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Biomedical subjects

B R Smith

Publications and source records attributed to B R Smith.

At least 127 records · Page 7Linked to original sources
PubMed1993

Autoimmune Addison's disease. Analysis of autoantibody binding sites on human steroid 21-hydroxylase.

Human steroid 21-hydroxylase (21-OH) expressed in an in vitro translation system was found to react specifically with adrenal autoantibodies from patients with Addison's disease. The epitopes on 21-OH which reacted with autoantibodies were studied by incorporating a series of terminal and internal deletions into the 21-OH gene and analysing the expressed proteins by Western blotting. N-Terminal deletions up to amino acid 280 had no effect on autoantibody binding whereas a series of C-terminal deletions and truncations (amino acids 281-494) showed marked effects. Our results indicate that a central segment (281-379) and a C-terminal segment (380-494) of 21-OH interact to form at least one major autoantibody binding site.

Addison Disease↗
PubMed1993

Aspirin does not inhibit adenosine diphosphate-induced platelet alpha-granule release.

The involvement of metabolites of arachidonic acid in platelet-dense granule secretion and secondary platelet-platelet interactions is well characterized. However, their role in heterotypic interactions dependent on alpha-granule secretion is less well understood. Using platelet-surface expression of P-selectin as a marker of alpha-granule secretion, we have shown that: (1) aspirin treatment of platelets at doses that block dense granule secretion does not inhibit alpha-granule secretion to adenosine diphosphate (ADP); (2) synergism between epinephrine and ADP in the induction of P-selectin expression is similarly unaffected by aspirin; and (3) the ability of P-selectin to mediate adhesion of activated platelets to monocytes and polymorphonuclear lymphocytes in whole blood is also unchanged by aspirin treatment. To further explore the mechanisms responsible for platelet alpha-granule secretion, we have shown that inhibition of Na+/H+ exchange by either acidification of the extracellular medium or amiloride treatment blocked ADP-induced P-selectin expression. In contrast, incubation with the platelet lipoxygenase inhibitor 5,8,11-eicosatrynoic acid, by itself and with aspirin, did not decrease ADP-induced P-selectin expression. We conclude that platelet alpha-granule secretion in response to ADP is dependent on intact Na+/H+ exchange but is independent of the lipoxygenase- and cyclooxygenase-dependent metabolites of arachidonic acid.

Adenosine Diphosphate↗
PubMed1993

Determination of the percentage of thiazole orange (TO)-positive, "reticulated" platelets using autologous erythrocyte TO fluorescence as an internal standard.

Determination of the percentage of thiazole orange (TO)-positive or "reticulated" platelets by flow cytometry has been advocated as an aid in the diagnosis of thrombocytopenic disorders. However, a reproducible method for determining control fluorescence and setting threshold values on a routine clinical basis has not been described. We used erythrocyte TO fluorescence in whole blood as an internal standard to set threshold markers for TO fluorescence of autologous, purified platelets. Since platelets have approximately a threefold higher TO fluorescence than erythrocytes, multiplying the erythrocyte threshold marker by 3 allowed a determination of the percentage of "reticulated" platelets in 29 normal controls. This value was 3.64% +/- 2.10% (S.D.) in men and 5.79 +/- 2.22% (S.D.) in women; there was a significant (P < 0.05) difference between normal men and women for this measurement. Applying this method to our earlier studies of normals and patients with immune thrombocytopenic purpura confirmed its ability to discriminate between these populations with similar sensitivity and specificity as previously reported. This method controls for fluctuations in TO labeling and fluorescence and does not require daily determination of a new normal control value.

Adult↗
PubMed1993

Cross-reactive idiotypes on high affinity IgG class human monoclonal thyroglobulin autoantibodies.

