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Biomedical subjects

A Nicholls

Publications and source records attributed to A Nicholls.

At least 37 records · Page 2Linked to original sources
PubMed1995

Ocular and renal sarcoidosis.

Sarcoidosis commonly presents in young adults with bilateral hilar lymphadenopathy, lung parenchymal disease and/or skin lesions. Ocular symptoms are the presenting feature in up to 10% of cases, but eye involvement can be demonstrated in around a quarter of all patients. Renal disease is much rarer, and may manifest with hypercalcaemic nephropathy, granulomatous interstitial nephritis, tubular dysfunction or glomerulonephritis. Eye and renal involvement are rarely found together, and may be confused with Wegener's granulomatosis or polyarteritis. We report a case of a young man who developed renal failure due to sarcoidosis soon after presenting with uveitis. The case illustrates an unusual combination of systemic features that may not be widely recognized.

Acute Kidney Injury↗
PubMed1994

The arthropathy of the Muckle-Wells syndrome.

Muckle-Wells syndrome (MWS) is a rare condition characterized by urticaria, arthralgias, deafness and amyloid nephropathy. The arthropathy is poorly documented. We describe the arthropathy occurring in four cases of MWS and discuss the management. Each patient developed recurrent bouts of transient synovitis. One patient developed a persistent sterile pyoarthrosis.

Adult↗
PubMed1993

Organ donation.

Explore the source record for details and available documents.

Ethics, Medical↗
PubMed1992

Detection and characterisation of an overmodified type III collagen by analysis of non-cutaneous connective tissues in a patient with Ehlers-Danlos syndrome IV.

The clinical and biochemical observations in a patient with a mild form of Ehlers-Danlos syndrome (EDS) type IV are described. The patient's skin fibroblasts produced markedly diminished amounts of type III collagen. SDS-polyacrylamide gel electrophoresis of collagens produced by cells obtained from other, non-cutaneous tissues showed two forms of collagen alpha 1(III) chains, a normal and a slow migrating, mutant form. Further analysis confirmed that the type III collagen molecules containing mutant alpha chains which were overmodified had a lower thermal stability and were poorly secreted into the extracellular medium. The protein defect was mapped by in situ cyanogen bromide digestion and was located in alpha 1(III) CB9, the C-terminal peptide of the collagen triple helix. This study shows that non-cutaneous connective tissues can be a useful source for the study of type III collagen defects in patients with EDS type IV.

Cells, Cultured↗
PubMed1992

Localized scleroderma and hemiatrophy in association with antibodies to double-stranded DNA.

Localized scleroderma involves primarily skin but also muscle, bone and synovium. Further associations and transitional forms have been reported. We report here two cases showing associations between localized scleroderma and vasculitis, mononeuritis multiplex, juvenile chronic arthritis and hemiatrophy. In particular our cases both possess antibodies to double-stranded DNA, a finding not previously reported.

Adolescent↗
PubMed1991

Extracting hydrophobic free energies from experimental data: relationship to protein folding and theoretical models.

Solubility and vapor pressure measurements of hydrocarbons in water are generally thought to provide estimates of the strength of the hydrophobic effect in the range 20-30 cal/(mol.A2). Our reassessment of the solubility data on the basis of new developments in solution thermodynamics suggests that the hydrophobic surface free energy for hydrocarbon solutes is 46-47 cal/(mol.A2), although the actual value depends strongly on curvature effects [Nicholls et al. (1991) Proteins (in press); Sharp et al. (1991) Science 252, 106-109]. The arguments to support such a significant increase in the estimate of the hydrophobic effect stem partly from theoretical considerations and partly from the experimental results of De Young and Dill [(1990) J. Phys. Chem. 94, 801-809] on benzene partition between water and alkane solvents. Previous estimates of the hydrophobic effect derive from an analysis of solute partition data, which does not fully account for changes in volume entropy. We show here how the ideal gas equations, combined with experimental molar volumes, can account for such changes. Revised solubility scales for the 20 amino acids, based on cyclohexane to water and octanol to water transfer energies, are derived. The agreement between these scales, particularly the octanol scale, and mutant protein stability measurements from Kellis et al. [(1989) Biochemistry 28, 4914-4922] and Shortle et al. [(1990) Biochemistry 29, 8033-8041] is good. The increased strength of the hydrophobic interaction has implications for the energetics of protein folding, substrate binding, and nucleic acid base stacking and the interpretation of computer simulations.

Alkanes↗
PubMed1991

Reconciling the magnitude of the microscopic and macroscopic hydrophobic effects.

The magnitude of the hydrophobic effect, as measured from the surface area dependence of the solubilities of hydrocarbons in water, is generally thought to be about 25 calories per mole per square angstrom (cal mol-1 A-2). However, the surface tension at a hydrocarbon-water interface, which is a "macroscopic" measure of the hydrophobic effect, is approximately 72 cal mol-1 A-2. In an attempt to reconcile these values, alkane solubility data have been reevaluated to account for solute-solvent size differences, leading to a revised "microscopic" hydrophobic effect of 47 cal mol-1 A-2. This value, when used in a simple geometric model for the curvature dependence of the hydrophobic effect, predicts a macroscopic alkane-water surface tension that is close to the macroscopic value.

Hydrocarbons↗
PubMed1991

Protein folding and association: insights from the interfacial and thermodynamic properties of hydrocarbons.

