Biomedical subjects
Publications and source records attributed to M Akashi.
A dose reconstruction was carried out on a case in which a worker was exposed to soft x rays using time motion studies, an ionization chamber for low energy photon measurements, and CdZnTe (CZT) spectrometry. The worker estimated his dose to be over 600 mSv. However, the doses to the skin and testes were evaluated to be 14 and 0.44 mSv, respectively, with an effective dose of 0.099 mSv.
Pressure-driven and temperature-driven transitions of two thermoresponsive polymers, poly(N-isopropylacrylamide) (pNIPAM) and poly(N-vinylisobutyramide) (pNVIBA)), in both a soluble linear polymer form and a cross-linked hydro-gel form, were examined by a dynamic light-scattering method and direct microscopic observation, respectively. Their behavior was compared with that of protein systems. Changes in some characteristic parameters in the time-intensity correlation functions of dynamic light-scattering measurement of aqueous solutions of pNIPAM at various pressures and temperatures showed no essential differences during temperature and pressure scanning and, as a whole, the motions of polymers in aqueous solutions were similar in two types of transitions until chain shrinkage occurred. The gels (cross-linked polymer gels) prepared from the thermoresponsive polymers also showed similar volume transitions responding to the pressure and temperature increase. In temperature transitions, however, gels showed drastic volume shrinkage with loss of transparency, while pressure-induced transition showed a slow recovery of transparency while keeping the size, after first transient drastic volume shrinkage with loss of transparency. At a temperature slightly higher than the transition under atmospheric temperature, so-called reentry of the volume change and recovery of the transparency were observed during the pressure-increasing process, which implies much smaller aggregation or non-aggregated collapsed polymer chains in the gel at higher pressures, indicating a certain mechanistic difference of the dehydration processes induced by temperature and pressure.
We present a rare case of perineal-onset Fournier's gangrene in a patient undergoing hemodialysis. A 51-year-old Japanese man manifested an acute-onset perineal pain with perirectal abscess; subsequently, the pain extended to the abdomen, chest, and loin despite quick treatment. His consciousness deteriorated to delirium and he died of septic shock on the third day of admission. Computed tomography (CT) revealed soft-tissue air along the right rectal wall, moreover, the infection extended to the anterior wall of the bladder and the right peripsoas muscle. On the basis of the clinical course and CT findings, the patient was diagnosed as having the complications of Fournier's gangrene, however, no scrotal lesions were detected. Fournier's gangrene is considered to be easily diagnosed on the basis of skin lesions, such as scrotal erythema and swelling. However, in the early stage, the diagnosis of Fournier's gangrene is difficult in a patient with perineal pain before the detection of skin lesions. In conclusion, definitely the key to improving the prognosis of this fulminant infection is the prompt recognition of the pathological process. Therefore, Fournier's gangrene should always be considered when patients undergoing hemodialysis manifest perirectal disorders, even when no scrotal lesions are detected, because there is the possibility of intra-abdominal and intra-retroperitoneal infections resulting in septic shock.
Regrettably, a criticality accident occurred at a uranium conversion facility in Tokai-mura, Ibaraki, Japan, on 30 September 1999. Radioactivities of 32P in urine, blood and bone samples of the victims, who were severely exposed to neutrons, were measured. 32P was induced in their whole bodies at the moment of the first nuclear release by the reaction 31P (n, gamma) 32P and 32S (n, p) 32P. A realistic biokinetic model was assumed, as the exchange of 32P between the extracellular fluid compartment and the soft tissue compartment occurs only through the intracellular compartment, and the model was used for preliminary calculations. Some acute excretion of 32P, caused by decomposition or elution of tissues which occurred at the time of the accident, may have happened in the victims' bodies in the first few days. The working hypotheses in the present work should initiate renewed discussion of 32P biokinetics.
A nuclear criticality accident occurred in Japan on September 30, 1999, which resulted in severe exposure of three victims to mixed flux of neutrons and gamma-rays. Estimated average doses for the three victims were 5.4 Gy of neutrons and 8.5 Gy of gamma-rays for Patient A, 2.9 Gy of neutrons and 4.5 Gy of gamma-rays for Patient B, and 0.81 Gy of neutrons and 1.3 Gy of gamma-rays for Patient C. They then suffered the consequences of the effects of ionizing radiation resulting in acute radiation syndrome. In Patients A and B, bone marrow failure was so severe that they received haematopoietic stem cell transplantation. The graft initially took successfully in both patients, although in Patient B it was later taken over by his own haematopoietic cells. They also suffered from severe skin lesions, later exhibited gastrointestinal bleeding and eventually died of multiple organ failure 82 and 210 days after the accident, respectively. The survival of these patients beyond the period of agranulocytosis means that bone marrow failure per se caused by exposure to ionizing radiation may now be overcome. Patient C also developed bone marrow failure and was treated with granulocyte colony-stimulating factor as well as supportive care. He recovered without major complications and is now under periodical follow-up. Remarkably, during the prodromal phase, all the patients exhibited hypoxaemia, two of whom also showed interstitial oedema of the lungs. In Patient C these manifestations improved within a week. The circumstances of the accident and the initial medical treatment of the victims are described.
