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Biomedical subjects

M Wu

Publications and source records attributed to M Wu.

At least 127 records · Page 7Linked to original sources
PubMed2000

The effect of preoperative transcatheter hepatic arterial chemoembolization on disease-free survival after hepatectomy for hepatocellular carcinoma.

BACKGROUND: Although surgical resection has produced better results than other therapies for local control of hepatocellular carcinoma (HCC), the long term results have not been satisfactory because of a low disease-free survival rate. The effects of preoperative transcatheter arterial chemoembolization (TACE) on improving disease-free survival of HCC after hepatectomy has remained controversial. METHODS: The current study was retrospective survey of 1725 patients who had hepatectomy for HCC between January 1990 and December 1995 and had follow-up data for 1457 cases. The follow-up rate was 84.5%. The significant prognostic factors were analyzed using a Cox proportional hazards survival model, and the disease-free survival was calculated by Kaplan-Meier estimation. Among 1457 cases, 120 patients underwent preoperative TACE and were divided into a one time TACE group, over two times TACE group, an effective group, and ineffective group. RESULTS: Multivariate analyses revealed significant prognostic factors as follows: preoperative TACE number, preoperative TACE effect, preoperative lesion number, intraoperative tumor thrombus, tumor size, tumor gross type, daughter nodules, vascular invasion, and postoperative alpha-fetoprotein value. Kaplan-Meier estimation showed that the 5-year disease-free survival rates of the over two times group, the one time group, and no TACE group were 51.0%, 35.5%, and 21.4%, respectively, and that the mean disease-free survival times of the three groups were 66.4, 22.5 and 12.5 months, respectively. The effective group had a 5-year disease-free survival rate of 56.8%, with a mean time of 90.1 months. CONCLUSIONS: Effective preoperative TACE may be one of the best methods, which can be clinically performed at present, for resectable HCCs including small HCCs for improving disease-free survival after hepatectomy. According to tumor size, range, location, hepatic function, and TACE effect, TACE can be performed 2-4 times preoperatively within 6 months.

Adolescent↗
PubMed2000

Strengthened arm-dimerization domain interactions in AraC.

Constitutive mutations were sought and found in the N-terminal arm of the Escherichia coli regulatory protein of the arabinose operon, AraC protein. A new mutation, N16D, was of particular interest. Asn-16 is not seen in the crystal structure of the AraC dimerization domain determined in the absence of arabinose, because the N-terminal arm 18 residues are disordered, but in the presence of arabinose, residues 7-18 fold over the arabinose and make many interactions with it. In this state Asn-16 lies near two positively charged amino acids, Lys-43 and Arg-99. We propose that the introduction of the negatively charged aspartic residue at position 16 creates a charge-charge interaction network among Asp-16, Lys-43, and Arg-99 that holds the arm to the dimerization domain even in the absence of arabinose. This frees the DNA-binding domains and allows them to bind cis to I(1)-I(2) half-sites and activate transcription. Mutating the two positively charged residues to alanines individually and collectively decreased or eliminated the constitutivity created by the N16D mutation.

AraC Transcription Factor↗
PubMed2000

Novel human esophagus-specific gene c1orf10: cDNA cloning, gene structure, and frequent loss of expression in esophageal cancer.

We have identified a novel human gene, designated C1orf10, using modified differential display PCR. The C1orf10 gene, which spans 5 kb in length, is composed of three exons. The deduced protein contains 495 amino acids with one transmembrane domain. The amino acid sequence of C1orf10 is characterized by the presence of a calcium-binding motif of about 90 amino acids at its N-terminal and a conserved consecutive repeat sequence of 60 amino acids that was identified previously only in bacterial ice nucleation proteins. In normal adult tissues, C1orf10 is highly expressed only in the esophagus and was undetectable in a total of 15 other tissues examined, suggesting its important role in esophageal cells. The expression of C1orf10 is either dramatically reduced or absent in esophageal cancer cell lines (3/3) as well as primary esophageal cancer tissues (35/37) compared with the corresponding normal esophageal mucosa. Using a radiation hybrid panel, C1orf10 was found to be located on chromosome 1q21. These findings suggest that expression of C1orf10 is unique to esophageal cells and that loss of its expression may play a role in the development of esophageal cancer.

