Autoimmune Addison's disease and 21-hydroxylase.
Explore the source record for details and available documents.
Addison Disease↗
Biomedical subjects
B R Smith
Publications and source records attributed to B R Smith.
Metabolism and radiosensitization of 4,5-dimethylmisonidazole, a ring-substituted analog of misonidazole.
4,5-Dimethylmisonidazole (DMM) is a ring-substituted derivative of the 2-nitroimidazole, misonidazole. 2-Nitroimidazoles are able to sensitize radioresistant hypoxic cells, and to kill them outright through bioreductive metabolism. The toxic process is believed to reflect the consequences of reductively activated drugs forming adducts with cellular (macro)molecules. Both this process and the radiosensitizing activity are thought to correlate with the electron affinity of radiosensitizing agents. In the present study, methyl groups were added to the imidazole ring of misonidazole in order to hinder adduct formation with cellular molecules after reductive-activation of the compound. It was anticipated that this would substantially decrease the hypoxic-cell toxicity of the parent drug. The presence of the two methyl groups reduced the half-wave reduction potential of DMM by about 70 mV, so we expected that its radiosensitizing ability would also decrease. In direct comparison with misonidazole, DMM, at equimolar concentrations, showed dramatically reduced binding to cellular macromolecules under bioreductive conditions, both in vivo, using a liver perfusion system, and in vitro, using tissue culture cells incubated under extreme hypoxia. However, DMM was only moderately less toxic than the parent compound, and showed greatly diminished radiation sensitization capacity. Since the decrease in toxicity was much less than expected, and the decrease in radiosensitization was much more than expected, this compound may be an important drug for continuing studies on the mechanisms of radiation sensitization, binding and cytotoxicity caused by electron affinic drugs.
Animals↗
A gamma delta+ T-cell leukemia bearing a novel t(8;14)(q24;q11) translocation demonstrates spontaneous in vitro natural killer-like activity.
A highly malignant human T-cell leukemia was identified by cell surface analysis as a member of the T-cell receptor (TCR) gamma delta lineage. Cytogenetic and molecular analysis showed a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on chromosome 14 and the distal end of chromosome 8 near the c-myc proto-oncogene locus. The gamma delta TCR of the leukemia blasts was functionally intact and could be activated to generate intracellular calcium flux and to target Fc receptor-mediated redirected tumor cell lysis. In addition, non-major histocompatibility complex restricted lysis of a limited target cell panel was shown by fresh leukemic blasts and by the in vitro-maintained leukemia cells that was comparable to known T-cell lines with natural killer-like activity. These data suggest that the T-cell leukemia potentially had in vivo functional cytolytic activity. However, whether this activity did contribute to the patient's clinical condition could not be determined.
Antigens, CD↗
Cardiopulmonary bypass induces leukocyte-platelet adhesion.
Cardiopulmonary bypass (CPB) has been demonstrated to activate platelets, producing an increased number of circulating platelets that have undergone alpha-granule release and express granule membrane protein-140 (GMP-140) on their surface. In vitro, GMP-140 mediates activated platelet adhesion to neutrophils (PMN) and monocytes, causing the formation of leukocyte-platelet conjugates. Using a newly developed assay that measures the percentage of circulating leukocyte-platelet conjugates in whole blood, we studied 17 patients undergoing CPB and have determined that (1) monocyte-platelet conjugates increased significantly during CPB, from 18% +/- 1.5% to 44% +/- 4.5% (mean +/- SEM) by the end of CPB, while PMN-platelet conjugates increased only slightly and lymphocyte-platelet conjugates decreased; (2) the time course of the increase in monocyte- and PMN-platelet conjugates paralleled that of the increase in circulating activated platelets, as determined by the presence of surface GMP-140; and (3) monocyte activation, as assessed by increased surface expression of CD11b, showed a gradual increase similar to the increase in monocyte-platelet conjugates, while PMN surface CD11b peaked immediately after the start of CPB. We conclude that CPB, through increased platelet GMP-140 expression, causes formation of monocyte-platelet, and to a lesser extent, PMN-platelet conjugates. The activation of monocytes and PMN on CPB, as evidenced by CD11b expression, occurs with differing time courses.
