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N Muñoz

Publications and source records attributed to N Muñoz.

At least 91 records · Page 5Linked to original sources
PubMed1996

Antioxidants, Helicobacter pylori and stomach cancer in Venezuela.

A randomized chemoprevention trial on precancerous lesions of the stomach is being conducted in Tachira State, Venezuela. The aims of the study are to evaluate the efficacy of vitamin supplementation in preventing the progression rate of precancerous lesions. Here we report on the pilot phase of the study in which two antioxidant preparations were evaluated on their ability to raise antioxidant levels in plasma and in gastric juice. The study aimed also to determine the antibiotic sensitivity profiles of Helicobacter pylori isolates prevalent in the area. Forty-three subjects with precancerous lesions (chronic gastritis, chronic atrophic gastritis, intestinal metaplasia and dysplasia) of the stomach were randomized to one of two antioxidant treatments. Treatment 1 (250 mg of standard vitamin C, 200 mg of vitamin E and 6 mg of beta-carotene three times a day) or treatment 2 (150 mg of standard vitamin C, 500 mg of slow release vitamin C, 75 mg of vitamin E and 15 mg of beta-carotene once a day) for 7 days. Blood levels of total vitamin C, beta-carotene and alpha-tocopherol and gastric juice levels of ascorbic acid and total vitamin C were measured before and after treatment on day 8. Both treatments increased the plasma levels of total vitamin C, beta-carotene and alpha-tocopherol/cholesterol but not those of ascorbic acid or total vitamin C in gastric juice. Treatment 1 was the best choice and resulted in a greater increase in the plasma levels of beta-carotene and alpha-tocopherol. H. pylori was cultured from 90% of the gastric biopsies; 35 isolates were identified which were highly resistant to metronidazole, a front-line antibiotic recommended against H. pylori in other settings.

Adult↗
PubMed1996

Prevalence of precancerous lesions of the stomach in Venezuela.

Gastric biopsies from 1477 participants in a chemoprevention trial for precancerous lesions of the stomach in Venezuela were evaluated for the prevalence of precancerous lesions and Helicobacter pylori infection. These study subjects were selected from participants in an early detection program for gastric cancer using double-contrast X-ray. Overall, 94% had some type of chronic gastritis (CG) and were positive for H. pylori using Giemsa stain, 49% had atrophic gastritis, 34% had intestinal metaplasia (IM), and 6.5% had dysplasia. There were only three subjects (0.2%) with normal gastric mucosa, and 4% had only superficial gastritis. The prevalence of all of these precancerous lesions increased with age, but there was no clear difference by gender. The prevalence of the various lesions was higher in the antral mucosa than in the fundic mucosa. H. pylori infection was strikingly frequent in our study population, with prevalence rates ranging from 73% in subjects with superficial gastritis to 95% in those with atrophic gastritis and IM and 98% in those with CG. The prevalence of H. pylori was equally high in males and females, and it was significantly positively associated with the degree of infiltration of poly- and mononuclear cells and with that of active regeneration; it was inversely correlated with the degree of atrophy, IM, and dysplasia. Our findings support the precancerous nature of the various gastric lesions and the etiological role of H. pylori infection in CG.

Adult↗
PubMed1996

Chemoprevention of stomach cancer.

A varied and balanced diet that is rich in fresh fruit and vegetables and poor in preserved foods is thought to represent the main protection against gastric cancer. Helicobacter pylori infection also appears to have a role in the disease; its eradication therefore represents another promising potential preventive measure. The effect of diet is supposed to be mediated by micronutrients with an antioxidant role, such as ascorbic acid, beta-carotene and alpha-tocopherol, which could act on different phases of the carcinogenic process, interrupting the progression of precancerous lesions towards cancer. The two trials ongoing in Latin America and the one planned in Europe all deal with the effect of antioxidants, with or without H. pylori eradication, on the progression/ regression rate of precancerous lesions of the stomach. The trial in Venezuela has an 80% power to detect a 50% reduction in the net progression of precancerous lesions in the group (from a high-risk population) undergoing a complex antioxidant treatment for 3 years. In this population a case-control study confirmed the protective effect of fresh fruits and vegetables in relation to gastric cancer. Other trials, which aimed to evaluate the chemopreventive potential of micronutrients on other cancer sites, have reported contradictory results concerning gastric cancer risk. When interpreting these results the following should be considered; a possible interaction between H. pylori infection and the antioxidants; the baseline levels of antioxidants in these populations; and the doses and duration of treatment.

