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E T Kimura

Publications and source records attributed to E T Kimura.

At least 19 recordsLinked to original sources
PubMed2004

Comparative genomics of two Leptospira interrogans serovars reveals novel insights into physiology and pathogenesis.

Leptospira species colonize a significant proportion of rodent populations worldwide and produce life-threatening infections in accidental hosts, including humans. Complete genome sequencing of Leptospira interrogans serovar Copenhageni and comparative analysis with the available Leptospira interrogans serovar Lai genome reveal that despite overall genetic similarity there are significant structural differences, including a large chromosomal inversion and extensive variation in the number and distribution of insertion sequence elements. Genome sequence analysis elucidates many of the novel aspects of leptospiral physiology relating to energy metabolism, oxygen tolerance, two-component signal transduction systems, and mechanisms of pathogenesis. A broad array of transcriptional regulation proteins and two new families of afimbrial adhesins which contribute to host tissue colonization in the early steps of infection were identified. Differences in genes involved in the biosynthesis of lipopolysaccharide O side chains between the Copenhageni and Lai serovars were identified, offering an important starting point for the elucidation of the organism's complex polysaccharide surface antigens. Differences in adhesins and in lipopolysaccharide might be associated with the adaptation of serovars Copenhageni and Lai to different animal hosts. Hundreds of genes encoding surface-exposed lipoproteins and transmembrane outer membrane proteins were identified as candidates for development of vaccines for the prevention of leptospirosis.

Animals↗
PubMed2003

Expression of Smad4 and Smad7 in human thyroid follicular carcinoma cell lines.

Smad proteins have been shown tomediate the signal transduction pathway downstream of the transforming growth factor beta (TGFbeta). TGFbeta induces the phosphorylation of Smad2 and Smad3 which associate with Smad4 and translocate to the nucleus where they regulate gene transcription; besides these stimulatory Smads, the inhibitory Smads, Smad6 and Smad7, oppose signaling by blocking receptors and interrupting the phosphorylation of Smads2/3. The loss of TGFbeta-sensitivity, caused by inactivation of components of TGFbeta signaling, as Smad4, underlies a wide variety of human disorders, including cancer. In addition, the overexpression of the inhibitory Smad7, which prevents the phosphorylation of Smad2/3 and consequently inhibits TGFbeta signaling pathways, was observed in some diseases. In the present study we investigated the expression of Smad4 and Smad7 in thyroid cell lines (NPA papillary carcinoma, WRO follicular carcinoma and ARO anaplastic carcinoma) by RT-PCR and immunocytochemistry. Our results show that Smad4 was expressed in all thyroid cell lines and controls analyzed, differently from other classes of tumors where Smad4 expression was deleted. On the other hand, Smad7 was overexpressed in ARO anaplastic cell line, the most malignant follicular thyroid carcinoma. Our data suggest that the abrogation of the TGFbeta response by Smad7 overexpression may be a mechanism for the tumor aggressiveness observed in undifferentiated thyroid tumors.

Adenocarcinoma, Follicular↗
PubMed2003

Comparative analyses of the complete genome sequences of Pierce's disease and citrus variegated chlorosis strains of Xylella fastidiosa.

Xylella fastidiosa is a xylem-dwelling, insect-transmitted, gamma-proteobacterium that causes diseases in many plants, including grapevine, citrus, periwinkle, almond, oleander, and coffee. X. fastidiosa has an unusually broad host range, has an extensive geographical distribution throughout the American continent, and induces diverse disease phenotypes. Previous molecular analyses indicated three distinct groups of X. fastidiosa isolates that were expected to be genetically divergent. Here we report the genome sequence of X. fastidiosa (Temecula strain), isolated from a naturally infected grapevine with Pierce's disease (PD) in a wine-grape-growing region of California. Comparative analyses with a previously sequenced X. fastidiosa strain responsible for citrus variegated chlorosis (CVC) revealed that 98% of the PD X. fastidiosa Temecula genes are shared with the CVC X. fastidiosa strain 9a5c genes. Furthermore, the average amino acid identity of the open reading frames in the strains is 95.7%. Genomic differences are limited to phage-associated chromosomal rearrangements and deletions that also account for the strain-specific genes present in each genome. Genomic islands, one in each genome, were identified, and their presence in other X. fastidiosa strains was analyzed. We conclude that these two organisms have identical metabolic functions and are likely to use a common set of genes in plant colonization and pathogenesis, permitting convergence of functional genomic strategies.

