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Biomedical subjects

Takao Kotani

Publications and source records attributed to Takao Kotani.

At least 19 recordsLinked to original sources

Quasiparticle self-consistent GW theory.

In past decades the scientific community has been looking for a reliable first-principles method to predict the electronic structure of solids with high accuracy. Here we present an approach which we call the quasiparticle self-consistent approximation. It is based on a kind of self-consistent perturbation theory, where the self-consistency is constructed to minimize the perturbation. We apply it to selections from different classes of materials, including alkali metals, semiconductors, wide band gap insulators, transition metals, transition metal oxides, magnetic insulators, and rare earth compounds. Apart from some mild exceptions, the properties are very well described, particularly in weakly correlated cases. Self-consistency dramatically improves agreement with experiment, and is sometimes essential. Discrepancies with experiment are systematic, and can be explained in terms of approximations made.

Journal Article↗

Ab initio prediction of conduction band spin splitting in zinc blende semiconductors.

We use a recently developed self-consistent GW approximation to present systematic ab initio calculations of the conduction band spin splitting in III-V and II-VI zinc blende semiconductors. The spin-orbit interaction is taken into account as a perturbation to the scalar relativistic Hamiltonian. These are the first calculations of conduction band spin splittings based on a quasiparticle approach; and because the self-consistent GW scheme accurately reproduces the relevant band parameters, it is expected to be a reliable predictor of spin splittings. The results are compared to the few available experimental data and a previous calculation based on a model one-particle potential. We also briefly address the widely used k x p parametrization in the context of these results.

Journal Article↗

Systemic candidiasis in a dog, developing spondylitis.

A 4-year-old male Shiba dog initially presented with pain of an undetermined origin and hypersensitivity to touch. Seven days later, the dog developed ataxia, hind-leg weakness and knuckling. The dog died on 20 days after presentation. Postmortem examination revealed a mass in the body of thoracic vertebra. Histopathologically, the mass consisted of granulomatous inflammation, including fungal organisms that were immunohistochemically positive for Candida albicans. Similar granulomatous lesions were observed in the systemic lymph nodes, kidneys, pancreas, spleen, prostate gland, thyroid glands and heart. This case was diagnosed as systemic candidiasis with spondylitis.

Animals↗

Olfactory neuroblastoma in a horse.

An 11-year-old thoroughbred gelding was euthanatized because of right nasal cavity tumor. The tumor consisted of round to oval cells with a scanty cytoplasm and hyperchromatic nuclei. Homer-Wright rosettes and pseudorosettes, as well as microcysts were seen. Neoplastic cells were immunoreactive to vimentin, S-100 protein, and neuron-specific enolase, glial fibrillary acidic protein and microtube-associated protein in varying degrees, indicating neurogenic nature. Based on these findings, this tumor was diagnosed as an olfactory neuroblastoma. Since this type is an uncommon tumor showing histological variety, the nature is discussed.

Animals↗

Synovial sarcoma of the tendon and tendon sheath in a dog.

A 19.5-year-old male mongrel dog developed a progressive lameness and swelling around the right carpus. A tumor (6 x 3 x 3 cm) was found in the caudal of distal antebrachium of the right forelimb, including tendons of the superficial digital flexor muscle and deep digital flexor muscle. No joint destruction was observed. The tumor consisted of round and spindle cells arranged in a compact sheet. There were occasional slit-like spaces or lumina, and areas rich in collagen fibers giving an appearance of tendon tissues. Neoplastic cells gave a positive immunoreaction to vimentin, but negative reactions to antibodies against S-100 protein, cytokeratin and myoglobin. Based on these findings, this tumor was diagnosed as a synovial sarcoma generating from the tendon and tendon sheath, which is very uncommon in dogs.

Animals↗

Expression of calbindin-D28K in sporadic nephroblastomas of the chicken.

Calbindin-D28K (Ca-D28K) is a calcium-binding protein. In the kidney, Ca-D28K is present in the distal nephron, but not in the proximal nephron. This site-specific distribution in the kidney indicates that Ca-D28K is a potential marker for the differentiation of the distal nephron. In this study, we have examined the expression of Ca-D28K in 25 sporadic cases of chicken nephroblastomas. All cases of nephroblastomas were composed of atypical tubular structures, blastemal cells, and fibrous stroma in varying degrees of differentiation. Immunohistochemically in all nephroblastoma specimens, Ca-D28K was expressed in the epithelial cells of the subsets of tubular structures, but not in the blastema or the stroma. These results suggested that the tubuli in the nephroblastomas are able to differentiate into the phenotype of distal nephrons. Furthermore, Ca-D28K might develop as a novel diagnostic marker for nephroblastomas because this molecule is reported to be completely negative in other renal tumors, including renal cell carcinoma, chromophobe carcinomas, and oncocytoma.

