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Biomedical subjects

Q Cheng

Publications and source records attributed to Q Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2002

Identification of molecular markers for the early detection of human squamous cell carcinoma of the uterine cervix.

To identify novel cellular genes that could potentially act as predictive molecular markers for human cervical cancer, we employed RT--PCR differential display, reverse Northern and Northern blot analysis to compare the gene expression profiles between squamous cell carcinoma biopsies and adjacent histo-pathological normal epithelium tissues. Twenty-eight cDNA clones were isolated that were demonstrated to be consistently over-expressed in squamous cell cervical cancer biopsies of FIGO stages 1B to 3B. Most importantly, it was observed that, in addition to their over-expression in cancer lesions, some of these genes are upregulated in the presumably histo-pathological normal adjacent tissues. Of particular interest is clone G30CC that has been identified to be the gene that encodes S12 ribosomal protein. When employed for RNA--RNA in situ hybridization experiments, expression of G30CC could be detected in the immature basal epithelial cells of histo-pathological normal tissues collected from cervical cancer patients of early FIGO stages. In comparison, the expression of G30CC was not detected in cervical tissues collected from patients admitted for surgery of non-malignant conditions. These results allow the distinct possibility of employing the ribosomal protein S12 gene as an early molecular diagnostic identifier for the screening of human cervical cancer and a potential target employed for cancer gene therapy trials.

Biomarkers, Tumor↗
PubMed2002

Cloning and functional expression of a fat body-specific chitinase cDNA from the tsetse fly, Glossina morsitans morsitans.

A chitinase cDNA, GChit1 was isolated from Glossina morsitans morsitans and shown to be specifically expressed in fat body tissue. GChit1 is encoded by a 1.6 kb mRNA with a putative open reading frame (ORF) of 460 amino acids (predicted pI=7.5, m.w.=51kDa) that contains a signal peptide domain and two potential N-linked glycosylation sites. The ORF exhibits homology to various chitinases characterized from insects. It has the conserved catalytic site residues and the cysteine-rich 3'-end domain associated with chitin binding although the serine/threonine rich domain is apparently missing. Southern blot data indicate that GChit1 is present as a single-copy locus in the Glossina genome. Northern analysis indicates that transcripts for GChit1 can be detected only from the fat body of adult flies. Similarly, chitinase activity could be detected in fat body but not in the gut or salivary gland tissues. The full-length cDNA was expressed in vitro in Drosophila S2 cells and the molecule was produced in a soluble form. Polyclonal antibodies raised against recGChit1 could recognize a protein of about 50 kDa in adult fat body extracts. In addition to fat body, chitinase protein was detected by Western analysis from the milk gland tissue of pregnant females as well as from the intrauterine larval and pupal developmental stages. No chitinase specific mRNA transcripts could be observed, however from larvae and pupae. The intrauterine larva of tsetse may receive the protein from its mother via the milk gland route. The molecular characteristics of GChit and its product and the potential role of this chitinase in tsetse biology are discussed.

Acetylglucosamine↗
PubMed2002

Tumor prevention by 9-cis-retinoic acid in the N-nitroso-N-methylurea model of mammary carcinogenesis is potentiated by the pineal hormone melatonin.

Our laboratory has demonstrated that treatment of MCF-7 breast cancer cells with melatonin (Mlt) followed 24h later with physiological concentrations of all-trans retinoic acid (atRA) results in apoptosis. These studies were extended into trials using the N-nitroso-N-methylurea (NMU)-induced rat mammary tumor model. Initial studies conducted by feeding the animals 9-cis-retinoic acid (9cRA in the chow) and administering melatonin by subcutaneous injection in the late afternoon demonstrated that the combination of Mlt and 9cRA was able to significantly prevent tumor development, and that the combination was more efficacious that either Mlt or 9cRA alone. In this report, we conducted studies to determine if lower doses of 9cRA could be used in combination with Mlt while still maintaining anti-tumor activity and if the route of administration of 9cRA (bolus (gavage) v.s. chronic (chow) routes) affected its interaction with Mlt. The studies presented here demonstrate that significantly reduced doses of 9cRA can be used in combination with Mlt while maintaining anti-tumor efficacy. Furthermore, our studies demonstrate that 9cRA is equally effective when it is administered chronically (chow) or as a bolus (gavage). These data demonstrate that the combined use of Mlt and 9cRA produces additive or synergistic effects, which are more efficacious than 9cRA alone. This combination of Mlt and 9cRA could be a potentially useful clinical treatment regimen for breast cancer since it allows the use of lower doses of retinoic acid, thus, avoiding the toxic side effects associated with the use of high dose retinoids.

