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S Shimohama

Publications and source records attributed to S Shimohama.

At least 145 records · Page 8Linked to original sources
PubMed1993

Changes in protein kinase C isozymes in the rat hippocampus following transient hypoxia.

The effects of hypoxia on protein kinase C (PKC) isozymes (alpha, beta I, beta II, and gamma) were examined in the hippocampus from rats subjected to hypoxic conditions (5% O2 in 95% N2) for 30 min in a chamber. Western blot analysis revealed that the total amounts of PKC-alpha (-26.0% of control) and -gamma (-32.7% of control) were decreased significantly at the end of hypoxia, which was followed by the reduction of that of PKC-beta II (-23.7% of control at 7 days after hypoxia). Whereas, the PKC activities, which were measured by the incorporation of [gamma-32P] into a specific PKC substrate peptide, in both the cytosolic and the particulate fractions did not change. The reductions of PKC-gamma and -alpha at the end of hypoxia may be related to the following neuronal degeneration.

Animals↗
PubMed1993

Reduction of low-molecular-weight acid phosphatase activity in Alzheimer brains.

Recent studies in Alzheimer brains have shown aberrant protein phosphorylation, suggesting an alteration in protein kinases and/or phosphoprotein phosphatases. In the present study, the activity of acid phosphatase was investigated in samples prepared from postmortem normal human and Alzheimer brains. p-Nitrophenyl phosphate, a nonprotein phosphoester, was used as a substrate for acid phosphatase. The separation profile on Sephadex G-100 gel filtration chromatography revealed that two major forms of high-molecular-weight and low-molecular-weight acid phosphatase were present in the crude extracts of both rat and human brains. Another class of zinc ion (Zn2+)-dependent acid p-nitrophenyl phosphatase was also detected in rat and human brains. In Alzheimer brains, the low-molecular-weight acid phosphatase activity was significantly decreased compared to that in control brains; however, the high-molecular-weight and Zn(2+)-dependent acid phosphatase activity in control and Alzheimer brains was not different. These results suggest that reduced activity of the low-molecular-weight acid phosphatase, which possesses phosphotyrosine protein phosphatase activity, might be linked to aberrant protein tyrosine phosphorylation found in Alzheimer brains.

Acid Phosphatase↗
PubMed1993

Changes in protein kinase C isozymes in the rat hippocampal formation following hippocampal lesion.

The cellular and regional distribution of the four protein kinase C (PKC) isoforms in the rat hippocampal formation and the response of PKC to lesions were determined by employing immunohistochemical and immunochemical techniques with antibodies specific to PKC(alpha), -(beta I), -(beta II), and -(gamma). PKC(alpha) intensely stained the periphery of the pyramidal cell in the stratum pyramidale. The granule cells, glial cells, and mossy fibers were anti-PKC(alpha) negative. The cytoplasm, axons, and dendrites of basket cells and interneurons in the hilus were labeled with anti-PKC(alpha). Anti-PKC(beta I) immunoreactivity was localized on the periphery of pyramidal cells and interneurons of the hilus, as well as the oriens, radiatum, and molecular layers of the CA regions. Anti-PKC(beta II) immunoreactivity was mainly cytoplasmic, extending into the dendrites in the hippocampal pyramidal cells and the dentate granule cells, and also in some glial cells. In the stratum radiatum of the CA1, anti-PKC(gamma) immunoreactivity localized to the pyramidal cell cytoplasm, extending into the dendrites. Following fimbria-fornix (FF) lesions, the anti-PKC(alpha) and -(beta I) staining of the pyramidal cell periphery was markedly reduced. The anti-PKC(gamma) staining of the pyramidal and granular cells of the dentate gyrus was reduced whereas the interneuron staining in the hilus was increased. In the FF-lesioned hippocampus, anti-PKC(alpha) and anti-PKC(beta II) labeled reactive glial cells, whereas anti-PKC(beta I) and -(gamma) did not. Quantitative Western blot analysis revealed a dramatic increase in the particulate/total PKC for all isozyme forms, although the total levels of PKC, except PKC(gamma), did not change following FF lesions. The PKC(gamma) concentration doubled after FF lesions. Perforant path lesions resulted in a marked alteration in the neuronal staining in dentate gyrus with anti-PKC(alpha) and -(beta I) and in increased numbers of anti-PKC(alpha)- and anti-PKC(beta II)-positive glial cells. Anti-PKC(gamma) staining did not change noticeably. The total PKC concentration did not change for isozymes alpha, beta I, and gamma, but PKC (beta II) concentration increased by 48% following perforant path lesions as detected by Western blot analysis. The particulate/total PKC decreased for all four isozymes although the reduction in PKC(beta I) concentration was not statistically significant. This change in PKC compartmentalization is in marked contrast to an increased level of particulate PKC following FF lesions. Thus, the effects of deafferentation and deafferentation for each PKC isoform were different.

