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Biomedical subjects

A Fontana

Publications and source records attributed to A Fontana.

At least 127 records · Page 7Linked to original sources
PubMed1998

TNF-alpha and IFN-gamma render microglia sensitive to Fas ligand-induced apoptosis by induction of Fas expression and down-regulation of Bcl-2 and Bcl-xL.

The immune response in the central nervous system (CNS) involves microglial cells which represent intraparenchymal antigen-presenting cells (APC). To control immune effector mechanisms it may be required to induce apoptosis of APC and thereby limit reactivation of T cells that have invaded the CNS. In the present study we investigated the susceptibility of primary murine microglia and of the murine microglial cell line BV-2 to undergo Fas-mediated apoptosis. Whereas resting microglia are resistant to Fas ligand (FasL) treatment, induction of FasL-mediated apoptosis was achieved by treatment with TNF-alpha or IFN-gamma. The effect of these cytokines was paralleled by up-regulation of Fas expression and down-regulation of Bcl-2 and Bcl-xL but not Bax. Activation of microglia by TNF-alpha and IFN-gamma was also accompanied by increased amounts of mRNA for the apoptosis inhibitor FLIP, an effect which did not protect the cells from FasL-induced apoptosis. The FasL-induced cell death pathway in microglia involves reactive oxygen intermediates because the antioxidants N-acetylcysteine and glutathione interfere with induction of apoptosis. Surprisingly, microglia constitutively express FasL on the cell surface. However, blocking of endogenous Fas-FasL interaction with Fas-Fc fusion protein did not enhance the survival of microglia, excluding the possibility of suicide or fratricide mechanisms. By their expression of FasL and their TNF-alpha/IFN-gamma-dependent sensitivity to the pro-apoptotic effect of exogenous FasL, microglial cells may influence the course of T cell-mediated diseases of the CNS.

Animals↗
PubMed1998

Chemical synthesis and structural characterization of the RGD-protein decorsin: a potent inhibitor of platelet aggregation.

Decorsin is a 39-residue RGD-protein crosslinked by three disulfide bridges isolated from the leech Macrobdella decora belonging to the family of GPIIb-IIIa antagonists and acting as a potent inhibitor of platelet aggregation. Here we report the solid-phase synthesis of decorsin using the Fmoc strategy. The crude polypeptide was purified by reverse-phase HPLC in its reduced form and allowed to refold in the presence of glutathione. The homogeneity of the synthetic oxidized decorsin was established by reverse-phase HPLC and capillary zone electrophoresis. The results of amino acid analysis after acid hydrolysis of the synthetic protein, NH2-terminal sequencing and mass determination (4,377 Da) by electrospray mass spectrometry were in full agreement with this theory. The correct pairing of the three disulfide bridges in synthetic decorsin was determined by a combined approach of both peptide mapping using proteolytic enzymes and analysis of the disulfide chirality by CD spectroscopy in the near-UV region. Synthetic decorsin inhibited human platelet aggregation with an IC50 of approximately 0.1 microM, a figure quite similar to that determined utilizing decorsin from natural source. In particular, the synthetic protein was 2,000-fold more potent than a model RGD-peptide (e.g., Arg-Gly-Asp-Ser) in inhibiting platelet aggregation. Thermal denaturation experiments of synthetic decorsin, monitored by CD spectroscopy, revealed its high thermal stability (Tm approximately 74 degrees C). The features of the oxidative refolding process of reduced decorsin, as well as the thermal stability of the oxidized species, were compared with those previously determined for the NH2-terminal core domain fragment 1-41 or 1-43 from hirudin. This fragment shows similarity in size, pairing of the three disulfides and three-dimensional structure with those of decorsin, even if very low sequence similarity. It is suggested that the less efficient oxidative folding and the enhanced thermal stability of decorsin in respect to those of hirudin core domain likely can be ascribed to the presence of the six Pro residues in the decorsin chain, whereas none is present in the hirudin domain. The results of this study indicate that decorsin can be obtained by solid-phase methodology in purity and quantities suitable for structural and functional studies and thus open the way to prepare by chemical methods novel decorsin derivatives containing unusual amino acids or even non-peptidic moieties.

