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Biomedical subjects

M Tsukada

Publications and source records attributed to M Tsukada.

At least 163 records · Page 9Linked to original sources
PubMed1985

Quantitative evaluation of monocyte differentiation by electron microscopy: impairment of differentiation ability in monocytes from children with acute lymphoblastic leukaemia.

The differentiation of monocytes was evaluated quantitatively by electron microscopy and was analyzed in relation to the clinical features of childhood acute lymphoblastic leukaemia (ALL). The monocyte cellular size increased and cell organellae became mature after a 72-h culture. Phagolysosome formation developed markedly- and the nucleus became circular--accompanied by chromatin deconcentration. The differentiation degree of the cell organellae was indexed and classified as mature by electron microscopy. The indexes of nuclear shape, chromatin deconcentration, cytoplasmonuclear ratio and vacuole formation increased with time. The total index increased linearly with time dependence. These results indicate that the ultrastructural parameters and indexes allowed a quantitative assessment of cell organellae and cellular differentiation of the monocyte. At the acute phase of ALL, the degrees of cell organnellae and cellular differentiation were significantly lower than the control. The above findings suggest that monocytes from children with ALL have impaired differentiation ability, which results in defective function of macrophages.

Cell Differentiation↗
PubMed1985

Different sensitivity of blocking effects of alpha-adrenoceptor blocking agents on vascular responses to intraluminal norepinephrine and periarterial stimulation in isolated dog arteries.

The stainless steel cannula inserting method was used to examine the effects of periarterial electrical nerve stimulation and intraluminal norepinephrine in the isolated and perfused mesenteric artery of the dog. The optimum conditions for inducing an increase in perfusion pressure over 50 mmHg to periarterial electrical stimulation were 3-5 msec duration, 40-50 volts and 10-20 Hz. After the treatment with phentolamine or prazosin, the vasoconstrictor response to norepinephrine was readily inhibited completely at a relative small dose of 0.3-3 micrograms. Periarterial stimulation-induced vasoconstriction was also significantly suppressed by a relatively large dose of 100 micrograms of phentolamine or prazosin in concentrations 30 to 100 times larger than that required for blocking the norepinephrine-induced constriction. Yohimbine in relatively small doses potentiated the stimulation-induced vasoconstriction, but rather suppressed it in a large dose. The constrictor response to periarterial stimulation was significantly suppressed by 1 and 10 micrograms of intraluminal tetrodotoxin. It is concluded that periarterial electrical stimulation in the cannula inserting method is useful for studying autonomic pharmacology and physiology in vasculature with due regard to the characteristics.

Adrenergic alpha-Antagonists↗
PubMed1985

Different sensitivities of vasoconstrictor responses to serotonin and KCl of isolated and perfused dog mesenteric arteries with and without endothelia.

The stainless steel cannula inserting method was used to investigate the effects of serotonin on isolated and perfused dog mesenteric arteries with and without intraluminal saponin treatment. By intraluminal administration, serotonin and potassium chloride caused dose-related vasoconstrictions. After intraluminal treatment with 3 mg of saponin, the potassium chloride-induced vasoconstrictor response was significantly enhanced, whereas the serotonin-induced one was not potentiated but rather reduced slightly.

Animals↗
PubMed1984

Subcellular aldehyde dehydrogenase activity and acetaldehyde oxidation by isolated intact mitochondria of rat brain and liver after acetaldehyde treatment.

The effect of treatment of rats with acetaldehyde on the subcellular NAD+-aldehyde dehydrogenase (EC 1.2.1.3, ALDH) activities and acetaldehyde oxidation by isolated intact mitochondria of the liver and the brain was studied. Inhalation of acetaldehyde caused a significant decrease in the liver mitochondrial low Km-ALDH activity, while brain mitochondrial ALDH activity remained unchanged. Acetaldehyde oxidation by isolated intact liver mitochondria decreased significantly but that by brain mitochondria remained unchanged after acetaldehyde inhalation. These findings raise the possibility that the brain enzyme may be exposed to lower concentration of acetaldehyde than the liver enzyme.

Acetaldehyde↗
PubMed1984

Redundancy reducing processes in single neurons.

Interaction mechanisms between excitatory and inhibitory impulse sequences operating on neurons play an important role for the processing of information by the nervous system. For instance, the convergence of excitatory and inhibitory influences on retinal ganglion cells to form their receptive fields has been taken as an example for the process of neuronal sharpening by lateral inhibition. In order to analyze quantitatively the functional behavior of such a system, Shannon's entropy method for multiple access channels has been applied to biological two-inputs-one-output systems using the theoretical model developed by Tsukada et al. (1979). Here we give an extension of this procedure from the point of view to reduce redundancy of information in the input signal space of single neurons and attempt to obtain a new interpretation for the information processing of the system. The concept for the redundancy reducing mechanism in single neurons is examined and discussed for the following two processes. The first process is concerned with a signal space formed by superposing two random sequences on the input of a neuron. In this process, we introduce a coding technique to encode the inhibitory sequence by using the timing of the excitatory sequence, which is closely related to an encoding technique of multiple access channels with a correlated source (Marko, 1966, 1970, 1973; Slepian and Wolf, 1973) and which is an invariant transformation in the input signal space without changing the information contents of the input. The second process is concerned with a procedure of reducing redundant signals in the signal space mentioned before.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The effect of cadmium on the collagen solubility of embryonic chick bone in tissue culture.

