Immunoelectrophoretic approach to the metabolic regulation of glutamine synthetase in Rhodopseudomonas capsulata E1F1: role of glutamine

Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn²⁺-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS glutamine synthetase - MOPS 2-(N-morpholine) propane sulfonate - MSX l-methionine-d,l-sulfoximine     

Comparative study of selective media for enumeration of Pseudomonas aeruginosa from water by membrane filtration

In the present study, mPA-D and mPA-E agar, modifications of mPA-C agar that reduce background fecal streptococci that interfere with the differentiation and enumeration of the Pseudomonas aeruginosa colonies grown in other mPA media, are proposed for use in analyzing natural water samples. In addition, the efficiencies of several culture media for the recovery of P. aeruginosa in water after membrane filtration and multiple-tube techniques are compared. The degree of selectivity, precision, efficiency, and sensitivity achieved with the proposed media exceeded that achieved by current methods. Furthermore, they yielded equal rates of accuracy and specificity. Incubation at 36 degrees C resulted in an improved recovery of stressed P. aeruginosa. In conclusion, we propose the use of mPA-D and mPA-E agar, both incubated at 36 degrees C for 24 to 48 h, for analyzing river water and seawater, respectively.     

Regulatory interaction of photosynthetic nitrate utilization and carbon dioxide fixation in the cyanobacterium Anacystis nidulans

The rate of photosynthetic nitrate utilization in Anacystis nidulans is strongly influenced by the availability of carbon dioxide. This dependence can be relieved by inhibiting the metabolism of the ammonium derived from nitrate reduction. Nitrate uptake seems to be modulated through a sensitive regulatory system integrating the photosynthetic metabolism of carbon and nitrogen, with CO₂ fixation products antagonizing the inhibitory effect of ammonium derivatives.     

A comparison of the dose-response behavior of canine airways and parenchyma

We compared the histamine responsiveness of canine airways and parenchymal tissues in six anesthetized paralyzed open-chest mongrel dogs, partitioning total lung resistance (RL) into airway resistance (Raw) and tissue viscance (Vti). Pressure was measured during tidal breathing (frequency was 0.3 Hz) at the trachea and in three alveolar regions by use of alveolar capsules. Measurements were taken before and after the delivery of increasing concentrations of aerosolized histamine (0.1-30 mg/ml). We found that Vti accounted for 78 +/- 8% of RL under base-line conditions; this proportion remained relatively constant throughout the histamine concentration-response curve. There was a significant correlation between percent change in Vti and percent change in Raw at all levels of histamine-induced constriction (P less than 0.001). Moreover, the sensitivity of the tissues and airways (defined as the concentration of histamine required to double resistance) was remarkably similar. We conclude that, at this frequency of ventilation, Vti accounts for the major portion of RL both under base-line conditions and after histamine-induced constriction. Although increases in RL cannot be attributed solely to events occurring in the airways, the close correlation between changes in Raw and Vti and the similar sensitivities of the two support the use of indexes reflecting changes in airway caliber as an indicator of overall lung histamine responsiveness.     

Bacterial endotoxin and tumor necrosis factor stimulate prostaglandin production by human decidua

The purpose of these studies was to determine the effect of bacterial endotoxin and tumor necrosis factor (TNF) on prostaglandin (PG) secretion by human decidua. Decidual explants were established from women undergoing elective cesarean sections before the onset of labor. Escherichia Coli endotoxin and purified human recombinant TNF (rh TNF) were incubated with decidual explants. PGF2 alpha and PGE2 biosynthesis was measured by radioimmunoassay. A significant increase in the release of all PGs into the media occurred in response to LPS and TNF. In the setting of an extraamniotic infection, bacterial and host secretory products (TNF) could trigger the onset of labor, activating the decidua to produce PGs.     

Cineanthropometric Study in Spanish Judoists

Anthropometric characteristics of proportionality, body composition and somatotype have been determined in a group of 72 Spanish judoists. The sample includes the junior male and female National Team, and seniors competitors in the last Olimpic Games held in 1992, and participants in the National Championship of 1993. The methodology has been used according to Weiner and Lourie(1981)and MOGAP procedures described by Borms et al. (1979). The obtained results show a similar proportionality profile and mesoendomorphic mean somatotype in both male and female series. However, were found significant differences between sexes as well as depending of weight categories.     

Sex influence on recombination frequency in Secale cereale L.

