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G Evans

Publications and source records attributed to G Evans.

At least 145 records · Page 8Linked to original sources
PubMed1997

A novel splice variant of the cell adhesion molecule BIG-2 is expressed in the olfactory and vomeronasal neuroepithelia.

We have cloned a mouse cDNA encoding a novel truncated form of the gene BIG-2 from the vomeronasal organ. The related proteins BIG-2 and BIG-1 possess a C-terminal glycosylphosphatidylinositol anchor, six immunoglobulin domains and four fibronectin type III repeats. They are related to certain axonal-associated cell adhesion molecules (AxCAMs) exhibiting most similarity to the TAG-1/F3 subgroup of neural cell adhesion molecules. The cDNA we have identified, termed BIG-2A, appears to represent a novel splice variant of BIG-2 possessing six Ig-like domains, a single fibronectin repeat and lacking the glycosylphosphatidylinositol-anchoring domain (GPI). To determine the expression of this gene, in situ hybridization analysis was performed in adult and developing mice using a riboprobe specific for BIG-2A. Maximum expression was observed in mature sensory cells of the vomeronasal neuroepithelium and a less intense signal was also evident in the olfactory neuroepithelium. These results suggest that alternative splicing of the BIG-2 gene transcript may play an important role in the organization of the vomeronasal and olfactory neuroepithelia.

Alternative Splicing↗
PubMed1997

The experience of caring for an adult child with schizophrenia.

The experience of caring for an adult child with schizophrenia was explored using phenomenological methodology. Nine parents who were the primary caretakers of an adult child with schizophrenia participated in qualitative interviews. The resulting transcripts were analyzed to discover the structure of the lived experience. The study revealed that the diagnosis of schizophrenia in a child is experienced by the parent as a destructive force that interrupts and radically transforms the normative family life trajectory. This grief-filled experience involves both the loss of an imagined, idealized child and a transformation of the physically present child into a needy stranger. Implications are discussed and applied to community-based, family-centered mental health care. Importantly, the revealed dissatisfaction with initial mental health evaluations suggests that modification of current practices could produce significant benefits.

Adaptation, Psychological↗
PubMed1997

Central nervous system relapse in acute promyelocytic leukaemia in patients treated with all-trans retinoic acid.

All-trans retinoic acid (ATRA) is currently recommended as standard treatment for acute promyelocytic leukaemia (APL). However, there has been increasing concern that ATRA is associated with unusual sites of relapse. We present three cases of APL previously treated with ATRA who ultimately relapsed within the central nervous system (CNS) and hypothesize that, by up-regulating intercellular adhesion molecules, ATRA may facilitate the passage of malignant promyelocytes across the blood-brain barrier.

Adult↗
PubMed1997

Capacitation status and fertility of fresh and frozen-thawed ram spermatozoa.

The effect of cryopreservation on the capacitation status and fertility of ram spermatozoa was observed. After the chlortetracycline staining technique was validated for ram spermatozoa, it was applied to fresh or long-term frozen-stored spermatozoa. Fresh spermatozoa displayed mainly the F pattern (non-capacitated; 61.3%), becoming B pattern (capacitated; 54%) and AR pattern (acrosome reacted; 41%) with incubation (6 h at 37 degrees C). In contrast, frozen spermatozoa displayed the B pattern (65.9%), becoming the AR pattern (64.2%) with incubation. This demonstrates that cryopreservation may cause membrane changes in ram spermatozoa functionally equivalent to capacitation. The differences in capacitation status did not affect in vitro fertilization rates between fresh and frozen spermatozoa, but pregnancy rates at Day 18 after intrauterine artificial insemination were higher for fresh than for frozen spermatozoa. This difference was not evident at Day 50, possibly as a result of the high embryonic loss between Days 18 and 50 when fresh unincubated and frozen incubated spermatozoa were inseminated. Further research is necessary to determine what part of the cryopreservation process is responsible for the membrane changes in ram spermatozoa.

Animals↗
PubMed1997

Effect of culture, incubation and acrosome reaction of fresh and frozen-thawed ram spermatozoa for in vitro fertilization and intracytoplasmic sperm injection.

