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Biomedical subjects

A J Roberts

Publications and source records attributed to A J Roberts.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effect of gonadotropin treatment on size, number, and cell proliferation of antral follicles in cows.

To determine the effects of gonadotropins on the size, number, and cell proliferation of antral ovarian follicles, cows received FSH-P or vehicle beginning on Day 2 after estrus, and ovaries were collected 6, 12, 24, or 48 hr after the initiation of FSH-P treatment or 24 or 48 hr after the initiation of vehicle treatment. Ovaries also were collected from untreated cows on Day 2 after estrus (pretreatment). Before fixation, all visible antral follicles were counted and their surface diameters were recorded. Proliferating cells were immunolocalized in fixed follicles by using a specific primary antibody against proliferating cell nuclear antigen (PCNA), and the labeling index (LI; percentage of cells staining positively for PCNA) was determined for granulosa and thecal cells. After 48 hr of treatment, FSH-P-treated cows had fewer (P < 0.01) small antral follicles and more medium and large antral follicles (P < 0.01 and P < 0.05, respectively) compared with vehicle-treated cows. Granulosa cell LI was negatively correlated (P < 0.05) with follicular diameter for vehicle-treated but not for FSH-P-treated cows. Analysis of covariance using follicular diameter as a covariate to adjust to a common diameter indicated that granulosa cell LI was greater (P < 0.05) at 24 and 48 hr in FSH-P-treated than in vehicle-treated cows; conversely, thecal cell LI was greater (P < 0.01) at 48 hr in FSH-P-treated compared with vehicle-treated cows but did not differ at 24 hr. Across all groups, the LI of cells located within the antral half of the granulosa cell layer was greater (P < 0.01) than that of cells located within the basal half. In conclusion, the stimulation of follicular development by exogenous gonadotropins increased or maintained the proliferation of granulosa and thecal cells concomitant with continued follicular growth. Therefore, enhanced follicular cell proliferation may be an important mechanism by which FSH-P superinduces the growth of antral follicles in cows.

Animals↗
PubMed1997

Circulating insulin-like growth factor I, insulin-like growth factor binding proteins, growth hormone, and resumption of estrus in postpartum cows subjected to dietary energy restriction.

The objective of this study was to determine whether serum concentrations of growth hormone (GH), IGF-I, IGF binding proteins (IGFBP), and glucose at wk 2 and 10 postpartum were associated with the ability of postpartum beef cows to resume cycling when maintained on a limited nutrient environment. Cows (n = 29) were individually fed either 130 or 170 kcal ME x BW-75 x d-1 during nonlactation and 170 or 210 kcal ME x BW-75 x d-1 during lactation for an average of 4.1 yr before sample collection. The proportion of cows that resumed estrus within 20 wk after parturition was less (P < .05) at the lower feeding rate (5 of 14) than at the higher feeding rate (11 of 15). Concentrations of IGF-I increased from wk 2 to 10 in cows that resumed cycling but not in cows that remained anestrous and were less (P < .05) at wk 2 and 10 in cows that remained anestrous compared to cows that resumed cycling. Circulating amounts of IGFBP-2 at wk 2 were greater (P < .05) and IGFBP-3 concentrations were lower (P < .05) in cows that remained anestrous compared to cows that resumed cycling. Cows on the lower feeding rate that did not cycle had lower body condition scores and greater concentrations of GH compared (P < .05) to other cows. At the higher feeding rate, body condition score and concentrations of GH did not differ between cows that did or did not resume cycling. Circulating concentrations of IGF-I and IGFBP-2 and -3 at wk 2 postpartum were indicators of the capacity of energy-restricted cattle to resume cycling after parturition.

Analysis of Variance↗
PubMed1997

Relationships of light and heavy fetuses to uterine position, placental weight, gestational age, and fetal cholesterol concentrations.

With emphasis on increasing litter size to improve productivity and profitability, lightweight pigs born will increase in number as litter size increases and may be problematic due to reduced neonatal survival of lightweight pigs. To study developmental aspects of lightweight fetuses, fetal and placental weights were evaluated at three stages of pregnancy (30, 70, and 104 d) from white composite gilts (n = 88, 123, and 135, respectively) in relation to uterine position of light and heavy fetuses. Fetal cholesterol concentrations were analyzed at the beginning (d 70) and end (d 104) of the in utero growth phase (last third of gestation). At 30 d of gestation, no differences were noted between fetal weight and position within the uterine horn, but at 70 d and 104 d of pregnancy, heavy fetuses were found at the tubal ends and light fetuses at the cervical ends of the uterus. Using the criteria of +/- 1 SD or +/- 2 SD of the mean and lower and upper 10 or 20% of fetal weights for each gestational age, light and heavy fetuses in conjunction with their placentas were different from population means at all stages of gestation. Cholesterol concentrations were lower in light fetuses (d 104) and increased in heavy fetuses. In 28 litters (d 104) selected for extremes in within-litter fetal weights, concentrations of IGF-I increased with fetal weight (P < .01), which suggests that growth and development of lightweight pigs may be limited by critical endocrine components.

