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Biomedical subjects

A Hayes

Publications and source records attributed to A Hayes.

At least 73 records · Page 4Linked to original sources
PubMed1997

Gabapentin monotherapy: II. A 26-week, double-blind, dose-controlled, multicenter study of conversion from polytherapy in outpatients with refractory complex partial or secondarily generalized seizures. The US Gabapentin Study Group 82/83.

This study evaluated gabapentin monotherapy in 275 patients with medically refractory complex partial or secondarily generalized seizures who were taking one or two antiepileptic drugs (AEDs). Following an 8-week baseline, patients received randomized dosages of gabapentin (600, 1,200, or 2,400 mg/d) during a 26-week double-blind phase comprising 2 weeks gabapentin add-on therapy, an 8-week AED taper, and a 16-week gabapentin monotherapy period. Patients exited the study if they experienced a protocol-defined exit event. Results of outcome measures, including time to exit, completion rate, and mean time on monotherapy, showed no significant differences among dosage groups. Possible reasons for this lack of a dose-response relationship include withdrawal seizures and the limited range of gabapentin dosages studied. Overall, 20% of patients completed the study. Completion rates were higher among patients who had discontinued one AED (23%) than two AEDs (14%), and higher among patients who were not withdrawn from carbamazepine (27%) than among those who were (16%).

Acetates↗
PubMed1996

The efficacy of single-dose aprotinin 2 million KIU in reducing blood loss and its impact on the incidence of deep venous thrombosis in patients undergoing total hip replacement surgery.

STUDY OBJECTIVE: To evaluate the efficacy of a 2 million KIU single dose of aprotinin on blood loss, transfusion requirements, and incidence of deep venous thrombosis (DVT) in patients undergoing total hip replacement surgery. DESIGN: Randomized study. SETTING: Operating theater at an orthopedic hospital. PATIENTS: 40 adult patients scheduled for total hip replacement surgery. INTERVENTIONS: Patients were randomized to two groups. Group A (n = 20) received 2 million KIU of aprotinin over 20 minutes, Group C (n = 20), the control group, received placebo. Anesthesia and surgical technique were standardized. MEASUREMENTS AND MAIN-RESULTS: Intraoperative blood loss, postoperative blood loss, transfusion requirements (48 hr), hemoglobin, coagulation parameters, and platelet counts were assessed. On the seventh postoperative day, all patients in both groups underwent venography to ascertain the incidence of DVT. We found no significant difference in blood loss or transfusion requirements between the two groups. Intraoperative and postoperative blood losses, coagulation parameters, and incidence of DVT did not differ significantly between the two groups. CONCLUSION: A single 2 million KIU bolus dose of aprotinin does not reduce perioperative blood loss or transfusion requirements. Aprotinin therapy, when used in conjunction with other antithrombotic therapies, does not increase the incidence of DVT after major orthopedic surgery.

Adult↗
PubMed1996

Application of finite elements to the stress analysis of articular cartilage.

A common effect of arthritic disease processes in synovial joints is deterioration of the articular cartilage. Therefore, an improved understanding of the relationships between the composition and structure of articular cartilage and the mechanical behaviour is a subject of considerable interest. The numerical modelling tool of finite element (FE) analysis has been widely applied to analyse the behaviour of articular cartilage under compressive stress. FE analysis enables parameters and boundary conditions to be investigated which are not accessible experimentally or analytically. The biphasic theory describes the constitutive behaviour of soft hydrated biological tissues, such as articular cartilage, and has been successfully implemented using FE analysis. The development of successively more comprehensive biphasic models is described here detailing the use of FE analysis in modelling experimental configurations such as indentation. Key work in the area is reviewed in this paper.

Animals↗
PubMed1996

Beneficial effects of voluntary wheel running on the properties of dystrophic mouse muscle.

