Biomedical subjects

Z Xu

Publications and source records attributed to Z Xu.

At least 469 records · Page 26Linked to original sources

PubMed1995

Ultrastructural changes following overhydration with irrigating fluids.

We studied ultrastructural alterations caused by intravenous infusion of 150 ml/kg of irrigating fluid containing mannitol and/or sorbitol in 15 rabbits. The osmolality of the solutions varied between 165 and 350 mosmol/kg. Specimens for electron microscopic examination were obtained from the kidney, brain and lung. Regardless of the choice of solute, the hypo-osmotic solutions caused damage to kidney and brain tissue by inducing marked interstitial and cellular oedema. No such changes were observed after administration of isosmotic irrigating fluid. We conclude that ultrastructural changes following overhydration with irrigating fluid vary with the osmolality of the solution but not with the choice of solute. Moreover, the consistent absence of tissue damage in the lungs suggests that the lung is not a primary target organ for the "TUR syndrome".

Animals↗

PubMed1995

[Experimental studies of embolization of different hepatotropic blood vessels using Bletilla striata in dogs].

Bletilla striata and gelfoam were used as embolizing agents for the embolization of various hepatotropic vessels in dogs. The results proved that Bletilla striata was superior to gelfoam. The mechanisms of embolization by Bletilla striata are attributable to following factors: non--absobent property, mechanical obstruction; effects on coagulative and anticoagulative systems and secondary obstruction resulted from the injury to wall of blood vessels.

Animals↗

PubMed1995

Disturbed intestinal movement, bile reflux to the stomach, and deficiency of c-kit-expressing cells in Ws/Ws mutant rats.

BACKGROUND & AIMS: Interstitial cells of Cajal (ICCs) are believed to initiate the basic contractile activity of the gastrointestinal tract. Because ICCs in the intestine of mice express c-kit receptor tyrosine kinase and because rats are more commonly used than mice for pathophysiological investigations of the gastrointestinal tract, the number of the c-kit messenger RNA-expressing cells was compared with gastrointestinal movement in rats. METHODS: The c-kit messenger RNA-expressing cells were detected by in situ hybridization. The autonomous contraction of excised segments of the ileum was recorded. The function of the pyloric sphincter was evaluated by measuring the content of bile acids in the stomach. RESULTS: The c-kit messenger RNA-expressing cells were not detectable in the stomach of Ws/Ws mutant rats with a small deletion at the tyrosine kinase domain of c-kit, and the number of c-kit messenger RNA-expressing cells decreased to 7% that of normal control rats in the ileum of Ws/Ws rats. The contractile activity of the ileum was apparently impaired, and the content of bile acids in the stomach was significantly increased in Ws/Ws rats. CONCLUSIONS: The abnormalities in the ileal movement and pyloric sphincter function in Ws/Ws rats were attributable to the deficiency of c-kit messenger RNA-expressing cells.

Animals↗

PubMed1995

The improved Allium/Vicia root tip micronucleus assay for clastogenicity of environmental pollutants.

