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Biomedical subjects

M C Pérez

Publications and source records attributed to M C Pérez.

At least 19 recordsLinked to original sources
PubMed2007

The corrosion of nickel-titanium rotary endodontic instruments in sodium hypochlorite.

AIM: To evaluate the corrosion resistance of nickel-titanium (NiTi) endodontic rotary instruments immersed in 5.25% sodium hypochlorite (NaOCl) solution. METHODOLOGY: The corrosion performance of NiTi instruments (S1 25 mm, ProTaper Dentsplay Maillefer, Ballaigues, Switzerland) was evaluated using commercial 5.25% NaOCl solution (pH = 12.3), and the same solution partially neutralized adding H2SO4 to reach pH = 10.1. Electrochemical measurements were carried out using a potentiostat equipped with a five-channel zero resistance ammeter (ZRA) for galvanic current measurements. The instruments were sectioned into three parts (cutting part, noncutting part and shank) and degreased with acetone and rinsing with demineralized water prior to being immersed in NaOCl solution for testing. Each set of the three parts constituted one 'virtual' instrument through the ZRA, giving access to the galvanic currents that circulate between the three parts. Nine instruments were employed to check the reproducibility of the electrochemical measurements. RESULTS: The corrosion potential (E(corr)) of the NiTi alloy reached the passive domain in approximately 20 s of immersion in the solution having a pH 10.1. After this initial period the potential remained steady, indicating that stable passivation was achieved. However, at pH 12.3 no stationary state was achieved even after 6000 s of immersion time. Thus, the alloy was not stable in this medium from a corrosion point of view. CONCLUSIONS: The corrosion resistance of NiTi alloy was enhanced by lowering the pH of NaOCl solution to 10.1, which allows the system to reach the stability domain of the passivating species TiO2 and NiO2.

Corrosion↗
PubMed2005

Effect of plane of nutrition on seasonality of reproduction in Spanish Payoya goats.

The aim of this study was to determine if there is a seasonal pattern of sexual activity in female Payoya goats and if this seasonality could be modulated by nutrition. During the experimental period of 20 months, 43 non-pregnant adults goats were penned under natural photoperiod at latitude 37 degrees 15'N. At the onset of the experiment, the animals were allocated to three experimental groups differing in the level of nutrition and whether the animals were entire or ovariectomized does. The high nutrition group (H, n = 16 entire does) receiving 1.5 times maintenance requirements. The low nutrition group (L, n = 16 entire does) and an ovariectomized and oestradiol treated group (OVX, n = 11 ovariectomized does) received a diet supporting their maintenance requirements. The groups were balanced for live weight (LW) and body condition score (BCS) at the beginning of the study. In entire goats, oestrus was tested daily using aproned males, ovulation rate was assessed by laparoscopy 7 days after identification of oestrus and plasma samples were obtained twice per week for progesterone assay. OVX goats were isolated from the other groups and bucks, plasma samples were assayed twice per week for LH and there were four intensive sampling periods during the year to determine LH pulsatility. LW and BCS were recorded for all animals once a week. A clear circannual cycle in live weight change was observed in all experimental groups, being relatively stable or slightly decreasing in summer and autumn and increasing during winter and spring. The effect of exposure to high (H) rather than low (L) nutrition was to cause earlier onset of ovarian activity (5 versus 17 August; P < 0.05), and expression of oestrous (16 August versus 2 September; P < 0.01) and later cessation of reproductive activity (ovulation 11 February versus 17 January; P < 0.01). Consequently, seasonal anoestrus was 32 days shorter in does on the higher plane of nutrition (P < 0.01). The seasonality of reproductive activity was confirmed in the OVX does, with reduced LH concentrations during spring and summer, and increased LH concentrations in autumn and winter. There was no effect of nutrition on ovulation rate. These results demonstrate that the female Payoya goat exhibits marked reproductive seasonality which is modulated by nutrition but possibly not ovulation rate.

