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Y Iwamura

Publications and source records attributed to Y Iwamura.

At least 73 records · Page 4Linked to original sources
PubMed1985

Diversity in receptive field properties of vertical neuronal arrays in the crown of the postcentral gyrus of the conscious monkey.

Single neuronal activity was recorded in the crown of the postcentral gyrus (areas 1 and 2) in 5 conscious monkeys. A total of 93 penetrations were made in the hand and finger region of 9 hemispheres and 827 neurons were isolated. The receptive field characteristics of neurons recorded along each of 88 penetrations which entered perpendicularly to the cortical surface were compared. The majority of neurons in this region were responsive to skin stimulation. In 54 penetrations, neurons related to different sensory submodalities were mixed. In 30, skin neurons predominated, and in 8, 'deep' neurons, while in the remaining 16 penetrations neurons related to different submodalities were equally mixed. In 16 penetrations, neurons responded exclusively to stimulation of skin, hair or nails. In 9 penetrations, neurons were exclusively related to joint manipulation or other types of 'deep' submodality. In 9 penetrations, unidentified neurons were in the majority. In each penetration, the receptive field positions varied considerably on the same finger or encompassed more than one finger. Although neurons of the same submodality, either skin or 'deep' tended to be set in an array, the most adequate stimulus could vary among neurons of a given array. The variability in the receptive field positions or the most adequate stimuli remained constant irrespective of the angle of the electrode penetration in the cortex. The results are compatible with the idea that vertically arranged neuronal array receive inputs of multiple sources, both thalamacortical and corticocortical, so that interactions between different inputs can readilly occur.

Afferent Pathways↗
PubMed1985

Vertical neuronal arrays in the postcentral gyrus signaling active touch: a receptive field study in the conscious monkey.

Single neuronal activity was recorded in the crown of the postcentral gyrus (areas 1 and 2) in 5 conscious monkeys. A total of 88 penetrations entered perpendicularly to the cortical surface. Among them, 6 examples are chosen and the receptive field characteristics of constituent neurons were described in some detail. Receptive fields of neurons recorded along a particular penetration were variable in their positions, but the largest receptive field usually covered the others. Neurons with the largest receptive fields were found most frequently in the infragranular layers. Often they included inhibitory receptive fields. The inhibitory receptive fields were arranged side-by-side to the excitatory ones, rather than in a center-surround fashion. The key stimulus common to neurons in a vertical penetration was the contact of an object to the receptive field achieved during animal's active behavior to manipulate the object. We thus designated the largest receptive field as a functional surface. Our results demonstrate that a vertical array of neurons in this cortical region can be regarded as a functional assemblage which deals with a set of information concerning one of various aspects of active touch.

Animals↗
PubMed1984

Changes in cellular DNA sequence adjacent to integrated viral genome in transplantable and nontransplantable guinea pig cells transformed by SV40.

Guinea pig (strain No13) kidney cells were transformed with SV40 (SVNo13). When this transformant was injected subcutaneously into syngeneic irradiated guinea pigs, tumors were produced in some animals. One of them became transplantable (ST13). Clones were obtained from cultured tumor cells (STC13). About one copy of the viral genome appeared to exist in both SVNo13 and STC13 clones as determined by reassociation kinetics. We have examined the distribution of integrated viral sequences in the host DNA by blot hybridization. In SVNo13, the blotting pattern with BamHI showed two main bands of 6.9 and 4.3 kilobases (kb), whereas in STC13 clones the 6.9-kb band was replaced with a shorter one of 6.1-kb. The blotting pattern with EcoRI also showed distinct changes between SVNo13 and STC13 clones. These results suggest either the occurrence of some mutations or deletions in the cellular DNA adjacent to the integrated viral genome or the transposition of viral DNA sequences during tumor development.

Animals↗
PubMed1982

Rearrangement of repeated DNA sequences during development of macronucleus in Tetrahymena thermophila.

Three clones of non-repetitive sequences and six clones containing repetitive sequences were obtained from micronuclear DNA of Tetrahymena thermophila. All the non-repetitive and three repetitive sequences had the same organization in micro- and macronuclear DNAs as revealed by blot hybridization. On the other hand, the remaining three clones with repetitive sequences had apparently different organization in the two nuclear DNAs. All these repetitive sequences showed a smear on the blot in addition to a number of discrete bands when micronuclear DNA was digested with EcoR I. In macronuclear DNAs, these sequences invariably became one or two bands and the smear disappeared. We conclude that, when a macronucleus develops from a micronucleus, the non-repetitive sequences amplify by more than 20 times with relatively few rearrangement, whereas some selected portions of repeated and/or repeat-contiguous sequences are amplified with rather extensive reorganization.

