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Biomedical subjects

K Takei

Publications and source records attributed to K Takei.

At least 127 records · Page 7Linked to original sources
PubMed1993

[Endothelin-1-induced vasoconstriction in retinal blood vessels in the rabbit].

Endothelin-1 (ET-1) is an endothelium-derived potent vasoconstrictor peptide which is synthesized in retinal vessels. In order to investigate its effect on retinal blood vessels, we injected ET-1 intravitreally (10(-12), 3 x 10(-12), 10(-11), 3 x 10(-11), 10(-10) mole) and examined the change in diameters of retinal arteries in rabbits by fundus photography. After injection of a high dose (10(-10) mole) of ET-1, fluorescein angiography was used to investigate whether complete occlusions of retinal blood vessels occurred or not. 3 x 10(-12) mole ET-1 induced contraction of retinal arteries and the contraction of those induced by 10(-10) mole ET-1 showed complete occlusion. A medium dose (10(-11) mole) of ET-1 caused repeated vasospasms and segmental vasoconstrictions of retinal blood vessels. Fluorescein angiograms revealed that retinal blood flow was interrupted transiently by injection of a high dose (10(-10) mole) of ET-1. These findings suggested that intravitreal injection of ET-1 could provide a new model of experimental transient occlusion of retinal vessels in rabbits.

Animals↗
PubMed1993

Synaptotagmin: a membrane constituent of neuropeptide-containing large dense-core vesicles.

Synaptotagmin is known to be a major membrane protein of synaptic vesicles (SVs) in neurons. We have now used an immunoisolation procedure to demonstrate that synaptotagmin is also present in the membranes of peptide containing large dense-core vesicles (LDCVs) of rat hypothalamus and bovine posterior pituitary. Synaptotagmin bead-immunoisolated organelles from these tissues primarily consisted of SVs but contained occasionally larger structures reminiscent of LDCVs that were absent from vesicle populations immunoisolated with a synaptophysin antibody. Furthermore, the vesicles immunoisolated with synaptotagmin beads contained significant amounts of neuropeptide Y (NPY). In contrast, vesicles immunoisolated with synaptophysin beads did not contain detectable levels of NPY. Sucrose density gradient fractionation of postnuclear supernatants obtained from the bovine posterior pituitary resulted in a bimodal distribution of synaptotagmin, corresponding to the positions of both SVs and neurosecretory granules. A similar distribution was found for cytochrome b561 and the 116 kDa subunit of the vacuolar proton pump. In contrast, the SV proteins synaptophysin, SV2, and p29 were restricted to the SV-containing fractions. Immunoisolation of small and large vesicles from the sucrose gradient confirmed the differential distribution of synaptotagmin and synaptophysin in the two types of secretory vesicles in nerve endings of the posterior pituitary. We conclude that synaptotagmin is a constituent of both SVs and peptide-containing secretory vesicles in the nervous system. Since both types of organelles undergo Ca(2+)-dependent exocytosis, these findings support a general role of synaptotagmin as an exocytotic Ca2+ receptor.

Animals↗
PubMed1993

Analysis of the components of electrically evoked response using a monopolar recording technique.

PURPOSE: To assess the significance of the components of the electrically evoked response. METHODS: Twenty-three normal subjects, six patients with macular holes, and three patients with retinal artery occlusion were tested. The electrically evoked responses were recorded from an occipital electrode by applying an electric current of 0.3 mA-2.0 mA with a duration of 5 msec and a frequency of 1.85 Hz. RESULTS: In the normal subjects, three rhythmic waves (N1P1, N2P2, N3P3) were frequently found with fewer individual differences in their latencies than in flash visual evoked potentials. It was found that the amplitude of N1P1 became larger in proportion to the stimulus strength, and that the amplitudes of N2P2 and N3P3 reached their ceiling peaks. The amplitudes of N2P2 were significantly reduced in the affected eyes of patients with a unilateral complete break of the macula and branch retinal artery occlusion including the macular area. Conversely, in one patient with central retinal artery occlusion, whose visual acuity was good because the cilioretinal artery was patent, the amplitude of N1P1 was significantly reduced in the affected eye. CONCLUSIONS: N2P2 in electrically evoked response might originate mainly in the macular area. The analysis of N2P2 may be useful for further clinical applications of electrically evoked response.

Adult↗
PubMed1992

[Radiation therapy of intracranial germinoma].

