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Biomedical subjects

J Levin

Publications and source records attributed to J Levin.

At least 19 recordsLinked to original sources
PubMed1992

Purification of Limulus polyphemus proclotting enzyme.

Horseshoe crabs (Limulus polyphemus and Tachypleus tridentatus) possess a proteolytic blood coagulation system within their amebocytes that, after release and endotoxin activation, generates a polymerized insoluble coagulin clot. Clotting enzyme from horseshoe crab amebocyte lysate is the protease that activates the clottable protein (coagulogen) which then forms the coagulin clot. Comparison of the previously published descriptions of this enzyme has revealed significantly discordant biochemical characteristics. We purified a 60-kDa proclotting enzyme from L. polyphemus amebocyte lysate to a single band on polyacrylamide gel electrophoresis. After electrophoresis, evaluation of enzymatic activity of this protein within gels demonstrated that the band of purified protein corresponded to enzymatic activity, as detected by amidolytic activity for chromogenic substrates and by gelation of coagulogen applied to the gel. The enzymatic activity was inhibited by serine protease inhibitors. The purified proclotting enzyme had a molecular weight and amino acid composition different from the previously published characterizations of proclotting enzymes from both L. polyphemus and T. tridentatus.

Amino Acids↗
PubMed1992

Evidence that interleukin-6 does not play a role in the stimulation of platelet production after induction of acute thrombocytopenia.

The induction of thrombocytopenia results in elevated levels of thrombopoietin (TPO), which can be detected in the plasma of experimental animals. Acute, severe thrombocytopenia (platelet count less than 5% of control) was produced in mice by the administration of either guinea pig or rabbit antimouse platelet antiserum. Control mice received equal volumes of normal serum. At various times after the induction of thrombocytopenia (0.5, 1, 2, 3, 4, 6, 12, and 24 hours) citrated plasma was collected, and circulating interleukin-6 (IL-6) levels were measured using the IL-6-dependent murine hybridoma cell line B9. At no time points after induction of thrombocytopenia were plasma IL-6 levels significantly different from control animals that received normal serum. However, injection of heterologous serum did result in slightly elevated plasma IL-6 levels (at 2 and 3 hours) compared with basal levels measured in uninjected animals. This brief increase was not related to the production of thrombocytopenia. Protein fractions from the plasma of thrombocytopenic rabbits were also tested for the presence of IL-6. Preparations that contained TPO, as shown by stimulation of megakaryocyte maturation in vitro, did not contain detectable levels of IL-6. The ability of the B9 assay to detect the elevation of IL-6 levels in murine or rabbit plasma was verified after the administration of bacterial endotoxin, which is known to increase circulating IL-6 concentrations. IL-6 levels were highly elevated in rabbit or mouse serum after the administration of 5 mg/kg or 1 mg/kg of endotoxin, respectively. Anti-IL-6 antiserum did not neutralize the in vitro megakaryocyte maturation activity of partially purified TPO from the plasma of thrombocytopenic rabbits. In addition, IgG purified from the same antiserum did not neutralize partially purified TPO, as shown after incubation with TPO and subsequent precipitation with agarose-bound protein A. These results show that, unlike TPO, levels of IL-6 do not increase after the induction of acute, severe thrombocytopenia, and strongly suggest that IL-6 does not mediate the thrombopoietic response to acute thrombocytopenia. Although prolonged administration of IL-6 has been shown to induce thrombocytosis, IL-6 and TPO are apparently different and immunologically distinct molecules.

Animals↗
PubMed1992

Composition of lipid A in the S and R forms of Shigella dysenteriae serovar 1.

A chemical analysis was performed of lipid A, isolated by acid hydrolysis of the lipopolysaccharide from the S and R forms of Shigella dysenteriae serovar 1. Differences in the moiety of both lipids and sugars were compared. The lipid portion consisted of a homologous series of fatty acids ranging from C12:0 to C18:0 (predominant homologues, C12:0, C14:0 and C16:0) and the homologous series of 3-hydroxy acids ranging from C12:0 to C16:0 (predominant homologue, 3-OH-C14:0). The major sugar portion consisted of D-glucosamine. The toxicity of lipid A in mice (LD50) ranged between 300-400 micrograms/mouse, and values from the Limulus amebocyte lysate assay were recorded as titres of 10(-5) to 10(-6) mg/ml.

