Renal chloride channel, CLCN5, mutations in Dent's disease.

Dent's disease is an X-linked renal tubular disorder characterized by low-molecular-weight proteinuria, hypercalciuria, nephrocalcinosis, nephrolithiasis, and renal failure. Patients with Dent's disease may also suffer from rickets and other features of the renal Fanconi Syndrome. Patients may have mutations in the X-linked renal chloride channel gene, CLCN5, which encodes a 746-amino-acid protein with 12-13 transmembrane domains. We have investigated the 11 coding exons of CLCN5 for mutations in eight unrelated patients with Dent's disease. Leukocyte DNA was used for the polymerase chain reaction amplification of CLCN5 and the products analyzed for single-stranded conformational polymorphisms (SSCPs). Abnormal SSCPs were sequenced and revealed eight mutations. These consisted of three nonsense mutations (Arg34Stop, Arg648Stop, Arg704Stop), four deletions involving codons 40, 86, 157, and 241, and one acceptor splice consensus sequence mutation tgcag --> tgaag. The mutations were confirmed either by restriction endonuclease or sequence-specific oligonucleotide hybridization analysis. In addition, an analysis of 110 alleles from 74 unrelated normal individuals demonstrated that the DNA sequence changes were not common polymorphisms. All of the mutations predict truncated chloride channels that are likely to result in a functional loss. Thus, our findings expand the spectrum of CLCN5 mutations associated with Dent's disease and the results will help to elucidate further the functional domains of this novel chloride channel.

The Miller procedure for mobile flat feet.

We studied the long-term results of the Miller operation at a mean age of 13 years in 22 patients (38 feet) with persistently symptomatic mobile flat feet associated with an isolated naviculocuneiform break. At a mean of 12 years (3 to 27) after surgery, 84% of the feet had a satisfactory clinical result. We conclude that the Miller operation is a useful procedure for adolescent patients with persistently symptomatic flat feet with an isolated break at the naviculocuneiform joint.

Mapping of an NH2-terminal ligand binding site of the insulin receptor by alanine scanning mutagenesis.

Affinity labeling studies and mutational analyses have implicated the involvement of a predicted domain of the insulin receptor (L1, amino acids 1-119) in ligand binding. In order to obtain a higher resolution localization of this ligand binding site, we have performed alanine scanning mutagenesis of this domain. Alanine mutant cDNAs encoding a secreted recombinant insulin receptor extracellular domain were expressed transiently in adenovirus transformed human embryonic kidney cells and the affinity of the expressed receptor for insulin was determined. Mutation of 14 amino acids located in four discontinuous peptide segments to alanine was disruptive of insulin binding: Segment 1, amino acids 12-15; Segment 2, amino acids 34-44; Segment 3, amino acids 64-67; and Segment 4, amino acids 89-91. The quantitative contribution of the four segments to the free energy of insulin binding was 1 > 3 > 2 > 4. Of the 14 amino acids whose mutation compromised insulin binding, 3 are charged, 3 hydrophobic, 5 aromatic, and 3 are amides.

Hypoadrenal crisis caused by disseminated histoplasmosis.

We report a case of disseminated histoplasmosis presenting with acute renal impairment due to adrenal insufficiency. The finding of bilateral adrenal gland enlargement on abdominal ultrasound examination led to a diagnostic CT-guided adrenal biopsy. Prolonged therapy with amphotericin and itraconazole resulted in a clinical cure, although the patient still requires adrenal replacement therapy.

Cation-induced restoration of insulin action in insulin-desensitized HTC cells.

