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Biomedical subjects

H Kon

Publications and source records attributed to H Kon.

At least 73 records · Page 4Linked to original sources
PubMed1981

Use of spin label and the flow-induced ESR spectral difference for studying erythrocyte deformation.

ESR spin-labeling method is expanded to measure the macroscopic visco-elastic properties of erythrocytes. A suspension of erythrocytes with an incorporated fatty acid spin label was forced to flow through a flat ESR sample cells, and the ESR spectral change caused by the shear flow was utilized to assess the cell deformability. Chemical cross-linking or heat denaturation of membrane proteins to make the cells less deformable without any morphological change was found to reduce the relative spectral difference (delta h/h). This result indicates that the spectral difference is related to the cell deformation that accompanies the orientation of the cells in the shear flow. In addition, the average decay time (tau av) for the spectral difference observed when the flow was abruptly interrupted became shorter with an increase in the degree of cross-linking or heat-denaturation abruptly interrupted became shorter with an increase in the degree of cross-linking or heat-denaturation at 49 degrees C. Since the observed tau av is much shorter than the expected rotational correlation time for the erythrocyte, the decay is attributed to the deformation recovery process. It is demonstrated that the measurements of both delta h/h and tau av by ESR spectroscopy give qualitative information on the viscosity and the elasticity of the cell membrane system.

Blood Viscosity↗
PubMed1981

Spin label study of erythrocyte deformability I. Electron spin resonance spectral change under shear flow.

A spin labeling method in electron spin resonance spectroscopy (ESR) is applied for the first time to study the deformability of human red blood cells (RBC). ESR measurements of a RBC suspension incubated with a fatty acid spin label were performed, using a narrow-gap flat ESR sample cell under various flow shear stresses (tau). Remarkable changes were observed in ESR spectra with tau, indicating that RBC are oriented in such a way that the greater part of the membrane surface is aligned parallel to the ESR cell walls. The diamide-treated, hardened RBC, in which the biconcave discoid shape remains intact under no shear stress, exhibit a smaller ESR spectral change with tau than the intact, demonstrating that the present method can be used to assess the deformation of RBC occurring with flow orientation. In particular, the relative amplitude of an ESR difference spectrum may be used as a measure of the elongation of RBC. The conclusion is further supported by experiments using glutaraldehyde-treated or heat-denatured RBC. All these ESR results are in good agreement with the corresponding results obtained by several different methods. The present spin labeling technique is thus proven to be applicable for evaluating RBC deformability.

Electron Spin Resonance Spectroscopy↗
PubMed1981

[Clinical experience of therapeutic use of cefmetazole (cefmetazon) or bronchopneumonia (author's transl)].

1. Therapeutic effects of cefmetazole (cefmetazon, CMZ) were examined in 22 cases of bronchopneumonia. 2. Among the 22 cases, 17 cases (77%) showed better response than 'effective'. However, 10 cases (91%) showed better response than 'effective' if a daily of 4 g (11 cases) was taken into consideration. 3. No particular symptomatic side effect of CMZ was shown. Abnormality in such laboratory tests as transaminase (1 case of GOT, and 2 cases of GPT) and 1 case of alkaline phosphatase were observed, and the abnormality was ascribable to CMZ administration.

Adult↗
PubMed1981

[A study on the mechanical properties of bone cement (methylmethacrylate) and its strength alteration in vivo (author's transl)].

UNLABELLED: Bone cement (Methylmethacrylate) is now extensively used for the fixation of various endoprostheses in orthopaedic surgery. Although considerable number of works have been accumulated on the use of this material, relatively little is known about its basic characteristics such as inherent physical properties and the strength alteration in vivo. In recent years, loosening of the prosthesis has become one of the major problems, jeopardizing the use of the prosthesis in conjunction with the bone cement. The aim of this study is to investigate the mechanical properties of the commonly available bone cements and, particularly, to see any chronological deterioration of the material in vivo. METHODS: 1. For the study of the mechanical properties, dumbbell-shaped test pieces were made of three different types of commercially available bone cement (Surgical Simplex, CMW and Palacos R) and tested under tension load using Shimazu Autograph in a temperature and moisture controlled room (Experiment I). 2. The same test pieces (Surgical Simplex and CMW) were imbedded in the paravertebral muscle of rabbits for one, six and sixteen months and, then, tested in the same fashion as in Experiment I (Experiment II). 3. The fracture surface of the test piece after the tension load testing was examined under a scanning electron-microscope to find any changes before and after the imbedding (Experiment III). RESULTS: 1. The bone cement showed a viscoelastic behavior under the tension load in vitro. 2. The modulus of elasticity was the smallest in Palacos R which showed the greatest amount of viscoelastic deformation in vitro. 3. The longer was the imbedded period, the weaker was the tensile strength. The amount of viscoelastic deformation tended to decrease with time, which resulted in the decrease of the total amount of deformation. The modulus of elasticity was the smallest in the sixteen week group in both Surgical Simplex and CMW. 4. The scanning electromicroscopic studies failed to reveal any significant changes on the fracture surface after the imbedding. CONCLUSION: In view of this considerable strength alteration of the bone cement in vivo, the author considers this would be an important factor leading the prosthesis into loosening other than the hitherto proposed various factors such as chemical damage of the bone by the monomer, thermal bone necrosis by the polymerization heat and fatigue fracture of the bone adjacent to the bone cement. While the improved technique in the use of the bone cement is mandatory, the author stressed the importance of further research into the better material or method for the interface between the bone and the prosthesis.

