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Biomedical subjects

N Wald

Publications and source records attributed to N Wald.

At least 91 records · Page 5Linked to original sources
PubMed1986

Serum retinol and subsequent risk of cancer.

In a prospective study of about 22,000 men attending a well person screening centre, serum samples were collected and stored. The concentration of retinol was measured in the stored serum samples from 227 men subsequently notified as having cancer and from 454 unaffected controls, matched for age, smoking history and duration of storage of the serum samples. The mean serum retinol concentration of the cancer subjects who developed cancer before the elapse of one year since the time blood was collected was significantly lower than the mean concentration of their matched controls (641 and 722 micrograms l-1 respectively, P less than 0.001). For subjects whose cancer developed one to two years after blood had been collected, the difference was less (650 and 701 micrograms l-1 respectively, P less than 0.01). For subjects whose cancer developed three or more years after blood was collected, the mean retinol level was higher than in their controls, although not statistically significantly so (694 and 663 micrograms l-1 respectively). These findings suggest that the inverse association between serum retinol and risk of cancer that was previously observed was due to low serum retinol being a metabolic consequence of cancer rather than a precursor of cancer.

Disease Susceptibility↗
PubMed1986

Probability of causation tables and their possible implications for the practice of diagnostic radiology.

In compliance with requirements in the Orphan Drug Act (97-414) of 1983, tables were recently constructed by an ad hoc committee of the National Institutes of Health (NIH) in which the probabilities that certain specific cancers are caused by previous radiation exposure are estimated. The reports of the NIH committee and a National Academy of Science oversight committee may have broad implications for the future practice of diagnostic radiology. The basis on which the probability of causation tables were established and some of the possible implications for diagnostic radiology are discussed.

Dose-Response Relationship, Radiation↗
PubMed1984

Placebo controlled trial of nicotine chewing gum in general practice.

Of 2110 adult cigarette smokers originally recruited to a study of the effect of antismoking advice in general practice, 429 who reported at follow up after one year that they had tried unsuccessfully to stop smoking were offered "a special antismoking chewing gum," either nicotine gum or a placebo gum, in a double blind study. Of 200 who were willing to try the gum, 101 were randomly allocated to the nicotine gum and 99 to the placebo gum. They were followed up at six months by an unannounced home visit, at which they were interviewed and asked to provide a breath sample for analysis of carbon monoxide. Twenty five claimed that they had stopped smoking, but, of them, seven exhaled levels of carbon monoxide indicative of continued smoking. Of the 18 in whom giving up smoking was validated, 10 had received active gum and eight placebo gum, a difference which was not significant (odds in favour of nicotine gum = 1.25, 95% confidence limits 0.47-3.31). The value of nicotine chewing gum, if any, can be quite small when it is used in general practice.

Carbon Monoxide↗
PubMed1984

Controlled trial of three different antismoking interventions in general practice.

Of 6052 adult patients who consulted their doctors in six Oxfordshire general practices between October 1980 and February 1981, 2110 (35%) were smokers. The smokers were allocated to one of four study groups--a control (non-intervention) group; a group that received verbal and written antismoking advice from the general practitioner; a group that received this advice and also a demonstration of exhaled carbon monoxide; and a group that received the advice plus the offer of further help from a health visitor. After one year 72% of smokers replied to a postal follow up questionnaire: 11% of the control group claimed to have stopped smoking compared with 15% in the group that received advice alone, 17% in the exhaled carbon monoxide group, and 13% in the health visitor group. Validation of these findings by assays of urinary concentrations of cotinine showed that between 24% and 40% of subjects may have misreported their smoking habits, but there was no indication that the rate of misreporting was higher in the intervention groups than in the control group. Giving advice routinely against smoking has a useful effect, and showing an immediate, personal, and potentially harmful consequence of smoking using a CO-oximeter may improve this, particularly in lower socioeconomic groups.

Carbon Monoxide↗
PubMed1984

Occupational exposure to hydrazine and subsequent risk of cancer.

