Search

NRG1 fusions are recurrent somatic genome alterations occurring across several tumor types, including invasive mucinous lung adenocarcinomas and pancreatic ductal adenocarcinomas and are potentially actionable genetic alterations in these cancers. We initially discovered CD74-NRG1 as the first NRG1 fusion in lung adenocarcinomas, and many additional fusion partners have since been identified. Here, we present the first CD74-NRG1 transgenic mouse model and provide evidence that ubiquitous expression of the CD74-NRG1 fusion protein in vivo leads to tumor development at high frequency. Furthermore, we show that ERBB2:ERBB3 heterodimerization is a mechanistic event in transformation by CD74-NRG1 binding physically to ERBB3 and that CD74-NRG1–expressing cells proliferate independent of supplemented NRG1 ligand. Thus, NRG1 gene fusions are recurrent driver oncogenes that cause oncogene dependency. Consistent with these findings, patients with NRG1 fusion-positive cancers respond to therapy targeting the ERBB2:ERBB3 receptors.

A subset of patients with advanced-stage classical Hodgkin Lymphoma (cHL) relapse or progress following standard treatment. Given their dismal prognosis, identifying this group of patients upfront represents an important medical need. While prior research has identified characteristics of the tumor microenvironment, which are associated with cHL outcomes, biomarkers that are developed and validated in this high-risk group are still missing. Here, we applied whole-slide image analysis (WSI), a quantitative, large-scale assessment of tumor composition that utilizes conventional histopathology slides. We conducted WSI on a study cohort with pre-treatment biopsies of 340 advanced-stage cHL patients enrolled in the HD12 and HD15 trials of the German Hodgkin Study Group (GHSG), and tested our results in in a validation cohort of 147 advanced-stage cHL patients within the GHSG HD18 trial. All patients were treated with BEACOPP-based regimens. By quantifying T cells, B cells, Hodgkin-Reed-Sternberg-cells and macrophages with WSI, 80% of all cells in the tumor tissue were identified. Crucially, low B cell count was associated with significantly reduced progression-free survival (PFS) and overall survival (OS), while T cell-, macrophage- and Hodgkin-Reed-Sternberg-cell content was not associated with the risk of progression or relapse in the study cohort. We further validated low B cell content as a prognostic factor of PFS and OS in the validation cohort and demonstrate good inter-observer agreement of WSI. WSI may represent a key tool for risk stratification of advanced-stage cHL that can easily be added to the standard diagnostic histopathology work-up.

Summary This paper examines the impact of participatory research and tests hypotheses on its effectiveness to increase the adoption of soil conservation and fertility management innovations in Southeast Asia. Participatory research activities are significant and positive in explaining the differential adoption rates of hedgerows, contour ridging, the usage of farm yard manure, and inorganic fertilizer over nonparticipants. Secondly, the impacts of the participatory approach on soil conservation and fertility management innovations are incorporated into models examining the reasons for change in land allocation and cassava yields. Results are mixed. We also find a positive impact to participatory research and extension activities on cassava yield that is not linked to new technology adoption.

Technical, metallurgical and ergonomic problems which were encountered during a three-year development period of a surgical ultrasonic aspirator are reported. The aim of the construction of a lighter, handier, piezo-driven handpiece with a durable titanium tip was achieved. A first version was extensively tested during more than 40 resections of brain tumours. A second prototype of a handpiece with an integrated aspiration and flushing facility will be soon evaluated clinically. Further applications and perspectives of ultrasonic aspiration are discussed.

A fundamental limitation in devising new therapeutic strategies for killing cancer cells with DNA damaging agents is the need to identify synthetic lethal interactions between tumor-specific mutations and components of the DNA damage response (DDR) in vivo. The stress-activated p38 mitogen-activated protein kinase (MAPK)/MAPKAP kinase-2 (MK2) pathway is a critical component of the DDR network in p53-deficient tumor cells in vitro. To explore the relevance of this pathway for cancer therapy in vivo, we developed a specific gene targeting strategy in which Cre-mediated recombination simultaneously creates isogenic MK2-proficient and MK2-deficient tumors within a single animal. This allows direct identification of MK2 synthetic lethality with mutations that promote tumor development or control response to genotoxic treatment. In an autochthonous model of non-small-cell lung cancer (NSCLC), we demonstrate that MK2 is responsible for resistance of p53-deficient tumors to cisplatin, indicating synthetic lethality between p53 and MK2 can successfully be exploited for enhanced sensitization of tumors to DNA-damaging chemotherapeutics in vivo., National Institutes of Health (U.S.) (Grant ES015339), National Institutes of Health (U.S.) (Grant GM60594), National Institutes of Health (U.S.) (Grant GM59281), National Institutes of Health (U.S.) (Grant CA112967), Janssen Pharmaceutical Ltd., Massachusetts Institute of Technology. Center for Environmental Health Sciences (Core Grant P30-CA14051), Massachusetts Institute of Technology. Center for Environmental Health Sciences (Core Grant ES-002109)

