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Biomedical subjects

Y A Zhang

Publications and source records attributed to Y A Zhang.

At least 19 recordsLinked to original sources
PubMed2003

Characterization of cDNA encoding immunoglobulin light chain of the mandarin fish (Siniperca chuatsi).

Immunoglobulin light chain cDNA sequences of a perciform fish, the mandarin fish Siniperca chuatsi were amplified from head kidney mRNA by reverse transcription (RT)-PCR and RACE methods using degenerated primer and gene specific ones. In cDNA sequences of the VL region, nucleotide exchanges were present mainly within CDRs, although a lesser degree of variability was also found in FRs. Moreover, the length of CDR1 and CDR3 in the mandarin fish is shorter than in most other fish species. In the middle of S. chuatsi CL region, a microsatellite sequence (AGC)(6-8) was found, which is also present in another perciform species, the spotted wolffish (Anarhichas minor). The comparison of amino acid sequence of the mandarin fish CL domain with those of other vertebrates showed the highest degree of similarity of 94.5% to the spotted wolffish, while the similarity with rainbow trout (Oncorhynchus mykiss) Ig L1 (62.7%) and channel catfish (Ictalurus punctatus) Ig LG (55.9%) isotypes is also higher. However, there is only 50% identity in the VL regions between the mandarin fish and the wolffish. The sequence similarity of the mandarin fish CL domain with those of higher vertebrate did not readily allow it to be classified as kappa or lambda isotype. The phylogenetic analyses also demonstrated that the CL genes of the mandarin fish and most other teleost fish cluster as a separate branch out of the mammal kappa and lambda branches.

Amino Acid Sequence↗
PubMed2003

Genetic differentiation in populations of the cestode Bothriocephalus acheilognathi (Cestoda, Pseudophyllidea) as revealed by eight microsatellite markers.

The genetic structure of populations of the fish cestode, Bothriocephalus acheilognathi collected from Bailianhe Reservoir (BLH), Changshou (CSH) and Liangzi (LZH) Lakes was investigated by using 8 microsatellite loci. A total of 108 adult worms were genotyped at each of the 8 loci. For the 3 populations, the mean number of alleles per locus ranged from 2.38 to 5.5, and the mean expected heterozygosity ranged from 0.432 to 0.559. The average polymorphic information content (PIC) was from 0.384 to 0.492. The significant Fis values indicated non-random mating within LZH and BLH populations. On the other hand, when samples were further classified into subpopulations at the level of host fish species, no or little heterozygote deficiency was detected at most loci, showing that cross-fertilization, predominantly, but not exclusively, must have occurred within the subpopulations. Microsatellite markers also revealed an unexpected high level of genetic differentiation, as measured by R(st) and N(m) values or by delta(u)2 genetic distance among subpopulations from different hosts. Factors influencing the population genetic structure and the parasite host specificity are discussed.

Alleles↗
PubMed2002

Molecular variation of Bothriocephalus acheilognathi Yamaguti, 1934 (Cestoda: Pseudophyllidea) in different fish host species based on ITS rDNA sequences.

The molecular variation in Bothriocephalus acheilognathi Yamaguti, 1934 from 11 species of freshwater fish collected in Australia, China, the Czech Republic, England and Hawaii was investigated by determining the nucleotide sequences of the internal transcribed spacer region. The length of the first and second internal transcribed spacer sequences of multiple individuals ranged from 553 to 571 bp and 553 to 615 bp, and the G + C content from 53.1 to 53.5%. The percentage sequence divergence varied between 0 and 0.9% in the ITS1 and 0 and 6.6% in the ITS2, respectively, indicating the occurrence of intraspecific variation. It is demonstrated that the fragment length variation resulted primarily from microsatellite polymorphisms present in the ITS region, especially in the ITS2 region. Phylogenetic analyses revealed that B. acheilognathi examined in this study consisted of three closely related genotypes with certain degrees of host-specificity, and the genotype representing isolates from Cyprinus carpio L. was the most common and diverse form within the species B. acheilognathi.

Animals↗
PubMed2001

Potential clinical application of antioncogene ribozymes for human lung cancer.

