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Biomedical subjects

D Son

Publications and source records attributed to D Son.

14 recordsLinked to original sources
PubMed2001

A review of mechanisms controlling ovulation with implications for the anovulatory effects of polychlorinated dibenzo-p-dioxins in rodents.

Polychlorinated dibenzo-p-dioxins (PCDDs) can impinge on female fertility by preventing ovulation. In this review, the aspects of normal ovulatory physiology most relevant to our current understanding of PCDD action on the ovary are briefly reviewed. This is followed by a comprehensive assessment of data relevant to the effects of PCDDs during ovulation in the rat. PCDDs interrupt ovulation through direct effects on the ovary in combination with dysfunction of the hypothalamo-hypophyseal axis.

Animals↗
PubMed2000

Molecular cloning and targeting of a fibrillarin homolog from Arabidopsis.

Fibrillarin is a nucleolar protein known to be involved in the processing of ribosomal RNA precursors. We isolated AtFbr1, a cDNA encoding a homolog of fibrillarin in Arabidopsis. The cDNA is 1.2 kb in size and encodes a polypeptide of 310 amino acid residues with a molecular mass of 33 kD. AtFbr1 is expressed at high levels in the flower and root tissue and at a slightly lower level in leaf tissue, whereas it was nearly undetectable in siliques. Expression of AtFbr1 was compared with that of the FLP (fibrillarin-like protein) gene identified by the Arabidopsis genome project. Abscisic acid treatment resulted in the down-regulation of the expression of both AtFbr1 and FLP genes in seedlings, although the degree of suppression was higher for FLP than for AtFbr1. In addition, the expression level of FLP decreased with the age of the seedlings, whereas AtFbr1 did not exhibit any detectable change. The subcellular localization of AtFbrl was studied with an in vivo targeting approach using a fusion protein, and was found to be correctly targeted to the nucleolus in protoplasts when expressed as a green fluorescent fusion protein (GFP). Deletion experiments showed that the N-terminal glycine- and arginine-rich region is necessary and sufficient to target AtFbr1 to the nucleolus.

Amino Acid Sequence↗
PubMed1998

Molecular cloning and characterization of the gene encoding glutathione reductase in Brassica campestris.

We have isolated the Brassica campestris cDNA encoding glutathione reductase of 502 amino acid residues with molecular mass of 54.5 kDa. The deduced amino acid sequences were 92.2%, and 79.5% identical to those of Arabidopsis thaliana, and pea, respectively. As expected, it exhibited a high degree of conservation within the region responsible for the redox reaction and for the binding of GSSG or NADPH. The gene was highly inducible by ozone fumigation or by paraquat treatment.

Amino Acid Sequence↗
PubMed1997

Isolation and characterization of a mammalian homolog of the Drosophila white gene.

The Drosophila melanogaster white gene is a member of the ABC transporter superfamily of ATPase transmembrane proteins and is involved in the cellular uptake of guanine and tryptophan. We have cloned and sequenced human and mouse homologs of white which share 55-58% amino acid similarity with the Drosophila protein. Northern analysis reveals that the mammalian homolog is highly expressed in several tissues, including brain, spleen, lung and placenta. We have localized the gene to human chromosome 21q22.3 by means of fluorescence in situ hybridization and linkage analysis using a (CA)n polymorphism. The human homolog maps to the interval between D21S212 and D21S171, a region which includes loci for bipolar affective disorder and a recessive form of deafness. Since tryptophan is a precursor for the neurotransmitter serotonin and neurotoxic metabolites of the kynurenine pathway, we propose that the human homolog of white is a suitable candidate gene for these neurological disorders in humans.

ATP-Binding Cassette Transporters↗
PubMed1992

Molecular cloning of an alanine aminotransferase from NAD-malic enzyme type C4 plant Panicum miliaceum.

We have determined the nucleotide sequence of a cDNA encoding AlaAT-2, which is believed to function in the C4-pathway of Panicum miliaceum. An open reading frame (1446 bp) encodes a protein of 482 amino acid residues. The deduced amino acid sequence of AlaAT-2 shows 44.2 and 44.8% homology with the amino acid sequences of AlaATs from rat and human livers, respectively. Northern blot analysis showed that the gene encoding AlaAT-2 in mesophyll and bundle sheath cells was the same and transcribed similarly in the cells. The level of translatable mRNA for AlaAT-2 increased dramatically during greening.

Alanine Transaminase↗
PubMed1991

Purification and characterization of alanine aminotransferase from Panicum miliaceum leaves.

