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Biomedical subjects

I Nathan

Publications and source records attributed to I Nathan.

At least 73 records · Page 4Linked to original sources
PubMed1979

Dilation of synthetic grafts and junctional aneurysms.

Dilation of prosthetic graft has been noted by authors in association with junctional aneurysm between the synthetic graft and host arteries. Dilation of graft materials was suspected as one of the etiologic factors of the junctional aneurysm. Increase in transverse diameter was observed as early as a few minutes to five years postimplantation in clinical cases. The phenomenon of dilation was studied experimentally. Nine different types of graft materials were tested using intraluminal pulse pressure of 100/60 mm Hg, and the transverse diameters were measured at various time intervals. Knitted grafts showed the more pronounced changes compared with the woven. Degree of dilation differed considerably among the different types of knitted grafts.

Aged↗
PubMed1979

Prostaglandins do not affect ion concentrations in human erythrocytes.

In an attempt to further our understanding of the mode of action of prostaglandins (PGs), experiments were performed in which sodium and potassium ion concentrations were measured in human erythrocytes exposed to various concentrations of PGs. No consistent effect was observed and it is concluded that such changes are not likely to underlie excitability alterations induced by PGs.

Erythrocytes↗
PubMed1979

Effect of beta-blockers on sodium and potassium content of human erythrocytes.

Recently, hyperpotassemia was reported in patients treated with propranolol, but the mechanism has not yet been delineated. We have investigated the effects of various beta-adrenergic blockers and of D-propranolol on the Na+ and K+ distribution intra- and extracellularly in human erythrocytes. K+ loss and Na+ gain by cells was demonstrated at drug concentrations of 10(-4) M or greater. D-Propranolol was more effective than L-propranolol, whereas pindolol was ineffective. Practolol increased Na+ content but did not influence K+. The results suggest that electrolyte redistribution across cell membranes is not a likely explanation for hyperpotassemia in patients treated with propranolol, or for the local anaesthetic effect of this drug.

Dose-Response Relationship, Drug↗
PubMed1979

Constant-pressure aortic root perfusion versus cardioplegia and hypothermia. Comparison of methods of myocardial protection.

Both coronary perfusion and hypothermic cardioplegia are widely used methods of myocardial protection during aortic valve replacement. A theoretical objection to coronary perfusion is that it is not synchronized with cardiac contractions. Accordingly, a special pump was designed to provide perfusion at a constant range of pressure. Twenty dogs were studied during 4 hours of bypass. In six dogs no manipulations were carried out and hearts were allowed to beat in a nonworking state. Seven dogs underwent 2 hours of aortic cross-clamping and constant-pressure aortic root perfusion. Seven dogs underwent 2 hours of uninterrupted aortic occlusion with myocardial protection being maintained by cold potassium-induced arrest, Contractility did not change significantly in any of the three groups. All animals demonstrated significant hyperemia after bypass but normal endocardial/epicardial flow ratios. Although compliance deteriorated in all groups, the most striking changes were seen following 4 hours of bypass alone or constant-pressure aortic root perfusion. Hypothermic potassium arrest, in contrast, provided a slightly greater degree of myocardial protection, perhaps both by limiting the degree of ischemic injury directly and by excluding the heart from the circulating blood and the pump oxygenator system.

Animals↗
PubMed1979

Hematologic values in healthy older people in the Negev area.

Of 1,500 volunteers aged 65 or more selected at random in the Negev area, 224 were found to be healthy and available for further examination. The population represented broadly the various ethnic groups among Jews in Israel. The mean hemoglobin level, hematocrit, red and white blood cell counts and differential count showed no differences other than those due to chance when compared with the corresponding values in a younger (20 to 48 years of age) group. The differences between men and women were similar to those found in the comparison group, with men having higher mean values for hemoglobin, hematocrit, and red blood cell count; in the study group, serum iron, total iron-binding capacity and percent saturation were higher in men in all age groups. No differences were found in mean values of white blood cell count and differential count within the study population. However, mean serum iron was lower, and mean platelet count, higher than in the younger comparison group. This survey supports the use of normal standards for adults when elderly patients are examined, regardless of different ethnic origin. However, the higher than normal platelet counts in subjects from Asia, Africa and Eastern Europe should be taken into account.

