Biomedical subjects

H Pan

Publications and source records attributed to H Pan.

At least 19 recordsLinked to original sources

PubMed2003

Effect of selective vs. non-selective cyclo-oxygenase inhibitors on fetal membrane prostaglandin synthesis.

Increased expression of the inducible isoform of cyclo-oxygenase (COX-2) and prostaglandin output from fetal membranes is a key stage in human parturition. Prostaglandin production can be inhibited by non-steroidal anti-inflammatory drugs (NSAIDs), but these may also inhibit cyclo-oxygenase enzymes in fetal tissues, and hence cause potentially serious side effects. We have compared the concentrations of NSAIDs that inhibit maximal PGE2 synthesis from intact human fetal membrane explants in vitro with those found in human plasma after standard anti-inflammatory treatment. The concentrations of all six drugs that caused a 50% inhibition of fetal membrane prostaglandin output were lower than average plasma levels achieved during treatment. This effect was greatest for nimesulide and indomethacin, indicating that these drugs require further study at low doses in vivo, as this could achieve the same tocolytic effect with diminished adverse fetal effect. These drugs were also the most potent inhibitors of fetal membrane prostaglandin output, consistent with their effects on COX-2 activity.

Adult↗

PubMed2002

The gene expression sequence of radiated mucosa in an animal mucositis model.

Oral mucositis is a common, dose-limiting, acute toxicity of radiation therapy administered for the treatment of cancers of the head and neck. Accumulating data would suggest that the pathogenesis of mucositis is complex and involves the sequential interaction of all cell types of the oral mucosa, as well as a number of cytokines and elements of the oral environment. While a number of studies have reported on gene expression of particular cell types in response to radiation, the overall response of irradiated mucosa has only been evaluated in a limited way. The present study was undertaken to evaluate the expression of a target group of genes using RNA quantification assays and, more broadly, to assess patterns of mucosal gene expression using DNA microarray hybridization. Our results demonstrate the sequential upregulation of a series of genes that, when taken collectively, suggest an intricate functional interaction.

Animals↗

PubMed2001

Modulation of endothelial cell growth arrest and apoptosis by vascular endothelial growth inhibitor.

Vascular endothelial growth inhibitor (VEGI), a new member of the tumor necrosis factor family, is an endothelial cell-specific gene and a potent inhibitor of endothelial cell proliferation, angiogenesis, and tumor growth. We report here that VEGI mediates the following two activities in endothelial cells: early G(1) arrest in G(0)/G(1) cells responding to growth stimuli, and programmed death in proliferating cells. G(0)/G(1)-synchronized bovine aortic endothelial cells were treated with VEGI before and after the onset of the growth cycle. When the cells were stimulated with growth conditions but treated simultaneously with VEGI, a reversible, early-G(1) growth arrest occurred, evidenced by the lack of late G(1) markers such as hyperphosphorylation of the retinoblastoma gene product and upregulation of the c-myc gene. Additionally, VEGI treatment led to inhibition of the activities of cyclin-dependent kinases CDK2, CDK4, and CDK6. In contrast, VEGI treatment of cells that had entered the growth cycle resulted in apoptotic cell death, as evidenced by terminal deoxytransferase labeling of fragmented DNA, caspase 3 activation, and annexin V staining, all of which were lacking in nonproliferating cells treated with VEGI. Additionally, stress-signaling proteins p38 and JNK were not as fully activated by VEGI in quiescent as compared with proliferating populations. These findings suggest a dual role for VEGI, the maintenance of growth arrest and induction of apoptosis, in the modulation of the endothelial cell cycle.

Animals↗

PubMed2001

Retention of multilineage differentiation potential of mesenchymal cells during proliferation in response to FGF.