Administration, Oral↗
PubMed2002

Molecular characterization of three gut genes from Glossina morsitans morsitans: cathepsin B, zinc-metalloprotease and zinc-carboxypeptidase.

Insect gut enzymes are involved in digestion of dietary proteins. Additionally, these enzymes have been implicated in the process of pathogen establishment in several insects including the tsetse fly (Diptera:Glossinidae), which is the vector for African trypanosomes. Both the male and female tsetse can transmit trypanosomes and are strict blood feeders during all stages of their development. Here, we describe the molecular characterization of three gut genes: cathepsin B (GmCatB), zinc-metalloprotease (GmZmp) and zinc-carboxypeptidase (GmZcp). The cDNA for GmCatB encodes a protein for 340 amino acids with a predicted molecular mass of 38.2 kDa, while the 854 bp GmZmp cDNA encodes a protein of 254 amino acids with a molecular mass of 29 kDa. The GmZcp cDNA is 1319 bp in length and has a 354 amino acids open reading frame for coding a 40 kDa protein. All three cDNAs have signal peptide sequences associated with their N-terminal domains and structure analysis indicates that GmCatB and GmZmp are expressed as zymogens with pro-domains proteolytically removed for activity. The activation domain associated with the carboxypeptidase sequences is lacking in GmZcp. While GmCatB transcription is constitutive, teneral flies express very low levels of transcripts for GmZmp and GmZcp prior to the first bloodmeal. Transcription of all genes is induced and remains high throughout the digestion cycle within a few hours following the first bloodmeal ingestion. Both GmCatB and GmZcp are parasite responsive, with the expression of both genes being higher in trypanosome infected flies.

Amino Acid Sequence↗
PubMed2001

Chemoprevention of NMU-induced rat mammary carcinoma with the combination of melatonin and 9-cis-retinoic acid.

In experimental trials using the N-nitroso-N-methylurea (NMU)-induced rat mammary tumor model, a significant decrease in tumor incidence (to 5%) was observed in rats treated with melatonin and 9-cis-retinoic acid (9 cRA) compared to controls (55%). Although 9cRA alone decreased tumor incidence to 26%, this response did not reach statistical significance. Tumor incidence was significantly inhibited to 20% in the animals that received melatonin and 9cRA on alternating days. Latency to tumor onset was prolonged in animals receiving either of the combination treatments compared with controls, and tumor multiplicity was also significantly decreased.

Adenocarcinoma↗
PubMed2001

Model for a factor IX activation complex on blood platelets: dimeric conformation of factor XIa is essential.