Anti-idiotypic antibodies have been developed in rabbits against three high affinity IgG class monoclonal human autoantibodies to thyroglobulin (Tg), which resemble polyclonal Tg antibodies in patients with autoimmune thyroid disease. Antibodies to 1E10 monoclonal anti-Tg (IgG2 kappa) recognised a cross-reactive idiotype (CRI) also present on 1D3 monoclonal anti-Tg (IG1 lambda) and on VB5 monoclonal anti-Tg (IgG2 lambda). The determinant to which anti-1E10 binds appears to involve, at least in part, the binding site for Tg. In contrast, anti-idiotypic antibodies raised against VB5 failed to bind to either 1E10 or 1D3, a finding consistent with previous studies on serum polyclonal Tg antibodies, which suggested that such antibodies exhibit a mixture of private and cross-reactive idiotypes. The observed sharing of idiotypic determinants was not related to subclass, light chain type or expression of a particular VH gene family in the heavy chain. Although binding of the anti-idiotypic antibodies to Tg antibodies in a panel of patients (including the donors of the lymphocytes used to produce the monoclonal antibodies) could not be detected, the monoclonal antibodies are representative of the donor patients' serum Tg antibodies, both in terms of IgG subclass and functional affinity. Thus these idiotypes may be present in patients' sera at levels below the detection limits of the assays employed. Cross-reactive regulatory idiotypes in mice often constitute a minor component of the anti-Tg repertoire. Consequently, it is possible that low levels of a CRI, such as the 1E10 CRI, may be involved in the regulation of the autoimmune response to Tg in man.

Animals↗
PubMed1993

Bidirectional effects of GABAergic agonists and antagonists on maintenance of voluntary ethanol intake in rats.

The effects of THIP (GABAA agonist) and picrotoxin (GABA antagonist) on the maintenance of voluntary ethanol ingestion were examined. Thirty-three male Long-Evans rats were initially exposed to a screening procedure in which increasing concentrations of ethanol (from 2% to 9%) were presented in a free choice with water, on an alternate day schedule. Following the screening procedure, the rats were exposed to five ethanol presentations at a concentration of 9%, which constituted the baseline period, and five additional ethanol presentations during which the effects of the GABAergic manipulations were determined (test period). During the test period, the animals received IP injections of either 16 mg/kg of THIP, 2 mg/kg of picrotoxin or saline. The results suggested that the differential GABA manipulations resulted in bidirectional effects on the consumption of ethanol. More specifically, the GABAA agonist THIP increased the intake of ethanol as compared to baseline measures, while the GABA antagonist picrotoxin decreased ethanol intake. Similarly, the administration of THIP increased ethanol preference. In contrast, preference for ethanol over water was decreased following the administration of picrotoxin. It appears that the effects of these GABAergic manipulations are specific to ethanol, since total fluid intake was not influenced by the administration of either drug (i.e., THIP or picrotoxin). In light of the literature suggesting that THIP and picrotoxin are active at different sites within the GABAA chloride-ionophore receptor complex, the present findings would suggest that the GABAA receptor may play a role in regulating the voluntary intake of ethanol.

Alcohol Drinking↗
PubMed1993

Rigid fixation of comminuted mandibular fractures.

Treatment of comminuted mandibular fractures has traditionally involved closed reduction with external fixation in an effort to avoid stripping periosteum from the bony segments. The purpose of this study was to evaluate retrospectively the success rate of rigid fixation used to treat 16 consecutive comminuted fractures of the mandible in 15 patients. The comminuted fractures were as follows: symphysis and body, 10; angle, 3; and ramus, 3. In 13 cases, AO stainless steel reconstruction plates were applied, with a minimum of three 2.7-mm tapped bone screws in each of the two stable segments. In most cases additional screws were placed into the comminuted fragments to stabilize them. In two patients, the mandibular ramus was comminuted (one case bilaterally), which made it impossible to place a large plate. These fractures were stabilized with multiple titanium miniplates (2.0 mm, tapped). All patients' fractures healed to a bony union without bone grafting. The mean maximum incisal opening at longest follow-up was 40 mm (range, 20 to 50 mm). All patients had a satisfactory facial form and none required further surgery for facial recontouring or malocclusion. Complications were observed in three patients. Two patients (13%) developed infections. Both infections were caused by loose hardware and responded to removal of the hardware and did not require any other treatment. One mandible refractured during manipulation after coronoidectomy to treat mandibular hypomobility, a sequellae of a gunshot wound that traversed both mandibular rami. This fracture healed after plate removal and a course of maxillomandibular fixation without bone grafting. This study suggests that rigid fixation of comminuted mandibular fractures is a viable treatment that satisfies the necessity for reestablishment of form and function with minimal morbidity.

