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Biomedical subjects

Akira Shirahata

Publications and source records attributed to Akira Shirahata.

At least 19 recordsLinked to original sources
PubMed2005

Postnatal development of orexin-A and orexin-B like immunoreactivities in the Eastern grey kangaroo (Macropus giganteus) hypothalamus.

The Eastern grey kangaroo (Macropus giganteus) is a marsupial, which is born in an extremely undeveloped state and has a long suckling period in the mother's pouch. In the present study, we examined the immunoreactivities of orexin-A (OXA) and orexin-B (OXB) in the hypothalamus of the Eastern grey kangaroo during the preweaning period, postweaning period and adulthood. In the preweaning period, only a few OXA- and OXB-like immunoreactive (LI) neurons and fibers were present and the intensity of staining was very weak. In the postweaning period, there was a pronounced increase in the numbers of OXA- and OXB-LI neurons and fibers and the intensity of the immunoreactivity was considerably stronger in comparison to the preweaning period. In the adult, the numbers of OXA- and OXB-LI neurons and fibers appeared to be slightly increased and the intensity was slightly stronger in comparison to the postweaning period. At all time periods, the distributions of OXA- and OXB-LI neurons was similar. The postnatal development of hypothalamic orexin neurons may be associated with developmental changes, including feeding behavior.

Animals↗
PubMed2005

Involvement in K+ access of Leu318 at the extracellular domain flanking M3 and M4 of the Na+,K+-ATPase alpha-subunit.

The effect of point mutation in the sequence 316TWLE319, which occurs in the extracellular loop flanking the third (M3) and the fourth (M4) transmembrane segment (L3/4) of the Na+,K+-ATPase alpha-subunit, was examined. Mutation of Glu319 to Asp yielded an enzyme with full activity, whereas substituting Glu319 to Ala resulted in a severe loss of activity. A negative charge was introduced along the sequence, one residue at a time, from Thr316 to Leu318 (by E-scanning) in the mutant construct with Glu319 already mutated to Gln. The activity that had been reduced to 60% by the mutation of Glu319 to Gln was restored upon the introduction of a negative charge by E-scanning. When Leu318 was replaced by Glu in a series of scanning experiments, the K+ sensitivity of the ATPase activity was lowered. The lowering of K+ sensitivity was further demonstrated when a mutation of Leu318 to Glu was introduced into the wild-type enzyme. Furthermore, mutants with Leu318 to Gln, Arg, and Phe displayed lower K+ sensitivity similar to that of Leu318 to Glu mutant. Leu318 may be in access path for K+, and any substitution at this position may interfere with access of K+ from outside the cell.

Animals↗
PubMed2005

Independent roles of eIF5A and polyamines in cell proliferation.

To examine the roles of active hypusinated eIF5A (eukaryotic translation initiation factor 5A) and polyamines in cell proliferation, mouse mammary carcinoma FM3A cells were treated with an inhibitor of deoxyhypusine synthase, GC7 (N1-guanyl-1, 7-diaminoheptane), or with an inhibitor of ornithine decarboxylase, DFMO (a-difluoromethylornithine), or with DFMO plus an inhibitor of spermine synthase, APCHA [N1-(3-aminopropyl)-cyclohexylamine]. Treatment with GC7 decreased the level of active eIF5A on day 1 without affecting cellular polyamine content, and inhibition of cell growth occurred from day 2. This delay reflects the fact that eIF5A was present in excess and was very stable in these cells. Treatment with DFMO or with DFMO plus APCHA inhibited cell growth on day 1. DFMO considerably decreased the levels of putrescine and spermidine, and the formation of active eIF5A began to decrease when the level of spermidine fell below 8 nmol/mg of protein after 12 h of incubation with DFMO. The combination of DFMO and APCHA markedly decreased the levels of putrescine and spermine and significantly decreased the level of spermidine, but did not affect the level of active eIF5A until day 3 when spermidine level decreased to 7 nmol/mg of protein. The results show that a decrease in either active eIF5A or polyamines inhibits cell growth, indicating that eIF5A and polyamines are independently involved in cell growth

Animals↗
PubMed2005

Fe(II)/Cu(I)-dependent P-type ATPase activity in the liver of Long-Evans cinnamon rats.

