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E Rock

Publications and source records attributed to E Rock.

52 records · Page 3Linked to original sources
PubMed1990

Abnormal fluidity state in membranes of malignant hyperthermia pig skeletal muscle.

The fluidity state was analyzed on sarcoplasmic reticulum membranes and phospholipid vesicles prepared from normal and malignant hyperthermia susceptible pig muscle. Electron spin resonance studies were performed to determine the fluidity state at the region near the polar headgroups and in the central core of the bilayer using 5-nitroxide (5-NS) and 16-nitroxide stearic acid (16-NS), respectively. With the 5-NS label, no differences were found between normal and malignant hyperthermia sarcoplasmic reticulum (MH SR) membranes whereas with the 16-NS label, a significant increase of the activation energy was shown with MH membranes. Lower values of fluorescence anisotropy observed with DPH-labeled MH membranes as compared with normal ones, confirmed the higher abnormal fluidity state of these membranes. The fluidizing effect of halothane, a triggering agent of malignant hyperthermia syndrome, was also studied in these membranes. We show that a relatively low concentration of the drug destabilized not only the diseased sarcoplasmic reticulum membranes but also the vesicles made of total phospholipids extracted from MH skeletal muscle. Together, these findings strongly suggest that an overall increase in membrane fluidity may be implied in the MH disease, improving the general membrane defect hypothesis for this syndrome.

Animals↗
PubMed1990

Impairment of ATP-linked reactions in mitochondria isolated from skeletal muscle of halothane-sensitive pigs.

Oxygen consumption was depressed in mitochondria isolated from halothane sensitive pig (HP) muscle. The calculation of the respiratory control ratio (RCR) indicated that mitochondria were more affected at the site-I level of the respiratory chain. Calcium accumulation in these mitochondria was not altered when driven by the oxidation of succinate. This process was abolished when linked to ATP as a source of energy. ATP transport was completely inhibited in (HP) mitochondria.

Adenosine Triphosphate↗
PubMed1990

Halothane-induced functional and structural modifications in sarcoplasmic reticulum membranes from pig skeletal muscle.

We investigated the effect of halothane on lipid and protein components of sarcoplasmic reticulum membranes isolated from pig trapezius muscle. We studied the relationships between the (Ca2(+)-Mg2+)-ATPase activity and the interaction of the anesthetic with lipid and protein moieties by means of EPR and fluorescence spectroscopic techniques. Our results clearly show that below 5 mumol per mg protein, halothane interacts mainly with the lipid components of the membrane. This interaction is shown to be localized in the central core of the phospholipid bilayer and to induce an increase of the membrane calcium permeability. The interaction with protein components only occurs at higher halothane concentrations and affects its conformational and functional states. These results are discussed with respect to new insights into diethylether-SR membrane interaction and to malignant hyperthermia syndrome in the pig.

Animals↗
PubMed1987

Effect of halothane on the Ca2+-transport system of surface membranes isolated from normal and malignant hyperthermia pig skeletal muscle.

Trapezius muscle from normal and malignant hyperthermia (MH) pigs was used to investigate the effects of halothane on contractile properties and on the calcium transport system of isolated surface membranes. We observed that (i) halothane, diluted in dimethyl sulfoxide, induced a higher isometric contracture response in MH muscle than in normal muscle, (ii) halothane had a more pronounced inhibitory effect on the sarcolemmal Ca2+-ATPase activity in MH membrane, and (iii) the actively accumulated calcium was released in higher amounts in MH muscle than in normal muscle. These results suggest that halothane might induce, in vivo, an important influx of extracellular calcium ions through the MH sarcolemmal membranes and this pool of intracellular calcium may constitute the trigger for the defective sarcoplasmic reticulum "calcium-induced calcium-release" system.

Acetylcholinesterase↗
PubMed1987

Effects of meal composition on gallbladder and gastric emptying in man.

Cholecystogastric scintigraphy, utilizing [99mTc]HlDA to label the gallbladder contents and [111In]DTPA to label different meals, was utilized to determine the relationships between gallbladder and gastric emptying after meals of differing composition. Gallbladder emptying was determined in response to a multicomponent meal and to monocomponent fat, carbohydrate, and protein meals and in response to isotonic and hypertonic dextrose and isotonic and hypertonic saline. Also, the gallbladder emptying responses to equivalent multicomponent solid and liquid meals were compared. Significant gallbladder emptying was observed in response to the multicomponent meal and the monocomponent fat, carbohydrate, and protein meals. The most rapid and complete gallbladder emptying was seen with the multicomponent meal and the monocomponent fat meal. Significant gallbladder emptying was stimulated, not only by isotonic and hypertonic dextrose, but also by hypertonic saline. The gallbladder emptied more rapidly after a liquid than after a solid meal.

Adult↗
PubMed1987

Effects of somatostatin on gallbladder emptying.

