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Biomedical subjects

S Usami

Publications and source records attributed to S Usami.

At least 73 records · Page 4Linked to original sources
PubMed1999

Citric acid production from xylan and xylan hydrolysate by semi-solid culture of Aspergillus niger.

Citric acid production from xylan and xylan hydrolysate was done by Aspergillus niger Yang no. 2 cultivated in a semi-solid culture using bagasse as a carrier. Yang no. 2 produced 72.4 g/l and 52.6 g/l of citric acid in 5 d from 140 g/l of xylose and arabinose, respectively. Yang no. 2 produced 51.6 g/l of citric acid in 3 d from a concentrated xylan hydrolysate prepared by cellulase treatment, containing 100 g/l of reducing sugars. Moreover, Yang no. 2 directly produced 39.6 g/l of citric acid maximally in 3 d from 140 g/l of xylan.

Aspergillus niger↗
PubMed1998

Molecular anatomy of a small chromosome in the green alga Chlorella vulgaris.

A contig covering the entire region of Chlorella vulgaris chromosome I (980 kb long), consisting of 33 cosmid clones has been constructed. By cross-hybridization with other chromosomal DNAs, universal structural elements were detected and localized on the contig. They were composed of at least three different elements: short interspersed DNA elements (SINE)-like elements, long interspersed DNA elements (LINE)-like elements and a putative centromere-like element. At least 36 copies of SINE-like elements were distributed over chromosome I with preferential locations on the right half of the chromosome. DNA fragments containing a SINE-like sequence showed a bent or curved DNA nature on polyacrylamide gel electrophoresis. LINE-like elements were clustered at the left terminus of chromosome I where they formed a tandem array of six copies immediately adjacent to the telomeric repeats. A long sequence element localized at a unique region of chromosome I also existed in a single copy on each chromosome and contained a sequence related to the reverse transcriptase domain of retrotransposons. This feature was compared with the reported centromere-associated elements of higher plants. With its comparative simplicity, the organization of Chlorella chromosome I genomic elements may serve as a prototypic experimental system for deciphering the complexity of huge plant chromosomes.

Base Sequence↗
PubMed1998

Molecular organization of a type of peripheral glutamate synapse: the afferent synapses of hair cells in the inner ear.

The synapses between sensory cells in the inner ear and the afferent dendrites of ganglion cells are well suited to investigations of fundamental mechanisms of fast synaptic signalling. The presynaptic elements can be isolated for electrophysiological and functional studies while the synapses can be easily recognized in the electron microscope due to their distinct morphological features. This allows for a broader range of correlative functional and structural analyses than can be applied to synapses in the central nervous system (CNS). As in most fast excitatory synapses in the CNS the transmitter in the afferent hair cell synapses appears to be glutamate or a closely related compound. Recent studies have revealed many of the key molecular players at this type of synapse and how they are spatially and functionally coupled. By use of high resolution immunogold cytochemistry it has been shown that AMPA glutamate receptors are specifically expressed in the postsynaptic specialization of afferent hair cell synapses (except at those established by outer hair cells in the organ of Corti) and that their density varies as a function of the distance from the release sites (demonstrated for the afferent contacts of inner hair cells). The glutamate transporter GLAST is localized in supporting cell membranes and concentrated in those membrane domains that face the synaptic regions. Glutamine synthetase and phosphate-activated glutaminase--which are responsible for the interconversion of glutamate and glutamine--are selectively localized in non-neuronal and neuronal elements, respectively. Taken together with quantitative immunogold data on the cellular compartmentation of glutamate and glutamine the above findings suggest that the sensory epithelia in the inner ear sustain a cycling of glutamate carbon skeletons. In this process, the supporting cells may carry out functions analogous to those of glial cells in the CNS. Functional and morphological analyses of the presynaptic membrane indicate that L-type Ca(2+)-channels and Ca(2+)-activated K(+)-channels are colocalized and clustered at the active zone. Influx through the L-type channels triggers synaptic release and their close spatial association with Ca(2+)-activated K(+)-channels appears to be critical for frequency tuning. The focal expression of different Ca(2+)-channels combined with a high intracellular buffering capacity permits several Ca(2+)-signalling pathways to operate in parallel without undue interference. The molecular organization of the afferent hair cell synapses reflects the functional demand for speed and precision and attests to the ability of the pre- and postsynaptic elements to target and anchor key proteins at specific membrane domains.

