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Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 811 records · Page 45Linked to original sources
PubMed1995

The structures of the human calcium channel alpha 1 subunit (CACNL1A2) and beta subunit (CACNLB3) genes.

Calcium influx in pancreatic beta-cells is regulated mainly by L-type voltage-dependent calcium channels (VDCCs) and triggers insulin secretion. The alpha 1 subunit (CACN4) and the beta subunit (beta 3) of VDCCs, both of which are expressed in pancreatic islets, are major components for the VDCC activity, and so they may play a critical role in the regulation of insulin secretion. We have determined the structures of the human CACN4 (CACNL1A2) and the human beta 3 (CACNLB3) genes. The CACNL1A2 gene spans more than 155 kb and has 49 exons. Most of the positions interrupted by introns are well conserved between the CACNL1A2 gene and the previously reported L-type VDCC alpha 1 subunit, CACNL1A1, gene. On the other hand, the CACNLB3 gene distributes in approximately 8 kb and comprises 13 exons, most of which are located together within approximately 5 kb. Comparisons of the genomic sequences of CACNL1A2 with the previously reported cDNA sequences indicate that there are a number of polymorphisms in the human CACNL1A2 gene. In addition, the PCR-SSCP procedure of exon 1 of CACNL1A2 revealed a change from 7 to 8 ATG trinucleotide repeats in a patient with non-insulin-dependent diabetes mellitus (NIDDM), resulting in an addition of methionine at the amino-terminus of CACN4. The determination of the structures of the human CACNL1A2 and CACNLB3 genes should facilitate study of the role of these genes in the development of NIDDM and also other genetic diseases such as long QT syndrome.

Base Sequence↗
PubMed1995

Complementation of virus movement in transgenic tobacco expressing the cucumber mosaic virus 3a gene.

Tobacco plants were transformed with the cucumber mosaic cucumovirus (CMV) 3a gene and the in planta-expressed 3a protein was detected immunologically. The 3a protein was predominantly localized in a subcellular fraction corresponding to the cytosol. Two frameshift and four deletion mutants were created within the 3a open reading frame of CMV RNA 3. Five of these mutants, containing an N-terminal, large central, or C-terminal 70-amino-acid deletion could not infect nontransformed tobacco plants, but could infect the 3a transgenic tobacco plants, and generally accumulated to wild-type levels. The sixth mutant, lacking the C-terminal 43 amino acids of the 3a protein, was able to infect nontransformed tobacco plants. A delay in accumulation of viral RNA in both the inoculated and the systemically infected leaves was demonstrated for one of the mutants. Thus, the CMV 3a protein is a virus movement protein, the functions of which can be complemented in a transgenic plant. The CMV 3a transgenic plants were able to complement the long-distance movement of a pseudorecombinant cucumovirus defective for this function in tobacco, as well as the cell-to-cell, but not the long-distance, movement of two other related viruses. However, these transgenic plants were unable to complement the long-distance movement of viruses from several other taxonomic groups that could move cell to cell but not long distance in tobacco.

Cucumovirus↗
PubMed1995

OR-1, a member of the nuclear receptor superfamily that interacts with the 9-cis-retinoic acid receptor.

We have cloned a member of the nuclear receptor superfamily. The cDNA was isolated from a rat liver library and encodes a protein of 446 aa with a predicted mass of 50 kDa. This clone (OR-1) shows no striking homology to any known member of the steroid/thyroid hormone receptor superfamily. The most related receptor is the ecdysone receptor and the highest homologies represent < 10% in the amino-terminal domain, between 15-37% in the carboxyl-terminal domain and 50-62% in the DNA binding domain. The expression of OR-1 appears to be widespread in both fetal and adult rat tissues. Potential DNA response elements composed of a direct repeat of the hexameric motif AGGTCA spaced by 0-6 nt were tested in gel shift experiments. OR-1 was shown to interact with the 9-cis-retinoic acid receptor (retinoid X receptor, RXR) and the OR-1/RXR complex to bind to a direct repeat spaced by 4 nt (DR4). In transfection experiments, OR-1 appears to activate RXR-mediated function through the DR4. Therefore OR-1 might modulate 9-cis-retinoic acid signaling by interacting with RXR.

Amino Acid Sequence↗
PubMed1995

Cucumber mosaic virus 3a protein potentiates cell-to-cell trafficking of CMV RNA in tobacco plants.

