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H Cárdenas

Publications and source records attributed to H Cárdenas.

At least 19 recordsLinked to original sources
PubMed2006

Steroidogenic changes and steady state amount of messenger RNA encoding steroidogenic enzymes, gonadotropin receptors and cell-death signalling in the dominant ovarian follicle during estradiol-induced atresia in cattle.

Changes in steroidogenic function and associated gene expression were characterized in dominant ovarian follicles (DF) of cattle where follicles were induced to become atretic by systemic administration of estradiol benzoate (EB). In experiment 1, follicular fluid (FF) steroid concentrations in the DF were measured at 12-hourly time points for 48 h in heifers treated with 1 mg EB i.m./500 kg body weight (EB; n=20) as compared with untreated controls (C; n=19). Treatment with EB promoted a transient reduction in circulating FSH, a rapid (12 h) and sustained reduction in FF estradiol, a rapid (12 h) but transient reduction in FF progesterone and a delayed (36 h) increase in FF testosterone concentrations. In experiment 2, whole follicular wall tissue was collected from DF of mature non-lactating cows allocated to a 0 h control group (0 HC: n=7), a 24h control group (24 HC; n=7) or an EB-treated group where tissue was collected 24 h after administration of 1 mg EB i.m./500 kg body weight (EB; n=8). As for experiment 1, EB promoted a transient reduction in circulating FSH, a pronounced reduction in FF estradiol and a smaller but significant reduction in FF progesterone concentrations. Semi-quantitative RT-PCR on follicular wall tissue revealed that the loss in estrogen activity at 24 h after EB was associated with two-fold reduction in aromatase mRNA, with an apparent acceleration in loss of 17alpha-hydroxylase mRNA. Expression of genes for gonadotropin receptors (LHR and FSHR) and a cell-death signalling pathway (Fas antigen and Fas ligand) were unchanged during the initial 24h of EB-induced atresia. These results suggest that EB initiates atresia in dominant ovarian follicles through a rapid suppression of follicular estradiol synthesis, an effect associated with down-regulation of the aromatase gene. A transient suppression in circulating FSH following administration of EB appears to have initiated these events, and it is suggested that subsequent processes involved in atresia follow this loss in estrogenic function.

Animals↗
PubMed2006

Androgens in female pig reproduction: actions mediated by the androgen receptor.

Androgens have potential actions in almost all the organs of males and females. In females, most organs contain some tissues with cells that have androgen receptors. Androgens can regulate cellular functions by binding to androgen receptors or be converted to other hormones. For example, testosterone can bind to the androgen receptor or be aromatised to oestradiol. Treating animals with testosterone, therefore, might elicit some androgenic and oestrogenic effects. Alternatively, testosterone can be converted to other androgens, which in turn, have more or less affinity with the androgen receptor and these new metabolites may or may not be aromatised to oestrogens. This review will highlight the roles of androgens in female mammals other than those as a substrate for oestrogen, with particular emphasis on the actions of the androgen receptors in uteri and ovaries of pigs. Utilising small dosages of an androgen receptor agonist, DHT (5alpha-dihydrotestosterone) we have observed that some uterine functions were inhibited while ovarian follicular development was augmented. These inhibitory and stimulatory effects of androgen therapy on reproductive organs can potentially be balanced to enhance ovulation rate and litter size in gilts and sows. Perhaps after future experimentation, new uses of androgens or anti-androgens could improve additional aspects of sow performance not presently under consideration.

Androgens↗
PubMed2005

Effects of cadmium on Na+ transport in the isolated skin of the toad Pleurodema thaul.

