Partitioning of NaPi cotransporter in cholesterol-, sphingomyelin-, and glycosphingolipid-enriched membrane domains modulates NaPi protein diffusion, clustering, and activity

In dietary potassium deficiency there is a decrease in the transport activity of the type IIa sodium/phosphate cotransporter protein (NaPi) despite an increase in its apical membrane abundance. This novel posttranslational regulation of NaPi activity is mediated by the increased glycosphingolipid content of the potassium-deficient apical membrane. However, the mechanisms by which these lipids modulate NaPi activity have not been determined. We determined if in potassium deficiency NaPi is increasingly partitioned in cholesterol-, sphingomyelin-, and glycosphingolipid-enriched microdomains of the apical membrane and if the increased presence of NaPi in these microdomains modulates its activity. By using a detergent-free density gradient flotation technique, we found that 80% of the apical membrane NaPi partitions into the low density cholesterol-, sphingomyelin-, and GM1-enriched fractions characterized as "lipid raft" fractions. In potassium deficiency, a higher proportion of NaPi was localized in the lipid raft fractions. By combining fluorescence correlation spectroscopy and photon counting histogram methods for control and potassium-deficient apical membranes reconstituted into giant unilamellar vesicles, we showed a 2-fold decrease in lateral diffusion of NaPi protein and a greater than 2-fold increase in size of protein aggregates/clusters in potassium deficiency. Our results indicate that NaPi protein is localized in membrane microdomains, that in potassium deficiency a larger proportion of NaPi protein is present in these microdomains, and that NaPi lateral diffusion is slowed down and NaPi aggregation/clustering is increased in potassium deficiency, both of which could be associated with the decreased Na/Pi cotransport activity in potassium deficiency.     

Full publication of papers presented at the 1995 through 1999 European Association of Plastic Surgeons annual scientific meetings: a systemic bibliometric analysis

From the multitude of oral presentations at major medical meetings, the most informative and highest-quality studies make it to full publication in peer-reviewed journals. The rate of publication may be regarded as an indicator of the scientific level of the meeting. Study of the publication rates of consecutive annual meetings allows for the evaluation of the consistency of the scientific level of these meetings and for comparison with publication rates of other meetings in the same field of interest. To grade how useful any publication is to other authors, one can furthermore measure how frequently they cite it in their own publications. Finally, the time lag between oral presentation and full publication is of importance to both its authors and the audience at the meeting. The main objectives of this study were to determine the publication rate of papers of various fields of interest as presented at five consecutive annual meetings of the European Association of Plastic Surgeons (EURAPS) and the time lag between these presentations and their publication. The authors compared their overall findings to those reported for other surgical specialties. Moreover, they identified and classified the journals in which the full publications appeared as an indicator of the scientific value of the meeting. They conclude that a greater than average number of papers presented at the 1995 through 1999 annual EURAPS meetings went on to full publication in peer-reviewed journals. Among these journals, Plastic and Reconstructive Surgery was the best source for information presented at the meetings. Although approximately 90 percent of the publications appeared before 3 years had passed after a meeting, additional publications may be expected to appear even more than 6 years after the meeting. Given the high publication rate and the high average normalized impact factor of the journals in which the presentations appeared, the five studied EURAPS meetings overall had high scientific value.     

Archaeological horizons and fluvial processes at the Lower Paleolithic open-air site of Revadim (Israel)

In this paper we present new data pertaining to the paleo-landscape characteristics at the Acheulian site of Revadim, on the southern coastal plain of Israel. Sedimentological, isotopic, granulometric and micromorphological studies showed that the archaeological remains accumulated in an active fluvial environment where channel action, overbank flooding and episodic inundation occurred. Measurements of total organic matter and its carbon isotopic composition indicate that the hominin activity at the site started at a period of relatively drier conditions, which coincided with erosion of the preceding soil sequence. This process led to the formation of a gently-undulating topography, as reconstructed by a GIS model. Later deposition documents relatively wetter conditions, as indicated by carbon isotopic composition. Formation processes identified at the site include fluvial processes, inundation episodes that resulted in anaerobic conditions and formation of oxide nodules, as well as small-scale bioturbation and later infiltration of carbonate-rich solutions that resulted in the formation of calcite nodules and crusts. The combination of micro-habitats created favorable conditions that repeatedly drew hominins to the area, as seen by a series of super-imposed archaeological horizons. This study shows that site-specific paleo-landscape reconstructions should play an important role in understanding regional variation among hominin occupations and in extrapolating long-term behavioral patterns during the Middle Pleistocene.     

Effect of the fuel system icing inhibitor diethylene glycol monomethyl ether on the biodegradation of jet fuel in soil

Microbial degradation of jet fuel leads to the accumulation of sludge in fuel distribution systems and storage tanks. To prevent this phenomenon, the biocidal anti-icing inhibitor diethylene glycol monomethyl ether (DiEGME) is routinely added to the fuel. The fate of DiEGME in soil and its consequent effect on the biodegradation of jet fuel by indigenous soil microflora have not been investigated. The aim of this work was to study the kinetics of biodegradation of jet fuel in dark rendzina soil, as affected by the presence of DiEGME. Our data show that the degradability in soil of jet fuel amended with DiEGME was tenfold higher than that of non-amended fuel. Consequently, there was an increase in the jet-fuel-utilizing soil microbial populations during the 100 days of incubation of soil samples amended with jet fuel containing DiEGME. Gas chromatograms of distilled fractions of jet fuel extracted from the soil demonstrated that most of the light fractions' extracts could not be detected at the end of the 100-day incubation. The relative concentration of aromatic compounds in the soil contaminated with DiEGME-amended jet fuel increased during incubation, demonstrating the lower biodegradation rate of these components compared with other fuel components. DiEGME was partially degraded by the general microbial population of the soil. Maximal DiEGME degradation was obtained with specific jet-fuel-utilizing microbial strains – Pseudomonas aeruginosa and Cladosporium resinae – that were added to a carbon-free mineral medium. The degradation rate of DiEGME by specific strains or by soil mixed populations bore an inverse relationship to the DiEGME concentration. The finding that DiEGME can be degraded by indigenous soil microorganisms may have facilitated its utilization also by jet-fuel-degrading microorganisms.     

