Root and microbial biomass dynamics under the canopy of the desert shrub Zygophyllum dumosum

Summary A study was done to evaluate the influence of soil moisture and rainfall on root and microbial biomass production under the canopy of the desert shrub Zygophyllum dumosum. During the study period the root biomass production increased following the early rains but subsequently declined, remaining fairly constant thoroughout the season. In contrast microbial biomass and soil organic matter increased during the rainy season and declined with the onset of the dry summer period. Based on our results we suggest that the moisture event and not the amount and the organic matter content regulate root and microbial biomass production at the 0 to 10 cm soil layer.Contribution of the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. paper no. 2617-E, 1989 series     

Inducible nitrate reductase of rice plants as a possible indicator for nitrification in water-logged paddy soils

When following the pattern of the disappearance of NH ₄ ⁺ –N from ammonium sulfate applied to the flooded soil-rice plant system (field and greenhouse experiments) during a growing season, it was observed that the lowest NH ₄ ⁺ –N level coincided with the highest value of NR activity in the leaves. Nitrate was detected in both the root and shoot systems of the rice plants and autotrophic nitrifiers (Nitrosomonas and Nitrobacter) were particularly abundant. Since it was also demonstrated in this work that the NR activity of rice plants grown with nitrate fertilization (growth chamber culture experiments) was inducible by its substrate, it can be assumed that NH ₄ ⁺ –N oxidation takes place in the water-logged soil studied. Therefore, the occurrence of the nitrification process following NH ₄ ⁺ –N fertilizer application can be predicted by thein vitro orin situ evaluation of the NR activity of the rice leaf as an indicator.     

Consequences of terbium (111) binding on the conformation and enzymatic activity of Guinea pig liver transglutaminase

Calcium ions are crucial for expression of transglutaminase activity. Although lanthanides have been reported to substitute for calcium in a variety of protein functions, they did not replace the calcium requirement during transglutaminase activity measurements. Furthermore, lanthanides strongly inhibited purified liver transglutaminase activity using either casein or fibrinogen as substrates. Terbium (III) inhibition of transglutaminase-catalyzed putrescine incorporation into casein was not reversed by the presence of 10–200 fold molar excess of calcium ions (Ki for Tb(III)=60 µM). Conformational changes in purified liver transglutaminase upon Tb(III) binding were evident from a biphasic effect of Tb(III) on transglutaminase binding to fibrin. Low concentrations of Tb(III) (1 µM to 10 µM inhibited the binding of transglutaminase to fibrin, whereas higher concentrations (20 µM to 100 µM promoted binding. Conformational changes in purified liver transglutaminase consequent to Tb(III) binding were also demonstrated by fluorescence spectroscopy due to Forster energy transfer. Fluorescence emission was stable to the presence of 200 mM NaCl and 100 mM CaCl₂ only partially quenched emission. Purified liver transglutaminase strongly bound to Tb(III)-Chelating Sepharose beads and binding could not be disrupted by 100 mM CaCl₂ solution. Our data suggest that Tb(III)-induced conformational changes in transglutaminase are responsible for the observed effects on enzyme structure and function. The potential applications of Tb(III)-transglutaminase interactions in elucidating the structure-function relationships of liver transglutaminase are discussed.     

Algesia and local responses induced by neurokinin A and substance P in human skin and temporal muscle

Neurokinin A (NKA), substance P (SP) and the two peptides combined (SP + NKA) were injected intracutaneously on the forearm and into the temporal muscle of healthy volunteers. Pain intensity, cutaneous wheal and flare responses and tenderness of the temporal muscle were quantitated. SP but not NKA induced cutaneous pain. This relates the algesic effect of SP to the specific N-terminal amino acid sequence of the peptide, not shared by NKA. NKA, however, potentiated the algesic effect of SP as SP + NKA induced a significantly prolonged cutaneous pain sensation. Both peptides induced wheals, but only SP induced flare. These results confirm previous studies relating wheal formation to the identical C-terminal amino acid sequence of the two peptides and flare reaction to the N-terminal part of SP. Injections into the temporal muscle did not cause pain or tenderness.     

