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M Montoya

Publications and source records attributed to M Montoya.

At least 37 records · Page 2Linked to original sources
PubMed1999

Intracellular rate-limiting steps in MHC class I antigen processing.

Quantitative aspects of the endogenous pathway of Ag processing and presentation by MHC class I molecules to CD8+ CTL were analyzed over a wide range of Ag expression in recombinant vaccinia virus-infected cells expressing beta-galactosidase as model Ag. Only the amount of starting Ag was varied, leaving other factors unaltered. Below a certain level of Ag synthesis, increasing protein amounts led to a sharp rise in recognition by CTL. Higher levels of Ag expression led to a saturation point, which intracellularly limited the number of naturally processed peptides bound to MHC and thereby also CTL recognition. The rate-limiting step was located at the binding of the antigenic peptide to MHC inside the vaccinia virus-infected cell or before this event.

Animals↗
PubMed1999

Survey of three bacterial louse-associated diseases among rural Andean communities in Peru: prevalence of epidemic typhus, trench fever, and relapsing fever.

Typhus and other louse-transmitted bacterial infections in Peruvian sierra communities are known to occur but have not recently been assessed. In this study, 194 of 1,280 inhabitants of four villages in Calca Province in the Urubamba Valley were included. Thirty-nine (20%) of the 194 volunteers had antibodies to Rickettsia prowazekii, whereas 24 (12%) had antibodies to Bartonella quintana and 2 against Borrelia recurrentis. There was a significant correlation between the presence of infesting ectoparasites and antibodies to R. prowazekii, as well as between antibodies to R. prowazekii and ectoparasite infestation and fever in the previous 6 months. The proportion of inhabitants infested with ectoparasites was significantly higher in the highest-altitude village than in the other three villages. Two volunteers' antibody levels suggested a recent typhus infection, but only B. quintana DNA was amplified from lice. Epidemic typhus remains extant in the area, and B. quintana infections were encountered and documented for the first time in South America.

Adult↗
PubMed1997

17 beta-Estradiol enhances the outgrowth and survival of neocortical neurons in culture.

Results of this investigation demonstrate that exposure to 17 beta-estradiol differentially and significantly regulates cortical nerve cell outgrowth depending on the cortical region. Parietal and occipital neurons treated with 1 nM 17 beta-estradiol showed a greater magnitude of neuronal outgrowth whereas outgrowth of temporal cortex neurons was decreased in the presence of 1 nM 17 beta-estradiol. Frontal cortex neurons showed a consistent enhancement of neuronal outgrowth that did not reach statistical significance. The dose response profile for 17 beta-estradiol regulation of the macromorphological features exhibited a bimodal dose response relationship whereas the dose response profile for 17 beta-estradiol regulation of the micromorphological features exhibited a dose response more characteristic of an inverted V-shaped function. An antagonist to the NMDA receptor antagonist, AP5, abolished the growth promoting effect of 17 beta-estradiol whereas the nuclear estrogen receptor antagonist ICI 182,780 did not. Lastly, neocortical neurons exposed to 17 beta-estradiol exhibited greater viability and survival than control neurons over a two week period. These data indicate that 17 beta-estradiol can enhance the growth and viability of select populations of neocortical neurons and that the growth promoting effects of 17 beta-estradiol can be blocked by an antagonist to the NMDA glutamate receptor and not by an antagonist to the estrogen nuclear receptor.

Animals↗
PubMed1995

Efficacy of Acylfulvene Illudin analogues against a metastatic lung carcinoma MV522 xenograft nonresponsive to traditional anticancer agents: retention of activity against various mdr phenotypes and unusual cytotoxicity against ERCC2 and ERCC3 DNA helicase-deficient cells.

Four second-generation Illudin analogues were synthesized and tested for antitumor activity using a metastatic lung carcinoma xenograft model resistant to conventional antitumor agents. One analogue, the parent illudofulvene-derivative called Acylfulvene, inhibited xenograft primary tumor growth and prolonged life span of tumor-bearing animals when administered i.p. or i.v. The efficacy of Acylfulvene exceeded that of mitomycin C, cisplatin, paclitaxol, the parent compound Illudin S, and an earlier analogue, dehydroilludin M. Promising features of this new analogue are: (a) the retention of in vitro activity against a variety of mdr tumor phenotypes including gp170+, gp150+, GSHTR-Pi, topoisomerase I, and topoisomerase II mutants; and (b) an apparent selective cytotoxicity toward cells deficient in either ERCC2 or ERCC3 DNA helicase activity.

