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Biomedical subjects

A J Stevenson

Publications and source records attributed to A J Stevenson.

35 records · Page 2Linked to original sources
PubMed1996

Pulmonary nodules: effect on detection of spiral CT pitch.

PURPOSE: To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed at standard pitch in the detection of pulmonary nodules. MATERIALS AND METHODS: Spiral CT scanning of the thorax was performed with a pitch of 1.0 in 109 patients with pulmonary nodules due to metastases. The patients were also randomly assigned to undergo further scanning with a pitch of 1.2 (n = 34), 1.5 (n = 37), 2.0 (n = 38) at the same scanning session. The scan pairs were analysed for number, size, and distribution of nodules. RESULTS: A bias toward undercounting was noted on scans with a pitch of 1.5 and 2.0; however, this was not statistically significant. Correlation coefficients were r = .982, r = .977, and r = .989 for scans of pitch 1.2, 1.5, and 2.0, respectively. Disease in one patient would have been prospectively understaged from findings on a scan of pitch 2.0 because of poor conspicuity of a small solitary nodule. CONCLUSION: Findings from scans with increased pitch generally agree well with those from scans with standard pitch; however, there is a greater risk of understaging of disease in patients with solitary nodules as pitch increases. Pitch should be limited to no greater than 1.5 for initial staging of pulmonary metastatic disease.

Adult↗
PubMed1994

Monitoring furosemide in racehorses participating in an EIPH program.

Analytical procedures were developed to monitor furosemide concentrations in post-race serum and urine samples obtained from horses participating in an exercise-induced pulmonary haemorrhage (EIPH) program. High performance liquid chromatography with ultraviolet light detection proved a reliable, sensitive method for measuring urinary furosemide concentrations up to 12 h after administration of either 150 or 250 mg of the drug to race horses. However, this method was unreliable for determination of serum furosemide concentration. High performance liquid chromatography with fluorescence detection proved a reliable, sensitive method for measuring serum furosemide concentration in horses administered 250 mg of the diuretic, permitting detection of approximately 5-10 ng/ml 6 h after treatment. This method was applied to field conditions where furosemide was administered to horses (between 150 and 250 mg intravenously) 4 h prior to the race. Analytical results assisted in establishing a threshold concentration of 85 ng/ml for serum furosemide. It was found that serum furosemide concentrations are a valid measure of compliance with furosemide administration in the EIPH program.

Animals↗
PubMed1994

Comparison of spiral-acquisition computed tomography and conventional computed tomography in the assessment of pulmonary metastatic disease.

In a prospective study, spiral-acquisition computed tomography (SACT) of the thorax was evaluated in 104 patients with extrathoracic malignancy and suspected pulmonary metastases, and was directly compared with conventional computed tomography (CCT) in 23 patients. The following parameters were assessed: lesion detectability; the effect on lesion detectability of reconstruction of scans at 5 mm and 10 mm slice increments; breathing artefact and slice misregistration. The radiation dose of the two techniques was measured using thermoluminescent dosimeters placed within an anthropomorphic chest phantom, and the visibility of simulated metastases inserted into the phantom was also compared using CCT, standard SACT and SACT with pitch greater than 1.0. Where metastases were present, SACT scans showed significantly better lesion detectability than CCT scans (p < 0.001). Image reconstruction of SACT data at 5 mm increments conferred no significant advantage in lesion detectability over 10 mm increment reconstructions. Compared with CCT, SACT scans showed reduced breathing artefact, and a complete absence of slice misregistration (p < 0.01). Phantom measurements of radiation dose and resolution were similar for both techniques. Increasing the pitch of the spiral in SACT caused only a small decrease in phantom resolution, but with the advantage of a reduction in the radiation dose. Spiral-acquisition CT is superior to conventional CT for the assessment of pulmonary metastatic disease.

Adolescent↗
PubMed1994

Fundamentals of bone marrow examination.

Bone marrow evaluation is an important and effective way of diagnosing and evaluating primary hematologic and metastatic neoplasms as well as nonhematologic disorders. Many variations exist for obtaining marrow samples (sites, instruments, techniques); however, the method outlined in this article has proven reliable. Complete evaluation of bone marrow samples should include a brief patient history, pertinent laboratory data, peripheral blood films, bone marrow aspirate smears and sections, and biopsy imprints and sections. Routine examination of the bone marrow as described previously is usually adequate for interpretation. However, application of additional studies using cytochemical, immunocytochemical, immunohistochemical, cytogenetic, and molecular techniques may prove to be of critical importance in the diagnosis of hematologic malignancies.

