PubMed Health⌕ Search

Biomedical subjects

L A Fitzpatrick

Publications and source records attributed to L A Fitzpatrick.

At least 37 records · Page 2Linked to original sources
PubMed1998

Duration of ovulation suppression with subcutaneous silicone implants containing norgestomet in Bos indicus heifers and cows.

The aim of this study is to determine the duration of suppressing oestrus or ovulation in Bos indicus heifers and cows using norgestomet (N) incorporated into a silicone implant. Twelve heifers and 18 cows undergoing oestrous cycles were allocated to one of two treatment groups (6 heifers and 9 cows per group). Animals were treated with a single subcutaneous (s.c.) silicone implant containing 3 mg of N or two identical silicone implants (6 mg of N in two silicone implants) on day 0 of the study. An analogue of prostaglandin F2-alpha was administered intramuscularly, to all animals on days 0 and 6 to induce regression of corpora lutea. Implants were removed from all animals on day 21. Animals were observed for signs of behavioural oestrus while implants were in situ and for 6 d following implant removal. Blood samples were collected on alternate days from day 0 to 20 and again on day 21 and analysed for plasma progesterone (P4). Transrectal ultrasonography was performed on days 0, 6, 10, 14, 18, 21, 24, 26,27, and along with concentration of P4 in plasma was used to confirm ovulation during the treatment period. The cumulative percentages of animals ovulating during the 21 days implants were in situ were 6.7% (3 mg of N in one silicone implant) and 0% (6 mg of N in two silicone implants)Intervals from implant removal to oestrus (mean +/- S.E.M.) did not differ significantly among animals treated with either 3 or 6 mg of N in silicone implants (46.8 +/- 7.0 vs. 55.4 +/- 7.1 h, P = 0.398). Variances in interval from implant removal to oestrus among animals treated with 3 or 6 mg of N in silicone implants were also homogeneous (P = 0.942). The mean diameter of the ovulatory follicle on day 21 was larger in the animals treated with 3 mg of N compared to animals treated with 6 mg of N in two silicone implants ( 13.1 +/- 0.8 vs. 9.7 +/- 0.7 mm, P = 0.005). We conclude that treatment with 3 mg of N in a silicone implant will suppress ovulation in Bos indicus heifers and most cows for 21 d. Six mg of N in two silicone implants will suppress ovulation for 21 d in both cows and heifers.

Animals↗
PubMed1998

Treatment with progesterone and 17 beta-oestradiol to induce emergence of a newly-recruited dominant ovulatory follicle during oestrus synchronisation with long-term use of norgestomet in Brahman heifers.

The aim of this study was to determine the effect on ovarian follicular growth and atresia, of acute treatment with either 100 mg of progesterone (n = 10), 200 mg of progesterone (n = 10), 10 mg of oestradiol + 100 mg of progesterone (n = 10), 10 mg of oestradiol (n = 10) or no treatment (n = 10), given on Day 10 of a 17-day treatment with a norgestomet implant in randomly cycling Bos indicus heifers. The fate of the dominant follicle on Day 10, emergence of the new cohort of follicles and the intervals from implant removal to ovulation were recorded by ultrasonography. Plasma concentrations of Luteinizing hormone (LH), progesterone and oestradiol were determined during the time when the norgestomet implant was in place. All treatments resulted in the emergence of a new cohort of follicles within 5 days of administration. The day of emergence of the ovulatory follicle tended to be delayed after treatment with 100 mg of progesterone (2.7 +/- 0.3 days after treatment), 200 mg of progesterone (3.7 +/- 0.5 days after treatment), 10 mg of oestradiol + 100 mg of progesterone (4.4 +/- 0.2 days after treatment) and 10 mg of oestradiol (4.6 +/- 0.4 days after treatment) compared to control heifers (1.4 +/- 1.4 days after time of treatment). The mean interval from implant removal to onset of oestrus was significantly shorter after treatment with 100 mg of progesterone (38.4 +/- 2.6 h) than after treatment with 200 mg of progesterone (61.5 +/- 3.9 h) but otherwise, the mean interval from implant removal to onset of oestrus did not differ. Oestrus synchrony, measured by the sample standard deviation of oestrus onset, was tighter in all treatment groups compared to untreated control heifers. The mean interval from implant removal to ovulation did not differ significantly between groups. The synchrony of ovulation, measured by the sample standard deviation of the interval from implant removal to ovulation, was significantly tighter after treatment with 100 mg of progesterone, 200 mg of progesterone and 10 mg of oestradiol compared to control heifers. Treatment with 10 mg of oestradiol resulted in ovulation in seven of 10 heifers before implant removal, three of which failed to ovulate after implant removal. Progesterone administered on Day 10 lowered plasma LH concentrations (P < 0.05), whereas treatment with oestradiol caused a surge of LH and ovulation. Progesterone administered with oestradiol prevented the LH surge. A combination treatment of oestradiol and progesterone given on Day 10 of a 17-day norgestomet treatment in a range of follicular states resulted in the consistent emergence of a new cohort of follicles which included the eventual ovulatory follicle.

