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Biomedical subjects

Q Zhang

Publications and source records attributed to Q Zhang.

At least 703 records · Page 39Linked to original sources
PubMed1996

Dieldrin pretreatment alters [14C]dieldrin and [3H]7,12-dimethylbenz[a]anthracene uptake in rainbow trout liver slices.

We previously demonstrated that pretreatment of rainbow trout with the organochlorine insecticide dieldrin altered in vivo disposition of a subsequent [14C]dieldrin dose. This was not explained by changes in total lipid content or the activity of common xenobiotic metabolizing enzymes. We hypothesized that dieldrin induced hepatic proteins responsible for organochlorine (OC) sequestration, transport, or excretion and that these changes reflected an adaptive response of trout to OC exposure. Here, uptake of 1.18 microM [14C]-dieldrin by precision cut liver slices was increased by dieldrin pretreatment of rainbow trout. Uptake of 0.118 and 1.18 microM [3H]-7,12-dimethylbenz[a]anthracene (DMBA) and efflux of 0.118 microM [3H]DMBA were significantly increased in slices from dieldrin-pretreated trout. Liver slice uptake of 10 but not 1.18 microM [3H]-estradiol and [3H]cholic acid was significantly increased by dieldrin pretreatment. There were no such significant differences for [3H]cholesterol, [3H]cholesterol-oleate, or [3H]oleic acid uptake. Dieldrin pretreatment did not alter hepatic microsomal metabolism of [3H]DMBA or [14C]benzo[a]pyrene or content of six cytochrome P450 isozymes, as quantitated by Western Blot analysis. These results provide further evidence that altered disposition of [14C]dieldrin and [3H]DMBA in dieldrin-pretreated trout was not explained by microsomal enzyme induction but reflected altered processes integral to hepatocellular transmembrane kinetics. These changes may have important implications for OC bioaccumulation by rainbow trout and demonstrate an interaction between dieldrin and DMBA in the absence of cytochrome P450 system induction.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

The accuracy of color Doppler flow imaging for the detection of symptomatic deep venous thrombosis in Chinese patients.

To evaluate the ability of color Doppler flow imaging (CDFI) to detect deep venous thrombosis (DVT), which is difficult to diagnose clinically, 67 limbs of 60 patients who presented with clinical signs strongly indicative of DVT during the period between June 1988 and June 1992, were examined. The iliac, common femoral, and superficial femoral veins were assessed with the patient in the supine position, and the popliteal vein was examined with the patient prone. Gentle but firm compression with the transducer probe was used to test for the presence of DVT. Ascending contrast venograms were also obtained within 24 h after the ultrasound procedure, with venography being used as the standard for comparison with CDFI. DVT was identified in 63 limbs by contrast venography and in 62 limbs by CDFI. The sensitivity and specificity of CDFI were 98.4% and 100%, respectively, while the positive and negative predictive values were 100% and 80%, respectively. The thromboses were classified into three patterns: the filling type, the local type, and mural thrombus, detected in 63%, 27%, and 10%, of the limbs respectively, with the filling type being the most common in this series. The results of our study illustrated that CDFI is highly sensitive and specific for detecting symptomatic DVT and that it should be gradually substituted for venography in such patients.

Adult↗
PubMed1996

Glucose influence on germ tube production in Candida albicans.

The influence of different glucose concentrations was tested in minimal synthetic medium on Candida albicans strain. After 18 hours of starvation, germ-tube (GT) production, amount of consumed glucose, oxygen and the pH of the medium were checked every hour from the beginning through the end of the experiment. Optimal GT production was obtained with 1 g/l of glucose. At this concentration the greatest glucose and oxygen consumption were also noted. No pH variations in the medium were observed in all of the glucose concentrations used. At 3 and 5 g/l glucose concentrations a lower GT production were obtained. The Crab-tree effect might interfere with GT production when glucose concentration is higher than 1 g/l. This data may support the hypothesis that GT production is strictly glucose dependent.

