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Biomedical subjects

M L Cross

Publications and source records attributed to M L Cross.

16 recordsLinked to original sources
PubMed1999

Intracellular survival of virulent Mycobacterium bovis and M. bovis BCG in ferret macrophages.

The intracellular survival of virulent Mycobacterium bovis and avirulent M. bovis BCG in ferret alveolar macrophages was investigated. In addition, the effects of endogenous and exogenous modulators of macrophage oxidative function on bacterial survival and growth in vitro were determined. Ferret macrophages limited the initial growth of BCG, while virulent M. bovis replicated within macrophages. Intracellular bacterial survival was unaffected by the addition of specific inhibitors of macrophage oxidative function. A T-cell supernatant (TCS), derived from mitogen-stimulated lymphocyte cultures, activated ferret macrophages for heightened oxidative burst performance. However, macrophages activated by TCS, bacterial LPS or a combination of both, failed to control infection, and actually enhanced the intracellular survival of M. bovis. These results are discussed in relation to the role of macrophages in mediating tuberculosis-related pathogenesis, with respect to the fact that ferrets are important wildlife vectors of bovine tuberculosis in New Zealand.

Animals↗
PubMed1999

Oxidative responses in ferret macrophages.

Although the basic function of T and B lymphocytes in ferrets has been known for some time, the function of mononuclear phagocytes has not been described in this species. The present study has characterised basic oxidative responses in ferret macrophages, and has investigated the effects of endogenous and exogenous modulators of macrophage function on oxidative capacity in vitro. Macrophages derived from the blood or lungs of ferrets were shown capable of generating the reactive oxygen intermediate (ROI) molecules superoxide and hydrogen peroxide, and secreting a lysosomal enzyme (acid phosphatase), in response to appropriate stimuli. A T cell supernatant (derived from mitogen-stimulated peripheral blood lymphocytes) was able to activate both blood- and lung-derived macrophages for enhanced ROI production, while specific ROI inhibitors (superoxide dismutase and catalase) were able to partially ablate ROI activity. The accumulation of nitrite in culture supernatants, as an indicator for the production of reactive nitrogen intermediates, could not be demonstrated by ferret macrophages derived from either tissue source. In contrast to the enhancing effects of TCS on the oxidative function of blood-derived macrophages, exposure to bacterial LPS caused marked suppression of ROI and lysosomal enzyme production by these cells. Finally, the generation of superoxide anion, following phagocytosis of live or heat-killed Mycobacterium bovis or zymosan, indicated that ROI production in response to phagocytic stimulation was relatively weak in ferret blood-derived macrophages. These results are discussed in relation to the study of immune function in a novel species, and with particular reference to research into tuberculosis (Tb), since ferrets are important wildlife vectors of bovine Tb in New Zealand.

Animals↗
PubMed1996

Macrophage function in deer.

Macrophage inflammatory and immune functions were characterised in red deer (cervus elaphus), for use as a model for natural infection with bovine tuberculosis. Highly enriched populations of deer macrophages were obtained from 14 day cultures of plastic-adherent peripheral blood mononuclear cells. Cervine macrophages produced superoxide anion in response to respiratory burst stimuli (serum-opsonised zymosan and phorbol myristic acetate), but nitric oxide production could not be detected under the conditions tested. The lysosomal enzymes acid phosphatase and lysozyme were detected at the intercellular and extracellular level. Stimulation with bacterial lipopolysaccharide extract (Escherichia coli LPS) enhanced the production of superoxide and acid phosphatase with a peak increase in activity observed after 2h. Production of interleukin 1 (IL-1) and tumour necrosis factor (TNF), determined using cytokine-sensitive cell lines and mRNA analysis (Northern blotting), indicated maximal secretion of both cytokines after 24 h stimulation with LPS, preceded by a peak in message accumulation at 2-6 h post-stimulation. Cervine macrophages stimulated proliferative responses in T cell-enriched lymphocyte populations derived from the peripheral blood of autologous animals that had been primed to mycobacterial antigens (Mycobacterium bovis Bacille Calmette-Guerin, BCG). Macrophages were able to stimulate responses after pulsing with particulate (BCG) or soluble (purified protein derivative) mycobacterial antigens. These results indicate that macrophage inflammatory and immune responses in red deer are similar to those in other mammalian species, and that macrophages may play an important role in resistance to mycobacterial infection.

