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PubMed2003

Differential gene expression profiles in colon epithelium of two rat strains with distinct susceptibility to colon carcinogenesis after exposure to PhIP in combination with dietary high fat.

Colon cancers develop through accumulation of multiple genetic and epigenetic alterations in colon epithelial cells, and the environment of the genetically altered epithelial cells may also have a substantial impact on their further development to cancer. In the present study, groups of 6-week-old F344 and ACI male rats, the former strain being susceptible to colon carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and the latter being relatively resistant, were subjected to a long-term carcinogenesis experiment using our intermittent feeding protocol of PhIP in combination with a high-fat diet, which serves as a relevant risk factor that promotes the development of colon cancers. Animals were sacrificed at 60 weeks, and global gene expression analyses of normal parts of colon epithelial tissues were conducted using a high-density oligonucleotide microarray to elucidate the differential gene expression profile (environment) in normal colonic regions between F344 and ACI strains. Of 8799 entries on the RatU34A array, 74 genes exhibited 3-fold or greater variation. A subset of genes encoding ribosomal RNAs and proteins were highly preferentially expressed in the F344 strain. In addition, genes encoding fatty acid binding proteins and the peroxisome membrane protein 70 appeared up-regulated in the susceptible F344 strain. In the ACI strain, a mismatch repair gene, Msh2, was preferentially expressed, at approximately 20-fold the F344 level, along with a gene encoding a detoxification enzyme, catechol-O-methyltransferase. The combined effects of the repertoire of these differentially expressed genes in normal colon epithelial tissues may account for the distinct susceptibilities of F344 and ACI strains to colon carcinogenesis.

Animals↗

PubMed2003

Correlations of anti-dsDNA and anti-ribosomal P autoantibodies with lupus nephritis.

Patients with systemic lupus erythematosus, with and without nephritis, were studied for their serological profiles. Patients were stratified into two groups defined by the presence or the absence of precipitating antibodies to ribosomal P proteins. It was found that 27 patients were positive for anti-P precipitins and the remaining 34 patients were studied for the presence of lesser amounts of anti-P antibodies by Western blot and ELISA tests. The nephritic patients were characterized most frequently by the presence of both autoantibodies to dsDNA and the ribosomal P proteins. In the group with anti-P precipitins, anti-dsDNA titers were much higher in the patients with nephritis than in those without nephritis. Thus, over a wide range of anti-ribosomal P antibody concentrations, the mutual occurrence of anti-P antibodies with anti-dsDNA antibodies was strongly associated with lupus nephritis.

Autoantibodies↗

PubMed1983

The ependymal secretion of the fetal and adult rat subcommissural organ. morphological aspects linked to the synthesis, storage and release of the secretory products.

Different localizations of secretory material are noted in adult and fetal subcommissural organ (SCO) in light microscopy. At the electron microscope level, the secretory ependymocytes reveal frequent associations among mitochondria and ribosomes of the endoplasmic reticulum (ER). In the SCO ependymocytes of the adult rat, the relationship between mitochondria and ribosomes of the ER is observed in the subgolgian zone, the ER cisternal profiles are smooth except where they face the mitochondria. Here, a constant interval of 40-45 nm separates the ribosome-coated ER membrane from the external membrane of the mitochondria. This association evidences a functional cooperation between mitochondria and ER, at least in some phases of the synthesis of the organ's gliosecretory material. By contrast, in the fetus (17-21 fetal day), the synthetic apparatus displays an entirely granular ER. The secretory products are stored as flocculent material which fills the ER cisternae. In the apical zone of the ependymocytes, as the membrane of the dense secretory granules fuses with the apical plasmalemma, the granules release their contents into the ventricular cavity. A possible link between the releasing process and the coated vesicles is discussed.

Animals↗

PubMed2001

The ribosomal S6 kinases, cAMP-responsive element-binding, and STAT3 proteins are regulated by different leukemia inhibitory factor signaling pathways in mouse embryonic stem cells.

