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Y Yang

Publications and source records attributed to Y Yang.

At least 1,495 records · Page 83Linked to original sources
PubMedDate not supplied

Optimization of dynamic culture conditions: effects on biosynthetic activities of chondrocytes grown in collagen sponges.

Application of mechanical stimulation, using dynamic bioreactors, is considered an effective strategy to enhance cellular behavior in load-bearing tissues. In this study, two types of perfusion mode (direct and free flow) are investigated in terms of the biosynthetic activities of chondrocytes grown in collagen sponges by assessment of cell proliferation rate, matrix production, and tissue morphology. Effects of the duration of preculture and dynamic conditioning are further determined. Our results have demonstrated that both bovine and human-derived chondrocytes demonstrate a dose-dependent response to flow rate (0-1 mL/min) in terms of cell number and glycosaminoglycan (GAG) content. This may reflect the weak adhesion of cells to the sponge scaffolds and the immature state of the constructs even after 3 weeks of proliferative culture. Our studies define an optimal flow rate between 0.1 and 0.3 mL/min for direct perfusion and free flow bioreactors. Using fresh bovine chondrocytes and a lower flow rate of 0.1 mL/min, a comparison was made between free flow system and direct perfusion system. In the free flow bioreactor, no cell loss was observed and higher GAG production was measured compared with static cultured controls. However, as with direct perfusion, the enhancement effect of free flow perfusion was strongly dependent on the maturation and organization of the constructs before the stimulation. To address the maturation of the matrix, preculture periods were varied before mechanical conditioning. An increase in culture duration of 18 days before mechanical conditioning resulted in enhanced GAG production compared with controls. Interestingly, additional enhancement was found in specimens that were further subjected to a prolonged duration of perfusion (63% increase after an additional 4 days of perfusion) after prematuration. The free flow system has an advantage over the direct perfusion system, especially when using sponge scaffolds, which have lower mechanical properties; however, mass transfer of nutrients is still more optimal throughout the scaffolds in a direct perfusion system as demonstrated by histological analysis.

Animals↗
PubMedDate not supplied

Attenuation of alcohol intake by extract of Hypericum perforatum (St. John's Wort) in two different strains of alcohol-preferring rats.

Extract of the common plant Hypericum perforatum L. (St John's Wort, SJW) has been used successfully for the treatment of mild to moderate depression since ancient times and has recently been studied clinically. Depression and alcoholism have some neurochemical similarities, such as low brain serotonin activities. Thus, we hypothesized that SJW extract, which contains 0.22% hypericin and 4.05% hyperforin, also may be effective in suppressing alcohol intake. To test this hypothesis, the effects of SJW extract on voluntary alcohol intake were studied in two different genetic animal models of human alcoholism: fawn-hooded (FH) and high-alcohol drinking (HAD) rats. FH and HAD rats received a single oral administration (5 ml/kg) of either vehicle or one of the five doses (100, 200, 400, 600, and 800 mg/kg) of SJW extract. The oral administration of SJW extract significantly (P < 0.0001) reduced alcohol intake in both FH and HAD rats. In a third study, FH rats did not develop tolerance to the suppressant effects of SJW on alcohol intake and preference following oral administration of (400 mg/kg) of the extract for 15 consecutive days. These promising findings suggest that SJW extract should be evaluated clinically as a potential therapeutic agent in the treatment of alcoholism.

Alcohol Deterrents↗
PubMedDate not supplied

An Xanthomonas citri pathogenicity gene, pthA, pleiotropically encodes gratuitous avirulence on nonhosts.

The pathogenicity gene, pthA, of Xanthomonas citri is required to elicit symptoms of Asiatic citrus canker disease; introduction of pthA into Xanthomonas strains that are mildly pathogenic or opportunistic on citrus confers the ability to induce cankers on citrus (S. Swarup, R. De Feyter, R. H. Brlansky, and D. W. Gabriel, Phytopathology 81:802-809, 1991). The structure and the function of pthA in other xanthomonads and in X. citri were further investigated. When pthA was introduced into strains of X. phaseoli and X. campestris pv. malvacearum (neither pathogenic to citrus), the transconjugants remained nonpathogenic to citrus and elicited a hypersensitive response (HR) on their respective hosts, bean and cotton. In X. c. pv. malvacearum, pthA conferred cultivar-specific avirulence. Structurally, pthA is highly similar to avrBs3 and avrBsP from X. c. pv. vesicatoria and to avrB4, avrb6, avrb7, avrBIn, avrB101, and avrB102 from X. c. pv. malvacearum. Surprisingly, marker-exchanged pthA::Tn5-gusA mutant B21.2 of X. citri specifically lost the ability to induce the nonhost HR on bean, but retained the ability to induce the nonhost HR on cotton. The loss of the ability of B21.2 to elicit an HR on bean was restored by introduction of cloned pthA, indicating that the genetics of the nonhost HR may be the same as that found in homologous interactions involving specific avr genes. In contrast with expectations of homologous HR reactions, however, elimination of pthA function (resulting in loss of HR) did not result in water-soaking or even moderate levels of growth in planta of X. citri on bean; the nonhost HR, therefore, may not be responsible for the "resistance" of bean to X. citri and may not limit the host range of X. citri on bean. The pleiotropic avirulence function of pthA and the heterologous HR of bean to X. citri are both evidently gratuitous.

