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Biomedical subjects

D Renouf

Publications and source records attributed to D Renouf.

7 recordsLinked to original sources
PubMed2005

Examination of the failure properties of the anterior cruciate ligament during the estrous cycle.

The purpose of this study was to determine whether the mechanical properties of the rat anterior cruciate ligament (ACL) vary when tested in vitro at different stages of the estrous cycle. Sixty female rats were allocated to four groups according to their stage of the estrous cycle: diestrus (n=16), proestrus (n=17), estrus (n=13) and metestrus (n=14). Right hindlimbs were harvested for mechanical testing and left hindlimbs were harvested for immunohistochemical staining to confirm the presence of the estrogen receptor. Results from the first relaxation test showed a significant difference between the estrus and proestrus stage, which was not observed in a second subsequent relaxation test. Likewise, no significant differences were found when comparing failure load and stiffness between the different stages of the estrous cycle. These results suggest that normal physiological fluctuations in estrogen during the estrous cycle did not alter the failure properties of the rat ACL.

Animals↗
PubMed1994

Pseudopregnancy in harp seals (Phoca groenlandica).

Concentrations of circulating progesterone were monitored in a captive breeding group of harp seals. Five females were monitored for 2 years, over which time they either became pregnant (four instances) or displayed an overt pseudopregnancy (five instances). Only one female exhibited consecutive pseudopregnancies. In all pseudopregnancies, serum progesterone values were high and remained high until July, which is close to the time when implantation normally occurs. After this time progesterone concentrations remained high, gradually declining to baseline values over the following four months. In the three females that were pregnant one year and pseudopregnant in the other year, the average progesterone concentration during pseudopregnancy was lower than that exhibited during pregnancy (P < 0.05). All females (except one) increased their mass, girth and condition index over the normal gestation period whether they were pregnant or pseudopregnant. The potential consequences of such a high rate of pseudopregnancy on the use of ovarian scars for estimating reproductive rates and population size are discussed.

Animals↗
PubMed1980

Masked hearing thresholds of harbour seals (Phoca vitulina) in air.

Two wild seals, maintained in captivity in good health, were trained to swim on verbal command to a spot 27 cm above the water, and subsequently to make a L or R turn to a pure tone vs no tone. White noise was present at 80, 70, or 60 db SPL. Masked thresholds were determined by a staircase method in 2-db steps at 2, 4, 8.6, and 15 kc/s (at 15 kc/s only noise at 60 db SPL was presented). Critical bandwidths in db were calculated, all of the order of 25 db (range of to 28 db). These values are close to those reported by Terhune and Ronald (J. Acoust.Soc.Am., 1975, 58, 515-516) for seals' aerial hearing but are unexplainably lower (i.e., worse) than for seals underwater. It was calculated that in their often noisy and visually restricted natural environment, a mother would not be able to hear her pup if separated by more than 8 m. This situation was generally corroborated by field observation on the breeding grounds.

Animals↗