Animals↗
PubMed1992

The safety and efficacy of ten percent pentastarch as a cardiopulmonary bypass priming solution. A randomized clinical trial.

Ten percent pentastarch is a low-molecular-weight hydroxyethyl starch with greater oncotic pressure and shorter intravascular persistence than 6% hetastarch. To evaluate its safety and efficacy as a component of cardiopulmonary bypass priming solution, we prospectively studied 90 patients undergoing coronary artery bypass grafting or valve replacement necessitating cardiopulmonary bypass (bubble oxygenator and moderate systemic hypothermia). Sixty patients were randomized to receive 75 gm of either 10% pentastarch (group P) or 25% albumin (group A), and 30 patients received lactated Ringer's solution alone (group C). Intravascular colloid osmotic pressure during cardiopulmonary bypass was highest with either of the colloid primes (15-minute measurement: group P, 15.7 +/- 2.2 mm Hg (mean +/- standard deviation); group A, 15.2 +/- 2.0 mm Hg; group C, 11.3 +/- 1.7 mm Hg; p less than 0.05, groups P and A compared with group C). This was associated with a lower volume requirement during cardiopulmonary bypass to maintain the venous reservoir (group P, 333 +/- 318 ml; group A, 483 +/- 472 ml; group C, 1332 +/- 1013 ml; p less than 0.05, groups P and A compared with group C). Urine output during cardiopulmonary bypass was similar in each group. Net intraoperative fluid balance was lowest in the colloid groups (groups P and A, 5.7 +/- 1.4 L; group C, 6.9 +/- 1.3 L; p less than 0.05, groups P and A compared with group C). Cardiac index shortly after weaning from cardiopulmonary bypass was greatest in group P (group P, 3.2 +/- 0.9; group A, 2.8 +/- 0.8; group C, 2.7 +/- 0.6 dyne.sec.cm-5; p less than 0.05, group P compared with group C). Changes in alveolar-arterial oxygen gradients, shunt fraction, and effective compliance were similar in all groups. During cardiopulmonary bypass, pentastarch appeared to cause the greatest degree of hemodilution, as suggested by the lowest hemoglobin, factor VII and IX levels and platelet count. The activated partial thromboplastin time was significantly prolonged during and immediately after cardiopulmonary bypass in group P relative to groups A and C (p less than 0.05), although there were no significant differences in the activated clotting time before cardiopulmonary bypass, during cardiopulmonary bypass, or after heparin neutralization. As well, clinical indices of hemostasis, including mediastinal drainage, red cell, platelet, and fresh frozen plasma requirements, and reoperation for excessive postoperative bleeding, were similar. We conclude that pentastarch, when used in cardiopulmonary bypass prime, is as safe as either albumin or Ringer's solution alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Coagulation↗
PubMed1992

Histologic studies of splenic megakaryocytes after bone marrow ablation with strontium 90.

We previously showed that purified strontium 90 produced sustained bone marrow ablation in mice, lowering platelet levels to less than 10% of normal 11 days after administration. Platelet levels later rose exclusively from splenic production and were maintained at a stable level (58% of normal) from 20 to 115 days after injection. However, there was no change in the total number or ploidy distribution of splenic megakaryocytes, as immunologically detected by flow cytometry. To further study the characteristics of splenic thrombopoiesis after bone marrow ablation by 90Sr, we measured the frequency, cross-sectional area, and endomitotic figures of histologically recognizable megakaryocytes (as well as bare megakaryocyte nuclei) in mouse spleen sections. During the hematopoietic nadir 9 days after injection of yttrium 90-free 90Sr, the size (area) of megakaryocyte cross-sections (mean +/- SD, 1079.3 +/- 661.6 microns 2; normal, 398.7 +/- 192.8 microns 2) was greater than for any other time studied, but megakaryocyte frequency (corrected for size) did not increase until day 16. Overall, splenic megakaryocytes in marrow-ablated mice 16 or more days after 90Sr injection showed substantial increases (p = 0.001 for both comparisons) in mean area (707.5 +/- 386.2 microns 2) and sectional frequency (mean +/- SEM, 4.52 +/- 0.20 per 1.83 mm2; normal, 0.78 +/- 0.06 per 1.83 mm2). Megakaryocyte bare nuclei and endomitotic figures were also more numerous after 90Sr, injection, suggesting acceleration of megakaryocyte maturation and platelet production. The induction of splenic platelet production after bone marrow ablation is associated with increased size of recognizable megakaryocytes, despite lack of change in overall splenic megakaryocyte ploidy.