Blood Platelets↗
Lymphoid irradiation results in long-term increases in natural killer cells in patients treated for Hodgkin's disease.
Therapeutic lymphoid irradiation has been shown to produce profound long-term alterations in lymphocyte subpopulations and immunologic responsiveness. Dual immunofluorescence flow cytometry and functional cytolytic assays were used to investigate the effects of lymphoid irradiation either alone or in combination with chemotherapy on T-cell and natural killer (NK) cell populations in the blood of patients treated for Hodgkin's disease. Patients treated with mantle and paraaortic lymphoid irradiation show significant increases in the proportion of cells bearing the NK cell phenotypic marker Leu-11 (CD16). These patients also display proportionately increased cytotoxicity against K562 tumor targets in vitro. A sizable number of these NK cells label dimly with Leu-2 (CD8) although they lack the pan-T-cell marker Leu-4 (CD3). The emergence after lymphoid irradiation of this population of Leu-11+2+ NK cells may lead to an apparent decrease in the ratio of helper to suppressor T-cells, although the actual ratio of these T-cell subsets generally is normal. These changes persist for years after the completion of radiation therapy. It was concluded that lymphoid irradiation may produce profound changes in NK cell populations in patients treated for Hodgkin's disease; the clinical significance of these changes is unclear.
Adolescent↗
Differential ethanol intake in Tryon maze-bright and Tryon maze-dull rats: implications for the validity of the animal model of selectively bred rats for high ethanol consumption.
The search for a genetically based "animal model of alcoholism" has led to the creation of extensive research programs using various combinations of initial ethanol preference screening techniques and breeding methods to yield rodents with primary genetic differences that contribute to high or low ethanol preference. The present experiment examined the ethanol intake of the Tryon rat strain, which were bred for high and low maze learning scores. It was observed that the Tryon Maze Bright rats displayed an unprecedented affinity for ethanol with stable intakes between 12.7 and 13.7 g/kg per day and preference ratios exceeding 0.75 for ethanol concentrations ranging between 15 and 29%. The pattern of ethanol intake of the Tryon Maze Dull rats resembled the ethanol intake pattern of other, non-selectively bred strains of rats, approximately 2-3 g/kg of absolute ethanol at preference ratios between 0.11 and 0.28. The affinity for ethanol observed for the Tryon Maze Bright rats seems to exceed the reported consumption patterns of rat strains specifically bred for high ethanol consumption although the Tryon rats were selectively bred for variables that were seemingly unrelated to ethanol intake.
Alcohol Drinking↗
Remoxipride, a specific D2 dopamine antagonist: an examination of its self-administration liability and its effects on d-amphetamine self-administration.
The self-administration liability of remoxipride, a specific dopamine D2 antagonist, by laboratory rats was evaluated using an intravenous self-administration paradigm. It was observed that remoxipride failed to support self-administration behavior across the three doses tested. In addition, remoxipride pretreatment attenuated d-amphetamine self-administration. The findings of the present study provide support for the notion that remoxipride appears to have functional similarity in self-administration paradigms as other D2 antagonists.
Animals↗
Microstructural analysis of the effects of THIP, a GABAA agonist, on voluntary ethanol intake in laboratory rats.
The effects of GABAA agonist THIP on the acquisition of voluntary ethanol intake and the pattern of food and water consumption were examined through the use of a computer-controlled data acquisition system. Twenty male Long-Evans rats were randomly assigned to two groups, one of which received THIP (16 mg/kg, IP) and the other an equal volume of saline. Subjects were presented with a free choice of ethanol and water immediately following drug injections, which occurred every other day. The initial concentration of ethanol presented was 2% and was increased by increments of 2% following the second presentation of each concentration, up to a maximum concentration of 10%. Subjects treated with THIP consumed significantly greater amounts of ethanol than did saline controls. A microstructural analysis of bout patterns suggested that the increased consumption of ethanol was a function of an increase in the size, duration, and frequency of ethanol drinking bouts. Food intake was also attenuated by THIP treatment. The results indicated that the decrease in total food intake was a function of a decrease in the frequency of the food bouts. However, in contrast to that observed for ethanol intake, the size and duration of the food bouts were unchanged. The qualitatively different patterns in the microstructure of consummatory behavior for ethanol and food following THIP treatment would suggest that differential mechanisms may mediate the food and ethanol effects observed in the present study. In addition, the differential effects of THIP on ethanol consumption relative to water would suggest that GABAA manipulations may play a role in influencing the acquisition of voluntary ethanol drinking.
