Middle ear effusion, ventilation tubes and neurological development in childhood

BACKGROUND

Otitis media with middle ear effusion (MEE) can be treated with ventilation tubes (VT) insertion, and it has been speculated that prolonged MEE in childhood can affect neurological development, which in turn may be important for later academic achievements.

OBJECTIVE

To investigate the association between middle ear effusion (MEE), treatment with ventilation tubes (VT) and childhood neurological development.

STUDY DESIGN

We examined 663 children from the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC2010) unselected mother-child cohort study. Children were followed by study pediatricians with regular visits from pregnancy until 3 years of age. MEE was diagnosed using tympanometry at age 1, 2 and 3 years. Information regarding VT from age 0-3 years was obtained from national registries. We assessed age at achievement of gross motor milestones from birth, language scores at 1 and 2 years, cognitive score at 2.5 years and general development score at age 3 years using standardized quantitative tests.

RESULTS

Children with MEE had a lower 1-year word production vs. children with no disease: (median 2, IQR [0-6] vs. 4, IQR [1-7]; p = 0.017), and a lower 1-year word comprehension (median 36; IQR [21-63] vs. 47, IQR [27-84]; p = 0.03). Children with VT had a lower 2-5-year cognitive score vs. children with no disease; estimate -2.34; 95% CI [-4.56;-0.12]; p = 0.039. No differences were found between children with vs. without middle ear disease regarding age at achievement of gross motor milestones, word production at 2 years or the general developmental score at 3 years.

CONCLUSION

Our study supports the previous findings of an association between MEE and concurrent early language development, but not later neurological endpoints up to the age of 3. As VT can be a treatment of those with symptoms of delayed development, we cannot conclude whether treatment with VT had positive or negative effects on neurodevelopment.

Distinct immune phenotypes in infants developing asthma during childhood

Early exposure to environmental triggers may elicit trajectories to chronic inflammatory disease through deregulated immune responses. To address relations between early immune competence and development of childhood asthma, we performed functional immune profiling of 186 parameters in blood of 541 18-month-old infants and examined links between their response phenotype and development of transient or persistent disease at 6 years of age. An abnormal neutrophil-linked antiviral response was associated with increased risk of transient asthma. Children who exhibited persistent asthma at year 6 showed enhanced interleukin-5 (IL-5) and IL-13 production in stimulated T cells at 18 months of age, which was associated with early life bacterial colonization of the airways. These findings highlight the early appearance of distinct immune characteristics in infants developing different asthma endotypes during childhood.

Early life bacterial airway colonization, local immune mediator response and risk of otitis media

Introduction. Acute otitis media (AOM) is the most common bacterial infection in early childhood, but the underlying mechanisms making some children more susceptible are poorly understood.Aim. To examine the associations between bacterial airway colonization in early life and the risk of AOM and tympanostomy tube insertion (TTI), and whether such associations are modulated by an insufficient local immune mediator response to bacterial colonization.Methodology. Bacterial cultures from hypopharyngeal samples were obtained at 1 week, 1 month and 3 months of age in the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC₂₀₁₀) cohort comprising 700 children. Twenty immune mediators were quantified from airway mucosal lining fluid sampled at 1 month. AOM symptoms were registered in a daily diary until 3 years. Information on TTI in the first 3 years was obtained from national registers.Results. Children colonized with Streptococcus pneumoniae at 1 month of age had increased incidence of AOM [aIRR 2.43 (1.14-5.21)] and children colonized with Moraxella catarrhalis at 1 month or Haemophilus influenzae at 3 months had an increased risk of TTI [aHR 1.45 (1.00-2.10) and 1.73 (1.10-2.71)]. There were no associations between the local immune mediator response to colonization and risk of AOM or TTI.Conclusion. Pathogenic bacterial airway colonization in early life was found to be associated with an increased risk of otitis media, albeit not consistently. These associations were independent of the local immune response to colonization.

Infectious diseases detected by screening after arrival to Denmark in internationally adopted children

AIM

To show the prevalence of selected infectious diseases among internationally adopted children (IAC) in Denmark.

