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Biomedical subjects

K Akaji

Publications and source records attributed to K Akaji.

At least 19 recordsLinked to original sources
PubMed2001

Peptide bond formation mediated by 4,5-dimethoxy-2-mercaptobenzylamine after periodate oxidation of the N-terminal serine residue.

[reaction in text] A thiol linker-attached peptide was prepared from a nonprotected peptide via an N(alpha)()-alpha-oxoacyl peptide. Selective oxidation of the N-terminal serine with sodium periodate gave the N(alpha)-glyoxyloyl peptide, reductive amination of which with 4,5-dimethoxy-2-(triphenylmethylthio)benzylamine gave an N(alpha)-4,5-dimethoxy-2-mercaptobenzyl glycyl peptide after removal of the trityl group. The N(alpha)-4,5-dimethoxy-2-mercaptobenzyl peptide can be condensed with a peptide thioester, and the linker is removable. This strategy provides a useful method for the synthesis of peptides using recombinant proteins.

Amino Acid Sequence↗
PubMed2001

Polypeptide synthesis using an expressed peptide as a building block for condensation with a peptide thioester: application to the synthesis of phosphorylated p21Max protein(1-101).

An expressed peptide proved to be useful as a building block for the synthesis of a polypeptide via the thioester method. A partially protected peptide segment, for use as a C-terminal building block, could be prepared from a recombinant protein; its N-terminal amino acid residue was transaminated to an alpha-oxoacyl group, the side-chain amino groups were then protected with t-butoxycarbonyl (Boc) groups, and. finally, the alpha-oxoacyl group was removed. On the other hand, an O-phosphoserine-containing peptide thioester was synthesized via a solid-phase method using Boc chemistry. These building blocks were then condensed in the presence of silver ions and an active ester component. During the condensation, epimerization at the condensation site could be suppressed by the use of N,N-dimthylformamide (DMF) as a solvent. Using this strategy, a phosphorylated partial peptide of the p21Max protein, [Ser(PO3H2)2.11]-p21Max(1-101), was successfully synthesized.

Basic-Leucine Zipper Transcription Factors↗
PubMed2001

Intra-ischemic hypothermia attenuates intercellular adhesion molecule-1 (ICAM-1) and migration of neutrophil.

Adhesion of neutrophil to the endothelium and subsequent transmigration has been reported to contribute to progression of focal ischemia. Hypothermia has been known to attenuate ischemic insult through various mechanisms of action. The authors evaluated the effect of hypothermia on expression of intercellular adhesion molecule-1 (ICAM-1) protein and on transmigration of neutrophil with immunohistochemical method. Transient focal ischemia model in rats was employed, and animals received 2 h of either normothermic or hypothermic ischemia. To confirm the effectiveness of hypothermia on neuroprotection, cortical infarct area was compared between the two groups. Our results demonstrated that hypothermia reduced both the number of microvessels expressing ICAM-1 and that of neutrophils migrating into ischemic tissue. Comparison of cortical infarct area showed persistent protective effect. This study indicates that reduction of ICAM-1 expression and subsequent reduction of migrating neutrophil in hypothermia can contribute to attenuation of ischemic damage.

Animals↗
PubMed2001

Cerebral microaneurysms found incidentally during aneurysm surgery.

Not uncommonly, cerebral microaneurysms are found incidentally during surgery for another previously diagnosed cerebral aneurysm(s). The frequency and angiographic characteristics of such incidental microaneurysms are retrospectively summarized. Seventeen patients were identified as harboring incidental microaneurysms, comprising 4.9% of the whole series. The middle cerebral artery (MCA) was the most frequent location (seven cases, 41%) of these microaneurysms. There was a tendency for MCA microaneurysms to be contiguous to a previously known, larger aneurysm at the same location. Neurosurgeons as well as interventional neuroradiologists should be aware of the possible presence of these incidental microaneurysms while treating patients with a cerebral aneurysm(s). Although the actual clinical implications of these incidental microaneurysms have not been elucidated, the few additional risks to patients already surgically exposed for the treatment of another aneurysm, along with the possible benefit of preventing their rupture and growth, would justify the surgical treatment of these microaneurysms.

