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Biomedical subjects

A Doran

Publications and source records attributed to A Doran.

At least 19 recordsLinked to original sources
PubMed2004

Magnetic stripe domains in coupled magnetic sandwiches.

Magnetic stripe domains in the spin reorientation transition region are investigated in (Fe/Ni)/Cu(001) and Co/Cu/(Fe/Ni)/Cu(001) using photoemission electron microscopy. For (Fe/Ni)/Cu(001), the stripe domain width decreases exponentially as the Fe/Ni film approaches the spin reorientation transition point. For Co/Cu/(Fe/Ni)/Cu(001), the Fe/Ni stripe orientation is aligned with the Co in-plane magnetization, and the stripe domain width decreases exponentially with increasing the interlayer coupling between the Fe/Ni and Co films. By considering magnetic stripes within an in-plane magnetic field, we reveal a universal dependence of the stripe domain width on the magnetic anisotropy and on the interlayer coupling.

Journal Article↗
PubMed2004

Vortex core-driven magnetization dynamics.

Time-resolved x-ray imaging shows that the magnetization dynamics of a micron-sized pattern containing a ferromagnetic vortex is determined by its handedness, or chirality. The out-of-plane magnetization in the nanometer-scale vortex core induces a three-dimensional handedness in the planar magnetic structure, leading to a precessional motion of the core parallel to a subnanosecond field pulse. The core velocity was an order of magnitude higher than expected from the static susceptibility. These results demonstrate that handedness, already well known to be important in biological systems, plays an important role in the dynamics of microscopic magnets.

Journal Article↗
PubMed2003

Magnetic phase transition in Co/Cu/Ni/Cu(100) and Co/Fe/Ni/Cu(100).

Magnetic phase transitions in coupled magnetic sandwiches of Cu/Co/Cu/Ni/Cu(100) and Cu/Co/Fe/Ni/Cu(100) are investigated by photoemission electron microscopy. Element-specific magnetic domains are taken at room temperature to reveal the critical thickness at which the magnetic phase transition occurs. The results show that a coupled magnetic sandwich undergoes three types of magnetic phase transitions depending on the two ferromagnetic films' thickness. A phase diagram is constructed and explained in the process of constructing Monte Carlo simulations, which corroborate the experimental results.

Journal Article↗
PubMed1990

Cognitive effects of corticosteroids.

In three independent studies with different designs and groups of subjects, the authors found that 1) depressed patients who did not suppress cortisol when given dexamethasone (compared to suppressors and normal control subjects), 2) healthy volunteers given a single 1-mg dose of dexamethasone (compared to those given placebo), and 3) healthy volunteers given 80 mg/day of prednisone for 5 days (compared to those given placebo) all made significantly more errors of commission in verbal memory tasks, with no significant change in their rates of errors of omission. These findings raise the possibility of specific corticosteroid-related cognitive impairments.

Adrenal Cortex Hormones↗
PubMed1990

Tennis elbow. A clinicopathologic study of 22 cases followed for 2 years.

Twenty-two elbows in 20 patients with persistent lateral pain due to epicondylitis had release of the common extensor origin and decortication of the lateral epicondyle. Specimens taken from the lateral epicondyle were examined histologically and compared with controls, and patients were reviewed clinically 2 (1/2-4) years after operation. Following surgery, symptoms were improved in 17 patients. Histologic examination of the bone-tendon junction revealed evidence of a repair response of variable degree, the most frequent features being mucopolysaccharide infiltration and bone formation. Fibrofatty degenerative changes were also present in some cases. There was no correlation between the intensity of the histologic reaction and the clinical outcome.

Adult↗
PubMed1989

Hook-pin fixation of subcapital fractures of the femur: an atraumatic procedure?

Eighty-seven patients with subcapital fractures of the femur treated by hook-pin fixation were reviewed clinically and radiologically with an average follow-up time of 29 months. There were 58 undisplaced and 29 displaced fractures. Seven per cent of the undisplaced and 31 per cent of the displaced fractures developed avascular necrosis (AVN) and failure of fixation was seen in 3.5 per cent and 10 per cent respectively. Overall, 23 per cent of patients developed healing complications of which just over one-half had revision arthroplasty. The AVN rate in the undisplaced group was relatively low, though there was no clear advantage over simple screw fixation. In contrast, the incidence of AVN in displaced fractures was higher than with other methods. Fixation failure was related to surgical error in most instances.

Adult↗
PubMed1989

Specificity of plasma HVA response to dexamethasone in psychotic depression.

Earlier reports have suggested that dexamethasone significantly increases levels of plasma homovanillic acid (HVA) in normal subjects, but that this effect may be altered in some depressed patients. To investigate the specificity of such alterations, we administered dexamethasone (1 mg p.o. at 11 p.m.) to 33 normal subjects, 27 depressed patients (8 with psychotic features), and 16 schizophrenic patients. Plasma for assay of cortisol and HVA was obtained at 4 p.m. before and on the day following dexamethasone administration. Dexamethasone induced significant increases in plasma HVA in the normal subjects and in the schizophrenic patients, but not in the depressed patients. Indeed, psychotically depressed patients tended to show a dexamethasone-associated decrease in plasma levels of HVA. In contrast to cortisol "suppression" or "nonsuppression," dexamethasone-induced changes in plasma levels of HVA (i.e., increases or decreases) sensitively and specifically discriminated between patients with affective and nonaffective psychoses.

Adult↗
PubMed1989

Silastic ball spacer arthroplasty in the management of hallux valgus and hallux rigidus.