Adenocarcinoma↗
PubMed1995

Transfection with human copper-zinc superoxide dismutase induces bidirectional alterations in other antioxidant enzymes, proteins, growth factor response, and paraquat resistance.

Transfection of a pSV2 human copper-zinc superoxide dismutase expression vector into murine fibroblasts resulted in stable transgenic clones producing increased amounts of copper-zinc superoxide dismutase. Two classes of transfectants were observed and were characterized by the presence or absence of an increase in endogenous glutathione peroxidase activity. In addition, increases and decreases in individual clones in the activities of manganese superoxide dismutase, glutathione reductase, and NADPH-reductase were detected. In general, these alterations in enzyme activity correlated to the cellular glutathione peroxidase/copper-zinc superoxide dismutase ratio. Parameters of cellular physiological functions were also altered, including cell division time, FGF and EGF response, fibronectin content, paraquat resistance, hydrogen peroxide release into media, and sensitivity to radiation. Some of these cellular parameters were also bidirectional and reflected the cellular glutathione peroxidase/copper-zinc superoxide dismutase ratio. Our results indicate that small deviations from the normal physiological copper-zinc superoxide dismutase/seleno-glutathione peroxidase ratios can have pronounced effects on other antioxidant enzymes, growth rate, growth factor response, and expression of proteins normally not associated with oxygen metabolism.

3T3 Cells↗
PubMed1994

Characterization of illudin S sensitivity in DNA repair-deficient Chinese hamster cells. Unusually high sensitivity of ERCC2 and ERCC3 DNA helicase-deficient mutants in comparison to other chemotherapeutic agents.

Illudins, novel natural products with a structure unrelated to any other known chemical, display potent in vitro and in vivo anti-cancer activity against even multi-drug resistant tumors, and are metabolically activated to an unstable intermediate that binds to DNA. The DNA damage produced by illudins, however, appears to differ from that of other known DNA damaging toxins. The sensitivity pattern of the various UV-sensitive cell lines differs from previously studied DNA cross-linking agents. Normally, the ERCC1- (excision repair cross complementing) and ERCC4-deficient cell lines are most sensitive to DNA cross-linking agents, with ERCC2-, ERCC3- and ERCC5-deficient cell lines having minimal sensitivity. With illudins the pattern is reversed, with ERCC2 and ERCC3 being the most sensitive. The sensitivity to illudins in complementation groups 1 through 3 is due to a deficiency of the ERCC1-3 gene products, as cellular drug accumulation studies revealed no differences in transport capacity or total drug accumulation. Also, a transgenic cell line in which ERCC2 activity was expressed through an expression vector regained its relative resistance to the illudins. The EM9 cell line, which displays sensitivity to monoadduct producing chemicals, was not sensitive. Thus, excision repair is involved in repair of illudin-induced damage and, unlike other anti-cancer agents, the involvement of ERCC2 and ERCC3 helicases is critical for repair to occur. The requirement for ERCC2 and ERCC3, combined with the finding that ERCC1 but not ERCC2 is upregulated in drug-resistant tumors, may explain the efficacy of illudins against drug-resistant tumors. The inhibition of DNA synthesis in cells within minutes after exposure to illudins at nanomolar concentrations may be related to the finding that the ERCC3 gene product is actually the p89 helicase component of the BTF2 (TFII) basic transcription factor and the high sensitivity of ERCC3-deficient cells to illudins.

Animals↗
PubMed1992

HPLC determination of a new anticancer agent (acylfulvene) in serum.

High performance liquid chromatography (HPLC) combined with effective preseparation steps (liquid extraction, solid-phase extraction, preconcentration procedures) was used in pharmacokinetic studies of a novel anticancer agent (acylfulvene) in serum. HPLC conditions were optimized for the analysis of model clinical samples and real serum samples with different contents of acylfulvene. Extraction recoveries for both extraction procedures were evaluated and linearity was achieved for a wide concentration range. Detection limit for acylfulvene in serum was 0.075 microgram/ml, preconcentration minimum 5 times was recommended, especially after the solid-phase extraction step. The HPLC assay was applied for pharmacokinetic studies of acylfulvene in dogs and rats and pharmacokinetic parameters were determined.

Animals↗
PubMed1990

Characterization of a factor-dependent acute leukemia cell line with translocation (3;3)(q21;q26).

