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Biomedical subjects

E Heinz

Publications and source records attributed to E Heinz.

At least 73 records · Page 4Linked to original sources
PubMed1983

Effect of K+ and H+ on sodium/citrate cotransport in renal brush-border vesicles.

The uptake of citrate by renal brush-border vesicles, prepared according to the method of Vannier, occurs by Na+-linked cotransport. It is 'positive rheogenic', i.e., stimulated by an (inside) negative, and inhibited by an (inside) positive electrical potential. The question arises whether, besides Na+, other ions (e.g., K+ and H+) participate in the cotransport. As to K+, neither an inward nor an outward directed K+ gradient has a significant effect on the citrate movement, but at equal concentrations of K+ inside and outside, equilibrium exchange of citrate, and to a smaller extent, the Na+-linked net uptake of citrate, are significantly stimulated. This observation is consistent with a hypothetical model in which K+ acts by accelerating both the empty and the fully loaded translocator. As to H+, citrate uptake is also stimulated by decreasing extravesicular pH, an effect previously attributed to protonization of the citrate anion in the assumption that the resulting secondary citrate anion is more acceptable to the translocator site. It was found, however, that the pH effect is still apparent if the concentration of the secondary citrate is kept constant by adjusting the total citrate concentration. This is taken as an argument against the above assumption and as being consistent with H+-linked cotransport. After the overshoot peak citrate exits slowly, and even after several hours does not attain equilibrium distribution, presumably owing to trapping by vesicular calcium.

Animals↗
PubMed1983

Similarities and differences in lipid metabolism of chloroplasts isolated from 18:3 and 16:3 plants.

Photosynthetically active chloroplasts retaining high rates of fatty acid synthesis from [1-(14)C]acetate were purified from leaves of both 16:3 (Solanum nodiflorum, Chenopodium album) and 18:3 plants (Amaranthus lividus, Pisum sativum). A comparison of lipids into which newly synthesized fatty acids were incorporated revealed that, in 18:3 chloroplasts, enzymic activities catalyzing the conversion of phosphatidate to diacylglycerol and of diacylglycerol to monogalactosyl diacylglycerol (MGD) were significantly less active than in 16:3 chloroplasts. In contrast, labeling rates of MGD from UDP-[(14)C]gal were similar for both types of chloroplasts.The composition and positional distribution of labeled fatty acids within the glycerides synthesized by isolated 16:3 and 18:3 chloroplasts were similar and in each case only a C18/C16 diacylglycerol backbone was synthesized. In nodiflorum chloroplasts, C18:1/C16:0 MGD assembled de novo was completely desaturated to the C18:3/C16:3 stage.Whereas newly synthesized C18/C18 MGD could not be detected in any of these chloroplasts if incubated with [(14)C]acetate after isolation, chloroplasts isolated from acetate-labeled leaves contained MGD with labeled C18 fatty acids at both sn-1 and sn-2 positions. Taken together, these results provide further evidence on an organellar level for the operation of pro- and eucaryotic pathways in the biosynthesis of MGD in different groups of plants.

Journal Article↗
PubMed1983

[Experience with a simple form for the evaluation of surgical risk due to nutritional status].

The diagnosis and determination of the nutritional status for the evaluation of a surgical risk is achieved on the basis of a simple documentation scheme: The aim of the presented study was the characterization of this specific check-up protocol to find out the usefulness and applicability of this scheme and its value for the recognition of the nutritional status as one of the factors determining the outcome of surgical patients. The results show that this simple procedure allows an equivalent ranging of patients in different classes of nutrition related states as the highly sophisticated, time, costs and staff consuming protocols which were published to define nutritional states in the last years. When the exact and differentiated status is not necessary the simple protocol gives the same information to judge the possible risk by nutritional deficiencies as the complicated protocols.

Female↗
PubMed1981

The residual protonmotive force in mitochondria after an oxygen pulse.

