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Biomedical subjects

M W Turner

Publications and source records attributed to M W Turner.

At least 73 records · Page 4Linked to original sources
PubMed1991

Childhood asthma: clinical and immunological changes over a decade.

A group of 26 Australian asthmatic children with laboratory-proven bronchial hyper-reactivity to the allergens of rye grass pollen and/or the house dust mite has been studied over a 9-year period. Clinical symptoms and drug scores were used to evaluate the severity of the patients' asthma and, wherever possible, blood samples were obtained before, during and after the rye grass pollen seasons. The cumulative symptom and drug scores for the 20 patients with bronchial hyper-reactivity to rye grass pollen extract tended to increase during and fall after each pollen season but the peaks were of decreasing amplitude over the 9 years. Since a proportion of these patients underwent hyposensitization to rye grass during year 1, longitudinal comparisons were made between year 2 and year 9. Comparing the individuals at the same three seasonal time-points revealed significantly lower drug scores in year 9 compared with year 2, and in parallel with this, significantly lower total IgE, IgE anti-rye and IgG anti-rye antibodies at all three assessment points. In the 14 patients with bronchial hyper-reactivity to house dust mite the severity of the asthma and the median levels of IgE and IgG mite specific antibodies all decreased over the study period. Despite the progressive improvement in asthma and diminishing immune responses to both rye grass and house mite in the patients, no immunological feature could be identified that correlated significantly with clinical outcome.

Adolescent↗
PubMed1990

An enzyme-linked immunosorbent assay for the determination of human IgG subclass antibodies directed against Branhamella catarrhalis.

An ELISA procedure to determine the distribution of human IgG subclass antibodies directed against the gram-negative bacterium Branhamella catarrhalis has been developed using commercially available monoclonal anti-IgG subclass antibodies. Using whole bacteria as coating antigen the specificity of the assay was determined and showed minimal cross-reactivity with a range of other bacteria. Estimations of IgG1, IgG2, IgG3, IgG4 and total IgG antibodies directed against this antigen were performed. All normal adult sera tested had measurable antibody levels of specific IgG1, IgG2, IgG3 and total IgG. Specific IgG4 was undetectable in the majority of adult sera. These assays will be of value for investigation of both children and adults with suspected immunodeficiency and recurrent upper respiratory tract infection.

Adult↗
PubMed1990

Branhamella catarrhalis: antigenic determinants and the development of the IgG subclass response in childhood.

A recently developed whole cell ELISA was used to investigate the development of IgG subclass antibodies to Branhamella catarrhalis in childhood. In addition, SDS-PAGE and immunoblotting were used to study the interaction between the outer membrane proteins (OMPs) of B. catarrhalis and IgG subclass antibodies. Specific IgG3 antibodies were undetectable or present only in low amounts in children less than 4 years old but were an important constituent of the response of older children. OMPs prepared from different isolates had similar molecular masses and bound IgG with identical immunoblotting patterns. Binding appeared subclass-specific, with IgG3 binding to the broadest range of OMPs. These findings should provide a better understanding of the pathogenic role of this organism and suggest possible strategies for the development of a vaccine.

Agammaglobulinemia↗
PubMed1990

Mucosal mast cell activation patterns in the rat following repeated feeding of antigen.

Groups of rats previously sensitized systemically on day 0 with a low dose of ovalbumin (OVA) were gavaged daily with ovalbumin or bovine serum albumin or a mixture of both proteins from day 14 to 18. Blood samples were obtained pre- and post-challenge and serum levels of the rat mast cell protease II (RMCPII) determined by immunoassay. Release of this specific mucosal mast cell mediator was only observed in animals challenged with ovalbumin and the initial challenge released levels of RMCPII 15-fold higher than normal resting levels (P less than 0.001). Subsequent daily challenges evoked the release of significantly lower levels of mediator (P less than 0.001 relative to day 14), but with one exception each test group released significantly more RMCPII than the matched control group on each day (P less than 0.001-P = 0.015). An increased uptake of BSA 'bystander' protein was observed when OVA-sensitized animals were repeatedly gavage-challenged with OVA but there was no correlation with the release of RMCPII mediator. After a 9-day rest period the levels of RMCPII released 6 hr post-challenge on day 26 were still significantly lower (P = 0.004) than the levels of mediator released on day 14. In contrast, animals not previously challenged were still capable of releasing high levels of mediator at the time of first mucosal contact. The levels of RMCPII detected in the serum after enteral protein antigen challenge never exceeded 6000 ng/ml and were lower than those previously observed in parasitized rats following intravenous antigen challenge.