Amino Acid Sequence↗
PubMedDate not supplied

Gene-for-genes interactions between cotton R genes and Xanthomonas campestris pv. malvacearum avr genes.

Six plasmid-borne avirulence (avr) genes were previously cloned from strain XcmH of the cotton pathogen, Xanthomonas campestris pv. malvacearum. We have now localized all six avr genes on the cloned fragments by subcloning and Tn5-gusA insertional mutagenesis. None of these avr genes appeared to exhibit exclusively gene-for-gene patterns of interactions with cotton R genes, and avrB4 was demonstrated to confer avr gene-for-R genes (plural) avirulence to X. c. pv. malvacearum on congenic cotton lines carrying either of two different resistance loci, B1 or B4. Furthermore, the B1 locus appeared to confer R gene-for-avr genes resistance to cotton against isogenic X. c. pv. malvacearum strains carrying any one of three avr genes: avrB4, avrb6, or avrB102. Restriction enzyme, Southern blot hybridization, and DNA sequence analyses showed that the XcmH avr genes are all highly similar to each other, to avrBs3 and avrBsP from the pepper pathogen X. c. pv. vesicatoria, and to the host-specific virulence gene pthA from the citrus pathogen X. citri. The XcmH avr genes differed primarily in the multiplicity of a tandemly repeated 102-base pair motif within the central portions of the genes, repeated from 14 to 23 times in members of this gene family. The complete nucleotide sequence of avrb6 revealed that it is 97% identical in DNA sequence to avrB4, avrBs3, avrBsP, and pthA and that 62-bp inverted terminal repeats mark the boundaries of homology between avrb6 and all members of this Xanthomonas virulence/avirulence gene family sequenced to date. The terminal 38 bp of both inverted repeats are highly similar to the 38-bp consensus terminal sequence of the Tn3 family of transposons. Up to 11 members of the avr gene family appear to be present in North American strains of X. c. pv. malvacearum, including XcmH. The high level of homology observed among these avr genes and their presence in multiple copies may explain the gene-for-genes interactions and also the observed high frequencies (10(-3) to 10(-4) per locus) of X. c. pv. malvacearum race change mutations. Five spontaneous race change mutants of XcmH suffered avr locus deletions, strongly indicating intergenic recombination as the primary mechanism for generating new races in X. c. pv. malvacearum.

Amino Acid Sequence↗
PubMedDate not supplied

Changes in angiotensin II metabolism contribute to the increased pressor response to angiotensin after chronic treatment with L-NAME in the spontaneously hypertensive rat.

1. Administration of nitric oxide (NO) synthase inhibitors, such as L-NAME, is associated with an increase in blood pressure and an increase in pressor responsiveness to infused angiotensin II (AngII). The present study was designed to investigate the contribution of changes in the metabolism of AngII to the enhanced pressor response to AngII in the spontaneously hypertensive rat (SHR; 14 weeks old) chronically treated with L-NAME. 2. Group I rats received L-NAME for 7 days (5 mg/kg per day) in their drinking water. Group II rats received water only. On day 7, rats were anaesthetized and metabolic clearance studies were performed. AngII concentrations in plasma and infusate were measured by radioimmunoassay. 3. Urinary NO2 was unchanged after L-NAME treatment, while NO3 decreased compared with control. Mean arterial pressure (MAP) was higher in the L-NAME treated rats than in control. After 30 min infusion of AngII, MAP increased significantly in both groups, although the increase was larger in L-NAME-treated than control rats. The metabolic clearance rate of AngII was significantly lower in L-NAME-treated rats than in the control group. 4. We conclude that chronic NO synthase inhibitors, such as L-NAME, cause a decrease in the rate at which AngII is metabolized. This decrease, in combination with the increase in the number of vascular AngII receptors, may account for the reported increase in pressor responsiveness to infused AngII.

