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Biomedical subjects

N Summers

Publications and source records attributed to N Summers.

11 recordsLinked to original sources
PubMed2001

Catheter-based electromechanical mapping to assess regional myocardial function: a comparative analysis with transthoracic echocardiography.

Recent studies using a nonfluoroscopic three-dimensional left ventricular mapping system showed considerable changes in voltage potentials and mechanical activity detected in ischemic and infarcted myocardial regions with mechanical dysfunction. This study examined the electromechanical characteristics in relation to regional wall motion assessed by echocardiography in patients with coronary artery disease. A 12-segment model of mapping (apical, mid, basal of septal, anterior, lateral, and inferior/posterior segments) was compared to echo wall motion score in 74 patients (836 segments). Unipolar voltage and local endocardial shortening signals were distinguished according to graded echo segmental rest scores (0 = normal, 1 = mild hypokinesis, 2 = moderate hypokinesis, 3 = severe hypokinesis, 4 = akinesis). Results show a significant difference in voltage potentials and shortening values in groups distinguished according to echocardiography motion score. The average voltage potentials and shortening values were highest in myocardial segments with normal or slightly reduced contractility and lowest in myocardial segments with moderate to severely impaired contractility scores (voltage: 12.3 +/- 5.0, 12.1 +/- 5.3, 10.7 +/- 5.4, 8.7 +/- 3.9, 7.1 +/- 3.0 mV, P = 0.0001; local shortening: 9.7 +/- 6.5, 8.4 +/- 5.9, 8.0 +/- 5.4, 5.6 +/- 6.3, 5.1 +/- 4.6%, P = 0.0001 in regions with segmental scores of 0, 1, 2, 3, 4 by echo, respectively). Using receiver-operating curve calculations, the area under the curve was 0.72 +/- 0.06 (voltage) and 0.67 +/- 0.05 (local shortening) without a significant difference between the two curves. The 90% thresholds for defining preserved vs. impaired contractility were 12.8 and 5.6 mV for voltage and 12.6% and 1.6% for local shortening. We conclude that electromechanical mapping correlates with regional changes in wall motion scores assessed by echo, showing a gradual proportional decrease in measured voltage and shortening signals in segments with impaired function.

Adult↗
PubMed2000

A comparison of inpatient and outpatient ASCT.

Outpatient high-dose chemotherapy and autologous stem cell transplantation (ASCT) has been shown to be feasible in terms of physical morbidity and mortality outcomes, but few data exist on the psychosocial impact of delivering such aggressive therapy in this manner. The purpose of this observational study was to compare effects of inpatient (n = 20) and outpatient (n = 21) modes of care on physical status, psychological well-being, quality of life, personal finances and caregiver burden. Most patients were treated according to their preference for inpatient or outpatient care. Those choosing outpatient care were screened for eligibility according to established criteria for ambulatory management. Measures were taken at baseline, then at days 4-6, 12-16 and 30 post ASCT. Results showed that overall, the psychological, physical, social and financial outcomes of the outpatient ASCT group were comparable, to or better than inpatients. Factors that seem to be important for successful outpatient management are previous experience with cancer treatment, a satisfying quality of life, physical well-being, patient's preference for a particular mode of care and physical proximity to the treatment centre. The study results suggest that outpatient ASCT is an efficient, effective and acceptable form of care for motivated patients and caregivers who have the physical and psychological capability and desire to receive cancer treatment in this manner.

Adult↗
PubMed2000

A study on dust emission, particle size distribution and formaldehyde concentration during machining of medium density fibreboard.

A study to characterise the quantity, particle size distribution and morphology of dust created during the machining of MDF was carried out. Four different types of MDF boards were included in this study, including a 'zero-formaldehyde' board that contains isocyanate-based resin, rather than urea-formaldehyde resin. In addition, natural softwood (pine) and natural hardwood (oak) were included in the study, for comparison with MDF. The results show that in general, the dust generated by machining MDF is comparable in terms of particle size distribution and morphology with the dust generated by similarly machining hardwood or softwood. The quantity of dust generated during sanding is higher for sanding MDF compared with sanding either hardwood or softwood. However, for sawing there is no significant difference between MDF and natural woods, in terms of the quantity of dust generated. Free formaldehyde in the air was less than 0.17mg m(-3) during machining of the Class B (higher formaldehyde potential) MDF board. There was no measurable isocyanate in the dust generated from the boards.