Animals↗
PubMed1998

Superstimulation of ovarian follicular growth with FSH oocyte recovery, and embryo production from Zebu (Bos indicus) calves: effects of treatment with a GnRH agonist or antagonist.

The capacity of heifer calves of a late sexually maturing Zebu (Bos indicus) genotype to respond to superstimulation with FSH at a young age and in vitro oocyte development were examined. Some calves were treated with a GnRH agonist (deslorelin) or antagonist (cetrorelix) to determine whether altering plasma concentrations of LH would influence follicular responses to FSH and oocyte developmental competency. Brahman calves (3-mo-old; 140 +/- 3 kg) were randomly assigned to 3 groups: control (n = 10); deslorelin treatment from Day -8 to 3 (n = 10); and cetrorelix treatment from Day -3 to 2 (n = 10). All calves were stimulated with FSH from Day 0 to 2, and were ovariectomized on Day 3 to determine follicular responses to FSH and to recover oocytes for in vitro procedures. Before treatment with FSH, heifers receiving deslorelin had greater (P < 0.001) plasma LH (0.30 +/- 0.01 ng/ml) than control heifers (0.17 +/- 0.02 ng/ml), while plasma LH was reduced (P < 0.05) in heifers treated with cetrorelix (0.13 +/- 0.01 ng/ml). Control heifers had a surge release of LH during treatment with FSH, but this did not occur in heifers treated with deslorelin or cetrorelix. All heifers had large numbers of follicles > or = 2 mm (approximately 60 follicles) after superstimulation with FSH, and there were no differences (P > 0.10) between groups. Total numbers of oocytes recovered and cultured also did not differ (P > 0.05) for control heifers and heifers treated with deslorelin or cetrorelix. Fertilization and cleavage rates were similar for the 3 groups, and developmental rates to blastocysts were also similar. Zebu heifers respond well to superstimulation with FSH at a young age, and their oocytes are developmentally competent.

Animals↗
PubMed1998

Comparison of three methods of acute administration of progesterone on ovarian follicular development and the timing and synchrony of ovulation in Bos indicus heifers.

The aim of this study was to induce the formation of a persistent dominant ovarian follicle and to compare the effects of 3 methods of acute administration of P4 on ovarian follicular development and on the timing and synchrony of ovulation. Stage of the estrous cycle was initially synchronized in Bos indicus heifers with a norgestomet implants (3 mg) for 10 d and with an analogue of PGF2 alpha (15 mg) on the first and last day of norgestomet treatment. Eight days after removal of the implants, heifers were randomly assigned to 4 groups. All heifers received a norgestomet implant (Day 0), which was removed 17 d later (Day 17); PGF2 alpha was administered on Days 0 and 4. Heifers in the control group (n = 5) received no other treatment. On Day 10 heifers in Group P4C (n = 5) were treated with a CIDR for 24 h; heifers in Group P4O (n = 5) were administered 100 mg i.m. of P4 in oil, while heifers in Group P4S (n = 5) were administered 100 mg i.m. of P4 in saline/alcohol. Data were analyzed using bootstrap estimates of location (mean) and spread (standard deviation; SD). Compared with the control heifers, day of emergence of the ovulatory follicle was delayed, and age and duration of dominance of the ovulatory follicle were reduced in the P4C and P4O heifers (P < 0.05) but not in the P4S heifers (P > 0.05). In all groups treated with P4 both the mean and variability (SD) in the timing of ovulation did not differ with that of the control group (P > 0.05) but there was less variability in the day of emergence, age, duration of dominance and diameter of the ovulatory follicle than in the control group (P < 0.05). Delayed timing and reduced synchrony (SD) of ovulation and greater age of the ovulatory follicle (P < 0.05) occurred in P4S heifers than in P4C heifers. We conclude that administration of 100 mg of P4 in oil is as effective as treatment with a CIDR for synchronizing emergence and ovulation of a newly recruited dominant follicle. However, reduced synchrony of ovulation, greater age of the ovulatory follicle and delayed timing of ovulation occurred following administration 100 mg of P4 in saline/alcohol compared with the CIDR device.

