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Biomedical subjects

D Yin

Publications and source records attributed to D Yin.

At least 37 records · Page 2Linked to original sources
PubMed2001

Resource utilization and hospital cost of HIV/AIDS care in Italy in the era of highly active antiretroviral therapy.

This study set out: (1) to describe resource utilization patterns among four groups of HIV-infected patients at different stages of the disease, and (2) to estimate the direct hospital costs of HIV/AIDS care among these patients in Italy. It is a multi-centre, prospective observational study conducted between August 1997 and July 1998. The 483 patients, enrolled in five infectious diseases departments located in different areas of Italy, were stratified into four groups according to their CD4+ lymphocyte cell count and status of AIDS Defining Illness (ADI) at enrolment. Average direct hospital costs (L = Italian Lire, 1997 exchange rate US$ 1 = 1,704 Italian Lire) were L.23,725,584 (US$ 13,923.5), L.15,208,287 (US$ 8,925.1), L.11,942,761 (US$ 7,008.7) and L.7,660,942 (US$ 4,495.9) for the four groups of patients. More than 80% of patients in the first group and about 65% of patients in the second group received highly active antiretroviral therapy (HAART). The proportion of patients receiving HAART in the third and fourth group increased from 37.1% to 56.5% and from 15.3% to 31.5%. The number of hospital days observed in this study was much lower than previously published numbers in Italy. These results may indicate a shift of costs from hospitalisation to outpatient care and ARV.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Analysis of the signal pathways involved in the regulation of fatty acid synthase gene expression by insulin and somatotropin.

Our previous studies have shown that somatotropin (ST) antagonizes insulin stimulation of fatty acid synthase (FAS) enzyme activity and gene transcription in adipocytes. In the present study, inhibitors of insulin and ST signaling pathways were used to dissect the mechanisms by which these hormones regulate FAS gene expression in 3T3-F442A adipocytes. Treating 3T3-F442A adipocytes with 10 microM PD98059, an inhibitor of mitogen-activated protein (MAP) kinase, did not affect the induction of FAS mRNA by insulin. When cells were cultured with H-89 (10 microM), GF109203X (10 microM), or staurosporine (100 nM), inhibitors of protein kinase A, protein kinase C, and Janus kinase (JAK) 2, respectively, the inhibitory effect of ST on FAS mRNA levels was not altered. However, H-89 significantly decreased the stimulatory effect of insulin on FAS mRNA abundance. Moreover, treatment with okadaic acid (1 microM), a serine/threonine phosphatase inhibitor, abolished the induction of FAS mRNA by insulin. These results suggest that serine/threonine dephosphorylation and protein kinase A-dependent pathways are involved in the regulation of FAS gene expression by insulin, but MAP kinase is probably not involved. Furthermore, our data indicate that protein kinase A, protein kinase C, and JAK2 do not mediate the effect of ST on regulation of FAS mRNA abundance.

3T3 Cells↗
PubMed2001

Transcriptional regulation of fatty acid synthase gene by somatotropin in 3T3-F442A adipocytes.