Mouse embryonic stem (ES) cells remain "pluripotent" in vitro in the continuous presence of leukemia inhibitory factor (LIF). In the absence of LIF, ES cells are irreversibly committed to differentiate into various lineages. In this study we have set up an in vitro assay based on the anti-apoptotic activity of LIF to distinguish pluripotent from "differentiation-committed" ES cells. We have examined the phosphorylation profiles of known (STAT3 and ERKs) and identified new (ribosomal S6 kinases (RSKs) and cAMP-responsive element-binding protein (CREB)) LIF-regulated targets in ES and in ES-derived neuronal cells. We have demonstrated that although STAT3, a crucial player in the maintenance of ES cell pluripotency, is induced by LIF in all cell types tested, the LIF-dependent activation of RSKs is restricted to ES cells. We have shown that LIF-induced phosphorylation of RSKs in ES cells is dependent on ERKs, whereas STAT3 phosphorylation is not mediated by any known MAPK activities. Our results also demonstrate that the LIF-dependent phosphorylation of CREB is partially under the control of the RSK2 kinase.

Animals↗

PubMed2002

Important contribution to catalysis of peptide bond formation by a single ionizing group within the ribosome.

The catalytic mechanism of peptide bond formation on the ribosome is not known. The crystal structure of 50S ribosomal subunits shows that the catalytic center consists of RNA only and suggests potential catalytic residues. Here we report rapid kinetics of the peptidyl transferase reaction with puromycin at rates up to 50 s(-1). The rate-pH profile of the reaction reveals that protonation of a single ribosomal residue (pK(a) = 7.5), in addition to protonation of the nucleophilic amino group, strongly inhibits the reaction (>100-fold). The A2451U mutation within the peptidyl transferase center has about the same inhibitory effect. These results suggest a contribution to overall catalysis of general acid-base and/or conformational catalysis involving an ionizing group at the active site.

Binding Sites↗

PubMed1976

The mammalian rete testis--a morphological examination.

The fine structure of the rete testis was examined in several primates, domestic animals and rodents. The rete testis consists of a series of interconnected wide channels lined with a simple cuboidal to columnar epithelium, resting on a thick basal lamina. Beneath the basal lamina dense bundles of collagen fibrils and a few blood vessels, lymphatics or nerve tissue are found. The epithelial cells are characterized by large, deeply indented nuclei, spherical or short rod-shaped mitochondria, supranuclear Golgi profiles, some cisterns of rough endoplasmic reticulum, free ribosomes and numerous micropinocytotic vesicles in the ectoplasmic regions. Smooth endoplasmic reticulum, secretory granules, lysosomes or other types of dense bodies are rarely seen. The apical surface of the cells bears numerous microvilli and a single very long flagellum which is presumed to be motile. Ajoining lateral cell membranes exhibit a juxtaluminal tight junction, elaborate interdigitations and desmosomes. The basal plasma membrane is highly irregular greatly increasing its surface area of contact with the underlying interstitium. The nuclei of the rete epithelial cells contain pale-staining, spherical structure, 2 mum in diameter, composed of circularly oriented fine filaments. The significance of the nuclear structures remains unknown. Thorotrast was injected into the lumen of the hamster and rat rete testis and 30 minutes later the proximal portion of the excurrent duct system of the testis was prepared for electron microscopy. Whereas the ductuli efferentes and first part of the epididymis possessed numerous apical vesicles filled with the thorotrast, this electron opaque substance was rarely found in the epithelium of the rete testis. Thus, incorporation of particulate matter into the lining cells of the rete from its lumen is apparently less active than in the epithelium of the ductuli and epididymis. Vascularly introduced intercellular tracer compounds such as lanthanum nitrate or horseradish peroxidase did not enter the lumen of the rete testis from the interstitium. The tracer molecules appeared to be blocked by the juxtaluminal tight junction separating adjacent epithelial cells. This latter observation suggests that a blood-testis barrier exists at the level of the rete testis epithelium. Although physiological studies have indicated that the composition of fluid secreted in the seminiferous epithelium is considerably modified in the rete testis, the present morphological study does not provide additional evidence to support a secretory or absorptive function for this region of the excurrent duct system of the testis.

Animals↗

PubMed1994

Fine structure of taste buds located on the lamb epiglottis.

