Diversity of sulfate-reducing bacteria from an extreme hypersaline sediment, Great Salt Lake (Utah)

The diversity of sulfate-reducing bacteria (SRB) inhabiting the extreme hypersaline sediment (270 g L(-1) NaCl) of the northern arm of Great Salt Lake was studied by integrating cultivation and genotypic identification approaches involving PCR-based retrieval of 16S rRNA and dsrAB genes, the latter encoding major subunits of dissimilatory (bi) sulfite reductase. The majority (85%) of dsrAB sequences retrieved directly from the sediment formed a lineage of high (micro) diversity affiliated with the genus Desulfohalobium, while others represented novel lineages within the families Desulfohalobiaceae and Desulfobacteraceae or among Gram-positive SRB. Using the same sediment, SRB enrichment cultures were established in parallel at 100 and at 190 g L(-1) NaCl using different electron donors. After 5-6 transfers, dsrAB and 16S rRNA gene-based profiling of these enrichment cultures recovered a SRB community composition congruent with the cultivation-independent profiling of the sediment. Pure culture representatives of the predominant Desulfohalobium-related lineage and of one of the Desulfobacteraceae-affilated lineages were successfully obtained. The growth performance of these isolates and of the enrichment cultures suggests that the sediment SRB community of the northern arm of Great Salt Lake consists of moderate halophiles, which are salt-stressed at the in situ salinity of 27%.     

Coexpression of Notch3 and Rgs5 in the pericyte-vascular smooth muscle cell axis in response to pulp injury

Recent studies have shown that the pulp of human teeth contains a population of cells with stem cell properties and it has been suggested that these cells originate from pericytes. Molecules of the Notch signaling pathway regulate stem cell fate specification, while Rgs5 represents an excellent marker for pericytes. Pathological conditions such as dental trauma and carious lesion stimulate pulp stem cells to elaborate reparative dentin. Previous studies have shown that genes involved in the Notch pathway are activated in response to pulp injury in rodent and humans. To demonstrate the importance of pericytes as a source of stem cells during dental repair, we have studied Rgs5 and Notch3 mRNA expression by in situ hybridization in developing, adult intact and injured rodent teeth. Furthermore, we have examined the distribution of Notch3 protein in carious and injured human teeth using immunohistochemistry. Overlapping expression patterns of Rgs5 and Notch3 were observed during rodent tooth development as well as immediately after injury. Both genes were expressed in vascular structures during development and in perivascular and single capillary cells of injured teeth. However, the expression patterns of Rgs5 and Notch3 were different during tooth repair, with relatively extensive Rgs5 expression along the pericyte-vascular smooth muscle cell axis in central pulp arterioles. These results show co-expression of Rgs5 and Notch3 in pericytes of developing and injured teeth and furthermore indicate the importance of vascular-derived stem cells during pulp healing.     

UPTAKE OF GLUCOSE ANALOGUES BY RAT BRAIN CORTEX SLICES: A KINETIC ANALYSIS BASED UPON A MODEL

Abstract— In slice preparations the exchange of dissolved substances between cells and incubation medium is delayed by diffusion through the extracellular space. The delay may seriously interfere with the study of membrane transport in terms of unidirectional fluxes across the cell membranes. A three-compartment serial model has been developed to describe exchange between slice and incubation medium. By aid of this model it is shown that the diffusion delay prevents determination of unidirectional fluxes for the two non-metabolizable glucose analogues 3-O-methylglucose and α-methyl-glucosidc. The membrane transport of the slowly transported α-methylglucoside can however be examined by aid of the model whereas the transport of 3-O-methylglucose is so rapid that it can not be examined with respect to V_max K_m and K_r. An attempt to determine these parameters will result in falsely large values which reflect extracellular diffusion and not membrane transport.     

Ontogenetic development of diffusional restriction to protein at the pial surface of the rat brain: an electron microscopical study