Somatotropin (ST) antagonizes insulin stimulation of fatty acid synthase (FAS) enzyme activity and gene transcription in adipocytes. Previous studies have shown that an insulin response element (IRE) is located in the proximal region of the FAS promoter (-71 to -50) and upstream stimulatory factor (USF) 1 binds to this IRE. The present study was conducted to initially evaluate whether there is a somatotropin response element (STRE) in the 5'flanking region of the FAS gene and to determine whether USF1 mediates the effect of ST on FAS gene transcription in 3T3-F442A adipocytes. Two 5' deletion FAS promoter constructs (pFAS-CATS4 and pFAS-CAT5), which contain the 5' flanking sequences of the rat FAS gene at -112 to +65 and -2195 to +65, respectively, were stably transfected into 3T3-F442A preadipocytes. Insulin stimulated chloramphenicol acetyltransferase (CAT) activity 1.7- and 4.7-fold (P < 0.05) in 3T3-F442A adipocytes transfected with pFAS-CATS4 and pFAS-CAT5, respectively. In contrast, bovine somatotropin (bST) attenuated the stimulatory effect of insulin on CAT activity by approximately 60% (P < 0.05) in both constructs. When 3T3-F442A adipocytes were treated with insulin (10 ng/mL) or insulin (10 ng/mL) plus bST (100 ng/mL) for 24, 48, or 72 h, neither insulin nor bST significantly affected USF1 mRNA levels. When human USF1 (hUSF1) cDNA probe was used, however, insulin increased the abundance of an unidentified transcript (named hUSF1-like mRNA) 11- to 25-fold (P < 0.05) and ST decreased the stimulatory effect of insulin on hUSF1-like mRNA levels by 50 to 90% (P < 0.05). Western blot analyses of nuclear extracts from cells treated with insulin (10 ng/mL) or insulin (10 ng/mL) plus bST (100 ng/mL) for 48 h demonstrated that the abundance of USF1 was not affected by insulin or ST. Furthermore, electrophoretic mobility shift analyses (EMSA) of nuclear extracts revealed that neither insulin nor ST had an effect on the binding of USF1 to the IRE. These results suggest that a STRE may be located within the first 112 bp of the FAS promoter and that USF1 does not directly mediate the effect of ST on transcription of the FAS gene in 3T3-F442A adipocytes.

3T3 Cells↗
PubMed2001

[A comparative study on the sensitivity and specificity of cholinesterase and glutathione s-transferase in Gammarus pulex L].

Studies on the influences of lindane, pirimiphos methyl, permethrin, zinc and dodecyl linear alkybenzene sulfonate (LAS) on the activity and toxicity of cholinesterase (ChE) and glutathione s-transferase (GST) in Gammarus pulex L. showed that only pirimiphos methyl caused a change in ChE activity in Gammarus, with a significant reduction in enzyme activity after 24 h and 48 h exposure. Both lindane and permethrin caused a change in GST activity in Gammarus, with a significant increase in enzyme activity after 48 h exposure. Lindane alos caused a significant increase in GST activity after 24 h exposure. Biomarkers ChE and GST were demonstrated a high degree of specificity and sensitivity in comparison to the lethality assay, but GST activity was less specific than ChE activity.

Animals↗
PubMed2001

Regional glucose metabolic increases in left auditory cortex in tinnitus patients: a preliminary study with positron emission tomography.

OBJECTIVE: To investigate the relationship between tinnitus and glucose metabolism in auditory cortex and whether positron emission tomography (PET) can be an objective tool in measuring tinnitus. METHODS: Eleven right-handed patients with severe tinnitus and ten right-handed control subjects participated in the 18F-FDG/PET study. Analysis with regions of interests was used to calculate asymmetry indices according to the formula: [(L-R) x 100/[(L + R) divided by 2]]. RESULTS: Glucose metabolism in the auditory cortex of tinnitus patients was asymmetric between the left and right auditory cortices, with that of the left being much higher than that of the right. The asymmetry indices of tinnitus patients was significantly higher than that of the control group (unpaired t test, P < 0.001). This revealed that the increased metabolic activity was present in the predominant left hemisphere with a significant focus on the superior and transverse temporal gyri (Brodmann areas 41 and 42, respectively corresponding to primary and secondary auditory cortex), and the results were independent of the subjective localization of the tinnitus sensation. CONCLUSION: It is suggested that the increased metabolism in the left auditory cortex is related to the tinnitus sensation. PET is capable of providing objective evidence for tinnitus and may be used as a potential tool in measuring tinnitus.

Adolescent↗
PubMed2001

[Randomized controlled trial for the effect of amrinone and aprotinin on proinflammatory cytokine release in patients with prosthetic valve replacement during perioperative period].

