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Y Lu

Publications and source records attributed to Y Lu.

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

CD28-dependent killing by human YT cells requires phosphatidylinositol 3-kinase activation.

CD28/B7 interactions have been demonstrated to provide a co-stimulatory signal for the generation of CD8+ cytotoxic T lymphocytes in the absence of CD4+ T helper cells. The CD28 signals required for induction of cytotoxicity have yet to be described. To investigate further the biochemical signaling pathways associated with CD28-dependent cytotoxicity, we have studied the human thymic leukemia cell line, YT. YT cells kill B7+ targets in a non-major histocompatibility complex (MHC)-restricted, CD28-dependent manner. CD28 ligation on the surface of YT cells caused a rapid increase in the tyrosine phosphorylation of four major cellular substrates with masses estimated to be 110, 95, 85, and 44 kDa. The 110 and 85 kDa substrates were identified as the catalytic and regulatory subunits, respectively, of phosphatidylinositol 3-kinase (PI3-K). Engagement of CD28 caused the rapid receptor association and activation of PI3-K but did not activate phospholipase C gamma. CD28-induced tyrosine phosphorylation and PI3-K activation was independent of p56lck protein tyrosine kinase (PTK) activity (previously reported to be associated with CD28) and was insensitive to inhibition by the PTK inhibitor herbimycin A. Two structurally and mechanistically dissimilar inhibitors of PI3-K, wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) also failed to block CD28-dependent tyrosine phosphorylation events or the association of PI3-K with the CD28 receptor. However, both drugs inhibited CD28-dependent cytotoxicity and CD28 receptor associated PI3-K activity with IC50 values similar to the reported IC50 values for PI3-K inhibition. Although herbimycin A did not significantly block the observed CD28-dependent tyrosine phosphorylation or PI3-K activation, herbimycin did block CD28-dependent cytotoxicity in a dose-dependent manner. These data support a role for PI3-K activation in the CD28-dependent initiation of cytotoxic effector function and suggest that a herbimycin sensitive step(s) is either CD28-independent, resides within a PI3-K-independent CD28 signaling pathway, or is downstream of CD28-dependent PI3-K activation.

Amino Acid Sequence↗
PubMed1996

Dual X-ray absorptiometry quality control: comparison of visual examination and process-control charts.

Dual X-ray absorptiometry (DXA) is widely used to monitor treatment efficacy in reducing the rate of bone mineral loss. In order to assure the validity of these measurements, instrument quality control of the DXA scanners becomes very important. This paper compares five quality control procedures (visual inspection, Shewhart chart with sensitizing rules, Shewhart chart with sensitizing rules and a filter for clinically insignificant mean changes, moving average chart and standard deviation, and cumulative sum chart [CUSUM]) in their ability to identify scanner malfunction by means of (1) an analysis of five longitudinal phantom data sets that had been collected during a clinical trial and (2) an analysis of simulated data sets. The visual inspection method is relatively subjective and depends on the operator's experience and attention. The regular Shewhart chart with sensitizing rules has a high false alarm rate. The Shewhart chart with sensitizing rules and an additional filter for clinically insignificant mean changes has the lowest false alarm rate but a relatively low sensitivity. The CUSUM method has good sensitivity and a low false alarm rate. In addition, this method provides an estimate of the date a change in the DXA scanner performance might have occurred. The method combining a moving average chart and a moving standard deviation chart came closest to the performance of the CUSUM method. Comparing the advantages and disadvantages of all methods, we propose the use of the CUSUM method as a quality control procedure for monitoring DXA scanner performance. For clinical trials use of the more intuitive Shewhart charts may be acceptable at the individual sites provided their scanner performance is followed up by CUSUM analysis at a central quality assurance center.

Absorptiometry, Photon↗
PubMed1996

Autocrine regulation of collagenase gene expression by TNF-alpha in U937 cells.

