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Biomedical subjects

Y Iwamura

Publications and source records attributed to Y Iwamura.

At least 37 records · Page 2Linked to original sources
PubMed1996

Coding of modified body schema during tool use by macaque postcentral neurones.

A tool is an extension of the hand in both a physical and a perceptual sense. The presence of body schemata has been postulated as the basis of the perceptual assimilation of tool and hand. We trained macaque monkeys to retrieve distant objects using a rake, and neuronal activity was recorded in the caudal postcentral gyrus where the somatosensory and visual signals converge. There we found a large number of bimodal neurones which appeared to code the schema of the hand. During tool use, their visual receptive fields were altered to include the entire length of the rake or to cover the expanded accessible space. These findings may represent neural correlates of the modified schema of the hand in which the tool was incorporated.

Animals↗
PubMed1996

Representation of reaching and grasping in the monkey postcentral gyrus.

In area 2 and further caudal part of the alert monkey's postcentral gyrus, we found neurons which were activated preferentially or only by monkey's self-initiated hand actions to reach or grasp objects. Among them we studied those neurons which were selective to either (1) projecting the arm and stretching digits toward an object (reaching); (2) grasping with the first and the second digit (radial grasp, precision grip); (3) grasping with the ulnar digits and palmar skin (ulnar grasp, whole hand grip); or (4) scratching or touching an object with distal digit pads and nails. Neurons of the radial grasp type were found in the lateral part of the digit region while all other types of neurons were found in the medial part. Each of hand action neurons was found in a cluster of neurons which had common receptive fields corresponding to effective sites for the particular type of grasping.

Animals↗
PubMed1996

Attention-induced neuronal activity in the monkey somatosensory cortex revealed by pupillometrics.

Detection of a sensory stimulus is facilitated when attention is directed towards the stimulus source. Neuronal substrates for this psychological effect were studied in monkeys performing an attention-demanding task, by simultaneous recording of neuronal activity and pupillary dilation as an indicator of attentive state. We found that neurons in the postcentral somatosensory cortex (SI) started to discharge concurrent with the pupil dilation onset which occurred well before the somatosensory stimulus. Neuronal firing rates were positively correlated with the degree of dilation, suggesting that the SI neural activity is under the direct influence of the attentional process.

Animals↗
PubMed1996

Cranial attachment of the gubernaculum associated with undescended testes.

Elongated epididymis is an abnormality encountered most frequently in patients who have an undescended testis (or testes). To clarify the implication of this anomaly in testicular descent, the anatomic configuration of paratesticular structures, especially the site of cranial attachment of the gubernaculum in relation to the configuration of the vas deferens, was evaluated in 54 undescended testes of 44 patients. Undescended testes were associated with an elongated epididymis in 42.5% of cases. Of these, the cranial gubernaculum was attached solely to the vas deferens in 73.9%. In this group, the cranial gubernaculum was attached to the most descended part of the loop of the vas deferens. No patient with a nonelongated epididymis had a gubernaculum attached solely to the vas deferens. These results suggest that the abnormal attachment of the cranial gubernaculum in the embryological stage might affect the mode of descent of adjacent paratesticular structures.

Child↗
PubMed1995

Postcentral neurons of alert monkeys activated by the contact of the hand with objects other than the monkey's own body.

In the caudal postcentral finger region near or in the anterior bank of the intraparietal sulcus of alert monkeys, we found neurons that were activated selectively by the contact of the hand to certain common objects such as bottle brushes, acrylic plates, parts of the stabilized monkey's chair, etc. All of these neurons were not activated when the monkey's hand was contacted with the monkey's own body. We concluded that these neurons are concerned with the haptic discrimination of common objects with the selectivity to one of various material variables of objects, and that the process involves differentiation of the object from the animal's own body.

Animals↗
PubMed1995

Detection of host DNA sequences including the H-2 locus of the major histocompatibility complex in schistosomes.

The mouse type 2 Alu (B2) sequence was detected in both DNAs of Schistosoma mansoni and S.japonicum except for the cercarial stage by the polymerase chain reaction (PCR). Using several kinds of mouse STMS (sequence tagged microsatellite site) primer sets, PCR products related to the host were found in the DNAs of S. mansoni as well as of S.japonicum. Products could be detected only in the DNA of S. japonicum using certain STMS primer sets. The fact that no products could be amplified from the DNAs of both parasites when other kinds of STMS primer sets were used suggests unequal incorporation of the host DNA into the schistosomes. Furthermore, the sequence of the N-terminal domain of H-2, the mouse major histocompatibility complex (MHC), was detected in the DNAs from S. mansoni miracidium, male adult and S. japonicum adults, whereas the sequence of the C2 domain of H-2 was found only in the DNAs of S. japonicum adults. This evidence that host DNA sequences, including the class I MHC, exist heterogeneously in the DNAs of schistosomes might provide an important insight for further understanding of host-parasite immune interactions.

Animals↗
PubMed1994

Bilateral hand representation in the postcentral somatosensory cortex.

