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Biomedical subjects

D Hall

Publications and source records attributed to D Hall.

At least 145 records · Page 8Linked to original sources
PubMed1989

Effectiveness of interval nitrate therapy in angina pectoris.

Because of rapid tolerance development, the use of multiple daily doses of oral nitrates or continuous application of transdermal nitrate systems can no longer be considered justified. Only with an interval treatment, which prevents nitrate accumulation in the plasma such that, from low baseline values, renewed administration of the drug results in a marked increase in plasma concentration, is it possible to utilize the antianginal and antiischaemic effects of nitrates for meaningful long-term treatment. For isosorbide dinitrate and isosorbide 5-mononitrate, as well as for transdermal nitroglycerin systems, interval treatment dosing regimens with maintained effectiveness documented in controlled studies have been delineated. To some degree, the principle of interval treatment can be achieved with continuously applied transdermal patches designed for discontinuous release of their content, which yield maintained though somewhat attenuated effects. Recent studies have shown that the tolerance to nitroglycerin, which develops within the first 12h of contact with currently available transdermal patches, can be prevented by gradually increasing the plasma concentration during this period of time. Evidence for clinically relevant rebound phenomena during interval treatment has not been observed.

Administration, Cutaneous↗
PubMed1989

High frequency edge enhancement in the detection of fine pulmonary lines. Parity between storage phosphor digital images and conventional chest radiography.

Fine linear structures represent a severe test of the minimum spatial resolution that is needed for digital chest imaging. We studied the comparative observer performance of storage phosphor digital imaging (1760 X 2140 pixel matrix, 10 bits deep), and conventional radiography (Lanex medium screen, Ortho C film) in the detection of simulated fine pulmonary lines superimposed on the normal chest when exposure factors were identical (20mR skin entrance dose at 141 kVp). Receiver operating characteristics analysis of 2160 observations by six readers found that high frequency edge-enhanced digital images (ROC area: 0.78 +/- 0.06) performed better than unenhanced digital images (ROC area: 0.70 +/- 0.07) (P less than 0.01 for paired t-test), and that edge enhanced digital images performed on a par with conventional radiography (ROC area: 0.78 +/- 0.09). We conclude that for the detection of fine linear structures, storage phosphor digital images can perform on a par with higher resolution conventional chest radiographs when a high frequency edge-enhancement algorithm is employed.

Adult↗
PubMed1989

Laryngeal papillomatosis: analysis of 113 patients.

Despite the low incidence of these diseases, both juvenile onset and adult onset laryngeal papillomatosis continue to concern otolaryngologists because treatment is often prolonged and unsatisfactory. Over many years various treatments have met with varied claims of success, yet no treatment today is universally accepted. We review the underlying clinical problems, the presentation, the treatment and eventual outcome of 113 patients seen at this hospital over the last 20 years with laryngeal papillomatosis. Using multivariate analysis of age at presentation, sex, smoking habits, initial site of disease, frequency of treatment and eventual outcome, two distinct patterns are revealed both between juvenile and adult onset disease and between male and female patients. Single-site lesions in adults have the best prognosis. Female children with multiple confluent lesions at presentation have the worst prognosis.

Adult↗
PubMed1989

Subtle gastric abnormalities in a canine model: detection with low-dose imaging with storage phosphors and its equivalence to conventional radiography.

The authors compared low-dose (32% of standard exposure) storage phosphor digital imaging (system resolution: 0.2-mm pixels, 10 bits) with isovoltage 75-kVp conventional radiography (standard exposure) in the detection of subtle simulated gastric abnormalities by using air contrast barium studies. Subtle simulated abnormalities (3-7-mm polyps, 4-15-mm ulcer craters, 4-11-mm-diameter edema, and 11-12-mm linear ulcers) were produced in resected canine stomachs. Receiver operating characteristic analysis of 1,800 observations by six readers indicated that the digital images with and without high-frequency edge enhancement were equivalent to conventional radiographs (mean receiver operating characteristic areas [+/- standard deviation]: 0.76 +/- 0.06, 0.78 +/- 0.04, and 0.77 +/- 0.04, respectively). The accuracy of the diagnosis was equivalent for all three modalities. The following mean accuracies of negative and positive responses, respectively, for unenhanced digital, edge-enhanced digital, and conventional images were determined: 0.71 +/- 0.05 and 0.41 +/- 0.07, 0.71 +/- 0.04 and 0.51 +/- 0.09, and 0.68 +/- 0.04 and 0.43 +/- 0.05. It was concluded that low-dose storage phosphor air-contrast barium studies were equivalent to conventional radiography in the detection of subtle gastric abnormalities.

