Biomedical subjects

L S Gray

Publications and source records attributed to L S Gray.

50 records · Page 3Linked to original sources

PubMed1991

Red cell survival studies in a patient with anti-Tca.

A radiolabeled, allogenic red cell survival study was performed on a patient who lacked the Cromer-related antigen Tca and who had developed the corresponding antibody. Red cell survival was 92% at 1 hour and 88% at 24 hours. Monocyte monolayer assays (MMA) and IgG subclass determinations were performed on samples from: (1) 1965, the period of initial antibody formation; (2) approximately two years before the red cell survival study; and (3) four months after the study. All samples reacted w+ to 1+ by the antiglobulin test. The earliest sample contained IgG1, IgG2, and IgG4 anti-Tca. Because there were 20.5% reactive monocytes in the MMA (normal range 0-3%), this antibody may have produced extravascular red cell destruction. In contrast to the initial example, the samples before and after the red cell survival study both contained IgG2 and IgG4 subclasses with 1.3% and 2.2% MMA reactivity, respectively. The current pattern of antibody subclass, the lack of reactivity in the MMA, and a red cell survival of 88% at 24 hours indicate that short-term transfusion support would have been well tolerated. This contrasts to the in vitro results obtained with the earliest sample, which suggest a clinically significant antibody. This appears to be the first report of a red cell alloantibody that remained serologically reactive but underwent a loss of its IgG1 fraction, which appeared capable of red cell destruction based on the MMA results.

Aged↗

PubMed1991

The amelioration of myopia using biofeedback of accommodation: a review.

The purpose of this review is to give an account of the issues raised by reports that myopia can be treated by operant conditioning or biological feedback. Devices are available that provide auditory feedback of accommodative state such that variation in tone frequency provides a means by which the patient can monitor his or her ability to induce changes in accommodation response, the task thus being to change the pitch of the tone in a direction corresponding to a more distant far point. The aim of a training programme is to reinforce and establish control over the accommodative response by a process akin to operant conditioning and subsequently to transfer the skill to normal visual environments such that a manifest reduction in myopia becomes apparent. Although there are reports that the technique can induce a reduction in myopia by up to 3 D the findings are of limited value owing to the lack of objective data, for example pre- and post-training cycloplegic refraction. The pre- and post-training measures of subjective letter acuity used by many studies are, with repeated trials, particularly vulnerable to individual differences in the ability to learn how to discriminate and interpret blurred images. The review concludes that more comprehensive clinical trials are needed before accommodation biofeedback can qualify as an established method of clinical treatment of myopia. The trials should be designed to encompass the following issues: the characteristics of a feasible physiological model linking accommodation and myopia development; the rationale with regard to patient selection; the technical performance of the optometer employed; the characteristics of the control group used; the criteria for assessment of myopic change; the transfer of training to performance in normal visual environments; the economic viability of the programme of training and equipment; and the skill, training and knowledge of the clinician implementing the training programme.

Accommodation, Ocular↗

PubMed1989

Pertussis toxin effects on T lymphocytes are mediated through CD3 and not by pertussis toxin catalyzed modification of a G protein.

Pertussis toxin (PT) has been shown to have a variety of effects on T lymphocyte function, and its activity has been used to suggest the involvement of a G protein in the early events of T lymphocyte activation. In this report, the effects of PT on T lymphocytes have been investigated in detail. PT at a concentration of 10 micrograms/ml rapidly stimulated early events that are normally induced by occupancy of the TCR complex in Jurkat cells and cloned, murine CTL including increased intracellular Ca2+ concentration, serine esterase release, and induction of Ag non-specific target cell lysis. However, 1-h treatment with this concentration of PT induced a state that was refractory to further receptor stimulation in Jurkat cells but not cloned CTL although substrate membrane proteins were modified to a similar extent in both cell lines. The functional effects of PT were mimicked by the B oligomer of PT which did not, however, catalyze ADP-ribosylation of membrane proteins. In addition, overnight exposure of Jurkat cells to a lower concentration of PT also modified substrate membrane proteins but did not inhibit receptor stimulation. These findings indicate that PT catalyzed ADP-ribosylation of a G protein does not account for the actions of the toxin on T lymphocytes. Finally, direct stimulation of increased intracellular Ca2+ concentration by PT and the B oligomer only occurred in T lymphocytes expressing CD3. This suggests that the mitogenic effect of PT holotoxin is mediated by the interaction of the B oligomer with CD3 and that this may account for many of the effects of PT holotoxin both in vivo and in vitro.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1989

Multicompartment analysis of the effects of plasmapheresis. Application to lipid kinetics in humans.

