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Cineradiography of uterine motility in the cycling ewe
Animal Reproduction Science, 1 (1978) 155--160 O Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
155
C I N E R A D I O G R A P H Y O F U T E R I N E M O T I L I T Y I N T H E C Y C L I N G EWE
R.E. FISCHEL*, A. TADMOR**, A.R. LEHRER*** and H. SCHINDLER*** *Roentgen Department, Kaplan Hospital (affiliated with the Hebrew University-Hadassah Medical School, Jerusalem), Rehovot (Israel) **Kimron Veterinary Institute, Bet Dagan (Israel) ***Institute of Animal Science, ARO, The Volcani Center, Bet Dagan (Israel) Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1976 Series, No. 275-E. (Received 7 June 1977; revised 31 May 1978)
ABSTRACT Fischel, R.E., Tadmor, A., Lehrer, A.R. and Sehindler, H., 1978. Cineradiography of uterine motility in the cycling ewe. Anirn. Reprod. Sci., 1: 155--160. Five cinehysterography sessions during oestrus and three during metoestrus were performed in four ewes for the assessment of uterine motility. Radio-opaque material was deposited in the uterine body through a permanent catheter in the cervix, and the changes in the shape and size of the uterine lumen, as well as the conveyance of radio-opaque material therein were traced. The changes in the lumen consisted of temporary widenings and constrictions resulting in segmentary divisions of the lumen. The radio-opaque material, which never passed the cervix or uterotubal junctions, was repeatedly conveyed to and fro between the uterine horns. One two-way transport was completed within about 40 s. These findings show the relation in vivo between uterine motility and the transport of particles in the uterine lumen, and the blocking activity of the cervix and the uterotubal junctions.
INTRODUCTION In p r e v i o u s studies, t h e m o t i l i t y o f the o v i r e u t e r u s was assessed b y visual scoring o f its c o n t r a c t i o n s (Brinsfield a n d H a w k , 1 9 6 9 ; C r o k e r a n d Shelton, 1 9 7 3 ; L e h r e r a n d Schindler, 1 9 7 4 ) , b y r e c o r d i n g t h e electrical a c t i v i t y o f t h e m y o m e t r i u m ( N a a k t g e b o r e n et al., 1 9 7 3 ; R o u s s e a u a n d P r u d ~ o m m e , 1 9 7 4 ) a n d b y m e a s u r i n g pressure changes inside t h e u t e r i n e wall ( S p i l m a n et al., 1 9 7 2 ; L e h r e r et al., 1974). In o r d e r t o o b t a i n a d d i t i o n a l k n o w l e d g e o f t h e c o m p o n e n t s c o m p r i s i n g u t e r i n e m o t i l i t y in c o n s c i o u s ewes, we n o w s t u d i e d its m a n i f e s t a t i o n s in the u t e r i n e l u m e n b y d e p o s i t i n g t h e r e r a d i o - o p a q u e m a t e r i a l a n d t r a c i n g t h e changes in its s h a p e a n d l o c a t i o n , using c i n e r a d i o g r a p h y .
156
MATERIALS AND METHODS Parous, cycling, nonlactating ewes served for the experiments. After preliminary experiments had shown that radio-opaque material deposited in the external cervical os did n o t traverse the cervix, permanent cannulation of the cervix was carried out by the following modification of the surgical approach of Wales and Restall (1971). At one end of a silicone rubber tube (medical grade, 1.0 mm i.d., 1.5 mm o.d.) a length of about 1 cm was thickened with medical adhesive (Silastic, silicone, type A, D o w Coming), thus forming a cylindrical bulb of a b o u t 5 mm diameter. After anaesthesia, achieved with an i.m. injection of R o m p u n (Bayer, Leverkusen, Federal Republic of Germany) according to b o d y weight, and laparotomy, a surgical thread was pulled with a flexible biopsy specimen forceps from the vaginal cavity to a small incision in the uterine wall, tied to the thin end of the silicone rubber tube, and drawn back in the caudal direction until the tube emerged outside the vulva and the thickened end of it was blocked inside the uterus by the internal os. No suturing was needed for long-term fixation (up to 9 months) of the cannula in the desired position. At least 2 weeks elapsed -- during which time the ewes had fully recovered from the operation -- between cervical cannulation and hysterographies. The hysterographies were performed when the ewes were in oestrus, as manifested by standing to mounting of a teaser ram, or within 48 h after its end (metoestrus). These stages of the oestrous cycle were chosen because they are characterized by increased myometrial activity and uterine contractions (Spilman et al., 1972; Croker and Shelton, 1973; Naaktgeboren et al., 1973; Rousseau and Prud'homme, 1974; Lehrer and Schindler, 1974; Lehrer et al., 1974). During the hysterography the fully conscious animals were lying on their backs in a laparotomy cradle (Hulet and Foote, 1968) which was fitted to