Animals↗
PubMed1997

The neurobiology of addiction: an overview.

Addiction can be defined in part as a compulsion to use alcohol or other drugs and the occurrence of withdrawal symptoms when long-term consumption ceases. In addition to physical symptoms related to nervous system hyperexcitability, withdrawal includes changes in mental state that may motivate renewed AOD consumption. The manifestations of addiction are associated with changes in nerve cell function by which the brain attempts to adapt to a drug's presence. These functional changes modulate a person's initial response to a drug, the establishment of long-term craving for the drug (i.e., addiction), and the persistent sense of discomfort that leads to relapse after abstinence has been achieved. Research is beginning to reveal how specific brain regions may be integrated to form neural circuits that modulate aspects of addiction.

Alcoholism↗
PubMed1997

Genetic differences in behavioral sensitivity to a neuroactive steroid.

Recent work found that lower endogenous levels of the gamma-aminobutyric acid-agonist, neuroactive steroid 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) may be correlated with increased ethanol withdrawal severity in the selectively bred Withdrawal Seizure-Prone and -Resistant mice. The present studies were conducted to determine whether decreased sensitivity to 3alpha,5alpha-THP was correlated with ethanol withdrawal hyperexcitability in another genetic mouse model, namely the C57BL/6 (B6) and DBA/2 (D2) inbred strains. These strains also differ in ethanol withdrawal severity (D2 >> B6). B6 and D2 male mice were injected with 3alpha,5alpha-THP (0-10 mg/kg i.p.) 15 min before the timed tail vein infusion of pentylenetetrazol. B6 mice were more sensitive than D2 animals to the anticonvulsant effect of 3alpha,5alpha-THP. Subsequent studies measured sensitivity to several of the pharmacological effects of 3alpha,5alpha-THP. B6 and D2 male mice were injected with 3alpha,5alpha-THP (0-32 mg/kg) before testing for locomotor activation (total number of entries) and anxiolysis (percent open arm entries) on the elevated plus maze, muscle relaxation (impairment of forelimb grip strength), ataxia (impairment of Rotarod performance) and seizure susceptibility to pentylenetetrazol. B6 mice were more sensitive than D2 animals to the anxiolytic, locomotor stimulant and anticonvulsant effects of 3alpha,5alpha-THP. In contrast, D2 mice were more sensitive than B6 mice to 3alpha,5alpha-THP-induced muscle relaxation and ataxia. Plasma 3alpha,5alpha-THP levels did not differ in the B6 and D2 mice injected with this steroid, suggesting that the strain differences were not pharmacokinetic. Collectively, the results in selectively bred Withdrawal Seizure-Prone and -Resistant mice and B6 and D2 inbred strains suggest that genetic differences in neuroactive steroid sensitivity and biosynthesis may contribute to ethanol withdrawal severity.

Animals↗
PubMed1996

Insulin-like growth factor I and insulin-like growth factor-binding proteins in bovine serum and follicular fluid before and after the preovulatory surge of luteinizing hormone.