Anaphylaxis↗
PubMed1990

The level of mannan-binding protein regulates the binding of complement-derived opsonins to mannan and zymosan at low serum concentrations.

When sera diluted to 5% in a buffer containing calcium and magnesium were incubated with mannan-coated ELISA plates, C4 fragments, properdin and factor B were bound to the plates as well as the expected opsonic C3 fragments, C3b and C3bi. The calcium-dependent lectin mannan-binding protein, which is structurally similar to C1q, was also shown to bind in this assay and analysis of sera from 179 healthy blood donors revealed that the binding levels of all these proteins were highly significantly correlated. Results obtained with a previously described C3b opsonic assay using zymosan also correlated with the mannan-binding levels. When the sera were diluted to 5% in the presence of Mg-EGTA there was no detectable binding of complement proteins to the mannan surface, confirming that no alternative pathway activation occurred at this serum concentration. When sera were diluted to 5% in a buffer containing EDTA in order to study immunoglobulin binding in the absence of complement activation, the levels of bound IgG1, IgG2, IgG3, IgA and IgM antibodies were found to be completely unrelated to the C3bi binding levels previously observed. The results suggest that in this experimental system using low concentrations of serum, mannan-binding protein initiates an antibody-independent mechanism of cleavage of the classical pathway component C4, which subsequently regulates the degree of cleavage of C3 and recruitment of alternative pathway proteins.

Carrier Proteins↗
PubMed1990

The generation of a 'tolerogen' after the ingestion of ovalbumin is time-dependent and unrelated to serum levels of immunoreactive antigen.

In an attempt to investigate the molecular basis of the mechanisms underlying oral tolerance, we have evaluated the molecular and biological features of ovalbumin subjected to intestinal processing. Immunoreactive ovalbumin absorbed by the gut was measured by a sandwich ELISA at different times after feeding 25 mg ovalbumin to adult mice. Ovalbumin was detected as early as 5 min after the feed (36.7 +/- 16 ng/ml; mean +/- 1 s.d.) and reached maximal levels at 1 h (73.3 +/- 20 ng/ml). Pooled mouse serum, collected 5 min or 1 h after the feed, was transferred intraperitoneally into the naive recipients. Suppression of systemic delayed-type hypersensitivity (DTH) was found in mice receiving 0.8 ml of serum obtained 1 h after ovalbumin feeding but not when using serum obtained 5 min after feeding. In order to transfer samples containing similar levels of ovalbumin, an increased amount (1.3 ml) of serum collected 5 min post-feed was used in further experiments but again failed to induce DTH tolerance. Serum samples obtained 5 and 60 min after ovalbumin feeding were analysed by fast-protein liquid chromatography (FPLC) fractionation followed by ELISA. Both the charge characteristics and molecular weight of intestinally absorbed ovalbumin were indistinguishable from native ovalbumin. Although intact native ovalbumin is the only molecular species detected by ELISA, the results suggest that this has no role in the suppression of DTH responses.

Administration, Oral↗
PubMed1989

Association of low levels of mannan-binding protein with a common defect of opsonisation.

Failure to opsonise bakers' yeast (Saccharomyces cerevisiae) is a defect found in 5-7% of the general population. In this study, the presence of the defect was linked with low levels of mannan-binding protein (MBP), a calcium-dependent serum lectin. Purified MBP corrected the defect in a dose-dependent way in an in-vitro assay measuring the deposition of complement moieties on a mannan-coated surface. There was a highly significant correlation between the serum MBP level and the generation of C3b opsonins in a population of healthy blood donors. The median MBP level of ten children previously shown to have the functional opsonic defect was 4.9 micrograms/l (range 2.5-35.0 micrograms/l) compared with 143 micrograms/l (range 2.5-880 micrograms/l) for a paediatric control group.

Adolescent↗
PubMed1989

Surgery, sepsis, and nonspecific immune function in neonates.

