Biomedical subjects

Q Shi

Publications and source records attributed to Q Shi.

At least 55 records · Page 3Linked to original sources

PubMed2001

Single sperm typing demonstrates that reduced recombination is associated with the production of aneuploid 24,XY human sperm.

To account for the increased proportion of paternal nondisjunction in 47,XXY males as compared to other trisomies, it has been suggested that the XY bivalent, with its reduced region of homology, is particularly susceptible to nondisjunction. Molecular studies of liveborn Klinefelter syndrome (47,XXY) individuals have reported an association between the absence of recombination in the pseudoautosomal region and nondisjunction of the XY bivalent. In this study we examined single sperm from a normal 46,XY male to determine if there is any alteration in the recombination frequency of aneuploid disomic 24,XY sperm compared to unisomic sperm (23,X or Y). Two DNA markers STS/STS pseudogene and DXYS15 were typed in sperm from a heterozygous man to determine if recombination had occurred in the pseudoautosomal region. Individual unisomic sperm (23,X or Y) were isolated using a FACStar(Plus) flow cytometer into PCR tubes. To identify disomic 24,XY sperm, 3-colour FISH analysis was performed with probes for chromosomes X,Y and 1. The 24,XY cells were identified using fluorescence microscopy, each disomic sperm was scraped off the slide using a glass needle attached to a micromanipulator and then put into a PCR tube. Hemi-nested PCR analysis of the two markers was performed to determine the frequency of recombination. A total of 329 unisomic sperm and 150 disomic sperm have been typed. The frequency of recombination between the two DNA markers was 38.3% for the unisomic sperm, similar to frequencies previously reported. The 24,XY disomic sperm had an estimated recombination frequency of 25.3%, however, a highly significant decrease compared to the unisomic 23,X or 23,Y sperm (chi(2) = 10.7, P = 0.001). This direct analysis of human sperm indicates that lack of recombination in the pseudoautosomal region is a significant cause of XY nondisjunction and thus Klinefelter syndrome.

Aneuploidy↗

PubMed2001

Intact nitric oxide synthase II gene is required for interferon-beta-mediated suppression of growth and metastasis of pancreatic adenocarcinoma.

Previous studies have shown that enforced expression of IFN-beta suppressed tumor growth and metastasis. In this report, we determined whether the induction of nitric oxide synthase II (NOS II) gene is required for IFN-beta-mediated antitumor activity using syngeneic mice with intact (NOS II+/+) or genetically disrupted (NOS II-/-) NOS II gene. PANC02-H7 highly metastatic murine pancreatic adenocarcinoma cells were transfected with an IFN-beta expression vector or a control pcDNA3 vector. The parental PANC02-H7, control vector-transfected, and IFN-beta-transfected cells were orthotopically implanted into the pancreas of syngeneic NOS II+/+ and NOS II-/- C57BL/6J mice. In NOS II+/+ C57BL/ 6J, both parental and control vector-transfected cells grew progressively in pancreas and produced numerous liver metastases and a large amount of malignant ascites, whereas IFN-beta-secreting cells did not. In NOS II-/- C57BL/6J mice, however, IFN-beta-secreting cells grew much more aggressively. Higher NO induction was detected in NOS II+/+ mice that received injections with IFN-beta-secreting cells than with the control cells, but it was not detected in NOS II-/- mice. These data suggested that IFN-beta secreted from tumor cells stimulates NO production by host cells and suppresses tumor growth and metastasis.

Adenocarcinoma↗

PubMed2001

Cigarette smoking and aneuploidy in human sperm.