Base Sequence↗
PubMed2001

The contribution of 700,000 ORF sequence tags to the definition of the human transcriptome.

Open reading frame expressed sequences tags (ORESTES) differ from conventional ESTs by providing sequence data from the central protein coding portion of transcripts. We generated a total of 696,745 ORESTES sequences from 24 human tissues and used a subset of the data that correspond to a set of 15,095 full-length mRNAs as a means of assessing the efficiency of the strategy and its potential contribution to the definition of the human transcriptome. We estimate that ORESTES sampled over 80% of all highly and moderately expressed, and between 40% and 50% of rarely expressed, human genes. In our most thoroughly sequenced tissue, the breast, the 130,000 ORESTES generated are derived from transcripts from an estimated 70% of all genes expressed in that tissue, with an equally efficient representation of both highly and poorly expressed genes. In this respect, we find that the capacity of the ORESTES strategy both for gene discovery and shotgun transcript sequence generation significantly exceeds that of conventional ESTs. The distribution of ORESTES is such that many human transcripts are now represented by a scaffold of partial sequences distributed along the length of each gene product. The experimental joining of the scaffold components, by reverse transcription-PCR, represents a direct route to transcript finishing that may represent a useful alternative to full-length cDNA cloning.

Expressed Sequence Tags↗
PubMed2001

Physiopathological effects of the administration of chronic cyanide to growing goats--a model for ingestion of cyanogenic plants.

Ingestion of cyanogenic plants, such as cassava and sorghum, has been associated with goitre and tropical pancreatic diabetes in both humans and animals. Thus, the objective of the present study was to determine the toxic effects on the thyroid and pancreas in growing goats of prolonged exposure to potassium cyanide (KCN). Thirty-four male goats were divided into five groups dosed with KCN at 0 (control). 0.3, 0.6, 1.2 or 3.0 mg/kg daily for 5 months. Blood samples were obtained in order to determine the glucose, cholesterol, thyroxine (T4), triiodothyronine (T3) and thiocyanate concentrations and for haematological studies; pancreas and thyroid gland were collected for histopathological study. The group receiving the highest dose of cyanide showed lower body weight gains and carcase weights and a decrease in plasma T3 concentrations compared to the control group. Reabsorption vacuoles in follicular colloid and normocytic normochromic anaemia were observed in the experimental animals. Inhibition of peripheral conversion of T4 to T3 is suggested. However, no diabetogenic effects were observed.

Animals↗
PubMed2000

Identification of human chromosome 22 transcribed sequences with ORF expressed sequence tags.

Transcribed sequences in the human genome can be identified with confidence only by alignment with sequences derived from cDNAs synthesized from naturally occurring mRNAs. We constructed a set of 250,000 cDNAs that represent partial expressed gene sequences and that are biased toward the central coding regions of the resulting transcripts. They are termed ORF expressed sequence tags (ORESTES). The 250,000 ORESTES were assembled into 81,429 contigs. Of these, 1, 181 (1.45%) were found to match sequences in chromosome 22 with at least one ORESTES contig for 162 (65.6%) of the 247 known genes, for 67 (44.6%) of the 150 related genes, and for 45 of the 148 (30.4%) EST-predicted genes on this chromosome. Using a set of stringent criteria to validate our sequences, we identified a further 219 previously unannotated transcribed sequences on chromosome 22. Of these, 171 were in fact also defined by EST or full length cDNA sequences available in GenBank but not utilized in the initial annotation of the first human chromosome sequence. Thus despite representing less than 15% of all expressed human sequences in the public databases at the time of the present analysis, ORESTES sequences defined 48 transcribed sequences on chromosome 22 not defined by other sequences. All of the transcribed sequences defined by ORESTES coincided with DNA regions predicted as encoding exons by genscan. (http://genes.mit.edu/GENSCAN.html).

Chromosomes, Human, Pair 22↗
PubMed1999

Expression of transforming growth factor beta1, beta2, and beta3 in multinodular goiters and differentiated thyroid carcinomas: a comparative study.

