Erythrocytes within pancreatic B-cells of corticosteroid-treated mice

An ultrastructural study of the endocrine pancreas of female ICR mice that received 21 daily injections of the synthetic glucocorticoid, Triamcinolone diacetate (8 mg/kg b.wt) revealed some examples of microhaemorrhage within islets of Langerhans, extravasation of erythrocytes, and the presence of erythrocytes within B-cells, where they undergo degradation to form myelin-like configurations.

Effects of bile salts of human erythrocytes. Plasma membrane vesiculation, phospholipid solubilization and their possible relationships to bile secretion

Glycocholate removed approximately 25% of the membrane acetylcholinesterase and 10% of the membrane phospholipid from intact human erythrocytes prior to the onset of cell lysis. At low concentrations (up to 6 mM), glycocholate caused human erythrocytes to become echinocytic and to pinch off microvesicles, whereas at higher concentrations glycocholate also specifically released components from the outer leaflet of the plasma membrane in a 'soluble' form (as defined by their presence in a 150 00 X g/60 min supernatant) and caused the cells to become stomatocytic. Whilst the phospholipdi profile of the 'soluble' material differed from that of the whole membrane, the profile of the microvesicle fraction was similar. The microvesicles were depleted in several membrane proteins with respect to phospholipids. These observations are discussed in relation to the possible role of bile salts in the origins of biliary phospholipid and protein.

Ultrastructure of parathyroid glands in triamcinolone-treated mice

6 weeks old ICR strain mice were given 21 daily injections of the synthetic glucocorticoid, triamcinolone diacetate (8 mg/kg body weight) and their parathyroid glands were examined by light and electron microscopy and compared with untreated litter-mate controls. Parathyroid glands are composed of a single basic cell type, but some cells are electron-dense ('dark' cells) and some less dense ('light' cells). There is considerable variability in numbers of light and dark cells from gland to gland. Following triamcinolone treatment the cells are arranged more in whorls, and there is a relative increase in the numbers of 'light' cells, which become more elongated, with pronounced nucleoli, and develop in many cases marked cytoplamsic vacuolation. Some cells show accumulations of lipid droplets. Interdigitations between adjacent cells become more complex, and the numbers of atrophic cells increase. The significance of the various cell conditions is considered. The ultrastructural appearances suggest that parathyroid gland cellular activity is stimulated in response to the drug-induced hypercorticoidism, but no overall glandular hypertrophy is found.

The exocrine pancreas in triamcinolone-treated mice. A light and electron microscopy study

6-week-old ICR strain female mice were given between 16 and 21 daily injections of the synthetic glucocorticoid, triamcinolone diacetate (8 mg/kg body weight). Portions of their pancreas were examined by light and electron microscopy and compared with untreated littermate controls. Despite marked variability from animal to animal and lobule to lobule, triamcinolone treatment induced increased zymogen depletion and also the development of large basal vacuoles in many acinar cells. At the ultrastructural level, acinar cells show pronounced mitochondrial swelling, which in many instances is accompanied by the development of myelin whorls. The number of cells with distended granular endoplasmic reticulum is increased as is the number of atrophying cells and cells apparently undergoing disintegration. In addition, there are indications of marked activation of interlobular perivascular macrophages which show marked vacuolation. Our observations suggest that pancreatic acinar cells show cytological changes as a result of experimental hypercorticoidism.

Evidence that biosynthesis of phosphatidylethanolamine, phosphatidylcholine, and triacylglycerol occurs on the cytoplasmic side of microsomal vesicles