Animals↗
PubMed1996

In vitro responses of cervine macrophages to bacterial stimulants.

The function of cervine (deer) mononuclear phagocytes is poorly defined. In the present study, the potential of cervine macrophages to generate phagocytic and immunoregulatory responses following stimulation with bacterial products was investigated. Blood-derived macrophages of red deer were cultured in vitro with particulate stimulants (Mycobacterium bovis BCG and Staphylococcus aureus SAC) or soluble stimulants (M. bovis PPD and Escherichia coli LPS), prior to assessment of phagocytic responses, prostaglandin secretion and cytokine production. Particulate stimulants induced vigorous phagocytic responses (superoxide anion generation, lysosomal enzyme release), secretion of prostaglandin E2 and transcription of mRNA specific for the cytokines IL-1 beta, IL-10 and TNF alpha, while soluble products invoked weaker responses. These results are discussed in relation to the role of cervine mononuclear phagocytes in regulating and participating in inflammatory and immune processes relevant to bacterial challenge.

Animals↗
PubMed1996

Interaction between the trauma team and families: lack of timely communication.

Families of critically ill patients desire early information regarding the condition of their relative. The purpose of this study was to determine how long family members waited before someone from the trauma team met with them to discuss the condition of their relative. This was a prospective, single-blinded study of a convenience sample of 63 trauma patients conducted at a trauma center. Observers recorded the time of arrival of the patient, time of family arrival, and the time the family was first contacted by the trauma team. Families arrived 38 +/- 35 minutes after the patient. The mean time families waited before contact with the trauma team was 37 +/- 34 minutes. This study shows that the trauma team is often slow in communicating with the family of the victim. One member of the caregiving team should be designated to advise the family on the condition of the patient as soon as possible.

Adolescent↗
PubMed1996

T cell responses to Mycobacterium bovis in red deer, a large animal model for tuberculosis.

Red deer (Cervus elaphus) represent an appropriate large animal model to study the immunology of tuberculosis, being naturally susceptible to Mycobacterium bovis infection. Cell-mediated immune responses were investigated in deer displaying protective- or disease-type reactions, following immunization with M. bovis bacille Calmette-Guerin (BCG) or infection with virulent M. bovis, respectively. T cell responses were measured as antigen-dependent cell proliferation and production of T cell growth factor (TCGF) following in vitro stimulation with M. bovis antigens (live or heat-killed BCG, or PPD). T cells from immunized deer proliferated less in response to soluble denatured culture antigen (purified protein derivative, PPD) than to particulate BCG, although there were no differences in the magnitude of these responses between the two groups of animals. Cells derived from immunized deer produced less TCGF than cells from infected deer when stimulated with PPD in vitro, although responses to BCG antigens were similar between the two groups. The majority of TCGF activity was neutralized by anti-IL-2 antibodies, regardless of the animal group or source of antigen used for in vitro stimulation. After 7 days in vitro culture with antigen, blast cells staining positively for alpha beta (CD4, CD8) and gamma delta T cell receptors were recorded. The majority of blasts were CD4+, although in immunized deer fewer CD4+ blasts were produced following in vitro stimulation with PPD than with BCG antigens. These results, together with previous reports from our laboratory, represent the only detailed examinations of T cell responses to M. bovis in this naturally-susceptible ruminant species.

Animals↗
PubMed1994

Differential modulation of murine cellular immune responses by salivary gland extract of Aedes aegypti.

