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Biomedical subjects

K Imakawa

Publications and source records attributed to K Imakawa.

At least 55 records · Page 3Linked to original sources
PubMed1988

Interferon RNA of embryonic origin is expressed transiently during early pregnancy in the ewe.

Ovine trophoblast protein-1 (oTP-1), an interferon of embryonic origin, is produced during the peri-implantation period of early pregnancy. Secretion of oTP-1 is detectable between days 13 and 21, but not beyond. In this study, the levels of oTP-1 mRNA in embryos were analyzed to determine if they reflected the transient nature of oTP-1 production. Total cellular RNA (tcRNA) was isolated from embryos representing day 12 (n = 5), 14 (n = 7), 16 (n = 5), 18 (n = 6), 20 (n = 4), and 22 (n = 5) of pregnancy and spotted on nylon membranes. Complementary RNA was transcribed from a specific oTP-1 cDNA (550 base pairs) template and applied (16-1000 pg) to nylon membranes to develop a standard curve. The fixed RNA samples were then allowed to hybridize with the 32P-labeled oTP-1 cDNA. oTP-1 mRNA was not detectable on day 12, increased to high levels (3.6 +/- 1.6 ng/ug of embryo DNA) on day 14, decreased about 5-fold by day 16, 15-fold by day 18, 170-fold by day 20, and 200-fold by day 22 of pregnancy. At day 14 oTP-1 mRNA comprised 0.060 +/- 0.019% of the tcRNA and was more abundant than actin mRNA. Northern analyses of pooled tcRNA representing each day of pregnancy showed that the oTP-1 probe hybridized to a single class of mRNA (approximately 1.1 kilobases) and confirmed the results obtained with dot blots.

Actins↗
PubMed1987

Endocrine mechanisms of puberty in heifers. Role of hypothalamo-pituitary estradiol receptors in the negative feedback of estradiol on luteinizing hormone secretion.

The hypothesis tested was that the decline in negative feedback of estradiol on secretion of luteinizing hormone (LH) that occurs as puberty approaches in heifers results from a decline in the number of receptors for estradiol in the hypothalamus and/or pituitary. In addition, associated changes in receptors for luteinizing hormone-releasing hormone (LHRH) in the pituitary, ovarian follicle development, and uterine growth were characterized. Fifty prepubertal heifers, 234 to 264 days of age, were used. Six heifers of median body weight were designated controls, and sequential blood samples were collected at 20-min intervals for 24 h every 2 wk from 249 days of age through puberty and analyzed for concentrations of LH. Frequency of LH pulses/24 h was regressed on number of days prepuberty to develop a prediction equation for puberty. Thirty of the remaining 44 heifers were killed at 253, 302, and 351 days of age (n = 10/group), and tissues for described analyses were collected. Three to 5 days before tissue collection, sequential blood samples were obtained from these heifers, as described for control heifers to determine frequency of release of LH. With this information, number of days prepuberty at the time of tissue collection was estimated from the prediction equation developed with data from control heifers. The average age at puberty in control heifers was 366 days. The average age at puberty of heifers that were not killed or included in the control group (n = 14) was 360 days. Receptor and morphological data were related to the estimated onset of puberty. Cytosolic concentration of receptors for estradiol (fmoles receptor/mg cytosolic protein) in the anterior hypothalamus, medial basal hypothalamus, and anterior pituitary declined (p less than 0.05) as puberty approached. No change in concentration of receptors for estradiol was observed in the stalk median eminence or preoptic area. The concentration of receptors for LHRH in the anterior pituitary did not change as puberty approached. Uterine weight increased rapidly during the 50 days preceding puberty. The number of small, medium, or large follicles and the wet, pressed, or dry weight of the ovaries did not change as puberty approached. Follicles with a diameter greater than 12 mm were found only in the 3 heifers estimated to be closest to puberty at the time of tissue collection. The hypothesis that the decline in estradiol feedback on secretion of LH during the prepubertal period in heifers may result from a decline in the concentration of binding sites for estradiol at the hypothalamus and/or pituitary is supported by this study.

Animals↗
PubMed1987

Effects of 17 beta-estradiol and diets varying in energy on secretion of luteinizing hormone in beef heifers.

An experiment was conducted to test the hypothesis that 17 beta-estradiol (E2) would not suppress secretion of luteinizing hormone (LH) in heifers fed a diet limited in energy during the period before the onset of nutritionally induced anestrus. Sixteen of 20 heifers that had been exhibiting normal estrous cycles (20 mo of age, 409 +/- 6 kg body weight) were ovariectomized, and half of them were assigned at random to receive an E2 implant. The ovariectomized heifers were assigned at random to receive diets that contained low (L; 5.8 Mcal X animal-1 X d-1, n = 8) or high levels of energy (H; 20.0 Mcal X animal-1 X d-1, n = 8) for 100 d. The other four heifers remained intact and were fed the L-diet. The intact heifers were utilized to determine the status of reproductive function in animals fed the L-diet. Heifers lost body weight rapidly after initiation of feeding the L-diet. Heifers fed the L-diet then stabilized at a lighter weight until the latter part of the experiment. One of the four intact heifers fed the L-diet became anestrus near the end of the study. Mean concentrations of LH in blood serum increased linearly (P less than .05) in ovariectomized heifers fed the L- and H-diet. Mean concentration of LH in heifers fed the H-diet that were implanted with E2 was similar to ovariectomized heifers fed the H-diet that received no E2. Mean LH in serum of ovariectomized heifers implanted with E2 fed the L-diet was suppressed and remained low throughout the study. Frequency of pulses of LH in ovariectomized heifers fed the L-diet was less (P less than .01) than that in ovariectomized heifers fed the H-diet. Estradiol decreased the number of pulses of LH in heifers fed the L-diet. We conclude that dietary energy restriction in beef heifers has a direct action on the hypothalamo-pituitary axis to lower the number of pulses of LH in the absence of ovarian steroids. However, ovarian E2 appears to suppress further secretion of LH in heifers fed limited levels of dietary energy before the onset of nutritional anestrus occurs, therefore, our working hypothesis is rejected.

Animals↗
PubMed1987

Suckling behavior of calves with dams varying in milk production.

Two experiments were performed to test the hypothesis that suckling behavior of calves with similar growth potential varies depending on cows' level of estimated milk production and stage of lactation. Eleven mature cows, which varied in estimated 205-d milk production (996 to 2354 kg/205 d), nursing heifer calves of similar growth potential were used in Exp. 1. Suckling behavior of calves was observed for two 24-h periods at three stages of lactation (average of 52, 104 and 167 d postpartum). Suckling frequency (suckling bouts/24 h) declined as milk production increased at 52 d of lactation (-.00382 bouts/kg milk) but was unrelated to milk production at later stages. Duration of suckling (minutes/suckling bout) increased with estimated level of milk production at all stages of lactation (means = .001556 min/kg milk). Total time suckling tended to increase as estimated level of milk production decreased at 52 d of lactation, but this component of suckling behavior was unaffected by milk level at later stages. Suckling frequency declined from 8.6 bouts/24 h at 52 d of lactation to 4.5 bouts/24 h at 167 d of lactation when averaged across all cows. Total minutes nursed/24 h declined in a similar manner (64 min/24 h to 44 min/24 h) between 52 and 167 d of lactation. Duration of each suckling bout did not change with stage. In the second experiment the relationship of suckling behavior to estimated milk production was evaluated at four early stages (average of 17, 38, 59 and 80 d postpartum) of lactation using 20 mature cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Influence of dietary-induced weight changes on serum luteinizing hormone, estrogen and progesterone in the bovine female.

The working hypothesis in the present study was that changes in concentrations and secretory patterns of luteinizing hormone (LH), 17 beta estradiol (E2), and progesterone in sexually mature beef heifers fed diets deficient in energy are related to changes in body weight of the animals. Another important component of the study was to determine if concentrations and secretion patterns of the reproductive hormones changed over time as feeding of the experimental diets continued. Twelve Red Angus X Hereford heifers (20 mo of age; 355 +/- 7 kg) were assigned randomly to receive a low- (L, n = 7) or high- (H, n = 5) energy diet for 100 days (Day 0 = day of initiation of dietary treatment). All heifers were exhibiting estrous cycles at regular intervals when the experiment was initiated and continued to exhibit estrous cycles at regular intervals throughout the study. Stage of the estrous cycle was synchronized in all 12 heifers by administration of prostaglandin F2 alpha (PGF2 alpha) on two occasions (Days 45 and 75) during the experiment. Serial blood samples (taken at 12-min intervals for 4 h) were collected at 0, 12, 24, 36, 48, and 60 h after the PGF2 alpha injections (Days 45-47 and 75-77) to determine patterns of LH secretion during the follicular phase of the estrous cycle. In addition, serial blood samples (taken at 20-min intervals for 18 h) to monitor LH secretion during the luteal phase of the estrous cycle, in which the stage of the cycle was standardized between heifers, were obtained (Days 59 and 89).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1986

Influence of season and estradiol on secretion of luteinizing hormone in ovariectomized cows.

