Helicobacter pylori in Barrett's esophagus.

Barrett's esophagus is an anatomicoclinical state in which, due to the prolonged action of gastroesophageal reflux, the squamous epithelium is replaced by columnar epithelium. Helicobacter pylori has been implicated in the pathogenesis of various gastrointestinal disorders and has occasionally been observed in Barrett's esophagus. The aim of this study is to determine the incidence of H. pylori in Barrett's esophagus and try to establish its role in the pathogenesis of this disorder. H. pylori was observed in 31 biopsies (44.3%) of the 70 studied, mainly when the epithelium is of the gastric atrophic-fundic type (p less than 0.01). Its presence shows no relation to the degree of inflammatory activity and does not seem, therefore, to play an important role in the pathogenesis of the lesion.     

Mutations affecting the enzymes involved in the utilization of 4-aminobutyric acid as nitrogen source by the yeast Saccharomyces cerevisiae

We present genetic evidence for the enzymes 4-aminobutyrate: 2-oxoglutarate aminotransferase (EC 2.6.1.19) and succinate-semialdehyde dehydrogenase [NAD(P)+] (EC 1.2.1.16) constituting the functional pathway for the utilization of 4-aminobutyric acid as a nitrogen source by Saccharomyces cerevisiae. We show that the pathway is induced by 4-aminobutyric acid and that the presence of the pathway enzymes probably requires the integrity of a positive control element.     

Isolation of Propionibacterium acnes from central nervous system infections

Propionibacterium acnes is a common skin colonizer and its involvement in central nervous system (CNS) infections may be related with previous neurosurgical procedures. P. acnes was isolated in pure or mixed cultures from ten patients with CNS infections during a 5-year period. The clinical presentation, treatment and outcome were retrospectively reviewed. Nine out of 11 patients had CNS infections after a neurosurgical procedure. The clinical presentation was: brain abscess (five patients), subdural or epidural empyema (four patients) and shunt meningitis (one patient). Three patients had also secondary meningitis. All patients received antibiotic therapy and all abscesses and empyemas were drained. The patient with shunt meningitis cured without catheter removal. Only one patient with a brain abscess by P. acnes died, but several months thereafter and as a consequence of a Gram-negative superinfection. P. acnes is a pathogen for the CNS and infections must be surgically managed under adequate antibiotic treatment.     

Immunocytolocalization of glutamine synthetase in mesophyll and phloem of leaves ofSolanum tuberosum L.

Summary Localization of glutamine synthetase inSolanum tuberosum leaves was investigated by techniques of Western tissue printing and immunogold electron microscopy. Anti-GS antibodies used in immunolocalization recognize two peptides (45 kDa and 42 kDa) on Western blots. Antibody stained tissue prints on nitrocellulose membranes allowed low resolution localization of GS. Immunostaining was most evident in the adaxial phloem of the leaf midribs and petiole veins. High-resolution localization of glutamine synthetase by immunogold electron microscopy revealed that this enzyme occurs in both the chloroplasts and the cytosol ofS. tuberosum leaf cells. However, GS was specifically associated with the chloroplasts of mesophyll cells and with the cytoplasm of phloem companion cells. The evidence for cell-specific localization of chloroplast and cytosolic GS presented here agrees with the recently reported cell-specific pattern of expression of GUS reporter gene, directed by promoters for chloroplast and cytosolic GS form in tobacco transgenic plants. These data provide additional clues to the interpretation of the functional role of these different isoenzymes and its relationship with their specific localization.Abbreviations BSA bovine serum albumin - EM electron microscope - GOGAT glutamate synthase - GS glutamine synthetase - GUS -glucuronidase - IgG immunoglobulin - PBS phosphate buffer saline - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Vasoactive intestinal polypeptide-like immunoreactivity during reproduction in doves: influence of experience and number of offspring

To assess the possibility that vasoactive intestinal polypeptide (VIP) plays a role in naturally occurring changes in prolactin secretion in ring doves, we used immunohistochemical techniques to measure VIP-like immunoreactivity in the brain as a function of stage of the reproductive cycle. Differences between parental and nonparental birds in VIP profiles were detected in the ventral portion of the infundibular region. More specifically, there is an increase in cell size and staining intensity in the ventral infundibulum of breeding birds compared to simultaneously processed tissue taken from control animals. In both sexes, an increase in size of VIP-like immunoreactive cells is detectable during courtship and early incubation, anticipating the increase in plasma prolactin levels. VIP cell size remains elevated from about Incubation Day 14 to Brooding Day 14, and a steady decrease is observed during the remaining posthatching period, as squab begin to feed independently. Compared to parents rearing one squab, those with two young have a prolonged interval of increased infundibular VIP immunoreactivity. Furthermore, doves with no previous experience of a breeding cycle exhibit prolonged VIP-like immunoreactivity compared to experienced parents, paralleling previously described differences between these groups in parental behavior.     

Common and rare species respond to similar niche processes in macroinvertebrate metacommunities

Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. 1) Are sets of common and rare species affected by similar niche and spatial processes? 2) How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine‐grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.     

Ecophysiological factors affecting growth,sporulation and survival of the biocontrol agent Penicillium oxalicum

The effect of temperature, pH, water potential and sources of nitrogen and carbon on the biocontrol agent Penicillium oxalicum were studied in vitro. The fungus is xerotolerant, mesophillic and has a wide pH tolerance. The parameters evaluated (germination, germ tube length, growth rate and sporulation) showed different sensitivities to the environmental factors. Peptone and free amino acids gave the highest growth rates and high levels of sporulation. Xylose, mannose and fructose gave the highest growth rates and mannose induced strong sporulation. The effect of nutrients (mannose + arginine) and water potential was also studied in vivo. The xerotolerant character of the fungus was confirmed. From this study we consider Penicillium oxalicum ecologically competent to perform effectively as a biocontrol agent in the soil environment. This revised version was published online in June 2006 with corrections to the Cover Date.     

The inflorescence in Commelinaceae

The structure of the synflorescence and the flowering unit (inflorescence) in Commelinaceae are characterized. The synflorescence is polytelic and the basic inflorescence type is a terminal pedunculate thyrse with an indeterminate central axis to which several to many cincinni are attached. Each thyrse is a florescence, and each cincinnus is a partial florescence. Variations mainly in the number of cincinni and in the number of flowers on each cincinnus determine the main differences found in the inflorescences of the different genera. Hypothesized developmental processes are described, with a view to finding relationships among different models characterized in the family as well as defining characters for cladistic studies, which may be useful to depict all the variations observed and serve as a guide for future phylogenetic studies.     

Suppressor cells present in the spleens of Trypanosoma cruzi-infected mice.

Infection with Trypanosoma cruzi decreases the ability of spleen cells from mice to respond to either T cell, concanavalin A (Con A), or B cell, lipopolysaccharide (LPS), mitogens. The effect of infection on the mitogenic response depends on the elapsed time between the day of infection and the time of mitogen presentation. Responses early in infection are normal, whereas later responses to either mitogen are depressed. Spleen cells from late trypanosome-infected mice inhibit the ability of normal spleen cells to respond to Con A or LPS. The cell in the T. cruzi-infected spleen cells responsible for this effect is nonadherent, sensitive to treatment with anti-mouse thymus serum plus complement, but insensitive to treatment with anti-immunoglobulin plus complement. These data indicate that infection with T. cruzi elicits over time the generation of T cells suppressive to T and B cell mitogenic responses.