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Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 919 records · Page 51Linked to original sources
PubMed1994

Central stimulation of renin secretion through serotonergic, noncardiovascular mechanisms.

The aims of the study were to determine; (1) whether activation of serotonin (5-HT) receptors in the brain increases renin secretion, and (2) whether the hypertensive effects of a 5-HT agonist and 5-HT releaser obscure their ability to stimulate renin release. Various drugs that increase serotonergic neuro-transmission can activate the secretion of renin from the kidneys. Many of these drugs can also elevate blood pressure. Changes in blood pressure can alter renin secretion by activating renal baroreceptor mechanisms, so that a decrease in perfusion pressure will increase renin secretion and vice versa. To address the first objective, the 5-HT agonist RU 24969 (0, 10, 100 and 200 micrograms/kg) and the 5-HT releaser p-chloroamphetamine (0, 50, 500 and 1,000 micrograms/kg) were injected intracerebroventricularly (ICV) at doses lower than those that are peripherally effective. ICV injection of RU 24969 dose-dependently increased plasma levels of renin. ICV injection of the 5-HT2A/5-HT2C antagonist LY53857 (50 micrograms/kg) inhibited the renin response to peripherally injected RU 24969 (0, 1, 5 and 10 mg/kg i.p.), suggesting that 5-HT2A/5-HT2C receptors in the brain mediate the effect of peripherally injected RU 24969 on renin secretion. In contrast, ICV injection of p-chloroamphetamine decreased renin secretion. To determine whether hypertensive actions could account for the differences between RU 24969 and p-chloroamphetamine, we measured the effects of both p-chloroamphetamine and RU 24969 on blood pressure and heart rate. ICV injection of p-chloroamphetamine (1,000 micrograms/kg) produced a large rise of 44 mm Hg at 2 min and 25 mm Hg at 5 min after injection, while ICV injection of RU 24969 (200 micrograms/kg) caused a slower and smaller blood pressure elevation of 18 mm Hg at 5 min after injection. To determine whether the hypertensive effects of both RU 24969 and p-chloroamphetamine could mask their effects on renin secretion, rats were pretreated with the alpha 1 antagonist prazosin. Administration of prazosin (1 mg/kg s.c.), which prevents the hypertensive effects of p-chloroamphetamine, exposed a stimulatory effect of ICV-injected p-chloroamphetamine (500 micrograms/kg) on renin secretion and potentiated the effect of RU 24969 (5 mg/kg i.p.) on renin release. In conclusion, these data suggest that both RU 24969 and p-chloroamphetamine increase renin secretion through central 5-HT receptors, and that these effects are partially obscured by their hypertensive actions.

Animals↗
PubMed1994

[The operational control studies of smear positive tuberculosis cases with short-course chemotherapy under the full-course management and supervision].

Two groups of smear positive ambulatory tuberculous patients were treated with the regimen of 2H2R3E3Z3/4H3R, 189 and 192 cases received full-management and full-course supervision respectively and the smear conversion rates at the completion of treatment are 98.9% and 96.9%. This suggests that it can get equal rate of successful chemotherapy with the standard full-course management compared with the full-course supervision.

Adolescent↗
PubMed1994

Determination of L-glutamate using flow injection analysis with immobilized L-glutamate oxidase reactor.

L-Glutamate oxidase (GOD) and horseradish peroxidase (HRP) were covalently coupled on alkylamine pretreated controlled pore glass (CPG) by means of glutaraldehyde. The immobilized enzymes were packed into a teflon tube and used in flow injection analysis (FIA) system for L-glutamate determination. A good linearity range was obtained at 0.1-2.0 mM, and the coefficient of variation was 0.7% (n = 8). More than 80 samples were measured within an hour. The stability of the immobilized GOD reactor was good, retaining 50% of its initial activity after 4 months storage in buffer at 4 degrees C. When the concentration of L-glutamate remained lower than 2.5 mM, the determination of L-glutamate in this system was not affected by pH and temperature within the range of 6.0-8.0 and 20-35 degrees C, respectively. The system was applied to determine L-glutamate in broth samples during L-glutamate fermentation and good correlations were achieved between results obtained with the FIA system, L-glutamate oxidase kit and Warburg's method.

Amino Acid Oxidoreductases↗
PubMed1994

The glutamate biosensor and its application to flow injection analysis system.

A micro-enzyme electrode was fabricated by cross-linking L-glutamate oxidase with glutaraldehyde on aminopropyl-platinized platinum wire. A flow injection analysis system with glutamate sensor was used for L-glutamate determination. The peak current is linearly related to the L-glutamate concentration in the range of 0.02-2.0 mM, with good performance, accuracy (CV = 0.4%), fast response (< 60s), and stability (> 20 days). The system was applied to determine the concentration of L-glutamate in a fermentation broth. The recovery rate was in the range of 98.7-107.5%.

