Search PubMed⌕ Search

Biomedical subjects

I Shimada

Publications and source records attributed to I Shimada.

At least 91 records · Page 5Linked to original sources
PubMed1994

Synthesis and characterization of sapecin and sapecin B.

Two insect defencins, sapecin and sapecin B, were chemically synthesized to confirm their structure and antibacterial activity and also to examine the possibility that these peptides bind to the same site on the large conductance calcium-activated potassium channel as charybdotoxin. Both synthetic peptides showed the same antibacterial activity as native sapecins, indicating that the synthetic peptides folded correctly in the chemical synthesis. Synthetic sapecins did not show an inhibitory effect on [125I]charybdotoxin binding to rat brain synaptic membranes, suggesting that sapecin B recognizes a different binding site from that of charybdotoxin despite the similar structural motif.

Amino Acid Sequence↗
PubMed1994

Capability of intensity discrimination in multiple receptor model of insect taste.

A simple model in which one CNS taste neuron integrates inputs from multiple peripheral receptors is introduced in order to investigate the mechanism of acute intensity taste discrimination in flies. Information theory is applied to evaluate the acute ability of discrimination provided by the model. The present analysis is carried out under two statistical conditions concerning the uncertainty of receptor response. Based on experimental data obtained by Smith et al. (1983), we estimate the mutual information entropy of the model. The numerical results obtained here indicate that the uncertainty observed in a single receptor response is dramatically reduced by the central integration. Furthermore, each of the eleven stimulus intensity levels experimentally applied by Smith et al., can be discriminated completely by integrating the responses of the realistic number of receptors (33-212). Such a great improvement of the differential sensitivity in the model resolves the discrepancy between the low differential sensitivity of single sugar receptors (Smith et al., 1983) and the high sensitivity obtained in the feeding behavior (Dethier and Rhoades, 1954; Dethier and Bowdan, 1984) of the blowfly.

Animals↗
PubMed1993

A multinuclear NMR study of the affinity maturation of anti-NP mouse monoclonal antibodies: comparison of antibody combining sites of primary response antibody N1G9 and secondary response antibody 3B62.

On the basis of multinuclear NMR data, the structures of the antibody combining sites of anti-4-hydroxy-3-nitrophenylacetyl (NP) antibodies were compared for N1G9, which is one of the primary response antibodies with low affinity for NP, and 3B62, which is one of the secondary response antibodies with high affinity for NP. It has been concluded, on the basis of the results of antibody engineering, that in most secondary response antibodies a Trp-->Leu exchange at position 33 of the heavy chain is primarily responsible for the increased affinity for NP [Allen, D., Simon, T., Sablitzky, F., Rajewsky, K., & Cumano, A. (1988) EMBO J. 7, 1995-2001]. Although 3B62 exhibits one of the highest affinities for NP, it lacks the Trp-->Leu exchange at position 33 of the heavy chain. A variety of stable isotope-labeled Fab analogues of N1G9 and 3B62 have been prepared. Chain-specific resonance assignments were made by recombination of the heavy chains and light chains of the Fab fragments. Binding experiments of a spin-labeled hapten and NOESY experiments have demonstrated that, compared with the environment of the antibody combining site of N1G9, the combination of mutations (including one codon deletion) and the particular D-JH rearrangement in the heavy chain of 3B62 affords a more hydrophobic environment, which is formed by one Tyr residue originating from the light chain and two Tyr residues originating from the heavy chain.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Solution conformation of an antibacterial peptide, sarcotoxin IA, as determined by 1H-NMR.

The solution conformation of sarcotoxin IA, which is an antibacterial peptide isolated from Sarcophaga peregrina with a molecular mass of 4 kDa, was determined by NMR spectroscopy and hybrid distance geometry/dynamical simulated annealing calculations. On the basis of 227 experimental constraints, including 185 distance constraints obtained from NOE and 42 constraints associated with 21 hydrogen bonds, a total of 18 converged structures of sarcotoxin IA were obtained. The final 18 converged structures exhibit backbone-atomic root-mean-square differences about the averaged coordinate positions of 0.070 +/- 0.027 nm for residues 3-23 and 0.040 +/- 0.017 nm for residues 28-38. It has been indicated that sarcotoxin IA consists of two amphiphilic alpha-helical regions, i.e. helix I (Leu3-Gln23) and helix II (Ala28-Ala38), with a hinge region (Gly24-Ile27), which connects helix I and helix II. We conclude that these two amphiphilic helical segments of sarcotoxin IA are of importance for the expression of the antibacterial activity.

