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Biomedical subjects

T Ohmoto

Publications and source records attributed to T Ohmoto.

At least 127 records · Page 7Linked to original sources
PubMed1996

Chromaffin cell survival from both young and old donors is enhanced by co-grafts of polymer-encapsulated human NGF-secreting cells.

Following polymer-encapsulation, human nerve growth factor-secreting baby hamster kidney fibroblasts (BHK-hNGF) were implanted into the striatum of hemiparkinsonian rats together with unencapsulated adrenal medullary chromaffin cells from either young (2 weeks) or old (12 months) donor rats. Animals receiving both BHK-hNGF cells and chromaffin cells exhibited significant decreases (39-56%) in apomorphine-induced rotational behaviour which was equivalent regardless of the age of the donor tissue. Histological analysis revealed that while survival of chromaffin cells without hNGF support was poor, co-grafts of adrenal medulla and BHK/hNGF cells increased chromaffin cell survival by 20 times. Again, this effect was independent of the age of the donor tissue. Retrieved capsules contained numerous viable encapsulated BHK-hNGF cells which continued to release hNGF. These results further indicate the potential use of intrastriatal implantation of encapsulated hNGF-secreting cells for augmenting the survival of co-grafted chromaffin cells as well as promoting the functional recovery of hemiparkinsonian rats.

Age Factors↗
PubMed1996

Genetic evidence for the functional redundancy of the calcineurin- and Mpk1-mediated pathways in the regulation of cellular events important for growth in Saccharomyces cerevisiae.

Saccharomyces cerevisiae mutants which exhibit phenotypes (calcium resistance and vanadate sensitivity) similar to those of calcineurin-deficient mutants were isolated. The mutants were classified into four complementation groups (crv1,2,3 and 4). Crv1 was allelic to cnb1, a mutation in the regulatory subunit of calcineurin. The nucleotide sequences of CRV2 and CRV3 genes which complemented the crv2 and crv3 mutations, respectively, are identical to those of BCK1/SLK1/SKC1/SSP31 and MPK1/SLT2, respectively, which are both involved in the MAP kinase cascade. A calcineurin-deletion mutation (delta cnb1), which by itself has no detectable effect on growth and morphology, enhanced some phenotypes (slow growth and morphological abnormality) of crv2 and crv3 mutants. These phenotypes of crv2 and crv3 mutants were partially suppressed by Ca2+ or by overproduction of the calcineurin subunits (Cmp2 and Cnb1). Like the calcineurin-deficient mutant, crv2 and crv3 mutants were defective in recovery from alpha-factor-induced growth arrest. The defect in recovery of the delta cnb1 mutant was suppressed by overexpression of MPK1. These results indicated that the calcineurin-mediated and the Mpk1- (Bck1-) mediated signaling pathways act in parallel to regulate functionally redundant cellular events important for growth.

Calcineurin↗
PubMed1996

Neural transplantation and trophic factors in Parkinson's disease: special reference to chromaffin cell grafting, NGF support from pretransected peripheral nerve, and encapsulated dopamine-secreting cell grafting.

Since adrenal medullary chromaffin cells produce catecholamines as wel l as several kinds of neurotrophic factors which affect dopamine neurons, the authors have investigated the methods to increase the survival of grafted chromaffin cells in parkinsonian model animals. Measurement of nerve growth factor (NGF) showed that NGF level at the distal stump of the pretransected peripheral nerve increased significantly, thus, we have applied cografting of chromaffin cells with this stump of the peripheral nerve to animal models of Parkinson's disease since chromaffin cell survival have been reported to be increased by supplementation of nerve growth factor (NGF) in vitro and in vivo. By this cografting approach, not only the chromaffin cell survival but also the host intrinsic dopaminergic system recovery were enhanced. This effect continued 2 years in our long-term study The effects of donor and host ages were investigated and the results showed that the effects were more prominent when young donors or hosts were used compared with aging donors or hosts. Although cografting of adrenal medulla with peripheral nerve was applied successfully in parkinsonian patients with favorable results, it may be difficult to apply this procedure in aged patients since this is autografting and adrenal medulla itself may be affected by the disease in aged patients. Polymer-encapsulated dopamine-secreting cells are another donor candidates and can be applied combined with stereotaxic thalamotomy or pallidotomy for the patients with Parkinson's disease in the near future.

