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Biomedical subjects

M Tsukada

Publications and source records attributed to M Tsukada.

At least 127 records · Page 7Linked to original sources
PubMed1989

Caloric restriction perturbs the pituitary-ovarian axis and inhibits mouse mammary tumor virus production in a high-spontaneous-mammary-tumor-incidence mouse strain (C3H/SHN).

Dietary restriction (DR) retards aging and extends maximum life span. It is also known to decrease the incidence of hormone-dependent tumors. In the present investigation, we focussed primarily on the influence of DR on the pituitary-ovarian axis, and subsequently on gene expression of the mouse mammary tumor virus. F1 females from the mating of SHN female and C3H male mice were used in this study, since these hybrids display a very high incidence of mouse mammary tumors. The mice weaned at 3 weeks were raised on either a calorically-restricted diet (DR: 50 kcal/week; N = 5) or on a control diet (C: 95 kcal/week N = 5) for 5 weeks. Three C57BL/6J Jcl ad libitum-fed female mice, 8 weeks of age, were used as reference animals since this strain has a very low incidence of mammary tumors. The mean cellular contents of prolactin (PRL) and growth hormone (GH) in the pituitary, as determined by immunohistochemistry, were found to be reduced in mice raised on the DR diet. The decrease in the mean cellular content of PRL (50% of the mean control value) was accompanied by a decrease in the number of lactotrophs (17% of the mean value of control diet mice). However, the decrease in cellular content of GH (53% of the mean control value) was not accompanied by a decrease in the number of somatotrophs (no. of somatotrophs in DR = 103% of mean control value). Histologically, ovaries from DR mice showed many growing and atretic follicles, with few corpora lutea. In contrast, both control-diet and reference (C57BL/6J Jcl) mice showed two or three corpora lutea per ovarian section. In accordance with this finding, DR mice had not established stable estrus cycles by 8 weeks of age, in contrast to both control-diet and reference mice. Since caloric restriction has been shown to decrease mammary tumor virus (MMTV) gene expression, MMTV production was investigated by electron microscopy to confirm the validity of our experimental conditions. In DR or reference C57BL/6J Jcl mice, MMTV particles were rarely found in the mammary gland samples, but were always found in samples from control mice. The development of mammary glands, as indicated by the number of villi or the development of the rough endoplasmic reticulum, was delayed in DR mice. Thus, it was concluded that caloric restriction decreases the number of lactrotrophs, inhibits ovulation and delays mammary gland development. This immature status is considered to be due to perturbations in the pituitary-ovarian axis by caloric restriction.

Animals↗
PubMed1989

Temperature-dependent formation of vacuolar and canalicular systems in association with degranulation in stimulated neutrophils.

Effects of temperature on the morphological changes and degranulation were studied in stimulated neutrophils. Neutrophils were stimulated by formyl-methionyl-leucyl-phenylalanine (FMLP) and cytochalasin B at 4 degrees C, 20 degrees C and 37 degrees C, and they were processed for electron microscopy and biochemical assays of myeloperoxidase (MPO) activity. When neutrophils were stimulated at 4 degrees C, they did not show apparent morphological changes nor release MPO activity. In the cells stimulated at 20 degrees C, there were many cytoplasmic vacuoles, localization of MPO-positive granules adjacent to the cell membrane and around the vacuoles, MPO-positive materials in the cavity of the vacuoles, and slightly decreased numbers of granules. They released moderate amounts of MPO activity. The neutrophils at 37 degrees C showed formation of small vacuoles and canaliculi and a marked decrease in the number of MPO-positive granules indicative of degranulation, and they released increased amounts of MPO activity. There were MPO-positive materials on the membrane and in the cavity of the vacuoles. Ruthenium red staining showed that the vacuoles were formed open outside the cell. These results indicate that the vacuolar systems are involved in degranulation in stimulated neutrophils and that their formation is dependent on temperature.

Cells, Cultured↗
PubMed1989

Pharmacological features of vascular responses of isolated rat common carotid arteries to vasoactive substances revealed by the cannula inserting method.

