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Biomedical subjects

D W Collins

Publications and source records attributed to D W Collins.

At least 19 recordsLinked to original sources
PubMed1992

Numerical classification of coding sequences.

DNA sequences coding for protein may be represented by counts of nucleotides or codons. A complete reading frame may be abbreviated by its base count, e.g. A76C158G121T74, or with the corresponding codon table, e.g. (AAA)0(AAC)1(AAG)9 ... (TTT)0. We propose that these numerical designations be used to augment current methods of sequence annotation. Because base counts and codon tables do not require revision as knowledge of function evolves, they are well-suited to act as cross-references, for example to identify redundant GenBank entries. These descriptors may be compared, in place of DNA sequences, to extract homologous genes from large databases. This approach permits rapid searching with good selectivity.

Animals↗
PubMed1992

A retinitis pigmentosa register for western Australia.

This paper describes the main elements of the Western Australian retinitis pigmentosa register including details of the data stored on the register, aspects of the coding systems used and some description of the tests employed in diagnosis of retinitis pigmentosa. The register is family based and contains data on affected individuals and on their unaffected relatives. As at November 1991, the register contained data for 391 individuals from 207 separate families. Of the 391 individuals, 240 had definite or probable retinitis pigmentosa and 26 were possibly affected. The remainder were unaffected family members. In many cases, both affected and unaffected family members are being studied serially and the register is designed to store and easily retrieve serial data to allow study of disease progression for individuals and within families.

Australia↗
PubMed1990

Thirteen years longitudinal study of computed tomography, visual electrophysiology and neuropsychological changes in Huntington's chorea patients and 50% at-risk asymptomatic subjects.

The aim of the study was to determine whether CT, visual electrophysiology and neuropsychological changes could assist with the detection of pre-clinical Huntington's chorea (HC). It was also hoped that the examination protocol would be of use in patients with early symptoms or signs of disease but with no family history of HC. Twenty-three patients with HC and 45 subjects at 50% risk, were studied serially. Each visit normally entailed a CT study without intravenous contrast, visual evoked response and eye movements studies, as well as a comprehensive psychiatric, neurological and neuropsychological assessment. Over the 13 years of the study 5 persons, initially symptom free on clinical grounds, developed HC. Of these, 3 had had early atrophy of the caudate nucleus on the first visit and 4 had shown abnormalities in the visual electrophysiology before becoming symptomatic. It is concluded that CT, visual electrophysiology and neuropsychological assessment may assist in the pre-clinical diagnosis of the at-risk HC subject and in the management of the early clinical case.

Adult↗
PubMed1985

Predicted early failure of cardiac pacemakers.

This paper describes a study on pacemaker longevity carried out on 65 subjects using mostly the Telectronics model 171 and model 173 pacemakers and based on an analysis of pacing rate reduction as a function of time since implant. Three different modes of rundown were observed. The shortest predicted lifetime was 23 months for a model 171 unit. This study was undertaken after the manufacturer and battery companies clearly delineated the existence of the problem and steps to be taken in the follow-up of patients. Careful analysis of medical records of the patients did not yield any correlation between sex, age, indications for implantation, initial pacing threshold, or amount of use of the pacemaker, and the early rundown of these pacemakers. Our study indicated that, in general, the model 173 had a shorter expected lifetime than the model 171. Using a reduction in pacing rate of 5.5 bpm from the rate at implant as the end-of-life indicator, the study showed that 16% of the model 173 pacemakers would need to be replaced within 3 years of implant and 78% within 6 years of implant. In the case of the model 171 units, 10% would need to be replaced within 3 years of implant and 48% within 6 years. Follow-up of patients with these units should be scheduled to monitor closely the rate of rundown in order to predict replacement dates.

Adult↗
PubMed1979

Quantitative studies of saccadic and pursuit eye movements in multiple sclerosis.