Amino Acid Oxidoreductases↗
PubMed1994

[Specific detection of Mycobacterium tuberculosis in clinical material by PCR and Southern blot].

An amplified fragment of 245 base pairs from IS-986 sequence hybridized specifically with DNA of M. tuberculosis complex strains. The fragment was labelled with digoxigenin. After amplification by PCR and southern blot hybridization with the dig-labelled probe, the limit of detection of purified genomic M. tuberculosis DNA amounted to 1 fg. We detected sputum, pleural and synovial fluid with active tuberculosis by PCR and southern blot, and the sensitivities were 81.0%, 64.2% and 57.7%, respectively. From the result of the experiment, it is a very useful method for diagnosis of tuberculosis by combining PCR with Southern blot.

Blotting, Southern↗
PubMed1994

[The alpha 1 subunit of voltage-dependent calcium channel expressed in pancreatic beta cells].

Calcium channels play an important role in insulin secretion from pancreatic beta cells, in which two different L-type voltage-dependent Ca2+ channels (VDCC), the beta cell/neuron type and the cardiac type are expressed. The former pre-dominant subtype gene (hCa CN4) consists of 49 exons spanning 120 kilo-bases. The promoter region of hCaCN4 is similar to that of housekeeping gene, which is extremely G+C rich and lacks a TATA-like sequence but has three possible binding regions for transcriptional factor Sp1. Changes of calcium channel mRNA in rat pancreatic islets after glucose infusion are introduced. It is important to investigate variations or mutations in the hCaCN4 gene, causing insufficient insulin secretion, leading to NIDDM.

Amino Acid Sequence↗
PubMed1994

Evidence that ACTH secretion is regulated by serotonin2A/2C (5-HT2A/2C) receptors.

The present study characterized the serotonin (5-HT) receptor subtypes mediating adrenal corticotropic hormone (ACTH) and corticosterone responses to 5-HT agonists in conscious rats. The 5-HT2A/5-HT2C agonist (+/-(-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HC1 (DOI) increased plasma ACTH and corticosterone in a dose-dependent manner. The 5-HT2A/5-HT2C antagonist ritanserin (0.01 and 0.1 mg/kg sc) inhibited the DOI-induced increase in plasma ACTH, but not corticosterone. Low doses of spiperone (0.01 and 0.1 mg/kg sc) significantly reduced the ACTH response to DOI. Because spiperone has a higher affinity for 5-HT2A than 5-HT2C receptors, these data suggest that DOI stimulates ACTH secretion through 5-HT2A receptors. 5-methoxy-3-[1,2,3,4-tetrahydro-4-pyridinyl]-1H-indole (RU 24969) is a potent 5-HT1A/1B and moderate 5-HT2C agonist that also has been suggested to release 5-HT. However, p-chlorophenylalanine (PCPA) did not reduce the effect of RU 24969 on plasma ACTH, suggesting that RU 24969 only acts as a direct agonist. 6-methyl-1-[1-methylethyl]ergoline-8-carboxylic acid (LY53857) injected into the lateral cerebral ventricles (i.c.v.) inhibited the ACTH, but not corticosterone response to peripheral injection of RU 24969, suggesting that central 5-HT2A/2C receptors mediate the ACTH response. LY53857 injection (i.c.v.) also inhibited the effect of p-chloroamphetamine (i.c.v.) on plasma ACTH. However, the corticosterone response was not inhibited by LY53857, suggesting a distinct location of 5-HT receptors regulating corticosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1994

Ocular toxoplasmosis in the fetus. Immunohistochemistry analysis and DNA amplification.

PURPOSE: Ocular toxoplasmosis is often the result of a congenital infection. However, the earlier stages of the ocular lesions in the fetus have not been well studied. The purpose of the present study is to analyze the ocular findings in four aborted fetuses that were infected congenitally with Toxoplasma gondii. METHODS: Eight eyes from four fetuses of 22 to 27.5 weeks with T. gondii infection were studied by routine and immunohistochemical techniques. Two of the four were also examined by polymerase chain reaction (PCR). RESULTS: In two cases, the results of gross and histopathologic of the eyes were normal; marked retinal necrosis was present in the other two cases. Although no toxoplasmic cysts were identified by routine histopathologic examination, antigens of the tachyzoite were detected by immunohistochemistry analysis in the areas of retinal necrosis. In one of the cases with ocular lesions, the presence of T. gondii was confirmed by PCR. The presence of ocular lesions correlated with the severity of pathologic changes in the central nervous system. Large numbers of T cells were observed in the retinal lesions and in the choroid. CONCLUSION: Retinal necrosis, neovascularization, and marked chorioretinal inflammations despite the absence of bradyzoites are characteristic findings in the fetal eyes infected with T. gondii, and infiltrating T lymphocytes play a role in early recognition of the toxoplasma organism.

