichorium intybusL.), a deep‐rooted forb, has potential for inclusion in pasture mixtures because of its reported drought tolerance and high productivity during summer months. This study examined how adding chicory to pasture mixtures affected forage yield, root growth, and soil moisture extraction under drought. The experiment was planted in August 2002. Movable rainout shelters were used to control water application in the field. Adding chicory to orchardgrass (Dactylis glomerataL.)–white clover (Trifolium repensL.) or perennial ryegrass (Lolium perenneL.)–white clover mixtures increased drought tolerance in 2003 when chicory constituted 24 to 39% of harvested forage biomass. Chicory mortality was high, decreasing from 39% of harvested forage yield under drought stress in early summer 2003 to 9% in late summer 2004. Improved yield under drought stress was not observed in 2004 when chicory constituted only 9 to 16% of the mixture. The three‐species mixtures in 2003 had greater root counts than the two‐species mixtures at soil depths below about 70 cm under well‐watered conditions, but a greater proliferation of roots at depths below 70 cm was observed for the two‐species mixture under drought stress. Both mixtures appeared capable of nighttime transfer of soil water from deep to shallow soil layers, thereby improving water availability to shallow roots. However, improved drought tolerance of the three‐species mixture was probably related to improved water use efficiency rather than to greater access to and extraction of deep soil moisture.

Radioiodinated phospholipid ether analogues have shown a remarkable ability to selectively accumulate in a variety of human and animal tumors in xenograft and spontaneous tumor rodent models. It is believed that this tumor avidity arises as a consequence of metabolic differences between tumor and corresponding normal tissues. The results of this study indicate that one factor in the tumor retention of these compounds in tumors is the length of the alkyl chain that determines their hydrophobic properties. Decreasing the chain length from C12 to C7 resulted in little or no tumor accumulation and rapid clearance of the compound in tumor-bearing rats within 24 h of administration. Increasing the chain length had the opposite effect, with the C15 and C18 analogues displaying delayed plasma clearance and enhanced tumor uptake and retention in tumor-bearing rats. Tumor uptake displayed by propanediol analogues NM-412 and NM-413 was accompanied by high levels of liver and abdominal radioactivity 24 h postinjection to tumor-bearing rats. Addition of a 2-O-methyl moiety to the propanediol backbone also retarded tumor uptake significantly. A direct comparison between NM-404 and its predecessor, NM-324, in human PC-3 tumor bearing immune-compromised mice revealed a dramatic enhancement in both tumor uptake and total body elimination of NM-404 relative to NM-324. On the basis of imaging and tissue distribution studies in several rodent tumor models, the C18 analogue, NM-404, was chosen for follow-up evaluation in human lung cancer patients. Preliminary results have been extremely promising in that selective uptake and retention of the agent in tumors is accompanied by rapid clearance of background radioactivity from normal tissues, especially those in the abdomen. These results strongly suggest that extension of the human trials to include other cancers is warranted, especially when NM-404 is radiolabeled with iodine-124, a new commercially available positron-emitting isotope. The relatively long physical half-life of 4 days afforded by this isotope appears well-suited to the pharmacodynamic profile of NM-404.

Increasing plant species diversity could enhance forage yield, resistance to weed invasion, and soil C accumulation in grazed pastures. Three forage mixtures (2, 3, or 11 species) were established on a farm in eastern Pennsylvania and grazed by dairy heifers or managed under a three‐cut hay system from 1999 to 2002. Net canopy photosynthesis was measured from early April to early October 2000 to 2002. Root distribution to a depth of 60 cm was measured in mid‐September each year, and soil C and N concentrations to a 15‐cm depth were determined in May 1999 and September 2002. The 11‐species mixture yielded 43% more forage dry matter than the two‐species mixture. This difference was mainly due to the inclusion of a few highly productive forage species in the 11‐species mixture. Canopy photosynthesis did not differ among mixtures in the spring, but in the summer was 50% greater in the 3‐ and 11‐species mixtures than the two‐species mixture. The 11‐species mixture also had 30 to 62% greater root biomass than the other two mixtures and a greater proportion of roots in deeper soil layers. Soil C either remained unchanged or decreased, depending on species composition, with the greatest decrease occurring in the 11‐species mixture. No relationship existed between changes in soil C concentration and either canopy photosynthesis or above‐ and belowground productivity. Deeper rooting could reduce drought stress by increasing access to deep soil moisture. Selecting forage mixtures to include specific desirable traits, such as greater rooting depth, could result in improved pasture performance.