Experiments were performed to localize the hepatic microsomal enzymes of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol biosynthesis to the cytoplasmic or lumenal surface of microsomal vesicles. Greater than 90 percent of the activities of fatty acid-CoA ligase (EC 6.2.1.3), sn-glycerol 3-phosphate acyltransferase (EC 2.3.1.15), lysophosphatidic acid acyltransferase, diacylglycerol acyltransferase (EC 2.3.1.20), diacylglycerol cholinephosphotransferase (EC 2.7.8.2), and diacylglycerol ethanolaminephosphotransferase (EC 2.7.8.1) was inactivated by proteolysis of intact microsomal vesicles. The phosphatidic acid phosphatase (EC 3.1.3.4) was not inactivated by any of the protease tested. Under conditions employed, <5 percent of the luminal mannose-6-phosphatase (EC 3.1.3.9) activity was lost. After microsomal integrity was disrupted with detergents, protease treatment resulted in a loss of >74 percent of the mannose-6-phosphatase activity. The latency of the mannose-6-phosphatase activity was not affected by protease treatment. Mannose-6-phosphatase latency was not decreased by the presence of the assay components of several of the lipid biosynthetic activities, indicating that those components did not disrupt the microsomal vesicles. None of the lipid biosynthetic activities appeared latent. The presence of a protease-sensitive component of these biosynthetic activities on the cytoplasmic surface of microsomal vesicles, and the absence of latency for any of these biosynthetic activities suggest that the biosynthesis of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol occurs asymmetrically on the cytoplasmic surface of the endoplasmic reticulum. The location of biosynthetic activities within the transverse plane of the endoplasmic reticulum is of particular interest for enzymes whose products may be either secreted or retained within the cell. Phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol account for the vast majority of hepatic glycerolipid biosynthesis. The phospholipids are utilized for hepatic membrane biogenesis and for the formation of lipoproteins, and the triacylglycerols are incorporated into lipoproteins or accumulate within the hepatocyte in certain disease states (14). The enzymes responsible for the biosynthesis of these glycerolipids (Scheme I) from fatty acids and glycerol-3P have all been localized to the microsomal subcellular fraction (12, 16, 29, 30). Microsomes are derived from the endoplasmic reticulum and are sealed vesicles which maintain proper sidedness. (11, 22). The external surface of these vesicles corresponds to the cytoplasmic surface of the endoplasmic reticulum. Macromolecules destined for secretion must pass into the lumen of the endoplasmic reticulum (5, 23). Uncharged molecules of up to approximately 600 daltons are able to enter the lumen of rat liver microsomes, but macromolecules and charged molecules of low molecular weight do not cross the vesicle membrane (10, 11). Because proteases neither cross the microsomal membrane nor destroy the permeability barrier of the microsomal vesicles, only the enzymes and proteins located on the cytoplasmic surface of microsomal vesicles are susceptible to proteolysis unless membrane integrity is disrupted (10, 11). By use of this approach, several enzymes and proteins have been localized in the transverse plane of microsomal membranes (11). With the possible exception of cytochrome P 450, all of the enzymes and proteins investigated were localized asymmetrically by the proteolysis technique (11). By studies of this type, as well as by product localization, glucose-6-phosphate (EC 3.1.3.9) has been localized to the luminal surface of microsomal vesicles (11) and of the endoplasmic reticulum (18, 19). All microsomal vesicles contain glucose-6-phosphatase (18, 19) which can effectively utilize mannose-6-P as a substrate, provided the permeability barrier of the vesicles has been disrupted to allow the substrate access to the active site located on the lumenal surface (4). An exact correspondence between mannose- 6-phosphate activity and membrane permeability to EDTA has been established (4). The latency of mannose-6-phosphatase activity provides a quantitative index of microsomal integrity (4.) Few of the microsomal enzymes in the synthesis of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol have been solubilized and/or purified, and little is known about the topography of these enzymes in the transverse or lateral planes of the endoplasmic reticulum. An asymmetric location of these biosynthetic enzymes on the cytoplasmic or lumenal surface of microsomal vesicles may provide a mechanism for regulation of the glycerolipids to be retained or secreted by the cell, and for the biogenesis of asymmetric phospholipid bilayers. In this paper, we report investigations on the localization of all seven microsomal enzymes (Scheme I) in the biosynthesis of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine, using the protease technique with mannose-6-phosphatase serving as luminal control activity. The latency of these lipid biosynthetic enzymes was also investigated, using the latency of mannose-6-phosphatase as an index of microsomal integrity.

