Biomedical subjects

R Webb

Publications and source records attributed to R Webb.

At least 73 records · Page 4Linked to original sources

PubMed2000

Measurement of the helicity of W bosons in top quark decays

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->lnu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a t&tmacr; sample isolated in 106+/-4 pb(-1) of data collected in p&pmacr; collisions at sqrt[s] = 1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V-A weak decay, we find that the fraction of W's with zero helicity in the top rest frame is F0 = 0.91+/-0. 37(stat)+/-0.13(syst), consistent with the standard model prediction of F0 = 0.70 for a top mass of 175 GeV/c(2).

Journal Article↗

PubMed2000

Observation of diffractive b-quark production at the fermilab tevatron

We report a measurement of the fraction of b quarks produced diffractively in &pmacr;p collisions at sqrt[s] = 1.8 TeV. Diffraction is identified by the absence of particles in a forward pseudorapidity region. From events with an electron of transverse momentum 9.5<p(e)(T)<20 GeV/ c within the pseudorapidity region |eta|<1.1, the ratio of diffractive to total b-quark production rates is found to be R(&bmacr;b) = [0.62+/-0.19(stat)+/-0.16(syst)]%. This result is comparable in magnitude to corresponding ratios for W and dijet production but significantly lower than expectations based on factorization.

Journal Article↗

PubMed2000

Anti-mesothelial markers in sarcomatoid mesothelioma and other spindle cell neoplasms.

AIMS: To undertake a comparative evaluation of three antimesothelial markers (thrombomodulin, cytokeratin 5/6 and calretinin) with broad spectrum cytokeratin (AE1/AE3) in differentiating between sarcomatoid mesothelioma and a spectrum of spindle cell neoplasms. METHODS AND RESULTS: Thirty-one malignant sarcomatoid mesotheliomas were studied. Calretinin expression was focally identified in 12 (39%) tumours and thrombomodulin and cytokeratin 5/6 immunoreactivity was seen in nine (29%) cases. In comparison there was strong diffuse cytoplasmic reactivity with the broad spectrum cytokeratin (AE1/AE3) in 24 of 31 (77%) tumours. Thirty mixed spindle cells neoplasms were studied. No calretinin expression was identified in any case. Thrombomodulin immunoreactivity was identified in four (16%) cases (two angiosarcomas, two high-grade sarcomas, not otherwise specified). Cytokeratin 5/6 expression was seen in one high-grade pulmonary sarcoma originally termed malignant fibrous histiocytoma. None of the antimesothelial markers was expressed in the four spindle cell carcinomas studied. In contrast, broad spectrum cytokeratin was diffusely expressed in all four spindle cell carcinomas (three pulmonary, one renal), both synovial sarcomas, both malignant mixed Müllerian tumours, one of three pulmonary leiomyosarcomas and two of nine sarcomas, not otherwise specified. CONCLUSIONS: Immunohistochemistry has a more limited role in the diagnosis and distinction of sarcomatoid mesothelioma from other spindle cell neoplasms. The combination of a broad spectrum cytokeratin with calretinin combines both high sensitivity (77% for AE1/AE3) with high specificity (100% for calretinin) for sarcomatoid mesothelioma and can be diagnostically useful. The mesothelial markers, thrombomodulin and cytokeratin 5/6, are not useful alone in the diagnosis of sarcomatoid mesothelioma as each shows insufficient antibody sensitivity, although together they complement calretinin.

Biomarkers, Tumor↗

PubMed2000

Growth and antrum formation of bovine preantral follicles in long-term culture in vitro.

