Difference in allelic expression of the CLCN1 gene and the possible influence on the myotonia congenita phenotype

Mutations in the CLCN1 gene, encoding a muscle-specific chloride channel, can cause either recessive or dominant myotonia congenita (MC). The recessive form, Becker's myotonia, is believed to be caused by two loss-of-function mutations, whereas the dominant form, Thomsen's myotonia, is assumed to be a consequence of a dominant-negative effect. However, a subset of CLCN1 mutations can cause both recessive and dominant MC. We have identified two recessive and two dominant MC families segregating the common R894X mutation. Real-time quantitative RT-PCR did not reveal any obvious association between the total CLCN1 mRNA level in muscle and the mode of inheritance, but the dominant family with the most severe phenotype expressed twice the expected amount of the R894X mRNA allele. Variation in allelic expression has not previously been described for CLCN1, and our finding suggests that allelic variation may be an important modifier of disease progression in myotonia congenita.     

Adult-onset type II citrullinemia and idiopathic neonatal hepatitis caused by citrin deficiency: involvement of the aspartate glutamate carrier for urea synthesis and maintenance of the urea cycle

Citrin is a mitochondrial aspartate glutamate carrier primarily expressed in the liver, heart, and kidney. We found that adult-onset type II citrullinemia is caused by mutations in the SLC25A13 gene that encodes for citrin. In this report, we describe the frequency of SLC25A13 mutations, the roles of citrin as a member of the urea cycle and as a member of the malate-aspartate shuttle, the relationship between its functions and symptoms of citrin deficiency, and therapeutic issues.     

Blockade of Ca2+‐activated K+ channels in T cells: an option for the treatment of multiple sclerosis?

Voltage- and Ca(2+)-dependent K(+) channels in the membrane of both T and B lymphocytes are important for the cellular immune response. In the current issue of the European Journal of Immunology, Reich et al. demonstrate that selective blockade of the intermediate-conductance Ca(2+)-activated K(+) channel (the IK channel encoded by the KCNN4 gene) prevents cytokine production in the spinal chord and ameliorates the development of EAE caused by injection of myelin oligodendrocyte glycoprotein (MOG)(35-55) in mice. These data renew the focus on the IK channel as a potential target for the development of new immune-suppressant drugs for the treatment of autoimmune diseases.     

Lack of FasL expression in cultured human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells have been proposed to play a part in maintaining the eye as an immune privileged organ. However, our knowledge of the implicated mechanism is still sparse. Fas ligand (FasL) expression of RPE cells is generally recognized to be essential for the immune privilege of the eye, but due to contradictory published results, it is unclear whether RPE cells express this molecule. The purpose of this study was to investigate the expression of FasL in RPE cells in vitro and in vivo. Cultured human fetal and adult RPE cells were examined by flow cytometry, Western blotting, RT-PCR and RNase Protection assay for FasL expression. Additionally, sections of ocular tissue were stained for FasL by immunohistochemistry. None of the used methods indicated FasL expression in cultured fetal or adult RPE cells of various passages. However, RPE cells in vivo, as judged from tissue sections, were positive for FasL, indicating a discrepancy between RPE cells in vitro and in vivo with regard to this molecule.     

Transcription from the gene encoding the herpesvirus entry receptor nectin-1 (HveC) in nervous tissue of adult mouse

Hepatitis C virus core protein, in addition to being a component of the viral capsid, has a number of regulatory functions. Here we showed two bodies of evidence indicating that a fraction of the core protein species is a substrate of the ubiquitin (Ub)-proteasome pathway of targeted proteolysis. First, the core protein processing the C-terminal hydrophobic region is metabolically unstable, and incubation with a proteasome inhibitor led to a significant accumulation of the protein. Second, an in vivo ubiquitylation assay indicates conjugation of multi-Ub chain to the unstable core protein. In contrast, a stable form of core protein, p21, is also able to be ubiquitylated, but it links to a single or only a few Ub moiety. Therefore, processing event(s) at the C-terminal hydrophobic domain of HCV core protein may affect the ubiquitylation pathway, particularly the efficiency of the multi-Ub chain assembly, resulting in stable, matured core proteins.     

Distinct protein interaction domains and protein spreading in a complex centromere

Fission yeast (Schizosaccharomyces pombe) centromeres are composed of large (40-100 kb) inverted repeats that display heterochromatic features, thus providing a good model for higher eukaryotic centromeres. The association of three proteins that mediate region-specific silencing across centromere 1 has been mapped by quantitative chromatin immunoprecipitation. Swi6 and Chp1 are confined to the flanking outer repeats and Swi6 can spread across at least 3 kb of extraneous chromatin in cen1. In contrast, Mis6 coats the inner repeats and central core. tRNA genes demarcate this transition zone. These analyses clearly define two distinct domains within this complex centromere which interact with different proteins.     

