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Biomedical subjects

G C England

Publications and source records attributed to G C England.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of clavulanic acid-potentiated amoxycillin on semen quality in dogs.

Two different doses of clavulanic acid-potentiated amoxycillin were evaluated for their effect upon semen quality and libido in dogs. There was no significant difference in either parameter between control dogs and dogs treated with clavulanic acid-potentiated amoxycillin at either 12.5 mgkg-1 or 25 mgkg-1 orally twice daily for 28 d. Despite the marked effect of certain antibiotic agents upon spermatogenesis, it appears that clavulanic acid-potentiated amoxycillin can be used in dogs at up to twice the therapeutic dosage recommended by the manufacturer without a deleterious effect upon semen quality.

Amoxicillin↗
PubMed1999

Comparison of sedative effects of romifidine following intravenous, intramuscular, and sublingual administration to horses.

OBJECTIVE: To compare sedative effects of romifidine following IV, IM, or sublingual (SL) administration in horses. ANIMALS: 30 horses that required sedation for routine tooth rasping. PROCEDURE: Horses (n = 10/group) were given romifidine (120 microg/kg) IV, IM, or SL. Heart rate, respiratory rate, head height, distance between the ear tips, thickness of the upper lip, response to auditory stimulation, response to tactile stimulation, and degree of ataxia were recorded every 15 minutes for 180 minutes. Tooth rasping was performed 60 minutes after administration of romifidine, and overall adequacy of sedation was assessed. RESULTS: IV and IM administration of romifidine induced significant sedation, but SL administration did not induce significant sedative effects. Scores for overall adequacy of sedation after IV and IM sedation were not significantly different from each other but were significantly different from scores for horses given romifidine SL. Sedative and other effects varied among groups during the first 60 minutes after drug administration; thereafter, effects of IV and IM administration were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Onset of action was fastest and degree of sedation was greater after IV, compared with IM, administration of romifidine, but duration of action was longer after IM administration. Sublingual administration did not result in clinically important sedative effects.

Acoustic Stimulation↗
PubMed1998

An investigation of capacitation and the acrosome reaction in dog spermatozoa using a dual fluorescent staining technique.

The processes of capacitation and acrosomal exocytosis of dog spermatozoa in vitro have yet to be fully investigated. Firstly, we investigated the effectiveness of a technique for staining dog spermatozoa with the fluorescent labels Hoechst 33258 and chlortetracycline. A modified fluorescence microscopy staining method was shown to be effective for the assessment of both viability and functional status in this species. Secondly, the presence of the ionophore A23187 in culture medium was shown to promote capacitation and the acrosome reaction of dog spermatozoa. We have therefore established that this dual fluorescent staining method can be used for monitoring these events in the dog, and it may be useful in future studies of optimal in vitro culture conditions.

Acrosome↗
PubMed1998

Nuclear staining and culture requirements for in vitro maturation of domestic bitch oocytes.

Oocyte nuclear staining and culture requirements for in vitro maturation (IVM) in the bitch have yet to be fully investigated. In the first part of this study we investigated 7 methods for labeling nuclear material (573 oocytes). The most favorable method involved fixation plus aceto-orcein staining and light microscopy. The influence of serum supplementation of the culture medium for IVM was then investigated (1292 oocytes). Culture was performed in media supplemented with no serum or with 5, 10 and 20% fetal calf serum (FCS) and 0.3 or 4% bovine serum albumin (BSA). Identifiable nuclear material was either a germinal vesicle (GV) or GV breakdown (GVBD). After 48 h in medium plus 0, 5, 10 or 20% FCS and 0.3 or 4% BSA, the percentage of oocytes matured to GVBD was 13, 9, 15, 23, 36 and 40%, and the percentage matured to metaphase I/anaphase I/metaphase II was 4, 12, 24, 14, 36 and 13%, respectively. After 96 h, maturation to GVBD was 31, 14, 21, 11, 50 and 38%, and to metaphase I/anaphase I/metaphase II it was 6, 5, 3, 19, 15 and 9%, respectively. Within the limits of this study, BSA or high concentrations of FCS appear to be optimal for bitch oocyte maturation in vitro.

Animals↗
PubMed1998

The effect of oocyte size and bitch age upon oocyte nuclear maturation in vitro.