Preabsorptive vs. postabsorptive control of ethanol intake in C57BL/6J and DBA/2J mice

Experimentally naive male mice of both strains were exposed to a two-bottle choice situation (ethanol vs. water) and their drinking behavior was observed during the first hour. DBA/2J mice developed a significant avoidance of 2% or 10% ethanol during the first 10 min. At 15 and 60 min following introduction of the bottles, no DBA mouse exhibited more than a 6 mg% blood ethanol level while all of the C57BL mice exceeded this concentration. Significant postabsorptive effects in the DBA mice seem unlikely at these very low blood ethanol values. Animals of both strains were examined for their ability to form lithium-induced conditioned taste aversions to 2% ethanol or 15% sucrose solutions. DBA mice readily formed conditioned aversions to both solutions, but the C57BL strain significantly avoided only the sucrose. C57BL mice appear to have difficulty in discriminating the 2% ethanol from distilled water. The neural sensitivity to ethanol was examined in both strains using the sleep time test and the grid test. C57BL mice were significantly more sensitive than DBA mice in both tests.

Phospholipid synthesis in isolated fat cells. Studies of microsomal diacylglycerol cholinephosphotransferase and diacylglycerol ethanolaminephosphotransferase activities

Diacylglycerol cholinephosphotransferase (EC 2.7.8.2) and diacylglycerol ethanolaminephosphotransferase (EC 2.7.8.1) activities were investigated in microsomes from isolated rat fat cells. Assays based on the conversion of CDP-[14C]choline of CDP-[14C]ethanolamine to phosphatidylcholine or phosphatidylethanolamine utilized ethanol-dispersed diacylglycerols and 1 to 5 microng of protein. Cholinephosphotransferase and ethanolaminephosphotransferase activities had similar dependences on MgCl2 and pH, and were inhibited similarly by CaCl2, organic solvents, Triton X-100, Tween 20, and dithiothreitol. Ethylene glycol bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid stimulated both activities similarly. With 1,2-dioleoyl-sn-glycerol, the cholinephosphotransferase activity had an apparent Km for CDP-choline of 23.9 micronM and a V max of 8.54 nmol/min/mg. CDP-ethanolamine and CDP were competitive inhibitors of the cholinephosphotransferase activity (apparent Kl values of 227 micronM and 360 micronM, respectively). With 1,2-dioleoyl-sn-glycerol, the ethanolaminephosphotransferase activity had an apparent Km of 18.3 micronM for CDP-ethanolamine and a V max of 1.14 nmol/min/mg. CDP-choline appeared to be a noncompetitive inhibitor of the ethanolaminephosphotransferase activity (apparent Kl of 1620 micronM). Inhibition of the ethanolaminephosphotransferase activity by CDP appeared to be of a mixed type. The dependences on diacylglycerols containing fatty acids 6 to 18 carbons in length were investigated...

Topographical dissection of sheep erythrocyte membrane phospholipids by taurocholate and glycocholate

1. Glycocholate and taurocholate removed significant amounts of membrane phospholipid from intact sheep erythrocytes before lysis of the cells occurred. The pre-lytic extract was enriched in sphingomyelin and correspondingly depleted in phosphatidylserine, phosphatidylinositol and phosphatidylethanolamine when compared to the original membrane. 2. In contrast, the phospholipid profiles of glycocholate and taurocholate extracts of unsealed ghosts, made at the same bile salt concentrations, were similar to that of the whole membrane. 3. These observations are related to the topography of the phospholipids in the membrane and to some aspects of bile formation.

