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Biomedical subjects

S Powell

Publications and source records attributed to S Powell.

At least 19 recordsLinked to original sources
PubMed1992

Chemodectoma of the head and neck: results of treatment in 84 patients.

Eighty-four patients with chemodectoma of the head and neck presented to the Royal Marsden Hospital between 1949 and 1985. For tumors arising at the skull base (glomus jugulare and glomus tympanicum) 46 were treated with radiotherapy alone resulting in an actuarial local control rate of 73% at 25 years; 13 were treated with surgery plus radiotherapy with no recurrences during a median follow-up of 9 years; 4 had surgery alone but all recurred by 7 years. For tumors of the soft tissues of the neck (carotid body and glomus vagale) 13 were treated with surgery alone with an actuarial control rate of 54% at 15 years; 4 were treated with radiotherapy which resulted in local control at 1, 2, 8 and 11 years; and one patient who received both surgery and radiotherapy remained controlled at 1 year. Although comparison between radiotherapy and surgery in terms of tumor control is not simple, the case is argued for more frequent use of radiotherapy at all sites. This case is strengthened by minimal morbidity from radiotherapy in doses which appear effective: in the range of 45-50 Gy in 25 daily fractions over 5 weeks.

Adult↗
PubMed1992

Antibody to hepatitis C virus in selected groups of a Canadian urban population.

In an anonymous survey, 433 sera from Canadian individuals of selected categories were tested for the presence of antibody to hepatitis C virus (HCV) using a recombinant antigen-based immunoassay. About 50% of intravenous drug abusers (IVDA), 10% of transfusion recipients and an overall average of 7.9% of male homosexuals were reactive for antibody to HCV. Individuals with jaundice and negative hepatitis B virus (HBV) serology were not reactive for antibody to HCV compared with 26.7% of those with positive HBV serology. Similarly 58% of male Federal prisoners with positive HBV serology were also HCV-antibody reactive compared with 15% of those with negative HBV serology. A prevalence of 1.2% was recorded for individuals not in any of the above groups. Of 433 sera, 92 were reactive and the discrimination in absorbance values between reactive and not reactive samples was good except for 13 sera, eight of which gave values considerably higher than the average negative value and five which were just above the positive threshold.

Alberta↗
PubMed1992

The fast flush test measures the dynamic response of the entire blood pressure monitoring system.

The fast flush test (FT) is the only test that allows clinicians to determine in vivo the natural frequency (fn) and damping coefficient (zeta) of an invasive blood pressure monitoring system. The underlying assumption to the validity of the FT is that it activates the whole system including the distal catheter. We devised an in vitro model of a typical invasive blood pressure monitoring system to determine whether this assumption was true. The model consisted of a conventional transducer with a flush device attached to various lengths of connecting tubing (91.4, 182.9, and 274.3 cm) terminated by four different diameter catheters (5.1 cm 14 G, 16 G, 18 G, and 20 G). A microtipped transducer catheter was inserted into the distal catheter tubing system. A FT was performed and the fn and zeta were recorded from the conventional transducer and simultaneously from the microtipped transducer catheter. Similar studies were conducted using the ROSE damping device as well as with systems including 0.1 ml of air near the conventional transducer. These studies utilized 18- and 20-G catheters with each of the three lengths of connecting tubing. All measurements of fn and zeta at the proximal conventional transducer were identical to those measurements as recorded by the distal microtipped transducer catheter. We conclude that the FT activates the whole monitoring system and that fn and zeta are the same throughout the system including the distal catheter.

Blood Pressure Monitors↗
PubMed1992

Allergic contact dermatitis and vulvar dermatoses.

Vulval itch and discomfort are often intractable symptoms and the response to standard therapy can be unsatisfactory. There is some evidence that vulvar sensitivity to irritants is higher than that of forearm skin, but the incidence of relevant allergic contact sensitivity amongst this patient population is unknown. The patch-test data over a 5-year period of 135 patients with persistent vulval symptoms were reviewed and 63 patients had positive results. Of these, 39 had positive results considered to be relevant to their clinical condition. Medicaments and their constituents were responsible for most of these reactions and more than half the patients had multiple allergies.

Adolescent↗
PubMed1992

The role of fiberoptic bronchoscopy for diagnosis of pulmonary tuberculosis in patients at risk for AIDS.