Ammonium Sulfate↗
PubMed1996

Single-fibre laser Doppler flowmetry and electromyography for evaluating microcirculation in forearm muscle during static and continuous handgrip contractions.

A technique is described for intramuscular measurement of muscle blood flow in the forearm, by using a 0.5-mm thin optical single-fibre for laser Doppler flowmetry (LDF) inserted percutaneously. Continuous recordings were performed of the brachioradial muscle during an 11-min series of alternating 1-min periods of increased static contraction and rest determined by an electronic handgrip forcemeter and surface electromyography (EMG) of the muscle. Stepwise increased handgrip contractions were performed at 10%, 20%, 30%, 40% and 50% maximal voluntary contraction (MVC). This was followed by a similar series of continuous contractions. Finally, an endurance test was performed with a handgrip force of 50% MVC maintained for as long as possible. A group of ten healthy men of different ages was studied. Signal processing was done on line by computer. Successive increases in rootmean square (rms)-EMG and a fall in the mean power frequency (MPF) of the EMG spectrum occurred during the series of static contractions, which evoked perceived local fatigue in the forearm. Muscle blood flow recorded simultaneously showed no change from resting level during contractions at 10%, 20% and 30% MVC, while at 40% and 50% MVC mean increases of 150% and 200% were recorded. Blood flows measured during the rest periods showed large variability with no significant changes. This was also found after continuous contractions of the same intensities. The endurance time was 1.2-3.5 min (mean 2.4 min). Muscle blood flow showed mean increases of 214%, 256% and 229% of resting level each minute of the maintained contraction. Nevertheless, EMG signs of local fatigue developed, such as a rise in rms-EMG and a fall in MPF, and the subject experienced local fatigue. To conclude, this technique of percutaneous, continuous LDF recorded, at high sensitivity, the microcirculation at different fluxes and EMG-defined muscle activity.

Adult↗
PubMed1996

Cutaneous CD56+ large T-cell lymphoma associated with high serum concentration of IL-2.

We report the case of a patient with a clinically aggressive large cell lymphoma (LCL) which expressed several T-lymphocyte markers and, in addition, CD56 and, to a lesser degree, CD68 antigens. A marked increase in serum concentration of interleukin (IL)-2 was found (490 and 167 pg/0.1 mL in two serum samples collected 6 months apart). This increase in IL-2 appeared unique to this lymphoma because serum concentration of IL-2 was not increased in any of the cases of various types of cutaneous lymphoproliferative disorders tested: mycosis fungoides-related cutaneous T-cell lymphoma (CTCL: 28 patients), granulomatous slack-skin syndrome (GS-SS: 1 patient), anaplastic large cell lymphoma (ALCL: 2 patients), subcutaneous gamma/delta T-cell lymphoma (gamma/delta-TCL: 1 patient), adult-type leukemia/lymphoma (ATLL: 1 patient), and lymphomatoid papulosis (LyP: 4 patients). Furthermore, the increase in IL-2 serum concentration appeared selective in this CD56+ large-cell lymphoma-bearing patient, because concentration of none of the five other cytokines tested (IL-4, IL-6, IFNgamma, GM-CSF, and TNFalpha) was increased. In contrast, soluble receptors for IL-2 and two of the other cytokines (IL-6, and TNFalpha) were markedly increased not only in this patient, but also in most patients with the other cutaneous lymphoproliferative disorders that we examined except for lymphomatoid papulosis. These data indicate that increased IL-2 serum concentration may help to diagnose a unique type of cutaneous CD56(+) large (T-) cell lymphoma and suggest that IL-2 way play a role of an autocrine growth factor for this lymphoma.

Aged↗
PubMed1996

Immune regulation in Cushing's syndrome: relationship to hypothalamic-pituitary-adrenal axis hormones.

