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G Powell

Publications and source records attributed to G Powell.

At least 19 recordsLinked to original sources
PubMed2000

The high oleate trait in the cultivated peanut [Arachis hypogaea L]. II. Molecular basis and genetics of the trait.

A peanut variety with high oleate content has previously been described. When this high oleate variety was used in breeding crosses, the F2 segregation ratio of high oleate to normal oleate progeny was 3:1 or 15:1 depending on the normal oleate varieties used in the crosses. These data suggested that the high oleate trait is controlled by two recessive genes, and some peanut varieties differ from the high oleate variety by mutations in one gene, while others differ by mutations in two genes. The objective of this study was to understand the molecular nature of the high oleate trait and the various segregation patterns. In the previous paper in this issue, we reported that the level of transcripts expressed by one (ahFAD2B) of two homoeologous genes for oleoyl-PC desaturases in cultivated peanut is significantly reduced in high oleate varieties. In this report, we examined gene expression by RT-PCR/restriction digestion in a cross that shows a one-gene segregation pattern for the high oleate trait. Our data showed that the severely reduced level of ahFAD2B transcript correlates absolutely with the high oleate phenotype in this cross, suggesting that the single gene difference is correlated with the ahFAD2B transcript level. When we tested the enzyme activity of the proteins encoded by ahFAD2A and ahFAD2B by expression of the cloned sequences in yeast, only the ahFAD2B gene product showed significant oleoyl-PC desaturase activity. These data, combined with the observation that ahFAD2A shows a change (D150N) in a residue that is absolutely conserved among other desaturases, raised the possibility that the ahFAD2A in these normal and high oleate lines is a mutant allele. In support of this hypothesis, we found that another ahFAD2A allele in a normal oleate peanut line does not have the D150N change. This peanut line displays a two-gene-segregation pattern for the high oleate trait. In conclusion, our results suggest that a mutation in ahFAD2A and a significant reduction in levels of the ahFAD2B transcript together cause the high oleate phenotype in peanut varieties, and that one expressed gene encoding a functional enzyme appears to be sufficient for the normal oleate phenotype.

Alleles↗
PubMed2000

The high oleate trait in the cultivated peanut [Arachis hypogaea L.]. I. Isolation and characterization of two genes encoding microsomal oleoyl-PC desaturases.

Plant oils rich in oleate are considered superior products compared to oils rich in polyunsaturated fatty acids. Peanut (Arachis hypogaea L.) is one of the major oilseed crops, and high oleate mutant varieties with as much as 85% oleate have been reported. We examined the possibility that this mutant phenotype resulted from reduction in the activity or the transcript level of microsomal oleoyl-PC desaturase. Two independently generated high oleate mutants, M2-225 and 8-2122, and their partially isogenic lines with a normal oleate phenotype were used in this study. Two cDNA sequences coding for microsomal oleoyl-PC desaturases, ahFAD2A and ahFAD2B, have been isolated from the developing peanut seed with a normal oleate phenotype. Cultivated peanut is an allotetraploid, and sequence comparisons with the genes from the putative diploid progenitor species suggested that ahFAD2A and ahFAD2B are non-allelic, but homeologous genes originating from two different diploid species. Northern analysis showed that the transcripts of oleoyl-PC desaturases are highly abundant in both normal and high oleate peanut seeds in the second stage of development. Differential digestion of the RT-PCR products revealed a restriction site polymorphism between ahFAD2A and ahFAD2B, and allowed us to examine the level of transcript expressed from each gene. The results indicate that ahFAD2A is expressed in both normal and high oleate peanut seeds, but the steady state level of the ahFAD2B transcript is severely reduced in the high oleate peanut varieties. These data suggested that the reduction in ahFAD2B transcript level in the developing seeds is correlated with the high oleate trait.

Amino Acid Sequence↗
PubMed1998

Role of the helper component in vector-specific transmission of potyviruses.

