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C Zhang

Publications and source records attributed to C Zhang.

At least 235 records · Page 13Linked to original sources
PubMed2000

Role of nitric oxide in lipopolysaccharide-induced oxidant stress in the rat kidney.

Lipopolysaccharide (LPS)-induced renal oxidant injury and the role of nitric oxide (NO) were evaluated using the inducible nitric oxide synthase (iNOS) inhibitor L-iminoethyl-lysine (L-NIL). One group of male rats received LPS (Salmonella minnesota; 2 mg/kg, i.v.). A second group received LPS plus L-NIL (3 mg/kg, i.p.). A third group received saline i.v. At 6 hr, iNOS protein was induced in the kidney cortex, and plasma nitrate/nitrite levels were increased from 4 +/- 2 nmol/mL in the Saline group to 431 +/- 23 nmol/mL in the LPS group. The value for the LPS + L-NIL group was reduced significantly to 42 +/- 9 nmol/mL. LPS increased blood urea nitrogen levels from 13 +/- 1 to 47 +/- 3 mg/dL. LPS + L-NIL reduced these levels significantly to 29 +/- 2 mg/dL. Plasma creatinine levels were unchanged in all groups. Tissue lipid peroxidation products in the kidney were increased from 0.16 +/- 0.01 nmol/mg in the Saline group to 0.30 +/- 0.03 nmol/mg in the LPS group. LPS + L-NIL reduced the values significantly to 0.22 +/- 0.02 nmol/mg. Intracellular glutathione levels were decreased in the kidneys from 1.32 +/- 0.1 nmol/mg in the Saline group to 0.66 +/- 0.08 nmol/mg in the LPS group. LPS + L-NIL increased the levels significantly to 0.99 +/- 0.13 nmol/mg. LPS increased the 3-nitrotyrosine-protein adducts in renal tubules as detected by immunohistochemistry, indicating the generation of peroxynitrite. L-NIL decreased adduct formation. These data indicated that LPS-induced NO generation resulted in peroxynitrite formation and oxidant stress in the kidney and that inhibitors of iNOS may offer protection against LPS-induced renal toxicity.

Animals↗
PubMed2000

In vitro stability of plasma-sprayed hydroxyapatite coatings on Ti-6Al-4V implants under cyclic loading.

The success of hydroxyapatite (HA)-coated Ti-6Al-4V implants relies on the long-term stability of HA coatings. In this study, the mechanical stability of plasma-sprayed HA coatings on Ti-6Al-4V implants under four-point cyclic bending was systematically investigated in both air and simulated body fluid (SBF) environments at room temperature. To have a clear view of the microscale damage evolution, the surface morphology change of HA coatings during cyclic loading was carefully examined by scanning electron microscopy at the same locations on the coating surfaces after four-point bending for 4, 6.5, 8.5, and 10 million cycles. Also, possible changes of other characteristics such as thickness, weight, crystallinity, and residual stress of HA coatings were measured as a function of loading cycles. Up to 10 million cycles of bending in air and SBF, we found no significant microcracking or coating spalling on the surface of coatings, and no significant changes in thickness, weight, crystallinity, or residual stress of the plasma-sprayed HA coatings. The experiment results indicate that thickness and crystallinity had no effects on the stability of the HA coatings. HA coating resistance to the cyclic four-point bending might result from the stress shielding effects of preexisting microcracks in the coatings.

Biocompatible Materials↗
PubMed2000

Male affiliation, cooperation and kinship in wild chimpanzees.