The effect of cadmium (Cd) on the solubility of bone collagen was examined in cultured tibiae from 9-day chick embryos. The solubility of collagen was not significantly increased by 8.9 microM Cd, but showed a significant increase at 13.4 microM Cd. As the [3H]hydroxyproline (Hyp) formation was inhibited by Cd at 8.9 and 13.4 microM [3H]Hyp formation and collagen solubility were investigated in the presence of 200 microM Fe2+, a metal which is known to prevent the inhibitory effects of Cd on prolyl hydroxylase in vitro. Fe affected neither a decrease in [3H]Hyp formation nor an increase in collagen solubility caused by Cd. This suggests that a Cd-induced increase in collagen solubility may be due to the decrease of lysyl oxidase activity, not to the formation of underhydroxylated collagen. Zn at 48 and 134 microM depressed the Cd-induced increase in collagen solubility, but caused no increase in collagen solubility. Our present and previous results suggest that Zn can protect the disturbance of both the collagen synthesis and the collagen cross linking caused by Cd.

Animals↗
PubMed1984

Vasoconstrictor responses induced by alpha-adrenoreceptor agonists before and after removal of the endothelial cells of dog mesenteric arteries.

The stainless cannula inserting method was used to investigate the effects of alpha-adrenoreceptor agonists (phenylephrine, alpha 1-agonist and xylazine alpha 2-agonist) and calcium chloride on isolated and perfused dog mesenteric arteries with and without saponin treatment. By intraluminal administration, phenylephrine and calcium chloride caused vasoconstriction in a dose-related manner whilst xylazine was without significant effect. After intraluminal treatment with 3 mg of saponin, the endothelia of the arteries were completely removed as confirmed by pathological examinations. Phenylephrine- and xylazine-induced responses were not influenced by saponin treatment whereas calcium chloride-induced constriction was significantly enhanced.

Adrenergic alpha-Agonists↗
PubMed1984

Impaired monocyte differentiation in children with acute lymphoblastic leukaemia: its evaluation by peroxidase activity and ultrastructure.

The ability of monocyte differentiation in childhood acute lymphoblastic leukaemia (ALL) was evaluated on the basis of the ultrastructure and peroxidase (PO) activity which could show the differentiation of cultured monocytes. In the control, PO activity limited to the granules decreased time-dependently during culture for 4 d, and was closely associated with the morphological development to macrophages. In childhood ALL, monocytes showed poor changes in both PO activity and morphological features during culture for 4 d compared to the control. Therefore, we conclude that monocyte to macrophage differentiation is impaired in childhood ALL.

Adolescent↗
PubMed1984

Vasoconstrictor responses of isolated and perfused canine mesenteric arteries to alpha-adrenoceptor agonists.

Using isolated and perfused canine mesenteric artery, vasoconstrictor responses to alpha-adrenoceptor stimulating agents were compared. The order of potencies for inducing vasoconstriction was epinephrine greater than norepinephrine greater than phenylephrine greater than methoxamine greater than dopamine much greater than tyramine greater than clonidine greater than or equal to xylazine. A selective alpha 2-stimulant, xylazine, did not induce any significant vasoconstrictor response. Tyramine produced only a slight vasoconstriction. Responses to norepinephrine, phenylephrine and methoxamine were competitively inhibited by phentolamine treatment. From these results, it is concluded that the adrenoceptor in the canine mesenteric artery may be characterized as an alpha 1-receptor and that release of norepinephrine by tyramine is not marked in this relatively large vessel.

Adrenergic alpha-Agonists↗
PubMed1982

Temporal pattern sensitive and nonsensitive responses in the cat's retinal ganglion cells.

In order to characterize temporal pattern sensitivity in the cat ganglion cells, a new analysis technique by semi-Markov models which was developed in the previous papers (Tsukada et al., 1975-1977) was applied to input-output relations of the receptive-field. Three types of statistical spot stimuli positioned in the center region of receptive fields were used. Each type of stimulus has an identical histogram in the inter-stimulus intervals and therefore the same mean and variance, but different correlations between adjacent inter-stimulus intervals (Type 1, positive; Type 2, negative; and Type 3, independent processes). From the output spike trains of cat retinal ganglion cells to each stimulus, mean, variance, and histogram were computed. As the result of investigating these data, we could draw the following conclusion from the resultant output interval histograms. The receptive-field-center responses of cat ganglion cells can be classified into two groups (Types L and N) according to the difference of responsiveness to the three types of statistical spot stimuli. A Type L response has the same histogram in interspike intervals for all three stimuli, and is not sensitive to the temporal pattern, while a Type N response has three different forms depending on each type of stimulus showing high sensitivity to the temporal pattern. These results were also simulated by the Markov chain model and discussed with relation to neural coding and classification of ganglion cell types.

Animals↗