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Biomedical subjects

H Maezawa

Publications and source records attributed to H Maezawa.

At least 19 recordsLinked to original sources
PubMed1992

Radiosensitivity of mouse skin epithelial cell line established in serum-free culture: an alternative to animal use.

A cultured line of murine skin epithelial cells was established to investigate the potential use of cultured cells as an alternative to animal use in radiation research. C3Hf/Sed newborn mouse skin cells have been successfully cultured in serum- and Ca(2+)-free medium with no terminal differentiation to keratinized cells. Presently, more than 25 passages have passed with no loss of stem cell capability. The radiosensitivity and repair of sublethal and potentially lethal radiation damages were investigated in this epithelial cell line. The population cell doubling time was 25 +/- 2.9 hr at 37 degrees C. The clonal growth of epithelial cells after irradiation was performed in the serum-free medium in the presence of lethally irradiated skin fibroblasts. Single dose survival curves of exponentially growing epithelial cells were investigated from the seventh to the twenty-third passages, and no significant changes in radiosensitivity and doubling time were found. The confluent epithelial cells also showed an identical sensitivity to radiation. The alpha/beta ratios of survival curves fitted by the linear quadratic model were 6.1 +/- 1.0 and 5.9 +/- 1.3 Gy for cells in exponential and confluent phases, respectively. The survival curve of epithelial cells left in confluence for 8 hr after irradiation showed a smaller beta value than that of cells plated immediately after irradiation with a resultant alpha/beta ratio of 9.5 +/- 3.8 Gy. This alpha/beta ratio was identical to those found in many animal experiments, suggesting a potential use of this cell line as an alternative to animal use. The magnitude of repair of sublethal damage following 6 Gy was greater than that following 3.9 Gy. Survival curves were also obtained following twice-a-day irradiations with no sign of rapid repopulation. These results are discussed by comparing with published in vivo and in vitro data.

Animal Testing Alternatives↗
PubMed1992

Iron(II) sulphate (Fricke solution) oxidation yields for 8.9 and 13.6 keV X-rays from synchrotron radiation.

The oxidation yields (G) for 8.86 and 13.55 keV X-rays produced by synchrotron radiation were measured using an iron(II) sulphate (Fricke) solution. Monoenergetic X-rays were produced using a silicon crystal monochromator. The X-rays were absorbed in 0.4 M sulphuric acid-iron(II) sulphate solution and FeIII ion yields were measured and corrected for escape fractions resulting from scattering using Monte Carlo calculations. Doses in the solution were determined using a thin window, parallel plate chamber calibrated against a primary standard free-air chamber at the Electrotechnical Laboratory (Osaka, Japan). Yields (G) of 1.50 +/- 0.06 and 1.43 +/- 0.06 mumol J-1 were obtained for 8.86 and 13.55 keV X-rays respectively.

Oxidation-Reduction↗
PubMed1992

Ca(2+)-activated K+ channel is present in guinea-pig but lacking in rat hepatocytes.

The mechanisms of norepinephrine-induced membrane responses in isolated hepatocytes from guinea-pigs and rats were compared using the suction-pipette, patch-clamp method, and intracellular Ca2+ concentration ([Ca2+]i) was measured using the Ca2+ fluorescent dye, Quin 2. The resting membrane potentials of isolated guinea-pig hepatocytes were -50 +/- 1 mV (mean +/- SD; n = 38), which is similar to that previously reported in rat hepatocytes by Sawanobori et al. (J Cell Physiol 139: 580-585, 1989). In guinea-pig hepatocytes, norepinephrine (6 microM) caused a membrane hyperpolarization, and norepinephrine (6 microM) or Ca(2+)-ionophore (A23187) (0.4 microM) caused a corresponding outward current. The sensitive current produced by norepinephrine and Ca(2+)-ionophore reversed its polarity at -74 +/- 9 mV (n = 7). The single channel recorded by cell-attached patch and inside-out patch had mean conductance of around 20 + 1 pS and was activated by 1 microM [Ca2+]i. On the other hand, neither norepinephrine (6-20 microM) nor Ca(2+)-ionophore (A 23187) (0.4 microM) caused any change in membrane potential and current in rat hepatocytes, whereas norepinephrine increased [Ca2+]i both in rat and guinea-pig hepatocytes to a similar degree. In the single-channel recording, we recorded single channels that had a mean conductance of 109.8 +/- 17.7 pS different from around 20 pS in guinea-pig. In inside-out patches, increased Ca2+ concentration from 10(-6) to 10(-3) M at the intracellular face of the membrane did not modify the single channel of rat hepatocytes. These results indicate that increased [Ca2+]i activates this channel in guinea-pigs, but that the channel activated by increased [Ca2+]i is lacking in rat hepatocytes membrane. Therefore, different mechanism operates in different species of liver cells to keep the constant state.

