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Biomedical subjects

A M MacLeod

Publications and source records attributed to A M MacLeod.

At least 55 records · Page 3Linked to original sources
PubMed1997

Expression of beta 1 integrins in IgA nephropathy.

AIM: To compare the expression of beta 1 integrins in renal biopsies from patients with IgA nephropathy with that found in normal human kidney. METHODS: Thirty renal biopsies from patients with IgA disease plus six control specimens were stained with monoclonal antibodies directed against the alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, alpha v, and beta 1 integrin chains using the alkaline phosphatase anti-alkaline phosphatase (APAAP) technique. The intensity of integrin expression was graded semiquantitatively by a pathologist unaware of the antibody used. RESULTS: Glomerular crescents stained strongly for alpha 3, alpha v, and beta 1, but integrin expression was greatly reduced or absent in fibrotic glomeruli. There were no alterations in the intensity of mesangial cell staining for any of the integrins tested. There was accentuated staining for the alpha 2, alpha 5, alpha v, and beta 1 chains in areas of interstitial scarring plus alpha 2, alpha 3, alpha v, and beta 1 on damaged tubules. Inflammatory cells expressed alpha 4, alpha 5, and beta 1. CONCLUSIONS: In IgA nephropathy the interstitium is the main site of altered beta 1 integrin expression. Glomerular crescents also express several beta 1 integrins, but we found no differences in the intensity of integrin expression on mesangial cells. Altered beta 1 integrin expression may play a role in tubulointerstitial scarring in IgA disease. Thus modulation of integrin expression might attenuate this process.

Antibodies, Monoclonal↗
PubMed1997

The expression of connexin 43 in human kidney and cultured renal cells.

Gap junctions enable intercellular communication and play an important role in a variety of vital cellular functions including differentiation and the control of growth. These junctions are formed by a hexameric of proteins known as connexins. We investigated the distribution of the connexin 43 (Cx43) gap junction protein in renal cells and human kidney using the alkaline phosphatase anti-alkaline phosphatase immunohistochemical technique with a monoclonal antibody directed against the cytoplasmic domain of this antigen. Strong staining was demonstrated on the vascular endothelium, the smooth muscle of larger vessels and on glomerular epithelial cells. In addition, Cx43 was expressed on proximal tubular cells, glomerular endothelial cells and occasional cells infiltrating the interstitium. In areas of tubular atrophy there was increased staining for Cx43. Using reverse transcription-polymerase chain reaction we have also demonstrated that cultured human and rat mesangial cells and human proximal tubular cells express Cx43 messenger RNA. In summary, we have described for the first time the distribution of Cx43 in human kidney and cultured renal cells.

Alkaline Phosphatase↗
PubMed1997

MRI can prevent unnecessary arthroscopy.

We compared the practice of four orthopaedic consultants as regards the use of MRI and arthroscopy to diagnose problems of the knee. In one year 324 arthroscopies and 66 MR scans were performed for this purpose. We found that MRI is a reliable and cheaper alternative to 'diagnostic arthroscopy'. We consider that patients with definite clinical signs merit an early 'therapeutic arthroscopy', but that all other knees should be investigated by MRI. This policy spares patients from unnecessary and expensive surgery. Arthroscopy for diagnostic purposes should be used only with a specific purpose. Modern MRI can and should replace "having a look".

Adolescent↗
PubMed1996

Mechanistic consequences of mutation of active site carboxylates in a retaining beta-1,4-glycanase from Cellulomonas fimi.

