Biomedical subjects
Publications and source records attributed to M Tsukada.
Using the cannula inserted method, vascular effects of nicotine were investigated in isolated, perfused dog intermediate auricular arteries, comparing with those of norepinephrine and tyramine. Norepinephrine and tyramine produced strong vasoconstrictions in a dose-related manner, but nicotine did not induce any significant vasoconstriction.
Using the cannula insertion method, we investigated the vascular response to acetylcholine (ACh) and other vasoactive substances. ACh consistently induced only vasoconstriction, whereas isoproterenol and norepinephrine usually induced dilatation. Vasoconstriction induced by phenylephrine was less potent than that induced by ACh. Clonidine and xylazine did not induce significant vascular responses. ACh-induced constrictions were readily inhibited by atropine and slightly potentiated by physostigmine. They were slightly but significantly inhibited by pirenzepine (a muscarinic M1-receptor antagonist), but not influenced by AF-DX 116 (a M2-receptor antagonist). 4-DAMP (4-diphenylacetoxy N-methylpiperidine; a M3-receptor antagonist), strongly inhibited the ACh-induced constrictions. They were not modified by bunazosin but slightly suppressed by diltiazem. Removal of the endothelium did not significantly modify the ACh-induced constrictions. From our results, we conclude that the simian facial vein has many constrictory muscarinic receptors, especially of the M3 subtype.
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Until this report, there have been no detailed analyses of the mouse mammary tumor virus (MMTV) loci in the mammary tumor prone strain SHN. Using a probe, which hybridizes to the env sequence of MMTV, Southern blotting of genomic DNA from the brain after digestion with EcoRI revealed 5 endogenous proviruses: Mtv-1 (4.5kb), Mtv-2 (11 kb), Mtv-8 (6.7kb), Mtv-17 (8.3kb) and a newly-found 6.5-kb fragment. F1-hybrid mice (C3H/He female x SHN male) also possessed the 6.5-kb fragment. Thus, we conclude that the 6.5-kb fragment is unique to SHN mice. Genomic DNA from mammary tumors of SHN mice showed MMTV insertions, suggesting that activation of an oncogene(s) occurred in this strain.
Phosphoglycerate kinase (PGK, EC 2.7.2.3), which is expressed specifically in sperm and spermatids, is an enzyme in the Embden-Meyerhof pathway that converts glucose to pyruvate. We developed an electrophoresis method to determine relative PGK-2 quantity and applied it to evaluate spermatogenesis activity. In the ethylene glycol monomethyl ether (EGME)-induced testicular toxicity, relative PGK-2 quantity had not decreased until 4 weeks of exposure. Mean relative PGK-2 quantities, defined as PGK-2 quantity over PGK-1 quantity in a pooled spleen sample (+/- SD) were: 1.43 +/- 0.32 for control animals (N = 10); 1.67 +/- 0.24 for the group exposed at 500 mg/kg for 5 days (N = 6); 1.85 +/- 0.58 for the group exposed at 500 mg/kg for 2 weeks (N = 6); 0.09 +/- 0.06 for the group exposed at 500 mg/kg for 4 weeks (N = 6); not detectable in animals exposed at 500 mg/kg for 5 weeks (N = 7); 0.208 +/- 0.103 for the group exposed at 250 mg/kg for 5 weeks (N = 6); and 1.35 +/- 0.38 for the group exposed at 125 mg/kg for 5 weeks (N = 6). These relative quantities showed a good correlation with sperm/spermatid counts (r = 0.823, p less than 0.01) and histological findings. These findings suggest that EGME has toxicity on primary spermatocytes and spermatogonia. In the case of sterility associated with a chromosomal abnormality (chromosomal translocation between chromosome X and 16), relative PGK-2 quantity was not detected in any of the seven adult (12 weeks of age) mice, although many primary spermatocytes were detected by histological examination.(ABSTRACT TRUNCATED AT 250 WORDS)
A water-insoluble silk fibroin membrane was prepared by immersing a silk fibroin membrane as cast in 50 vol% aqueous methanol solution for different periods of time at 25 degrees C. To use the membrane as a biomaterial, oxygen and water vapour permeability, transparency, mechanical property and enzymatic degradation behaviour in vitro of the membrane in the wet state were investigated. These physico-chemical properties changed according to the condition of the methanol treatment. The membrane had oxygen permeability, water vapour permeability, transparency and biodegradability.
During aging processes, the liver is exposed continuously to both endogenous and exogenous chemicals which result in various degrees of hepatic damage. Hepatocytes maintain mitotic potential so that damaged cells are replaced by proliferation of selected clones of cells. Changes in the clonality after hepatic damage were investigated using carbon tetrachloride (CCl4) as a model hepatotoxin. The changes in clonality were determined by the alteration of the electrophoretic patterns of the allozyme, phosphoglycerate kinase-1A/1B (PGK-1A/1B), the locus of which is on the X-chromosome. In mammalian females random inactivation of one of the two X-chromosomes, of either paternal or maternal origin, are known to result in phenotype mosaicism. Heterozygous female (PGK-1a/1b) mice were obtained by crossing female (PGK-1b/1b) and male (PGK-1a/-) C3H/He mice. Liver samples were collected from these mice 5 days before (by biopsy) and 18 days after dosing with CCl4 (1 ml/kg, i.p.). Quantitative evaluation of the electrophoretic bands showed significant changes (percent change more than 7.2%, P less than 0.01) in the relative PGK-1A activity in 4 out of 10 cases. In one mouse a remarkable change, from 83.0 to 59.2%, was observed. Thus we concluded that selective hepatocyte proliferation occurs after cellular damage. We speculated that this process may play an important role in the aging of the liver.
