Bovine viral diarrhea virus cyclically impairs long bone trabecular modeling in experimental persistently infected fetuses.

Persistent infection (PI) with bovine viral diarrhea virus (BVDV) has been associated with osteopetrosis and other long bone lesions, most commonly characterized as transverse zones of unmodeled metaphyseal trabeculae in fetuses and calves. This study was undertaken to characterize the morphogenesis of fetal long bone lesions. Forty-six BVDV-naïve pregnant Hereford heifers of approximately 18 months of age were inoculated with noncytopathic BVDV type 2 containing media or media alone on day 75 of gestation to produce PI and control fetuses, respectively, which were collected via cesarean section on days 82, 89, 97, 192, and 245 of gestation. Radiographic and histomorphometric abnormalities were first detected on day 192, at which age PI fetal long bone metaphyses contained focal densities (4 of 7 fetuses) and multiple alternating transverse radiodense bands (3 of 7 fetuses). Day 245 fetuses were similarly affected. Histomorphometric analysis of proximal tibial metaphyses from day 192 fetuses revealed transverse zones with increased calcified cartilage core (Cg.V/BV, %) and trabecular bone (BV/TV, %) volumes in regions corresponding to radiodense bands (P < .05). Numbers of tartrate resistant acid phosphatase positive osteoclasts (N.Oc/BS, #/mm(2)) and bone perimeter occupied (Oc.S/BS, %) were both decreased (P < .05). Mineralizing surface (MS/BS, %), a measure of tissue level bone formation activity, was reduced in PI fetuses (P < .05). It is concluded that PI with BVDV induces cyclic abnormal trabecular modeling, which is secondary to reduced numbers of osteoclasts. The factors responsible for these temporal changes are unknown but may be related to the time required for osteoclast differentiation from precursor cells.

Transplacental infection with non-cytopathic bovine viral diarrhoea virus types 1b and 2: viral spread and molecular neuropathology.

Infection with bovine viral diarrhoea virus (BVDV) represents a reproducible natural animal model in which to study mechanisms of transplacental viral infection. In the present study, BVDV-seronegative heifers were challenged intranasally with non-cytopathic BVDV of genotype 1b or 2. Fetuses were retrieved by caesarean section 7-114 days post-challenge of the dam and subjected to virological, histopathological and immunohistochemistry(IHC) studies. Gross and histopathological changes were only seen in fetuses infected at gestational age 75-85 days and retrieved at gestational age 190 days. Viral antigen could be detected in most tissues from 14 days post-infection, but the primary target organs for histopathological changes were brain, liver and spleen. In the brain, microscopical changes included leucomalacia and macrophage infiltration of meninges and neuropil. Viral antigen was detected in neurons, oligodendrocyte precursors and infiltrating macrophages. IHC revealed normal to slightly increased expression of hypoxia-inducible factor-1alpha (HIF-1alpha) in the infected fetuses, with evidence of neuronal apoptosis and induction of inducible nitric oxide synthase (iNOS) and phospho-p38alpha mitogen-activated protein kinase (MAPK). These findings suggest that hypoxia may play only a limited role in the pathogenesis of the neural lesions. By contrast, virus-induced cytokine cascades, as part of the fetal innate immune response, and apoptosis of neurons and glial precursor cells may be central to the development of lesions.

Regulation of interferon-stimulated genes in peripheral blood leukocytes in pregnant and bred, nonpregnant dairy cows.

