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Biomedical subjects

T Sakaki

Publications and source records attributed to T Sakaki.

At least 19 recordsLinked to original sources
PubMed1997

Retinoblastoma protein expression and MIB-1 correlate with survival of patients with malignant astrocytoma.

BACKGROUND: Regulatory coupling of cell proliferation and apoptosis is suggested by recent findings with regard to certain tumors, such as the finding of tumor resistance to anticancer therapy caused by inhibition of apoptosis. The processes leading to apoptosis appear to be regulated by a variety of oncogenes and tumor suppressor genes. In the current study, the relation between apoptosis and expression of retinoblastoma protein (pRB) was assessed in 50 primary anaplastic astrocytomas (AAs) and 46 recurrent tumors in the same patients as the primary tumors after macroscopic total surgical resection and chemoradiotherapy. METHODS: Apoptotic cells were identified by the in situ 3'-end labeling technique. Proliferative potential, pRB expression, and p53 expression were evaluated immunohistochemically using anti-Ki-67 (MIB-1), anti-pRB, and anti-p53 antibodies, respectively. The prognostic value of these biologic markers in AA patients undergoing treatment was also evaluated. RESULTS: The mean apoptotic index (AI) was 0.91 +/- 0.70% for specimens obtained at the initial surgery and 2.32 +/- 1.71% for those obtained at recurrence. There was no apparent correlation between the AI and the MIB-1 staining index (MI) in primary AAs, whereas significantly higher AI and MI were observed in recurrent pRB negative cases than in their pRB positive counterparts. The survival of patients with AAs showing a high MI and negative pRB immunostaining was significantly shorter than in the other cases. Neither the size of the apoptotic fraction nor the p53 expression in primary tumor correlated with the overall survival. CONCLUSIONS: The clinical outcome of patients with AA may be associated with aberrant pRB function and increased proliferative activity rather than an inability of tumor cells to undergo apoptosis.

Adult↗
PubMed1997

Expression of tPA mRNA in the facial nucleus following facial nerve transection in the rat.

Plasminogen activators (PAs) have been suggested to play a role in neuronal migration and glial cell proliferation in the developing CNS. Less is known, however, about the role of PAs in the mature nervous system. To elucidate the role of tissue type plasminogen activator (tPA) in the nervous system we used in situ hybridization to study the expression of tPA mRNA within the rat facial nucleus after facial nerve transection. We also studied the effect of MK-801 on tPA mRNA expression in order to investigate whether the previously reported N-methyl-D-aspartate (NMDA) receptor activation is involved in this model. tPA mRNA was expressed in the ipsilateral facial motoneurones from 6 h after injury. This expression continued for at least 2 weeks after facial nerve transection. Administration of MK-801 before axonal injury did not affect the expression of tPA mRNA in the facial nucleus. These data suggest that tPA might be involved in the regenerative process without NMDA receptor activation in mature facial neurones.

Animals↗
PubMed1997

Shortened telomere length and increased telomerase activity in hamster pancreatic duct adenocarcinomas and cell lines.

Recently, shortened telomere length and increased telomerase activity have been demonstrated in various human cancers. In the study reported here, we ascertained whether gene changes are characteristic of pancreatic cancers. Hamster duct carcinomas and cell lines were investigated by Southern blot analysis for telomere restriction fragment (TRF) length and by the telomeric repeat amplification protocol (TRAP) assay for telomerase activity. Comparison with normal pancreas and spleen revealed shortened TRF length and markedly increased telomerase activity in primary pancreatic duct carcinomas induced by the rapid-production model as well as in a transplantable carcinoma and the cell lines. The enzyme level was 86.0-215.7 times the low levels found in control pancreas and spleen tissues. Late-passage Syrian hamster embryo cells, known to be immortalized and tumorigenic, had shorter TRFs than the original cells in primary culture did. These results indicate that hamster pancreatic duct carcinoma cells are immortalized, with the potential for proliferation ad infinitum, and provide a model for basic therapeutic research into the substances targeting telomerase.

Adenocarcinoma↗
PubMed1997

Loss and apoptosis of smooth muscle cells in intracranial aneurysms. Studies with in situ DNA end labeling and antibody against single-stranded DNA.