This study examined Fe(II)-dependent ATPase activity in OTG (octylthioglucoside) -treated microsomes isolated from Wistar and LEC rats. The ATPase activity of the liver OTG-microsomes from Wistar rats increased sharply in the 5-150 microM range of Fe(II) with a K0.5 value of 23.9+/-3.6 microM, while the activity of LEC rat liver microsomes increased with increasing Fe(II) up to 500 microM with a K0.5 value of 64.4+/-8.1 microM. The K0.5 values for Fe(II)-dependent ATPase activity of spleen OTG-microsomes were nearly identical at 59.3 microM in the Wistar rat and 63.7 microM in the LEC rats with a similar level of activity at each Fe(II) concentration in both strains of animals. These results indicated that there are two types of Fe(II)-dependent ATPase with different Fe(II) sensitivity, a high sensitive (H) and a low sensitive (L) type, and that the H-type activity was specific to the liver. The H-type activity was, however, deficient in the liver of LEC rats that accumulate copper and iron in hepatocytes as a result of mutations in the Wilson's disease protein (WNDP). On the basis of these results, together with the similarity in optimal conditions required for full activity of the enzyme, we conclude that the Fe(II)-dependent ATPase (H-type) and WNDP may be identical.

Adenosine Triphosphatases↗
PubMed2005

Antisense recognition of the HER-2 mRNA: effects of phosphorothioate substitution and polyamines on DNA.RNA, RNA.RNA, and DNA.DNA duplex stability.

The HER-2 gene is overexpressed in a subset of breast, ovarian, lung, and pancreatic cancers. Antisense oligonucleotides suppress gene expression depending on the stability of the DNA.RNA hybrids formed at the target site. Polyamines, the cellular cations that interact with DNA and RNA, may influence hybrid stability in the cell. Therefore, we studied the ability of natural polyamines (putrescine, spermidine, and spermine) and a series of their structural analogues to stabilize DNA.RNA and RNA.RNA duplexes using melting temperature (T(m)) measurements and circular dichroism (CD) spectroscopy. Phosphodiester (PO) and phosphorothioate (PS) oligonucleotides (ODNs) (15 nucleotides, 5'-CTCCATGGTGCTCAC-3') targeted to the initiation codon region of the HER-2 mRNA, and complementary RNA and DNA ODNs, were used in this study. The relative order of thermal stability was as follows: RNA.RNA > PO-DNA.RNA > PO-DNA.PO-DNA > PS-DNA.RNA > PS-DNA.PO-DNA > PS-DNA.PS-DNA. The ability of polyamines to stabilize the duplexes improved with the cationicity of the polyamine, with hexamines being more effective than pentamines, which in turn were more effective than tetramines and triamines. However, chemical structural effects were clearly evident with isovalent homologues of spermidine and spermine. CD spectra showed B and A conformations, respectively, for the DNA and RNA helices. DNA.RNA hybrids adopted an intermediate structure between the B and A forms. These data help us to understand the role of endogenous polyamines in DNA.RNA hybrid stabilization, and provide information for designing novel polyamines to facilitate the use of antisense ODNs for controlling HER-2 gene expression.

Base Sequence↗
PubMed2005

Treatment of intestinal perforation in extremely low-birthweight infants.

BACKGROUND: The mortality of intestinal perforation in extremely low-birthweight infants (ELBWI) is high. It still remains to be determined whether peritoneal drainage is a definitive treatment instead of laparotomy. The authors used bedside peritoneal drainage (BSPD) as the diagnostic procedure, and exchange transfusion (ET) as the preparatory procedure for invasive stress of laparotomy. The treatment protocol is composed primarily of laparotomy combined with BSPD and ET. METHODS: ELBWI who developed intestinal perforation during hospitalization between 1993 and 2000 were treated according to the aforementioned protocol. Their medical records were examined retrospectively. RESULTS: Eight ELBWI were identified. The subjects' birthweights ranged from 553 to 892 g and the gestational age ranged from 23 to 26 weeks. The subjects consisted of five cases with idiopathic intestinal perforation, two cases with necrotizing enterocolitis, and one case with meconium plug syndrome. Laparotomy was performed in all cases, and BSPD was performed in seven cases. Intestinal perforation was definitively diagnosed by X-ray only in three cases, while by stool-like drainage in BSPD in the other five cases. Seven (87.5%) cases survived. CONCLUSION: In this limited experience, the treatment mainly composed of laparotomy combined with BSPD and ET appeared beneficial.

