Dystrophin and utrophin influence fiber type composition and post-synaptic membrane structure

The X-linked muscle wasting disease Duchenne muscular dystrophy is caused by the lack of dystrophin in muscle. Protein structure predictions, patient mutations, in vitro binding studies and transgenic and knockout mice suggest that dystrophin plays a mechanical role in skeletal muscle, linking the subsarcolemmal cytoskeleton with the extracellular matrix through its direct interaction with the dystrophin-associated protein complex (DAPC). Although a signaling role for dystrophin has been postulated, definitive data have been lacking. To identify potential non-mechanical roles of dystrophin, we tested the ability of various truncated dystrophin transgenes to prevent any of the skeletal muscle abnormalities associated with the double knockout mouse deficient for both dystrophin and the dystrophin-related protein utrophin. We show that restoration of the DAPC with Dp71 does not prevent the structural abnormalities of the post-synaptic membrane or the abnormal oxidative properties of utrophin/dystrophin-deficient muscle. In marked contrast, a dystrophin protein lacking the cysteine-rich domain, which is unable to prevent dystrophy in the mdx mouse, is able to ameliorate these abnormalities in utrophin/dystrophin-deficient mice. These experiments provide the first direct evidence that in addition to a mechanical role and relocalization of the DAPC, dystrophin and utrophin are able to alter both structural and biochemical properties of skeletal muscle. In addition, these mice provide unique insights into skeletal muscle fiber type composition.     

Mechanical characteristics of skinned and intact muscle fibres from the giant barnacle,Balanus nubilus

Intact muscle fibres fromBalanus nubilus develop tensions of up to 600 kN sd m⁻² during electrical stimulation. The rise of tension occurs with a half-time (177 ms at 12° C) about fivefold longer than that of tetanised frog muscle at the same temperature. The response of myofibrillar bundles to a rapid stretch resembles that of frog muscle but has a y_o value (i.e. the size of an instantaneous release necessary to just discharge tension) which is ca. 2.5 times smaller, and phase 2 of the tension transient (the “quick phase”) occurs at a rate comparable to that of frog muscle. In contrast, the ATPase activity (0.018 mmoles · kg wet weight⁻¹ · s⁻¹) of this preparation and its maximum shortening velocity (0.15–0.16 muscle lengths · s⁻¹) are both at least fivefold slower than frog muscle. These findings can be accounted for by a cross-bridge cycle in barnacle muscle in which events prior and subsequent to the tension generating step(s) occur at a rate at least fivefold slower than comparable steps in frog muscle, but the step(s) associated with tension development occur at similar rates in the two preparations. Since the rate of mechanical relaxation in barnacle muscle is modified in the presence of intracellular calcium buffers and by depolarisation-induced elevation of the free calcium during the relaxation phase, it is proposed that the time course of relaxation is not determined exclusively by the kinetics of the cross-bridge cycle, but is also dependent on the free calcium concentration during relaxation.     

A BALB/c congenic strain of mice that carries a genetic locus (Ityr) controlling resistance to intracellular parasites.

BALB/c.DBA/2 Idh-1b-Ityr-Pep-3b congenic mice were developed by introgressively backcrossing the Idh-1b and Pep-3b markers of DBA/2 mice onto the BALB/c pi mice. This introduced a 30-centimorgan chromosome 1 segment of DBA/2 chromatin that contained the Ityr gene. BALB/c.DBA/2 Idh-1b-Ityr-Pep-3b mice were resistant to in vivo infections by Salmonella typhimurium, Mycobacterium bovis, and Leishmania donovani.     

Methylenetetrahydrofolate reductase and thymidylate synthase genotypes and risk of acute graft-versus-host disease following hematopoietic cell transplantation for chronic myelogenous leukemia.

Methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TS) play key roles in intracellular folate metabolism. Polymorphisms in these enzymes have been shown to modify toxicity of methotrexate (MTX) after hematopoietic cell transplantation. In this study, we evaluated the risk of acute graft-versus-host disease (GVHD) associated with genetic variation in recipient and donor MTHFR and TS genotypes to assess whether genotype alters the efficacy of MTX in acute GVHD prophylaxis. Data on the transplantation course were abstracted from medical records for 304 adults who received allogeneic hematopoietic cell transplants. MTHFR (C677T and A1298C) and TS (enhancer-region 28-base pair repeat, TSER, and 1494del6) genotypes were determined using polymerase chain reaction/restriction fragment length polymorphism and TaqMan assays. Multivariable logistic regression was used to assess the associations between genotypes and risk of acute GVHD. Compared with recipients with the wild-type MTHFR 677CC genotype, those with the variant 677T allele showed a decreased risk of detectable acute GVHD (677CT: odds ratio, 0.8; 95% confidence interval, 0.4-1.6; 677TT: odds ratio, 0.4; 95% confidence interval, 0.2-0.8; P for trend = .01). The variant MTHFR 1298C allele in recipients was associated with an increased risk of acute GVHD compared with the wild-type MTHFR 1298AA genotype (1298AC: odds ratio, 2.0; 95% confidence interval, 1.1-3.9; 1298CC: odds ratio, 3.6; 95% confidence interval, 1.0-12.7; P for trend < .01). No association with risk of acute GVHD was observed for donor MTHFR genotypes or for recipient or donor TS genotypes, with the exception of an increase in acute GVHD among recipients whose donors had the TSER 3R/2R genotype (odds ratio, 3.0; 95% confidence interval, 1.3-7.2). These findings indicate that host, but not donor, MTHFR genotypes modify the risk of acute GVHD in recipients receiving MTX, in a manner consistent with our previously reported associations between MTHFR genotypes and MTX toxicity. A direct trade-off between drug toxicity and drug efficacy may play a role. Alternatively, the systemic folate environment, regulated by host tissues, might influence donor T-cell growth and activity.     

Children''s perceptions of chronic illness: the roles of disease symptoms, cognitive development, and information

This experiment considered the acceptance of chronically illchildren by their peers as a result of the peer's level of cognitivedevelopment, the type of disease, and the amount of informationprovided. The results of multivariate and univariate analysesof variance indicate that (a) children's comprehension of illnessescan be improved significantly with the provision of explanatoryinformation, although preoperational children are less ableto retain specifics, (b) preoperational children as well asuninformed children perceived themselves as significantly morevulnerable to contagion, (c) the more observable illness wasseen as significantly less attractive, and (d) provision ofinformation about the nature of a highly observable illnesstended to decrease rather than increase attraction.     

Hypersensitivity to airborne spitting cobra snake venom.

BACKGROUND: Although the cytolytic, neurotoxic, and hemolytic actions of snake venoms are well known, the ability of airborne inhaled snake venom of the spitting cobra to induce asthma in snake handlers has not been reported. OBJECTIVE: To report the allergenicity of inhaled snake venom in a snake handler who developed increasing hypersensitivity to airborne venom, produced by spitting cobras during public demonstrations. METHODS: Serum samples were obtained from 2 handlers (our study patient and another snake handler who reported developing wheezing when handling spitting cobras), and desiccated venom was obtained from 9 species to which the handlers were exposed. Serum from an asymptomatic and nonatopic snake handler exposed to the same snake species was used as a control. Phosphate-buffered saline extracts were prepared from the desiccated venom, proteins in the venom extracts were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunoblotting was performed. Inhibition enzyme-linked immunosorbent assays (ELISAs) were performed to demonstrate cross-reactivity. RESULTS: The study patient had never been previously bitten by a cobra. Wheezing occurred rapidly on inhalational exposure and was reversed by inhalation of salbutamol. The patient had developed IgE antibodies to 9 different snake venoms on Western immunoblots, with major IgE binding proteins of 59 to 63 kDa and 8 to 15 kDa. The cross-reactive nature of the IgE epitopes in the venoms in the different species was also confirmed by 50% inhibition of IgE binding in an ELISA by preincubation with unrelated species. Life-threatening sensitivity of the patient was sustained after a long period of avoidance. CONCLUSIONS: We propose that aerosolized snake venom be considered a new potential source of allergens that may result in anaphylaxis on subsequent exposure. Further studies of the development of specific IgE sensitization following snakebites and the risks of such sensitization should be conducted on snake handlers, particularly those who demonstrate the spitting species.     

Immunity to Influenza in Ferrets X. Intranasal Immunization of Ferrets with Inactivated Influenza A Virus Vaccines

The response of ferrets after intranasal inoculation of inactivated A/Hong Kong/68 (H3N2) influenza virus vaccines is reported. Normal ferrets given either saline vaccine in drops or freeze-dried vaccine in an aerosol intranasally did not produce detectable serum or nasal hemagglutination inhibiting antibody and were found to be completely susceptible to challenge infection with A/Hong Kong/68 virus. Intranasal saline vaccine did not produce an additive effect on the response of ferrets simultaneously given the same vaccine intramuscularly with adjuvant. Ferrets primed by previous infection with A/PR/8/34 (H0N1) influenza virus, however, responded to intranasal immunization with saline A/Hong Kong/68 virus vaccine and produced serum and nasal antibody. These animals were found to be partially resistant to challenge infection, in contrast to similar animals given saline vaccine intramuscularly which were completely resistant to challenge infection. Primed ferrets did not respond after immunization with the freeze-dried aerosol vaccine, but this may have been due to a failure of the aerosol to be inhaled satisfactorily.