Long-term field research has revealed that male chimpanzees, Pan troglodytes, affiliate and cooperate in several contexts. Assuming close genetic relationship among males, affiliative and cooperative behaviour have been hypothesized to evolve through the indirect effects of kin selection. We tested the hypothesis that matrilineal genetic relatedness affects patterns of male social affiliation and cooperation in an unusually large community of chimpanzees at the Ngogo study site, Kibale National Park, Uganda. Field observations indicated that six behavioural measures of affiliation and cooperation among 23 adult males were significantly correlated with each other. Sequences of the first hypervariable portion of the mtDNA genome revealed that three pairs of males and one quintet shared mtDNA haplotypes. Matrix permutation tests using behavioural and genetic data showed that males that affiliated and cooperated with each other were not closely related through the maternal line. These findings add to a growing body of empirical evidence that suggest kinship plays an ancillary role in structuring patterns of wild chimpanzee behaviour within social groups. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Increased response to intrastriatal L(+)-2-amino-4-phosphonobutyrate (L-AP4) in unilateral 6-hydroxydopamine-lesioned rats.

Unilateral intrastriatal injection of the prototype Group III metabotropic glutamate receptor agonist L(+)-2-amino-4-phosphonobutyrate (L-AP4) induces rotation in rats with ipsilateral unilateral 6-hydroxydopamine lesions of the nigrostriatal projection but not in unlesioned control animals [Kearney et al., (1998) Neuroscience 87:881-891]. We studied differences in striatal neuron Fos-like immunoreactivity expression, striatal neuron Fos-like immunoreactivity localization, and regional [(14)C]-2-deoxyglucose uptake after unilateral intrastriatal injection of L-AP4 between control and unilateral 6-hydroxydopamine lesioned rats. There was a left shift of the dose response curve with more striatal neurons expressing Fos-like immunoreactivity at lower doses of L-AP4 in 6-hydroxydopamine lesioned animals. In unlesioned striata, L-AP4 injections tended to induce Fos-like immunoreactivity in striato-pallidal projection neurons. In lesioned animals, the majority of striatal neurons expressing Fos-like immunoreactivity were striatonigral projection neurons. In both control and lesioned animals, intrastriatal injection of L-AP4 produced widespread decreases in [(14)C]-2-deoxyglucose uptake in basal ganglia nuclei and related regions, but the magnitude of this effect increased markedly in lesioned animals. Striatal dopamine denervation enhances the response of striatal neurons to intrastriatally injected L-AP4 with an apparent shift in the type of striatal projection neuron responding to L-AP4.

Adrenergic Agents↗
PubMed2000

Thyroid hormone regulates slow skeletal troponin I gene inactivation in cardiac troponin I null mouse hearts.

Two main troponin I genes, cardiac (cTnI) and slow skeletal (ssTnI), are expressed in the mammalian heart under the control of a developmentally regulated program. ssTnI is expressed first in embryonic and fetal heart, and is then downregulated by an unknown mechanism after birth. Unlike other contractile protein genes, ssTnI is not re-expressed during hypertrophy or end-stage heart failure in rats and humans. In the present study, we also show that ssTnI re-expression does not occur in hypertrophic mouse heart. To investigate ssTnI downregulation further, cTnI knockout mice were used to examine a possible role for thyroid hormone. Northern blot analysis of euthyroid animals showed a time-dependent loss of ssTnI mRNA that was similar for wild-type, heterozygous and homozygous cTnI mutant mice. In cTnI null mice made hyperthyroid by l -thyroxine, the duration of ssTnI expression assessed by both mRNA and protein content was abbreviated compared with the euthyroid group. Hyperthyroid cTnI null mice also died significantly earlier than euthyroids (postnatal day 14 v day 18). In cTnI null mice made hypothyroid by addition of phenylthiouracil to the drinking water, ssTnI expression was prolonged and mice survived until day 20 or 21. Overall, the results indicate that inactivation of the ssTnI gene occurs even in the absence of cTnI mRNA and protein indicating that these are not critical signals for ssTnI down regulation in the heart. In contrast, thyroid hormone influences the time course of ssTnI expression and the life span of cTnI null mice probably through a transcriptional regulation of ssTnI in the heart.

Animals↗
PubMed2000

Phylogenetic investigations of the stephanoberyciformes and beryciformes, particularly whalefishes (Euteleostei: Cetomimidae), based on partial 12S rDNA and 16S rDNA sequences.

