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Biomedical subjects

L Feldman

Publications and source records attributed to L Feldman.

At least 73 records · Page 4Linked to original sources
PubMed1992

Development of an atraumatic small centrifugal pump for second-generation cardiopulmonary bypass.

A small and light direct-drive centrifugal pump has been developed for cardiopulmonary bypass. In the development process, blood compatibility studies including a hemolysis study, an in vitro fluid dynamic performance study, and in vivo durability and feasibility studies were performed. The centrifugal pump with a 50 mm diameter impeller resulted in almost the same index of hemolysis value as did a Bio-Medicus centrifugal pump. Heat dissipation from the motor was prevented by using a flexible drive cable. Forty-eight-hour sealing durability around the driving axis was accomplished by using a fluoro-rubber V-ring that connected to the hard chrome-plated stainless steel. In vitro and in vivo performances of the pump were satisfactory. Thrombus formation behind the impeller was prevented by using a holed impeller that generated blood flow from the back to the surface of the impeller. Elimination of air during priming procedures was also easier with this modification. This centrifugal pump has one-quarter of the priming volume, size, and weight of magnetically coupled centrifugal pump systems.

Animals↗
PubMed1992

[Clinical and biochemical study of 9 patients with hereditary elliptocytosis].

Using clinical, functional and biochemical criteria, we studied the red blood cell membrane of nine caucasic patients from four families with hereditary elliptocytosis (HE). From a clinical point of view, seven cases were classified as compensated mild HE in whom anemia and splenomegaly are absent and reticulocytosis is slightly elevated or normal. Two cases were uncompensated mild HE with anemia, reticulocytosis, splenomegaly and erythrocytic fragmentation. (Table 1). Three individuals from one family displayed a significant reduction of protein 4.1 by polyacrylamide gel electrophoresis; one of them was uncompensated HE. The patterns of limited tryptic digestion and dimer/tetramer proportion of spectrin were normal. The study of red cell deformability by ectacytometry revealed that the cell deformability under isotonic conditions was decreased in all HE patients and the curve obtained had trapezoidal shape (Fig. 3). We found that the deformability index correlated well with the degree of anemia, but no correlation was observed between clinical findings, morphological phenotype and specific molecular etiology. According to our knowledge, this is the first report on molecular and functional studies in HE in Argentina.

Adult↗
PubMed1992

[Cryosurgery in ventricular tachycardia. Value of myocardial hypothermia in the extension of thr depth of cryogenic lesions].

A desirable goal in surgery for ventricular tachycardia seems to be the development of a direct technique avoiding ventriculotomy, which has well-known harmful effects on the function of the left ventricle. This study is aimed at creating deep cryolesions, reaching to the subendocardial layers, on a closed ventricle. Forty-five cryolesions were performed with extracorporeal circulation in 15 piglets, applying a nitrogen protoxide tube (8 mm, -80 degrees C) on the left ventricle for two minutes. In each animal, 3 cryolesions were created at three different myocardial temperatures: 37 degrees C, 28 degrees C and 10 degrees C. The lesions created at a myocardial temperature of 10 degrees C were significantly (p < 0.01) larger and deeper than those performed at 37 and 28 degrees C. Two cryolesions made at 10 degrees C appeared to extend through the wall. The diameter of the lesions was not as greatly influenced by myocardial temperature. Myocardial temperature very significantly increases the depth of cryolesions, thus allowing them to extend to the subendocardial myocardial layers. Thus the destruction of subendocardial ventricular arrhythmogenic targets by the epicardial application of low temperatures, while preserving the function of the left ventricle as much as possible, may be considered.

Animals↗
PubMed1992

Four unique monoclonal antibodies to the putative receptor binding domain of erythropoietin inhibit the biological function of the hormone.

We have produced a series of monoclonal antibodies (MoAbs) to amino acid region 99-129 of human erythropoietin (Epo) that distinguish unique structural features within this putative receptor binding domain of the hormone. The MoAbs recognize denatured Epo with widely different sensitivities on a Western blot and differentially bind to native Epo in solution. In addition, three of the four MoAbs neutralize the biological activity of Epo in a concentration-dependent fashion in vitro. Neutralization was measured both by inhibition of Epo-induced differentiation in Rauscher murine erythroleukemia cells and by inhibition of Epo-induced proliferation in normal murine splenic erythroid precursors. Characterization of the structural epitopes recognized by each of these four reagent MoAbs should provide us with important information concerning the requirements for hormone-receptor interaction.