Drainage↗
PubMed2005

Control of spermidine and spermine levels in rat tissues by trans-4-methylcyclohexylamine, a spermidine-synthase inhibitor.

In rat tissues, a decrease in spermidine, accompanied by an increase in spermine was induced by the oral administration (once daily for either 1 week or 1 month) of trans-4-methylcyclohexylamine (4MCHA), a spermidine synthase inhibitor. This is similar to the changes observed in polyamine content when cell growth is arrested. The body-weight gain of the rats tended to decrease with increasing doses of 4MCHA. A decrease in spermidine, combined with a moderate increase in spermine, was observed dose-dependently in all of the tissues tested, with a relatively fast clearance of 4MCHA. Manipulating the polyamine content of tissues, by daily administration of 100 mumol 4MCHA for 1 week, made it possible to estimate the effects of simultaneously added spermidine or spermine on endogenous polyamine contents. The altered polyamine levels, obtained after daily administration for 1 week, were maintained during the extended 1-month period, with growth-dependent alteration. The results show it is possible to produce experimental rats with a higher spermine:spermidine ratio than control rats to investigate the physiological significance of spermidine downregulation and spermine upregulation in vivo.

Alkenes↗
PubMed2005

Bis(ethyl)norspermine potentiates the apoptotic activity of the pure antiestrogen ICI 182780 in breast cancer cells.

We studied the effects of ICI 182780 and bis(ethyl)norspermine (BE-3-3-3) on cell growth and apoptosis of estrogen receptor-positive MCF-7 breast cancer cells. Combination treatment with 100 nM ICI 182780 and 5 microM BE-3-3-3 for 6 days inhibited cell growth by 74.3+/-8.4% in MCF-7 cells, compared to that of 25.4+/-5.8 and 45.8+/-12.2%, respectively, when ICI 182780 and BE-3-3-3 were used as single agents. Treatment with 100 nM ICI 182780 and 5 microM BE-3-3-3 as single agents resulted in 9.1+/-1.0% and 35.1+/-4.5% apoptosis, respectively, as measured by APO-BRDU assay. When ICI 182780 and BE-3-3-3 were used in combination, the percentage of apoptosis was 60.6+/-3.8%. Improved efficacy of ICI 182780 and BE-3-3-3 combination on growth inhibition was observed for T-47D cells also. Western blot analysis showed that combinations of ICI 182780 and BE-3-3-3 caused down-regulation of the anti-apoptotic Bcl-2 and Bcl-XL proteins and increased the level of the pro-apoptotic Bax protein. Combination treatment also increased caspase-8 activation. Analysis of polyamine levels 48 h after combination treatment showed that spermidine and spermine levels were down regulated significantly. These studies indicate a potentially effective combination strategy for breast cancer treatment. Our results also link the down-regulation of polyamine pathway to apoptotic cell death and regulation of mediators of cell death.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

[Prolonged cerebral salt wasting following craniopharyngioma surgery and posterior reversible encephalopathy syndrome: a case report].

A 9-year-old boy was admitted to our hospital with daytime urinary incontinence for the past one year. MRI showed craniopharyngioma occupying the third ventricle. The tumor was excised by interhemispheric approach. Because hyponatremia and polyuria with high renal loss of sodium were observed on postoperative day 3, hydrocortisone and DDAVP were replaced. On postoperative day 24, successive general convulsions and hyponatremia recurred, and MRI FLAIR imaging showed marked brain edema in the bilateral parieto-occipital lobes. This finding disappeared late in the course of treatment, and the case was diagnosed as posterior reversible encephalopathy syndrome. The pathophysiology of cerebral salt wasting and posterior reversible encephalopathy syndrome in a craniopharyngioma patient are also discussed in the article.

Brain↗
PubMed2004

Formation of DNA nanoparticles in the presence of novel polyamine analogues: a laser light scattering and atomic force microscopic study.