Administration, Intravaginal↗
PubMed1998

Arterial calcification and not lumen stenosis is highly correlated with atherosclerotic plaque burden in humans: a histologic study of 723 coronary artery segments using nondecalcifying methodology.

OBJECTIVES: This study was designed to evaluate whether calcium deposition in the coronary arteries is related to atherosclerotic plaque burden and narrowing of the arterial lumen. BACKGROUND: Many studies have recently documented the feasibility of electron beam computed tomography to detect and quantify coronary artery calcification in patients. Although these studies suggest a general relation between calcification and severity of coronary artery disease, the value of coronary calcium in defining atherosclerotic plaque and coronary lumen narrowing is unclear. Previous pathologic comparisons have failed to detail such a relation in identical histologic sections. This finding may be due to atherosclerotic remodeling. METHODS: A total of 37 nondecalcified coronary arteries were processed, sectioned at 3-mm intervals (723 sections) and evaluated by computer planimetry and densitometry. RESULTS: A significant relation between calcium area and plaque area was found on a per-heart basis (n = 13, r = 0.87, p < 0.0001), per-artery basis (left anterior descending coronary artery [LAD]: n = 13, r = 0.89, p < 0.0001; left circumflex coronary artery [LCx]: n = 11, r = 0.7, p < 0.001; right coronary artery [RCA]: n = 13, r = 0.89, p < 0.0001) and per-segment basis (n = 723, r = 0.52, p < 0.0001). In contrast, a poor relation existed between residual histologic lumen area and calcium area for individual hearts (r = 0.48, p = NS), individual coronary arteries (LAD: r = 0.59, p = NS; LCx: r = 0.10, p = NS; RCA: r = 0.59, p = NS) and coronary segments (r = 0.07, p = NS). Longitudinal changes in external elastic lamina areas were highly correlated with changes in plaque area values (r = 0.60, p < 0.0001), whereas lumen area did not correlate with plaque size change (r = 0.01, p = NS). CONCLUSIONS: Coronary calcium quantification is an excellent method of assessing atherosclerotic plaque presence at individual artery sites. Moreover, the amount of calcium correlates with the overall magnitude of atherosclerotic plaque burden. This study suggests that the remodeling phenomenon is the likely explanation for the lack of a good predictive value between lumen narrowing and quantification of mural calcification.

Adult↗
PubMed1998

Influence of temperature on adenovirus-mediated gene transfer.