The meristematic mitotic cells of plant roots are appropriate and efficient cytogenetic materials for the detection of clastogenicity of environmental pollutants, especially for in situ monitoring of water contaminants. Among several cytological endpoints in these fast dividing cells, such as chromosome/chromatid aberrations, sister-chromatid exchanges and micronuclei, the most effective and simplest indicator of cytological damage is micronucleus formation. Although the Allium cepa and Vicia faba root meristem micronucleus assays (Allium/Vicia root MCN) have been used in clastogenicity studies about 12 times by various authors in the last 25 years, there is no report on the comparison of the efficiency of these two plant systems and in different cell populations (meristem and F1) of the root tip as well as under adequate recovery duration. In order to maximize the efficiency of these bioassays, the current study was designed to compare the Allium and the Vicia root MCN assays on the basis of chromosome length, peak sensitivity of the mitotic cells, and the regions of the root tip where the MCN are formed. The total length of the 2n complement of Allium chromosomes is 14.4 microns and the total length of the 2n complement of Vicia is 9.32 microns. The peak sensitivity determined by serial fixation at 12-h intervals after 100 R of X-irradiation is 44 h. The slope of the X-ray dose-response curve of Allium roots derived from the meristematic regions was lower than that derived from cells in the F1 region. Higher efficiency was also demonstrated when the MCN frequencies were scored from the F1 cells in both Allium and Vicia treated with formaldehyde (FA), mitomycin C (MMC), and maleic hydrazide (MH). The results indicated that scoring of MCN frequencies from the F1 cell region of the root tip was more efficient than scoring from the meristematic region. The X-ray linear regression dose-response curves were established in both Allium and Vicia cell systems and the coefficients of correlations, slope values were used to verify the reliability and efficiency of these two plant cell systems. Based on the dose-response slope value of 0.894 for Allium and 0.643 for Vicia, the Allium root MCN was a more efficient test system. The greater sensitivity of the Allium roots is probably due to the greater total length of the diploid complement and the higher number of metacentric chromosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Allium↗

PubMed1995

Regional suppression by lesions in the anterior third ventricle of c-fos expression induced by either angiotensin II or hypertonic saline.

Angiotensin II (250 pmol) infused into the cerebral ventricles of male rats induces the expression of c-fos in the subfornical organ, supraoptic and paraventricular nuclei of the hypothalamus, as well as in the lateral parabrachial nucleus, locus coeruleus and the nucleus of the solitary tract in the brainstem. Electrolytic lesions of the anteroventral third ventricle, principally the subcommissural (ventral) median preoptic nucleus, inhibited the dipsogenic response to i.c.v. angiotensin II and also suppressed c-fos expression in supraoptic nucleus, paraventricular nucleus, lateral parabrachial nucleus, locus coeruleus and nucleus of the solitary tract but not in the subfornical organ or dorsal median preoptic nucleus. The stimulating effect of i.c.v. angiotensin II on corticosterone was also reduced. Median preoptic nucleus lesions also suppressed the expression of c-fos following i.v. infusions of 6 micrograms angiotensin II in supraoptic nucleus and paraventricular nucleus but not in subfornical organ, dorsal median preoptic nucleus, lateral parabrachial nucleus, locus coeruleus and nucleus of the solitary tract. Median preoptic nucleus lesions reduced the dipsogenic effects of an intragastric infusion of hypertonic (1.5 M) saline and suppressed c-fos expression in supraoptic nucleus and paraventricular nucleus compared to sham-lesioned rats. However, c-fos expression was unaltered in subfornical organ, dorsal median preoptic nucleus lesions had no effect on the increased corticosterone induced by hypertonic saline. Subfornical organ lesions did not alter dipsogenic responses to i.c.v. angiotensin II, nor was the i.c.v. angiotensin II-induced expression of c-fos suppressed in the basal forebrain. These experiments show that the ventral median preoptic nucleus (but not the subfornical organ), part of the anteroventral third ventricle, is critical for the expression of c-fos in more caudal areas of the brain following i.c.v. angiotensin II. c-fos expression in supraoptic nucleus and paraventricular nucleus following i.v. angiotensin II is also dependent on an intact median preoptic nucleus, suggesting that supraoptic nucleus and paraventricular nucleus activation may be dependent on the median preoptic nucleus, and that suppression following i.c.v. infusions is not due to mechanical obstruction to infused peptide. However, there is a clear separation of the effects of i.c.v. and i.v. angiotensin II on brainstem structures. The median preoptic nucleus (but not the subfornical organ) seems essential for activation following the former but not the latter, suggesting alternative mechanisms for the effect of i.v. angiotension II on the brainstem.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiotensin II↗

PubMed1995

6Li nuclear magnetic resonance chemical shifts, coordination number and relaxation in crystalline and glassy silicates.

