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D A Clark

Publications and source records attributed to D A Clark.

At least 91 records · Page 5Linked to original sources
PubMed1997

Anti-inflammatory properties of interleukin-10 administration in hapten-induced colitis.

Therapeutic efficacy of interleukin-10 administration in colonic inflammation was assessed in rats. Following intracolonic instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS), subcutaneous administration of 1-1000 micrograms/kg per day interleukin-10, or a placebo (0.9% NaCl) was commenced and continued for 5 days. Interleukin-10 administered at 1, 10 and 100 micrograms/kg per day significantly reduced myeloperoxidase activity by 34, 57, and 28%, respectively, compared to the placebo-treated group, which was paralleled by an attenuation of colonic tumor necrosis factor alpha (TNF-alpha) content. In contrast, the severity of mucosal necrosis was not affected by interleukin-10 administration at the dose range used. In addition, the 10-fold elevation in nitric oxide release, 5-fold rise in colonic nitrite production and enhanced expression of inducible nitric oxide synthase, associated with TNBS colitis, was not suppressed by interleukin-10. Interleukin-10 gene expression was elevated during the first 14 days of TNBS colitis. We conclude that 5 days administration of interleukin-10 in TNBS colitis displays mild anti-inflammatory properties which were not mediated via a nitric oxide-dependent pathway, but may involve TNF-alpha.

Animals↗
PubMed1997

Peroxynitrite-induced apoptosis in epithelial (T84) and macrophage (RAW 264.7) cell lines: effect of legume-derived polyphenols (phytolens).

Peroxynitrite (ONOO-) has been proposed as a mediator of gut inflammation and as an inducer of cell death by apoptosis. Phytolens (PHY), a water-soluble extract of polyphenolic antioxidants from nonsoy legumes (Biotics Research Corp, patent pending), was evaluated as a cytoprotective agent in human colonic (T84) and murine macrophage (RAW 264.7) cell lines. In the antioxidant testing, PHY showed a significant free radical scavenging ability against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and superoxide (O2.) radicals with an IC50 of 4.44 and 5.87 microg/ml against DPPH and O2., respectively. Apoptosis (DNA fragmentation) was measured by an ELISA technique. Cells were exposed to oxidative stress by treating them with peroxynitrite (100-300 microM) for 4 h in the presence and absence of PHY. Peroxynitrite elicited a dose-dependent increase in DNA fragmentation in both cell lines compared to the control group receiving decomposed ONOO-. PHY (10, 30, or 50 microg/ml) significantly attenuated the degree of apoptosis in T84 cells induced by ONOO- (P < 0.05). PHY (10-100 microg/ml) did not directly affect T84 cell viability or induce apoptosis after 4 h or overnight exposure. RAW 264.7 cells exposed to PHY alone (>30 microg/ml) for 4 h displayed decreased cell viability (P < 0.05) and increased apoptosis (P < 0.05). Phytolens may have beneficial effects on inflammation by attenuating peroxynitrite-induced apoptosis. The sparing of epithelial cells while compromising the viability of macrophages suggests that PHY may be beneficial in autoimmune disorders.

Animals↗
PubMed1997

An information processing model of anxiety: automatic and strategic processes.

A three-stage schema-based information processing model of anxiety is described that involves: (a) the initial registration of a threat stimulus; (b) the activation of a primal threat mode; and (c) the secondary activation of more elaborative and reflective modes of thinking. The defining elements of automatic and strategic processing are discussed with the cognitive bias in anxiety reconceptualized in terms of a mixture of automatic and strategic processing characteristics depending on which stage of the information processing model is under consideration. The goal in the treatment of anxiety is to deactivate the more automatic primal threat mode and to strengthen more constructive reflective modes of thinking. Arguments are presented for the inclusion of verbal mediation as a necessary but not sufficient component in the cognitive and behavioral treatment of anxiety.

Anxiety↗
PubMed1997

Peroxynitrite-induced apoptosis in T84 and RAW 264.7 cells: attenuation by L-ascorbic acid.

