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Biomedical subjects

M Oratz

Publications and source records attributed to M Oratz.

At least 19 recordsLinked to original sources
PubMed1989

Hepatic radionuclide planar imaging.

99mTc colloid scans, hepatobiliary scans with IDA derivatives, 67Ga scans, and labeled red blood cells or indium-labeled white blood cells are the major imaging procedures that are currently widely available to visualize the liver. The use of labeled antibodies to a specific tumor is being explored as an investigative procedure but is complicated by the high circulating background activity. In this overview of planar liver radionuclide imaging, it was emphasized that these procedures are noninvasive, may be performed at the bedside, are inexpensive, and provide important data for formulating the further investigation of intrahepatic masses, gallbladder disease, vascular and inflammatory diseases. The functional status of the liver is the basis of the radionuclide imaging procedures, and the more accurate anatomic technique do not give these data.

Humans↗
PubMed1986

Prolonged feeding of ethanol to the young growing guinea pig. III. Effect on the synthesis of the myocardial contractile proteins.

Prolonged ingestion of ethanol may lead to a cardiomyopathy, and studies in the experimental animal have demonstrated alterations in protein metabolism. These changes include depression of protein synthesis with acetaldehyde in the acute experiment, in vitro, and after chronic ethanol ingestion in vivo. The present studies were initiated to see if the inhibition of protein synthesis following prolonged ethanol ingestion involved myocardial contractile proteins. Newly weaned guinea pigs, weighing 350 g, were placed on a regimen of normal laboratory diet with 10% ethanol in the drinking water. Calorie-matched controls, drinking dextromaltose in the water, were simultaneously run. After 40 weeks of ingesting 10% ethanol in the drinking water, hearts from growing guinea pigs were removed and synthesis of myocardial contractile proteins (myosin heavy chains, light chains (LC1, LC2), actin, and tropomyosin) assayed in vitro with 3H-labeled amino acids. With aging, there was a decrease in the rates of synthesis of all the contractile proteins. After 40 weeks of ethanol ingestion, the synthetic rates of myosin heavy and light chains and tropomyosin were the same as in calorie-matched controls, but the synthetic rate of actin was significantly decreased by 20% (p less than 0.01). This decrease in actin synthesis may be the first indication of ultimate inhibition of synthesis of all the contractile proteins which may lead to myofibrillar disorganization and vacuolization reported after chronic ethanol ingestion.

Animals↗
PubMed1985

Ethanol and cardiac protein synthesis.

Acute exposure of the heart to ethanol does not appear to alter the rate of young guinea pig cardiac protein synthesis when assayed in vitro. In contrast, the primary metabolite of ethanol, acetaldehyde, markedly diminishes synthesis despite its chronotropic and inotropic effects. On the other hand, after 11-13 weeks of ethanol-drinking during growth and maturation, the synthetic capacity of the working right ventricle was decreased when measured in vitro with normal perfusate. Assay of synthesis of the contractile proteins myosin heavy and light chains, actin and tropomyosin suggests a change in synthesis or pool size of actin reflected in an alteration of relative synthesis of this protein compared to that of heavy chains. The relative synthesis of the other proteins remained at control levels. When hearts from ethanol-drinking and matched control animals were perfused under conditions of severe ischemia, there was a profound fall in protein synthesis in all hearts, and ethanol did not enhance the inhibition of synthesis. However, the hearts from ethanol-drinking animals showed a more marked and significant impairment of maintaining ejection pressure with a marked increase in coronary resistance as the perfusion progressed. It is postulated that some impairment of protein metabolism may occur during prolonged ethanol exposure, which may influence the cardiac response of another induced stress, e.g., ischemia.

Acetaldehyde↗
PubMed1983

Effects of nutrition and alcohol on albumin synthesis.

Albumin synthesis was studied in the isolated perfused rabbit liver under the influence of the stresses of fasting and acute alcohol and acetaldehyde exposure. Fasting clearly depressed albumin production and disaggregated the endoplasmic membrane-bound polysomes. Acute exposure to alcohol produced the same results. Acetaldehyde 2 mg% resulted in a depression of albumin synthesis but the polysomes were not disaggregated. The metabolism of alcohol was necessary for polysome disaggregation. The acute effects of ethanol and fasting were quite similar and it might be considered that the alcohol was acting like a pharmacologic fast. Employing the liver from a fasted donor specific amino acids infused into the liver at levels of 10 mM reversed the acute effects of fasting and the acute effects of exposure to ethanol. However when the two stresses of fasting and alcohol were combined the same amino acids were not effective. In studying albumin synthesis and/or secretion it is necessary to carefully define the nutritional status of the experimental model.

Acetaldehyde↗
PubMed1982

Prolonged feeding of ethanol to the young growing guinea pig: 1. The effect on protein synthesis in the afterloaded right ventricle measured in vitro.

Newly weaned guinea pigs weighing approximately 300 g were fed normal laboratory diets with drinking water containing 5.5% ethanol as the sole source of liquid for periods of 8-11 weeks. Growth was continuous with this diet. After this period, hearts were removed from anesthetized animals and perfused for 3 hr in a perfusion system in which pressure may be induced in the right ventricle in the face of constant coronary flow. Protein synthesis, assayed from the incorporation of labeled lysine and phenylalanine, was compared to that in hearts from identically treated weight-matched control animals who had been drinking water without ethanol. Protein synthesis in hearts from ethanol-drinking animals was decreased in the right ventricles exposed to normal pulmonary pressure, but was unchanged in the contracting but not working left ventricles. The data suggest that prolonged exposure even to low levels of ethanol in the growing animal may interfere with the cardiac protein synthetic response to the normal work stress.

