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Biomedical subjects

B Chan

Publications and source records attributed to B Chan.

At least 73 records · Page 4Linked to original sources
PubMed1995

Staphylococcus aureus stimulates neutrophil recruitment by stimulating interleukin-8 production in dog trachea.

The present study examined whether neutrophil recruitment in dog airways by Staphylococcus aureus is mediated by interleukin-8 (IL-8). S. aureus culture supernatant was superfused into an isolated tracheal segment in six dogs, and neutrophil recruitment and IL-8 concentrations were measured in the superfusate. Dog IL-8 was cloned, expressed in Escherichia coli, purified by chromatography, and shown to be biologically active. With the use of an enzyme-linked immunoabsorbent assay (ELISA) for the measurement of dog IL-8, we showed that S. aureus supernatant induced neutrophil recruitment and increased IL-8 concentration in the superfusate in a time-dependent manner. The chemotactic activity present in the superfusate 6 h after superfusion with S. aureus was inhibited by an anti-IL-8 antibody. S. aureus supernatant also stimulated IL-8 production and gene expression by cultured canine tracheal epithelial cells. These results provide evidence that IL-8 plays a major role in S. aureus-induced neutrophil recruitment in the airways by stimulating IL-8 production in airway cells.

Amino Acid Sequence↗
PubMed1995

Viral infection potentiates the increase in airway blood flow produced by substance P.

We examined the effect of respiratory tract infection with Sendai virus on the responsiveness of airway blood flow to substance P (SP) in rats. Pathogen-free rats were inoculated with either Sendai virus suspension or sterile viral growth medium into each nostril. Five days later, we measured airway and esophageal blood flows before and immediately after injection of SP or histamine into the left ventricle of rats in both groups using a modification of the reference-sample microsphere technique. Viral infection potentiated the increase in airway blood flow evoked by SP but not by histamine. We also examined the effect of neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) on the SP-induced increase in airway blood flow. Both phosphoramidon (NEP inhibitor) and captopril (ACE inhibitor) potentiated the increase in airway blood flow produced by SP in pathogen-free rats. In the presence of both peptidase inhibitors, a submaximal dose of SP increased blood flow to a similar level in infected and pathogen-free rats. Thus decreased activity of both ACE and NEP may be involved in the exaggerated increase in airway blood flow evoked by SP in virus-infected rats.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Plasma extravasation in the rat trachea induced by cold air is mediated by tachykinin release from sensory nerves.

Cold air was delivered to anesthetized, artificially ventilated, pathogen-free F344 rats via a tracheal cannula. Inhalation of cold air increased Evans blue dye extravasation in the trachea in a time-dependent (1 to 10 min) manner. Plasma extravasation increased after 3 min exposure to cold air and reached a maximum after 10 min exposure. The neutral endopeptidase inhibitor, phosphoramidon (2.5 mg/kg, intravenously), increased by 84% the plasma extravasation induced by inhalation of cold air for 1 min. The plasma extravasation evoked by 5 min exposure to cold air was abolished by the NK1 tachykinin receptor antagonist, CP-99,994 (4 mg/kg, intravenously); was reduced 30% by the B2 bradykinin receptor antagonist, HOE140 (0.1 mumol/kg, intravenously); and was not affected by H1 (pyrilamine, 10 mg/kg, intraperitoneally) or H2 (cimetidine, 10 mg/kg, intraperitoneally) histamine receptor antagonists or the cyclooxygenase inhibitor indomethacin (5 mg/kg, intravenously). In rats infected with Sendai virus, plasma extravasation evoked by inhalation of cold air was greater than in pathogen-free rats. Pretreatment with CP-99,994 (4 mg/kg, intravenously) inhibited completely the plasma extravasation induced by cold air in virus-infected rats. These findings indicate that cold air increases plasma extravasation in the rat trachea by a neurogenic mechanism that involves the release of tachykinins from sensory nerves. Kinin release may also play a role in this neurogenic inflammatory response.

