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W Cao

Publications and source records attributed to W Cao.

At least 145 records · Page 8Linked to original sources
PubMed1995

Partial activation of CD8+ T cells by a self-derived peptide.

T cells are normally activated when the peptide for which they are specific is presented to them in the context of the appropriate major histocompatibility complex (MHC) (class I and Class II for CD8+ and CD4+ T cells, respectively). An increasing body of evidence indicates that structural homologues of the immunogenic peptide can partially activate or antagonize CD4+ T cells. CD8+ T cells may also be partially antagonized by such peptides, and self-derived peptides of this type may play a role in CD8+ T cell selection in the thymus. Activated CD8+ T cells lyse their targets by perforin-dependent granule exocytosis and by inducing apoptosis mediated by CD95 (also known as Fas or APO1) with its ligand (CD95L). Here we show that a clone of Kd-restricted CD8+ T cells specific for influenza haemagglutinin, which can also be activated in a crossreactive manner by a peptide derived from a myeloma tumour immunoglobulin heavy-chain variable region (IgVH) to kill by both routes, kills only by the CD95-CD95L pathway when stimulated by the corresponding germline IgVH peptide. As this germline IgVH peptide differs from the tumour peptide only at a single position buried in the MHC-binding groove, this indicates that CD95-CD95L-mediated killing can be triggered independently of the perforin-mediated pathway, and can be selectively affected by changes in MHC conformation.

Amino Acid Sequence↗
PubMed1995

Biogenesis of ISP6, a small carboxyl-terminal anchored protein of the receptor complex of the mitochondrial outer membrane.

To study the biogenesis of ISP6, an outer membrane component of the mitochondrial protein translocation complex, two fusion proteins have been made by fusing ISP6 to either the carboxyl- or amino-terminal end of the mouse dihydrofolate reductase (DHFR). In vitro import experiments showed that when DHFR was placed at the carboxyl-terminal end of ISP6, the resulting fusion protein 6-DHFR inserted into mitochondrial membrane less efficiently than the other form of the fusion proteins. In vivo this fusion protein lost its ability to suppress the temperature-sensitive phenotype of an isp42 mutant, while the other fusion protein DHFR-6, which was found targeted correctly to mitochondria, suppressed the mutant as well as the wild-type ISP6. Further analysis showed that the binding and insertion of DHFR-6 to mitochondrial outer membrane was not affected by deletion of either of the two mitochondrial protein receptors or by the predigestion of mitochondrial surface proteins prior to import. Additional data indicated that ISP42, which closely associates with ISP6 in the translocation complex, does not likely play the role of a targeting partner for ISP6. In summary, these data suggest that ISP6 may target to mitochondria by sequences at its carboxyl terminus and that the import process of ISP6 is most likely distinct from that of most other mitochondrial precursors, which are recognized by protein receptors on mitochondrial surface.

Amino Acid Sequence↗
PubMed1995

Stringent and relaxed specificities of TaqI endonuclease: interactions with metal cofactors and DNA sequences.

We have studied the roles of metal cofactors Mg2+ and Mn2+ in modulating substrate specificities during the enzymatic cycle of TaqI endonuclease using steady state and single-turnover kinetics. In the presence of Mg2+, stringent discrimination of TaqI against single base-pair changes (star sites) is manifested by the loss of tight, specific binding in the early stage of the enzymatic cycle. In the presence of Mn2+, relaxed specificity for a star site sequence is attributed to formation of three distinct classes of the ternary complexes: the highly activated TaqI-cognate-Mn2+ complex; the partially activated TaqI-star-Mn2+ complex; and the ground state, inactive TaqI-nonspecific-Mn2+ complex. In addition to a high affinity for a TaqI-DNA complex, Mn2+ also binds to TaqI in a DNA-independent fashion. This may facilitate enzyme activation, which could account for the observed relaxation in substrate specificity. Thus, the TaqI-DNA-Mn2+ complex could be formed by either of two pathways: TaqI binding to DNA followed by the binding of Mn2+ or TaqI first binding to Mn2+ followed by the addition of DNA. The inactive, nonspecific TaqI-star-Mg2+ complex virtually prohibits transition state interactions, but a TaqI-star-Mn2+ complex attains a measurable single-turnover rate. In the late stages of the enzymatic cycle, high affinity of Mn2+ to a TaqI-DNA complex and to the TaqI enzyme may also account for a slower rate of product release.

