Biomedical subjects

G Pang

Publications and source records attributed to G Pang.

At least 37 records · Page 2Linked to original sources

PubMed2001

T cells augment monocyte and neutrophil function in host resistance against oropharyngeal candidiasis.

The purpose of this study was to identify the cell populations involved in recovery from oral infections with Candida albicans. Monoclonal antibodies specific for CD4+ cells, CD8+ cells, and polymorphonuclear leukocytes were used to deplete BALB/c and CBA/CaH mice of the relevant cell populations in systemic circulation. Monocytes were inactivated with the cytotoxic chemical carrageenan. Mice were infected with 10(8) C. albicans yeast cells and monitored for 21 days. Systemic depletion of CD4+ and CD8+ T lymphocytes alone did not increase the severity of oral infection compared to that of controls. Oral colonization persisted in animals treated with head and neck irradiation and depleted of CD4+ T cells, whereas infections in animals that received head and neck irradiation alone or irradiation and anti-CD8 antibody cleared the infection in a comparable fashion. The depletion of polymorphonuclear cells and the cytotoxic inactivation of mononuclear phagocytes significantly increased the severity of oral infection in both BALB/c and CBA/CaH mice. High levels of interleukin 12 (IL-12) and gamma interferon (IFN-gamma) were produced by lymphocytes from the draining lymph nodes of recovering animals, whereas IL-6, tumor necrosis factor alpha, and IFN-gamma were detected in the oral mucosae of both naïve and infected mice. The results indicate that recovery from oropharyngeal candidiasis in this model is dependent on CD4+-T-cell augmentation of monocyte and neutrophil functions exerted by Th1-type cytokines such as IL-12 and IFN-gamma.

Animals↗

PubMed2000

Circulating T-cell response to Helicobacter pylori infection in chronic gastritis.

BACKGROUND: Helicobacter pylori elicits a specific humoral and cellular immune response. There is increasing evidence that the type of T-cell response contributes to clinical outcome in H. pylori infection. MATERIALS AND METHODS: The host response to H. pylori infection in 34 subjects with chronic gastritis was examined in terms of T-cell proliferation and cytokine production in whole-blood cultures stimulated or unstimulated with H. pylori acid-glycine extract antigens (AGE). RESULTS: The proliferative response in whole-blood cultures was similar for both H. pylori-positive and -negative subjects stimulated with H. pylori AGE. While an increase in interferon-gamma (IFN-gamma) production was observed from both H. pylori-positive and -negative subjects with gastritis, significantly higher levels of IFN-gamma were detected in the former when stimulated with H. pylori AGE. In contrast, interleukin 4 (IL-4) was undetectable regardless of antigen stimulation. However, if an in situ IL-4 antibody capture assay was used, antigen-independent production of IL-4 was detected, but there was no difference between H. pylori-positive and -negative subjects with gastritis. After eradication of H. pylori, antigen-induced production of IL-4 was increased, with no decrease in the levels of secretion of IFN-gamma. IL-4 production was dependent on CD4+ T cells, as addition of anti-CD4 but not anti-CD8 mouse monoclonal antibody or matched IgG isotype to the whole-blood culture inhibited the production of IL-4. CONCLUSION: The results suggest that a shift toward a balanced Th1-Th2 response due to an increase in antigen-induced IL-4 production from CD4+ T cells follows eradication. We suggest that the downregulation of mucosal inflammation consequent on reduction in antigen levels or removal of downregulation after eradication of H. pylori contributes to this shift in cytokine balance.

Adult↗

PubMed2000

Non-urease producing Helicobacter pylori in chronic gastritis.

