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B Matsumoto

Publications and source records attributed to B Matsumoto.

At least 19 recordsLinked to original sources
PubMed2000

Lower gastrointestinal bleeding secondary to Dieulafoy-like lesion of the rectum.

Two cases of gastrointestinal hemorrhage resulting from Dieulafoy-like lesion of the rectum are presented. Both patients developed acute episodes of massive lower gastrointestinal hemorrhage requiring transfusions. Colonoscopy was performed in both instances and lesions were localized. The patients were successfully treated by alcohol and epinephrine injection. Colonoscopy assisted in earlier diagnosis and added therapeutic options to the treatment regimen for this lesion.

Aged↗
PubMed1999

Identification and immunolocalization of actin cytoskeletal components in light- and dark-adapted octopus retinas.

Photoreceptors in the octopus retina are of the rhabdomeric type, with rhabdomeres arising from the plasma membrane on opposite sides of the cylindrical outer segment. Each rhabdomere microvillus has an actin filament core, but other actin-binding proteins have not been identified. We used immunoblotting techniques to identify actin-binding proteins in octopus retinal extracts and immunofluorescence microscopy to localize the same proteins in fixed tissue. Antibodies directed against alpha-actinin and vinculin recognized single protein bands on immunoblots of octopus retinal extract with molecular weights comparable to the same proteins in other tissues. Anti-filamin identified two closely spaced bands similar in molecular weight to filamin in other species. Antibodies to the larger of the Drosophila ninaC gene products, p174, identified two bands lower in molecular weight than p174. Anti-villin localized a band that was significantly less in molecular weight than villin found in other cells. Epifluorescence and confocal microscopy were used to map the location of the same actin-binding proteins in dark- and light-adapted octopus photoreceptors and other retinal cells. Antibodies to most of the actin-binding proteins showed heavy staining of the photoreceptor proximal/supportive cell region accompanied by rhabdom membrane and rhabdom tip staining, although subtle differences were detected with individual antibodies. In dark-adapted retinas anti-alpha-actinin stained the photoreceptor proximal/supportive cell region where an extensive junctional complex joins these two cell types, but in the light, immunoreactivity extended above the junctional complex into the rhabdom bases. Most antibodies densely stained the rhabdom tips but anti-villin exhibited a striated pattern of localization at the tips. We believe that the actin-binding proteins identified in the octopus retina may play a significant role in the formation of new rhabdomere microvilli in the dark. We speculate that these proteins and actin remain associated with an avillar membrane that connects opposing sets of rhabdomeres in light-adapted retinas. Association of these cytoskeletal proteins with the avillar membrane would constitute a pool of proteins that could be recruited for rapid microvillus formation from the previously avillar region.

Actinin↗
PubMed1999

Ectopic expression of alpha B-crystallin in Chinese hamster ovary cells suggests a nuclear role for this protein.

alpha B-crystallin (alpha B) is known to be a cytosolic, small heat shock-like multimeric protein that has anti-aggregation, chaperone-like properties. The expression of the alpha B-crystallin gene is developmentally regulated and is induced by a variety of stress stimuli. Importantly, alpha B-crystallin expression is enhanced during oncogenic transformation of cells, in a number of tumors, and most notably, in many neurodegenerative disorders, including Alzheimer's disease and multiple sclerosis. Other than its perceived role as a structural protein in the ocular lens, the actual function of alpha B-crystallin in cellular physiology remains unknown. We have stably transfected CHO cells with an inducible alpha B-cDNA-MMTV-promoter construct that allows the synthesis of recombinant alpha B-crystallin only upon exposure of these cells to dexamethasone. Using immunostaining and conventional and confocal microscopy, we have examined the subcellular distribution of the ectopically expressed alpha B-crystallin. We find that in addition to being in the cytoplasm, the protein resides in the nuclear interior in the interphase nucleus. Double labeling with anti alpha B-crystallin and anti-tubulin, concanavallin, and wheat germ agglutinin, respectively, revealed that during cell division alpha B-crystallin is excluded from condensed chromatin and the nascent nuclei. However, the protein again appears in the newly formed nuclei after the completion of cytokinesis suggesting a conditional, regulatory role for alpha B-crystallin in the nucleus.

Animals↗
PubMed1997

Quantification of cerebellar structures with MRI.