Base Sequence↗
PubMed1995

Effects of rapamycin on growth factor-stimulated vascular smooth muscle cell DNA synthesis. Inhibition of basic fibroblast growth factor and platelet-derived growth factor action and antagonism of rapamycin by FK506.

Rapamycin (RPM) is a potent and effective immunosuppressant which we have shown previously to inhibit intimal thickening in rat allograft and balloon-injured arteries. In this report, we have examined the effects of RPM on growth factor-induced vascular smooth muscle cell (VSMC) DNA synthesis. RPM potently inhibited platelet-derived growth factor (PDGF) (IC50 = 5 x 10(-9) M) and basic fibroblast growth factor (bFGF) (IC50 = 8 x 10(-10) M)-induced VSMC DNA synthesis. In contrast, only the highest concentrations of FK506 and CsA significantly altered PDGF- or bFGF-induced VSMC DNA synthesis. Addition of RPM (10(-9) M) at as late as 46 hr after growth factor addition still effectively suppressed bFGF- or PDGF-induced DNA synthesis by 76% and 54%, respectively. The extent of the antagonism of RPM's inhibition of bFGF-induced VSMC DNA synthesis by FK506 was inversely proportional to RPM concentration and directly proportional to FK506 concentration.

Animals↗
PubMed1995

Inhibition of smooth muscle cell proliferation in vitro by leflunomide, a new immunosuppressant, is antagonized by uridine.

Chronic rejection in the form of graft vascular disease (GVD) continues to plague clinical transplantation of vascularized organs. The histopathology of this lesion is characterized by neointimal hyperplasia, smooth muscle cell proliferation, and obliterative arteriopathy. Due to the lack of effective medical therapy for preventing or reversing these chronic vascular changes, retransplantation remains the final resort in treatment. Some of the newer immunosuppressive agents, including the new isoxazole derivative leflunomide (LFM), have shown efficacy in preventing chronic rejection in animal models of transplantation. Although its mechanism of action remains incompletely elucidated, previous work using lymphocytes in vitro suggests that the drug might act as a tyrosine kinase inhibitor, an inhibitor of de novo pyrimidine biosynthesis, or both. In order to elucidate whether the efficacy of LFM in vivo is attributable not only to anti-proliferative effects on the recipient immune system but also to direct effects on mesenchymal cells in the donor organ, we examined the effects of LFM on a transformed 9E11G murine smooth muscle cell (M-SMC) line in vitro. We demonstrate here that the active metabolite of LFM, A77 1726, dose-dependently inhibits the constitutive and growth-factor stimulated proliferation of M-SMC in vitro. Furthermore, the anti-proliferative effect of the drug can be reversed by the addition of uridine to the culture medium. These results suggest that inhibition of uridine biosythesis appears to be a mechanism by which LFM exerts anti-proliferative effects on both lymphocytes and smooth muscle cells, and this dual action may be responsible for its efficacy in preventing GVD in vivo.

Aniline Compounds↗
PubMed1995

Inhibition of smooth muscle cell proliferation in vitro by leflunomide, a new immunosuppressant, is antagonized by uridine.

Chronic rejection in the form of graft vascular disease (GVD) continues to plague clinical transplantation of vascularized organs. The histopathology of this lesion is characterized by neointimal hyperplasia, smooth muscle cell proliferation, and obliterative arteriopathy. Due to the lack of effective medical therapy for preventing or reversing these chronic vascular changes, retransplantation remains the final resort in treatment. Some of the newer immunosuppressive agents, including the new isoxazole derivative leflunomide (LFM), have shown efficacy in preventing chronic rejection in animal models of transplantation. Although its mechanism of action remains incompletely elucidated, previous work using lymphocytes in vitro suggests that the drug might act as a tyrosine kinase inhibitor, an inhibitor of de novo pyrimidine biosynthesis, or both. In order to elucidate whether the efficacy of LFM in vivo is attributable not only to anti-proliferative effects on the recipient immune system but also to direct effects on mesenchymal cells in the donor organ, we examined the effects of LFM on a transformed 9E11G murine smooth muscle cell (M-SMC) line in vitro. We demonstrate here that the active metabolite of LFM, A77 1726, dose-dependently inhibits the constitutive and growth-factor stimulated proliferation of M-SMC in vitro. Furthermore, the anti-proliferative effect of the drug can be reversed by the addition of uridine to the culture medium. These results suggest that inhibition of uridine biosynthesis appears to be a mechanism by which LFM exerts anti-proliferative effects on both lymphocytes and smooth muscle cells, and this dual action may be responsible for its efficacy in preventing GVD in vivo.