An electrical admittance based index of thoracic intracellular water during head-up tilt in humans

During 50 degrees head-up tilt (HUT), the number of erythrocytes within the thorax has been shown to be reduced by approximately 25% and this level is retained during a maintained tilt, whilst that in the thigh increases by approximately 70%. To evaluate whether the electrical admittance of intracellular water (ICW) may be used to monitor this redistribution of red cells in humans, we determined the regional difference in the reciprocal value of the impedance at 1.5 and 100 kHz for the thorax (thoraxICW) and for the leg (legICW). In ten subjects all variables remained unchanged during head-down tilt but during HUT, presyncopal symptoms were induced in eight subjects after a mean of 27 (SEM 7) min as mean heart rate dropped from 85 (SEM 4) to 66 (SEM 3) beats x min(-1), mean arterial blood pressure from 80 (SEM 3) to 60 (SEM 5) mmHg, and mean oxygen saturation of venous blood from 76 (SEM 2)% to 73 (SEM 3)% (P < 0.05). The mean haematocrit increased from 50 (SEM 5)% to 52.5 (SEM 3.5)% (P < 0.01) and mean central venous pressure decreased during tilting (from a mean of 1 (SEM 1) to a mean of -1 (SEM 1) mmHg; P < 0.05) and returned to value at rest during the maintained tilt. Mean thoracic impedances increased by 7.0 (SEM 1.0) ohms (1.5 kHz) and 5.4 (SEM 1.2) ohms (100 kHz), and mean leg impedances decreased by 9.3 (SEM 1.2) ohms (1.5 kHz) and 3.1 (SEM 1.0) ohms (100 kHz) (P < 0.01). Mean thoraxICW decreased at 40 degrees HUT and remained reduced by 11 (SEM 2) S x 10(-4) (P < 0.05) until the presyncopal symptoms developed, at which time it was lower by 16 (SEM 2) S x 10(-4) (P < 0.01). Mean legICW increased from 97 (SEM 15) to 99 (SEM 15) S x 10(-4) (P = 0.08) during HUT but decreased during maintained tilt (to 94 (SEM 15) S x 10(-4); P < 0.05). The results suggested that during HUT, the difference in electrical admittance at a high and a low frequency current reflects the reduced number of red cells within the thorax.     

Distribution of whaleworm (Anisakis simplex,Nematoda, Ascaridoidea) L3 larvae in three species of marine fish; saithe (Pollachius virens (L.)), cod (Gadus morhua L.) and redfish (Sebastes marinus (L.)) from Norwegian waters

The frequency distribution of Anisakis simplex L3 larvae between host tissues was investigated in three host species: saithe, cod and redfish. Fish were sampled from Norwegian coastal waters and examined for the presence of A. simplex in muscle and viscera. In all three of the host species, A. simplex larvae were most frequently detected in the viscera; the percentages of total infection for saithe, cod and redfish were 99.6%, 97.8% and 88.0%, respectively. In general, the distribution patterns of A. simplex L3 between muscle and viscera were not significantly affected by host size. The observations that distributions vary between species and are not affected by host size do not support an earlier hypothesis which states that A. simplex L3 distributions are determined by an optimal pre-encapsulation migratory distance within host tissues. In contrast, it is suggested that A. simplex L3 distributions are governed by the conditions encountered within host tissues, and are possibly related to the availability of nutrients. Received: 9 July 1997 / Accepted: 15 September 1997     

Muscle fibre type,efficiency, and mechanical optima affect freely chosen pedal rate during cycling

This study investigated the variation in freely chosen pedal rate between subjects and its possible dependence on percentage myosin heavy chain I (%MHC I) in m. vastus lateralis, maximum leg strength and power, as well as efficiency. Additionally, the hypothesis was tested that a positive correlation exists between percentage MHC I and efficiency at pre-set pedal rates but not at freely chosen pedal rate. Twenty males performed cycling at low and high submaximal power output ( approximately 40 and 70% of the power output at which maximum oxygen uptake (VO(2max)) was attained at 80 r.p.m.) with freely chosen and pre-set pedal rates (61, 88, and 115 r.p.m.). Percentage MHC I as well as leg strength and power were determined. Freely chosen pedal rate varied considerably between subjects: 56-88 r.p.m. at low and 61-102 r.p.m. at high submaximal power output. This variation was only partly explained by percentage MHC I (21-97%) as well as by leg strength and power. Interestingly, %MHC I correlated significantly with the pedal rate at which maximum peak crank power occurred (r = -0.81). As hypothesized, %MHC I and efficiency were unrelated at freely chosen pedal rate, which was in contrast to a significant correlation found at pre-set pedal rates (r = 0.61 and r = 0.57 at low and high power output, respectively). Conclusions: Subjects with high percentage MHC I chose high pedal rates close to the pedal rates at which maximum peak crank power occurred, while subjects with low percentage MHC I tended to choose lower pedal rates, favouring high efficiency. Nevertheless, the considerable variation in freely chosen pedal rate between subjects was neither fully accounted for by percentage MHC I nor by leg strength and power. Previously recognized relationships between percentage Type I ( approximately %MHC I) and efficiency as well as between pedal rate and efficiency were confirmed for pre-set pedal rates, but for freely chosen pedal rate, these variables were unrelated.