Cigarette smoke contains chemicals which are capable of inducing aneuploidy in experimental systems. These chemicals have been shown to reach the male reproductive system, increasing oxidative DNA damage in human sperm and lowering semen quality. We have examined the association between smoking and aneuploid sperm by studying 31 Chinese men with similar demographic characteristics and lifestyle factors except for cigarette smoking. None of the men drank alcohol. These men were divided into three groups: nonsmokers (10 men), light smokers (< 20 cigarettes/day, 11 men), and heavy smokers (> or = 20 cigarettes/day, 10 men). There were no significant differences in semen parameters or in age across groups. Two multi-color fluorescence in situ hybridizations (FISH) were performed: two-color FISH for chromosomes 13 and 21, and three-color FISH for the sex chromosomes using chromosome 1 as an internal autosomal control for diploidy and lack of hybridization. The mean hybridization efficiency was 99.78%. The frequency of disomy 13 was significantly higher in light and heavy smokers than in non-smokers, while no significant differences in the frequency of disomy 21, X or Y were observed across groups. Significant inter-donor heterogeneity in every category of disomic sperm examined was found in both light and heavy smokers, while in nonsmokers only XY disomy showed significant inter-donor differences. Thus, we conclude that cigarette smoking may increase the risk of aneuploidy only for certain chromosomes and that men may have different susceptibilities to aneuploidy in germ cells induced by cigarette smoking. Mol. Reprod. Dev. 59: 417-421, 2001.

Adult↗

PubMed2001

Recombination in the pseudoautosomal region in a 47,XYY male.

Males with a 47,XYY karyotype generally have chromosomally normal children, despite the high theoretical risk of aneuploidy. Studies of sperm karyotypes or FISH analysis of sperm have demonstrated that the majority of sperm are chromosomally normal in 47,XYY men. There have been a number of meiotic studies of XYY males attempting to determine whether the additional Y chromosome is eliminated during spermatogenesis, with conflicting results regarding the pairing of the sex chromosomes and the presence of an additional Y. We analyzed recombination in the pseudoautosomal region of the XY bivalent to determine whether this is perturbed in a 47,XYY male. A recombination frequency similar to normal 46,XY men would indicate normal pairing within the XY bivalent, whereas a significantly altered frequency would suggest other types of pairing such as a YY bivalent or an XYY trivalent. Two DNA markers, STS/STS pseudogene and DXYS15, were typed in sperm from a heterozygous 47,XYY male. Individual sperm (23,X or Y) were isolated into PCR tubes using a FACStarPlus flow cytometer. Hemi-nested PCR analysis of the two DNA markers was performed to determine the frequency of recombination. A total of 108 sperm was typed with a 38% recombination frequency between the two DNA markers. This is very similar to the frequency of 38.3% that we have observed in 329 sperm from a normal 46,XY male. Thus our results suggest that XY pairing and recombination occur normally in this 47,XYY male. This could occur by the production of an XY bivalent and Y univalent (which is then lost in most cells) or by loss of the additional Y chromosome in some primitive germ cells or spermatogonia and a proliferative advantage of the normal XY cells.

Adult↗

PubMed2001

Favorable histologic findings and tensile strength at 14 years in knitted polyester aortofemoral and femoropopliteal grafts in the same patient.

Patent right and left limbs of an aortobifemoral knitted polyester graft and a patent left femoropopliteal graft, both implanted for 14 years, were removed 40 hr postmortem from a 63-year-old man. Healing studies were performed, using routine and immunocytochemistry staining scanning electron microscopy (SEM), and transmission electron microscopy (TEM) on multiple samples taken from sites sufficiently far from the anastomoses to avoid pannus healing. Evaluation by weight-elongation comparison with a fresh graft demonstrated that structural stability and strength were well preserved. Anastomoses were patent with no remarkable intimal hyperplasia. There was no thrombus on the flow surface of either graft. Histologic studies of these grafts revealed uniform through-wall tissue ingrowth and extensive patches of endothelial cells scattered over the flow surface, confirmed by factor VIII, SEM, and TEM. These findings document that long-term stable tensile strength and healing with flow surface endothelialization can be attained with knitted polyester grafts in the human.

Aorta↗

PubMed2001

Synthesis and pharmacology of site specific cocaine abuse treatment agents: a new synthetic methodology for methylphenidate analogs based on the Blaise reaction.

