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C Brownie

Publications and source records attributed to C Brownie.

31 records · Page 2Linked to original sources
PubMed1988

Preliminary study on serum enzyme changes in Long Evans rats given parenteral ochratoxin A, aflatoxin B1 and their combination.

Long Evans rats of both sexes were each administered a total of 250 micrograms aflatoxin B1 (AFB1), ochratoxin-A (OCH-A) or 500 micrograms AFB1 + OCH-A (1:1 ratio) in corn oil over 5 equal daily intraperitoneal (IP) injections of 50 micrograms/rat/day. Control rats were given a total of 1.25 ml corn oil over 5 equal daily IP injections of 0.25 ml/rat. All rats were observed daily for clinical signs of toxicity. Twenty-four hr following the last injection all rats were weighed, killed, examined for gross pathologic lesions and blood samples collected for routine hematologic and serum chemistry evaluation. All rats gained weight over the treatment period. Though not significantly different among the treatment groups, weight gain was significantly greater for males (54.0 g) than females (33.8 g). Routine hematology showed no difference among treatment groups. Serum enzyme aspartate aminotransferase (AST = SGOT) activities were indicative of hepatoxicity. Lactate dehydrogenase (LDH) activity was significantly increased in the AFB1 and AFB1 + OCH-A treatment groups, signifying a possible interaction between these 2 mycotoxins. LDH isoenzyme fractionation studies would be helpful in delineating the organ system(s) involved and the possible diagnostic value of this interaction.

Aflatoxin B1↗
PubMed1986

Teratogenic effect of calcium edetate (CaEDTA) in rats and the protective effect of zinc.

The calcium chelate of EDTA (CaEDTA) currently is the drug of choice in the treatment of lead intoxication. This study investigated the teratogenic potential of CaEDTA, administered parenterally during periods of organogenesis and determined if incorporating zinc into EDTA would protect against teratogenic effects. Four doses (2, 4, 6, and 8 mmol/m2/day) of CaEDTA, two concentrations (8 and 20 mmol/m2/day) of ZnEDTA and ZnCaEDTA (molar ratio 0.5:0.5:1) were used, and a saline control (0.9% NaCl). Timed-pregnant Long-Evans rats were assigned at random to the treatment groups, 20 per dose for each chelate and 30 to the saline control. Rats were injected with the chelate or saline solution sc, twice daily during the 11th through 15th days of gestation. Pups removed by cesarean section on the 21st day were processed for osseous and visceral examination. Additional animals per treatment group were used for maternal plasma and liver and fetal zinc determinations. Results showed increases in several abnormalities (submucous cleft, cleft palate, adactyly-syndactyly, curly tail, abnormal rib and vertebrae) with increasing amounts of CaEDTA. No malformations were seen with ZnEDTA at either dose or with ZnCaEDTA at 8 mmol/m2/day. However, submucous cleft was seen in 6 of 20 litters from the dams receiving the higher dose of ZnCaEDTA. It was concluded that CaEDTA is teratogenic in rats at concentrations which, except for decreased weight gain, produce no discernible toxicity to the dam, and which are comparable to the recommended therapeutic dosage in humans (1500 mg/m2/day corresponding to 4 mmol/m2/day). Protection is afforded by incorporating zinc in the chelate.

Abnormalities, Drug-Induced↗
PubMed1986

The effects of exposure misclassification on estimates of relative risk.

In epidemiologic studies, individuals may be misclassified with respect to exposure to a risk factor for disease. Such misclassification causes the relative risk of disease associated with the exposure in the population to be biased toward the null value. Here, a formula is derived for the apparent relative risk under misclassification (R) as a function of the sensitivity (U) and specificity (V) of the test for exposure and of the true relative risk (R) and true prevalence of exposure (P(E] in the population. The relative influence of U and V on the bias in R depends both on R and on P(E), with U tending to be more influential at higher values of P(E). When there is misclassification of exposure, variation in P(E) may bias comparisons of relative risk between groups or exposures, either by producing spurious differences or by masking true differences, and may generate spurious trends associated with a third variable such as age. Because the possible effects of misclassification of exposure on relative risk are complex and not easily generalized, the potential degree of bias should be evaluated individually in each situation.

Diagnostic Errors↗
PubMed1986

Comparing indicators of health or nutritional status.

The performance of an indicator of health or nutritional status depends on its sensitivity and specificity properties over a range of cut-offs. Frequently, it is of interest to compare indicators to pick the best for a given purpose, such as screening for disease or monitoring to detect changes in prevalence of inadequate nutriture. Relative operating characteristic (ROC) analysis provides an objective method for making this comparison, but the application of this methodology as described for epidemiologists in this Journal is now outdated for most indicators. Recent developments are noted and an alternative analysis for use with continuous Gaussian data is presented here. The estimators and statistical test procedures proposed here are compared with the previously described methods, by means of a computer simulation study. The new procedures are found to be superior for continuous Gaussian data, and have the practical advantage that they do not require use of a specialized computer program. The implications of these results for comparing indicators to be used to monitor population prevalences are discussed.

