M tuberculosis drug resistance in AIDS.
Explore the source record for details and available documents.
AIDS-Related Opportunistic Infections↗
Biomedical subjects
J Levin
Publications and source records attributed to J Levin.
A domain of TEL conserved in a subset of ETS proteins defines a specific oligomerization interface essential to the mitogenic properties of the TEL-PDGFR beta oncoprotein.
TEL is a novel member of the ETS family of transcriptional regulators which is frequently involved in human leukemias as the result of specific chromosomal translocations. We show here by co-immunoprecipitation and GST chromatography analyses that TEL and TEL-derived fusion proteins form homotypic oligomers in vitro and in vivo. Deletion mutagenesis identifies the TEL oligomerization domain as a 65 amino acid region which is conserved in a subset of the ETS proteins including ETS-1, ETS-2, FLI-1, ERG-2 and GABP alpha in vertebrates and PNTP2, YAN and ELG in Drosophila. TEL-induced oligomerization is shown to be essential for the constitutive activation of the protein kinase activity and mitogenic properties of TEL-platelet derived growth factor receptor beta (PDGFR beta), a fusion oncoprotein characteristic of the leukemic cells of chronic myelomonocytic leukemia harboring a t(5;12) chromosomal translocation. Swapping experiments in which the TEL oligomerization domain was exchanged by the homologous domains of representative vertebrate ETS proteins including ETS-1, ERG-2 and GABP alpha show that oligomerization is a specific property of the TEL amino-terminal conserved domain. These results indicate that the amino-terminal domain conserved in a subset of the ETS proteins has evolved to generate a specialized protein-protein interaction interface which is likely to be an important determinant of their specificity as transcriptional regulators.
Amino Acid Sequence↗
A simple, fluorescent method to internally label platelets suitable for physiological measurements.
Current methods for studying platelet survival in vivo are limited by the use of radioisotopes, with their inherent safety and regulatory concerns, systemic drug administrations that produce biochemical modifications of platelet functions, or external labeling techniques, which may produce artifacts due to surface modifications. For these reasons, we sought to develop a simple, nonisotopic method for labeling platelets internally, thereby producing platelets more likely to have in vivo properties equivalent to native cells. Murine platelets in protein-free buffer were fluorescently labeled internally by incubation with 2.5 microM 5-chloromethyl fluorescein diacetate (CMFDA), and without washing, were injected into mice for platelet survival studies. CMFDA-labeled platelets were unactivated, as shown by minimal P-selectin expression. When tested in vitro for function by aggregometry, the response of CMFDA-labeled platelets to collagen and thrombin was identical to that of unlabeled platelets. Flow cytometric analysis demonstrated that CMFDA platelets were an intensely stained, unimodal population that was completely separated from unlabeled platelets. The mean half-life of labeled platelets in the murine circulation was 37.5 +/- 4.5 hr (+/-1 SD), and the mean survival time was 3.1-3.3 days (n = 24), similar to results reported using 51Cr and (111)In. No evidence of in vivo transfer of dye from labeled platelets to unlabeled cells was observed. CMFDA produces a population of platelets that are nonradioactively, internally labeled with a highly fluorescent, stable product. The labeled platelets function equivalently to native platelets, as demonstrated by immunocytometry and aggregometry, and importantly, in vivo, by normal platelet survival.
Animals↗
Influence of complement on the allospecific antibody response to a primary vascularized organ graft.
The induction of antibody responses against T cell-dependent antigens has been reported to be influenced by complement. We therefore asked if the primary induction of alloantibodies against transplantation antigens, an important determinant of transplant outcome, is complement sensitive and whether this has functional implications. We transplanted rat kidney allografts into fully major histocompatibility complex-mismatched recipients, in which complement activation was inhibited by daily injection of soluble recombinant human complement receptor type 1 (sCR1). Control allograft recipients were injected with saline. Animals in the control group showed a marked antibody response against donor-specific antigens and an increase in the proportion of activated B and T splenocytes by day 5 after transplantation. Complement-inhibited rats showed a reduced level of antibody binding on target cells sharing the same histocompatibility antigens as the donor strain (p < 0.001), and a reduced level of activated splenic B (p < 0.01) and T (p < 0.01) cells. In a functional assay, the plasma of complement-inhibited rats showed reduced cytotoxic activity against donor-specific cells, and their grafts contained less bound antibody than controls. Analysis beyond 6 days was obscured due to the development of antibodies against sCR1. We conclude that complement activation facilitates the induction of the alloantibody response. Sparing of vascular injury and prolongation of graft survival, previously reported in complement-inhibited rats (Pratt J. R. et al., Am. J. Path. 1996, 149: 2055), could therefore be due to down-regulation of the B cell response as well as reduced complement-dependent cytotoxicity. Inhibition of complement may provide an ancillary approach to the prevention of allospecific antibody formation and the prolongation of allograft survival in primary kidney grafting.
