Biological evaluation of intervertebral disc cells in different formulations of gellan gum‐based hydrogels

Gellan gum (GG)‐based hydrogels are advantageous in tissue engineering not only due to their ability to retain large quantities of water and provide a similar environment to that of natural extracellular matrix (ECM), but also because they can gelify in situ in seconds. Their mechanical properties can be fine‐tuned to mimic natural tissues such as the nucleus pulposus (NP). This study produced different formulations of GG hydrogels by mixing varying amounts of methacrylated (GG‐MA) and high‐acyl gellan gums (HA‐GG) for applications as acellular and cellular NP substitutes. The hydrogels were physicochemically characterized by dynamic mechanical analysis. Degradation and swelling abilities were assessed by soaking in a phosphate buffered saline solution for up to 170 h. Results showed that as HA‐GG content increased, the modulus of the hydrogels decreased. Moreover, increases in HA‐GG content induced greater weight loss in the GG‐MA/HA‐GG formulation compared to GG‐MA hydrogel. Potential cytotoxicity of the hydrogel was assessed by culturing rabbit NP cells up to 7 days. An MTS assay was performed by seeding rabbit NP cells onto the surface of 3D hydrogel disc formulations. Viability of rabbit NP cells encapsulated within the different hydrogel formulations was also evaluated by Calcein‐AM and ATP assays. Results showed that tunable GG‐MA/HA‐GG hydrogels were non‐cytotoxic and supported viability of rabbit NP cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Poststreptococcal reactive arthritis in children: is it really a different entity from rheumatic fever?

Poststreptococcal reactive arthritis (PSRA) is an acute, nonsuppurative arthritis following documented streptococcal infections. Although most authors accepted it as a different entity, the differences from acute rheumatic fever (ARF) are not clear. To document and compare the clinical and laboratory characteristics of PSRA and ARF, 24 patients with PSRA and 20 with ARF were enrolled in the study. The latency period from upper respiratory tract infection was shorter in patients with PSRA ( P<0.01). However, 25% of the patients with ARF had also short (<10 days) latency periods. Although symmetric and nonmigratory arthritis were more frequent in patients with PSRA, there was no significant difference for the distribution of mono-, oligo-, and polyarticular disease between PSRA and ARF patients. The frequency of small joint and hip involvement was also similar between the patient groups. Unresponsiveness of articular symptoms to salicylate therapy within 72 h was more frequent in patients with PSRA (P<0.001). However, in a substantial part of the patients with ARF (nine patients, 45%), joint symptoms also had no response during the first 72 h. Since there is a considerable overlap of symptoms, signs, and laboratory features of PSRA and ARF, a line between these two entities could not be easily drawn. We conclude that these two conditions are actually different presentations of the same disease.     

Platelet glycoproteins IIb and IIIa as a calcium channel in liposomes

Human platelet membrane glycoproteins IIb and IIIa (GPIIb and IIIa) were incorporated into phospholipid vesicles by the reverse-phase technique to assess the ability of GPIIb and IIIa to function as a Ca2+ channel. Movement of Ca2+ across the lipid bilayer was quantitated by injection of proteoliposomes with encapsulated Fura-2 into Ca2+ buffers and measurement of Fura-2 fluorescence as an indicator of Ca2+ influx. Reciprocally, to assess the function of proteins in an inside-out orientation, Ca2+-loaded vesicles were injected into Ca2+-free buffer and Ca2+ efflux monitored by a calcium electrode. Incorporation of the IIb-IIIa complex produced significant facilitation of Ca2+ movement across the lipid bilayer. No net transmembrane Ca2+ movement was seen with dissociated IIb and IIIa. Movement of Ca2+ was proportional to the transmembrane Ca2+ gradient. Ca2+ movement into the vesicles was inversely proportional to extravesicular NaCl from 25 to 150 mmol/L, analogous to several studies in the intact platelet. Adenosine triphosphate had no effect on Ca2+ movement into or out of the vesicles. Specific inhibition of a Ca2+ shift into the vesicles was seen with M148, a monoclonal antibody to IIb/IIIa, while no inhibition was observed with a panel of other anti-IIb/IIIa monoclonal antibodies. This suggests that a specific site on the complex or orientation of the complex is essential for calcium channel function. These data demonstrate that the GPIIb/IIIa complex can serve as a passive Ca2+ channel across a phospholipid bilayer and has the potential to play a role in Ca2+ flux across the platelet plasma membrane.     

Factor V deficiency in Philadelphia-positive chronic myelogenous leukemia

Factor V deficiency has been identified in 8 of 8 patients 7--20 yr of age, with Philadelphia-positive (Ph1+) chronic myelogenous leukemia (CML). In these 8 patients, factor V deficiency was not due to hepatic dysfunction, factor V inhibitors, or disseminated intravascular coagulation. In 3 patients, factor V activity rose 10%--12% (0.10--0.12 U/ml) after the infusion of 28--31 ml/kg body weight of fresh frozen plasma (FFP). The rise persisted less than 14 hr. The mean measured postinfusion rise in factor V was 18% of the expected rise calculated from the volume of FFP infused in the patients' plasma volume. In 4 patients, a small transient rise in factor V activity occurred after splenectomy or plateletpheresis. Factor V deficiency was completely corrected after a marked reduction in bone marrow cellularity in 2 patients with Ph1+ CML treated with extensive chemotherapy, total body irradiation, and bone marrow transplantation. Factor V deficiency was retrospectively observed in 6 of 20 patients, ages 20--80 yr, with Ph1+ CML and 3 of 6 patients with other myeloproliferative disorders. The factor V deficiency appears to be associated with the large myeloid- megakaryocytic cell mass characteristic of CML and other myeloproliferative disorders.     

Multivessel Coronary Thrombosis in a Patient with Idiopathic Thrombocytopenic Purpura

A 49-year-old woman who had idiopathic thrombocytopenic purpura was admitted to our hospital with severe chest pain. Electrocardiography revealed inferolateral myocardial infarction. The patient underwent immediate coronary angiography, which revealed thrombi in the left coronary system. Percutaneous intervention was not indicated, because the thrombi had occluded the distal segments of multiple coronary arteries. Administration of tirofiban satisfactorily dissolved the thrombi.Key words: Coronary thrombosis, multivessel; myocardial infarction; platelet aggregation inhibitors/therapeutic use; purpura, thrombocytopenic, idiopathic/therapy; tirofibanIdiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder in which autoantibodies bind platelets, leading to their sequestration by the reticuloendothelial system.¹ Patients with ITP typically have mucocutaneous bleeding. Although such reports are rare, thrombotic complications such as acute myocardial infarction (MI) and stroke also occur in patients with ITP.^2–4 We present the case of a middle-aged woman with ITP who sustained an acute MI caused by multivessel coronary thrombosis.