Amino Acid Sequence↗
PubMed1998

Interferon-gamma antagonizes transforming growth factor-beta2-mediated immunosuppression in murine Toxoplasma encephalitis.

The in vivo modulating activity of recombinant transforming growth factor (TGF)-beta2 on acute toxoplasmosis was evaluated in both Toxoplasma gondii susceptible C57BL/6 and resistant BALB/c mice. TGF-beta2 lethally exacerbated Toxoplasma encephalitis in C57BL/6, but not in BALB/c mice. In C57BL/6 mice, TGF-beta2 induced a profound dose-dependent increase of the intracerebral parasitic load as well as a reduction of IFN-gamma levels in serum and cerebrospinal fluid with a coincident decrease of MHC class II antigen expression of macrophages, microglial cells, and B cells. Furthermore, TGF-beta2-treated C57BL/6 mice showed a reduced activation of CD4+ and CD8+ T cells and a diminished recruitment of immune cells to the brain. The TGF-beta2-mediated development of lethal toxoplasmosis in C57BL/6 mice was abolished by treatment with recombinant interferon (IFN)-gamma.

Animals↗
PubMed1998

First chemical study of patagonian nudibranchs: A new seco-11, 12-spongiane, tyrinnal, from the defensive organs of tyrinna nobilis

The Patagonian nudibranch Tyrinna nobilis contains a number of terpenoids, the novel seco-11,12-spongiane tyrinnal (1) and the known sesquiterpenoids dendrolasin (2), pallescensin A (3), and dehydropallescensin-2 (4). The metabolites probably derive from dietary sponges, thus suggesting a parallelism between the ecological relationships of T. nobilis and those of mollusks of genus Cadlina. The structure of 1 was determined by spectroscopic methods.

Journal Article↗
PubMed1998

New cyclic polyketide peroxides from okinawan marine sponge plakortis sp

Three new cyclic peroxides (2-4) have been isolated from the Okinawan marine sponge Plakortis sp., and the structures were elucidated by extensive spectroscopic analyses. The absolute stereochemistries of 2 and 3 were determined by chemical conversion, whereas that of the dioxane ring of 4 was assigned by the modified Mosher's method.

Journal Article↗
PubMed1998

Transgenerational effects of abusive violence on the children of Vietnam combat veterans.

This study examined the relationship between participation in abusive violence in Vietnam and behavioral disturbances among children aged 6-16 in the next generation. As part of the National Vietnam Veterans Readjustment Study (NVVRS) detailed data were obtained on a national sample of male veterans who were living in households with children aged 6-16 (N = 257). Interviews with spouses/partners were used to evaluate current family relationships and child behavior. Children of veterans who participated in abusive violence showed more behavioral disturbance than children of other Vietnam veterans even after multivariate analysis was used to adjust for other factors such as PTSD symptoms, combat exposure, and postmilitary family relationships. Participation in abusive violence appears to affect parent-child relationships in a way that adversely influences children living at home.

Adolescent↗
PubMed1998

Psychological benefits and liabilities of traumatic exposure in the war zone.

Data from the National Vietnam Veterans Readjustment Study on 1,198 Vietnam theater veterans were used to examine the psychological benefits and liabilities of traumatic exposure in the war zone. Psychological benefits and liabilities were found to be largely independent of one another and to be related positively to the dose of traumatic exposure. Additionally, there was a curvilinear trend in the form of an inverted U, such that psychological benefits, most notably solidarity with others, were stronger at intermediate compared to high and low levels of exposure. Psychological benefits counteracted and psychological liabilities passed through the effects of traumatic exposure on posttraumatic stress disorder (PTSD). The psychological benefit of self-improvement moderated the effects of the psychological liability of self-impoverishment on PTSD.

