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Biomedical subjects

A Hamilton

Publications and source records attributed to A Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1995

Non-11p constitutional chromosome abnormalities in Wilms' tumor patients.

The incidence in Wilms' tumor patients of constitutional chromosome defects other than those involving the short arm of chromosome 11 was examined using data on 5,854 patients registered in the National Wilms Tumor Study. Trisomy 18 and Turner syndromes were found to occur at higher rates than expected based on chromosome surveys of newborns. Four patients were reported to have trisomy 18; all of these patients were over 5 years of age at the time of diagnosis of Wilms' tumor and none survived longer than six months. Four patients were reported to have Turner syndrome; these patients are currently doing well and have all survived at least 3 years following diagnosis. Two of the Turner patients and one of the trisomy 18 patients had horse-shoe kidneys; we speculate that this renal anomaly may contribute to the higher rates of tumor in these patients. No clear pattern was found among patients with other chromosome defects, although two patients had defects involving 2q37.

Adolescent↗
PubMed1995

Magnesium sulfate prophylaxis after cardiac operations.

One hundred patients undergoing elective cardiac operations were randomized into placebo (n = 54) and magnesium (n = 46) groups. The magnesium group received six doses of 2.4 g (19.2 mEq) magnesium sulfate intravenously in the first 24 hours after the cardiac operation. The magnesium group had higher serum magnesium concentrations postoperatively (1.09 +/- 0.20 versus 0.75 +/- 0.13 mmol/L; p < 0.0001), postoperative day 1 (1.49 +/- 0.34 versus 0.70 +/- 0.12 mmol/L; p < 0.0001) and postoperative day 2 (0.96 +/- 0.19 versus 0.76 +/- 0.07 mmol/L; p < 0.0001). Patients in the magnesium group had a lower incidence of ventricular tachyarrythmias (VTs) (17.3% versus 51.9%; p = 0.0006), less need for treatment (6.5% versus 20.3%; p < 0.0001), fewer VT episodes/patient (0.3 +/- 0.8 versus 1.39 +/- 1.9; p < 0.0001), and a reduction in the severity of VTs as measured by the modified Lown grade (p = 0.0002). No differences were demonstrated with respect to supraventricular tachyarrythmias. The magnesium group had reduced absolute creatine kinase-MB levels (5.3 +/- 4.2 versus 28.4 +/- 28 IU/L; p = 0.001) as well as creatine kinase-MB fraction (0.01 +/- 0.02 versus 0.05 +/- 0.04; p = 0.001) on postoperative day 1. Serum magnesium concentrations were lower during VTs than during periods of sinus rhythm (0.75 +/- 0.75 versus 1.02 +/- 0.35 mmol/L; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Brain maturation estimation using neural classifier.

Quantitative electroencephalographic (EEG) signal analysis has revealed itself as an important diagnostic tool in the last few years. Through the use of signal processing techniques, new quantitative representations of EEG data are obtained. To automate the diagnosis, a problem of supervised classification must be solved on these. Artificial Neural Networks provide an alternative to more traditional classifier systems for this task. The objective of this paper is to perform a comparison between several classifiers in a particular problem, the brain maturation prediction. The data preprocessing/feature extraction process and the methodology for making the comparison are described. Performance of the methods is evaluated in terms of estimated percentage of correctly classified subjects.

Adolescent↗
PubMed1994

Interstitial irradiation versus interstitial thermoradiotherapy for supratentorial malignant gliomas: a comparative survival analysis.

PURPOSE: To compare the survival of two groups of patients with supratentorial malignant gliomas who were treated on two sequential protocols with either interstitial thermoradiotherapy or with interstitial irradiation without hyperthermia. METHODS AND MATERIALS: Between 1988-1992, patients with anaplastic astrocytoma or glioblastoma multiforme were treated at the University of Arizona on a Phase I/II protocol of interstitial thermoradiotherapy with ferro-magnetic seeds. The treatment protocol consisted of debulking surgery, a course of external beam radiotherapy and hyperthermia given immediately before and after brachytherapy. The survival of patients so treated was compared with that of a similar group of patients treated with interstitial brachytherapy alone at the Barrows Neurological Institute between 1982-1990. RESULTS: Twenty-five patients with primary tumors treated at the time of initial presentation with thermoradiotherapy were compared with a control group of 37 patients treated with interstitial brachytherapy alone. All primary patients were followed for a minimum of 34 months post implant. Multivariate analysis based on proportional hazards models showed that hyperthermia (p = 0.027), patient age (p < or = 0.00001) and histology (anaplastic astrocytoma vs. glioblastoma multiforme, p = 0.0017) were the only factors significantly associated with survival in this data set. From the fitted model, the hazard of dying when treated with hyperthermia was .53 times (95% confidence intervals 0.29-0.94) than that of the control group. In addition, we treated a small group of patients with recurrent tumors (13 with brachytherapy alone, and eight with thermoradiotherapy) and found no survival difference (p = 0.62). CONCLUSION: Within the constraints of the selection factors and the different treatment parameters used in these studies, we conclude that an interstitial thermoradiotherapy boost confers a statistically significant survival benefit to patients with primary high grade gliomas when compared to interstitial brachytherapy alone.

