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Effects of Microsurgical Removal of the Rabbit Uterotubal Junction
Effects of Microsurgical Removal of the Rabbit Uterotubal ]unction AMNON DAVID, M.D.,* BENJAMIN G. BRACKETT, D.V.M., PH.D., and CELSO-RAMON GARCIA, M.D.
of a postovulatory functional blocking mechanism at the uterotubal junction ( UTJ) keeping newly fertilized ova in the oviducts from 72 to £6 hr., is well recognized in many mammals. 1 • 2 • 9 • 16 The physiologic significance of this retention which follows speedy transit of ova through the ampulla remains unknown. Nonetheless, for some mammals, including the rabbit, no anatomic or histologic evidence of such a functional block has been demonstrated. 7 • 9 • 14 The purpose of this investigation, then, was to determine whether resection of the UTJ alters this retention process. Using a microsurgical technic described below, the UTJ was excised, and the effect on ovum transport was observed. The UTJ in this study was defined as the segment between isthmus and uterine horn, which encompassed an area from about 1.5 em. of the proximal end of the isthmus and included the thickened wall of the uterine horn to which the isthmus is connected (this thickness is minimal). • . Our observations were directed to localizatio~ of the ova, to assess the contribution of the UTJ and to the delaying mechanism of ovum transport.
THE EXISTENCE
MATERIAL AND METHODS
Twenty-five mature, New Zealand, White rabbit does (weighing between 3500 and 4500 gm. ) were used. The does were anesthetized with pentobarbital sodium, given intravenously. A unilateral resection of the UTJ was performed in each animal. An excision was made comprising 0.25-0.5 From the Division of Reproductive Biology, Department of Obstetrics and Gynecology, University of Pennsylvania, School of Medicine, Philadelphia, Pa. The authors are greatly indebted to the technical assistance of Mrs. Eve Kelly, Mrs. Anne Hoffman, and Mr. Jim Butler. *Ford Foundation Research Fellow. Permanent address: Tel-Hashomer Hospital, Tel-Aviv Medical School, Israel.
250
VoL. 20, No.2,
1969
UTEROTUBAL JuNcTION REMOVAL
251
em. of uterus and 1.0-1.5 em. of the proximal end of the isthmus. Dissection was performed using a Zeiss operating microscope, with Barraquer modification.* The microscope was mounted on an Operation I floorstand with rotating axes coaxial with the optical axis. Magnification of lOX to 40X was used. Hemostasis was maintained and anastomosis of the oviductal isthmus to the uterine horn was performed, using delicate microsurgical instruments. t Nylon ( 8-0) and silk ( 6-0) suture material mounted on atraumatic neediest was used. The anastomosis of the remaining isthmus to the uterine horn was performed with the aid of a polyethylene tubule splint ( P.E. 10§). One end of the tubule was introduced into the freshly opened isthmus and gently directed through the oviduct and out through the fimbriated end. The other end of the tubule was passed into the uterine cavity to the level of the cervix. Because of the disproportionate isthmic and uterine horn diameters, the opening of the proximal end of the isthmus was bivalved (transverse, fish-mouth-like opening) . Four individual sutures were passed at the four cardinal points traversing the wall of the horn going through the isthmic wall and returning in the opposite direction ( 2.5 mm. from the initial point of entry of the suture). This results in an eversion of the edges of the walls of the isthmus and horn as the suture is tied. The sutures were placed under the serosa, through the myometrium and above the endometrium of the uterine horn, and through the muscular layer and endosalpinx of the isthmus, producing a layer-to-layer anastomosis. Meticulous peritonealization was carried out to obviate adhesions. The end of the polyethylene tubule emanating from the fimbria} ostium was brought through the abdominal wall and anchored subcutaneously to the rectus fascia. A dose of 150,000 I.U. of benzathine long-acting penicillin G suspension ( Bicillinl\) was routinely given I.M. after the operation. Rabbits were then caged individually and fed Purina Rabbit Chow and water ad libitum. The opposite oviduct and uterine horn served as a control. After 15 days, the rabbits were explored under general anesthesia, and the polyethylene tubule removed. The abdominal cavity and the region of the anastomosis were inspected. Animals with anatomic pelvic organ distortion were discarded, except those with minimal adhesions and visibly unconstrained oviducts. The retained rabbits were then isolated for 21 days in individual cages, to insure an estrous state (proven by the acceptance of the male). Each doe was then bred twice to fertile bucks, and sacrificed 9-10 days later. At that time, the number of corpora *Manufactured by Carl Zeiss, West Germany. tWeck and Co., N. Y. +Davis & Geck, Danbury, Conn. §Clay-Adams, Inc., New York. IIWyeth Laboratories, Philadelphia, Pa.
