Viscoelastic behaviour of human mesenchymal stem cells

Background  

In this study, we have investigated the viscoelastic behaviour of individual human adult bone marrow-derived mesenchymal stem cells (hMSCs) and the role of F-actin filaments in maintaining these properties, using micropipette aspiration technique together with a standard linear viscoelastic solid model.     

Pentosan polysulfate promotes proliferation and chondrogenic differentiation of adult human bone marrow-derived mesenchymal precursor cells

Introduction  

This study was undertaken to determine whether the anti-osteoarthritis drug pentosan polysulfate (PPS) influenced mesenchymal precursor cell (MPC) proliferation and differentiation.     

Experimental stress in inflammatory rheumatic diseases: a review of psychophysiological stress responses

Introduction  

Stressful events are thought to contribute to the aetiology, maintenance and exacerbation of rheumatic diseases. Given the growing interest in acute stress responses and disease, this review investigates the impact of real-life experimental psychosocial, cognitive, exercise and sensory stressors on autonomic, neuroendocrine and immune function in patients with inflammatory rheumatic diseases.     

Diverse catalytic activities in the alphabeta-hydrolase family of enzymes: activation of H2O, HCN, H2O2, and O2

The article describes the observation of novel catalytic activities in the alphabeta-hydrolase superfamily apparently unrelated to ester hydrolysis and unexpected biochemical observations relating to the structure and function of the serine catalytic triad in these enzymes. One common feature of these novel activities is the activation of a small diatomic molecule, but via diverse chemistry. Possible mechanisms of catalysis are discussed.     

Postsynaptic density antigens: preparation and characterization of an antiserum against postsynaptic densities

Long-term immunization of rabbits with postsynaptic densities (PSD) from bovine brain produced an antiserum specific for PSD as judged by binding to subcellular fractions and immunohistochemical location at the light and electron microscope levels. (a) The major antigens of bovine PSD preparations were three polypeptides of molecular weight 95,000 (PSD-95), 82,000 (PSD-82), and 72,000 (PSD-72), respectively. Antigen PSD-95, also present in mouse and rat PSDs was virtually absent from cytoplasm, myelin, mitochondria, and microsomes from rodent or bovine brain. Antigens PSD-82 and PSD-72 were present in all subcellular fractions from bovine brain, especially in mitochondria, but were almost absent from rodent brain. The antiserum also contained low-affinity antibodies against tubulin. (b)Immunohistochemical studies were performed in mouse and rat brain, where antigen PSD-95 accounted for 90 percent of the antiserum binding after adsorption with purified brain tubulin. At the light microscope level, antibody binding was observed only in those regions of the brain where synapses are known to be present. No reaction was observed in myelinated tracts, in the neuronal cytoplasm, or in nonneuronal cells. Strong reactivity was observed in the molecular layer of the dentate gyrus, stratum oriens and stratum radiatum of the hippocampus, and the molecular layer of the cerebellum. Experimental lesions, such as ablation of the rat entorhinal cortex or intraventricular injection of kainic acid, which led to a major loss of PSD in well- defined areas of the hippocampal formation, caused a correlative decrease in immunoreactivity in these areas. Abnormal patterns of immunohistochemical staining correlated with abnormal synaptic patterns in the cerebella of reeler and staggerer mouse mutants. (c) At the electron microscopic level, immunoreactivity was detectable only in PSD. The antibody did not bind to myelin, mitochondria or plasma membranes. (d) The results indicate that antigen PSD-95 is located predominantly or exclusively in PSD and can be used as a marker during subcellular fractionation. Other potential uses include the study of synaptogenesis, and the detection of changes in synapse number after experimental perturbations of the nervous system.     

Acid-base catalysis in the extradiol catechol dioxygenase reaction mechanism: site-directed mutagenesis of His-115 and His-179 in Escherichia coli 2,3-dihydroxyphenylpropionate 1,2-dioxygenase (MhpB)

The extradiol catechol dioxygenases catalyze the non-heme iron(II)-dependent oxidative cleavage of catechols to 2-hydroxymuconaldehyde products. Previous studies of a biomimetic model reaction for extradiol cleavage have highlighted the importance of acid-base catalysis for this reaction. Two conserved histidine residues were identified in the active site of the class III extradiol dioxygenases, positioned within 4-5 A of the iron(II) cofactor. His-115 and His-179 in Escherichia coli 2,3-dihydroxyphenylpropionate 1,2-dioxygenase (MhpB) were replaced by glutamine, alanine, and tyrosine. Each mutant enzyme was catalytically inactive for extradiol cleavage, indicating the essential nature of these acid-base residues. Replacement of neighboring residues Asp-114 and Pro-181 gave D114N, P181A, and P181H mutant enzymes with reduced catalytic activity and altered pH/rate profiles, indicating the role of His-179 as a base and His-115 as an acid. Mutant H179Q was catalytically active for the lactone hydrolysis half-reaction, whereas mutant H115Q was inactive, implying a role for His-115 in lactone hydrolysis. A catalytic mechanism involving His-179 and His-115 as acid-base catalytic residues is proposed.     

Crystallization and preliminary x-ray investigation of purine-nucleoside phosphorylase from Escherichia coli

Crystals of purine-nucleoside phosphorylase from Escherichia coli have been grown from solutions of ammonium sulfate. The crystals are hexagonal with space group P6(1)22 or P6(5)22; the axes are alpha = 106.5 A and c = 241.3 A. The crystals are moderately stable to x-rays and diffract beyond 3.0-A resolution. It appears that the molecule, which is a hexamer, utilizes the 2-fold symmetry of the space group, resulting in three subunits/asymmetric unit.