The relationship of 4-aminobutyric acid metabolism to ammoniagenesis in renal cortex

Mitochondrial 4-aminobutyrate aminotransferase in rat kidney can utilize pyruvate as the acceptor for the amino group of 4-aminobutyrate. Renal 4-aminobutyrate aminotransferase activity at saturating equimolar concentration of 4-aminobutyrate and 5 mM pyruvate is 42.8 ± 2.5 μmol/g protein per h (mean ± S.E.M.) or 70% of 4-aminobutyrate aminotransferase activity with equimolar α-ketoglutarate. 4-Aminobutyrate aminotransferase in brain does not transaminate with pyruvate. Since pyruvate is an important mitochondrial metabolite in kidney, net disposal of glutamate via the 4-aminobutyrate pathway is possible. The renal 4-aminobutyrate pathway in the rat has other distinctive features when compared with the pathway in rat brain. Most inhibitors of rat neuronal glutamate decarboxylase were ineffective against the renal form of the enzyme, but 20 mM semicarbazide inhibited the latter form by 80% (P < 0.001) in vitro and reduced renal 4-aminobutyrate content by 75% (P < 0.001) in vivo. In the presence of 20 mM semicarbazide, ammoniagenesis by rat renal cortex slices incubated in 1 mM glutamine was inhibited 26% (P < 0.01). Semicarbazide was proportionately less effective (15% inhibition) when ammoniagenesis was stimulated (+243%) in slices prepared from chronically acidotic animals, and was no deterrant to ammoniagenesis when non-acidotic slices were incubated in supraphysiologic concentrations of 10 mM glutamine. We conclude that whereas integrity of the renal 4-aminobutyrate pathway may contribute to glutamate disposal and thus ammoniagenesis under physiologic conditions, the pathway is a passive participant in the overall process of ammoniagenesis.     

Purification and partial characterization of citrate synthase from Phaseolus vulgaris mitochondria

Citrate synthase (E.C. 4.1.3.7) has been isolated from bean mitochondria by an improved procedure. The purified enzyme had a specific activity of 50. In most respects (e.g. sedimentation constant, K_ms, pH sensitivity and ionic strength inhibition) the enzyme is similar to that prepared from mammalian sources. The feature distinguishing the plant enzyme from the others was its inhibition by several sulfhydryl reagents. The substrates conferred either complete protection (acetyl coenzyme A) or partial protection (oxalacetic acid) against the inhibition. Dithiothreitol (DTT) was capable of partially reversing the inhibition. The efficacy of DTT varied with the sulfhydryl reagent and was inversely related to the period of incubation of the enzyme with the reagent.     

Tropical forest and mangrove history from southeastern Mexico: a 5000 yr pollen record and implications for sea level rise

A 250 cm long core from El Palmar, a swamp area located along the Rio Hondo river in the south of the Yucatan Peninsula, near the Belizean border, reveals the environmental history of the mangrove and tropical forest of the last 5000 years. The period between 5000 and 4600 b.p. shows sandy deposits, which form the early infill and development of the swamp. A medium-statured tropical forest covered the area and members of the Moraceae and Fabacaeae dominated this early forest. The period between 4600 and 4000 b.p. presents a clear change to a mangrove system with Conocarpus erecta and Rhizophora mangle as dominant trees. This vegetational change is due to flooding of the Rio Hondo river, which deposits sediments of high salinity due to higher sea-level. The medium-statured forest became established at some distance from the swamp area. After 4400 b.p. C. erecta appears as the dominant mangrove species and the R. mangle stands are less predominant in the area. The tropical forest was close to the swamp area and was mainly composed of members of the Moraceae, Arecaceae and Fabaceae as dominant taxa of this vegetational mosaic.     

New World Monkeys and Color

The visual worlds of most primates are rich with potential color signals, and many representatives of the order have evolved the biological mechanisms that allow them to exploit these sources of information. Unlike the catarrhines, platyrrhines typically have sex-linked polymorphic color vision that provides individuals with any of several distinct types of color vision, including both trichromatic and dichromatic variants. In recent years, this polymorphism has been the target of an expanding range of research efforts. As a result, researchers now reasonably understand the proximate biology underlying the polymorphisms, and a number of ideas have emerged as to their evolution. Progress has also been made in illuminating how color vision capacities may be related to the particular visual tasks that New World monkeys face.     

Evaluation of secondary infertility in the gorilla

Reproductive failure in two female gorillas in the Los Angeles Zoo led to evaluation for secondary infertility. Male factor was excluded by noting routine conceptions in other individuals in the same group, and by behavioral observations of coital activity with the infertile females. Biochemical evidence of ovarian function was obtained by urinary sex steroid analysis. Continuity of the reproductive tract of the infertile apes was then studied by hysterosalpingography and laparoscopy while their general health was evaluated by ultrasonography and physical examination. Progressive, multiorgan involvement with Echinococcus vogeli was documented and mebendazole therapy begun. The investigation of secondary infertility in great apes by combined methods is safe and accurate, but requires special equipment and experienced personnel.     

Storage of Wheat FoliagePrior to Enzyme-Linked Immunosorbent Assay for Detection of Wheat Soil-Borne Mosaic Virus

Plant samples, collected at various times during a growing season, are frequently stored prior to evaluating resistance to wheat soil-borne mosaic virus (WSBMV) by enzyme-linked immunosorbent assay (ELISA). Leaves of winter wheat cvs Sage and Vona, showing symptoms of WSBMV infection, were cut in half along the midrib. Each half was either: 1) refrigerated at 4 °C, 2) frozen at ?20 °C, 3) frozen at –70 °C, or 4) desiccated with CaCl₂. Relative virus antigen titres were evaluated for individual leaf halves by ELISA. ELISA absorbance means from desiccated leaf halves were consistently higher than absorbance means from corresponding leaf halves that had been frozen. This distinction suggests that virus antigen decreases during freezing but is retained during chemical desiccation. All 4 methods of storage were found to be suitable for short-term storage prior to qualitative evaluations by ELISA, but chemical desiccation was the superior method for long-term storage and for storage of foliar samples prior to quantitative evaluations by ELISA.