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Biomedical subjects

M G Sarzala

Publications and source records attributed to M G Sarzala.

At least 19 recordsLinked to original sources
PubMed1986

The lipid composition of erythrocyte ghosts from a patient with congenital paramyotonia.

The membrane lipid and fatty acid compositions of red blood cells from a paramyotonia patient were investigated. Cholesterol and total phospholipid contents in paramyotonia were not different from control. Only the sphingomyelin content was lower, and thus the molar ratio of phosphatidylcholine/sphingomyelin was higher than normal. The major abnormality concerned the fatty acid pattern. In all the phospholipid classes saturated fatty acids were increased and unsaturated fatty acids were decreased. The overall ratio of saturated/unsaturated fatty acids was 2.1 vs 1.6 in controls. Similar findings have been reported for the sarcolemma from paramyotonia patients. Thus, the results indicate that the membrane defect in this disease may be generalized.

Erythrocyte Membrane↗
PubMed1982

Studies on sarcoplasmic reticulum from slow-twitch muscle.

Vesicles were isolated from membranes of the sarcoplasmic reticulum (SR) of rabbit slow-twitch muscle by differential and sucrose density gradient centrifugation after homogenization. In some experiments, the vesicles were further fractionated by loading them with calcium oxalate followed by centrifugation in a sucrose density gradient. Protein composition of the isolated vesicles was complex and differed from the protein composition of fast-twitch muscle vesicles. However, other protein components, which were also present in fast-twitch muscle SR vesicles, have been identified: Ca2 + -dependent ATPase, calsequestrin, 160 000 molecular weight glycoprotein and 53 000 molecular weight glycoprotein. The amount of the Ca2 + -dependent ATPase and calsequestrin was several times lower in the slow-twitch muscle SR vesicles. This has been observed in both the original and the loaded vesicles. The slow-twitch muscle SR vesicles showed active calcium transport, Ca2 + -dependent ATPase activity, and the formation of the phosphorylated intermediate under conditions similar to those established for fast-twitch muscle SR. However, these activities, when expressed per mg of total protein, were several times lower than the analogous activities in the SR vesicles isolated from fast-twitch skeletal muscle. When the same enzyme activities were expressed per mg of the 105 000 molecular weight ATPase, the values obtained were very similar in both kinds of vesicles. The results indicate that the slow rate of calcium transport, found in slow-twitch muscle SR vesicles, may be related to a low content of the calcium-transporting ATPase in the membrane.

Animals↗
PubMed1979

Rotational motion and evidence for oligomeric structures of sarcoplasmic reticulum Ca2+-activated ATPase.

The rotational motion of the sarcoplasmic reticulum Ca2+-activated ATPase (ATP phosphohydrolase, EC 3.6.1.3) has been investigated by measuring the decay of laser flash-induced dichroism with the covalently attached triplet probe eosin isothiocyanate. The Arrhenius plot for rotational mobility indicates two discontinuities at approximately 15 degrees C and approximately 35 degrees C. The experimental data are rationalized in terms of a sudden conformeric change in the ATPase at 15 degrees C and a temperature-dependent equilibrium existing between the conformationally altered ATPase and oligomeric forms of it in the temperature range 15-35 degrees C. The enzymatic activity, as indicated by a discontinuity in the Arrhenius plot for the rate of ATP hydrolysis, appears to be sensitive only to the change at 15 degrees C. There is a strong correlation between the activation energy below 15 degrees C for rotational motion (33.6 +/- 2.2 kcal/mol) and enzymatic activity (34 +/- 4 kcal/mol).

Animals↗
PubMed1978

Studies on the heterogeneity of sarcoplasmic reticulum vesicles.