Because approximately 80% of reported patients with somatostatinomas have gallstones, this study was performed to determine the effects of exogenous somatostatin on gallbladder emptying responses to liquid and solid meals, direct cholinergic stimulation by bethanechol, indirect cholinergic stimulation by sham feeding, and intravenously administered octapeptide of cholecystokinin. Gallbladder emptying was quantitated using 99mTc-HIDA and a gamma-camera on line to a digital computer. Somatostatin, administered at a dosage of 7 micrograms/kg X h, prevented the gallbladder emptying responses to both test meals, sham feeding, and bethanechol. The maximal gallbladder emptying response to octapeptide of cholecystokinin at 5.0 ng/kg X min was reduced from 93.2% +/- 4.8% to 57.1% +/- 9.9% (p less than 0.01) and to octapeptide of cholecystokinin at 0.5 ng/kg X min from 91.3% +/- 5.3% to 14.8% +/- 4.2% (p less than 0.01). These findings suggest that somatostatin is a potent inhibitor of gallbladder emptying in humans. This may be an important factor in the development of gallstones in patients with somatostatinomas.

Adult↗
PubMed1986

Gallbladder emptying response to sham feeding in humans.

Cholescintigraphy, using 99mTc-HIDA, was employed to determine the gallbladder emptying response to sham feeding of a steak and potato meal, and to compare it with the emptying responses to direct cholinergic stimulation by bethanechol and to ingestion of the test meal. The maximal cumulative gallbladder emptying response to sham feeding was 44.1% + 10.1%, which was not significantly different from the response to bethanechol. Cholinergic blockade with atropine eliminated the emptying response to sham feeding. Also, sham feeding did not stimulate gallbladder emptying in patients with vagotomy. This study suggests that intact vagus nerves and cholinergic pathways are required in order for the gallbladder to respond to sham feeding. The precise mechanism for this effect has not been elucidated.

Adult↗
PubMed1985

Simultaneous preparation of membrane fractions from small amounts of skeletal muscle: a study on mitochondrial and microsomal fractions from MedJ mice.

This work is the first biochemical study of skeletal muscle membranes isolated from mice displaying an inherited neuromuscular disease: MedJ strains. It is focused on the research of a possible alteration of membrane biological activities related to this disease. We describe a procedure which allows the simultaneous preparation of mitochondrial and microsomal fractions from a small amount of skeletal muscle. When EGTA and BSA are present in the buffers, functional mitochondria can be prepared. Under these conditions we found that no major modification occurs for this disease at the mitochondrial inner membrane level. A dramatic impairment of a calcium active transport activity found in the microsomal fraction obtained from MedJ is noticed, suggesting that some modification may occur at this level.

Animals↗
PubMed1985

Cholinergic effects on gallbladder emptying in humans.

The role of cholinergic mechanisms in the control of gallbladder emptying has not been defined. In this report a scintigraphic technique using 2,6-dimethylphenylcarbamoylmethyl iminodiacetic acid labeled with technetium 99m to visualize the gallbladder and its emptying and diethylenetriamine pentaacetic acid labeled with indium 111 to visualize the stomach and its emptying was used to study 43 normal subjects and 18 patients with vagotomies. Direct cholinergic stimulation with bethanechol induced significant gallbladder emptying. Cholinergic blockade with atropine sulfate decreased the gallbladder emptying responses to a liquid meal, a solid meal, and the infusion of cholecystokinin-octapeptide. In patients with vagotomies, gallbladder emptying was decreased despite accelerated gastric emptying of an ingested liquid meal. The gallbladder emptying response to cholecystokinin-octapeptide was augmented in patients who had undergone vagotomy. These studies suggest that cholinergic receptors may be important in the regulation of human gallbladder emptying.

Adult↗
PubMed1984

Isolation and characterization of plasma membranes from rabbit skeletal muscle.

An improved procedure was developed for the isolation of skeletal muscle plasma membranes. This method includes a DNAse treatment of the homogenate prior to the isolation of membranes by differential and sucrose gradient centrifugation techniques. We obtained two light fractions which were highly enriched in many biochemical and chemical plasma membrane markers. These fractions were shown to be mostly inside-out vesicles containing a Ca2+-ATPase activity. These results suggested that this enzyme could participate in the extrusion of calcium ions from the muscle cells.

5'-Nucleotidase↗
PubMed1982

Abnormal gallbladder emptying in patients with gallstones.

In this study, gallbladder and gastric emptying were compared in 15 normal subjects and 15 patients with gallstones. A noninvasive technique which used two gamma-emitting radiopharmaceutical agents to image the gallbladder and stomach simultaneously was employed. Technetium-99m-HIDA was used as a gamma-emitting marker for the gallbladder and indium-111-DTPA was mixed with a standard liquid meal in order to stimulate gallbladder emptying and to measure gastric emptying. In patients with gallstones, gallbladder emptying was diminished significantly compared to normal subjects. In contrast, emptying of the stomach was normal. The gallbladder emptying responses to octapeptide of cholecystokinin, administered either as bolus or infusion doses, were similar in normal subjects and patients with gallstones. These studies suggest that gallbladder emptying may be abnormal in patients with gallstones. The explanation for this abnormality and its relationship to the development of gallstones has not been determined.

Adult↗
PubMed1982

Scintigraphic evaluation of gastric emptying.