Farmers in Asia like to grow cassava because the crop will tolerate long dry periods and poor soils, and will produce reasonable yields with little inputs. Most farmers realize, however, that cassava production on slopes can cause severe erosion, while production without fertilizer inputs may lead to a decline in soil productivity. Research has shown that cassava yields can be maintained for many years with adequate application of fertilizers, and that there are various ways to reduce erosion. Adoption of erosion control practices, however, has been minimal as farmers generally see little short-term benefits of these practices. To enhance the adoption of soil conserving practices and improve the sustainability of cassava production, a farmer participatory research (FPR) approach was used to develop not only the best soil conservation practices, but also to test new varieties, fertilization and cropping systems that tend to produce greater short-term benefits. The FPR methodology was initially developed in 2-3 sites each in China, Indonesia, Thailand and Vietnam, but has now extended to about 99 villages in Thailand, Vietnam and China. The methodology includes the conducting of RRAs in each site, farmer evaluation of a wide range of practices shown in demonstration plots, FPR trials with farmerselected treatments on their own fields, field days with discussions to select the best among the tested practices, scaling-up to larger fields, and farmer participatory dissemination to neighbors and other communities. Based on the results of these trials, farmers have readily adopted better varieties, fertilization and intercropping practices, and many farmers have now adopted the planting of contour hedgerows to control erosion. The resulting increases in cassava yields in Asia over the past eight years have increased the annual gross income of cassava farmers by an estimated 250 million US dollars.

Cassava has been grown in Thailand for many years. Land is usually prepared by plowing with a 3-disk plow followed by a 7-disk harrow and ridging. This method of land preparation results in a very loose soil, which is free of weeds and easy to plant. However, it has also led to the formation of a compacted subsoil or hardpan. A trial on alternative methods of land preparation was conducted at three sites from 2001 to 2004 to determine the effect of land preparation on the yields of four cassava cultivars. The results indicate that on average for three years in a farmer's field near Rayong Field Crops Research Center, tillage treatments had a significant effect on the fresh root yield of the four cassava cultivars. Using a subsoiler followed by 3-disk plow produced the highest fresh root yield of 24.60 t/ha, while the no-tillage treatment produced the lowest yield of 19.26 t/ha. At the Thai Tapioca Development Institute site, there were significant differences among tillage treatments for fresh root yield of the four cassava cultivars. Using the subsoiler followed by a chisel plow produced the highest fresh root yield of 21.59 t/ha and the second highest net income; this was followed by the no-tillage treatment (which brought in the highest net income). At Khaw Hin Sorn Research Station of Kasetsart University, tillage treatments also had a significant effect on fresh root yields. Using a 3-disk plow followed by 7-disk harrow and ridging up-and-down the slope produced the highest fresh root yield of 32.21 t/ha, but using a 3-disk plow followed by a 7-disk harrow, with or without subsoiling, brought in the highest net incomes. Among the four cultivars, there was no significant difference in fresh root yield; however, they differed in starch content.

Total nutrient uptake and nutrients removed in harvested plant parts were determined for cassava grown for either root or forage production, maize, sorghum, peanut, mungbean, pineapple and sugarcane. All crops were grown in replicated plots on 7% slope on a sandy loam soil in Sri Racha, Thailand, during a 4 1/2-year period. Erosion losses associated with each crop were also determined by weighing at monthly intervals the soil sediments that had collected in plastic covered channels at the bottom of each plot. Cassava for root production had the lowest total uptake of major nutrients of all crops except mungbean. The amounts of N and P removed in the harvested plant parts were also much lower than those removed by other crops, while the amount of K removed by cassava was similar to other crops but much lower than pineapple or cassava grown for forage. This latter crop had a very high nutrient uptake and removal, especially that of N, K, Ca and Mg. On an annual basis, soil losses due to erosion were highest in cassava grown for roots, followed by cassava for forage, sugarcane, mungbean, sorghum, peanut, maize and pineapple. Thus, when cassava is grown for root production on slopes, it is likely to cause more erosion than most other crops due to its wide spacing and slow initial canopy development. Cassava farmers should therefore be encouraged to use special management practices that reduce erosion. However, it is unlikely that cassava causes soil degradation by depleting the soil nutrient supply, as N and P removal in the harvested part of the plant was actually lower than, and K removal was similar to that of other crops tested.

