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Biomedical subjects

G Evans

Publications and source records attributed to G Evans.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of a 97-kDa phosphotyrosylprotein regulated by multiple cytokines.

We have examined the signal transduction pathways of a number of cytokines that interact with receptors that are members of the hematopoietin receptor superfamily. A 97-kDa protein was phosphorylated on tyrosine in response to stimulation of appropriate target cells with interleukin (IL)-2, IL-3, granulocyte-macrophage colony-stimulating factor (CSF), granulocyte-CSF, or erythropoietin. These data suggest that a 97-kDa phosphotyrosylprotein represents a point of convergence for signal transduction by a number of growth factor receptors that do not have homology with any known protein tyrosine kinase. To address the possibility that p97 may represent a tyrosine kinase involved in multiple signal transduction pathways, we tested the capacity of this protein to bind a tyrosine kinase substrate or ATP. Indeed, a 97-kDa phosphotyrosylprotein purified from IL-2-stimulated lymphoid cells as well as granulocyte-macrophage-CSF-stimulated myeloid cells bound to a polymer of glutamic acid and tyrosine which is a tyrosine kinase substrate. Further, a 97-kDa phosphotyrosylprotein present in both lineages also bound 8-azido-ATP. These data indicate that a 97-kDa phosphotyrosylprotein with properties consistent with those of a protein tyrosine kinase is involved in the signal transduction pathways of certain members of the newly identified hematopoietin receptor superfamily and may represent an early point of convergence in the stimulus-response coupling of multiple cytokine receptors.

Adenosine Triphosphate↗
PubMed1992

Isolation and mapping of polymorphic cosmid clones used for sublocalization of the multiple endocrine neoplasia type 1 (MEN1) locus.

Multiple endocrine neoplasia type 1 (MEN1) is characterized by neoplasia of the parathyroids, the pancreas, and the pituitary. Tumorigenesis involves unmasking of a recessive mutation at the MEN1 locus, which has been mapped to the centromeric part of chromosomal region 11q. In order to localize the MEN1 gene further and to make its isolation possible, a number of new markers were isolated. Two radiation-reduced somatic cell hybrids were identified that only contained markers close to and flanking the MEN1 region. DNA from these hybrids was used for the construction of a cosmid library, and clones containing human inserts were isolated. In addition, cosmid clones were isolated for locus expansion of 7 other markers that were mapped to the 11q12-13.2 region. The 33 newly isolated clones together with 25 previously published markers from this region were analyzed in a panel of radiation-reduced somatic cell hybrids. From the hybridization pattern, the region was divided into 11 parts. New restriction fragment length polymorphisms were identified in 7 of the newly isolated cosmid clones and in one plasmid. These were then used to sublocalize meiotic cross-overs more precisely in two MEN1 families, thus refining the mapping of the disease gene.

Blotting, Southern↗
PubMed1992

Immune response to a murine coronavirus: identification of a homing receptor-negative CD4+ T cell subset that responds to viral glycoproteins.

The lymphocyte proliferative response to mouse hepatitis virus, strain JHM (MHV-JHM), a well-described cause of chronic and acute neurological infections, has been studied using vaccinia virus recombinants expressing individual MHV proteins. The surface (S) and transmembrane (M) glycoproteins were the most active proteins in causing proliferation of lymphocytes isolated from immunized adult mice, whereas lymphocytes from persistently infected mice proliferated only in response to the S protein. The cells from immunized mice which proliferated most actively in response to MHV were positive for the CD4 antigen and secreted interferon-gamma. In addition, the most responsive subset of cells did not express gp90MEL-14, the lymph node-specific homing receptor. The results identify a subpopulation of CD4+ T cells that may be an important component of the cell-mediated immune response to this virus. The data also suggest that response to the M protein is important in preventing disease progression in C57BL/6 mice since cells which recognize this protein are absent from persistently infected mice.

Animals↗
PubMed1992

DNA sequences amplified in cancer cells: an interface between tumor biology and human genome analysis.

There is growing evidence that amplification of specific genes is associated with tumor progression. While several proto-oncogenes are known to be activated by amplification, it is clear that not all the genes involved in DNA amplification in human tumors have been discovered. Our approach to the identification of such genes is based on the 'reverse genetics' methodology. Anonymous amplified DNA fragments are cloned by virtue of their amplification in a given tumor. These sequences are mapped in the normal genome and hence define a new genetic locus. The amplified domain is isolated by long-range cloning and analyzed along three lines of investigation: new genes are sought that can explain the biological significance of the amplification; the structure of the domain is studied in normal cells and in the amplification unit in the cancer cell; attempts are made to identify molecular probes of diagnostic value within the amplified domain. This application of genome technology to cancer biology is demonstrated in our study of a new genomic domain at chromosome 10q26 which is amplified specifically in human gastric carcinomas.