the X-ray table. Radio-opaque material ("Diaginol" Viscous, May and Baker Ltd., Dagenham, Great Britain; or "Lipiodole Ultra-fluide", Laboratoires Andre Guerbet, Aulnay.Sous-Bois, France) at a temperature of about 38 ° C was slowly injected through the cervical cannula until it reached the uterine b o d y as seen under X-ray control on a TV screen. Ten to 15 ml of contrast medium ensured a clear outline of the uterine lumen. The amount of the contrast medium had no visible influence on the pattern of the uterine motility. Changes which occurred in the shape and location of the radio-opaque material after the end of its injection were traced by cineradiography with a frequency of 16 frames/s. RESULTS AND DISCUSSION A total of eight cinehysterography sessions, lasting at least 2 h each, were performed with four ewes, two of which served in more than one session. In order to have an extended follow-up of the radio-opaque material in the
157
Fig. 1. Uterine motility of an oestrous ewe, as revealed by cineradiography. The consecutive pictures were picked out 6--8 s apart. Note the changes in shape and size of the uterine lumen and the rapid conveyance of radio-opaque material therein. Ca = catheter in the cervix; L H = left uterine horn; R H = right uterine horn; Bif -- bifurcation; Car -- uterine caruncles; a = complete luminal closure; b = luminal constriction; c = luminal widening. (1--3) Consecutive constrictions and emptying of the left uterine horn. (4) Dilated filledright horn and the almost e m p t y left horn. (5) Constricting and emptying right horn and the dilation and fillingof the left horn are seen. (6) Left h o r n is dilated a n d filled.
158
uterus, several cinehysterographies were obtained at intervals during each session, starting immediately after the injection. Fig.1 shows a sequence of single frames chosen from different spots -- 6 - 8 s apart -- along a continuous representative cinehysterogram. It can be seen that uterine motility was manifested by changes in the shape and size of the lumen as well as by conveyance of radio-opaque material inside the uterine body and from one horn to the other. Transport of the material from the left uterine horn to the right one and back to the left horn was completed within about 40 s. The changes in the lumen consisted of temporary constrictions and widenings which occurred repeatedly at different loci, or areas along the lumen of one or both horns. These internal changes are probably related to the constrictions, reported in other studies (Brinsfield and Hawk, 1969; Lehrer and Schindler, 1974), which move to and fro along the uterine external surface. The constrictions and widenings resulted in a segmentary division of the lumen which was especially pronounced at times when the constrictions turned into complete luminal closures. The manifestations of uterine motility described above did not change with time during a session nor differ between individuals. The capability of the non-human uterus to convey radio-opaque materials in a one-way cranial direction was also observed in the heifer by X-ray after autopsy (Rowson, 1955) and by cinehysterography in the rabbit in vivo (Krehbiel and Carstens, 1939). However, in addition to those findings, the ovine uterus in the present study conveyed radio-opaque material to and fro, in both a cranial and caudal direction. Dead spermatozoa which were deposited in the ovine uterus near the uterocervical junction (Lightfoot and Restall, 1971) or near the uterotubal junction (Mattner, 1963), were also found to migrate in both a cranial and caudal direction. These authors concluded that uterine contractions are the main transporting force. This conclusion was indirectly confirmed when sperm migration was found to be reduced after inhibition of uterine contractions with Halothane anaesthesia (Lightfoot and Restall, 1971). Our results also support this conclusion, since the uterine contractions were directly observed to convey radio-opaque material which, according to Thibault (1973), can be considered to respond similarly to dead spermatozoa. However, the involvement of other forces -- such as mere diffusion or conveyance by uterine fluids -cannot be excluded, since no knowledge exists whether or not immotile spermatozoa migrate in the lumen of an immotile uterus. According to Mattner's (1963) experiments, the duration of transuterine migration of dead spermatozoa from one uterotubal junction to the other is up to 4 h -- the time lapse between sperm deposition and autopsy of the ewes. The present study showed that the migration can be completed within seconds. The present results also suggest that a spermatozoon can be repeatedly conveyed to and fro between the uterine horns, as occurred with the radio-opaque material.
