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Biomedical subjects

E Rubin

Publications and source records attributed to E Rubin.

At least 163 records · Page 9Linked to original sources
PubMed1987

Effect of ethanol on amylase secretion and cellular calcium homeostasis in pancreatic acini from normal and ethanol-fed rats.

The effects of ethanol on stimulus-secretion coupling were assessed by studying amylase release, Ca2+-homeostasis, and changes in physical properties of membranes in isolated rat pancreatic acini. In acini from normal rats, ethanol (50 mM and above) in vitro caused a dose-dependent stimulation of amylase release and an increase in cytosolic free Ca2+ concentration. Ethanol did not affect amylase secretion stimulated by cholecystokinin-octapeptide (CCK8), a secretagogue that acts by increasing cytosolic free Ca2+ levels, but did potentiate the secretion of amylase induced by vasoactive intestinal peptide (VIP) which raises intracellular cAMP. Ethanol also increased the rate of 45Ca2+ exchange. In acini labeled with the spin-probe 12-doxyl stearic acid, ethanol disordered the pancreatic plasma membranes. By contrast, in acini from animals that had chronically (6-7 weeks) ingested ethanol, the membranes were resistant to this disordering effect of ethanol. Chronic ethanol feeding lowered the total cellular calcium content and ionophore (A23187)-releasable pools of acinar calcium (11 and 24% respectively), and led to a 15-30% decrease in the rate of 45Ca2+ exchange. Chronic ethanol ingestion also lowered the basal rate of amylase secretion, but ethanol in vitro stimulated amylase secretion more than in control preparations. However, these differences in basal and ethanol-induced amylase secretion were not accompanied by corresponding changes in intracellular free Ca2+. The data suggest that ethanol perturbs cell membranes and also disturbs cellular Ca2+ homeostasis. These effects may explain its actions as a weak Ca2+-mediated secretagogue. However, the membrane alterations induced by chronic ethanol feeding do not prevent the ethanol-induced interference with cellular calcium homeostasis.

Amylases↗
PubMed1987

A high-performance liquid chromatographic microassay employing a liquid-solid extraction technique for etintidine in plasma.

This paper describes a new, rapid solid extraction method for the determination of etintidine in plasma. The method employs a semiautomatic sample preparation system. Plasma samples and the internal standard (cimetidine) were applied onto octyl-bonded silica extraction columns. The extraction columns were then subjected to Tris buffer and water wash and were subsequently loaded onto an automatic sample injection system. The contents of the extraction columns were eluted on-line with a mobile phase of acetonitrile:methanol:0.1% ammonium hydroxide (85:10:5, by volume) onto a silica analytical column and detected by UV absorption at 229 nm. The chromatographic condition separates etintidine from some of its metabolites and other endogenous components in plasma. The detection limit for etintidine was 0.02-0.05 microgram/ml when 0.2 ml of plasma was used. This method has been used for the determination of plasma etintidine levels in humans and mice after oral administration of etintidine and was found to be suitable for pharmacokinetic/bioavailability studies of etintidine in humans and animals. The method can also be used for the quantitative determination of cimetidine and certain metabolites of etintidine.

Animals↗
PubMed1987

Malignant gestational trophoblastic disease: CT findings.

Eight patients with malignant gestational trophoblastic disease had CT of the pelvis as part of their staging before chemotherapy. CT appearance of the uterus fell into three major types: normal size with irregular areas of hypodensity, uniform enlargement with areas of hypodensity, and focal areas of enlargement with or without areas of hypodensity. Patients with the second and third types were much more likely to have distant metastases and to require hysterectomy for successful treatment. CT findings of tumor nodules in the parametrium or myometrium were confirmed in three of the four surgical specimens of the uterus available for correlation. Myometrial tumor nodules were seen as areas of focal enlargement or as irregular eccentric areas of hypodensity. In one patient, parametrial extension was seen as an enhancing mass adjacent to the uterus. CT may be accurate in defining the extent of myometrial and adnexal disease and may have prognostic and therapeutic value.

Adult↗
PubMed1987

Magnetic resonance imaging of bone marrow in hairy cell leukemia: correlation with clinical response to alpha-interferon.

