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Biomedical subjects

R D Blair

Publications and source records attributed to R D Blair.

At least 19 recordsLinked to original sources
PubMed1992

Improving organ donation: compensation versus markets.

Proposals suggesting monetary compensation of organ donors to increase donation rates for transplantation are founded on the ethical premise that the principal criterion for organ procurement policy should be patients' health and not the personal preferences and philosophies of policymakers. In this paper, we argue that a market-based organ procurement system is superior to both the current altruistic-based system and a system based on compensation without a market. A market system would address both the problem of potential donors refusing to donate and that of their never being asked, whereas the altruistic system addresses neither problem and a system of compensation addresses only the former. Empirical evidence suggests that the latter (not being asked) is the predominant cause of the current shortage of organs. Our discussion shows that collection rates are likely to be substantially higher under a market system.

Altruism↗
PubMed1989

Frozen shoulder and other shoulder disturbances in Parkinson's disease.

The frequency of shoulder disturbances, particularly frozen shoulder, has not been assessed previously in Parkinson's disease. In a survey of 150 patients compared with 60 matched control subjects a significantly higher incidence of both a history of shoulder complaints (43% vs. 23%) and frozen shoulder (12.7% vs. 1.7%) was found in the Parkinson's disease population. Those developing a frozen shoulder had initial disease symptoms indicative of akinesia twice as frequently as tremor while the ratio was reversed in those without frozen shoulder. In at least 8% of the patients frozen shoulder was the first symptom of disease, occurring 0-2 years prior to the onset of more commonly recognised features. Parkinson's disease should be added to the list of causes of frozen shoulder, and clinicians must be aware that the latter is often the presenting symptom of Parkinson's disease.

Activities of Daily Living↗
PubMed1986

Levodopa dose-related fluctuations in presumed olivopontocerebellar atrophy.

The parkinsonism that occurs in some patients with olivopontocerebellar atrophy (OPCA) can cause diagnostic confusion with idiopathic Parkinson's disease (IPD). The response to levodopa is usually a distinguishing feature, the OPCAs either failing to benefit or losing efficacy relatively quickly. A fluctuating response to levodopa in those OPCA patients who do benefit has not been emphasized in the literature previously. Reported here are three patients with presumed OPCA, dominated by parkinsonian features, who eventually developed typical fluctuations with morning akinesia, wearing off, and periodic lack of response related to meals. These fluctuations were a major source of disability and an important reason for diagnostic confusion with IPD. The possible mechanisms of these fluctuations are discussed.

Aged↗
PubMed1984

Parkinson's disease in 1984: an update.

This update reviews several important topics in the field of Parkinson's disease, including etiologic studies, the types and mechanisms of drug complications and their treatment, when and how to begin treatment, the association of dementia with Parkinson's disease, and the development of the newer research tools. The recent discovery of a highly selective neurotoxin (MPTP) that causes parkinsonism in humans and other primates and the use of positron emission tomography in living patients should improve our understanding of the cause of cell death in Parkinson's disease and assist in the development of more definitive treatment for this common, disabling neurologic condition.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1984

Characteristic alterations in responses to imposed wrist displacements in parkinsonian rigidity and dystonia musculorum deformans.

The amplitude and temporal modulation of the segmented EMG activity in flexor carpi radialis, evoked by imposed angular wrist extension, was studied with respect to the level of pre-existing background activity in rigid parkinsonian (PK) and dystonia musculorum deformans (DMD) patients. The interdependence of the evoked M1 and M2-3 segments on pre-existing background EMG activity and initial velocity of imposed displacement was established previously for a normal population. Individual responses of 21 parkinsonian and 12 dystonic patients were compared to the established normal "response volume". The augmented magnitude of the M2-3 segment in rigid PK patients, which correlates to the measure of rigidity, could not be accounted for by the low level of pre-existing EMG activity. Therefore, increased descending facilitation does not impinge directly on alpha motoneurons. Paradoxical excitation in the shortened muscle and resetting of tonic tremor of the stretched muscle by the imposed wrist extension are two other demonstrated abnormalities which may also contribute to PK rigidity. In contrast, DMD patients demonstrated normal amplitude modulation of the M1 and M2-3 segments, but exhibited a disturbance of normal temporal mechanisms that result in constant duration of the M1 and M2-3 responses with imposed force step loads.

Adult↗
PubMed1984

Characteristics of EMG responses to imposed limb displacement in patients with vascular hemiplegia.