In patients with acquired immunodeficiency syndrome (AIDS)-associated pulmonary Mycobacterium tuberculosis (MTB) (group 1), we analyzed whether the addition of transbronchial biopsy (TBB) and bronchial brushings augmented the diagnostic MTB yield over nonbiopsy sampling. Positive acid-fast bacilli (AFB) smears from combined sputum, bronchoalveolar lavage (BAL), and washings were 30 percent compared with 37 percent when brushings and TBB were added (p = NS). The addition of TBB increased culture yield from 96 percent to 100 percent (p = NS). Similar results were seen in patients with pulmonary MTB without human immunodeficiency virus (HIV) risk factors (group 2). Group 1 patients most commonly had a nonspecific inflammation on TBB histopathology and had a lower incidence of granuloma formation than group 2 (p less than 0.05). Our results suggest that more invasive sampling with bronchial brushings and TBB does not contribute to the microscopic, bacteriologic, or histopathologic diagnosis of pulmonary MTB, independent of AIDS risk factors.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Modification of the percutaneous approach to peritoneal dialysis catheter placement under peritoneoscopic visualization: clinical results in 78 patients.

The placement of percutaneous peritoneal dialysis catheters under direct peritoneoscopic visualization is a relatively new technique for establishing peritoneal dialysis access. In this study, in which a modification of the Seldinger technique was used to facilitate the placement of the peritoneoscope, the experience with 82 consecutive catheterization procedures in 78 patients is reported. In 2 (2.4%) of 82 catheterization procedures, we were unable to enter the peritoneal cavity but experienced no other complications unique to the percutaneous approach. Of the 80 successful catheterization procedures, 76 represented first-time catheter placement and constituted a population subjected to life-table analysis examining catheter survival rates, the time to first cutaneous exit site or s.c. tunnel infection, and the time to first episode of peritonitis. After a follow-up period of 50.1 patient yr, 11 catheters were lost because of catheter dysfunction. Other clinical complications included peritoneal fluid leaks at the cutaneous exit site in 11 instances (0.22/patient yr), cutaneous exit site infection in 7 instances (0.14/patient yr), s.c. tunnel infection in 2 instances (0.04/patient yr), and 34 episodes of peritonitis (0.68/patient yr). The results of this study demonstrate that the suggested modification of the percutaneous placement of peritoneal dialysis catheters, under peritoneoscopic visualization, is a viable method for establishing peritoneal access.

Adult↗
PubMed1991

Clonal variation of DNA repair in a human glioma cell line.

Clonal heterogeneity in response to ionizing radiation was found for a human glioma cell line, IN859. We have investigated the most sensitive clone, the most resistant clone and the parent line for differences in DNA repair fidelity using the method of plasmid reconstitution. Significant differences in repair fidelity were found between the two clones, and between the sensitive clone and the parent line. The resistant clone and the parent line showed the greater repair fidelity. A comparison of two different restriction enzymes, which cleave the plasmid with blunt or cohesive-ended double-strand breaks, did not reveal differences in repair fidelity. Equal numbers of plasmids were integrated in each cell line, but the sensitive clone showed a higher frequency of misrepair of cleaved plasmid. Misrepair was characterized by partial or complete loss of sequence at the site of plasmid cleavage. We conclude that the radiosensitive clone exhibits increased misrepair.

Blotting, Southern↗
PubMed1991

A quantitative approach to the characterization of cumulative and average solvent exposure in paint manufacturing plants.

Previous reports have attributed a range of neurobehavioral effects to low-level, occupational solvent exposure. These studies have generally been limited in their exposure assessments and have specifically lacked good estimates of exposure intensity. In the present study, the authors describe the development of two exposure variables that quantitatively integrate industrial hygiene sampling data with estimates of exposure duration--a cumulative exposure (CE) estimate and a lifetime weighted average exposure (LWAE) estimate. Detailed occupational histories were obtained from 187 workers at two paint manufacturing plants. Historic industrial hygiene sampling data for total hydrocarbons (a composite variable of the major neurotoxic solvents present) were grouped according to 20 uniform, temporally stable exposure zones, which had been defined during plant walk-through surveys. Sampling at the time of the study was used to characterize the few zones for which historic data were limited or unavailable. For each participant, the geometric mean total hydrocarbon level for each exposure zone worked in was multiplied by the duration of employment in that zone; the resulting products were summed over the working lifetime to create the CE variable. The CE variable was divided by the total duration of employment in solvent-exposed jobs to create the LWAE variable. The explanatory value of each participant's LWAE estimate in the regression of simple visual reaction time (a neurobehavioral test previously shown to be affected by chronic solvent exposure) on exposure was compared with that of several other exposure variables, including exposure duration and an exposure variable based on an ordinal ranking of the exposure zones.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Industry↗
PubMed1991

Human papillomavirus in prostatic cancer: no evidence found by in situ DNA hybridization.

Human papillomavirus has been associated with benign squamous tumors, intraepithelial neoplasia, and invasive squamous cancer. The role of human papillomavirus as the most likely precursor of cervical dysplasia is well studied. We know of no available information as to the possible role of human papillomavirus in prostatic hyperplasia and cancer. We studied formalin-fixed paraffin-embedded tissues of 20 cases of glandular hyperplasia and 20 cases of prostatic cancer by in situ DNA hybridization for human papillomavirus using commercially available biotinylated DNA probes detected by an avidin-biotin peroxidase technique. We found no evidence of DNA hybridization to human papillomavirus-6, -11, -16, -18, -31, -33, or -35 in prostate tissue. Our results show no association between prostatic cancer or hyperplasia and the human papillomavirus genomes that were studied.