Angiotensin II↗
PubMedDate not supplied

Development of a new assay for measurement of total angiotensin-converting enzyme after inhibition.

1. We set out to develop a simple, rapid, highly sensitive and reproducible assay to quantify total angiotensin-converting enzyme (ACE) in serum and tissues after ACE inhibition. 2. Total ACE was measured by dissociating ACE inhibitor from the enzyme using zinc chelation (EDTA). The enzyme reconstituted with zinc ion (ZnSO4) was then measured by enzymatic fluorimetric assay. Angiotensin-converting enzyme inhibition was produced in vitro by incubation of enalaprilat or perindoprilat with human serum or cell membranes from rat heart. To achieve the highest recovery rate, we studied concentrations of EDTA from 1 to 300 mmol/L with a pH range from 4 to 13, where the incubation times of EDTA were between 1 and 12 h. After washing off ACE inhibitor and excess EDTA, the resulting concentrates and pellets were then resuspended with Tris buffer containing ZnSO4 to restore ACE activity. 3. The optimal assay conditions to dissociate the drug from the enzyme were 300 mmol/L EDTA in Tris buffer at pH 11 for 12 h with cell membranes and 23 mmol/L EDTA at the same pH incubated for 4 h with serum. The recovery of ACE activity was 81.7 +/- 15.8 and 97.3 +/- 2.9% in tissues and serum, respectively. Intra- and interassay variability coefficients were 5.6 and 12.8% in tissue, respectively, 3.2 and 13.0% in serum, respectively. The method allows quantification of ACE in 100 microliters or less serum and 20 mg or less tissue. 4. The total ACE concentration after ACE inhibition can be determined by this assay, which is suitable for micro-sampling studies of both tissue and serum ACE levels.

Angiotensin-Converting Enzyme Inhibitors↗
PubMedDate not supplied

Expression of oncofetal fibronectin and syndecan-1 mRNA in 18 human lung cancer cell lines.

It has been suggested that fibronectin (FN) and syndecan play an important role in many aspects of cell-substrate interactions including cell adhesion. We hypothesized that oncofetal FN (onfFN) and syndecan play an important role in the process of adhesion of several human lung cancer cell lines. To test this, levels of onfFN in the culture supernatant were measured by an enzyme-linked immunosorbent assay in 18 human lung cancer cell lines. In addition, expressions of onfFN and syndecan-1 mRNA were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). Of 18 lung cancer cell lines, 3 cell lines (all adenocarcinoma) released a significant amount of onfFN in culture supernatants. Of the 18 cell lines tested, 6 cell lines expressed a significant amount of mRNA for onfFN and 4 expressed a significant amount of mRNA for syndecan-1. Levels of onfFN and expressions of mRNA for onfFN and syndecan-1 were consistently higher in non-small cell lung cancer cell lines than in small cell lung cancer cell lines. In addition, cell lines that expressed mRNA for onfFN and syndecan-1 tended to adhere to culture dishes. Syndecan-1 expression was significantly higher in attached cells compared with nonattached cells within the same cell line. Differences in onfFN and syndecan synthesis may explain some in vitro and in vivo characteristics of lung cancer.

Cell Adhesion↗
PubMedDate not supplied

Stressful life events of dental students and salivary immunoglobulin A.

To study the perceived sources of stressful events in dental students and the relationship between their self-perceived stress levels and salivary IgA. Undergraduates as well as postgraduates at the Faculty of Dentistry, National University of Singapore were surveyed one month after the new term. A 38-item dental environmental stress (DES) questionnaire, with subscales of academic work (AW), clinical factors (CF), faculty and administration factors (FA) and personal factors (PF), was used to identify the potential stressors in the dental environment. A 4-point perceived stress scale was used to rank their self-perceived stress levels. Enzyme linked immunosorbent assay method was used to determine the salivary IgA level. One hundred and thirty students (81.3%--valid response rate) participated in the study. Overall, students ranked AW with the highest score (mean 2.76), followed by CF (2.67), FA (2.24) and PF (2.16). Among the 38 items of DES questionnaire, 1st year students perceived "fear of being unable to catch up if behind" as the most stressful event (mean 3.30). For 2nd and 3rd year students, examination and grades had the highest scores (mean 3.28, 3.19, respectively). Completing graduation requirements was the most important stressor for 4th year students (mean 3.89). Post graduates perceived atmosphere created by clinical faculty was most stressful to them (mean 3.05). The mean total perceived stress scores were highest (22.1) in 1st year students and lowest (21.0) in postgraduates, however, no significant different among various classes. First year students had had the lowest IgA secretion rates (geometric mean [GM] 46.8 microg/min), significantly lower (p<0.05) than postgraduates (GM 79.4 microg/min). An inverse correlation was noted between perceived stress scale and log IgA secretion rates (r= -0.20, p= 0.002). AW was also significantly inversely correlated with salivary IgA (r= -0.18, p= 0.04). Dental students in different academic years perceived different important stressors. Salivary IgA secretion rate correlated inversely with self perceived stress.