The various isoforms of transforming growth factor-beta (TGFbeta) are growth-inhibiting cytokines for cells of epithelial origin. In malignant thyroid tumors, several studies documented a high expression of TGFbeta in the majority of thyroid follicular cells suggesting a possible role as an inhibitor of cell proliferation. In contrast to this uniform pattern of TGFbeta expression in thyroid cancer, scarce and controversial data have been reported on the expression of TGFbeta in benign multinodular goiter. In the present study, we therefore analyzed the expression of TGFbeta1, TGFbeta2, and TGFbeta3 in normal thyroid tissue, multinodular goiters and papillary thyroid carcinomas by immunohistochemistry. In normal thyroid tissue, expression of the 3 TGFbeta isoforms was barely detectable. However, in the carcinomas, almost all epithelial cells displayed immunoreactivity for the three TGFbeta isoforms. In the nodules from multinodular goiters, all 3 isoforms were found to be expressed although the immunolocalization of the 3 proteins was highly variable. TGFbeta-immunostaining was found in scattered clusters of variable size and, its expression pattern was heterogenous among individual cells within single follicles. TGFbeta-positivity was present in spite of immunostaining for proliferating cell nuclear antigen (PCNA), a marker for actively proliferating cells. In conclusion, this study shows that thyroid carcinomas and benign tumors express the TGFbeta1, TGFbeta2, and TGFbeta3 isoforms. In contrast to the abundant and homogeneous expression in differentiated thyroid carcinomas, TGFbeta expression displays a highly variable interfollicular and intrafollicular pattern in multinodular goiters, suggesting an important role of TGFbeta isoforms in tumorigenesis of thyroid cells.

Adenocarcinoma, Follicular↗
PubMed1996

Acquired and naturally occurring resistance of thyroid follicular cells to the growth inhibitory action of transforming growth factor-beta 1 (TGF-beta 1).

While the multifunctional proteins of the transforming growth factor-beta (TGF-beta) family have a potent antiproliferative effect on thyroid follicular cell growth, increased expression of TGF-beta in proliferating thyroid cells and in thyroid tumours has recently been described, suggesting a secondary counter-regulatory role of these proteins. We have studied further this apparent paradox in vitro using FRTL-5 cells, 5 continuous cell strains from feline multinodular goitres (MNG) and 29 primary cultures prepared from human MNG. While dose dependent inhibition of FRTL-5 cell growth was confirmed, a variable fraction of these cells was naturally resistant towards TGF-beta 1, thus explaining the large interassay variability of growth inhibition (36 to 98% within 2 days, n = 19). After 40 days of continuous exposure, FRTL-5 cells became fully refractory towards TGF-beta 1 inhibition, due to the selective growth of naturally resistant subclones, as demonstrated for example by microscopic observation of three-dimensionally growing collagen-embedded cell clusters. The refractoriness could still be demonstrated even after several cell passages. In addition, 2 out of 5 feline thyroid cell strains obtained from feline MNG and 18 out of 29 primary cultures from human MNG showed a high degree of refractoriness towards TGF-beta. We conclude that constitutively TGF-beta resistant cells may occur in thyroid glands and that persistent TGF-beta refractoriness may secondarily be acquired. Resistant cells may escape regular growth control mechanisms and hence may contribute to the notorious heterogeneity of thyroid growth and to nodular transformation.

Animals↗
PubMed1994

Polyclonal and monoclonal thyroid nodules coexist within human multinodular goiters.

Although somatic mutations have been identified in a subset of thyroid nodules, the pathogenesis of nodules in multinodular goiters remains unclear. Clonal analysis indicates whether a nodule arises from the polyclonal proliferation of a group of cells or forms a clone from a genetically altered cell. Individual thyroid nodules have been shown to be of polyclonal or monoclonal origin. In this study we examined the clonality of several different nodules in patients with multinodular goiters. Clonality was established using the X-chromosomal probe M27 beta, which detects a multiallelic polymorphism at the locus DXS255 in 90% of females. Twenty-five nodules from 9 multinodular goiters were analyzed; 9 nodules were polyclonal, and 16 were monoclonal. Three goiters contained only polyclonal nodules, whereas 3 contained only monoclonal nodules. Polyclonal and monoclonal nodules coexisted in 3 goiters. In 2 goiters, the monoclonal nodules were shown to derive from different progenitor cells. We conclude that polyclonal and monoclonal nodules may coexist in multinodular goiters and that monoclonal nodules can originate from different cells. The coexistence of polyclonal and monoclonal nodules suggests that different pathogenic mechanisms occur simultaneously or that monoclonal nodules emerge secondarily from a polyclonal population due to a growth advantage from a genetically altered cell.

