Date of Award

1981

Embargo Period

8-1-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physiology

College

College of Graduate Studies

First Advisor

Christopher M. Fredericks

Second Advisor

Henry F. Martin

Third Advisor

George E. Tempel

Fourth Advisor

Perry V. Halushka

Fifth Advisor

H. Oliver Williamson

Abstract

A microminiature force transducer has been developed and used to record both acutely and chronically the motility of the rabbit reproductive tract. This device, which is comprised of two matched piezoresistive silicon sensors bonded to a titanium beam strip, is durable, physically stable, and highly sensitive to bending forces (gage factor, 140). The reproductive function of 26 rabbits in which two such devices were chronically implanted on the right isthmus was examined in detail. The animals in which these devices were implanted healed quickly with no evidence of infection or other pathological change. No alterations were noted between right (implanted) and left side or between experimental or nonsurgical control animals in the number of corpora lutea, number of uterine implants, number of viable conceptuses, fertility, pregnancy rates, rates of ovum transport, or peripheral plasma levels of progesterone or estradiol. The fact that no significant differences existed indicates that neither the implantation surgery nor the chronic presence of these devices on the reproductive tract disturbed normal reproductive function. Acute recordings were made in 20 rabbits and revealed continuous, rhythmic contractile activity in both the oviduct and uterus. Chronic recordings were made in 14 unanesthetized rabbits throughout the 72 hour period encompassing ovulation and ovum transport, and revealed patterns of motility which were markedly different from the acute, but were consistent throughout the periovulatory period. This activity, with the exception of the period immediately following implantation surgery, was characterized by distinct bursts (B) of intense contractile activity, interspersed with periods (interburst, IB) of relative quiescence. Recordings made under light pentobarbital anesthesia immediately following surgery revealed high amplitude, continuous activity, superimposed on a relatively constant baseline. By five days postsurgery, the distinct bursting pattern was present in all animals. Although the basic pattern of Band IB periods persisted throughout this period, significant changes occurred in the durations of its components. B durations increased with all values significantly greater (p < 0.01) than their paired estrus values from 24 hours forward. IB and interevent (IE) durations diminished somewhat at 24 hours, and then significantly increased. The proportion of time spent in bursting activity (BP) was significantly (p < 0.01) greater at 24 hours (33%) than at estrus (27%). Although BPs declined at 60 and 72 hours, these values differed from estrus with a p < 0.10. Progesterone (P) surged from estrus values to a peak, at 6 hours, fell until 24 hours, and gradually increased through 72 hours. All poststimulus P values were significantly (p < 0.01) greater than the estrus values. The B, IB, and IE durations at 72 hours were all significantly (p < 0.05) and positively correlated with the P levels of the 6 hour surge. The B durations at 72 hours were positively correlated with the 72 hour P (p < 0.05). This data support the view that changes in isthmic contractility affect ovum movement by altering the luminal resistance to its movement. It further suggests the importance of the periovulatory changes in P in the regulation of this activity. An analysis of the frequency content of the motility records revealed that frequency components found at all times throughout the 72 hour periovulatory period were primarily located between 0.06 and 0.20 Hz. Peak components were found to occur at 0.11 and 0.04 Hz, except for the components at 24 hours post stimulus. At 24 hours, there was a shift in peak components to 0.09 Hz. The significant changes in frequency predicted by some investigators were not noted.

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