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Biomedical subjects

J Kaldor

Publications and source records attributed to J Kaldor.

At least 91 records · Page 5Linked to original sources
PubMed1988

Antibody response to Campylobacter pylori in diverse ethnic groups.

Antibody response to Campylobacter pylori was measured in ethnic groups of Vietnamese, El Salvadorean and Ethiopian origin. The results were compared with the previously reported antibody titres found in sera of culture positive and culture negative patients, patients suffering from duodenal ulcer, white Australian blood donors and Australian Aboriginals. While in Vietnamese the prevalence of serologically positive sera was found to be similar to the white Australian population, numbers of serologically positive sera in El Salvadorean and Ethiopian ethnic groups was found to be very high. The high incidence of serologically positive sera in the Ethiopians correlated with the reported high incidence of duodenal ulcer in this population.

Adolescent↗
PubMed1988

Antibody response to Campylobacter pylori in an ethnic group lacking peptic ulceration.

The association between duodenal ulcer, gastritis and gastroduodenal colonization with Campylobacter pylori suggests a causal role for this newly described bacterium. In an attempt to challenge the verity of this association we studied a group of people in whom duodenal ulcer is apparently absent. Serological evidence of infection was sought with a sensitive, specific ELISA assay for C. pylori specific IgG and was compared with results from control sera from teenagers referred for respiratory viral serology, volunteer blood bank donors, patients with duodenal ulcers and patients in whom the presence or absence of C. pylori had been determined by histological and microbiological examination of gastric tissue. A relatively isolated group of Australian Aborigines in whom peptic ulceration is virtually unknown, was observed to possess age-specific mean C. pylori antibody levels comparable those found in a group of white Australian dyspeptic patients without microbiological evidence of infection with this organism. The antibody levels of Aborigines were lower than those found in an aged-matched group of 'healthy' white Australians, both of these groups having levels which were significantly lower than the levels found in culture positive white Australian dyspeptic patients. It was found that 21/144 'healthy' white Australians (14.6%) had antibody levels greater than or equal to the lower 99% confidence interval of the mean level found in culture positive patients, while only 2/274 Aborigines (0.7%) had such elevated levels. By contrast, 89/142 (62.7%) patients with endoscopically proven duodenal ulcer had similarly elevated specific antibody levels. These differences were highly significant. We consider these findings to be consistent with the hypothesis that C. pylori is important in the pathogenesis of duodenal ulcer.

Adolescent↗
PubMed1988

Epidemiological studies of the relationship between carcinogenicity and DNA damage.

The new methods for studying DNA damage in vivo offer cancer epidemiologists both a new study endpoint and a refinement of exposure measurement. Up to the present, they have not been applied in studies that satisfy standard epidemiological criteria. In particular, more attention must be paid to the selection of study samples and to ensuring adequate numbers of study subjects. There are substantial problems in studying the link between DNA damage and carcinogenesis at the individual level, including the long latency and the multifactorial etiology of most cancers. Acute leukaemia induced by alkylating agent therapy represents one of the few human situations in which such studies are feasible, since patients are exposed at carefully measured and recorded doses, the risk is high and specific, and follow-up is good. A considerable saving in resources could be achieved by storing samples from a large number of treated patients and carrying out analyses of DNA damage only in those from people who develop leukaemia and from suitably chosen matched controls.

Antineoplastic Agents↗
PubMed1987

Campylobacter jejuni/Campylobacter coli-associated Guillain-Barré syndrome. Immunoblot confirmation of the serological response.

Immunoblot (Western blot) examination of the sera of 45 patients with the Guillain-Barré syndrome demonstrated that between three and five immunoreactive bands that were characteristic of a recent Campylobacter jejuni/Campylobacter coli infection were present in 22 of these patients. The immunoblots paralleled the serological response that is found in campylobacter enteritis and confirmed the specificity of our previous enzyme-linked immunosorbent assays (ELISAs), which indicates that antecedent C. jejuni/C. coli infection is common in patients with the Guillain-Barré syndrome. We postulate that, under certain circumstances, demyelination is initiated by the leakage of campylobacter-specific antibody across the blood-nerve barrier.

