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Biomedical subjects

M Wetzel

Publications and source records attributed to M Wetzel.

At least 19 recordsLinked to original sources
PubMed2004

Vulnerability of mouse cortical neurons to doxorubicin-induced apoptosis is strain-dependent and is correlated with mRNAs encoding Fas, Fas-Ligand, and metalloproteinases.

Cell surface death receptor-mediated neuronal apoptosis, which is a critical component of neurodegeneration, is modulated by matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). Doxorubicin (Dox) induces neuronal death by the activation of death receptor pathways. Recently, we demonstrated that Dox-induced neuronal apoptosis is regulated by the balance of MMP-3 and TIMP-3 in rat cortical cultures. Inbred mouse strains exhibit differential susceptibility to cell death stimuli in vivo. Prior to employing transgenic approaches to further investigate the roles of TIMP-3 and MMP-3 in neuronal death, we examined whether inbred mice display strain-dependent vulnerability to Dox. We induced neuronal apoptosis with Dox in primary neuronal cultures established from cerebral cortices of embryonic day 15 C57BL/10 or C57BL/6 mice. Using fluorescence activated cell sorting for neurons, we found that C57BL/6 cortical cultures exhibit a 28% greater neuronal death following Dox treatment than C57BL/10. Real-time PCR of unstimulated cultures revealed that C57BL/10 cortical cultures have reduced basal mRNA levels encoding the pro-apoptotic proteins: Fas, FasL, and TIMP-3, but increased levels of the anti-apoptotic molecule MMP-3 as compared to C57BL/6. Furthermore, C57BL/10 cultures treated with Dox displayed an enhanced induction of mRNA transcripts that encode anti-apoptotic MMPs. These results show that C57BL/10 cortical cultures are more resistant to death receptor-mediated apoptotic cell death as compared to C57BL/6, and suggest that this difference is related to Fas, FasL, and MMP expression. Strain-dependent differences in response to apoptotic stimuli may be an important consideration for developing transgenic models of neurodegeneration.

Animals↗
PubMed2003

Tissue inhibitor of metalloproteinases-3 and matrix metalloproteinase-3 regulate neuronal sensitivity to doxorubicin-induced apoptosis.

Metalloproteinase activity at the cell surface influences cellular sensitivity to extrinsic death vs. survival signals in a variety of cell types, through proteolytic shedding of cell surface signalling molecules. Tissue inhibitor of metalloproteinases-3 (TIMP-3) is a unique natural metalloproteinase inhibitor that plays a pro-apoptotic role through its ability to inhibit metalloproteinases that proteolytically cleave death receptors and their ligands from the cell surface. To study the convergence of metalloproteinase activity and death receptor signalling in neurons, we established an in vitro model of neuronal apoptosis utilizing the chemotherapeutic drug, doxorubicin (Dox). Primary cultures established from embryonic rat cerebral cortices displayed robust and selective neuronal apoptosis in response to Dox, an effect that was dependent on the activation of the death receptor, Fas. We demonstrate that both TIMP-3 and matrix metalloproteinase-3 (MMP-3) are constitutively expressed by primary cortical neurons in culture, and selectively modulated Fas-mediated neuronal apoptosis induced by Dox. Metalloproteinase inhibition by TIMP-3 was found to be necessary for Dox-induced neuronal death, whereas addition of active MMP-3 markedly attenuated apoptosis and diminished Fas-Fas ligand interaction at the cell surface. These observations implicate a physiological role for the balance of TIMP-3 and MMP-3 activity at the neuronal surface in regulating death receptor sensitivity. The convergence of metalloproteinase activity and death receptor signalling at the cell surface may influence neuronal cell death vs. survival decisions.

Animals↗
PubMed2001

Opioids, opioid receptors, and the immune response.

It is now clear that opioid receptors participate in the function of the cells of the immune system, and evidence suggests that opioids modulate both innate and acquired immune responses. We review literature here which establishes that mu-, kappa-, and delta-opioid compounds alter resistance to a variety of infectious agents, including the Human Immunodeficiency Virus (HIV). The nature of the immunomodulatory activity of the opioids has been the subject of a great deal of research over the last ten years. There is increasing evidence that effects of opioids on the immune response are mediated at several levels. Modulation of the inflammatory response appears to be a target of these compounds, including effects on phagocytic activity, as well as the response of cells to various chemoattractant molecules. Moreover, findings from several laboratories have demonstrated the impact of opioid treatment on antibody responses, and the molecular basis for this effect is likely due, at least in part, to the modulation of both cytokine and cytokine receptor expression. Future research should provide a clearer understanding of the cellular and molecular targets of opioid action within the immune system.

Antibodies, Viral↗
PubMed2001

Should an angiotensin-converting enzyme inhibitor be standard therapy for patients with atherosclerotic disease?

