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Biomedical subjects

J Black

Publications and source records attributed to J Black.

At least 91 records · Page 5Linked to original sources
PubMed1998

Investigations into the neurologic basis of narcolepsy.

The understanding of narcolepsy has been enhanced by neurophysiologic investigations in humans and by pharmacologic and biochemical studies using the canine model of narcolepsy. Repetitive microsleeps have a more deleterious effect on performance than several short complete naps during the day. Under normal living conditions, the nocturnal sleep of narcoleptic patients is disrupted, and the spectral analysis of central EEG leads shows less delta power density per epoch than it does in age-matched controls, who have an absence or decrease of the usual decay in delta power across the night. Cataplexy is associated with a drop in H-reflex, even during partial cataplectic attacks. Monitoring of heart rate and intra-arterial blood pressure during cataplexy in humans shows a decrease in heart rate and an increase in blood pressure with onset of cataplexy, but the change in heart rate is secondary to the change in blood pressure. Investigations of narcoleptic Doberman pinschers have implicated several neurotransmitters in the brainstem and amygdala. In vivo dialysis and in situ injections of carbachol indicate that the pontine reticular formation is not the only muscarinic cholinergic region involved, but data support the existence of a multisynaptic descending pathway involved in the muscle atonia of cataplexy. Carbachol injections into the basal forebrain induce status cataplecticus. Experimental findings suggest a hypersensitivity of the overall muscarinic cholinergic system and that this hypersensitive cholinergic system is linked to the limbic system. An increase in the postsynaptic D2 dopaminergic receptor is observed in the amygdala of narcoleptic dogs compared with controls, with impairment of dopamine release. The associated findings suggest that an abnormal cholinergic-dopaminergic interaction could underlie the pathophysiology of narcolepsy.

Animals↗
PubMed1998

Metal release in patients who have had a primary total hip arthroplasty. A prospective, controlled, longitudinal study.

UNLABELLED: There is an increasing recognition that, in the long term, total joint replacement may be associated with adverse local and remote tissue responses that are mediated by the degradation products of prosthetic materials. Particular interest has centered on the metal-degradation products of total joint replacements because of the known toxicities of the metal elements that make up the alloys used in the implants. We measured the concentrations of titanium, aluminum, cobalt, and chromium in the serum and the concentration of chromium in the urine of seventy-five patients during a three-year prospective, longitudinal study. Twenty patients had had a so-called hybrid total hip replacement (insertion of a modular cobalt-alloy femoral stem and head with cement and a titanium acetabular cup without cement), fifteen had had insertion of an extensively porous-coated cobalt-alloy stem with a cobalt-alloy head and a titanium-alloy socket without cement, and twenty had had insertion of a proximally porous-coated titanium-alloy stem with a cobalt-alloy head and a titanium socket without cement. The remaining twenty patients did not have an implant and served as controls. The results of our study showed that, thirty-six months postoperatively, patients who have a well functioning prosthesis with components containing titanium have as much as a threefold increase in the concentration of titanium in the serum and those who have a well functioning prosthesis with cobalt-alloy components have as much as a fivefold and an eightfold increase in the concentrations of chromium in the serum and urine, respectively. The predominant source of the disseminated chromium-degradation products is probably the modular head-neck junction and may be a function of the geometry of the coupling. Passive dissolution of extensively porous-coated cobalt-alloy stems was not found to be a dominant mode of metal release. CLINICAL RELEVANCE: Increased concentrations of circulating metal-degradation products derived from orthopaedic implants may have deleterious biological effects over the long term that warrant investigation. This is a particularly timely concern because of recent clinical trends, including the reintroduction of metal-on-metal bearing surfaces and the increasing popularity of extensively porous-coated devices with large surface areas of exposed metal. Accurate monitoring of the concentrations of metal in the serum and urine after total hip replacement also can provide insights into the mechanisms of metal release. Our findings suggest that fretting corrosion at the head-neck coupling is an important source of metal release that can lead to increased concentrations of chromium in the serum. Determinations of the concentrations of metal in the serum and urine may be useful in the diagnosis of patients who are symptomatic after a total joint replacement as increased levels are indicative of at least one mode of mechanical dysfunction (for example, fretting corrosion) of the device.

Adult↗
PubMed1998

Using the evaluation of the Dalhousie Outpost Nursing Program for responsive social action.

