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Biomedical subjects

W T Bosu

Publications and source records attributed to W T Bosu.

At least 19 recordsLinked to original sources
PubMed2001

Ovarian follicle apoptosis at the onset of standing estrus in virgin and repeat-breeder dairy heifers.

There is evidence that repeat breeding in dairy cattle can be caused by both extrinsic, environmental factors and intrinsic, animal factors. In repeat-breeder heifers (RBH), disturbed endocrine patterns and estrous events result in a subsequent decreased fertility associated with delayed ovulation. Whether infertility is also due to the presence of an unsuitable follicular environment impairing normal fertilization, remains to be determined. At the onset of standing estrus, ovaries were obtained from 7 strictly defined RBH and 5 virgin heifers (VH) of the Swedish Red and White breed. Detection of apoptosis in the preovulatory and three subordinate follicle walls was done by using the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) technique at light microscopy level. The follicles were histologically assessed for degree of atresia. The ultrastructure of the follicle wall and recovered oocytes was studied using transmission electron microscopy. The overall degree of apoptosis in membrana granulosa and theca interna of preovulatory and subordinate follicles did not differ between RBH and VH, but the numbers of TUNEL-positive cells differed significantly between preovulatory and subordinate follicles in both RBH and VH. There was a strong relationship between density of apoptotic cells and degree of atresia. No differences in follicle wall apoptosis nor morphology were detectable, suggesting that repeat breeder heifers enter standing estrus with the same morphological prerequisites as normal animals, considering follicular structure.

Animals↗
PubMed1996

Natural and endotoxin-induced atresia of preantral and early antral follicles is characterized by DNA internucleosomal cleavage.

Preantral follicles (PAF) and early antral follicles (EAF) were isolated from bovine ovaries and classified under a stereomicroscope as atretic or healthy. The atretic follicles were all considered as group I (in vivo atresia), whereas healthy follicles were assigned to five groups (group II, in vivo normal control; group III, in vitro normal control; group IV, in vitro induced atresia; groups V and VI, Lipopolysaccharide (LPS)-induced atresia in vitro). Group I and II follicles were immediately snap-frozen (-70 degrees C) until DNA extraction, whereas group III-VI follicles were incubated (39 degrees C, 5% CO2, 95% air) for periods up to 72 hr under various conditions. Group III follicles were maintained in complete medium (M199, bovine calf serum, sodium pyruvate, epidermal growth factor, insulin, transferrin, sodium selenite, penicillin, streptomycin, and amphotericin), whereas group IV follicles were incubated in the same medium, but without serum. Group V and VI follicles were maintained in complete medium, but in the presence of LPS (10 or 50 micrograms/ml, respectively). Results showed that follicles incubated in the absence of serum and those exposed to both doses of LPS became atretic. DNA isolated from all atretic follicles showed fragmentation typical of that described for apoptosis; this was also confirmed by in situ DNA labeling and histology. Atretic follicles did not produce estradiol (P < 0.001), but progesterone values increased with follicle size (P < 0.001) and time of incubation (P < 0.001). We concluded that in the absence of serum or in the presence of LPS, follicles undergo atresia via apoptosis.

Animals↗
PubMed1996

Endotoxin-induced apoptosis in ovarian follicles is partially blocked by 2-methylthioATP or 2-chloroATP.

The purposes of this study were to determine how early in time endotoxin can trigger apoptosis of bovine ovarian follicles in vitro, and to further characterize if these inductions are mediated via adenine nucleotides and the P2 purinergic receptors. Healthy preantral and early antral follicles (400 and 700 microns) isolated from bovine ovaries were sandwiched between two layers of collagen gel and incubated (39 degrees C, 5% CO2, 95% air) for various time periods up to 72 hr, floating in complete medium with either 2-methylThioATP or with 2-ChloroATP, or with or without LPS (10 or 50 micrograms/ml), or with combinations of LPS with 2-MethylThioATP or 2-ChloroATP. Data from histological examination, and in situ detection of apoptotic DNA cleavage, showed that by 2 hr from start of incubation, both doses of LPS had triggered apoptosis of granulosa cells (P < 0.001), and simultaneously decreased estradiol concentrations to nondetectable levels (P < 0.001), but progesterone values increased (P < 0.001) with time of incubation. Both 2-MethylThioATP and 2-ChloroATP inhibited (P < 0.001) LPS (10 and 50 micrograms/ ml)-induced apoptosis by 30% to 100%. We concluded that adenine nucleotides play a fundamental role in endotoxin-induced apoptosis/atresia of bovine follicles, probably via the P2 purinergic receptors. It is possible that during the first 2 hr of incubation, the apoptotic events associated with LPS-induced follicular atresia might not be detectable with the procedures used in this study.

