摘要:

MV‐678 [1‐(8‐methoxy‐4,8‐dimethynonyl)‐4‐(1‐methylethyl)benzene], a recently developed insect growth regulator, increased the hepatic cytochrome P‐450‐dependent monooxygenase enzymes that metabolize endogenous and exogenous chemicals. In an initial set of experiments, male and female rats received 0, 50, or 800 mg/kg·d of MV‐678 by gavage for 3 d, and in a second set of experiments, male rats received 0, 50, or 800 mg/kg·d of MV‐678 by gavage for 30 d. A significant incrase in both absolute and relative liver weight, microsomal protein content, cytochrome P‐450 content, NADPH‐cytochrome P‐450 reductase activity, and ehtylmorphine N‐demethylase activity was observed in male and female rats at the high dose level at 3 d. Similar increases were observed in the 800‐mg/kg·d males at 30 d. Hepatocellular hypertrophy and proliferation of endoplasmic reticulum observed at both 3 and 30 d correspond to and was consistent with microsomal enzyme induction. Reversibility of both induction and changes in morphology was determined by measuring the same parameters in animals treated for 30 d after a 15‐ or 30‐d recovery period. At 15 d recovery, all biochemical parameters at the high dose level, except relative liver weight and microsomal ethylmorphine N‐demethylase activity, had returned to control levels. No significant differences between the control and high dose group animals were noted at 30 d recovery. The hepatocellular changes observed in the high‐dose group at 30 d were less apparent at 15 d recovery, and absent at 30 d recovery.

ISSN:0098-4108    

DOI:10.1080/15287398609530912

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Ozone, an important component of photochemical air pollution, has been shown to cause morphological and functional changes in the lung after acute, high‐level exposure in controlled animal studies. Previous exposures of rats to 0.8 ppm ozone for 18 h showed trends toward decreased lung volumes, as well as modifications in phospholipid composition of lung lavage fluid. These results suggested that exposure to ozone may have diminished the ability of surfactant to reduce surface tension. The purpose of this pilot study was to determine if changes in the surface tension of lavaged pulmonary surfactant occur with ozone exposure. The lavage fluid from rats exposed to ozone at 0.8 ppm for 18 h had a 360% increase in protein and a 30% Increase in lipid phosphorus content. Lung lavage samples from ozone‐exposed rats were more potent in reducing surface tension as measured on a Wilhelmy plate balance. This difference was evident whether determined with half the total lavage or with equivalent microgram amounts of lipid phosphorus. It is concluded that at this dose and duration of ozone exposure, contrary to our hypothesis, surface‐tension‐lowering ability of surfactant increases and therefore does not appear to be a contributory factor in the previously observed changes in pulmonary function.

ISSN:0098-4108    

DOI:10.1080/15287398609530913

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A tissue culture study was conducted on the effects of chromium on chondrocytic differentiation. Mesenchymal cells from stage 22–24 chick limb buds were dispersed and cultured as micromasses, where they differentiated into chondrocytes. Addition of chromium(VI) to the cultures indicated that the production of proteoglycans (as detected by Alcian blue staining) was more sensitive to chromium's effects than was cell proliferation. Whereas Alcian blue nodule formation was inhibited by 1 μM Cr(VI), cell proliferation (as detected by cell counts) was not. Chromium (VI) was added to cultures at daily intervals, and these studies indicated that the interval of d 1–2 was the most sensitive period. ADP‐ribose transferase activity in these cultures was measured; the pattern of enzyme activity in control cultures was high 1 and 24 h after the start of culture, decreased abruptly between 24 and 48 h, and then decreased more gradually. In the presence of Cr(VI), elevated ADP‐ribose transferase levels were maintained throughout the culture period. We suggest that, in presence of 1.0 μM chromium(VI) or higher concentrations, the balance of events favors nucleolytic action rather than repair of damage.

ISSN:0098-4108    

DOI:10.1080/15287398609530914

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287398609530901

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor