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Biomedical subjects

W J Nicholson

Publications and source records attributed to W J Nicholson.

At least 55 records · Page 3Linked to original sources
PubMed1980

Early diastolic sound of constrictive pericarditis.

In two patients with constrictive pericarditis an absent or faint early diastolic sound became prominent with squatting, phenylephrine infusion or injection of contrast medium and was obliterated by nitroglycerin. The lability of the sound allowed correlations to be made with acute changes in the right ventricular pressure curve. By eliciting an otherwise inaudible early diastolic sound, squatting may be a useful bedside maneuver in the diagnosis of constrictive pericarditis.

Adult↗
PubMed1980

Comparative lead emissions from conventional and jacketed ammunition.

Because of the adverse health effects associated with excessive exposure to lead in firing ranges, attempts have been made to develop ammunition which could prevent such undesirable exposure. This study provides evidence that it is possible to reduce lead exposure significantly at the source of emission with the use of copper and nylon jacketed bullets.

Environmental Exposure↗
PubMed1980

Environmental asbestos concentrations in the United States.

Measurements were made of chrysotile concentrations in buildings with asbestos-lined return air plenums, in buildings with damaged asbestos surfacing material, in the houses of asbestos workers, and around buildings while asbestos-containing fireproofing material was being sprayed on steelwork. The data obtained demonstrate significant environmental contamination by asbestos: 43/89 air samples exceeded 50 ng/m3, although only 2/89 samples exceeded 1000 ng/m3. These findings should prompt appropriate control or remedial action.

Air↗
PubMed1979

Disopyramide-induced ventricular fibrillation.

Three cases are described with documented ventricular fibrillation shortly after the patients received disopyramide in moderate dosage. Electrocardiograms showed markedly prolonged Q-T intervals in two patients and a prominent U wave with a prolonged Q-U interval in one patient, but no change in QRS width. Disopyramide-induced ventricular fibrillation appears to be similar to that caused by quinidine and is an indication to discontinue the drug.

Administration, Oral↗
PubMed1979

Long-term mortality experience of chrysotile miners and millers in Thetford Mines, Quebec.

Among a cohort of 544 men with at least 20 years of employment in chrysotile mining and milling at Thetford Mines, Canada, 16% of the deaths were from lung cancer and 15% from asbestosis. The excess over expected deaths from these causes account for 43 of 178 deaths in the group. The risk of death of asbestosis, at equal times fron onset of exposure, is very similar in miners and millers, factory workmen and insulators. The ratio of observed to expected deaths from lung cancer is similar in the miners and millers and factory workers, but higher in insulators. The risk of death of mesothelioma in miners and millers is decidedly less than the other two groups. The exact causes of the reduced risk in this category are not yet completely clarified.

Adult↗
PubMed1979

The contamination of Lake Superior with amphibole gangue minerals.

Iron ore called taconite is mined in the Biwabik Iron Formation in the Eastern Mesabi region of the Mesabi Range, in eastern Minnesota. After mining, ore is shipped to Silver Bay, Minnnesota for processing and wet magnetic extraction. Tailings from the process are dumped, as a slurry, into a man-made containment delta constructed in Lake Superior. Submicroscopic amphibole fibers and/or cleavage fragments, a component of the gangue, apparently escape from the delta at Silver Bay, and enter Lake Superior. These particles contaiminate the potable water supplies of municipalities drawing directly from the lake. One of the gangue minerals is the amphibole grunerite, whose asbestiform variety is called amosite. Major emphasis of this study was directed at identification of submicroscopic particle pollutants, based on morphology, structure and chemical composition. Quantitative determination of fibrous amphibole phases, present in a range of water samples, was undertaken. Transmission electron microscopy, selected area electron diffraction, and an electron microprobe technique was used for identification and enumeration and this information was compared with data sets determined from standards. Grunerite fiber and/or acicular cleavage fragments, in some instances indistinguishable from asbestiform grunerite, are present in the tailings, lake water and drinking water of a number of municipalities, a result of contamination of the lake at the Silver Bay milling operation. This amphibole is found in drinking water in concentrations which range from 0.6 to 2.8 X 10(6) fiber/liter. The risk to health, associated with direct ingestion of grunerite fiber is unknown and is extrapolated from the asbestiform grunerite (amosite) data base. The biological activity of other fibrous amphiboles observed, unrelated to any asbestiform silicate variety, is presently unknown and warrants investigation.

Asbestos↗
PubMed1978

Aortic root dissection complicating coronary bypass surgery.