Methodological issues have limited neuroimaging studies of cerebellar structures. In this article we describe a method that addresses some of these limitations and phantom studies that examine the validity of the image manipulations. We compared volumes derived from 3D Spoiled Gradient Recalled Acquisition MR images sliced with respect to three different alignment methods: one based on cerebellar landmarks, another on cerebral landmarks and a third on the plane of acquisition. Examination of coefficients of variation, coefficients of error and convergent validity suggests that although regional cerebellar volumes based on cerebellar landmarks provide the best estimates of the true volumes, observed differences between volume measurements from alignments based on cerebellar or cerebral landmarks were generally not significant and were inconsequential. In this case, the measure was improved with alignment along local, relevant cerebellar landmarks. A set of phantom experiments showed that realignment, reslicing and interpolation in 3-dimensional image processing exerted, at most, trivial distortion on the estimates of actual object volumes.

Adult↗
PubMed1997

Evidence from normal and degenerating photoreceptors that two outer segment integral membrane proteins have separate transport pathways.

Detachment of the neural retina from the retinal pigment epithelium induces photoreceptor degeneration. We studied the effects of this degeneration on the localization of two photoreceptor outer segment-specific integral membrane proteins, opsin and peripherin/rds, in rod photoreceptors. Results from laser scanning confocal microscopic and electron microscopic immunolocalization demonstrate that these two proteins, normally targeted to the newly-forming discs of the outer segments, accumulate in different sub-cellular compartments during photoreceptor degeneration: opsin immunolabeling increases throughout the photoreceptor cell's plasma membrane, while peripherin/rds immunolabeling occurs within cytoplasmic vesicles. The simplest hypothesis to explain our results is that these proteins are transported in different post-Golgi transport vesicles and separately inserted into the plasma membrane. More complex mechanisms involve having the two co-transported and then opsin finds its way into the plasma membrane but peripherin/rds does not, remaining behind in vesicles. Alternatively, both insert into the plasma membrane but peripherin/rds is recycled into cytoplasmic vesicles. We believe the data most strongly supports the first possibility. Although the transport pathways for these proteins have not been fully characterized, the presence of peripherin/rds-positive vesicles adjacent to the striated rootlet suggests a transport role for this cytoskeletal element. The accumulation of these proteins in photoreceptors with degenerated outer segments may also indicate that their rate of synthesis has exceeded the combined rates of their incorporation into newly forming outer segment disc membranes and their degradation. The accumulation may also provide a mechanism for rapid recovery of the outer segment following retinal reattachment and return of the photoreceptor cell to an environment favorable to outer segment regeneration.

Animals↗
PubMed1997

Light-/dark-induced changes in rhabdom structure in the retina of Octopus bimaculoides.

We examined rhabdom structure and the distribution of filamentous actin in the photoreceptor outer segments of the retina of Octopus bimaculoides. Animals were dark- or light-adapted, fixed, embedded and sectioned for light and electron microscopy. Statistical analyses were used to compare relative cross-sectional areas of rhabdom microvilli and core cytoplasm within and between the two lighting conditions. Dark-/light-adapted rhabdoms were also prepared for confocal laser scanning microscopy and labeled with fluorescence-tagged phalloidin. Results show differences in the morphology of dark- and light-adapted octopus rhabdoms with the cross-sectional areas of the rhabdoms increasing in dark-adapted retinas and diminishing in the light. Comparisons between the lighting conditions show that an avillar portion of the photoreceptor outer segment membrane, prominent in the light-adapted retina, is recruited to form new rhabdomere microvilli in dark-adapted eyes. Filamentous actin was associated with the avillar membrane in light-adapted retinas, which may indicate that actin and other microvillus core proteins remain linked to the avillar membrane to support rapid microvillus formation in the dark. Photopigment redistributions also occur in light- and dark-adapted retinas, and this study suggests that these changes must be coordinated with the simultaneous breakdown and reformation of the rhabdomere microvilli.

Actins↗
PubMed1996

The actin network in the ciliary stalk of photoreceptors functions in the generation of new outer segment discs.