Adult↗
PubMed2000

Post-ischemic hypothermia delayed neutrophil accumulation and microglial activation following transient focal ischemia in rats.

Following ischemia, inflammation has been demonstrated to be involved in the progression of the tissue damage. Intra-ischemic hypothermia has been shown to attenuate the adverse activities of neutrophils and microglia. We investigated whether neutrophil accumulation and/or microglial activation is attenuated in post-ischemic hypothermia following transient focal ischemia in rats. After 1 h of ischemia, the neutrophil accumulation and the microglial activation was evaluated immunohistochemically. Percent infarct area was compared at 1, 2, 3, 5, and 7 days after ischemia/reperfusion. In hypothermia, the neutrophil accumulation was delayed but not attenuated. In normothermia, the accumulation reached the peak at 2 days after ischemia. The peak shifted to 3 days in hypothermia. Similarly, the microglial activation was delayed in hypothermia. Comparison of the infarct area showed significant protection by hypothermia at 1 and 2 days after reperfusion. However, hypothermia failed to show significant protection after 3 days and later. These results show that the delayed neutrophil accumulation and the microglial activation can be responsible for the loss of persistent protection in post-ischemic hypothermia.

Animals↗
PubMed2000

Postischemic hypothermia attenuates apoptotic cell death in transient focal ischemia in rats.

Hypothermia confers potent neuroprotection against ischemic injury. Attenuation of apoptosis by hypothermia can be one of the responsible mechanisms. In this study, in situ DNA nick-end labeling (TUNEL) and immunostaining of Bax protein were performed to evaluate the effect of postischemic hypothermia on apoptotic cell death, employing rodent transient focal ischemia. Animals received 1 hour of transient focal ischemia. Brain temperature was maintained at 37.5 +/- 0.5 degrees C during ischemia. Immediately after reperfusion, animals were assigned to either a normothermic or hypothermic group. In hypothermia, animals were cooled and brain temperature was lowered to 34.5 +/- 1.0 degrees C. Prolonged hypothermia was maintained for 16 hours and animals rewarmed. In both groups, TUNEL and immunostaining of Bax was performed. In normothermia, the number of TUNEL positive cells reached the peak at 2 days after ischemia and decreased gradually. In hypothermia, the peak was shifted to 3 days after ischemia. The number of TUNEL positive cells in hypothermia was persistently below that of normothermia. Similarly, in hypothermia, immunostaining of Bax showed attenuated immunoreactivity compared with that in normothermia. In conclusion, postischemic hypothermia reduced both the number of TUNEL positive cells and immunoreactivity of Bax, which may be one of the responsible mechanisms with which hypothermia exerts neuroprotection.

Animals↗
PubMed2000

Glomus jugulare tumor presenting with intracerebellar hemorrhage.

What is believed to be the first case of a glomus jugulare tumor presenting with intracerebellar hemorrhage is described. A 25-year-old normotensive man suddenly suffered from severe headache, nausea, vomiting, vertigo, and ataxia due to an intracerebellar hemorrhage. Magnetic resonance imaging and angiography revealed a highly vascular jugulare foramen tumor extending into the intracranial space adjacent to the hematoma. Total removal of the tumor was performed successfully via the combined pre- and retrosigmoid approach, and the histologic diagnosis was a glomus jugulare tumor. We concluded that one of the numerous draining veins on the surface of intracranial tumor, which were observed during the operation, was the origin of the intracerebellar hemorrhage.

Case Reports↗
PubMed2000

Synthesis of a molt-inhibiting hormone of the American crayfish, Procambarus clarkii, and determination of the location of its disulfide linkages.