BACKGROUND

Each year approximately 200 IAC arrive in Denmark. These are at increased risk of infectious diseases rarely seen in Danish children. Studies from the 1990s showed that 60% of IAC had infectious diseases and that the majority of these were undetected without screening.

METHODS

The study is a prospective study of medical records from children seen in the adoption clinic at Copenhagen University Hospital in the period 2009-2013. Screening was done for hepatitis A (HAV), B (HBV) and C (HCV), syphilis, HIV, tuberculosis (TB) and intestinal parasites.

RESULTS

In 245 IAC tested, 2% had evidence of recent HAV infection, 3% with HBV and one child with HCV, and no cases of HIV were found. One child had antibodies against syphilis (anti-Trpa AB positivity), and 2% were latently infected with tuberculosis. We found 30% infected with pathogenic intestinal parasites. Only 46% had serologic evidence of immunisation against HBV.

CONCLUSION

The prevalence of infections in IAC was lower than previously reported but compared to the general population, a higher prevalence of intestinal parasites, hepatitis and tuberculosis was found. We recommend that IAC are offered screening shortly after arrival.

Identification of Platelet Antigens by Monoclonal Antibodies Using Crossed Immunoelectrophoresis with Immunoblotting of the Monoclonal Antibody

A method is described for the identification of antigens by monoclonal antibodies. This is applicable whenever precipitating antibodies to the same antigens from a different species are available. The method is based upon: 1) Separation and immunoprécipitation of cellular proteins with a polyspecific antiserum in crossed immunoelectrophoresis in the presence of the non-denaturing detergent Triton X-100 and the monoclonal antibody. 2) Coprecipitation of the monoclonal antibody with its antigen. 3) Subsequent passive transfer of the monoclonal antibody in the antibody-antigen complex onto a nitrocellulose membrane. 4) Visualization of the blotted antibody using an enzyme-linked secondary antibody and a chromogenic substrate. 5) Identification of the corresponding antigen by comparisons to the immunoprecipitate pattern of the original immunoplate. To test this method we have analyzed the detection of the antigens recognized by six previously described monoclonal antibodies against platelet membrane proteins and von Willebrand factor. Specific immunoblots were obtained in each case using small amounts of monoclonal antibodies. Thus, the technique provides an alternative when epitopes are denatured by SDS, and avoids the use of radioactively labelled monoclonal antibodies.

Antibiotics in Pregnancy Increase Children's Risk of Otitis Media and Ventilation Tubes

OBJECTIVES

To study the association between antibiotic intake in pregnancy and the development of otitis media and placement of ventilation tubes (VTs) in the offspring under the hypothesis that antibiotics in pregnancy may alter the offspring's propensity for disease.

STUDY DESIGN

Data from the 700 children in the Copenhagen Prospective Studies on Asthma in Childhood 2010 unselected birth cohort study were used. Information on maternal antibiotic use and other exposures during pregnancy was collected prospectively from interviews and validated in national registries. Otitis media episodes were registered in a prospective diary for 3 years. Information regarding children's VTs was obtained from national registries.

RESULTS

There were 514 children who had diary information and were included in the analysis regarding otitis media episodes. For VTs analysis, 699 children were included. Thirty-seven percent of the mothers received antibiotics during pregnancy, and this was associated with increased risk of otitis media (adjusted hazard ratio 1.30; 95% CI 1.04-1.63; P = .02). The risk of receiving VTs was especially associated with third trimester antibiotics (adjusted hazard ratio 1.60; 95% CI 1.08-2.36, P = .02). The risk of otitis media increased with increasing number of treatments (per-level adjusted hazard ratio 1.20; 95% CI 1.04-1.40; P = .02), but for VTs this association was not significant after adjustment.

CONCLUSION

Maternal use of antibiotics during pregnancy is associated with an increased risk of otitis media and VT insertions in the offspring. Antibiotics late in pregnancy mainly contributed to these effects, pointing toward potential transmission of an unfavorable microbiome from mother to child.