BACKGROUND: Taste buds located on the aryepiglottal folds and laryngeal surface of the epiglottis are the principal receptors responsible for the initiation of the laryngeal chemoreflex. In contrast to the wealth of information available concerning the ultrastructure of oral taste buds, little comparable data exists for taste buds located at the entrance to the larynx. Therefore, the present study was designed to investigate the fine structure of taste buds located on the lamb epiglottis. MATERIALS: Stained thick and semi-serial thin sections from taste buds located on the lamb epiglottis were examined with light and electron microscopy. RESULTS: Based on morphological criteria, three types of cells could be identified in the taste bud: Type I, Type II, and basal cells. Both Type I and Type II cells extended into the apical taste pore, but there were differences between these two cell types with regard to nuclear profiles, electron density, and the relative density of ribosomes, apical mitochondria, and rough and smooth endoplasmic reticulum. Basal cells did not extend a process into the taste pore. Nerve processes were observed throughout the taste bud. Synapses were observed between both Type I and Type II cells and nerve fibers. These synapses exhibited membrane thickenings and accumulations of clear and dense-cored vesicles of varying proportions in the taste cell cytoplasm adjacent to membrane specializations. CONCLUSIONS: The taste buds located on the lamb epiglottis share several structural similarities to taste buds located in the oral cavity and other regions of the pharynx and larynx of many mammalian species. The presence of synapses on both Type I and Type II cells of the lamb epiglottal taste bud suggests that both cell types are involved in laryngeal chemoreception.

Animals↗

PubMed1980

The pregeniculate nucleus of the monkey (Macaca multatta). II. A study at the electron microscopic level.

An electron microscope study of the ultrastructure of the pregeniculate nucleus of the monkey (Macaca mulatta) shows it to contain three neuronal types and four varieties of presynaptic terminals. Type I neurons are found only in the inner lamina, have small rounded profiles with few axosomatic synapses; the cytoplasm is poor in organelles and the nucleus is deeplly infolded. Type II neurons were observed infrequently and only in the outer lamina; they have large oblong profiles, exhibiting many axosomatic contacts, and containing abundant cytoplasm rich in organelles, particularly arrays of granular and agranular endoplasmic reticulum. Type III neurons were the most frequently seen and are found in both laminae; their profiles are elliptical and exhibit only a few axosomatic synapses. The cytoplasm surrounding the infolded nucleus is moderately rich in organelles with agranular endoplasmic reticulum predominating. These three neuronal types were found to correlate well with types of neurons found in material stained with cresylecht violet or impregnated by the Golgi method. Four presynaptic terminal types were discerned: a small cup-shaped profile containing spheroid vesicles and found predominantly in the outer lamina, a larger elliptical profile containing flattened spheroid vesicles, a large ramifying profile also containing round vesicles and largely restricted to the inner lamina, and a rounded profile containing larger flattened vesicles. Three days after eye enucleation, darkened degenerating profiles containing vesicles and forming asymmetric synapses were observed in the inner lamina, while the third terminal type described above could no longer be seen. The first three types are usually associated with asymmetric synaptic densities, whereas in the case of the last type, the postsynaptic synapse is symmetrical. The profile of this last terminal type was also sometimes observed to be both postsynaptic as well as presynaptic to other profiles; however, it was never observed to contain ribosomes. Such a pre- and postsynaptic terminal always forms part of the in series or triadic configuration of terminals occasionally observed in the pregeniculate nucleus.U

Animals↗

PubMed2004

Annual patterns in bacterioplankton community variability in a humic lake.

Bacterioplankton community composition (BCC) was monitored in a shallow humic lake in northern Wisconsin, USA, over 3 years using automated ribosomal intergenic spacer analysis (ARISA). Comparison of ARISA profiles of bacterial communities over time indicated that BCC was highly variable on a seasonal and annual scale. Nonmetric multidimensional scaling (MDS) analysis indicated little similarity in BCC from year to year. Nevertheless, annual patterns in bacterioplankton community diversity were observed. Trends in bacterioplankton community diversity were correlated to annual patterns in community succession observed for phytoplankton and zooplankton populations, consistent with the notion that food web interactions affect bacterioplankton community structure in this humic lake. Bacterioplankton communities experience a dramatic drop in richness and abundance each year in early summer, concurrent with an increase in the abundance of both mixotrophic and heterotrophic flagellates. A second drop in richness, but not abundance, is observed each year in late summer, coinciding with an intense bloom of the nonphagotrophic dinoflagellate Peridinium limbatum. A relationship between bacterial community composition, size, and abundance and the population dynamics of Daphnia was also observed. The noted synchrony between these major population and species shifts suggests that linkages across trophic levels play a role in determining the annual time course of events for the microbial and metazoan components of the plankton.