DNA data were collected from a number of acanthomorph fishes for 12S rDNA (30 sequences) and 16S rDNA (39 sequences) to investigate the phylogenetic relationships of genera within Cetomimidae (whalefishes) and of this family within the Stephanoberyciformes/Beryciformes assemblage. The Cetomimidae are apparently monophyletic. Within the family, species of Gyrinomimus and Cetomimus form a clade but the former genus is paraphyletic with respect to the latter. Cetostoma is sister to Ditropichthys rather than to Gyrinomimus plus Cetomimus as suggested by morphological analyses. Rondeletiidae + Cetomimidae + Barbourisiidae are shown, as expected from morphological analyses, as a monophyletic group in the 12S rDNA analyses, but not in the 16S rDNA or combined analyses, although the shortest trees showing the group require only one extra step in each case. These three families plus Melamphaidae (our sample of Stephanoberyciformes) are not shown as a group in any analysis, with Melamphaidae being sister to Berycidae in the 16S and combined analyses, but dispersed in the 12S analyses. Maximum-parsimony trees without imposed constraints are notably shorter than trees constrained to show ordinal groupings or either of the two main current hypotheses of Stephanoberyciformes/Beryciformes relationships. The length difference is highly significant for most comparisons using either 12S or 16S rDNA sets or their combination, and significant or nearly so for all comparisons. In particular, the Beryciformes is unlikely to be monophyletic. The Holocentridae are included, with high bootstrap and Bremer support, in a clade of non-beryciforms comprising the Gempylidae, Zeidae, and Atheriniformes (the only higher acanthomorphs sampled) and not with other Beryciform families. In these data, the Berycidae are the sister to the Melamphaidae, a stephanoberyciform family.

Animals↗
PubMed2000

Percutaneous sacral third nerve root neurostimulation improves symptoms and normalizes urinary HB-EGF levels and antiproliferative activity in patients with interstitial cystitis.

OBJECTIVES: A highly effective treatment for interstitial cystitis (IC) remains elusive. We determined whether sacral third nerve root (S3) percutaneous neurostimulation (PNS) might be effective in relieving symptoms of IC, as well as in normalizing urinary factors that are specifically altered in IC. METHODS: Six consecutive patients with symptoms and cystoscopic findings compatible with IC underwent 5 days of continuous S3 neurostimulation by way of leads placed percutaneously into the S3 foramen. Patients filled out voiding frequency diaries and pain and urgency questionnaires before PNS and at the end of PNS when the leads were removed. Urine specimens were collected at these two time points and measured for heparin-binding epidermal growth factor-like growth factor (HB-EGF) by enzyme-linked immunosorbent assay and for antiproliferative factor (APF) activity by (3)H-thymidine uptake by normal human bladder urothelial cells. RESULTS: S3 PNS significantly improved all measured parameters toward normal values. Voiding frequency decreased twofold from 23.1 +/- 4.6 to 10.6 +/- 4.0 voids daily during PNS (P = 0.0001). Pelvic pain on a scale of 1 to 10 decreased from 7.0 +/- 1.6 to 2.3 +/- 3.2 (P = 0.05). Urinary urgency on a scale of 1 to 10 decreased from 6.0 +/- 2.2 to 1.8 +/- 1.7 (P = 0. 02). Urinary HB-EGF concentration increased sevenfold from 1.5 +/- 2. 1 to 11.0 +/- 1.7 ng/mL (P <0.0001), and urinary APF activity decreased from -76.1% +/- 31% to -4.5% +/- 8.8% (P = 0.005). CONCLUSIONS: S3 PNS significantly decreased symptoms and normalized urinary HB-EGF and APF activity in patients with IC. These results suggest that permanent S3 PNS may be beneficial in treating IC.

Cell Division↗
PubMed2000

Chemical gradient in plasma-sprayed HA coatings.