Adult↗
PubMedDate not supplied

Tolerance of patients and postoperative results: topical anesthesia for strabismus surgery.

PURPOSE: To assess patient tolerance and the postoperative results of intraoperative adjustment of strabismus surgery under topical anesthesia. METHODS: Twenty-four patients with strabismus underwent rectus muscle recession under topical anesthesia without the use of additional systemic analgesics and sedatives. Patient tolerance was estimated according to the sites of procedure. In addition, the angle of strabismus was measured 1 day, 6 weeks, and 1 year postoperatively. RESULTS: Of the 24 patients identified (11 men and 13 women; mean age: 24 years), 16 had exotropia, 7 were esotropic, and 1 was hypertropic. During the operation, 17 patients never expressed any pain, and 7 patients complained of discomfort on muscle manipulation. Postoperatively, the success rate was 95.8% (23 patients) the first day after surgery, 79.2% (19 patients) after 6 weeks, and 70.8% (17 patients) after 1 year. CONCLUSION: Intraoperative adjustment performed with the patient under topical anesthesia is recommended in all cooperative cases of strabismus surgery and is comfortable for patients.

Adolescent↗
PubMedDate not supplied

Pirital virus (Arenaviridae) infection in the syrian golden hamster, Mesocricetus auratus: a new animal model for arenaviral hemorrhagic fever.

Adult Syrian golden hamsters inoculated intraperitoneally with Pirital virus, a recently discovered member of the Tacaribe complex of New World arenaviruses, developed a progressively severe, fatal illness with many of the pathologic features observed in fatal human cases of Lassa fever and other arenaviral hemorrhagic fevers. Most of the animals became moribund by Day 5 and were dead by Day 7 after inoculation. The most consistent histopathologic changes included interstitial pneumonitis, splenic lymphoid depletion and necrosis, and multifocal hepatic necrosis without significant inflammatory cell infiltration. The liver changes ranged from single cell death by apoptosis to coagulative necrosis of clusters of hepatocytes. Immunohistochemical studies of the liver demonstrated the presence and accumulation ot Pirital virus antigen within hepatocytes as well as Kupffer cells. An in situ terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay showed progressively increasing apoptotic activity in the liver of infected hamsters. A human hepatoblastoma cell line (Hep G2/C3A) inoculated with Pirital virus also developed progressive cell destruction and accumulation of viral antigen, as demonstrated by immunofluorescence. Results of this pilot study suggest that the Pirital virus-hamster model is a very promising new small animal model for studying the pathogenesis of arenavirus infections, particularly, the mechanism of direct virus-induced hepatic injury. It may also be useful for testingantiviral agents for treatment of arenaviral hemorrhagic fevers.

Animals↗
PubMedDate not supplied

Induction of humoral immune response and protective immunity in chickens against Salmonella enteritidis after a single dose of killed bacterium-loaded microspheres.

