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Biomedical subjects

S L Hong

Publications and source records attributed to S L Hong.

At least 19 recordsLinked to original sources
PubMed2006

Test-retest reliability and criterion validity of the Chinese version of CBCL, TRF, and YSR.

BACKGROUND: Psychometric properties of the Chinese version of CBCL, TRF, and YSR were understudied. This study aimed at examining their test-retest reliability and criterion validity. METHODS: Three Chinese community and clinic samples were recruited in Hong Kong. The parents, teachers, and youths respectively completed the CBCL, TRF, and YSR. RESULTS: The Chinese CBCL, TRF, and YSR were test-retest reliable and valid. However, there was score/case attenuation at retest. CBCL and TRF appeared to screen externalizing and ADHD problems better, while YSR screened internalizing problems better. CONCLUSIONS: Clinicians should be cautious about score/case attenuation at retest while using CBCL, TRF, and YSR to chart patients' progress. They should also recognize their different strengths in screening various disorders.

Adolescent↗
PubMed2006

Change in the organization of degrees of freedom with learning.

The authors examined the effects of learning on the change in the organization of the mechanical and dynamical degrees of freedom in 5 men who performed a ski-simulator task. A 3-dimensional analysis of the motion of the total-body center of mass and the segmental centers of mass (head, torso, thighs, and shanks) over practice showed that the recruitment of mechanical degrees of freedom was strongly influenced by anatomical and task constraints. Principal components analysis of the body segments' motions revealed that practice shifted their relative contributions but did not change the number of principal components. The present findings show that there can be independence in the patterns of change in the mechanical and dynamical degrees of freedom that arise from practice.

Adolescent↗
PubMed2005

Practice effects on local and global dynamics of the ski-simulator task.

This experiment examined the acquisition of the global and local dynamics of the changes in the total body center of mass-platform and inter-limb coordination motions over the course of practice (20, 30 s trials each day for 7 days) in the ski-simulator task. Four blocks of trials, representative of early, moderate, and extensive practice were analyzed through power spectrum and coherence analyses. The oscillation frequencies of the knee joints became tuned to that of the platform-performer system and there were changes due to practice in the lower inter-limb coordination dynamics independent of the center of mass and platform coordination pattern. Acquisition of global level dynamics occurs to achieve a stable task solution that can allow for degenerate frequency- and phase-locking of the mechanical degrees of freedom at both the local intra- and inter-limb levels.

Adolescent↗
PubMed2000

Multimerization potential of the cytoplasmic domain of the human immunodeficiency virus type 1 transmembrane glycoprotein gp41.

We previously demonstrated that an envelope mutant of human immunodeficiency virus type 1 lacking the entire cytoplasmic domain interferes in trans with the production of infectious virus by inclusion of the mutant envelope into the wild-type envelope complex. We also showed that the envelope incorporation into virions is not affected when the wild-type envelope is coexpressed with the mutant envelope. These results suggest that an oligomeric structure of the cytoplasmic domain is functionally required for viral infectivity. To understand whether the cytoplasmic domain of human immunodeficiency virus type 1 transmembrane protein gp41 has the potential to self-assemble as an oligomer, in the present study we fused the coding sequence of the entire cytoplasmic domain at 3' to the Escherichia coli malE gene, which encodes a monomeric maltose-binding protein. The expressed fusion protein was examined by chemical cross-linking, sucrose gradient centrifugation, and gel filtration. The results showed that the cytoplasmic domain of gp41 assembles into a high-ordered structural complex. The intersubunit interaction of the cytoplasmic domain was also confirmed by a mammalian two-hybrid system that detects protein-protein interactions in eucaryotic cells. A cytoplasmic domain fragment expressed in eucaryotic cells was pulled down by glutathione-Sepharose 4B beads via its association with another cytoplasmic domain fragment fused to the C terminus of the glutathione S-transferase moiety. We also found that sequences encompassing the lentiviral lytic peptide-1 and lentiviral lytic peptide-2, which are located within residues 828-856 and 770-795, respectively, play a critical role in cytoplasmic domain self-assembly. Taken together, the results from the present study indicate that the cytoplasmic domain of gp41 by itself is sufficient to assemble into a multimeric structure. This finding supports the hypothesis that a multimeric form of the gp41 cytoplasmic domain plays a crucial role in virus infectivity.

ATP-Binding Cassette Transporters↗
PubMed1994

Characterization of cytosolic phospholipases C from porcine aortic endothelial cells.

