Non-motile mutants of Helicobacter pylori and Helicobacter mustelae defective in flagellar hook production

Flagellar hooks were purified from Helicobacter pylori and Helicobacter mustelae. The 70 × 16nm H. pylori hook was composed of FIgE subunits of 78kDa, while the 72 × 16nm H. mustelae hook was composed of 87kDa subunits. N-terminal sequence was obtained for the FIgH proteins of both species, and for an internal H. mustelae FlgE peptide. Degenerate oligonucleotide primers allowed amplification of a 1.2 kb fragment from the H. mustelae chromosome, which carried part of the flgE gene. The corresponding H. pylori gene was cloned by immunoscreening of a genomic library constructed in λZAP Express, The translated H. pylori flgE sequence indicated a protein with limited homology with the hook proteins from Salmonella typhimurium and Treponema phagedenis. Mutants of H. pylori and H. mustelae defective in hook production generated by allele replacement were non-motile and devoid of flagellar filaments but produced both flagellin subunits, which were localized in the soluble fraction of the cell. The level of flagellin production was unchanged in the mutants, indicating that the regulation of flagellin expression in Helicobacter differs from that in the Enterobacteriaceae.     

The control of boron accumulation by two genotypes of wheat

The mechanism of boron (B) uptake in wheat was studied using two genotypes with known differences in their ability to accumulate B. Influx and efflux of B was measured in the roots of intact 21 d old plants.Roots grown in 15 M B, when transferred to solutions containing 1mM B showed a rapid increase in B content for up to 60 min, after which no further increase was evident up to 4 h. No genotypic difference in B influx was apparent over these time periods. Roots grown in 1mM B for 7 d and then rinsed in B-free solutions quickly lost most of B that they contained within 1 hour; little further efflux was observed over the following three hours. As with the influx, no genotypic difference in B flux was evident.It is suggested that the lack of genotypic difference in the short-term B fluxes could be due to a masking effect of extracellular B bound in the cell walls of the roots.Department of Botany, University of Adelaide     

Topography of short portal vessels in the rat pituitary gland: a scanning electron-microscopic and morphometric study of corrosion cast replicas

We applied scanning electron microscopy combined with imaging and morphometric techniques to analyze the dorsal topography and morphology of short portal vessels linking the capillary beds of the pituitary neural and anterior lobes in adult male albino rats. The pituitary microvasculature was replicated by intracarotid injection of Batson's No. 17 compound producing plastic casts that were advantageous for comprehensive morphometric analyses using an imaging device. The analysis revealed the existence of two types of portal vessels having quantitatively different morphological properties. The bilateral venular plexus of 3–4 vessels located at the base of the infundibular stalk (each venule measuring 300 m in length and 32 m in diameter) appears to be the major part of the short portal system in the dorsum of the rat pituitary gland. Narrower capillary-like shunt vessels (6.8 m in diameter), of about the same length as the venules, were situated throughout other subregions of the intermediate lobe cleft. The short portal vessels of both types made direct anastomoses with the capillary networks in the neural and anterior lobes. The neural lobe capillaries were twice as numerous (1324 per mm²), and only half as wide (6.2 m), as the sinusoidal capillaries in the anterior lobe (density of 637 per mm²; diameter of 13.7 m). The topographical position of the portal venular system suggests that the caudolateral subregions of the pituitary neural and anterior lobes have a functional relationship dependent on rapid interlobe transfer of neurohumoral factors such as hormones via the portal blood. This process appears to be supplemented throughout the rest of the cleft between the two lobes by a small number of capillary shunts that supply the epithelial cell lobules of the intermediate lobe in situ. The findings collectively indicate that this portal system provides a constant stream of neurohumoral information that is shared moment-by-moment between the pituitary neural and anterior lobes.     

Optimization of in vitro bud induction and plantlet formation from mature embryos of Aleppo pine (Pinus halepensis Mill.)

Summary Studies were undertaken to optimize tissue culture conditions for micropropagation of Aleppo pine (Pinus halepensis Mill.) from mature embryos and various explants of the embryo. Over 90% of the embryo explants gave rise to adventitious buds within 4 wk. Intact embryos were the most suitable explants for shoot bud induction. Both isolated cotyledons and hypocotyls produced adventitious buds, but these developed slowly and failed to elongate. N⁶-Benzyladenine (BA) alone at 5.0μM was the most effective cytokinin when added to gelled to gelled von Arnold and Eriksson’s (AE) medium containing 3% sucrose. Adventitious bud development was achieved on hormone-free AE medium, and shoot elongation was optimum on three quarter-strength Bornman’s MCM medium, with 0.1% conifer-derived activated charcoal. Shoots were multiplied on three-quarter strength MCM medium, containing 5μM BA. To induce adventitious roots on the elongated shoots, pulse treatment with 1 mM IBA for 6 h, followed by the transfer of the shoots to sterile peat:vermiculite (1:1) mixture, was beneficial. After acclimatization for 3 to 4 wk under mist, almost all the rooted shoots could be transplanted successfully to the greenhouse, where the plants exhibited normal growth habit. Histologic studies on the ontogeny of adventitious shoot formation from mature embryo explants revealed temporal structural changes in different parts of the explant. Induction of mitotic divisions on the shoot-forming medium resulted in the formation of meristemoids in the epidermal and subepidermal layers of the explant, located initially at both the tips of the cotyledons and the axils of adjacent cotyledons. Shoot buds arising in the axils of adjacent cotyledons were due to new cell division and not to any preexisting meristem.     

