Biomedical subjects

F Sun

Publications and source records attributed to F Sun.

At least 91 records · Page 5Linked to original sources

PubMed1997

Recruitment of individually (all-or-none) responding cells, rather than amplitude enhancement, is the single-cell mechanism subserving the dose-responsive activation of intracellular calcium second messenger signaling by the human luteinizing-hormone receptor.

We have investigated at the single-cell level how the human LH receptor mediates a dose-responsive increase in intracellular free calcium-ion concentrations ([Ca2+]i). In human embryonic kidney cells (293 cells) stably transfected with the full-length human LH receptor cDNA. Intact dimeric LH, but not LH beta- or alpha-subunits, evoked specific [Ca2+]i signals. High-resolution fluorescence (fura-2) video-microscopy demonstrated cell-to-cell variability in [Ca2+]i signaling responses in individual cells, viz., an all-or-none spike (9%), spike-and-plateau (25%), or plateau (52%) types of temporal signal. Oscillatory [Ca2+]i responses were observed in 12-14% of LH-stimulated cells unrelated to LH concentration. The LH dose-response originated by higher concentrations of LH recruiting more individually responding cells (rather than altering [Ca2+]i signal amplitude), and eliciting a [Ca2+]i rise more rapidly, i.e., at reduced latency. Cobalt did not abolish the LH-stimulated [Ca2+]i spike-and-plateau response, but decreased the percentage of cells with a plateau pattern. Quench experiments demonstrated influx of Mn2+ following the [Ca2+]i spike, thus directly documenting divalent cation inflow during the plateau phase. Adenylyl-cyclase activation with forskolin or treatment with a cAMP analog failed to elicit the biphasic [Ca2+]i response, and pertussis toxin (PTX) did not alter LH-stimulated [Ca2+]i signaling. However, overnight preincubation with LH reduced the percentage of [Ca2+]i-responding cells following re-exposure to LH to 5.7% (vs 72% in control), suggesting LH-induced desensitization of the LH-receptor directed [Ca2+]i signal. In summary, the present studies of human LH receptor signal transduction at the single-cell level show that increasing concentrations of LH achieve a dose-dependent intracellular Ca2+ signaling response by recruiting an increasing number of [Ca2+]i-responding cells, while concomitantly decreasing the temporal latency of the biphasic [Ca2+]i signal without altering the amplitude of its spike phase. Prolonged exposure to LH appears to desensitize the LH receptor-driven [Ca2+]i signal.

Adenylate Cyclase Toxin↗

PubMed1997

Expression of functional GABAA receptors in transfected L929 cells isolated by immunomagnetic bead separation.

Transient cotransfection of fibroblasts, with plasmids encoding individual GABAA receptor (GABAAR) subunits, has provided a model to characterize the pharmacological and kinetic properties of receptor subtype combinations. However, identifying transfected cells for electrophysiological recording is often difficult due to low transfection efficiencies. Selection of transfected cells has required cotransfection with a marker gene and fluorescence microscopic localization prior to recording. To circumvent these problems, two GABAAR subtypes combinations in transfected L929 cells were isolated with a novel biomagnetic separation system. Cell selection was accomplished by cotransfection with a plasmid (pHook-1) encoding a single-stranded cell surface antibody (sFv), which bound to ferromagnetic beads, coated with an antigen (phOx). Bead-covered cells were then magnetically separated from non-transfected cells. Bead-selected cells cotransfected with alpha 6, beta 3 and gamma 2L subtypes, expressed GABAAR currents in 95% (41/43) of cells recorded. Cells cotransfected with alpha 5, beta 3 and gamma 2L subtypes had an EC50 for GABA of 5.4 microM and a Hill slope of 1.4. Membrane patches from cells expressing the alpha 5 beta 3 gamma 2L isoform demonstrated single channel currents with a main conductance state of 23 pS. Magnetic bead immunoselection provides a purified population of transfected cells well suited for whole cell and single channel recording.

Animals↗

PubMed1997

Pooling strategies for establishing physical genome maps using FISH.

Often, in biological studies, it is necessary to identify an organism's chromosomes. In some organisms the individual chromosomes can be identified by staining procedures while many other species have a very large number of chromosomes, often of similar size, which defy identification by traditional staining methods. We have devised strategies, based on fluorescent in situ hybridization (FISH), which allow the assignment of a preset number of probes to each chromosome without prior chromosome identification. By hybridizing mixtures of probes labeled with different colored fluorescent molecules, the chromosomal origin of each probe can be determined.