In vitro maturation in the bitch has yet to be fully investigated, and perfection of the technique is essential for future gamete salvage programs in endangered canine species. For optimal success with these techniques, knowledge of the individual animal and of oocyte effects upon maturational competence would be useful. Two factors were therefore studied using an aceto-orcein staining technique, which has been shown to be effective for monitoring nuclear maturation of canine oocytes following oocyte culture in medium supplemented with bovine serum albumin (BSA). Oocytes of different sizes were cultured in vitro and their nuclear maturation monitored. It was shown that the selection of oocytes which had acquired meiotic competence through adequate intrafollicular growth was important for in vitro maturation. In vitro maturation of oocytes from bitches aged 1 to 6 yr, and from those 7 yr and older was then compared, and it was found that oocytes from young bitches had a greater potential to mature than those collected from the older animals.

Age Factors↗
PubMed1998

The canine oocyte penetration assay; its use as an indicator of dog spermatozoal performance in vitro.

In vitro maturation and fertilisation has yet to be thoroughly investigated in the dog and is work that is required before gamete salvage programmes can be established in endangered canine species. Due to the differences which exist between the reproductive function of Canidae and other domestic species, in vitro requirements of both the oocyte and spermatozoa may also differ, and these remain to be established. The objective of this study was to investigate the ability of in vitro capacitated canine spermatozoa to penetrate the zona pellucida of in vitro matured canine oocytes. Two methods, one which utilised the fluorescent nuclear label Hoechst 33258 in combination with an aceto-orcein stain with light microscopy, and another using the fluorescence microscopy method alone were effective for staining both oocyte nuclear material and penetrated spermatozoal heads. These techniques only rarely allowed identification of both in the same oocyte. Using this assay, two to capacitate and acrosome react in vitro as measured by the chlortetracycline and Hoechst 33258 dual fluorescence staining method. No correlation however was found between acrosomal status of spermatozoa and spermatozoal penetration of homologous oocytes, although some relationship was observed. In addition, it was found that the effect of the stage of oocyte nuclear maturation had no effect upon spermatozoal penetration and that immature oocytes could be penetrated by spermatozoa in this species.

Acrosome↗
PubMed1998

Ultrasonographic assessment of abnormal pregnancy.

Ultrasonographic imaging is widely used in small animal practice for the diagnosis of pregnancy and the determination of fetal number. Ultrasonography can also be used to monitor abnormal pregnancies, for example, conceptuses that are poorly developed for their gestational age (and therefore are likely to fail), and pregnancies in which there is embryonic resorption or fetal abortion. An ultrasound examination may reveal fetal abnormalities and therefore alter the management of the pregnant bitch or queen prior to parturition. There are, however, a number of ultrasonographic features of normal pregnancies that may mimic disease, and these must be recognized.

Abortion, Veterinary↗
PubMed1997

Effect of romifidine and romifidine-butorphanol for sedation in dogs.

The sedative and physiological effects of intravenous romifidine at 120 micrograms/kg were compared with intravenous romifidine (120 micrograms/kg) followed immediately by intravenous butorphanol (0.1 mg/kg) in 18 clinically normal adult beagles in a blinded randomised change-over study. Following the injection of romifidine alone the dogs became recumbent and there was an increase in a subjective score awarded to the degree of sedation. Heart rate and respiratory rate decreased and minor bradyarrhythmias were noted. The romifidine-butorphanol combination produced a significant decrease in the time to the onset of sedation and increase in the sedative effect and duration of action compared with romifidine alone. With the exception of a further decrease in heart rate and respiratory rate, there were no additional side effects following the use of the romifidine-butorphanol combination. The marked sedative effect associated with this combination would appear to be useful in the clinical situation where an increased degree of sedation is required.

Adrenergic alpha-Agonists↗
PubMed1997

Dose-sparing effects of romifidine premedication for thiopentone and halothane anaesthesia in the dog.

Two intravenous doses of romlfidine (40 and 80 micrograms/kg) and a placebo were compared as premedicants for anaesthesia induced with thiopentone and maintained using halothane in oxygen. Romifidine significantly and linearly reduced the induction dose of thiopentone; placebo-treated dogs required 15.1 +/- 3.6 mg/kg, while dogs treated with 40 micrograms/kg and 80 micrograms/kg romifidine required 6.5 +/- 1.6 and 3.9 +/- 0.3 mg/kg thiopentone, respectively. Romifidine also significantly and linearly reduced the end tidal halothane concentration necessary to maintain a predetermined level of anaesthesia; placebo-treated dogs required 1.6 +/- 0.3 per cent halothane, while dogs treated with 40 micrograms/kg and 80 micrograms/kg romifidine required 1.3 +/- 0.4 and 0.8 +/- 0.2 per cent, respectively. Romifidine produced a significant shortening in the recovery from anaesthesia, and the higher dose of romifidine significantly improved the overall quality of anaesthesia.