Cadmium ions applied to either (outer or inner) surface of the isolated toad skin dose-dependently increased the short-circuit current (SCC), the potential difference (V) and the active sodium conductance (G(Na)) in the concentration range 0.07-0.50mM. Maximal stimulatory effect was over 30% with an EC(50) of about 0.1mM. The effect of the highest concentration used (0.75mM) decreased considerably, and when it was applied to the inner surface (10 experiments), induced between 30% and 40% inhibition of the electric parameters in four experiments. Pretreatment with amiloride inverted the stimulatory effect of externally applied Cd(2+), suggesting competitive action on the apical Na(+) channel. The effect of noradrenaline (NA) was increased after outer application of Cd(2+) and decreased after inner application of the metal: the latter effect might be due to cadmium inhibition of the activity of Na(+),K(+)-ATPase. On the other hand, pretreatment with amiloride was followed by partial although transient reversal of its effects by serosal Cd(2+), which might be explained by action of cadmium on cytoplasmic lysine residues concerned with Na(+) channel gating. The amiloride test showed that the increment of the electric parameters was due principally to stimulation of the driving potential for Na(+) (V-E(Na(+))) and that inhibition was accompanied by a reduction in the V-E(Na(+)) and by a significant decrease in skin resistance indicating possible disruption of membrane or cell integrity. These data are in favor of the possibility that externally applied Cd(2+) activates toad skin ion transport, partly by increasing apical sodium conductance and also by stimulating the V-E(Na(+)), and that internally applied Cd(2+), with easier access to membrane and cellular constituents, may inhibit the sodium pump.

Amiloride↗
PubMed2005

Iron affects the structure of cell membrane molecular models.

The effects of Fe(3+) and Fe(2+) on molecular models of biomembranes were investigated. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and of dimyristoylphosphatidylethanolamine (DMPE), classes of phospholipids located in the outer and inner moieties of cell membranes, respectively. X-ray studies showed that very low concentrations of Fe(3+) affected DMPC organization and 10(-3)M induced a total loss of its multilamellar periodic stacking. Experiments carried out with Fe(2+) on DMPC showed weaker effects than those induced by Fe(3+) ions. Similar experiments were performed on DMPE bilayers. Fe(3+) from 10(-7)M up to 10(-4)M had practically no effect on DMPE structure. However, 10(-3)M Fe(3+) induced a deep perturbation of the multilamellar structure of DMPE. However, 10(-3)M Fe(2+) had no effect on DMPE organization practically. Differential scanning calorimetry measurements also revealed different effects of Fe(3+) and Fe(2+) on the phase transition and other thermal properties of the examined lipids. In conclusion, the results obtained indicate that iron ions interact with phospholipid bilayers perturbing their structures. These findings are consistent with the observation that iron ions change cell membrane fluidity and, therefore, affect its functions.

Calorimetry, Differential Scanning↗
PubMed2003

Distribution and changes in amounts of the androgen receptor in the pig uterus during the estrous cycle, early pregnancy and after treatment with sex steroids.

Two experiments were performed to examine the expression of the androgen receptor (AR) gene in the pig uterus. In experiment 1, immunohistochemistry (IHC) was used to determine the distribution of the AR in uterine tIssue of pigs when collected at the first day of estrus (day 0) and the mid-luteal phase (day 12) of the estrous cycle, or early pregnancy (day 12, n=4 gilts per group). In experiment 2, AR immunostaining and AR mRNA in uterine tIssue were compared among ovariectomized gilts (n=4 per group) following treatment for 4 days with daily injections of: (1) progesterone (2 mg/kg bodyweight (BW)), (2) estradiol-17beta (E(2,) 2 micro g/kg BW), (3) E(2) plus progesterone (same dosages as 1 and 2 combined), (4) 5alpha-dihydrotestosterone (DHT, 7 micro g/kg BW), or (5) vehicle (corn oil). Data were analyzed using ANOVA. In experiment 1, nuclear staining for AR in luminal and glandular epithelia was strong and did not differ in intensity between the two locations. Immunostaining of AR in the myometrium was less (P<0.001) intense than in the luminal and glandular epithelia. Nuclei of stromal cells contained AR immunostaining that varied in intensity from strong (mainly in subepithelial stroma) to weak or no staining. Stages of the estrous cycle or early pregnancy did not influence AR immunostaining in the endometrial epithelia and myometrium. In experiment 2, immunostaining of AR in glandular and luminal epithelia and myometrium of ovariectomized gilts treated with vehicle or DHT was less (P<0.05) than in gilts treated with E(2), progesterone, or E(2) plus progesterone. Immunostaining of AR did not differ between ovariectomized gilts treated with vehicle or DHT, or between gilts treated with E(2), progesterone, or E(2) plus progesterone. In both experiments, intensity of AR immunostaining was greater in glandular epithelium located at the adluminal region compared with glandular epithelium located at the basal region of the endometrium. Competitive reverse-transcription PCR (RT-PCR) indicated a stimulatory effect (P<0.01) of E(2) on amounts of AR mRNA in whole endometrium. This increase in AR mRNA after E(2) treatment was not detected when E(2) was combined with progesterone. Endometrial AR mRNA was not influenced by DHT or progesterone relative to vehicle-treated gilts. In conclusion, immunoreactive AR is mainly present in luminal and glandular epithelia of the pig uterus and to a lesser extent in the myometrium, and does not change significantly during the estrous cycle or early pregnancy. Expression of the AR gene in the pig endometrium and myometrium appears to be regulated by E(2) and progesterone.