This study evaluated different sperm treatments for fertilization of sheep oocytes by intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF). In Experiment 1, fresh and frozen semen was separated by Percoll centrifugation and incubated at 30 degrees C or 39 degrees C in HSOF or BSOF medium for 1 h before use for IVF or ICSI. For IVF, oocytes were inseminated and incubated with sperm for 30 min, 4 h and 19 h. Sperm were assessed for acrosome integrity after Percoll centrifugation and 1 h incubation, and those used for IVF were assessed after each period of exposure to the oocytes. Fertilization rates after ICSI were higher for fresh than for frozen-thawed sperm and were highest 19 h after IVF with fresh or frozen-thawed sperm in the presence of HSOF at 30 degrees C. In Experiment 2, fresh semen was separated by Percoll centrifugation and incubated for 5 h in HSOF, and the acrosome reaction was induced with lysophosphatidylcholine. Acrosome integrity was then assessed. Fertilization rates after ICSI were similar for acrosome-reacted and control spermatozoa. These results suggest that induction of the acrosome reaction in spermatozoa before ICSI is unnecessary, whereas a capacitating treatment of spermatozoa is required before IVF.

Acrosome↗
PubMed1997

Effect of hormone pre-treatment of prepubertal sheep on the production and developmental capacity of oocytes in vitro and in vivo.

Twenty 3-6-week-old Merino lambs were given either 3, 1 or 0 treatments of 50 microg oestradiol benzoate and (48 h later) a 1.5 mg Norgestamet implant left in situ for 9 days (3-, 1- and 0CYCLE+G). On Day 7 after the last implant insertion, and on the same day for 0CYCLE+G, each lamb received 400 I.U. pregnant mare serum gonadotrophin and 6 mg follicle-stimulating hormone (FSH). The reproductive tracts were removed for oocyte collection 24 h after FSH. Reproductive tracts were also collected from 16-24-week-old lambs (n = 31) (0CYCLE-G). The number of antral follicles per ovary was similar for the 3-, 1- and 0CYCLE+G treatments. Similar rates of in vitro maturation and monospermic fertilization were obtained for all groups. The proportion of blastocysts per cleaved oocyte was higher for 1CYCLE+G (50.5%) than for 3CYCLE+G (32.9%), 0CYCLE+G (24.3%), and 0CYCLE-G (11.8%) (P < 0.05). Viable fetuses were obtained at Day 93 of pregnancy after transfer of embryos from all treatments. These results indicate that a single treatment with oestrogen and progesterone, prior to gonadotrophin stimulation, will increase the yield and developmental capacity of oocytes from prepubertal sheep.

Animals↗
PubMed1997

The African-American Health Project (AAHP): study overview and select findings on high risk behaviors and psychiatric disorders in African American men.

The AAHP investigated the neurobehavioral and psychosocial sequelae of HIV-1 and substance use in urban African American men. A community resident sample of 502 African American men stratified by HIV-1 serostatus, drug use and sexual orientation were recruited. A comprehensive battery of measures of neurobehavioral and health status, lifestyle and psychosocial characteristics were administered to all participants, and a stratified sub-sample of 120 participants were tested using state of the art brain imaging techniques to investigate differences in the functional and neurophysiologic effects of HIV-1 and substance use. An overview of the methodology of the AAHP and results on high risk sexual and substance use behaviors, and psychiatric disorders are presented and discussed. The sample was primarily HIV-negative (63%), heterosexual (49% gay or bisexual) and a high percentage used substances during the past year (56% used drugs and 30% moderate/heavy drinkers). High-risk sexual practices were relatively prevalent, and a high percentage reported a history of STDs and other infections. Finally, 25% had a current psychiatric disorder, with gays/bisexuals and HIV-seropositives evidencing greater psychiatric vulnerability. More research is needed to further explore the apparent greater risk for psychiatric disorders among gay and bisexual men, and to determine whether being African American and lower social class exacerbate this risk.