Culture of preantral follicles has important biotechnological implications through its potential to produce large quantities of oocytes for embryo production and transfer. A long-term culture system for bovine preantral follicles is described. Bovine preantral follicles (166 +/- 2.15 micrometer), surrounded by theca cells, were isolated from ovarian cortical slices. Follicles were cultured under conditions known to maintain granulosa cell viability in vitro. The effects of epidermal growth factor (EGF), insulin-like growth factor (IGF)-I, FSH, and coculture with bovine granulosa cells on preantral follicle growth were analyzed. Follicle and oocyte diameter increased significantly (P < 0.05) with time in culture. FSH, IGF-I, and EGF stimulated (P < 0.05) follicle growth rate but had no effect on oocyte growth. Coculture with granulosa cells inhibited FSH/IGF-I-stimulated growth. Most follicles maintained their morphology throughout culture, with the presence of a thecal layer and basement membrane surrounding the granulosa cells. Antrum formation, confirmed by confocal microscopy, occurred between Days 10 and 28 of culture. The probability of follicles reaching antrum development was 0.19 for control follicles. The addition of growth factors or FSH increased (P < 0.05) the probability of antrum development to 0.55. Follicular growth appeared to be halted by slower growth of the basement membrane, as growing follicles occasionally burst the basement membrane, extruding their granulosa cells. In conclusion, a preantral follicle culture system in which follicle morphology can be maintained for up to 28 days has been developed. In this system, FSH, EGF, and IGF-I stimulated follicle growth and enhanced antrum formation. This culture system may provide a valuable approach for studying the regulation of early follicular development and for production of oocytes for nuclear/embryo transfer, but further work is required.

Animals↗

PubMed2000

An analysis of excess mortality not predicted to occur by APACHE III in an Australian level III intensive care unit.

The APACHE III derived standardized mortality ratio has been suggested as a statistic to measure intensive care unit (ICU) effectiveness. From 1991 data collected on 519 consecutive admissions to the Royal Adelaide Hospital ICU a standardized mortality ratio of 1.25 was calculated. Of the 174 deaths only 95 had a prediction of death greater than 0.5. As part of a quality assurance study we undertook a retrospective case note audit to try to identify factors that were associated with the low mortality prediction (< 0.5) in hospital deaths. Firstly we analysed the patient population that died to determine the factors that were different between patients who had a mortality prediction of greater than 0.5 versus those who had a mortality prediction of less than 0.5. Next we analysed the patient population with a mortality prediction of less than 0.5 and compared actual survivors with patients who died in hospital. Amongst low mortality prediction patients admitted to the Royal Adelaide Hospital ICU we identified age, a history of acute myocardial infarction, presentation to ICU after a cardiac arrest or with an elevated creatinine and the development of acute renal failure and septicaemia during the ICU admission as being associated with in-hospital mortality. We also documented that late hospital deaths on the ward after ICU discharge occurred more frequently with low predicted hospital mortality ICU patients. Factors other than the APACHE III score may be associated with hospital deaths of ICU patients.

APACHE↗

PubMed2000

Expression of mRNA encoding IGF-I, IGF-II and type 1 IGF receptor in bovine ovarian follicles.

IGFs regulate gonadotrophin-stimulated proliferation and differentiation of granulosa and theca cells in vitro. However, the detailed pattern of mRNA expression of IGFs in bovine follicles remains controversial. The objectives of this study were therefore to describe the temporal and spatial pattern of expression of mRNA encoding IGF-I, IGF-II and the type 1 IGF receptor in bovine follicles in vivo. The expression of mRNA encoding IGF-II was detected in theca tissue from around the time of antrum formation up to and during the development of dominance. No IGF-II mRNA expression was detected in granulosa cells. In the majority of follicles we were unable to detect mRNA encoding IGF-I in either granulosa or theca tissue from follicles at any stage of development. Occasionally low amounts of mRNA encoding IGF-I were detected in the theca externa and connective tissue surrounding some follicles. Type 1 IGF receptor mRNA was detected in both granulosa and theca cells of preantral and antral follicles. Expression was greater in granulosa tissue compared with theca tissue. We also measured IGF-I and -II mRNA in total RNA isolated from cultured granulosa and theca cells using reverse transcriptase PCR. In contrast to the in vivo results, IGF-II mRNA was detected in both granulosa and theca tissue. IGF-I mRNA was detected in theca tissue and in very low amounts in granulosa cells. Using a specific IGF-I RIA we were unable to detect IGF-I immunoreactivity in granulosa conditioned cell culture media. Using immunohistochemistry we detected IGF-I immunoreactivity in some blood vessels within the ovarian stroma. We conclude from these results that IGF-II is the principal intrafollicular IGF ligand regulating the growth of bovine antral follicles. In preantral follicles the expression of mRNA encoding type 1 IGF receptor but absence of endogenous IGF-I or -II mRNA expression, highlights a probable endocrine mechanism for the IGF regulation of preantral follicle growth.

