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Biomedical subjects

H Pfeifer

Publications and source records attributed to H Pfeifer.

At least 19 recordsLinked to original sources
PubMed1990

[Color stability of light curing composites].

Eight commercial and two experimental light cured composite have been tested for color stability after experimental aging. Color differences were measured by computer-controlled spectrophotometry and expressed in terms of L*A*B* color coordinates (CIELAB). Although three composites with a high content of anorganic filler showed the best color stability and the material with the lowest anorganic filler content showed the greatest discoloration, there was no strong correlation between the amount of anorganic filler on the one hand and color stability after experimental aging on the other.

Color↗
PubMed1989

Tumours of the respiratory tract in rats and hamsters following chronic inhalation of engine exhaust emissions.

The potential carcinogenic effect of inhaled automobile exhaust emissions was examined in rodents. Both rats and hamsters were exposed to the emissions from (1) a gasoline engine, (2) a gasoline engine fitted with a three-way catalytic converter, (3) a diesel engine and (4) a diesel engine with particle filtration. Exposures were for 16 hours per day, 5 days per week, for 2 years. All hamsters were sacrificed at the end of the 2-year exposure period, whereas the rats surviving after 2 years of exposure were maintained for a further 6-month observation period without additional exposure to emissions. Some of the hamsters in each treatment group were pretreated with diethylnitrosamine to induce respiratory tract tumours. No statistically significant changes were seen in the incidence of respiratory tract tumours in emission-exposed hamsters compared to controls. This lack of a treatment-related effect was seen in both the nitrosamine pretreated and the non-pretreated hamsters. There was no increase in the incidence of lung tumours in rats exposed to filtered diesel exhaust or to the exhaust from the gasoline or gasoline-catalyst engines. There was a statistically significant increase in the incidence of lung tumours in rats exposed to diesel engine emissions compared to controls. A clear dose response was evident in both males and females, although the incidence of lung tumours was markedly higher in females (96% in rats surviving beyond 2 years) than in males (44% in rats surviving beyond 2 years). An increased incidence of lung tumours was observed only in rats exposed to mean concentrations of diesel soot particles of either 2200 or 6600 micrograms/m3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

31P-NMR spectroscopy and ultrastructural studies on nephrotoxicity of cyclosporine A.

NMR-spectroscopy and electron microscopy were applied in order to find out whether nephrotoxic effects of cyclosporine A in combination with ischaemia on rat kidney are of significance for the energy metabolism of the organ. CSA was administered in daily doses of 15 mg/kg rat over 20 days. Use was made of the particular advantage of 31P-NMR-spectroscopy to follow up the dynamics of high-energy phosphate concentrations in the same tissue. Ultrastructural changes were observed in the region of the proximal tubule. Some mitochondria showed degenerative changes, others increased density of cristae. The total number of mitochondria was increased. This observation together with the coexistence of vacuolarly degenerated mitochondria and mitochondria with increased activity after CSA treatment is interpreted as expression of a compensatory mechanism that keeps constant the totality of high-energy phosphates despite damage to some mitochondria.

Adenine Nucleotides↗
PubMed1984

[Chemotherapy with cisplatin-bleomycin and subsequent radiotherapy in advanced head and neck tumors].

42 patients with advanced stage III and IV squamous cell carcinoma of the head and neck were treated with initial cisplatin and bleomycin chemotherapy and subsequent radiotherapy. 39 were evaluable for results, and 3 for toxicity only. 8 patients suffered from stage III and 31 from stage IV tumors, of these 10 with distant metastases. 5 patients underwent later a rescue operation. 27 were previously untreated (= group A) including 2 cases with localized relapses beyond the margins of surgical and/or radiotherapeutic treatment fields. 12 patients had a recurrence within pretreated areas (= group B). The induction chemotherapy alone showed the following results: In group A 4 (15%) CR, 10 (37%) PR, 7 (26%) MR; in group B 3 (25%) PR, 2 (17%) MR. The subsequent radiotherapy mostly consisted of a 65 Gy tumor dose given in 61/2 weeks. The results after completion of the combined modality therapy were: In group A 44% CR, 28% PR; in group B 10% CR and 30% PR. No patient resistant to the initial chemotherapy responded to the radiotherapy. The median survival time of stage III patients was 20 months but only 7 months in stage IV patients. 4 of all live with NED now between 30+ and 41+ months; 1 patient is alive with relapse. All the others are dead after a survival time of max. 32 months, included the 5 with rescue operation. In general, hematologic and renal toxicities were not severe, but nausea and vomiting were the worst tolerated side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