The appropriate radiation dose and field for the treatment of intracranial germinoma were investigated in 33 patients. Recurrences were observed in 4 cases treated with local field irradiation only, and all of them were recognized at the margin of the radiation field or under the dose (less than 25 Gy) area. This suggests that whole cranial irradiation (dose of 25 to 30 Gy) should be added even if the tumor is solitary. The effective dose for cerebrospinal dissemination appears to be 25-35 Gy, but prophylactic CNS irradiation seems unnecessary for patients who have not undergone surgical procedures. Changes in mental status were seen in 5 patients (26.3%). Doses of over 59 Gy may be related to this complication.

Adolescent↗
PubMed1992

Exo-endocytotic recycling of synaptic vesicles in developing processes of cultured hippocampal neurons.

In mature neurons synaptic vesicles (SVs) undergo cycles of exo-endocytosis at synapses. It is currently unknown whether SV exocytosis and recycling occurs also in developing axons prior to synapse formation. To address this question, we have developed an immunocytochemical assay to reveal SV exo-endocytosis in hippocampal neurons developing in culture. In this assay antibodies directed against the lumenal domain of synaptotagmin I (Syt I), an intrinsic membrane protein of SVs, are used to reveal exposure of SV membranes at the cell surface. Addition of antibodies to the culture medium of living neurons for 1 hr at 37 degrees C resulted in their rapid and specific internalization by all neuronal processes and, particularly, by axons. Double immunofluorescence and electron microscopy immunocytochemistry indicated that the antibodies were retained within SVs in cell processes and underwent cycles of exo-endocytosis in parallel with SV membranes. In contrast, another endocytotic marker, wheat germ agglutinin, was rapidly cleared from the processes and transported to the cell body. Antibody-labeled SVs were still present in axons several days after antibody loading and became clustered at presynaptic sites in parallel with synaptogenesis. These results demonstrate that SVs undergo multiple cycles of exo-endocytosis in developing neuronal processes irrespective of the presence of synaptic contacts.

Calcium-Binding Proteins↗
PubMed1992

[An investigation of cyclosporine A (CyA) nephrotoxicity by lithium clearance].

It has been widely recognized that cyclosporine A (CyA) is useful in transplantation of the kidneys. On the other hand, the nephrotoxicity as one of its adverse effects is clinically important. There have been accumulated pieces of pathological evidence that CyA causes the renal proximal tubule damage. However, there are few reports available on the changes in the proximal tubular function. Recently, lithium clearance (CLi) has been employed to assess the proximal tubular function in CyA nephrotoxicity, because lithium ions are mainly reabsorbed throughout the proximal tubules in the same proportion as sodium and water. Several studies have already shown that long-term CyA administration results in a decrease in CLi reflecting enhanced lithium ion reabsorption. I studied, in male Sprague-Dawley rats, 1) whether short term and small dose of CyA administration which does not induce the renal tubular cell damage affects CLi and 2) the possibility that high salt intake influences CLi in CyA nephrotoxicity. Then, I divided rats into 6 groups: three groups were allowed the access to water, but the other three groups of rats were allowed to drink only saline. Group 2 and 3 were received 12.5 mg/kg and 25 mg/kg, respectively, of CyA intraperitoneally every day. As for creatinine clearance (Ccr), Ccr of group 3 (CyA 25) was the lowest, being significantly different from the other two groups. The most important result is fractional reabsorption of sodium and water in the proximal tubule. There is a significant difference between 1-A (vehicle, H2O) and 2-A (CyA 12.5, H2O), but no significant difference between 1-B (vehicle, saline) and 2-B (CyA 12.5, saline).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Ca2+ stores in Purkinje neurons: endoplasmic reticulum subcompartments demonstrated by the heterogeneous distribution of the InsP3 receptor, Ca(2+)-ATPase, and calsequestrin.

The nature of second messenger-responsive intracellular Ca2+ stores in neurons remains open for discussion. Here, we demonstrate the existence in Purkinje cells (PCs) of endoplastic reticulum (ER) subcompartments characterized by an uneven distribution of three proteins involved in Ca2+ storage and release: the inositol 1,4,5-trisphosphate (InsP3) receptor, Ca(2+)-ATPase, and calsequestrin. Ca(2+)-ATPase and the InsP3 receptor have a widespread, although not identical, distribution throughout the ER. Calsequestrin is localized throughout the smooth ER and is particularly concentrated in pleiomorphic vesicles with a moderately electron-dense core, which appear to represent a subcompartment of the smooth ER. In double-labeling experiments many of these vesicles were unlabeled by InsP3 receptor antibodies. These results suggest a key role of the ER as an intracellular Ca2+ store and demonstrate a possible structural basis for distinct intracellular Ca2+ pools regulated by different second messengers.