A molt-inhibiting hormone (Prc-MIH) of the American crayfish, Procambarus clarkii, a member of the type II CHH family, was chemically synthesized and the location of its three disulfide linkages was determined. Prc-MIH consists of 75 amino acid residues and was synthesized by a thioester method. Two peptide segments, Boc-[Cys(Acm)(7,24,27), Lys(Boc)(19)]-Prc-MIH(1-39)-SCH(2)CH(2)CO-Nle-NH(2) and H-[Cys(Acm)(40,44,53), Lys(Boc)(42,51,67)]-Prc-MIH(40-75)-NH(2), were prepared using peptides obtained via the Boc solid-phase method. Condensation of the building blocks in the presence of silver chloride, 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine, and N, N-diisopropylethylamine, followed by removal of the protecting groups, gave the reduced form of Prc-MIH(1-75)-NH(2). This product was converted to the native form of Prc-MIH (synthetic Prc-MIH) in a buffer which contained cysteine and cystine. The synthetic Prc-MIH showed the same behavior by RP-HPLC and biological activity assays as the natural Prc-MIH. The disulfide bond between Cys7 and Cys44 was determined by isolation of a fragment from an enzymatic digest of the synthetic Prc-MIH by RP-HPLC, followed by mass analysis. The disulfide bonds between Cys24 and Cys40 and between Cys27 and Cys53 were determined by comparing the elution position of an enzymatic digest of the synthetic Prc-MIH with authentic chemically synthesized samples, which contained three types of possible disulfide linkages.

Animals↗
PubMed1999

A new class of anti-HIV agents: synthesis and activity of conjugates of HIV protease inhibitors with a reverse transcriptase inhibitor.

Conjugates of HIV protease inhibitors with a reverse transcriptase inhibitor were synthesized, which expressed excellent antiviral activity compared with that of the individual components. The remarkable antiviral activity of the conjugated compounds may be due to their penetration into the cell and later splitting into two different classes of anti-HIV agents.

Anti-HIV Agents↗
PubMed1999

Small dipeptide-based HIV protease inhibitors containing the hydroxymethylcarbonyl isostere as an ideal transition-state mimic.

The human immunodeficiency virus (HIV) codes for an aspartic protease known to be essential for retroviral maturation and replication. HIV protease is formed from two identical 99 amino acid peptides. We synthesized [(NHCH2CH2-S-CH2CO)51-52, Ala67,95]HIV-1 protease using the thioether chemical ligation method, and then prepared the [(NHCH2CH2-S-CH2CO)51-52, Ala67,95, Cys98]HIV-1 protease dimer analogue covalently linked by a disulfide bridge. These HIV-1 protease analogues effectively cleaved the Tyr-Phe-type substrate, but had weak affinity to the Tyr-Pro-type substrate. Consequently, the molecular recognition of the protease analogues differs from that of the wild-type enzyme. Based on the substrate transition state, we designed and synthesized a novel class of HIV protease inhibitors containing an unnatural amino acid, (2S, 3S)-3-amino-2-hydroxy-4-phenylbutyric acid, named allophenylnorstatine, with a hydroxymethylcarbonyl (HMC) isostere. The stereochemistry of the hydroxyl group was significant for the enzyme inhibition and the HMC group interacted excellently with the aspartic acid carboxyl groups of HIV protease active site in the essentially same hydrogen-bonding mode as the transition state. Small dipeptide-based HIV protease inhibitors containing the HMC isostere were studied as advantageous compounds. Among them, a dipeptide-based HIV protease inhibitor, KNI-577, exhibited potent antiviral activities, low cytotoxicity, and good pharmacokinetic properties.

Amino Acid Sequence↗
PubMed1999

Late hemorrhage from persistent pseudoaneurysm in vertebral artery dissection presenting with ischemia: case report.

