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Biomedical subjects

H Iwata

Publications and source records attributed to H Iwata.

At least 37 records · Page 2Linked to original sources
PubMed2004

Adsorption of enantiomeric poly(lactide)s on surface-grafted poly(L-lactide).

We show that resistance of densely grafted polymer layers to adsorption of chemically identical free chains, which is known to be caused by entropic expulsion of free chains from the grafted layer, can be suppressed using the grafted and free chains of opposite stereoconfiguration. Specifically, we study adsorption of poly(L-lactide) (PLLA) and its enantiomer poly(D-lactide) (PDLA) onto layers of surface-grafted PLLA in acetonitrile and chloroform by infrared spectroscopy (IR). The grafted layers with thicknesses ranging from 7 to 35 nm are produced by ring-opening polymerization of L-lactide from hydroxyl end-groups of a self-assembled monolayer on gold. The IR data indicate that adsorption on the bare gold surface is the same for the L- and D-form of the polymer. However, covering the gold with the surface-grafted PLLA produces a significant decline in the adsorption of free PLLA and, by contrast, a strong enhancement in the adsorption of free PDLA. In addition, the IR data indicate that the adsorbed PDLA chains are stereocomplexed with the grafted PLLA chains. Thus, entropic expulsion of free chains from the grafted layer, which is responsible for the resistance of surface-grafted PLLA to adsorption of free PLLA, is suppressed in the case of free PDLA by stereocomplexation between the grafted and free chains.

Journal Article↗
PubMed2004

Chain elongation suppression of cyclic block copolymers in lamellar microphase-separated bulk.

Chain elongation suppression of cyclic block copolymers in microphase-separated bulk was determined quantitatively. Solvent-cast and annealed films are confirmed to show alternating lamellar structure and their microdomain spacing D increases with increasing total molecular weight M according to the relationship D proportional, variant M0.59, which agrees quite consistently with the theoretically predicted power law, i.e., D proportional, variant M3/5. This result is in contrast to the well-established issue for linear block copolymers, where the relationship D proportional, variant M2/3 has been confirmed to hold both experimentally and theoretically. This means that chain elongation of each component block is suppressed considerably, owing to their looped conformation in strongly segregated bulk.

Journal Article↗
PubMed2004

Contamination by persistent organochlorines in cetaceans incidentally caught along Brazilian coastal waters.

Wide ranges of organochlorine residues were determined in the blubber of franciscana (Pontoporia blainvillei), estuarine dolphin (Sotalia guianensis), Atlantic spotted dolphin (Stenella frontalis), and long-beaked common dolphin (Delphinus capensis) incidentally caught along Brazilian coastal waters. Concentrations of DDTs and PCBs were the highest, followed by CHLs, TCPMOH, dieldrin, TCPMe, heptachlor epoxide, HCB, and HCHs. Unexpectedly, significant pollution of PCBs, DDTs, TCPMe, and TCPMOH were observed in cetaceans from Brazil, implying the occurrence of local sources in the Southern Hemisphere comparable to those in the Northern Hemisphere, probably by high industrialization in Brazil. On the other hand, CHLs, HCB, HCHs, heptachlor epoxide, and dieldrin residue levels in Brazilian dolphins were much lower than those in other species from the Northern Hemisphere. Significant correlations of TCPMe and TCPMOH were found along with PCBs and DDTs, indicating the highly bioaccumulative nature of all these compounds and/or possible similar pollution sources.

Animals↗
PubMed2004

Dioxins and related compounds in human breast milk collected around open dumping sites in Asian developing countries: bovine milk as a potential source.