Adult↗
PubMed2000

Muscarinic tone sustains impulse flow in the septohippocampal GABA but not cholinergic pathway: implications for learning and memory.

Systemic infusions of the muscarinic cholinergic receptor antagonists atropine and scopolamine (atr/scop) produce an amnesic syndrome in humans, subhuman primates, and rodents. In humans, this syndrome may resemble early symptoms of Alzheimer's disease. Behavioral studies in rats have demonstrated that the medial septum/diagonal band of Broca (MSDB), which sends cholinergic and GABAergic projections to the hippocampus, is a critical locus in mediating the amnesic effects of atr/scop. The amnesic effects of atr/scop in the MSDB have been presumed but not proven to be caused by a decrease in hippocampal acetylcholine (ACh) release after blockade of a muscarinic tone in the MSDB. Using electrophysiological recordings and fluorescent-labeling techniques to identify living septohippocampal neurons in rat brain slices, we now report that, contrary to current belief, a blockade of the muscarinic tone in the MSDB does not decrease impulse flow in the septohippocampal cholinergic pathway; instead, it decreases impulse flow in the septohippocampal GABAergic pathway via M(3) muscarinic receptors. We also report that the muscarinic tone in the MSDB is maintained by ACh that is released locally, presumably via axon collaterals of septohippocampal cholinergic neurons. As such, cognitive deficits that occur in various neurodegenerative disorders that are associated with a loss or atrophy of septohippocampal cholinergic neurons cannot be attributed solely to a decrease in hippocampal acetylcholine release. An additional, possibly more important mechanism may be the concomitant decrease in septohippocampal GABA release and a subsequent disruption in disinhibitory mechanisms in the hippocampus. Restoration of impulse flow in the septohippocampal GABA pathway, possibly via M(3) receptor agonists, may, therefore, be critical for successful treatment of cognitive deficits associated with neurodegenerative disorders such as Alzheimer's and Parkinson's disease.

Acetylcholine↗
PubMed2000

Down-regulation of the Diphthamide biosynthesis protein 2-like gene during retinoid-induced differentiation and apoptosis: implications against its tumor-suppressor activity.

Retinoids, synthetic and natural analogs of retinoic acid (RA) have profound effects on the proliferation and differentiation of many cell types; this accounts for their beneficial effects in the treatment of certain neoplasias. We have employed mRNA differential display to characterize genes associated with differentiation and apoptosis induced by all-trans RA in human lung cancer cells. We have identified a cDNA corresponding to the sequence of the known gene diphthamide biosynthesis protein 2-like (DPH2L). Although the function of this gene remains unknown, as it was first isolated from the critical region of deletion on chromosome 17p13.3 in human ovarian carcinoma, it has been regarded as a candidate tumor-suppressor gene. In this report, we provide evidence that DPH2L is down-regulated during differentiation or apoptosis in several cancer cell lines after treatment with all-trans RA or N-(4-hydroxyphenyl)retinamide and during cell-cycle arrest. Moreover, stable expression of DPH2L-specific anti-sense construct leads to inhibition of cell proliferation. Our results suggest that DPH2L in not a conventional tumor-suppressor gene. Instead, it may be a growth regulator and its down-regulation might be permissive for the transition from cell growth to differentiation or apoptosis. DPH2L might be a useful tool in the prognosis of neoplastic diseases.

Adenosine Diphosphate Ribose↗
PubMed2000

Domain effects on the DNA-interactive properties of bacteriophage T4 gene 32 protein.

