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Biomedical subjects

A C Allen

Publications and source records attributed to A C Allen.

At least 91 records · Page 5Linked to original sources
PubMed1974

Familial congenital absence of adrenal glands; evaluation of glucocorticoid, mineralocorticoid, and estrogen metabolism in the perinatal period.

The patient was the fourth of affected male siblings. Cortisol (1.3 micrograms per cent), cortisone (9.6), and corticosterone sulfate (0.1) concentrations were low in cord blood. The larger amount of cortisone may have originated from maternal cortisol. Aldosterone was undetectable in cord blood, indicating lack of fetal secretion or maternofetal transfer. Unexpectedly normal concentrations of 11-deoxycorticosterone (DOC) sulfate in cord serum could represent maternal transfer of DOC, with subsequent fetal sulfurylation. Low estrone and estradiol concentrations in maternal and cord serum were consistent with absence of the fetal adrenals. Despite the low levels of the steroids, the propositus had a normal lecithin-sphingomyelin ratio at 38 weeks' gestation. Circulatory insufficiency developed within half an hour after birth and responded to gluco- and mineralocorticoid therapy. The three untreated siblings died between 14 and 67 hours of age. It is evident that early recognition of this condition may be lifesaving.

Adrenal Gland Diseases↗
PubMedDate not supplied

Structural features of IgA molecules which contribute to IgA nephropathy.

IgA nephropathy (IgAN) is characterised by the mesangial deposition of polymeric IgA1 (pIgA1). pIgA1 production is reduced in the mucosal immune system in IgAN and increased in the marrow; this switch may be secondary to a defect in gammadeltaT cell control of IgA production. However this does not explain the mechanism by which pIgA1 deposits in the mesangium. There is no direct evidence that classical immune complex deposition occurs in IgAN and alternative mechanisms resulting from physicochemical abnormalities of the IgA1 molecule, particular altered glycosylation, have been proposed. IgA1 has a distinctive hinge region which is a site for O-glycosylation. There is reduced terminal galactose on the hinge region O-glycans of circulating IgA1 in IgAN, perhaps due to a defect in B cell beta1,3 galactosyltransferase. A concomitant O-glycan defect in mesangial IgA1 has not yet been proven. Altered hinge O-glycosylation may have substantial impact on the quaternary structure of the IgA1 molecule influencing its capacity to interact with matrix proteins, IgA receptors on mesangial cells and leucocytes, and complement; it may therefore play a key role in the pathogenesis of mesangial deposition of IgA1 and subsequent glomerular injury in IgAN.

Amino Acid Sequence↗
PubMedDate not supplied

Methodological approaches to the analysis of IgA1 O-glycosylation in IgA nephropathy.

IgA nephropathy (IgAN) is a common form of glomerulonephritis in which IgA1 molecules deposit in the renal mesangium, leading to progressive glomerular inflammatory injury in a significant proportion of patients. The mechanisms underlying the pathogenesis of IgAN remain poorly understood, but altered O-glycosylation, a physicochemical abnormality of IgA1 observed in these patients, may be a contributory factor. Although many studies have reported aberrant IgA1 O-glycosylation in IgAN, the precise structural nature of the defect remains to be fully characterised, and analysis of IgA1 O-glycans has proved technically challenging. Three main strategies have been employed: lectin binding to the O-glycans in situ on the whole IgA1 molecule; mass spectroscopy of isolated O-glycosylated glycopeptides; and size/charge separation of free O-glycans released from IgA1. In this review, the basic principles, strengths and weaknesses of each of these methodological approaches are considered, together with a summary of the data obtained from their use. One of the common criticisms of many studies of IgA1 O-glycosylation is the method of IgA1 purification employed, and therefore, this issue is also critically discussed.

Chromatography, Affinity↗