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Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 739 records · Page 41Linked to original sources
PubMed1996

Determination of the Neurospora crassa CYS 3 sulfur regulatory protein consensus DNA-binding site: amino-acid substitutions in the CYS3 bZIP domain that alter DNA-binding specificity.

CYS3 is the positive-acting global regulatory protein involved in the sulfur control circuit in Neurospora crassa and belongs to the family of bZIP DNA-binding proteins. Here we report a characterization of native DNA-binding sites recognized by CYS3. DNA footprinting experiments and systematic mutational analysis were used to define the consensus CYS3-binding sequence, 5'-ATGPuPyPuPyCAT, a 10-bp palindrome. The sequence 5'-ATGACGTCAT acts as a strong binding site, and all single nucleotide changes within this sequence resulted in a reduction, or even complete loss, of CYS3 DNA-binding. Site-directed mutagenesis was employed to study two uncharged residues, serine 113 and phenylalanine 116, in the basic region of the CYS3 protein bZip DNA-binding domain. Ser113 appears to be directly involved in a specific interaction with nucleotide 2 of the binding site, possibly by making a direct contact with this base, and Phe116 contributes significantly to DNA-binding affinity.

Amino Acid Sequence↗
PubMed1996

Serotonergic regulation of renin and prolactin secretion.

Drugs that, directly or indirectly produce activation of serotonin (5-HT) receptors increase plasma concentrations of both prolactin and renin. The serotonergic regulation of prolactin and renin secretion share several common characteristics. Serotonergic neurons originating in the dorsal raphe and terminating in the hypothalamus stimulate the secretion of both prolactin and renin. Destruction of cells in the hypothalamic paraventricular nucleus (PVN) inhibits both the prolactin and renin responses to 5-HT agonists and 5-HT-releasing drugs. Activation of 5-HT2 receptors increases the secretion of both prolactin and renin, while activation of other 5-HT receptor subtypes has differential effects on these hormones. However, there are also differences between the serotonergic mechanisms that regulate the secretion of prolactin and renin. Activation of 5-HT1A receptors increases the secretion of prolactin but not of renin. In addition, activation of peripheral 5-HT2 receptors stimulates the secretion of renin, while activation of peripheral 5-HT3 receptors increases plasma levels of prolactin but not renin. In humans, the effect of 5-HT-releasing drugs and 5-HT agonists on plasma prolactin concentrations has been studied to a greater extent than effects on most other hormones. In contrast, the renin response to 5-HT agonists and 5-HT releasers has not been well characterized in humans. Because of the important role of the renin-angiotensin system in cardiovascular regulation, studies on the serotonergic regulation of renin release in humans could increase our understanding of cardiovascular disorders associated with altered serotonergic function. Examples include anxiety and consequences of cocaine abuse. In conclusion, comparing the serotonergic regulation of prolactin and renin secretion indicates similarities that might shed light on common brain mechanisms that regulate neuroendocrine function.

Animals↗
PubMed1996

Immunological studies of rabbit antibodies against hemorrhagic fractions of Crotalus viridis viridis venom: role of crossreacting antibodies in neutralization.

1. Crude Prairie rattlesnake (Crotalus viridis viridis) venom was fractionated by HPLC DEAE anion exchange chromatography. Both acidic and basic protein fractions were assayed for hemorrhagic activity in vivo. 2. The acidic fractions that showed the highest hemorrhagic activities were pooled and divided into two samples. One sample was treated with EDTA and heat to inactivate and denature the hemorrhagic toxins; the other sample was left in native form. Both denaturated and native samples were used as immunogens for production of polyvalent antibodies in rabbits. 3. Neutralizing ability for hemorrhage of the antiserum raised against the native sample was about 50% greater than that of antiserum raised against the denatured sample. There was no correlation between ELISA reactivity and neutralizing ability of the antisera. 4. Antiserum raised against native hemorrhagic fractions showed extensive ELISA crossreactivities with the nonhemorrhagic basic proteins. The crossreacting antibodies accounted for 61% of the total ELISA reactivity and 54% of the total neutralizing ability of the antiserum. Treatment of the hemorrhagic fractions with EDTA induced a fundamental conformational change of the molecules, which was reflected in significantly increased ELISA reactivities. Antivenom raised in rabbits had high neutralizing potency compared to Wyeth antivenom (0.38 mg IgG was able to completely neutralize the hemorrhagic lesions induced by 10 micrograms crude C. v. viridis venom). However, when it was quantitatively compared with commercial Wyeth antivenom, no significant advantages were found.