Adult↗
PubMed1994

A comparison of survival between radiosurgery and stereotactic implants for malignant astrocytomas.

The purpose of this paper is to compare the survival of three groups of patients with high grade supratentorial gliomas who were treated on three sequential protocols with surgical resection, external beam fractionated radiotherapy and a boost to the residual contrasting enhancing mass by either interstitial brachytherapy (IB, n = 33), by interstitial thermoradiotherapy (IT, n = 25) or by stereotactic radiosurgery (SRS, n = 19). The primary aim of this study was to evaluate the role of different boosting techniques in the initial management of primary brain tumors. External beam radiotherapy doses were escalated from one study to the next so that the median doses given to the IB, the IT, and the SRS groups were 41.4 Gy, 48.4 Gy, and 59.4 Gy, respectively. The median dose of interstitial irradiation or stereotactic radiosurgery, were 40 Gy, 32.2 Gy and 10 Gy, respectively, for the same groups. Follow-up was such that all living patients had been followed for a minimum of 30, 27, 4 months in the IB, IT, and SRS groups, respectively; hence, twelve-month survival was 52% (95% CI: 34%-69%), 80% (95% CI: 64%-96%), and 51% (95% CI: 24%-78%) in the same respective groups. Using a multivariate Cox proportional hazards model, treatment with IT conferred a survival advantage over IB (p = 0.029). Furthermore, survival of patients treated with SRS did not significantly differ from that of patients treated with an implant with or without hyperthermia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Immunochemical studies of heat-shock protein 80 of Histoplasma capsulatum.

A monoclonal antibody (MAb) of the IgG1 subclass, with greater activity to the yeast than the mycelial phase of Histoplasma capsulatum was raised and was found to predominantly recognize a molecule of 80 kDa by immunoblot. Enzymatic deglycosylation and chemical degradation, followed by reaction with MAb 69F on Western blots showed the molecule to be O-glycosylated, and immunofluorescence studies showed it to be heat-inducible and its distribution to be cytoplasmic and possibly cell membraneous. There was no apparent staining of the cell wall. Culture filtrate was positive by ELISA and Western blot when reacted with MAb 69F. In addition, ELISA and Western blot demonstrated that a similar epitope was present in other fungal species. The glycoprotein had a pI of approximately 4.7. N-terminal amino acid sequencing revealed this molecule to be homologous to members of the heat-shock protein 70 family and to a recently described antigen from H. capsulatum.

Amino Acid Sequence↗
PubMed1994

Immunohistochemical detection of a novel 22- to 25-kilodalton glycoprotein of Paracoccidioides brasiliensis in biopsy material and partial characterization by using species-specific monoclonal antibodies.

Two murine monoclonal antibodies (MAbs) specific to Paracoccidioides brasiliensis (as determined by enzyme-linked immunosorbent assay [ELISA] and Western blot [immunoblot]) were produced by using a modification of standard hybridization protocols, with cyclophosphamide included as an immunomodulator to abolish responses to highly cross-reactive immunodominant epitopes. MAbs PS14 and PS15 are two different clones which exhibit similar characteristics by ELISA and Western blot. They are directed against a 22- to 25-kDa antigen which is present in P. brasiliensis and which could not be identified in other dimorphic fungi by ELISA or Western blot. Partial purification of the antigen was accomplished by isoelectric focusing, and deglycosylation studies suggested that the 22- to 25-kDa antigen is a glycoprotein with a pI of between 4.5 and 5 and that O-linked sugars may be part of the recognized epitope. The MAbs stained the cytoplasm of P. brasiliensis yeast and hyphal cells in cryostat sections of fresh cultures of the fungus. In addition, the MAbs stained the wall of paracoccidioidomycotic granulomas, as well as the cytoplasm of the fungus, as determined by the use of immunofluorescence, immunoperoxidase, and immuno-alkaline phosphatase staining techniques in paraffin-embedded sections of human biopsy material, and they failed to stain granulomas resulting from other clinical conditions. These findings suggest that these MAbs have potential use in the immunohistochemical identification of P. brasiliensis.

