Biomedical subjects
G L Williams
Publications and source records attributed to G L Williams.
Medicated syrups and caries.
Explore the source record for details and available documents.
The postweaning rise of tonic luteinizing hormone secretion in anestrous cows is not prevented by chronic milking or the physical presence of the calf.
The objective of the following study was to examine the ability of frequent milking, the physical presence of the calf, and their combination to prevent a postweaning rise in tonic luteinizing hormone (LH) secretion, estrus, and ovulation. Thirty Hereford cows were allowed to suckle their calves ad libitum until 17-21 days post partum and confirmed as anestrus. They were then assigned alternately by order of calving to 1 of 5 treatment groups: (1) Suckled (S) ad libitum; (2) Nonsuckled (NS)--calf removed for 102 h; (3) Nonsuckled--calf present (NSC)--calf remained with cow, but muzzled to prevent suckling for 102 h; (4) Nonsuckled--milked 8 times a day (NSM)--calf removed for 102 h and cow hand-milked for 10 min every 2 h from 0700 to 2100 h; (5) Nonsuckled--calf present--milked 8 times a day (NSMC)--combination of 3 and 4. Luteinizing hormone secretion patterns, estrous activity, and ovulation were monitored throughout the experiment. Prior to treatment (Day 0), mean pulse frequency (pulses/6 h), mean concentrations (ng/ml), and median concentrations (ng/ml) of LH did not differ (p greater than 0.45) between groups, and were 0.7 +/- 0.15, 2.8 +/- 0.14, and 2.6 +/- 0.11, respectively. Marked rises (p less than 0.01--p less than 0.03) in LH pulse frequency were observed in all groups except S between 48 and 54 h after onset of treatment. Mean and median concentrations of LH were lower (p less than 0.02) in S cows than in all other groups at 48-54 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Isolation of Haemophilus influenzae genes that suppress Escherichia coli polA mutations.
Haemophilus influenzae was found to produce a DNA polymerase that was similar to polymerase I of Escherichia coli. E. coli polA mutants were used as backgrounds for the selection of H. influenzae polA suppressor genes. Six different H. influenzae fragments were isolated that could suppress E. coli polA mutations. None of the suppressors appeared to encode the H. influenzae equivalent of the E. coli polA gene. One type of clone, represented by pGW41, caused a polymerase I activity to appear in a suppressed polA1 mutant. Plasmids from the pGW41 class contained two genes (pol-2 and pol-3) that were both required for polA suppression. Mutated nonsuppressing derivatives of the pGW41 class were used to create H. influenzae mutants that were deficient in polymerase I.
Relationships among dietary lipid intake, serum cholesterol and ovarian function in Holstein heifers.
Experiments were performed to determine whether serum concentrations of total cholesterol (TC) undergo cyclic changes during the estrous cycle of dairy heifers and to assess the relationship between serum concentrations of TC and ovarian steroid hormones. The effects of a hypercholesterolemic diet upon luteal progesterone secretion also were determined. Experiment 1 involved five dairy heifers exhibiting normal estrous cycles. Serum concentrations of TC, progesterone, testosterone and estradiol-17 beta were determined in blood samples collected throughout a complete estrous cycle. A transient decline in TC was observed during the luteal phase of all heifers beginning on d 2 and reached a nadir 6 d after estrus. Highest mean concentrations of TC occurred between d -2 and +2 (96.3 +/- 8.2 mg/dl), which were markedly higher (P less than .05) than the lowest mean concentrations (76.3 +/- 10.3 mg/dl) observed on d 6. Concentrations of serum TC were negatively correlated (r = -.40; P less than .01) with progesterone between d 2 and 9. Serum TC was not correlated with testosterone or estradiol-17 beta. In Exp. 2, seven cycling Holstein heifers were fed a control diet for 70 d (Stage I), a diet containing 15% whole sunflower seed as a source of supplemental dietary lipid for 70 d (Stage II) and then the control diet for 70 d (Stage III). Diets were isocaloric and isonitrogenous. All heifers were synchronized with prostaglandin F2 alpha after wk 5 in each of the three feeding stages.(ABSTRACT TRUNCATED AT 250 WORDS)
The effect of repeated mating at short intervals on reproductive performance of gilts.