Permeability characteristics of erythrocyte ghosts prepared under isoionic conditions by a glycol-induced osmotic lysis

A detailed study has been made of the permeability characteristics of human erythrocyte ghosts prepared under isoionic conditions by a glycol-induced lysis (Billah, M.M., Finean, J.B., Coleman, R. and Michell, R.H. (1976) Biochim. Biophys. Acta 433, 45-54). Impermeability to large molecules such as dextran (average molecular weight 70 000) was restored immediately and spontaneously after each of the 5-7 lyses that were required to remove all of the haemoglobin. Permeabilities to smaller molecules such as MgATP2-, [3H]inositol and [14C]choline were initially high but could be greatly reduced by incubation at 37 degrees C for an hour. The extent of such resealing decreased as the number of lyses to which the ghosts had been subjected increased. Both removal of haemoglobin and permeabilities to small molecules were affected significantly by pH, CA3+ concentrations and divalent cation chelators. Maximum resealing was achieved in ghosts prepared in the basic ionic medium (130 mM KCl, 10 nM NaCl, 2 mM MgCl2, 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES)) at pH 7.0 (0 degrees C) and with a calcium level around 10(-5) M. Acidic pH facilitated the removal of haemoglobin whilst the presence of divalent cation chelators showed down its release. Retention of K+ by ghosts leaded with K+ during the first lysis and subsequently incubated at 37 degrees C was substantial but lation chelators slowed down its released. Retention of K+ by ghosts loaded with K+ during the first lysis and subsequently incubated at 37 degrees C was substantial but little K+ could be retained within the haemoglobin-free ghosts. Permeability of the ghosts to K+ after one lysis was affected by temperature, pH, Ca2+ concentrations and by the presence of divalent cation chelators.

Effects of different bile salts upon the composition and morphology of a liver plasma membrane preparation. Deoxycholate is more membrane damaging than cholate and its conjugates

1. Rat liver plasma membrane preparations were incubated with various bile salts at 0 or 37 degrees C. the bile salts caused the removal of various amounts of proteins, membrane enzymes and phospholipids; the extent and nature of these losses, and the morphological changes which accompanied them, varied with the detergent used. 2. Cholate, taurocholate and glycocholate removed appreciable amounts of protein from the saline-washed membranes, and considerable amounts of both phospholipids and the membrane enzymes, 5-nucleotidase, alkaline phosphatase, alkaline phosphodiesterase 1 and L-leucyl-beta-naphtylamidase. These losses were greater at 37 that at 0 degrees C. The material remaining contained membrane-like profiles, many of vesicular form, even when the preparation was almost completely devoid of phospholipids. 3. Deoxycholate, both at 0 and 37 degrees C, removed more protein, membrane enzymes and phospholipids than did cholate and its conjugates. The material remaining was mainly granular and unorganised and the only remaining features were structures resembling the nexus, and occasional desmosomes. 4. Deoxycholate, a dihydroxy bile salt, therefore appears to cause greater perturbation of membrane structure than the trihydroxy bile salt, cholate, and its conjugates. The results may have implications for the effects of bile salts upon the membranes of liver cells during bile salt secretion and the production of bile.

Plasma-membrane components can be removed from isolated lymphocytes by the bile salts glycocholate and taurocholate without cell lysis

Glycocholate and taurocholate removed from isolated pig lymphocytes a proportion of the cells' complement of 5'-nucleotidase, alkaline phosphatase and alkaline phosphodiesterase I before cell lysis. This may indicate a loss of externally orientated plasma-membrane components.

Triacylglycerol synthesis in isolated fat cells. Studies on the microsomal diacylglycerol acyltransferase activity using ethanol-dispersed diacylglycerols