Contrary to a previous report, electron microscopic studies on the Fny strain of cucumber mosaic virus (CMV)-infected tobacco tissues revealed that plasmodesmata were not structurally modified during CMV infection, nor were virions ever observed in plasmodesmata connecting infected cells. To further explore the basis of CMV infection, experiments were performed on the CMV 3a ORF. The 3a protein of CMV was expressed in and purified from Escherichia coli. The purified protein was labeled with fluorescein isothiocyanate (FITC) and subsequently microinjected into mesophyll cells of mature leaves of Nicotiana tabacum cv. Turkish Samsun NN. Within a brief period (as little as 1 sec), the microinjected FITC-labeled CMV 3a protein moved into neighboring cells. Co-injection of unlabeled CMV 3a protein with 9.4-kDa fluorescein-conjugated dextran (F-dextran) resulted in extensive cell-to-cell movement (diffusion) of the F-dextran, indicating that the 3a protein can interact with and dilate plasmodesmata. Furthermore, co-injection of unlabeled 3a protein with fluorescently labeled infectious CMV RNA molecules resulted in rapid and extensive cell-to-cell transport. In contrast, a mutant form of the 3a protein was unable to traffic from cell to cell, to increase the size exclusion limit of plasmodesmata, or to potentiate cell-to-cell trafficking of CMV RNA molecules. Microinjection studies performed on transgenic tobacco plants expressing the CMV 3a protein indicated that fluorescently labeled CMV RNA moved out of the target cell into the surrounding mesophyll tissue. In addition, expression of the CMV 3a protein also potentiated the cell-to-cell movement of 9.4-kDa F-dextran. Collectively, these results provide direct experimental evidence that the CMV 3a protein functions as the movement protein of CMV. These findings are consistent with the hypothesis that CMV moves from cell-to-cell in the form of a ribonucleoprotein complex.

Base Sequence↗
PubMed1995

Neuroendocrine profile of the potential anxiolytic drug S-20499.

The neuroendocrine profile of the serotonin 5-HT1A receptor agonist and potential anxiolytic drug (+)-4[N-(5-methoxy-chroman-3-yl)N-propylamino]butyl-8-azaspiro-(4, 5)-decane - 7,9-dione (S-20499) was examined in conscious male rats. S-20499 (0.01-20 mg/kg i.p.) dose-dependently elevated plasma adrenocorticotropin (ACTH) and corticosterone concentrations, with maximal effects observed at 15-30 and 30-60 min respectively. S-20499 also reduced plasma prolactin concentration, and did not alter plasma renin activity. S-20499 (1 mg/kg i.p.) also reduced blood pressure and heart rate within 10 min, suggesting reduced sympathetic output. Pretreatment with the 5-HT1A receptor antagonists (-)-pindolol (0.3 mg/kg i.p.) or spiperone (0.01 or 3 mg/kg s.c.) significantly attenuated the stimulatory effects of S-20499 on plasma ACTH and/or corticosterone concentrations. The data suggest that S-20499 stimulates the hypothalamic-pituitary adrenal axis by activating 5-HT1A receptors, although activation of dopamine D2 receptors may contribute to these responses. Like other 5-HT1A receptor agonists, S-20499 does not increase renin secretion. Additionally, it reduces prolactin secretion, presumably by acting as a weak dopamine D2 receptor agonist in the pituitary.

Adrenocorticotropic Hormone↗
PubMed1995

An in vivo model for receptor tyrosine kinase autocrine/paracrine activation: auto-stimulated KIT receptor acts as a tumor promoting factor in papillomavirus-induced tumorigenesis.

Constitutive overactivation of growth factor receptors through autocrine/paracrine mechanisms occurs frequently in cancer cells and are thought to play a critical role in carcinogenesis. In the present report, we propose a refined in vivo model which explains the significance of these mechanisms in tumour development. We have previously established transgenic mouse lines containing human papillomavirus type 16 (HPV16) E6E7 oncogenes, in male mice of which a Leydig cell tumor developes with a very high incidence. Not only HPV transgene but also the c-kit proto-oncogene receptor tyrosine kinase and its ligand Steel Factor (SLF) were coexpressed in all tumors analysed. This coexpression of c-kit/SLF was also found in two other Leydig cell tumor lines. Moreover, the proliferation of transgenic tumor cells was attenuated by treatment with a c-kit neutralizing antibody in vitro, strongly suggesting that tumorigenesis is closely related to stimulation of receptors through ligand induction. To confirm the significance of these findings, a defective mutation of the SLF gene in a laboratory mouse, the Steel-Dickey (Sld) mutation, was introduced into a line of transgenic mice showing 100% incidence of the tumor. In Sld-E6E7 transgenic mice, tumorigenesis was initiated but numbers of tumor cells were markedly reduced compared with transgenic mice carrying both wild type SLF allele, showing that c-kit activation through the induction of SLF is essential for testicular tumorigenesis, especially in tumour promotion. This transgenic mice system should be a useful in vivo model for clarifying the implication of growth factor autostimulation in carcinogenesis.