Animals↗

Expression and adhesive activity of SC1, an Ig superfamily cell adhesion molecule, in sporadic nephroblastomas of chicken.

SC1, an immunoglobulin superfamily cell adhesion molecule, is transiently expressed during avian embryogenesis by a variety of cell types. This molecule has a homophilic binding activity with SC1 itself and promotes neurite projection from embryonic neurons. However, the potential role of this molecule in pathologic tissue specimens from chickens has yet to be elucidated. In this study, we examined the expression and functional role of SC1 in the sporadic nephroblastomas of chickens. Western blot analysis showed SC1 to be recognized as approximately 100 kDa and enriched in embryonic metanephros with a lower level in the adult kidney, while it was overexpressed in nephroblastomas. Immunohistochemically, SC1 was abundantly found in the tubular epithelia and blastemal cells of embryonic metanephros. In contrast, it had almost completely disappeared in the adult kidney; parts of the distal convoluted and intermediated tubules, collecting ducts, and Bowman's capsule slightly expressed SC1. In all 32 cases of nephroblastoma, SC1 was overexpressed in most characteristic components in tumors such as neoplastic epithelia with various types of differentiation, blastemal cell condensations, and glomeruloid bodies. Primary culture cells from a nephroblastoma expressed SC1 on the cell surface, whereas cells from the adult kidney showed only weak expression. A cell aggregation assay revealed that the dissociated cells from a nephroblastoma have strong aggregation activity, which was inhibited by anti-SC1 antibody. In contrast, the self-aggregation of adult chicken kidney cells was weaker than that of the tumor and not inhibited by the antibody. These findings suggest that the expression of SC1 might play a potential role in both the structural formation of nephroblastomas, based on its adhesive activity, and normal renal development.

Activated-Leukocyte Cell Adhesion Molecule↗

Differential immunoexpressions of cytoskeletons in renal epithelial and interstitial cells in rat and canine fibrotic kidneys, and in kidney-related cell lines under fibrogenic stimuli.

Myofibroblasts play an important role in chronic renal interstitial fibrosis. However, the origin and developmental mechanisms remain to be elucidated. The myofibroblasts may express various cytoskeletons during the development. Immunoexpressions of vimentin, desmin and alpha-smooth muscle actin (alpha-SMA) were analyzed using experimentally (cisplatin and unilateral ureteral obstruction) induced rat and spontaneous canine fibrotic kidneys or kidney-related cell lines incubated with transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor-BB (PDGF-BB) or their combination at various concentrations. In rat fibrotic kidneys, both renal epithelia and interstitial cells showed positive reactions to alpha-SMA and vimentin, supporting epithelial-mesenchymal transition (EMT) theory; however, renal epithelia did not react to desmin, though interstitial cells were reactive. Renal epithelia in canine fibrotic kidneys did not show a positive reaction to alpha-SMA, whereas interstitial cells reacted strongly to alpha-SMA; conversely, renal epithelia reacted strongly to desmin, but interstitial cells did not; vimentin expression was infrequently seen in renal epithelia and interstitial cells of canine kidneys. Exposure of TGF-beta1 to porcine renal epithelial cells (LLC-PK1), rat renal interstitial cells (NRK-49F), and rat immature mesenchymal cells (MT-9) dose-dependently increased selectively alpha-SMA-positive cell numbers. Moreover, PDGF-BB exhibited an additive effect on TGF-beta1-induced alpha-SMA expression in these cell lines when simultaneously added. alpha-SMA was the most plastic cytoskeleton under fibrogenic stimuli. This study shows that there are interspecies differences in cytoskeletal immunoexpressions of renal epithelia or interstitial cells between rat and canine fibrotic kidneys, and that the derivation of renal myofibroblasts may be heterogeneous, such as renal epithelia, interstitial cells or immature mesenchymal cells.

Actins↗

Mutation at the Lmx1a locus provokes aberrant brain development in the rat.