The ability of salivary gland extract (SGE) of Aedes aegypti to modulate cellular immune responses was investigated in a mouse model. Cytokine production was induced in naive and antigen-primed murine (BALB/c) spleen cells in vitro by stimulation with the T cell mitogen concanavalin A or the T cell-dependent antigen ovalbumin (OVA), respectively. Inclusion of Ae. aegypti SGE in in vitro culture with naive cells caused significant suppression of the cytokines interleukin-2 (IL-2) and interferon gamma in culture supernatants, while levels of other cytokines (IL-4 and IL-5) were unaffected by SGE. In contrast, SGE did not affect cytokine production by antigen-activated cells derived from OVA-primed mice. To determine whether SGE could inhibit the responsiveness of cells to exogenous cytokine stimuli, optimized quantities of lymphocyte growth factor cytokines IL-2 and IL-4 were added to SGE-treated spleen cells and the degree of cellular proliferation was determined. Cellular proliferation in response to IL-2 was markedly suppressed by prior exposure of cells to SGE, while the proliferative response to IL-4 was also affected by SGE but to a lesser extent. These results confirm that mosquito SGE can modulate host immune responses, and suggest that in Ae. aegypti modulation is directed primarily against cytokines associated with type 1 lymphocyte responses. The mode of immunomodulation and the possible relevance of these results to vector-borne disease research are discussed.

Aedes↗
PubMed1994

Modulation of murine cellular immune responses and cytokines by salivary gland extract of the black fly Simulium vittatum.

Salivary gland extract (SGE) of the blood-feeding black fly Simulium vittatum is known to modulate immunological responses. In the present study, the ability of S. vittatum SGE to modulate responses during heterologous antigenic challenge was investigated in a murine model, with particular emphasis on characterizing the patterns of cytokine response. Mice were injected repeatedly with SGE or saline (sham), then challenged with the T dependent antigen ovalbumin (OVA) to generate antigen-specific lymphoblasts. Spleen cells from OVA-primed mice were then co-cultured with OVA in vitro to stimulate cytokine secretion. Cells from mice that had been injected with SGE prior to OVA challenge produced lower levels of interleukins 5 and 10 (IL-5 and IL-10) in in vitro culture, when stimulated with OVA, compared to mice that had been sham-injected with saline. Levels of IFN-gamma, IL-2 and IL-4 did not differ significantly between SGE- and saline-injected groups. Mice injected repeatedly with SGE prior to OVA challenge had fewer circulating eosinophils than sham-injected mice, while other leukocyte levels were unaffected by SGE. Prior exposure to SGE did not affect levels of serum IgE or IgA significantly. The effect of SGE on the ability of murine spleen cells to respond in vitro to the recombinant cytokines IL-2 and IL-4 was also investigated. Naive spleen cells pre-incubated with SGE proliferated less in response to both IL-2 and IL-4 in in vitro culture than cells pre-incubated with saline as a control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Localized leucocyte response to Ichthyophthirius multifiliis establishment in immune carp Cyprinus carpio L.

O-group carp (Cyprinus carpio) which had been immunized against Ichthyophthirius multifiliis by controlled infections were challenged by topical application of theronts to the caudal fin. The parasites which established were examined ultrastructurally, and host leucocyte responses were compared with those observed in primary infections. In the primary exposure group eosinophils and (to a lesser extent) basophils were the predominant cells infiltrating infection sites. In contrast, parasite development in immunized fish initiated localized leucocytic infiltrations which were dominated by eosinophilic granular cells (EGCs) and basophils. Greater localized phagocytosis was recorded in immunized fish by neutrophils, macrophages and resident epidermal filament cells. In vitro studies indicated that pronephric leucocytes from immunized fish displayed enhanced non-specific phagocytosis. In the skin, leucocytes were observed in close proximity to the trophozoite surface in both immunized and primary exposure fish, often undergoing lysis and release of cellular contents. However, there was no evidence of active cell adherence nor of any cell-mediated damage incurred to the parasite in either case. These observations are discussed in relation to the possible role of leucocytes in mediating pathogenesis and immune responses.

Animals↗
PubMed1993

Antibody responses of BALB/c mice to salivary antigens of hematophagous black flies (Diptera: Simuliidae).

