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Biomedical subjects

W J Morrison

Publications and source records attributed to W J Morrison.

At least 19 recordsLinked to original sources
PubMed1992

Spontaneous development of protective anti-T cell receptor autoimmunity targeted against a natural EAE-regulatory idiotope located within the 39-59 region of the TCR-V beta 8.2 chain.

The development of experimental autoimmune encephalomyelitis (EAE) in Lewis rats is mediated by V beta 8.2+ T cells specific for myelin basic protein. One consequence of this biased expression of V beta 8.2 is the spontaneous development of regulatory T cells and antibodies against residues 39-59 of the V beta 8.2 sequence. Moreover, a synthetic V beta 8.2-39-59 peptide could induce protection against and speed recovery from EAE. T cells and antibodies specific for V beta 8.2-39-59 could transfer protection from EAE. Recently, we reported that the protective T cell epitope is subsumed within the V beta 8-44-54 sequence. We now report that protection induced by V beta 8-44-54 lasted at least 102 days and produced "split tolerance," enhancing anti-myelin basic protein antibody titers but reducing anti-myelin basic protein T cell frequency. The shorter V beta 8-44-54 peptide induced a distinct set of antibodies that did not cross-react with the longer V beta 8.2-39-59 peptide, although both specificities could stain V beta 8.2+ T cells and were equally protective against EAE. However, the V beta 8.2-39-59 peptide, but not the V beta 8-44-54 peptide, would appear to represent the natural idiotope: antibodies to V beta 8.2-39-59 that develop spontaneously during EAE could be boosted to higher titers only by the V beta 8.2-39-59, but not by other TCR peptides from the V beta 8.2 sequence, including V beta 8-44-54 that contains the functional T cell epitope. These results suggest that natural processing of the TCR V beta-chain favors the formation of a peptide that resembles the V beta 8.2-39-59 sequence. The B cell epitope present on the V beta 8-44-54 sequence was evident only in the absence of residues 39-43 and 55-59, suggesting that the two peptides possess distinct conformations. However, the V beta 8-44-54 B cell epitope is most likely expressed on the V beta 8.2+ T cells, either as a low affinity determinant on the intact TCR alpha/beta heterodimer or as a cryptic epitope bound in the cleft of surface MHC molecules.

Amino Acid Sequence↗
PubMed1992

Transforming growth factor-beta enhances the in vivo effector function and memory phenotype of antigen-specific T helper cells in experimental autoimmune encephalomyelitis.

Transforming growth factor-beta (TGF-beta) had a profound effect on the in vitro phenotypic development of Ag-activated Th cells and enhanced the in vivo effector function of these cells upon adoptive transfer. Previous studies have shown that there are two types of Th cell populations found in unimmunized animals, naive helper cells, which are short-lived and express low levels of CD44 and high levels of CD45R and Mel-14, and memory helper cells, which have a long life span and express high levels of CD44 and low levels of CD45R and Mel-14. Culturing of Ag-specific murine Th cell lines and clones in the presence of TGF-beta greatly enhanced both the memory phenotype of the cultured cells and the effector function upon adoptive transfer in experimental autoimmune encephalomyelitis. Histologic evaluation of spinal cords from recipients receiving passively transferred murine T cell lines cultured with TGF-beta revealed large demyelinated plaques (multiple sclerosis-like) that were not present in animals receiving cells cultured with Ag alone. TGF-beta also enhanced the capability of myelin basic protein-specific Lewis rat T cell lines to transfer experimental autoimmune encephalomyelitis and potentiated a purified protein derivative-specific rat helper cell line to transfer delayed type hypersensitivity. Thus, the effects of TGF-beta did not appear to be limited by species specificity, Ag specificity, or in vivo T cell function. This is the first study showing that TGF-beta can potentiate the development and maintenance of the Th cell memory phenotype in vitro and enhance their in vivo effector function in an animal disease model.

