Identification of a receptor for an extinct virus

The resurrection of endogenous retroviruses from inactive molecular fossils has allowed the investigation of interactions between extinct pathogens and their hosts that occurred millions of years ago. Two such paleoviruses, chimpanzee endogenous retrovirus-1 and -2 (CERV1 and CERV2), are relatives of modern MLVs and are found in the genomes of a variety of Old World primates, but are absent from the human genome. No extant CERV1 and -2 proviruses are known to encode functional proteins. To investigate the host range restriction of these viruses, we attempted to reconstruct functional envelopes by generating consensus genes and proteins. CERV1 and -2 enveloped MLV particles infected cell lines from a range of mammalian species. Using CERV2 Env-pseudotyped MLV reporters, we identified copper transport protein 1 (CTR1) as a receptor that was presumably used by CERV2 during its ancient exogenous replication in primates. Expression of human CTR1 was sufficient to confer CERV2 permissiveness on otherwise resistant hamster cells, and CTR1 knockdown or CuCl(2) treatment specifically inhibited CERV2 infection of human cells. Mutations in highly conserved CTR1 residues that have rendered hamster cells resistant to CERV2 include a unique deletion in a copper-binding motif. These CERV2 receptor-inactivating mutations in hamster CTR1 are accompanied by apparently compensating changes, including an increased number of extracellular copper-coordinating residues, and this may represent an evolutionary barrier to the acquisition of CERV2 resistance in primates.     

A pilot comparative study of fissurectomy/diltiazem and fissurectomy/botulinum toxin in the treatment of chronic anal fissure

Background  

Treatment of chronic anal fissure (CAF) by fissurectomy with botulinum toxin A (BTA) injection results in a healing rate of greater than 90%. BTA injection, however, can cause incontinence and perianal sepsis. The decrease in sphincter pressure following topical treatment with 2% diltiazem cream (DTC) is comparable to that following BTA injection but with potentially fewer complications and at less cost. We report the shortterm results of a pilot study comparing fissurectomy with BTA and fissurectomy followed by DTC for the treatment of CAF.     

VIPP1, a nuclear gene of Arabidopsis thaliana essential for thylakoid membrane formation

The conversion of light to chemical energy by the process of photosynthesis is localized to the thylakoid membrane network in plant chloroplasts. Although several pathways have been described that target proteins into and across the thylakoids, little is known about the origin of this membrane system or how the lipid backbone of the thylakoids is transported and fused with the target membrane. Thylakoid biogenesis and maintenance seem to involve the flow of membrane elements via vesicular transport. Here we show by mutational analysis that deletion of a single gene called VIPP1 (vesicle-inducing protein in plastids 1) is deleterious to thylakoid membrane formation. Although VIPP1 is a hydrophilic protein it is found in both the inner envelope and the thylakoid membranes. In VIPP1 deletion mutants vesicle formation is abolished. We propose that VIPP1 is essential for the maintenance of thylakoids by a transport pathway not previously recognized.     

Vipp1 deletion mutant of Synechocystis: a connection between bacterial phage shock and thylakoid biogenesis?

Plant chloroplasts originated from an endosymbiotic event by which an ancestor of contemporary cyanobacteria was engulfed by an early eukaryotic cell and then transformed into an organelle. Oxygenic photosynthesis is the specific feature of cyanobacteria and chloroplasts, and the photosynthetic machinery resides in an internal membrane system, the thylakoids. The origin and genesis of thylakoid membranes, which are essential for oxygenic photosynthesis, are still an enigma. Vipp1 (vesicle-inducing protein in plastids 1) is a protein located in both the inner envelope and the thylakoids of Pisum sativum and Arabidopsis thaliana. In Arabidopsis disruption of the VIPP1 gene severely affects the plant's ability to form properly structured thylakoids and as a consequence to carry out photosynthesis. In contrast, Vipp1 in Synechocystis appears to be located exclusively in the plasma membrane. Yet, as in higher plants, disruption of the VIPP1 gene locus leads to the complete loss of thylakoid formation. So far VIPP1 genes are found only in organisms carrying out oxygenic photosynthesis. They share sequence homology with a subunit encoded by the bacterial phage shock operon (PspA) but differ from PspA by a C-terminal extension of about 30 amino acids. In two cyanobacteria, Synechocystis and Anabaena, both a VIPP1 and a pspA gene are present, and phylogenetic analysis indicates that VIPP1 originated from a gene duplication of the latter and thereafter acquired its new function. It also appears that the C-terminal extension that discriminates VIPP1 proteins from PspA is important for its function in thylakoid formation.     

Histamine and cyclic AMP in isolated canine parietal cells.