Mesenchymal stem cells (MSC) that can differentiate to various connective tissue cells may be useful for autologous cell transplantation to defects of bone, cartilage, and tendon, if MSC can be expanded in vitro. However, a short life span of MSC and a reduction in their differentiation potential in culture have limited their clinical application. The purpose of this study is to identify a growth factor(s) involved in self-renewal of MSC and the maintenance of their multilineage differentiation potential. Fibroblast growth factor-2 (FGF-2) markedly increased the growth rate and the life span of rabbit, canine, and human bone marrow MSC in monolayer cultures. This effect of FGF-2 was more prominent in low-density cultures than in high-density cultures. In addition, all MSC expanded in vitro with FGF-2, but not without FGF-2, differentiated to chondrocytes in pellet cultures. The FGF+ MSC also retained the osteogenic and adipogenic potential throughout many mitotic divisions. These findings suggest that FGFs play a crucial role in self-renewal of MSC.

Animals↗

PubMed2001

A novel member of the WD-repeat gene family, WDR11, maps to the 10q26 region and is disrupted by a chromosome translocation in human glioblastoma cells.

Allelic deletions of 10q25-26 and 19q13.3-13.4 are the most common genetic alterations in glial tumors. We have identified a balanced t(10;19) reciprocal translocation in the A172 glioblastoma cell line which involves both critical regions on chromosomes 10 and 19. In addition, loss of an entire copy of chromosome 10 has occurred in this cell line suggesting that the translocation event may provide a highly specific critical inactivating event in a gene responsible for tumorigenesis. Positional cloning of this translocation breakpoint resulted in the identification of a novel chromosome 10 gene, WDR11, which is a member of the WD-repeat gene family. The WDR11 gene is ubiquitously expressed, including normal brain and glial tumors. WDR11 is composed of 29 exons distributed over 58 kilobases and oriented towards the telomere. The translocation resulted in deletion of exon 5 and consequently fusion of intron 4 of WDR11 to the 3' untranslated region of a novel member, ZNF320, of the Krüppel-like zinc finger gene family. Since ZNF320 is oriented toward the centromere of chromosome 19, both genes appeared on the same derivative chromosome der(10). The chimeric transcript encodes the WDR11 polypeptide, which is truncated after the second of six WD-repeats. ZNF320 is also expressed in A172 cells, although it is not clear if the translocation affects the expression of the altered gene because of the presence of another unrearranged gene on chromosome 19. We suggest that, because of its localization in a region frequently showing LOH and the observation of inactivation of this gene in glioblastoma cells, WDR11 is a candidate gene for the frequently proposed tumor suppressor gene in 10q25-26 which is involved in tumorigenesis of glial and other tumors showing frequent alterations in the distal 10q region.

Alleles↗

PubMed2001

Maintenance of serotonin in the intestinal mucosa and ganglia of mice that lack the high-affinity serotonin transporter: Abnormal intestinal motility and the expression of cation transporters.

The enteric serotonin reuptake transporter (SERT) has been proposed to play a critical role in serotonergic neurotransmission and in the initiation of peristaltic and secretory reflexes. We analyzed potential compensatory mechanisms and enteric function in the bowels of mice with a targeted deletion of SERT. The guts of these animals were found to lack mRNA encoding SERT; moreover, high-affinity uptake of 5-HT into epithelial cells, mast cells, and enteric neurons was present in the SERT +/+ bowel but absent in the SERT -/- bowel. However, both the SERT +/+ gut and the -/- gut expressed molecules capable of transporting 5-HT, but with affinities and selectivity much lower than those of SERT. These included the dopamine transporter (DAT) and polyspecific organic cation transporters OCT-1 and OCT-3. DAT and OCT immunoreactivities were present in both the submucosal and myenteric plexuses, and the OCTs were also located in the mucosal epithelium. 5-HT was found in all of its normal sites in the SERT -/- bowel, which contained mRNA encoding tryptophan hydroxylase, but no 5-HT was present in the blood of SERT -/- animals. Stool water and colon motility were increased in most SERT -/- animals; however, the increase in motility (diarrhea) occasionally alternated irregularly with decreased motility (constipation). The watery diarrhea is probably attributable to the potentiation of serotonergic signaling in SERT -/- mice, whereas the transient constipation may be caused by episodes of enhanced 5-HT release leading to 5-HT receptor desensitization.

Animals↗

PubMed2001

[Role of mitochondrial lesion in pathogenesis of sporadic rett syndrome].

