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Biomedical subjects

T Yamazaki

Publications and source records attributed to T Yamazaki.

At least 487 records · Page 27Linked to original sources
PubMed1994

Nuclear magnetic resonance structure of an SH2 domain of phospholipase C-gamma 1 complexed with a high affinity binding peptide.

The solution structure of the C-terminal SH2 domain of phospholipase C-gamma 1 (PLC-gamma 1), in complex with a phosphopeptide corresponding to its Tyr-1021 high affinity binding site on the platelet-derived growth factor receptor, has been determined by nuclear magnetic resonance spectroscopy. The topology of the SH2-phosphopeptide complex is similar to previously reported Src and Lck SH2 complexes. However, the binding site for residues C-terminal to the phosphotyrosine (pTyr) is an extended groove that contacts peptide residues at the +1 to +6 positions relative to the pTyr. This striking difference from Src and Lck reflects the fact that the PLC-gamma 1 complex involves binding of a phosphopeptide with predominantly hydrophobic residues C-terminal to the pTyr and therefore serves as a prototype for a second class of SH2-phosphopeptide interactions.

Amino Acid Sequence↗
PubMed1994

Individual ionization constants of all the carboxyl groups in ribonuclease HI from Escherichia coli determined by NMR.

All of the individual carboxyl groups (the side-chain carboxyl groups of Asp and Glu, and the C-terminal alpha-carboxyl group) in Escherichia coli ribonuclease HI, which is an enzyme that cleaves the RNA strand of a RNA/DNA hybrid, were pH-titrated, and their ionization constants (pKa) were determined from an analysis of the pH-dependent chemical shifts of the carboxyl carbon resonances obtained from 1H-13C heteronuclear two-dimensional NMR. The pKa values in the enzyme varied widely among individual residues, for example, in the unusual pKa values for two important catalytic residues, Asp10 (pKa 6.1) and Asp70 (pKa 2.6). Moreover, remarkable two-step titrations were observed for these carboxylates. The binding of Mg2+ ion to the enzyme, which is the cofactor necessary for catalytic activity, caused no significant change in the pKa values of the carboxyl groups, except for that of Asp10. The variations of the pKas that were dependent on the microenvironment in the protein were theoretically reproduced to compare with the experimental results by a numerical calculation, using a continuum electrostatic model. Most of the significant pKa decreases were brought about through strong electrostatic interactions with the neighboring basic amino acids, Arg or Lys. The pKa shifts and the two-step titrations of Asp10 and -70, which are close to each other, were interpreted to be due to the neighboring effect of two functional groups, as observed in the interacting titratable groups of a dicarboxyl compound or in the active site carboxylates of lysozyme and aspartic protease. The role of Asp10 in the catalytic action is either to be the proton donor to the RNA moiety or the binding partner of the Mg2+ ion cofactor. Asp70, on the other hand, is considered to be the proton acceptor from a water molecule.

Amino Acid Sequence↗
PubMed1994

Secondary structure and signal assignments of human-immunodeficiency-virus-1 protease complexed to a novel, structure-based inhibitor.

We report comprehensive NMR studies in solution of the human-immunodeficiency-virus (HIV)-1 protease. Stable solutions of the protease were obtained by complexing the protein to a designed cyclic urea inhibitor DMP 323. A variety of triple-resonance experiments provided essentially complete 1H, 13C and 15N NMR signal assignments of the protease. These assignments, together with short-range NOE constraints, coupling constants and hydrogen-exchange data, yielded the secondary structure of the protease in solution. The results reported herein open the way to the determination of the high-resolution three-dimensional solution structures of protease/inhibitor complexes, as well as to studies of protease dynamics and solvent interactions.

Amino Acid Sequence↗
PubMed1994

Genetic linkage analyses of Romano-Ward syndrome (RWS) in 13 Japanese families.

