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Biomedical subjects

B Thornton

Publications and source records attributed to B Thornton.

At least 19 recordsLinked to original sources
PubMed2006

Impact of defoliation intensity and frequency on N uptake and mobilization in Lolium perenne.

The aim of the study was to evaluate the impact of defoliation intensity, defoliation frequency, and interactions with N supply on N uptake, N mobilization from and N allocation to roots, adult leaves, and growing leaves. Plants of Lolium perenne were grown under two contrasted N regimes. Defoliation intensity treatments consisted of a range of percentage leaf area removal (0, 25, 50, 75, or 100%). These treatments were applied in parallel to a set of plants previously undefoliated, and to a second set of plants which had been defoliated several times at a constant height. A (15)N tracer technique was used to quantify N uptake, mobilization, and allocation over a 7 d period. A significant reduction in plant N uptake was observed with the removal of more than 75% of lamina area, but only with high N supply. As defoliation intensity increased, the amount of N taken up and subsequently allocated to growing leaves during the labelling period was maintained at the expense of N allocation to roots and adult leaves. Increasing defoliation intensity increased the relative contribution of roots supplying mobilized N to growing leaves and decreased the relative contribution of adult leaves. Defoliation frequency did not substantially alter N uptake, mobilization, and allocation between roots, adult and growing leaves on a plant basis. However, tiller number per plant was largely increased under repeated defoliation, hence indicating that allocation and mobilization of N to growing leaves, on the basis of individual tillers, was decreased by defoliation frequency.

Adaptation, Physiological↗
PubMed2004

Inhibition of nitrate influx by glutamine in Lolium perenne depends upon the contribution of the HATS to the total influx.

Plants of Lolium perenne L. were grown in sterile solution culture supplied with 2 mol m(-3) nitrogen as either nitrate or ammonium. Glutamine at 5 mol m(-3) was added to the nutrient solution of half the plants for 24 h. Root nitrate influx (at external nitrate concentrations 0-2000 mmol m(-3)) and amino acid concentrations were determined. In a second experiment the concentration of the added glutamine was varied from 0-5 mol m(-3) and nitrate influx determined at 250 and 2000 mmol m(-3). The maximum rate of influx attributed to the high affinity transport system (HATS) was reduced by 66% by the presence of glutamine achieved through an 84% reduction in its constitutive component and a 59% reduction in its inducible component. Influx attributed to LATS was unaffected by the addition of glutamine. The inhibition of total nitrate influx by glutamine was positively related to the contribution of HATS to the total influx. In both nitrate- and ammonium-grown plants, the concentration of glutamine required to inhibit nitrate influx significantly was lower when influx was determined at 250 mmol m(-3) compared with 2000 mmol m(-3) nitrate. The addition of glutamine increased its concentrations in root tissue. However, the results cannot be attributed to changes in glutamine alone as its addition also resulted in increased concentrations of other amino acids. Implications for plants growing under field conditions are discussed.

Amino Acids↗
PubMed2002

Short-term changes in xylem N compounds in Lolium perenne following defoliation.

Previous studies have indicated that an increased asparagine to glutamine ratio (Asn : Gln) occurs in the xylem fluid of Lolium perenne 24 h after defoliation. However, the absolute changes in Asn and Gln leading to the increased Asn : Gln ratio are unknown. The present study tested the hypotheses that: (1) defoliation-induced changes in xylem amino acid composition occur in L perenne within the first 24 h following defoliation, irrespective of phasing with respect to the diurnal light/dark cycle; and (2) the increase in Asn : Gln ratio in the xylem fluid of L perenne following defoliation is due to an increase in Asn content. Plants of L perenne L. 'Aurora' were grown in flowing solution culture for 40 d. Plants were then either left intact, defoliated at the end of the light period or defoliated at the end of the dark period. 15N-labelled NO3- was supplied following defoliation to discriminate between the recovery of N absorbed prior to, and following, defoliation. Xylem samples were collected over the subsequent 24 h period with amino acids speciated by GC-MS. There was support for the first hypothesis: increased Asn : Gln ratios occurred within the first 24 h, irrespective of the phasing of defoliation with respect to light/dark cycles. The second hypothesis was not supported: the concentration of all amino acids in the xylem exudate declined after defoliation, and the increased Asn : Gln ratio was accounted for by a disproportionately large reduction in Gln levels. Low concentrations of amino acids in the xylem of defoliated plants precluded accurate discrimination of their nitrogen content into pre- and post-defoliation sources.

