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Biomedical subjects

T Hidaka

Publications and source records attributed to T Hidaka.

At least 217 records · Page 12Linked to original sources
PubMed1988

Stimulation of polyadenosine diphosphoribose synthesis by DNA lesions induced by sodium chromate in Chinese hamster V-79 cells.

Polyadenosine diphosphoribose [poly(ADP-ribose)] synthesis was stimulated by DNA lesions induced with Na2CrO4 and methyl methanesulfonate (MMS) in Chinese hamster V-79 cells. Na2CrO4 and MMS induced DNA single-strand breaks in a concentration-dependent manner; however, the breaks induced by Na2CrO4 were "protein associated" while those induced by MMS were not. MMS stimulated in a dose-dependent fashion the synthesis of poly(ADP-ribose) up to 6-fold above the control. Na2CrO4 also induced poly(ADP-ribose) synthesis, but the level of synthesis was less than 3-fold. Control experiments demonstrated that Na2CrO4 treatment of cells did not affect their ability to synthesize poly(ADP-ribose) in response to DNA damage. Treatment of cells with Na2CrO4 and MMS induced more poly(ADP-ribose) synthesis than each agent alone; however, whenever Na2CrO4 was utilized, the breaks required proteinase K to be detected. Following removal of extracellular chromate, the DNA strand breaks induced by 0.2 mM Na2CrO4 were repaired quickly during the first hour but more slowly for the next 3 h. In the presence of 3-aminobenzamide, an inhibitor of poly(ADP-ribose) synthesis, the repair of DNA breaks was reduced. These results suggest that DNA protein-associated breaks produced by Na2CrO4 were recognized by poly(ADP-ribose) polymerase and that there are differences in poly(ADP-ribose) synthesis in response to Na2CrO4 and MMS. The results also suggest that the repair of breaks induced by Na2CrO4 are associated with poly(ADP-ribose) synthesis, but perhaps because most of these breaks are protein associated, there is less stimulation of poly(ADP-ribose) synthesis.

Animals↗
PubMed1988

Changes of membrane fluidity and Na+,K+-ATPase activity during cellular differentiation in the guinea pig epidermis.

The dynamic properties of plasma membrane in epidermal cells were determined by means of electron spin resonance using two kinds of doxyl stearic acid spin labeling agents: 5-DSA and 12-DSA. 5-DSA and 12-DSA are stearic acid analogues with a nitroxide radical ring at the 5th and 12th carbon positions, and these motions reflect molecular motion of lipid bilayer surrounding the hydrophilic region and the hydrophobic region, respectively. Guinea pig epidermal cells were separated into three regions of keratinocytes by Percoll density gradient centrifugation; the upper, middle, and lower epidermal cells. The order parameter S values for 5-DSA and 12-DSA incorporated into the isolated keratinocytes increased, suggesting a decrease in the plasma membrane fluidity, as cells approached the upper epidermal cell layer. The Na+,K+-ATPase activity as a plasma membrane-bound enzyme was determined in each epidermal cell region, and was found to decrease gradually as the cells approached the upper layer. Accordingly, the differentiation of epidermal cells in the keratinization process was found to be associated with a decrease in plasma membrane fluidity and with a decline of Na+,K+-ATPase activity.

Animals↗
PubMed1988

Increased platelet thromboxane synthesis in renal glomerular diseases.

Washed platelets were prepared from healthy children and adults, and patients with renal glomerular diseases, and incubated with [1-14C] arachidonate to measure the generation capacities of thromboxane (Tx) A2 and 12-hydroxyeicosatetraenoate (12-HETE). Tx generation capacity of platelets was significantly higher in patients with chronic glomerulonephritis, purpura nephritis and lupus nephritis than in healthy control subjects. There was no significant increase in minimal change nephrotic syndrome. 12-HETE showed a decreasing tendency in the glomerular diseases, which was restored to normal level by in vitro addition of indomethacin. Such increased Tx generation capacity of platelets may cause abnormal enhancement of platelet functions and conceivably constitute an aggravating factor of glomerular and microvascular damage in the affected kidney.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1988

Effect of SUN 1165, a new potent antiarrhythmic agent, on the kinetics of rate-dependent block of Na channels and ventricular conduction of extrasystoles.

Effects of SUN 1165, disopyramide, lorcainide, and mexiletine were studied either on the kinetics of onset of and recovery from rate-dependent depression of maximum rate of rise of phase 0 action potential (Vmax) in isolated guinea pig papillary muscles using standard microelectrode techniques or on intraventricular conduction time of extrasystoles evoked at varied coupling intervals in anesthetized dogs. SUN 1165 and lorcainide produced a slow-developing rate-dependent block of Vmax with the rate constant of 0.12 AP-1 and 0.09 AP-1, respectively. Mexiletine also produced a rate-dependent block of Vmax, but with very rapid onset so as not to be fitted by a single exponential curve. Disopyramide produced an intermediate rate-dependent block of Vmax with the rate constant of 0.46 AP-1. The time constants for recovery from the rate-dependent block for SUN 1165, lorcainide and disopyramide were 27.3-28.2, 23.2, and 17.0 s, respectively, while that for mexiletine was 0.118 s. SUN 1165, lorcainide, and disopyramide slowed ventricular conduction time of extrasystoles at all coupling intervals of 800-250 ms. On the other hand, mexiletine slowed conduction time at short coupling intervals of 500-250 ms. These findings suggest that, like lorcainide, SUN 1165 belongs to class Ic antiarrhythmic agents, and that SUN 1165 and lorcainide as well as disopyramide with slow and intermediate kinetics and mexiletine with fast kinetics may inhibit ventricular extrasystoles conducted at long and short range of coupling intervals, respectively.

