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Biomedical subjects

M Iizuka

Publications and source records attributed to M Iizuka.

At least 163 records · Page 9Linked to original sources
PubMed1992

Evidence for the existence of isozymes of glucose isomerase from Streptomyces phaeochromogenes.

Glucose isomerase from Streptomyces phaeochromogenes was purified from a commercial preparation, Swetase, by DEAE-cellulose, Bio-Gel A-0.5 m, and hydroxyapatite column chromatographies. It was found to be 2 fractions; F-A, not adsorbed on hydroxyapatite and F-B, adsorbed on hydroxyapatite. They were homogeneous in ordinary and SDS-PAGE and had similarities in some enzymatic and physico-chemical properties. The differences, however, were found in the N-terminal amino acid, which was only serine for F-A while it was serine and alanine for F-B, and also in their peptide mapping patterns of digests with trypsin, Achromobacter protease I, and cyanogen bromide. The results suggest that glucose isomerase from S. phaeochromogenes was composed of the two kinds of isozymes and that each of isozymes was a tetramer constituted of non-identical subunits.

Aldose-Ketose Isomerases↗
PubMed1992

Crohn's disease associated with diffuse lymphoid hyperplasia of the large intestine: a possible role of the lymph follicle in HLA-DR antigen expression on epithelium.

A 14-year-old girl diagnosed as Crohn's disease had lymphoid hyperplasia throughout the large bowel. Biopsy specimens from the lymphoid hyperplasia demonstrated non-caseous granulomas within the lymph follicles. An immuno-histochemical study of biopsy specimens showed that HLA-DR antigens were expressed on epithelium close to the lymph follicle, which was observed in all specimens containing the lymph follicle. This case provides evidence for the importance of the lymph follicle in the etiopathogenesis of Crohn's disease by demonstration of non-caseous granulomas within the lymph follicle and expression of HLA-DR antigens on epithelium close to the lymph follicle.

Adolescent↗
PubMed1992

[Estimation of pulmonary vascular permeability by indocyanine green in permeability pulmonary edema].

In this study we attempted to estimate pulmonary vascular permeability by indocyanine green (ICG). Permeability pulmonary edema was produced in 9 adult dogs by injecting 0.08 ml/kg oleic acid. We injected 50 mg ICG intravenously in 18 dogs (9 dogs with pulmonary edema and 9 control dogs). We measured the time course of ICG concentrations in pulmonary arterial blood, ICG concentration of peripheral lung tissue, tissue/serum ICG concentration ratios, and wet/dry lung weight ratios. The following results were obtained. The time course of ICG concentration in pulmonary arterial blood showed peak values at 2 minutes and became constant at 5 or 10 minutes after injection. The ICG concentration in peripheral lung tissue, tissue/serum ICG concentration ratios, and wet/dry lung weight ratios in the pulmonary edema group were significantly higher than those in the normal group. There was a strong linear correlation between wet/dry lung weight ratio and ICG concentration in peripheral lung tissue, with correlation coefficients of r = 0.936 (p < 0.01) in the right lung and r = 0.901 (p < 0.01) in the left lung. From these results, we conclude that estimation of pulmonary vascular permeability by ICG is a useful method.

Animals↗
PubMed1991

Response of newly established mouse myeloid leukemic cell lines to MC3T3-G2/PA6 preadipocytes and hematopoietic factors.

Some mouse myeloid leukemias induced by X-irradiation and serially transplanted into syngenic mice do not proliferate in vitro even in the presence of hematopoietic factors. To examine whether such leukemic cells can proliferate in response to stromal cells, we cocultured them with MC3T3-G2/PA6 (PA6) preadipocytes, cells that can support the growth of hematopoietic stem cells. All leukemias developed into in vitro cell lines, showing a dependence on contact with the PA6 cells. Two cell lines responded to none of the known hematopoietic factors including interleukin-3 (IL-3), IL-4, IL-5, IL-6, GM-CSF, G-CSF, M-CSF, and Epo. These results demonstrate that the mechanism of the action of PA6 cells is different from that of any of the known hematopoietic factors, and that, because these two leukemic cell lines retained the ability to grow in vivo, responsiveness to the known hematopoietic factors is not essential for the leukemic cell growth in vivo. Furthermore, all leukemic cell lines could respond also to the preadipocytes fixed with formalin, paraformaldehyde, or glutaraldehyde, suggesting that some molecule(s) associated with the surface of PA6 cells or with extracellular matrix secreted by the preadipocytes is responsible for the leukemic cell growth.

Adipose Tissue↗
PubMed1991

Convergence of one-dimensional diffusion processes to a jump process related to population genetics.

