Biomedical subjects
Publications and source records attributed to D Zhao.
A specific calculation of a family of spread functions of the new type SISAM with only one grating, which is equal in effect to two grating, is made as a function of the dimension of light source and the modulation amplitude and their optimum values are determined.
The characteristic infrared spectra of eight novel 9-methoxy benzoxanthene-3, 4-dicarboximide fluorescent dyes was studied and the substiuent influences on the spectrum nature was also pointed out. The nature of N-substituent group in the imide ring affects the position of v(c=o) by mesomeric and inductive effects. Imides give the rise to two vc=o absorptions, namely v(a)(c=o) and v(as)(c=o) (1600-1700cm(-1)). The separations between v(a)(c=)o and v(as)(c=o) were about 36-43cm(-1).
We examined the relation of an ischemic syndrome with the progression of coronary disease early (<3 years) after multiple bypass grafting utilizing an internal mammary artery and saphenous vein grafts. Data indicate that an ischemic syndrome is associated with progression of native coronary disease distal to the graft or total occlusion of the saphenous vein graft in most cases.
OBJECTIVES: The purpose of this study was to evaluate the flexure strength, elastic modulus, and fracture toughness (mode I, mode II, and mixed mode) of resin and four specially made dental restorative composite materials. METHODS: Testing was done on prismatic bars in flexure and disk specimens in diametral compression. Fracture strengths were analyzed using Weibull statistics. Statistical analysis consisted of a one-way analysis of variance followed by a Tukey multiple means analysis for each of the materials. In addition, the fracture strengths were analyzed using Weibull statistics due to the brittle behavior exhibited by these materials. RESULTS: The experimental results showed that the addition of fillers resulted in a significant three-fold increase in flexure modulus and a significant 30-50% increase in fracture toughness from the resin. As was indicated by the different Weibull modulus values, strength data obtained from four-point bending were not related with strength data from three-point bending. A straight notch vs. a relatively sharp V-notch gave higher fracture toughness values. Fracture toughness was dependent on the depth of a straight notch and was practically independent of the V-notch depth. Mode I and II fracture toughness in two composites (75Sr and 75Sr10) were carried out on precracked disk specimens in diametral compression. The results of mode I toughness were close to those obtained from the flexure testing. The mode II toughness values were greater than the mode I values by more than 30%. The data fit an equation of the form KI/KIC + (KII/KIIC)2 = 1(where KI, KII are the mode I and II stress intensity factors and KIC, KIIC are the respective critical values). SIGNIFICANCE: Notching technique, testing configuration (three-point vs. four-point loading), and method of testing (bar vs. disk) have significant effect on the fracture properties.
We report the analysis of a number of lines of Drosophila melanogaster containing insertions of the yeast gal4 gene. By crossing a UAS-lacZ fusion gene as a reporter into these lines, we analysed the expression patterns of beta-galactosidase during oogenesis. Since there is no expression of GAL4 in the germ-line in these experiments, this is an ideal system for the analysis of expression patterns in sub-sets of follicle cells. These lines provide ideal markers for sets of follicle cells, e.g. anterior or posterior polar cells for studying genetic interactions in oogenesis; however, they can also be used in the same way as conventional enhancer traps to clone nearby genes with similar expression patterns. The advantages of this dual gal4/UAS system over conventional enhancer trapping includes the possibility of GAL4-directed misexpression and antisense expression studies to establish the function of the genes we identified during follicle cell determination and differentiation. These studies could lead to the isolation of homologous genes crucial in mammalian oogenesis. Understanding how the somatic cells and germ cells interact to promote growth and maturation of the mammalian follicle and oocyte could well be crucial for improving the fertility of eggs used for in-vitro fertilization programmes, and could provide methods for assessing the quality of eggs.
It was shown by Koshy et al. [1990, Proc. Natl Acad. Sci USA, 87, 8697-8701; 1994, Biochem. J., 299, 347-350] that the substitution of proline 30 by alanine (P30A) of Drosophila melanogaster and rat cytochromes c exhibited decreased stabilities in both the heme iron-methionine sulfur (Fe-S) bond and overall protein conformation. Now we have found that the stability properties of the equivalent mutant of Rhodobacter capsulatus cytochrome c2 (P35A) are somewhat different. Based on optical and NMR spectroscopies, the Rb.capsulatus P35A alkaline transition (pKalk) was found to be unchanged with respect to the wild type, suggesting that the mutation in Rb.capsulatus cytochrome c2 has little effect on the stability of the Fe-S bond. However, Rb.capsulatus conformational stability was found to be decreased by 1.6 kcal/mol in the oxidized state. The difference in the stability properties of the equivalent proline to alanine substitutions in various species underscores the importance of studying mutations in more than one species before drawing generalizations about the role of conserved residues in protein structure and function.
