Biomedical subjects

A Dewar

Publications and source records attributed to A Dewar.

At least 19 recordsLinked to original sources

PubMed2006

The long-term effects of perinatal glucocorticoid exposure on the host defence system of the respiratory tract.

Glucocorticoids are used to mature the fetal lung at times of threatened premature delivery. These drugs modify leukocyte profiles when administered in adulthood, but their effects on the mature host defence system following administration during the perinatal period are incompletely understood. In this study, the long-term effects of perinatal dexamethasone exposure on rodent host defence cells in the pulmonary airspaces, the perivascular compartment of the lung, and the blood were investigated. Rats were treated prenatally (gestational days 16-19) or neonatally (postnatal days 1-7) by inclusion of dexamethasone in the mothers' drinking water (1 microg/ml). The pups were then allowed to develop to adulthood (P60-80), at which time respiratory tissues were collected for light and electron microscopy and bronchoalveolar lavage (BAL), and blood for cell count and fluorescent activated cell-sorting (FACS) analysis. Prenatal treatment had no effect on any parameter examined. Following neonatal dexamethasone exposure, light microscopy of the lung tissue revealed a significant reduction in the number of cells in the perivascular space in both the central and the peripheral regions of the adult lung, but no differences in the number of cells in the airspaces. Neonatal dexamethasone exposure was also characterized by a significant reduction in the total number of white cells in the peripheral blood in adulthood and in particular, the number of lymphocytes relative to neutrophils was significantly reduced at maturity in these animals. The results show that neonatal, but not prenatal, dexamethasone exposure significantly alters the distribution of host defence cells in the blood and lung at maturity compared with control animals. The early neonatal period is characterized by the stress hyporesponsive period in the rat, when endogenous glucocorticoid levels are very low. Therefore, exogenous glucocorticoids administered during this time are likely to have marked "programming" effects on glucocorticoid-sensitive tissues.

Animals↗

PubMed2005

Keratinocyte growth factor therapy in murine oleic acid-induced acute lung injury.

Alveolar type II (ATII) cell proliferation and differentiation are important mechanisms in repair following injury to the alveolar epithelium. KGF is a potent ATII cell mitogen, which has been demonstrated to be protective in a number of animal models of lung injury. We have assessed the effect of recombinant human KGF (rhKGF) and liposome-mediated KGF gene delivery in vivo and evaluated the potential of KGF as a therapy for acute lung injury in mice. rhKGF was administered intratracheally in male BALB/c mice to assess dose response and time course of proliferation. SP-B immunohistochemistry demonstrated significant increases in ATII cell numbers at all rhKGF doses compared with control animals and peaked 2 days following administration of 10 mg/kg rhKGF. Protein therapy in general is very expensive, and gene therapy has been suggested as a cheaper alternative for many protein replacement therapies. We evaluated the effect of topical and systemic liposome-mediated KGF-gene delivery on ATII cell proliferation. SP-B immunohistochemistry showed only modest increases in ATII cell numbers following gene delivery, and these approaches were therefore not believed to be capable of reaching therapeutic levels. The effect of rhKGF was evaluated in a murine model of OA-induced lung injury. This model was found to be associated with significant alveolar damage leading to severe impairment of gas exchange and lung compliance. Pretreatment with rhKGF 2 days before intravenous OA challenge resulted in significant improvements in PO2, PCO2, and lung compliance. This study suggests the feasibility of KGF as a therapy for acute lung injury.

Acute Disease↗

PubMed2005

Nitric oxide levels and ciliary beat frequency in indigenous New Zealand children.

