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Biomedical subjects

K Okamoto

Publications and source records attributed to K Okamoto.

At least 163 records · Page 9Linked to original sources
PubMed2000

New functional aspects of cathepsin D and cathepsin E.

Cathepsin D (CD) and cathepsin E are representative lysosomal and nonlysosomal aspartic proteinases, respectively, and play an important role in the degradation of proteins, the generation of bioactive proteins, antigen processing, etc. Recenty, several lines of evidence have suggested the involvement of these two enzymes in the execution of neuronal death pathways induced by aging, transient forebrain ischemia, and excessive stimulation of glutamate receptors with excitotoxins. CD has also been shown to mediate apoptosis induced by various stimuli and p53-dependent tumor suppression. To gain more insight into in vivo functions of CD, mice deficient in this enzyme were generated. The mutant animals showed a progressive atrophy of the intestinal mucosa, a massive destruction of lymphoid organs, and a profound accumulation of ceroid lipofuscin, and developed a phenotype resembling neuronal ceroid lipofucinosis, suggesting that CD is essential for proteolysis of proteins regulating cell growth and tissue homeostasis. It has also been shown that CD molecules secreted from human prostate carcinoma cells are responsible for the generation of angiostatin, a potent endogenous inhibitor of angiogenesis, suggesting its contribution to the prevention of tumor growth and angiogenesis-dependent growth of metastases. Interestingly, pro-CD from human breast carcinoma cells showed a significantly lower angiostatin-generating activity than that from prostate carcinoma cells. Since deglycosylated CD molecules from both carcinoma cells showed a low angiostatin-generating activity, this discrepancy appeared to be attributed to the difference in the carbohydrate structures of CD molecules between the two cell types and to contribute to their potency to prevent tumor growth and metastases.

Angiostatins↗
PubMed2000

Asymptomatic CTG expansion at the SCA8 locus is associated with cerebellar atrophy on MRI.

Spinocerebellar ataxia type 8 (SCA8) is the first example of dominantly inherited ataxia reported to be caused by a dynamic mutation of the untranslated CTG trinucleotide repeat. We performed genetic and clinical analyses of a family with an isolated case with young onset cerebellar ataxia carrying an expanded 95 CTA/CTG repeats, and revealed that the asymptomatic father was also carrying a much greater expansion of 136 repeats. This paternal transmission developed a large contraction of -41 CTG repeats. The ataxia patient showed almost pure cerebellar symptoms, and a cerebral MRI of the patient demonstrated significant atrophy of the cerebellar vermis and hemispheres with preservation of brainstem and cerebrum. Although the father did not show any neurological abnormalities, his MRI demonstrated mild atrophy of the cerebellar hemispheres. The genetic phenomenon on this family has not been observed in other types of SCAs, and this reduced penetrance may cause reproduction of sporadic SCA8 frequently. Therefore, we must perform careful interviews regarding family history, and suggest the genetic and neuroradiological investigations on family members when we encounter a sporadic patient with the CTG expansion at the SCA8 locus.

Adult↗
PubMed2000

The involvement of the neuronal Golgi apparatus and trans-Golgi network in the human olivary hypertrophy.

We studied the Golgi apparatus (GA) and trans-Golgi network (TGN) in the human olivary hypertrophy by immunohistological methods with organelle specific antibodies against the medial cisternae of the organelle (MG160) and the trans-Golgi network (TGN46). The GA and TGN of enlarged neurons in the inferior olivary nuclei in the early stages after central tract lesions lost the normal network-like configuration, and they were reduced to numerous small disconnected granules (fragmentation). In chronic stages after lesions, the GA and TGN of vacuolated or enlarged neurons showed a variety of morphological profiles, such as normal-looking patterns, fragmentation, reduction in number, and aggregation around nuclei or at a distance in the cytoplasm. In patients with multiple system atrophy, the GA and TGN of the neurons in the inferior olivary nuclei showed almost similar findings to those seen in the chronic stages after brainstem lesions. These results suggest that the GA and TGN are affected in degenerating neurons by anterograde transneuronal mechanisms.

Aged↗
PubMed2000

Impaired neurotransmitter systems by Abeta amyloidosis in APPsw transgenic mice overexpressing amyloid beta protein precursor.