Air Pollutants, Occupational↗
PubMed1999

Analysis of sperm chromosome complements before, during, and after chemotherapy.

Sperm chromosomal abnormalities were assessed in testicular cancer patients before, during, and after BEP (bleomycin, etoposide, cisplatin) chemotherapy (CT). Multicolor fluorescence in situ hybridization (FISH) analysis was employed to detect aneuploidy for chromosomes 1, 12, X, and Y, and diploidy. Sperm samples were cryopreserved and coded before analysis to facilitate "blind" analysis. Complete results at all time points was available for only one patient. A total of 60,400 sperm were analyzed: 20,004 before CT, 20,005 during CT, and 20,391 after CT. There was a significant increase in the frequency of 24,XY sperm during (0.33%) and post-CT (0.34%) compared to pre-CT (0.14%). This study suggests that there may be a significantly increased risk of chromosomal abnormalities in sperm of CT patients during and immediately post-CT, similar to that shown in animal models.

Adult↗
PubMed1998

Compliance of clinical stage I nonseminomatous germ cell tumor patients with surveillance.

PURPOSE: We evaluate compliance and its effect on the outcome of patients with clinical stage I nonseminomatous germ cell tumor who underwent post-orchiectomy surveillance at the Tom Baker Cancer Centre. MATERIALS AND METHODS: From 1980 to 1994, 76 evaluable patients underwent surveillance at the Tom Baker Cancer Centre. The surveillance protocol consisted of clinical evaluation, chest x-ray and serum tumor marker measurements monthly in year 1, every 2 months in year 2, every 6 months in years 3 to 5 and yearly in years 6 to 10. Abdomen and pelvic computerized tomography (CT) were scheduled every 2 months in year 1 and every 4 months in year 2. Noncompliance was defined as missing 2 or more consecutive clinic visits, tumor marker measurements or chest x-rays or 1 or more CT scans. RESULTS: Compliance with clinical evaluations was 61.5% in year 1 and 35.5% in year 2, whereas compliance with CT was only 25% and 11.8% in years 1 and 2, respectively. By univariate analysis diagnosis before 1990 predicted noncompliance, while age, marital status and distance from the center did not. Recurrent disease was detected in 28 patients (37%) at a median of 5.5 months after orchiectomy (range 1 to 49.5). Among the 47 compliant patients 23 had relapse and none died. Among the 29 noncompliant patients 5 had relapse and 2 died with central nervous system disease. CONCLUSIONS: Overall compliance with this surveillance program was poor but this study was too small to demonstrate whether poor compliance adversely affects overall survival.

Adolescent↗
PubMed1998

Effectiveness of megestrol acetate in patients with advanced cancer: a randomized, double-blind, crossover study.

PURPOSE: To evaluate the effect of megestrol acetate at a lower dose than previously investigated on the symptoms of cachexia in patients with advanced cancer. METHODS: A total of 84 patients with advanced, solid tumours not responsive to hormone therapy were enrolled in this double-blind, crossover study. During phase 1, patients were randomly assigned to receive megestrol acetate (160 mg 3 times daily) for 10 days or placebo. During phase 2, after a 2-day washout period, patients received the alternate treatment for 10 days. Patients underwent daily assessments of activity, nausea, appetite and well-being by means of a visual analogue scale (VAS). In addition, nutritional status (weight, tricep skinfold measure, arm muscle circumference), energy intake, fatigue (Piper Fatigue Scale) and quality of life (Functional Living Index-Cancer [FLIC]) were assessed. RESULTS: Among the 53 evaluable patients megestrol acetate resulted in a significant improvement in appetite (p = 0.005), activity (p = 0.007) and well-being (p = 0.03). There was no significant change in the intensity of nausea, nutritional parameters, energy intake or FLIC scores. There was a significant improvement in 2 of the 3 factors measured by the Piper Fatigue Scale and in the overall fatigue score. Upon completion of the study, while still blind to the treatment condition, 30 patients indicated that they felt better overall after megestrol, 15 said they felt better after placebo, and 10 indicated no preference (p = 0.001). CONCLUSION: Treatment with megestrol acetate results in rapid and significant improvement of symptoms in terminally ill patients at lower doses than previously reported. The effects are not secondary to nutritional changes. The FLIC quality-of-life questionnaire was unable to detect these changes.