The hypotheses that secretion of luteinizing hormone (LH) varies with season and that estradiol may modulate the seasonal fluctuation in secretion of LH in cows were investigated. Seven mature cows were ovariectomized approximately 30 days before initiation of the experiment. Three of the ovariectomized cows (OVX-E2) were administered a subcutaneous estradiol implant that provided low circulating levels of 17 beta-estradiol. The remaining 4 cows (OVX) were not implanted. From December 21, 1982, to September 20, 1984, blood samples were collected sequentially (at 10-min intervals for 6 h) at each summer and winter solstice, and each spring and autumn equinox. In addition, from March 17, 1983, to March 17, 1984, sequential samples were collected midway between each solstice and equinox. Concentration of LH was measured in all samples, and concentration of estradiol was measured in pools of samples. An annual cycle in mean serum concentration of LH and amplitude of LH pulses was detected in both groups of cows. The seasonal pattern did not differ in the two treatment groups. Serum concentration of LH and amplitude of LH pulses were highest around the spring equinox, decreased gradually to the autumn equinox, and then increased and peaked again during the following spring equinox. Frequency of LH pulses and concentration of estradiol in serum did not vary with season. Circulating concentrations of LH and amplitude of pulses tended to be higher in OVX-E2 than OVX cows throughout the experimental period. Frequency of pulses of LH was lower in OVX-E2 than OVX cows throughout the experiment. Concentrations of estradiol were higher in the implanted cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of restriction of dietary energy intake during the prepubertal period on secretion of luteinizing hormone and responsiveness of the pituitary to luteinizing hormone-releasing hormone in heifers.

The working hypothesis that a low plane of nutrition during the prepubertal period delays puberty in heifers by retarding the prepubertal increase in secretion of luteinizing hormone (LH) was investigated. Secretion of LH and the responsiveness of the pituitary to LH-releasing hormone (LHRH) were compared in heifers fed a growing diet (which allowed spontaneous occurrence of puberty; n = 12; control) or an energy deficient diet (which delayed puberty; n = 11; delayed) during the prepubertal period. The dietary treatments were initiated when the heifers were 299 +/- 14 (mean +/- SD) d of age (d 0 of the experiment) and continued until d 175 of the experiment (474 +/- 14 d of age). Weight gains were .79 +/- .05 (mean +/- SE) and .21 +/- .03 kg X head-1 X d-1 for control and delayed heifers, respectively. Puberty occurred on d 120 +/- 14 of the experiment (428 +/- 13 d of age) in control heifers, whereas none of the delayed heifers attained puberty during the feeding period. Serum concentration of LH and the frequency of LH pulses increased rapidly during the 175-d feeding period in control heifers. In delayed heifers, serum LH concentration increased less rapidly and no increase in pulse frequency was detected during the experimental period. Amplitude of LH pulses tended to be higher in control than delayed heifers. Responsiveness of LH secretion to LHRH was lower in delayed than control heifers. It is speculated that failure of secretion of LH to increase is the causative factor for delayed puberty when dietary energy is limited during the prepubertal period in heifers.

Animals↗
PubMed1986

Regulation of pulsatile LH secretion by ovarian steroids in the heifer.

Two experiments were conducted to evaluate relationships among luteinizing hormone (LH), estradiol-17 beta (E2) and progesterone secretion during the preovulatory period in the heifer after prostaglandin F2 alpha (PGF2 alpha)-induced regression of the corpus luteum. A second objective was to elucidate the effects of E2 in regulating LH secretion. In Exp. 1, LH, E2 and progesterone concentrations were determined in serial samples collected during the preovulatory period after PGF2 alpha-induced luteal regression in five Red Angus X Hereford heifers. Progesterone declined to 1 ng/ml by 12 h after the second injection of PGF2 alpha. Frequency of LH pulses increased linearly (P less than .01), whereas no change in amplitude of LH pulses was detected before the preovulatory LH surge. This resulted in a linear increase (P less than .01) in mean LH concentrations. Estradiol also increased in a linear manner (P less than .01), and the rise in E2 was parallel to the increase in mean LH concentrations. In Exp. 2, 12 Angus X Hereford heifers were ovariectomized and administered either 13.5- or 27-cm silastic implants containing E2 at ovariectomy. Four heifers served as nonimplanted controls. Thirty-one days after ovariectomy all heifers were bled at 12-min intervals for 6 h. Frequency of LH pulses declined linearly (P less than .03) while mean LH (P less than .09) and pulse amplitude (P less than .01) increased linearly as E2 dose increased. These results indicate that a reduction in progesterone increases the frequency of LH pulses during the follicular phase of the estrous cycle in cattle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Endocrine changes during restoration of estrous cycles following induction of anestrus by restricted nutrient intake in beef heifers.

