PubMed Health⌕ Search

Biomedical subjects

N Muñoz

Publications and source records attributed to N Muñoz.

At least 181 records · Page 10Linked to original sources
PubMed1966

Electron microscopy of Staphylococcus aureus cell wall lysis.

Virgilio, Rafael (Escuela de Química y Farmacia, Universidad de Chile, Santiago, Chile), C. González, Nubia Muñoz, and Silvia Mendoza. Electron microscopy of Staphylococcus aureus cell wall lysis. J. Bacteriol. 91:2018-2024. 1966.-A crude suspension of Staphylococcus aureus cell walls (strain Cowan III) in buffer solution was shown by electron microscopy to lyse slightly after 16 hr, probably owing to the action of autolysin. The lysis was considerably faster and more intense after the addition of lysozyme. A remarkable reduction in thickness and rigidity of the cell walls, together with the appearance of many irregular protrusions in their outlines, was observed after 2 hr; after 16 hr, there remained only a few recognizable cell wall fragments but many residual particulate remnants. When autolysin was previously inactivated by trypsin, there was a complete inhibition of the lytic action of lysozyme; on the other hand, when autolysin was inactivated by heat and lysozyme was added, a distinct decrease in the thickness of the cell walls was observed, but there was no destruction of the walls. The lytic action of lysozyme, after treatment with hot 5% trichloroacetic acid, gave rise to a marked dissolution of the structure of the cell walls, which became lost against the background, without, however, showing ostensible alteration of wall outlines. From a morphological point of view, the lytic action of autolysin plus lysozyme was quite different from that of trichloroacetic acid plus lysozyme, as shown by electron micrographs, but in both cases it was very intense. This would suggest different mechanisms of action for these agents.

Bacteriolysis↗
PubMedDate not supplied

Mother to child transmission of hepatitis B virus in the Philippines.

A follow-up study of mother to infant transmission of hepatitis B virus was conducted in the Philippines between 1981 and 1983. The prevalence of HBsAg among 527 mothers was 8.5%. Overall, seven out of 17 (41.2%) infants born to HBsAg carrier mothers became HBsAg positive within the first 12 months of life. The risk of becoming HBsAg positive was about 20 times higher for infants born to HBsAg positive mothers than for infants born to HBsAg negative mothers (OR = 18.9, 95% Ci = 2.0-86.6). The risk was even higher if the mother was a carrier of both HBsAg und HBeAg (OR = 91.0, 95% Ci = 49.2-164.8). However, the risk of transmission was very low if the mother was an HBsAg carrier and anti-HBe positive. It was estimated that mother to infant transmission accounts for about one third of HBsAg positivity at one year of age. The implications of these findings in the planning of vaccination campaigns to prevent HBV infections are discussed.

Adolescent↗
PubMedDate not supplied

Worldwide distribution of human papillomavirus types in cytologically normal women in the International Agency for Research on Cancer HPV prevalence surveys: a pooled analysis.

BACKGROUND: The proportion of women infected with human papillomavirus (HPV) varies greatly across populations, as might the distribution of HPV types. We aimed to compare HPV-type distribution in representative samples of women from different world regions. METHODS: Women were randomly selected from the general population of 13 areas from 11 countries (Nigeria, India, Vietnam, Thailand, Korea, Colombia, Argentina, Chile, the Netherlands, Italy, and Spain). A standardised protocol was used for cervical specimen collection. All HPV testing was by GP5+/6+ PCR-based EIA. The proportion of HPV-positive women infected with different HPV types was compared by study area and between pooled regions with age-adjusted odds ratios (ORs) with corresponding 95% floating CIs. FINDINGS: 15 613 women aged 15-74 years without cytological abnormalities were included in a pooled analysis. Age-standardised HPV prevalence varied nearly 20 times between populations, from 1.4% (95% CI 0.5-2.2) in Spain to 25.6% (22.4-28.8) in Nigeria. Although both overall HPV prevalence and HPV16 prevalence were highest in sub-Saharan Africa, HPV-positive women in Europe were significantly more likely to be infected with HPV16 than were those in sub-Saharan Africa (OR 2.64, p=0.0002), and were significantly less likely to be infected with high-risk HPV types other than HPV16 (OR 0.57, p=0.004) and/or low-risk HPV types (OR 0.44. p=0.0002). Women from South America had HPV-type distribution in between those from sub-Saharan Africa and Europe. Heterogeneity between areas of Asia was significant. INTERPRETATION: Heterogeneity in HPV type distribution among women from different populations should be taken into account when developing screening tests for the virus and predicting the effect of vaccines on the incidence of infection.

Adolescent↗
PubMedDate not supplied

Acceptability of a human papillomavirus (HPV) trial vaccine among mothers of adolescents in Cuernavaca, Mexico.

