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Biomedical subjects

N Lawson

Publications and source records attributed to N Lawson.

At least 55 records · Page 3Linked to original sources
PubMed1990

The effects of the partial beta 1-agonist xamoterol on heart rate and ventricular arrhythmias in patients with mild to moderate heart failure.

A major concern with the use of oral inotropes in chronic heart failure is their propensity to exacerbate cardiac arrhythmias. In a double-blind randomized placebo-controlled crossover study of xamoterol, a novel beta 1-partial agonist, 24 h ambulatory electrocardiograms were obtained in 26 patients prior to and at the end of 13-week treatment periods. During treatment with xamoterol there was no significant change in mean hourly number of ventricular extrasystoles compared with baseline and placebo (30 +/- 17 vs 56 +/- 42 and 18 +/- 7, respectively), or in the number of patients showing complex forms (multiform VEs, pairs, ventricular tachycardia) (20/26 vs 19/26 and 19/26, respectively), or ventricular tachycardia alone (5/26 vs 4/26 and 6/26, respectively). Xamoterol therapy also stabilized heart rate variability over the 24 h period.

Adrenergic beta-Agonists↗
PubMed1990

Prolonged aldose reductase inhibition in chronic peripheral diabetic neuropathy: effects on microangiopathy.

A 2-year randomized placebo-controlled double-blind trial of 250 mg day-1 of the aldose reductase inhibitor Sorbinil in severe symptomatic chronic peripheral neuropathy was performed in 21 diabetic patients. Due to adverse reactions 8 patients completed the trial on Sorbinil and 6 patients on placebo. Despite differences in baseline neurophysiological parameters, duration of diabetes, and presence of retinopathy between the placebo and treatment groups, there were no initial differences in in vitro platelet aggregation, albumin excretion rate (AER) or muscle capillary basement membrane thickness. After 2 years the median deterioration in AER in the placebo group was 18.4 micrograms min-1 (range 2.6-64.8 micrograms min-1). This deterioration was significant (p less than 0.03). The change in AER in the Sorbinil group was +1.25 (-10.7 to +20.4) micrograms min-1, an insignificant change. In vitro platelet responsiveness to collagen and adenosine diphosphate (ADP) increased in the placebo group (median change max% collagen + 8 (+2 to +30)%; ADP +4.5 (0 to +20)% compared with a fall in the Sorbinil treated patients (median change; collagen -17.5 (-2 to -40)%, p less than 0.05; ADP, -4 (0 to -25)%, p less than 0.05). Muscle capillary basement membrane thickness was measured in only 3 patients in each group and did not alter significantly during the trial. All 12 neurophysiological measurements showed no significant changes between the treatment and placebo groups. The data suggest that aldose reductase inhibition has effects on platelet reactivity and microalbuminuria.

Aldehyde Reductase↗
PubMed1990

The usefulness of faecal haemoglobin, albumin and alpha-1-antitrypsin in the detection of gastrointestinal bleeding.

A pilot study was undertaken to find out whether faecal haemoglobin, albumin and alpha-1-antitrypsin from patients with gastrointestinal disorders could distinguish active bleeders from non-active bleeders and healthy volunteers. Alpha-1-antitrypsin is not as readily degraded by endogenous and bacterial breakdown as haemoglobin and albumin and consequently could be a better marker for occult bleeding.

Adolescent↗
PubMed1990

Impact of microangiopathy on chronic symptomatic peripheral neuropathy.

The role of microvascular disease in the aetiology of diabetic peripheral neuropathy remains controversial. Muscle capillary basement membrane thickening (MCBMT) and increased albumin excretion rates (AER) are features of generalized diabetic microangiopathy and may relate to the severity of neuropathy. We have studied 19 patients with neuropathy of greater than 12 months duration and assessed relationships between the severity of neuropathy and MCBMT, AER, presence of retinopathy, age and duration of diabetes. Nine patients had retinopathy and 10 did not. The two groups of patients were well matched for age, type of diabetes and HbA1% but diabetic patients with retinopathy had significantly longer duration of diabetes (median duration 22 yr, range 3-42 yr compared with patients without retinopathy (6 yr range 1-20 yr p less than 0.05). The group with retinopathy had significantly greater median MCBMT 3,077 A (range 741-10,732 A) than their age matched non-diabetic controls 2,256 A (1,290-4,406 A p less than 0.02) or the 10 diabetic patients without retinopathy 1,599 A (805-5,152 A). The patients with retinopathy also had greater median AER 88 micrograms/min (range 8-200 micrograms/min) compared with patients without retinopathy 8 micrograms/min (2-63 micrograms/min p less than 0.05), and had significantly more severe neuropathic features on a 12 point neurophysiological ranking scale (p less than 0.05). This study showed an association between retinopathy and severity of neuropathy but there were no associations between severity of neuropathy or AER with MCBMT. Severe chronic peripheral neuropathy is associated with microangiopathic complications.

Albuminuria↗
PubMed1990

A predominantly adrenaline-secreting phaeochromocytoma.

