The effect of extractants on degradation of L-glutamate and L-arginine in the course of shaking and filtration at low temperature

Summary. The effects of demineralized water (DEMI H₂O) and 0.5 M ammonium acetate (0.5 M AAc) on losses of L-glutamic acid and L-arginine in the course of shaking and filtration at low temperature (6 °C) were tested. The concentration of L-glutamic acid decreased by 6.3% in DEMI H₂O and by 4.9% in 0.5 M AAc, whereas the L-arginine concentration decreased by 6.0% (DEMI H₂O) and 10.7% (0.5 M AAc). We found a significantly (P < 0.05) higher degradation of L-arginine in 0.5 M AAc compared with that of DEMI H₂O.     

Uptake and degradation of EDTA by Escherichia coli

It was found that Escherichia coli exhibited a growth by utilization of Fe(III)EDTA as a sole nitrogen source. No significant growth was detected when Fe(III)EDTA was replaced by EDTA complexes with other metal ions such as Ca²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺, and Zn²⁺. When EDTA uptake was measured in the presence of various ions, it was remarkable only when Fe³⁺ was present. The cell extract of E. coli exhibited a significant degradation of EDTA only in the presence of Fe³⁺. It is likely that the capability of E. coli for the growth by utilization of Fe(III)EDTA results from the Fe³⁺-dependent uptake and degradation of EDTA.     

Potential metabolites of dimethoate produced by bacterial degradation

Microbial degradation of pesticide has been recognized as a potential solution for the disposal of pesticide. Two bacterial strains namely Bacillus licheniformis and Pseudomonas aeruginosa, which were isolated from water and fish intestine, respectively, were allowed to grow in mineral salt solution. The acetonitrile extracts of the bacterial cultures were subjected to thin layer chromatography using two different solvent systems: hexane–chloroform–methanol and cyclohexane–acetone–chloroform. The chromatogram revealed the presence of four metabolites of dimethoate with different R_f values, in the original P. aeruginosa strain using both hexane–chloroform–methanol and cyclohexane–acetone–chloroform solvent systems. Total disappearance of dimethoate spot occurred in the culture of B. licheniformis strain at day 3. Thus, the present study establishes the bacterial degradation of dimethoate and also suggests the role of bacteria in the bioremediation of pesticides.     

The nuclear proteasome and the degradation of oxidatively damaged proteins

Summary. The accumulation of oxidized proteins is known to be linked to some severe neurodegenerative diseases like Alzheimer’s, Parkinson’s and Huntington’s disease. Furthermore, the aging process is also accompanied by an ongoing aggregation of misfolded and damaged proteins. Therefore, mammalian cells have developed potent degradation systems, which selectively degrade damaged and misfolded proteins. The proteasomal system is largely responsible for the removal of oxidatively damaged proteins form the cellular environment. Not only cytosolic proteins are prone to oxidative stress, also nuclear proteins are readily oxidized. The nuclear proteasomal system is responsible for the degradation of these proteins. This review is focused on the specific degradation of oxidized nuclear proteins, the role of the proteasome in this process and the regulation of the nuclear proteasomal system under oxidative conditions.     

The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens

 The rate of expansion of bacterial colonies of S. liquefaciens is investigated in terms of a mathematical model that combines biological as well as hydrodynamic processes. The relative importance of cell differentiation and production of an extracellular wetting agent to bacterial swarming is explored using a continuum representation. The model incorporates aspects of thin film flow with variable suspension viscosity, wetting, and cell differentiation. Experimental evidence suggests that the bacterial colony is highly sensitive to its environment and that a variety of mechanisms are exploited in order to proliferate on a variety of surfaces. It is found that a combination of effects are required to reproduce the variation of bacterial colony motility over a large range of nutrient availability and medium hardness. Received: 29 April 1999     

Ubiquitin dependent and independent protein degradation in the regulation of cellular polyamines

Summary. Protein degradation mediated by the ubiquitin/proteasome system is the major route for the degradation of cellular proteins. In this pathway the ubiquitination of the target proteins is manifested via the concerted action of several enzymes. The ubiquinated proteins are then recognized and degraded by the 26S proteasome. There are few reports of proteins degraded by the 26S protesome without ubiquitination, with ornithine decarboxylase being the most notable representative of this group. Interestingly, while the degradation of ODC is independent of ubiquitination, the degradation of other enzymes of the polyamine biosynthesis pathway is ubiquitin dependent. The present review describes the degradation of enzymes and regulators of the polyamine biosynthesis pathway.     

