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Biomedical subjects

H Ojima

Publications and source records attributed to H Ojima.

At least 37 records · Page 2Linked to original sources
PubMed1999

Papillary adenoma of the distal common bile duct.

A 73-year-old man with a papillary adenoma located in the distal common bile duct is reported. He underwent pylorus-preserving pancreatoduodenectomy. The lesion in the common bile duct featured papillary proliferation of the epithelium and fibrous elements with diffuse infiltration by inflammatory cells. Positive staining for MIB-1 (Ki-67) and p53 was identified in the nuclei of the proliferative epithelium. These findings suggested the malignant potential of this lesion. Further progress in imaging diagnostic techniques should increase the frequency with which such lesions are discovered. Even now, if mural irregularities and defects are found in the extrahepatic biliary system, especially the distal common bile duct, the possibility of such borderline biliary adenoma should be taken into consideration when making a diagnosis.

Adenoma, Bile Duct↗
PubMed1998

Distribution, morphology, and gamma-aminobutyric acid immunoreactivity of horizontally projecting neurons in the macaque inferior temporal cortex.

In area TE of the macaque inferior temporal cortex, horizontal axons running parallel to the pial surface mediate interactions between laterally displaced sites across the cortex. We examined the spatial distribution and the types of cells that give rise to these horizontal axons, which are important factors in determining the nature of the lateral interactions in TE. Intracortical injections of retrograde tracers labeled columnar clusters of cells and cells diffusely scattered within TE. The clusters were 0.35 +/- 0.11 mm (mean +/- SD) in diameter and were laterally distributed up to 6 mm from the injection site. Labeled cells were found in layers 2 to 6, with only a few labeled cells seen in layer 4. The clustering of labeled cells in layers 5 and 6 was looser than that in layers 2 and 3. Intracellular staining of the retrogradely labeled cells revealed that the majority of them were typical or modified pyramidal cells, both within and between the clusters. Only a few nonpyramidal interneurons were also stained at the fringe of the tracer injection site. Consistent with these results, only a small proportion of the retrogradely labeled cells exhibited gamma-aminobutyric acid (GABA)-like immunoreactivity, mostly found within 1 mm from the injection site. The results indicate that direct horizontal interactions in TE are predominantly mediated by pyramidal or modified pyramidal cells in layers 2, 3, 5, and 6 and are primarily excitatory in nature. The contribution of GABAergic interneurons to direct horizontal interactions is restricted to only short-distance projections.

Animals↗
PubMed1998

An ultrastructural study of p75 neurotrophin receptor-immunoreactive fiber terminals in the reticular thalamic nucleus of young rats.

The reticular thalamic nucleus (RT) receives cholinergic fibers from both the basal forebrain and the brainstem. Recent studies have shown that the p75 neurotrophin receptor (p75NTR) is synthesized in cholinergic neurons in the basal forebrain but not in those in the brainstem. In this study, to identify cholinergic fibers originating from the basal forebrain, we used a monoclonal antibody against p75NTR (192-IgG) and characterized the ultrastructure of the immunoreactive fiber terminals in the rostral part of the RT in 3-week-old rats. Light microscopy revealed that p75NTR-immunoreactive fine fibers and varicosities were distributed throughout the nucleus. From electron micrographs, three types of labeled terminals were identified. The first type of labeled fiber terminals (63 out of 106) was consistently small, contained densely packed vesicles, and established asymmetrical synaptic contacts with heavy and bushy postsynaptic thickening on distal dendritic profiles; the second type (18 out of 106) established asymmetrical synaptic contacts with very slight postsynaptic thickening; and the third type (25 out of 106) of labeled terminals contained pleomorphic vesicles and established symmetrical synaptic contacts with more proximal dendritic surfaces than the first two types. In addition to the above, labeled dendritic profiles receiving non-labeled asymmetrical and symmetrical synaptic contacts were identified. These findings suggest that the basal forebrain cholinergic system establishes a variety of synaptic connections in the RT and influences cortical activity indirectly via thalamocortical pathways, as well as via direct projections to the cortex.

Animals↗
PubMed1998

Molecular heterogeneity of Vicia villosa-recognized perineuronal nets surrounding pyramidal and nonpyramidal neurons in the guinea pig cerebral cortex.

Of three monoclonal antibodies (mAbs Cat 301, 1B5 and 473) which recognize epitopes on perineuronal nets (PnNs), only mAb 473 displayed considerably varied degrees of staining intensity on Vicia villosa-labeled pyramidal (P) neurons (5%, intensely; 54%, very weakly; and 41%, unstained). These results indicate the heterogeneity on molecular structure or composition of the terminal N-acetylgalactosamine-containing PnNs within P class as well as between P and nonpyramidal classes.

