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Biomedical subjects

J Shu

Publications and source records attributed to J Shu.

At least 37 records · Page 2Linked to original sources
PubMed1998

[Chemical constituents of Drosera peltata Smith var. lunata (Buch.-Ham.) C.B. clarke collected in Tibet].

OBJECTIVE: To investigate the chemical constituents of the whole plant of Drosera peltata var. lunata collected in Tibet. METHOD: Compounds were separated by means of pH gradient extraction and rechromatography on silica gel, and the structures were determined by spectral analysis and physicochemical evidence. RESULT: Five crystalline compounds were obtained and elucidated as plumbagin(1), droserone(2), hydroxydroserone(3), beta-sitosterol(4) and stigmasterol(5) respectively. CONCLUSION: Compound 3 and 5 were isolated from the plant for the first time.

Drosera↗
PubMed1997

Oncogenic transformation potentiates apoptosis, S-phase arrest and stress-kinase activation by etoposide.

The exact mechanisms for the selective toxicity of chemotherapeutic drugs against tumor cells are not fully understood. We designed a series of experiments to test the possibility that the positive proliferative signal initiated by oncogenes might change the sensitivity for apoptosis induction by the anticancer drug etoposide (VP16), an inhibitor of topoisomerase II (Topo II). Treatment with VP16 induced significantly increased apoptosis in NIH3T3 cells transformed by oncogenic src, ras or raf, compared with the normal 3T3 cells. Apopototic changes involved nuclear DNA fragmentation, morphological alterations and decreased viability. Furthermore it was shown that stress-activated protein kinase (SAPK) was activated much more strongly in all three transformed lines compared to untransformed cells by VP16 treatment, while slight activation of extracellular signal-regulated kinase (ERK1) was observed in all four cell lines. In addition, the transformed cells displayed arrest in mid-S-phase following the treatment, whereas NIH3T3 cells were primarily arrested in late S and G2/M phase. Finally, the cyclin-dependent kinase inhibitor p21 WAF1 was induced in all four cell lines, although induction of p53 was not detected in any of these cell lines. Taken together our results demonstrated that oncogenic transformation can sensitize the cells to apoptosis induction, stress kinase activation and cell cycle arrest in response to VP16 treatment. These results may have important implications for understanding the selective toxicity of anti-cancer drugs in tumor cells.

3T3 Cells↗
PubMed1997

A new method of culturing and transferring iris pigment epithelium.

PURPOSE: To optimize a culture technique and transfer iris pigment epithelial (IPE) cells for cellular studies in vitro. METHODS: Porcine iris tissues were obtained, and IPE cells were isolated and cultured at high densities by plating them in the form of drops. Spherically shaped structures containing a high concentration of cells were formed after 7 to 10 days of culture. Cells were subcultured by transferring spheres to new culture dishes without employing enzymatic dissociation. The purity of IPE cells was determined by pigmentation and cytokeratin labeling. Proliferation was assessed by incorporation of 5-bromo-2'-deoxyuridine. Cellular structure was analyzed under the light and electron microscopes and function was assayed by rod outer segment phagocytosis. RESULTS: Iris pigment epithelial cells, when cultured at high densities, tended to form elevated spherical structures containing viable cells. The cultured cells were pigmented and showed positive labeling with a monoclonal cytokeratin antibody. The IPE cells proliferated and migrated from the spheres to form monolayers. Cells originating from the transferred spheres also continued to proliferate and to migrate in a similar manner to the originally cultivated cells to form monolayers after 7 to 10 days. These cells were able to phagocytose rod outer segments. CONCLUSIONS: This new method provides a simple method of culturing a large quantity of IPE cells. The high yield of pure IPE cells and the ease of transfer provide an ideal means to study them at the cellular level.

Animals↗
PubMed1996

Activation of JNK/SAPK pathway is not directly inhibitory for cell cycle progression in NIH3T3 cells.

In this study the induction of stress activated protein kinase (SAPK) activity by protein synthesis inhibitors was shown not to inhibit cellular proliferation. Anisomycin induced strong SAPK activity at non-inhibitory concentrations for either protein or DNA synthesis, while the other two inhibitors, emetine and cycloheximide, blocked cell cycle progression without strong SAPK induction. With all three inhibitors, the induction of SAPK activity was always accompanied by protein synthesis inhibition to some extent. Stimulation of mRNA expression of the genes c-jun, c-fos and c-myc correlated well with SAPK induction, but not with cell cycle inhibition. With concentrations of each inhibitor able to block DNA synthesis, no induction of message for the cyclin dependent kinase inhibitor waf-1 was observed; while induction of gadd45 message indicated that the cells might be responding to growth-arrest or DNA damage. The inability of microinjected E2F/DP1 transcription factor proteins to overcome the inhibition of DNA synthesis induced by protein synthesis inhibitors indicate that blockage of an early event in cell cycle progression had occurred. These results indicate that the SAPK induction by protein synthesis inhibitors has no proliferative consequences.