Air↗
PubMed1995

Role of recruited neutrophils in interleukin-8 production in dog trachea after stimulation with Pseudomonas in vivo.

Cell-free supernatant of Pseudomonas aeruginosa (PA) recruits neutrophils into the airways indirectly by inducing the production of chemotactic factors, including interleukin-8 (IL-8). PA products stimulate IL-8 expression selectively in surface airway epithelium, gland ducts, serous cells, and recruited neutrophils. To examine the relative contribution of neutrophils in IL-8 release in the airway lumen, we studied the effect of inhibition of neutrophil recruitment on IL-8 concentration in tracheal fluid after introduction of PA supernatant into the dog trachea in vivo. Tracheal superfusion with PA supernatant caused neutrophil recruitment and increased the IL-8 concentration in the tracheal lumen; NPC 15669 inhibited both effects. To study whether migration of neutrophils into the airway lumen per se induces their expression of IL-8, we compared effects of local introduction of IL-8 and of PA supernatant into the trachea on IL-8 expression in neutrophils recruited into the trachea. PA supernatant, but not exogenous IL-8 alone, induced IL-8 mRNA expression in neutrophils recruited into the trachea. To determine what product(s) of PA stimulate IL-8 expression in neutrophils, we examined neutrophils isolated from peripheral blood. PA supernatant induced IL-8 production in neutrophils, an effect reproduced by PA lipopolysaccharide and inhibited by polymyxin B. These results suggest that neutrophils recruited into the airway lumen play a major role in local IL-8 production in airways in response to bacteria such as PA, depending on the presence of stimuli such as lipopolysaccharide.

Animals↗
PubMed1994

Tachykinins and kinins in antigen-evoked plasma extravasation in guinea-pig nasal mucosa.

The plasma extravasation evoked by instillation of 5% ovalbumin in the nasal mucosa of sensitized guinea-pigs was potentiated by the neutral endopeptidase inhibitor, phosphoramidon, and was reduced by the tachykinin NK1 receptor antagonist, CP-96,345. The bradykinin B2 receptor antagonist, HOE 140, also reduced the plasma extravasation evoked by the antigen. The combination of HOE 140 and CP-96,345 did not increase further the inhibition caused by HOE 140 alone. Plasma extravasation evoked by instillation of capsaicin was abolished by CP-96,345. HOE 140 blocked and CP-96,345 markedly reduced plasma extravasation caused by instillation of bradykinin. Plasma extravasation evoked by instillation of substance P was not affected by HOE 140. We conclude that antigen challenge causes plasma extravasation in the nasal mucosa of sensitized guinea-pigs, an effect that is due in part to the release of tachykinins from sensory nerve endings. Our evidence suggests that tachykinin release in response to antigen is provoked mainly by the release of kinins.

Animals↗
PubMed1994

Treatment of murine lupus with monoclonal antibodies to lymphocyte function-associated antigen-1: dose-dependent inhibition of autoantibody production and blockade of the immune response to therapy.

Monoclonal antibodies (mAb) to lymphocyte function-associated antigen-1 (LFA-1) have been used successfully in vivo to inhibit immune responses and to block inflammatory reactions. To determine whether these effects of anti-LFA-1 could retard autoimmune disease, we treated lupus-prone NZB/NZW F1 (B/W) mice with a rat mAb to LFA-1 (anti-CD11a). Mice received high-dose therapy (500 micrograms twice weekly), low-dose therapy (40 micrograms thrice weekly), or phosphate-buffered saline from age 5 months to age 10 months. Treatment with high doses of anti-CD11a suppressed both the immune response to the rat mAb and the production of autoantibodies to double-stranded DNA. In contrast, treatment with low doses of anti-CD11a elicited an immune response to the rat mAb and did not suppress autoantibody production. The immunosuppressive effects of high doses of anti-CD11a were not due to target cell depletion. In fact, treatment induced a marked lymphocytosis which involved all lymphocyte subsets equally. Despite inhibiting autoantibody production, high-dose therapy had only modest effects on longevity.