Adaptation, Psychological↗
PubMed1998

Cancer cell sensitization to fas-mediated apoptosis by sodium butyrate.

Cancer cells often resist Fas-mediated apoptosis even when the Fas receptor is expressed at the cell surface. We show here that human and rat colon cancer cells undergo massive apoptosis when they are exposed to soluble Fas ligand in the presence of sodium butyrate, an agent that induces by itself only a low rate of apoptosis. Sodium butyrate potentiates Fas-dependent apoptosis in seven out of eight colon cancer cell lines. Sodium butyrate does not increase Fas receptor cell surface expression and does not modify cell levels of Bcl-2, Bcl-xL, Bcl-xS and Bax. Sodium butyrate also induces tumor cell sensitization to the apoptotic effect of the combination of TNF-alpha and IFN-gamma, but it does not modify the level of the FADD/Mort1 adaptator molecule, at the connection between Fas- and TNF-dependent apoptosis pathways. Because the clinical toxicity of butyrate is low, its ability to enhance Fas-signal delivery in cancer cells could be of therapeutic interest.

Adaptor Proteins, Signal Transducing↗
PubMed1998

FasL induces Fas/Apo1-mediated apoptosis in human embryonic kidney 293 cells routinely used to generate E1-deleted adenoviral vectors.

Human embryonic kidney 293 cells contain the E1 region of adenovirus type 5, and thus sustain, through transcomplementation, the production of recombinant E1-deleted adenovirus vectors. During attempts to produce recombinant adenovirus expressing the apoptosis-inducing molecule Fas ligand (FasL) under the control of a very strong truncated major immediate-early human cytomegalovirus (MIEhCMV) promoter, we discovered that 293 cells were not surviving the initial cotransfection with a shuttle plasmid encoding the mouse FasL; and pJM17, a plasmid containing the genome of adenovirus type 5 with deletions in the E1-E3 regions, in an unpackagable form. Investigation of the reason for massive cell death after cotransfection led us to determine that 293 cells express the FasL receptor. Fas-Apo1 (CD95), and respond with apoptosis to the cross-linking of Fas-Apo1 with either IgM monoclonal antibodies or FasL. Therefore, we decided to generate adenoviral vectors expressing FasL, under the control of tissue-specific and/or-inducible promoter elements. Our findings can explain difficulties several groups have had in generating recombinant adenoviral vectors expressing FasL using 293 cells, as well as the lower titres reported.

Adenoviridae↗
PubMed1998

Idiopathic oedema with increased cytokine production: a pathogenetic link?

We describe four patients with idiopathic oedema and elevated cytokines. All patients shared increased serum concentrations of soluble interleukin-2 receptors (sIL-2R). In three patients tumour necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma) and interleukin-2 (IL-2) were transiently elevated. There was no evidence for an underlying disease. Based on experimental and clinical data it is hypothesized that oedema formation in our patients is the consequence of cytokine induced alteration of endothelial cells.

Adult↗
PubMed1998

Coping and parental history of cardiovascular disorders influence blood pressure in women tested during different phases of their menstrual cycles.

An anger-provocation paradigm was used to assess coping and stress reactivity in 20 women with a positive parental history of cardiovascular disorders and 14 women whose parents had no cardiovascular disease. Frequency of seeking social support in the natural environment was assessed, as were systolic and diastolic blood pressures, while the women performed anger-inducing arithmetic and speech-stressor tasks during the premenstrual and postmenstrual phases. Premenstrually, the women with a positive cardiac history sought support less frequently than those with a negative history. No differences were found between the groups postmenstrually. When the women were identified according to the frequency with which they sought social support, those who more often sought support registered lower baseline blood pressure levels than those women who less often sought support during both cycle phases. Extending the stress-buffering effects of social support to include efforts at seeking support is discussed.

Adaptation, Psychological↗
PubMed1998

Coping and appraisal of daily stressors predict heart rate and blood pressure levels in young women.