Animals↗
PubMed1997

Labeling of pyramidal and nonpyramidal neurons with lectin Vicia villosa during postnatal development of the guinea pig.

Labeling of cortical neurons with a lectin, Vicia villosa (VVA), was investigated in guinea pigs aged 1 day old to adult. Lectin histochemistry revealed a perineuronal sheath, which outlined the cell bodies, apical dendrites, and axon initial segments, in distinct populations of pyramidal and nonpyramidal neurons. Their laminar positions were segregated, with the pyramidal neurons confined to layer 5 and the nonpyramidal neurons distributed mainly in layers 3-5. The VVA-labeled substance(s) was detected at the interfaces between neurons and cellular elements present in the perisynaptic region, including glial processes and fine axons. However, it was excluded from synaptic clefts of presynaptic terminals. Double immunohistochemistry revealed that most of the VVA-labeled neurons were also labeled perineuronally with a monoclonal antibody, Cat 301, and vice versa. Dendritic patterns of the VVA-labeled pyramidal neurons were studied further by intracellular injection of Lucifer yellow into fixed slices. Apical dendrites had a considerable thickness before arborizing into a few daughter branches in layer 3 or 4, suggesting a morphological resemblance to intrinsic, bursting pyramidal neurons defined physiologically in vitro. During postnatal development, there was a global spatiotemporal pattern in the onset of VVA labeling of the cortical neurons. The labeling progressed from medial and posterior cortical areas, which are closely related to the hippocampal formation, to more lateral and anterior areas, which are less closely related. The labeling patter thus tends to follow the order of the phylogenetical development of the isocortex.

Animals↗
PubMed1997

Temporal integration and duration tuning in the dorsal zone of cat auditory cortex.

The present study examined auditory cortical neurons, the responses of which depended on the duration of noise bursts. We recorded from 150 neurons with response latencies exceeding 30 msec and from 28 neurons with OFF responses to auditory stimuli in the dorsal zone of cat auditory cortex. Of 150 long-latency neurons, 132 displayed some form of duration selectivity. Seventy-eight were classified as selective for long durations. Among the long-duration-selective neurons, 30 responded only to noise burst stimuli with durations longer than a minimal threshold and were classified further as duration threshold neurons. Of 132 duration-selective neurons, 41 responded selectively to noise bursts of short duration; 13 showed maximal responses to noise bursts of a particular duration and could be regarded as duration-tuned neurons. OFF-response neurons included ones that were long-duration-selective, duration-tuned, and nonduration-selective. Duration tuning has been described previously only at the midbrain level in amphibians and bats. The present finding of sensitivity to sound duration in at least one region of cat auditory cortex indicates that this form of neural tuning may be important for hearing in all vertebrates, and for processing of sound at multiple levels in the auditory pathway. The duration tuning in the cat auditory cortex was much broader, and the best duration was distributed over a wider range than in the bat inferior colliculus. We suggest that the duration selectivity of the long-latency neurons results from integration along the time domain of a stimulus during the latent period.

Acoustic Stimulation↗
PubMed1997

Infrequent overexpression of p53 protein in Epstein-Barr virus-associated gastric carcinomas.

Epstein-Barr virus (EBV) infection was studied in a total of 412 patients with poorly differentiated gastric adenocarcinoma by in situ hybridization for EBV-encoded small RNA. EBV-specific RNA was detected in tumor cell nuclei of 83 (20.1%) of 412 gastric carcinomas, of which 60 were histologically subclassified as gastric carcinoma with lymphoid stroma (GCLS). All EBV-positive gastric carcinomas as well as 90 randomly selected EBV-negative gastric carcinomas were further studied for p53 protein expression by immunohistochemistry. The overexpression of p53 protein was demonstrated in only 7 (8.4%) of 83 EBV-positive gastric carcinomas. This was in marked contrast to the frequency of 34.4% in EBV-negative gastric carcinomas. In addition, a few p53-positive nuclei were characteristically scattered in the tumors of many EBV-positive GCLS, but this was not regarded as p53 overexpression arising from mutation of the gene. Our findings suggested that EBV-associated gastric carcinomas may arise through a different mechanism from other types of gastric carcinomas without EBV infection.

Adenocarcinoma↗
PubMed1997

Cortical convergence originating from domains representing different frequencies in the cat AI.

