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Biomedical subjects

J C Stevens

Publications and source records attributed to J C Stevens.

At least 19 recordsLinked to original sources
PubMed1992

Conditions associated with carpal tunnel syndrome.

With use of a comprehensive medical records-linkage system, we identified the comorbid conditions and risk factors in the residents of Rochester, Minnesota, who had a diagnosis of carpal tunnel syndrome during 1961 through 1980. In 43.2% of the 1,016 patients, no associated conditions were found on review of the medical records, whereas associated conditions were documented in 56.8%. The most frequent of these conditions were Colles' fracture, rheumatoid arthritis, hormonal agents or oophorectomy (or both), diabetes mellitus, and, among men, occupations that involved excessive use of the hands. Rheumatoid arthritis, diabetes mellitus, and pregnancy were significantly more frequent among the study patients with carpal tunnel syndrome than in the general population of Rochester, Minnesota. The standardized morbidity ratio was 3.6 for rheumatoid arthritis, 2.3 for diabetes mellitus, and 2.5 for pregnancy. The population attributable risk for pregnancy among women 15 to 44 years old was 7.0%. The standardized morbidity ratio for polymyalgia rheumatica was not significantly increased.

Adolescent↗
PubMed1992

Characteristics of Groningen tracheo-oesophageal speaking valves prior to insertion and after removal for failure.

The Groningen valve was first used in Sheffield in 1986 in a patient who underwent laryngectomy for malignant disease. Since then it has been the main tracheo-oesophageal prosthesis used on our Unit for speech rehabilitation post-laryngectomy. This biflanged device inserted primarily or as a secondary procedure remains in situ until failure occurs either because of leakage or because increased effort is required to produce satisfactory phonation. This in vitro study we examined the differences between new valves prior to insertion and those removed for failure. The mean forward opening pressures were shown to be similar in the two populations but the mean forward resistances were increased in those valves which were defective (P less than 0.001). In addition the mean reverse opening pressure was found to be significantly lower in the defective valves when compared with their new counterparts (P less than 0.05).

Adult↗
PubMed1992

An apparatus to measure pressure, flow and speech parameters in patients producing speech using the Groningen valve prosthesis.

We present a validated method of determining in vivo pressure, flow and voice parameters from patients using tracheo-oesophageal voice prostheses post laryngectomy. This apparatus was constructed simply using equipment which should be available in most large Otolaryngology Departments. There was good agreement between measurements made over two separate sessions of in vivo opening pressure, maximum flow through the device and maximum voice amplitude and these were significant. These measurements may be useful in monitoring patient progress and also in elucidating the mechanics of prosthesis failure.

Airway Resistance↗
PubMed1992

Aging and spatial acuity of touch.

Spatial acuity of the skin of the fingertip deteriorates markedly with age, as assessed by 2-point thresholds measured with a forced-choice method in 80 subjects between the ages of 18 and 91 years. This loss of "minimum separable" acuity appears to be pervasive, demonstrably affecting many middle-aged and a great majority of the elderly persons tested. Mean threshold was 1.95 mm for young (18-33 years), 2.68 mm for middle-age (41-63 years), and 5.03 mm for elderly (66-91 years) subjects. Over half of the variance in 2-point threshold was attributable to age (r = .74). Threshold on the arm, measured in subsets of 15 young and 15 elderly, was also age-dependent, but (reckoned as a percentage) the difference is minor compared to the finger. Analysis implies that the perception of tactile patterns, in general, and tactile reading (braille, Optacon) by the sensory handicapped, in particular, could run into age-related difficulty by reason of impairment of spatial acuity at the most basic level.

Adolescent↗
PubMed1992

Post-lumbar puncture headaches: experience in 501 consecutive procedures.

To ascertain the frequency and risk factors for post-lumbar puncture headache, we studied all adults who had an ambulatory lumbar puncture (LP) in a 1-year period. Patients filled out a questionnaire detailing their headache experience on the day of, and the 6 days following, LP. Those who did not return the questionnaire were telephoned. We systematically collected and analyzed many items, including the lumbar puncturist's experience, the degree of difficulty of the LP, CSF findings, final diagnosis, and the patient's demographic characteristics. Patients reporting headache before LP were more likely to report post-LP headaches. In addition to this, younger female patients with a lower body mass index have the highest risk of developing post-LP headaches. CSF opening pressure, cells, and protein, patient's position during LP, the duration of recumbency following LP, and the amount of CSF removed at the time of LP did not influence the occurrence of headache.

Adolescent↗
PubMed1992

The human hepatic cytochromes P450 involved in drug metabolism.

