Equilibria of the anomeric and ring forms of ammonium 3-deoxy-d-manno-octulosonate in deuterium oxide

The tautomeric composition of a solution of ammonium 3-deoxy-d-manno-octulosonate (KDO, 1a) in D₂O at 28° was assessed by means of ¹³ C-F.t.-n.m.r. spectroscopy. The results revealed the presence of 6?0 and 11 % of the α and β anomers of the pyranose, and 20 and 9 % of the two furanoses, and suggested, but did not unequivocally prove, that the major furanose form is the α anomer. To facilitate interpretation of the spectral results for 1, ammonium 3,5-dideoxy-d-arabino(or ribo)-octulosonate (3a) was prepared by the reaction of 5-deoxy-d-erythro-pentose with sodium oxalacetate at pH 11. A chromatographically homogeneous, noncrystalline sample of 3 was obtained by lyophilization, and characterized as its (4-nitrophenyl)hydrazone (m.p. 162-163°). The ¹³C-n.m.r. spectrum of a solution of 3a in D₂O revealed it to be substantially all in the α-pyranose form. No signals were obtained for the possible 1,4-lactone of 3. As the 1,5-lactone and furanose forms are impossible for 3, it exhibited no signals analogous to those attributed to furanoid 1. On the basis of these results for 3, the two lactone forms of 1 were excluded from consideration, and the three pairs of ¹³C-n.m.r. signals observed at ≈45, 86, and 104 p.p.m. were assigned to the furanose forms of 1.     

Effect of Ca2+ and Mg2+ upon the reassociation byEscherichia coli of material released by ethylenediaminetetraacetate

Parameters involved in reconstitution of the outer membrane permeability described by Brunner, Caputo, and Treick [3] were examined. The most efficient reconstitution was obtained when divalent cations accompanied the addition of exogenous outer membrane material. Studies indicated that the effectiveness of Ca²⁺ or Mg²⁺ to promote reassociation of outer membrane material, and subsequent protection against actinomycin D, was dependent upon the strain ofEscherichia coli. More specifically, the data suggest that the effectiveness of the different divalent cations in promoting reassociation was determined by the relative amounts of F1 and F2 fractions released by ethylenediaminetetraacetate (EDTA). Reconstitution was shown by cell survival to be as high as 25% and dependent upon the total amount of material released from the outer membrane by EDTA. Between 50 and 80% of the bound material could be removed from the cells by subsequent EDTA treatment.     

Social organization of confined male collared lemmings (Dicrostonyx groenlandicus Traill)

This study describes and quantifies the social organization and agonistic behaviour of adult male collared lemmings (Dicrostonyx groenlandicus) in an indoor enclosure. Five groups of four lemmings were observed during separate 8-day tests. Experimental design permitted an increase in group size while density remained constant. When in groups of two, males established stable dominant-subordinate relationships and, when in groups of four, they formed stable non-linear dominance hierarchies. For either group size, frequency of agonistic behaviour declined over time. Habituation, formation of dominance relationships and spatio-temporal partitioning of space are suggested as possible explanations of this decline. Percentage of initial body weight lost during the experiments varied inversely with social rank. Possible causes of this weight loss are discussed. Social relationships in this study are discussed in light of field observations of male lemming home range distribution.     

The stepwise synthesis of methyl α-isomaltooligoside derivatives and methyl α-isomaltopentaoside

Methyl 2,3,4-tri-O-benzyl-α-D-glucopyranoside was treated with 2,3,4-tri-O-benzyl-6-O-(N-phenylcarbamoyl)-1-O-tosyl-D-glucopyranose in diethyl ether to give methyl 2,3,4,2',3',4'-hexa-O-benzyl-6'-O-(N-phenylcarbamoyl)-α-isomaltoside. The disaccharide was decarbanilated in ethanol with sodium ethoxide to give methyl 2,3,4,2',3',4'-hexa-O-benzyl-α-isomaltoside. The sequence of coupling with the same 1-O-tosyl-D-glucose derivative followed by removal of the N-phenylcarbamate group was repeated until the hexasaccharide derivative, methyl octadeca-O-benzyl-α-isomaltohexaoside, was formed. Methyl α-isomaltopentaoside was prepared by debenzylation of the corresponding benzylated oligosaccharide. The structures of the oligosaccharides were determined with the aid of both ¹H- and ¹³C-n.m.r. spectroscopy. From spectral data, we estimate the coupling reaction to be 95% stereoselective.     