The microstructure and inhomogeneous features of plasma-sprayed hydroxyapatite coatings on titanium substrates have been examined using the time-of-flight secondary ion mass spectroscopy (ToF-SIMS), micro-Raman spectroscopy and nano-indentation techniques. The crystalline and amorphous areas in coatings can be identified by the elastic modulus difference. The concentration gradient of O and OH ions was detected in the through-thickness direction of coatings. Lack of O and OH ions near the titanium interface implies the existence of phases other than HA, and might result in excessive adsorption of the coatings near the interface in HA-coated Ti implants.

Alloys↗
PubMed2000

Tumor necrosis factor-alpha soluble receptor p55 (sTNFp55) and risk of preeclampsia in Peruvian women.

We conducted a large case-control study to assess the risk of preeclampsia with elevated sTNFp55 concentrations (markers of excessive TNF-alpha release) in Peruvian women. A total of 125 women with preeclampsia and 179 normotensive women were included in a study conducted during the period, June 1997 through January 1998. Antepartum (third-trimester) plasma sTNFp55 was measured by enzyme linked immunosorbent assay. Mean plasma sTNFp55 concentrations were 32.4% higher among preeclampsia cases (920.1+/-30.4 pg/ml) as compared with controls (694.8+/-15.0 pg/ml, Student's t-test P<0.001). There was a strong linear increase in risk of preeclampsia with increasing concentrations of sTNFp55 (linear trend P-value <0. 001). After adjusting for confounding factors, women in the highest quartile experienced a 10-fold increased risk of preeclampsia as compared with women in the lowest quartile (adjusted odds ratio, 10.3; 95% confidence interval, 4.1-25.9). Compared with women in the highest quartile, women in the second and third quartiles experienced a 3-fold or greater increased risk of preeclampsia (adjusted odds ratios were 3.1 and 3.8, respectively). Excessive TNF-alpha release (as measured by the detection of the soluble receptor sTNFp55 in maternal plasma collected before delivery) is increased in pregnancies complicated by preeclampsia as compared with normotensive pregnancies. These findings are consistent with most previous studies.

Adolescent↗
PubMed2000

At the maize/Agrobacterium interface: natural factors limiting host transformation.

BACKGROUND: Agrobacterium tumefaciens has been successfully harnessed as the only natural vector for the incorporation of foreign genes into higher plants, but its use in the grain crops is often limited. Low transformation efficiency has been partly attributed to a failure in the initial events in the transformation process, specifically in the capacity of the VirA/VirG two-component system to induce expression of the virulence genes. RESULTS: Here we show that the root exudate of Zea mays seedlings specifically inhibits virulence gene expression, determine that 2-hydroxy-4,7-dimethoxybenzoxazin-3-one (MDIBOA), which constitutes > 98% of the organic exudate of the roots of these seedlings, is the most potent and specific inhibitor of signal perception in A. tumefaciens-mediated gene transfer yet discovered, and develop a model that is able to predict the MDIBOA concentration at any distance from the root surface. Finally, variants of A. tumefaciens resistant to MDIBOA-mediated inhibition of vir gene expression have been selected and partially characterized. CONCLUSIONS: These results suggest a strategy in which a plant may resist pathogen invasion by specifically blocking virulence gene activation and yet ensure that the 'resistance factor' does not accumulate to levels sufficient to impose toxicity and selection pressure on the pathogen. The data further establish that naturally occurring inhibitors directed against signal perception by the VirA/VirG two-component regulatory system can play an important role in host defense. Finally, selected variants resistant to specific MDIBOA inhibition may now be used to extend the transformation efficiency of maize and possibly other cereals.

Agrobacterium tumefaciens↗
PubMed2000

Comparison of bone formation responses to parathyroid hormone(1-34), (1-31), and (2-34) in mice.