Animals↗
PubMed1996

Cross-system agreement among demographic subgroups: DSM-III, DSM-III-R, DSM-IV and ICD-10 diagnoses of alcohol use disorders.

Increasing importance is being placed on the appropriateness of methodologies for different population subgroups, such as women as well as men, non-Whites as well as Whites, and older and younger individuals. In the alcohol field, this applies to a number of areas, including the agreement between diagnoses of alcohol use disorders by different sets of diagnostic criteria. We tested the agreement between DSM-III, DSM-III-R, DSM-IV and ICD-10 criteria for alcohol dependence and abuse in demographic subgroups of a sample of 962 community residents screened for heavy drinking in the previous 12 months. Good to excellent agreement was found for current diagnoses of dependence across all subgroups and classification systems. For past diagnoses, agreement was good across all subgroups for comparisons that did not involve DSM-III, and quite low for comparisons of DSM-III to other classification systems across subgroups. With few exceptions, cross-system agreement for diagnoses of alcohol abuse was poor. This result was also consistent across demographic subgroups. Results suggest that studies can be compared equally well for diagnoses of alcohol dependence subsequent to DSM-III for males and females. Whites and non-Whites, and older and younger respondents. Abuse remains a problematic category psychometrically across all demographic categories, even in this sample of largely untreated household residents.

Adolescent↗
PubMed1996

Differential effects of oral losartan and enalapril on local venous and systemic pressor responses to angiotensin I and II in healthy men.

This double-blind, placebo-controlled crossover study was designed to differentiate the pharmacodynamic effects of the angiotensin II receptor antagonist losartan from the angiotensin converting enzyme inhibitor enalapril. Effects of placebo, enalapril (10 mg), and losartan (20 and 100 mg) on local venous and systemic pressor responses to angiotensin I and II were compared in eight healthy male subjects. Treatments were administered orally approximately 4 hours before agonist infusions into a dorsal hand vein. Local changes in hand vein diameter and systemic blood pressure were monitored during the infusions. The 100 mg dose of losartan attenuated local venoconstrictor and systemic pressor responses to angiotensin I and II. In contrast, enalapril blocked only responses to angiotensin I. Both losartan and enalapril increased plasma renin concentration compared with placebo. These results are consistent with direct antagonism of angiotensin II receptors by losartan and with indirect effects of enalapril through inhibition of angiotensin converting enzyme.

Administration, Oral↗
PubMed1996

Agreement between DSM-III, DSM-III-R, DSM-IV and ICD-10 alcohol diagnoses in US community-sample heavy drinkers.

DSM-III-R, DSM-IV and ICD-10 definitions of alcohol dependence were all developed from the concept of the Alcohol Dependence Syndrome, and thus have a common theoretical link. This link is not shared by DSM-III, and no link exists between definitions of abuse in the different classification systems. The level of agreement on diagnoses produced by the different systems has practical as well as theoretical implications. We tested this agreement in 962 US household residents randomly sampled and screened for heavier than average drinking in the last 12 months. Agreement for most comparisons involving diagnoses of current dependence ranged from good to excellent, with no clear pattern of lower agreement for DSM-III. However, agreement on past dependence was sharply lower for comparisons involving DSM-III than those involving the other classification systems. This appeared to be due to the DSM-III requirement for physiological dependence and the apparently emerging nature of the disorder in this relatively young, non-treatment sample. Comparisons for abuse were generally poor for current as well as past diagnoses. Implications of the findings are discussed.

Adolescent↗
PubMed1996

Expression of fos-like immunoreactivity in the hypothalamus of the ring dove (Streptopelia risoria) at the onset of incubation.