The humoral antibody responses to salivary antigens of Simulium vittatum Zetterstedt were investigated in a BALB/c mouse laboratory model. Production of antisera was stimulated by intraperitoneal immunization with salivary gland extract or by feeding flies directly on depilated mice. Antibody responses in these two groups of mice were compared by western blotting, thus characterizing "true" salivary immunogens present in salivary gland extract. Immunized mice developed IgG, IgM, and IgE antibodies which recognized several salivary gland components, ranging in molecular weight between 26 and 67 kDa. Sera from bitten mice recognized fewer antigens, indicating that some components of the salivary gland extract were poorly immunogenic or absent from the saliva secreted during blood feeding. Antisera raised against S. vittatum also were used to identify cross-reactive immunogens and allergens in salivary gland extracts from other New World simuliids (Simulium argus Williston, S. metallicum Bellardi, and S. ochraceum Walker). SDS-PAGE protein profiles indicated a high degree of similarity between salivary gland extract of S. vittatum and S. argus, and several cross-reacting antigens were identified by western blotting. In contrast, protein profiles of S. ochraceum and S. metallicum differed from the former species, both qualitatively and quantitatively. Antisera demonstrated a low degree of cross-reactivity against salivary gland extract of S. ochraceum, whereas no cross-reactivity was detected against S. metallicum. These observations were confirmed using a monoclonal antibody raised against S. vittatum salivary gland extract (designated SVSG.1.F10), which showed cross-reactivity against S. argus but failed to recognize salivary gland components of either S. ochraceum or S. metallicum.

Animals↗
PubMed1993

Modulation of murine immunological responses by salivary gland extract of Simulium vittatum (Diptera: Simuliidae).

The influence of Simulium vittatum Zetterstedt salivary gland extract on several immunological mechanisms was investigated in murine model hosts (laboratory mice). These mechanisms included the expression of major histocompatibility complex class II cell surface molecules, the in vitro mitogen responsiveness of lymphoid cells, and the antibody responses to heterologous foreign antigens (sheep erythrocytes). Experiments were designed to determine the influence of salivary gland extract following in vivo inoculation or in vitro inclusion in cell culture. In vivo inoculation of salivary gland extract reduced the percentage of Ia+ cells in spleen cell populations, although this difference was ameliorated by a 2 d in vitro culture period, regardless of whether salivary gland extract was included in culture. Salivary gland extract had no effect on Ia expression by cells derived from regional lymph nodes or the skin (epidermis). In vivo inoculation with salivary gland extract did not affect the responsiveness of splenic lymphocytes to mitogens, whereas in vitro exposure to salivary gland extract reduced both T and B cell mitogenesis. Finally, antibody responses to sheep erythrocytes were enhanced if salivary gland extract was included as a coinoculant, although this was expressed only at the systemic level regardless of the route of antigen delivery. In light of these results, immunomodulatory functions of black fly saliva are postulated; they are operative at different levels on different subcompartments of the immune system, possibly via cytokine modulation.

Animals↗
PubMedDate not supplied

Transitioning preterm infants with nasogastric tube supplementation: increased likelihood of breastfeeding.

OBJECTIVE: To compare nasogastric tube and bottle supplementation as two means of transitioning preterm infants to breastfeeding within an established breastfeeding support program. DESIGN: Prospective, randomized controlled trial; mothers and health care providers, who were not blinded. SETTING: Metropolitan private regional perinatal center; 40-bed intensive-care nursery. PARTICIPANTS: Eighty-four preterm breastfed infants whose birth weight was 1,000-2,500 g. MAIN OUTCOME MEASURES: Rates of exclusive and partial breastfeeding at discharge from the intensive-care nursery, and at 3 days, 3 months, and 6 months after discharge. RESULTS: Compared with infants receiving bottle supplements, infants receiving nasogastric tube supplements were more likely to be breastfeeding at discharge and at 3 days, 3 months and 6 months, after adjusting for confounding variables. Odds ratios (confidence intervals = 95%) showed that the group receiving nasogastric supplements was 4.5 times (1.4 to 15) more likely to be breastfed at discharge and 9.4 times more likely to be fully breastfed (3.1 to 28.4). There were significantly fewer apnea and bradycardia episodes in the group receiving nasogastric supplements, although they had more episodes that required stimulation for resolution. Groups were not different with respect to length of hospitalization and infant weight at discharge. CONCLUSIONS: Using nasogastric tube supplementation during transition to oral feedings increases the likelihood of breastfeeding at discharge, 3 days, 3 months, and 6 months. This intervention requires a program with skilled personnel and an environment that allows the mother and infant to be in close physical proximity. Further study should investigate differences in the effects on maternal confidence, imprinting, and suck mechanism when preterm infants are bottle fed and breastfed.

Adolescent↗