The free radicals nitric oxide and superoxide react to form peroxynitrite (ONOO-), a potent cytotoxic oxidant. This study was designed to evaluate whether addition of L-Ascorbic acid (AsC) into the culture medium decreases peroxynitrite-induced apoptosis in human intestinal epithelial (T84) and murine macrophage (RAW 264.7) cell lines. In Experiment 1, T84 and RAW 264.7 cells were divided in two protocols: (1) treated with 100-300 microM ONOO- and incubated for 4 h, and (2) treated with 10-100 microM ONOO- and incubated overnight (14 h). In Experiment 2, T84 and RAW 264.7 cells were treated with 300 microM ONOO- and 500 microM AsC and incubated for 4 h. In Experiment 3, T84 and RAW 264.7 cells were preincubated for 2 h with 500 microM AsC then exposed to 300 microM ONOO- for 4 h. Cell viability (necrosis) was assessed by trypan blue dye exclusion. Apoptosis was quantified with a cell death detection ELISA assay. In the 4 h protocol, ONOO- induced apoptosis in T84 and RAW 264.7 cells, at levels of 100-300 microM. Concentrations of ONOO- greater than 300 microM caused necrosis. In contrast, extension of the protocol to 14 h indicated that ONOO- induced apoptosis at lower concentrations (50;-75 microM), with concentrations > 75 microM resulting in necrosis. AsC administered to the media or with preincubation plus washout, decreased peroxynitrite-induced apoptosis in T84 and RAW 264.7 cells. These results indicate that ONOO- may contribute to the pathophysiology of gut inflammation by promoting cell death and ascorbic acid may protect against peroxynitrie-induced damage.

Animals↗
PubMed1997

Twenty years of cognitive assessment: current status and future directions.

This commentary examines a number of methodological and conceptual issues that were raised in this special section on cognitive assessment. Although progress has been made in a number of areas since cognitive-clinical researchers first addressed the assessment of cognition almost 20 years ago, important conceptual and methodological questions still remain unresolved. These include questions about the validity of retrospective self-report questionnaires of cognition, the low convergent validity between different assessment methods, and the failure to specify the range of generalizability of specific cognition measures. Further advances in cognitive assessment will depend on a more concerted research focus on the methodological and conceptual issues raised in this special section.

Cognitive Behavioral Therapy↗
PubMed1997

Peroxynitrite-induced apoptosis in human intestinal epithelial cells is attenuated by mesalamine.

BACKGROUND & AIMS: Peroxynitrite (PN), a potent oxidant, has been implicated in the pathogenesis of gut inflammation and epithelial cell apoptosis. The aim of this study was to investigate mesalamine, a standard therapy for inflammatory bowel disease, to see if it attenuates PN-induced cytotoxicity in human intestinal epithelial cells and if mesalamine directly interacts with PN or its precursor, nitric oxide. METHODS: T84 and HT29 cells were divided in several protocols: mesalamine was administered 2 hours before, simultaneously, or 30 minutes after PN. T84 cells, grown in filter chamber inserts, were used to determine if basolateral or apical administration of PN initiated apoptosis and epithelial barrier function. The effects of mesalamine on PN decomposition and NO half-life were determined. RESULTS: Mesalamine resulted in a dose-dependent decrease in PN-induced apoptosis, whether mesalamine was administered before (>10 micromol/L; IC50, 16 micromol/L), simultaneously (25-200 micromol/L; IC50, 24 micromol/L), or 30 minutes (200 micromol/L) after PN exposure. Mesalamine protected the epithelial barrier function of T84 cells against PN. Mesalamine rapidly degraded PN, whereas the half-life of NO was not affected. CONCLUSIONS: The beneficial effects of mesalamine in the treatment of inflammatory bowel disease may involve an attenuation of PN-induced cell injury and apoptosis through direct and indirect mechanisms without affecting NO levels.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Decidua-associated suppressor cells in abortion-prone DBA/2-mated CBA/J mice that release bioactive transforming growth factor beta2-related immunosuppressive molecules express a bone marrow-derived natural suppressor cell marker and gamma delta T-cell receptor.