Fos immunocytochemistry was used in the ring dove (Streptopelia risoria) to identify areas in the forebrain and hypothalamus which might be involved in the expression of incubation behaviour and the associated changes in neuroendocrine function. In this species, both sexes participate in incubation which becomes fully established after laying the second egg in the two egg clutch. The eggs hatch after 14-15 days incubation. Observations were made in both sexes 16-18 h after laying the first egg, 3-5 h after laying the second egg, and after 12-14 days of incubation. Non-breeding birds were used as controls. Fos-labelled cells were observed in several forebrain areas in both sexes irrespective of reproductive status but their numbers did not change during incubation. In the hypothalamus, very few fos-labelled cells were seen in non-breeding birds but appeared in both sexes in the nucleus preopticus medialis after egg laying and after 12-14 days of incubation. Fos-labelled cells also appeared in the nucleus tuberis (=arcuate nucleus) in both sexes after laying the first or second egg and less abundantly, after 12-14 days incubation. Additionally, in males only, fos-labelled cells were seen after the laying of the first and second eggs in the rostral area of the nucleus tuberis close to the walls of the third ventricle. These observations suggest that the fos-labelled cells in the nucleus preopticus medialis may be involved in the expression of incubation behaviour while those in the nucleus tuberis may be involved in the regulation of gonadotrophin or prolactin secretion.

Animals↗
PubMed1996

The impact of cocaine on plasma growth hormone levels in the adult male rat.

Little is known about the neuroendocrine impact of cocaine as it relates to pituitary growth hormone secretion. In these studies, in adult male rats, intracerebroventricular administration of cocaine caused a potent dose-related suppression of circulating growth hormone (GH) in animals sacrificed 15 min after drug administration. We conclude that in the adult male rat cocaine suppresses plasma GH levels.

Animals↗
PubMed1996

Role of tyrosine kinases, protein kinase C, and protein kinase A in the regulation of interferon-alpha production induced by herpes simplex virus type 1.

Herpes simplex virus 1 (HSV-1) is able to induce interferon-alpha production by natural IFN-alpha-producing cells. In this study, signal transduction in this process was examined. It was found that sequestering of calcium by EGTA abolished IFN-alpha induction by HSV-infected cells. Stimulation of human PBMC by HSV-1-infected fibroblasts resulted in the production of inositol triphosphate (InsP3) and tyrosine phosphorylation of cellular proteins. The protein kinase C inhibitor, H7, and the tyrosine kinase inhibitor, herbimycin A, were able to suppress IFN-alpha gene expression as determined by IFN bioassay and RT-PCR. An IFN-alpha-specific ELISpot assay revealed that herbimycin A and H7 remarkably decreased the number of IFN-alpha-producing cells. PMA or calcium ionophore A23187 alone did not increase IFN-alpha production. However, PMA in conjugation with ionophores increased IFN-alpha production as early as 2 h. HA1004 and 2',5'-dideoxyadenosine, which are potent inhibitors of PKA pathway, had no effect on IFN-alpha production. In contrast, BrcAMP, a specific PKA activator, inhibited the IFN-alpha secretion and number of IFN-alpha-producing cells and to a lesser extent reduced the level of IFN-alpha mRNA. Our results indicate that protein kinase C, tyrosine kinases, and protein kinase A are involved in the regulation of IFN-alpha production in response to HSV-1.

Base Sequence↗
PubMed1996

Cloning and analysis of the alternative oxidase gene of Neurospora crassa.

Mitochondria of Neurospora crassa contain a cyanide-resistant alternative respiratory pathway in addition to the cytochrome pathway. The alternative oxidase is present only when electron flow through the cytochrome chain is restricted. Both genomic and cDNA copies for the alternative oxidase gene have been isolated and analyzed. The sequence of the predicted protein is homologous to that of other species. The mRNA for the alternative oxidase is scarce in wild-type cultures grown under normal conditions, but it is abundant in cultures grown in the presence of chloramphenicol, an inhibitor of mitochondrial protein synthesis, or in mutants deficient in mitochondrial cytochromes. Thus, induction of alternative oxidase appears to be at the transcriptional level. Restriction fragment length polymorphism mapping of the isolated gene demonstrated that it is located in a position corresponding to the aod-1 locus. Sequence analysis of mutant aod-1 alleles reveals mutations affecting the coding sequence of the alternative oxidase. The level of aod-1 mRNA in an aod-2 mutant strain that had been grown in the presence of chloramphenicol was reduced several fold relative to wild-type, supporting the hypothesis that the product of aod-2 is required for optimal expression of aod-1.