The exoglucanase/xylanase Cex from Cellulomonas fimi is a retaining glycosidase which functions via a two-step mechanism involving the formation and hydrolysis of a covalent glycosyl-enzyme intermediate. The roles of three conserved active site carboxylic acids in this enzyme have been probed by detailed kinetic analysis of mutants modified at these three positions. Elimination of the catalytic nucleophile (E233A) results in an essentially inactive enzyme, consistent with the important role of this residue. However addition of small anions such as azide or formate restores activity, but as an inverting enzyme since the product formed under these conditions is the alpha-glycosyl azide. Shortening of the catalytic nucleophile (E233D) reduces the rates of both formation and hydrolysis of the glycosyl-enzyme intermediate some 3000-4000-fold. Elimination of the acid/base catalyst (E127A) yields a mutant for which the deglycosylation step is slowed some 200-300-fold as a consequence of removal of general base catalysis, but with little effect on the transition state structure at the anomeric center. Effects on the glycosylation step due to removal of the acid catalyst depend on the aglycon leaving group ability, with minimal effects on substrates requiring no general acid catalysis but large (> 10(5)-fold) effects on substrates with poor leaving groups. The Brønsted beta 1g value for hydrolysis of aryl cellobiosides was much larger (beta 1g approximately -1) for the mutant than for the wild-type enzyme (beta 1g = -0.3), consistent with removal of protonic assistance. The pH-dependence was also significantly perturbed. Mutation of a third conserved active site carboxylic acid (E123A) resulted in rate reductions of up to 1500-fold on poorer substrates, which could be largely restored by addition of azide, but without the formation of glycosyl azide products. These results suggest a simple strategy for the identification of the key active site nucleophile and acid/base catalyst residues in glycosidases without resort to active site labeling.

Binding Sites↗
PubMed1996

Tachykinin NK1 receptor antagonists act centrally to inhibit emesis induced by the chemotherapeutic agent cisplatin in ferrets.

These studies have compared the pharmacological profile of two non-peptide human type neurokinin1 (hNK1) receptor selective antagonists, L-741,671 and a quaternised compound L-743,310. In radioligand binding studies L-741,671 and L-743,310 had high affinity for ferret and cloned hNK1 receptors [Ki (nM) ferret 0.7 and 0.1; human 0.03 and 0.06, respectively] but low affinity for rodent NK1 receptors [Ki (nM) 64 and 17, respectively] suggesting that ferret receptors have hNK1-like binding pharmacology. Studies in vivo showed that L-741,671 and L-743,310 had equivalent functional activity in the periphery (ID50s of 1.6 and 2 micrograms/kg i.v., respectively) as measured by inhibition of plasma protein extravasation evoked in the oesophagus of guinea pigs by resiniferatoxin (7 nmol/kg i.v.). Using an in situ brain perfusion technique in anaesthetised rats, L-741,671 was shown to be much more brain penetrant than the quaternary compound L-743,310 which had an entry rate similar to the poorly brain penetrant plasma marker inulin. These compounds thus provided an opportunity to compare the anti-emetic effects of equi-active hNK1 receptor antagonists with and without brain penetration to central NK1 receptor sites. When tested against cisplatin-induced emesis in ferrets, L-741,671 (0.3, 1 and 3 mg/kg i.v.) produced marked dose-dependent inhibition of retching and vomiting but L-743,310 was inactive at 3 and 10 micrograms/kg i.v. In contrast, direct central injection of L-741,671 and L-743,310 (30 micrograms) into the vicinity of the nucleus tractus solitarius or L-743,310 (200 micrograms) intracisternally was shown to inhibit retching and vomiting induced by i.v. cisplatin. L-741,671 and L-743,310 had equivalent functional activity, at the same dose, against cisplatin-induced emesis when injected centrally. These observations indicated that had L-743,310 penetrated into the brain after systemic administration it would have been active in the cisplatin-induced emesis assay and so show that brain penetration is essential for the anti-emetic action of systemically administered NK1 receptor antagonists.

Animals↗
PubMed1996

Integrins and disease.

1. Adhesion is a vital property of cells. It provides a stable environment for cell growth and differentiation and allows cells to migrate. 2. The interaction between cells and their extracellular matrices is also an important factor in the regulation of further protein deposition. Likewise, matrix proteins can influence cellular function thus creating a complex feedback mechanism. 3. The adherence of cells to each other, their extracellular matrices and endothelial surfaces is mediated by a variety of membrane proteins collectively known as adhesion molecules. 4. Adhesion molecules can be further divided into four subfamilies: the integrins, the selectins, the cadherins and the immunoglobulin superfamily. This article will review our current knowledge of the integrin family of adhesion receptors, focusing principally on their role in the pathogenesis of human disease.

Cardiovascular Diseases↗
PubMed1996

Survival on renal replacement therapy in Europe: is there a 'centre effect'?