Animals↗
PubMed1991

Protection against experimental encephalomyelitis. Idiotypic autoregulation induced by a nonencephalitogenic T cell clone expressing a cross-reactive T cell receptor V gene.

The recovery process in experimental autoimmune encephalomyelitis (EAE) in Lewis rats is characterized by an increasing diversity of T cell clones directed at secondary epitopes of myelin basic protein. Of particular interest, residues 55 to 69 of guinea pig basic protein could induce protection against EAE. A nonencephalitogenic T cell clone, C455-69, that was specific for this epitope transferred protection against both active and passive EAE. Clone C4 was found to express V beta 8.6 in its Ag receptor, and residues 39 to 59 of the TCR V beta 8.6 sequence were found to be highly crossreactive with the corresponding residues 39 to 59 of TCR V beta 8.2, which is known to induce protective anti-idiotypic T cells and antibodies. Like the TCR V beta 8.2 peptide, the V beta 8.6 sequence induced autoregulation and provided effective treatment of established EAE. Thus, the EAE-protective effect of the guinea pig basic protein 55-69 sequence was most likely mediated by T cell clones such as C4 that could efficiently induce anti-TCR immunity directed at a cross-reactive regulatory idiotope.

Animals↗
PubMed1991

Clonal diversity of basic protein specific T cells in Lewis rats recovered from experimental autoimmune encephalomyelitis.

T cell lines selected from Lewis rats recovered from experimental autoimmune encephalomyelitis (EAE) respond not only to the immunodominant 72-89 epitope of basic protein (BP), but also to secondary epitopes including the I-A restricted 43-67 region of guinea pig (Gp) BP and the I-E restricted 87-99 sequence of rat (Rt) BP. The current study demonstrates at the clonal level the diversity of T cell responses to Gp- and Rt-BP in EAE-recovered rats. As predicted from the response pattern of BP-selected T cell lines, T cell clones from the lines responded to both the dominant and secondary epitopes of BP. In addition, a new majority clonal type was identified that responded to whole BP but not to epitopes represented on enzymatic cleavage fragments or synthetic peptides spanning the BP molecule. Clones representative of each of the three types of Gp-BP responses were characterized for phenotype, major histocompatibility complex restriction, and biologic activity in vivo. All of the clones were strongly CD4+ and co-expressed CD8 at modest levels as measured by both immunofluorescence and Northern blots. All three T cell specificities were I-A restricted. However, only the 72-89 responsive clone could transfer clinical EAE, due most likely to its unique ability to respond to Rt-BP. In contrast, the Gp-BP 43-67 reactive T cell clone transferred protection against EAE, whereas the whole Gp-BP reactive clone transferred delayed-type hypersensitivity response but was neither encephalitogenic nor protective. Thus, the recovery process from EAE is distinguished by an increased diversity of protective clones as well as innocuous clones that may be spawned as encephalitogenic T cells are regulated.

Animals↗
PubMed1990

Antibodies specific for VB8 receptor peptide suppress experimental autoimmune encephalomyelitis.

Recent studies from our laboratory have shown, for the first time, that a synthetic peptide from that TCR VB chain used preferentially by encephalitogenic T cells induced the formation of protective, MHC class I-restricted T cells and prevented the development of EAE in Lewis rats. In this report we 1) demonstrate that immunization with the TCR-VB8-39-59 peptide generated peptide-specific antibodies that protect against experimental autoimmune encephalomyelitis induced by either of the two distinct encephalitogenic epitopes of basic protein, and 2) characterize the production and biologic functions of rat and rabbit antibody responses to the TCR peptide. The antibodies in both species increased in titer over time, were highly specific for the immunogen by direct reaction and inhibition assays, stained only VB8+ T cells, and suppressed clinical signs and to lesser extent the number of histologic lesions of experimental autoimmune encephalomyelitis mediated by VB8+ T cells. Coupled with our previous work, these results indicate that both humoral and cellular responses to the TCR-VB8-39-59 peptide can contribute independent immunoregulatory effects on encephalitogenic T lymphocytes that use common V region genes in response to epitopes of myelin basic protein.