BACKGROUND: Vertebral artery dissection lesions tend to resolve spontaneously, but abnormal findings such as aneurysmal-dilatation occasionally persist. However, the clinical features and pathological findings in such cases have never been verified. CASE DESCRIPTION: A 62-year-old man presented with left cerebellar infarction. Angiography showed the "pearl and string sign" in the left vertebral artery, and he was diagnosed as having left vertebral artery dissection. Repeated angiography showed persistent aneurysmal dilatation with irregular stenosis. Eleven years after the cerebellar infarction, the patient presented with a subarachnoid hemorrhage from an aneurysm of the left vertebral artery, and the lesion was explored via the left suboccipital approach. The vertebral artery was firm, making the placement of a clip impossible, so the lesion was treated by coating of the bleeding point. The patient died of pneumonia and hyperglycemia on postoperative day 15. Postmortem examination revealed an organized intramural hematoma, thickening of the intima, and fibrous degeneration of the media of the vertebral artery, a fusiform, distended thin arterial wall with intimal disruption at the aneurysmal dilatation, and arteriosclerosis of all cerebral arteries. CONCLUSION: This case indicates that persistent aneurysmal dilatation of a dissection is a pseudoaneurysm prone to rupture, and that healing of the affected vessels might be severely compromised in the presence of pathological conditions such as arteriosclerosis and disturbed intraluminal blood flow in the dissected lesions.

Aortic Dissection↗
PubMed1999

[A case of enlarged infundibular dilatation diagnosed by vertebral angiograms with carotid compression and neuroendoscope].

A case of enlarged infundibular dilatation diagnosed by vertebral angiograms with carotid compression was reported. A 57-year-old woman suffered from headache. She underwent MRA which revealed left internal carotid artery aneurysm. Left common carotid angiograms suggested a left saccular internal carotid artery aneurysm (4 mm x 6 mm) without a posterior communicating artery. However, it was confirmed to be an enlarged infundibular dilatation on left vertebral angiograms with carotid compression. It was confirmed at operation microscopically and neuroendoscopically, and the dilatation was treated by coating. When carotid angiograms reveal no posterior communicating artery, it is difficult to differentiate the origin of posterior communicating artery from internal carotid artery-posterior communicating artery junction aneurysms. Vertebral angiograms with carotid compression is useful for the differentiation for the exact diagnosis.

Aneurysm↗
PubMed1998

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells.

Adrenomedullin (AM), a potent vasorelaxant and natriuretic peptide isolated from human pheochromocytoma, is present in the kidney and secreted from endothelial cells (EC) and vascular smooth muscle cells (VSMC), but the functional role of AM is still unclear. To clarify the significance of AM as a local regulator, we investigated its secretion and action in cultured cells, and examined the effects of neutralization using a specific monoclonal antibody against AM. The prepared antibody directed against the ring structure showed a high affinity for human and rat AM. Using radioimmunoassay with this antibody, we found significant secretion from cultured rat mesangial cells (MC) of a 6-kDa mature form of AM as seen from EC and VSMC. The addition of AM into cultured cells dose-dependently increased cAMP production and potently inhibited PDGF-stimulated thymidine incorporation. Pretreatment with the monoclonal antibody completely abolished cAMP increase induced by exogenous AM. Moreover, antibody neutralization of endogenously secreted AM in cultured EC, but not in MC or VSMC, markedly (by approximately 70%) reduced basal cAMP production and significantly (1.7-fold) enhanced DNA synthesis. These results indicate that AM, acting as an autocrine/paracrine regulator, exerts an antiproliferative action on EC and MC, and suggest its role as a local modulator of endothelial and mesangial function.

Adrenomedullin↗
PubMed1997

A reductive acidolysis final deprotection strategy in solid phase peptide synthesis based on safety-catch protection.

