Experimental and theoretical studies of Si-Cl and Ge-Cl σ-bond activation reactions by iridium-hydride.

We report the iridium hydride-mediated Si-Cl and Ge-Cl σ-bond activation in a low-polarity toluene solution owing to diphosphine-chelation, in which the Si-Cl and Ge-Cl σ-bonds are readily cleaved through an SN2-type pathway via the formation of a free chloride anion.

Presence of C-type natriuretic peptide (CNP) in guinea pig caecum: role and mechanisms of CNP in circular smooth muscle relaxation.

The distribution and role of C-type natriuretic peptide (CNP) in the gastrointestinal tract are still unclear. This study was designed to investigate the distribution of CNP in guinea pig caecum and the inhibitory mechanisms of CNP in caecal circular smooth muscle cells. CNP immunoreactivity was recognized in smooth muscle cells, myenteric and submucosal neurons of the caecum by immunohistochemistry. CNP mRNA expression was demonstrated in both freshly dispersed and cultured smooth muscle cells by reverse-transcription polymerase chain reaction. CNP inhibited 1 nmol L(-1) cholecystokinin octapeptide (CCK-8)-induced smooth muscle cell contraction in a dose-dependent manner, with an IC(50) value of 0.24 nmol L(-1), and significantly stimulated the production of intracellular cyclic guanosine monophosphate. Furthermore, inhibitors of both soluble and particulate guanylate cyclase (GC) partially but significantly inhibited CNP-induced relaxation. This is the first report demonstrating that CNP localizes in gastrointestinal smooth muscle cells and the enteric nervous system. These results suggest that CNP acts locally through neural and autocrine pathways to modulate colonic motility via both particulate and soluble GC systems. These two pathways appear to be through natriuretic peptide receptor (NPR)-B, which has particulate GC domain, and NPR-C, which activates soluble GC, judging from previous findings that NPR-A is not expressed in these cells.

Syntheses and physical properties of quasi-one-dimensional halogen-bridged Cu(II)(-)Pt(IV) mixed-metal complexes [Cu(chxn)(2)][PtX(2)(chxn)(2)]X(4).

Quasi-one-dimensional halogen-bridged Cu(II)-Pt(IV) mixed-metal complexes of the form [Cu(chxn)(2)][PtX(2)(chxn)(2)]X(4), where chxn = 1R,2R-diaminocyclohexane and X is either Cl or Br, have been synthesized. The crystal structures of these compounds have been determined by single-crystal X-ray diffraction. The Cl-bridged compound crystallizes in the space group I222 with dimensions a = 24.237(1) A, b = 5.103(1) A, c = 6.854(1) A, and V = 847.7(1) A(3) and with Z = 1. The Br-bridged complex crystallizes in the space group I222 with dimensions a = 23.700(8) A, b = 5.344(5) A, c = 6.978(8) A, and V = 883.8(8) A(3) and with Z = 1. These structures are isomorphic to each other and to homometal [Pt(chxn)(2)][PtX(2)(chxn)(2)]X(4) complexes. In these complexes, the planar [Cu(chxn)(2)] and the octahedral [PtX(2)(chxn)(2)] groups are stacked alternatively with the axial bridging halogen ions, forming linear chain structures. The neighboring [Cu(chxn)(2)] and [PtX(2)(chxn)(2)] moieties along the chains are linked by hydrogen bonds between amino hydrogens and the counteranions (X). Moreover, there are hydrogen bonds among the neighboring chains that form a two-dimensional hydrogen-bonded network parallel to the bc plane. Therefore, the Cu(II) and Pt(IV) units are two-dimensionally ordered. The b axes correspond to the Cu(II)-Pt(IV) separations, which are shorter than those of [Pt(chxn)(2)][PtX(2)(chxn)(2)]X(4) due to the smaller ionic radius of the Cu(II) ions. In the XP spectra, the Pt(IV) 4f(7/2) and Pt(IV) 4f(5/2) binding energies in homometal [Pt(chxn)(2)][PtX(2)(chxn)(2)]X(4) are lower than those of [Cu(chxn)(2)][PtX(2)(chxn)(2)]X(4) (X = Cl and Br), indicating that the electron-phonon interaction in Cu(II)-Pt(IV) compounds is stronger than that in Pt(II)-Pt(IV) compounds. In the Raman spectra, nu(Pt(IV)(-)X) of the homometal Pt(II)-Pt(IV) complexes is lower than that of the Cu(II)-Pt(IV) complexes, indicating again that the electron-phonon interaction in Cu(II)-Pt(IV) compounds is stronger than that of Pt(II)-Pt(IV) compounds. The temperature-dependent magnetic susceptibilities of the Cu(II)-Pt(IV) complexes show weak antiferromagnetic interactions between Cu(II) components along the chain axes.

CNS changes in DRPLA with dementia and personality changes: CT, MR and SPECT findings.

CNS changes in a case of DRPLA associated with dementia and personality changes were observed by CT, MR and SPECT. Brain CT and MR of the patient revealed progressive cortical atrophy which was recognized in parallel with the clinical course of the progression of dementia and personality changes. SPECT using 123I-iodoamphetamine (IMP) disclosed a diffuse low perfusion of the cerebral cortex, especially in the frontal and temporal lobes. These findings suggest that the dementia and personality changes in this case might be concerned with a dysfunction of the cerebral cortex.

A comparative study of the lipid composition of white, intermediate, red and heart muscle in rats.

The detailed lipid composition of white (rectus femoris), intermediate (soleus), red (diaphragm) and heart muscle isolated from fed and 48-h-fasted male rats was determined. 1. Contents of phospholipid and total cholesterol were high, with increasing levels of aerobic oxidation in muscles. Triacylglycerol content was highest in red muscle, moderate in heart and intermediate muscle and lowest in white muscle. 2. The molar percentages of phosphatidylethanolamine and cardiolipin were high and those of phosphatidylcholine, phosphatidylinositol and phosphatidylserine were low, with increasing levels of aerobic oxidation in muscles. 3. The molar percentage of alkenyl-acyl type was higher in phosphatidylethanolamine than in phosphatidylcholine which consisted predominantly of diacyl type. Heart and intermediate muscle had lower content of alkenyl-acyl type and higher contents of diacyl type in phosphatidylethanolamine as compared with white muscle, whereas the class composition in phosphatidylcholine were nearly the same among the muscles examined. 4. The contents of 18 : 0 in phosphatidylcholine and 18 : 0, 18 : 2 and 20 : 4 in phosphatidylethanolamine were high and those of 16 : 0 in phosphatidylcholine and 22 : 6 in phosphatidylethanolamine were low, accompanying approximately the increase in the levels of aerobic oxidation in muscles. The fatty acid composition of triacylglycerol was similar in all the muscles examined. 5. The fasting had little effect on the lipid patterns of the various types of muscles except for those of phospholipids in heart muscle. These results were discussed in relation to the cell structure and function for energy metabolism in various muscles.

Experimental anemia induced by excess iron excretion.

The effect of desferrioxamine on several hematological parameters was studied in growing rats. Animals given desferrioxamine intramuscularly (150 mg/kg daily) had increased urinary iron after one week, and decreased hemoglobin after 2 weeks. The difference in hemoglobin concentration between the treated and control groups was significant after 4 weeks of treatment with desferrioxamine, but the difference in the numbers of erythrocytes was not significant. The anemia was of hypochromic type. Desferrioxamine at this dosage did not retard growth. These findings support our previously reported concept of "iron-losing anemia".