Amino Acid Sequence↗
PubMed1989

Specific ganglioside binding to receptor sites on T lymphocytes that couple to ganglioside-induced decrease of CD4 expression.

The binding of different gangliosides to rat T-helper lymphocytes was characterized under conditions that decrease CD4 expression on different mammalian T-helper lymphocytes. Saturation binding by monosialylated [3H]-GM1 to rat T-lymphocytes was time- and temperature-dependent, had a dissociation constant (KD) of 2.2 +/- 1.4 microM and a binding capacity near 2 fmoles/cell. Competitive inhibition of [3H]-GM1 binding demonstrated a structural-activity related to the number of unconstrained sialic acid moieties on GM1-congeneric gangliosides. A comparison between the results of these binding studies and ganglioside-induced decrease of CD4 expression demonstrated that every aspect of [3H]-GM1 binding concurs with ganglioside modulation of CD4 expression. It is concluded that the specific decrease of CD4 expression induced by pretreatment with gangliosides involves the initial process of ganglioside binding to specific sites on CD4+ T-helper lymphocytes.

Animals↗
PubMed1989

Staurosporine potentiates platelet activating factor stimulated phospholipase C activity in rabbit platelets but does not block desensitization by platelet activating factor.

The possible involvement of protein kinase C activation in regulating PAF-stimulated PLC activity was studied in rabbit platelets. PAF (100 nM for 5 seconds) stimulated incorporation of 32P into proteins and caused [3H]InsP3 levels to increase about 260% of control. These responses were compared after platelets were pretreated with either PAF, phorbol 12-myristate 13-acetate (PMA) or staurosporine and also after pretreatments with staurosporine followed by PAF or PMA. Pretreating platelets with staurosporine potentiated PAF-stimulated [3H]InsP3 levels by 54% and blocked protein phosphorylation. Pretreatments with PAF and PMA caused PAF-stimulated [3H]InsP3 levels to decrease to 115 and 136%, respectively. Staurosporine pretreatment blocked the decrease caused by the PMA pretreatment but not that by PAF. This study demonstrates that PAF-stimulated PLC activity is negatively affected by protein kinase C (PKC) activation and that inhibition of PKC activity did not prevent desensitization of PLC by PAF.

Alkaloids↗
PubMed1989

Desensitization of platelet-activating factor-stimulated protein phosphorylation in platelets.

Treatment of 32P-labeled rabbit platelets with platelet-activating factor (PAF) caused a time- and dose-dependent phosphorylation of several proteins including five major phosphorylated proteins with apparent molecular weights of 20,000, 35,000, 40,000, 65,000, and 150,000. Both PAF and thrombin caused a rapid increase followed by a decrease in phosphorylation of proteins, indicating the occurrence of a phosphorylation-dephosphorylation process. Four separate PAF receptor antagonists, CV-3988, CV-6209, SRI-63-441, and SRI-63-675 drastically reduced the PAF-stimulated protein phosphorylation. The order of potency was SRI-63675 greater than SRI-63441 greater than or equal to CV-6209 greater than CV-3988. These antagonists had no effect on thrombin-stimulated protein phosphorylation. Pretreatment of platelets with PAF (0.1 nM) completely abolished any further protein phosphorylation by the same concentration of PAF. PAF pretreatment shifted the dose response of protein phosphorylation by about 2 log units, to the right. When platelets were treated with PAF (10 nM) for 10 min, this abolished phosphorylation of proteins by any concentration of PAF. These studies indicated a homologous desensitization of protein phosphorylation. Interestingly, PAF-pretreated platelets still exhibited phosphorylation of proteins by thrombin. On the other hand, a lack of protein phosphorylation by PAF or thrombin was observed in platelets preexposed to thrombin and this demonstrated a heterologous desensitization. It is concluded that phosphorylation of proteins by PAF is a PAF receptor-coupled event and that this process is desensitized in platelets preexposed to PAF. The fact that both the activation of phosphoinositide-specific phospholipase C and the phosphorylation of proteins are desensitized in PAF-pretreated platelets suggests that a close "regulatory" intercommunication between these processes exists.