The quantitative effect of plasmapheresis on concentrations of intravascular solutes is described by a minimal two-compartment model, which allows exit to and entry from a nonplasma body pool of the solute. This novel method is simple and capable of determining endogenous metabolic turnover of physiologically important plasma constituents in both therapeutic and experimental settings. The model was suggested by the therapeutic use of plasmapheresis in hyperlipidemia, and the turnover rates of triglyceride and cholesterol were calculated for one patient treated with chronic plasmapheresis. It is concluded that at least a two-compartment model is necessary to quantitatively describe the effect of plasmapheresis on any substance that undergoes appreciable endogenous turnover (metabolic clearance rate greater than 1.1 times plasmapheresis rate when both rates are in units of volume per time). Calculation of endogenous turnover rate with the use of measurements of the concentration of a solute in plasma before and after plasmapheresis and in the total plasmapheresate and measurement of the volume of plasma removed, volume of plasma substitute infused, and total plasmapheresis time is detailed. This method avoids the use of isotopic labeling experiments. In turn, the endogenous turnover rate may predict the efficacy of therapeutic plasmapheresis.

Blood Glucose↗

PubMed1988

Spatial and temporal characteristics of the increase in intracellular Ca2+ induced in cytotoxic T lymphocytes by cellular antigen.

The increase in intracellular Ca2+ concentration [( Ca2+]i) in cytolytic T lymphocytes in response to target cell binding was investigated by ratio image fluorescence microscopy. Ca2+ mobilization from intracellular stores occurred at a site distal to target cell contact and was transient. Extracellular Ca2+ influx resulted in an increase in [Ca2+]i that was prolonged and distributed more proximal to the target cell. Oscillations in [Ca2+]i were observed after target cell contact, although the periodicity was dependent on the presence of extracellular Ca2+. The Ag-specific reorientation of cytoplasmic granules occurred well after [Ca2+]i had begun to decline to a resting level, but was dependent on extracellular Ca2+. These studies indicate that the Ag-stimulated increase in [Ca2+]i exhibits considerable spatial and temporal variation, and that these characteristics are altered by the availability of extracellular Ca2+. The results also suggest that these changes in [Ca2+]i may play a role in the cytoplasmic events that accompany T cell-mediated cytolysis.

Animals↗

PubMed1988

Increased intracellular cyclic adenosine monophosphate inhibits T lymphocyte-mediated cytolysis by two distinct mechanisms.

Cholera toxin (CT), but not pertussis toxin (PT), treatment of cloned murine CTL inhibited target cell lysis in a dose-dependent fashion. The effects of CT were mimicked by forskolin and cyclic adenosine monophosphate (cAMP) analogues. Inhibition of cytotoxicity by CT and cAMP analogs was mediated in part by attenuation of conjugate formation. Additionally, both CT and cAMP analogs blocked the increase in intracellular Ca2+ induced by stimulation of the TCR complex by mAbs. These findings indicate that cAMP inhibits the activity of CTL by two distinct mechanisms and suggests a role for this second messenger in CTL-mediated cytolysis.

Animals↗

PubMed1988

Evaluation of adenosine triphosphate and 2,3-diphosphoglycerate after twenty-four hours in red cells washed for neonatal transfusion.

Adenosine triphosphate and 2,3-diphosphoglycerate concentrations in 14 U of CPDA-1 stored red cells (PRBC) and washed red cells (WRBC) were measured to assess indirectly the quality of WRBC for neonatal transfusion after 24 h. The results indicate that there is no difference in red cell ATP and 2,3-DPG concentrations between PRBC and WRBC after a 24-hour period.