Age Factors↗
PubMed1996

Histological analysis of microencapsulated dopamine-secreting cells in agarose/poly(styrene sulfonic acid) mixed gel xenotransplanted into the brain.

PC12 cells were encapsulated within agarose/poly-(styrene sulfonic acid) (agarose/PSSa) mixed gel and xenotransplanted into the brains of guinea pigs. The immunoprotection capability and biocompatibility of the agarose/PSSa microcapsules were evaluated. Tyrosine hydroxylase-positive PC12 cells within the microcapsules were observed in all guinea pigs at least 5 weeks after transplantation. PC12 cells had a relatively uniform small size and occasionally formed cell clusters; however, cell necrosis was not apparent. The host reaction to agarose/PSSa microcapsules was minimal. The degree of glial fibrillary acidic protein-positive astrocyte density around the microcapsules was similar to that around the injection tracks. Necrosis around the brain/microcapsule interface was not apparent as assessed by Nissl staining. Normal-appearing neurons were observed in close vicinity to the capsule. High-performance liquid chromatography with electrochemical detection showed basal and potassium-evoked release of dopamine from the PC12 cell-enclosed microcapsules in vitro. We conclude that encapsulation using agarose/PSSa mixed gel can not only isolate the enclosed cells from the host immune system but can also allow diffusional exchange of nutrients and neurotransmitters. Encapsulation using agarose/PSSa mixed gel may expand the range of donor tissues for neural transplantation.

Animals↗
PubMed1996

The relationship between brain surface elastance and brain reexpansion after evacuation of chronic subdural hematoma.

BACKGROUND: Brain stiffness has been thought to be a factor affecting brain re-expansion after the evacuation of chronic subdural hematoma. METHODS: As an index of brain stiffness, the pressure for compressing the brain using an ophthalmodynamometer was defined as brain-surface elastance. This elastance in 14 patients was measured and analyzed in relation to brain re-expansion. RESULTS: Patients with an enlarged subdural space on computed tomography 1 month after the operation had higher elastance. There was a correlation between high elastance and high age. CONCLUSIONS: Measuring the elastance after evacuation of the hematoma may help predict the persistence of a subdural space.

Aged↗
PubMed1996

Actions of picrodendrin antagonists on dieldrin-sensitive and -resistant Drosophila GABA receptors.

1. A series of terpenoid compounds, recently isolated from Picrodendron baccatum, share a picrotoxane skeleton with picrotoxinin, an antagonist of ionotropic GABA receptors. Referred to as picrodendrins, they inhibit the binding of [35S]-tert-butylbicyclophosphorothionate (TBPS) to rat GABAA receptors. Hitherto, their effects on GABA receptors have not been investigated electrophysiologically. Under two-electrode voltage-clamp, the actions of picrodendrins and related terpenoids have been assayed on homooligomeric GABA receptors formed by the expression of a Drosophila GABA receptor subunit (RDLac) in Xenopus oocytes. 2. All the terpenoids tested, dose-dependently antagonized currents induced by 30 microM (EC50) GABA. 3. Tutin and its analogues (dihydrotutin and isohyenanchin) differ in the structure of their axial C4 substituents. Of these compounds, tutin, which bears an isopropenyl group at this carbon atom, was the most potent antagonist of RDLac homo-oligomers, whereas isohyenanchin, which bears a hydroxyisopropyl group, was the least potent antagonist tested. 4. Picrodendrins differ mainly in the structure of their C9 substituents. The IC50s of picrodendrins ranged from 17 +/- 1.3 nM (picrodendrin-Q) to 1006 +/- 1.3 nM (picrodendrin-O). As such, the most potent picrodendrins (Q, A and B) were approximately equipotent with picrotoxinin as antagonists of RDLac homo-oligomers. 5. Certain picrodendrin compounds effected a use-dependent blockade of RDLac homo-oligomers. Such a biphasic block was not observed with tutin analogues. 6. Picrotoxin-resistant RDLacA3025 homo-oligomers, which have a single amino acid substitution (A302S) in the 2nd transmembrane region, were markedly less sensitive to picrodendrin-O than the wild-type, dieldrin-sensitive, homo-oligomers. 7. The relative potency of tutin analogues demonstrates that the structure-activity relationship of the C4 substituent of picrotoxane-based compounds is conserved in vertebrates and insects. However, the relative order of potency of picrodendrins on RDLac homo-oligomers is distinctly different from that observed in previous radioligand binding studies performed on vertebrate GABAA receptors. As picrodendrin compounds differ in the structure of their C9 substituents, these data suggest that the optimal convulsant pharmacophores of vertebrate GABAA receptors and RDLac homo-oligomers differ with respect to this substituent.

