Heterogeneous expression of Ca(2+) handling proteins in rabbit sinoatrial node.

We investigated the densities of the L-type Ca(2+) current, i(Ca,L), and various Ca(2+) handling proteins in rabbit sinoatrial (SA) node. The density of i(Ca,L), recorded with the whole-cell patch-clamp technique, varied widely in sinoatrial node cells. The density of i(Ca,L) was significantly (p<0.001) correlated with cell capacitance (measure of cell size) and the density was greater in larger cells (likely to be from the periphery of the SA node) than in smaller cells (likely to be from the center of the SA node). Immunocytochemical labeling of the L-type Ca(2+) channel, Na(+)-Ca(2+) exchanger, sarcoplasmic reticulum Ca(2+) release channel (RYR2), and sarcoplasmic reticulum Ca(2+) pump (SERCA2) also varied widely in SA node cells. In all cases there was significantly (p<0.05) denser labeling of cells from the periphery of the SA node than of cells from the center. In contrast, immunocytochemical labeling of the Na(+)-K(+) pump was similar in peripheral and central cells. We conclude that Ca(2+) handling proteins are sparse and poorly organized in the center of the SA node (normally the leading pacemaker site), whereas they are more abundant in the periphery (at the border of the SA node with the surrounding atrial muscle).     

Species-specific difference in distribution of voltage-gated L-type Ca(2+) channels of cardiac myocytes

Ca²⁺influx via sarcolemmal voltage-dependent Ca²⁺ channels(L-type Ca²⁺ channels) is the fundamental step inexcitation-contraction (E-C) coupling in cardiac myocytes.Physiological and pharmacological studies reveal species-specificdifferences in E-C coupling resulting from a difference in thecontribution of Ca²⁺ influx and intracellularCa²⁺ release to activation of contraction. We investigatedthe distribution of L-type Ca²⁺ channels in isolatedcardiac myocytes from rabbit and rat ventricle by correlativeimmunoconfocal and immunogold electron microscopy. Immunofluorescence labeling revealed discrete spots in the surface plasma membrane and transverse (T) tubules in rabbit myocytes. In ratmyocytes, labeling appeared more intense in T tubules than in thesurface sarcolemma. Immunogold electron microscopy extended thesefindings, showing that the number of gold particles in the surfaceplasma membrane was significantly higher in rabbit than rat myocytes.In rabbit myocyte plasma membrane, the gold particles were distributedas clusters in both regions that were associated with junctionalsarcoplasmic reticulum and those that were not. The findings areconsistent with the idea that influx of Ca²⁺ via surfacesarcolemmal Ca²⁺ channels contributes to intracellularCa²⁺ to a greater degree in rabbit than in rat myocytes.

     

Occurrence and disappearance of a non-native goby Rhinogobius sp. OR in relation to hydrological conditions in the Kamo River,southwestern Japan

Ichthyological Research - We monitored the abundance of a non-native (Rhinogobius sp. OR) and two native stream gobies (R. fluviatilis and R. nagoyae) over a decade, from 1995 to 2004, in a fixed...     

Presence of the Kv1.5 K(+) channel in the sinoatrial node.

The aim of this study was to establish, using immunolabeling, whether the Kv1.5 K(+) channel is present in the pacemaker of the heart, the sinoatrial (SA) node. In the atrial muscle surrounding the SA node and in the SA node itself (from guinea pig and ferret), Western blotting analysis showed a major band of the expected molecular weight, approximately 64 kD. Confocal microscopy and immunofluorescence labeling showed Kv1.5 labeling clustered in atrial muscle but punctate in the SA node. In atrial muscle, Kv1.5 labeling was closely associated with labeling of Cx43 (gap junction protein) and DPI/II (desmosomal protein), whereas in SA node Kv1.5 labeling was closely associated with labeling of DPI/II but not labeling of Cx43 (absent in the SA node) or Cx45 (another gap junction protein present in the SA node). Electron microscopy and immunogold labeling showed that the Kv1.5 labeling in atrial muscle is preferentially associated with desmosomes rather than gap junctions.     