There has been recent, renewed interest in studies of gastric emptying due in part to the introduction of new therapies for peptic ulcer diseases and attempts to better understand gastric physiology. Of the methods available for studying gastric emptying patterns, nuclear medicine techniques are optimal due to their noninvasive character, reproducibility and quantitative ability. The modulation of gastric emptying is multifactorial, and includes motor control, electrical activity, hormonal influences, and the composition of the meal itself: liquid vs solid; protein, carbohydrate and fat content; fiber or particle size; osmolality; pH; and pharmacologic agents. Because of the ease of performing gastric emptying studies using radiolabeled physiologic meals, these tests are being employed with increasing frequency in the evaluation of patients with disorders such as diabetic gastroparesis, postgastrectomy gastroparesis or dumping syndrome, and in the study of normal gastric physiology in man. Present data suggests that combined liquid-solid, dual radionuclide studies afford the greatest information regarding simultaneous gastric emptying patterns of liquid and solid components of a meal, and that single radionuclide, solid tests of gastric emptying are the more sensitive technique for determining subtle abnormalities of gastric emptying, when only a single tracer is employed.

Gastric Emptying↗
PubMed1982

Gastric emptying of a physiologic mixed solid-liquid meal.

The purposes of this study were to use a noninvasive scintigraphic technique to measure gastric emptying of liquids and solids simultaneously, to study the interactions between emptying of the liquid and solid components of meals in normal subjects, and to employ dual isotope gastric scintigraphy to evaluate gastric emptying of liquids and solids in patients with clinical evidence of gastric outlet obstruction. The solid component of the test meal consisted of chicken liver, labeled in vivo with Tc-99m sulfur colloid, and the liquid component was water mixed with In-111 DTPA. The rates of emptying were quantitated using a gamma camera on line to a digital computer. Twenty normal subjects were studied using this combined solid-liquid meal. Ten of them also ingested a liquid meal alone and ten a solid meal alone. Liquid emptied from the stomach significantly more rapidly than did solids. The emptying curve for liquids was exponential compared to a linear emptying curve for solids. The gastric emptying rate of the liquid component was slowed significantly by simultaneous ingestion of solids, but the emptying rate of solids was not affected by liquids. Several patients with clinical gastric outlet obstruction were evaluated. Both combined and selective abnormalities for gastric emptying of liquids and solids were demonstrated.

Adult↗
PubMed1982

Effect of bolus composition on esophageal transit: concise communication.

The technique of esophageal scintigraphy was developed as a sensitive, quantitative, noninvasive test of esophageal transit. Esophageal scintigraphy was performed in 40 asymptomatic normal volunteers in order to determine the effect on esophageal transit of the following: body posture (sitting vs. supine), liquid vs. solid, the solid being either a standard #4 gelatin capsule of the size used for antibiotic capsules, or a cube of solid food such as cooked chicken liver. The results showed that liquids emptied completely from the esophagus after one swallow, whether supine or sitting. Capsules or liver cubes, when ingested without water, frequently remained in the esophagus for up to two hours without the subject's having any sensation that the solid had not left the esophagus. Both capsules and liver cubes cleared the esophagus better in the upright than in the supine position. When gelatin capsules were swallowed with as little as 15 ml of water, but after a preliminary sip of water, there was complete transit in each case. The study suggests that the practice of assisting patients into a sitting position and instructing them to take a sip of water before attempting to swallow a capsule will assure better transit of the capsule even when swallowed with as little as 15 ml of water. This may reduce the incidence of esophagitis following oral antibiotics, and of esophageal erosions from aspirin-containing medications.

Capsules↗
PubMedDate not supplied

Analysis of lipid composition of sarcoplasmic reticulum membranes from normal and malignant hyperthermic pig skeletal muscle.

In search of a general membrane defect hypothesis for malignant hyperthermia syndrome, we analysed the lipid profiles of heavy sarcoplasmic reticulum membranes isolated from normal and malignant hyperthermia longissimus dorsi pig muscle. Malignant hyperthermia susceptibility was assessed by halothane challenge of pigs. Sarcoplasmic reticulum membranes from malignant hyperthermia susceptible pigs differed significantly from control ones in the cholesterol content and phosphatidylethanolamine/phosphatidylcholine ratio; both were higher in former membranes. These latter lipid modifications were in agreement with the significant increase of their bulk lipid viscosity, as evidenced by an increase of diphenyl hexatriene fluorescence anisotropy. The increased level of phosphatidylethanolamine associated with the decreased content of phosphatidylcholine in malignant hyperthermic membranes was shown to be a potential consequence of depressed activities of both phospholipid N-methyltransferase I and II activities. Finally, the distribution of fatty acids in these particular phospholipids showed no change in phosphatidylcholine molecules, whereas the percentage of arachidonate and stearate in the phosphatidylethanolamine species were respectively higher and lower in malignant hyperthermic membranes. These differences in major phospholipids content and the enrichment of a metabolically important fatty acyl chains in malignant hyperthermia sarcoplasmic reticulum membranes strongly suggest that the lipid metabolism may contribute to the molecular mechanism of malignant hyperthermia syndrome.

Animals↗