A reductive acidolysis final deprotection strategy in solid phase peptide synthesis was developed using a new safety-catch type of semi-permanent protecting groups and new linkers which were derived from 4-methylsulfinylbenzyl protection. This new strategy was based on a two-dimensional protection scheme employing acid-labile temporary and acid-stable but reductive acidolysis-cleavable semi-permanent protecting groups. By using this strategy, we successfully synthesized four model peptides, of which two contained C-terminal amide.

Amino Acid Sequence↗
PubMed1997

Cerebellar infarction with hydrocephalus caused by spontaneous extracranial vertebral artery dissection--case report.

A 38-year-old male suffered sudden onset of rotational vertigo without headache. Consciousness disturbance developed on the 3rd day after the onset. Computed tomography showed cerebellar infarction with obstructive hydrocephalus. External ventricular drainage was performed. Angiography showed bilateral extracranial vertebral artery dissection. Antiplatelet therapy was given. Repeat angiography showed improvement of the dissection. His neurological deficits completely resolved. Vertebral artery dissections may cause both lateral medullary or cerebellar infarction and hydrocephalus due to the cerebellar infarction manifesting as various symptoms so careful evaluation and treatment are required.

Adult↗
PubMed1996

Synthesis of human C-type natriuretic peptide 22 using chlorotrityl resin and tetrafluoroboric acid deprotection.

Human C-type natriuretic peptide 22 (hCNP22), the third member of the natriuretic peptide family, was efficiently synthesized by Fmoc-based peptide chain construction on a 2-chlorotrityl (Clt) resin, followed by deprotection using tetrafluoroboric acid (HBF4). The use of Clt resin was effective in suppressing racemization at the C-terminal cysteine residue caused by the base treatment for Fmoc-cleavage. The disulfide bond of hCNP22 was constructed using the silyl chloride-sulfoxide method to avoid oxidation at the Met residue. Using amino acid- and dipeptide-resin derivatives, the effects of bases, protecting groups and resin supports on the racemization at the C-terminal Cys residue were examined in detail.

Amino Acid Sequence↗
PubMed1996

[Studies on development of disulfide bond forming reaction and the application to regioselective disulfide formation].

An efficient method for the disulfide bond formation in peptides by the silylchloride-sulfoxide system is described. Methyltrichlorosilane in trifluoroacetic acid, in the presence of diphenylsulfoxide, is found to cleave various S-protecting groups of cysteine to form cystine directly within 10 to 30 min. No side reactions were observed with nucleophilic amino acids such as Met, His, or Tyr, except for Trp, under the reaction conditions of the silylchloride-sulfoxide treatment. A chlorination of the indole moiety of unprotected Trp, rather than the sulfur-sulfur bond formation, is a dominant reaction when the peptide containing unprotected Trp is treated with the chlorosilane-sulfoxide. However, the disulfide bond can be formed efficiently with no modification at the indole ring by the treatment of the peptide having formyl-protected Trp residue with the silylchloride-sulfoxide system. The formyl group is removed by a brief treatment at basic pH without affecting the disulfide bond formed by the silylchloride-sulfoxide treatment. Total synthesis of human insulin, a two chain peptide containing three disulfide bonds, was achieved unambiguously by sequential and selective formation of disulfide bonds in the protein for the first time. The key reaction in the synthesis is regioselective formation of three disulfide bonds separately using the silyl chloride method described above. Prior to the insulin synthesis, it was confirmed by the syntheses of double-disulfide peptides: b-hANP, unnatural parallel dimer of a-hANP, and human endothelin-1 that no disulfide exchange occurred during the silyl chloride treatment. Using three orthogonal thiol protecting groups, Trt, Acm, and But, three disulfide bonds of human insulin were efficiently constructed by the successive reactions using thiolysis, iodine oxidation, and the sily1 chloride method. Each reaction for the stepwise disulfide formation proceeded within 15 to 60 min with no polymeric product and no solubility problem. The synthetic human insulin had the correct structure and was indistinguishable from natural human insulin.

Amino Acid Sequence↗