Functional characterization of the MTC-associated germline RET-K666E mutation: evidence of oncogenic potential enhanced by the G691S polymorphism

Activating mutations of RET, a gene encoding two isoforms of a tyrosine kinase receptor physiologically expressed in several neural crest-derived cell lineages, are associated with the inherited forms of medullary thyroid carcinoma (MTC). The identification and characterization of novel RET mutations involved in MTC is valuable, as RET gene testing plays a crucial role in the management of these patients. In an MTC patient, we have identified a germline c.1996A>G transition in heterozygosis leading to K666E substitution. In addition, the conservative S904S (c.2712C>G) and the non-conservative functional G691S (c.2071G>A) polymorphisms have been identified. Through functional studies, we demonstrate for the first time that K666E is a gain-of-function mutation with oncogenic potential, based on its ability to transform NIH3T3 cells. It was not possible to define whether K666E is a de novo or inherited RET variant in the patient, as the family history was negative for MTC, and the carrier status of family members could not be tested. Our results, together with a recent report of co-segregation of the mutation in three MTC families, suggest that K666E is a causative MTC mutation. As we have shown that the same patient allele carries both K666E and G691S variants, the latter known to increase downstream RET signaling, a possible role for the G691S polymorphism has also been investigated. We have demonstrated that, although RET-G691S is not oncogenic per se, it enhances the transforming activity of the RET-K666E mutant, thus suggesting a modifier role for this functional polymorphism.     

Large Brunner＇s gland adenoma： Case report and literature review

Brunner's gland adenoma(BGA)is a very rare benigntumour of the duodenum,which is usually asymptomaticand discovered incidentally at endoscopy.Occasionally,this lesion may be large,causing upper gastrointestinalhaemorrhage or intestinal obstruction.The case had alarge Brunner's gland adenoma,presenting melena thatwas managed by endoscopic excision.     

Perineurioma of the sciatic nerve: a possible cause of idiopathic foot drop in children: report of 4 cases

The authors report on a loss of foot dorsiflexion in pediatric-age individuals and suggest that the possible cause could be a perineurioma of the sciatic nerve. The authors describe 4 cases in which foot drop in the absence of sensory discomfort was the heralding sign of perineurioma of the sciatic nerve. Magnetic resonance imaging showed a focal enlargement of the sciatic nerve, but the tumor was confined only to its lateral compartment. Treatment in 2 cases involved excision of the affected segment and subsequent graft repair. The two other patients shared the same clinical, radiological, and surgical findings, but no nerve biopsy sample was obtained; the patients underwent only a tibialis posterior muscle transfer. Long-term recovery of nerve function never occurred. Because tumor resection and nerve graft yield no functional results, a tendon transfer to restore walking may be the sole useful surgical procedure in these cases. Removal of the tumor may not be necessary because long-term follow-up confirms that perineuriomas are self-limiting and the final prognosis is favorable.     

Not the same everywhere

BACKGROUND: Learning environments overtly or implicitly address patient-centered values and have been the focus of research for more than 40 years, often in studies about the "hidden curriculum." However, many of these studies occurred at single medical schools and used time-intensive ethnographic methods. This field of inquiry lacks survey methods and information about how learning environments differ across medical schools. OBJECTIVE: To examine patient-centered characteristics of learning environments at 9 U.S. medical schools. DESIGN: Cross-sectional internet-based survey. PARTICIPANTS: Eight-hundred and twenty-three third- and fourth-year medical students in the classes of 2002 and 2003. MEASUREMENTS: We measured the patient-centeredness of learning environments with the Communication, Curriculum, and Culture (C3) Instrument, a 29-item validated measure that characterizes the degree to which a medical school's environment fosters patient-centered care. The C3 Instrument contains 3 content areas (role modeling, students' experiences, and support for students' patient-centered behaviors), and is designed to measure these areas independent of respondents' attitudes about patient-centered care. We also collected demographic and attitudinal information from respondents. RESULTS: The variability of C3 scores across schools in each of the 3 content areas of the instrument was striking and statistically significant (P values ranged from .001 to .004). In addition, the patterns of scores on the 3 content areas differed from school to school. CONCLUSIONS: The 9 schools demonstrated unique and different learning environments both in terms of magnitude and patterns of characteristics. Further multiinstitutional study of hidden curricula is needed to further establish the degree of variability that exists, and to assist educators in making informed choices about how to intervene at their own schools.     

