A Doubly Fmoc-Protected Aspartic Acid Self-Assembles into Hydrogels Suitable for Bone Tissue Engineering

Hydrogels have been used as scaffolds for biomineralization in tissue engineering and regenerative medicine for the repair and treatment of many tissue types. In the present work, we studied an amino acid-based material that is attached to protecting groups and self-assembles into biocompatible and stable nanostructures that are suitable for tissue engineering applications. Specifically, the doubly protected aspartic residue (Asp) with fluorenyl methoxycarbonyl (Fmoc) protecting groups have been shown to lead to the formation of well-ordered fibrous structures. Many amino acids and small peptides which are modified with protecting groups display relatively fast self-assembly and exhibit remarkable physicochemical properties leading to three-dimensional (3D) networks, the trapping of solvent molecules, and forming hydrogels. In this study, the self-assembling fibrous structures are targeted toward calcium binding and act as nucleation points for the binding of the available phosphate groups. The cell viability, proliferation, and osteogenic differentiation of pre-osteoblastic cells cultured on the formed hydrogel under various conditions demonstrate that hydrogel formation in CaCl₂ and CaCl₂-Na₂HPO₄ solutions lead to calcium ion binding onto the hydrogels and enrichment with phosphate groups, respectively, rendering these mechanically stable hydrogels osteoinductive scaffolds for bone tissue engineering.     

Repair of all the components of the syndrome of aortic regurgitation and VSD

There is still no agreement about the need for, timing, andtype of repair of the Syndrome of VSD and AR (syndrome of Laubry     

Three-dimensional sonographic evaluation of the common bile duct.

OBJECTIVE: To assess the accuracy of three-dimensional sonographic measurements of the common bile duct compared with standard two-dimensional anteroposterior measurement of the common duct. METHODS: Fifty-five consecutive patients referred for abdominal sonography underwent standard two-dimensional abdominal sonography followed by three-dimensional sonographic data acquisition of the right upper quadrant. A radiologist blinded to the results of the two-dimensional examination later measured the three-dimensional long axis anteroposterior common duct diameter and three-dimensional short axis anteroposterior and transverse common duct diameters. RESULTS: The mean average common duct diameter as measured by two-dimensional sonography (long axis anteroposterior) was 3.6 mm. The mean average common duct diameter as measured by long axis anteroposterior three-dimensional sonography was 4.1 mm. The mean average common duct diameter as measured by anteroposterior short axis three-dimensional sonography was 4.1 mm, and by transverse short axis three-dimensional sonography, it was 4.4 mm. The two-dimensional common duct measurement correlated with the long axis anteroposterior three-dimensional measurement (P < .001), the short axis anteroposterior three-dimensional measurement (P < .001), and the short axis transverse three-dimensional measurement (P < .005) by the Spearman rank order correlation coefficient test. CONCLUSIONS: Three-dimensional sonographic measurements of the common bile duct correlate highly with two-dimensional measurements, validating the use of three-dimensional sonography as a reliable method for evaluation of common bile duct size.     

Plasma glutamate and glycine levels in patients with amyotrophic lateral sclerosis

Defective glutamate (Glu) metabolism and glutamate excitotoxicity have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). Glycine (Gly), the main inhibitory neurotransmitter, has been shown to potentiate excitatory transmission. In the present study, the levels of Glu and Gly in fasting plasma were measured by high performance liquid chromatography (HPLC) in 20 healthy volunteers and in 65 untreated ALS patients. Increased plasma Glu levels were observed in ALS (p=0.05), correlating with longer disease duration (p=0.03, beta=0.34) and male gender (p=0.02). Furthermore, the increase was found only in the spinal subtype of the disease (p=0.03), while in the bulbar subtype, no significant increase was noted. As regards plasma Gly, no difference was observed between patients and controls; however female patients had higher levels than males. The above results are compatible with the "glutamate hypothesis" of ALS and suggest that the spinal and bulbar-onset subtypes of the disease may be biochemically different.     

On the in vivo action of erythropoietin: a quantitative analysis

The composite response of the erythron to exogenous erythropoietin has been studied in normal, splenectomized, and polycythemic mice. After stimulation the normal animal doubled its marrow nucleated red cells by the 3rd day with little further change by the 5th. Nucleated red cells within the spleen began to increase sharply on the 2nd day and, by the 5th, exceeded those in the marrow. The total nucleated erythroid response represented a fourfold increase. Reticulocytes lagged behind the expansion of the nucleated red cell mass, but by the 5th day the original ratio was re-established. Hemoglobin synthesis was increased, but the ratio of hemoglobin synthesized in nucleated red cells and reticulocytes was basically unchanged. Early displacement of marrow reticulocytes into circulation and the production of a larger red cell also occurred. No evidence of a change in the number of erythroid mitoses was found; only a slight decrease in the average cell cycle time was demonstrated. Thus, whereas erythropoietin stimulation induced several changes in erythropoiesis, the increased number of cells entering into the maturing pool appeared to be of greatest quantitative significance.Splenectomy reduced the proliferative response of the erythron over 5 days stimulation to three-fourths that found in the normal animal. This difference, also reflected in a proportionately lower reticulocyte response and increment in circulating red cell mass, suggests that erythropoiesis within the mouse marrow is spatially or otherwise restricted and that the spleen provided a supplemental area of erythroid expansion.     

Current Status of Antiplatelet Agents to Prevent Stroke

Stroke is one of the leading causes of disability; most are due to atherothrombotic mechanisms. About one third of ischemic strokes are preceded by other stroke or transient ischemic attacks. Stroke survivors are at high risk for vascular events (i.e., cerebrovascular and cardiovascular). Prevention of recurrent stroke and other major vascular events can be accomplished by control of risk factors. Nonetheless, the use of antiplatelet agents remains the fundamental component of secondary stroke prevention strategy in patients with noncardioembolic disease. Currently, the uses of aspirin, clopidogrel, or aspirin plus extended-release dipyridamole are valid alternatives for stroke or transient ischemic attack patients. To maximize the beneficial effects of these agents, the treatment should be initiated as early as possible and continue on a lifelong basis.