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Biomedical subjects

Q Dong

Publications and source records attributed to Q Dong.

At least 127 records · Page 7Linked to original sources
PubMed1994

Identification of amino acid-base contacts in the Myc-DNA complex by site-specific bromouracil mediated photocrosslinking.

Myc binds to a 6 bp 2-fold symmetric DNA site: 5'-C-3A-2C-1G+1T+2G+3-3'. Using site-specific 5-bromouracil mediated photocrosslinking, we show that His336 of Myc contacts, or is close to, the thymine 5-methyl group at 2-fold symmetry-related positions -2 and +2 of the DNA site in the Myc-DNA complex. Our results strongly suggest that homologous amino acids of Myc and Max make equivalent contacts in the respective protein-DNA complexes.

Amino Acid Sequence↗
PubMed1994

Androgen receptor function during undernutrition.

Hypothalamo-pituitary inhibition of reproductive function during undernutrition is well known, however, the physiological mechanisms leading to suppression of gonadotrophin secretion are not clear. A variety of studies have indicated that testicular negative feedback on LH secretion is enhanced during food restriction. To evaluate directly the suppression by endogenous androgens on hypothalamic GnRH pulse generator activity during food restriction and examine the mechanism underlying the increased testicular steroidal feedback, we examined (1) circulating bioactive LH (bLH) levels in response to selective cerebral androgen blockade by intraventricular administration of an androgen receptor antagonist (hydroxyflutamide, SCH 16423) and (2) the binding capacity and affinity of androgen receptors in medio-basal hypothalamus, pituitary and prostate during undernutrition of intact mature male rats. Hydroxyflutamide (20 micrograms in 10 microliters vehicle), but not vehicle alone, markedly increased bLH levels in both food restricted and ad-lib fed rats. However, the faster (geometric mean 11.4 vs 27.7 min) and greater (47.2 vs 21.9 ng/ml) increase in bLH level in food restricted compared with ad-lib fed controls demonstrates an enhanced sensitivity to blockade of androgenic negative feedback during undernutrition. Food restriction increased androgen receptor binding capacity in pituitary (3.36 vs 0.77 fmol/mg protein) but not in medio-basal hypothalamus or prostate while binding affinity was unchanged by undernutrition in all 3 tissues. These studies reveal that undernutrition both enhances tonic, androgen receptor-mediated feedback suppression of GnRH secretion and increases in pituitary (but not hypothalamic) androgen receptor numbers to cause inhibition of LH secretion.

Androgen Receptor Antagonists↗
PubMed1994

The sss gene product, which affects pyoverdin production in Pseudomonas aeruginosa 7NSK2, is a site-specific recombinase.

Pyoverdin production by Pseudomonas aeruginosa strain 7NSK2 was induced by Zn(II) in the presence of iron. A mutant was isolated in which Zn(II) no longer induced pyoverdin production. The sss gene which was inactivated in this mutant was cloned and sequenced. Its protein sequence showed 50% identity to the XerC protein of Escherichia coli, which is a member of the lambda integrase family of site-specific recombinases. An open reading frame was found upstream of sss whose protein sequence showed strong identity to DapF, the diaminopimelate epimerase. In E. coli, xerC is part of a multicistronic unit that also contains dapF. The sss gene of P. aeruginosa could restore site-specific recombination at cer in an E. coli xerC mutant and the E. coli xerC gene could complement a genomic sss mutation in P. aeruginosa.

Amino Acid Sequence↗
PubMed1994

Fears in Chinese children and adolescents and their relations to anxiety and depression.

In the present study, we examined the pattern and intensity of fear in 825 Chinese children and adolescents. Although many of the fears paralleled those reported in Western samples (Australia, England and the United States), some differences were noted. In particular, Chinese children and adolescents reported heightened levels of social-evaluative fears. This pattern was especially evident for children between 11 and 13 years of age. A developmental-cultural hypothesis was put forth to account for these findings. In addition, modest relations were found between our measure of fear and measures of anxiety and depression. Results were explored in terms of the uniqueness of the constructs of fear, anxiety and depression and their contributions to a more global construct of negative distress, labeled 'negative affectivity'.

Adolescent↗
PubMed1994

Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: mechanisms and applications.

Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy metals. It harbors the megaplasmids pMOL28 and pMOL30 which carry resistance determinants to Co2+, Ni2+, CrO(4)2-, Hg2+, Tl+, Cd2+, Cu2+ and Zn2+. Among the best characterized determinants are the cnr operon (resistance to Co, Ni) on pMOL28 and the czc operon on pMOL30 (resistance to Co, Cd and Zn). Although the two systems reveal a significant degree of amino acid similarity in the structural genes, the regulation of the operons is different. The resistance mechanism in both cases is based on efflux. The efflux mechanism leads to a pH increase outside of the cytoplasmic membrane. Metals are sequestered from the external medium through the bioprecipitation of metal carbonates formed in the saturated zone around the cell. This latter phenomenon can be exploited in bioreactors designed to remove metals from effluents. The bacteria are immobilized on composite membranes in a continuous tubular membrane reactor (CTMR). The effluent continuously circulates through the intertubular space, while the external surface of the tubes is in contact with the growth medium. Metal crystals are eventually removed by the effluent stream and collected on a glass bead column. The system has been applied to effluents containing Cd, Zn, Co, Ni and Cu. By introducing catabolic plasmids involved in the aerobic degradation of PCBs and 2,4-D into metal-resistant A. eutrophus strains, the application range was widened to include effluents polluted with both organic and inorganic substances. Biosensors have been developed which are based on the fusion of genes induced by metals to a reporter system, the lux operon of Vibrio fischeri. Bacterial luciferases produce light through the oxidation of fatty aldehydes. The gene fusions are useful both for the study of regulatory genes and for the determination of heavy metal concentrations in the environment.

Alcaligenes↗
PubMed1994

Effect of undernutrition on pulsatile luteinizing hormone (LH) secretion in castrate and intact male rats using an ultrasensitive immunofluorometric LH assay.

The recent development of an ultrasensitive immunofluorometric rat LH assay makes possible evaluation of pulsatile LH secretion in intact male rats under physiological conditions of minimal volume blood sampling without requiring orchidectomy. Specifically, we applied this assay to determine the effect of macronutrient restriction on pulsatile LH secretion in the presence or absence of testes. In testes-intact rats, halving of food intake for 7 days while maintaining micronutrient supply caused a reduction of mean, maximal, and basal LH levels and LH pulse amplitude (all P < 0.05) compared with those in ad libitum fed controls. The loss of body weight was positively correlated with decreases in mean LH level, pulse amplitude, and area under the curve (all P < 0.009). In contrast, the same food restriction in castrated rats caused an increase in pulse length and area under the curve and a decrease in pulse frequency, but did not change mean, maximal, and basal LH levels or LH pulse amplitude compared to castrated ad libitum fed controls (all P < 0.02). The observed positive correlations between body weight and the LH secretion parameters in intact rats were absent or reversed in castrated rats. This study demonstrates qualitatively different effects of macronutrient restriction on pulsatile LH secretion in castrated and intact rats, indicating that it is not necessary valid to extrapolate consequences of undernutrition on LH secretion from castrate to intact male rats. We conclude that undernutrition-induced inhibition of LH secretion involves both an indirect suppression of LH secretion via amplification of endogenous testicular negative feedback as well as more direct suppression of GnRH release.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Treatment of adolescent myopia by pressure plaster of semen impatientis on otoacupoints.

295 cases (424 eyes) of adolescent myopia were treated by pressure plaster of Semen Impatientis on otoacupoints with a cure rate of 44.3% and a total effective rate of 98.5%. 36 random cases (69 eyes) were compared with the same number of similar control cases. Findings were that the therapeutic effects of the pressure plaster group excelled significantly those of the control group.

Acupuncture Points↗
PubMed1994

Characterization of the swine adipocyte A1 adenosine receptor using an optimized assay system.

The radioligand binding assay of A1 adenosine receptors in adipocyte crude plasma membrane from Yucatan miniature swine was optimized by evaluating 17 factors involved in the assay. Significant effects of CHAPS, adenosine deaminase, EDTA, pre-rinsing glass fiber filters and pH were found for the binding measurements. Using the optimized procedure, [3H]8-cyclopentyl-1,3-dipropylxanthine, ([3H]-DPCPX) binding to A1 adenosine receptors in swine subcutaneous adipocyte crude plasma membrane was measured; Bmax and Kd values were 479 +/- 77 fmol/mg protein and 0.87 +/- 0.10 nM, respectively. Values for mesenteric adipose tissue from sedentary swine and subcutaneous adipose tissue from exercise-trained swine were also measured.

Adenosine Deaminase↗
PubMed1993

Design of antineoplastic agents on the basis of the "2-phenylnaphthalene-type" structural pattern. 2. Synthesis and biological activity studies of benzo]b]naphtho[2,3-d]furan-6,11-dione derivatives.

