Prevalence of gene sequences coding for hypervariable regions of Opa (protein II) in Neisseria gonorrhoeae

Opas (protein IIs) are a family of surface-exposed proteins of Neisseria gonorrhoeae. Each strain of N. gonorrhoeae has multiple (10-11) genes encoding for Opas. Identifiable elements in opa genes include the coding repeat within the signal sequence, conserve 5' and 3' regions, and hypervariable regions (HV1 and HV2) located within the structural gene. N. gonorrhoeae strains appear to have many biological properties in common that are either HV-region-mediated or associated with the presence of specific HV regions, suggesting that HV regions could be found in many clinical isolates. Oligonucleotides from three source strains representing three conserved regions of opa, 12 HV1 regions, and 14 HV2 regions were used by dot blot analysis to probe 120 clinical isolates of N. gonorrhoeae. The probe for the coding repeat hybridized to all 120 strains, the 3' conserved-region probe reacted with 98% of the strains, and the 5' conserved-region probe with 90% of the strains. Nine HV1 probes hybridized to 3.3-39.2% of the strains, and 13 of the HV2 probes hybridized to 1.7-25% of the isolates. Analysis of the number of probes that hybridized to each of the isolates showed that 19% did not hybridize with any of the HV1 probes and 25% did not hybridize with any of the HV2 probes. Approximately three-quarters of the isolates hybridized with one, two or three of the HV1 probes or one, two or three of the HV2 probes; 89% of the isolates hybridized to least one HV1 or one HV2 probe. The data indicate that some genes encoding HV regions of N. gonorrhoeae Opa proteins are widely distributed in nature.     

13C-nuclear magnetic resonance spectra of compounds containing β-D-fructofuranosyl groups or residues

¹³C-N.m.r. spectra have been recorded for sucrose, melezitose, levan, inulin, palatinose, and D-fructose. Except for the last, each compound contains a different O-substituted D-fructofuranose residue or group, or β-D-fructofuranosyl residue or group. On the basis of chemical-shift displacements, resulting from O-substitution at specific carbon atoms, resonances can be assigned to the carbon atoms of the β-D-fructofuranosyl residue. Fortuitously, the α-D-glucopyranosyl group present in some of these compounds exhibits resonances that do not obscure the β-D-fructofuranosyl resonances. O-Substitution of the β-D-fructofuranosyl residue causes a downfield displacement of the corresponding, linked-C resonance; however, the other major resonances of this residue are not affected by bulky substituents. Members of a series of levan fractions, the products of partial, acid hydrolysis of Streptoccoccus salivarius levan, were then examined for changes in relative degree of branching.     

Splicing of yeast tRNA precursors: a two-stage reaction.

Soluble extracts of S. cerevisiae splice tRNA precursors which contain intervening sequences. The reaction goes to completion and requires ATP for the production of mature sequence tRNA. In the absence of ATP, half-tRNA molecules accumulate. Similar half-tRNA molecules appear as kinetic intermediates and accumulate if splicing is inhibited with pure, mature tRNA. Half-tRNA molecules have been purified. These half-tRNAs are efficiently ligated in an ATP-dependent reaction that is inhibited by added mature tRNA. The product of ligation is the expected mature sequence tRNA. The excised intervening sequence has also been identified. These results suggest an enzymatic mechanism for splicing which involves two independent steps.     

Cocaine and lithium: neurobiological antagonism in the serotonin biosynthetic system in rat brain.

Cocaine reduced the uptake and conversion of tryptophan to serotonin in rat brain striate tissue and enhanced tryptophan hydroxylase activity in lateral midbrain cell bodies and striate nerve endings. Lithium augments the uptake and conversion measures and reduces the enzyme activity in cell bodies and nerve endings. The cocaine effects on all four measures were antagonized by three days of lithium pretreatment.     

Lysogenization by bacteriophage lambda: III. - Multiplicity dependent phenomena occuring upon infection by lambda

Lysogenization by bacteriophage λ involves at least two multiplicity dependent processes [2, 3]. For the purpose of comparison, other multiplicity dependent phenomena which occur upon infection by λ have been reviewed. These include the inhibition of host'syntheses as already described by others [9] and two phenomena which are shown to be multiplicity dependent, host killing by phage unable to replicate and inhibition of cell division. It is also demonstrated that, in at least two cases (lysogenization by phage able to replicate and killing by phage unable to replicate) the multiplicity dependent character disappears at slow cellular growth rates. The significance of these results is discussed with regard to three models which are susceptible to account for multiplicity dependent phenomena in general.     

Rainfall manipulation experiments as simulated by terrestrial biosphere models: Where do we stand?

Changes in rainfall amounts and patterns have been observed and are expected to continue in the near future with potentially significant ecological and societal consequences. Modelling vegetation responses to changes in rainfall is thus crucial to project water and carbon cycles in the future. In this study, we present the results of a new model‐data intercomparison project, where we tested the ability of 10 terrestrial biosphere models to reproduce the observed sensitivity of ecosystem productivity to rainfall changes at 10 sites across the globe, in nine of which, rainfall exclusion and/or irrigation experiments had been performed. The key results are as follows: (a) Inter‐model variation is generally large and model agreement varies with timescales. In severely water‐limited sites, models only agree on the interannual variability of evapotranspiration and to a smaller extent on gross primary productivity. In more mesic sites, model agreement for both water and carbon fluxes is typically higher on fine (daily–monthly) timescales and reduces on longer (seasonal–annual) scales. (b) Models on average overestimate the relationship between ecosystem productivity and mean rainfall amounts across sites (in space) and have a low capacity in reproducing the temporal (interannual) sensitivity of vegetation productivity to annual rainfall at a given site, even though observation uncertainty is comparable to inter‐model variability. (c) Most models reproduced the sign of the observed patterns in productivity changes in rainfall manipulation experiments but had a low capacity in reproducing the observed magnitude of productivity changes. Models better reproduced the observed productivity responses due to rainfall exclusion than addition. (d) All models attribute ecosystem productivity changes to the intensity of vegetation stress and peak leaf area, whereas the impact of the change in growing season length is negligible. The relative contribution of the peak leaf area and vegetation stress intensity was highly variable among models.