Biomedical subjects
R Tanaka
Publications and source records attributed to R Tanaka.
Integration in descending motor pathways controlling the forelimb in the cat. 1. Pyramidal effects on motoneurones.
Stimulation of the contralateral pyramid and intracellular recording from forelimb motoneurones was used to investigate corticimotoneuronal pathways in the cat. A train of pyramidal volleys evokes short-latency EPSPS in flexor motoneurones and in many extensor motoneurones. The latency for the onset after the effective pyramidal volley-usually the third - strongly indicates a disynaptic linkage. These disynaptic EPSPs were common in triceps motoneurones to fast heads but rare in those to slow heads. Pyramidal IPSPs with a slightly longer latency, suggesting a trisynaptic linkage, were found in both flexor and extensor motoneurones. They were common in motoneurones to slow heads of triceps. Disynaptic pyramidal IPSPs were found only occasionally. In addition pyramidal volleys may evoke late large EPSPs and/or IPSPs in any combination with the short-latency PSPs.
Integration in descending motor pathways controlling the forelimb in the cat. 2. Convergence on neurones mediating disynaptic cortico-motoneuronal excitation.
With intracellular recording from forelimb motoneurones the spatial facilitation technique has been used to investigate interaction between descending pathways and forelimb afferents. As previously shown for the hindlimb, pyramidal volleys effectively facilitate interneuronal transmission in reflex pathways from different primary afferents. Evidence is presented suggesting disynaptic excitation from corticospinal fibres of interneurones in the reciprocal Ia inhibitory pathway. Interneurones of other reflex pathways from group I muscle afferents recieve monosynaptic pyramidal excitation. During pyramidal facilitation volleys in cutaneous afferents may evoke PSPs in motoneurones after a central delay of 1.3 ms suggesting that the minimal linkage is disynaptic. Information regarding convergence on the neurones intercalated in the disynaptic cortico-motoneuronal pathway was obtained by investigating the effect from primary afferents and from other descending pathways on the disynaptic pyramidal EPSPs. Volleys in cutaneous and group I muscle affferents facilitate transmission in the disynaptic cortico-motoneuronal transmission with a time course showing oligosynaptic (probably monosynaptic) action the intercalated neurone. Rubrospinal volleys likewise effectively facilitate disynaptic cortico-motoneuronal pathway with a time course showing oligosynaptic (probably monosynaptic) action on the intercalated neurone. Rubrospinal volleys likewise effectively facilitate disynaptic cortico-motoneuronal transmission with a time course showing monosynaptic action on the intercalated neurone. Spatial facilitation experiments involving three tests revealed that those intercalated neurones which receive convergent monosynaptic excitation from corticospinal and rubrospinal fibres are excited also from cutaneous forelimb afferents. Disynaptic cortico-motoneuronal transmission was also monosynaptically facilitated by stimuli in the dorsal mesencephalic tegmentum probably activating tectospinal fibres. Disynaptic, presumed tectospinal EPSPs were facilitated from cutaneous forelimb afferents. The convergence onto the neurones intercalated in the disynaptic excitatory cortico-motoneuronal pathway suggests that these neurones integrate the activity in different descending pathways and primary forelimb afferents.
Nucleoside triphosphate and cation requirement for dopamine uptake by plain synaptic vesicles isolated from rat cerebrums.
Plain synaptic vesicles were partially purified from rat cerebrums and their [3H]dopamine uptake was investigated. The addition of MgCl2 plus ATP and of CaCl2 plus ATP increased the uptake 16 times and 5.5 times, respectively, higher than the control level, whereas the separate addition of these agents augmented the level at most 2.5 times. GTP stimulated the uptake as well as ATP, whereas UTP was one-third as effective and CTP, ADP, and AMP were all ineffective. Adenylyl imidodiphosphate was not only ineffective, but strongly reduced the ATP-dependent uptake. The half-maximal level of the ATP-dependent uptake was reached within 1.5 min after the start of incubation at 25 degrees C. The incorporation peaked at 5-10 min, then gradually declined to half-maximum at 45 min. This decline was prevented by the further addition of small amounts of CaCl2. There was no uptake at 0 degrees C, and the incorporation rate was at least 2 times faster at 37 degrees C than it was at 25 degrees C. The apparent Michaelis constant for [3H] dopamine was 1.6 muM. The half maximal inhibition of uptake was obtained at 0.1 muM reserpine; neither colchicine nor ouabain showed significant inhibition. The ATP-dependent uptake was not affected by K+, Na+, and Cl-, but was drastically decreased by isotonic phosphate buffer.
