Mg2+ restriction downregulates NCC through NEDD4-2 and prevents its activation by hypokalemia.

Hypomagnesemia is associated with reduced kidney function and life-threatening complications and sustains hypokalemia. The distal convoluted tubule (DCT) determines final urinary Mg2+ excretion and, via activity of the Na+-Cl- cotransporter (NCC), also plays a key role in K+ homeostasis by metering Na+ delivery to distal segments. Little is known about the mechanisms by which plasma Mg2+ concentration regulates NCC activity and how low-plasma Mg2+ concentration and K+ concentration interact to modulate NCC activity. To address this, we performed dietary manipulation studies in mice. Compared with normal diet, abundances of total NCC and phosphorylated NCC (pNCC) were lower after short-term (3 days) or long-term (14 days) dietary Mg2+ restriction. Altered NCC activation is unlikely to play a role, since we also observed lower total NCC abundance in mice lacking the two NCC-activating kinases, STE20/SPS-1-related proline/alanine-rich kinase and oxidative stress response kinase-1, after Mg2+ restriction. The E3 ubiquitin-protein ligase NEDD4-2 regulates NCC abundance during dietary NaCl loading or K+ restriction. Mg2+ restriction did not lower total NCC abundance in inducible nephron-specific neuronal precursor cell developmentally downregulated 4-2 (NEDD4-2) knockout mice. Total NCC and pNCC abundances were similar after short-term Mg2+ or combined Mg2+-K+ restriction but were dramatically lower compared with a low-K+ diet. Therefore, sustained NCC downregulation may serve a mechanism that enhances distal Na+ delivery during states of hypomagnesemia, maintaining hypokalemia. Similar results were obtained with long-term Mg2+-K+ restriction, but, surprisingly, NCC was not activated after long-term K+ restriction despite lower plasma K+ concentration, suggesting significant differences in distal tubule adaptation to acute or chronic K+ restriction.

Successful transduction of liver in hemophilia by AAV-Factor IX and limitations imposed by the host immune response.

We have previously shown that a single portal vein infusion of a recombinant adeno-associated viral vector (rAAV) expressing canine Factor IX (F.IX) resulted in long-term expression of therapeutic levels of F.IX in dogs with severe hemophilia B. We carried out a phase 1/2 dose-escalation clinical study to extend this approach to humans with severe hemophilia B. rAAV-2 vector expressing human F.IX was infused through the hepatic artery into seven subjects. The data show that: (i) vector infusion at doses up to 2 x 10(12) vg/kg was not associated with acute or long-lasting toxicity; (ii) therapeutic levels of F.IX were achieved at the highest dose tested; (iii) duration of expression at therapeutic levels was limited to a period of approximately 8 weeks; (iv) a gradual decline in F.IX was accompanied by a transient asymptomatic elevation of liver transaminases that resolved without treatment. Further studies suggested that destruction of transduced hepatocytes by cell-mediated immunity targeting antigens of the AAV capsid caused both the decline in F.IX and the transient transaminitis. We conclude that rAAV-2 vectors can transduce human hepatocytes in vivo to result in therapeutically relevant levels of F.IX, but that future studies in humans may require immunomodulation to achieve long-term expression.

Impact of a community-based exercise program on children and adolescents with disabilities.

The purpose of this study was to determine if participation in a community-based fitness program improves: a) strength and endurance, b) self-concept and quality of life, and c) positive social interactions among participants with disabilities. Nineteen children completed the study (10 experimental group, 9 control group). Pre/post testing included body mass index (BMI), energy expenditure index (EEI), Presidential Fitness Test (PFT), strength testing using a handheld dynamometer, PedsQL, and the Piers-Harris 2 Self-Concept Scale (PH-2). The experimental group participated in an 8-week exercise program two times per week and were given a home exercise program (HEP). No statistically significant differences were observed in BMI, EEI, PFT, strength, quality of life, or self-concept. A statistically significant difference in social interactions was found between the first and second half of the exercise program while the children performed group activities and ran track based on repeated measures MANOVA at p<0.05. While changes in fitness may not be observed following an 8-week exercise program, improvements in social interactions may be possible.

Role of prothrombin complex concentrates in reversing warfarin anticoagulation: a review of the literature.

