Biomedical subjects

Y Iwamura

Publications and source records attributed to Y Iwamura.

At least 19 recordsLinked to original sources

PubMed2002

Processing of tactile and kinesthetic signals from bilateral sides of the body in the postcentral gyrus of awake monkeys.

Earlier studies pointed out that in the primary somatosensory cortex (SI) the receptive fields (RF) of bilateral neurons were related exclusively to the body midline. We recently found a substantial number of neurons with bilateral RFs on hand digits, shoulders/arms or legs/feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake macaque monkeys. The RFs of these neurons were generally of the most complex types found in this region of the cortex, and thus they were considered to be at the highest level along the hierarchical chain of information processing. We conclude that there are two types of bilateral RFs in the postcentral gyrus, one representing the midline structures such as the intraoral cavity, chin or trunk and the other related to limb structures such as fingers, hands, arms, shoulders, legs and girdles. Functional significance of the bilateral activity could be understood in behavioral context as it is seen more extensively in the body parts where bilateral coordination is essential.

Animals↗

PubMed2001

Cervical intradural disc herniation.

STUDY DESIGN: A case report of anterior en bloc resected cervical intradural disc herniation and a review of the literature. OBJECTIVE: To discuss the pathogenesis of cervical intradural disc herniation. SUMMARY OF BACKGROUND DATA: Including this study case, only 17 cases of cervical intradural disc herniation have been reported. There have been few detailed reports concerning the pathogenesis of cervical intradural disc herniation. METHODS: A cervical intradural disc herniation at C6-C7, with localized hypertrophy and segmentally ossified posterior longitudinal ligament, is reported in a 45-year-old man who had Brown-Sequard syndrome diagnosed on neurologic examination. Neuroradiologic, operative, and histologic findings, particularly the pathology of the anterior en bloc resected posterior vertebral portion of C6 and C7, were evaluated for discussion of the pathogenesis. RESULTS: Adhesion of dura mater and hypertrophic posterior longitudinal ligament was observed around a perforated portion of the herniated disc, and histologic study showed irregularity in fiber alignment accompanied by scattered inflammatory cell infiltration and hypertrophy in the posterior longitudinal ligament. The cervical intradural disc herniation was removed successfully and followed by C5-Th1 anterior interbody fusion with fibular strut graft. Neurologic recovery was complete except for minor residual sensory disturbance in the leg 7 years after the surgery. CONCLUSIONS: Cervical intradural disc herniation is an extremely rare condition. The pathogenesis remains obscure. Only 16 cases have been reported in the literature, and there has been little discussion concerning the local pathology of the herniated portion. The pathogenesis of the disease in the patient reported here was considered to be the adhesion and fragility of dura mater and posterior longitudinal ligament. This was caused by hypertrophy, with chronic inflammation and ossification of the posterior longitudinal ligament sustaining chronic mechanical irritation to the dura mater, leading to perforation of the herniated disc by an accidental force.

Cervical Vertebrae↗

PubMed2001

Gastric pneumatosis associated with duodenal stenosis and malrotation.

Pneumatosis intestinalis, which is linear or cystic gas within the bowel wall, is usually found in premature babies in association with necrotizing enterocolitis. Gastric pneumatosis defined as intramural gas of the stomach is a rare sign during infancy. We report an infant with Down's syndrome and a duodenal web with obvious gastric pneumatosis.

Down Syndrome↗

PubMed2001

Self-images in the video monitor coded by monkey intraparietal neurons.

When playing a video game, or using a teleoperator system, we feel our self-image projected into the video monitor as a part of or an extension of ourselves. Here we show that such a self image is coded by bimodal (somatosensory and visual) neurons in the monkey intraparietal cortex, which have visual receptive fields (RFs) encompassing their somatosensory RFs. We earlier showed these neurons to code the schema of the hand which can be altered in accordance with psychological modification of the body image; that is, when the monkey used a rake as a tool to extend its reach, the visual RFs of these neurons elongated along the axis of the tool, as if the monkey's self image extended to the end of the tool. In the present experiment, we trained monkeys to recognize their image in a video monitor (despite the earlier general belief that monkeys are not capable of doing so), and demonstrated that the visual RF of these bimodal neurons was now projected onto the video screen so as to code the image of the hand as an extension of the self. Further, the coding of the imaged hand could intentionally be altered to match the image artificially modified in the monitor.

Action Potentials↗

PubMed2001

Horizontal and vertical transmission of mouse class I MHC sequence in Schistosoma mansoni.