3T3 Cells↗
PubMed1996

Cytotoxic effects of kainate ligands on HEK cell lines expressing recombinant kainate receptors.

Exposure of neurons either for prolonged periods of time or to high concentrations of excitatory amino acids (EAA), such as glutamate, results in neuronal death. Kainate also causes cell toxicity through the glutamate receptors. However, it is unclear whether the kainate receptor itself mediates any of the toxic responses. In the present study, HEK cells expressing the GluR6 +/- KA2 receptor subunit(s) were studied for their susceptibility to toxicity through the kainate receptor by kainate ligands. The natural ligand, glutamate, did not result in toxicity to the recombinant cell lines over that observed with the untransfected HEK cells, whereas kainate produced a 2-3-fold increase in LDH in both the HEK/GluR6 (ANOVA, P = 0.0001) and HEK/GluR6 + KA2 (ANOVA, P = 0.0002) cell lines following treatment with various dosages, but did not affect the HEK cells. Similar 2-3-fold increases in LDH activity were detected in both recombinant cell lines following treatment with 100 nM of SYM2081 ((2S,4R)-4-methylglutamic acid), a dose at which agonistic activity is elicited. The rank order potencies for eliciting toxicity are consistent with the previously reported EC50 values (SYM2081 > kainate > > > glutamate). Surprisingly, the kainate antagonist, NBQX, was the most toxic of the compounds tested although it had an affinity for the kainate receptor similar to glutamate. Treatment with as little as 10 nM elicited a dramatic increase in toxicity (6-10-fold) in the recombinant cell lines. At 1 microM, NBQX was significantly more toxic (Fisher PLSD, P < 0.05) than any of the other compounds tested. Thus, it appears that cell toxicity can be mediated via kainate receptor through two independent mechanisms: activation and blockage of the kainate receptor.

Cell Line↗
PubMed1996

Prostaglandin A2 blocks the activation of G1 phase cyclin-dependent kinase without altering mitogen-activated protein kinase stimulation.

Prostaglandin A2 (PGA2) reversibly blocked the cell cycle progression of NIH 3T3 cells at G1 and G2/M phase. When it was applied to cells synchronized in G0 or S phase, cells were blocked at G1 and G2/M, respectively. The G2/M blockage was transient. Microinjected oncogenic leucine 61 Ras protein could not override the PGA2 induced G1 blockage, nor could previous transformation with the v-raf oncogene. The serum-induced activation of mitogen-activated protein kinase was not inhibited by PGA2 treatment. These data suggest that PGA2 blocks cell cycle progression without interfering with the cytosolic proliferative signaling pathway. Combined microinjection of E2F-1 and DP-1 proteins or microinjected adenovirus E1A protein, however, could induce S phase in cells arrested in G1 by PGA2, indicating that PGA2 does not directly inhibit the process of DNA synthesis. In quiescent cells, PGA2 blocked the normal hyperphosphorylation of the retinoblastoma susceptible gene product and the activation of cyclin-dependent kinase (CDK) 2 and CDK4, in response to serum stimulation. PGA2 treatment elevated the p21Waf1/Cip1/Sdi1 protein expression level. These data indicate that PGA2 may arrest the cell cycle in G1 by interfering with the activation of G1 phase CDKs.

3T3 Cells↗
PubMed1996

Sequential extraction analysis of heavy metals using a chelating agent (NTA) to counteract resorption.

The geochemical partitioning of Pb, Ni and Zn in contaminated quartz-rich sediment and soil samples was characterized by sequential extraction analysis in the presence and absence of nitrilotriacetic acid (NTA). With NTA, levels of metals recovered are higher in the earlier steps and lower in the later steps of the procedure. This suggests that post-extraction resorption is effectively counteracted by chelation, thereby improving the accuracy of the method. An NTA concentration of 200 mg liter(-1) appears to be sufficient for counteracting resorption without causing significant dissolution of non-targeted phases in the samples studied. However, experiments using reference materials spiked with solutions containing Pb, Ni, Cu and Zn suggest that resorption will remain a problem when large amounts of strong sorbents such as organic matter are present. The results also show that although post-extraction resorption does occur in the absence of NTA, the magnitude of resorption is small (<20 to 30% of the summed total of metal present in the sample) in quartz-rich sediments.