Incidence and Determinants of Ventilation Tubes in Denmark

Background and objectives

Many children are treated for recurrent acute otitis media and middle ear effusion with ventilation tubes (VT). The objectives are to describe the incidence of VT in Denmark during 1997–2011 from national register data, furthermore, to analyze the determinants for VT in the Copenhagen Prospective Studies on Asthma in Childhood₂₀₁₀ (COPSAC₂₀₁₀) birth cohort.

Methods

The incidence of VT in all children under 16 years from 1997–2011 were calculated in the Danish national registries. Determinants of VT were studied in the COPSAC₂₀₁₀ birth cohort of 700 children.

Results

Nationwide the prevalence of VT was 24% in children aged 0 to 3 three years, with a significant increase over the study period. For all children 0–15 years, the incidence of VT was 35/1,000. In the VT population, 57% was male and 43% females. In the COPSAC₂₀₁₀ birth cohort, the prevalence of VT during the first 3 years of life was 29%. Determinants of VT were: maternal history of middle ear disease; aHR 2.07, 95% CI [1.45–2.96] and siblings history of middle ear disease; aHR 3.02, [2.11–4.32]. Paternal history of middle ear disease, presence of older siblings in the home and diagnosis of persistent wheeze were significant in the univariate analysis but the association did not persist after adjustment.

Conclusion

The incidence of VT is still increasing in the youngest age group in Denmark, demonstrating the highest incidence recorded in the world. Family history of middle ear disease and older siblings are the main determinants for VT.

Effect of Vitamin D3 Supplementation During Pregnancy on Risk of Persistent Wheeze in the Offspring: A Randomized Clinical Trial

IMPORTANCE

Observational studies have suggested that increased dietary vitamin D intake during pregnancy may protect against wheezing in the offspring, but the preventive effect of vitamin D supplementation to pregnant women is unknown.

OBJECTIVE

To determine whether supplementation of vitamin D3 during the third trimester of pregnancy reduces the risk of persistent wheeze in the offspring.

DESIGN, SETTING, AND PARTICIPANTS

A double-blind, single-center, randomized clinical trial conducted within the Copenhagen Prospective Studies on Asthma in Childhood 2010 cohort. Enrollment began March 2009 with a goal of 708 participants, but due to delayed ethical approval, only 623 women were recruited at 24 weeks of pregnancy. Follow-up of the children (N = 581) was completed when the youngest child reached age 3 years in March 2014.

INTERVENTIONS

Vitamin D3 (2400 IU/d; n = 315) or matching placebo tablets (n = 308) from pregnancy week 24 to 1 week postpartum. All women received 400 IU/d of vitamin D3 as part of usual pregnancy care.

MAIN OUTCOMES AND MEASURES

Age at onset of persistent wheeze in the first 3 years of life. Secondary outcomes included number of episodes of troublesome lung symptoms, asthma, respiratory tract infections, and neonatal airway immunology. Adverse events were assessed.

RESULTS

Of the 581 children, persistent wheeze was diagnosed during the first 3 years of life in 47 children (16%) in the vitamin D3 group and 57 children (20%) in the control group. Vitamin D3 supplementation was not associated with the risk of persistent wheeze, but the number of episodes of troublesome lung symptoms was reduced, and the airway immune profile was up-regulated (principal component analysis, P = .04). There was no effect on additional end points. Intrauterine death was observed in 1 fetus (<1%) in the vitamin D3 group vs 3 fetuses (1%) in the control group and congenital malformations in 17 neonates (5%) in the vitamin D3 group vs 23 neonates (8%) in the control group. [table: see text].

CONCLUSIONS AND RELEVANCE

The use of 2800 IU/d of vitamin D3 during the third trimester of pregnancy compared with 400 IU/d did not result in a statistically significant reduced risk of persistent wheeze in the offspring through age 3 years. However, interpretation of the study is limited by a wide CI that includes a clinically important protective effect.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00856947.