BACKGROUND: Helicobacter pylori infection is the commonest cause of gastritis. Different patterns of immune response to H. pylori infection and characteristics of bacteria are considered to contribute to clinical outcomes. AIM: To determine characteristics of the host H. pylori relationship in subjects with non-ulcer dyspepsia and a histological diagnosis of gastritis. METHODS: Thirty-five subjects with chronic gastritis undergoing endoscopy (mean age 53 years, range 24-82, 14 male and 21 female) were studied, none of whom was on nonsteroidal anti-inflammatory drugs or antibiotics. H. pylori infection was determined by rapid urease test (CLOtest), culture, antibody and RT-PCR for Ure C, Cag A and 26 kDa gene and histology. Cytokine production of mucosal IL-6 and IL-8 were measured by ELISA. RESULTS: Fifteen subjects were positive by CLOtest and/or bacterial culture. In these subjects histology showed numerous helical forms of H. pylori (Group I). Nine subjects were negative by CLOtest, bacterial culture, and mRNA for urease C fragment, but positive by PCR for the 26 kDa protein encoding gene. Histology in these subjects showed the presence of either coccoid forms (four), or scant helical forms (two), or mixed coccoid/helical forms (three) (Group II). Eleven subjects were negative by all methods of detection (Group III). IgG and IgA antibody levels in serum (p<0.05) and gastric tissue culture supernatant (p<0.001) were significantly higher in Group I than those in Group II or III. There were significant differences in the IgG serum and IgA supernatant antibody levels (p<0.01 and p<0.05) when Group II was compared to Group III. Supernatant IL-6 levels were significantly higher in Group I (p<0.01) than those from Groups II and III. IL-8 levels were higher in Group I (p<0.01) and Group II (p<0.05) when compared to Group III. CONCLUSIONS: 'H. pylori-negative' gastritis can be associated with a non-urease producing form of H. pylori, with a reduction in both local and systemic antibody levels and mucosal pro-inflammatory cytokines.

Adult↗

PubMed2000

Use of self-report to monitor overweight and obesity in populations: some issues for consideration.

OBJECTIVE: To examine the validity of self-reported height and weight data reported over the telephone in the 1997 NSW Health Survey, and to determine its accuracy to monitor overweight and obesity in population surveys. METHOD: Self-reported and measured heights and weights were collected from 227 people living in Western Sydney, who had participated in the NSW Health Survey 1997. RESULTS: Self-reported (SR) weights and heights led to misclassification of relative weight status. BMI, based on measured weights and heights, classified 62% of males and 47% of females as overweight or obese, compared with 39% and 32%, respectively, from self-report. CONCLUSIONS: Caution should be used when interpreting SR height and weight data from surveys, because BMI derived from these is likely to underestimate the true prevalence of overweight and obesity. IMPLICATIONS: SR data have a place in nutrition monitoring because they are relatively inexpensive and easy to collect. However, classifying people into weight categories on the basis of accepted cut-points, using SR heights and weights, yields inaccurate prevalence estimates. Periodic sub-studies of the validity of SR heights and weights are needed to indicate the extent to which the validity of SR is changing.

Adolescent↗

PubMed2000

Conditioning rhinitis in allergic humans.

A classical Pavlovian paradigm pairing an olfactory cue with allergen challenge for a single training trial was used to produce conditioned histamine release and conditioned nasal airflow decrease in seasonal allergic rhinitis sufferers. There was no conditioned increase in subjective symptoms. Histamine release and airflow decrease showed evidence of extinction by a second test trial. A second study comparing the effects of the number of training trials showed that three training trials produced greater histamine release and airflow decrease than a single training trial, suggesting stronger effects with additional training.

Humans↗

PubMed2000

Electronic portal imaging with an avalanche-multiplication-based video camera.

The aim of this study is to investigate the degree to which the imaging quality of an existing (video-based) electronic portal imaging device (EPID) system may be improved by using an avalanche-multiplication-based video camera (called the avalanche-gain method). Due to avalanche multiplication in the target of the video camera tube, the new camera can be made up to several hundred times more sensitive than a camera using a conventional video (e.g., Saticon) tube. As a result, the camera noise which limits the performance of current video-based EPIDs should be overwhelmed and made negligible. The detective quantum efficiency (DQE) of an EPID using the avalanche-gain method has been measured with 6 MV and 18 MV beams obtained using a linear accelerator. It is shown that the camera noise is indeed much smaller than quantum noise and that the DQE of the system is significantly increased compared to conventional video-based EPIDs. Variation of DQE of the avalanche-gain video portal system with a change of demagnification was also investigated. It has been shown that the improvement of optical coupling has less effect in this system than that in a conventional video-based EPID system.