The cotton fiber zinc-binding domain of cellulose synthase A1 from Gossypium hirsutum displays rapid turnover in vitro and in vivo

Little is known about the assembly and turnover of cellulose synthase complexes commonly called rosettes. Recent work indicates that rosette assembly could involve the dimerization of CesA (cellulose synthase catalytic subunit) proteins regulated by the redox state of the CesA zinc-binding domain (ZnBD). Several studies in the 1980s led to the suggestion that synthase complexes may have very short half-lives in vivo, but no recent work has directly addressed this issue. In the present work, we show that the half-life of cotton fiber GhCesA1 protein is <30 min in vivo, far less than the average membrane protein. We also show that the reduced monomer of GhCesA1 ZnBD is rapidly degraded when exposed to cotton fiber extracts, whereas the oxidized dimer is resistant to degradation. Low rates of degradation activity were detected in vitro by using extracts from fibers harvested during primary cell-wall formation, but activity increased markedly during transition to secondary cell-wall synthesis. In vitro degradation of reduced GhCesA1 ZnBD is inhibited by proteosome inhibitor MG132 and also by E64 and EGTA, suggesting that proteolysis is initiated by cysteine protease activity rather than the proteosome. We used a yeast two-hybrid system to identify a putative cotton fiber metallothionein and to confirm it as a protein that could interact with the GhCesA1 ZnBD. A model is proposed wherein active cellulose synthase complexes contain CesA proteins in dimerized form, and turnover and degradation of the complexes are mediated through reductive zinc insertion by metallothionein and subsequent proteolysis involving a cysteine protease.     

Reduced bone mineral density and increased bone metabolism rate in young adult patients with 21-hydroxylase deficiency

CONTEXT: Patients with congenital adrenal hyperplasia (CAH) receive glucocorticoids as replacement therapy. Glucocorticoid therapy is the most frequent cause of drug-induced osteoporosis. OBJECTIVE: The objective of the study was to evaluate bone mineral density (BMD) and bone metabolism in CAH patients. DESIGN: This was a cross-sectional observational study. SETTING: The study was conducted at a referral center for pediatric endocrinology. PATIENTS AND OTHER PARTICIPANTS: Thirty young patients with the classical form of CAH (aged 16.4-29.7 yr) treated with glucocorticoid from diagnosis (duration of treatment 16.4-29.5 yr) and 138 healthy controls (aged 16.0-30.0 yr) were enrolled. MAIN OUTCOME MEASURES: BMD was measured in the lumbar spine and whole body by dual-energy x-ray absorptiometry. Bone formation and resorption rates were estimated by serum measurements of bone-specific alkaline phosphatase and C-terminal telopeptide of type I collagen, respectively. RESULTS: CAH patients were shorter than controls (women -6.8 and men -13.3 cm). Therefore, several methods were used to account for the effect of this difference on bone measurements. Whole-body BMD measurements were significantly lower, compared with controls (P < 0.03), after controlling for height (on average -2.5% in females and -9.3% in male patients). No differences were found in lumbar spine measurements. Bone-specific alkaline phosphatase and C-terminal telopeptide of type I collagen serum concentrations were higher in CAH patients than control subjects (P < 0.04). BMD measurements and bone metabolism markers did not correlate with the actual glucocorticoid dose or mean dose over the previous 7 yr. CONCLUSIONS: Young adult patients with the classical form of CAH have decreased bone density values, compared with healthy controls. This may put them at risk of developing osteoporosis early in life.     