Adult↗
PubMed1993

Morphological and functional polymorphism within clonal thyroid nodules.

Thirty-nine thyroid nodules, removed because of recent growth, were analyzed morphologically by serial histological sections for the classical histomorphological hallmarks of follicular cell replication and for immunohistochemically demonstrable overexpression of the growth-associated ras-gene product p21ras. Clonal analysis was performed using the highly informative probe M27 beta that detects polymorphisms on the locus DXS255 of the X-chromosome. Twenty-four nodules were of clonal and 15 nodules were of poly-clonal origin. Only 3 out of the 24 clonal nodules were histomorphologically uniform. In all others, the structural hallmarks of active growth and the P21ras growth-marker expression were remarkably heterogeneous throughout the tumors. There were no histomorphological characteristics distinguishing these clonal tumors from polyclonal nodules. Even if a clonal thyroid tumor may be originally homogeneous in respect to the parameters studied here, mechanisms must exist that create wide heterogeneity of growth and of morphogenetic potential among the individual follicular cells during further expansion of the nodule. Thus, clonal nodules are much more common in nodular goiters than hitherto assumed on grounds of the classical morphological criteria. The diagnosis of a true monoclonal nodule can no longer rely on morphological and functional criteria alone but requires molecular or cytogenetic analysis of clonality.

Adult↗
PubMed1991

Central role of brown adipose tissue thyroxine 5'-deiodinase on thyroid hormone-dependent thermogenic response to cold.

As judged by the response of uncoupling protein and key enzymes, brown adipose tissue (BAT) is highly dependent upon the local generation of T3 catalyzed by the tissue type II T4 5'-deiodinase (5'-D-II). In hypothyroid rats treated with T3 or T4, the capacity to withstand cold seems better correlated with the normalization of BAT responses than with the liver thyroid status. 5'D-II is activated by cold via sympathetic nervous system (SNS) stimulation, and the activation generates enough T3 to nearly saturate BAT nuclear T3 receptor (NTR) in euthyroid rats. In hypothyroidism, 5'D-II is highly stimulated by the SNS and hypothyroxinemia. In the present studies we have taken advantage of this situation to test 1) the capacity of 5'D-II to maintain nuclear T3 in rats with various degrees of hypothyroxinemia, and 2) the hypothesis that thyroid hormone-dependent BAT-facultative thermogenesis, rather than the effect of thyroid hormone on obligatory thermogenesis (basal metabolic rate), is the basic mechanism by which thyroid hormone confers protection against acute cold exposure. We treated methimazole-blocked rats (undetectable plasma T4 and T3) for a week with either subreplacement doses of T4 (0.5, 1, 2, and 4 micrograms/kg.day) or replacement doses of T4 or T3 (8 or 3 micrograms/kg.day, respectively). Sources and content of BAT nuclear T3 were studied at 25 C and after 48 h at 4 C by labeling the plasmaborne T3 (T3[T3]) with [131I]T3 and the locally generated T3 (T3[T4]) with [125I]T4. Neither the kinetics of nuclear-plasma exchange of T3[T3], the time of appearance of T3[T4] in BAT nuclei, nor NTR maximal binding capacity (0.71 ng T3/mg DNA) was affected by hypothyroidism. Kinetic analyses indicated a maximal BAT NTR occupancy of 40% at euthyroid serum T3 concentrations if T4 is not present. Replacement with T4 normalized both serum T4 and T3, while replacement with T3 normalized serum T3; for all other doses of T4, serum T4 and T3 concentrations were predictably related to the dose. 5'D-II activity decreased with increasing doses of T4, but for each dose of T4, this activity was 2-4 times greater at 4 C than at 25 C. BAT NTR occupancy normalized with 2 micrograms T4/kg in rats maintained at 25 C and with 4 micrograms T4/kg in cold-exposed rats, although in neither condition were serum T4 and T3 normalized nor more than 30% of NTR occupied by plasma T3.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue, Brown↗
PubMed1985

Acute, subchronic, and chronic toxicity studies with 3-O-demethylfortimicin A disulfate, a new aminocyclitol antibiotic.