Blotting, Southern↗
PubMed1992

Isolation of a zinc finger motif (ZNF75) mapping on chromosome Xq26.

We report here the partial characterization of a new human zinc finger (ZNF75) gene of the Kruppel type mapping to the long arm of the X chromosome. A cosmid clone was isolated from a library specific to the Xq24-qter region by hybridization to a degenerate oligonucleotide representing the link between two contigous fingers of the C2H2 type. The sequence of the pertinent cosmid fragments demonstrated five consecutive zinc finger motifs, all pertaining to the Kruppel family. A reading frame starting at least 75 amino acids before the first zinc finger and ending 11 amino acids after the last one was identified; comparison with other ZF genes suggests that this genomic fragment represents the carboxy-terminal exon of the gene. Homology of approximately 55% in the zinc finger region was detected with many zinc finger genes including mouse Zfp-35 and human ZFN7 cDNA clones. Mapping using a panel of sematic cell hybrids and chromosomal in situ hybridization localized the gene to Xq26, in a region not previously known to contain zinc finger genes.

Amino Acid Sequence↗
PubMed1992

Should prospective NHS employees have routine blood counts?

The results of pre-employment haematological screening from 958 prospective National Health Service (NHS) workers were reviewed. Although many abnormalities were found, few were judged to be clinically significant. In only one case did the examination affect employment. Haematological screening is an unnecessary part of the pre-employment medical assessment of prospective NHS employees.

Adult↗
PubMed1992

Evidence that platelet-activating factor suppresses uterine oxytocin-induced 13,14-dihydro-15-keto-prostaglandin F2 alpha release and phosphatidylinositol hydrolysis in the ewe.

This study was conducted to determine whether platelet-activating factor (PAF) (1) attenuated oxytocin-induced secretion of the prostaglandin (PG) F2 alpha metabolite, PGFM, by the ovine uterus in situ and (2) inhibited the generation of the inositol phosphate secondary messengers by endometrial tissue in response to oxytocin challenge in vitro. Ovariectomized ewes received steroid replacement to mimic the luteal phase. Six ewes received intrauterine injections of 200 micrograms PAF/uterine horn/day on Days 11-15, and 6 ewes were treated with vehicle. All ewes received 1 microgram oxytocin i.v. on Days 13-16. Pretreatment of ewes with PAF significantly suppressed PGFM release in response to oxytocin on Days 14 and 15 (p less than 0.005) compared to vehicle-treated ewes. PAF was not administered on Day 16, and the PGFM response to oxytocin was not different between groups. In a second experiment, ewes were given intrauterine injections of 200 micrograms PAF/uterine horn/day (n = 8) or vehicle (n = 7) on Days 11-15, and all ewes received 1 microgram oxytocin i.v. on Days 13 and 14. On Day 15 the uterus was removed, and the incorporation of 3H-inositol into inositol phosphates was determined in caruncular endometrium. Treatment of ewes with PAF in vivo reduced inositol monophosphate (IP1) generated by oxytocin (10(-6) M) by 56.4%, compared to that in endometrium from vehicle-treated controls, and also inhibited the incorporation of 3H-inositol into glycerophosphoinositol (GPI). If PAF was added to the endometrium during the incubation in vitro, the attenuation of inositol phosphate generation did not occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Cerebral metabolic dysfunction in AIDS: findings in a sample with and without dementia.

Positron-emission tomography was coupled with neurological and neuropsychological evaluation to study regional cerebral activity and neurologic status in two groups. Seventeen patients with full-blown AIDS and 14 seronegative control subjects were studied using [18F]2-fluoro-2-deoxy-D-glucose in a resting state. The AIDS group had relative regional hypermetabolism in the basal ganglia and thalamus; stepwise multiple-regression analyses revealed a significant relationship for the AIDS group between temporal lobe metabolism and severity of dementia on the AIDS Dementia Complex Rating Scale. These results suggest that the basal ganglia, thalamus, and temporal lobes are differentially affected in AIDS.

AIDS Dementia Complex↗
PubMed1992

Luteinizing hormone pulses, follicle-stimulating hormone and control of follicle selection in sheep.

The growth of large oestrogenic follicles that have the potential to ovulate if given an appropriate luteinizing hormone (LH) signal is dictated by the plasma concentration of follicle-stimulating hormone (FSH). Basal amounts of LH are essential for this FSH-induced follicle growth, but pulses of LH do not appear to be essential. The fall in FSH concentration during the follicular phase of the oestrous cycle in sheep, and the subsequent withdrawal of FSH from other developing follicles may not be sufficient to explain follicle selection. There is little evidence to support an active suppression of the growth of other follicles by a factor(s) produced by the dominant, or selected follicle. It is possible that LH pulses cause active atresia of non-selected follicles. The selected follicle is the one that can survive the fall in plasma FSH and the large increase in LH pulses during the follicular phase and selection may simply be a case of being the follicle(s) that is present at the correct time to receive adequate FSH and develop sufficiently to survive the inhibitory effects of LH pulses. Several mechanisms whereby LH pulses may inhibit follicle growth are suggested, and avenues for future research, particularly related to the expression of the LH receptor on granulosa cells of the developing follicle, are outlined.