Animals↗
PubMed1992

Bone marrow cell differential counts obtained by multidimensional flow cytometry.

Five-dimensional flow cytometric analysis of normal bone marrow aspirates was utilized to determine the frequency of neutrophils, eosinophils, monocytes, lymphocytes, nucleated erythrocytes, reticulocytes, platelets, and a cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils. Each of these bone marrow cell populations had unique features with respect to forward light scatter, orthogonal light scatter, and staining with Thiazole-Orange, LDS-751, and CD45 labeled with Phycoerythrin (PE). The identity of the cell populations was verified by sorting each of the cell populations and subsequent light microscopic examination of the cells. The frequencies of the nucleated bone marrow cell subpopulations of 50 normal donors were for neutrophils, mean 72.3%; SD +/- 5.1; 95% limits, 70.9-73.8%; eosinophils, mean 1.8%; SD +/- 1.3; 95% limits, 1.4-2.1%; monocytes, mean, 2.8%; SD +/- 1.2; 95% limits, 2.5-3.1%; lymphocytes, mean 12.1%; SD +/- 3.6; 95% limits 11.1-13.2%; nucleated erythrocytes, mean 8.9%; SD +/- 3.9; 95% limits, 7.8-10.1%; and the cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils, mean 1.6%; SD +/- 1.2; 95% limits, 1.3-1.9%. The percentage of reticulocytes in bone marrow aspirates from 50 normal donors correlated with the reticulocyte frequency in the peripheral blood of these donors. However, the mean frequency of reticulocytes was significantly greater (p < 0.0001) in bone marrow (mean 2.19%; SD +/- 0.88) than in peripheral blood (mean 1.71%; SD +/- 0.88). The technique could discriminate between immature and mature reticulocytes based on the brighter staining with both Thiazole-Orange and LDS-751 of the immature reticulocytes. This was confirmed by cell sorting of both reticulocyte populations, which revealed larger clumps of New Methylene Blue staining material in the brighter Thiazole-Orange and LDS-751 stained reticulocytes. The immature reticulocytes were present in normal bone marrow, but not in normal peripheral blood. As expected, a significantly greater frequency of nucleated cells was found in bone marrow aspirates (mean 0.85%; SD +/- 0.59) than in peripheral blood (mean 0.20%; SD +/- 0.11). The frequency of platelets was significantly lower in bone marrow (mean 1.24%; SD +/- 0.69) than in peripheral blood (mean 2.94%, SD +/- 1.14). Flow cytometric bone marrow analysis can provide clinical laboratories with a technique that generates quantitative bone marrow cell differentials and potentially can reduce the need for light microscopic examination of bone marrow smears.

Benzothiazoles↗
PubMed1992

Cell cycle status of murine megakaryocyte and granulocyte-macrophage colony-forming cells in bone marrow and spleen.