Adenine Nucleotides↗
PubMed1996

Adrenocortical function in the domestic cat during treatment with levonorgestrel.

Levonorgestrel was administered via a subcutaneous, slow-release silastic implant to 10 queens. Five other queens served as controls. Their adrenocortical function was assessed by the adrenocorticotrophic hormone (ACTH) stimulation test before and after one, two, six and 12 months of treatment. In addition, the gross anatomy and histology of the adrenal gland were examined post mortem in six of the treated cats. In both the control and treated queens the plasma cortisol concentrations (pre and post ACTH) were significantly different (P < 0.05) at different times. However, there were no significant differences between the plasma cortisol concentrations (pre and post ACTH) of the treated and control queens. No gross or microscopical abnormalities were visible in the adrenal glands of the treated queens.

Adrenal Cortex↗
PubMed1995

Endotoxin stimulates secretion of cortisol, but not ACTH in heifers pretreated with suppressive doses of a glucocorticoid.

The ability of triamcinolone acetonide (TA) to suppress actions of lipopolysaccharide (LPS) in the pituitary-adrenal axis was examined in Holstein heifers. The study was carried out using repeated measure/split plot factorial design involving four heifers which were repeatedly used in four experimental groups thus yielding eight experimental units (EU). Each EU received two treatments, the first at zero hour and the second at 28 h. Heifers in Groups I (n = 2) and II (n = 2) were given sterile saline as treatment (TRT) 1. For TRT 2, group I was given sterile saline, and group II received Escherichia coli lipopolysaccharide (LPS). In group III (n = 2) and group IV (n = 2) triamcinolone acetonide was given as TRT 1. Sterile saline (SAL) was TRT 2 for GP III, and group IV heifers received LPS. Administration of LPS elicited increases in concentrations of the stress hormones ACTH (P < 0.05) and cortisol (P < 0.001) in SAL-pretreated heifers. However, in TA-pretreated animals, the endotoxin could only cause increase (P < 0.001) in concentrations of cortisol, but not ACTH. Therefore, the significant response of cortisol to LPS stimulation suggest that, at doses used in this study, triamcinolone acetonide did not suppress LPS-triggered cortisol secretion from adrenal zonae fasciculata and reticularis cells. The LPS-induced ACTH response appears to have been blunted by prior administration of triamcinolone acetonide.

Adrenal Cortex↗
PubMed1994

The contraceptive effects of levonorgestrel in the domestic cat.

The effects of subdermal implantation of levonorgestrel (LNG) on reproduction were studied in domestic cats (Felis domestica). Levonorgestrel was administered via a slow-release subdermal silastic implant to 10 queens. The implants contained 16 mg of LNG and were designed to release 60 micrograms of the drug daily. Each treated queen received one implant. Five queens (control, group 1) received subdermal silastic implants containing no drug. Changes in body weight, mammary gland structure (determined by palpation), serum blood glucose concentrations, and reproductive factors (occurrence of estrous cycles, serum progesterone concentrations, and pregnancy) were monitored for 1 year. Four treated queens (treatment/recovery, group 2) were used to investigate reproductive function following 12 months of LNG treatment. To assess effects of treatment on macroscopic and microscopic anatomic features of reproductive and nonreproductive tissues, the remaining six cats (treatment/histology, group 3) were studied. Hemiovariohysterectomy was performed in two queens each at 0, 2, and 6 months of the study. Later, the remainder of the reproductive tract was harvested at necropsy (two after 2 months of treatment, two after 6 months, two after 12 months) to assess change in individual queens. Nonreproductive tissues were also examined at necropsy to determine effects of LNG in these six queens. All queens retained the implants during the period of study without detectable discomfort. Estrus was suppressed and no pregnancies were recorded in the four LNG-treated cats that were housed with a male. Treatment with LNG had no effect on body weight, physical mammary gland structure, or serum blood glucose concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Serum cortisol changes in heifers induced by lipid X: a monosaccharide precursor in the biosynthesis of Gram-negative endotoxin.

