Body and brain development following exposure to 60Co gamma-irradiation during pregnancy in mice

We studied the dose-response effects of gamma-irradiation on the weight gains of the body and the brain in ICR mice exposed to various doses of 60Co gamma-irradiation ranging from 0 to 1.5 Gy on day 13 of pregnancy (El3). We found that 0.5 Gy gamma-irradiation caused a significant reduction in brain weight but not in body weight among 6-week-old mice. Higher doses (1.0, 1.5 Gy) seriously inhibited body and brain development, resulting in significantly low weights at 6 weeks of age. A significantly lower brain weight among fetuses exposed to 1.5 Gy was found as early as 24 hours after exposure, while significant reductions in the body weight of these same fetuses appeared 3 days after exposure. The effects of radiation on brain and body development were similar for both males and females.

Complexation and chiral recognition thermodynamics of gamma-cyclodextrin with N-acetyl- and N-carbobenzyloxy-dipeptides possessing two aromatic rings

The stability constants (K) and the standard free energy (deltaG degrees ), enthalpy (deltaH degrees ), and entropy changes (deltaS degrees ) for the complexation of gamma-cyclodextrin with 34 enantiomeric and diastereomeric N-acetyl- and N-carbobenzyloxy-d/l-dipeptides with two aromatic moieties were determined in aqueous buffer solution at 298.15 K by titration microcalorimetry. Chiral recognition of the enantiomeric dipeptide pairs by gamma-cyclodextrin was found to be fairly poor, exhibiting only small percentage differences in K, while the diastereomeric dipeptides were discriminated to much greater extent with affinity differences of up to 6-7 times. The complex structures of several selected pairs were elucidated by NMR techniques. Combining the microcalorimetric and NMR data, the complexation and chiral recognition behavior of gamma-cyclodextrin is discussed in particular in terms of the length, bulkiness, and flexibility of the tether connecting the two aromatic moieties in a guest.

Extra amino group-containing gramicidin S analogs possessing outer membrane-permeabilizing activity

Novel (2S,4R)- and (2S,4S)-4-aminoproline residue-containing analogs of the cyclic decapeptide antibiotic gramicidin S were synthesized, which exhibited marked permeabilizing activity on the outer membrane of gram-negative bacteria.

Frequent expression of smooth muscle markers in malignant fibrous histiocytoma of bone

BACKGROUND/AIMS

Malignant fibrous histiocytoma (MFH) of bone, a relatively rare primary malignant bone tumour, is a distinct clinicopathological entity as opposed to MFH derived from soft tissue. Although the true histogenesis of this condition is still controversial, a considerable number of cases of MFH in soft tissue show positive immunohistochemical reactivity for muscle markers such as desmin, common muscle actin (HHF35), and alpha smooth muscle actin (SMA), suggesting that MFH cells are myofibroblastic in nature.

METHODS

This study investigated immunoreactivity for several different muscle markers in 19 cases of MFH of bone together with reverse transcription polymerase chain reaction (RT-PCR) analysis on frozen tissue samples that were available in four cases, and compared the data with those found in 11 cases of osteosarcoma and 11 cases of soft tissue MFH treated over the same period.

RESULTS

Immunohistochemistry revealed that MFH of bone showed relatively frequent expression of smooth muscle markers, including calponin (nine cases), alpha-SMA (nine cases), and SM22alpha (18 cases), and this was confirmed by RT-PCR analysis. However, only one, two, and three cases of MFH of bone showed positive staining for desmin, MyoD1, and HHF35, respectively. Similarly, 11 osteosarcoma cases were relatively frequently positive for alpha-SMA (five cases), calponin (four cases), and SM22alpha (seven cases), and less frequently positive for desmin (one case), MyoD1 (none), and HHF35 (none). In contrast, very few MFH of soft tissue cases (n = 11) showed positive reactivity for all of these muscle markers. It has recently been reported that human bone marrow stromal cells also express various kinds of smooth muscle markers including alpha-SMA and calponin.

CONCLUSIONS

These results suggested that MFH of bone may derive from mesenchymal stromal cells in bone marrow and has a more myofibroblastic differentiation than soft tissue MFH.

Myocardial hamartoma of the right atrium in a dog

A myocardial hamartoma of the right atrium is described in an 8-year-old dog that died from pneumonia. At necropsy, a firm, mottled, dark-brown right atrial appendage, of normal shape but slightly enlarged, was found incidentally. On section, the right atrial appendage was composed of a grey-tan, solid mass. Histological features of the mass were as follows: the component cells were mature cardiac muscle cells; the mass contained all of the components of the normal heart wall (i.e., epicardium, myocardium and endocardium), but the arrangement of the component tissues was disorganized; growth of the mass was non-invasive, and continuity of the component cells with adjacent normal myocardial cells was evident, suggesting a congenital origin. This appears to be the first report of congenital myocardial hamartoma in any animal other than man.

