Biomedical subjects

C Punzengruber

Publications and source records attributed to C Punzengruber.

59 records · Page 4Linked to original sources

PubMed1979

Ionized and bound calcium inside isolated sarcoplasmic reticulum of skeletal muscle and its significance in phosphorylation of adenosine triphosphatase by orthophosphate.

Calcium loading of skeletal muscle sarcoplasmic reticulum performed passively by incubation with high calcium concentrations (0.5--15 mM) on ice gives calcium loads of 50--60 nmol/mg sarcoplasmic reticulum protein. This accumulated calcium is not released by EGTA [ethyleneglycol bis-(2-aminoethyl)-N,N,N',N'-tetraacetic acid], but almost completely released by ionophore X-537A plus EGTA or phospholipase A plus EGTA treatment and is therefore assumed to be inside the sarcoplasmic reticulum. This calcium is distributed in one saturable and one non-saturable calcium compartment, as derived from the dependence of the calcium load on the calcium concentration in the medium. These compartments are assigned to bound and ionized calcium inside the sarcoplasmic reticulum, respectively. Maximum calcium binding under these conditions was 33 nmol/mg protein with an apparent half-saturation constant of 5,8 nmol/mg free calcium inside, or between 1.2 and 0.6 mM free calcium inside, assuming an average vesicular water space of 5 or 10 microliter/mg protein, respectively. Calcium-dependent phosphorylation of sarcoplasmic reticulum calcium-transport ATPase from orthophosphate depends on the square of free calcium inside, whilst inhibition of phosphorylation depends on the square of free calcium in the medium. Calcium-dependent phosphorylation appears to be determined by the free calcium concentrations inside or outside allowing calcium binding to the ATPase according to the two classes of calcium binding constants for low affinity calcium binding or high affinity calcium binding, respectively. It is further suggested that the saturation of the low-affinity calcium-binding sites of the ATPase facing the inside of the sarcoplasmic reticulum membrane is responsible for the greater apparent orthophosphate and magnesium affinity in calcium-dependent phosphorylation than in calcium-independent phosphorylation from orthophosphate. Maximum calcium-dependent phosphoprotein formation at 20 degrees C and pH 7.0 is about 4 nmol/mg sarcoplasmic reticulum protein.

Adenosine Triphosphatases↗

PubMed1978

Calcium gradient-dependent and calcium gradient-independent phosphorylation of sarcoplasmic reticulum by orthophosphate. The role of magnesium.

Phosphorylation of the calcium-transport ATPase of skeletal muscle sarcoplasmic reticulum by inorganic phosphate was investigated in the presence or absence of a calcium gradient. The maximum phosphoprotein formation in the presence of a calcium gradient at 20 degrees C and pH 7.0 is approximately 4 nmol/mg sarcoplasmic reticulum protein, but only between 2.4 and 2.8 nmol/mg protein in the absence of a calcium gradient, using Ionophore X-537 A or phospholipase-A-treated sarcoplasmic reticulum vesicles. Maximum phosphoprotein formation independent of calcium gradient at 20 degrees C and pH 6.2 is in the range of 3.6--4 nmol/mg protein. Half-maximum phosphoprotein formation dependent on calcium gradient was achieved with 0.1--0.2 mM free orthophosphate at 10 mM free magnesium or at 0.1--0.2 mM free magnesium at 10 mM free orthophosphate. Phosphoprotein formation independent of calcium gradient is in accordance with a model which assumes, firstly, the formation of a ternary complex of the ATPase protein with orthophosphate and magnesium (E . Pi . Mg) in equilibrium with the phosphoprotein (E-Pi . Mg) and, secondly, an interdependence of both ions in the formation of the ternary complex. The apparent equilibrium constant was 0.6 and the apparent dissociation constants KMg, KMg', KPi and KPi' were 8.8, 1.9, 7.2 and 1.5 mM respectively, assuming a total concentration of the phosphorylation site per enzyme of 7 nmol/mg protein.

Animals↗

PubMedDate not supplied

Factors affecting penetration of retrograde coronary venous injections into normal and ischemic canine myocardium: assessment by contrast echocardiography and digital angiography.