OBJECTIVE: The transfer of recombinant genes to donor organs may allow for novel therapeutic approaches to the challenges of acute and chronic rejection. Adenoviral vectors are capable of efficient gene transfer, but use of these vectors during donor organ preservation may be less efficient due to the low temperature. This study was designed to examine the effect of temperature on the efficiency of adenovirus-mediated gene transfer. METHODS: Gene transfer to human endothelial cells, porcine vascular smooth muscle cells and cultured rat thoracic aortas was examined. Incubation with an adenoviral vector encoding for E. coli beta-galactosidase was performed for 1 h at three different temperatures: 4 degrees C, 10 degrees C and 37 degrees C. Transgene expression was assessed by histochemical staining for beta-galactosidase in transduced cells and by evaluation of beta-galactosidase activity in organ cultures. RESULTS: Both in human endothelial cells and vascular smooth muscle cells the percentage of positively staining cells following transduction at 37 degrees C was significantly greater than at 4 degrees C and at 10 degrees C (30.55 +/- 7.26% vs. 14.29 +/- 3.79% and 12.43 +/- 2.47%, respectively for endothelial cells, P < 0.01 vs. 4 degrees C and 10 degrees C; and 28.25 +/- 4.52% vs. 17.91 +/- 3.76% and 16.63 +/- 3.92%, respectively for smooth muscle cells, P < 0.05 vs. 4 degrees C, P < 0.01 vs. 10 degrees C). Beta-galactosidase activity was significantly greater in aortas transduced at 37 degrees C than in vessels transduced at 4 degrees C and 10 degrees C (289,700 +/- 113,300 vs. 149,600 +/- 54,390 and 108,800 +/- 23,140 relative chemiluminesce units/mg of total protein, respectively; P < 0.05 vs. 4 degrees C, P < 0.001 vs. 10 degrees C). CONCLUSIONS: The present study demonstrates that the efficiency of adenovirus-mediated gene transfer is significantly reduced at lower temperatures. The need for cold preservation of donor organs may render efficient adenovirus-mediated gene transfer more difficult in the transplantation setting.

Adenoviridae↗
PubMed1998

Gender and relaxation to C-type natriuretic peptide in porcine coronary arteries.

Experiments were designed to determine whether or not relaxations of coronary arterial smooth muscle to C-type natriuretic peptide (CNP) vary according to gender, and if so, to determine mechanisms for the differences. Rings of coronary arteries without endothelium from sexually mature male and female Yorkshire pigs were suspended in organ chambers for measurement of isometric force. Cumulative concentration-responses to CNP (10(-9)-10(-7) M) were obtained in the absence and presence of either K+ channel blockers (charybdotoxin, apamine, or glibenclamide, 10(-7) M) or the clearance-receptor antagonist C-ANP (10(-6) M) during contractions to prostaglandin F2alpha (2 microM). Relaxations to CNP were significantly less in arteries from male compared with female pigs and were significantly attenuated by charybdotoxin and glibenclamide in both sexes. However, apamine reduced relaxations to CNP only in arteries from female pigs. C-ANP significantly potentiated relaxations to CNP only in arteries from male pigs. In separate experiments, cyclic guanosine monophosphate (cGMP) was measured by radioimmunoassay at specified times after the addition of CNP (10(-7) M). Peak increases in cGMP were greater and occurred earlier in arteries from female than from male pigs; these differences were eliminated by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (10(-4) M). These results demonstrate three mechanisms that contribute to gender differences in CNP-mediated relaxation of coronary arterial smooth muscle: activation of low conductance Ca2+-activated K+ channels, natriuretic peptide clearance receptors, and activity/regulation of phosphodiesterases.

Animals↗
PubMed1998

Effect of acute treatment with progesterone on the timing and synchrony of ovulation in Bos indicus heifers treated with a norgestomet implant for 17 days.