The working hypotheses in this experiment were: that ovarian estradiol would inhibit luteinizing hormone (LH) secretion in heifers that were anestrus as a result of restricted dietary energy intake and the responsiveness of LH secretion to estradiol negative feedback would decrease during the period when restoration of estrous cycles occurred following feeding of diets adequate in energy. Fifteen heifers weighing 341 +/- 12 (mean +/- SE) kg were fed a diet containing 50% of the energy required for maintenance until 40 to 50 d following cessation of estrous cycles. Heifers were assigned to intact control (C, n = 5), ovariectomized (OVX, n = 5) or ovariectomized-estradiol-17 beta-implanted (OVX + E2, n = 5) treatments. Heifers were subsequently provided a high-energy (HE) diet until termination of the study. Progesterone concentrations indicating cessation of corpus luteum function were detected after heifers had lost 71 +/- 8 kg body weight over 186 +/- 28 d. Control heifers re-initiated estrous cycles as indicated by increased progesterone concentrations in serum at 49 +/- 9 d after initiation of feeding the HE diet (360 +/- 18 kg body weight). Initiation of pulsatile LH secretion was observed in heifers by d 12 following OVX. Estradiol suppressed LH secretion in OVX + E2 heifers during the period of nutritional anestrus in C heifers. Suppressive effects of E2 on LH secretion continued in OVX heifers after C heifers had initiated corpus luteum function. Therefore, the working hypothesis that LH secretion is inhibited by E2 in the nutritionally anestrous heifer is accepted but responsiveness to estradiol does not subside with re-initiation of estrous cycles, thus this working hypothesis is rejected.

Anestrus↗
PubMed1985

Effects of copulation on timing of the LH surge following synchronization of estrus in the bovine.

Forty-four crossbred postpubertal bovine females were used to study how mating with a bull affected estradiol-17beta (E(2)) secretion and timing of the preovulatory LH surge. Estrous cycles were synchronized with two injections of prostaglandin-F(2alpha) (PGF(2alpha)) 11 d apart. Females were either isolated from males (NE) or exposed to epididectomized bulls (BE) after the second PGF(2alpha) injection. Females exposed to bulls were allowed to mate once and then were separated from the bull. Blood samples were collected at 2-h intervals from the second PGF(2alpha) injection until 12-h post injection to monitor progesterone (P(4)) and luteinizing hormone (LH) concentrations and at hourly intervals from 12 h to 60 h post-injection to monitor LH secretion and timing of the preovulatory LH surge. Samples were also collected at 4-h intervals until 60 h post-injection to monitor estrogen (E(2)) secretion. LH surges were detected in 16 and 14 of 22 females from the BE and NE groups, respectively, during the 60-h period after PGF(2alpha) injection Mean P(4) concentrations and time of P(4) decline to <1 ng/ml were not different between the two treatment groups (P>0.30). Mean E(2) concentration during the 60-h sampling period was different (P<0.003) between BE and NE groups, and a significant treatment effect (P<0.002) occurred 48 h, 52 h and 60 h after the second PGF(2alpha) injection. However, mean LH concentration before the LH surge, duration of the LH surge and peak LH concentration during the surge were not different between the BE and NE groups (P>0.40). Mean time for the second PGF(2alpha) injection to the beginning of the LH surge was 51.6 +/- 1.5 h (X +/- S E) for the females not exposed to bulls and 48.5 +/- 1.4 h for females exposed to bulls (P>0.14). In this study, the presence of and/or mating by a bull did not affect LH secretion or timing of the preovulatory LH surge after PGF(2alpha) administration.

Journal Article↗
PubMed1984

Endocrine mechanisms of puberty in heifers: estradiol negative feedback regulation of luteinizing hormone secretion.