Both from irreversible thermodynamics and from mass-action kinetics it can be derived that upon anaerobiosis in an oxygen-pulse experiment the protonmotive force across a mitochondrial membrane undergoes a sudden drop. Under representative conditions the protonmotive force after the drop (the residual protonmotive force) is shown to be less than 3 kJ . mol-1 as opposed to steady-state values for the protonmotive force of 19 kJ . mol-1. It is concluded that correction for proton leakage in pulse experiments by back extrapolation underestimate proton leakage. Consequently the observed H+/O stoichiometries must underestimate the true H+/O ratios.

Hydrogen-Ion Concentration↗
PubMed1981

Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts.

Soluble acyl-CoA:sn-glycerol 3-phosphate acyltransferases (EC 2.3.1.15) which are localized in chloroplasts were purified from leaves of Pisum sativum and Spinacia oleracea and obtained free from interfering activities. The purification raised the specific activities by factors of about 1,000 for pea and 200 for spinach preparations. In pea chloroplasts, acyltransferase activity occurs in two soluble forms with apparent isoelectric points of 6.3 and 6.6. For both forms, the same molecular weight of about 42,000 was determined. The enzyme from spinach chloroplasts showed a slightly higher molecular weight and a lower isoelectric point of 5.2.The enriched enzyme fractions possessed a specificity for glycerol 3-phosphate as acyl acceptor and did not use dihydroxyacetone phosphate. Besides acyl-CoA, acyl-acyl carrier protein also can function as acyl donor. With acyl-CoA as acyl donor, the enzyme shows a high positional specificity, since the predominant product is 1-acylglycerol 3-phosphate.Different acyl-CoAs, when offered separately, were all accepted as substrates, whereas incubations with mixtures of palmitoyl-, stearoyl-, and oleoyl-CoA demonstrated a preference for oleic acid. The acyltransferase from spinach displays higher selectivity than does the enzyme from pea and, therefore, may be responsible for the preferred esterification of oleic acid at the C-1 position in chloroplast lipids and the exclusion of palmitic acid from this position as observed during in vivo labeling experiments.

Journal Article↗
PubMed1981

Phospholipid composition of chlorophyll-free mitochondria isolated via protoplasts from oat mesophyll cells.

Mitochondria were isolated from oat primary leaves via mesophyll protoplasts and subjected to phospholipid analysis. In mesophyll cells mitochondria account for only small proportions of cellular phospholipids (in the order of 5%) and proteins (in the order of 2%). Contamination by lipids from other membranes was insignificant as indicated by the absence or very low levels of chlorophyll, galactolipids and steryl glycosides. The absence of 3-trans-hexadecenoic acid in phosphatidylglycerol from mitochondria of green cells serves an an additional criterion of purity. The phospholipid mixture extracted from these mitochondria resembles phospholipids in mitochondria from non-green tissues regarding composition as well as fatty acid profiles. Therefore, mitochondria maintain a rather constant lipid profile and in contrast to plastids do not respond at this level to differences in the physiological status of their housing cell. Palmitic acid in mitochondrial phosphatidylcholine and phosphatidylethanolamine is primarily localized at the C-1 position of the glycerol moiety. Two enzymatic activities so far not described in mitochondria, formation of acylgalactosyl diacylglycerol and hydrolysis of acyl-CoA, were found in the purified mitochondrial fraction.

Chlorophyll↗
PubMed1980

Na+-linked cotransport of glycine in vesicles of Ehrlich cells.

Vesicles have been prepared from Ehrlich cells by using a method based on the early experiments of Forte et al. (Forte, J.G., Forte, T.M. and Heinz, E. (1973) Biochim. Biophys. Acta 298, 827-841) with some minor modifications, using the filter technique. From electron micrographs and from the sensitivity of these vesicles towards osmotic pressure changes in the medium induced by (nonpermeant) sucrose, it is concluded that the vesicles are closed. The counterflow phenomenon with glycine and Na+-linked contransport of glycine appears to indicate that these vesicles are still functioning. The observation of the overshoot phenomenon interpreted in terms of theoretical predictions confirms that the active accumulation of glycine is energized by the Na+ electrochemical potential gradient. In particular, the contribution of the electrical components of these gradients is evidenced by the effects of the anion of the added sodium salt or of the addition of valinomycin. In contrrast to observations by others we found that ouabain does not directly affect Na+-linked cotransport of glycine whereas HgCl2 does so. Nor could any significant overshoot be demonstrated in the absence of an Na gradient. Since these vesicles were not metabolically active, these experiments do not exclude the possibility that in intact cells glycine is in addition transported primarily or partially actively.

