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Biomedical subjects

D Forman

Publications and source records attributed to D Forman.

At least 163 records · Page 9Linked to original sources
PubMed1989

Are nitrates a significant risk factor in human cancer?

This article focuses on the relationship between exposure to nitrates in the environment and subsequent risk of human cancer. The question of whether or not nitrates represent a cancer hazard is one of the most important public health issues arising from research into N-nitroso compounds. The reason for concern results from the endogenous reduction of nitrate to nitrite and subsequent nitrosation of amines, amides and proteins to give rise to carcinogenic N-nitroso compounds. The human evidence relating nitrate exposure to cancer, especially gastric cancer, has been largely based on geographic correlation studies, a relatively weak form of epidemiological methodology. In sum, this evidence and that from a small number of individually based studies does not support the hypothesis of a straightforward cause and effect association between nitrate exposure and cancer risk. Because many other factors besides nitrate are involved in the endogenous formation of N-nitrosation compounds, it is possible that exposure to nitrate is not a rate-limiting factor in most circumstances. This makes the setting of regulatory standards for nitrate exposure from the environment a complex issue.

Carcinogens↗
PubMed1988

N-nitrosoproline excretion in patients with gastric lesions and in a control population.

N-Nitrosoproline (NPRO) excretion was measured in a group of hospital in-patients who were identified as either bearing gastric lesions or having apparently healthy stomachs. NPRO was assayed in background 24-h urine samples and then in urines collected after loading doses of nitrate and proline. The presence of gastric lesions was associated with altered gastric juice pH and nitrite concentration, but not with NPRO excretion. The significance of NPRO excretion as a marker of endogenous nitrosation is dependent on the interpretation of this result.

Adult↗
PubMed1987

Estimation of dietary intake of nitrate and nitrite in Great Britain.

A survey was conducted of the dietary intake of nitrate and nitrite of 747 people aged 15-74 yr living in four regions in Britain. The mean intakes from food were estimated to be about 95 mg nitrate and 1.4 mg nitrite. Vegetables contributed over 90% of the nitrate intake and cured meats 65% of the nitrite intake. The contribution from drinking-water was estimated to add a further 13.5 mg, about 12% of total intake, but varied greatly depending upon water nitrate concentration. Residents of Oxford and the South-east had a higher intake of dietary nitrate, due to a greater vegetable consumption, whereas those from North Wales and the North-east had a higher nitrite intake due mainly to a greater consumption of bacon. The consumption of relatively low ascorbic acid/high nitrate vegetables was significantly greater in Oxford and the South-east. Smoking appeared to inhibit the uptake of circulating nitrate into the saliva, especially at higher levels of dietary nitrate intake. The efficiency of reduction of nitrate to nitrite in vivo and the effect of differing rates of this conversion on the relative importance of different dietary items as potential sources of nitrite are discussed.

Adolescent↗
PubMed1987

The availability of dietary nitrate for the endogenous nitrosation of L-proline.

Urinary excretion of N-nitrosoproline (NPRO) following ingestion of a high-nitrate salad meal, without then with an oral dose of 500 mg L-proline, was investigated in 16 healthy volunteers. The mean excretion rate following consumption of the high-nitrate meal alone was significantly lower than that measured after ingestion of the salad plus proline. Supplementation of the same meal (plus proline) with vitamin C from dietary sources resulted in a significant decrease in mean urinary NPRO levels in healthy subjects. The nitrosation-inhibiting effect of vitamin C was not affected by an increase in the fat content of the meal. Supplementation of the high-nitrate salad with alcohol or coffee did not affect subsequent urinary NPRO levels. No significant difference was observed in the urinary NPRO concentrations of smokers and nonsmokers after ingestion of high-nitrate salad (with or without vitamin C) plus proline.

Ascorbic Acid↗
PubMed1986

Oral contraceptives and hepatocellular carcinoma.

A series of 26 white women aged under 50 who developed hepatocellular carcinoma in a non-cirrhotic liver were studied for the possible role of oral contraceptives. Eighteen of the women had used the "pill" for a median of eight years. Over 1300 women whose use of the pill had been determined in another study served as controls. Patients and controls were divided into five age and four calendar groups and the relative risks associated with oral contraceptives calculated by multivariate analysis. Short term use of the pill was not associated with an increased risk of tumour development; nevertheless, use for eight years or more was associated with a 4.4-fold increased risk (p less than 0.01). When patients with markers of hepatitis B virus infection were excluded the relative risk was 7.2 (p less than 0.01). In both instances the absolute risk for developing hepatoma remained low.