Phospholipases C (PLCs) are ubiquitous enzymes which play key roles in the response of cells to extracellular agonists. Endothelial cells are involved in myriad normal and pathophysiologic functions. Although it is known that agonists activate PLCs in endothelial cells, second messengers form, and cellular responses ensue, more knowledge is needed about the specific types of PLCs in these cells. To this end, cytosolic PLCs from porcine aortic endothelial cells were partially purified by ammonium sulfate fractionation and column chromatography on DEAE-Sepharose CL-6B and heparin-agarose. Three PLC isozymes immunologically similar to bovine brain PLC-beta, PLC-gamma, and PLC-delta were identified. The relative levels of PLC activities in the cytosol were: PLC-beta, 50%; PLC-gamma, 44%; PLC-delta, 6%. The level of PLC-beta activity in porcine endothelial cells appeared higher than the levels reported for several established cell lines, suggesting that this enzyme may play a specific role in endothelial cell function. Elution profiles of PLC activity with phosphatidylinositol 4,5-bisphosphate (Ptdlns(4,5)P2) as substrate were similar to those with phosphatidylinositol (Ptdlns) as substrate, indicating that cytosolic PLCs hydrolyze both Ptdlns and Ptdlns(4,5)P2 and no Ptdlns(4,5)P2-specific PLC was present in the cytosol. The catalytic properties of the partially purified PLC isozymes from porcine endothelial cells were similar to their counterparts from bovine brain. These include the dependence of hydrolysis of Ptdlns on Ca2+, the optimal Ca2+ concentrations for the hydrolysis of Ptdlns and Ptdlns(4,5)P2, the pH optima, and the stimulatory effects of deoxycholate.

Animals↗
PubMed1994

[Studies on semi-synthesis of cephalotaxine esters and correlation of their structures with antitumor activity].

Ten esters of cephalotaxine with amino acids possessing widely different structural features have been synthesized and tested for antitumor activity. Preliminary data showed that compound 6 is the most active one. However, it is still less potent than harringtonine. Other synthetic esters possess varying activities at 10 micrograms/ml. Preliminary structure activity relationship of these esters was discussed.

Antineoplastic Agents, Phytogenic↗
PubMed1993

Glycoconjugate mediated endothelial cell adhesion to Dacron polyester film.

PURPOSE: The purpose of this study was to explore new strategies for enhancing specific cell type attachment to biomaterials using immobilized lectins for cell surface glycoconjugates. The lectin Ulex europaeus I (UEA I) has a high affinity for human vascular endothelial cell surface glycoconjugates. METHODS: UEA I was covalently bound to polyethylene terephthalate (Dacron) with the cross-linking agent 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride to achieve oligosaccharide-mediated endothelial cell attachment to this otherwise nonadherent surface. RESULTS: Experiments with radiolabeled UEA I demonstrated covalent linkage of as much as 1.35 micrograms/cm2. The lectin binding site is available after the reaction, as demonstrated in experiments a neoglycoprotein. Adhesion studies reveal a 100-fold increase in endothelial cell attachment for the UEA I/polyethylene terephthalate surface (99.7 +/- 29.6 cells/high-power field) when compared with untreated (0.7 +/- 0.5), crosslinking agent (0.4 +/- 0.3), and denatured UEA I (1.2 +/- 1.1) control groups. Five vascular endothelial cell lines adhered to the UEA I/polyethylene terephthalate surface, whereas monocytes, smooth muscle cells, and fibroblasts did not. CONCLUSION: These results imply new strategies for endothelialization of prosthetic grafts and promotion of selective cell adherence to biomaterials, with emphasis on carbohydrate interactions. Moreover, this experimental system offers a model for exploring the biologic significance of the endothelial cell-UEA I ligand.

Cell Adhesion↗
PubMed1992

Nasal mucosa sensitization with toluene diisocyanate (TDI) increases preprotachykinin A (PPTA) and preproCGRP mRNAs in guinea pig trigeminal ganglion neurons.

Toluene diisocyanate (TDI) induces respiratory allergy in mammals. Using immunohistochemistry and in situ hybridization histochemistry, the present study examined effects of nasal mucosa sensitization by TDI on the immunoreactivity for substance P (SP) and calcitonin gene-related peptide (CGRP) and on the expression of their mRNAs in guinea pig trigeminal ganglion and their terminals. Single intranasal application of TDI (acute experiment) did not induce nasal allergy-like behaviours and failed to cause changes of SP and CGRP immunoreactivity and in the expression of preprotachykinin A (PPTA) mRNA and preproCGRP mRNA coding for SP and CGRP respectively in the trigeminal ganglion neurons. However, repeated application of TDI (chronic experiment) caused a dramatic increase of SP and CGRP immunoreactivity in peripheral neurites of sensory nerves in the nasal mucosa but a slight increase in the spinal trigeminal nucleus, a decrease of the same immunoreactivities in the cell bodies of the trigeminal ganglion neurons, and an increase of the expression of PPTA and preproCGRP mRNA in the same neurons. These findings suggest that chronic exposure of the nasal mucosa to TDI apparently causes enhancement of both the biosynthesis of SP and CGRP and their axonal transport in the trigeminal system.