Previous studies have shown that concentrations of insulin-like growth factor (IGF)-binding proteins (BPs) in bovine follicles before the preovulatory surge of LH are inversely associated with estradiol concentrations, such that decreases in IGFBPs occur with advanced development of antral follicles and atresia is associated with increases in IGFBPs. In the present study, we evaluated serum and follicular fluid at different times after the preovulatory surge of LH to determine whether changes in IGF-I and IGFBPs are associated with the marked changes in the steroidogenic capacity that occur in follicle during this period. Serum and fluid from small follicles (> or = 5-mm diameter) and the preovulatory follicle were collected from cows at the onset of standing estrus or 8.5 and 20.5 h after administration of 100 micrograms GnRH at the onset of estrus (n = 4/time). Concentrations of IGF-I (determined by RIA) did not differ (p > 0.10) among times but were lower (p < 0.05) in fluid from small and preovulatory follicles than those in serum. Profiles of IGFBPs (evaluated by ligand blot analysis) differed among serum and fluid from small and preovulatory follicles. Preovulatory follicles contained IGFBP-3 with little or no other IGFBPs detected. Amount of IGFBP-3 and progesterone did not differ with time of sample collection, but a 13- to 15-fold reduction in estradiol-17 beta and androstenedione occurred between 8.5 and 20.5 h after the LH surge. Small follicles contained IGFBP-2, -3, -4, and -5 (determined by immunoprecipitation). The amount of 28-29-kDa IGFBPs (small form of IGFBP-5 and [or] glycosylated form of IGFBP-4) was inversely associated with concentrations of androstenedione. The 31-kDa form of IGFBP-5 was positively correlated with concentration of progesterone. Serum contained IGFBP-2, -3, and -4, but not IGFBP-5. Circulating IGFBP-2, but not other IGFBPs, decreased by 50% from estrus to 20.5 h after GnRH. In summary, amounts of IGF-I or IGFBPs in preovulatory follicular fluid did not change in response to an LH surge, even though estradiol and androstenedione decreased markedly. The absence of IGFBPs other than IGFBP-3 in bovine preovulatory follicles may allow for increased availability of IGF-I, which is proposed to be important for oocyte maturation and ovulation.

Androstenedione↗
PubMed1996

Intra-amygdala muscimol decreases operant ethanol self-administration in dependent rats.

Dependence is an important factor motivating continued alcohol use in human alcoholics. Development of a model of ethanol (EtOH) consumption in dependent animals would advance the understanding of reinforcement after chronic EtOH exposure and allow for the investigation of the neuropharmacological mechanisms mediating reinforcement in dependent versus nondependent animals. In the present study, rats were trained to lever press for 10% EtOH, surgically implanted with bilateral guide cannulae in the amygdala, and either made dependent on EtOH by exposure for 2 weeks to EtOH or exposed to air in identical vapor chambers. Upon removal, the rats were placed in operant boxes and allowed to respond on levers for 10% EtOH or water during a 12-hr period. Rats were removed briefly at approximately 6.5 hr for intra-amygdala injections of saline or the GABAA receptor agonist muscimol. After the test period, rats were returned to the vapor chambers for 4 days before retest. EtOH-dependent animals responded more for EtOH across the 12-hr test period than did air control nondependent rats; this difference became more pronounced with repeated test sessions. Intra-amygdala muscimol significantly decreased responding for EtOH in EtOH-dependent rats, but had no effect in nondependent controls. These data suggest that the reinforcing effects of EtOH and neurotransmitter pathways mediating reward are altered after the development of dependence, and they support the use of this paradigm for further investigations into the neuropharmacology of EtOH dependence.

Alcoholism↗
PubMed1996

Preparation and measurement of artificial enamel lesions, a four-laboratory ring test.

Transversal microradiography is the most widely accepted method used to study changes in mineral content profiles. In spite of its widespread use, relatively little information is available on its validity and reproducibility. Following the recommendation of the Consensus Conference on Intraoral Model Systems, this study was designed to explore reproducibility of lesion analysis within a laboratory and comparability of analysis among various laboratories. Incipient enamel lesions were produced by four research groups using both a common ('standard') and a local ('preferred') protocol. Sections were produced by each group and allocated to 'mixed' bags of specimens, which were analysed by the groups. With the chosen scheme some sections were analysed six times by the same group (as an internal reference standard) while others were analysed by all four groups. The data for the mineral content profiles were expressed as the integrated mineral loss (IML) value and lesion depth. The results showed the lesions produced with the standard protocol to be in the range 2,000-3,000 vol% mineral x microns for IML. The IML of the lesions produced with the preferred protocol varied between 1,800 and 6,300 vol% mineral x microns. Variation in IML values could be attributed to the biological variation between lesions, but also to time (of microradiograph production) and measurement effects, calibration of the magnification of the specimens, and the parameters used in the algorithm to calculate IML. Some of these parameters also affected the lesion depth. It is advised to standardise (or at least report) the method of calculation of IML, and to include a reference lesion between analyses in a longitudinal study as an internal standard. With the data produced, it was calculated that the number of lesions required to differentiate between preventive treatments varied substantially among laboratories. The recommendations given will improve the power of the screening methods for caries-preventive agents for which microradiography is an essential analytical method.

Analysis of Variance↗
PubMed1995

Corticosteroids enhance convulsion susceptibility via central mineralocorticoid receptors.