Asparagine↗
PubMed2001

Uptake of glycine by non-mycorrhizal Lolium perenne.

Plants of Lolium perenne were grown in sterile solution culture. 15N-labelled glycine (Gly) coupled with gas chromatograph mass spectrometry was used to prove that non-mycorrhizal plants of L. perenne are capable of acquiring N in the form of intact Gly. It was estimated that a minimum of 80% of Gly-N uptake, over a 3 h period, was as intact Gly, though possible processes resulting in deviation from this estimate are discussed. The relative incorporation of 15N derived from Gly uptake into serine (Ser) compared with other amino acids in the root amino acid pool suggested the enzyme serine:glyoxylate aminotransferase was at least partly responsible for the synthesis of Ser from Gly. Defoliation was shown to reduce Gly uptake by L. perenne. The addition of either 25 mol x m(-3) sucrose or 50 mol x m(-3) glucose to the uptake solution of defoliated plants increased Gly-N uptake compared with both defoliated plants without sugars and with undefoliated plants. Addition of a glucose analogue, 3-O-methyl-D-glucopyranose, that is absorbed but not metabolized by plants, did not affect Gly uptake by defoliated plants. Increasing pH from 3.5 to 9.2 caused a reduction in Gly uptake. Results of the effects of defoliation and pH are consistent with Gly uptake by L. perenne being by an energy-dependent proton symport. When either or Gly were supplied to plants at equimolar concentrations, uptake was five times greater than that of Gly at pH 6 and 13 times greater at pH 9.

Amino Sugars↗
PubMed1999

A pilot study: use of fludarabine for refractory dermatomyositis and polymyositis, and examination of endpoint measures.

OBJECTIVE: To study the effects of the adenine analog, fludarabine, on patients with refractory dermatomyositis and polymyositis, and to assess variables used in following myositis patients during medical intervention. METHODS: Patients whose myositis was not controlled by prednisone and at least one other immunosuppressive medication were entered into a pilot study during which they received 6 monthly cycles of intravenous fludarabine. Patients were assessed at baseline, every other month, and at month 7 for primary outcome measures of strength and function. Other measurements including peripheral blood cell subsets, muscle enzymes, and various assessments of disease activity were followed monthly during the fludarabine infusion period and for up to 6 months post therapy. RESULTS: Of 16 patients who entered the study, 4 patients were classified as improved, and 7 patients were classified as unchanged. Five patients who withdrew before month 7 were classified as treatment failures. Fludarabine caused a significant and prolonged lymphopenia without an increase in infectious complications over that seen with other immunosuppressive agents used for myositis. A sudden death of one patient at the end of the study was not thought to be drug related. Variables followed during the study emphasized the distinction between patient functional improvement and disease remission. CONCLUSION: A subset of patients with refractory myositis may benefit from fludarabine therapy and controlled trials are indicated. Refinement and validation of variables useful for following myositis patients await larger studies.

Adult↗
PubMed1998

Cost-effectiveness of coronary artery bypass surgery in octogenarians.

OBJECTIVE: The objective of this retrospective cohort study was to determine whether coronary artery bypass graft (CABG) surgery is effective and cost-effective relative to medical management of coronary artery disease (CAD) in the elderly. SUMMARY BACKGROUND DATA: The aging of the U.S population and the improvements in surgical techniques have resulted in increasing numbers of elderly patients who undergo this surgery. The three randomized, controlled trials (RCTs) that established the efficacy of CABG surgery completed patient enrollment from 19 to 24 years ago excluded patients older than 65 years. Although information regarding outcomes of CABG in this population is mainly available in case series, a major lacuna exists with respect to information on quality of life and cost effectiveness of surgery as compared with medical management. METHODS: The authors retrospectively formed surgical and medically managed cohorts of octogenarians with significant multivessel CAD. More than 600 medical records of patients older than 80 years who underwent angiography at our institution were reviewed to identify 48 patients who were considered reasonable surgical candidates but had not undergone surgery. This cohort was compared with 176 patients who underwent surgery. RESULTS: The cost per quality-adjusted life year saved was $10,424. At 3 years, survival in the surgical group was 80% as compared with 64% in the entire medical cohort and 50% in a smaller subset of the medical cohort. Quality of life in patients who underwent surgery was measurably better than that of the medical cohort with utility index scores, as measured by the EuroQoL, (a seven-item quality of life questionnaire) of 0.84, 0.61, and 0.74, respectively. CONCLUSIONS: Performing CABG surgery in octogenarians is highly cost-effective. The quality of life of the elderly who elect to undergo CABG surgery is greater than that of their cohorts and equal to that of an average 55-year-old person in the general population.