A rat short-tail mutation with neurological defects (named queue courte, qc) was discovered. Histopathology in adult qc/qc rats revealed hypoplasia of the cerebellum and hippocampus, maldevelopment of the choroid plexus and corpus callosum. These abnormalities are strongly reminiscent of the phenotypic abnormalities found in the shaker short-tail or dreher (dr) mouse mutation at the LIM homeobox transcription factor 1 alpha locus (Lmx1a). The qc mutation is an autosomal recessive and has been mapped to the dr homologous region on rat chromosome 13, and Northern blot analysis demonstrated no expression of Lmx1a in qc/qc rats. Narrowing and distortion of the ventricles were observed from embryonic day 17 (E17) in qc/qc rats. From E17, fusion of the opposing neuroepithelium and formation of neuroepithelial rosettes were also found. Arrangements of neuroepithelial cells were disturbed and processes of radial glia were disoriented in the fused lesions. Neuronal migration analysis using BrdU immunohistochemistry revealed defective migration from the neuroepithelium toward the neocortex and mesencephalon in qc/qc rats. These findings suggest that the qc mutation is involved in development of the ventricular system and dorsal migration of neurons.

Animals↗

Cisplatin-induced renal interstitial fibrosis in neonatal rats, developing as solitary nephron unit lesions.

Cisplatin (CDDP)-induced renal lesions in rats prove a useful model for analysis of the pathogenesis of post-tubular injury-renal interstitial fibrosis. This study investigated the histopathological changes in 10-day-old neonatal rats induced by a single injection of CDDP (4.5 mg/kg). Compared with age-matched controls, on postinjection (PI) days 1 to 6, the number of apoptotic cells, demonstrable with TUNEL method, was significantly increased in CDDP-treated neonates, and there was no marked epithelial necrosis nor fibrotic lesions. Fibrotic lesions began to be developed solitarily around some nephrons with dilated ducts in the corticomedullary junction on PI day 10 and the lesions became more prominent until PI day 20. The alpha-SMA-positive myofibroblastic cells were seen exclusively in the fibrotic lesions. Additionally, the numbers of macrophages reacting with EDI (specific for exudate macrophages), ED2 (for resident macrophages), and OX6 (recognizing MHC class II antigens expressed in antigen-presenting macrophages/dendritic cells) were significantly increased around the affected renal tubules. A greater immunoreaction for TGF-beta1 was seen mostly in the renal epithelial cells of CDDP-treated neonates. These findings indicated that macrophage populations and myofibrolastic cells as well as TGF-beta1 may be responsible for the production of neonatal renal interstitial fibrosis. Compared with CDDP-injected adult rats that develop extensive interstitial fibrosis (Yamate et al., J Comp Pathol, 1995), the formation of fibrotic lesions was delayed, and the lesions were limited to the area around the affected nephrons; this could be attributable to differences in renal morphology between neonates and mature kidney of adult rats.

Actins↗

Ultrastructural and morphometrical evaluation of the parathyroid gland in iron-lactate-overloaded rats.

Iron lactate was given to Sprague-Dawley rats intravenously at the dosage of 10 mg/kg/day and the early effects on the parathyroid gland were examined ultrastructurally along with the blood level of parathyroid hormone (PTH) after single, 3-day or 6-day administration. Blood levels of electrolytes and other parameters related to osteoclast dynamics were also measured by blood chemistry and histopathology. The plasma parathyroid hormone (PTH) level was elevated in the single and 3-day dosing group but was reduced in the 6-day dosing group. Histopathologically, an increase of osteoclasts in the primary spongiosa was observed in the 3- and 6-day dosing groups. Image analysis of the parathyroid gland revealed that the average area of the storage granule decreased during a experimental period, with the number of storage granules decreasing in the 3- and 6-day dosing group. The chief cells of the parathyroid gland were moderately atrophied in the 6-day dosing group. These results demonstrate that iron lactate immediately promotes discharge of PTH from the storage granules after the treatment and induces an increase of osteoclasts in the primary spongiosa. The findings collectively suggest a pathophysiological mechanism of iron lactate-induced osteopenia in rats.

Animals↗

Immunohistochemical and morphometrical studies on myelin breakdown in the demyelination (dmy) mutant rat.

The demyelination (dmy) rat is a unique mutant exhibiting severe myelin breakdown in the central nervous system (CNS). In this study, we conducted immunohistochemical and morphometrical investigations in the dmy rat. From around 6 weeks of age, the affected rats developed ataxia especially in the hindlimbs. Afterwards, ataxia worsened rapidly, resulting in complete paralysis of the hindlimbs and recumbency. Histopathology at 7 to 10 weeks of age revealed myelin destruction throughout the white matter of the CNS in the dmy rats. The most severely affected lesions were distributed in the corpus callosum, capsula interna, striatum, subcortical white matter, cerebellar peduncle, and ventral and lateral parts of the spinal cord. Immunohistochemistry demonstrated prominent astrogliosis and many ED-1 positive macrophages in the myelin-destructed areas. Until the 4th week, no significant differences in myelin thickness and fiber diameter were found between dmy and control rats. However, from 5 weeks of age, myelin thickness of residual myelinated fibers in dmy rats became significantly less than that in controls. These data indicated that the dmy phenotype shows a prolonged period of myelin destruction, suggesting that dmy mutation affects the adequate maintenance of myelin.