Animals↗
PubMed1992

B-lymphocyte-derived burst-promoting activity is a pleiotropic erythroid colony-stimulating factor, E-CSF.

Human B-lymphocyte-derived erythroid burst-promoting activity (B-BPA) is a pleiotropic, lineage-specific regulator of erythropoiesis. Our present data indicate that B-BPA plays an important role as an erythroid colony-stimulating factor (E-CSF) in modulating progenitor growth and differentiation throughout erythropoiesis. E-CSF has discrete effects on both early (erythroid burst-forming units, BFU-E) and late (erythroid colony-forming units, CFU-E) progenitors from normal bone marrow. In serum-substituted fibrin clot cultures, E-CSF stimulates the proliferation of BFU-E, resulting in an increase in the number of erythroid bursts over a wide range of erythropoietin (Epo) concentrations. We now have shown that E-CSF also acts on CFU-E by increasing their sensitivity to Epo markedly, resulting in a tenfold left-shift in the Epo dose-response curve. Using purified target-cell populations of human and murine erythroleukemia cells that are Epo-independent for growth, we have found that E-CSF stimulates cell proliferation directly, increasing the plating efficiency of these cells in suspension culture by 50%-165%. B-BPA also increased proliferation of these cells in semi-solid medium. Importantly, the combination of E-CSF and Epo resulted in a profound increase in the growth and maturation of the resultant colonies. Therefore, the data indicate that E-CSF can regulate the growth of cells independently of added Epo and, in addition, can synergize with Epo in regulating the growth and differentiation of erythroid progenitors.

Animals↗
PubMed1991

Biological activity and structural stability of N-deglycosylated recombinant human erythropoietin.

Controversy exists regarding the functional role of N-linked oligosaccharides in the hormone erythropoietin. We have now examined the role of carbohydrates in the hormone's action using quantitative enzymatic deglycosylation. N-deglycosylated hormone exhibited full biological activity and potency in vitro. Denaturing with 6M urea and renaturing revealed that both the native and N-deglycosylated forms recovered full activity as long as the intrachain disulfide bonds remained intact. Therefore, receptor recognition, subsequent biological activity and maintenance of tertiary structure are intrinsic properties of the polypeptide chain of erythropoietin.

Animals↗
PubMed1991

Erythropoietin receptors induced by dimethyl sulfoxide exhibit positive cooperativity associated with an amplified biologic response.

Erythropoietin triggers the differentiation of erythrocyte progenitors by binding to receptors on their plasma membrane. We report here that pretreatment of erythropoietin-responsive murine erythroleukemia cells with chemical inducers resulted in a striking increase in erythropoietin-specific hemoglobinization. This amplification of the erythropoietin biologic response was accompanied by the induction of a new population of high-density receptors (approximately 20,000 per cell) exhibiting marked positive cooperativity. Erythropoietin binding to new receptors displayed a convex upward Scatchard plot and a Hill coefficient (nH) of 6.75. Measurement of erythropoietin receptor mRNA demonstrated an initial decrease in receptor transcript followed by an approximately 2- to 3-fold increase after 24-48 hr. This increase in receptor message does not appear to account for the magnitude of the receptor up-regulation by dimethyl sulfoxide. We propose that this positive cooperativity reflects the interaction (clustering) of receptors, presumably through the formation of homooligomers or heterooligomers, and that this receptor interaction may amplify the erythropoietin signal transduction pathway.

Animals↗
PubMed1991

Late arterial hemorrhage secondary to a Greenfield filter requiring operative intervention.

Retroperitoneal hematomas associated with Greenfield filters have been described and are generally characterized as clinically insignificant. We report a retroperitoneal hematoma that was associated with a Greenfield filter and that required operative intervention because of hemodynamic instability. At operation a lumbar arterial laceration apparently caused by a protruding filter prong was identified and ligated. The implications of this occurrence for filter placement indications are discussed. The potential life-threatening severity of filter-associated hematomas is emphasized.

Arteries↗
PubMed1990

Conversational time patterns and mutual influence in parent-child interactions: a time series approach.