Bacteriophage T4 gene 32 protein, a model for single-strand specific nucleic acid-binding proteins, consists of three structurally and functionally distinct domains. We have studied the effects of the N and C domains on the protein structure and its nucleic acid-interactive properties. Although the presence of the C domain decreases the proteolytic susceptibility of the core (central) domain, quenching of the core tryptophan fluorescence by iodide is unaltered by the presence of the terminal domains. These results suggest that the overall conformation of the core domain remains largely independent of the flanking domains. Removal of the N or the C terminus does not abolish the DNA renaturation activity of the protein. However, intact protein and its three truncated forms differ in DNA helix-destabilizing activity. The C domain alone is responsible for the kinetic barrier to natural DNA helix destabilization seen with intact protein. Intact protein and core domain potentiate the DNA helix-destabilizing activity of truncated protein lacking only the C domain (*I), enhancing the observed hyperchromicity while increasing the melting temperature. Proteolysis experiments suggest that the affinity of core domain for single-stranded DNA is increased in the presence of *I. We propose that *I can "mingle" with intact protein or core domain while bound to single-stranded DNA.

Bacteriophage T4↗
PubMed2000

In vitro nuclear reconstitution could be induced in a plant cell-free system.

A cell-free system derived from carrot cell cytosol extract has been developed for reassembling nuclear structure around the added demembranated sperm chromatin of Xenopus. Morphological evidence suggests that reassembled nuclei display the typical characteristics of normal eukaryotic nuclei, such as double-layered nuclear membrane and nuclear pores. Micrococcal nuclease treatment indicates that remodeling of the demembranated sperm chromatin has occurred and the structure of nucleosome is formed during nuclear reconstitution. These data indicate that the nuclear reconstitution can be induced in cell-free systems from plants, and the self-assembly of the nucleus is ubiquitous in both animal and plant cells.

Animals↗
PubMed2000

Induction of apoptosis in glioma cell lines by TRAIL/Apo-2l.

TRAIL/Apo-2L, a novel cytokine, is a member of the tumor necrosis factor (TNF) family and serves as an extracellular signal triggering apoptosis. TRAIL/Apo-2L is capable of killing various transformed cells but not unstimulated primary T cells. In this study, five human glioma cells (U87, U118, U178, U563, and A172) were examined for their susceptibility to the apoptotic effects of TRAIL/Apo-2L. TRAIL/Apo-2L cDNA was isolated by RT-PCR, and recombinant TRAIL/Apo-2L protein was purified by the pMAL-c2 system (New England Biolabs, Beverly, MA). Exposure of A172 cells to bacterially expressed soluble TRAIL/Apo-2L fusion protein at a concentration of 1 microg/ml resulted in significant cell death over a 24-h period. Three experiments were performed to suggest that the TRAIL/Apo-2L killing was through the induction of apoptosis of A172 target cells. In addition, the expression of TRAIL/Apo-2L in different glioma cells was found to be variable, and TRAIL/Apo-2L-induced apoptosis was in a cell type-dependent manner. Some correlation between the susceptibility to TRAIL/Apo-2L and the expression level of one of its cognate receptors, DR4, was observed. In addition, cycloheximide worked synergistically with TRAIL/Apo-2L to induce apoptosis in glioma cells.

Apoptosis↗
PubMed2000

Influence of the N-1 alkyl chain length of cannabimimetic indoles upon CB(1) and CB(2) receptor binding.

The N-1 alkyl side chain of the aminoalkylindole analogues (AAI) has been implicated as one of a three-point interaction with the cannabinoid CB(1) receptor. In this study, the morpholinoethyl of WIN 55,212-2 was replaced with carbon chains of varying lengths ranging from a methyl to heptyl group. Additional groups were added to the naphthoyl and the C2 positions of the molecule. These structural changes revealed that high affinity binding to the CB(1) and CB(2) receptors requires an alkyl chain length of at least three carbons with optimum binding to both receptors occurring with a five carbon side chain. An alkyl chain of 3-6 carbons is sufficient for high affinity binding; however, extension of the chain to a heptyl group results in a dramatic decrease in binding at both receptors. The unique structure of the cannabimimetic indoles provides a useful tool to define the ligand-receptor interaction at both cannabinoid receptors and to refine proposed pharmacophore models.

Animals↗
PubMed2000

An integrated deletion and physical map encompassing l71Rl, a chromosome 7 locus required for peri-implantation survival in the mouse.

l71Rl, a locus that maps just proximal to the pink-eyed dilution (p) locus in mouse chromosome 7, was initially identified as being required for early post-implantation survival. We define further the null phenotype of l71Rl as peri-implantation lethal, with homozygous mutant embryos degenerating between embryonic day 4.5 (E4.5) and E5. 5. We constructed an integrated deletion/physical map covering a 1. 82-Mb chromosomal segment extending proximally from p. This map defines the minimum critical interval for l71Rl as an 80- to 300-kb region. This sequence-ready deletion/physical map should enable the cloning and characterization of the l71Rl gene(s).