Animals↗
PubMed1992

[Effect of bradykinin, ionophore A23187 and trypsin on prostacyclin release from calf and pig aorta endothelial cells].

This paper details the methods of establishing stock culture and subculture of calf and pig aorta endothelial cells and the effects of bradykinin, ionophore A23187, trypsin and arachidonic acid (AA) on the release of prostacyclin (PGI2) from the cells. The release was measured by 6-keto PGF1 alpha radioimmunoassay. The results showed that the stimuli significantly increased the release of PGI2 in the two endothelial cell types (P < 0.01, n = 8), and the release was much stronger in pig than in calf endothelial cells under the experimental conditions. We therefore suggest that the reactivities of the two endothelial cells to the stimuli differ. The results offer useful information for further research of the mechanism of their pharmacologic actions on endothelial cells and their relationship with PGI2.

Animals↗
PubMed1989

Bradykinin-induced activation of phospholipase A2 is independent of the activation of polyphosphoinositide-hydrolyzing phospholipase C.

This study evaluates the role of phosphatidylinositol 4,5-bisphosphate (PIP2) and its metabolites as possible mediators in the activation of phospholipases A2 in porcine aortic endothelial cells. We compared the time courses of bradykinin-induced turnover of phosphoinositides and the appearance of unesterified arachidonic acid (uAA) and eicosanoids. The metabolism of phosphoinositides was examined in cells prelabeled with [3H]inositol, which has a similar distribution as the endogenous inositol lipids. At 37 degrees C, bradykinin induced a rapid rise in lysophosphatidylinositol (lyso-PI) and inositol 1,4,5-trisphosphate (IP3) as well as a decrease in PIP2. Lyso-PI formation was detected at 10 s, as early as PIP2 degradation and IP3 formation. This suggests that the activation of PIP2-hydrolyzing phospholipase C and PI-hydrolyzing phospholipase A2 are simultaneous. However, at 30 degrees C, lyso-PI formation was detected in the absence of an increase in IP3 indicating that the activation of phospholipase A2 does not require the accumulation of IP3. The time course of formation of uAA and eicosanoids were examined in [3H]arachidonic acid-prelabeled cells. The 3H radioactivity was distributed among the phospholipid classes and subclasses the same as the endogenous phospholipids. Bradykinin stimulated the intracellular accumulation of uAA, detectable at 5 s, earlier than that of 1,2-diacylglycerol and phosphatidic acid. Such immediate formation of uAA further supports the notion that activation of phospholipase A2 is a very early event during the interaction of bradykinin with porcine endothelial cells, and that PIP2 hydrolysis is not prerequisite for the initial activation of phospholipase A2.

Animals↗
PubMed1986

von Willebrand factor abnormalities and endothelial cell perturbation in a patient with acute thrombotic thrombocytopenic purpura.

The plasma of a 63-year-old patient with an initial acute, fatal episode of thrombotic thrombocytopenic purpura (TTP) contained agglutinated platelets and a factor VIII-related von Willebrand factor (vWF) antigen level that was elevated seven-fold above normal. Unusually large vWF multimers derived from endothelial cells were detected in her plasma at the onset of the TTP episode. This is the first patient in whom vWF abnormalities indicative of in vivo endothelial cell damage or perturbation have been found during an acute episode of TTP.

Antigens↗
PubMed1985

Prostacyclin synthesis and deacylation of phospholipids in human endothelial cells: comparison of thrombin, histamine and ionophore A23187.

Thrombin, histamine and ionophore A23187 stimulated human endothelial cells to release arachidonic acid and synthesize prostaglandins. To compare the activation of arachidonic acid release by these three stimuli in endothelial cells, we examined the intracellular lipid metabolism by prelabeling the cells with [14C]stearic acid and [3H]arachidonic acid. Thrombin stimulated the loss of 3H and 14C label from intracellular phospholipids. At the same time [3H]arachidonic acid and prostaglandins were released into the incubation medium. Thin layer chromatography analysis indicated that prostacyclin is the major metabolite formed followed by PGF2 alpha, PGE2, HHT and PGD2. In addition, several intracellular lipid metabolites were accumulated. These include: phosphatidic acid and 1,2-diacylglycerol detected by increase of both 14C and 3H radioactivity; lysophosphatidylinositol, lysophosphatidylethanolamine, and to a smaller extent lysophosphatidylcholine and lysophosphatidylserine detected by increase of 14C radioactivity. Like thrombin, both histamine and ionophore A23187 also stimulated release of arachidonic acid and synthesis of prostaglandins. Despite the different nature of the agonists, the type and the relative amount of prostaglandins synthesized in response to histamine and A23187 were similar to that stimulated by thrombin. The relative extents of hydrolysis of phospholipids and the accumulation of phosphatidic acid, 1,2-diacylglycerol and lysophospholipids are similar to that of 3H radioactivity and prostacyclin released into the medium and follow the order: ionophore A23187 greater than thrombin greater than histamine. These results suggest that in human endothelial cells, histamine, thrombin and ionophore A23187 directly or indirectly activated both phospholipase C and phospholipase A2 and these activations most likely involve mobilization of Ca2+.

