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Biomedical subjects

B Muñoz

Publications and source records attributed to B Muñoz.

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

Incidence of trichiasis in a cohort of women with and without scarring.

BACKGROUND: Blindness from trachoma is a significant problem for many underdeveloped countries. While active trachoma is common in children, trichiasis, the potentially blinding sequella, develops in adulthood and affects mainly women. Little is known about factors associated with the development of trichiasis. METHODS: The 7-year incidence of trichiasis and its association with ocular chlamydia infection was examined in a cohort of women from a hyperendemic area. A total of 4,932 women 18 years and older, living in 11 villages in Central Tanzania, were examined in 1989. A follow-up examination in 1996 was performed on all women with scars living in six of the 11 villages and on a random sample of women without scars from the same villages. Trachoma was graded clinically, chlamydia infection was ascertained at follow-up using polymerase chain reaction-enzyme immunoassay (PCR-EIA). RESULTS: A total 523 of the women with scars and 503 of the women without scars were re-examined. Forty-eight of the women with scars (incidence, 9.2%) and three of the women without scars (0.6%) developed trichiasis in the 7-year period. Prevalence of chlamydia infection was significantly higher in the group with scars (11.7% versus 7.1%). Trichiasis cases were more likely to be older, and to have chlamydia infection at follow-up odds ratio (95% confidence interval) 2.5 (1.1-5.7). CONCLUSION: The 7-year incidence rate in the population with scars was high, over 1% per year. Ocular chlamydia infection was more common in the group with scars at baseline and was also associated with being a trichiasis case, suggesting the importance of potentially long-term chlamydia infection in the progression to trichiasis. Antibiotic distribution programmes for trachoma control should include women with scars.

Adult↗
PubMed1999

Vegetarians and cardiovascular risk factors: hemostasis, inflammatory markers and plasma homocysteine.

We studied hemostatic and inflammatory cardiovascular risk factors (CVRF), and total plasma homocysteine (tHcy) in 26 vegetarians (23 lacto- or ovolactovegetarians and 3 vegans), matched by age, sex and socioeconomic status with omnivorous controls. Vegetarians had significantly lower proportion of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in plasma lipids, significantly shortened bleeding time, and increased blood platelet count and in vitro platelet function (aggregation and secretion). Plasma levels of all coagulation or fibrinolytic factors and natural inhibitors synthesized in the liver were lower in vegetarians than in controls. Whereas for some factors this decrease was statistically significant (fibrinogen, factor VIIc, antithrombin III, protein S, plasminogen) for the remaining (factors VIIIc, Vc, prothrombin, protein C) a trend in the same direction was found. For hemostatic proteins of predominantly extrahepatic origin (von Willebrand factor. tPA, PAI-1) this tendency was not present. No significant differences in inflammatory proteins (C-reactive protein and alpha1-protease inhibitor) were detected in both groups. tHcy was significantly increased in vegetarians, and correlated only with cobalamin levels. The increased platelet function and tHcy found in vegetarians may counteract the known cardiovascular health benefits of vegetarian diet (VD).

Adult↗
PubMed1999

Tranexamic acid inhibits fibrinolysis, shortens the bleeding time and improves platelet function in patients with chronic renal failure.

BACKGROUND: A defect in platelet function is the main determinant of the prolonged bleeding time in chronic renal failure (CRF). We previously reported a significant correlation between platelet abnormalities and elevated plasma markers of plasmin and thrombin generation. Our aim was to explore the effect of inhibiting both plasmin action with tranexamic acid (TA) and thrombin production with low molecular weight heparin (LMWH), on the bleeding time (BT) and platelet function in patients with CRF. METHODS: 37 patients with CRF (mean creatinine 8.6 +/- 4.4 mg/dl) under conservative treatment, with prolonged BT, entered this study and received TA during 6 days, with (n = 24) and without LMWH (n = 13). BT, platelet aggregation/secretion, platelet granule contents, von Willebrand factor and parameters of coagulation and fibrinolysis were recorded before and at the end of treatment. RESULTS: The BT was shortened in 26/37 (67%) patients. This effect was associated with significant improvement of platelet aggregation and secretion, with decrease to a normal range of fibrin/fibrinogen degradation products, mild increase in plasmin-antiplasmin complexes and pronounced reduction of circulating plasminogen. No differences were seen among patients with or without LMWH. No serious side effects or complications were observed. INTERPRETATION: These findings indicate that the activation of fibrinolysis plays a significant role in the defect of primary hemostasis in patients with CRF. Inhibition of plasmin activity with TA shortens the BT and improves platelet function in the majority of patients with severe disease.