Insulin desensitization of amino acid uptake in HTC cells was induced by preincubation with 4 or 10 micrograms/ml insulin. Insulin binding after desensitisation was decreased by both insulin concentrations due to a 45-49% decrease in insulin receptor numbers. Desensitization with 4 micrograms/ml insulin increased the ED50 for half-maximal stimulation of amino acid uptake from 19.5 +/- 9.2 ng/ml in control cells to 84.0 +/- 8.3 ng/ml (P less than 0.0001). It also decreased the maximal insulin response of amino acid uptake from 1.40 +/- 0.10 to 1.14 +/- 0.10 nmol/mg protein, indicating the production of a mild postreceptor defect. Desensitization with 10 micrograms/ml insulin completely abolished this insulin response. When cellular receptors were down-regulated with 4 micrograms/ml insulin and restimulated with insulin in the presence of 0.03 mM ruthenium red (RR) or 10 mM Ca2+, both the insulin response and insulin binding were increased. Insulin binding was restored to levels comparable to those observed in control cells by an increase in receptor affinity. The ED50 of amino acid uptake decreased to 20.5 +/- 7.3 ng/ml insulin in the presence of RR and to 42.2 +/- 8.9 ng/ml in the presence of 10 mM Ca2+ (both P less than 0.0001 from down-regulated cells). In addition, the maximal insulin response increased from 1.14 +/- 0.10 to 1.40 +/- 0.10 and 1.45 +/- 0.10 nmol/mg protein, respectively. Preincubation with 10 micrograms/ml insulin prevented the effect of RR and Ca2+ on the recovery of insulin responses. These experiments suggest that insulin-desensitized cells undergo a progressive loss of their insulin response and that RR and Ca2+ provide useful reagents to investigate the mechanisms of this process because they can counteract the decrease in insulin response by increasing receptor affinity and receptor-effector coupling.

High affinity insulin binding and insulin receptor-effector coupling: modulation by Ca2+.

Insulin binding and insulin stimulated amino acid and glucose uptake were determined in cultured HTC hepatoma cells in the presence of Ca2+ and ruthenium red (RR) in order to further characterise the putative calcium binding site on the receptor. These ions increased insulin receptor high affinity binding and the sensitivity of these responses to insulin. The insulin concentration required to half-maximally stimulate amino acid uptake decreased significantly from 26.9 +/- 5.8 ng/ml to 6.0 +/- 1.3 ng/ml in the presence of 10 mM Ca2+ and to 1.3 +/- 0.5 ng/ml in the presence of RR. The effect of Ca2+ and RR was more pronounced on insulin stimulated glucose uptake. These agents also increased receptor-effector coupling, reducing the percentage of occupied receptors required for maximal insulin stimulation of amino acid uptake from 10.8% in control cells to 3.4 and 1.4% in the presence of Ca2+ and RR respectively. The receptor occupancy required to produce maximal insulin responses on glucose uptake decreased from 20% (control) to 3.8% (Ca2+ and RR). We hypothesize that since Ca2+ and RR have similar effects, that occupation of Ca2+ binding sites on the receptor produces a conformational change in the insulin receptor which increases insulin receptor affinity, insulin sensitivity and acts on an early post-receptor event responsible for coupling binding to insulin action.

Habitual dislocation of the patella in flexion.

Thirty-five patients with habitual dislocation of the patella in flexion were reviewed; eight were bilaterally affected. Each had undergone quadricepsplasty with an average follow-up of 6 years 9 months. Bands or contractures, most commonly in vastus lateralis, the iliotibial tract and rectus femoris were seen in each. Redislocation was seen in 12 knees. At review, 79% of the knees were normal. Quadriceps lengthening is an essential part of treatment and must be performed proximally. Causes for failure include reformation of contractures and failure to correct the initial abnormality fully.

The Gruca operation for congenital absence of the fibula.

An alternative to Syme's amputation for congenital absence of the fibula is described in this paper. Nine children have had the ankle reconstructed using the Gruca technique with a very satisfactory result in eight. This procedure is not suitable for every patient and in most unilateral cases the operation can only be regarded as an interim procedure because of progressive leg-length inequality. The decision to remove the foot may be delayed and it allows childhood to be spent without resort to prostheses. However, the procedure can be considered as the definitive operation in cases of bilateral deformity.

Encephalopathy in renovascular hypertension associated with the use of oral contraceptives.