Animals↗
PubMed1993

Alteration of human platelet protein kinase C with normal aging.

Using a two-site enzyme immunoassay, we determined the content of type II protein kinase C (PKC) in human platelets from 24 donors of various ages without any neurological, hematological or malignant disorders. The content of type II PKC in the membranous fraction was positively correlated with aging. The content of PKC in the cytosolic fraction tended to decline with aging, but the correlation was not significant. The total amount of PKC also had no significant correlation with aging. Age-related changes in platelet protein content were not observed. These results suggested that the subcellular distribution of type II PKC in human platelets is altered with normal aging.

Adolescent↗
PubMed1993

Neuronal damage in the rat hippocampus induced by in vivo hypoxia.

Rats were subjected to hypoxia for 30 min in a chamber containing 5% O2 and 95% N2. The distribution of damaged neurons in the hippocampus was then examined at various predetermined times, ranging from 3 hours to 21 days after hypoxia. Hematoxylin-eosin stained sections showed shrunken and eosinophilic neurons in the CA3 and CA4 regions. Similar, but less severe, changes were also observed in the granule cell layer of the dentate gyrus. In contrast, neurons in the CA1 region were relatively resistant to hypoxia. These results showed the susceptibility of the hippocampus to hypoxia, although the affected neurons are not the same as those vulnerable to ischemia.

Animals↗
PubMed1993

Assessment of protein kinase C isozymes by two-site enzyme immunoassay in human brains and changes in Alzheimer's disease.

We assessed the amount of protein kinase C (PKC) in samples from postmortem normal human and Alzheimer's disease (AD) brains by a two-site enzyme immunoassay that quantitatively identified types alpha, beta, and gamma isozymes. In the normal human brain matter, type beta was the main type present, the majority of each isozyme of PKC being present in the membranous fraction of the brain tissues. In AD brains, the amount of type beta PKC was significantly reduced in the membranous fraction of the temporal cortical tissues. The amounts of types alpha and gamma in the membranous fraction and types alpha, beta, and gamma in the cytosolic fraction in AD brains were lower than in the control brains, but the difference was not significant. There was also a significant decrease in the levels of PKC in the membranous fraction of AD brains, as measured by radioactive phorbol ester binding. These results suggest that the type beta PKC isozyme is mainly present in the human temporal cortex and that reduced levels of type beta PKC in the membranous fraction may reflect a biochemical deficit related specifically to the pathogenesis of AD.

Aged↗
PubMed1992

Phosphatidylinositol-specific phospholipase C activity in the postmortem human brain: no alteration in Alzheimer's disease.

The activity of phospholipase C (PLC) which hydrolyzes exogenous phosphatidylinositol (PI), was investigated in samples prepared from postmortem normal human brains and Alzheimer disease brains. The enzyme activity did not change significantly after rat brains were left for 24 h at room temperature. The PI-specific PLC activity in the Alzheimer cytosolic and particulate fractions was not significantly different from that in the control fractions. The PI-specific PLC activity as a function of the free Ca2+ concentration was also similar between control and Alzheimer brains. These results suggest that the PI-specific PLC activity is not altered in Alzheimer's disease.

Aged↗
PubMed1992

Localization of protein kinase C in human skeletal muscle.

The immunolocalization of protein kinase C (PKC) isozymes alpha, beta I and beta II, was investigated in human skeletal muscle. All three isozymes were present on the muscle fiber surface membrane and within the muscle fibers. The alpha-isozyme was most clearly delineated on the surface membrane of the muscle fiber and on small blood vessels in the connective tissue. The axons of myelinated intramuscular nerves stained intensely for the beta I isozyme, whereas the endoneurial connective tissue reacted more strongly for the alpha- and beta II-isozymes. PKC isozymes may regulate intracellular signal transduction in human skeletal muscle, as in the other tissues, but their exact role in muscle remains unknown.