The microbial degradation of azimsulfuron and its effect on the soil bacterial community

AIMS: Azimsulfuron is a recently introduced sulfonylurea herbicide useful in controlling weeds in paddy fields. To date very little information is available on the biodegradation of this pesticide and on its effect on the soil microbial community. The aim of this work was to study its biodegradation both in slurry soil microcosms and in batch tests with mixed and pure cultures. METHODS AND RESULTS: Azimsulfuron was applied to forest bulk soil in order to study its effect on the structure of the bacterial soil community, as detectable by denaturant gradient gel electrophoresis (DGGE) analyses. Biodegradation and abiotic processes were investigated by HPLC analyses. In addition, a microbial consortium was selected, that was able to use azimsulfuron as the sole energy and carbon source. One of the metabolites produced by the consortium was isolated and identified through LC-MS analyses. Cultivable bacteria of the consortium were isolated and identified by 16S rDNA sequencing (1400 bp). CONCLUSIONS: Azimsulfuron treatment seems to have the ability to cause changes in the bacterial community structure that are detectable by DGGE analyses. It is easily biodegraded both in microcosms and in batch tests, with the formation of an intermediate that was identified as 2-methyl-4-(2-methyl-2H-tetrazol-5-yl)-2H-pyrazole-3-sulfonamide. SIGNIFICANCE AND IMPACT OF THE STUDY: The study increases the knowledge on the biodegradation of azimsulfuron and its effects on the soil microbiota.     

The effect of taurine on polymorphonuclear leukocyte functions in endotoxemia

Summary. The aim of the present study was to measure MPO activity in PMN leukocytes after endotoxin administration, and to compare the levels of NO₂ ⁻ competing with taurine for reaction with HOCl. Furthermore we aimed to determine TauCl levels, a product of MPO–H₂O₂–Halide system, and to evaluate anti-inflammatory properties of PMN in endotoxemia. In addition, our second objective was to investigate the effect of taurine, an antioxidant amino acid, on anti-bactericidal and anti-inflammatory functions of PMN after administration of endotoxin together with taurine. All experiments were performed with four groups (control, taurine, endotoxemia, and taurine plus endotoxin) of ten guinea pigs. After endotoxin administration (4 mg/kg), MPO activities increased and taurine levels decreased. Therefore levels of TauCl, NO₂ ^•− increased. We observed the effects of taurine as conflicting. When taurine was administrated alone (300 mg/kg), all of these parameters decreased. Consequently, we suggested that taurine is influential in infected subjects but not on healthy ones as an antioxidative amino acid. In addition, we believe that in vivo effects of taurine may differ from those in vitro depending on its dosage.     

The effect of tryptophan administration on ileum contractility and oxidant status in mice

Summary. L-Tryptophan (TRP) is the precursor amino acid for the synthesis of serotonin (5-HT). 5-HT is effective both on the food intake and gastrointestinal system contractility. The aim of this study was to search the effects of systemic TRP treatment on 5-HT levels of ileum and searching the effect of ileal contractility and oxidant status. Swiss-albino mice were divided into two groups: 1. Control, 2. TRP-treated (100 mg/kg/24 h, i.p., for 7 days). Body weights were recorded at the beginning and at the end of experiments. Acetylcholine-induced contractile responses in the isolated ileum were recorded on polygraph. Ileal tissue malondialdehyde and glutathione levels determined by spectrophotometric and ileal tissue 5-HT levels were measured by immunohistochemical methods. TRP treatment decreased body weight and increased ileal contractile response. In the TRP-treated group, ileum malondialdehyde levels increased and glutathione levels decreased. Immunohistochemical detection showed that ileal 5-HT levels were increased by TRP treatment. There is a relationship between increased oxidative stress and increased contractility in the ileal tissue of the TRP-treated animals. These effects may be related to increased ileal 5-HT synthesis.     

