Biomedical subjects

J Q Yu

Publications and source records attributed to J Q Yu.

7 recordsLinked to original sources

PubMed2006

Different effects of chilling on respiration in leaves and roots of cucumber (Cucumis sativus).

The effects of chilling on respiration (SHAM-resistant, cytochrome pathway and KCN-resistant, alternative pathway), temperature sensitivity, relative electrolyte conductivity, and degrees of oxidative stress (H(2)O(2) and malonaldehyde (MDA) contents) were separately examined in leaves and roots of cucumber (Cucumis sativus L.). After chilling at 8 degrees C for 4 days, both total respiration and KCN-resistant respiration in roots increased at different measurement temperatures. In contrast, SHAM-resistant respiration remained unchanged. In comparison, chilling significantly decreased the total respiration in leaves and this decrease was mostly due to a decrease in SHAM-resistant respiration. Chilling apparently decreased the sensitivity of KCN-resistant respiration to changes of temperature. The reduction levels of ubiquinone pool (UQr/UQt) increased both in chilled leaves and roots whilst pyruvate content increased only in chilled roots, but not in chilled leaves. Furthermore increases of H(2)O(2) and MDA contents were much greater in leaves than in roots. The same trend was also observed for ion leakage from tissues. Taken together, the results suggested that the higher chilling tolerance of roots was associated with their high total respiration and KCN-resistant respiration.

Cold Temperature↗

PubMed2004

Bioavailability of butachlor and myclobutanil residues in soil to earthworms.

To establish chemical extraction procedures for predicting bioavailability of butachlor and myclobutanil in soil, several solvent systems, including methanol, methanol-water (9:1), methanol-water (1:1), acetone-water (5:3), petroleum ether and water, were assessed for their feasibility in determining extractability of the target compounds from soil samples. Experimental data showed that the extractability of butachlor and myclobutanil by the solvents was well linearly correlated with their bioavailability to Eisenia foetida and Allolobophora caliginosa, indicating that these extraction procedures may be efficient for predicting bioavailability of the two pesticides. The concentrations of the pesticides accumulated in E. foetida and A. caliginosa varied with species, suggesting that the availability of the soil-sequestered pesticide is a species-dependent process.

Acetanilides↗

PubMed1996

4-Hydroxyphenyl retinamide is a highly selective activator of retinoid receptors.

Retinoids have shown promise as anti-cancer and cancer preventative agents. All-trans-N-(4-hydroxyphenyl)retinamide (4HPR) belongs to a new group of retinoids that not only inhibit the proliferation of cancer cells but also can induce apoptosis in certain cancer cells. Because of its increased efficacy against cancer cells and its low toxicity it has been entered into a number of clinical trials. However, its mechanism of action is not known, and it had been assumed that it is not a true retinoid. Here we analyze its ability to function as an activator of nuclear retinoid receptors (RARs and RXRs). We observe that, in transactivation assays, 4HPR is a potent transactivator with RARgamma and a moderate activator with RARbeta but is not an activator with RARalpha and RXRalpha. Furthermore, RARgamma-selective transactivation by 4HPR is enhanced on some response elements and reduced on others when compared to natural retinoids. In contrast to transactivation, 4HPR in transrepression assays functions mostly with RARalpha, RARbeta, and RXRalpha. Optimal receptor activation is seen at 4HPR concentrations at which it is a potent growth inhibitor and inducer of apoptosis. We conclude that 4HPR is a highly selective activator of retinoid receptors. We propose that this selective activation of the nuclear receptors is likely to be the basis for its specific biological activities and its favorable pharmaceutical properties.

Anticarcinogenic Agents↗

PubMed1996

The role of Ca2+ and protein kinase C in the acrosome reaction of giant panda (Ailuropoda melanoleuca) spermatozoa.

Fresh semen was collected from adult male giant pandas and the role of Ca2+, Ca2+ ionophore A23187 and protein kinase C (PKC) in sperm motility and acrosome reaction (AR) was assessed by lens culinaris agglutinin conjugated with fluorescein isothiocyanate (FITC-LCA) labeling and transmission electron microscopy. The AR in giant panda spermatozoa was characterized by vesiculation of the outer acrosomal membrane through its invagination. Both the sperm motility and the AR rate decreased significantly (p < 0.05) in Ca2+-free and low Ca2+ medium. The addition of 10 microM Ca2+ ionophore A23187 potently stimulated AR. After incubation for capacitation, the PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated AR in a dose-dependent manner and its effect could be overcome by the PKC inhibitor staurosporine. These results suggest that Ca2+ and PKC play an important role in the sperm acrosome reaction of the giant panda.