Human coagulation factor XI (FXI) is a plasma serine protease composed of 2 identical 80-kd polypeptides connected by a disulfide bond. This dimeric structure is unique among blood coagulation enzymes. The hypothesis was tested that dimeric conformation is required for normal FXI function by generating a monomeric version of FXI (FXI/PKA4) and comparing it to wild-type FXI in assays requiring factor IX activation by activated FXI (FXIa). FXI/PKA4 was made by replacing the FXI A4 domain with the A4 domain from prekallikrein (PK). A dimeric version of FXI/PKA4 (FXI/PKA4-Gly326) was prepared as a control. Activated FXI/PKA4 and FXI/PKA4-Gly326 activate factor IX with kinetic parameters similar to those of FXIa. In kaolin-triggered plasma clotting assays containing purified phospholipid, FXI/PKA4 and FXI/PKA4-Gly326 have coagulant activity similar to FXI. The surface of activated platelets is likely to be a physiologic site for reactions involving FXI/FXIa. In competition binding assays FXI/PKA4, FXI/PKA4-Gly326, and FXI have similar affinities for activated platelets (K(i) = 12-16 nM). In clotting assays in which phospholipid is replaced by activated platelets, the dimeric proteins FXI and FXI/PKA4-Gly326 promote coagulation similarly; however, monomeric FXI/PKA4 has greatly reduced activity. Western immunoblot analysis confirmed that activated monomeric FXI/PKA4 activates factor IX poorly in the presence of activated platelets. These findings demonstrate the importance of the dimeric state to FXI activity and suggest a novel model for factor IX activation in which FXIa binds to activated platelets by one chain of the dimer, while binding to factor IX through the other.

Blood Coagulation↗
PubMed2001

Suppression of neuronal hyperexcitability and associated delayed neuronal death by adenoviral expression of GABA(C) receptors.

The excessive neuronal excitation underlying several clinically important diseases is often treated with GABA allosteric modulators in an attempt to enhance inhibition. An alternative strategy would be to enhance directly the sensitivity of postsynaptic neurons to GABA. The GABA(C) receptor, normally found only in the retina, is more sensitive to GABA and demonstrates little desensitization compared with the GABA(A) receptor. We constructed an adenovirus vector that expressed cDNA for both the GABA(C) receptor rho(1) subunit and a green fluorescent protein (GFP) reporter and used it to transduce cultured hippocampal neurons. Transduced neurons were identified by fluorescence, double immunocytochemistry proved colocalization of the rho(1) protein and the reporter, Western blot verified the expected molecular masses, and electrophysiological and pharmacological properties confirmed the presence of functional GABA(C) receptors. rho(1)-GFP transduction resulted in an increased density of GABA(A) receptors as well as expression of novel GABA(C) receptors. This effect was not reproduced by addition of TTX or Mg(2+) to the culture medium to reduce action potentials or synaptic activity. In a model of neuronal hyperexcitability induced by chronic blockade of glutamate receptors, expression of GABA(C) receptors abolished the hyperactivity and the consequent delayed neuronal death. Adenovirus-mediated neuronal GABA(C) receptor engineering, via its dual mechanism of inhibition, may offer a way of inhibiting only those hyperexcitable neurons responsible for clinical problems, avoiding the generalized nervous system depression associated with pharmacological therapy.

Action Potentials↗
PubMed2001

Modulating artificial membrane morphology: pH-induced chromatic transition and nanostructural transformation of a bolaamphiphilic conjugated polymer from blue helical ribbons to red nanofibers.

Design and characterization of helical ribbon assemblies of a bolaamphiphilic conjugated polymer and their color-coded transformation into nanofibers are described. An L-glutamic acid modified bolaamphiphilic diacetylene lipid was synthesized and self-assembled into right-handed helical ribbons with micron scale length and nano scale thickness under mild conditions. The ribbon structures were further stabilized by polymerizing well-aligned diacetylene units to form bisfunctional polydiacetylenes (PDAs). Transitions from flat sheets to helical ribbons and tubes were observed by transmission electron microscopy. The helical ribbons appear to originate from the rupture of flat sheets along domain edges and the peeling off between stacked lipid layers. These results point to the applicability of chiral packing theory in bolaamphiphilic supramolecular assemblies. Contact mode atomic force microscopy observations revealed that high order existed in the surface packing arrangement. Hexagonal and pseudorectangular packings were observed in flat and twisted regions of the ribbons, respectively, suggesting a correlation between microscopic morphologies and nanoscopic packing arrangements. The tricarboxylate functionalities of the bolaamphiphilic lipid provide a handle for the manipulation of the bisfunctional PDAs' morphology. Increasing solution pH caused the fraying of helical ribbons into nanofibers accompanied by a sharp blue-to-red chromatic transition. A dramatic change in circular dichroism spectra was observed during this process, suggesting the loss of chirality in packing. A model is proposed to account for the pH-induced morphological change and chromatic transition. The color-coded transition between two distinct microstructures would be useful in the design of sensors and other "smart" nanomaterials requiring defined molecular templates.