Non-small-cell lung cancer frequently contains oncogenetic defects (mutations in ras, retinoblastoma, and p53 genes) that contribute to disease pathophysiology. Recent studies and clinical trials have focused on gene therapy approaches that either replace the function of defective tumor-suppressor genes such as p53 or inactivate mutant oncogenes such as ras. Ribozymes are RNA molecules with highly specific intrinsic enzymatic activity against target RNA sequences, which can discriminate mutant sequences that differ by a single base from their wild-type counterparts. Following binding to the RNA substrate by base-pair complementation, the ribozyme cleaves the target RNA irreversibly, then releases itself for new rounds of subsequent cleavage, resulting in significantly improved target:effector stoichiometry as compared with antisense oligonucleotides of the same specificity. Transcript-specific ribozymes have been used extensively for experimental oncogene inactivation. Ribozymes are effective for targeting mutant ras, p53, or the multidrug-resistant gene product for lung cancer cells in vitro. However, their in vivo effect is not well defined against this malignancy. We recently characterized the antitumor properties of an anti-K-ras ribozyme specific for the K-ras codon 12 mutation (GGT-->GTT). When delivered as a transgene by an adenoviral vector (ADV), the K-ras ribozyme (KRbz) suppressed growth of lung tumor xenografts expressing the relevant mutation, whereas the corresponding antisense sequence lacking catalytic activity did not. Multiple intratumoral (3-5) injections of KRbz-ADV were effective in producing complete tumor regressions of preexisting tumor xenografts. Clinical trials are under consideration to examine the applicability of this anti-K-ras ribozyme for treatment of non-small-cell lung cancers expressing the relevant mutation.

Journal Article↗
PubMed2000

Occurrence of Bothriocephalus acheilognathi in cyprinid fish from three lakes in the flood plain of the Yangtze River, China.

Cyprinid fish, Hemiculter leucisculus, Cultrichthys erythropterus and Culter dabryi, were sampled from Liangzi, Honghu and Tangxun lakes in the flood plain of the Yangtze River. The cestode Bothriocephalus acheilognathi Yamaguti, 1934 was found in the 3 lakes, but C. erythropterus sampled from Liangzi lake was found uninfected due probably to the small sample size. Findings of the cestode in the 3 lakes represent the first record of the parasite in the flood plain of the Yangtze River, indicating that B. acheilognathi may be distributed much wider in China than previously recognized.

Animals↗
PubMed2000

Cortical degeneration in the absence of neurotrophin signaling: dendritic retraction and neuronal loss after removal of the receptor TrkB.

To examine functions of TrkB in the adult CNS, TrkB has been removed from neurons expressing CaMKII, primarily pyramidal neurons, using Cre-mediated recombination. A floxed trkB allele was designed so that neurons lacking TrkB express tau-beta-galactosidase. Following trkB deletion in pyramidal cells, their dendritic arbors are altered, and cortical layers II/III and V are compressed, after which there is an apparent loss of mutant neurons expressing the transcription factor SCIP but not of those expressing Otx-1. Loss of neurons expressing SCIP requires deletion of trkB within affected neurons; reduction of neuronal ER81 expression does not, suggesting both direct and indirect effects of TrkB loss. Thus, TrkB is required for the maintenance of specific populations of cells in the adult neocortex.

Animals↗
PubMed2000

Characteristics of the inhibitory effect of calmodulin on specific [125i]omega-conotoxin GVIA binding to crude membranes from chick brain.

The characteristics of the inhibitory effect of calcium ion (Ca2+)/calmodulin (CaM) on specific [125I]-omega-conotoxin GVIA (125I-omega-CTX) binding and on the labeling of 125I-omega-CTX to crude membranes from chick brain were investigated. The inhibitory effect of Ca2+/CaM depended on the concentrations of free Ca2+ and CaM. The IC50 values for free Ca2+ and CaM were about 2.0 x 10(-8) M and 3.0 microg protein/ml, respectively. The inhibitory effect of Ca2+/CaM was attenuated by the CaM antagonists W-7, prenylamine and CaM-kinase II fragment (290-309), but not by the calcineurin inhibitor FK506. Ca2+/CaM also inhibited the labeling of a 135-kDa band (which was considered to be part of N-type Ca2+ channel alpha1 subunits) with 125I-omega-CTX using a cross-linker. These results suggest that Ca2+/CaM affects specific 125I-omega-CTX binding sites, probably N-type Ca2+ channel alpha1 subunits, in crude membranes from chick whole brain.

Animals↗
PubMed2000

Anti-tumorigenic effect of a K-ras ribozyme against human lung cancer cell line heterotransplants in nude mice.