APPsw transgenic mice showing substantial features of brain Abeta amyloidosis such as senile plaques and behavioral abnormalities were examined by immunostaining to determine whether Abeta deposits could induce the subsequent disturbance of neurotransmitter systems including somatostatin, substance P and choline acetyltransferase (ChAT), which are prominent in the Alzheimer's disease brain. Somatostatin, substance P and ChAT disappeared in the areas of senile plaque and were accumulated in dystrophic neurites around the amyloid cores. These findings suggest a potential role of brain Abeta amyloidosis in disturbance of the neurotransmitter systems leading to memory disturbance of Alzheimer's disease.

Amygdala↗
PubMed2000

Outcome of prophylactic radical lymphadenectomy with gastrectomy in patients with early gastric carcinoma without lymph node metastasis.

BACKGROUND: Prophylactic extended lymphadenectomy with gastrectomy may prolong survival in patients with early gastric carcinoma without lymph node metastasis. However, the therapeutic value of extensive lymphadenectomy in patients with early gastric carcinoma remains controversial. METHODS: The authors retrospectively analyzed 423 patients with early gastric carcinoma without lymph node metastasis who underwent gastrectomy and did not die of other diseases to evaluate the effect of prophylactic extended lymphadenectomy on postoperative survival. The postoperative survival rate of patients who underwent prophylactic extended lymphadenectomy was compared with that of patients who underwent prophylactic limited lymphadenectomy. RESULTS: Although extended lymphadenectomy did not appear to improve the postoperative survival rate of patients with mucosal tumors, it did improve the postoperative survival rate of patients with submucosal tumors. Whether prophylactic extended lymphadenectomy was performed significantly affected outcome in patients with early gastric carcinoma who had submucosal tumors without regional lymph node metastasis. CONCLUSIONS: Extensive lymphadenectomy with gastrectomy should be performed to prolong the survival of the patients with submucosal tumors.

Aged↗
PubMed2000

Crystal structures of bovine milk xanthine dehydrogenase and xanthine oxidase: structure-based mechanism of conversion.

Mammalian xanthine oxidoreductases, which catalyze the last two steps in the formation of urate, are synthesized as the dehydrogenase form xanthine dehydrogenase (XDH) but can be readily converted to the oxidase form xanthine oxidase (XO) by oxidation of sulfhydryl residues or by proteolysis. Here, we present the crystal structure of the dimeric (M(r), 290,000) bovine milk XDH at 2.1-A resolution and XO at 2.5-A resolution and describe the major changes that occur on the proteolytic transformation of XDH to the XO form. Each molecule is composed of an N-terminal 20-kDa domain containing two iron sulfur centers, a central 40-kDa flavin adenine dinucleotide domain, and a C-terminal 85-kDa molybdopterin-binding domain with the four redox centers aligned in an almost linear fashion. Cleavage of surface-exposed loops of XDH causes major structural rearrangement of another loop close to the flavin ring (Gln 423Lys 433). This movement partially blocks access of the NAD substrate to the flavin adenine dinucleotide cofactor and changes the electrostatic environment of the active site, reflecting the switch of substrate specificity observed for the two forms of this enzyme.

Animals↗
PubMed2000

Aldehyde dehydrogenase (ALDH) 2 associates with oxidation of methoxyacetaldehyde; in vitro analysis with liver subcellular fraction derived from human and Aldh2 gene targeting mouse.

A principal pathway of 2-methoxyethanol (ME) metabolism is to the toxic oxidative product, methoxyacetaldehyde (MALD). To assess the role of aldehyde dehydrogenase (ALDH) in MALD metabolism, in vitro MALD oxidation was examined with liver subcellular fractions from Japanese subjects who carried three different ALDH2 genotypes and Aldh2 knockout mice, which were generated in this study. The activity was distributed in mitochondrial fractions of ALDH2*1/*1 and wild type (Aldh2+/+) mice but not ALDH2*1/*2, *2/*2 subjects or Aldh2 homozygous mutant (Aldh2-/-) mice. These data suggest that ALDH2 is a key enzyme for MALD oxidation and ME susceptibility may be influenced by the ALDH2 genotype.

Acetaldehyde↗
PubMed2000

Basophilic cytoplasmic inclusions in a case of sporadic juvenile amyotrophic lateral sclerosis.