DNA, Viral↗
PubMed1991

Disseminated tuberculosis in the acquired immunodeficiency syndrome era.

To assess the influence of human immunodeficiency virus type 1 (HIV)-induced immunodeficiency on the clinical, radiographic, and pathologic features of disseminated tuberculosis (TB), we studied 79 patients presenting in 1984 through 1987 with miliary or focal disseminated disease due to Mycobacterium tuberculosis, as well as 4 additional non-HIV patients diagnosed after 1987. Clinically defined acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) was present in 51 (Group 1). A total of 20 had TB unrelated to HIV disease (Group 2). The remaining 12 were excluded because the role of HIV could not be determined. Clinical features were similar between groups aside from younger age; lower hemoglobin, total leukocyte, lymphocyte, and platelet counts; and more frequent tuberculin anergy (90 versus 40%) in AIDS/ARC patients (p less than or equal to 0.03). Chest radiographs showed a miliary pattern in about half of each group. Pleural effusion occurred only in AIDS/ARC patients (24%, p = 0.02), but intrathoracic lymphadenopathy was present in about a third of each group. Tissue biopsies (n = 70) usually revealed necrotizing granulomatous inflammation in each group, with a tendency to greater necrosis and more numerous acid-fast bacilli in Group 1. Granulomas were usually poorly formed in AIDS/ARC patients (59 versus 18%, p = 0.01). Autopsy of 9 AIDS/ARC patients with overwhelming miliary TB revealed a "nonreactive" histologic pattern with poorly organized or absent granulomas, extensive necrosis, and numerous bacilli. HIV-related disseminated TB causes a major constitutional illness with a high short-term mortality (25%).(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Complex↗
PubMed1991

Percutaneous catheter drainage for acute empyema. Improved cure rate using CAT scan, fluoroscopy, and pigtail drainage catheters.

Percutaneously inserted pigtail nephrostomy catheters were used to treat empyemas in 12 patients. Thoracic computed tomographic (CT) scan and fluoroscopy were used to localize precisely and place the catheters into loculated collections of fluid. Percutaneous catheter drainage (PCD) of empyema was successful in seven of seven patients (100%) in whom standard tube thoracostomy (STT) had initially failed and in three of five patients (60%) who had PCD as the initial drainage procedure. Overall, PCD was successful in treating empyema in ten of 12 patients (83%). The procedure was well tolerated and there were no complications. PCD is a safe and effective method for drainage of loculated empyemas as the initial procedure or after STT has failed.

Acute Disease↗
PubMed1990

A novel, rapid method for the isolation of terminal sequences from yeast artificial chromosome (YAC) clones.

The recent development of yeast artificial chromosome (YAC) vectors has provided a system for cloning fragments that are over ten times larger than those that can be cloned in more established systems. We have developed a method for the rapid isolation of terminal sequences from YAC clones. The YAC clone is digested with a range of restriction enzymes, a common linker is ligated to the DNA fragments and terminal sequences are amplified using a vector specific primer and a linker specific primer. Sequence data derived from these terminal specific products can be used to design primers for a further round of screening to isolate overlapping clones. The method also provides a convenient method of generating Sequence Tagged Sites for the mapping of complex genomes.

Base Sequence↗
PubMed1990

Radiation-induced brachial plexus injury: follow-up of two different fractionation schedules.

All 449 breast cancer patients treated with post-operative radiotherapy to the breast and lymph nodes between 1982 and 1984 have been followed for 3-5.5 years. In this group two different fractionation schedules were used, one five times a fortnight and one daily, both over 6 weeks. The calculated dose to the brachial plexus was 45 Gy in 15 fractions or 54 Gy in 30 fractions. These schedules are equivalent doses using the standard NSD formula. The diagnosis of a brachial plexus injury was made clinically and computed tomography was used to distinguish radiation injury from recurrent disease. The actuarial incidence of a radiation-induced brachial plexus injury for the whole group was 4.9% at 5.5 years. No cases were seen in the first 10 months following radiotherapy. The incidence rises between 1 and 4 years and then starts to plateau. When the large fraction size group is compared with the small fraction size group the incidence at 5.5 years is 5.9% and 1.0%, respectively (p = 0.09). Two different treatment techniques were used in this group but were not found to contribute to the probability of developing a brachial plexus injury. It is suggested that radiation using large doses per fraction are less well tolerated by the brachial plexus than small doses per fraction; a commonly used fractionation schedule such as 45 Gy in 15 fractions may give unacceptably high brachial plexus morbidity; and the use of small doses per fraction or avoiding lymphatic irradiation is advocated.

Brachial Plexus↗