Adrenergic alpha-Agonists↗
PubMed1997

Effect of preovulatory endocrine events upon maturation of oocytes of domestic bitches.

The effect of preovulatory endocrine changes upon oocyte maturation was investigated in a combined in vivo and in vitro study. A preliminary study was performed to investigate the effect of endocrine influences in vivo on subsequent oocyte maturation in vitro. A hemi-ovariectomy was performed in four bitches during pro-oestrus at the first detected rise of plasma progesterone (mean progesterone 2.36 +/- 0.58 ng ml-1) and a second performed during oestrus immediately before ovulation, 1-4 days later (mean progesterone 4.96 +/- 0.75 ng ml-1). The mean numbers of high quality (grade 1) oocytes with identifiable nuclear material collected per pro-oestrous ovary was 15.5 +/- 9.88, and per oestrous ovary was 31.75 +/- 23.76. All of the grade 1 oocytes harvested were cultured for 96 h, after which 37% and 19% of pro-oestrous oocytes had matured to germinal vesicle breakdown (GVBD) and metaphase I/anaphase I/metaphase II (MI/AI/MII), respectively, whereas 41% and 11% of oestrous oocytes had matured to GVBD and MI/AI/MII, respectively. There was no significant difference in maturation between the two groups of oocytes. In a second study, high quality grade 1 oocytes harvested from bitches in the late luteal or anoestrous stage of the oestrous cycle were cultured in medium supplemented with either 1 microgram oestradiol ml-1 (64 oocytes), 1 microgram progesterone ml-1 (52 oocytes), a combination of oestradiol and progesterone (50 oocytes), or no supplementation (55 oocytes). The mean numbers of high quality (grade 1) oocytes with identifiable nuclear material collected per luteal ovary was 9.71 +/- 7.96, and per anoestrous ovary was 8.33 +/- 5.61. The number of oocytes obtained per bitch was highly variable, and may have been affected by the stage of oestrous cycle. After 48 h, maturation to GVBD was 56, 33, 50 and 50%, and to MI/AI/MII was 13, 17, 20 and 4% for each treatment respectively, and after 96 h was 45, 59, 63 and 63% and 10, 0, 4 and 0%, respectively. There was no significant difference in maturation between the four groups. The hormonal environment in vivo did not affect subsequent in vitro maturation of high quality oocytes. Similarly, culture in steroid hormone supplemented medium did not improve maturation in vitro of high quality oocytes. The effects upon oocytes from specific preovulatory follicles were not studied.

Animals↗
PubMed1997

Effect of progestogens and androgens upon spermatogenesis and steroidogenesis in dogs.

Two different progestogens, mixed testosterone esters, and a combination of progestogen and androgens were evaluated for their effect on semen quality and peripheral plasma testosterone and LH concentration in dogs. Megestrol acetate (2 mg kg-1) given orally for 7 days, and medroxyprogesterone acetate (10 mg kg-1) given subcutaneously produced no change in semen quality compared with that of control dogs. Higher doses of megestrol acetate (4 mg kg-1) produced minor secondary sperm abnormalities, whereas 20 mg medroxyprogesterone acetate kg-1 produced a rapid and significant decrease in sperm motility, morphology and output. The effect of progestogen was probably mediated by action upon the epididymis, since semen quality declined rapidly, morphological changes were the result of more secondary sperm abnormalities, and there was no suppression of plasma LH concentration. Mixed testosterone esters (5 mg kg-1) produced a significant decline in semen quality, which occurred 3 weeks after treatment and persisted for 3 months. There was an increase in the number of primary sperm abnormalities, and it was thought that the effect was probably related to suppression of gonadotrophin resulting in an effect on spermatogenesis. The combination of mixed testosterone esters (5 mg kg-1) and medroxyprogesterone acetate (20 mg kg-1) produced a rapid and profound decrease in semen quality. It was postulated that the effect of this combination of treatment on semen quality was mediated directly by the progestogen upon the epididymal phase of development, and the androgen causing suppression of gonadotrophins. Indeed a reduction in the plasma LH concentration was noted, and both primary and secondary sperm abnormalities were present. The dog appears to differ from other species in the sensitivity of the pituitary-hypothalamus to progestogen feedback. Gonadotrophin suppression does not occur even when high doses of progestogens are used and there are no significant effects on libido. However, combinations of progestogens and androgens may provide a clinically useful method of reversible contraception in the dog.

Animals↗