Animals↗
PubMed1996

Role of extracellular matrix in experimental vasospasm. Inhibitory effect of antisense oligonucleotide on collagen induction.

BACKGROUND AND PURPOSE: Although it has been suggested that collagen plays a role in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage, there has been no constructive research to prove it directly. In this study we stopped the transcription of the procollagen type I gene by introducing antisense oligonucleotides for its mRNA in a rat femoral artery model of vasospasm induced by blood and assayed the changes in the vasoconstrictive activity of the vessel and expression of the procollagen mRNA. METHODS: We applied antisense, sense, or missense oligonucleotides, located at the carboxyl propeptide region for alpha 1(I) procollagen mRNA, onto the femoral artery in a rat femoral artery model of vasospasm. The diameter of the artery was measured by angiography. The transcription level of the procollagen gene in the arterial tissue was assayed by use of reverse transcription-polymerase chain reaction. Morphological change in the artery was observed with aldehyde-fuchsin-Masson-Goldner staining. RESULTS: In the model, when the artery was exposed to antisense oligonucleotides in pluronic gel for 5 days to prevent arterial contraction, the contraction was inhibited at a significant level (76.0% +/- 5.6) when compared with that in control experiments using sense oligonucleotides (64.0% +/- 2.4), missense oligonucleotides (63.5% +/- 3.5), or gel alone (62.1% +/- 5.8). The application of antisense oligonucleotide resulted in a marked decrease in alpha 1(I) procollagen mRNA expression as determined by polymerase chain reaction, indicating that the collagen reduction by antisense oligonucleotides occurred at the transcription level. Histological staining suggested that collagen accumulation at the site in the artery where antisense oligonucleotide had been administered was indeed less than that in the control artery. CONCLUSIONS: The results indicate that the induction of procollagen type 1 could cause pathogenesis of the arterial contraction induced by blood in a rat femoral vasospasm model.

Animals↗
PubMed1996

Chromaffin cell survival and host dopaminergic fiber recovery in a patient with Parkinson's disease treated by cografts of adrenal medulla and pretransected peripheral nerve. Case report.

A 55-year-old woman with severe Parkinson's disease was treated by cografting adrenal medulla with pretransected peripheral nerve into the bilateral caudate nuclei. The patient showed modest improvement of her akinesia; this effect persisted for 1 year after transplantation, when she suddenly died from upper gastrointestinal bleeding unrelated to the grafting procedure. At autopsy, a large number of tyrosine hydroxylase-immunoreactive chromaffin cells were observed within the caudate graft sites and a dense network of host dopaminergic fibers was visualized. This autopsy finding is very important for the field of experimental and clinical chromaffin cell grafting because it is the first evidence that cografts using pretransected peripheral nerve might enhance the survival of chromaffin cells and the recovery of host dopaminergic fibers in humans suffering from Parkinson's disease.

Adrenal Medulla↗
PubMed1996

Cografting with polymer-encapsulated human nerve growth factor-secreting cells and chromaffin cell survival and behavioral recovery in hemiparkinsonian rats.