Adult↗
PubMed1986

Cancer of the liver and the use of oral contraceptives.

A case-control study of the use of oral contraceptives was conducted among women certified as having died from cancer of the liver in the period 1979-82 and in the age range 20-44 years. An age matched group of women who died from other causes, not related to use of oral contraceptives, in the same period were used as controls. Information about use of oral contraceptives was obtained from the general practitioners' notes for both cases and controls. Information was obtained for 30 women with histologically confirmed liver cancer, 19 with hepatocellular carcinoma and 11 with cholangiocarcinoma, and for 147 controls. The results were analysed after adjusting for age at diagnosis and year of birth and showed that use of oral contraceptives was associated with a significantly (p less than 0.05) raised relative risk for hepatocellular carcinoma of 3.8 (95% confidence interval 1.0 to 14.6) and use for eight years or more was associated with a significantly (p less than 0.01) increased relative risk of 20.1 (2.3 to 175.7). There were no apparent increases in risk for cholangiocarcinoma. Despite the small number of cases in this study and the methodological problems in assessing use of oral contraceptives from general practitioners' notes, the results were consistent with other similar studies. Although in the United Kingdom primary liver cancer remains an exceptionally rare disease, especially in young women, further research on the role of oral contraceptives is needed in those countries where it is a much more common disease.

Adenoma, Bile Duct↗
PubMed1986

Cancer of the cervix uteri and vitamin A.

The concentrations of retinol and beta carotene were measured in serum samples taken from 113 women with cervical cancer, 32 with invasive and 81 with pre-invasive disease, and compared with those from 226 age-matched control women. There was little difference in serum retinol levels between women with cancer of the cervix, at any stage, and the control women, after adjusting for potential confounding factors. Serum beta carotene concentrations were likewise similar in women with invasive disease and the controls. However mean beta carotene levels were significantly reduced in women with pre-invasive disease compared to the controls (221.3 cf. 291.6 micrograms l-1, P less than 0.05). This reduction was more evident amongst women with a diagnosis of carcinoma-in-situ (mean 213.1 micrograms l-1 than amongst those with severe dysplasia (mean 228.7 micrograms l-1. There is a negative trend between beta carotene and risk of pre-invasive disease which is of borderline significance. These data have also been used to investigate the effects of smoking and oral contraceptive usage on the serum levels of retinol and beta carotene. Both habits tend to increase retinol and decrease beta carotene concentrations.

Carcinoma in Situ↗
PubMed1986

Mortality of nitrate fertiliser workers.

An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been employed in the production of fertilisers between 1946 and 1981 and who had been occupationally exposed to nitrates for at least one year were followed up until 1 March 1981. In total, 304 deaths were observed in this group and these were compared with expected numbers calculated from mortality rates in the northern region of England, where the factory was located. Analysis was also carried out separately for a subgroup of the cohort who had been heavily exposed to nitrates--that is, working in an environment likely to contain more than 10 mg nitrate/m3 for a year or longer. In neither the entire cohort nor the subgroup was any significant excess observed for all causes of mortality or for mortality from any of five broad categories of cause or from four specific types of cancer. A small excess of lung cancer was noted more than 20 years after first exposure in men heavily exposed for more than 10 years. That men were exposed to high concentrations of nitrate was confirmed by comparing concentrations of nitrates in the saliva of a sample of currently employed men with control men, employed at the same factory but not in fertiliser production. The men exposed to nitrate had substantially raised concentrations of nitrate in their saliva compared with both controls within the industry and with men in the general population and resident nearby. The results of this study therefore weight against the idea that exposure to nitrates in the environment leads to the formation in vivo of material amounts of carcinogens.

Aged↗
PubMed1986

Activation of ethanol metabolism in humans by fructose: importance of experimental design.