Humans↗

PubMed2000

Cellular and cytokine correlates of mucosal protection in murine model of oral candidiasis.

Host protection against Candida albicans infection in a model of oral candidiasis involving infection-prone [DBA/2 (H-2(d))] and less infection-prone [BALB/c (H-2(d))] mouse strains was analyzed in terms of antibody and cellular responses, and in terms of cytokine patterns from regional lymph node cells. There was a selective expansion of gamma/delta(+) T-cell receptor cells, which correlated with the patterns of colonization in both mouse strains, with higher numbers of gamma/delta T cells detected in BALB/c mice. Antigen-induced T-cell proliferation was significantly higher in BALB/c mice than in DBA/2 mice. Higher levels of serum immunoglobulin G (IgG) and salivary IgA antibodies were detected in BALB/c mice than in DBA/2 mice, but only after the infection was cleared. The cervical lymph node cells from infected mice were assessed for interleukin-4 (IL-4), IL-12, and gamma interferon (IFN-gamma) mRNA gene expression by reverse transcription-PCR and protein production in the culture supernatants following restimulation in vitro. In BALB/c mice, an early increase in levels of IL-4, IFN-gamma, and IL-12 correlated with rapid elimination of C. albicans. In DBA/2 mice, where resolution of infection was delayed, IL-4 message expression was delayed and the IL-4 secretion level was lower. Neutralization of IL-4 by multiple injections of an anti-IL-4 monoclonal antibody in BALB/c mice resulted in increased carriage rate and delayed clearance of the yeasts. Collectively, the data suggest that the T-cell response to C. albicans in the regional lymph nodes which correlates best with rapid oral clearance of C. albicans is a balanced Th0 cytokine response involving early secretion of both IFN-gamma and IL-4.

Animals↗

PubMed2000

Influenza virus inhibits lysozyme secretion by sputum neutrophils in subjects with chronic bronchial sepsis.

Neutrophils are central to the control of infection within the bronchial mucosa. To determine whether the link between bacterial and viral infection in the respiratory tract can be partly explained by acute reduction of neutrophil function, we examined the influence of influenza virus on lysozyme secretion by sputum neutrophils obtained from patients with bronchiectasis. Sputum neutrophils infected with influenza A virus had a significantly reduced capacity to secrete lysozyme but not myeloperoxidase. Influenza virus A strains were more effective in inhibiting lysozyme secretion than were influenza B virus strains. Reduction of bactericidal activity was similarly reduced by different strains of influenza A virus, but an influenza virus B strain had no effect. Our results show that downregulation of sputum neutrophil function characterized by lysozyme secretion and bactericidal activity could contribute to reduction in the capacity to control bacterial colonization in the respiratory tract following influenza virus infection.

Bronchiectasis↗

PubMed2000

Giardia lamblia rearranges F-actin and alpha-actinin in human colonic and duodenal monolayers and reduces transepithelial electrical resistance.