Animals↗

PubMed2000

Nitrogen metabolism and fertility in cattle: II. Development of oocytes recovered from heifers offered diets differing in their rate of nitrogen release in the rumen.

In vitro blastocyst production was determined for oocytes recovered postmortem from 48 beef x dairy heifers offered low (Low NH3) or high (High NH3) plasma ammonia-generating diets during the period of late antral follicle development. Following the establishment of a reference estrus (d 0), the experimental diets were offered for an 18-d period starting on d 3 and during which a second estrus was induced (d 16) 4 d before the animals were slaughtered. Blood samples collected at varying intervals were analyzed for ammonia, urea, progesterone, and LH. Ovarian folliculogenesis was monitored daily by transrectal ultrasonography. Ovaries were collected at slaughter and cumulus-oocyte complexes were aspirated from small (1 to 4 mm) and medium-sized (> 4 to 8 mm) sized follicles. In vitro-matured and -fertilized putative d-1 zygotes were cultured for a further 7 d in vitro and embryo development and metabolism were assessed. Relative to the low-NH3-generating diet, the high-NH3-generating diet increased peak postprandial levels of plasma ammonia (326.1 +/- 43.3 vs 52.1 +/- 7.4 micromol/L; P < .001), mean levels of plasma urea (7.0 vs 5.7 mmol/L; SED = .2; P < .001), peak levels of plasma progesterone prior to induced luteolysis (8.9 +/- .4 vs 6.8 +/- .3 microg/L; P < .001), and follicular fluid levels of ammonia (267 +/- 18 vs 205 +/- 20 nmol/mL; P < .05) and progesterone (351 +/- 69 vs 199 +/- 26 ng/mL; P < .05). The timing and level of the preovulatory LH surge was not affected by dietary treatment. Of oocytes cultured, cleavage (47.4 vs 62.4%; P = .02) and blastocyst production (10.9 vs 20.6%; P = .06) rates were reduced when the oocytes were derived from heifers offered the high- rather than the low-NH3-generating diets. There were interactions between dietary treatment and follicle size class, which indicated that fewer blastocysts were produced from cleaved oocytes derived from medium-sized follicles of heifers offered the high-NH3 treatment but that de novo protein synthesis was increased in such embryos. In conclusion, exposure to high levels of ammonia and(or) urea in vivo can significantly compromise the subsequent capacity of oocytes to develop to blastocysts in vitro, and oocytes recovered from medium-sized follicles are particularly sensitive to this effect.

Ammonia↗

PubMed2000

Which is the best deprivation predictor of foetal and infant mortality rates?

This study investigates which, if any, population-based indicator of deprivation best predicts foetal and infant mortality rates in England. For the year 1995, the deprivation levels of 364 English Local Authorities were compared; using the three commonly used indicators, Jarman score, Townsend score and percentage unemployed. The predictive value of these for stillbirth, neonatal and infant mortality rates was then calculated. The three deprivation indicators were highly inter-correlated (r=0.866-0.924). For each mortality rate, the correlation with deprivation did not differ significantly for the three indicators of deprivation. We conclude, when comparing these outcomes in different areas of England, that any of the three deprivation indicators may be used to adjust for deprivation.

England↗

PubMed2000

Expression of mRNA encoding insulin-like growth factors I and II and the type 1 IGF receptor in the bovine corpus luteum at defined stages of the oestrous cycle.