Fed human male subjects 18 to 30 years of age received 0.85 g/kg of ethanol p.o. as vodka followed by a second drink (0.3-0.4 g/kg) given 3 to 4 hr later. Blood ethanol levels reached approximately 100 mg% after both doses. Breath samples were taken every 20 to 30 min, and the rate of ethanol elimination was determined. Subjects returned 1 to 2 weeks later and the study was repeated with fructose (1.0 g/kg). When ethanol and fructose were given simultaneously, the peak blood ethanol values reached were reduced significantly. This resulted in calculated increases in the apparent volume of distribution of ethanol; however, the slope (beta) of the ethanol elimination curve was not increased. Thus, under these conditions, fructose appeared to have minimal effects on rates of ethanol elimination (ca. 10%). In another experimental design, subjects received 1 g/kg of fructose 1 hr after ethanol. Under these conditions, fructose did not affect the peak blood ethanol concentration or the apparent volume of distribution; however, the slopes of the ethanol elimination curves (beta) were increased significantly by fructose. Further, the time estimated to eliminate the ethanol completely was reduced by 90 min with fructose. Under these conditions, the stimulation of ethanol elimination by fructose was 20 to 30%. This increase in the rate of ethanol elimination was observed in every subject studied. Similar results were obtained with rats. To understand why blood ethanol values were lower when ethanol and fructose were given simultaneously, female Sprague-Dawley rats were given ethanol alone (1.5 g/kg) or ethanol and fructose (1 g/kg) simultaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The syndrome of inappropriate secretion of antidiuretic hormone in the maxillofacial trauma patient.

The maxillofacial trauma patient whose neurologic status undergoes a rapid and serious deterioration may have a severe hyponatremia secondary to the inappropriate secretion of antidiuretic hormone (SIADH). Other causes of hyponatremia must be ruled out, especially posttraumatic cerebral salt wasting, which necessitates a different mode of therapy. A case of SIADH is reported, and the work-up and differential diagnosis of posttraumatic hyponatremia are discussed.

Adolescent↗
PubMed1985

Exposure to vinyl chloride and angiosarcoma of the liver: a report of the register of cases.

The Association of Plastic Manufacturers in Europe maintains a register of all cases of angiosarcoma of the liver (ASL) resulting from exposure to vinyl chloride monomer (VCM). This register has recorded all known VCM related cases of the disease worldwide that have been histologically confirmed. Although likely to be incomplete, it is the most comprehensive tabulation of such cases available and, by the end of 1984, 118 men had been registered. The information from analysis of the cases currently on the register is used to make an approximate projection of the number of cases to be expected in the future. The conclusion from this projection is that the industry is reaching the halfway stage in the appearance of VCM related ASL.

Adult↗
PubMed1985

Developmental alterations in pulmonary function of the lamb.

Pulmonary function was evaluated in 40 lambs ranging in age from 106 to 161 postconceptual days. Preterm lambs were delivered by cesarean section and newborn lambs were delivered vaginally. All animals were mechanically ventilated and had indwelling catheters. Measurements of transpulmonary pressure, airflow, tidal volume and functional residual capacity enabled calculations of lung compliance, specific compliance, lung conductance and specific conductance. Regression analysis indicated that lung compliance, lung conductance and functional residual capacity increased with developmental age; whereas, specific compliance and specific conductance decreased with maturity. These data quantitate the developmental alterations in the pulmonary function of preterm, term and newborn lambs.

Aging↗
PubMed1984

Apparent doubling of frequency of undescended testis in England and Wales in 1962-81.

Examination of Hospital Inpatient Enquiry data for England and Wales for the years 1962-81 shows that the annual number of discharges with a diagnosis of undescended testicle has risen by a factor of 2.3. Cohort analysis suggests that the cumulative rate to age 15 of discharge for undescended testis has risen from 1.4% for the 1952 birth-cohort to 2.9% for the 1977 birth-cohort. Whether this is a reflection of an increase in true cryptorchidism is not known. Changes in known risk factors for cryptorchidism--exogenous oestrogen exposure, being first-born, and low birth-weight--cannot fully account for the apparent increase. With the tendency to carry out orchidopexies on apparently undescended testes at younger ages in order to preserve fertility, it is possible that a considerable number of boys with retractile testes that would have descended naturally at puberty are now being operated upon.

Adolescent↗