Animals↗
PubMed2005

Pyrrolidon carboxypeptidase activities in the hypothalamus-pituitary-thyroid and hypothalamus-pituitary-ovary axes of rats with mammary gland cancer induced by N-methyl nitrosourea.

Pyrrolidon carboxypeptidase is an omega-peptidase that hydrolyses N-terminal pyroglutamyl residues from biologically active peptides such as gonadotropin-releasing and thyrotrophin-releasing hormones. We previously described a decrease in both rat and human pyrrolidon carboxypeptidase activity with breast cancer, suggesting that gonadotropin-releasing hormone may be an important local intracrine, autocrine and/or paracrine hormonal factor in the pathogenesis of breast cancer while playing a role in the tumoral process. However, the other susceptible substrate of pyrrolidon carboxypeptidase, thyrotrophin-releasing hormone, may also be modified with breast cancer, supporting an association between breast cancer and thyroid disorders. The present work analyses soluble and membrane-bound pyrrolidon carboxypeptidase activities in the hypothalamus-pituitary-thyroid and hypothalamus-pituitary-ovary axes in N-methyl nitrosourea-induced breast cancer in rats. Our aim was to determine the possible relationship between gonadotropin-releasing hormone and thyrotrophin-releasing hormone regulation through pyrrolidon carboxypeptidase activity. We propose that pyrrolidon carboxypeptidase activity dysregulation at various local and systemic levels may participate in the initiation, promotion and progression of breast cancer induced in rat by N-methyl nitrosourea through the increase in gonadotropin-releasing hormone. Since pyrrolidon carboxypeptidase activity also acts on thyrotrophin-releasing hormone, the dysregulation of this enzyme's activity could indirectly affect hypothalamus-pituitary-thyroid axis function, and thus potentially represent a link between the diseases of thyroid and breast cancer.

Animals↗
PubMed2001

SC-1, an antimycotic spirostan saponin from Solanum chrysotrichum.

A new antimycotic steroidal saponin named SC-1 has been isolated from the leaves of Solanum chrysotrichum by bioassay-guided fractionation. The structure of SC-1 was characterized as 3-O-[beta-quinovopyranosyl(1-->6)-beta-glucopyranosyl(1-->6)-beta- glucopyranosyl]chlorogenin on the basis of spectral analyses and chemical evidence.

Antifungal Agents↗
PubMed2000

[Epidemiologic study of infection by hepatitis C virus in a hemodialysis unit].

OBJECTIVE: To analyze the prevalence of infection, the frequency of HCV genotypes and the epidemiology characteristics among the patients in hemodialysis treatment in one 25 years old hospital hemodialysis center and one 15 years old secondary unit by a transversal cross-section study in 1998. PATIENTS AND METHODS: 171 hemodialyzed-patients were studied. Patients sera were analyzed by the presence of HCV antibodies anti-VHC by a enzymoimmunoassay (Abbott Cientifica) and the presence of antibodies was confirmed by a line immunoassay (Inno-LIA HCV AbIII) and by the presence of VHC-RNA by reverse transcriptase PCR (Cobas Amplicor HCV). Genotypes were determinate by reverse hybridization (Inno-LIA HCV III). RESULTS: Fifty (29.2%) of the patients were HCV antibody positive. Forty-five (26.3%) were HCV-RNA positive, all of them with antibodies positive. The distribution of genotypes was: 1b, 34 (75.5%); 4f, 4 (8.9%); 1a, 3 (6.7%); 1, 3 (6.7%) and 1 case could not be typed (2.2%). In 14 patients (28.0%), seroconversions were documented Twenty-one patients (42.0%) were diagnosed when the routine tests were available and 15 patients (30.0%) were diagnosed pre-dialysis. The multivariate analysis showed that the risk of HCV infection was greater for patients who had been more 8 years on dialysis (OR: 6.22; 95% CI: 1.24-31.07). CONCLUSIONS: Data presented indicate that the prevalence of HCV infections in our hemodialysis units and the number of seroconversions were high and the HCV subtype 1b was more frequent; because of this, the screening by both serological and molecular methods is necessary, at least twice a year, to identify all the infected patients. Besides, we think that is necessary to increase the control of the completion of the Universal Precautions.