Encapsulated cell grafting is one approach for the delivery of neurotransmitters and/or neurotrophic factors to the brain. Baby hamster kidney (BHK) cells were genetically modified to secrete high levels of human nerve growth factor (hNGF). Following polymer encapsulation, these cells were implanted into the left lateral ventricle or the left striatum 1.5 mm away from striatally cografted unencapsulated adrenal medullary chromaffin cells in hemiparkinsonian rats. Although the animals receiving adrenal medulla alone or adrenal medulla with intraventricular hNGF-secreting cell grafting did not show recovery of apomorphine-induced rotational behavior, the animals receiving adrenal medulla with intrastriatal hNGF-secreting cell implants showed a significant recovery of rotational behavior 2 and 4 weeks after transplantation. Histological analysis revealed that in animals receiving adrenal medulla with intraventricular hNGF-secreting cell grafting, the number of tyrosine hydroxylase-immunoreactive (TH-IR) surviving chromaffin cells tended to be higher (approximately five to six times) than in animals receiving adrenal medulla alone; however, this increase did not reach statistical significance. In contrast, in animals receiving adrenal medullary cells together with intrastriatal hNGF-secreting cells, the number of TH-IR surviving chromaffin cells was more than 20 times higher than that in animals receiving adrenal medullary cells alone. Analysis of retrieved capsules revealed that hNGF continued to be released by encapsulated BHK-hNGF cells after 4 weeks in vivo. Moreover, histological analysis confirmed the presence of numerous viable encapsulated BHK-hNGF cells. These results indicate the potential use of intrastriatal implantation of encapsulated hNGF-secreting cells for augmenting the survival of cografted chromaffin cells as well as promoting the functional recovery of hemiparkinsonian rats. These data indicate that this approach may have potential application for treating Parkinson's disease.

Animals↗
PubMed1996

Inhibition of vascular contraction by intracisternal administration of preproendothelin-1 mRNA antisense oligoDNA in a rat experimental vasospasm model.

To clarify the role of endothelin-1 (ET-1) in the etiology of hemolysate-induced contraction of vessels, the authors introduced antisense oligoDNA for preproendothelin-1 (ppET-1) messenger RNA in a rat model of vasospasm. Phosphorothioate antisense oligoDNAs for ppET-1 were injected into the cisterna magna. Fluorescein isothiocyanate-labeled phosphorothioate antisense oligoDNAs were proven by fluorescence chasing to be incorporated into the vascular wall. Striking inhibitory effects of experimental vasospasm were observed in the basilar artery (BA) in which the oligoDNAs were injected. The vascular contraction was significantly inhibited by oligoDNAs after 20 minutes of hemolysate exposure, which suggested that ET synthesis started approximately 20 minutes after hemolysate stimulation. Expression of ppET-1 in the BA in which the spasm was inhibited was markedly suppressed at the transcription level. The results indicate that ET-1 may play an important role in hemolysate-induced vasoconstriction in rats. In addition, the antisense approach in the cerebrospinal fluid might be a useful tool for preventing cerebral vasospasm.

Animals↗
PubMed1996

[Encapsulated dopamine-secreting cells transplanted into the brain: a possible therapy for Parkinson's disease].

Encapsulation of neurosecretory cells within a semipermeable membrane may possibly isolate the enclosed cells from the host immune system and allow inward diffusion of nutrients and outward diffusion of neurotransmitters. Moreover, the encapsulation procedure may prevent the tumor formation of enclosed cells, when they are derived from tumor cells. In the present study, PC12 cells, a dopaminergic cell line derived from a rat pheochromocytoma, were enclosed within an agarose/poly (styrene sulfonic acid) (agarose/PSSa) mixture and transplanted into the brains of rats (allogeneic transplantation) or guinea pigs (xenogeneic transplantation). Tyrosine hydroxylase (TH) immunoreactive PC12 cells within the microcapsules were observed in all rats and guinea pigs at least up to five weeks after transplantation. PC12 cells were round in shape and of relatively uniform small size. Although PC12 cells occasionally formed cell clusters, the formation of a tumor was not observed. The host reaction to agarose/PSSa microcapsules was minimum. The degree of glial fibrillary acidic protein (GFAP) positive astrocyte density around the microcapsules was similar to that around injection tracks. There was no apparent immunological rejection around the capsules. High-performance liquid chromatography with electrochemical detection (HPLC-EC) showed basal and potassium-evoked release of dopamine from the PC12 cell-enclosed microcapsules in vitro. Although our data is preliminary, we believe that agarose/PSSa microcapsules are promising for producing semipermeable membranes that enable allo-and xenotransplantation of neurosecretory cells into the brain in the absence of systemic immunosuppression. This approach is expected to be applied in Parkinson's disease in the near future.

Adrenal Gland Neoplasms↗
PubMed1996

[Usefulness of neoadjuvant brachytherapy in the treatment of pineoblastoma: a case report].