Transmission of corticospinal IPSPs to cat forelimb motoneurones via high cervical propriospinal neurones and La inhibitory interneurones.
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Experimental parainfluenza type 1 virus-induced encephalopathy in adult mice. Pathogenesis of chronic degenerative changes in the CNS.
The pathogenicity of the 6/94 strain of parainfluenza type 1 virus, originally isolated from multiple sclerosis brain, was studied in adult mouse brains. Intracerebral inoculation of the virus caused mononuclear cell infiltration in the form of perivascular cuffing and a diffuse exudation into the parenchymal tissue, preferentially in cerebral white matter, that resulted in marked degeneration over a 90-day observation period. Immunofluorescent staining revealed viral antigen in the ependymal lining cells only during the first seven days after infection. No correlation was found between the severity of the brain lesions and the level of circulating antiviral antibody, preexisting or newly produced.
C-G translocation in acute myelocytic leukemia with low neutrophil alkaline phosphatase activity.
A consistent chromosome abnormality of C-G translocation, t(8;21)(q22;q22), was found in 15 acute myelocytic leukemia (AML) patients with low neutrophil alkaline phosphatase (N-AP) activity. Granulocytes of these patients also had specific morphologic abnormalities. The bone marrow showed a tendency to relatively good maturation of leukemic cells for the disease AML. Clinical courses of the patients were mild and median survival was longer than that of patients with normal or high N-AP activity (p = 0.065, suggestive difference). Three out of six male patients with these type of AML had missing Y chromosome in addition to C-G translocation. The results suggest that specific cytogenetic abnormality of C-G translocation would be significantly associated with AML. Contrasting with low N-AP activity and the Philadelphia chromosome in chronic myelocytic leukemia, the findings in AML may offer additional evidence towards the possible relations between alkaline phosphatase activity and C or G chromosome.
A simplified instrument for solid-state high-gamma dosimetry.
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Intracisternal virus-like particles in brain of a multiple sclerosis patient.
Doughnut-shaped particles, 55-65 nm in diameter, were revealed by electron microscopy in the cisterns of the rough endoplasmic reticulum of cells from an active lesion in autopsied brain tissue from a multiple sclerosis patient. The morphology of the particles closely resembled that of coronaviruses.
Reciprocal Ia inhibition and voluntary movements in man.
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Reciprocal Ia inhibition in spastic hemiplegia of man.
The results of the present electrophysiological investigation have shed some light on the mechanisms underlying many clinical signs, at least, in patients with capsular hemiplegia. A tentative interpretation of them is given below. Cerebral lesions due to haemorrhage or infarction in the area of the middle cerebral artery interrupt an extensive part of the corticospinal tract and disturb many other descending pathways involved in voluntary performance. In consequence, a marked reduction in the ability to drive the spinal motor apparatus occurs, resulting in weakness of motor power. Here, we refer only to muscle power but not to performance. For example, the disturbance of voluntary contraction by clonus is disregarded (cf. fig. 8). On the other hand, the same lesions also release the spinal reflexes from inhibition by the higher levels of the brain and cause increased excitability in flexors and extensors. In the lower extremity, this is much more makred in extensors and extensor spasticity becomes a dominant sign clinically. Any release effect on the flexor system is largely cancelled by the high activity of the reciprocal Ia inhibitory pathway from extensors and only a fragment of it is occasionally revealed in some patients as an H-reflex in pre-tibial muscles or as weak Ia inhibition of the triceps surae. Reduced driving power of the brain may be compensated by raised excitability in the spinal cord and spastic extensors are thus naturally in a better condition to preserve motor power. Flexor muscles are doubly crippled by reduced descending impulses and strong reciprocal inhibition by the Ia impulses from the spindles of the extensor muscles.