Four hundred and twenty seven men with varying degrees of occupational exposure to hydrazine, a weak animal carcinogen, were studied to see if they provided any evidence of carcinogenicity to man. The observed mortality was close to that expected for lung cancer, other cancers, and all other causes, irrespective of the level of exposure. There were 49 deaths (61.47 expected) from all causes including five deaths from lung cancer (6.65 expected). The results show that no obvious hazards associated with hydrazine exposure have yet appeared but because of the small number of men studied they can only exclude gross hazards.

Chemical Industry↗
PubMed1982

Effect of estimating gestational age by ultrasound cephalometry on the specificity of alpha-fetoprotein screening for open neural-tube defects.

A total of 1268 women had a maternal serum alpha-fetoprotein (AFP) screening test for open neural-tube defects between 15 and 22 weeks gestation and a routine ultrasound examination at their first antenatal visit. All had a singleton infant without a neural-tube defect. AFP values were expressed as multiples of the normal median at the relevant gestational age (MoM). The percentage of women with raised maternal serum AFP levels was less when gestation was estimated by the fetal biparietal diameter (BPD) than when the time since the first day of the last menstrual period (LMP) was used; 1.8% compared with 2.3% at a serum AFP cut-off level of 2.5 MoM. Different ultrasound policies were compared for their effect on AFP screening and the best was found to be routine BPD measurement used together with a higher cut-off level than usual. For example, using a cut-off level of 3.0 MoM the detection rate for open spina bifida at 16-18 weeks gestation would be about 88% and the proportion of unaffected singleton pregnancies with raised levels only 0.9%. These results are materially better than those achieved by a policy of scanning only those women with a raised AFP level (79% and 1.4% respectively with a more conventional cut-off level of 2.5 MoM) or, in addition, scanning those with doubtful gestational ages (82% and 1.7% respectively with a cut-off level of 2.5 MoM).

Cephalometry↗
PubMed1982

Partial reversal of radiation-induced immunosuppression by T-lymphocyte lysate.

BN rats were irradiated with 500 rad of 60Co 1 day before immunization with 0.1 mg of ovalbumin in alum hydroxide gel. The onset of reaginic and haemagglutinating antibody synthesis was suppressed to a non-detectable level for at least 3-4 weeks. When these irradiated rats were injected intraperitoneally with 10(8) viable or sonicated thymocytes 1 day after irradiation, the suppressed reaginic and haemagglutinating antibody synthesis was successfully restored. This suggests that: (i) thymocytes can restore the radiation-induced immunosuppression, but viability of thymocytes is not essential in this immune restoration; (ii) active biological molecules exist in the cytoplasmic pool of the normal thymocytes which can restore the radiation-induced immunosuppression; and (iii) the thymus not only plays a central role in the normal morphological development of the lymphoid system and its functional immunological maturation, but may also play an important role in the reversal of radiation-induced immunosuppression. To investigate tissue specificity of the factors that are actively engaged in the restoration of the suppressed immune response, peripheral lymphocytes, spleen cells, bone marrow cells and kidney cells were also tested. The results demonstrated that both peripheral lymphocytes and spleen cells could restore the suppressed immune response, but not bone marrow cells or kidney cells. This suggests that the active factors may be present only in T lymphocytes. Since the active factors could be found in the tissues other than thymocytes and non-stimulated lymphocytes, they appear to be different from thymosin, transfer factor or lymphokines derived from sensitized lymphocytes, and they were most likely not synthesized de novo.

Animals↗
PubMed1981

Trends in tar, nicotine, and carbon monoxide yields of UK cigarettes manufactured since 1934.

The tar, nicotine, and carbon monoxide yields of cigarettes manufactured in the United Kingdom between 1934 and 1979 were studied. Over this period the average tar yield decreased by 49%, the nicotine yield by 31%, the carbon monoxide yield by 11%, all estimated on a sales-weighted basis. The average tar yield decreased progressively after the second world war, owing both to the introduction of filter cigarettes and to changes in the manufacture of plain cigarettes. The average nicotine yield increased initially, decreased by 43% from about 1950 to 1974, but increased again by 9% between 1974 and 1979. The average carbon monoxide yield started to decrease after about 1961; while it decreased substantially in plain cigarettes, the rapid increase in sales of filter cigarettes at this time, at the expense of plain cigarettes, largely offset the reduction in carbon monoxide yield that would otherwise have occurred. As with nicotine, carbon monoxide yield showed a small rise in later years (4% between 1976 and 1979). The trends in tar yield may well explain the reduction in lung cancer in the UK better than has been suspected hitherto. The trends in nicotine and carbon monoxide yields are probably not sufficiently different to distinguish which of them might be the more likely cause of cardiovascular disease.

