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Biomedical subjects

F Schroeder

Publications and source records attributed to F Schroeder.

At least 181 records · Page 10Linked to original sources
PubMed1981

Drug-induced surface membrane phospholipid composition in murine fibroblasts.

The effects of drug on phospholipid composition of cell surface membranes are not well understood at this time. The effects of membrane-active drugs and membrane depolarization on the phospholipid composition were determined in murine LM fibroblasts. Receptor-aggregating drugs such as concanavalin A and cytoskeleton-disrupting agents such as colchicine, vinblastine, and cytochalasin B decreased phosphatidylserine content of the plasma membrane from 5.4 +/- 1.5% to as low as 1.4 +/- 0.2%. In addition, concanavalin A and colchicine increased the phosphatidylglycerol content from 6.9 +/- 1.6% to 13.1 +/- 0.7% and 10.6 +/-1.7%, respectively, while vinblastine and cytochalasin B had no effect. Pentobarbital decreased the content of phosphatidylinositol+ phosphatidylserine and of phosphatidylglycerol almost 2-fold. Propranolol, ethanol, and depolarization with 120 mM KCl had small or ne effects on plasma membrane phospholipid composition. None of the above drugs or treatments significantly altered the asymmetric distribution of phosphatidylethanolamine across the LM cell plasma membrane under the conditions tested. In addition, energy inhibitors that deplete the proton-motive force of the cell (NaN3 and KCN) and inhibitors of ATP synthesis such as NaAsO4 did not affect the asymmetric distribution of phosphatidylethanolamine. It is concluded that the mechanism of action of membrane-active drugs such as concanavalin A, vinblastine, colchicine and pentobarbital may involve alterations in plasma membrane composition. It also appears that microfilaments, microtubules, beta-adrenergic receptors, membrane fluidity, and membrane potential are not critical for the regulation of the asymmetric distribution of membrane phosphatidylethanolamine.

Animals↗
PubMed1981

Differential scanning calorimetry and fluorescence probe investigations of very low density lipoprotein from the isolated perfused rat liver.

Isolated rat livers were perfused at 37 degrees C with blood-free, defined medium containing delipidized bovine serum albumin (BSA), BSA-oleate, or BSA-palmitate. Very low density lipoproteins (VLDL) were isolated from the perfusate at 12 degrees C and lipid components were extracted and purified. Differential scanning calorimetry indicated multiple phase alterations in intact VLDL. The extracted triglycerides exhibited phase alterations at similar temperatures as the intact VLDL. The small quantities of cholesteryl esters present in the VLDL generally did not greatly affect the VLDL triglyceride transitions. The extracted phospholipids showed detectable transitions that were abolished by cholesterol at mole ratios found in the respective VLDL. The phase behavior of VLDL and its component triglycerides was associated with the degree of unsaturation of the infusate fatty acid, and by variation of fatty acid chain length. The structural differences between VLDL lipid fractions noted by DSC were also monitored by fluorescence probes. The data indicated that in the intact VLDL the physical properties of the 'interior core' lipids can affect the properties of the 'surface monolayer'. In addition, Arrhenius plots of corrected fluorescence indicated that trans-parinarate and diphenyl-hexatriene detected different characteristic breakpoint temperatures in the phospholipids. The breakpoints of triglycerides were highly dependent on the type of fatty acid in the infusate, but were similar to those noted in intact VLDL. Finally, the breakpoints in Arrhenius plots of fluorescence probe parameters did not necessarily coincide with onset or end temperatures of DSC transitions.

Animals↗
PubMed1981

Effects of ethanol and related drugs on the physical and functional properties of brain membranes.

The fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) was incorporated into myelin and synaptic plasma membrane fractions prepared from mouse brain. The absorption-corrected fluorescence and polarization of the fluorescent probe a molecule and the membrane absorbance were measured simultaneously, using a computer-centered spectrofluorimeter. In vitro exposure of synaptic membranes to ethanol (25-100 mM) decreased all three parameters in a dose-dependent manner. The order of sensitivity was: corrected fluorescence greater than or equal to polarization much greater than absorbance. Myelin was not affected by these concentrations of ethanol, indicating a selective effect on synaptic membranes. The polarization of fluorescence of DPH in synaptic membranes was also decreased by tert-butanol, pentobarbital, and cis- and trans-vaccinic acid. The results suggest that ethanol and related drugs perturb the hydrophobic interior of synaptic membranes. These compounds also increased the exposure of synaptic sulfhydryl groups and inhibited the depolarization- and ATP-dependent uptake of calcium by synaptosomal preparations. These results suggest that the perturbation altered the conformation of synaptic proteins and inhibited the transport of calcium by synaptosomal membranes.

Animals↗
PubMed1980

Regulation of aminophospholipid asymmetry in murine fibroblast plasma membranes by choline and ethanolamine analogues.

The regulation of the asymmetric distribution of aminophospholipids in mammalian cell plasma membranes is not understood at this time. One approach to determine the nature of such regulatory mechanisms is to attempt alteration of the plasma membrane phospholipid composition. Choline analogues such as N,N'-dimethylethanolamine and N-monomethylethanolamine lowered the quantity of phosphatidylethanolamine in the plasma membrane of LM fibroblasts grown in defined medium without serum. Ethanolamine supplementation increased the phosphatidylethanolamine content while ethanolamine analogues such as 2-amino-2-methyl-1-propanol, 2-amino-1-butanol, 1-aminopropanol, and 3-aminopropanol did not alter the aminophospholipid content significantly. The transverse distribution of aminophospholipids in the plasma membrane was determined by use of a chemical labelling reagent trinitrobenzenesulfonic acid. The percent phosphatidylethanolamine trinitrophenylated by trinitrobenzenesulfonate in the outer plasma membrane monolayer of LM cells supplemented with choline analogues was not altered. In contrast, ethanolamine analogue supplementation increased the percentage of aminophospholipid in the outer monolayer 2--3-fold. Ethanolamine analogue-containing phospholipids were distributed asymmetrically across the plasma membrane with 85 to 91% being located in the inner monolayer of the plasma membrane, a distribution similar to that of phosphatidylethanolamine. The fatty acyl composition of aminophospholipids in the outer monolayer was in all cases more saturated than in the corresponding phospholipids of the inner monolayer. However, choline analogues and especially the ethanolamine analogues reduced this difference. Thus, base analogues of choline and ethanolamine may alter the aminophospholipid asymmetry, the surface charge, and the acyl chain asymmetry of LM cell plasma membranes.

Animals↗
PubMed1980

Effect of fatty acids on physical properties of microsomes from isolated perfused rat liver.

A computer-centered spectrofluorimeter was used to examine the physicochemical properties of hepatic microsomes and microsomal lipids obtained from isolated rat livers perfused with medium containing palmitate or oleate. The fatty acid composition and degree of unsaturation of the liver microsomal lipids reflected that the fatty acid present in the perfusate. The absorption corrected fluorescence, relative fluorescence efficiency, polarization, and fluorescence anisotropy of several fluorescent probe molecules were measured to determine if their different microenvironments may be altered by the type of fatty acid infused. The probe molecules beta--parinaric acid and 1,6-diphenyl-1,3,5-hexatriene had higher values for each of these parameters when incorporated into microsomes obtained from livers perfused with a medium containing palmitate than with oleate. The same parameters measured for cholesta-5,7,9(11)-trien-3 beta-ol and N-phenyl-1-naphthylamine were not altered. These differences appeared to be primarily due to alterations in microviscosity of the probe microenvironments since the rotational correlation time of 1,6-diphenyl-1,3,5-hexatriene was 25% lower in the microsomes from livers perfused with oleate as compared to livers perfused with palmitate. Thermal discontinuities in Arrhenius plots were noted in the intact microsomes but not in the isolated microsomal lipids with the fluorescence probe molecule beta-parinaric acid. Break points occurred at 10 degrees C and 26 degrees C for microsomes from livers perfused with palmitate and at 12 degrees C and 17 degrees C for microsomes from livers perfused with oleate containing medium. These results suggest that the physicochemical properties of liver microsomes were determined in part by the fatty acid in the perfusate.