Unlike 7Li magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra, 6Li MAS NMR spectra of silicates are dominated by chemical shift effects, often have a very high resolution and hence can provide significant structural information. In this study we demonstrate a good correlation between 6Li isotropic chemical shifts and oxygen coordination number, and use this result to describe the range of coordination environments for Li in silicate glasses. We also show that the second-order quadrupolar shift for 7Li can often be derived from 7Li and 6Li MAS spectra acquired at a single magnetic field. For a series of natural lepidolite samples with significant but varying contents of Mn and Fe, spin-lattice relaxation data show a power-law behavior and a three-dimensional distribution of paramagnetic centers, but homonuclear dipolar couplings can be important. The 6Li spectrum for lithium orthosilicate (which has three-, four-, five- and six-coordinated Li) is consistent with that predicted by the X-ray structure.

Crystallization↗

PubMed1995

Amperometric thin film biosensors based on glucose dehydrogenase and Toluidine Blue O as catalyst for NADH electrooxidation.

Amperometric glucose sensors were constructed based on solid graphite electrodes, surface-modified with NAD+ dependent glucose dehydrogenase (GDH), Toluidine Blue O (TBO), and protective ionic polymers. The electrocatalytic oxidation of NADH was evaluated from cyclic voltammetry with TBO dissolved, adsorbed, and electrostatically or covalently bound to polymers. The NADH and glucose sensors constructed were investigated and operated at 0 mV vs. Ag/AgCl using single potential step chronoamperometry. The operational stability of the glucose sensors was limited by leakage of NAD+. A glucose sensitivity much higher than carbon paste electrode was found. A sensitivity as high as 25 microA cm-2 mM-1 was achieved.

Biosensing Techniques↗

PubMed1995

Increasing neurofilament subunit NF-M expression reduces axonal NF-H, inhibits radial growth, and results in neurofilamentous accumulation in motor neurons.

The carboxy-terminal tail domains of neurofilament subunits neurofilament NF-M and NF-H have been postulated to be responsible for the modulation of axonal caliber. To test how subunit composition affects caliber, transgenic mice were generated to increase axonal NF-M. Total neurofilament subunit content in motor and sensory axons remained essentially unchanged, but increases in NF-M were offset by proportionate decreases in both NF-H and axonal cross-sectional area. Increase in NF-M did not affect the level of phosphorylation of NF-H. This indicates that (a) in vivo NF-H and NF-M compete either for coassembly with a limiting amount of NF-L or as substrates for axonal transport, and (b) NF-H abundance is a primary determinant of axonal caliber. Despite inhibition of radial growth, increase in NF-M and reduction in axonal NF-H did not affect nearest neighbor spacing between neurofilaments, indicating that cross-bridging between nearest neighbors does not play a crucial role in radial growth. Increase in NF-M did not result in an overt phenotype or neuronal loss, although filamentous swellings in perikarya and proximal axons of motor neurons were frequently found.

Amino Acid Sequence↗

PubMed1995

Effect of dietary fat or tamoxifen on the expansion of cells harboring Ha-ras oncogenes in mammary glands from methylnitrosourea-treated rats.

Diets containing high levels of fat enhance the formation of methylnitrosourea (MNU)-induced mammary gland adenocarcinomas in rats, while administration of the antiestrogen tamoxifen decreases the incidence of these tumors. It is not known, however, at what stage during tumor development the fat or tamoxifen exert their effects. Here we have used a PCR/liquid hybridization and gel retardation assay to determine the effects of dietary fat and tamoxifen on the growth rate of cells harboring an Ha-ras oncogene in the mammary glands of rats at various times following MNU administration. Glands from animals on a high-fat diet had significantly higher mutant cell fractions than those on a low-fat diet at both 30 and 75 days following MNU treatment. In contrast, there was no difference between the mutant cell fractions of tamoxifen-treated animals and controls at either 30 or 70 days. These results suggest that dietary fat promotes tumor formation early in carcinogenesis by stimulating the growth of cells harboring Ha-ras mutations, while tamoxifen delays the appearance of tumors either by acting as a tumoristatic or tumoricidal agent, or by acting to eliminate or retard the growth of preneoplastic cells just prior to the emergence of tumors.

