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Biomedical subjects

J K Harrison

Publications and source records attributed to J K Harrison.

117 records · Page 7Linked to original sources
PubMed1986

Effect of cholera toxin on the activation of adenylate cyclase by calmodulin in bovine striatum.

The effect of cholera toxin on activation of adenylate cyclase by the endogenous Ca2+-binding protein, calmodulin, GTP, dopamine, and forskolin was investigated in bovine striatum. Adenylate cyclase activity was measured in washed membrane fractions prepared from homogenates that had been preincubated with cholera toxin. Pretreatment of striatal membranes with cholera toxin increased the response of adenylate cyclase to GTP, calmodulin, and forskolin as compared to vehicle controls. After cholera toxin pretreatment, the maximal response of adenylate cyclase to GTP was increased 4.7-fold and the apparent Ka for GTP was reduced 3-fold. The apparent Vmax for calmodulin was doubled after cholera toxin pretreatment. The activation of adenylate cyclase by forskolin was increased by cholera toxin, but the effect on kinetic parameters was not determined due to solubility considerations. In contrast, dopamine-stimulated adenylate cyclase activity was abolished after cholera toxin pretreatment. Examination of a concentration-response curve for cholera toxin in altering these activities revealed that calmodulin-stimulated adenylate cyclase was maximally affected at lower concentrations of cholera toxin than was activation by GTP and forskolin. Cholera toxin also affected the interaction between calmodulin and GTP. In the absence of cholera toxin, calmodulin decreased the apparent Ka for GTP nearly 10-fold. After cholera toxin pretreatment, however, calmodulin could not further decrease the apparent Ka for GTP but increased the maximal response to GTP by 30%. Calmodulin could potentiate GTP activation by stabilizing the interaction between Ns and the catalytic subunit, an action which could be negated by prior treatment with cholera toxin. ADP-ribosylation of the striatal homogenates with [32P]NAD demonstrated predominant labeling of a band of Mr 45,000 which corresponds to the known molecular weight of the alpha-subunit of the stimulatory GTP-binding protein, Ns. These results suggest that the activational state of Ns can affect the stimulation of adenylate cyclase by calmodulin and forskolin. Calmodulin and forskolin may act at separate sites on the catalytic subunit that can allosterically interact with Ns.

Adenosine Diphosphate Ribose↗
PubMed1984

Regulation of calmodulin- and dopamine-stimulated adenylate cyclase activities by light in bovine retina.

Neural retina from most species contains 3,4- dihydroxyphenylethylamine (dopamine) receptors coupled to stimulation of adenylate cyclase activity. It has been demonstrated that release of dopamine from its neurons and subsequent occupation of dopamine receptors is increased by light. In this study, we have shown that adenylate cyclase activity in bovine retina is highly responsive to the endogenous Ca2+-binding protein, calmodulin, and that calmodulin can increase dopamine-sensitive adenylate cyclase activity in bovine retina. We further demonstrate that both dopamine- and calmodulin-stimulated adenylate cyclase activities can be regulated by alterations in light. Bovine retinas were dissected from the eye under a low-intensity red safety light, defined as dark conditions, and incubated for 20 min in an oxygenated Krebs Henseleit buffer under either dark or light conditions. The retinas were then homogenized and adenylate cyclase activity measured in a particulate fraction washed to deplete it of endogenous Ca2+ and calmodulin. Activation of adenylate cyclase activity by calmodulin, dopamine, and the nonhydrolyzable GTP analog, guanosine-5'-(beta,gamma-imido)triphosphate ( GppNHp ), was significantly (60%) greater in particulate fractions from retinas that had been incubated under dark conditions as compared to those incubated under light conditions. Basal, Mn2+-, and GTP-stimulated adenylate cyclase activities were not altered by changes in lighting conditions. Calmodulin could increase the maximum stimulation of adenylate cyclase by dopamine in retinas incubated under either dark or light conditions, but the degree of its effect was greater in retinas incubated under light conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

Ethical conflict in long-term care: is legislation the answer?

The Omnibus Budget Reconciliation Act of 1987 radically redefined the relationship between nursing facilities and their residents. To explore the impact of this autonomy-enhancing but controversial legislation on nursing operations in skilled nursing facilities, two focus groups were convened. Nurse administrators identified ways in which the recently implemented legislation facilitates or inhibits resolution of the ethical conflicts they face. Participants concluded that legislation alone was insufficient to create needed reform in long-term care and recommended a multifaceted approach. A model is presented for creating a community of caring that identifies regulatory reform, professional empowerment, and organizational redesign as catalysts for a change.

Adult↗
PubMedDate not supplied

Balloon aortic valvuloplasty.

Balloon aortic valvuloplasty is a percutaneous, therapeutic option for patients with severe aortic stenosis, yet the effectiveness of this procedure is dependent on the morphology of the stenotic aortic valve and the respective mechanism of dilation. In younger patients with congenital aortic stenosis, acute and intermediate-term results are good. However, in adult patients, in whom degenerative aortic stenosis is the most common cause, the acute clinical and hemodynamic benefits of balloon aortic valvuloplasty are not lasting, as restenosis occurs in most patients within 6 months. Sympatomatic relief for adults undergoing balloon aortic valvuloplasty is only apparent in patients with normal left ventricular function, who generally are also candidates for aortic valve replacement. Furthermore, the long-term survival for adults after balloon aortic valvuloplasty is similar to the natural history of untreated severe aortic stenosis. In this article, the mechanism of balloon aortic valvuloplasty, as well as its clinical and hemodynamic effects, are reviewed in the context of the different morphological types of aortic stenosis. In addition, two large registries of adult patients treated with balloon aortic valvuloplasty provide important information regarding the acute and long-term results of this procedure and are reviewed.

Adult↗
PubMedDate not supplied

Chemokines and Alzheimer's disease.

In recent years, increasing attention has been focused on chemokines as inflammatory mediators in the CNS. The limited number of studies that have investigated chemokine and chemokine receptor expression in Alzheimer's disease (AD) brain and in cell culture models seem to support a role for inflammation in AD pathogenesis. Here we provide a review of these studies, but in addition, point out the possible role of chemokines as communication molecules between neurons and microglia. Understanding neuron-microglia interactions is essential for understanding AD pathogenesis, and disturbances in chemokine-mediated intercellular communication may contribute toward a generalized impairment of microglial cell function.

Alzheimer Disease↗
PubMedDate not supplied

Serving the public good: professionalizing the hospital corporation.

Economic concerns dominate hospital planning and policy decisions as hospitals seek to become more productive, competitive, and profitable. Professional concerns of quality care and public service may conflict with the profit-motivated business model. Nurse executives will have to be creative and politically astute to promote the integration of a professional model of service in this cost-conscious environment.

Administrative Personnel↗