Cytochalasin D (CD) interferes with the morphogenesis of outer segment disc membrane in photoreceptors. Disruption of either the actin network in the ciliary stalk, where membrane evagination is initiated, or the actin core of the calycal processes, whose position could define the disc perimeter, could be responsible. We have attempted to determine which of these local F-actin populations is involved in membrane morphogenesis and what step in the process is actin-dependent. Biocytin accumulation in nascent discs, detected by fluorescent avidin and laser scanning confocal microscopy (LSCM), provided a means of labeling abnormal discs and a measure of disc membrane addition. F-actin content and distribution were assessed using fluorescent phalloidin and LSCM. First, we examined the effects of a range of CD dosages (0.1, 1.0, or 10.0 microM) on rod photoreceptors in Xenopus laevis eyecup cultures. Ectopic outgrowth of discs, evaluated by LSCM and transmission electron microscopy (TEM), occurred at each concentration. Phalloidin labeling intensified in the ciliary stalk with increasing CD concentration, indicating F-actin aggregation. In contrast, it diminished in the calycal processes, indicating dispersal; TEM showed that calycal process collapse ensued. Disruption was evident at a lower concentration in the ciliary stalk (0.1 microM) than in the calycal processes (1.0 microM). TEM confirmed that the calycal processes remained intact at 0.1 microM. Thus, CD's action on the ciliary stalk network is sufficient to disrupt disc morphogenesis. Second, we examined the effect of CD on temperature-induced acceleration of the rate of disc formation. In the absence of CD, a 10 degrees C temperature shift increased the disc formation rate nearly three-fold. CD (5 microM) caused a 94% inhibition (P < 0.025) of this response; yet, the rate of membrane addition to ectopically growing discs exhibited the expected three-fold increase. Thus, CD's action interferes with the generation of new discs.

Actins↗
PubMed1996

Cortical gray matter volume deficit in patients with first-episode schizophrenia.

OBJECTIVE: A cortical gray matter deficit has been found in cross-sectional studies of patients with chronic schizophrenia. The purpose of this study was to examine whether this deficit is present early in the course of illness. METHOD: The authors measured cortical gray matter volume on magnetic resonance images acquired within 6 months of onset of illness from 22 patients with first-episode schizophrenia and 51 age-matched comparison subjects from the Stony Brook First Episode Study. RESULTS: A significant cortical gray matter deficit and lateral ventricular enlargement were found in schizophrenic patients relative to the comparison group. CONCLUSIONS: The presence of the cortical gray matter deficit close to onset of illness supports the role of preexisting structural brain deficits in the genesis of schizophrenia.

Adult↗
PubMed1995

Retinoid cycling proteins redistribute in light-/dark-adapted octopus retinas.

In cephalopods, the complex rhodopsin-retinochrome system serves to regenerate metarhodopsin and metaretinochrome after illumination. In the dark, a soluble protein, retinal-binding protein (RALBP), shuttles 11-cis retinal released from metaretinochrome located in the photoreceptor inner segments to metarhodopsin present in the rhabdoms. While in the rhabdoms, RALBP delivers 11-cis retinal to regenerate rhodopsin and in turn binds the all-trans isomer released by metarhodopsin. RALBP then returns all-trans retinal to the inner segments to restore retinochrome. The conventional interpretation of retinoid cycling is contradicted by immunocytochemical studies showing that, in addition to rhodopsin, retinochrome is present in the rhabdomal compartment, making possible the direct exchange of chromophores between the metapigments with the potential exclusion of RALBP. By using immunofluorescence and laser scanning confocal microscopy, we have precisely located opsin, aporetinochrome, and RALBP in light-/dark-adapted octopus retinas. We found differences in the distribution of all three proteins throughout the retina. Most significantly, comparison of cross sections though light- and dark-adapted rhabdoms showed a dramatic shift in position of the proteins. In the dark, opsin and retinochrome colocalized at the base of the rhabdomal microvilli. In the light, opsin redistributed along the length of the microvillar membranes, and retinochrome retreated to a location that is perhaps extracellular. RALBP was present in the core cytoplasm of the photoreceptor outer segments in the dark, and RALBP moved to the periphery in the light. Because of the colocalization of opsin and retinochrome in the dark, we believe that the two metapigments participate directly in chromophore exchange. RALBP may serve to transport additional chromophore from the inner segments to the rhabdoms and may not be immediately involved in the exchange process.

Adaptation, Ocular↗
PubMed1995

Changes in the organization and expression of cytoskeletal proteins during retinal degeneration induced by retinal detachment.