Animals↗
PubMed1989

Antagonism of platelet activating factor receptor binding and stimulated phosphoinositide-specific phospholipase C in rabbit platelets.

The objective of this study was to establish whether binding of platelet activating factor (PAF) to its receptor was integral to the stimulation of phosphoinositide-specific phospholipase C (PLC) in rabbit platelets. Saturation binding curves for [3H]PAF indicated that the PAF receptor has a dissociation constant (KD) of 28.72 nM. In comparison, PAF-stimulated PLC activity, as monitored by [3H]inositol triphosphate production, increased at lower concentrations and had an half-maximal effective concentration (EC50) value of 1.5 nM. Unlabeled PAF inhibited [3H]PAF binding competitively and demonstrated two binding sites, a high affinity site with an inhibitory constant (Ki) of 2.65 nM and a low affinity site with a Ki of 0.80 microM. The inhibitory effects of four PAF antagonists, CV-3988, CV-6209, SRI 63-441 and SRI 63-675 on the binding of [3H]PAF were compared to the effects of the antagonists on PAF-stimulated PLC activity. The four antagonists inhibited [3H]PAF binding almost completely whereas their ability to inhibit PAF-stimulated PLC activity varied. CV-3988, SRI 63-441 and SRI 63-675 had half-maximal inhibitory concentration (IC50) values of 0.28, 0.78 and 0.42 microM, respectively, whereas CV-6209 was more potent at inhibiting [3H]PAF binding (IC50 = 7.73 nM). The SRI 63-441 and SRI 63-675 inhibited PLC totally with an IC50 value of 0.78 and 1.27 microM, respectively. The CV-3988 and CV-6209 showed a maximal PLC inhibition of about 45% with "apparent IC50" values of 1.05 and 0.17 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Transbilayer effects of ethanol on fluidity of brain membrane leaflets.

Previous work on membrane effects of ethanol focused on fluidization of the bulk membrane lipid bilayer. That work was extended in the present study to an examination of ethanol's effect on lipid domains. Two independent methods were developed to examine the effects of ethanol on the inner and outer leaflets of synaptic plasma membranes (SPM). First, differential polarized phase and modulation fluorometry and selective quenching of diphenyl-1,3,5-hexatriene (DPH) were used to examine individual leaflets. Both limiting anisotropy and rotational relaxation time of DPH in SPM indicated that the outer leaflet was more fluid than the inner leaflet. Second, plasma membrane sidedness selective fluorescent DPH derivatives, cationic 1-[4-(trimethylammonio)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH) and anionic 3-[p-6-phenyl)-1,3,5-hexatrienyl]phenylpropionic acid (PRO-DPH), confirmed this transmembrane fluidity difference. TMA-DPH and PRO-DPH preferentially localized in the inner and outer leaflets of SPM, respectively. Ethanol in vitro had a greater fluidizing effect in the outer leaflet as compared to the inner leaflet. Thus, ethanol exhibits a specific rather than nonspecific fluidizing action within transbilayer SPM domains. This preferential fluidization of the SPM outer leaflet may have a role in ethanol affecting transmembrane signaling in the nervous system.

Animals↗
PubMed1988

Desensitization of receptor-coupled activation of phosphoinositide-specific phospholipase C in platelets: evidence for distinct mechanisms for platelet-activating factor and thrombin.