Adult↗
PubMed1997

Chromosomal abnormalities in sperm from testicular cancer patients before and after chemotherapy.

Sperm chromosome abnormalities were assessed in testicular cancer patients before and after treatment with BEP (bleomycin, etoposide, cisplatin). The frequencies of disomy for chromosomes 1, 12, X, Y and XY were assessed along with diploid frequencies and sex ratios by multicolour fluorescence in situ hybridization (FISH). For each cancer patient, a minimum of 10,000 sperm was assessed for each chromosome probe before and after chemotherapy (CT). Data was analysed "blindly" by coding the slides. A total of 161097 sperm were analyzed, 80,445 before and 80,642 after treatment. The mean disomy frequencies were 0.11% pre-CT vs 0.06% post-CT for chromosome 1, 0.18% vs 0.15% for chromosome 12, 0.10% vs 0.9% for the X chromosome, 0.13% vs 0.10% for the Y chromosome and 0.25% vs 0.20% for XY sperm. There was no significant difference in the frequency of disomy pre-CT vs post-CT for any chromosome except that chromosome 1 demonstrated a significant decrease after CT. The "sex ratios" and frequency of diploid sperm were also not significantly different in pre and post-CT samples with 50.2% X-bearing sperm pre-CT and 50.5% X post-CT and 0.14% diploid sperm pre-CT vs 0.15% diploid sperm post-CT. There was no significant donor heterogeneity among the cancer patients. None of the values in the cancer patients differed significantly from 10 normal control donors. Thus our study suggests that BEP chemotherapy does not increase the risk of numerical chromosomal abnormalities in human sperm.

Adult↗
PubMed1997

Analysis of human sperm karyotypes in testicular cancer patients before and after chemotherapy.

Sperm karyotype analysis was performed on testicular cancer patients before and after treatment with BEP (bleomycin, etoposide, and cisplatin). A total of 788 sperm chromosome complements was studied, 236 before chemotherapy (CT) and 552 post-CT. There was no significant difference in the total frequency of sperm chromosomal abnormalities pre-CT (10.2%) compared to post-CT (10.7%). Similarly, there were no significant differences in the frequencies of numerical abnormalities (2.5% pre-CT vs. 2.4% post-CT) or structural abnormalities (6.4% pre-CT vs. 7.4% post-CT). The percentage of X-bearing sperm was also not significantly different before (46.3%) and after CT (50.1%). The results in cancer patients were not significantly different from those in control donors. This study corroborates results from our previous analysis of these same men using multicolor fluorescence in situ hybridization for assessment of aneuploidy for chromosomes 1, 12, X, Y, and XY. Together, these two studies suggest that the sperm of men receiving BEP chemotherapy are not at increased risk of chromosomal abnormalities two or more years after treatment.

Adult↗
PubMed1987

Models for the three-dimensional structure of renin inhibitors bound in the active site of human renin: an analysis of the properties that produce tight binding.

Three-dimensional models of the octapeptide segment of renin substrate and of several inhibitors characterized by a modified scissile bond were constructed at the active site of human renin. The substrate and inhibitor models were based on the structure of pepstatin solved by x-ray crystallography to a resolution of 1.8 A. The renin structure, previously reported by us, was based on the structures of homologous aspartyl proteases solved by x-ray diffraction techniques to a resolution of 2.1 A or higher. An energy minimization program, CHARMM, was used to refine these structures with respect to the optimal interaction of the enzyme and its inhibitor, and to calculate the energy of each inhibitor-enzyme interaction. The results indicate that the most significant difference between the binding of inhibitors and of the natural substrate is caused by a reduction in electrostatic rather than conformational strain.

Binding Sites↗