Campylobacter Infections↗
PubMed1987

Aflatoxin exposure, hepatitis B virus infection and liver cancer in Swaziland.

A study was carried out in Swaziland to assess the relationship between aflatoxin exposure, hepatitis B infection, and the incidence of liver-cell carcinoma, which is the most commonly occurring malignancy among males in Swaziland. Levels of aflatoxin intake were evaluated in dietary samples from households across the country, and crop samples taken from representative farms. Prevalence of hepatitis B markers was estimated from the serum of blood donors, and liver cancer incidence was recorded for the years 1979-83 through a national system of cancer registration. Across 4 broad geographic regions, there was a more than 5-fold variation in the estimated daily intake of aflatoxin, ranging from 3.1 to 17.5 micrograms. The proportion of HBV-exposed individuals was very high (86% in men), but varied relatively little by geographic region; the prevalence of carriers of the surface antigen was 23% in men, and varied from 21 to 28%. Liver cancer incidence varied over a 5-fold range, and was strongly associated with estimated levels of aflatoxin. In an analysis involving 10 smaller subregions, aflatoxin exposure emerged as a more important determinant of the variation in liver cancer incidence than the prevalence of hepatitis infection. Aflatoxin estimates from crop samples appeared to be a reasonable surrogate for dietary measurements. A comparison with dietary aflatoxin levels measured in an earlier survey in Swaziland suggested that programmes aimed at reducing contamination levels had had some success.

Aflatoxins↗
PubMed1987

Empirical Bayes estimates of age-standardized relative risks for use in disease mapping.

There have been many attempts in recent years to map incidence and mortality from diseases such as cancer. Such maps usually display either relative rates in each district, as measured by a standardized mortality ratio (SMR) or some similar index, or the statistical significance level for a test of the difference between the rates in that district and elsewhere. Neither of these approaches is fully satisfactory and we propose a new approach using empirical Bayes estimation. The resulting estimators represent a weighted compromise between the SMR, the overall mean relative rate, and a local mean of the relative rate in nearby areas. The compromise solution depends on the reliability of each individual SMR and on estimates of the overall amount of dispersion of relative rates over different districts.

Age Factors↗
PubMed1987

Intragastric nitrosation and precancerous lesions of the gastrointestinal tract: testing of an etiological hypothesis.

The N-nitrosoproline (NPRO) test was used to study whether subjects with precancerous conditions of the stomach have an elevated potential for endogenous nitrosation. The highest yield of NPRO after ingestion of beetroot juice (as a source of nitrate) and proline was seen in subjects whose pH of fasting gastric juice was about 1.5-2. No increased level of NPRO was detected in subjects with more advanced lesions, compared to those with a normal stomach. Counts of total and nitrate-reducing bacteria were positively correlated with the pH of gastric juice but did not correlate with the urinary level of NPRO in the same individuals. Bacteria and intragastric nitrosation are discussed as possible etiological factors in human stomach cancer.

Adult↗
PubMed1986

Epidemiology of campylobacter diarrhoea.

Campylobacter diarrhoea was diagnosed bacteriologically in 535 patients. Most of these patients required hospitalization, but no fatalities were recorded. The age-specific incidence of campylobacter enteritis showed a trimodal distribution. Overseas travel was a factor in 14% of all cases. Food, including "fast food", may be an important source of infection. Campylobacter enteritis was more prevalent during summer than winter. Campylobacter bacteraemia was detected in only four cases. Biotyping was performed on 285 of the strains that were isolated. Biotype analysis showed that there was a clustering of cases of certain biotypes, even though community-wide outbreaks were not recognized in the period of review.

Adolescent↗
PubMed1986

Serum and urinary methionine concentrations in severe hepatic failure of viral hepatitis. Relevance to development of encephalopathy and prognosis.