Formalin-inactivated Salmonella enteritidis phage type 4 strain 119/95 (SE) was encapsulated in biodegradable poly (DL-lactide co-glycolic acid) PLGA; (65:35) microspheres by a modified water-in-oil-in-water (w/o/w) double-emulsion solvent extraction/evaporation technique. These SE-loaded microspheres (SE-MS) were porous and spherical in shape with diameters of 0.4-10 microm and 20-80 microm in two preparations. SE-MS were subsequently used to vaccinate specific-pathogen-free chickens in a single dose in order to investigate the potency of a single-dose vaccination in inducing immune responses and protective immunity. In Experiment 1, 4-wk-old chickens that were vaccinated intramuscularly with 20-80-microm SE-MS generated long lasting (over 6 mo) and persistently high serum anti-SE immunoglobulin (Ig)G antibody response. In Experiment 2, 2-wk-old chickens were vaccinated orally with 0.4-10-microm or intramuscularly with 20-80-microm SE-MS and challenged with 10(9) colony-forming units of homologous SE strain at 6 wk postvaccination. When challenged intramuscularly, one each of the orally vaccinated (n = 10) and the intramuscularly vaccinated birds (n = 10) showed clinical signs and death, whereas all of the nonvaccinated control birds (n = 12) were sick and 11 of them were killed. When challenge was via oral route, 26.1% of cloacal swabs and 24.0% of organs (liver, spleen, and cecum) collected from orally vaccinated birds (n = 35) were positive for SE, comparable to 27.9% of feces and 18.7% of organs from the intramuscularly vaccinated birds (n = 35). These figures were significantly lower than those for nonvaccinated birds (n = 30) from which 59.3% of feces and 44.0% of organs tested SE positive (P < 0.05). The humoral immune response was also determined after vaccination with a single dose. The intramuscular vaccination elicited higher serum IgG response than oral administration, but the latter elicited a significant intestinal mucosal IgA antibody response. This is the first evidence that chickens vaccinated with killed SE-loaded PLGA microspheres, intramuscularly and orally in a single dose, developed systematic and local immune responses, thereby conferring protective immunity.

Administration, Oral↗
PubMedDate not supplied

The nature of inner cellular lining of the expanded polytetrafluoroethylene vascular graft: immunohistochemical study.

Histological and immunohistochemical studies of the healing processes of expanded polytetrafluoroethylene (PTFE) vascular graft were performed. In the animal experiment, endothelial cell lining, confirmed by immunohistochemical staining for anti-Factor VIII related antigen, existed nearly over all of the pannus. The endothelial cells also formed to some extent over the graft without pannus. Endothelialization showed a close dependency on the surface condition of the underlying tissue rather than on a time factor. In the human experiment, an endothelial island was observed in the middle portion of the graft in one case, supporting the hypothesis of the blood stream origin of endothelial cells.

Aged↗
PubMedDate not supplied

Healing of the resected liver stump: its process and the significance of portal blood flow.

In an effort to investigate the healing process of resected liver stump and the significance of portal and hepatic arterial flow. In addition to hepatectomy in the first group, an arterial and a portal branch were ligated in the second and third groups, respectively. It was demonstrated that portal branch ligation influenced a delay in healing of resected liver stump rather than hepatic arterial branch ligation. It is assumed that portal blood flow is more responsible for liver stump healing as well as hepatic regeneration than is hepatic arterial flow.

Animals↗
PubMedDate not supplied

Experimental study of morphological changes after gastroplasty.

Twelve rabbits were sacrificed one and three days, one, two, four and eight weeks after horizontal gastroplasty in order to investigate morphological changes after operation. Histology of the proximal pouch of the stomach showed various degrees of mucosal damage and a close relationship between its severity and high pH of the pouch. This suggested the usefulness of pH measurement of the gastric juice in the proximal pouch as an indicator of mucosal damage after gastroplasty.

Animals↗
PubMedDate not supplied

O6-methylguanine-DNA methyltransferase and human cancer chemotherapy.

Two kinds of human tumor cell strains having different activity of O6-methylguanine-DNA methyltransferase (O6-MT) were transplanted into nude mice. Mice were then injected intraperitoneally (i.p.) with the bifunctional agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride(ACNU). The tumors with low O6-MT activity were quickly suppressed or cured. This result suggests that some tumors, if determined to have low O6-MT activity, might be cured if the host is treated with ACNU. This observation may open a new approach to experimental cancer chemotherapy. Treatment with ACNU of experimental animals bearing HeLaMR tumors (which have low O6-MT activity and are Mer-), resulted in the regression of the tumors or their disappearance. In animals bearing HeLaS3 tumors (which have high O6-MT activity and are Mer+) the tumors were hyperplastic.

Animals↗
PubMedDate not supplied

The role of free radicals in the development of radiation interstitial pneumonitis.

We examined the morphologic changes in the lung tissue of Wistar rats after chest irradiation and determined sequentially the content of free radicals (FR) using electron spin resonance. The activity of superoxide dismutase (SOD) was also assessed using the chemical glow method of xanthine oxidase. After chest irradiation, the content of FR in the lung progressively increased and the activity of SOD progressively decreased. We discuss here the role of the FR in the developing process of radiation interstitial pneumonitis.

Animals↗