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Biomedical subjects

G H Davis

Publications and source records attributed to G H Davis.

At least 37 records · Page 2Linked to original sources
PubMed1993

Changes in liveweight and behaviour of alpaca dams and offspring following weaning.

The effects of offspring sex, weight, age, and level of interaction with the dam on responses to weaning were examined to assist in the development of a weaning protocol for alpacas. In the first study, preand post-weaning activities, and weight change over Days -12-0,0-7 and 7-16 with respect to weaning, were recorded for 20 dam-offspring (hembra-cria) pairs aged 81-200 days. Pre-weaning changes in dam and offspring weights were positively related (P<0.05). Although heavier crias tended to be found closer to their dams than lighter crias (P<0.05) no additional effect of age on the dam-offspring relationship was found. Following weaning, cria growth rates were low over Days 0-7 but improved over Days 7-16, and hembra weight change followed the same pattern. Over Days 0-2, grazing and sitting activities of hembras and crias were replaced by standing and walking along paddock fencelines, although by Day 2 fenceline activities had decreased (P<0.05). Crias which were more frequently observed at fencelines had lower post-weaning growth rates (P<0.05). In the second study, pre-weaning sucking behaviour, and weight change over Days -30-0, 0-8 and 8-16 with respect to weaning, were recorded for 19 hembra-cria pairs aged 124-160 days. During 10 hours of observation on Days -5 and -4, the total duration of sucking by individual crias varied from 0-18 minutes, and the mean +/- SEM duration of sucking was 1.94 +/- 0.113 minutes. Cria sucking behaviour was positively related to growth rate prior to and weight at weaning (P<0.05). As in the first study, pre-weaning changes in dam and offspring weights were positively related (P<0.05). Following weaning, growth rates of the crias were depressed and the hembras lost weight over Days 0-8 and 8-16. The changes in growth rate and behaviour in Studies 1 and 2 indicated that weaning can be stressful for hembras and crias. However, there was no evidence from either study that pre-weaning behavioural or physical characteristics were related to the changes.

Journal Article↗
PubMed1993

Ovaries of ewes homozygous for the X-linked Inverdale gene (FecXI) are devoid of secondary and tertiary follicles but contain many abnormal structures.

Ewes homozygous (II) for the Inverdale prolificacy gene (FecXI) located on the X chromosome are infertile with "streak" ovaries. The aims of this study were to examine the ovarian morphology and plasma and tissue (or extracellular fluid) hormone concentrations in II ewes in comparison to control (++) animals. All II animals (n = 11) were found to contain no normal ovarian follicles beyond the primary stage of development despite their being similar in number of germ cells to the ++ ewes. The II animals had high plasma gonadotropin levels and undetectable estradiol and progesterone, and in addition 6 of 9 ewes had undetectable plasma inhibin concentrations. II ewes contained large numbers of oocyte-free follicles ("nodules") that were often found as clusters in the innermost regions of the cortex. In addition, 6 of 11 ewes contained abnormal luteal- or granulosa cell-like structures and other unusual formations. In three II animals the abnormal structures were visible on the ovarian surface, and the plasma inhibin concentrations in these ewes were significantly higher than in the ++ ewes (p < 0.05). Collectively these findings suggest that two copies of the FecXI mutation impair the resumption of growth of primordial follicles and may in some instances lead to the development of abnormal structures having a morphology consistent with that observed for ovarian tumors.

Animals↗
PubMed1992

Infertility due to bilateral ovarian hypoplasia in sheep homozygous (FecXI FecXI) for the Inverdale prolificacy gene located on the X chromosome.

Ewes heterozygous (I+) for the Inverdale prolificacy gene (FecXI) located on the X chromosome have ovulation rates about 1.0 units higher than noncarriers. The purpose of this study was to examine the reproductive performance of ewes that were either heterozygous or homozygous (II) carriers of the Inverdale gene. Carrier rams (I) were mated with heterozygous ewes (I+) to produce females, half of which were expected to be I+ and half II. The 59 female progeny were examined by laparoscopy at 8 mo or 1.5 yr of age; 48% were found to have nonfunctional "streak" ovaries, which were about one eighth the volume of normal ovaries and showed no sign of follicular activity. There were four examples of full sib pairs where within each pair one had normal ovaries and the other had streak ovaries. Since these streak ovaries have not been observed in ewes known to be I+ or noncarriers (++), it is concluded that this condition is associated with animals homozygous for the Inverdale gene.

Animals↗
PubMed1991

Evidence for the presence of a major gene influencing ovulation rate on the X chromosome of sheep.