OBJECTIVE: To explore the effect of amrinone and aprotinin on whole-body inflammatory response in the patients with prosthetic valve replacement during perioperative period. METHODS: 24 patients undergoing prosthetic valve replacement were randomized to control group (group A, n = 8), aprotinin group (group B, n = 8) and amrinone combined with aprotinin group (group C, n = 8). In the aprotinin group, 3 x 10(6) of aprotinin was added to the priming solution of the extracorporeal circulation (ECC). In the amrinone combined with aprotinin group 3 x 10(6) of aprotinin was added to the priming solution of the ECC and amrinone began with a bolus of 1 mg/kg followed by a maintenance infusion of 8 micrograms/(kg.min). The control group received an equivalent prime volume without aprotinin. Venous blood samples were drawn before the operation, at the end of ECC, 1 hour after the end of ECC, and one day after the operation respectively. Enzyme-linked immunosorbent assay techniques were used to measure each of the cytokines. RESULTS: Before ECC, there were no differences of the levels of IL-6 and IL-8 among groups (P > 0.05). After ECC, the levels of IL-6 and IL-8 increased significantly in all groups (P < 0.05). The levels on day one after the operation were still higher than those before the operation in all groups (except the level of IL-8 in group C), but no statistical significance was observed. (P > 0.05). At 1 hour after the end of ECC, the level of IL-6 in group B was lower than that in group A, and the level of IL-6 in group C was lower than that in group B, but there was no statistically significant difference (P > 0.05); At the end of ECC, the level of IL-8 in group B was lower than that in group A and the level of IL-8 in group C was lower than that in group B, but no significant difference was noted (P > 0.05). It was also observed that the level of IL-8 was lower in group C than group A or B at 1 hour after the end of ECC. CONCLUSION: Although amrinone and aprotinin have antiinflammatory activity, but pump prime only aprotinin or aprotinin combined with amrinone may fall in preventing proinflammatory cytokine release (IL-6, IL-8) completely in patients with prosthetic valve replacement during ECC perioperative period.

Adult↗
PubMed2000

Mechanisms of inactivation of human S-adenosylhomocysteine hydrolase by 5',5',6',6'-tetradehydro-6'-deoxy-6'-halohomoadenosines.

In an effort to design more specific and potent inhibitors of S-adenosylhomocysteine (AdoHcy) hydrolase, we investigated the mechanisms by which 5',5',6', 6'-tetradehydro-6'-deoxy-6'-halohomoadenosines (X = Cl, Br, I) inactivated this enzyme. The 6'-chloro (a) and 6'-bromo (b) acetylenic nucleoside analogues produced partial ( approximately 50%) loss of enzyme activity with a concomitant ( approximately 50%) reduction of E-NAD(+) to E-NADH. In addition, Ade and halide ions were released from the inhibitors in amounts suggestive of a process involving enzyme catalysis. AdoHcy hydrolase, which was inactivated with compound a, was shown to contain 2 mol of the inhibitor covalently bound to Lys318 of two subunits of the homotetramer. These data suggest that the enzyme-mediated water addition at the 5' position of compound a or b produces an alpha-halomethyl ketone intermediate, which is then attacked by a proximal nucleophile (i.e., Lys318) to form the enzyme-inhibitor covalent adduct (lethal event); in a parallel pathway (nonlethal event), addition of water at the 6' position produces an acyl halide, which is released into solution and chemically degrades into Ade, halide ion, and sugar-derived products. In contrast, compound c completely inactivated AdoHcy hydrolase by converting 2 equiv of E-NAD(+) to E-NADH and causing the release of 2 equiv of E-NAD(+) into solution. Four moles of the inhibitor was shown to be tightly bound to the tetrameric enzyme. These data suggest that compound c inactivates AdoHcy hydrolase by a mechanism similar to the acetylenic analogue of Ado described previously by Parry et al. [(1991) Biochemistry 30, 9988-9997].

Adenine↗
PubMed2000

Closer proximity between opposing domains of vertebrate calmodulin following deletion of Met(145)-Lys(148).