Adrenal Glands↗
PubMed1994

Cost reduction in cardiac surgery.

OBJECTIVE: To reduce surgical waiting lists at the University of Alberta Hospitals. A cost reduction program was initiated, allowing more cases to be performed on the same budget. Reducing the cost of delivering health care services has become necessary as demands upon the system increase. METHODS: Data were retrospectively gathered on patients having open heart surgery at the University of Alberta Hospitals between March 1, 1991 and February 29, 1992. Group 1 were patients operated on before the start of the cost reduction program (September 1, 1991) and group 2 were those operated on after. Student's t test and logistic regression were use to compare population characteristics and to correlate dependent variables. RESULTS: Demographic features and severity indices were not different. Operating time decreased from 4.5 +/- 1.5 to 4 +/- 1 h, P < 0.002. Preoperative, intensive care unit (ICU) and postoperative ward length of stay were reduced (P < 0.002). Total length of stay went from 19.3 +/- 22.7 to 13.8 +/- 10.7 days, P < 0.001. Operating room, nursing and x-ray costs decreased, P < 0.002. Hospital costs declined from $14,182 +/- 16,464 to $10,710 +/- 7,332, P < 0.001. Multiple regression showed hospital stay, ICU, operating room time, severity of illness and age to be significant determinants of cost, P < 0.03 for each. Waiting time and number of patients on the waiting list declined significantly as surgical lists increased. Mortality and rate of readmission following discharge were not different between the two groups. CONCLUSIONS: Substantial cost savings can be made by changing practice patterns, without adverse consequences. ICU and hospital length of stay are the most important cost determinants.

Alberta↗
PubMed1994

The role of anterior surgery for vertebral fractures with and without cord compression.

The indications for anterior surgery are well defined in the upper and lower cervical spine if one accepts the importance of early restoration of stability for improved patient rehabilitation. Cannulated screw fixation of Type II fractures of the odontoid peg is a highly specialized procedure that requires technical expertise still only available at a limited number of orthopaedic centers. The engineering improvements in internal fixation for the anterior cervical spine, allied with an increasing expertise in instrumentation, have increased the tendency toward anterior stabilization for all unstable lower cervical fractures, except irreducible dislocations, irrespective of the mechanism of injury. Most thoracolumbar fractures with less than 50% to 60% canal compromise can be adequately dealt with by posterior surgery, largely because of the powerful correction inherent in the short segment, pedicle crew systems available. Anterior surgery continues to have a role in the correction of severe disruption, late deformity, and chronic anterior cord compression. No ideal anterior internal fixation system exists, but the Kaneda device is undoubtedly the strongest. The timing and indications for intervention for acute cord compression remain controversial in the absence of neurologic deterioration, although the route is undisputedly anterior in view of the usual site of compression.

Cervical Vertebrae↗
PubMed1993

Maori attitudes to diabetes and diabetes health care delivery in north Canterbury.

AIMS: The study aims were as follows: (1) To obtain information regarding Maori attitudes to diabetes and to the services provided by a specialist diabetes clinic in Christchurch; (2) to initiate discussion about local diabetes health care delivery for Maori. METHODS: A questionnaire was designed following advice from professional Maori health researchers, with the aim of assessing Maori attitudes to diabetes and specialist diabetes services, available in Christchurch. RESULTS: The questionnaire was delivered to 51 (77%) of the 66 Maori with noninsulin dependent diabetes (NIDDM), attending a specialist diabetes clinic in Christchurch. Although 47 of the 51 subjects were able to name one or more diabetes complications, only five subjects named heart disease as a complication, despite the fact that heart disease is a major cause of mortality in NIDDM: Subjects were selected on the basis of being hospital specialist clinic attenders and the majority were satisfied with currently available services, yet 10 of the 51 subjects indicated that they would prefer marae-based to hospital-based diabetes health care, if they had a choice. CONCLUSIONS: The process of questionnaire interview and dissemination of results proved to be a cost-effective means of initiating local discussion about future directions for Maori diabetes health care delivery.