An anger-provocation paradigm was used to assess the effects of coping processes and appraisal of daily stressors on stress reactivity in 33 normotensive undergraduate women. Participants performed a mental arithmetic and an interpersonal conflict task during the pre- and postmenstrual phases of their menstrual cycles. Increased use of the emotion-focused coping processes of tension reduction and positive reappraisal was correlated with lower levels of baseline heart rate, whereas distancing was associated with higher levels of systolic blood pressure reactivity during the conflict task. Perceiving daily stressors as more stressful was associated with higher baseline diastolic blood pressure levels. The authors concluded that the transactional model of stress is useful for generating hypotheses about factors that predict heart rate and blood pressure levels in women.

Adaptation, Physiological↗
PubMed1998

Effects of compensation-seeking on treatment outcomes among veterans with posttraumatic stress disorder.

The desire to acquire or increase financial compensation for a psychiatric disability is widely believed to introduce a response bias into patients' reports of their symptoms and their work performance. The hypothesized effects of compensation-seeking in inhibiting improvement from treatment are examined. Data from outpatient (N = 455) and inpatient (N = 553) programs for the treatment of posttraumatic stress disorder and associated disorders in the Department of Veterans Affairs were used to compare outcomes for veterans who were and were not seeking compensation. Outcome was measured as pre/post improvement in symptoms and work performance over the course of 1 year after the initiation of treatment. No compensation-seeking effect was observed among outpatients, but a significant effect was found for some inpatients. The effect for inpatients was manifested essentially by patients in a program type which was designed to have an extremely long length of stay, thus triggering a virtually automatic increase in payments. Like outpatients, inpatients in programs with a moderate length of stay did not manifest a compensation-seeking effect on improvement. Although not permitting a definitive explanation, the preponderance of the evidence favors the overstatement of symptoms rather than either the severity or the chronicity of the disorder as the most likely explanation for the compensation-seeking effect that was observed. For patients treated in standard outpatient and short-stay inpatient programs, compensation does not seem to affect clinical outcomes adversely.

Ambulatory Care↗
PubMed1998

Duty-related and sexual stress in the etiology of PTSD among women veterans who seek treatment.

OBJECTIVE: The stressful experiences of women serving in the military have been a focus of increasing concern. A model of the impact of stress related to military duty and stress related to sexual abuse and harassment on the development of posttraumatic stress disorder (PTSD) among female veterans was evaluated. METHODS: Structural equation modeling was applied to data from 327 women treated in a VA clinical program for women with stress disorders. The model was a chronological one and included variables related to the women's premilitary experience, their military service, and their postmilitary experience. RESULTS: Altogether 48 percent of the sample served overseas, and 12 percent were exposed to enemy fire. A total of 63 percent reported experiences of physical sexual harassment during military service, and 43 percent reported rape or attempted rape. Both duty-related and sexual stress were found to contribute separately and significantly to the development of PTSD. Sexual stress was found to be almost four times as influential in the development of PTSD as duty-related stress. Postmilitary social support played a highly significant mediational role between sexual stress during military service and development of PTSD. CONCLUSIONS: Women's exposure to sexual stress in the military is much more prevalent than previously believed. It is particularly toxic for the development of PTSD. Correct assessment is essential to effective treatment.

Adult↗
PubMed1998

Service system integration, access to services, and housing outcomes in a program for homeless persons with severe mental illness.

OBJECTIVES: This study evaluated the hypothesis that greater integration and coordination between agencies within service systems is associated with greater accessibility of services and improved client housing outcomes. METHODS: As part of the Access to Community Care and Effective Services and Supports program, data were obtained on baseline client characteristics, service use, and 3-month and 12-month outcomes from 1832 clients seen at 18 sites during the first year of program operation. Data on interorganizational relationships were obtained from structured interviews with key informants from relevant organizations in each community (n = 32-82 at each site). RESULTS: Complete follow-up data were obtained from 1340 clients (73%). After control for baseline characteristics, service system integration was associated with superior housing outcomes at 12 months, and this relationship was mediated through greater access to housing agencies. CONCLUSIONS: Service system integration is related to improved access to housing services and better housing outcomes among homeless people with mental illness.