Cassava (Manihot esculenta Crantz) is usually grown by poor farmers in the tropics with a minimum of inputs. Continuous production under these conditions can lead to soil nutrient depletion. On sloping land, cassava cultivation can also cause severe erosion if the crop is not properly managed. This paper reviews the literature to show that cassava does extract large amounts of nutrients, especially potassium (K), from the soil. However, when nutrient extraction is calculated on the basis of per unit quantity dry-matter produced, cassava extracts much less N and P than, and similar amounts of K to, most other crops. Long-term fertility trials indicate that, without adequate K fertilization, cassava yields eventually decline due to K depletion, except in those soils containing large amounts of K-bearing minerals. While cassava production may result in severe erosion when grown on steep slopes, simple agronomic practices can usually maintain soil losses within acceptable levels. The effect different cultivation practices on erosion and yield varies from location to location, and the most appropriate practices can be identified through simple erosion-control trials on farmers' fields. Thus, productivity of continuously grown cassava fields can be maintained through judicious use of fertilizers and soil management practices that control erosion.

Within the Hamiltonian approach in Coulomb gauge the ghost and gluon propagators are determined from a variational solution of the Yang-Mills Schroedinger equation showing both gluon and heavy quark confinement. The continuum results are in good agreement with lattice data. The ghost form factor is identified as the dielectric function of the Yang-Mills vacuum and a connection between the Gribov-Zwanziger scenario and the dual Meissner effect is established. The topological susceptibility is calculated., Comment: 8 pages, 9 figures, Invited talk given by H. Reinhardt at the international conference on "Selected Problems in Theoretical Physics, Dubna 23-27 June 2008"

One-year simple NPK trials were conducted in 22 locations in four regions of Colombia to determine the response of cassava (Manihot esculenta Crantz) to N, P and K and to relate this response to the available P and K contents of the soil, as well as to the N, P, and K concentrations in youngest fully expanded leaf (YFEL) blades sampled at 3–5 months after planting. It was found that cassava responded mainly to P applications in the low-P soils of the Eastern Plains and of Cauca Department, to K applications only in the Eastern Plains and to N applications principally in the sandy, low-OM soils of the Atlantic Coast. By relating the relative response to P and K to the available P and exchangeable K content of the soil, respectively, critical levels of 4 mg P/kg and 0.17 me K/100 g (both extracted with Bray II) were determined. Similarly, critical levels of 5.6% N, 0.41% P and 1.42% K were determined in YFEL-blades.

The vacuum wave functional of Coulomb gauge Yang-Mills theory is determined within the variational principle and used to calculate various Green functions and observables. The results show that heavy quarks are confined by a linearly rising potential and gluons cannot propagate over large distances. The 't Hooft loop shows a perimeter law and thus also indicates confinement., Comment: 7 pages, 2 figures, proceedings of the XXV International Symposium on Lattice Field Theory, July 30-4 August 2007, Regensburg, Germany

It is argued that within the continuum functional formalism, there is no need to supply a further (spatially independent) gauge constraint to complete the Coulomb gauge of Yang-Mills theory. It is shown explicitly that a natural completion of the gauge-fixing leads to a contradiction with the perturbative renormalizability of the theory., Comment: 4 pages, no figures

In Southeast Asia, many of the poorest farmers live in areas with limited potential for crop production. Cassava (Manihot esculenta Crantz) is an important crop on these soils, because it is easy to grow, requires few external inputs, and its roots and leaves can be used as human or animal feed. Cassava is also planted as an industrial crop for production of animal feed and starch where market conditions are developed. The wide variety of end uses makes it a popular crop and an effective vehicle for improving the livelihood of poor upland farmers.