In order to make new analogs of the dopamine (DA) uptake inhibitor methylphenidate, a synthetic methodology based on the Blaise reaction was developed. The reaction between alpha-bromophenylacetic acid esters, zinc and alpha-cyano-omega-mesylates gave stable primary enamines. After reduction of the enamines with cyanoborohydride, the amines could be cyclized to methylphenidate analogs in which the amine ring size and aromatic ring were varied. These compounds were tested for inhibitory potency against [(3)H]WIN 35,428 binding to the cocaine recognition site and [(3)H]DA uptake using rat striatal tissue. When the heterocyclic ring size was varied, the six-membered ring of methylphenidate appeared to be the optimum ring size. When the aryl ring was varied the 4-trifluoromethylphenyl analog was less potent than methylphenidate, the beta-naphthyl congener was considerably more potent, whereas the alpha-naphthyl congener was less potent. Most of the compounds tested had ratios of uptake to binding inhibition (discrimination ratio) that were similar to cocaine and were therefore not lead compounds for the development of cocaine antagonists.

Animals↗

PubMed2001

Antitumor agents 210. Synthesis and evaluation of taxoid-epipodophyllotoxin conjugates as novel cytotoxic agents.

Five compounds composed of a taxoid (paclitaxel or cephalomannine) and a 4'-O-demethyl epipodophyllotoxin derivative joined by an imine linkage were prepared and evaluated as cytotoxic agents and inhibitors of mammalian DNA topoisomerase II. Compounds 12 and 14-16 exhibited comparable or better activity than the unconjugated epipodophyllotoxin derivatives in most tumor cell lines, and 12, 15, and 16 also showed enhanced activity against paclitaxel-resistant cells. Compound 13, which contains an epipodophyllotoxin moiety at both the taxoid 2' and 7 positions, did not stimulate protein-DNA breaks, but was 2-fold more potent than 12 and 15 and comparable to GL-331 in the topo II inhibitory assay.

Antineoplastic Agents↗

PubMed2001

Salivary anticandidal activity and saliva composition in an HIV-infected cohort.

This study investigated salivary anticandidal activity and salivary composition in stimulated whole saliva of 18 advanced HIV-infected patients and compared these values to healthy controls. Stimulated whole saliva from HIV-infected patients showed decreased anticandidal activity. The flow rate was reduced by 40% as compared with controls. The saliva flow rate for HIV-infected patients who had recoverable yeast in their saliva was reduced as compared to HIV-infected patients without recoverable yeast. For HIV-infected patients, the saliva concentrations of lactoferrin, secretory IgA and Cl- were increased while the secretion rate of lysozyme, total protein and K+ were reduced. There was no difference in any parameter as a function of taking the antifungal drug fluconazole. There was no association between salivary anticandidal activity and any salivary component. This study shows reduced anticandidal activity and salivary flow rate in HIV-infected patients. These alterations may contribute to their increased incidence of oral candidal infections.

Adult↗

PubMed2001

Regulation of interleukin-8 expression by nitric oxide in human pancreatic adenocarcinoma.

The regulation of interleukin-8 (IL-8) expression by nitric oxide (NO) was determined in human pancreatic cancer cell lines. CaPan-2 and FG human pancreatic adenocarcinoma cells were incubated for 24 h in medium alone or medium containing a cytokine mixture in the presence or absence of an NO synthase (NOS) inhibitor, N(G)-monomethyl-L-arginine (NMA). The NOS activity and level of IL-8 expression were determined. IL-8 expression was induced in the two cell lines. A low level of NOS activity was detectable only in CaPan-2 cells. Moreover, the presence of NMA did not reverse the induction of IL-8. The FG cells were then engineered to produce a physiologic level of NO and incubated in medium alone or medium containing 1 mM NMA. No significant IL-8 expression was induced in those producing a low level of NO, whereas IL-8 expression was induced in those producing a high level of NO. Inhibition of NO production by NMA reversed this effect. Incubation of FG cells with an NO donor, S-nitroso-D,L.-acetyl-penicillamine (SNAP), led to a concentration-dependent and time-dependent induction of IL-8 expression. This NO-mediated upregulation of IL-8 expression correlated with an increase in IL-8 gene transcription and mRNA stability. Our results indicate that NO is involved in the regulation of IL-8 expression in and contributes to the progression of human pancreatic cancer.