In ruminants, pregnancy results in up-regulation of a large number of IFN-stimulated genes (ISG) in the uterus. Recently, one of these genes was also shown to increase in peripheral blood leukocytes (PBL) during early pregnancy in sheep. Our working hypothesis is that conceptus signaling activates maternal gene expression in PBL in dairy cattle. The objectives of this study were to characterize ISG expression in PBL from pregnant (n = 20) and bred, nonpregnant (n = 30) dairy cows. Steady-state levels of mRNA for Mx1, Mx2, beta2-microglobulin, ISG-15, IFN regulatory factor-1, and IFN regulatory factor-2 were quantified. Holstein cows were synchronized to estrus and artificially inseminated (d 0). Blood samples were collected (coccygeal venipuncture) on d 0 and 16, 18, and 20 d after insemination for progesterone analysis and PBL isolation. Pregnancy was confirmed by transrectal ultrasonography at approximately 40 d after breeding. A status x day interaction was detected for Mx1, Mx2, and ISG-15 gene expression. When analyzed within day, levels of mRNA for ISG-15 and Mx1 were greater in pregnant compared with bred, nonpregnant cows on d 18 and 20, respectively. Expression of the Mx2 gene increased in the pregnant group compared with bred, nonpregnant cows on d 16, 18, and 20 after insemination. beta2-Microglobulin, IFN regulatory factor-1, and IFN regulatory factor-2 were not different between groups. The results clearly indicated that components of the innate immune response are activated in PBL during the period of pregnancy recognition and early embryo signaling. The physiological implications of these changes on maternal immune function are as yet unknown; however, they do provide a unique opportunity to identify bred, nonpregnant, cows 18 d after insemination in dairy cattle.

Cloning of interferon-stimulated gene 17: the promoter and nuclear proteins that regulate transcription.

A member of the interferon-stimulated gene (ISG) family encodes a 17-kDa ubiquitin homolog called ISG17 that is induced in the bovine uterine endometrium by interferon-tau (IFN-tau) during early pregnancy. The bovine (b) ISG17 cDNA shares 30% identity with a tandem ubiquitin repeat and 70% identity with human (h) ISG15. The present experiments were designed to sequence the bISG17 gene, compare general structure with the hISG15 gene, and to identify transcription factors that were induced by IFN-tau in bovine endometrial (BEND) cells. The promoter of the bISG17 gene was similar to the hISG15 gene in placement of a tandem IFN-stimulatory response element (ISRE) at position -90, but unique in the presence of three additional ISREs at positions -123, -332, and -525. IFN-tau (25 nM) induced nuclear proteins in BEND cells that interacted with a tandem bISG17 ISRE in electrophoretic mobility shift assay (EMSA). IFN-regulatory factor-1 (IRF-1) bound to this ISRE based upon supershift EMSA using antiserum against IRF-1. IFN-tau activated STAT-1 (signal transducer and activator of transcription-1) and -2 by 0.5 h, and IRF-1 by 2 h in BEND cells. It is concluded that the bISG17 gene is similar to the hISG15 gene, retains an ISRE that interacts with IRF-1, and is possibly induced initially by the STATs and later by IRF-1 in response to IFN-tau during early pregnancy.

Molecular cloning and characterization of complementary deoxyribonucleic acids corresponding to bovine trophoblast protein-1: a comparison with ovine trophoblast protein-1 and bovine interferon-alpha II.

Bovine trophoblast protein-1 (bTP-1) is a secreted glycoprotein that consists of several forms differing slightly in mol wt and isoelectric point. It is produced by bovine conceptuses after about day 15 of pregnancy and is believed to play a key role in signalling the presence of an embryo to the mother. In this study, a series of recombinant cDNA clones corresponding to the mRNA for bTP-1 have been isolated from cDNA libraries representing day 18-19 bovine conceptus poly(A)+ mRNA. Base sequencing of several cDNAs indicated that multiple mRNAs for bTP-1 exist. Northern blotting and primer extension experiments showed that the mRNAs average about 1 kilobase in length. One apparently full-length cDNA clone consisted of 1035 bases up to the beginning of the poly(A) tail. It contained an open reading frame of 195 codons which began at a position 79 bases from the 5' end. Its entire sequence was 85% identical to that of a cDNA for the immunologically related ovine trophoblast protein-1 (oTP-1) and about 79% identical to that for a bovine interferon-alpha II (IFN alpha II). The highest conservation of sequence (greater than 90%) was noted in the 3'-untranslated sequences of the bTP-1 and oTP-1 cDNAs. The deduced amino acid sequence of bTP-1 shared 80% identity with oTP-1, between 45-55% with human, rodent, porcine, and bovine IFNs of the alpha 1 subfamily and about 70% with a bovine IFN alpha II. A single potential site for N-glycosylation was noted at Asn78. These results show that bTP-1, like its ovine counterpart oTP-1, is structurally related to the IFN alpha S. We suggest that these embryonic IFNs play a role in controlling immunoreactions at the trophoblast-uterus interface as well as triggering other maternal responses to pregnancy.

