Biomedical subjects

H Cardenas

Publications and source records attributed to H Cardenas.

At least 19 recordsLinked to original sources

PubMed2006

Deficient expression of monoamine oxidase A in the endometrium is associated with implantation failure in women participating as recipients in oocyte donation.

Successful implantation depends both on the quality of the embryo and on the endometrial receptivity. The latter depends on progesterone-induced changes in gene expression, a process that has been characterized by microarray analysis. One of the genes whose transcription appears to be enhanced during the receptive period is monoamine oxidase A (MAO-A). Our first objective was to confirm the increased expression of MAO-A in the endometrium during the receptive phase of spontaneous normal cycles using real time PCR and immunofluorescence. The second objective was to examine the endometrial expression of MAO-A during the receptive phase induced by exogenous estradiol (E(2)) and progesterone in patients whose endometrium was shown to have been either receptive or non-receptive to embryo implantation in repeated cycles of oocyte donation. Results showed that MAO-A transcript levels increased between the pre-receptive (LH+3) and receptive phase (LH+7) in all spontaneous cycles examined, with a median increase of 25-fold. Immunofluorescent labelling demonstrated MAO-A localization to the glandular and luminal epithelium with an increasing positive score between LH+3 and LH+7. Conversely, prior failure of embryo implantation was associated with a 29-fold decrease in MAO-A mRNA levels and a substantial reduction in MAO-A protein immunofluorescent label score. These results show a strong association between endometrial receptivity and MAO-A expression in the endometrial epithelium, suggesting an important role for this enzyme in normal implantation.

Adult↗

PubMed2001

Increased adhesiveness and internalization of Neisseria gonorrhoeae and changes in the expression of epithelial gonococcal receptors in the Fallopian tube of copper T and Norplant users.

Interaction of Neisseria gonorrhoeae with the oviductal epithelium in vitro was examined in 2 cm length segments obtained after surgical sterilization from users of copper T intrauterine device (IUD) or Norplant and control women. Segments perfused with N.gonorrhoeae suspensions were incubated from 30 min up to 4 h, fixed, frozen and cut in 6--10 microm sections. Bacteria were detected immunohistochemically with rabbit anti-gonococcal serum followed by light and confocal microscopy. Adhesion and internalization of gonococci by epithelial cells were observed at all incubation times, and both were higher in explants from users of copper T IUD or Norplant implants than controls. The epithelium of controls expressed CD66 and syndecan-1; but CD46 was found in only one out of six cases. The epithelium of copper T IUD users expressed CD66 but not syndecan-1 or CD46. Users of Norplant exhibited expression of CD46, CD66 and syndecan-1. Label was always found along the luminal border of the epithelium. There were more intraepithelial lymphocytes in users of contraceptive methods than in controls. Results indicate that (i) N.gonorrhoeae invade the oviductal epithelium from the first minutes of exposure, (ii) the epithelium is constitutively endowed with two known receptors for the gonococcus, CD66 and syndecan-1, (iii) copper T IUD and Norplant users exhibit higher rates of attachment and internalization of the gonococcus into the oviductal epithelium associated with changes in expression of gonococcal receptors.

Adult↗

PubMed2001

PAF receptor and PAF acetylhydrolase expression in the endosalpinx of the human Fallopian tube: possible role of embryo-derived PAF in the control of embryo transport to the uterus.