Antifibrinolytic Agents↗
PubMed1998

Racial differences in lens opacities: the Salisbury Eye Evaluation (SEE) project.

The purpose of this study was to determine racial differences in the prevalence of different types of lens opacities and cataract surgery. Between 1993 and 1995, the Salisbury Eye Evaluation (SEE) Project enrolled a representative sample of 2,520 community-dwelling persons aged 65-84 years in Salisbury, Maryland, 26.4% of whom were African-American. Participants received a full eye examination, and photographs were taken for documentation of lens status. Photographs were graded using a standardized grading system for the presence of cortical, nuclear, or posterior subcapsular cataract (PSC) opacification in at least one eye. The odds of having cortical opacities were 4.0 times greater among African Americans than among Caucasians (95% confidence interval (CI) 3.3-4.8). Caucasians were significantly more likely to have nuclear opacities (odds ratio = 2.1, 95% CI 1.7-2.6) and PSC opacities (odds ratio = 2.5, 95% CI 1.7-3.6). The odds of cataract surgery were 2.8 times higher among Caucasians, but these differences did not explain the differences in the prevalence of different types of lens opacities by racial group. With lower rates of nuclear and PSC opacities than Caucasians, African Americans may have a lower demand for cataract surgery. However, even with these differences, there is still significant unnecessary loss of vision due to cataract among older African Americans, for whom programs to ensure access to surgical care are indicated.

Aged↗
PubMed1998

Sunlight exposure and risk of lens opacities in a population-based study: the Salisbury Eye Evaluation project.

CONTEXT: Exposure to UV-B radiation in sunlight has been shown to increase the risk of cataract formation in high-risk occupational groups, but risk to the population has not been quantified. OBJECTIVES: To determine the ocular exposure to UV-B radiation in sunlight for a population of older persons and to determine the association between UV-B and lens opacities. DESIGN: The Salisbury Eye Evaluation project, a population-based cohort of older adults. SETTING: Salisbury, Md. PARTICIPANTS: A total of 2520 community-dwelling 65-year-old to 84-year-old adults in Salisbury, Md, from 1993 to 1995, of whom 26.4% were African Americans. MAIN OUTCOME MEASURE: Association of photographically documented cortical opacity 3/16 or greater in at least 1 eye with ocular UV-B exposure, reported in Maryland sun-years of exposure. RESULTS: The odds of cortical opacity increased with increasing ocular exposure to UV-B (odds ratio [OR], 1.10; 95% confidence interval [CI], 1.02-1.20). The relationship was similar for women (OR, 1.14; 95% CI, 1.00-1.30) and for African Americans (OR, 1.18; 95% CI, 1.04-1.33). Analyses of the ocular dose by each age group after the age of 30 years showed no vulnerable age group, suggesting damage is based on cumulative exposure. CONCLUSIONS: Although this population of older Americans has relatively low ocular exposure to UV-B in sunlight, there is still an association between ocular exposure and increasing odds of cortical opacity. Our study found an association among African Americans, which, to our knowledge, has not been reported previously. All sex and racial groups would benefit from simple methods to avoid ocular sun exposure.

Aged↗
PubMed1997

Endothelial cell markers in chronic uremia: relationship with hemostatic defects and severity of renal failure.