Adult↗
PubMed1997

Hoechst staining and exposure to UV laser during flow cytometric sorting does not affect the frequency of detected endogenous DNA nicks in abnormal and normal human spermatozoa.

Controlling the sex of offspring by the separation of X and Y chromosome-bearing spermatozoa using flow cytometry has been reported as a clinical technique aiding prevention of X-linked diseases. Although this technique has resulted in several hundred normal births in animals and at least one human birth, there is still concern over its genetic safety due to the involvement of two potentially mutagenic agents: UV light and the fluorochrome dye, Hoechst 33342 (H33342). Human spermatozoa, particularly those considered abnormal, may be more likely to suffer DNA damage following exposure to mutagenic agents, compared with other mammalian species. The stability of normal fresh and decondensed human spermatozoa were examined after exposure to a range of levels of UV and H33342 staining, using an assay that detects endogenous nicks in the DNA of spermatozoa. The stability of abnormal and normal, fresh and frozen-thawed human spermatozoa was examined following UV laser, H33342 staining and flow cytometry treatments utilizing the same assay. There was an increase in the presence of endogenous nicks when spermatozoa were decondensed compared with fresh spermatozoa. There was no increase in the incidence of nicks in any group of spermatozoa after UV and fluorochrome exposure compared with controls without exposure.

Animals↗
PubMed1997

Recurrent venous thromboembolic disease and factor XI concentrate in a patient with severe factor XI deficiency, chronic myelomonocytic leukaemia, factor V Leiden and heterozygous plasminogen deficiency.

There are increasing concerns about the potential thrombogenic risks associated with the use of factor XI concentrates. We describe the case of a 49 year-old man with chronic myelomonocytic leukaemia and severe factor XI deficiency (< 1 u/dl), in whom the use of factor XI concentrate appeared to be associated with the development of venous thromboembolic disease. Subsequent investigations revealed the presence of both the factor V Leiden abnormality and heterozygous plasminogen deficiency. This case highlights the risks associated with the use of factor XI concentrates and suggests that these risks may be further increased in patients with an inherited or acquired prothrombotic abnormality or an underlying malignancy. Prothrombotic screening of patients with severe factor XI deficiency may be indicated particularly in younger patients in whom treatment with factor XI concentrates is a possibility.

Factor V↗
PubMed1997

Clarifying plasma melatonin profiles in domestic pigs: a critical and comparative evaluation of two radioimmunoassay systems.

The results of a direct radioimmunoassay (RIA) for porcine plasma melatonin, suggesting a relationship among plasma melatonin, feed intake and photoperiod, were investigated by comparison with the results of an extracted RIA. These findings were further examined by analysis of a small number of samples using gas chromatography-mass spectrometry (GCMS). The results identified inadequacies in the specificity of the direct RIA and failed to provide evidence for an effect of feed intake on melatonin secretion. Instead, it appeared that feed restriction exacerbated nonspecificity in the direct RIA. The cause of nonspecificity, and its effect on analysis of daily plasma melatonin profiles, were examined. The plasma component(s) responsible for nonspecificity was (were) not identified. However, the results suggest that characteristics of the antiserum used in the direct RIA are involved in the mechanism by which nonspecificity is induced. Results obtained using the extracted assay revealed that plasma melatonin concentrations in prepubertal gilts and pregnant sows exhibit a diurnal pattern, in which concentrations are low during daylight and modestly increased during darkness. Using the direct RIA, the same profiles exhibited highly variable melatonin concentrations showing little association with the light-dark cycle. Thus, assay specificity was identified as a factor contributing to inconsistencies in the literature describing plasma melatonin in the domestic pig and the importance of rigorous validation of RIAs was demonstrated. Furthermore, the results indicate that plasma melatonin concentrations in domestic pigs, as in other mammalian species, are entrained by the light-dark cycle.

Animals↗
PubMed1997

Political ideology and popular beliefs about class and opportunity: evidence from a survey experiment.

