Behavior of plasma insulin and GIP in obese patients subjected to biliopancreatic bypass

Biliopancreatic bypass for obesity entails a 2/3 distal gastrectomy with Roux-en-Y reconstruction, being the small bowel transected at its midpoint and the enteroenteroanastomosis placed 50 cm proximal to the ileocecal valve. Insulin and GIP fasting and meal-stimulated plasma concentrations were determined in 13 nonobese healthy volunteers, in 13 nonoperated obese patients, in 11 subjects within two months, in 12 subjects four to twelve months, and in 7 subjects fifteen to twenty months after operation. Insulin in the obese patients was significantly higher than in the control group. Postoperatively these patients showed a sharp reduction in basal and postprandial values. Plasma insulin levels, both basally and following the test meal, were very similar in the 15-20 month and the control group. Plasma GIP fasting level, meal-stimulated peak and integrated response in the obese group were higher than in control group. Due to the extreme variability among subjects in the obese group, the difference was significant only for the mean peak response. All values were greatly reduced after surgery. The mean fasting level in the 15-20 month group was very similar to that in the control group, and both peak and integrated responses were significantly lower than in the preoperative and control groups.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Survival and Nodulating Ability of Indigenous and Inoculated Rhizobium leguminosarum biovar trifolii in Sterilized and Unsterilized Soil Treated with Sewage Sludge

Rhizobium leguminosarum biovar trifolii was detected in soil from 41 of 47 plots, within nine sewage sludge-treated sites with different soil characteristics and heavy metal contents. However, although population size varied widely, there was no consistent correlation with soil heavy metal concentration. Indigenous populations in 20 plots within four selected sites retained their ability to induce effective nodule formation after incubation of soil in the dark for 165 days. In sterilized (γ-irradiated) soil, Rhizobium survival varied from 0.01% to 95% depending on the soil sample and strain used. Metal-resistant strains with non-mucoid colonies survived less well than mucoid metal-sensitive strains. Received: 26 June 2000/Accepted: 31 July 2000     

A rationalization of the acidic pH dependence for stromelysin-1 (Matrix metalloproteinase-3) catalysis and inhibition

The pH dependence of matrix metalloproteinase (MMP) catalysis is described by a broad bell-shaped curve, indicating the involvement of two unspecified ionizable groups in proteolysis. Stromelysin-1 has a third pK(a) near 6, resulting in a uniquely sharp acidic catalytic optimum, which has recently been attributed to His(224). This suggests the presence of a critical, but unidentified, S1' substructure. Integrating biochemical characterizations of inhibitor-enzyme interactions with active site topography from corresponding crystal structures, we isolated contributions to the pH dependence of catalysis and inhibition of active site residues Glu(202) and His(224). The acidic pK(a) 5.6 is attributed to the Glu(202).zinc.H(2)O complex, consistent with a role for the invariant active site Glu as a general base in MMP catalysis. The His(224)-dependent substructure is identified as a tripeptide (Pro(221)-Leu(222)-Tyr(223)) that forms the substrate cleft lower wall. Substrate binding induces a beta-conformation in this sequence, which extends and anchors the larger beta-sheet of the enzyme. substrate complex and appears to be essential for productive substrate binding. Because the PXY tripeptide is strictly conserved among MMPs, this "beta-anchor" may represent a common motif required for macromolecular substrate hydrolysis. The striking acidic profile of stromelysin-1 defined by the combined ionization of Glu(202) and His(224) allows the design of highly selective inhibitors.     

Effects of arsenate (AS5+) on growth and production of glutathione (GSH) and phytochelatins (PCS) in Chlorella vulgaris

The effect of arsenate (As5+) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated. C. vulgaris was tolerant to As5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent, indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5 mg/L in media containing 200 mg/L As5+ suggesting that GSH plays a more prominent role in the detoxification of As5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As5+ detoxification, whereas above this concentration As5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defense mechanisms, such as increased production of GSH. The overall findings complement field studies which suggest C. vulgaris as an increasingly promising low cost As phytoremediation method for developing countries.     

Prey life-history and bioenergetic responses across a predation gradient

To evaluate the importance of non-consumptive effects of predators on prey life histories under natural conditions, an index of predator abundance was developed for naturally occurring populations of a common prey fish, the yellow perch Perca flavescens, and compared to life-history variables and rates of prey energy acquisition and allocation as estimated from mass balance models. The predation index was positively related to maximum size and size at maturity in both male and female P. flavescens, but not with life span or reproductive investment. The predation index was positively related to size-adjusted specific growth rates and growth efficiencies but negatively related to model estimates of size-adjusted specific consumption and activity rates in both vulnerable (small) and invulnerable (large) size classes of P. flavescens. These observations suggest a trade-off between growth and activity rates, mediated by reduced activity in response to increasing predator densities. Lower growth rates and growth efficiencies in populations with fewer predators, despite increased consumption suggests either 1) a reduction in prey resources at lower predator densities or 2) an intrinsic cost of rapid prey growth that makes it unfavourable unless offset by a perceived threat of predation. This study provides evidence of trade-offs between growth and activity rates induced by predation risk in natural prey fish populations and illustrates how behavioural modification induced through predation can shape the life histories of prey fish species.     

Stock-specific changes in growth rates, food conversion efficiencies, and energy allocation in response to temperature change in juvenile Atlantic cod

Under common environments, populations of laboratory reared (Grand Banks, GB and Gulf of Maine, GOM) and wild caught (Fortune Bay, FB and Bonavista Bay, BB; Newfoundland) juvenile cod Gadus morhua responded similarly to temperature change in specific growth rates, food conversion efficiencies, condition factors, liver water content, and muscle water content. However, GOM cod had higher condition factors, and showed differences from GB cod in phenotypic plasticity of hepatosomatic index to temperature. These differences were not present in a different population comparison between FB and BB cod. All populations had higher growth rates and food conversion efficiencies at warmer temperatures, and exhibited compensatory growth when temperature was increased. The results suggest relatively larger genetic differences between GB and GOM cod than between FB and BB cod, and indicate that the faster growth of southern populations in the wild is not due to a higher genetic capacity for growth rate.     

Competition of As and other Group 15 elements for surface binding sites of an extremophilic Acidomyces acidophilus isolated from a historical tin mining site

An arsenic-resistant fungal strain, designated WKC-1, was isolated from a waste roaster pile in a historical tin mine in Cornwall, UK and successfully identified to be Acidomyces acidophilus using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS) proteomic-based biotyping approach. WKC-1 showed considerable resistance to As⁵⁺ and Sb⁵⁺ where the minimal inhibitory concentration (MIC) were 22500 and 100 mg L⁻¹, respectively, on Czapex-Dox Agar (CDA) medium; it was substantially more resistant to As⁵⁺ than the reference strains CBS 335.97 and CCF 4251. In a modified CDA medium containing 0.02 mg L⁻¹ phosphate, WKC-1 was able to remove 70.30% of As⁵⁺ (100 mg L⁻¹). Sorption experiment showed that the maximum capacity of As⁵⁺ uptake was 170.82 mg g⁻¹ dry biomass as predicted by the Langmuir model. The presence of Sb⁵⁺ reduced the As⁵⁺ uptake by nearly 40%. Based on the Fourier-transform infrared spectroscopy (FT-IR) analysis, we propose that Sb is competing with As for these sorption sites: OH, NH, CH, SO₃ and PO₄ on the fungal cell surface. To our knowledge, this is the first report on the impact of other Group 15 elements on the biosorption of As⁵⁺ in Acidomyces acidophilus.