Stereochemistry of protected ornithine side chains of gramicidin S derivatives: X-ray crystal structure of the bis-Boc-tetra-N-methyl derivative of gramicidin S

An X-ray crystallographic analysis of the bis-Ndelta-Boc-tetra-Nalpha-methyl derivative of gramicidin S, cyclo(-Val-MeOrn(Boc)-Leu-d-MePhe-Pro-)2, was undertaken successfully (R-factor = 0.088). As expected, the main chain adopts an antiparallel pleated beta-sheet conformation, but the pleated sheet is slightly twisted, and the sense of twisting is opposite to that found in the reported crystal structures of the gramicidin S-urea complex and the bis-Ndelta-(trichloroacetyl) and bis-Ndelta-(m-bromobenzoyl) derivatives of gramicidin S. In agreement with the observed resistance toward N-methylation, the urethane NH groups of the protected Orn side chains are hydrogen bonded to the carbonyl groups of the d-Phe residues. However, the side-chain-main-chain hydrogen bonding is in the i --> i - 3 mode, although hydrogen bonding in the i --> i + 2 mode was deduced from a 1H NMR study of protected gramicidin S derivatives and was actually found in the crystal structures of the diacylated gramicidin S.

Role of BLNK in oxidative stress signaling in B cells

BLNK (B cell linker protein) represents a central linker protein that bridges the B cell receptor-associated kinases with a multitude of signaling pathways. In this study, we have investigated the role of BLNK in oxidative stress signaling in B cells. H2O2 treatment of B cells induced a rapid tyrosine phosphorylation of BLNK in a H2O2 dose-dependent manner, which was inhibited in Syk-deficient DT40 cells. Calcium mobilization in BLNK-deficient as well as Syk-deficient and phospholipase C (PLC)-gamma2-deficient cells after H2O2 treatment was completely abolished. These were derived from decreased inositol 1,4,5-trisphosphate generation through PLC-gamma2 in BLNK-deficient cells. Moreover, viability of BLNK-deficient as well as PLC-gamma2-deficient cells after exposure to low doses of H2O2 was dramatically enhanced compared with that of the wild-type cells. Furthermore, c-Jun N-terminal kinase activation following high doses of H2O2 stimulation, but not low doses of H2O2 stimulation, was abrogated in BLNK-deficient as well as Syk-deficient cells. These findings have led to the suggestion that BLNK is required for coupling Syk to PLC-gamma2, thereby accelerating cell apoptosis in B cells exposed to low doses of H2O2.

Syk expression and novel function in a wide variety of tissues

Syk protein-tyrosine kinase has been implicated in a variety of hematopoietic cell responses, in particular immunoreceptor signaling events that mediate diverse cellular responses including proliferation, differentiation, and phagocytosis. On the other hand, Syk exhibits a more widespread expression pattern in nonhematopoietic cells like fibroblasts, epithelial cells, breast tissue, hepatocytes, neuronal cells, and vascular endothelial cells and has been shown to be functionally important on these cell types. Thus, Syk appears to play a general physiological function in a wide variety of cells. In this article, we briefly review the current literature regarding the expression and novel function of Syk in various cells and tissues.

Syk expression in endothelial cells and their morphologic defects in embryonic Syk-deficient mice

Mice deficient in the Syk tyrosine kinase showed severe petechiae in utero and died shortly after birth. The mechanism of this bleeding, however, remains unknown. Here it is shown that this bleeding is caused by morphologic defects of Syk-deficient endothelial cells during embryogenesis. Immunoblot and reverse transcriptase-polymerase chain reaction Northern blot analysis indicated that Syk is expressed in several endothelial cell lines. Immunocytochemical analysis also confirmed that Syk is expressed in the normal embryonic endothelial cells and is absent in Syk-deficient mice. Furthermore, electron microscopic analysis of Syk-deficient mice revealed an abnormal morphogenesis and a decreased number of endothelial cells. The results indicate a critical role for Syk in endothelial cell function and in maintaining vascular integrity in vivo.

Adhesion via CD43 induces Syk activation and cell proliferation in TF-1 cells

The effect of adhesion via CD43 (leukosialin, sialophorin) on cell proliferation and phosphorylation signaling were examined in a growth factor-dependent hematopoietic progenitor cell line, TF-1. TF-1 cells promptly resulted in death after withdrawal of growth factors. However, the viable cell number increased when TF-1 cells were cultured on anti-CD43 monoclonal antibody-coated plates. In this case, sustained activation of protein tyrosine kinase Syk and extracellular signal-regulated kinase (Erk) 1/2 were detected. Overexpression of exogenous Syk on TF-1 cells by the adenovirus vector system induced enhancement of the cell proliferation accompanied with enhancement of the Erk activation by a dominant-positive effect. The signal transducer and activator of transcription (STAT) 5 seemed not to be associated with the CD43-mediated cell proliferation. These results indicated that adhesion via CD43 induces the proliferation of TF-1 cells in the absence of growth factors in part by Syk-dependent Erk 1/2 signaling.

