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Biomedical subjects

S Rapoport

Publications and source records attributed to S Rapoport.

At least 37 records · Page 2Linked to original sources
PubMed1986

Indium-111 platelet scintigraphy for the diagnosis of acute venous thrombosis.

Platelets labeled with indium-111 have been used successfully as a marker of active thrombosis in man. To establish the diagnostic accuracy of platelet scintigraphy in comparison to contrast venography in the diagnosis of acute lower limb venous thrombosis, we evaluated 103 consecutive patients divided into two groups. Platelets were labeled by the indium-111 oxine method. Patients from group I (n = 73, 56 had venograms) were asymptomatic and underwent platelet scintigraphy 1.1 +/- 0.6 days (mean +/- 1 SD) after a major orthopedic procedure. Patients from group II (n = 30, all had venograms) were symptomatic and underwent platelet scintigraphy 1.2 +/- 1.7 days after venography. In group II, 15 patients with positive findings on contrast venography were treated with intravenous heparin; five others with positive venograms did not receive heparin until platelet scintigraphy was completed. Both platelet scintigraphy and contrast venography were evaluated by two blinded observers. Only studies with blinded agreement of both platelet scintigraphy and contrast venography were included in the analysis. Sensitivity and specificity of platelet scintigraphy for the whole limb were 93% and 97% in group I and 42% and 67% in group II. The lower sensitivity in group II was most likely attributable to therapy with heparin. These results demonstrate that platelet scintigraphy, a test that permits imaging for up to five days after a single injection, correlates favorably with contrast venography in patients who have not received heparin and may be used as a surveillance test in high-risk patients. The role of platelet scintigraphy in acutely symptomatic patients requires further evaluation.

Aged↗
PubMed1986

ATP production and consumption of rabbit reticulocytes increase in an amino-acid-enriched medium.

The ATP production and the main processes of ATP consumption, globin synthesis, Na+, K+-ATPase, and proteolysis of rabbit reticulocytes in two different media (1. complete medium with amino acids and glucose and 2. glucose containing electrolyte medium) were measured. The ATP formation in the complete medium amounts to 157 mmol/l X h which is 28% higher than in the incomplete medium. The increased ATP formation rate is due to increased ATP consumption by the more than doubled protein synthesis in the complete medium, whereas proteolysis and Na+,K+-ATPase are nearly unchanged. The increase in the glucose consumption in the complete medium is not fully accounted for by the increased oxidative degradation of glucose in the citric acid cycle and by lactate accumulation.

Adenosine Triphosphate↗
PubMed1985

Metabolism of polyunsaturated fatty acids by rabbit reticulocytes.

Rabbit reticulocytes obtained by repeated bleeding metabolize exogenous [1-14C]linoleic acid and [1-14C]arachidonic acid by three different pathways. 1. Incorporation into cellular lipids: 50% of the fatty acids metabolized are incorporated into phospholipids, mainly phosphatidylcholine (32.8%) but also into phosphatidylethanolamine (12%), whereas about 10% of the radioactivity was found in the neutral lipids (mono- di- and triacylglycerols, but not cholesterol esters). 2. Formation of lipoxygenase products: 30% of the fatty acids metabolized are converted via the lipoxygenase pathway mainly to hydroxy fatty acids. Their formation is strongly inhibited by lipoxygenase inhibitors such as 5,8,11,14-eicosatetraynoic acid or nordihydroguaiaretic acid. Inhibition of the lipoxygenase pathway results in an increase of the incorporation of the fatty acids into cellular lipids. 15-Hydroxy-5,8,11,13(Z,Z,Z,E)eicosatetraenoic acid and 13-hydroxy-9,11(Z,E)-octadecadienoic acid are incorporated by reticulocytes into cellular lipids and also are metabolized via beta-oxidation. The metabolism of arachidonic acid and linoleic acid is very similar except for a higher incorporation of linoleic acid into neutral lipids. 3. beta-Oxidation of the exogenous fatty acids: about 10% of the polyenoic fatty acids are metabolized via beta-oxidation to 14CO2. Addition of 5,8,11,14-eicosatetraynoic acid strongly increased the 14CO2 formation from the polyenoic fatty acids whereas antimycin A completely abolished beta-oxidation. Erythrocytes show very little incorporation of unsaturated fatty acids into phospholipids and neutral lipids. Without addition of calcium and ionophore A23187 lipoxygenase metabolites could not be detected.