Rat ventral prostate as an independent source of inhibin-like material

Castration had no effect on prostatic inhibin-like activity as compared to normal controls. Consequent upon castration there is a significant reduction in the inhibin content of the ventral prostate on a per gland basis. However, when expressed as a function of protein content, there is no change. The data suggest that the very same epithelial cells which under the influence of androgen carry out the characteristic exocrine secretory activity are responsible for the synthesis and secretion of inhibin-like material.     

The effect of glucose-6-phosphate isomerase genotype onin vitro specific activity andin vivo flux inMytilus edulis

Four samples of the musselMytilus edulis were taken between 1984 and 1987 from Stony Brook, New York, and used to study the glucose-6-phosphate isomerase (GPI) polymorphism in this species.In vitro specific activity andin vivo flux measured in the same animals were found to be significantly correlated. A significant effect of GPI genotype on flux was observed in one of the samples; overall, significant evidence of effect of genotype on enzyme activity was also obtained. GPI activities of common genotypes tend to deviate less from the population mean than those of rare (frequency less than 5%) genotypes. This suggests the possibility that rare GPI genotypes are rare as a consequence of having biochemical properties that deviate from an optimum level and, therefore, having a lower fitness. In support of this hypothesis, we found in one of our samples that shell length is a concave function of GPI activity with an intermediate optimum activity level. The financial support provided to P.J.N.S. by the Luso-American Educational Commission (Fulbright Program), the Instituto Nacional de Investigacao Científica (Portugal), and the Faculdade de Ciências da Universidade de Lisboa during several stages of this research is gratefully acknowledged. Financial support from the Ministerio de Educatión y Ciencia (Spain) in the form of a postdoctoral Fulbright/MEC fellowship to M.S. is also gratefully acknowledged. Research was supported by National Science Foundation Grant BSR-8415060 to R.K.K. This is contribution No. 736 from the Program in Ecology and Evolution, State University of New York at Stony Brook. On leave from Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande C2, Lisboa, Portugal.     

Is the ‘microbial loop’ an early warning indicator of anthropogenic stress?

Various components of the Microbial loop such as bacteria, heterotrophic nanoflagellates and autotrophic picoplankton were analyzed, for the first time across the Great Lakes, during a cruise in the summer of 1988. In addition, the size fractionated primary productivity using carbon-14 techniques was also determined. The statistical analysis indicated that bacteria, autotrophic picoplankton and ultraplankton/picoplankton productivity were significantly higher in Lakes Ontario and Erie than Lakes Huron and Michigan. The autotrophic picoplankton and ultraplankton/picoplankton productivity was higher in Lake Erie compared to Lake Ontario.The autotrophic picoplankton showed sensitivity to nutrients and contaminants in various types of environments. A dramatic decrease of autotrophic picoplankton in eutrophic-contaminated areas, such as Ashbridges Bay, Hamilton Harbour and western Lake Erie was observed. Conversely, in Saginaw Bay, another eutrophic environment, the autotrophic picoplankton were significantly higher than in Lake Huron. The sensitivity of autotrophic picoplankton to nutrients/contaminants might have implications to trophic interactions. Our results suggest that structural and functional characteristics of the microbial loop may be operating differently in stressed versus unstressed ecosystems. The possibility of using autotrophic picoplankton as an early warning indicator of environmental perturbation is proposed.     