The relationship between cyclic AMP production and the response of isolated canine parietal cells to histamine has been examined. Histamine increased cyclic AMP generation, and this effect correlated with histamine stimulation of oxygen consumption and aminopyrine accumulation. Metiamide inhibited histamine-stimulated cyclic AMP generation and oxygen consumption in a parallel fashion. At concentrations below 100 microM, isobutyl AMP production and oxygen consumption in a similar fashion. However, with IMX above 100 microM, histamine caused no further increases in oxygen consumption, despite markedly enhanced cyclic AMP generation. Neither carbachol nor gastrin increased cyclic AMP production beyond that produced by IMX alone, and the combinations of histamine and carbachol and of histamine and gastrin produced no greater cyclic AMP generation than produced by histamine. These findings support a close relationship between cyclic AMP production and the action of histamine but not of carbachol or gastrin on isolated parietal cells. The mechanisms underlying the potentiating interactions between histamine, carbachol, and gastrin involve step(s) beyond stimulation of cyclic AMP generation.     

Actions of histamine, secretin, and PGE2 on cyclic AMP production by isolated canine fundic mucosal cells.

Cyclic AMP production was studied in isolated canine fundic gastric mucosal cells. Histamine, prostaglandin E2 (PGE2), and secretin increased cyclic AMP production by unenriched mucosal cells. In separated cell fractions, histamine stimulation of cyclic AMP production correlated with the parietal cell content of the fractions. Secretin in concentrations above 1 nM stimulated cyclic AMP production, and this effect correlated with the pepsinogen content of the separated cell fractions. At concentrations above 1 microM, PGE2 stimulated cyclic AMP production; this effect was found in all separated cell fractions and was not associated with any of the available cell markers. PGE2 stimulation of cyclic AMP production was, however, negatively correlated with the parietal cell content. Thus, histamine stimulated cyclic AMP production by parietal cells and secretin stimulated production of cyclic AMP by chief cells. PGE2 stimulation of cyclic AMP production could not be localized to a single cell type but occurred primarily in nonparietal cells.     

Gastrin receptors on isolated canine parietal cells.

The receptors in the fundic mucosa that mediate gastrin stimulation of acid secretion have been studied. Synthetic human gastrin-17-I (G17) with a leucine substitution in the 15th position ( [Leu15]-G17) was iodinated by chloramine T; high saturable binding was found to enzyme-dispersed canine fundic mucosal cells. 127I-[Leu15]-G17, but not 127I-G17, retained binding potency and biological activity comparable with uniodinated G17. Fundic mucosal cells were separated by size by using an elutriator rotor, and specific 125I-[Leu-15]-G17 binding in the larger cell fractions was highly correlated with the distribution of parietal cells. There was, however, specific gastrin binding in the small cell fractions, not accounted for by parietal cells. Using sequential elutriation and stepwise density gradients, highly enriched parietal and chief cell fractions were prepared; 125I-[Leu15]-G17 binding correlated positively with the parietal cell (r = 0.98) and negatively with chief cell content (r = -0.96). In fractions enriched to 45-65% parietal cells, specific 125I-[Leu15]-G17 binding was rapid, reaching a steady state at 37 degrees C within 30 min. Dissociation was also rapid, with the rate similar after 100-fold dilution or dilution plus excess pentagastrin. At a tracer concentration from 10 to 30 pM, saturable binding was 7.8 +/- 0.8% per 10(6) cells (mean +/- SE) and binding in the presence of excess pentagastrin accounted for 11% of total binding. G17 and carboxyl terminal octapeptide of cholecystokinin (26-33) were equipotent in displacing tracer binding and in stimulating parietal cell function ( [14C]aminopyrine accumulation), whereas the tetrapeptide of gastrin (14-17) had a much lower potency. Proglumide inhibited gastrin binding and selectively inhibited gastrin stimulation of parietal cell function. Canine parietal cells have specific receptors for gastrin that mediate stimulation of parietal cell function. Gastrin receptors were undetectable on chief cells, and yet present on another smaller mucosal cell(s).     

Prophylactic versus Selective Use of Surfactant in Preventing Morbidity and Mortality in Preterm Infants

No abstract available.     

Frequency, intensity, species, and strains of oral Candida vary as a function of host age.

While the age of the host has been suggested as a determining factor in yeast carriage, no studies in which the genetic relatedness of isolates has been assessed in combination with the frequency and intensity of carriage as a function of host age have been performed in a single geographical locale and over a short time window. Therefore, by using a simple plating protocol to determine the frequency and intensity of carriage, sugar assimilation patterns to determine species, and Southern blot hybridization with the DNA fingerprinting probe Ca3 combined with computer-assisted analysis to determine the genetic relatedness of strains of Candida albicans, yeast carriage was analyzed as a function of age. All test individuals lived in the Iowa City, Iowa, locale and, except for some of the 0.5- to 1.5-year-olds, were dentate. The results demonstrate that for this test population, the frequency, average intensity, predominant species, and genetic relatedness of C. albicans strains varied as a function of host age. In addition, comparison with oral commensal organisms from the Ann Arbor, Mich., locale confirms the geographical specificity of C. albicans strains and the existence of an Iowa City-enriched strain which is most prevalent in elderly individuals.