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Biomedical subjects

C Dunlop

Publications and source records attributed to C Dunlop.

14 recordsLinked to original sources
PubMed2000

Changes in anesthetic sensitivity and glutamate receptors in the aging canine brain.

This study investigated whether the aging process in dogs is associated with an increased sensitivity to inhalation anesthesia and whether age-related changes in glutamate receptors are related to the increased sensitivity. The mean minimum alveolar concentration (MAC) of isoflurane was 1.82 +/- .08% for 2-3 year olds and 1.45 +/- .06% for 11 years olds, indicating that there was an increased potency of isoflurane in the older dogs as compared to the young. These older animals also showed a significant decrease in binding of [3H]glutamate and [3H]dizocilpine ([3H]MK801) to N-methyl-D-aspartate (NMDA) receptors in multiple cortical and hippocampal regions. The density of binding to NMDA receptors in the cortex, using a single concentration of ligand, correlated significantly with individual MAC values. These results demonstrate that dogs experience an increase in anesthetic potency with increased age, similar to humans, and that age-related changes in the NMDA receptor may represent one mechanism underlying this increased sensitivity to anesthesia.

Aging↗
PubMed1999

A prospective randomized trial evaluating the haemodynamic role of incompetent calf perforating veins.

AIM: This study was undertaken to determine the haemodynamic effect of incompetent calf perforating veins in patients with uncomplicated varicose veins and long saphenous incompetence. METHODS: Thirty-eight limbs from 35 patients were studied. All patients had uncomplicated varicose veins with both long saphenous and calf perforator incompetence on duplex ultrasonography. Patients were randomized to have incompetent calf perforators ligated or left intact, in addition to saphenofemoral junction ligation, strip of long saphenous vein to knee and stab avulsion of any visible varicosities in the leg. Patients were assessed with air plethysmography pre-operatively and 3 months postoperatively. RESULTS: Superficial venous surgery improved venous volume, venous filling index and ejection fraction in the patient cohort. No significant haemodynamic difference was demonstrated between the two groups of patients who were randomized. CONCLUSIONS: At present, the results of this study do not support the use of routine perforator ligation during superficial surgery for uncomplicated varicose veins.

Adult↗
PubMed1998

Paraoxonase active site required for protection against LDL oxidation involves its free sulfhydryl group and is different from that required for its arylesterase/paraoxonase activities: selective action of human paraoxonase allozymes Q and R.

Human serum paraoxonase (PON 1) exists in 2 major polymorphic forms (Q and R), which differ in the amino acid at position 191 (glutamine and arginine, respectively). These PON allozymes hydrolyze organophosphates and aromatic esters, and both also protect LDL from copper ion-induced oxidation. We have compared purified serum PONs of both forms and evaluated their effects on LDL oxidation, in respect to their arylesterase/paraoxonase activities. Copper ion-induced LDL oxidation, measured by the production of peroxides and aldehydes after 4 hours of incubation, were reduced up to 61% and 58%, respectively, by PON Q, but only up to 46% and 38%, respectively, by an equivalent concentration of PON R. These phenomena were PON-concentration dependent. Recombinant PON Q and PON R demonstrated similar patterns to that shown for the purified serum allozymes. PON Q and PON R differences in protection of LDL against oxidation were further evaluated in the presence of glutathione peroxidase (GPx). GPx (0.1 U/mL) alone reduced copper ion-induced LDL oxidation by 20% after 4 hours of incubation. The addition of PON R to the above system resulted in an additive inhibitory effect on LDL oxidation, whereas PON Q had no such additive effect. The 2 PON allozymes also differed by their ability to inhibit initiation, as well as propagation, of LDL oxidation. PON Q was more efficient in blocking LDL oxidation if added when oxidation was initiated, whereas PON R was more potent when added 1 hour after the initiation of LDL oxidation. These data suggest that the 2 allozymes act on different substrates. Both PON allozymes were also able to reduce the oxidation of phospholipids and cholesteryl ester. PON Q arylesterase activity was reduced after 4 hours of LDL oxidation by only 28%, whereas the arylesterase activity of PON R was reduced by up to 55%. Inactivation of the calcium-dependent PON arylesterase activity by using the metal chelator EDTA, or by calcium ion removal on a Chelex column, did not alter PON's ability to inhibit LDL oxidation. However, blockage of the PON free sulfhydryl group at position 283 with p-hydroxymercuribenzoate inhibited both its arylesterase activity and its protection of LDL from oxidation. Recombinant PON mutants in which the PON free sulfhydryl group was replaced by either alanine or serine were no longer able to protect against LDL oxidation, even though they retained paraoxonase and arylesterase activities. Overall, these studies demonstrate that PON's arylesterase/paraoxonase activities and the protection against LDL oxidation do not involve the active site on the enzyme in exactly the same way, and PON's ability to protect LDL from oxidation requires the cysteine residue at position 283.