Animals↗

PubMed1997

Common genomic variation in the APOC3 promoter associated with variation in plasma lipoproteins.

We hypothesized that common genomic variation that affected the expression and/or function of the products of the APOC3, APOE, FABP2, and PON1 genes would be associated with variation in biochemical phenotypes in a previously unstudied human sample. We determined genotypes of functional genomic variants of APOC3, APOE, FABP2, and PON1 in 509 adult aboriginal Canadians from an isolated community in Northern Ontario. We tested for genotype associations with plasma lipoprotein traits. We found that (1) common variation at nucleotide -455 of the APOC3 promoter was associated with variation in plasma triglycerides (P = .006) and (2) common variation of APOE determining plasma isoforms of apo E was associated with variation in plasma apo B (P = .009). Analysis of subjects classed by APOC3 markers showed that homozygosity for presence of a C at nucleotide -455 and a T at nucleotide -482 was associated with significantly increased plasma triglycerides in both men and women. Furthermore, this allele was approximately twice as frequent in subjects within the highest quartile of plasma triglycerides as in subjects within the lowest quartile. Since the DNA variation detected by the APOC3 markers affects in vitro expression of the gene product, it is possible that the marker itself caused the associations. However, the associations could also have resulted from linkage disequilibrium with other functional variants in APOC3 or the closely linked APOA1 and/or APOA4 genes.

Adolescent↗

PubMed1997

Common genomic variants associated with variation in plasma lipoproteins in young aboriginal Canadians.

We hypothesized that common genomic variants would be associated with variation in lipoprotein phenotypes in young subjects. We determined genotypes of FABP2, PON, APOC3, and APOE in 188 aboriginal Canadians, aged 9 to 17 years. We found that 13 of 32 possible genotype-phenotype associations were significant: (1) the FABP2 codon 54 genotype was associated with variation in plasma triglycerides (P = .045); (2) the PON codon 192 genotype was associated with variation in plasma total and LDL cholesterol and apoB (P = .0099, P = .0088, and P = .016, respectively); (3) the APOC3 insulin-response-element genotype was associated with variation in plasma triglycerides, HDL cholesterol, apoA-I, the total cholesterol to HDL cholesterol ratio, and the apoB to apoA-I ratio (P = .0014, P = .0069, P = .045, P = .0021, and P = .0081, respectively); and (4) the APOE restriction isotype was associated with variation in plasma LDL cholesterol, apoB, the total cholesterol to HDL cholesterol ratio, and the apoB to apoA-I ratio (P = .025, P = .034, P = .045, and P = .047, respectively). The average young age and relative absence of age-dependent secondary environmental factors could have eased the identification of small genetic effects on lipoprotein phenotypes in this study sample.

Adolescent↗

PubMed1997

Angiotensinogen gene variation associated with variation in blood pressure in aboriginal Canadians.

We measured blood pressure and related clinical phenotypes in 497 adult native Canadians from an isolated community in Northern Ontario. We analyzed their DNA for genotypes of angiotensinogen. We found that the frequency of the T235 variant of the angiotensinogen gene was 0.89 in this sample. This variant was associated with a significantly increased systolic pressure but not diastolic pressure. We also found that sex and body mass were each highly significantly associated with variation in both systolic and diastolic pressures. We found a significant association between age and variation in systolic pressure but not diastolic pressure. We also found a highly significant association between plasma apolipoprotein B concentration and variation in diastolic pressure but not systolic pressure. The high frequency of the angiotensinogen T235 variant suggests that subjects in this young, essentially normotensive population might be predisposed to hypertension, which may become more apparent in the presence of secondary factors.

Adult↗

PubMed1997

[Effect of frostbite under hypoxia on microcirculatory perfusion in rats].

