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Biomedical subjects

K Saitoh

Publications and source records attributed to K Saitoh.

At least 19 recordsLinked to original sources
PubMed2003

Kinetics of v-src-induced epithelial-mesenchymal transition in developing glandular stomach.

The oncogene function in primary epithelial cells is largely unclear. Recombination organ cultures in combination with the stable and transient gene transfer techniques by retrovirus and electroporation, respectively, enable us to transfer oncogenes specifically into primary epithelial cells of the developing avian glandular stomach (proventriculus). In this system, the epithelium and mesenchyme are mutually dependent on each other for their growth and differentiation. We report here that either stable or transient expression of v-src in the epithelium causes budding and migration of epithelial cells into mesenchyme. In response to the transient expression of v-Src or a constitutive active mutant of MEK, we observed immediate downregulation of the Sonic hedgehog gene and subsequent elimination of E-cadherine expression in migrating cells, suggesting the involvement of MAP kinase signaling pathway in these processes. v-src-expressing cells that were retained in the epithelium underwent apoptosis (anoikis) and detached from the culture. Continuous expression of v-src by, for example, Rous sarcoma virus (RSV) was required for the epithelial cells to acquire the ability to express type I collagen and fibronectin genes (mesenchymal markers), and finally to establish the epithelial-mesenchymal transition. These observations would partly explain why RSV does not apparently cause carcinoma formation, but induces sarcomas exclusively.

Animals↗
PubMed2003

Basal ganglia efferents to the brainstem centers controlling postural muscle tone and locomotion: a new concept for understanding motor disorders in basal ganglia dysfunction.

The present study is designed to elucidate how basal ganglia afferents from the substantia nigra pars reticulata (SNr) to the mesopontine tegmental area of the brainstem contribute to gait control and muscle-tone regulation. We used unanesthetized and acutely decerebrated cats (n=27) in which the striatum, thalamus and cerebral cortex were removed but the SNr was preserved. Repetitive stimulation (50 Hz, 10-60 microA, for 5-20 s) applied to a mesencephalic locomotor region (MLR), which corresponded to the cuneiform nucleus, and adjacent areas, evoked locomotor movements. On the other hand, stimulation of a muscle-tone inhibitory region in the pedunculopontine tegmental nucleus (PPN) suppressed postural muscle tone. An injection of either glutamatergic agonists (N-methyl-D-aspartic acid and kainic acid) or GABA antagonists (bicuculline and picrotoxin) into the MLR and PPN also induced locomotion and muscle-tone suppression, respectively. Repetitive electrical stimuli (50-100 Hz, 20-60 microA for 5-20 s) delivered to the SNr alone did not alter muscular activity. However stimulating the lateral part of the SNr attenuated and blocked PPN-induced muscle-tone suppression. Moreover, weaker stimulation of the medial part of the SNr reduced the number of step cycles and disturbed the rhythmic alternation of limb movements of MLR-induced locomotion. The onset of locomotion was delayed as the stimulus intensity was increased. At a higher strength SNr stimulation abolished the locomotion. An injection of bicuculline into either the PPN or the MLR diminished the SNr effects noted above. These results suggest that locomotion and postural muscle tone are subject to modulation by GABAergic nigrotegmental projections which have a partial functional topography: a lateral and medial SNr, for regulation of postural muscle tone and locomotion, respectively. We conclude that disorders of the basal ganglia may include dysfunction of the nigrotegmental (basal ganglia-brainstem) systems, which consequently leads to the production of abnormal muscle tone and gait disturbance.

Animals↗
PubMed2003

Changing prevalent T serotypes and emm genotypes of Streptococcus pyogenes isolates from streptococcal toxic shock-like syndrome (TSLS) patients in Japan.

We surveyed T serotypes and emm genotypes of Streptococcus pyogenes isolates from streptococcal toxic shock-like syndrome (TSLS) patients. T1 (emm1) remained dominant through 1992 to 2000, but the dominant T3 (emm3.1) strains from 1992 to 1995 disappeared during 1996-2000. Strains of several emm genotypes emerged during 1996-2000, indicating alterations in the prevalent strains causing TSLS.