The mechanisms of epithelial injury in giardiasis remain unknown. The effects of live Giardia lamblia on cellular G-actin, F-actin, alpha-actinin, and electrical resistance of human intestinal epithelial monolayers were investigated using SCBN and Caco2 cell lines grown on chamber slides or Transwell filter membranes. In separate experiments, some monolayers were also exposed to sonicated trophozoites, some to supernatant from live G. lamblia cultures, and some with or without the Ca2+ channel blocker verapamil. After 2, 24, or 48 hr of coincubation with G. lamblia, monolayers were assessed for cytoskeletal arrangement under fluorescence and confocal laser microscopy, and transepithelial electrical resistance was measured. Exposure to live G. lamblia trophozoites induced localized condensation of F-actin and loss of perijunctional alpha-actinin while G-actin remained unchanged. Confocal laser microscopy indicated that F-actin rearrangement was not affected by verapamil and was localized within the terminal web area. Coincubation of monolayers with G. lamblia lysates or with spent medium alone similarly rearranged F-actin. Verapamil alone did not alter F-actin. Electrical resistance of SCBN and Caco2 monolayers exposed to G. lamblia was significantly decreased versus controls regardless of whether live or lysed trophozoite samples were used. The results indicate that G. lamblia-induced epithelial injury is associated with F-actin and alpha-actinin rearrangements in the terminal web area via mechanisms independent of extracellular Ca2+. These alterations are associated with reduced transepithelial electrical resistance and are due at least in part to trophozoite products.

Actinin↗

PubMed2000

Effects of CH-100, a chinese herbal medicine, on acute concanavalin A-mediated hepatitis in control and alcohol-fed rats.

BACKGROUND: Administration of concanavalin A (Con A) leads to acute hepatitis that involves T-cell activation and inflammatory mediator production in mice and rats. We examined the role of CH-100, a Chinese herbal medicine previously trialed in human hepatitis C, in the prevention of Con A-related, T-cell-mediated, acute liver injury in rats. METHODS: Female Wistar rats were fed 40% ethanol, 2% sucrose, or isocaloric sucrose for 8 weeks. At the same time, these animals were fed either the Chinese herbal medicine CH-100 (4 tablets/kg body weight/ day) or placebo in chow daily. Blood from the tail vein was collected for endotoxin (lipopolysaccharide) assay at 0, 4, and 8 weeks of ethanol consumption. Twenty-four hours after injection of Con A (20 mg/kg body weight) or phosphate-buffered saline, blood from the tail vein was collected for alanine aminotransferase and tumor necrosis factor (TNF)-alpha assays. Liver-associated CD4+ T cells were isolated from liver perfusates and then cultured with Con A (5 microg/ml) at 37 degrees C for 24 hr. Supernatants were harvested for TNF-alpha assay. The proportion of CD4+ T cells in blood and liver perfusates was measured. Liver samples were collected for histopathological analysis. RESULTS: Lipopolysaccharide levels were significantly reduced in CH-100-treated ethanol-fed rats compared with placebo-treated rats. After Con A injection, alanine aminotransferase levels were lower at 12 and 24 hr in herb-treated rats compared with placebo-treated rats. Furthermore, serum TNF-alpha levels were lower in ethanol-fed rats on herbal treatment. A significant decrease in TNF-alpha production by liver-associated CD4+ T cells in culture was observed in CH-100-treated ethanol-fed rats. CH-100 treatment was associated with a decreased percentage of CD4+ cells in both blood and liver perfusate in all groups. Herb-treated rats displayed markedly less hepatic necrosis and a reduced CD4+ T-cell infiltrate in portal areas than did placebo-fed rats. CONCLUSIONS: The results demonstrate that CH-100 modified the T-cell response to Con A injection. The effect was more marked in ethanol-fed rats, which suggests a possible role for CH-100 in treating alcoholic liver disease.

Alanine Transaminase↗

PubMed2000

Estimating supply requirements for forward medical treatment facilities.

The Naval Health Research Center designed, developed, and used a systematic process to review Marine Corps medical supply requirements. This approach consisted of identifying the medical tasks required to treat patients with specific injuries and illnesses and determining the supplies and equipment required to perform each task. Subject matter experts reviewed treatment briefs, tasks, supplies, and equipment and examined their value to Marine Corps medical providers in forward areas of care. By establishing the clinical requirement for each item pushed forward, the Naval Health Research Center model was able to reduce the logistical burden carried by Marine Corps units and enhance far-forward clinical capability. The result of this effort is a model to estimate supplies and equipment based on a given casualty stream distribution. This approach produces an audit trail for each item and allows current authorized medical allowance list configurations to be revised using information such as type of conflict anticipated, expected duration, and changes in medical doctrine.