BACKGROUND: Prostaglandin-E(2) and platelet-activating factor (PAF) are embryonic-derived signals that time embryo passage into the uterus in the mare and hamster respectively. PAF-like activity is detectable in the spent media of preimplantation human embryos and it has been suggested that PAF may be the embryonic signal that controls embryo transport to the uterus in our species. The actions of PAF are regulated at the level of its synthesis and degradation as well as the expression of a specific cell surface receptor (PAFr). The enzyme PAF acetylhydrolase (PAF-AH) degrades PAF. This study was undertaken to examine whether or not PAFr and PAF-AH are expressed in the human Fallopian tube and to identify the cell types in which they are expressed. METHODS: The presence of PAFr mRNA in tissue extracts was investigated using reverse transcription-polymerase chain reaction. We amplified the predicted amplicon for PAFr mRNA from RNA samples extracted from Fallopian tubes. The expression of PAF-AH was detected by Western blot and the localization of PAFr and PAF-AH proteins was detected by immunohistochemistry. RESULTS: Utilizing antibodies against PAFr and PAF-AH, co-localization of the two proteins in the epithelium and stromal cells were demonstrated. CONCLUSIONS: These observations show that the human Fallopian tube expresses PAFr and PAF-AH at a location compatible with the proposed paracrine role of early embryo-derived PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2000

Expression of intercellular adhesion molecule 1 (ICAM-1) on the human oviductal epithelium and mediation of lymphoid cell adherence.

The epithelium of the human oviduct expresses the major histocompatibility complex (MHC) class II and shows endocytic properties towards luminal antigens. Therefore, the epithelial cells might behave as antigen-presenting cells, inducing a local immune response. The activation of antigen-specific T cells not only requires presentation of the peptide antigen by MHC class II, but also the presence of co-stimulatory molecules in the antigen-presenting cells. Therefore, the expression of the intercellular adhesion molecule 1 (ICAM-1) was examined in the epithelium of the human oviduct. Most oviducts showed epithelial ICAM-1 expression, as assessed by immunocytochemistry, western blot analysis and RT-PCR assay, and the expression was restricted to the luminal border of ciliated and secretory cells. Interferon gamma, interleukin 1 and lipopolysaccharide treatments increased the percentage of ICAM-1-positive cells in primary cultures, indicating that the expression of ICAM-1 in the oviduct might be upregulated in vivo by inflammatory cytokines or bacterial infections. Binding assays between allogenic phytohaemagglutinin-activated lymphocytes and epithelial monolayers expressing ICAM-1 demonstrated that this molecule stimulated lymphocyte adherence. The presence of ICAM-1, in addition to MHC class II, supports the putative role of the oviductal epithelium in antigen presentation. The exclusive apical distribution of ICAM-1 indicates that T-cell activation would occur in a polarized manner. Binding of lymphoid cells to the surface of the oviductal epithelium may help to retain these immune cells that are required for the clearance of pathogens.

Adult↗

PubMed1999

Protective effects of estrogen in a rat model of age-related cataracts.

Women have a higher incidence of cataracts, and epidemiologic data suggest that the increased risk may be caused by a lack of estrogen in postmenopausal years. We have examined the effects of estrogen on methylnitrosourea (MNU)-induced cataractogenesis in Sprague-Dawley rats. Animals were ovariectomized, injected with MNU, and treated with estradiol or estrone by a continuous-release, subcutaneous Silastic implant, or they received an empty Silastic implant (no hormone). In the no-hormone group, rats developed opaque lenses approximately 6 months after MNU treatment. By 8 months, 74% (14/19) of the no-hormone rats had evident opacity in one or both eyes by simple gross inspection; 58% (22/38) of the eyes in this group were opaque. Estradiol or estrone treatment reduced the incidence of cataractous eyes to 12% or 25%, respectively. Lenses were examined under a dissecting microscope for light transmission. The lenses of the group treated with no hormone had light transmission of 26% +/- 9.2%, whereas lenses from the estradiol-treated animals had light transmission of 72% +/- 5.8%. Histological examination revealed that the anterior cortices of the opaque lenses were disrupted and showed the hallmark signs of age-related cataracts; in addition, some eyes that appeared clear by macroscopic examination showed the early histologic signs of cataractogenesis. It was demonstrated with reverse transcription-PCR that lens cells express both alpha and beta types of estrogen receptor, suggesting that the protective effects of the hormones may be a direct, receptor-mediated phenomenon. Thus, the MNU-treated, ovariectomized rat serves as a model for age-related cataractogenesis, and observation of a clear protective effect of estrogens in this system supports the implications of epidemiologic data.