OBJECTIVE: To investigate the role of mitochondrial lesion in children with Rett syndrome (RTT). METHODS: The platelets from 6 cases with Rett syndrome and 9 normal controls were fused with mitochondrial DNA-lacking rho degrees cell by polyethylene glycol-mediated fusion technique. The oxygen free radical was evaluated by the polarography with substrates of vitamine C and TMPD (N, N, N', N'-tetramethyl-p-phenlene diamine). The rate of apoptosis was determinated by flow cytometry. The apoptosis was observed by electronic microscope and TUNEL method. The t test between groups was adopted in study. RESULTS: In RTT patients, the anticyano-respiration significantly increased by 23% (t = 4.76, P < 0.01). After 6-hour coincubation with 100 micromol/L H(2)O(2), the rate of apoptosis is (3.6 +/- 1.1) % in normal control, and (9.9 +/- 2.7) % in RTT group with significant difference (t = 6.30, P < 0.01), the existence of apoptosis was confirmed by electronic microscope and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling (TUNEL). CONCLUSION: After mitochondrial DNA transfer, the oxygen free radical increased in mitochondrial respiratory chain in cybrids of RTT children. RTT cybrid cell lines demonstrated an increased sensitivity to H(2)O(2)-induced apoptotic cell death as compared to control cybrids. The mitochondrial lesion might play a role in the pathogenesis of Rett syndrome.

Apoptosis↗

PubMed2001

Regions of microsynteny in Magnaporthe grisea and Neurospora crassa.

A bacterial artificial chromosome (BAC) clone containing 110,467 bp of genomic DNA from Magnaporthe grisea was sequenced, annotated, and compared to the genomes of Neurospora crassa, Candida albicans, and Saccharomyces cerevisiae. Twenty-six open reading frames (ORFs), involved in multiple biochemical pathways, were identified in the BAC sequence. A region of 53 kb, containing 18 of the 26 ORFs, was found to be syntenic to a portion of the N. crassa genome. Subregions of complete colinearity as well as interrupted colinearity were present. No synteny was evident with either C. albicans or S. cerevisiae. The identification of syntenic regions containing highly conserved genes across two genera that have been evolutionarily separated for approximately 200 million years elicits many biological questions as to the function and identity of these genes.

Candida albicans↗

PubMed2001

Cloning, mapping, and characterization of a human homologue of the yeast longevity assurance gene LAG1.

We have identified LASS2, a previously unknown human homologue of the yeast longevity assurance gene LAG1. The LASS2 transcript is highly expressed in liver and kidney, which is very different from the expression of the previously identified human LAG1 homologue LAG1Hs-1. Radiation hybrid mapping studies indicated that LASS2 is located on chromosome 1q11. Yeast two-hybrid screening and glutathione S-transferase pull-down assays showed that the LASS2 protein interacts with several membrane-associated receptors or transporters. Furthermore, LASS2 protein was able to inhibit the colony formation of human hepatoma cells in vitro, which suggests that this gene may be involved in the regulation of cell growth.

Amino Acid Sequence↗

PubMed2001

Haplotype analysis of the myotonic dystrophy type 1 (DM1) locus in Taiwan: implications for low prevalence and founder mutations of Taiwanese myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disorder caused by a CTG trinucleotide expansion at the DM1 locus. In this study, we investigated the frequency distribution of various CTG repeats in normal alleles and haplotyped the normal and expanded DM1 locus in a group of Taiwanese people. In the 496 normal chromosomes examined, up to 18 alleles with different CTG lengths from 5 to 30 repeats were found and the frequency of (CTG)(>18) alleles was only 1.4% (7/496), predicting a low prevalence of DM1. In addition, there is no absolute association between (CTG)(5-19) alleles and Alu insertion/deletion polymorphism observed on normal chromosomes. All DM1 alleles examined, however, were found to be associated with the Alu insertion. Further detailed genetic analysis demonstrated that at least eight haplotypes, including a new haplotype (L), were present in the Taiwanese population and that all DM1 alleles were with the same haplotype (haplotype A) as that identified in Canadian and Japanese DM1 populations. These findings support the notion that the out-of-Africa DM1 alleles were originated by stepwise expansion from a pool of large-sized normal chromosomes with haplotype A.