Previous studies have implicated insulin-like growth factors I and II (IGF-I and -II), in the regulation of ovarian function. The present study investigated the localization of mRNA encoding IGF-I and -II and the type 1 IGF receptor using in situ hybridization to determine further the roles of the IGFs within the bovine corpus luteum at precise stages of the oestrous cycle. Luteal expression of mRNA encoding IGF-I and -II and the type 1 IGF receptor was detected throughout the oestrous cycle. The expression of IGF-I mRNAvaried significantly during the oestrous cycle. IGF-I mRNA concentrations were significantly higher on day 15 than on day 10, and IGF-I mRNA in the regressing corpus luteum at 48 h after administration of exogenous prostaglandin was significantly greater than in the early or mid-luteal phase (days 5 and 10). In contrast, there was no significant effect of day of the oestrous cycle on expression of mRNA for IGF-II and the type 1 IGF receptor in the corpus luteum. Expression of IGF-II mRNA was localized to a subset of steroidogenic luteal cells and was also associated with cells of the luteal vasculature. mRNA encoding the type 1 IGF receptor was widely expressed in a pattern indicative of expression in large and small luteal cells. These data demonstrate that the bovine corpus luteum is a site of IGF production and reception throughout the luteal phase. Furthermore, this study highlights the potential of IGF-II in addition to IGF-I in the autocrine and paracrine regulation of luteal function.

Analysis of Variance↗

PubMed1999

Missing lithotroph identified as new planctomycete.

With the increased use of chemical fertilizers in agriculture, many densely populated countries face environmental problems associated with high ammonia emissions. The process of anaerobic ammonia oxidation ('anammox') is one of the most innovative technological advances in the removal of ammonia nitrogen from waste water. This new process combines ammonia and nitrite directly into dinitrogen gas. Until now, bacteria capable of anaerobically oxidizing ammonia had never been found and were known as "lithotrophs missing from nature". Here we report the discovery of this missing lithotroph and its identification as a new, autotrophic member of the order Planctomycetales, one of the major distinct divisions of the Bacteria. The new planctomycete grows extremely slowly, dividing only once every two weeks. At present, it cannot be cultivated by conventional microbiological techniques. The identification of this bacterium as the one responsible for anaerobic oxidation of ammonia makes an important contribution to the problem of unculturability.

Ammonia↗

PubMed1999

Ovarian and hormonal responses of cows to treatment with an analogue of gonadotrophin releasing hormone and prostaglandin F2 alpha.

Blood samples were taken from 11 cows and their ovaries were scanned by ultrasound at least daily. Around day 5 of an induced cycle, they were injected with 10 micrograms buserelin, an analogue of gonadotrophin releasing hormone, and on day 12 they received 0.5 mg cloprostenol, an analogue of prostaglandin F2 alpha (PGF2 alpha). Two days later six of the cows (the treated group) received a second injection of 10 micrograms buserelin, but the remaining five received no further treatment (control group). The dominant, that is, the largest follicle in each cow disappeared after the first buserelin injection and was replaced by a new one which grew synchronously in all the cows until after the treatment with PGF2 alpha. Ovulation occurred significantly earlier after PGF2 alpha in the treated group than in the control group (72 to 96 hours v 96 to 120 hours; P < 0.05). Plasma progesterone concentrations then increased more rapidly in the treated group than in the control group and were significantly higher on days 3 and 4 after ovulation (P < 0.05).

Animals↗

PubMed1999

MyoR: a muscle-restricted basic helix-loop-helix transcription factor that antagonizes the actions of MyoD.