Pathological specimens were collected from 14 unruptured and 13 ruptured aneurysms at the time of clipping and studied in order to assess the underlying mechanism of rupture by investigating degeneration of the aneurysmal wall and possible involvement of apoptosis. Immunohistochemistry with anti-actin antibody showed few smooth muscle cells in the ruptured aneurysms and replacement of the muscularis layer by a fibro-hyalin tissue. However, at least one layer of smooth muscle cells was clearly observed in the unruptured aneurysms. Thus, smooth muscle cells in the wall of the ruptured aneurysms were much more degenerated than those in the wall of unruptured aneurysms. In addition, unruptured aneurysms with an angiographically smooth wall showed well-layered positive staining for anti-smooth muscle actin antibody while those with irregular shapes rarely reacted. We found, for the first time, evidence of DNA fragmentation in the aneurysmal wall. Apoptotic bodies were detected by means of a terminal transferase (TdT)-mediated dUTP biotin nick end labelling technique (TUNEL) and an anti-single-stranded DNA antibody in 54% (7/13) of the ruptured aneurysms. In contrast, apoptotic bodies were found in only 7% (1/14) of the unruptured cases. These results suggest that apoptotic cell death might be involved in the rupture of aneurysms.

Actins↗
PubMed1997

Acute subdural hematomas due to rupture of cortical arteries: a study of the points of rupture in 19 cases.

BACKGROUND: Several cases of acute subdural hematomas (ASDHs) due to rupture of cortical arteries are reported. They have several characteristic features: (1) their outcome is relatively good; (2) the cause is a trivial head injury; (3) patients are elderly; (4) a lucid interval is recognized; (5) hypertension is associated in many cases; and (6) cerebral contusion is absent. However, there has been no report about the points of rupture in the cortical arteries. METHODS: In 19 of the 125 patients with ASDHs admitted to our department, the cause of ASDH was bleeding from cortical arteries. The bleeding points were detected at surgery. Cases associated with cerebral contusion during or after the operation were excluded. In this article, we describe the clinical findings and the sites of bleeding from arteries in 19 cases of ASDH due to rupture of cortical arteries. RESULTS: The sites of ruptured arteries were as follows: prefrontal artery in one of 23 identified arteries (4.3%); precentral artery in five (21.7%); central artery in four (17.3%); anterior parietal artery in four (17.3%); angular artery in three (13.0%); middle temporal artery in four (17.3%); and posterior temporal artery in two arteries (8.7%). Two ruptured arteries in the same craniotomy were observed in four patients (17.3%). All points of rupture were located near the sylvian fissure (within 3 cm length around the sylvian fissure) and none in the base or vertex of the brain. CONCLUSION: If an ASDH occurs following a trivial head injury, rupture of cortical arteries should be considered as a possible cause. Wide craniotomy sufficiently covering the region surrounding the sylvian fissure should be performed to obtain hemostasis of bleeding points.

Acute Disease↗
PubMed1997

Interlocking-clipping technique for giant aneurysms of the internal carotid artery: technical case report.

OBJECTIVE AND IMPORTANCE: Direct clipping of giant intracranial aneurysms is sometimes difficult. A unique technique using multiple fenestrated clips for closing a giant aneurysm is described. CLINICAL PRESENTATION: A 65-year-old woman presented with a 10-month history of headache and gait disturbance. Cerebral angiography disclosed an unruptured giant aneurysm of the right internal carotid artery. INTERVENTION: Surgical exposure confirmed the presence of a giant aneurysm with the splaying and incorporation of the parent artery and a number of perforating arteries originating from the dome. Four angled and three straight fenestrated clips were applied in tandem to the aneurysm to reconstruct the parent artery and preserve the perforating vessels. Through their blades and heads, the closely arranged clips were successfully interlocked. CONCLUSION: This "interlocking-clipping" technique is a modification of the tandem clipping technique. The aim of this approach is to enhance closing pressure and allow a more stable "seating" of the clips in giant cerebral aneurysms.

Aged↗
PubMed1997

Specific changes in human brain after hypoglycemic injury.