In order to reveal the cortical convergence, two different anterograde tracers were injected in the cat primary auditory cortex (AI). These tracers were located side by side in AI, at loci representing different best frequencies. Patches of labeled fibers were found mainly dorsal and ventral to each injection site. Patches located immediately dorsal and ventral to the injection sites did not overlap each other, but those located most distant from the injection sites overlapped significantly. Areas where the overlapping of labeled fibers were found correspond to the dorsal zone and secondary auditory field. The results suggest that the cortical convergence representing different frequency information takes place outside AI.

Animals↗
PubMed1996

Dual termination modes of corticothalamic fibers originating from pyramids of layers 5 and 6 in cat visual cortical area 17.

Terminal morphology of corticothalamic fibers originating from cat area 17 was examined. Injections of an anterograde axonal tracer, phaseolus vulgaris leucoagglutinin (PHA-L), in area 17 resulted in labeling of small boutons in the dorsal lateral geniculate, perigeniculate, and thalamic reticular nuclei and in labeling of large boutons in the lateral nucleus of lateral posterior-pulvinar, ventral lateral geniculate, and pulvinar nuclei. Since it is well known that the dorsal geniculate nucleus is a major corticothalamic target for layer 6 pyramids and the lateral posterior-pulvinar complex is that for layer 5 pyramids, the findings indicate that layer 5 pyramids in cat area 17 project axons ending with large boutons, while layer 6 pyramids project those ending with small boutons.

Animals↗
PubMed1996

Synaptic relationships between axon terminals from the mediodorsal thalamic nucleus and layer III pyramidal cells in the prelimbic cortex of the rat.

A combined study of anterograde axonal degeneration and Golgi electron microscopic technique was designed to examine the distribution and density of axon terminals from the mediodorsal thalamic nucleus (MD) over layer III pyramidal cells in the prelimbic cortex of the rat. The reconstructive analysis of serial ultrathin sections of gold-toned apical and basal dendrites of layer III pyramidal cells showed that degenerating thalamocortical axon terminals from MD formed asymmetrical synaptic contacts predominantly with dendritic spines of the identified basal dendrites as well as apical dendrites. There was little difference in the numerical density of thalamocortical synapses from MD per unit length of both apical and basal dendrites.

Animals↗
PubMed1996

Linear systems analysis of activating processes of complement system as a defense mechanism.

The complement system is an important element of the host defense mechanism, although its kinetics and characteristics as a system are still unclear. We have investigated its temporal changes and system properties from the view point of system engineering. The temporal changes of sequential activating processes of the system were expressed by 26 non-linear differential equations using reported values of rate constants and serum concentration for each component. The intermediate products in the activating processes increased parabolically while the membrane attack component as the final product, increased linearly. The little change in inactive precursors afforded validity for system linearization. Linear systems analysis revealed that the system which was insensitive to the changes in rate constants was unstable. The system became stable when the feed-back input from the final product was set to operate on the first step of the activating processes. Seven uncontrollable variables were insensitive to changes in rate constants or system optimization that minimized the changes in concentrations of components in the complement system. The singular values of the complement system were reduced and the impulse responses of the system were improved when the system was optimized. When stronger minimization was imposed on the changes of concentration of the components in the complement system, the singular values were reduced more, the magnitude of the impulse responses was depressed further and the responses terminated earlier than those when the elements in the weighting matrix of concentration of the components were set to be unity. By this potent minimization, the influences of changes in rate constants on the singular values were diminished. The present theoretical analysis is presented to evaluate the ability of defense mechanism of complement system.

Animals↗
PubMed1995

Electron microscopic evidence that axon terminals from the mediodorsal thalamic nucleus make direct synaptic contacts with callosal cells in the prelimbic cortex of the rat.

A combined study of anterograde axonal degeneration and HRP retrograde labeling has shown that there exist monosynaptic connections between afferent fibers from the mediodorsal thalamic nucleus (MD) and callosal cells in the prelimbic cortex of the rat. Degenerating axon terminals from MD made asymmetrical synaptic contacts with dendritic spines from apical dendrites of layer III pyramidal cells that were retrogradely labeled with HRP after its injection into the prelimbic cortex contralateral to MD lesions.

Afferent Pathways↗
PubMed1995

Two classes of cortical neurones labelled with Vicia villosa lectin in the guinea-pig.

