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Soil aggregation is important for maintaining soil surface integrity and allowing water to infiltrate, rather than runoff and cause erosion. The effect of grazing animals on soil aggregation compared with other conservation management strategies in the Southern Piedmont USA is not well known. We tested a hypothesis that grazing animals might negatively affect soil aggregation characteristics. Water-stable macroaggregates ([is greater than] 0.25 mm), mean-weight diameter, and their stabilities were (i) similar between conservation-tillage cropping and tall fescue (Festuca arundinacea Schreb.)-common bermudagrass (Cynodon dactylon L.) pasture; (ii) similar between 15- to 19-yr-old grazed and hayed hybrid bermudagrass; (iii) 7 to 14% greater in 30-yr-old than in 10-yr-old grazed tall fescue and hybrid bermudagrass pastures; (iv) similar among long-term grazingland, hayland, and forestland; and (v) 5 to 11% lower under cattle grazing than under monthly haying or unharvested management during the first 4 yr following conversion of cultivated cropland to pastureland. Water-stable aggregate distribution at a depth of 0 to 50 mm was 0.30 [+ or -] 0.07 g [g.sup.-1] in the 1.0- to 4.75-mm class, 0.46 [+ or -] 0.07 g [g.sup.-1] in the 0.25- to 1.0-mm class, 0.15 [+ or -] 0.02 g [g.sup.-1] in the 0.05- to 0.25-mm class, and 0.07 [+ or -] 0.01 g [g.sup.-1] in the [is less than] 0.05-mm class, averaged across management systems and replications (n = 56). Total glomalin of the 1.0- to 4.75-mm dry-stable aggregate class was highly related to whole soil organic C content, but neither of these properties was particularly well related with water-stable macroaggregation, mean-weight diameter, or their stabilities. We conclude, overall, that grazing of pastures in the Southern Piedmont USA has little detrimental effect on soil aggregate distribution and stability and is comparable in soil conservation with other land conservation strategies.

Improvement in structure of degraded soils or prevention of degradation of structure in healthy soils requires an understanding of processes contributing to aggregate stability. The impact of cropping systems on a specific molecule that contributes to aggregate stability is part of the process that has not been elucidated. The relationship between aggregate stability and glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, was studied during the first 3 yr in transition from plow tillage (PT) to no tillage (NT) maize (Zea mays L.). Results showed a high linear correlation ([r.sup.2] = 0.78, n = 32) between glomalin concentration in aggregates and aggregate stability. Increases in both aggregate stability and glomalin were measurable from year to year in NT plots, but NT was significantly higher than PT after 2 or 3 yr (P [is less than] 0.05). Comparison of NT plots after 3 yr with nearby soil in grass cover indicated that there was 20% greater stability and 45% higher concentration of glomalin in the grass-covered soil. Comparison of PT and NT (3 yr) interrow samples with intrarow samples indicated that plant roots and NT management may have a synergistic effect on aggregate stabilization. These results show that cropping systems should be evaluated for the impact on production of glomalin by AM fungi.

Glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, is a major component of the humus fraction of soil organic matter. Glomalin is extracted from soil and hyphae of AM fungi by using sodium citrate at 121 degrees C in multiple 1-h cycles, but extensive extraction does not solubilize all glomalin in all soils. Efficacies of 100 mM sodium salts of citrate, borate or pyrophosphate (pH 9.0, 121 degrees C) were tested for two 1-h cycles for hyphae from four AM fungal isolates and four 1-h cycles for seven soils from four US geographic regions. Residual soil glomalin was examined by pyrophosphate extraction of soils previously extracted with citrate or borate followed by extraction of all soils after treatment with NaOH. Hyphal extracts were compared using Bradford-reactive total protein (BRTP) values, and extracts from soils were compared using BRTP, percentage C and C weight. No difference among extractants was detected for AM fungal isolates or across soils. The residual glomalin across soils for extractants contained the following percentages of the total BRTP: pyrophosphate, 14%; borate, 17%; and citrate, 22%. Comparisons among individual soils indicated that pyrophosphate extracted significantly more BRTP (10-53%) than borate or citrate in six soils and borate was equal to pyrophosphate in one soil. Extraction with borate should be compared with pyrophosphate before initiating an experiment. For routine extractions of ca. 85% of the glomalin across a variety of soils, sodium pyrophosphate appears to be equal to or better than borate and better than citrate.