Adult↗
PubMed1996

Human papillomavirus and cancers of the upper aerodigestive tract: a review of epidemiological and experimental evidence.

Human papillomaviruses (HPVs) are recognized as important causes of cancer of the anogenital tract and may be involved also in the etiology of cancers of the upper aerodigestive tract (UADT). Epidemiological and experimental evidence lend some support to this possibility. Increased risk of cancer of the oral cavity, pharynx, and larynx subsequent to the occurrence of cancer of the cervix has been found and suggests common etiological factors besides smoking. HPV has been found in a substantial proportion of benign UADT lesions, most notably laryngeal papillomas and oral verrucal-papillary lesions. Largest and most accurate case series (i.e., > 15 UADT cancer cases, based on best HPV detection techniques) showed HPV DNA in 46% of cancers of the oral cavity and pharynx, 15% of cancers of the esophagus, and 24% of cancers of the larynx, with however, great discrepancies from one study to another. An additional 14 case series with a comparison group of noncancer patients revealed approximately a 4-fold higher HPV prevalence in UADT cancer tissues than in normal ones. The only two strictly designed case-control studies dealt with cancer of the oral cavity and provided inconclusive results, possibly because of interference of primary treatment with HPV detection in buccal exfoliated cells. An increasing bulk of experimental and in vitro evidence suggests that at least a proportion of UADT cancers harbor a relatively high copy number of HPV DNA. E6/E7 region transcripts and a clonal association with HPV have been demonstrated in these tumors. The combination of a good study design with reliable and noninvasive viral measurement will ultimately allow researchers to elucidate the role of HPV in the development of UADT cancer. Allowance for the strong effect of smoking, alcohol drinking, and betel quid chewing on UADT cancer and exclusion of noncausal associations will be the most difficult challenges of such studies.

Animals↗
PubMed1996

Chemoprevention trial on precancerous lesions of the stomach in Venezuela: summary of study design and baseline data.

A double-blind, placebo-controlled trial is being conducted in a population at high risk for gastric cancer in Venezuela. The main aim of the trial is to assess the effect of antioxidant vitamins (beta-carotene, vitamin C and vitamin E) in blocking the progression of precancerous lesions of the stomach. Within the framework of a screening programme for stomach cancer, 2200 subjects of 35-69 years of age have been recruited. At study entry, a dietary questionnaire was completed, and gastroscopy with the collection of seven gastric biopsies was performed. After baseline examinations, the study participants were randomized to receive antioxidant treatment or placebo for three years. The treatment phase will be completed in mid-1998. At the end of the treatment phase, the investigations performed at study entry will be repeated. Before the initiation of the trial, various pilot studies were carried out that showed an extremely high prevalence of Helicobacter pylori infection (over 90%). Two eradication trials using anti-H. pylori treatments that give good results in Europe and North America gave very poor results in our study population. The low eradication rates achieved (5-20%) suggest a high prevalence of antibiotic-resistant H. pylori strains or high reinfection rates. These disappointing results led to deletion of an anti-H. pylori treatment phase of the main trial.

Adult↗
PubMed1996

The causal link between HPV and cervical cancer and its implications for prevention of cervical cancer.