A 61-year-old woman who presented with diabetes, nausea, weight loss and sweating was found to have a phaeochromocytoma secreting adrenaline, with a small amount of N-methyladrenaline. There was no significant increase in noradrenaline secretion. She was normotensive, and developed profound hypotension in response to the alpha-adrenergic antagonist phenoxybenzamine. These features are unusual in phaeochromocytoma, but similar features occurred in the very few previous reported cases of pure adrenaline-secreting phaeochromocytoma. We conclude that it is important to identify such patients, so that they should not be given alpha-adrenergic antagonist drugs.

Adrenal Gland Neoplasms↗
PubMed1989

The acute effects of intravenous xamoterol ('Corwin', I.C.I. 118, 587) on resting and exercise haemodynamics in patients with mild to moderate heart failure.

The known properties of xamoterol, a partial beta 1-agonist, provide a basis to pharmacologically modulate cardiac responses to variations in sympathetic tone. Haemodynamic variables were assessed at rest and on exercise before and after intravenous xamoterol (0.2 mg kg-1), in 30 patients with mild to moderate cardiac failure. Xamoterol produced significant improvements in resting cardiac index (2.51 +/- 0.15 to 2.80 +/- 0.14 l min-1 m-2; P less than 0.001), stroke volume (62 +/- 4 to 75 +/- 5 mljbeat-1; P less than 0.001) and stroke work index (42.4 +/- 3.6 to 47.7 +/- 3.9 gm beat-1 m-2; P less than 0.01). This occurred despite a significant reduction in heart rate (78 +/- 3 to 74 +/- 2 beats min-1; P less than 0.05). There were also significant reductions in systemic vascular resistance (1990 +/- 141 to 1669 +/- 112 dynes s-1 cm-5; P less than 0.01) and double product (1146 +/- 46 to 1051 +/- 41 mmHg min-1 x 10(-1); P less than 0.05), with no significant changes in systolic blood pressure, pulmonary wedge pressure or ejection fraction. Xamoterol significantly attenuated the heart rate response to exercise (112 +/- 4 to 97 +/- 3 beats min-1; P less than 0.001), with no impairment in the expected exercise induced increase in cardiac index. This was due to the significant increase in stroke volume from 81 +/- 6 to 95 +/- 7 ml beat-1 (P less than 0.001). There were no significant changes in resting or exercise noradrenaline levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1989

Activity of the unstimulated renin-angiotensin-aldosterone system in type 1 diabetic patients with and without proteinuria.

There have been conflicting reports of the activity of the renin-angiotensin-aldosterone system in diabetes. We studied the activity of the unstimulated renin-angiotensin-aldosterone system in 73 consecutive Type 1 diabetic patients with varying degrees of albuminuria. Patients with elevated albumin excretion rates had elevated median plasma renin activity (macroalbuminuric 2.2, range 0.5-8.2, p less than 0.05; microalbuminuric 2.3, 0.7-7.1, p less than 0.001; vs normoalbuminuric 1.0, 0.2-4.5 nmol l-1 h-1) and higher systolic blood pressure (macroalbuminuric 141 +/- 27 vs normoalbuminuric 116 +/- 13 mmHg, mean +/- SD, p less than 0.01) compared with those with normal albumin excretion rates. Aldosterone secretion and function were normal in all patients studied.

Adult↗
PubMed1989

Increased levels of vaccenic acid in bronchogenic carcinoma tissue.

Employing capillary gas liquid chromatography the levels of palmitic, palmitoleic, stearic, oleic, cis-vaccenic, linoleic, arachidonic and docosahexaenoic acids were measured in lung tissue and lung tumours from 28 patients undergoing surgery for bronchogenic carcinoma. There were significant increases in the majority of fatty acids in tumour tissue compared to normal tissue when the results were expressed in absolute units. However, when the relative changes in fatty acid concentration were studied, the most consistent findings were a significant rise in vaccenic acid and a fall in palmitic acid in tumour tissue compared to normal tissue. This change in the vaccenic:palmitic acid ratio may reflect specific changes in fatty acid metabolism in bronchogenic carcinoma tissue involving a delta-9 desaturase.

Adult↗
PubMed1988

Microalbuminuria in diabetic subjects with chronic peripheral neuropathy.

Fifty-five patients with chronic peripheral neuropathy, 31 with and 24 without retinopathy, had albumin excretion rates determined on 2-h supine urine collections on three occasions by a radioimmunoassay method. Four patients with retinopathy had albustix-positive proteinuria and were excluded from subsequent analysis. Microalbuminuria was found in 20 of the 27 patients with retinopathy compared with 10 of the 24 patients with neuropathy alone. The mean albumin excretion rate (AER) was higher in neuropathic patients with retinopathy than in those patients with neuropathy alone (41.2 +/- 40.3 vs 18.8 +/- 33.2 micrograms/min, P less than 0.01). Multivariate analysis of the data was performed and this revealed a correlation coefficient of R2 = 0.33 (P less than 0.01) for AER as the dependent variable with respect to the independent variables HbA1, systolic blood pressure and known duration of diabetes. There was, however, no significant contribution separately of these individual variables to the regression equation. Microalbuminuria was significantly associated with retinopathy although almost half of the patients with neuropathy alone had microalbuminuria. The association between microalbuminuria and neuropathy even in the absence of retinopathy provides support for a microvascular element in the pathogenesis of diabetic neuropathy.

