Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO trimethylamine-N-oxide     

Isolation and structural analysis of a peptide containing the novel tyrosyl-glucose linkage in glycogenin.

The glucosylation site on glycogenin, the protein primer required for de novo glycogen synthesis, has been identified. The glucose is attached at position C1 in a glycosidic linkage with a unique tyrosine, and the sequence surrounding this residue was found to be: His-Leu-Pro-Phe-Ile-Tyr-Asn-Leu-Ser-Ser-Ile-Ser-Ile-Tyr(Glc)-Ser-Tyr-Leu -Pro- Ala-Phe-Lys. The same tyrosine residue is glycosylated whether glycogenin is isolated as a complex with the catalytic subunit of glycogen synthase, or covalently attached to glycogen. The possibility that insulin and growth factors may enhance glycogen synthesis via stimulation of the priming reaction is discussed.     

Factors affecting the activity patterns of black-backed jackals Canis mesomelas

Daily activity levels of black-backed jackals Canis mesomelus were determined in southern Africa through direct observation and radio-tracking. Jackals have a bigeminus activity pattern that is closely paralleled by the activity levels of some of their most important prey. Although differences due to sex, age, study area and season of year were found, this activity pattern was most markedly influenced by light conditions during both the crepuscular and the nocturnal periods.     

Calcium ion transport across discs of the cortical flesh of apple fruit in relation to fruit development

Transport of Ca²⁺ through discs of apple fruit tissue was examined in tissue taken at different stages of fruit development. Transport rates decreased with fruit development when cation exchange was the predominant influence on transport (with 10⁻⁶ M ⁴⁵CaCl₂ as the source solution). This decrease was associated with a reduction in relative cell wall surface area, cation exchange capacity and cell wall yield that occurred during fruit growth. When diffusion was the major transport force, and when transport was influenced by solution infiltration of the tissue disc (10⁻² M ⁴⁵CaCl₂ in the source solution), transport rates increased during fruit growth. This increment was related to increases in air space of the tissue. Ca²⁺ transport through apple fruit tissue is influenced by the extent and nature of the cell wall, changing proportions of air space and Ca²⁺ concentration in the extracellular solution.     

Candidate glycophospholipid precursor for the glycosylphosphatidylinositol membrane anchor of Trypanosoma brucei variant surface glycoproteins

Trypanosoma brucei variant surface glycoproteins are apparently synthesized with a hydrophobic carboxyl-terminal peptide that is cleaved and replaced by a complex glycosylphosphatidylinositol membrane anchor within 1 min of the completion of polypeptide synthesis. The rapidity of this carboxyl-terminal modification suggests the existence of a prefabricated core glycolipid that would be transferred en bloc to the variant surface glycoprotein polypeptide. We report the purification and chemical characterization of a glycolipid from T. brucei that has properties consistent with a role as a variant surface glycoprotein glycolipid donor. This candidate glycolipid precursor has been defined by thin-layer chromatography of extracts of trypanosomes metabolically labeled with radioactive myristic acid, ethanolamine, glucosamine, mannose, and phosphate and by enzymatic, chemical, and gas chromatographic-mass spectrometric analysis. Mild alkali released 100% of the myristic acid, and reaction with phospholipase A2 released 50%. Nitrous acid deamination generated dimyristylphosphatidylinositol, and periodate oxidation released phosphatidic acid. Treatment of purified glycolipid with phosphatidylinositol-specific phospholipase C released dimyristylglycerol and a water-soluble glycan that was sized on Bio-Gel P-4 columns. The candidate precursor contained mannose, myristic acid, phosphate, and ethanolamine with an unsubstituted amino group, but not galactose.     

Localization of phospholamban in smooth muscle using immunogold electron microscopy

Phospholamban, the putative regulator of the Ca2+-ATPase in cardiac sarcoplasmic reticulum, was immunolocalized in canine visceral and vascular smooth muscle. Gently disrupted tissues were labeled with an affinity-purified phospholamban polyclonal antibody and indirect immunogold, using preembedding techniques. The sarcoplasmic reticulum of smooth muscle cells was specifically labeled with patches of immunogold distributed in a nonuniform fashion, while the sarcolemma did not appear to contain any phospholamban. The outer nuclear envelopes were also observed to be heavily labeled with the affinity-purified phospholamban polyclonal antibody. These findings suggest that phospholamban may play a role in the regulation of cytoplasmic and intranuclear calcium levels in smooth muscle cells.     

