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Biomedical subjects

T Yamamoto

Publications and source records attributed to T Yamamoto.

At least 19 recordsLinked to original sources
PubMed1979

Kinetic aspects of the antigen-antibody reaction in various radioimmunoassays: effect of delayed addition of labeled or unlabeled antigens on sensitivity of assay.

The kinetics of the antigen-antibody reaction were examined systematically in four kinds of double-antibody radioimmunoassay (RIA). In all the RIAs, the dose-response curves obtained on delayed addition by 24 to 48 h of labeled antigens (curves B), were shifted downwards and to the left of those obtained on simultaneous addition of the reagents (curves A), resulting in improved sensitivity of the assay. On the contrary, the dose-response curves obtained on delayed addition of unlabeled antigens (curves C), were shifted upwards and to the right of curves A, resulting in reduced sensitivity. In human thyrotropin (hTSH) RIA, curves B and C approached curves A very little, even after 168 h of incubation. A similar phenomenon was observed with anti-hTSH antisera from five different sources at two incubation temperatures, and the dilution curves of 125I-labeled hTSH and unlabeled hTSH appeared to be parallel. Therefore, the phenomenon observed with hTSH RIA could not be attributed to the assay conditions or to peculiar properties of the reagents used. In insulin RIA, the reversibilities of the shifts of curves B and C were slight but comparable to those observed in hTSH RIA. In 1-3,5,3'-triiodothyronine RIA, curves B and C gradually approached curves A on prolonged incubation and curves B became nearly identical with curves A after 98 h of incubation. On the other hand, in alpha-fetoprotein (AFP) RIA, curves B and C did not approach curves A, even on prolonged incubation for up to 288 h. The "equilibrium affinity constants" of the antibodies were of the same order of magnitude, thus it is unlikely that differences in the constants can account for the differences in the reversibility of these RIAs. In APF RIA, a significant amount of the antigen-antibody complex was precipitated without second antibody after centrifugation at 3000 X g. These findings suggest that the extent of dissociation of the immune complexes depends on their size, which in turn is related to the molecular weight of the antigen.

Antigen-Antibody Reactions↗
PubMed1979

APUD-type recepto-secretory cells in the chicken lung.

The epithelium of the intrapulmonary airways of the chicken lung has been studied by fluorescence and electron microscopy. Numerous intensely yellow-fluorescent cells occur in the epithelium of the primary and secondary bronchi. The cell cytoplasm contains characteristic granular vesicles with an electron-dense central core. The vesicles react positively to chromaffin and argentaffin treatment, indicating that they are possible storage sites for amines. Synapse-like junctions occur between the granular cells and the intraepithelial nerve endings, filled with numerous mitochondria, suggesting that these granular cells may have a dual function as both receptor and endocrine cell.

APUD Cells↗
PubMed1979

Localization of vagal cardioinhibitory preganglionic neurons with rat brain stem.

In chloralose-urethane anesthetized spinal rats, electrical stimulation of systematically chosen points over the entire caudal brain stem area was carried out to explore the site(s) responsible for vagally mediated bradycardia. A dorsomedial locus including the nucleus dorsalis and the adjacent structures, the nucleus tractus solitarius, the nucleus commissuralis and the area postrema, and a ventrolateral locus around the nucleus ambiguus were found to elicit bradycardia with low threshold and high responsiveness. In another series of experiments, horseradish peroxidase (HRP) was iontophoretically administered through a glass capillary microelectrode into the identified cardiac branch of the vagus nerve of rats in order to localize more precisely the cells of origin of vagal cardioinhibitory fibers within the brain stem. Distribution of the HRP-labeled cells was not confined to one area, but these cells were found within the nucleus dorsalis, the reticular formation surrounding the nucleus ambiguus and an intermediary zone between the two nuclei. Such a pattern of distribution of vagal cardioinhibitory preganglionic cells is discussed in relation to phylogenetic and ontogenetic development of the vagal motor nuclei.

Animals↗
PubMed1979

Milky spots (Taches laiteuses) as structures which trap asbestos in mesothelial layers and their significance in the pathogenesis of mesothelial neoplasia.

The UICC standard sample of asbestos, crocidolite, was injected subcutaneously into the flanks of CBA/lac mice. Asbestos fibres were found in milky spots in the serosal cavities more than 442 days after the injection, in the form of either naked fibres or asbestos bodies. Milky spots were the only structure in which asbestos fibres were observed in the mesothelial layer. The fact that asbestos fibres were found in the liver, spleen, kidney, brain, etc., in addition to milky spots, suggested that they were transported by the blood stream throughout the body. This assumption was confirmed by the similar distribution of asbestos after intravenous administration. The vascular and cellular structure of milky spots is such that they are particularly likely to trap blood-borne asbestos fibres. Hyperplastic changes were observed in milky spots after both subcutaneous and intravenous administration of asbestos in mice. The possible involvement of milky spots in the genesis of tumors of the mesothelium following exposure of animals to asbestos is discussed.