The hypothesis that luteinizing hormone (LH) secretion in prepubertal females is responsive to estradiol negative feedback and that decreased feedback occurs as puberty approaches was tested in heifers. In the first experiment, seven heifers were maintained prepubertal by dietary energy restriction until 508 days of age (Day 0). All heifers were placed on a high-energy diet on Day 0 at which time they received no additional treatment (CONT), were ovariectomized (OVX) or were ovariectomized and subcutaneously implanted with estradiol-17 beta (OVX-E2). This feeding regimen was used to synchronize reproductive state in all heifers. A second experiment was performed with 16 prepubertal heifers using the same treatments at 266 days (Day 0) of age (CONT, OVX and OVX-E2) but no dietary intake manipulation. In both experiments, LH secretion increased rapidly following ovariectomy in OVX heifers. In the initial experiment, LH secretion was maintained at a low level in OVX-E2 heifers until a synchronous rapid increase was noted coincidental with puberty in the CONT heifer. In the second experiment, LH secretion increased gradually in OVX-E2 heifers and attained castrate levels coincidental with puberty in CONT heifers. A gradual increase in LH secretion occurred as puberty approached in CONT heifers. These results indicate that: a) LH secretion in prepubertal heifers is responsive to estradiol negative feedback; and b) estradiol negative feedback decreases during the prepubertal period in beef heifers.

Age Factors↗
PubMed1984

Effect of suckling and ovariectomy on the control of luteinizing hormone secretion during the postpartum period in beef cows.

Twenty-two mature pluriparous beef cows were randomly assigned to one of six treatments in a 2 X 3 factorial experiment in order to study the role of suckling and ovarian factors on control of the tonic and episodic release of luteinizing hormone (LH). Twelve cows remained intact (INT) and 10 were ovariectomized (OVX) within 4 days following the day of parturition (Day 0). The suckling intensities were nonsuckled (0), suckled once daily for 30 min (1) and suckled ad libitum by two calves (2). Blood samples were collected at 15-min intervals for 6 h weekly, from Days 6 to 76 postpartum. The postpartum intervals to initiation of ovarian luteal function were 31 +/- 3, 41 +/- 4 and 67 +/- 1 days (means +/- SEM) for INT cows with 0, 1 and 2 suckling intensities, respectively. Mean LH concentrations and frequency of LH pulses increased as time of ovulation approached in INT cows. In OVX animals, both mean LH concentrations and frequency of LH pulses increased as time postovariectomy progressed. No differences were detected in mean LH concentrations or frequency of LH pulses between the two suckled OVX groups. Mean LH in the OVX-0 cows was greater on Days 13, 20 and 27 postpartum when compared to the respective days in suckled OVX cows. Frequency of LH pulses tended to be lower (P less than 0.10) in both suckled OVX groups when compared with OVX-0 cows from Day 6 to Day 55 postpartum. It is postulated that suckling and ovarian factors act together during the postpartum period to suppress LH levels and frequency of LH pulses in beef cows.

Animals↗
PubMed1984

Luteinizing hormone secretion after withdrawal of exogenous progestogen in heifers fed three levels of dietary energy.

As experiment was conducted with 15 Angus X Hereford heifers that were 16 mo of age at the time the experiment was initiated. The heifers were assigned randomly in equal numbers to be fed low (L), maintenance (M) or high (H) energy diets for 191 d. Overall average weight for heifers at the time the experiment was initiated was 294 +/- 6 kg. All heifers were exhibiting estrous cycles at regular intervals and estrus was synchronized using a progestogen implant (norgestomet) in combination with an injection of estradiol valerate and norgestomet before initiation of dietary treatments. Dietary treatments started at time of implant removal and this day was designated as d 0. Blood samples were collected every other day from d 150 to 160 and progesterone concentrations were quantified to evaluate estrous cycle activity. In order to resynchronize the reproductive state, all heifers were retreated with norgestomet implants and injected with the estradiol valerate and norgestomet combination on d 160. Implants were removed on d 170. Serial blood samples were collected for 4-h periods at 20-min intervals starting at 0, 10, 20 and 30 h after implant removal and luteinizing hormone (LH) concentrations were quantified. Progesterone was quantified in samples collected at daily intervals (170 to 191 d) to evaluate whether a normal estrous cycle occurred subsequent to removal of the implant. Four of five heifers in each of the L and M treatment groups were not cycling, whereas all heifers in the H treatment were cycling at the time of progestogen implantation on d 160.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Influence of exposure to bulls on resumption of estrous cycles following parturition in beef cows.