We demonstrate in this work that the surface tension, water-organic solvent, transfer-free energies and the thermodynamics of melting of linear alkanes provide fundamental insights into the nonpolar driving forces for protein folding and protein binding reactions. We first develop a model for the curvature dependence of the hydrophobic effect and find that the macroscopic concept of interfacial free energy is applicable at the molecular level. Application of a well-known relationship involving surface tension and adhesion energies reveals that dispersion forces play little or no net role in hydrophobic interactions; rather, the standard model of disruption of water structure (entropically driven at 25 degrees C) is correct. The hydrophobic interaction is found, in agreement with the classical picture, to provide a major driving force for protein folding. Analysis of the melting behavior of hydrocarbons reveals that close packing of the protein interior makes only a small free energy contribution to folding because the enthalpic gain resulting from increased dispersion interactions (relative to the liquid) is countered by the freezing of side chain motion. The identical effect should occur in association reactions, which may provide an enormous simplification in the evaluation of binding energies. Protein binding reactions, even between nearly planar or concave/convex interfaces, are found to have effective hydrophobicities considerably smaller than the prediction based on macroscopic surface tension. This is due to the formation of a concave collar region that usually accompanies complex formation. This effect may preclude the formation of complexes between convex surfaces.

Algorithms↗
PubMed1991

Hydroxamic acids and hydroxyureas as novel, selective 5-lipoxygenase inhibitors for possible use in asthma.

Inhibition of 5-lipoxygenase (5-LO) is a potential target for therapeutic intervention in asthma. Acetohydroxamic acids such as BW A4C are potent and selective 5-LO inhibitors in vitro and also inhibit 5-LO activity in vivo following oral administration. In man, BW A4C is metabolised relatively rapidly (t1/2 = approx. 2h) but nevertheless inhibits 5-LO with reasonable persistence. Chemical modification of BW A4C has resulted in compounds, including the alpha-methyl analogues BW B218C and BW A360C and the hydroxyurea BW B70C, that retain high in vitro potency as selective 5-LO inhibitors and, compared to BW A4C, have a higher potency and longer duration of action in vivo. Members of both the hydroxamic acid and hydroxyurea series of 5-LO inhibitors are presently being considered as potential anti-asthma drugs.

Anaphylaxis↗
PubMed1990

Resource needs of an occupational health service to accommodate a hepatitis B vaccination programme.

The administrative, organizational and clinical commitment of an occupational health department to implement the DHSS recommendation for a hepatitis B vaccination programme for the health care workers in a District General Hospital was reviewed to evaluate the resource implications needed to accommodate the additional workload. The deficiencies observed in the existing DHSS guidance in implementing the plan are described. It is suggested that the Department of Health, while making future recommendations for vaccination, should be more precise in identifying those at risk, in describing the desired titre to be achieved after vaccination, and in describing the follow-up plan for those who accept the vaccination, those who refuse and those who do not seroconvert. The recommendation should describe the commitment of the Health Authorities and must include recommendations for appropriate and adequate resources to support such a programme. Vaccination for 1000 employees at risk required 4000 additional consultations necessitating 16 additional hours of occupational health commitment per week. Eighteen months after initiating the vaccination programme, 677 employees had accepted the vaccine. After receiving 3 vaccines 508 (75 per cent) recipients had protective seroconversion (anti-Hbs greater than 100 I.U.) and a further 61 (9 per cent) converted after the 4th injection, thereby offering protective immunity to 84 per cent of the recipients. During the period 84 (12.4 per cent) were lost to follow-up. Recommendations have been made to accommodate the additional commitment through the vaccination programme to standardize our care and prevent disruption of the existing service.

Health Plan Implementation↗
PubMed1990

Mortality associated with captopril and enalapril: a report from the DHSS Hypertension Care Computing Project.

In 1986, the Committee on Safety of Medicines published a report suggesting that enalapril may have an adverse effect on renal function. The prescription event monitoring scheme subsequently published figures on adverse drug reactions and mortality for patients treated with enalapril. They concluded that enalapril did not have an adverse effect on renal function and survival. Similar data were not available for captopril, as the drug was marketed before prescription event monitoring had been developed. In the Department of Health and Social Security (DHSS) Hypertension Care Computing Project (DHCCP), 368 hypertensive patients treated with captopril and 371 treated with enalapril were followed for an average of 3.1 and 1.6 years, respectively. Thirty-two patients died; none had renal failure as an underlying cause of death. The death rate was similar in both drug groups, at 17.5 (enalapril) and 24.0 (captopril) per 1000 patient-years. The present report shows that, for patients treated for high blood pressure, the relative risk of mortality with captopril compared with enalapril was 1.37, an insignificant difference (95% confidence interval 0.63, 2.98).

Acute Kidney Injury↗
PubMed1990

Consistent linkage of dominantly inherited osteogenesis imperfecta to the type I collagen loci: COL1A1 and COL1A2.

The segregation of COL1A1 and COL1A2, the two genes which encode the chains of type I collagen, was analyzed in 38 dominant osteogenesis imperfecta (OI) pedigrees by using polymorphic markers within or close to the genes. This was done in order to estimate the consistency of linkage of OI genes to these two loci. None of the 38 pedigrees showed evidence of recombination between the OI gene and both collagen loci, suggesting that the frequency of unlinked loci in the population must be low. From these results, approximate 95% confidence limits for the proportion of families linked to the type I collagen genes can be set between .91 and 1.00. This is high enough to base prenatal diagnosis of dominantly inherited OI on linkage to these genes even in families which are too small for the linkage to be independently confirmed to high levels of significance. When phenotypic features were compared with the concordant collagen locus, all eight pedigrees with Sillence OI type IV segregated with COL1A2. On the other hand, Sillence OI type I segregated with both COL1A1 (17 pedigrees) and COL1A2 (7 pedigrees). The concordant locus was uncertain in the remaining six OI type I pedigrees. Of several other features, the presence or absence of presenile hearing loss was the best predictor of the mutant locus in OI type I families, with 13 of the 17 COL1A1 segregants and none of the 7 COL1A2 segregants showing this feature.

Chromosomes, Human, Pair 17↗