Animals↗
PubMed2002

Androgen receptor and follicle-stimulating hormone receptor in the pig ovary during the follicular phase of the estrous cycle.

Follicle-stimulating hormone (FSH) is an important regulator of follicular development. Some effects of FSH on ovarian follicles might be enhanced by androgens. The main objectives of the present study were to examine expression of the androgen receptor (AR) and FSH receptor (FSHR) in late developing follicles in pigs. Ovaries were collected from gilts on days 13, 15, 17, and 19 of the estrous cycle (day 0 = first day of estrus, n = 4 gilts/day), a period coincident with the follicular phase. One ovary was processed for immunohistochemistry (IHC) of AR. Samples of surface wall from the largest follicles (4-5 per gilt) were dissected from the other ovary, pooled and processed for determination of AR and FSHR mRNAs using reverse transcription-polymerase chain reaction (RT-PCR). Intense AR immunostaining was present in nuclei of granulosa cells of preantral and antral follicles. AR immunoreactivity was also present in the nuclei of oocytes. Weak staining for AR was observed in cells of the theca interna, ovarian surface epithelium, and in most cells of the ovarian stroma. Relative amounts of immunoreactive AR in granulosa cells of late developing follicles, or small antral follicles (< 2 mm), did not differ between days 13, 15, 17, and 19. However, amounts of AR in granulosa cells of small antral follicles was greater (P < 0.05) than in the largest follicles present in the same ovary. The relative amounts of AR mRNA in tissue from the largest follicles on days 13, 15, 17, and 19 did not differ; however, amounts of FSHR mRNA in the same follicles were not different between days 13, 15, and 17, but decreased (P < 0.05) by day 19. Results indicate that during the follicular phase in gilts, the AR protein is mainly present in granulosa cells. Relative amounts of AR protein in granulosa cells and mRNA in walls of late developing follicles did not significantly change from day 13 to 19; however, amounts of FSHR mRNA decreased in preovulatory follicles by day 19 of the estrous cycle.

Amino Acid Sequence↗
PubMed2002

Increased ovulation rate in gilts treated with dihydrotestosterone.

Treatment with testosterone increases ovulation rate in pigs. The present study was conducted to examine the effects of 5alpha-dihydrotestosterone (DHT), a non-aromatizable androgen receptor ligand, on ovulation rate and amounts of androgen receptor and FSH receptor mRNAs in postpubertal gilts. In Expt 1, ovulation rate in response to daily i.m. injections of 0, 6, 60 or 600 microg DHT kg(-1) body weight from day 13 of the oestrous cycle (day 0 = day 1 of oestrus) to the following oestrus increased with each dose of DHT (P < 0.05). The mean increase in number of corpora lutea ranged from approximately three to 17 over the three dosages of DHT. In Expt 2, gilts treated daily with 60 microg DHT kg(-1) body weight during the early follicular phase (from day 13 to day 16), coincident with follicular recruitment, or the late follicular phase (day 17 to oestrus), had higher (P < 0.05) rates of ovulation compared with gilts that received vehicle, and were not different from gilts treated with DHT from day 13 to oestrus. Percentage recovery of day 3 embryos was not altered when gilts were treated from day 13 to day 16 or from day 17 to oestrus; however, treatment of gilts with DHT from day 13 to oestrus decreased recovery of day 3 (Expt 1) or day 11 (Expt 2) conceptuses. Daily administration of 6 microg DHT kg(-1) body weight to gilts from day 13 of the oestrous cycle to the following oestrus (Expt 3) did not affect the relative amounts of androgen receptor mRNA, but increased (P < 0.05) the amounts of FSH receptor mRNA in preovulatory follicles as determined by RT-PCR. The results of these experiments indicate that androgens may regulate ovulation rate in gilts. One of the roles of androgens might be regulation of the amounts of FSH receptor mRNA in ovarian follicles.

