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Biomedical subjects

Y Du

Publications and source records attributed to Y Du.

At least 163 records · Page 9Linked to original sources
PubMed1996

Effects of food deprivation on induction of neural progestin receptors by estradiol in Syrian hamsters.

Food deprivation, as well as treatment with metabolic inhibitors, suppress steroid hormone-induced estrous behavior in ovariectomized (OVX) Syrian hamsters. Previous work indicates that 48 h of food deprivation decreases the number of detectable estrogen receptor immunoreactive (ERIR) cells in the ventromedial hypothalamus (VMH) and the area just lateral to it (VLH), increases the number of ERIR cells in the medial preoptic area (MPO), and has no effect on the number of ERIR cells in the nucleus of the solitary tract in OVX hamsters. The present study examined the effects of food deprivation on neural progestin receptor binding using an in vitro binding assay and on progestin receptor immunoreactivity (PRIR) in estradiol-primed, OVX hamsters. Parallel behavior tests for sexual behavior were also performed in both experiments. OVX hamsters received 2.5 micrograms estradiol benzoate and were fed ad libitum or food deprived at the same time. Forty-eight hours later, animals were killed in preparation for the immunocytochemistry or progestin receptor assay. Binding assays indicated that 48-h food deprivation decreased progestin receptor levels in the preoptic area and had no effect in the mediobasal hypothalamus, an area that includes the VMH and the arcuate nucleus (ARH). Immunocytochemical analysis confirmed these findings. Food deprivation caused a decrease in sexual receptivity and in the number of detectable PRIR cells in the MPO and medial amygdala but had no effect on the number of detectable PRIR cells in the VMH/VLH, the ARH, or the anteroventral periventricular nucleus. These results suggest that food deprivation modulates progestin receptor binding and PRIR in a site-specific manner. In addition, the effects of food deprivation on neural ERIR and PRIR are significantly different.

Animals↗
PubMed1996

Regulation of the gene-encoding angiotensin II receptor in vascular tissue.

Specific angiotensin (Ang)-dependent mechanisms significantly contribute to vascular development and function, and to the pathophysiology of hypertension. The effects of Ang II are mediated by binding to specific receptors. The focus of most studies has been changes in vascular function and structure in response to Ang II. Relatively little is known regarding the molecular basis of changes in the vascular Ang II receptor. We have recently found that, without altering blood pressure, Ang II infusion at a dose of 25 ng.kg.min-1 decreases expression of the gene-encoding Ang II type 1 (AT1) receptor in both the aorta and resistant arteries. This suggests that exogenous Ang II negatively regulates AT1 mRNA expression in these tissues. Furthermore, hypertension induced by reduced renal mass plus high salt intake upregulates AT1 mRNA expression in the hypertrophied aorta and heart. In this model, the reduction of Ang II formation by captopril without decreasing blood pressure prevents the increase in AT1 mRNA in the aorta but not in the heart. This suggests that the regulation of AT1 gene expression in the heart may be pressure-dependent while there is an Ang II-dependent mechanism operant in the aorta. The precise tissue-specific control mechanisms for AT1 gene expression remain to be defined.

Angiotensin II↗
PubMed1995

Overproduction and rapid purification of human fast skeletal beta troponin T using Escherichia coli expression vectors: functional differences between the alpha and beta isoforms.