Improved cultivars of narrow leaf plantain (Plantago lanceolataL.) have received increasing attention as possible pasture species for the northeastern USA because of their productivity during drought and high nutritive value. However, the cultivars currently available do not have sufficient freezing tolerance to survive northeastern U.S. winters. This experiment examined the relationship between shoot growth rate and root:shoot partitioning during cold‐hardening and the freezing tolerance of ‘Lancelot’ and ‘Tonic’ plantain compared with ‘PG700’, an experimental line collected from the eastern USA. I hypothesized that PG700 would exhibit reduced shoot structural growth and increased carbohydrate storage in roots during cold‐hardening, resulting in increased freezing tolerance and survival. In growth chamber experiments, seedlings were cold hardened for 21 d and then frozen at −12°C for 3 h. Survival was evaluated after a 21‐d recovery period. The experiment was conducted twice. Survival was greatest for PG700 (58%), followed by Lancelot (33%) and Tonic (18%) (P< 0.01). When combined across cultivars, survival was 59% in Trial 1 compared with 11% in Trial 2 (P< 0.01). None of the measured parameters including overall root and shoot growth or relative partitioning between roots and shoots were related to cultivar differences in freezing tolerance. Reduced survival in Trial 2 was accompanied by high nitrogen uptake and vigorous shoot relative to root growth during the cold‐hardening period. Thus, reduced shoot growth was accompanied by increased freezing tolerance when differences in survival were induced by environmental effects but was not related to genetic differences in survival.

Some producers believe that planting pastures to several forage species benefits sustainability of grazing systems. We conducted a grazing study to determine if forage species diversity in pastures affects herbage productivity and weed invasion. One‐hectare pastures were planted to four mixtures in August 2001 and then grazed with lactating dairy cattle during 2002 and 2003. The mixtures were two species [orchardgrass (Dactylis glomerataL.) and white clover (Trifolium repensL.)], three species [orchardgrass, white clover, and chicory (Cichorium intybusL.)], six species [orchardgrass, tall fescue (Festuca arundinaceaSchreb.), perennial ryegrass (Lolium perenneL.), red clover (Trifolium pratenseL.), birdsfoot trefoil (Lotus corniculatusL.), and chicory], and nine species [the six‐species mixture plus white clover, alfalfa (Medicago sativaL.), and bluegrass (Poa pratensisL.)]. When rainfall was plentiful (2003), there were no differences in herbage yield among the mixtures; all averaged 9800 kg ha−1dry matter. During 2002, which was dry, the two‐species mixture produced less herbage than the other mixtures (4800 vs. 7600 kg ha−1dry matter). The proportion of nonsown species in the sward was lower for the six‐ and nine‐species mixtures than the two‐and three‐species mixtures, indicating less weed invasion for these complex mixtures. Red clover and chicory proportions decreased by 80% after 2 yr, and orchardgrass dominated in all pastures by May 2004. We conclude that planting a mixture of grasses, legumes, and chicory will benefit herbage production during dry years and will reduce weed invasion for a few years after planting under management similar to ours. Producers would have to reestablish the chicory and legume components relatively frequently to maintain these benefits.

Plant–plant interactions during seedling establishment can markedly affect the composition of pasture communities. This research examined the emergence, mortality, and early growth of four forage species commonly found in temperate northeastern U.S. pastures. Species were selected based on functional group (grass vs. legume) and relative drought tolerance. Drought‐tolerant species included ‘Penlate’ orchardgrass (Dactylis glomerataL.) and ‘Viking’ birdsfoot trefoil (Lotus corniculatusL.), while drought‐sensitive species included ‘Basion’ perennial ryegrass (Lolium perenneL.) and ‘Will’ white clover (Trifolium repensL.). Seeds were sown as monocultures, as grass–legume binary mixtures, and as a complex, four‐species mixture. Mixture complexity had only minor effects on seedling emergence. However, legume mortality was significantly reduced in the complex compared with other mixtures in a year when high temperature and drought stress limited seedling establishment. In most cases there was a negative effect of neighbors on survival as evidenced by reduced clustering of surviving compared with emerged seedlings and by a negative relationship between mortality rate and distance to the nearest neighbor. However, in a drought year, perennial ryegrass mortality decreased as distance to the nearest neighbor decreased, suggesting that survival was facilitated by the presence of neighbors. Although mixture complexity had significant effects on seedling emergence and mortality, species composition in the binary and complex mixtures could be predicted based on emergence and survival of monocultures. It appears that seedling emergence information gleaned from monocultures can be a useful tool for predicting initial species composition of more complex mixtures.