PURPOSE: The goal of this study was to determine the changes in the organization of the retinal cytoskeleton after experimental retinal detachment. METHODS: Cat retinas were detached from the retinal pigment epithelium and then processed for Western blot analysis and fluorescence microscopy. Proteins examined included glial fibrillary acidic protein (GFAP), vimentin, tubulin, and actin. Sections were viewed using a laser scanning confocal microscope. RESULTS: GFAP and vimentin: At 1 day after detachment, there was an aggregation of intermediate filaments in the endfoot of Müller cells. At 3 days, intermediate filament containing Müller cell processes could be detected within the subretinal space, and, at 28 days, these processes formed large glial scars in the subretinal space. beta-tubulin: At 3 days after detachment, an increase in immunolabeling could be detected within the Müller cell endfoot and in Müller cell processes within the subretinal space. Actin: At 3 days after detachment, rhodamine-phalloidin staining decreased in the inner segments, the photoreceptor synaptic terminals, and the outer limiting membrane. CONCLUSIONS: The decrease in labeling of the photoreceptor inner segment and synaptic terminal cytoskeleton may be a key indicator of early changes in photoreceptors after detachment. The increase in cytoskeletal proteins GFAP, vimentin, and tubulin within the retinal Müller cells after detachment may help to stabilize this cell type as it hypertrophies during glial scar formation. Inhibition of this response may aid in the treatment of diseases in which Müller cell hypertrophy plays a role.

Animals↗
PubMed1994

Rapid changes in the expression of glial cell proteins caused by experimental retinal detachment.

We examined the expression of several proteins normally present in Müller's glia after the production of experimental retinal detachment in adult cats. Retinas were detached for one-half to seven days, after which the tissue was processed for correlative immunocytochemistry and biochemistry. Previous studies demonstrated that the intermediate filament proteins glial fibrillary acidic protein and vimentin, increase after long-term retinal detachment (30 to 60 days), whereas glutamine synthetase, carbonic anhydrase C, and cellular retinaldehyde-binding protein all decrease to barely detectable levels. Alterations in Müller cell protein expression are rapid and specific events that can be detected as early as two days after retinal detachment. By seven days, levels of protein expression are similar to those in the long-term retinal detachments. Within the first week after injury the Müller cell processes hypertrophy and begin forming glial scars, which indicates that early intervention may be required to halt or reverse the effects of detachment.

Animals↗
PubMed1993

Kinetic stabilization of microtubule dynamic instability in vitro by vinblastine.

The antiproliferative action of vinblastine at low concentrations appears to result from modulation of the polymerization dynamics of spindle microtubules rather than from depolarization of the microtubules [Jordan, M. A., Thrower, D., & Wilson, L. (1991) Cancer Res. 51, 2212-2222; (1992) J. Cell. Sci. 102, 401-416]. In the present study, we used differential interference contrast video microscopy to analyze the effects of vinblastine on the growing and shortening dynamics (dynamic instability) of individual bovine brain microtubules in vitro. With microtubules which were either depleted of microtubule-associated proteins (MAPs) or rich in MAPs, low concentrations of vinblastine (0.2 microM-1 microM) suppressed the growing and shortening rates and increased the percentage of time that the microtubules spent a state of attenuated activity, neither growing nor shortening detectably. Vinblastine also suppressed the duration of microtubule growing and shortening, and increased the duration of the attenuated state, during which the microtubules neither grew nor shortened detectably. Consistent with previous data obtained using radiolabeled nucleotide exchange in microtubule suspensions [Jordan, M. A., & Wilson, L. (1990) Biochemistry 29, 2730-2739], vinblastine suppressed growing and shortening dynamics at the kinetically more rapid plus ends. The results suggest that vinblastine kinetically stabilizes microtubule ends by modulating the gain and loss of the stabilizing GTP or GDP-Pi "cap", which is believed to be responsible for the transitions between the growing and shortening phases. The data support the hypothesis that (1) low concentrations of vinblastine inhibit mitosis by kinetically stabilizing the polymerization dynamics of spindle microtubules and that (2) the dynamics of spindle microtubules are critical for the proper progression of mitosis.

Animals↗
PubMed1992

Reconstitution of the photoreceptor-pigment epithelium interface: L-glutamate stimulation of adhesive interactions and rod disc shedding after recombination of dissociated Xenopus laevis eyecups.