[The risk of infections in internationally adopted children is real]

Each year approximately 400 internationally adopted children (IAC) come to Denmark from countries with high prevalences of infectious diseases. Former studies of IAC have shown that approximately 1% of the IAC are infected with Hepatitis A, 3-6% with Hepatitis B, mostly asymptomatic infections. 8-27% have gastrointestinal parasites and 1-7% have tuberculosis, but 3-21% have a positive Mantoux test. The studies found none with HIV or HCV and only a few with syphilis. The vaccination status was often deficient and the serology results did not match the vaccination records. All studies conclude that screening of IAC is recommended.

Probing Interfacial Characteristics of Rubrene/Pentacene and Pentacene/Rubrene Bilayers with Soft X-Ray Spectroscopy

The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.

Post-annealing effect on the electronic structure of Mn atoms in Ga(₁-x)Mn(x)As probed by resonant inelastic x-ray scattering

The electronic structure of as-grown and post-annealed Ga(₁-x)Mn(x)As epilayers (x≈0.055) has been investigated using resonant inelastic x-ray scattering. Mn L₂,₃ x-ray emission spectra show that the integral intensity ratio of Mn L₂ to L₃ emission lines increases with annealing temperature and comes close to that of manganese oxide. The oxygen K-emission/absorption spectra of post-annealed Ga₀.₉₄₅Mn₀.₀₅₅As show 1.5-3.0 times higher degree of oxidation on the film surface than that of the as-grown sample. These experimental findings are attributed to the diffusion of Mn impurity atoms from interstitial positions in the GaAs host lattice to the surface where they are passivated by oxygen.

Clopidogrel increases expression of chemokines in peripheral blood mononuclear cells in patients with coronary artery disease: results of a double-blind placebo-controlled study

BACKGROUND

Chemokines and platelet activation are both important in atherogenesis. Platelet inhibitors are widely used in coronary artery disease (CAD), and we hypothesized that the platelet inhibitor clopidogrel could modify chemokines in CAD patients.

OBJECTIVES

We sought to investigate the effect of clopidogrel on the expression of chemokines and chemokine receptors in peripheral blood mononuclear cells (PBMC) in CAD patients.

PATIENTS/METHODS

Thirty-seven patients with stable angina were randomized to clopidogrel (n = 18) or placebo (n = 19). PBMC, blood platelets and plasma were collected at baseline and after 7-10 days in the patients, and in 10 healthy controls. mRNA levels of chemokines and chemokine receptors in PBMC were analyzed by ribonuclease protection assays and real-time reverse transcriptase polymerase chain reaction. Platelet activation was studied by flow cytometry.

RESULTS

(i) At baseline, the gene expression of the regulated on activation normally T-cell expressed and secreted (RANTES) chemokines and macrophage inflammatory peptide (MIP)-1beta in PBMC, the expression of CD62P and CD63 on platelets and the levels of platelet-derived microparticles (PMP) were elevated in angina patients comparing healthy controls; (ii) markers of platelet activation were either reduced (CD63) or unchanged (CD62P, PMP, beta-thromboglobulin) during clopidogrel therapy; (iii) in contrast, clopidogrel significantly up-regulated the gene expression of RANTES and MIP-1beta in PBMC, while no changes were found in the placebo group; (iv) a stable adenosine 5'-diphosphate metabolite attenuated the release of MIP-1beta, but not of RANTES, from activated PBMC in vitro.

CONCLUSIONS

Even if we do not argue against a beneficial role for clopidogrel in CAD, our findings may suggest potential inflammatory effects of clopidogrel in CAD.

Structure and reactivity of surface oxides on Pt(110) during catalytic CO oxidation

We present the first structure determination by surface x-ray diffraction during the restructuring of a model catalyst under reaction conditions, i.e., at high pressure and high temperature, and correlate the restructuring with a change in catalytic activity. We have analyzed the Pt(110) surface during CO oxidation at pressures up to 0.5 bar and temperatures up to 625 K. Depending on the pressure ratio, we find three well-defined structures: namely, (i) the bulk-terminated Pt(110) surface, (ii) a thin, commensurate oxide, and (iii) a thin, incommensurate oxide. The commensurate oxide only appears under reaction conditions, i.e., when both and CO are present and at sufficiently high temperatures. Density functional theory calculations indicate that the commensurate oxide is stabilized by carbonate ions (CO3(2-)). Both oxides have a substantially higher catalytic activity than the bulk-terminated Pt surface.