Aging↗

PubMed1999

Variability of breast sucking, associated milk transfer and the duration of lactational amenorrhoea.

Quantitative relationships between physical parameters of sucking, milk transfer and the duration of amenorrhoea were examined in normal mother-baby pairs under exclusive breastfeeding. Sucking pressures were recorded twice on the second and once on the fifth month after birth, during complete breastfeeding episodes, by means of a catheter attached to the nipple and connected to a pressure transducer, the signals of which were analysed by computer. Babies were weighed before and after each sucking episode to estimate milk transfer. In the first nursing episode after noon, 2-month-old babies sucked from 140 to > 800 times during 4-15 min from the first breast, obtaining from 20 to > 100 g milk. The physical parameters of sucking and milk transfer exhibited high inter-individual but low intra-individual variabilities. There were significant differences in the physical parameters of sucking and milk transfer efficiency between first and second breast and between the second and fifth months after birth. Milk transfer efficiency was inversely correlated with time occupied by non-sucking pauses > or = 1.5 s, and was directly correlated with mean intersuck intervals in the first breast and with duration of the sucking episode, number of sucks, mean pressure and area under the pressure curve in the second breast. There was no correlation between the physical parameters of sucking and duration of lactational amenorrhoea (n = 62). However, significantly more mothers had amenorrhoea lasting > 180 days among those whose babies spent a longer proportion of the nursing episode in non-sucking pauses > or = 1.5 s. This finding indicates that sensory stimulation of the nipple produced during a nursing episode by stimuli other than sucking itself may have an important role in sustaining lactational amenorrhoea. It is concluded that nursing episodes have a complex structure that allows the development of a breastfeeding phenotype in each mother-baby pair, exhibiting important inter-individual variability. The present analysis does not support the contention that this source of variability accounts for the variability in the duration of lactational amenorrhoea.

Amenorrhea↗

PubMed1998

Endocytosis and MHC class II expression by human oviductal epithelium according to stage of the menstrual cycle.

The epithelium is the first barrier against pathogens invading the lumen of the human oviduct. Its expression of class II major histocompatibility complex (MHC class II) proteins suggests that it might play a role in antigen presentation during the local immune response. To study the role of the oviductal epithelium in antigen processing, its endocytic properties and MHC class II expression were examined. For assay of endocytosis, fluorescein isothiocyanate-labelled bovine serum albumin (BSA-FITC) or Escherichia coli (E. coli-FITC) was infused into the lumen. One-centimetre pieces of oviduct were incubated for 2 h and processed for fluorescence and confocal microscopy, and transmission electron microscopy. Incorporation into secretory and ciliated epithelial cells was observed, which was unrelated to the phase of the menstrual cycle. Small pieces of the organs were frozen and processed for immunohistochemistry. Most oviducts expressed MHC class II (HLA.DR) in the epithelium and in some cases this was coincident with endocytosis, but there was no statistically significant association between this expression and either endocytotic activity or the phase of the menstrual cycle. Results demonstrate that the epithelium of the human oviduct exhibits endocytic properties towards luminal soluble and particle antigens, which is not related either to MHC class II expression or to the phase of the menstrual cycle.

Adult↗

PubMed1998

Is there a mucosal immune system associated with the mammalian oviduct?

The oviduct is a key component of the reproductive system where essential states such as spermatozoa capacitation, fertilization and early embryo development take place. Recently, an additional role for the entire female reproductive tract has emerged with important implications for our understanding and management of reproductive health, namely, its role in mounting local immune responses against microbial pathogens. Most of the evidence about mucosal immune responses in the female reproductive tract is related to the vagina, with less information available for the uterus. The less known segment in this regard is the oviduct, which prompted us to review and summarize the current state of knowledge on the immune system at the level of the mammalian oviduct. A comprehensive search was conducted in Medline and--for the last two years--also in Current Contents. Result demonstrate that the mammalian oviduct is endowed with many of the elements that characterize a mucosal immune system. However, there are gaps in our knowledge that, in addition to important interspecies differences, make it essential to explore further some fundamental questions regarding this system.