Introduced (nonnative) species account for nearly all of the forage grasses used in northeastern USA forage systems. We evaluated accessions of the native cool‐season species, Eastern bottlebrush grass (Elymus hystrixvar. hystrixL.), from the northeastern USA for yield, persistence, plant morphological traits, and nutritive value. Thirteen accessions and one commercial ecotype of bottlebrush grass were transplanted into single‐row field plots in late summer of 2000 at Beltsville, MD, Rock Springs, PA, and Big Flats, NY. Two orchardgrass (Dactylis glomerataL.) cultivars were included for reference. Yield, persistence, morphology (leaf width, length, mass, area, and tillers per plant), and nutritive value data were collected during 2001 and 2002. Bottlebrush grass was eliminated by the bluegrass billbug (Sphenophorus parvulusGyllenhal) at Rock Springs in spring of 2001. At Big Flats and Beltsville, the bottlebrush grass accessions produced as much dry matter per plant as the commercial ecotype. Orchardgrass yielded four times as much dry matter as the mean of all bottlebrush grass entries (102 g vs. 26 g per plant averaged for years and locations). The low productivity of bottlebrush grass resulted from reduced tillering especially during regrowth. There was very little regrowth of bottlebrush grass during late summer in all environments. Survival of bottlebrush grass was 36% during 3 yr vs. 84% for orchardgrass. Differences in nutritive value among accessions were due mainly to differences in leaf‐to‐stem mass ratio. Eastern bottlebrush grass has limited potential for use as a forage grass in the northeastern USA.

Pasture productivity under harsh environments can be increased by planting more drought‐resistant species or by increasing species diversity. This research was conducted under two large (10.2 × 26.8 m) rainout shelters combined with a drip irrigation system to provide deficit, normal, and excessive moisture conditions. A two‐species mixture containing the relatively drought‐tolerant species, orchardgrass (Dactylis glomerataL.) and red clover (Trifolium pretenseL.) and two five‐species mixtures were compared with a mixture containing the drought‐sensitive species, white clover (Trifolium repensL.) and Kentucky bluegrass (Poa pratensisL.), which are the predominant species in northeastern USA pastures. Plots were clipped from mid‐May to early October in 2000 and 2001 on a schedule that mimicked management‐intensive grazing practices. The five‐species mixture containing chicory (Cichorium intybusL.), orchardgrass, Kentucky bluegrass, perennial ryegrass (Lolium perenneL.), and white clover had the greatest dry matter yield at all moisture levels. Yield in that mixture increased 89% in the dry, 61% in the normal, and 43% (by weight) in the wet treatments compared with the white clover/Kentucky bluegrass mixture. Increased yield was primarily due to the robust growth of chicory which dominated the mixture, accounting for 71% of harvested biomass by the fall of 2001. In addition, white clover growing in the mixture with chicory had improved leaf water relations and greater relative growth rates than white clover growing in the two‐species mixture. Including the functional attribute of a deep‐rooted forb appeared to be more important than species richness, per se, in improving forage yield.

More than a century since Charles Darwin stated that diverse grasslands produce more herbage than monocultures, scientists still debate the relationship between species diversity and ecosystem function. Postulated benefits of diversity in experimental grasslands include greater and more stable primary production along with more efficient nutrient use. These benefits have been extrapolated to forage and grazing land systems with little supporting objective data. Most information on the potential benefits of increased plant diversity comes from studies of synthesized grasslands that have not included domestic grazing animals. We explore this debate relative to the management of temperate forage and grazing lands. Plant species diversity refers to the number of species (richness) and their relative abundance (evenness) within a defined area. Plant relations influence biodiversity responses through positive (e.g., facilitation, N2fixation, hydraulic lift) and negative interactions (e.g., competitive exclusion, allelopathy). Early 20th century research on complex mixtures of forage species (limited to grasses and legumes) for pasture indicated equivocal results regarding benefits of species‐rich mixtures and typically recommended using the best adapted species in simple grass–legume mixtures. Recent research indicates potential herbage yield benefits from species‐rich mixtures for pastures. Limited animal productivity research on species‐rich mixtures indicates variable responses and much more research is needed. Grazing land productivity is a primary focus for biodiversity benefits because of the direct economic relevance to producers. However, taking a broader view of the multifunctionality of grazing lands to include environmental and aesthetic benefits to humans reveals a great scope for using biodiversity in grazing land management.