The effect of taurine on renal ischemia/reperfusion injury

Summary. Ischemia-reperfusion (I/R) injury is one of the most common causes of renal dysfunction. Taurine is an endogenous antioxidant and a membrane-stabilizing, intracellular, free beta-amino acid. It has been demonstrated to have protective effects against I/R injuries to tissues other than kidney. The aim of this study was to determine whether taurine has a beneficial role in renal I/R injury. Forty Wistar-Albino rats were allocated into four groups as follows: sham, taurine, I/R, and I/R + taurine. Taurine 7.5 mg/kg was given intra-peritoneally to rats in the groups taurine and I/R + taurine. Renal I/R was achieved by occluding the renal arteries bilaterally for 40 min, followed by 6 h of reperfusion. Immediately thereafter, blood was drawn and tissue samples were harvested to measure 1) serum levels of BUN and creatinine; 2) serum and/or tissue levels of malondialdehyde (MDA), glutathione (GSH), glucose 6-phosphate dehydrogenase (G-6PD), 6-phosphogluconate dehydrogenase (6-PGD) and glutathione reductase (GSH-red); 3) renal morphology; and 4) immunohistochemical staining for P-selectin. Taurine administration reduced I/R-induced increases in serum BUN and creatinine, and serum and tissue MDA levels (p < 0.05). Additionally, taurine lessened the reductions in serum and tissue glutathione levels secondary to I/R (p < 0.05). Taurine also attenuated histopathologic evidence of renal injury, and reduced I/R-induced P-selectin immunoreactivity (p < 0.05). Overall, then, taurine administration appears to reduce the injurious effects of I/R on kidney.     

The effect of glutamine supplementation and physical exercise on neutrophil function

Glutamine is the most abundant free amino acid in the body. Its primary source is skeletal muscle, from where it is released into the bloodstream and transported to a variety of tissues. Several studies have shown that glutamine is important for rat and human neutrophil function and that these cells utilize glutamine at high rates. Physical exercise has also been shown to induce considerable changes in neutrophil metabolism and function. As neutrophils represent 50-60% of the total circulating leukocyte pool and play a key role in inflammation, both physical exercise and glutamine might be expected to regulate the inflammatory process. In this review, the changes in neutrophil function induced by physical exercise and glutamine supplementation are compared.     

Arginine degradation by arginase in mitochondria of soybean seedling cotyledons

 Arginase (EC 3.5.3.1) localization was studied in soybean (Glycine max L.) seedling cotyledons. Subcellular fractionation in a discontinuous Percoll gradient showed that arginase was localized in the mitochondrion. Arginine (Arg) uptake by mitochondria was demonstrated by co-sedimentation of [³H]Arg-derived label and the mitochondrial marker enzyme cytochrome c oxidase. Arginine uptake was complete in about 10 min. Since detergent but not NaCl released most label, we conclude that Arg was taken up and not bound to the organellar surface. Arginine transport was not saturable, at least up to 20 mM. Basic amino acids were the best inhibitors of Arg uptake. The uncoupler 2,4-dinitrophenol did not inhibit Arg uptake. At least 30% of l-[guanido-¹⁴C]Arg taken up by mitochondria was degraded by arginase in seedling cotyledons, while little or no degradation was detected in mitochondria from developing embryos, even though the Arg uptake level was similar in both mitochondrial preparations. These results are consistent with our previously reported pattern of arginase expression and urea accumulation during embryo development and seed germination (A. Goldraij and J.C. Polacco, 1999, Plant Physiol. 119: 297–303). The lack of Arg degradation allows developing embryos to conserve Arg, the main N-reserve amino acid utilized by germinating soybean. Received: 7 July 1999 / Accepted: 21 September 1999     

The effect of dispersal on single-species nonautonomous dispersal models with delays

