Essential function in chloroplast recognition of the ferredoxin transit peptide processing region

Molecular Genetics and Genomics - Plant ferredoxin is a nuclear-encoded chloroplast protein that is synthesized in the cytoplasm as a transit peptide-containing precursor molecule. To identify...     

Classical plant taxonomic ambiguities extend to the molecular level

Summary The molecular evolution of cytochrome c from angiosperms is compared to that from vertebrates. On the basis of a cladistic analysis from 26 plant species, compared to that from 27 vertebrate species, we find that although the vertebrate sequences yield reasonably well-defined minimal trees that are congruent with the biological tree, the plant sequences yield multiple minimal trees that are not only highly incongruent with each other, but none of which is congruent with any reasonably biological tree. That is, the plant sequence set is much more homoplastic than that of the animal. However, as judged by the relative rate test, the extent of divergence, and degree of functional constraint, cytochrome c evolution in plants does not appear to differ from that of vertebrates.     

Carbon metabolism in Bradyrhizobium japonicum bacteroids

Abstract Carbon metabolism in Bradyrhizobium japonicum bacteroids is reviewed. Additionally, the bacteroid tricarboxylic acid (TCA) cycle and its regulation under oxygen-limited conditions is considered, with emphasis on possible sites of TCA cycle rate-limiting reactions. Furthermore, we consider other adaptive pathways that may be employed by these organisms while in symbiosis. These pathways include: (1) a poly-β-hydroxy-butyrate shunt, (2) a malate-aspartate shuttle, (3) an α-ketoglutarate-glutamate shunt, (4) a modified dicarboxylic acid cycle, and (5) fermentation pathways leading to lactate, acetaldehyde and ethanol. The effects of oxygen limitation on host carbon metabolism are also considered briefly.     

Dynamics of small autocatalytic reaction networks—I. bifurcations,permanence and exclusion

Catalysis in replication networks has become an important issue in biophysics and other areas of biology. Examples are RNA catalysis, idiotype recognition in the immune response and dynamical models of Maynard-Smith games in sociobiology. Chemical reaction networks describing catalysed, template-induced reproduction of three species are analysed in full generality. The nine-dimensional parameter space is reduced to three relevant angular coordinates which determine completely the phase portraits (PPs) and the bifurcation patterns. All cases are classified and all generic as well as most of the nongeneric transitions are listed and described. This paper has been reproduced directly from disc using a LA-T_EX system.     

Site of action for endotoxin-induced cortisol release in the suppression of preovulatory luteinizing hormone surges

The study was conducted to identify the mechanisms of endotoxin/cortisol action in the suppression of preovulatory LH surges in heifers infused with Escherichia coli (E. coli ) endotoxin. The hypotheses tested were that 1) endotoxin stimulates the release of progesterone, possibly from the adrenal leading to the LH blockade; 2) cortisol released in response to endotoxin infusion blocks the synthesis of estradiol at the ovarian level, culminating in a failure of the LH surge. Eight Holstein heifers were given two injections of prostaglandin F(2alpha) (PG), 11 d apart, to synchronize estrus. Starting from 25 h after the second injection of PG (PG-2), the uterus of each heifer was infused either with 5 ml of pyrogen-free water (control, n = 3) or with E. coli endotoxin (5 mug/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 h for 10 treatments. Blood samples were obtained every 15 min for 1 h before infusion and again 2 h after each infusion, then hourly until 1 h before the next infusion. After the tenth infusion, blood was collected daily until estrus. Serum progesterone concentrations remained at baseline values (< 1 ng/ml) in control and treated heifers. The total amount of progesterone measured starting 24 to 84 h after PG-2 injection was not different between control and treated heifers (P 0.05). In the control heifers, serum estradiol concentrations remained basal (< 10 pg/ml) until 4 h before the LH surge. Serum estradiol concentrations increased to 20 +/- 5.6 pg/ml, 4 h before the LH surge in control heifers (LH surge occurred 60 to 66 h after the PG-2 injection). There were no changes in serum estradiol concentrations in treated heifers during the sampling period, and the concentrations remained < 10 pg/ml. The total amount of estradiol measured in control heifers was higher (P < 0.05) than in treated heifers. The results if this study suggest that increases in cortisol concentrations after the infusion of endotoxin might block the synthesis of estradiol at the ovarian level, resulting in the failure of a preovulatory LH surge to occur.     

The effect of Escherichia coli endotoxin on luteal function in Holstein heifers

This study was undertaken to elucidate the possible role of endotcxin in mediating premature luteolysis in the well- documented phenomenon of short estrous cycles in postpartum dairy cows. Four groups of Holstein heifers (n = 4 to 6 each) received either intrauterine infusion of sterile culture medium (Group I); intrauterine infusion of Escherichia coli (E. coli ) endotoxin (5 mug/kg) in sterile culture medium (Group II); intrauterine administration of 10 ml of a 24-h culture of a strain of E. coli isolated from the uterus of a cow with metritis (approximately 10(9) colony forming units/ml; Group III); or intravenous administration of E. coli endotoxin (5 mug/kg; Group IV) on Day 7-9 of the estrous cycle. Blood samples were collected every 48 h during the pretreatment estrous cycle and up to the administration of the experimental treatment, thereafter 4-h samples were collected for 5 d. Sample collection was then performed every 48 h for the remainder of the treatment cycle and the post treatment cycle. Serum concentrations of progesterone and plasma concentrations of 15-keto-13, 14-dihydroprostaglandin F(2alpha) (PGFM) were determined by radionmmunoassay. Intrauterine infusion of endotoxin had no effect on the cycle length or on hormone concentrations, while infusion of viable E. coli organisms tended to shorten the estrous cycle. Intravenous administration of endotoxin produced a sharp increase in both progesterone and PGFM concentrations, followed by a transient decrease in progesterone concentrations. Cycle length remained unchanged. It was concluded that the intact endometrium prevents the uptake of endotoxin although pathogenic E. coli organisms may disrupt the endometrial integrity sufficiently to shorten the estrous cycle by premature luteolysis. It is postulated that intravenous administration of endotoxin influences luteal function by the activation of the arachidonic acid cascade, by a direct effect on the corpus luteum, or via other mediators.     

The purification and characterization of a fatty acid binding protein specific to pig (Sus domesticus) adipose tissue.

Western-blot analysis using antiserum to 3T3-L1-cell fatty acid binding protein (FABP) revealed that pig adipose tissue contains a 15 kDa protein immunologically similar to the murine protein. This 15 kDa protein was purified from pig adipose tissue by sequential application of Sephadex G-50 gel filtration, cation exchange and covalent chromatography on Thiol-Sepharose-4B. The purity of the pig protein was established by two-dimensional polyacrylamide-gel electrophoresis. Isoelectric focusing indicated that the pig adipose FABP (a-FABP) exists with two charge isoforms (pI 5.1 and 5.2), both of which persist after delipidation. The N-terminus of the purified pig a-FABP was blocked; however, cleavage with CNBr allowed recovery of a 12-amino-acid peptide which was identical with the murine a-FABP sequence (residues 36-48) at 10 of 12 positions. The pig a-FABP bound 12-(9-anthroyloxy)oleic acid saturably and stoichiometrically, with an apparent dissociation constant of 1.0 microM. Northern-blot analysis using the cDNA for the murine 3T3-L1 FABP revealed that the pig a-FABP was expressed exclusively in adipose tissue.