Plasma von Willebrand factor antigen, soluble thrombomodulin, and tissue factor were increased in 31 patients with severe chronic renal failure (creatinine clearance <20 ml/min) under conservative treatment, whereas plasminogen activator inhibitor antigen did not differ significantly from healthy controls. No correlation among plasma levels of these proteins was found. Three patterns of relationship between endothelial cell markers and hemostatic defects were identified: 1) Plasma thrombomodulin, a marker of endothelium damage, was found an independent predictor of bleeding time and platelet aggregation, and secretion defects, and was also related to the severity of renal failure; 2) von Willebrand factor antigen, an index of endothelial cell activation and secretion, was significantly correlated with intravascular markers of thrombin and plasmin generation and with platelet adenosine triphosphate content, but not with plasma creatinine levels; and 3) tissue factor and plasminogen activator inhibitor antigen levels were not statistically correlated with the diverse hemostatic defects. Activation of coagulation and fibrinolysis, secondary to endothelial cell activation, appearing early during the evolution of chronic renal failure, is pathogenically related to the platelet dysfunction, and probably to development of atherosclerosis and thrombotic events in this disease. The progression of chronic renal failure, through endothelial cell damage, would lead to aggravation of the platelet functional defect potentiating the hemorrhagic risk.

Antigens↗
PubMed1997

Prevalence of dry eye among the elderly.

PURPOSE: To study the demographics and estimate the prevalence of dry eye among elderly Americans. METHODS: A population-based prevalence study was performed in 2,520 residents of Salisbury, Maryland, aged 65 years and older as of September 1993. The population was derived from the Health Care Financing Administration Medicare database. After completing a standardized questionnaire pertaining to dry eye symptoms, 2,420 subjects underwent Schirmer and rose bengal tests and anatomic assessment of the meibomian glands. RESULTS: In this population, 14.6% (363/2,482) were symptomatic, defined as reporting one or more dry eye symptoms often or all the time; 2.2% (53/2,448) were symptomatic and had a low Schirmer test result (< or = 5 mm), and 2% (48/2,432) were symptomatic and had a high rose bengal test score (> or = 5). Furthermore, 3.5% (84/2,425) were symptomatic and had either a low Schirmer score or a high rose bengal score, and 0.7% (17/2,420) were symptomatic and had both a low Schirmer score and a high rose bengal score. No association of symptoms or signs was seen with age, sex, or race. Although anatomic features of meibomianitis were associated with the presence of symptoms (P = .01), 76% (67/88) of the individuals with these anatomic features were asymptomatic; 10.5% (260/2,480) reported that they currently use artificial tears or lubricants. CONCLUSIONS: Symptoms and signs of dry eye are common among the elderly but were not associated with age, race, or sex in this population-based sample of elderly Americans. Extrapolating to the United States population aged 65 to 84 years, the study yields an estimate of 4.3 million who experience symptoms of ocular irritation often or all the time.

Aged↗
PubMed1997

Severe disease in children with trachoma is associated with persistent Chlamydia trachomatis infection.

The immediate study objective was to determine if variable disease severity in children with trachoma could be attributable in part to host variation in the ability to clear Chlamydia trachomatis infection. Identification of sibling cohorts with these variant phenotypes would be useful for immunogenetic studies. A weekly survey for 3 months in a trachoma-hyperendemic village using detection of chlamydial DNA and grading of disease severity indicated that 62% (33/53) of children had at least one infection episode. Of those, 64% (21/33) who were persistently infected had both significantly higher mean chlamydial DNA loads and more severe trachoma than did sporadically infected children. Of importance, duration of infection differed between siblings in 60% (6/10) of families. The results suggest that chlamydial load and duration of infection determine the chronic nature of severe disease in trachoma and that host variable efficiency for chlamydial clearance between siblings is in part determined by host variation.

Adenoviruses, Human↗
PubMed1997

Assessment of ocular exposure to ultraviolet-B for population studies. Salisbury Eye Evaluation Project Team.

We have developed an empirical model with which to estimate the ocular exposure in the UVB wavelength band. This model incorporates aspects of personal behavior, geographic location, season and wavelength that have been developed from population-based data. This model, in conjunction with job history interviews, allows the estimate of cumulative exposures from age 30 in our population-based study. We present data on average annual exposure by age, gender, race, education and reported photophobia. The exposures in the general population are considerably lower than exposures reported in previous works based on occupational groups. There is a statistically significant difference between males and females, with females having lower exposures. African-Americans have median exposures similar to whites. Exposures decrease with education and with reported photophobia. These data provide the basis for characterizing lifetime exposure for the general population. The variability of exposure is much greater than found in occupational groups and includes numbers in the lowest exposure. The model should permit determination of a dose-response relationship with eye disease, even to the lower dose ranges.