Amino Acid Sequence↗
PubMed1996

Selectivity of class-III antiarrhythmic action of clofilium in guinea pig ventricular myocytes.

Clofilium is an antiarrhythmic agent with a supposedly predominant class-III action which is related to impairment of K+ channel function. We investigated membrane currents in cardiac myocytes isolated from guinea pig ventricle to evaluate the selectivity of action of clofilium on K+ currents. For measurement of action potentials or membrane currents, the single electrode patch clamp technique was applied in current- or voltage-clamp mode, respectively. Clofilium (30 mu M) irreversibly prolonged the action potential duration in guinea pig myocytes. In contrast, the concomitant reduction in plateau phase was completely reversible. The delayed rectifier K+ current Ikappa, was reduced. The rapidly activating component of Ikappa, which has been defined by its sensitivity to the compound E-4031, was also reduced by clofilium. The inward rectifier was slightly inhibited by the drug. Clofilium reversibly reduced L-type Ca2+ current. Sodium current was inhibited in a use-dependent manner. This effect was not reversible but proceeded after washout of the compound. Therefore, clofilium affects both inward and outward currents in mammalian cardiac myocytes in a similar concentration range. The effects on multiple membrane currents may contribute to the antiarrhythmic action of the drug.

Action Potentials↗
PubMed1996

Functional in vivo studies of the Neurospora crassa cys-14 gene upstream region: importance of CYS3-binding sites for regulated expression.

Sulphate transport in Neurospora crassa is achieved by two distinct sulphate permeases, I and II, encoded by the cys-13 and cys-14 genes, respectively. The synthesis of both sulphate permeases is subject to sulphur repression and requires the global positive-acting regulatory protein CYS3, CYS3, a bZIP DNA binding protein, regulates cys-14 expression at the transcriptional level and binds in vitro specifically to three DNA-recognition sites, A, B, and C, in the cys-14 upstream region. In vivo functional analysis of the cys-14 promoter was carried out with 5' deletions and by deletions or mutations of CYS3 DNA-binding sites. The most distal CYS3-binding site, C, located 1.4kb upstream of the transcriptional start site, is necessary and sufficient to mediate strong transcriptional activation by CYS3; moreover, site C was able to function equally well when it was located at variable distances upstream of the cys-14 gene. Site B, located 1 kb upstream, alone is able to support a moderate degree of cys-14 expression. Site A is not required and does not appear to play any functional role in cys-14 expression, even though it is in close proximity to the transcriptional start site. The presence of multiple copies of CYS3-binding elements A or B in the cys-14 promoter results in a parallel increase of regulated gene expression. When a transforming cys-14 gene becomes integrated at ectopic locations in the host genome, it can be expressed in an unregulated fashion, presumably by coming under the control of other promoter elements. Our results also suggested that at least one enzyme in the sulphate catabolic pathway requires a functional CYS3 protein for expression.

Anion Transport Proteins↗
PubMed1996

Pharmacological and second messenger signalling selectivities of cloned P2Y receptors.

