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Biomedical subjects

R McLean

Publications and source records attributed to R McLean.

At least 19 recordsLinked to original sources
PubMed1998

Development and optimisation of a generic micellar electrokinetic capillary chromatography method to support analysis of a wide range of pharmaceuticals and excipients.

A micellar electrokinetic capillary chromatography (MECC) method has been developed and validated to allow the analysis of a wide range of water soluble and insoluble acidic, basic and neutral drugs and excipients. An electronic database has been established to demonstrate the wide applicability of the method. The method has been validated and is now in routine use. In particular, acceptable injection precision is obtained through use of internal standards. Optimal sensitivity was obtained by using low UV wavelength detection. The method allows a number of cost and time saving benefits.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1998

The area of complete scotopic spatial summation enlarges with age.

The maximal area of complete scotopic spatial summation (Ricco's area) was determined for 50 subjects ranging in age from 19 to 87 yr. Increment thresholds were measured for 10-ms, 520-nm circular test lights of varying diameters that were superimposed and concentric with a 10 degrees, 640-nm circular background. The test lights were imaged in Maxwellian view along the horizontal meridian, 6 degrees nasal from a foveal fixation point. The results demonstrate a statistically significant enlargement of Ricco's area with age. The average angular subtenses of Ricco's areas for the ten youngest (mean = 26 yr) and ten oldest (mean = 75 yr) observers were approximately 48 and 69 arc min, respectively. Model simulations based on a series of optical transfer functions of the eye and varying degrees of intraocular light scatter for younger and older observers show that preneural factors cannot account for these results. Therefore changes in neural mechanisms must be invoked to explain the enlargement in the size of Ricco's area under scotopic conditions.

Adult↗
PubMed1995

Colon transit scintigraphy using oral indium-111-labeled DTPA. Can scan pattern predict final diagnosis?

Colon transit scintigraphy (CTS) was performed in 100 consecutive patients with idiopathic constipation using oral indium-111-labeled DTPA. Criteria were defined to allow classification of studies as normal, slow transit constipation (STC), or obstructed defecation (OD). Results were compared with final clinical diagnosis in 100 and findings of defecating proctography in 70. Of those with a scintigraphic diagnosis of STC, this was also the final diagnosis in 75% (33 of 44), and the scintigraphic diagnosis of OD was confirmed in 61% (17 of 28). Of 28 normal or equivocal scans, the final diagnosis was STC in only two (4%) but OD in 10 (21%). Fifty-four percent of patients with STC and 71% with OD had abnormal proctograms. The correlation between CTS and proctography was mediocre, occurring in 54% of patients. CTS has a valuable role in the diagnostic work-up of patients with idiopathic constipation.

Aged↗
PubMed1993

Re-evaluating the need for hospitalization following synovectomy using Yttrium-90 silicate.

In 51 patients treated with Yttrium-90 (Y-90) synovectomy for rheumatoid (inflammatory) arthritis (IA) and OA of the knee we found that decreased retained knee activity (RKA) and increased extra-articular activity in lymph nodes and liver are more likely to be found in IA than OA and following bilateral knee injections. Joint inflammation, as assessed by radionuclide blood pool scan but not by SF white cell count, correlates with decreased RKA and increased activity in lymph nodes. Intra-articular steroid had no significant effect on retention or extra-articular uptake. Strict hospital immobilization improves RKA of Y-90 in IA but not in OA. Y-90 synovectomy in OA shows good RKA and low extra-articular uptake. We recommend strict immobilization following Y-90 synovectomy, particularly in IA patients and/or those with high joint blood flow.

Adult↗
PubMed1991

Hemodynamic profiles of prostaglandin E1, isoproterenol, prostacyclin, and nifedipine in experimental porcine pulmonary hypertension.

BACKGROUND AND METHODS: We compared the hemodynamic effects of four vasodilators in experimental embolic pulmonary hypertension in a randomized controlled trial, using nine pigs weighing 16 to 23 kg. After anesthesia induction and cannulation with arterial, central venous, and thermodilution output pulmonary artery catheters, animals were repetitively embolized with glass beads (60 to 160 mu) in order to establish pulmonary hypertension (pulmonary artery pressure [PAP] doubled from baseline). Prostaglandin E1 (PGE1), isoproterenol, prostacyclin (PGI2), and nifedipine were compared at doses producing equivalent reduction in systemic BP. RESULTS: Only PGE1 and PGI2 decreased both PAP and pulmonary vascular resistance (PVR). PGE1 decreased PAP from 39 +/- 1 to 33 +/- 1 mm Hg; prostacyclin decreased PAP from 38 +/- 1 to 31 +/- 1 mm Hg and produced the largest increase in cardiac output (Qt). Isoproterenol did not change PAP, markedly increased heart rate (162 +/- 8 to 216 +/- 11 beats/min), and resulted in significant arrhythmias. Nifedipine increased PVR from 1044 +/- 113 to 1125 +/- 100 dyne.sec.cm-5 and decreased Qt. CONCLUSIONS: Vasodilators demonstrate unique hemodynamic drug profiles. Isoproterenol infusion is characterized by tachycardia and arrhythmias. Both PGE1 and PGI2 effectively decrease PAP and PVR. Nifedipine depressed Qt significantly in this glass-bead embolization model of acute pulmonary hypertension.