Computers↗
PubMed1986

Constant-parameter capture-recapture models.

Jolly (1982, Biometrics 38, 301-321) presented modifications of the Jolly-Seber model for capture-recapture data, which assume constant survival and/or capture rates. Where appropriate, because of the reduced number of parameters, these models lead to more efficient estimators than the Jolly-Seber model. The tests to compare models given by Jolly do not make complete use of the data, and we present here the appropriate modifications, and also indicate how to carry out goodness-of-fit tests which utilize individual capture history information. We also describe analogous models for the case where young and adult animals are tagged. The availability of computer programs to perform the analysis is noted, and examples are given using output from these programs.

Aging↗
PubMed1986

Testing for a treatment effect in the presence of nonresponders.

Good (1979, Biometrics 35, 483-489) introduced a new randomization test for the two-sample problem where a proportion 1 - p of the treatment group does not respond to the treatment, and suggested that the Wilcoxon test is not effective for this situation. We show to the contrary that the Wilcoxon test is quite useful when p greater than or equal to .6 and point out an error in his definition of a one-tailed randomization test.

Animals↗
PubMed1984

Selecting a screening cut-off point or diagnostic criterion for comparing prevalences of disease.

Comparisons of population prevalences of disease or of inadequate nutriture, across locations or over time (as in monitoring to detect a change in prevalence) are important activities in epidemiology and public health. The data collected are often counts based on a dichotomy of a continuous indicator variable, and performance of the test procedure depends on the cut-off point used. This cut-off may be chosen to optimize performance, on the assumption that the indicator has a mixed normal distribution with unknown mixing proportion corresponding to the unknown prevalence of disease. Results of James (1978, Biometrics 34, 265-275) are applied and extended to the context of monitoring. Charts are presented to facilitate determination of the optimal cut-off, and examples are given for several indicators of nutritional status.

Biometry↗
PubMed1983

Prevalences of anemia and iron deficiency anemia in Black and White women in the United States estimated by two methods.

Prevalences of anemia were estimated by two methods for 742 Black and 3,074 White nonpregnant women of childbearing age drawn from a large probability sample of the United States civilian noninstitutionalized population (NHANES I). One method defines the prevalence of anemia as the proportion of women with hemoglobin levels below a 12 g/dl "cut-off". The second method defines the prevalence of anemia as the proportion of women whose hemoglobin values are shifted downwards relative to a distribution of hemoglobin values of non-anemic women. Estimates produced by both methods suggest a higher prevalence of anemia in Black than in White women. Estimates produced by the "cut-off" method, however, are higher than those from the "distribution" method for both racial groups, probably because the "cut-off" method results in large overestimates in populations where anemia prevalence is low. The "distribution" method is further used to estimate the contribution of iron deficiency to anemia. Essentially all anemia in White women and a high proportion of anemia in Black women is associated with iron deficiency in the US civilian noninstitutionalized population. Iron supplementation trials are needed in order to define the magnitude of the problem accurately and plan appropriate public health programs.

Adolescent↗
PubMed1976

Models allowing for age-dependent survival rates for band-return data.

Seber [1970] and Robson and Youngs [1971] developed a statistical model for a tag-recapture experiment on an exploited animal population in which banded or tagged individuals are released into a population each year, and the bands from harvested individuals are returned by hunters or fishermen in following years. Consideration of certain biological and ecologicw models for an experimental situation where data are recorded separately for birds released as adults and as young-of-the-year. In particular, the effect of different survival rates of young birds, and the effect of migration on reporting rates, are taken into account in the models presented in this study. Maximum likelihood estimators of parameters are derived under the different models, and procedures are developed to discriminate between alternative models as well as provide non-discriminant goodness-of-fit tests.

Age Factors↗
PubMedDate not supplied

Experimental infection of turkeys with Mycoplasma gallisepticum of low virulence, transmissibility, and immunogenicity.

Three-week-old turkeys were inoculated intranasally with approximately 10(6) colony-forming units (CFU) of putative variant Mycoplasma gallisepticum (MG) strains M876, M35, or the virulent S6 reference strain. Uninoculated turkeys in each group served as contact sentinels. The hemagglutination-inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) were used to determine serologic responses. MG was isolated from 100% and 92% of S6- and M876-inoculated turkeys, respectively, on day 7 PI. However, culture-positive rates among M876-inoculated turkeys declined more rapidly, transmission to contact sentinels took longer and occurred at lower rates, and serologic responses measured by HI and ELISA were lower than in S6-infected turkeys. Testing sera from inoculated turkeys for antibodies to MG in homologous and heterologous ELISA systems indicated that strain M876 was significantly (P less than 0.05) less immunogenic than S6 (days 62 and 95 PI), and that the homologous ELISA was more sensitive (P less than 0.005). MG strain M35 failed to infect turkeys in three attempts, even though the inocula used were viable on culture media.

Animals↗