This paper examines popular understanding of class inequalities in opportunity using an experimental approach to assess implicit as well as explicit comprehension. Three competing representations of popular beliefs are compared: a 'class inequality' model, implying widespread belief in class-related inequalities of opportunity; a 'meritocratic' view of achievement, in which emphasis is placed on individual responsibility; and an 'ideological polarization' model, which assumes that beliefs emphasizing class inequality or merit vary with left-right ideology. Predictions derived from these ideas are tested using a national survey with an experimental design, in which respondents are presented with vignettes designed to elicit their beliefs as to how and why people from different class backgrounds obtain middle-class or working-class occupations. As predicted by the class inequality model, there is clear evidence of the impact of tacit assumptions about class structured inequality of opportunity on expectations, judgments of responsibility and explanations of occupational attainment. Even among right-wing respondents, who are more likely to endorse the rhetoric of individual responsibility, there remains an implicit awareness of social class influences on life-chances, suggesting the pervasive presence of these beliefs in popular understanding of social processes.

Data Collection↗
PubMed1996

Birth of a male lamb derived from an in vitro matured oocyte fertilised by intracytoplasmic injection of a single presumptive male sperm.

The developmental competence of in vitro matured ovine oocytes, cytoplasmically injected with single male or female chromosome-bearing sperm, was investigated. Eighty-five unsorted, 92 'female-sorted' and 74 'male-sorted' ram sperm were injected into in vitro matured sheep oocytes and, two to four hours later, placed into the oviducts of 28 oestrous sheep. The sperm were separated according to sex by analysis of their DNA content with a flow cytometer. One pregnancy was diagnosed by ultrasound after 55 days and a 3 kg male lamb was born after 150 days gestation. This lamb was derived from an oocyte injected with 'male-sorted' sperm.

Animals↗
PubMed1996

Pertussis.

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Adolescent↗
PubMed1996

The Albany Medical College Ventilator Walker.

This report describes the design and use of a wheeled walker that can accommodate a ventilator and oxygen tanks. It is constructed of aluminum tubing. The front of the walker has receptacles to support a Mark 7 Bird Ventilator and oxygen tanks. The back end of the walker has a bench seat that is lifted to allow entry into the walker. The seat provides rigidity and stability to the frame of the walker. The walker has been used in the Medical Intensive Care Unit of the Albany Medical Center to facilitate early ambulation of patients who are ventilator dependent or who require a portable source of oxygen to begin ambulation training.

Aged↗
PubMed1996

Fertility of ram spermatozoa pellet-frozen in zwitterion-buffered diluents.

The fertility (positive ultrasound scanning 60-75 days after insemination) of ram spermatozoa frozen in Tris- or zwitterion/glucose/egg yolk/glycerol-based diluents was examined during the natural breeding season (autumn). In Experiment 1 Tris-citrate, high glucose and Hepes-NaOH diluents were used and ewes (n = 266) were inseminated (induced oestrus) with 20 (uterus) or 180 (cervix) million motile spermatozoa. There was no difference in fertility (range: 10.9-71.1%) between diluents, despite the superior post-thawing motility and progressive velocity of spermatozoa in Hepes-NaOH compared with the other diluents (P < 0.001). In Experiment 2, there was no difference in fertility (range: 4.1-50.0%) between Tris-citrate and Hepes-NaOH diluents after insemination (induced oestrus) of ewes (n = 290) with 10 (uterus) or 100 (cervix) million motile spermatozoa, respectively. In Experiment 3 Tris-citrate, Hepes-NaOH and Pipes-NaOH diluents were used and ewes (n = 492) were inseminated (natural oestrus) with 8 or 24 (uterus), or 80 or 240 (cervix) million motile spermatozoa. There were no differences in fertility (range: 35.4-52.9%) between insemination doses or diluents despite the superior motility and acrosome integrity in the zwitterion compared with the Tris-citrate diluents (P < 0.001). In all experiments, the fertility of frozen spermatozoa was higher for intrauterine than cervical insemination (51.9 vs 22.1%, n = 1 048; P < 0.01). It was concluded that post-thawing in vitro quality was superior and the fertility comparable after freeze-thawing spermatozoa in zwitterion compared with Tris-citrate diluents.

Animals↗
PubMed1996

Developmental capacity, energy metabolism and ultrastructure of mature oocytes from prepubertal and adult sheep.