Animals↗
PubMed2000

Segregation analysis of esophageal cancer in a moderately high-incidence area of northern China.

In order to explore the mode of inheritance of esophageal cancer in a moderately high-incidence area of northern China, we conducted a pedigree survey on 225 patients affected by esophageal cancer in Yangquan, Shanxi Province. Segregation analysis was performed using the REGTL program of S.A.G.E. The results showed that Mendelian autosomal recessive inheritance of a major gene that influences susceptibility to esophageal cancer provided the best fit to the data. In the best-fitting recessive model, the frequency of the disease allele was.2039. There was a significant sex effect on susceptibility to the disease. The maximum cumulative probability of esophageal cancer among males with the AA genotype was 100%, but, among females, it was 63.5%. The mean age at onset for both men and women was 62 years. The age-dependent penetrances for males with the AA genotype by the ages of 60 and 80 years were 41.6% and 95.2%, respectively, whereas, for females, they were 26.4% and 60.5%, respectively. Incorporating environmental risk factors-such as cigarette smoking, pipe smoking, alcohol drinking, eating hot food, and eating pickled vegetables-into the models did not provide significant improvement of the fit of the models to these data. The results suggest a major locus underlying susceptibility to esophageal cancer with sex-specific penetrance.

Adult↗
PubMed2000

Cholinergic excitation of septohippocampal GABA but not cholinergic neurons: implications for learning and memory.

The medial septum/diagonal band (MSDB), which gives rise to the septohippocampal pathway, is a critical locus for the mnemonic effects of muscarinic drugs. Infusion of muscarinic cholinergic agonists into the MSDB enhance learning and memory processes both in young and aged rats and produce a continuous theta rhythm in the hippocampus. Intraseptal muscarinic agonists also alleviate the amnesic syndrome produced by systemic administration of muscarinic receptor antagonists. It has been presumed, but not proven, that the cellular mechanisms underlying the effects of muscarinic agonists in the MSDB involve an excitation of septohippocampal cholinergic neurons and a subsequent increase in acetylcholine (ACh) release in the hippocampus. Using a novel fluorescent labeling technique to selectively visualize live septohippocampal cholinergic neurons in rat brain slices, we have found that muscarinic agonists do not excite septohippocampal cholinergic neurons, instead they inhibit a subpopulation of cholinergic neurons. In contrast, unlabeled neurons, confirmed to be noncholinergic, septohippocampal GABA-type neurons using retrograde marking and double-labeling techniques, are profoundly excited by muscarine. Thus, the cognition-enhancing effects of muscarinic drugs in the MSDB cannot be attributed to an increase in hippocampal ACh release. Instead, disinhibitory mechanisms, caused by increased impulse flow in the septohippocampal GABAergic pathway, may underlie the cognition-enhancing effects of muscarinic agonists.

Acetylcholine↗
PubMed2000

Conformationally constrained substance P analogues: the total synthesis of a constrained peptidomimetic for the Phe7-Phe8 region.

A lactam-based peptidomimetic for the Phe7-Phe8 region of substance P has been synthesized. The synthesis used an anodic amide oxidation to selectively functionalize the C5-position of a 3-phenylproline derivative. The resulting proline derivative was coupled to a Cbz-protected phenylalanine, and an intramolecular reductive amination strategy used to convert the coupled material into a bicyclic piperazinone ring skeleton. The net result was a dipeptide building block that imbedded one of two proposed receptor bound conformations for the Phe7-Phe8 region of substance P into a bicyclic ring skeleton. The building block was then converted into a constrained substance P analogue with the use of solid-phase peptide synthesis. A similar intramolecular reductive amination strategy was used to synthesize a substance P analogue having only Phe7 constrained, and the original 3-phenylproline was converted into a substance P analogue having only Phe8 constrained. All of the analogues were examined for their ability to displace substance P from its NK-1 receptor.