Angiotensin-converting enzyme (ACE) inhibitors appear to possess unique cardioprotective benefits, even when used in patients without high blood pressure or left ventricular dysfunction (the traditional indications for ACE inhibitor therapy). The ACE inhibitors improve endothelial function and regress both left ventricular hypertrophy and arterial mass better than other antihypertensive agents that lower blood pressure equally as well. These agents promote collateral vessel development and improve prognosis in patients who have had a coronary revascularization procedure (i.e., percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery). Insulin resistance, present not only in type 2 diabetes but also commonly in patients with hypertension or coronary artery disease, or both, sensitizes the vasculature to the trophic effects of angiotensin II and aldosterone. This may partly explain the improvement in prognosis noted when patients who have atherosclerosis or diabetes are treated with an ACE inhibitor. Therapy with ACE inhibitors has also been shown, in two large, randomized trials, to reduce the incidence of new-onset type 2 diabetes through largely unknown mechanisms. The ACE inhibitors are safe, well tolerated and affordable medications. The data suggest that most people with atherosclerosis should be considered candidates for ACE inhibitor therapy, unless they are intolerant to the medication, or have systolic blood pressures consistently <100 mm Hg. Patients who show evidence of insulin resistance (with or without overt type 2 diabetes) should also be considered as candidates for prophylactic ACE inhibitor therapy. Although angiotensin receptor blockers should not be considered equivalent to ACE inhibitors for this indication, they may be a reasonable alternative for patients intolerant of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

Purified NS2B/NS3 serine protease of dengue virus type 2 exhibits cofactor NS2B dependence for cleavage of substrates with dibasic amino acids in vitro.

Dengue virus type 2 NS3, a multifunctional protein, has a serine protease domain (NS3pro) that requires the conserved hydrophilic domain of NS2B for protease activity in cleavage of the polyprotein precursor at sites following two basic amino acids. In this study, we report the expression of the NS2B-NS3pro precursor in Escherichia coli as a fusion protein with a histidine tag at the N terminus. The precursor was purified from insoluble inclusion bodies by Ni(2+) affinity and gel filtration chromatography under denaturing conditions. The denatured precursor was refolded to yield a purified active protease complex. Biochemical analysis of the protease revealed that its activity toward either a natural substrate, NS4B-NS5 precursor, or the fluorogenic peptide substrates containing two basic residues at P1 and P2, was dependent on the presence of the NS2B domain. The peptide with a highly conserved Gly residue at P3 position was 3-fold more active as a substrate than a Gln residue at this position. The cleavage of a chromogenic substrate with a single Arg residue at P1 was NS2B-independent. These results suggest that heterodimerization of the NS3pro domain with NS2B generates additional specific interactions with the P2 and P3 residues of the substrates.

Amino Acid Sequence↗
PubMed2000

A T-cell-selective interleukin 2 mutein exhibits potent antitumor activity and is well tolerated in vivo.

Human interleukin 2 (IL-2; Proleukin) is an approved therapeutic for advanced-stage metastatic cancer; however, its use is restricted because of severe systemic toxicity. Its function as a central mediator of T-cell activation may contribute to its efficacy for cancer therapy. However, activation of natural killer (NK) cells by therapeutically administered IL-2 may mediate toxicity. Here we have used targeted mutagenesis of human IL-2 to generate a mutein with approximately 3,000-fold in vitro selectivity for T cells over NK cells relative to wild-type IL-2. We compared the variant, termed BAY 50-4798, with human IL-2 (Proleukin) in a therapeutic dosing regimen in chimpanzees, and found that although the T-cell mobilization and activation properties of BAY 50-4798 were comparable to human IL-2, BAY 50-4798 was better tolerated in the chimpanzee. BAY 50-4798 was also shown to inhibit metastasis in a mouse tumor model. These results indicate that BAY 50-4798 may exhibit a greater therapeutic index than IL-2 in humans in the treatment of cancer and AIDS.

Animals↗
PubMed1999

The natural history of cavernous malformations: a prospective study of 68 patients

