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Biomedical subjects

C R Ahrens

Publications and source records attributed to C R Ahrens.

9 recordsLinked to original sources
PubMed2000

Neonatal dexamethasone treatment increases the risk for pulmonary hypertension in adult rats.

Dexamethasone (Dex) treatment during a critical period of lung development causes lung hypoplasia in infant rats. However, the effects of Dex on the pulmonary circulation are unknown. To determine whether Dex increases the risk for development of pulmonary hypertension, we treated newborn Sprague-Dawley rats with Dex (0.25 microg/day, days 3-13). Litters were divided equally between Dex-treated and vehicle control (ethanol) rats. Rats were raised in either room air until 10 wk of age (normoxic groups) or room air until 7 wk of age and then in a hypoxia chamber (inspired O(2) fraction = 0.10; hypoxic groups) for 3 wk to induce pulmonary hypertension. Compared with vehicle control rats, Dex treatment of neonatal rats reduced alveolarization (by 42%; P < 0.05) and barium-filled pulmonary artery counts (by 37%; P < 0.05) in 10-wk-old adults. Pulmonary arterial pressure and the ratio of right ventricle to left ventricle plus septum weights (RV/LV+S) were higher in 10-wk-old Dex-treated normoxic rats compared with those in normoxic control rats (by 16 and 16% respectively; P < 0.05). Small pulmonary arteries of adult normoxic Dex-treated rats showed increased vessel wall thickness compared with that in control rats (by 15%; P < 0.05). After 3 wk of hypoxia, RV/LV+S values were 36% higher in rats treated with Dex in the neonatal period compared with those in hypoxic control rats (P < 0.05). RV/LV+S was 42% higher in hypoxic control rats compared with those in normoxic control rats (P < 0.05). We conclude that Dex treatment of neonatal rats caused sustained lung hypoplasia and increased pulmonary arterial pressures and augmented the severity of hypoxia-induced pulmonary hypertension in adult rats.

Angiography↗
PubMed1994

Political perception among young Australians: affective versus cognitive appraisal.

We investigated the role of affect in the political perceptions of a sample of Australian university students (N = 185). Following the procedure of Abelson, Kinder, Peters, and Fiske (1982), we compared affective and cognitive appraisals of three Australian politicians (Bob Hawke, John Howard, and John Bjelke-Petersen) and examined their respective influence on favorability judgments. Affective appraisals were less consistent than cognitive appraisals, and affect was a significant predictor of favorability, with certain idiosyncratic exceptions. Bjelke-Petersen elicited comparatively consistent affective reactions. The affective reactions elicited by Hawke were inconsequential to favorability. Two dimensions of negative affect for Hawke revealed a differential impact of negative affect on favorability.

Adolescent↗
PubMed1992

Absorbed dose determination for tomographic implant site assessment techniques.

A set of data to compare the absorbed dose delivered by tomographic implant site assessment techniques was generated. Absorbed doses were measured in fourteen anatomic sites from (1) computed tomography scans and (2) a series of tomographic cuts performed on a linear tomography unit. The doses to the thyroid gland, the active bone marrow, the brain, the salivary glands, and the eyes were determined with the use of a tissue-equivalent phantom with lithium fluoride thermoluminescent dosimeters at the appropriate locations.

Absorption↗
PubMed1991

Bullet identification with radiography.

The authors provide a simple radiographic method for estimating bullet weight and caliber of both deformed and undeformed bullets that enables accurate determination of caliber for the gamut of bullet shapes, with known degrees of confidence. The weight-determination procedure is based on the correlation between bullet cross-sectional area, as derived from three orthogonal radiographs, and bullet weight, as determined from a data base of the properties of 48 bullets removed from humans. Different equations were developed for bullets weighing 5.8 g or less, or more than 5.8 g. For relatively undeformed bullets an additional method calculated caliber directly from the diameter of the bullet body on radiographs. Both methods enabled correct prediction of the weight and caliber of the bullets; if one method could not be used, results of the other were reliable. Testimony based on these results has been accepted in a local police case and may meet requirements for testimony in U.S. court cases involving gunshots.

Firearms↗
PubMed1990

Preoperative versus postoperative irradiation in the prophylaxis of heterotopic bone formation in rats.

Irradiation treatment, commenced within 1-5 days post-surgery, reliably prophylaxes heterotopic bone formation but is painful and impairs desirable postop immobilization. To compare pre- versus post-op radiation, we bilaterally implanted bone matrix pellets into the thighs of 111 30-day-old Long Evans rats. Rats were randomized to time of radiation initiation (2 days pre-op, 1 hr pre-op, or 2 days post-op) and dose (300, 800, 1800, 2400, or 3000 cGy in 1 fraction). Pellets were removed on post-op day 16 or 48 and evaluated histologically and radiologically. Histologic analysis showed dose-related suppression in bone formation, that is, 40%, 27%, 6.8%, 2.5%, 6.4%, and 0.0% bone formed among sites receiving 0, 300, 800, 1800, 2400, and 3000 cGy, respectively. The difference in bone formation between control and irradiated implant sites was significant at every dose level in all treatment groups (p less than or equal to .03). There was no statistically significant difference in overall bone formation between post-op (7.1%) and 1 hr pre-op (5.3%) groups, whereas 2 day pre-op rats formed significantly more bone (12.6%). Stratified by dose, however, there were no significant differences between treatment groups except at 800 cGy. At this dose, 2 day pre-op rats formed more bone (10.6%) than 1 hr pre-op (6.6%) or post-op (3.3%) groups. Results suggest that a) radiation given shortly prior to a stimulus inducing proliferation among multipotential cells may inhibit subsequent proliferation and/or differentiation, and b) clinical formation of heterotopic bone may be preventable via modest doses of irradiation delivered shortly prior to surgery.

Animals↗
PubMed1976

An evaluation of rare earth screen/film combinations.

The physical and imaging characteristics of a number of commercially available rare earth screen/film combinations were evaluated and compared to those of conventional calcium tungstate/X-Omat RP-14 systems. All systems were evaluated for base-plus-fog density, relative speed, resolution, noise, and overall performance. The results indicate that despite certain limitations, rare earth screen/film combinations offer significant advantages for imaging.

Calcium↗