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Biomedical subjects

B L Hart

Publications and source records attributed to B L Hart.

At least 145 records · Page 8Linked to original sources
PubMed1968

Neonatal castration: influence on neural organization of sexual reflexes in male rats.

Most male rats castrated 4 days after birth and given exogenous testosterone in adulthood were sexually motivated but incapable of completing the mating sequence with an ejaculatory response. When tested for sexual reflexes after spinal transection, these animals displayed impairment of genital responses. Similarly treated 12-day castrates exhibited a complete mating sequence and had normal sexual reflexes. Thus neonatal testicular androgen appears to have an organizational influence at the spinal level on neural tissue mediating sexual reflexes.

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PubMed1967

Testosterone regulation of sexual reflexes in spinal male rats.

Castrated male rats with complete midthoracic spinal transections were maintained on exogenous testosterone; they showed intermittent clusters of genital responses consisting of erections, quick flips, and long flips of the penis when gentle pressure was con stantly applied to its base. The number of these genital responses per 30-minute test was markedly influenced by withdrawal or administration of testosterone.

Animals↗
PubMedDate not supplied

Segmentation of small structures in MR images: semiautomated tissue hydration measurement.

Segmentation of small anatomic structures in noisy magnetic resonance (MR) images is inherently challenging because the edge information is contained in the same high-frequency image component as the noise. The authors overcame this obstacle in the analysis of the sural nerve in the ankle by processing images to reduce noise and extracting edges with an edge detection algorithm less sensitive to noise. Anatomic accuracy of the segmentation was confirmed by a neuroradiologist. A nerve hydration coefficient was determined from the signal intensity of the nerve in these segmented images. These semiautomated measurements of hydration agreed closely with those obtained with a previously described manual method (n = 44, P = .76). Each image in the study was analyzed identically, with no modification of the computer algorithm parameters. The data suggest that this robust method may be useful in a multicenter evaluation of diabetes treatment protocols.

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PubMedDate not supplied

Grooming in impala: role of oral grooming in removal of ticks and effects of ticks in increasing grooming rate.

In Experiment 1, five adult female impala were fitted with harnesses that restrained oral self-grooming of the anterior part of the body. At the same time, six cohoused female impala were fitted with control harnesses that allowed normal oral grooming. The impala were allowed to habituate to the harnesses for 10 days, and both groups were then exposed to larval ticks (Boophilus decoloratus) by herding them into a tick-seeding corral. During the third week following tick seeding, when female ticks were estimated to have developed into engorging adults, the impala were immobilized, tick numbers on the animals sampled by patch sampling, and the harnesses removed. Observations continued for 5 days following removal of the harnesses. Twenty-minute focal observations were conducted daily on each impala during the habituation, tick-seeded, and postharness phases. Restrained impala had a median of 20 times more adult female ticks (both engorged and unengorged) than control impala. Oral grooming, which had been suppressed in the restrained impala during habituation and tick-seeded phases, increased 10-fold once the harnesses were removed and occurred 2.5 times more frequently than in control impala during the postharness phase. In Experiment 2, 15 adult female impala were seeded with larval ticks as in Experiment 1; in week 3 after tick seeding all ticks were removed from animals by application of an acaricide. Grooming was recorded during 3 weeks of baseline observations prior to tick seeding, 3 weeks after tick seeding, and then for 3 weeks beginning 1 week after acaricide treatment. Oral grooming and scratch grooming significantly increased from baseline during tick seeding and significantly declined following removal of the ticks with acaracide. Taken together, the two experiments demonstrate that oral grooming is very effective and important in removing fitness-compromising ticks in free-ranging impala. Correspondingly, exposure to, and subsequent infestation by, ticks increases the rate of grooming.

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