Skeletal muscle development is controlled by a family of muscle-specific basic helix-loop-helix (bHLH) transcription factors that activate muscle genes by binding E-boxes (CANNTG) as heterodimers with ubiquitous bHLH proteins, called E proteins. Myogenic bHLH factors are expressed in proliferating undifferentiated myoblasts, but they do not initiate myogenesis until myoblasts exit the cell cycle. We describe a bHLH protein, MyoR (for myogenic repressor), that is expressed in undifferentiated myoblasts in culture and is down-regulated during differentiation. MyoR is also expressed specifically in the skeletal muscle lineage between days 10.5 and 16.5 of mouse embryogenesis and down-regulated thereafter during the period of secondary myogenesis. MyoR forms heterodimers with E proteins that bind the same DNA sequence as myogenic bHLH/E protein heterodimers, but MyoR acts as a potent transcriptional repressor that blocks myogenesis and activation of E-box-dependent muscle genes. These results suggest a role for MyoR as a lineage-restricted transcriptional repressor of the muscle differentiation program.

Amino Acid Sequence↗

PubMed1999

Ipratropium bromide nasal spray 0.03% and beclomethasone nasal spray alone and in combination for the treatment of rhinorrhea in perennial rhinitis.

BACKGROUND: Perennial rhinitis is a common condition that affects up to 10% to 20% of the population. Multiple agents are frequently administered since no single agent provides complete relief. Studies assessing the benefit/risk of combined therapy are important especially for newly approved agents such as ipratropium bromide nasal spray 0.03%, a topical anticholinergic agent, approved specifically for the treatment of rhinorrhea in allergic and non-allergic perennial rhinitis. OBJECTIVE: To compare the efficacy and safety of the combined use of ipratropium bromide nasal spray 0.03% (42 microg per nostril tid) and beclomethasone dipropionate nasal spray (84 microg per nostril bid) against that of either active agent alone for the treatment of rhinorrhea. DESIGN: Multicenter, 6-week, double-blind, randomized active- and placebo-controlled, parallel trial. SETTING: Allergist and general practitioner clinical practices. PATIENTS: Five hundred thirty-three patients with perennial rhinitis (279 allergic and 274 non-allergic), 8 to 75 years of age, who had at least a mild degree of severity of rhinorrhea for a minimum of 2 hours per day during the 1 week screening period as well as congestion or sneezing also of at least mild severity. INTERVENTION: Either (1) ipratropium bromide nasal spray 0.03% (42 microg per nostril tid) plus beclomethasone dipropionate nasal spray (84 microg per nostril bid), (2) ipratropium bromide nasal spray 0.03% (42 microg per nostril tid) alone, (3) beclomethasone dipropionate nasal spray (84 microg per nostril bid) alone, or (4) vehicle [matching placebo nasal spray for the ipratropium bromide (2 sprays per nostril tid)] or beclomethasone dipropionate (2 sprays per nostril bid). MAIN OUTCOME MEASURE: Severity and duration of rhinorrhea, and patient and physician global assessment of control of rhinorrhea. RESULTS: Ipratropium bromide nasal spray plus beclomethasone nasal spray was more effective than either active agent alone or vehicle in reducing the average severity and duration of rhinorrhea during 4 weeks of treatment. The advantage of ipratropium bromide plus beclomethasone nasal spray was evident by the first day of combined treatment and continued throughout the 2-week treatment period. Ipratropium bromide nasal spray had a faster onset of action during the first week of treatment and reduced the duration of rhinorrhea more than beclomethasone. Beclomethasone nasal spray was more effective in reducing the severity of congestion and sneezing than ipratropium. In patients who had not responded well to a nasal steroid prior to participation in the study based on a questionnaire administered at screening, ipratropium bromide was as effective in the steroid non-responders as steroid responders, whereas beclomethasone was more effective in steroid responders. Combined active therapy was well tolerated with no increase in adverse events over that seen previously with ipratropium bromide or beclomethasone nasal spray alone. CONCLUSIONS: The combined use of ipratropium bromide nasal spray with beclomethasone dipropionate nasal spray is more effective than either active agent for the treatment of rhinorrhea, and does not result in a potentiation of adverse drug reactions. Ipratropium bromide nasal spray 0.03% alone should be considered in patients for whom rhinorrhea is the primary symptom, and its use in combination with a nasal steroid should be considered in patients where rhinorrhea is one of the predominant symptoms, or in patients with rhinorrhea not fully responsive to other therapy.