Adenocarcinoma↗

PubMed2001

Regulation of interleukin-8 expression by tumor-associated stress factors.

Tumor and host cells frequently express interleukin-8 (IL-8). IL-8 has been shown to be motogenic, mitogenic, and angiogenic and to play important roles in human tumor progression. IL-8 expression can be induced by numerous stress factors present in the tumor environment, such as hypoxia, acidosis, hyperglycemia, hyperosmotic pressure, high cell density, hyperthermia, radiation, and chemotherapeutic agents. Understanding the mechanisms of IL-8 expression and regulation will be helpful in designing potential therapeutic modalities targeting IL-8 to control tumor growth and metastasis.

Animals↗

PubMed2001

Activated PAK4 regulates cell adhesion and anchorage-independent growth.

The serine/threonine kinase PAK4 is an effector molecule for the Rho GTPase Cdc42. PAK4 differs from other members of the PAK family in both sequence and function. Previously we have shown that an important function of this kinase is to mediate the induction of filopodia in response to activated Cdc42. Since previous characterization of PAK4 was carried out only with the wild-type kinase, we have generated a constitutively active mutant of the kinase to determine whether it has other functions. Expression of activated PAK4 in fibroblasts led to a transient induction of filopodia, which is consistent with its role as an effector for Cdc42. In addition, use of the activated mutant revealed a number of other important functions of this kinase that were not revealed by studying the wild-type kinase. For example, activated PAK4 led to the dissolution of stress fibers and loss of focal adhesions. Consequently, cells expressing activated PAK4 had a defect in cell spreading onto fibronectin-coated surfaces. Most importantly, fibroblasts expressing activated PAK4 had a morphology that was characteristic of oncogenic transformation. These cells were anchorage independent and formed colonies in soft agar, similar to what has been observed previously in cells expressing activated Cdc42. Consistent with this, dominant-negative PAK4 mutants inhibited focus formation by oncogenic Dbl, an exchange factor for Rho family GTPases. These results provide the first demonstration that a PAK family member can transform cells and indicate that PAK4 may play an essential role in oncogenic transformation by the GTPases. We propose that the morphological changes and changes in cell adhesion induced by PAK4 may play a direct role in oncogenic transformation by Rho family GTPases and their exchange factors.

Animals↗

PubMed2001

Transformation of chicken embryo fibroblasts by v-src uncouples beta1 integrin-mediated outside-in but not inside-out signaling.

Adhesion of cells to extracellular matrix is mediated by integrin family receptors. The process of receptor-ligand binding is dependent on metabolic energy and is regulated by intracellular signals, termed inside-out signals. The strength of the initial alpha5beta1-mediated adhesion of v-src-transformed chicken embryo fibroblasts (v-srcCEF) was similar to that of normal CEF. A chemically cross-linked fibronectin substrate was able to restore cell spreading and the ability of v-srcCEF to assemble a fibronectin matrix. Over time, v-srcCEF showed decreased adhesion due to the reduction of alpha5beta1-fibronectin bonds consequent on the reduction of substrate-bound fibronectin due to the secretion of proteases by v-srcCEF. Excess synthesis of hyaluronic acid by v-srcCEF also reduced the alpha5beta1-fibronectin bonds and contributed to cell detachment at later times in culture. Thus, the adhesion defects were not due to a failure of alpha5beta1 function and adhesion of the v-srcCEF was alpha5beta1 dependent. Integrin-mediated adhesion also produces signals that affect cell proliferation and cell differentiation. An early consequence of these "outside-in" signals was the phosphorylation of FAK Y397 in direct proportion to the number of alpha5beta1-fibronectin bonds formed. In contrast, v-srcCEF had an increased level of phosphorylation on five different tyrosines in FAK, and none of these phosphorylation levels were sensitive to the number of alpha5beta1-fibronectin bonds. In the absence of serum, CEF proliferation was sensitive to changes in alpha5beta1-mediated adhesion levels. Transformation by v-src increased the serum-free proliferation rate and made it insensitive to alpha5beta1-mediated adhesion. Thus, the v-srcCEF were insensitive to the normal outside-in signals from alpha5beta1 integrin.