Using the cannula inserting method, we studied vascular responses of isolated rat common carotid arteries to 15 vasoactive substances. Intraluminal injections of phenylephrine, norepinephrine (NE), angiotensin II, 5-hydroxytryptamine (5-HT) and prostaglandin F2 alpha (PGF2 alpha) induced a strong vasoconstriction in such a way that a maximum increase in perfusion pressure amounted to approximately 50 mmHg. The order of their potencies were as follows: Phenylephrine greater than or equal to NE greater than or equal to angiotensin II greater than PGF2 alpha greater than or equal to 5-HT much greater than KCl. The selective alpha-2 agonists, xylazine and clonidine, induced nor or a slight vasoconstriction. Tyramine, ATP and acetaldehyde induced only a slight constriction. Histamine, adenosine and acetylcholine (ACh) induced no effect. In preparations preconstricted by a high dose of NE, ACh and isoproterenol induced a vasodilation in a dose-related manner. It is concluded that the cannula inserting method is useful for investigating vascular responses in isolated and perfused rat vessels.

Acetylcholine↗
PubMed1989

Electronic structure of DNA by DV-X alpha cluster calculations: II. d(GG).d(CC), d(CG)2, d(GC)2 A and B conformations. (Part 2) Sugars and bases.

The electronic structure of d(GG).d(CC), d(CG)2, d(GC)2 which are stacked base pairs in the DNA double helix, are elucidated for both A and B conformations in detail by DV-X alpha cluster calculations. These three DNA double helix fragments are contracted from the same bases, G and C, but the electronic structures of the fragments for both A and B conformations are different from each other characteristically. There are some delicate differences in the admixture of the orbital components and the overlap populations of intra- and inter- strand stacked bases among the stacking isomers. On the other hand, the electronic states of sugars differ in the 5'-3' direction, but are not almost dependent on stacked base pairs.

Cytosine Nucleotides↗
PubMed1988

Heterogeneity of macrophages evidenced by variability in their glycoconjugates.

Staining rat tissues with a battery of 15 lectin-horseradish peroxidase conjugates showed that macrophages contain glycoconjugates possessing terminal alpha, beta-galactose, N-acetylgalactosamine, fucose, and N-acetylneuraminic acid, plus two terminal disaccharides. Dissimilar binding of lectins by different phagocyte populations in the same or different organs evidenced variability in glycoconjugates according to the location of the macrophages. With a group of four lectins, macrophages stained most intensely in lung, next strongest in splenic red pulp and lymph node sinuses, and weakest in skin and liver. Two populations of macrophages were newly recognized in spleen on the basis of content of fucose-rich glycoconjugate. These included a necklace-like band of macrophages at the border between marginal zone and germinal center and distinctive macrophages dispersed throughout the marginal zone. In lymph nodes, phagocytes stained strongly in the germinal centers and weakly in sinuses for glycoconjugate with N-linked oligosaccharides and conversely for glycoconjugate with terminal beta-galactose. Variable lectin binding indicated heterogeneity of thymic macrophages. Lectin cytochemistry offers increased sensitivity for detecting macrophages in tissue sections, provides selective staining that shows the prevalence and distribution of the phagocytes and differentiates macrophages into separate subtypes.

Animals↗
PubMed1988

Possible mechanism of acetaldehyde-induced noradrenaline release from sympathetic nerve terminals in isolated blood vessels.

1. Vasoconstrictor responses to acetaldehyde were investigated in isolated and perfused canine intermediate auricular (ear) arteries. 2. Single injections of small doses of acetaldehyde (1-3 mumol) induced vasoconstriction in a dose-related manner and showed no tachyphylaxis. On the other hand, large doses of acetaldehyde (10-30 mumol) frequently caused tachyphylaxis when injected at 10 min intervals. 3. After tyramine treatment, constrictions induced by a large dose of acetaldehyde were consistently restored temporarily. 4. The acetaldehyde-induced vasoconstriction was inhibited by bunazosin, a potent alpha 1-adrenoceptor antagonist. 5. A small dose of imipramine blocked tyramine-induced vasoconstriction, but had no significant influence on noradrenaline (NA)-induced constrictions, and caused slight potentiation of acetaldehyde-induced constrictions. 6. Hydrocortisone treatment did not modify tyramine-induced vasoconstrictions and slightly suppressed NA- and acetaldehyde-induced constrictions but not significantly. 7. It is suggested that acetaldehyde causes a release of NA from a NA store of the sympathetic nerve terminals which is different from the tyramine-sensitive NA store, and that the acetaldehyde-sensitive NA store may be readily filled up with NA from the tyramine-sensitive store.

Acetaldehyde↗
PubMed1987

Spike trains in rat periaqueductal gray depend on the stochastic properties of interacting electrical stimulation trains.