A conjecture on the convergence of diffusion models in population genetics to a simple Markov chain model is proved. The notion of bi-generalized diffusion processes and their limit theorems are used systematically to prove the conjecture. Three limits; strong selection-weak mutation limit, moderate selection-weak mutation limit, weak selection-weak mutation limit are considered for typical diffusion models in population genetics.

Genetics, Population↗
PubMed1991

Extended expression of liver functions of hepatocytes in collagen-contained cell aggregates (cell packs).

The functions of hepatocytes under the collagen-contained cell aggregate (cell pack) conditions were studied using liver-specific protein synthesis. Freshly isolated murine hepatocytes were suspended in the medium containing collagen and centrifuged, and the resultant cell masses were cultured on the porous membranes floating on the medium. In these cultures cells were attached to each other three-dimensionally with collagen present in the intercellular spaces. Cultured hepatocytes in the cell pack maintained high and stable activity in the expression of their functions for more than 2 weeks, even when cultured with the medium lacking any hormones and serum, whereas hepatocytes in monolayer cultures lost their functions within a week. Similarly, when the cell packs of rat hepatocytes were transplanted into rat spleens, they could retain viability in the form of cell aggregate with the expression of liver-specific albumin mRNA at a higher level than in the transplanted cell suspensions. The lifespan and the initial expression level of hepatocellular functions in culture were similar to that of the cell pack in cell aggregates without collagen and in cellular monolayers on the collagen gel respectively. It was concluded that the condition where cells are in contact with each other has an important role in the expression of hepatocellular functions and collagen present in the intercellular spaces enhances the functional levels.

Albumins↗
PubMed1991

Acute effect of percutaneous transluminal mitral commissurotomy on QT interval: possible role of afterload in contraction-excitation feedback.

Percutaneous balloon valvuloplasty for pulmonary or aortic stenosis results in QT prolongation, a finding supporting the presence of contraction-excitation feedback in man. Though afterload reduction alters the QT interval, the effect of changes in preload on ventricular repolarization is yet unknown. To test whether diastolic stretch modified ventricular repolarization, the change in the QT interval was determined in 15 patients who underwent percutaneous transluminal mitral commissurotomy (PTMC) for mitral stenosis. After successful PTMC, the QT interval was prolonged in five, shortened in two, and was unchanged in eight patients, but the mean QT interval in 15 patients did not change (406 +/- 31 msec versus 412 +/- 40 msec, p = NS). However, linear regression analysis revealed a strong correlation between changes in the QT interval and those in systemic vascular resistance (r = -0.83, p less than 0.01). These data indicated that changes in the QT interval after PTMC were small compared with those seen with valvuloplasty for pulmonary or aortic stenosis, and were dependent on afterload but not on preload.

Adult↗
PubMed1991

Effects of isoflurane and fentanyl on ischemic myocardium in dogs: assessment by end-systolic measurements.

The effect of anesthetics on ischemic myocardium to which blood was supplied by a stenotic coronary artery was investigated in dogs. The ischemia was assessed by regional wall motion (ultrasonic dimension technique) using fractional shortening (FS) [(EDL - ESL)/EDL x 100] and end-systolic pressure-segment length relationships (ESPLR). The latter is considered to be a more load-independent measure of regional myocardial function. Isoflurane and fentanyl were chosen as anesthetics of current interest. On reducing the left circumflex coronary artery (LCX) flow to approximately 50% of its resting value, a decrease in FS and a rightward shift in ESPLR were observed in myocardium perfused by the LCX. Simultaneously, increases in FS were observed in the nonischemic area perfused by the left anterior descending coronary artery (LAD), which was most likely due to the intraventricular unloading effect. No significant changes of ESPLR were observed in the area supplied by LAD. Isoflurane induced a dose-dependent decrease in FS and a rightward shift in ESPLR in the ischemic myocardial segment, whereas fentanyl caused an increase in FS and tended to shift ESPLR leftward in the same area. The results suggest that isoflurane may have deleterious effects on preexisting myocardial ischemia, whereas fentanyl may not when loading conditions are taken into consideration. Fractional shortening and ESPLR seem to provide similar information about regional myocardial function.

Anesthesia, Inhalation↗
PubMed1991

The coalescent process in models with selection, recombination and geographic subdivision.

A population genetic model with a single locus at which balancing selection acts and many linked loci at which neutral mutations can occur is analysed using the coalescent approach. The model incorporates geographic subdivision with migration, as well as mutation, recombination, and genetic drift of neutral variation. It is found that geographic subdivision can affect genetic variation even with high rates of migration, providing that selection is strong enough to maintain different allele frequencies at the selected locus. Published sequence data from the alcohol dehydrogenase locus of Drosophila melanogaster are found to fit the proposed model slightly better than a similar model without subdivision.

Alcohol Dehydrogenase↗
PubMed1991

Fixation probability in spatially changing environments.