252
DAVID ET AL.
FERTILITY & STERILITY
Fig. 1. After resection of UTJ and meticulous hemostasis, polyethylene tubule is inserted through lumen into oviduct.
lutea on both the control and operated sides was recorded, as well as registering the number of blastocysts implanted in each respective horn. These were correlated with the site of implantation and the appearance of the implanted blastocysts. Figures 1-5 depict the various steps of the procedure described above. RESULTS Of 25 rabbits, 2 died 1-3 days after the anastomosis. Two others refused the male although isolated twice for a period of 21 days. In these 2 rabbits, Japarotomy disclosed a paucity of follicles in either ovary; in none were corpora lutea or adhesions found, and the anastomosis was patent. Patency was assessed by instilling fluid through the oviduct into the uterus. Ten additional rabbits failed to have pregnancies in either side despite many corpora lutea present in their ovaries. In these 10 animals, many adhesions had formed immobilizing their oviducts. Dissection of these adhesions around the oviducts disclosed that the fallopian tubes were not distended with accumulated fluid. Moreover, the anastomosed area was patent. Eleven rabbits were pregnant on both sides (Table 1). The condition of 8 of these animals was good. In 2 there were fine adhesions between omentum and bladder and between intestines. However, in all
Fig. 2 (top). Other end of the polyethylene tubule is drawn through uterine cavity. Suture is placed through subperitoneal structure through muscular layer but avoiding endometrium. Fig. 3 (bottom). Fine suture is seen in place bridging muscular layer of oviduct to uterus. Four similar sutures placed equidistant from each other are used.
254
DAVID ET AL,
FERTILITY
&
STERILITY
instances the oviducts and uterine horns were free and mobile. One of the animals had a marked subcutaneous infection; however, no significant adhesions were found in the abdominal cavity. Since bleeding occurred during the handling of the periadnexal structures of the control side in
Fig. 4 (top). Separate approximation with peritonealization is accomplished to achieve anastomosis. Fig. 5 (bottom). Five implantation sites located in left horn (nonoperated) and two implantation sites in right horn ( UTJ excised and anastomosis achieved). Animal sacrificed for evaluation and photography.
Rabbit 1, and sutures to control the bleeding impaired the fimbriae and ovarian vascularity, no comparative results are available for this animal. A good correlation between the number of corpora lutea and the number of implantations of the control side was found: a total of 52 corpora lutea with 50 implantations or 96% implanted blastocysts. These implants were normally developed. On the operated side, the ovaries displayed a total of 63 corpora lutea with only a total of 26 blastocysts implanted. Thus, only 41% of the ova on the operated side were capable of implantation. All of the blastocysts which did implant were normal in size and appearance.
VoL.20,No.2,1969
TABLE
1. Reproductive Data after Removal of the Uterotubal Junction Operated side
Rabbit
1 2 3 4 5 6 7 8 9 10 11 ToTAL
255
UTEROTUBAL }UNCTION REMOVAL
Condition 6 wk. after anastomosis
Good Good Good Good Adhesions Good Infection under skin Adhesions Good Good Good
Corpora lutea
Implantat ions
Control
.~ide
·-----Corpora lutea
Tmplantat ions ~
7 8 3 6 3 7 1 5 O* 4 2 5 O* 5 3 5 2 6 2 5 3 7 26 63 (41% of the ova implanted)
6 5 5 3 .1) 5 8 8 4 4 6 6 3 3 5 5 50 52 (96% of the ova implanted) 6 .5 5 5
*At time of dissection, no evidence of obstruction was noted at site of anastomosis.