Animals↗
PubMed1989

Temporal trends of human immunodeficiency virus type 1 (HIV-1) infection among inmates entering a statewide prison system, 1985-1987.

Acquired immune deficiency syndrome (AIDS) became the leading cause of death among Maryland State prisoners in 1985. To identify the prevalence, risk factors, and temporal trends for infection with the human immunodeficiency virus type 1 (HIV-1) in the statewide prison system, excess sera were obtained from incoming male inmates during specified periods between April and June 1985, 1986, and 1987. Correctional medical personnel also provided demographic variables of age, race, offense category, sentence, jurisidiction, and an indicator of intravenous drug use. Once rendered anonymous, specimens were assayed for antibody to HIV-1, using ELISA and Western blot techniques. For data from April to June 1985, 1986, and 1987, the crude prevalence of anti-HIV-1 was 7.1, 7.7, and 7.0%, respectively. Although one-third of incoming inmates were identified as intravenous drug users (IVDUs), the drug use variable was missing for 70% of the 1985 sample, and 40% of the 1986 sample. Several strategies were used to examined temporal trends in the context of missing data. Univariate analyses suggested no substantial change over time for either HIV-1 seroprevalence or risk of infection among IVDUs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1988

Comparison of local tumor recurrence following excision with the CO2 laser, Nd:YAG laser, and Argon Beam Coagulator.

This study compares the incidence of local tumor recurrence following primary excision with the CO2 laser, Nd:YAG laser (contact), Argon Beam Coagulator, or electrocautery. One hundred eight Fisher 344 rats with R3230AC mammary tumors (1.6 +/- 0.04 [SD] cm diameter) were used. All animals were randomized into groups of similar tumor size. In groups C and CS, excision was performed with a Sharplan 1060 CO2 laser (TEMoo, 25 W, continuous wave [CW], 0.2-mm spot size). Wounds in group CS were "sterilized" (0.5-mm spot size, 25 W, CW) by gently heating the wound without causing blanching or charring. In group N, a 0.4-mm contact Laser Blade and a Cooper 8000 Nd:YAG laser at 20 W CW was used. In groups SA1 and SA2, tumors were excised with the scalpel, and hemostasis and wound "sterilization" were accomplished with the Bard System 6000 Argon Beam Coagulator (ABC) at 40 W and 4 liters/min argon gas flow in SA1 and 12 liters/min in SA2. In group E, excision was accomplished at 40 W blend mode, 10 W spray mode. In group EA, excision was accomplished at 60 W cutting current, and hemostasis was achieved with the ABC. The animals were examined for evidence of recurrence for 34 days postoperatively. Mortalities were excluded from analysis. The incidence of recurrence was 11/14 (79%) in C, 6/16 (38%) in CS, 10/14 (71%) in SA1, 6/13 (46%) in SA2, 6/15 (40%) in N, 7/10 (70%) in EA, and 3/15 (20%) in E. Group E is statistically different (P less than .01) from groups EA, C, and SA1. Group C was different (P less than .01) from groups E, CS, and N. These results demonstrate an inverse relationship between tumor recurrence and local thermal effects at the surgical site. The ABC did not increase tumor recurrence. Contact YAG surgery was similar to CO2 laser excision and "sterilization." An attempt to study the influence of gas flow and pressure on local tumor recurrence and metastases should be made.

Adenocarcinoma↗
PubMed1988

Synthetic cataract teaching system for phacoemulsification.