Adult↗
PubMed1992

[An adult case of transverse myelitis with erythema infectiosum].

We reported an adult case of transverse myelitis with erythema infectiosum. A 33-year-old female was admitted to Kyoto University Hospital because of a weakness in the lower extremities and "cloth-wearing" sensation of the trunk and legs. One month before admission, she became febrile and developed a symmetrical erythema on the extremities. At the same time she noticed a slight weakness of the legs and numbness in her fingers and toes, which disappeared next few days. A week later, she again developed a fever, severe weakness of the legs and "cloth-wearing" sensation on the trunk, and erythema appeared on the cheek. Physical examination on admission revealed a weakness and hyperreflexia in the extremities, in particular, knee and ankle jerk, and hypesthesia of the trunk and legs below the level of Th6. Cerebrospinal fluid (CSF) examination revealed 181/mm3 cells (mononuclear cell dominant) and 30 mg/dl protein. Magnetic resonance imaging, CT and electrophysiological studies indicated no abnormalities. IgM antibody against human parvovirus (B19) was detected in the serum and CSF. She was diagnosed as transverse myelitis with parvovirus infection and was medicated with prednisolone 40-60 mg/day, and improved gradually with the residua of a mild weakness of the legs and hypesthesia on the trunk between the level of Th6 and Th10.

Adult↗
PubMed1991

Trophic effect of beta-amyloid precursor protein on cerebral cortical neurons in culture.

We investigated the effect of human beta-amyloid precursor protein (APP) on rat primary cerebral cortical neurons cultured in a serum-free medium. Two secretory APP species (APP667 and APP592) with and without the protease inhibitor domain were produced by COS-1 cells transfected with APP cDNAs, which encode the N-terminal portions of APP770 and APP695. Both highly purified APP species, when added to the medium, enhanced neuronal survival and neurite extension in a dose-dependent manner with a maximum effect at approximately 100 nM. These results suggest that secreted forms of APP have trophic activity for cerebral cortical neurons.

Amyloid beta-Protein Precursor↗
PubMed1991

Presence of calpain II immunoreactivity in senile plaques in Alzheimer's disease.

Calpains are calcium-dependent neutral cysteine proteinases. We utilized a specific anti-calpain II antibody to examine immunohistochemically whether calpain II is associated with pathological changes in Alzheimer's disease (AD). Calpain II was mainly expressed in the neurons in control human brains. In AD brains, intense immunoreactivity was present in the dystrophic neurites of senile plaques. These results suggest that calpain II is involved in the pathogenesis of AD.

Alzheimer Disease↗
PubMed1991

Differential expression of protein kinase C isozymes in rat glial cell cultures.

Protein kinase C (PKC) is a family of closely related enzymes implicated in molecular processes involved in growth and differentiation in a variety of cells. We studied the presence and distribution of 4 PKC isozymes in glial cell cultures of the rat hippocampus employing antisera raised against synthetic peptides predicted from the cDNA sequences corresponding to the C-terminal portion of 4 PKC isoforms, alpha, beta I, beta II, and gamma. PKC(alpha) and -(beta II), but neither PKC(beta I) nor -(gamma) isoforms were detected in glial cultures of the rat hippocampus. Anti-PKC(alpha) immunostained all glial cells, whereas anti-PKC(beta II) faintly stained about 20% of total glial cells resembling the type-2 astrocyte that were GFAP immunopositive, with few processes. Anti-PKC(beta II) did not stain about 80% of the glial fibrillary acidic protein (GFAP)-immunopositive cells with a few thick processes which resembled the type-1 astrocyte. A few cells that stained intensely with anti-PKC(beta II) were GFAP immunopositive and possessed fine, but well-developed, multiple processes. Faint PKC(beta II) immunoreactivity was also detected among anti-MBP-positive cells (possibly oligodendrocytes), RCA-1-positive cells (possibly microglia), and small, oval, anti-GFAP-positive cells. These results suggest the involvement of distinct PKC isoforms in different glial functions.