The cell cycle status of megakaryocyte colony-forming cells (Meg-CFC) and granulocyte-macrophage colony-forming cells (GM-CFC) from the spleen and bone marrow of C57BL mice was evaluated by determining the effects of hydroxyurea (OHU) or cytosine arabinoside (Ara-C), both in vivo and in vitro, upon colony-forming cells (CFC). The concentrations of cells in culture (2 x 10(6) to 4 x 10(6)/ml for spleen and 0.25 x 10(5) to 1.0 x 10(5)/ml for bone marrow) did not alter cell cycle status of either Meg-CFC or GM-CFC. Determination of cell cycle status following in vivo administration of OHU indicated that 25.2% of Meg-CFC and 28.1% of GM-CFC in the spleen, and 26.0% of Meg-CFC and 29.5% of GM-CFC in the bone marrow, were in cycle. In vitro incubation of CFC with OHU showed that in the spleen 25.1% of Meg-CFC and 24.2% of GM-CFC were engaged in DNA synthesis, whereas in bone marrow 28.5% of Meg-CFC and 29.2% of GM-CFC were synthesizing DNA. Incubation with Ara-C, in vitro, gave similar results, with 26.0% of Meg-CFC and 26.2% of GM-CFC in the spleen, and 27.1% of Meg-CFC and 31.4% of GM-CFC in the bone marrow, in cycle. In summary, significant differences were not observed between the cell cycle status of Meg-CFC and GM-CFC, whether derived from spleen or bone marrow. In vitro and in vivo measurements (with OHU) and in vitro measurements with two cytotoxic drugs (OHU versus Ara-C) also provided similar results. The data suggest that the regulation of DNA synthesis in both Meg-CFC and GM-CFC in the murine spleen and bone marrow is similar.

Animals↗
PubMed1992

Correlation of in vitro and in vivo biological activities during the partial purification of thrombopoietin.

We have evaluated three in vitro assays for megakaryocyte maturation as monitors of biological activities of thrombopoietin (TPO). The in vitro measurements, that is, potentiation of murine megakaryocyte colonies in soft agar cultures, growth of single murine megakaryocytes in soft agar, and acetylcholinesterase production in liquid cultures of murine bone marrow cells, were correlated with measurements of thrombopoiesis stimulatory activity in vivo, based on labeling of newly formed platelets with [75Se]selenomethionine. Protein fractions produced during the purification of TPO from the plasma of thrombocytopenic rabbits were used to evaluate the in vitro assays. Potentiation of murine megakaryocyte colony growth in soft agar was least valuable as a TPO assay, due to variability. Growth of single megakaryocytes in vitro, in a serum-free, agar culture system, correlated well with measurement of thrombopoiesis-stimulating activity in vivo, in regard to increases in specific activity during the purification, and was the most sensitive of the three assays. The serum-free, liquid culture assay also correlated well with the in vivo assay, and it had the additional advantage of being feasible for evaluation of the large numbers of protein fractions produced by high-resolution chromatographic procedures. Using the liquid culture system to assay fractions from gel permeation high performance liquid chromatography, a biologically active fraction with a molecular weight range of 40-47 kd was identified.

Acetylcholinesterase↗
PubMed1992

Effects of interleukin 3 and interleukin 6 on platelet recovery in mice treated with 5-fluorouracil.

We have studied the effects of murine recombinant interleukin 3 (IL-3) and human recombinant interleukin 6 (IL-6) on platelet recovery after administration of 5-fluorouracil (5-FU) to mice. 5-FU at 250 mg/kg body weight was administered as a single i.p. injection, and treatment with IL-3 alone, IL-6 alone, or a combination of IL-3 plus IL-6 was initiated immediately following the 5-FU or after a delay of 2 days. In addition, the effects of the combination of IL-3 plus IL-6 were evaluated following delays in initiation of their administration until 4 or 6 days after 5-FU treatment. In all schedules, the IL-3 and IL-6 treatments were discontinued 8 days following 5-FU. IL-3 and IL-6 were given s.c. three times daily; each injection of IL-3 was 80,000 U, each injection of IL-6 was 5000 U, and the combination comprised separate injections of IL-3 and IL-6 at the same respective doses. The combination of IL-3 and IL-6, initiated immediately or 2 days following 5-FU, diminished the platelet nadir and increased platelet counts on individual days during the recovery phase, thus apparently decreasing the time required for recovery to a normal platelet level. However, using self-modeling nonlinear regression, in order to analyze variability in the duration of thrombocytopenia, statistically significant shortening of the period of thrombocytopenia could not be consistently demonstrated. Neither IL-3 alone nor IL-6 alone had any effect on the above parameters. Recovery of hematocrit values and white blood cell levels was unaffected by administration of either IL-3 or IL-6 alone or the combination of both cytokines. We propose that IL-3 and IL-6 can act synergistically to enhance platelet recovery following 5-FU-mediated thrombocytopenia, but their modification of the response to 5-FU is modest.