Animals↗
PubMed1998

Select types of supporting cell in the inner ear express aquaporin-4 water channel protein.

Aquaporins (AQPs) confer a high water permeability on cell membranes and play important parts in secretory and absorptive epithelia in kidney and other organs. Here we investigate whether AQPs are expressed in the sensory epithelia of the inner ear, where a precise volume regulation is crucial. By use of specific antibodies it was found that the inner ear contains AQP1 and 4 while being devoid of detectable levels of AQP2, 3 or 5. Immunofluorescence and postembedding immunogold labelling revealed a strictly non-epithelial distribution of AQP1, confirming previous data. In contrast, AQP4 protein and mRNA (visualized by in situ hybridization) were concentrated in select types of supporting cell, including Hensen's cells and inner sulcus cells. Immunogold particles signalling AQP4 were confined to the basolateral plasma membrane of Hensen's cells and to the basal plasma membrane of Claudius cells and inner sulcus cells. AQP4 was also found in supporting cells of the vestibular end organs, but was absent from transitional epithelial cells and dark cells. Strong labelling for AQP4 and AQP4-mRNA was associated with the central part of the cochlear and vestibular nerves. Hair cells were consistently unlabelled. Our findings indicate that AQP4 may facilitate osmotically driven water fluxes in the sensory epithelia of the inner ear and thus contribute to the volume and ion homeostasis at these sites.

Animals↗
PubMed1998

Changes of perilymphatic glutamate and cochlear blood flow following ischemia.

Dynamic changes of perilymphatic glutamate and cochlear blood flow were measured simultaneously in the guinea pig following cochlear ischemia. Glutamate was measured by the microdialysis technique with a probe inserted into the scala tympani at the basal turn. Cochlear blood flow was monitored with a laser-Doppler probe on the lateral wall of the second cochlear turn. Both parameters were measured before and after electrocauterization of the anterior inferior cerebellar artery and other vessels supplying the internal auditory canal. In four animals, glutamate increased with a decline of cochlear blood flow and then decreased with recovery of blood flow. No normalization of glutamate was observed in seven animals with a persistent decrease of blood flow. The results of this study indicate that the glutamate regulating system in the cochlea is dependent on cochlear blood flow.

Animals↗
PubMed1998

Effects of disturbed flow on endothelial cells.

Atherosclerotic lesions tend to localize at curvatures and branches of the arterial system, where the local flow is often disturbed and irregular (e.g., flow separation, recirculation, complex flow patterns, and nonuniform shear stress distributions). The effects of such flow conditions on cultured human umbilical vein endothelial cells (HUVECs) were studied in vitro by using a vertical-step flow channel (VSF). Detailed shear stress distributions and flow structures have been computed by using the finite volume method in a general curvilinear coordinate system. HUVECs in the reattachment areas with low shear stresses were generally rounded in shape. In contrast, the cells under higher shear stresses were significantly elongated and aligned with the flow direction, even for those in the area with reversed flow. When HUVECs were subjected to shearing in VSF, their actin stress fibers reorganized in association with the morphological changes. The rate of DNA synthesis in the vicinity of the flow reattachment area was higher than that in the laminar flow area. These in vitro experiments have provided data for the understanding of the in vivo responses of endothelial cells under complex flow environments found in regions of prevalence of atherosclerotic lesions.

Arteriosclerosis↗
PubMed1998

Anomer-selective glucosylation of l-menthol by yeast alpha-glucosidase.

l-Menthol was glucosylated by the alpha-glucosidase (EC 3.2.1.20) of Saccharomyces cerevisiae using maltose as the glucosyl donor. When 50 mg of l-menthol and 1.6 M maltose in 10 mM citrate-phosphate buffer (pH 5.5) were incubated at 45 degrees C, l-menthyl alpha-D-glucopyranoside (alpha-MenG) was alpha-anomer-selectively formed as a product. The specificity of the alpha-linkage was confirmed by 13C-NMR analysis. In the reaction mixture after 2 h, alpha-MenG was mainly accumulated in a crystalline form and the concentration of dissolved alpha-MenG was constant at 1.4 mM. The molar conversion yield of alpha-MenG produced based on the supplied l-menthol was maximally 30.7% at 48 h of reaction.

Catalysis↗
PubMed1998

Quantitative immunogold cytochemistry reveals sources of glutamate release in inner ear ischemia.