The sites of implantation were at variable distance from the area of anastomosis. DISCUSSION
Following ovulation, rabbit ova pass rapidly through the ampulla to the ampullary-isthmic region, where fertilization is believed to occur. 9 • 11 The newly fertilized ova then slowly descend toward the uterine homs. The time spent in the different segments of the oviduct is variable,9 but the 3-4 day total appears to be constant. It is felt that the delay in transit of the fertilized ova at the tubal level allows time for maturation in preparation for implantation. 4 Such alterations in timing may jeopardize the future development of the early conceptuses by impairing their ability to implant. In the present experiments, the results indicate that when the UTJ is excised, the ova implant in a lower than normal proportion. This alteration may represent a more rapid ovum transport through the newly anastomosed oviduct since the physiologic blocking has been removed thus resulting in immaturity and rejection of most of the ova. Faulty implantation should probably not be ascribed to the microsurgical technic itseH, since the sutures did not pass through the endometrium into the uterine cavity and impinged only through the muscular thickness of the walls. Havranek et al., using rats, showed that when sutures are placed in such a manner,
256
DAVID ET AL.
FERTILITY
& STERILITY
normal implantations were found. Moreover, these authors show that even when the threads pass through the lumen they do not always prevent implantation, as stated by Greenwald. 10 Black and Asdell demonstrated the existence of a physiologic block at the uterine end of the rabbit oviduct which prevents the entry of ova into the uterus. A valve-like action was described. This block was also described in the ewe 8 and seems to be under hormonal control, being affected by both estrogen and progesterone levels. When estrogen secretion temporarily drops after ovulation, progesterone diminishes oviductal contractions; resistance, which drops at the UTJ, as defined in this study, is under hormonal control. 1 • 2 • 12 The present experiments carried out in vivo support the findings of Black and AsdelP· 2 Moreover, ciliary activity, which increases from ovulation time, 3 and muscular contractions15 were no longer opposed in the normal manner. A 41% ovum implantation on the operated side indicates that the fimbria! pick-up mechanism was operating. Flushings of such operated oviducts immediately after ovulation time recovered a normal complement of ova. 6 One may conclude therefore, that the decreased number of implantations on the operated side stems either from the interference with the transport of the ova, or from impairment of implantation, or from both. The alteration in transport would appear more likely since fertilized ova reaching the uterine cavity prematurely will degenerate. 5 No implanted degenerating blastocysts, nor scars indicative of early implantations which later degenerated, were observed. The evidence presented above supports the need for UTJ control of thP nassage of gametes through the oviducts of rabbits. The Peed for such deveJonment is inferred by the more uniform degree of implantation sites when the UTJ is present. SUMMARY The effect of the removal of the uterotubal junction on implantation was observed in New Zealand rabbit does. In each animal studied. one UTT was removed, and an anastomosis of tl1e remaining oviduct to the uterinP horn was performed by a microsurgical procedure. The contralateral UTJ wa'i Jeft intact thereby providing a control. Twenty-six of 63 ova ( 41%) implanted normally on the operated sides, while 50 of 52 ova ( 96%) implanted normally on the control sides. These observations indicate that sperm migration, fertilization, and ovum transport can occur in the absence of the UTJ. However, the discrepancy between operated and control sides is probably best explained as a failure
VoL. 20, No.2, 1969
UTEROTUBAL JuNCTION REMOVAL
257