1. Four different phospholipase C (PLC)-activating P2Y receptors have been cloned and stably expressed in 1321N1 human astrocytoma cells. These include the human homologues of the P2Y1, P2Y2 and P2Y4 receptors and the rat homologue of the P2Y6 receptor. 2. The nucleotide selectivities of these four receptors have been compared directly by measuring inositol phosphate accumulation in response to nucleotides under conditions in which the initial purity and stability of agonist was rigidly assured and quantitatively assessed. 3. The P2Y1 receptor is specific for adenine nucleotides and slightly more sensitive to disphosphates than triphosphates. When expressed in 1321N1 astrocytoma cells, it couples selectively to the stimulation of PLC and not to the inhibition of adenylyl cyclase. 4. The P2Y2 receptor is activated by UTP and ATP with similar potency and is not activated by nucleoside diphosphates. Diadenosine terraphosphate is a potent agonist at this receptor. 5. The P2Y4 receptor is highly selective for UTP over ATP and is not activated by nucleoside disphosphates. 6. The P2Y6 receptor is activated most potently by UDP, but weakly or not at all by UTP, ADP and ATP. The P2Y6 receptor appears to be identical to the uridine nucleotide-specific receptor previously characterized in C6-2B rat glioma cells. 7. We have identified a P2Y receptor on C6 glioma cells that inhibits adenylyl cyclase but has no effect on PLC. This receptor exhibits a pharmacological selectivity similar but not identical to that of the P2Y1 receptor. When the P2Y1 receptor was expressed in these C6 cells, it conferred an inositol lipid signalling response to adenine nucleotides that was pharmacologically identical to that of the P2Y1 receptor. Thus, the P2Y receptor of C6 glioma cells represents an additional receptor that exhibits the classical pharmacological selectivity of a P2Y1-R, but which couples to adenylyl cyclase rather than to PLC.

Adenosine Triphosphate↗
PubMed1996

Second messenger cascade specificity and pharmacological selectivity of the human P2Y1-purinoceptor.

1. The coding sequence of the P2Y1-purinoceptor was cloned from a human genomic library. 2. The open reading frame encodes a protein of 373 amino acids that is 83% identical to the previously cloned chick and turkey P2Y1-purinoceptor and is > or = 95% homologous to the recently cloned rat, mouse, and bovine P2Y1-purinoceptors. 3. The human P2Y1-purinoceptor was stably expressed in 1321N1 human astrocytoma cells using a retroviral vector. Although the P2Y1-purinoceptor agonist, 2MeSATP, had no effect on inositol phosphate accumulation in cells infected with the P2Y1-purinoceptor virus. No effect of 2MeSATP on cyclic AMP accumulation was observed in P2Y1-receptor-expressing 1321N1 cells. 4. The pharmacological selectively of 18 purinoceptor agonists was established for the expressed human P2Y1-purinoceptor. 2MeSATp was more potent than ATP but less potent than 2MeSADP. ADP also was more potent than ATP. A similar maximal effect was observed with most agonists tested. However, alpha, beta-MeATP had no effect and 3'-NH2-3'-deoxyATP and A2P4 were partial agonists. The order of potency of agonists for activation of the turkey P2Y1-purinoceptor, also stably expressed in 1321N1 cells, was identical to that observed for the human P2Y1-purinoceptor. 5. C6 glioma cells express a P2Y-purinoceptor that inhibits adenylyl cyclase but does not activate phospholipase C. Expression of the human P2Y1-purinoceptor in C6 cells conferred 2MeSATP-stimulated inositol lipid hydrolysis to these cells. The phospholipase C-activating human P2Y1-purinoceptor could be delineated from the endogenous P2Y-purinoceptor of C6 glioma cells by use of the P2-purinoceptor antagonist, PPADS, which blocks the P2Y1-purinoceptor but does not block the endogenous P2Y-purinoceptor of C6 cells. P2-purinoceptor agonists also exhibited differential selectivities for activation of these two P2Y-purinoceptors.

Amino Acid Sequence↗
PubMed1996

Direct positive chronotropic effects of angiotensin II and angiotensin III in pithed rats and in rat isolated atria.