2,3-Diphosphoglycerate↗

PubMed1988

Early events in target-cell lysis by cytotoxic T cells.

Using ratio-imaging fluorescence microscopy, we have investigated the changes in intracellular Ca2+ [( Ca2+]i) that occurred in cytotoxic T lymphocytes (CTL) upon target-cell binding. This process resulted in a rapid increase in [Ca2+]i, which was localized in the region of the CTL in contact with the target cell. This increase was mediated both by influx from the external medium as well as by release from intracellular stores. Although the magnitude of the initial increase in [Ca2+]i was not dependent upon the presence of extracellular Ca2+, influx was necessary for sustained elevation of [Ca2+]i. Inasmuch as target-cell lysis by the CTL clone used is dependent on extracellular Ca2+, this suggests that a prolonged elevation of [Ca2+]i is necessary for lytic function. It was also shown that the increase in [Ca2+]i and its subsequent decay show several pulsations. The mechanism by which these variations are generated and their possible function is not known. Finally, a role for K+ efflux in the control of the antigen-induced increase in [Ca2+]i was demonstrated. Thus it is becoming clear that signal transduction in CTL is remarkably complex, involving several ionic species and second messengers.

Animals↗

PubMed1987

The role of K+ in the regulation of the increase in intracellular Ca2+ mediated by the T lymphocyte antigen receptor.

The regulation of the increase in intracellular calcium ([Ca2+]i) occurring in cytolytic T lymphocytes (CTLs) upon their interaction with antigen was examined. This [Ca2+]i increase and lytic function were insensitive to verapamil, a Ca channel blocker. An antigen-independent increase in [Ca2+]i was not induced by depolarization of CTLs with excess extracellular K+, suggesting that Ca2+ influx is not mediated by the ubiquitous voltage-gated Ca channel. The antigen-induced [Ca2+]i increase was inhibited by prior membrane hyperpolarization with valinomycin. Hyperpolarization occurred under normal circumstances in CTLs exposed to antigen-receptor-specific antibodies. This potential change was Ca2+-dependent and inhibited by K channel blockade. Conversely, K channel blockade augmented the antigen-specific [Ca2+]i increase while markedly decreasing the K+ efflux associated with CTL lytic function. Therefore, either membrane potential or intracellular K+ regulates the antigen-specific [Ca2+]i increase in CTLs.

Animals↗

PubMed1987

Demonstration of a calcium influx in cytolytic T lymphocytes in response to target cell binding.

By using the Ca2+-sensitive dye indo-1, an antigen-specific increase in intracellular Ca2+ in cloned cytolytic T lymphocytes (CTL) was measured under conditions that were permissive for T cell-mediated cytolysis. To synchronize lethal hit delivery in a suspension of effector and target cells, a modification of the cation pulse method in which Ca2+ is added to preformed conjugates of CTL and target cells was used. Conjugate formation was unaffected by the absence of extracellular Ca2+ under these conditions. Lytic activity of these cloned CTL was markedly reduced in the absence of extracellular Ca2+ and was restored upon Ca2+ repletion. When indo-1-loaded CTL were preincubated with target cells in the absence of extracellular Ca2+, a marked antigen-specific increase in indo-1 fluorescence, indicative of an increase in intracellular Ca2+, was observed after repletion of extracellular Ca2+. This increase in intracellular Ca2+ was shown to be due solely to changes in the CTL and not the target cell within the time course of the experiment, and results from the influx of extracellular Ca2+. Antibody to the T cell receptor for antigen also evokes a similar increase in intracellular Ca2+ in CTL under these conditions. This method provides a means for the direct examination of the response of CTL to cellular antigen as well as soluble antibody and is a versatile and valuable tool for the study of CTL function.

Animals↗

PubMed1986

Cytolytic T lymphocyte effector function requires plasma membrane chloride flux.