Age Factors↗
PubMed1977

Plasma constituent (s) inhibiting platelet adhesiveness.

Adhesiveness in citrated whole blood is critically pH dependent at hydrogenion concentrations close to the physiological range. While platelets in platelet-rich plasma (PRP) adhere poorly in glass-bead columns, washed platelets and particularly gel-filtered platelets (GFP), prepared from PRP, are adhesive, Separation of PRP on a Sepharose 2B column revealed the presence of an inhibitor of adhesiveness of GFP. The inhibitory compound is thermostable and nondialyzable. It is inactivated completely by pronase digestion and partally by trypsin digestion. It is distinct from any one of the known platelet factors. Washed erythrocytes and erythrocyte membranes attenuate the potency of the inhibitor. Following separation by isoelectric focusing, the inhibitory activity is limited primarily to a single fraction with an isoelectric point of 5.1 containing equal amounts of proteins and lipids. Two protein bands are revealed by sodium dodecyl sulfate-gel electrophoresis of the purified fraction. It is concluded that PRP contains a compound, apparently a lipoprotein, which inhibits platelet adhesiveness.

Adult↗
PubMed1976

Impairment of ADP-induced platelet aggregation by hashish components.

ADP-induced aggregation of washed human platelets is inhibited by the hashish components delta1-tetrahydrocannabinol (THC) and cannabidiol (CBD). The inhibition is counteracted by added ADP. When the cannabinoids are present at concentrations higher than 10(-5)M, the platelets aggregate non-reversibly, independently of an added inducer, apparently due to lysis and release of endogenous inducers. THC is clearly more potent than CBD in exhibiting the biphasic effect. Collagen- and thrombin-induced aggregation of washed platelets are hardly affected by the cannabinoids. THC and CBD also curtail ADP-induced reversible aggregation in platelet-rich plasma, while serotonin release and irreversible aggregation, caused by either ADP, collagen or thrombin, are not affected by the cannabinoids in platelet-rich plasma. The data point to associated sites for ADP and the cannabinoids on the platelet membrane.

Adenosine Diphosphate↗
PubMed1974

Leucyl-transfer ribonucleic acid synthetase in senescing tobacco leaves.

1. The activity of leucyl-tRNA synthetase obtained from tobacco leaves declined by 50% over a period of 4 days senescence induced by detachment. In addition tRNA(Leu) from senescing leaves was charged to a lesser extent than tRNA(Leu) extracted from mature leaves immediately after detachment. 2. tRNA(Leu) was charged with a synthetase preparation from either mature or senescent leaves and chromatographed on an RPC 3 column. The elution profile showed that the marked decline in specific activity of leucyl-tRNA synthetase in senescent leaves was not associated with a loss of acylation of any isoacceptor of tRNA(Leu).

Aging↗
PubMedDate not supplied

Interaction of a novel fluorescent analog of interferon-gamma with transformed cells.

A fluorescent analog of human recombinant interferon-gamma (IFN-gamma) was prepared for the first time. The recovered pyrene-labeled IFN-gamma (py-IFN-gamma), with an estimated seven pyrene molecules per IFN-gamma, retained over half of its original biological activity. Binding of py-IFN-gamma to human amnion WISH cells showed appreciable enhancement in fluorescence polarization from 0.055 to 0.215 and in fluorescence lifetime from 56 to 80 ns. The ratio of the vibronic peaks did not change, indicating that the pyrene molecules remained in water environment even after binding. Py-IFN-gamma provides a novel tool for unraveling the mechanism of the initial interaction between this antiproliferative lymphokine and its target, cancer cell membrane receptors. Its fluorescence could provide the means to follow receptor recycling when it occurs.

Cell Line, Transformed↗
PubMedDate not supplied

Hemolytic disease of the newborn due to anti-PP1 P k (anti-Tj a).