Animals↗
PubMed1985

Maturation of rabbit reticulocytes: susceptibility of mitochondria to ATP-dependent proteolysis is determined by the maturational state of reticulocyte.

A simple procedure is described to separate reticulocytes of different maturity in high yield. It is shown that exhaustion of supply of mitochondria susceptible to degradation by the lipoxygenase-ATP-dependent proteolysis system limits the extent of breakdown of mitochondria during in vitro maturation. The susceptibility of mitochondria depends on the maturity of the reticulocytes. Incubation in the presence of calcium ions and calcium ionophore leads to full susceptibility of mitochondria in immature reticulocytes but has no effect on those in mature reticulocytes which are already fully susceptible to degradation. Conditions which lead to rapid degradation of mitochondria do not affect the behaviour of the reticulocyte count. There appears to be no obligatory connection between the breakdown of mitochondria and of ribosomes.

Adenosine Triphosphate↗
PubMed1985

Detection of platelet deposition at the site of peripheral balloon angioplasty using indium-111 platelet scintigraphy.

Restenosis after balloon angioplasty may be mediated through platelet deposition at the site of arterial dilatation. The purpose of this study was to determine whether platelet deposition at the site of dilatation could be detected using indium-111 platelet scintigraphy. Fifteen patients, aged 60 +/- 9 years, with iliac or femoral (n = 12), renal artery (n = 2) or distal aortic (n = 1) stenoses were studied. All patients received intravenous heparin at the time of dilatation. Labeled platelets containing 471 +/- 65 muCi indium-111 were injected 0.25 to 4 hours after dilatation and 1 to 24 hours after imaging. In 11 of 12 patients with iliac and femoral dilatations, focal uptake was demonstrated at the angioplasty site. In 4 patients (2 patients with renal, 1 patient with iliofemoral, and 1 with distal aortic stenoses), uptake at the dilatation sites was not detected. This preliminary study indicates that despite intravenous heparin, platelets accumulate at sites of balloon dilatation. Platelet scintigraphy may be useful in predicting sites of future narrowing after angioplasty and may be used to test the efficacy of antiplatelet therapy in retarding restenosis.

Adult↗
PubMed1985

Proteolysis of mitochondria in reticulocytes during maturation is ubiquitin-dependent and is accompanied by a high rate of ATP hydrolysis.

The ATP-dependent breakdown of mitochondria-containing stroma proceeds via the ubiquitin-requiring pathway. The proteolysis is linked to a large ATP-cleaved consumption amounting to 1 ATP per peptide bond or more. Proteins of mitochondria-containing stroma are much better substrates of ATP-ubiquitin-dependent proteolysis than heat-denatured ones. Hemin suppresses both proteolysis and ATP hydrolysis.

Adenosine Triphosphate↗
PubMed1985

Pseudoaneurysm: a complication of faulty technique in femoral arterial puncture.

Pseudoaneurysm is a well-documented but rare complication of retrograde femoral arterial puncture. We present six patients in whom pseudoaneurysm complicated this procedure. The pseudoaneurysm arose from the superficial femoral artery in five patients and from the profunda femoris artery in one. An arteriovenous fistula also arose from the superficial femoral artery in one patient. In no patient did the pseudoaneurysm arise from the common femoral artery. Two mechanisms are postulated as to why pseudoaneurysms rarely complicate puncture of the common femoral artery.

Aneurysm↗
PubMed1985

Hepatoma, arterioportal shunting, and hyperkinetic portal hypertension: therapeutic embolization.

Four patients with hepatocellular carcinoma, shunting of blood from the hepatic artery to the portal vein, and hyperkinetic portal hypertension were treated by transcatheter embolization of the hepatic artery. In three acutely bleeding patients variceal hemorrhage was controlled by the embolization. Following embolization hepatofugal portal venous flow became hepatopetal in all four patients. No serious complications were encountered. When hepatoma is complicated by arterioportal shunting and hyperkinetic portal hypertension, occlusion of the fistula by transcatheter embolotherapy can reduce the portal pressure.

Aged↗
PubMed1984

Descending paralysis resulting from occult wound botulism.

