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Biomedical subjects

R R Smith

Publications and source records attributed to R R Smith.

At least 19 recordsLinked to original sources
PubMed1999

An EPR investigation of surfactant action on bacterial membranes.

The effects of the surfactants, alcohol ethoxylate, amine ethoxylate, amine oxide and SDS on cell membranes were investigated using the lipid soluble spin label 5-doxyl stearic acid (5-DS). Electron paramagnetic resonance (EPR) spectroscopy revealed that the action of the surfactants was to significantly increase membrane fluidity of Proteus mirabilis, Staphylococcus aureus and Saccharomyces cerevisiae. The action of these surfactants as biocides was investigated and found to be dependent on the type of organism tested. There was, however, no direct correlation between enhanced membrane fluidity observed due to the action of the surfactants and biocidal activity. Data presented suggest that perturbing the fluidity of the cytoplasmic membrane is not immediately responsible for cell death.

Cell Membrane↗
PubMed1999

Glucocorticoid resistance in premature pubarche and adolescent hyperandrogenism.

To determine whether glucocorticoid resistance due to mutations in the glucocorticoid receptor (GRL) gene is associated with premature pubarche, hirsutism, or oligo/amenorrhea, we performed single-strand conformational polymorphism analysis of genomic DNA obtained from 25 children and 16 adolescent girls referred for the evaluation of premature pubarche, hirsutism, or oligo/amenorrhea. A missense mutation, N363S, and a presumed polymorphism in the 3'-UTR of exon 9alpha were identified. We conclude that glucocorticoid resistance due to GRL mutations is an infrequent cause of mild hyperandrogenism.

3' Untranslated Regions↗
PubMed1999

The presence of the 21-hydroxylase deficiency carrier status in hirsute women: phenotype-genotype correlations.

OBJECTIVE: To determine the role of heterozygosity for mutations in the 21-hydroxylase gene (CYP21) in the pathogenesis of hyperandrogenism. DESIGN: Controlled clinical study. SETTING: Tertiary care institutional hospital. PATIENT(S): Forty hirsute women and 13 healthy control women. INTERVENTION(S): The source of androgen excess was determined by the changes in serum testosterone levels in response to a single 3.75-mg i.m. dose of triptorelin. MAIN OUTCOME MEASURE(S): CYP21 molecular genetic analysis and serum 17-hydroxyprogesterone levels. RESULT(S): Eight patients and one control were heterozygous carriers of CYP21 mutations. Two patients with adrenal hyperandrogenism and one patient with ovarian hyperandrogenism, who carried the V281L mutation had an increased ACTH-stimulated 17-hydroxyprogesterone level (>4.1 ng/mL) that persisted during gonadal suppression. Another patient with adrenal hyperandrogenism carried the V281L mutation, and her ACTH-stimulated 17-hydroxyprogesterone level was elevated only during gonadal suppression. Four patients (three with idiopathic hirsutism, one with ovarian hyperandrogenism) and one control were carriers of CYP21 mutations typically associated with classic congenital adrenal hyperplasia but had normal basal and ACTH-stimulated 17-hydroxyprogesterone levels. Nine patients without CYP21 mutations had increased ACTH-stimulated 17-hydroxyprogesterone levels; these decreased to normal in six of the patients during gonadal suppression. CONCLUSION(S): The response of serum 17-hydroxyprogesterone to ACTH does not predict CYP21 carrier status. No clear concordance was found between the CYP21 genotype and the functional origin of androgen excess.

17-alpha-Hydroxyprogesterone↗
PubMed1999

Suboccipital resection of a medial acoustic neuroma with hearing preservation.

BACKGROUND: Many reports indicate that acoustic neuromas greater than 2.0 cm should be removed without hearing preservation attempted, even if hearing is present preoperatively. These studies advocate a translabyrinthine approach because the likelihood of hearing preservation is low. Medial acoustic neuromas, unlike the more common lateral tumors that involve the internal auditory canal, originate medial to that portion of the eighth nerve complex where the cochlear and vestibular nerves are fused. This anatomical feature suggests that these tumors may be amenable to resection with hearing preservation. METHODS: A patient with a 3.5 cm medial acoustic neuroma and useful preoperative hearing is presented. RESULTS: Gross total tumor removal with functional hearing was achieved after a two-stage procedure using a suboccipital approach. CONCLUSION: Based on the anatomico-pathologic features in this case, we believe that, if a patient has reasonable preoperative hearing (speech discrimination score > 70%) and a medial acoustic neuroma, an approach to preserve hearing should be considered regardless of tumor size.

Female↗
PubMed1999

Identity in political context: lesbian/gay representation in the public sphere.

Discourses constructed to represent lesbians and gay men in the public sphere generate an essentialist identity which is both necessary and damaging. Legislative debate illustrates the production of a constrictive and homogeneous identity rejected by many gay/lesbian scholars and activists. Discussion of the rhetorical power of identity claims has produced alternative stances toward variant sexuality. This discussion can be advanced by challenging dominant constructions of civil rights and the public sphere.

