Effect of acute exposure to 3660 m altitude on orthostatic responses and tolerance.

Orthostatic reflexes were examined at 375 m and after 60 min of exposure in a hypobaric chamber at 3660 m using a 20-min 70 degrees head-up tilt (HUT) test. Mean arterial blood pressure, R wave-R wave interval (RRI), and mean cerebral blood flow velocity (MFV) were examined with coarse-graining spectral analysis. Of 14 subjects, 7 at 375 m and 12 at 3660 m were presyncopal. Immediately on arrival to high altitude, breathing frequency and MFV increased, and endtidal PCO2, RRI, RRI complexity, and the parasympathetic nervous system indicator decreased. MFV was similar in HUT at both altitudes. The sympathetic nervous system indicator increased with tilt at 3660 m, whereas parasympathetic nervous system indicator decreased with tilt at both altitudes. Multiple regression analysis of supine variables from either 375 or 3660 m and the time to presyncope at 3660 m indicated that, after 1 h of exposure, increased presyncope at altitude was the result of 1). ineffective peripheral vasoconstriction, despite increased cardiac sympathetic nervous system activity with HUT, and 2). insufficient cerebral perfusion owing to cerebral vasoconstriction as the result of hypoxic hyperventilation-induced hypocapnia.     

Plasmids in Leuconostoc oenos

A new procedure was used to isolate 11 plasmids from eight Leuconostoc oenos strains. Plasmid DNA was not detected in 34 other strains of this species. Plasmid sizes ranged from 2.47 to 4.61 kilobase pairs. This is the first report of extrachromosomal elements in L. oenos.     

In-situ localization of chalcone synthase mRNA in pea root nodule development

In this paper studies on the role of flavonoids in pea root nodule development are reported. Flavonoid synthesis was followed by localizing chalcone synthase (CHS) mRNA in infected pea roots and in root nodules. In a nodule primordium, CHS mRNA is present in all cells of the primordium. Therefore it is hypothesized that the Rhizobium Nod factor induces cell division in the root cortex by stimulating the production of flavonoids that function as auxin transport inhibitors. In nodules CHS mRNA is predominantly present in a region at the apex of the nodule consisting of meristematic and cortical cells. These cells are not infected by Rhizobium. Therefore it is postulated that CHS plays a role in nodule development rather than in a defence response. In roots CHS mRNA is located at a similar position as in nodules, suggesting that CHS has the same function in both root and nodule development. When nodules are formed by mutants of Rhizobium leguminosarum bv. viciae that are unable to secrete β(1-2) glucan and to synthesize the O-antigen containing LPS I, CHS genes are also expressed in regions of the nodule that are infected by Rhizobium. It is postulated that the impaired development of nodules formed by these mutants is due to an induction of a plant defence response.     

Identification and physical characterization of yeast glucoamylase structural genes

Summary Each one of at least three unlinked STA loci (STA1, STA2 and STA3), in the genome of Saccharomyces diastaticus controls starch hydrolysis by coding for an extracellular glucoamylase. Cloned STA2 sequences were used as hybridization probes to investigate the physical structure of the family of STA genes in the genomes of different Saccharomyces strains. Sta⁺ strains, each carrying a single genetically defined STA locus, were crossed with a Sta^– strain and the segregation behavior of the functional locus (i.e. Sta⁺) and sequences homologous to a cloned STA2 glucoamylase structural gene at that locus were analyzed. The results indicate that in all strains examined there is a multiplicity of sequences that are homologous to STA2 DNA but that only the functional STA loci contain extensive 5 and 3 homology to each other and can be identified as residing on unique fragments of DNA; that all laboratory yeast strains examined contain extensive regions of the glucoamylase gene sequences at or closely linked to the STA1 chromosomal position; that the STA1 locus contains two distinct glucoamylase gene sequences that are closely linked to each other; and that all laboratory strains examined also contain another ubiquitous sequence that is not allelic to STA1 and is nonfunctional (Sta^–), but has retained extensive sequence homology to the 5 end of the cloned STA2 gene. It was also determined that the DEX genes (which control dextrin hydrolysis in S. diastaticus), MAL5 (a gene once thought to control maltose metabolism in yeast) and the STA genes are allelic to each other in the following manner: STA1 and DEX2, STA1 and MAL5, and STA2 and DEX1 and STA3 and DEX3.     