Equine endometrial gene expression changes during and after maternal recognition of pregnancy.

The mechanism for maternal recognition of pregnancy (MRP) in horses is unknown. To maintain a pregnancy, a mobile conceptus must be recognized by the uterus before d 14 postovulation (PO). This recognition prevents endometrial secretion of PGF2α on d14 through 16, which would otherwise initiate luteolysis. The objective of this study was to evaluate gene expression in the endometrium of pregnant and nonpregnant mares during and after MRP to identify possible genes involved during this time. Twelve normally cycling mares were used in a crossover design and randomly assigned to a specific collection day. Endometrial samples were collected from a pregnant and nonpregnant (nonmated) mare on cycle d 12, 14, 16, and 18 (n = 3/d) PO. Microarray analysis comparing the endometrial gene expression in pregnant and nonpregnant mares revealed no differences at d 12. Ten genes were identified to have consistently higher or lower expression levels in the endometrium from pregnant versus nonpregnant mares on d 14, 16, and 18 (P < 0.001). The expression of these 10 genes was further analyzed with real-time PCR. d 14, 16, and 18 gene expression patterns were consistent with the microarray analysis, but on d 12, 4 of the 10 were identified as differentially expressed. Endometrial samples were then collected on d 13 PO (n = 3) and processed for western blot and immunohistochemical analysis of 2 proteins due to their reproductive significance. SPLA2 and DKK1 antibody specificity were confirmed via western blot analysis but were not different in samples from pregnant and nonpregnant mares (P = 0.114 and P = 0.514, respectively) and cellular localization was examined by immunohistochemical analysis. This is the first study to describe gene expression and cellular localization in the endometrium at the time of MRP for these genes and suggests that the uterus does not prepare to support a pregnancy until d 14. The function of these genes may be critical in the process of MRP.

Polyubiquitin up-regulation in corpora lutea of prostaglandin-treated ewes.

Genes that encode mRNAs for ubiquitin are activated by cells in metabolic distress. Cytosolic proteins that consequently become conjugated to ubiquitin are targeted for degradation. We hypothesized that ubiquitin mediates the endocrine demise of the corpus luteum induced by prostaglandin (PG) F2 alpha. Indeed, polyubiquitin gene expression increased abruptly (within 2 h) in luteal tissues of ewes treated with PGF2 alpha-before the precipitous decline in glandular progesterone accumulation indicative of functional luteolysis. A corresponding elevation in ubiquitin immunostaining was localized to large (PG-sensitive) luteal cells. It is suggested that luteal progesterone biosynthesis is disrupted by ubiquitination of steroidogenic regulatory proteins-perhaps those involved in the mechanics of mitochondrial delivery and side-chain cleavage of cholesterol.

Polyubiquitin up-regulation in corpora lutea of prostaglandin-treated ewes.

Genes that encode mRNAs for ubiquitin are activated by cells in metabolic distress. Cytosolic proteins that consequently become conjugated to ubiquitin are targeted for degradation. We hypothesized that ubiquitin mediates the endocrine demise of the corpus luteum induced by prostaglandin (PG) F2alpha. Indeed, polyubiquitin gene expression increased abruptly (within 2 h) in luteal tissues of ewes treated with PGF2alpha--before the precipitous decline in glandular progesterone accumulation indicative of functional luteolysis. A corresponding elevation in ubiquitin immunostaining was localized to large (PG-sensitive) luteal cells. It is suggested that luteal progesterone biosynthesis is disrupted by ubiquitination of steroidogenic regulatory proteins--perhaps those involved in the mechanics of mitochondrial delivery and side-chain cleavage of cholesterol.

Transient ubiquitin cross-reactive protein gene expression in the bovine endometrium.

