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C Pereira

Publications and source records attributed to C Pereira.

At least 91 records · Page 5Linked to original sources
PubMed1989

Quantitative inter-relationships between aflatoxin B1 carcinogen dose, indole-3-carbinol anti-carcinogen dose, target organ DNA adduction and final tumor response.

A number of recent studies have described inhibitor-mediated reductions in the covalent DNA binding and tumorigenicity of various carcinogens, in species such as rats, mice and rainbow trout (Salmo gairdneri). Since inhibitory effects have, in most cases, been reported after testing at one carcinogen and one inhibitor level only, the detailed relationships between carcinogen dose, inhibitor dose, in vivo DNA binding and final tumor response are not well understood in any species. To determine these relationships we have employed the trout model in a combined DNA binding/tumor dose-response protocol using approximately 10,000 animals. Trout were pretreated with one of five different dose-levels of indole-3-carbinol (I3C), a naturally occurring anti-carcinogen found in cruciferous vegetables such as broccoli and cabbage. After 4 weeks, animals received the same dietary level of I3C for a further 2 weeks together with [3H]aflatoxin B1 (AFB1) in the dose-range 10-320 p.p.b. From tanks containing 150 animals (three tanks per I3C-AFB1 dose-point), 15 fish were selected at random in order to assess hepatic AFB1-DNA binding levels. Remaining animals were returned to control diet for determination of tumor response at 12 months. Linear increases in DNA binding occurred with dose of AFB1 at each I3C dose-level. Successive increases in I3C dose gave dose-related decreases in AFB1-DNA binding, resulting in a series of curves of decreasing slope. Shifts in DNA-binding slopes were compared quantitatively with horizontal displacements towards higher carcinogen dose in corresponding tumor dose-response curves. At I3C doses of less than or equal to 2000 p.p.m., the inhibitor-altered tumor response was predicted precisely by changes in dose received (DNA adducts formed) in the target organ. These data constitute the first direct evidence of pure anti-initiating activity by a natural anti-carcinogen found in human diet, where all animals were treated at the same time and under identical conditions of exposure in both DNA binding and tumor studies. The data are discussed further in view of (i) their implications for DNA binding-carcinogenicity correlations and the concept of 'molecular dosimetry', and (ii) limitations in the current database on anti-carcinogenesis as regards in vivo potency information, particularly for 'ambivalent modulators' which exhibit both inhibitory and promotional activity.

Aflatoxin B1↗
PubMed1988

Current status of cytogenetic procedures to detect and quantify previous exposures to radiation.

The estimation of the magnitude of a dose of ionizing radiation to which an individual has been exposed (or of the plausibility of an alleged exposure) from chromosomal aberration frequencies determined in peripheral blood lymphocyte cultures is a well-established methodology, having first been employed over 25 years ago. The cytogenetics working group has reviewed the accumulated data and the possible applicability of the technique to the determination of radiation doses to which American veterans might have been exposed as participants in nuclear weapons tests in the continental U.S.A. or the Pacific Atolls during the late 1940s and 1950s or as members of the Occupation Forces entering Hiroshima or Nagasaki shortly after the nuclear detonations there. The working group believes that with prompt peripheral blood sampling, external doses to individuals of the order of about 10 rad (or less if the exposure was to high-LET radiation) can accurately be detected and measured. It also believes that exposures of populations to doses of the order of maximum permissible occupational exposures can also be detected (but only in populations; not in an individual). Large exposures of populations can also be detected even several decades after their exposure, but only in the case of populations, and of large doses (of the order of 100 to several hundred rad). The working group does not believe that cytogenetic measurements can detect internal doses from fallout radionuclides in individuals unless these are very large. The working group has approached the problem of detection of small doses (less than or equal to 10 or so rad) sampled decades after the exposure of individuals by using a Bayesian statistical approach. Only a preliminary evaluation of this approach was possible, but it is clear that it could provide a formal statement of the likelihood that any given observation of a particular number of chromosomal aberrations in a sample of any particular number of lymphocytes actually indicates an exposure to any given dose of radiation. It is also clear that aberration frequencies (and consequently doses) would have to be quite high before much confidence could be given to either exposure or dose estimation by this method, given the approximately 3 decades of elapsed time between the exposures and any future blood sampling.(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Radiation-Induced↗
PubMed1988

Comparative effect of dietary butylated hydroxyanisole and beta-naphthoflavone on aflatoxin B1 metabolism, DNA adduct formation, and carcinogenesis in rainbow trout.