Journal Article↗
PubMed1996

Asian student migration to Australia.

"This paper presents an overview of Asian student migration to Australia, together with an analysis of political and educational aspects of the overseas student programme. It focuses on some significant consequences of this flow for Australia. The characteristics of key student groups are contrasted to provide some perspective of the diversity of historical and cultural backgrounds, with the source countries of Malaysia, Indonesia and PRC [China] selected as case studies. Since the issue of PRC students in Australia has attracted considerable public attention and policy consideration, particular focus is placed on their experience." (SUMMARY IN FRE AND SPA)

Asia↗
PubMed1995

A time-dependent loss of retrograde transport ability in distally axotomized rubrospinal neurons.

Studies on the effect of axotomy on adult intrinsic central projection neurons have generally assumed that the severed proximal axonal stumps were still capable of retrogradely transporting tracer at varying times after injury. Failure of transport was interpreted as neuronal death, which is at odds with current understanding that central projection neurons survived distal axotomy. We used lumbar spinal cord-projecting rubrospinal neurons of the rat as a model to evaluate the ability of injured neurons to transport tracer retrogradely at different times after distal axotomy. We examined only the caudal part of the red nucleus, since rubrospinal neurons are concentrated here. In control animals, tracer applied to the rubrospinal tract at the T10 vertebral level labeled ventrolateral rubral neurons, while C3 application marked all rubral neurons. From 3 days after a T10 axotomy and tracer application, most ventrolateral neurons were no longer labeled by another tracer application at the C3 vertebral level via an axonal cut. The phenomenon was not caused by tracer toxicity, since a T10 tractotomy without tracer application also prevented these axotomized neurons from being labeled when treated similarly. Thus, neuronal retrograde transport capability was seriously retarded 3 days after a distal axotomy. Loss of retrograde transport may merely suggest that a mechanism no longer in service has been switched off, or perhaps it may insulate injured neurons from the effect of lesion site-derived factors. Using this property, we were able to localize cervical spinal cord-projecting rubrospinal neurons in the caudal red nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Asian female students in Australia: temporary movements and student migration.

"The most significant population movement affecting Australia in recent years has been a dramatic growth in the number of short term arrivals.... While a substantial literature has evolved concerning overseas students' temporary migration and settlement, there has been only limited demographic analysis undertaken to date, including minimal attempt to explore the participation and specific student experience of women. This paper seeks to address this omission through presentation of a detailed analysis of the characteristics of Asian female students within the overall student movement, together with a preliminary exploration of issues related to their personal and academic transition."

Australia↗
PubMed1995

The containment of toxic wastes: I. Long term metal movement in soils over a covered metalliferous waste heap at Parc lead-zinc mine, North Wales.

In order to stabilise and contain a toxic metalliferous waste heap at Parc Mine, North Wales, it was covered with 30-40 cm layer of quarry waste in 1977-1978, and sown with a grass/clover seed mixture. This study has examined subsequent metal movement in the cover material and its effect on vegetation. The results, especially when compared with previous observations, give no evidence of upward migration of metals by capillarity in the cover material. Sideways movement of leachate, however, appears to be carrying the metals into the cover material on the sloping sides, giving rise to increasing concentrations of heavy metals in the vegetation and dieback in some places. Root growth on the flat top of the heap is greater than on the slope, but the roots have not penetrated the waste and the contents of Pb, Zn and Cd in surface vegetation remain low. Surface covering of toxic waste with coarse materials restricting capillary rise is therefore a valid reclamation technique so long as lateral movement of toxic leachate can be controlled.

Journal Article↗
PubMed1994

Anti-IgM and anti-IgG modulate c-fos RNA levels differently in human B lymphocytes.

One component of the B cell activation cascade is the induction of the protooncogene c-fos. Data presented here demonstrate that stimulation of mIgM-bearing cells with either anti-IgM or the combination of PDB plus ionomycin generated comparable levels of c-fos RNA. Furthermore, a synergistic response was observed when the cells were treated with selected concentrations of anti-IgM plus either PDB or ionomycin. In contrast, stimulation of mIgG-bearing B cells with anti-IgG did not induce the c-fos RNA levels that were seen when these cells were treated with the combination of PDB plus ionomycin. Treatment of mIgG-bearing cells with only the combination of anti-IgG plus ionomycin yielded a synergistic response and anti-IgG plus PDB did not. Thus, induction of c-fos RNA appears to be different in mIgM- and mIgG-bearing B cells after stimulation through mIg.