Animals↗

PubMed1998

Lactation inhibits the potentiating effect of galanin upon the GnRH-induced LH release observed in diestrous-1 rat.

Recent demonstrations of no changes in hypothalamic gonadotropin releasing hormone (GnRH) gene expression and GnRH levels detected at the pituitary gland in diestrous and lactating rats, indicate that lactational hypogonadotropism in this species is not associated with inhibition of hypothalamic GnRH synthesis and secretion. Hypothalamic galanin potentiates GnRH effects on luteinizing hormone (LH) secretion in male and cycling rats. To explore the interaction between GnRH and galanin during lactation, we studied in vitro the effects of pulsatile stimulation with those peptides upon LH synthesis and secretion from rat pituitaries on diestrous 1 or day 10 of lactation. Hemipituitaries were separately incubated in 1 ml Dulbecco's Minimal Essential Medium supplemented with 1% penicillin-streptomycin and fetal calf serum, at 37 degrees C in 5% CO2-air. The hemipituitaries were stimulated during 12 h with hourly pulses, 6 min each, of (a) gonadotropin releasing hormone (GnRH 25 ng/pulse), (b) rat galanin (600 ng/pulse), (c) GnRH plus galanin, or (d) saline. Medium was collected before each pulse to determine LH by radioimmunoassay. After the 12 h pulsatile regime total RNA was extracted and both actin and beta-LH mRNA were determined by reverse transcriptase polymerase chain reaction. There was a significant stimulation of LH secretion by GnRH (ANOVA, p < 0.001) without significant differences between diestrous and lactation pituitaries. Galanin alone did not modify LH secretion but it potentiated the effect of GnRH upon pituitaries from diestrous (p = 0.036) but not lactating rats. Neither peptide alone or its combination modified pituitary beta-LH mRNA levels. Results show that galanin regulates differently the secretion and synthesis of LH at the pituitary level. The disappearance of galanin-induced potentiation of GnRH effects upon LH secretion during lactation might contribute to the hypogonadotropism of lactation in the rat.

Animals↗

PubMed1996

Sucking pressure and its relationship to milk transfer during breastfeeding in humans.

Breast sucking pressure has been only partially characterized in humans and its quantitative relationships with milk transfer and endocrine maternal responses are unknown. A method to record sucking pressure and milk transfer during complete sucking episodes is described. A tubing connected at one end to a pressure transducer was attached to the nipple so that the baby sucked both the nipple and the catheter during breastfeeding. The transducer's signals were fed into a commercial computer system designed to digitize and analyse physiological signals. A total of 27 recordings, 13 of which were from a single breast and 14 from both breasts were evaluated. Average values for the mean and maximum sucking pressures were -50 and -197 mmHg, respectively; the median intersuck interval was 0.7 s; and duration of the sucking episode was 7 min. Diverse sucking pressure patterns were observed due to different mixes of sucking bursts with steady sucking and stable versus decreasing pressure and frequency throughout each sucking episode. The amount of milk transferred to the baby was estimated from the difference in body weight immediately before and after each episode. Milk transfer from the second breast was 58% lower than from the first; this was associated with a significant decrease in grams of milk transferred per suck or per minute without significant changes in sucking pressure. The data suggest that there is a change in the maternal physiological response to sucking between the first and second breast. This report shows the feasibility of measuring the sucking pressure developed by human babies during complete nursing episodes, and offers great potential to explore the relationships between the physical parameters of sucking and maternal physiological responses, such as hormonal changes, milk yield and duration of lactational amenorrhoea.

Breast Feeding↗

PubMed1996

Maintenance of hypothalamic GnRH release during lactation in the rat: a push-pull perfusion study.