of the oviduct, in the absence of the UTJ, to retain ova until they are ready to implant. C.-R. G. Suite 106 Dulles Hospital of University of Pennsylvania Philadelphia, Pa. 19104
REFERENCES 1. BLACK, D. L., and AsDELL, S. A. Transport through the rabbit oviduct. Amer ] Physiol192:63, 1958. 2. BLACK, D. L., and AsDELL, S. A. Mechanism controlling entry of ova into rabbit uterus. Amer] Physiol197:1215, 1959. 3. BoRRELL, U., NILSSON, 0., and WESTMAN, A. Ciliary activity in the rabbit fall"oian tube during estrus and after copulation. Acta Obst Gynec Scand 36:22, 1957. 4. CHANG, M. C. Development and fate of transferred rabbit ova or blastocysts in relation to the ovulation time of recipients. ] Exp Zool 114:197, 1950. 5. CHANG, M. C., and HARPER, M. J. K. Effects of Ethinyl-estradiol on egg transport and development in the rabbit. Endocrinology 78:680, 1966. 6. DAviD, A. Unpublished data. 1967. 7. DAviD, A., and CzERNOBILSKY, B. A comparative histologic study of the uterotubal junction in the rabbit, rhesus monkey, and human. Amer ] Obstet Gynec 101:411, 1968. 8. EDGAR, D. G., and AsDELL, S. A. The valve-like action of the utero-tubal junction of the ewe. ] Endocr 21:315, 1960. 9. GREENWALD, G. S. A study of the transport of ova through the rabbit oviduct. Fertil Steril12:80, 1961. 10. GREENWALD, G. S. Interruption of pregnancy in the rat by a uterine suture. ] Reprod Fertil 9:9, 1965. J 1. GuPTA, D. N., KARKUN, J. N., and KAR, A. B. Biochemical composition of different pC'rtkns of rabbit Fallopian tube. Indian ] Exp Biol 5:124, 1967. 12. HARTMAN, C. G. "Ovulation, Fertilization and the Transport and Viability of Eggs and Spermatozoa." In Sex and Internal Secretions ( ed. 2). Williams & Wilkins, Baltimore, 1939, p. 630. 13. HAvRANEK, F., DYKOVA, H., and TicKY, M. The effect of an intrauterine suture on fertility in the rat. ] Reprod Fertil14: 15, 1967. 14. LEE, F. C. The tubo-uterine junction of various mammals. Johns Hopkins Hasp Bull 42:335, 1928. 15. MASTROIANNI, L., TR. The structure and function of the fallopian tube. Clin Obst Gynec 5:781, 1962. 16. PINcus, G. Observations on the living eggs of the rabbit. Proc Roy Soc London [B] 107:132, 1930.
of a postovulatory functional blocking mechanism at the uterotubal junction ( UTJ) keeping newly fertilized ova in the oviducts from 72 to £6 hr., is well recognized in many mammals. 1 • 2 • 9 • 16 The physiologic significance of this retention which follows speedy transit of ova through the ampulla remains unknown. Nonetheless, for some mammals, including the rabbit, no anatomic or histologic evidence of such a functional block has been demonstrated. 7 • 9 • 14 The purpose of this investigation, then, was to determine whether resection of the UTJ alters this retention process. Using a microsurgical technic described below, the UTJ was excised, and the effect on ovum transport was observed. The UTJ in this study was defined as the segment between isthmus and uterine horn, which encompassed an area from about 1.5 em. of the proximal end of the isthmus and included the thickened wall of the uterine horn to which the isthmus is connected (this thickness is minimal). • . Our observations were directed to localizatio~ of the ova, to assess the contribution of the UTJ and to the delaying mechanism of ovum transport.
THE EXISTENCE
MATERIAL AND METHODS
Twenty-five mature, New Zealand, White rabbit does (weighing between 3500 and 4500 gm. ) were used. The does were anesthetized with pentobarbital sodium, given intravenously. A unilateral resection of the UTJ was performed in each animal. An excision was made comprising 0.25-0.5 From the Division of Reproductive Biology, Department of Obstetrics and Gynecology, University of Pennsylvania, School of Medicine, Philadelphia, Pa. The authors are greatly indebted to the technical assistance of Mrs. Eve Kelly, Mrs. Anne Hoffman, and Mr. Jim Butler. *Ford Foundation Research Fellow. Permanent address: Tel-Hashomer Hospital, Tel-Aviv Medical School, Israel.
