Identification of non-amplifying CYP21 genes when using PCR-based diagnosis of 21-hydroxylase deficiency in congenital adrenal hyperplasia (CAH) affected pedigrees

Steroid 21-hydroxylase deficiency is among the most common inborn errors of metabolism in man. Characterization of mutations in the 21- hydroxylase gene (CYP21) has permitted genetic diagnosis, facilitated by the polymerase chain reaction (PCR). The most common mutation is conversion of an A or C at nt656 to a G in the second intron causing aberrant splicing of mRNA. Homozygosity for nt656G is associated with profoundly deficient adrenal cortisol and aldosterone synthesis, secondary hypersecretion of adrenal androgens, and a severe form of congenital adrenal hyperplasia (CAH) characterized by ambiguous genitalia and/or sodium wasting in newborns. During the course of genetic analysis of CYP21 mutations in CAH families, we and others have noticed a number of relatives genotyped as nt656G homozygotes, yet showing no clinical signs of disease. A number of lines of evidence have led us to propose that the putative asymptomatic nt656G/G individuals are incorrectly typed due to dropout of one haplotype during PCR amplification of CYP21. For prenatal diagnosis, we recommend that microsatellite typing be used as a supplement to CYP21 genotyping in order to resolve ambiguities at nt656.      

Interaction between rod and cone systems in dichoptic visual masking

The brightness of a brief flash of light is reduced by the suitable presentation of a second flash in an adjacent region of the visual field. This making effect (metacontrast) can be induced dichoptically, that is with the test flash presented to one eye and the masking flash to the other. By a suitable choice of wavelengths and conditioning field, the test flash may be arranged to effectively stimulate only rod receptors and the masking flash only cone receptor. A dichoptic masking effect is still obtained.     

Effects of cholinergic and adrenergic blocking agents on the activity of the eccrine sweat glands

1. The effects of blocking agents on the responsiveness of the cast' pad and human forearm sweat glands have been studied.2. Of the anti-adrenergic substances examined (dibenamine, phenoxybenzamine, bretylium, guanethidine and phentolamine) only high doses of guanethidine and phentolamine produced any consistent and significant measure of blockade, and small doses of atropine were as effective as these large doses of guanethidine or phentolamine.3. It is concluded from the blockade of chemical stimulation as well as transmission by these substances that (1) there are only cholinergic fibres innervating eccrine sweat glands, and (2) any inhibitory action by anti-adrenergic substances is due to interaction with cholinergic receptors in the glands.     

Impaired proliferative responses of peripheral blood B cells from splenectomized subjects to phorbol ester and ionophore.

The responses of peripheral blood B cells to mitogenic stimulation were examined in 12 splenectomized subjects without residual splenic function, as determined by pitted erythrocyte counts. These were compared to a group of healthy controls matched for age and sex. Polyclonal anti-immunoglobulin evoked a normal transient elevation in intracellular free Ca2+ in splenectomized subjects, thereby suggesting that the early events of the signal transduction pathway are not impaired. However, mitogenic stimulation by pre-treatment with phorbol ester and culture in presence of a calcium ionophore (Ionomycin) resulted in reduced uptake of 3H-thymidine and subsequent proliferation. Nevertheless, entry into the mitotic cycle, as assessed by expression of Ki67, was slightly, but not significantly impaired. Unlike in normal controls, where up to 7% of freshly-isolated B cells were Ki67+, almost no Ki67+ peripheral B cells were observed in splenectomized subjects. The data are consistent with the hypothesis that peripheral B cells in splenectomized subjects are in a reduced state of activation compared with normal controls and require additional growth factor stimulation before they can undergo mitosis.     

Coeliac disease, adenocarcinoma of jejunum and in situ squamous carcinoma of oesophagus

The development of both adenocarcinoma of the jejunum and in situ squamous carcinoma of the oesophagus in an adult coeliac patient is described. Good evidence that adenocarcinoma of jejunum occurs more frequently in patients with coeliac disease has recently become available though this association has been suggested for some time. While oesophageal carcinoma has long been associated with coeliac disease, in situ carcinoma of oesophagus has not been previously described in these circumstances. We feel that the risk of this complication, as calculated from published series, warrants a screening programme for oesophageal malignancy in adult coeliacs.     

Retinoic acid receptor beta variant‐related colonic hypoganglionosis

Retinoic acid receptor beta (RARB) variants are heavily linked to pathologies of neural crest cell migration. The purpose of this report is to present a 23‐month‐old male with the previously described R387C RARB gain‐of‐function variant whose gastrointestinal issues and long‐term constipation lead to the discovery of colonic hypoganglionosis. This case further delineates the pattern of malformation associated with RARB variants. The findings are also consistent with the known etiology of aganglionic colon due to failed neural crest cell migration.     

Defective potassium currents in ataxia telangiectasia fibroblasts

Similarities exist between the progressive cerebellar ataxia in ataxia telangiectasia (AT) patients and a number of neurodegenerative diseases in both mouse and man involving specific mutations in ion channels and/or ion channel activity. These relationships led us to investigate the possibility of defective ion channel activity in AT cells. We examined changes in the membrane potential of AT fibroblasts in response to extracellular cation addition and found that the ability of AT fibroblasts to depolarize in response to increasing concentrations of extracellular K⁺ is significantly reduced when compared with control fibroblasts. Electrophysiological measurements performed with a number of AT cell lines, as well as two matched sets of primary AT fibroblast cultures, reveal that outward rectifier K⁺ currents are largely absent in AT fibroblasts in comparison with control cells. These K⁺ current defects can be corrected in AT fibroblasts transfected with the full-length ATM cDNA. These data implicate, for the first time, a role for ATM in the regulation of K⁺ channel activity and membrane potential.     

Composition of the secretion from the eccrine sweat glands of the cat's foot pad

1. The sweat composition from the cat's foot pad was examined at various rates of secretion. Sodium pentobarbitone or chloralose anaesthesia were used.2. Cat's pad sweat contains lactate, glucose is almost absent, and the sodium and chloride concentrations increased with increasing sweat rate. In these respects the secretion resembles human eccrine sweat.3. The sodium, chloride, and potassium concentrations are much higher than in human sweat; also the potassium level decreased with increasing rate. Consequently, whereas human sweat is hypotonic with respect to the plasma, cat's pad sweat is slightly hypertonic with respect to the plasma even at low rates of secretion. In contrast to human sweat glands, which produce a slightly acidic secretion containing ammonia, cat's pad sweat glands produce an alkaline secretion containing bicarbonate. Also in contrast to human sweat, lactate levels decreased with increasing sweat rate.