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Biomedical subjects

R Wu

Publications and source records attributed to R Wu.

At least 343 records · Page 19Linked to original sources
PubMed1990

The Pisum sativum mitochondrial gene encoding cytochrome oxidase subunit I has an unusual transcription pattern.

We report the transcriptional analysis of the mitochondrial (mt) gene encoding cytochrome oxidase subunit I (COXI). A probe made from the protein-coding region of the pea coxI gene hybridized to four RNA transcripts, two of which are much larger than necessary to encode the COXI polypeptide. The RNA hybridization was repeated with a series of sequential probes made from the 5'-untranslated region. The results of these experiments indicated that all four transcripts initiate between 2.8 and 2.1 kb upstream from the protein-coding region. Furthermore, the pattern of hybridization to these sequential probes was unusual, suggesting that introns are spliced out of the 5'-transcribed, but untranslated, region. A sequence located within one of the sequential probes is repeated elsewhere in the pea mt genome. Transcript termini were mapped for the 5' and 3' ends and putative regulatory sequences were located.

Base Sequence↗
PubMed1990

Molecular analysis of an alcohol dehydrogenase-encoding genomic clone (adh2) from rice.

An alcohol dehydrogenase-encoding gene was isolated from a rice genomic library. The coding region was sequenced, and the gene was identified as adh2. The nucleotide sequence of this gene contains an open reading frame which is interrupted by nine introns. Sequences that are important for eukaryotic gene expression, e.g. the TATA box, polyadenylation signal, intron/exon junction and putative splicing branch sites, are found in the expected locations in the rice adh2. A sequence related to the hexanucleotide core of regulatory elements identified in anaerobically induced plant genes is also present in the 5' region of the rice adh2.

Alcohol Dehydrogenase↗
PubMed1990

Regulation of differentiation and keratin protein expression by vitamin A in primary cultures of hamster tracheal epithelial cells.

Hamster tracheal epithelial (HTE) cells maintained in primary culture show the induction of specific keratin species under vitamin A-deficient conditions. A comparison was made between the morphology and the expression of keratins in HTE cells in vivo and in primary culture with and without vitamin A. HTE cells cultured in serum-free, vitamin A-supplemented medium formed a simple cuboidal, ciliated monolayer and produced four simple epithelial keratins (7, 8, 18, and 19). In contrast, vitamin A-deficient HTE cells, which were squamous-like and stratified in culture, produced a more complex keratin pattern, with the induction of four additional keratin species (5, 6, 14, and 17). A keratin pair whose expression serves as a marker of stratified epithelia was induced, as well as a single keratin species unique to lesions of squamous metaplasia in vitamin A-deficient hamster tracheal organ cultures. Thus it appears that HTe cells retain the ability to respond to a deficiency in vitamin A through squamous differentiation and increased keratin production when removed from the intact organ and maintained in primary culture in a chemically defined medium. This system may be useful for the study of mechanisms underlying the squamous differentiation of respiratory epithelial cells in the development of bronchogenic tumors.

Animals↗
PubMed1990

Structural characterization of a rice actin gene.

We have isolated and sequenced a full-length cDNA clone containing information for the rice actin gene RAc1. Transcript terminus mapping and sequence alignment between the RAc1 cDNA clone and a previously isolated RAc1 genomic clone were used to determine the structure of the RAc1 gene. This allowed us to make the first complete structural characterization of a plant actin gene. The analysis revealed the presence of a 5'-noncoding exon, separated by an intron, from the first translated exon of the RAc1 gene. This is one of the few reported cases of a plant gene containing such a 5'-noncoding exon. Sequence comparison between the previously isolated plant actin genes suggests that such an exon may be a common feature of plant actin gene structure. The present study also confirms that the rice actin gene family is composed of at least eight unique members.

Actins↗
PubMed1990

Characterization of the rice (Oryza sativa) actin gene family.

Four rice (Oryza sativa) genomic actin genes have been characterized. The rice actin genes show a conservation of intron number and position that is characteristic of plant actins. Sequence comparisons revealed that the plant actins generally have a high degree of inter- and intraspecific sequence heterogeneity. However, one rice actin gene has a much higher degree of nucleotide sequence identity to a previously isolated actin sequence from Arabidopsis thaliana than to any other plant actin gene. This leads us to suggest that the two sequences may represent functionally homologous genes which arose from an ancient actin gene lineage that was separated by the divergence of the dicot and monocot plants. Genomic DNA blot analysis showed that the rice actin gene family contains at least eight unique members. RNA hybridization analysis revealed that individual rice actin genes can display different patterns of transcript accumulation. The observed differences in sequence and transcript accumulation patterns suggest that the individual rice actin genes may differ in their transcriptional regulation and/or cellular function.