The aim of the present study was to develop a treatment protocol for the precise synchronization of oestrus that would avoid the development of persistent dominant ovarian follicles. Bos indicus heifers, in which oestrous cycles had been presynchronized, were allocated randomly, according to the day of their oestrous cycle, to one of five treatment groups. All heifers received a subcutaneous ear implant containing 3 mg of norgestomet for 17 days starting on day 0 and an injection of an analogue of prostaglandin F2 alpha on days 0 and 4. Heifers in group 1 (control group; n = 7) received no other treatment, while heifers in groups 2 (n = 8), 3 (n = 7), 4 (n = 7), and 5 (n = 7) received a single progesterone-releasing controlled internal drug release device (CIDR) for 24 h on days 10, 12, 14 and 16, respectively. Treatment with a single CIDR delayed the mean time of ovulation and the day of emergence of the ovulatory follicle in heifers treated on days 14 and 16 compared with control heifers (P < 0.05). There was less variation in the interval to ovulation in heifers treated on day 10 compared with other treated heifers (P < 0.05). The variation among heifers in the day of emergence of the ovulatory follicle and the age of the ovulatory follicle at ovulation was less for all groups treated with a CIDR than for the control group (P < 0.05). The duration of dominance and variation in the duration of dominance of the ovulatory follicle was less in heifers treated with a CIDR device on days 10 and 16 than for control heifers (P < 0.05). Mean age (days from emergence to ovulation) of the ovulatory follicle did not differ among treatment groups (P > 0.05). Concentrations of LH and oestradiol decreased coincident with increased concentrations of progesterone on the days of CIDR treatment in treated compared with control heifers (P < 0.02) but increased again after removal of the CIDR. A smaller proportion of follicles in the growing phase of follicular development at the time of CIDR treatment become atretic compared with follicles that had reached a plateau phase of follicular growth (14.3% (1/7) versus 90.5% (19/21), respectively; P < 0.001). It was concluded that acute treatment with progesterone can influence the growth pattern of ovarian follicular development. However, the effect varies with the stage of ovarian follicular development. Short term treatment with progesterone 7 days before the end of a 17 day period of norgestomet treatment resulted in precise synchrony of ovulation without the ovulation of a persistent dominant ovarian follicle.

Animals↗
PubMed1998

Micro-CT imaging of structure-to-function relationship of bone microstructure and associated vascular involvement.

We are exploring methods of quantitating the 3D microstructure of bone in a way that will provide quantitative information about the functional status of the bone. The basic strategy is to image the spatial distribution of a selected, local, marker of function (e.g., material properties or new bone formation) and relate this to the simultaneously imaged 3D anatomic microstructure. Many of these approaches are extensions of well-established 2D imaging techniques (e.g., use of fluorophores and autoradiography) to 3D micro-CT. Local stresses throughout the microstructure can be estimated from the 3D geometry (and change in that geometry in response to stress applied to the outside of the bones) and correlated to the local function. In addition to study of bone, we are also exploring calcification of arterial walls, both within the bone and outside the bone, such as coronary arteries. Arterial calcification in ovariectomised rats has been observed.

Animals↗
PubMed1997

Increased cellular expression of matrix proteins that regulate mineralization is associated with calcification of native human and porcine xenograft bioprosthetic heart valves.

Dystrophic mineralization remains the leading cause of stenotic or regurgitant failure in native human and porcine bioprosthetic heart valves. We hypothesized that cellular expression of noncollagenous matrix proteins (osteopontin, osteocalcin, and osteonectin) that regulate skeletal mineralization may orchestrate valvular calcification. Porcine bioprosthetic heart valves and native human heart valves obtained during replacement surgery were analyzed for cells, matrix proteins that regulate mineralization, and vessels. Cell accumulation and calcification were correlated for both valve types (rho = 0.75, P = 0.01, native; rho = 0.42, P = 0.08, bioprosthetic). Osteopontin expression correlated with cell accumulation (rho = 0.58, P = 0.04) and calcification (rho = 0.52, P = 0.06) for bioprosthetic valves. Osteocalcin expression correlated with calcification (rho = 0.77, P = 0.04) and cell accumulation (rho = 0.69, P = 0.07) in native valves. Comparisons of calcified versus noncalcified native and bioprosthetic valves for averaged total matrix protein mRNA signal score revealed increased noncollagenous proteins mRNA levels in calcified valves (P = 0.07, group I vs. group II; P = 0.02, group III vs. group IV). When stratified according to positive versus negative mRNA signal status, both calcified bioprosthetic valves (P = 0.03) and calcified native valves (P = 0.01) were significantly more positive for noncollagenous proteins mRNA than their noncalcified counterparts. Local cell-associated expression of proteins regulating mineralization suggests a highly coordinated mechanism of bioprosthetic and native valve calcification analogous to physiologic bone mineralization. Modulation of cellular infiltration or cellular expression of matrix proteins that regulate mineralization, may offer an effective therapeutic approach to the prevention of valve failure secondary to calcification.