A strictly factor-dependent cell line (UCSD/AML1) was established from a patient with the syndrome of multilineage acute leukemia with high platelets. The patient's cells and the cell line karyotype were 45,XX,-7,t(3;3)(q21;q26), typical of the syndrome of acute leukemia with high platelets. The cell line expresses CD34, CD7, TdT, and myeloid (CD13, CD14, CD33) and megakaryocyte/platelet (CD36, CD41, CD42b, CDw49b) antigens. In short-term culture, UCSD/AML1 cells proliferate in response to interleukin-3 (IL-3), IL-4, IL-6, macrophage colony-stimulating factor (M-CSF), and granulocyte-macrophage CSF (GM-CSF), but not IL-1, IL-2, IL-5, or G-CSF. In long-term culture, proliferation can be sustained by GM-CSF, IL-6, or M-CSF. When maintained in GM-CSF, a small percentage of cells form multinucleated megakaryocyte-like giant cells. Culture with GM-CSF combined with IL-6, but not with IL-6 alone, increased giant cell formation fourfold to sevenfold. IL-6 alone or in combination with GM-CSF increased expression of platelet-related antigens. In contrast, culture with phorbol ester induced formation of macrophage-like cells. UCSD/AML1 is the first human acute nonlymphocytic leukemia cell line established from a patient with an acute leukemia syndrome associated with a specific chromosome abnormality.

Acute Disease↗
PubMed1988

Stability of St. Louis encephalitis viral antigen detected by enzyme immunoassay in infected mosquitoes.

The use of enzyme immunoassay to detect St. Louis encephalitis (SLE) viral antigen in vector mosquitoes enhances the effectiveness of surveillance because infected mosquitoes can be identified more rapidly than with conventional virus isolation systems and because it is a simple and accessible procedure. Infectivity among mosquitoes experimentally infected with SLE virus was lost within 24 h after the mosquitoes were stored at 27 degrees C and 80% relative humidity; however, viral antigen remained stable under these conditions and could be detected by enzyme immunoassay 2 weeks later. Desiccation further extended the period during which antigen could be detected to 6 weeks. Absorbances were higher in infected mosquitoes stored at 27 degrees C than in mosquitoes frozen continuously. Absorbances in infected mosquitoes also increased after repeated freezing and thawing and sonication. Both phenomena may be related to the release of antigen from decaying or disrupted cells. The relative stability of SLE viral antigen at ambient temperatures lends flexibility to schemes which use direct antigen detection to identify vectors. Surveillance systems can be designed without regard to collecting living mosquitoes, and a cold chain in unnecessary to preserve specimens, thus reducing the cost of surveillance and expanding the geographic areas to which it is accessible.

Animals↗
PubMed1987

Detection of St. Louis encephalitis virus antigen in mosquitoes by capture enzyme immunoassay.

Surveillance methods that measure St. Louis encephalitis (SLE) virus activity in nature may provide forewarning of its epidemic occurrence in humans. An antigen capture enzyme immunoassay was developed to detect SLE virus in infected mosquitoes. The assay detected purified SLE viral antigen at a concentration of 62 pg/0.1 ml when antigen was incubated overnight; 250 pg/0.1 ml was detected in a single-day assay (antigen incubated for 3 h). The assay detected 67.9 and 70.8% of laboratory-prepared pools of infected mosquitoes after 3 h and overnight incubation, respectively. The sensitivity of the procedure was 90.5% in identifying pools with infectious titers greater than dex 3.0. The specificity of the assay was controlled by retesting positive pools preincubated with SLE virus and normal antibodies, which led to a diminution of signal in the pools containing viral antigen. The procedure was suitably specific in discriminating between SLE and related flaviviruses, detecting only high infectious doses of heterologous antigens.

Animals↗
PubMed1987

Development changes in the human cardiac isomyosin distribution: an immunohistochemical study using monoclonal antibodies.