Four cases are presented of aortic root dissection after aortocoronary bypass surgery in which the origin of the intimal tear was at or very near the aortic site of saphenous vein anastomosis. Two cases were documented at autopsy. In one of two cases diagnosed with aortography, the patient underwent surgical correction and survived. All patients had long-standing severe hypertensive cardiovascular disease or severe generalized atherosclerotic disease, or both. Clinical awareness of aortic dissection after coronary bypass surgery in this group of patients should make early diagnosis with successful surgical correction feasible.

Aged↗
PubMed1978

Mortality experience of styrene-polystyrene polymerization workers. Initial findings.

A group of 560 individuals has been identified as employed on 1 May 1960 with at least five years seniority in a plant manufacturing styrene and polystyrene. In this plant workplace exposures included styrene, benzene and ethylbenzene, among other materials. All of the 560 individuals have been traced through 1975 and their vital status determined. Expected and observed deaths, by cause, were determined from 1 May 1960 or the tenth anniversary of employment in the plant through 31 December 1975. Over this relatively short period of time a deficit of deaths compared to that of the general population was observed (106.41 expected versus 83 observed). Among the 83 deaths, one was of leukemia, one of lymphoma and an additional death was accompanied by leukemia. A review of 361 additional death certificates revealed five additional cases of leukemia and four of lymphoma. The available information from the limited follow-up in time of the time of the cohort and from the randomly collected death certificates, while suggestive of a possible risk, is not definitive.

Adult↗
PubMed1977

Cancer following occupational exposure to asbestos and vinyl chloride.

A review is presented of the various factors important in the identification of carcinogenic disease from occupational and environmental exposure to asbestos and vinyl chloride. The long lapsed period, usually of 20 or more years from first exposure to these materials, is discussed, as well as the requirement for sufficiently long observation periods in prospective epidemiological studies. The multiple-factor etiology of lung cancer involving cigarette smoking and asbestos exposure is illustrated. The risks of asbestos-related cancers to other than those directly working with the material are discussed in a variety of circumstances, and finally the effectiveness of control procedures for vinyl chloride and asbestos are compared.

Asbestos↗
PubMed1976

Case study 1: asbestos--the TLV approach.

A review of the control of carcinogenic exposures using the TLV approach presents a prospect of limited effectiveness. With asbestos, as with any carcinogen, no threshold is known below which no health effect may be manifest. At best, we have only limited dose-response information at levels much above those of practical concern. In the case of asbestos, current exposures can only be described crudely at any level of exposure, and health effects are only known for past high, but ill-defined, exposures. Limited information exists on the effects of synergistic interactions with other materials. The current U.S. TLV, based on data concerned with occurrence of asbestosis, has not been evaluated with regard to possible effectiveness in the prevention of asbestos cancer. Yet cancer is the heart of the asbestos-hazard problem. Finally, enforcement of the existing TLV, especially for asbestos has been limited, frequently absent, and often ineffective. Workers are exposed in many situations to levels much above the current standard. As discouraging as this picture may seem, a TLV can be useful for stimulating the development and application of engineering-control procedures. The application of these procedures, however, must be specified and mandated in future standards to lower worker exposures to the minimum commensurate with existing technology. As technology is developed that makes lower exposure levels possible in a large part of the industry, TLVs should be reduced to take advantage of that technology.

Air Pollutants, Occupational↗
PubMed1976

Clinical studies of styrene workers: initial findings.

Styrene monomer is a high volume chemical used chiefly in production of polystyrene. A clinical survey of 493 production workers was undertaken at the oldest and largest monomer production, polymerization, and extrusion facility in the U.S. Relative exposure durations and levels were obtained from occupational histories. Significant differences between the high and low exposure groups were found with regard to history of acute prenarcotic symptoms, acute lower respiratory symptoms, prevalence of FEV 1/FV less than 75 per cent, and elevated GCTP. Other liver function tests, chest x-ray, FVC less than 80 per cent, and hematological parameters showed no distinct pattern. A concomitant mortality study has been mounted and is in progress.

Adult↗
PubMed1976

Echocardiographic oscillating flap in aortic root dissecting aneurysm.

A patient had a history, physical findings, and chest x-ray film suggesting type I aortic dissection. This diagnosis could not be confirmed angiographically. Echocardiographic studies predicted both the presence of dissection and the anatomic findings at surgery. A regularly oscillating echo corresponding to the intimal flap was found in the false lumen. This is suggested as a new echocardiographic finding in dissecting aneurysm.

Aortic Aneurysm↗
PubMed1975

Exposure to asbestos in the use of consumer spackling, patching, and taping compounds.

Analysis of representative samples of spackling, patching, and jointing compounds, purchased at retail stores in the New York City area, has shown that some contain asbestos minerals as well as other biologically active substances. Measurements suggest that home repair work involving the use of such materials may result in exposure to dust at concentrations sufficient to produce disease.

Asbestos↗