Acetylene↗
PubMed2001

Adsorptive behavior and electrochemical determination of the anti-fungal agent ketoconazole.

The adsorptive properties and electrochemical behavior of ketoconazole, an oral anti-fungal agent, are demonstrated at a glassy carbon electrode. The adsorption of the compound obeys the Frumkin isotherm with an interaction factor (alpha) of 0.985 and adsorptive coefficient (beta) of 1.98 x 10(6) L mol(-1). The Gibbs energy of adsorption (deltaG) is -3.59 x 10(4) J mol(-1) at 25 degrees C. A very sensitive electroanalytical method has been developed for determination of the drug with a detection limit of 4.0 x 10(-11) mol L(-1). Relationships between stripping current and concentration of ketoconazole were linear in the range 10(-6)-10(-10) mol L(-1) with different preconcentration periods. The method has been used to measure the ketoconazole content of tablets.

Adsorption↗
PubMed2001

Molecular characterization of two serine proteases expressed in gut tissue of the African trypanosome vector, Glossina morsitans morsitans.

Serine proteases are major insect gut enzymes involved in digestion of dietary proteins, and in addition they have been implicated in the process of pathogen establishment in several vector insects. The medically important vector, tsetse fly (Diptera:Glossinidiae), is involved in the transmission of African trypanosomes, which cause devastating diseases in animals and humans. Both the male and female tsetse can transmit trypanosomes and both are strict bloodfeeders throughout all stages of their development. Here, we describe the characterization of two putative serine protease-encoding genes, Glossina serine protease-1 (Gsp1) and Glossina serine protease-2 (Gsp2) from gut tissue. Both putative cDNA products represent prepro peptides with hydrophobic signal peptide sequences associated with their 5'-end terminus. The Gsp1 cDNA encodes a putative mature protein of 245 amino acids with a molecular mass of 26 428 Da, while the predicted size of the 228 amino acid mature peptide encoded by Gsp2 cDNA is 24 573 Da. Both deduced peptides contain the Asp/His/Ser catalytic triad and the conserved residues surrounding it which are characteristic of serine proteases. In addition, both proteins have the six-conserved cysteine residues to form the three-cysteine bonds typically present in invertebrate serine proteases. Based on the presence of substrate specific residues, the Gsp1 gene encodes a chymotrypsin-like protease while Gsp2 gene encodes for a protein with trypsin-like activity. Both proteins are encoded by few loci in tsetse genome, being present in one or two copies only. The mRNA expression levels for the genes do not vary extensively throughout the digestive cycle, and high levels of mRNAs can be readily detected in the gut tissue of newly emerged flies. The levels of trypsin and chymotrypsin activities in the gut lumen increase following blood feeding and change significantly in the gut cells throughout the digestion cycle. Hence, the regulation of expression for trypsin and chymotrypsin occurs at the post-transcriptional level in tsetse. Both the coding sequences and patterns of expression of Gsp1 and Gsp2 genes are similar to the serine proteases that have been reported from the bloodfeeding insect Stomoxys calcitrans.

Amino Acid Sequence↗
PubMed2001

Identification of genes required for excision of CTnDOT, a Bacteroides conjugative transposon.