Age Factors↗
PubMed1981

Relative synthesis of cardiac contractile proteins. Evidence for synthesis from the same precursor pool.

The relative molar synthesis of cardiac contractile proteins has been measured in the perfused heart under control haemodynamic conditions. This synthesis, of myosin heavy chains, individual light chains (1 and 2), actin and tropomyosin, was determined from isolated guinea-pig hearts perfused for 3h simultaneously with constant specific radioactivities and concentrations of [3H]lysine and [3H]phenylalanine. The data strongly suggest that all of the proteins studied were synthesized from the same precursor pools of lysine and phenylalanine, since the ratio of the specific activities of the two labels was the same in all of the proteins. Measurement of molar synthesis of each contractile protein was the same with either labelled amino acid. Under control haemodynamic-perfusion conditions, the relative molar synthesis of the contractile proteins was actin greater than heavy chains greater than light chain 2 greater than light chain 1 greater than tropomyosin.

Actins↗
PubMed1981

Protein secretion in suspensions of isolated rat hepatocytes: no influence of acute ethanol administration.

The effect of ethanol on the secretion of proteins was studied in hepatocytes isolated from 24-h fasted rats and from fed rats. Hepatocytes were isolated after collagenase disruption of the liver and incubated in a standard medium containing amino acids, bovine albumin, glucose, penicillin and streptomycin in HEPES buffer. Cell viability was determined by urea production and trypan blue exclusion. When studying protein export, a model had to be chosen in which the labeling is accomplished before the addition of the test agents. Cells were incubated with [3H]valine for 2.5 and 7.5 min followed by a 15-mM valine chase and the incubates were adjusted to final concentrations of ethanol of 50 mM, 100 mM, colchicine 5-50 microM or cycloheximide 18 microM. Cells and media were harvested at various times, and counts incorporated into medium and cell protein were determined. Cycloheximide inhibited protein synthesis by 99%, decreased protein secretion by 10-20%, but did not further inihibit protein labeling when given after the chase confirming the chase's effectiveness. Colchicine inhibited protein release by 27-54% depending on the dose. With control cells labeled protein and specifically albumin appeared in the medium 20 min from the start of the pulse and this release of protein was not inhibited by 50 mM or 100 mM ethanol incubated with cells from the same animal whether the donor has been fed or fasted. The values for the ethanol-treated cells ranged from 94.0 to 113% of the control values from 30 to 120 min after the addition of the pulse. Lactate levels were markedly elevated, and urea synthesis decreased in the presence of either 50 mM EtOH or 100 mM EtOH. Thus using a method that can distinguish the effect of ethanol on synthesis from secretion, it is concluded that acute exposure to EtOH does not interfere with protein secretion.

Animals↗
PubMed1980

Effects of ethanol on protein synthesis and secretion.

Liver protein synthesis involves a complex series of reactions which is influenced by hormones, nutritional state and general health of an animal. The secretory processes for proteins, such as albumin, also interact with the protein synthetic machinery of the liver. Alcohol may affect synthesis and/or secretion at a number of loci and the mechanism of alcohol's action could depend on the immediate state of the experimental tissue. Ethanol was shown to interfere with albumin synthesis and the effect was shown to differ when livers from fed and fasted animals were compared. The ethanol effects were also dependent on the metabolism of ethanol rather than on the simple presence of this drug. Acetaldehyde decreased albumin synthesis but in a manner which was distinct from the ethanol effect. Acute ethanol administration under the conditions used in our studies had little effect on secretion of prelabeled proteins from hepatocytes. The implications of studies of the effects of ethanol on liver protein synthesis and secretion are discussed.

Acetaldehyde↗
PubMed1980

The effects of acetaldehyde and disulfiram on albumin synthesis in the isolated perfused rabbit liver.

Acetaldehyde infusions inhibit albumin synthesis in the liver from fed donors but not in the livers from fasted donors. The inhibition of acetaldehyde metabolism with 4-MP and disulfiram reverses this finding, suggesting that acetaldehyde per se is not the toxic agent. Disulfiram stimulates albumin synthesis in livers from fasted donors, and the presence of acetaldehyde does not prevent this process. The effects of ethanol infusions cannot be explained as due to the presence of acetaldehyde; some intermediate metabolic step may be the basis of the inhibition of albumin production and polysome disaggregation in the presence of ethanol.

Acetaldehyde↗
PubMed1980

Post ischemic reperfusion and anoxic perfusion in the isolated heart: alteration in distribution of radionuclides and in protein synthesis.

1. Reperfusion after ischemia and perfusion with total anoxia were studied in the isolated guinea pig heart model which permits right ventricular loading and constant coronary perfusion. Deprivation of oxygen in both situations resulted in a marked shift of circulation from the left to the right ventricle with markedly increased spaces of distribution of 99mTc radionuclides and albumin in the latter. 2. In view of the complexities of measuring protein synthesis during ischemia, continuous anoxic perfusion was used to evaluate this parameter in anoxic induced arrest. There was a profound fall in protein synthesis associated with this arrest, accompanied by a fall in ATP, creating phosphate, glycogen, potassium, and a rise in lactate production. The fall in protein synthesis was more marked in the left ventricle, despite the absence of work while it was still beating. 3. The changes in synthesis were almost completely prevented by initiating cardiac arrest with high K+ (16 meq/l) at the same time as anoxia; energy metabolism remained near normal, and recovery of contractility was nearly complete. 4. The studies demonstrated the differences in vascular distribution between the ventricles after ischemia or with perfusion anoxia, the possible difference in availability of substrate to the two ventricles under these conditions, as well as the difference in protein synthetic response, and further support the protective effect of potassium induced arrest on the hypoxic heart.

Animals↗