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Biomedical subjects

J Nickels

Publications and source records attributed to J Nickels.

At least 19 recordsLinked to original sources
PubMed1991

Thyroid gland: US screening in a random adult population.

High-frequency ultrasound examination of the thyroid was performed in 253 subjects (130 women and 123 men; age range, 19-50 years) that were randomly selected from the population in an area of Finland where goiter is not endemic. Thyroid echo abnormalities were detected in 69 subjects (27.3%). Prevalence of abnormalities increased with age, and women showed more lesions than did men in each of the 3 decades. The abnormality was solitary in 39 subjects (57%), multiple in 15 (22%), and diffuse in 15 (22%). Of the 68 individual nodules, 48 (70%) were smaller than 1 cm in diameter. Anechoic rounded nodules 1-5 mm in diameter were found in 28 subjects. Fine-needle aspiration biopsy was performed in 30 subjects. Cytologic examination revealed no unequivocal malignancies. In eight subjects (3.2%) with a diffuse echo abnormality, cytologic evaluation indicated lymphocytic thyroiditis. It is concluded that the prevalence of small thyroid echo abnormalities in a randomly selected adult population is rather high, a fact that supports use of a conservative approach to these types of findings.

Adult↗
PubMed1990

Formaldehyde exposure and respiratory cancer among woodworkers--an update.

Respiratory cancer was examined in relation to occupational formaldehyde exposure in a case-referent study (136 cases, 408 referents) nested in a woodworker cohort. Plant- and time-specific job-exposure matrices were constructed for formaldehyde exposure. Over 3 ppm-months of formaldehyde exposure was associated with an odds ratio of 1.4 [90% confidence interval (90% CI) 0.5-4.1]. The odds ratios for lung cancer were near unity, the excess risk concentrating on the upper respiratory tract. That for combined exposure to formaldehyde-phenol exposure (all respiratory cancers) was 1.6 (90% CI 0.6-4.4) but 1.0 for formaldehyde only. No consistent exposure-response patterns emerged for the level, duration, or cumulative exposure. The results are hardly more than debatable support for the hypothesis concerning formaldehyde as a carcinogen in humans, the possible risk seemingly concentrating on the upper respiratory tract rather than the lung.

Case-Control Studies↗
PubMed1989

Thyroid gland: US screening in middle-aged women with no previous thyroid disease.

To determine the prevalence of thyroid nodules in the healthy population, ultrasonography (US) of the thyroid gland was performed in 101 women aged 49-58 years in an urban area in southern Finland where goiter is not considered endemic. Subjects with any previous thyroid disease were excluded. Thyroid nodules or abnormalities of the echo structure were found in 36 (35.6%) subjects. Seventeen (47.2%) subjects had solitary nodules, 14 (38.9%) had multiple nodules, and five (13.9%) had diffuse abnormalities. Subjects with abnormal findings at US were further examined with fine-needle aspiration biopsy. Clinical examination and blood tests were performed for evaluation of levels of thyroxine, thyroid-stimulating hormone, and thyroid antibodies. One patient had a leukemic thyroid nodule, but no primary thyroid malignancies were found. In most cases, cytologic findings were benign and nonspecific, with a variable amount of degenerative changes. Three atoxic multinodular goiters and two cases of Hashimoto thyroiditis were detected. The results are in accordance with autopsy studies indicating that focal nodular changes of the thyroid gland are common in middle-aged women.

Biopsy, Needle↗
PubMed1987

m-Xylene inhalation destroys cytochrome P-450 in rat lung at low exposure.

Rats were exposed to 0, 75, 150 or 300 ppm (1 ppm = 1 cm3/m3 = 4.35 mg/m3) m-xylene for 24 h and then killed. In the lungs, the cytochrome P-450 decreased to 45, 13 and 20% of the control value with the increasing exposure intensity and the activity of 7-ethoxycoumarin O-deethylase to 70, 27 and 14%, respectively. The activity of epoxide hydrolase increased slightly after exposures both at 150 (1.6-fold) and 300 cm3/m3 (1.4-fold), while the other measured drug-metabolizing enzyme activities showed no consistent changes. The non-protein sulfhydryl group content of the lungs was not affected. The concentrations of m-xylene in blood indicated that the solvent uptake increased in the different exposure groups more than expected, based on atmospheric concentrations alone. Morphologic studies of the lungs with scanning electron microscopy showed no apparent changes after exposure to 300 cm3/m3 or after a high oral dose (2 ml/kg/day, 3 days). Inhalation exposure to m-xylene for 5 weeks (7 h/day, 4 days/week) at a concentration of 300 ppm lowered the contents of cytochrome P-450 in rat lungs to 65% and the activity of 7-ethoxycoumarin O-deethylase to 41% without any other marked effects on the other drug-metabolizing enzymes or on the levels of non-protein sulfhydryl groups. In this study, the selective destruction of cytochrome P-450 in rat lung could be shown both after acute and subacute exposures and at concentrations low enough to warrant occupational concern.