Assuming that center vortices are the confining gauge field configurations, we argue that in gauges that are sensitive to the confining center vortex degrees of freedom, and where the latter lie on the Gribov horizon, the corresponding ghost form factor is infrared divergent. Furthermore, this infrared divergence disappears when center vortices are removed from the Yang-Mills ensemble. On the other hand, for gauge conditions which are insensitive to center vortex degrees of freedom, the ghost form factor is infrared finite and does not change (qualitatively) when center vortices are removed. Evidence for our observation is provided from lattice calculations., Comment: 3 pages, 2 figures

The frustrated Ising model in two dimensions is revisited. The frustration is quantified in terms of the number of non-trivial plaquettes which is invariant under the Nishimori gauge symmetry. The exact ground state energy is calculated using Edmond's algorithm. A novel cluster algorithm is designed which treats gauge equivalent spin glasses on equal footing and allows for efficient simulations near criticality. As a first application, the specific heat near criticality is investigated., Comment: 4 pages, 4 eps figures included

We investigate the dependence of the Yang-Mills wave functional in Coulomb gauge on the Faddeev-Popov determinant. We use a Gaussian wave functional multiplied by an arbitrary power of the Faddeev-Popov determinant. We show, that within the resummation of one-loop diagrams the stationary vacuum energy is independent of the power of the Faddeev-Popov determinant and, furthermore, the wave functional becomes field-independent in the infrared, describing a stochastic vacuum. Our investigations show, that the infrared limit is rather robust against details of the variational ans\"atze for the Yang-Mills wave functional. The infrared limit is exclusively determined by the divergence of the Faddeev-Popov determinant at the Gribov horizon., Comment: 9 pages, no figures

The Yang-Mills Schr\"odinger equation is variationally solved in Coulomb gauge for the vacuum sector using a trial wave functional, which is strongly peaked at the Gribov horizon. We find the absence of gluons in the infrared and also a confining quark potential., Comment: 4 pages, 5 figures, revtex

The Yang-Mills Schr��dinger equation is solved in Coulomb gauge for the vacuum by the variational principle using an ansatz for the wave functional, which is strongly peaked at the Gribov horizon. A coupled set of Schwinger-Dyson equations for the gluon and ghost propagators in the Yang-Mills vacuum as well as for the curvature of gauge orbit space is derived and solved in one-loop approximation. We find an infrared suppressed gluon propagator, an infrared singular ghost propagator and a almost linearly rising confinement potential., 24 pages, revtex, 13 figures

Cassava is generally grown by poor farmers living in marginal areas with adverse climatic and soil conditions. The crop is very suitable for these conditions because of its exceptional tolerance to drought and to acid, infertile soils. It is often grown on sloping land because of its minimal requirement for land preparation, and its ability to produce reasonably good yields on eroded and degraded soils, where other crops would fail. It has been shown (Quintiliano et al., 1961; Margolis and Campos Filho, 1981; Putthacharoen et al., 1998), however, that growing cassava on slopes can result in severe erosion, with high soil and nutrient losses. Thus cassava cultivation on slopes requires adequate cultural and soil conservation practices that minimize erosion (Howeler, 1994). Cassava is well adapted to poor or degraded soils because of its tolerance to low pH, high levels of exchangeable aluminium (Al) and low concentrations of phosphorus (P) in the soil solution. Studying the effect of pH on the growth of several crops grown in flowing nutrient solution, Islam et al. (1980) reported that cassava and ginger (Zingiber officinale) were more tolerant of low pH (< 4) than tomatoes (Lycopersicon esculentum), wheat (Triticum aestivum L.) or maize (Zea mays L.). Centro Internacional de Agricultura Tropical (CIAT; 1978) and Howeler (1991a) also reported that cassava and cowpeas (Vigna unguiculata) were more tolerant of acid soils with high levels of exchangeable Al, and were much less responsive to lime applications than common beans (Phaseolus vulgaris), rice (Oryza sativa), maize and sorghum (Sorghum vulgaris).

A model for the infrared sector of SU(2) Yang-Mills theory, based on magnetic vortices represented by (closed) random surfaces, is presented. The model quantitatively describes both confinement and the topological aspects of Yang-Mills theory. Details (including an adequate list of references) can be found in hep-lat/9912003 and hep-lat/0004013, both to appear in Nucl. Phys. B., Comment: 3 latex pages, 1 epsf figure; talk presented by M.Engelhardt at the Conference "Quark Confinement and the Hadron Spectrum IV" (CONFINEMENT IV), Vienna, 3.-8.7.2000, to appear in the proceedings

The baryon structure is investigated in a covariant diquark-quark model. In this approach baryons emerge as relativistic bound states of a constituent quark and a $0^{+}$ or $1^{+}$ diquark. After solving the Bethe-Salpeter Equation for the scalar diquark quark system in ladder approximation we couple various external currents to the constituents of the baryon to probe its internal structure. The quark and the diquarks are assumed to be confined which is implemented by suitable choices for the propagators. This leads to nontrivial vertex functions between the constituents and the external current. Baryonic matrix elements are then evaluated to extract observable formfactors., Comment: 10 pages, LaTeX, 5 figures, uses sprocl.sty epsf.sty, talk given at 'Diquarks 3', Torino, Oct. 28-30,1996; to appear in the proceedings