This paper describes a surgical training system for teaching and practicing the necessary skills to perform phacoemulsification, endocapsular phacoemulsification, and small incision intraocular lens insertion techniques. The surgical system includes head, bilateral globes, removable corneas, and replaceable synthetic cataracts of varying density. This synthetic system simulates ocular surgery more closely than previously used animal eyes and allows the surgeon to practice new techniques in laboratory courses and in the operating facility.

Cataract Extraction↗
PubMed1988

Identification of encapsulated and non-encapsulated Yersinia pestis by immunofluorescence tests using polyclonal and monoclonal antibodies.

Rabbit polyclonal hyperimmune antibodies to Yersinia pestis, and a mouse monoclonal antibody against the capsular antigen fraction 1 (F1) were compared in immunofluorescence (IF) tests. Fluorescent antibody conjugates were prepared from polyclonal antisera to four F1 positive Y. pestis strains; the conjugated antibody to strain A1122 gave the strongest IF staining of F1 positive and F1 negative Y. pestis strains. Indirect assays were rejected in favour of direct assays utilizing polyclonal and monoclonal reagents because the increased background staining reduced the effective contrast of bacterial visualisation. Polyclonal conjugates gave fairly homogeneous staining of Y. pestis bacterial populations, but in monoclonal assays a skew distribution of fluorescence intensity was observed, the majority of bacteria being poorly stained. The proportion of cells stained well by the monoclonal sufficed for easy identification of Y. pestis of the F1 positive phenotype however, and staining was not affected by washing the bacteria or treating them with formaldehyde. Y. pestis strains of the F1 positive genotype reacted with the monoclonal if bacteria were grown at 37 degrees C but not if the growth temperature was reduced to 25 degrees C thus preventing capsule production. The polyclonal conjugate reacted with bacteria of these strains that had been grown at either temperature. Strains of F1 negative genotype grown at either temperature reacted with the polyclonal conjugate but not with the monoclonal. Cross reactions between the polyclonal reagents and Y. enterocolitica biovar 2, serovar O 8 could not be removed by selective absorption; however, the monoclonal antibody gave no cross reaction. The F1 phenotypic status of bacterial preparations was verified by ELISA measurement of the fraction 1 antigen concentration. Antigen levels for F1 positive and F1 negative phenotypes differed by about three logs for suspensions of Y. pestis harvested from solid media. The polyclonal and monoclonal direct IF tests applied to spleen and blood smears of laboratory mice infected with Y. pestis were able to differentiate between lethal infection with an F1 positive strain carrying all four classical virulence determinants, an F1 positive vaccine strain, and an F1 negative strain.

Animals↗
PubMed1988

When does nitrate tolerance develop? What dosages and which intervals are necessary to ensure maintained effectiveness?

To address the issues of tolerance development and its circumvention during long-term treatment with nitrates, several controlled studies have been performed. In patients with coronary artery disease, during long-term treatment with isosorbide dinitrate (ISDN) in sustained-release form at dosages of 20 mg t.i.d., 40 mg t.i.d. and 60 mg t.i.d., both the rate of anginal attacks and the ischaemic reaction to exercise were unaffected. After a marked acute anti-ischaemic effect to 40 mg ISDN in nonsustained-release form, during chronic administration of the same dose four times daily, in association with continuously-high nitrate plasma concentrations, similarly, there were no significant effects. On use of nitroglycerin (NTG) transdermal patches delivering 10 mg, 15 mg and 30 mg per 24 hours, respectively, renewed patch application after 24 hours was not met with the same marked response observed after initial application. Clearly attenuated effects could be seen within 8 to 12 hours. These results show that tolerance development is incurred when the incrementation in plasma concentration after a repeated nitrate dose is of relatively limited magnitude with respect to baseline values. The observation of rapid reversibility of nitrate tolerance lead to the concept of interval treatment which on daily use incorporates a sufficiently long period without nitrate administration. On use of a nitrate-free treatment interval employing a regimen of 20 mg ISDN nonsustained-release form twice daily in the morning and at midday, 120 mg ISDN sustained-release form once daily or 50 or 100 mg isosorbide 5-mononitrate once daily, maintained effectiveness has been documented, as it has also been shown for treatment with NTG patches delivering 10 mg per 24 hours on incorporation of a 12-hour patch-free interval. The currently available patch system with discontinuous NTG delivery does not incur a complete loss of action but a considerable attenuation of its effects indicates the need for further refinements. Thus interval treatment guarantees maintenance of nitrate effects, albeit with the limitation that 24-hour therapeutic coverage is not enabled.