Five patients with progressive hairy cell leukemia were treated with recombinant alpha 2-interferon and examined prospectively at 3-month intervals using serial bone marrow biopsies and magnetic resonance (MR) imaging. Pretreatment iliac crest marrow biopsies demonstrated hairy cell infiltration involving 30-90% of marrow cellularity. Concurrent pretreatment coronal images of the proximal femurs and pelvis using MR revealed extensive marrow involvement that varied in distribution from patchy to diffuse. At 6 months, all patients had responded to alpha 2-interferon with improvement in peripheral blood counts and decrease in lymphoid infiltration on marrow biopsy to 15-40%. Six-month follow-up MR scans demonstrated decreasing marrow leukemia infiltration and increasing marrow fat. MR bone marrow imaging appears useful in the initial diagnosis of hairy cell leukemia, for monitoring the response to treatment, and possibly for predicting relapse.

Bone Marrow↗
PubMed1987

The treatment of hairy cell leukemia with alpha 2b-interferon: experience with 27 patients treated more than one year.

Thirty-six patients with progressive hairy cell leukemia were treated with recombinant alpha 2b-interferon injected subcutaneously 2 X 10(6) IU/m2, three times a week. Twenty-seven patients completed 12 months of therapy and were randomized either to receive 6 months of continued interferon or to go off treatment. At the time of randomization, two patients had achieved a complete response, 22 a partial response, and three a minimal response. Three patients have relapsed, one while receiving interferon during the randomization period and two who were off therapy for 6 months. The outpatient regimen of interferon administration was well tolerated, with the principal acute toxicities being fever and an influenza-like syndrome and the major long-term toxicity being mild-moderate fatigue.

Humans↗
PubMed1986

Immunochemical evidence for an inactive form of cytochrome oxidase in mitochondrial membranes of ethanol-fed rats.

Previous studies have established that rats fed ethanol chronically exhibit a 50% decrease in hepatic mitochondrial cytochrome oxidase compared to pair-fed controls, based on both heme aa3 content and specific activity. To determine whether the 'missing' 50% of cytochrome oxidase is present in the membrane but catalytically inactive, or entirely absent, we used immunochemical techniques to determine the content of cytochrome oxidase protein in hepatic submitochondrial particles. Rabbit antiserum against purified rat liver cytochrome oxidase precipitated cytochrome oxidase from detergent-solubilized submitochondrial particles. Immunoinhibition titrations of a fixed amount of anti-oxidase serum with increasing amounts of submitochondrial particle protein showed that similar percentages of added oxidase activity were recovered in supernatants after immunoprecipitation with preparations from both alcoholic and control rats. Similarly, titrations of a fixed amount of submitochondrial particle protein with increasing amounts of antiserum showed comparable decreases in oxidase activity. Equivalent amounts of protein were obtained in immunoprecipitates from both preparations. Immunoprecipitates demonstrated comparable oxidase subunit profiles by electrophoresis, except that one additional band, migrating in the region of oxidase subunit IV, was present in samples from alcoholic rats. The data indicate that cytochrome oxidase immunologic reactivity is quantitatively similar in both types of membranes. The results suggest that the 'missing' cytochrome oxidase is actually present within the membranes of alcoholic animals in an inactive form, apparently devoid of heme aa3.

Animals↗
PubMed1986

Effect of ethanol on tropomyosin in solution and in reconstituted thin filaments.

The effects of ethanol at concentrations below 10% on the conformation of tropomyosin, its end-to-end polymerization, its binding to F-actin, and its effects on actomyosin ATPase activity were studied. Ethanol stabilized the tropomyosin conformation by shifting the helix thermal unfolding profile to higher temperatures, and increased the end-to-end polymerization of tropomyosin. Ethanol-induced changes in the excimer fluorescence of pyrene-tropomyosin indicated that its conformation was stabilized by ethanol both free and bound to F-actin. Effects of tropomyosin and tropomyosin-troponin on actomyosin ATPase activity were measured under conditions for which tropomyosin binding to F-actin increases the activity. Under conditions for which the binding of tropomyosin to F-actin is optimum, in the presence of tropomyosin, the actomyosin ATPase activity decreased as the ethanol concentration increased, further indicating that ethanol induces a structural change in the tropomyosin-F-actin complex. Under conditions for which the binding of tropomyosin to F-actin is weak (low salt or high temperature), addition of ethanol increased the ATPase activity due to increased binding of tropomyosin to F-actin. Thus, ethanol appears to modify actomyosin ATPase activity by increasing the binding of tropomyosin to F-actin and affecting the structure of tropomyosin in the tropomyosin-F-actin filament.