Adult↗
PubMed1994

Expression of a cloned P2Y purinergic receptor that couples to phospholipase C.

P2Y purinergic receptors previously have been shown to couple either to activation of phospholipase C through a pertussis toxin-insensitive mechanism or to inhibition of adenylyl cyclase through pertussis toxin-sensitive members of the G1 family of G proteins. These and other pharmacological data strongly suggest that multiple P2Y purinergic receptors exist. Webb et al. [FEBS Lett. 324:219-225 (1993)] cloned a cDNA that, when expressed in frog oocytes, displayed the general pharmacological characteristics of a P2Y purinergic receptor but whose second messenger linkage was not resolved. We have now cloned the meleagrid (turkey) homologue of the previously cloned chick P2Y purinergic receptor and have stably expressed it in a heterologous human cell line (1321N1 astrocytoma cells) to establish its signaling properties. The purinergic receptor agonist 2-methylthio-ATP (2MeSATP) stimulated a marked activation of phospholipase C in 1321N1 cells stably expressing the meleagrid receptor. The order of potency of a series of analogues of ATP and ADP for stimulation of phospholipase C by the receptor expressed in 1321N1 cells [2MeSATP = 2-methylthio-ADP > adenosine 5'-O-(2-thio)diphosphate > ADP > 2-chloro-ATP = adenosine 5'-O-(3-thio)triphosphate > or = ATP > adenylyl-imidodiphosphate > UTP] was similar to that observed for P2Y purinergic receptors in turkey erythrocytes and many other tissues and was markedly different from those of the P2U and P2X purinergic receptor subtypes. Stimulation of inositol lipid hydrolysis by P2Y purinergic agonists was not affected by preincubation of cells with pertussis toxin. In contrast to its marked effects on phospholipase C activity, 2MeSATP caused only a small and variable inhibition of cAMP accumulation. Ribonuclease protection analysis of turkey tissues showed that this P2Y purinergic receptor is most highly expressed in blood and brain. Taken together, these results indicate that a phospholipase-C-activating P2Y purinergic receptor has been cloned and stably expressed in 1321N1 astrocytoma cells.

Animals↗
PubMed1994

[Epidemiology of adenovirus pneumonia in Beijing, 1976-1990].

From 1976 to 1990 for 15 consecutive epidemic years, virological examinations were carried out on 2,757 hospitalized infants and children infected with pneumonia. Ninety-nine strains of types 3 and 7 adenovirus (Ad3,Ad7) isolated from 50s to 90s were analyzed with 12 DNA restriction endonucleases. Results showed the epidemiologic characteristics of adenovirus (Adv) pneumonia in Beijing. Epidemic occurred yearly, but there was no severe outbreak of Adv pneumonia as in 1958. Ad3 and Ad7 were the main etiologic agents of Adv pneumonia. Ad7 was dominant in 1976-1980; while Ad3 was more prevalent in 1981-1990. DNA restriction endonuclease analysis revealed six genome types of Ad7 and three genotypes of Ad3. 7a1, 7a4, 7b and 7g occurred in 1958, 1965, but disappeared between 1980-1990; 3a2 was first detected in 1962. From 1980 to 1990, 7d and 3a2 were the dominant genome types. Among the Ad7 strains only one strain of 7d1 was identified; all others were 7d. 3a4 and 3a6 first appeared in 1984 and 1986, respectively. The changes of epidemic patterns seemed correlated with the variations of genome types.

Adenovirus Infections, Human↗
PubMed1994

Manometric determination of esophageal length.

OBJECTIVE: Two hundred and fifty-two esophageal manometric studies were reviewed retrospectively to determine the length of esophagus and its relationship to disease, sex, height, and weight. METHODS: For all studies, solid state intraluminal transducers were used, with patients in the supine position. Esophageal length was defined as the difference between the high pressure zone of the upper esophageal sphincter and proximal margin of the lower esophageal sphincter. The mean length of the esophagus was 22.9 +/- 0.2 cm (+/- SEM) in all patients and volunteers (excluding those with achalasia). RESULTS: The 40 patients with achalasia had a significantly (p < 0.05) longer mean esophageal length (24.5 +/- 0.5 cm) than normal volunteers or other patient groups with scleroderma, GERD, chest pain, and dysphagia. Excluding patients with achalasia, 96 males had a significantly (p < 0.05) longer mean esophageal length (23.6 +/- 0.3 cm) than 116 females (22.4 +/- 0.3 cm). A normal distribution of esophageal length was demonstrated in all subjects (excluding those with achalasia). Esophageal length showed poor correlation with either height (r2 = 0.15) or body weight (r2 = 0.003). CONCLUSION: esophageal length showed considerable intersubject variation. Patients with achalasia had a longer esophagus consistent with esophageal dilation. Males had a longer esophagus than females. Esophageal length did not correlate with either height or weight.