Biopsy, Needle↗
PubMed1993

Evaluation of isotope proctography in constipated subjects.

Twelve patients with longstanding constipation were examined by isotope proctography. Radio-labelled potato mash was inserted rectally to provoke the urge to defaecate and expulsive manoeuvres were recorded using a Gamma-camera. The method illustrated dynamic alterations in the anorectal angles (ARA) which became more acute on 'squeezing', less so on coughing and more obtuse on straining, and maximally so on evacuation. The pelvic floor (PF) movements were consistently upwards on squeezing, less so on coughing, downwards on straining, and maximally so on evacuation. A useful addition was the measurement of the completeness of evacuation and the time involved. The results were comparable to radiological videoproctography (P < 0.01), but the isotope method gave greater discrimination for both ARA and PF movement changes. It also allowed correlations to be made between the pelvic floor descent (P < 0.05) and anorectal angle changes (P < 0.01) with rectal evacuation.

Adult↗
PubMed1992

Plasma elimination and urinary excretion of procaine after administration of different products to standardbred mares.

Plasma and urinary concentrations of procaine were examined in Standardbred mares after subcutaneous administration of various doses (80 mg to 1600 mg) of procaine hydrochloride. Regardless of dose, peak plasma procaine values occurred within 1 h, but remained detectable in a dose-dependent manner, with procaine present at 1 h with the 80 mg dose and 6 h at the 1600 mg dose. Similarly, peak urinary procaine concentrations were attained within 1.5 to 3 h, irrespective of dose, while detection time was dose-dependent, being 23 h for 80-200 mg doses but as long as 30-54 h with the 1600 mg dose. When mares were given a single intramuscular injection of a penicillin G-procaine preparation (Ethacillin, Cillimycin, Penamycin, Derapen A, Azimycin or Diathal), peak plasma procaine concentrations varied and were reached from 10 min to 3 h in all cases, with detection from 3 to 20 h after drug administration. Although the peak urinary levels of procaine occurred between 30 mins and 6 h, detection in urine in most cases was as long as 78-120 h except for Diathal for which detection was limited to 54 h. Daily administration of a penicillin G-procaine preparation (Pen-Di-Strep) for 5 days produced a biphasic peak in plasma procaine at 3 and at 6-9 h with detection from 16 to 23 h after drug treatment. Although peak urinary procaine values were reached at similar times after single or multiple injections, the duration of detection was markedly longer (425 h) after the multiple-dose regimen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Comparison of temperature profiles (DeVeTherm) and conventional venography in suspected lower limb thrombosis.

In 124 patients admitted with suspected acute deep venous thrombosis, the screening value of a new thermographic scanner, DeVeTherm, was evaluated using conventional venography as a reference. The sensitivity of the scanner was calculated at 92% and the specificity at 25%. The predictive value of positive temperature profiles was 0.48, and that of negative temperature profiles, 0.82. On the basis of these results neither the accuracy nor the potential savings justify using temperature profiles alone as a screening test for this condition.

Adult↗
PubMed1990

The influence of furosemide on plasma elimination and urinary excretion of drugs in standardbred horses.

A study of the effects of intravenous administration of either 150 mg or 250 mg of furosemide to standardbred mares pre-treated with other drugs was undertaken to determine whether a unique pattern of drug elimination into urine and from plasma for each compound occurred. Furosemide significantly reduced the plasma concentrations of codeine compared to control 2-6 h after furosemide administration. In contrast, the plasma concentrations of theophylline, phenylbutazone, pentazocine, guaifenesin and flunixin were not markedly altered by furosemide. In the case of acepromazine, clenbuterol and fentanyl, the data generated were insufficient to state with certainty whether or not furosemide affected the plasma concentrations of these three drugs. A significant reduction was noted in the urinary concentrations of guaifenesin, acepromazine, clenbuterol, phenylbutazone, flunixin, fentanyl and pentazocine within 1-4 h of furosemide administration. The urinary concentrations of theophylline remained reduced as long as 8 h after furosemide injection. Furosemide administration to horses pre-treated with codeine resulted in depression of urinary morphine concentrations 2-4 h and 9-12 h after furosemide injection. A lower furosemide dose (150 mg) produced changes in drug urinary excretion and plasma elimination equivalent to the higher dose (250 mg). It is evident that furosemide affects the urinary and plasma concentrations of other co-administered drugs but not in a predictable fashion, which limits the extrapolation of these results to as yet untested drugs.

