Biomedical subjects

Z Yang

Publications and source records attributed to Z Yang.

At least 649 records · Page 36Linked to original sources

PubMed1996

Vanadium affects macrophage interferon-gamma-binding and -inducible responses.

Mouse WEHI-3 cells were exposed overnight to vanadium [V; ammonium metavanadate (NH4VO3) or vanadium pentoxide (V2O5)] to determine whether documented V-induced immunomodulation might arise from altered macrophage (M phi) interactions with interferon-gamma (IFN gamma) or altered IFN gamma-inducible responses. Binding studies performed at 22 degrees C indicated that although NH4VO3-pretreated cells had approximately 48% fewer actively-binding Class I IFN gamma receptors, binding affinities were 1.5-fold greater than that of control cell receptors; Class II expression was unaffected but affinities were reduced 2-fold. Postbinding IFN gamma-receptor complex internalization was unaffected by V pretreatment. Spontaneous production of both hydrogen peroxide and superoxide anion was significantly increased by treatment with both V compounds. Total hydrogen peroxide and superoxide production was increased by stimulation of IFN gamma-primed cells with zymosan, but relative increases in primed V-treated cells were lower than that in controls. Vanadium-treated cells also displayed decreased rates of IFN gamma-induced changes in [Ca2+]i levels secondary to increased resting [Ca2+]i levels. Although V-treated cells did not display significant increases in I-A expression after IFN gamma treatment, increased numbers of I-A+ cells (irrespective of priming) and lower maximal antigen densities than observed on I-A+ control cells were evident. Results from this study show that V exposure may produce alterations in M phi-mediated functions, in part, by modifying cell interactions with IFN gamma and subsequent IFN gamma-dependent functional parameters.

Animals↗

PubMed1996

Bacterial lipopolysaccharide-stimulated nitric oxide generation is unrelated to concurrent cytotoxicity of bovine alveolar macrophages.

Nitric Oxide (NO) is a reactive metabolite produced by stimulated macrophages, and it has been demonstrated to exert cytotoxic actions on a number of microbes, parasites, and tumor cells. In addition, NO has been reported to have an autotoxic effect on murine macrophages, its site of synthesis. We have investigated the relationship of NO generation to cytotoxicity of bovine alveolar macrophages (AM) in vitro, and have also assessed the effects of several modulators of cellular function on this relationship. NO was generated in cultures of AM using sodium nitroprusside (SNP) and measured as [nitrite]. Cellular viability of AM reflected a strong, negative correlation with the concentration of NO/nitrite in supernatants (r = -0.987). Supernatants with nitrite concentrations in excess of 30 microMs were correlated with cytotoxicity. AM stimulated with the potent combination of endotoxin (Lipopolysaccharide, LPS; 10 ng/ml) and recombinant bovine IFN gamma (100 U/ml) also exhibited cytotoxicity over a 48-hour incubation period, and cells deteriorated to an average viability of 72.3% as compared to unstimulated control macrophages. In some cases the viability of macrophages was much lower. Even though LPS-mediated cytotoxicity occurred, the [nitrite] produced in supernatants during the 48-hour period (12.23 microMs) was well below the minimum concentration of SNP-generated NO required to induce cytotoxicity to macrophages. N(G)-monomethyl-L-arginine (N(G)MMA, 2 mM) is a competitive inhibitor of NO synthesis and was found to reduce nitrite concentrations from 12.23 microMs to 1.56 microMs in supernatants of LPS-stimulated AM, but this reduction did not promote increased viability of AM. Other modulators of cellular function including phenylbutazone (PBZ, 100 microMs), flunixin meglumine (FM, 100 microMs) and interleukin-4 (IL-4, 100 ng/ml) modestly inhibited synthesis of NO, but did not improve cellular viability. These results suggest that relatively high concentrations of exogenously-generated NO are toxic to AM in vitro, but the quantity of endogenously-generated NO synthesized by LPS-stimulated bovine AM is usually below the threshold for toxicity. Cytotoxicity occurs independently of NO synthesis, and factors other than NO are apparently responsible for LPS-related cytotoxicity to bovine macrophages.

Animals↗

PubMed1996

Analysis of the CD14 receptor associated with bovine alveolar macrophages.