A 30-year-old male drug abuser developed ophthalmoplegia, bulbar paralysis, and limb weakness responsive to edrophonium. However, potentiation of a low-amplitude evoked muscle action potential was produced with repetitive nerve stimulation at 10 Hz, and the clinical and electrophysiological data suggested the diagnosis of botulism. The source of botulism type B toxin was a clinically obscure cyst produced by subcutaneous infiltration of cocaine two weeks prior to the onset of symptoms. The patient improved with chronic administration of pyridostigmine bromide and plasmapheresis. Wound botulism may be underdiagnosed because of confusion with inflammatory neuropathy or myasthenia gravis. Neuromuscular transmission studies in patients with acute craniosomatic paralysis can prevent such oversights.

Adult↗
PubMed1984

The effect of phenylhydrazine on protein breakdown in rabbit reticulocytes.

In contrast to reticulocytes produced by bleeding reticulocytes produced by injections of phenylhydrazine exhibit a sizeable Antimycin A- and a large salicylhydroxamic acid (SHAM)-resistant proteolysis. In their cytosol there exist both ATP-independent and ATP-dependent protease systems. The substrate of proteolysis are denatured and aggregated proteins arising from reactions of phenylhydrazine with cell constituents. In phenylhydrazine-induced reticulocytes there is an overlap between the basic biological process of maturation-dependent proteolysis of mitochondria and the breakdown of denatured and aggregated "abnormal" proteins.

Adenosine Triphosphate↗
PubMed1983

Calcium exerts an indirect effect on ATP-dependent proteolysis of rat liver mitochondria.

The ATP-dependent proteolysis of rat liver mitochondria prepared in electrolyte-poor sucrose media requires the presence of Ca2+. Lanthanum, an inhibitor of Ca2+ uptake, inhibits the proteolysis. In contrast, proteolysis of mitochondria prepared in a salt medium does not require Ca2+, nor is it inhibited by lanthanum. It is concluded that Caa+ exerts its effect in an indirect manner, by causing swelling and thereby increasing the accessibility of the membrane proteins of the inner mitochondrial membrane.

Adenosine Triphosphate↗
PubMed1983

Ionic lanthanum passage across cerebral endothelium exposed to hyperosmotic arabinose.

Hyperosmotic media infused into the cerebral circulation open the blood-brain barrier to protein and colloid. The mechanism whereby such substances cross the affected vessels is still disputed. We describe here the transendothelial route taken by ionic lanthanum (La3+), a small electron-dense tracer which, unlike colloidal lanthanum, can be administered to the living animal. In adult rats, 2.9 ml of hyperosmotic (1.4 M) arabinose was infused into the internal carotid artery as a 30-s bolus, followed by 5 mM LaCl3. To find the extravasated La3+, which is invisible by light microscopy, horseradish peroxidase (HRP) was injected simultaneously into the femoral vein. The hyperosmotic treatment resulted in exudation of both HRP and La3+ primarily around cerebral arterioles. The La3+ crossed arterioles through successive tight junctions between endothelial cells. Although the tight junctions were not discernibly opened, they must have become permeable because the extracellular pools between successive tight junctions were penetrated by the La3+. These pools are normally inaccessible to La3+. Luminal and abluminal pits and cytoplasmic vesicles, some of them containing La3+, formed intraendothelial clusters. Their role, if any, in the transfer of ion remains uncertain.

Animals↗
PubMed1983

Splanchnic and peripheral disposal of oral glucose in man.

Oral glucose (92 g) was administered to 22 healthy, young volunteers undergoing hepatic vein catheterization, and net splanchnic glucose output (SGO) was measured during the basal period and for 4 h after glucose ingestion. In the basal state, SGO averaged 1.90 +/- 0.11 mg/min X kg. After glucose, SGO rose to a peak value of 6.65 +/- 0.83 mg/min X kg at 30 min and returned to baseline by 3 h. Total SGO over 4 h was 69 +/- 4 g; assuming complete absorption of the load, this amount represented 75% of the oral glucose. In a subgroup of six subjects, leg glucose uptake was simultaneously quantitated by femoral vein catheterization and leg blood flow measurement. In the postabsorptive state, glucose uptake by one leg was 24 +/- 8 mg/min and increased to a mean value of 76 +/- 7 mg/min during the 4 h after glucose ingestion. Overall, 18 +/- 2 g/4 h of glucose were taken up by one leg, which extrapolates to a total body muscle uptake of 65 +/- 4 g over 4 h. We conclude that in normal man, well over 2/3 of an oral glucose load escapes splanchnic removal, and that the peripheral tissues quantitatively play the dominant role in glucose disposal.

Adult↗