Animals↗

PubMed1995

Deletions of both alpha 5(IV) and alpha 6(IV) collagen genes in Alport syndrome and in Alport syndrome associated with smooth muscle tumours.

Diffuse oesophageal leiomyomatosis (DL), an inherited smooth muscle proliferation process, has been reported to be associated with Alport syndrome (AS), a familial nephropathy, mainly dominant X-linked inherited, and characterized by ultrastructural changes of the glomerular basement membrane. The COL4A5 gene, encoding the alpha 5 chain of type IV collagen, has been identified as the site of mutations in families with X-linked AS. Recently, a novel alpha 6(IV) collagen chain encoding gene has been mapped closely upstream of COL4A5, and disruption of the 5' end of both genes has been reported in four patients with DL and AS (DL-AS). Here, we report a long-range restriction map around the COL4A6 locus, and show that the COL4A5/COL4A6 deletion observed in seven patients with DL-AS encompasses only the two first exons of COL4A6, with a breakpoint located in the second intron of COL4A6, whose size exceeds 65 kb. Furthermore, we demonstrate that three patients with AS without DL, known to have a deletion of the 5' part of the COL4A5 gene, display a larger deletion in COL4A6. Moreover, a COL4A6 mRNA product was detected by reverse-transcription-polymerase chain reaction in an oesophageal tumour sample of a patient with DL-AS. These results suggest that DL-AS could be caused by an abnormal truncated alpha 6(IV) chain.

Adolescent↗

PubMed1995

Expression of follicle-stimulating hormone and luteinizing hormone receptor messenger ribonucleic acids in bovine follicles during the first follicular wave.

The objective of the present study was to characterize expression of mRNAs encoding FSH and LH receptors during follicular development and at different stages of the first follicular wave in cattle. Following estrus, groups of heifers (3-5 per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography; Day 0), or on Days 2, 4, 6, 8, or 10 after initiation of the first wave. FSH and LH receptor mRNAs were detected within follicles > or = 4 mm and in some smaller follicles by in situ hybridization and were quantified by image analysis. FSH receptor mRNA was expressed in granulosa cells of all growing follicles, starting in some follicles with only one layer of granulosa cells. Irrespective of day of the follicular wave, the level of expression of FSH receptor mRNA in granulosa cells of healthy antral follicles ranging from 0.5 to 14 mm in diameter did not vary significantly with follicular size (r = 0.02, p > 0.10). Expression of LH receptor mRNA was first observed in theca interna cells of follicles shortly after antral formation. Irrespective of day of the follicular wave, the levels of LH receptor mRNA in theca interna cells of healthy antral follicles ranging from 0.5 to 14 mm increased with follicular size (r = 0.39, p < 0.01). In granulosa cells, LH receptor mRNA was expressed only in healthy follicles > 9 mm in diameter and was first observed in the dominant follicles collected on Day 4. Expression of mRNA for LH receptor, but not for FSH receptor, changed (p < 0.01) with the stage of the first follicular wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Possible role of osteopontin in deposition of calcium phosphate in human pilomatricomas.

Human pilomatricomas are benign epidermal appendage tumors composed of hair matrix-like basaloid cells and keratinized remnant cells referred to as shadow cells. Deposition of calcium phosphate usually occurs in the shadow cell nests. Because osteopontin is believed to be involved in the deposition of calcium phosphate in bones, we asked whether osteopontin messenger RNA also is expressed in pilomatricomas. Using Northern blotting and in situ hybridization we detected osteopontin messenger RNA in pilomatricoma tissues but not in normal skin tissue. By the combination of in situ hybridization and immunohistochemistry, osteopontin messenger RNA-expressing cells were identified as CD68-positive macrophages surrounding the shadow cell nests. Immunohistochemistry of anti-human osteopontin antibodies revealed that the localization of osteopontin protein was consistent with that of calcium phosphate. The present results suggest that osteopontin produced by macrophages may play a significant role in the deposition of calcium phosphate in the shadow cell nests of pilomatricomas.