Previous studies have suggested the existence of a bovine homolog of the membrane-associated CD14 receptor (mCD14) on macrophages, and functional similarity of bovine mCD14 receptor activity to that reported for other species. Bovine alveolar macrophages (bAM) reportedly possess two mRNA transcripts of 1.5 and 3.1 kb for CD14, rather than a single 1.5 kb transcript as reported for other species. The purpose of this study was to determine the molecular mass of the bovine CD14 receptor, and to determine if the two mRNA transcripts for bovine CD14 yield either a single or two different gene products. Culture supernatant from 125I-surface-labeled bAM was examined for the existence of bovine CD14 using SDS-PAGE and autoradiography. A single protein band of 49 kD was immunoprecipitated from the supernatant using anti-CD14 monoclonal antibodies (MAb). Macrophage-derived mRNA was subjected to hybrid-selection using a human CD14 cDNA probe immobilized on a nitrocellulose filter. The resultant, selected bovine mRNA was then utilized for in vitro translation, and protein of 38-40 kD was synthesized. This size is consistent with an unglycosylated CD14 receptor protein. Protein was also synthesized from total RNA by in vitro translation, and was immunoprecipitated with anti-CD14 monoclonal antibodies. A doublet-band of protein was seen at 38 kD using SDS-PAGE and autoradiography. Anti-CD14 antibodies were also used to inhibit serum- and LPS-dependent bovine macrophage activation as measured by tissue factor expression, which is compatible with the presence and function of CD14 receptors on macrophages. These results collectively demonstrate that a receptor consistent with CD14 is present on bovine macrophages, the form of the receptor released into supernatants is 49 kD, and that it functions as an LPS receptor on these cells.

Animals↗

PubMed1996

Phylogenetic analysis using parsimony and likelihood methods.

The assumptions underlying the maximum-parsimony (MP) method of phylogenetic tree reconstruction were intuitively examined by studying the way the method works. Computer simulations were performed to corroborate the intuitive examination. Parsimony appears to involve very stringent assumptions concerning the process of sequence evolution, such as constancy of substitution rates between nucleotides, constancy of rates across nucleotide sites, and equal branch lengths in the tree. For practical data analysis, the requirement of equal branch lengths means similar substitution rates among lineages (the existence of an approximate molecular clock), relatively long interior branches, and also few species in the data. However, a small amount of evolution is neither a necessary nor a sufficient requirement of the method. The difficulties involved in the application of current statistical estimation theory to tree reconstruction were discussed, and it was suggested that the approach proposed by Felsenstein (1981, J. Mol. Evol. 17: 368-376) for topology estimation, as well as its many variations and extensions, differs fundamentally from the maximum likelihood estimation of a conventional statistical parameter. Evidence was presented showing that the Felsenstein approach does not share the asymptotic efficiency of the maximum likelihood estimator of a statistical parameter. Computer simulations were performed to study the probability that MP recovers the true tree under a hierarchy of models of nucleotide substitution; its performance relative to the likelihood method was especially noted. The results appeared to support the intuitive examination of the assumptions underlying MP. When a simple model of nucleotide substitution was assumed to generate data, the probability that MP recovers the true topology could be as high as, or even higher than, that for the likelihood method. When the assumed model became more complex and realistic, e.g., when substitution rates were allowed to differ between nucleotides or across sites, the probability that MP recovers the true topology, and especially its performance relative to that of the likelihood method, generally deteriorates. As the complexity of the process of nucleotide substitution in real sequences is well recognized, the likelihood method appears preferable to parsimony. However, the development of a statistical methodology for the efficient estimation of the tree topology remains a difficult open problem.

Animals↗

PubMed1996

Probability distribution of molecular evolutionary trees: a new method of phylogenetic inference.