Animals↗
PubMed1995

A near-upstream element in a plant polyadenylation signal consists of more than six nucleotides.

A plant polyadenylation signal consists of three distinct components: a far-upstream element (FUE) that can control utilization of several polyadenylation sites, one or more near-upstream elements (NUEs) that control utilization of each site in a transcription unit, and polyadenylation site (CSs) themselves. NUEs have previously been suggested to be related to the mammalian polyadenylation signal AAUAAA. However, many plant genes do not contain AAUAAA-like motifs near their polyadenylation sites. To better understand the nature of NUEs, we conducted a systematic analysis of the NUE for one polyadenylation site (site 1) in the pea rbcS-E9 gene; this NUE lacks an AAUAAA motif. Linker substitution studies showed that the NUE for site 1 in this gene resides in the sequence AAAUGGAAA. Single-nucleotide substitutions in this domain had modest effects on the functioning of this NUE. Replacement of part of this sequence with the sequence AAUAAA increased the efficiency of this NUE. However, alteration of nucleotides immediately 3' of the AAUAAA reversed this effect. Our results indicate that the NUE for site 1 consists of as many as 9 nucleotides, that these 9 bases do not include an element that is intolerant of single base changes, that the sequence AAUAAA can function as a NUE for site 1, and that sequences flanking AAUAAA can affect the efficiency of functioning as a NUE.

Base Sequence↗
PubMed1995

Argyrophilic nucleolar organizer regions. A revised version of the Ag-NOR-staining technique.

Silver staining techniques developed to demonstrate argyrophilic nucleolar organizer regions (Ag-NORs) have been widely applied in a variety of cell kinetic studies, using the mean number of AgNORs in tumour cells as a marker for malignancy of certain types of neoplasms. However, the AgNOR techniques currently available are not entirely satisfactory, as unspecific silver precipitates readily form in the sections. On the other hand, the contrast staining may be so weak as to render identification of the AgNORs difficult. In the present study, some of the key factors influencing the outcome of AgNOR staining were evaluated in a more systematic way. A modified AgNOR staining procedure is now proposed, giving highly contrasting AgNORs with minimal unspecific silver precipitation, thus facilitating both manual and computerized counting. The new technique involves the use of microwave irradiation in order to shorten the processing time, the use of gelatin as a protective colloid, and a Farmer's solution to optimize the specificity of the technique.

Adrenal Cortex Neoplasms↗
PubMed1995

Esophagopharyngeal distribution of refluxed gastric acid in patients with reflux laryngitis.

BACKGROUND & AIMS: A variety of otolaryngological abnormalities have been attributed to the contact of gastroesophageal refluxate with respective structures of the aerodigestive tract. The aim of this study was to determine and compare the pharyngoesophageal distribution of gastric acid refluxate between patients with proven laryngitis attributed clinically to gastroesophageal reflux and three control groups. METHODS: An ambulatory 24-hour simultaneous three-site pharyngoesophageal pH monitoring technique was used to measure reflux parameters in the pharynx, proximal esophagus, and distal esophagus. RESULTS: Between-group comparison showed no significant difference in the reflux parameters in the distal esophagus between the studied groups. A significantly higher percentage of distal reflux episodes reached the proximal esophagus in the laryngitis group than in the control groups (P < 0.01), and the number of pharyngeal reflux episodes and time of acid exposure were significantly higher in the laryngitis group than in the control groups (P < 0.001). CONCLUSIONS: Compared with normal controls and patients with gastroesophageal reflux disease, pharyngeal reflux of gastric acid is significantly more prevalent and the ratio of proximal to distal esophageal acid reflux episodes is significantly increased in patients with posterior laryngitis. Simultaneous three-site ambulatory pharyngoesophageal pH monitoring may provide supporting evidence when the diagnosis of reflux-induced aerodigestive tract lesions is considered.

