Mild muscular features in tenascin-X knockout mice, a model of Ehlers-danlos syndrome.

INTRODUCTION: Tenascin-X (TNX) is an extracellular matrix (ECM) glycoprotein, the absence of which in humans leads to a recessive form of Ehlers-Danlos syndrome (EDS), a group of inherited connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. A mouse model of TNX-deficient type EDS has been used to characterize the dermatological, orthopedic, and obstetrical features. The growing insight in the clinical overlap between myopathies and inherited connective tissue disorders asks for a study of the muscular characteristics of inherited connective tissue diseases. Therefore, this study aims to define the muscular phenotype of TNX knockout (KO) mice. MATERIALS AND METHODS: We performed a comprehensive study on the muscular phenotype of these TNX KO mice, consisting of standardized clinical assessment, muscle histology, and gene expression profiling of muscle tissue. Furthermore, peripheral nerve composition was studied by histology and electron microscopy. RESULTS: The main findings are the presence of mild muscle weakness, mild myopathic features on histology, and functional upregulation of genes encoding proteins involved in ECM degradation and synthesis. Additionally, sciatic nerve samples showed mildly reduced collagen fibril density of endoneurium. DISCUSSION: The muscular phenotype of TNX KO mice consists of mild muscle weakness with histological signs of myopathy and of increased turnover of the ECM in muscle. Furthermore, mildly reduced diameter of myelinated fibers and reduction of collagen fibril density of endoneurium may correspond with polyneuropathy in TNX-deficient EDS patients. This comprehensive assessment can serve as a starting point for further investigations on neuromuscular function in TNX KO mice.

Identification and characterization of multiple species of tenascin-X in human serum.

We analysed the diversity of tenascin-X (TNX) species in serum and studied parameters that could affect determination of TNX levels in serum. Using western blot analysis we identified at least seven distinct TNX species, ranging from 75 kDa to the presumably full-length 450 kDa form. Purification of serum TNX followed by sequence analysis positively identified two major TNX species of 75 and 140 kDa. We found that serum TNX binds to tropoelastin but not to fibrillar collagens. We conclude that serum TNX is composed of distinct molecular species that retain functional activity.

A clinical and cardiovascular survey of Ehlers-Danlos syndrome patients with complete deficiency of tenascin-X.

BACKGROUND: We recently described a new autosomal recessive type of Ehlers-Danlos syndrome (EDS) based on a deficiency of the extracellular matrix protein tenascin-X (TNX). TNX-deficient patients have hypermobile joints, hyperextensible skin and show easy bruising. Because of the reported cardiovascular abnormalities in other EDS types and the excessive haematoma formation after mild trauma in TNX-deficient individuals, we investigated whether cardiovascular or coagulation abnormalities occur in these patients. METHODS: We examined seven TNX-deficient patients. One of them had a mitral valve prolapse and died postoperatively after valve replacement, before the study was completed. RESULTS: Bleeding time and coagulation factors (INR, APTT, PT and fibrinogen) were all within the normal range. Ultrasonographic examination of the carotid and femoral arteries showed normal vessel wall compliance and distensibility. Echocardiography showed a slight billowing of the mitral valve in two patients from one family. All patients had normal diameters of aortic root and ascending aorta. CONCLUSION: Although the patient group is small, there are no indications of generalised cardiovascular abnormalities in this type of EDS. We would recommend echocardiography for all these patients at the first evaluation and when a cardiac murmur appears.

A western gray whale mitigation and monitoring program for a 3-D seismic survey, Sakhalin Island, Russia.