Physiological and molecular effects of brassinosteroids on Arabidopsis thaliana

We examined the effects of brassinosteroids on Arabidopsis thaliana (L.) Henyh. ecotype Columbia in order to develop a model system for studying gene regulation by plant steroids. Submicromolar concentrations of two brassinosteroids, brassinolide and 24-epibrassinolide, stimulated elongation of Arabidopsis peduncles and inhibited root elongation, respectively. Furthermore, brassinolide altered the abundance of specific in vitro translatable mRNAs from peduncles and whole plants of Arabidopsis. Root elongation in the auxin-insensitive Arabidopsis mutant axr1 was inhibited by 24-epibrassinolide but not by 2,4-D, indicating an independent mode of action for these growth regulators in this physiological response.Abbreviations BR brassinolide - EBR 24-epibrassinolide; 2.4-D,2,4-dichlorophenoxyacetic acid - KPSC 10 mM potassium phosphate, pH 6.0, 2% sucrose, 50 g/ml chloramphenicol - PAGE polyacrylamide gel electrophoresis     

ON THE LOW HERITABILITY OF LIFE-HISTORY TRAITS

Life-history traits such as longevity and fecundity often show low heritability. This is usually interpreted in terms of Fisher's fundamental theorem to mean that populations are near evolutionary equilibrium and genetic variance in total fitness is low. We develop the causal relationship between metric traits and life-history traits to show that a life-history trait is expected to have a low heritability whether or not the population is at equilibrium. This is because it is subject to all the environmental variation in the metric traits that affect it plus additional environmental variation. There is no simple prediction regarding levels of additive genetic variance in life-history traits, which may be high at equilibrium. Several other patterns in the inheritance of life-history traits are readily predicted from the causal model. These include the strength of genetic correlations between life-history traits, levels of nonadditive genetic variance, and the inevitability of genotype-environment interaction.     

Characterization of the serotoninergic system in the C57BL/6 mouse skin.

We showed expression of the tryptophan hydroxylase gene and of tryptophan hydroxylase protein immunoreactivity in mouse skin and skin cells. Extracts from skin and melanocyte samples acetylated serotonin to N-acetylserotonin and tryptamine to N-acetyltryptamine. A different enzyme from arylalkylamine N-acetyltransferase mediated this reaction, as this gene was defective in the C57BL6 mouse, coding predominantly for a protein without enzymatic activity. Serotonin (but not tryptamine) acetylation varied according to hair cycle phase and anatomic location. Serotonin was also metabolized to 5-hydroxytryptophol and 5-hydroxyindole acetic acid, probably through stepwise transformation catalyzed by monoamine oxidase, aldehyde dehydrogenase and aldehyde reductase. Activity of the melatonin-forming enzyme hydroxyindole-O-methyltransferase was notably below detectable levels in all samples of mouse corporal skin, although it was detectable at low levels in the ears and in Cloudman melanoma (derived from the DBA/2 J mouse strain). In conclusion, mouse skin has the molecular and biochemical apparatus necessary to produce and metabolize serotonin and N-acetylserotonin, and its activity is determined by topography, physiological status of the skin, cell type and mouse strain.     

Soybean isoflavonoids and their metabolic products inhibit in vitro lipoprotein oxidation in serum

Isoflavonoids are compounds present in many legumes, but are derived in the human diet mainly from soybeans and various soybean-based food products. The major isoflavonoids occurring in soy are the glycosides of genistein and daidzein. The metabolic products of genistein metabolism in humans have not been clearly shown. The two main products of daidzein metabolism in humans appear to be equol and O-desmethylangolensin. Increasing evidence suggests that oxidative modification to low-density lipoprotein is involved in atherogenesis, and that natural antioxidants that prevent or inhibit oxidative damage to low-density lipoprotein may beneficially influence atherogenesis. In the present experiments, the effects of genistein and daidzein, and the daidzein metabolites equol and O-desmethylangolensin on Cu²⁺-induced oxidation of lipoproteins in serum were examined. Three concentrations of each compound (0.1 μM, 1 μM, 10 μM) were tested for antioxidant activity in six individual serum samples. All compounds tested inhibited lipoprotein oxidation. The minimum concentration for significant inhibition was 1 μM for genistein and daidzein (P < 0.05), and 0.1 μM equol and O-desmethylangolensin (P < 0.05). Equol and O-desmethylangolensin were more potent inhibitors of in vitro lipoprotein oxidation in serum than the two major dietary isoflavonoids. This study has demonstrated that soybean isoflavonoids and metabolic products of daidzein metabolism inhibit lipoprotein oxidation in vitro. Human intervention studies are needed to determine if these compounds can influence oxidation in vivo.