Actins↗
PubMed1986

Endocytosis in sickle erythrocytes: a mechanism for elevated intracellular Ca2+ levels.

Staining of sickle cells with the fluorescent probes chlortetracycline (a Ca2+ probe) and diindocarbocyanine (a general membrane probe) revealed the presence of Ca2+-containing vesicles which are not found in normal erythrocytes. These vesicles increase in number upon deoxygenation, and are apparently formed by endocytosis, as judged by the use of the extracellular fluorescent probe lucifer yellow. The presence of vesicles is not restricted to any particular morphological or density class of cells in the general population.

Anemia, Sickle Cell↗
PubMed1986

Membrane tolerance to ethanol is rapidly lost after withdrawal: a model for studies of membrane adaptation.

The structural properties of liver microsomes and erythrocytes obtained from rats that had been chronically administered ethanol were examined by electron spin resonance (ESR) following ethanol withdrawal for 1-10 days. Membranes obtained from control animals exhibited considerable molecular disordering upon the addition of ethanol in vitro (50-100 mM). Conversely, microsomal and erythrocyte membranes from alcoholic animals were resistant to this disordering by ethanol (membrane tolerance). These membrane properties were also apparent in lipid bilayers comprised of either total lipids or phospholipids isolated from the control and alcoholic animals. While several weeks of ethanol administration were required for both erythrocytes and microsomes to develop membrane tolerance, erythrocytes from alcoholic animals were disordered by ethanol in vitro after the animals had been withdrawn from ethanol for only 1 day. The same rapid loss of tolerance was observed in microsomes after 2 days of withdrawal. The same time course for the loss of tolerance was observed in lipid bilayers prepared from the total lipid and phospholipid extracts. No significant differences in the cholesterol/phospholipid ratio were observed between the microsomal or erythrocyte membranes isolated before and after withdrawal. Thus, alterations in the microsomal and erythrocyte phospholipids, and not cholesterol content, were responsible for conveying membrane tolerance. Membrane structural properties can be rapidly adjusted in a mammalian system in response to the withdrawal of the external membrane perturbant ethanol. The withdrawal model, which begins with established membrane tolerance and leads to rapid and complete loss of tolerance, provides a model to analyze the compositional changes responsible for this tolerance to disordering by ethanol.

Adaptation, Physiological↗
PubMed1986

Phosphatidylinositol from ethanol-fed rats confers membrane tolerance to ethanol.

The presence of ethanol disorders (fluidizes) biological membranes, but its chronic administration confers resistance to this perturbation (membrane tolerance). The latter effect has been invoked as an explanation for behavioral tolerance in alcoholics, but the molecular basis for membrane tolerance is obscure. To study the molecular mechanisms of this acquired resistance to disordering, we fed rats ethanol (36% of total calories) for 35 days, after which we quantitatively separated the phospholipids of hepatic microsomal membranes by high-performance liquid chromatography. Multilamellar vesicles were prepared from the recombined phospholipid classes, and their physical properties were examined by electron spin resonance. Vesicles composed of phospholipids from untreated rats were disordered (fluidized) in the presence of ethanol, whereas those made from phospholipids of ethanol-fed rats were resistant to this effect. When phosphatidylcholine (66.5 mol %), phosphatidylethanolamine (21 mol %), or phosphatidylserine (4.0 mol %) from ethanol-fed rats replaced their corresponding phospholipids in vesicles prepared from microsomal phospholipids from untreated rats, the membranes were still disordered by ethanol. In contrast, when 2.5-8.5 mol % phosphatidylinositol from ethanol-fed rats replaced phosphatidylinositol from untreated rats, the reconstituted membranes were rendered resistant to ethanol-induced disordering. Liver microsomal phosphatidylinositol (2.5-8.5 mol %) from ethanol-fed rats also conferred membrane tolerance to vesicles composed of bovine liver and brain phospholipids, an effect which demonstrates that the ability of phosphatidylinositol to confer membrane tolerance is not restricted to the microsomal membrane.

