Structure of myostatin·follistatin-like 3: N-terminal domains of follistatin-type molecules exhibit alternate modes of binding

TGF-β family ligands are involved in a variety of critical physiological processes. For instance, the TGF-β ligand myostatin is a staunch negative regulator of muscle growth and a therapeutic target for muscle-wasting disorders. Therefore, it is important to understand the molecular mechanisms of TGF-β family regulation. One form of regulation is through inhibition by extracellular antagonists such as the follistatin (Fst)-type proteins. Myostatin is tightly controlled by Fst-like 3 (Fstl3), which is the only Fst-type molecule that has been identified in the serum bound to myostatin. Here, we present the crystal structure of myostatin in complex with Fstl3. The structure reveals that the N-terminal domain (ND) of Fstl3 interacts uniquely with myostatin as compared with activin A, because it utilizes different surfaces on the ligand. This results in conformational differences in the ND of Fstl3 that alter its position in the type I receptor-binding site of the ligand. We also show that single point mutations in the ND of Fstl3 are detrimental to ligand binding, whereas corresponding mutations in Fst have little effect. Overall, we have shown that the NDs of Fst-type molecules exhibit distinctive modes of ligand binding, which may affect overall affinity of ligand·Fst-type protein complexes.     

Membrane-bound CC chemokine inhibitor 35K provides localized inhibition of CC chemokine activity in vitro and in vivo

CC chemokines mediate mononuclear cell recruitment and activation in chronic inflammation. We have shown previously that gene transfer using recombinant adenoviruses, encoding a soluble CC chemokine-binding protein of vaccinia virus 35K, can dramatically reduce atherosclerosis and vein graft remodeling in apolipoprotein E knockout mice. In this study, we report the development of a membrane-bound form of 35K (m35K), tagged with GFP, which allows for localized, broad-spectrum CC chemokine blockade. In vitro experiments indicate that m35K-expressing cells no longer undergo CC chemokine-induced chemotaxis, and m35K-expressing cells can locally deplete the CC chemokines RANTES (CCL5) and MIP-1alpha (CCL3) from supernatant medium. This sequestration of CC chemokines can prevent chemotaxis of bystander cells to CC, but not CX(3)C chemokines. Intraperitoneal injection of mice with an adenovirus-encoding m35K leads to a significant (44%) decrease in leukocyte recruitment into the peritoneal cavity in a sterile peritonitis model. Intravenous adenovirus-encoding m35K delivery leads to m35K expression in hepatocytes, which confers significant protection against liver damage (75% reduction in liver enzymes) in a Con A-induced hepatitis model. In summary, we have generated a membrane-bound CC chemokine-binding protein (m35K) that provides localized broad-spectrum CC chemokine inhibition in vitro and in vivo. m35K may be a useful tool to study the role of CC chemokines in leukocyte trafficking and block the recruitment of monocytes in chronic inflammation.     

Effects of training history on resurgence in humans

This experiment assessed the effects of training history on resurgence in three college students. Four-choice arbitrary-matching-to-sample trials occurred in two components of a multiple schedule. An A1 or A2 sample stimulus and four (B) comparison stimuli occurred on AB trials, and a C1 or C2 sample stimulus and four (D) comparison stimuli occurred on CD trials. By the end of training, accuracy and latency measures were comparable across separate discriminations, selecting B2 in the presence of A2 and selecting D2 in the presence of C2, despite a lengthier training correlated with the former discrimination. Next, in the presence of A2 and C2, respectively, responses to B2 and D2 were extinguished and responses to B3 and D3 were reinforced. These responses to B3 and D3 then were extinguished in a final condition. In this final condition, resurgence to B2 occurred for each participant, whereas resurgence to D2 occurred for only one participant. Thus, there was greater resurgence of the discrimination with the lengthier training history, despite the discriminations being similar in terms of accuracy and latency before extinction. This result, therefore, can be classified as a latent, or remote, behavioral history effect.     