Alcohol Drinking↗
Pharmacology of agents used in bone marrow transplant conditioning regimens.
Explore the source record for details and available documents.
Antineoplastic Agents↗
Analysis of carbohydrate residues on human thyroid peroxidase (TPO) and thyroglobulin (Tg) and effects of deglycosylation, reduction and unfolding on autoantibody binding.
The contribution of carbohydrate residues and peptide chain conformation to autoantibody binding sites on human thyroid peroxidase (TPO) and thyroglobulin (Tg) has been investigated. In addition the nature of carbohydrate residues associated with human TPO has been studied. 125I-labelled human TPO and Tg were treated with the following glycosidases: EndoD, EndoH, neuraminidase, O-glycanase, neuraminidase followed by O-glycanase and PNGaseF. Thereafter binding to different sera containing TPO autoantibodies and Tg autoantibodies was assessed using solid phase protein A to separate antibody-bound and free labelled antigens. In addition, labelled Tg and TPO were treated with reducing agent (dithiothreitol) or sodium acetate buffer pH 7.5, 5.5 and 3.2 (followed by neutralisation with 2 M Tris pH 8.3) prior to antibody binding studies. Furthermore, the effect of deglycosylation and treatment with acid buffers on TPO enzyme activity was studied. The nature of carbohydrate residues associated with hTPO was analysed by assessment of the effects of different glycosidases on 125I-TPO mobility on SDS-PAGE followed by autoradiography and by the use of lectins. Deglycosylation of labelled Tg and TPO had no clear effect on Tg and TPO autoantibody binding. Reduction of labelled Tg and TPO resulted in almost complete loss of autoantibody binding with all sera studied. Furthermore, adjusting the pH of labelled TPO or Tg transiently to pH 5.5 lowered autoantibody binding in the case of all the sera and the effect was more marked at pH 3.2. TPO enzyme activity (guaiacol assay) of unlabelled TPO was decreased after treatment with EndoH but not with other glycosidases. The low pH buffers affected unlabelled TPO enzyme activity measured by iodide assay. Treatment of 125I-labelled TPO with EndoH, neuraminidase and PNGaseF caused marked changes in the double band pattern characteristic of TPO on analysis by SDS gel electrophoresis (TPO doublet). Analysis of changes in the mobility of the 2 bands of the doublet after treatment with different glycosidases and binding studies with lectins indicated that both high mannose and complex type sugar residues were associated with hTPO. The high mannose type residues were associated mostly with the lower band of the hTPO doublet whereas complex type residues were associated mostly with the upper band. Overall, our studies indicate that (1) the major autoantibody binding sites on hTPO and hTg are conformational, (2) sugar residues do not appear to be important in forming the autoantibody binding sites on hTPO and hTg, and (3) both high mannose type and complex type sugar residues are associated with hTPO.
Autoantibodies↗
Cloning of a human autoimmune response: preparation and sequencing of a human anti-thyroglobulin autoantibody using a combinatorial approach.
Thyroid lymphocyte RNA from a Hashimoto patient exhibiting high titre serum IgG autoantibodies against thyroglobulin (Tg) has been used to construct a Fab library in phage lambda. Screening of this library with radioiodinated Tg has permitted the cloning of an anti-Tg antibody (MH52) with an affinity of 4.5 x 10(9) molar-1 as determined by inhibition ELISA. Sequence analysis showed MH52 to be an authentic antibody of the IgG1/K isotype with variable region genes from the VHI and VKIII families in combination with the JH3, DK4 and JK2 gene segments. The MH52 light chain gene showed high sequence homology (93%) with the germline gene used by several rheumatoid factors and some DNA autoantibodies. Greater divergence from the germline was observed in the case of the MH52 heavy chain gene which showed 86% homology with a germline heavy chain gene isolated from human liver. Overall the similarity between the genes coding for MH52 and the genes coding for some other autoantibodies of non-related specificity might suggest that similar regulatory processes control the formation of these different autoantibodies.