250
VoL. 20, No.2,
1969
UTEROTUBAL JuNcTION REMOVAL
251
em. of uterus and 1.0-1.5 em. of the proximal end of the isthmus. Dissection was performed using a Zeiss operating microscope, with Barraquer modification.* The microscope was mounted on an Operation I floorstand with rotating axes coaxial with the optical axis. Magnification of lOX to 40X was used. Hemostasis was maintained and anastomosis of the oviductal isthmus to the uterine horn was performed, using delicate microsurgical instruments. t Nylon ( 8-0) and silk ( 6-0) suture material mounted on atraumatic neediest was used. The anastomosis of the remaining isthmus to the uterine horn was performed with the aid of a polyethylene tubule splint ( P.E. 10§). One end of the tubule was introduced into the freshly opened isthmus and gently directed through the oviduct and out through the fimbriated end. The other end of the tubule was passed into the uterine cavity to the level of the cervix. Because of the disproportionate isthmic and uterine horn diameters, the opening of the proximal end of the isthmus was bivalved (transverse, fish-mouth-like opening) . Four individual sutures were passed at the four cardinal points traversing the wall of the horn going through the isthmic wall and returning in the opposite direction ( 2.5 mm. from the initial point of entry of the suture). This results in an eversion of the edges of the walls of the isthmus and horn as the suture is tied. The sutures were placed under the serosa, through the myometrium and above the endometrium of the uterine horn, and through the muscular layer and endosalpinx of the isthmus, producing a layer-to-layer anastomosis. Meticulous peritonealization was carried out to obviate adhesions. The end of the polyethylene tubule emanating from the fimbria} ostium was brought through the abdominal wall and anchored subcutaneously to the rectus fascia. A dose of 150,000 I.U. of benzathine long-acting penicillin G suspension ( Bicillinl\) was routinely given I.M. after the operation. Rabbits were then caged individually and fed Purina Rabbit Chow and water ad libitum. The opposite oviduct and uterine horn served as a control. After 15 days, the rabbits were explored under general anesthesia, and the polyethylene tubule removed. The abdominal cavity and the region of the anastomosis were inspected. Animals with anatomic pelvic organ distortion were discarded, except those with minimal adhesions and visibly unconstrained oviducts. The retained rabbits were then isolated for 21 days in individual cages, to insure an estrous state (proven by the acceptance of the male). Each doe was then bred twice to fertile bucks, and sacrificed 9-10 days later. At that time, the number of corpora *Manufactured by Carl Zeiss, West Germany. tWeck and Co., N. Y. +Davis & Geck, Danbury, Conn. §Clay-Adams, Inc., New York. IIWyeth Laboratories, Philadelphia, Pa.
252
DAVID ET AL.
FERTILITY & STERILITY
Fig. 1. After resection of UTJ and meticulous hemostasis, polyethylene tubule is inserted through lumen into oviduct.
lutea on both the control and operated sides was recorded, as well as registering the number of blastocysts implanted in each respective horn. These were correlated with the site of implantation and the appearance of the implanted blastocysts. Figures 1-5 depict the various steps of the procedure described above. RESULTS Of 25 rabbits, 2 died 1-3 days after the anastomosis. Two others refused the male although isolated twice for a period of 21 days. In these 2 rabbits, Japarotomy disclosed a paucity of follicles in either ovary; in none were corpora lutea or adhesions found, and the anastomosis was patent. Patency was assessed by instilling fluid through the oviduct into the uterus. Ten additional rabbits failed to have pregnancies in either side despite many corpora lutea present in their ovaries. In these 10 animals, many adhesions had formed immobilizing their oviducts. Dissection of these adhesions around the oviducts disclosed that the fallopian tubes were not distended with accumulated fluid. Moreover, the anastomosed area was patent. Eleven rabbits were pregnant on both sides (Table 1). The condition of 8 of these animals was good. In 2 there were fine adhesions between omentum and bladder and between intestines. However, in all
Fig. 2 (top). Other end of the polyethylene tubule is drawn through uterine cavity. Suture is placed through subperitoneal structure through muscular layer but avoiding endometrium. Fig. 3 (bottom). Fine suture is seen in place bridging muscular layer of oviduct to uterus. Four similar sutures placed equidistant from each other are used.