Most forage grasses grown in the northeastern USA are introduced species. Interest in native plant species for conservation and production has increased because of new federal policies. We evaluated northeastern accessions of the native cool‐season grass Virginia wildrye (Elymus virginicusL.) for yield, persistence, and plant morphological traits. Thirteen accessions, one cultivar (Omaha), and one commercial ecotype of Elymuswere transplanted into single‐row field plots in late summer of 2000 at Beltsville, MD, Rock Springs, PA, and Big Flats, NY. Two orchardgrass (Dactylis glomerataL.) cultivars were the checks. Yield and morphology (leaf width, length, mass, area, and tillers per plant) data were collected during 2001 and 2002. The Elymusaccessions produced as much dry matter (28–57 g per plant) as the cultivar and commercial ecotype. Orchardgrass yielded more than twice as much dry matter than the mean of all Elymusentries (94 vs. 34 g per plant averaged for years and locations). The difference in productivity was related to reduced tillering in Elymusespecially during regrowth. Yield per plant was strongly correlated (r= 0.62–0.81, P< 0.01) with the number of tillers per plant. Differences in productivity were also reflected in leaf blade traits, with Elymushaving a lower leaf area and mass than orchardgrass. Leaf traits were positively correlated (r= 0.35–0.56, P< 0.05) with plant yield. Some northeastern Elymusaccessions would probably perform as well as the commercial sources of Elymusin conservation plantings.

Interest in native plant species for conservation and production has increased because of new federal policies. We evaluated accessions of the native cool‐season grass Virginia wildrye (Elymus virginicusL.) from the northeastern USA for nutritive value and its association with plant morphological traits. Thirteen accessions, one cultivar (Omaha), and one commercial ecotype of Elymuswere transplanted into single‐row field plots in late summer of 2000 at Beltsville, MD, Rock Springs, PA, and Big Flats, NY. Two orchardgrass (Dactylis glomerataL.) cultivars were included. Primary growth was harvested in April (Beltsville) or May (Rock Springs and Big Flats) of 2001 and 2002 and analyzed for neutral detergent fiber (NDF), crude protein (CP), and digestible NDF (dNDF). Nutritive value measures were related to plant morphological attributes [leaf width, length, area, and leaf‐to‐stem mass ratio (LSR)]. Virginia wildrye accessions differed (P< 0.01) in nutritive value and often had lower NDF and higher CP and dNDF than the commercial ecotype, Omaha cultivar, and orchardgrass. The LSR accounted for most of the variation in nutritive value. Orchardgrass was more mature at harvest than Elymusentries and thus lower in nutritive value. Neutral detergent fiber was negatively correlated with LSR (r= −0.26 to −0.74, P< 0.05), whereas CP and dNDF were positively correlated (r= 0.36 to 0.80 for CP and 0.44 to 0.74 for dNDF, P< 0.05). Neutral detergent fiber was also positively correlated (r= 0.27 to 0.86, P< 0.05) with leaf length. Virginia wildrye is comparable to other cool‐season grasses in nutritive value.