Ocular movements were studied in 108 patients with established or suspected multiple sclerosis using an on-line computer-based electro-oculographic technique. In one group of patients peak eye movement velocities alone were measured during horizontal refixation saccades. In a second group saccade reaction times and accuracies were measured in addition to velocities, while in a subgroup a quantitative analysis of horizontal pursuit eye movements was also carried out. With the saccade velocity test abnormalities were present in 44 per cent of cases studied and were subclinical in 18 per cent. Abnormalities were found in 57 per cent of cases in whom the detailed saccade analysis was performed, including 48 per cent of patients with clinically normal eye movements. Saccade reaction time and accuracy were more sensitive parameters than saccade velocity, and the highest yield of abnormalities was obtained when all three were taken into consideration. Abnormalities of pursuit movements were found in 71 per cent of cases studied and were frequently subclinical. Abnormalities of saccadic and pursuit movements were not always present together in the same patient, and the overall yield of abnormalities was higher when the results of both types of study were taken into account. The yield of abnormalities with the eye movement studies was somewhat lower than with the pattern-reversal VEP in the clinically definite multiple sclerosis group, but was higher in patients in the other categories. Subclinical abnormalities of eye movement were found in a significant number of patients with normal VEPs. The finding of such an abnormality in patients with spinal cord syndromes allowed reclassification of 14 patients to a category with a higher degree of diagnostic certainty. It is concluded that quantitative electro-oculography is a valuable adjunct to the clinical evaluation of eye movements and has an important role in the investigation of patients suspected of multiple sclerosis.

Adult↗
PubMed1978

On-line electro-oculography.

The design and use of an on-line PDP 11/40-based system for quantitative study of ocular kinetics are described. The system can be used in neurophysiological or ophthalmological applications. Two different techniques are presented. In one, horizontal, vertical or oblique eye motion can be studied, in the other horizontal eye motion only. Several parameters of eye motion can be measured including saccadic velocity, eye movement latency and accuracy of refixation. For ophthalmological EOG applications the system allows measurement of the absolute voltage excursion corresponding to a horizontal eye movement of a specific amplitude. The system consists of five software programs and supporting signal processing equipment. The software package runs under the RSX11M executive.

Computers↗
PubMed1978

Pattern-reversal visual evoked potential. Method of analysis and results in multiple sclerosis.

A detailed method of analysis of the pattern-reversal visual evoked potential is presented. This method takes into account a number of parameters in addition to the latency of the major surface-positive component (P2) and has been tested in a group of 50 normal subjects and in 98 patients with established or suspected multiple sclerosis (MS). It was found that this more detailed form of analysis improved the detection rate of abnormal responses in the MS subjects particularly in those classified in the suspected category. The potential value of this form of analysis, particularly in clinical neurophysiology laboratories where the recording of visual evoked potentials is the only technique employed in the investigation of patients with suspected MS, is discussed.

Adolescent↗
PubMed1978

A quantitative review of the performance of implanted cardiac pacemakers, Medtronic Model No. 5944.

One of the service functions of the Sir Charles Gairdner Hospital Department of Biophysics since 1972 has been the routine performance testing of pacemakers implanted by the Hospital's Cardiologists. This service was set up to measure pacemaker pulse parameters with a view to detecting battery depletion. It was also found to be of great help in showing lead insulation deterioration, intermittent capture and movement of the catheter tip within the right ventricle, information that is frequently of help to the Cardiologists in planning acute or elective pacemaker replacement.

Electric Conductivity↗
PubMed1978

Computer analyses of auditory evoked cortical potentials in schizophrenic subjects.

Averaged cortical evoked potentials from single clicks were recorded from 51 patients and controls. The patient group consisted of 40 subjects with a diagnosis of 'nuclear' schizophrenia, and 11 subjects with diagnoses including mania, anxiety neurosis and personality disorder. Changes in auditory evoked cortical responses (AECR's) were most marked in clinically stable, dysphoric, chronic schizophrenics. These subjects showed reproducible, low amplitude, 'untidy' responses in which the amplitude of the primary peak was lower than the amplitude of later peaks. Chronic schizophrenics who were rated as being depressed, showed a more 'normal' AECR. AECR changes during the memorising of nonsense syllables demonstrated a functional separation between early and later peaks of the AECR. It was postulated that the AECR changes in schizophrenia and during memorising result from pathological patterns of cortical desynchronisation produced by altered mid-brain activity different from that of anxious arousal, and that the clinical 'steady-state' of chronic schizophrenia is reflected in the 'steady-state' desynchronisation changes in the AECR.

Acoustic Stimulation↗
PubMed1978

The contribution of evoked potentials in the functional assessment of the somatosensory pathway.

