[Vasa previa: Of the diagnosis to neonatal prognosis]

Vasa previa is a rare complication of pregnancy (1/2000 to 1/6000) with a high fetal mortality rate (75 to 100%). We will discuss two case reports of vasa previa: the first was diagnosed before labor, while the second was during delivery. In the first case, the diagnosis of vasa previa was confirmed by a transvaginal ultrasound and color doppler, while the second case involved late diagnosis during delivery and after gross examination of the placenta. Risk factors for vasa previa are: low-lying placenta, bilobed or succenturiate lobed placenta, velamentous and in vitro fertilization (IVF). Antenatal diagnosis of vasa previa is crucial because it allows for prophylactic caesarean section and prevents severe Benckiser's hemorrhage responsible for a very high neonatal mortality.

Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition

The BFW model introduced by Bohman, Frieze, and Wormald [Random Struct. Algorithms, 25, 432 (2004)], and recently investigated in the framework of discontinuous percolation by Chen and D'Souza [Phys. Rev. Lett. 106, 115701 (2011)], is studied on the square and simple-cubic lattices. In two and three dimensions, we find numerical evidence for a strongly discontinuous transition. In two dimensions, the clusters at the threshold are compact with a fractal surface of fractal dimension d(f)=1.49±0.02. On the simple-cubic lattice, distinct jumps in the size of the largest cluster are observed. We proceed to analyze the tree-like version of the model, where only merging bonds are sampled, for dimension two to seven. The transition is again discontinuous in any considered dimension. Finally, the dependence of the cluster-size distribution at the threshold on the spatial dimension is also investigated.

Nesprin 1 is critical for nuclear positioning and anchorage

Nesprin 1 is an outer nuclear membrane protein that is thought to link the nucleus to the actin cytoskeleton. Recent data suggest that mutations in Nesprin 1 may also be involved in the pathogenesis of Emery-Dreifuss muscular dystrophy. To investigate the function of Nesprin 1 in vivo, we generated a mouse model in which all isoforms of Nesprin 1 containing the C-terminal spectrin-repeat region with or without KASH domain were ablated. Nesprin 1 knockout mice are marked by decreased survival rates, growth retardation and increased variability in body weight. Additionally, nuclear positioning and anchorage are dysfunctional in skeletal muscle from knockout mice. Physiological testing demonstrated no significant reduction in stress production in Nesprin 1-deficient skeletal muscle in either neonatal or adult mice, but a significantly lower exercise capacity in knockout mice. Nuclear deformation testing revealed ineffective strain transmission to nuclei in muscle fibers lacking Nesprin 1. Overall, our data show that Nesprin 1 is essential for normal positioning and anchorage of nuclei in skeletal muscle.

Progressive myopathy and defects in the maintenance of myotendinous junctions in mice that lack talin 1 in skeletal muscle

The development and function of skeletal muscle depend on molecules that connect the muscle fiber cytoskeleton to the extracellular matrix (ECM). beta1 integrins are ECM receptors in skeletal muscle, and mutations that affect the alpha7beta1 integrin cause myopathy in humans. In mice, beta1 integrins control myoblast fusion, the assembly of the muscle fiber cytoskeleton, and the maintenance of myotendinous junctions (MTJs). The effector molecules that mediate beta1 integrin functions in muscle are not known. Previous studies have shown that talin 1 controls the force-dependent assembly of integrin adhesion complexes and regulates the affinity of integrins for ligands. Here we show that talin 1 is essential in skeletal muscle for the maintenance of integrin attachment sites at MTJs. Mice with a skeletal muscle-specific ablation of the talin 1 gene suffer from a progressive myopathy. Surprisingly, myoblast fusion and the assembly of integrin-containing adhesion complexes at costameres and MTJs advance normally in the mutants. However, with progressive ageing, the muscle fiber cytoskeleton detaches from MTJs. Mechanical measurements on isolated muscles show defects in the ability of talin 1-deficient muscle to generate force. Collectively, our findings show that talin 1 is essential for providing mechanical stability to integrin-dependent adhesion complexes at MTJs, which is crucial for optimal force generation by skeletal muscle.