BACKGROUND AND PURPOSE: Very few reports are available on serial changes in the human brain after severe hypoglycemic injury. The aim of this study was to investigate sequential neuroradiological changes in brains of patients after hypoglycemic coma compared with those after cardiac arrest previously studied with the same methods. METHODS: We repeatedly studied CT scans and MR images obtained at 1.5 T in four vegetative patients after profound hypoglycemia associated with diabetes mellitus. RESULTS: In all patients, consecutive CT scans showed symmetrical, persistent low-density lesions with transient enhancement in the caudate and lenticular nuclei and transient enhancement in the cerebral cortex 7 to 14 days after onset. Serial MR images consistently revealed symmetrical lesions of persistent hyperintensity and hypointensity on T1- and T2-weighted images, respectively, in the caudate and lenticular nuclei, cerebral cortex, substantia nigra, and/or hippocampus from 8 days to 12 months after onset. CONCLUSIONS: Repeated MR images revealed specific lesions in the bilateral basal ganglia, cerebral cortex, substantia nigra, and hippocampus, which suggests the particular vulnerability of these areas to hypoglycemia in the human brain. We speculate that the localized lesions represent tissue degeneration, including some combination of selective neuronal death, proliferation of astrocytic glial cells, paramagnetic substance deposition, and/or lipid accumulation. The absence of localized hemorrhages on MR images in hypoglycemic encephalopathy is in marked contrast to the presence of regional minor hemorrhages in postischemic-anoxic encephalopathy.

Aged↗
PubMed1997

Dural arteriovenous fistula caused by jugular vein stenosis--case report.

A 32-year-old female presented with a dural arteriovenous fistula in the transverse-sigmoid sinus caused by stenosis of the left internal jugular vein. The feeding arteries were embolized, resulting in nearly complete disappearance of the fistula. This case supports the idea that dural arteriovenous fistula is an acquired lesion caused by intravenous hypertension.

Adult↗
PubMed1997

Fetal cavernous angioma--case report.

A neonate male who developed cavernous angioma was born with a severe intraventricular hemorrhage and intraparenchymal hemorrhage in the basal ganglia. magnetic resonance imaging revealed a large, non-enhanced hematoma that packed the lateral ventricle. Surgery on the 2nd day of life verified a cavernous angioma associated with minimal hemosiderin and gliosis. Fetal cavernous angiomas, unlike such malformations in other age groups, can present with a devastating hemorrhage because of the lack of gliosis in the surrounding brain.

Cerebral Hemorrhage↗
PubMed1997

Mobilization of the internal carotid artery for basilar artery aneurysm surgery. Technical note.

The authors describe a technique for mobilization of the internal carotid artery (ICA) for basilar artery (BA) aneurysm surgery. Using the epidural approach, the anterior clinoid process, orbital roof, and optic canal are drilled away. The ICA is made mobile to the C3 segment by cutting the dural ring and dissecting the ICA from the carotid groove. The ophthalmic artery is then dissected from the optic canal. This mobilization of the ICA secures wide operative fields on both its medial and lateral sides and permits complete clipping of BA aneurysms.

Basilar Artery↗
PubMed1997

Comparison of C1-2 posterior fusion and decompression of the vertebral artery in the treatment of bow hunter's stroke.

Bow hunter's stroke results from vertebrobasilar insufficiency caused by mechanical occlusion or stenosis of the vertebral artery (VA) at the C1-2 level on head rotation. Surgical treatment of this condition may be chosen to avoid life-threatening accidents or because patients complain that conservative treatments such as verbal warnings or use of a neck brace to limit head and neck rotation are ineffective and thus restrict their lifestyle. Posterior fusion involving C1-2 has long been used to limit atlantoaxial rotational movements. However, it has the serious disadvantage that the range of head motion is severely reduced. Recently, decompression of the atlantoaxial portions of the affected VA has been used because it does not limit physiological neck movements. However, no long-term follow-up review of patients who have undergone this procedure has been conducted, and it is unclear whether this procedure always provides relief of symptoms. To answer this question, the results of C1-2 posterior fusion were compared with decompression of the VA for the treatment of bow hunter's stroke.

Aged↗
PubMed1997

[Cerebral infarction due to bacterial emboli associated with methamphetamine abuse].