A 24-year-old woman presented with progressive muscle atrophy and weakness of the right upper extremity. Subsequently her weakness rapidly extended to the left upper extremity, neck and lower extremities. Neurological examination disclosed involvement of the lower motor neuron system. She died 7 months after the onset. There was neuronal loss and reactive gliosis in the anterior horns of the spinal cord and much less frequently in the motor cortex. Basophilic cytoplasmic inclusions were observed in the thalamus and brain stem as well as the upper and lower motor neurons. Ultrastructurally, the inclusions lacked a limiting membrane and consisted of a meshwork of filamentous structures associated with granules. The inclusions failed to react with antibodies against phosphorylated neurofilament or cystatin C. Most of the inclusions show no reaction with anti-ubiquitin antibody, however, a few inclusions show granular reaction product deposits with this antibody. The inclusions were not immunostained with antibodies against TGN46 and MG-160, markers of the trans-Golgi network and the medial cisternae of the Golgi apparatus, respectively, suggesting that they were not derived from the Golgi apparatus which was fragmented.

Adult↗
PubMed2000

Bacterial cryptochrome and photolyase: characterization of two photolyase-like genes of Synechocystis sp. PCC6803.

Photolyase is a DNA repair enzyme that reverses UV-induced photoproducts in DNA in a light-dependent manner. Recently, photolyase homologs were identified in higher eukaryotes. These homologs, termed crypto-chromes, function as blue light photoreceptors or regulators of circadian rhythm. In contrast, most bacteria have only a single photolyase or photolyase-like gene. Unlike other microbes, the chromosome of the cyanobacterium SYNECHOCYSTIS: sp. PCC6803 contains two ORFs (slr0854 and sll1629) with high similarities to photolyases. We have characterized both genes. The slr0854 gene product exhibited specific, light-dependent repair activity for a cyclo-butane pyrimidine dimer (CPD), whereas the sll1629 gene product lacks measurable affinity for DNA in vitro. Disruption of either slr0854 or sll1629 had little or no effect on the growth rate of the cyanobacterium. A mutant lacking the slr0854 gene showed severe UV sensitivity, in contrast to a mutant lacking sll1629. Phylogenetic analysis showed that sll1629 is more closely related to the cryptochromes than photolyases. We conclude that sll1629 is a bacterial cryptochrome. To our knowledge, this is the first description of a bacterial cryptochrome.

Base Sequence↗
PubMed2000

The roles of platelet-activating factor and endothelin-1 in renal damage after total hepatic ischemia and reperfusion.

BACKGROUND: This study was designed to verify the involvement of platelet-activating factor (PAF) in renal damage associated with hepatic ischemia and reperfusion (HIR) injury through the release of endothelin (ET)-1 and to determine the modulating effect of a specific PAF receptor antagonist on these insults in rats. METHODS: Male rats pretreated with either normal saline as a vehicle (NS group) or intravenous TCV-309, a PAF receptor antagonist (TCV group), were subjected to 120 min of total hepatic ischemia under an extracorporeal portosystemic shunt. Plasma aspartate transaminase, creatinine, blood urea nitrogen, and ET-1 levels and the relative renal wet weight were determined under nonischemic conditions and at 1, 3, and 6 hr of reperfusion after hepatic ischemia. Changes in mean arterial blood pressure and renal tissue blood flow measurements in the kidney were determined throughout the experiment. RESULTS: Increased plasma aspartate transaminase, creatinine, blood urea nitrogen, and ET-1 levels and the relative renal wet weight after HIR in the NS group were significantly suppressed by TCV-309 pretreatment. Mean arterial blood pressure and renal tissue blood flow after HIR in the TCV group were significantly improved when compared with those in the NS group. These effects resulted in attenuation of structural hepatic and renal damage with the improvement of 7-day survival (62%). CONCLUSIONS: The present study demonstrates that renal damage as well as critical liver injury is produced after reperfusion following 120 min of total hepatic ischemia. A PAF receptor antagonist may be therapeutically useful to protect against these types of damage via indirect modulation of plasma ET-1 levels.

Animals↗
PubMed2000

A multivariate analysis of blood vessel and lymph vessel invasion as predictors of ovarian and lymph node metastases in patients with cervical carcinoma.