Administration, Cutaneous↗
PubMed1988

Transmission of HIV-1 within a statewide prison system.

To assess the incidence of infection with HIV-1 in the Maryland state prison system, inmates with excess sera stored from specified intake periods between April and June 1985 and 1986 were approached in May 1987 to volunteer for venipuncture. Of the 2286 inmates for whom intake specimens were stored, 1038 (45.4%) no longer incarcerated as of April 1987 were excluded from the study; another 319 missed the survey. Of the 929 eligible inmates approached for the study, 446 (48%) consented and 422 (94.6%) provided a specimen. Twenty-nine (6.6%) were confirmed seropositive at time of entry into prison, indicating that infection had occurred prior to incarceration. Baseline seropositives were more likely (P less than 0.05) to be non-violent offenders, committed in Baltimore City, and black. The 393 participants seronegative at baseline provided a total of 482 prison-years of potential exposure to infection. Two inmates seroconverted with baseline specimens seronegative on Western blot and follow-up sera confirmed positive; their duration of pre-incarceration detention was 69 and 146 days, respectively. No interruption of incarceration was recorded for these two inmates. The rate of infection in this prison sample, which does not include an average of 2 months of pre-incarceration detention for the study sample, was 0.41% per prison-year.

Acquired Immunodeficiency Syndrome↗
PubMed1988

A focused casework approach to the treatment of child abuse: a controlled comparison.

Two contrasting therapies for the treatment of child abuse were compared in a randomised design: a focused casework approach to the whole family and a structured play therapy approach to the child. The Patterson coding system was used as an outcome measure. There was a high drop-out rate from both the therapies, but of those who completed the treatment, there was a greater improvement in the focused casework regime on some of the comparisons made.

Adolescent↗
PubMed1988

The development of play for children in hospitals: British and European perspectives.

Play in hospitals has developed alongside of changes toward a more family-centered model of care. The recreational and educational role of play has been significantly extended toward a therapeutic purpose. This article considers the relationships between play workers and teachers, nurses and parents, and presents some European examples of the use of play in hospitals. Finally, problems encountered in the operation of play programs are discussed in the context of ensuring the viability of play in the hospital.

Child↗
PubMed1988

Respiratory symptoms and alterations in pulmonary function tests in swine producers in Saskatchewan: results of a survey of farmers.

To determine whether farmers who produced swine in animal confinement chambers in Saskatchewan were at increased risk of developing respiratory dysfunction, we carried out a respiratory health questionnaire and spirometric pulmonary function test measurements, including forced expired volume in 1 second (FEV1), forced vital capacity (FVC), and the ratio of FEV1 to FVC (FEV1/FVC x 100), on 504 farmers who indicated that they raised swine, and 448 rural-dwelling nonfarming control subjects. Swine producers had lower values for FVC and FEV1 than did the control subjects. However, FEV1/FVC x 100 was somewhat higher in the swine producers. The reduction in FEV1 with retained FEV1/FVC ratio is suggestive of restrictive disease. However, the fact that the FEV1/FVC ratio is only modestly higher in swine producers than in control subjects suggests that there may be a mixed restrictive/obstructive condition in these workers.

Adult↗
PubMed1988

Outbreak of hepatitis A on an offshore petroleum platform, Alaska.

An outbreak of 8 cases of hepatitis A among the 36-member crew of an offshore Alaska petroleum production platform was linked to a previous outbreak in an urban day-care center. Transmission of hepatitis A on the platform related most plausibly to refrigerated food items contaminated by a cook with mild disease. Control efforts included identifying and treating contacts of case patients who had traveled far from the platform before becoming ill. Early serologic confirmation of diagnosed cases and rapid reporting to public health authorities are essential to prevent disease transmission. Timely investigation can limit the administration of immune globulin to persons at high risk of contracting the disease.

Adult↗