In this study we used a mouse model system to compare the in vivo effects of parathyroid hormone(1-34) [PTH(1-34)] with that of PTH(1-31) or PTH(2-34) analogs. Daily subcutaneous administration of PTH(1-34) for 15 days caused a dose-dependent increase in the serum osteocalcin level and bone extract alkaline phosphatase activity, markers of bone formation. PTH(2-34) was much less potent, whereas PTH(1-31) was equipotent in stimulating bone formation parameters in mice. PTH(1-34) caused significant increases in serum calcium (after 4 h) and tartrate-resistant acid phosphatase activity in bone extract (after 4 h), whereas PTH(2-34) and PTH(1-31) were less potent. Because PTH(1-31) caused a smaller increase in bone resorption parameters compared to PTH(1-34), despite similar effects on bone formation parameters, we evaluated the long-term anabolic effects of PTH(1-31) and PTH(1-34) in mice. Weekly evaluations of serum osteocalcin levels demonstrated that daily injections of PTH(1-34) and PTH(1-31) at 80 microg/kg body weight increased serum osteocalcin levels within 1 week of the start of treatment, which were maintained during the entire 22 week treatment. Assessment of bone density at the end of the treatment period with peripheral quantitated computed tomography (pQCT) revealed that PTH(1-34) caused a significantly greater increase in femoral bone density compared to PTH(1-31) at the middiaphysis (18% vs. 9% over vehicle control; p < 0.001). Both PTH(1-34) and PTH(1-31) increased periosteal circumference compared to vehicle (p < 0.01) without a significant difference between the two treatments. In contrast, PTH(1-34) caused a significantly greater reduction in endosteal circumference than PTH(1-31) (p < 0.001). Both analogs significantly increased maximum load and area of moment of inertia over the vehicle group. In conclusion, our findings suggest that PTH(1-34) and PTH(1-31) may exhibit different anabolic effects at the periosteum vs. endosteum in the long bones of mice.

Animals↗
PubMed2000

Probing the structure of monomers and dimers of the bacterial virus phi29 hexamer RNA complex by chemical modification.

All dsDNA viruses multiply their genome and assemble a procapsid, a protein shell devoid of DNA. The genome is subsequently inserted into the procapsid. The bacterial virus phi29 DNA translocating motor contains a hexameric RNA complex composed of six pRNAs. Recently, we found that pRNA dimers are building blocks of pRNA hexamers. Here, we report the structural probing of pRNA monomers and dimers by chemical modification under native conditions and in the presence or absence of Mg2+. The chemical-modification pattern of the monomer is compared to that of the dimer. The data strongly support the previous secondary-structure prediction of the pRNA concerning the single-stranded areas, including three loops and seven bulges. However, discrepancies between the modification patterns of two predicted helical regions suggest the presence of more complicated, higher-order structure in these areas. It was found that dimers were formed via hand-in-hand and head-to-head contact, as the interacting sequence of the right and left loops and all bases in the head loop were protected from chemical modification. Cryoatomic force microscopy revealed that the monomer displayed a check-mark shape and the dimer exhibited an elongated shape. The dimer was twice as long as the monomer. Direct observation of the shape and measurement of size and thickness of the images strongly support the conclusion from chemical modification concerning the head-to-head contact in dimer formation. Our results also suggest that the role for Mg2+ in pRNA folding is to generate a proper configuration for the right and head loops, which play key roles in this symmetrical head-to-head organization. This explains why Mg2+ plays a critical role in pRNA dimer formation, procapsid binding, and phi29 DNA packaging.

Bacillus Phages↗
PubMed2000

A new subdivision, marginal division, in the neostriatum of the monkey brain.

A new subdivision, the "marginal division" (MrD), was discovered at the caudal border of the striatum and surrounds the rostral edge of the globus pallidus in the rat brain in our previous studies. The neuronal somata of the MrD are mostly fusiform in shape with their long axes lining dorsoventrally. The MrD is more densely filled with substance P (SP)-, Leucine-enkephalin (L-Enk)-, dynorphin B-, neurotensin-, somatostatin- and cholecystokinin (CCK)-immunoreactive fibers and terminal-like structures than the rest of the striatum. The MrD was confirmed in the cat neostriatum as well. The present study intended to explore whether the MrD exists in the monkey neostriatum (putamen) with Nissl, histochemical and immunohistochemical methods. A band of fusiform neurons were obviously identified at the caudomedial edge of the putamen. These neurons lie outside the lateral medullary lamina and indirectly surround the rostrolateral border of the globus pallidus. The abundance of SP-, L-Enk-, neuropeptide Y-, CCK-, dopamine- and serotonin-positive fibers and terminal-like structures with a few positive fusiform neurons accumulating at the caudomedial border of the putamen obviously distinguishes this zone from the rest of neostriatum and globus pallidus. The acetylcholinesterase (AChE) positive and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) containing fusiform neurons are distinctly visualized in the same zone. The morphological figure and the location of these neurons, and the histochemical and immunohistochemical characteristics of this area coincide well with those of the MrD in the rat and cat striatum. This study thus convincingly identifies the existence of the MrD in the monkey neostriatum. It is fairly asserted that the MrD is a universal structure in the mammalian brain.