Adult↗
PubMed1993

Activation in stored platelet concentrates: correlation between membrane expression of P-selectin, glycoprotein IIb/IIIa, and beta-thromboglobulin release.

By using two distinct measurements of alpha-degranulation (surface P-selectin [alpha-granule membrane protein-140] expression and beta-thromboglobulin [beta-TG] release) and quantitation of glycoprotein (GP) IIb/IIIa surface density, stored platelet concentrates were evaluated to determine a) which method of measuring platelet alpha-granule release was more sensitive in detecting early platelet activation; b) whether Day 1 levels of activation predicted the extent of activation or cell lysis on Day 5 of storage; and c) whether changes in surface GPIIb/IIIa density were primarily dependent on platelet activation. By using samples from paired and unpaired units stored for 1, 3, and 5 days, four observations could be made. 1) A flow cytometric assay for the percentage of P-selectin-positive platelets was more sensitive for early detection of platelet activation than was measurement of beta-TG release. This finding was most likely due to enhanced sensitivity in detecting platelets that had undergone partial alpha-granule release. 2) Total P-selectin expression correlated with beta-TG release, which indicated that the extent of alpha-granule membrane fusion with the external platelet membrane was proportional to the amount of alpha-granule contents released into the supernatant. 3) All of the activation measurements on Day 1 predicted the activation values, but did not predict the degree of cell lysis (measured by lactate dehydrogenase discharge), on Day 5 of storage. 4) Surface GPIIb/IIIa density was increased on the subset of P-selectin-positive platelets as compared with the P-selectin-negative subset at all times during storage, but, within each subset, GPIIb/IIIa surface density did not significantly increase over the time of storage.

Antigens, CD↗
PubMed1993

Interactions between HIV-1 and cytomegalovirus in human osteosarcoma cells carrying both viruses.

Cytomegalovirus (CMV) and the human immunodeficiency virus type 1 (HIV-1) may interact in the pathogenesis of AIDS. We compared CMV replication in human osteosarcoma (HOS) cells to that in HOS cells genetically engineered to contain an envelope-deficient HIV-1 proviral construct (designated HOS-HXG). Following acute CMV infection of each cell line, HOS-HXG cells contained higher numbers of intranuclear CMV nucleocapsids than did HOS cells. Infectious CMV could be persistently detected in culture supernatant fluids of the CMV-infected HOS-HXG cells, whereas CMV was lost over several weeks from HOS cells infected with CMV in parallel. HIV-1 CMV pseudotypes were not detected in supernatant fluids from CMV-infected HOS-HXG cells. On day 119 after CMV infection, these cultures were superinfected with HIV-1. These dually infected HOS-HXG cells produced infectious HIV-1 and exhibited markedly enhanced CMV replication compared to parental CMV-infected HOS-HXG cells. Two different HIV-1 tat gene function antagonists, Ro24-7429 and chemically modified antibodies to the Tat protein, did not inhibit the replication of CMV in either acute or persistent infections of HOS-HXG cells at concentrations that inhibited HIV-1 replication.

Antiviral Agents↗
PubMed1993

Cytomegalovirus antigenemia: clinical correlations in transplant recipients and in persons with AIDS.