The number of stimulant-drug addicts has recently been on the rise again, and they are being increasingly encountered in the emergency room. There are also frequent reports of cerebrovascular disorders complicating drug toxicity. These cerebrovascular disorders have included subarachnoid hemorrhage, intracranial hematoma, and a few cases of cerebral infarction. Here, we report the case of a 37-year-old male with drug toxicity, consciousness disorder, and hyperthermia. He was in a coma with a temperature of 43.1 degrees C and blood pressure of 58/35 mmHg when brought to our hospital. His condition worse rapidly deteriorated, and he died the same day. Cerebral infarction caused by gram-positive bacillus embolism, not necrotizing angiitis, was found at autopsy. Because drug addicts, especially stimulant-drug addicts, tend to inject themselves drug under unsanitary conditions, the possibility of this type of complication is always present. This is the first such case ever reported, and is therefore regarded as a rare complication of stimulant-drug intoxication.

Adult↗
PubMed1996

Molecular engineering study on electron transfer from NADPH-P450 reductase to rat mitochondrial P450c27 in yeast microsomes.

We have reported the localization on yeast microsomes for a modified P450c27 (mic-P450c27) that contains the microsomal targeting signal of bovine P450c17 in front of the mature form of rat mitochondrial P450c27 (Sakaki, T., Akiyoshi-Shibata, M., Yabusaki, Y., and Ohkawa, H. (1992) J. Biol. Chem. 267, 16497-16502). In this study, we found that mic-P450c27 could be reduced by NADPH in the yeast microsomes without supplement of its physiological redox partners, adrenodoxin and NADPH-adrenodoxin reductase. In order to elucidate the direct electron transfer from NADPH-P450 reductase to mic-P450c27, we carried out simultaneous expression of mic-P450c27 and yeast P450 reductase. The reduction rate of mic-P450c27 was increased by overproduction of yeast P450 reductase, roughly in proportion to the reductase content in the microsomes. In addition, we constructed a fused enzyme between mic-P450c27 and yeast P450 reductase. The reduction rate of heme iron in the fused enzyme was too rapid to be measured. These recombinant yeast microsomes showed a notable 27-hydroxylation activity toward 5beta-cholestane-3alpha,7alpha, 12alpha-triol in the absence of adrenodoxin and adrenodoxin reductase. Finally, we purified mic-P450c27 from the recombinant yeast microsomes and reconstituted the hydroxylation system in liposomal membranes using the purified mic-P450c27 and yeast NADPH-P450 reductase. Mic-P450c27 was reduced by NADPH and showed its monooxygenase activity on the reconstituted system. Therefore, yeast NADPH-P450 reductase alone was found to transfer two electrons from NADPH to mic-P450c27. These results clearly show that mic-P450c27 not only localizes on the microsomes but also functions as a microsomal cytochrome P450 that accepts electrons from NADPH-P450 reductase.

Animals↗
PubMed1996

Cloning and expression in Escherichia coli and Saccharomyces cerevisiae of a novel tobacco cytochrome P-450-like cDNA.

A cDNA library constructed from poly(A)+ RNA of tobacco BY2 cells treated with 2,4-dichlorophenoxyacetic acid was screened by using a synthetic oligonucleotide corresponding to the heme binding region of avocado CYP71A1. A cloned 2-kb cDNA designated as cTBP contained an open reading frame of 1593 bp encoding a protein of molecular size of 58916. The deduced amino acid sequence included a cysteine residue corresponding to fifth ligand of heme-Fe at 497th. The coding sequence was expressed under the control of tac promoter and rrnB terminator in Escherichia coli to yield 7 to 10 nmol P450 equivalent per litre of the culture in the presence of delta-aminolevulinic acid. The modified coding sequences in which NH2-terminal residues 2-25 were replaced by the NH2-terminal 18 amino acid residues of microsomal bovine CYP17 were also expressed under the control of ADH promoter and terminator in Saccharomyces cerevisiae to yield 29 and 30 pmol of P450 equivalent/mg protein in the microsomal fraction, respectively. On co-expression of each of the modified coding sequences and yeast NADPH-cytochrome P-450 oxidoreductase gene, the yeast microsomes exhibited 7-ethoxycoumarin O-deethylase activity. Based on these results, tobacco cTBP was found to encode a novel P450-like species with a monooxygenese activity related to xenobiotic metabolism.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Alterations of retinoblastoma, p53, p16(CDKN2), and p15 genes in human astrocytomas.