OBJECTIVE: Survival is the ultimate outcome measure in renal replacement therapy (RRT) and may be used to compare performance among centres. Such comparison, however, is meaningless if the influences of comorbidity, age and early deaths are not considered. We therefore studied survival rates on RRT in seven centres in Europe after taking into account the influence of age, early deaths, primary renal diagnoses, and comorbidity. DESIGN: A retrospective survival analysis was carried out on 1407 patients who commenced RRT in seven centres across five European countries during a 7-year period. Patients were stratified into low-, medium- and high-risk groups based mainly on comorbidity and to a lesser extent on age at commencement of RRT. Kaplan-Meier survival and Cox's proportional hazards model were used to compare survival. RESULTS: Before risk stratification overall 2-year survival across the seven centres ranged from 60.2 to 85.3% (69.3-89.9%) after excluding early deaths) masking a range of survivals of 27.4% for the high-risk group with the worst survival to 100% in the low-risk group with the best survival. After excluding early deaths 2-year survival in the low risk groups (n=622) was greater than 90% in all centres. Multivariate analysis showed that the mortality risk increased four fold from low- to medium- and a further 1.6-fold from medium- to high-risk group. However, despite this adjustment for comorbidity and age there still remained a significant difference in survival among some centres, i.e. a 'centre effect' which ranked the centres. CONCLUSION: Risk stratification diminishes the variance in survival between centres but a centre effect remains despite adjusting for age and comorbidity. Multicentre prospective studies are urgently required to identify the reasons for this apparent centre effect.

Adult↗
PubMed1996

Angiotensin-converting-enzyme inhibitors in the management of cardiac failure: are we ignoring the evidence?

The benefits of angiotensin-converting enzyme (ACE) inhibition in the management of cardiac failure have been extensively documented. However, little is known about its impact upon the investigation and management of this condition. We assessed how patients diagnosed as having cardiac failure were investigated, which patients were treated with ACE inhibitors and with what dosages. We reviewed the case notes of all 343 patients discharged from Aberdeen Royal Infirmary 1 July-31 December 1992 with a diagnosis of cardiac failure. In addition, a questionnaire was sent to the general practitioners of the 166 patients still alive in October 1994. Only 40% of patients were discharged from hospital on ACE inhibitors. In 58.8%, the diagnosis of cardiac failure was based purely on clinical or radiological grounds. At discharge, 76.1% of patients were on lower doses of ACE inhibitors than those used in the major survival studies; with 68.9% receiving similar doses two years later. The majority of patients with heart failure are under-investigated and under-treated.

Adult↗
PubMed1996

Free tensor fasciae latae flap reconstruction of defects of the chest and abdominal wall: selection of recipient vessels.

Reconstruction of a full thickness defect of the abdominal or chest wall requires a combination of a rigid or semi-rigid layer and skin cover. The tensor fasciae latae (TFL) flap is unique in that it provides both of these in substantial quantities, but the most difficult aspect of using this flap in the anterior chest and abdomen is finding suitable recipient vessels. We describe a series of nine cases in which full thickness defects of the chest and abdominal wall were repaired using free vascularised TFL flaps. The recipient vessels included the gastroepiploic vessels (n = 2), the deep inferior epigastric artery (n = 3), the internal mammary artery (n = 2), and the superior thyroid and acromiothoracic arteries (n = 1 each). The gastroepiploic and internal mammary vessels are preferred because of their reliability and because the flap pedicle enters the centre of the deep surface of the flap so that if these vessels are used, circumferential tight closure of the fascial layer can be achieved, with consequent decreased risk of vessel kinking and future herniation.

Abdominal Muscles↗
PubMed1996

The epidemiology of chronic renal failure and provision of renal services in Albania.