Animals↗
PubMed1991

Fertility of superovulated ewes following intrauterine or oviducal insemination with fresh or frozen-thawed semen.

Two experiments were conducted with mature Merino ewes to investigate the effects of time and site of insemination of fresh and frozen-thawed semen on the fertility of superovulated ewes. In Experiment 1, each ewe was treated with an intravaginal progestagen sponge and PMSG and/or FSH. They were inseminated in the uterus with fresh or frozen-thawed semen (approximately 100 x 10(6) motile sperm) at 24, 44 or 64 h after sponge withdrawal. Ova were recovered at 88 h after sponge withdrawal and classified as fertilized if they had pronuclei or had cleaved. Mean fertilization rates of recovered ova were 60.0, 93.7 and 87.8% for fresh semen and 46.1, 98.2 and 26.1% for frozen-thawed semen at each of the insemination times (24, 44 and 64 h) respectively. Overall, fertilization rates were higher for fresh semen than for frozen-thawed semen (P less than 0.01), but there was an interaction with time of insemination (P less than 0.01). Following insemination with frozen-thawed semen at 64 h, only 61% of the fertilized ova developed to the 2- to 4-cell stage by the time of embryo recovery; this was less than in any of the other groups (P less than 0.05). In Experiment 2, ewes were inseminated with 100 x 10(6) motile fresh or frozen-thawed semen in the uterus or in the oviducts at 64 h after sponge withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Superovulation of Merino ewes with an ovine pituitary follicle stimulating hormone extract.

In order to investigate the effectiveness of ovine FSH as a superovulatory gonadotrophin in sheep, three batches (oFSH-1, oFSH-2 and oFSH-3) of crude follicle stimulating hormone (FSH) extracts were prepared from ovine pituitaries by protein fractionation. The extracts were characterized in radioimmunoassays (RIA), radioreceptor assays (RRA) and bioassays. A FSH:LH (luteinizing hormone) ratio of 1:0.71 and 1:0.18 was calculated from oFSH-1 in RIA and RRA respectively. oFSH-1 was more potent than NIH-oFSH-S12 in RRA, with a potency ratio of 1:0.65 calculated at 50% binding. In mouse bioassay, oFSH-2 was effective in inducing folliculogenesis. The potency of oFSH-3 as an ovarian stimulatory hormone was tested in a field trial on sheep. Thirty-one mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 6, 12 or 24 mg doses of oFSH-3 were injected twice daily for 3 days (n = 10 or 11). Each ewe was inseminated in the uterus with fresh semen 24 h after pessary withdrawal. Ova or embryos were recovered by mid-ventral laparotomy 6 or 7 days after pessary withdrawal. The dose of oFSH-3 had a significant effect on the ovulatory response (P less than 0.01); the mean ovulation rates were 1.5 +/- 0.2, 12.6 +/- 2.8 and 13.1 +/- 2.9 following injection with 6, 12 or 24 mg of the gonadotrophin respectively. The dose of the gonadotrophin injected had no effect on the mean percentages of ova recovered or fertilized. The overall ova recovery and fertilization rates (%) were 67.8 +/- 6.4 and 92.2 +/- 5.1 respectively. (ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1991

Application of reproductive technology to the Australian livestock industries.

Current use of reproductive technology in the Australian livestock industries is limited, though it increased in line with higher prices for beef and wool through the 1980s. The required techniques, many of which were developed in Australia, are available and the level of expertise is comparable to the best in the world. However, the extensive pastoral industries do not readily lend themselves to these procedures. Only in the dairy industry is artificial insemination used to a significant degree. On the other hand, application of the technology in the pastoral industries is confined largely to studs and breeding cooperatives which provide breeding animals for producer flocks and herds. Hence the impact of applied technology may be more widespread than first appears. Until recently, little regard was paid to application of the technology along sound breeding principles. Artificial insemination and multiple ovulation and embryo transfer (MOET) have not been used so much in planned breeding programmes aimed at local improvement of stock, but more to proliferate genes of reputedly superior stock, imported either from overseas or elsewhere in Australia. This is particularly true of MOET, where the incentive to use it is commonly a short term cash gain made from proliferating breeding stock of a particularly valuable and usually novel strain or breed. Recent technological improvements which render the use of reproductive technology cheaper and more effective will lead to its more widespread use in commercial practice. Techniques for embryo freezing and splitting have been greatly simplified and quickly put into practice. The novel livestock technologies of in vitro oocyte maturation and fertilization have already found commercial application overseas. Fecundity-enhancing products have also been adopted by the livestock industries. There is potential value for greater use of reproductive technology in the livestock industries provided it is implemented according to sound breeding principles and provided associated management practices are applied simultaneously.