Aniline Compounds↗
PubMed1995

Longitudinal studies of blood pressure in children.

A longitudinal study of six years was conducted to find out the pattern of longitudinal changes of blood pressure and to affirm the "tracking phenomenon" of blood pressure in children in China. We initially measured blood pressure and related parameters of 2,946 children (aged 4-14 years) in 1981 at Fanshan county, Beijing, and then two follow-up remeasurements were conducted in 1985 and 1987, respectively. The results indicated that: the average level of blood pressure increases with age even after adjusting for height and weight; tracking coefficients of systolic blood pressure range from weak to moderate levels, increasing with age. Only 30% of the children whose systolic blood pressure was beyond the 90th percentile of the systolic pressure distribution at the first examination remained at the same region after four years. Multiple stepwise regression was used to determine factors correlated with blood pressure. Our results indicate that systolic blood pressure in children is correlated with body weight, pulse rate, serum glucose and HDL-C, while diastolic blood pressure is correlated only with pulse rate and serum glucose.

Adolescent↗
PubMed1995

[Use of parenteral nutritional support in patients with gastric cancer: the relationship of protein turn over, immunocompetence and tumor cell kinetics].

In order to elucidate the effect of preoperative parenteral nutritional support (PNS) on protein metabolism, host immunocompetence and tumor cell kinetics, two prospective trials were made in patients with gastric cancer. All the patients were given PNS for 7 days in addition to oral intake. The positive nitrogen balance and increase of protein anabolic rate was greater in PNS groups than in control group. There was a moderate increase in NKC after PNS. The rise in CD4+ was significant (P < 0.05). The percentage of G0/G1 cells fell after PNS (P < 0.01), while that of the whole proliferative phase (S + G2 + M) rose (P < 0.05). These changes were not noted in normal gastric mucosa. In conclusion, despite of stimulating tumor cell proliferation, PNS helps to promote whole body protein synthesis and to amelio-rate the immunocompetence of advanced gastric cancer patients before operation.

Adult↗
PubMed1995

[Reversal of acute hypoxic pulmonary hypertension with inhalation of nitric oxide].

The effect of inhalation of nitric oxide (NO) gas on acute hypoxic pulmonary hypertension was studied. Eighteen mongrel dogs were divided into two groups: hypoxic control group (FIO2 = 11%, n = 10) and NO inhalation group (FIO2 = 11%, NO inspiratory concentration = 44 ppm, n = 8). In the control group, the increase percent of mean pulmonary arterial pressure (mPAP) was 30.6% +/- 5.5%, 47.8% +/- 11.3%, 46.0% +/- 9.3%, 37.0% +/- 6.3% respectively at 5th, 15th, 30th and 60th minute after hypoxic ventilation. In the NO inhalation group, mPAP increment was 4.6% +/- 3.7%, 0.5% +/- 6.0%, 0.7% +/- 6.8%, 7.2% +/- 6.1%, respectively (all P < 0.01, compared with the control group). Inhaled nitric oxide also reduced the pulmonary vascular resistance significantly during hypoxic ventilation, but it had no remarkable effect on the systemic arterial pressure and vascular resistance. These results indicated that inhalation of nitric oxide gas may be used to treat acute hypoxic pulmonary hypertension.

Administration, Inhalation↗
PubMed1995

[Effect of NG-nitro-L-arginine methylester on the secretion of endothelin-1 in vivo and in cultured endothelial cells].

We investigated the effect of nitric oxide, derived from L-arginine on the production of endothelin-1 in vivo and in cultured endothelial cells. In mechanically ventilated anesthetized dogs (n = 5), mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR) and plasma endothelin-1 level of the femoral artery during hypoxic ventilation (FIO2 = 0.10) were 3.3 +/- 0.4kPa, 68.7 +/- 10.2kPa.s-1/L and 47.2 +/- 17.4ng/L respectively. NG-nitro-L-arginine methylester (L-NAME), an inhibitor of nitric oxide synthase, increased the peak value of mPAP and PVR during hypoxic ventilation to 4.9 +/- 0.6 kPa and 160.9 +/- 34.6kPa. s/L and its effect lasted for 3 hours. Meanwhile, plasma endothelin-1 level in the femoral artery was increased to 68.2 +/- 20.6, 72.8 +/- 20.9, 75.8 +/- 22.7 ng/L at 60, 120, 180 minutes respectively after the injection of L-NAME (P < 0.05 vs hypoxic control before the injection). In cultured endothelial cells from human umbilical veins, endothelin-1 level of culture medium increased significantly in 10(-11) and 10(-7) mol/L L-NAME group (n = 9, P < 0.05 vs control group). These findings indicate that endogenous nitric oxide is an inhibitory modulator of hypoxic pulmonary vasoconstriction and that nitric oxide inhibits the production of endothelin-1 in vivo and in cultured vascular endothelial cells.