Analysis of Variance↗
PubMed2001

Effects of AlCl3 on toad skin, human erythrocytes, and model cell membranes.

Aluminum, a very abundant metal, could play a toxic role in several pathological processes, including neurodegeneration. Although the effects of Al(III) on biological membranes have been extensively described, direct information concerning the molecular basis of its biological activity is rather scanty. To examine aluminum challenges on cell membranes, various concentrations of AlCl3 in aqueous solutions were incubated with human erythrocytes, isolated toad skin, and molecular models of biomembranes. The latter consisted of multilayers of dimyristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine, representing phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane. These specimens were studied by scanning electron microscopy, electrophysiological measurements, and x-ray diffraction. The results indicate that Al(III) in the concentration range of 10-100 microM induced the following structural and functional effects: (i) change in the normal discoid shape of human erythrocytes to echinocytes due to the accumulation of Al(III) ions in the outer moiety of the red cell membrane; (ii) perturbation of dimyristoylphosphatidylcholine, and to a lesser extent of dimyristoylphosphatidylethanolamine bilayers, and (iii) decrease in the short-circuit current and in the potential difference of the isolated toad skin, effects that are in accordance with a time-dependent modulation of ion transport in response to changes in the molecular structure of the lipid bilayer.

Aluminum↗
PubMed2001

Estrogen receptor beta in the sheep ovary during the estrous cycle and early pregnancy.

Objectives were to sequence and examine the expression of the estrogen receptor beta (ERbeta) in the sheep ovary. The sequence of the ovine ERbeta (oERbeta) was determined using reverse-transcription polymerase chain reaction (RT-PCR) and cloning techniques. The reading frame of oERbeta contained 527 amino acids and exhibited high overall homology with cow (98%), rat (88%), and human (88%) ERbeta. In addition, an oERbeta isoform having a 139-base pair deletion (oERbeta1) was identified. The predicted amino acid sequence of this isoform is lacking the ligand-binding and carboxyl-terminal transactivation domains. The oERbeta protein and mRNA were determined in ovaries obtained from ewes on Days 0 (first day of estrus), 2, 6, and 10 of the estrous cycle and Day 30 of gestation. Immunohistochemistry showed that oERbeta protein was located in granulosa cells, the ovarian surface epithelium, endothelium, and Day 2 corpus luteum (CL). Weak immunostaining for ERbeta was detected in the theca interna. Relative steady-state amounts of oERbeta mRNA in the CL were determined using semiquantitative RT-PCR. Amounts of oERbeta mRNA were greater (P < 0.05) during CL formation (Day 2) than at later stages. The oERbeta to oERbeta1 mRNA ratio was lower (P < 0.05) on Day 2 than on Day 10 or Day 30 due to a decrease in amounts of oERbeta1. Results indicate that the oERbeta is a 527-amino acid protein expressed in specific cells of the ovary. Changes in relative amounts of full-length oERB and a deletion isoform in CL occurred during the estrous cycle, suggesting that these two types of ERbeta might regulate estrogen actions during early CL development in sheep.

Amino Acid Sequence↗
PubMed2000

[Pseudoprognathism frequency and masseter muscle activity in operated cleft lip patients].