Spike trains flowing into the periaqueductal gray (PAG) might be discriminated from one another by PAG neurons on the basis of the distribution or sequence of their respective interspike intervals. The various sequences of interspike intervals characteristic of spontaneous PAG unit activities were assessed in a preliminary experiment. These sequences were then simulated by means of appropriate mathematical functions. These functions allowed the production of stimulation trains that were applied to two PAG sites to induce spike trains with similar sequences in order to reveal the sensitivity of PAG neurons to the stochastic structure of afferent spike trains. We placed emphasis on parameters of the spike train that proved to be altered independently of any alteration of the corresponding parameters in the stimulation train. The mean pulse rate is the simplest example of such a parameter as it was never altered in the stimulation train. Alterations of either the distribution or sequence of pulses in the stimulation train were found to affect the mean discharge rate in a number of cases (30-40% of the cases). Despite their moderate degree (20-30% mean rate alteration) such differential effects could correspond to stimulation-induced differential behavioral effects as was shown in a previous study. Furthermore, a specific dependence of the generated spike trains on the sequential structure of the stimulation train was observed in some cases when appropriate stimulation trains were simultaneously applied to another PAG stimulation site. This fact is worth considering in relation to the integrative function of the PAG neuronal network.

Action Potentials↗
PubMed1987

Vasoconstrictor effects of endogenous digitalis-like factors extracted from urine of hypertensive patients.

The vascular effects of endogenous digitalis-like factors (EDLFs) extracted from the urine of hypertensive patients were investigated in isolated and perfused intermediate auricular and mesenteric arterial preparations of dogs. EDLFs produced a transient vasoconstriction in a dose-related manner in intermediate auricular arteries but only a slight constriction in mesenteric arteries. Ouabain induced a long-lasting vasoconstriction with tachyphylaxis in intermediate auricular arteries, but it did not constrict mesenteric arteries. EDLF-induced vasoconstrictions were reproducible and were not modified by alpha-adrenoceptor blockade. They were slightly suppressed by a potent calcium entry blocker, verapamil, in doses which markedly suppressed KCl-induced vasoconstrictions. Noradrenaline- and KCl-induced vasoconstrictions were not significantly modified by either EDLF or ouabain. From these results, it is concluded that EDLF has clear vasoconstrictor properties which are not due to adrenergic or calcium entry mechanisms and that there are differences in the vasoconstrictor effects of EDLFs with respect to different vascular beds. This is similar to what was found with ouabain.

Animals↗
PubMed1987

Blocking effects of nipradilol on vasoconstrictor responses to periarterial nerve stimulation and alpha-adrenoceptor agonists in isolated and perfused canine mesenteric arteries.

The stainless steel cannula inserting method was used to observe effects of nipradilol and prazosin on responses to periarterial electrical nerve stimulation and intraluminal administration of noradrenaline or phenylephrine in isolated and perfused canine mesenteric arteries. With small doses, nipradilol slightly potentiated vasoconstrictor responses to noradrenaline, but not periarterial stimulation. With a relatively large dose, nipradilol almost uniformly suppressed both periarterial stimulation-induced and noradrenaline- or phenylephrine-induced vasoconstriction. On the other hand, prazosin inhibited noradrenaline-induced vasoconstriction at small doses but not periarterial nerve stimulation-induced vasoconstrictions. At any doses, prazosin strongly inhibited noradrenaline-induced constrictions more markedly than periarterial stimulation-induced constrictions. It is concluded that nipradilol has a dominant inhibitory property on periarterial nerve stimulation-induced constriction in isolated canine mesenteric arteries.

Adrenergic alpha-Antagonists↗
PubMed1987

Potentiating effect of tyramine on acetaldehyde-induced vasoconstriction in isolated dog mesenteric arteries.

The stainless steel cannula inserting method was used to investigate the effects of acetaldehyde on isolated and perfused dog mesenteric arteries. Acetaldehyde when intraluminally administered induced a marked vasoconstriction, but repetitive injections of acetaldehyde caused tachyphylaxis. Acetaldehyde-induced vasoconstrictions were blocked by bunazosin, an alpha-1 adrenoceptor antagonist. After tyramine treatment, the acetaldehyde-induced constriction was consistently restored temporarily. It is suggested that tyramine may induce a release of norepinephrine mostly from the vesicle to the neuronal cytosol, and acetaldehyde may cause a release of norepinephrine from the cytosol to the extracellular space in the isolated canine mesenteric artery.

Acetaldehyde↗