Heterodimerization of FGF-receptor 1 and PDGF-receptor-alpha: a novel mechanism underlying the inhibitory effect of PDGF-BB on FGF-2 in human cells

Previous evidence has shown that platelet-derived growth factor-BB (PDGF-BB) and fibroblast growth factor-2 (FGF-2) directly interact with high affinity, leading to potent reciprocal inhibitory effects on bovine endothelial cells and rat vascular smooth muscle cells. In this study, we report that PDGF-BB inhibits a series of FGF-2-induced events, such as proliferation of human umbilical vein endothelial cells (HUVECs), FGF-2 cellular internalization, phosphorylation of intracellular signaling factors including p38, rac1/cdc42, MKK4, and MKK3/6, and phosphorylation of FGF-receptor 1 (FGF-R1). PDGF-receptor-alpha (PDGF-Ralpha) was found to mediate PDGF-BB inhibitory effects because its neutralization fully restored FGF-2 mitogenic activity and internalization. Additional biochemical analyses, coimmunoprecipitation experiments, and FRET analysis showed that FGF-R1 and PDGF-Ralpha directly interact in vitro and in vivo and that this interaction is somehow increased in the presence of the corresponding ligands FGF-2 and PDGF-BB. These results suggest that FGF-R1/PDGF-Ralpha heterodimerization may represent a novel endogenous mechanism to modulate the action of these receptors and their ligands and to control endothelial cell function.     

Effect of the dipeptidyl peptidase-4 inhibitor sitagliptin as monotherapy on glycemic control in patients with type 2 diabetes

OBJECTIVE: To examine the efficacy and safety of once-daily oral sitagliptin as monotherapy in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: In a randomized, double-blind, placebo-controlled study, 741 patients (baseline HbA(1c) [A1C] 8.0%) were randomized to sitagliptin 100 or 200 mg or placebo for 24 weeks. RESULTS: Sitagliptin 100 and 200 mg produced significant (P < 0.001) placebo-subtracted reductions in A1C (-0.79 and -0.94%, respectively) and fasting plasma glucose (-1.0 mmol/l [-17.1 mg/dl] and -1.2 mmol/l [-21.3 mg/dl], respectively). Patients with baseline A1C >or=9% had greater reductions in placebo-subtracted A1C with sitagliptin 100 and 200 mg (-1.52 and -1.50%, respectively) than those with baseline A1C <8% (-0.57 and -0.65%) or >or=8 to <9.0% (-0.80 and -1.13%, respectively). In a meal tolerance test, sitagliptin 100 and 200 mg significantly decreased 2-h postprandial glucose (PPG) (placebo-subtracted PPG -2.6 mmol/l [-46.7 mg/dl] and -3.0 mmol/l [-54.1 mg/dl], respectively). Results for the above key efficacy parameters were not significantly different between sitagliptin doses. Homeostasis model assessment of beta-cell function and proinsulin-to-insulin ratio improved with sitagliptin. The incidence of hypoglycemia was similar, and overall gastrointestinal adverse experiences were slightly higher with sitagliptin. No meaningful body weight changes from baseline were observed with sitagliptin 100 (-0.2 kg) or 200 mg (-0.1 kg). The body weight change with placebo (-1.1 kg) was significantly (P < 0.01) different from that observed with sitagliptin. CONCLUSIONS: In this 24-week study, once-daily sitagliptin monotherapy improved glycemic control in the fasting and postprandial states, improved measures of beta-cell function, and was well tolerated in patients with type 2 diabetes.     

Mechanisms of the adaptive immune response inside the central nervous system during inflammatory and autoimmune diseases

In this review we will discuss the unique features that make the central nervous system (CNS) a specialized microenvironment where immune responses are tightly regulated in order to properly face pathogens without damaging the neural cells. We will show how every paradigm of this theoretical model has been addressed by the scientific literature over the past decades providing new insights on the immune response within the CNS. In particular, new light has been shed on the trafficking of the immune cells inside and outside the CNS. Dendritic cells (DCs) have been described in the context of structures in direct contact with the cerebrospinal fluid (CSF) and their migration, upon antigen encounter, outside the CNS into deep cervical lymph nodes (DCLNs) has been further clarified. T-cells, B-cells, and antibody-secreting cells (ASCs) have been found in the CSF and CNS parenchymal lesions of inflammatory disorders and their phenotype depicted. Moreover, in chronically inflamed CNS, ectopic lymphoid structures have been observed and a germinal center reaction similar to the one found in peripheral lymph nodes has been described. These structures may play a role in the maintenance and expansion of the local autoimmune response. Although the complex interactions between immune and neural cells still remain far to be elucidated, the data discussed here suggest that the physiopathology of the adaptive immune response inside the CNS mimics, although in a mitigated fashion, what occurs in other organs and tissues.