Bacterial Physiological Phenomena↗

PubMed1984

A diploid epithelial cell line from normal adult rat liver with phenotypic properties of 'oval' cells.

A diploid epithelial cell line (termed WB-F344) was isolated from the liver of an adult male Fischer-344 rat and the phenotypic characteristics of the cells were studied. These cells measure approximately two-fifths the volume of freshly isolated hepatocytes. They are histochemically negative for glucose-6-phosphatase and weakly positive for gamma-glutamyl transpeptidase. They produce extensive intercellular reticulin fibers which stain immunocytochemically for fibronectin, and they synthesize both alpha-fetoprotein and albumin, but they do not accumulate glycogen particles. Ultrastructurally, they are polygonal cells with numerous intercellular desmosomes and nexus junctions, and they are partially surrounded by basement membrane-like material. Cytoplasmic organelles include few, but sometimes dilated profiles of rough endoplasmic reticulum, lysosomes, abundant free ribosomes, sparse smooth endoplasmic reticulum and Golgi membranes, microbodies, and small, pleomorphic mitochondria. They express A and C isozymes of aldolase, K isozyme of pyruvate kinase, LDH2 to LDH5 isozymes of lactate dehydrogenase, and 'fetal liver'-type alkaline phosphatase isozyme. When compared with the phenotypes of isolated and purified normal hepatocytes, biliary epithelial (ductular) cells and 'oval' cells isolated from livers treated with chemical carcinogens, the phenotypic properties of the liver epithelial cell line in culture most resemble those of the 'oval' cells.

Animals↗

PubMed1993

Study of Listeria monocytogenes contamination in a dairy plant and characterization of the strains isolated.

From 1988 to 1990, a dairy plant was examined for Listeria contamination. Three hundred and forty samples were collected and analysed for the presence of Listeria. Sixty-one Listeria strains (L. monocytogenes, 44, and L. innocua, 17) were isolated from four varieties of cheese, cheese brines, process equipment and plant environment. The L. monocytogenes strains were recovered during the ripening and rind washing stages and not before, so it is likely that cheese contamination occurred at these points in the manufacturing process. The characterization of the isolated L. monocytogenes strains by serotyping and phage typing showed different serovars and phagovars. Some strains with the same serovar and the same phagovar were isolated from cheeses and process equipment (shelves) indicating that cheese contamination occurs during ripening. Only one profile was found from the analysis of the ribosomal ribonucleic acid (rRNA) gene restriction patterns of 38 L. monocytogenes strains with different serovars and phagovars. This suggests that all L. monocytogenes strains isolated in the dairy plant could have been derived from a single ancestral group.

Animals↗

PubMed2002

An rRNA mutation identifies the apicoplast as the target for clindamycin in Toxoplasma gondii.

Toxoplasma gondii is a protozoan sensitive to several inhibitors of prokaryotic translation (e.g. clindamycin, macrolides and tetracyclines). A priori, two prokaryotic-like organelles, the 'apicoplast' (a non-photosynthetic plastid) and the mitochondrion, are likely targets for these drugs. Without using overt mutagenesis, we selected two independent clones (ClnR-4 and ClnR-21) with strong and stable clindamycin resistance. Several lines with substantial but lower levels of resistance were also isolated with (XR-46) or without (ClnR-23) overt mutagenesis. The ClnR-4 and ClnR-21 mutants uniquely possess a G-->U point mutation at position 1857 of the apicoplast large-subunit rRNA, whereas no mutation was identified in this region for ClnR-23 or XR-46. Position 1857 corresponds to position 2061 in Escherichia coli where it is predicted to bind clindamycin. The mutation is present in all the apicoplast rDNA copies (an estimated 12 per organelle), indicative of a strong selective advantage in the presence of clindamycin. In the absence of drug, however, such a mutation is unlikely to be neutral, as the G is a critical contributor to the transpeptidation reaction and absolutely conserved in all kingdoms. This may explain why ClnR-4 shows a slight growth defect in vitro. These mutants provide direct genetic evidence that apicoplast translation is the target for clindamycin in Toxoplasma. Further, their sensitivity profiles to other antibiotics specific for the large ribosomal subunit (macrolides and chloramphenicol) and, intriguingly, the small subunit (doxycycline) argue that these drugs also target the apicoplast ribosome.