The cytochromes P450 are a superfamily of hemoproteins that catalyze the metabolism of a large number of xenobiotics and endobiotics. The type and amount (i.e., the animal's phenotype) of the P450s expressed by the animal, primarily in the liver, thus determine the metabolic response of the animal to a chemical challenge. A majority of the characterized P450s involved in hepatic drug metabolism have been identified in experimental animals. However, recently at least 12 human drug-metabolizing P450s have been characterized at the molecular and/or enzyme level. The characterization of these P450s has made it possible to "phenotype" microsomal samples with respect to their relative levels of the various P450s and their metabolic capabilities. The purpose of this review is to compare and contrast the human P450s involved in drug metabolism with their related forms in the rat and other experimental species.

Cytochrome P-450 Enzyme System↗
PubMed1991

Molecular basis for a functionally unique cytochrome P450IIB1 variant.

Liver microsomes from phenobarbital-treated rats of four inbred strains expressing distinct allelic variants of cytochrome P450IIB1 were analyzed. The Wistar Munich (WM) strain exhibited 5- to 10-fold lower androstenedione 16 beta-hydroxylase activity (a specific P450IIB1 marker) than the Lewis, Wistar Kyoto, and Wistar Furth strains. The androstenedione 16 beta-hydroxylase in the WM liver microsomes was refractory to inactivation by N-(2-p-nitrophenethyl)chlorofluoroacetamide, a selective P450IIB1 inactivator in the other three strains. Purified P450IIB1-WM was insensitive to the inactivator and exhibited 5-fold lower androstenedione 16 beta-hydroxylase, testosterone 16-hydroxylase, and 7-ethoxycoumarin deethylase activities but the same benzphetamine demethylase activity and slightly higher androstenedione 16 alpha-hydroxylase activity than a P450IIB1 purified from outbred Sprague-Dawley rats, which appears to correspond to the form in Lewis rats. The stereoselectivity of androstenedione 16-hydroxylation catalyzed by P450IIB1-WM (16 beta-OH:16 alpha-OH = 1.4) is thus distinct from that (16 beta-OH:16 alpha-OH = 12-15) of other P450IIB1 preparations described. A cDNA encoding P450IIB1-WM was cloned and sequenced, revealing a single amino acid substitution (Gly-478----Ala) compared with the published sequence (Fujii-Kuriyama, Y., Mizukami, Y., Kawajiri, K., Sogawa, K., and Muramatsu, M. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 2793-2797). Heterologous expression of P450IIB1 and P450IIB1-WM confirmed the striking difference in androstenedione metabolite profiles, strongly implicating the involvement of Ala-478 in defining the distinctive catalytic properties of P450IIB1-WM.

Alleles↗
PubMed1979

Lateral approach for exploration of the parathyroid gland.

The common use of automated metabolic screening has led to the early discovery of many patients with hyperparathyroidism and an increase in the number of operations performed upon the parathyroid glands. Approaching the parathyroid glands and the posterior aspect of the thyroid lateral to the sternohyoid and sternothyroid muscles has facilitated surgical exploration of these structures and has increased the rate of success of these operations. This approach has been used with 100 per cent success in 67 of 117 operations performed for hyperparathyroidism since 1973.

Adenoma↗
PubMed1978

Preduodenal portal vein: Two cases with differing presentation.

Preduodenal or precholedochal veins are rare developmental anomalies of considerable surgical importance. Injury to these structures because of failure to recognize them during operations for unrelated diseases may result in thrombosis or hemorrhage. We recently encountered this anomaly twice, once in a newborn infant with duodenal obstruction and once in a 54-year-old woman undergoing cholecystectomy. The preduodenal vein was not the primary cause of obstruction in the infant, but injury to the previously unrecognized percholedochal vein in the woman resulted in a considerable loss of blood. Besides describing and illustrating these two cases, we also discuss the anatomy and the embryology of these structures and briefly review the patterns of 44 previously reported cases that we found.

Arteriovenous Malformations↗
PubMed1978

Computed tomography and radionuclide imaging in the evaluation of ischemic stroke.

One hundred forty-one patients with cerebral or cerebellar infarction were examined by computed tomography (CT) as soon after the ictus as possible. The examination was repeated in 7 days, and a radionuclide brain scan was performed. The overall detection rate for ischemic infarction was approximately equal for both techniques, ranging from 58% for radionuclide scanning to 66% for the delayed CT. Almost half of the supratentorial infarcts examined by CT on the day of the ictus were demonstrated. Mass effect was observed as early as the first day and as late as the 25th day.

Adolescent↗