Platelet-activating factor (PAF) receptor-coupled activation of phosphoinositide-specific phospholipase C (PLC) was studied in platelets that were made refractory, by short-term pretreatments, to either PAF or thrombin. Generation of [3H]inositol triphosphate ( [3H]IP3) was monitored specifically for this purpose. [3H]Inositol-labeled rabbit platelets that were incubated (10 min) with increasing concentrations of PAF and subsequently challenged by the same concentration of PAF had greatly diminished PLC activity ( [3H]IP3 production) as compared to controls. Platelets incubated (10 min) with fixed concentrations of PAF and then challenged with increasing concentrations of PAF had log-dose response curves of [3H]IP3 production progressively shifted to the right (i.e., to higher concentrations) and were depressed as the PAF pretreatment with 10 nM PAF became completely refractory to further PAF stimulation of PLC. Washing the pretreated platelets with either buffer or buffer containing 0.5% bovine serum albumin did not restore the PAF for 10 min), platelets remained fully responsive to thrombin (2 units/ml)-stimulated production of [3H]IP3. Platelets pretreated with increasing concentrations of thrombin (0.15-2 units/ml) for different times (5-40 min) became refractory to both thrombin and PAF. It is concluded that PAF receptor-coupled activation of PLC becomes refractory (desensitized) in platelets preexposed to PAF, whereas platelets pretreated with thrombin are desensitized to both thrombin and PAF. It is proposed that thrombin has two transmembrane pathways leading to the activation of PLC, one shared with PAF and another utilizing separate mechanistic inputs.

Blood Platelets↗
PubMed1987

A decision-driven system to collect the patient history.

We have developed a computer-administered history designed to directly interview hospitalized patients with pulmonary disease. A frame-based decision system is used to direct the history and to generate a one- to five-member differential diagnostic list based on this history. This system incorporates a cognitive model of question selection and a Bayesian scoring algorithm. Structures to control the choice of questions are embedded in the diagnostic frames and in a QUERY program that makes the final choice of questions. We have compared the behavior of this decision-driven approach with a history taken using a paper questionnaire. The paper-based history presents 182 questions to every patient and captured 75% of 85 pulmonary diseases in its differential lists. The decision-driven system asks 50.7 +/- 31.0 (mean +/- standard deviation) and captured 74% of 61 pulmonary diseases. Our experience suggests that the use of a computerized diagnostic knowledge base to direct the selection of pertinent questions can substantially reduce the number of questions necessary to collect a diagnostically useful patient history.

Artificial Intelligence↗
PubMed1978

Cytogenetic localization of the acid phosphatase-1 gene in Drosophila melanogaster.

A translocation in which a segment of chromosome 3 is inserted into the Y chromosome was found to contain the acid phosphatase-1 gene (Acph-1). In flies hyperploid for that gene, acid phosphatase-1 levels are proportional to the dose of the gene. The locus is placed within the salivary chromosome subdivisions 99D and 99E on the basis of its inclusion in the translocated segment and on the previous placement of the claret locus. Several chromosomal rearrangements involving heterochromatic breakpoints and euchromatic breakpoints adjacent to 99D-99E were tested for possible postiion-effect variegation of acid phosphatase-1. No decrease in the synthesis of the electorphoretic subunit encoded by the relocated gene was observed within any of the rearrangements.

Acid Phosphatase↗
PubMed1976

Pneumatosis intestinalis in association with connective tissue disease.

Pneumatosis intestinalis in association with connective tissue diseases is an unusual combination whose pathogenesis is not yet understood. Furthermore, steroid medication, often used to treat these diseases, may itself cause pneumatosis. Three cases of scleroderma, systemic lupus erythematosus, and amyloidosis in association with pneumatosis and without prior steroid therapy are presented. The small vessel occlusive pathologic processes in these diseases may cause focal areas of mucosal ischemia resulting in small, perhaps transient ulcerations that allow gas to enter the gut wall from the lumen.

Adult↗
PubMedDate not supplied

Transmembrane signalling associated with ganglioside-induced CD4 modulation.