Predispositions to essential hypertension and cardiovascular diseases are possibly associated with gene polymorphisms of the renin-angiotensin system. Gene polymorphisms of angiotensinogen and angiotensin-converting enzyme genes have been suggested to be risk factors for hypertension and myocardial infarction. Concerning the polymorphism of aldosterone synthase (CYP11B2) gene, earlier studies have shown inconsistent results in terms of its relation to hypertension. In the present case-control study, we investigated the association of -344T/C polymorphism in the promoter region of human CYP11B2 gene with genetic predisposition to hypertension. The genotype of -344T/C polymorphism was determined in essential hypertension subjects (n=250) and normotensive subjects (n=221). The distributions of three genotypes (TT, TC, and CC) were significantly different between the hypertensive and the normotensive groups (chi(2)=9.61, P=0.008). Namely, the frequency of C allele was higher in the hypertensive patients than in the normotensive subjects (34.2 vs 26.5%, P=0.010). Our data suggest that the -344C allele of CYP11B2 gene polymorphism is associated with the genetic predisposition to develop essential hypertension.
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Novel thermo-responsive inorganic-organic hybrid gels were prepared by hybridizing porous silica and poly(N-isopropylacrylamide) gels (PNIPAAm gel). The internal pores of the silica were filled with PNIPAAm gel to give a thermo-responsive drug reservoir. Brilliant blue FCF (BB) was also added to the hybrid gels for release. The BB release rate was faster above the lower critical solution temperature (LCST) of the PNIPAAm gel than below the LCST. When the temperature changed across the LCST, reversible and thermo-responsive release behavior was observed. The transition of the release behavior upon changing the temperature was similar to the behavior of the PNIPAAm gel itself. The BB release rate can be controlled simply by changing the amount of PNIPAAm gel loaded into the silica.
The development of a dosage form that improves the absorption of peptide and protein drugs via the gastrointestinal tract is one of the greatest challenges in the pharmaceutical field. Many researchers have taken up the challenge, using approaches including mucoadhesive drug delivery, colon delivery, particulate drug delivery such as nanoparticles, microcapsules, liposomes, emulsions, micelles, and so on. The objective of this article is to provide the reader with outlines of novel nanoparticle technologies for oral peptide delivery based on polymer chemistry. The physicochemical properties of nanoparticles and their behavior on exposure to physiological media are greatly dominated by their chemical structures and surface characteristics. We will especially focus on the design of nanoparticles composed of novel graft copolymers having a hydrophobic backbone and hydrophilic branches as drug carriers.
Previously, we developed a novel alternate soaking process and clarified that bone-like apatite was formed on/in organic polymer hydrogel matrices using this process. The present study focused on the apatite coating on hydrophilic polymer grafted poly(ethylene) (PE) films with various grafting densities and commonly used hydrophilic polymers, poly(acryl amide) (PAAm) and poly(acrylic acid) (PAAc) were employed. From X-ray diffraction analysis, hydroxyapatite was coated on PAAm- or PAAc- grafted PE films. The amount of apatite coated on PAAm-grafted PE (PAAm-g-PE) films increased with an increase in the reaction cycles and the grafting density of PAAm. Similar to PAAm-g-PE, the amount of apatite coated on PAAc-grafted PE (PAAc-g-PE) films increased linearly with an increase in the grafting density of the PAAc up to around 30 microg/cm2. While, no significant increase in the apatite coating on the PAAc-g-PE films was observed even after 50 reaction cycles when the grafting densities of PAAc were over 30 microg/cm2. Apatite coating was not observed on original PE films. Scanning electron microscopic images reveal that the aggregation of apatite crystals on all PAAm-g-PE films and PAAc-g-PE films with grafting density from 10 to 30 microg/cm2. On the other hand, a dense apatite layer with some cracks was coated when the grafting density of the PAAc chains was over 30 microg/cm2. These results indicated that it was possible to coat apatite on hydrophilic polymer grafted PE films by an alternate soaking process and that the apatite crystal morphology could be controlled as a function of polymer type and density.
In order to interpret how cells recognize biomaterials, nucleic factor-kappa B (NF-kappaB) activation in the attached HeLa S3 cells on various substrates was evaluated. As substrates, materials of hydrophilic nature (cellulose, poly(acrylamide)-grafted poly(ethylene) (PAAm-g-PE), and lipids films) were used. The contemporary assay method for NF-kappaB was modified to fit our system. As a result, NF-kappaB activation varied depending on the substrates. The NF-kappaB outcome was induced significantly in the HeLa S3 cells that had adhered onto the lipid films in a short time. On the other hand, high levels of NF-kappaB induction were observed in the HeLa cells adhered to the celluose and PAAm-g-PE after a 24 h incubation period. The induction of NF-kappaB by cell-material interaction is discussed from the point of view of biocompatibility.