Recently, interest in the roles of central nervous system mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) has increased. In vitro results have implicated MR in the enhancing effects of corticosteroids and GR in the suppressing effects of corticosteroids on hippocampal excitability. Although indirect evidence exists suggesting that opposing actions of central MR and GR occur in vivo, direct evidence from studies employing receptor agonists and antagonists is only beginning to emerge. Work in our laboratory suggests that increased corticosterone levels are associated with increased severity of ethanol, pentobarbital, and diazepam withdrawal. Further work with chemical convulsants suggests that MR mediate excitatory effects of corticosteroids on convulsion susceptibility. The circadian rhythm in convulsion susceptibility varies with the circadian rhythm of plasma corticosterone levels and MR binding. The types of convulsions affected by manipulations of MR activity are believed to be of limbic origin, suggesting that limbic convulsions may be alleviated by the use of specific MR antagonists. In addition, because MR are substantially bound at rest and maximally occupied during the circadian peak in corticosteroid levels and during stressor exposure, these receptors are implicated in the maintenance of and in changes in the arousal state of animals.

Alcohol Withdrawal Delirium↗
PubMed1995

Genetic analysis of the corticosterone response to ethanol in BXD recombinant inbred mice.

The genetic control over the corticosterone response to ethanol (EtOH) and its possible relationship to other EtOH-related traits was examined using BXD recombinant inbred (RI) strains derived from an F2 cross of C57BL/6J (B6) and DBA/2J (D2) progenitor strains. Quantitative trait locus (QTL) analysis of corticosterone levels 1 hr following EtOH suggested the influence of a single major gene on this trait. Two loci were predicted to account for 47% of the genetic variance in plasma corticosterone levels 6 hr following EtOH, whereas 3 loci were predicted to account for 78% of the genetic variance in corticosterone levels 7 hr following EtOH. Markers associated with corticosterone levels 7 hr following EtOH and corrected corticosterone levels 6 hr post-EtOH overlapped with ones found to influence acute and chronic EtOH withdrawal severity, suggesting some degree of common genetic determination between these traits. Overall these results indicate that gene action significantly influences stress responsiveness and suggest possible chromosomal locations of these genes.

Alcohol Drinking↗
PubMed1995

Effect of acute glucose antagonism on hypophyseal hormones and concentrations of insulin-like growth factor (IGF)-I and IGF-binding proteins in serum, anterior pituitary, and hypothalamus of ewes.

The objectives of this study were to determine whether 2-deoxy-D-glucose (2DG), a metabolic inhibitor of glucose, 1) differentially affected release of LH, growth hormone (GH) and prolactin (PRL); 2) decreased anterior pituitary response to GnRH; and 3) altered concentrations of insulin-like growth factor I (IGF-I) and intensity of 125I-IGF-I binding to proteins (IGFBPs) in serum, anterior pituitary (AP), and hypothalamus (preoptic are [POA], medial basal hypothalamus [MBH], and stalk median eminence [SME]). In trial 1, mature, ovariectomized, crossbred ewes were treated with a single s.c. injection of either saline (n = 5) or 2DG (n = 5; 0.1 g/kg BW). Administration of 2DG suppressed (p < 0.05) concentrations of LH but did not affect (p > 0.05) serum concentrations of GH or PRL. In trial 2, ovariectomized ewes received injections of saline or 2DG, and each group was subdivided to receive either saline or GnRH analog (5 micrograms; Des-Gly10-[D-Ala6]) 2 h later. Administration of 2DG suppressed (p < 0.05) serum concentrations of LH before administration of GnRH; however, release of LH in response to exogenous GnRH was greater (p < 0.05) in ewes that received 2DG. Treatment with 2DG did not affect (p > 0.05) concentrations of FSH before or after administration of GnRH. In trial 3, 10 ovariectomized ewes were slaughtered 2 h after treatment with saline (n = 5) or 2DG (n = 5). Serum and tissues collected at slaughter (AP, MBH, SME, and POA) were analyzed for concentrations of IGF-I by RIA and intensity of 125I-IGF-I binding to proteins by ligand blotting.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Neuroactive steroid sensitivity in withdrawal seizure-prone and -resistant mice.

Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) mice, which were selectively bred for severe (WSP) or mild (WSR) handling-induced convulsions (HICs) following chronic ethanol inhalation, were found to differ in sensitivity to the anticonvulsant effects of the neuroactive steroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-P. 3 alpha,5 alpha-P (5 or 10 mg/kg, ip) significantly increased seizure thresholds to pentylenetetrazol in ethanol-native males of both the WSP and WSR lines. In general, WSP mice were more sensitive than WSR mice to the anticonvulsant effect of 3 alpha,5 alpha-P. Subsequent studies in male WSP mice exposed to ethanol vapor or air for 24 hr demonstrated enhanced sensitivity to the anticonvulsant effect of 3 alpha,5 alpha-P (0.5-20 mg/kg, ip) during ethanol withdrawal. Only the highest dose affected HICs in air-exposed animals, whereas both the two highest doses significantly reduced HICs in ethanol-exposed mice. These results provide the first demonstration that 3 alpha,5 alpha-P attenuates ethanol withdrawal convulsions and indicate enhanced sensitivity to the anticonvulsant effect of 3 alpha,5 alpha-P in animals withdrawing from ethanol dependence.

Alcohol Withdrawal Delirium↗
PubMed1995

Role of models in assessing new agents for caries prevention--non-fluoride systems.

While fluoride is an effective anti-caries agent, the search for more effective alternative therapies continues. A wide range of non-fluoride anti-caries agents has been postulated, and this paper reviews some of the pre-clinical models that have been utilized in their evaluation and some of the pitfalls that must be avoided. Using data on the potential anti-caries efficacy of phosphopeptides obtained from casein, the caution that must be applied in extrapolating laboratory data to predict clinical performance is discussed. Evaluation strategies that focus on only one potential mode of action (e.g., inhibition of demineralization) may overestimate the true clinical efficacy which may arise from a combination of two or more effects (e.g., inhibition of demineralization and stimulation of remineralization). Although laboratory and in situ data predict anti-caries efficacy for sodium trimetaphosphate in combination with fluoride, this was not found in three-year clinical trials. A possible reason for this, the lack of suitable calibration methods, is discussed. Finally, some comments on the appropriateness of laboratory evaluation strategies are made.

Animals↗
PubMed1995

Insulin-like growth factor-I (IGF-I) and IGF-binding proteins in bovine sera and pituitaries at different stages of the estrous cycle.

The objective of this study was to determine whether concentrations of hypophyseal and serum insulin-like growth factor-I (IGF-I) and binding activities of serum and hypophyseal IGF-binding proteins (IGFBPs) differ with stage of the estrous cycle in mature beef cows. Cows were assigned to the following stages of the estrous cycle based on serum concentrations of progesterone (P4) and ovarian structures at death: days 1-5 (day 0 = estrus; n = 18), days 6-10 (n = 24), days 11-16 (n = 39), and days 17-21 (n = 7). Serum samples collected at death and anterior pituitary homogenates were analyzed for IGF-I, LH, and FSH by RIA. Serum and pituitary IGFBPs were evaluated by ligand and immunoblot analyses. Serum samples contained IGFBP activity at 44 and 40 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 30 kDa (IGFBP-5), 28 kDa, and 24 kDa. The intensity of binding by the different sized proteins in serum remained constant throughout the estrous cycle. IGFBPs detected in anterior pituitaries included a 36-/40-kDa doublet (IGFBP-3), a 32-kDa protein (IGFBP-2), and a 29-kDa IGFBP (IGFBP-5). The intensity of [125I]IGF-I binding to IGFBPs was greater (P < 0.05) during days 11-16 than days 1-5 or days 6-10 of the estrous cycle and was intermediate (P > 0.05) during days 17-21. Serum concentrations of LH were low (< 0.4 ng/ml) during days 1-16 of the estrous cycle, but increased (P < 0.05) approximately 3- to 4-fold during days 17-21. LH concentrations in the anterior pituitary increased (P < 0.05) from the postovulatory period (548 +/- 52 micrograms/g; days 1-5) to the late luteal phase (791 +/- 39 micrograms/g; days 11-16) and were intermediate (P > 0.05) during the preovulatory phase (707 +/- 85 micrograms/g; days 17-21). Concentrations of IGF-I and FSH in the anterior pituitary and serum did not differ (P > 0.05) by stage of the estrous cycle. A positive correlation among the different IGFBPs in the pituitary (P < 0.01) and between each pituitary IGFBP and serum P4 (P < 0.05) existed. The significance (P < 0.0002) of the correlation between pituitary IGFBP-3 and P4 was greater (P < 0.02) than that between the other pituitary IGFBPs and P4. In summary, IGFBP activity in the anterior pituitary, but not that in serum, changed with stage of the estrous cycle in association with serum concentrations of P4. The absence of similar changes in serum or anterior pituitary concentrations of IGF-I supports the hypothesis that IGFBPs may regulate the actions of IGF-I on gonadotropin release from the anterior pituitary gland during the estrous cycle of beef cattle.