The Dalhousie Outpost Nursing Program is designed specifically to prepare registered nurses to provide primary health care in northern Canadian Aboriginal communities where there are no resident physicians. In 1993, the program was extensively evaluated, using a responsive participatory approach that is consistent with the direction of health care in Canada. The evaluation documented the effectiveness of the program and permitted diverse views to be expressed. Most importantly, the evaluation enabled the voice of Aboriginal people living in northern communities to be heard. Dalhousie School of Nursing has used the evaluation results to provide some direction for program planning in the context of Canadian health reform.

American Indian or Alaska Native↗
PubMed1998

Randomized comparison of intramuscular artemether and intravenous quinine in adult, Melanesian patients with severe or complicated, Plasmodium falciparum malaria in Papua New Guinea.

An open-label, randomized, controlled trial was used to compare the safety and efficacy of intramuscular artemether (a loading dose of 3.2 mg/kg, followed by 1.6 mg/kg daily for 4 days) and intravenous quinine (a loading dose of 20 mg quinine dihydrochloride/kg, followed first by 10 mg/kg every 8 h, each injection taking 4 h, for at least 48 h, and then oral quinine for a total of 7 days) in the management of strictly defined severe/complicated malaria in Melanesian adults. Four (12%) of the 33 patients who enrolled and completed follow-up died (one of the 15 who received artemether and three of the 18 who received quinine). Overall, cerebral malaria was uncommon (6%) whilst jaundice was common (76%). The time taken to clear 50% of parasites was less in those treated with artemether (median = 8 h; range = 2-24 h) than in the patients given quinine (median = 14 h; range = 2-25 h; P = 0.05). Temperature defervescence was also quicker in those treated with artemether (median = 32 hours; range = 20-112 h) than in those in the quinine group (median = 48 h; range = 28-88 h; P = 0.034). Hypoglycaemia was not observed in any patient treated with artemether but complicated therapy in 11 (79%) of the 14 patients given quinine who had not had pre-treatment spontaneous hypoglycaemia. No serious adverse effects were attributable to artemether. The Plasmodium falciparum infections observed during the 1 month of follow-up, in three patients who had received artemether and two who had been given quinine, were probably due to recrudescence. Plasmodium vivax parasitaemias were also observed during follow-up, in one or two patients in each treatment group. Artemether appears safe in Melanesian adults and is probably as effective as intravenous quinine in the treatment of severe or complicated falciparum malaria.

Adult↗
PubMed1998

Complications following blepharoplasty.

Surgical correction of eyelid deformities yields a very high level of aesthetic improvement, and fortunately, complications following blepharoplasty are rare. But diligent care is required by nurses to assure that these complications remain uncommon. This article will describe the major and minor complications of traditional blepharoplasty and discuss the nurse's role in risk management to reduce the incidence of these complications.

Blepharoplasty↗
PubMed1997

Scanning and transmission electron microscopic findings during RPE wound healing in vivo.

OBJECTIVE: To examine the scanning (SEM) and transmission (TEM) electron microscopic features of an in vivo rabbit model of retinal pigment epithelial (RPE) wound healing. METHODS: Hydraulic debridement of the RPE was performed in one eye of each of 35 pigmented rabbits using a pars plana vitrectomy approach. Five of the 35 eyes were examined by either SEM or TEM on each of the following postoperative days: 0, 2, 4, 7, 14, 28 and 56. RESULTS: TEM revealed that hydraulic RPE debridement results in only focal damage to the RPE basement membrane portion of Bruch's membrane and that this damage is repaired by day 7 without ultrastructural sequelae. SEM and TEM disclosed that the RPE cells at the margin of the debrided bed become flattened and enlarged and evolve a cytoskeletal reorganization with altered apical-basal polarity consistent with the development of a migrating phenotype. This is followed by gradual restoration to a more normal stationary RPE phenotype after initial closure (reepithelialization) of the RPE defect on day 7. RPE hyperplasia also occurs and may contribute to this repair process. Tight junctions are re-established among the apical surfaces of monolayered and multilayered RPE cells by day 7, coinciding with the restoration of the blood outer retinal barrier. CONCLUSION: Hydraulic debridement of the RPE in vivo is a useful investigational model that provides important insight into the pathogenesis of outer retinal disorders and their treatment with such techniques as submacular surgery or RPE transplantation.

Animals↗