Effects of voluntary exercise on the isometric contractile, fatigue, and histochemical properties of hindlimb dystrophic (mdx and 129ReJ dy/dy) skeletal muscles were investigated. Mice were allowed free access to a voluntary running wheel at 4 wk of age for a duration of 16 (mdx) or 5 (dy/dy) wk. Running performance of mdx mice (approximately 4 km/day at 1.6 km/h) was inferior to normal mice (approximately 6.5 km/day at 2.1 km/h). However, exercise improved the force output (approximately 15%) and the fatigue resistance of both C57BL/10 and mdx soleus muscles. These changes coincided with increased proportions of smaller type I fibers and decreased proportions of larger type IIa fibers in the mdx soleus. The extensor digitorum longus of mdx, but not of normal, mice also exhibited improved resistance to fatigue and conversion towards oxidative fiber types. The dy/dy animals were capable of exercising, yet ran significantly less than normal animals (approximately 0.5 km/day). Despite this, running increased the force output of the plantaris muscle (approximately 50%). Taken together, the results showed that exercise can have beneficial effects on dystrophic skeletal muscles.

Aging↗
PubMed1996

Effects of beta 2-agonist administration and exercise on contractile activation of skeletal muscle fibers.

Clenbuterol, a beta 2-adrenoceptor agonist, has therapeutic potential for the treatment of muscle-wasting diseases, yet its effects, especially at the single-fiber level, have not been fully characterized. Male C57BL/10 mice were allocated to three groups: Control-Treated mice were administered clenbuterol (2 mg.kg-1. day-1) via their drinking water for 15 wk; Trained-Treated mice underwent low-intensity training (unweighted swimming, 5 days/wk, 1 h/day) in addition to receiving clenbuterol; and Control mice were sedentary and untreated. Contractile characteristics were determined on membrane-permeabilized fibers from the extensor digitorum longus (EDL) and soleus muscles. Fast fibers from the EDL and soleus muscles of Treated mice exhibited decreases in Ca2+ sensitivity. Endurance exercise offset clenbuterol's effects, demonstrated by similar Ca2+ sensitivities in the Trained-Treated and Control groups. Long-term clenbuterol treatment did not affect the normalized maximal tension of fast or slow fibers but increased the proportion of fast fibers in the soleus muscle. Training increased the proportion of fibers with high and intermediate succinate dehydrogenase activity in the EDL and soleus muscles, respectively. If clenbuterol is to be used for treating muscle-wasting disorders, some form of low-intensity exercise might be encouraged such that potentially deleterious slow-to-fast fiber type transformations are minimized. Indeed, in the mouse, low-intensity exercise appears to prevent these effects.

Adrenergic beta-2 Receptor Agonists↗
PubMed1995

Separable binding sites for the natural agonist endothelin-1 and the non-peptide antagonist bosentan on human endothelin-A receptors.

A three-dimensional model for the transmembrane domains of human endothelin-A receptor was built using structural information from bacteriorhodopsin and sequence alignment to other guanine-nucleotide-binding regulatory(G) protein-coupled receptors. Based on this model, 18 amino acids located at the inside of the receptor were mutated and analyzed for binding of the natural ligand endothelin-1 and bosentan, a recently described potent orally active endothelin antagonist [Clozel, M., Breu, V., Gray, G., Kalina, B., Löffler, B.-M., Burri, K., Cassal, J.-M., Hirth, G., Müller, M., Neidhart, W. & Ramuz, H. (1994) Pharmacological characterization of bosentan, a new potent orally active nonpeptide endothelin receptor antagonist, J. Pharmacol. Exp. Ther. 270, 228-235]. Mutation of Gly97, Lys140, Lys159, Gln165 and Phe315, located in transmembrane region 1, 2, 3, 3, and 6, respectively, caused reduced specific binding of 125I-labelled endothelin-1, despite an expression level similar to wild-type endothelin-A receptor. Mutation of Tyr263, Arg326 and Asp351 preserved endothelin-1 binding but caused reduced binding of bosentan. These amino acids, located on transmembrane regions 5, 6 and 7, respectively, are conserved among endothelin-A and endothelin-B receptors but not in other G-protein-coupled receptors. These observations demonstrate a dissociation of the binding site for the peptidic natural agonist endothelin-1 and the synthetic non-peptide antagonist bosentan. They provide the molecular basis for bosentan being a specific antagonist for both, endothelin-A as well as endothelin-B receptors and may in combination with studies on structure/activity relationship support the design of novel and more potent endothelin receptor antagonists.

Amino Acid Sequence↗
PubMed1995

Ethylene glycol permeation and toxicity in the rabbit common carotid artery.