In accordance with its important role in prehensile activity, a large cortical area is devoted to representation of the digits. Within this large cortical zone in the macaque somatosensory cortex, the complexity of neuronal receptive field characteristics increases from area 3b to areas 1 and 2 (refs 1-7). This increase in complexity continues into the upper bank of the intraparietal sulcus, where the somatosensory cortex adjoins the parietal association cortex. In this bank, callosal connections are much denser than in the more anterior part of this cortical zone. We have now discovered a substantial number of neurons with receptive fields on the bilateral hands. It was previously thought that neuronal receptive fields were restricted to the contralateral side in this cortical zone. Neurons with bilateral receptive fields were not found after lesioning the postcentral gyrus in the contralateral hemisphere. The majority of these neurons had receptive fields of the most complex types, representing multiple digits, indicating that the interhemispheric transfer of information occurs at higher levels of the hierarchical processing in each hemisphere.

Animals↗
PubMed1993

Rostrocaudal gradients in the neuronal receptive field complexity in the finger region of the alert monkey's postcentral gyrus.

In the primate postcentral gyrus, the cytoarchitectonic characteristics gradually shift from those of koniocortex to more homotypical parakoniocortex along its rostrocaudal axis. To find the physiological correlates of these changes we examined a large body of data accumulated during a series of our experiments with alert monkeys. Along the rostrocaudal axis of the postcentral gyrus, we found a gradual and continuous increase in the number of neurons with converging receptive fields and those in which receptive field positions or submodalities were not determined. Deep or skin submodality neurons were dominant in area 3a or 3b respectively. The proportion of skin submodality neurons decreased gradually from area 3b to the more caudal part of the gyrus. The proportion of deep submodality neurons was almost constant from area 3b to area 2 inclusive; they were not the majority in area 2. The data are consistent with the hierarchical scheme, i.e., within the postcentral gyrus sensory information is processed from the primary sensory receiving stage to the more associative, integrative stages.

Animals↗
PubMed1993

Development of reliable artificial liver support (ALS)--plasma exchange in combination with hemodiafiltration using high-performance membranes.

A new artificial liver support system (ALSS) consisting of plasma exchange (PE) in combination with hemodiafiltration (HDF) using high-performance membranes of polymethyl methacrylate (PMMA) and cellulose triacetate (CTA) was developed to efficiently remove middle molecules from plasma and treat fulminant hepatic failure (FHF) complicated by the onset of hepatic coma. Twenty-seven patients with FHF due to viral hepatitis, two with type A (HA), nine with type B (HB), and 16 with type non-A, non-B (NANB) underwent therapy with this new ALSS over the last five years. Three patients with an exacerbation of chronic HB and 15/16 with type NANB hepatitis were treated with interferon (IFN) also. Of these, 25 patients (92.6%) regained consciousness and 15 (55.6%) [1/2 (50%) with type A, 6/9 (66.7%) with type B and 8/16 (50%) with type NANB hepatitis] survived. Including four patients who survived with intensive care and plasma exchange alone, 19/31 (61.3%) patients survived. Because of its biocompatibility, both survivors and nonsurvivors could be sustained with the ALSS without complications for long periods (19.3 days for the survivors and 32.4 days for nonsurvivors). With this ALSS the ability to sustain life for such prolonged periods allows hepatic regeneration to occur and result in patient survival. It is anticipated that this new ALSS will not only be of value in cases of fulminant hepatic failure but that it may also play a role in sustaining life for those awaiting liver transplantation.

Adult↗
PubMed1993

Host-related DNA sequences are localized in the body of schistosome adults.

The localization of host (mouse)-related DNA sequences in the adults and cercariae of Schistosoma japonicum and S. mansoni was examined by in situ hybridization using 32P-labelled probes. The hybridization signals to the sequences of the mouse type C and type A retroviruses were clearly observed in the subtegumental layer and inner tissues of S. japonicum adults. In contrast, it was hard to find any signals to these sequences in S. mansoni adults. Distinct signals to the env-specific region of the mouse ecotropic type C retrovirus were observed in the subtegumental layer and inner tissues of S. mansoni adults. No signal to the sequence of the mouse type B retrovirus was found on the sections of either schistosome adult. The signals to the sequence of the genomic clone SmM51 derived from male S. mansoni were found in the tissues of both the schistosome adults. The signals to the sequences of the mouse type A and env-specific region of ecotropic type C retroviruses were not seen in the cercariae of each species, whereas the signals to the sequence of SmM51 were detected in S. mansoni cercariae. These observations suggest that host-related DNA sequences might be incorporated unequally into the schistosome genome during development in the final host.

Animals↗
PubMed1993

Diagnosis of childhood BK virus cystitis by electron microscopy and PCR.

A case of BK virus cystitis in a 5 year old boy is reported. This patient, who was not immunocompromised, had had acute cystitis for two weeks. Many intracytoplasmic inclusions were observed in urinary sediment smears stained by the Papanicolaou method. Electron microscopic examination showed virus particles, presumed to be human polyomavirus, in the nuclei of the degenerated urothelial cells. A DNA sequence of the BK virus was detected in 200-300 urothelial cells in Papanicolaou stained smears by the polymerase chain reaction. BK virus is an unusual cause of symptomatic cystitis in a healthy child.