Administration, Inhalation↗
PubMed1987

Acute biological effects of commercial cresyl diphenyl phosphate in rats.

A commercial cresyl diphenyl phosphate preparation was analyzed to contain approximately 35% of triphenyl phosphate, 45% of cresyl diphenyl phosphates, 18% of dicresyl phenyl phosphates and 2% of tricresyl phosphates. The product was almost free of the o-cresyl isomers as revealed by the analysis of its alkaline hydrolysis products. A single intraperitoneal injection (150 or 300 mg/kg) caused an induction of microsomal cytochrome P-450 in the liver of Wistar rats with a concomitant increase in the activities of mixed function monooxygenases and proliferation of smooth endoplasmic reticulum 24 h after the treatment. These effects were not detected in the kidneys. The morphological changes in hepatocytes included the enlargement of nuclei and mitochondria with increased cristae. The hepatic morphology returned to normal 2 weeks after the treatment. The activity of pseudocholine esterase in blood was inhibited 4 h and 24 h after the injection but the effect levelled off. The concentration of the organophosphates in blood and liver decreased rapidly with only traces detected in blood after 24 h. No effects on the activities of cerebral and muscle acetylcholine esterase were observed. The treatment (300 mg/kg) inhibited the brain--2',3'-cyclic nucleotide 3'-phosphohydrolase through the 2-week observation period associated with demyelination in peripheral nerves.

Animals↗
PubMed1986

Mucosal morphology of ileal conduits with particular reference to urinary infections.

Mucosal biopsies were obtained for histological and electron microscopical studies from 20 patients with ileal urinary conduits. Special interest was focused on problems of urinary tract infections and their possible role in the pathogenesis of these changes. Chronic inflammation with mild to total villous atrophy was found as well as reduction in the amount of mucosal glands. Ultrastructurally the main cellular elements of the ileal epithelium and mucosa were preserved. The age of the conduit did not seem to be decisive in the histological findings. Also recurrent infections could not be shown to be responsible for the changes in the conduit mucosa. In irradiated patients, fibrotic changes in the lamina propria of the conduit mucosa were apparent and the microvilli especially short and scanty.

Adult↗
PubMed1985

Biochemical and morphological effects of long-term inhalation exposure of rats to ethylbenzene.

Male Wistar rats were exposed (six hours/day, five days/week) to 0, 50, 300 or 600 p.p.m. of ethylbenzene vapour in the air, and killed after 2, 5, 9 or 16 weeks of exposure. After 600 p.p.m., liver-microsomal protein but not cytochrome P-450 concn. was slightly increased; NADPH-cytochrome c reductase was increased maximally by 30% (1.3-fold), 7-ethoxycoumarin O-deethylase (1.8-fold) and UDPG-transferase (2.3-fold). The increase in liver-cytosolic D-glucuronolactone dehydrogenase paralleled the glucuronidation activity (less than or equal to 2-fold). In the kidneys, only 7-ethoxycoumarin O-deethylase (less than or equal to 3.5-fold) and UDPG-transferase (less than or equal to 1.8-fold) showed dose-related increases. Ethylbenzene exposure did not deplete hepatic glutathione (GSH); kidney GSH was slightly increased (less than or equal to 1.3-fold) according to dose. Urine excretion of thioethers was increased with dose, and at 600 p.p.m. was eight times control levels. At 600 p.p.m. there was no increase in serum alanine aminotransferase activity, and liver cells showed slight proliferation of smooth endoplasmic reticulum, slight degranulation and splitting of rough endoplasmic reticulum and enlarged mitochondria, but no necrosis.

Air Pollutants, Occupational↗
PubMed1985

Formaldehyde exposure and respiratory and related cancers. A case-referent study among Finnish woodworkers.

A case-referent study was undertaken to investigate the associations between formaldehyde exposure and respiratory and related cancers. Fifty-seven such cancers from a retrospective cohort of male woodworkers formed the case group. They were matched by year of birth with 171 referents. Exposure to formaldehyde was assessed with job-exposure matrices. The median of the time-weighted average concentration was about 1 ppm, and the mean duration of exposure was 10 years among the exposed. Odds ratios (OR) were calculated for formaldehyde exposure (1.44), peak exposure to formaldehyde (1.26), and exposure to formaldehyde-containing wood dust (1.22). None of the values exceeded unity with statistical significance. Allowance was also made for a 10-year period from the onset of exposure. Birth year, cigarette smoking and exposure to wood dust, chlorophenols, pesticides, and terpenes were controlled by stratification. The adjusted ORs did not change appreciably. The highest OR was 1.95 for formaldehyde exposure without allowance for minimum latency, adjusted for exposure to terpenes. No exposure-response relation was observed for the level, duration, or dose (ppm-years) of formaldehyde exposure. The result is nonpositive and may be explained by absence of effect, by too short a follow-up, or by insufficient power for detecting a mild excess risk.