Animals↗
Relationship of adverse events to serum drug levels in patients receiving high-dose azithromycin for mycobacterial lung disease.
We treated 39 elderly human immunodeficiency virus-noninfected patients with Mycobacterium avium complex and/or Mycobacterium abscessus lung disease with azithromycin (600 mg daily), given initially as monotherapy. Adverse events occurred in 33 of 39 patients (85%) receiving azithromycin alone, most commonly gastrointestinal (GI) symptoms (32 of 39, or 82%) and hearing impairment (10 of 39, or 26%). Twenty-four of 39 patients (62%) required a lower dose or withdrawal of the drug. The mean serum level in patients who required a dose reduction because of hearing impairment was 0.8 +/- 0.4 microg/mL, and that in patients whose reduction was necessitated by GI symptoms was 0.7 +/- 0.4 microg/mL; in comparison, the mean serum level was 0.3 +/- 0.16 microg/mL in patients with no adverse events (P = .004 and .003, respectively). Decreasing the daily dose to 300 mg resulted in resolution of most adverse events. Serum levels with monotherapy were comparable to levels after the addition of other antituberculous drugs that included rifampin or rifabutin. Thus, a 300-mg rather than 600-mg daily dose of azithromycin is better tolerated by elderly patients, and serum levels appear unaffected by other antituberculous agents, including rifampin.
Adult↗
Hemoglobin increases mortality from bacterial endotoxin.
Cell-free hemoglobin (Hb) is being developed as an erythrocyte substitute. We have previously demonstrated that cell-free Hb is an endotoxin-binding protein which disaggregates endotoxin and subsequently increases the biological activity of endotoxin in several in vitro assays. Because much of the morbidity and mortality associated with gram-negative bacterial infection is the result of pathophysiologic responses to bacterial lipopolysaccharide (LPS; endotoxin), we studied the effect of Hb on LPS-mediated mortality. Hb infused intravenously into mice before, coincident with, or after intraperitoneal LPS injection substantially increased LPS-related mortality from <5% to 50 to 70% 24 h after administration of LPS and from 50% to 60 to 90% at 48 h. Enhanced mortality was observed over a range of doses of injected LPS. At a given LPS dose, enhancement of mortality was shown to be dependent on the dose of Hb administered. Unmodified native human Hb, alpha-alpha-cross-linked human Hb, and beta-beta-cross-linked human or bovine Hb all were shown to enhance LPS-mediated mortality. Depressed reticuloendothelial cell function may have contributed to the enhanced mortality from LPS in the presence of Hb. Therefore, Hb-based blood substitutes, which are currently undergoing clinical trials, may intensify the potentially fatal effects of the sepsis syndrome in patients with trauma, infection, or hypotension who receive Hb for erythrocyte replacement.
Animals↗
A conversation with a physician and a cancer patient. Interview by Judith D Burke.
Explore the source record for details and available documents.
Aged↗
Localization of megakaryocytes in normal mice and following administration of platelet antiserum, 5-fluorouracil, or radiostrontium: evidence for the site of platelet production.
The relative contributions of various organs to platelet production is controversial. In this study, serial histologic sections of bone marrow, spleen, liver, and lung from normal C57BL/6J mice and mice that had received three different agents which perturb normal murine thrombopoiesis (platelet antiserum, 5-fluorouracil, and radioactive strontium) were examined for the presence of megakaryocytes, utilizing morphologic and immunohistochemical techniques for their identification. In liver and lung tissue, megakaryocytes (including their naked nuclei or large cytoplasmic fragments) were rare in whole cross-sections (which included blood vessels) from normal and perturbed mice, even during periods of strong stimulation of thrombopoiesis. In contrast, megakaryocyte numbers were greatly increased in bone marrow and/or spleen tissue in these circumstances. We conclude that: 1) the bone marrow and spleen are the major thrombopoietic organs in the mouse, and 2) an insignificant fraction of thrombocytopoiesis occurs in the murine liver or lung, even during periods of greatly increased platelet production or following loss of the spleen and/or bone marrow.