254
DAVID ET AL,
FERTILITY
&
STERILITY
instances the oviducts and uterine horns were free and mobile. One of the animals had a marked subcutaneous infection; however, no significant adhesions were found in the abdominal cavity. Since bleeding occurred during the handling of the periadnexal structures of the control side in
Fig. 4 (top). Separate approximation with peritonealization is accomplished to achieve anastomosis. Fig. 5 (bottom). Five implantation sites located in left horn (nonoperated) and two implantation sites in right horn ( UTJ excised and anastomosis achieved). Animal sacrificed for evaluation and photography.
Rabbit 1, and sutures to control the bleeding impaired the fimbriae and ovarian vascularity, no comparative results are available for this animal. A good correlation between the number of corpora lutea and the number of implantations of the control side was found: a total of 52 corpora lutea with 50 implantations or 96% implanted blastocysts. These implants were normally developed. On the operated side, the ovaries displayed a total of 63 corpora lutea with only a total of 26 blastocysts implanted. Thus, only 41% of the ova on the operated side were capable of implantation. All of the blastocysts which did implant were normal in size and appearance.
VoL.20,No.2,1969
TABLE
1. Reproductive Data after Removal of the Uterotubal Junction Operated side
Rabbit
1 2 3 4 5 6 7 8 9 10 11 ToTAL
255
UTEROTUBAL }UNCTION REMOVAL
Condition 6 wk. after anastomosis
Good Good Good Good Adhesions Good Infection under skin Adhesions Good Good Good
Corpora lutea
Implantat ions
Control
.~ide
·-----Corpora lutea
Tmplantat ions ~
7 8 3 6 3 7 1 5 O* 4 2 5 O* 5 3 5 2 6 2 5 3 7 26 63 (41% of the ova implanted)
6 5 5 3 .1) 5 8 8 4 4 6 6 3 3 5 5 50 52 (96% of the ova implanted) 6 .5 5 5
*At time of dissection, no evidence of obstruction was noted at site of anastomosis.
The sites of implantation were at variable distance from the area of anastomosis. DISCUSSION
Following ovulation, rabbit ova pass rapidly through the ampulla to the ampullary-isthmic region, where fertilization is believed to occur. 9 • 11 The newly fertilized ova then slowly descend toward the uterine homs. The time spent in the different segments of the oviduct is variable,9 but the 3-4 day total appears to be constant. It is felt that the delay in transit of the fertilized ova at the tubal level allows time for maturation in preparation for implantation. 4 Such alterations in timing may jeopardize the future development of the early conceptuses by impairing their ability to implant. In the present experiments, the results indicate that when the UTJ is excised, the ova implant in a lower than normal proportion. This alteration may represent a more rapid ovum transport through the newly anastomosed oviduct since the physiologic blocking has been removed thus resulting in immaturity and rejection of most of the ova. Faulty implantation should probably not be ascribed to the microsurgical technic itseH, since the sutures did not pass through the endometrium into the uterine cavity and impinged only through the muscular thickness of the walls. Havranek et al., using rats, showed that when sutures are placed in such a manner,
256
DAVID ET AL.