BACKGROUND: As a consequence of a growth inhibition of middle third of the face, cleft lip surgery could lead to a pseudoprognathism. However, this is not always the case. Also, when facial architecture is changed, the activity of muscles such as the masseter could be disturbed. AIM: To study masseter electromyographic activity in operated cleft lip patients. MATERIAL AND METHODS: Forty two patients with cleft lip (25 male, aged 13 to 35 years old) were studied. All were operated during their first year of life. An electromyography of masseter muscle was performed and from a teleradiography, ANB and Gonion angles were obtained. Forty healthy subjects conformed the control group. RESULTS: The sample was divided in two groups. A group of 20 patients had a significantly lower EMG voltage than control subjects (662 +/- 228 and 1511 +/- 340 microV respectively, p < 0.001). Only seven patients had an anteriorly inverted bite with a mean ANB of + 1.7 and a mean molar relation of -4.8, figures that confirm the presence of pseudoprognathism. CONCLUSIONS: Eighty three percent of cleft lip patients do not have cephalometric parameters of pseudoprognathism and half of the patients have a lower masseter activity.

Adolescent↗
PubMed1999

Interactions of Al(acac)3 with cell membranes and model phospholipid bilayers.

Aluminum is a neurotoxic agent; however, little information has been obtained regarding its molecular cytotoxicity and the effects on the stability of biological membranes. This is mainly due to the ill-defined chemical speciation of the metal compounds. For this reason, the present study used aluminum acetylacetonate, (Al(acac)3), a neutral, chemically well-defined, hydrolytically stable and lipophilic compound. To understand the molecular mechanism of its interaction with cell membranes, Al(acac)3 was incubated with human erythrocytes, isolated toad skin and molecular models of biomembranes. The latter consisted of multilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoyphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The results showed that Al(acac)3 interacted with the erythrocyte membrane modifying its normal discoid morphology to both echinocytic and stomatocytic shapes. This finding indicates that the Al complex was inserted in both the outer and inner layers of the red cell membrane, a conclusion supported by X-ray diffraction analyses of DMPC and DMPE bilayers. Electrophysiological measurements performed on toad skin revealed a significant decrease in the potential difference and short-circuit current responses after application of Al(acac)3, effects interpreted to reflect inhibition of the active transport of ions. Al(acac)3 was active on both surfaces of the skin suggesting that the membrane was permeated by the metal complex. It is concluded that Al(acac)3 both alters the molecular structure of the lipid bilayer, thereby modifying the biophysical properties of the cell membrane, and changes its physiological properties.

Animals↗
PubMed1997

Effect of the rate of progesterone decline at luteolysis on the ovulatory follicles and subsequent estrous cycle length in ewes.

Follicular and interestrous characteristics were examined in 34 ewes after experiencing either a rapid decline in plasma concentrations of progesterone at luteolysis [prostaglandin F2 alpha (PGF2 alpha)-induced] or a slow rate of decline, lasting over 72 h. All ewes were given PGF2 alpha on day 10 (day 0 = estrus). A slow rate of decline was established in 17 ewes by the intravenous infusion of progesterone initially at 72 ml h-1, delivering 4.5 mg progesterone h-1, then decreasing the infusion rate by 1 ml h-1 for the next three days. Seventeen additional ewes, predestined to experience a rapid decline in progesterone, were infused with vehicle. In Experiment 1, after infusion, ewes (6 ewes/group) were necropsied at the onset of estrus and follicle diameter was determined, follicular fluid was aspirated and the remaining follicular wall was microscopically examined to determine the number of granulosa cell layers. In Experiment 2, the interestrous interval, after infusion, was observed in both groups of ewes (11 ewes/group). Ewes experiencing a rapid rate of progesterone decline at luteolysis had no differences in follicle diameter nor follicular concentration of progesterone or estradiol but their ovulatory follicles contained fewer (P < 0.01) granulosa cell layers and the resulting estrous cycle was longer (P < 0.05) than ewes experiencing a slow rate of progesterone decline.

Abortifacient Agents, Nonsteroidal↗
PubMed1997

Short-term effects of exogenous estradiol-17 beta on blastocyst development during the period of elongation in swine.

