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Biomedical subjects

S C Lewis

Publications and source records attributed to S C Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1988

Dermal carcinogenic activity of petroleum-derived middle distillate fuels.

In general, the carcinogenic potential of petroleum-derived materials is related to the polycyclic aromatic hydrocarbon (PAH) content. Thus it has been assumed that liquids which boil below the PAH distillation range (i.e., below approx. 370 degrees C (700 degrees F) would not be carcinogenic. Several early studies supported this conclusion but were of relatively short duration. Several recent and more rigorous studies have shown that repeated application of certain petroleum-derived materials boiling between approximately 177-370 degrees C (350-700 degrees F) (i.e., middle distillate fuels) can produce tumors in mouse skin. The current studies assessed the tumorigenic potential of a series of middle distillates which varied with respect to boiling range, composition, and source of blending stocks. All of the samples produced evidence of weak tumorigenic activity which was characterized by low tumor yields and long median latencies. However, the majority of the tumor yields were significantly different from the control. There were no apparent differences in response among the samples. Thus the various parameters examined did not substantially influence tumor outcome. In particular, there was no association of tumorigenic activity with aromatic carbon content; this finding, coupled with evidence that PAH levels were low, suggested that the tumorigenic responses were not PAH-dependent. In addition to the tumors, there was evidence of non-neoplastic dermal changes including hyperplasia. These may have contributed to the tumorigenic responses; however, the actual mechanism of tumor induction is unknown.

Administration, Cutaneous↗
PubMed1987

A comparison of developmental toxicity evident at term to postnatal growth and survival using ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and ethanol.

This study was designed to compare an abbreviated evaluation of uterine contents at term (teratology probe) with a modified Chernoff-Kavlock assay (postnatal study), [Chernoff N, Kavlock RJ: J Toxicol Environ Health 10:541-550, 1982]. Mice were intubated during gestation and were evaluated for signs of toxicity. In the teratology probe, uterine contents were examined at term. In the postnatal study, offspring were examined and weighed through day 22 postpartum. Ethylene glycol monoethyl ether (EGEE) produced embryo lethality and malformations, and decreased fetal weight at a dose level which was not maternally toxic in the teratology probe. In the postnatal study, EGEE decreased litter size and neonatal body weight; while litter size continued to decrease beyond the neonatal period, body weights of surviving pups were not significantly different from control. Pups exposed prenatally to EGEE developed kinked tail which was not apparent in fetuses or neonates. Maternally toxic dose levels of ethylene glycol monobutyl ether and ethanol were associated with increased embryo lethality in teratology probe studies. In postnatal studies, there were no significant effects on pup growth or survival at maternally toxic dose levels. Preliminary conclusions regarding maternal and developmental toxicity were comparable based on the teratology probe or postnatal study. Both assays measure litter size and offspring weight, but the teratology probe measures resorption incidence which may be a more sensitive index of prenatal death than number of live born. Neither fetal weight nor neonatal weight reliably predict permanent alteration of growth. A postnatal study permits detection of internal malformations or functional defects which reduce postnatal survival and gross abnormalities which appear postnatally.

Animals↗
PubMed1987

Evaluation of the dermal carcinogenic potential of liquids produced from the Cold Lake heavy oil deposits of northeast Alberta.

This study assessed the dermal carcinogenic potential of raw bitumen derived from the Cold Lake Oil Sands deposit (located in Northeast Alberta, Canada) and two liquids which were under evaluation as part of a process to refine the crude bitumen at the Cold Lake site. The crude bitumen was dermally carcinogenic, inducing tumors in 26% of the treated animals with a median latency of 106 weeks. This response was significantly greater than the tumor yield previously reported for a raw bitumen derived from Athabasca tar sands by the Syncrude process, but was not substantially different from the carcinogenic potential of two crude petroleum oils. The GO-FINING product, a high boiling (259-519 degrees C), catalytically cracked gas oil was a relatively potent dermal carcinogen, inducing tumors in 86% of the treated animals with a median latency of 46 weeks. This result is consistent with the fact that the GO-FINING product contained appreciable levels of high boiling aromatic compounds. The HYCRACKING product, a high boiling (102-498 degrees C), severely hydroprocessed liquid was noncarcinogenic. This result was also consistent with the compositional data; the high boiling components were predominantly saturated species. Thus the carcinogenic properties of the liquid products prepared by these two processes were as predicted from the compositional information.

Alberta↗
PubMed1986

Influence of housing conditions for mice on the results of a dermal oncogenicity bioassay.

Male C3H/HeJ mice were thrice weekly given 25 microliter applications of 0.25, 0.05, or 0.01% (w/w) benzo(a)pyrene (BaP) in acetone, or acetone alone, to clipped dorsal skin from 12 to 14 weeks of age for the remainder of their life spans. There were two groups of 40 mice for each treatment regimen, one group being housed in conventional stainless-steel wire mesh cages and the other in polycarbonate cages with wood shavings held in an enclosed ventilated cabinet. Under both housing conditions, tumor incidence was directly related and latency inversely related to BaP concentration. The time-adjusted incidence of epidermal neoplasms was significantly greater for the groups housed in polycarbonate cages. Mortality rates were directly related to BaP concentration and were significantly enhanced by the polycarbonate-cage housing conditions for the high and intermediate concentrations. Survival patterns for the two acetone control groups were similar. These findings indicate that differences in housing conditions can influence both the incidence and the latency of local neoplasms produced in response to the chronic application of a carcinogen in dermal oncogenesis bioassays.

Animals↗
PubMed1986

Evaluation of the dermal carcinogenic potential of tar sands bitumen-derived liquids.