Four aphid species were tested for their ability to transmit tobacco etch (TEV) and turnip mosaic (TuMV) potyviruses. Myzus persicae and Aphis gossypii transmitted both viruses efficiently from infected plants, whereas Lipaphis erysimi transmitted only TuMV and Myzus ascalonicus was a poor or non-transmitter of either virus. Similar electrically monitored probing patterns were produced by M. persicae, L. erysimi and M. ascalonicus, ruling out behavioural differences as the cause of differential transmission. Transmission results similar to those from infected plants were obtained when these aphids acquired homologous virus/helper component (HC) mixtures through membranes. With heterologous virus/HC mixtures, M. persicae remained a highly efficient vector and M. ascalonicus a non-vector, but L. erysimi became an efficient vector of TEV if acquired in the presence of TuMV HC and A. gossypii transmitted both viruses less efficiently when acquired with TuMV HC. Transmission was highly correlated with the retention of virus in the stylets, as determined by autoradiography of 125I-labelled virions. The results show that constituent(s) of or in the food canal of different aphid species differ in their ability to interact with specific HCs, leading to qualitative or quantitative differences in ability to retain and subsequently transmit specific potyviruses.

Animals↗
PubMed1998

Different cup migration in rheumatoid arthritis and arthrosis: a radiographic analysis of 127 uncemented acetabular cups.

We compared retrospectively the radiographic migration profiles of 82 acetabular components in 61 patients having rheumatoid arthritis with those of 45 hips having arthrosis who underwent a standardized technique of cementless arthroplasty with the Zweymüller prosthesis (Alloclassic). We used a modification of Dickob's technique of digital migration analysis that corrects for magnification errors and horizontal pelvic tilt. The rheumatoid patients were stratified as having oligoarticular, polyarticular, or mutilating arthritis. The overall rate of acetabular loosening in rheumatoid hips after mean 88 (26-117) months was 4%. Loosening was seen only in cases with mutilating arthritis and acetabular protrusion, where the direction of cup migration was also clearly different from that detected in the other types of rheumatoid arthritis and in arthrosis. The different patterns of cup migration in cementless hip replacement for rheumatoid arthritis, depending on disease severity, is of importance when comparing outcome of total hip arthroplasty in rheumatoid patients.

Adult↗
PubMed1997

Is clozapine safe in the elderly?

OBJECTIVE: The aim of this paper is to assess the risk/benefit ratio of clozapine in the elderly. METHOD: MedLine and Internet searches, followed by cross-checking for further articles, identified the references. Reports on efficacy as well as side effects were examined. Five psychogeriatric patients treated by the authors are presented. RESULTS: The review of the literature highlighted the lack of studies on the use of clozapine in the elderly. Retrospective studies and case reports dominate. There is only one double-blind placebo-controlled study of six patients extant. Although efficacy seemed to parallel that in the younger age groups, the incidence of leukopenia, agranulocytosis, postural hypotension and confusion was greater in the elderly. Two of the five patients reported by the authors developed agranulocytosis, bringing the Australian experience of agranulocytosis in patients over 65 years of age to 4/55. CONCLUSION: The risk/benefit ratio in the elderly is distinctly higher than found in the younger population. With specific reference to agranulocytosis alone, the frequently quoted risk of 1% for patients is likely to be 5-10 times higher in the over 65 population. Caution is advised when prescribing clozapine in the psychogeriatric population.

Aged↗
PubMed1996

Microchips versus stethoscopes, part 2: Revisiting OSCAR at the Foothills Hospital.

Several years have passed since the Foothills Hospital in Calgary installed a multi-million-dollar computerized patient-information system. When it arrived, the computer system known as OSCAR created controversy, anxiety and arguments among clinical caregivers who found it tedious, time consuming and cumbersome. Gregory Powell looks at how OSCAR has since changed the clinical landscape at Foothills.

Alberta↗
PubMed1996

Photophobia and lithium.

CLINICAL PICTURE: We report the case of a 45 year old woman who developed photophobia after 6 months on lithium at non-toxic levels. TREATMENT AND OUTCOME: Lithium was reintroduced twice and on both occasions this side-effect reoccurred within days. CONCLUSIONS: Photophobia has only been described previously as a symptom of lithium intoxication.

Antimanic Agents↗
PubMed1995

Personality and psychosocial function after brain injury.

