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Biomedical subjects

J Chu

Publications and source records attributed to J Chu.

At least 73 records · Page 4Linked to original sources
PubMed1999

A simple explanation for taxon abundance patterns.

For taxonomic levels higher than species, the abundance distributions of the number of subtaxa per taxon tend to approximate power laws but often show strong deviations from such laws. Previously, these deviations were attributed to finite-time effects in a continuous-time branching process at the generic level. Instead, we describe herein a simple discrete branching process that generates the observed distributions and find that the distribution's deviation from power law form is not caused by disequilibration, but rather that it is time independent and determined by the evolutionary properties of the taxa of interest. Our model predicts-with no free parameters-the rank-frequency distribution of the number of families in fossil marine animal orders obtained from the fossil record. We find that near power law distributions are statistically almost inevitable for taxa higher than species. The branching model also sheds light on species-abundance patterns, as well as on links between evolutionary processes, self-organized criticality, and fractals.

Animals↗
PubMed1999

Endothelial cell DNA transfer and expression using petri dish electroporation and the nonreplicating vaccinia virus/T7 RNA polymerase hybrid system.

The nonreplicating vaccinia virus MVA/T7 RNA polymerase hybrid system was tested with Petri dish electroporation for ectopic gene expression in human umbilical vein endothelial cells (HUVECs). A range of voltages (150-450 V), pulse times (10-40 ms), DNA concentrations (0-20 microg/ml) and infection levels (0-15 multiplicities of infection) were tested for effects on T7 promoter-directed chloramphenicol acetyltransferase (CAT) activity after MVA/T7RP infection. MVA/T7RP-directed expression was transient and at least 10 000-fold in excess of nonviral, cytomegalovirus enhancer-directed expression. Use of a Petri dish electrode with the MVA/T7RP system showed increased viability compared with a cuvette electrode. Overexpression of interleukin-2 alpha subunit (IL2Ralpha) pro- tein followed by anti-IL2Ralpha-directed magnetic immunoaffinity cell sorting allowed isolation of the transfected population. The high fidelity of cellular sorting was shown by segregation of CAT activity in the IL2Ralpha-sorted population after transfection of T7 promoter-directed bicistronic IL2Ralpha/CAT DNA. Expression of a panel of proteins including the fluorophore green fluorescent protein as detected by fluorescence microscopy and p21cip1, p27kip1, pp60c-src, FGF-1, pRb, p107 and pRb2/p130 proteins was also achieved. Thus, use of the nonreplicating vaccinia virus/T7 RNA polymerase expression system with Petri dish electroporation is feasible for certain applications for the manipulation of HUVECs by gene transfer.

Bacteriophage T7↗
PubMed1999

Distribution of two HIV-1-resistant polymorphisms (SDF1-3'A and CCR2-64I) in East Asian and world populations and its implication in AIDS epidemiology.

Chemokine receptor CCR2 and stromal-derived factor (SDF-1) are involved in HIV infection and AIDS symptom onset. Recent cohort studies showed that point mutations in these two genes, CCR2-64I and SDF1-3'A, can delay AIDS onset > or = 16 years after seroconversions. The protective effect of CCR2-64I is dominant, whereas that of SDF1-3'A is recessive. SDF1-3'A homozygotes also showed possible protection against HIV-1 infection. In this study, we surveyed the frequency distributions of the two alleles at both loci in world populations, with emphasis on those in east Asia. The CCR2-64I frequencies do not vary significantly in the different continents, having a range of 0.1-0.2 in most populations. A decreasing cline of the CCR2-64I frequency from north to south was observed in east Asia. In contrast, the distribution of SDF1-3'A in world populations varies substantially, and the highest frequency was observed in Oceanian populations. Moreover, an increasing cline of the SDF1-3'A frequency from north to south was observed in east Asia. The relative hazard values were computed to evaluate the risk of AIDS onset on the basis of two-locus genotypes in the east Asian and world populations.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age.

The timing and nature of the arrival and the subsequent expansion of modern humans into eastern Asia remains controversial. Using Y-chromosome biallelic markers, we investigated the ancient human-migration patterns in eastern Asia. Our data indicate that southern populations in eastern Asia are much more polymorphic than northern populations, which have only a subset of the southern haplotypes. This pattern indicates that the first settlement of modern humans in eastern Asia occurred in mainland Southeast Asia during the last Ice Age, coinciding with the absence of human fossils in eastern Asia, 50,000-100,000 years ago. After the initial peopling, a great northward migration extended into northern China and Siberia.