Aryldialkylphosphatase↗
PubMed1997

Traumatic retinopathy resembling acute macular neuroretinopathy.

BACKGROUND: Acute macular neuroretinopathy (AMNR) is an uncommon disease of uncertain aetiology. We report on four males who developed unilateral changes following trauma which closely resembled acute macular retinopathy. METHODS: Retrospective review of selected cases. RESULTS: Four male patients developed a central or paracentral scotoma immediately or soon after an accident in which they suffered moderately severe bodily injury without direct ocular trauma. Vision was reduced in three patients. All four patients had characteristic well-circumscribed, dark macular lesions best seen using red-free light. The lesions cleared slowly in the two cases who returned for review. CONCLUSIONS: A picture that closely resembles AMNR may be seen after trauma. The mechanism may involve a sudden rise in ocular venous pressure. This may be an unrecognized cause of visual loss after non-ocular trauma which may be regarded as functional. The subtle retinal lesions may be overlooked unless the fundi are examined in red-free light and the macular dark areas are compared.

Acute Disease↗
PubMed1991

Clinical investigations of halothane and isoflurane for induction and maintenance of foal anesthesia.

Fifty-eight foals were divided into two groups for study of aspects of the clinical anesthetic management of foals and to characterize effects of halothane (n = 30) and isoflurane (n = 28) in foals. There were no significant differences (P greater than 0.05) in the demographics of the two groups. Results of hemograms and biochemical analysis of venous blood samples before and after anesthesia were either not influenced or only mildly (clinically unimportant) affected by either agent. Like adult horses, foals have an increased PaCO2 when anesthetized with inhaled anesthetics. We could detect no difference in the magnitude of increase in PaCO2 with either anesthetic. Anesthetic induction and recovery was most rapid with isoflurane. The quality of induction and recovery was similarly acceptable with either agent. Heart rate during isoflurane was not significantly different from conscious conditions but during halothane, heart rate was significantly less than control except at 91-120 min when statistical significance was not detected. These results support the clinical impression that foals can be safely and reliably anesthetized with either agent.

Anesthesia, Inhalation↗
PubMed1990

Effects of five hours of constant 1.2 MAC halothane in sternally recumbent, spontaneously breathing horses.

Circulatory and respiratory effects of five h of constant 1.06 per cent alveolar halothane in oxygen were identified in eight healthy horses, which breathed spontaneously, were otherwise unmedicated and positioned in sternal recumbency. Only a few important significant (P less than 0.05) changes occurred with time. Total peripheral resistance was about 15 per cent lower after two hours of constant dose halothane than after 30 mins of constant dose (P less than 0.05) and accounted for the significant 10 per cent reduction in mean carotid arterial blood pressure. By 5 h, the reduction in resistance and arterial blood pressure was 20 and 25 per cent respectively. Heart rate increased progressively with time and the increase became significant at 5 h (15 per cent increase). However, the heart rate change was not large enough to alter cardiac output. There were no major time-related changes in PaO2 or PaCO2. Three of four horses recovered from anaesthesia had markedly elevated serum creatine kinase levels and clinical signs of severe post anaesthetic myopathy.

Acid-Base Equilibrium↗
PubMed1988

Botulinum toxin in ophthalmology.