Naturally occurring soil organic compounds stabilize potentially toxic elements (PTEs) such as Cu, Cd, Pb, and Mn. The hypothesis of this work was that an insoluble glycoprotein, glomalin, produced in copious amounts on hyphae of arbuscular mycorrhizal fungi (AMF) sequesters PTEs. Glomalin can be extracted from laboratory cultures of AMF and from soils. Three different experiments were conducted. Experiment 1 showed that glomalin extracted from two polluted soils contained 1.6-4.3 mg Cu, 0.02-0.08 mg Cd, and 0.62-1.12 mg Pb/g glomalin. Experiment 2 showed that glomalin from hyphae of an isolate of Gigaspora rosea sequestered up to 28 mg Cu/g in vitro. Experiment 3 tested in vivo differences in Cu sequestration by Cu-tolerant and non-tolerant isolates of Glomus mosseae colonizing sorghum. Plants were fed with nutrient solution containing 0.5, 10 or 20 microM of Cu. Although no differences between isolates were detected, mean values for the 20 microM Cu level were 1.6, 0.4, and 0.3 mg Cu/g for glomalin extracted from hyphae, from sand after removal of hyphae and from hyphae attached to roots, respectively. Glomalin should be considered for biostabilization leading to remediation of polluted soils.

To measure and manage for C sequestration in heterogeneous rangeland systems, we need to more fully understand spatial patterns of soil resources. Spatial distributions of aggregate stability and soil carbon were investigated in a semiarid rangeland in New Mexico, USA. Soil was analyzed from plant interspaces, black grama (Bouteloua eriopoda (Torr.) Torr.), and mesquite (Prosopis glandulosa Torr.) in a landscape-replicated study. Aggregate stability at the 250 microm scale, carbonate C, organic C and N, C:N ratio, and glomalin, were all highest under mesquite. Soil C:N ratio was the best predictor of aggregate stability. Estimates of metric tons of C per hectare in the top 10 cm were highly variable at patch and landscape scales, varying from 4.2 to 10.5 under mesquite and from 3.0 to 7.0 in interspaces. High variability of aggregate stability and soil C has important implications for C sequestration. We argue that this multi-scale soil heterogeneity must be considered when measuring and managing for C sequestration.

Social reinforcers such as spouse behaviors have been hypothesized to be important in maintaining chronic pain behavior. This study used direct observation to test whether solicitous and aggressive spouse behaviors systematically precede and follow patient pain behaviors. Fifty chronic pain patients and spouses and 33 control couples were videotaped performing specified tasks. Spouse solicitous behaviors were significantly more likely to precede and follow nonverbal pain behaviors, and nonverbal pain behaviors were significantly less likely to follow spouse aggressive behaviors in pain than in control couples. Within couples, spouse solicitous behaviors preceded and followed verbal and nonverbal pain behaviors beyond chance levels more often in pain than in control couples. Results support an operant conceptualization of factors maintaining chronic pain behaviors.

A method for the chemical modification of gamma-carboxyglutamic acid (Gla) residues in proteins is introduced that has the combined advantages of mildness, a high degree of specificity, and the ability to introduce a radiolabel at modification sites for ease in quantitation. Unlike other Gla modification procedures which are performed in the lyophilized state at 110 degrees C, this procedure is carried out in solution at 37 degrees C. The addition of morpholine and formaldehyde to a slightly acidic solution of bovine prothrombin fragment 1 (residues 1-156) results in the conversion of Gla residues to gamma- methyleneglutamic acid (gamma- MGlu ). The extent of modification is controlled by the relative amounts of modification reagents to protein. A 100-fold molar excess of reagents to fragment 1 produced a protein molecule containing two gamma- MGlu residues, while a modification run at 10,000-fold molar excess of reagents to protein yielded fragment 1 containing eight gamma- MGlu residues per molecule. The specificity of this modification is illustrated by the interaction of native and modified protein with antibody populations directed against fragment 1. Native fragment 1, 8 gamma- MGlu fragment 1, and 2 gamma- MGlu fragment 1 show fairly similar behavior toward whole anti-fragment 1 serum. Differential behavior was exhibited by the native and modified proteins toward a subpopulation of antibodies specific to the calcium ion conformation of fragment 1. Unmodified fragment 1 displayed a strong affinity for these antibodies; however, the 2 gamma- MGlu fragment 1 exhibited a moderate affinity and the 8 gamma- MGlu fragment 1 did not bind to these antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

