Functional expression and properties of the human skeletal muscle sodium channel

Full-length deoxyribonucleic acid, complementary (cDNA) constructs encoding the-subunit of the adult human skeletal muscle Na⁺ channel, hSkM1, were prepared. Functional expression was studied by electrophysiological recordings from cRNA-injectedXenopus oocytes and from transiently transfected tsA201 cells. The Na⁺ currents of hSkM1 had abnormally slow inactivation kinetics in oocytes, but relatively normal kinetics when expressed in the mammalian cell line. The inactivation kinetics of Na⁺ currents in oocytes, during a depolarization, were fitted by a weighted sum of two decaying exponentials. The time constant of the fast component was comparable to that of the single component observed in mammalian cells. The block of hSkM1 Na⁺ currents by the extracellular toxins tetrodotoxin (TTX) and -conotoxin (CTX) was measured. The IC₅₀ values were 25 nM (TTX) and 1.2 M (CTX) in oocytes. The potency of TTX is similar to that observed for the rat homolog rSkM1, but the potency of CTX is 22-fold lower in hSkM1, primarily due to a higher rate of toxin dissociation in hSkM1. Single-channel recordings were obtained from outside-out patches of oocytes expressing hSkM1. The single-channel conductance, 24.9 pS, is similar to that observed for rSkM1 expressed in oocytes.     

Mouse homologues of the human AZF candidate gene RBM are expressed in spermatogonia and spermatids, and map to a Y chromosome deletion interval associated with a high incidence of sperm abnormalities

An RNA-binding motif (RBM) gene family has been identified on the human Y chromosome that maps to the same deletion interval as the 'azoospermia factor' (AZF). We have identified the homologous gene family (Rbm) on the mouse Y with a view to investigating the proposal that this gene family plays a role in spermatogenesis. At least 25 and probably >50 copies of Rbm are present on the mouse Y chromosome short arm located between Sry and the centromere. As in the human, a role in spermatogenesis is indicated by a germ cell-specific pattern of expression in the testis, but there are distinct differences in the pattern of expression between the two species. Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are female due to a position effect resulting in non-expression of Sry ; sex-reversing such mice with an Sry transgene produces males with a high incidence of abnormal sperm, making this the third deletion interval on the mouse Y that affects some aspect of spermatogenesis. Most of the copies of Rbm map to this deletion interval, and the Yd1males have markedly reduced Rbm expression, suggesting that RBM deficiency may be responsible for, or contribute to, the abnormal sperm development. In man, deletion of the functional copies of RBM is associated with meiotic arrest rather than sperm anomalies; however, the different effects of deletion are consistent with the differences in expression between the two species.      

Distribution of mutations in the PEX gene in families with X-linked hypophosphataemic rickets (HYP)

Mutations in the PEX gene at Xp22.1 (phosphate-regulating gene with homologies to endopeptidases, on the X-chromosome), are responsible for X-linked hypophosphataemic rickets (HYP). Homology of PEX to the M13 family of Zn2+ metallopeptidases which include neprilysin (NEP) as prototype, has raised important questions regarding PEX function at the molecular level. The aim of this study was to analyse 99 HYP families for PEX gene mutations, and to correlate predicted changes in the protein structure with Zn2+ metallopeptidase gene function. Primers flanking 22 characterised exons were used to amplify DNA by PCR, and SSCP was then used to screen for mutations. Deletions, insertions, nonsense mutations, stop codons and splice mutations occurred in 83% of families screened for in all 22 exons, and 51% of a separate set of families screened in 17 PEX gene exons. Missense mutations in four regions of the gene were informative regarding function, with one mutation in the Zn2+-binding site predicted to alter substrate enzyme interaction and catalysis. Computer analysis of the remaining mutations predicted changes in secondary structure, N-glycosylation, protein phosphorylation and catalytic site molecular structure. The wide range of mutations that align with regions required for protease activity in NEP suggests that PEX also functions as a protease, and may act by processing factor(s) involved in bone mineral metabolism.      

Untersuchungen über die elektrophoretische Wanderungsgeschwindigkeit kompletter und inkompletter A-, B- und Rh (D)-Antikörper

Medical Microbiology and Immunology - In der Säulen-Elektrophorese-Apparatur nachSvensson mit äthanolisierter Cellulose nachFlodin u.Kupke als Trägerstoff wurden sechs Seren von...     

Use of the PATH Alliance database to measure adherence to IDSA guidelines for the therapy of candidemia