Integrated self-transmissible elements called conjugative transposons have been found in many different bacteria, but little is known about how they excise from the chromosome to form the circular intermediate, which is then transferred by conjugation. We have now identified a gene, exc, which is required for the excision of the Bacteroides conjugative transposon, CTnDOT. The int gene of CTnDOT is a member of the lambda integrase family of recombinases, a family that also contains the integrase of the Gram-positive conjugative transposon Tn916. The exc gene was located 15 kbp from the int gene, which is located at one end of the 65 kbp element. The exc gene, together with the regulatory genes, rteA, rteB and rteC, were necessary to excise a miniature form of CTnDOT that contained only the ends of the element and the int gene. Another open reading frame (ORF) in the same operon and upstream of exc, orf3, was not essential for excision and had no significant amino acid sequence similarity to any proteins in the databases. The deduced amino acid sequence of the CTnDOT Exc protein has significant similarity to topoisomerases. A small ORF (orf2) that could encode a small, basic protein comparable with lambda and Tn916 excision proteins (Xis) was located immediately downstream of the CTnDOT int gene. Although Xis proteins are required for excision of lambda and Tn916, orf2 had no effect on excision of the element. Excision of the CTnDOT mini-element was not affected by the site in which it was integrated, another difference from Tn916. Our results demonstrate that the Bacteroides CTnDOT excision system is tightly regulated and appears to be different from that of any other known integrated transmissible element, including those of some Bacteroides mobilizable transposons that are mobilized by CTnDOT.

Amino Acid Sequence↗
PubMed2001

Study on examinee's dose delivered in computed tomography.

Dose profiles are presented resulting from computed tomography (CT). The profiles are positioned at the central axis, 1 cm away from the outer surface of the phantom, for single and multiple scans. A Hitachi W-1000 scanner is used with a thermoluminescent dosimeter (TLD), and standard dosimetry head and trunk phantoms. Regression equations are found linking the dose resulting from scattered radiation associated with a single scan to the distance from the scanning centre. The impact on the CT dose index value (CTDI) for varying integrating lengths is analysed. Some problems associated with CT dose measurement are noted, which may assist in the practical application of IBSS (International Basic Standard of Radiation Protection and Safety of Radiation Sources) guide levels.

Abdomen↗
PubMed2001

Antibody against surface-bound C5a peptidase is opsonic and initiates macrophage killing of group B streptococci.

The capsular polysaccharides of group B streptococci (GBS) are a primary focus of vaccine development. Immunogenicity and long-lasting protection are best achieved by conjugating polysaccharides to a T-cell-dependent protein antigen. Streptococcal C5a peptidase (SCPB) is a conserved surface protein that is expressed by all streptococcal serotypes tested to date, and it is a possible carrier protein that could itself induce a protective immune response. Clearance of GBS from lungs, mucosal surfaces, or blood probably depends on the opsonophagocytic response of tissue-specific macrophages and polymorphonuclear leukocytes (PMNs). In this study, we examined the potential of antibody directed against SCPB from a serotype II strain to enhance the capacity of mouse bone marrow macrophages (from primary cultures) and human PMNs in whole blood to kill GBS in vitro. Our experiments demonstrated that Streptococcus serotypes Ia, Ib, II, III, and V, preopsonized with anti-SCPB antibody, were killed more rapidly by cultured macrophages and PMNs in whole blood than were nonopsonized GBS. The increased rate of killing was accompanied by an increased macrophage oxidative burst. Furthermore, opsonization was serotype transparent. Immunization with SCPB conjugated to capsular polysaccharide type III produced polysaccharide-specific antibodies. It is interesting that this antiserum promoted serotype-independent killing of streptococci. These data support the use of SCPB in a GBS polysaccharide conjugate vaccine. SCPB not only enhanced the immunogenicity of polysaccharide components of the vaccine, but it might also induce additional serotype-independent protective antibodies.

Adhesins, Bacterial↗
PubMed2001

Cloning and characterization of a gene cluster for cyclododecanone oxidation in Rhodococcus ruber SC1.