Troponin T (TpnT), an essential component of the Ca(2+)-regulatory troponin complex, is involved in protein-protein interactions with other thin-filament proteins during muscle contraction in vertebrate striated muscle (VSM). The isoforms of TpnT are encoded by members of a multigene family which, by alternate splicing, produces a complex pattern of isoproteins in VSM. The functional domains of TpnT are only tentatively identified and structure-function analysis on this protein is limited due to the heterogeneity of the multiple isoforms. We reasoned that the overproduction and purification of a single TpnT species in Escherichia coli would provide an insight into these studies, besides being useful in crystallizing the protein. We cloned the human fast skeletal beta TpnT-encoding cDNA (beta TpnTf) in three expression vectors. Overexpression was achieved in an E. coli BL21 (DE3) lysogen using a T7 RNA polymerase promoter-based vector, pET17b. The unfused recombinant protein was purified by a simple and rapid procedure in a biologically active and immunoreactive form. This is the first successful synthesis of a complete beta TpnTf polypeptide from any species using an in vitro expression system. Purified human beta TpnTf, a predominant fetal form, was less Ca(2+)-sensitive and exhibited considerably reduced affinity for troponin C and tropomyosin, as compared to the rabbit fast skeletal alpha TpnT, a predominant adult isoform. These results provide a biochemical correlate to the age-related differences in Ca2+ sensitivity of tension development in vertebrate fast skeletal muscles.

Base Sequence↗
PubMed1995

The mouse plasma membrane Ca2+ pump isoform 1 promoter: cloning and characterization.

The expression of plasma membrane Ca2+ pump (PMCA) is regulated by various hormones or agonists via multiple second messenger pathways. Two different 5' segments of the PMCA1 gene (isoform 1) were cloned from a mouse genomic library. While one segment contained the 3' end of intron 1 and exon 2, the other segment was found to encompass the 5'-flanking region of the gene, exon 1, and the 5' portion of intron 1. Sequence analysis of the 5'-flanking region suggested the presence of the putative promoter. Four sites for initiation of transcription (spanning 64 bp) were identified by RNase protection assay and primer extension analysis. The promoter region was very GC-rich, contained no "TATA box," but had a "CAAT box" at -51. Comparison of sequence with known cis-regulatory motifs disclosed that the 5'-flanking region has a number of potential regulatory elements including an AP-1 site at -354, AP-2 binding sites at -267 and -123, Sp1 binding sites at -127, -111, and +3, and a cyclic AMP response element binding protein site at -67. To demonstrate promoter activity, a segment containing 611 bp of the promoter region (from -442 to +169) was subcloned in front of a promoterless chloramphenicol acetyltransferase (CAT) gene. This segment was able to drive the expression of chloramphenicol acetyltransferase in transient transfections of mouse (or human) neuroblastoma cells as well as rat aortic endothelial cells. Deletion analysis demonstrated that a fragment from -256 to +169 showed strong promoter activity, while a fragment from -117 to +169 had CAT activity that was not different from the vector control. The promoter was stimulated threefold by phorbol ester and twofold by cyclic AMP. These results provide further proof indicating up-regulation of the PMCA1 gene by multiple second messenger pathways.

Animals↗
PubMed1995

A genetic map of microsatellite markers on rat chromosome 7.

Nine microsatellite loci were mapped to rat Chromosome (Chr) 7 by genetic linkage and somatic cell hybrid analysis. These loci include the gene encoding a member of the IID sub-family of cytochrome P450 (Cyp2d), a gene with repetitive sequences expressed during myotube formation (D7Arb1e), four anonymous loci, D7Arb81, D7Arb208, D7Arb569, D7Arb609a, and three DNA loci defined by MapPair markers R245, R513, and R1071. The nine loci were all identified by PCR-based microsatellite polymorphism analysis and were characterized in 40 F2 intercross progeny of Fischer (F344/N) and Lewis (LEW/N) rats for segregation analysis. These markers formed a single linkage group spanning 76.8 cM with the following order and distances: D7Arb569-11.4 cM-D7Arb81-9.7 cM-R513-2.6 cM-Cyp2d-0.0 cM-R245-1.3 cM-D7Arb1e-10.4 cM-R1071-15.9 cM-D7Arb609a-15.4 cM-D7Arb208. Physical mapping of Cyp2d by somatic cell hybrid analysis allowed us to assign this linkage group to rat Chr 7. For each marker, two to six alleles were detected in a panel of 16 inbred rat strains (ACI/N, BN/SsN, BUF/N, DA/Bkl, F344/N, LER/N, LEW/N, LOU/MN, MNR/N, MR/N, SHR/N, SR/Jr, SS/Jr, WBB1/N, WBB2/N, WKY/N).