The segmented EMG activity in flexor carpi radialis to imposed wrist movements was studied in 18 hemiplegic subjects with vascular lesions of the sensorimotor cortex or internal capsule and compared to that in age-matched normal subjects. The segmented EMG activity in the stretched muscle was normalized against the maximum M response elicited by electrical stimulation of its peripheral nerve in hemiplegic and normal subjects. This M response was used to estimate the maximal activity of the motoneuron pool. Twelve of the hemiplegic patients showed a stereotyped abnormal segmentation pattern of the EMG activity characterized by: an increased M1 segment of prolonged duration with both an increased sensitivity to low initial velocities of displacement and an increased slope of the input-output relationship for the range of velocities tested; absent or diminished activity during the interval of the normal M2-3 segment; and a late component not evident in normal subjects. The increased magnitude of the EMG activity during the M1 interval, markedly exceeded the normal range of control values. A method to demonstrate the response distribution of the interrelationship of the magnitude of the M1 segment using two variables (background EMG activity and initial velocity) for individual responses rather than average responses is presented. The results of the study indicate that: the increased excitability, reflected in the enhanced EMG over the M1 segment does not result from increased levels of resting alpha motoneuron activity and may result from disruption of polysynaptic internuncial influences on alpha motoneurons; the absent or diminished activity over the interval of the normal M2-3 segment may partially result from the interruption of a transcortical reflex by the vascular lesions.

Aged↗
PubMed1978

The influence of a visual cue on muscle stretch reflexes.

Evidence has recently been presented indicating that muscle stretch reflexes have a large supraspinal component. The finding introduces the possibility that stretch reflex parameters may be modifiable by stimuli involving other modalities besides stretch. In this investigation, the effects of a visual cue on the reflex portions of the EMG activity following a sudden muscle stretch were examined. The results, obtained from the flexor carpi radialis muscles of six normal awake subjects, failed to show any significant change in the EMG parameters as a result of visual cues occurring at the instant of onset of muscle stretch. This was interpreted as indicating that visual inputs do not reach the areas of brain involved in the supraspinal reflex in sufficient time to modify the reflex.

Adult↗
PubMed1978

The electromyographic response to sudden stretches of limb muscles in normal human subjects.

The electromyographic (EMG) activity following a sudden stretch applied to wrist flexor or extensor muscles was investigated using a method which enabled the individual records and cumulative results of 30 trials to be observed simultaneously. The results showed that in each case the spinal reflex EMG burst was followed by one or two additional reflex bursts. The second of these latter bursts, when present, occurred in one of two distinct latency ranges. Thus, three distinct latency ranges were observed for reflex bursts following the spinal reflex burst. A possible explanation for these results is that there are three distinct long-loop reflexes, one or two of which may be active following a muscle stretch. The present results do not distinguish whether any or all of these long-loop reflexes are segmental or supraspinal in origin.

Adult↗
PubMed1977

Home parenteral nutrition.

Home parenteral nutrition on a permanent basis can be done by patients who are reasonably intelligent and well motivated. The various aspects of such a scheme are described with reference to three patients in the Waikato area who have had extensive bowel resections. Use of A-V loop vein grafts avoids the necessity for indwelling plastic shunts or catheters.

Arteriovenous Shunt, Surgical↗
PubMed1977

Chronic peritoneal dialysis in the management of diabetics with terminal renal failure.

Twelve diabetics with terminal renal failure were maintained on chronic peritoneal dialysis (PD) for 2-28 months (average 10 months). 7/12 survived more than 1 year. Blood glucose levels were well controlled by the use of supplemental, intradialysis, intraperitoneal insulin. The incidence of dialysis-related complications, including peritonitis was not significantly higher than in controls. Neurophysiological studies revealed a high incidence of neuropathy initially with progression in most patients. Radiological studies revealed initial vascular calcifications in 7 out of 12 patients with progression in 4. Retinopathy did not progress significantly. PD is a suitable alternative to hemodialysis in the management of end-stage diabetic nephropathy.

Adult↗
PubMed1975

Dorsal column stimulation. Its effect on the somatosensory evoked response.

Several authors have shown that dorsal column stimulation (DCS) modifies appreciation of pain. We studied the effects of DCS on the somatosensory evoked response (SER) in six subjects. Somatosensory evoked responses to stimulation of the tibial nerve and effects of varying frequencies and intensities of DCS on SER components were recorded. During DCS there was attenuation of late SER components with little effect on early components. Stimulus intensities greater than necessary to relieve pain suppressed all SER components. Our findings suggest that the minimal effective DCS variables to relieve pain are those that produce selective suppression of late SER components.

Adult↗
PubMed1975

Familial paralysis of horizontal gaze. Associated with pendular nystagmus, progressive scoliosis, and facial contraction with myokymia.

Paralysis of horizontal gaze, pendular nystagmus, and progressive scoliosis were manifestations of an autosomal recessive genetic disease in four siblings. Bilateral facial myokymia with continuous facial contraction developed in the oldest patient. Electromyographic examination of his facial muscles after facial nerve block at the stylomastoid foramen showed absence of all muscle potentials, consistent with a supranuclear origin of the myokymia. Normality of convergence, vertical gaze, and pupillary constrictor reflex activity assured integrity of midbrain ocular motor function. Absence of horizontal vestibulo-ocular reflexes signified involvement of the pontine tegmentum in this distinctive heredofamilial syndrome.

Adolescent↗