Administration, Inhalation↗

PubMed1999

Social class and census-based deprivation scores: which is the best predictor of stillbirth rates?

This study investigates whether social class or a census-based deprivation score is a better predictor of stillbirth rates using data for 1993-5 for residents of South Thames (West) Region. Social class is routinely coded for 10% of live births and 100% of stillbirths. A Townsend deprivation score was assigned to each stillbirth and each live birth with a social class code, according to their electoral ward of residence. In unifactorial analyses of stillbirth rate the relationship was stronger with social class (P = 0.008) than with Townsend score (P = 0.11). Both relationships were strengthened by including those births recorded as social class 'other' ['other' vs. social class I odds ratio (OR) = 2.27, P < 0.001; lower vs. upper septile deprivation score OR = 1.45, P = 0.07)]. When social class and Townsend score were analysed together, the ORs for social class remained similar to before, but the Townsend ORs were reduced and non-significant overall. We conclude that social class, which is based on data on each individual, is a better predictor of stillbirth than Townsend score, which is based on data from the area of residence. We recommend further investigation of the stillbirth risk in the subgroups that make up the 'other' social class.

Analysis of Variance↗

PubMed1999

Long-term ovarian function in sheep after ovariectomy and transplantation of autografts stored at -196 C.

We have previously demonstrated that ovarian function and fertility can be preserved in sheep after castration by autotransplantation of cryopreserved strips of ovarian cortex. In the current experiments we have investigated the long term survival of such grafts by detailed measurements of ovarian function for a period of nearly 2 yr after autotransplantation. After ovariectomy and transplantation of frozen/thawed grafts, the concentrations of FSH and LH rose to castrate levels for about 14 weeks before falling gradually to reach near-normal levels at about 60 weeks. In the breeding season from October 1994 to March 1995, all ewes had 5-10 estrous cycles that were similar in length to those in the 4 control ewes. Luteal function as indicated by the progesterone concentration was identical before and 11 months after transplantation. In contrast, the basal concentrations of FSH and LH were persistently raised throughout the luteal phase, but showed a normal decline during the follicular phase. The concentration of inhibin A in ovarian venous plasma measured at the end of the experiment 22 months after transplantation was significantly lower than that in control ewes (mean +/- SE, 409 +/- 118 vs. 1914 +/- 555 pg/ml; P < 0.004). Transplantation of frozen/thawed ovarian tissue to SCID mice demonstrated that about 28% of primordial follicles survived the procedure. All of the ovaries transplanted into sheep contained large antral follicles and/or cysts, but very few primordial oocytes when recovered at autopsy after 22 months. These results demonstrate that despite a drastic reduction in the total number of primordial follicles, cyclical ovarian function is preserved in sheep after autotransplantation of frozen/thawed ovarian tissue and provide experimental confirmation that such a technique could provide a means of preserving fertility in women undergoing chemo- or radiotherapy for malignant disease.

Animals↗

PubMed1999

Control of early cardiac-specific transcription of Nkx2-5 by a GATA-dependent enhancer.

The homeobox gene Nkx2-5 is the earliest known marker of the cardiac lineage in vertebrate embryos. Nkx2-5 expression is first detected in mesodermal cells specified to form heart at embryonic day 7.5 in the mouse and expression is maintained throughout the developing and adult heart. In addition to the heart, Nkx2-5 is transiently expressed in the developing pharynx, thyroid and stomach. To investigate the mechanisms that initiate cardiac transcription during embryogenesis, we analyzed the Nkx2-5 upstream region for regulatory elements sufficient to direct expression of a lacZ transgene in the developing heart of transgenic mice. We describe a cardiac enhancer, located about 9 kilobases upstream of the Nkx2-5 gene, that fully recapitulates the expression pattern of the endogenous gene in cardiogenic precursor cells from the onset of cardiac lineage specification and throughout the linear and looping heart tube. Thereafter, as the atrial and ventricular chambers become demarcated, enhancer activity becomes restricted to the developing right ventricle. Transcription of Nkx2-5 in pharynx, thyroid and stomach is controlled by regulatory elements separable from the cardiac enhancer. This distal cardiac enhancer contains a high-affinity binding site for the cardiac-restricted zinc finger transcription factor GATA4 that is essential for transcriptional activity. These results reveal a novel GATA-dependent mechanism for activation of Nkx2-5 transcription in the developing heart and indicate that regulation of Nkx2-5 is controlled in a modular manner, with multiple regulatory regions responding to distinct transcriptional networks in different compartments of the developing heart.