Amino Acid Sequence↗
PubMed1993

Structural study of the oligosaccharide moieties of sphingolipid activator proteins, saposins A, C and D obtained from the spleen of a Gaucher patient.

We have determined and compared the structures of the oligosaccharide moieties of saposin A, C and D purified from the spleen of a patient with Gaucher disease. These saposins, together with saposin B, are small glycoproteins, derived from separate domains of a single precursor, prosaposin, and are required for the lysosomal hydrolysis of various sphingolipids. The characteristic features of the oligosaccharide moieties of saposin A are (a) the predominance of a fucosylated trimannosyl core structure and (b) the occurrence of several different oligomannose-type and N-acetyllactosamine-type oligosaccharides. Saposin C contains (a) a predominance of oligomannose-type oligosaccharides and monoantennary oligosaccharides and (b) the presence of four different oligosaccharides having bisecting N-acetylglucosamine residues (found only in this saposin). Saposin D is distinguished by the occurrence of oligomannose-type oligosaccharides, which comprise nearly 90% of its total oligosaccharides. The possible reasons for the unique glycosylation of each saposin is discussed.

Carbohydrate Sequence↗
PubMed1993

Structural elucidation of a variety of GalNAc-containing N-linked oligosaccharides from human urinary kallidinogenase.

Fifteen different structures of terminal GalNAc-containing N-linked oligosaccharides from human urinary kallidinogenase have been identified. These N-linked oligosaccharides were mostly neutral, because sialic acid content was lower than 0.13 mol of sialic acid/mol of sugar chain, and sulfate was not detected. The oligosaccharides were released from pepsin-digested protein by glycoamidase A (from almond) digestion. The reducing ends of the oligosaccharide chains were aminated with a fluorescent reagent, 2-aminopyridine. The resulting mixture of pyridylamino derivatives of the oligosaccharides were separated by high performance liquid chromatography on an ODS-silica column, and 15 oligosaccharides were isolated. The structure of each oligosaccharide fraction was analyzed by two-dimensional sugar mapping, component sugar analysis, high resolution proton nuclear magnetic resonance and methylation analysis. It was found that each N-linked oligosaccharide associated with human urinary kallidinogenase contains unsubstituted GalNAc residues at the nonreducing terminal. These 15 oligosaccharides include 5 biantennary, 7 triantennary, and 3 tetraantennary oligosaccharides.

Acetylgalactosamine↗
PubMed1993

Effector functions of a mouse IgG that lacks the entire CH1 domain. C1q binding and complement fixation in the absence of antigen.

C1q binding and complement fixation were examined of a short-chain IgG2a antibody that lacks the entire CH1 domain. This short-chain antibody has been reported to have a low level of constitutive complement-activating activity in the absence of Ag. Two-dimensional SDS/PAGE and cation-exchange chromatography have demonstrated that two types of IgG2a proteins are secreted by the short-chain IgG2a antibody producing cell line. It has been shown that 1) the difference between these two types of the IgG2a proteins is whether the two L chains are linked by a disulfide bridge or not, and 2) C1q-binding and complement-activating activities are expressed only when the inter L chain disulfide bridge does not exist. A molecular model is presented for the active form of the short-chain IgG2a antibody.

Animals↗
PubMed1993

A temporal model of animal behavior based on a fractality in the feeding of Drosophila melanogaster.

We present a new temporal model of animal behavior based on the ethological idea that the internal states of the individual essentially determine the behavior. The internal states, however, are conditioned by the external stimuli. This model, including environmental and internal parameters, predicts a fractal property of the behavior, that is, an inverse power law distribution of the duration. Being consistent with the model, we have found a fractal property of feeding in Drosophila melanogaster: The dwelling time of starved flies on food showed a clear inverse power law distribution. The dependence of the fractal dimension on the intensity of food stimuli has been observed, and the predicted change into an exponential distribution was proved.