Amino Acid Sequence↗
GABAergic involvement in the acquisition of voluntary ethanol intake in laboratory rats.
Treatment with the GABAA agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) or the GABAB agonist baclofen was shown to enhance the acquisition of voluntary ethanol consumption in laboratory rats. THIP administration resulted in an increased intake of absolute ethanol without an increase in total fluid intake. In contrast, baclofen administration, while increasing ethanol intake in a manner similar to that seen with THIP, also increased total fluid intake, indicating that its effects may not be specific to an interaction with ingested ethanol. The data obtained in the present study support the notion that GABAergic mechanisms, particularly those related to the GABAA receptor, may be involved in the acquisition of voluntary ethanol consumption in laboratory rats.
Alcohol Drinking↗
Can medical rationing be made rational?
Explore the source record for details and available documents.
Attitude of Health Personnel↗
Selective depletion of bone marrow T lymphocytes with anti-CD5 monoclonal antibodies: effective prophylaxis for graft-versus-host disease in patients with hematologic malignancies.
Seventy-one patients with hematologic malignancies received bone marrow from a histocompatible sibling (n = 48) or a partially matched relative (n = 23) that had been depleted of CD5+ T cells with either an anti-CD5 mooclonal antibody (MoAb) plus complement (anti-Leu1 + C) or an anti-CD5 MoAb conjugated to ricin A chain (ST1 immunotoxin [ST1-IT]). These patients received intensive chemoradiotherapy consisting of cytosine arabinoside, cyclophosphamide, and fractionated total body irradiation. Both anti-Leu1 + C and ST1-IT ex vivo treatments effectively depleted bone marrow of T cells (97% and 95%, respectively). Overall, primary and late graft failure each occurred in 4% of evaluable patients. The diagnosis of myelodysplasia was a significant risk factor for graft failure (P less than .001), and if myelodysplastic patients were excluded, there were no graft failures in major histocompatibility complex (MHC)-matched patients and 2 of 23 (8.7%) in MHC-mismatched patients. The actuarial risk of grade 2 to 4 acute graft-versus-host disease (GVHD) was 23% in MHC-matched patients and 50% in MHC-mismatched patients. In MHC-matched patients, acute GVHD tended to be mild and treatable with corticosteroids. Chronic GVHD was observed in 6 of 36 (17%) MHC-matched patients and none of 11 MHC-mismatched patients. There were no deaths attributable to GVHD in the MHC-matched group. Epstein-Barr virus-associated lymphoproliferative disorders were observed in 3 of 23 MHC-mismatched patients. The actuarial event-free survival was 38% in the MHC-matched patients versus 21% in the MHC-mismatched patients. However, if outcome is analyzed by risk of relapse, low-risk patients had a 62% actuarial survival compared with 11% in high-risk patients. These data indicate that the use of anti-CD5 MoAbs can effectively control GVHD in histocompatible patients, and that additional strategies are required in MHC-mismatched and high-risk patients.
Adolescent↗
Dynamics of leukocyte-platelet adhesion in whole blood.
The dynamics of leukocyte-platelet adhesion and platelet-platelet interaction in whole blood are not well understood. Using different platelet agonists, we have studied the whole blood kinetics of these heterotypic and homotypic interactions, the relative abilities of different leukocyte subsets to participate in platelet adhesion, and the ligands responsible for adhesion. When platelet aggregation was inhibited by the Arg-Gly-Asp-Ser (RGDS) peptide, thrombin stimulation of whole blood resulted in platelet expression of granule membrane protein 140 (GMP-140) and, simultaneously, a marked increase in the percentage of monocytes and neutrophils (PMN) binding platelets, as well as an increase in the number of platelets bound per monocyte and PMN. Lymphocytes were unaffected. Monocytes bound more platelets and at an initially faster rate than PMN. This increase in monocyte and PMN adhesion to platelets was completely inhibited by the blocking monoclonal antibody (MoAb), G1, to GMP-140. When the combination of epinephrine and adenosine diphosphate (epi/ADP) was used as a less potent agonist in the presence of RGDS, GMP-140 expression per platelet was less, and while monocyte-platelet conjugates formed, PMN-platelet conjugates did not. With epi/ADP in the absence of RGDS, there was an immediate, marked decrease in the percentage of all leukocytes with bound platelets, simultaneous with an increase in the percentage of unbound platelet aggregates. As these platelet aggregates dissociated, the percentage of monocytes and PMN with adherent platelets increased, with monocytes again binding at a faster initial rate than PMN. This recovery of monocyte and PMN adhesion to platelets was also inhibited by the G1 MoAb. We conclude that: (1) monocytes and PMN bind activated platelets in whole blood through GMP-140; (2) monocytes have a competitive advantage over PMN in binding activated platelets, particularly when less potent platelet agonists are used; and (3) platelet aggregate formation initially competes unactivated platelets off leukocytes; subsequent aggregate dissociation allows the now activated platelets to readhere to monocytes and PMN through GMP-140. These studies further elucidate the dynamic interaction of blood cells and possible links between coagulative and inflammatory processes.