This article reviews epidemiologic evidence linking human papillomavirus (HPV) to cervical cancer. The authors conclude that over 90% of all cervical cancers can be attributed to certain HPV types-HPV 16 accounting for the largest proportion (roughly 50%) followed by HPV 18 (12%), HPV 45 (8%), and HPV 31 (5%). Recognition of this circumstance has far-reaching implications for primary and secondary prevention of this malignancy. At present, prophylactic and therapeutic HPV vaccines are under development, and HPV typing is being integrated into pilot study screening programs in a few developed countries. In developing countries, well conducted conventional screening programs remain the best approach for the control of cervical cancer until a safe and efficient HPV vaccine can be developed for use by the general population.

Adenocarcinoma↗
PubMed1995

Determinants of plasma pepsinogen levels in a population at high risk for stomach cancer in Venezuela.

Determinants of plasma pepsinogens (PG) levels were studied in 1365 participants in a chemoprevention trial for gastric pre-cancerous lesions being conducted in Venezuela. Gastric biopsies, plasma samples and information on smoking and dietary habits were obtained at baseline examination. Both PG-I and PG-II levels increased progressively with the level of Helicobacter pylori infection in gastric biopsies, resulting in no clear trend in the I/II ratio. Instead, there was a progressive decrease in the I/II ratio with increasing degrees of infiltration of polynuclear cells and monocytes, atrophy, intestinal metaplasia and the stage of pre-cancerous lesions. The mean I/II ratios for atrophic gastritis or more advanced lesions were less than 4.0. When subjects with the I/II ratio 4 or higher were used as controls, severe reduction in the I/II ratio (< 2.0) was inversely associated with tobacco consumption. This may be due to a pharmacological effect of nicotine. The severe reduction of I/II ratio was also inversely associated with fresh fruit consumption. In addition, a decreased I/II ratio was positively associated with rice/pasta and arepas (tortilla made from corn) consumption and inversely associated with plantain consumption. Possible effects of vitamins and starchy food on the development of atrophic gastritis need to be studied further.

Adult↗
PubMed1995

Prevalence of human papillomavirus in cervical cancer: a worldwide perspective. International biological study on cervical cancer (IBSCC) Study Group.

BACKGROUND: Epidemiologic studies have shown that the association of genital human papillomavirus (HPV) with cervical cancer is strong, independent of other risk factors, and consistent in several countries. There are more than 20 different cancer-associated HPV types, but little is known about their geographic variation. PURPOSE: Our aim was to determine whether the association between HPV infection and cervical cancer is consistent worldwide and to investigate geographic variation in the distribution of HPV types. METHODS: More than 1000 specimens from sequential patients with invasive cervical cancer were collected and stored frozen at 32 hospitals in 22 countries. Slides from all patients were submitted for central histologic review to confirm the diagnosis and to assess histologic characteristics. We used polymerase chain reaction-based assays capable of detecting more than 25 different HPV types. A generalized linear Poisson model was fitted to the data on viral type and geographic region to assess geographic heterogeneity. RESULTS: HPV DNA was detected in 93% of the tumors, with no significant variation in HPV positivity among countries. HPV 16 was present in 50% of the specimens, HPV 18 in 14%, HPV 45 in 8%, and HPV 31 in 5%. HPV 16 was the predominant type in all countries except Indonesia, where HPV 18 was more common. There was significant geographic variation in the prevalence of some less common virus types. A clustering of HPV 45 was apparent in western Africa, while HPV 39 and HPV 59 were almost entirely confined to Central and South America. In squamous cell tumors, HPV 16 predominated (51% of such specimens), but HPV 18 predominated in adenocarcinomas (56% of such tumors) and adenosquamous tumors (39% of such tumors). CONCLUSIONS: Our results confirm the role of genital HPVs, which are transmitted sexually, as the central etiologic factor in cervical cancer worldwide. They also suggest that most genital HPVs are associated with cancer, at least occasionally. IMPLICATION: The demonstration that more than 20 different genital HPV types are associated with cervical cancer has important implications for cervical cancer-prevention strategies that include the development of vaccines targeted to genital HPVs.

Adult↗
PubMed1995

Cervical cancer and herpes simplex virus type 2: case-control studies in Spain and Colombia, with special reference to immunoglobulin-G sub-classes.