The mouse major histocompatibility complex (MHC) class I sequence was detected in 8-week-old Schistosoma mansoni by in situ polymerase chain reaction (in situ PCR). The signals to the mouse class I MHC sequence were observed in the nuclei of the mesenchymal and reproductive cells of S. mansoni. Signals were also observed in the cytoplasm of the tegumental tubercles. This finding suggested the possibility of MHC gene transfer from the host to schistosomes. Furthermore, the class I MHC sequence was detected in the DNA extracted from the cercariae of S. mansoni by nested PCR. Neither the nucleotide sequence of class I MHC detected in adult worm DNA nor that of class I MHC detected in the host (mouse) DNA was identical with that of class I MHC detected in the cercarial DNA. From the data we assumed that S. mansoni may have retained their own mouse class I MHC sequence in their genome throughout their life-cycle.

Animals↗

PubMed2001

Bilateral activity and callosal connections in the somatosensory cortex.

Earlier studies recording single neuronal activity in the postcentral somatosensory cortex of monkeys converged in suggesting that the bilateral receptive fields were related exclusively to the body midline including the trunk, perioral face, and oral cavity. These neurons were recorded mostly in the rostral part of the gyrus, areas 3b and 1. However, the authors recently found a substantial number of neurons with bilateral receptive fields on extremities, hand/digits, shoulders/arms, or legs/feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus. The authors review these results and discuss functional implications of the bilateral representation in the postcentral somatosensory cortex.

Animals↗

PubMed2000

Bilateral receptive field neurons and callosal connections in the somatosensory cortex.

Earlier studies recording single neuronal activity with bilateral receptive fields in the primary somatosensory cortex of monkeys and cats agreed that the bilateral receptive fields were related exclusively to the body midline and that the ipsilateral information reaches the cortex via callosal connections since they are dense in the cortical region representing the midline structures of the body while practically absent in the regions representing the distal extremities. We recently found a substantial number of neurons with bilateral receptive fields on hand digits, shoulders-arms or legs-feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake Japanese monkeys (Macaca fuscata). I review these results, discuss the functional implications of this bilateral representation in the postcentral somatosensory cortex from a behavioural standpoint and give a new interpretation to the midline fusion theory.

Animals↗

PubMed2000

Bilateral receptive field neurons in the hindlimb region of the postcentral somatosensory cortex in awake macaque monkeys.

Single-neuron activities were recorded in the hindlimb region of the primary somatosensory cortex and part of area 5 in awake Japanese monkeys. A total of 1050 units were isolated from five hemispheres of four animals. Receptive fields (RFs) and submodalities were identified for 90% of isolated neurons in areas 3a and 3b. The percentage decreased as the recoding site moved to the more caudal areas. Deep or skin submodality neurons were dominant in area 3a or area 3b, respectively. Deep submodality neurons increased in more caudal areas and were the majority in areas 2 and 5. These observations were consistent with those in the hand and/or digit or arm and/or trunk region. The identified neurons were classified by their RF positions into four types: the foot, leg, foot and leg, or hindlimb and other body parts type. Among 831 identified neurons, 33 neurons had bilateral RFs, 14 had ipsilateral RFs, and the rest (N=784) had contralateral RFs. The relative incidence of neurons with bilateral or ipsilateral RFs among identified neurons was less than 1% in areas 3a, 3b, and 1, and 16% or 25% in areas 2 or 5, respectively. Within areas 2 and 5, the percentage of neurons with bilateral or ipsilateral RFs was significantly smaller in the foot type (5%) than in other RF types (24-57%). RFs of the foot type were on the sole or single toe but never on multiple toes. These observations contrasted with the previous findings that neurons with bilateral RFs were more frequently seen in the hand and/or digit region and that RFs on multiple digit tips were dominant there. The present study thus demonstrated that neurons with bilateral RFs do exist in the hindlimb region. Similarly to the forelimb region, they were found mostly in areas 2 and 5, the caudalmost areas of the postcentral gyrus and hierarchically higher stages in information processing. The relative paucity of neurons with bilateral RFs on the foot, especially those with RFs on multiple toes, may reflect functional differences between the foot and the hand.

Action Potentials↗

PubMed2000

Horizontal and vertical transfer of mouse endogenous retroviral DNA sequences in schistosomes.