Adenosine Diphosphate↗
Activated and unactivated platelet adhesion to monocytes and neutrophils.
To examine the possible receptor-ligand pairs mediating adhesion of activated and "unactivated" platelets to leukocytes and the kinetics of leukocyte-platelet binding, we developed a flow cytometric assay using isolated cell fractions to accurately measure heterotypic cell adhesion, including both total leukocyte-platelet conjugate formation as well as the number of platelets bound per leukocyte. We have shown that (1) activated platelet binding to both polymorphonuclear leukocytes (PMN) and monocytes is dependent on both a specific epitope (blocked by monoclonal antibody G1) of granule membrane protein-140 (GMP-140) and the presence of divalent cations; (2) unactivated platelets bind to 87% of viable, resting monocytes but to only 34% of PMN; (3) the receptor(s) on unactivated platelets that mediate adhesion to PMN and monocytes do not require divalent cations and become nonfunctional after thrombin activation; and (4) the kinetics of platelet adhesion to monocytes and PMN indicate that monocyte adhesion is favored over neutrophil adhesion. We conclude that platelet-heterotypic cell adhesion is a dynamic process reflecting the activation status of the platelet and differential binding abilities of leukocytes.
Antibodies, Monoclonal↗
Maximum likelihood estimation of non-uniform transmitter release probabilities at the crayfish neuromuscular junction.
The classical model of quantal release of neurotransmitter assumes that a fixed number of quantal units are available for release in the presynaptic terminal, and that each unit has the same probability of being released. This model also assumes that different units are released independently of one another. We consider two variations of the classical model. In the first case we assume that release is independent, but with potentially different release probabilities at different sites. In the second case we allow for dependence among the release units. A maximum likelihood procedure for the estimation of model parameters is developed, and an estimator of the number of quantal units is proposed. The performance of the method is assessed through a simulation study, and the procedures are applied to the analysis of a sequence of post-synaptic potentials recorded intracellularly at the crayfish neuromuscular junction. Goodness of fit and hypothesis test procedures reject the classical model in favor of an independent release mechanism with differing release probabilities. A more general release mechanism, allowing for dependence in the release process, also provides a good fit to the data analyzed.
Animals↗
Differential effects of an early housing manipulation on cocaine-induced activity and self-administration in laboratory rats.
Several reports in the literature suggested that environmental influences which are reflected in the social housing conditions of the rat may play a role in the expression of individual differences in drug self-administration. The present experiments were performed in order to further examine the effects of early housing manipulations, as reflected by grouped or isolation housing, on cocaine-induced behavioral responding. The first study examined the effects of this manipulation on the locomotor stimulant properties of cocaine. The results suggested that grouped housing produced a significantly greater increase in cocaine-induced locomotion than was observed in animals housed in isolation. Experiment 2 examined the effects of housing manipulations on the self-administration of cocaine under a continuous reinforcement schedule. Differences in the rate of cocaine self-administration were only observed at the lowest dose tested. Responding at all other doses was equivalent, including the optimal dose for both groups, suggesting that the housing manipulations failed to affect the reinforcing efficacy of cocaine. The present investigation suggests that, while the early housing manipulation produced a differential sensitivity in rats to the stimulant properties of cocaine, the same manipulation failed to alter the sensitivity of rats to the reinforcing properties of cocaine as assessed through self-administration.
Analysis of Variance↗