BACKGROUND: A scenario that must be considered when testing prophylactic human papillomavirus (HPV) vaccines in teenagers is the parents' acceptability of their daughters' participation in the study. METHODS: A survey was carried out in a random sample of 880 women between the ages of 15 and 49 years in the metropolitan area of Cuernavaca, Mexico. These women were interviewed to obtain information concerning their knowledge of risk factors for cervical cancer and their perception of the usefulness of vaccines. Afterward, they were provided with information on the main risk factors for cervical cancer and the future availability of a human papillomavirus (HPV) vaccine to prevent cervical cancer. Finally, we explored, with parents, the possible acceptability of an HPV vaccine for their teenaged daughters. The degree of acceptability and its association with a series of sociodemographic and reproductive factors were assessed. RESULTS: The respondents had little knowledge regarding the etiology of cervical cancer. Only 1.9% said that the principal risk factor was infection with HPV; however, 84.2% were aware of the usefulness of vaccines and 83.6% of the women indicated that they would allow their daughters to participate in a trial to evaluate the effectiveness of an HPV vaccine that helps prevent cervical cancer. The main factor associated with the acceptance of a possible vaccine against HPV was the knowledge of the usefulness of vaccines [odds ratio (OR) = 6.5, 95% confidence interval (CI) 5.2-8.2]. Likewise, a history of two or more sexual partners (OR = 2.2, 95% CI 1.3-3.6) increased acceptability. Acceptance was not associated with the number of live births (never vs. ever OR = 0.9, 95% CI 0.3-2.1). There were 525 women with children over the age of 10 years (59.6%); prevalence of acceptability among these women was 80.1%, not statistically different from the remainder of the sample (p >0.05). CONCLUSIONS: Acceptance of a potential HPV vaccine was high in this sample of Mexican women. Initiation of HPV vaccine clinical trials and immunization campaigns that target school children and/or teenagers who are not sexually active should include educational programs aimed at mothers of these individuals. Knowledge of the benefits of a preventive vaccine as well as the etiology and risk factors of cervical cancer should be emphasized.

Adolescent↗
PubMedDate not supplied

Risk factors for HPV DNA detection in middle-aged women.

BACKGROUND AND OBJECTIVES: Strong epidemiologic evidence indicates that human papillomavirus (HPV) is the main etiologic factor of cervical cancer. A few cohort studies suggest that most HPV infections are transient in young women and that persistent HPV infections are more common in older women. Little is known about the determinants of persistent HPV infections. The present study was aimed at increasing our knowledge about these determinants. GOALS: To identify risk factors for genital HPV DNA detection among cytologically normal middle-aged women. STUDY DESIGN: Eight hundred ten women who participated as control subjects in three case-control studies on cervical cancer in Spain, Colombia, and Brazil were included in this study. After an interview, women underwent a gynecologic examination with collection of exfoliated cells for a Papanicolaou smear and HPV DNA detection. Human papilloma virus DNA was detected by polymerase chain reaction (PCR)-based hybridization techniques. RESULTS: The HPV positivity rate was 10.5% in the whole population, but was higher in the areas with high incidence of cervical cancer (17% in Brazil and 13% in Colombia) than in Spain (4.9%), which is a low-risk area for cervical cancer. Age was related to the prevalence of HPV DNA in Brazil, but not in Spain and Colombia. In univariate analyses in all three countries, the prevalence of HPV DNA was positively associated with the number of lifetime sexual partners and inversely associated with the levels of family income and with age at first sexual intercourse. There was four times increase in the odds ratio (OR) of HPV infection in women who had six or more lifetime sexual partners compared with those with one or less. The use of any kind of contraceptive tended to decrease the OR for HPV detection. Their ORs ranged from 0.44 (barrier methods) to 0.48 (oral contraceptives). In Spain and Colombia, antibodies against Chlamydia trachomatis were positively associated with the prevalence of HPV DNA. In a final multivariate model, the positive associations with lifetime number of sexual partners, socioeconomic status, and C. trachomatis persisted. CONCLUSIONS: These results support the sexual transmission of HPV and suggest that socioeconomic status and antibodies to C. trachomatis are independent predictors of HPV detection in middle-aged cytologically normal women.

Adult↗
PubMedDate not supplied

Cervical cancer and human papillomavirus: epidemiological evidence and perspectives for prevention.

Cervical cancer is a major public health problem, as it is the second most common cancer in women world-wide after breast cancer. About 80% of the half a million cases estimated to occur annually in the world, occur in developing countries. The epidemiological evidence linking human papillomavirus (HPV) to cervical cancer is reviewed. It is concluded that over 90% of cervical cancers can be attributed to certain HPV types. HPV 16 accounts for the highest proportion (50%) followed by HPV 18 (12%), HPV 45 (8%) and HPV 31 (5%). The association with these HPV types are very strong and consistent with odds ratios over 15 in all case-control studies in high- and low-risk countries for cervical cancer. However, HPV is not a sufficient cause of this malignancy; certain cofactors are necessary for a proportion of HPV persistent infections to eventually progress to cancer. These include host factors such as histocompatibility types and immunological response, hormonal influences and infections with other sexually transmitted agents such as Chlamydia trachomatis. In addition, results from our studies carried out in Spain and Colombia support the hypothesis that male carriers of HPV play an important role in the development of cervical cancer in their wives. The recognition of the central role of HPV in cervical cancer has far-reaching implications for the primary and secondary prevention of this malignancy. Prophylactic and therapeutic HPV vaccines are now under development and HPV typing is being integrated into screening programmes in pilot studies in a few developed countries. In developing countries, well conducted conventional screening programmes remain the best approach for the control of cervical cancer until a safe and efficient HPV vaccine can be used in the general population.

Carcinoma in Situ↗
PubMedDate not supplied

Epidemiology of gastric cancer and perspectives for prevention.

The most recent estimates of the world-wide incidence of cancer indicate that gastric cancer was in 1990 the second most frequent cancer in the world (after lung cancer), with about 900000 new cases diagnosed every year. Steady declines in the rates have been observed everywhere in the last few decades, but the absolute number of new cases per year is increasing mainly because of ageing of the population. The exact causes of the decline of gastric cancer are not well understood, but must include improvements in diet, food storage (e.g., refrigeration) and, possibly, the decline of Helicobacter pylori infection. Dietary modifications and, possibly, vitamin supplements remain one of the most important tool for the prevention of gastric cancer. Control of H. pylori infection, by means of eradication or immunization, is also likely to offer great potential for the prevention of this important malignancy.

Case-Control Studies↗