The acyl-CoA:1,2-diacylglycerol acyltransferase (EC 2.3.1.20) activity of isolated fat cells was predominantly (89%) localized to the microsomal subcellular fraction by assays based on the conversion of 1,2-[3H]diacyl-sn-glycerol to triacylglycerol using 1 to 4 mug of protein. A complementary assay based on the conversion of [3H]palmitoyl-CoA to triacylglycerol was developed. These methods, 100 to 1000 times more sensitive than those previously employed, were used to characterize the microsomal activity. The choice of dispersing agent for addition of diacylglycerol to the reaction mixture was crucial. Addition of diacylglycerol in ethanol resulted in the highest diacylglycerol acyltransferase activity of the methods tested. Tween 20, which has previously been employed as the dispersing agent, severely inhibited the activity. A broad pH optimum from 7.4 to 8.0 was noted and several salts stimulated the activity more than 2-fold. The activity was unstable at temperatures of 28 degrees and above. Dependences on acyl-CoAs containing 6 to 18 carbon atoms were investigated using bacterial diacylglycerol. Acetyl- and butyryl-CoA were not substrates. Highest diacylglycerol acyltransferase activities were observed with decanoyl-CoA and lower activities were noted with longer and shorter saturated chains. Maximal activity with oleoyl-CoA was only 34% of that seen with stearoyl-CoA. No simple relationship between the critical micellar concentrations of the acyl-CoAs employed and diacylglycerol acyltransferase activity was observed. The dependences on diacylglycerols containing fatty acids 6 to 18 carbon atoms in length were investigated with [3H]palmitoyl-CoA. While all the 1,2-diacyl-sn-glycerols tested were substrates, diacylglycerol acyltransferase activity was highest with 1,2-dioleoylglycerol. Maximum activity with the bacterial diacylglycerol was 86% that with 1,2-dioleoylglycerol. The diacylglycerol concentrations required for half-maximal velocity were 20 to 40 muM for long chain diacylglycerols and 2 to 3 muM for short chain diacylglycerols; these were 75- to 750-fold lower than previously reported. Microsomal diacylglycerol acyltransferase specific activities from isolated cells around 50 nmol/min/mg, 10- to 50-fold higher than previously reported from adipose tissue, were typical using dioleoylglycerol and palmitoyl-CoA as substrates. Diacylglycerol acyltransferase specific activities were 17-fold higher in microsomes from isolated fat cells than any other tissue examined. The diacylglycerol acyltransferase appears to have specificity with respect to acyl-CoAs and diacylglycerols, but a definitive interpretation is limited by the lack of data on the physical properties of these substrates in solution under the conditions employed.

Detergent extraction of erythrocyte ghosts. Comparison of residues after cholate and Triton X-100 treatments

1. Human erythrocyte ghosts were extracted with individual free and conjugated bile salts and, for comparison, with Triton X-100 under conditions approximating to physiological temperature, pH and tonicity. 2. Treatment with cholate, glycocholate, taurocholate, or with Triton X-100 gave lipid-depleted residues. These could still be seen as ghost-like profiles by phase contrast microscopy. Deopxycholate brought about complete membrane dissolutiom. 3. The cholate residue gave a trilamellar image by electron microscopy and in condensed form gave a smaller membrane repeat than untreated membranes. It had a polypeptide composition representing mainly integral proteins. 4. The Triton X-100 residue had a granular profile in the electron microscope and a polypeptide composition largely representing peripheral proteins.

Preparation of erythrocyte ghosts by a glycol-induced osmotic lysis under isoionic conditions

A procedure has been developed for obtaining haemoglobin-free, erythrocyte ghosts under ionic conditions approximating that of the cell cytoplasm. Haemolysis was effected by incorporating glycol into cells suspended in the isoionic medium and then diluting with a large volume of glycol-free medium. The ghosts were of uniform spherical shape throughout the preparative procedure and were impermeable to macromolecules. Analysis of polypeptides by sodium dodecyl sulphate-gel electrophoresis at each stage of preparation and comparison with ghosts prepared under hypo-ionic conditions served to distinguish membrane components from those of cytoplasm.

The topographical location and unique nature of a glucokinase associated with the Golgi apparatus of rat liver

A particulate glucokinase was recovered in the Golgi-rich fraction of rat liver prepared by the method of Morré [Methods Enzymol. (1971) 22, 130-148], thus extending the demonstration by Berthillier et al. [Biochim. Biophys. Acta (1973), 293, 370-378] of particulate glucokinase activity in a microsomal subfraction that showed enrichment in Golgi characteristics. The purity of this fraction was examined and it was then subjected to several treatments, the action of Triton X-100, freezing and thawing, and sonication to establish the topographical location of the glucokinase activity thus solubilized. The evidence suggests that the glucokinase activity is either soluble in the lumen of the Golgi apparatus or loosely associated with the inside of the Golgi membranes.