Sixty-two feet in 39 patients who were treated by insertion of a silastic ball spacer prosthesis into the first metatarsophalangeal joint for hallux valgus or hallux rigidus have been reviewed with a follow-up time of between 2 and 6 years. Twenty-one results (34%) were excellent, 27 (43%) were fair, 13 (21%) were poor, and one was revised. Seventeen feet (27%) had some metatarsalgia at followup. Results were disappointing in the young patients; in 19 cases of hallux valgus under the age of 45, 8 were either poor or had been revised. The original concept of the silastic ball spacer was to maintain great toe length and prevent proximal migration of the sesamoids. However 60% of these feet showed settling of the prosthesis or new bone formation around the prosthesis and 54% had more than 2 mm proximal migration of the sesamoid bones. The symptomatic results in these patients were similar to those in whom great toe length had been successfully maintained. The silastic ball spacer infrequently achieves its aims, however maintenance of hallux length does not seem to be important in the symptomatic result.

Adult↗
PubMed1989

Total hip replacement in the renal transplant recipient.

Osteonecrosis of the femoral head is a severely disabling complication of steroid immunosuppression in renal transplant patients. We report 31 total hip arthroplasties in 21 renal transplant recipients with an average follow-up of six years. There were no problems with wound healing or infection despite full immunosuppression. Four hips developed symptomatic loosening but the other results were excellent, comparing well with other methods of treatment for osteonecrosis. Ten patients died during the follow-up period. Total hip replacement is a safe and effective treatment for transplant recipients and, in view of their limited life expectancy, should be considered at an early stage in their treatment.

Aged↗
PubMed1988

Alprazolam augmentation of the antipsychotic effects of fluphenazine in schizophrenic patients. Preliminary results.

Alprazolam was added, under double-blind conditions, to stable fluphenazine hydrochloride regimens in 12 symptomatic, chronically ill inpatients with schizophrenia. The addition of alprazolam was associated with significant, albeit modest, reductions in global psychosis, thought disorder, and paranoia ratings, with a return to pretreatment levels on discontinuation of alprazolam treatment. Improvement in "negative symptoms" such as emotional withdrawal paralleled the changes in "positive symptoms" but did not, in itself, reach statistical significance. There were no significant changes in group mean plasma levels of homovanillic acid or 3-methoxy-4-hydroxyphenylglycol during alprazolam treatment, although group mean serum cortisol levels were significantly decreased by alprazolam treatment. Patients who responded favorably to alprazolam treatment were significantly more psychotic or anxious before treatment, were older, showed significant alprazolam-associated reductions in plasma levels of homovanillic acid, and had significantly more prominent prefrontal cortex atrophy on computed tomographic scans than patients in whom alprazolam was without therapeutic effect. These preliminary data, based on a small sample, suggest that some patients with schizophrenia who are only partially responsive to standard neuroleptic treatment may benefit from the addition of triazolobenzodiazepines, such as alprazolam.

Adult↗
PubMed1988

Fractures of the distal femur: the role of the Zickel supracondylar fixation device.

Supracondylar fractures of the femur are often difficult to manage, especially in the elderly whose osteoporotic bone renders internal fixation tenuous. The Zickel supracondylar device provides a dynamic, medullary fracture fixation secure enough to allow unsupported early mobilization even in the elderly. The device can be inserted through small incisions, minimizing surgical injury. Interlocking screws prevent shortening and rotation and allow its use even in comminuted fractures. In 16 patients with non-pathological fractures, follow-up was possible on 14. There were 7 excellent, 5 satisfactory and 2 unsatisfactory results. There were no failures. Follow-up ranged from 6 months to 2 years. The device also proved effective in four patients with pathological fractures, the closed insertion allowing the benefit of early radiotherapy. This small but varied series shows the value of the Zickel supracondylar device in this difficult fracture.

Adolescent↗
PubMed1987

CSF corticotropin-releasing hormone in depressed patients and normal control subjects.

The authors studied CSF corticotropin-releasing hormone (CRH) and plasma cortisol in 22 depressed patients and 18 normal control subjects. CRH levels were similar in the two groups. Depressed patients who were nonsuppressors on the dexamethasone suppression test had significantly higher levels of CRH than suppressors did. The depressed patients' CRH levels were significantly correlated with 4:00 p.m. postdexamethasone plasma cortisol levels. While the inclusion of a depressed patient with an outlier CRH value resulted in the loss of statistical significance for both of these findings, the authors suggest that these results support the hypothesis that hypercortisolism in depressed patients in part reflects a defect at or above the hypothalamus, resulting in hypersecretion of CRH.

Adult↗
PubMed1986

Chronic corticosterone administration in rats: behavioral and biochemical evidence of increased central dopaminergic activity.

Chronic corticosteroid treatment in humans in frequently complicated by behavioral changes. The present study suggests that chronic steroid administration in rats has distinct neurochemical consequences which are behaviorally relevant. Ten male Sprague-Dawley rats received 7 daily injections of corticosterone, following which they exhibited increased caudate homovanillic acid as well as an attenuated decline in vertical and ambulatory movement (functional measures of dopamine activity) compared to placebo-treated rats. A subgroup of steroid-treated rats which was more behaviorally responsive to corticosterone also showed increased caudate 5-hydroxyindole acetic acid and decreased prefrontal cortex dopamine and serotonin. These results are discussed in relation to the known behavioral side effects of chronic corticosteroid administration in man and the psychiatric manifestations of naturally occurring states of hypercortisolemia.

Animals↗