Animals↗
PubMed1992

[Electrically evoked responses in patients with macular holes].

The Electrically Evoked Response (EER) was analyzed in 7 patients with macular holes in order to determine whether EER reflects macular function. The EER was recorded from an occipital electrode (Oz) by applying a constant electric current of 1.0 mA with a duration of 5 msec and frequency of 1.85 Hz. In five patients with unilateral complete break of macula, each amplitude for the P2 component from the affected eyes was significantly smaller than that from contralateral eyes. However there was no such difference in both eyes of two patients with bilateral macular holes. No significant difference was shown in the amplitude for the P1 and P3 components of EER. These results strongly suggest that the retinal origin of P2 may mainly be in the macular area and that analysis of P2 might be useful to determine further clinical applications of EER.

Aged↗
PubMed1991

GABA and pancreatic beta-cells: colocalization of glutamic acid decarboxylase (GAD) and GABA with synaptic-like microvesicles suggests their role in GABA storage and secretion.

GABA, a major inhibitory neurotransmitter of the brain, is also present at high concentration in pancreatic islets. Current evidence suggests that within islets GABA is secreted from beta-cells and regulates the function of mantle cells (alpha- and delta-cells). In the nervous system GABA is stored in, and secreted from, synaptic vesicles. The mechanism of GABA secretion from beta-cells remains to be elucidated. Recently the existence of synaptic-like microvesicles has been demonstrated in some peptide-secreting endocrine cells. The function of these vesicles is so far unknown. The proposed paracrine action of GABA in pancreatic islets makes beta-cells a useful model system to explore the possibility that synaptic-like microvesicles, like synaptic vesicles, are involved in the storage and release of non-peptide neurotransmitters. We report here the presence of synaptic-like microvesicles in beta-cells and in beta-cells. Some beta-cells in culture were found to extend neurite-like processes. When these were present, synaptic-like microvesicles were particularly concentrated in their distal portions. The GABA synthesizing enzyme, glutamic acid decarboxylase (GAD), was found to be localized around synaptic-like microvesicles. This was similar to the localization of GAD around synaptic vesicles in GABA-secreting neurons. GABA immunoreactivity was found to be concentrated in regions of beta-cells which were enriched in synaptic-like microvesicles. These findings suggest that in beta-cells synaptic-like microvesicles are storage organelles for GABA and support the hypothesis that storage of non-peptide signal molecules destined for secretion might be a general feature of synaptic-like microvesicles of endocrine cells.

Animals↗
PubMed1991

Association of Rab3A with synaptic vesicles at late stages of the secretory pathway.

Rab3A is a small GTP-binding protein highly concentrated on synaptic vesicles. Like other small GTP-binding proteins it is thought to cycle between a soluble and a membrane-associated state. To determine at which stage of the life cycle of synaptic vesicles rab3A is associated with their membranes, the localization of the protein in neurons and neuroendocrine cells at different developmental and functional stages was investigated. In all cases, rab3A was colocalized with synaptic vesicle markers at the cell periphery, but was absent from the Golgi area, suggesting that rab3A associates with vesicles distally to the Golgi complex and dissociates from vesicle membranes before they recycle to this region. Immunofluorescence experiments carried out on frog motor end plates demonstrated that massive exocytosis of synaptic vesicles is accompanied by a translocation of rab3A to the cell surface. The selective localization of rab3A on synaptic vesicles at stages preceding their fusion with the plasmalemma suggests that the protein is part of a regulatory machinery that is assembled onto the vesicles in preparation for exocytosis.

Animals↗
PubMed1991

Nuclear membrane antigen specific to nerve and muscle tissues.

A monoclonal antibody, 2F7, raised against a nuclear protein subfraction recognized the nuclear membrane of nervous and muscular tissues of guinea pig, rat and rabbit, but no other tissue was stained. In the nervous system, both neurons and glial cells were labelled. An electron microscopic immunohistochemical study demonstrated that 2F7 antibody labelled the inner surface of the nuclear membrane. Western blot analysis on the nuclear envelope fraction containing nuclear lamina revealed that this antibody reacted to two minor component proteins of 80 and 82KDa. These 2F7 antigens expressed preferentially in the nervous and muscular tissues were distinct from the major nuclear envelope proteins reported so far and might be related to neuronal or muscular tissue-specific functions.