Animals↗
PubMed1993

A structural study of the asparagine-linked oligosaccharide moiety of duck ovomucoid.

Asparagine-linked oligosaccharides of duck ovomucoid were released quantitatively from the protein by digestion with glycoamidase A (from almond), the reducing ends of the oligosaccharide chains thus obtained were aminated with a fluorescent reagent, 2-aminopyridine, and the mixture of pyridylamino derivatives of the oligosaccharides was separated using two different types of high performance liquid chromatography (HPLC) on a reversed phase column and an amide adsorption column. More than sixteen different oligosaccharides were separated and the structures were characterized by a combination of the 2-dimensional sugar mapping technique using HPLC, exoglycosidase digestion, and proton nuclear magnetic resonance measurements (1- and 2-dimensional). Furthermore, the HPLC profile of duck ovomucoid oligosaccharides was compared with previously reported profiles obtained from quail and chicken ovomucoids.

Animals↗
PubMed1993

Molecular structural studies of effector functions of a mouse immunoglobulin G that lacks the entire CH1 domain: small-angle X-ray scattering, nanosecond fluorescence depolarization and stable isotope-aided NMR analyses.

Molecular structural studies are reported of a short-chain mouse IgG2a antibody that lacks the entire CH1 domain. We have recently shown that (1) this short-chain antibody comprises two components in which the inter light-chain disulfide bridge does and does not exist, and (2) these two components are different in the constitutive complement-activating activity [Mizutani et al. (1993) J. Immunol. 150, 131-138]. Structures were compared for these two components on the basis of small-angle X-ray scattering, nanosecond fluorescence depolarization and isotope-aided NMR data. It has been discussed how the presence and absence of the inter light-chain disulfide bridges affect the complement-activating activity of the two components of the short-chain antibody.

Animals↗
PubMed1993

[A case of herpes simplex encephalitis presenting complete destruction of the medial portions in the bilateral temporal lobes].

A 57-year old man, who had suffered from herpes simplex encephalitis and had been cured without antiviral agents, was admitted to our hospital three years after the encephalitis. He had a complete loss of memory for events subsequent to the encephalitis and a retrograde amnesia for the several years leading up the encephalitis. MRI revealed the abnormalities located in the limbic system, especially the medial portions in the bilateral temporal lobes of the cerebrum were completely destroyed. We consider that this case suggests the specific affinity of herpes simplex virus especially for the medial portions in the temporal lobes of the cerebrum.

Amnesia, Retrograde↗
PubMed1993

[Transcranial Doppler monitor in the case of selective cerebral perfusion].

Six patients underwent ascending aorta and aortic arch replacement for aneurysmal disease between 1991.12-1992.2 using the cardiopulmonary bypass technique with selective cerebral perfusion from right axillary artery. For four patients, intraoperative transcranial Doppler monitorings of left MCA flow velocity were done. We added left carotid artery perfusion for 5 patients because of old age; 1, intraoperative finding of anisocoria; 1 and low left MCA flow velocity on the TCD monitor; 3. After the addition of left side perfusion, the left MCA flow velocity on the TCD monitor recovered to normal level in the 3 patients. TCD reflected the cerebral perfusion state every minutes and seemed to be very useful monitor in selective cerebral perfusion. It also suggested that unilateral cerebral perfusion does not supply enough blood flow in contralateral side of brain in many cases. To another patient who also underwent aortic arch replacement, we examined preoperatively left MCA flow velocity on the TCD monitor under left carotid artery compression. This "carotid artery compression test" was thought to suggest the degree of right to left intracranial collateral blood flow via Willis's circle. TCD image, when the left carotid artery was clamped, was compared with the result of preoperative "carotid artery compression test". But we can't evaluate the results quantitatively now.

Aged↗
PubMed1993

[6 cases of CABG post coronary stent].