The development and fine structure of ultimobranchial glands in larval anurans. II. Bufo viridis, Hyla arborea, and Rana ridibunda

A comparative optical microscopic and ultrastructural study on the ultimobranchial (UB) glands of three common species of Israeli anurans: Bufo viridis, Hyla arborea, and Rana ridibunda during metamorphosis is presented. The UB glands typically consist of a single follicle with a central lumen, though occasionally secondary follicles are present in Hyla and Rana. A single UB cell type is found which appears either in a very electron-dense "dark" form or as a less dense "light" form, though the ratio of dark: light cells from gland to gland at any one stage of metamorphic development is quite variable. By the end of metamorphosis in Bufo and Hyla all the UB cells are usually of the light variety, whereas in Rana the dark cells persist. The organelles of these secretory cells including secretory granules, granular endoplasmic reticulum, free ribosomes, tonofilaments, microtubules, Golgi bodies, and lipid droplets, their distribution, abundance, and possible functions in relation to metamorphosis are described. Apocrine secretion into the central lumen of the gland is also described and discussed.

Basolateral plasma membranes of intestinal epithelial cells. Identification by lactoperoxidase-catalysed iodination and isolation after density perturbation with digitonin

Lactoperoxidase-catalysed iodination was used to label intestinal epithelial cell sheets with 125I. The iodination was carried out under conditions that allowed little penetration of lactoperoxidase into the cells and membrane-bound 125I therefore provided an effective marker for following plasma-membrane fragments through subcellular-fractionation procedures. 2. After homogenization and isopycnic zonal centrifugation through sucrose gradients two peaks of membrane-bound 125I were detected. One coincided with brush border enzymes such as alkaline phosphatase, disaccharidases and L-leucine B-naphthylamidase, whereas the other was coincident with the major peak of (Na++K+)-stimulated ATPase (adenosine triphosphatase), which has been thought to be concentrated in the basolateral plasma membranes of these cells. Neither peak of 125I reflected the distribution of any marker for an intracellular organelle. 3. A larger proportion of the (Na++K+)-stimulated ATPase, and thus of the basolateral plasma-membrane material, was found in a crude 'mitochondrial' fraction. It was not readiily separated from mitochondria by conventional techniques of subcellular fractionation. 4. Treatment of the 'mitochondrial' fraction with digitonin increased the density of basolateral plasma membrane but had little effect on mitochondrial density. A purified preparation of digitonin-loaded basolateral plasma membranes was isolated at a density of 1.20-1.22 by isopycnic centrifugation. 5. The enzymic composition of this preparation of basolateral plasma membranes is compared with previous preparations isolated from intestinal mucosal 'scrape' materials and from isolated cells.

Enzyme profiles of mammalian bile

The activities of subcellular marker enzymes in bile and liver homogenate from several mammalian species have provided information on the specificity of protein release during bile formation. The presence of significant amounts of the plasma membrane enzymes alkaline phosphodiesterase I and leucyl-beta-naphthylamidase in bile, in addition to alkaline phosphatase and 5'-nucleotidase, and the relative absence of intracellular enzymes lends support to the view that bile salt liberation from the hepatocyte is accompanied by a partial solubilization of the plasma (canalicular) membrane without extensive damage to the whole hepatocyte.

