Interaction of pigeon cytochrome c-(43-58) peptide analogs with either T cell antigen receptor or I-Ab molecule

We determined that a pigeon cytochrome c-derived peptide, p43-58, possesses two anchor residues, 46 and 54, for binding with the I-Ab molecule that are compatible to the position 1 (P1) and position 9 (P9) of the core region in the major histocompatibility complex (MHC) class II binding peptides, respectively. In the present study to analyze each binding site between P1 and P9 of p43-58 to either I-Ab or T cell antigen receptor (TCR), we investigated T cell responses to a series of peptides (P2K, P3K, P4K, P5K, P6K, P7K, and P8E) that sequentially substituted charged amino acid residues for the residues at P2 to P8 of p43-58. T cells from C57BL/10 (I-Ab) mice immunized with P4K or P6K did not mount appreciable proliferative responses to the immunogens, but those primed with other peptides (P2K, P3K, P5K, P7K, and P8E) showed substantial responses in an immunogen-specific manner. It was demonstrated by binding studies that P1 and P9 functioned as main anchors and P4 and P6 functioned as secondary anchors to I-Ab. Analyses of Vbeta usage of T cell lines specific for these analogs suggested that P8 interacts with the complementarity-determining region 1 (CDR1)/CDR2 of the TCR beta chain. Furthermore, sequencing of the TCR on T cell hybridomas specific for these analogs indicated that P5 interacts with the CDR3 of the TCR beta chain. The present findings are consistent with the three-dimensional structure of the trimolecular complex that has been reported for TCR/peptide/MHC class I molecules.     

Prolonged sevoflurane, isoflurane and halothane anaesthesia in oxygen using rebreathing or non-rebreathing system in cats

Effects of prolonged sevoflurane, isoflurane and halothane anaesthesia in oxygen on clinical, cardiopulmonary, haematologic, and serum biochemical findings were compared in healthy, premedicated cats breathing spontaneously during 6 h of anaesthesia using rebreathing (semi-closed circuit) or non-rebreathing (Bain coaxial circuit) system. Recovery from anaesthesia with sevoflurane was more rapid than that with halothane or isoflurane in both systems. Respiration and heart rates during sevoflurane anaesthesia were similar to those during isoflurane rather than halothane anaesthesia in both systems. The degree of respiratory acidosis during prolonged sevoflurane anaesthesia was similar to that during isoflurane anaesthesia, and was less than that during halothane anaesthesia in both rebreathing and non-rebreathing systems. Prolonged sevoflurane anaesthesia induced mean arterial pressure similar to isoflurane or halothane anaesthesia in the non-rebreathing system, but it depressed mean arterial pressure less than isoflurane or halothane anaesthesia in the rebreathing system. Time related increase in the arterial carbon dioxide partial pressure was observed during halothane anaesthesia especially in the rebreathing system, however, no significant time-related changes in cardiopulmonary variables were observed during either sevoflurane or isoflurane anaesthesia in both systems. There were no significant differences among sevoflurane, isoflurane and halothane anaesthesia in serum biochemical values in both systems.     

Mechanical properties and microstructure in sintered and HIPed SiC particle/Si3N4 composites

Pressureless sintered (PLS) and gas-pressure sintered (GPS) Si₃N₄, PLS and GPS SiC particle/Si₃N₄ composites, and PLS + HIP and GPS + HIP SiC particle/Si₃N₄ composites were produced. Investigation of their mechanical properties showed that PLS + HIP and GPS + HIP composites, containing SiC particles in the beta-silicon nitride grains, yield higher bending strength, although its fracture toughness remains at the same level. This is attributed to the fact that the added SiC particles inhibit excessive growth of beta-Si₃N₄ grains without changing the fracture behaviour. However, this investigation also found precipitation during the reaction between SiC and nitrogen in gas pressure sintering, resulting in a low Young's modulus and low density in the GPS composite.     