159
In our preliminary experiments, radio-opaque material deposited in the vagina of oestrous ewes was never seen to enter the cervix and uterus. This finding conforms with Roentgen studies in the rabbit (Noyes et al., 1958; Edgar and Asdell, 1960b; Akester and Inkster, 1961), except in one in which the vulva was artificially stimulated with the finger following the deposition of the radio-opaque material in the vagina (Krehbiel and Carstens, 1939). When deposited in the uterus, the radio-opaque material was never seen by us to enter the Fallopian tubes, which agrees with findings in the rabbit in vivo (Krehbiel and Carstens, 1939) but not with those in the heifer after autopsy (Rowson, 1955). The retention by the external cervical os and the uterotubal junctions of radio-opaque material in the vagina or in the uterus, respectively, provides a direct visual proof of the blocking exerted by these sites on free passage of fluids, inert particles and perhaps even living spermatozoa along the female genital tract (Hafez and Black, 1969; Bedford, 1972; Thibault, 1973). According to Edgar and Asdell (1960a), tubal fluids do not traverse the uterotubal junction into the uterus of oestrous or metoestrous ewes. The blocking was attributed by these authors to an oestrogen-induced oedema and flexure of the wall of the uterotubal junction. It is, perhaps, this mechanism which blocks the passage of radio-opaque material in the opposite direction, i.e., from the uterus to the Fallopian tubes, as was found in the present study. The existence of sperm transport, in spite of the barrier, points to the importance of sperm motility for passage through the cervix and uterotubal junctions in the ewe (Mattner, 1963; Mattner and Braden, 1969; Lightfoot and Restall, 1971), although immotile spermatozoa were found to traverse these sites in some ewes (Mattner, 1963; Lightfoot and Restall, 1971), even after inhibition of the contractions of the genital tract (Lightfoot and Restall, 1971). ACKNOWLEDGEMENTS
This investigation was supported by a grant from the United States Department of Agriculture under P.L. 480. The authors gratefully acknowledge the technical assistance of Messrs Y. Dimmerman, E. Heifer, M. Meidler and the late Z. Odbak; and the operation of the Roentgen equipment by Mr D. Levidor.
REFERENCES
Akester, A.R. and Inkster, I.J.,1961. Cineradiographic studies of the genital tract of the rabbit. J. Reprod. Fertil., 2: 507--508. Bedford, J.M., 1972. Sperm transport, capacitation and fertilization. In: H. Balin and S. Glasser (Editors), Reproductive Biology. Excerpta Medica, Amsterdam, pp. 338--392. Brinsfield, T.H. and Hawk, H.W., 1969. Modification of the direction of uterine contractions by intra-uterine devices in the ewe. J. Reprod. Fertil., 18: 535--537. Croker, K.P. and Shelton, J.N., 1973. Influence of stage of cycle, progestagen treatment and dose of oestrogen on uterine motility in the ewe. J. Reprod. Fertil., 32: 521--524.
160
Edgar, D.G. and Asdell, S.A., 1960a. The valve-like action of the uterotubal junction of the ewe. J. Endocrinol., 21: 315--320. Edgar, D.G. and Asdell, S.A., 1960b. Spermatozoa in the female genital tract. J. Endocrinol., 21: 321--326. Hafez, E.S.E. and Black, D.L., 1969. The mammalian uterotubal junction. In: E.S.E. Hafez and R.J. Blandau (Editors), The Mammalian Oviduct. The University of Chicago Press, Chicago, Ill., pp. 85--126. Hulet, C.V. and Foote, W.C., 1968. Rapid technique for observing the reproductive tract of living ewes. J. Anim. Sci., 27: 142--145. Krehbiel, R.H. and Carstens, H.P., 1939. Roentgen studies of the mechanism involved in sperm transportation in the female rabbit. Am. J. Physiol., 125: 571--577. Lehrer, A.R. and Schindler, H., 1974. Uterine motility of the ewe during the estrous cycle. J. Anita. Sci., 38: 86--88. Lehrer, A.R., Fischler, H., Schindler, H. and Brown, M., 1974. Telemetry of uterine motility in the cycling ewe. J. Anim. Sci., 38: 89--94. Lightfoot, R.J. and Restall, B.J., 1971. Effects of site of insemination, sperm motility and genital tract contractions on transport