Antigens, Bacterial↗
PubMed2002

Medullary reticulospinal tract mediating the generalized motor inhibition in cats: II. Functional organization within the medullary reticular formation with respect to postsynaptic inhibition of forelimb and hindlimb motoneurons.

We compared postsynaptic inhibitory effects on forelimb motoneurons and those on hindlimb motoneurons during generalized motor inhibition evoked by stimulating the medullary reticular formation in decerebrate cats. Here, we address two questions. First, whether the medullary inhibitory effects upon forelimb motoneurons are equivalent to those upon hindlimb motoneurons. Second, whether there is a somatotopographical organization within the medullary reticular formation in terms of inhibitory connections with motoneurons. Repetitive stimulation (20-50 microA, 50-100 Hz) delivered to the dorsomedial medullary reticular formation bilaterally suppressed muscle tone of both the forelimbs and hindlimbs. The medullary stimulation hyperpolarized the membrane potentials of the forelimb (5.4+/-1.8 mV, n=46) and hindlimb (5.4+/-2.0 mV, n=59) motoneurons together with a decrease in input resistance. The degree of membrane hyperpolarization and input resistance was not different in the forelimb and hindlimb motoneurons. The medullary stimulation also depressed the capability of generating antidromic and orthodromic spikes in the motoneurons. Stimuli with pulse trains (one to three pulses, 5-10-ms intervals, 20-50 microA) applied to the medullary inhibitory region induced a mixture of excitatory and inhibitory postsynaptic potentials in the motoneurons. The most noteworthy potentials were the inhibitory postsynaptic potentials with a late latency. They were observed in most forelimb (n=57/58, 98.3%) and hindlimb (n=63/64, 98.4%) motoneurons. The inhibitory potentials in forelimb motoneurons had a latency of 25-30 ms and a peak latency of 35-40 ms, and those in hindlimb motoneurons had a latency of 30-35 ms and a peak latency of 50-60 ms. A difference was not observed in the location of the effective sites for evoking the inhibitory effects in the forelimb and hindlimb motoneurons. These sites were homogeneously distributed in the dorsomedial part of the medullary reticular formation corresponding to the location of the nucleus reticularis gigantocellularis. From these findings we suggest that there is an equivalent amount of the postsynaptic inhibitory effects exerted on forelimb and hindlimb motoneurons during medullary-induced generalized motor inhibition. In addition, the medullary reticular formation may be functionally organized as a homogeneous or non-specific region in terms of the medullary reticulospinal inhibitory connections with forelimb and hindlimb motoneurons.

Animals↗
PubMed2001

Age-related hypermethylation of the hMLH1 promoter in gastric cancers.

To determine whether methylation of the hMLH1 promoter is related to increasing age and gastric carcinogenesis, we examined hMLH1 methylation and expression in 100 gastric cancers. hMLH1 methylation and aberrant protein expression were observed in 9 and 13 cancers, respectively. Normal and intestinal metaplastic tissues adjacent to cancers with hypermethylation did not exhibit any hMLH1 methylation, indicating that it may be specific to gastric cancers. The frequency of hMLH1 methylation significantly increased with age. These results suggest that hMLH1 methylation plays an important role in gastric carcinogenesis in old people.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Optimized conditions of bio-mimetic artificial membrane permeation assay.