With monoclonal antibodies (Mab) specific for myosin heavy chain (MHC) isozymes, we have investigated the isomyosin content of atrial, ventricular and conductive fibers of 19 human fetuses (ranging from 14-36 weeks of gestation) and 3 newborns (2 days-2 weeks). In addition, the conduction system of 2 human adult hearts was studied. The fetal atrium is composed mostly of alpha-MHC during the first 23 weeks of gestation. beta-MHC is already expressed as traces at 14 weeks of gestation, and its expression increases progressively until birth, resulting in a great augmentation in beta-MHC. During this course, beta-MHC always predominates in certain areas (the crista terminalis and the interatrial septum) but not in other areas (the auricles). Preceding birth, the fetal ventricle is composed mostly of beta-MHC. From 14 weeks of gestation to birth, alpha-MHC is expressed in very rare fibers. Then, after birth, a large number of fibers simultaneously synthesize alpha-MHC. The AV node and His bundle system were labelled with anti-alpha and anti-beta Mab in fetal, newborn, and adult hearts with a double gradient of distribution: spatial (a higher proportion of alpha-containing fibers in the AV node than in the distal portion of the bundle of branches) and temporal (a higher proportion of alpha-containing fibers at a given point in fetal development than in the adult heart). One of the twenty-five hearts studied had an isomyosin distribution pattern not accorded to its age. Interestingly, it was clinically diagnosed as having idiopathic hypertrophic cardiomyopathy.

Antibodies, Monoclonal↗
PubMed1984

The participation of Hispanics in US schools of Public Health, 1975-79.

Hispanic student and faculty representation at US Schools of Public Health from 1975-1979 was investigated. Findings indicate a substantial underrepresentation of Hispanic students and faculty members at these schools. Hispanic public health graduates were found to be less likely than other graduates to receive an MPH degree or a doctorate. It appears that the University of Puerto Rico graduates one-half of all Hispanic graduates and employs two-thirds of all Hispanic public health faculty.

Education, Graduate↗
PubMed1981

Transovarial transmission of St. Louis encephalitis virus by Culex pipiens complex mosquitoes.

Experiments were conducted to determine whether transovarial transmission (TOT) of St. Louis encephalitis (SLE) virus occurs in Culex pipiens complex mosquitoes, the principal vectors of SLE virus in the central-eastern United States. In 1978, field-collected mosquitoes from Memphis, Tennessee, and McLeansboro, Illinois, were used; during 1979, colonized mosquitoes from Chicago, Illinois, and Memphis, Tennessee, were used. Mosquitoes were infected by feeding on viremic chicks inoculated with an SLE virus strain isolated from Cx. pipiens complex mosquitoes collected from Memphis, Tennessee, in 1976. During the 1979 experiments, progeny larval and adult mosquitoes were held at two temperatures, 18 and 25 degrees C. Progeny were tested for virus by plaque assay in duck embryo cell cultures and by inoculation of Aedes albopictus C6/36 cells and examination by immunofluorescence. In 1978, most of the progeny tested were from the first ovarian cycle, and a single occurrence of TOT was documented. In 1979, a single TOT occurred from 46,856 first ovarian cycle progeny, whereas 7 of 9,234 progeny of the second ovarian cycle were infected. The rate of TOT was higher for progeny of Memphis than Chicago mosquitoes, and for mosquitoes held at 18 degrees C than at 25 degrees C; however, these differences were not statistically significant. Four positive pools were females, and three were fed on chicks for transmission attempts. The positive Chicago mosquito pool failed to transmit, but both Memphis pools successfully transmitted virus. The overall rates of TOT of SLE virus in progeny of the first and second ovarian cycle were, respectively, 1/45, 151 and 1/1,460. The significance of these results as they relate to the natural history of SLE virus is discussed.

Animals↗
PubMedDate not supplied

The women's health initiative estrogen replacement therapy is neurotrophic and neuroprotective.

The current study investigated the neurotrophic and neuroprotective action of the complex formulation of conjugated equine estrogens (CEEs), the most frequently prescribed estrogen replacement therapy in the United States and the estrogen replacement therapy of the Women's Health Initiative. Morphologic analyses demonstrated that CEEs significantly increased neuronal outgrowth in hippocampal, basal forebrain, occipital, parietal and frontal cortex neurons. Dose-response analyses indicated that the lowest effective concentration of CEEs exerted the maximal neurotrophic effect with greatest potency occurring in hippocampal and occipital cortex neurons. CEES induced highly significant neuroprotection against beta amyloid(25-35), hydrogen peroxide and glutamate-induced toxicity. Rank order of potency and magnitude of CEE-induced neuroprotection in the brain regions investigated was hippocampal neurons > basal forebrain neurons > cortical neurons. In hippocampal neurons pre-exposed to beta amyloid(25-35), CEEs halted Abeta(25-35)-induced cell death and protected surviving neurons from further cell death induced by Abeta(25-35). Because CEEs are the estrogen replacement therapy of the Women's Health Initiative, results of the current study could provide cellular mechanisms for understanding effects of CEEs on cognitive function and risk of Alzheimer's disease derived from this prospective clinical trial.

Adenosine Triphosphate↗