Sarcomere length measurement permits high resolution normalization of muscle fiber length in architectural studies

The use of sarcomere length to normalize fiber length in architectural studies is commonly practiced but has not been explicitly validated. Using mouse hindlimb muscles as a model system, ankle joints were intentionally set to angles ranging from 30° to 150° and their muscles fixed. Tibialis anterior (TA), extensor digitorum longus (EDL) and soleus muscles were removed and their raw fiber length measured. Sarcomere length was then measured for each fiber length sample and fiber length was normalized to a standard sarcomere length. As expected, raw fiber length was dependent on tibiotarsal angle (P<0.0005 for all muscles, r2 range 0.22–0.61), while sarcomere length normalization eliminated the joint-angle dependent variation in fiber length (P>0.24, r2 range 0.001–0.028). Similarly, one-way ANOVA revealed no significant differences in normalized fiber length among ankle angles for any of the three muscles (P>0.1), regardless of animal size. To determine the resolution of the method, power calculations were performed. For all muscles studied, there was >90% chance of detecting a 15% fiber length difference among muscles and >60% chance of detecting fiber length differences as small as 10%. We thus conclude that the use of sarcomere length normalization in architectural studies permits resolution of fiber length variations of 15% and may even be effective at resolving 10%fiber length variations.

Recurrent syncope as a chronic disease: preliminary validation of a disease-specific measure of functional impairment

BACKGROUND

A disease-specific measure of functional health in syncope would provide an important outcome measure for use either in clinical trials or in the clinical management of patients with recurrent syncope.

METHODS AND MEASUREMENTS

In a previous study the authors used formal functional status measures to determine physical and psychosocial impairment in recurrent syncope. This study provides a preliminary assessment of a disease-specific measure of function. The measure was pilot tested on 84 subjects, and validated in a separate cohort of 49 patients. The measure consists of 1) an 11-question matrix of yes/no questions, assessing the ways that syncope interferes with a patient's life (the result is expressed as a proportion of the total number of ways that syncope might interfere and is called the Impairment Score), and 2) three Likert-scale questions that assess the patient's fear and worry about syncope. Correlations were obtained between scores on the disease-specific measure and other measures of functional health.

RESULTS

Among the 49 patients in the test cohort, final scores on the disease-specific measure correlated with both physical and psychosocial dimension scores on a measure of functional status, the Sickness Impact Profile (r = 0.35-0.36, p = 0.01), and with five of ten subscale scores on a measure of psychological distress, the Symptom Checklist 90-R (r = 0.30-0.43, p = 0.004-0.02).

CONCLUSIONS

This new disease-specific quality-of-life measure in syncope measures both physical and psychosocial components of impairment and could be a valuable adjunct in measuring outcomes in syncope patients.

Impairment of physical and psychosocial function in recurrent syncope

Physical and psychosocial function have rarely been assessed in syncope. We used two valid and reliable measures of health status, the Sickness Impact Profile (SIP) and the Symptom Checklist 90 (SCL-90-R), to assess functional impairment in 62 patients with recurrent syncope seen in a syncope specialty clinic. Mean total SIP scores were markedly elevated at 17 (SD = 14), indicating a level of impairment similar to severe rheumatoid arthritis and chronic low back pain. SIP psychosocial scores were significantly greater than SIP physical scores (20 vs 11, p less than 0.0001). SCL-90-R scores were also high, comparable to those of psychiatric inpatients. Somatization, anxiety and depression dimensions of the SCL-90-R were particularly elevated. SCL-90-R subscale scores were highly correlated with SIP psychosocial scores (all r greater than 0.4, and p less than 0.001). Neither age nor number of comorbid diseases correlated with measures of psychosocial function, suggesting that syncope itself causes psychosocial impairment. Although this was a referral population, these data suggest that function can be seriously impaired by syncope, that the degree of impairment is similar to that reported in other chronic diseases, and that syncope leads to significantly greater psychosocial than physical impairment.