Bovine ubiquitin cross-reactive protein (boUCRP) is secreted by the endometrium from days 15 to 26 of pregnancy in response to conceptus-derived interferon-tau (IFN-tau). We hypothesized that the gene encoding boUCRP was under transcriptional control by the conceptus and IFN-tau. Northern blots using radiolabeled UCRP cDNA revealed a single UCRP transcript of approximately 700 b that was present (P < 0.05) in endometrial cells cultured with 25 nM rboIFN-tau. The UCRP mRNA was not detected in endometrium on days 15, 17, 18 or 19 of the estrous cycle (n = 4 cows on each day) or in spleen, kidney, liver, corpus luteum or muscle. Bovine UCRP mRNA was detectable (P < 0.05) in endometrium from pregnant cows by day 15, reached highest levels by day 17, remained elevated on days 18, 19 and 21, and then declined to amounts on day 26 that were not detectable. Northern blot using radiolabeled ubiquitin cDNA revealed presence of the two major ubiquitin transcripts UbB (1.2 Kb) and UbC (2.6 Kb) in all tissues examined. The bovine UCRP cDNA did not cross-hybridize with these ubiquitin transcripts. We conclude that transcription of the UCRP gene is transient during early pregnancy and regulated by IFN-tau.

Pregnancy-specific protein B induces release of an alpha chemokine in bovine endometrium.

Pregnancy-specific protein B (PSPB), is secreted from binucleate trophoblast of the bovine conceptus as early as day 15 of pregnancy. The objective of this experiment was to determine if PSPB induced uterine proteins. PSPB was purified from day 120 cotyledons using antibody-based affinity chromatography. Endometrium from day 14 nonpregnant cows (n = 3) was prepared for explant (3H-Leu added) culture. Radiolabeled proteins released into medium were dialyzed, separated using 1D-PAGE, and detected using fluorography and densitometry. PSPB (0, 0.5, 5, 25 & 50 nM) caused a concentration-dependent increase in the release of a radiolabeled 8-kDa uterine protein. Western blots revealed that the 8-kDa protein cross-reacted with antibody against granulocyte chemotactic protein-2 (GCP-2). PSPB also induced release of GCP-2 by bovine endometrial (BEND) cells in primary culture. The induction of GCP-2 by PSPB was blocked by addition of antiserum against PSPB (1:4 molar ratio). This is the first indication that PSPB has a hormonal role in inducing GCP-2, an alpha chemokine that also is induced by interferon-tau during early pregnancy. This chemotactic cytokine may be integral to mediating adhesion, inflammation and angiogenesis associated with early implantation.

alpha 1-Adrenergic receptor binding in the spontaneously hypertensive rat.

Increased sympathetic outflow from the central nervous system to the periphery may contribute to the initiation of hypertension in spontaneously hypertensive rats (SHR). As this alteration in sympathetic activity may be mediated in part by alpha-adrenergic receptors in the central nervous system, the current study examined alpha 1-adrenergic receptors in various brain areas of SHR and normotensive Wistar-Kyoto control rats (WKY). The alpha 1-adrenergic receptor number and apparent affinity constants of brain sections of both young prehypertensive animals (4 weeks old) and mature hypertensive animals (12 weeks old) were studied with the alpha 1-adrenergic receptor antagonist [3H]WB-4101 to label the alpha-adrenergic receptor. Five brain regions were studied: rostral hypothalamus, caudal hypothalamus, locus ceruleus, nucleus tractus solitarius, and frontal cortical poles. In comparison to normotensive controls, mature hypertensive rats had a significantly greater density (p less than 0.05) of the alpha 1-adrenergic receptors in the rostral hypothalamus (+11%), caudal hypothalamus (+25%), and frontal cortical poles (+20%). Significantly greater (p less than 0.05) alpha 1-adrenergic receptor density was found in the rostral hypothalamus (+27%), caudal hypothalamus (+60%), and locus ceruleus (+39%) of the young prehypertensive SHR compared with age-matched WKY. These results indicate the presence of altered adrenergic receptor systems in the brains of genetically hypertensive animals and suggest that changes in the receptor systems take place during establishment of the hypertension.

The Interferon Stimulated Genes (ISG) 17 and Mx have different temporal and spatial expression in the ovine uterus suggesting more complex regulation of the Mx gene.

