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Biomedical subjects

J Gordon

Publications and source records attributed to J Gordon.

At least 19 recordsLinked to original sources
PubMed1992

Second-messenger pathways involved in the regulation of survival in germinal-centre B cells and in Burkitt lymphoma lines.

Spontaneous apoptosis in germinal-centre (GC) B cells can be prevented by treatment with anti-immunoglobulin (Ig). By contrast, susceptible group-I Burkitt lymphoma (BL) cells can be driven to apoptosis by anti-Ig. The second-messenger pathways involved in the regulation of apoptosis in GC B lymphocytes and in BL cell lines were studied using pharmacological agonists or inhibitors of intracellular calcium ([Ca2+]i) and protein kinase C (PKC). Anti-Ig was found to mobilize Ca2+ in group-I cells. Pre-incubation with the Ca2+ chelator EGTA partially reduced apoptosis induced by anti-Ig or by Ca2+ ionophore in group-I BL cells. Activation of PKC with phorbol ester reduced such Ca(2+)-driven programmed cell death (PCD) to control levels of apoptosis. Apoptosis in group-I BL cell lines could also be triggered by the kinase inhibitors staurosporine and Ro-31-8220 at concentrations selective for PKC activity. Expression of the bcl-2 protein in BL group-I cells following gene transfer affords protection from apoptosis induced by ionomycin or anti-Ig. In the present study, bcl-2 was additionally found to protect from apoptosis driven by staurosporine. The high levels of spontaneous apoptosis exhibited by normal GC B cells were reduced, but not abrogated, by co-culture with phorbol ester. These results indicate that, in group-I BL cells, imbalance in the phosphoinositide pathway of signalling, in favour of [Ca2+]i and away from PKC, results in apoptosis: constitutive phosphorylation of key proteins by PKC may therefore suppress apoptosis in BL as well as in GC B cells.

Apoptosis↗
PubMed1992

Ligation of CD23 triggers cAMP generation and release of inflammatory mediators in human monocytes.

Transduction through the CD23 molecule (Fc epsilon RII) was analyzed in normal human monocytes using monoclonal antibodies to CD23 (MHM6 and 135) and IgE/anti-IgE immune complexes. Monocytes expressing an increased amount of CD23 molecules were obtained by stimulation with IL-4 (30 U/ml). Anti-CD23 mAb as well as IgE/anti-IgE immune complexes were unable to induce any significant calcium mobilization [Ca2+]i in CD23-bearing monocytes whereas they elicited [Ca2+]i increase in B lymphocytes of the same donors. Despite their failure to induce calcium mobilization, the same CD23 ligands triggered a dose-dependent increase of intracellular cAMP, with a maximum 20 to 30 min after the onset of stimulation. This effect is mediated via CD23 inasmuch as: 1) F(ab)'2 fragments are as active as intact anti-CD23 mAb and 2) it is not observed in CD23- monocytes. The increase in cAMP was only partially altered in the presence of 1 microM indomethacin suggesting that it was not due to the release of PG. The possible role of CD23 in the activation of human monocytes was next documented by showing that anti-CD23 mAb and IgE/anti-IgE immune complexes induced the generation of IL-6 and of thromboxane B2 by CD23+ but not by CD23- monocytes. In addition, the IgE/anti-IgE-induced IL-6 production was potentiated in the presence of cAMP inducer such as the beta 2-adrenoceptor agonist salbutamol. These results indicate that ligation of CD23 induces cAMP generation in CD23+ human monocytes and that CD23 may regulate the IgE-dependent functions in normal human monocytes.

Acute-Phase Reaction↗
PubMed1992

Inositol lipids and phosphates in the proliferation and differentiation of lymphocytes and myeloid cells.

It is established that receptor-stimulated hydrolysis of phosphatidylinositol 4,5-bisphosphate is an essential signalling reaction in the responses of many haemopoietic cells to stimuli: examples include platelet activation, antigen-driven initiation of cell proliferation in mature B and T lymphocytes and histamine release by mast cells, and chemotaxis and oxygen radical generation by neutrophils. However, the roles of inositol lipids and phosphates in the development of haemopoietic and immune cells are less well understood. This paper discusses three such situations: the sequential employment of phosphatidylinositol 4,5-bisphosphate hydrolysis and cyclic AMP accumulation as two signals essential to the action of the B lymphocyte-stimulatory cytokine interleukin 4; the involvement of antigen receptor-triggered inositol lipid hydrolysis in apoptotic elimination of immature anti-self T lymphocytes in the fetal mouse thymus; and the possible role of changes in the levels of abundant inositol polyphosphates in the differentiation of HL-60 promyelocytic cells and of normal human myeloid blast cells.

Bone Marrow Cells↗
PubMed1992

Factors modifying survival pathways of germinal center B cells. Glucocorticoids and transforming growth factor-beta, but not cyclosporin A or anti-CD19, block surface immunoglobulin-mediated rescue from apoptosis.