Ganglioside (GM1) treatment of CD4+ human CEM lymphoma cells stimulated transient phosphoinositide (PI) breakdown, production of inositol phosphates (IP), protein phosphorylation and rapid decrease of CD4 surface expression. A comparison between the actions of GM1 and other agents that affect these signal transduction pathways demonstrated a distinct mechanism for GM1-induced decrease of CD4. GM1 stimulated both phospholipase C activity and protein phosphorylation but had no effect on either cellular cAMP levels or tyrosine kinase activity. Phorbol myristate acetate (PMA) stimulated protein phosphorylation and caused a significant decrease in surface display of CD4. Both of these processes were blocked by pretreating cells with the protein kinase C (PKC) inhibitor H7. These results demonstrate that GM1 stimulates PI turnover and induces a rapid decrease of CD4 surface expression by processes that do not activate adenylate cyclase or tyrosine kinase. They further demonstrate that the mechanism for GM1-induced decrease of CD4 is distinct from the CD4 internalization processes mediated by PKC activity.

Adenylyl Cyclases↗
PubMedDate not supplied

Ganglioside (GM1)-treated T cells shed CD4.

In previous studies (Morrison et al., 1990), we showed that ganglioside (GM1) modulation of CD4 was associated with activation of phospholipase C and increased production of inositol triphosphate, but not with activation of protein kinase C. These results demonstrated a unique signal transduction pathway related to GM1 modulation of CD4 on T cells and raised the question as to whether intracellular Ca2+ levels and related protein kinases would be affected by GM1-induced signalling. We now show that GM1 modulation of CD4 from human T cells corresponds to decreased cellular Ca2+ without significant changes in cellular protein phosphorylation. In the course of this study we discovered that T cells challenged with GM1 exhibited new proteins in their surrounding media. Fractionation of cellular and supernatant proteins show that cells treated with GM1 released proteins with an approximate molecular weight (Mr) of 49,000. This was exclusive of GM1 protein association and GM1-induced protein phosphorylation. Immunoblots demonstrated the presence of CD4 in GM1-treated cell supernatants. Western immunoblots using anti-CD4 antibodies detected a lower Mr form (49,000) of CD4 in the supernatants of GM1-treated cells. These studies further define the unique nature of GM1 signalling relating to modulation of CD4 and demonstrate that the fate of GM1 modulated CD4, in part, involves protein shedding.

CD4 Antigens↗
PubMedDate not supplied

Response to platelet-activating factor in human platelets stored and aged in plasma. Decrease in aggregation, phosphoinositide turnover, and receptor affinity.

Human platelet concentrates were stored in polyolefin bags at 22 to 24 degrees C on a horizontal shaker for up to 8 days. At different intervals, aliquots of platelet-rich plasma (PRP) were removed aseptically and five variables, i.e., platelet counts, morphology, platelet-activating factor (PAF)-stimulated aggregation, phosphoinositide turnover, and [3H]PAF binding to platelet receptors, were studied. The number of platelets did not change during the 8 days of storage. Scanning electron microscopy of the platelets revealed a gradual morphologic change from biconcave flat discs to irregular, crenated forms. The PAF-induced aggregation of platelets declined with time of storage. A decrease to 50 percent of the Day 1 aggregatory response to PAF was evident on Day 2, and there was a further decline to about 20 percent by Day 6. Similarly, PAF receptor-coupled phosphoinositide turnover, as monitored by 32P incorporation into individual phosphoinositides, decreased dramatically with storage. After 2 to 3 days of storage, the phosphoinositide turnover was reduced to 50 percent of the original response, and it continued to decline to about 25 percent of original response by Day 5 or 6. The binding of [3H]PAF to washed human platelets indicated subtle changes between Days 2 and 4, which became more noticeable by Day 6. These results have raised the possibility of changes in the number of the receptors and/or their affinity for the ligand during storage. We conclude that although the number of platelets was maintained during storage for 8 days, a general deterioration of their responses to PAF occurred at the levels of cell surface receptor, transmembrane signaling (phosphoinositide turnover), and response (aggregation).

Binding, Competitive↗