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.     

Acute and chronic effects of an anionic surfactant on some freshwater tubificid species

We report the results of research on acute and chronic effects of linear alkylbenzensulfonate (LAS) on two tubificid species. 96 h LC₅₀ assay values were estimated at 10° for Limnodrilus hoffmeisteri and Branchiura sowerbyi exposed to different concentrations of LAS dissolved in water, both with and without sediment. The presence of sediments modified LAS toxicity and increased values: NOEC and LOEC resulted in values 2.5 times higher for Branchiura sowerbyi and 4–4.5 times for Limnodrilus hoffmeisteri, when the sediments were present. The chronic effects induced by a long exposure to LAS were evaluated for different stages of the biological cycle of Branchiura sowerbyi. Using concentrations between the NOEC and LOEC (0.5, 2.5, and 5 ppm), with control, we could observe that: 1) at 5 ppm the cocoons were laid precociously compared to controls, 2) in all treated series the number of cocoons was lower than in controls, 3) the mean number of oocytes per cocoon was lower for the worms submitted to LAS, compared to the control, 4) the period of embryonic development was similar for all used concentrations and for control, and 5) the number of degenerated cocoons was unchanged by the LAS treatment.     

Benthic algal biomass and productivity in high subarctic streams,Alaska

Year-round measurements of the standing crop of epilithic algae (as chlorophyll a concentration) in two streams — one second and one fourth order (map scale 1:63 360) — in interior Alaska (64°–65° N) were only about one tenth that reported from streams of temperate North America. Cell densities in these streams, however, were similar to those in comparable temperate streams. Year-round domination of the benthic flora by very tiny diatoms (Achnanthes spp.) may explain the apparent disparity between low chlorophyll a content and nearly average cell densities. Chlorophyll a standing crop in a more alkaline groundwater-fed stream, however, was higher and within the range of similarly sized temperate streams. Maximum chlorophyll a standing crop varied positively with alkalinity in 5 clear-water streams where standing crop was measured on natural or artificial substrates. Seasonal mean concentrations of sestonic chlorophyll a (used as estimates of benthic algal chlorophyll a standing crop) varied directly and significantly with alkalinity among ten clear-water streams; and, with total phosphorus among 8 of 10 clear-water and 5 brown-water streams studied. During the summer, when there is little darkness, gross primary productivity (as estimated by the diurnal dissolved-oxygen method) was similar to that of northern temperate streams. Gross primary productivity was also seen to vary directly with alkalinity in 5 clear-water streams of this region.U.S. Fish and Wildlife Service     

Changing household composition,labor patterns,and fertility in a highland New Guinea population

The European demographic transition of the nineteenth century is often proposed as a model for demographic change in twentieth century developing nations, and economic development is seen as leading to an inevitable reduction in total fertility in these nations. This paper examines data from the Gainj of Papua New Guinea, a natural fertility population with very low reproductive output, and suggests that the effects of development on fertility change are much more complex than a simple demographic transition model would suggest. Looking at two variables known to contribute significantly to low total fertility among the Gainj, late age at first birth for women and long interbirth intervals, the paper suggests that households, in their recruitment and allocation of labor, may exert a mediating influence in the relationship between economic development and fertility.     

Cellular localization of cytochrome c 553 in the N2-fixing cyanobacterium Anabaena variabilis

The in situ location of the electron carrier protein cytochrome C ₅₅₃ (cyt c ₅₅₃) has been investigated in both vegetative cells and heterocysts of the cyanobacterium Anabaena variabilis ATCC 29413 using the antibody-gold technique, carried out as a post-ernbedding immunoelectron microscopy procedure. When using a rabbit polyclonal anti-cyt c ₅₅₃ specific antiserum an intense labelling, associated mainly with the cell periphery (cytoplasmic membrane and periplasmic area), was seen in both heterocysts and vegetative cells. The selective release of most of the cellular cyt c ₅₅₃ during a Tris-EDTA treatment confirms a periplasmic localization of this protein in A. variabilis. The results indicate that most of cyt c ₅₅₃ is located in the periplasmic space. The roles ascribed to this protein in both respiration and photosynthesis in cyanobacteria are discussed.Abbreviations Cyt c ₅₅₃ cytochrome c ₅₅₃ - PBS phosphate buffered saline (20 mM sodium phosphate, 0.9% NaCl, pH 7.4) - PMSF phenylmethylsulfonyl fluoride Recipient of a Research Fellowship of the Alexander von Humboldt Foundation (Bonn, FRG) for a leave to the University of Konstanz.     