We synthesized a pentamine (3-3-3-3) and two hexamine (3-3-3-3-3 and 3-4-3-4-3) analogues of the natural polyamine, spermine (3-4-3) and studied their effectiveness in condensing pGL3 plasmid DNA, using light scattering and atomic force microscopic (AFM) techniques. The midpoint concentration of the polyamines on pGL3 condensation (EC50) was 11.3, 10.6, 1.5, 0.49 and 0.52 micro M, respectively, for 3-4-3, norspermine (3-3-3), 3-3-3-3, 3-3-3-3-3 and 3-4-3-4-3 in 10 mM Na cacodylate buffer. Dynamic laser light scattering study showed a decrease in hydrodynamic radii of plasmid DNA particles as the number of positive charges on the polyamines increased. AFM data showed the presence of toroids with outer diameter of 117-191 nm for different polyamines, and a mean height of 2.61 +/- 0.77 nm. AFM results also revealed the presence of intermediate structures, including those showing circumferential winding of DNA to toroids. The dependence of the EC50 on Na+ concentration suggests different modes of binding of spermine and its higher valent analogues with DNA. Our results show a 20-fold increase in the efficacy of hexamines for DNA condensation compared to spermine, and provide new insights into the mechanism(s) of DNA nanoparticle formation. These studies might help to develop novel nonviral gene delivery vehicles.

Lasers↗
PubMed2004

Structural and functional relationship among diamines in terms of inhibition of cell growth.

Following the report that agmatine has an anti-proliferative effect on cell growth through induction of antizyme [Satriano et al. (1998) J. Biol. Chem. 273, 15313-15316], we examined the effects of 16 different diamines on cell growth. Many diamines had little or no effect on cell growth, but agmatine and 1,6-hexanediamine had anti-proliferative effects, with agmatine having the strongest effect. Inhibition of cell growth occurred after 2 days, and inhibitory effects paralleled the degree of antizyme induction. Decreased spermine levels indicated that induction of spermidine/spermine N(1)-acetyltransferase was also involved in the inhibition of cell growth by agmatine and 1,6-hexanediamine. The frameshift efficiency (ratio of antizyme synthesis with or without frameshift) measured in a rabbit reticulocyte cell-free system was also increased by 1,3-propanediamine and cis-1,4-cyclohexanediamine in addition to agmatine and 1,6-hexanediamine. However, the intracellular levels of 1,3-propanediamine and cis-1,4-cyclohexanediamine were low when these compounds were added to the cell-culture medium. Other diamines had no effect on cell growth or frameshift efficiency. The results suggest that the presence of two amino-groups separated by an appropriate distance is important for the enhancement of frameshifting by diamines.

Acetamides↗
PubMed2004

Decreased platelet aggregation of platelet concentrate during storage recovers in the body after transfusion.

BACKGROUND: Previous reports have shown that storage decrease the ability of PLTs to aggregate in the form of PLT concentrate (PC). Nevertheless, there are few reports that have studied the PLT function in blood samples obtained from recipients after PLT transfusion. In this study, this issue was addressed by examining the ability of PLTs to aggregate after being transfused into the blood stream. STUDY DESIGN AND METHODS: PC was transfused to the patients with extremely low PLT counts resulting from chemotherapy. The maximum extent of PLT aggregation and size of the aggregates were compared between PLT in stored PC before transfusion with the PLT-rich plasma (PRP) from the recipients after transfusion and with PRP from patients with moderate decrease in PLT counts after chemotherapy. RESULTS: The maximum extent of PLT aggregation was significantly higher in PRP collected from the patients after transfusion compared to the extent obtained before transfusion. There were no significant differences in the maximum extents of PLT aggregation between the PRP collected from the recipients after PC transfusion and, in the same patients, when PLT counts were moderately low. CONCLUSION: These results suggest that the observed decreased in PLT aggregation after storage can improve in the body after transfusion, and transfused PLTs have similar aggregation ability compared to the PLTs derived from the patient.

Adenosine Diphosphate↗
PubMed2004

Increasing incidence of critical liver disease among causes of death in Japanese hemophiliacs with HIV-1.