Actins↗
PubMed1990

Chemosensory conditioning of Hermissenda crassicornis.

Bite-strike responses of Hermissenda crassicornis, elicited by chemosensory stimulation of the lips, were found to be modified when food extracts were paired with rotation-produced stimulation of the statocysts. Animals that received repeated pairings of an extract of 1 food (conditioned stimulus, CS) with rotation exhibited suppressed bite-strike responses to that food for up to 48 hr after training. This suppression was usually specific to the trained food and was pairing-specific as well. Discriminative conditioning was also demonstrated. Animals trained with 1 CS paired with rotation and a second CS that was unpaired (CS-) showed suppressed bite-strike responses to the first CS. The results demonstrate that Hermissenda can learn to avoid foods that reliably signal an aversive event and may allow an analysis of higher order conditioning phenomena.

Animals↗
PubMed1990

Isolation of an efficient actin promoter for use in rice transformation.

We have characterized the 5' region of the rice actin 1 gene (Act1) and show that it is an efficient promoter for regulating the constitutive expression of a foreign gene in transgenic rice. By constructing plasmids with 5' regions from the rice Act1 gene fused to the coding sequence of a gene encoding bacterial beta-glucuronidase, we demonstrate that a region 1.3 kilobases upstream of the Act1 translation initiation codon contains all of the 5'-regulatory elements necessary for high-level beta-glucuronidase (GUS) expression in transient assays of transformed rice protoplasts. The rice Act1 primary transcript has a noncoding exon separated by a 5' intron from the first coding exon. Fusions that lack this Act1 intron showed no detectable GUS activity in transient assays of transformed rice protoplasts. Deletion analysis of the Act1 5' intron suggests that the intron-mediated stimulation of GUS expression is associated, in part, with an in vivo requirement for efficient intron splicing.

Actins↗
PubMed1990

Expression of mucin synthesis and secretion in human tracheobronchial epithelial cells grown in culture.

The effects of culture conditions on growth and differentiation of human tracheobronchial epithelial (HTBE) cells have been defined. Epithelial cells were dissociated from tissues by protease treatment and were plated on tissue culture dishes in F12 medium supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, cholera toxin, bovine hypothalamus extract, and retinol. HTBE cells did not express any mucociliary function (ciliogenesis or mucin secretion) on tissue culture plastic, but they could be passaged 3 to 5 times with a total of 10 to 25 population doublings. Cells from early passages re-express both these functions when transplanted to tracheal grafts. When tissue culture plates were coated with collagen film or collagen gel substrata, cell attachment and proliferation were stimulated. However, the expression of mucous cell function in culture occurred only when cells were plated on collagen gel substrata and vitamin A (retinol) was present in the medium. Mucous cell differentiation under optimal conditions was defined by ultrastructural studies, by immunologic studies with mucin-specific monoclonal antibodies, and by carbohydrate and amino acid compositional analyses of mucin-like glycoproteins purified from culture medium. These results demonstrate for the first time that HTBE cells can express mucin synthesis and secretion under appropriate culture conditions.

Amino Acids↗
PubMed1990

Growth and characterization of normal human keratinocytes in F12 serum-free medium.

In a F12 medium supplemented with epidermal growth factor (20 ng/ml), insulin (5 micrograms/ml), transferrin (5 micrograms/ml), hydrocortisone (1 microM), cholera toxin (40 ng/ml), endothelial cell growth supplement (15 ng/ml) and retinoic acid (1 x 10(-7) M) on Vitrogen coated culture dishes, normal adult and newborn human foreskin keratinocytes were cultured for 4- and 2-time with population doublings (PD) accumulated as 8 and 12, respectively. The cells grown in this medium possessed a basaloid, undifferentiated and hyperproliferating nature, with a population doubling time of about 24 hours at early passage. Between the 1st and 2nd subcultures, cell proliferation was the most active. Delaying the time of first subculture lowered the rate of cell proliferation. The keratin of the cultured cells was studied by immunoblotting and revealed the presence of permanent keratin markers of the human skin (AE1 50 kDa and AE3 58kDa) as well as a relatively high intensity of a proliferating marker (AE1 48 kDa) and a relatively low intensity of a differentiation marker (AE3 67 kDa).