In a flock of highly prolific Romney ewes obtained from industry flocks, one ewe (A281), with a production record of 33 lambs born in 11 lambings, produced a number of female descendants with high ovulation rates. The mode of inheritance of this trait was determined in a series of four progeny tests of male descendants of this ewe. The first progeny test produced strong evidence for a new major gene affecting ovulation rate in this family line; this finding was supported by two subsequent progeny tests. The fourth progeny test was designed to test the hypothesis that this gene is carried on the X chromosome. The results showed that six sons of a carrier ram did not inherit the gene, but it was passed on to three of his five maternal grandsons. This finding, together with evidence of genetic segregation in the progeny of carrier females, demonstrates for the first time the presence of a major gene for prolificacy specifically located on the X chromosome. The effect of the gene is to increase ovulation rate by about one additional egg per ewe.

Animals↗
PubMed1991

Management of acute paroxysmal supraventricular tachycardia in pregnancy.

The treatment of paroxysmal supraventricular tachycardia (PSVT) in pregnancy is not unlike treatment for the general population. The physician should feel confident that the pharmacologic agents ordinarily used to treat this common problem in the general population are safe for both mother and fetus when administered under monitored conditions. In treating paroxysmal supraventricular tachycardia in pregnancy, when both vagal maneuvers and exhaustive medical therapy fail, synchronized, direct-current cardioversion is a safe and effective form of treatment.

Anti-Arrhythmia Agents↗
PubMed1990

Selective reduction of multifetal pregnancies.

Selective reduction was carried out in 46 multifetal pregnancies by means of potassium chloride injection into the pericardial region of the fetus. There were three indications for the procedure: to improve perinatal outcome and to increase the likelihood that a term infant would be born in a multifetal pregnancy (34 women); to allow the birth of a healthy infant without the birth of a congenitally abnormal coexisting fetus (8 women); and to preserve a singleton pregnancy when the woman would otherwise have the whole pregnancy terminated (4 women). Of the 80 fetuses left after reduction 75 (94%) have survived. In 3 cases ultrasound scanning showed cardiac activity in the injected fetus 20-30 min after the initial injection despite 2 min of asystole immediately after the injection; repeated injection, carried out the same day, led to fetal death in all 3 cases. Selective reduction of multifetal pregnancies for the three indications described is an ethically justifiable option for the management of multifetal pregnancy, to which there are no public policy obstacles.

Congenital Abnormalities↗
PubMed1990

Immunopathological investigations during the course of arthritis induced in rats by Streptococcus agalactiae.

A large single intraperitoneal injection of sonicated cells of Streptococcus agalactiae O90R induced polyarthritis in Wistar rats. The arthritis reaction score was monitored according to redness, edema, severity and deformity of rat ankle and wrist joints. The inflammation of joints was confirmed by radiology and histology. Acute arthritis was initiated within 48 h and the chronic form continued for more than 30 days. Although serum immunoglobulin was elevated within 48 h, anti-streptococcal antibody was detected only at later times (by enzyme-linked immunosorbent assay and Arthus-type hypersensitivity reactions) and neither serum nor splenocytes of arthritic rats were able to transfer disease to susceptible, normal rats. From these observations and the finding of streptococcal antigen in joint macrophages (by immunogold labelling) we conclude that arthritis is related to persistent streptococcal fragments rather than to antibody or immune complexes.

Animals↗
PubMed1990

Phenotypic conversion of Pseudomonas aeruginosa in cystic fibrosis.

Pseudomonas aeruginosa strains isolated from cystic fibrosis patients were tested for production of exoenzymes, sensitivity to pooled normal human serum, and colony morphology. Strains isolated from patients exhibiting a severe form of the disease were seen to produce a decreased range of exoenzymes, to show an increase in their serum sensitivity, and to be predominantly mucoid in colonial character compared with strains isolated from patients with a milder form of the disease. These results suggest that P. aeruginosa undergoes phenotypic changes with respect to exoenzyme secretion, serum sensitivity, and colony form as the clinical condition of the cystic fibrosis patient changes.

Adolescent↗
PubMed1990

Mosaicism in chorionic villus sampling: an association with poor perinatal outcome.

Prenatal diagnosis by first-trimester chorionic villus sampling was successful in 4319 pregnancies involving 4395 fetuses. Cytogenetic information was obtained by both rapid cytotrophoblastic preparation and monolayer mesenchymal tissue culture. Chromosomal mosaicism was present in 55 of 4319 (1.3%). The abnormal cell line involved the cytotrophoblast in 79.6% of the mosaic specimens. None of the abnormalities found in the cytotrophoblast were confirmed in the fetus when the tissue culture was normal, supporting the belief that the cells of the mesenchymal core more truly reflect the chromosomal constitution of the fetus. However, a significant increase in the perinatal loss rate in the placental mosaic group was noted when compared with the nonmosaics: 16.7 versus 2.7% (P = .0001). These findings suggest that placental mosaicism may be a cause of perinatal loss.