The acute LD50 for 3-O-demethylfortimicin A disulfate (ODMF) in mice and rats were 419 and 778 mg activity/kg (dosages are expressed in terms of antibiotic activity (potency), rather than on a weight basis) for single-dose im administration and, 90 and 96 mg activity/kg for single-dose iv administration, respectively. No drug-related gross or microscopic lesions were found in rabbits given single iv infusions of ODMF at dosages of 10 to 400 mg activity/kg. Minimal to mild muscle irritation was seen in rabbits given im concentrations of 3.8 or 7.5% ODMF at dosages of 48 or 93 mg ODMF activity/kg. In 1-month iv studies in dogs treated with ODMF at dosages of 0.4, 1, 4, or 8 mg activity/kg/day, and in concurrent studies in rats treated with ODMF dosages of 1, 3, 6, or 12 mg activity/kg/day, treated animals remained essentially free of adverse effects. In 1-month im studies in dogs treated with ODMF at dosages of 1, 4, 8, or 16 mg activity/kg/day, no renal lesions occurred after an ODMF dosage of 1 mg activity/kg/day. Concurrent im studies in rats treated with ODMF at dosages of 6, 12, 24, or 48 mg activity/kg/day showed that ODMF dosages of 6 and 12 mg activity/kg/day did not produce renal lesions. In 6-month chronic im studies in dogs with ODMF dosages of 0.5, 1, or 4 mg activity/kg/day or gentamicin sulfate (GS) dosages of 2 mg activity/kg/day, and in concurrent studies in rats treated with ODMF dosages of 0.5, 2, or 6 mg activity/kg/day or GS dosages of 3 mg activity/kg/day, less severe local irritation and nephrotoxicity occurred after treatments with ODMF than with GS. In both rats and dogs treated by either the iv or the im route of administration, higher concentrations of ODMF and GS were found in the kidneys than in the sera. Mean serum and tissue concentrations of GS were higher than those of ODMF. Local tissue irritation and nephrotoxicity were lower with ODMF than with GS on a milligram activity per kilogram basis.

Aminoglycosides↗
PubMed1984

Carcinogenic evaluation of estazolam via diet in CD strain Sprague-Dawley rats and B6C3F1 mice for 2 years.

A comparative toxicity and carcinogenicity study was carried out for 2 years with estazolam, a benzodiazepine, via diet in Sprague-Dawley rats (0.5, 2, and 10 mg/kg/day) and in B6C3F1 mice (0.8, 3, and 10 mg/kg/day). In rats, no biologically significant changes were seen with respect to mortality, clinical signs, food consumption, or occurrence of palpable masses. Body weight gain in females (10 mg/kg/day) was depressed 12.6% and reflected a maximum-tolerated dosage (females). Spontaneous and incidental nonneoplastic lesions were consistent with aging in this species and unrelated to drug treatment. No biologically significant differences in tumor incidences occurred. Mice were more responsive to estazolam as suggested by (1) increased mortality (males) at 10 mg/kg/day, (2) increased food consumption and body weight gains (females), (3) withdrawal signs characterized by hyperactivity/aggressiveness and convulsions, and (4) appearance of dose-related nodular hyperplasia of the liver due to the relatively high dosages used coupled with the propensity of benzodiazepines to enhance liver enzyme induction. Several spontaneous benign and malignant tumors observed in all groups were not considered to be drug related. Based on the findings in these studies, estazolam was not considered to be carcinogenic when administered via diet to either rats at 0.5, 2, and 10 mg/kg/day or to mice at 0.8, 3, and 10 mg/kg/day for 2 consecutive years.

Animals↗
PubMed1976

Regression of corpora lutea in the rabbit after injection of a gonadotropin-releasing peptide.

We have shown that a potent agonist of the luteinizing hormone injected on either Day 11 of pseudopregnancy of Day 15 of pregnancy causes luteinization of ovarian follicles and a rapid regression of functional corpora lutea. Serum levels of progesterone declined markedly within 3 days of peptide injection in pregnant animals. In the presence of regressing corpora lutea, fetal resorption occurs which can be prevented by estradiol (500 ng, twice a day) or progesterone. Daily levels of estradiol below 4 mug did not maintain either corpora lutea weight or fetal survival, whereas 4 mug of the steroid maintained corpora lutea weight, but not pregnancy.

Animals↗