Three trials involving 87 gilts were completed to investigate the role of additional sexual stimulation on various reproductive parameters. Forty-five gilts were mated twice at 12-h intervals at second pubertal estrus with intact boars beginning 12 h after detection of sexual receptivity (control group). Forty-two gilts were exposed to a vasectomized boar 15 min following each fertile mating to provide additional copulatory stimulus (treatment group). This additional exposure improved (P less than .01) conception rate (100 vs 84%). No statistical differences were observed in number of corpora lutea (CL), number of viable embryos (VE) or number of total embryos (TE) at d 30. These results suggest that additional mating stimuli may have a beneficial effect on conception rate. While the use of additional males resulted in more pregnant females, it likely did not have an effect on litter size.
The effects of the insecticide acephate on the growth and nutrient uptake of an aquatic bacterium.
The effects of high (1000 ppm) and low (1 ppm) concentrations of acephate on the rate of growth and nutrient uptake by an aquatic bacterium (identified as Chromobacterium lividum ) were investigated. This insecticide increased doubling time, decreased maximum cellular yield, and reduced cell size when C. lividum was grown in the presence of high acephate concentrations. Total [14C]glucose and 14C-labeled amino acids uptake rates were reduced by the high acephate concentration. The high acephate concentration did not affect active uptake of [14C]cycloleucine, a nonmetabolized amino acid analogue. Low concentration of acephate had little apparent influence upon these metabolic processes.
Evidence against chronic teat stimulation as an autonomous effector of diminished gonadotropin release in beef cows.
The current experiment was performed to examine the acute and cumulative effects of chronic manual teat stimulation on the tonic pattern of luteinizing hormone (LH) secretion in beef cows. Additionally, we characterized the plasma profile of prolactin and cortisol release to evaluate whether changes in the concentrations of these hormones occurred in response to teat stimulation and whether such changes were related to gonadotropin secretion. Six weeks after ovariectomy, nonlactating beef females were paired by age and assigned randomly to a control group (n = 3) or a stimulation group (n = 3). Stimulated cows were subjected to 20 min of continuous manual teat stripping every 4 h for 24 h. Blood samples were collected from all cows at 10-min intervals beginning 1 h before and continuing for 2 h after the onset of each stimulation period in treated animals. Numerous episodes of prolactin and cortisol release were observed in control and treated animals throughout the 24-h experiment. The percentage of stimulations accompanied by prolactin and cortisol releases for each of the three treated animals was 100 and 100, 16.7 and 50, and 50 and 100, respectively. The number of prolactin peaks observed the hour after onset of teat stimulation was greater (P less than .06) than the number observed the hour before. However, the number of cortisol peaks was not statistically related to teat stimulation. Overall, mean concentrations of prolactin and cortisol were not increased by teat stimulation. Luteinizing hormone pulse frequency (1.6 +/- .1 pulses/h) and mean LH concentrations (12.1 +/- .6 ng/ml) were not acutely or chronically affected by teat stimulation and were not related to prolactin or cortisol release. We conclude that mechanical stimulation of the teat is not singly effective in altering the pattern or quantity of tonic LH release in ovariectomized cows.
Urinary excretion of methylparaben and its metabolites in preterm infants.
A high-performance liquid chromatographic (HPLC) assay to quantitate methylparaben in urine was developed. Standard curves were linear and recovery of the paraben from urine averaged 82.6%. The urinary excretion of methylparaben in six preterm infants (less than or equal to 31 weeks gestational age), who were receiving intramuscular injections of a paraben-containing gentamicin formulation, ranged from 13.2 to 88.1%. Small quantities of the metabolite, p-hydroxybenzoic acid, were detected by GC-MS.
Pharmacokinetics of gentamicin in very low birth weight preterm infants.
Low birth weight preterm infants with suspected infection were administered gentamicin intramuscularly every 18 h (2.5 mg/kg) or 24 h (3.0 mg/kg). For both dosage regimens plasma gentamicin levels were monitored during a dosage interval on three separate occasions over a 10 day period. Both regimens gave satisfactory plasma concentrations and there was no important statistically significant difference between the two. The body clearance of gentamicin correlated with gestational age (r = 0.76, p less than 0.01). The results indicate either regimen may be useful in the clinical situation but from a practical standpoint administration every 24 h may be easier to comply with then every 18 h.
The effect of intrauterine infusions of prostaglandin E2 on luteal function in nonpregnant gilts.