The carcinogenic potential of Athabasca tar sands and six experimental liquids derived from crude bitumen was evaluated utilizing the mouse epidermal carcinogenesis model. Tar sands, bitumen, and untreated naphtha produced few, if any, tumors. Three thermally and catalytically cracked liquids, light (nominal boiling range: 149-316 degrees C) and heavy (nominal boiling range: greater than 316 degrees C) gas oils and gas oil blend (boiling range: greater than 316 degrees C), produced a significant number of epidermal neoplasms. A synthetic crude oil, prepared by blending naphtha and light and heavy gas oils, was moderately carcinogenic; however, the activity of this sample fell within the range of values obtained in studies of crude petroleum samples. Since the bitumen-derived streams do not differ substantially in carcinogenic potency from petroleum-derived materials of comparable boiling range and process history, industrial hygiene practices which limit exposures to levels comparable to those observed in the petroleum-refining industry should provide similar measures of protection.

Animals↗
PubMed1976

Psychosocial consequences of therapeutic abortion King's termination study III.

A follow-up study is reported of a consecutive series of 360 women who underwent termination of first trimester pregnancies by vacuum aspiration. Each patient received brief counselling before termination. Follow-up examinations were carried out by means of detailed, structured interviews at three months and between 15 months and two years (mean: 18 months) after termination. Outcome was assessed in terms of psychiatric symptoms, guilt feelings, and adjustment in marital and other interpersonal relationships, sexual responsiveness and work record. Compared with ratings of psychosocial adjustment before termination, significant improvement had occurred at follow-up in respect of psychiatric symptoms, guilt feelings and interpersonal and sexual adjustment; there was no significant change in marital adjustment. Adverse psychiatric and social sequelae were rare.

Abortion, Therapeutic↗
PubMed1976

Correlation of lead and cadmium in human urine.

A statistical evaluation of the relationship between elevated concentrations of lead and cadmium in human urine is presented. The importance of the 24-hour continuously collected urine sample is confirmed.

Cadmium↗
PubMed1976

Disability social distance hierarchy for population subgroups.

This investigation studied the disability attitudes of ten population subgroups including the general public, professionals, college and grade school students and disabled individuals. A total of 2576 subjects were tested in a seven-year period with one of three instruments. The results showed that a stable hierarchy of preference characterized these seemingly disparate groups.

Attitude to Health↗
PubMed1974

King's termination study. II. Contraceptive practice before and after outpatient termination of pregnancy.

A selection of psychological and social factors present in 360 women who underwent legal termination of pregnancy are related to their contraceptive practice. One-third of the group were ignorant about contraceptive methods, ignorance being more common in women from social classes IV and V and in those under the age of 19. Nearly half of those who had some knowledge of contraceptive practice became pregnant after knowingly taking a risk. A total of 41% had been using some form of contraception immediately before conception. The reliability of contraceptive methods used was found to be inversely related to neuroticism scores obtained from the Eysenck Personality Inventory, neuroticism being highest in women who had not used any form of contraception.Of 91% of the group seen three months after their termination 86% were using reliable contraceptive methods. A follow-up study one or two years after termination has shown that 81% of the 215 women contacted so far are using a reliable method of contraception; two unwanted pregnancies have occurred but both were due to contraceptive failure. This satisfactory outcome has been ascribed to the system of counselling all women before and after termination.

Abortion, Legal↗
PubMed1971

Outpatient termination of pregnancy.

Termination of pregnancies ranging from 6 to 10 weeks' gestation is described in 127 women who attended the hospital as outpatients. The technique employed was to aspirate the products of conception through a narrow plastic tube using a high negative pressure. Infiltration of the cervix with local anaesthetic proved so effective that the procedure could be carried out on the fully conscious patient. The short time taken to evacuate the uterus, the small blood loss, and the low incidence of complications in the latter part of the study suggest that the technique is a valuable procedure. Relatively more women can be terminated as outpatients than as inpatients with a corresponding reduction in the demands made on gynaecological beds.

Abortion, Legal↗
PubMedDate not supplied

Routine oral nutritional supplementation for stroke patients in hospital (FOOD): a multicentre randomised controlled trial.

BACKGROUND: Undernutrition is common in hospital patients with stroke, can develop or worsen in hospital, and is associated with poor outcomes. We aimed to establish whether routine oral nutritional supplements improve outcome after stroke. METHODS: The FOOD trials are a family of three pragmatic, multicentre, randomised controlled trials. We measured the outcomes of stroke patients who could swallow and who were randomly allocated normal hospital diet or normal hospital diet plus oral nutritional supplements until hospital discharge. The primary outcome was death or poor outcome (modified Rankin scale [MRS] grade 3-5), 6 months after enrollment, measured unaware of treatment allocation. Analysis was by intention to treat. FINDINGS: Between Nov 1, 1996, and July 31, 2003, 4023 patients were enrolled by 125 hospitals in 15 countries. Only 314 (8%) patients were judged to be undernourished at baseline. Vital status and MRS at the end of the trial were known for 4012 and 4004 patients, respectively. Supplemented diet was associated with an absolute reduction in risk of death of 0.7% (95% CI -1.4 to 2.7) and an increased risk of death or poor outcome of 0.7% (-2.3 to 3.8). INTERPRETATION: We could not confirm the anticipated 4% absolute benefit for death or poor outcome from routine oral nutritional supplements for mainly well nourished stroke patients in hospital. Our results would be compatible with a 1% or 2% absolute benefit or harm from oral supplements. These results do not support a policy of routine oral supplementation after stroke.

Aged↗