Three alanine aminotransferases, two minor (AlaAT-1, AlaAT-3) and one major (AlaAT-2), were detected by native gel electrophoresis of leaf extracts from Panicum miliaceum L. AlaAT-2 was purified to homogeneity and a specific polyclonal antibody was raised against it which did not react with the other two forms of the enzyme. The enzyme, with an apparent molecular size of 102 kDa, appeared to be a dimer of a single 50-kDa polypeptide. The enzyme has a relatively broad pH optima with similar curves for the forward and reverse directions, ranging between 6.5 and 7.5. The Km values of this enzyme were 6.67, 0.15, 5.00, and 0.33 mM for alanine, 2-oxoglutarate, glutamate, and pyruvate, respectively. The activity of AlaAT-2 was found to increase markedly during leaf greening in parallel with the increase of immunochemically titrated protein, and it is suggested to function in the C4 photosynthetic cycle.

Alanine Transaminase↗
PubMed1983

Effects of calcium and verapamil on vesicourethral smooth muscle of rabbits.

Isolated smooth muscle strips from the rabbit bladder body, bladder base, and proximal urethra were contracted with ionic calcium (Ca2+) alone and with the calcium-selective ionophore A23187, acetylcholine, norepinephrine, adenosine triphosphate (ATP), and direct electrical stimulation. The effects of Ca2+ and the calcium entry blocker verapamil on spontaneous muscle activity and on contractions induced by these agonists were examined. Ca2+ -free Tyrode's solution and verapamil, 1 x 10(-7)M and above, relaxed all of the vesicourethral smooth muscle strips. In addition verapamil, 1 x 10(-8) to 1 x 10(-6) M depending on the particular stimulant employed, noncompetitively inhibited smooth muscle contractions elicited by Ca2+, acetylcholine, norepinephrine, ATP, and direct electrical stimulation. It was concluded that transmembrane Ca2+ influx was important not only in the maintenance of tone and spontaneous phasic muscle activity, but also for the activation of contractions induced by all of the stimulants tested. The data also suggest that intracellular Ca2+ fraction(s) participate in the contractile responses to acetylcholine and norepinephrine challenge, but not to contractions evoked by ATP or electricity.

Acetylcholine↗
PubMedDate not supplied

Impaired ovulation by 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) in immature rats treated with equine chorionic gonadotropin.

Several studies have established that 2,3,7,8 tetrachloro-p-dioxin (TCDD) blocks ovulation. The main purpose of this study was to determine if induced ovulation was delayed temporarily by TCDD. The ovulation model used was that of the gonadotropin-primed intact or hypophysectomized rat. Immature intact female Sprague-Dawley rats (IIR) were given 32 microg TCDD/kg by gavage on day 24 of age. The next day equine chorionic gonadotropin (eCG) (5 IU) was injected sc to stimulate follicular development. The number of ova in the oviducts, the ovulation rate, and steroid concentrations were determined at 72, 96, 120, and 144 h after eCG. Immature female Sprague-Dawley rats (IHR) were hypophysectomized on day 23 of age. On day 26, the IHR were given 20 microg TCDD/kg by gavage. The next day eCG (10 IU) was injected sc to stimulate follicle development and at 52 h after eCG, 10 IU human chorionic gonadotropin (hCG) was given to induce ovulation. The same parameters as in IIR were determined in IHR at 72, 96, and 120 h after eCG. TCDD decreased body and ovarian weight gains in both IIR and IHR. In IIR, TCDD delayed ovulation by 24 to 48 h reducing the number of ova shed as well as the number of animals ovulating at 72 and 96 h after eCG. In IHR, however, TCDD reduced only the number of ova shed but caused no delay in ovulation. The IIR treated with TCDD had low levels of progesterone (P4) at 72 and 96 h after eCG but high levels of estradiol (E2) at the same time points. This sustained high level of E2 production coincided with a transient decrease in serum concentrations of androstenedione (A4). The alteration of steroid hormones by TCDD was restored to normal by 48 h after ovulation in IIR. Serum P4 concentration was not altered by TCDD in IHR at 72 h after eCG but was decreased thereafter. The delay in ovulation induced by TCDD in IIR indicates the disruption of the hypothalamus-pituitary-ovary axis during proestrus. The decrease in number of ova shed in IHR induced by exogenous gonadotropins indicates an additional direct ovarian effect of TCDD in blocking ovulation.

Administration, Oral↗