Cross-Sectional Studies↗
PubMed1999

[The importance of polymerase chain reaction in the diagnosis of enterovirus infections of the central nervous system in children. Clinico-epidemiologic characteristics].

BACKGROUND: To compare the diagnosis utility of a reverse transcription-polymerase chain reaction (RT-PCR) for detection of enteroviral RNA in cerebrospinal fluid (CSF) in comparison to viral culture for central nervous system infections in pediatric population and to know the clinic epidemiological characteristics of this infection. METHODS: From June to December of 1997, 116 CSF samples of children were included in the study. The samples were inoculated in MRC-5 and HEP-2 and the enterovirus RNA was detected with AMPLICOR-Enterovirus (Roche Diagnostic System). The virus were typed by neutralization. RESULTS: 36 samples were positive (30 were positive for RT-PCR and 6 for RT-PCR and viral culture). The media time in detect the CPE was 4.8 days. The viruses found were four echovirus 6, one echovirus 30 and one echovirus 7. Fifteen children were under 6 months (93.3% under two months) and 21 children over 6 months with a media age of 81 months (range, 38-160 months). In over 6 months old children, the most frequent clinical presentation was meningitis aseptic syndrome with pleocytosis and in under 6 months old ones was fever and only 60% of these children had pleocytosis. The evolution was good in all the cases. CONCLUSIONS: AMPLICOR-Enterovirus is a sensitive method for the diagnosis of enteroviral meningitis. The clinical manifestations are different with the age and due to the absence of neurological symptoms and pleocytosis in the patients under two months, we think that it is necessary to study the presence of enterovirus with genetic amplification methods in this population of patients.

Central Nervous System Infections↗
PubMed1998

Hemodynamic effect of 17 beta-estradiol in absence of NO in ovariectomized rats: role of angiotensin II.

Previous reports correlate plasma levels of estrogen with increased nitric oxide (NO) production. To investigate whether the hemodynamic effects of estrogens are mediated by NO, we compared the hemodynamic changes induced by 17 beta-estradiol (100 micrograms/kg) in the absence and presence of the NO synthesis inhibitor N omega-nitro-L-arginine methyl ester (L-NAME). All protocols were performed in ovariectomized, conscious rats. Estradiol alone resulted in no significant changes in cardiac index (CI) or mean arterial pressure (MAP). However, in the presence of L-NAME, estradiol induced a significant increase in total peripheral resistance (TPR) of 37.3 +/- 11.7% and a decrease in CI of 27 +/- 4.9%, without changes in MAP. Previous blockade of angiotensin II AT1 receptors with losartan prevented any change in CI and TPR induced by 17 beta-estradiol in the presence of L-NAME. These observations suggest that NO is necessary to offset a vasoconstrictor action of angiotensin II, which is stimulated by estradiol administration.

Angiotensin II↗
PubMed1998

Expression of functional estrogen receptors and galanin messenger ribonucleic acid in immortalized luteinizing hormone-releasing hormone neurons: estrogenic control of galanin gene expression.