The rate of permeation of ethylene glycol (EG) and the maximum concentration that can be tolerated without functional damage was measured in the rabbit common carotid artery. Pairs of arteries were perfused on ice, one (the control) with a high K+ balanced salt solution containing 100 mM TES (CPTES), and the other with ethylene glycol/CPTES solutions. The concentration of EG was increased in a stepwise manner in order to reduce osmotically induced changes in endothelial cell volume. The final concentration was 10, 20, or 40% EG (w/w). After exposure for 20 min, the EG was then removed at room temperature using stepwise decreasing concentrations of ethylene glycol in the presence of 3% mannitol. After this, the contractile function of the smooth muscle was tested at 37 degrees C with noradrenaline and the integrity of the endothelium was assessed structurally by vital staining and functionally by its capacity to produce endothelium-derived relaxation factor in response to administration of acetylcholine. The tissue concentration reached 8.6% after 30 min of exposure to 10% EG. The contractile function of the smooth muscle was unaffected by EG at all concentrations. There was a significant (50%) reduction in the ACh-induced relaxation of contracted arteries after exposure to 40% EG (P < 0.02) but this was not associated with any detectable loss of cells or damage to the endothelium. It was concluded that EG warrants further investigation as a cryoprotectant for blood vessels.

Animals↗
PubMed1995

Psychiatric nursing: what does biology have to do with it?

There is a plethora of research that investigates the mind/body connection. This article provides a review of the advances in biological psychiatry, which includes the areas of psychobiology and psychoneuroimmunology (PNI). Psychobiology is the branch of biological psychiatry that examines the biology of thoughts, feelings, and behavior. Current research findings that illuminate the neurotransmitter systems of the brain are highlighted. Psychoneuroimmunology is a relatively new branch of science that strives to show the connections between psychology, neurology, and immunology. Research in the area of PNI has yielded much information useful to nursing. Implications of this knowledge for psychiatric nursing are addressed.

Antidepressive Agents↗
PubMed1995

Mercy Healthcare's CARE 2000: an evolution in progress.

In a learning environment of shared governance, continuous quality improvement, and redesign principle application, disciplines of Mercy Healthcare San Diego produced their patient care delivery redesign model, Creative Actions Reflecting Excellence. Nurses, pharmacists, medical technologists, respiratory care practitioners, physicians, educators, managers, and many other professional and technical partners converted change and transition into opportunities. As disciplines understood and appreciated each other's unique and shared contributions, quality of care, stakeholder satisfaction, and process efficiencies increased.

Decision Making, Organizational↗
PubMed1995

Adults in the pediatric emergency department: a fish out of water?

UNLABELLED: Adults (> 17 years) occasionally seek care in pediatric emergency departments (PED). We reviewed the records of adults treated in our PED from September 1992 to August 1993 to better understand their needs. Patients were classified based on their relationship to our hospital: 1) no previous medical care association (new), and 2) adult patients followed in our clinics for chronic diseases (chronic). Data were analyzed using frequencies and comparison of means by Student's t test or chi 2. A follow-up phone call or written survey was used to assess quality of care and satisfaction. Of 40,895 patients, 384 were adults (0.9%). Ages ranged from 18 to 73 years (median = 21 years, mean = 25 years) with 49% men. Most adults were seen between 3:00 PM and 10:59 PM; 84% were triaged as urgent or emergent. There were 140 new, and 230 chronic, patients. Fourteen were not classified because of lack of information. The mean age of new adults was 33 years, median 29 years; 53% were hospital employees. Forty percent of new adults had preexisting illnesses. Most common problems were cardiac/hypertension (27%), blunt trauma (22%), eye splash (13%), and lacerations (9%). Forty eight percent were transferred to an adult hospital, and 20% of transferred patients were admitted overnight. Chronic adult patients were younger (mean 21 years, P < 0.001); fever/infection (37%), minor trauma (17%), and gastro-intestinal problems (12%) predominated; 36% were admitted. The average time in the PED was 70 minutes for new and 202 minutes for chronic patients (P < 0.001). CONCLUSIONS: Chronic patients present with problems much like those of their younger counterparts, and the PED is prepared to manage them. New adult patients present with adult problems: chest pain, hypertension, blunt trauma, and eye foreign body, and the PED should be prepared to manage these.

Adolescent↗
PubMed1994

Contractile properties and temperature sensitivity of the extraocular muscles, the levator and superior rectus, of the rabbit.