New Zealand children's morbidity from respiratory disease is high. This study examines whether subclinical ciliary abnormalities underlie the increased prevalence of respiratory disease in indigenous New Zealand children. A prospective study enrolled a group of healthy children who were screened for respiratory disease by questionnaire and lung function. Skin-prick tests were performed to control for atopy. Exhaled and nasal NO was measured online by a single-breath technique using chemiluminescence. Ciliary specimens were obtained by nasal brushings for assessment of structure and function. The ciliary beat frequency (CBF) (median CBF, 12.5 Hz; range, 10.4-16.8 Hz) and NO values (median exhaled NO, 5.6 ppb; range, 2.3-87.7 ppb; median nasal NO, 403 ppb; range, 34-1,120 ppb) for healthy New Zealand European (n=58), Pacific Island (n=61), and Maori (n=16) children were comparable with levels reported internationally. No ethnic differences in NO, atopy, or CBF were demonstrated. Despite an apparently normal ciliary beat, the percentage of ciliary structural defects was 3 times higher than reported controls (9%; range, 3.6-31.3%), with no difference across ethnic groups. In conclusion, it is unlikely that subclinical ciliary abnormalities underlie the increased prevalence of respiratory disease in indigenous New Zealand children. The high percentage of secondary ciliary defects suggests ongoing environmental or infective damage.

Adolescent↗

PubMed2004

Automated quantitation of peripheral blood neutrophil activation in patients with myocardial ischaemia.

BACKGROUND: Coronary ischaemic syndromes are associated with neutrophil activation. The Bayer automated haematology analysers can detect increased light scatter of neutrophil populations, which correlates with neutrophil activation. We aimed to assess the role of an automated analyser in detecting systemic neutrophil activation in peripheral blood samples of patients with coronary ischaemia. METHODS: A prospective cross-sectional study was undertaken in 18 patients with chronic stable angina, 9 with unstable angina and 26 normal control subjects. Whole blood samples were taken to assess neutrophil count and light scatter, and serum samples were taken from some patients for assessment of Troponin T, C-reactive protein (CRP) and myeloperoxidase (MPO). In addition, whole blood was stimulated in vitro with interleukin (IL)-8 and N-formyl-methionyl-leucyl-phenylalanine (fMLP) to assess changes in neutrophil light scatter detected by the analyser. RESULTS: Neutrophil light scatter was increased in patients with chronic stable and unstable angina compared to normal control subjects (normal subjects 74.1 (73.3, 75.0) (mean arbitrary units (95% confidence intervals, (CI)) vs. 78.6 (76.9, 80.3) in the chronic stable angina group P<0.001 and 77.1 (75.3, 79.0) in the unstable angina group P<0.007). In vitro stimulation of whole blood produced comparable increases in neutrophil light scatter when morphological changes in neutrophils were demonstrable under electron microscopy. CONCLUSIONS: Automated measurement of neutrophil activation by light scatter is possible using the Advia 120 analyser and is superior to a neutrophil count in discriminating groups with angina. This technique may be useful in monitoring disease activity and progression in coronary artery disease and in guiding the use of anti-inflammatory therapies.

Adult↗

PubMed2004

Inhibition of adherence of Mycobacterium avium complex and Mycobacterium tuberculosis to fibronectin on the respiratory mucosa.

Mycobacterium species adhere to the respiratory mucosa via mucus and fibronectin of extracellular matrix exposed by damaged epithelium. We have investigated whether inhibiting adherence to fibronectin influences subsequent infection of human respiratory tissue by Mycobacterium avium complex and Mycobacterium tuberculosis. Human respiratory tissue was pretreated with mycobacterial fibronectin attachment proteins prior to infection with M. avium complex and M. tuberculosis and the number of recoverable bacteria over time was compared to untreated controls. Inhibition significantly reduced recovery of M. avium complex at 15min (P= 0.02), 7days (P = 0.04), and 14 days (P= 0.03); whereas recovery of M. tuberculosis was only reduced at 15 min (P = 0.01) and not at later timepoints. We conclude that M. avium complex and M. tuberculosis infection of the mucosa proceeds by different mechanisms, since M. tuberculosis infection is independent of fibronectin adherence.

Adhesins, Bacterial↗

PubMed2004

Effects of airborne World Trade Center dust on cytokine release by primary human lung cells in vitro.