In this study, concentrations of dioxins and related compounds (DRCs)--such as polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls--were found in human breast milk from women living near dumping sites of municipal waste and reference sites in India, Cambodia, Vietnam, and the Philippines during 1999 to 2000. DRCs were detected in all human breast milk samples analyzed, demonstrating that residents in these Asian developing countries have been exposed to these contaminants. In India, the concentrations of DRCs in human breast milk from women living near the investigated dumping site were notably higher than those from women living near reference sites and from women in other Asian developing countries. Toxic equivalent quantity (TEQ) levels of DRCs were comparable with or higher than those reported in the general populations of developed countries since 1990. In contrast, levels of these contaminants in human breast milk in women from Cambodia and Vietnam were not significantly different between milk from women living near the dumping and reference sites. These results indicate that significant pollution sources for DRCs are present in Indian dumping sites and that residents there have been exposed to relatively higher levels of these contaminants. TEQ levels in human breast milk from the dumping site in India tended to decrease with an increase in the number of previous deliveries by mothers, whereas no significant relationship was observed in Cambodia, Vietnam, or the Philippines. This suggests that mothers who have been exposed to relatively high levels of DRCs transfer greater amounts of these contaminants to the first infant than later ones through breast-feeding, which in turn implies that the first children of these mothers might be at higher risk from DRCs. When the residue levels of DRCs in bovine milk collected from the Indian dumping site and reference sites were examined, TEQ levels in bovine milk from the dumping site were higher than those from reference sites. This result suggests that bovine milk is a potential source of DRCs for residents living near the dumping site in India. To our knowledge, this is the first comprehensive study on exposure to DRCs of residents living in proximity to open dumping sites of municipal waste in Asian developing countries.

Adolescent↗
PubMed2004

ProNectin F-grafted-ethylene vinyl alcohol copolymer (EVAL) as a liquid type material for treating cerebral aneurysm--an in vivo and in vitro study.

The authors aimed to develop a liquid material for embolization of aneurysms. In vitro and in vivo performances of the new embolic material were examined by cell culture and using an aneurysm model made in common carotid arteries (CCAs) of adult rats. Engineered protein ProNectin F (PnF), which contains 13 sites of an arginine-glycine-aspartic acid (RGD), was grafted onto ethylene vinyl alcohol copolymer (EVAL-g-PnF). The liquid material, EVAL-g-PnF dissolved in DMSO, was infused into an aneurysm model. The blood segments were harvested 2, 5, and 14 days and examined histologically. A number of bovine coronary artery endothelial cells became able to attach to and form cobblestone-like islands on the EVAL by incorporating PnF. The aneurysm model infused with the EVAL-g-PnF solution revealed that the aneurysm lumen was filled with proliferated fibroblasts and macrophages. On the other hand, the aneurysm model treated with unmodified EVAL showed that the cavity was almost filled with EVAL mass and that fibroblasts and macrophages filled a narrow space between the EVAL mass and the cavity wall. The results indicate that EVAL-g-PnF could be more suitable for reorganizing the cavity of an aneurysm than native EVAL.

Aneurysm↗
PubMed2003

Mapping QTLs influencing rice floral morphology using recombinant inbred lines derived from a cross between Oryza sativa L. and Oryza rufipogon Griff.

To understand the genetic basis of floral traits associated with the mating system in rice, we analyzed pistil, stamen and glume traits using a recombinant inbred line population, derived from a cross between an Asian cultivated rice ( Oryza sativa L.), Pei-kuh, and a wild rice ( Oryza rufipogon Griff.), W1944. Quantitative trait loci (QTLs) affecting floral morphology were detected by composite interval mapping using a linkage map constructed using 147 markers, mostly RFLPs. A total of 7, 4, 14 and 6 QTLs were detected for traits related to pistil, stamen, and size and shape of the glume, respectively. Comparison of 31 QTLs affecting these organs revealed ten QTLs affecting the different organs in four adjacent regions on chromosomes 2, 4, 5 and 10, but most QTLs (68%) were located separately on the whole chromosomes. Although four QTLs for stigma breadth, anther length and thickness of lemma and palea explained more than 25% of the total phenotypic variance, most QTLs (87%) had smaller effects. These results suggest that quantitative variation observed for pistil, stamen and glume traits is controlled by several distinct genes with small effects.

Chromosome Mapping↗
PubMed2003

Experimental model to estimate intestinal viability using charge-coupled device microscopy.