Isolated sarcoplasmic reticulum vesicles from rabbit white muscle were separated into a light (15--20% of total microsomes) and a heavy (80--85%) fraction by density gradient centifugation. The ultrastructure, chemical composition, enzymic activities and localization of membrane components in the vesicles of both fractions were investigated. From the following results it was concluded that both fractions are derived from the membranes of the sarcoplasmic reticulum system of the muscle: (i) The protein pattern of both fractions is essentially the same, except for different ratios of acidic, Ca2+-binding proteins. (ii) The 105000 dalton protein of the light fraction cross-reacts immunologically with the Ca2+-dependent ATPase of the heavy fraction. (iii) Ca2+-dependent ATPase, although of different specific activity, is found in both fractions. After rendering the vesicles leaky, specific activities in both fractions reach the same value. The light fraction was found to consist of "inside-out" vesicles by the following criteria: (i) No Ca2+ accumulation can be measured and the Ca2+-dependent ATPase activity is low and variable. (ii) The rate of trypsin digestion is lower and, compared to the heavy microsomes, a different ratio of degradation products is obtained. (iii) The sarcoplasmic reticulum membrane has a highly asymmetrical lipid distribution. This distribution of aminophospholipids is opposite to that in vesicles of heavy fraction. The light sarcoplasmic reticulum fraction has a higher phospholipid to protein ratio than the heavy one. This is consistent with the possibility that the two fractions derive from different parts of the sarcoplasmic reticulum system.

Adenosine Triphosphatases↗
PubMed1977

Sarcoplasmic reticulum vesicles and glycogen-protein particles in microsomal fraction of skeletal muscle.

1. Heavy microsomal fraction (HM) of rabbit skeletal muscle obtained by differential centrifugation between 8 000-30 000 g and consisting of sarcoplasmic reticulum (SR) vesicles contains variable amounts of glycogen and reveals some activity of phosphorylase b. The monomer of this enzyme of mol. wt. about 100 000 co-migrates in SDS-polyacrylamide gel electrophoresis with the main SR protein--Ca2+,Mg2+--dependent ATPase. 2. The highest specific activity of phosphorylase and the highest content of glycogen is present in the light microsomal (LM) fraction (30 000-100 000 g). 3. Contrary to the ATPase, phosphorylase b is released from the microsomal fraction by treatment with EDTA and is resistant to trypsin. 4. Both HM and LM fractions can be further fractionated on continuous sucrose density gradient at high speed. Main fraction of HM consists of highly purified SR vesicles. The second, small fraction of HM is identical with the main fraction of LM and consists of two populations: vesicles of structure and properties different from those of SR vesicles, and the particles of a complex of glycogen with some glycolytic enzymes.

Animals↗
PubMed1975

Changes in the structure, composition and function of sarcoplasmic-reticulum membrane during development.

The structure, chemical composition and function of the microsomal fraction, isolated by differential centrifugation and purified on sucrose gradients, from muscle of fetal, newborn and young rabbits were characterized and compared with those of sarcoplasmic reticulum vesicles from adult muscle. Negative staining shows that the microsomal vesicles isolated from muscles of embryos and newborn animals are smooth, in contrast to vesicles obtained from adult muscle which contain 4-nm particles on their surface. The particles appear first in the microsomal vesicles from muscles of 5--8-day-old rabbits. Their number increases with the age of the animals. Ca2+-pump protein, with molecular weight about 100000, accounts for 10% of the total protein content in sarcoplasmic reticulum membrane, isolated at the earliest stages of development analysed. Its amount increases continuously with the rabbit's age to the adult value of about 70% of total sarcoplasmic reticulum protein. The low amount of 100000-dalton protein and lack of 4-nm surface particles in sarcoplasmic reticulum vesicles obtained from fetal and newborn rabbits are strictly correlated with the low activity of Ca2+-dependent ATPase and the ability to take up Ca2+. These activities rise in parallel with the age of the rabbits. On the other hand, Mg2+-dependent ATPase activity is very high at the early stages of development and declines continuously to a low value in sarcoplasmic reticulum from adult muscle. The sarcoplasmic reticulum membrane from fetal and newborn rabbits contains a higher amount of lipids as compared with the membrane present in the muscle of adult animals. The ratio of both phospholipid to protein and neutral lipid to protein decreases with the age of the rabbits. The composition of sarcoplasmic reticulum phospholipids also changes during development.

Adenosine Triphosphatases↗