The imbalance between normal insulin-like growth factor-I (IGF-I) and markedly increased IGF binding protein (IGFBP) plasma levels plays a pathogenic role for growth retardation and catabolism in children with chronic renal failure. To investigate the mechanism of these alterations, experiments were performed in an experimental model of uremia in rats (5/6 nephrectomy) and in pair-fed and ad libitum-fed sham-operated controls Using a specific solution hybridization/RNase protection assay, we observed a marked reduction of hepatic IGF-I messenger RNA (mRNA) abundance at steady state in uremic animals (37 +/- 5% of control) compared both with pair-fed (65 +/- 10%) and ad libitum-fed controls (100 +/- 11%) (P < 0.001). Reduced IGF-I gene expression was clearly organ-specific; it was most pronounced in liver (significant vs., pair-fed controls) and lung and muscle tissue (significant vs., ad libitum-fed controls); no change was observed in kidney and heart tissue. To determine a potential mechanism of reduced hepatic IGF-I gene expression in uremia, the hepatic GH receptor gene expression in the same experimental animals was analyzed by specific solution hybridization/RNase protection assay. Uremic animals had a 20-30% reduction of hepatic GH receptor mRNA abundance compared with controls. Hepatic GHBP expression in uremia was decreased in parallel. Despite the reduction of hepatic IGF-I mRNA abundance, plasma IGF-I levels in uremia were not different from ad libitum-fed controls. This discrepancy is explained by an increased concentration of IGFBPs in uremic plasma. By RIA, plasma IGFBP-1 levels in uremia were increased 4-fold; by Western immunoblot, plasma IGFBP-2 levels were increased 7-fold and plasma IGFBP-4 levels were increased 2-fold compared with both control groups. Intact IGFBP-3 (M(r), approximately 48 kDa) and low molecular IGFBP-3 fragments were not significantly different among the three groups. By Northern blot analysis, hepatic IGFBP-1 mRNA levels in uremia were 2-fold higher than in controls. IGFBP-2 mRNA abundance in liver tissue was increased 4-fold, whereas in kidney there was a significant reduction of IGFBP-2 mRNA (30% of control). IGFBP-4 mRNA was increased by 50% in kidney but not in liver. Plasma insulin and corticosterone levels were not different among the groups. Our study shows that hepatic IGF-I gene expression was specifically reduced in uremia, partially as the consequence of a reduced hepatic GH receptor gene expression. One of the mechanisms contributing to increased IGFBP levels in uremia is increased hepatic gene expression of IGFBP-1 and IGFBP-2. The imbalance between reduced hepatic IGF-I production and increased hepatic IGFBP-1 and 2 production is likely to play a pathogenic role for catabolism and growth failure in CRF.
To investigate the relationship between mitochondrial enzyme activities and mitochondrial function after cervical cord injury, cervical cord model was prepared using Allen method in cats. Changes in mitochondrial Na+, K(+)-ATPase, Ca2+, Mg(2+)-ATPase, superoxide dismutase (SOD) activities, contents of malondialdehyde (MDA) and mitochondrial function in cervical cord were observed by different biochemical methods. The results showed that mitochondrial Na+, K(+)-ATPase, CA2+, Mg(2+)-ATPase, SOD activities decreased; mitichondral respiratory control rate (RCR), P/O ratio and oxidative phosphorylation rate (OPR) were also depressed is compared with control group (P < 0.05), but MDA level significantly increased compared to control group (P < 0.01). The results demonstrate that there is close correlation, between mitochondrial ATPase. SOD activities and mitochondral function, suggesting that mitochondrial pathophysiological alteration plays important roles in the secondary damage after cervical cord injury.