Adult↗
PubMed1997

A comprehensive assessment of visual impairment in a population of older Americans. The SEE Study. Salisbury Eye Evaluation Project.

PURPOSE: The Salisbury Eye Evaluation Project is a longitudinal study of risk factors for age-related eye diseases and the impact of eye disease and visual impairment on physical disability. In this article, the authors report the prevalence of visual impairment in their population and explore the relations among the various measures of visual function. METHODS: A population-based sample of 2520 residents of Salisbury, Maryland, between the ages of 65 and 84 years were enrolled in the study. Twenty-six percent of participants were black. Vision tests included best-corrected Early Treatment Diabetic Retinopathy Study acuity, Pelli-Robson contrast sensitivity with and without glare, Randot stereoacuity, and 60 degrees Humphrey visual fields. RESULTS: Visual function decreased linearly with age for the acuity, contrast sensitivity, glare, and visual field tests. Stereoacuity remained constant into the mid-70s and declined at an accelerating rate thereafter. Black participants had lower contrast sensitivity, reduced stereoacuity, and worse visual fields, at all ages compared to white participants; however, white participants were more sensitive to glare. The overall prevalence of visual acuity impairment in blacks was 5.6% versus 3.0% for whites, using the traditional United States definition (worse than 20/40 to better than 20/200) and 3.3% for blacks versus 1.6% for whites, using the World Health Organization definition (worse than 20/60 to 20/400). Acuity was correlated moderately with contrast sensitivity, stereoacuity, and visual fields (Spearman rho = 0.50, 0.35, and 0.34, respectively). The correlation between acuity and glare sensitivity was low (rho = 0.12). CONCLUSIONS: Many aspects of visual function, not just acuity, decline with age. Black participants have more visual impairement than do white participants for all tests except glare sensitivity. The prevalence of visual acuity impairement in the Salisbury Eye Evaluation population is lower than that reported by other studies using similar test procedures. Low-to-moderate correlations among vision test scores suggest that several different dimensions of visual function are being assessed.

Aged↗
PubMed1997

Visible and ultraviolet-B ocular-ambient exposure ratios for a general population. Salisbury Eye Evaluation Project Team.

PURPOSE: To estimate the numerical value of the ocular-ambient exposure ratio (OAER) (ratio of the facial exposure to that on a horizontal plane) as a function of wavelength band, season, and job category and to establish the effect of various modifiers, such as geography and the use of hats, for use in general population studies. METHODS: Two hundred sixty-four persons within several job categories representing the jobs in our Salisbury, Maryland, population were instrumented with ultraviolet-B (UVB) and visible band sensors for 1 complete day. Studies were done over all four seasons, both with and without hats. RESULTS: OAERs in the UVB wavelength band generally are higher than in the visible (13% versus 6%), display no significant variation with job category, show a seasonal effect (highest in the winter-spring [18%], lowest in the summer [10%], and intermediate in the fall [14%]), and are reduced 34% by the use of hats. In the visible wavelength band, OAERs are affected weakly by job function, although this variation is not significant, display a seasonal effect with three seasons as in the UVB, and are not affected significantly by the use of hats. In neither the UVB nor the visible portions of the spectrum did the authors find an effect on the OAER due to photophobia or eye color. CONCLUSIONS: With the authors' exposure model, the authors have at their disposal a valuable tool for exploring the relation between UVB, UVA, and visible radiation and a number of age-related eye diseases.

Environmental Exposure↗
PubMed1997

Self-reported assessment of dry eye in a population-based setting.

PURPOSE: To report on a subjective dry eye assessment method for use in large-scale research, to evaluate its application in a population-based study of dry eye among elderly persons in the United States, and to apply novel techniques to improve simple questionnaire item summaries. METHODS: A dry eye questionnaire was administered to a population-based sample of 2520 volunteers ages 65 to 84 years in Salisbury, Maryland. Individual symptoms and signs, counts of symptoms and signs, and latent class model summary of item responses were evaluated for validity and internal consistency. RESULTS: Approximately 15% of participants reported experiencing one or more of six dry eye symptoms often or all the time; 20% reported experiencing three or more symptoms sometimes, often or all the time. Four groups were derived on the basis of symptomatology, using latent class analysis. The groups exhibited face validity, revealed symptom patterns that added specificity to simple symptom counts, and were qualitatively similar when derived separately within population subgroups. Internal consistency was moderate (Cronbach's alpha = 0.61), indicating some variability in reporting. CONCLUSIONS: Dry eye symptoms are commonly reported in a representative elderly population. Symptom data were moderately consistent, suggesting their usefulness for dry eye assessment if properly summarized. A latent class summary revealed biologically meaningful summary patterns of symptoms reported in this population and holds promise for use in risk factor investigations and in clinical trials.