The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17 August-9 September 2001. The key environmental issue was protection of the critically endangered western gray whale (Eschrichtius robustus), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially capable of producing physical injury. A 4-5 km buffer was established to avoid displacing western gray whales from feeding areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers. Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June-August to August-September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19% to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in(3) to 1,640 in(3)) relative to initial plans. "Ramp-up" (="soft-start") procedures were implemented. Monitoring activities were conducted as needed to implement some mitigation measures, and to assess residual impacts. Aerial and vessel-based surveys determined the distribution of whales before, during and after the seismic survey. Daily aerial reconnaissance helped verify whale-free areas and select the sequence of seismic lines to be surveyed. A scout vessel with MMOs aboard was positioned 4 km shoreward of the active seismic vessel to provide better visual coverage of the 4-5 km buffer and to help define the inshore edge of the 4-5 km buffer. A second scout vessel remained near the seismic vessel. Shore-based observers determined whale numbers, distribution, and behavior during and after the seismic survey. Acoustic monitoring documented received sound levels near and in the main whale feeding area. Statistical analyses of aerial survey data indicated that about 5-10 gray whales moved away from waters near (inshore of) the seismic survey during seismic operations. They shifted into the core gray whale feeding area farther south, and the proportion of gray whales observed feeding did not change over the study period. Five shutdowns of the air guns were invoked for gray whales seen within or near the buffer. A previously unknown gray whale feeding area (the Offshore feeding area) was discovered south and offshore from the nearshore Piltun feeding area. The Offshore area has subsequently been shown to be used by feeding gray whales during several years when no anthropogenic activity occurred near the Piltun feeding area.Shore-based counts indicated that whales continued to feed inshore of the Odoptu block throughout the seismic survey, with no significant correlation between gray whale abundance and seismic activity. Average values of most behavioral parameters were similar to those without seismic surveys. Univariate analysis showed no correlation between seismic sound levels and any behavioral parameter. Multiple regression analyses indicated that, after allowance for environmental covariates, 5 of 11 behavioral parameters were statistically correlated with estimated seismic survey-related variables; 6 of 11 behavioral parameters were not statistically correlated with seismic survey-related variables. Behavioral parameters that were correlated with seismic variables were transient and within the range of variation attributable to environmental effects. Acoustic monitoring determined that the 4-5 km buffer zone, in conjunction with reduction of the air gun array to 14 guns and 1,640 in(3), was effective in limiting sound exposure. Within the Piltun feeding area, these mitigation measures were designed to insure that western gray whales were not exposed to received levels exceeding the 163 dB re 1 microPa (rms) threshold. This was among the most complex and intensive mitigation programs ever conducted for any marine mammal. It provided valuable new information about underwater sounds and gray whale responses during a nearshore seismic program that will be useful in planning future work. Overall, the efforts in 2001 were successful in reducing impacts to levels tolerable by western gray whales. Research in 2002-2005 suggested no biologically significant or population-level impacts of the 2001 seismic survey.

Dermal connective tissue development in mice: an essential role for tenascin-X.

Deficiency of the extracellular matrix protein tenascin-X (TNX) causes a recessive form of Ehlers-Danlos syndrome (EDS) characterized by hyperextensible skin and hypermobile joints. It is not known whether the observed alterations of dermal collagen fibrils and elastic fibers in these patients are caused by disturbed assembly and deposition or by altered stability and turnover. We used biophysical measurements and immunofluorescence to study connective tissue properties in TNX knockout and wild-type mice. We found that TNX knockout mice, even at a young age, have greatly disturbed biomechanical properties of the skin. No joint abnormalities were noted at any age. The spatio-temporal expression of TNX during normal mouse skin development, during embryonic days 13-19 (E13-E19), was distinct from tropoelastin and the dermal fibrillar collagens type I, III, and V. Our data show that TNX is not involved in the earliest phase (E10-E14) of the deposition of collagen fibrils and elastic fibers during fetal development. From E15 to E19, TNX starts partially to colocalize with the dermal collagens and elastin, and in adult mice, TNX is present in the entire dermis. In adult TNX knockout mice, we observed an apparent increase of elastin. We conclude that TNX knockout mice only partially recapitulate the phenotype of TNX-deficient EDS patients, and that TNX could potentially be involved in maturation and/or maintenance of the dermal collagen and elastin network.

Policy: advanced practice nursing issues and challenges--specialty association viewpoints.

Specialty nursing associations were queried about issues and challenges facing advanced practice nurses (APNs) today. APNs can seize opportunities to participate in shaping public policy that will advance advanced practice nursing and ultimately improve client well-being.