Adult↗
PubMed1995

Transformation of China's rural health care financing.

In the late 1970s China launched its agricultural reforms which initiated a decade of continued economic growth and significant transformation of the Chinese society. The agricultural reforms altered the peasants' incentives, weakened community organization and lessened the central government's control over local communities. These changes largely caused the collapse of the widely acclaimed rural cooperative medical system in China. Consequently China experienced a decreased supply of rural health workers, increased burden of illnesses, disintegration of the three tier medical system, reduced primary health care, and an increased demand for hospital medical services. More than ten years have elapsed since China changed its agricultural economic system and China is still struggling to find an equitable, efficient and sustainable way of financing and organizing its rural health services. The Chinese experiences provided several important lessons for other nations: there is a need to understand the limits of the market forces and to redefine the role of the government in rural health care under a market economy; community participation in and control of local health financing schemes is essential in developing a sustainable rural health system; the rural health system needs to be dynamic, rather than static, to keep pace with changing demand and needs of the population.

China↗
PubMed1995

Hypothalamic paraventricular, but not supraoptic neurons, mediate the serotonergic stimulation of oxytocin secretion.

The purpose of the present studies was to determine whether cells in the hypothalamic paraventricular (PVN) or supraoptic (SON) nuclei mediate the serotonergic stimulation of oxytocin secretion. The serotonergic stimulus consisted of injection of the 5-HT-releasing drug p-chloroamphetamine (8 mg/kg, IP). The validity of this approach was verified by comparing this drug with another 5-HT releaser, d-fenfluramine (5 mg/kg, IP). Both 5-HT releasers increased plasma oxytocin concentration. Furthermore, the 5-HT uptake blocker fluoxetine (10 mg/kg, IP) blocked the effects of both p-chloroamphetamine and d-fenfluramine on plasma oxytocin concentrations, suggesting that both 5-HT releasers must be taken up through the 5-HT transporter into 5-HT nerve terminals to increase oxytocin secretion. In the lesion experiments, cells in the hypothalamic PVN or SON were destroyed by injection of the cell-selective neurotoxin ibotenic acid. The PVN lesions reduced basal levels and inhibited the effect of p-chloroamphetamine (8 mg/kg, IP) on plasma oxytocin concentration. In contrast, SON lesions did not alter basal oxytocin levels and did not reduce the oxytocin response to p-chloroamphetamine, suggesting that the SON is not involved in the serotonergic stimulation of oxytocin secretion. Site specificity of the PVN lesions was confirmed when injections of ibotenic acid into the hypothalamic dorsomedial nucleus (DMN), immediately caudal to the PVN, potentiated the oxytocin response to p-chloroamphetamine, suggesting that the DMN exerts an inhibitory influence on the secretion of oxytocin. Taken together, the data suggest that the serotonergic stimulation of oxytocin secretion involves PVN, but not SON, oxytocin neurons.

Animals↗
PubMed1995

The effect of genetically expressed cardiac titin fragments on in vitro actin motility.

Titin is a striated muscle-specific giant protein (M(r) approximately 3,000,000) that consists predominantly of two classes of approximately 100 amino acid motifs, class I and class II, that repeat along the molecule. Titin is found inside the sarcomere, in close proximity to both actin and myosin filaments. Several biochemical studies have found that titin interacts with myosin and actin. In the present work we investigated whether this biochemical interaction is functionally significant by studying the effect of titin on actomyosin interaction in an in vitro motility assay where fluorescently labeled actin filaments are sliding on top of a lawn of myosin molecules. We used genetically expressed titin fragments containing either a single class I motif (Ti I), a single class II motif (Ti II), or the two motifs linked together (Ti I-II). Neither Ti I nor Ti II alone affected actin-filament sliding on either myosin, heavy meromyosin, or myosin subfragment-1. In contrast, the linked fragment (Ti I-II) strongly inhibited actin sliding. Ti I-II-induced inhibition was observed with full-length myosin, heavy meromyosin, and myosin subfragment-1. The degree of inhibition was largest with myosin subfragment-1, intermediate with heavy meromyosin, and smallest with myosin. In vitro binding assays and electrophoretic analyses revealed that the inhibition is most likely caused by interaction between the actin filament and the titin I-II fragment. The physiological relevance of the novel finding of motility inhibition by titin fragments is discussed.

Actins↗