The effect of extremely low frequency magnetic field (ELMF, 15 Hz, 18 mT) on ischemic brain produced by ligation of general carotid artery in left side was studied in rats. The results showed that the degree of brain blood vessel dilation was higher in magnetic field group than that in control group at the 1st, 3rd and 6th hour after ligation and the extent of damage of neurocyte was apparently lighter in magnetic field group than that in control group at the 3rd and 6th hour after ischemia. It indicates that ELMF stimulation improves the brain blood circulation after brain ischemia and alleviates the brain ischemic reaction.
The combined substances composed of chitosan gel and rough abstract contained schwanns cell (RSC) plus extra nerve growth factor (NGF) were filled in silicone chambers to bridge a 10 mm nerve gap in rat. The RSC were created by removing autonerve's epineurium and perineurium. The very same other silicone chambers with only NGF saline solution were used as control. Electrophysiologic recording and transverse section imaging analysis at 12 weeks postoperatively showed better result in the experimental group, compared with the control group. The research suggests a new tissue engineering method for repairing nerve gap.
Seismic tomography revealed a low seismic velocity (-5%) and high Poisson's ratio (+6%) anomaly covering about 300 square kilometers at the hypocenter of the 17 January 1995, magnitude 7.2, Kobe earthquake in Japan. This anomaly may be due to an overpressurized, fluid-filled, fractured rock matrix that contributed to the initiation of the Kobe earthquake.
We sought to evaluate the significance of endogenous hyaluronic acid levels and in vivo uptake of exogenous hyaluronic acid as markers of liver endothelial cell damage and correlate these findings to graft survival/function in a rat orthotopic liver transplant model. Endogenous hyaluronic acid levels were measured after orthotopic liver transplantation performed with freshly explanted livers, with livers preserved for 30 hr, and after sham operation. Exogenous hyaluronic acid uptake was evaluated in six study groups: fresh liver grafts, livers preserved for 12 hr, 24 hr, 30 hr and 48 hr, and sham-operated livers. Endogenous hyaluronic acid levels fell after orthotopic liver transplantation with freshly harvested livers and after sham operation, but rose in animals transplanted with livers preserved for 30 hr (P<0.01 vs. sham operation). In the preserved group, there was no difference in endogenous hyaluronic acid levels between survivors and nonsurvivors. Uptake of exogenous hyaluronic acid was significantly lower after orthotopic liver transplant with grafts preserved for 12 hr than after sham operation or orthotopic liver transplant with nonpreserved livers (P<0.05). Hyaluronic acid uptake further deteriorated in the 24-, 30-, and 48-hr groups. No significant difference in hyaluronic acid elimination rate was found when results obtained from livers preserved for extended periods (>12 hr) were compared in survivors and nonsurvivors. Hyaluronic acid uptake was reevaluated in surviving animals after 2 weeks. Completely restored function was observed in all survivors, indicating recovery of endothelial cells. We conclude that endogenous hyaluronic acid levels and exogenous hyaluronic acid uptake are reliable markers of liver sinusoidal endothelial cell function and that normal or moderately compromised hyaluronic acid uptake is associated with good graft function. On the other hand, endothelial cell dysfunction suggested by poor hyaluronic acid elimination is not a completely reliable predictor of subsequent deterioration of graft function in rat liver transplantation.
Retinoic acid, a developmental signal implicated in the formation of the neural axis, is present at high levels in the early embryonic trunk region, where it is synthesized by a novel dehydrogenase. Here we show that the same enzyme is inducible by retinoic acid in P19 teratocarcinoma cells, and we report the cloning from P19 cells of a cDNA encoding a novel dehydrogenase, named retinaldehyde dehydrogenase-2 (RALDH-2). Expression in COS cells shows RALDH-2 to be highly effective in oxidation of retinaldehyde, with no detectable activity on any other aldehyde tested. In situ hybridization histochemistry on the embryonic trunk reveals RALDH-2 mRNA both in mesoderm and neuroectoderm, with highest neuroectodermal expression in the ventral horn of the spinal cord at two restricted locations along the anteroposterior axis, presumably the subpopulation of motoneurons that innervate the limbs.