BACKGROUND: Intraoperative assessment of intestinal viability following release of strangulation remains difficult. The aim of this study was to establish clinical standards for the evaluation of intestinal viability by charge-coupled device (CCD) microscopy. METHODS: A rat ileus model with strangulation for between 15 and 120 min was used. The images obtained by CCD microscopy were used to calculate maximum velocity (V (max)) ratio (ratio of V (max) of blood cell transition in the experimental segment to that in the reference segment) and S ratio (the ratio of S-the effective area of the vascular bed against the total area of the vascular bed-in the experimental segment to that in the reference segment). Rats were divided into group 1, comprising animals that survived for 7 days or more, and group 2, which consisted of animals that died within 4 days. RESULTS: V (max) ratio and S ratio in group 1 were both significantly higher than those in group 2 (P < 0.01). No death occurred at a V (max) ratio of 0.76 or higher and an S ratio of 0.61 or more, while there were no survivors with a V (max) ratio of 0.54 or less and an S ratio of 0.51 or less. CONCLUSION: V (max) ratio and S ratio could be used as indices for evaluation of intestinal viability.

Animals↗
PubMed2003

Telomerase, p53 and PCNA activity in osteosarcoma.

AIMS: The aim of this study was to investigate telomerase activity and to assess the correlation between telomerase activity, tumor proliferative activity and p53 overexpression in osteosarcoma tumor samples. METHODS: Using a telomerase polymerase chain reaction-enzyme-linked immunoassay based on the telomeric repeat amplification protocol method, we examined telomerase activity in 26 primary osteosarcoma specimens. P53 overexpression was identified using immunohistochemical staining, and tumor proliferative activity was assessed by immunohistochemical staining of PCNA. RESULTS: Telomerase activity was detected at a relatively low level in five of 26 osteosarcoma tissue specimens. P53 was detected in eight of 21 cases. There was no significant correlation between telomerase activity and p53 overexpression (p=0.325). There was a significant correlation between PCNA staining and telomerase activity (p=0.0075). CONCLUSION: Difference between the telomerase activity and p53 overexpression in osteosarcoma suggests that p53 and telomerase may not cooperate in tumor proliferation. Correlation of telomerase activity to PCNA expression suggests that telomerase activity may also useful for evaluate proliferative activity in osteosarcoma.

Adolescent↗
PubMed2003

Hepatocyte growth factor gene transfer into the liver via the portal vein using electroporation attenuates rat liver cirrhosis.

Although a variety of gene transfer methods to the liver have been designed, there are some problems such as the transfection efficiency and safety. In the present study, we developed a modified method of gene transfer into the liver by infusion of plasmid DNA via the portal vein followed by electroporation. After green fluorescence protein gene transfer, transgene expressions were detected in 24 h, and then maximally at 3 days, and persisted for 3 weeks. Histological analysis revealed that very mild tissue damage was induced in the liver to which electroporation was applied. In the second study, human hepatocyte growth factor (HGF) was more detected in the liver injected with 500 microg of human HGF gene than 100 microg of human HGF gene. However, serum HGF did not increase with 100 or 500 microg of human HGF gene. Moreover, 500 microg of HGF gene transfer into the liver by using this method could achieve the long survival of all dimethylnitrosamine-treated rats and attenuate the fibrous regions in the liver. These results suggest that HGF gene transfer into the liver via the portal vein using electroporation might be one of the useful methods for the treatment of various liver diseases.

Animals↗
PubMed2003

Pedicle bone grafting versus transtrochanteric rotational osteotomy for avascular necrosis of the femoral head.

Segmental collapse occurs in the early stage of avascular necrosis (AVN) of the femoral head, and is associated with a poor prognosis. Since it develops at a relatively young age, the long-term outcome after total hip replacement is a major concern. We have compared the long-term results of pedicle bone grafting (PBG) with those of transtrochanteric rotational osteotomy (TRO). In the PBG group there were 23 men (27 hips) and three women (4 hips) with a mean age at the time of surgery of 38 years and a mean follow-up of 13 years. In the TRO group there were 44 men (55 hips) and 19 women (22 hips) with a mean age at the time of surgery of 39 years and a mean follow-up of seven years. Failure was defined as a need for total hip replacement or a Harris hip score below 70. The long-term results were similar for the two groups. The survival rates at five and ten years were 85% and 67%, respectively, in the PBG group, and 71% and 61%, respectively, in the TRO group, according to Kaplan-Meier survivorship analysis. In the TRO group patients in stage II had significantly better results that those in stage III.

Adult↗
PubMed2002

Development and characterization of microsatellite markers for Cryptomeria japonica D.Don.