In order to investigate adhesive interactions between photoreceptor and pigment epithelial cells, we have mechanically separated neural retinas from Xenopus laevis eyecups and then recombined the tissues in vitro. When tissue pairs are incubated in a defined medium, cell-cell contact is achieved within 3 hr. However, the average proportion of reassembled eyecups in which photoreceptor outer segments interdigitate with epithelial microvilli is limited. Furthermore, rod disc shedding does not take place in these cultures, even following a dark to light transition. When recombined tissues are placed in medium supplemented with 12 mM L-glutamate, retinal reattachment is enhanced and there is a four-fold increase in epithelial phagosome content. The positive effect of excitatory amino acid exposure on shedding, however, is restricted to regions where visual and epithelial cells interdigitate. These results indicate that re-establishment of cell contact may be necessary for shedding of apical disc membranes prior to their engulfment by the epithelium. While reattachment is not affected by pre-incubation of separated tissues in normal medium, rod photoreceptors fail to undergo membrane turnover in response to L-glutamate if a delay of 1 hr or more is interposed between isolation of the retina and its recombination with the pigment epithelium. This is probably due to a decline in retinal function in culture, since a similar preincubation of the pigment epithelium prior to reassembly with a freshly isolated retina does not inhibit the shedding response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of retinal detachment on rod disc membrane assembly in cultured frog retinas.

The authors compared rod outer segment (ROS) disc membrane assembly rates in detached and attached frog retinas to determine if there was a rapid impairment of membrane assembly in response to retinal detachment. Membrane assembly was quantified in vitro by incubating retinas in medium containing Lucifer yellow, which is entrapped by nascent discs. Video microscopy was used to detect incorporation of the dye. During the first 10 hr after separation of the retina from the retinal pigment epithelium (RPE), ROS-disc membrane assembly in isolated Xenopus laevis neural retinas continued at a near normal rate, 0.81 microns/10 hr, a 13% reduction (P less than .01), compared with the 0.93 microns/10 hr observed in attached control retinas. The morphology of the OS appeared normal in most rod photoreceptors by transmission electron microscopy, although vesiculation of the most basal OS membranes was seen in a small population (25%) of rods. Approximately 90% of rod photoreceptors continued to assemble OS membranes for more than 10 hr after detachment, but by the end of 2 days, only 55% were still making new discs. The percentage of rods with normal basal OS membranes also decreased (to approximately 50%). Therefore, only 25% were assembling morphologically normal discs 2 days after detachment. In attached control regions, rod photoreceptors showed a comparatively minor response to culture conditions; assembly of morphologically normal discs continued for 2 days in about 85% and ceased in only 10%. These results indicate that the effects on disc membrane assembly of disrupting photoreceptor-RPE interaction in vitro initially are slight but become progressively severe with time.

Animals↗
PubMed1990

Identification and localization of a beta-1 receptor from the integrin family in mammalian retinal pigment epithelial cells.

The distribution of an adhesion receptor from the integrin family was mapped in cultured mammalian retinal pigment epithelial cells (RPE), and in primate RPE cells in vivo, using antibodies to the human fibronectin receptor (FnR) in conjunction with indirect immunofluorescence and immunoelectron microscopy. Protein homogenates from human RPE or MG-63 cells were separated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions. On Western blots of proteins from both cell types, anti-FnR and a monoclonal antibody to the beta 1 subunit of human FnR each recognized a single band with a molecular mass of approximately 115 kDa. After 1-6 weeks in culture human, monkey and feline RPE cells gradually acquired a morphology and cytoskeletal arrangement typical of a mature cuboidal epithelium. The distribution of anti-FnR labeling changed dramatically in accordance with the cells' phenotype. In preconfluent cells, labeling consisted of streaks and flecks of fluorescence at the termini of stress fibers and at putative sites of cell substratum attachment. As the cells became confluent and acquired an epithelioid morphology, the bulk of anti-FnR labeling shifted to the peripheral cytoplasm and appeared as a cross-hatched meshwork. In fully differentiated RPE cells anti-FnR labeling consisted of a dense punctate pattern on or close to the apical cell surface that coincided with the distribution of f-actin as shown by phalloidin staining, and to the distribution of apical microvilli as identified by scanning electron microscopy. In addition, a compacted rim of fluorescence appeared at the cells' lateral margins that was also virtually identical to the phalloidin staining pattern. No basal surface labeling was apparent at this stage. At the ultrastructural level, FnR was localized to the apical surface of nonpermeabilized RPE cells and, in particular, to the plasma membrane of apical microvilli in vitro and in vivo using an indirect, pre-embedding method. The results strongly suggest that: (1) a membrane receptor/s containing the integrin beta 1 subunit is normally present on the plasma membrane of apical microvilli and on the lateral cell surfaces of cultured mammalian RPE cells; and (2) this receptor also is present on the plasmalemma of RPE apical microvilli in vivo.

Animals↗