The activity of estradiol on the LHRH neuronal network is crucial in the regulation of reproduction. In vivo, estradiol induces galanin (GAL) gene expression in LHRH neurons and GAL/LHRH colocalization is sexually dimorphic and neonatally determined by steroid exposure. The effects of estradiol on LHRH neurons, however, are considered to be indirect because estrogen receptors (ER) have not been detected in LHRH neurons in vivo. Using immortalized mouse LHRH neurons (GT1-7 cells), we demonstrated by RT-PCR and Southern blotting that GT1-7 cells express ER messenger RNA (mRNA). Sequencing of the amplification products indicated that GT1-7 ER is of the alpha-subtype (ER alpha). Additionally, estrogen receptors in GT1-7 cells were characterized by competitive radioligand receptor binding and IC50 values for 17beta-estradiol and ICI-182,780 were found to be 0.24 and 4.1 nM, respectively. The ability of endogenous GT1-7 cell ER to regulate transcription was determined in transient transfection studies using a construct that consisted of a luciferase reporter gene that is driven by tandem estrogen response elements (ERE) and a minimal herpes simplex virus thymidine kinase promoter. 17Beta-estradiol was found to enhance luciferase activity by 2.5-fold at physiological concentrations with an ED50 value of 47 pM. This induction was completely inhibited by ICI-182,780 which had an IC50 value of 4.8 nM. Raloxifene, tamoxifen, 4-hydroxytamoxifen, and droloxifene also fully blocked estrogen-mediated luciferase induction with IC50 values of 58.4, 89.2, 33.2, and 49.8 nM, respectively. In addition, GAL mRNA was detected and identified by RT-PCR followed by Southern blotting using a rat GAL complementary DNA (cDNA) probe. The ability of 17beta-estradiol to modulate expression of the endogenous GAL gene in immortalized LHRH neurons was also determined. Quantitative RT-PCR demonstrated that physiological concentrations of estrogen increase GAL gene expression by 2-fold with an ED50 value of 23 pM. ICI-182,780, raloxifene, and droloxifene completely blocked this induction. In summary, our data demonstrate the presence of ER alpha and GAL mRNA in GT1-7 cells. The ER in GT1-7 cells is biologically active because 17beta-estradiol enhances both endogenous GAL gene expression and an ERE-driven reporter gene. These results suggest that estrogenic control of GAL gene expression in immortalized LHRH neurons may be transduced by ER. Thus, hypothalamic-derived LHRH neurons appear to have the capacity to be directly regulated by estrogen.

Animals↗
PubMed1998

[Usefulness of determining low-avidity IgG antibodies in the diagnosis of primary rubella infection in pregnant women].

BACKGROUND: It is necessary to have an easy and quickly test to distinguish "false positive" rubella IgM results and residual antibodies from the antibodies produced in the primary infection, in pregnant women. The avidity of IgG antibodies test seems to differentiate between primary rubella infection and past infections, reinfections or postvaccination, showing its utility in the diagnosis of primary infection in other infectious diseases. METHOD: For 30 months, 178 sera from 157 patients with clinical and/or epidemiological rubella suspicion or with a positive rubella IgM result as result of an accidental serological finding, were remitted to our laboratory for a serological follow up. We distinguished 3 patient groups: outbreak group, 112; pregnant women, 36, and newborn 11. Rubella IgM antibodies by indirect EIA previous the rheumatoid factor absorption; IgG antibodies of low avidity by indirect EIA previous treatment of serum with 6 M urea, were detected in the sera. It considered a positive result, a rubella avidity index (AI) < 50%. RESULTS: In the epidemic outbreak group, 90.2% of the patients were not vaccinated. 80% of cases occurred in young men between 14 an 20 years old. From 109 patients (97.3%) with rubella IgG antibodies, 92 (84.4%) showed AI-IgG lower than 50%. In this group, the mean rate of AI-IgG rubella was 29.0%. In the pregnant women group, except for two of them, rubella IgM antibodies were an accidental finding in a serological pregnancy screening. Thirty patients (83.8%) showed AI-IgG rubella > 50%. The two pregnant women who had evidence of clinical and epidemiological rubella showed AI-IgG rubella of 37.4% and 20.9%. Another four pregnant women showed AI-IgG rubella close to cut-off (44.7-49.0%). The mean AI-IgG rubella in this group was 71.8%. The mean AI-IgG Rubella between the epidemic outbreak group and the pregnant women group, 29.0 and 71.8% respectively, was statistical significance (p < 0.001). CONCLUSIONS: The avidity IgG test is simple and quickly, and it allow to exclude most of positive results because of residual IgM antibodies and false reactive.

Adolescent↗
PubMed1998

[Prevalence of hepatitis C virus genotypes: epidemiology and histologic characteristics].