1. Contractile and fatigue-resistance characteristics, temperature sensitivity (10-37 degrees C) of contraction, and histochemical fibre types were determined for two of the extraocular muscles, the superior rectus and levator palpebrae superioris (levator), of the rabbit. 2. The levator displayed similar contractile characteristics (time to peak, half-relaxation time of twitch response, and twitch-tetanus force ratio) to mammalian fast-twitch limb muscle at room temperature (20 degrees C). However, normalized twitch and tetanic force levels were significantly less than those found in limb muscle. The superior rectus displayed the characteristics of even faster contraction than the levator at 20 degrees C, but generated lower maximum force levels than the levator. 3. The twitch response of the superior rectus showed a biphasic relaxation phase. This response was not due to non-twitch (tonic) fibres present in the superior rectus as it was unaffected by propranolol application during muscle stimulation. 4. The superior rectus and levator displayed significantly less fatigue in the tetanic force response than fast-twitch limb muscles did in response to a fatiguing electrical stimulation protocol. The levator was significantly more fatigue resistant than the superior rectus. 5. The force responses of both extraocular muscles displayed a similar dependence on temperature (10-37 degrees C) to limb skeletal muscles. 6. The superior rectus and levator exhibited a high proportion of fast-twitch muscle fibres (type II) as shown by myosin ATPase staining. Succinate dehydrogenase activity indicated that these muscles showed a high oxidative capacity, with a staining intensity typical of type I or type II A fibres of limb muscles. 7. The results emphasize the morphological and functional complexity of mammalian extraocular muscles. The combination of very fast contractile properties with high oxidative capacity make these muscles well suited to their role in eye/eyelid movement.

Animals↗
PubMed1994

Changes in protein distribution in the rat during prolonged "systemic injury".

A model of prolonged systemic injury was generated in the rat by three sequential injections of turpentine, delivered at 2-day intervals. The model was then used to identify the subsequent changes in the distribution of tissue protein and the effects of the changes in skin protein on the tensile strength of healing skin wounds. The model produced a sustained acute phase response during the 6 days of the study, including a significant (26%) reduction in the plasma glutamine concentration (P < 0.01), which was not achieved with a single injection of turpentine. When compared with pair-fed controls, the animals injected with turpentine had 18% more nitrogen in the liver (P < 0.05), 25% less in the gastrocnemius muscle (P < 0.01), and a similar amount in the upper small intestine. There was also a 30% loss of nitrogen from dorsal skin (P < 0.001) and a 15% loss from ventral skin (P < 0.01), with a parallel loss of collagen (measured as hydroxyproline). Ten days after the first injection of turpentine, the dorsal skin was still 18% thinner than that of the pair-fed controls (P < 0.01): this was associated with an 18% reduction in the bursting strength of linear skin wounds (P < 0.05). Such changes were not observed in pair-fed controls. These studies demonstrate that systemic injury (independent of dietary intake) causes a preferential loss of protein from peripheral tissues (skin, muscle) and preservation of protein in splanchnic tissue (liver, intestine). They also suggest that the loss of skin protein including collagen is quantitatively important, with functional consequences in reducing the bursting strength of surgical skin wounds.

Acute-Phase Reaction↗
PubMed1994

Crystals in equine articular cartilage.

Crystal deposits have been observed in equine articular cartilage and identified by scanning electron microscopy and X-ray diffraction as octacalcium phosphate and calcium pyrophosphate dihydrate. Of 89 equine fetlock joints examined 10 contained evidence of calcification visible by eye. It is suggested that the deposition of crystals may be a mediator of arthritis in horses and may also cause damage directly.

Animals↗
PubMed1994

The coding of spatial position by the human visual system: effects of spatial scale and retinal eccentricity.

In this study we investigate the nature of the computations that underlie the encoding of spatial position by the human visual system. Specifically, we explore the relationship between alignment accuracy and retinal eccentricity for stimuli where local luminance, local contrast, and orientation cues do not underlie performance. Spatial scale is especially important for such a comparison because of the well documented spatial inhomogeneity of the human visual field. The results suggest that the relationship between spatial localization and eccentricity is invariant with spatial scale if accuracy and eccentricity are expressed in terms of the stimulus envelope size. We show that the photoreceptor disarray does not determine the limit to performance for this task, the limit is post-receptoral and can be modelled in terms of a positional uncertainty within the early filters located before the response envelope has been extracted. This uncertainty varies with eccentricity in a similar way within each spatial array.

Contrast Sensitivity↗