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Biomedical subjects

A Green

Publications and source records attributed to A Green.

At least 433 records · Page 24Linked to original sources
PubMed1990

Dihydropteridine reductase activity in eluates from dried blood spots: automation of an assay for a national screening service.

We describe the automation, using a Cobas Bio centrifugal analyser, of a method for dihydropteridine reductase (DHPR) assay in eluates from dried blood spots. This is used as part of a routine screening service of neonates with hyperphenylalaninaemia in the United Kingdom. Automation reduced reagent volumes and analysis time by about 80% and improved the precision of the assay. Relating DHPR activity to haemoglobin concentration of the eluate further improved the precision of the assay and removed some differences in 'apparent' DHPR activity between samples from different countries and different age groups.

Age Factors↗
PubMed1990

Relationship between plasma and red cell biopterins in acute and chronic hyperphenylalaninaemia.

Biopterin concentrations in red blood cells were higher in patients with chronic hyperphenylalaninaemia than following a single oral dose of phenylalanine, although the plasma concentrations were similar. These findings suggest that tetrahydrobiopterin is synthesized in immature red blood cells in response to hyperphenylalaninaemia. The less marked increase in plasma biopterin suggests slow release from a tissue reservoir. The maintenance of a differential between erythrocyte and plasma biopterin concentrations suggests that some mechanism retains biopterin intracellularly.

Acute Disease↗
PubMed1990

The use of cyclosporin A in adult nephrotic syndrome: nine cases and literature review.

Nine adult patients with resistant nephrotic syndrome were treated with cyclosporin A (CyA). All had failed to respond to high dose corticosteroids with or without cyclophosphamide. Three patients had minimal change disease, 3 had focal sclerosing glomerulosclerosis (FSGS), 2 had mesangiocapillary GN, and one had membranous nephropathy. The mean age of the patients was 26.4 years (range 16 to 39 years). CyA was given orally twice daily at a mean dose of 6.7 mg/kg/24 hours (range 6-10 mg/kg/24 hours). Four patients achieved full remission, two patients went into partial remission and three failed to respond. Two patients developed clinical nephrotoxicity, which reversed on dose reduction or cessation of CyA. All 3 patients with minimal change disease who responded subsequently relapsed after stopping CyA, but remitted rapidly on reintroduction of the drug. We suggest that the mode of action of CyA in nephrotic syndrome may be related to intra-renal vasoconstriction in addition to its direct immunosuppressive effect. In this limited series, we found that CyA can be an effective therapy for otherwise refractory nephrotic syndrome, although relapse on withdrawal of CyA may well be a significant clinical problem.

Adult↗
PubMed1990

Clinical and histopathologic findings in adults with the nephrotic syndrome.

The clinical and histopathologic findings in 225 Irish adults with nephrotic syndrome were reviewed. Membranous nephropathy was the most common lesion found (28%), followed by proliferative glomerulonephritis (17%), and focal sclerosing glomerulonephritis (16%). Minimal change disease was the least frequent cause for idiopathic nephrotic syndrome (12%). The major secondary cause of nephrotic syndrome was amyloidosis (13%). The patients were analysed for the predictive value of the level of renal function, presence or absence of hypertension, and the degree of proteinuria. It was not possible to determine the nature of the underlying lesion giving rise to the nephrotic syndrome using any of these variables. There was also no significant difference between primary and secondary glomerular disease with regard to these factors. It is concluded that renal biopsy remains the only definitive method of establishing the underlying lesion causing idiopathic nephrotic syndrome.

Adolescent↗
PubMed1990

Decrease in A1 adenosine receptors in adipocytes from spontaneously hypertensive rats.