Tumor necrosis factor alpha (TNF-alpha) has been shown to induce the production of interstitial collagenase by fibroblasts and chondrocytes. We investigated the role of TNF-alpha in collagenase gene expression by U937 monocyte/macrophage cells. Transcription of the TNF-alpha gene was observed after 0.5 h of phorbol myristate acetate (PMA) stimulation. Collagenase mRNA expression was not observed until 5-7 h of activation with PMA. TNF-alpha was detected in the culture supernatants 2-3 h before transcription of the collagenase gene. Neutralization of TNF-alpha protein with anti-TNF-alpha antibodies significantly reduced collagenase mRNA expression. Protein kinase C (PKC) and protein tyrosine kinase (PTK) inhibition essentially abolished both PMA-induced TNF-alpha protein secretion and collagenase mRNA expression. Collagenase gene expression induced by exogenous TNF-alpha in U937 cells stimulated with a suboptimal concentration of PMA was suppressed by PTK, but not PKC, inhibition. The pyrrolidine derivative of dithiocarbamate, a potent inhibitor of nuclear factor-kappa B (NF-kappa B) activation, resulted in a marked reduction in collagenase gene transcription, however, no reduction of TNF-alpha secretion was noted. Anti-TNF-alpha antibodies inhibited PMA-induced NF-kappa B activation. These observations demonstrate an important role for TNF-alpha in the autocrine regulation of collagenase gene expression by U937 cells. Additionally, TNF-alpha-induced PTK and NF-kappa B activation were important in collagenase gene expression in this cell line.

Antibodies↗
PubMed1996

Human papillomavirus detection of endometrioid carcinoma with squamous differentiation of the uterine corpus.

Many studies have shown a link between human papillomavirus (HPV) and cervical carcinoma. However, studies on the association of HPV with endometrioid carcinoma of the corpus uteri are sparse and controversial. In this study, 33 formalin-fixed, paraffin-embedded tissue samples of endometrioid carcinoma with squamous cell differentiation in grade 1 (adenoacanthoma) and 10 additional samples of endometrioid carcinoma with less squamous cell differentiation in grade 2 or 3 (adenosquamous carcinoma) were examined by the hybrid capture system for the presence of the 14 most common anogenital HPV types, consisting of low-risk HPV types 6, 11, 42, 43, and 44, and intermediate- and high-risk HPV types 16, 18, 31, 33, 35, 45, 51, 52, and 56. No evidence of high-risk HPV DNA types was found in any of these samples. The low- risk HPV DNA types were found in three samples and showed borderline results (+/-) in 6 samples by the hybrid capture system. The 43 samples were tested by dot blot hybridization with HPV probes 6/11, 16/18, and 31/33/35. Only 1 sample was positive for HPV 6/11. The results of this study did not indicate an association between HPV infection and endometrioid carcinoma with squamous cells, though the endometrial mucosa of the corpus uteri is anatomically connected to the endocervical epithelium, and in some cases HPV has been postulated to possibly cause squamous cell differentiation of the endometrium. Our findings are in accord with the concept that HPV infection leading to malignancy is highly site- and tissue-specific. In conclusion, the endometrium may not be a suitable host epithelium for HPV replication and maturation.

Carcinoma, Endometrioid↗
PubMed1996

Human papilloma virus DNA: a factor in the pathogenesis of mammary Paget's disease?

The paraffin sections from 20 nipples with Paget's disease (10 central intraductal and 10 invasive ductal carcinomas) were analyzed for human papilloma virus (HPV) DNA of the low- and intermediate/high-risk groups. Polymerase chain reaction (PCR) and dot (slot) blot hybridization were used for the detection of HPV DNA types 6/11/16/18/31/33/35. In addition, we examined the c-erbB-2 oncogene expression in the specimens to differentiate benign cells in the surface epithelium of the nipple and areola from Paget cells. We found that the oncogene expression of the c-erbB-2 displayed a strong signal in the Paget cells. Using PCR and dot (slot) blot hybridization, we could not detect the HPV DNAs that are specific for the low- and intermediate/high risk-groups in the 20 cases of Paget's disease. Our results showed for the first time that this type of virus did not contribute to the pathogenesis of Paget's disease.

Breast Neoplasms↗
PubMed1996

Interleukin-1 alpha and interleukin-6 in the urine, kidney, and bladder of mice inoculated with Escherichia coli.

After bladder inoculation of mice using the pyelonephritogenic Escherichia coli strain DS17, urinary interleukin-1 alpha (IL-1 alpha) peaked at 0.5 h post infection (mean 233 pg/ml), interleukin-6 (IL-6) at 2 h (mean 572 pg/ml), and leukocyturia at 4 h, all three persisting for more than 24 h. In the kidneys IL-1 alpha peaked at 2 h, persisted over 24 h (mean 900-1,000 pg/ml), and decreased over 2-6 days post inoculation to a mean value of 208 pg/ml. Control kidneys showed low IL-1 alpha values. IL-6 in the kidneys peaked at 5 h (mean 9,999 pg/ml) but normalized, i.e., similar to control kidneys, by 48 h (mean 105 pg/ml). A similar cytokine response, but with tenfold lower levels, was found in the bladder tissue. The isogenic P-negative E. coli mutant DS178 elicited lower IL-6 in the kidneys at 5 h, but persisted in higher numbers in the kidneys at 6 days. Bacterial counts and cytokine levels correlated both in the kidneys and in bladder tissue, (r = 0.50-0.76, P < 0.001). Characterization of the immune response gives a better understanding of the relative importance of different bacterial characteristics for the local inflammatory process and is needed for studies of its pharmacological down-regulation.

