Effect of hormones and antihormones on phospholipase A2 activity in human endometrial stromal cells

Phospholipase A₂ activity was studied in isolated human endometrial predecidual cells, and in human endometrium collected from day 19–23 of the menstrual cycle, by performing a radiochemical assay. Phospholipase A₂ activity on day 20 was significantly higher than other days (P < 0.001), and the activity was found to gradually decrease after day 20 of the menstrual cycle. The effects of the hormones estradiol and progesterone, and antihormones tamoxifen and RU 486, were studied on the phospholipase A₂ activity in isolated predecidual stromal cells. Estradiol produced a significant stimulatory effect (P < 0.001) on phospholipase A₂ activity in predecidual cells, and this effect was antagonized by tamoxifen. The combination of estradiol and tamoxifen was significantly different from estradiol alone (P < 0.001), but not from tamoxifen alone. RU 486 alone significantly increased (P < 0.001) phospholipase A₂ activity in predecidual stromal cells. However, progesterone had no effect on phospholipase A₂ activity in predecidual stromal cells.     

A Model for diffusion controlled bioavailability of crude oil components

Crude oil is a complex mixture of several different structural classes of compounds including alkanes, aromatics, heterocyclic polar compounds, and asphaltenes. The rate and extent of microbial degradation of crude oil depends on the interaction between the physical and biochemical properties of the biodegradable compounds and their interactions with the non-biodegradable fraction. In this study we have systematically altered the concentration of non-biodegradable material in the crude oil and analyzed its impact on transport of the biodegradable components of crude oil to the microorganisms. We have also developed a mathematical model that explains and accounts for the dependence of biodegradation of crude oil through a putative bioavailability parameter. Experimental results indicate that as the asphaltene concentration in oil increases, the maximum oxygen uptake in respirometers decreases. The mathematically fitted bioavailability parameter of degradable components of oil also decreases as the asphaltene concentration increases.     

Identification,characterization, and developmental profile of a high molecular weight,juvenile hormone-binding protein in the hemolymph of the migratory grasshopper,Melanoplus sanguinipes

In the hemolymph of Melanoplus sanguinipes, a high molecular weight juvenile hormone binding protein (JHBP) was identified by photoaffinity labelling and found to have a M_r of 480,000. The JHBP, purified using native gel electrophoresis followed by electroelution, has an equilibrium dissociation constant for JH III of 2.1 nM and preferentially binds JH III over JH I. Antibody raised against JHBP recognized only the 480,000 band. Under denaturing conditions the native JHBP gave a single band with a M_r 78,000. The antibody against native JHBP recognized only the 78,000 protein in SDS-treated hemolymph samples, indicating that JHBP is a hexamer in this species. The concentration of JHBP fluctuates in both the sexes during nymphal and adult development in parallel with total protein content of hemolymph. © 1995 Wiley-Liss, Inc.     

Some blood genetic markers of selected tribes in Western Saudi Arabia

A total of 292 randomly selected subjects belonging to two indigenous Arab tribes (Harbi and Ghamid) and two immigrant tribes (Mograbi and Mowallad), residents in Western Saudi Arabia, have been tested for genetic variants of six blood groups, four serum proteins, and five red cell enzyme systems. The distribution of the polymorphic systems was different between indigenous and immigrant tribes, and the present Arab population shows a considerable degree of admixture from the surrounding countries, in particular Africa.     

Glutamine Synthetase in Oligodendrocytes and Astrocytes: New Biochemical and Immunocytochemical Evidence

The results of recent immunocytochemical experiments suggest that glutamine synthetase (GS) in the rat CNS may not be confined to astrocytes. In the present study, GS activity was assayed in oligodendrocytes isolated from bovine brain and in oligodendrocytes, astrocytes, and neurons isolated from rat forebrain, and the results were compared with new immunochemical data. Among the cells isolated from rat brain, astrocytes had the highest specific activities of GS, followed by oligodendrocytes. Oligodendrocytes isolated from white matter of bovine brain had GS specific activities almost fivefold higher than those in white matter homogenates. Immunocytochemical staining also showed the presence of GS in both oligodendrocytes and astrocytes in bovine forebrain, in three white-matter regions of rat brain, and in Vibratome sections as well as paraffin sections.     

Solubilization of active GLP-1 (7–36)amide receptors from RINm5F plasma membranes

Glucagon-like peptide-1 (7–36)amide (GLP-1 (7–36)amide) represents a physiologically important incretin in mammals including man. Receptors for GLP-1 (7–36)amide have been described in RINm5F cells. We have solubilized active GLP-1 (7–36)amide receptors from RINm5F cell membranes utilizing the detergents octyl-β-glucoside and CHAPS; Triton X-100 and Lubrol PX were ineffective. Binding of radiolabeled GLP-1(7–36)amide to the solubilized receptor was inhibited conentration-dependently by addition of unlabeled peptide. Scatchard analysis of binding data revealed a single class of binding sites with K_a= 0.26 ± 0.03 nM and B_max= 65.4 ± 21.24 fmol/mg of protein for the membrane-bound receptor and K_a= 22.54 ± 4.42 μM and B_max= 3.9 ± 0.79 pmol/mg of protein for the solubilized receptor. The binding of the radiolabel to the solubilized receptor was dependent both on the concentrations of mono- and divalent cations and the protein/detergent ratio in the incubation buffer. The membrane bound receptor is sensitive to guanine-nucleotides, however neither GTP-γ-S nor GDP-β-S affected binding or labeled peptide to solubilized receptor. These data indicate that the solubilized receptor may have lost association with its G-protein. In conclusion, the here presented protocol allows solubilization of the GLP-1(7–36)amide receptor in a functional state and opens up the possibility for further molecular characterization of the receptor protein.     