Glutamate is thought to be a major neurotransmitter between hair cells and afferent dendrites in the inner ear. However, excessive glutamate is known to be excitotoxic, and may be involved in ischemic neuronal damage in the central nervous system. The glutamate concentration in the perilymph has been reported to increase during ischemia, but the source of glutamate is still unclear. In the present study, we have used post-embedding immunogold cytochemistry to analyse changes in the cellular distribution of glutamate in the guinea pig organ of Corti during ischemia. The areal gold particle densities in the inner hair cells of the ischemic side were lower than those of the control side, indicating that glutamate may be released from the hair cells during ischemia. Adjacent supporting cells (border cells) also showed a decrease in particle density, suggesting that they constitute an additional source of glutamate.

Animals↗
PubMed1998

Cochlear implantation in a patient with profound hearing loss with the A1555G mitochondrial mutation.

OBJECTIVE: This study aimed to describe the performance of a cochlear implant in a patient with profound hearing loss with the A1555G mitochondrial mutation. SETTING: The study was conducted at two university hospitals. PATIENT: A 50-year-old Japanese man in whom bilateral profound hearing loss developed after administration of streptomycin at the age of 23 participated. The pedigree of the family showed exclusively maternal transmission of hearing impairment. INTERVENTION: Genetic study and auditory rehabilitation with a cochlear implant were performed. RESULTS: The A1555G point mutation was identified from the patient's mitochondrial DNA. Since activation of the implant, the patient has been using it successfully with a monosyllable recognition score of 78% using Japanese word lists for speech audiometry. CONCLUSIONS: The current case indicated that cochlear implantation may be a valuable choice of therapy for the patient with profound hearing loss with the A1555G mutation. The excellent auditory performance with a cochlear implant suggests that hearing loss associated with this mutation is primarily caused by insult to the cochlear tissue containing rich mitochondria (i.e., hair cells or stria vascularis or both), not to the cochlear nerve and its central connections.

Antibiotics, Antitubercular↗
PubMed1997

Cloning and sequencing of the cDNA encoding lipase I from Trichosporon fermentans WU-C12.

A cDNA clone encoding extracellular lipase I (TFL I) from Trichosporon fermentans WU-C12 was isolated and characterized. The TFL I cDNA was isolated from a lambda gt10-based cDNA library using as a probe a 0.8 kb fragment, amplified by PCR with synthetic oligonucleotide corresponding to the partial amino acid sequences of TFL I. The cDNA encodes a protein consisting of 563 amino acids containing a putative signal peptide of 19 amino acids. The deduced amino acid sequence shares 99.5% overall identity with that of lipase II (GCL II) from Geotrichum candidum ATCC 34614, whereas TFL I is a trimer enzyme and GCL II monomer. Southern hybridization with the TFL I cDNA as a probe revealed that WU-C12 contained two different lipase genes.

Amino Acid Sequence↗
PubMed1997

Identification of the amino acid residues responsible for cold tolerance in Flaveria brownii pyruvate,orthophosphate dikinase.

Pyruvate,orthophosphate dikinase (PPDK), an enzyme important in C4 photosynthesis, is typically a cold-sensitive enzyme. However, a cold-tolerant form of the enzyme has been isolated from the leaves of Flaveria brownii. Using an E. coli expression system and the PPDK cDNAs from F. brownii (cold-tolerant), F. bidentis (cold-sensitive) and maize (intermediately cold-tolerant), site-directed mutagenesis studies indicated that as few as three amino acids residues (of 880 residues) strongly influence the cold sensitivity of Flaveria PPDK. Gel filtration analysis of the PPDK expressed in E. coli showed that subunit association and cold tolerance are closely linked.

Amino Acid Sequence↗
PubMed1997

Cell death in the inner ear associated with aging is apoptosis?

Programmed cell death (apoptosis) in the inner ear of senescence-accelerated mouse was identified using specific labeling of fragmented DNA (the TUNEL method). In spite of some inter-individual differences, the apoptotic cells were predominantly found in the phylogenetically newer part of the inner ear, the cochlea and the saccules. In the saccules, sensory hair cells as well as supporting cells were positively labeled. In the cochlea, positive staining was detected in inner and outer hair cells, pillar cells, Deiters' cells, interdental cells, the stria vascularis (marginal cells, intermediate cells, basal cells), and cells in Reissner's membrane. The present results suggest that age-related cell death, which may cause hearing impairment and dysequilibrium, is due to apoptosis occurring in the inner ear.