Butylated hydroxyanisole (BHA) and beta-naphthoflavone (BNF), both chemicals with anti-carcinogenic properties in some experimental animals, were compared for effects on aflatoxin B1 (AFB1) metabolism, hepatic DNA adduct formation and carcinogenesis in the rainbow trout. Dietary BHA had no effect on the hepatic tumor incidence when fed at 0.03 or 0.3% 4 weeks prior to and during a 4 week dietary exposure of 10 p.p.b. AFB1. BNF, when fed at 0.005 or 0.05% under similar conditions, significantly reduced tumor response, which confirms previous results in trout (Nixon et al., Carcinogenesis, 5, 615-619, 1984). BHA fed at either 0.03 or 0.3% for 8 weeks had no post-initiation effect on the 52 week hepatic tumor incidence of trout exposed to a 0.5 p.p.m. AFB1 solution as embryos. A similar post-initiation exposure to 0.05% BNF significantly enhanced AFB1 tumor response. The influence of dietary BHA and BNF on AFB1 metabolism and DNA adduct formation and persistence in trout were examined. A 3 week pre-treatment with 0.3% dietary BHA had no effect on in vivo hepatic nuclear AFB1-DNA adduct formation at 0.5, 1, 2 and 7 days after AFB1 i.p. injection. By contrast 0.05% dietary BNF reduced hepatic AFB1-DNA adducts to 33-60% of control levels at 0.5, 1, 2 and 4 days after AFB1 exposure. This was accompanied by significantly lower blood and liver levels of AFB1 during the first 24 h after i.p. injection. Livers of BNF trout also contained 4-fold more of the less carcinogenic metabolite, aflatoxin M1, and 50% less aflatoxicol (AFL), a metabolite with similar carcinogenicity as AFB1. Bile AFL-glucuronide levels were significantly decreased in BNF-fed trout, but total bile glucuronides were significantly increased due to a 15-fold increase in aflatoxicol-M1 glucuronide. Freshly isolated hepatocytes from BHA-fed fish, when incubated with AFB1 for 1 h, showed no difference in levels of AFB1-DNA adducts or ratios of AFB1 metabolites when compared to hepatocytes isolated from fish fed a control diet only. By contrast, dietary BNF has been previously shown to greatly enhance AFM1 production, reduce AFL production, and significantly reduce AFB1-DNA adduct formation in isolated trout hepatocytes (Bailey et al., Natl. Cancer Inst. Monograph, 65, 379-385, 1984). These results indicate that dietary BHA up to 0.3% does not alter AFB1 metabolism or DNA adduction in trout, nor does it inhibit or promote AFB1 hepatocarcinogenesis in this species.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗
PubMed1984

The family heart dietary intervention program: community response and characteristics of joining and nonjoining families.

A random sample of 501 eligible families was selected from a designated neighborhood in Portland, Oregon, and given the opportunity to join a 5-year intervention program promoting a low-fat and low-cholesterol eating pattern designed to reduce risk for coronary heart disease. Participation entailed three baseline assessments of clinical, dietary, and psychological indices, periodic follow-up measurements, and monthly small group meetings led by psychologists and nutritionists. A prior home health survey allowed comparisons of respondents from joining and nonjoining families in terms of reported health status, health beliefs, health locus of control, knowledge about health and nutrition, and demographic characteristics. Almost half (47%) of all invited families agreed to join this long-term nutrition intervention program and completed the necessary baseline assessments. Factors discriminating joiners and nonjoiners were not generally consistent with the health belief model of preventive health behavior. Joiners were similar to nonjoiners in terms of perceived susceptibility to disease, family health histories, and reports of elevated plasma cholesterol levels in the family. However, families with hypertensive members were less likely to join this heart disease prevention program. Positive predictors of participation included higher occupational status, greater knowledge about heart disease, a more internal health locus of control, and the belief that there are few barriers preventing the adoption of a healthier low-fat eating pattern. These findings indicate that there is widespread community interest in optimal nutrition, and they also provide suggestions as to what motivates the general public to take preventive health actions.