Alan B. Scott selected, researched and developed Type A Botulinum toxin for clinical use in ophthalmology. This unique drug has proved invaluable for treatment of a number of conditions which are difficult to treat in ophthalmology and in a variety of other disciplines. The indications, methods and problems of its use are described and the results of treatment of 133 patients are discussed. Up to December 1986 over 13,000 patients have been treated in a multicentre international trial without significant complications.

Aged↗
PubMed1988

Botulinum toxin--the rationale of its use.

Treatment with Oculinum, (Botulinum toxin, Type A), may induce three possible effects. These are a pharmacologic inhibitory effect, a mechanical effect and a sensory effect.

Botulinum Toxins↗
PubMed1988

Stereoscopic evoked responses to crossed and uncrossed disparity accompanying simulated refractive error.

Evoked potentials were recorded to the occurrence of a disparate stimulus in dynamic random dot stereograms. Seven adult males, all of whom had vision which was normal or corrected to normal, participated in the experiment. Subjects viewed 100 ms duration stimuli which embodied 30 arc min of either crossed or uncrossed disparity under four conditions of spherical overcorrection: -0.25, +1.0, +2.0, +3.0 dioptres. The first condition, essentially normal refraction, yielded reliable behavioural reports of the stimulus and clear evoked potentials to both crossed and uncrossed disparity. With increasing overcorrection the behavioural reports became less reliable, and the evoked potentials were degraded for both conditions of disparity. The responses to the crossed disparity condition, however, showed significantly less degradation in both behavioural and electrophysiological measures. The implications of this finding may be that there are separate cortical subsystems for the processing of crossed and uncrossed disparity and that the former is more robust under non-ideal viewing conditions.

Adult↗
PubMed1984

Exogenous ocular candidiasis associated with intravenous heroin abuse.

Seven young men developed disseminated candidiasis within 10 days of a single episode of intravenous heroin abuse. Sequential development of eye and skin lesions was noted in all cases. The bone or costal cartilage was involved in five. Ocular manifestations of candidiasis included episcleritis, chorioretinitis, and endophthalmitis. A presumptive diagnosis of candida chorioretinitis was established rapidly by culture of Candida albicans from involved skin and costal cartilage. Systemic therapy with amphotericin B plus 5-fluorocytosine resulted in cure of the episcleritis, chorioretinitis, osteomyelitis, costochondritis, and skin infection. Pars plana vitrectomy with local instillation of amphotericin B was required to cure chorioretinitis associated with vitreal extension of infection.

Adult↗
PubMed1981

Contractile properties and ultrastructure of extensor digitorum longus and soleus muscles in spinal cord transected rats.

The spinal cord of rats 25 days of age was transected at the thoracic level, and the contractile properties as well as the ultrastructure of their extensor digitorum longus (EDL) and soleus muscles was examined. In the normally slow-twitch soleus muscle, the operation produces a marked reduction of contraction time as well as the appearance of other contractile characteristics of a fast-twitch muscle, namely, post-tetanic potentiation and cooling potentiation of the isometric twitch. This operation has little effect on the fast-twitch EDL. The ultrastructure of the EDL is similarly unaffected by the motor paralysis introduced by transection, but little change to the soleus structure was found, except for an increase in sarcoplasmic reticulum surface to fibre volume ratio. These results provide little evidence that muscle structure, especially the amount of sarcoplasmic reticulum, plays a major role in the determination of contractile speed, and confirms that structure may be regulated independently by the nerve.

Animals↗
PubMed1979

A comparison of crown-rump length measurements using a real-time scanner in an antenatal clinic and a conventional B-scanner.

In a series of 168 patients in the first trimester of pregnancy, fetal crown-rump length (CRL) measurements were attempted in the Antenatal Clinic using a linear-array real-time ultrasound scanner. The measurements could not be made in 23 of the patients; most of them had a gestational age of less than 10 weeks and the difficulty in obtaining measurements was usually due to an underfilled maternal bladder. When compared with CRL measurements obtained with a conventional B-scanner, a good correlation was obtained (r = 0.92); 80 per cent of the 'real-time' values fell within a range of +/- 5 mm of the conventional values. In all patients the estimates of gestational age using the two methods were within one week of each other.

Anthropometry↗