Two female patients aged 19 years and 27 years presented with hypertensive encephalopathy and were subsequently found to have renal artery stenosis due to fibromuscular dysplasia. Both patients had had normal blood pressures recorded within the previous 6 months whilst taking the oral contraceptive pill. Their neurological state returned to normal with hypertensive control and in one case the hypertension was cured by dilatation of the renal artery stenosis by balloon angioplasty.

PIP: 2 cases reports are described of patients with renal artery stenosis who presented with hypertensive encephalopathy, normal blood pressures having been recorded within the previous 6 months while taking oral contraceptives (OCs). A 27-year-old woman, admitted to the hospital following 2 grand mal fits, had suffered from increasing headaches, nausea, and vomiting over the previous month. Her blood pressure had been elevated at 160/110 mmHg 1 week prior to admission but had been normal over previous 11 years while taking OCs (various formulations of combined estrogen and progestogen) which she had stopped taking 2 months previously. She was a nonsmoker. Her blood pressure was controlled with atenolol, nifedipine, and bendrofluazide, and her conscious level returned to normal with no further fits. An intravenous urogram revealed a small left kidney with a delayed nephrogram, and subsequent arteriography showed bilateral medial fibromuscular dysplasia with a narrow stenosis of the left renal artery. Attempted balloon angioplasty was unsuccessful due to arterial spasm. 4 months after presentation she became pregnant. Blood pressure was controlled with methyl dopa during pregnancy which progressed uneventfully to full term. In the 2nd case, a 19-year old girl became confused and suffered a grand mal convulsion. She had complained of headaches over the previous 3 days. Her blood pressure had been normal over the previous 6 months while taking Logynon (phased formulation of ethinylestradiol and levonorgestrel). She was a nonsmoker. On admission to the hospital, she suffered further generalized convulsions. Despite control of her convulsions with intravenous chlormethiazole, her blood pressure rose to 220/140 mmHg, and this was controlled with intravenous hydralazine and propranolol. The following day she was conscious and was changed to oral therapy. A renogram and DMSA scan showed normal sized kidneys, but there was evidence of decreased blood flow to the left kidney with an increased transit time. Renal arteriography showed a stenosis of the left renal artery, typical of intimal fibromuscular dysplasia, which was dilated by balloon angioplasty. Anti-hypertensive medication was withdrawn postoperatively, and her blood pressure has remained well controlled. In both of the cases the onset of hypertension was rapid with encephalopathy being the presenting feature. Hypertensive encephalopathy is well recognized as a presenting feature of renal transplant artery stenosis but not in cases of native renal artery stenosis. 1 of the patients had stopped using OCs 2 months before presentation, suggesting that although there may have been an association between OC use and the development of fibromuscular dysplasia, it could not be implicated in the mode of presentation.

Familial hyperinsulinemia complicated by extreme insulin resistance during pregnancy: a probable postreceptor defect.

Detailed studies of a family with hyperinsulinemia are reported. The index patient, a 30-yr-old woman with polycystic ovary syndrome, presented with gestational diabetes which was completely resistant to insulin in the presence of severe endogenous hyperinsulinemia. Sensitivity to insulin was regained after delivery. Therapy with cyproterone acetate and ethinyl estradiol for hirsutism exacerbated the hyperinsulinemia toward the levels occurring in pregnancy, with a concomitant deterioration of glucose tolerance. Five other members of her family also were found to have hyperinsulinemia together with high concentrations of circulating C-peptide. Antibodies to insulin and to insulin receptors were not detected, insulin antagonists were not increased, and insulin degradation in the circulation was normal. Insulin extracted from the patient's serum was identical to normal insulin by the criteria of Sephadex chromatography, placental membrane insulin receptor binding, and stimulation of 2-deoxyglucose uptake in isolated rat adipocytes. Although [125I]insulin binding to erythrocytes of all family members and to the patient's placental membranes was markedly reduced, binding to fibroblast cultures from the patient was normal. Insulin-stimulated glucose transport in these fibroblasts also was normal, but there was a mild (20%) reduction in the concentration of cytochalasin B-binding sites in erythrocyte ghosts. Insulin resistance in this family may be due to a partial defect distal to the insulin receptor. This is asymptomatic unless metabolic stresses (pregnancy or steroid administration) are superimposed.