Adolescent↗
PubMed1982

Radioimmunoassay for hepatitis B core antigen.

Serum hepatitis B core antigen (HBcAg) is an important marker of hepatitis B virus replication. We describe an easy, sensitive radioimmunoassay for determination of HBcAg in detergent-treated serum pellets containing Dane particles. Components of a commercial kits for anti-core determination are used, and HBcAG is measured by competitive inhibition of binding of 125I-labeled antibodies to HBcAg with HBcAg-coated beads. We assayed of HBcAG in the sera of 49 patients with hepatitis B surface antigen (HBsAg)-positive chronic hepatitis, 50 patients with HBsAg-negative chronic hepatitis, and 30 healthy volunteers. HBcAg was detected in 41% of patients with HBsAg-positive chronic hepatitis but not in patients with HBsAg-negative chronic hepatitis. Hepatitis Be antigen (an antigen closely associated with the core of Dane particles) determined in the same sera by radioimmunoassay, was not detected in 50% of HBcAg-positive sera.

Cross Reactions↗
PubMed1979

Intradermal responses to common bacterial antigens: influences of sex and clinical condition.

Intradermal responses to antigens of 12 common bacteria were evaluated in 218 dermatologic and 155 respiratory patients. Women responded more frequently than men and respiratory patients responded significantly more frequently than dermatologic patients to certain antigens. Interpretation of interspecies associations of responses suggested that certain organisms may be key species in the development of bacterial hypersensitivity.

Antigens, Bacterial↗
PubMed1978

Contact dermatitis in Salvador, Brazil.

In Salvador, Brazil, 536 patients were patch tested with 24 contact allergens. The most common sensitizers included potassium dichromate, thimerosal, hydroquinone, nitrofurazone ointment and nickel sulfate. The results of this South American study are compared with those published by North American and European dermatologists. Low frequencies of positive reactions were encountered in Salvador to some substances, including mercury bichloride and p-phenylenediamine. The influences of climate and life style in determining patterns of contact sensitivity are discussed.

Adult↗
PubMedDate not supplied

Control of Trypanosoma cruzi epimastigote motility through the nitric oxide pathway.

Trypanosoma cruzi epimastigote motility can be enhanced by addition of L-arginine, to the culture. This effect is blocked by N-methyl-L-arginine, a competitive inhibitor of the nitric oxide synthase. N-methyl-D-aspartate and L-glutamate, two agonists of the NMDA/L-glutamate receptor, also enhanced motility. This stimulation is blocked by MK-801 a noncompetitive antagonist of the NMDA receptor. In addition, sodium nitroprusside, a guanylyl cyclase stimulator and 8-Br-cyclic GMP, and analog of cyclic GMP, also stimulated epimastigote motility. It is suggested that an increase of intracellular cyclic GMP levels mediated by nitric oxide may be responsible for the increase in epimastigote motility.

Amino Acids↗
PubMedDate not supplied

Aeroallergens sensitization in an allergic paediatric population of Cova da Beira, Portugal.