One-dimensional PtO2 at Pt steps: formation and reaction with CO

Using core-level spectroscopy and density functional theory we show that a one-dimensional (1D) oxide structure forms at the steps of the Pt(332) surface after exposure. The 1D oxide is found to be stable in an oxygen pressure range, where bulk oxides are only metastable, and is therefore argued to be a precursor to the Pt oxidation. As an example of the consequences of such a precursor exclusively present at the steps, we investigate the reaction of CO with oxygen covered Pt(332). Albeit more strongly bound, the oxidic oxygen is found to react more easily with CO than oxygen chemisorbed on the Pt terraces.

Oxidation of Pt(110)

Using scanning tunneling microscopy and temperature programmed desorption we investigate the Pt(110) surface under strongly oxidizing conditions involving either high-pressure O2 or atomic oxygen exposure. At low temperatures, only disordered Pt oxide structures are observed. After annealing ordered surface oxide islands are observed to coexist with a highly stable reconstructed (12x2)-O chemisorption structure. From density functional theory calculations a model for the surface oxide phase is revealed. The phase is found to be metastable, and its presence is explained in terms of stabilizing defects in the chemisorption layer and reduced Pt mobility.

Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions

A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different alpha-oxygen-substituted, racemic aldehydes were initially transformed by asymmetric HWE reactions into mixtures of two major alpha,beta-unsaturated esters, possessing opposite configurations at their allylic stereocenters as well as opposite alkene geometry. Subsequently, these isomeric mixtures of alkenes could be subjected to palladium-catalyzed allylic substitution reactions with carbon, nitrogen, and oxygen nucleophiles. In this latter step, the respective (E) and (Z) alkene substrate isomers were observed to react with opposite stereospecificity: the (E) alkene reacted with retention and the (Z) alkene with inversion of stereochemistry with respect to both the allylic stereocenter and the alkene geometry. Thus, a single gamma-substituted ester was obtained as the overall product, in high isomeric purity. The method was applied to a synthesis of a subunit of the iejimalides, a group of cytotoxic macrolides.

Platelet shape change induced by the peptide YFLLRNP

Platelet shape change represents an early response to activating agents. Whereas the PAR-1-activating peptide SFLLRN induces a total platelet activation, YFLLRNP brings the process only to the shape change step in a process independent of the cytosolic Ca2+ concentration. In this paper, the YFLLRNP-induced shape change has been observed in human citrated platelet-rich plasma (PRP). Scanning electron microscopy of platelets activated by 300 microM YFLLRNP showed platelets that had changed shape and extended long pseudopods. The protein content of the material sedimenting at 13,000 x g from 1% Triton X-100 extracts increased during the shape change, indicating a reorganization of the cytoskeleton. This was supported by electrophoresis. The GP IIb-IIIa complex was not activated, however, and the platelets that had undergone shape change did not support clot retraction. As no increase in binding of FITC-labeled annexin V (FITC-annexin V) was observed, the extensive shape change was not associated with a disturbance of the membrane phospholipid asymmetry. Platelet aggregation was never observed with 300 microM YFLLRNP, but could be seen at much higher concentrations, neither was secretion from dense granules observed at 300 microM as no extracellular ATP could be observed. These studies confirm and extend the concept of the Ca2+-independent shape change as a distinct and sharply delineated process that, in itself, may be of little pathophysiological importance if such "partly activated" platelets occur in the circulation.

The charge-heterogeneity of human fibrinogen as investigated by 2D electrophoresis

The charge-heterogeneity of human plasma fibrinogen subunit chains was characterized by two-dimensional electrophoresis (2DE). Western blotting with antibodies specific for the gamma-chain demonstrated that the gamma-chains focus at varying isoelectric points (pI). This microheterogeneity was also observed in fibrinogen secreted from hepatocytic cells and in recombinant fibrinogen expressed in Chinese hamster ovary (CHO) cells. Further, covalent gammagamma-dimerization by FXIIIa was not influenced by the charge-heterogeneity, and removal of the carbohydrate did not reduce the number of gamma-chain pI variants. These observations suggest that the microheterogeneity of the gamma-chain is a multifactorial phenomenon that is not due to physiologic modification of the glycoprotein in circulation.

