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W Augustin

Publications and source records attributed to W Augustin.

70 records · Page 4Linked to original sources
PubMed1981

Studies on the regulation of mitochondrial ATP formation in rabbit reticulocytes.

Respiration and phosphorylation in functionally intact isolated reticulocyte mitochondria are controlled by the extramitochondrial ATP/ADP ratio. Mitochondrially bound hexokinase exhibits an apparent preference against mitochondrially formed ATP, as indicated by the lower apparent Km values under phosphorylating conditions. Thereby the control characteristics are shifted to higher ATP/ADP ratios compared to hexokinase free mitochondria. Respiration of intact reticulocytes was estimated to be smaller than had to be expected from the ATP/ADP ratios of total cells roughly corresponding to the cytosolic values. Inhibition of respiration leads to small drop of total adenine nucleotides and lowers the phosphorylation potential directly determined or calculated from metabolite indicators. Compartmentation of ADP by protein binding is discussed as a possible reason for the difference of determined and calculated phosphorylation potentials and the apparent discrepancy between the regulation of mitochondrial ATP-formation in isolated mitochondria and intact reticulocytes.

Adenosine Diphosphate↗
PubMed1981

A simple procedure for the enrichment of reticulocytes by isodense differential centrifugation on silicone oil mixtures.

Utilizing age-dependent differences in the density of red cells, a mixture of silicone oils with density of 1.0806 g/ml was used for the enrichment of rabbit reticulocytes. During concentration, heavy cells, mainly consisting of erythrocytes, move into the silicone oil, whereas the reticulocytes remain above the oil. Suspensions of apparently intact cells with reticulocyte counts of 87 +/- 7.8% and a recovery rate of about 37% were reproducibly obtained. Neither inhibition of cell respiration nor depletion of adenine nucleotides were observed after this enrichment procedure. A micro-modification in hematocrit capillaries seems to be applicable to obtain rapid information about reticulocyte contents in blood samples without staining and counting of cells.

Animals↗
PubMed1981

[Studies into prostaglandin levels of amniotic fluid in early pregnancy (author's transl)].

Equivalents of primary prostaglandins A and B as well as E and F were determined in the amniotic fluid of 64 clinically intact women in early pregnancy. The prostaglandin levels of the A and B groups were continuously lowered, between the ninth and 32nd weeks of pregnancy, while prostaglandin E revealed gradual rise from 57 pg/ml, in the ninth and tenth weeks, to 100 pg/ml, between the 29th and 32nd weeks. Prostaglandin F levels behaved similarly, between the 16th and 21st as well as between the 29th and 32nd weeks, mean values being 60 pg/ml or 75 pg/ml, respectively. High prostaglandin F levels, as recorded between the ninth and twelfth weeks of pregnancy (244 pg/ml), were probably attributable to mode by which amniotic fluid has been collected. Collection in that phase of pregnancy was transcervically, following cervix dilation during abortion, which differed from transabdominal amniocentesis in more advanced pregnancy. The above findings are discussed with regard to their physiological and clinical relevance.

Amniotic Fluid↗
PubMed1978

Investigations on prostaglandin levels in amniotic fluid and maternal blood during late pregnancy.

Prostaglandin E and F equivalents have been measured during late pregnancy in amniotic fluid and maternal venous blood by radioimmunoassay after purification on silicic acid columns. In amniotic fluid levels of both prostaglandins exhibit a tendency to increase, in particular after 36 weeks of gestation, possibly most markedly 20--4 h before the onset of labour. The PG E/F-ratio in amniotic fluid may slightly decrease during the late gestational age. In maternal venous blood variable low levels of both prostaglandins were observed without any correlation to the age of gestation.

Amniotic Fluid↗
PubMed1977

Synthesis of phospholipids in mitochondria and other membrane fractions of rabbit reticulocytes.