Adolescent↗
PubMed1994

Establishment of a small animal model for human Helicobacter pylori infection using germ-free mouse.

OBJECTIVE: To understand why oral inoculation of Helicobacter pylori resulted in continuous colonization of the stomach in germ-free athymic mice, but only temporary colonization in mice that were not germ-free. METHODS: We inoculated germ-free and "not-germ-free" euthymic mice with H. pylori and studied the resulting colonization of the stomach, comparing it against the germ-free athymic mouse model. In addition, we investigated Lactobacillus in the above-described three mouse groups. RESULTS: H. pylori were detected in all germ-free athymic mice and all germ-free euthymic mice continuously. However, in all euthymic mice that were not germ-free, H. pylori was detected only temporarily after inoculation. Lactobacilli were detected only in the not-germ-free mouse group. The number of H. pylori in the germ-free euthymic mice was significantly lower than in the germ-free athymic mice during the period of this study after inoculation. CONCLUSIONS: We therefore suggest that the growth of H. pylori may be suppressed by the immunological system and eradicated by Lactobacilli previously inhabiting the stomach.

Animals↗
PubMed1993

The leu-1 gene of Neurospora crassa: nucleotide and deduced amino acid sequence comparisons.

The Neurospora crassa leu-1 gene encodes beta-isopropylmalate dehydrogenase (IPMDH; EC 1.1.1.85), an enzyme in the leucine biosynthetic pathway. We determined the nucleotide sequence of the entire leu-1 gene and of four independent cDNA clones. By comparing the genomic and cDNA sequences, four introns were identified in the 5' portion of the gene and a single open reading frame was established. One of the introns is located within the 5'-noncoding region of the transcript. The deduced amino acid sequence encoded by leu-1 was aligned with that of the homologous yeast enzyme and extensive sequence identity was uncovered. The lesion present in a conventional leu-1 mutant was identified as the insertion of a single base pair.

3-Isopropylmalate Dehydrogenase↗
PubMed1993

Tb(III) and Eu(III) as fluorescent probes to investigate the metal-binding sites of trichosanthin.

Tb(III) and Eu(III) ions were used as fluorescent probes in the study of the trichosanthin (TCS). The fluorescence of Tb(III) was increased considerably when bound to TCS to replace the Ca(II) ions. The nonradiative energy transfer from fluorescent tryptophan (Trp) residues to the bound Tb(III) or Eu(III) took place. From a Foster d-d nonradiative energy transfer mechanism, it was obtained that the average distance between the bound Tb(III) and the Trp residue is 1.27nm. The results indicate that the major groups in TCS bound to Ca(II) ions should be the carboxylic side groups of the glutamic acid and/or aspartic acid. The fluorescent quenching of Ca(II)-free TCS by adding Tb(III) or Eu(III) into TCS from which the Ca(II) ions had been removed was discussed as well.

Binding Sites↗
PubMed1993

Long-term fluoxetine, but not desipramine, inhibits the ACTH and oxytocin responses to the 5-HT1A agonist, 8-OH-DPAT, in male rats.

The present studies determined whether serotonin 5-HT1A receptor-mediated function is modified by chronic exposure to antidepressants. Hormone responses to the 5-HT1A agonist, 8-OH-DPAT, were evaluated after long-term exposure to two antidepressants, the 5-HT uptake blocker, fluoxetine, and the norepinephrine uptake blocker, desipramine (DMI). In addition, the density and affinity of 5-HT1A receptors in the hypothalamus and cerebral cortex were measured. Male rats received fluoxetine (10 mg/kg i.p.), DMI (5 mg/kg i.p.) or saline injections once daily for 21 days. 8-OH-DPAT (0-500 micrograms/kg s.c.) was administered 18 h after the final antidepressant injection and 15 min before sacrifice. 8-OH-DPAT significantly increased plasma ACTH, corticosterone, oxytocin and prolactin, but not renin or vasopressin concentrations. Chronic injections of fluoxetine inhibited the ACTH, corticosterone and oxytocin responses to 8-OH-DPAT, suggesting reduced 5-HT1A receptor function. In contrast, chronic DMI did not alter the hormone responses to 8-OH-DPAT. The density and affinity of 5-HT1A receptors in the frontal cortex or hypothalamus were not altered by either fluoxetine or DMI. To verify that the observed effects require prolonged exposure to fluoxetine, rats received a single injection of fluoxetine (10 mg/kg, i.p.), 3 h before 8-OH-DPAT (0-500 micrograms/kg s.c.). Acute fluoxetine did not reduce any of the hormone responses to 8-OH-DPAT. In conclusion, the results suggest that chronic, but not acute, exposure to fluoxetine decreases 5-HT1A receptor function. This effect is not seen in rats chronically exposed to DMI.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