Hormones of the hypothalamic-pituitary-adrenal (HPA) axis are connected closely with immune measures. To investigate whether Cushing's syndrome (CS) is associated with immune dysregulation, we compared the percentage of specific lymphocyte subsets as well as natural cell activity (NKCA) in 48 patients with Cushing's syndrome and 48 age- and sex-matched normal controls. Lymphocyte subset analysis included the percentage of lymphocytes expressing CD3 (total T), CD4 (T helper/inducer), CD8 (T suppressor/cytotoxic) and CD56 (NK cell) antigens. Baseline plasma concentrations of cortisol, ACTH and beta-endorphin as well as 24 h urinary-free cortisol (UFC) levels also were determined. Results indicated a decrease in the percentage of CD4+ cells (p < 0.05), an increase in percentage of CD8+ cells (p < 0.05), a decrease in CD4/CD8 ratios (p < 0.01), and a reduction in NKCA (p < 0.05) in patients with CS compared to matched controls. We also found significant negative correlations between NKCA on the one hand and 24 h UFC (p < 0.05) and plasma beta-endorphin (p < 0.05) on the other. These results indicate there is immune dysregulation in CS patients which can be explained in part by an increase in HPA-axis hormones.

Adrenocorticotropic Hormone↗
PubMed1996

GABAA receptors modulate early spontaneous excitatory activity in differentiating P19 neurons.

P19 embryonic carcinoma (EC) stem cells are pluripotent and are efficiently induced to differentiate into neurons and glia with retinoic acid (RA) treatment. Within 5 days, a substantial number of differentiating P19 cells express gene products that are characteristic of a neuronal phenotype. P19 neurons were used as a model to explore the relationship between neuronal "differentiation" in vitro and the acquisition of gamma-aminobutyric acid (GABAA) receptors and functional GABA responses. Pulse-labeling experiments using bromodeoxyuridine indicated that all neurons had become postmitotic within 3-4 days after treatment with RA. This was confirmed by a reduction in the immunocytochemical detection of the undifferentiated stem cell antigen SSEA-1. Subsequently, a transient expression of nestin was observed during the first 5 days in vitro (DIV) after exposure to RA. By 5-10 DIV after RA, a significant number of neurons (approximately 80-90%) expressed immunocytochemically detectable glutamate decarboxylase and GABA coincident with the acquisition of membrane binding sites for tetanus toxin. These phenotypic markers were maintained for > 30 DIV after RA. Under current-clamp conditions, random, low-amplitude, spontaneous electrical activity appeared in neurons within the first few days after RA treatment and this was blocked by the specific GABAA receptor antagonist bicuculline. Thereafter, the appearance and progressive increases in the frequency of spontaneous action potentials in P19 neurons were observed that were similarly attenuated by bicuculline. In neurons > 5 DIV after RA, exogenous application of GABA elicited similar action potentials. The onset of excitatory responses to GABA or muscimol in voltage-clamped neurons appeared immediately after the cessation of neuronal mitosis and before the previously reported acquisition of responses to glutamate. In fura-2 imaging studies, the exogenous application of GABA resulted in neuron-specific increases in intracellular Ca2+. Thus, P19 neurons provide an in vitro model for the study of the early acquisition and properties of electrical excitability to GABA and the expression of functional GABAA receptors.

Action Potentials↗
PubMed1996

The dlt operon in the biosynthesis of D-alanyl-lipoteichoic acid in Lactobacillus casei.

The D-alanine incorporation system allows Lactobacillus casei to modulate the chemical properties of lipoteichoic acid (LTA) and hence control its proposed functions, i.e., regulation of autolysin action, metal ion binding, and the electromechanical properties of the cell wall. The system requires the D-alanine-D-alanyl carrier protein ligase (Dcl) and the D-alanyl carrier protein (Dcp). Our results indicate that the genes for these proteins are encoded in the dlt operon and that this operon contains at least 2 other genes, dltB and dltD. The aim of this paper is to describe the genetic organization of the operon, the role of the D-alanyl carrier protein, and the function of the putative protein encoded by dltB in the intramembranal translocation of the activated D-alanine.