Romano-Ward syndrome (RWS) is an autosomal dominant disorder characterized by prolongation of the electrocardiographic QT interval, with clinical manifestations that include recurrent syncope and sudden death from ventricular arrhythmias. Presymptomatic diagnosis is difficult because of the variability in these signs among carriers, but it is important for clinical management to prevent sudden cardiac death. To find an LQT (long QT) locus in Japanese patients and to identify DNA markers useful for presymptomatic diagnosis, linkage analyses were undertaken in 13 Japanese families with RWS patients by means of two DNA markers located on 11p15.5. One of these marker loci, HRAS, was previously reported to be tightly linked to the LQT locus in another ethnic group. Our analyses of homogeneity suggest evidence for genetic heterogeneity of RWS within the Japanese population.

Adult↗
PubMed1994

Increase in myocardial interstitial norepinephrine during a short period of coronary occlusion.

The neurally intact in vivo beating hearts of cats were used to examine the influence of a short period of coronary occlusion on regional myocardial norepinephrine levels. Using a cardiac dialysis technique, dialysate norepinephrine levels were measured as an index of myocardial interstitial norepinephrine levels, and the left anterior descending coronary artery was occluded for 10 min. In anesthetized cats, 10 min occlusion increased the dialysate norepinephrine level in the ischemic region but not in the non-ischemic region. To investigate the influence of neuronal norepinephrine uptake on occlusion-induced dialysate norepinephrine response, a neuronal uptake inhibitor (desipramine) was locally administered to both regions with the dialysis perfusate. In the ischemic region, 10 min occlusion significantly increased the dialysate norepinephrine level from the control level in the presence of desipramine. We concluded that 10 min coronary occlusion was associated with an increase in the myocardial interstitial norepinephrine level in the ischemic region. This increase in the early phase of ischemia was not attributed to attenuation of neuronal norepinephrine uptake function.

Animals↗
PubMed1994

Ligand-induced internalization and phosphorylation-dependent degradation of growth hormone receptor in human IM-9 cells.

The human growth hormone (hGH) induced a marked reduction in the number of human growth hormone receptors (hGHR) within 60 min, as assessed by immunoblotting of the crude membrane fraction from human IM-9 cells, without an increase in soluble forms of hGHR. The disappearance of hGH-induced hGHR was markedly inhibited by reagents that raise the internal pH of acidic organella and partially by protease inhibitors. These results suggest that hGH stimulation results in degradation of internalized hGHRs, where proteases in acidic compartments such as lysosomes may be involved. The relationship between the hGH concentration and the number of residual cell surface hGHRs 60 min after hGH stimulation yielded a curve with an inverted bell shape showing maximum internalization at 10 nM hGH. A similar relationship was shown in the hGHR degradation. The fact that the ligands in excess gave reduced internalization and degradation supports the idea that dimerization of hGHRs on the cell surface through the bivalent ligand hGH is required for their internalization and subsequent degradation. Following hGH stimulation, several hGHR-associated proteins including JAK2 were phosphorylated. These phosphorylations were inhibited by pretreatment with a protein kinase inhibitor, staurosporine. The hGHR internalization, however, was not markedly affected by the inhibitor. In contrast, the staurosporine inhibited the degradation of hGHR in a dose-dependent manner. These results suggest that staurosporine-sensitive phosphorylation is not required for the hGHR internalization, but the phosphorylation is involved in the degradation of hGHR.

Alkaloids↗
PubMed1994

Ultrasonographic diagnosis of juvenile colonic polyps.

To reduce the risks of air-contrast barium enemas and colonoscopy, we studied the use of saline enemas for ultrasonographic examination of children with rectal bleeding. Thirty-nine children, from 2 years 8 months to 8 years 3 months of age, were examined. Juvenile colonic polyps were ultrasonographically demonstrated and histologically confirmed in 25 children; all the polyps were solitary and pedunculated, and were located in the splenic flexure in 3 children, the descending colon in 6, the sigmoid colon in 12, and the rectum in 4. Ultrasonographic findings by hydrocolonic ultrasonography were identical to those obtained by immersion ultrasonography of removed specimens. Hypoechoic areas within more hyperechoic polyps were shown histologically to be dilated glandular canals. The 14 children in whom no abnormal ultrasonographic findings were shown had no further rectal bleeding after resuming regular defecation, and 5 of these 14 had negative colonoscopic findings. No adverse reactions were noted in any child during or after the saline enema examination. We conclude that ultrasonographic examination with a saline enema is a safe and accurate method of assessing children with rectal bleeding, especially for the diagnosis of juvenile colonic polyps.