OBJECTIVE: To analyse the prevalence of HCV genotypes among patients from Gran Canaria and the relation with the routes of viral transmission, date of primoinfection and severity of hepatic lesion. PATIENTS AND METHODS: 179 patients were studied. In 61 patients the date of exposure was determinate. Liver biopsies were obtained in 139 patients. Genotypes were determinate by reverse hybridisation using InnoLiPA genotyping kit (Innogenetics). RESULTS: The distribution of genotypes was: 1b, 114 (63.7%), 1a, 30 (16.7%); 1, 17 (9.5%); 3a, 7 (3.9%); 4c/4d, 6 (3.3%); 2, 1 (0.5%); 2a/2c, 2 (1.1%), 3, 1 (0.5%) and 4f, 1 (0.5%). We did not find any case of coinfection with a second genotype. In univariable analysis, we found statistically differences in sex (78.9% of women infected with genotype 1b compared with 55.1% of men, p < 0.01 and 31.6% of men infected with 1a, 3a and 4c/4d compared with 15.7% of women, p < 0.01) and age (median age in genotype 1b 45 +/- 12 years vs 36 +/- 9 years in the other genotypes, p < 0.01). HCV subtypes 1a and 3a were predominant in patients IVDA (47.6% and 23.85% respectively) and 1b in blood transfusion receptors (71.2%) (p < 0.01). In 40.2% of the patients, the sources of infection were unknown. In the multivariable logistical regression analysis we found the only factor influencing the genotypes distribution was the transmission mechanism (p < 0.001) and sex and age are relationated with the transmission mode. The media infection duration in patients infected with 1b was 22 +/- 11 years vs 9 +/- 6 years in the other genotypes. We found differences in the liver histologic findings and the age of the patient, but not in the different genotypes. CONCLUSIONS: Our study reflects the higher frequency of HCV subtype 1b in our area and a different prevalence of genotypes in relation to mode of transmission. Our results suggest that in our media the liver damage seems to be directly influenced by the age of the patient, but not influenced by HCV genotype.

Adult↗
PubMed1997

[Performance of the IgG avidity test in patients with cytomegalovirus disease].

BACKGROUND: IgG antibodies produced early in infection has a low avidity to their respective epitopes, so that an assay to detect those antibodies could be easily used to diagnose a recent primary infection. A prospective study of anti-CMV IgG avidity test in patients with microbiological evidence of active CMV infection was made. METHODS: One hundred thirty-five patients were studied. All patients sera were tested for CMV antibodies "pool" IgG/IgM, IgM and antibody IgG avidity index (AI). Furthermore, samples of blood leucocytes from immunosuppressed patients to detect CMV viremia by conventional and shell-vial cell culture isolation and to detect CMV antigenemia, were processed. The avidity index IgG-CMV (AI IgG-CMV) less than 60% was defined as a positive result. CMV infection and disease were defined. RESULTS: The avidity index was < 60% in 16.3% of all patients and in 68.7% of patients with CMV disease. AI IgG-CMV was positive in 81.8% of patients with primary CMV disease and 9.1% with secondary CMV disease. The mean avidity index reading was 35% in primary CMV disease, 88.3% in secondary CMV disease (p < 0.001) and 87.9% in infected patients without CMV disease criterion (p < 0.001). The sensitivity, specificity, VPP and VPN of avidity index IgG-CMV were 85.7%, 97.4%, 75.0% and 94.9% respectively, in primary CMV disease diagnostic respect to all patients with microbiological evidence of active CMV infection. CONCLUSIONS: Avidity index IgG-CMV seems to be a good serological test to diagnose primary CMV disease with only one serum, probably with independence of patients immune state.

Adult↗
PubMed1996

[Disseminated infection by Mycobacterium scrofulaceum: apropos of 3 cases].