Animals↗
PubMed1991

Expression of protein kinase C isozymes in primary neuronal cultures of the rat cerebellum.

Protein kinase C (PKC), a family of closely related enzymes, has been implicated in molecular processes involved in differentiation in a variety of cells, including neuronal cells. We studied the presence and distribution of four PKC isozymes immunocytochemically in primary neuronal cultures of the rat cerebellum. We employed four anti-PKC antisera raised against synthetic peptides predicted from the cDNA sequence of the C-terminal portion of four PKC isozymes, alpha, beta I, beta II, and gamma. The majority of neurons were PKC(beta II) immunoreactive both in the early and late (14 days) stage of culture, whereas PKC(alpha)-, (beta I)-, and (gamma)-immunoreactive neurons were most abundant in the late stage of culture. Immunoreactivity of each PKC was high in the cytoplasm, processes, and growth cones. Prominent nuclear staining was observed with anti-PKC(gamma) antibody. These results are in contrast with in vivo results where each PKC isozyme is localized in a distinct population of neurons and subcellular compartment, suggesting the presence of regulatory mechanisms for PKC expression and compartmentalization in vivo.

Animals↗
PubMed1991

Reassessment of [3H]glutamate binding to human brain membrane preparations.

We studied [3H]glutamate binding to human brain membrane preparations. We found that the binding assay of [3H]glutamate should be done at 4 degrees C using glass-fiber filters pretreated with polyethyleneimine, sterile incubation buffer, and membrane preparations pretreated with a detergent. Under these assay conditions, we have characterized the three subtypes of glutamate receptors: N-methyl-D-aspartate-, quisqualate- and kainate-sensitive binding sites. Scatchard analysis revealed that the N-methyl-D-aspartate-sensitive [3H]glutamate binding sites consisted of a single component with a dissociation constant (Kd) of 28.2 +/- 2.8 nM and total concentration (Bmax) of 36.2 +/- 3.6 fmol/mg protein (N = 8). These data were much different from those presented in previous studies.

Aged↗
PubMed1991

Aberrant accumulation of phospholipase C-delta in Alzheimer brains.

Since phosphoinositide-specific phospholipase C (PLC) is one of the key molecules in signal transduction, the authors assessed its involvement in Alzheimer's disease (AD). Immunostaining of a specific antibody against the PLC isozyme, PLC-delta, demonstrated that this enzyme was abnormally accumulated in neurofibrillary tangles (NFT), the neurites surrounding senile plaque (SP) cores, and neuropil threads in AD brains. Western blot analysis confirmed that PLC-delta was concentrated in the paired helical filament (PHF)-rich fraction of AD brains. Antibodies to other PLC isozymes did not produce positive immunostaining of these pathologic structures. Moreover, diffuse and amorphous deposits of PLC-delta were found to precede the accumulation of fibrillary deposits. These results suggest that PLC-delta accumulation is a crucial event that ultimately may contribute to the formation of PHF.

Aged↗
PubMed1990

Changes in signal transduction in Alzheimer's disease.

We studied the signal transduction system including the receptor and protein kinase C (PKC) in Alzheimer's disease (AD) brains. We used 3H-TCP as a ligand for the NMDA receptor-ion channel complex. The total concentrations of 3H-TCP binding sites were significantly reduced in AD frontal cortex. 3H-TCP binding sites spared in AD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. We utilized antibodies to assess the degree of involvement of different PKC isoforms in AD. The concentration of PKC (beta II) was lower in AD particulate fractions and higher in AD cytosol fractions. Immunocytochemical studies revealed reduced numbers of anti-PKC (beta II)-immunopositive neurons. Anti-PKC (alpha) faintly stained entire plaques and surrounding glial cells. Anti-PKC (beta I) stained dystrophic plaque neurites. Anti-PKC (beta II) stained the amyloid-containing portions of plaques. These results suggest an involvement of second messenger cascades in the pathogenesis of AD in addition to neurotransmitters and their receptors.

Aged↗
PubMed1990

[3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine ([3H]TCP) binding in human frontal cortex: decreases in Alzheimer-type dementia.

We studied [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine [( 3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer-type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40-50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X-100-treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. These results suggest that the primary change in NMDA receptor-ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal.

Alzheimer Disease↗