A critical role for Syk in endothelial cell proliferation and migration

Syk is a protein-tyrosine kinase that is widely expressed in haematopoietic cells and involved in coupling activated immunoreceptors to downstream signaling. On the other hand, Syk-deficient mice showed severe petechiae in utero and died shortly after birth. Recently we have shown the expression of Syk in endothelial cells and morphological defects of these cells in embryonic Syk-deficient mice. Here we report that both proliferation and migration of human umbilical vein endothelial cells were severely impaired by adenovirus-mediated expression of Syk dominant negative mutants. Furthermore, a close relationship between Syk kinase activity and extracellular signal-regulated kinase activation was suggested. Our results indicate that Syk plays a critical role in endothelial cell functions, including morphogenesis, cell growth, migration, and survival, and contributes to maintaining vascular integrity in vivo.

Structure and function of Syk protein-tyrosine kinase

Non-receptor type of protein-tyrosine kinase Syk contains 2 Src homology 2 (SH2) domains in tandem and multiple autophosphorylation sites. Syk is activated upon binding of tandem SH2 domains to immunoreceptor tyrosine-based activating motif (ITAM) and plays an essential role in lymphocyte development and activation of immune cells. Syk is critical for tyrosine phosphorylation of multiple proteins which regulate important pathways leading from the receptor, such as Ca(2+) mobilization and mitogen-activated protein kinase (MAPK) cascades. Recent findings reveal that expression of Syk appears to be involved in a wide variety of cellular functions and pathogenesis of malignant cancer. These observations have demonstrated that Syk is a key molecule that controls multiple physiological functions in cells.

Local Ca(2+) transients and distribution of BK channels and ryanodine receptors in smooth muscle cells of guinea-pig vas deferens and urinary bladder

1. The relationship between Ca(2+) sparks spontaneously occurring at rest and local Ca(2+) transients elicited by depolarization was analysed using two-dimensional confocal Ca(2+) images of single smooth muscle cells isolated from guinea-pig vas deferens and urinary bladder. The current activation by these Ca(2+) events was also recorded simultaneously under whole-cell voltage clamp. 2. Spontaneous transient outward currents (STOCs) and Ca(2+) sparks were simultaneously detected at -40 mV in approximately 50 % of myocytes of either type. Ca(2+) sparks and corresponding STOCs occurred repetitively in several discrete sites in the subplasmalemmal area. Large conductance Ca(2+)-dependent K(+) (BK) channel density in the plasmalemma near the Ca(2+) spark sites generating STOCs was calculated to be 21 channels microm(-2). 3. When myocytes were depolarized from -60 to 0 mV, several local Ca(2+) transients were elicited within 20 ms in exactly the same peripheral sites where sparks occurred at rest. The local Ca(2+) transients often lasted over 300 ms and spread into other areas. The appearance of local Ca(2+) transients occurred synchronously with the activation of Ca(2+)-dependent K(+) current (I(K,Ca)). 4. Immunofluorescence staining of the BK channel alpha-subunit (BKalpha) revealed a spot-like pattern on the plasmalemma, in contrast to the uniform staining of voltage-dependent Ca(2+) channel alpha1C subunits along the plasmalemma. Ryanodine receptor (RyR) immunostaining also suggested punctate localization predominantly in the periphery. Double staining of BKalpha and RyRs revealed spot-like co-localization on/beneath the plasmalemma. 5. Using pipettes of relatively low resistance, inside-out patches that included both clustered BK channels at a density of over 20 channels microm(-2) and functional Ca(2+) storage sites were obtained at a low probability of approximately 5%. The averaged BK channel density was 3-4 channels microm(-2) in both types of myocyte. 6. These results support the idea that a limited number of discrete sarcoplasmic reticulum (SR) fragments in the subplasmalemmal area play key roles in the control of BK channel activity in two ways: (i) by generating Ca(2+) sparks at rest to activate STOCs and (ii) by generating Ca(2+) transients presumably triggered by sparks during an action potential to activate a large I(K,Ca) and also induce a contraction. BK channels and RyRs may co-localize densely at the junctional areas of plasmalemma and SR fragments, where Ca(2+) sparks occur to elicit STOCs.

Allylindation of cyclopropenes in organic and aqueous media: switching the regio- and stereoselectivity based on the chelation with a hydroxyl group and the crystal structure of the cyclopropylindium product

Hydroxy-bearing cyclopropenes react with allylindium reagents to undergo clean allylindation both in organic and aqueous media, in which the chelation of the hydroxyl group to indium plays the central role. The regio- and stereoselectivity have been regulated both by the location of the hydroxyl group in the molecules and the reaction solvents. In particular, the allylindation in water shows marked differences from that in organic solvents; the regio- and stereoselectivity have totally been reversed compared with those in organic solvents. Unusually stable cyclopropyl-indium compounds have been isolated from the reaction of 1-(omega-hydroxyalkyl)cyclopropenes and the structure has fully been established by X-ray crystallography.