BACKGROUND: Mycobacterium avium-M. Intracellulare complex and Mycobacterium kansasii cause most of nontuberculous mycobacteria infections in AIDS patients in Spain. Mycobacterium scrofulaceum is rarely isolated as a cause of disseminated disease and most of case have been reported before the AIDS occurrence. METHODS: Three clinical cases of patients with disseminated disease caused by M.scrofulaceum and AIDS are reviewed. RESULTS: Clinical presentation in all cases was similar to those of other disseminated mycobacterial infection, and was also linked to severe immunosuppression (CD4 cell count < 100 CD4/mm3). CONCLUSIONS: In our area, M. scrofulaceum is the second species of nontuberculous mycobacteria causing disseminated disease in AIDS patients. The most frequent species is M. avium-M. intracellulare complex. For diagnosis an AIDS patient complaining of febrile syndrome without foci and severe immunosuppression, is mandatory to obtain blood cultures and biopsy or adenopathy aspirates if present. To our knowledge, these are the first reports in our country.

AIDS-Related Opportunistic Infections↗
PubMed1994

Renal effects of nitric oxide synthesis inhibition in cirrhotic rats.

In the present study, we have characterized the renal response to inhibition of endogenous nitric oxide (NO) synthesis [intravenous NG-nitro-L-arginine methyl ester (L-NAME) for 3 h] in anesthetized cirrhotic rats, with (ASC) and without (CIR) ascites, at doses that do not change blood pressure (BP). Administration of L-NAME induced opposite effects on water (UV) and sodium (UNaV) excretion in cirrhotic and control animals. Infusion of 1 microgram.kg-1.min-1 of L-NAME in CIR (n = 5) decreased renal plasma flow (RPF) at the end of the 3-h period, whereas UV, UNaV, and glomerular filtration rate (GFR) were unaltered. In contrast, infusion of L-NAME at 10 micrograms.kg-1.min-1 in six more CIR increased UV and UNaV significantly by the 1st h, without changes in BP or GFR, and these parameters remained elevated throughout the experiment. Infusion of 1 microgram.kg-1.min-1 in ASC (n = 6) did not change BP or GFR but significantly enhanced UV and UNaV after the 1st h. These effects were prevented by pretreatment with L-arginine (0.1 mg.kg-1.min-1) in another group of ASC infused with 1 microgram.kg-1.min-1 of L-NAME. These results indicate that, in ASC and CIR cirrhotic rats, inhibition of NO synthesis at nonpressor does improves renal excretion of sodium and water via a decrease in tubular reabsorption. NO is an important mediator of the renal excretory and hemodynamic alterations of experimental liver cirrhosis.

Amino Acid Oxidoreductases↗
PubMed1994

[Comparative study of the serologic response of IgA and IgM type in the diagnosis of acute toxoplasmosis].

BACKGROUND: IgM serologic response in the diagnosis of acute toxoplasmosis presents interpretation problems. A comparative study with IgA detection of antibodies was performed. METHODS: A parallel serologic study was carried out with IgM and IgA enzymoimmunoassay enhancement techniques in the sera of patients suspected of having toxoplasmosis. RESULTS: Positive results for IgM and/or IgA were presented in 74 sera (47 patients): 86.3% for the former and 58.9% for the latter (p < 0.001). The group of IgA-/IgA+ sera presented a low mean of proportionality index (PI): 1.6 versus the IgM+ sera group in the context of IgG seroconversion with a PI of 3.4 (p < 0.001). Out of the 9 patients with demonstrated IgG, all were IgA+ and seven IgM+. CONCLUSIONS: The present data seem to support greater specificity of the determination of IgA antibodies than that of IgM in the diagnosis of acute toxoplasmosis.

Acute Disease↗
PubMed1994

[Bone marrow aplasia and gold salts. Review of the literature apropos of 2 cases].

Bone marrow aplasia remains the most serious adverse effect with gold therapy. Its prevalence is still a controversial issue and at present it is not possible to give accurate figures on its frequency. Two patients diagnosed of rheumatoid arthritis are reported. They underwent chrysotherapy and developed bone marrow aplasia within a 2-month period of therapy. The pathogenic mechanism of blood dyscrasias secondary to gold salts is still unknown. The best available method in the prevention of this serious condition is the periodical obtention of complete blood counts.

Anemia, Aplastic↗