Acute Disease↗
Strategies in a managed care system: one agency's experience.
On July 1, 1995, the Illinois Department on Aging and Council for Jewish Elderly began a 3-year venture called the Managed Community Care Demonstration Project (MCCDP). This prospective, capitated system is an offshoot of Illinois Community Care Program, the existing fee-for-service program of home and community-based services for the poor elderly. The authors describe the genesis of the MCCDP and its design as well as the strategies CJE has undertaken to succeed in a managed care system. The authors then focus on how the changes have affected the care manager's role and responsibilities.
Aged↗
Delayed-type hypersensitivity in mast cell-deficient mice: dependence on platelets for expression of contact sensitivity.
Previous studies of cutaneous T cell-mediated responses in mice have obtained pharmacologic, morphologic, and immunologic evidence pointing to a critical role for local mast cells in release of the vasoactive amine serotonin (5-HT) to mediate early, initiating events that are required for elicitation of these responses. However, the role of mast cells in initiating these T cell-mediated cutaneous responses has been questioned due to the presence of relatively intact delayed-type hypersensitivity responses, such as contact sensitivity (CS), in mast cell-deficient mice whose skin contains only 1 % normal mast cell numbers. The contribution of other potential local sources of 5-HT, such as circulating platelets, at the site of a delayed-type hypersensitivity or CS response in these mast cell-deficient strains, has not been investigated. Therefore, we studied the effect of systemic platelet depletion, produced with an anti-platelet Ab, on blood and tissue levels of 5-HT, and on in vivo T cell-mediated cutaneous sensitivity responses, in W/Wv and Sl/Sld mast cell-deficient mice. The results showed that: 1) platelet depletion severely reduced whole blood 5-HT; 2) tissue levels of 5-HT, in mast cell-deficient mice, depended in large part on the presence of circulating platelets, and 3) specific depletion of platelets markedly suppressed CS responses in both W/Wv and Sl/Sld mast cell-deficient mice, and only moderately reduced CS in normal +/+ congenic mast cell-sufficient controls, but did not decrease CS in beige mice, with platelet granules that are defective in storage of 5-HT. We concluded that platelets may provide 5-HT crucial for the initiation of cutaneous T cell-mediated immune responses, such as CS.
Animals↗
Soluble (1-->3)-beta-D-glucan purified from Candida albicans: biologic effects and distribution in blood and organs in rabbits.
(1-->3)-beta-D-glucan is a ubiquitous constituent of fungi, and elevated plasma glucan levels are commonly present in patients with deep mycosis or fungemia. The pharmacokinetics, biologic effects, and distribution in blood and organs of iodine 125-labeled (1--> 3)-beta-D-glucan purified from Candida albicans organisms were analyzed in rabbits during the 24-hour period after intravenous administration of this constituent. The intravascular half-life of beta-glucan was 1.8 minutes in the low-dose group (9.3 micrograms/kg, n = 3) and 1.4 minutes in the high-dose group (222 micrograms/kg, n = 3), and the total body clearance was 1.12 +/- 0.30 ml/min and 1.17 +/- 0.16 ml/min (mean +/- SD), respectively (not significantly different). The serum concentration of (1-->3)-beta-D-glucan was also biologically determined by a test using coagulation factor G of the Japanese horse-shoe crab (G test). There was good correlation between the clearance of beta-glucan measured biologically and isotopically. During the 24-hour period of observation the rabbits remained well and beta-glucan failed to alter blood cell counts, tumor necrosis factor levels, or lipid metabolism. 125I-labeled beta-glucan associated with the blood cellular compartment initially was less than 3% (the majority in the platelets) and decreased further during the following 2-hour period. Over 97% of circulating 125I-labeled beta-glucan was associated with the cell-free plasma, and the majority of this glucan in plasma appeared not to be associated with lipoproteins. The liver contained more than 80% of the 125I-labeled beta-glucan detected in the six major organs analyzed.