The treatment strategy and prognosis of pineal cell tumors are still subjects of debate because of their rarity and the mixture of pineoblastoma and pineocytoma as components. Pineoblastoma is believed to be the more malignant tumor and total gross resection of this tumor is very difficult because of its invasive tendency and location. Although the effectiveness of external irradiation and chemotherapy has been reported, the outlook for patients with this tumor is extremely poor. We treated a case of pineoblastoma with a single total resection nine months after interstitial irradiation and chemotherapy. In this case, brachytherapy was successful as neoadjuvant therapy for decreasing the tumor's volume and clarifying its boundary. The patient was a 36-year-old woman who had complained of occipital headache for about a month. On admission, neurological examination revealed bilateral papilloedema but, otherwise, there were no deficits. A magnetic resonance image (MRI) showed a homogeneously enhanced tumor in the pineal region and obstructive hydrocephalus. Two weeks after ventriculo-peritoneal shunting, a stereotactic needle biopsy was performed using a BRW MRI-guided stereotactic apparatus, and three catheters for interstitial brachytherapy were implanted into the tumor through the biopsy tract. Iridium-192 seeds were inserted through the catheters and kept there for 8 days to irradiate 40 Gy at the tumor periphery. Four courses of chemotherapy with carboplatin (400 mg/m2) and VP-16 (400 mg/m2) were administered after brachytherapy. Repeat MRI scans every month showed a gradual regression of tumor volume. However, the tumor did not disappear and no further decrease in tumor volume was observed 8 months after brachytherapy. A suboccipital craniotomy was performed 9 months after brachytherapy and en bloc tumor resection was achieved readily via an infratentorial supracerebellar approach. After receiving another course of chemotherapy and external irradiation at 40 Gy, the patient was discharged without any symptoms and no residual tumor or recurrence was observed for 24 months after brachytherapy and 15 months after surgery. The clinical course of this case suggests that a combination of stereotactic biopsy and brachytherapy with chemotherapy followed by surgery may be a good strategy for the treatment of pineal cell tumors regardless of their histopathological features.

Adult↗
PubMed1996

[Topographic organization of the ventral striatum afferent projection from amygdaloid complex and hippocampal formation].

The organization of the striatal afferent fibers from the amygdaloid complex and hippocampal formation was studied in the monkey with particular emphasis on specific projections of the ventral striatum. Retrograde tracers were injected into the different regions of the ventral (limbic) striatum and dorsolateral (sensorimotor) striatum. Labeled neurons were observed in the various regions of the amygdaloid complex and hippocampal formation. The medial ventral striatum received dense projections from the amygdala (the basal nucleus and the magnocellular division of the accessory basal nucleus), and the hippocampus (subiculum, CA1 and CA3). The shell of the nucleus accumbens (calbindin-D28k negative region) also received dense projections from the amygdala (the basal nucleus and the magnocellular division of the accessory basal nucleus), and the hippocampus (subiculum). The injections into the core of the nucleus accumbens showed scattered labeled neurons in the amygdala, and only a few labeled neurons in the hippocampus. The lateral ventral striatum received few inputs from the amygdala and hippocampus. In contrast to the ventral striatum, the dorsolateral striatum received no projection from the amygdala or the hippocampus. The connectional similarities between the medial ventral striatum and the shell of the nucleus accumbens suggest that although the medial ventral striatum is not calbindin-D28k negative, it may be regarded as a transitional zone between the shell and the rest of the ventral striatum.

Amygdala↗
PubMed1996

Malignant astrocytomas with homozygous CDKN2/p16 gene deletions have higher Ki-67 proliferation indices.