It is demonstrated that the field strength approach to Yang Mills theories has essential features of the dual description. In D=3 this approach is formulated in terms of gauge invariant variables., Comment: 7 pages LaTeX with sprocl.sty style-file

The Yang-Mills functional integral is studied in an axial variant of 't Hooft's maximal Abelian gauge. In this gauge Gau\ss ' law can be completely resolved resulting in a description in terms of unconstrained variables. Compared to previous work along this line starting with work of Goldstone and Jackiw one ends up here with half as many integration variables, besides a field living in the Cartan subgroup of the gauge group and in D-1 dimension. The latter is of particular relevance for the infrared behaviour of the theory. Keeping only this variable we calculate the Wilson loop and find an area law., Comment: 43 pages REVTeX, 6 figures

The $����$--mixing generated by the isospin breaking of the current quark masses $m_{u} \neq m_{d}$ is studied within the bosonized NJL model in the gradient expansion. The resulting effective meson lagrangian naturally incorperates vector meson dominance. By including pion loops an excellent description of both the pion electromagnetic form factor and of the $��^+��^-$ phase shifts in the vector--isovector channel is obtained. The $����$--mixing can be treated in the static approximation but is absolutely necessary to reproduce the fine structure of the electromagnetic form factor, while the pion loops are necessary to obtain the correct energy dependence of the phase shifts., 11 LaTeX pages, 4 figures available upon request

We investigated the form factors of the nucleon associated with the nonet vector current in the framework of the generalized Yabu--Ando approach to the chiral soliton of the Nambu--Jona--Lasinio model. We introduce a variational parameter to improve the predictions for the baryon mass splittings and, in addition, we take into account $1/N_c$ rotational corrections to accommodate the empirical isovector magnetic moment of the nucleon. We find that the strange magnetic moment lies between -0.05 and 0.25., Comment: 3 pages, LaTeX file. Talk given at the conference: Hadron 95, July 9th-14th, 1995, Manchester

In this letter we reconsider the previously given description of heavy mesons within a bosonized extended NJL model that combines heavy quark and chiral symmetry. In that work the naive gradient expansion of the quark determinant was used, which satisfactorily works in the light sector but does not adequately describe the heavy $(0^+,1^+)$ mesons. By investigating the exact momentum dependence of the quark loop we demonstrate that the naive gradient expansion in the heavy sector is not the right method to treat the unphysical $q\bar{q}$--thresholds which would be absent in confining theories. We propose a modified gradient expansion which adequately extrapolates from the low--momentum region beyond threshold. This expansion gives a satisfactory description even of the $(0^+,1^+)$ heavy mesons whose masses are significantly above threshold., Comment: 13 pages (LaTeX, 4 figures included as uuencoded ps.files using epsf.tex); HUB-IEP-94/14, UNITUE-THEP-18/1994

A thorough study is performed of the analytical properties of the fermion determinant for the case that the time components of (axial) vector fields do not vanish. For this purpose the non--Hermitian Euclidean Dirac Hamiltonian is generalized to the whole complex plane. The Laurent series are proven to reduce to Taylor series for the corresponding eigenvalues and --functions as long as field configurations are assumed for which level crossings do not occur. The condition that no level crossings appears determines the radius convergence. However, the need for regularization prohibits the derivation of an analytic energy functional because real and imaginary parts of the eigenvalues are treated differently. Consistency conditions for a Minkowski energy functional are extracted from global gauge invariance and the current field identity for the baryon current. Various treatments of the Nambu--Jona--Lasinio soliton are examined with respect to these conditions. Motivated by the studies of the Laurent series for the energy functional the Euclidean action is expanded in terms of the $��$--field. It is argued that for this expansion the proper--time regularization scheme has to be imposed on the operator level rather than on an expression in terms of the one--particle eigenenergies. The latter treatment is plagued by the inexact assumption that the Euclidean Dirac Hamiltonian and its Hermitian conjugate can be diagonalized simultaneously. It is then evident that approaches relying on counting powers of the $��$--field in the one--particle eigenenergies are, UNITU-THEP-13/1994, 34 LaTeX pages, 5 figures appended as postscript file