of spermatozoa in the ewe. J. Reprod. Fertil., 26" 1--13. Mattner, P.E., 1963. Spermatozoa in the genital tract of the ewe. III. The role of spermatozoan motility and of uterine contractions in transport of spermatozoa. Aust. J. Biol. Sci., 16: 877--884. Mattner, P.E. and Braden, A.W.H., 1969. Comparison of the distribution of motile and immotile spermatozoa in the ovine cervix. Aust. J. Biol. Sci., 22: 1069--1070. Naaktgeboren, C., Van Der Weyden, G.C., Klopper, P.J., Kroon, C.H., Schoof A.G. and Taverne, M.A.M., 1973. Electrophysiological observations of uterine motility during the oestrous cycle in sheep. J. Reprod. Fertil., 35: 511--518. Noyes, R.W., Adams, C.E. and Walton, A., 1958. Transport of spermatozoa into the uterus of the rabbit. Fertil. Steril., 9: 288--299. Rousseau, J.P. and Prud'homme, M.J., 1974. Etude electromyographique de la motricit~ de l'uterus chez la brebis. Action des hormones. Ann. Biol. Anita. Biochim. Biophys., 14: 67--85. Rowson, L.E.A., 1955. The movement of radio-opaque material in the bovine uterine tract. Br. Vet. J., 111: 334--342. Spilman, C.H., Howe, G.R. and Black, D.L., 1972. Alteration of uterine motility in the ewe by an intrauterine device. J. Reprod. Fertil., 28: 269--272. Thibault, C., 1973. Sperm transport and storage in vertebrates. J. Reprod. Fertil., Suppl., 18: 39--53. Wales, R.G. and Restall, B.J., 1971. The uterus of the ewe. I. Secretion from the cannulated uterus. Aust. J. Biol. Sci., 24: 1009--1020.
155
C I N E R A D I O G R A P H Y O F U T E R I N E M O T I L I T Y I N T H E C Y C L I N G EWE
R.E. FISCHEL*, A. TADMOR**, A.R. LEHRER*** and H. SCHINDLER*** *Roentgen Department, Kaplan Hospital (affiliated with the Hebrew University-Hadassah Medical School, Jerusalem), Rehovot (Israel) **Kimron Veterinary Institute, Bet Dagan (Israel) ***Institute of Animal Science, ARO, The Volcani Center, Bet Dagan (Israel) Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1976 Series, No. 275-E. (Received 7 June 1977; revised 31 May 1978)
ABSTRACT Fischel, R.E., Tadmor, A., Lehrer, A.R. and Sehindler, H., 1978. Cineradiography of uterine motility in the cycling ewe. Anirn. Reprod. Sci., 1: 155--160. Five cinehysterography sessions during oestrus and three during metoestrus were performed in four ewes for the assessment of uterine motility. Radio-opaque material was deposited in the uterine body through a permanent catheter in the cervix, and the changes in the shape and size of the uterine lumen, as well as the conveyance of radio-opaque material therein were traced. The changes in the lumen consisted of temporary widenings and constrictions resulting in segmentary divisions of the lumen. The radio-opaque material, which never passed the cervix or uterotubal junctions, was repeatedly conveyed to and fro between the uterine horns. One two-way transport was completed within about 40 s. These findings show the relation in vivo between uterine motility and the transport of particles in the uterine lumen, and the blocking activity of the cervix and the uterotubal junctions.
INTRODUCTION In p r e v i o u s studies, t h e m o t i l i t y o f the o v i r e u t e r u s was assessed b y visual scoring o f its c o n t r a c t i o n s (Brinsfield a n d H a w k , 1 9 6 9 ; C r o k e r a n d Shelton, 1 9 7 3 ; L e h r e r a n d Schindler, 1 9 7 4 ) , b y r e c o r d i n g t h e electrical a c t i v i t y o f t h e m y o m e t r i u m ( N a a k t g e b o r e n et al., 1 9 7 3 ; R o u s s e a u a n d P r u d ~ o m m e , 1 9 7 4 ) a n d b y m e a s u r i n g pressure changes inside t h e u t e r i n e wall ( S p i l m a n et al., 1 9 7 2 ; L e h r e r et al., 1974). In o r d e r t o o b t a i n a d d i t i o n a l k n o w l e d g e o f t h e c o m p o n e n t s c o m p r i s i n g u t e r i n e m o t i l i t y in c o n s c i o u s ewes, we n o w s t u d i e d its m a n i f e s t a t i o n s in the u t e r i n e l u m e n b y d e p o s i t i n g t h e r e r a d i o - o p a q u e m a t e r i a l a n d t r a c i n g t h e changes in its s h a p e a n d l o c a t i o n , using c i n e r a d i o g r a p h y .