Acepromazine↗
PubMed1987

Presence of salicylic acid in standardbred horse urine and plasma after various feed and drug administrations.

Plasma and urinary levels of salicylic acid were examined in Standardbred mares after administration of various feeds, containing different compositions of hay. In addition, horses were administered acetylsalicylic acid orally and methyl salicylate topically. Elevated salicylic acid levels were observed in horse urine and plasma in animals fed lucerne hay. The plasma and urinary elimination of salicylic acid exhibited a diurnal pattern which was related to the type of feed and the feeding schedule. Within 24 h after oral administration of acetylsalicylic acid, plasma and urine salicylic acid levels were consistent with residual levels observed after feeding lucerne hay. Elimination of salicylic acid was rapid and complete, with a half-life between 5 and 7 h. Topical administration of methyl salicylate (8.4 g) produced elevated urinary salicylic acid levels for 6 h. A smaller dose of methyl salicylate (3.4 g) did not elevate plasma or urine salicylic acid levels above those observed following administration of lucerne hay.

Administration, Oral↗
PubMed1978

Renal and hepatic nucleic acid metabolism in neonates: relation to experimental duration, chlorphentermine dose as well as subsequent withdrawal.

Daily oral administration of either 20, 40 or 60 mg/kg chlorphentermine for 7 days significantly increased liver and kidney DNA levels, which were not elevated further even after a 3 week treatment period. Although cessation of drug administration for 3 weeks resulted in a return of hepatic DNA levels to control values, a rise in renal DNA was still observed after this withdrawal period. Whereas 20 mg/kg chlorphentermine for 7 days failed to markedly alter the incorporation of thymidine into kidney and liver DNA, significant enhancement was noted in neonates receiving 40 or 60 mg/kg drug and quantitatively greater incorporation occurred when the agent was given for 21 days. While a signficant augmentation in nucleic acids synthesis was seen 1 week after animals were removed from 40 or 60 mg/kg anorectic, a restoration to control levels occurred after a 3 week abstinence period. Treatment with 20 mg/kg for 1 week followed by withdrawal resulted in a significant rise in the incorporation of thymidine into renal and hepatic DNA. In contrast, drug administration for 3 weeks followed by 21 days abstinence resulted in a return to control levels in the incorporation of thymidine into kidney and liver DNA, except for renal tissue removed from 20 mg/kg. Our data demonstrate that the chlorphentermine-induced alterations in renal and hepatic DNA metabolism are dose-dependent, related to duration of exposure as well as reversible.

Animals↗
PubMedDate not supplied

Determination of procaine in equine plasma and urine by high-performance liquid chromatography.

The variability in plasma and urine equine procaine measurement between three independent laboratories using current methods led to the development of a sensitive, reliable, and reproducible high-performance liquid chromatographic method. Standardbred mares were administered either a penicillin G procaine preparation intramuscularly or procaine hydrochloride subcutaneously, and blood and urine were collected at defined time intervals. By HPLC the detection limits for procaine in plasma and urine were 1 and 10 ng/mL, respectively. In contrast procaine in plasma could not be detected by GC-NPD, while the urinary detection limit was 50 ng/mL. The concentration of fluoride in the collection tubes and repetitive freeze-thawing modified plasma procaine measurement. Urinary pH was a factor in estimation of urine procaine levels with greater recovery and reproducibility of results at pH 5 as compared to pH 7. This HPLC method provides a simple, sensitive, and reliable quantitation of procaine in equine plasma and urine.

Animals↗
PubMedDate not supplied

Biomarkers in occupational volatile organic chemical exposure.

Evidence exists that in certain groups of workers exposed to volatile organic chemicals, there is subclinical renal damage and dysfunction. Also, there is activation of biological mechanisms that are suggested links between volatile organic chemical exposure and renal disease. Notably, the workers studied are employed in factories where exposures are considered controlled, with on-site professional health and safety management. Recent studies continue to indicate an increased risk of renal disease in those exposed to volatile organic chemicals.

Air Pollutants↗