The effect of bull exposure on the resumption of estrous activity following parturition was studied in an experiment using mature Hereford and Hereford X Angus beef cows. In the spring of 1981 and 1982, cows were assigned by breed and calving date to one of two treatment groups. Cows were exposed to bulls either from 3 to 85 d postpartum (BE; n = 45, 1981; n = 35, 1982) or from 53 to 85 d postpartum (NE; n = 39, 1981, n = 36, 1982). Blood samples were collected from all cows once weekly from calving until 85 d postpartum to determine progesterone concentrations. The first increase in progesterone, which indicated onset of estrous cycles occurred at 43 +/- 2 vs 63 +/- 2 d (P less than .01) in 1981 and at 39 +/- 2 vs 61 +/- 3 d (P less than .01) postpartum in 1982 in BE cows and NE cows, respectively. Early postpartum exposure of cows to bulls reduced the postpartum anestrous interval.

Animals↗
PubMedDate not supplied

Analysis of transcriptional control elements in the 5'-upstream region of ovine interferon-tau gene using feeder-independent caprine trophoblast cell line, HTS-1.

Interferon-tau (IFNtau) is a protein secreted from the embryonic trophectoderm of ruminant ungulates during peri-implantation period. This protein acts on the uterine endometrium, which indirectly maintains corpus luteum function, and is therefore considered essential for the process of maternal recognition of pregnancy. Transcriptional regulation of IFNtau genes had been examined using human choriocarcinoma cell lines, JEG-3 or JAR, however, molecular mechanisms by which cell and term specific IFNtau expression are regulated have not been elucidated. Recently, a feeder cell free-trophoblast cell line derived from Shiba-goat placenta, termed HTS-1, was established. In the present investigation, the 5'-upstream region of ovine IFNtau (oIFNtau) gene was analysed using this cell line, which would provide a more suitable system for studies of the ovine trophoblast specific gene than human choriocarcinoma cells. Variously modified 5'-upstream sequences of the oIFNtau gene fused to a luciferase reporter gene were transiently transfected into HTS-1 cells, and human JEG-3 cells were used as a control. These results and co-transfection with expression vectors revealed that Ets-2 binding site in the promoter region was important in HTS-1, whereas AP-1 that binds to the enhancer region was a major activator in JEG-3. By electrophoretic mobility shift assay, a nuclear protein from HTS-1 cells was confirmed to bind specifically to the Ets-2 site of oIFNtau promoter region. Differences in amounts of AP-1 and Ets-2 protein were demonstrated in nuclear extracts from HTS-1, JEG-3 and ovine conceptuses. Substantial differences on oIFNtau gene transcriptions found between caprine HTS-1 and human JEG-3 cells suggest that this cell line could be valuable in the elucidation of a molecular mechanism(s) by which oIFNtau gene expression is regulated in a cell specific manner.

5' Flanking Region↗
PubMedDate not supplied

Detection of transforming growth factor-alpha and epidermal growth factor receptor mRNA and immunohistochemical localization of their proteins in the ovine uterus during the early implantation period.

Accumulated evidence suggests that growth factors of the epidermal growth factor (EGF) family play an important role in the murine implantation process. In the sheep, however, the uterine distribution of these factors and their receptor, EGF receptor (EGF-R), during implantation is not known. This study examined the presence of mRNA transcripts and immunohistochemical localization for transforming growth factor-alpha (TGF-alpha), the potent EGF-family member, and EGF-R in the ovine uterus during the early implantation period. By reverse transcriptase-polymerase chain reaction and sequencing of the products, the presence of TGF-alpha and EGF-R mRNA transcripts were detected in the endometrium on Days 14, 16 and 20 (Day 0 = day of mating). Immunohistochemical analysis revealed that the luminal and glandular epithelial cells and some stromal cells of the endometrium and the trophectoderm were positive for TGF-alpha and EGF-R on Days 14 and 15. Distinct staining for TGF-alpha was observed in the glandular epithelium of deep endometrial areas and strong immunoreactivity for EGF-R was found in the trophectoderm. On Days 16, 18 and 20, although the staining pattern for TGF-alpha was similar to that on the previous days, the immunoreactivity for EGF-R in the stromal cells increased and that in the gland decreased. A distinct immunoreactivity for EGF-R was found in the trophectoderm throughout the days examined. These results suggest that TGF-alpha expressed in the endometrium and trophectoderm may exert effects locally on these tissues during implantation in sheep. Furthermore, it is speculated that the temporal changes in the uterine EGF-R distribution may be related to the endometrial microvascular development.

Animals↗