Binding, Competitive↗
PubMed2000

Actin-dependent propulsion of endosomes and lysosomes by recruitment of N-WASP.

We examined the spatial and temporal control of actin assembly in living Xenopus eggs. Within minutes of egg activation, dynamic actin-rich comet tails appeared on a subset of cytoplasmic vesicles that were enriched in protein kinase C (PKC), causing the vesicles to move through the cytoplasm. Actin comet tail formation in vivo was stimulated by the PKC activator phorbol myristate acetate (PMA), and this process could be reconstituted in a cell-free system. We used this system to define the characteristics that distinguish vesicles associated with actin comet tails from other vesicles in the extract. We found that the protein, N-WASP, was recruited to the surface of every vesicle associated with an actin comet tail, suggesting that vesicle movement results from actin assembly nucleated by the Arp2/3 complex, the immediate downstream target of N-WASP. The motile vesicles accumulated the dye acridine orange, a marker for endosomes and lysosomes. Furthermore, vesicles associated with actin comet tails had the morphological features of multivesicular endosomes as revealed by electron microscopy. Endosomes and lysosomes from mammalian cells preferentially nucleated actin assembly and moved in the Xenopus egg extract system. These results define endosomes and lysosomes as recruitment sites for the actin nucleation machinery and demonstrate that actin assembly contributes to organelle movement. Conversely, by nucleating actin assembly, intracellular membranes may contribute to the dynamic organization of the actin cytoskeleton.

Actins↗
PubMed2000

TNF-alpha induced over-expression of GFAP is associated with MAPKs.

Increased levels of tumor necrosis factor-alpha (TNF-alpha), a pluripotent cytokine that is reportedly mitogenic to astrocytes, are associated with the expression of glial fibrillary acidic protein (GFAP), the most specific marker for astrocytes, in many neuropathological conditions, including brain injury, CNS infection, Creutzfeldt-Jakob disease and Alzheimer's disease. Here, we show that treatment of cultured astrocytes with TNF-alpha resulted in dramatic over-expression of GFAP, associated with a substantial activation of the mitogen activated protein kinase (MAPK) Erk2 (extracellular signal-regulated protein kinase). We also demonstrate that TNF-alpha-induced over-expression of GFAP was significantly attenuated by the MAPK inhibitor PD98059. We conclude that TNF-alpha may upregulate GFAP through the MAPK signaling pathway. Because increased GFAP is a hallmark of reactive gliosis, understanding the mechanisms that regulate GFAP expression may facilitate development of strategies to minimize the gliosis associated with many brain diseases.

Animals↗
PubMed2000

c-Kit triggers dual phosphorylations, which couple activation and degradation of the essential melanocyte factor Mi.

Microphthalmia (Mi) is a bHLHZip transcription factor that is essential for melanocyte development and postnatal function. It is thought to regulate both differentiated features of melanocytes such as pigmentation as well as proliferation/survival, based on phenotypes of mutant mouse alleles. Mi activity is controlled by at least two signaling pathways. Melanocyte-stimulating hormone (MSH) promotes transcription of the Mi gene through cAMP elevation, resulting in sustained Mi up-regulation over many hours. c-Kit signaling up-regulates Mi function through MAP kinase phosphorylation of Mi, thereby recruiting the p300 transcriptional coactivator. The current study reveals that c-Kit signaling triggers two phosphorylation events on Mi, which up-regulate transactivation potential yet simultaneously target Mi for ubiquitin-dependent proteolysis. The specific activation/degradation signals derive from MAPK/ERK targeting of serine 73, whereas serine 409 serves as a substrate for p90 Rsk-1. An unphosphorylatable double mutant at these two residues is at once profoundly stable and transcriptionally inert. These c-Kit-induced phosphorylations couple transactivation to proteasome-mediated degradation. c-Kit signaling thus triggers short-lived Mi activation and net Mi degradation, in contrast to the profoundly increased Mi expression after MSH signaling, potentially explaining the functional diversity of this transcription factor in regulating proliferation, survival, and differentiation in melanocytes.

Animals↗