Effects of a prostaglandin E1 analogue, misoprostol, on renal function in dogs receiving nephrotoxic doses of gentamicin

OBJECTIVE: To determine whether the prostaglandin E1 analogue, misoprostol, could preserve renal function in dogs receiving nephrotoxic doses of gentamicin. ANIMALS: 12 (6/group) healthy sexually intact male dogs. PROCEDURE: All dogs were given high doses of gentamicin (10 mg/kg of body weight, i.v., q 8 h, for 8 consecutive days). Six dogs (treatment group) received misoprostol (3 microgram/kg, p.o., q 8 h for the duration of the study) and 6 dogs (control group) received vehicle (1 capsule, p.o., q 8 h). Renal function was assessed before treatment (day 0) and on days 3, 6, 9, and 11 after initiation of treatment by measurement of serum biochemical variables, urine specific gravity, and exogenous creatinine clearance. Serum electrolyte and protein concentrations and presence of proteinuria, glycosuria, and cylindruria were also determined. At the end of the study, renal histopathologic changed were evaluated. RESULTS: Dogs receiving misoprostol had significant reduction in exogenous creatinine clearance with time, compared with dogs receiving vehicle (P = 0.0264). Dogs receiving misoprostol tended to develop more severe azotemia, hyperphosphatemia, and renal histopathologic changes; however, results were not significantly different between groups. CONCLUSION: Misoprostol (3 microgram/kg, p.o., q 8 h) did not preserve renal function and may have exacerbated gentamicin-induced nephrotoxicosis in this group of dogs. CLINICAL RELEVANCE: Supplementation of vasodilatory prostanoids may exacerbate renal dysfunction in dogs receiving high doses of gentamicin.     

3'-end processing and kinetics of 5'-end joining during retroviral integration in vivo

Retroviral replication depends on integration of viral DNA into a host cell chromosome. Integration proceeds in three steps: 3'-end processing, the endonucleolytic removal of the two terminal nucleotides from each 3' end of the viral DNA; strand transfer, the joining of the 3' ends of viral DNA to host DNA; and 5'-end joining (or gap repair), the joining of the 5' ends of viral DNA to host DNA. The 5'-end joining step has never been investigated, either for retroviral integration or for any other transposition process. We have developed an assay for 5'-end joining in vivo and have examined the kinetics of 5'-end joining for Moloney murine leukemia virus (MLV). The interval between 3'-end and 5'-end joining is estimated to be less than 1 h. This assay will be a useful tool for examining whether viral or host components mediate 5'-end joining. MLV integrates its DNA only after its host cell has completed mitosis. We show that the extent of 3'-end processing is the same in unsynchronized and aphidicolin-arrested cells. 3'-end processing therefore does not depend on mitosis.     

Effect of N-palmitoylethanolamine on energy-dependent transport of Ca2+ in vesicles of myometrium sarcolemma and their phospholipid composition

N-palmitoylethanolamine (NPE) was studied for their effect on calcium pump of pig myometrium sarcolemma. NPE in concentration of 10 microM, stimulated by 28-46% Mg2+, ATP-dependent accumulation of Ca2+ in vesicles of plasmatic membrane of uterus myocytes taking absolutely no effect on passive release of this cation from them. NPE modified phospholipid composition of sarcolemma, causing the increase of percentage content of phosphatidylinositol (by 20.2%) and lysophosphatidylcholine (2.7 times). While NPE effects transport Ca2+, Mg(2+)-ATPase solubilized from plasmatic membrane and purified due to the method of affinity chromatography on calmodulin-sepharose 4B, no activating effect of NPE on the calcium pump was observed. And what is more, a weakly expressed tendency to inhibition (by 14-15%, respectively) of the rate of Ca2+, Mg(2+)-dependent enzymic hydrolysis of ATP has been revealed. It is supposed that the effect of NPE on active transmembrane transport of Ca2+ is an important link in the general mechanism of contraction-relax of the myometrium and is, apparently, connected with its modifying effect on the lipid composition of the sarcolemma.     

Association between the low threshold calcium spike and activation of NMDA receptors in guinea-pig substantia nigra pars compacta neurons

The aim of this study was to examine the interaction between N-methyl-D-aspartate (NMDA) receptor activation and the low threshold calcium spike (LTS) of phasically firing neurons in the rostral part of the substantia nigra pars compacta (SNpc) in mid-brain slices. Bath perfusion of 10 microM NMDA gradually increased the LTS area and the effect reached a maximum after 6 min of perfusion. This enhancement of the LTS by NMDA was blocked both by a competitive and non-competitive NMDA receptor antagonist, 50 microM D-AP5 and 10 microM MK801, respectively, demonstrating that this effect of NMDA was mediated through NMDA receptors. Prolonged exposure to increasing concentrations of NMDA (0.1-100 microM) progressively decreased the LTS area. The higher doses led to an irreversible marked depolarization and decrease of the membrane resistance. These results suggest that the LTS of SNpc neurons can trigger a NMDA receptor-dependent response which may have physiological and pathological roles.     