A total of 74 brain-injured patients and 46 non-neurologically matched controls consecutively admitted to a specialist medical rehabilitation unit, were administered the 'Headley Court psychosocial rating scale' and four questionnaires examining personality traits of 'locus of control', 'use of humour', 'optimism' and 'easy-going disposition'. Both pre- and post-injury personality ratings were obtained. The relatives of all participants were sent the same scales. Personality changes are reported in each of the four areas; however, time post-injury appears to be a significant factor in the type of change reported; in this cross-sectional study, at 6 and 12 months post-injury, changes are noted in all variables except locus of control, whereas at 18 months post-injury only 'easy-going disposition' showed significant change, at 24 months post-injury changes were noted in all variables except optimism, and at 30 months post-injury no changes were noted. In the present study, examining a period of 2.5 years post-injury, the personality changes remain static once they have occurred. Despite widespread reports in the literature on the importance of pre- and post-trauma personality to good psychosocial functioning, the present study found that it was only an 'easy-going disposition' post-trauma that was consistently related to good psychosocial functioning. Reasons for this are discussed.

Adaptation, Psychological↗
PubMed1994

Donor leg morbidity after pedicled rectus femoris muscle flap transfer for abdominal wall and pelvic reconstruction.

The pedicled rectus femoris muscle and myocutaneous flap has found application for a variety of soft tissue defects of the groin, pelvis, and lower abdomen. Although a number of authors have discussed the usefulness of this muscle flap, few have documented the morbidity from loss of this muscle in the leg. We have studied 7 patients who underwent unilateral rectus femoris muscle transfer, comparing strength of the donor knee to the normal knee. All patients were studied using a computerized dynamometer for strength of knee flexion and contraction. We found that loss of the rectus femoris in patients not undergoing a postoperative program of therapy led to an average decrease in strength about the knee of 24% to 28%, depending on the motion measured. A single patient who underwent an intensive postoperative therapy program had return of normal strength in his donor leg. Despite this common loss of strength, patient complaints were few and the results of reconstruction appeared to outweigh this loss of strength.

Abdominal Muscles↗
PubMed1994

What events precede violent incidents in psychiatric hospitals?

BACKGROUND: The study aimed to identify, classify and measure the relative frequency of events preceding violent incidents in psychiatric hospitals. METHOD: Possible antecedents for 1000 incidents in three associated psychiatric hospitals over 13 months were investigated with an 'untoward incident database'. RESULTS: From eyewitness accounts, 921 incidents (92%) could be related to one of 15 categories of antecedent involving characteristics of the patient, or of the hospital regime, or interactions with other individuals. Overall, the most common antecedents involved patients who were generally agitated or disturbed (286), restrictions on patients associated with the routine hospital regime (192) or provocation by other patients, relatives or visitors (175). Incidents arising from staff members initiating contact with patients were very rare (7). Twenty-one patients were involved in 10 or more incidents, including 19 (90%) who were detained under the Mental Health Act. These patients were more likely to commit assaults after certain antecedents (self-harm, absconding or arson) which were serious incidents in themselves. CONCLUSIONS: Staff training on specific safety issues will be needed under the new Management of Health and Safety at Work Regulations.

Adult↗
PubMed1994

Parathyroid hormone-related protein in human term placenta and membranes.

Parathyroid hormone-related protein (PTHrP), the hypercalcaemia of malignancy factor, is expressed in the tissues of the human uteroplacental unit, including the placenta, amnion and chorion. We have used three region-specific immunoassays to quantitate and compare the distribution of PTHrP in tissues obtained at term following spontaneous labour and vaginal delivery or elective Caesarean section. In non-labouring women highest PTHrP(1-86) and (37-67) immunoreactivity was found in amnion covering the placenta, rather than the decidua parietalis of the uterus (reflected amnion) (median 1020 vs 451 fmol/g; 2181 vs 1444 fmol/g respectively). In labouring women, the PTHrP(1-86) concentration in reflected amnion was inversely correlated with the interval between rupture of the membranes and delivery. Tissue PTHrP(1-86) concentrations were lower in placenta than in chorion and amnion (medians 12, 109 and 664 fmol/g respectively) and, in all tissues, PTHrP(1-34) and (37-67) concentrations were significantly higher than that of PTHrP(1-86). Bioactive PTHrP(1-34) was detected in placenta, chorion and amnion using the ROS cell bioassay. The PTHrP(1-86) concentration (mean +/- S.E.M. = 41.4 +/- 4.5 pmol/l) was high in amniotic fluid at term, although in maternal and cord plasma levels were only modestly increased. The molecular forms of PTHrP present in tissues and amniotic fluid were investigated by column chromatography which confirmed its molecular heterogeneity and suggested that processing is tissue-specific and occurs at both amino- and carboxy-terminals of the peptide.