Two case-control studies, including 449 histologically confirmed cases of cervical intra-epithelial neoplasia (CIN) III and 425 controls, and 2 studies on invasive cervical cancer, involving 316 histologically confirmed cases and 330 population controls, were conducted in Colombia and Spain to assess the role of herpes simplex virus type 2 (HSV-2) in cervical neoplasia. Antibodies to this virus were also measured in the sera of 931 husbands of cases and controls. A serological assay using type-specific antigens, glycoprotein C for type I (gC-I) and glycoprotein G for type 2 (gG-2) was employed. Immunoglobulin-G (IgG) sub-classes, IgG1 and IgG3, were measured in women positive for HSV-2 antibodies. No increase in risk of CIN III or invasive cancer was found in women whose sera or whose husbands' sera were positive to HSV-2. However, compared with women negative to HSV-2, the risk of CIN III progressively increased with increasing levels of IgG1. The trend was statistically significant in Colombia. There was also a statistically significant increasing trend in risk of invasive cancer with levels of IgG1 in Spain. The levels of IgG3 and its ratio to IgG1, which may indicate recurrent infections, were not associated with the risk of either type of cancer. When the association with IgG1 was analyzed by human papillomavirus (HPV) DNA status, as determined by polymerase chain reaction, the trend was clearer in women whose HPV status was not determined or in those with negative HPV DNA. These results suggest that the role of HSV-2 is merely marginal and do not support the hypothesis that recurrent HSV-2 infections are of importance for cervical neoplasia.

Adult↗
PubMed1995

Inter-observer variation in cytological and histological diagnoses of cervical neoplasia and its epidemiologic implication.

Inter-observer variation in cytohistological diagnosis was assessed for 1506 cervical smears and 883 histological slides from four case-control studies on cervical neoplasia. The kappa statistic among a panel of three cytopathologists was highest for diagnosis of invasive cancer (0.70 for cytology and 0.74 for histology), followed by normal/inflammatory in cytology (0.68) and CIN III in histology (0.58). There was also nearly perfect agreement between the final panel diagnoses and the original diagnoses made by local cytopathologists, except for those of CIN III. Inter-observer variation in diagnosis for CIN III was inversely associated with age, number of children (in histology) and sexual activity (in cytology). However, the odds ratios for CIN III calculated by each cytopathologist's diagnosis were not different from each other for any etiologic factor. These results indicate that the diagnoses of invasive cancer and of normal/inflammatory changes are highly reproducible and that the inter-observer variation does not have much impact on the etiologic risk estimates.

Adult↗
PubMed1995

Serologic response to human papillomavirus type 16 (HPV-16) virus-like particles in HPV-16 DNA-positive invasive cervical cancer and cervical intraepithelial neoplasia grade III patients and controls from Colombia and Spain.

A human papillomavirus (HPV) type 16 virus-like particle-based ELISA was used to assess antivirion immune responses in 300 women participating in cervical cancer case-control studies in Colombia and Spain. Virion IgG antibodies were detected in the sera of 51% and 59% of women with HPV-16 DNA-positive invasive cervical cancer and 81% and 73% of women with HPV-16 DNA-positive cervical intraepithelial neoplasia grade III (CIN III) in Colombia and Spain, respectively. Capsid antibodies were detected in 22% and 3% of cancer controls (P < .001) and in 43% and 10% of CIN III controls (P = .010) from Colombia and Spain, respectively. Since Colombia has an 8-fold higher incidence of cervical cancer, these results demonstrate an association between ELISA positivity and cancer risk. Capsid antibody responses did not correlate with humoral responses of the same women to HPV-16 E6 and E7 oncoproteins.

Antibodies, Viral↗
PubMed1995

Prevalence of Helicobacter pylori infection and gastritis among young adults in China.