Animals↗
PubMed1994

Recognition of an immunoglobulin VH epitope by influenza virus-specific class I major histocompatibility complex-restricted cytolytic T lymphocytes.

There are two immunogenic sites on the type A influenza A/Japan/57 (H2N2) hemagglutinin (HA) that can be recognized by class I major histocompatibility complex (MHC), H-2Kd-restricted cytolytic T lymphocytes (CTLs). One of these sites encompasses two distinct partially overlapping epitopes, which span HA residues 204-212 and 210-219. During the analysis of the fine specificity of CTL clones directed to the HA 210-219 epitope, we found that one clone 40-2 also recognized the myeloma cell line P3x63-Ag8. P3x63-Ag8 is derived from the MOPC 21 myeloma and expresses an immunoglobulin (Ig) heavy chain variable region (VH) gene which is a member of the murine 7183 VH gene family. Recognition was specific for the endogenously processed MOPC 21 heavy chain in association with the Kd molecules, since the SP2/0 derivative of P3x63-Ag8, which does not make a functional Ig H chain, is not recognized. The VH epitope recognized by clone 40-2 could be mapped to a 10 amino acid peptide spanning MOPC 21 VH residues 49-58. Cross-reactivity for the VH gene product was also demonstrable in some heterogeneous populations of CTL generated in response to influenza virus infection. These results represent the first demonstration of cross-reactivity for an endogenously processed product of a self-Ig by the CTL directed to a foreign antigen and raise the possibility that the Ig VH expression may regulate the CD8+ T cell response to foreign antigens.

Amino Acid Sequence↗
PubMed1994

Selective effects of retinal dopamine depletion on partial ischemia-induced electroretinographic hyperresponses in rabbits.

The interaction of retinal dopamine depletion and partial ischemia on the a- and b-wave amplitudes and implicit times of the electroretinogram was examined in adult pigmented rabbits. Seven days after 6-hydroxydopamine treatment, which resulted in a depletion of the amine, partial retinal ischemia was induced by raising the intraocular pressure. As expected, moderate elevation of intraocular pressure produced increases in both a- and b-wave amplitudes. Amplitude hyperresponses were significantly reduced in dopamine-depleted retinas. These reductions were more prominent with relatively lower intensities. However, response delays were not shortened but lengthened by 6-hydroxydopamine pretreatment. Together, these results point to a selective role of dopamine in partial retinal ischemia induced by moderate elevation of intraocular pressure in rabbits.

Animals↗
PubMed1994

Carbon dioxide interactions with irradiance and temperature in potatoes.

Separate controlled environment studies were conducted to determine the interaction of CO2 with irradiance and interaction of CO2 with temperature on growth of three potato cultivars. In the first study, an elevated CO2 concentration of 1000 micromoles mol-1 and an ambient CO2 of 350 micromoles mol-1 were maintained at the photosynthetic photon fluxes (PPF) of 17 and 34 mol m-2 d-1 with 12 h photoperiod, and at the PPF of 34 and 68 mol m-2 d-1 with 24 h photoperiod (400 and 800 micromoles m-2 s-1 PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes were significantly increased with CO2 enrichment, but the CO2 stimulation was less with higher PPF and longer photoperiod. Shoot dry weight was affected more by photoperiod than by PPF and CO2 concentrations. The elevated CO2 concentration increased leaf CO2 assimilation rates and decreased stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperiod. In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 micromoles mol-1 were combined with two air temperature regimes of 16 and 20 degrees C under a 12 h photoperiod. At harvest, 35 days after transplanting, tuber and total dry weights of potatoes reached a maximum with 1000 micromoles mol-1 CO2 at 16 degrees C, but continued to increase up to 2000 micromoles mol-1 CO2 at 20 degrees C. Plant growth was greater at 20 degrees C than at 16 degrees C under all CO2 concentrations. At 16 degrees C specific leaf weight increased substantially with increasing CO2 concentrations as compared to 500 micromoles mol-1 CO2, but increased only slightly at 20 degrees C. This suggests a carbohydrate build-up in the leaves at 16 degrees C temperature that reduces plant response to increased CO2 concentrations. The data in the two studies indicate that a PPF of 34 mol m-2 d-1, 20 degrees C temperature, and 1000-2000 micromoles mol-1 CO2 produces optimal tuber yield in potatoes.