Biological oxidation of cyclic ketones normally results in formation of the corresponding dicarboxylic acids, which are further metabolized in the cell. Rhodococcus ruber strain SC1 was isolated from an industrial wastewater bioreactor that was able to utilize cyclododecanone as the sole carbon source. A reverse genetic approach was used to isolate a 10-kb gene cluster containing all genes required for oxidative conversion of cyclododecanone to 1,12-dodecanedioic acid (DDDA). The genes required for cyclododecanone oxidation were only marginally similar to the analogous genes for cyclohexanone oxidation. The biochemical function of the enzymes encoded on the 10-kb gene cluster, the flavin monooxygenase, the lactone hydrolase, the alcohol dehydrogenase, and the aldehyde dehydrogenase, was determined in Escherichia coli based on the ability to convert cyclododecanone. Recombinant E. coli strains grown in the presence of cyclododecanone accumulated lauryl lactone, 12-hydroxylauric acid, and/or DDDA depending on the genes cloned. The cyclododecanone monooxygenase is a type 1 Baeyer-Villiger flavin monooxygenase (FAD as cofactor) and exhibited substrate specificity towards long-chain cyclic ketones (C11 to C15), which is different from the specificity of cyclohexanone monooxygenase favoring short-chain cyclic compounds (C5 to C7).

Amino Acid Sequence↗
PubMed2001

GABA(C) rho(1) subunits form functional receptors but not functional synapses in hippocampal neurons.

The ability to control the physiological and pharmacological properties of synaptic receptors is a powerful tool for studying neuronal function and may be of therapeutic utility. We designed a recombinant adenovirus to deliver either a GABA(C) receptor rho(1) subunit or a mutant GABA(A) receptor beta(2) subunit lacking picrotoxin sensitivity [beta2(mut)] to hippocampal neurons. A green fluorescent protein (GFP) reporter molecule was simultaneously expressed. Whole cell patch-clamp recordings demonstrated somatic expression of both bicuculline-resistant GABA(C) receptor-mediated and picrotoxin-resistant GABA(A) receptor-mediated GABA-evoked currents in rho(1)- and beta(2)(mut)-transduced hippocampal neurons, respectively. GABAergic miniature inhibitory postsynaptic currents (mIPSCs) recorded in the presence of 6-cyano-7-nitroquinoxalene-2,3-dione, Mg(2+), and TTX revealed synaptic events with monoexponential activation and biexponential decay phases. Despite the robust expression of somatic GABA(C) receptors in rho(1)-neurons, no bicuculline-resistant mIPSCs were observed. This suggested either a kinetic mismatch between the relatively brief presynaptic GABA release and slow-activating rho(1) receptors or failure of the rho(1) subunit to target properly to the subsynaptic membrane. Addition of ruthenium red, a presynaptic release enhancer, failed to unmask GABA(C) receptor-mediated mIPSCs. Short pulse (2 ms) application of 1 mM GABA to excised outside-out patches from rho(1) neurons proved that a brief GABA transient is sufficient to activate rho(1) receptors. The simulated-IPSC experiment strongly suggests that if postsynaptic GABA(C) receptors were present, bicuculline-resistant mIPSCs would have been observed. In contrast, in beta(2)(mut)-transduced neurons, picrotoxin-resistant mIPSCs were observed; they exhibited a smaller peak amplitude and faster decay compared with control. Confocal imaging of transduced neurons revealed rho(1) immunofluorescence restricted to the soma, whereas punctate beta(2)(mut) immunofluorescence was seen throughout the neuron, including the dendrites. Together, the electrophysiological and imaging data show that despite robust somatic expression of the rho(1) subunit, the GABA(C) receptor fails to be delivered to the subsynaptic target. On the other hand, the successful incorporation of beta(2)(mut) subunits into subsynaptic GABA(A) receptors demonstrates that viral transduction is a powerful method for altering the physiological properties of synapses.

Animals↗
PubMed2001

Four polyoxygenated cyclohexenes from the Chinese tree, Uvaria purpurea.

Two novel polyoxygenated cyclohexenes, 6-methoxyzeylenol (3) and 2-acetoxyzeylenone (4), together with two known compounds, zeylenol (1) and zeylenone (2), were isolated from the heartwood of the Chinese tree, Uvaria purpurea. Zeylenol (1) and zeylenone (2) both showed inhibitory activity toward the root growth of Lactuca sativa. Their structures were established by spectroscopic and chemical methods.

Annonaceae↗