Two trials were conducted to study the effects of intrauterine infusions of prostaglandin E2 (PGE2) on luteal function in nonpregnant gilts. Cannulae were surgically implanted on day 9 postestrus into the lumen of each horn with a cephalic vein cannula inserted for collection of peripheral blood. Intrauterine infusions of 0, 25, 75 or 200 microg of PGE2 were initiated at 0900 h on day 12 and administered thereafter every 12 hr until estrus or day 22 in the first trial. The second trial protocol included an increase in the dose of PGE2 administered as well as the frequency of infusion. Infusion of 0, 200, 300 or 400 microg PGE2 was begun at 0300 h on day 12 and continued every 6 hr until estrus or day 22. Cephalic plasma samples for progesterone analysis were collected every six hours from 0300 h on day 11 to 2100 h on day 26 in both trials. In Trial 1 mean plasma progesterone concentrations for all treatments were not different (P>0.05) from the controls on any given day of the estrous cycle. Interestrous interval was unaffected by intrauterine infusion of PGE2. The mean plasma progesterone concentrations for all treatments were not different (P>0.05) from the controls on days 11-18 of the estrous cycle in Trial 2. However, plasma progesterone concentrations for the 200-microg and 300-microg PGE2 groups appeared to be greater than the controls on days 14 and 15, indicating a possible delay in the decline of progesterone for these groups. The mean plasma progesterone concentrations for the treatment groups were lower (P<0.05) than the controls on days 20-26 of the cycle. treatment cycle length did not differ (P>0.05) from previous cycle length; thus treatment with PGE2 had no effect on interestrous interval. PGE2 may have retarded the decline of progesterone secretion by the corpus luteum in some cases, but at these dosages and frequencies of administration PGE2 was ineffective in prolonging luteal maintenance.
Coincident secretion of follicle-stimulating hormone and luteinizing hormone in early postpartum beef cows: effects of suckling and low-level increases of systemic progesterone.
The current experiment was conducted with beef cows during the first 2 weeks postpartum (PP) to determine the effects of suckling and low-level increases of systemic progesterone on secretory characteristics of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in peripheral plasma. Variables measured included mean gonadotropin concentrations, FSH/LH pulse frequencies, pulse amplitudes and synchrony of coincident release. Suckled (S) cows had lower (P less than 0.01-P less than 0.05) mean concentrations of FSH and LH in plasma, lower (P less than .05) FSH and LH pulse frequencies and a lower (P less than 0.05) pulse synchrony (21.6 vs 72.3% coincident pulses) than nonsuckled (NS) cows on Day 7 PP. Neither FSH nor LH pulse amplitude was affected by suckling. Similar differences existed for mean gonadotropin concentrations, pulse frequencies and pulse synchrony on Day 14 PP between S and NS cows. Implanting cows with progesterone implants on Day 7 PP, which chronically increased plasma progesterone to 0.5-0.6 ng/ml, increased (P less than 0.05) mean plasma FSH and LH concentrations, FSH and LH pulse frequencies and pulse synchrony (87.5 vs. 66.3%) in NS-implanted (NSI) versus NS-nonimplanted (NSNI) cows. Progesterone implants had no beneficial effect in S cows. Thus, three major findings seem pertinent: 1) associated with the suckling-induced depression of episodic gonadotropin release was a marked decline in FSH/LH pulse synchrony; 2) a high degree of FSH/LH pulse synchrony (72-88%) was restored in the absence of suckling when gonadotropin pulse frequency increased to 4-5/6 h; 3) the absence of suckling, followed by the provision of low-level progesterone stimulation for 7 days, appeared to have additive effects on FSH and LH secretion. These results provide evidence that the neuroendocrine block associated with suckling in early PP beef cows is, in addition to being associated with depressed LH release, comprised of characteristic anomalies in FSH secretion, FSH/LH pulse synchrony and failure to respond to a putative hypothalamo-hypophyseal potentiator, progesterone.
Time of the preovulatory LH surge in the gilt and sow relative to the onset of behavioral estrus.
Two experiments were conducted to study the time of occurrence of the preovulatory LH surge in pigs. Sampling every ten minutes in six cycling gilts before and after onset of standing estrus revealed the preovulatory surge began from 8 hr before to 12 hr after the lordosis reflex was elicited. Three of six gilts initiated the preovulatory LH release coincident with the onset of estrus. Data from 28 postpartum sows, with samples drawn every six hours commencing with the onset of estrus, indicated maximum LH levels were present at the first observance of estrus. Six of the 28 sows had an LH peak 18-24 hr after the onset of estrus.