Africa↗
PubMed1999

Effects of epidermal growth factor and dibutyryl cyclic adenosine monophosphate on the migration pattern of astrocytes grafted into adult rat brain.

OBJECTIVE: Neonatal rat astrocytes transplanted into host brains migrate in specific patterns, which are determined by the developmental stage of the host brain and the region of implantation. We hypothesized that the differentiation state of the implanted astrocytes could also affect astrocyte migration. METHODS: Astrocytes derived from neonatal rats (1-4 d) were placed in culture and exposed to growth- or differentiation-promoting agents (e.g., epidermal growth factor or dibutyryl cyclic adenosine monophosphate). Treated cells were then injected into different regions of the adult rat brain. At 3, 6, and 9 days after implantation, the extent and pattern of astrocyte migration after injection into the cortex, hippocampus, and corpus callosum were assessed. RESULTS: Astrocytes pretreated with either factor did not migrate during the first 3 days after implantation into the host cortex and hippocampus, whereas untreated cells migrated extensively by Day 3. After 9 days, implanted cells that had been pretreated with dibutyryl cyclic adenosine monophosphate began to demonstrate migratory activity, whereas those exposed to epidermal growth factor remained at the site of implantation. These findings corresponded to the effects of these agents in culture. On the other hand, cells implanted into the corpus callosum migrated in spite of pretreatment. CONCLUSION: Epidermal growth factor and dibutyryl cyclic adenosine monophosphate each altered the cells in culture such that they were inhibited from migrating after transplantation into the host cortex and hippocampus. This finding suggests that the activation of either growth or differentiation cascades partially inhibits the migratory ability in these cells either through effects on their internal migratory potentials or their responsiveness to external migratory signals. In contrast, cells implanted into the corpus callosum migrated in spite of pretreatment, suggesting that this structure may present migratory cues sufficient to override the effects of treatment.

Animals↗
PubMed1999

Twitch-obtaining intramuscular stimulation (TOIMS) in acute partial radial nerve palsy.

Twitch Obtaining Intramuscular Stimulation (TOIMS) is useful in the management of chronic nerve-related pain. The best understanding of the mechanism of action of TOIMS can occur on treating acute nerve-related symptoms. An opportunity to use TOIMS treatments in an acute, partial left radial palsy within 24 hours of onset did occur. Following treatment to the affected triceps and brachioradialis muscles, there was an immediate improvement in the amplitude, area and conduction velocity of the left radial motor and sensory nerves at the lower arm level. There was also improvement in numbness and all symptoms abolished after four treatments. Serial multiple motor unit action potential (multi-MUAP) analysis performed in the triceps and extensor communis (EDC) showed signs of motor unit enlargement. The triceps MUAPs showed an increase in duration and size index (area/amplitude) by the 3rd month. Both parameters stabilized at 18 months. Phases increased at the 6th month only. In EDC, the size index increased progressively by the 3rd month. The duration increased at the 6th month with stabilization by the 18th month. Phases and turns increased on day 3 examination only. EDC showed reduction in the firing rate with time. By relaxing the muscles through the effects of intramuscular exercise and also by improving local ischemia, TOIMS averted prolonged conduction abnormalities and probably a more serious axonal injury.

Acute Disease↗
PubMed1999

[Genetic polymorphisms of five STR loci in a Chinese Han population].

OBJECTIVE: To understand the allele structure and genetic polymorphism at five STR loci in Chinese Han population, and construct a preliminary database. METHODS: EDTA-blood specimens were collected from the unrelated individuals. The DNA samples were extracted with Chelex method and were amplified by PCR technique. The PCR products were analyzed using both the PAGE horizontal electrophoresis with discontinuous buffer system and the automated fluorescence detection approach. RESULTS: Four STRs consist of simple repeat motifs, while one STR contains a complex repeat structure. The STR polymorphisms at all of the five loci have been observed in Chinese Han population. CONCLUSION: The obtained data are beneficial to understanding the population genetics of the five STR loci in Chinese Han population. As a simple approach, the PAGE horizontal electrophoresis can be employed for typing the five STR markers.

Alleles↗
PubMed1999

[Investigation of Y chromosome and polymorphism of 5 Chinese ethnic groups in Yunnan Province, China].