Potassium channels in basolateral membrane vesicles from pars convoluta of rabbit proximal tubule

The characteristics of 86Rb+ fluxes through conductive channels in basolateral-membrane vesicles isolated from pars convoluta of rabbit proximal tubule were investigated. In KCl loaded vesicles a transient accumulation of 86Rb+ was observed which was inhibited by BaCl2. The accumulation was driven by an electrical diffusion potential, as shown in experiments using membrane vesicles loaded with Li2SO4 and an outwardly directed Li+ gradient established with a Li(+)-ionophore. The vesicles containing the channel showed a cation selectivity with the order K+ = Rb+ much greater than Li+ greater than or equal to Na+ greater than choline+. The 86Rb+ flux was dependent on intravesicular Ca2+. Increasing concentrations of Ca2+ gradually decreased the 86Rb+ uptake.     

Na+-gradient-dependent stimulation of renal transport of rho-aminohippurate.

Transport of rho-aminohippurate was studied by the use of a preparation of rabbit kidney basolateral-membrane vesicles and in rat kidney-cortex slices under anaerobic conditions. With both preparations clear evidence of Na+-gradient stimulation of rho-aminohippurate transport ('overshoot') was obtained. These results thus indicate that a significant aspect of active rho-aminohippurate transport is by co-transport with Na+, and they appear to resolve previous disagreements concerning the role of Na+. Vesicle studies with a potential-sensitive dye suggested that rho-aminohippurate may be transported electroneutrally, i.e. in a 1:1 complex with Na+.     

Glycerol Phosphate Dehydrogenase, Glucose-6-Phosphate Dehydrogenase, and Lactate Dehydrogenase: Activities in Oligodendrocytes, Neurons, Astrocytes, and Myelin Isolated from Developing Rat Brains

Abstract: Glycerol phosphate dehydrogenase (GPDH), glucose-6-phosphate dehydrogenase (G6PDH), and lactate dehydrogenase (LDH) activities were determined in Oligodendrocytes, neurons, and astrocytes isolated from the brains of developing rats. The activity of each enzyme was significantly lower in both neurons and astrocytes than in Oligodendrocytes. The GPDH activity in Oligodendrocytes increased more than 4-fold during development, and at 120 days cells of this type had 1.4-fold the specific activity of forebrain homogenates. The G6PDH activities in Oligodendrocytes from 10-day-old rats were 1.4-fold the activities in the forebrain homogenates. The activities of this enzyme in Oligodendrocytes were progressively lower at later ages, such that at 120 days the cells had 0.8 times the specific activities of homogenates. The Oligodendrocytes had 0.6 times the homogenate activities of LDH at 10 days, and this ratio had decreased to 0.2 by 120 days. These enzymes were also measured in myelin isolated from 20-, 60-, and 120-day-old rats. By 120 days the specific activities of G6PDH and LDH in myelin were <8% of the respective activities in homogenates. The GPDH activity in myelin was, however, at least 20% the specific activity in the homogenates, even in the oldest animals. It is proposed that LDH could be used as a marker for oligodendroglial cytoplasm in subfractions of myelin and in myelin-related membrane vesicles.     

Properties of Bovine Oligodendroglia Isolated by a New Procedure Using Physiologic Conditions

A new class of procedures, previously shown to permit the isolation of pure oligodendroglia from whole rat cerebrum, has been applied with equal or greater success for the bulk isolation of this cell type from bovine white matter. Thus, the generality of this approach has been demonstrated. The bovine preparations have a purity of greater than 90% intact, phase-bright oligodendroglia and are obtained in a yield of 8 x 10(6) cells per gram of white matter. Within 1 day it is possible to obtain a preparation containing 60 mg of protein from a single cell type. These cells show a higher degree of ultrastructural preservation of all cytoplasmic constituents than previously obtained. The values for protein (33 pg/cell), DNA (5.4 pg/cell), and lipid (5-6 pg/cell) are very similar to those obtained with an earlier procedure. The cell lipids are rich in galactolipid, which comprises 20% of the total. The activity of the "myelin-specific" enzyme, 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37), is 4.7 mumol/min/mg protein, similar to that obtained previously for isolated oligodendroglia and about 25-40% of that found in myelin. The activity of 5'-nucleotidase (EC 3.1.3.5) in the cells is about 10% of that in myelin or white matter.