The decidua of allopregnant mice contains a novel population of Thy1 Lyt1 CD4 CD8 asialoGM1- non-B small lymphocytic suppressor cells that release transforming growth factor (TGF) SS2-related suppressor molecules. The "null" phenotype of this cell population is similar to some bone marrow-derived natural suppressor cell (NSC) populations, and the latter may release TGF(beta)s. We now report that the TGF beta2-producing suppressor cells in the uterine decidua of DBA/2-mated CBA/J female mice-linked to prevention of abortions-are inactivated effectively by 1E5/B5.1 but not by 2C1.1 rat monoclonal antibodies to murine pregnancy-associated splenic NSC in the presence of complement. Immunostaining of a subpopulation of cells in decidua with 1E5/B5.1 but not with 2C1.1 was shown by flow cytometry. Release of suppressor factor was also abrogated by 1E5/B5.1 + complement but not by 2C1.1 + complement, and the suppressor factor was specifically neutralized by anti-TGF beta2 and not by anti-TGF beta3. Splenic pregnancy NSC are susceptible to 2C1.1, produce TGF beta1, and express CD3 and alpha beta T-cell receptor (TcR) chains. Release of suppressor factor by the decidual NSC was abrogated by treatment with anti-CD3 (145 2C11) and anti-TcR gamma delta (GL4) monoclonal antibodies + complement, but not by anti-TcR alpha beta (H57) + complement; and cells sorted using anti-TcR gamma delta (GL3) released suppressive activity in vitro. Slightly more suppressive activity was released by implantation-site decidua where there was no epithelium than from epithelialized inter-implantation-site decidua; no significant activity was released from placental tissue, but combining implantation-site tissue with placental tissue led to release of enhanced levels of immunosuppressive activity. There appear to be subtypes of bone marrow-derived TcR+ NSC with different phenotypes and tissue localization patterns in pregnancy. The previously reported dependence of decidual NSC activity on the presence of soluble signals from fetal trophoblast may be explainable by the ability of cells bearing TcR gamma delta to recognize and react to placental trophoblast cell antigen.

Abortion, Veterinary↗
PubMed1997

Human cytotrophoblastic cells absorb the NK blocking activity of monoclonal BA11.

PROBLEM: R80K is a polymorphic alloantigeneic protein present on human placental trophoblast and on paternal B lymphocytes and monocytes. This protein, unlike the former candidate TLX antigen, stimulates a protective maternal immune response in vivo. A murine monoclonal BA11 antibody, directed against R80K, prevents abortion in three murine pregnancy-failure models and inhibits human and murine NK activity. We attempted to define the target of BA11 in the human NK assay system. METHODS: A CELISA method was used to detect R80K antigen on the surface of different cells using the BA11 antibody. The effect, on human peripheral blood NK activity against K562, by BA11 before and after absorption by different cells, including the K562 target, was determined. RESULTS: R80K was detected on term placental syncytio and cytotrophoblast and on BeWo cells, by CELISA. BA11 suppressed NK lysis of K562 cell sin a dose-dependent manner. Absorption of the BA11 by BeWo and by cytotrophoblastic cells significantly decreased the NK-inhibitory activity. There was minimal absorption by K562 and BA11-pretreateed K562 cells remained susceptible to NK lysis. By contrast, BA11-pretreated peripheral blood cells lost all NK activity. CONCLUSIONS: The inhibition of NK killing of K562 cells by BA11 is more complex than simple masking of a trophoblast cell-associated molecule in K562 necessary for recognition in NK cells.

Absorption↗
PubMed1997

Regulation of abortion by gamma delta T cells.

PROBLEM: T cells are present at the feto-maternal interface, but their function during pregnancy has not been fully elucidated. T cells bearing gamma delta T-cell receptor (TCR) may be particularly important, as some subsets can react to trophoblast cells by producing cytokines, such as interleukin-2 (IL-2). METHOD: We depleted T cells bearing the gamma delta receptor by injecting monoclonal antibodies (mAb) into females of the abortion-prone animal model CBA x DBA/2. We investigated the percentage and number of gamma delta T-cell receptor positive (TCR)+ cells in decidua and spleen during pregnancy in control and gamma delta-depleted female mice. Pregnant females were also exposed to ultrasonic sound stress to boost the abortion rate. RESULTS: Stress failed to increase the abortion rate in the gamma delta TCR-depleted mice. FACScan analysis show that the ratio of cells bearing the gamma delta TCR dramatically decreased after injection of mAB to the gamma delta TCR in spleen and decidua, these cells recovered six days after depletion, showing a change in cytokine pattern. Levels of TNF-alpha in decidual gamma delta T cells decreased; similar effects of decreasing Th1 cytokines could be observed in splenic gamma delta T cells. We further identified increased levels of intracellular TNF-alpha in the V delta 4 subset in the decidua, compared to spleen. CONCLUSIONS: Trophoblast recognition by the V delta 4 T-cell subset in the decidua may cause the release of abortogenic cytokines such as TNF-alpha. Depletion of such gamma delta TCR T cells during early pregnancy may promote successful pregnancy outcome in normal pregnancy and prevent stress-induced abortions.