The fixation probability of a mutant in a subdivided population with spatially varying environments is investigated using a finite island model. This probability is different from that in a panmictic population if selection is intermediate to strong and migration is weak. An approximation is used to compute the fixation probability when migration among subpopulations is very weak. By numerically solving the two-dimensional partial differential equation for the fixation probability in the two subpopulation case, the approximation was shown to give fairly accurate values. With this approximation, we show in the case of two subpopulations that the fixation probability in subdivided populations is greater than that in panmictic populations mostly. The increase is most pronounced when the mutant is selected for in one subpopulation and is selected against in the other subpopulation. Also it is shown that when there are two types of environments, further subdivision of subpopulations does not cause much change of the fixation probability in the no dominance case unless the product of the selection coefficient and the local population size is less than one. With dominance, the effect of subdivision becomes more complex.

Biological Evolution↗
PubMed1991

High-molecular-weight Ly-5 isoforms expressed on T cells: activation-dependent expression.

Interleukin 2 (IL-2)-dependent granular T lymphocyte (GTL) lines derived from murine spleen were shown to express a Ly-5 antigen with the so-called 'B220-epitope' recognized by 6B2 mAbs, which were normally exhibited on B-lineage cells. Immunoprecipitation analysis revealed that the Ly-5 isoform on GTL lines represented the highest-molecular-weight Ly-5 so far described (260 kd), distinct from the B220 isoform on a pre-B cell line (240 kd). The size difference between them was also evident after the endoglycosidase treatment (210 versus 190 kd), strongly suggesting that these Ly-5 isoforms had core proteins of distinct size. Sequential immunoprecipitation by 6B2 and 14.8 mAbs further indicated that the 260 kd Ly-5 on GTL lines predominantly expressed '6B2 epitope' while '14.8 epitope' dominated in the B220 (240 kd) on a pre-B cell line. Northern blot analysis of the Ly-5 transcripts using probes for the known alternative exons failed to show any evidence for mRNA of the 260 kd Ly-5 distinct from that of B220. Polymerase chain reaction analysis, however, suggested that the 260 kd isoform mRNA might be transcribed from a distinct promoter with a yet undefined exon(s). The 6B2+ Ly-5 isoform was hardly detected on normal splenic T cells, but was shown to be induced rapidly on the majority of T cells following IL-2 stimulation in vitro, indicating that this particular Ly-5 isoform behaved as an 'activation antigen' on T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Alpha-adrenoceptor-mediated inotropism and beta-adrenoceptor-mediated inotropism in isolated rabbit ventricles: a comparison in mechanical effects and energetic efficiency.

We assessed alpha-adrenoceptor-mediated inotropism in comparison with beta-adrenoceptor-mediated inotropism in whole left ventricle. We used an isolated perfused isovolumic rabbit heart preparation, which enables one to assess contractility and time course of contraction as well as energetic efficiency. Left ventricular pressure (LVP) and volume were measured with an intraventricular fluid-filled balloon. Myocardial oxygen consumption was assessed from the oxygen tension of coronary effluent. Both isoproterenol (n = 7) and phenylephrine (n = 7) increased LV developed pressure (LVDP). Isoproterenol shortened the time to peak pressure (Tmax) from 171 +/- 6 to 142 +/- 7 ms (p less than 0.01) and the time constant of LV pressure decay (TBF) from 44.8 +/- 2.7 to 32.8 +/- 1.9 ms (p less than 0.01). In contrast, phenylephrine slightly but significantly prolonged Tmax from 178 +/- 4 to 184 +/- 4 (p less than 0.05) and did not alter TBF. Both isoproterenol and phenylephrine increased O2 consumption, whereas only phenylephrine increased the force-time integral from 14.0 +/- 1.5 to 17.2 +/- 2.1 g.s (p less than 0.01). These results confirmed in the whole heart preparation that alpha- and beta-adrenoceptor-mediated inotropisms had qualitatively different effects on the time course of contraction and energetic efficiency.

Animals↗
PubMed1991

Generation of functional murine macrophage lines employing a helper-free and replication-defective SV40-retrovirus: cytokine-dependent growth.

By using a helper-free and replication-defective recombinant retrovirus encoding the SV40 early antigens (MV40), we have established continuous macrophage (M phi) lines. All of the lines were nonproducer M phi's with differentiated M phi functions such as phagocytosis, cytotoxicity, and IL-1 and TNF production. To determine the effects of several cytokines on growth of mature M phi's, the responsiveness of these established M phi lines to various cytokines was investigated in methylcellulose culture. Their response patterns to several cytokines alone and in combination were different, implying that there might be mature M phi subpopulations with distinct growth profiles regulated by several cytokines. On the other hand, all of the lines efficiently yielded a number of colonies in response to interleukin-4 (IL-4) alone. Moreover, IL-4 cooperated with interleukin-3 (IL-3) to enhance colony formation of all the lines. A similarly synergistic effect was observed in combination of IL-4 and macrophage-colony stimulating factor (M-CSF) in almost all the lines. Similar results were obtained with colony formation of fresh thioglycolate-induced M phi's. These observations suggested that IL-4 was involved in growth of mature M phi's. Our present results suggest that the helper-free and replication-defective MV40 is of use to obtain continuous and functional cell lines from primary M phi's.