Aged↗
PubMed1997

[Skin and mucous membrane hemorrhages: clinical assessment, study sequence and relative frequency of hereditary diseases of the hemostasis in a Chilean population].

BACKGROUND: Skin and mucous membrane hemorrhages are distinctive manifestations of hereditary diseases of primary hemostasis and, among them, the different types of von Willebrand disease and of platelet function disorders are the most prevalent. AIM: To know the relative frequency of these disorders and to know the clinical features of patients with mucocutaneous hemorrhages. PATIENTS AND METHODS: Five hundred eighty nine patients whose main symptom was the presence of mucocutaneous hemorrhages were studied. Bleeding time, platelet count, coagulant activity of factor VIII (FVIII:C), FvW: Ag and FvW: CoRis and ABO blood group were measured in all patients in a first stage. According to the results of these tests, further studies were decided. RESULTS: In patients younger than 13 years old, male predominated and, in older patients, females consulted with higher frequency. There was a higher proportion of individuals with O blood type than in the normal population. Bleeding time was abnormal in 330 patients (56%). One hundred ten patients (19%) had won Willebrand disease and, among them, one third had a normal bleeding time. Isolated reduction of factor WII activity was found in 66 patients (11%, 51 males) and 32 of these had normal bleeding time. Eighty one patients (14%) were considered to have an hereditary platelet function defect. A precise diagnosis was not achieved in 332 patients (56%). CONCLUSIONS: Among patients consulting for mucocutaneous hemorrhages, 19% had von Willebrand disease, 11 had an isolated reduction of factor VIII activity, 14% had platelet function defects and in 56%, a precise diagnosis was not reached.

ABO Blood-Group System↗
PubMed1996

Risk factors for constant, severe trachoma among preschool children in Kongwa, Tanzania.

Trachoma, an ocular infection caused by Chlamydia trachomatis, is the second leading cause of blindness worldwide. The blinding sequelae, which occur in middle age, are felt to be the result of numerous or lengthy episodes of severe inflammatory trachoma in childhood. Risk factors for constant, severe trachoma were identified in a group of children enrolled in a longitudinal study in Kongwa, Tanzania, where villages were randomized in a clinical trial of mass treatment and a behavior modification campaign. In 1989, each of 1,417 randomly selected children had photographs taken of an upper eyelid for determination of their trachoma status. The photographs were graded by a reader who was masked as to the village and date of each photograph. Risk factor data on the family's socioeconomic status, distance to water, and hygiene practices were obtained at baseline. Follow-up examinations occurred 2, 6, and 12 months from baseline. Data from all four time points were available for 82% of the children enrolled. Overall, 10% of the children had constant, severe trachoma, defined as severe trachoma at three or four examinations. The odds ratio for severe trachoma was 1.9 for female children (95% confidence interval 1.3-2.7). Familial cattle ownership and having one or more siblings with trachoma at baseline were also significantly related to the odds of having severe trachoma. Children with a sustainably clean face had lower odds (odds ratio = 0.4, 95% confidence interval 0.3-0.7). A subgroup of 10% of children in these hyperendemic communities always seemed to have severe trachoma, despite enrollment in a mass treatment campaign. Improved face-washing plus antibiotic treatment may decrease the likelihood that these children will be at risk for blinding complications in adulthood.

Animals↗
PubMed1996

Hemostatic disorder of uremia: the platelet defect, main determinant of the prolonged bleeding time, is correlated with indices of activation of coagulation and fibrinolysis.