Hydrolysis of erythrocyte membrane phospholipids by a preparation of phospholipase C from Clostridium Welchii. Deactivation of (Ca-2+, Mg-2+)-ATPase and its reactivation by added lipids

1. Haemoglobin-free erythrocyte ghosts were prepared in 40 imosM bicarbonate buffer, pH 7.4, containing 1 mM EDTA (40 imosM/l mM EDTA). The ghost preparation was highly permeable on preparation but partially resealed on incubation in media containing Ca-2+. 2. A partially purified preparation of phospholipase C from Clostridum welchii caused an increase in observed Mg-2+-ATPase activity, reflecting a change in the permeability of the ghost to substrate. The phospholipase did not decrease Mg-2+-ATPase even at the highest levels tested. Mg-2+-ATPase activity could therefore be used as a permeability indicatior in these experiments. 3. Both (Ca-2+, Mg-2+)-ATPase activities of the ghosts were progressively lost as a result of the phospholipid hydrolysis induced by phospholipase C. 4. When a haemolysin in the commercial preparation was destroyed by heat-treatment, deactivation of the (Ca-2+, Mg-2+)-ATPase and (Na+, K+, Mg-2+)-ATPases were still observed but permeability changes were greatly reduced. 5. The products of phospholipase action were not inhibitory to the Ca-2+, Mg-2+)-ATPase. 6. Lysolecithin brought about a reactivation of the (Ca-2+, Mg-2+)-ATPase which was superimposed upon permeability changes in the preparation. 7. Reactivation of the (Ca-2+, Mg-2+)-ATPase was brought about by a nonlytic, mixed lipid preparation without significant effect upon permeability. 8. Human erythrocyte (Ca-2+, Mg-2+)-ATPase therefore appears to be an enzyme which responds to perturbation of the lipid environment in the membrane and is a "lipid-dependant" enzyme.

Response generalization in two categories of classroom behavior

Research has demonstrated that working behaviors and academic performance can be manipulated in classroom settings. However, generalization to one group of behavior when the other group is being manipulated has not been sufficiently explored. 19 male adolescent institutionalized delinquents were randomly assigned to 2 groups. Programmed instruction, and a script economy were the treatment conditions. Group 1 was reinforced for working behavior while Group 2 was reinforced for academic performance. Programmed instruction did not produce changes in either working or academic performance, while both groups showed increases in appropriate working behavior as a result of the script economy, with Group 1 showing the greatest change. A trend of improved achievement test scores was established for both groups, with Group 2 making slightly greater gains.

Red Sea Drillings

Recent drilling in the Red Sea has shown that much of the basin is underlain by evaporites of a similar age to that of evaporites found in the Mediterranean Sea. These evaporites and their structural positions indicate that other brine areas are present-and, indeed, several others have been discovered.

Glycerylphosphorylcholine phosphodiesterase in rat liver. Subcellular distribution and localization in plasma membranes

1. A simple new assay for glycerylphosphorylcholine phosphodiesterase is described, in which radioactive glycerylphosphorylcholine is used as substrate and the reaction products are separated by adsorption on an anion-exchange resin. 2. Rat liver subcellular fractions contained both particulate (58%) and soluble (42%) glycerylphosphorylcholine phosphodiesterase. Both activities released free choline from glycerylphosphorylcholine. 3. The particulate glycerylphosphorylcholine phosphodiesterase was recovered mainly in the nuclear and microsomal fractions and showed a distribution similar to those of 5'-nucleotidase and alkaline phosphodiesterase I, both of which are constituents of the liver plasma membrane. 4. During purification of plasma membranes glycerylphosphorylcholine phosphodiesterase, 5'-nucleotidase and alkaline phosphodiesterase I showed largely similar behaviour, indicating that glycerylphosphorylcholine phosphodiesterase is also localized in liver plasma membranes. Slight differences in the distributions of these three enzymes in density-gradient separations are discussed in relation to the possibility that they are unevenly distributed on different areas of the cell surface. 5. The differences between glycerylphosphorylcholine phosphodiesterase and alkaline phosphodiesterase I indicate that these two activities are not functions of a single enzyme. 6. The glycerylphosphorylcholine phosphodiesterase of liver plasma membranes has a pH optimum of 8.5 and a K(m) for glycerylphosphorylcholine of 0.95mm. It is inhibited by EDTA and fully reactivated by a variety of bivalent cations (and Fe(3+)).