Alleles↗

PubMed2001

Analysis of the cat eye syndrome critical region in humans and the region of conserved synteny in mice: a search for candidate genes at or near the human chromosome 22 pericentromere.

We have sequenced a 1.1-Mb region of human chromosome 22q containing the dosage-sensitive gene(s) responsible for cat eye syndrome (CES) as well as the 450-kb homologous region on mouse chromosome 6. Fourteen putative genes were identified within or adjacent to the human CES critical region (CESCR), including three known genes (IL-17R, ATP6E, and BID) and nine novel genes, based on EST identity. Two putative genes (CECR3 and CECR9) were identified, in the absence of EST hits, by comparing segments of human and mouse genomic sequence around two solitary amplified exons, thus showing the utility of comparative genomic sequence analysis in identifying transcripts. Of the 14 genes, 10 were confirmed to be present in the mouse genomic sequence in the same order and orientation as in human. Absent from the mouse region of conserved synteny are CECR1, a promising CES candidate gene from the center of the contig, neighboring CECR4, and CECR7 and CECR8, which are located in the gene-poor proximal 400 kb of the contig. This latter proximal region, located approximately 1 Mb from the centromere, shows abundant duplicated gene fragments typical of pericentromeric DNA. The margin of this region also delineates the boundary of conserved synteny between the CESCR and mouse chromosome 6. Because the proximal CESCR appears abundant in duplicated segments and, therefore, is likely to be gene poor, we consider the putative genes identified in the distal CESCR to represent the majority of candidate genes for involvement in CES.

Abnormalities, Multiple↗

PubMed2001

Hippocampal and anterior cingulate activation deficits in patients with geriatric depression.

OBJECTIVE: The authors assessed frontotemporal function in patients with geriatric depression, a debilitating and increasingly prevalent disorder that has not been examined with brain activation paradigms. METHOD: Six depressed elderly patients and five healthy comparison subjects underwent high-sensitivity [(15)O]H(2)O positron emission tomography scans during a paced word generation task and a resting condition. RESULTS: Bilateral activation deficits were noted in the dorsal anterior cingulate gyrus and hippocampus of the depressed geriatric patients relative to the comparison subjects. Patients had memory deficits that correlated with lower hippocampal activity during both rest and activation. CONCLUSIONS: These initial findings suggest that hippocampal and dorsal anterior cingulate hypoactivation may constitute contributing neural substrates of geriatric depression. They also suggest that hippocampal dysfunction is related to the memory dysfunction characteristic of this disorder.

Age Factors↗

PubMed2001

Delineation of CTG repeats and clinical features in a Taiwanese myotonic dystrophy family.

Myotonic dystrophy (DM) is an inherited, autosomal dominant muscular disease which is primarily caused by a CTG trinucleotide expansion mutation on chromosome 19q13.3. The size of this trinucleotide repeat is related both to the age of onset and to the severity of the clinical manifestation. This disease is very rare in Taiwan, and clinical and genetic study on DM has not yet been documented in this area. Here, we present both clinical features and degrees of CTG expansion for a Taiwanese DM family. All of the DM patients examined in this family showed obvious clinical manifestations by age 30, which included facial and limb muscle weakness with atrophy, myotonia, and ptosis. In addition, individual DM members also exhibited variable phenotypes, which may reflect the complexity of the pathogenic mechanism. Because the collection of blood specimens was considered to be an invasive procedure, a genetic study on this DM family was performed using buccal cells. Our results confirmed that four members showing classic symptoms of DM had CTG repeat expansion in the DMI locus, and that one member with ptosis and minor muscle weakness in the right foot was a normal homozygote for CTG repeat. These data demonstrate that buccal cells can provide clear and reliable results, and thus, are suitable for a family study of DM.

Alleles↗

PubMed2001

[Establishment of platelet-mediated transmitochondrial cell model].

