The Salmonella typhimurium glycine cleavage enzyme system

Summary A glycine cleavage enzyme system, inducible by glycine, has been demonstrated in Salmonella typhimurium. The induced enzyme levels, however, are only about 20% of the induced levels found in Escherichia coli. Starting with a serine auxotroph, mutants were isolated that grow with a serine supplement, but not with a glycine supplement. Three independently isolated mutants have reduced or nondetectable glycine cleavage enzyme levels. The new mutations, designated gcv, were mapped between the serA and lys genes at 62.5 min on the S. typhimurium chromosome.Abbreviations C1 one-carbon - GCV glycine cleavage - GM glucose minimal - L agar Luria agar - LB Luria broth - Tc tetracycline     

The “ricochet effect” and prey capture in colonial spiders

Summary Increased prey capture efficiency in colonial spiders is a consequence of the ricochet effect, as prey are captured after they bounce off several webs in succession. In this study, the prey capture of three species of colonial spiders in the genus Metepeira from Mexico are compared. These species, from different habitats, show varying levels of social organization (group size and withingroup spacing) that affect prey capture from ricochets. Metepeira sp. a (a presumed new species tentatively named atascadero) from desert grassland habitats, occur solitarily or in small groups, and gain little from prey ricochets: prey capture rates are low and variance in prey captured/spider is high. M. spinipes, from mesic agricultural sites, occur in groups of 10–150, and show a ricochet effect resulting in more and larger prey, and reduced variance in capture rate. M. incrassata, from tropical rainforest/agricultural sites, occur in large colonies of hundreds to thousands of individuals, and show a similar ricochet effect. The ricochet effect does not influence taxonomic composition of prey in either M. atascadero or M. spinipes, but does in tropical M. incrassata. This result, however, is primarily due to the capacity of certain taxa (eg., Lepidoptera), more common in the tropics, to escape more easily from spider webs. A comparison of prey capture efficiency of colonial M. incrassata with that of solitary M. atascadero shows that the ricochet effect provides an increase in efficiency across all size classes of prey.     

A scanning electron-microscopic study of the peripolar cell of the rat renal glomerulus

Summary The interior of Bowman's capsules of rat kidneys has been examined by scanning electron microscopy, and a distinctive population of cells around the exposed vascular poles of glomerular tufts were identified. The cells were situated in the annular groove at the root of the glomerulus, between the parietal epithelial cells and the podocytes. These peripolar cells were dendritic cells with long processes embracing the glomerular arterioles. Up to three peripolar cells were present at each vascular pole and they were mainly distributed in the glomeruli of the outer third of the renal cortex. This first detailed study of the surface morphology of the glomerular peripolar cell supports the suggestion that changes in the diameter of the polar region of the glomerular tuft may cause variations in stretching of the cuff of peripolar cells, and hence modulation of their secretory activity.     

Degradation of fluorene in soil by fungus Phanerochaete chrysosporium

During investigation of biodegradation in soil, we have found that classical or standard techniques for introduction of compounds and the growth of fungus into soil are ill-defined and inadequate. In response to this deficiency, a method for controlled introduction of extractable compounds and for the growth of fungus in soils has been developed. This method was successfully used to study the degradation of fluorene in soil by the fungus Phanerochaete chrysosporium.     

Isolation and Characterization of Mutants of Clostridium acetobutylicum ATCC 824 Deficient in Acetoacetyl-Coenzyme A:Acetate/Butyrate:Coenzyme A-Transferase (EC 2.8.3.9) and in Other Solvent Pathway Enzymes

Mutants of Clostridium acetobutylicum ATCC 824 exhibiting resistance to 2-bromobutyrate or rifampin were isolated after nitrosoguanidine treatment. Mutants were screened for solvent production by using an automated alcohol test system. Isolates were analyzed for levels of butanol, ethanol, acetone, butyrate, acetate, and acetoin in stationary-phase batch cultures. The specific activities of NADH- and NADPH-dependent butanol dehydrogenase and butyraldehyde dehydrogenase as well as those of acetoacetyl-coenzyme A:acetate/butyrate:coenzyme A-transferase (butyrate-acetoacetate coenzyme A-transferase [EC 2.8.3.9]) (CoA-transferase), butyrate kinase, and phosphotransbutyrylase were measured at the onset of stationary phase. Rifampin-resistant strain D10 and 2-bromobutyrate mutant R were found to be deficient in only CoA-transferase, while several other mutants exhibited reduced butyraldehyde dehydrogenase and butanol dehydrogenase activities as well. The colony morphology of 2-bromobutyrate mutant R was similar to that of the parent on RCM medium; however, it had about 1/10 the level of CoA-transferase and increased levels of butanol dehydrogenase and butyraldehyde dehydrogenase. A nonsporulating, spontaneously derived degenerated strain exhibited reduced levels of butyraldehyde dehydrogenase, butanol, dehydrogenase, and CoA-transferase compared with those of the original strain. When C. acetobutylicum ATCC 824 was grown on medium containing low levels of 2-bromobutyrate, an altered colony morphology was observed. Not all strains resistant to 2-bromobutyrate (12 mM) were non-solvent-producing strains.     

Neuropeptide gene expression and neural activity: Assessing a working hypothesis in nucleus caudalis and dorsal horn neurons expressing preproenkephalin and preprodynorphin

1. The working hypothesis that neuropeptide gene expression in a neuron is an indicator of that neuron's physiological activity is discussed. 2. Representative examples from the literature are presented to support the hypothesis. 3. Further, we discuss the regulation of expression of two opioid peptides, preproenkephalin and preprodynorphin, in laminae I and II of the spinal cord and in nucleus caudalis of the trigeminal nuclear complex, where they may play a role in pain modulation. 4. The expression of the opioid peptide genes can be induced by both painful and nonnoxious stimuli in neurons in time-dependent and sensory-specific fashions.     

Increased frequency of 6-thioguanine-resistant peripheral blood lymphocytes in Werner syndrome patients

Summary The frequency of spontaneous 6-thioguanine (TG)-resistant peripheral blood lymphocytes in five unrelated Werner syndrome (WS) patients was determined using an autoradiographic labeling assay. The average frequency of TG-resistant lymphocytes was eightfold higher in WS patients than in sex- and age-matched normal control donors. This finding and previous identification of increased spontaneous chromosomal rearrangements and deletions in WS cells or cell lines suggest that WS is a human genomic instability or mutator syndrome.