There are continuing concerns regarding the respiratory health effects of airborne particulate matter (PM) after the destruction of the World Trade Centre (WTC). We examined cytokine (interleukin [IL]-8, IL-6, tumor necrosis factor-alpha) release by primary human lung alveolar macrophages (AM) and type II epithelial cells after exposure to WTC PM2.5 (indoor and outdoor), PM10-2.5 (indoor), and PM53-10 (outdoor), fractionated from settled dusts within 2 months of the incident. There was an increase in AM cytokine/chemokine release at 5 and/or 50 microg/well WTC PM, which fell at 500 microg/well. Type II cells did not release tumor necrosis factor-alpha, and the increase in IL-8 and IL-6, although significant, was lower than that of AM. Respirable PM generated by the WTC collapse stimulates inflammatory mediator release by lung cells, which may contribute to the increased incidence of respiratory illness since September 11th 2001.

Air Pollutants↗

PubMed2003

Investigation of mycobacterial colonisation and invasion of the respiratory mucosa.

BACKGROUND: The pathogenesis of Mycobacterium avium complex and Mycobacterium tuberculosis in the respiratory tract is poorly understood, as are the reasons for their differing virulence. We have previously shown that their initial adherence to the mucosa is identical. METHODS: The interaction of M avium complex, M tuberculosis, and M smegmatis with human respiratory tissue was investigated in an organ culture model with an air interface. Tissue was infected for intervals up to 14 days and assessed by scanning electron microscopy for adherent bacteria or cultured for recoverable bacteria. RESULTS: The mean number of adherent bacteria/mm(2) (and the viable count of macerated tissue, cfu/ml) at 15 minutes, 3 and 24 hours, 7 and 14 days were: M avium complex 168 (153), 209 (136), 289 (344), 193 (313), 14140 (16544); M tuberculosis 30 (37), 39 (23), 48 (53), 1 (760), 76 (2186); M smegmatis 108 (176), 49 (133), 97 (81), 114 (427), 34 (58), (n=6). There was no significant change in morphology between infected and uninfected tissue or tissue infected with the different species over 14 days. The number of M avium complex on the mucosa and recovered from tissue increased over time (p=0.03). M tuberculosis decreased on the surface, but recoverable bacteria increased (p=0.01). M smegmatis numbers on the mucosa and recovered from tissue decreased. Sectioned tissue showed M avium complex and M tuberculosis in submucosal mucus glands and M tuberculosis penetrating epithelial cells in one experiment. CONCLUSIONS: The initial adherence to the mucosa of the three species was similar, but after 14 days they varied in their interaction with the tissue in a manner compatible with their pathogenicity.

Bacterial Adhesion↗

PubMed2002

Interaction of Mycobacterium tuberculosis with human respiratory mucosa.

OBJECTIVE: Endobronchial infection is associated with pulmonary tuberculosis in the majority of cases. We have investigated the adherence of Mycobacterium tuberculosis to the human respiratory mucosa. DESIGN: Organ cultures constructed with human tissue were infected with M. tuberculosis in the presence or absence of mycobacterial fibronectin attachment cell surface proteins and examined by scanning electron microscopy. RESULTS: M. tuberculosis adhered mainly to extracellular matrix (ECM) in areas of mucosal damage, but not to ciliated mucosa, intact extruded cells, basement membrane or collagen fibres. Bacteria also adhered to fibrous but not globular mucus and occasionally to healthy unciliated mucosa, open tight junctions and to extruded cells that had degenerated, exposing their contents. There was a significant reduction (p<0.05) in the number of bacteria adhering to ECM after pre-incubation of bacteria with fibronectin and after pre-incubation of the tissue with M. avium fibronectin attachment protein (FAP) and M. bovis antigen 85B protein, in a concentration dependent manner. The combined effect of FAP and antigen 85B protein was significantly greater than either protein alone. Bacterial adherence to fibrous mucus was not influenced by fibronectin. CONCLUSION: We conclude that M. tuberculosis adheres to ECM in areas of mucosal damage at least in part via FAP and antigen 85B protein.

Acyltransferases↗

PubMed2001

Platelet-endothelial cell adhesion molecule-1 (PECAM-1)-deficient mice demonstrate a transient and cytokine-specific role for PECAM-1 in leukocyte migration through the perivascular basement membrane.