Management of upper limb problems in arthrogryposis.

The management of upper limb problems in arthrogryposis multiplex congenita (AMC) is described on the basis of the author's own experience gained from the care of a large number of affected children. Emphasis is placed on evaluation of the disability by repeated testing and observation. In many cases, the deformities will be accepted and improvements in function will be gained by orthoses or attention to details of seating, dressing, and toileting. Surgery is indicated in some cases, especially at the elbow, to obtain mobility, flexor power, or both. Arthrodesing the wrist is also useful in some cases. When surgery is indicated, it is often desirable to rearrange all three levels--shoulder, elbow, and wrist.

Reversible renal failure due to isolated renal sarcoidosis.

Renal impairment in sarcoidosis is usually due to hypercalcaemia and nephrocalcinosis but can also be caused by granulomatous nephritis or interstitial nephritis without sarcoid granulomata. A variety of types of glomerulonephritis have also been described in sarcoidosis but these rarely cause impaired renal function. Renal failure as an isolated manifestation of sarcoidosis is uncommon. A 66-year-old woman presented with a 1-year history of lethargy, polyuria and nocturia. Clinical examination was unremarkable and she had impaired renal function (urea 18 mmol/l (108 mg%) and creatinine 380 mumol/l (4.3 mg%)). As her kidneys were normal in size, she underwent renal biopsy, which revealed granulomatous interstitial nephritis. Reevaluation showed no other evidence of sarcoidosis and she had impaired urinary acidification and concentrating capacities. Therapy with corticosteroids produced a marked improvement in symptoms and renal function. This case confirms the view that granulomatous sarcoid nephritis is steroid sensitive and that full recovery can be expected provided interstitial fibrosis and scarring do not occur.

Reciprocal modulation of insulin and insulin-like growth factor-I receptor affinity by calcium.

In contrast to its stimulation of insulin binding to human placental membranes, calcium inhibited the binding of insulin-like growth factor-I. The effects on receptors for both peptides were half-maximal at 2 mM calcium, and were entirely due to alterations in high affinity binding sites for the respective ligands. Calcium decreased the affinity of insulin-like growth factor-I sites, while stimulating the expression of high affinity insulin sites. Competition by each peptide at the receptor for the other peptide was enhanced by calcium. Modulation by calcium might provide a mechanism to amplify functional differences between the two structurally similar receptors.

The 1960s epidemic of arthrogryposis multiplex congenita: a survey from the United Kingdom, Australia and the United States of America.

Arthrogryposis multiplex congenita is believed to be a specific clinical entity which is aetiologically unrelated to the "arthrogryposis-like" deformities of known neurological diseases such as myelomeningocele and myelodysplasia. The observation that the condition appeared to be three times as common in Melbourne, Australia, as in four centres in the United Kingdom (Wynne-Davies and Lloyd-Roberts 1976), prompted this survey of 132 patients: 73 from the United Kingdom, 34 from Australia and 25 from Wilmington, Delaware, USA. The survey aimed to established the same criteria for diagnosis in the three countries and to search for prenatal and genetic aetiological factors. It was shown that all centers treated more newborn children with this disorder during the 1960s than either before or after that period. All cases were sporadic and there was no family association with talipes equinovarus, congenital dislocation of the hip or hereditary neuromuscular disease. "Environmental" findings from all three centers were similar and it was concluded that arthrogryposis multiplex cogenita is a non-genetic disease of early pregnancy, associated with a variety of unfavourable intra-uterine factors. In addition, an unknown but possibly viral environmental agent may have been present to a significant extent only during recent decades and is now declining.