Animals↗

PubMed2001

NF-Y antagonizes renin enhancer function by blocking stimulatory transcription factors.

We previously reported that the promoter proximal portion of the mouse renin enhancer contains a binding site for NF-Y (Ea) that overlaps with a positive regulatory element (Eb). In the context of the renin enhancer, NF-Y acts to oppose enhancer activity. We tested the hypothesis that NF-Y acts as a negative regulator by physically blocking the binding of transcription factors to element-b (Eb). Increasing the spacing between the NF-Y binding site (Ea) and Eb by 2, 5, or 10 nucleotides increased activity of the enhancer to the same extent as mutations abolishing NF-Y binding. The increase in transcription caused by increasing the spacing between Ea and Eb was not due to a shift of NF-Y from a negative regulator to a positive regulator because there was no loss of activity when Ea was also mutated. Oligonucleotides containing the normal or increased spacing mutants still allowed the binding of both NF-Y to Ea and transcription factors to Eb. In fact, we present evidence that both NF-Y and the Eb-binding factor(s) can each bind together on the same oligonucleotide containing either a 5- or 10-bp spacing between Ea and Eb. Our data strongly suggest that the mechanism by which NF-Y opposes renin enhancer activity is to sterically block the binding of factors to Eb.

Animals↗

PubMed2001

Mouse models of metastatic pancreatic adenocarcinoma.

Pancreatic adenocarcinoma is a deadly disease. Its etiology is unknown, and metastatic disease kills the majority of patients who have it. Effective prevention is clearly the ultimate goal for eradicating this disease provided that the effects of environmental and genetic elements on pancreatic cancer development are fully understood. Currently, it appears that the control of pancreatic cancer metastasis is of immediate urgency. Fulfillment of this difficult task relies on knowledge of the cellular and molecular biology of metastasis. The use of relevant animal models will help define each aspect of this complicated process.

Adenocarcinoma↗

PubMed2001

A novel, clinically relevant animal model of metastatic pancreatic adenocarcinoma biology and therapy.

In this study, we report a metastatic model of Panc02 murine pancreatic adenocarcinoma. Parental Panc02 cells were orthotopically implanted into the pancreas of syngeneic C57BL/6 mice. Tumor cells were isolated from liver micrometastases 90 d after tumor implantation and established as a culture (Panc02-H1). The Panc02-H1 cells were then implanted into the pancreas of mice. Liver metastases were then collected and established as Panc02-H2 cells. This process was repeated until the Panc02-H7 cell line was established. These cells were extremely aggressive after implantation as manifested by progressive growth in the pancreas, peritoneal dissemination, and distant metastasis to multiple organs, including the liver and lungs. Moreover, Panc02-H7 cells expressed the inducible nitric oxide synthase gene at a very low level in culture and produced highly vascularized tumors having a large number of infiltrating macrophages. Collectively, this model system should be a valuable tool for investigating the molecular mechanisms governing pancreatic cancer growth and metastasis and exploring potential treatment modalities for this disease.

Adenocarcinoma↗

PubMed2001

Aneuploidy in human spermatozoa: FISH analysis in men with constitutional chromosomal abnormalities, and in infertile men.