Candidemia is an increasing complication of the care of complex patients. Adherence to Infectious Diseases Society of America (IDSA) guidelines for the treatment of candidemia was investigated to assess the impact of compliance on outcomes of therapy. Data on the epidemiology, diagnosis, and treatment of patients with invasive fungal infections (IFIs) was extracted from the PATH Alliance registry, a prospective, multicenter, observational database of invasive fungal infections. Patients with proven candidemia were evaluated for adherence to the IDSA guidelines in terms of choice, dosage, and duration of antifungal therapy. Removal of central venous catheters and time to treatment initiation were assessed. Four-week survival data were compared. Of the 418 patients with candidemia who were included in the study, 361 patients with the necessary data sets were identified, of whom 262 (72.6%) were treated within the IDSA guidelines for the treatment of candidemia (IDSA group); the remaining 99 (27.4%) patients received treatment different from the guidelines (non-IDSA group). Kaplan-Meier (KM) survival analysis for patients in the IDSA and non-IDSA group showed mortality rates of 21.9 and 13.6%, respectively; the difference between the two groups was not statistically significant (P = 0.093). Following the exclusion of patients requiring mechanical ventilation or acute cardiac support, the modified survival KM curves were similar between the two groups. Significantly more patients in the IDSA group required mechanical ventilation and tunneled central catheters, had a concomitant IFI, and received caspofungin. The duration of treatment and inappropriate dosing did not appear to have had a significant impact on survival. Most of the deviations from IDSA guidelines were due to the inappropriate duration and dosing of therapy. No significant difference in mortality was noted between the IDSA and non-IDSA groups. The basis of these differences merit further study. Presented in part at the 44th Annual Meeting of Infectious Disease Society of America, Toronto, Canada, 2006.     

Erfolgreiche Behandlung einer thyreotoxischen Krise durch kontinuierliche Plasmapherese am Blutzellseparator

Zusammenfassung Bei einem 26jährigen Patienten im thyreotoxischen Koma erwies sich die kontinuierliche Plasmapherese am IBM-Blutzellseparator klinisch als akut wirksame Krisentherapie. Schon während der Plasmapherese mit Austausch von 51 Plasma in 3 1/2 h wurde der Patient aus einem tiefen Koma heraus ansprechbar. Mit den 51 Plasma wurden 633 µg Thyroxin (T₄) und 13,6 µg Trijodthyronin (T₃) entzogen. Dies führte erstaunlicherweise nicht zu einem Abfall der Gesamtspiegel von T₄ und T₃ im Serum, ein Befund, der als Hinweis auf einen raschen Rückstrom aus dem Gewebe in die Blutbahn zu interpretieren ist. Die freien Schilddrüsenhormonspiegel nahmen dagegen signifikant ab, erkennbar am Abfall der Werte des T₃-in vitro-Tests und der T₄- und T₃-Ausscheidung im Urin. Diese Befunde zeigen auf, daß neben dem Entzug von Schilddrüsenhormon vor allem die Zufuhr freier Bindungsstellen für Schilddrüsenhormon mit dem Spenderplasma bei der Behandlung der thyreotoxischen Krise von Bedeutung ist.Mit Unterstützung der Sonderforschungsbereiche SFB 51¹ und SFB 37²     

Case report: glomus tumor of the colon

Glomus tumors are tumors of pericytic origin and are usually found in the distal extremities. Glomus tumors have rarely been reported in viscera. The authors report a glomus tumor of the colon that caused rectal bleeding in a 40-yr-old man and was biopsied and excised endoscopically. The histology and immunohistochemical profile of the tumor are described and the literature on visceral glomus tumors is reviewed.     

Amnesic effects of bilateral lesions placed in the hyperstriatum ventrale of the chick after imprinting

Summary The purpose of this study was to investigate whether bilateral lesions to a part of the hyperstriatum ventrale (IMHV) impair retention if they are placed after chicks have been imprinted. Domestic chicks were hatched and reared in darkness and exposed to an imprinting (training) stimulus for 2 h commencing 22 h post hatch. The chicks were then anaesthetised and bilateral lesions placed in IMHV (N = 16) birds, hyperstriatum accessorium (HA; N = 16) or the lateral part of the cerebral hemispheres (LCA; N = 16). Forty-eight sham-operated chicks served as controls. Chicks were returned to the dark incubator, and, 15–20 h after the operation, their approach towards the training stimulus and to a second novel stimulus was measured. The controls and the chicks with lesions in HA and LCA showed a strong preference for the training stimulus and hence a high level of retention. The preferences of these three experimental groups did not differ significantly from one another. The mean preference of chicks with lesions in IMHV was significantly less than that of the sham-operated controls (P<0.01) and of chicks lesioned in HA (P<0.05). Bilateral lesions to IMHV therefore selectively impair retention of a preference acquired through imprinting. This impairment is unlikely to be a non-specific consequence of defective sensory processing or motor performance because the four groups did not differ from each other in (i) the time taken accurately to peck a rocking bead, (ii) the accuracy of pecking millet seeds and (iii) the performance of a simultaneous visual discrimination task involving heat reinforcement.Supported by grants from the Science Research Council, the Leverhulme Trust, the Wellcome Trust and FAPESP (Brazil)     

Monocyte-mediated growth control and the induction of tumor cell death

In the present article a hypothesis is put forward and supporting data are referred that explain the elimination of tumorigenic cells as a consequence of their failure to comply with the rules of ubiquitous negative growth control mechanisms involving among others also mononuclear phagocytes as effector cells. This hypothesis does not invoke the recognition of altered cell surface structures on tumorigenic cells as the basis for discriminating them from normal cells and thus avoids one of the most irritating problems of hypothetical tumor defense mechanisms involving the recognition of spontaneously arising tumor cells as 'non-self' by immunologic effector cells.