Animals↗
PubMed1994

Identification of mutations in the alpha 3(IV) and alpha 4(IV) collagen genes in autosomal recessive Alport syndrome.

Alport syndrome (AS) is an hereditary disease of basement membranes characterized by progressive renal failure and deafness. Changes in the glomerular basement membrane (GBM) in AS suggest that the type IV collagen matrix, the major structural component of GBM, is disrupted. We recently isolated the genes for two type IV collagens, alpha 3(IV) and alpha 4(IV), that are encoded head-to-head on human chromosome 2. These chains are abundant in normal GBM but are sometimes absent in AS. We screened for mutations in families in which consanguinity suggested autosomal recessive inheritance. Homozygous mutations were found in alpha 3(IV) in two families and in alpha 4(IV) in two others, demonstrating that these chains are important in the structural integrity of the GBM and that there is an autosomal form of AS in addition to the previously-defined X-linked form.

Adolescent↗
PubMed1994

Airway vasodilation by bradykinin is mediated via B2 receptors and modulated by peptidase inhibitors.

We studied the effect of exogenous bradykinin on blood flow in the airway microcirculation of anesthetized F344 rats in vivo. We made three successive determinations of airway blood flow and cardiac output using a modification of the reference sample microsphere technique. Injection of bradykinin into the left ventricle increased airway blood flow in a dose-related manner. Pretreatment with the bradykinin B2 receptor antagonist, Hoe 140, completely abolished bradykinin-, but not histamine-induced vasodilation. A bradykinin B1 receptor agonist, [des-Arg9]bradykinin, did not affect airway blood flow. We also studied the effect of inhibitors of angiotensin-converting enzyme (captopril) and neutral endopeptidase (phosphoramidon) on bradykinin-induced vasodilation. Pretreatment with captopril, but not phosphoramidon, potentiated the bradykinin-induced vasodilation. However, the addition of phosphoramidon further potentiated the effect of captopril. We conclude that injection of bradykinin into the left ventricle produces a dose-related vasodilation in the airway microcirculation mediated via B2 receptors, an effect that is modulated primarily by angiotensin-converting enzyme and, to a lesser extent, by neutral endopeptidase.

Animals↗
PubMed1994

Pseudomonas stimulates interleukin-8 mRNA expression selectively in airway epithelium, in gland ducts, and in recruited neutrophils.

Neutrophils may play important roles in chronic airway diseases. Pseudomonas is a common pathogen in some chronic airway diseases, and expression of the neutrophil chemoattractant interleukin-8 (IL-8) is induced by Pseudomonas in various cells in vitro. Here we examine the localization of IL-8 mRNA expression after incubating human and dog bronchi with Pseudomonas supernatant in vitro. To examine IL-8 expression in recruited neutrophils, we also superfused the dog bypassed tracheal segment with Pseudomonas supernatant in vivo and measured neutrophil number and IL-8 concentration in luminal fluid; simultaneously, we introduced Pseudomonas supernatant by catheter in a peripheral airway. After 6 h, we analyzed IL-8 mRNA expression and localization in removed tissue. Unincubated bronchi showed no IL-8 mRNA expression, but incubation with Pseudomonas supernatant in vitro resulted in IL-8 mRNA expression in surface epithelial, gland duct, and a subpopulation of serous gland cells. In vivo, introduction of Pseudomonas supernatant into dog trachea and peripheral airways caused IL-8 mRNA expression in epithelial and gland duct cells but also in the recruited neutrophils. Pseudomonas lipopolysaccharide alone was without effect in vitro and in vivo. We conclude that Pseudomonas products, but not lipopolysaccharide, stimulate IL-8 expression in airways and that this expression occurs primarily in surface epithelial and gland duct cells, thus bringing the chemoattractant to the bacterial site. Furthermore, IL-8 expression in recruited neutrophils provides a potential mechanism for positive feedback of this protective antibacterial response.

Adult↗
PubMed1994

Interleukin 6 promotes murine lupus in NZB/NZW F1 mice.