Animals↗
PubMed1988

General pharmacological studies on N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate. 3rd communication: effect on cardiovascular system.

In this general pharmacological study of N-[2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), its effects on the cardiovascular and respiratory systems were studied. SUN 1165, at doses of up to 1.0 mg/kg i.v., had almost no effect. SUN 1165, at doses of 3.0 and 6.0 mg/kg i.v., caused dose-dependent decreases in blood pressure, common carotid, vertebral, coronary, hepatic and femoral artery and portal vein blood flows, cardiac contractility, heart rate and myocardial oxygen consumption. SUN 1165 increased urine volume and urinary excretion of electrolytes in rats at a dose of 100 mg/kg p.o. SUN 1165 decreased renal plasma flow and urinary excretion of electrolytes in anesthetized dogs at 6.0 mg/kg i.v., but at the antiarrhythmic doses (1.0-3.0 mg/kg i.v. in dogs), it had almost no effects on renal function. SUN 1165 had almost no effect on the autonomic nervous systems in anesthetized dogs. These results suggest that SUN 1165 at the antiarrhythmic doses do not have any effects on the respiratory and cardiovascular systems, renal function and autonomic nervous systems in rats and dogs, but that when administered at high doses, it has inhibitory effects on respiratory and cardiovascular system and renal function. In conclusion, SUN 1165 seems to be a novel antiarrhythmic drug relatively free of cardiovascular, respiratory, renal and autonomic effects.

Animals↗
PubMed1987

Six chloroplast genes (ndhA-F) homologous to human mitochondrial genes encoding components of the respiratory chain NADH dehydrogenase are actively expressed: determination of the splice sites in ndhA and ndhB pre-mRNAs.

Sequences (ndhA-F) homologous to human mitochondrial genes for components of the respiratory chain NADH dehydrogenase have been found in the chloroplast DNA of tobacco. The ndhA, D, E and F sequences corresponding to the mitochondrial URF1, 4, 4L and 5 are located in the small single copy region, the ndhB sequence corresponding to URF2 in the inverted repeat and the ndhC sequence corresponding to URF3 in the large single copy region of the chloroplast DNA. Northern blot hybridization revealed that all six ndh sequences are actively expressed in the chloroplasts. The ndhA and ndhB sequences contain single introns and the splice sites of their pre-mRNAs were determined by reverse transcription analysis. These findings suggest that potential components of an NADH dehydrogenase are synthesized in the chloroplasts.

Amino Acid Sequence↗
PubMed1987

Effects of vitamin E, vitamin B2 and selenite on DNA single strand breaks induced by sodium chromate (VI).

The effects of vitamin E, vitamin B2 and selenite on DNA single strand breaks induced by Na2CrO4 were examined by alkaline elution. Incubation of Chinese hamster V-79 cells with alpha-tocopherol succinate (vitamin E) for 24 h prior to exposure to Na2CrO4 resulted in a decrease of DNA breaks produced by this compound. However, similar pretreatment with riboflavin (vitamin B2) or Na2SeO3 resulted in an enhanced formation of breaks induced by Na2CrO4. Pretreatment with Na2SeO3 resulted in increased levels of glutathione in these cells while levels of glutathione remained the same with vitamin E or vitamin B2. These results suggest that Na2CrO4 induced DNA breaks appear to be mediated by the formation of free radicals and/or cellular reductive metabolism.

Animals↗
PubMed1987

[Steroid profiles in patients with amenorrhea during induction of ovulation with HMG].

Serum concentrations of various hormones in seven normal women were measured daily for 5 days before and after ovulation. Steroid levels were also measured in severe amenorrheic patients during the induction of ovulation with HMG-HCG. Blood samples from the patients of II grade amenorrhea were collected on the day when the cervical mucus increased more than 200 mm3 in HMG therapy. HCG was given after the blood samples were obtained. Ovulation was successfully induced in six patients and they were classified as group I. In 8 patients induction of ovulation did not succeed and these patients were classified as group II. Hormone levels including LH, FSH, estradiol (E2), progesterone (P4), 17 alpha OH-P4 (17P4), delta 4 androstenedione (delta 4 A), testosterone (Tes.), pregnenolone (P5), 17 alpha OH-P5 (17P5), DHA, delta 5 androstenediol (delta 5 AD), and 20 alpha OH-P4 (20P4) were measured by specific RIA. The following results were obtained. Steroid levels during normal ovulatory cycle: Levels of E2 (380 +/- 16 pg/ml), P5 (6.9 +/- 4.1 ng/ml), and Tes. (3.3 +/- 1.2 ng/ml) showed a peak on the day before LH surge. A significant increase in P4, 17P5 and 20P4 levels was observed after ovulation. Hormone levels in group I: FSH in group I was significantly higher while LH was lower than that in normal women measured during -1 to -3 days from LH surge. On the other hand, among the steroids measured, significantly low Tes. and high 17P5, and E2 levels were noticed in group I. Comparison of hormone levels between group I and II: FSH and LH levels showed no significant difference between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Amenorrhea↗
PubMed1987

Severe fetal supraventricular bradyarrhythmia without fetal hypoxia.

Cardiac anatomy and rhythm were evaluated in a fetus at 39 weeks' gestation in a pregnant woman referred because of severe fetal bradycardia with a persistent fetal heart rate of 50-60 beats per minute. M-mode echocardiograms revealed supraventricular bradyarrhythmia. Umbilical cord blood analysis did not, however, reveal fetal hypoxia. Diagnostic methods of fetal bradyarrhythmia are discussed, and the importance of differentiating bradyarrhythmia from bradycardia due to fetal hypoxia is emphasized.

Adult↗