The role of chiral transformations in effective theories modeling Quantum Chromo Dynamics is reviewed. In the context of the Nambu--Jona--Lasinio model the hidden gauge and massive Yang--Mills approaches to vector mesons are demonstrated to be linked by a special chiral transformation which removes the chiral field from the scalar--pseudoscalar sector. The role of this transformation in the presence of a topologically non--trivial chiral field is illuminated. The fermion determinant for such a field configuration is evaluated by summing the discretized eigenvalues of the Dirac Hamiltonian. This discretization is accomplished by demanding certain boundary conditions on the quark fields leaving a finite model space. The properties of two sets of boundary conditions are compared. When the topologically non-trivial chiral transformation is applied to the meson fields the associated transformation of the boundary conditions is shown to be indispensable. A constructive procedure for transforming the boundary conditions is developed., Comment: LaTeX, 21 pages, one postscript figure attached, UNITU-THEP-6/1994

The classical Yang-Mills equations are solved for arbitrary semi-simple gauge groups in the Schwinger-Fock gauge. A new class of SU(N) instantons is presented which are not embeddings of SU(N-1) instantons but have non-trivial SU(N) color structure and carry winding number $n=N(N^{2}-1)/6$. Explicit configurations are given for SU(3) and SU(4) gauge groups. By means of the Atiyah Manton procedure Skyrmion fields are constructed from the SU(N) instantons. These Skyrmions represent exotic baryon states., Comment: 10 LaTex pages (1 figure available on request), UNITUE-THEP-10-1993

The recently developed method to investigate mesonic fluctuations off the chiral soliton in the Nambu--Jona--Lasinio model is applied to kaons in the S--wave channel. It is shown that for commonly accepted choices of parameters the presence of the soliton and the lack of confinement in this model provide an unphysical (valence) quark threshold which is lower than the kaon mass. Choosing parameters such that this threshold is avoided a bound state is obtained in the S--wave channel. After semiclassical quantization this state acquires the quantum numbers of an odd parity $\Lambda$ and is predicted at about 420MeV above the nucleon mass., Comment: 20 pp LaTeX, 4 figures postscript-files included at the end of the LaTeX-file

Within renormalizable theories the triangle diagram correctly reproduces the lifetime of the neutral pion $\pi ^0$. However, effective relativistic quark models which contain a second scale besides the quark mass seem unable to give the correct value for this quantity. In the Instanton Liquid Model this second scale is the mean instanton radius, in the NJL model it is the cutoff. The role of the cutoff within a path integral derivation of the chiral anomaly is clarified and the importance of higher order terms contributing to the $\pi ^0$ decay width and other anomalous processes is pointed out., Comment: 6 pages, UNITUE-THEP-19/1992

Many screening methodologies have been developed for identifying acid-soil tolerant genotypes of the major foodcrops and pasture species, both in the temperate regions and in the tropics. These include rapid screening tests in nutrient solutions and in soils in the greenhouse, as well as field screening techniques. The methodologies are described and their relative advantages and disadvantages discussed. Different formulas and graphical methods are presented for classifying germplasm into different categories of Al-tolerance, depending on specific selection objectives. Finally, recent progress in identifying Al-tolerant germplasm of wheat, barley, maize, sorghum, rice, beans, cowpea, soybeans, peanut, sweet potato and cassava is discussed.

A three different sites with acid soils in Colombia field trials with cassava were monitored for frequency of VA mycorrhiza. Increasing levels of phosphorus (P) from 0 to 200 kg P/ha had been applied. The fields differed in the composition of species of VA mycorrhizal fungi. At all sites infections of the roots by the total mycorrhizal population decreased with increasing P fertilization, but at two sites the relative frequency and activity of one species,Glomus manihotis, increased with increasing P applications. This species was only present at two sites, and only in these sites a cassava yield response to up to 200 kg P was found. The differential activity of fungal species was confirmed in greenhouse trials, whereEntrophospora colombiana was found to be most effective at 50 kg P andG. manihotis, at 200 kg P.