The tendency for germinal center (GC) B cells to enter apoptosis is suppressed on engaging antigen receptor with immobilized anti-immunoglobulin; cross-linking of surface CD40 by monoclonal antibodies provides an additional signal for rescuing GC cells from programmed death. These observations are believed to reflect events that, in vivo, would allow for the selection of centrocytes which have undergone somatic mutation on Ig V-region genes to generate antigen receptor of high affinity. The purpose of the present study was to identify factors capable of modifying the survival pathways of GC cells. Transforming growth factor-beta, at an optimal concentration of 1 ng/ml, was found to inhibit surface immunoglobulin (sIg)-mediated rescue of GC cells but had no influence on survival promoted through CD40. Both routes of rescue were blocked by the glucocorticoid prednisolone at pharmacological concentrations (ID50 = 10(-7) M). Cyclosporin A, an antagonist of sIg-mediated signaling in resting B cells, failed to block rescue of GC cells through either of the receptor-activated pathways. Antibody to CD19--which also suppresses the activation of resting B cells--not only left GC cell rescue undiminished, but rather provided a modest survival signal of its own; interferon-alpha behaved similarly while interferon-gamma failed to influence GC cell survival in either direction.

Antibodies↗
PubMed1992

Enhancing in vitro fertilization of mouse oocytes by partial zona pellucida digestion.

This work was undertaken in order to evaluate the effect of partial zona digestion on fertilization in vitro of mouse oocytes and assess zona surface changes induced by the procedure. Three hundred forty-six oocytes allocated for treatment were exposed to Ham's F-10 medium supplemented with 0.5% Pronase for either 3 min (188 oocytes) or 5 min (158 oocytes); 324 oocytes served as controls. Oocyte losses incurred as a result of the procedure were small (15 oocytes; 4.3%). Control and Pronase-treated oocytes were each divided into four subgroups and inseminated with 5 x 10(5), 5 x 10(4), 5 x 10(3), or 5 x 10(2) sperm cells/ml. Fertilization was assessed 8 hr following insemination by the appearance of two pronuclei and development to the two- to four-cell stage the following day. The morphology of the zona pellucida following Pronase treatment was assessed by phase-contrast and scanning electron (SEM) microscopies performed immediately after treatment. Fertilization rate of control oocytes was 80% at a sperm concentration of 500,000/ml and gradually declined to approximately 30% at 500 cells/ml. In contrast, treated oocytes inseminated with 500 sperm cells/ml demonstrated a normal rate of fertilization. At this low sperm concentration the longer Pronase treatment was significantly (P less than 0.05) more efficient in enhancing fertilization (69 and 88% for 3 and 5 min of Pronase treatment, respectively). Polyspermic fertilization was not observed in any of the subgroups. Phase-contrast microscopic examination of oocytes at the time of Pronase treatment showed an initial swelling of the zona pellucida for 30-60 sec with a time-dependent increase in its transparency.

Animals↗
PubMed1992

Germinal centres in T-cell-dependent antibody responses.

For more than a century follicles have been recognized as a site of intense cell proliferation and cell death. At last the significance of this activity is beginning to emerge: antigen-driven B-cell proliferation, somatic mutation, positive and negative selection, and memory and plasma cell development all appear to take place within the follicle.

Animals↗
PubMed1992

In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus aureus.

The in-vitro activity of povidone-iodine (PVP-I) and chlorhexidine (CHX) against 33 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated by a quantitative suspension test method. Bactericidal potency was measured by the logarithmic reduction factors (LRFs) achieved with each strain, tested at dilutions 25-800 over exposure times 30-300 s using a challenge of approximately 10(7) colony forming units (cfu) ml-1. The mean LRFs achieved over all dilutions, times and strains were significantly higher for PVP-I than CHX. PVP-I exhibited a superior killing effect whether measured by rate of kill or final LRF achieved. This difference was highly significant as judged by analysis of variance (P less than 0.001). Full efficacy of an antiseptic has been defined as a safe LRF greater than five. Over the dilution range 25-200 this was achieved by CHX with only three of 33 strains. In contrast, PVP-I achieved full efficacy with all 33 strains.

Chlorhexidine↗
PubMed1992

Lack of [3H]quinuclidinyl benzylate binding to biologically relevant binding sites on mononuclear cells.

We analyzed the binding characteristics of [3H]quinuclidinyl benzylate ([3H]QNB), a muscarinic cholinergic ligand, to rat and human mononuclear cells (MNC). Under various assay conditions, atropine-sensitive, saturable binding occurred with an apparent Kd of 10 nM. Conditions which disrupted the MNC membrane reduced total binding and eliminated specific binding. Muscarinic agonists were unable to inhibit [3H]QNB binding to MNC at concentrations up to 10(-2) M. Stereoisomers dexetimide and levetimide were equipotent inhibitors of binding (IC50 2 x 10(-5) M). We conclude that, although atropine-sensitive binding of [3H]QNB to MNC occurs, the binding is not consistent with the presence of a biologically relevant muscarinic cholinergic receptor.