Animals↗
PubMed1991

Effects of nifedipine on diastolic abnormalities in low-flow and pacing-induced ischemia in isolated rat hearts.

An animal experimental model which stimulates human effort angina, especially in terms of diastolic abnormalities, was developed using isovolumically beating perfused rat hearts. Using this model, we studied the effects of nifedipine, a Ca2+ channel blocker, on diastolic properties during pacing-induced ischemia. When the preload of the left ventricle was set at a low level, low-flow ischemia (coronary perfusion pressure of 40 mmHg) plus tachycardia (480 beats/min for 4 min) did not induce an increase in left ventricular end-diastolic pressure (LVEDP). However, with a high preload, low-flow ischemia plus pacing tachycardia induced an increase in LVEDP of 8.4 +/- 5.4 mmHg (p less than 0.01) and a prolongation of the time constant of ventricular pressure decline (6.8 +/- 4.6 msec, p less than 0.05) immediately after pacing tachycardia. Pretreatment with nifedipine (3 x 10(-8) M) prevented the rise in LVEDP induced by pacing tachycardia. Thus, in isolated perfused hearts, diastolic abnormalities similar to those seen in angina pectoris were obtained by low-flow ischemia plus pacing tachycardia. The response to nifedipine suggested that an alteration of Ca2+ movement may play an important role in the increase in left ventricular stiffness under these conditions.

Angina Pectoris↗
PubMed1991

Coenzyme Q10 attenuates the progression of cardiomyopathy in hamsters.

Coenzyme Q10 (10 mg/kg/day) or digoxin (2 micrograms/kg/day) was given orally to cardiomyopathic hamsters (BIO 14.6) for 8 weeks from 12 weeks of age. The left ventricular weight per gram of body weight (mg/g) was lower (p less than 0.01) in the coenzyme Q10 group (3.09 +/- 0.13) than in the digoxin (3.32 +/- 0.20) and control (3.44 +/- 0.14) groups. Left ventricular function was evaluated in isovolumically beating hearts. Left ventricular developed pressure (63 +/- 5 vs. 54 +/- 10 mmHg, p less than 0.05), -dP/dt (1385 +/- 100 vs. 1211 +/- 136 mmHg/sec, p less than 0.05), and -dP/dt (1068 +/- 126 vs. 896 +/- 141 mmHg/sec, p less than 0.05) were greater in the coenzyme Q10 than in the control group. The time constant of left ventricular relaxation was shorter in the coenzyme Q10 group than in the control group (25 +/- 3 vs. 28 +/- 3 msec, p less than 0.05). By contrast, in the digoxin group, the indices of left ventricular function did not differ from the control group. These results suggest that coenzyme Q10, but not digoxin, attenuated disease progression and preserved left ventricular function in cardiomyopathic hamsters.

Animals↗
PubMed1991

Myocardial contractility and contraction duration are unrelated in the left ventricle with moderate pressure-overload hypertrophy.

Both myocardial contractility and contraction duration were assessed load-independently in isolated hypertrophic and control rat hearts. Hemodynamic parameters for isolated isovolumically contracting hearts were compared for 7 Wistar rats with DOCA-salt induced hypertrophy (LVH) and 7 controls. Loads were altered by changing the volume of an intraventricular balloon. Myocardial contractility was assessed in terms of the shortening-afterload (Sm-sigma aft), and the ejection fraction-afterload (EF-sigma aft) relations at common preloads, based upon the systolic myocardial stiffness concept. Indices of contraction duration (time to maximum stiffness, pressure time integral divided by peak pressure and the time required for left ventricular (LV) peak pressure to be reduced by a half) were prolonged in LVH. Multiple regression analyses indicated that the degree of hypertrophy was an independent determinant of the contraction duration. The Sm-sigma aft and EF-sigma aft relations at common preloads demonstrated normal contractility in the LVH group. The time constant of the fall in LV pressure and the diastolic myocardial stiffness remained normal in the LVH group. Thus, we introduced the new approach to load-independently assess both the myocardial contractility and the contraction duration in a whole ventricle. A prolonged contraction duration in the presence of normal myocardial contractility was observed in a ventricle with moderate pressure-overload hypertrophy.

Animals↗