FERTILITY
& STERILITY
normal implantations were found. Moreover, these authors show that even when the threads pass through the lumen they do not always prevent implantation, as stated by Greenwald. 10 Black and Asdell demonstrated the existence of a physiologic block at the uterine end of the rabbit oviduct which prevents the entry of ova into the uterus. A valve-like action was described. This block was also described in the ewe 8 and seems to be under hormonal control, being affected by both estrogen and progesterone levels. When estrogen secretion temporarily drops after ovulation, progesterone diminishes oviductal contractions; resistance, which drops at the UTJ, as defined in this study, is under hormonal control. 1 • 2 • 12 The present experiments carried out in vivo support the findings of Black and AsdelP· 2 Moreover, ciliary activity, which increases from ovulation time, 3 and muscular contractions15 were no longer opposed in the normal manner. A 41% ovum implantation on the operated side indicates that the fimbria! pick-up mechanism was operating. Flushings of such operated oviducts immediately after ovulation time recovered a normal complement of ova. 6 One may conclude therefore, that the decreased number of implantations on the operated side stems either from the interference with the transport of the ova, or from impairment of implantation, or from both. The alteration in transport would appear more likely since fertilized ova reaching the uterine cavity prematurely will degenerate. 5 No implanted degenerating blastocysts, nor scars indicative of early implantations which later degenerated, were observed. The evidence presented above supports the need for UTJ control of thP nassage of gametes through the oviducts of rabbits. The Peed for such deveJonment is inferred by the more uniform degree of implantation sites when the UTJ is present. SUMMARY The effect of the removal of the uterotubal junction on implantation was observed in New Zealand rabbit does. In each animal studied. one UTT was removed, and an anastomosis of tl1e remaining oviduct to the uterinP horn was performed by a microsurgical procedure. The contralateral UTJ wa'i Jeft intact thereby providing a control. Twenty-six of 63 ova ( 41%) implanted normally on the operated sides, while 50 of 52 ova ( 96%) implanted normally on the control sides. These observations indicate that sperm migration, fertilization, and ovum transport can occur in the absence of the UTJ. However, the discrepancy between operated and control sides is probably best explained as a failure
VoL. 20, No.2, 1969
UTEROTUBAL JuNCTION REMOVAL
257
of the oviduct, in the absence of the UTJ, to retain ova until they are ready to implant. C.-R. G. Suite 106 Dulles Hospital of University of Pennsylvania Philadelphia, Pa. 19104
REFERENCES 1. BLACK, D. L., and AsDELL, S. A. Transport through the rabbit oviduct. Amer ] Physiol192:63, 1958. 2. BLACK, D. L., and AsDELL, S. A. Mechanism controlling entry of ova into rabbit uterus. Amer] Physiol197:1215, 1959. 3. BoRRELL, U., NILSSON, 0., and WESTMAN, A. Ciliary activity in the rabbit fall"oian tube during estrus and after copulation. Acta Obst Gynec Scand 36:22, 1957. 4. CHANG, M. C. Development and fate of transferred rabbit ova or blastocysts in relation to the ovulation time of recipients. ] Exp Zool 114:197, 1950. 5. CHANG, M. C., and HARPER, M. J. K. Effects of Ethinyl-estradiol on egg transport and development in the rabbit. Endocrinology 78:680, 1966. 6. DAviD, A. Unpublished data. 1967. 7. DAviD, A., and CzERNOBILSKY, B. A comparative histologic study of the uterotubal junction in the rabbit, rhesus monkey, and human. Amer ] Obstet Gynec 101:411, 1968. 8. EDGAR, D. G., and AsDELL, S. A. The valve-like action of the utero-tubal junction of the ewe. ] Endocr 21:315, 1960. 9. GREENWALD, G. S. A study of the transport of ova through the rabbit oviduct. Fertil Steril12:80, 1961. 10. GREENWALD, G. S. Interruption of pregnancy in the rat by a uterine suture. ] Reprod Fertil 9:9, 1965. J 1. GuPTA, D. N., KARKUN, J. N., and KAR, A. B. Biochemical composition of different pC'rtkns of rabbit Fallopian tube. Indian ] Exp Biol 5:124, 1967. 12. HARTMAN, C. G. "Ovulation, Fertilization and the Transport and Viability of Eggs and Spermatozoa." In Sex and Internal Secretions ( ed. 2). Williams & Wilkins, Baltimore, 1939, p. 630. 13. HAvRANEK, F., DYKOVA, H., and TicKY, M. The effect of an intrauterine suture on fertility in the rat. ] Reprod Fertil14: 15, 1967. 14. LEE, F. C. The tubo-uterine junction of various mammals. Johns Hopkins Hasp Bull 42:335, 1928. 15. MASTROIANNI, L., TR. The structure and function of the fallopian tube. Clin Obst Gynec 5:781, 1962. 16. PINcus, G. Observations on the living eggs of the rabbit. Proc Roy Soc London [B] 107:132, 1930.