Approximately 15-30% of human non-small cell lung cancers (NSCLC) carry K-ras mutations, among which point mutations at codon 12 are the most common. This study characterizes the anti-tumor effect of an anti-K-ras ribozyme adenoviral vector (KRbz-ADV; replication-deficient, E1-deleted Ad5 backbone) against NSCLC lines that express the relevant mutation (K-ras codon 12 GGT --> GTT; H441 and H1725). KRbz-ADV significantly inhibited tumor cell growth (38-94% reduction by 3H-thymidine uptake) in a time- and dose-dependent manner, but produced minimal growth inhibition on normal epithelial cells, or NSCLC H1650 cells that lack the relevant mutation. The in vivo anti-tumorigenic effect of KRbz-ADV treatment was characterized with cell line xenografts in nu/nu mice. Pre-treatment with KRbz-ADV (10 or 20 p.f.u. per cell) completely abrogated subcutaneous engraftment of H441 (n = 13) or H1725 cells (n = 8), as compared with a 100% tumor take and progressive tumor growth in animals that received untreated tumor cells, or control vector (luciferase-adenovirus/Luc-ADV)-treated tumor cells. Pre-treatment with a mutant anti-K-ras ribozyme adenoviral vector (mutKRbz-ADV), which has the same specificity as KRbz but lacks ribozyme catalytic activity, did not produce an anti-tumorigenic effect. The in vivo effect of KRbz-ADV treatment was further examined by initiating injections (2 x 10(9) p.f.u.) at 7 days after tumor induction. Pre-existing tumor growth was reduced by 39% by a single intratumoral injection. Repeat injections (three or five KRbz-ADV-intratumoral injections at 2 x 10(9) p.f.u. every other day) resulted in complete tumor regression in five of seven mice. In contrast, single or multiple injections of control vector Luc-ADV did not significantly alter tumor xenograft outcome. Ribozyme expression was confirmed in H441 cells that demonstrated reduced growth after KRbz-ADV treatment. Reduced growth corresponded to significantly lowered levels of K-ras mRNA, as defined by RT-PCR (51% of untreated level, n = 3) and RNase protection assay (56% of untreated level, n = 4) analyses. Further, 37.5% of KRbz-ADV-treated cells underwent apoptosis, as compared with 11.7%, and 19.0% in untreated and Luc-ADV-treated cultures, respectively. A significantly higher proportion of KRbz-ADV-treated H441 cells (58.2%) underwent apoptosis when maintained under anchor-independent conditions that simulate in vivo tumorigenesis ('anoikis'). This is the first report that demonstrates that KRbz-ADV can effectively inhibit in vivo tumorigenesis, and produces regression of pre-existing human lung tumor xenografts having the relevant K-ras mutation.

Adenoviridae↗
PubMed2000

Inhibitory effects of tetrahydroisoquinoline derivatives on Ca2+ and Na+ channels in crude nerve endings.

Semi-synthetic tetrahydroisoquinoline derivatives prepared from natural alkaloids, possess Ca2+ antagonistic properties. These derivatives significantly blocked KCl-stimulated Ca2+ uptake (In chick and rat crude nerve endings) which can be partially inhibited by the selective N-type Ca2+ channel blocker omega-conotoxin GVIA or the selective P-type Ca2+ channel blocker omega-agatoxin IVA. Moreover, PX42 (10 microM; for the tetrahydroisoquinoline compounds in this study) could inhibit the activity of calmodulin-dependent phosphodiesterase and block veratridine-induced (or tetrodotoxin-sensitive) Na+ uptake. The possible mechanism(s) of non-selective inhibition of ion channels of PX42 is discussed.

Animals↗
PubMed2000

Generation of a ribozyme-adenoviral vector against K-ras mutant human lung cancer cells.

ras mutations represent one of the most common oncogenetic lesions in human non-small cell lung cancer (NSCLC) and adversely affect the survival of patients afflicted with this disease. ras-directed gene therapy in the past employed primarily antisense oligonucleotides (AS-ODN) or expression vectors (such as a viral vector construct) that deliver the antisense sequence to inactivate the mutant oncogene message. These approaches produced minimal toxicity, and yet were limited in efficacy. Ribozymes present a viable alternative in antisense therapy by virtue of their renewable catalytic capability for site-specific RNA cleavage. We recently produced an adenoviral vector with a hammerhead ribozyme transgene (KRbz) that is specific for the K-ras codon 12 mutant sequence GUU, given the considerations that (a) in the United States, approx 30% of human NSCLCs express K-ras oncogene mutations, nearly all of which reside in codon 12; (b) anti-K-ras, anti-H, as well as anti-N-ras hammerhead ribozymes are potent growth inhibitors in various human cancers tested; and (c) in vitro and animal model studies suggest that ribozymes directed at oncogene (K- and H-ras C-fos, BCR-ABL) or human immunodeficiency viral gene messages are more effective than their antisense counterpart. This article describes the techniques involved in the production of the KRbz-adenoviral vector that is specific for the K-ras mutation GTT, and summarizes its in vivo antitumor effect against NSCLC xenografts expressing the relevant K-ras mutation in athymic mice.