Polymeric nanospheres with a polystyrene core and a glucosyloxyethyl methacrylate (GEMA) oligomer corona were synthesized by the free radical coplymerization of styrene (M(1)) plus a GEMA macromonomer (M(2)) at various molar ratios (M(1)/M(2) = 50-150) in the presence of AIBN (1 mol % to the total monomer) in an ethanol/water (3/2, v/v) solvent. The size of the nanospheres was controlled from 300 to 620 nm by altering the monomer ratio. The size distributions were significantly narrow. The amount of glucose conjugated per unit surface area of the nanosphere, which was analyzed by the anthron-sulfuric acid method, was 1.01-2.28 microg cm(-1), which increased with an increase in size. The transmittance of a solution of dispersed nanospheres (the corresponding glucose concentration was 73 microM) increased by the addition of the glucose-binding protein concanavalin A (Con A) (1-50 microM), indicating that the nanospheres were being precipitated by the cross-linking of ConA. An enzyme-linked lectin assay (ELLA) revealed that Con A bound to the glucose on the nanospheres 250-700-fold more than to monomeric glucose. The binding activity to the nanospheres was less than that to a GEMA oligomer, and decreased with an increase in the amount of GEMA oligomer grafted onto the nanosphere, possibly because of steric hindrance of the lectin binding to the glucose on the nanospheres. The polystyrene core-glycopolymer corona nanosphere is a useful material for studying sugar-biomolecule recognition.
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gamma-Ray irradiation of chitosan flakes and introduction of hydrophobic chains onto hydroxyl groups are discussed. At 25 kGy, chain degradation without cross-linking reduces the molecular weight to one-fourth; however, structural characterization by FT-IR, 1H NMR, and 13C CP/MAS NMR indicates that the saccharide units are maintained. Introduction of hydrophobic chains is accomplished by introduction of alkylamine groups onto the chitosan carbonyl imidazole precursor. The chitosan coupling reaction is improved and can be done homogeneously as a result of gamma-ray irradiation. The optimum conditions for phthalimido group deprotection are studied to generate a unique product with a hydrophobic chain attached mainly at the hydroxyl group (C-6 and/or C-3) while the amino group (C-2) is retained as characterized by FT-IR and 1H NMR. The final product shows fair solubility in organic solvents, such as DMSO, DMAc, DMF, and pyridine.
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This case report describes the medical follow-up of a 46-y-old (at the time of exposure) man who in 1971 accidentally exposed the fingers of his right hand to gamma-ray radiation from an iridium source that was used for nondestructive testing [estimated radiation dose: 26 Gy to 90 Gy (2,600 rad to 9,000 rad)]. No prominent acute injury was detected except for leukocytopenia (800 mm(-3)) and thrombocytopenia (15,000 mm(-3)). Three years later, the first, second, and third fingers presented repeated infection and started to develop contracture. Twenty-two years after exposure, he underwent amputation of the first and second fingers, and a toe graft was done. Radiological examinations prior to and following the operation revealed atrophic change of the finger bones and arterial injuries. Angiographic findings coincided with the region and extent of radiation injury of the fingers, which indicates that arterial damage is involved in the development of this chronic disorder.
L929 cell adhesion on various lipid films prepared by Langmuir-Blodgett methods (LB method) were studied. L929 cells adhered to every lipid film similar to tissue culture poly(styrene) (TCPS). The mRNA expression of both collagen and HSP47 in adherent cells were evaluated by the RT-PCR method. mRNA expression of collagen was not altered during adhesion and proliferation duration, while HSP47 mRNA expression changed depending on culture time. L929 cells adhered to L-alpha-dipalmitoylphosphatidylcholine (DPPC)-films showed little HSP47 mRNA expression. It was suggested that DPPC films regulate L929 cell function via unique serum protein adsorption.
A poly(vinyl alcohol) (PVA)-coating on polyethylene films, prepared by repetitive adsorption/drying in an aqueous PVA solution, accelerated hydroxyapatite (HAp) deposition by an altemate soaking in aqueous solutions containing Ca2+ and PO4(3-) ions. X-ray photoelectron spectra of the surface of the HAp-deposited film showed the presence of calcium and phosphorus of a suitable peak ratio for HAp formation. X-ray diffraction analyses also revealed peaks corresponding to HAp. Scanning electron microscopic observation showed the surface of the HAp layer to be smooth, with nano-ordered dotted threads in networks. A simple PVA coating on a surface will serve as a novel system for accelerated HAp formation via alternating soaking.