A newborn infant of genotype P2p suffering from ABO-like hemolytic disease was born to a mother of the very rare genotype pp. The disease was severe enough to require exchange transfusions with pp blood. The mother and other members of the family with the same rare pp blood provided compatible donor blood for transfusions of the mother herself and for replacement transfusion of her affected infant. The mothers serum contained IgM molecules and also IgG molecules capable of crossing the placenta to induce a hemolytic process on the infant's red blood cells. The genotype of the P1 negative father was very likely P2P2 so that the genotype of the affected infant had to be P2p. A search of the literature revealed an earlier report from Japan in which the genotype of the P1 positive father was P1P2. As was to be expected the genotype of this affected infant was P2p.

Abortion, Spontaneous↗
PubMedDate not supplied

Evaluation of a new polyacrolein microsphere (acrobead) protein A column: an in vitro study using the blood of patients with immune thrombocytopenia or malignancies.

The present study describes the use of a new polyacrolein microsphere (acrobead) protein A column. This method enables immunomodulation by the perfusion of whole blood. The efficacy of the column and its adverse effects following perfusion of blood of patients with immune thrombocytopenic purpura (ITP) or malignancies were investigated. Concurrent experiments in which blood was perfused through an acrobead lactoglobulin column were carried out. Cellular blood components were mildly affected during the procedure. A moderate decrease in platelet number, to a nadir of 90 x 10(3) per microL (90 x 10(9)/L), was documented. During the hemoperfusion of ITP patients' blood, plasma hemoglobin reached levels of 25 to 40 mg per dL, a level similar to that found in banked blood during storage. Plasma tumor necrosis factor level, which serves as an indicator of monocytic activation, increased after 90 minutes of hemoperfusion. IgG and immune complexes were removed. The specific activities (removal of mg Ig/mL bead) of acrobead protein A columns, using blood from patients with ITP or malignancies, were 4.9 and 4.5 mg IgG per mL of bead, respectively. The diminution of platelet-specific IgG in the plasma of patients with ITP was documented as well. There was no activation of the fibrinolytic system as examined by D-dimers. The use of this new technique, which incorporates the method of direct hemoperfusion, is suggested for future clinical studies.

Antigen-Antibody Complex↗
PubMedDate not supplied

A comparison of predictive outcomes of APACHE II and SAPS II in a surgical intensive care unit.

The Acute Physiologic Score and Chronic Health Evaluation (APACHE) II and the Simplified Acute Physiologic Scale (SAPS) II are two of the more commonly employed predictors of outcome and performance in the intensive care unit setting. However, controversy persists about whether the scores generated by these systems have similar predictive value. This study compared the predicted mortalities derived from APACHE II and SAPS II and contrasted them to the actual mortality in a surgical intensive care unit (SICU). Data for 1665 patients admitted to the SICU between July 1994 and August 1997 were entered into an SICU computerized database. From recorded demographic, hemodynamic, and laboratory data, APACHE II and SAPS II scores were obtained with corresponding predicted mortalities. Patients were stratified by age into categories of less than and greater than 65 years old. Predicted mortalities by APACHE II and SAPS II were compared for each group. An additional analysis included a comparison of survivors and nonsurvivors. There was no significant difference in predicted mortality between APACHE II and SAPS II in any of the groups. Actual mortality was 30 of 486 (6.2%) in patients less than 65 years of age and 73 of 1179 (6.2%) in patients 65 years of age or greater. The APACHE II and SAPS II predicted mortalities (mean +/- SD) for patients less than 65 years of age were 10.5% +/- 10.6% and 10.9% +/- 13.3%, respectively (P > .05). The APACHE II and SAPS II predicted mortalities in patients 65 years of age or greater were 19.1% +/- 17.8% and 18.7% +/- 21.0%, respectively (P > .05). Similarly, when patients were stratified by survival status, no significant difference was present between groups. However, in individual patients, a difference between APACHE II and SAPS II scores was often present. We conclude that although disparities between APACHE II and SAPS II predicted mortalities in individual patients may be significant, APACHE II and SAPS II have similar predictive value in a large SICU patient population. However, both APACHE II and SAPS II systems overestimate mortality in SICU patients. Based on our results, we conclude that either system can be used to measure quality of care in the SICU; however, neither system can be reliably applied to a single patient.

APACHE↗