We have investigated whether the insulin resistance reported to occur in hypertension is due to decreased insulin receptors or to adenosine receptors in adipocyte membranes. Membranes were isolated from adipocytes from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKy) rats and assayed for insulin receptors and A1 adenosine receptors. The two groups of membranes bound 125I-insulin equally, but in contrast the SHR membranes bound approximately 25% less 125I-HPIA ([(-)-N6-p-hydroxyphenylisopropyl adenosine], an A1 adenosine receptor agonist) than the WKy (P less than .005). Scatchard analysis demonstrated that this was due to a lower number of receptors in the SHR. The affinity of the receptor for HPIA was approximately 0.7 nmol/L in both groups. 5'-Nucleotidase activity was approximately 40% higher in membranes from SHR than WKy (P less than .001), indicating that adipocytes from SHR have a higher capacity for adenosine production. This may cause increased adenosine concentrations in the SHR adipose tissue, leading to adenosine receptor down-regulation. Since we have previously demonstrated that adenosine receptor down-regulation can lead to insulin resistance, these findings may partly account for the insulin resistance of hypertension.

5'-Nucleotidase↗
PubMed1990

Hemispheric involvement in shadowing vs. interpretation: a time-sharing study of simultaneous interpreters with matched bilingual and monolingual controls.

A time-sharing study used shadowing and interpretation/paraphrasing tasks to evaluate lateralization in professional interpreters individually matched to bilingual and monolingual controls. A two-step multivariate general linear model procedure was used to determine lateralized effects and extent of disruption produced by the tasks. Results revealed the monolingual group to be left lateralized for both tasks, but the two bilingual groups were lateralized in the LH only for shadowing. The monolingual group was significantly different from the bilingual groups in the pattern of hand asymmetry for interpretation/paraphrasing. The findings replicate outcomes of prior repeated measures analysis of variance procedures on percentage of change scores. However, new information is added by the more refined analysis. The findings are also discussed in terms of previous laterality studies using similar tasks and subject samples.

Adult↗
PubMed1990

Effects of calcium channel blockade on calcium homeostasis in mild to moderate essential hypertension.

Calcium channel blockers may alter parathyroid hormone secretion in vitro, which would alter calcium homeostasis. To determine the chronic effect of calcium channel blockade in vivo, we conducted a randomized, double blind, 16 week study comparing the effects of two pharmacologic antihypertensive agents, the calcium channel blocker diltiazem and the angiotensin-converting enzyme inhibitor captopril on parameters of calcium homeostasis. Both diltiazem and captopril lowered blood pressure to a similar degree. Neither drug produced any significant change in blood levels of total and ionized calcium, magnesium, or phosphorus, which affect the regulation of parathyroid hormone and vitamin D. In addition, at eight or 16 weeks following initiation, neither drug altered the serum levels of parathyroid hormone (PTH) or 1,25-(OH)2-vitamin D3 (1,25-D). Chronic calcium channel blockade with diltiazem does not alter serum parameters of calcium homeostasis and, thus, should not affect bone mineralization.

Adult↗
PubMed1990

Effect of dietary calcium supplementation on blood pressure and calciotropic hormones in mineralocorticoid-salt hypertension.

In order to determine the effect of dietary calcium supplementation on blood pressure and calciotropic hormones, we studied two groups (n = 12 each) of mineralocorticoid [deoxycorticosterone (DOC)]-salt hypertensive rats, one receiving a normal-calcium diet (0.6% calcium, as calcium carbonate) and the other a high-calcium diet (2.5% calcium), over an 8-week period. Dietary calcium supplementation significantly attenuated the rise in blood pressure. Serum ionized calcium concentrations were significantly decreased from baseline levels in both groups but tended to be higher among the calcium-supplemented rats. Serum concentrations of parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 (1,25-D) were significantly higher in the DOC-salt rats than in normotensive rats fed normal rat chow [PTH: 49 +/- 4 versus 15 +/- 0.9 pg/ml (means +/- s.e.m.); 1,25-D: 108 +/- 7 versus 73 +/- 13 pg/ml, in DOC-salt and normotensive rats, respectively]. In the DOC-salt rats, dietary calcium supplementation did not significantly lower the elevated serum concentration of PTH (from 49 +/- 4 to 40 +/- 4 pg/ml; NS), but did significantly reduce that of 1,25-D (from 108 +/- 7 to 66 +/- 8 pg/ml; P less than 0.01). Since 1,25-D may increase vascular smooth muscle calcium uptake, dietary calcium supplementation may lower blood pressure in DOC-salt hypertension, in part, by suppressing 1,25-D.

Animals↗