Animals↗
PubMed2000

Characterization of a family with dominant hypophosphatasia.

A kindred with dominant hypophosphatasia resulting from an alanine to threonine substitution at position 99 of the alkaline phosphatase protein is described. The clinical findings of individual members of the kindred were assessed by oral and physical examinations, or from the descriptions of multiple family members. The proband displayed enamel hypoplasia and premature loss of fully rooted primary anterior teeth, which were shown by histological examination to lack cementum. Serum alkaline phosphatase (ALP) and a vitamin B6 panel, and urine phosphoethanolamine (PEA) were measured on 21 family members. Based upon the clinical and laboratory tests, affected and unaffected status was assigned. Parametric linkage analysis of the kindred using different dominant models and frequency distributions for the disease allele and the mutation gave lodscores > 4.2 and confirmed the strong linkage between the disease and the mutation. Assuming the defined mutation causes the disease, the reliability of clinical and laboratory tests is assessed.

Alanine↗
PubMed2000

Photoelectron spectroscopy of ammonia via a fast predissociative state

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative A state of ammonia, using nano- and femtosecond lasers. The multiphoton scheme involves (1 + 1), (2 + 2), (2 + 2) + 1 and (2 + 2) + 2 photon processes. We have found a progression of stretching vibrations v1 in the PE spectrum when pumping NH3 A v2 = 0, 1 and 3 as intermediate states. The stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting effect as well as above threshold multiphoton ionization.

Journal Article↗
PubMed2000

Simultaneous quantitative determination of norgestrel and progesterone in human serum by high-performance liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization.

A selective, reliable and rapid method for the simultaneous determination of progesterone and norgestrel concentrations in human serum after taking oral contraceptive tablet has been developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) with atmospheric pressure chemical ionization (APCI) interface. The norethisterone was used as the internal standard. Selected transitions of m/z 313/245 for norgestrel, m/z 315/97 for progesterone and m/z 299/109 for norethisterone were monitored using multiple reaction monitoring (MRM) mode for quantitation. The assay was linear over the concentration range of 0.2-50 ng mL-1 for norgestrel and progesterone. The lower level of quantitation in human serum was obtained at 0.2 ng mL-1 for both norgestrel and progesterone using optimum tuning parameters. The intra-assay precision and inter-assay precision do not exceed 10 and 9%, respectively. The method has been applied to the determination of norgestrel and progesterone in serum of female volunteers.

Adult↗
PubMed2000

Diurnal regulation of Hsp70s in leaf tissue.

Steady-state mRNA levels for three Hsp70s were found to be regulated by a distinctive light/dark mechanism in spinach leaves. Messenger RNAs for the chloroplast stromal and two cytosolic forms displayed a diurnal expression pattern under isothermal conditions that appeared to be independent of circadian control. While protein blot data showed relatively constant Hsp70 protein levels, the higher Hsp70 mRNA levels in the light paralleled the diurnal cycle of total cell protein synthesis. Fractionation studies showed that the major cytosolic Hsp70 cognate group was associated with polysomes. Therefore, the variation of Hsp70 mRNAs is consistent with the diurnal metabolic activity of plant photosynthetic cells in which the demand of protein biogenesis for chaperone function and tissue temperature are highest during the day.

Chloroplasts↗