Tirana, the only dialysis facility in Albania (pop 4 million), has a stock of 12 patients and three haemodialysis machines. To determine the need for renal services in Albania we studied the incidence and outcome of patients with chronic renal failure (CRF) referred to the renal service in Tirana (pop 300 000) over 1 year. Case-notes of all patients with a serum creatinine concentration > or = 300 mumol/l during the study period (1992) were examined and outcome at 2 years recorded for each patient. In all, 84 patients (mean age 41.6 +/- 17.5 years, 56% male) were referred to nephrologists of whom 35 (42%) came from Tirana, giving an annual incidence of 116 per million pop. 77% were under 40 and had no co-morbid illness. Glomerulonephritis, the most common renal diagnosis, affected 26% patients. 22% patients (mean age 38 +/- 18.1) died within 2 years and only 5% received dialysis. The mean age of those who received dialysis was 29 +/- 8.3 compared with those who were not dialysed (42 +/- 18.0). The 59 patients (24 from Tirana i.e. 80 per million) who were alive with advanced CRF (creatinine > 500) had a mean creatine of 623 +/- 93 mumol/l and would be candidates for dialysis. Patients with progressive renal failure in Albania are regularly followed and treated with antihypertensives and dietary modification. The need for RRT, however, is not being met even for young patients with no co-morbidity.

Adult↗
PubMed1995

Identification of 3,5-dihydro-2-aryl-1H-pyrazolo[3,4-c]quinoline-1,4(2H)-diones as novel high-affinity glycine site N-methyl-D-aspartate antagonists.

Almost all of the existing known antagonists at the glycine site of the N-methyl-D-aspartate (NMDA) receptor have a low propensity for crossing the blood-brain barrier. It has been suggested that in many cases this may be due to the presence of a carboxylic acid which is a common feature of most of the potent full antagonists at this receptor. In this study, 2-aryl-1H-pyrazolo[3,4-c]quinoline-1,4(2H)-diones were found to have high-affinity binding at the glycine receptor. In particular, structure-activity studies identified 7-chloro-3,5-dihydro-2-(4-methoxyphenyl)-1H-pyrazolo[3,4-c]quinoline- 1,4(2H)-dione as the most potent of a series of analogues with an IC50 of 3.3 nM. The measured pKa values in this class of compounds (typically 4.0) indicate they are of equivalent acidity to carboxylic acids. Functional antagonism was demonstrated by inhibition of NMDA-evoked responses in rat cortical slices. Anticonvulsant activity in DBA/2 mice was achieved after dosing by direct injection into the cerebral ventricles, but no activity was seen after systemic administration, suggesting low brain penetration with this class of antagonists.

Animals↗
PubMed1995

Synthesis and biological evaluation of NK1 antagonists derived from L-tryptophan.

The 3,5-bis(trifluoromethyl)benzyl ester of N-acetyl-L-tryptophan (3), which was derived from the screening lead N-ethyl-L-tryptophan benzyl ester, has been used as a starting point to identify high-affinity substance P receptor antagonists with improved in vivo activity. Altering the ester moiety to an amide or ether led to a substantial loss in binding affinity, but conversion to a ketone provided compounds with affinity comparable to the equivalent esters. A homochiral synthesis of the key intermediate amino ketone 15 was developed which allows its preparation on a large scale. From this intermediate a range of amine-containing acylamino derivatives were prepared with affinity optimized in the morpholinylbutyramide 161 which has an IC50 of 0.17 nM at the human NK1 receptor. In addition to improving affinity, the amino group also provided aqueous solubility for a number of these derivatives. When tested in vivo the quinuclidine derivative L-737,488 (16i) was found to be an orally active (ID50 = 1.8 mg/kg) inhibitor of substance P-induced dermal extravasation in the guinea pig.

Amines↗
PubMed1995

Death during the first 90 days of dialysis: a case control study.

Comparison of survival data among centers may be used to assess performance, but may be influenced by the number of patients who die during the first 90 days of renal replacement therapy (RRT). Data published by registries in Europe do not detail these deaths, and US data generally exclude them from analysis for financial reasons. To study factors influencing such deaths we compared 42 patients who died within 90 days of first commencing RRT in one Scottish renal unit (group A) between 1971 and 1992 with 42 age- and sex-matched controls who started RRT over the same period and survived longer (group B). Patients who died within 90 days of RRT ranged in age from 25.3 to 83.7 years and had a mean age of 65.2 (SEM, 1.6; 95% confidence interval, 61.9 to 68.4). The proportion of patients who died during the first 90 days of RRT increased from 2% of all patients treated before 1981 to 12% in subsequent years. Thirty-three patients in group A received emergency dialysis via temporary venous access compared with only nine in group B (P < 0.055). There were more patients in group A with a diagnosis of arteriosclerotic renal artery stenosis (14 v 1) and with a history of smoking (15 v 2) than in group B (P < 0.0005). Median renal or nonrenal follow-up before RRT was 1.1 month in group A and 10.6 months in group B (P < 0.0001). Fewer patients in group A had no coexisting disease (1 v 17; P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Patients' perception of health on renal replacement therapy: evaluation using a new instrument.