Aging↗
PubMed1997

Differential localization of delta glutamate receptors in the rat cerebellum: coexpression with AMPA receptors in parallel fiber-spine synapses and absence from climbing fiber-spine synapses.

The delta 2 glutamate receptors are prominently expressed in Purkinje cells and are thought to play a key role in the induction of cerebellar long-term depression. The synaptic and subsynaptic localization of delta receptors in rat cerebellar cortex was investigated with sensitive and high-resolution immunogold procedures. After postembedding incubation with an antibody raised to a C-terminal peptide of delta 2, high gold particle densities occurred in all parallel fiber synapses with Purkinje cell dendritic spines, whereas other synapses were consistently devoid of labeling. Among the types of immunonegative synapse were climbing fiber synapses with spines and parallel fiber synapses with dendritic stems of interneurons. At the parallel fiber-spine synapse, gold particles signaling delta receptors were restricted to the postsynaptic specialization. By the use of double labeling with two different gold particle sizes, it was shown that delta and AMPA GluR2/3 receptors were colocalized along the entire extent of the postsynaptic specialization without forming separate domains. The distribution of gold particles representing delta receptors was consistent with a cytoplasmic localization of the C terminus and an absence of a significant presynaptic pool of receptor molecules. The present data suggest that the delta 2 receptors are targeted selectively to a subset of Purkinje cell spines and that they are coexpressed with ionotropic receptors in the postsynaptic specialization. This arrangement could allow for a direct interaction between the two classes of receptor.

Animals↗
PubMed1997

Discrete cellular and subcellular localization of glutamine synthetase and the glutamate transporter GLAST in the rat vestibular end organ.

Glial cells play an important role in the removal and metabolism of synaptically released glutamate in the central nervous system (CNS). It is not clear how glutamate is handled at peripheral glutamate synapses, which are not associated with glia. Glutamate is a likely transmitter in the synapse between the hair cells and afferent dendrites of the vestibular end organ. Immunocytochemistry was performed to investigate the distribution at this site of the high affinity glutamate transporter GLAST and glutamate metabolizing enzyme glutamine synthetase. Confocal microscopy revealed that GLAST and glutamine synthetase were co-localized in supporting cells apposed to the immunonegative hair cells. Postembedding immunoelectron microscopy revealed that GLAST was heterogeneously distributed along the plasma membranes of the supporting cells, with higher concentrations basally (at the level of the afferent synapses) than apically. Both immunoreactivities were also present in non-neuronal cells in the vestibular ganglion. The present findings suggest that glutamate released at the afferent synapse of vestibular hair cells may be taken up by adjacent supporting cells and converted into glutamine. Thus, at this peripheral synapse, the supporting cells may carry out functions similar to those of glial cells in the CNS.

ATP-Binding Cassette Transporters↗
PubMed1997

Genetic and clinical features of sensorineural hearing loss associated with the 1555 mitochondrial mutation.

Five Japanese families showing aminoglycoside-induced hearing loss were genetically as well as clinically investigated. A mitochondrial mutation at nucleotide 1555 was found in 28 out of 32 subjects. One hundred American control subjects did not show any evidence of the mutation at nucleotide 1555, suggesting that the 1555 A-->G (A1555G) mitochondrial mutation may be found more frequently among populations in the Asian continent. Many subjects who harbor this mitochondrial mutation exhibit a mild, high-frequency, progressive hearing loss even without aminoglycoside injection. The results presented here appear to support the hypothesis that the A1555G mutation may play a more general role in causing hearing loss.

Aminoglycosides↗
PubMed1997

Three familial cases of hearing loss associated with enlargement of the vestibular aqueduct.

The present report describes three familial cases of recessive hearing loss associated with enlargement of the vestibular aqueduct (EVA). Six siblings from three families showed EVA. The common characteristic of these patients was the presence of congenital, high-frequency, fluctuating sensorineural hearing loss. These cases suggest that EVA may be a useful discriminator between different types of recessive hearing loss.

Adolescent↗
PubMed1997

Neoagarobiose as a novel moisturizer with whitening effect.

Neoagarobiose, a disaccharide, showed a higher hygroscopic ability than glycerol or hyaluronic acid, typical moisturizing reagents. Beside, neoagarobiose whitened B16 murine melanoma cells, and showed low cytotoxicity. Therefore neoagarobiose was a rare reagent showing both moisturizing and whitening effects.

Animals↗