The value of evoked potentials in studying conduction in the somatosensory pathway was assessed in patients with various neurological disorders. In patients with multiple sclerosis (MS) abnormalities of the cervical response (N14) were found particularly in longstanding cases but also in the early stages of the disease, even in patients without sensory symptoms or signs, and were reversible in some patients. The cortical response was also abnormal in some cases but the two were not always affected together. In Friedreich's ataxia both the cervical and cortical responses were usually abnormal. Subclinical abnormalities of the cervical responses were found in some patients with hereditary spastic paraparesis or mixed forms of spinocerebellar ataxia. The cervical responses were also abnormal in patients with peripheral neuropathy and cervical radiculopathy, and in some patients with brain-stem or thalamic lesions. Cervical and cortical responses were normal in the lateral medullary syndrome, whereas the cortical response was markedly abnormal in patients with high brain-stem or cerebral hemisphere vascular lesions. Cortical and subcortical responses were abnormal in some patients with stereotactic thalamic lesions. Enhanced cortical responses were found in patients with lesions at different levels in the CNS. The most marked enhancement was observed in patients with familial myoclonic epilepsy. Lesser degrees were found in some patients with MS, progressive supranuclear palsy, thalamic lesions, brain-stem encephalitis and syringomyelia. Enhanced responses were usually found in patients with minimal or no clinical sensory involvement. It is postulated that this type of abnormality results from an interference to the inhibitory mechanisms which normally operate at various levels in the somatosensory pathway. It is concluded that evoked potential studies are a valuable adjunct to the clinical evaluation of sensation, and that they may provide useful information on the pathophysiology of conduction in the somatosensory pathway.

Brain Diseases↗
PubMed1977

Evoked potentials, saccadic velocities, and computerized tomography in diagnosis of multiple sclerosis.

One hundred and two patients with suspected or established multiple sclerosis (MS) were investigated by one or more of the following techniques: measurement of visual evoked potentials (VEP); measurement of cervical and cortical somatosensory evoked potentials (SEP); measurement of horizontal saccadic eye movement velocities (SV); and computerised axial tomography of the cranium and orbits (CT). Each of the techniques was valuable in detecting abnormalities, some of which were subclinical, in many patients. More abnormalities were found in patients studied by more than one technique, the most being detected in patients who were studied by all five techniques. We conclude that the techniques have a complementary role in investigating suspected MS.

Adult↗
PubMed1977

Vector cardiographic assessment of implanted cardiac pacemakers.

The design and use of an on-line PDP 11/40 based vector cardiographic pacemaker assessment system is described. The system has been designed for comprehensive, automated testing of either fixed rate or demand implanted cardiac pacemakers. It is accurate and can be operated by a laboratory assistant without special training. Pacemaker parameters extracted are pulse height, width, rate, energy index and the frontal plane vector length and angle at maximum inspiration and during quiet breathing. In addition, a graphical representation of the patient's ECG and the pacemaker pulse is obtained on a computer graphics terminal. Patient data are written to cartridge disk for permanent record following the test. At each subsequent test of the implanted pacemaker, the data on disk are addended with the latest quantitative results. A separate off-line FORTRAN program can interrogate disk files for detailed analysis of patient data and display of parameter trends since implantation.

Computers↗
PubMed1977

Saccadic velocities in multiple sclerosis and myasthenia gravis.

Horizontal saccadic eye movement velocities have been measured in patients with multiple sclerosis and myasthenia gravis using a computerised electrooculographic technique. The ability to detect subclinical abnormalities of eye movement with this technique indicates that it is of diagnostic value in patients with suspected multiple sclerosis who present with only a single symptomatic lesion in the central nervous system. The technique is also of value in the diagnosis of myasthenia gravis as it provides a means of quantifying the response of the extra-ocular muscles to anticholinesterase preparations.

Adult↗
PubMed1977

Electrophysiological and computerised tomography findings in multiple sclerosis: a comparative study.

102 patients with multiple sclerosis (MS) have been investigated by one or more of the following techniques: visual evoked potentials, cervical and cortical somatosensory evoked potentials, horizontal saccadic eye movement velocities, and computerised axial tomography of the cranium and orbits. It has been found that with each technique it is possible to detect abnormalities, which may be subclinical, in a significant proportion of patients. The proportion with abnormal results was greater in patients studied by more than 1 technique and was greatest in those patients who were studied by each of the 5 techniques. It is concluded that the techniques used have a complementary role in the investigation of patients suspected of having MS.

Adult↗