Several parameters of primary hemostasis and markers of activation of coagulation and fibrinolysis were measured in 48 patients with severe (creatinine clearance < 20 ml/min) chronic renal failure (CRF) without dialysis and disease or drugs affecting hemostasis. Bleeding time (BT) was prolonged in 25/48 patients, and was correlated with age of patients, severity of renal failure, hematocrit, impairment in platelet aggregation-secretion and decrease in platelet ATP content. Defects in von Willebrand factor played no role in the prolongation of the BT. Multivariate analysis showed that only platelet dysfunction and severity of renal disease were independent predictors of the BT in uremia. The platelet functional disorder was significantly correlated with a reduction in platelet ATP and ADP. High levels of plasma thrombin-antithrombin complexes (TAT), prothrombin fragment F1 + 2, fibrinogen and factor VIIc were observed in patients with CRF, as described in prethrombotic states. Plasmin-antiplasmin complexes (PAP), fibrinogen and fibrin degradation products (FgDP, FnDP) were significantly increased, and the activity of plasminogen activator inhibitor (PAI-1) was slightly reduced, denoting an activation of fibrinolysis. A negative correlation was found between platelet levels of ATP and ADP with plasma TAT, F1 + 2 and PAP. Furthermore, plasma PAI-1 activity was negatively correlated with the BT and was lower in patients with prolonged BT as compared with controls and patients with normal BT. These links between primary hemostasis and activation of coagulation and fibrinolysis suggest that increased intravascular generation of thrombin and/or plasmin is an important mediator of the defects in primary hemostasis, prolongation of the BT and, probably, bleeding in CRF.

Adolescent↗
PubMed1996

[Activated C protein resistance: laboratory study and prevalence of the defect in the Chilean population].

Activated protein C resistance (APCR) or Factor V Leiden has been recently described as the most prevalent hemostatic abnormality associated with venous thrombosis. In patients with familial thrombophilia, the prevalence of APCR is 19-60% and around 20% in sporadic venous thrombosis. APCR is usually measured by the degree of prolongation of Activated Partial Thromboplastin Time (APTT) on patient's plasma, induced by addition of APC in comparison to normal plasma. At the molecular level the defect is caused by a single-point mutation in the gene for factor V (FV) (G1.691-->A), that predicts the replacement of Arg506 by Glutamine. This mutation makes activated factor V resistant to inactivation by APC. Since the prevalence of the defect is highly variable among different populations, the objective of this work was to study its frequency in our population and in patients with thrombophilia. We defined the normal range for APTT ratio (APTT + APC/APTT - APC) in a group of 73 healthy volunteers in whom the presence of FV Q506 mutation was searched using Mull enzyme digestion of PCR amplified genomic fragment containing the nucleotide 1.691. The lower limit of APTT ratio established in this group was 2.13. APCR was found in 6 out of 159 control subjects (3.8%) and in 14/50 (28%) of patients with thrombosis. In 13 cases as a single defect and in one associated to type I protein C deficiency. All the APCR patients and control subjects were heterozygotes by gene analysis. The results demonstrate that in our population APCR is also the most common defect associated with thrombosis, in accordance with a high prevalence in the population. The ability to screen for this defect will permit the identification of carriers that would benefit of preventive therapy at risk situations.

Base Sequence↗
PubMed1996

[Hemophilia A: analysis of intron 18 and intron 7 of factor VIII gene and their role in a diagnostic strategy for carrier detection in a Chilean population].

Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. A larger number of different mutations in the VIII gene have been identified. Thus, the detection of female carriers, depends upon the analysis of DNA polymorphisms in and near the factor VIII gene. Our aim was to develop a strategy, earlier reported, for carrier testing in families at risk of hemophilia A. In this study, we analyzed the DNA polymorphisms in 26 affected families, with use of the factor VIII intragenic polymorphisms identified by the restriction enzymes BclI and AlwNI, and by differential hybridization with sequence-specific oligonucleotide probes recognizing BclI and AlwNI polymorphism. While the DNA polymorphism detected by BcilI site in intron 18 of the factor VIII gene was informative for 38% families studied, the AlwNI/intron 7 polymorphism provided additional information (4%). The carrier status of the remaining 58% could be determined utilizing the other polymorphisms suggested by strategy. The two polymorphic sites used combined with the other polymorphisms, intragenic and extragenic, can generate levels of informativeness greater than 98%. We concluded that the strategy for carrier testing would be a good alternative in genetic counselling for hemophilia A, but its limitations must be carefully taken into account.

Chile↗