Carrier Proteins↗
PubMed1996

Functional significance of the Fas molecule in naive lymphocytes.

The Fas molecule mediates apoptotic signal in many cell types. Mouse mutations (lpr, lprcg, gld), which impair the function of Fas, cause spontaneous autoimmune disease. We generated Fas-deficient (Fas-/-) mice by homologous recombination. In embryonic stem cells Fas-/- mice developed lpr-like disease, confirming that the abnormality of Fas is causal in the lpr phenotype. We also made Fas-/- chimeric mice composed of a mixture of Fas+/+ and Fas-/- cells. The chimeric mice also showed the lpr phenotype. In Fas-/-, chimeric mice, the Fas-deficient population expanded progressively among mature T and B lymphocytes. The expansion of Fas-deficient lymphocytes occurred at the naive, pre-primed, lymphocyte stage. These results suggest that the Fas molecule functions not only after antigenic stimulation, as previously hypothesized, but also at the naive lymphocyte stage.

Animals↗
PubMed1996

2-oxoacid:ferredoxin oxidoreductase from the thermoacidophilic archaeon, Sulfolobus sp. strain 7.

The purified 2-oxoacid:ferredoxin oxidoreductase of a thermoacidophilic and aerobic crenarchaeote, Sulfolobus sp. strain 7, consists of 70-kDa alpha and 37-kDa beta subunits, and contains one thiamine pyrophosphate (TPP), one [4Fe-4S]2+.1+ cluster, and two magnesium atoms per alpha beta structure. It exhibits a broad substrate specificity toward 2-oxoacids such as 2-oxoglutarate, 2-oxobutyrate, and pyruvate. The gene encoding the archaeal oxidoreductase was cloned, and the two open reading frames encoding the alpha (632 amino acids) and beta subunits (305 amino acids), respectively, were sequenced. Careful sequence alignment revealed several consensus motifs of this enzyme family, as well as possible cofactor binding residues of the Sulfolobus enzyme. This new structural information also indicates that (i) several genetic fusions and reorganization of the early, possibly alpha beta gamma delta-type enzyme similar to those from hyperthermophiles have taken place during evolution of the 2-oxoacid:ferredoxin (flavodoxin) oxidoreductase superfamily, which might have occurred in different ways in early aerobic archaea and early anaerobic bacteria, and that (ii) enzymes with different subunit compositions should have an essentially similar catalytic mechanism with one TPP and at least one [4Fe-4S] cluster as the minimal set of redox centers.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1996

Regulation of the estrogen receptor and its messenger ribonucleic acid in the ovariectomized sheep myometrium and endometrium: the role of estradiol and progesterone.

Estrogen receptor (ER) mRNA is dramatically increased in sheep myometrium and endometrium during glucocorticoid-induced premature labor and term spontaneous labor. However, the underlying mechanism for the up-regulation of uterine ER in labor is still unknown. We used ovariectomized (OVX) non-pregnant sheep to analyze the role of estradiol and progesterone in the regulation of myometrial and endometrial ER protein and ER mRNA in vivo. Twenty-one OVX ewes were treated with saline (n = 6), or with estradiol infused i.v. for 2 days (50 micrograms/day, n = 5), or with an intravaginal progesterone sponge for 10 days (containing 0.3 g progesterone, n = 5), or with an intravaginal progesterone sponge for 10 days with estradiol (50 micrograms/day) administered on Days 9 and 10 with the progesterone sponge still in place (n = 5). The ER protein concentration in both cytosolic and nuclear compartments, analyzed by Western blot, increased significantly (P < 0.05) in the myometrium after estradiol treatment, while progesterone alone had no detectable effect on ER level. Elevated ER protein was observed only in the nuclear fraction of endometrium. However, when estradiol was given together with progesterone treatment, progesterone antagonized the up-regulatory effect of estradiol on the ER level both at the endometrium and myometrium. The changes in cellular ER mRNA followed the pattern observed at the ER protein level. Estrogen receptor mRNA was elevated significantly (p < 0.01) only in estradiol-treated ewes. Expression of the ER gene in ewes receiving progesterone alone or progesterone combined with estradiol was similar to that of the control group. From these observations we conclude that ER gene expression and active ER synthesis in nonpregnant sheep myometrium and endometrium are estradiol-dependent. Progesterone antagonizes this estrogen action. Progesterone down-regulated the elevated ER mRNA when used together with estradiol. In situ hybridization showed that ER mRNA was evenly distributed in the smooth muscle cells and blood vessels of the myometrium and the epithelial cells of the glands in endometrium. In conclusion, we have observed estradiol-dependent activation of ER gene expression as well as active ER synthesis in the nonpregnant sheep myometrium and endometrium. Progesterone acted as an antagonist of estradiol on ER gene expression.