1. The direct positive chronotropic effects of angiotensin II (AII) and its degradation products angiotensin III (AIII) and angiotensin IV (AIV) were established in pithed rats and in rat spontaneously beating right atria. 2. In pithed rats, AII, AIII and AIV caused dose-dependent tachycardia with similar maximal responses (110 beats min-1). The beta-adrenoceptor antagonist propranolol (3.37 x 10(-6) mol kg-1) but not the alpha 1-adrenoceptor antagonist prazosin (2.38 x 10(-7) mol kg-1) significantly reduced these effects (P < 0.05; n = 7-8), but 20-25% of the responses could not be blocked by propranolol. 3. In isolated atria, AII, AIII and AIV caused concentration-dependent increases in beating rate with similar maximal responses to AII and AIII (34.3 +/- 0.4 and 34.7 +/- 0.4 beats min-1; n = 9-10), and a lower maximal response to AIV (26.8 +/- 0.6 beats min-1; P < 0.05; n = 8). AIII was about 9 times less potent than AII, whereas AIV proved approximately 3800 times less potent than AII. Neither propranolol (1 microM) nor prazosin (1 microM) could influence the effects of the angiotensin peptides. 4. In isolated atria, the selective AT1-receptor antagonist, losartan (10, 100 and 300 nM) caused parallel rightward shifts of the concentration-response curves for AII and AIII, whereas the selective AT2- receptor antagonist PD123177 (1 microM) did not influence the effects of AII and AIII. The aminopeptidase-A and -M inhibitor amastatin (10 microM), significantly steepened the slope of the AIII curves and increased the potency of AIII about 6 fold. Amastatin did not influence the responses to AII. 5. Our results indicate that both in vivo and in vitro, exogenous AII and AIII induced a direct dose-dependent chronotropic effect, which is independent of the adrenergic system. This chronotropic effect is mediated by AT1-subtype receptors.

Adrenergic alpha-Antagonists↗
PubMed1996

Diversity of soil actinomycetes in yunnan, china.

Since 1978, about 4,200 soil samples have been collected from 22 selected areas of various vegetational and climatic types throughout the province of Yunnan. Actinomycetes of 29 genera were isolated by the methods employed. The correlations between diversity and climate were grouped into tropical, subtropical plateau, cool temperate mountain, and snowy mountain types. Actinomycete populations of the first two types were more complex than were the other ones. Correlations between actinomycete diversity and vegetation were also attempted. Six types of vegetation were compared. The diversity of actinomycetes was greatest in soil samples of a primeval forest, with an average of 9.0 genera isolated, followed by secondary forest and vegetable farmland samples, with averages of 6.7 and 6.5 genera isolated, respectively. The upper limit for the occurrence of thermophilic actinomycetes is about 3,500 m above sea level in Yunnan. Psychrophilic actinomycetes were isolated at up to the same altitude. In addition, the drier and poorer the soil was and the cooler the climate was, the lower the count of actinomycetes was and the higher the percentage of streptomycetes observed was. The genus Streptomyces appears to be the most important in ecological function. It represents up to 90% of all soil actinomycete diversity in Yunnan and is likely an important characteristic of the soil actinomycete population.

Journal Article↗
PubMed1996

Acute and chronic angiotensin hypertension: neural and nonneural components, time course, and dose dependency.

We examined the mechanisms mediating hypertension in conscious rats during acute and chronic infusion of angiotensin II (ANG II) at pressor doses (50, 100, and 200 ng.kg-1.min-1). Trimethaphan-induced blood pressure reduction was inversely related to the acute dose of ANG II, consistent with a constrictor action of ANG II on vascular smooth muscle and withdrawal of sympathetic tone. During chronic ANG II infusion, the entire increase in mean arterial pressure (MAP) was inhibited by trimethaphan, consistent with neural mediation. During acute ANG II hypertension, the AT1-specific receptor blocker losartan induced a large fall in MAP (64 +/- 4 mmHg) in ganglion-blocked (chlorisondamine) rats, whereas, during chronic ANG II hypertension, losartan had only a small hypotensive effect (11 +/- 3 mmHg). To determine the time course of the change from vascular smooth muscle action to neural action, we measured MAP in response to trimethaphan during the first 24 h of ANG II infusion. After 5 h, the minimal MAP in response to trimethaphan was significantly higher than that before ANG II. After 10 h of infusion, trimethaphan decreased MAP to pre-ANG II levels. That is, the neural component was fully active after only 10 h of infusion in rats. Finally, chronic administration of ANG II resulted in a dose-related increase in MAP that, at all doses, was completely inhibited by trimethaphan. These findings are consistent with ANG II acting primarily on vascular smooth muscle during acute infusion and via neural pathways during chronic treatment. The transition from direct smooth muscle to indirect neural action is rapid in rats (< 10 h), and the MAP and neural responses to ANG II are dose related during chronic hypertension.

Acute Disease↗