An experiment was conducted to measure the changes in serum cortisol and luteinising hormone (LH) concentrations in heifers during the luteal phase of the oestrous cycle after the administration of lipid X and Gram-negative endotoxin. Nine heifers whose oestrous cycles were synchronised with prostaglandin F2 alpha were assigned at random on day 10 after the second prostaglandin injection to one of the following groups. Group 1 heifers (n = 3) received 5 micrograms kg-1 bodyweight of Escherichia coli endotoxin as an intrauterine infusion and one hour later received an intravenous injection of lipid X (5 micrograms kg-1 bodyweight). The treatment was reversed in group 2 heifers (n = 3), endotoxin was administered one hour after the lipid X treatment. Group 3 heifers (n = 3) received endotoxin infusion and lipid X treatment at the same time. Similar dosages and routes of administration were used in all the groups for lipid X and endotoxin treatments. Blood samples were collected once every 15 minutes for seven hours, beginning once hour before and six hours after the initial treatment. In group 1 heifers there was a fourfold increase in serum cortisol concentrations within 30 minutes after both the treatments (from 6.5 to 24.6 ng ml-1 and from 7.3 to 29.5 ng ml-1 respectively). In group 2 heifers the cortisol concentrations increased from the baseline concentrations of 7.2 to 33.2 ng ml-1 within 30 minutes after lipid X treatment and remained at 22.5 ng ml-1 during endotoxin treatment. There was a further increase in cortisol concentrations (28.9 ng ml-1) after the endotoxin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Temporal changes in metabolites of prostanoids in milk of heifers after intramammary infusion of Escherichia coli organisms.

A study was conducted to characterize the changes in the concentrations of three metabolites of prostanoids in the milk of a) heifers (n = 14; control) inoculated with Escherichia coli (E. coli) organisms into the udder and b) in heifers (n = 10; treatment) vaccinated with E. coli bacterin and treated similar to control heifers. Milk samples were obtained from the challenged quarter and analyzed for the concentrations of stable metabolites of thromboxane A2 (TXB2), prostacyclin (PCM) and prostaglandin E2 (PGEM) using radioimmunoassays. In control heifers milk TXB2 concentrations were significantly higher (P = 0.03) compared to treated heifers. Milk PCM concentrations increased significantly (P = 0.02) in control and treated heifers after the respective treatments, however, differences between the two groups were not significant. Milk PGEM concentrations also increased significantly (P = 0.02) in control and treated heifers after the respective treatments, and there were no differences between the two groups. Results of the present study suggest that, the prostanoids have a role in the pathophysiologic process of coliform mastitis.

Animals↗
PubMed1990

Absorption of Escherichia coli endotoxin (lipopolysaccharide) from the uteri of postpartum dairy cows.

An experiment was conducted to test the hypothesis that Escherichia coli (E. coli ) endotoxin is readily absorbed from uteri of early postpartum cows and that the absorbed endotoxin provokes systemic relcase of prostaglandins. Eleven postpartum Holstein dairy cows (aged 3 to 7 yr) with normal puerperium were selected and divided into a treatment group (n=7), which received intrauterine infusions of E. coli endotoxin, and a control group (n=4), which received intrauterine infusions of 10 ml of saline on Days 5 and 20 post partum. Blood samples were collected once every 30 min for 6 h starting from the time of infusion. Harvested sera samples were analyzed for concentrations of stable metabolites of prostacyclin (PCM), prostaglandin F(2alpha) (PGFM), and thromboxane A(2) (TXB(2)). Plasma samples were qualitatively tested for the presence of endotoxin. Endotoxin was detected in the plasma samples of cows that received endotoxin on Day 5 post partum 4 h after the infusion. Endotoxin was not detected in any of the samples from control cows on Days 5 and 20 post partum or from treatment group cows on Day 20 post partum. Cows treated on Day 5 post partum showed increases in serum PGFM concentrations from 710 +/-64pg/ml to peak concentrations of 1223 +/- 47 pg/ml within 2 h, followed by a decline to baseline concentrations within 4 h. The amount of PGFM released in treated cows on Day 5 post partum was higher (P < 0.05) than in control cows on Day 5 or in treated and control cows on Day 20 post partum. Serum PCM concentrations increased from 156+/-24 pg/ml to peak concentrations of 1348+/-127 pg/ml within 1 h. The amount of PCM released in treated cows on Day 5 postpartum was higher (P< 0.05) than in control cows on Day 5 or in treated and control cows on Day 20 post partum. The TXB(2) concentrations increased from 315+/-38 pg/ml to peak concentrations of 5043 +/- 242 pg/ml within 1 h and fell to baseline concentrations within 5 h. The amount of TXB(2) concentrations released in treated cows on Day 5 post partum was significant (P < 0.05) compared with those of cows in the other groups. The results support the hypothesis that uteri of early postpartum cows are capable of absorbing endotoxin, and the absorbed endotoxin provokes changes in the serum concentrations of prostanoids.

