Membrane topology and multimeric structure of a mechanosensitive channel protein of Escherichia coli.

We have studied the membrane topology and multimeric structure of a mechanosensitive channel, MscL, which we previously isolated and cloned from Escherichia coli. We have localized this 15-kDa protein to the inner membrane and, by PhoA fusion, have shown that it contains two transmembrane domains with both the amino and carboxyl termini on the cytoplasmic side. Mutation of the glutamate at position 56 to histidine led to changes in channel kinetics which were dependent upon the pH on the periplasmic, but not cytoplasmic side of the membrane, providing additional evidence for the periplasmic positioning of this part of the molecule. Tandems of two MscL subunits expressed as a single polypeptide formed functional channels, suggesting an even number of transmembrane domains per subunit (amino and carboxyl termini on the same side of the membrane), and an even number of subunits per functional complex. Finally, cross-linking studies suggest that the functional MscL complex is a homohexamer. In summary, these data are all consistent with a protein domain assignment and topological model which we propose and discuss.     

Thermo- and Photoperiodicity and Involvement of Gibberellins during Day and Night Cycle on Elongation Growth of Begonia x hiemalis Fotsch

The effects of thermo- and photoperiodicity on elongation growth and on endogenous level of gibberellins (GAs) in Begonia x hiemalis during various phases of the day-night cycle have been studied. Plant tissue was harvested during the day and night cycle after temperature and photoperiodic treatments and analyzed for endogenous GAs using combined gas chromatography and mass spectrometry. Elongation growth increased when the difference between day and night temperature (DIF = DT − NT) increased from a negative value (−9.0 and −4.5°C) to zero and with increasing photoperiod from 8 to 16 h. When applied to the youngest apical leaf, gibberellins A₁, A₄, and A₉ increased the elongation of internodes and petioles. GA₄ had a stronger effect on elongation growth than GA₁ and GA₉. In relative values, the effect of these GAs decreased when DIF increased from −9 to 0°C. The time of applying the GAs during a day and night cycle had no effect on the growth responses. In general, endogenous levels of GA₁₉ and GA₂₀ were higher under negative DIF compared with zero DIF. The level of endogenous GA₁ in short day (SD)-grown plants was higher under zero DIF than under negative DIF, but this relationship did not appear in long day (LD)-grown plants. The main effects of photoperiod seem to be a higher level of GA₁₉ and GA₁ at SD compared with LD, whereas GA₂₀ and GA₉ show the opposite response to photoperiod. No significant differences in endogenous level of GA₁, GA₉, GA₁₉, and GA₂₀ were found for various time points during the diurnal day and night cycle. Endogenous GA₂₀ was higher in petiole and leaf compared with stem, whereas there were no differences of GA₁, GA₉, and GA₁₉ between plant parts. No clear relationship was found between elongation of internodes and petioles and levels of endogenous GAs. Received December 26 1996; accepted July 1, 1997     

A School Health Project Can Uplift the Health Status of School Children in Nepal

BackgroundSchool health is effective in helping students achieve health literacy, enhance their health-related behaviors, and thereby improve their health status. However, in resource-limited countries, evidence is limited to show the impact of school health. We determined the association of the school health and nutrition (SHN) project activities on students’ a) health knowledge, b) hygiene practices, and c) health outcomes, one year after the project completion.MethodsThis is a cross-sectional study conducted among the schools with the SHN project and without the project in four districts of Nepal. We recruited 604 students from six schools in the project group and 648 students from other six schools in the comparison group. We used a self-administered questionnaire to collect the data, and analyzed them using regression models and a structural equation model (SEM).ResultsStudents from the SHN project group reported the decreased odds of worm infestation (AOR = 0.50, 95% CI: 0.34 to 0.75) and diarrhea/ dysentery infection (AOR = 0.67, 95% CI: 0.47 to 0.97) compared to those in the comparison group. Furthermore, the SEM analysis also showed that the students in the project group were more likely to have better health outcomes (β = 0.03, p< 0.05).ConclusionStudents in the SHN project group were more likely to have better health outcomes compared to those in the comparison group, even after one year of the project completion. As it can bring about sustainable changes for students, it should be scaled up in other parts of the country.     

Development of species‐specific primers for rapid diagnosis of Tetranychus urticae,T. kanzawai,T. phaselus and T. truncatus (Acari: Tetranychidae)

Species diagnosis is of the utmost importance to both pest management and plant quarantine services. Because of difficulties in the morphological diagnosis of spider mites, molecular techniques are of great value to rapidly and accurately diagnose closely related species. We examined four species of genus Tetranychus (the green and red forms of T. urticae, and T. kanzawai, T. phaselus and T. truncatus), which are found in Korea and are of significance to plant quarantine services. DNA samples isolated from a single egg, larva or adult weighed 64–188 ng. We designed species‐specific primers by performing sequence alignment for 107 sequences of the ribosomal internal transcribed spacer 2 (ITS2) region, which we obtained from GenBank, and sequences generated in this study. Specific nucleotides of each species were selected for designing primers specific for each species. Each species‐specific primer pair, when used to perform PCR analyses, detected only the species from which it originated. However, a T. urticae‐specific primer pair did not discriminate between the green and red forms of this species. These species‐specific primers can be applied in practice for the rapid and accurate diagnosis of spider mite species in plant quarantine and in agricultural fields.     

Desmarestia antarctica (Desmarestiales,Phaeophyceae), a new ligulate Antarctic species with an endophytic gametophyte

Desmarestia antarctica Moe & Silva, a new species from the Antarctic Peninsula and the Scotia Arc, is distinguished from all other ligulate members of the genus by the arrangement of zoosporangia, which are produced together with paraphyses in a raised sorus. Among all species in the genus, onlyD. anceps Montagne shares this feature.Desmarestia antarctica is the first species of the genus for which an endophytic gametophyte is demonstrated, the usual host beingCurdiea racovitzae De Wildeman, a red alga of the familyGracilariaceae. The sporophyte contains only a moderate concentration of acid compared to Northern Hemisphere ligulate species, while physodes that probably contain polyphenolic compounds form noticeable speckles and dark margins in preserved plants. Often more than one axis arises from a single holdfast, probably as the result of compounding rather than proliferation.Dedicated to Prof. DrLothar Geitler on the occasion of the 90th anniversary of his birthday.     

Dietary zinc status reversibly alters both the feeding behaviors of the rats and gene expression patterns in diencephalon

Nutritional status influences feeding behaviors, food preferences, and taste sensations. For example, zinc-deficient rats have been reported to show reduced and cyclic food intake patterns with increased preferences for NaCl. Although some impairments of the central nervous and endocrine systems have been speculated to be involved in these phenomena, the effects of short-term zinc deficiency on the brain have not been well examined to date. In this study, we performed a comprehensive analysis of the gene expression patterns in the rat diencephalon, which is a portion of the brain that includes the hypothalamus and thalamus, after short-term zinc deficiency and also during zinc recovery. The rats showed reduced and cyclic food intake patterns with increased salt preferences after a 10-day dietary zinc deficiency. A comparative analysis of their diencephalons using cDNA microarrays revealed that approximately 1% of the genes expressed in the diencephalons showed significantly altered expression levels. On the other hand, a 6-day zinc supplementation following the deprivation allowed for the recovery to initial food intake behaviors and salt preferences. The expression levels of most of the genes that had been altered by exposure to zinc deficient conditions were also recovered. These results show that feeding behaviors, taste preferences and gene expression patterns in the diencephalon respond quickly to changing zinc levels.