Cova da Beira is an interior central region of Portugal, with a population of 93,000 inhabitants. The first pollen counts performed in Portugal revealed the highest values of the country in this area. The aim of this study was to assess the aeroallergens sensitization in an allergic population, according to the age groups. In a 5 year period (1995-2000) 1790 consecutive outpatients were observed for suspected allergic symptoms. We included in this study all the 557 paediatric (< or = 15 years old) observed patients (317 male (57%) and 240 female (43%) with an average age of 7.6 < or = 4.2 years old). They were divided in three age groups (Group I: < or = 5 yr; Group II: 6-10 yr; Group III: 11-15 yr). 371 patients were submitted to skin prick tests to aeroallergens. 86.5% of these patients were sensitised to at least one allergen extract. The most representative aeroallergens sensitization were grasses mixture (44.9%), D. pteronyssinus (32.5%), D. farinae (29.1%), Olea europea (27.5%), Parietaria judaica (23.4%), cat dander (16.1%), Artemisia vulgaris (17.6%), Robinia pseudoacacia (12.2%), Platanus acerifolia (11.4%), Tilia cordata (11.4%) moulds mixture (11.2%), Plantago lanceolata (10.6%), dog dander (10.4%), and Pinus radiata (7.5%). The sensitisation to indoor aeroallergens, was similar in all age groups and it was less important than that of pollens. The prevalence of sensitisation to grasses was the greatest in all ages and the house dust mites sensitization was the second most prevalent. The highest pollens counts in this region could explain the early sensitisation even in young children.

Adolescent↗
PubMedDate not supplied

Prevalence and factors associated to the epidemic neuropathy in a population assisted by a family doctor in Cuba.

With the outbreak of an epidemic neuropathy (EN) of unknown ethiology, a study of the prevalence and factors associated to the disease was carried out in the Zamora community, municipality of Marianao, Havana City. There were 11 patients identified with EN for a prevalence rate of 1.7/100. The major risk group was the one between 45 and 64 years of age, female sex, black skin. In the univaried analysis, a high prevalence ratio (PR) was found linked to beverage intake (PR = 5.32 95%; confidence intervals (CI) = 1.2-24.4), frequent drugs intake (PR = 6.59; CI = 1.8-24.6), consumption of edible of non certified fats (PR = 4.48; CI = 1.2-16.7) and the smoking habit (PR = 3.6; CI = 1.1-12.2). More than 73/100 (CI = 68.7-78.3) of the people under serologic study were infected with Coxsakie virus A-9 (strain 47) isolated from a patient still under research. It seems there are many factors like linder intake, antecedents of hemorrhagic conjunctivitis, nutritional aspects and others that, with the virus isolated were associated with this epidemiologic situation.

Adolescent↗
PubMedDate not supplied

Magnetization-transfer histogram analysis of the cervical cord in patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Previous studies have failed to show significant correlations between the number and extent of T2 spinal cord lesions and the clinical status of multiple sclerosis (MS) patients. We evaluated 1) whether it is feasible to create magnetization transfer-ratio (MTR) histograms of the cervical cord in patients with MS by using two different acquisition schemes, and 2) whether cervical cord MTR histogram metrics were different from those of healthy control subjects and between MS patients with and without locomotor disability. METHODS: We obtained two sets of gradient-echo sequences with and without a saturation pulse from 90 MS patients and 20 sex- and age-matched healthy control subjects. One set consisted of 20 axial, contiguous slices with a thickness equal to 5 mm. The other set consisted of 17 sagittal slices with a thickness equal to 3 mm and an interslice gap equal to 0.3 mm. After image coregistration and removal of tissues around the cervical cord, MTR histograms were created. The average MTR, the peak height, and the peak position of the histograms were measured. All of these measurements were from the whole of the cervical cord, thus including both MS lesions and normal-appearing tissue. RESULTS: When comparing the MTR histograms obtained using axial, contiguous, 5-mm-thick slices, MS patients had significantly lower average cervical cord MTR and peak height than did control subjects. When comparing the MTR histograms obtained using sagittal, 3-mm-thick slices, MS patients also had significantly lower average cervical cord MTR and peak location than did control subjects. Patients with locomotor disability had significantly lower average cord MTR and peak location than those without. CONCLUSION: This study shows that it is feasible to obtain MTR histograms of the cervical cord from MS patients by using different acquisition schemes. Our results also suggest that the assessment of MS cervical cord damage, achieved using MTR histograms, may lead to a better understanding of the clinical manifestations of the disease.

Adult↗