Animals↗

PubMed1974

Concomitant effects of insulin on surface membrane conformation and polysome profiles of serum-starved BALB-C 3T3 fibroblasts.

By scanning and transmission electron microscopy we have shown that insulin rapidly reversed changes in surface membrane conformation and polysome profile induced by the transfer of actively growing Balb/c 3T3 fibroblasts from a serum-containing to a serum-free medium. Morphometric analysis of polysome profiles revealed a 94% aggregation of total f ribosomes during logarithmic growth. This figure fell to 78% after 18 h of serum starvation. The number of f ribosomes per unit area of cytoplasm also fell. 1 h of insulin treatment restored aggregation to 92% and increased the number of f ribosomes per unit area of cytoplasm by 22%. Scanning electron microscopy of logarithmically growing cells revealed an abundance of surface microvilli, whereas serum starvation promoted a smooth surface with few microvilli. After 1 h of insulin treatment, microvilli reappeared with a distribution and subcellular organization characteristic of exponential growth. This study shows the combined and rapid effect of insulin on the regulation of polysome formation and the promotion of a specific surface membrane conformation in cultured cells. The observations are consistent with the knowledge that insulin, acting on the surface membrane, can influence such parameters as membrane transport, and the rates of protein and RNA synthesis.

Animals↗

PubMed1993

Widespread colonization of personnel at a Veterans Affairs medical center by methicillin-resistant, coagulase-negative Staphylococcus.

A serial prospective survey of nasal colonization of hospital personnel by methicillin-resistant coagulase-negative staphylococci (MRCNS) was conducted at a Veterans Affairs medical center on three occasions over a 16-month period. The epidemiological typing systems used to assess relatedness included antimicrobial susceptibility profiles; biotyping; phage typing; plasmid profiles; restriction fragment length polymorphism (RFLP) analysis with ribosomal RNA; and plasmid hybridization with a 1.68-MD plasmid as the DNA probe. Forty-three percent of all personnel and 62% of all nurses were colonized with MRCNS. Nurses on the wards (72%) and in the intensive care unit (73%) were significantly more likely to be colonized with MRCNS than nurses who had less contact with patients or those who worked in the operating room. The molecular epidemiological typing systems indicated some degree of relatedness among the strains. Specifically, riboprobe analysis revealed a Dice coefficient of > 90%. However, each typing system detected dissimilarity among strains. Further studies are needed to determine the role that such human reservoirs of MRCNS serve in horizontal transmission to and subsequent infection of hospitalized patients.

Bacteriophage Typing↗

PubMed1979

Maxillofacial synovial sarcoma. Light- and electron-microscopic study of two cases.

The light microscopy and ultrastructural features of two maxillofacial synovial sarcomas are presented. By light microscopy, one of the tumors revealed the typical biphasic pattern while the other was predominantly fibrosarcomatous. Ultrastructurally, both cases revealed a biphasic pattern. Epithelial-like cells displayed abundant mitochondria, Golgi profiles, electron-dense bodies, cytolysosomes, and thin filaments. Stromal cells were spindle-shaped and provided with smaller cytoplasm and scant organelles, mainly consisting of profiles of rough endoplasmic retuculum, mitochondria, and free ribosomes. Pseudoglandular spaces lined by cuboidal to flattened epithelial-like cells with apical microvilli were numerous. Basal lamina and intercellular junctions were prominent in one case, but sparse in the other. The most undifferentiated tumor revealed many intercellular clefts containing filopodia among the epithelial-like cells; occasional intracyltoplasmic lumina were also present. These findings are somewhat similar to those reported in normal and nonneoplastic diseases of the synovium. However, the location of the tumors in areas normally devoid of synovium suggests one more that they might arise from nonspecialized primitive mesenchyme.

Child↗

PubMed1996

Novel Psychrobacter species from Antarctic ornithogenic soils.