Patients' perception of their health is an important outcome measure in the management of chronic disease. Comparing that perception from patients receiving different forms of renal replacement therapy (RRT) with data from the general population could be used to monitor the effectiveness of treatment. The short form 36 (SF-36) questionnaire is a general measure of health status which has been validated in the UK and uses eight health scales comprising physical function, social function, role limitation (physical and emotional), mental health, energy, pain and overall health. Using the SF-36 questionnaire, the perception of health of patients receiving RRT was compared with data from healthy control subjects. One hundred and seventy-two of 185 (93%) patients receiving RRT--transplant (n = 102), haemodialysis (n = 43), and peritoneal dialysis (n = 27) completed the questionnaire; scores were compared with those from 542 healthy control subjects. The perception of health of haemodialysis and peritoneal dialysis patients was significantly worse than transplanted patients and controls in six of the eight scales (P < 0.05 dialysis versus transplant and controls). That of transplanted patients was worse in only two and better in one of the eight scales compared with the general population (P < 0.05). Patients were also stratified into low, medium, and high-risk groups based on age and comorbidity and were analysed irrespective of treatment modality. Scores were significantly different across the risk groups in five of the eight scales. We conclude that the SF-36 questionnaire is acceptable to patients on RRT and enables the perception of health of patients receiving RRT to be compared with that of the general population.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Free flaps in the aged and infirm.

Some of the most dramatic advances in reconstructive surgery have involved microvascular free-flap transfers. Although initial studies stressed the need for the procedures to be restricted to the healthy, with no evidence of vascular disease, it has become apparent that such restrictions need not apply if adequate patient care is available. Refinements of technique and development of new operations have made the free flap available to all. In particular, the procedure has been found to have unique benefits in the elderly and infirm population.

Age Distribution↗
PubMed1994

The acid/base catalyst in the exoglucanase/xylanase from Cellulomonas fimi is glutamic acid 127: evidence from detailed kinetic studies of mutants.

The exoglucanase/xylanase Cex from Cellulomonas fimi hydrolyzes beta-1,4-glycosidic bonds with net retention of anomeric configuration, releasing the disaccharides beta-cellobiose or beta-xylobiose. It uses a double-displacement mechanism involving a glycosyl-enzyme intermediate which is formed and hydrolyzed with general acid/base catalytic assistance. Glu127 was proposed as the acid/base catalyst on the basis of sequence alignments, and mutants at this position were constructed in which the glutamic acid is replaced by alanine or glycine. The following kinetic analysis provides firm support for the assignment of Glu127 as the acid/base catalyst and suggests a more general strategy for identification of this residue in other glycosidases. Substrates which do not require protonic assistance for initial bond cleavage exhibit kcat/Km values similar to those of wild-type enzyme, whereas substrates which do require assistance have kcat/Km values over 6000-fold smaller. Thus rate constants for glycosylation are affected to different degrees by this substitution, depending upon their need for acid catalysis. The deglycosylation rate constant is decreased 200-fold by such substitution, due to the removal of general base catalytic assistance. In the presence of sodium azide a new product, beta-cellobiosyl azide, is formed with these mutants whereas only cellobiose is formed with wild-type enzyme or the Glu127Asp mutant under similar conditions. Addition of azide results in very significant increases in kcat values, ranging from 8-fold for 4''-nitrophenyl cellobioside to over 200-fold for 2'',4''-dinitrophenyl cellobioside, whereas kcat/Km values for these substrates remain essentially constant. No effects on rate upon azide addition are seen with substrates containing aglycons of poor leaving group ability.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