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In this study, two alternative three-dimensional (3D) models of horseradish peroxidase (HRP-C)-differing mainly in the structure of a long untemplated insertion-were refined, systematically assessed, and used to make predictions that can both guide and be tested by future experimental studies. A key first step in the model-building process was a procedure for multiple sequence alignment based on structurally conserved regions and key conserved residues, including those side chains providing ligands to the two Ca2+ binding sites. The model refinements reported here include (1) optimization of side-chain conformations; (3) addition of structural waters using a template-independent procedure; (2) structural refinement of the untemplated 34 amino acid insertion located between the F and G helices, using both energy criteria and NMR data; (4) unconstrained energy optimization of the refined models. Using these procedures, two refined structures of HRP-C were obtained, differing mainly in the conformation of this long insertion. The presence of residues in this insertion that could potentially interact with bound substrates suggests a functional role that may be related to the general ability of class III peroxidases to form stable 1:1 complexes with a variety of substrates. The structural validity of the models was systematically assessed by a variety of criteria. Most notably, the ProsaII z scores and Profiles 3D scores of the two HRP-C models indicated that they are significantly better than would be obtained by simple amino acid replacement, using any of the known structures as a template. These two 3D HRP-C models, were then used to predict candidate residues for the assignment of NOESY cross-peaks previously noted in 2D-NMR studies. Specifically, the residues known as Ile X, Phe A, Phe B, aliphatic residue Q, and Ile T. Candidate substrate binding sites were also identified and compared with experimentally based predictions. This work is timely because new X-ray structures are anticipated that will facilitate the validation of these procedures.
The optimized g-tensor parameters for the oxidized form of Rhodobacter capsulatus cytochrome c2 in solution were obtained using a set (50) of backbone amide protons. Dipolar shifts for more than 500 individual protons of R. capsulatus cytochrome c2 have been calculated by using the optimized g-tensor and the X-ray crystallographic coordinates of the reduced form of R. capsulatus cytochrome c2. The calculated results for dipolar shifts are compared with the observed paramagnetic shifts. The calculated and the observed data are in good agreement throughout the entire protein, but there are significant differences between calculated and experimental results localized to the regions in the immediate vicinity of the heme ligand and the region of the front crevice of the protein (residues 44-50, 53-57, and 61-68). The results not only indicate that the overall solution structures are very similar in both the reduced and oxidized states, but that these structures in solution are similar to the crystal structure. However, there are small structural changes near the heme and the rearrangement of certain residues that result in changes in their hydrogen bonding concomitant with the change in the oxidation states; this was also evident in the data for the NH exchange rate measurements for R. capsulatus cytochrome c2.
OBJECTIVE: To investigate the effects of platelet activating factor (PAF) receptor and its antagonist on secondary damage after spinal cord injury. METHODS: We extracted spinal cord neurocyte membrane protein in cats by improved Domigo method. The specific binding sites of PAF were measured by 3H-PAF radioligand binding test. RESULTS: There were both high affinity binding sites and low affinity binding sites of PAF on spinal cord neurocyte membrane. The Kd1, Bmax1, Kd2 and Bmax2 of PAF receptor on spinal cord neurocyte membrane at 2, 6 hours and 1 week after trauma significantly decreased as compared to sham-operated control group (P < 0.01). PAF receptor antagonist BN52021 could reduced water content and Even's blue content of injured spinal cord tissue, also improve pathological change of spinal cord tissue after trauma. CONCLUSIONS: PAF receptor plays an important role in inducing pathophysiological process of secondary damage after trauma. PAF receptor antagonist can effectively prevent and treat secondary damage after trauma.
The effects of a series of substances on the biological function of endothelin (ET) are reported. The substances used are: synthetic inhibitors of endothelium derived relaxing factors (EDRFs), inhibitor of big-endothelin converting enzyme phosphoramidon, antiserum of endothelin, antagonists of endothelin A receptor BQ123 and JKC301, and two Chinese anti-snake venom herb medicines Lobelia radicans Thumb and Taris polyphylla Smith var. chinensis (Franch) Hara. The results showed that inhibiting the production of nitric oxide (NO) could stimulate ET release from vascular endothelium, elevate plasma ET and increase blood pressure. These changes could be reversed by L-arginine (L-Arg), the substrate of nitric oxide synthase (NOS). The amount of ET released by arterial endothelium could be increased or inhibited by inhibiting or stimulating the synthesis of prostacyclin (PGI2). The plasma ET level and blood pressure in both SHR and WKY rats could be decreased by giving phosphoramidon (PhR). The above results indicate that the biological effects of ET could be antagonized by inhibiting the synthesis or release of ET, decreasing the level of plasma ET, blocking the binding of ET with its receptor and using some Chinese anti-snake venom herb medicines.