To investigate the structural linkage between the opposing globular domains in vertebrate calmodulin (CaM), we have constructed a CaM mutant (CaMX(145)) deficient in the last four amino acids between Met(145) and Lys(148) at the carboxyl terminal. Circular dichroism and fluorescence spectroscopic measurements were used to detect changes in the average secondary and tertiary structure of CaMX(145) in comparison to full-length CaM. Complementary measurements of the maximal calcium-binding stoichiometry and ability to activate the plasma membrane (PM) Ca-ATPase permit an assessment of the functional significance of observed structural changes. In comparison with native CaM, we find that CaMX(145) exhibits (i) a large reduction in alpha-helical content, (ii) a dramatic decrease in the average spatial separation between the opposing globular domains, (iii) the loss of one high-affinity calcium-binding site, and (iv) a diminished binding affinity for the PM-Ca-ATPase. Thus, the sequence near the carboxyl terminus functions to stabilize high-affinity calcium binding at one site and facilitates important intramolecular interactions that maintain CaM in an extended conformation. However, despite the large conformational changes resulting from deletion of the last four amino acids at the carboxyl terminal, CaMX(145) can fully activate the PM-Ca-ATPase. These results indicate that target protein binding can restore the nativelike structure critical to function, emphasizing that the structure of the central helix is not critical to CaM function under equilibrium conditions. Rather, the central helix functions to maintain the spatial separation between the opposing domains in CaM that may be critical to high-affinity binding and the rapid activation of the PM-Ca-ATPase, which are necessary for optimal calcium signaling. Thus, following initial association between CaM and target proteins, structural changes involving the carboxyl-terminal sequence have the potential to play an important role in triggering the structural collapse of CaM that facilitates the rapid and cooperative binding of the opposing globular domains with target proteins, which is important to high-affinity binding and rapid enzyme activation.

Allosteric Regulation↗
PubMed2000

Substrate binding stabilizes S-adenosylhomocysteine hydrolase in a closed conformation.

Comparison of crystal structures of S-adenosylhomocysteine (AdoHcy) hydrolase in the substrate-free, NAD(+) form [Hu, Y., Komoto, J., Huang, Y., Gomi, T., Ogawa, H., Takata, Y., Fujioka, M., and Takusagawa, F. (1999) Biochemistry 38, 8323-8333] and a substrate-bound, NADH form [Turner, M. A., Yuan, C.-S., Borchardt, R. T., Hershfield, M. S., Smith, G. D., and Howell, P. L. (1998) Nat. Struct. Biol. 5, 369-376] indicates large differences in the spatial arrangement of the catalytic and NAD(+) binding domains. The substrate-free, NAD(+) form exists in an "open" form with respect to catalytic and NAD(+) binding domains, whereas the substrate-bound, NADH form exists in a closed form with respect to those domains. To address whether domain closure is induced by substrate binding or its subsequent oxidation, we have measured the rotational dynamics of spectroscopic probes covalently bound to Cys(113) and Cys(421) within the catalytic and carboxyl-terminal domains. An independent domain motion is associated with the catalytic domain prior to substrate binding, suggesting the presence of a flexible hinge element between the catalytic and NAD(+) binding domains. Following binding of substrates (i.e., adenosine or neplanocin A) or a nonsubstrate (i.e., 3'-deoxyadenosine), the independent domain motion associated with the catalytic domain is essentially abolished. Likewise, there is a substantial decrease in the average hydrodynamic volume of the protein that is consistent with a reduction in the overall dimensions of the homotetrameric enzyme following substrate binding and oxidation observed in earlier crystallographic studies. Thus, the catalytic and NAD(+) binding domains are stabilized to form a closed active site through interactions with the substrate prior to substrate oxidation.

Adenosylhomocysteinase↗
PubMed2000

Chronic restraint stress promotes lymphocyte apoptosis by modulating CD95 expression.