Multifactorial approach and superior treatment efficacy in renal patients with the aid of nurse practitioners. Design of The MASTERPLAN Study [ISRCTN73187232]

Background

Patients with chronic kidney disease (CKD) are at a greatly increased risk of developing cardiovascular disease. Recently developed guidelines address multiple risk factors and life-style interventions. However, in current practice few patients reach their targets. A multifactorial approach with the aid of nurse practitioners was effective in achieving treatment goals and reducing vascular events in patients with diabetes mellitus and in patients with heart failure. We propose that this also holds for the CKD population.

Design

MASTERPLAN is a multicenter randomized controlled clinical trial designed to evaluate whether a multifactorial approach with the aid of nurse-practicioners reduces cardiovascular risk in patients with CKD. Approximately 800 patients with a creatinine clearance (estimated by Cockcroft-Gault) between 20 to 70 ml/min, will be included. To all patients the same set of guidelines will be applied and specific cardioprotective medication will be prescribed. In the intervention group the nurse practitioner will provide lifestyle advice and actively address treatment goals. Follow-up will be five years. Primary endpoint is the composite of myocardial infarction, stroke and cardiovascular mortality. Secondary endpoints are cardiovascular morbidity, overall mortality, decline of renal function, change in markers of vascular damage and change in quality of life. Enrollment has started in April 2004 and the study is on track with 700 patients included on October 15th, 2005. This article describes the design of the MASTERPLAN study.     

Guidelines for indications for coronary revascularization in The Netherlands

In 1996 the Minister of Public Health, Welfare and Sports in The Netherlands published a 'Planning Decree Special Interventions in the Heart'. She requested from the professional organizations guidelines for the indications for interventions in the heart. A working group was formed with representatives from the Dutch professional organizations for cardiology and thoracic surgery, to address this issue for patients with coronary artery disease. The working group confirmed the need to discuss all patients who are considered for either elective or emergency revascularization during a multidisciplinary consultation in (or with) one of the specialized Dutch hospitals. During this meeting of the 'heart team', at least one interventional cardiologist and one thoracic surgeon should be present. There are three possible outcomes of the heart team's consultations for each patient: drug therapy only ('conservative management'), coronary surgery or catheter intervention. For each case, the team should indicate the expected benefit, the risk of the intervention, the urgency and the estimated waiting time. The guidelines presented in this paper address these issues for three patient categories: stable angina pectoris, unstable angina pectoris and acute myocardial infarction.     

Bacterial swimming strategies and turbulence

Most bacteria in the ocean can be motile. Chemotaxis allows bacteria to detect nutrient gradients, and hence motility is believed to serve as a method of approaching sources of food. This picture is well established in a stagnant environment. In the ocean a shear microenvironment is associated with turbulence. This shear flow prevents clustering of bacteria around local nutrient sources if they swim in the commonly assumed "run-and-tumble" strategy. Recent observations, however, indicate a "back-and-forth" swimming behavior for marine bacteria. In a theoretical study we compare the two bacterial swimming strategies in a realistic ocean environment. The "back-and-forth" strategy is found to enable the bacteria to stay close to a nutrient source even under high shear. Furthermore, rotational diffusion driven by thermal noise can significantly enhance the efficiency of this strategy. The superiority of the "back-and-forth" strategy suggests that bacterial motility has a control function rather than an approach function under turbulent conditions.     