The activity of the gonadotropin-releasing hormone (GnRH) pulse generator during lactation was assessed by direct determination of GnRH levels impinging upon the pituitary gland. Sprague-Dawley rats were implanted on day 15 of pregnancy with a push-pull perfusion cannula directed to the anterior pituitary. All implanted animals showed normal parturition, maternal behavior and lactation. Push-pull perfusions were performed in 15 rats suckling 11.0 +/- 0.8 pups (range 4-15) on day 7-20 of lactation and repeated on diestrous 1 after weaning in some of the same animals. GnRH content of the samples was assayed by RIA. GnRH pulses were clearly detected during lactation. Mean GnRH secretion rate was 1.9 +/- 0.3 pg/10 min (chi +/- SE, range between 0.5 and 3 pg/10 min) and interpulse interval was 37.5 +/- 1.7 min (range between 27 and 50 min). There was a significant decrease of about 19% in the interpulse interval after weaning. There was no significant difference in GnRH pulse amplitude nor in GnRH secretion rate between lactation and diestrous. These results demonstrate that nursing does not suppress the GnRH pulse generator in the rat.

Animals↗

PubMed1994

Effects of progesterone pretreatment on fertility of gilts mated at an induced pubertal estrus.

The effects of progesterone (100 mg/d, im) on pubertal fertility were examined in 247 gilts over 3 experiments. In the first experiment, 128 gilts were exposed to progesterone for 0, 2, 4 or 8 d before receiving PMSG (750 IU) 1 d later. The number of large (>4mm) follicles or corpora lutea (CL) were determined on the day of PMSG injection, Day 0 (onset of estrus), Day 1 or Day 10 (n=8). In the second experiment, embryonic survival was observed in 68 gilts after induction of estrus with PG600 (400 IU PMSG, 200 IU hCG). Vehicle or progesterone was previously administered for 2 d to these gilts, and they were allowed 1, 2, or 3 d between the last progesterone injection and PG600. In Experiment 3, a field trial was conducted in which 51 gilts received vehicle or progesterone for 2 d, followed by a 3-d interval before injection of PG600 to induce estrus. The gilts were allowed to farrow. Treatment with progesterone 1 d before PMSG increased (P<0.05) the number and size of preovulatory follicles and increased (P<0.05) the number of corpora lutea. However, the percentage of gilts pregnant by Day 10, the number of embryos recovered per gilt and embryonic survival were reduced (P<0.05) with progesterone pretreatment. Utilizing a smaller dose of PMSG (750 vs 400 IU) with PG600 negated the effects of progesterone pretreatment on ovulation rate. When the interval between progesterone treatment and PG600 was lengthened to 3 d embryonic survival to Day 30 improved but was similar to that of the vehicle/PG600 treated gilts. Fertility, as defined as conception rate and litter size, was similar between gilts exposed to vehicle or progesterone. These results indicate that pretreatment with progesterone up to the day before PMSG might improve follicular development and ovulation rate at the pubertal estrus with a dose of 750 IU of PMSG but not with the 400 IU (PG600). Reducing the dose of PMSG to 400 IU and allowing for 3 d between progesterone and gonadotropin treatment reduced the incidence of uterine infections but resulted in a fertility rate similar to that of gilts receiving PG600 alone.

Journal Article↗

PubMed1994

Histomorphology, oLH and hCG receptors, and testosterone secretion in vitro in Rambouillet rams from lines in which females had been selected for low or high reproductive rate.