156
MATERIALS AND METHODS Parous, cycling, nonlactating ewes served for the experiments. After preliminary experiments had shown that radio-opaque material deposited in the external cervical os did n o t traverse the cervix, permanent cannulation of the cervix was carried out by the following modification of the surgical approach of Wales and Restall (1971). At one end of a silicone rubber tube (medical grade, 1.0 mm i.d., 1.5 mm o.d.) a length of about 1 cm was thickened with medical adhesive (Silastic, silicone, type A, D o w Coming), thus forming a cylindrical bulb of a b o u t 5 mm diameter. After anaesthesia, achieved with an i.m. injection of R o m p u n (Bayer, Leverkusen, Federal Republic of Germany) according to b o d y weight, and laparotomy, a surgical thread was pulled with a flexible biopsy specimen forceps from the vaginal cavity to a small incision in the uterine wall, tied to the thin end of the silicone rubber tube, and drawn back in the caudal direction until the tube emerged outside the vulva and the thickened end of it was blocked inside the uterus by the internal os. No suturing was needed for long-term fixation (up to 9 months) of the cannula in the desired position. At least 2 weeks elapsed -- during which time the ewes had fully recovered from the operation -- between cervical cannulation and hysterographies. The hysterographies were performed when the ewes were in oestrus, as manifested by standing to mounting of a teaser ram, or within 48 h after its end (metoestrus). These stages of the oestrous cycle were chosen because they are characterized by increased myometrial activity and uterine contractions (Spilman et al., 1972; Croker and Shelton, 1973; Naaktgeboren et al., 1973; Rousseau and Prud'homme, 1974; Lehrer and Schindler, 1974; Lehrer et al., 1974). During the hysterography the fully conscious animals were lying on their backs in a laparotomy cradle (Hulet and Foote, 1968) which was fitted to the X-ray table. Radio-opaque material ("Diaginol" Viscous, May and Baker Ltd., Dagenham, Great Britain; or "Lipiodole Ultra-fluide", Laboratoires Andre Guerbet, Aulnay.Sous-Bois, France) at a temperature of about 38 ° C was slowly injected through the cervical cannula until it reached the uterine b o d y as seen under X-ray control on a TV screen. Ten to 15 ml of contrast medium ensured a clear outline of the uterine lumen. The amount of the contrast medium had no visible influence on the pattern of the uterine motility. Changes which occurred in the shape and location of the radio-opaque material after the end of its injection were traced by cineradiography with a frequency of 16 frames/s. RESULTS AND DISCUSSION A total of eight cinehysterography sessions, lasting at least 2 h each, were performed with four ewes, two of which served in more than one session. In order to have an extended follow-up of the radio-opaque material in the
157
Fig. 1. Uterine motility of an oestrous ewe, as revealed by cineradiography. The consecutive pictures were picked out 6--8 s apart. Note the changes in shape and size of the uterine lumen and the rapid conveyance of radio-opaque material therein. Ca = catheter in the cervix; L H = left uterine horn; R H = right uterine horn; Bif -- bifurcation; Car -- uterine caruncles; a = complete luminal closure; b = luminal constriction; c = luminal widening. (1--3) Consecutive constrictions and emptying of the left uterine horn. (4) Dilated filledright horn and the almost e m p t y left horn. (5) Constricting and emptying right horn and the dilation and fillingof the left horn are seen. (6) Left h o r n is dilated a n d filled.