[Prednisolone treatment of respiratory syncytial virus infection. A randomized, controlled trial of 147 children]

OBJECTS

Our objective was to evaluate the effect of systemic prednisolone as an adjunct to conventional treatment with beta 2-agonist, fluid replacement and respiratory support in hospitalized infants younger than 24 months with respiratory syncytial virus (RSV) infection.

METHODS

The study was randomized, double-blind and placebo-controlled. During the winter of 1995-96, 147 infants less than two years of age hospitalized with RSV infection were allocated to treatment with either systemic prednisolone mixture 2 mg/kg daily or placebo for 5 days.

RESULTS

Our main outcome measures were: 1. Acute effect variables: duration of stay in hospital, use of medicine and supportive measures while in hospital. 2. At follow-up one month after discharge: duration of illness, start in day care center, morbidity and use of medicine. 3. At follow-up one year after discharge: morbidity, use of medicine and skin prick tests with allergens.

CONCLUSION

Prednisolone treatment had no effect on any of the outcome measures. We find our results in agreement with the largest studies reported earlier; therefore, corticosteroid, whether by systemic route or by inhalation, should not be prescribed to infants with RSV infection.

Detection of biotinylated proteins in crossed immunoelectrophoresis gels: studies on platelet membrane receptors and microparticles

Biotinylation can be used as an alternative for surface labeling of cell membrane proteins. The use of the water soluble N-hydroxysulfosuccinimide (NHSS)-biotin or the more lipophilic N-hydroxysuccinimide (NHS)-biotin reagent has been investigated in the present study labeling two central receptor complexes on the platelet surface, i.e. the glycoprotein (GP) Ib-IX and the GP IIb-IIIa complexes involved in platelet adhesion and aggregation. Lack of labeling of the intracellularly located albumin was used as a negative control. The labeling has been studied using crossed immunoelectrophoresis in the PhastSystem format after extraction of the labeled cells in Triton X-100, and it is shown that, using enzyme-conjugated avidin and chromogenic substrates, the biotinylated proteins can be visualized directly in the dried electrophoresis gel without the need for a transfer to a blotting membrane as is used after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Suitable conditions for biotinylation and for visualization in the crossed immunoelectrophoresis gels are described. Further, surface-biotinylation of platelets was used to observe shedding of microparticles as a consequence of formation of the complement membrane attack complex. For this purpose the formation and composition of the biotinylated microparticles were observed by flow cytometry and crossed immunoelectrophoresis.

Complement-mediated permeabilization of platelets by monoclonal antibodies to CD9: inhibition by leupeptin, and effects on the GP Ib-actin-binding protein system

Two monoclonal antibodies to CD9 of the IgM and IgG2a categories (FN 52 and FN 99), reproducibly induced platelet alterations in platelet-rich plasma by activation of the complement system with membrane incorporation of the pore-forming C5b-9 complex. The permeabilization could be monitored by measurements of extracellular ATP and observed as a shape change followed by an increase in light transmission in the aggregometer, and was associated with formation of tiny platelet aggregates. This could be accomplished by only minor lysis observed as extracellular lactate dehydrogenase (LDH). When leupeptin was added prior to, or immediately after the antibody, a total inhibition of the platelet alterations could be obtained. When added soon after the shape change, leupeptin had little effect on the liberation of ATP. However, whereas the ability of the platelets to become agglutinated by ristocetin was lost during the complement-mediated platelet alterations, addition of leupeptin immediately after the shape change, prevented this loss. The lost ability of the permeabilized platelets to undergo ristocetin-induced agglutination is not ascribed to degradation of GP Ib as this was relatively little affected in these studies as compared to the actin-binding protein (ABP) which was profoundly degraded. This protein represents a link between GP Ib and the submembraneous cytoskeleton, and the inhibition of its degradation by leupeptin, was clearly demonstrated. Experiments with digitonin-induced permeabilization showed that leupeptin did not inhibit permeabilization as such, but it did prevent the loss of ristocetin-induced agglutination even with this inducer.