Adult↗
PubMed1997

Topoisomerase-I inhibitors for human malignant glioma: differential modulation of p53, p21, bax and bcl-2 expression and of CD95-mediated apoptosis by camptothecin and beta-lapachone.

Beta-lapachone and camptothecin are structurally unrelated agents thought to inhibit topoisomerase-I activity through distinct mechanisms. We find that beta-lapachone is much more potent than camptothecin in inducing acute cytotoxic effects on human malignant glioma cells. Acute cytotoxicity induced by both drugs is apoptotic by electron microscopy, but not blocked by inhibitors of RNA or protein synthesis and not associated with changes in the expression of bcl-2, bax, p53, p21 or GADD45 proteins. In contrast, prolonged exposure of glioma cells to both drugs for 72 hr results in growth inhibition and apoptosis, with EC50 values around 1 microM. None of 7 glioma cell lines tested were resistant to either drug. LN-229 cells which have partial p53-wild-type activity show enhanced expression of p53, p21 and bax protein, whereas bcl-2 levels decrease, after exposure to camptothecin. In contrast, beta-lapachone increases bax protein expression in the absence of p53 activation. T98G cells are mutant for p53. In these cells, p53 levels do not change and p21 is not induced. bax accumulation in T98G cells is induced by both drugs, with bcl-2 levels unaltered. Surprisingly, ectopic expression of murine bcl-2 fails to abrogate the toxicity of either drug. Camptothecin, but not beta-lapachone, sensitizes human malignant glioma cells to apoptosis induced by the cytotoxic cytokines, tumor necrosis factor-alpha and CD95 ligand. Thus, both drugs have potent anti-glioma activity that may be mediated by enhanced bax expression but is not inhibited by ectopic bcl-2 expression. Camptothecin-like agents are particularly promising for immunochemotherapy of malignant glioma using cytotoxic drugs and CD95 ligand.

Apoptosis↗
PubMed1997

Differential activity of bcl-2 and ICE enzyme family protease inhibitors on Fas and puromycin-induced apoptosis of glioma cells.

Fas ligand is a potent inducer of apoptosis in human glioma cells by the Fas/Fas ligand pathway. With comparable efficiency, metalloprotease inhibitors including puromycin and bestatin induce apoptosis in glioma cells. To evaluate the involvement of potential components involved in Fas ligand- and metalloprotease inhibitor-induced apoptosis, we investigated the effect of anti human Fas antibody, soluble Fas ligand and puromycin on cultures of human malignant glioma cell lines (LN-18, LN-229, T98G). Stimulation with Fas ligand lead to apoptotic cell death within 16 h. Costimulation with the translational inhibitor cycloheximide and the transcription blocker actinomycin D did not reduce Fas ligand toxicity. In contrast, apoptosis induced by puromycin was blocked by cycloheximide and decreased by subtoxic doses of actinomycin D in all three gliomas. Whereas inhibition of caspase activity with the general inhibitor zVAD-fmk resulted in a complete block of Fas ligand-induced cell death, puromycin-mediated apoptosis was found to be unaffected by zVAD-fmk as well as by more specific inhibitors for caspase-1 (Interleukin-1 beta converting enzyme) and caspase-3 (CPP32/Yama). Other prominent components involved in many apoptotic pathways as bcl-2 and reactive oxygen intermediates were also examined. Bcl-2 which protects glioma cells from Fas ligand-induced cell death, was shown to have only a small protective effect on puromycin-induced apoptosis. The tested radical scavengers did not reduce Fas- or puromycin-mediated killing of human glioma cells.

Amino Acid Chloromethyl Ketones↗