Spontaneous histiocytic sarcoma with possible origin from the bone marrow and lymph node in Donryu and F-344 rats

High resolution P-waves of 28 patients having a mean age of 45 years and affected by isolated mitral valve stenosis (nine of whom showed paroxysmal atrial fibrillation) have been compared with those obtained from 30 healthy subjects about 35 years old. Our primary aim was to characterize the signal-averaged P-wave in mitral valve stenosis. Parameters which differed between the two groups in time domain analysis were the P-wave duration, the abscissa of the maximum positive voltage amplitude, the peak-to-peak amplitude and the integrated voltage-time product, which turned out to be greater in the patient class than in the healthy set; furthermore, in the frequency domain analysis, amplitudes in the range from 37 to 60 Hz were greater in healthy subjects than in patients. A successive analysis carried out to predict those patients with mitral valve stenosis who are at risk of developing paroxysmal atrial fibrillation showed that the P-wave duration and the amplitudes (in the range 60-106 Hz) were the most distinctive parameters, but, unfortunately, without any significant difference with respect to those of patients with mitral valve stenosis alone. Finally, some correlations between the age, the P-wave duration and the left atrial diameter of patients, were revealed to exist only in patients affected by episodes of atrial fibrillation.     

Responsibility of electric resistance of polyethyleneimine-grafted carbon black against alcohol vapor and humidity

Crystalline polyethyleneimine (PEI(C)) was successfully grafted onto carbon black surface by direct condensation of imino groups of PEI with carboxyl groups on the surface using N,N′-dicyclohexylcarbodiimide as a condensing agent. The electric resistance of a composite prepared from PEI(C) and PEI(C)-grafted carbon black drastically increased to 10³ – 10⁴ times of initial resistance in methanol, ethanol, and water vapor. But the change of electric resistance of the composite hardly observed in hexane and toluene vapor. These results suggest the possibility of detection of a slight change of crystalline structure of PEI by the absorption of solvent as a large increase of electric resistance of the composite. Received: 11 April 1997/Revised: 16 June 1997/Accepted: 23 June 1997     

Human butyrylcholinesterase L330I mutation belongs to a fluoride-resistant gene, by expression in human fetal kidney cells

We noticed a Japanese male showed low serum butyrylcholinesterase (BCHE) activity on health examination. The phenotyping analysis revealed a reduced dibucaine number (DN) and an especially low fluoride number (FN), similar to an FS phenotype. A homozygous missense mutation, a T to A transversion at nucleotide 988, was identified in his BCHE gene. This mutation resulted in the replacement of leucine by isoleucine at codon 330 (L330I). DN and FN of recombinant BCHE(L330I) secreted by human fetal kidney cells were compared to recombinant wild-type(usual gene) BCHE and normal serum BCHE. These results showed this amino acid substitution of BCHE, Leu330 to Ile, really caused the abnormal DN and FN. We conclude that the BCHE L330I mutation is a fluoride-resistant gene, a Japanese type fluoride-resistant gene.     

Difference in antigen presentation pathways between cortical and medullary thymic epithelial cells

Antigen presentation by thymic epithelial cells (TEC) to T cells that undergo maturation is one of the major events in the selection of the T cell repertoire. We have already reported that medullary TEC lines (mTEC) established from newborn C57BL/6 (H-2b) mice are able to present a soluble antigen, ovalbumin (OVA), to OVA-specific, I-Ab restricted helper T cell lines but cortical TEC (cTEC) lines are not (Mizuochi, T. et al., J. Exp. Med. 1992. 175: 1601). In this report, to clarify the cause of this difference, we analyzed the biochemical nature as well as the distribution of both major histocompatibility complex (MHC) class II molecules and invariant chains (Ii) in both TEC by immunoprecipitation and laser confocal scanning microscopic analysis, as well as the expression of mRNA encoding H-2Ma or H-2Mb. Our results demonstrate that cTEC and mTEC are both able to present peptide antigens to peptide-specific, I-Ab-restricted helper T cell hybridoma and are able to present class II MHC alloantigens to an I-Ab-specific T cell line, that mRNA for H-2Ma and H-2Mb are expressed in both TEC, that cTEC and mTEC apparently incorporate tetramethylrhodamine isothiocyanate-labeled OVA in the same manner, and that the SDS-stable MHC class II molecules, onto which peptides were loaded, are formed in both cTEC and mTEC. However, these molecules were more rapidly degraded in mTEC than in cTEC. In addition, two Ii-derived polypeptides of approximately 21 kDa and 10 kDa were precipitated by the anti-class II monoclonal antibody Y3P; 10-kDa polypeptides were detected in the both TEC, while 21-kDa polypeptides were detected only in cTEC. Finally, beta chains of MHC class II with less sialylated oligosaccharides were precipitated from the cell surface of cTEC. Taken together, these results suggest that there are substantial differences in the antigen-presenting pathways of cTEC and mTEC, and these difference might be responsible for T cell selection events in the thymus.