Abortion, Spontaneous↗
PubMed1997

Stress triggered abortions are associated with alterations of granulated cells into the decidua.

PROBLEM: Stress is known to be abortogenic in animals and humans. An increased decidual release of cytokines such as TNF-alpha and reduction in TGF-beta 2-related immunosuppressive activity has been proposed as the triggering mechanism. Substance P release by nerves in endometrium/decidua has been found to be the key neurotransmitter in this pathway. It is still unclear which cells are stimulated by substance P to produce the increased TNF-alpha level. METHOD: As a measure of local activation, the granulation of granulated material gland (GMG) cells was measured by flow cytometry after sonic plus immobilization stress of mice or substance P treatment of GMG cells (both isolated GMG cells and GMG-cell containing decidua). TNF-alpha release from decidua and isolated GMG cells was investigated using a TNF-alpha bioassay. The degranulation of uterine mast cell, another potential source of TNF-alpha, was examined in situ by Toluidine blue staining. RESULTS: We observed a striking increase in percentage of degranulated mast cells (8% -->24%) in the uteri of stressed animals, whereas the granularity of GMG cells was decreased by stress but increased with treatment with substance P in vitro. Isolated GMG cells appeared to release in vitro cytotoxins active in the TNF-alpha bioassay, but the magnitude of this activity was not increase by stress or by substance P treatment. In contrast, disaggregated decidual tissue which is known to release increased amounts of TNF-alpha after stress, did increase activity in response to substance P in vitro. CONCLUSIONS: Uterine mast cells show activation as reflected by degranulation after stress exposure of pregnant mice and mast cells might be the cellular link between the neurotransmitter substance P and increase in decidual TNF-alpha release that leads to abortion.

Abortion, Spontaneous↗
PubMed1997

Soluble receptors neutralizing TNF-alpha and IL-1 block stress-triggered murine abortion.

PROBLEM: In several models of abortion in rodents, the success or failure of the implanted embryos is determined by a balance between pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-2, interleukin-1 (IL-1), and gamma-interferon, and cytokines that counteract the former, such as interleukin-10 and transforming growth factor-beta 2 (TGF-beta 2)-related suppressor factor. Stress can trigger abortions in susceptible strains of mice and is thought to reflect the pathogenesis of some types of miscarriage in human pregnancy. In mice, stress increases levels of the abortogenic cytokine TNF-alpha and decreases the suppressive activity of TGF-beta 2-related factor via a neurotransmitter substance P (SP)-dependent pathway. Evidence for a role of pro-inflammatory cytokines in SP-mediated abortions in vivo is indirect. METHODS: Direct evidence for a role of IL-1 and TNF-alpha in stress-triggered abortions was sought by injecting pregnant female mice with soluble receptors neutralizing TNF-alpha (rhuTNFR:Fc) or IL-1 (rmIL-IR) beginning 1 day after implantation and prior to stress. RESULTS: The stress-triggered abortion rate was reduced by 68% when either TNF-alpha or IL-1 antagonists were injected. The stress-triggered decreased TGF-beta 2-like suppressive activity in the maternal uterine decidua was not restored by injection of either antagonist; indeed the soluble IL-1 receptor significantly reduced suppressive activity in unstressed control mice, and soluble TNF-alpha receptor had a lesser effect. CONCLUSIONS: Both IL-1 and TNF-alpha play a role in the pathogenesis of stress-triggered abortions, and may induce a compensatory physiological increase in suppressive activity in normal pregnancy counteracting pro-inflammatory cytokines.

Abortion, Veterinary↗