A new method is presented for inferring evolutionary trees using nucleotide sequence data. The birth-death process is used as a model of speciation and extinction to specify the prior distribution of phylogenies and branching times. Nucleotide substitution is modeled by a continuous-time Markov process. Parameters of the branching model and the substitution model are estimated by maximum likelihood. The posterior probabilities of different phylogenies are calculated and the phylogeny with the highest posterior probability is chosen as the best estimate of the evolutionary relationship among species. We refer to this as the maximum posterior probability (MAP) tree. The posterior probability provides a natural measure of the reliability of the estimated phylogeny. Two example data sets are analyzed to infer the phylogenetic relationship of human, chimpanzee, gorilla, and orangutan. The best trees estimated by the new method are the same as those from the maximum likelihood analysis of separate topologies, but the posterior probabilities are quite different from the bootstrap proportions. The results of the method are found to be insensitive to changes in the rate parameter of the branching process.

Animals↗

PubMed1996

Maximum-Likelihood Models for Combined Analyses of Multiple Sequence Data

Abstract. Models of nucleotide substitution were constructed for combined analyses of heterogeneous sequence data (such as those of multiple genes) from the same set of species. The models account for different aspects of the heterogeneity in the evolutionary process of different genes, such as differences in nucleotide frequencies, in substitution rate bias (for example, the transition/transversion rate bias), and in the extent of rate variation across sites. Model parameters were estimated by maximum likelihood and the likelihood ratio test was used to test hypotheses concerning sequence evolution, such as rate constancy among lineages (the assumption of a molecular clock) and proportionality of branch lengths for different genes. The example data from a segment of the mitochondrial genome of six hominoid species (human, common and pygmy chimpanzees, gorilla, orangutan, and siamang) were analyzed. Nucleotides at the three codon positions in the protein-coding regions and from the tRNA-coding regions were considered heterogeneous data sets. Statistical tests showed that the amount of evolution in the sequence data reflected in the estimated branch lengths can be explained by the codon-position effect and lineage effect of substitution rates. The assumption of a molecular clock could not be rejected when the data were analyzed separately or when the rate variation among sites was ignored. However, significant differences in substitution rate among lineages were found when the data sets were combined and when the rate variation among sites was accounted for in the models. Under the assumption that the orangutan and African apes diverged 13 million years ago, the combined analysis of the sequence data estimated the times for the human-chimpanzee separation and for the separation of the gorilla as 4.3 and 6.8 million years ago, respectively.

Journal Article↗

PubMed1996

Immunohistochemical analysis of growth factor expression and localization in gastric coronary vein of cirrhotic patients.

This study was designed to investigate the expression and localization of PDGF, bFGF, EGF, and TGF alpha in gastric coronary vein of cirrhotic (n = 30) and non-cirrhotic patients (n = 10) using immunohistochemical technique. The strongly positive immunostaining rate were 93%, 89%, 70% and 68% respectively in cirrhotic patients. The immunostaining was negative in non-cirrhotic patients. The damage to endothelium, hypertrophy and hyperplasia of vascular smooth muscle cells and vascular remodeling were seen in gastric coronary vein of cirrhotic patients. These results suggested that gastric coronary vein could produce growth factor during cirrhosis, the growth factor can act on the vascular function and/or structure via autocrine-paracrine mechanism.

Adult↗

PubMed1996

Portal hypertensive vascular lesions.

The aim of present study is to assess the pathological changes of gastric coronary vein in cirrhotic patients (n = 30) by immunohistochemical and morphological observation. The damage to endothelium, hypertrophy and hyperplasia of smooth muscle and increament of ECM were found in gastric coronary vein of cirrhotic patients. The vessel wall hardened and thickened with decrease of elasticity. The results showed that the portal hypertension could accompany with portal hypertensive vascular lesions.

Adult↗

PubMed1996

Disposable sensor for biochemical oxygen demand.

Disposable-type microbial sensors were prepared for the determination of biochemical oxygen demand (BOD). The yeast, Trichosporon cutaneum, was directly immobilized on the surface of miniature oxygen electrodes using an ultraviolet crosslinking resin (ENT-3400). The oxygen electrodes (15 mm x 2 mm x 0.4 mm) were made on silicon substrates using micromachining techniques. They were Clark-type two-electrode systems with-1021 mV applied to the working electrode. Typical response times of the BOD sensors were in the range of 7-20 min. At 20 degrees C, the sensors' dynamic range was from 0 to 18 mg/1 BOD when a glucose/glutamate BOD standard solution was used. The lower limit of detection was 0.2 mg/l BOD. This value was one order of magnitude lower than that of sensors previously reported. The sensors' operational lifetime of 3 days was satisfactory for a disposable type. The sensors' responses were reproducible to within 8% relative standard deviation. The BOD sensors' were applied to untreated and treated waste waters from industrial effluents and municipal sewage. BOD values determined using these sensors correlated well with those determined by the conventional 5-day BOD determination method.