Objectives were to examine the effects of a single dose (4 mg) of estradiol-17 beta (E2) on blastocyst development around the period of elongation. Proestrus gilts were induced to ovulate with 750 IU of hCG and were mated before ovulation (normal mating, 24 to 32 h post-hCG) or after ovulation had begun (delayed mating, 43 h post-hCG). This difference in time of mating has been demonstrated to result in approximately a 7-h difference in time of blastocyst elongation. Normally and delay-mated gilts were ovariohysterectomized at 278 h post-hCG or injected with E2 or vehicle (corn oil) at 278 h and then ovariohysterectomized at 290 h post-hCG (five or six gilts per group). Blastocyst size was measured and concentrations of E2, retinol, uteroferrin, insulin-like growth factor-I (IGF-I), uterine plasmin/trypsin inhibitor (UPTI) and protein in uterine flushings were quantified. Blastocyst size and components of uterine flushings did not differ (P > 0.05) between normally and delay-mated gilts at 278 h post-hCG. However, at 290 h post-hCG, normally mated gilts had larger (P < 0.01) blastocysts (small spheres to filamentous) and their flushings tended to contain less (P < 0.07) amounts of retinol than those of delay-mated gilts whose blastocysts ranged from small spheres to ovoidals. Normally mated gilts receiving E2 at 278 h had smaller (P < 0.01) blastocysts and less (P < 0.05) amounts of retinol at 290 h post-hCG than gilts receiving vehicle. Conversely, delay-mated gilts treated with E2 or vehicle did not differ (P > 0.05) in blastocyst size and amounts of components of uterine flushings at 290 h post-hCG. Normally mated gilts treated with vehicle had litters in the process of elongating at 290 h post-hCG. Mean blastocyst size (P < 0.001) and amounts of components of uterine flushings (except for IGF-I) in these gilts were greater (P < 0.05, UPTI = 0.06) than in normally mated gilts at 278 h post-hCG, whose blastocysts were spherical. Among gilts not treated with E2 (278 h and 290 h pooled), mean blastocyst size was positively correlated (P < 0.05) with amounts of retinol, E2, uteroferrin and total protein. Results indicated that a single dose of E2 given before elongation altered blastocyst development depending on how close blastocysts were to onset of elongation at the time of E2 treatment.

Acid Phosphatase↗
PubMed1997

Administration of testosterone from day 13 of the estrous cycle to estrus increased the number of corpora lutea and conceptus survival in gilts.

The effects of exogenous androgens on the number of corporea lutea (CL) and conceptus survival were examined in crossbred gilts. In Exp. 1, gilts received 1 mg of testosterone per day from d 13 (d = 0 first day of estrus, n = 21) or d 16 until estrus (n = 23). Gilts in the vehicle group received corn oil (n = 20). Gilts were mated and on d 11.5 their concepti and CL were evaluated. In Exp. 2, conceptus survival was examined at the 4- to 8-cell, early blastocyst or hatching blastocyst stages for gilts given vehicle or 1 mg testosterone from d 13 (24 gilts per group). In Exp. 3, gilts received 1 mg of androstenedione (n = 20) or vehicle (n = 18) per day from 13 d to estrus and then were mated and evaluated on d 11.5. Results from Exp. 1 indicated that the number of CL was greater (P < .04) in gilts treated with testosterone from d 13 to estrus than in gilts receiving vehicle (16.4 vs 14.8, respectively). Similarly, the number (P < .01) and recovery rate (P < .04) of blastocysts were greater in gilts treated with testosterone from d 13 to estrus than in gilts treated with testosterone from d 16 to estrus in gilts receiving vehicle (number, 15.3 vs 12.8 or 12.8; recovery rate, 95 vs 87 or 86%, respectively). Gilts treated testosterone or vehicle did not exhibit differences (P > .05) in number of normal concepti at the 4- to 8-cell and hatching stages. However, prior treatment with testosterone delayed conceptus death; gilts treated with testosterone had more (P < .01) normal concepti at the intermediate stage (early blastocyst) than those treated with vehicle (treatment x embryo stage interaction, P < .05). In Exp. 3, androstenedione treatment did not influence (P > .10) the number of CL or the number and recovery rates of d-11.5 blastocysts. Treating gilts with testosterone from d 13 of the estrous cycle to the following estrus increased the number of CL and blastocyst survival, perhaps by improving some, as yet unknown, aspect(s) of oocyte quality.

Androstenedione↗
PubMed1995

Luteinizing hormone pulsatile release and the length of lactational amenorrhoea.