BK Virus↗
PubMed1992

A new cell line (XTY) from a tumor of Xenopus laevis.

A new cell line (XTY) was derived from a tumor of a female Xenopus laevis. This cell line has been proliferating in standard amphibian culture medium for more than 4 years (470 generations) and has a doubling time of 75.5 h at 25 degrees C. The cells aggregate into large groups, and their stellate morphology and the expression of desmin demonstrated by immunocytochemistry suggest that their origin is not epithelial.

Animals↗
PubMed1992

[Detection and identification of pathogenic bacteria by polymerase chain reaction with primers from DNA sequence of ribosomal RNA].

Applicability of the polymerase chain reaction method for identification of pathogenic bacteria was examined with the primers synthesized from the ribosomal RNA gene sequence containing both homologous and species-specific regions of bacterial species from Mycoplasma to Mycobacteria. Two out of the nine sets of promoters prepared, each covering about 650 nucleotides spanning from 16S RNA to 23S RNA regions, produced the corresponding DNA fragments from all the strains tested, and another set did so from all species but Mycoplasma. This method enabled one to detect and identify E. coli in a sample containing 2 x 10(2) CFU. The restriction enzyme patterns of the PCR products obtained with Hae-III, Hha-I, Mbo-I, Msp-I, Rsa-I and Taq-I were so characteristic as to differentiate one species from another. Ten strains of E. coli showed identical restriction patterns and 10 of S. aureus also showed identical patterns indicating that the restriction pattern is species-specific. The method may be applicable to detection and identification of a certain species bacteria which are suspected to be consealed in water or food samples, or clinical specimens, especially when the consealed bacterial genus or species can not be predicted.

Base Sequence↗
PubMed1992

Co-deletions of the retinoblastoma gene and Wilms' tumor gene and rearrangement of the Krev-1 gene in a human insulinoma.

We found deletions of both alleles of the retinoblastoma gene (Rb) and the candidate Wilms' tumor gene (WT33) in a surgically resected human insulinoma by blot hybridization. Rearrangement of Krev-1, a transformation suppressor gene, was also detected in this case. The clinical and histological findings suggested that this tumor would be a benign insulinoma. The result suggests that the inactivation of multiple tumor suppressor genes could be involved even in the development of benign human tumors.

Aged↗
PubMed1991

BHV-1 adsorption is mediated by the interaction of glycoprotein gIII with heparinlike moiety on the cell surface.

The gIII glycoprotein of bovid herpesvirus 1 (BHV-1) has been shown to mediate the adsorption of the virions to cells (K. Okazaki, E. Honda, T. Minetoma, and T. Kumagai, 1987, Arch. Virol. 97, 297-307). In this study, the cellular receptor for BHV-1 was investigated. Addition of heparin to the virus inoculum and treatment of the cells with heparinase prevented the virus from adsorbing to and infecting the cells. Of the major glycoproteins of BHV-1 only gIII was found to bind specifically to heparin. The binding of gIII was inhibited by a monoclonal antibody against antigenic site Ia, which interferes with the adsorption of the virus. These findings indicate that the virus adsorption to cells is mediated by interaction of the gIII antigenic site Ia with a heparinlike moiety on the cell surface, which serves as a receptor for BHV-1.

Adsorption↗
PubMed1991

Existence of host-related DNA sequences in the schistosome genome.

DNA sequences homologous to the mouse intracisternal A particle and endogenous type C retrovirus were detected in the DNAs of Schistosoma japonicum adults and S. mansoni eggs. Furthermore, other kinds of repetitive sequences in the host genome such as mouse type 1 Alu sequence (B1), mouse type 2 Alu sequence (B2) and mo-2 sequence, a mouse mini-satellite, were also detected in the DNAs from adults and eggs of S. japonicum and eggs of S. mansoni. Almost all of the sequences described above were absent in the DNAs of S. mansoni adults. The DNA fingerprints of schistosomes, using the mo-2 sequence, were indistinguishable from each other and resembled those of their murine hosts. Moreover, the mo-2 sequence was hypermethylated in the DNAs of schistosomes and its amount was variable in them. These facts indicate that host-related sequences are actually present in schistosomes and that the mo-2 repetitive sequence exists probably in extra-chromosome.

Animals↗
PubMed1991

[Amplification of L-myc oncogene in malignant meningioma. Case report].

Amplification of L-myc oncogene was noticed in a malignant meningioma originating from the right sphenoidal wing of a 54-year-old female. The patient underwent three surgical resections plus radiotherapy over a period of 11 years and then the growth rate of the tumor became much greater with a severely invasive appearance. Using Southern blot hybridization, L-myc amplification was examined on the specimen resected at the fourth operation. As a result, approximately five-fold amplification was confirmed, which has not been previously reported except for that in a small cell carcinoma of the lung. This result may suggest that L-myc amplification is responsible to some extent for the malignant transformation in this meningioma.

Female↗