Biosensing Techniques↗

PubMed1996

Direct transfer of a foreign MHC gene into human melanoma alters T cell receptor V beta usage by tumor-infiltrating lymphocytes.

The direct introduction of foreign genes into tumors shows promise as a therapeutic modality to enhance tumor immunogenicity. Hence, melanoma nodules were directly injected with a vector encoding an allogeneic MHC class I molecule, HLA-B7. Tumor-infiltrating lymphocytes (TIL) were isolated from cutaneous melanoma biopsies before and after HLA-B7 gene transfer. TIL were expanded in interleukin-2 (IL-2) by standard techniques for approximately 4 weeks, then analyzed for T cell receptor V beta usage by quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Prior to gene transfer. TIL V beta usage was found to be highly restricted, the only one to four V beta families being expressed and one or two of these families representing more than 90% of the repertoire. As anticipated, TIL V beta usage varied among patients expressing different HLA types. However, V beta 13 was over-represented in that six of eight patients utilized V beta 13 as a dominant family, regardless of HLA type. Following HLA-B7 gene transfer, TIL V beta usage was markedly altered: (1) V beta families that dominated following gene transfer differed from the V beta families utilized by TIL prior to treatment, and (2) introduction of the HLA-B7 gene resulted in a more diverse repertoire with an increase in the number of V beta families represented. In two patients, TIL were evaluated before treatment and from multiple, distinct melanoma nodules following gene transfer. In these two patients, a comparison was made between TIL V beta profiles obtained after treatment from nodules that had been injected with the HLA-B7 gene or left untreated. Interestingly, the V beta repertoires of TIL from uninjected nodules following gene transfer were similar to that of TIL from injected nodules, rather than pretreatment TIL. These data demonstrate a direct immunological effect of foreign MHC gene transfer into human melanoma, and suggest that local expression of an allogeneic MHC molecule generates systemic alterations in the antitumor immune response.

CD4 Antigens↗

PubMed1996

Osteogenesis in extraskeletally implanted porous calcium phosphate ceramics: variability among different kinds of animals.

Synthetic porous calcium phosphate ceramics (HA/TCP) were implanted intramuscularly and subcutaneously in dogs, pigs, goats, rabbits and rats, designed to make a comparative study of the host tissue responses to porous HA/TCP ceramics in different kinds of animals. Specimens were harvested at 15, 30, 45, 60, 90 and 120 days after implantation. Decalcified and undecalcified sections were made and examined by light microscopy. Obvious bone formation could be detected in some specimens harvested from dogs and pigs after 45 days intramuscular implantation or after 60 days subcutaneous implantation. At days 90 and 120, an extensive amount of bone formed in all specimens implanted in dogs and pigs. However, no histologically detectable bone formation was observed in any specimen implanted intramuscularly and subcutaneously in goats, rabbits and rats until 120 days. It is demonstrated from this finding that the synthetic porous calcium phosphate ceramics are capable of inducing osteogenesis when implanted in non-bony sites, but this ability varies between different kinds of animals. Earlier periods of observation in specimens harvested from dogs showed that bone differentiation in the pore regions of the ceramics follows a complex process involving invasion of the fibrovascular connective tissues at day 15, appearance of polymorphic mesenchymal cells near the invading vasculature and at the interface with the ceramics at day 30, differentiation of osteoblasts and formation of bone matrix in direct contact with the surface of the ceramics at day 45, and finally remodelling of the fibrous connective tissue into an extensive amount of bone at days 60, 90 and 120.

Animals↗

PubMed1996

Water vapour-treated hydroxyapatite coatings after plasma spraying and their characteristics.