Interferon stimulated gene 17 (ISG17) and Mx are up-regulated in the ruminant uterus in response to interferon-tau (IFNtau) during early pregnancy. Recent evidence strongly indicates that expression of ISGs occur only in stroma (ST) and glandular epithelium (GE) during this time as a result of transcriptional repression by interferon regulatory factor two (IRF-2) expression in the LE. The present report tested this hypothesis by examining mRNA and protein expression of ISG17 and Mx in serial uterine cross-sections obtained from cyclic and early pregnant ewes. In situ and immunocytochemical analysis revealed that ISG17 mRNA and protein were low to undetectable, whereas Mx mRNA was expressed in the lumenal (LE) and superficial GE at all days of the estrous cycle examined. Both ISG17 and Mx mRNA increased in the stratum compactum ST between Days 11 and 13, and expression extended into the deep GE and stratum spongiosum ST on Days 15 through 17 in pregnant ewes. Interestingly the Mx gene continued to be strongly expressed in LE and superficial GE through Day 17 of pregnancy, whereas ISG17 remained low to undetectable in these cells. Collectively, this study highlights the complexity of the uterine environment by unequivocally illustrating differential temporal and spatial expression of the IFN-responsive genes ISG17 and Mx.

Preoperative laboratory screening in healthy Mayo patients: cost-effective elimination of tests and unchanged outcomes.

We reviewed the results of preoperative screening laboratory tests in asymptomatic healthy patients who underwent elective surgical procedures at our institution in 1988. Substantially abnormal results were found in 160 of 3,782 patients. All such abnormalities involved five tests: aspartate aminotransferase, glucose, potassium, platelet count, and hemoglobin. Thirty of the abnormal test results were predictable on the basis of the history or physical examination. The abnormal test result prompted further assessment in 47 patients. No surgical procedure was delayed, and no association was noted between adverse outcome and any preoperative laboratory abnormality. Because of our findings in this analysis and similar studies on specific tests from other institutions, we no longer require preoperative laboratory screening tests for healthy patients.

Collagen gene expression in rat left ventricle: interactive effect of age and exercise training.

Whether or not exercise training of sufficient intensity and duration to produce left ventricle (LV) hypertrophy also regulates deposition of interstitial collagen and cross-linking at the pretranslational level is unknown. Therefore, the effects of exercise training on gene expression for the two principal fibrillar collagens in LV, types I and III, were assessed in young adult (5 mo), middle-aged (15 mo), and old (26 mo) rats. We also evaluated the potential interaction of changes in mRNA for these procollagens with alterations in LV extracellular matrix characteristics by simultaneously measuring collagen concentration (hydroxyproline) and extent of mature collagen cross-linking (hydroxylysylpyridinoline, HP). Ten weeks of treadmill running resulted in LV hypertrophy and an increased maximal oxygen uptake in all three age groups of trained rats compared with sedentary controls. Percent collagen in rat LV almost doubled (P < 0.0001) from 5 to 26 mo of age, an increase unaffected by exercise training. With aging, a significant decline in expression of mRNAs for both collagen type I (P < 0.005) and type III (P < 0.001) was observed in LV free wall (LVF) but not septum (LVS). Training prevented this decline in LVF mRNAs for the two principal fibrillar collagens in middle-aged rats whereas it attenuated the decline in senescent animals. HP concentration increased significantly with aging in both LVF (P < 0.005) and LVS (P < 0.01). Training modulated this effect, but again only in LVF, so that HP was significantly lower (P < 0.05) in this region of the LV in old trained rats compared with sedentary counterparts. We conclude that exercise training modulates the effects of aging on collagen gene mRNAs and HP cross-linking regionally within the LV.

Direct effect of phenylethylamine upon isolated rat aortic strip.

Phenylethylamine (PEA) has been implicated in a number of central and peripheral nervous system disorders. Its possible mechanisms of action include stimulation via catecholamine release and direct stimulation by PEA. We have examined the effects of PEA on isolated vascular smooth muscle (VSM) to further explore the mechanism by which PEA produces contraction in this tissue. Helical strips of rat aorta were suspended in a muscle bath. Smooth muscle contractions were recorded via force transducer. PEA elicited a concentration dependent contraction from these strips with a threshold near 10(-6) M and a maximum response at 5 X 10(-3) M. Pretreatment of rats with reserpine dramatically reduced the norepinephrine (NE) content of kidney, heart and spleen of these animals but did not prevent the action of PEA on VSM. The presence of phentolamine (10(-4) M) completely blocked the strip response to PEA. The presence of propranolol (10(-7) or 10(-4) M) altered but did not block the VSM response to PEA. These results argue that the effects of PEA upon the aortic strip preparation involve a direct action of this amine upon VSM.