The pattern of luteinizing hormone (LH) pulsatile release and the mean concentrations of follicle-stimulating hormone, oestradiol and progesterone were studied in nursing and non-nursing women. Blood samples were drawn at 5 min intervals between 10:00 and 14:00 h and between 22:00 and 02:00 h at months 3-4, 5-6, 7-8 and 9-10 postpartum in nursing women and in the follicular phase in non-nursing women. In nursing women, mean LH concentrations at months 3-4 were significantly lower than in non-nursing cycling women only in the subgroup which subsequently experienced > 6 months of lactational amenorrhoea, although all were fully nursing with a similar suckling frequency. LH pulses in plasma were found at all times in nursing women. There were no significant differences in the frequency (about four pulses every 4 h), amplitude or duration of LH pulses related to the duration of amenorrhoea, nor did these parameters vary significantly between amenorrhoeic or cycling nursing women and non-nursing women. Nursing amenorrhoeic women exhibited a normal frequency of LH pulse well in advance of the resumption of the first post-partum menses, suggesting that mechanisms other than the suppression of the gonadotrophin-releasing hormone pulse generator intervened in the inhibition of ovarian function during lactation.

Adult↗
PubMed1994

Administration of testosterone during the follicular phase increased the number of corpora lutea in gilts.

The effects of 0 (vehicle), 1, 10, or 100 mg of testosterone, administered on d 17 and 18 of the estrous cycle (d 0 = 1st d of estrus), on the number of preovulatory follicles on d 19 or the number of corpora lutea (CL) and blastocysts on d 11 of the subsequent cycle were examined in 82 gilts. The mean number of preovulatory follicles increased (P < .01) in a dose-dependent manner. Likewise, gilts that received 1, 10, or 100 mg of testosterone had more (P < .05) CL than gilts treated with vehicle. The mean number of blastocysts increased (P = .06) in gilts receiving 1 mg of testosterone but decreased (P < .05) in gilts treated with 10 mg of testosterone compared with gilts receiving vehicle. Similarly, recovery rates of blastocysts decreased (P < .05) in gilts treated with 10 or 100 mg of testosterone relative to gilts administered 0 or 1 mg of testosterone. Plasma concentrations of testosterone and estradiol increased (P < .05) 2 h following administration of 1 mg of testosterone on d 17 of the estrous cycle. These results indicate that although the 10- and 100-mg dosages of testosterone were detrimental to blastocyst survival, the 1-mg dosage increased synthesis of estradiol and the number of CL and d-11 blastocysts.

Animals↗
PubMed1994

Effects of administration of human chorionic gonadotropin or progesterone before maternal recognition of pregnancy on blastocyst development and pregnancy in sheep.

A series of four experiments with 258 ewes was conducted to determine whether blastocyst size could be altered before normal luteolysis and, if so, how this affected fertility. In Exp. 1 and 2, nonmated and mated ewes, respectively, were treated with hCG (100 IU), progesterone (12 mg), or vehicle on d 11.5 (d 0 = onset of estrus). In Exp. 3 and 4, field trials were conducted to compare the effects of either hCG or progesterone treatment on d 11.5 on subsequent pregnancy rates. In Exp. 1, hCG transiently increased (P < .01) concentrations of progesterone and estradiol in plasma, whereas progesterone treatment increased only plasma progesterone. Neither hCG nor progesterone affected the duration of the estrous cycle. In Exp. 2, d-13 blastocysts were longer (3.5 +/- 1.6 vs .8 +/- .5 cm; Mean +/- SE; P < .05), and concentrations of protein and interferon tau (IFN tau) in uterine flushings were greater (10.7 vs 1.2 micrograms; P < .05) in hCG than in vehicle-treated ewes. Progesterone treatment did not affect blastocyst development. In Exp. 3, pregnancy rates tended to be greater (P < .10) in ewes given hCG than in those given vehicle (44/47; 94% vs 40/48; 83%); however, administration of progesterone in Exp. 4 had no effect on pregnancy rates (P < .14; 41/45; 91% vs 37/46; 80%; control ewes). These results indicate that treatment with hCG on d 11.5 stimulated uterine secretions and conceptus growth sufficiently to influence pregnancy rates.

Animals↗