A novel way to enhance the ability of hydroxyapatite (HA) coatings in resisting degradation was revealed. The as-received plasma sprayed HA coatings were kept in water vapour at 125 degrees C, with a pressure of 0.15 MPa for 6 h; most of the amorphous phase in the coating was converted into crystalline HA and enhanced the crystallinity significantly. Meanwhile, the alpha-tricalcium phosphate, tetracalcium phosphate and CaO which decomposed from HA during plasma spraying were also transformed into crystalline HA. The dissolution experiment in distilled water at room temperature showed that the post-water vapour-treated coatings were more stable than post-heat-treated ones. The average interfacial tensile bond strength between HA and substrate before and after water vapour treatment was 45.0 and 39.1 MPa, respectively.

Biocompatible Materials↗

PubMed1996

Effect of particle size on molten states of starting powder and degradation of the relevant plasma-sprayed hydroxyapatite coatings.

Crystallinity of hydroxyapatite (HA) coatings is an important parameter to evaluate their stability. Variation of the size distribution of the starting powder is one way to alter crystallinity of coatings. The fundamental reason might be the variation of molten states of HA powders with different particle sizes. In the experiments, HA particles sized between 1 and 180 microns were divided into six groups by sieving. It was observed that the trend of crystallinity of coatings on particle size is not linear but fluctuates. The fluctuation of crystallinity was caused by the alteration of molten states of HA powders with different size distributions. It is concluded that the molten state of starting powder also fluctuated with particle size but the trend was different from that of crystallinity. Coatings sprayed with different particle sizes were immersed in deionized water for 1 month. After immersion, severe degradation and break-up were observed on the surface of coatings with the highest crystallinity, which were sprayed with large sized HA powders. It may be the high porosities in these coatings that cause the severe degradation. This shows that high crystallinity is not necessarily related to high stability of coatings and microstructure is of great importance when stability of coatings is considered.

Biocompatible Materials↗

PubMed1996

Nitric oxide production and expression of inducible nitric oxide synthase by bovine alveolar macrophages.

Alveolar macrophages play a central role in host defense in the lower respiratory tract. Production of the reactive intermediate nitric oxide (NO), via expression of inducible nitric oxide synthase (iNOS) is an important microbicidal effector mechanism possessed by macrophages. In this study, cytokine regulation of NO production by bovine alveolar macrophages (bAM) was evaluated. Bovine alveolar macrophages were exposed to one or more of the following: recombinant human (rh) and recombinant bovine (rb) IFN gamma, rh- and rbIL-1 beta, rbGM-CSF, rhTNF alpha, rhIL-4, endotoxin (LPS), fetal bovine serum (FBS), mitogen-stimulated bovine splenic supernatant (SS), and purified human TGF beta-1. LPS alone, or in combination with SS, rbIFN gamma, or rbIL-1 beta stimulated production of NO in a time and dose dependent fashion. Recombinant bovine IFN gamma, rbIL-1 beta, and rhTNF alpha in combination produced maximal stimulation which was not further enhanced by LPS. Recombinant human IFN gamma, rhIL-1 beta, and rbGM-CSF had minimal effect either as single stimuli, or in combination with LPS, rbIFN gamma, rbIL-1 beta, or rhTNF alpha. Nitric oxide production was inhibited by rhIL-4, and the L-arginine analogue antagonists of iNOS, N-G-monomethyl-L-arginine (NGMMA) and aminoguanidine (AG). Purified human TGF beta-1 did not inhibit NO production. Messenger RNA for iNOS was maximally expressed by 8 h and remained detectable for at least 48 h. Expression of iNOS mRNA induced by cytokines and LPS varied with strength of the stimulus as determined by nitrite production in culture supernatant.

Animals↗

PubMed1996

Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments.

To identify the structural basis for the observed physiological effects of myosin regulatory light chain phosphorylation in skinned rabbit skeletal muscle fibers (potentiation of force development at low calcium), thick filaments separated from the muscle in the relaxed state, with unphoshorylated light chains, were incubated with specific, intact, myosin light chain kinase at moderate (pCa 5.0) and low (pCa 5.8) calcium and with calcium-independent enzyme in the absence of calcium, then examined as negatively stained preparations, by electron microscopy and optical diffraction. All such experimental filaments became disordered (lost the near-helical array of surface myosin heads typical of the relaxed state). Filaments incubated in control media, including intact enzyme in the absence of calcium, moderate calcium (pCa 5.0) without enzyme, and bovine serum albumin substituting for calcium-independent myosin light chain kinase, all retained their relaxed structure. Finally, filaments disordered by phosphorylation regained their relaxed structure after incubation with a protein phosphatase catalytic subunit. We suggest that the observed disorder is due to phosphorylation-induced increased mobility and/or changed conformation of myosin heads, which places an increased population of them close to thin filaments, thereby potentiating actin-myosin interaction at low calcium levels.