Reproductive difficulties are associated intimately with cytogenetic abnormalities. This article reviews multicolour fluorescence in situ hybridization studies on spermatozoa from men with constitutional chromosomal abnormalities and the consequences for spermatozoa, and on chromosomal abnormalities in the spermatozoa of infertile men who have normal somatic karyotypes. In 47,XYY men, the frequencies of 24,XY and 24,YY spermatozoa appear to be < or = 1%. Klinefelter (47,XXY) and mosaic Klinefelter patients had sperm aneuploidy frequencies of 2-25% and 1.5-7.0%, respectively. Robertsonian translocation carriers had 3-27% spermatozoa unbalanced for the chromosomes involved in the translocation, with a possible modest interchromosomal effect, but none of the increased frequencies of chromosomal disomy approached 1%. The frequency of chromosomally unbalanced spermatozoa in reciprocal translocations averages 50%, is strongly dependent on the chromosomes involved in the individual translocation, and may be slightly increased as a result of a small interchromosomal effect. Infertile men with a normal karyotype and low sperm concentration or certain types of morphologically abnormal spermatozoa have a significantly increased risk of producing aneuploid spermatozoa, particularly for the sex chromosomes. An increased risk of sperm aneuploidy was not observed in infertile men with poor sperm motility or in those with a normal karyotype and normal semen parameters.

Aneuploidy↗

PubMed2001

An open-label study of the treatment efficacy of olanzapine for Tourette's disorder.

BACKGROUND: An open-label trial was performed to explore efficacy and safety of olanzapine, an atypical neuroleptic with diverse receptor activity including both dopamine-2 and serotonin-2A and -2C antagonism, for treatment of Tourette's disorder. METHOD: Ten adult patients aged 20 to 44 years with Tourette's disorder were treated using an open-label, flexible dosing schedule for 8 weeks. Three patients who continued olanzapine were reevaluated after 6 months. Three subjects were psychotropic medication naive, 5 patients experienced intolerable side effects with conventional neuroleptics, and 2 patients had remote (> or = 10 years) successful response to conventional neuroleptics. Tic severity was rated by the Yale Global Tic Severity Scale; weight, vital signs, and adverse effects were assessed weekly. Electrocardiogram, laboratory studies, and comorbid symptoms, assessed by the Yale-Brown Obsessive Compulsive Scale and ADHD Behavior Checklist for Adults, were measured at baseline and at week 8. RESULTS: Two of 10 patients prematurely discontinued olanzapine owing to excessive sedation. Of 8 patients who completed the 8-week trial, 4 (50%) demonstrated reduction of global tic severity scores by > or = 20 points, and 6 (75%) demonstrated reductions by > or = 10 points. No significant changes in comorbid symptoms were demonstrated. Sedation, weight gain, increased appetite, dry mouth, and transient asymptomatic hypoglycemia were the most common side effects. Tic improvements were maintained in 3 patients reassessed 6 months later. Final olanzapine dosages ranged from 2.5 mg to 20 mg daily (mean = 10.9 mg/day). CONCLUSION: This open-label study suggests that olanzapine should be explored as a potential alternative to conventional neuroleptic medications for treatment of motor tics and Tourette's disorder.

Adult↗

PubMed2001

Changes in serum interleukin-8 and interleukin-12 levels in patients with ischemic heart disease in a Chinese population.

Increasing evidence has indicated the important roles of inflammation and immune response in the development of atherosclerosis and ischemic heart disease (IHD). We measured the serum interleukin (IL)-8 and IL-12 levels of patients with unstable angina pectoris (UAP) and patients with acute myocardial infarction (AMI), and compared findings with those of normal subjects. The results showed that the serum level of IL-8 was significantly higher in patients with UAP and patients with AMI than in healthy control subjects. To our knowledge, this is the first report that serum IL-12 level was elevated in patients with AMI but not in patients with UAP. These findings suggest that IL-8 and IL-12 are involved in the process of IHD, and serum IL-12 may be a marker for differentiating AMI from UAP.

Aged↗