Adolescent↗
PubMed1999

Temporal bone: comparison of isotropic helical CT and conventional direct axial and coronal CT.

OBJECTIVE: The objective of the study was to compare helical CT (with reformation of coronal images from the axial data set) with conventional direct axial and coronal CT of the temporal bones. SUBJECTS AND METHODS: Nineteen patients underwent both conventional 1-mm direct axial and coronal CT and helical 0.5-mm axial CT. The helical data set was reconstructed at 0.2-mm increments, and axial and coronal images were reconstructed in a plane similar to that of the conventional study, with a slice width of 0.5 mm and 0.5-mm increments. Forty small structures were evaluated independently by three observers, who were unaware of the method of imaging. Observers graded the 40 structures using a modified Likert scale. The graded differences between the two techniques were evaluated using a paired t test. Correlation between observers' gradings was evaluated using analysis of variance. RESULTS: The helical CT technique scored significantly higher than the conventional technique for many individual structures and groups of structures (scutum [p = .041], stapes footplate [p = .006], stapes crura [p = .004], oval window [p = .026], crista falciformis [p = .006], whole temporal bone [P = .012], middle ear [p = .033], inner ear [p = .021], ossicles [p = .044], and stapes [p = .010]). The correlation coefficient among observers was .91 for the whole temporal bone. CONCLUSION: Helical CT using 0.5-mm technique and reconstruction produces diagnostic images comparable with or superior to conventional 1-mm technique because helical CT can obtain thinner slices.

Adolescent↗
PubMed1999

Use patterns for antipsychotic medications in medicaid patients with schizophrenia.

OBJECTIVE: We investigated the use patterns for antipsychotic medications generated by Medicaid patients with schizophrenia. METHOD: Paid claims data from the California Medicaid program (Medi-Cal) were used to identify 2655 patients with schizophrenia. Data from 1987-1996 were used, during which time Medi-Cal maintained prior authorization restrictions on second generation antipsychotic drugs. Prescription records were used to identify 3 patterns of antipsychotic drug use: no drug therapy for over 1 year; delayed onset of antipsychotic drug therapy; and switches in antipsychotic drugs within 1 year. Multiple logistic regression models were used to identify factors affecting these antipsychotic drug use patterns. RESULTS: Conventional antipsychotic medications account for over 98% of all patient treatment episodes. Over 24% of patients with schizophrenia do not use any antipsychotic medication for periods lasting up to 1 year. Over 24% of treated patients delayed the use of antipsychotic medications at least 30 days. For those patients who did not delay their use of antipsychotic medications, over 47% switched or augmented their initial antipsychotic medication during the first treatment year. Only 11.6% of treated patients achieved 1 year of uninterrupted antipsychotic drug therapy. The mean duration of uninterrupted therapy was 142 days. DISCUSSION: Antipsychotic drug use patterns suggest that conventional antipsychotic medications do not meet the therapeutic needs of patients with schizophrenia.

Ambulatory Care↗
PubMed1998

Consensus opinion on diagnosis of cerebral circulatory arrest using Doppler-sonography: Task Force Group on cerebral death of the Neurosonology Research Group of the World Federation of Neurology.

BACKGROUND AND PURPOSE: Oscillating flow or systolic spikes are typical Doppler-sonographic flow signals found in the presence of cerebral circulatory arrest, which if irreversible, results in brain death. The Neurosonology Research Group (NSRG) of the World Federation of Neurology (WFN) created a Task Force Group in order to evaluate the role of Doppler-sonography as a confirmatory test for determining brain death. METHODS: The available evidence from the literature has been reviewed and discussed by a group of experts, the members of the Task Force Group on cerebral death of the NSRG. RESULTS AND CONCLUSIONS: Extra- and intracranial Doppler-sonography is a useful confirmatory test to establish irreversibility of cerebral circulatory arrest as optional part of a brain death protocol. Doppler-sonography is of special value when the therapeutic use of sedative drugs renders electroencephalography unreliable. Doppler-sonographic criteria are defined and guidelines for the use of Doppler-sonography in this setting are presented.

Blood Flow Velocity↗
PubMed1998

The hochschild cohomology problem for von neumann algebras.

In 1967, when Kadison and Ringrose began the development of continuous cohomology theory for operator algebras, they conjectured that the cohomology groups Hn(M, M), n >/= 1, for a von Neumann algebra M, should all be zero. This conjecture, which has important structural implications for von Neumann algebras, has been solved affirmatively in the type I, IIinfinity, and III cases, leaving open only the type II1 case. In this paper, we describe a positive solution when M is type II1 and has a Cartan subalgebra and a separable predual.

Journal Article↗
PubMed1998

Primary intravascular lymphomatosis associated with Mycobacterium marinum.