Inhibition of phorbol ester-induced PGF2alpha secretion by IFN-tau is not through regulation of protein kinase C.

Inhibitory effect of IFN-tau on phorbol ester (PdBu)-induced PGF2alpha secretion was hypothesized to be manifested by the regulation of protein kinase C (PKC) in bovine endometrial (BEND) cells. Following 12 h stimulation with PdBu, cells were unresponsive to freshly added PdBu. Pretreatment of cells with a PKC inhibitor abolished PGF2alpha secretion in response to PdBu. Therefore, PdBu induction of PGF2alpha secretion is through activation of PKC. The alpha, epsilon, iota and lambda isotypes of the PKC family were identified by Western blotting. Cells were then treated with medium alone (control), PdBu or PdBu + IFN-tau for 3 or 6 h. The PdBu-induced secretion of PGF2alpha was suppressed by IFN-tau. At 3 and 6 h, PKCalpha and PKCepsilon were detected both in the cytosolic and membrane fractions of unstimulated cells. There was a clear reduction of PKCalpha in the cytoplasm induced by PdBu and PdBu + IFN-tau at 3 and 6 h. The total abundance (cytoplasm and membrane fractions) of PKCalpha was lower in the PdBu + IFN-tau than PdBu alone. These temporal responses indicate a PKCalpha responsiveness of BEND cells to PdBu and PDBu + INF-tau with some evidence that IFN-tau causes a slight but detectable reduction in PKCalpha when added with PdBu. However, IFN-tau-induced decrease in the total abundance of PKCalpha was not enough to affect negatively the translocation of the PKCalpha to the membrane. Therefore, IFN-tau's ability to suppress secretion of PGF2alpha is unlikely due to an interference with the PdBu-induced activity of PKC.

Inhibition by tocopherol of prostaglandin-induced apoptosis in ovine corpora lutea.

Accumulation of toxic oxidants within corpora lutea is a prelude of apoptotic cell death. Vitamin E (alpha-tocopherol) is a biological antioxidant that protects cells from the inductive effects of reactive oxygen on DNA damage and nuclear/cytoplasmic condensation that dictate apoptosis. Ewes were challenged with a luteolytic dose of PGF2 alpha on d 10 of the estrous cycle. The acute decline in circulatory progesterone indicative of the onset of functional luteolysis was not affected by systemic administration of alpha-tocopherol; however, corpora lutea consequently (beyond 24 h) rebounded from the steroidogenic insult. Luteal tissues obtained at 24 h after PGF2 alpha revealed that internucleosomal DNA fragmentation and cellular collapse were inhibited by alpha-tocopherol. These observations indicate that regressive corpora lutea can be spared from terminal involution by diminishing the apoptotic influence of luteolytic hormone with an antioxidant.

Uterine-conceptus interactions and reproductive failure in cattle.

The dialogue between trophectoderm cells of the conceptus and epithelial cells of the endometrium is critical to CL maintenance and embryo survival. The signal transduction mechanisms by which bovine interferon (IFN)-tau regulates cyclooxygenase (COX)-2 expression and secretion of prostaglandin F2alpha (PGF2alpha) in bovine endometrial (BEND) cells is examined. Stimulation of Protein Kinase C with a phorbol ester (phorbol 12, 13 dibutyrate [PDBu]) activates COX-2 gene expression and PGF2alpha secretion via the mitogen-activated protein kinase (MAPK) pathway. Interferon-tau attenuates PDBu activation of PGF2alpha secretion, but this inhibitory effect appears to be independent of the MAPK pathway. Embryonic IFN-tau, acting through a Type I IFN receptor, activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway resulting in activation or repression of interferon-stimulated genes. Experimental evidence is provided that IFN-tau regulation of STATs regulates gene expression of COX-2 in a manner that decreases secretion of PGF2alpha. Maternal regulation of the antiluteolytic pathway is discussed relative to the ability of the polyunsaturated fatty acid, eicosapentaenoic (EPA), to decrease endometrial secretion of PGF2alpha and progesterone to increase both conceptus development and IFN-tau secretion.