Regulation of B-Raf kinase activity by tuberin and Rheb is mammalian target of rapamycin (mTOR)-independent

Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome with manifestations that can include seizures, mental retardation, autism, and tumors in the brain, retina, kidney, heart, and skin. The products of the TSC1 and TSC2 genes, hamartin and tuberin, respectively, heterodimerize and inhibit the mammalian target of rapamycin (mTOR). We found that tuberin expression increases p42/44 MAPK phosphorylation and B-Raf kinase activity. Short interfering RNA down-regulation of tuberin decreased the p42/44 MAPK phosphorylation and B-Raf activity. Expression of Rheb, the target of the GTPase-activating domain of tuberin, inhibited wild-type B-Raf kinase but not activated forms of B-Raf. The interaction of endogenous Rheb with B-Raf was enhanced by serum and by Ras overexpression. A farnesylation-defective mutant of Rheb co-immunoprecipitated with and inhibited B-Raf but did not activate ribosomal protein S6 kinase, indicating that farnesylation is not required for B-Raf inhibition by Rheb and that B-Raf inhibition and S6 kinase activation are separable activities of Rheb. Consistent with this, inhibition of B-Raf and p42/44 MAPK by Rheb was resistant to rapamycin in contrast to Rheb activation of S6 kinase, which is rapamycin-sensitive. Taken together these data demonstrate that inhibition of B-Raf kinase via Rheb is an mTOR-independent function of tuberin.     

Risk of whole body radiation exposure and protective measures in fluoroscopically guided interventional techniques: a prospective evaluation

BACKGROUND: Fluoroscopic guidance is frequently utilized in interventional pain management. The major purpose of fluoroscopy is correct needle placement to ensure target specificity and accurate delivery of the injectate. Radiation exposure may be associated with risks to physician, patient and personnel. While there have been many studies evaluating the risk of radiation exposure and techniques to reduce this risk in the upper part of the body, the literature is scant in evaluating the risk of radiation exposure in the lower part of the body. METHODS: Radiation exposure risk to the physician was evaluated in 1156 patients undergoing interventional procedures under fluoroscopy by 3 physicians. Monitoring of scattered radiation exposure in the upper and lower body, inside and outside the lead apron was carried out. RESULTS: The average exposure per procedure was 12.0 PlusMinus; 9.8 seconds, 9.0 PlusMinus; 0.37 seconds, and 7.5 PlusMinus; 1.27 seconds in Groups I, II, and III respectively. Scatter radiation exposure ranged from a low of 3.7 PlusMinus; 0.29 seconds for caudal/interlaminar epidurals to 61.0 PlusMinus; 9.0 seconds for discography. Inside the apron, over the thyroid collar on the neck, the scatter radiation exposure was 68 mREM in Group I consisting of 201 patients who had a total of 330 procedures with an average of 0.2060 mREM per procedure and 25 mREM in Group II consisting of 446 patients who had a total of 662 procedures with average of 0.0378 mREM per procedure. The scatter radiation exposure was 0 mREM in Group III consisting of 509 patients who had a total 827 procedures. Increased levels of exposures were observed in Groups I and II compared to Group III, and Group I compared to Group II.Groin exposure showed 0 mREM exposure in Groups I and II and 15 mREM in Group III. Scatter radiation exposure for groin outside the apron in Group I was 1260 mREM and per procedure was 3.8182 mREM. In Group II the scatter radiation exposure was 400 mREM and with 0.6042 mREM per procedure. In Group III the scatter radiation exposure was 1152 mREM with 1.3930 mREM per procedure. CONCLUSION: Results of this study showed that scatter radiation exposure to both the upper and lower parts of the physician's body is present. Protection was offered by traditional measures to the upper body only.     

Sensing and adapting to acid stress

Bacteria and archaea occupy a considerable diversity of niches that vary with respect to the physical conditions. Survival and colonisation requires the capacity to sense, and adapt to, environmental change. In this short review we consider the issues of adaptation to acidic conditions, in particular the mechanisms that might be employed by different bacteria to respond to the specific challenges of their niche. We lay particular emphasis on the protection of the cytoplasm during alterations of the cytoplasmic pH and, in the Gram negative bacteria, on recent work that suggests that protection of the periplasm is critical for survival of exposure to extreme acid. Finally, we discuss potential mechanisms by which pH might be sensed and consider the insights gained from proteins that sense and respond specifically to changes in pH. This revised version was published online in August 2006 with corrections to the Cover Date.