Aged↗
PubMed1997

Effects of the calciotrophic peptides calcitonin and parathyroid hormone on prostate cancer growth and chemotaxis.

BACKGROUND: The most common site of metastases in prostate cancer is the skeleton and occurs in 70-80% of patients with prostate carcinoma. Calciotrophic peptides are important in the growth and development of normal bone matrix. METHODS: Three human prostate carcinoma cells lines, DU-145, PC-3, and LNCaP, were exposed to varying concentrations of parathyroid hormone (PTH) or calcitonin (CT). Cell proliferation and chemotaxis were assessed. RESULTS: Proliferation increased in LNCaP cells in a dose-dependent manner following treatment with PTH. Proliferation was not altered in PC-3 cells in response to PTH. Proliferation was decreased in DU-145 and PC-3 cells and increased in LNCaP cells after treatment with CT. Cell chemotaxis was increased in the presence of PTH in DU-145 and PC-3 cells compared to vehicle-treated controls. CONCLUSIONS: The combined proliferation and chemotaxis data suggest that PTH has a dual role in prostate carcinoma resulting in an increase in the number and migration of selected prostate cancer cells. With CT, chemotaxis was unchanged in the DU-145 and PC-3 cells and significantly elevated in the LNCaP cell line. The calciotrophic hormones, PTH and CT, may play an integral role in the regulation of prostate cell growth and metastases.

Calcitonin↗
PubMed1997

Selective alpha v beta 3 integrin blockade potently limits neointimal hyperplasia and lumen stenosis following deep coronary arterial stent injury: evidence for the functional importance of integrin alpha v beta 3 and osteopontin expression during neointima formation.

UNLABELLED: Lumen loss from vascular restenosis remains a leading cause of chronic revascularization failure. OBJECTIVE: We hypothesized that cell-matrix adhesion, migration, and differentiation events that underlie restenosis are mediated by alpha v beta 3 integrin-ligand interactions. METHODS: Using immunohistochemistry and in situ hybridization, we examined the spatial and temporal vessel wall expression of alpha v beta 3 and osteopontin following deep coronary arterial injury. Cell migration and adhesion assays were performed to demonstrate the affinity and specificity of XJ 735 for various vessel wall integrins. The effects of XJ 735 (a selective cyclic Arg-Gly-Asp (RGD) peptidomimetic alpha v beta 3 antagonist) on neointimal hyperplasia and lumen stenosis were tested in a porcine coronary injury model. Normolipemic swine underwent oversized stent injury followed by XJ 735 administration (9 animals, 28 lesions; 1 mg/kg bolus + 7 days 4 mg/kg/d infusion + 21 days 2 mg/kg i.v. bolus 12 hourly) or placebo (10 animals, 30 arterial lesions). RESULTS: Maximal alpha v beta 3 immunoreactivity was observed between 7-14 days following injury in the neointima, media, and adventitia. Maximal osteopontin mRNA signal in the neointima, media, and adventitia was observed at 14, 7 and 28 days respectively. IC50 for XJ 735 alpha v beta 3-mediated inhibition of human and porcine endothelial cell adhesion, and vascular smooth muscle cell migration, ranged from 0.6 to 4.4 microM. In contrast, IC50 for porcine or human alpha IIb/beta 3, alpha 4 beta 1, alpha v beta 5, and alpha 5 beta 1 inhibition exceeded 100 microM. Steady state XJ 735 plasma levels exceeded 5 microM. Despite slightly higher injury scores in XJ 735 treated animals, significant reductions in mean neointima area (43% reduction; p = 0.0009), and mean percent lumen stenosis (approximately 2.9 fold reduction; p = 0.04) were observed in XJ 735 treated animals. XJ 735 treatment did not significantly alter the relative size of the arterial injury and reference sites (geometric remodeling). Comparison of neontima area vs. injury score regression lines revealed significant reductions in slope (p = 0.0001) and intercept (p = 0.0001) for XJ 735. CONCLUSIONS: Selective alpha v beta 3 blockade is an effective anti-restenosis strategy that potently limits neointimal growth and lumen stenosis following deep arterial injury. The co-ordinate spatial and temporal upregulation of alpha v beta 3 expression following vessel wall injury, and the high affinity and specificity of XJ 735 for alpha v beta 3, confirms the importance of this integrin in adhesive and migratory cell-matrix events underlying coronary restenosis.