Effects of pH and co-solvents on the bio-mimetic artificial membrane permeation assay were investigated to determine the optimal conditions for the prediction of oral absorption. The permeability (P(am)) of 33 structurally diverse drugs to the PC/PE/PS/PI/CHO/1,7-octadiene membrane system (bio-mimetic lipid (BML) membrane) was measured at pH 5.5, 6.5, and 7.4. The pH dependence of P(am) was in accordance with the pH partition theory. The better prediction of oral absorption (fraction of a dose absorbed) was shown under the pH 5.5 condition (r=0.866, n=25) and/or pH 6.5 (r=0.865, n=28), rather than pH 7.4 (r=0.767, n=24). Then, the appropriate conditions for determining the permeability of poorly soluble compounds were examined. Dimethysulfoxide (DMSO), ethanol (EtOH) and polyoxyethyleneglycol 400 (PEG 400) were added up to 30% to the transport medium as solubilizers. DMSO, EtOH and PEG 400 decreased P(am) of hydrocortisone and propranolol. For example, DMSO (30%) decreased P(am) of hydrocortisone by 60% and by 70% in the case of propranolol. DMSO and PEG 400 also decreased P(am) of ketoprofen. In contrast, EtOH produced an opposite effect on permeability, i.e. an increased P(am) of ketoprofen. Therefore, the high concentration of these co-solvents could lead to the under- or overestimation of drug permeability.

Algorithms↗
PubMed2001

The von Hippel-Lindau tumor suppressor protein mediates ubiquitination of activated atypical protein kinase C.

The von Hippel-Lindau tumor-suppressor protein (pVHL) forms a protein complex (VCB-Cul2) with elongin C, elongin B, Cul-2, and Rbx1, which functions as a ubiquitin-protein ligase (E3). The alpha-subunits of the hypoxia-inducible factors have been identified as targets for the VCB-Cul2 ubiquitin ligase. However, a variety of cellular defects caused by the depletion of pVHL cannot be explained solely by the ubiquitin-mediated degradation of hypoxia-inducible factor-alpha. We show here that a member of the atypical protein kinase C (PKC) group, PKClambda, is ubiquitinated by the pVHL-containing E3 enzyme. An active PKClambda mutant is ubiquitinated more extensively than wild-type PKClambda in HEK293 cells, and the ubiquitination is further enhanced by the overexpression of pVHL. The activation of wild-type PKClambda by serum stimulation of cells enhances the ubiquitination of the protein, supporting the notion that active PKClambda is preferentially ubiquitinated by VCB-Cul2 ubiquitin ligase. Furthermore, we show that PKClambda can be ubiquitinated in vitro in a cell-free ubiquitination assay using purified recombinant components including VCB-Cul2. Given the known function of aPKC in the regulation of cell polarity and cell growth, PKClambda may be a target of pVHL in its function as a tumor suppressor.

Cell Line↗
PubMed2001

Distinction between space groups having principal rotation and screw axes, which are combined with twofold rotation axes, using the coherent convergent-beam electron diffraction method.

23 sets of space groups remain indistinguishable by the convergent-beam electron diffraction (CBED) method. Recently, Tsuda, Saitoh, Terauchi, Tanaka & Goodman [Acta Cryst. (2000), A56, 359-369] demonstrated that the coherent CBED method can distinguish two space-group pairs (I23, I2(1)3) and (I222, I2(1)2(1)2(1)) by observing the relative arrangements of 2-fold-rotation and 2(1)-screw axes. The other ten space-group sets, which are composed of principal rotation and screw axes and other 2-fold-rotation axes such as P321 and P3(1)21 (P3(2)21), are shown to be distinguishable using the coherent CBED method.

Journal Article↗
PubMed2001

Morphological diagnoses of the Japan adult leukemia study group acute myeloid leukemia protocols: central review.