Adult↗
PubMed1984

Toxicity of polymethylmethacrylate thermodegradation products.

Polymethylmethacrylate was thermally degraded in air at 300 degrees C and the volatile decomposition products studied with gas chromatography-mass spectrometry. The main product was monomeric methacrylate, although many other compounds existed among the products. Electron spin resonance spectroscopy revealed the presence of free radicals. Wistar rats were exposed to the fumes of the plastic (300 degrees C) and their lungs and brain studied for biochemical effects. In the lung, the activity of 7-ethoxycoumarin O-deethylase decreased and an initial inhibition of glutathione peroxidase and superoxide dismutase was observed. The contents of reduced nonprotein sulfhydryl groups were decreased in the lung and brain. The exposures enhanced the activities of acetylcholine esterase, creatine kinase and NADPH-diaphorase in the brain. Scanning electron microscopy of the exposed lungs showed disorganization of ciliated cells, and the epithelial serous cells (Clara cells) were damaged.

Animals↗
PubMed1984

Trinitrotoluene-induced effects on rat heme metabolism.

A single injection (100 mg/kg body wt) of trinitrotoluene in rats caused decreased delta-aminolevulinic acid synthase activity in reticulocytes and decreased erythrocyte coproporphyrin concentration 48 hr after the intraperitoneal dosage. For comparison, liver delta-aminolevulinic acid synthase was unaffected while heme synthase activity was below the control range at the same time. Heme oxygenase activity increased simultaneously. These effects are likely to lead to a negative heme balance and may be developed for a biological exposure test to trinitrotoluene in occupational health service.

5-Aminolevulinate Synthetase↗
PubMed1984

Pulmonary granulomatous reaction: talc pneumoconiosis or chronic sarcoidosis?

A chronic pulmonary granulomatous reaction was associated with an almost identical clinical picture in two patients exposed to talc. In both patients lung biopsy showed the deposition of talc particles and a heavy granulomatous reaction. At the time of diagnosis the Kveim test result was negative in both patients, urinary calcium excretion was normal, and there were no extrapulmonary manifestations and no response to steroid treatment. These findings point against sarcoidosis. The serum angiotensin-converting enzyme level, however, was raised in both patients. It was concluded that the patient who was exposed to talc in the rubber industry had a true talc pneumoconiosis. The other patient, who was exposed to cosmetic talcum powder, suffered from chronic sarcoidosis with talc deposition in the lungs, since an enlarged axillar lymph node containing granulomatous inflammation was discovered after two years' follow up. These cases show that it may be extremely difficult to differentiate between chronic sarcoidosis and talc pneumoconiosis even after careful clinical and histological analysis.

Chronic Disease↗
PubMed1983

Hypolipidemia and peroxisome proliferation induced by phenoxyacetic acid herbicides in rats.

Male Wistar rats were treated daily by gavage with two phenoxy herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D)(100-200 mg/kg body wt) and 4-chloro-2-methylphenoxyacetic acid (MCPA) (100-200 mg/kg body wt), and with the chemically different glyphosate N-phosphonomethyl glycine (300 mg/kg body wt) 5 days per week for 2 weeks. A hypolipidemic drug, clofibrate [ethyl-2-(4-chlorophenoxy)-2-methylpropionate], which is structurally related to phenoxy acids, was used as a positive control (200 mg/kg body wt). 2,4-D and MCPA had several effects similar to those of clofibrate: all three compounds induced proliferation of hepatic peroxisomes, decreased serum lipid levels, and increased hepatic carnitine acetyltransferase and catalase activities. 2,4-D and MCPA, but not clofibrate, decreased lipoprotein lipase activity in the adipose tissue to about a third of the control value but did not change the lipoprotein lipase activity in the heart muscle. The data suggest that these compounds cause hypolipidemia not by enhancing the storage of peripheral lipids in adipose tissue but by preferentially increasing lipid utilization in the liver. Glyphosate caused no peroxisome proliferation or hypolipidemia, suggesting that these effects are associated with the structural similarity between phenoxy acid herbicides and clofibrate.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1983

Bone cysts containing silicone particles in bones adjacent to a carpal silastic implant.

Silastic implants for a wide variety of medical purposes are in current and frequent use worldwide. Only recently there have been reports of the migration of silicone to the surrounding tissues via lymphatics. In the present material of nine cases with carpal implants followed for more than two years, bone cysts developed in the surrounding bones on five occasions. The only cysts so far investigated thoroughly contained foreign body reaction, and silicone could be detected by electron probe microanalysis. A long-term follow-up is suggested whenever these implants are used.

Adult↗