We evaluated a rapid immunoperoxidase technique for the detection of cytomegalovirus (CMV) antigenemia in peripheral blood neutrophils of 56 transplant recipients (117 specimens) and 36 persons with AIDS (59 specimens). Antigenemia was 92% sensitive and 98% specific for the detection of clinical CMV infection in transplant recipients and 100% sensitive and 86% specific in persons with AIDS. Overall, CMV antigenemia was a more rapid and sensitive method for the detection of clinical CMV infection than either shell vial culture or conventional tube culture of blood.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Film loan policies of radiology departments.

Last year, the AHRA Southern Region Statistical Resource Committee surveyed its members about their departments' film loan policies. This article presents the results of that survey, providing information on such topics as lending original films, charging for copies, and protecting against liability. While there doesn't seem to be a standard approach to releasing films, survey findings suggest that liability issues and cost factors are of great concern in determining which policy should be adopted.

Confidentiality↗
PubMed1993

Mixture estimation and the neurophysiological quantal hypothesis.

Quantal release models provide a mechanistic description of the process by which neurotransmitter is released from the nerve cell. The usual such model assumes that the quantity of transmitter released after nerve depolarization follows a finite mixture distribution with an unknown number of components, and with constraints on component means and variances. General procedures for estimating the dimension of a finite mixture model are discussed, and applied to the analysis of a quantal release data set.

Action Potentials↗
PubMed1993

Cyanamide on ethanol intake: how does it really work?

Cyanamide, an aldehyde dehydrogenase inhibitor, has been shown to suppress voluntary ethanol consumption in animals. Studies were carried out to compare the effect of cyanamide on ethanol, saccharin-quinine and water intake in a restricted (10 min) access and in a free-choice nonrestricted access paradigm. An immediate and constant increase in fluid consumption was observed in the restricted access schedule paradigm independent of the fluid tested as cyanamide affected the consumption of all fluids including water. In the nonrestricted access study, cyanamide significantly increased total fluid intake. However, while saccharin-quinine-drinking animals treated with cyanamide demonstrated no change in intake preference, ethanol consumption was suppressed with a concomitant decrease in preference for ethanol. The present findings suggested that cyanamide may possess at least two, paradigm-specific, independent properties. It may enhance the consumption of fluid in general; however, it may also have a specific effect on ethanol intake when animals have continuous ethanol availability.

Alcohol Drinking↗
PubMed1993

Reticulated platelets in the evaluation of thrombopoietic disorders.

The laboratory diagnosis of immune platelet destruction has relied predominantly on the presence or absence of megakaryocytes in bone marrow. Recently, examination of peripheral blood platelets for high RNA content (reticulated platelets) or for elevated levels of platelet-associated IgG have been suggested as less invasive diagnostic tests. We used thiazole orange fluorescence labeling to determine the percentage of circulating reticulated platelets and two antibodies with different specificities directed against human IgG to measure platelet-associated IgG by flow cytometry in 59 patients with either immune thrombocytopenic purpura (n = 23) or chemotherapy-induced thrombocytopenia (n = 36). The percentage of reticulated platelets in patients with immune thrombocytopenia was significantly increased (38.6% +/- 27.4% [mean +/- 1 SD]), compared with patients receiving chemotherapy and normal subjects (7.2% +/- 3.3% and 2.9% +/- 2.2%, respectively). However, 17% of patients with immune thrombocytopenia had reticulated platelet values in the range observed for normal subjects and for patients with chemotherapy. Although one third of patients with immune thrombocytopenia had very high platelet IgG levels, the majority could not be distinguished from patients receiving chemotherapy solely on this basis. Combining the reticulated platelet determination with the IgG data did not improve the sensitivity or specificity of the reticulated platelet determination alone. We conclude that a flow cytometric assay for reticulated platelets is a better discriminant than flow-measured platelet IgG for diagnosing immune platelet destruction. We further postulate that the subset (17%) of patients with immune destruction who have relatively low percentages of reticulated platelets may represent patients with an inappropriately low thrombopoietic response.

Adult↗