p16 is involved in a cell-cycle regulatory cascade that includes cyclin-dependent kinase 4 (cdk4), cyclin D1 and pRb. Alterations of each of these components have been described in primary human glioblastoma multiforme (GBM) or GBM cell lines, and alterations of the individual components of this pathway appear inversely correlated with one another. While this suggests that disruption of any individual component has similar oncogenic effects, homozygous deletions of the CDKN2/p16 gene are the most common genetic alteration. We investigated the relationship between homozygous CDKN2/ p16 deletions and cellular proliferation in 50 primary astrocytomas (2 WHO grade I pilocytic astrocytoma, 15 grade II astrocytomas, 20 grade III anaplastic astrocytomas and 13 grade IV GBMs). Using a comparative multiplex PCR assay, homozygous deletions of the CDKN2/p16 gene were detected in 5 anaplastic astrocytomas (25%) and 6 GBMs (46%), but in none of the lower-grade tumors. Ki-67 immunohistochemistry was used to assess the number of proliferating cells in the same samples used for molecular genetic analysis. In both anaplastic astrocytomas and GBMs, Ki-67 proliferation indices were significantly higher in tumors with CDKN2/p16 deletions (20%) than in those without deletions (10%; p = 0.0001). These results suggest that homozygous CDKN2/p16 deletions in high-grade astrocytomas may have a more deleterious effect on cell cycle control than the other aberrations in the p16-cdk4-cyclin D1-pRb pathway, and may provide one explanation for why homozygous CDKN2/p16 deletions are more common genetic events in high-grade astrocytomas than RB mutations or CDK4 amplification.

Adult↗
PubMed1995

Cloning and characterization of the Saccharomyces cerevisiae SVS1 gene which encodes a serine- and threonine-rich protein required for vanadate resistance.

A novel Saccharomyces cerevisiae (Sc) SVS1 gene was cloned as a multicopy suppressor of vanadate (Vn) sensitivity (VnS) due to a calcineurin (CaN) null mutation. SVS1 encoded a 260-amino-acid protein abundant in Ser and Thr residues, with a putative signal sequence at the N terminus. Deletion of SVS1 resulted in increased sensitivity to Vn, but not to other metallic ions or drugs. Northern analysis of the SVS1 mRNA indicated that the induction of the gene occurred specifically in the response to Vn. These results suggested that Sc has a mechanism to enhance the tolerance to Vn by increasing the expression of SVS1. The results of genetic experiments suggested that CaN and the Svs1 proteins act in separate pathways to enhance the tolerance to Vn.

Amino Acid Sequence↗
PubMed1995

Expression of Cu,Zn-superoxide dismutase mRNA after cold and contusion injury in the rat brain.

We analyzed the expression of Cu,Zn-superoxide dismutase (SOD) mRNA in both contusion and cold injury. Twenty-three rats were divided into 3 groups: a control group, a contusion group, and a cold injury group. Six hours after the injury, the rats were decapitated and the gray matter was resected from 3 portions: the core of the injured cortex, its periphery, and a distal portion on the non-lesion side. Based on the specific gravity of each sample, almost the same degree of edema developed in both injury groups. The mRNA expression in the cold injury group, however, significantly decreased in all portions. The extremely low temperature associated with cold injury is a possible cause of the decrease in Cu,Zn-SOD mRNA.

Animals↗
PubMed1995

Neovascularization of rat fetal neocortical grafts transplanted into a previously prepared cavity in the cerebral cortex: a three-dimensional morphological study using the scanning electron microscope.

Neovascularization within syngeneic rat fetal neocortical grafts transplanted into a previously prepared cavity in the cerebral cortex was studied 1 to 3 months after transplantation, utilizing scanning electron microscopy of vascular corrosion casts. The grafts were easily identified and the outer surface of the grafts, especially at the host-graft interface, was surrounded by large regenerated vessels of leptomeninges and connective tissue (e.g. dura). Large vessels originating from the choroid plexus also coated the grafts in animals whose lateral ventricles had been opened at the time of cavitation. These large regenerated vessels were mainly observed on the surface of the grafts, and they ramified markedly to form capillary networks in the vicinity of the host-graft interface. Occasionally several relatively large regenerated vessels were noted to extend into the grafts, and to ramify and connect with graft capillary networks having the same features as that of the host brain. Moreover, direct vascular connections between host capillaries and those within the grafts were observed. In some animals, arteries and arterioles which fed the grafts were identified in the perimeter of the grafts with their characteristic morphology. The interior microvasculature structure of the grafts was largely composed of the capillary network of graft origin, and of several relatively large penetrating vessels originating from the regenerated leptomeningeal vessels or the vessels of the choroid plexus. The present study demonstrated that the blood supply to the solid grafts transplanted into the previously prepared cavities originated primarily from the regenerated host vessels. These host vessels perfused the intrinsic graft vessels via new anastomoses which formed predominantly at the host-graft interface.

Animals↗