White clover (Trifolium repensL.) persists in pastures mainly by stolon growth. Morphologically complex (i.e., highly branched stolons) plants of white clover generally persist longer. We hypothesized that biotic and abiotic stresses limit white clover production on grazing lands by fragmenting plants into smaller, less competitive individuals. We measured changes in the size and structure of plants in a white clover–orchardgrass (Dactylis glomerataL.) sward during a drought (1999) and a favorable growing season (2000) in grazed pastures on a southeastern Pennsylvania farm. A natural infestation of clover root curculio [Sitona hispidulus(Fabricus)] and blue clover weevil [Ischnopterapion virens(Herbst)] provided an opportunity to examine the interaction of abiotic and biotic stress on stolon structure. White clover plants were dug from two orchardgrass (‘Pennlate’)–white clover (‘Will’) pastures during April to November 1999 and 2000. Stolon structure and damage from blue weevil and curculio larvae were determined monthly. Drought in 1999 reduced stolon production, branching, and rooting in white clover. Stolon length (cm m−2) in 1999 was 50% of that in 2000. Clover root curculio damaged up to 25% of clover roots and 20 to 40% of stolons were damaged by weevils. Insect damage was greatest on primary stolons. With favorable rainfall during late 1999 and in 2000, white clover recovered from fragmentation and produced nearly twice the stolon length, mass, and density in the next grazing season despite insect damage levels of 10 to 30%. Climate and biotic stresses are the major factors controlling oscillations of white clover stolon density in pastures of the northeastern USA.

Nephrotoxicity is a frequent complication of treatment with ifosfamide in children. Although renal damage may be acute and reversible, chronic toxicity may develop with potentially serious consequences. Chronic nephrotoxicity due to ifosfamide may lead to a wide variety of subclinical and clinical manifestations. Proximal tubular dysfunction is the commonest presentation, and may lead to a Fanconi syndrome, including hypophosphataemic rickets and proximal renal tubular acidosis. Glomerular impairment is also common, whilst distal tubular impairment has been described but is relatively rare. Although full reversibility has been described occasionally, there is no information about the very long-term outcome of chronic ifosfamide nephrotoxicity. We studied a cohort of 12 children 1 and 10 years after completion of ifosfamide treatment. There was no statistically significant change in either glomerular or tubular toxicity in the group as a whole over this time period. However, marked improvements were seen in some aspects of toxicity in some patients, and deterioration was observed in others. We concluded that considerable nephrotoxicity is still present 10 years after completion of ifosfamide treatment, but that the outcome varies between individual patients. Although several risk factors for the development of chronic nephrotoxicity have been described, total ifosfamide dose, patient age at treatment, previous or concurrent cisplatin treatment, and unilateral nephrectomy are the most important. Nevertheless, it remains difficult to predict the occurrence of this toxicity with confidence. The pathogenesis of ifosfamide nephrotoxicity is poorly understood. There is an urgent need for the development and clinical investigation of nephroprotective strategies. Med Pediatr Oncol 2003;41:190–197, © 2003 Wiley-Liss, Inc.

‘Ceres Tonic’ and ‘Grasslands Lancelot’ narrow‐leaf plantain (Plantago lanceolataL.) and ‘Grasslands Puna’ chicory (Cichorium intybusL.) have received considerable interest as potential new forages for the northeastern USA because of their reported drought tolerance and high forage quality. However, all three cultivars were developed under New Zealand conditions and may not have sufficient winter hardiness to survive northeastern USA winters. Growth chamber and field studies were conducted to determine the freezing tolerance and winter survival of these new forages under well‐watered and drought conditions. Winter survival of chicory in the field ranged from 73% of marked plants in the wet treatment to 93% following summer drought. Likewise, winter survival of plantain in the field increased from 3% in the wet treatment to 41% in the dry treatment. Survival of Lancelot plantain in the growth chamber increased from 4% in the well‐watered to 16% in the drought treatment. However, survival of Tonic plantain and Puna chicory in the growth chamber was not affected by drought. Chicory survival was greater than survival of plantain in both controlled and field environments. Puna chicory appears to have sufficient winter hardiness to survive winters in the northeastern United States. Although Lancelot had slightly greater survival than Tonic, neither plantain cultivar had sufficient freezing tolerance to be recommended for use in the northeastern USA. Improved cultivars will need to be developed from populations that have evolved under more severe winter conditions before plantain can become a viable forage for most of this region.