In this paper, single-species nonautonomous dispersal models with delays are considered. An interesting result on the effect of dispersal for persistence and extinction is obtained. That is, if the species is persistent in a patch then it is also persistent in all other patches; if the species is permanent in a patch then it is also permanent in all other patches; if the species is extinct in a patch then it is also extinct in all other patches. Furthermore, some new sufficient conditions for the permanence and extinction of the species in a patch are established. The existence of positive periodic solutions is obtained in the periodic case by employing Teng and Chen's results on the existence of positive periodic solutions for functional differential equations. Received: 26 June 2000 / Revised version: 6 October 2000 / Published online: 10 April 2001     

The apoptotic effect of intercalating agents on HPV-negative cervical cancer C-33A cells

Summary. Cervical cancer is one of the leading causes of female cancer death worldwide with about 500,000 deaths per year. Both mitomycin C and cisplatin are alkylating agents, which bind and intercalate DNA, and thus used as anti-cancer drugs. In these studies, we focused on investigating the apoptotic effects of intercalating agents on HPV-negative cervical cancer C-33A cells. Accordingly, C-33A cells were treated with carboplatin, mitomycin C or cisplatin. Cell cycle analysis revealed that treatment with mitomycin C and cisplatin but not with carboplatin resulted in apoptosis. Both mitomycin C and cisplatin induced apoptosis in C-33A cells via caspase-8 and -3 processing in a Fas/FasL-dependent manner and also suppressed IL-18 expression, while they down-regulated IκB expression and up-regulated p65 expression. These results suggest that both mitomycin C and cisplatin induce apoptosis, not only via the caspase-8 and -3 dependent Fas/FasL pathway, but also via the regulation of NF-κB activity and IL-18 expression in HPV-negative cervical cancer C-33A cells.     

The inhibitory effect of various indolyl amino acid derivatives on arginase activity in macrophages

Summary. Numerous indolyl amino acids and their derivatives inhibited arginase activity. The inhibition was found to be non-competitive, – at least partly – allosteric, and independent on manganese ions in the active site, and it cannot be explained by the dissociation of arginase homotrimers. Indole alone is weakly inhibitory; however, the presence of three-carbon side chains and their net charges is favorable for the inhibition. The binding of the inhibitory compounds caused only minor changes in the steric structure of arginase: a slight increase in α-helix content was detected by circular dichroism together with a decrease in parallel pleated sheet and β-turn sections. A slight alteration in the tertiary structure was also found using tryptophane fluorescence studies, but buried apolar side chains were not transposed to the protein surface. Computer studies that were performed did not provide additional structural information. Authors’ address: András Hrabák, Department of Medical Chemistry, Molecular Biology and Patho-biochemistry, Semmelweis University Medical School, Budapest, VIII. Puskin u. 9., H-1444 POB 260, Hungary     

The effect of taurine depletion on the contractile properties and fatigue in fast-twitch skeletal muscle of the mouse

Summary. Taurine as well as tauret (retinyliden taurine) levels were measured in locust Locusta migratoria compound eyes. HPLC measurements revealed relatively low taurine levels (1.9 ± 0.16 mM) in dark-adapted eyes. Glutamate, aspartate and glycine levels were 2.0 ± 0.2, 2.7 ± 0.4 and 3.0 ± 0.37 mM, respectively, while GABA was present only in trace amounts. After about 4 h of light adaptation at 1500–2000 lx, amino acid levels in the compound eye were as follows: taurine, 1.8 ± 0.17 mM; glutamate, no change at 2.1 ± 0.2 mM; aspartate sharply increased to 4.7 ± 0.7 mM; glycine slightly decreased to 2.8 ± 0.3 mM; and GABA trace levels. In the compound eye of locust Locusta migratoria, the existence of endogenous tauret in micro-molar range was established. In the dark, levels were several times higher compared with compound eye after light adaptation 1500 lx for 3 h, as estimated by TLC in combination with spectral measurements. Existence of tauret in compound eye is of special interest because in the compound eye, rhodopsin regeneration is based on photoregeneration.     

