A genetic defect resulting in mild low-renin hypertension

Severe low-renin hypertension has few known causes. Apparent mineralocorticoid excess (AME) is a genetic disorder that results in severe juvenile low-renin hypertension, hyporeninemia, hypoaldosteronemia, hypokalemic alkalosis, low birth weight, failure to thrive, poor growth, and in many cases nephrocalcinosis. In 1995, it was shown that mutations in the gene (HSD11B2) encoding the 11beta-hydroxysteroid dehydrogenase type 2 enzyme (11beta-HSD2) cause AME. Typical patients with AME have defective 11beta-HSD2 activity, as evidenced by an abnormal ratio of cortisol to cortisone metabolites and by an exceedingly diminished ability to convert [11-3H]cortisol to cortisone. Recently, we have studied an unusual patient with mild low-renin hypertension and a homozygous mutation in the HSD11B2 gene. The patient came from an inbred Mennonite family, and though the mutation identified her as a patient with AME, she did not demonstrate the typical features of AME. Biochemical analysis in this patient revealed a moderately elevated cortisol to cortisone metabolite ratio. The conversion of cortisol to cortisone was 58% compared with 0-6% in typical patients with AME whereas the normal conversion is 90-95%. Molecular analysis of the HSD11B2 gene of this patient showed a homozygous C-->T transition in the second nucleotide of codon 227, resulting in a substitution of proline with leucine (P227L). The parents and sibs were heterozygous for this mutation. In vitro expression studies showed an increase in the Km (300 nM) over normal (54 nM). Because approximately 40% of patients with essential hypertension demonstrate low renin, we suggest that such patients should undergo genetic analysis of the HSD11B2 gene.     

Effect of buthionine sulfoximine, a synthesis inhibitor of the antioxidant glutathione, on the murine nigrostriatal neurons

This study analyzed the effects of acute systemic treatment with buthionine sulfoximine (BSO), a synthesis inhibitor of the antioxidant reduced glutathione (GSH), on dopaminergic neurons of the murine nigrostriatal pathway. Part 1 of the study established a dose-response curve and the temporal pattern of GSH loss and recovery in the substantia nigra and striatum following acute BSO treatment. Part 2 of the study determined the effect of acute BSO treatment on the morphology and biochemistry of nigrostriatal neurons. We found that decreases in GSH levels had profound morphological effects, including decreased catecholamine fluorescence per cell, increased levels of lipid peroxidation and lipofuscin accumulation, and increased numbers of dystrophic axons in dopaminergic neurons of the nigrostriatal pathway. However, no measurable effects were observed in biochemical levels of either dopamine or its metabolites. These changes mimic those that have been reported to occur in the nigrostriatal system of rodents with advancing age. Our data suggest that reduction of GSH via BSO treatment results in the same types of nigrostriatal degenerative effects that occur during the aging process and consequently is a good model system for examining the role of GSH in protecting this area of the brain against the harmful effects of age-related oxidative stress.     

Expression and purification of large nebulin fragments and their interaction with actin

cDNA clones encoding mouse skeletal muscle nebulin were expressed in Escherichia coli as thioredoxin fusion proteins and purified in the presence of 6 M urea. These fragments, called 7a and 8c, contain 28 and 19 of the weakly repeating approximately 35-residue nebulin modules, respectively. The nebulin fragments are soluble at extremely high pH, but aggregate when dialyzed to neutral pH, as assayed by centrifugation at 16,000 x g. However, when mixed with varying amounts of G-actin at pH 12 and then dialyzed to neutral pH, the nebulin fragments are solubilized in a concentration-dependent manner, remaining in the supernatant along with the monomeric actin. These results show that interaction with G-actin allows the separation of insoluble nebulin aggregates from soluble actin-nebulin complexes by centrifugation. We used this property to assay the incorporation of nebulin fragments into preformed actin filaments. Varying amounts of aggregated nebulin were mixed with a constant amount of F-actin at pH 7.0. The nebulin aggregates were pelleted by centrifugation at 5200 x g, whereas the actin filaments, including incorporated nebulin fragments, remained in the supernatant. Using this assay, we found that nebulin fragments 7a and 8c bound to actin filaments with high affinity. Immunofluorescence and electron microscopy of the actin-nebulin complexes verified that the nebulin fragments were reorganized from punctate aggregates to a filamentous form upon interaction with F-actin. In addition, we found that fragment 7a binds to F-actin with a stoichiometry of one nebulin module per actin monomer, the same stoichiometry we found in vivo. In contrast, 8c binds to F-actin with a stoichiometry of one module per two actin monomers. These data indicate that 7a can be incorporated into actin filaments to the same extent found in vivo, and suggest that shorter fragments may not bind actin filaments in the same way as the native nebulin molecule.     

Treatment of onychomycosis and tinea pedis with intermittent itraconazole therapy

A 40-year-old woman had a 10-year history of dermatophyte-related toenail onychomycosis (tinea unguium) and dry-type tinea pedis, which had failed to respond to previous therapy with topical antifungal agents or oral griseofulvin. The patient was successfully treated with four cycles of intermittent itraconazole therapy (that is, 400 mg/d for 1 week per month for 4 months). At the end of this time, the tinea pedis had resolved and the onychomycosis improved significantly after four cycles were completed. Twelve months after the onset of therapy, both conditions had resolved completely according to both clinical and mycologic criteria. Itraconazole was well tolerated, with no side effects reported. These observations suggest that itraconazole intermittent dosing is a highly effective therapy for the treatment of onychomycosis caused by dermatophyte organisms, because it provides a high cure rate after only a short course of therapy.     

Circadian rhythm in the response of central 5-HT1A receptors to 8-OH-DPAT in rats

Professional practice changes in the operating room have led to the development of a new role for nurses--as surgical assistants. Essentially, the surgical assistant nurse helps ensure the patient's safety while providing technical and clinical assistance to the surgeon in such areas as exposing and manipulating tissues, suturing fascia and using various specialized instruments. The surgical assistant nurse function is being implemented through a pilot project at the Institut de cardiologie de Montréal. Developed by representatives of the nursing and surgical departments there, the project was approved by the Collège des médecins du Québec in April 1995 and subsequently by the institute's council of physicians, dentists and pharmacists. It has also gained recognition from the Ordre des infirmières et infirmiers du Québec (OIIQ). The pilot project incorporated a 186-hour training program, which was delivered from May to September 1995 according to three distinct learning modules: maintenance of a safe environment for the patient, clinical assistance and technical assistance. A tutorial approach to learning included individual and team work, simulation exercises, technical courses, lab work and practical training in the operating room. At the end of the training program, two surgical assistant nurses began practising in their new role. An evaluation of the project will be performed in September 1996.     

On the antioxidant activity of melatonin

Melatonin has been widely reported to be an effective antioxidant. Studies of its ability to inhibit the autoxidation of lipids in homogeneous solution and in model heterogeneous systems show that melatonin is not a peroxyl radical trapping antioxidant. In contrast, melatonin can inhibit metal ion-catalyzed oxidation processes.