Leukaemia and transient leukaemia in Down syndrome

Summary We have reviewed 215 published cases of leukaemia and transient leukaemia in Down syndrome. There is an over-representation of mosaic trisomy 21, possibly the result, at least in part, of a survival effect. The most intriguing observation is a bimodal distribution of maternal age, produced largely because cases with true leukaemia have a significantly higher maternal age than cases with transient leukaemia (33.5 versus 29.5 years). In conjunction with evidence that meiosis I non-disjunction is infrequent in transient leukaemia, this suggests different mechanisms for the etiology of leukaemia and transient leukaemia, and favours a locus predisposing to transient leukaemia proximal to the centromere on the long arm of chromosome 21.     

Induction of vancomycin resistance in Enterococcus faecium by inhibition of transglycosylation

Vancomycin resistance has recently been recognized among clinical isolates of enterococci. Resistance is inducible, and associated with production of a novel 39 kDa membrane protein. The mechanism by which exposure to vancomycin, which does not penetrate the cell membrane, induces resistance is unknown. In the vancomycin resistant strain Enterococcus faecium 228, resistance was also inducible by moenomycin, suggesting that inhibition of the transglycosylation step in peptidoglycan synthesis may be required for induction of resistance. Cytoplasmic pools of peptidoglycan precursors were increased after exposure to vancomycin or moenomycin, representing a potential means for regulation of induction.     

A review of the in vitro and in vivo neurochemical characterization of the NMDA/PCP/Glycine/Ion channel receptor macrocomplex

Conclusions Current neurochemical studies of the NMDA receptor macromolecular complex are yielding new insights into the interactions of the subunits of this complex and the associated potential clinical benefits of selective modulation of these subnits. Such studies offer the great potential for a new generation of pharmacotherapies for a wide range of CNS disorders, including stroke, a condition for which there is currently no effective pharmacological treatment. However, it is essential to understand that the first generation products in this area may not be optimal pharmacotherapies, such that haracterization of possible receptor subtypes and understanding the molecular biology of the component proteins of the receptor complex will be crucial in the design of the optimal pharmacological modulators of the NMDA receptor complex.Special issue dedicated to Dr. Erminio Costa     

Post-castration rebound of an androgen regulated prostatic gene

Summary After castration, the rat dorsolateral prostate M-40 mRNA initially decreased then rebounded to precastrated levels. The cellular site of M-40 expression and its renewed expression after castration was defined by in situ hybridization histochemistry. In situ hybridization with either a ³²P-labeled or biotin-labeled M-40 cDNA probe demonstrated that M-40 mRNA levels were higher in the lateral than dorsal prostate. A second androgen regulated gene, RWB, also was highly expressed in the lateral prostate. The biotinylated cDNA probes provided microscopic resolution of the expressing cells, revealing two distinct morphologies of lateral epithelium which expressed both the M-40 and RWB mRNA. These morphologies appeared in ducts which contained either epithelial cell sheets that were highly convoluted or thinner epithelial cells with a minimal degree of convolution. The RWB mRNA decreased in both cell populations in response to androgen withdrawal. The decline and reappearance of M-40 mRNA also appeared in both epithelial cell types. These data demonstrated that after castration the M-40 mRNA initially decreased as expected for an androgen sensitive gene and then progressed to a fully inducible state. The mechanism of this progression remains to be elucidated.