Animals↗
PubMed1996

Role of chromium(IV) in the chromium(VI)-related free radical formation, dG hydroxylation, and DNA damage.

A reactive Cr(IV) ester was synthesized from a reaction of CrO3 with 2,4-dimethyl-2,4-pentanediol as verified by electron spin resonance (ESR) and magnetic susceptibility measurements. ESR spin trapping studies demonstrate that the Cr(IV) ester is capable of generating hydroxyl free radical (.OH) through a Fenton-like mechanism (Cr(IV)+H2O2-->Cr(V)+.OH+OH-) with a concomitant generation of Cr(V) species (g = 1.9787). Cr(IV) caused DNA strand breaks as measured by electrophoretic assays. H2O2 enhanced the DNA strand breaks via .OH formation by a Cr(IV)-mediated Fenton-like reaction. In the Cr(IV)/H2O2 system, formate did not block Cr(V) formation, but prevented DNA damage, indicating that .OH radicals, and not Cr(V), caused the DNA damage. Reaction of Cr(VI) with ascorbate was also used as a source of Cr(IV). Incubation of Cr(VI), ascorbate, and DNA caused DNA strand breaks. A free radical trap, 5,5-dimethyl-1-pyrroline (DMPO), only slightly inhibited the DNA damage. Addition of Mn(II), which inhibited Cr(IV), caused significant protection. H2O2 enhanced the DNA damage via Cr(IV)-mediated .OH radical generation and Mn(II) inhibited the damage, again showing that Cr(IV) and its related .OH generation caused DNA strand breaks. HPLC measurements showed that .OH radicals generated by a Cr(IV)-mediated Fenton-like reaction generated 8-hydroxy-2'-deoxyguanosine from 2'-deoxyguanosine. The results demonstrate that Cr(IV) and its generated .OH radicals are capable of damaging DNA. Moreover, in comparison with Cr(V), Cr(IV) is a more potent DNA damaging agent.

Chromium↗
PubMed1996

Mutations in subunits of the epithelial sodium channel cause salt wasting with hyperkalaemic acidosis, pseudohypoaldosteronism type 1.

Autosomal recessive pseudohypoaldosteronism type I is a rare life-threatening disease characterized by severe neonatal salt wasting, hyperkalaemia, metabolic acidosis, and unresponsiveness to mineralocorticoid hormones. Investigation of affected offspring of consanguineous union reveals mutations in either the alpha or beta subunits of the amiloride-sensitive epithelial sodium channel in five kindreds. These mutations are homozygous in affected subjects, co-segregate with the disease, and introduce frameshift, premature termination or missense mutations that result in loss of channel activity. These findings demonstrate the molecular basis and explain the pathophysiology of this disease.

Animals↗
PubMed1996

Sites and types of UV-induced mutations leading to inactivation of the growth-arresting activity in p21 (sdi1/cip1/waf1) cDNA.

The p53-regulated gene product p21 (sdi1,cip1,waf1) negatively regulates cell growth and has been suggested to be a potential tumour-suppressor gene. To determine the sites and types of mutations which inactivate the growth-arresting activity in sdi1 cDNA, plasmids containing sdi1 cDNA and the neomycin-resistant gene were irradiated with UV light and transfected into CHO cells. The UV irradiation increased number of the geneticin-resistant colonies which should have the UV-mutated sdi1 cDNA. Sdi1 mRNA was expressed in 23 out of 36 colonies (64%). In 13 sdi1 cDNA sequences analysed, mutations were found at codon 46 in nine cDNAs, and one each at codons 34, 54, 66 and 73. All the mutation sites are in the CDK-binding region. Ten mutations (77%) (codons 46 and 66) are C to T transition mutation at the dipyrimidine sequences, which is the major type of the UV-induced mutation.

Animals↗
PubMed1996

Tumour necrosis factor soluble receptors I and II and interleukin-1 receptor antagonist in acute pyelonephritis in relation to bacterial virulence-associated traits and renal function.