Abortion, Spontaneous↗
PubMed1989

Extracellular and surface-bound biological activities of Vibrio fluvialis, Vibrio furnissii and related species.

Twenty-seven Vibrio strains were assessed for virulence-associated biological activities, including iron chelation, hydrolases, haemolysis and haemagglutination. All strains hydrolysed DNA, chitin, gelatin and casein, produced siderophores, and lysed red blood cells. All V. fluvialis, V. cholerae and V. mimicus strains exhibited diverse lipolytic activity distinct from more discriminate lipolysis by V. furnissii. V. furnissii manifested fibrin and mucin hydrolysis but no phosphate or esculin hydrolysis, for which V. fluvialis varied. No strains hydrolysed urea, alginate or keratin. V. fluvialis, V. furnissii and V. mimicus strains failed to exhibit the mannose-sensitive haemagglutination typical of V. cholerae. Some activities may distinguish otherwise phenotypically similar species. Species tested commonly possessed biological activities that may contribute to virulence, although there was no apparent correlation with isolation from human sources.

Hemagglutination↗
PubMed1989

Concentrations of FSH are elevated in new-born ewe lambs carrying the Booroola F gene but not in lambs from a prolific Romney strain.

Concentrations of FSH were measured in new-born lambs in Booroola Merino x Romney and Booroola Merino flocks where the Booroola F gene was segregating, and in progeny from sires of a prolific strain of Romney sheep. FSH concentrations increased with age and liveweight in Booroola Merino x Romney ewe lambs to reach peak concentrations at 4-6 weeks of age. Significantly higher mean concentrations were recorded in ewe lambs homozygous for the Booroola gene (FF) compared with non-carrier (+ +) ewe lambs. Concentrations in heterozygous (F+) ewe lambs were intermediate. Maximum differences between the genotypes were recorded at 6 weeks of age. Significantly higher FSH concentrations were also recorded in F-gene-carrier female lambs when compared to non-carriers in two other flocks. FSH concentrations remained low in ram lambs up to 12 weeks of age, and there were no differences between Booroola genotypes. The progeny of one ram from the prolific Romney family had high ovulation rates at 18 months of age. The progeny of other related rams showed no increase in ovulation rates at 18 months of age. Concentrations of FSH in the high-ovulation-rate progeny at 3 and 5 weeks of age did not differ from those in the low-ovulation-rate progeny, but were lower than those in the progeny of an FF Booroola Merino x Romney ram. These results support the hypothesis that neonatal concentrations of FSH are higher in lambs carrying the Booroola F gene, but not in all prolific strains since high FSH concentrations were not recorded in daughters from a prolific Romney flock.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Isolation of medically significant Vibrio species from riverine sources in south east Queensland.

Vibrio and Vibrio-like bacteria were isolated from water, sediments, plants and faeces from eight riverine sites in South East Queensland, Australia, using filtrations, enrichments and selective growth on thiosulphate-citrate-bile salts-sucrose (TCBS) and Simidu agars. Isolates (402 in toto) were classified by numerical analysis of phenotypic characteristics and comparison with fifteen reference cultures. Of the isolates 41 (10.2%) were identified as Vibrio cholerae, 33 (8.2%) as V. fluvialis and 118 (29.4%) as motile Aeromonas species. Other isolates resembled V. parahaemolyticus, V. alginolyticus, V. vulnificus and V. hollisae. No isolates were positively identified as V. damsela or Plesiomonas shigelloides. Vibrio species tolerant of low salt levels and aeromonads were widely distributed in riverine locations but more halophilic species were restricted to more saline areas. Simidu agar failed to select for vibrios as effectively as TCBS agar. Enrichment for 18 h produced more isolates than for 6 h.

Culture Media↗
PubMed1986

Immunoelectrophoretic analysis of Streptococcus agalactiae serotype Ia antigens.

Rabbit antibodies to heat-killed whole cells of Streptococcus agalactiae serotype Ia were used to establish an antigen map using Triton X-100 sonicates of homologous cells and crossed immunoelectrophoresis. A total of 11 antigens were identified but the density of immunoprecipitates was varied and only seven could be reliably detected, one of which dominated the immunoprecipitate pattern by its intensity. The antigens were partially characterized by immunological, chemical and cell-location methods. Five of the antigens contained carbohydrate and two of those were sensitive to trypsin and probably represent cell-wall compounds. Of the three most prominent antigens, one was surface located and represented the type and shared type antigens (Iabc), one was a cell-wall carbohydrate and very sensitive to periodate, and one was a protein/carbohydrate complex which was heat-labile and trypsin sensitive. Group B epitopes were detected in three immunoprecipitates. Cross-reactions between type Ia and other serotypes and streptococci were recorded.

Antigens, Bacterial↗