OBJECTIVE: Cavernous malformations are angiographically occult cerebrovascular malformations found in approximately 0.5% of the population. To help further understand the natural history of these lesions, we prospectively followed 68 patients harboring cavernous malformations. METHODS: The 68 patients in this study were all diagnosed radiographically (67 patients) or surgically (1 patient) and were entered into a patient database. Age, sex, clinical symptoms, seizure frequency, focal neurological deficits, and presence or absence of extralesional hemorrhage were all recorded at presentation. Patients were then followed prospectively to determine the rate of hemorrhage and new-onset seizures. RESULTS: The mean follow-up per patient was 5.2 years, and the total follow-up was 352.9 patient-years. There was an average of 3.4 lesions per patient. Thirteen of the patients (19%) had familial cavernous malformations. Patients with familial disease were more likely to have multiple lesions than patients with sporadic disease (85% versus 25%, respectively [P = 0.001]). Initial presentation included headache (65%), seizures (49%), and focal neurological deficit (46%). Eleven symptomatic, radiologically proven, extralesional hemorrhages occurred during the 352.9 patient-years of follow-up for an overall hemorrhage rate of 3.1% per patient-year. Female patients had a significantly higher prospective hemorrhage rate (4.2% per patient-year versus 0.9% per patient-year [P = 0.04]). A history of hemorrhage at presentation was not a risk factor for subsequent hemorrhage during follow-up. The rate of new-onset seizures was 2.4% per patient-year. CONCLUSION: The clinical presentation and prospective hemorrhage rate reported here agree well with findings of other prospective studies. This information, combined with our new-onset seizure rate, should aid clinicians caring for patients with cavernous malformations.

Journal Article↗
PubMed1998

An immune cell-selective interleukin 4 agonist.

Interleukin 4 (IL-4) is a pleiotropic cytokine. Of the cell types responsive to IL-4, T cells express one IL-4 receptor (IL-4R) type, IL-4Ralpha/IL-2Rgamma (class I IL-4R), whereas endothelial cells express another type, IL-4Ralpha/IL-13Ralpha (class II IL-4R). It was hypothesized that IL-4 variants could be generated that would be selective for cell types expressing the different IL-4Rs. A series of IL-4 muteins were generated that were substituted in the region of IL-4 implicated in interactions with IL-2Rgamma. These muteins were evaluated in T cell and endothelial cell assays. One of these muteins, containing the mutation Arg-121 to Glu (IL-4/R121E), exhibited complete biological selectivity for T cells, B cells, and monocytes, but showed no activity on endothelial cells. Receptor binding studies indicated that IL-4/R121E retained physical interaction with IL-2Rgamma but not IL-13Ralpha; consistent with this observation, IL-4/R121E was an antagonist of IL-4-induced activity on endothelial cells. IL-4/R121E exhibits a spectrum of activities in vitro that suggest utility in the treatment of certain autoimmune diseases.

B-Lymphocytes↗
PubMed1995

Comparison of cyclosporin A, verapamil, PSC-833 and cremophor EL as enhancing agents of VP-16 in murine lymphoid leukemias.

Although verapamil, cyclosporin A. cremophor EL and PSC-833 are active as multidrug resistance modulators, there has been limited study of these compounds as possible chemotherapy enhancing agents against drug-sensitive tumors. We compared these agents as modifiers of VP-16 cytotoxicity in vitro and modifiers of VP-16 efficacy in vivo against drug-sensitive P388 and L1210 leukemias. Our study indicates that cyclosporin A enhances VP-16 cytotoxicity to a significantly greater extent than equimolar concentrations of verapamil or PSC-833. Although cremophor EL shows significantly greater activity than verapamil in VP-16 cytotoxicity enhancement in vitro, it is ineffective when added to VP-16 therapy of mice bearing L1210 leukemia.

Animals↗
PubMed1994

Predicting medical student success in a clinical clerkship by rating students' nonverbal behavior.

OBJECTIVE: To evaluate the relative contribution of affective and cognitive skills to ratings of students' clinical performance by their supervisors. METHODS: Each students' nonverbal behavior was analyzed by examining 33 nonverbal behavioral characteristics in videotape of each of 36 students interviewing a parent or patient three times during a 4-week pediatric clerkship. These ratings were then compared with the student's formal academic evaluation. RESULTS: The 33 nonverbal behavioral characteristics rated for each student were reduced to five composite variables. Three of these correlated significantly with the final grade, providing an affective profile of the highly rated student. Regression analysis of the five composite variables revealed that affective skills accounted for at least 46% of the variance in the students' final grades (multiple R = .68, P = .0015). CONCLUSIONS: Ratings of students' affective characteristics were highly related to clinical evaluations in this pediatric setting. Students who were evaluated highly had a specific affective profile that could be described by analysis of their nonverbal behaviors.

Adult↗
PubMed1994

Assaults by patients on psychiatric residents at three training sites.