Depending on the duration and severity, psychological tension and physical stress can enhance or suppress the immune system in both humans and animals. Although it is well established that stress alters the release of various hormones and neurotransmitters, the mechanisms by which stress affects immune responses remain elusive. We report here that mice subjected to chronic 12-hour daily physical restraint for two days exhibited a significant reduction in splenocytes, a process likely mediated by apoptosis as demonstrated by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay. CD95 (Fas/APO-1) expression in splenic lymphocytes of stressed mice was substantially increased. Interestingly, Fas-immunoglobulin fusion protein and blocking antibodies against CD95 ligand inhibit stress-induced reduction in lymphocytes. The stress-induced changes in CD95 expression and lymphocyte number could be blocked by naltrexone or naloxone, specific opioid receptor antagonists, indicating a pivotal role of endogenous opioids in this process. In addition, the reduction of splenocytes in this model system seems to be independent of the hypothalamo-pituitary-adrenal axis, as both adrenalectomized and sham-operated mice exhibited similar responses to chronic stress. Moreover, chronic physical restraint failed to induce a decrease in lymphocyte numbers in CD95-deficient (Fas(lpr/lpr)) mice. Therefore, stress modulates the immune system through CD95-mediated apoptosis dependent on endogenous opioids.

Animals↗
PubMed2000

Chiral nonsteroidal affinity ligands for the androgen receptor. 1. Bicalutamide analogues bearing electrophilic groups in the B aromatic ring.

A series of chiral analogues of bicalutamide bearing electrophilic groups (isothiocyanate, N-chloroacetyl, and N-bromoacetyl) on aromatic ring B of the parent molecule were synthesized. These compounds were designed as affinity ligands for the androgen receptor (AR). We prepared the (R)- and (S)-optical isomers of these compounds as pure enantiomers. The AR binding affinities of these compounds were measured in a competitive binding assay with the radiolabeled high-affinity AR ligand, [(3)H]mibolerone. In accordance with our previous results for the enantiomers of bicalutamide, we found that all (R)-isomers demonstrated much higher binding affinity to the AR as compared to their corresponding (S)-isomers. The para-substituted affinity ligands in ring B bound the AR with higher affinities than the corresponding meta-substituted analogues. Oxidation of thioester affinity ligands to their sulfonyl analogues for the para-substituted compounds decreased AR binding affinities and similar modification increased binding affinities for corresponding meta-analogues. The least potent para-substituted sulfonyl compounds had higher AR binding affinities than the most potent meta-substituted sulfonyl compounds. Overall, the para-substituted unoxidized molecules demonstrated the highest AR binding affinity. Subsequent research using AR exchange assays and Scatchard analyses showed that the isothiocyanate affinity ligands (R)-7, (R)-9, and (R)-10 reported herein are the first specific chemoaffinity ligands for the AR.

Androgen Antagonists↗
PubMed2000

Glutamyl hydrolase. pharmacological role and enzymatic characterization.

gamma-Glutamyl hydrolase (GH, EC 3.4.19.9) is a lysosomal and secreted glycoprotein that hydrolyzes the gamma-glutamyl tail of antifolate and folate polyglutamates. Tumor cells that have high levels of GH are inherently resistant to classical antifolates, and further resistance can be acquired by elevations in GH following exposure to this class of antitumor agents. The highest level of expression in normal tissues occurs in the liver and kidney in humans. When panels of tumors are compared with normal tissues, GH expression is elevated in cancerous hepatic and breast tissue. A second poly-gamma-glutamate hydrolyzing enzyme, glutamate carboxypeptidase II, is a transmembrane protein whose active site is on the outside of the cell, occurring in the prostate gland, small intestine, brain, kidney, and tumor neovasculature. It is a high-affinity (nanomolar), low-turnover, zinc co-catalytic enzyme. In contrast, GH is a low-affinity (micromolar), high-turnover enzyme that has a cysteine at the active site. Data are presented suggesting that Cys110 is the nucleophile that attacks the gamma-amide linkage and causes hydrolysis. GH is being evaluated as an intracellular target for inhibition in order to enhance the therapeutic activity of antifolates and fluorouracil.