Changes of microcirculatory perfusion in rats following cold injury of right hind leg under hypoxia were investigated. Male Wistar rats weighing 200 +/- 20 g were randomly divided into three groups: frostbite at normoxia (FN) group; frostbite during acute hypoxia (4 h at 6000 m simulated altitude, FAH) group and frostbite during hypoxia after acclimation (exposure to hypoxia at 6000 m, 4 h daily for 4 weeks, FHAC) group. The results showed that the microcirculatory perfusion of both hind legs decreased markedly in FN after cold injury. It suggests that the frostbite damage can affect microcirculatory perfusion of another leg besides the region of frostbite. The fall of microcirculatory perfusion before freezing in FAH group indicated that there was a compensatory blood redistribution during acute hypoxia. The changes of microcirculatory perfusion in FAH group post-freezing indicated that acute hypoxia can aggravate the frostbite damage. The microcirculatory perfusion of FHAC group pre-freezing was significantly lower than that of FN and FAH group, and after freezing the perfusion of frostbitten leg in FHAC group was significantly lower than that in FN group, suggesting that hypoxia acclimation may cause disturbance of microcirculation and worsen the frostbite damage at high altitude.

Acclimatization↗

PubMed1997

[The properties of protease from Bacillus sphaericus C3-41].

The production and properties of protease from Bacillus sphaericus strain C3-41 were reported in this paper. It was found out that the secrete of extracellular protease began at the exponential phase, reached a maximum at the early phase of sporangium and then decrease rapidly. The production conditions of the protease have been studied. The protease preparation was purified by salting out with ammonium sulfate and by chromatography fractionating on Sephadex G-100. The purified enzyme have a specific activity of 6741.5 U/mg protein and a molecular weight of 42,000. The optimal activities of the protease were around pH11.0 and at 4 degrees C respectively. The enzyme was stable at pH5.0-12.0. The proteolytic activity was inhibited by phenylmethylsulphony fluoride (PMSF) and EDTA, but not by IAA, SA and DTT. The activity was inhibited in the presence of Al3+, Hg2+, Fe3+, Cu2+ and Fe2+. The enzyme was sensitive to higher temperature, but was quite stable in the presence of Ca2+.

Bacillus↗

PubMed1997

Clustering of Caucasian Leber hereditary optic neuropathy patients containing the 11778 or 14484 mutations on an mtDNA lineage.

Leber hereditary optic neuropathy (LHON) is a type of blindness caused by mtDNA mutations. Three LHON mtDNA mutations at nucleotide positions 3460, 11778, and 14484 are specific for LHON and account for 90% of worldwide cases and are thus designated as "primary" LHON mutations. Fifteen other "secondary" LHON mtDNA mutations have been identified, but their pathogenicity is unclear. mtDNA haplotype and phylogenetic analysis of the primary LHON mutations in North American Caucasian patients and controls has shown that, unlike the 3460 and 11778 mutations, which are distributed throughout the European-derived (Caucasian) mtDNA phylogeny, patients containing the 14484 mutation tended to be associated with European mtDNA haplotype J. To investigate this apparent clustering, we performed chi2-based statistical analyses to compare the distribution of LHON patients on the Caucasian phylogenetic tree. Our results indicate that, unlike the 3460 and 11778 mutations, the 14484 mutation was not distributed on the phylogeny in proportion to the frequencies of the major Caucasian mtDNA haplogroups found in North America. The 14484 mutation was next shown to occur on the haplogroup J background more frequently that expected, consistent with the observation that approximately 75% of worldwide 14484-positive LHON patients occur in association with haplogroup J. The 11778 mutation also exhibited a moderate clustering on haplogroup J. These observations were supported by statistical analysis using all available mutation frequencies reported in the literature. This paper thus illustrates the potential importance of genetic background in certain mtDNA-based diseases, speculates on a pathogenic role for a subset of LHON secondary mutations and their interaction with primary mutations, and provides support for a polygenic model for LHON expression in some cases.

Chi-Square Distribution↗

PubMed1997

[Frozen-preserved tarsus of eyelid from new born in the repair of palpebral defect].

In order to repair palpebral defects resulted from various causes, frozen tarsus of eyelid from newborn was used. From Jan. 1993 to Feb. 1995, the frozen preserved tarsus of eyelid from new-born was used to repair the palpebral defect in 10 cases. These defects were resulted following operation in traumatic defect in 5 cases, tramatic defect in 3 cases and congenital defect in 2 cases. After 3 month to 3 years follow-up, no refection reaction was found and no complication was occurred. The external appearance following repair was good. The overall successful rate was 100%. It was suggested that the frozen preserved tarsus from new-born was a safe and reliable material in the repair of palpebral defects.

Adolescent↗

PubMed1996

Structure--activity relationships of the didemnins.