Animals↗
PubMed1991

Thallium-201 stress scintigraphy in Takayasu arteritis.

Thirty-eight women with Takayasu arteritis were studied using thallium-201 stress myocardial scintigraphy to assess the prevalence and pathophysiology of the perfusion abnormality. Twenty (53%) had abnormal scintigraphic findings (group A). Abnormal scans were divided into 3 groups: permanent defects in 6, reversible defects in 7 and slow washout in 7. The remaining 18 patients had normal scintigrams (group N). Group A had a tendency to be older and to have a high prevalence of complicated significant aortic regurgitation. Interventricular thickness plus left ventricular posterior wall thickness (26 +/- 7 vs 17 +/- 2 mm, p less than 0.01) and left ventricular mass (267 +/- 121 vs 133 +/- 39 g, p less than 0.01) were all greater in group A on echocardiography. The mean value of the central aortic pressure in systole was 170 +/- 15 mm Hg in the 7 catheterized patients in group A. Coronary ostial stenoses were present in 2 group A patients who showed reversible defects on scintigrams. These data indicate that the abnormal perfusion detected by imaging in patients with Takayasu arteritis was responsible for a decrease in coronary reserve or myocardial damage, or both, due to long-standing systemic hypertension or aortic regurgitation. Coronary artery disease should be considered if a reversible defect is present.

Adult↗
PubMed1991

Organic anion transport study in mutant rats with autosomal recessive conjugated hyperbilirubinemia.

The EHBR is a mutant rat strain with congenital conjugated hyperbilirubinemia bred from a Sprague-Dawley rat. Transport of conjugated bilirubin, indocyanine green, and tetrabromosulfophtalein from liver to bile is severely impaired in these rats. Serum bilirubin amounts to 6.0 +/- 0.05 mg/dl (n = 4) in adult rats, with 97% conjugates. The bile flow is reduced to about 65% of the control group, whereas total bile acid in 10-min bile samples is similar. Liver histology of 10 week-old rats revealed neither intracellular pigmentation nor architectural abnormalities.

Animals↗
PubMed1991

Serum ketone response to glucagon as a marker of insulin dependency in diabetics.

The serum ketone response to glucagon was measured in 10 patients with IDDM and 37 with NIDDM. In both groups, serum 3-hydroxybutyrate increased significantly after intravenous injection of 1 mg glucagon. The difference between the serum level of 3-hydroxybutyrate at 30 min and basal level [delta 3-OHBA(30')] was 133 +/- 25 mumol/l in the patients with IDDM, 13 +/- 8 mumol/l in those with NIDDM treated by diet alone or with oral hypoglycemic agents and 23 +/- 13 mumol/l in those with NIDDM treated with insulin. The delta 3-OHBA(30') was significantly greater in IDDM patients than in both groups of NIDDM patients (P less than 0.001). The delta 3-OHBA(30') was greater than 87 mumol/l in eighty percent of IDDM patients, but smaller than 87 mumol/l in both groups of NIDDM patients. The delta 3-OHBA(30') was correlated with the difference between the plasma level of C-peptide at 6 min and basal level [delta CPR(6')] (r = -0.540, P less than 0.001). The delta 3-OHBA(30') was not correlated with fasting plasma levels of glucose, fructosamine or hemoglobin A1c. These observations show that measurement of the serum ketone response to glucagon is a useful marker of insulin dependency. In order to determine insulin dependency, the simultaneous measurement of concentrations of ketones and C-peptide is indicated during the glucagon stimulation test.