Pituitary and ovarian responses of postpartum dairy cows to progesterone priming and single or double injections of gonadotropin-releasing hormone.
Utilizing single or double pulses of gonadotropin-releasing hormone (GnRH), with or without progesterone pretreatment, we induced ovulation in dairy cows on day 14 postpartum. In experiment 1, neither progesterone priming nor repetitive injection of GnRH enhanced pituitary LH or FSH secretion compared to a single GnRH injection. However, pretreatment with 100 mg progesterone tended (P<0.1) to enhance luteal progesterone secretion during the induced cycle. We confirmed this observation in a second experiment by utilizing a larger number of cows. Cows given 100 mg progesterone prior to a single 200 microg injection of GnRH exhibited higher (P<0.05) concentrations of serum progesterone on days 12 and 16 of the induced cycle (days 26 and 30 postpartum). These results suggest that progesterone pretreatment may influence luteal progesterone secretion following ovulation. This appears to occur via an ovarian mechanism which is independent of pituitary gonadotropin secretion.
Countercurrent transfer of testosterone by the ovarian vascular pedicle of the cow: evidence for a relationship to follicular steroidogenesis.
Explore the source record for details and available documents.
Relationship of plasma testosterone concentrations to pituitary-ovarian hormone secretion during the bovine estrous cycle and the effects of testosterone propionate administered during luteal regression.
Explore the source record for details and available documents.
Effect of suckling on pituitary responsiveness to gonadotropin-releasing hormone throughout the early postpartum period of beef cows.
The objective of this study was to compare pituitary responsiveness to gonadotropin-releasing hormone (GnRH) throughout the early postpartum period (PP) in beef cows suckling in single calf vs cows which had calves removed at birth. The experiment utilized 48 cows in a 2 X 4 factorial. Main effects studied were suckling status (suckled or nonsuckled) and days PP (d 3, 10, 20 or 30). Covariates studied were pre-treatment concentrations of progesterone (P), estradiol-17 beta (E), luteinizing hormone (LH) and follicle stimulating hormone (FSH). Suckled (S) cows nursed one calf, while nonsuckled (NS) cows had calves removed at birth. Treatment was a single im injection of 100 micrograms GnRH dissolved in saline. Pre-GnRH plasma concentrations of E, P, LH and FSH and post-treatment plasma concentrations of LH and FSH were determined at 15 min intervals (-30 to 360 min) in blood samples collected via jugular cannulae. Post-treatment plasma concentrations of P were determined at 6 (n = 23) or 8 (n = 23) days after treatment to monitor ovarian response. Concentrations of E, LH and FSH before GnRH injection did not differ (P greater than .1) between S and NS cows at any PP stage and data were pooled for statistical analyses. Pre-treatment LH, but not FSH, increased (r = .43; P less than .002 (with days PP and concentrations of LH were greater (P less than .05) at 30 d than at 3 d PP. Pre-treatment P was greater (P less than .05) in NS than in S cows on d 30 PP and P was correlated (r = .51; P less than .01) with days PP in NS cows. However, the frequency of cows exhibiting plasma P greater than or equal to 1 ng/ml prior to GnRH was low on all days studied and was similar for both groups. LH release after GnRH was correlated with increasing days PP in both S (r = .73; P less than .001) and NS (r = .61; P less than .002) cows, Releasable FSH was not related to days PP in either group. Mean peak LH and total LH released were greater (P less than .025 and P less than .05), respectively) in S than in NS cows at 30 d PP. Mean peak FSH and total FSH released were greater (P less than .05 and P less than .07, respectively) at 10 and 30 d PP in S cows than in NS cows. Pre-treatment E, but no P, LH or FSH was positively related (P less than .01) to GnRH-mediated LH release in both groups. When pre-treatment E was partitioned into separated regressions for S (ES) and NS (ENS) cows, increased pituitary LH response in S cows on d 30 appeared to be due in part to a greater sensitivity of S cows to E modulation. We found no evidence to suggest that pituitary responsiveness per se is decreased in beef cows suckling a single calf.
Synthesis and antiherpetic activity of some 4-[(aryloxy)alkyl]pyrazoles.
Explore the source record for details and available documents.