Animals↗
PubMed1997

A comparison of dissected follicle numbers and follicle counts on the ovarian surface for the evaluation of ovarian follicular populations in Bos indicus cows.

Ovaries (n = 140) from 70 mixed-age multiparous, lactating Brahman cross (3/4 - 7/8 Bos indicus) cows were used to examine the hypothesis that counts of follicles visible on the surface of the ovaries of Bos indicus cows and their classification into diameter size classes, are closely correlated with numbers of follicles in those size classes found by complete dissection of the ovary. Immediately after ovariectomy, mean diameters (long and short axes averaged) of all follicles > or = 2 mm visible on the surface of each ovary were measured. All follicles > or = 2 mm were dissected from the ovaries, excess stroma removed and follicle diameters measured under a stereomicroscope using an ocular graticule. For each ovary, follicles were classified in either small (< 4 mm), medium (4-8 mm) or large (> 8 mm) categories based on either diameters of surface or dissected follicles. Data for numbers of surface and dissected follicles (mean +/- SE) in small, medium, large categories and total follicle numbers, respectively, were 24.4 +/- 1.6 vs. 28.0 +/- 1.9, 1.6 +/- +0.2 vs. 11.6 +/- 1.0, 0.5 +/- 0.1 vs. 0.7 +/- 0.1 and 26.4 +/- 1.6 vs. 40.4 +/- 2.5. Correlation coefficients (r) for counts of surface and dissected follicles in small, medium, large and total follicle numbers were 0.76, 0.40, 0.69 and 0.79, respectively. Medium size follicles presented only a small translucent area on the surface of the ovary, leading to an underestimate of numbers when categorised by surface evaluation. Counts of follicles visible on the surface of the ovaries of Bos indicus cows and their classification into size classes based on estimated diameter, are closely correlated with numbers of follicles in those size classes found at dissection of the ovary for small (< 4 mm), large (> 8 mm) and total follicles but not for medium sized (4-8 mm) follicles.

Animals↗
PubMed1997

Effect of 48 h treatment with 17 beta-oestradiol or progesterone on follicular wave emergence and synchrony of ovulation in Bos indicus cows when administered at the end of a period of progesterone treatment.

The objective of this study was to determine the effect of treatment with additional progesterone (P4) or 17 beta-oestradiol (E2) at the end of a period of P4 treatment on ovarian follicular development, ovulation time, and plasma gonadotrophin and steroid hormone concentrations of Bos indicus cows. Initially, two injections of PGF2 alpha were given 14 days apart, and at the time of the second injection (Day 0) all cows received a single P4-releasing controlled internal drug release (CIDR) device that was removed 10 days later. Control cows (Group 1, n = 8) received no other treatment. On Day 8, cows in Group 2 (n = 8) and Group 3 (n = 8) received either a s.c. implant containing E2, or a second CIDR device, respectively. All CIDR devices and E2 implants were removed at a similar time on Day 10. Treatment with E2 or P4 delayed mean (+/- SD) time of ovulation (113.1 +/- 25.6 h, 153.4 +/- 44.5 h and 150.8 +/- 25.1 h for Groups 1, 2 and 3, respectively; P < 0.05) and the mean time (+/- SD) of the luteinising hormone (LH) peak (87.4 +/- 24.5 h, 124.3 +/- 45.0 h and 122.3 +/- 25.04 h for Groups 1, 2 and 3, respectively; P < 0.05). Both treatments delayed the mean (+/- SD) day of emergence of the ovulatory follicle (7.7 +/- 3.6 days, 11.3 +/- 1.7 days and 11.1 +/- 1.5 days for Groups 1, 2 and 3, respectively; P < 0.05), and reduced the variability in the day of emergence of the ovulatory follicle (P < 0.05) compared with the control cows. Variability in age and duration of dominance of the ovulatory follicle was greater in control animals compared with treated animals (P < 0.05). Treatment with E2 on Days 9 and 10 did not alter mean concentrations of gonadotrophins in the cows in Group 2 compared with control cows (P > 0.05), whereas treatment of cows with an additional CIDR device resulted in greater mean concentrations of FSH and lesser concentrations of LH on Day 9 (P < 0.05) compared with cows in Groups 1 and 2. By Day 10 mean concentrations of gonadotrophins were similar among cows in all three groups. Concentrations of E2 were less in cows in Group 3 compared with cows in Groups 1 and 2 from Day 9 to Day 11 (P < 0.05). We conclude that treatment with either E2 or P4 can influence the pattern of ovarian follicular development and ovulation in cattle; however, the mechanism of action of the two treatments may differ. Atretogenic treatments for ovarian follicles applied at the end of a period of progesterone treatment did not improve synchrony of ovulation.