1. Reticulocytosis of 40-50% was obtained in rabbits by daily bleeding. Reticulocytes (plus erythrocytes) were subfractionated into plasma membrane fraction, mitochondria and the post-mitochondrial fraction. 2. In all fractions, fatty acids were incorporated into phospholipids. This process was ATP dependent and represented acylation of lysophospholipids. 3. Incorporation of fatty acids into lysophosphatidic and phosphatidic acids occurred only in the presence of sn-glycerol 3-phosphate and was observed in mitochondria and the post-mitochondrial fraction. It represents a two-step acylation of sn-glycerol 3-phosphate. 4. Incorporation of phosphorylcholine from CDPcholine into phosphatidylcholine was observed in the mitochondrial and the post-mitochondrial fractions. This activity was correlated with NADPH-cytochrome c reductase and was probably connected with the remnants of the endoplasmic reticulum.

Animals↗
PubMed1977

Studies on NAD+ permeability in intact mitochondria from rabbit reticulocytes.

Functionally intact mitochondria from rabbit reticulocytes are characterized by a low NAD+ level after the preparation (0.29 nmoles NAD+ + NADH/mg protein). They are apparently impermeable for NADH and exhibit a slow net uptake of NAD+. From the increase of O2-uptake in state 3 and the increase of NADH concentration in state 4 of respiration after the addition of NAD+ we concluded that 3--10 min are necessary for the saturation with NAD+ at 23 degrees C. 2mM NAD+ extramitochondrially are not sufficient to saturate the mitochondria with NADH and probably NAD+, too. Because of the net uptake of NAD+ we assume that reticulocyte mitochondria lose NAD+ during their preparation. If they are incubated with the physiological concentration of 300 micrometer NAD+, which was found in reticulocytes, a value of 1.9 nmoles NAD+ + NADH mg protein was calculated. At an extramitochondrial NAD+ concentration of 300 micrometer, reticulocyte mitochondria exhibit an almost maximal O2-uptake in the presence of oxaloacetate or alpha-ketoglutarate. It is concluded that the mitochondria in intact reticulocytes contain the "normal" complement of NAD+ + NADH.

Animals↗
PubMedDate not supplied

Oxidative stress affects pancreatic proteins during the early pathogenesis of rat caerulein pancreatitis.

Rats received up to four subcutaneous injections of caerulein (20 microg/kg) in hourly intervals to induce a mild edematous pancreatitis. A single dose of caerulein resulted in significant oxidative modification of proteins in pancreatic homogenates as compared to saline-injected controls (p < 0.01). Repeated injections of the secretagogue were unable to induce a further increase in modified proteins. Protein oxidation preceded the formation of the lipid peroxidation product malondialdehyde as well as edema and the increase in serum amylase by 1-2.5 h. Western blotting for oxidatively modified proteins confirmed the results of the quantitative measurements and did not reveal individual, selectively modified proteins. These findings indicate that oxidative stress and oxidative protein modification are very early events in the initial period of caerulein pancreatitis. This may explain the poor success rate of most studies that administered antioxidants therapeutically during or after initiation of pancreatitis.

Amylases↗
PubMedDate not supplied

[Endogenous prostaglandin level in the amniotic fluid in premature labor].

Radioimmunological determinations of prostaglandin (PG) levels have been performed in amniotic fluid samples from 53 patients with signs of premature labour in order to characterize the significance of the PG system for the initiation and progress of preterm deliveries compared with term deliveries. Statistically not significant slightly increased levels of both PG E- and PG F-equivalents during premature labour were observed when compared with undisturbed pregnancies of the same gestational age, but never reached concentrations characteristic for term pregnancies without uterine contractions. Patients, in whom premature labour could not be prevented exhibited elevated PG levels parallel to cervical dilatation during the course of parturition remaining, however, pronounced below that detected at comparable cervical state and duration of labour during term deliveries. It is concluded that at the gestational age of preterm labour the PG producing system is still immature, rendering the PG cascade to a minor functional role than during spontaneous term labour. A prognostic value of PG determinations and indications for a causal treatment of premature labour with PG synthesis inhibitors are not supported by the present investigations.

Amniotic Fluid↗