Animals↗
PubMed2000

Anti-galactose-alpha(1,3) galactose antibody production in alpha1,3-galactosyltransferase gene knockout mice after xeno and allo transplantation.

Antibodies (Abs) that mediate the hyperacute rejection and acute vascular rejection/delayed xenograft rejection of pig organs in humans and Old World primates are predominantly directed at a single carbohydrate epitope, galactose-alpha1,3-galactose (alpha1,3Gal). The T-cell dependence of elicited anti-alpha1,3Gal Ab responses in humans and Old World primates is controversial. In this study we have characterized anti-alpha1,3Gal Ab production in mice with disrupted alpha1,3-galactosyltransferase genes (GT-Ko mice) and determined the T-cell dependence of anti-alpha1,3Gal Ab responses, following xenograft and allograft transplantation. GT-Ko mice produce natural anti-alpha1,3Gal IgM and IgG in an age-dependent manner, however, these Abs could not elicit hyperacute rejection nor affect the rate of cardiac xenograft (3-5 days) or allograft rejection (7-9 days). Transplantation of xenogeneic Lewis rats hearts elicited modest anti-alpha1,3Gal Ab, but vigorous xenoAb responses. The anti-alpha1,3Gal Ab response was restricted to the IgM and IgG3 subclass while the xenoAb response comprised IgM and all four IgG subclasses. Transplantation of allogeneic C3H hearts elicited weak anti-alpha1,3Gal Ab responses that were primarily IgM, but vigorous alloAb responses. Despite the restriction of elicited anti-alpha 1,3Gal Ab responses to the IgM and IgG3 isotypes, these responses are T-cell dependent. The ability of allografts to elicit weak anti-alpha1,3Gal but strong allo-Ab responses, can be explained by the dependence of alpha1,3Gal-specific B cells on cognate help from T cells.

Age Factors↗
PubMed2000

The sensitivity of carboxyl-terminal methionines in calmodulin isoforms to oxidation by H(2)O(2) modulates the ability to activate the plasma membrane Ca-ATPase.

The oxidative modification of methionines within the primary sequence of calmodulin (CaM) results in an inability to activate the PM-Ca-ATPase fully, and may contribute to alterations in calcium homeostasis under conditions of oxidative stress. To identify differences in the sensitivities of CaM isoforms to oxidative modification, we have compared the function and patterns of oxidative modification resulting from the exposure of CaM isolated from bovine testes and wheat germ to H(2)O(2). In comparison to CaM isolated from wheat germ, vertebrate CaM is functionally resistant to oxidant-induced loss of function. The decreased functional sensitivity of vertebrate CaM correlates with a 75 +/- 3% reduction in the rate of oxidative modification of a methionine near the carboxyl terminus (i.e., Met(144) or Met(145)). The extent of oxidative modification to other methionines in these CaM isoforms is similar. These results suggest that the sensitivity of Met(144) or Met(145) to oxidation modulates the ability of CaM to activate the PM-Ca-ATPase. Consistent with this interpretation, a CaM mutant in which glutamines were substituted for Met(144) and Met(145) fully activates the PM-Ca-ATPase irrespective of the oxidative modification of the other seven methionines to their corresponding methionine sulfoxides. The extent of oxidative modification to individual methionines in vertebrate CaM by H(2)O(2) correlates with the time-averaged surface accessibility of individual sulfurs calculated from molecular dynamics simulations. Thus, the sensitivity of individual methionines to oxidative modification is directly related to the solvent accessibility. These results indicate that sequence differences between vertebrate and plant CaM alter the sensitivity of methionines near the carboxyl terminus to oxidative modification because of alterations in their solvent accessibility. We suggest that these sequence differences between CaM isoforms have a regulatory role in modulating the functional sensitivity of CaM to conditions of oxidative stress.

Amino Acid Sequence↗