Animals↗
Changes in blood coagulation during and following cardiopulmonary bypass: lack of correlation with clinical bleeding.
Although previous studies have documented a wide variety of derangements in laboratory measurements of blood coagulation and platelets during cardiopulmonary bypass, limited data are available concerning the magnitude of these changes and any association with excessive bleeding. To determine whether abnormalities in commonly available laboratory tests for the evaluation of coagulation, fibrinolysis and hemostasis correlate with postoperative blood loss and transfusion requirements as measures of clinical outcome, 47 consecutive patients undergoing coronary artery bypass grafting with hypothermic cardiopulmonary bypass (CPB) were studied prospectively at 12 time points before, during, and following CPB. Routine blood coagulation tests, coagulation factor levels (fibrinogen, V, VII, VIII, and IX) and fibrinolysis (FDP) became abnormal within 15 minutes after patients were placed on CPB, remained abnormal for the duration of CPB, and recovered at varying rates after discontinuation of CPB. Mean factor V levels declined by the greatest percentage, to 15% of normal, followed by factor VIII which decreased to 30%. Platelet counts declined to below 100 x 10(9)/L after the initiation of CPB and remained low in the postoperative period. Twenty-eight percent of patients had mediastinal output > or = 100 mL per hour during the immediate postoperative period, and were considered to be "bleeders." There were no clinically relevant differences in any of the laboratory measurements between patients with normal postoperative blood loss and those defined as bleeders. Thus, the absence of significant correlations between various laboratory measurements of hemostasis and actual postoperative bleeding indicates that these laboratory derangements are transient, are not predictive of clinically important hemostatic abnormalities, and should not be used in isolation to guide the use of blood components in these patients. Furthermore, although bleeders received more blood components, there was surprisingly little effect on the coagulation factor levels measured.
Adult↗
Interpretation of data in multidimensional spaces and its application to Coulomb-explosion imaging.
Explore the source record for details and available documents.
Journal Article↗
Involvement of the central loop of the lactose permease of Escherichia coli in its allosteric regulation by the glucose-specific enzyme IIA of the phosphoenolpyruvate-dependent phosphotransferase system.
Allosteric regulation of several sugar transport systems such as those specific for lactose, maltose and melibiose in Escherichia coli (inducer exclusion) is mediated by the glucose-specific enzyme IIA (IIAGlc) of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). Deletion mutations in the cytoplasmic N and C termini of the lactose permease protein, LacY, and replacement of all cysteine residues in LacY with other residues did not prevent IIAGlc-mediated inhibition of lactose uptake, but several point and insertional mutations in the central cytoplasmic loop of this permease abolished transport regulation and IIAGlc binding. The results substantiate the conclusion that regulation of the lactose permease in E. coli by the PTS is mediated by a primary interaction of IIAGlc with the central cytoplasmic loop of the permease.
Allosteric Regulation↗
The Fiji School of Medicine: a volunteer's experience.
Explore the source record for details and available documents.
Curriculum↗
The haemodynamic correlations of the cardiopulmonary flow index, a relatively non-invasive technique for diagnosis of myocardial pump insufficiency.
The cardiopulmonary flow index (CPFI) is the ratio of cardiopulmonary blood volume to stroke volume. OBJECTIVE. To compare the CPFI derived from a first-pass radiocardiogram and electrocardiogram with the usual haemodynamic measurements obtained by bedside catheterisation. DESIGN. Sixty-one patients in a coronary care unit who had flow-directed pulmonary artery catheterisation for clinical indications had a CPFI recorded together with the usual haemodynamic measurements and calculations. RESULTS. In patients with myocardial pump failure without significant pulmonary disease, linear regression analysis indicated that the best fit for the CPFI could be obtained with a model that used the inverse of stroke index and pulmonary capillary wedge pressure as independent variables. Ninety-six per cent of the variation in CPFI can be explained by variations in pulmonary capillary wedge pressure and stroke index. The CPFI correlated less well with these variables in patients with concomitant lung disease. CONCLUSION. The CPFI is a potentially useful and relatively non-invasive index of haemodynamic function in acutely ill patients without significant pulmonary disease.
Blood Volume↗
Medical aid and racial bias in caesarean section rates.
Explore the source record for details and available documents.
Cesarean Section↗