Mutual influencing processes are assumed to be the basic building blocks in establishing parent-child bonding and in influencing cognitive and language behavior. A study by Jasnow and Feldstein (1986) revealed that, within the temporal domain of speech, preverbal (9-month-old) infants and their mothers exhibit a pattern of mutual influence (attunement) in their average durations of switching pauses. The general purpose of this research was to extend those findings to children with higher verbal functioning. In addition, parent and child genders, nature of the interaction, and specific aspects of parents' personalities, expressiveness, and instrumentality were considered. Each parent interacted with their 4- or 5-year-old son or daughter in each of two conversations--unstructured (social conversation) and structured (task activity). Conversations were processed by an automated computer system yielding objective measure of turns, vocalizations, pauses, and switching-pause durations. To examine interspeaker influence of attunement of temporal speech patterns, "influence coefficients" were computer for each speaker on a "turn-by-turn" basis using time series regression. Analysis of these coefficients revealed that: (1) Mutual influence is most evident with switching-pause duration. (2) Structure in the conversation (as defined by the task or parental instrumentality) seems to facilitate attunement for vocalization and switching pause duration. (3) Attunement with girls seems to occur equally well with both parents, while boys exhibit a style of temporal patterning influence which suggests greater identification with the father. (4) Expressiveness seems to facilitate attunement to the child's switching-pause duration.

Adult↗
PubMed1989

B-lymphocyte-derived erythroid burst-promoting activity is distinct from other known lymphokines.

Previously we have demonstrated that, in contrast to various panspecific or multilineage hematopoietic growth factors, lymphocyte-derived erythroid burst-promoting activity (BPA) is lineage specific, stimulating BFU-E proliferation in serum-free culture by up to 600% of control values while failing to enhance nonerythroid colony formation. To further determine the cellular source(s) of this important erythropoietic growth regulator, we have separated normal nonadherent peripheral blood and splenic lymphocytes by nylon wool fractionation, SRBC rosetting, and panning with monoclonal antibodies (MoAbs). These unstimulated T- and B-lymphocyte-enriched populations were used as cell sources to produce conditioned media (CM) and to prepare plasma membranes (PM). When CM fractions or purified PM were assayed in serum-free human bone marrow culture, BPA was localized entirely to the B-lymphocyte-derived fractions. While CM or PM from unstimulated T lymphocytes failed to stimulate BFU-E proliferation, activation of T cells by either phytohemagglutinin-M (1%) or concanavalin A (Con A; 5 micrograms/mL) induced the expression of a factor on the PM and in the resultant CM that stimulated the formation of erythroid bursts. In addition to enhancing BFU-E proliferation, this T-cell factor stimulated the proliferation of CFU-GM and CFU-GEMM in serum-free culture. When compared biochemically (in terms of temperature stability, localization by ammonium sulfate fractionation, and sensitivity to dithiothreitol) or immunochemically (using antibodies specific for lymphocyte-derived BPA, GM-CSF, or interleukin-3 [IL-3]), as well as by lineage specificity, B- and activated T-lymphocyte-derived growth factors appeared to be distinct. The burst stimulatory activities expressed by recombinant human GM-CSF and IL-3 were immunologically distinct from that associated with octylglucoside extracts of plasma membranes from resting B lymphocytes. Our results suggest that the BFU-E-directed growth-promoting activity released from activated T lymphocytes is apparently due to GM-CSF, while both resting and mitogen-stimulated normal B lymphocytes express erythroid-specific BPA and neither GM-CSF nor IL-3.

B-Lymphocytes↗
PubMed1989

Stomal varices: percutaneous transhepatic embolization.

Peristomal varices occasionally form in patients with chronic liver disease who have surgically created intestinal anastomoses and stomas. Hemorrhage from these varices carries an estimated mortality of 3%-4% per episode, as opposed to the 30%-40% mortality associated with gastroesophageal variceal bleeding. The cases of four patients who underwent transhepatic mesenteric vein catheterization with embolization of stomal varices for recurrent, intractable bleeding are presented. In three of the four patients there was no additional hemorrhage for at least 5 months. One patient was lost to follow-up. There were no complications. Since stomal variceal hemorrhage has a low mortality, transhepatic embolization is presented as a means of hemorrhage control when sclerotherapy fails and when shunt surgery presents an unacceptably high rate of morbidity and mortality relative to the underlying disease.

Aged↗
PubMed1988

Percutaneous cholecystostomy of an ectopic gallbladder.

Percutaneous cholecystostomy and drainage of a retrohepatic gallbladder were performed in a patient with sclerosing cholangitis. Correlative imaging using computed tomography, ultrasound, percutaneous transhepatic cholangiography, and sulfur colloid liver scan of this unusual anomaly are presented herein.

Cholecystostomy↗
PubMed1988

Embryonal rhabdomyosarcoma: presentation as a parotid gland mass.