Urinary tract infections activate both mucosal and systemic inflammatory responses reflected by elevation of cytokine concentrations in serum and urine. We determined urine and serum concentrations of tumour necrosis factor soluble receptors I and II (sTNFR I and sTNFR II) and interleukin-1 receptor antagonist (IL-1ra) in 41 women with acute pyelonephritis caused by Escherichia coli, 2 weeks after the infection, during a subsequent episode of cystitis or asymptomatic bacteriuria and also later when the same patients were free from bacteriuria. Concentrations of sTNFR I, sTNFR II and IL-1ra were related to the expression of five virulence markers of E. coli, glomerular filtration rate (GFR) and to the concentration of C-reactive protein (CRP) in serum. Patients with acute pyelonephritis had elevated serum concentrations of sTNFR I and sTNFR II compared to healthy women (P < 0.001 for both comparisons). The concentrations of sTNFR I and sTNFR II in urine were significantly higher in patients with acute pyelonephritis compared to controls (P < 0.001 in both cases). The concentration of sTNFR II in urine was higher in patients infected by E. coli producing haemolysin (P = 0.05) and in patients infected by E. coli expressing hydrophobic properties (P = 0.05) compared to patients infected by strains without these virulence traits. Patients who had high concentrations of sTNFR II in serum during acute pyelonephritis had lower GFR at follow-up (r = -0.48, P = 0.05). Patients who responded with a marked increase in CRP had higher sTNFR I and sTNFR II in urine (r = 0.58, P < 0.01 and r = 0.48, P < 0.01, respectively). The concentrations of sTNFR I and sTNFR II in serum and urine decreased during follow-up and were lower 2 weeks after the infection when all patients were free from bacteriuria. IL-1ra in serum was elevated during pyelonephritis (P < 0.001) while that in urine was significantly lower compared to controls (P < 0.001). It is concluded that the increased concentrations of TNF receptors may block the cytotoxic and inflammatory actions and reduce the sensibility of renal cells to TNF alpha-mediated effects.

Acute Disease↗
PubMed1996

Aspiration cytology of neoplastic and non-neoplastic ovarian cysts: is it accurate?

To evaluate the role of aspiration cytology in the distinction between neoplastic and non-neoplastic ovarian cysts, we examined the cytology of 81 aspirates from 80 women 14-67 years of age. We then correlated results with subsequent histology or the clinical follow-up. Aspiration were performed during laparoscopy (32 cases) or immediately after surgical removal of the tumors (49 cases). The cysts ranged in size from 1.0 to 43.0 cm. Papanicolaou-stained cytospin preparations of samples were evaluated, and the lesions were classified into non-neoplastic (68 cases), benign neoplasms (four cases), and malignant neoplasms (nine cases). Cytologic impressions were correlated with histologic findings in 74 cases and with the clinical follow-up in the remaining seven. Nine of the 12 (75%) cystadenocarcinomas, including two serous neoplasms of low malignant potential (LMP), were correctly diagnosed as malignant by cytology. There were no false-positive results. On the other hand, of the 26 benign neoplasms (19 cystadenomas and seven mature cystic teratomas), only four teratomas (15%) could be subclassified specifically. The remaining 68 aspirates were classified as non-neoplastic. Seventy-seven percent of all proven non-neoplastic cysts measured < 8.0 cm, whereas 77% of all benign and malignant neoplastic cysts were > 8.0 cm. The overall diagnostic accuracy was improved from 63% to 69% when cyst size was taken into consideration. In malignant cysts the diagnostic sensitivity was 75%, specificity 100%, and overall accuracy 96%. We arrived at the following conclusions: Aspiration cytology is an accurate predictor of malignancy in ovarian cystic lesions, but because the sensitivity of the technique is not high enough, one should not rely on aspiration cytology alone; The differential diagnosis between cystadenocarcinomas and tumors of low malignant potential cannot be made by cytology; Although it is difficult to distinguish between benign neoplasms and non-neoplastic benign cysts, diagnostic accuracy will improve when the size of the lesion is considered; Aspiration cytology can provide particularly useful information in young women with functional cysts of the ovary to avoid an unnecessary operation; Acellular cyst fluids should not be considered nondiagnostic because they represent benign cysts in the majority of cases; false-negative results of fine-needle aspiration of cystic ovarian lesions is usually due to low cellularity of the sample and secondary degenerative changes; negative fine-needle aspiration results should be followed clinically.

Adolescent↗
PubMed1996

Drug-induced in vitro inhibition of neutrophil-endothelial cell adhesion.