Biomass↗
PubMed1994

Solid matrix and liquid culture procedures for growth of potatoes.

This report discusses the advantages and limitations of several different procedures for growth of potatoes for CELSS. Solution culture, in which roots and stolons are submerged, and aeroponic culture were not found useful for potatoes because stolons did not produce tubers unless a severe stress was applied to the plants. In detailed comparison studies, three selected culture systems were compared, nutrient film technique (NFT), NFT with shallow media, and pot culture with deep media. For the NFT and NFT plus shallow media, plants were grown in 0.3 m2 trays and for the deep medium culture, in 20 liter pots. A 1 cm depth of arcillite, a baked montmorillonite clay, was used as shallow media (NFT-arc). Peat-vermiculite mixture was used to fill the pots for the deep media. Nutrient solution, modified half-strength Hoagland's, was recirculated among the tray culture plants with pH automatically controlled at 5.5, and conductivity maintained at approximately 1100 microS cm-1 by adding stock nutrients or renewing the solution. A separate nutrient solution was used to water the pot plants four times daily to excess and the excess was discarded. Plants of Norland cv. were utilized and transplanted from sterile-propagated stem cutting plantlets. The plants were grown for 66 days under 12 h photoperiod in a first study and grown for 54 days under 24 h photoperiod in a second study. Under both photoperiods, total plant growth was greater in NFT-arc than in either NFT or pot culture. Under 12 h photoperiod, tuber dry weight was 30% higher with NFT-arc, but 50% lower with NFT, than with pot culture. Under 24 h photoperiod, however, tuber dry weight in both NFT and NFT-arc was only 20% of that in pot culture. The NFT and NFT-arc produced a greater shoot growth and larger number of small tubers than pot culture, especially with 24 h photoperiod. It is concluded that there are serious limitations to the use of NFT alone for growth of potatoes in a CELSS system. These limitations can be minimized by using a modified NFT with a shallow layer of media, such as arcillite, yet additional work is needed to ensure high tuber production with this system under long photoperiods.

Aquaculture↗
PubMed1994

Effects of dextromethorphan on ischemia induced electroretinogram changes in rabbit.

The present study was undertaken to determine whether dextromethorphan (DM), a potent N-methyl-D-aspartate antagonist, could attenuate the effects of ischemia on rabbit ERG. Retinal ischemia was induced by increasing intraocular pressure to 120 mm Hg for 30, 60, or 90 min. DM was intravenously administered before ischemia and maintained throughout the entire experimental period. ERGs were recorded prior to, during, and after ischemia. The results indicate that the b-wave hyperresponses and the delays in implicit times induced by 30 min. ischemia were suppressed by the administration of DM. Similar findings were obtained when ischemia lasted for 60 min, except that DM did not improve delayed implicit times, suggesting that cellular injury is still present. ERG changes resulting from 90 min ischemia were not reversed by DM treatment. Effects of DM treatment on a-wave were less prominent. Together, our results further support that DM can to some extent alleviate ischemic injury in the rabbit retina.

Animals↗
PubMed1994

[The effect of acute pulmonary alveolar hypoxia on canine plasma endothelin-1 levels].

The effect of acute pulmonary alveolar hypoxia on plasma endothelin (ET)-1 levels was observed in 10 anesthetized dogs (hypoxic group). Plasma ET-1 like immunoreactivity (-LI) levels increased significantly at the fifth, fifteenth, sixtieth minute after hypoxia (fractional inspiratory O2 concentration 10%), but they had no remarkable change at the thirtieth minute. It was suggested that the first peak of ET-1-LI levels (the fifth minute) might be caused by the release of endothelin-1 which was formed before hypoxia and the second peak could be associated with the secretion of ET-1 after hypoxia. The effect of ligustrazine on plasma ET-1-LI levels during hypoxia was also investigated in other 8 anesthetized dogs. Plasma ET-1-LI levels reduced significantly at the fifth minute after the injection of ligustrazine, compared with the hypoxic group. The result demonstrated that ligustrazine can inhibit the release of ET-1, which could be correlated with the blockade of calcium channel caused by ligustrazine.

Animals↗