Albuminuria↗
PubMed1987

Determination of erythrocyte fatty acids by capillary gas liquid chromatography.

A capillary gas liquid chromatography method was established for the routine determination of fatty acid profiles from washed erythrocyte membranes. Only the five major fatty acids found in erythrocytes (palmitic, stearic, oleic, linoleic and arachidonic acids) had acceptable precision (CVs less than 10.0%) for use in establishing quantitative differences between groups of individuals. Reference values were established for the relative amounts of these five fatty acids in adults. Significant alterations in the relative concentrations of oleic and arachidonic acids were found after storage at +4 degrees C for 24 h, which has important implications in the study of changes in erythrocyte fatty acids in cancer and diabetes.

Chromatography, Gas↗
PubMed1987

Erythrocyte fatty acid profiles in patients with bronchogenic carcinoma.

The use of the erythrocyte stearic:oleic acid ratio in the diagnosis and prognosis of bronchogenic carcinoma has been assessed. Although there was a significant difference (P less than 0.02) in the erythrocyte stearic:oleic acid ratio between bronchogenic carcinoma patients and healthy adults, the large overlap observed in the two groups rendered the test unsuitable for the diagnosis of malignancy. Furthermore, there was no consistent rise in this ratio after surgical resection, indicating the test to be of little prognostic use. A new explanation for the lower stearic:oleic acid ratios in certain patients has been postulated.

Adult↗
PubMed1987

An alternative explanation for the changes in erythrocyte fatty acids observed in diabetes mellitus.

Fatty acids in erythrocyte membranes and plasma were determined by capillary gas-liquid chromatography in 27 controls and 44 subjects with insulin-dependent diabetes mellitus. Significant decreases in stearic acid (P less than 0.00003) and arachidonic acid (P less than 0.001) and significant increases in palmitic acid (P less than 0.00003) were observed in erythrocytes from diabetic patients. The stearic:oleic acid ratios and arachidonic:linoleic acid ratios in erythrocytes were significantly lower in diabetic patients than in controls (P less than 0.0003 and less than 0.0007, respectively). The relative concentration of palmitic acid in plasma (as a percentage of the sum of the five major fatty acids) was increased in diabetic patients, as compared with controls (P less than 0.0125). We observed no other significant differences in fatty acids in plasma, making it unlikely that changes in fatty acids in erythrocyte membranes in diabetic patients can be accounted for simply by alterations in the fatty acids in plasma. We propose that impaired metabolic control associated with diabetes mellitus may interfere with the maintenance of fatty acid profiles in erythrocyte membranes against the concentration gradients in plasma.

Adolescent↗
PubMed1986

Exocrine pancreatic function as determined in a same-day test with use of bentiromide and p-aminosalicylic acid.

We describe a new approach to the bentiromide test of exocrine pancreatic function, p-Aminosalicylic acid (PAS), a compound closely related to the bentiromide fragment p-aminobenzoic acid (PABA), is used as a marker of the pharmacokinetic behavior of PABA to derive a PABA excretion index. This index is identical to that derived with [14C]-PABA. Concentrations of both PABA and PAS are measured in urine by "high-performance" liquid chromatography, which avoids the drug interferences encountered with established assays of PABA. We discuss the practical and diagnostic advantages of this new approach to the bentiromide test.

4-Aminobenzoic Acid↗
PubMed1986

Assessment of a time-resolved fluoroimmunoassay for thyrotropin in routine clinical practice.

We assessed the use of a dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) system to measure thyrotropin (thyroid-stimulating hormone, TSH) in routine clinical practice. The assay is simple and precise, with intrabatch CV of less than 10% down to 0.1 milli-int. unit/L. When compared with free thyroxin, total thyroxin, and triiodothyronine measurements in 142 patients, the present assay most sensitively indicated hyperthyroidism and, in conjunction with free thyroxin, most sensitively indicated hypothyroidism. Free thyroxin was the most specific assay (lowest number of falsely increased or decreased results) in detecting thyroid disorders, with a specificity of 93.6% as compared with 85.1% for TSH, 81.9% for thyroxin, and 77.6% for triiodothyronine.

Evaluation Studies as Topic↗
PubMed1985

Practical assessment of the NBT-PABA pancreatic function test using high performance liquid chromatography determination of p-aminobenzoic acid in urine.

A practical method for determining p-aminobenzoic acid in urine by high-performance liquid chromatography has been assessed. The technique is quick, requires no extraction steps and has good precision. Using this method, healthy individuals had a p-aminobenzoic acid excretion index of 94% +/- 18 (mean +/- 1 SD). Patients with proven, severe chronic exocrine pancreatic dysfunction had index values of less than 5-25%. Unlike chemical methods available, there were no interferences in any of the urines tested, nor did 12 compounds tested interfere with the analysis.

4-Aminobenzoic Acid↗