Animals↗
PubMed1980

EPR study of dimerization and conformational change of Cu(II)-cytochrome c and its undeca- and octapeptide.

The EPR study of cytochrome c in which FE(III) ion is replaced with Cu(II) shows that there are two types of monomer (a: 4 less than pH less than 6, and b: 6 less than pH less than 11.5) and two types of dimer (A: pH less than 4 and B: pH less than 11.5) formed depending upon the pH value of the solution. Computer simulation of the EPR spectra of the dimers indicates that the structure of the dimer A has a larger lateral shift than in the dimer B. It is also shown that in monomer a, the imidazole nitrogen of 18-His is not bound to Cu(II), while it is bound in the monomer b. In the undeca- and octapeptide of Cu(II)-cytochrome c, polymers are formed in acidic solutions. As the pH is raised, depolymerization proceeds to yield the monomer and the dimer. The structure of the dimer in both peptides is found to be similar to that of the dimer B of Cu(II)-cytochrome c. In the monomer of the peptides, neither the imidazole of 18-His nor the imidazole added in excess is bound to Cu(II) in the entire pH range. It is also concluded that the dimerization in Cu(II)-porphyrins interferes with the apical coordination of basic ligand, or vice versa.

Chemical Phenomena↗
PubMed1979

NADPH cytochrome P-450 reductase activation of quinone anticancer agents to free radicals.

With NADPH as the electron donor, rat liver NADPH cytochrome P-450 reductase (NADPH:ferricytochrome oxidoreductase, EC 1.6.2.4) catalyzes the single-electron reduction of several quinone antibiotics to a semiquinone or free radical state. The benzanthraquinones adriamycin, daunorubicin, carminomycin, 7-O-methylnogalarol, and aclacinomycin A and the N-heterocyclic quinones streptonigrin and mitomycin C are activated to free radical intermediates which can transfer their single electron to molecular oxygen to form superoxide. The overall Km range for this electron transfer is 0.4 to 42.1 X 10(-4) M. We postulate that the formation of the "site-specific free radical/ intermediate is central to the cytotoxic action of these antibiotics.

Animals↗
PubMed1977

Comparative EPR study on high-spin ferric porphine complexes and cytochrome P-450 having rhombic character.

Comparative EPR studies were made on two high-spin Fe(III) porphine model systems and mammalian liver microsomal cytochromes P-450, all of which exhibit approximately the same degrees of rhombicity in their EPR spectra. Comparison of g values and linewidths as a function of temperature, and of the microwave power saturation demonstrated that EPR characteristics of P-450 are more similar to the Fe(III) porphines having the thiolate axial ligand than in the other model systems, the mixed crystals of Fe(III) porphine with the corresponding free base porphine, in which no thiolate ligand is involved. There is, however, a discrepancy between P-450 and the model thiolates with respect to the size of the zero-field parameter D. These observations indicate that P-450 heme has essential structural features in common with thiolates but the Fe-S bond of P-450 may be modified from its normal orientation in model thiolates, probably as a result of the constraints imposed by the protein structure.

Animals↗
PubMed1976

Does Freund's adjuvant denature protein antigens? EPR studies of emulsified hemoglobin.

Use of complete Freund's adjuvant for production of antibodies to study protein conformation is valid only if emulsification in adjuvant does not denature protein antigens. Using electron paramagnetic resonance to observe directly the protein in situ in the opaque emulsions, we demonstrate that hemoglobin is not denatured by emulsification or storage in adjuvant for 24 hr at 4 degrees C, conditions comparable to the usual handling of antigens before immunization.

Antigens↗