Amino Acid Sequence↗

PubMed1995

Molecular dissection of PapD interaction with PapG reveals two chaperone-binding sites.

P pili are composite adhesive fibres that allow uropathogenic Escherichia coli to gain a foothold in the host by binding to receptors present on the uroepithelium via the adhesin PapG. The assembly of P pili requires a periplasmic chaperone, PapD, that has an immunoglobulin-like three-dimensional structure. PapD-subunit complex formation involves a conserved anchoring mechanism in the chaperone cleft and a 'molecular zippering' to the extreme C-terminus of pilus subunits. A chaperone-binding assay was developed using fusions of the C-terminus of PapG to maltose-binding protein (MBP/G fusions) to investigate whether chaperone-subunit complex formation requires additional interactions. PapD bound strongly to an MBP/G fusion containing the C-terminal 140 amino acids of PapG (MBP/G175-314) but only weakly to the MBP/G234-314 fusion containing 81 C-terminal residues, arguing that the region between residues 175-234 contains additional information that is required for strong PapD-PapG interactions. PapD was shown to interact with a PapG C-terminal truncate containing residues 1-198 but not a truncate containing residues 1-145, suggesting the presence of a second, independent PapD interactive site. Four peptides overlapping the second site region were tested for binding to PapD in vitro to further delineate this motif. Only one of the peptides synthesized was recognized by PapD. The MBP/G fusion containing both binding sites formed a tight complex with PapD in vivo and inhibited pilus assembly by preventing chaperone-subunit complex formation.

ATP-Binding Cassette Transporters↗

PubMed1995

The calibration and use of plane-parallel ionization chambers for dosimetry of electron beams.

The AAPM TG 39 protocol has proposed three different methods of calibrating plane-parallel ionization chambers, i.e., in-phantom irradiation with a high-energy electron beam and in-phantom and in-air 60Co irradiation. To verify the consistency of the three methods, we have measured Ngaspp values using each of these techniques for the five most commonly used plane-parallel chambers considered by the protocol. Our results demonstrate that the measured Ngaspp values for the three different methods for any of the chambers agree to within +/- 0.6%. Once Ngaspp was measured, the determination of absorbed dose for electron beams with different energies for an AECL Therac 20 and Philips SL25 was carried out according to the AAPM TG 39 protocol. The results show that the determination of the absorbed dose outputs for any of the five chambers agree to within +/- 0.7% for electron-beam energies of 4-20 MeV if all five chambers had Ngaspp values determined by the electron-beam method. The uncertainties are well within the expected error for these approaches.

Cobalt Radioisotopes↗

PubMed1995

Expression of messenger ribonucleic acid encoding cytochrome P450 side-chain cleavage, cytochrome p450 17 alpha-hydroxylase, and cytochrome P450 aromatase in bovine follicles during the first follicular wave.

The objective of the present study was to investigate changes in the expression of messenger RNAs (mRNAs) encoding cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17 alpha-hydroxylase (P450c17), and cytochrome P450 aromatase (P450arom) at different stages of the first follicular wave of the bovine estrous cycle. Groups of heifers (three to five per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography, day 0) or on days 2, 4, 6, 8, and 10 after initiation of the first follicular wave following estrus. Expression of mRNAs encoding P450scc, P450c17, and P450arom was detected by in situ hybridization and quantified by image analysis. P450scc mRNA was localized to theca interna cells of large preantral follicles and also to granulosa cells of follicles 4 mm or greater in diameter. mRNA for P450c17 was localized exclusively to theca interna cells, whereas P450arom mRNA was localized to granulosa cells of follicles 4 mm or greater in diameter. There were changes in mRNA levels for all three enzymes in thecal and/or granulosa cells at different times of the first follicular wave. Before identification of the dominant follicle (i.e. on days 0 and 2), there was no change in expression of P450scc and P450c17 mRNAs, whereas expression of P450arom mRNA was higher on day 2 than on day 0. Maximal mRNA levels for all three enzymes were observed on day 4. By day 6, P450scc and P450c17 mRNA levels were reduced compared to those on day 4, whereas P450arom mRNA levels remained elevated. On day 8, mRNA levels for all three enzymes were reduced. After initiation of the second follicular wave (day 10), dominant follicles from the first wave were at an advanced stage of atresia. P450scc and P450arom mRNAs were undetectable in granulosa cells, and very low levels of P450scc and P450c17 mRNAs were observed in theca interna cells. Before identification of the dominant follicle, mRNA levels for all three enzymes were similar within a cohort of follicles. Therefore, expression of these enzymes may not be associated with the mechanism of selection of the dominant follicle during a follicular wave.