Adult↗
PubMed1993

Pulse stream VLSI circuits and systems: the EPSILON neural network chipset.

An analogue CMOS VLSI neural processing chip has been designed and fabricated. The device employs "pulse-stream" neural state signalling and is capable of computing some 360 million synaptic connections per second. In addition to basic characterisation results, the performance of the chip in solving "real-world" problems is also demonstrated. The experience gained from the development of this device has resulted in the design of a second "pulse-stream" chip with improved performance and features. It is anticipated that this second device will be integrated into a standard bus-based system and find early application in robotic control.

Computers, Analog↗
PubMed1993

School nutrition survey.

Food we eat has an important influence on health and well-being. Many eating habits are established in childhood. 456 children aged eight to 12 years participated in this survey of food eaten at school. Of all the food items eaten as a snack, 48.6% were categorised as junk. 75.8% of the sandwiches brought to school for lunch were made with white bread. Of the remaining food items brought for lunch 63.5% were of the junk variety. Compared with those who brought a snack or lunch from home, those given money to buy their own were more likely to eat junk (p < 0.01). Food eaten at school reflects approximately one third of a child's daily food intake but health food practises for even a third of food intake may be of a value for health and long term eating habits. Nutritional education with the reinforcement of high nutritional standards in schools could improve the situation.

Child↗
PubMed1992

Treatment of malignant gliomas with interstitial irradiation and hyperthermia.

A Phase I study of interstitial thermoradiotherapy for high-grade supratentorial gliomas has been completed. The objective of this trial was to test the feasibility and toxicity of hyperthermia induced by ferromagnetic implants in the treatment of intracranial tumors. The patient population consisted of 16 males and 12 females, with a median age of 44 years and a median Karnofsky score of 90. Nine patients had anaplastic astrocytoma while 19 had glioblastoma multiforme. Twenty two patients were treated at the time of their initial diagnosis with a course of external beam radiotherapy (median dose 48.4 Gy) followed by an interstitial implant with Ir-192 (median dose 32.7 Gy). Six patients with recurrent tumors received only an interstitial implant (median dose 40 Gy). Median implant volume for all patients was 55.8 cc and median number of treatment catheters implanted per tumor was eighteen. A 60-minute hyperthermia treatment was given through these catheters just before and right after completion of brachytherapy. Time-averaged temperatures of all treatments were computed for sensors located within the core of (> 5 mm from edge of implant), and at the periphery of the implant (outer 5 mm). The percentage of sensors achieving an average temperature > 42 degrees C was 61% and 35%, respectively. Hyperthermia was generally well tolerated; however, there have been 11 minor toxicities, which resolved with conservative management, and one episode of massive edema resulting in the death of a patient. In addition, there were three major complications associated with the surgical implantation of the catheters. Preliminary survival analysis shows that 16 of the 28 patients have died, with a median survival of 20.6 months from diagnosis. We conclude that interstitial hyperthermia of brain tumors with ferromagnetic implants is feasible and carries significant but acceptable morbidity given the extremely poor prognosis of this patient population.

Adult↗
PubMed1992

A prospective randomized trial of chemonucleolysis and conventional disc surgery in single level lumbar disc herniation.

The role of chemonucleolysis as an alternative to disc surgery is still disputed. The authors conducted a prospective randomized controlled trial of chemonucleolysis and conventional disc surgery involving 92 patients with L4-5 or L5-S1 disc herniation who failed to respond to conservative treatment. There were 46 patients in each group, matched for demographic, clinical characteristics, and co-interventions. Independent examiners assessed patients before treatment, at 6 weeks after, 3 months after, and 1 year after treatment. A comprehensive method of outcome assessment involving physiological outcome, functional outcome, cost outcome, and psychological outcome was employed. Nine chemonucleolysis patients and one disc surgery patient required additional surgery for failure of initial treatment (P less than 0.02). The outcomes at 6 weeks and at 3 months were better in the surgical group, but at 1 year the differences were not significant. The authors conclude that chemonucleolysis as a minimally invasive technique produces inferior short-term results and offers no advantage over conventional discectomy.

Adult↗