Xeromammography in the Early Detection of Breast Cancer: Community Hospital Experience and Approach

Community hospitals can do much in the general effort toward earlier detection of breast cancer. Using xeromammography in the department of general radiology of one community hospital, 21 cases of occult carcinoma were detected in 2,392 patients in a two year period. Patients were both symptomatic and asymptomatic. This percentage is comparable to results in previously published series of similar patient populations, and can be expected to be slightly higher than screening populations of totally asymptomatic patients. In 24 percent of cases of occult carcinoma there was axillary node involvement, compared with 42 percent axillary node involvement in cases of nonoccult carcinoma.Early detection efforts are currently centered on improving thoroughness in physical examinations, stressing breast self-examination and identifying patients in high-risk categories. These, together with proper periodic use of mammograms, will yield the highest rate of early carcinoma detection until more sensitive biologic markers are developed.     

VAMP2 and synaptotagmin mobility in chromaffin granule membranes: implications for regulated exocytosis

Granule-plasma membrane docking and fusion can only occur when proteins that enable these reactions are present at the granule-plasma membrane contact. Thus, the mobility of granule membrane proteins may influence docking and membrane fusion. We measured the mobility of vesicle associated membrane protein 2 (VAMP2), synaptotagmin 1 (Syt1), and synaptotagmin 7 (Syt7) in chromaffin granule membranes in living chromaffin cells. We used a method that is not limited by standard optical resolution. A bright flash of strongly decaying evanescent field produced by total internal reflection was used to photobleach GFP-labeled proteins in the granule membrane. Fluorescence recovery occurs as unbleached protein in the granule membrane distal from the glass interface diffuses into the more bleached proximal regions, enabling the measurement of diffusion coefficients. We found that VAMP2-EGFP and Syt7-EGFP are mobile with a diffusion coefficient of ∼3 × 10⁻¹⁰ cm²/s. Syt1-EGFP mobility was below the detection limit. Utilizing these diffusion parameters, we estimated the time required for these proteins to arrive at docking and nascent fusion sites to be many tens of milliseconds. Our analyses raise the possibility that the diffusion characteristics of VAMP2 and Syt proteins could be a factor that influences the rate of exocytosis.     

Modelling to infer the role of animals in gambiense human African trypanosomiasis transmission and elimination in the DRC

Gambiense human African trypanosomiasis (gHAT) has been targeted for elimination of transmission (EoT) to humans by 2030. Whilst this ambitious goal is rapidly approaching, there remain fundamental questions about the presence of non-human animal transmission cycles and their potential role in slowing progress towards, or even preventing, EoT. In this study we focus on the country with the most gHAT disease burden, the Democratic Republic of Congo (DRC), and use mathematical modelling to assess whether animals may contribute to transmission in specific regions, and if so, how their presence could impact the likelihood and timing of EoT.By fitting two model variants—one with, and one without animal transmission—to the human case data from 2000–2016 we estimate model parameters for 158 endemic health zones of the DRC. We evaluate the statistical support for each model variant in each health zone and infer the contribution of animals to overall transmission and how this could impact predicted time to EoT.We conclude that there are 24/158 health zones where there is substantial to decisive statistical support for some animal transmission. However—even in these regions—we estimate that animals would be extremely unlikely to maintain transmission on their own. Animal transmission could hamper progress towards EoT in some settings, with projections under continuing interventions indicating that the number of health zones expected to achieve EoT by 2030 reduces from 68/158 to 61/158 if animal transmission is included in the model. With supplementary vector control (at a modest 60% tsetse reduction) added to medical screening and treatment interventions, the predicted number of health zones meeting the goal increases to 147/158 for the model including animal transmission. This is due to the impact of vector reduction on transmission to and from all hosts.     

siRNA-directed inhibition of HIV-1 infection

RNA interference silences gene expression through short interfering 21 23-mer double-strand RNA segments that guide mRNA degradation in a sequence-specific fashion. Here we report that siRNAs inhibit virus production by targeting the mRNAs for either the HIV-1 cellular receptor CD4, the viral structural Gag protein or green fluorescence protein substituted for the Nef regulatory protein. siRNAs effectively inhibit pre- and/or post-integration infection events in the HIV-1 life cycle. Thus, siRNAs may have potential for therapeutic intervention in HIV-1 and other viral infections.