We investigated the effects of energy restriction on the pituitary-ovarian axis and on a hormone responsive gene, the mouse mammary tumor virus (MMTV). Female C3H/SHN F1-hybrid mice, known to display a high incidence of mammary tumors, ate an energy-restricted diet (48 kcal/wk) or a control diet (95 kcal/wk) beginning at the time of weaning. By 67 wk of age, 12 of 32 mice in the control group, but none of the 33 mice in the energy-restricted group, had developed mammary tumors. Six tumor-free mice from each group were studied in detail at 67 wk of age. All six tumor-free control mice, but none of the six energy-restricted mice, showed uterine endometrial hyperplasia at autopsy. Mice subjected to energy restriction did not display an estrous cycle. The average levels of MMTV mRNA in mammary glands and uteri were strongly reduced by energy restriction. MMTV mRNA levels in mammary glands from control mice were two orders of magnitude lower than those in mammary tumors. Energy restriction lowered the percentage of pituitary mammatropes and suppressed proliferation of mammatropes with advancing age. Energy restriction thus appeared to inhibit endometrial hyperplasia and to decrease MMTV production at the mRNA level in the mammary glands and in the uterus. These effects may be a consequence of hormonal changes originating at the pituitary-ovarian axis.
Using the cannula inserting method, vasodilator responses to alpha 2-adrenoceptor agonists (clonidine, guanabenz, DJ7141 and xylazine) were investigated in isolated and perfused rat common carotid arteries. Alpha 2-adrenoceptor agonists dose-dependently induced a vasodilation in preparations preconstricted by noradrenaline. The potencies were in the order of clonidine greater than guanabenz greater than DJ-7141 greater than or equal to xylazine. Removal of the endothelium inhibited ACh-induced vasodilation, but not the alpha 2-agonist-induced dilation. Atropine treatment inhibited ACh-induced vasodilation, but not the alpha 2-agonist-induced dilation. Alpha 2-agonist-induced dilations were not modified by beta-blockade, which significantly suppressed isoprenaline-induced vasodilations. The potent alpha 2-adrenoceptor antagonist DG5128 did not influence the alpha 2-agonist-induced vasodilation. In preparations preconstricted by PGF2 alpha, clonidine and xylazine never induced a vasodilation, and clonidine frequently induced vasoconstrictions that were completely blocked by bunazosin. It is concluded that alpha 2-adrenoceptor agonist-induced vasodilation is independent from the existence of the endothelium, and that it is not related to vascular beta- and alpha 2-adrenoceptors and muscarinic receptors, suggesting that the alpha 2-adrenoceptor agonist-induced vasodilation is due to an antagonistic activity towards the vascular alpha 1-adrenoceptors.
Using the cannula inserting method, we investigated the vascular responses to norepinephrine (NE), phenylephrine and isoprenaline (Isp) in isolated, perfused simian facial veins. NE usually induced only a vasodilation in non-preconstricted veins. Phenylephrine consistently induced only a slight vasoconstriction, and Isp produced only a vasodilation. NE-induced vasodilations were reversed to vasoconstrictions after treatment with a relatively larger dose of propranolol. It is concluded that simian facial veins have a spontaneous intrinsic tone and dominant abundant beta-adrenoceptors but sparse alpha 1-adrenoceptors.
Immunohistochemical studies of the gastrointestinal tract were carried out to characterize the cells exhibiting immunoreactivity for chromogranin A (CGA), a glycosylated protein primarily found in secretory granules of the adrenal medulla. Double immunostaining for gastrointestinal hormones and CGA revealed that in the bovine gastrointestinal tract CGA immunoreactivity occurs in mucosal epithelial cells containing gastrin, glucagon, substance P or motilin, but not in those containing somatostatin. Combined staining with anti-CGA serum and Grimelius' silver demonstrated frequent association of the two stains in a variety of endocrine cells. However, intracellular distribution of the two stains was different: CGA-immunoreactivity was detected in both supra- and infranuclear cytoplasm, whereas Grimelius' silver was mostly localized in the infranuclear region. These results suggest that CGA is the target of Grimelius' silver, as postulated recently (Rindi et al., 1986), but that some subcellular structure-related modification of molecules such as sialation is necessary for the positive Grimelius reaction.
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ON-center and OFF-center receptive fields of cat retinal ganglion cells can be divided into two categories: sensitive (type N) and insensitive (type L) to three statistical temporal visual stimuli with different second order statistics but identical first order statistics (Tsukada et al. 1982). The temporal pattern sensitivity of type N response is closely related to the nonlinear stage of Y cells depending on the interaction between center and surround mechanism. The temporal pattern sensitivity of type N responses has a spatial profile within the receptive field; it is highly sensitive in the center region of the receptive field and less sensitive toward the field periphery. The temporal pattern sensitivity in the center region of the receptive field to statistical properties (irregular or regular) of a surrounding flash annulus shows modulation like a switching element: when the surrounding area is stimulated by a more regular flash stimulus with normal distribution of inter-stimulus intervals the system is sensitive (switching on) to the temporal pattern, while a change to an irregular one with an exponential distribution makes it insensitive (switching off) to the temporal pattern.