Child↗
PubMed1994

The relationship between DNA structural variation and activities of P elements in P and Q strains of Drosophila melanogaster.

To characterize the relationship between P element activities and their structures, we cloned P elements from genomic libraries of three isogenic P and Q strains derived from natural populations in Japan. These P elements were mapped with BamHI, AvaII and PstI and were classified by their size. The majority of P elements cloned were classified as either complete or relatively small P elements rather than medium size. The numbers of full length (2.9 kb) P elements per haploid genome of NP280 (P), AK194 (weak P) and WY113 (Q) were at least four, five and one, respectively. However, the 2.9 kb P element of WY113 was thought to be defective since this strain has no transposase activity. In our previous work, we demonstrated that the ORF 3-deleted P element is essential for P cytotype determination in WY113. A similar P element also exists in NP280, and this may have an important role for P cytotype determination in this strain. Two and one copies of the KP element, a deletion derivative of the P element, were found in NP280 and AK194, respectively. One of four complete P elements in NP280 was fully sequenced, and the base sequence was completely identical to that of p pi 25.1 originally derived from the U.S.A. This result is consistent with the notion that these P elements have a relatively recent origin in Drosophila melanogaster.

Animals↗
PubMed1994

Molecular analysis of Gpdh null mutations that arose in mutation accumulation experiments in Drosophila melanogaster.

In order to clarify the cause of null mutations in enzyme loci, the molecular structure of six null mutations in the Gpdh locus (encoding alpha GPDH: alpha glycerol-3-phosphate dehydrogenase (NAD+), E.C. 1.1.1.8; map position at 2-17.8) that arose in mutation accumulation experiments was examined. A restriction map analysis showed that five of the mutations are insertional mutations whereas the sixth is a deletion. The Gpdh regions of these null mutations were then cloned and sequenced. The inserted DNA fragments are all internally deleted P elements measuring 1.1 kb in length. Two are a KP element and two others are a HP element. All the insertions occur in the region near the initiation signal of transcription. The deletion encompasses the seventh and eighth exons over a length of 1.1 kb. These results therefore indicate that the null mutation rate at the Gpdh locus is largely influenced by P elements.

Animals↗
PubMed1994

Stenotic bicuspid aortic valve associated with a ventricular septal defect in an adult presenting with congestive heart failure: a rare observation.

This report is concerned with an adult presenting with stenotic bicuspid aortic valve associated with a ventricular septal defect (VSD). The association between aortic regurgitation (AR) and VSD has often been described, but that between a stenosed aortic valve and VSD has been rarely observed, although bicuspid aortic valves and ventricular septal defects are probably the two most common congenital heart defects. The development of congestive heart failure in the presented case was considered to be due to an increase in the left to right shunt through the VSD. This was attributable to a progressive elevation in left ventricular pressure as a result of the development, with age, of stenosis of the bicuspid aortic valve.

Aged↗
PubMed1994

Arthritis and ankylosis in twy mice with hereditary multiple osteochondral lesions: with special reference to calcium deposition.

A murine autosomal recessive mutant named twy (tiptoe walking-Yoshimura) mouse showing multiple osteochondral lesions including ankylosis of the vertebral column and limb joints underwent sequential histopathological analysis of posterior limb joint lesions and intervertebral disc lesions. In the articular cartilage, a decrease in alcian blue-positive extracellular matrix and the presence of degenerated collagen fibers were found at the age of around 4-8 weeks. Calcium deposits in the articular cartilage were found at that time and later in the articular space and synovial tissue. Calcium deposits were also found in the intervertebral discs at 4 weeks. Using electron microscopy, some of the crystals were seen inside small vesicles. In both joints, degeneration of, and calcium deposition in, the articular cartilage progressed with age, finally producing bony ankylosis. These histological observations suggest that calcification and degeneration of the articular cartilage are the major factors in the pathogenesis of joint disorders in the twy mouse, and this mutant mouse provides a good model for studying the process and mechanism of osteoarthritic lesions, destructive arthritis and ankylosis.

Aging↗