Journal Article↗
PubMed1990

Site of action for endotoxin-induced cortisol release in the suppression of preovulatory luteinizing hormone surges.

The study was conducted to identify the mechanisms of endotoxin/cortisol action in the suppression of preovulatory LH surges in heifers infused with Escherichia coli (E. coli ) endotoxin. The hypotheses tested were that 1) endotoxin stimulates the release of progesterone, possibly from the adrenal leading to the LH blockade; 2) cortisol released in response to endotoxin infusion blocks the synthesis of estradiol at the ovarian level, culminating in a failure of the LH surge. Eight Holstein heifers were given two injections of prostaglandin F(2alpha) (PG), 11 d apart, to synchronize estrus. Starting from 25 h after the second injection of PG (PG-2), the uterus of each heifer was infused either with 5 ml of pyrogen-free water (control, n = 3) or with E. coli endotoxin (5 mug/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 h for 10 treatments. Blood samples were obtained every 15 min for 1 h before infusion and again 2 h after each infusion, then hourly until 1 h before the next infusion. After the tenth infusion, blood was collected daily until estrus. Serum progesterone concentrations remained at baseline values (< 1 ng/ml) in control and treated heifers. The total amount of progesterone measured starting 24 to 84 h after PG-2 injection was not different between control and treated heifers (P 0.05). In the control heifers, serum estradiol concentrations remained basal (< 10 pg/ml) until 4 h before the LH surge. Serum estradiol concentrations increased to 20 +/- 5.6 pg/ml, 4 h before the LH surge in control heifers (LH surge occurred 60 to 66 h after the PG-2 injection). There were no changes in serum estradiol concentrations in treated heifers during the sampling period, and the concentrations remained < 10 pg/ml. The total amount of estradiol measured in control heifers was higher (P < 0.05) than in treated heifers. The results if this study suggest that increases in cortisol concentrations after the infusion of endotoxin might block the synthesis of estradiol at the ovarian level, resulting in the failure of a preovulatory LH surge to occur.

Journal Article↗
PubMed1990

The effect of Escherichia coli endotoxin on luteal function in Holstein heifers.

This study was undertaken to elucidate the possible role of endotcxin in mediating premature luteolysis in the well- documented phenomenon of short estrous cycles in postpartum dairy cows. Four groups of Holstein heifers (n = 4 to 6 each) received either intrauterine infusion of sterile culture medium (Group I); intrauterine infusion of Escherichia coli (E. coli ) endotoxin (5 mug/kg) in sterile culture medium (Group II); intrauterine administration of 10 ml of a 24-h culture of a strain of E. coli isolated from the uterus of a cow with metritis (approximately 10(9) colony forming units/ml; Group III); or intravenous administration of E. coli endotoxin (5 mug/kg; Group IV) on Day 7-9 of the estrous cycle. Blood samples were collected every 48 h during the pretreatment estrous cycle and up to the administration of the experimental treatment, thereafter 4-h samples were collected for 5 d. Sample collection was then performed every 48 h for the remainder of the treatment cycle and the post treatment cycle. Serum concentrations of progesterone and plasma concentrations of 15-keto-13, 14-dihydroprostaglandin F(2alpha) (PGFM) were determined by radionmmunoassay. Intrauterine infusion of endotoxin had no effect on the cycle length or on hormone concentrations, while infusion of viable E. coli organisms tended to shorten the estrous cycle. Intravenous administration of endotoxin produced a sharp increase in both progesterone and PGFM concentrations, followed by a transient decrease in progesterone concentrations. Cycle length remained unchanged. It was concluded that the intact endometrium prevents the uptake of endotoxin although pathogenic E. coli organisms may disrupt the endometrial integrity sufficiently to shorten the estrous cycle by premature luteolysis. It is postulated that intravenous administration of endotoxin influences luteal function by the activation of the arachidonic acid cascade, by a direct effect on the corpus luteum, or via other mediators.