A simple spectrophotometric method was developed to measure serum and urinary methionine concentrations. Serum methionine concentrations of greater than 200 mumol/L were found only in patients who were suffering from severe liver failure. In patients who died because of severe liver failure, a continuing increase in the methionine concentration was associated with a deteriorating mental state, while in patients who recovered the serum methionine concentration remained below 200 mumol/L during the coma stage. Urinary methionine to creatinine ratios above 300 were found only in specimens from patients who died. Sera and urine specimens from patients who were suffering from uncomplicated viral hepatitis showed no increase in methionine concentrations, while sera from patients with renal impairment and urinary specimens from patients who were suffering from chronic active hepatitis showed normal or only mildly elevated methionine concentrations.

Acute Disease↗
PubMed1986

An empirical comparison of methods used to estimate carcinogenic potency in long-term animal bioassays: lifetable vs summary incidence data.

Two methods for estimating carcinogenic potency from animal carcinogenesis bioassays (TD50-defined in the paper) are compared, one based on lifetable data and one based on summary incidence data. The lifetable analysis adjusts for the differential effects of toxicity among dose groups and for differences in the time pattern of tumor incidence, while summary incidence analysis does not. However, summary data are all that are usually available in the published results of animal cancer tests. Using NCI bioassay results which provide full lifetable data, we compare lifetable and summary estimates of potency and their statistical significance as well as the estimated shape of the dose-response curve. There is substantial agreement between these methods of analysis in terms of potency estimation, although lifetable estimates are usually more potent. But, there are some notable differences in the estimated shape of the dose-response curve, suggesting that both target site selection and method of analysis play an important role in risk estimation.

Actuarial Analysis↗
PubMed1986

Response of experimental animals to human carcinogens: an analysis based upon the IARC Monographs programme.

Only the results of epidemiological studies can be used to establish a causal relationship between an exposure to an agent and human cancer; however, such studies often cannot be carried out due to limitations of population or latent period or to the presence of mixed exposures. It is essential, therefore, that the validity be established of extrapolating to humans the results obtained from long-term carcinogenicity tests in animals. The responses of experimental animals to known and suspected human carcinogens, as evaluated in the IARC Monographs series, were analysed as an indication of the sensitivity of animal tests for predicting human carcinogens. Although the response was high - 84% - it would have been even higher had all the compounds been adequately tested experimentally. An additional finding was that for many exposures causally related to human cancer, there is a target organ in common between humans and at least one animal species, despite many inherent physiological differences. These findings show clearly the importance of experimental carcinogenicity studies in the primary prevention of cancer.

Animals↗
PubMed1986

Models for respiratory cancer in nickel refinery workers.

Lung and nasal sinus cancer death rates among employees of a nickel refinery in South Wales were examined from the standpoint of quantifying the relationship between exposure and the risk of these two cancers. Areas in the refinery associated with high risk were identified by using a matched case-control approach, and a simple index of exposure for each man was constructed accordingly based on the duration of time spent in these areas. The dependence of relative risk and absolute excess risk for lung and nasal sinus cancers on age at first employment, calendar period of first employment, time since first employment, and duration of exposure in high-risk areas was then analyzed. The relative risk for nasal sinus cancer increased sharply with increasing age at first exposure but remained roughly constant throughout the period of follow-up, while that for lung cancer was independent of age at first exposure and dropped sharply with increasing time since first employment. The implications and limitations of these analyses are discussed in relation to the multistage theory of carcinogenesis and occupational risk assessment.

Adult↗
PubMed1986

Misclassification in case-control studies with two dichotomous risk factors.

The effects of misclassification are considered for a case-control study in which the effects of two dichotomous risk factors on disease risk are under investigation. When only one of the risk factors is misclassified, the summary odds ratio associated with that factor based on expected cell counts is biased towards unity, and the magnitude of the apparent interaction between the two variables is altered. When the misclassified variable is a confounder, the summary odds ratio for the exposures of interest remains partly confounded. Extensive tabulations of the results are given, for a range of prevalences, relative risks and misclassification rates of the factors. Even misclassification rates as low as 10% can prevent adequate control of confounding. The implications of this finding for the interpretation of epidemiological studies are examined.

Disease↗