Antibodies, Anti-Idiotypic↗
PubMed1994

Asian immigrant settlement and adjustment in Australia.

"This article provides a broad assessment of the settlement and adjustment of people born in the many countries of Asia who are resident in Australia, based on recently available data from the 1991 Census of Population and Housing. It examines some indicators of economic adjustment such as performance in the labor market, and some indicators of social adjustment, such as acquisition of English language proficiency."

Acculturation↗
PubMed1994

People movements between Australia and Asian-Pacific nations: trends, issues and prospects.

"This article examines the growth and diversification of...permanent, long and short-term movements of people from Asia and the Pacific and the growth in immigrant and local-born Australians departing Australia to live and work in Asia. The occasional controversies surrounding the growth of Asian arrivals and Australia's current push to integrate with the booming Asian economies are examined. The article concludes with a general discussion of the economic, social, cultural, and international consequences of the two-way movements of people between Australia and its Asian and Pacific neighbors."

Asia↗
PubMed1993

[A study of transpial migration of implanted serotonergic neurons in rat spinal cord].

Transpial migration of implanted 5-HT neurons from the subarachnoid space into the spinal cord was studied in adult Wistar rats. Embryonic raphe tissue or cell suspension containing 5-HT cells was used as grafts. The implanted 5-HT cells were monitored by 5-HT immunohistochemical method. The results are as follows: (1) 10 d after cutting the spinal cord at lower thoracic level, 5-HT fibers disappeared in the transected spinal cord. (2) Raphe tissue was implanted into the subarachnoid space of the thoracic lumbar segment after the spinal cord was cut. One month later, 5-HT positive cells could be found in the transected spinal cord with fibers extending into both the grey and the white matters. (3) If the raphe cell suspension instead was implanted, a number of 5-HT positive cells appeared in the grey matter near the implanted region and the distribution of these cells in the grey matter was quite consistent with the implanted range of the cell suspension in the subarachnoid space. The 5-HT positive cells which had entered into the spinal cord sent out fibers and reestablished a new fiber network in the grey matter. (4) After implantation, the number of the 5-HT positive fibers in the transected grey matter became more and more sparsely distributed with increasing distance from the cell bodies and the 5-HT positive fibers reappeared in the white matter were much less than that in the grey matter. Present results show that the implanted 5-HT neurons are able to migrate transpially from the subarachnoid space into the spinal cord.

Animals↗
PubMed1976

Administration of aspartame in non-insulin-dependent diabetics.

A study was designed to determine the effect of the consumption of the nutritive sweetener aspartame on non-insulin-dependent diabetics. Forty-three adult diabetics between the ages of 21 and 70 completed a 90-day study; all were diabetics whose conditions were managed by diet and/or hypoglycemic agents. Participants in the blind study were instructed to continue their usual diet and to take two capsules of an assigned preparation three times daily with meals, either the aspartame or the placebo. The 1.8 g of aspartame administered is approximately three times the expected daily consumption of aspartame if used as a sweetener to replace sugar. Throughout the study subjects were examined for (1) symptoms of intolerance, (2) fasting plasma phenylalanine levels exceeding 4 mg/100 ml, and (3) deterioration of diabetic control. At the conclusion of the study subjects exhibited no symptoms that could be traced to the administration of aspartame or the placebo, and diabetic control was unaffected by the chronic administration of these substances. Aspartame seems to be well tolerated by non-insulin-dependent diabetics.

Adult↗
PubMedDate not supplied

Modulation of cellular immune responses by cold water swim stress in the rat.

Alterations of cell-mediated immune responses in the rat produced by 5-day (one 3-min stress session each day for 5 days) and 1-day (three 3-min stress sessions within 12 h) cold water stress administration were investigated. Mitogenic responses to concanavalin A (Con A) and lipopolysaccharide (LPS), interleukin-2 (IL-2) production, CD4+/CD8+ T-cell ratios, and natural killer (NK) cell activity of blood and spleen lymphocytes were increased by the 5-day cold water stress. Responses to Con A and LPS, IL-2 production, and CD4+ and CD8+ percentages of blood and spleen lymphocytes were decreased by the 1-day cold water stress. Corticosterone levels were increased by both the 1-day and 5-day cold water stress. Cold water stress, as a natural stressor, may have its own unique pattern of neuroendocrine changes because of the accompanying body temperature variations that may influence immune functions.

Animals↗