Critical liver diseases are now major causes of death in HIV-1-infected patients after the remarkable improvement in the clinical status resulting from highly active antiretroviral therapy. We report the results of an analysis on causes of deaths related to liver diseases based on our surveillance of hemophiliacs infected with HIV-1 up until May 31, 2002. A total of 1,405 patients (hemophilia A, 1,084, and hemophilia B, 321) were registered. The cumulative number of deaths was 534 (hemophilia A, 414, and hemophilia B, 120) by May 31, 2002. Hepatic disease due to HCV infection was found in 29.8% (95% confidence interval: 20.3-40.7%) of the total cases with known causes of death after 1997, whereas this value was 14.0% (95% confidence interval: 10.8-17.7%) before 1997 (p < 0.01). We observed an increasing incidence of critical hepatic diseases among HIV-1-infected hemophiliacs, thus suggesting that treatment of HCV infection is essential for HIV-1-infected hemophiliacs.

Cause of Death↗
PubMed2004

Mammalian spermidine synthase--identification of cysteine residues and investigation of the putrescine binding site--.

Homology modeling and inhibitory studies using substrate analogs were undertaken to construct a possible three-dimensional structure, including the putrescine-binding site, of rat spermidine synthase based on its primary sequence. Of the ten cysteine residues of the enzyme, six residues were chemically determined as sulfhydryl; similarly, one residue (C25) was determined as the disulfide. Using the model obtained from the Swiss-Model protein-modeling server, and based on the crystal structure of the Thermotoga maritima enzyme, the three remaining residues were assigned as sulfhydryl. Discussions are presented on the counterpart of the C25 residue, based on the apparent role of the bacterial N-terminal peptide region in reinforcing the binding between protomers in a functional oligomeric form. The active sites of the bacterial and mammalian versions of the enzyme were very similar. The putrescine-binding site of the rat enzyme was investigated using IC(50) values of the analogs of two known potent inhibitors, n-butylamine and trans-4-methylcyclohexylamine (4MCHA). Our results indicated that 5-amino-1-pentene and 4MCHA possess comparable inhibitory activities towards the enzyme.

Amino Acid Sequence↗
PubMed2004

[Acquired von Willebrand syndrome with autoimmune hemolytic anemia].

A 17-year-old female underwent examination due to the chief complaints of epistaxis and bleeding from the gums. In addition to hemolytic anemia (Coombs positivity), she was found to have a marked reduction in the von Willebrand factor antigen (vWF:Ag) and ristocetin cofactor activity (vWF:RCo). Anti vWF antibodies mainly comprised of IgG1 fractions were also detected, so acquired von Willebrand syndrome (AvWS) with autoimmune hemolytic anemia (AIHA) was diagnosed. The recovery of vWF:Ag and vWF:RCo following administration of a factor VIII concentrate containing vWF was good, but the half life was short at about two hours and the collagen binding activity and vWF:RCo in mixing tests with control plasma were only mildly inhibited. Therefore, the anti vWF antibody in the present case was thought not to inhibit vWF function but to be involved in clearance promotion. Hemostatic control during hemorrhage was performed using a factor VIII concentrate containing vWF. With the administration of prednisolone thereafter, anti vWF antibodies disappeared at the same time as there was improvement in the AIHA. Throughout the course the patient contracted acute hepatitis A, became pregnant and gave birth, but there were no clear effects on the clinical phenotype of AvWS.

Adolescent↗
PubMed2003

[Present and expected role of the nurse in Japanese hemophilia care: result of a questionnaire survey of hemophiliacs and their families].

Since 1970, many hemophilia centers have been opened in the United States and Western Europe. In these centers, nurse coordinators (NCs) play an important role as key persons in improving the QOL of hemophiliacs with a variety of problems. On the other hand, NCs have not been stationed in most Japanese hemophilia centers, although many doctors and nurses in charge of hemophilia care desire that NCs participate in hemophilia treatment. Therefore, a survey of hemophiliacs and their families was conducted to clarify the role of the nurse in Japanese hemophilia care. The results obtained from the analysis of responses concerning 393 patients indicated that about two thirds of the respondents had never consulted with nurses in regard to their disease. Although the total number of items of care and support which were offered by nurses to the patients was 739, the total number of these items which were expected to be offered from nurses to the patients was 1078. These results indicate that the introduction of NCs is necessary for hemophilia care in Japan.

Adolescent↗