In recent years, percutaneous transluminal coronary angioplasty (PTCA) has been actively carried out as a therapeutic method of the ischemic cardiopathies, and Stent therapy has been clinically applied as settlement method of problematical points of the acute occlusion and dissection of the coronary artery by PTCA. We experienced 6 cases necessitated coronary artery bypass graft (CABG) after insertion of Palmaz-Schatz Stent until March 1992. The emergent bypass was carried out in 3 of 6 cases because thrombotic occlusion developed although Stent was inserted in thrombotic occlusion after PTCA, while 2 cases were not life-saved because of the cardiac function was worsened before operation. Other 3 cases were life-saved by expectant treatment even though stenosis developed again after Stent therapy. Stent therapy is a useful method, while severity in cases using CABG and operative complexity are expected by development of new problematical point in the future.

Aged↗
PubMed1992

A receptor-binding peptide from human interleukin-6: isolation and a proton nuclear magnetic resonance study.

In order to locate the receptor-binding region of human interleukin-6 (IL-6), twelve peptide fragments were prepared by digestion of IL-6 with lysylendopeptidase. A significant activity of the receptor-binding was observed only for a peptide Ile88-Lys121, although the activity was estimated at 10(4)-fold less than that of intact IL-6. Solution structure of the peptide Ile88-Lys121 was analyzed by using two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The results indicate the presence of alpha-helices in the regions Leu93-Phe106 and Glu110-Ser119. On the basis of the NMR data, we also prepared two peptides. Four-fold less binding activity than that of the peptide Ile88-Lys121 was observed for the peptide Ile88-Arg105, but no activity for the peptide Glu110-Lys121. These results suggest that the helical peptide Ile88-Arg105 composes a part of the receptor-binding region.

Amino Acid Sequence↗
PubMed1992

Isotope-edited nuclear magnetic resonance study of Fv fragment of anti-dansyl mouse monoclonal antibody: recognition of the dansyl hapten.

An isotope-edited proton nuclear magnetic resonance study is reported of Fv, which is the smallest antigen recognition unit composed of VH and VL domains. Fv has been obtained by clostripain digestion of a short-chain anti-dansyl mouse IgG2a monoclonal antibody [Igarashi, T., Sato, M., Katsube, Y., Takio, K., Tanaka, T., Nakanishi, M., & Arata, Y. (1990) Biochemistry 29, 5727-5733]. A variety of stable-isotope-labeled anti-dansyl Fv analogues have been prepared. The aromatic proton resonances for all Tyr residues of the Fv fragment have been assigned in the absence and presence of epsilon-dansyl-L-lysine by means of isotope-edited homonuclear and heteronuclear two-dimensional NMR experiments. On the basis of the established assignments, it has been concluded that the dansyl ring is bound through Tyr-96H and Tyr-104H to both ends of H3, the third hypervariable region of the heavy chain. We also suggest that the antigen binding results in the formation of a hydrophobic core comprising the dansyl ring and the aromatic rings of Tyr-96H and Tyr-104H.

Animals↗
PubMed1992

Three-dimensional solution structure of the B domain of staphylococcal protein A: comparisons of the solution and crystal structures.

The three-dimensional solution structure of the recombinant B domain (FB) of staphylococcal protein A, which specifically binds to the Fc portion of immunoglobulin G, was determined by NMR spectroscopy and hybrid distance geometry-dynamical simulated annealing calculations. On the basis of 692 experimental constraints including 587 distance constraints obtained from the nuclear Overhauser effect (NOE), 57 torsion angle (phi, chi 1) constraints, and 48 constraints associated with 24 hydrogen bonds, a total of 10 converged structures of FB were obtained. The atomic root mean square difference among the 10 converged structures is 0.52 +/- 0.10 A for the backbone atoms and 0.98 +/- 0.08 A for all heavy atoms (excluding the N-terminal segment from Thr1 to Glu9 and the C-terminal segment from Gln56 to Ala60, which are partially disordered). FB is composed of a bundle of three alpha-helices, i.e., helix I (Gln10-His19), helix II (Glu25-Asp37), and helix III (Ser42-Ala55). Helix II and helix III are antiparallel to each other, whereas the long axis of helix I is tilted at an angle of about 30 degrees with respect to those of helix II and helix III. Most of the hydrophobic residues of FB are buried in the interior of the bundle of the three helices. It is suggested that the buried hydrophobic residues form a hydrophobic core, contributing to the stability of FB.(ABSTRACT TRUNCATED AT 250 WORDS)

Amides↗