Alpha sarcoglycan is required for FGF-dependent myogenic progenitor cell proliferation in vitro and in vivo

Mice deficient in α-sarcoglycan (Sgca-null mice) develop progressive muscular dystrophy and serve as a model for human limb girdle muscular dystrophy type 2D. Sgca-null mice suffer a more severe myopathy than that of mdx mice, the model for Duchenne muscular dystrophy. This is the opposite of what is observed in humans and the reason for this is unknown. In an attempt to understand the cellular basis of this severe muscular dystrophy, we isolated clonal populations of myogenic progenitor cells (MPCs), the resident postnatal muscle progenitors of dystrophic and wild-type mice. MPCs from Sgca-null mice generated much smaller clones than MPCs from wild-type or mdx dystrophic mice. Impaired proliferation of Sgca-null myogenic precursors was confirmed by single fiber analysis and this difference correlated with Sgca expression during MPC proliferation. In the absence of dystrophin and associated proteins, which are only expressed after differentiation, SGCA complexes with and stabilizes FGFR1. Deficiency of Sgca leads to an absence of FGFR1 expression at the membrane and impaired MPC proliferation in response to bFGF. The low proliferation rate of Sgca-null MPCs was rescued by transduction with Sgca-expressing lentiviral vectors. When transplanted into dystrophic muscle, Sgca-null MPCs exhibited reduced engraftment. The reduced proliferative ability of Sgca-null MPCs explains, at least in part, the severity of this muscular dystrophy and also why wild-type donor progenitor cells engraft efficiently and consequently ameliorate disease.     

Inhibin B levels in adolescents and young adults with type 1 diabetes

OBJECTIVE/METHODS: To assess exocrine and endocrine testicular function in subjects with diabetes, we evaluated serum inhibin B, gonadotrophins and testosterone levels in 33 male adolescent and young adult patients affected by type-1 diabetes (age 21.0 +/- 5 years; range 14.2-33.3), with a mean disease duration of 12.7 +/- 5.8 years (range 1.5-25.3) and various metabolic control (HbA1c 7.8 +/- 1.5%; range 5.5-13.2) and compared them with those of an age-matched group of 36 healthy control subjects (age 19.5 +/- 4.1 years; range 13.6-28.1). Both patients and controls had a testicular volume >or=15 ml. Inhibin B was measured by ELISA method. RESULTS/CONCLUSION: Diabetics and controls had comparable inhibin B (203 +/- 74 vs. 221 +/- 69 pg/ml, respectively) and follicle-stimulating hormone (FSH) levels, while luteinizing hormone (LH) and testosterone levels were significantly higher in the diabetic group. Inhibin B was negatively correlated both in patients and controls with FSH, while a negative correlation with LH was found only in the diabetic group. We conclude that our young diabetic males, after a mean disease duration of 12 years and various metabolic control, had inhibin B and FSH levels comparable to those of normal subjects. Therefore, they seem to have a regular testicular function and in particular a normal seminiferous tubule/Sertoli cell activity despite sustained hyperglycemia.     

Increased conformational rigidity of humic substances by oxidative biomimetic catalysis

A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed by Fe(TDCPPS)Cl. HPSEC further showed that the polymerization reaction turned the loosely bound humic supramolecular structures into more stable conformations which could no longer be disrupted by the disaggregating effect of acetic acid. DRIFT spectroscopy suggested the formation of new alkyl and aromatic ethers following the oxidative coupling with the biomimetic catalyst. CPMAS-(13)C NMR and EPR spectra suggested a reduced molecular mobility of humic components and enhanced stabilization of free radicals in larger oxidized fragments. All findings concur in indicating that the biomimetic catalysis by Fe(TDCPPS)Cl increased the molecular mass and chemical rigidity of humic materials by formation of intermolecular covalent bonds via a free-radical mechanism. The development of a technology based on oxidative polymerization by biomimetic catalysis may be of importance in controlling the properties and reactivity of humic matter for industrial and environmental applications.     

Two-component signal transduction pathways regulating growth and cell cycle progression in a bacterium: a system-level analysis

Two-component signal transduction systems, comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein–protein interactions. These signaling pathways have also been demonstrated to play a role in coordinating bacterial cell cycle progression and development. Here we report a system-level investigation of two-component pathways in the model organism Caulobacter crescentus. First, by a comprehensive deletion analysis we show that at least 39 of the 106 two-component genes are required for cell cycle progression, growth, or morphogenesis. These include nine genes essential for growth or viability of the organism. We then use a systematic biochemical approach, called phosphotransfer profiling, to map the connectivity of histidine kinases and response regulators. Combining these genetic and biochemical approaches, we identify a new, highly conserved essential signaling pathway from the histidine kinase CenK to the response regulator CenR, which plays a critical role in controlling cell envelope biogenesis and structure. Depletion of either cenK or cenR leads to an unusual, severe blebbing of cell envelope material, whereas constitutive activation of the pathway compromises cell envelope integrity, resulting in cell lysis and death. We propose that the CenK–CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. Finally, the ability of our in vitro phosphotransfer profiling method to identify signaling pathways that operate in vivo takes advantage of an observation that histidine kinases are endowed with a global kinetic preference for their cognate response regulators. We propose that this system-wide selectivity insulates two-component pathways from one another, preventing unwanted cross-talk.     

Lactulose and mannitol intestinal permeability detected by capillary electrophoresis

Aim of this study was to set up a method by capillary electrophoresis to detect lactulose and mannitol in urine after an oral load, and to estimate the intestinal permeability in controls and in type I diabetes patients. The underivatized carbohydrates were monitored by indirect UV detection using sorbate, cetyltrimethylammonium bromide and LiOH as background electrolyte. Urines were purified by solid phase extraction, shaken with cation exchange resin, filtered and analysed. Carbohydrates migrated in <10 min in relation to their pK(a) and M(r). Controls (n = 33) and patients (n = 23) had an excretion ratio lactulose/mannitol 0.025 (0.018-0.051) and 0.067 (0.050-0.127), respectively (p < 0.01, median, interquartile range).