Age Factors↗
PubMed1994

Sex-related differences in the bone mineral density of atrophic mandibles.

The bone mineral content in a standardized site was measured in 25 edentulous mandibles with dual-photon absorptiometry. The results of the bone mineral content examinations demonstrated a significant difference between the sexes. With advancing age of the subjects, the values measured in the men's mandibles tended to increase slightly, whereas those in the women's mandibles tended to decrease. As a functional adaptation to preserve the stability of the male atrophic mandible, the amount of inner cortical bone is increased. Explanations for this observation are discussed. That the mandibles of men and women change differently with increasing age should be considered in routine examinations, because osteoporosis may be regarded as a cofactor of residual ridge resorption in women.

Age Factors↗
PubMed1994

Personality correlates of the Hypercompetitive Attitude Scale: validity tests of Horney's theory of neurosis.

This study focused on assessing the concurrent validity of Horney's ideas about the personalities of hypercompetitive individuals based on her theory of neurosis. One hundred and sixty university men and women provided data by responding to a test battery of personality inventories containing measures of hypercompetitive attitudes and several theoretically relevant constructs. The results strongly support Horney's contentions. Stepwise multiple regression analysis indicated that hypercompetitive individuals were high in narcissism, Type E orientation, and several aspects of sensation seeking. The discussion centered on hypercompetitiveness as a mental health problem in American society and on the scale's utility in the diagnosis of the problem and in the assessment of therapeutic change in clients.

Adolescent↗
PubMed1993

Statistical analyses on the success potential of osseointegrated implants: a retrospective single-dimension statistical analysis.

Osseointegrated implants are a form of therapy that is finding increasing application in dental treatment. Long-term success can be ensured if the results of recall examinations are systematically documented. Life table analyses are being used to a growing extent to ensure objective assessment of the success of osseointegrated implants. With the help of the statistical method designed by Kaplan-Meier and Cutler-Ederer in 1958, the survival time of the implant can be calculated and the relationship between various covariables and the service time of the implants can be determined. This study calculates the success potential of 683 osseointegrated implants (IMZ and Brånemark) using the customary input-output statistics and life table analyses to explain the discrepancy between the two statistical methods, based on the results obtained.

Age Factors↗
PubMed1993

Assessment of the full content of physique stereotypes with a free-response format.

A major limitation of physique stereotyping research is that American subjects have used a restricted set of traits provided by the experimenter to evaluate endomorphs, mesomorphs, and ectomorphs. A free-response procedure was used in Study 1 to identify the full domain of traits associated with each physique. Although many of the traits identified were similar to those used in previous research, a number of new trait dimensions were uncovered. In Study 2, the large number of traits generated with the free-response format was reduced by combining synonyms. This new set of traits was placed in semantic differential format and given to a new sample of subjects to evaluate. The results paralleled those of the first study with the exception that ectomorphs were seen more favorably. This discrepancy, as well as the fact that raters listed trait antonyms within each of the three major physiques in Study 1, suggests the possibility of unique subtypes within the global stereotypes. Examples of these subtypes are proposed.

Adult↗
PubMed1992

Report of twelve years experience in open study of Skinner herpes simplex vaccine towards prevention of herpes genitalis.

Three hundred and forty-seven subjects at risk for herpes genitalis were vaccinated with Skinner vaccine, NFUAc.HSV1.(S-MRC5), and were followed for an average duration of 2 years representing a total consortship of 664.4 years. Based on survey information obtained during this consortship, there were estimated to be 3076 recurrences which summated to 3.5 years total duration of disease and comprised at least 6794 lesions; there were an estimated 51997 episodes of intercourse including at least 241 episodes of unprotected intercourse in the presence of herpetic lesions. The rate of contraction of herpes genitalis was 6 of 54 consorts (11.1%) who received one vaccination and 7 of 293 (2.4%) who received two, three of four vaccinations. There was no evidence of physical or psychological side effects from vaccination.

Adolescent↗
PubMed1991

Relationship between physical attractiveness, physical effectiveness, and self-esteem: a cross-sectional analysis among adolescents.