Blood–brain, blood–CSF and ventricular CSF–brain barriers to protein, are present very early in brain development. In order to determine whether the outer pial surface of the brain also restricts free penetration of macromolecules, the dorso-lateral part of the sensorimotor cortex from rats at embryonic day 12 (E12), 14, 16, and 18, the day of birth (P0), and adult rat, was studied by electron microscopical techniques. Potassium ferrocyanide, Ruthenium Red and immunogold labelling of endogenous albumin were used to investigate junctional structures and the sites of restriction to albumin diffusion. At E12, large fenestrated sinusoids were present in the pia-arachnoid and the brain surface was formed by an incomplete layer of neuroepithelial and presumptive radial glial end feet, but capillaries in the pia-arachnoid showed no fenestrations at E14 or later. From E14, we observed the progressive appearance of distinct junctional structures between the glial end feet which, to our knowledge, have not been described before. Analysis of albumin distribution from E16 to P0 suggests that the junctions may contribute to restriction of diffusion between the subarachnoid space and the brain extracellular fluid. The restriction to the penetration of protein at both the pial and the ependymal surfaces may ensure the isolation of the neural environment during a critical phase in development of the nervous system. The changes in the structure of the junctions between E12 and P0 suggests a transitional series of embryonic junctional types, which eventually give way to the mature junctions of the adult. Parallels between the embryonic glial junctions and junctions described in adult invertebrate brain, suggest some interesting parallels in junctional development in phylogeny and ontogeny.     

The effect of intravital chelation with dimercaprol,calcium disodium edetate, 1-10-phenantroline and 2,2′-dipyridyl on the sulfide silver stainability of the rat brain

Summary Dimercaprol, calcium disodium edetate, 1-10-phenantroline and 2,2-dipyridyl were injected intraperitoneally in adult albino rats in doses ranging from 10 to 1500 mg per kg body weight. Ten animals were injected intracerebrally. At various survival times (2 minutes to several hours) their effects on the staining pattern of heavy metals as revealed by the sulfide silver method of Timm were determined. EDTA was virtually ineffective while dimercaprol, phenantroline and dipyridyl reduced the staining in many regions of the brain. A noteworthy effect of phenantroline was that it reduced the staining of a cortical area, corresponding remarkably well in extent, shape and location to the neocortical somatosensory area.     

The matri-cellular proteins 'cysteine-rich, angiogenic-inducer, 61' and 'connective tissue growth factor' are regulated in experimentally-induced sepsis with multiple organ dysfunction

Organ failure is a severe complication in sepsis for which the pathophysiology remains incompletely understood. Recently, the matri-cellular cysteine-rich, angiogenic induced, 61 (Cyr61/CCN1); connective tissue growth factor (Ctgf/CCN2); and nephroblastoma overexpressed gene (Nov/CCN3) (CCN)-protein family have been attributed organ-protective properties. Their expression is sensitive to mediators of sepsis pathophysiology but a potential role in sepsis remains elusive. To provide an initial assessment, 50 rats were subjected to 18?h of cecal-ligation and puncture or sham operation. Hepatic and pulmonary CCN1 mRNA displayed an average 7.4- and 3.3-fold induction, while its cardiac expression was unchanged. The changes coincided with excessive hepatic and pulmonary inflammatory gene activation and a restricted cardiac inflammation. Furthermore, hepatocytes displayed a dosage-dependent CCN1 mRNA response in?vitro, supporting a cytokine-mediated CCN1 regulation in sepsis. CCN2 mRNA was 2.2-fold induced in the liver, while 2.0-fold and 1.4-fold repressed in the heart and lung. Meanwhile, it did not respond to TNF-α exposure in?vitro, which indicates different means of regulation than for CCN1. Taken together, this study provides the first evidence for multi-organ regulation of CCN1 and CCN2 in early stages of sepsis, and implies the eruption of inflammatory mediators as a potential mechanism behind the observed CCN1 regulation.     

Benthic algal biomass in an unshaded first-order lowland stream: distribution and regulation

The vertical distribution of algal biomass in the bed sediment and the seasonal development of benthic algae on stones and fine-grained sediments were studied in a small unshaded stream. In addition, field experiments were conducted on the role of irradiance and phosphorus in regulating algal biomass. We found that algal biomass was high at a sediment depth of ten centimetres. Comparison of studies on algal biomass where different depths of the sediment are used should therefore be made with caution. Substrata-dependent differences in algal biomass development were substantial. While algal biomass development on stones was controlled by macroinvertebrate grazing, that on the fine-grained sediment followed the dynamics of incident irradiance, but was attenuated by sediment rebedding. Because of the high grazing pressure on algal biomass on stony substrata, no significant response to phosphorus enrichment was attained. In contrast, algal biomass development on fine-grained sediments was phosphorus-limited. Heavy shading of the fine-grained sediments did not significantly affect algal biomass development, thus suggesting that phosphorus limitation prevents algae from fully utilizing the light resource in this stream. This revised version was published online in July 2006 with corrections to the Cover Date.