Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli.

Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.     

Nucleotide sequence of the second psbG gene in Synechocystis 6803. Possible implications for psbG function as a NAD(P)H dehydrogenase subunit gene

Nucleotide sequencing of the second Synechocystis 6803 psbG gene, psbG2 shows the predicted polypeptide to be 219 amino acids long. It is less similar to chloroplast psbG genes than is the Synechocystis psbG1 copy. Alignment with seven other psbG protein sequences, including that from the Paramecium mitochondrial genome reveals a central highly conserved region common to each. This is discussed as evidence supporting the proposal that the psbG polypeptide is a NAD(P)H dehydrogenase (complex I) subunit in cyanobacteria, chloroplasts and mitochondria.     

Do pollen beetles need pollen? The effect of pollen on oviposition,survival, and development of a flower‐feeding herbivore

Abstract.  1. Pollen is considered to be an important dietary component for many species of flower-feeding herbivores. Its influence on oviposition site selection by the pollen beetle Meligethes aeneus , and on the development of its larvae was investigated.
2. The effects of pollen presence and absence on adult, egg, and larval incidence in the field, and on larval development in the laboratory were compared through the use of Synergy, a composite hybrid oilseed rape Brassica napus variety comprising male-fertile (with pollen) and male-sterile (without pollen) plants.
3. In the field, adult females were more abundant on male-fertile plants during flowering, and a greater proportion of male-fertile than male-sterile buds were accepted for oviposition. These data indicate a possible role of pollen in oviposition site selection by female pollen beetles.
4. The numbers of first instar larvae on the two plant lines did not differ; however, more second instars were found on male-fertile than on male-sterile flowers. This suggests a greater larval survival on male-fertile plants, possibly due to the more readily available food resources and better nutrition afforded by the presence of pollen.
5. Laboratory experiments confirmed that a diet which included pollen improved survival to adulthood and resulted in heavier pupae and adults; however, pollen was not obligatory for larval survival and development.
6. The pollen beetle, previously thought to be an obligate pollen feeder, is therefore more generalist in its requirements for development. These findings may relate to the nutritional and behavioural ecology of other flower-feeding herbivores.     

Mouse and rat cells undergo rapidly inducible changes in polypeptide secretion following infection with Kirsten murine sarcoma virus

Characteristic changes in the secreted polypeptides of Kirsten murine sarcoma virus (KiMSV) transformed mouse and rat cell lines could be detected 48 hours after infection of phenotypically normal cells with this virus and correlated with detection of the KiMSV encoded polypeptide p21.     

Vitellogenin mRNA in locust fat body: coordinate induction of two genes by a juvenile hormone analog

Levels of vitellogenin (Vg) mRNA in Locusta migratoria fat body were determined as indicators of gene expression induced by the juvenile hormone analog methoprene. After injection of methoprene into juvenile hormone-deprived locusts, excised fat bodies were cultured with [3H]leucine for immunochemical assay of Vg synthesis, and RNA was assayed for Vg mRNA content by hybridization with probes from the previously cloned locust Vg genes A and B. In general, the rise in Vg mRNA paralleled the rise in Vg synthesis. During the primary response to methoprene (in female locusts in which the corpora allata had been destroyed immediately after emergence), Vg mRNA was first detected after 18-24 hr and accumulated rapidly between 36 and 48 hr. The secondary response (in locusts allatectomized during vitellogenesis and kept until Vg disappeared) was accelerated, as Vg mRNA was detectable at 12 hr and titers rose steeply after 18 hr. When Vg synthesis was prematurely induced by injection of methoprene into fifth-stage female larvae, the kinetics of mRNA accumulation were similar to those of primary stimulation in the adult. After allatectomy of vitellogenic females, fat body Vg mRNA decayed with a half-life of about 24 hr, roughly paralleling the decline in Vg synthesis. Assays with the two Vg probes showed coordinate accumulation of gene A and gene B messages under all conditions tested: during primary and secondary stimulation in adult females and in the low-level response obtained by treating male larvae with methoprene.     