The in situ polymerase chain reaction (PCR) results revealed that mouse type A and type C retroviral sequences were transmitted horizontally from the host to schistosomes. The signals to these retroviral sequences were observed in the nuclei of the mesenchymal and reproductive cells of 8-week Schistosoma japonicum. These signals were also detected in the nuclei of the mesenchymal and reproductive cells and in the cytoplasm of the tegumental tubercles of 24-week S. mansoni. Furthermore, mouse type A retroviral sequence was detected in the DNA extracted from the cercariae of both species. However, mouse type C retroviral sequence and mouse type 2 Alu sequence (B2) were difficult to detect in the cercarial DNA of either species. These findings may indicate that some host sequences are propagated in the schistosome progeny, that is to say, not only horizontal but also vertical transfer of the host gene may occur in schistosomes.

Animals↗

PubMed2000

Deficits of masticatory movements caused by lesions in the orofacial somatosensory cortex of the awake cat.

The purpose of this study was to determine the role of somatosensory cortex (SI) in the control of orofacial movements during eating. We identified perioral and tongue projection regions of the cat SI and destroyed cells in one region by injecting kainic acid. The effects on orofacial behavior were then studied over a period of 4-6 weeks. Cats with unilateral lesions in the perioral region (PL-cats) dropped food from the contralateral side of the mouth in the early phase. Failure in erection of the contralateral whisker hairs during masticatory movements and delay of the masticatory start were observed throughout the experimental period. Furthermore, in the late phase, PL-cats showed prolongations of the masticatory and food intake periods, which were accompanied by the increase in the number of swallows and chewing cycles. Cats with unilateral lesions in the tongue region (TL-cats) showed the prolongation of the masticatory period in the early phase, which was accompanied by the increase in the number of swallows and chewing cycles. TL-cats did not show the prolongation of the food intake period and failure in erection of the contralateral whisker hairs. In both PL- and TL-cats, masticatory and swallowing rhythms were normal.

Animals↗

PubMed1999

Acute exercise causes mitochondrial DNA deletion in rat skeletal muscle.

The present study was conducted to determine the effects of acute overload exercise on mitochondrial DNA and the structure of skeletal muscles. Rats were forced to run for 20 min until reaching complete exhaustion. We detected the large-scale deletion (7052 bp) of mitochondrial DNA by the nested polymerase chain reaction, and also observed mitochondrial ultrastructural changes in the soleus muscle.

Animals↗

PubMed1999

Localization of mouse type 2 Alu sequence in schistosomes.

Localization of the type 2 Alu sequence (B2), a highly repetitive DNA sequence in the mouse genome, was examined by in situ polymerase chain reaction (in situ PCR) in schistosomes. The signals to the B2 sequence were detected in the cytoplasm of the tegumental membrane and in the nuclei of the mesenchymal, testicular, ovarian and vitelline cells of 8-week Schistosoma japonicum. In contrast, it was difficult to detect any signals of this sequence in 8-week S. mansoni, whereas in 24-week male S. mansoni the signals were observed in the cytoplasm of the tegumental tubercles and in the nuclei of the mesenchymal and testicular cells. On the other hand, in 24-week female S. mansoni the signals were found in the nuclei of the mesenchymal, ovarian and vitelline cells but not found in the tegument. On the contrary, no hybridization band of the B2 sequence was detected in the amplified DNA of 3-week schistosomula of either species. These observations proved that the host DNA sequences existed in restricted schistosome cells and were accumulated in the schistosome body during their development.

Alu Elements↗

PubMed1998

Nuclear-recessive mutations of factors involved in mitochondrial translation are responsible for age-related respiration deficiency of human skin fibroblasts.

We addressed the question of whether both mitochondrial and cytoplasmic translation activities decreased simultaneously in human skin fibroblasts with the age of the donors and found that the age-related reduction was limited to mitochondrial translation. Then, to determine which genome, mitochondrial or nuclear, was responsible for this age-related, mitochondria-specific reduction, pure nuclear transfer was carried out from mitochondrial DNA (mtDNA)-less HeLa cells to four fibroblast lines, two from aged subjects, one from a fetus, and one from a patient with cardiomyopathy, and their nuclear hybrid clones were isolated. A normal fibroblast line from the fetus and a respiration-deficient fibroblast line from the patient were used as a positive and a negative control, respectively. Subsequently, the mitochondrial translation and respiration properties of the nuclear hybrid clones were compared. A negative control experiment showed that this procedure could be used to isolate even nuclear hybrids expressing overall mitochondrial respiration deficiency, whereas no respiration deficiencies were observed in any nuclear hybrids irrespective of whether their mtDNAs were exclusively derived from aged or fetal donors. These observations suggest that nuclear-recessive mutations of factors involved in mitochondrial translation but not mtDNA mutations are responsible for age-related respiration deficiency of human fibroblasts.