Over-anticoagulation is a common problem with warfarin therapy and can lead to major or life-threatening bleeding. The goal of urgent warfarin reversal is to elevate or replace vitamin K-dependent clotting factors. In the United States, fresh frozen plasma (FFP) is considered the standard of care for warfarin reversal. Prothrombin complex concentrates (PCCs) offer an alternative to FFP for rapidly replacing deficient clotting factors and correcting the international normalized ratio (INR). However, few prospective clinical trials have been conducted to evaluate the effectiveness of these concentrates relative to other treatment modalities. A review of the published literature over the last 30 years found that PCCs offer a rapid and specific method for replacing vitamin K-dependent clotting factors and restoring normal hemostasis in the context of over-coagulation. In those studies in which PCCs were compared with FFP, PCCs were found more effective in shortening the time to INR correction and were associated with a low risk of thrombotic adverse events. Evidence-based treatment guidelines are needed to optimize the use of PCCs for warfarin reversal.

The reliability of the Vestibular Autorotation Test (VAT) in patients with dizziness.

OBJECTIVE: To establish intrarater and interrater reliability of the Vestibular Autorotation Test (VAT) (Western Systems Research Inc., Pasadena, CA) in a clinical sample of individuals reporting dizziness. STUDY DESIGN: Ninety-eight patients with reports of dizziness referred for vestibular function testing performed repeated trials of horizontal VAT. A subsample of 49 individuals repeated the test for a second rater. RESULTS: Approximately 66% of subjects were unable to meet the performance criterion of six consecutive trials where data was displayed at frequencies > or =3.9 Hz with coherence values held constant trial to trial. There was a good level of intrarater reliability for gain independent of the effects of practice (intraclass correlation coefficient [ICC] = 0.78 [95% confidence interval [CI]: 0.69-0.87] to 0.95 [(95% CI: 0.93-0.97]). A significant difference in intrarater reliability was found when the first three trials were compared to the last three trials for phase (ICC ranged from 0.04 [95% CI: 0.00-0.31] to 0.96 [95% CI: 0.93-0.97]) and asymmetry (ICC ranged from 0.39 [95% CI: 0.17-0.56] to 0.73 [95% CI: 0.32-0.81]) particularly at frequencies > or =4.3 Hz. Interrater reliability was good to excellent across all variables at frequencies < or =3.9 Hz. CONCLUSIONS: Many patients had difficulty performing the VAT. The reliability estimates for phase and asymmetry, but not gain, were significantly affected by practice. Careful attention to patient preparation, instruction, and test monitoring including sufficient patient practice before data collection are likely to be critical factors to ensure quality data.

Temporal and spatial characteristics of gait during performance of the Dynamic Gait Index in people with and people without balance or vestibular disorders.

BACKGROUND AND PURPOSE: Understanding underlying gait characteristics during performance of the Dynamic Gait Index (DGI) could potentially guide interventions. The purpose of this study was to describe the characteristics and reliability of gait performance during the level walking items of the DGI in people with balance or vestibular dysfunction. The study was a cross-sectional investigation with 2-group comparisons. SUBJECTS AND METHODS: Forty-seven subjects (mean age=59.2 years, SD=8.5, range=24-90) participated in the study; 26 were control subjects, and 21 were subjects with balance or vestibular dysfunction. Three trials of each level gait item were administered to subjects as they ambulated on an instrumented walkway. Test-retest reliability was determined by use of an intraclass correlation coefficient (3,1) 2-way random-effects model for gait parameters associated with continuous walking and the item requiring turning and stopping quickly. Mean gait parameter differences between control subjects and subjects with balance or vestibular disorders were compared by use of a multivariate analysis of variance for each gait task. RESULTS: The reliability of most gait parameters during DGI performance were fair to excellent between trials. Subjects with balance or vestibular disorders demonstrated differences in gait characteristics compared with control subjects. The heterogeneity of the group of subjects with balance or vestibular disorders does not permit inferences to be drawn regarding the relationship between gait and any specific balance or vestibular diagnosis. The results are most pertinent to people with chronic balance or vestibular disorders. DISCUSSION AND CONCLUSION: Gait parameters underlying dynamic walking appeared to be relatively reliable across multiple trials and distinguished subjects with balance or vestibular disorders. Evaluating a person's performance on items of the DGI may be useful in identifying gait deviations and in evaluating gait improvements as a result of interventions.

Haemostatic Failure of Prothrombin Complex Concentrates during Elective Dental Procedure.

One haemophilia A patient with an inhibitor was exposed to a graded surgical procedure and treated with Prothrombin Complex Concentrates (PCC). Hemostasis was not obtained until the inhibitor was neutralized and the patient�s factor VIII level was normal. This patient is presented to emphasize that PCC are not nearly as effective as once hoped in producing hemostasis in inhibitor patients. Consequently, major decisions should not be made presuming efficacy of these products in inhibitor patients.