Adult↗
PubMed1992

p53 overexpression correlates with increased survival in patients with squamous carcinoma of the tongue base.

Epidermal growth factor receptor (EGFR), transforming growth factor alpha (TGFA), and p53 are frequently overexpressed in squamous cell carcinomas (SCC) of the upper aerodigestive tract. We chose to study SCC of the tongue base, which is often advanced at presentation and fatal, to evaluate whether overexpression correlates with survival. Complete follow-up was available for 20 patients, 18 of whom had stage III or IV disease. A number of clinical (age, sex, stage of disease) and histologic (tumor grade, keratinization, mitotic rate, perineural invasion, lymphatic invasion, vascular invasion, host response) variables were analyzed. None of these variables correlated with survival. Immunohistochemical analysis was performed on paraffin-embedded tissue from each patient. Because EGFR and TGFA expression were routinely found in normal squamous epithelium, overexpression was considered present if greater uptake of the antibody was manifested by a deeper immunostain. In contrast, p53 oncoprotein was not detected in normal epithelium, so detection of the antibody was believed to indicate overexpression. EGFR was overexpressed in 60% of tumors, TGFA in 35%, and p53 in 20%. Those patients who had an overexpression of p53 had a greater mean survival than those who did not (48 versus 16 months, respectively, p = 0.06). This difference was significant for patients with clinical stage IV lesions (p = 0.03). EGFR overexpression and TGFA overexpression did not correlate with survival. p53 may serve as a biologic marker indicative of improved survival potential.

Adult↗
PubMed1992

Bayesian estimation of streptomycin pharmacokinetics.

Streptomycin dose requirements were determined in an 83-year-old man with renal impairment who was being treated for miliary tuberculosis. Concentration measurements were interpreted using a Bayesian parameter estimation program. Estimated creatinine clearance (1.1 L/h) was used as a starting value for streptomycin clearance, and volume was initially assumed to be 0.3 L/kg. Bayesian estimates of clearance were close to the starting value and declined from 1.4 L/h to 0.9 L/h during the course of therapy. Volume was higher than the initial estimate (0.4-0.5 L/kg), possibly due to the patient having a low albumin and being underweight. Satisfactory concentrations were maintained for several weeks with doses of 500 mg every 36-48 h.

Aged↗
PubMed1992

Color appearance across the retina: effects of a white surround.

Hue and saturation scaling was used to measure the appearance of spectral lights as a function of stimulus size at loci spaced across the horizontal meridian. At a given locus, each hue (red, yellow, green, and blue) grew as a function of stimulus size to some asymptotic value. Growth functions fitted to the hue data were used to derive the sizes of perceptive fields of the hue mechanisms. We had previously investigated the size scales of these fields by using stimuli presented on a dark background: Field sizes for all mechanisms increased with eccentricity, this increase was greater on the temporal than on the nasal retina, and the retinal size scales of the different hue mechanisms were not the same. We now report the results of repeating the study with stimuli embedded in a white surround rather than in darkness. The main effects of the white surround were as follows: Sizes of perceptive fields of all mechanisms were smaller everywhere than with the dark surround. For small fields, stimuli appeared everywhere more saturated with the white surround, but larger stimuli appeared less saturated.

Adolescent↗
PubMed1992

Occupancy of CD72 (the CD5 counterstructure) enhances interleukin-4-dependent CD23 expression in resting B lymphocytes.

CD72, the human homologue of murine Lyb-2, was recently identified as a counterstructure to CD5. An antibody to CD72 (BU40) has been found to mimic interleukin-4 (IL-4) both in its ability to activate resting B cells into the early G1 phase of cell cycle and to augment the expression of major histocompatibility complex (MHC) class II antigen; unlike IL-4, the CD72-clustered antibody fails to induce the expression of CD23. We now report that engagement of CD72 by the IgG monoclonal antibody BU40 potentiates the capacity of IL-4--when used at optimal concentrations--to promote CD23 production in human B cells. The degree of enhancement arising from occupancy of CD72 ranged from two- to fivefold. Importantly, antibody to CD72 was also found to diminish the concentration required for IL-4 to promote CD23 expression to a level equivalent to that maximally achieved when using IL-4 alone. Engagement of CD72 by BU40 not only increased the amount of cell-associated CD23 induced by IL-4 but also led to augmented release of soluble material into the culture medium. Monovalent Fab fragments of BU40 antibody were as efficient as intact antibodies at synergizing with IL-4 for enhanced expression and release of CD23: thus simple tethering without the need for receptor cross-linking was sufficient to invoke change through CD72. Enhancement of CD23 expression via CD72 appeared to be selective for IL-4-dependent induction: the turn on of CD23 by tumour-promoting phorbol ester was left unaltered on the addition of BU40 antibody. Engagement of CD72 had no effect on the IL-4-promoted hyperexpression of surface IgM. The findings are discussed within the context of the molecular and functional interactions occurring during T-B collaboration.

Antibodies, Monoclonal↗