3-Hydroxybutyric Acid↗
PubMed1991

Effects of K-shell X-ray absorption of intracellular phosphorus on yeast cells.

The effects of K-shell absorption of phosphorus atoms on yeast cells were investigated using synchrotron X-rays that were tuned to the resonance absorption peak (2153 eV). Three types of cellular effect (cell inactivation, induction of gene conversion at the trp-5 locus, and cell membrane impairment (changes in the permeability] were measured. It was demonstrated that the enhancement factor was 1.4 at the resonance peak regarding both lethality and the induction of gene conversion in reference of off-peak irradiation (2146 and 2160 eV). No difference was found between the two off-peak irradiation energies. No cell membrane impairment was detected, irrespective of the X-ray photon energies employed within the fluence range tested. These results strongly suggest that K-shell X-ray absorption in the resonance mode by cellular phosphorus atoms causes significantly more cellular effects than the off-resonance mode of absorption, probably via some specific changes induced in the phosphates of the DNA strand. Calculations using the number of phosphorus atoms in a defined size of the trp locus (2127 base pairs) on the DNA and the absorption cross-section of the resonance mode of phosphorus showed that gene conversion is inducible at a rate of 0.13 per X-ray photon absorption per locus. These results are discussed regarding the modes of K-shell photoabsorption.

Absorption↗
PubMed1991

Biological effects of Auger processes of bromine on yeast cells induced by monochromatic synchrotron X-rays.

The biological effects of inner-shell ionization in bromine atoms incorporated into DNA in the form of bromodeoxyuridine monophosphate (BrdUMP), induced by monochromatized synchrotron X-rays, were studied using a deoxythymidine monophosphate (dTMP)-permeable mutant of yeast, Saccharomyces cerevisiae. The BrdUMP-incorporated yeast cells were irradiated with monochromatic X-rays of 13.51 or 13.45 keV, between which the bromine K-absorption edge (13.47 keV) is located. The cells were 1.07 times more sensitive to irradiation by 13.51 keV X-rays than at 13.45 keV, while dTMP-incorporated cells did not show any difference in sensitivity. In the presence of a radioprotector during irradiation, BrdUMP-incorporated cells showed a larger enhancement (1.20). These enhancements observed in the bromine-incorporated cells cannot be explained only by an increase of the absorbed dose due to a substitution of CH3 group of thymine by bromine. It may be concluded that a major part of the enhancement was caused by inner-shell photoionization, followed by an Auger cascade of the bromine in the DNA. The quantum yield of lethality caused by the photoabsorption of bromine K-shell is not affected by the presence of cysteamine, suggesting the biological enhancement by the Auger processes may not be influenced by chemical protection.

Bromodeoxyuridine↗
PubMed1991

Enhanced killing effect on 5-bromodeoxyuridine labelled bacteriophage T1 by monoenergetic synchrotron X-ray at the energy of bromine K-shell absorption edge.