Alcoholism↗
PubMed1986

Alteration of red cell membrane organization in sickle cell anaemia.

Bee venom phospholipase A2 and the fluorescent probe merocyanine 540 were used to examine plasma membrane phospholipid organization in the spicules released by deoxygenation and reoxygenation of sickle red cells, as well as in reversibly and irreversibly sickled erythrocytes. Digestion of phosphatidyl ethanolamine in spicules was comparable to that of phosphatidyl choline, and these structures were stained by the fluorescent probe. Both assays suggest that membrane lipid asymmetry is disrupted in spicules. The residual cells, from which the spicules were derived, retain the normal asymmetry in phospholipid distribution between the outer and inner leaflets of the plasma membrane bilayer. Comparable experiments with cell fractions enriched in irreversibly sickled cells revealed a partial enhancement of phosphatidyl ethanolamine digestion, confirming the similar experiments of Lubin et al (1981). Staining of these cells with merocyanine 540, however, did not reveal a subfraction of stainable cells, indicating that this increase in phosphatidyl ethanolamine digestion is not due to the presence of a small fraction of cells which have completely lost their membrane asymmetry.

Anemia, Sickle Cell↗
PubMed1986

Sputum examination for the diagnosis of Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome.

The diagnostic utility of sputum examination in patients with Pneumocystis carinii pneumonia secondary to the acquired immunodeficiency syndrome (AIDS) has so far not been determined. Sputum was induced in 43 patients with AIDS or suspected AIDS just prior to fiberoptic bronchoscopy, scheduled because of an unexplained pulmonary infiltrate on a chest radiograph. Pneumocystis carinii pneumonia was diagnosed by sputum examination and/or by a bronchoscopic procedure in 20 patients. Of these, sputum samples were positive for Pneumocystis organisms in 11 (55%) of 20 patients tested, bronchial washings were positive in 11 (79%) of 14 patients tested, brush biopsies were positive in 9 (53%) of 17 patients tested, and transbronchial lung biopsies were positive in 18 (90%) of 20 patients tested. The presence of P. carinii cysts in sputum did not correlate with the presence of alveolar macrophages in sputum nor with the volume of sputum. Sputum examination for P. carinii organisms, employed as a first diagnostic step in patients with AIDS with pulmonary infiltrates, may frequently obviate the need for bronchoscopy.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Dietary carbohydrate level determines the effect of long-term ethanol ingestion on rat pancreatic amylase content.

We studied the effects of long-term ethanol feeding on pancreatic amylase content in the rat. Because the level of pancreatic amylase depends on the carbohydrate content in the diet, the effects of ethanol ingestion were investigated at different levels of dietary carbohydrate, with fat providing the balance of calories. Animals were maintained on these diets for 3 weeks. In control animals, a reduction in carbohydrate from 47% to 11% of total calories lowered pancreatic amylase content by 60% (from 76.1 +/- 7 U/mg protein to 30.6 U/mg protein). However, in rats that consumed 11% of total calories as carbohydrate, long-term ethanol ingestion (36% of total calories) lowered the amylase content by a further 60% (from 30.6 U/mg protein to 11.8 U/mg protein). By contrast, when the dietary carbohydrate level was maintained at a high (40%) level, long-term ethanol ingestion slightly increased pancreatic amylase content. Pancreatic lipase was not affected by long-term ethanol ingestion at either low (6%) or high (35%) levels of fat. The reduction in the level of amylase caused by ethanol feeding with a low dietary carbohydrate intake was not associated with changes in the fasting blood levels of glucose, insulin, or glucagon. Long-term ethanol ingestion did not lead to morphologic changes in the acini or in the size, shape, or number of granules, as observed by light and electron microscopy. These results suggest that long-term ethanol ingestion has differential effects on pancreatic amylase, depending on the level of carbohydrate in the diet.

Amylases↗