Effects of stream order and season on mineralization of [14C]-phenol in streams

Mineralization of trace levels of [¹⁴C]-phenol by heterotrophic microorganisms was quantified at 4 sites along a river continuum in southwestern Virginia. Significant phenol mineralization rates were detected in surface sediment and seston samples at all sites from August 1985 through May 1986. Phenol degradation was strongly affected by season (ANOVA; P < 0.0001). From a baseline rate in August (range: 1.19 × 10^-5 to 897 × 10^-4 mg phenol mineralized mg AFDW^-1 h^-1) phenol mineralization rose to a yearly maximum in October (range: 1.21 × 10^-4 to 1.16 × 10^-3 mg phenol mineralized mg AFDW^-1 h^-1) despite decreasing stream temperatures. This autumnal peak in phenol degradation was attributed to the pulsed input of allochthonous detritus, especially leaf litter, which contains substantial quantities of phenols and related compounds. Although phenol mineralization was significant in these streams, phenols were metabolized at much slower rates than more labile compounds present in the dissolved organic matter (DOM) pool. Estimates of turnover rates for three major components of DOM revealed that glucose and glutamate turnover rates (0.064–0.140 h^-1 mg sediment AFDW^-1 and 0.140–0.610 h^-1 mg sediment AFDW^-1, respectively) were, respectively, 2.2–4.7 × and 9.6–16.9 × greater than phenol turnover rates (0.015–0.064 h^-1 mg sediment AFDW^-1). Although the relatively low rates of utilization of refractory phenolic materials suggest that these compounds may accumulate and become more prevalent components of the DOM pool, phenol concentrations at the 4 study sites remained below detectable levels (i.e., < 1 g 1^-1) throughout the study. Consequently, it seems that although phenolic materials are metabolized more slowly than labile DOM, phenols are degraded at rates which preclude accumulation in the water column.     

Sensitive bioassays for determining residues of sulfonylurea herbicides in soil and their availability to crop plants

Sulfonylurea herbicides are potent inhibitors of plant growth and are extremely active against a wide spectrum of weeds. They are used at very low rates (10–50 g ai/ha) and cause rapid inhibition of root and shoot growth of young plants. Routine chemical assays for detecting low levels of these compounds are difficult and there is need to develop sensitive bioassay methods for detecting their extremely low residue levels in the soil.This paper describes a simple pot bioassay method with a self watering system using turnip (Brassica rapa) seedlings as test plants for quantitative determination of sulfonylurea herbicides. Results are presented with six of these compounds whose activity was investigated in widely differing substrates. The potential availability to plants was calculated from the dose-response curves in different substrates. The dose-response relationship has been described by a specifically developed computer model. Details are also given of a direct seeded bioassay method with controlled watering system using several test species for detection of sulfonylurea herbicides. The potential uses and practical applications of both techniques are discussed.     

Effects of age and physical performance capacity on distribution and composition of high-density lipoprotein subfractions in men

The influences of age and maximal aerobic capacity (VO2max) on serum lipoproteins with special regard to the concentration, composition and distribution of high density lipoprotein (HDL) subfractions were investigated in 51 healthy males of different characteristics: younger than 35 years, untrained (n = 14, mean age 28.2 years, SD 6.0; VO2max, 47.9 ml.kg-1.min-1, SD 5.8) and trained (n = 11, mean age 27.9 years, SD 4.3; VO2max, 61.1 ml.kg-1.min-1, SD 5.1), older than 50 years untrained (n = 14, mean age 58.9 years, SD 5.9, VO2max, 29.3 ml.kg-1.min-1, SD 5.3) and trained (n = 12, mean age 59.3 years, SD 7.2, VO2max, 45.7 ml.kg-1.min-1, SD 7.7). The fasting-state serum concentrations of total cholesterol, tri-acylglycerol and lipoprotein-cholesterol were measured. The HDL-subfractions were separated by density (rho) gradient ultracentrifugation. Concentrations of cholesterol, cholesterylester, tri-acylglycerol, phospholipids, apolipoprotein (apo) A-I and A-II were measured in the subfractions HDL2b: rho = 1.063-1.100 g.ml-1; HDL2al: rho = 1.00-1.110 g.ml-1; HDL2a2: rho = 1.110-1.150 g.ml-1; HDL3: rho = 1.150-1.210 g.ml-1. Elderly untrained subjects showed increased serum concentrations of total-, very low- and low density lipoprotein-cholesterol and elevated tri-acylglycerol levels. The HDL-cholesterol concentration was decreased, due to reduced concentrations of HDL2-subfractions. Significant changes in the composition of HDL2-subfractions were found in elderly untrained subjects. The HDL2-subfractions had more protein, a decreased apoA-I:A-II ratio and less phospholipids in comparison to HDL2-subfractions from younger untrained and trained, and elderly trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)