Journal Article↗
PubMed1990

Quantitative morphologic study of the pituitary and thyroid glands of dogs administered L-thyroxine.

To determine the effects of long-term thyroxine treatment, histomorphometric analysis was performed on the pituitary and thyroid glands of healthy dogs, dogs treated for 9 weeks with a replacement dose of L-thyroxine, and dogs at 6 weeks after cessation of thyroxine treatment. In treated dogs, the volume density of thyrotropes decreased during thyroxine treatment and increased 6 weeks after cessation of treatment, compared with thyrotropes of healthy nontreated dogs. The activity of the thyroid gland was decreased in dogs during thyroxine treatment, as evidenced by decreases in epithelial volume density, epithelial height, and follicular area, and increase in colloid volume density, compared with thyroid gland activity in nontreated dogs. After cessation of thyroxine treatment, the thyroid gland had decreased colloid area, follicular area, and epithelial volume density, and increased interstitial volume density, compared with the thyroid gland of healthy nontreated dogs. Thyroxine treatment resulted in suppression of pituitary thyrotropes and thyroid follicular activity.

Animals↗
PubMed1990

Thyroid function tests in euthyroid dogs treated with L-thyroxine.

The effects of treatment with L-thyroxine (1 mg/m2 of body surface/d, PO, for 8 weeks) on the thyroxine (T4) and triiodothyronine (T3) responses to thyrotropin (TSH) and thyrotropin-releasing hormone (TRH) administration were determined in 10 euthyroid Beagles; 4 other dogs acted as controls. The TSH response test was performed before treatment and at weeks 2, 4, and 8 of treatment in all dogs and at 2 and 4 weeks after cessation of treatment in 6 dogs. The TRH response test was performed before treatment and at week 6 of treatment in all dogs and at 5 weeks after cessation of treatment in 6 dogs. Suppression of the T3 response to TSH was evident at treatment week 2, whereas the T4 response was suppressed at week 4 and remained suppressed for the duration of the study. Four weeks after stopping treatment, T4 and T3 responses to TSH in 2 dogs were within the hypothyroid range. The T4 response to TRH was completely suppressed after 6 weeks of thyroxine treatment, but returned to pretreatment values by 5 weeks after cessation of treatment. Suppression of thyroid and pituitary function is evident after administration of a replacement dose of L-thyroxine to euthyroid dogs.

Animals↗
PubMed1989

Surgical management of urovagina and associated infertility in a cow.

Severe urovagina, secondary to a calving injury, was diagnosed as the cause of necrotizing endometritis and infertility in a Holstein cow. Urethral extension surgery resulted in resolution of the urovagina and endometrial recovery. Temporary paresis of the bladder was a postsurgical complication. The cow conceived promptly after insemination, but suffered similar injuries subsequently during calving.

Animals↗
PubMed1989

Temporal changes in serum prostaglandin F2alpha and oxytocin in dairy cows with short luteal phases after the first postpartum ovulation.

Luteolysis in the cow depends upon an interaction between prostaglandin F2alpha (PGF2alpha) and oxytocin. The objectives of our study were 1) to determine oxytocin concentrations in postpartum dairy cows and 2) to identify the temporal relationship between oxytocin and PGF2alpha release patterns during luteolysis in normal and abbreviated estrous cycles in the postpartum period. Serum oxytocin and PGF2alpha metabolite (PGFM) concentrations from nine cows which had short estrous cycles (<17 d) were compared with those of six cows which had normal estrous cycles. Serum basal oxytocin concentrations in short estrous cycle cows (23.7 to 31.1 pg/ml) were higher (P<0.05) than those of normal estrous cycle cows (14.6 to 19.8 pg/ml). Oxytocin concentrations increased to peak values in both short and normal cycle cows, during luteolysis. Basal PGFM concentrations (112.2 to 137.4 pg/ml) were higher in cows with short cycle (P<0.05) than in cows with normal cycles (62.9 to 87.5 pg/ml). The increase in PGFM concentrations during luteolysis was significant in both normal cycle and short cycle cows (P<0.05). Increases in serum PGFM concentrations were always associated with increases in serum oxytocin concentrations in normal cycle and short cycle cows and the levels decreased simultaneously before the subsequent estrus. Results support the idea of a positive relationship between PGF2alpha and oxytocin concentration during the estrous cycle as well as a possible synergistic action of these hormones in the induction of luteolysis in dairy cattle.

Journal Article↗