Morphometric, meristic character and electrophoretic analyses of two Irish populations of twaite shad, Alosa fallax (Lacépède)

Since 1911 a rare lacustrine form of twaite shad, Alosa fallax killarnensis Regan (1916), has been known to occur in the Killarney Lakes. During the summers of 1985 and 1986 a gill netting programme in Lough Leane for brown trout, Salmo trutta L., yielded 32 shad (1985) and 64 shad (1986) as a by-catch. These fish were deep frozen and compared with a sample of 59 marine twaite shad, taken on rod and line from St Mullin's, Co. Carlow, which had entered the River Barrow to spawn.
Morphometric, meristic and electrophoretic character analyses were carried out on the two populations. The three analyses, particularly the isoelectric focusing, confirmed a high degree of genetic similarity. The two major differences found were the dwarfed size of the Killarney shad and the increased numbers of gill rakers carried on the first branchial arch. The merits and demerits of assigning the term subspecies to the Killarney shad are discussed in the light of the available evidence produced.     

Modulation of experimental allergic encephalomyelitis with anti-T suppressor factor antibodies

mAb reactive with T suppressor factors (TsF) were used to alter the course of myelin basic protein-induced experimental allergic encephalomyelitis in (SJL/J x PL/J)F1 mice. In vivo administration of mAb 14-12, reactive with effector TsF, exacerbated the clinical expression of encephalomyelitis as evidenced by prolonged periods of total limb paralysis in affected animals. This aggravation of disease signs is probably related to the inhibition of effector Ts function by mAb 14-12 thus allowing T cell autoreactivity to proceed unchecked. Disease course was influenced more favorably by i.v. administration of mAb 14-30 reactive with a subset of inducer TsF. Ten days of treatment with this mAb resulted in a reduction in the incidence and severity of disease, noted as the development of minimal limb weakness but no paralysis in the majority of affected animals. Adoptive transfer experiments revealed the presence of Ag-specific Ts in mAb 14-30-treated mice that inhibited recipient Lyt-1+ responses to myelin basic protein, the immunizing autoantigen. Suppression by transferred Ts was revealed only by treatment of the donor population with anti-Lyt-1.2 plus C, however, indicating a role for contrasuppressor activity in the regulation of autoimmune T cell function. Results are considered relevant to the potential for immunotherapeutic management of multiple sclerosis in man.     

Alu-PCR: characterization of a chromosome 6-specific hybrid mapping panel and cloning of chromosome-specific markers.

The Alu-polymerase chain reaction (Alu-PCR) was applied to selectively amplify DNA sequences from human chromosome 6 using a single primer (A1) directed to the human Alu consensus sequence. A specific amplification pattern was demonstrated for a panel of eight somatic cell hybrids containing different portions of chromosome 6. This PCR pattern permits the identification of submicroscopic DNA alterations and can be utilized as a reference for additional chromosome 6-specific hybrids. To obtain new chromosome 6-specific markers we established two libraries from PCR-amplified sequences using two somatic cell hybrids (MCH381.2D and 640-5A). Out of a total of 109 clones that were found to be chromosome 6 specific, 13 clones were regionally assigned. We also included a procedure that allows the isolation of chromosome 6-specific markers from hybrids that contain human chromosomes other than 6. Our results will contribute to the molecular characterization of chromosome 6 by fostering characterization of somatic cell hybrids and by the generation of new regionally assigned DNA markers.     

Variation in the mutagenic potential of acridines in Salmonella typhimurium, with stage of the culture

The mutagenic potential of proflavine differed by up to two orders of magnitude in three strains of Salmonella typhimurium carrying the frameshift marker hisC3076, depending upon the stage of the culture. In cultures at a specific stage, proflavine showed decreased mutagenesis in a recA as compared with a wildtupe or uvrB derivative. The related compound 9-aminoacridine also showed marked variation in mutagenic potential with the stage of the bacterial culture, but was equally mutagenic in all three strains, at least in log phase cells. Within the literature, there are conflicting data regarding the mutagenicity of acridines, and the contribution of repair enzymes to this event. We suggest that many of the reported differences can be related to the variations in bacterial growth conditions in different laboratories, and urge authors to supply more details of these.