OBJECTIVE: To investigate the polymorphism of DYS287 in the Han, Dai, Lahu, Wa and Tibetan groups living in Yunnan Province, China. METHODS: YAP element was detected by PCR amplification and agarose gel electrophoresis. RESULTS: With 150bp product in all Han,Dai, Lahu and Wa individuals, YAP element is absent. In 11 Tibetan individuals out of 30, YAP element is present and the PCR product is 455bp. CONCLUSION: As an important and stable genetic marker, DYS287 can provide reliable evidence in evolution study.

China↗
PubMed1999

The role of the monopolar electromyographic pin in myofascial pain therapy: automated twitch-obtaining intramuscular stimulation (ATOIMS) and electrical twitch-obtaining intramuscular stimulation (ETOIMS).

OBJECTIVE: To show that the monopolar pin electrode has a role in the control of radiculopathy related myofascial pain and fibromyalgia using the automated twitch-obtaining intramuscular stimulation (ATOIMS) and electrical twitch-obtaining intramuscular stimulation (ETOIMS) methods. METHOD: A hand-held ATOIMS device facilitated the insertion, oscillation and retraction of the monopolar pin into motor end-plate regions. The device oscillated the pin at 2 Hz for three times in two seconds. ETOIMS method employed micro-stimulation at 2 Hz for two seconds/point. Obtaining muscle twitches were the goals of both treatments. This is a retrospective study of two patients with fibromyalgia who received these treatments. Patient #1 with chronic low back > neck pain, underwent treatments which included the L2-S1 myotomes and patient #2 with chronic neck pain > low back pain, received treatments to the bilateral C2-T1 myotomes. Both received treatments also to bilateral C3-S1 paraspinal muscles. Treatments to both began with ETOIMS for two months and five months respectively. Following this period, they both received ATOIMS and ETOIMS to the same muscles in the same treatment session. The combined procedure sessions continued for the same treatment duration as for ETOIMS only sessions. Both patients recorded daily visual analog pain levels. RESULTS: Significant reductions in pain levels occurred with the increase in number of ETOIMS treatment sessions. More significant pain level reductions occurred with combined ATOIMS & ETOIMS treatments than with ETOIMS only treatments. The monopolar pin served both procedures well and there were no complications. CONCLUSIONS: The monopolar pin has a very promising role in the management of radiculopathy related myofascial pain using the ATOIMS and ETOIMS methods.

Adult↗
PubMed1999

[Expression of bcl-2 gene in the evolution of chronic myelogenous leukemia to blast crisis and its implication].

OBJECTIVE: To investigate the expression of bcl-2 gene and cell apoptosis and cell cycle in bone marrow of chronic myelogenous leukemia (CML). METHODS: APAAP assay and in situ hybridization were used for the expression of BCL-2 protein and bcl-2 mRNA in fresh bone marrow samples from 60 cases of CML. Flow cytometry was used to assess the extent of apoptosis and cell cycle percentage. RESULTS: The expression of bcl-2 gene had no statistical difference between CMLs at presentation and in chronic phase, but was much lower in blast crisis (P < 0.05). The percentage of bcl-2 mRNA positive cells was consistent with BCL-2 protein expression. In addition, BCL-2 protein was related to the Hb levels, BPC, and immature cells in the peripheral blood and bone marrow. Notably, the extent of apoptosis in accelerated phase/blast crisis was much lower than that in chronic phase(P = 0.028), while the cell cycle had no difference. CONCLUSION: High level of bcl-2 gene expression and low extent of apoptosis in bone marrow cells of CML might partially be the mechanism of poor prognosis of blast crisis, and this provides a new experimental basis for early diagnosis and treatment of CML blast crisis.

Adolescent↗
PubMed1999

[Biological properties of reconstructed mouse hematopoiesis with hematopoietic stem cells transfected by bcl-2 gene].