OBJECTIVE: To establish a transmitochondrial cell model for further researches on molecular genetics of mitochondrial related disease. METHODS: The fusion process was conducted between mitochondrial DNA-lacking rho degrees cell (a gift from NIH) and platelet using polyethylene glycol as fusion promoting reagent. The fusion cells were confirmed by PCR and electronic microscopic cytochemistry. The mitochondrial morphology and function of 3 families of Rett syndrome were investigated. RESULTS: The platelet-mediated transmitochondrial cell model was constructed successfully. The frequency of transformation ranged from 0.5 to 1.6 clones in 10(4) recipient cells. The mitochondrial vacuolation was occasionally observed in 2 cases of Rett syndrome. CONCLUSION: Transmitochondrial cell model can be applied to assessment of the mitochondrial morphology and function of fusion cells and is found to be of great use in evaluating the gene expression of mitochondrial genome at different levels.

Blood Platelets↗

PubMed2001

[Identification of Amomum villosum, Amomum villosum var. xanthioides and Amomum longiligulare on ITS-1 sequence].

OBJECTIVE: To identify Amomum villosum Lour. and some their adulterants on molecular biology. METHOD: The DNA of Amomum villosum Lour. and some their adulterants were extracted, and amplified using ITS-1 primer. The amplificed DNA were purified and then sequenced by direct PCR sequencing method. RESULT: The ITS-sequence of all of the samples are 248 bp in size. But there are 7 bases in Amomum villosum Lour var. xanthioides (Wall.ex Bak) T.L. Wu et Senjen and 12 hases in Amomum longiligulare T.L. Wu. differing from Amomum villosum Lour. CONCLUSION: The ITS-1 sequence can be used to identify effectively Amomum villosum Lour. and their adulterants.

Amomum↗

PubMed2001

[DNA character of the cholesteatoma].

OBJECTIVE: To compare the DNA character with in cholesteatoma tissues with that in normal skin. METHOD: DNA content within 25 cholesteatoma tissues and 10 normal postauricular skin was measured with flow cytometry. RESULT: The content of cholesteatoma tissues and postauricular skin specimens are a normal euploid. The cell number during S phase of cholesteatoma (10.9 +/- 2.32)% was higher than that in normal skin(7.31 +/- 2.82)%. CONCLUSION: Although the cholesteatoma has a very high proliferating character, the result suggest it isn' t a malignant tumor.

Adolescent↗

PubMed2001

[Ion single channel signal restoration and parameters' estimation based on the hidden Markov models].

The single ion channel signal is stochastic ionic current on the order of 1 pA recorded by patch clamp. Because the weakness of the signal, the background noise always dominates in the recordings, the threshold detector traditionally used in patch clamp to denoise and restore the channel signal can't work satisfactorily. This problem was analyzed mathematically, and a signal restoring and parameters estimating scheme called HMM algorithm was studied. The algorithm has been validated by simulation and the results suggest it performs effectively in the situation of low signal to noise ratio where the threshold detector fails completely.

Algorithms↗

PubMed2000

Binding sites in Escherichia coli dihydrofolate reductase communicate by modulating the conformational ensemble.

To explore how distal mutations affect binding sites and how binding sites in proteins communicate, an ensemble-based model of the native state was used to define the energetic connectivities between the different structural elements of Escherichia coli dihydrofolate reductase. Analysis of this model protein has allowed us to identify two important aspects of intramolecular communication. First, within a protein, pair-wise couplings exist that define the magnitude and extent to which mutational effects propagate from the point of origin. These pair-wise couplings can be identified from a quantity we define as the residue-specific connectivity. Second, in addition to the pair-wise energetic coupling between residues, there exists functional connectivity, which identifies energetic coupling between entire functional elements (i.e., binding sites) and the rest of the protein. Analysis of the energetic couplings provides access to the thermodynamic domain structure in dihydrofolate reductase as well as the susceptibility of the different regions of the protein to both small-scale (e.g., point mutations) and large-scale perturbations (e. g., binding ligand). The results point toward a view of allosterism and signal transduction wherein perturbations do not necessarily propagate through structure via a series of conformational distortions that extend from one active site to another. Instead, the observed behavior is a manifestation of the distribution of states in the ensemble and how the distribution is affected by the perturbation.

Binding Sites↗