Carbon Monoxide↗
PubMed1981

The effect of maternal weight on maternal serum alpha-fetoprotein levels.

In 902 singleton pregnancies, maternal serum alpha-fetoprotein (AFP) levels between 15 and 20 weeks of pregnancy were significantly related to maternal weight (r = 0.24, p less than 0.0001). Lighter women had on average higher AFP levels than heavier women, perhaps on account of the greater concentration of AFP in their relatively smaller volume of blood. The mean AFP level for women weighing less than 45 kg was 68% higher than the mean level for women weighing 85 kg or more. Maternal weight was found to be an important factor which could account for false positive AFP results in antenatal screening for open neural tube defects. A policy of adjusting maternal serum AFP values according to maternal weight among women with borderline positive results could reduce the number having a diagnostic amniocentesis with only a negligible loss of detection for open spina bifida. With such a policy, using a cut-off level of 2.5 x normal median, the false positive rate in the 902 women screened would have been reduced fom 2.8% to 2.0%.

Body Weight↗
PubMed1981

Chromosomal methods in population studies.

A brief description of chromosome aberrations and sister chromatid exchange (SCE) as cytogenetic endpoints for evaluation of DNA damaging agents is presented. Problems associated with the use of cytogenetic assays as population monitors of radiation and chemical exposures are discussed. Adequate cell sample size requirements and accurate assessment of cummulative exposure effects with increasing age are stressed as important considerations for reliable cost-benefit analysis of population studies involving low level exposures. Examples of population studies using SCE as an indicator of specific chemical exposures are cited, and factors contributing to variations in control baseline SCE levels are discussed. Possible implications of population cytogenetic data on general public health are suggested.

Chromosome Aberrations↗
PubMed1980

Low serum-vitamin-A and subsequent risk of cancer. Preliminary results of a prospective study.

In a prospective study of about 16 000 men, serum samples were collected and stored. Vitamin-A (retinol) levels were later measured in the stored samples from the 86 men who were subsequently notified as having developed cancer and in the stored samples from 172 controls who did not develop cancer. Low retinol levels were associated with an increased risk of cancer. The association was independent of age, smoking habits, and serum-cholesterol level aand was greatest for men who developed lung cancer (mean retinol level 187 i.u./dl compared with 229 i.u./dl for the controls, p < 0.005). The risk of cancer at any site for men with retinol levels in the lowest quintile was 2.2 times greater than the risk for men with levels in the highest quintile (p < 0.025). These results suggest that measures taken to increase serum-retinol levels in man may lead to a reduction in cancer risk.

Adult↗
PubMed1980

Induced acute non-lymphocytic leukemia following long-term chemotherapy: a study of 20 cases.

Twenty individuals developed acute non-lymphocytic leukemia (ANLL) following long-term chemotherapy for other disorders. The primary disorders included non-Hodgkin's lymphoma (five), Hodgkin's disease (five), carcinoma (four), multiple myeloma (three), chronic leukemia (two), and rheumatoid arthritis. Leukemia developed from 11-132 months (mean approximately 60 months) following institution of chemotherapy and all cases have occurred since 1974. Pre-leukemic cytopenias were present in 15 individuals. Fifteen of the 20 patients had chromosome analyses and 14 were abnormal. The leukemia was invariably refractory to chemotherapy with a median survival of only two months. Of the patients autopsied, only one individual had any evidence of the primary malignancy. This study illustrates the need for surveillance for secondary ANLL following long-term chemotherapy with/without radiotherapy. Duration of optimal chemotherapy for the primary disease must be determined by control trials and weighed against the risk of developing a secondary leukemia.

Adult↗