Animals↗

PubMed1996

Kallistatin, a novel human tissue kallikrein inhibitor: levels in body fluids, blood cells, and tissues in health and disease.

Kallistatin, a human serine proteinase inhibitor, is a newly identified tissue kallikrein inhibitor. It binds strongly to tissue kallikrein but weakly to other serine proteinases such as chymotrypsin and elastase. The tissue distribution and changes in kallistatin levels in human diseases were characterized by using specific monoclonal and polyclonal antibodies against kallistatin. Kallistatin antigen levels in blood cells, fluids, and tissues measured with a specific enzyme-linked immunosorbent assay showed displacement curves that were parallel with those in purified kallistatin, indicating their immunologic identity. Expression of kallistatin mRNA in platelets, neutrophils, lymphocytes, monocytes, endothelial cells, hepatocytes, and colon and prostate carcinoma cells was identified by reverse transcription-polymerase chain reaction followed by Southern blot analysis. Plasma kallistatin concentration was 22.1 +/- 3.5 micrograms/ml in 30 normal subjects and 21.1 +/- 3.8 micrograms/ml in 5 patients with C1 inhibitor deficiency. A significantly reduced kallistatin level (7.2 +/- 2.5 micrograms/ml, p < 0.001) was seen in plasma samples from 9 patients with liver disease and 10 patients with sepsis (7.7 +/- 3.5 micrograms/ml, p < 0 .001). Further, kallistatin levels in 10 women taking oral contraceptives (19.8 +/- 3.8 micrograms/ml) and 21 pregnant women (14.9 +/- 3.3 microg/ml) were significantly lower than those seen in healthy individuals. These data suggest that kallistatin is found in plasma, is produced mostly in the liver, and can be consumed during sepsis. Its consumption in sepsis may indicate a protective role to prevent blood pressure lowering.

Antibodies, Monoclonal↗

PubMed1996

The geography of availability and driving after drinking.

This paper reports on an analysis of geographically based data from four communities conducted to evaluate relationships between measures of the physical availability of alcohol and rates of driving after drinking. From a review of the literature, it was expected that rates of driving after drinking would be directly related to the availability of alcohol at on-premise establishments. Based on theoretical arguments regarding the life activities which underlie drinking and driving it was expected that the effects of availability upon these outcomes would extend significantly beyond the local areas of outlets. Taking into account the geographic variations in environmental characteristics (road network density, traffic flow, population density), and socioeconomic (age, gender, race, marital status, income, employment) and drinking characteristics (rates of abstention, frequency and quantity of use) of resident populations, a spatial analysis of drinking driving and alcohol-related crashes was conducted. The results of the analysis showed that physical availability was unrelated to self-reports of driving after drinking and driving while intoxicated and significantly related to rates of single vehicle night-time crashes. In the latter case, physical availability affected both local and adjacent area rates of crashing.

Accidents, Traffic↗

PubMed1996

Statistical properties of a DNA sample under the finite-sites model.

Statistical properties of a DNA sample from a random-mating population of constant size are studied under the finite-sites model. It is assumed that there is no migration and no recombination occurs within the locus. A Markov process model is used for nucleotide substitution, allowing for multiple substitutions at a single site. The evolutionary rates among sites are treated as either constant or variable. The general likelihood calculation using numerical integration involves intensive computation and is feasible for three or four sequences only, it may be used for validating approximate algorithms. Methods are developed to approximate the probability distribution of the number of segregating sites in a random sample of n sequences, with either constant or variable substitution rates across sites. Calculations using parameter estimates obtained for human D-loop mitochondrial DNAs show that among-site rate variation has a major effect on the distribution of the number of segregating sites; the distribution under the finite-sites model with variable rates among sites is quite different from that under the infinite-sites model.

Animals↗