细菌降解双酚类化合物的分子机制研究进展

双酚类化合物(bisphenols,BPs)作为工业原料及药物和个人护理品的重要成分之一,在自然界中广泛分布。BPs作为类雌性激素造成的生态风险已成为全球备受关注的环境问题之一。研究人员使用不同方式分离得到菌株或菌群,尝试对BPs进行无害化降解,目前已取得了一些重要的研究进展。本文对近年来细菌降解BPs的相关研究进行了系统梳理,重点关注以双酚A(bisphenol A,BPA)为典型BPs的细菌降解,总结不同路径中的关键作用基因,讨论相同路径中酶的差异及作用方式,并分析其对BPA的降解效果。本文也简要总结了双酚S(bisphenolS,BPS)和其他BPs的细菌降解研究情况。通过总结讨论现有成果,分析细菌降解BPs中尚需深入研究的内容,探寻未来BPs细菌降解机理及应用的研究方向。     

The effect of temperature on membrane hydraulic conductivity

The objective of this study was to use the temperature dependence of water permeability to suggest the physical mechanisms of water transport across membranes of osmotically slowly responding cells and to demonstrate that insight into water transport mechanisms in these cells may be gained from easily performed experiments using an electronic particle counter. Osmotic responses of V-79W Chinese hamster fibroblast cells were measured in hypertonic solutions at various temperatures and the membrane hydraulic conductivity was determined. The results were fit with the general Arrhenius equation with two free parameters, and also fit with two specific membrane models each having only one free parameter. Data from the literature including that for human bone marrow stem cells, hamster pancreatic islets, and bovine articular cartilage chondrocytes were also examined. The results indicated that the membrane models could be used in conjunction with measured permeability data at different temperatures to investigate the method of water movement across various cell membranes. This approach for slower responding cells challenges the current concept that the presence of aqueous pores is always accompanied by an osmotic water permeability value, P(f)>0.01 cm/s. The possibility of water transport through aqueous pores in lower-permeability cells is proposed.     

Interpretation of the temperature dependence of rate constants in biosensor studies

A comparison is made between Arrhenius and transition-state analyses of the temperature dependence of rate constants reported in four published biosensor studies. Although the Eyring transition-state theory seemingly affords a more definitive solution to the problem of characterizing the activation energetics, the analysis is equivocal because of inherent assumptions about reaction mechanism and the magnitude of the transmission coefficient. In view of those uncertainties it is suggested that a preferable course of action entails reversion to the empirical Arrhenius analysis with regard to the energy of activation and a preexponential factor. The former is essentially equivalent to the enthalpy of activation, whereas the magnitude of the latter indicates directly the extent of disparity between the frequency of product formation and the universal frequency factor (temperature multiplied by the ratio of the Boltzmann and Planck constants) and hence the likelihood of a more complicated kinetic mechanism than that encompassed by the Eyring transition-state theory.     

The effect of artificial defaunation on bacterial assemblages of intertidal sediments

The use of the artificial defaunation of sediments is widespread among studies examining the disturbance and recovery of benthic macrofaunal communities. Standard methods of defaunation include driving the sediment to anoxia, freezing and sieving. In this study we performed a field experiment to test the assumption that the bacterial assemblages are unaffected by these methods of defaunation. Same-sized patches of sediment were defaunated by covering sediment with plastic sheeting (weighted by concrete blocks), freezing or sieving (1-mm mesh). Macrofaunal counts of sediment cores, taken to determine the effectiveness of each defaunation method, indicated that although none of the treatments removed 100% of macrofauna, all resulted in reduced macrofaunal presence, with the sieved treatment being the most effective. Bacterial samples were taken over the course of a month to determine both the initial and long-term effects of defaunation on bacterial community structure. Numerical effects were determined via epifluorescence microscopy, whereas differences in community composition were followed using PCR and denaturing gradient gel electrophoresis (DGGE). The anoxic treatments resulted in significant numerical changes in both active and total cell counts over time, while the frozen and sieved treatments caused less apparent changes. All of the treatments initially changed the composition of the community; however, anoxic and sieved treatments resulted in subtle changes while the frozen treatment produced more notable and variable changes within the community. The composition of the bacterial community in all of the treatment plots trended towards recovery, or convergence towards that of ambient sediments, by the t = 25-day sampling period.