Field inoculation trials with cassava (Manihot esculenta Crantz) were conducted in Quilichao (typic Dystropept soil) and Carimagua (Haplustox soil). In Quilichao, with a large and effective native VA-mycorrhizal (VAM) population, inoculation withGlomus manihotis did not increase cassava yields significantly, neither when different sources and levels of inoculum material were used, nor with different cassava cultivars, or after stabilizing soil temperature through mulching. Field inoculation did result in a decrease of the coefficient of variation with respect to yield. The high dependency of cassava on an effective VAM association was indicated by a marked decrease in yield after eradication of native VAM by soil sterilization. In Carimagua, with a lower native VAM population, mycorrhizal inoculation withG. manihotis increased yields significantly at intermediate levels of 100 kg/ha of applied P, using either inoculum of cassava orPanicum maximum roots or inoculum of a soil-root mixture of maize or tropical kudzu. Higher or lower levels of P decreased the effect of inoculation on yield. There were no significant differences among P sources, ranging from highly soluble triple superphosphate to low solubility rock phosphates. Inoculation with different VAM isolates had a variable effect on cassava yields, and showed that there may be an interaction between P fertilizer level and isolate efficiency. It is concluded that there may be a potential to increase yields or decrease the fertilizer P requirements of cassava through field inoculation with effective VAM isolates, in the vast areas of acid infertile Oxisols and Ultisols with low native VAM fungal populations, represented by Carimagua.

Cassava (Manihot esculenta Crantz) was grown in the greenhouse and in the field at different levels of phosphorus applied, with or without inoculation with VA mycorrhiza in sterilized or unsterilized soil. When grown in a sterilized soil to which eight levels of P had been applied the non-inoculated plants required the application of 3200 kg P ha−1 to reach near-maximum yield of plant dry matter (DM) at 3 months. Inoculated plants, however, showed only a minor response to applied P. Mycorrhizal inoculation in the P check increased top growth over 80 fold and total P uptake over 100 fold. Relating dry matter produced to the available P concentration in the soil (Bray II), a critical level of 15 ppm P was obtained for mycorrhizal and 190 ppm P for non-mycorrhizal plants. This indicates that the determination of critical levels of P in the soil is highly dependent on the degree of mycorrhizal infection of the root system. In a second greenhouse trial with two sterilized and non-sterilized soils it was found that in both sterilized soils, inoculation was most effective at intermediate levels of applied P resulting in a 15–30 fold increase in DM at 100 kg P ha−1. In the unsterilized soil inoculation had no significant effect in the quilichao soil, but increased DM over 3 fold in the Carimagua soil, indicating that the latter had a native mycorrhizal population less effective than the former. When cassava was grown in the field in plots with 11 levels of P applied, uninoculated plants grown in sterilized soil remained extremely P deficient for 4–5 months after which they recuperated through mycorrhizal infection from unsterilized borders or subsoil. Still, after 11 months inoculation had increased root yields by 40%. In the non-sterilized soil inoculation had no significant effect as the introduced strain was equally as effective as the native mycorrhizal population. These trials indicate that cassava is extremely dependent on an effective mycorrhizal association for normal growth in low-P soils, but that in most natural soils this association is rapidly established and inoculation of cassava in the field can only be effective in soils with a low quantity and quality of native mycorrhiza. In that case, plants should be inoculated with highly effective strains.

Two cassava (Manihot esculenta Crantz.) cultivars were planted in fertilized and non-fertilized plots to determine the accumulation and distribution of dry matter and nutrients in the plant and the effect on soil fertility. At monthly intervals eight plants were harvested and separated into four parts, the upper, middle and lower thirds of the aerial growth, and the roots, while each aerial part was divided into leafblades, petioles, and stem. These samples were analyzed for dry matter (DM) and nutrient content. Soil samples were also taken at monthly intervals and analyzed. Results indicated that in cassava DM accumulation was slow during the first 2 months, increased rapidly during the next 4 months and slowed down during the final 6 months as DM production was partly offset by leaf fall. At harvest (12 months) DM was present mainly in roots, followed by stem, leaves and petioles. Nutrient concentrations varied between plant parts and with the age of both the tissue and the plant. The concentration of most nutrients was highest between 2 and 3 months and then declined. Each nutrient had its own particular concentration profile within the plant. Thus, N, P and S concentrations tended to be high in the leaves, while those of K, Ca and Mg were high in petioles and stem; the Mn concentration was particularly high in petioles, whereas Fe concentration was low in petioles but high in roots. B and Cu were evently distributed within the plant. Most nutrients accumulated initially in leaves and stem, but were translocated to roots in the latter part of the growth cycle. Only Ca, Mg and Mn accumulated more in stems than roots. Removal of accumulated nutrients in the root harvest can seriously deplete nutrient reserves in the soil, particularly that of K, and to a lesser extent for N. Soil pH, exchangeable Al, Ca, Mg as well as available P were not greatly affected by plant growth, while exchangeable K decreased markedly during the crop cycle.