Bovine corpus luteum regression and estrous response following treatment with alfaprostol.

Two trials evaluated bovine corpus luteum (CL) regression and estrous response following treatment with alfaprostol (AP), a prostaglandin F2 alpha analogue. Expression of at least one estrous cycle (16 to 26 d) and a palpable mid-cycle CL were required prior to random assignment of females to receive 0, .38, .75, 1.50 or 2.25 mg AP/100 kg body weight. Alfaprostol was evaluated in Brahman cows and heifers that were treated on d 11 to 13 (trial 1) and in Simmental X Brahman-Hereford (crossbred) heifers that were treated on d 8 to 10 or d 11 to 13 of the estrous cycle (trial 2). In trial 1, Brahman heifers appeared to require a higher AP dose (greater than .38 mg/100 kg body weight) to elicit luteolysis and expression of estrus than Brahman cows. Alfaprostol treatment (greater than or equal to .75 mg/100 kg body weight) induced (P less than .0001) luteolysis followed by estrus in Brahman cows and heifers. In trial 2, crossbred heifers that received AP on d 8 to 10 appeared to require a higher dose of AP (greater than .38 mg/100 kg body weight) to elicit luteolysis and estrus than heifers that received AP on d 11 to 13 of the estrous cycle. Alfaprostol treatment greater than or equal to .75 mg/100 kg body weight on d 8 to 10 and d 11 to 13 of the estrous cycle induced (P less than .0001) luteolysis followed by estrus in crossbred heifers.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for seasonal and nutritional modification of ovarian and pituitary function in crossbred heifers and Brahman cows.

Alterations in endocrine response in the bovine female after consumption of monensin or exposure to changes in season were observed in two experiments. Thirty-three monensin-fed (M) or control (C) crossbred heifers in Exp. 1A were given a porcine follicle stimulating hormone (FSH-P) challenge on d 16 to 21 postestrus. Nine M heifers ovariectomized (OVX) on d 11 after the FSH-challenged estrus had a greater number of smaller corpora lutea (CL; P less than .005) than did nine d 11 OVX C heifers. Serum progesterone (P4) concentrations were greater in M on d 5 through 13 following the FSH-challenged estrus (P less than .001). Seven M and seven C Brahman cows in Exp. 1B given an identical FSH challenge had similar increases in CL number and size. In Exp. 2, blood samples were obtained from 14 M and 13 C Brahman cows during winter (WI), early spring (ESp) and late spring (LSp) to characterize the preovulatory LH surge. During each seasonal period, blood samples were taken hourly from estrus through 24 h postestrus for each cow. Only one of five WI-C cows had a preovulatory LH surge compared to five of five WI-M cows (P less than .01). No differences were found in the number of cows having an LH surge in ESp or LSp groups. Analysis of combined WI and ESp group values indicated a difference in timing of the LH surge by M or C treatment. Of those cows that had an LH surge, only three of 10 C had peak LH values later than the first sample taken, compared with 10 of 15 M (P less than .10). A heightened LH response was detected in M cows in all comparisons of LH surge profiles (P less than .005). Concurrent with changes in season from WI to ESp was an increase in number of C cows having an LH surge (one of five vs nine of 10; P less than .005), and elevated LH values in ESp-C and M groups compared with WI-C and M groups (P less than .05). Midluteal blood samples taken after every estrus indicated P4 to be greatest in February M cows (P less than .10) and P4 tended to be greater in February and lower in January for all groups. Conclusions are that monensin affects the FSH-P-induced ovulation rate of bovine females of all ages. Seasonal effects occurring between the shortest and longest days of the year exert their greatest influence on the preovulatory LH surge and P4 concentrations in Brahman cows between January and March. Seasonal effects appear to be partially modulated by nutritional factors.