BACKGROUND: To the authors' knowledge there are few available data regarding the influence of lymphovascular space invasion, which has been examined separately as two components (lymphatic vessel invasion [LVI] and blood vessel invasion [BVI]), in the metastasis of cervical carcinoma. METHODS: LVI and BVI, which include capillary vessel invasion, were reviewed retrospectively based on the histopathologic slides of 239 women with cervical carcinoma who were treated with radical hysterectomy. The correlation between lymph node and/or ovarian metastases and LVI, BVI, and other histopathologic factors was investigated by multiple logistic regression analysis. The influence of LVI and BVI on survival was examined by Cox regression analysis. RESULTS: The rate of incidence of LVI was higher than that of BVI in all stages of cervical carcinoma (P < 0.0001 for International Federation of Gynecology and Obstetrics Stage IB and Stage II disease and P < 0.05 for Stage III disease). The incidence rate of BVI increased as LVI became more prominent and there was a significant correlation between the two findings (P < 0.0001). BVI was more frequent in adenocarcinoma/adenosquamous carcinoma than in squamous cell carcinoma (P < 0.05). LVI (P < 0.0001) and parametrial invasion (P < 0.0001) were significantly related to lymph node metastasis on multivariate analysis. Conversely, BVI (P < 0.05) and parametrial invasion (P < 0.0025), as well as adenocarcinoma or adenosquamous carcinoma (P < 0.0005), were significantly related to ovarian metastasis on multivariate analysis. With regard to the prognostic significance of these components, it was found that BVI (hazards ratio [HR] = 2.0), ovarian metastasis (HR = 6.5), and lymph node metastasis (HR = 5.5) were significantly related to a poor prognosis in women with cervical carcinoma. CONCLUSIONS: Ovarian metastasis may occur via hematogenous spread of cervical carcinoma. The results of the current study suggest that BVI, including capillary vessels, that is diagnosed separately from LVI using hematoxylin and eosin stained sections may be an important prognostic factor for patients with cervical carcinoma.

Carcinoma, Adenosquamous↗
PubMed2000

Sublytic complement attack increases intracellular sodium in rat skeletal muscle.

BACKGROUND: Although excessive complement activation and deranged sodium homeostasis in skeletal muscle are characteristic in sepsis, their relationship has not been examined. This study was designed to determine if sublytic complement activation can directly mediate changes in myocellular sodium content. MATERIALS AND METHODS: Fast-twitch extensor digitorum longus muscles were freshly isolated from infant rats. Unsensitized muscles were incubated at 30 degrees C for 60 min in the media containing 10% human or rat serum under conditions of no complement activation, activation by zymosan, inactivation by heat, C7 or C9 deficiency, selective inhibition of complement pathway, and inhibition of Na(+)-K(+) ATPase by ouabain. Intracellular sodium ([Na(+)](i)) and potassium ([K(+)](i)) contents of the muscles, myocellular ATP, and LDH release from the muscles were then determined. RESULTS: Normal human serum significantly increased [Na(+)](i) and the [Na(+)](i)/[K(+)](i) ratio in the muscles as well as zymosan-activated serum. Heat inactivation, C7 deficiency, and inhibition of the alternative pathway completely abolished the cationic changes. Average LDH release was identical in all groups and less than 6%. Complement activation did not impair ouabain-sensitive Na(+)-K(+) ATPase activity in the muscles or alter myocellular ATP. Thus, the observed alterations are not likely due to dysfunction of Na(+)-K(+) pump or depletion of myocellular energy. Instead, alterations in [Na(+)](i) were dependent upon the amount of C9 added to C9-deficient serum, which suggests that the alterations are likely dependent on transmembrane pores created by membrane attack complexes (MAC). CONCLUSIONS: Sublytic amounts of MAC formed as a result of complement activation can directly alter [Na(+)](i) in ex vivo skeletal muscle.

Adenosine Triphosphate↗
PubMed2000

Fragmentation of the Golgi apparatus of the anterior horn cells in patients with familial amyotrophic lateral sclerosis with SOD1 mutations and posterior column involvement.

The Golgi apparatus (GA) of the anterior horn cells in the spinal cord was examined by immunohistological methods with an antibody against the MG-160 protein, a conserved intrinsic membrane sialoglycoprotein of the medial cisternae of the GA, in three patients with familial amyotrophic lateral sclerosis (FALS) with posterior column involvement. Large motor neurons in the anterior horns were markedly reduced in number and 10 of total 14 remaining large motor neurons showed fragmentation and a reduction in the number of the elements of the GA. The fragmentation of the GA was identical to that previously reported in motor neurons of the spinal cord and motor cortex from patients with sporadic ALS and in transgenic mice expressing the G93A mutation of the gene encoding the Cu/Zn superoxide dismutase months before the onset of paralysis. This is the first report of fragmented GA of the anterior horn cells in patients with FALS with posterior column involvement. The findings suggest that the GA is a common target in the neuronal degeneration in sporadic and FALS.