Age Factors↗

All-electron self-consistent GW approximation: application to Si, MnO, and NiO.

We present a new kind of self-consistent GW approximation based on the all-electron, full-potential linear muffin-tin orbital method. By iterating the eigenfunctions of the GW Hamiltonian, self-consistency in both the charge density and the quasiparticle spectrum is achieved. We explain why this form of self-consistency should be preferred to the conventional one. Some results for Si (a representative semiconductor) are presented. Finally we consider many details in the electronic structure of the antiferromagnetic insulators MnO and NiO. Excellent agreement with experiment is shown for many properties, suggesting that a Landau quasiparticle (energy band) picture provides a reasonable description of electronic structure even in these correlated materials.

Journal Article↗

Rat mutations cvd and hob with cerebellar malformations map to chromosome 2.

In this paper, we executed genome mapping and comparative mapping analyses for cvd and hob, autosomal recessive mutations with cerebellar vermis defect and cerebellar dysplasia in the rat. For the linkage analysis, we produced three sets of backcross progeny, (ACI x CVD)F(1) and (F344 x CVD)F(1) females crossed to a cvd homozygous male rat, and (HOB x WKY)F(1) males crossed to hob homozygous female rats. Analysis of the segregation patterns of simple sequence length polymorphism (SSLP) markers scanning the whole rat genome allowed the mapping of these autosomal recessive mutations to rat Chromosome (Chr) 2. The most likely gene order is D2Mgh12 - D2Rat86 - D2Mit15 - D2Rat185 - cvd - D2Rat66 - D2Mgh13, and D2Mit18 - Fga -D2Mit14 - D2Rat16 - hob - D2Mgh13. Crossing test between a proven cvd heterozygous and a hob heterozygous rats demonstrated their allelism. Furthermore, comparative mapping indicated the cvd locus corresponds to mouse chromosome 3 and a strong candidate gene Unc5h3, a causative gene for the rostral cerebellar malformation mouse, was implicated.

Alleles↗

Angioarchitecture of tumors induced by two different cloned cell lines established from a transplantable rat malignant fibrous histiocytoma.

Angiogenesis, a biologic process whereby endothelial cells divide and migrate to form new blood vessels, is a key step in tumor growth, invasion, and metastasis. In the present study, we investigated the differences in angioarchitecture between two different tumors induced by cloned cell lines (MT-8 and MT-9), derived from a transplantable rat malignant fibrous histiocytoma, by scanning electron microscopy of vascular corrosion casts. During a 3-week observation period after implantation, the growth of MT-8 tumors appeared to be faster than that of MT-9 tumors. Histologically, MT-8 tumors were of the uniformly undifferentiated sarcoma type arranged in characteristic organoid structures, and MT-9 tumors showed a storiform growth pattern. In MT-8 tumors, neovascularization occurred by sprouting at postimplantation (PI) week 1, and the newly formed capillaries gradually became more tortuous. In MT-9 tumors, at PI week 1, the corrosion casts of newly formed capillaries mainly showed a wavy course but no finger-like outgrowths of capillaries were seen. At PI weeks 2 and 3, the sprouting was seen specifically in MT-9 tumors, forming basket-like structures and glomeruloid structures of capillaries. These results indicate that angiogenesis or angioarchitecture of MT-8 tumors is different from that of MT-9 tumors, depending on the differences in their tumor histology and by the features like absence or presence of basket-like structures and glomeruloid structures of capillaries.

Animals↗

Relationship of interstitial edema with L-cysteine-induced sperm granulomas in the pubertal rat epididymis.