1. Leukocyte-endothelial cell interactions play an important role during ischaemia-reperfusion events. Adhesion molecules are specifically implicated in this interaction process. 2. Since defibrotide has been shown to be an efficient drug in reducing damage due to ischaemia-reperfusion in many experimental models, we analysed the effect of defibrotide in vitro on leukocyte adhesion to endothelial cells in basal conditions and after their stimulation. 3. In basal conditions, defibrotide (1000 micrograms ml-1) partially inhibited leukocyte adhesion to endothelial cells by 17.3% +/- 3.6 (P < 0.05), and after endothelial cell stimulation (TNF-alpha, 500 u ml-1) or after leukocyte stimulation (fMLP, 10(-7) M), it inhibited leukocyte adhesion by 26.5% +/- 3.4 and 32.4% +/- 1.8, respectively (P < 0.05). 4. In adhesion blockage experiments, the use of the monoclonal antibody anti-CD31 (5 micrograms ml-1) did not demonstrate a significant inhibitory effect whereas use of the monoclonal antibody anti-LFA-1 (5 micrograms ml-1) significantly interfered with the effect of defibrotide. 5. This result was confirmed in NIH/3T3-ICAM-1 transfected cells. 6. We conclude that defibrotide is able to interfere with leukocyte adhesion to endothelial cells mainly in activated conditions and that the ICAM-1/LFA-1 adhesion system is involved in the defibrotide mechanism of action.

Cell Adhesion↗
PubMed1996

A new source localization algorithm with no requirement of one-to-one source correspondence between biplane radiographs.

Conventional source localization algorithms require a one-to-one source correspondence between films. This requirement makes source localization cumbersome and error prone because multiple sources must be carefully digitized and some sources can be obscured or missed. A new source localization algorithm is described in this paper. The algorithm fits a ribbon or needle image on film to a linear-quadratic equation, then analytically determines the 3-D ribbon locus by its image on the other projection, and finally localizes the sources in the ribbon by tracing along the ribbon image. Only three points per ribbon per film are required, and corresponding points need not be identified on the other film. Phantom experiments and tests on clinical cases demonstrate that the source localization algorithm can increase the efficiency by a factor of up to 5, improve accuracy to about 1 mm, and reconstruct obscured or shifted sources without decreased accuracy and efficiency. The simplicity and minimal entry of data make this technique desirable for clinical use.

Algorithms↗
PubMed1996

Evidence that the Bacillus subtilis pyrimidine regulatory protein PyrR acts by binding to pyr mRNA at three sites in vivo.

The Bacillus subtilis pyr operon is regulated by a transcriptional attenuation mechanism that requires the PyrR regulatory protein. Multicopy plasmids that could be transcribed to yield segments of RNA from the attenuation regions of the pyr operon induced derepression of chromosomal pyr genes, whereas plasmids that could not yield pyr RNA did not. We conclude that pyr RNA acts by titrating the PyrR protein and preventing it from regulating pyr attenuation.

Bacillus subtilis↗
PubMed1996

Transcriptional attenuation of the Bacillus subtilis pyr operon by the PyrR regulatory protein and uridine nucleotides in vitro.

Transcriptional attenuation of the pyrimidine biosynthetic (pyr) operon from Bacillus subtilis was reconstituted with an in vitro system that consisted of pyr DNA templates, B. subtilis RNA polymerase, four ribonucleoside triphosphates, and the purified B. subtilis PyrR regulatory protein. The templates used each specified one of the three known attenuation regions of the pyr operon. Runoff (read-though) and terminated transcripts of the predicted lengths were the only major products synthesized. Transcription of the template that specifies the 5' leader attenuation region of the operon was examined in detail. Termination of transcription at the attenuator was strongly promoted by the combination of PyrR plus UMP. The concentration of UMP required for half-maximal effect was 2.5 microM. UTP also promoted termination in the presence of PyrR, but concentrations 10-fold higher than UMP were required; UDP was only effective at 100 times the concentration of UMP. Other pyrimidine and purine metabolites tested did not affect termination. PRPP, which like UMP is a substrate for the uracil phosphoribosyltransferase activity of PyrR, antagonized UMP-dependent transcriptional termination, but uracil did not. Transcriptional attenuation by PyrR plus UMP was also demonstrated in vitro with templates from the other two pyr attenuation regions. The results strongly support the model for transcriptional regulation of the B. subtilis pyr operon previously proposed by R. J. Turner, Y. Lu, and R. L. Switzer (J. Bacteriol. 176:3708-3722, 1994).

Bacillus subtilis↗