A morphological review system of the Japan Adult Leukemia Study Group has developed from the AML-87 through the AML-92 experience. We reviewed 1427 (90%) of 1592 cases enrolled in the AML-87, -89, or -92 protocols for morphology; 1408 (88%) were eligible. The rate of diagnostic concordance between each institute and the Committee on Morphological Diagnosis ranged from 76% to 80%. Acute myeloid leukemia (AML) subtypes were as follows: AML M0, 27 (2%); M1, 179 (13%); M2, 472 (34%); M3, 358 (25%); M4, 265 (19%); M5, 57 (4%); M6, 39 (3%); and M7, 11 (1%). The reason for the high number of patients with AML M3 is that many M3 patients were enrolled in the AML-92 protocol, which contained all-trans-retinoic acid. AML M0, M6 and M7 belonged to the poor prognostic groups. Auer bodies were found in 284 (53%) of 538 patients who survived significantly longer than those without Auer bodies in AML-87/-89. In AML-92 except for AML M3, 259 (43%) of 602 cases were Auer+ and also showed better survival rates. The survival of patients with >50% myeloperoxidase (MPO)-positive blast cells was better than those with < or =50% MPO+ blast cells in AML-87/-89. This trend was also seen in AML-92 excluding M3. AML with trilineage dysplasia (AML/TLD) is characterized as a subtype of de novo AML that shows morphological dysplasia of mature hematopoietic cells on a background of leukemic blast cells The number of patients with AML/TLD was 89 (16.5%) of 545 patients reviewed in AML-87/-89. AML-92, except for M3, showed a higher rate of patients with TLD (161 cases; 27.6%) because there were no patients with TLD in the AML M3 group. Survival rates for AML/TLD were worse than those for AML/non-TLD in both the AML-87/-89 and -92 protocols. Eighty percent of all cases (793/986) entered in AML-92 were analyzed cytogenetically. Fifty-one cases were not available for karyotyping because of a lack of mitoses or inappropriate preparations. The most frequent karyotype was normal, which accounted for 34.2%. The t(15;17), t(8;21), and inv(16) karyotypes, which are regarded as good risk factors, were 23.8%, 9.2%, and 1.6%, respectively. Abnormal chromosomes 5, 7, t(9;22), and t(6;9) were considered to be poor or intermediate risk factors As a new system of karyotyping begins in the ongoing AML protocol, useful chromosomal data will be obtained in the near future.

Acute Disease↗
PubMed2001

PCDD/DF formations by the heterogeneous thermal reactions of phenols and their TiO2 photocatalytic degradation by batch-recycle system.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) formation by the thermal reactions of phenols with CuCl2 under oxygen flux were carried out in relation to their formation mechanisms. To evaluate the effect of photocatalytic degradation of titanium dioxide (TiO2) thin film prepared by the sol-gel method, the photocatalysis of PCDD/DFs in acetonitrile/water solution by batch-recycle system was conducted. For the thermal reaction system of powder mixtures of 2,4,5-trichlorophenol (2,4,5-TCP) and CuCl2, the formation rates were 8.1 microg/g-2,4,5-TCP/min for total PCDD/DFs and 6.9 microg/g-2,4,5-TCP/min for PCDDs, and total PCDD/DF rate was higher by approximately 40 fold compared to phenol vapor/oxygen/CuCl2 powder system. For the system of 2,4,5-TCP, PCDDs were mainly formed via ortho-phenoxyphenols (POP) intermediate by the condensation of 2,4,5-trichlorophenate. For PCDD/DF photocatalytic degradations, most PCDD congeners photodecomposed rapidly and the rates presented more than 70% (as dechlorination rates of 76% for PCDDs) at 24 h after irradiation, using PCDD/DFs formed with 2,4,5-TCP. The rate constants were in the order of 4.8-6.1 x 10(-3) min(-1), assuming the pseudo-first-order reactions for their low levels.

Air Pollutants↗
PubMed2001

Comparative study of fibrous dysplasia and osteofibrous dysplasia: histopathological, immunohistochemical, argyrophilic nucleolar organizer region and DNA ploidy analysis.