Animals↗
PubMed1979

Enhancement by asbestos of oncogenesis by Moloney murine sarcoma virus in CBA mice.

Five micrograms of finely ground crocidolite asbestos (UICC standard sample) were injected intraperitoneally into 3-week-old CBA mice, together with 10(5) FFU of Moloney murine sarcoma virus. Altogether 44 out of 61 mice (72.1%) so treated developed palpable intraperitoneal tumours, and half of these died of such tumours within 100 days. The same amount of quartz and carbon similarly administered gave lower tumour incidences, namely, 19.4% (3.2% fatal) and 11.9% (1.5% fatal) respectively. Only 1 out of 59 mice inoculated with the virus alone developed a palpable intraperitoneal tumour, and this regressed spontaneously within 10 days of its first appearance. No tumours were encountered in mice treated with either asbestos, quartz or carbon alone. All the neoplasms had the appearance, under the light microscope, of anaplastic sarcomas. Most of them were confined to the serosal surface of the abdominal cavity, although invasion of underlying tissues was observed in some of the animals that died. Electron microscopical examination of tumours revealed the presence of C-type particles budding off from cellular surface. Some neoplastic cells showed characteristic features of mesothelial lining cells. The role of milky spots (taches laiteuses) in oncogenesis by asbestos and virus, especially in the induction of mesothelioma, is discussed.

Animals↗
PubMed1979

Electrophysiological evidence for axonal sprouting of cerebellothalamic neurons in kittens after neonatal hemicerebellectomy.

Changes in cerebello-cerebral responses after hemicerebellectomy were investigated in 19 kittens by laminar field potential analysis in the cerebral cortex. In all of 11 kittens operated on before 11 days of age and kept for more than 16 days after surgery, marked cerebello-cerebral responses were evoked not only contralaterally as in intact animals but also ipsilaterally. In none of 16 intact kittens ranging in age from 2 to 14 days was there a detectable response in the cerebral cortex to stimulation of the ipsilateral cerebellar nucleus. Pathways responsible for the ipsilateral cerebello-cerebral responses were investigated by destruction of the thalamic VL nucleus and by unitary recordings from cerebellar nuclear neurons with antidromic activation on stimulation of the thalamus. From the latter investigation, a remarkable increase in the number of neurons with bilateral projections upon the thalamus was seen in the surgically treated kittens. Stimulation of the VL thalamic nucleus contralateral to the remaining hemicerebellum induced a marked response in the frontal cortex not only ipsilaterally as in intact animals but also contralaterally. The latter response was considered to be mediated by an axon reflex of the bilateral projection neurons. Destruction of that VL nucleus abolished the contralateral cerebello-cerebral response whereas the ipsilateral cerebello-cerebral response remained unchanged. It is concluded, that in kittens, hemicerebellectomized in the early postnatal period, nuclear neurons in the remaining cerebellum sprout axon collaterals growing into the thalamus ipsilateral to the spared hemicerebellum and that these sprouting axon collaterals make synpases on the thalamic neurons projecting upon the cerebral cortex.

Age Factors↗
PubMed1979

Morphological evidence for axonal sprouting of cerebellothalamic neurons in kittens after neonatal hemicerebellectomy.

Changes in cerebellothalamic projections in kittens after neonatal hemicerebellectomy were studied by the retrograde and anterograde horseradish peroxidase (HRP)-tract-tracing methods. The number of cerebellar nuclear neurons labeled retrogradely with HRP injected into the ipsilateral VA-VL complex of the thalamus was much more numerous in neonatally hemicerebellectomized kittens than in intact kittens. Presumed terminals of ipsilateral cerebellothalamic fibers labeled anterogradely with HRP injected into the cerebellar nuclei were also distributed more densely and extensively in the thalamic areas, especially in the VA-VL complex, of hemicerebellectomized kittens than in the thalamic areas of the control kittens. These results are in good accordance with those obtained from the previous electrophysiological study (Kawaguchi et al., 1979) and offer corroborating evidence for axonal sprouting of cerebellothalamic neurons after neonatal hemicerebellectomy.

Afferent Pathways↗
PubMed1979

Ultrastructural types of cell in adrenal cortical adenoma with primary aldosteronism.

By means of electron microscopy, three types of cell were identified in the adrenal cortical adenomas obtained by surgery from three patients with primary aldosteronism. They were zona glomerulosa-type cells, compact cells and clear cells. The former two types of cell were quite similar to those found in the zona glomerulosa and the zona reticularis respectively. The clear cell with large lipid vacuoles possessed mitochondria similar to those found in the outer zona fasciculata. The ultrastructure of the vacuoles was rather complex and their relationship to those in the zona fasciculata cell was not clear. Glycogen particles in the beta-form, which were present in the zona glomerulosa and reticularis cell but not in the zona fasciculata cell, were observed within the cytoplasm of this tumour cell. The clear cells of the tumours were therefore considered to possess features of both the zona glomerulosa and the zona fasciculata cell.

Adenoma↗