Animals↗
PubMed1991

Effects of season, GnRH administration and lupin supplementation on the ovarian and endocrine responses of merino ewes treated with PMSG and FSH-P to induce superovulation.

Administration of gonadotrophin releasing hormone (GnRH) 24 h after sponge withdrawal did not affect the numbers of corpora lutea (CL) or persistent large follicles (LF) in ewes superovulated with 400 I.U. pregnant mare serum gonadotrophin and 12 mg follicle stimulating hormone in spring (11.6 +/- 0.9 v. 13.0 +/- 0.9 CL and 0.8 +/- 0.9 v. 0.9 +/- 0.3 LF, for +GnRH and -GnRH ewes, respectively). However, it did increase the ovulatory response of ewes superovulated in autumn (15.8 +/- 1.2 v. 11.8 +/- 1.1 CL). The incidence of ewes with prematurely regressed CL was also greater in autumn than in spring (21/89 v. 5/88). Supplementary feeding with lupin grain in autumn had no effect on numbers of CL but did increase the incidence of ewes with LF (18/48 v. 7/46) and caused a marked reduction in the incidence of ewes with regressed CL (1/44 v. 20/45). For ewes treated in autumn, there were no effects of lupin supplementation or GnRH administration on peak oestradiol-17 beta (E2) or peak luteinizing hormone (LH) levels. However, when peak E2 concentrations in the plasma were adjusted for numbers of preovulatory follicles, higher concentrations were observed for ewes in the +lupin/-GnRH group (12.4 +/- 2.9 pg mL-1) than in other treatment groups (range 4.3 +/- 0.4 to 5.7 +/- 0.3 pg mL-1). Moreover, the time of the LH peak was advanced by both lupin supplementation and GnRH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1991

Drug contamination from opening glass ampules.

Recently there have been several reports of postoperative sepsis due to the intravenous injection of contaminated solutions of propofol (Diprivan). The mechanism by which this contamination occurred has not been identified. This study sought to determine whether bacterial contamination of the contents of glass ampules can be decreased by swabbing the neck of the vial with alcohol prior to opening. Glass ampules of 1% propofol and 1% lidocaine were swabbed with a solution of Staphylococcus epidermidis. Half of these ampules were subsequently wiped with alcohol pads prior to being opened. An aliquot from each ampule was pipetted into a nutrient broth and allowed to incubate overnight at 37 degrees C. These solutions were plated on agar, incubated for 24 h, and then examined for bacterial growth. Three of the eight lidocaine ampules and six of the eight propofol ampules not cleaned with alcohol demonstrated evidence of bacterial contamination. The contents of all ampules that had been wiped with alcohol prior to being opened remained sterile (P less than 0.001 vs. non-alcohol-treated group for propofol ampules and P = 0.20 vs. non-alcohol-treated group for lidocaine ampules). These data suggest that bacterial contamination of propofol and lidocaine may occur as a result of opening glass ampules. Wiping the outside of the ampule with alcohol immediately prior to opening may decrease this risk.

Alcohols↗
PubMed1991

Conception rates in European fallow does (Dama dama dama) following intrauterine insemination with frozen-thawed semen from Mesopotamian fallow (Dama dama mesopotamica) and crossbred (Dama dama dama x Dama dama mesopotamica) bucks.

Ninety eight parous fallow does received laparoscopic intrauterine insemination of frozen-thawed semen at one of 2 fixed intervals following oestrus synchronisation treatment. Semen was collected from a Mesopotamian (Dama dama mesopotamica) and a crossbred (F1) (Dama dama dama x Dama dama mesopotamica) fallow buck. Does were inseminated at either 56 or 66 hours after the removal of an intravaginal controlled internal drug releasing device. Eighty eight does received a single straw of frozen-thawed semen containing a total of 50 x 10(6) spermatozoa, while the remaining 10 received split straws containing 25 x 10(6) spermatozoa. Overall, the use of F1 semen containing 50 x 10(6) spermatozoa resulted in a 68% (17/25) conception rate compared with the Mesopotamian semen, which resulted in a 41% (26/63) conception rate. Conceptions were also achieved using 25 x 10(6) spermatozoa of either Mesopotamian or F1 semen (3/8 versus 2/2, respectively). Overall, the conception rate was higher for F1 than Mesopotamian semen (P less than 0.025) and there was a significant interaction with time of insemination (P less than 0.05); for F1 semen there was no difference in conception rate at the 2 insemination times, but for Mesopotamian semen conception was significantly higher (P less than 0.005) following insemination at 66 hours than at 56 hours.

Animals↗