Animals↗
PubMed1979

Plasma membrane aminophospholipid distribution in transformed murine fibroblasts.

The possibility that the asymmetric distribution of aminophospholipids may be an intrinsic property of mammalian plasma membranes was examined in LM cells, a transformed murine fibroblast cell line. The cells were grown in suspension culture in a chemically defined medium without lipid, protein, or serum and then treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). A maximum of 4% of LM cell plasma membrane phosphatidylethanolamine and 5% of the phosphatidylserine was labelled with TNBS. Furthermore, long chain and unsaturated fatty acids were preferentially esterified to the non-derivatized phosphatidylethanolamine (inner monolayer) as compared to phosphatidylethanolamine derivatized with TNBS (outer monolayer). Isethionyl acetimidate, an alternative non-penetrating reagent, confirmed the results obtained with TNBS and provided supportive evidence for the highly asymmetric distribution of phosphatidylethanolamine; 6% of the phosphatidylethanolamine was labelled with isethionyl acetimidate. When the penetrating reagent methylacetimidate was used, more than 80% of the phosphatidylethanolamine was derivatized. Although the growing of the LM cells in 10% calf serum significantly increased plasma membrane phosphatidylcholine while decreasing phosphatidylethanolamine, calf serum had no significant effect on phosphatidylethanolamine or phosphatidylserine asymmetry.

Animals↗
PubMed1979

A food satiation and oral hygiene punishment program to suppress chronic rumination by retarded persons.

Food satiation and oral hygiene punishment were used to treat the non-life-threatening rumination of two institutionalized profoundly retarded persons. Satiation consisted of allowing the clients to eat until a satiation criterion of food refusal was achieved or until two full meal portions were consumed. The oral hygiene procedure consisted of cleansing the clients' teeth and gums with Listerine for 2 minutes following each instance of rumination. In the formal study, three conditions--baseline, satiation, and satiation plus oral hygiene--were used following the lunch meal in a multiple-baseline across-subjects design. One client's rumination decreased from an average of 89.5% during baseline to 48.8% during the satiation condition and to 3% during satiation plus oral hygiene. The second client's rumination decreased from a baseline average of 49.9% to 7.9% during satiation and to 1.4% during satiation plus oral hygiene. Generalization probes taken following the breakfast and dinner meals showed a systematic decline in rumination as the various conditions were implemented following the lung meal. In the 16-week follow-up, rumination was treated following all meals with oral hygiene, and satiation was used at one of the daily meals for 1 week on a rotating basis. Rumination remained at a near-zero level following all meals throughout the follow-up. Thereafter, a maintenance program was conducted by the ward staff. The satiation plus oral hygiene punishment treatment program appears to be an immediate, effective, enduring, and humane method of treating the non-life-threatening rumination of retarded individuals.

Adult↗
PubMed1978

Retention of acyl groups in LM cell fibroblasts with altered phospholipid composition.

Incorporation and loss of membrane lipids were measured in murine fibroblasts grown in suspension culture with [2-14C]acetate in a chemically defined medium devoid of serum or lipid. Greater than 98 and 94% of the 14C present in the phospholipids and neutral glycerides respectively was found in the fatty acyl groups. During a 3-day growth period LM fibroblasts lost 65% of their 14C-labelled acyl groups from the phospholipids and 36% from the neutral lipids. Selective retention of 14C in individual isolated phospholipid and neutral lipid species occurred only in phosphatidylethanolamine. Retention of acyl groups in the phospholipids or neutral glycerides was not a property of LM suspension cultured fibroblasts. Supplementation of the LM cells with choline analogues, such as N,N'-dimethylethanolamine, N-monomethylethanolamine, or ethanolamine instead of choline, decreased the loss of 14C-labelled fatty acids from phospholipid and neutral lipid. Ethanolamine supplementation resulted in increased loss of 14C from desmesterol as well as decreased incorporation of 14C into desmosterol. Thus, polar head group manipulation affected acyl group composition, acyl group retention, and sterol metabolism in suspension cultured LM cells.

Acetates↗