The variation in recombination frequency (rf) is important to plant breeders since their major objective is to obtain favorable recombinants of linked genes. One source of variation in rf is sex. Sex differences for recombination frequencies were studied in four of the seven chromosomes of Secale cereale L. cv Ailés using isozyme and storage protein loci and were determined on the basis of reciprocal crosses between heterozygous plants of cv. Ailés and homozygous plants of the inbred line Riodeva. The differences were found to be strongly segmentspecific. In some cases the level of crossing-over in male and female meiosis was about the same (between Pgm1 and Ndh1 loci on chromosome arm 4RS). However, for most of the chromosome segments in 1R, 3RL and 6RL the male rf was significantly higher than the female rf. Different hypotheses about the mechanisms of plant sex differences for recombination are discussed.     

An inquiry into the selective protection of glycine during the radiolysis of glycine-alanine mixtures in aqueous solutions and its implications to the preservation of optically active amino acids in the early earth

Akaboshi et al. (1990) has found an unexpected protection of the achiral amino acid, glycine, towards ionizing radiation at the expense of the selective destruction of the chiral amino acids, alanine and aspartic acid. The present work examines the mechanism of this protection for the case of alanine. We have developed a computer model for the radiolysis of glycine, alanine and glycine-alanine mixtures in aqueous solution. It is established that this protection is due in part to the reaction of the α-radical of glycine with alanine to regenerate a more stable α-radical, according to the following reaction, $$ \cdot CH(NH_3^ + )CO_2^ - + CH_3 CH(NH_3^ + )CO_2^ - \to CH_2 (NH_3^ + )CO_2^ - + CH_3 \dot C(NH_3^ + )CO_2^ -$$ The rate constant of this reaction was estimated to be ≤10⁴M^-1s^-1. The implications for this selective protection of glycine are considered for a hypothetical case in which there would be an enrichment of about 10% ofL-alanine in the primitive ocean and taking the glycine/alanine ratios obtained in CH₄-and CO₂- dominated atmospheres using electric discharge experiments. It is predicted that alanine would be rapidly destroyed and radioracemized in spite of the fact that the concentration of alanine is equal or significantly lower than that of glycine. Assuming that chiral amino acids were a prerequisite for the origin of life, it can be deduced that life could have appeared in a relatively short period of time unless there was a constant supply of optical amino acids from extraterrestrial sources.     

Characterization of homologous DNA recombination activity in normal and immortal mammalian cells.

Homologous DNA recombination levels were measured in normal and spontaneously immortalized murine and human fibroblasts, and in a number of primate and murine established fibroblast cell lines. Immortal cell lines and tumor-derived clones homologously recombined extrachromosomal plasmid substrates at frequencies approximately 100-fold higher than did normal cells. To further explore the mechanism responsible for this phenotype, homologous recombination frequency was measured using nuclear extracts derived from normal and immortalized murine and human fibroblasts. Extracts prepared from immortal cells catalyzed high levels of homologous recombination, whereas very little recombination activity was detected in extracts prepared from normal fibroblasts. Similarly, only extracts derived from immortal cells contained strand-transferase activity as measured by the recently described pairing-on-membrane assay. Mixing experiments indicated that a recombination enhancing factor or factors present in immortal cells, rather than a recombination inhibitor in normal cells, was responsible for the enhanced homologous recombination activity observed using extracts derived from the former.     

Antioxidants in peripheral nerve

Oxidative stress and antioxidants have been related in a wide variety of ways with nervous tissue. This review attempts to gather the most relevant information related to a) the antioxidant status in non pathologic nervous tissue; b) the hypothesis and evidence for oxidative stress (considered as the disequilibrium between prooxidants and antioxidants in the cell) as the responsible mechanism of diverse neurological diseases; and c) the correlation between antioxidant alterations and neural function, in different experimental neuropathies. Decreased antioxidant availability has been observed in different neurological disorders in the central nervous system, for example, Parkinson's disease, Alzheimer's disease, epilepsy, amyotrophic lateral sclerosis, cerebral ischaemia, etc. Moreover, the experimental manipulation of the antioxidant defense has led in some cases to interesting experimental models in which electrophysiological alterations are associated with the metabolic modifications induced. In view of the electrophysiological and biochemical effects of some protein kinase C inhibitors on different neural experimental models, special attention is dedicated to the role of this kinase in peripheral nervous tissue. The nervous tissue, central as well as peripheral, has two main special features that are certainly related to its antioxidant metabolism: the lipid-enriched membrane and myelin sheaths, and cellular excitability. The former explains the importance of the glutathione (GSH)-conjugating activity towards 4-hydroxy-nonenal, a biologically active product of lipid peroxidation, present in nervous tissue and in charge of its inactivation. The impairment of the latter by oxidative damage or experimental manipulation of antioxidant metabolism is discussed. Work on different experimental neuropathies from author's laboratory has been primarily used to provide information about the involvement of free radical damage and antioxidants in peripheral nerve metabolic and functional impairment.