Solid tumors occur infrequently during childhood. Rhabdomyosarcoma is the most common soft tissue sarcoma occurring in children. Therapeutic advances during the last 15 years have lead to a vast improvement in cosmetic and functional results and in overall survival. A case report of rhabdomyosarcoma of the parotid gland and a review of the literature are presented to highlight these advances.

Adenoma, Pleomorphic↗
PubMed1988

Cardiac output and regional myocardial contraction in anorexia nervosa.

The study measured cardiac output and assessed regional myocardial contraction in 14 patients with anorexia nervosa, some of whom also had bulimia, and in 15 controls. The experimental and control groups were not significantly different in age or body surface area (p = greater than 0.05). To evaluate regional myocardial contraction, 12 of 14 anorexia nervosa-bulimia (ANB) patients were studied in the acute phase and once serially at a mean interval of 1.5 years by assessing the movement of each left ventricular wall segment toward the center of the ventricle as imaged in the precordial short axis. Cardiac output was measured in the ascending aorta by pulsed Doppler for control subjects and for 13 ANB patients. Regional myocardial contraction was normal for all controls, but eight of 14 ANB patients showed regional myocardial contraction abnormalities. Between studies, four of these eight demonstrated improved regional myocardial contraction, three remained unchanged, and one was worse. Mean cardiac output was markedly reduced in ANB patients (2.6 L/min) compared to controls (4.5 L/min) (p = less than 0.001). The low cardiac output in ANB patients was reflected as reduced mean ascending aortic velocity/second (18.5 cm/s) compared to a mean of 22.8 cm/s for controls (p = less than 0.02). Mean ascending aortic area was slightly smaller for ANP patients. Mean peak ascending aortic velocity was significantly lower in ANB patients than in controls (p = less than 0.02). Mitral valve prolapse was seen during at least one examination in seven of 14 ANB patients (0/15 controls) and disappeared in two of three patients following hydration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

A subclavian line complication: embolisation of an arteriovenous fistula.

We report a case illustrating the successful non-surgical management of an arteriovenous fistula resulting from central line placement. After diagnosis by angiography transcatheter embolotherapy of the internal mammary artery provided an alternative to thoracotomy in treating this unusual complication.

Adult↗
PubMed1988

Acetylated lipoproteins impair erythroid growth factor release from endothelial cells.

Endothelial cells are a known source of hematopoietic growth-enhancing factors, including platelet-derived growth factor (PDGF). In addition, endothelium interacts directly with plasma lipoproteins which have been shown to modulate hematopoiesis. To determine the relationship of these properties, we measured the release of an erythroid growth-enhancing factor from bovine endothelial cells under lipid-loaded and control conditions. Human bone marrow cells cultured under serum-free conditions form more erythroid, granulocyte/macrophage, and mixed hematopoietic colonies when supplemented with endothelial cell-conditioned medium (ECCM) than do controls (P less than 0.05). The activity is expressed over a wide range of erythropoietin, lymphocyte-conditioned medium (LCM), recombinant human interleukin-3, and colony-stimulating factor (CSF) concentrations, and is related to ECCM dose. In contrast, enhancing activity in ECCM prepared with 0-400 micrograms/ml acetylated low density lipoproteins (AcLDL) or native LDL is diminished to 0% in a dose-dependent fashion (relative to ECCM from unexposed cells or from cells incubated with very low density lipoproteins, P less than 0.05). Upon dilution, medium prepared from cells incubated with LDL shows a rightward shift in the dose-response curve for erythroid colony formation, while that prepared from AcLDL loaded cells demonstrates a downward shift, indicating that the inhibitory activities are kinetically distinct. Delipidation of ECCM prior to addition to marrow culture removes the inhibitory action of native LDL (P less than 0.05) but not that of AcLDL (P greater than 0.10). Immunochemical analysis suggests that the erythropoietic activity in ECCM is unrelated to that of PDGF, recombinant human CSF, and erythroid burst-promoting activity (BPA) present in LCM. This conclusion is supported by Northern blot analysis of endothelial cells using a cDNA probe for the v-sis homologue of the PDGF beta chain and by immunoprecipitation of metabolically labeled PDGF. The relative amounts of c-sis transcripts and of secreted PDGF were similar in endothelial cells incubated with or without AcLDL. We conclude that AcLDL impair the synthesis or release of an erythropoietic growth-enhancing factor(s) which is biologically distinct from PDGF and BPA present in LCM.

Acetylation↗