Although the pathogenesis of sperm granulomas is complicated, the leakage of spermatozoa into extraluminal tissues is regarded as a crucial event. It has been previously shown that pubertal rats injected with L-cysteine develop interstitial edema followed by sperm granulomas in the epididymis. In this study we investigated the relationships between these two lesions in 6-week old rats given daily intraperitoneal injections of L-cysteine (1,000 mg/kg body weight) for 4 weeks. Rats were examined during weeks 0, 1, 2, 3 and 4 after the first injection. Interstitial edema (moderate or severe) and sperm granulomas were seen in the corpus and cauda epididymis of L-cysteine-treated rats in study weeks 2, 3, and 4. There was no marked alteration of basement membrane of the epididymal ducts in the edematous tissues as shown by immunohistochemistry with an antilaminin antibody. However, the extravasation of Evans blue dye given I hour before necropsy suggested that the severe interstitial edema was due to increased vascular permeability. In addition, a small number of neutrophils were seen in the edematous tissues, suggesting that they might play a role in the increased vascular permeability and leakage of epididymal fluid. Interestingly, slight interstitial edema was observed in the caput epididymis in both control and L-cysteine-treated rats in early study weeks 0, 1, and 2. It is speculated that this change was related to the leakage of epididymal fluid due to increased intraluminal pressure depending on rat epididymal maturation. Taken together, these findings suggest that the severe interstitial edema results from increased vascular permeability. This, along with increased intraluminal pressure, might be the trigger for duct rupture, the prerequisite for sperm granuloma formation associated with excessive doses of L-cysteine.

Animals↗

Establishment and characterization of transplantable tumor line (KB) and cell lines (KB-P and KB-D8) from a rat thymus-derived dendritic cell sarcoma.

A transplantable tumor line (KB) was established in syngeneic rats from a naturally occurring sarcoma that had arisen in the thymus of a 24-month-old male F344 rat. Further, a cell line (KB-P) was induced from KB and a cloned cell line (KB-D8) was isolated from KB-P. The primary thymic tumor and KB tumors showed heterogeneous histological growth patterns such as sheet-like, ill-defined bundle, fascicular and interwoven fashions, consisting of spindle cells, oval cells and histiocytic large round cells. Immunohistochemically, neoplastic cells in KB tumors and KB-P and KB-D8 cultures reacted to vimentin and were labeled with antibodies of OX6 (for rat major histocompatibility complex class-II antigens), ED5 (for rat follicular dendritic cells; FDCs) and RED-1 (for interdigitating dendritic cells) in varying degrees, indicating that neoplastic cells exhibited the immunophenotypes of rat dendritic cells. In addition, neoplastic cells were immunoreactive to ED1 (for rat monocytes/macrophages) and ED2 (for rat tissue macrophages), and also showed positive reactions to histiocytic lysosomal enzymes such as acid phosphatase and non-specific esterase. Ultrastructurally, neoplastic cells had cell surface projections, cisterna-like structures and variously developed lysosomes in the cytoplasm. Based on these findings, the present tumor was regarded as dendritic cell-derived sarcoma capable of expressing macrophage-like and histiocytic nature. A reverse-transcription polymerase chain reaction method revealed that the addition of lipopolysaccharide dose dependently increased the expression of mRNA of transforming growth factor-beta1, a proinflammatory factor, in KB-D8 cells. The transplantable line (KB) and cell lines (KB-P and KB-D8) may become useful tools for studying the histogenesis and pathobiological functions of dendritic cells.

Animals↗

Establishment of a transplantable tumor line (IP) derived from rat pulmonary carcinoma, developing humoral hypercalcemia of malignancy in IP-bearing rats.

A transplantable tumor line (IP) was established in syngeneic rats from a spontaneous pulmonary carcinoma found in a male F344 rat aged 25 months. A tissue fragment of IP grew into a nodule, 2-3 cm in diameter, 2-3 weeks after implant, and IP has been serially passed through 26 generations. Lined by cuboidal or columnar epithelial cells, the primary tumor consisted of completely alveolar architecture. However, IP tumors developed various growth patterns such as glandular, acinar, trabecular, cord, and solid, and consisting of epithelial cells showing cellular atypia. Ultrastructurally, neoplastic cells had microvilli, basement membranes, and desmosomes, and occasional cells possessed dense cytoplasmic granules. Interestingly, it was shown by the immunohistochemistry, the RT-PCR method, and immunoradiometric assay that IP tumor cells produce parathyroid hormone-related protein (PTHrP). During a 3-week observation period after implant, IP-bearing rats showed severe emaciation, hypercalcemia, and hypophosphatemia, as well as an increase in osteoclastic areas and a decrease in shaft thickness of the femurs. These were considered to be due to a marked elevation of plasma PTHrP levels. Furthermore, IP-bearing rats developed calcification in various organs including the kidneys, lungs, and heart. These findings in IP-bearing rats were similar to those of humoral hypercalcemia of malignancy (HHM) reported in human cancer patients. PTHrP plays a central role in the development of HHM, but the mechanisms of HHM remain poorly understood. IP may become a useful model for studying the pathogenesis of HHM and the pathophysiological role of PTHrP.

Actins↗