Equipment and Supplies↗

PubMed1999

Coccoid forms of Helicobacter pylori can be viable.

Controversy exists as to whether the coccoid form of Helicobacter pylori can exist in a viable form. Conversion of helical to coccoid morphology occurs in culture over several days. In this study, the morphology was correlated with parameters of genetic integrity in the reference NCTC 11637 strain over 21 days of culture. The capacity to regrow colonies of helical form was demonstrated from a culture where the coccoid form constituted up to 95% and negligible urease activity could be detected. Urease enzyme activity and its mRNA decreased between day 0 and 10 while 26 kD mRNA and 16S rRNA were expressed unchanged for up to 14 and 21 days of culture, respectively. Expression of mRNA for the Cag A gene behaved in a similar fashion to that of urease. No evidence of DNA fragmentation was detected. These data suggest that a viable form of non-urease producing H. pylori exists after short to intermediate culture and that some if not all of these viable bacteria have coccoid morphology.

Antigens, Bacterial↗

PubMed1999

Ethanol-altered liver-associated T cells mediate liver injury in rats administered Concanavalin A (Con A) or lipopolysaccharide (LPS).

BACKGROUND: Recent work from our laboratory implicates T cells in the pathogenesis of alcoholic liver disease. We have studied the role of liver-associated T cells in acute hepatitis produced in control rats administered Concanavalin A (Con A) after adoptive transfer of T cells from alcohol-consuming animals. METHODS: Liver-associated T cells from ethanol-consuming rats were transferred via tail vein to nonethanol-consuming rats. They then received Con A (20 mg/kg body weight) intravenously. This produced a severe hepatitis. Serum was collected for the assay of alanine aminotransferase (ALT) and cytokines. RESULTS: Hepatic necrosis was accompanied by an increase in plasma levels of ALT, interleukin-6, and tumor necrosis factor-alpha. These increases correlated with increased production of interleukin-6 and tumor necrosis factor-alpha in culture of liver-associated T cells stimulated or unstimulated with Con A. Immunohistology staining showed increased infiltration of inflammatory cells comprised of neutrophils and mononuclear cells, which included greater numbers of CD4+ T cells in the portal tract areas and around the central vein. Focal and lobular necrosis was seen with inflammatory cells in the necrotic area. Hepatocytes isolated from the liver showed increased apoptosis compared with rats that received liver-associated T cells from nonethanol-consuming rats. Injection of endotoxin LPS, in the same model, was associated with less hepatocyte injury indicating a distinct role for T cells as opposed to Kupffer cells in this model of liver disease. CONCLUSIONS: Chronic ethanol consumption induces a lesion in a pool of liver-associated T cells which can mediate liver injury after polyclonal mitogen activation.

Alanine Transaminase↗

PubMed1999

[The apoptosis and proliferation after photorefractive keratectomy].

OBJECTIVE: To search the correlation between the apoptosis and proliferation of keratocytes and investigate the influence of phototherapeutic keratectomy (PTK) and mechanical epithelial scrape (MES) on keratocyte apoptosis and proliferation. METHODS: Rabbit corneas received photorefractive keratectomy (PRK, -9.9 diopters, 6 mm diameter). Animals were evaluated subsequently up to 6 months after surgery by in vivo confocal microscopy. Corneas were prepared for H.E. staining, corneal cell apoptosis was evaluated by terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) to detect DNA fragmentation. RESULTS: Loss of keratocytes and keratocyte death were found anteriorly in the remaining stroma at 4h after PRK. Activated keratocytes observed by confocal microscopy repopulated within 1 month. A significant elevation of apoptosis was detected in keratocytes and epithelium at 4h, 3d, 1m after PRK. The level of keratocyte apoptosis was parallel to the loss of keratocytes at the early stage and was correlated with keratocyte proliferation in the later stage, PTK-PRK was associated with lower levels of central corneal apoptosis and activated keratocytes than MES-PRK. CONCLUSION: It is suggested that the loss of keratocytes and keratocyte apoptosis be correlated with keratocyte activation and proliferation, which may result in haze and regression after PRK, and PTK-PRK induce lower level of early keratocyte apoptosis and late keratocyte activation than MES-PRK.