Alleles↗
PubMed1995

Genetic map of 16 polymorphic markers forming three linkage groups assigned to rat chromosome 4.

Sixteen polymorphic markers, including markers for eight new loci, forming three linkage groups, were assigned to rat Chromosome (Chr) 4 by linkage analysis of the progeny of an F2 intercross of Fischer (F344/N) and Lewis (LEW/N) inbred rats. One gene, Igk, was mapped by restriction fragment length polymorphism (RFLP) analysis. One marker for Tcrb was identified by the polymorphic insertion of a repetitive LINE element. The remaining 14 markers contained polymorphic simple sequence repeats (SSRs). Ten were identified in genes (Tgfa, Npy, Prss1, Prss2, Aldr1, Iapp, Prp, Eno2, Cacnl1a1, and Il6), one was identified in a sequence related to a gene (Egr4l1), and three were identified in anonymous DNA segments. The SSR markers were highly polymorphic in 16 inbred rat strains. These markers expand the genetic map of the rat and should be useful in future genetic studies of inbred rats.

Animals↗
PubMed1995

Regional distribution of messenger RNA encoding the insulin-like growth factor type 2 receptor in the rat lower brainstem.

Distribution of messenger RNA (mRNA) encoding the insulin-like growth factor (IGF) type 2 receptor (IGF2R) is investigated in the rat lower brainstem by in situ hybridization histochemistry. Cells with IGF2R mRNA are distributed widely in a region-specific manner. It is expressed in: (1) motor nuclei such as the oculomotor nucleus, trochlear nucleus, motor trigeminal nucleus, abducens nucleus, facial nucleus, ambiguus nucleus, dorsal motor nucleus of vagus and hypoglossal nucleus; (2) several sensory-related nuclei like the mesencephalic trigeminal nucleus, ventral nucleus of the lateral lemniscus, lateral and spinal vestibular nuclei, ventral and dorsal cochlear nuclei and nucleus of the trapezoid body; and (3) other regions such as the red nucleus, dorsal raphe nucleus, pontine nuclei, three cerebellar nuclei (medial, interposed and lateral), Purkinje cells, cells in the granular layer of the cerebellum, locus coeruleus, several areas of the reticular nucleus and area postrema.

Animals↗
PubMed1995

Genetic map of eight microsatellite markers comprising two linkage groups on rat chromosome 6.

Five genes and three anonymous DNA loci were mapped to rat chromosome 6 by genetic linkage and somatic cell hybrid analyses. The eight loci were all identified by PCR-based microsatellite polymorphism analysis and were characterized in 40 F2 intercross progeny of Fischer (F344/N) and Lewis (LEW/N) inbred rats for segregation analysis. These markers formed two linkage groups spanning, respectively, 58.1 cM and 4.0 cM. The first linkage group is comprised of two anonymous DNA loci and four genes with the following map order and distances: D6Cep8 (previously D3)-17.9 cM-D6Arb309-2.5 cM-Vsnl1 (neural visinin-like protein)-20.4 cM-Prkar2b (type IIb regulatory subunit of cAMP-dependent protein kinase)-8.8 cM-Fkhl1 (forkhead-like transcription factor BF-1)-8.5 cM-Rnu1c (18-3A U1 RNA). The second linkage group is comprised of one gene, Ckb (creatine kinase, brain) and one anonymous DNA locus, D6Arb54, separated by 4.0 cM. For each marker, two to eight alleles were detected in a panel of 16 inbred rat strains (ACI/N, BN/SsN, BUF/N, DA/Bk1, F344/N, LER/N, LEW/N, LOU/MN, MNR/N, MR/N, SHR/N, SR/Jr, SS/Jr, WBB1/N, WBB2/N, and WKY/N). Comparative mapping information indicated that rat chromosome 6 exhibits syntenic conservation with mouse chromosome 12. Homologs of the rat chromosome 6 loci have been identified on human chromosomes 2, 7, and 14.