Aging↗

PubMed1998

Representation of the midline trunk, bilateral arms, and shoulders in the monkey postcentral somatosensory cortex.

Single neuronal activities were recorded in the arm/trunk region of the postcentral gyrus in awake Japanese monkeys. A total of 1608 units were isolated from four hemispheres of two animals, and receptive fields (RFs) and submodalities were identified in 1162 units. Deep or skin submodality neurons were dominant in area 3a or area 3b, respectively. The deep/skin ratio increased as the recording site moved from area 3b to the more caudal areas. In areas 3a and 3b, neuronal RFs were almost exclusively on either the arm or trunk. In areas 2 and 5, neurons with RFs on the trunk decreased and those with RFs on the hand or covering more than one body part, etc. increased. We found a total of 107 neurons with bilateral RFs and 56 with ipsilateral RFs, while the rest (n=999) were with contralateral RFs. Bilateral or ipsilateral neurons of skin submodality (n=37) were found in areas 1, 2, and 5. Twenty six (70%) had RFs on the trunk and/or occiput, five on the forelimb, and the rest (n=6) on both the trunk and forelimb (the combined type). Among 33 skin bilateral neurons, 90% (n=30) had RFs across the midline. Bilateral or ipsilateral neurons responding to joint manipulation (n=104) were found in areas 2 and 5. Most of them were activated by manipulation of the shoulder and/or elbow (the proximal type, n=72, 69%). There were 25 neurons of the combined type (both the proximal and distal joints were effective, 24%). Bilateral or ipsilateral neurons of deep-others submodality (n=20) were found in areas 1, 2, and 5. The forelimb type (n=12, 60%) was dominant in this category. The combined-type neurons in both the skin- and joint-manipulation categories were found only or mostly in area 5. These results indicate the presence of hierarchical processing for bilateral as well as contralateral information within the arm/trunk region of the postcentral gyrus.

Animals↗

PubMed1998

Hierarchical somatosensory processing.

Recent studies of the postcentral and additional somatosensory cortices support a hierarchical scheme for information processing. In the postcentral gyrus, the complexity of receptive field properties increases with caudal progression from area 1. It has been reported that the anterior bank of the intraparietal sulcus, the caudalmost part of the postcentral gyrus, is responsible for the systematic integration of bilateral body parts, as well as of somatic and visual information.

Animals↗

PubMed1997

Mastication-related neurons in the orofacial first somatosensory cortex of awake cats.

In the orofacial area of the first somatosensory cortex (SI), we recorded single unit activity from 699 neurons in 11 awake cats. Fifty-two percent (362/699) were mastication-related neurons (MRNs) showing activity related to some aspects of masticatory movements. MRNs were divided into three types by their activity patterns: (1) the rhythmical type, showing rhythmical bursts in pace with the masticatory rhythm; (2) the sustained type, showing a sustained firing during the period of taking food and (3) the transient (biting) type, showing intense discharges in coincidence with biting hard food. MRNs had mechanoreceptive fields in the perioral, tongue, periodontal and mandibular regions. The activities of perioral rhythmical-MRNs, mandibular transient-MRNs, tongue rhythmical-MRNs and periodontal transient-MRNs were correlated with food texture, while perioral rhythmical-MRNs, perioral sustained-MRNs and tongue sustained-MRMs were not. Both facial and intraoral MRNs were scattered throughout the facial and intraoral projection areas in SI. These findings provide evidence that the orofacial SI monitors masticatory movements for food ingestion.

Afferent Pathways↗

PubMed1997

Induction of a particular deletion in mitochondrial DNA by X rays depends on the inherent radiosensitivity of the cells.

We examined whether X radiation induces a particular deletion in the mitochondrial DNA (mtDNA) of the cells of two human squamous cell carcinoma lines with different sensitivity to radiation and in a radiosensitive ataxia telangiectasia (AT) cell line. We used polymerase chain reaction (PCR) to quantify the accumulation of a particular 4977-bp deletion (delta mtDNA4977). PCR products of delta mtDNA4977 were detectable after exposure to 10 Gy in the radioresistant squamous cell carcinoma cells, 2 Gy in the radiosensitive squamous cell carcinoma cells and 1 Gy in the radiosensitive AT cells. These observations suggest that ionizing radiation induces the delta mtDNA4977 in human cells and that the radiation doses required to induce this deletion reflect the sensitivity of cells to radiation.

Carcinoma, Squamous Cell↗

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↗