Animals↗
PubMed1996

Molecular basis of size and antigenic variation of a Mycoplasma hominis adhesin encoded by divergent vaa genes.

The molecular basis for the size and antigenic diversity of the variable adherence-associated (Vaa) antigen, a major surface protein and a putative adhesin (of Mycoplasma hominis, is described. Size-variant alleles of the single-copy vaa gene encode abundant surface lipoproteins containing one to four nearly identical, tandem repetitive units of 121 amino acids in the central region of the mature Vaa product. Gain or loss of central repeats in vaa genes gives rise to distinct size-variant Vaa antigens in clonal populations of this organism. The N-terminal and repeat regions of Vaa contain highly conserved sequences, while the C-terminal region, implicated as the adherence-mediating module, is highly variable and divergent among different strains of this pathogen. Sequence variation in this region may underlie the strain-dependent binding of some monoclonal antibodies to Vaa products. The Vaa antigen is expressed in vivo during chronic, active arthritis associated with M. hominis infection and is highly immunogenic in the human host. Size variation and C-terminal antigenic divergence of Vaa could affect the adherence of M. hominis and evasion of antibody-mediated immunity, thereby contributing to the organism's adaptive capability in the human host. Variation in vaa genes reveals a distinct pattern of mutations generating mycoplasma surface variation.

Adhesins, Bacterial↗
PubMed1996

The D-Alanyl carrier protein in Lactobacillus casei: cloning, sequencing, and expression of dltC.

The incorporation of D-alanine into membrane-associated D-alanyl-lipoteichoic acid in Lactobacillus casei requires the 56-kDa D-alanine-D-alanyl carrier protein ligase (Dcl) and the 8.9-kDa D-alanyl carrier protein (Dcp). To identify and isolate the gene encoding Dcp, we have cloned and sequenced a 4.3-kb chromosomal fragment that contains dcl (dltA). In addition to this gene, the fragment contains three other genes, dltB, d1tC, and a partial dltD gene. dltC (246 nucleotides) was subcloned from this region and expressed in Escherichia coli. The product was identified as apo-Dcp lacking the N-terminal methionine (8,787.9 Da). The in vitro conversion of the recombinant apo-Dcp to holo-Dcp by recombinant E. coli holo-ACP synthase provided Dcp which accepts activated D-alanine in the reaction catalyzed by Bcl. The recombinant D-alanyl-Dcp was functionally identical to native D-alanyl-Dcp in the incorporation of D-alanine into lipoteichoic acid. L. casei Dcp is 46% identical to the putative product of dltC in the Bacillus subtilis dlt operon (M. Perego, P. Glaser, A. Minutello, M. A. Strauch, K. Leopold, and W. Fischer, J. Biol. Chem. 270:15598-15606, 1995), and therefore, this gene also encodes Dcp. Comparisons of the primary sequences and predicted secondary structures of the L. casei and B. subtilis Dcps with that of the E. coli acyl carrier protein (ACP) were undertaken together with homology modeling to identify the functional determinants of the donor and acceptor specificities of Dcp. In the region of the phospho-pantetheine attachment site, significant similarity between Dcps and ACPs was observed. This similarity may account for the relaxed acceptor specificity of the Dcps and ACPs in the ligation Of D-alanine catalyzed by Dcl. In contrast, two Dcp consensus sequences, KXXVLDXLA and DXVKXNXD, share little identity with the rest of the ACP family and, thus, may determine the donor specificity of D-alanyl-Dcp in the D-alanylation of membrane-associated D-alanyl-lipoteichoic acid.