BACKGROUND: Alterations of the suppressor genes, such as the retinoblastoma (RB), p53, p16(CDKN2), and p15 genes, have been reported in human gliomas. These genes have been suggested as the cell cycle regulatory genes at the G1-S checkpoint. METHODS: Alterations of the RB, p53, p16(CDKN2), and p15 genes in human astrocytomas were screened by single strand conformation polymorphism analysis of polymerase chain reaction products (PCR-SSCP analysis) and then confirmed by dideoxy sequencing. In addition, the expression of RB and p16 protein was examined by Western blot analysis. RESULTS: Aberrations of the RB gene were found in 3 of 23 surgical astrocytoma specimens (13%). Mutations were found at codon 754 in exon 22 (Val-->Gly), codon 519 in exon 17 (Thr-->Pro), and one base deletion at codon 903 resulting in stop codon at codon 905 in exon 26. These mutational locations were all near the regions associated with the functional domains of the RB gene. Aberrations of the p53 gene were found in 4 cases (17.4%). These mutations were found at codons 146 (Trp-->Gly) and 165 (Gln-->His) in exon 5, codon 73 (Val-->Glu) in exon 4, and codon 313 (Ser-->Asn) in exon 9. In addition, alterations of the p16(CDKN2) gene were found, with 5 cases (21.7%) having homozygous deletions, and 2 cases (8.7%) harboring point mutations. No p15 gene alteration was detected. The expression of p16 protein was undetectable in 10 cases (43.5%) by Western blot analysis, demonstrating an inverse correlation with the expression of RB protein. CONCLUSIONS: A few cases had overlapping alterations, and the incidence of one or more RB, p53, or p16(CDKN2) changes appeared to be relatively high in human astrocytomas. These results suggest that cell cycle regulatory gene alterations may play an important role in the development of gliomas.

Astrocytoma↗
PubMed1996

Amelioration of ischemic brain damage by the preischemic administration of propentofylline (HWA285) in a rat focal ischemia.

The protective effect of the propentofylline (HWA285) in a rat focal ischemia was investigated. The preischemic administration of HWA285 (10 mg/kg i.p.) significantly reduced the volume of ischemic damage both in the neocortex and the striatum. The postischemic administration of HWA285 failed to ameliorate ischemic damage. These findings suggest the therapeutic potential for ischemic core of the striatum. The neuroprotective mechanism may be related to its inhibition of both glutamate and dopamine release in the early period of focal ischemia.

Animals↗
PubMed1996

Multiple forms of human P450 expressed in Saccharomyces cerevisiae. Systematic characterization and comparison with those of the rat.

We systematically characterized the levels and substrate specificity of P450s from humans and rats to extrapolate drug metabolism data from experimental animals to humans. Human P450s (CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 2D6, 2E1, and 3A4) were expressed in Saccharomyces cerevisiae and purified. Rat P450s were purified from hepatic microsomes of rats. We investigated the catalytic activities of purified P450s in a reconstituted system. Human CYP2B6 and rat CYP2B1 had high lidocaine N-deethylation activity. Human and rat CYP2D forms had high debrisoquine 4-hydroxylation activity. Human CYP3A4 and rat CYP3A2 had high testosterone 2 beta- and 6 beta-hydroxylation activities in a modified reconstituted system with a lipid mixture. The hydroxylation site of testosterone by CYP2B6 (16 alpha- and 16 beta-positions) agreed with that by rat CYP2B1. Human CYP2E1 had the highest lauric acid (omega-1)-hydroxylation activity and also had catalytic properties similar to those of rat CYP2E1. Human CYP2A and 2C forms had catalytic properties in testosterone metabolism different from those of rats. Antibodies raised against purified P450s were used to measure the levels of hepatic P450s. The level of CYP3A4 was the highest in human hepatic microsomes, comprising 30-40% of the total P450. CYP2C9 comprised 10-20% of the total. The levels of CYP1A2, 2A6, 2C8, 2D6, and 2E1 were moderate (5-15% of total P450). CYP2B6 content was very low. The information of this study is useful for drug metabolism and toxicological studies.

Animals↗