Ths experimental study described myocardial echo contrast enhancement through coronary venous injections. Retrograde administration of renografin was performed in 15 closed-chest dogs. Two-dimensional echocardiography was used to study myocardial echo contrast enhancement before and after coronary artery occlusion. Digital subtraction venography was used to assess delivery, drainage and shunting of the retrograde injectate. Systolic/diastolic blood pressure in the great cardiac vein measured 7 +/- 3/1 +/- 0.6 mm Hg and increased to 29 +/- 11/5 +/- 3 after coronary sinus occlusion and to 55 +/- 2.3/15 +/- 12 mm Hg during coronary sinus contrast injection. Myocardial contrast echo appearance in a midpapillary left ventricular short axis cross-section was limited to the anteroseptal region, extending to 28.4 +/- 11.3% of the section circumference after great cardiac vein injections and 35.3 +/- 17% after coronary sinus injections (difference NS). After occlusion of the left anterior descending coronary artery, great cardiac vein contrast injections resulted in opacification of 36.6 +/- 9.7% of the section circumference (N.S. vs preocclusion control) and opacified most, but not all asynergic segments. After occlusion of the circumflex coronary artery, myocardial echo contrast uptake was restricted to the septum and the anterior wall. The ischemic and asynergic posterolateral myocardial segments were not opacified. Digital subtraction coronary venography revealed rapid drainage of retrogradely injected contrast to the right atrium, in spite of coronary sinus balloon occlusion via venovenous anastomoses. Retrograde coronary venous contrast injections may help define myocardial regions which are accessible with retrograde coronary venous interventions.

Angiography, Digital Subtraction↗

PubMedDate not supplied

Effect of angiotensin II infusion on a prostaglandin I2-metabolite and on left ventricular function.

Angiotensin II's influence on circulating levels of prostaglandin I2 metabolite 6-keto-PGF1-alpha were determined during a pharmacological stress test of left ventricular function in 10 control subjects and 5 patients with coronary artery disease. Angiotensin II infusion (1.5 +/- 0.34 micrograms/min) led to a significant increase of mean arterial blood pressure in both study groups (p less than 0.001). Heart rate decreased in control subjects (p less than 0.01) whereas in patients with coronary artery disease no significant change occurred. Global left ventricular ejection fraction determined by gated blood pool scanning decreased significantly in both study groups (p less than 0.05). The lack of reflex bradycardia in patients with coronary artery disease may be due to a compensatory increased sympathetic tone, prohibiting a more pronounced decline in ejection fraction. 6-keto-PGF1-alpha levels could be measured only in 6 of 15 persons. In the others they were below the limit of detection of the assay (70 pg/ml). During angiotensin II infusion 6-keto-PGF1-alpha increased significantly and could be determined in all persons. Patients with coronary artery disease reached slightly higher 6-keto-PGF1-alpha levels than controls (119 +/- 19 pg/ml versus 91.5 +/- 7 pg/ml; n.s.). Thus although angiotensin II infusion leads to vasoconstriction and increases peripheral resistance it also stimulates the production of vasodilating prostaglandins which may play a role in preserving microcirculation.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Efficacy of cyclosporin A in systemic sclerosis.

In this open pilot study, the potential therapeutic efficacy of Cyclosporin A (CsA) in systemic sclerosis (scleroderma) was investigated. Eight patients with severe scleroderma (skin manifestation and at least three organ manifestations such as pulmonary, intestinal, cardiac, renal, and severe hypertension) were included in the study. CsA administration was started at a dose of 5 mg per kg body weight per day and then, to obtain whole blood levels of 300-500 ng/ml, adjusted to a mean dosage of 4.3 mg/kg/day. Therapeutic effects were evaluated by monitoring the measures of cutaneous, pulmonary, cardiac, gastrointestinal, and renal involvement as well as laboratory parameters. After 6 to 12 months of CsA-administration, cutaneous abnormalities improved in seven, arterial oxygen tension slightly increased in four, pulmonary hypertension decreased in five, and smooth muscle esophageal contraction amplitudes improved in three patients. However, the disease progressed in one patient. No serious side effects were observed, and occurring renal side effects were mild. Taken together, these observations indicate that CsA administration may be effective mainly in the skin involvement, but also in some organ manifestations of scleroderma. The results of this pilot investigation therefore indicate that a controlled study of the efficacy of CsA in scleroderma is needed and ought to be performed.

Adult↗