The objective of this study was to determine whether gross or histomorphological components of the testes, capacity and dissociation constants (Kd) of testicular oLH and hCG receptors, and gonadotrophin-stimulated testosterone secretion in vitro differed among Rambouillet rams from lines selected for low or high female reproductive rate and from rams of a random-bred control line. Lines had been selected for approximately 20 years. Data were collected from 22-month-old rams during the late breeding season. Rams among lines did not differ (P > 0.05) in gross testicular characteristics or most histomorphological characteristics. However, the percentage volume of interstitial vascular tissue was greater (P < 0.05) for rams from lines selected for low female reproductive rate than for rams from lines selected for high female reproductive rate. Receptor sites per Leydig cell and binding capacities of oLH and hCG receptors per testis, per gram of parenchyma, and per milligram of membrane protein did not differ (P > 0.05) among lines. The Kd values for oLH and hCG receptors did not differ (P > 0.05) among lines; however, receptor sites per Leydig cell, capacities of testicular parenchyma to bind gonadotrophin and Kd values were higher (P < 0.05) for oLH than for hCG receptors. Total oLH- and hCG-stimulated testosterone secretion in vitro did not differ (P < 0.05) among lines. In conclusion, selection for or against reproductive rate in Rambouillet ewes has not altered gross or most histomorphometric characteristics of the testes of male offspring, with the exception that selection against reproductive rate increased the proportion of testicular volume occupied by vascular tissue within the interstitium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Single unit components of the hypothalamic multiunit electrical activity associated with the central signal generator that directs the pulsatile secretion of gonadotropic hormones.

Vertebrate reproduction is dependent on the operation of a central signal generator that directs the episodic release of gonadotropin-releasing hormone, a neuropeptide that stimulates secretion of the pituitary gonadotropic hormones and, thereby, controls gonadal function. The electrophysiological correlates of this pulse generator are characterized by abrupt increases in hypothalamic multiunit electrical activity (MUA volleys) invariably associated with the initiation of secretory episodes of luteinizing hormone. Using cluster analysis, we extracted single units from the multiunit signals recorded from the mediobasal hypothalamus of four intact and four ovariectomized rhesus monkeys. Of the 40 individual units identified in this manner, 24 increased their frequency with the MUA volleys. The onset and termination of these single-unit bursts occurred coincidently with those of the MUA volleys in both intact and ovariectomized animals, indicating that the longer duration of the MUA volleys characteristic of the gonadectomized animals was due not to the sequential activation of different units but to the longer bursts of the individual cells. Four other units showed decreases in firing rate during the MUA volleys, while the frequency of the remainder did not change. All the examined units were active during the intervals between the volleys of electrical activity. The results indicate that the MUA volleys associated with the activity of the gonadotropin-releasing hormone pulse generator represent the simultaneous increase in firing rate of some individual hypothalamic neurons and the decrease in the frequency of others.

Action Potentials↗

PubMed1993

Additive effect of RU 486 and anordrin on pregnancy interruption in the mouse.

The effect of various doses of anordrin and RU 486, alone or combined, on serum progesterone (P) levels, fetal resorption, and recovery of ovulation was studied in mice. Each drug was given as a single sc injection on day 7 of pregnancy and autopsy was performed on days 8, 9, or 11. Serum P was normal at 24 h but fell significantly 48 h after treatment with anordrin (0.05 mg). Doses of 0.05 or 0.2 mg anordrin were effective in interrupting pregnancy in 30% and 70% of pregnant mice, respectively. RU 486, 0.01 mg per mouse, induced a pronounced decrease of P levels 24 h after treatment and interrupted pregnancy in 50% of pregnant mice. The combined treatment with submaximal doses of anordrin plus RU 486 did not further decrease P levels, but increased the proportion of mice with fetal resorptions to 90%. The combination of small doses of anordrin with RU 486 had an additive effect on pregnancy termination. The additive effect required a dose of RU 486 above the threshold level. Direct observation of aborted fetuses indicated that the resorptive process occurred earlier with RU 486 than with anordrin. Recovery of ovulation was associated with pregnancy termination in a high proportion of mice treated with either drug or their combination.

Abortion, Induced↗

PubMed1993

Sperm transport and distribution during the puberal transition in ewe lambs.