Acyl Carrier Protein↗
PubMed1996

Functional and physical interactions between the Epstein-Barr virus (EBV) proteins BZLF1 and BMRF1: Effects on EBV transcription and lytic replication.

The Epstein-Barr virus (EBV) proteins BZLF1 and BMRF1 are both essential for lytic EBV replication. BZLF1 is a transcriptional activator which binds directly to the lytic origin of replication (oriLyt) and plays a critical role in the disruption of viral latency. The BMRF1 protein is required for viral polymerase processivity. Here we demonstrate that the BMRF1 gene product functions as a transcriptional activator and has direct (as well as indirect) interactions with the BZLF1 gene product. The BMRF1 gene product activates an essential oriLyt promoter, BHLF1, but does not activate two other early EBV promoters (BMRF1 and BHRF1). Direct interaction between the BMRF1 and BZLF1 gene products requires the first 45 amino acids of BMRF1 and the bZip domain of BZLF1. The effect of the BZLF1-BMRF1 interaction on early EBV transcription is complex and is promoter specific. The oriLyt BHLF1 promoter is activated by either the BZLF1 or BMRF1 gene product alone and is further activated by the combination of the BZLF1 and BMRF1 gene products. Enhanced activation of BHLF1 transcription by the BMRF1-BZLF1 combination does not require direct interaction between these proteins. In contrast, BZLF1-induced activation of the BMRF1 promoter is inhibited in the presence of the BMRF1 gene product. A point mutation in the BZLF1 protein (amino acid 200), which prevents in vitro interaction with the BMRF1 protein but which does not reduce BZLF1 transactivator function, allows the BZLF1 protein to activate the BMRF1 promoter equally well in the presence or absence of the BMRF1 gene product. Therefore, direct interaction between the BZLF1 and BMRF1 proteins may inhibit BZLF1-induced transcription of the BMRF1 promoter. BZLF1 mutated at amino acid 200 is as efficient as wild-type BZLF1 in promoting replication of an oriLyt plasmid. However, this mutation reduces the ability of BZLF1 to induce lytic replication of the endogenous viral genome in D98/HE-R-1 cells. Our results indicate that functional and physical interactions between the BMRF1 and BZLF1 proteins may modulate the efficiency of lytic EBV infection. The BMRF1 gene product clearly has a transcriptional, as well as replicative, role during lytic EBV infection.

Antigens, Viral↗
PubMed1996

Peak oxygen consumption and ventilatory thresholds on six modes of exercise.

In order to compare responses on six modes of exercise for maximal oxygen consumption (VO2peak) and ventilatory thresholds (VT-1, VT-2), 10 male recreational exercisers (23 +/- 3 yrs) completed incremental maximal tests on treadmill, stationary skier, shuffle skier, stepper, stationary cycle, and rower. After extensive habituation, VO2peak, VT-1, and VT-2 were determined during each maximal bout. A MANOVA followed by ANOVAs, Tukey post hoc tests, and noncentral F tests indicated that the treadmill elicited a significantly higher peak oxygen consumption than did the other modes, and the skier and stepper values were higher than the rower. VO2 at VT-1 was higher on the treadmill than cycle. The treadmill also elicited a higher VO2 at VT-2 than the shuffle skier, cycle, and rower. However, no differences were observed among modes for VT-1 and VT-2 when expressed as a percentage of VO2peak. These results suggest that the treadmill elicits a higher aerobic capacity measure than other modes, but the ventilatory threshold responses (% VO2peak) are similar among modes.

Adult↗