Bioactivities of 42 didemnin congeners, either isolated from the marine tunicates Trididemnun solidum and Aplidium albicans or prepared synthetically and semisynthetically, have been compared. The growth inhibition of various murine and human tumor cells and plaque reduction of HSV-1 and VSV grown on cultured mammalian cells were used to assess cytotoxicity and antiviral activity. Biochemical assays for macromolecular synthesis (protein, DNA, and RNA) and enzyme inhibition (dihydrofolate reductase, thymidylate synthase, DNA polymerase, RNA polymerase, and topoisomerases I and II) were also performed to specify the mechanisms of action of each analogue. Immunosuppressive activity of the didemnins was determined using a mixed lymphocyte reaction (MLR) assay. These assays revealed that the native cyclic depsipeptide core is an essential structural requirement for most of the bioactivites of the didemnins, especially for cytotoxicities and antiviral activities. The linear side-chain portion of the peptide can be altered with a gain, in some cases, of bioactivities. In particular, dehydrodidemnin B, tested against several types of tumor cells and in in vivo studies in mice, as well as didemnin M, tested for the mixed lymphocyte reaction and graft vs host reaction in murine systems, showed remarkable gains in their in vitro and in vivo activities compared to didemnin B.

Animals↗

PubMed1996

A mathematical analysis of in vitro molecular selection-amplification.

We construct a mathematical model for in vitro molecular selection with amplification. Using DNA-protein binding as the illustrative example, we obtain an expression for the probability that a randomly selected molecule from the final in vitro selection products is a molecule with the highest binding affinity. Experiments of this type have been reported for several examples of DNA binding proteins. Our study requires a model of the DNA-protein binding constant between DNA molecules and the target protein. The relationship between binding constants and selection probabilities is presented under simplifying but reasonable assumptions. From our analysis, we find that for successful in vitro selection experiments there should be a certain relationship between the number of polymerase chain reaction cycles and the concentration of free protein. The results obtained should be widely applicable to a variety of selection-amplification procedures.

DNA↗

PubMed1996

[An ultrastructural study on human retina with late glaucoma].

OBJECTIVE: To study the pathologic changes of retina in glaucoma. METHOD: Retinas from 6 cases with absolute glaucoma were observed by transmission electron microscope. RESULT: It was found that the nerve fiber layer was significantly thin and the axons were severely damaged even lost; the ganglion cells nearly disappeared and a number of cell-like bodies were seen instead; the nerve cells of the outer and inner nuclear layers were degenerated, decreased in number, and disorderly arranged; the outer segments of the cone and rod cells became degenerative and edematous. CONCLUSION: In advanced glaucoma the degeneration and atrophy of the ganglion cells and their nerve axons were the major pathologic changes of the retina that lead to the permanent damage of visual function.

Female↗

PubMed1996

[Highly metastatic model of human hepatocellular carcinoma established in nude mice using orthotopic organ selection of metastatic variant from patient specimens].

We succeeded in establishing a highly metastatic model of human hepatocellular carcinoma (HCC) in athymic nude mice (LCI-D20). The metastatic variant was obtained by using orthotopic implantation of histologically intact tumor tissue selected from 30 fresh surgical specimens. It exhibited various features seen in clinical liver cancer patients: local growth, regional invasion, spontaneous intrahepatic, lymphnode and pulmonary metastases, and peritoneal seeding with bloody ascites. All mice with the implant-tumor died within 6 weeks due to serious metastasis. The 100% rate of transplantability and metastasis maintained for over 16 passages. The morphological characteristics of implant tumor cells were similar to those of the original specimen by histological and electronmicroscopic observation, and kept on secreting alpha-fetoprotein (AFP) in recipient animals. Those data from DNA content analysis by flow cytometry (D. I. value, 1.61) and chromosome karyotype revealed the existence of hypotriploid and hypertriploid cells. The results demonstrated that orthotopic implantation model of human HCC displayed features of human clinical HCC in animals. It should allow development of new treatment modalities and study of metastatic mechanism of human HCC.

Animals↗

PubMed1996

[The effect of antisense H-ras on growth and metastasis of a high metastatic tumor model of human hepatoma in nude mice LCI-D20].