Adult↗
PubMed1989

Rice alcohol dehydrogenase genes: anaerobic induction, organ specific expression and characterization of cDNA clones.

Anaerobiosis rapidly induces alcohol dehydrogenase (ADH), an enzyme of the fermentation pathway, in different parts of rice seedlings. After initiation of anaerobiosis, the activity of the enzyme increases linearly for 3 days or more. The ADH activity is anaerobically inducible even in mature rice leaves in contrast to maize which shows no induction in mature leaves. Rice ADH activity can also be induced by an auxin analog, 2,4-dichlorophenoxyacetic acid, under aerobic conditions. The experimental results show that anaerobiosis increases the ADH mRNA level, indicating that the ADH enzyme is regulated at the transcriptional level. Starch gel electrophoresis of a protein extract from rice shows 3 distinct forms of ADH. The amounts of the 3 forms vary with the organ, suggesting that the expression of ADH genes is organ-specific. Sequencing data show that the two different cloned cDNA copies of ADH mRNAs are derived from two different genes.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1989

Serotonin modulation of Hermissenda type B photoreceptor light responses and ionic currents: implications for mechanisms underlying associative learning.

Type B photoreceptors in the eyes of the nudibranch mollusc Hermissenda have previously been shown to exhibit enhanced steady-state depolarizing light responses, increases in steady-state light-induced impulse frequency and a decrease in resting membrane conductance on days following exposure to repeated pairings of light and rotation. These training-produced changes in the electrophysiological properties of B cells have been attributed to reductions in a voltage-dependent K+ current (IA), a calcium-activated K+ current (IK-Ca), and enhancement of a voltage-dependent Ca2+ current (ICa). Current- and voltage-clamp analysis of the effects of serotonin (5-HT) upon B cells revealed that 5-HT mimicked many of the effects of associative training. 5-HT enhanced the steady-state light response and decreased resting membrane conductance of B cells. Voltage-clamp analysis revealed five distinct effects of 5-HT upon the voltage-, calcium-, and light-dependent ionic conductances of B photoreceptors. In the dark-adapted cell, 5-HT enhanced but then suppressed IA, IK-Ca, and enhanced ICa. The presentation of 5-HT in combination with light accelerated the reduction of K+ currents. 5-HT also transiently reduced the fast component of light-induced inward current (INa-light), and enhanced a slower component of light-induced inward current. In an accompanying paper, 5-HT is shown to be localized within the cerebropleural neuropil where terminals presynaptic to B photoreceptors are located. Disruption of serotonergic neurotransmission by a variety of drugs is also shown to reduce the pairing-specific differences in Type B photoreceptor cumulative depolarization and resting membrane conductance decreases that are produced by in vitro conditioning. Collectively, the results indicate that 5-HT plays an important role in mediating the conductance changes produced in Type B photoreceptors by associative training.

Animals↗
PubMed1989

Conformational characterization of a single-site mutant of murine epidermal growth factor (EGF) by 1H NMR provides evidence that leucine-47 is involved in the interactions with the EGF receptor.

Epidermal growth factor (EGF) is a small protein containing 53 amino acids and three disulfide bonds. There is significant current interest in structure-function relationships in EGF and EGF-like proteins, including the homologous type-alpha transforming growth factors. The Leu-47 residue of murine EGF (mEGF) is one of several that are strongly conserved among the EGF-like growth factors, suggesting that it may contribute to the active site of mEGF. In several different binding assays, the activity of the mutant analog in which Leu-47 is replaced by Ser [( Ser47]mEGF) ranges from 8 to 18 times weaker than that of wild-type mEGF. The NMR data summarized in this paper demonstrate that the significant differences in the binding activities of wild-type and [Ser47]mEGF cannot be attributed to structural changes remote from the three-dimensional site of mutation. The only minor conformational changes that are indicated by these data involve side chains of residues proximal to Leu-47 in the three-dimensional structure. Therefore, Leu-47 and/or residues spatially adjacent to Leu-47 constitute part of the active site of mEGF.

Animals↗