Carcinoma, Non-Small-Cell Lung↗
PubMed1999

Experience of urgent reconstruction of electrical injuries.

Although there have been great advances in the treatment of electrical injuries in the last 20 years, the extremity loss ratio in electrical injuries remains at an unacceptably high level. The primary reason for this is the progressive tissue necrosis and enlargement of the necrosis in the wound. The goal in this study is to examine possible ways to break the necrotic malignancy circle and save the form and function of damaged extremities. As a result of systematic experimental and clinical research, a comprehensive urgent reconstruction alternative for electrical injuries has been proposed. The alternative includes the following principles: debriding the wound as early as possible after injury; preserving as much as possible the vital tissue structures, such as nerve, vessels, joints, tendons, and bone, even when they have undergone devitalization or local necrosis; transplanting these vital tissues during the first surgery if the functional reconstruction requires; nourishing the wound bed by covering with tissue flaps that have rich blood supply; improving flap survival by continuous irrigations with a compound medicine beneath the flaps for a 24- to 72-hour period after surgery; providing general treatment with vasoactive agents and antibiotics. This paper summarizes our experience of using this method in the treatment of 105 electrical injury patients (a total of 309 wounds) in the time period from 1 January 1986 to 31 December 1996. Satisfying results were obtained, with the extremity loss ratio decreasing to 7% as compared to 41.5% during the 10 years preceding 1984 at the same hospital. Thus, the urgent comprehensive reconstruction alternative presented here is an effective and workable method to manage electrical injuries.

Adolescent↗
PubMed1999

Cortical neurons require Otx1 for the refinement of exuberant axonal projections to subcortical targets.

Information processing in the nervous system depends on the creation of specific synaptic connections between neurons and targets during development. The homeodomain transcription factor Otx1 is expressed in early-generated neurons of the developing cerebral cortex. Within layer 5, Otx1 is expressed by neurons with subcortical axonal projections to the midbrain and spinal cord. Otx1 is also expressed in the precursors of these neurons, but is localized to the cytoplasm. Nuclear translocation of Otx1 occurs when layer 5 neurons enter a period of axonal refinement and eliminate a subset of their long-distance projections. Otx1 mutant mice are defective in the refinement of these exuberant projections, suggesting that Otx1 is required for the development of normal axonal connectivity and the generation of coordinated motor behavior.

Animals↗
PubMed1999

The inhibitory effect of the toxic fraction from sea urchin (Toxopneustes pileolus) venom on 45Ca2+ uptake in crude synaptosome fraction from chick brain.

The effects of toxic peaks (P-I, P-II and P-III eluted from Sephadex G-200 column) from the sea urchin Toxopneustes pileolus on time-dependent 45Ca2+ uptake in chick P2 fraction (crude synaptosome fraction) were studied under physiological ionic conditions. Time-dependent 45Ca2+ uptake was inhibited by P-II and P-III, but not by P-I. P-II had the greatest inhibitory effect. The inhibitory effect of P-II was not due to the inhibition of 45Ca2+ binding on P2 fraction, because P-II did not affect 45Ca2+ binding in osmotic-shocked P2 fraction. P-II did not affect KCl-stimulated 45Ca2+ uptake in P2 fraction, (Ca(2+)-Mg2+)-ATPase activity in the synaptic plasma membrane (SPM) fraction, or (Na(+)-K+)-ATPase and Mg(2+)-ATPase activities in osmotically-shocked P2 fraction. In contrast, the Na+/Ca2+ exchanger blocker 2',4'-dichlorobenzamil (DCB; 100 microM), with a poor specificity, inhibited not only time-dependent 45Ca2+ uptake but also KCl-stimulated 45Ca2+ uptake, (Ca(2+)-Mg2+)-ATPase, Mg(2+)-ATPase and (Na(+)-K+)-ATPase. Involvement of Na(+)-Ca2+ exchanger in the time-dependent 45Ca2+ uptake was ruled out, since it was not inhibited by replacement of Na+ with Li+ in reaction medium. These results suggested that the inhibition by P-II on time-dependent 45Ca2+ uptake appeared to be more specific than the commercially available Na+/Ca2+ exchanger blocker DCB, although the mechanism is not clear yet.

Animals↗
PubMed1998

Intrinsic polarity of mammalian neuroepithelial cells.