Animals↗
PubMed1980

Protective effects of S-sulfonated human gamma globulin against experimental infections in mice.

S-sulfonated gamma globulin (GGS), newly developed as a safe drug for intravenous use, was studied for its protective effects against some experimental infections in mice. Gamma globulin showed a good protective activity against infections due to Streptococcus pneumoniae and Escherichia coli and was moderately active against infections due to Staphylococcus aureus and Pseudomonas aeruginosa. In most cases, the potency of GGS was almost the same as that of original native gamma globulin. The duration of GGS activity in vivo was found to be comparable to that of native gamma globulin and much higher than that of pepsin-digested gamma globulin. In the control of infection due to E. coli, specific antibody was found to play a central role in the antibacterial action of GGS. When GGS was administered in combination with the antibiotics gentamicin and cefazolin for the control of infections due to S. pneumoniae or E. coli, a clear synergistic effect was observed.

Animals↗
PubMed1979

Induction of SV40-related transplantation immunity in mice by BK virus-transformed cells.

The reactivity of tumor-specific transplantation antigens (TSTAs) induced by SV40 and BK virus (BKV) was studied in Balb/Ccr mice with SV40-transformed tumor cells (mKSA-4AC). The mice, which had received BKV-transformed mouse or hamster cells, were highly resistant to the challenge with mKSA-4AC. The mKSA-rejected animals, however, were as susceptible as non-immunized ones to the subsequent challenge with Moloney sarcoma virus (Kirsten)-transformed cells. The result shows that BKV-transformed cells have a TSTA immunologically related closely to that induced by SV40.

Animals↗
PubMed1978

Functional organization of receptive fields in the cat somatosensory cortex. I: Integration within the coronal region.

The receptive fields (RF) of the neurons in the coronal region of the first somatosensory cortex (SI) were studied in a preparation of unanesthetized paralyzed cats. The majority of units responded to simple light mechanical stimuli to the hairy or glabrous skin. There were units with slightly larger RFs and more complex properties, such as those preferentially responding to the moving skin stimuli with directional selectivity. The receptive fields tend to be larger in the more rostral (area 3a) or medial coronal (area 3b) region than in the caudal region (area 3b). The largest RFs intermingled among focal ones included other smaller RFs in the vicinity. Their configurations were different at different loci in the coronal region. It is suggested that the coronal SI region is organized in terms of multiple clusterings of units, each with particular receptive field characteristics. The representation of a single peripheral locus on the forepaw can thus be multiple, if it appeared in more than one of such clusterings of receptive fields.

Animals↗
PubMed1978

Functional organization of receptive fields in the cat somatosensory cortex. II: Second representation of the forepaw in the ansate region.

The receptive fields (RF) of the neurons in the ansate region of the first somatosensory cortex (SI) were studied in unanesthetized paralyzed cats. Along the ansate sulcus, the forepaw dorsum was represented laterally, and the ventral surface of the paw was represented medially. These representations of the distal forepaw were found to be different from those in the coronal region in that they take parts of the larger and elongated receptive fields along the forearm axis. The principle of multiple representation of the forepaw on SI proposed in the preceding paper was thus confirmed and extended in this study. Many units in the ansate region showed complex receptive characteristics different from those in the coronal region. The convergence of skin and deep submodality was observed in units recorded in area 2 in the deep fold along the ansate sulcus, border zone along area 5. The functional organization of SI in terms of its cytoarchitectonic differentiation and thalamocortical relationships was discussed.

Animals↗
PubMed1975

Studies on differentiation of Mûllerian ducts in the quail, Coturnix coturnix japonica. II. Effects of sex hormones on nucleic acid synthesis in isolated female ducts.

The present investigations were carried out in an effort to determine the mechanisms underlying differentiation in the avian Müllerian duct, especially the asymmetrical differentiation of the female ducts. Using the isolated female ducts of Japanese quail, the incorporations of 3H-uridine and 14C-thymidine were determined in vitro at several embryonic stages. Incorporation of 3H-uridine was altered with some synchronous fluctuation during the embryonic period in both the left and right ducts, while 14C-thymidine incorporation first decreased rapidly and subsequently, only slightly, during the same period. By administering sex hormones in vitro nucleotide incorporation was affected to an appreciable extent characteristic of the duct at each stage. This hormonal susceptibility was also periodically altered during duct differentiation. The growing left duct continued to receive an apparent stimulation under the hormonal conditions, while the involuting right duct was sometimes inhibited under the same conditions. Such hormonal susceptibilities may explain the asymmetrical differentiation of the female left and right ducts during this embryonic period.

Animals↗