Animals↗
PubMed1995

Critical role for glucocorticoid receptors in stress- and ethanol-induced locomotor sensitization.

Locomotor sensitization, the augmentation of the locomotor-activating effects of stimuli with repeated exposure, is being evaluated as a partial model for several phenomena including drug addiction. Alteration of dopaminergic systems has been found in sensitized animals and dopamine neurotransmission appears to be crucial for the expression of sensitized behaviors. However, stress hormones, which are released after exposure to many of the stimuli that produce sensitization, may also be involved in the development of this phenomenon. Corticosterone appears to be important in the development of amphetamine sensitization and glucocorticoid receptors (GR) have been hypothesized to mediate this effect. The purpose of these experiments was first, to determine whether repeated restraint stress sensitizes DBA/2J mice to the activating effect of ethanol (EtOH), and second, to explore the role of GR in stress- and EtOH-induced sensitization with the GR antagonist, RU 38486. This antagonist was administered before restraint or i.p. EtOH (1.5 g/kg) on each of 10 consecutive days of pretreatment. In addition, plasma corticosterone levels were determined at various points throughout the pretreatment period and on test days. The results demonstrated that 10 consecutive days of 2-hr restraint sensitized mice to EtOH's locomotor-stimulating effect. Both stress- and EtOH-induced sensitization were attenuated by administration of RU 38486 during the pretreatment phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Follicular development and superovulation response in cows administered multiple FSH injections early in the estrous cycle.

To determine whether follicular development, superovulation and embryo production were affected by the absence or presence of a dominant follicle, cows were administered injections of FSH twice daily in the early (Days 2 to 6, estrus=Day 0) or middle stage (beginning on Day 10 or 11) of the estrous cycle. Treatment with FSH early in the cycle stimulated follicular development in 83 to 100% of all cows from 4 groups evaluated at different times after PGF2alpha treatment on Days 6 and 7. However, the proportion of cows with >2 ovulations varied from 31 to 62.5%, indicating that induction of follicular development may occur in the absence of superovulation. When compared with cows treated in the middle of the cycle, no differences were observed in the proportion of cows with >2 ovulations (31 vs 20%), ovulation rate. (26.0+/-6.3 vs 49.6+/-25.8), production of ova/embryos (13.3+/-3.2 vs 14.4+/-3.4), or the number of transferable embryos (8.0+/-3.6 vs 5.4+/-1.5; early vs middle, respectively). The proportion of the total number of embryos collected that were suitable for transfer was greater (P<0.01) in cows treated early in the cycle (60%) than at midcycle (37.5%). The diameter of the largest follicle observed by ultra-sound prior to initiation of FSH treatment in the early stage of the cycle (10.0+/-2.0 mm) was smaller (P<0.05) than at midcycle (16.8+/-1.3 mm). These results demonstrate that superinduction of follicular development is highly consistent after FSH treatment at Days 2 to 6 of the cycle and that superovulation and embryo production are not less variable than when FSH is administered during the middle of the cycle. However, superovulation in the early stage of the cycle may increase the proportion of embryos suitable for transfer.

Journal Article↗
PubMed1994

Corticosterone increases severity of acute withdrawal from ethanol, pentobarbital, and diazepam in mice.

It has been suggested that withdrawal from several subclasses of central nervous system (CNS) depressants involves common underlying mechanisms. For example, mice genetically selected for severe ethanol withdrawal convulsions (Withdrawal Seizure Prone or WSP) have also been found to express severe withdrawal following treatment with barbiturates and benzodiazepines. Corticosteroids appear to modulate severity of withdrawal from CNS depressants. Therefore, it was hypothesized that corticosterone would enhance withdrawal convulsions following acute ethanol, pentobarbital, and diazepam in WSP mice. Corticosterone (20 mg/kg) administered following each of these drugs significantly increased severity of handling-induced convulsions during withdrawal. Corticosterone did not affect pre-withdrawal convulsion scores or handling-induced convulsions of drug-naive mice. These results suggest that withdrawal convulsions following acute ethanol, pentobarbital, and diazepam are sensitive to modulation by corticosterone and they support the hypothesis that stress may increase drug withdrawal severity.

Animals↗