Treatment of cytotoxic murine T lymphocytes (CTL) with certain stilbene disulfonate derivatives results in a dose-related loss of lytic capacity. This effect is reversible and apparently not a function of drug toxicity. Additionally, CTL function is inhibited by isosmotic replacement of extracellular chloride with several relatively membrane-impermeable chloride analogues. Both inhibitory manipulations act on the effector rather than the target cell and are effective only during delivery of the lethal hit. These results suggest that delivery of the lethal hit may involve CTL exocytosis.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1986

Acute intravascular hemolytic anemia in the black rhinoceros: hematologic and immunohematologic observations.

To investigate the syndrome of acute intravascular hemolytic anemia in the black rhinoceros (Diceros bicornis), laboratory techniques used in the differential diagnosis of hemolytic anemias were performed on blood samples from 6 black rhinoceroses: 3 nonrelated healthy rhinoceroses, 1 rhinoceros with iron deficiency anemia, and 2 rhinoceroses with intravascular hemolysis. Osmotic fragility, erythrocyte membrane protein composition, hemoglobin electrophoresis, and hemoglobin stability did not distinguish between healthy and affected (anemia or hemolysis) rhinoceroses. Polyclonal antiglobulin reagents were prepared in rabbits, using whole rhinoceros serum and purified rhinoceros immunoglobulin G. These reagents were nonreactive against erythrocytes of the healthy and iron-deficient rhinoceroses. Reactions with RBC from the rhinoceros with fatal hemolytic anemia indicated increased membrane coating by the third component of complement; this was not evident in a second rhinoceros that survived a hemolytic event.

Anemia, Hemolytic↗

PubMed1983

Differential binding of IgG anti-D and IgG autoantibodies to reticulocytes and red blood cells.

125I IgG anti-D binding to reticulocytes obtained by density fractionation is reduced relative to that bound to all other red cell (RBC) fractions. Maximum D antigen reactivity occurs following reticulocyte maturation with no detectable change in D reactivity of mature RBC throughout their life span. Reticulocytes have in the range of about 60% of the content of mature RBC. Previously reported increased anti-D agglutinability and binding to old RBC it is not due to an intrinsic increase in D antigen with age, but results from an 'apparent' decrease in anti-D binding to young RBC fractions due to reticulocyte enrichment. IgG RBC autoantibodies obtained by elution from the RBC of eight Coombs-positive blood donors, probably associated with alpha-methyldopa (alpha-MD) administration, showed decreased binding to reticulocytes as determined by 125I protein A (PA). Reticulocytes bound about 70% of the IgG bound to mature RBC, indicating that the membrane antigenic determinant defined by these autoantibodies was incompletely expressed in the reticulocyte. This difference in IgG autoantibody binding between reticulocytes and mature RBC is similar to the decreased D antigen content of reticulocytes and consistent with an autoantibody determinant associated with the Rh complex. Direct testing of density fractionated Coombs-positive RBC in four out of five patients with autoimmune haemolytic anaemia (AIHA) showed reduced quantities of IgG on reticulocytes. The distribution of IgG between reticulocytes and mature RBC may be useful in serologically characterizing patients with AIHA and in identifying subpopulations of patients with this disorder.

Anemia, Hemolytic, Autoimmune↗

PubMed1982

Interaction 125I-protein A with erythrocyte-bound IgG.

The molar combining ratio of 125I-PrA to RBC-bound 125I-labeled IgG anti-D was 0.72 +/- 0.044. There was a significant decrease in the PrA-to-IgG combining ratio when anti-D was bound to protease-modified RBCs or to unmodified RBCs sensitized at low ionic strength, 0.49 +/- 0.034 and 0.56 +/- 0.006, respectively. These findings indicate that the interaction of RBC-bound IgG with PrA may be influenced by alterations in membrane structure, surface density, and distribution of the IgG receptor and possibly other steric factors. The quantity of RBC-bound IgG on RBCs sensitized with unlabeled serum anti-D and anti-Kell could be quantitatively assessed and correlated with antiglobulin agglutinability. Unlabeled alloantibodies were detected with the 125I-PrA at IgG densities lower than those detectable with the standard antiglobulin test. 125I-PrA, in contrast to the antiglobulin reaction, has the potential of providing increased sensitivity as well as quantitative data in assessing IgG alloantibody- or autoantibody-sensitized RBCs. (J Lab Clin Med 99:399, 1982.)

Animals↗