Animals↗
PubMed1997

Influence of the luteinizing hormone-releasing hormone agonist, deslorelin, on patterns of estradiol-17 beta and luteinizing hormone secretion, ovarian follicular responses to superstimulation with follicle-stimulating hormone, and recovery and in vitro development of oocytes in heifer calves.

The objective of this study was to determine the effects of inducing pituitary desensitization by treatment with an LHRH agonist (deslorelin) on reproductive hormone secretion and ovarian follicular status in heifer calves, before and during stimulation with FSH. The recovery and in vitro development of oocytes was also investigated. Brahman (Bos indicus) calves, 6 mo old, received either no treatment from Day 0 to Day 8 and injections of FSH on Days 9, 10, and 11 (controls, n = 10), or bioimplants of deslorelin on Day 0 and injections of FSH on Days 9, 10, and 11 (deslorelin calves, n = 10). Ovarian follicular characteristics were determined on Days -2, 0, and 8 by ultrasonography; follicle sizes (2-4 mm, 5-7 mm, 8-9 mm, or > or = 10 mm) were recorded. Ovaries were removed surgically on Day 12, surface follicle numbers and sizes were recorded, and oocytes were aspirated, graded (A-grade, B-grade, denuded, atretic), and prepared for in vitro fertilization and culture. Blood samples were taken throughout the experiment to monitor plasma concentrations of LH, estradiol-17 beta (estradiol) and progesterone. Treatment with deslorelin desensitized the pituitary in heifer calves and altered patterns of LH and estradiol secretion. There were no apparent consistent effects of deslorelin treatment on follicle numbers and growth. A higher number of combined A-grade and B-grade oocytes were obtained from heifers treated with deslorelin, which, in turn, resulted in twice the number of blastocysts. Treatment with an LHRH agonist provides a model for studying the hormonal requirements for follicle growth and in vivo oocyte maturation in heifer calves.

Analysis of Variance↗
PubMed1997

Effect of magnesium on parathyroid cells: evidence for two sensing receptors or two intracellular pathways?

It currently remains controversial as to the intracellular mechanisms coupled to the inhibition of parathyroid hormone (PTH) secretion that are modulated by extracellular divalent cations. To study mechanisms responsible for regulation of PTH release by cations, we investigated the effect of Mg2+ on cytosolic Ca2+ levels ([Ca2+]i) and PTH secretion in single isolated bovine parathyroid cells. Addition of 9.0 mM Mg2+ evoked a spike of [Ca2+]i in approximately 80% of cells in the presence of extracellular Ca2+. Mg2+ decreased steady-state [Ca2+]i, which represented inhibition of influx of extracellular Ca2+ in 13-78% of cells. The percentage of cells that had a decline in steady-state [Ca2+]i after exposure to Mg2+ was dependent on the extracellular Ca2+ concentration. The effect of Mg2+ on intracellular Ca2+ response was dose dependent. Extracellular Mg2+ inhibited PTH secretion in cells that showed decline in steady-state [Ca2+]i, although cells that showed a spike after addition of Mg2+ secreted more PTH than cells that did not show a spike. The spike of [Ca2+]i and decline in steady-state [Ca2+]i that occur in response to extracellular Mg2+ may be caused independently by two distinct mechanisms that differentially regulate secretion of PTH.

Animals↗