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J R Decker

Publications and source records attributed to J R Decker.

14 recordsLinked to original sources
PubMed1990

Overview of reproductive and developmental toxicity studies of 1,3-butadiene in rodents.

A series of studies to further evaluate the developmental and reproductive toxicity of inhaled 1,3-butadiene was sponsored by the National Toxicology Program. Pregnant Sprague-Dawley rats (24-28/group) and Swiss (CD-1) mice (18-22/group) were exposed to atmospheric concentrations of 0, 40, 200, or 1000 ppm 1,3-butadiene for 6 hr/day on days 6 through 15 of gestation (dg) and killed on dg 18 (mice) or dg 20 (rats). Subsequently, the uterine contents were evaluated; individual fetal body weights were recorded; and external, visceral, and skeletal examinations were performed. In rats, maternal toxicity was observed in the 1000-ppm group in the form of reduced extragestational weight gain and, during the first week of treatment, decreased body weight gain. Under these conditions, there was no evidence of developmental toxicity in rats. In contrast, results of the mouse developmental toxicity study indicated that the fetus may be more susceptible than the dam to inhaled 1,3-butadiene. Maternal toxicity was observed in mice at the 200- and 1000-ppm 1,3-butadiene exposure levels, whereas 40 ppm and higher concentrations of 1,3-butadiene caused significant exposure-related reductions in the mean body weights of male fetuses. Mean body weights of female fetuses were also reduced at the 200- and 1000-ppm exposure levels. No increased incidence of malformations was observed in either study. Other studies addressing male reproductive and mutagenesis end points were performed with B6C3F1 mice (sperm-head morphology) and Swiss (CD-1) mice (dominant lethal study).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1986

Toxicity of formaldehyde vapor in B6C3F1 mice exposed for 13 weeks.

Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 2, 4, 10, 20, or 40 ppm of formaldehyde vapor 6 h/day, 5 days/week for 13 weeks. Clinical abnormalities (dyspnea, listlessness, and hunched posture), significant mortality, and body weight loss were observed in the 40 ppm groups. Pathologic changes were observed in the nose, larynx, trachea, and bronchi of treated males and females and in the uterus and ovaries of treated females. Squamous metaplasia and inflammation were present in the nasal tissues of male and female mice in the 10, 20, and 40 ppm groups and in the larynx of males and females in the 20 and 40 ppm groups. The trachea had squamous metaplasia and hyperplasia of the epithelium in addition to submucosal fibrosis and inflammation in the 20 and 40 ppm groups. In some mice, epithelial-lined, irregular connective tissue bands spanned the tracheal lumen. Metaplasia of the bronchial epithelium was confined to the 40 ppm exposure groups. These effects on the respiratory system were more prevalent in male than in female mice. Hypoplasia of the uterus and ovaries, probably secondary to body weight loss, was confined to the 40 ppm exposure group. In conclusion, 13-week inhalation exposures of B6C3F1 mice to 10, 20, and 40 ppm of formaldehyde vapor induced histologic lesions in the upper respiratory system and concentrations of 40 ppm were lethal to those mice.

Animals↗
PubMed1982

Controlled-delivery vapor generator for animal exposures.

A vapor generation system is described which provides long-term stable vapor concentrations for inhalation bioassay tests with laboratory animals. Liquid is pumped from a reservoir by a micrometering pump to the surface of a cylindrical vaporizer covered with a glass fiber wick. An 80-watt heater and temperature sensor, embedded in the cylinder, control the vaporizer temperature. Pump rates of 0.01 to 20 mL/min and surface temperatures greater than 100 degrees C can be achieved. To minimize condensation on delivery-tube walls, the vaporizer is positioned in the dilution air inlet tube leading directly into the 2-m3 exposure chamber. During exposure of rats, mice and rabbits to eleven different chemicals for periods ranging from 4 hours to over 400 daily 6-hour exposure periods, concentrations from 25 to 10,000 ppm were achieved with a dilution air flow of 280 L/min. Chamber concentrations were routinely maintained within 10% of target levels. Stable pump rates provide a method of calculating vapor concentration independent of chemical analysis. Long-term generation stability and ease of operation reduce labor requirements compared to previous generation techniques.

Animals↗
PubMed1980

Effects of 60-Hz electric fields on avoidance behavior and activity of rats.

In repeated short-term tests (four sessions, each of 45-minute duration), and one longer test (a 23.5-hour session), behavior of rats was evaluated in a long, narrow shuttlebox. One side of the box was exposed to an electric field at various strengths, while a visually identical opposite side was shielded from exposure. In the short-term tests, rats generally remained shielded from electric fields of 90 kV/m and greater during the first session, and maintained this response in subsequent sessions. In the longer test, this same preference response was demonstrated at field strengths of 75 kV/m and greater; however, at 25 and 50 kV/m, rats exhibited a statistically significant preference for the exposed region of the shuttlebox, but only during the light portion of a 12-hour light: 12-hour dark cycle. Exposed animals made more traverses than sham-exposed controls between the two ends of the shuttlebox during the first hour of the test. The experimental data support the hypothesis that the observed behavioral effects are the result of direct interaction of the electric field with the animal, and not the result of secondary factors such as electric shocks, corona discharge, audible noise, ozone, or vibration of the experimental apparatus.

Animals↗
PubMed1976

Automated rodent respiratory monitor and histogram computer--a preliminary report.

The system described in this paper was designed to monitor total inhaled volume (V), tidal volume (VT), and respiratory frequency (f) of Fisher rats before, during, and after exposure to cigarette smoke. The systems consists of three major subsystems: plethysmograph, analog signal conditioner, and histogram computer. The volume type whole body plethysmograph incorporates a rubber nose seal. Tidal flow rate (V) from the tube, measured by a pneumotachometer, is integrated by the signal conditioning system to obtain VT and V. Both V and V are displayed on a strip chart recorder. A rat will often exhibit considerable sniffing, especially in the presence of cigarette smoke. Consequently, average tidal volume (VT) and average respiratory frequency (f) are not accurate measurements of typical VT and f. Sensitivity of the system to changes in typical VT and f is important snce the system will be used to evaluate the effects of subtle differences in types of experimental cigarettes. A microprocessor was used in conjunction with a cathode ray tube to compute and display both the VT and respiratory period (T = 1/f) as histograms. From the histograms the most common (typical) VT (mode of the histogram) and the most common T can be easily observed and recorded. The histogram computer also calculates and digitally displays VT and f.

Analog-Digital Conversion↗