Stimulation of the pedunculopontine nucleus (PPN) is known to induce changes in arousal and postural/locomotor states. Previously, PPN stimulation was reported to induce prolonged responses (PRs) in extracellularly recorded PnC neurons in the decerebrate cat. The present study used intracellular recordings in semihorizontal slices from rat brain stem (postnatal days 12–21) to determine responses in PnC neurons following PPN stimulation. Two-thirds (65%) of PnC neurons showed PRs after PPN stimulation. PnC neurons with PRs had higher amplitude afterhyperpolarizations (AHP) than non-PR (NPR) neurons. Both PR and NPR neurons were of mixed cell types characterized by “A” and/or “LTS,” or neither of these types of currents. PnC cells showed decreased AHP duration with age, due mostly to decreased AHP duration in NPR cells. The longest mean duration PRs were induced by stimulation at 60 and 90 Hz compared with 10 or 30 Hz. Maximal firing rates in PnC cells during PRs were induced by PPN stimulation at 60 Hz compared with 10, 30, or 90 Hz. BaCl2superfusion blocked PPN stimulation-induced PRs, suggesting that PRs may be mediated by blockade of potassium channels, in keeping with increased input resistance observed during PRs. Depolarizing pulses failed to elicit, and hyperpolarizing pulses failed to reset, PPN stimulation-induced PRs, suggesting that PRs may not be plateau potentials. Pharmacological testing revealed that nifedipine superfusion failed to block PPN stimulation-induced PRs; i.e., PRs may not be calcium channel-dependent. The muscarinic cholinergic agonist carbachol induced depolarization in most PR neurons tested, and the muscarinic cholinergic antagonist scopolamine reduced or blocked PPN stimulation-induced PRs in some PnC neurons, suggesting that some PRs may be due to muscarinic receptor activation. The nonspecific ionotropic glutamate receptor antagonist kynurenic acid failed to block PPN stimulation-induced PRs, as did the metabotropic glutamate receptor antagonist (R, S)-αmethyl-4-carboxyphenylglycine, suggesting that PRs may not be mediated by glutamate receptors. These findings suggest that PPN stimulation-induced PRs may be due to increased excitability following closing of muscarinic receptor-sensitive potassium channels, allowing PnC neurons to respond to a transient, frequency-dependent depolarization with long-lasting stable states. PPN stimulation appears to induce PRs using parameters known best to induce locomotion. This mechanism may be related to switching from one state to another (e.g., locomotion vs. standing or sitting, waking vs. non-REM sleep or REM sleep).

Radiolabelled recombinant human interleukin-8 (IL-8) with its homologue neutrophil-activating peptide-2 (NAP-2) have been compared for imaging acute sterile inflammatory lesions in rats. 125I-IL-8 and 125I-NAP-2 were prepared by reaction with chloramine-T and injected intravenously into male rats bearing subcutaneous carrageenan abscesses in their left hindlimbs. Left hindlimb and right hindlimb activities were determined from serial total-body scintigrams between 1 h and 96 h post-injection as regional per cent injected activity corrected for physical decay (IA). Time-activity curves for 125I-IL-8 and 125I-NAP-2 in the carrageenan-containing left hindlimbs were similar in that both peaked at 1-3 h post-injection (IL-8, 4.9±0.5IA; NAP-2, 4.8±1.9IA) and decreased exponentially thereafter. However, while the lesioned-to-control limb activity ratio (LC) for 125I-IL-8 only approximately doubled during the imaging period (1.7±0.3 at 1 h vs 3.7±1.0 at 24 h post-injection), LC for 125I-NAP-2 more than tripled, rising from 1.5±0.4 at 1 h to 5.3±0.7 by 72 h post-injection. It is concluded that while both radiolabelled IL-8 and NAP-2 may prove useful for clinical imaging, radiolabelled NAP-2 may provide better discrimination of inflammatory lesions from normal tissue at later times post-injection.

Seedling establishment is a critical phase in pasture management. Knowledge of the seedling development of new forages is necessary to develop management practices and recommend species mixtures for pasture seedings. We compared seedling growth and development of prairiegrass (Bromus willdenowiiKunth = BcatharticusVahl), grazing bromegrass (BstamineusDesv.), and orchardgrass (Dactylis glomerataL.) in controlled environment and field studies. Seedlings were sampled weekly for 7 wk in the growth chamber and greenhouse beginning 8 to 10 d after planting (DAP). The number and mass of leaves and roots were recorded. In the field, leaf development was measured during spring and fall of 1997, and leaf and root development were measured during spring and fall of 1999. Forage dry matter (DM) yield was measured in clipped field plots during 1998 to 2000. Grazing bromegrass had more leaves, about twice the number of tillers per seedling, and a greater seedling mass than other grasses. Grazing bromegrass also had 50 to 100% more tillers m−2than other grasses in clipped field plots. The larger seedling size and greater tiller density, however, did not translate into greater yield in clipped plots. Grazing bromegrass yielded 10 to 15% less than orchardgrass or prairiegrass. Because of their large seedlings and rapid development, prairiegrass and grazing bromegrass probably should be used at a lower seeding rate or perhaps not used in seed mixtures with small‐seeded grasses. Seedlings of these grasses should be fully established by 40 to 50 DAP under favorable moisture and temperatures in the spring and late summer.

The effect of age on bone formation in the limb lengthening model of distraction osteogenesis (DO) was investigated in two studies using Sprague—Dawley (SD) rats from two colonies at various ages (CAMM: 9 vs 24 months, Harlan: 4 vs 24 months). External fixators were placed on the right tibiae of 30 male SD rats (20 CAMM, 10 Harlan) and mid‐diaphyseal osteotomies were performed. Distraction was performed at 0.2 mm bid for 20 days (CAMM) or 14 days (Harlan). The experimental (DO) and control (contra‐lateral) tibiae were removed for high‐resolution radiography and decalcified histology. Videomicroscopy was used to quantitate radiodensity, histology (matrix type) and relative areas of cell proliferation, which was identified by proliferating cell nuclear antigen (PCNA) immunochemistry. Both studies demonstrated an age‐related decrease in the percent mineralized bone (radiodensity) in the distraction gap (CAMM 9 vs 24 months: 68% vs 51%, P< 0.003; Harlan 4 vs 24 months: 95% vs 36%, P< 0.001) and no significant colony or distraction time‐specific difference was seen between the two colonies of 24‐month‐old rats. Histology was performed on the Harlan rats. The DO gaps in the 24‐month‐old rats demonstrated less endosteal new bone compared to the 4‐month‐old rats (P< 0.01), but equivalent periosteal new bone. In 4‐month‐old rats, PCNA‐immunostained cells were organized along the primary matrix front (where the first deposition of osteoid occurs) extending across both periosteal and endosteal surfaces. In 24‐month‐old rats, PCNA + cells were organized in zones along the periosteal new bone fronts only and irregularly scattered throughout the endosteal gap within a fibrovascular non‐ossifying matrix. These results indicate that 24‐month‐old rats have a relative deficit in endosteal bone formation which may not be related to cell proliferation but rather to cell organization. This model reflects the clinical situation where radiographic findings in older patients demonstrate significant delays in mineralization during DO. We believe this model of DO in aged rats presents unique in vivo opportunities to test hypotheses concerning (1) the effects of aging on bone repair, (2) the effects of pharmacological agents on bone repair in a geriatric setting, and (3) to study the mechanisms underlying DO. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

These studies were designed to determine the reliability of in vitro tensile testing to measure the temporal development of regenerate bone strength in rats during limb lengthening (distraction osteogenesis, DO). External fixators were placed on the right tibiae of 36 virus‐free, 400–450 g male Sprague Dawley rats, and osteotomies (n= 33) were performed. Distraction was initiated the following morning (0 day latency) at 0.4 mm/day and continued to day 20. The 8 mm gap was allowed to consolidate for up to 50 days (day 70 postop). Contralateral unoperated and operated (fixator only) controls were included. On days 20, 30, 50 and 70 postop, the rats were anesthetized, and their tibiae were radiographed prior to undergoing sacrifice for histological or tensile analysis. On day 70, an additional group was tested by three‐point bending. Radiodensity measurements demonstrated progressive mineralization of the DO gap, and histology confirmed typical intramembranous ossification of collagen bundles oriented parallel to the distraction force. Tensile stiffness increased significantly between days 20 and 30 postop, this increase correlated with initial radiographic and histologic bridging of the DO gap. Energy to failure and ultimate tensile strength increased progressively to day 70. At day 70, the force to failure for three‐point bending was 65% of control tibiae. In conclusion, in vitro tensile testing provides a reliable method to test the development of structural integrity during the early stages of DO. Therefore, the biomechanical effects of postulated modulators of bone repair can be measured during early stages (bone formation, bridging, early consolidation) of DO in a rat model. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.