Progenitor cells in the mammalian forebrain can undergo either symmetric or asymmetric cell divisions by varying their cleavage orientation. In asymmetric divisions, cells distribute apically and basally localized proteins differentially to their daughters. Here we explore the intrinsic polarity of neuroepithelial cells in the developing telencephalon. Actin microfilaments are concentrated apically, forming beltlike structures that encircle spots of gamma-tubulin immunoreactivity. Staining for N-cadherin, beta-catenin, and the tyrosine kinase substrates pp120 and paxillin is also enriched at the lumenal surface, presumably due to the localization of these proteins at adherens junctions. Phosphotyrosine immunoreactivity is concentrated apically in rings, suggesting that adherens junctions are enriched for signaling molecules. In mitotic cells it appears that adherens junction proteins and phosphotyrosine immunoreactivity may be inherited either symmetrically or asymmetrically, depending on the cell's cleavage orientation during mitosis. The differential inheritance of junctional proteins may determine whether a daughter cell can respond to extrinsic signals after mitosis.

Actin Cytoskeleton↗
PubMed1997

Relationship between specific binding of 125I-omega-conotoxin GVIA and GTP binding protein: effects of the GTP analogues, mastoparan and A1F4-.

We investigated whether the specific binding or labeling of 125I-omega-CgTX on crude membranes from chick whole brain was affected when endogenous GTP binding protein (G protein) was activated by GTP analogues, mastoparan (MP) and aluminum fluoride (AIF4-; AICl3 + NaF). Both GTPgammaS and Gpp(NH)p attenuated the inhibitory effect of selective N-type Ca channel inhibitors such as aminoglycoside antibiotics (AGs) or dynorphine (1-13)(Dyn) on specific 125I-omega-CgTX binding in a dose-dependent manner. On the other hand, the inhibitory effects of the divalent metal cations Cd2+, Co2+, Mg2+ and Mn2- on such binding were not attenuated by GTPgammaS. MP and AIF4- also attenuated the inhibitory effect of Neo on this binding similar to GTPgammaS. The attenuating effect of MP was enhanced by the presence of Mg2+ in a dose-dependent manner. However, GTP analogues, MP and AIF4-, did not affect binding or labeling without AGs or Dyn. GTPgammaS, MP and AIF4- also attenuated the specific labeling of a 215-kDa band in crude membranes with 125I-omega-CgTX using the cross-linker DSS (non-reduced condition) in the presence of Neo. These results indicate that there are direct or indirect relationships between N-type Ca channels and G proteins via binding sites for AGs or MP.

Aluminum Compounds↗
PubMed1997

A GFP reporter system to assess gene transfer and expression in human hematopoietic progenitor cells.

Hematopoietic stem cells are widely recognized as attractive targets for gene therapy but current protocols to transduce these cells using recombinant retroviral vectors are inefficient. To evaluate optimization of retroviral transduction of hematopoietic stem cells and stability of gene expression in their progeny, the green fluorescent protein (GFP) was explored as a reporter. We first improved sensitivity of detection > 100-fold over that achieved previously by using a novel retroviral vector (termed MGIN) expressing a high level of an enhanced GFP gene. Primitive human hematopoietic cells bearing the CD34 surface antigen and lacking lineage differentiation markers (CD34+ Lin-) were transduced with the MGIN vector using a clinically applicable supernatant procedure. Under the conditions employed, > 75% of the target cells retained the CD34+ Lin- primitive phenotype after 4-5 days in culture, of those > or = 25% expressed a high level of GFP detectable by both flow cytometric analysis and fluorescence microscopy. When transduced cells were cultured in clonogenic progenitor assays, GFP fluorescence was readily detected in situ, indicating that GFP expression was stable and not detrimental to the differentiative potential of the transduced CD34+ Lin- cells. We conclude that GFP is effective as a vital marker to quantity retrovirus-mediated gene transfer into human hematopoietic and perhaps other types of stem/progenitor cells, and monitor gene expression during their subsequent cell lineage determinations.

Antigens, CD34↗
PubMed1995

Enzymatic and immunologic identification of succinic semialdehyde dehydrogenase in rat and human neural and nonneural tissues.

We have identified succinic semialdehyde dehydrogenase protein in rat and human neural and nonneural tissues. Tissue localization was determined by enzymatic assay and by western immunoblotting using polyclonal antibodies raised in rabbit against the purified rat brain protein. Although brain shows the highest level of succinic semialdehyde dehydrogenase activity, substantial amounts of enzyme activity occur in mammalian liver, pituitary, heart, and ovary. We further demonstrate the absence of succinic semialdehyde dehydrogenase enzyme activity and protein in brain, liver, and kidney tissue samples from an individual affected with succinic semialdehyde dehydrogenase deficiency, thereby verifying the specificity of our antibodies.

Aldehyde Oxidoreductases↗