Alprostadil↗
PubMed1991

Evaluation of the Quantitative Buffy Coat (QBC) method to detect malaria-infected red blood cells.

The conventional thin blood film method of detecting malaria is a long and tedious procedure, requiring significant technical expertise. In this study, we compared the Quantitative Buffy Coat (QBC) capillary tube method, which requires only minimal technical training, to the thin blood film method, and found it to be not only more rapid but also more sensitive than the thin blood film method in the detection of parasitized red blood cells. We do not suggest that the QBC capillary method can replace the conventional thin blood film method for the detection of malaria since it does not identify or quantitate the parasite species, only that it would serve as a valuable screening test.

Animals↗
PubMed1990

Role of bone scintigraphy in the early diagnosis of discitis.

Nine cases of recorded discitis are presented, in which scintigraphy played an important part in the diagnosis. The patients (five men (aged 21-75 years) and four women (aged 40-73 years)) had a history of back pain varying in duration from two days to three months. Final diagnosis was confirmed microbiologically (seven patients) or radiographically (two patients). Bone scintigraphy was a valuable diagnostic procedure for discitis with earlier detection than plain radiography in three patients and similar initial detection to that of third generation computed tomography. Single photon emission computed tomographic imaging increased diagnostic confidence by indicating the involvement of the adjacent vertebral bodies rather than of the pedicles or spinous processes.

Adult↗
PubMed1989

Pylorus-preserving pancreatectomy: functional results.

The pylorus-preserving technique is reported as improving the functional results of pancreatectomy but it is complicated in the early postoperative period by delayed recovery of gastric function in a proportion of patients. We have examined early and late gastrointestinal function in a prospective study of 16 patients having this procedure. The late results appear better than reported results for conventional Whipple resection and the delay in early recovery does not appear to have any late sequelae, provided that it does not require gastric bypass for relief.

Adult↗
PubMed1985

Thyroid dysgenesis in monozygotic twins: variants identified by scintigraphy.

The unusual occurrence of neonatal hypothyroidism in monozygotic twins is reported. Scintigraphy demonstrated that permanent hypothyroidism in one resulted from an ectopic suprahyoid thyroid, while in the other, the transient hypothyroid state was associated with thyroid hemiagenesis. These findings suggest that the anomalies represent variants of the same developmental aberration.

Congenital Hypothyroidism↗
PubMed1977

Effect of iron saturation of transferrin on hepatic iron uptake: an in vitro study.

Studies were performed to delineate the effect of percentage of saturation of transferrin and total iron concentration on the rate of uptake of iron by the perfused rat liver. Normal and iron-deficient rat livers were perfused with sera that contained varying concentrations of 59Fe-labeled iron and transferrin saturation. Varying the percentage of saturation of transferrin while maintaining a constant concentration of iron did not influence the hepatic uptake of iron. However, raising the concentration of iron in the perfusate while maintaining a constant saturation of transferrin did increase the uptake of iron by the liver. At similar concentrations of iron and transferrin saturation, iron-deficient livers took up greater amounts of iron than did normal livers. In our experiments, the hepatic uptake of transferrin-bound iron is determined by (1) the concentration of iron in perfusate and (2) the status of iron stores in the liver being perfused.

Animals↗
PubMed1975

Amidines and related compounds. 6. Studies on structure-activity relationships of antihypertensive and antisecretory agents related to clonidine.

Correlations of antihypertensive and antisecretory activities with various structural modifications of the antihypertensive agent clonidine (2-(2,6-dichlorophenylimino)imidazolidine) are described. Eleven chemical classes of compounds containing an "amidine" moiety were prepared in this study. The antihypertensive activity of these compounds was evaluated in metacorticoid hypertensive rats and unanesthetized neurogenic hypertensive dogs following oral administration. Antisecretory activity was evaluated in fistula rats by measuring pH and volume of gastric secretion. Two compounds, 2-(2,6-dimethylphenylimino)imidazolidine and 2-(2,6-dichlorophenylimino)pyrrolidine, are particularly effective antisecretory agents with minimal antihypertensive activity.

Amidines↗