Journal Article↗

PubMed1993

Tissue factor contributes to microvascular defects after focal cerebral ischemia.

BACKGROUND AND PURPOSE: Microvascular perfusion defects occur after occlusion and reperfusion of the middle cerebral artery in examples of focal cerebral ischemia. In addition to cellular (eg, polymorphonuclear leukocyte) contributors to the focal "no-reflow" phenomenon, activation of coagulation may also play a role. We have tested a potential role of tissue factor-mediated coagulation in the microvascular perfusion defects seen after focal cerebral ischemia-reperfusion in a baboon model of reversible middle cerebral artery occlusion with the murine anti-tissue factor monoclonal antibody TF9-6B4. Tissue factor is the principal resident procoagulant substance in cerebral tissues and has a distinct perivascular distribution. METHODS: Microvascular patency in the basal ganglia after 3-hour middle cerebral artery occlusion and 1-hour reperfusion was quantified by computerized video imaging of carbon-tracer perfused tissues. Animals were randomized to receive intravenous TF9-6B4 (10 mg/kg) 10 minutes before middle cerebral artery occlusion (n = 6) or no treatment (n = 6) in an open study. RESULTS: In the control animals, a significant decrease in patency was confirmed in microvessels less than 30 microns in diameter. Infusion of TF9-6B4 before middle cerebral artery occlusion produced a stable maximal level of circulating antibody within 10 minutes, which lasted the duration of ischemia and reperfusion. An increase in reflow in microvessels of all size classes occurred after TF9-6B4 infusion, which was significant in those 7.5 to 30 microns (P = .038) and 30 to 50 microns (P = .013) in diameter. CONCLUSIONS: These results indicate that tissue factor-mediated events may also contribute to no-reflow in noncapillary microvessels after focal cerebral ischemia.

Animals↗

PubMed1992

Tissue factor localization in non-human primate cerebral tissue.

Tissue factor (TF), the principal procoagulant of human brain, resides in specific regions of the non-human primate central nervous system. Immunohistochemical studies employing murine anti-human TF monoclonal antibodies (MoAbs) detected TF antigen in the cortex, basal ganglia, cerebellum, and cervical spinal cord in three normal baboon subjects. Although significantly less prominent than human cortical gray matter, a distinct partition of TF in gray matter > white matter was noted. The gray matter predilection of TF was confirmed in primate temporal and parietal lobe cortex by both sandwich ELISA and one-stage coagulation assay. Variation in the relative quantity of TF antigen was observed by ELISA among the three subjects studied. Procoagulant activity followed the pattern of TF antigen (cortical gray matter > basal ganglia > or = cerebellum > cortical white matter), and was 96.5-98.5% inhibitable by a function inhibiting anti-human TF MoAb combination. TF antigen was associated with the microvasculature of all cerebral tissues studied, and spared capillaries most selectively in the cerebral cortex, basal ganglia, and cerebellum. These findings suggest a highly specific ordering of TF antigen and related procoagulant activity in the central nervous system of the baboon, confined primarily to gray matter parenchyma, and to the non-capillary microvasculature.

Animals↗

PubMedDate not supplied

Monte Carlo estimation of errors in 13C-NMR relaxation studies of a DNA oligomer duplex.

An analysis of errors has been done with the Monte Carlo method for natural abundance 13C-NMR relaxation studies of a DNA duplex. Repeated measurements of the longitudinal relaxation time, T1, and the heteronuclear NOE were made at 90.6 MHz on the duplexed DNA pentanucleotide, [d(TCGCG)]2. The deviations averaged over all carbons were 13% for T1 and 9% for NOE. These relative deviations were applied to generate 100 values of T1 and NOE with normal distributions about the measured mean values for each carbon. A new version of MOLDYN, called McMOLDYN, has been written, which was used to generate 100 values of T1 and NOE with normal distributions corresponding to the measured errors; the same error distributions were also applied to measurements at 125.8 MHz. The order parameter, S2, and the effective internal correlation time, tau e, in the Model-Free Approach have been optimized from the distributions simulated by McMOLDYN. McMOLDYN also permits the automated entry of multiple sets of initial guesses for the output parameters S2, tau e, and tau m. In addition, McMOLDYN adds cross-relaxation terms from chemical shift anisotropy, increasingly important as spectrometer magnetic fields get higher. Between the two parameters optimized, S2 has the smallest relative error, estimated at 15% on average, which means that S2 is a well-defined parameter. However, tau e is very poorly defined with the average relative error estimated 85%; it is typically found in the range of 30-300 ps.

Anisotropy↗