The intracellular distribution of the neurotoxin 2,4-diaminobutyric acid (DABA) in mature leaves of the perennial legume Lathyrus sylvestris L. var ;Lathco' (flatpea) was determined using subcellular fractions from mesophyll protoplasts. Chloroplasts contained about 15% of the cellular DABA. At least 75% of the DABA was vacuolar, based on the assumptions that each protoplast contained a single vacuole and that acid phosphatase occurred exclusively in the vacuole. DABA was not detectable in peroxisomal and mitochondrial fractions. Because the vacuole is not a major site of amino acid synthesis, this distribution implicates synthesis of DABA within chloroplasts with subsequent transport to and storage within the vacuoles of the mesophyll cells.

An immunoblotting procedure was developed to overcome the difficulty in identifying root colonization by a vesicular-arbuscular mycorrhizal fungus. The procedure utilized a murine monoclonal antibody that reacts with a protein in spores and hyphae of Glomus occultum, a fungus characterized by abundant production of hyaline spores and nonstaining intraradical infection. Minimally disturbed whole roots were squashed on nitrocellulose membranes. After inactivation of endogenous peroxidase, an indirect enzyme-linked immunosorbent assay was performed on the nitrocellulose with peroxidase-conjugated anti-mouse antibody as the second antibody. Antigen from G. occultum, revealed by a precipitating stain, was seen as purple dots on the nitrocellulose, which also retained the impression of the root.

Root-soil cores were collected from forage grasses growing in a subtropical region of Texas and tested for acetylene reduction activity. The population density of nitrogen-fixing bacteria was measured, using various media and incubation conditions. Bacteria were confirmed as nitrogen fixing, using the acetylene reduction assay, and were classified according to standard biochemical and cultural methods. The majority of the nitrogen-fixing bacteria isolated from roots were Enterobacter cloacae or Klebsiella pneumoniae. Root-associated, nitrogen-fixing bacteria were isolated from 21 of 24 root-soil cores. The population densities of nitrogen-fixing bacteria ranged from approximately 10 to 3 x 10 per g of root. Population density on roots was significantly correlated with the rate of acetylene reduction but the relationship was not linear.

We produced a monoclonal antibody against Rhizobium trifolii 162x95. This antibody in cell culture supernatant was used in an indirect enzyme-linked immunosorbent assay to differentiate strain 162x95 from naturalized strains in the Appalachian region. Nodules crushed in 0.1 to 0.2 ml of phosphate-buffered saline and used to charge enzyme-linked immunosorbent assay plates gave strong absorbance readings. Heat-inactivated and noninactivated portions of 162x95 cultures were strongly reactive, indicating that the antigen is probably a carbohydrate. Of 10 strains from California, where 162x95 was isolated, 6 strongly cross-reacted with the antibody. The cellular protein patterns in a sodium dodecyl sulfate-polyacrylamide gradient gel of cross-reactive strains were essentially identical. A Western blot analysis indicated that the antibody was against a 19.8-kilodalton band. The Western blot analysis also revealed that the polyvalent antiserum contained other strongly reacting antibodies with molecular weights of approximately 20,000, indicating the possibility that other monoclonal antibodies to detect strain 162x95 may be produced. However, the available antibody has been shown to be useful for short-term experiments. Based upon protein profiles and immunological reactions, there are 4 or 5 California strains rather than 10.

Spore morphology is currently used to identify species of vesicular-arbuscular mycorrhizal fungi. We report the first use of a highly specific immunological method for identification of a vesicular-arbuscular mycorrhizal fungus. Two monoclonal antibodies were produced against Glomus occultum. Monoclonal antibodies reacted strongly with both spores and hyphae in an indirect enzyme-linked immunosorbent assay. All other mycorrhizal (29 species) and nonmycorrhizal (5 species) fungi tested were nonreactive with the monoclonal antibodies. A single spore of G. occultum was detectable in the presence of high numbers of spores of other vesicular-arbuscular mycorrhizal fungi. Variation in the reaction of G. occultum isolates from West Virginia, Florida, and Colombia suggests that monoclonal antibodies may differentiate strains.