The productivity of mesocyclops leuckrarti (Claus) in Lake Kinneret (Israel)

Specific rates of growth (Cw) of Mesocyclops leuckarti, young male and female instars varied between 0.03–0.26 and 0.03–0.17 g_(w.w.)/g_(w.w.)/day respectively at 15° and 22°C, whilst at IV–V copepodid stages females showed a higher Cw values. During 1969–1975 the averages of productivity and monthly P/B ratios were 44 (±23) g_(w.w.) (= 5g_(w.w.)/m²/month) and 3.1 respectively. P/B ratios were highly correlated (r(sup2)=0.98) with temperature changes. Metabolic parameters and P/B ratios were found to be similar to other water bodies in the world indicating an adaptation of M. leuckarti to different conditions.     

Plasma levels of catechols during reflexive changes in sympathetic nerve activity

Relationships between changes in levels of catechols and directly recorded sympathetic nerve activity were examined using simultaneous measurements of renal sympathetic nerve activity and arterial and renal venous concentrations of norepinephrine (NE), dihydroxyphenylalanine (dopa), and dihydroxyphenylglycol (DHPG) during reflexive alterations in renal sympathetic nerve activity in anesthetized, adrenal-demedullated rats. Nitroprusside infusion increased renal sympathetic nerve activity by 90%, arterial levels of dopa by 96%, NE by 326%, and DHPG by 141%. Phenylephrine infusion increased arterial DHPG levels by 81% and decreased renal sympathetic nerve activity by 37% and NE levels by 26%; arterial dopa levels were unchanged. Ganglionic blockade by chlorisondamine (with concomitant phenylephrine infusion to maintain MAP) decreased renal sympathetic nerve activity by 65% and NE concentrations by 37%; arterial dopa concentrations were unchanged, and DHPG concentrations increased by 60%. Proportionate responses of arterial levels of NE were strongly related to proportionate changes in renal sympathetic nerve activity. Clearance of DHPG from arterial plasma was prolonged by phenylephrine-induced hypertension and by nitroprusside-induced hypotension. The results suggest that changes in arterial NE levels reflect changes in sympathetic activity; changes in dopa levels reflect changes in catecholamine biosynthesis; and changes in DHPG levels depend on reuptake of released NE and on hemodynamic factors affecting DHPG clearance.     

Components of the Human SWI/SNF Complex Are Enriched in Active Chromatin and Are Associated with the Nuclear Matrix

Biochemical and genetic evidence suggest that the SWI/SNF complex is involved in the remodeling of chromatin during gene activation. We have used antibodies specific against three human subunits of this complex to study its subnuclear localization, as well as its potential association with active chromatin and the nuclear skeleton. Immunofluorescence studies revealed a punctate nuclear labeling pattern that was excluded from the nucleoli and from regions of condensed chromatin. Dual labeling failed to reveal significant colocalization of BRG1 or hBRM proteins with RNA polymerase II or with nuclear speckles involved in splicing. Chromatin fractionation experiments showed that both soluble and insoluble active chromatin are enriched in the hSWI/SNF proteins as compared with bulk chromatin. hSWI/SNF proteins were also found to be associated with the nuclear matrix or nuclear scaffold, suggesting that a fraction of the hSWI/SNF complex could be involved in the chromatin organization properties associated with matrix attachment regions.     

Albumin Stimulates the Activity of the Human UDP-Glucuronosyltransferases 1A7, 1A8, 1A10, 2A1 and 2B15, but the Effects Are Enzyme and Substrate Dependent

Human UDP-glucuronosyltransferases (UGTs) are important enzymes in metabolic elimination of endo- and xenobiotics. It was recently shown that addition of fatty acid free bovine serum albumin (BSA) significantly enhances in vitro activities of UGTs, a limiting factor in in vitro–in vivo extrapolation. Nevertheless, since only few human UGT enzymes were tested for this phenomenon, we have now performed detailed enzyme kinetic analysis on the BSA effects in six previously untested UGTs, using 2–4 suitable substrates for each enzyme. We also examined some of the previously tested UGTs, but using additional substrates and a lower BSA concentration, only 0.1%. The latter concentration allows the use of important but more lipophilic substrates, such as estradiol and 17-epiestradiol. In five newly tested UGTs, 1A7, 1A8, 1A10, 2A1, and 2B15, the addition of BSA enhanced, to a different degree, the in vitro activity by either decreasing reaction’s K _m, increasing its V _max, or both. In contrast, the activities of UGT2B17, another previously untested enzyme, were almost unaffected. The results of the assays with the previously tested UGTs, 1A1, 1A6, 2B4, and 2B7, were similar to the published BSA only as far as the BSA effects on the reactions’ K _m are concerned. In the cases of V _max values, however, our results differ significantly from the previously published ones, at least with some of the substrates. Hence, the magnitude of the BSA effects appears to be substrate dependent, especially with respect to V _max increases. Additionally, the BSA effects may be UGT subfamily dependent since K _m decreases were observed in members of subfamilies 1A, 2A and 2B, whereas large V _max increases were only found in several UGT1A members. The results shed new light on the complexity of the BSA effects on the activity and enzyme kinetics of the human UGTs.