Animals↗
PubMed1980

Electrically silent cotransport on Na+, K+ and Cl- in Ehrlich cells.

A cotransport system for Na+, K+ and Cl- in Ehrlich cells is described. It is insensitive towards ouabain but specifically inhibited by furosemide and other 'high ceiling' diuretics at concentrations which do not affect other pathways of the ions concerned. As the furosemide-sensitive fluxes of these ions are no affected by changes in membrane potential, and as their complete inhibition by furosemide does not appreciably alter the membrane potential, they appear to be electrically silent. Application of the pulse-response methods in terms of irreversible thermodynamics reveals tight coupling between the furosemide-sensitive flows of Na+, K+ and Cl- (q close to unity for all three combinations) at a stoichiometry of 1: 1 : 2. The site for each of the ions appears to be rather specific: K+ can be replaced by Rb+ but not by other cations tested whereas Cl- can be poorly replaced by Br- but not by NO(-)3, in contradistinction to the Cl(-)-OH- exchange system. The cotransport system appears to function in cell volume regulatin as it tends to make the cell swell, thus counteracting the shrinking effect of the ouabain-sensitive (Na+, K+) pump. The experiments presented could not clarify whether the cotransport process is a primary or secondary active one; while incongruence between transport and conjugated driving force seems to indicate primary active transport, it is very unlikely that hydrolysis of ATP supplies energy for the transport process, since thre is not stimulation of ATP turnover observable under operation of the cotransport system.

Adenosine Triphosphate↗
PubMed1980

Distribution of radioactive lipids between envelopes and thylakoids from chloroplasts labelled in vivo.

Spinach leaves were labelled with 14CO2 for subsequent isolation of radioactive chloroplasts, which were separated into envelopes and thylakoids. The analyses carried out with the lipid extracts from these membranes were concerned with the following questions: are chloroplast envelopes a functional interface between endoplasmic reticulum and thylakoids, do they also play a predominant role in galactolipid biosynthesis in vivo, and is it possible to demonstrate galactolipid export from envelopes into thylakoids? Taken together the results show that lipid export is apparently too fast in vivo to be followed by the labelling and separation technique used, since thylakoid lipids contained always far more total label than envelope counterparts, whereas the specific activity of envelope lipids was higher. Phosphatidylcholine, which has been suggested to function as acyl carrier between endoplasmic reticulum and chloroplasts, was never found labelled to any extraordinary extent in envelopes. Envelopes may be regarded as small, but rapidly turned over lipid pools.

Chloroplasts↗
PubMed1980

Labelling in vivo and in vitro of molecular species of lipids from chloroplast envelopes and thylakoids.

Lipid mixtures from chloroplast envelope and thylakoid membrane were isolated after different labelling times in vivo and in vitro and separated into major components. The isolated compounds were subjected to analyses such as separation of molecular species, determination of radioactivity in fatty acids and water-soluble hydrolysis products and radio gas-liquid chromatography of fatty acid mixtures. In the case of monogalactosyl and digalactosyl diacylglycerol these procedures were also applied to several individual molecular species. To investigate the extent of de novo synthesis these species were also used for methylation studies and their fatty acids subjected to alpha-oxidation. In envelope membranes diacylglycerols and monogalactosyl diacylglycerols may each be separated into several distinct and non-mixing pools. Molecules made de novo with oligoene fatty acids are very efficient substrates for galactosylation in vivo. The time-dependent changes in patterns of galactolipid molecular species may indicate a desaturation of acyl chains operating in close contact to intact lipids. After isolation, envelopes incorporated UDP-[14C]galactose into completely different patterns of galactolipids and molecular species pointing to changed properties of this membrane system or to a loss of regulatory factors.

Chloroplasts↗