Cell surface substance(s) containing terminal N-acetylgalactosamine (GaINAc) was localized in the cerebral cortex of the guinea-pig. Vicia villosa and Glycine max, both specific to GaINAc, labelled the surface of the cell body of multipolar and triangular neurones. The labelling extended to the apical dendrite and axon initial segment in the triangular neurones. They were distributed exclusively in layer 5. Most of the labelled multipolar neurones contained a calcium-binding protein, parvalbumin (Pv), while none of the triangular neurones did. The findings indicate that, in the guinea-pig, pyramidal neurones as well as non-pyramidal interneurones are enwrapped by GaINAc-containing substances and suggest that this enwrapping does not seem to be linked to Pv production.

Aging↗
PubMed1993

[Dendritic arborization patterns of interneurons labeled with a lectin, Vicia villosa, in rat cerebral cortex: studies by intracellular injection of lucifer yellow using aldehyde-fixed slices].

In order to characterize the dendritic field of a number of interneurons in the cerebral cortex, the labeling of extracellular sugar chains which define a subset of interneurons was combined with the subsequent intracellular filling of dyes in aldehyde-fixed tissue. Neurons whose cell body had been outlined by a lectin, Vicia villosa (VVA), which recognizes terminal N-acetylgalactosamine, were intracellularly injected with a fluorescent tracer, Lucifer yellow (LY), in the rat parietal cortex under direct visualization. After immunohistochemical detection of LY, somal morphology and the dendritic fields of injected neurons were reconstructed from serial sections and characterized in each of the layers II/III, IV, V and VI. Multipolar, flask-shaped and bitufted somata were VVA-positive. Multipolar neurons with round soma and spherical dendritic field were found in layers II/III, IV and V, while those with vertically elongated dendritic fields were found in layer VI. Cell bodies were located roughly in the center of the spherical or cylindrical dendritic fields. Neurons with apparently multipolar but flask- or pear-shaped soma were found frequently in layer IV, and much less frequently in layer II/III and VI. The majority of the dendrites originated from the neck portion of flask and formed a roughly spherical dendritic field with the cell body located more or less eccentrically. Some neurons in layer IV had an oval, somewhat vertically elongated soma and displayed a typical bitufted dendritic arborization pattern with vertically elongated dendritic fields. The overall dendritic field sizes of the cells gradually increased at deeper layers of the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗
PubMed1992

Ranges of dynamic motion of the wrist in healthy young and middle-aged men.

The difference in the range of dynamic motion of the wrist between young and middle-aged men was studied. To analyse wrist function easily, a new quantitative evaluation technique for wrist circumduction using a biaxial flexible electrogoniometer was introduced. A phase plane was made from two-channel signals of the electrogoniometer, and the 'ROM (range of motion) Index' for wrist circumduction was defined. Twelve healthy young men (age 19-31 years) and twelve healthy middle-aged men (age 45-63 years) were studied. Under forearm fixed conditions, there was no difference of the ROM Index between the two age groups. A significant decrease of the ROM Index in the middle-aged group was found in the non-dominant wrists without forearm fixation. The four quadrantal analysis of wrist circumduction clarified that this difference appeared especially in the radiodorsal direction. These results suggest that in the middle-aged men, the motor function involving the radiocarpal and midcarpal joints does not decrease, but that for the proximal and distal radioulnar joints in the non-dominant side drops.

Adult↗
PubMed1989

Cholinergic innervation of the rat cerebellum: qualitative and quantitative analyses of elements immunoreactive to a monoclonal antibody against choline acetyltransferase.

Cholinergic innervation of the rat cerebellum was investigated immunohistochemically by using a monoclonal antibody against choline acetyltransferase. Immunoreactive structures included: 1) a subpopulation of mossy fibers and glomerular rosettes; 2) thin varicose fibers, which were closely associated with the Purkinje cell layer and also found in the molecular layer; and 3) relatively dense networks of varicose fibers distributing in the cerebellar nuclei. Quantitative analysis indicated that a great many immunoreactive rosettes were localized in lobules IXc and X, although their density in lobule X was approximately four times that in the lobule IXc. A considerable number of immunoreactive structures were also present in all other lobules. In the hemispheres they were confined to a zone immediately beneath the Purkinje cell layer, whereas in the vermis they were scattered throughout the granular layer. Most of the immunoreactive fibers found in the molecular layer coursed toward the pial surface and were distributed within the inner half of the molecular layer. In the cerebellar nuclei, portions of the medial nucleus and magnocellular portion of the lateral nucleus had moderately dense networks of immunoreactive fibers, whereas loose networks of fibers were observed in the posterior interposed nucleus. Other parts of the cerebellar nuclei contained a smaller number of varicose fibers.

Animals↗