Intravascular lymphomatosis (i.v.l.) is a rare condition in which neoplastic cells preferentially infiltrate blood vessels of the central nervous system. Nonspecific symptoms associated with i.v.l. include dementia, seizures, and multifocal cerebrovascular events. i.v.l. was discovered at autopsy of a patient whose neurological deficits were predated by a particularly aggressive form of Mycobacterium marinum soft-tissue infection. It is speculated that i.v.l. may have had an occult effect on the patient's cell-mediated immunity that predisposed him to this normally innocuous mycobacteria.

Blood Vessels↗
PubMed1997

General practitioners as providers of minor surgery--a success story?

BACKGROUND: It is now recognized that many minor surgical procedures can be appropriately performed in a general practitioner setting; the government has introduced a list of minor operations, for which it is prepared to pay a limited fee, and it is now time to see whether this service can be expanded. AIM: To demonstrate that a group of general practitioners (GPs) with a particular interest in minor surgery can offer an expanded service both to their own patients and also to the patients of neighbouring colleagues, whether fundholding or non-fundholding, within a health authority area. METHOD: The West Kent Health Authority awarded a contract for 500 minor operations to a group practice of five GPs. At the end of the first year, 511 operations had been performed, and the results and implications are discussed. RESULTS: The target of 500 minor operations was met and passed in the first year. Thirty-five neighbouring GPs referred their patients directly. All were offered an initial appointment within one week and had their operation performed within one month, unless they had expressed a preference for an alternative date. Several unsuspected malignancies were discovered-no complications were recorded, patients' and referring doctors' satisfaction was high and the scheme was judged to have been a success in their eyes. CONCLUSION: GPs can provide an efficient, cost-effective minor surgery service, which is popular with patients and referring colleagues. Whether this is the way we wish to organize minor surgery in the future needs further discussion.

Delivery of Health Care↗
PubMed1996

Increased intracranial pressure and the cerebrospinal fluid spaces.

Increased intracranial pressure is a frequent accompaniment to many of the disease processes affecting the brain and its coverings. Such increased pressure is associated with significant morbidity and mortality. This article briefly reviews the pathophysiology of increased intracranial pressure and addresses the clinical and neuroradiological presentation of increased pressure. As part of the discussion, the concept of hydrocephalus and its treatment and complications are addressed.

Blood Volume↗
PubMed1996

Hematopoietic bone marrow hyperplasia: correlation of spinal MR findings, hematologic parameters, and bone mineral density in endurance athletes.

PURPOSE: To determine the frequency of hematopoietic hyperplasia on spinal magnetic resonance (MR) images in endurance athletes and to correlate MR alterations with clinical parameters. MATERIALS AND METHODS: In 15 endurance athletes, MR images of the lumbar spine were analyzed for hematopoietic hyperplasia; vertebral T1 and T2 were determined. Bone mineral density (BMD) was determined, blood tests were performed, and maximum oxygen consumption (VO2max) was measured. RESULTS: Nine subjects showed evidence of hematopoietic hyperplasia: Eight showed T1 prolongation, and six had patchy or diffuse T1 hypointensity. No definite correlation existed between hematopoietic hyperplasia and duration of training, hematologic results, or VO2max levels. Borderline significance existed between hematopoietic hyperplasia and anemia (P = .103) and intensity of training (P = .09). BMD had no statistically significant effect on T1. CONCLUSION: Changes in BMD do not appear to contribute to MR marrow changes that are consistent with hematopoietic hyperplasia. Depleted iron reserves or increased hematopoiesis probably contribute to hematopoietic hyperplasia in endurance athletes.

Adult↗
PubMed1996

Case report: CT and MRI of intracranial dermoid causing headache.

This case shows an unusual intracranial cause of chronic headache in a 30-year-old female. Computerized tomography and magnetic resonance imaging were used to demonstrate an intracranial, dermoid cyst located in the left middle cranial fossa. Droplets of fat-like material, which leaked from this cyst, were present in the basilar subarachnoid spaces and left sylvian fissure. Since the surgical excision of the cyst, the patient has not had any severe headaches.

Adult↗
PubMed1995

Gliofibroma: CT and MRI.

We describe CT and MRI appearances in two children with pathologically proven gliofibromas, in the cerebrum and cerebellum. A striking finding was lack of high signal on T2-weighted MRI.

Biomarkers, Tumor↗
PubMed1995

Spontaneous extracranial carotid artery dissection in children.

Dissection of cerebral arteries as a cause of stroke is rarely recognized in children. Two patients with stroke due to extracranial carotid artery dissection are reported. A 7-year-old girl with a 2-week history of right arm chorea had a left basal ganglia infarct and is receiving haloperidol for persistent chorea. The second patient, a 15-year-old boy, developed aphasia and right hemiparesis a day before admission during a football game without obvious trauma. He had a large left middle cerebral artery infarct and died of cerebral edema and herniation. We believe that strokes due to arterial dissection are more common than currently recognized, partly because of a lack of history of trauma, and suggest that cerebral artery dissection be considered as an etiology of childhood strokes. Greater awareness of arterial dissection as a cause of stroke and availability of noninvasive techniques like magnetic resonance angiography should result in a more accurate diagnosis and improved prognosis in these patients.

Adolescent↗