Evaluation of Extensor Mechanism in Revision Knee Arthroplasty

Background

The success of revision total knee arthroplasty depends on adequate exposure that does not produce complications. The purpose of this study was to compare the results of revision total knee arthroplasty between V-Y quadricepsplasty (QP) and quadriceps snip (QS) approaches.

Astrocytoma adhesion to extracellular matrix: functional significance of integrin and focal adhesion kinase expression

Evidence is accumulating implicating a role for integrins in the pathogenesis of cancer, a disease in which alterations in cellular growth, differentiation, and adhesive characteristics are defining features. In the present report we studied a panel of 8 human astrocytoma cell lines for their expression of integrin subunits by RT-PCR, and of integrin heterodimers by immunoprecipitation analyses. The functionality of integrin heterodimers was assessed using cell attachment assays to plastic or single matrix substrates. Downstream effects of integrin activation were studied by western blot analyses of FAK expression in human astrocytoma cell lines growing on plastic and on a fibronectin matrix, and in 13 primary human brain tumor specimens of varying histopathological grade. Furthermore, we studied tyrosine phosphorylation of FAK in astrocytoma cells growing on plastic versus fibronectin. Finally, we analyzed the effects of intermediate filament gene transfer on FAK phosphorylation in SF-126 astrocytoma cells. Our data show that astrocytoma cell lines express various integrin subunits by RT-PCR, and heterodimers by immunoprecipitation analyses. The beta1 and alphav integrin subunits were expressed by all astrocytoma cell lines. The alpha3 subunit was expressed by all cell lines except SF-188. By immunoprecipitation, the fibronectin receptor (alpha5beta1 integrin heterodimer) and the vitronectin receptor (alphavbeta3) were identified in several cell lines. Astrocytoma cell attachment studies to human matrix proteins suggested that these integrin heterodimers were functional. Using confocal laser microscopy, we showed that FAK was colocalized to actin stress fibers at sites of focal adhesion complexes. By western blot, FAK was variably but quite ubiquitously expressed in human astrocytoma cell lines, and in several primary human astrocytoma specimens. When U373 and U87 MG astrocytoma cells bind to a fibronectin matrix, FAK is phosphorylated. GFAP-transfected SF-126 human astrocytoma cells were shown to overexpress the phosphorylated form of FAK only when these cells were placed on a fibronectin matrix. This result is of interest because it suggests that manipulations of the astrocytoma cytoskeleton per se can bring about potential signaling changes that channel through integrins and focal adhesion sites leading to activation of key kinases such as FAK.     

Mechanical properties and biomineralization of multifunctional nanodiamond-PLLA composites for bone tissue engineering

Multifunctional bone scaffold materials have been produced from a biodegradable polymer, poly(L-lactic acid) (PLLA), and 1-10% wt of octadecylamine-functionalized nanodiamond (ND-ODA) via solution casting followed by compression molding. By comparison to pure PLLA, the addition of 10% wt of ND-ODA resulted in a significant improvement of the mechanical properties of the composite matrix, including a 280% increase in the strain at failure and a 310% increase in fracture energy in tensile tests. The biomimetic process of bonelike apatite growth on the ND-ODA/PLLA scaffolds was studied using microscopic and spectroscopic techniques. The enhanced mechanical properties and the increased mineralization capability with higher ND-ODA concentration suggest that these biodegradable composites may potentially be useful for a variety of biomedical applications, including scaffolds for orthopedic regenerative engineering.     

Reevaluating the mechanisms of focal ictogenesis: The role of low‐voltage fast activity

The mechanisms that control the transition into a focal seizure are still uncertain. The introduction of presurgical intracranial recordings to localize the epileptogenic zone in patients with drug‐resistant focal epilepsies opened a new window to the interpretation of seizure generation (ictogenesis). One of the most frequent focal patterns observed with intracranial electrodes at seizure onset is characterized by low‐voltage fast activity in the beta‐gamma range that may or may not be preceded by changes of ongoing interictal activities. In the present commentary, the mechanisms of generation of focal seizures are reconsidered, focusing on low‐voltage fast activity patterns. Experimental findings on models of temporal lobe seizures support the view that the low‐voltage fast activity observed at seizure onset is associated with reinforcement and synchronization of inhibitory networks. A minor role for the initiation of the ictal pattern is played by principal neurons that are progressively recruited with a delay, when inhibition declines and synchronous high‐voltage discharges ensue. The transition from inhibition into excitatory recruitment is probably mediated by local increase in potassium concentration associated with synchronized interneuronal firing. These findings challenge the classical theory that proposes an increment of excitation and/or a reduction of inhibition as a cause for the transition to seizure in focal epilepsies. A new definition of ictogenesis mechanisms, as herewith hypothesized, might possibly help to develop new therapeutic strategies for focal epilepsies.     

Calcium signaling in endocardial and epicardial ventricular myocytes from streptozotocin-induced diabetic rats

Aims/IntroductionAbnormalities in Ca²⁺ signaling have a key role in hemodynamic dysfunction in diabetic heart. The purpose of this study was to explore the effects of streptozotocin (STZ)‐induced diabetes on Ca²⁺ signaling in epicardial (EPI) and endocardial (ENDO) cells of the left ventricle after 5–6 months of STZ injection.Materials and MethodsWhole‐cell patch clamp was used to measure the L‐type Ca²⁺ channel (LTCC) and Na⁺/Ca²⁺ exchanger currents. Fluorescence photometry techniques were used to measure intracellular free Ca²⁺ concentration.ResultsAlthough the LTCC current was not significantly altered, the amplitude of Ca²⁺ transients increased significantly in EPI‐STZ and ENDO‐STZ compared with controls. Time to peak LTCC current, time to peak Ca²⁺ transient, time to half decay of LTCC current and time to half decay of Ca²⁺ transients were not significantly changed in EPI‐STZ and ENDO‐STZ myocytes compared with controls. The Na⁺/Ca²⁺ exchanger current was significantly smaller in EPI‐STZ and in ENDO‐STZ compared with controls.ConclusionsSTZ‐induced diabetes resulted in an increase in amplitude of Ca²⁺ transients in EPI and ENDO myocytes that was independent of the LTCC current. Such an effect can be attributed, at least in part, to the dysfunction of the Na⁺/Ca²⁺ exchanger. Additional studies are warranted to improve our understanding of the regional impact of diabetes on Ca²⁺ signaling, which will facilitate the discovery of new targeted treatments for diabetic cardiomyopathy.     

First record of species Dicranotaenia synsacculata Macko, 1988 (Cestoda, Hymenolepididae) of the goldeneye Bucephala clangula (Linneus, 1758) in Poland

During parasitological studies of 32 specimens of the goldeneye Bucephala clangula L., twenty seven cestode specimens were found. Four of them, isolated from the jejunum of two young female hosts, were determinated as Dicranotaenia synsacculata Macko, 1988. We based on the shape of cirrus fused with sacculus accessorius internus, shape and size of scolex and other organs. This is the first record of this species in Poland.