Acylation↗
PubMed1985

Therapy of chronic relapsing thrombotic thrombocytopenic purpura with prednisone and azathioprine.

As a 51-year-old woman recovered from an initial acute episode of thrombotic thrombocytopenic purpura (TTP), her plasma was found to contain unusually large von Willebrand factor (vWF) multimers. Clinical, hematological, and vWF studies of her siblings and children were normal. The unusually large vWF forms were presumably derived from endothelial cells, persisted in her plasma after recovery, and were associated with recurrent episodes of TTP during the subsequent 6 months. After the last episode of relapse they disappeared from her plasma following 3 1/2 weeks of therapy with prednisone and did not return during 17 months of treatment with prednisone and/or azathioprine. She is now receiving no drugs, has normal plasma vWF forms, and has not had any more episodes of TTP. We conclude that our patient had an acquired defect in the conversion of unusually large vWF multimers derived from endothelial cells to the somewhat smaller vWF forms usually present in circulation. The defect may have been immune-mediated, because it was eliminated during therapy with immunosuppressive drugs.

Azathioprine↗
PubMed1985

Genetics of ergoline alkaloid formation in Penicillium roquefortii.

Auxotrophic, spore color, and alkaloid biosynthetic mutants of Penicillium roquefortii were selected after N-methyl-N'-nitro-N-nitrosoguanidine treatment. Diploids were obtained via protoplast fusion techniques, and the segregants from a diploid were genetically analyzed. The data demonstrated the potential of parasexual recombination in this organism. Evidence was obtained which suggests that the his and sts (sensitivity to Sulfatase) genes may be linked. The genetic information obtained in this study can serve as a starting point for further mapping of genes in P. roquefortii, and indications are that this organism may serve as a promising vehicle for the genetic study of the formation of ergoline alkaloids.

DNA, Fungal↗
PubMed1985

Effects of fresh-frozen plasma and its cryosupernatant fraction on von Willebrand factor multimeric forms in chronic relapsing thrombotic thrombocytopenic purpura.

Remission plasma samples of some patients with chronic relapsing thrombotic thrombocytopenic purpura (TTP) contain unusually large von Willebrand factor (vWF) multimers similar to those produced by normal human endothelial cells in culture. The infusion of the cryosupernatant fraction of normal plasma is as effective as normal fresh-frozen plasma (FFP) in the treatment or prevention of TTP episodes in patients with the chronic relapsing form of TTP. Three patients with chronic relapsing TTP during remission have unusually large vWF multimers present in their plasma. Two of the patients were transfused once with FFP, one of the two received cryosupernatant on three occasions, and the third patient was studied before and immediately after plasma exchange. Unusually large vWF multimers decreased or disappeared from patient plasma samples within 1/2 to 1 1/2 hours following the transfusion of FFP (on two occasions) or cryosupernatant (on two of three occasions), and immediately after plasma exchange (on one occasion). The patient who received cryosupernatant was studied serially after the infusions. Unusually large vWF multimers returned to her plasma within ten to 24 hours and persisted thereafter. Unusually large vWF multimers did not disappear from patient remission plasma samples, or from the culture medium removed from normal human endothelial cells, when these fluids were incubated in vitro with either normal FFP or cryosupernatant. We conclude that an activity in FFP, and its cryosupernatant fraction, promoted the rapid in vivo disappearance of unusually large vWF multimers from the plasma of two patients with chronic relapsing TTP in remission, and plasma exchange reversed the abnormality in a third patient who was in partial remission. Neither FFP nor cryosupernatant directly converted unusually large multimers to smaller vWF forms in vitro in the fluid phase. These results indicate that an activity in the cryosupernatant fraction of normal plasma is involved in vivo in controlling the metabolism of unusually large vWF multimers, and that this process is defective in some chronic relapsing TTP patients.

Adult↗