An audit of 143 neonatal surgical operations identified low birth weight infants as being at particular risk of developing post-operative sepsis following major surgical trauma. Activity of the nonspecific immune system was examined pre- and post-operatively in order to elucidate the susceptibility to post-operative sepsis of these infants. A chemiluminescence micro-method was developed specifically for this purpose. Neonatal plasma was shown to have significantly impaired opsonising activity, and activity was further reduced in low birth weight infants. Levels of immunoglobulin and complement factors were also reduced, particularly in the low birth weight infant. Following major surgical trauma polymorph activity was significantly lower in low birth weight infants than in mature neonates.

Anti-Bacterial Agents↗
PubMed1989

A highly cationic protein in plasma and urine of children with steroid-responsive nephrotic syndrome.

We postulated that the reduction of surface negative charge on the glomerular capillary wall, which is believed to underlie the proteinuria of steroid-responsive nephrotic syndrome (SRNS), might be due to the presence of a cationic substance which binds to and neutralizes the negative charge on cells and membranes. Using a method to detect charge neutralizing substances based on inhibition of binding of the cationic dye Alcian blue 8GX to heparin, plasma and urine from children with SRNS were found to contain a protease-sensitive charge-neutralizing factor, which was not present in plasma or urine of healthy individuals. This factor has been partially purified from SRNS plasma and urine by ion exchange chromatography on QAE Sephadex, gel filtration on Sephadex G150, and FPLC on Mono-S. This cationic protein, which binds to and neutralizes the charge on heparin, may also neutralize the negative charge on the glomerular capillary wall and may thus be involved in the pathogenesis of SRNS.

Cations↗
PubMed1989

Few food diets in the treatment of atopic eczema.

Sixty six children with severe atopic eczema were treated with highly restricted ('few food') diets followed, if they improved, by serial reintroduction of excluded foods. Twenty four patients (36%) improved considerably during the few food phase of the diet. Fifteen of these (23% of the study group) maintained this improvement on dietary treatment, of whom three abandoned the diet after periods ranging from six to 10 months, despite continued benefit, because they found the dietary restrictions too arduous. Thus 12 out of 66 children (18%) with severe eczema experienced prolonged and useful benefit from this dietary manoeuvre. Double blind food challenges performed in 10 patients failed to establish that parental identification of provoking foods is reliable. A search for historical and in vitro predictors of diet responsiveness was unsuccessful in this series.

Adolescent↗
PubMed1989

Failure to induce oral tolerance to protein antigens in neonatal mice can be corrected by transfer of adult spleen cells.

We have examined the mechanisms that prevent the induction of oral tolerance to protein antigens in neonatal mice. Serum collected from adult mice 1 h after feeding ovalbumin (1 mg/g body wt) was adoptively transferred to mice aged 1, 3, and 42 d (40 microL/g body wt). Whereas delayed-type hypersensitivity was significantly suppressed in adult recipients relative to control groups, no suppression of systemic delayed-type hypersensitivity was found in neonatal recipients. In attempts to identify the immunologic deficiency that prevents mature reactivity to protein antigens in neonates, adult splenocytes were transferred intraperitoneally (10(8) cells/recipient) 24 h before a feed of OVA (1 mg/g body wt) to neonates. Significant suppression of their systemic DTH response, but not of their anti-ovalbumin IgG antibody response was observed, indicating that spleen cell transfer only partially confers adult-type reactivity. Similar results were obtained using a second protein antigen, BSA. Our observations suggest that the failure to induce oral tolerance to protein antigens in neonatal mice is not simply due to immature antigen processing by the gut, but probably reflects cellular and/or antigen handling immaturity of the neonatal immune system.

Administration, Oral↗
PubMed1989

The kinetics of oral hyposensitization to a protein antigen are determined by immune status and the timing, dose and frequency of antigen administration.

We have investigated the immunological consequences of feeding a protein antigen to previously immunized animals. BALB/c mice were systemically primed with ovalbumin (OVA) in complete Freund's adjuvant (CFA) and fed with high (10 mg/g body weight), medium (1 mg/g body weight) or low (1 microgram/g body weight) doses of OVA once (Day 1, 7 or 14) or sequentially for 5 days (Days 1-5, 7-11, 14-18). The specific IgG antibody response was suppressed only by early feeds of high-dose OVA (Days 1-5). Medium-dose OVA fed on Day 14 or low-dose OVA fed at any stage after immunization enhanced the IgG antibody response. In contradistinction, systemic delayed-type hypersensitivity responses (DTH) were usually suppressed by early feeds of high or medium doses of OVA but never after feeding low-dose OVA. The results suggest that systemic DTH and IgG antibody responses to oral antigen are subject to different control mechanisms in previously primed animals. Such responses depend on the immune status of the animal and are controlled by antigen dose, time and frequency of feeding. The immunological effects observed are also demonstrable following adoptive transfer of spleen cells collected 14 days after multiple feeds of high-dose OVA to immunized mice. Our findings suggest that oral hyposensitization after systemic immunization is regulated by (suppressor) spleen cells which are activated by gut-processed antigen.