Amino Acid Substitution↗
PubMed2000

Molecular and clinical analyses of spinocerebellar ataxia type 8 in Japan.

OBJECTIVE: To clarify the molecular and clinical features of the newly identified spinocerebellar ataxia type 8 (SCA8). METHODS: We analyzed the CTG repeat region of the SCA8 gene in a series of Japanese patients with cerebellar ataxia. We also investigated the frequency of the CTG repeat length in Japanese normal elderly subjects older than age 79. Morphometric measurements on the cerebral MRI were compared between patients with SCA8 and SCA6. RESULTS: The number of the combined CTA/CTG repeats of six affected SCA8 alleles was 106.3+/-24.4 (mean +/- SD) ranging from 89 to 155 and that of normal elderly subjects was 24.3+/-4.4 (n = 104 alleles) ranging from 15 to 34. The mean age at onset of the SCA8 cases was 53.8+/-19.7 years, with a range from 20 to 73 years. One father and daughter from an SCA8 family showed remarkable paternal anticipation. The number increase from father to daughter was + 16 CTG repeats, with a 31-year acceleration of onset. The six identified SCA8 patients were clinically characterized by high frequencies of incoordination of trunk and limbs, ataxic dysarthria, impaired smooth pursuit, and horizontal nystagmus, and the MRI showed significant atrophy of the cerebellar vermis and hemispheres compared with that of normal controls. There was no significant difference between SCA8 and SCA6 on the morphometric MRI study. CONCLUSIONS: The CTG repeat expansions in the SCA8 alleles were much greater than the range of repeats in normal elderly subjects. The SCA8 phenotype manifested by cerebellar symptoms and atrophy corresponded to features of the autosomal dominant cerebellar ataxia type III (ADCA III).

Adult↗
PubMed2000

Doxorubicin-loaded poly(ethylene glycol)-poly(beta-benzyl-L-aspartate) copolymer micelles: their pharmaceutical characteristics and biological significance.

Doxorubicin (DOX) was physically loaded into micelles prepared from poly(ethylene glycol)-poly(beta-benzyl-L-aspartate) block copolymer (PEG-PBLA) by an o/w emulsion method with a substantial drug loading level (15 to 20 w/w%). DOX-loaded micelles were narrowly distributed in size with diameters of approximately 50-70 nm. Dimer derivatives of DOX as well as DOX itself were revealed to be entrapped in the micelle, the former seems to improve micelle stability due to its low water solubility and possible interaction with benzyl residues of PBLA segments through pi-pi stacking. Release of DOX compounds from the micelles proceeded in two stages: an initial rapid release was followed by a stage of slow and long-lasting release of DOX. Acceleration of DOX release can be obtained by lowering the surrounding pH from 7.4 to 5.0, suggesting a pH-sensitive release of DOX from the micelles. A remarkable improvement in blood circulation of DOX was achieved by use of PEG-PBLA micelle as a carrier presumably due to the reduced reticuloendothelial system uptake of the micelles through a steric stabilization mechanism. Finally, DOX loaded in the micelle showed a considerably higher antitumor activity compared to free DOX against mouse C26 tumor by i.v. injection, indicating a promising feature for PEG-PBLA micelle as a long-circulating carrier system useful in modulated drug delivery.

Adenosarcoma↗
PubMed2000

Absence of Wee1 ensures the meiotic cell cycle in Xenopus oocytes.

Meiotic cells undergo two successive divisions without an intervening S phase. However, the mechanism of S-phase omission between the two meiotic divisions is largely unknown. Here we show that Wee1, a universal mitotic inhibitor, is absent in immature (but not mature) Xenopus oocytes, being down-regulated specifically during oogenesis; this down-regulation is most likely due to a translational repression. Even the modest ectopic expression of Wee1 in immature (meiosis I) oocytes can induce interphase nucleus reformation and DNA replication just after meiosis I. Thus, the presence of Wee1 during meiosis I converts the meiotic cell cycle into a mitotic-like cell cycle having S phase. In contrast, Myt1, a Wee1-related kinase, is present and directly involved in G(2) arrest of immature oocytes, but its ectopic expression has little effect on the meiotic cell cycle. These results strongly indicate that the absence of Wee1 in meiosis I ensures the meiotic cell cycle in Xenopus oocytes. Based on these results and the data published previously in other organisms, we suggest that absence of Wee1 may be a well-conserved mechanism for omitting interphase or S phase between the two meiotic divisions.

Animals↗