158
uterus, several cinehysterographies were obtained at intervals during each session, starting immediately after the injection. Fig.1 shows a sequence of single frames chosen from different spots -- 6 - 8 s apart -- along a continuous representative cinehysterogram. It can be seen that uterine motility was manifested by changes in the shape and size of the lumen as well as by conveyance of radio-opaque material inside the uterine body and from one horn to the other. Transport of the material from the left uterine horn to the right one and back to the left horn was completed within about 40 s. The changes in the lumen consisted of temporary constrictions and widenings which occurred repeatedly at different loci, or areas along the lumen of one or both horns. These internal changes are probably related to the constrictions, reported in other studies (Brinsfield and Hawk, 1969; Lehrer and Schindler, 1974), which move to and fro along the uterine external surface. The constrictions and widenings resulted in a segmentary division of the lumen which was especially pronounced at times when the constrictions turned into complete luminal closures. The manifestations of uterine motility described above did not change with time during a session nor differ between individuals. The capability of the non-human uterus to convey radio-opaque materials in a one-way cranial direction was also observed in the heifer by X-ray after autopsy (Rowson, 1955) and by cinehysterography in the rabbit in vivo (Krehbiel and Carstens, 1939). However, in addition to those findings, the ovine uterus in the present study conveyed radio-opaque material to and fro, in both a cranial and caudal direction. Dead spermatozoa which were deposited in the ovine uterus near the uterocervical junction (Lightfoot and Restall, 1971) or near the uterotubal junction (Mattner, 1963), were also found to migrate in both a cranial and caudal direction. These authors concluded that uterine contractions are the main transporting force. This conclusion was indirectly confirmed when sperm migration was found to be reduced after inhibition of uterine contractions with Halothane anaesthesia (Lightfoot and Restall, 1971). Our results also support this conclusion, since the uterine contractions were directly observed to convey radio-opaque material which, according to Thibault (1973), can be considered to respond similarly to dead spermatozoa. However, the involvement of other forces -- such as mere diffusion or conveyance by uterine fluids -cannot be excluded, since no knowledge exists whether or not immotile spermatozoa migrate in the lumen of an immotile uterus. According to Mattner's (1963) experiments, the duration of transuterine migration of dead spermatozoa from one uterotubal junction to the other is up to 4 h -- the time lapse between sperm deposition and autopsy of the ewes. The present study showed that the migration can be completed within seconds. The present results also suggest that a spermatozoon can be repeatedly conveyed to and fro between the uterine horns, as occurred with the radio-opaque material.
159
In our preliminary experiments, radio-opaque material deposited in the vagina of oestrous ewes was never seen to enter the cervix and uterus. This finding conforms with Roentgen studies in the rabbit (Noyes et al., 1958; Edgar and Asdell, 1960b; Akester and Inkster, 1961), except in one in which the vulva was artificially stimulated with the finger following the deposition of the radio-opaque material in the vagina (Krehbiel and Carstens, 1939). When deposited in the uterus, the radio-opaque material was never seen by us to enter the Fallopian tubes, which agrees with findings in the rabbit in vivo (Krehbiel and Carstens, 1939) but not with those in the heifer after autopsy (Rowson, 1955). The retention by the external cervical os and the uterotubal junctions of radio-opaque material in the vagina or in the uterus, respectively, provides a direct visual proof of the blocking exerted by these sites on free passage of fluids, inert particles and perhaps even living spermatozoa along the female genital tract (Hafez and Black, 1969; Bedford, 1972; Thibault, 1973). According to Edgar and Asdell (1960a), tubal fluids do not traverse the uterotubal junction into the uterus of oestrous or metoestrous ewes. The blocking was attributed by these authors to an oestrogen-induced oedema and flexure of the wall of the uterotubal junction. It is, perhaps, this mechanism which blocks the passage of radio-opaque material in the opposite direction, i.e., from the uterus to the Fallopian tubes, as was found in the present study. The existence of sperm transport, in spite of the barrier, points to the importance of sperm motility for passage through the cervix and uterotubal junctions in the ewe (Mattner, 1963; Mattner and Braden, 1969; Lightfoot and Restall, 1971), although immotile spermatozoa were found to traverse these sites in some ewes (Mattner, 1963; Lightfoot and Restall, 1971), even after inhibition of the contractions of the genital tract (Lightfoot and Restall, 1971). ACKNOWLEDGEMENTS
This investigation was supported by a grant from the United States Department of Agriculture under P.L. 480. The authors gratefully acknowledge the technical assistance of Messrs Y. Dimmerman, E. Heifer, M. Meidler and the late Z. Odbak; and the operation of the Roentgen equipment by Mr D. Levidor.
REFERENCES
Akester, A.R. and Inkster, I.J.,1961. Cineradiographic studies of the genital tract of the rabbit. J. Reprod. Fertil., 2: 507--508. Bedford, J.M., 1972. Sperm transport, capacitation and fertilization. In: H. Balin and S. Glasser (Editors), Reproductive Biology. Excerpta Medica, Amsterdam, pp. 338--392. Brinsfield, T.H. and Hawk, H.W., 1969. Modification of the direction of uterine contractions by intra-uterine devices in the ewe. J. Reprod. Fertil., 18: 535--537. Croker, K.P. and Shelton, J.N., 1973. Influence of stage of cycle, progestagen treatment and dose of oestrogen on uterine motility in the ewe. J. Reprod. Fertil., 32: 521--524.
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