Animals↗
PubMed1992

Selective cutaneous hyperpigmentation in mice following zidovudine administration.

BACKGROUND AND DESIGN: C57BL/6N mice fed zidovudine in their drinking water develop selective hyperpigmentation of the tails and footpads. Zidovudine-fed and identical control mice were observed and sequential biopsy specimens were obtained. Routine light microscopy, electron microscopy, and image analysis of unstained biopsy specimens were used to evaluate the extent, nature, and amount of cutaneous hyperpigmentation. RESULTS: Beginning at day 14 selective hyperpigmentation of the tails and footpads of the mice was noted. Histologic evaluation revealed a gradual increase in melanin, beginning in the lower levels of the epidermis, with eventual pigmentation of the stratum corneum. Electron microscopy demonstrated a sixfold increase in melanosomes in the tail skin of the zidovudine-fed mice. Using image cytometry, melanin was quantitatively shown to increase, paralleling the clinically apparent hyperpigmentation. The hyperpigmentation was reversible on discontinuation of zidovudine. CONCLUSIONS: This animal model parallels the human in developing reversible and selective hyperpigmentation on administration of zidovudine. In this model the increased pigmentation is due to increased numbers of melanosomes within epidermal keratinocytes. Image cytometry may be useful in semiquantitatively studying the pathogenesis of various disorders of hyperpigmentation.

Animals↗
PubMed1991

New trends in the use of Al(OH)3-conjugated endotoxins and their subunits from the S- and R-forms of Shigella dysenteriae serovar 1 for model vaccination purposes.

The lipopolysaccharides, lipopolysaccharide-protein complexes and their lipids A, isolated from Shigella dysenteriae 1, exhibited lethal toxicity (LD50 300-400 micrograms per mouse), pyrogenicity (0.01-1.0 microgram), activity in the Limulus test (10(-3)-10(-12) mg ml-1) and produced a positive local Shwartzman reaction. It was found that these substances bound to Al(OH)3 were capable of successfully protecting mice from challenge with both homologous and heterologous infections (up to 90% of mice survived a challenge with LD100), whereas immunization with substances with no biological carrier exhibited very low or zero protective effects. Furthermore, the positive cross-reactivity of lipids A in the agar immunodiffusion test confirms the wide applicability for vaccination purposes.

Aluminum Hydroxide↗
PubMed1991

Relationship between the basic personality inventory and the NEO-Personality Inventory in a nonpatient sample.

The relation between psychopathology measured by Jackson's 1989 Basic Personality Inventory and personality dimensions measured by Costa and McCrae's 1985 NEO-Personality Inventory was investigated in a nonpatient sample of 457 female subjects. The results contribute to the validation of both instruments and agree with the relevant findings reported in the literature. They also provide support for the cross-cultural invariance of these instruments.

Adolescent↗
PubMed1991

Multidimensional flow cytometric blood cell differentiation without erythrocyte lysis.