A technique to study mycorrhizal effects on growth and P-uptake of cassava (Manihot escultenta, Crantz) grown in flowing solution culture is described. Phosphorus concentrations were carefully maintained constant at 0.1, 1, 10 and 100 μM by daily analyses and adjustment of the nutrient solutions. Inoculation with mycorrhizal roots hada positiveeffect on P content of plant tissue and/or plant growth only at the two lowest P-concentrations in soulution. These concentrations are two to three orders of magnitude lower than those normally used in conventional nutrient solution cultures.

To study the risk of developing rubeosis iridis following vitrectomy, the use of preoperative iris fluorescein angiography was prospectively investigated on patients with diabetes mellitus, without any clinically detectable iris or angle neovascularization. With increasing severity of fluorescein leakage, the risk of iris neovascularization with or without glaucoma, six months after vitreous surgery, is significantly increased. It was also determined whether postoperative steroid therapy (periocular triamcinolone acetonide and topical prednisolone phosphate) reduces the risk of developing iris neovascularization after vitrectomy. Controlled and treated patient eyes did not differ significantly in the degree of rubeosis. However, neovascular glaucoma statistically occurred more frequently in the nonsteroid group.

Summary Eight cassava (Manihot esculenta) cultivars were grown with or without mycorrhizal inoculation in flowing solution cultures containing approximately 0.1, 1, 10 or 100 μM phosphate. Rice (Oryza sativa), maize (Zea mays), cowpea (Vigna unguiculata) and French bean (Phaseolus vulgaris) were included in the experiment for comparative purposes. Cassava required a higher external phosphorus concentration for maximum yield (≥ 10 μM) than the other species (≥ 1 μM) regardless of the inoculation treatments. Roots of inoculated cassava plants were heavily infected with VA endophytes at 0.1 and 1 μM phosphate, but not at 10 or 100 μM. Non-inoculated cassava plants were free of infection, and no infections were observed in any treatment on the other species. At 1 μM phosphate, infection of cassava roots was associated with large increases in whole plant dry wt, concentration of phosphorous in tops and roots, and total phosphorus uptake. At 0.1 μM phosphate there were also substantial increases in phosphorus concentration in tops and roots but the infected cassava plants were still severely phosphorus deficient and growth was not improved. The results are discussed in relation to the present state of knowledge about the phosphorus nutrition of cassava.

The programmed nutrient addition technique was used in a series of 5 experiments to determine the response in growth and micronutrient content of cassava (Manihot esaulenta Crantz) cv. M Aus 10, to 8 supply levels of boron, copper, iron, manganese and zinc respectively. The experiments were of 9 weeks duration and utilized 22 litre pots of nutrient solution. The supply levels for each micronutrient covered the range from severe deficiency to toxicity. Critical tissue concentrations for deficiencies determined by relating total dry matter production to the nutrient concentration in the youngest fully expanded leaf blades were (μg/g): boron 35, copper 6, manganese 50, and zinc 30. Likewise, critical concentrations for toxicities in the same index tissue were (μg/g): boron 100, copper 15, manganese 250, and zinc 120. In the iron experiment, the data were too variable to allow precise determination of critical concentrations for deficiency and toxicity. Critical micronutrient concentrations in the pe...

Since high corticosteroid levels are important in achieving inhibition of intraocular cellular proliferation, we studied the clearance of an intravitreally injected slowly dissolving corticosteroid in the rabbit eye. Triamcinolone acetonide (0.5 mg) disappeared rapidly in eyes that underwent a combined vitrectomy and lensectomy (average, 6.5 days) and more slowly in eyes that underwent vitrectomy only (average, 16.8 days) compared with unoperated normal rabbit eyes (average, 41 days). The ophthalmoscopic disappearance of the white crystals correlated well with a sensitive colorimetric test for clearance of the corticosteroid. Direct observation is therefore an accurate method of assessing the absorption of the corticosteroid. If used therapeutically, this study suggests that more frequent injections of triamcinolone acetonide would be necessary in eyes that underwent vitrectomy, compared with normal eyes.

Greenhouse and field experiments were conducted on the effect of VA mycorrhiza (VAM) on the growth of cassava, various tropical grass and legume species, as well as beans, coffee and tea. A large number of VAM fungal species were evaluated for effectivity in increasing cassava growth and P uptake in acid low-P soils. The effectivity of VAM species and isolates was highly variable and dependent on soil pH and fertilizer applications, as well as on soil temperature and humidity. Two species, Glomus manihotis and Entrophospora colombiana were found to be most effective for a range of crops and pastures, at low pH and at a wide range of N, P, and K levels.