Sperm transport through and distribution within the anterior reproductive tract were evaluated at either 2 or 22 h after artificial insemination in ewe lambs at first (1E; n = 15) or third (3E; n = 14) estrus and in mature (MAT; n = 12) ewes. Each ewe was inseminated immediately upon detection of estrus with 7.5 x 10(8) progressively motile sperm placed into the external os cervix. Ewes were hysterectomized at either 2 or 22 h after insemination. Sperm were recovered from the uterus, isthmi, and ampullae by flushing with sterile .9% saline. The distribution of sperm recovered from the uterus, isthmus, and ampulla did not differ (P > .10) among 1E, 3E, and MAT ewes at either 2 or 22 h. However, there was a tendency (P = .08) for more sperm to be recovered from the anterior reproductive tract in 3E and MAT ewes than from that in 1E ewes. There was a time of hysterectomy x anatomical segment interaction (P < .05) for percentage of sperm recovered of the total number of sperm in the inseminate because more sperm were recovered from the isthmus and ampulla at 22 h than at 2 h after insemination. Percentages of 1E, 3E, or MAT ewes from which sperm were recovered from the anterior reproductive tract did not differ (P > .10). However, sperm were recovered from the oviducts in a greater (P < .05) percentage of ewes at 22 h after insemination than at 2 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Cortisol and prolactin concentrations during three different seasons in relocated Brahman and Hereford bulls.

The objective of this study was to evaluate seasonal changes of cortisol and prolactin (PRL) concentrations in Brahman and Hereford bulls moved to locations that differ in geographical and environmental conditions. Postpubertal Hereford bulls from Montana (n = 15) and Nebraska (n = 15) and Brahman bulls from Texas (n = 18) were located in or relocated to Montana, Nebraska or Texas so that each location had 5 Montana Herefords, 5 Nebraska Herefords and 6 Texas Brahman bulls. Blood samples were collected at 20-minute intervals for 8 hours in November (Fall 1), April (Spring) and November (Fall 2) of the next year. These dates corresponded to 6, 12 and 18 months, respectively, after relocation in May of the first year. Cortisol concentrations were higher (P<0.05) in Fall 1 than in Fall 2 and were higher (P<0.05) for bulls in Montana than for bulls in Texas. The decrease in cortisol concentrations from Fall 1 to Fall 2 was negatively related (P<0.05) to age and weight. There was a three-way interaction (P<0.05) of breed-type origin, location and season for PRL concentrations. Seasonal patterns of PRL concentrations differed between relocated Texas Brahman and Hereford bulls, and patterns for relocated bulls differed from those of the nonrelocated bulls. Seasonal patterns of PRL were influenced to a greater extent by relocation in Texas Brahman bulls than in Hereford bulls.

Journal Article↗

PubMed1992

Effects of stress upon plasma estradiol and progesterone levels and the rate of oviductal embryo transport in the rat.

The possibility that changes in sex steroid levels associated with stress could alter the rate of oviductal embryo transport was investigated in the rat. To this end, the effect of cold-swimming and cold-restraint upon estradiol (E2) and progesterone (P) serum levels and embryo transport were assessed. Swimming in water at 16 degrees C for 10 min two or four times between 16:00 and 22:00 h on day 3 of pregnancy caused a modest acceleration of embryo transport that was not associated with decreased fertility. Restraint at 10 degrees C for 2 h between 13:00 and 15:00 h on the first 4 days of pregnancy did not affect embryo transport. Both stimuli increased corticosterone serum levels. Cold-swimming produced a severe hypothermia as compared to cold-restraint and increased serum E2, decreasing significantly the ratio P/E2. Cold-restraint increased the P/E2 ratio. When rats swam in cold water for 10 min twice and were rewarmed by immersion in water at 38 degrees C during 20 min, embryo transport was accelerated despite that no changes occurred in the blood levels of sex steroids. It is concluded that oviductal embryo transport is minimally affected by stress in the rat and that the effect of acute immersion may be independent of alterations in circulating sex steroid levels.

Animals↗