OBJECTIVE: To investigate if treatment with antisense H-ras oligodeoxynucleotides (ODNs) modulates tumor growth, apoptosis and metastasis of a high metastatic tumor model of human hepatocellular carcinoma (HCC) in nude mice LCI-D20, in which over-expression of H-ras has been identified. METHODS: LCI-D20 cells in primary culture were treated with 10 mumol/L antisense ODNs in vitro. 1.5 x 10(6) LCI-D20 cells with or without pretreatment were inoculated into each elevated subcutaneous (s.c) flap in fourteen nude mice, 6 animals for antisense H-ras ODN treated cells, 4 for H-ras non-specific antisense ODN treated cells, the rest 4 for cells without pretreatment. RESULTS: In in vitro cell culture study, 5-day continuous suppression of H-ras expression by antisense H-ras ODNs resulted in significant inhibition of the proliferation of LCI-D20 cells (t = 31.529, P < 0.01). Cell cycle analysis showed a significant decrease in S phase (36.0 +/- 1.4) and a remarkable increase in G1/G0 fraction (56.7 +/- 1.1) after exposure to antisense H-ras ODNs in comparison with the cells without any treatment (58.5 +/- 0.9, t = 13.519, P < 0.01, 37.4 +/- 0.7, t = 14.802, P < 0.01). In situ end-labeling (ISEL) detection showed that apoptotic cell death was significantly increased in cells with 5-day treatment of antisense H-ras ODNs (34.0% +/- 4.5%) in comparing with cells without treatment (2.5% +/- 1.2%, t = 13. 434, P < 0.01) or treated with non-specific antisense ODNs (4.8% +/- 1.4%, t = 12.453, P < 0.01) at the corresponding time. In in vivo experiment, after six-week observation, tumor growth in antisense H-ras treated animals was significantly retarded in comparison with that of the untreated (t = 3.509, P < 0.01) or nonspecific antisense ODN treated animals (t = 3.452, P < 0.01). CONCLUSIONS: Specific inhibition of H-ras expression by antisense H-ras ODNs could not only induce apoptotic cell death, inhibit the growth rate of LCI-D20 cells in vitro and in vivo, but also alter in vivo tumorigenesity and metastatic potential of LCI-D20 cells.

Animals↗

PubMed1996

[The antiobesity effect of acupuncture and it's influence on water and salt metabolism].

For the purpose of understanding the antiobesity effect of acupuncture and it's influence on water and salt metabolism in the patients suffering from simple obesity, we have observed the changes of symptoms and signs, obesity indices, blood sodium, blood potassium, mOsm of plasma and urinary aldosterone before and after acupuncture treatment in 75 patients with simple obesity (12 cases with edema, 33 cases without edema). The results showed that the total effective rate of antiobesity treatment for one month was 89.3%. Before acupuncture the concentrations of blood sodium and aldosterone of the patients with edema were significantly higher than those of normal persons or the patients without edema, but the concentration of blood potassium and mOsm of plasma of the patients with edema were significantly lower than those of normal persons or the patients without edema. After acupuncture treatment the concentrations of blood sodium and aldosterone decreased markedly and the concentration of blood potassium and mOsm of plasma increased remarkably in the patients with edema. It indicated that acupuncture treatment not only had a good antiobesity effect, but also improved the water and salt metabolism of the patients with obesity by the regulation of nervous system and body fluid.

Acupuncture Therapy↗

PubMed1995

Whole genome amplification of single cells: mathematical analysis of PEP and tagged PCR.

We construct a mathematical model for two whole genome amplification strategies, primer extension preamplification (PEP) and tagged polymerase chain reaction (tagged PCR). An explicit formula for the expected target yield of PEP is obtained. The distribution of the target yield and the coverage properties of these two strategies are studied by simulations. From our studies we find that polymerase with high processivity may increase the efficiency of PEP and tagged PCR.

Computer Simulation↗

PubMed1995

Genomic mapping by end-characterized random clones: a mathematical analysis.

Physical maps can be constructed by "fingerprinting" a large number of random clones and inferring overlap between clones when the fingerprints are sufficiently similar. E. Lander and M. Waterman (Genomics 2: 231-239, 1988) gave a mathematical analysis of such mapping strategies. The analysis is useful for comparing various fingerprinting methods. Recently it has been proposed that ends of clones rather than the entire clone be fingerprinted or characterized. Such fingerprints, which include sequenced clone ends, require a mathematical analysis deeper than that of Lander-Waterman. This paper studies clone islands, which can include uncharacterized regions, and also the islands that are formed entirely from the ends of clones.

Chromosome Mapping↗