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Biomedical subjects

L S Peck

Publications and source records attributed to L S Peck.

6 recordsLinked to original sources
PubMed2003

Reduced oxygen at high altitude limits maximum size.

The trend towards large size in marine animals with latitude, and the existence of giant marine species in polar regions have long been recognized, but remained enigmatic until a recent study showed it to be an effect of increased oxygen availability in sea water of a low temperature. The effect was apparent in data from 12 sites worldwide because of variations in water oxygen content controlled by differences in temperature and salinity. Another major physical factor affecting oxygen content in aquatic environments is reduced pressure at high altitude. Suitable data from high-altitude sites are very scarce. However, an exceptionally rich crustacean collection, which remains largely undescribed, was obtained by the British 1937 expedition from Lake Titicaca on the border between Peru and Bolivia in the Andes at an altitude of 3809 m. We show that in Lake Titicaca the maximum length of amphipods is 2-4 times smaller than other low-salinity sites (Caspian Sea and Lake Baikal).

Altitude↗
PubMed1982

Effects of pituitary stalk transection on endocrine function in Pony mares.

The pituitary stalk was transected in 10 Pony mares by a surgical approach that involved dorsal reflection of the brain and micro-dissection from the ventro-lateral aspect of the pituitary. Diabetes insipidus was the most immediate and marked result, requiring extensive electrolyte and antidiuretic therapy for approximately 48 h after operation. Fluid stasis then developed and no further supportive measures were necessary. Endocrine challenge tests with GnRH and TRH before and after stalk transection indicated a loss of responsiveness (GnRH) or suppressed responsiveness (TRH) after the operation. This technique permits isolation of the pituitary from its hypothalmic releasing and/or inhibiting hormones and therefore permits more refined study of the hypothalamic-pituitary axis.

Animals↗
PubMed1982

Effects of pinealectomy in Pony mares.

When mares were pinealectomized in summer or in winter there was no difference in the annual ovulation date of these animals and of pineal-intact controls during the first post-operative breeding season but in the second season the ovulation date of the winter pinealectomized mares was significantly delayed, suggesting a long-term but clear pineal involvement in seasonal reproductive patterns. Exposure of pinealectomized mares to a stimulatory photoperiod failed to advance the average date of first annual ovulation and was similar to that of intact mares receiving no stimulatory lighting. The results indicate that pinealectomy blocks the ability to respond to photostimulation. In intact mares plasma melatonin concentrations were significantly increased during darkness (P less than 0 . 003) but pinealectomized mares demonstrated no significant time trends.

Animals↗
PubMed1982

Melatonin rhythms in Pony mares and foals.

Melatonin concentrations in intact (N = 3) and sham-operated (N = 3) mares during March were greater (P less than 0 . 05) during the night than during the day, but this pattern was not seen in 3 mares from which the superior cervical ganglia had been removed bilaterally. When 4 Pony mares were exposed to a photoperiod of 10L:14D for 3 weeks and then to continuous darkness (0L:24D) for another 3 weeks, melatonin levels were greater (P less than 0 . 05) at the end of the 0L:24D period than during the earlier period and still displayed rhythmic fluctuations but were no longer co-ordinated with equivalent day/night rhythms or among mares. When melatonin rhythms were monitored in 3 mares and their foals housed in open pens exposed to natural lighting, significant time trends in melatonin concentrations were observed in mares when the foals were aged 1-3, 4-6 and 7-11 weeks, but foals did not display significant times trends in melatonin until they were 7-11 weeks old.

Aging↗
PubMedDate not supplied

Evaluation of CMC and HA solutions for adhesiolysis.

Aqueous hyaluronic acid (HA) and carboxymethylcellulose (CMC) solutions were tested as tissue-protective coatings during lysis of surgical adhesions by blunt dissection or electrocautery in a rat cecal abrasion model. Phosphate-buffered saline (PBS) was used as a tissue coating solution in 200 female Sprague-Dawley rats prior to controlled cecal abrasion with a surgical gauze-tipped rotary abrader (four 1.5-cm-diameter areas; 70 g weight/60 revolutions/130 rpm). One-week after this initial cecal abrasion, rats were operated on again and adhesions were scored and lysed. The rats were randomly assigned to receive experimental tissue coating solutions either before (prelysis; n = 160) or after (postlysis; n = 40) adhesiolysis. Animals with prelysis coatings were further divided into blunt dissection or electrocautery adhesiolysis groups and were tested with 2 mL cecal coating of PBS, 0.4% HA, 0.5% CMC, or 1.0% CMC tissue coating solutions (n = 20/group). Rats treated postlysis received 2 mL cecal coating plus 2 mL intraperitoneal instillation of PBS, 1.8, 1.9, or 2.0% CMC. One week after adhesiolysis, rats were operated on again for final adhesion scoring. Prelysis tissue coating with 0.5 or 1.0% CMC solution appeared to inhibit adhesion reformation after blunt dissection, whereas 0.4% HA was not effective in this model. Solutions applied before electrocautery dissection or after blunt dissection were ineffective.

Animals↗