Development to the blastocyst stage was assessed for oocytes obtained from prepubertal and adult sheep matured and fertilized in vitro. The proportion of cleaved oocytes reaching the blastocyst stage was significantly lower for oocytes derived from prepubertal sheep than for those from adult sheep (7.4% and 24.6% respectively). There were no differences in the metabolism of glucose, glutamine or pyruvate between oocytes matured in vivo and in vitro, or of glucose or pyruvate between oocytes from prepubertal and adult sheep. Glutamine metabolism by mature oocytes from prepubertal sheep was significantly lower than that by oocytes from adult sheep. Ultrastructural studies revealed no differences in the morphology of cytoplasmic organelles of oocytes matured in vitro from prepubertal and adult sheep, but differences in the volume fraction and size of mitochondria and cortical granules were observed. These data suggest that mature oocytes from prepubertal sheep do not possess the developmental potential of their adult-derived counterparts, and this phenomenon may be associated with metabolic and ultrastructural anomalies.

Aging↗
PubMed1996

Ovine endometrium synthesizes and releases platelet-activating factor, which can cause the release of prostaglandin F2 alpha by the uterus in situ.

Explanted endometrial tissue from ovariectomized ewes that had received hormone replacement to mimic the luteal phase released platelet-activating factor (PAF) into medium in vitro. On Day 14, 310.1 (261-2185), and on Day 15, 424.4 (14.1-590.7) pg PAF (median 25th-75th percentile; p > 0.05) was released per 100 mg endometrial tissue after a 20-min incubation. A regulatory and final enzyme in the PAF biosynthetic pathway, lysoPAF:acetyltransferase, was also present with a specific activity of 0.533 +/- 0.124 pmol acetate/50 micrograms protein/30 min in Day 14 endometrial tissue and 0.810 +/- 0.468 in Day 15 tissue (mean +/- SEM; p > 0.05). PAF:acetylhydrolase, the metabolic enzyme regulating PAF's half-life, was present in uterine luminal washings, with a specific activity of 3.78 +/- 1.37 nmol acetate released/min/mg protein on Day 14 and 3.41 +/- 0.34 on Day 15 (mean +/- SEM; p > 0.05). Intrauterine infusion of 50-400 micrograms PAF caused a dose-dependent release of prostaglandin (PG) F2 alpha (measured as venous 14-dihydro-15-keto-prostaglandin F2 alpha, PGFM) within 10 min on Days 13-15. The enantiomeric form of PAF was significantly less effective in inducing a rise in venous PGFM. WEB 2086 is reported to be a competitive receptor antagonist for PAF, but a 10-fold excess of WEB 2086 failed to inhibit PAF-induced release of PGFM. It was observed that this dose of WEB alone induced PGFM release, suggesting that in this model this agent may not work as a true competitive antagonist. Repeat challenges at intervals of 0, 90, and 120 min with either 200 micrograms PAF or micrograms oxytocin resulted in a marked tachyphylaxis of response by the third challenge. This desensitization after repeated PAF challenge suggests a specificity of its actions. Infusion of 200 micrograms PAF on Day 14 or 15 at five 60-min intervals resulted in a tachyphylaxis such that by the fourth and fifth challenges, essentially no response was observed. The tachyphylaxis that was induced by four repeat challenges with PAF had no apparent effect on the capacity of the uterus to respond to a fifth challenge with oxytocin. Thus, PAF and oxytocin both caused homologous desensitization of their own capacity to mobilize uterine PGF2 alpha, but PAF did not cause heterologous desensitization of the response to oxytocin. This failure of heterologous desensitization suggests differences in the mechanism of action of the two ligands. Kinetic binding studies showed that PAF did not compete for the oxytocin receptor in vitro. This result demonstrated that the ovine endometrium produces PAF and responds to it by the release of PGF2 alpha in situ. The dynamics of the response elicited by PAF were similar to those of oxytocin, yet the two mediators apparently act separately. PAF may be a modulator of PGF2 alpha release by the ovine uterus during the luteal phase.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