Based on the "2-phenylnaphthalene-type" structural pattern hypothesis developed in our laboratory, a number of benzo[b]naphtho[2,3-d]furan-6,11-diones were designed, synthesized, and evaluated in vitro for their inhibitory action against the growth of human promyelocytic leukemia cells (HL-60), small-cell lung cancer (SCLC), SCLC cells resistant to cisplatin (SCLC/CDDP), National Cancer Institute's disease-oriented primary antitumor 60 cell-line panel, and drug-stimulated topoisomerase II-mediated DNA cleavages. Many compounds designed were found to possess potent activity in one or more of the biological tests. In general, activity found in one of the cell lines tested is often echoed in other cell lines and many also expressed substantial inhibitory activity against topoisomerase II-mediated cleavage activities. One of these compounds, 3-[2-(dimethylamino)ethoxy]-1-hydroxybenzo[b]naphthol[2,3-d]furan- 6,11-dione (8j), exhibited strong inhibitory activity throughout the entire series of test panel. Thus, it appears that the proposed structural pattern hypothesis has received substantial support through experimental verification.

Antineoplastic Agents↗
PubMed1993

Mutational studies of human DNA polymerase alpha. Identification of residues critical for deoxynucleotide binding and misinsertion fidelity of DNA synthesis.

Conserved site-directed mutations were introduced into the second most conserved amino acid region, region II, of the human DNA polymerase alpha catalytic subunit. These mutants were expressed in the baculovirus system and purified to near homogeneity. The mutants had polymerase activity ranging from 4 to 60% compared with the wild type polymerase alpha. Steady-state kinetic analysis of mutants G841A, D860A, D860S, D860N, Y865S, and Y865F demonstrated no significant difference in their Km values for primer-template compared with that of the wild type enzyme. In contrast, mutants D860A, Y865S, and Y865F showed a 5-10-fold increase in the Km for deoxynucleotide triphosphate (dNTP) compared with the wild type enzyme. DNA synthetic fidelity studies of these mutants showed that mutant Y865S but not Y865F had a greater than 10-fold higher misinsertion efficiency than the wild type enzyme in Mg(2+)-catalyzed reactions. However, with Mn2+ as the metal activator, Y865S and Y865F demonstrated a 2- and 9-fold higher misinsertion efficiency, respectively. These results indicate that Asp860 and Tyr865 in region II of human DNA polymerase alpha are involved in incoming dNTP substrate binding. Using three deoxynucleotide structural analogs as probes, we show that the nucleotide base is the structural requirement for dNTP binding with Tyr865. Furthermore, abolishing the hydrophobic phenyl ring side chain of Tyr865 by replacing tyrosine with serine rendered the enzyme resistant to aphidicolin. Results of these studies strongly suggest that the phenyl ring of Tyr865 directly interacts with the nucleotide base moiety of the dNTP and plays a critical role in the misinsertion fidelity of DNA synthesis. Although mutation of Gly841 to Ala did not affect the binding of primer-template, it had a significant decrease in kcat, an increase in Km for dNTP, a striking decrease of processivity, and also resistance to aphidicolin. Thus, mutation of this residue, Gly841, which is highly conserved among the alpha-like DNA polymerases, appears to affect both catalysis and substrate deoxynucleotide binding. This suggests that Gly841 is essential for the maintenance of the overall structure of the polymerase alpha catalytic site.

Amino Acid Sequence↗
PubMed1993

Mutational studies of human DNA polymerase alpha. Serine 867 in the second most conserved region among alpha-like DNA polymerases is involved in primer binding and mispair primer extension.

The second most conserved region of alpha-like DNA polymerases, region II, spans a block of 40 amino acid residues centered at the core sequence -DFNSLYPSII-. In the previous paper, we described mutational studies of 3 amino acid residues in region II which includes 2 amino acid residues in the core sequence. We showed that residues Asp860 and Tyr865 in the core sequence are involved in substrate deoxynucleotide triphosphate (dNTP) binding. We further showed that the phenyl moiety of the Tyr865 side chain interacts with the incoming dNTP and is responsible for the misinsertion fidelity of the enzyme. In this report, we investigated the function of 2 serine residues, Ser863 and Ser867, in this core sequence. Mutation of these 2 Ser residues to either Ala or Thr yielded mutant enzymes with similar Km for dNTPs, kcat, processivity, and misinsertion fidelity of DNA synthesis as the wild type enzyme. However, mutation of Ser867 to Ala demonstrated a 30-fold increase in Km for primer-template and a 5-fold higher KD for binding primer-template. DNA footprinting experiments of primer with the dideoxynucleotide terminus indicated that the structural feature of the primer recognized by Ser867 is the 3'-OH terminus. Single-stranded DNA inhibition data suggest that removal of the hydroxyl side chain of Ser867 affects the polymerase's interaction with primer and not with template. Mutation of Ser867 to Ala also decreases the mutant enzyme's Km for dNTP to extend a mispaired primer and thus enhances its capacity to extend a mispaired primer terminus. These data support the conclusion that the hydroxyl side chain of Ser867 of human DNA polymerase alpha is involved in primer interaction during DNA synthesis and plays an essential role in mispair extension fidelity of DNA synthesis.