Animals↗

PubMed1999

[Excimer laser photorefractive keratectomy for lower to moderate myopia: 5 year follow-up].

OBJECTIVE: To evaluate the long-term effectiveness and safety of photorefractive keratectomy (PRK) for patient with lower to moderate myopia. METHODS: 148 myopic eyes (-1.5 to -6.00 D) after PRK follow-up of more than 5 years were analyzed. RESULTS: Uncorrected visual acuity was >or= 1.0 in 136 eyes (91.9%), >or= 0.8 in 4 eyes (2.7%) and >or= 0.6 in 8 eyes (5.4%). The mean spherical equivalent change was from (-4.43 +/- 0.97) D to (-0.12 +/- 0.22) D, and the keratometric power (K value) was reduced from (43.81 +/- 1.10) D to (41.36 +/- 1.30) D in the 5 years of follow-up (P < 0.01). CONCLUSION: The long-term effectiveness of PRK for myopia (-1.5 to -6.00 D) is satisfactory.

Female↗

PubMed1999

[The effects of fluoride on the bonding strength of brackets].

OBJECTIVE: To evaluate the effect of using fluoride during and after etching on the bonding strength of brackets. METHODS: 45 extracted human premolar were divided into three groups: Group 1, control, not applying fluoride. Group 2, applying fluoride during etching. Group 3, applying fluoride after etching. In each group, the teeth were treated with etching and fluoride respectively and stored in water for 24 hours. Then brackets bonding strength were measured. RESULTS: The results showed that there was not significant difference among the three groups. CONCLUSION: Fluoride can be used to prevent enamel white spot.

Acid Etching, Dental↗

PubMed1999

[Scanning electron microscopy study on different orthodontic methods of using fluoride in enamel white spot prevention].

OBJECTIVE: To determine which method of topical fluoride application could make the enamel uptake more fluoride. METHODS: 12 extracted human premolars were divided into three groups of 4 teeth each: Group 1, control and not applying fluoride; Group 2, applying fluoride during etching; Group 3, applying fluoride after etching. In each group, the teeth were treated with etching and fluoride respectively. The specimens were then examined with scanning electron microscopy. RESULTS: The results showed that there were more reaction products on the enamel surface of Group 3. CONCLUSION: There was more fluoride uptake into the enamel treated with fluoride after etching.

Acid Etching, Dental↗

PubMed1999

[A retrospective study of morphologic basis for the extraction decision in Class II, division 1 malocclusion].

OBJECTIVE: To compare the dentofacial characteristics of persons with Class II, Division 1 malocclusion treated with either an extraction or a nonextraction approach. Such comparison might help identify which parameters influence the extraction decision. METHODS: Lateral cephalograms were available on 81 cases of Class II, Division 1 malocclusion, 42 were treated with 4 premolar extractions and 39 were treated with non-extraction. The cephalometric analysis of West China University of Medical Sciences and Model Analysis were used, RESULTS: Patients in the extraction group had larger FMA, FMIA and lower anterior facial height. In the group of extraction, the upper anterior teeth tipped more anteriorly, and the tooth size-arch length discrepancy and the depth of Spee curve were greater significantly. But the saggital discrepancy and soft tissue's profiles had no significant difference between two groups. CONCLUSION: The stability of the triangle of Tweed, the tooth size-arch discrepancy and the depth of Spee curve were the keys to decide weather extraction or not.

Adolescent↗