Transplantation of autologous rabbit BM-derived mesenchymal stromal cells embedded in hyaluronic acid gel sponge into osteochondral defects of the knee

BACKGROUND: Mesenchymal stromal cells (MSC) have the potential to differentiate into distinct mesenchymal tissues including cartilage, suggesting that these cells are an attractive cell source for cartilage tissue engineering approaches. Various methods, such as using hyaluronan-based materials, have been employed to improve transplantation for repair. Our objective was to study the effects of autologous transplantation of rabbit MSC with hyaluronic acid gel sponges into full-thickness osteochondral defects of the knee. METHODS: Rabbit BM-derived MSC were cultured and expanded with fibroblast growth factor (FGF). Specimens were harvested at 4 and 12 weeks after implantation, examined histologically for morphologic features, and stained immunohistochemically for type II collagen and CD44. RESULTS: The regenerated area after autologous transplantation of hyaluronic acid gel sponge loaded with MSC into the osteochondral defect at 12 weeks after surgery showed well-repaired cartilage tissue, resembling the articular cartilage of the surrounding structure, of which the histologic score was significantly better than that of the untreated osteochondral defect. In the regenerated cartilage, type II collagen was found in the pericellular matrix of regenerative chondrocytes, while CD44 expression in the regenerative tissue could not be revealed. DISCUSSION: These data suggest that the autologous transplantation of MSC embedded in hyaluronan-based material may support chondrogenic differentiation and be useful for osteochondral defect repair.     

Regulation of cargo‐selective endocytosis by dynamin 2 GTPase‐activating protein girdin

In clathrin‐mediated endocytosis (CME), specificity and selectivity for cargoes are thought to be tightly regulated by cargo‐specific adaptors for distinct cellular functions. Here, we show that the actin‐binding protein girdin is a regulator of cargo‐selective CME. Girdin interacts with dynamin 2, a GTPase that excises endocytic vesicles from the plasma membrane, and functions as its GTPase‐activating protein. Interestingly, girdin depletion leads to the defect in clathrin‐coated pit formation in the center of cells. Also, we find that girdin differentially interacts with some cargoes, which competitively prevents girdin from interacting with dynamin 2 and confers the cargo selectivity for CME. Therefore, girdin regulates transferrin and E‐cadherin endocytosis in the center of cells and their subsequent polarized intracellular localization, but has no effect on integrin and epidermal growth factor receptor endocytosis that occurs at the cell periphery. Our results reveal that girdin regulates selective CME via a mechanism involving dynamin 2, but not by operating as a cargo‐specific adaptor.     

The Relationship between Child Maltreatment and Emotion Recognition

Child abuse and neglect affect the development of social cognition in children and inhibit social adjustment. The purpose of this study was to compare the ability to identify the emotional states of others between abused and non-abused children. The participants, 129 children (44 abused and 85 non-abused children), completed a children’s version of the Reading the Mind in the Eyes Test (RMET). Results showed that the mean accuracy rate on the RMET for abused children was significantly lower than the rate of the non-abused children. In addition, the accuracy rates for positive emotion items (e.g., hoping, interested, happy) were significantly lower for the abused children, but negative emotion and neutral items were not different across the groups. This study found a negative relationship between child abuse and the ability to understand others’ emotions, especially positive emotions.     

Macromolecule-small molecule interactions; introduction of additional binding sites in polyethyleneimine by disulfide cross-linkages

Polyethyleneimine and its acyl derivatives have been thiolated with thiobutyrolactone and the SH groups introduced have been crosslinked in the presence of and in the absence of methyl orange, respectively. After crosslinking of the polymers, the bound methyl orange was removed. The resultant two kinds of crosslinked polymers have been examined for their ability to bind methyl orange. The polymer crosslinked in the presence of methyl orange shows more binding sites and stronger binding than does the polymer crosslinked in the absence of methyl orange. It seems, therefore, that the conformation of the polymer may be molded to provide sites that can accommodate a specific small molecule.