Amino Acid Sequence↗
PubMed1993

LH pulsatility, biopotency, and clearance during undernutrition in orchidectomized mature rats.

The effect of food restriction on circulating luteinizing hormone (LH) levels in orchidectomized rats is controversial. The present study demonstrates that decreasing food intake by 50% for 3-10 days in orchidectomized rats increases LH pulse amplitude, length, area under pulse curve, and mean levels but decreases LH pulse frequency compared with ad-lib fed, orchidectomized controls. The effects on pulsatile LH secretion of food reduction by 50% with or without dilution by cellulose to maintain food volume in orchidectomized rats were also examined. Food volume influences pulsatile LH secretion independent of macronutrient effect after 3 days of food restriction, but subsequently macronutrient deprivation predominates. The exaggerated increase in LH levels in orchidectomized rats subject to food restriction for 7 days was not due to immunochemical or chromatographic heterogeneity or alteration in biopotency of circulating LH molecules. Intravenously injected 125I-labeled rat LH analyzed by noncompartmental modeling revealed that neither LH clearance nor mean residence time was reduced by food restriction. We conclude that during food restriction in orchidectomized rats, increases in LH pulse amplitude exceed and precede the decreases in LH pulse frequency, although the early changes in pulse amplitude are predominantly due to reduced food volume rather than macronutrient deprivation.

Aging↗
PubMed1993

[Combined operation for the foreign body in the eye complicated with traumatic cataract: an analysis of 88 cases].

The foreign body in the eye complicated with traumatic cataract is one of the common causes of blindness. The rate of blindness ranges from 20% to 48.9%. This paper analyses combined operation for 88 cases of foreign body in the eye with traumatic cataract. The visual acuity below 0.05 accounted for 85.2% of the cases before operation and reduced to 27.3% after operation. Postoperatively, the corrected visual acuities were from 0.06 to 1.5 in 73.3% of the cases and 0.6 to 1.5 in 22.7% respectively. The patients should be treated with combined operation earlier. The way of operation depends on the property and the location of foreign body and the situation of lens. Chinese-Western medicine treatment should be used postoperatively to control the tissue response. Combined operation can improve the effect, reduce the complication, the number of operation and decrease medical expenses.

Adolescent↗
PubMed1993

[The relations between acupuncture manipulations and responsive discharges of deep receptors].

Twenty-nine rabbits were used. The spindle, tendon organ, light and heavy pressure receptors in medial gastrocnemius muscle were identified by recording discharges of single afferent fiber in medial gastrocnemius nerve from fine filaments by dissection. The discharge patterns of the receptors responding to the manipulations, i.c. lift and thrust, twist and twirl, rotate, scrape flick the needle and finger-pressure were observed. Data at 85 units were collected totally. Every type of deep receptor can react to any manipulation. The discharge patterns of different receptors were alike when stimulated with same manipulation, but there were different patterns while varying manipulations acting on the same receptor. These are due to the movement forms, the force amount, the time duration of the manipulations. All these facts are nearly the same as in cutaneous receptors. Acupuncture effect on deep receptors was not limited to one point but within a certain area, namely distant effect existed. The area size varied from receptor to receptor and from manipulation to manipulation. Because of the distant effect on receptors by acupuncture, and the lose of responsibility in units when receptor destroyed, we suggest that effective acupuncture stimulation is induced mainly due to the receptor deformation, which is caused by the stress from pressure, stretch and vibration of acupuncture. In view of the needling sensation is closely related to the curative effects, the receptors dealing with needling sensation are analysed according to this series works and other facts, we further advance the opinion that the receptors of deep pain are the chief material foundation to induce the sensation of hand needling.

Acupuncture Therapy↗