Forward light scattering, orthogonal light scattering, and the fluorescence intensities of unlysed peripheral blood cells, labeled with CD45-phycoerythrin and the nucleic acid dyes LDS-751 and thiazole orange, were measured simultaneously, utilizing a flow cytometer. Erythrocytes, reticulocytes, platelets, neutrophils, eosinophils, basophils, monocytes, lymphocytes, nucleated erythrocytes, and immature nucleated cells occupied unique positions in the five-dimensional space created by the listmode storage of the five independent parameters. A software program was developed which identified and enumerated each of these cell populations. Platelets in this study were identified by LDS-751 staining, in addition to their forward and orthogonal light-scattering characteristics. Validation of this approach was obtained by demonstrating that all CD41- or CD42-expressing platelets also stained with LDS-751. Furthermore, the staining by LDS-751 did not change following platelet activation with ADP. The quantification of erythrocytes, platelets, neutrophils, eosinophils, monocytes, and lymphocytes correlated well with data obtained with a commercial hematology whole blood analyzer (H-1). Reproducibility of the identification of these populations was shown by repeated measurement of the same sample and by staining and analysis of multiple aliquots of identical blood samples. Stability studies demonstrated that 8 hours after blood collection, the number of damaged cells increased. This could be measured by a greater thiazole orange uptake by the damaged cells. This investigation demonstrates the feasibility of multidimensional flow cytometric blood cell differentiation for an automated whole blood cell analysis without the necessity of erythrocyte lysis. The ability to simultaneously identify reticulocytes, nucleated erythrocytes, and immature nucleated cells in one measurement is unique and promises to be a powerful tool for the assessment of abnormal blood samples.

Antibodies, Monoclonal↗
PubMed1979

Comparison of 99mTc and 131I scans in thyroid function studies.

Thyroid function was studied in 170 patients, using technetium-99m (99Tc) and oral radio-iodine (131I); 110 patients had normal thyroid function, and 60 had hyperthyroidism. The 20-minute 99mTc uptake gave an accurate assessment of thyroid function in 95% of patients, and the 24-hour 131I uptake was accurate in 92%. One hundred 99mTc and 131I scintiscans were compared by 3 observers. Scans obtained with each isotope were of comparable quality, and in only 1 patient were both scans of poor quality. 99mTc is as good as 131I for assessing thyroid function and morphology, but has several advantages over 131I.

Evaluation Studies as Topic↗
PubMed1979

Radiocolloid imaging in primary liver cancer and amoebic liver abscess. Accuracy of differential diagnosis and extent of inter-observer variability.

Radiocolloid liver scans from 58 patients with primary liver cancer and 56 patients with amoebic liver abscess were examined 'blind' and independently by three nuclear physicians and one registrar in training in order to evaluate the accuracy of the differential diagnosis between the two conditions and to assess the extent of inter-observer variability in the interpretation of these scans. Each of the observers incorrectly interpreted about 12% of scintiphotographs and at least one observer was wrong in 25% of the scans. The difference in diagnostic accuracy between individual observers was not statistically significant. Observers disagreed in 21,6% of the scans. The main reasons for misdiagnosis were failure to realize that excessive extrahepatic uptake of radiocolloid can occur with liver abscesses, and the indistinguishable appearance of the defect or defects in some cases of primary liver cancer and amoebic liver abscess. This margin of error and of inter-observer variability must be borne in mind when interpreting liver scans of patients thought to have either primary liver cancer of amoebic liver abscess.

Colloids↗
PubMed1979

Humoral control of thrombopoiesis.

There is increasing evidence that an important mechanism by which platelet production is regulated depends upon a humoral substance (thrombopoietin) that affects the production of platelets by megakaryocytes. Plasma from thrombocytopenic donors increases the rate of appearance or concentrations of subsequently administered Na235SO4 or selenomethionine-75Se in platelets. Both isotopes are initially incorporated into the cytoplasm of megakaryocytes, and labeled platelets appear in the circulation after their production and release from megakaryocytes. Thrombopoiesis-stimulating activity also can be detected in the plasma of normal donors when endogenous thrombopoiesis has been suppressed in recipient assay animals by the hypertransfusion of platelets. Recent studies have indicated that certain fractions of plasma from throbocytopenic donors are also capable of stimulating thrombopoiesis in recipient animals. The nature of thrombopoietin(s) and its mechanism of action remain unknown. However, currently available data indicate that thrombopoiesis-stimulating factors may act both on diploid precursors and immature megakaryocytes and upon maturing megakaryocytes. The site of production of thrombopoietin also is unknown. Although the sensor that regulates thrombopoietin or other humoral mediators of thrombopoiesis has not been identified, it appears that platelet numbers, per se, are not the sole variable to which megakaryocytopoiesis eventually responds.

Ammonium Sulfate↗