5-Bromo-2'-deoxyuridine labelled bacteriophage T1 was irradiated with monoenergetic X-rays obtained from synchroton radiation with the energies at 13.51 keV and 12.40 keV, just above and below the K-shell absorption edge (13.41 keV) of bromine, respectively. Phage samples were irradiated under three conditions, wet N2 gas, dry N2 gas and in vacuum, with water contents (g H2O/g sample) of 60, 2.6 and 0%. At 12.40 keV the D0 in kGy were 1.1 ("wet"), 1.9 ("dry") and 2.5 ("vacuum") for the Br-labelled phages and 1.6 ("wet"), 2.4 ("dry") and 6.2 ("vacuum") for unlabelled phages. The results clearly demonstrated that the X-ray sensitivities decreased with decrease in water contents. Br-enhancement ratios, ER = D0 (unlabelled)/D0 (Br-labelled), varied from 1.4 ("wet", 12.40 keV) to 2.5 ("vacuum", 13.51 keV). Auger enhancements which were defined by energy-dependent enhancement factor, Fen = [ER(13.51 keV)-ER(12.40 keV)]/ER(12.40 keV), were 0.09 +/- 0.09, 0.29 +/- 0.07 and 0.02 +/- 0.03 under "wet", "dry" and "vacuum" conditions, respectively. The change in Auger enhancement under "dry" condition in comparison with "wet" condition could be explained due to less of water. However the Auger enhancement decreased sharply under "vacuum" condition as the water content was zero. The reason for the sharp decrease in Auger enhancement under "vacuum" condition is difficult to understand. A possible explanation is discussed in the text.

Bromodeoxyuridine↗
PubMed1991

Increased thrombomodulin values in plasma of diabetic men with microangiopathy.

To study the significance of plasma thrombomodulin (TM) values in diabetes mellitus, we determined plasma TM in 34 patients with non-insulin-dependent diabetes mellitus (NIDDM) men, mean age 54 (SE 2) years. Plasma TM was determined by an enzyme immunoassay with anti-TM monoclonal antibodies. The plasma TM values were significantly greater in NIDDM patients with nephropathy than in patients without nephropathy (P less than 0.001). Also, a significant positive correlation was noted between the concentration of plasma TM and serum creatinine (r = 0.55, P less than 0.001). The plasma TM values of the patients with retinopathy were significantly greater than the values of those without it (P less than 0.002). Furthermore, we noted a significant positive correlation (r = 0.78, P less than 0.001) between plasma TM and the severity of diabetic retinopathy as graded by Scott's classification. These results suggest a close relationship between TM and diabetic microangiopathy.

Adult↗
PubMed1991

Study on cholesteryl ester transfer activity in coronary heart disease.

The net cholesterol transfer activity from high density lipoprotein (HDL) to low density lipoprotein (LDL) was determined in the patients with coronary heart disease (CHD) to examine its effect on the pathogenesis of arteriosclerosis. Furthermore, in the CHD patients with high HDL cholesterolemia (more than 60 mg/dl), the HDL particle size was measured by high performance liquid chromatography. A significant cholesteryl ester transfer activity (P less than 0.02) was noted in the CHD patients with low HDL cholesterolemia (less than 60 mg/dl). The rate of cholesteryl ester transfer activity (cholesteryl ester transfer activity/hour) inversely correlated with the serum HDL cholesterol value (r = -0.483, P = 0.096) in the patients with CHD. These results suggest that an increase of CETA caused a low HDL cholesterol value in the CHD patients with low HDL cholesterolemia and it may have the risk of causing CHD. However, an increase of the CETA was not found in the CHD patients with high HDL cholesterolemia compared to the normal subjects, the HDL particle size being significantly greater than that in the normal subjects. In the CHD patients with high HDL cholesterolemia, the large size of HDL may have the risk of causing CHD.

Apolipoproteins↗
PubMed1990

Degradation and metabolism of indocyanine green: high-pressure liquid chromatographic analysis.

Degradation of indocyanine green solution by exposure to light was studied by high-pressure liquid chromatography. Indocyanine green in an aqueous medium exposed to light changed rapidly into an unknown product. The plasma clearance rate and the biliary excretion rate of the unknown product were much slower than those of indocyanine green. Spectrophotometric scan revealed that the unknown product had almost the same absorption spectrum as indocyanine green. Therefore, if degraded indocyanine green solution were to be used in a liver function test, the clearance of indocyanine green assayed by spectrophotometry would apparently be much lower than that of undegraded indocyanine green. According to fast atom bombardment mass spectrometry, the molecular weight of the unknown product was 723, whereas that of indocyanine green was 775. The analysis of rat bile after injection of indocyanine green by high-pressure liquid chromatography revealed that about 1% of the administered indocyanine green was metabolized in the rat liver.

Animals↗