To investigate the role of IL-6 in systemic lupus erythematosus (SLE), we selectively inhibited IL-6 in lupus-prone NZB/NZW F1(B/W) mice by chronic administration of a rat mAb to mouse IL-6. Anti-IL-6 alone elicited an anti-rat response that blocked its biologic effects. To circumvent this problem, we rendered B/W mice tolerant to the rat mAb by administration of anti-CD4 concurrent with the first dose of anti-IL-6. Thereafter, the mice received weekly injections of anti-IL-6 alone. There were two control groups: one group received the tolerizing regimen of anti-CD4 along with a control rat IgG1 mAb (GL113) instead of anti-IL-6; the other control group received PBS. Mice that received anti-CD4 were tolerant to the rat mAb for 6 mo. Throughout this period, treatment with anti-IL-6 prevented production of anti-dsDNA, significantly reduced proteinuria, and prolonged life. Mice that received anti-IL-6 without anti-CD4 developed an immune response to the rat mAb and then developed anti-dsDNA antibodies, proteinuria, and mortality comparable with control mice. These findings establish that IL-6 promotes autoimmunity in B/W mice. They further indicate that, although mAb to IL-6 can suppress murine lupus, the development of host immunity to the mAb abrogates its beneficial effects. Finally, this is the first study to demonstrate that a brief course of anti-CD4 can induce tolerance to another therapeutic mAb, in this case an anti-cytokine mAb.

Animals↗
PubMed1993

In vivo imaging of baboon and human dopamine transporters by positron emission tomography using [11C]WIN 35,428.

[11C]WIN 35,428 was evaluated as a specific in vivo radioligand for the dopamine transporter site by PET scanning in nonhuman primates and humans. In studies with a baboon (Papio anubis), [11C]WIN 35,428 accumulated in brain regions containing dopamine transporters, i.e., the striata. This accumulation was partially blocked by prior administration of (-)cocaine (4 mg/kg, i.v.). Placement of a unilateral lesion of dopamine-containing nerve terminals with MPTP resulted in a unilateral reduction in [11C]WIN 35,428 accumulation in the striatum on the side of the lesion. Imaging of D2 dopamine receptors with [11C]NMSP in the same MPTP-treated animals showed much less reduction in the postsynaptic D2 dopamine receptors as compared to the much larger reduction in the dopamine transporters labeled with [11C]WIN 35,428. A total of ten normal human volunteers (five males and five females) with ages ranging from 19 to 81 years were studied. The caudate/cerebellar and putamen/cerebellar ratios ranged from 4.4 to 5.7 90 min after injection of the tracer. Preliminary kinetic modeling with arterial plasma sampling resulted in an average binding potential (k3/k4) of 4.98 in the caudate nucleus and 5.13 in putamen. To demonstrate in vivo blockade with dopamine reuptake inhibitors, two subjects received prior oral doses of 6 mg mazindol. Subject 5 had significant reductions of 29% in the caudate/cerebellar ratio at 90 min, 35% in the putamen/cerebellar ratio at 90 min, 45% in the caudate k3/k4 ratio from 6.7 to 3.7, and 46% in the putamen k3/k4 from 4.7 to 2.5. Subject 8 had significant reductions of 20% in both the caudate/cerebellar ratio and the putamen/cerebellar ratio at 90 min. During the human PET studies, a number of neuropsychological tests and physiological measurements were performed. No significant changes were found after administration of the [11C]WIN 35,428 alone. Taken together, these data indicate that [11C]WIN 35,428 is a promising radioligand for future studies of neuropsychiatric disorders that involve the dopamine transporter site.

Adult↗
PubMed1993

Organizational and administrative factors influencing the adoption of consortia programs by rural hospitals.