In the present study, the relative contributions of physical attractiveness and physical effectiveness to the self-esteem were examined among four different grade-levels of adolescents (mean ages; 12.5, 14.6, 16.3, 18.3 years old). Overall, both attractiveness and effectiveness were significantly related to the self-esteem of males and females. In contrast to previous research, attractiveness and effectiveness did not appear to be differentially important to the self-esteem of males and females and consistent patterns were evident across the different grade-levels. These results are believed to reflect changes occurring in sex-role expectations and socialization.

Adolescent↗
PubMed1989

The older cardiac transplant donor. Relation to graft function and recipient survival longer than 6 years.

A donor age of less than 35 years has long been considered crucial for heart transplantation. Because of limited donor heart supply and increasing demand for cardiac transplants, we attempted to expand the donor pool by using hearts from older individuals. This study was designed to determine if older donor hearts adversely affected cardiac transplant patient prognosis by predisposing them to graft failure from coronary artery disease, ventricular dysfunction, or death. Since 1982, 314 heart transplants have been performed at our institutions. Potential donors were deemed fit if there was no history of heart disease, the chest x-ray film was normal, the electrocardiogram showed nonspecific changes only, and blood pressure was maintained without major pharmacological support. In 47 (15%), donor age was 35 years or greater (group 1: mean age, 39 years; range, 35-49 years). In 267 (85%), donor age was less than 35 years (group 2: mean age, 23 years; range, 2-34 years). Mean group 1 recipient age was 55 years (range, 39-68 years) compared with 46 years (range, 0.7-66 years) in group 2 (p less than 0.01). Pretransplant inotropic support, mechanical support, or both were required in 15 (33%) group 1 patients and in 41 (16%) group 2 patients (p less than 0.01). Group 1 and 2 follow-up intervals were 1.1 +/- 1.0 and 1.8 +/- 1.4 years (mean +/- SD), respectively (p less than 0.0001). Overall survival was 64% versus 65%, group 1 versus group 2, and life table analysis showed no significant difference between the groups. There were three of 17 (18%) deaths due to coronary artery disease in group 1 and 20 of 87 (23%) in group 2 (p = NS). Seven patients in group 2 and none in group 1 required retransplant because of coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Asymptomatic telephone ECG transmissions as an outpatient surveillance system of ventricular arrhythmias: relationship to quantitative ambulatory ECG recordings.

Although ambulatory ECG recordings provide quantitative information in the follow-up of patients with ventricular arrhythmias, they are performed infrequently, potentially missing serious arrhythmias in the unmonitored periods. Telephone ECG systems offer "real-time" ECG information, theoretically functioning as an arrhythmia surveillance system. Thus we incorporated frequent telephone ECG transmissions in two antiarrhythmic drug protocols. The first investigation was designed to show the relationship of telephone and ambulatory ECGs in patients with frequent ventricular tachycardia (VT). The second protocol selected patients with "nonlife-threatening" frequent premature ventricular complexes (PVCs) in whom a second placebo period was instituted to simulate the clinical situation of asymptomatic arrhythmia increase. In both drug trials there was a strong linear relationship between the log-transformed PVC counts of telephone ECG and concomitant PVC, couplet, and VT frequencies on ambulatory ECG. In the VT population, greater than or equal to 1 PVC on telephone ECG reflected the presence of VT on ambulatory ECG (sensitivity 87%; specificity 77%). In the second study, telephone ECG transmissions with PVCs on three consecutive transmissions reflected the change from less than or equal to 10 PVCs/hour to greater than or equal to 40 PVCs/hour on ambulatory ECG within 48 hours. These data support the concept that daily surveillance by means of telephone ECG provides arrhythmia information of qualitative clinical relevance.

Ambulatory Care↗
PubMed1987

Patient education program to teach energy conservation behaviors to patients with rheumatoid arthritis: a pilot study.

We report a prospective, randomized pilot study comparing a new workbook-based program, designed to teach patients with rheumatoid arthritis (RA) energy conservation behaviors, with standard occupational therapy (OT). Sixteen patients took part in the new program and nine received the standard therapy. Data on the number of tender or swollen joints, grip strength, walk time, activities of daily living, psychologic adjustment to illness, and daily activity log, were measured before and three months after intervention. Eleven percent of those who received standard therapy and 50% of those who received the workbook increased their amount of physically active time (p = .10). Twenty-two percent of the control group and 50% of those in the workbook group achieved a better balance of rest and physical activity (p = .07). We conclude that the adoption of energy conservation behaviors is different in the two groups. This initial study suggests that interrupting physical activity with rest periods may result in increased physical activity in patients with RA.

Arthritis, Rheumatoid↗