Fibrous dysplasia and osteofibrous dysplasia are both benign fibro-osseous lesions of the bone. We retrospectively studied the clinicopathological findings in 90 cases of fibrous dysplasia and 17 cases of osteofibrous dysplasia. In these cases, the expression of proliferating cell nuclear antigen (PCNA) and the presence of argyrophilic nucleolar organizer regions (AgNOR), as well as DNA ploidy, were examined. The bones affected by fibrous dysplasia were the maxilla, femur and frontal bone. Osteofibrous dysplasia occurred exclusively in the tibia or fibula. The average age of patients with fibrous dysplasia (24.0 years) was higher than that of patients with osteofibrous dysplasia (12.9 years). Fibrous dysplasias were divided into four major histological subtypes: Pagetoid, Chinese alphabet, small bone and parallel bone. Bone lining cells, which are known as resting osteoblasts, were seen in some cases of fibrous dysplasia. Cartilage differentiation was not seen in osteofibrous dysplasia. PCNA expression was strongly positive in the nuclei of osteoblasts around the bone trabeculae in osteofibrous dysplasia, but negative in the nuclei of bone lining cells around the bone trabeculae in fibrous dysplasia. The number of AgNOR in osteofibrous dysplasia was slightly higher than that in fibrous dysplasia. Both fibrous dysplasia and osteofibrous dysplasia were diploid. These features suggest that fibrous dysplasia can be differentiated from osteofibrous dysplasia by anatomical site, patient age, histological appearance, cartilage differentiation and PCNA positivity. DNA content by image cytometry is not a useful tool for differentiating these two diseases.

Adolescent↗
PubMed2001

Structural study of an Al73Ni22Fe5 decagonal quasicrystal by high-angle annular dark-field scanning transmission electron microscopy.

A water-quenched Al73Ni22Fe5 decagonal quasicrystal was investigated by the selected-area electron diffraction, convergent-beam electron diffraction and high-angle annular dark-field scanning transmission electron microscope methods. The alloy shows very sharp spots and nearly no diffuse scattering in the diffraction patterns, belongs to centrosymmetric space group P10(5)/mmc and is constructed almost by one type of 2 nm diameter atom cluster having mirror symmetry with a highly quasicrystalline order arrangement. Although a small number of 2 nm atom clusters having five-fold symmetry exists, which are similar to those observed in melt-quenched Al70Ni15Fe15, the structure of Al73Ni22Fe5 is considered to basically be the same as that of water-quenched Al72Ni20Co8, which is constructed only by mirror symmetry clusters arranged with a very high quasiperiodicity. The number of valence electrons per atom (e/a) of the present alloy (1.92) is very close to that of Al72Ni20Co8 (1.90), but differs from those of phases constructed by only the five-fold symmetry clusters. This implies that these alloys are Hume-Rothery electron compounds, whose structures are determined primarily by e/a value.

Journal Article↗
PubMed2001

The structure of Si nanocrystals on SiC.

Si nanocrystals grown on cubic SiC have been characterized using high-resolution transmission electron microscopy. At lower temperatures nanocrystals grow in two different orientations, whereas at higher temperatures they grow in a single preferred orientation. The nanocrystals are shown to be unstrained; in some cases possibly due to the presence of a thin amorphous wetting layer.

Letter↗
PubMed2001

Effects of Ca(2+) and calmodulin on the motile activity of characean myosin in vitro.

It is well known that the cytoplasmic streaming of characean cells is readily inhibited by Ca(2+). However, neither the actin-activated MgATPase nor the in vitro motile activity of purified characean myosin were inhibited by Ca(2+). Recently, amino acid sequence of characean myosin was determined in our laboratory and the sequence revealed that characean myosin contains six calmodulin binding sites in the neck region. We also detected calmodulin in quickly prepared characean myosin fraction. It is, therefore, possible that the insensitivity of characean myosin to Ca(2+) is due to the dissociation of some calmodulin molecules from the neck region during the course of protein purification. To determine strictly the Ca(2+) sensitivity of characean myosin, we intentionally used crude preparation of characean myosin to reduce the possibility of calmodulin dissociation and examined the motile activity of characean myosin in vitro in the presence of excess characean calmodulin. We could not observe any drastic inhibition of characean myosin activity by Ca(2+). The results suggest that the brief cessation of cytoplasmic streaming is not caused by the direct inhibition of myosin activity by Ca(2+).

Actins↗