Animals↗
PubMed1995

Differential regulation of angiotensin II receptor subtypes in rat kidney by low dietary sodium.

This study was designed to determine whether expression of renal messenger RNA (mRNA) encoding the two known angiotensin II type 1 (AT1) receptor subtypes (AT1A and AT1B) can be regulated by dietary sodium. Seven-week-old male Wistar rats were fed a low-sodium diet (0.07%, n = 9) or a normal-sodium diet (0.5%, n = 9 [control]) for 14 days. A rat AT1 complementary DNA (cDNA) probe, which hybridizes to mRNA encoding both the AT1A and AT1B receptor subtypes, and cDNA probes, which are selective for AT1A or AT1B mRNA, were used in Northern blot or in situ hybridization analysis. By use of Northern blot analysis, renal mRNA levels for the AT1 and AT1A receptors in rats fed a low-sodium diet were found to be increased twofold (P < .05) compared with control. Because renal AT1B mRNA content was not detected by Northern blot analysis, quantitative image analysis of in situ hybridization with a digoxigenin-labeled cRNA probe made from AT1B cDNA was used. In situ hybridization analysis indicated that AT1B mRNA was expressed in the proximal and collecting tubules of the kidney in rats fed a normal-sodium diet. The low-sodium diet significantly decreased the percent positive staining area of AT1B mRNA in the renal cortex (5.51 +/- 0.77% versus 2.73 +/- 0.35%, P < .05) and medulla (4.76 +/- 0.70% versus 2.01 +/- 0.43%, P < .05) compared with the control diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Distinct mechanisms of upregulation of type 1A angiotensin II receptor gene expression in kidney and adrenal gland.

We previously demonstrated that type 1A angiotensin II (Ang II) receptor (AT1A) is the predominant renal subtype and is upregulated by a low sodium diet. We have now tested the hypothesis that upregulation of AT1A mRNA induced by sodium deficiency is renal specific and is mediated by activation of type 1 Ang II receptor (AT1). Male Wistar rats were divided into four groups (n = 5 each) and treated for 2 weeks with normal sodium diet (0.5%), normal sodium plus 3 mg/kg per day losartan, low sodium diet (0.07%), or low sodium diet plus losartan. At the end of the 2 weeks, body weight and mean arterial pressure were not different among the four groups (P > .05). Plasma renin activity was elevated by losartan treatment, sodium restriction, or the combination of the two versus control (P < .05). Northern blot analysis showed that the ratio of renal AT1A to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA was increased by losartan treatment, sodium restriction, or the combination of the two versus control (P < .05). In contrast, the ratio of adrenal AT1A to GAPDH mRNA was increased only by sodium restriction versus three other groups (P < .05). Thus, sodium deficiency increases AT1A mRNA in both kidney and adrenal gland, while Ang II receptor blockade by losartan prevents low sodium-induced AT1A mRNA only in adrenal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1995

[Analysis of genetic properties of meiotic products from an interspecific triploid fusion-hybrid itself constructed by protoplast fusion in Saccharomvces].

A genetically stable interspecific triploid fusion-hybrid between a diploid Saccharomyces cerevisiae var. ellopsoideus and a haploid Saccharomyces diastaticus was constracted by protoplast fusion technique. Experimental results indicate that such hybrid can be induced to sporulate as a sexual hybrid. Genetic analysis of the complete and non-complete tetrads demonstrates that the prototrophic interspecific triploid fusion-hybrid HU-KDF-240 selected by nutritional complementation experienced segregation and exchange for the genetic markers, and showed parental ditype and recombination in the meiotic process of sporulation. The results of the tetrad analysis of the hybrid HU-KDF-240 showed a 1:2 segregation ratio for soluble starch fermenting and non-fermenting characters and a 1:1 segregation ratio for genetic markers of the auxotrophic character in 349 complete and non-complete tetrads from 186 asci of the hybrid.

Cloning, Molecular↗