Amnion↗
PubMed1992

Combined effects of laser irradiation and chemical inhibitors on the dissolution of dental enamel.

It has previously been shown that the susceptibility of human teeth to acid dissolution can be reduced by the presence of various chemical agents in the dissolution medium or by pretreatment of the teeth with laser irradiation. Now synergism between these two approaches to improving acid resistance has been demonstrated. Extracted human teeth were irradiated with a continuous-wave carbon dioxide laser at a wavelength of 10.6 microns. Energy doses of either 65 or 130 J/cm2 given over periods of 2 or 4 s, respectively, were applied and the teeth subjected to a severe acid challenge (0.1 M acetate buffer, pH 4.5, no calcium or phosphate common ion present) for 24 h. Mineral loss was assessed by measurement of mineral density profiles with quantitative microradiography. Experiments were carried out in the presence or absence of three chemical inhibitors with distinctly different mechanisms of action: ethane-1-hydroxy-1, 1-diphosphonic acid, fluoride, and dodecylamine HCl. Laser irradiation alone was found to lead to increased resistance of the teeth to acid challenge, with the higher energy dose being more effective than the lower dose. Each of the chemical inhibitors was effective on both lased and unlased teeth, with the percent reduction of dissolution greater when the inhibitors were applied to teeth lased with an energy dose of 130 J/cm2 which were already more resistant to acid challenge than were unlased teeth or teeth lased with a dose of 65 J/cm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1991

Level of medical care required for mass gatherings: the XV Winter Olympic Games in Calgary, Canada.

STUDY OBJECTIVE: To determine the level of medical care required for mass gatherings and describe the types of medical problems encountered in a major winter event. DESIGN: Standard charts were available for 3,395 encounters. Interviews with medical staff showed that the few unrecorded encounters were for very minor medical problems. A four-tiered triage system (low, moderate, urgent, and emergent) developed before the Games was applied to each chart retrospectively by a single emergency physician. Chi-squared tests were used to test significant differences. SETTING: This winter sporting and entertainment event had 12 urban and rural venues. Medical staff (98 physicians, 161 nurses, and 337 first-aid attendants) were based in 28 advanced life support (ALS) clinics. The medical service operated for four weeks. TYPE OF PARTICIPANTS: There were 1.8 million spectator-days. Patients included spectators, athletes, and support staff. INTERVENTIONS: First-aid attendants referred patients to the clinics, where nurses conducted initial assessments and referred patients to physicians at the venue, or more rarely, to local hospital emergency departments. Paramedic ambulances were stationed at the venues. The triage system was not used for patient management. MEASUREMENTS AND MAIN RESULTS: Only 40 urgent and one emergent medical problems were encountered. The majority of patients could have been managed by trained nurses working alone under standing orders. Fifty patients were transported to the hospital by ground ambulance and three by helicopter. No significant differences were found in the low acuity levels experienced at indoor urban venues, outdoor urban venues, and the rural cross-country ski venue. The Alpine ski venue was characterized by significantly higher acuity and a long prehospital transfer phase. CONCLUSION: Owing to the low acuity encountered and the availability of Calgary's ALS ambulance service, we concluded that physician-based ALS teams were not required for patient management at the urban venues. Such teams were found to be required at the rural Alpine ski venue. Other reasons for using physicians are discussed, as is development of a standard triage system for mass gatherings.

Alberta↗