The major histocompatibility complex of primates

The major histocompatibility complex (MHC) encodes cell surface glycoproteins that function in self-nonself recognition and in allograft rejection. Among primates, the MHC has been well defined only in the human; in the chimpanzee and in two species of macaque monkeys the MHC is less well characterized. Serologic, biochemical and genetic evidence indicates that the basic organization of the MHC linkage group has been phylogenetically conserved. However, the number of genes and their linear relationship on the chromosomes differ between species. Class I MHC loci encode molecules that are the most polymorphic genes known. These molecules are ubiquitous in their tissue distribution and typically are recognized together with nominal antigens by cytotoxic lymphocytes. Class II MHC loci constitute a smaller family of serotypes serving as restricting elements for regulatory T lymphocytes. The distribution of class II antigens is limited mainly to cell types serving immune functions, and their expression is subject to up and down modulation. Class III loci code for components C2, C4 and Factor B (Bf) of the complement system.Interspecies differences in the extent of polymorphism occur, but the significance of this finding in relation to fitness and natural selection is unclear. Detailed information on the structure and regulation of MHC gene expression will be required to understand fully the biologic role of the MHC and the evolutionary relationships between species. Meanwhile, MHC testing has numerous applications to biomedical research, especially in preclinical tissue and organ transplantation studies, the study of disease mechanisms, parentage determination and breeding colony management. In this review, the current status of MHC definition in nonhuman primates will be summarized. Special emphasis is placed on the CyLA system of M. fascicularis which is a major focus in our laboratory. A highly polymorphic cynomolgus MHC has been partially characterized and consists of at least 14 A locus, 11 B locus, 7 C locus class I allelic specificities, 9 Ia-like class II antigens and 6 Bf (class III) variants.     

Characterization of the specific pyruvate transport system in Escherichia coli K-12.

A mutant of Escherichia coli K-12 lacking pyruvate dehydrogenase and phosphoenolpyruvate synthase was used to study the transport of pyruvate by whole cells. Uptake of pyruvate was maximal in mid-log phase cells, with a Michaelis constant for transport of 20 microM. Pretreatment of the cells with respiratory chain poisons or uncouplers, except for arsenate, inhibited transport up to 95%. Lactate and alanine were competitive inhibitors, but at nonphysiological concentrations. The synthetic analogs 3-bromopyruvate and pyruvic acid methyl ester inhibited competitively. The uptake of pyruvate was also characterized in membrane vesicles from wild-type E. coli K-12. Transport required an artificial electron donor system, phenazine methosulfate and sodium ascorbate. Pyruvate was concentrated in vesicles 7- to 10-fold over the external concentration, with a Michaelis constant of 15 microM. Energy poisons, except arsenate, inhibited the transport of pyruvate. Synthetic analogs such as 3-bromopyruvate were competitive inhibitors of transport. Lactate initially appeared to be a competitive inhibitor of pyruvate transport in vesicles, but this was a result of oxidation of lactate to pyruvate. The results indicate that uptake of pyruvate in E. coli is via a specific active transport system.     

Membrane-murein attachment at the leading edge of the division septum: a second membrane-murein structure associated with morphogenesis of the gram-negative bacterial division septum.

Electron microscopy of plasmolyzed cells of Salmonella typhimurium revealed a continuous zone of membrane-murein attachment at the leading edge of the division septum at all stages of septal invagination. The membrane-murein attachment site had a characteristic ultrastructural appearance and remained as a bacterial birth scar at the new pole of each of the two daughter cells after cell separation. The continuous zone of membrane-murein attachment at the leading septal edge represents the second organelle based on a topologically ordered domain of membrane-murein adhesion to be described at the site of cell division.     

Crystallization and preliminary x-ray investigation of sarcoplasmic calcium-binding protein from Nereis diversicolor

Crystals of sarcoplasmic calcium-binding proteins from Nereis diversicolor have been grown from solutions of ammonium sulfate. The crystals are monoclinic, space group P2(1); the axes are a = 43.65 (1), b = 56.05 (1), c = 65.77 (1) A, and beta = 92.58 (2) degrees. The crystals are quite stable to x-rays and diffract beyond 2.5 A resolution. The asymmetric unit contains two protein molecules.