Studies with neutralizing antibodies have indicated roles for platelet-endothelial cell adhesion molecule-1 (PECAM-1) in leukocyte migration through the endothelium and the perivascular basement membrane. Because some of these findings have been contentious, this study aimed to explore the role of PECAM-1 in leukocyte migration by analyzing leukocyte responses in interleukin 1beta (IL-1beta)- and tumor necrosis factor-alpha (TNFalpha)-activated cremasteric venules of PECAM-1-deficient mice using intravital and electron microscopy. Although no differences in levels of leukocyte rolling flux or firm adhesion were observed, a delay in leukocyte transmigration in response to IL-1beta, but not TNFalpha, was detected in PECAM-1-deficient mice. Electron microscopy indicated that this delay occurred at the level of perivascular basement membrane. To address the cytokine specificity of PECAM-1 dependence, in vitro experiments demonstrated that TNFalpha, but not IL-1beta, could induce rapid adhesion of murine neutrophils to protein-coated surfaces, suggesting that TNFalpha elicited leukocyte transmigration in wild-type mice via direct stimulation of leukocytes. In summary, the results suggest a regulatory role for PECAM-1 in leukocyte migration through the perivascular basement membrane, a role that appears to be cytokine-specific and associated with the ability of the cytokine to stimulate rapid neutrophil adhesion.

Animals↗

PubMed2001

Membrane blebbing during apoptosis results from caspase-mediated activation of ROCK I.

The execution phase of apoptosis is characterized by marked changes in cell morphology that include contraction and membrane blebbing. The actin-myosin system has been proposed to be the source of contractile force that drives bleb formation, although the biochemical pathway that promotes actin-myosin contractility during apoptosis has not been identified. Here we show that the Rho effector protein ROCK I, which contributes to phosphorylation of myosin light-chains, myosin ATPase activity and coupling of actin-myosin filaments to the plasma membrane, is cleaved during apoptosis to generate a truncated active form. The activity of ROCK proteins is both necessary and sufficient for formation of membrane blebs and for re-localization of fragmented DNA into blebs and apoptotic bodies.

3T3 Cells↗

PubMed2001

Protecting strategies used by sufferers of catastrophic illnesses and injuries.

The purpose of this research was to describe strategies used by sufferers of catastrophic illnesses and injuries. Participants were adult men and women with a variety of serious illnesses and injuries. Qualitative research approaches to data collection and data analysis, using grounded theory methods were employed. Descriptions of the participants indicate that several strategies are used; this discussion focuses on strategies to protect themselves from further suffering. Situations where participants use protecting strategies are identified and described. The findings indicate how care-recipients try to lessen the burden on their care-givers and to protect them from the stress of the sufferer's problems.

Adaptation, Psychological↗

PubMed2001

Determinants of nurses' intention to administer opioids for pain relief.

A statewide cross-sectional survey was conducted in Australia to identify the determinants of registered nurses' intention to administer opioids to patients with pain. Attitudes, subjective norms and perceived control, the key determinants of the Theory of Planned Behavior, were found to independently predict nurses' intention to administer opioids to these patients. Perceived control was the strongest predictor. Nurses reported positive overall attitudes towards opioids and their use in pain management. However, many negative attitudes were identified; for example, administering the least amount of opioid and encouraging patients to have non-opioids rather than opioids for pain relief. The findings related to specific attitudes and normative pressures provide insight into registered nurses' management of pain for hospitalized patients and the direction for educational interventions to improve registered nurses' administration of opioids for pain management.

Attitude of Health Personnel↗

PubMed2001

Inflammation in cystic fibrosis airways: relationship to increased bacterial adherence.

It is unclear whether inflammation in the cystic fibrosis (CF) lung relates predominantly to bacterial infection, or occurs as a direct consequence of mutant cystic fibrosis transmembrane conductance regulator (CFTR) protein. Interleukin (IL)-8 secretion from CF and non-CF cell lines, and from CF and non-CF human primary nasal epithelial cells incubated with or without Pseudomonas aeruginosa, was measured. Activation of nuclear factor-kappaB (NF-kappaB) in unstimulated CF and non-CF nasal epithelial cells, cell lines and murine tissues was measured by gel-shift assays. No significant difference in basal IL-8 production or NF-kappaB activation was observed between CF and non-CF primary nasal cells. However, CF cells exhibited a significantly (p<0.01) increased IL-8 secretion following P. aeruginosa stimulation. Equalization of the increased P. aeruginosa adherence observed in CF cells, to non-CF levels, resulted in comparable IL-8 secretion. Further, IL-8 production did not differ with mutations which result in either correctly localized CFTR, or in partial/total mislocalization of this protein. Similar levels of NF-kappaB activation were observed in a number of organs of wildtype and CF mice. Finally, IL-8 secretion and NF-kappaB activity were not consistently increased in CF cell lines. Cos-7 cell transfection with plasmids expressing deltaF508 or G551D mutant CFTR protein resulted in increased activation of a p50-containing NF-kappaB complex, but IL-8 secretion was similar to wild-type cells. The authors conclude that the stimulus produced by Pseudomonas aeruginosa is the predominant inflammatory trigger in their models.