This study was designed to assess the effects of various hospital and environmental characteristics on the involvement of rural hospitals in forming and governing consortia and adopting consortia programs. The study focused on the 127 hospitals that are members of the nine rural consortia developed by grants from the Robert Wood Johnson Foundation during 1989 under its Hospital-Based Rural Hospital Consortia Program. Hospital involvement in the formation and governance of the consortia was found to be far less than expected for these grass-roots organizations. Only 38 percent of the administrators said that their hospitals were involved in developing the consortia, and 44 percent said that they played a role in determining the program menu. Governing board and medical staff involvement was even more limited. Program adoption rates were found to be related to both the types of programs offered by the consortia and the characteristics of the hospitals. In general, greater involvement of physicians and governing board members in hospital decisions was found to enhance program adoption rates, but the influence varied by type of involvement in the hospital and program content.

Chief Executive Officers, Hospital↗
PubMed1992

Structural and functional characterisation of recombinant human haemoglobin A expressed in Saccharomyces cerevisiae.

Recombinant human HbA, produced by co-expressing alpha-globin and beta-globin chains in the yeast Saccharomyces cerevisiae, has been characterised extensively both physically and functionally. Structural studies using N-terminal sequence analysis, peptide mapping, amino acid composition analysis and electrospray MS demonstrated that the recombinant protein was identical to standard HbA purified from erythrocytes. The functional properties of the recombinant protein were assessed using equilibrium and kinetic measurements of oxygen and carbon monoxide binding. The oxygen-binding studies demonstrated that the yeast-derived HbA behaved as a fully functional, cooperative tetramer (Hill coefficient, 2.9), exhibited a normal Bohr effect and response to phosphate, and displayed a rate of oxygen dissociation identical to that of the native human molecule. The recombinant protein also showed the same characteristics of carbon monoxide combination as the standard protein. These studies demonstrate that yeast provides an ideal system for the production of Hb for structural and functional analysis and a potentially useful source of HbA for formulation into a Hb-based oxygen carrier.

Amino Acids↗
PubMed1991

Denervation of transplanted porcine lung causes airway obstruction.

Lung transplantation can be complicated by a form of small airway obstruction known as bronchiolitis obliterans. We tested the hypothesis that lung denervation causes small airway obstruction in young pigs (10 +/- 1 weeks). Control pigs had an innervated native lobe, and study pigs had either a denervated native lobe or a denervated transplant lobe. Transplanted pigs received standard immunosuppression. At 10 weeks we measured isolated left lobe pulmonary mechanics. Dynamic resistance in both study groups was significantly higher than in the lobectomy group, whereas dynamic compliance in both study groups was significantly lower than in the lobectomy group. No significant difference in resistance or compliance was noted between the transplant and reimplant groups. Histologic changes consistent with rejection were noted in the transplant lobes. We conclude that the small airway obstruction noted in this model is due to operative denervation rather than to immunosuppression or rejection.

Animals↗
PubMed1990

The organization of open complexes between Escherichia coli RNA polymerase and DNA fragments carrying promoters either with or without consensus -35 region sequences.

Transcription initiation at the Escherichia coli galP1 promoter does not depend on specific nucleotide sequences in the -35 region. Footprint analysis of transcriptionally competent complexes between E. coli RNA polymerase and DNA fragments carrying galP1 shows that RNA polymerase protects sequences as far upstream as -55, whereas sequences around the -35 region are exposed. In contrast, with galP1 derivatives carrying -35 region sequences resembling the consensus, RNA polymerase protects bases as far as -45, and the -35 region is fully protected. Taken together, our data suggest that the overall architecture of RNA polymerase-promoter complexes can vary according to whether or not consensus -35 region sequences are present; in the absence of these sequences, open complex formation requires distortion of the promoter DNA. However, the unwinding of promoter DNA around the transcription start is not affected by the nature of the -35 region sequence. With a galP1 derivative carrying point mutations in the spacer region that greatly reduce promoter activity, the protection of bases by RNA polymerase around the -10 sequence and transcription start site is reduced. In contrast, protection of the region upstream of -25 is unaffected by the spacer mutations, although sequences from -46 to -54 become hypersensitive to attack by potassium permanganate, indicating severe distortion or kinking of this zone. We suggest that, with this galP1 derivative, RNA polymerase is blocked in a complex that is an intermediate on the path to open complex formation.

Base Sequence↗