Animals↗
PubMed1991

[Comparison of electrically evoked response (EER) and visual evoked potential (VEP) by topography and dipole-tracing].

To study the possibility of the clinical application of the electrically evoked response (EER) of the visual system, we analyzed P2 of EER as well as P100 of flash VEP by means of topography and dipole-tracing. By applying a constant electric current of 1.0 mA (duration 5 msec, frequency 1.39 Hz) and a strobo flash light of 0.6 Joules (frequency 1.39 Hz) to each eye, P2 and P100 were recorded respectively. It was found that the source generators of P2 and P100 showed the same localization and dipole vector. The results indicated flat the significance of P2 in applying EER clinically was comparable to the P100 of VEP.

Adult↗
PubMed1990

P29: a novel tyrosine-phosphorylated membrane protein present in small clear vesicles of neurons and endocrine cells.

A novel membrane protein from rat brain synaptic vesicles with an apparent 29,000 Mr (p29) was characterized. Using monospecific polyclonal antibodies, the distribution of p29 was studied in a variety of tissues by light and electron microscopy and immunoblot analysis. Within the nervous system, p29 was present in virtually all nerve terminals. It was selectively associated with small synaptic vesicles and a perinuclear region corresponding to the area of the Golgi complex. P29 was not detected in any other subcellular organelles including large dense-core vesicles. The distribution of p29 in various subcellular fractions from rat brain was very similar to that of synaptophysin and synaptobrevin. The highest enrichment occurred in purified small synaptic vesicles. Outside the nervous system, p29 was found only in endocrine cell types specialized for peptide hormone secretion. In these cells, p29 had a distribution very similar to that of synaptophysin. It was associated with microvesicles of heterogeneous size and shape that are primarily concentrated in the centrosomal-Golgi complex area. Secretory granules were mostly unlabeled, but their membrane occasionally contained small labeled evaginations. Immunoisolation of subcellular organelles from undifferentiated PC12 cells with antisynaptophysin antibodies led to a concomitant enrichment of p29, synaptobrevin, and synaptophysin, further supporting a colocalization of all three proteins. P29 has an isoelectric point of approximately 5.0 and is not N-glycosylated. It is an integral membrane protein and all antibody binding sites are exposed on the cytoplasmic side of the vesicles. Two monoclonal antibodies raised against p29 cross reacted with synaptophysin, indicating the presence of related epitopes. P29, like synaptophysin, was phosphorylated on tyrosine residues by endogenous tyrosine kinase activity in intact vesicles.

Animals↗
PubMed1990

Xenogeneic neural transplantation: role of vasculature and MHC antigen in immunological rejection.

The reconstruction of blood vessels in a graft is one of the important events inducing immunological rejection. First, we investigated the reconstruction of blood vessels in a graft by using a monoclonal antibody against mouse endothelial surface antigen 1. Secondly, the lymphocyte proliferative response to Ia antigen were examined in mixed lymphocyte cultures by using monoclonal antibodies against Ia antigen. The results show that the blood vessels originating in the host tissue inoculate with those originating in the donor graft tissue and that the expression of Ia antigen on the vascular endothelial cells plays an important role in the immunological rejection through sensitization of peripheral lymphocytes.

Animals↗
PubMed1990

[The management of drooling in patients with cerebral palsy--submandibular duct relocation].

Drooling is a significant problem demonstrated by individuals of all ages with a variety of etiologies such as neurological disorders, cerebral palsy, mental retardation and others. Persistent drooling not only creates troublesome hygienic problems for patients, teachers, nurses, and playmates because of the constant soiling of clothes, toys, and work materials, but also causes an odor from their clothing and bibs. The older patient with normal cognition is disturbed by the drooling and may become depressed and reclusive. Successful management of drooling alleviates these problems, improves appearance and self-esteem and significantly reduces the time involved in the care of the sufferers. The author, who had studied at the University of Toronto for 2 years, acquired the technique of submandibular duct relocation under the guidance of Dr. Crysdale. We carried out the surgical procedure of submandibular duct relocation for drooling on six patients who had cerebral palsy. The surgical procedure resulted in a dramatic decrease in drooling and odor levels. All of them improved in appearance, and the time involved in the care of the suffers was significantly reduced. The complication of ranula, however, appeared in two cases, which suggested a much higher frequency than that in the report of Crysdale. It seems that a detailed explanation to parents and teachers about the advantages and disadvantages of submandibular duct relocation is important.

Cerebral Palsy↗