Animals↗

PubMed1999

Immune cells and cytokine production in the bovine corpus luteum throughout the oestrous cycle and after induced luteolysis.

Immune cells and their cytokine products have powerful local effects within body tissues. There has been great interest in the potential role of these cells, not only during destruction of the corpus luteum but also during its functional lifespan. In this study, lymphocytes, macrophages and major histocompatibility complex class II molecules were quantified using immunohistochemistry and the reverse transcription-polymerase chain reaction was used to detect mRNA for tumour necrosis factor alpha and interferon gamma within corpora lutea from three groups of cows: (1) corpora lutea collected at an abattoir and assessed visually into four stages (stage I (days 1-5), stage II (days 6-12), stage III (days 13-18) and stage IV (days 19-21) of the oestrous cycle); (2) corpora lutea collected around natural luteolysis (days 14-20); and (3) corpora lutea collected 6, 12 and 24 h after prostaglandin F 2 alpha-induced luteolysis. The numbers of T lymphocytes (CD5+ and CD8+) were significantly higher (P < 0.05) at stage IV and from day 16 onwards, before functional luteolysis. There were significantly higher numbers (P < 0.01) of macrophages at stages I, III and IV compared with stage II in visually staged tissue. Major histocompatibility complex class II molecules were increased (P < 0.05) at stages I and IV compared to stage II and at all times after induced luteolysis. Using reverse transcription-polymerase chain reaction, mRNA encoding tumour necrosis factor alpha and interferon gamma was detected in all luteal tissue collected around natural luteolysis and after induced luteolysis. These findings, particularly the increase in T lymphocytes before functional luteolysis, provide further evidence of a significant role for the immune system in affecting reproductive function in cows.

Animals↗

PubMed1999

Molecular mechanisms regulating follicular recruitment and selection.

Ovarian follicular growth and development is an integrated process encompassing both extraovarian signals, such as gonadotrophins and metabolic hormones, and intraovarian factors. Follicular development has been classified into gonadotrophin-independent and -dependent phases. In the latter, FSH provides the primary drive for follicular recruitment and LH is required for continued development of follicles to the preovulatory stage. A transient increase in circulating FSH precedes the recruitment of a group of follicles, and these recruited follicles are characterized by expression of mRNAs encoding P450scc and P450arom in granulosal cells. As follicles mature, there is a transfer of dependency from FSH to LH, which may be part of the mechanism(s) involved in selection of follicles for continued growth. Indeed, changes in the pattern of expression of mRNA for gonadotrophin receptors and steroid enzymes within follicular cells appear to be closely linked to changes in peripheral concentrations of gonadotrophins. The mechanism of selection of dominant follicles still requires clarification, but seems to be linked to the timing of mRNA expression encoding LHr and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in granulosal cells. Additional intraovarian systems, including the ovarian IGF and activin/inhibin systems, also exert a role. For example, it appears that the development of follicular dominance in cows is associated with the FSH-dependent inhibition of the expression of mRNA encoding insulin-like growth factor binding protein 2 (IGFBP-2) in granulosal cells. In conclusion, the integration of these endocrine signals and intraovarian factors within follicles determines whether follicles continue to develop and become dominant or are diverted into apoptotic pathways leading to atresia.

3-Hydroxysteroid Dehydrogenases↗