Animals↗
PubMed1988

Isolation of the early phase of chylomicron formation in intestinal epithelial cells of rats.

Lipid is first observed electron microscopically in the rough endoplasmic reticulum of intestinal epithelial cells during active lipid absorption. We have been able to isolate this subcellular fraction by using discontinuous sucrose gradients of 0.25/0.86/1.11 M sucrose. A preliminary low speed centrifugation of mucosal homogenate removed the heavier subcellular organelles. The resulting supernatant was centrifuged at 5.25 x 10(6) x g.min. The pellet from this centrifugation was placed on top of the gradient and the fractions isolated at the density interfaces after centrifugation at 25.5 x 10(6) x g.min. The isolated fractions were characterized enzymatically and electron microscopically. Electron microscopically, the fractions were predominantly composed of rounded vesicles decorated with ribosomes. Most contained lipid droplets whose diameters were 453 nm in the lighter membranes and 245 nm in the membranes isolated from the heavier density region. The vesicles contained NADPH cytochrome c reductase and glucose-6-phosphatase activity indicative of the presence of microsomes. Contamination with other subcellular organelles was minimal. These studies demonstrate a method which enables the isolation of vesicles containing chylomicron-sized particles which are from the earliest phase of chylomicron formation. Isolation of chylomicrons from these vesicles will enable a better understanding of the maturation process of chylomicrons as they traverse the intestinal epithelial cell.

Animals↗
PubMed1988

Sporadic aluminum osteomalacia: identification of patients at risk.

Chronic dialysis patients at risk for aluminum osteomalacia in areas of low water-aluminum content are not well identified. We, therefore, studied retrospectively a cohort of 59 patients who underwent bone biopsy at two hospital-based dialysis centers in Montreal (water aluminum content less than 10 micrograms/L). Overall, 25% of patients biopsied had aluminum-related osteomalacia defined by aluminum staining of more than 30% of the trabecular surface and low levels of bone formation as measured by tetracycline labeling. Multiple linear regression analysis showed high predialysis serum creatinine (P less than .05) and the amount of aluminum prescribed per month (P less than .05) as the most important determinants of aluminum staining. We conclude that aluminum-related osteomalacia can be a frequent disease entity in areas of low water-aluminum content. Our findings also suggest predialysis serum creatinine and the amount of aluminum prescribed per month are risk factors for the development of aluminum-related osteomalacia. Though the relationship between serum creatinine and aluminum staining of trabecular bone is unclear, serum creatinine is probably a marker for adequacy of dialysis in these patients.

Aluminum↗
PubMed1988

Intestinal hypersensitivity reactions in the rat. I. Uptake of intact protein, permeability to sugars and their correlation with mucosal mast-cell activation.

We have confirmed previous observations that intestinal anaphylaxis induced in rats previously sensitized to ovalbumin (OVA) is associated with an increased uptake of an unrelated 'bystander' protein, bovine serum albumin (BSA) fed 1 hr previously. In this study, this enhanced protein uptake was associated with an increased lactulose/rhamnose excretion ratio after administration of these sugars, although there was no correlation between the two measurements. One hour after antigen challenge the serum levels of rat mast-cell protease II (RMCPII), a specific marker for mucosal mast-cell secretion, were significantly higher than both the pre-challenge levels and those of sham-challenged controls (P less than 0.002). There was a significant positive correlation between the serum levels of RMCPII and the lactulose/rhamnose excretion ratios (P less than 0.05), but no such correlation existed between RMCPII and BSA levels in the challenged rats. In other studies the urinary lactulose/rhamnose ratios of rats with cetrimide-induced gut damage were found to be significantly increased, although BSA uptake into the serum remained unaltered. We conclude that there is no simple correlation between gut permeation of low-molecular weight sugars and and the uptake of macromolecular proteins.

Animals↗