OBJECTIVE: To observe resistance to radiochemical agents in the mice reconstructed hematopoiesis with hematopoietic stem cells transfected by bcl-2 gene. METHODS: The plasmid containing bcl-2 cDNA retrovirus vector was transfected to PA317 cells with Lipofecaine kite. A PA317 cell clone(D3) with high virus titer was obtained through G418 selection. The virus supernatant of D3 clone cells was used to transfect mouse embryo-liver hematopoietic stem cells. Hematopoiesis in the mice treated with lethal dose irradiation was reconstructed by hematopoietic stem cells transfected with bcl-2 gene. The resistance to radiochemical agents in the mice with reconstructed hematopoiesis was evaluated according to the number of WBC of periphereal blood and mononuclear cells of bone marrow, CFU-S and CFU-S regeneration. RESULTS: The expression of bcl-2 protein was increased in the hematopoietic cells transfected by bcl-2 gene. The mice reconstructed hematopoiesis by stem cells transfected bcl-2 gene can tolerate high dose combined with chemotherapy and radiation of middle dose. The mice reconstructed hematopoiesis with stem cells transfected bcl-2 gene survived over one year, no tumors were found. CONCLUSION: The mice with reconstructed hematopoiesis by stem cells carried bcl-2 gene possess the ability of resistance to radiochemical agents, even only part of hematopoietic stem cells were transfected with bcl-2 gene.

Animals↗
PubMed1998

SLP-76-Cbl-Grb2-Shc interactions in FcgammaRI signaling.

SLP-76 and Cbl are complex adapter proteins that have the capacity to bind to smaller adapter proteins, such as Grb2, which subsequently binds the nucleotide exchange protein Sos in the transmission of intracellular signals. SLP-76, Cbl, Shc, and Grb2 have been implicated in immunoreceptor tyrosine-based activation motif (ITAM) signaling, leading to activation of Ras. However, their mechanism of action has not been determined. To date, there have been no reports of SLP-76 involvement in FcgammaRI-receptor signaling and no data exist for an interaction between Cbl, Shc, and SLP-76 in vivo. We provide evidence that SLP-76, Cbl, and Shc are tyrosine phosphorylated on FcgammaRI-receptor stimulation and are associated with the adapter protein Grb2 in gamma-interferon-differentiated U937 cells (U937IF). The interactions between SLP-76 and Cbl and SLP-76 and Grb2 are present in resting U937IF cells. However, the interaction between SLP-76 and Grb2 becomes augmented twofold on FcgammaRI-receptor aggregation. Our results provide the first evidence for a phosphorylation-dependent interaction between SLP-76 and Shc, induced at least 10-fold on FcgammaRI receptor stimulation. Our data indicate that a significant portion of a multimolecular complex containing Cbl, SLP-76, Shc, and Grb2 is distinct from a trimolecular complex containing the Ras guanine nucleotide exchanger Sos, Shc, and Grb2. FcgammaRI-induced tyrosine phosphorylation of SLP-76, Cbl, Shc, and the highly induced SLP-76-Shc interaction provide the first evidence that SLP-76 and Cbl are involved in FcgammaRI signaling and suggest a functional significance for these interactions in FcgammaRI signal relay in the control of Ras in myeloid cells.

Adaptor Proteins, Signal Transducing↗
PubMed1998

[Distribution of three STR loci in Jingpo ethnic group in Yunnan province].

OBJECTIVE: This study was aimed at the use of old blood stains for investigating the distribution of three STR loci in Jingpo ethnic group. METHODS: DNA extraction from old blood stains (106 in number) and multiplex amplification of CSF1PO, TPOX and TH 01 were carried out. Using denaturing polyacrylamide gel electrophoresis and silver stain, the authors investigated the distribution of allele frequencies of CSF1PO, TPOX and TH01 loci in a Jingpo ethnic group in the southwestern part of Yunnan province. RESULTS: 7 alleles and 26 genotypes of CSF1PO locus,7 alleles and 19 genotypes of TPOX locus, and 6 alleles and 18 genotypes of TH01 locus were observed. CONCLUSION: The satisfactory results demonstrate that multiplex amplification of CSF1PO, TPOX and TH01 is sensitive and the old stain of a drop of blood is sufficient for such amplification.

Asian People↗
PubMed1998

The effects of arginine vasotocin on the calling behavior of male cricket frogs in changing social contexts.

We investigated the effects of the neurohypophysial peptide, arginine vasotocin (AVT), on the calling behavior of male Acris crepitans during and immediately following a simulated acoustic agonistic encounter. AVT did not block the aggressive response to agonistic calls, as the changes in temporal call characteristics in response to the encounter were similar to those of saline-treated males. However, AVT caused males to begin calling sooner during the agonistic encounter and to call significantly more than saline males during and after the agonistic encounter. In addition, AVT-treated males maintained a higher dominant frequency compared to saline animals during and following the agonistic encounter. Changes in temporal characteristics in the period following the agonistic encounter indicated that control males were more likely to exhibit a rebound effect which resulted in larger changes in calling parameters compared to AVT-treated animals. The results indicate that AVT causes changes in calling behavior in male A. crepitans during and following an agonistic encounter that are consistent with animals highly motivated to maintain vigorous active calling throughout changing social conditions.