Ornithogenic soil is derived from the deposition of the fecal matter of various species of birds and is a major source of nutrient input in the Antarctic marine ecosystem. A significant proportion of microbiota of ornithogenic soil collected from an Adélie penguin colony in eastern Antarctica (Vestfold Hills ice-free zone) consisted of gram-negative, coccoid bacteria identified on the basis of their phospholipid ester-linked fatty acid and lipid class profiles as Psychrobacter strains. Phenotypic, genotypic, and 16S ribosomal DNA phylogenetic analyses revealed that the Antarctic psychrobacters belonged to three distinct groups. Comparisons with Psychrobacter immobilis and Moraxella phenylpyruvica reference cultures isolated from fish, seawater, poultry, and human clinical specimens revealed the relationships of these groups within the genus Psychrobacter. Two of the groups represent the following two novel species: Psychrobacter urativorans sp. nov. (type strain, strain ACAM 534) and Psychrobacter frigidicola sp. nov. (type strain, strain ACAM 304). The third group of strains included members of the previously described species P. immobilis (Juni and Heym 1986). In addition, M. phenylpyruvica (Bøvre and Henriksen 1967) is renamed Psychrobacter phenylpyruvicus comb. nov. (type strain, strain ACAM 535) on the basis of 16S ribosomal DNA phylogenetic data. In general, the genus Psychrobacter could be differentiated from the related genera Moraxella and Acinetobacter by the fact that the members of the genus Psychrobacter are psychrotolerant or psychrophilic and halotolerant, which reflects the ubiquitous distribution of the genus in both marine and terrestrial environments. On the basis of the results of this and previous studies, the genus Psychrobacter is the predominant genus in ornithogenic soils in Antarctica and is diverse.

Antarctic Regions↗

PubMed2006

Microbial ecology in the age of genomics and metagenomics: concepts, tools, and recent advances.

Microbial ecology examines the diversity and activity of micro-organisms in Earth's biosphere. In the last 20 years, the application of genomics tools have revolutionized microbial ecological studies and drastically expanded our view on the previously underappreciated microbial world. This review first introduces the basic concepts in microbial ecology and the main genomics methods that have been used to examine natural microbial populations and communities. In the ensuing three specific sections, the applications of the genomics in microbial ecological research are highlighted. The first describes the widespread application of multilocus sequence typing and representational difference analysis in studying genetic variation within microbial species. Such investigations have identified that migration, horizontal gene transfer and recombination are common in natural microbial populations and that microbial strains can be highly variable in genome size and gene content. The second section highlights and summarizes the use of four specific genomics methods (phylogenetic analysis of ribosomal RNA, DNA-DNA re-association kinetics, metagenomics, and micro-arrays) in analysing the diversity and potential activity of microbial populations and communities from a variety of terrestrial and aquatic environments. Such analyses have identified many unexpected phylogenetic lineages in viruses, bacteria, archaea, and microbial eukaryotes. Functional analyses of environmental DNA also revealed highly prevalent, but previously unknown, metabolic processes in natural microbial communities. In the third section, the ecological implications of sequenced microbial genomes are briefly discussed. Comparative analyses of prokaryotic genomic sequences suggest the importance of ecology in determining microbial genome size and gene content. The significant variability in genome size and gene content among strains and species of prokaryotes indicate the highly fluid nature of prokaryotic genomes, a result consistent with those from multilocus sequence typing and representational difference analyses. The integration of various levels of ecological analyses coupled to the application and further development of high throughput technologies are accelerating the pace of discovery in microbial ecology.

DNA, Ribosomal↗

PubMed1991

Equine synovial tendon sheaths and bursae: a transmission electron microscope study.

A transmission electron microscope study was undertaken to investigate the details of the synovial tendon sheath and bursal lining in horses. The lining cells appeared to be fibroblasts and were buried in a finely granular ground substance. Generally these cells had poor cytoplasmic organelles, sparse short profiles of rough endoplasmic reticulum (RER), few scattered ribosomes and, occasionally, a poorly developed Golgi complex. However, a few lining cells appeared more active, having pronounced RER with dilated cisternane. The surface of the lining cells, particularly those with dilated RER, had filipodia of different shapes, which in some instances appeared to surround a detached matrix. This feature might indicate that these cells are capable of phagocytosis. In young animals, the lining was more or less akin to that of the adult. However, the lining cells were virtually indistinguishable from the fibroblasts in the subconnective tissue.

Animals↗