Animals↗

PubMed1995

[An immunohistochemical study of HLA-DR expression in salivary glands from patients with Sjogren's syndrome].

Specimens of salivary gland tissue from 21 cases of SS were analyzed by ABC immunohistochemistry technicue with a monoclonal antibody to HLA-DR. The results showed that positive immunostaining for HLA-DR were found in duct cells, acinar cells and a part of infiltrating cells respectively. The proportions of duct and acinar cells expressing HLA-DR were not increased between SS and controls. However, there are differences in their staining intensity. The HLA-DR expression on the epithelial cells in SS was most intense than in controls. Our data suggest that the HLA-DR expression of SS may be regarded as an important factor in local immune rections.

Adult↗

PubMed1995

[Myelin basic protein level in serum of patients with chronic cor pulmonale in acute phase].

With a sensitive enzyme-linked immunoadsorbent assay that can detect as little as 0.5ng/ml of myelin basic protein (MBP), we studied serum specimens from 34 patients with chronic cor pulmonale (CP) and 33 patients with chronic bronchitis (CB) during acute attack in hospital and 30 control subjects. The results showed that the serum mean MBP level of CP patients was markedly higher than those of CB patients and controls (P < 0.01), but no statistically significant differences were found between CB patients and controls (P > 0.05). There was a positive correlation between elevated levels of serum MBP and carbon dioxide partial pressure (PaCO2). This suggested that elevated serum MBP levels may be associated with brain destruction by hypercapnia and hypoxia of CP patients.

Acute-Phase Reaction↗

PubMed1995

B7-1 expression decreases tumorigenicity and induces partial systemic immunity to murine neuroblastoma deficient in major histocompatibility complex and costimulatory molecules.

Neuroblastoma may escape an immune attack by virtue of its low expression of surface accessory molecules essential in the antitumor response. Murine neuroblastoma, neuro-2a, was transduced with the retroviral vector LB7-1SN to examine the influence of B7-1 expression on the immune response directed against a low major histocompatibility class (MHC) I and class II negative, B7-2, and ICAM-1 negative tumor. Using a retroperitoneal model for implantation of neuroblastoma in its natural site, we demonstrated that expression of B7-1 by neuro-2a reduces its tumorigenicity. Coinjection of B7-1-positive and -negative cells improved survival compared with mice receiving B7-1-negative cells alone. This was dependent on the ratio of B7-1+ to B7-1- neuro-2a cells injected. CD8+ and not CD4+ T-cell depletion significantly increased tumor-induced mortality in syngeneic A/J mice, indicating that B7-1 decreases tumorigenicity primarily by direct constimulation of CD8+ T cells. Rejection of N-2a/B7-1 tumors or preimmunization with irradiated N-2a/B7-1 cells die not increase protection to challenge with unmodified neuro-2a cells over mice vaccinated with N-2a/neo. Furthermore, cytotoxic T lymphocyte (CTL) precursor frequencies were not significantly higher after in vivo priming and in vitro stimulation with irradiated N-2a/B7-1 compared with N-2a/neo, indicating that B7-1 costimulation by the tumor, in the absence of adequate antigen presentation by MHC molecules, may limit the generation of effective CTLs.

Animals↗