Aggression↗
PubMed1998

STAT1 is involved in signal transduction in the EPO induced HEL cells.

Erythropoietin (EPO) is the major regulator of mammalian erythropoisis, which stimulates the growth and differentiation of hematopoietic cells through interaction with its receptor (EPO-R). Here we use HEL cells (a human erythro-leukemia cell line) as a model to elucidate the pathway of signal transduction in the EPO-induced HEL cells. Our data show that the EPOR (EPO receptor) on the surface of HEL cells interacts with the Janus tyrosine protein kinase (Jak2) to transduce intracellular signals through phosphorylation of cytoplasmic proteins in EPO-treated HEL cells. Both STAT1 and STAT5 in this cell line are tyrosine-phosphorylated and translocated to nucleus following the binding of EPO to HEL cells. Furthermore, the binding of both STAT1 and STAT5 proteins to specific DNA elements (SIE and PIE elements) is revealed in an EPO-dependent manner. Our data demonstrate that the pathway of signal transduction following the binding of EPO to HEL cells is similar to immature erythroid cell from the spleen of mice infected with anemia strain of Friend virus.

Blotting, Western↗
PubMed1998

Staging of oesophageal carcinoma by endoscopic ultrasound: preliminary experience.

BACKGROUND: Endoscopic ultrasound (EUS) is a relatively recent imaging modality that is capable of visualizing oesophageal tissue layers and para-oesophageal structures. Current pre-operative staging of oesophageal cancer is less than satisfactory, and a modality which may improve pre-operative staging, thus allowing a more rational approach to choice of treatment, may be a welcome addition to current techniques. The purpose of the present study was to evaluate the accuracy of EUS in the staging of oesophageal carcinoma in a consecutive cohort of patients. METHODS: Forty-three patients with oesophageal cancer were prospectively staged with EUS using the radial scanning Olympus EUM-3 echo-endoscope. In the 28 patients who underwent surgery EUS staging was correlated with operative and histological findings to evaluate the EUS accuracy rate of assessing tumour depth (T stage), and the presence of nodal involvement (N stage) using internationally accepted TNM staging criteria. RESULTS: Endoscopic ultrasound accuracy rates for overall T-staging was 61% whereas that of N-staging was 75%. The overall TNM pathological staging was 75% accurate by EUS. CONCLUSIONS: Compared to published literature figures for oesophageal staging by computed tomography scanning (39-54%) these results demonstrate that EUS has a reasonable accuracy rate for staging. Endoscopic ultrasound may prove to be a useful additional modality in the management of oesophageal cancer.

Adenocarcinoma↗
PubMed1998

[Establishment and biological characterization of a transplantable BALB/c mouse erythroblastic leukemia model].

OBJECTIVE: Biological characterization of a BALB/c mouse transplantable erythroblastic leukemia model EL9611. METHODS AND RESULTS: The original erythroblastic leukemia (EL) mouse was obtained by 7,12-DMBA induction. The spleen cell suspension from the original EL mouse was injected into the same inbred BALB/c strain mice. After successive transplantation for 20 generations, the incidence of EL was 100% without spontaneous remission. There was a linear relationship between the survival time of the EL mice and the number of leukemic cells inoculated. When 10(6) leukemic cells were inoculated intravenously, the EL mice survived 10.2 +/- 1.3 days. Invasion of leukemic cells involved mainly in the bone marrow, the spleen and the liver. There was no obvious infiltration of leukemic cells in lymph-nodes and thymus. In peripheral blood, there were a large number of leukemic cells and most of them were basophilic or polychromatophilic erythroblasts. At the advanced stage, the mice developed anemia and thrombocytopenia. The reaction of the leukemic cells for hemoglobin staining was positive or weakly positive. While the peroxydase reaction was negative, Thy-1 antigen and Fc-recepter were not presented. No virus-like particles was found in the cells under electron microscope. EL9611 leukemia model was sensitive to some antitumor drugs used in clinical therapy. CONCLUSION: The establishment of EL9611 leukemia model offered a useful tool for studying proliferation and differentiation of erythroid cells, as well as pathogenesis and experimental treatment of non-virus erythroid malignancy.

9,10-Dimethyl-1,2-benzanthracene↗