Adolescent↗

PubMed2000

Divergent effects of platelet-endothelial cell adhesion molecule-1 and beta 3 integrin blockade on leukocyte transmigration in vivo.

The final stage in the migration of leukocytes to sites of inflammation involves movement of leukocytes through the endothelial cell layer and the perivascular basement membrane. Both platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) and the integrin alphavbeta3 have been implicated in this process, and in vitro studies have identified alphavbeta3 as a heterotypic ligand for PECAM-1. In the present study we have addressed the roles of these molecules by investigating and comparing the effects of PECAM-1 and alphavbeta3 blockade on leukocyte migration in vivo. For this purpose we have examined the effects of neutralizing Abs directed against PECAM-1 (domain 1-specific, mAb 37) and beta3 integrins (mAbs 7E3 and F11) on leukocyte responses in the mesenteric microcirculation of anesthetized rats using intravital microscopy. The anti-PECAM-1 mAb suppressed leukocyte extravasation, but not leukocyte rolling or firm adhesion, elicited by IL-1beta in a dose-dependent manner (e.g., 67% inhibition at 10 mg/kg 37 Fab), but had no effect on FMLP-induced leukocyte responses. Analysis by electron microscopy suggested that this suppression was due to an inhibition of neutrophil migration through the endothelial cell barrier. By contrast, both anti-beta3 integrin mAbs, 7E3 F(ab')2 (5 mg/kg) and F11 F(ab')2 (5 mg/kg), selectively reduced leukocyte extravasation induced by FMLP (38 and 46%, respectively), but neither mAb had an effect on IL-1beta-induced leukocyte responses. These findings indicate roles for both PECAM-1 and beta3 integrins in leukocyte extravasation, but do not support the concept that these molecules act as counter-receptors in mediating leukocyte transmigration.

Abciximab↗

PubMed2000

Giant lamellar bodies as a feature of pulmonary low-grade MALT lymphomas.

AIMS: Giant lamellar bodies (GLBs) are rare pulmonary inclusions, most frequently described in sclerosing haemangiomas. Following a recent report of their presence in a case of pulmonary lymphoma of MALT origin, our aims were to determine their frequency in pulmonary lymphoproliferative disorders, examine their structure and investigate their aetiology further. METHODS AND RESULTS: We reviewed a series of 29 pulmonary lymphomas (23 low-grade, six high-grade) and 18 cases of reactive pulmonary lymphoid hyperplasia. Five of 23 (22%) low-grade lymphomas contained GLBs, 4/4 of which stained for surfactant apoprotein A but not for surfactant apoprotein B. No GLBs were seen in 18 cases of reactive pulmonary lymphoid hyperplasia or six high-grade primary pulmonary lymphomas. Ultrastructural examination revealed concentrically arranged extracellular material forming roughly spherical structures up to 25 microm in diameter. The GLBs were often surrounded by foamy cells and cholesterol clefts, supporting an origin, at least in part, from products of cell breakdown and surfactant degradation. CONCLUSION: These findings support the idea that the presence of lamellar bodies is in part due to stasis of products arising from degradation of surfactant, in association with certain types of chronic pulmonary pathology. Given their absence in reactive pulmonary lymphoid hyperplasia, the presence of GLBs as an epiphenomenon in a pulmonary lymphoid infiltrate should warrant careful investigation with regard to the diagnosis of low-grade MALT lymphoma.