Studies on a patient with thrombocytopenia, giant platelets and a platelet membrane glycoprotein Ib with reduced amount of sialic acid

A 70-year-old patient with a life-long bleeding tendency, giant platelets and thrombocytopenia (10-40 x 10(9) platelets/l) has been studied. This is a condition often associated with lack of platelet membrane glycoprotein Ib (GP Ib). Electron microscopy of fixed platelets incubated with monoclonal antibodies to GP Ib (AN 51, AP 1) and gold-labelled goat anti-mouse IgG, showed a distinct distribution of GP Ib on the patient's platelets, however. Crossed immunoelectrophoresis and SDS-PAGE demonstrated a reduced mobility of the patient's GP Ib which could be explained by absence of sialic acid. Blotting with peroxidase-conjugated peanut agglutinin confirmed this conclusion. This lectin binds to galactose-N-acetyl-galactosamine residues exposed terminally when sialic acid is absent from the carbohydrate side-chains. Such binding could be seen with normal GP Ib only after neuraminidase treatment. Fluorescence studies with FITC-conjugated peanut agglutinin showed binding of the lectin to intact patient platelets, indicating that lack of sialic acid was not introduced during the platelet isolation procedure. Neither could the lack of sialic acid be attributed to increased neuraminidase activity as studied in vitro. Platelets treated with neuraminidase in vivo or in vitro are rapidly cleared from the circulation. Therefore the patient's thrombocytopenia may be associated with the reduced amount of GP Ib sialic acid. As far as we know, similar cases have not been described previously.

The use of PhastSystem crossed immunoelectrophoresis with immunoblotting to demonstrate a complex between glycoprotein Ib and the actin-binding protein (ABP) of human platelets

The study shows how a technique described in an accompanying paper can be applied to solve a biological problem. The technique makes use of the observation that a monoclonal antibody that has been coprecipitated with its antigen during crossed immunoelectrophoresis can be transferred to a nitrocellulose membrane and visualized. Previous studies using crossed immunoelectrophoresis of Triton X-100 extracts of platelets have indicated that a particular immunoprecipitate (peak III) of the membrane receptor glycoprotein Ib (GP Ib) might contain a complex between the receptor and the actin-binding protein (filamin). When a monoclonal antibody (PM6/317) directed towards the actin-binding protein was added to a platelet extract prior to immunoelectrophoresis and blotting, this was visualized on the blot as a replica of the peak III immunoprecipitate. This demonstrates a colocalization of GP Ib and the actin-binding protein in the precipitate, and thus the existence of a complex between the membrane receptor and the cytoskeletal protein.

Identification of platelet antigens by monoclonal antibodies using crossed immunoelectrophoresis with immunoblotting of the monoclonal antibody

A method is described for the identification of antigens by monoclonal antibodies. This is applicable whenever precipitating antibodies to the same antigens from a different species are available. The method is based upon: Separation and immunoprecipitation of cellular proteins with a polyspecific antiserum in crossed immunoelectrophoresis in the presence of the non-denaturing detergent Triton X-100 and the monoclonal antibody. Coprecipitation of the monoclonal antibody with its antigen. Subsequent passive transfer of the monoclonal antibody in the antibody-antigen complex onto a nitrocellulose membrane. Visualization of the blotted antibody using an enzyme-linked secondary antibody and a chromogenic substrate. Identification of the corresponding antigen by comparisons to the immunoprecipitate pattern of the original immunoplate. To test this method we have analyzed the detection of the antigens recognized by six previously described monoclonal antibodies against platelet membrane proteins and von Willebrand factor. Specific immunoblots were obtained in each case using small amounts of monoclonal antibodies. Thus, the technique provides an alternative when epitopes are denatured by SDS, and avoids the use of radioactively labelled monoclonal antibodies.