A comparison of the body height of the Israeli-born and immigrants to Israel

This paper reports a study of body height in the adult Jewish population of Israel, comparing native-born with immigrant groups. The sample tested included 1,411 men and 961 women, all clinically healthy according to the results of multiphasic screening. The phenomenon observed in other immigration-absorbing countries also holds for Israel: native Israelis are significantly taller than their immigrant counterparts. The findings were verified over different age and working activity strata, and thus may be taken to reflect the influence of better socioeconomic and environmental conditions on the bodily development of those born in Israel.     

Energetics of cell-cell and cell-biopolymer interactions

The energy vs distance balance of cell suspensions (in the presence and in the absence of extracellular biopolymer solutions) is studied, not only in the light of the classical Derjaguin-Landau-Verwey-Over-beek (DLVO) theory (which considered just the electrostatic (EL) and Lifshitz-van der Waals (LW) interactions), but also by taking electron-acceptor/electron-donor, or Lewis acid-base (AB) and osmotic (OS) interactions into account. Since cell surfaces, as well as many biopolymers tend to have strong monopolar electron-donor properties, they are able to engage in a strong mutual AB repulsion when immersed in a polar liquid such as water. The effects of that repulsion have been observed earlier in the guise of hydration pressure. The AB repulsion is, at close range, typically one or two orders of magnitude stronger than the EL repulsion, but its rate of decay is much steeper. In most cases, AB interactions are quantitatively the dominant factor in cell stability (when repulsive) and in “hydrophobic interactions” (when attractive). OS interactions exerted by extracellularly dissolved biopolymers are weak, but their rate of decay is very gradual, so OS repulsions engendered by biopolymer solutions may be of importance in certain long-range interactions. OS interactions exerted by biopolymers attached to cells or particles (e.g., by glycocalix glycoproteins), are very short-ranged and usually are negligibly small in comparison with the other interaction forces, in aqueous media.     

Analysis of epitope expression and the functional repertoire of recombinant complement receptor 2 (CR2/CD21) in mouse and human cells

We transfected human complement receptor 2 (CR2/CD21) cDNA containing eukaryotic expression constructs into CR2-negative mouse L cells and human K562 erythroleukemia cells. We subsequently selected stably transformed cells that expressed human CR2, as assessed by flow microfluorimetry analysis and immunoprecipitation of 125I-labeled surface membranes using the monoclonal anti-CR2 antibody, HB5. Utilizing flow microfluorimetry analysis, epitopes recognized by anti-CR2 mAb HB5, OKB7, B2, and four other anti-CR2 antibodies were detected on CR2 expressing transfectants but not parental cells. In addition, CR2 expressing transfected cells efficiently formed rosettes with sheep erythrocyte intermediates bearing human C3bi and C3d, but not C4b or C3b, consistent with the known ligand specificity of CR2. CR2 containing transfectants were also demonstrated to specifically bind EBV. Infection with EBV of CR2 expressing L cells and K562 cells resulted in mean expression of Epstein-Barr nuclear Ag (EBNA) at 48 h in 0.35% of CR2 expressing L cells and 3.7% of CR2 expressing K562 cells. Parental L cells and K562 cells did not express EBNA after EBV infection. These results indicate that CR2 alone is sufficient to transfer both C and EBV receptor functions to heterologous cells. In addition, expression of EBNA was found to be significantly higher in human K562 than mouse L cells, both expressing the same recombinant receptor. These results suggest that mechanisms other than CR2 binding lead to inefficient EBV infection and/or EBNA synthesis in mouse fibroblasts.     

Mapping of the variegate porphyria (VP) gene: Contradictory evidence for linkage between VP and microsatellite markers at chromosome 14q32

The gene for variegate porphyria (VP), an autosomal dominant disease with a high prevalence in South Africa, evidently due to a founder effect, was previously mapped to chromosome 14q32. In the current study this localization was evaluated by linkage and haplotype analyses using microsatellite markers spanning a region of more than 20 cM on chromosome 14q32. In many recent studies linkage disequilibrium between disease and marker loci has been utilized to map genes in founder populations, but we could not find any association between VP and the markers used in this study. Our data suggest that the allocation of VP to chromosome 14q32 may be incorrect. Received: 1 September 1995 / Revised: 1 November 1995