Improved psychological well-being, quality of life, and health practices in moderately overweight women participating in a 12-week structured weight loss program

The first objective of this study was to confirm that 4 days of head-down tilt (HDT) were sufficient to induce orthostatic intolerance, and to check if 4 days of physical confinement may also induce orthostatic intolerance. Evidence of orthostatic intolerance during tilt-up tests was obtained from blood pressure and clinical criteria. The second objective was to quantify the arterial and venous changes associated with orthostatic intolerance and to check whether abnormal responses to the tilt test and lower body negative pressure (LBNP) may occur in the absence of blood pressure or clinical signs of orthostatic intolerance. The cerebral and lower limb arterial blood flow and vascular resistance, the flow redistribution between these two areas, and the femoral vein distension were assessed during tilt-up and LBNP by ultrasound. Eight subjects were given 4 days of HDT and, 1 month later, 4 days of physical confinement. Tilt and LBNP test were performed pre- and post-HDT and confinement. Orthostatic intolerance was significantly more frequent after HDT (63%) than after confinement (25%, P < 0.001). Cerebral haemodynamic responses to tilt-up and LBNP tests were similar pre- and post-HDT or confinement. Conversely, during both tilt and LBNP tests the femoral vascular resistances increased less (P < 0.002), and the femoral blood flow reduced less (P < 0.001) after HDT than before HDT or after confinement. The cerebral to femoral blood flow ratio increased less after HDT than before (P < 0.002) but remained unchanged before and after confinement. This ratio was significantly more disturbed in the subjects who did not complete the tilt test. The femoral superficial vein was more distended during post-HDT LBNP than pre-HDT or after confinement (P < 0.01). In conclusion, 4 days of HDT were enough to alter the lower limb arterial vasoconstriction and venous distensibility during tilt-up and LBNP, which reduced the flow redistribution in favour of the brain in all HDT subjects. Confinement did not alter significantly the haemodynamic responses to orthostatic tests. The cerebral to femoral blood flow ratio measured during LBNP was the best predictor of orthostatic intolerance.     

Expression of CCKB/gastrin receptor isoforms in gastro-intestinal tumour cells

Anti-serum raised against the human cholecystokinin B (CCKB)/gastrin receptor was used in Western blotting to differentiate the cellular locations of receptor isoforms expressed by human gastro-intestinal (GI) tumour cell lines. Using anti-serum directed against the amino-terminal extracellular tail of the CCKB/gastrin receptor, 8/9 cell lines were shown to express immunoreactive proteins of either m.w. 70 or 40 kDa, or both. Both isoforms were found to be associated with intracellular, non-nuclear membranes, whereas only the 70 kDa protein was expressed in the plasma membrane. Receptor expression was related to gastrin production and secretion. Both progastrin and glycine-extended gastrin-17 were produced and secreted by the tumour cell lines; however, carboxy amidated gastrin was not detected by radioimmunoassay. A CCKB/gastrin receptor transfectant NIH3T3 cell line did not produce detectable gastrin and showed exclusive expression of the 70 kDa receptor on the plasma membrane. One cell line had <50 pg/ml cell-associated progastrin and no detectable receptor form. Cell lines expressing 50-150 pg/ml had both 40 and 70 kDa receptor forms. Those expressing >150 pg/ml progastrin had only the 40 kDa isoform, which was shown to be exclusively expressed on intracellular, non-nuclear membranes, in one of the cell lines. Of the 4 cell lines exclusively expressing the lower m.w. receptor, 3 had gastrin present within the cell, which was not secreted. Thus, if cell-associated gastrin induces a proliferative effect, it may be by an intracrine pathway. Our study has identified the presence of CCKB/gastrin receptor isoforms in different cellular locations and may help toward understanding the complex autocrine and intracrine pathways mediated by gastrin peptides.     

MARs mission update

Genes are organized as chromatin domains and positioned in the nucleus through regions of nuclear matrix association, termed MARs. Although well-studied, the mechanisms regulating expression of the beta-globin locus remain an enigma. Here, we show that certain MAR sequences of the beta-globin locus are conserved and reiterated throughout the genome in association with other genes of the hematopoietic lineage. Further, the density of the MARs within the beta-globin locus and the sharing of these sequences by the various members of this gene cluster suggest that they may provide critical gene regulatory components.