OBJECTIVE: This study attempted to determine how often psychiatric residents are exposed to violence, the types of violence they encounter, and what institutional changes might increase their safety. METHODS: Safety conditions at two private general hospitals and one state hospital that served as training sites for a psychiatric residency program were assessed through a survey of psychiatric residents and site visits to the hospitals. The survey asked residents to quantify violent incidents occurring in the emergency rooms, wards, and clinics at each site. The site visits focused on safety issues related to staff training, physical layout, staffing patterns, current policies, and compliance with policies. RESULTS: All 47 residents in the training program responded to the survey. None reported serious injury, although as many as 56 percent had been physically assaulted on the wards of one hospital, and 54 percent of residents had encountered a weapon in one emergency room. Almost all residents had been verbally threatened or had witnessed violence to others. A paradoxical finding of the survey was that the residents felt safest in the hospital that had the highest rate of violence. The site visits revealed that deficiencies in the safety procedures were allowing weapons to be brought into patient care areas. CONCLUSIONS: Psychiatric residents are often exposed to dangerous situations, although serious injury is rare. Residents' beliefs about their level of safety seem to be influenced more by how competent they perceive the staff to be than by the frequency of violence. The findings from the site visits pointed to two steps to increase safety: creating a weapon-free environment by searching all patients and finding ways to improve compliance with existing safety measures.

Data Collection↗
PubMed1992

Cyclosporin A potentiation of VP-16: production of long-term survival in murine acute lymphatic leukemia.

Our prior in vitro studies on the correction of multidrug resistance by cyclosporin A (CsA) prompted us to investigate the effect of CsA and VP-16 in vivo. CsA given simultaneously at 2 or 10 mg/kg with VP-16 to BDF/1 mice bearing parental drug-sensitive P388 or L1210 lymphatic leukemia produced a 100% increase in survival as compared with VP-16 treatment alone. CsA-containing regimens also promoted 60-day survival in a significant number of P388 or L1210 leukemia-bearing mice as compared with animals receiving VP-16 in the absence of CsA (P < 0.02 and P < 0.001, respectively). CsA enhancement of the survival of mice bearing these lymphatic leukemias is restricted to VP-16, since the addition of CsA to therapeutic agents such as vincristine, daunorubicin, methotrexate, or cisplatin had no effect on survival.

Animals↗
PubMed1991

Development of cyclosporin A mediated immunity in L1210 leukaemia.

Cyclosporin A (CsA) is an effective modulator of multidrug resistance (MDR) in vitro and in murine tumour systems in vivo. We now report the production of immunity to L1210 leukaemia by the addition of CsA to VP-16 therapy of leukaemic BDF/1 mice. VP-16/cyclosporin A tumour immunity induction arises as a consequence of active therapy independently of immunisation with modified tumour cells. The addition of CsA to VP-16 prolongs survival of BDF/1 host mice bearing L1210 leukaemia beyond that produced by equivalent dose VP-16 alone. A subpopulation of 60-day surviving mice after combined VP-16/CsA are immune to rechallenge with the same leukaemia inoculum to which they were originally exposed. Spleen cells from immune mice adoptively transfer anti-L1210 leukaemia immunity to untreated BDF/1 mice in a dose dependent, statistically significant manner. Adoptive transfer experiments additionally suggest active recruitment of immunologic response in recipient animals: (1) We have been able to perpetuate leukaemia immunity in four sequential cohorts of naive recipient mice. This propogation of adoptive immunity is accomplished by use of spleen cells harvested from each preceeding passively-protected animal cohort; (2) Cyclophosphamide pretreatment of adoptive transfer recipient mice abrogates the ability of their splenocytes to perpetuate passive protection in sequential adoptive transfer experiments.

Animals↗
PubMed1987

Enhancement by cyclosporin A of daunorubicin efficacy in Ehrlich ascites carcinoma and murine hepatoma 129.

Cyclosporin A abrogates pleiotropic drug resistance in certain experimental tumors. Its impact on drug-sensitive tumors has not been investigated. Our studies show that in drug-sensitive Ehrlich ascites carcinoma and hepatoma 129 cyclosporin A enhances daunorubicin inhibition of DNA synthesis in vitro and prolongs survival of host mice in vivo. Of particular interest is that cyclosporin A converts ineffective daunorubicin regimens into those which result in prolongation of host mice survival. Other agents known to reverse pleiotropic drug resistance are reported to exert their effects by increasing intracellular drug accumulation. In contrast, our studies of drug transport in drug-sensitive Ehrlich ascites carcinoma and hepatoma 129 show that cyclosporin A causes minimal enhancement of [3H]daunorubicin uptake without inhibition of [3H]daunorubicin efflux in both the presence and absence of interrupted active daunorubicin efflux. This suggests that the mechanism of action of daunorubicin enhancement by cyclosporin A in drug-sensitive tumors is not simply the result of increased intracellular daunorubicin accumulation. In vivo dosages of cyclosporin A in the current study are comparable to those which can be used with reasonable safety in humans. We conclude that cyclosporin A may be useful in the potentiation of anthracycline antibiotic therapy directed against drug-sensitive as well as drug-resistant tumors.

Animals↗