To investigate the prevalence of gastritis and H. pylori infection among young Chinese in Henan Province, a high incidence area for oesophageal cancer in China, the gastric mucosa was examined in 194 asymptomatic subjects, aged 15-26 years, in the course of an epidemiological study of precursor lesions of oesophageal cancer. Histopathological grading of gastritis and determination of H. pylori infection were performed on haematoxylineosin and Warthin-Starry stained section. An enzyme-linked immunosorbent assay was used to detect the presence of serum IgG antibodies to H. pylori. A very high prevalence of gastritis (93.8%) was found: 71 subjects (36.6%) presented with superficial gastritis (14 active), 94 (48.5%) with diffuse gastritis (92 active) and in 17 cases (8.8%) diffuse gastritis (16 active) was accompanied by focal atrophy. Silver staining detected H. pylori in 166 (85.6%) of the study participants. However, serological techniques identified H. pylori in only 109 (56.2%). H. pylori was seen in all the 119 cases showing histological signs of active gastritis, in 41 of the 63 cases (65%) without activity, and also in 50% (6/12) of histologically normal subjects. H. pylori infection was found to be associated with a 2.5-fold higher prevalence of chronic atrophic gastritis compared with non-atrophic gastritis. A family history of stomach cancer, consumption of pickled vegetables more than twice a month, and a high monthly salt consumption (> 500 g/month) also showed a positive association.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Hot and cold mate drinking and esophageal cancer in Paraguay.

A hospital-based case-control study, including 131 cases of esophageal cancer and 381 controls, was carried out in Paraguay to investigate the role of hot and cold mate drinking in esophageal cancer risk. Detailed information on mate drinking and on tobacco smoking, alcohol consumption, and dietary habits was obtained by interview. Amount and duration of cold or hot mate drinking were not associated with esophageal cancer risk. However, temperature at which mate was drunk was significantly associated with risk. As compared to drinkers of warm or hot mate, drinkers of very hot mate had an increased risk for esophageal cancer even after adjusting for the strong effects of alcohol and tobacco consumption (adjusted odds ratio = 2.4; 95% confidence interval = 1.3-4.3). This effect seemed to be mainly due to the temperature at which mate cocido (one of the two ways in which hot mate is prepared) was drunk (odds ratio = 6.5; 95% confidence interval = 3.2-12.2). As expected, very strong dose-response associations were found for alcohol consumption and cigarette smoking. After correcting for these and the consumption of other food groups, diets rich in fats and red meats, especially beef, were associated with esophageal cancer risk. In conclusion, the findings from this study suggest that cold mate drinking does not increase the risk of esophageal cancer. This study identifies the very hot temperature at which mate is drunk, and not the amount or the duration, as an important risk factor for esophageal cancer in this population. Alcohol drinking and tobacco smoking remain, nevertheless, the main risk factors for esophageal cancer in Paraguay.

Adult↗
PubMed1994

Intestinal metaplasia types and the risk of gastric cancer: a cohort study in Slovenia.

Between 1967 and 1976, 1,525 Slovenian patients with a histological diagnosis of intestinal metaplasia (IM) were classified according to subtype of IM based on morphology and mucin staining; 518 cases were diagnosed with type I, 197 with type II and 275 with type III, but in 291 the diagnosis of IM was not confirmed. Patients who had developed cancer or died up to 1986 were identified by record linkage at the Slovenia Cancer Registry and the Central Population Registry in Slovenia. A total of 34 incident cases of gastric cancer occurring at least 6 months after the diagnosis of IM were identified. The standardised incidence ratio (SIR) for stomach cancer was 2.23 in the whole cohort. It was highest for IM type III, followed by type II and IM-unconfirmed, but not increased for type I. The relative risk (RR) of developing gastric cancer based on Cox's proportional hazards model was 2.14 for type II and 4.58 for type III, compared with type I. The RR was especially increased for a subgroup of type III secreting sulphomucins in their goblet cells in comparison with types I-II negative to sulphomucins. Our results confirm that subtyping of IM is useful for identifying individuals at high risk for gastric cancer.

Adult↗