Aged↗

PubMed2000

The role of Mycobacterium avium complex fibronectin attachment protein in adherence to the human respiratory mucosa.

Mycobacterium avium complex (MAC) are opportunistic respiratory pathogens that infect non-immunocompromised patients with established lung disease, although they can also cause primary infections. The ability to bind fibronectin is conserved among many mycobacterial species. We have investigated the adherence of a sputum isolate of MAC to the mucosa of organ cultures constructed with human tissue and the contribution of M. avium fibronectin attachment protein (FAP) to the process. MAC adhered to fibrous, but not globular mucus, and to extracellular matrix (ECM) in areas of epithelial damage, but not to intact extruded cells and collagen fibres. Bacteria occasionally adhered to healthy unciliated epithelium and to cells that had degenerated exposing their contents, but never to ciliated cells. The results obtained with different respiratory tissues were similar. Two ATCC strains of MAC gave similar results. There was a significant reduction (P < 0.05) in the number of bacteria adhering to ECM after preincubation of bacteria with fibronectin and after preincubation of the tissue with M. avium FAP in a concentration-dependant manner. The number of bacteria adhering to fibrous mucus was unchanged. Immunogold labelling demonstrated fibronectin in ECM as well as in other areas of epithelial damage, but only ECM bound FAP. A Mycobacterium smegmatis strain had the same pattern of adherence to the mucosa as MAC. When the FAP gene was deleted, the strain demonstrated reduced adherence to ECM, and adherence was restored when the strain was transfected with an M. avium FAP expression construct. We conclude that MAC adheres to ECM in areas of epithelial damage via FAP and to mucus with a fibrous appearance via another adhesin. Epithelial damage exposing ECM and poor mucus clearance will predispose to MAC airway infection.

Adenoids↗

PubMed2000

Interaction of Bordetella pertussis with human respiratory mucosa in vitro.

The human respiratory tract pathogen Bordetella pertussis is the major cause of whooping cough in infants and young children, and also causes chronic cough in adults. B. pertussis infection damages ciliated epithelium in the respiratory tract. However, the interaction of the bacterium with the respiratory mucosa is poorly understood, and previous studies have either utilized animal tissue which may not be appropriate, or isolated cell systems which lack the complexity of the respiratory mucosa. We have studied the interaction of B. pertussis strain BP536 with human nasal turbinate tissue in an air-interface organ culture over 5 days. We have also compared infection by BP536 with two other strains, Tohama I and CN2992, to determine whether the interactions observed with BP536 are consistent, and, in both nasal turbinate and adenoid organ cultures at 24 h, to determine whether there were differences between tissue from different parts of the respiratory tract. BP536 adhered to cilia, most commonly at their base, and disorganized their spatial arrangement, they also adhered to damaged tissue and mucus, but very rarely to unciliated cells. Within the first 24 h there was a five-fold increase in bacterial density on ciliated cells, and the total number of adherent bacteria increased up to 96 h. Infection caused increased mucus at 24h and an increase in damaged epithelium from 72 h which involved both ciliated and unciliated cells. The number of residual ciliated cells did not decrease after 72 h. The three different strains of B. pertussis exhibited similar interactions with the mucosa, and there was no tissue specificity for adenoid or turbinate tissue. We conclude that B. pertussis adhered to multiple sites on the mucosa and caused hypersecretion and epithelial damage which are the pathological changes described in vivo.

Adenoids↗

PubMed2000

Nurses' experiences in giving bad news to patients with spinal cord injuries.

Nurses, as well as patients and their families, have unique communication needs when a patient has suffered a spinal cord injury. This qualitative study used grounded theory methods to describe how nurses working on an acute spinal cord unit manage this sensitive situation. Twenty-two registered nurses participated in focus group interviews designed to elicit their experiences with patients and their needs as healthcare professionals. Five major themes emerged from analysis of the data: being the bearer of bad news, strategies used by the nurses to give bad news, the role of the patients, the role of the families, and meeting the nurses' needs. The findings indicate that nurses are placed in a position of being the bearers of bad news; it is not always possible or even desirable to avoid the situation. To maintain the patients' hope and preserve their own integrity, nurses must develop strategies to address the patients' needs.

Acute Disease↗