Malignant transformation of hamster brain cells in vitro by human papovavirus Bk.
Human papovavirus BK caused the malignant transformation in vitro of brain cells prepared from newborn hamsters. The transformed cells produced BK virus T antigen and grew as tumors after sc inoculation ito hamsters that developed antibodies to BK virus T antigen. The histopathology of the tumors revealed an undifferentiated glioma.
Characterization of ATPases of plain synaptic vesicle and coated vesicle fractions isolated from rat brains.
The plain synaptic vesicle and the ocated vesicle fractions were isolated from rat brains, and the ATPase [EC 3.6.1.3] activities were characterized in terms of ionic effects, drug effects, and protein components. Coated vesicle fraction contained three times as much actomysin-like proteins as plain vesicle fraction, although both fractions had an identical ratio of actin-like protein to myosin-like protein. The ATPases of these two fractions were activated by both Mg2+ and Ca2+, and, in the presence of either of the cations, were inhibited by KCl. Reserpine activated plain vesicle ATPase only in the presence of Cl-. Colchicine and vinblastine inhibited coated vesicle ATPase only. The results are consistent with the view that actomyosin-like proteins are involved in the synaptic retrieval process.
Disynaptic inhibition of spinal motoneurones from the motor cortex in the monkey.
1. The neuronal mechanism of disynaptic inhibition of spinal motoneurones by the corticospinal tract was investigated in Macaca irus. Surface stimulation or weak intracortical stimulation was used in order to evoke the inhibition. Intracellular records were taken from motoneurones in lumbar segments. 2. Both the disynaptic i.p.s.p.s evoked from group Ia afferents and the disynaptic i.p.s.p.s evoked from corticospinal fibres were found to be depressed by conditioning stimulation of motor axons to antagonistic muscles. Mutual facilitation of the actions from these two fibre systems occurred when nerve impulses set up in them reached the explored spinal segment synchronously. These observations led to the conclusion that disynaptic i.p.s.p.s from group Ia afferents and from the motor cortex are mediated by common interneurones. 3. No evidence either for or against projections of the same pyramidal tract cells to motoneurones of one motor nucleus and to interneurones interposed between group Ia afferents and motoneurones of an antagonistic muscle could be obtained by comparing cortical areas from which monosynaptic e.p.s.p.s and disynaptic i.p.s.p.s were evoked in the different motor nuclei. 4. The areas from which the disynaptic i.p.s.p.s were evoked in individual motoneurones appeared to be similar in size to the areas of cortical monosynaptic projections to motoneurones and showed similar degrees of overlap, indicating that the projections of pyramidal tract cells to Ia inhibitory interneurones are as extensive as to motoneurones and that they are similarly organized.
Intestinal absorption characteristics of buformin and phenformin in rats.
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The pancreatic alpha and beta cells responses to 1-arginine and insulin-induced hypoglycaemia in hyperthyroidism.
In order to assess the secretory capacity of the pancreatic alpha and beta cells in patients with hyperthyroidism, the plasma glucagon and insulin responses to 1-arginine and insulin-induced hypoglycaemia in 12 patients were compared with those in 6 normal subjects. The response of beta cell to hypoglycaemia was evaluated by measuring the decrease in plasma C-peptide immunoreactivity (CPR) level. There was a negligible rise in blood glucose and plasma insulin levels in the patients, whereas a significant increase occurred in normal subjects during the arginine infusion. Although no difference in the fasting plasma glucagon concentration between the two groups was found, 30 min after the beginning of the arginine infusion, the plasma glucagon levels rose to a peak of 252 +/- 35 pg/ml in the patients, a value significantly lower than 387 +/- 53 pg/ml in the normal subjects. The insulin-induced hypoglycaemia caused no significant difference in the peak values of plasma glucagon between the two groups. There was a sigificant difference in the peak values of plasma glucagon between the two groups; There was a significant fall in plasma CPR after the insulin injection in both groups but the per cent decrement was rather greater in the patients than in the normal subjects.
Sister chromatid exchanges in peripheral lymphocytes of atomic bomb survivors and of normal individuals exposed to radiation and chemical agents.
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[CT 1341 (Althesin-Glaxo) for anesthetic for dilatation and curettage].
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