Thirty four microsatellite markers for Cryptomeria japonica D. Don were developed by searching three types of library: a database of C. japonica cDNA sequences, a standard non-enriched genomic DNA library and a microsatellite-enriched library using magnetic particles. The enrichment of microsatellite sequences using magnetic particles is very efficient compared to the other two methods both in terms of the numbers of markers generated, and in the polymorphism they detect. The microsatellites developed from the genomic DNA library generally have longer repeat sequences and are more polymorphic than those from cDNA. All the developed microsatellite markers in this study showed polymorphism among 28 plus trees selected from locations scattered throughout Japan. The mean number of alleles per locus (MNA) detected in the 28 plus trees ranged from 2 to 21 with an average of 7.5. The Polymorphism Information Content (PIC) ranged from 0.160 to 0.936 with an average of 0.666. Co-dominant segregation of alleles in a three-generation pedigree of C. japonica was demonstrated at 34 microsatellite loci, and the segregation was not distorted from Mendelian expectation for all loci. In 12 out of 34 loci, a null allele was detected. Key relationships between polymorphic parameters, such as MNA and PIC, and the characteristics of microsatellite sequences, such as the longest repeat number, total repeat number and total number of nucleotides, were investigated using rank correlation coefficients, Kendall's tau. A positive correlation was found between repeat lengths and polymorphisms. The markers provide sufficient resolution for investigating gene flow within forests and seed orchards, and for genome mapping.

Alleles↗
PubMed2002

Organochlorine and butyltin residues in deep-sea organisms collected from the western North Pacific, off-Tohoku, Japan.

Organochlorine (OCs) and butyltin (BTs) residues were determined in deep-sea organisms collected from the western North Pacific, off-Tohoku, Japan. Among OCs, concentrations of polychlorinated biphenyls (PCBs) and DDTs (DDTs and its metabolites) were the highest in deep-sea organisms (maximum concentrations of 6,700 and 13,000 ng/g lipid wt, respectively). Chlordane compounds (CHLs) were the next most abundant OCs, and hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the lowest. BTs were also detected at maximum concentrations of 570 ng/g wet wt. Concentrations of PCBs, CHLs and BTs in deep-sea organisms collected from the western North Pacific, off-Tohoku, were generally lower than those in deep-sea and shallow water organisms from Japanese coastal waters. On the other hand, considerable variations in the concentrations of OCs were found among deep-sea organisms analyzed. Several carnivorous fishes such as snubnosed eel, lanternshark and grenadiers accumulated some OCs such as PCBs, DDTs and CHLs at high concentrations of up to a few microg/g levels. In addition, the residue pattern of OCs and BTs in fishes showed a specific trend according to the sampling depth; higher concentrations of PCBs, DDTs and CHLs and lower concentrations of HCHs, HCB and BTs were found in fishes collected from greater depth (approximately 1,000 m) compared to those from shallower waters. This trend is consistent with the results of our earlier study on mesopelagic myctophid fishes. Results of this study suggest vertical transport of hydrophobic OCs such as PCBs, DDTs and CHLs and its accumulation in benthic deep-sea organisms.

Animals↗
PubMed2002

Effect of elastic compression stockings in patients with varicose veins and healthy controls measured by strain gauge plethysmography.

BACKGROUND/AIMS: Oedema is one of the most frequent signs of chronic venous insufficiency and may be present at all stages of this disorder. The aim of this study was to compare the effects of four different types of elastic compression stockings on oedema prevention in patients with varicose veins. METHODS: An increase in foot volume after elevation of the leg was evaluated by strain gauge plethysmography in 20 limbs with varicose veins and 14 normal limbs, and the effects of four different compression stockings--8, 14, 22 and 30-40 mmHg--were compared. RESULTS: All stockings significantly reduced the foot volume increase compared with the no stockings patient group and the normal group. There was no significant difference in the volume increase in the normal group for all four stockings, while there was a significantly smaller volume increase in the 22 mmHg stocking compared to the 14 mmHg stocking in the patient group. Between the 22 mmHg and 30-40 mmHg stockings or between the 14 mmHg and 8 mmHg stockings, there was no significant difference in the volume increase. CONCLUSION: Elastic stockings, even with a pressure as low as 8 mmHg, can prevent oedema in patients with varicose veins, as well as in normal controls. However, the 22 mmHg and 30-40 mmHg stockings were better at preventing foot oedema in patients with varicose veins than those exerting less compression.

Bandages↗