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Biomedical subjects

C Koch

Publications and source records attributed to C Koch.

At least 145 records · Page 8Linked to original sources
PubMed1998

Immunohistochemical investigation of the tissue distribution of mannan-binding lectin in non-infected and virus-infected chickens.

This paper describes the results of immuno-histochemical staining for chicken mannan-binding lectin (MBL) in formalin-fixed tissue sections from non-infected chickens, and from chickens infected with infectious laryngotracheitis virus (ILTV) or infectious bursal disease virus (IBDV). In the non-infected chickens, MBL was detected in the cytoplasm of a few hepatocytes and in the germinal centres of the caecal tonsils, whereas sections of kidney, heart muscle, spleen, cerebrum, thymus, adrenal gland, bursa of Fabricius, bone marrow and trachea were without staining. In the ILTV-infected chickens, an intense staining reaction for MBL was detected in the cytoplasm of all hepatocytes and on the surface of, and inside, ILTV-infected cells. Also in the IBDV-infected chickens, an intense staining reaction for MBL was detected in the cytoplasm of all hepatocytes. No staining was seen in the follicles of the bursa of Fabricius, but MBL was present in non-identified cells in the interstitium, and in the cytoplasm of macrophage-like cells, located peripheral to the ellipsoid of the spleen. These findings indicate the liver as the primary site of MBL synthesis, and points to up-regulation as a result of the viral infections. The location outside the liver could indicate a role of MBL in the immune defence.

Animals↗
PubMed1998

Serum levels, ontogeny and heritability of chicken mannan-binding lectin (MBL).

Mannan-binding lectin (MBL) is a serum lectin found in mammals and recently also in birds. It is thought to play an important role in the innate immune defence through binding to surface carbohydrates on micro-organisms followed by complement activation via the MBL pathway. This results in opsonization or direct complement-mediated killing. To gain further knowledge about the physiology and function of the protein, we developed an enzyme-linked immunosorbent assay for chicken MBL and used this to investigate the level of MBL in different chicken strains during embryogenesis, early and adult life. The MBL concentrations in 308 chickens, representing 14 different strains, showed a non-Gaussian, unimodal distribution profile with a mean concentration of 5.8 micrograms/ml (range 0.4-37.8 micrograms/ml). No difference between the strains could be demonstrated and no chickens were found deficient in MBL. Ontogenetic studies showed that MBL is already detectable in embryos at a gestational age of 10 days (11 days before hatching). At hatching, the level is comparable to the level found in adult chickens. This level is fairly stable during the first weeks of life, but a deficiency state develops at 4 weeks of age, whereafter the level is normalized again at 5 weeks of age. Chickens with relatively low or high MBL levels were bred with cockerels having similar MBL levels and this resulted in F1 generations with significantly different MBL levels, suggesting that the protein level is genetically influenced.

Animals↗
PubMed1998

Reconstitution of opsonizing activity by infusion of mannan-binding lectin (MBL) to MBL-deficient humans.

Mannan-binding lectin (MBL, previously named mannan-binding protein, MBP) is a serum collectin, which activates complement upon binding to microbial carbohydrates. This results in opsonization of the microorganisms as well as direct complement-mediated killing. Clinical evidence indicates that MBL has an important role in the innate immune defence against various pathogens. Genetically determined MBL deficiency is associated with increased susceptibility to infections. We have infused two MBL-deficient individuals with clinical grade MBL, purified from pooled donor plasma, in doses sufficient to attain normal concentration of MBL in serum. This resulted in normalization of complement-mediated opsonization. An initial rapid decrease in the serum concentration of MBL was followed by a slower decline with an estimated half-life of about 6 days. No adverse effects were observed and anti-MBL antibodies could not be detected following several MBL infusions. One of the two MBL recipient, a two-year-old girl, who had been suffering from repeated infections from the age of 4 months, was given a total of six MBL infusions. She has subsequently remained healthy for more than three years.

Adult↗
PubMed1998

The concordance of intraoperative left ventricular wall-motion abnormalities and electrocardiographic S-T segment changes: association with outcome after coronary revascularization. Multicenter Study of Perioperative Ischemia (McSPI) Research Group.

BACKGROUND: Transesophageal echocardiography (TEE) and Holter electrocardiography (ECG) are used to detect intraoperative ischemia during coronary artery bypass graft surgery (CABG). Concordance of these modalities and sensitivity as indicators of adverse perioperative cardiac outcomes are poorly defined. The authors tried to determine whether routine use of Holter ECG and TEE in patients with CABGs has clinical value in identifying those patients in whom myocardial infarction (MI) is likely to develop. METHODS: A total of 351 patients with CABG and both ECG- and TEE-evaluable data were examined for the occurrence of ischemia and infarction. The TEE and five-lead Holter ECGs were performed continuously during cardiac surgery. The incidence of MI (creatine kinase-MB > or = 100 ng/ml) within 12 h of arrival in the intensive care [ICU] unit, new ECG Q wave on ICU admission or on the morning of postoperative day 1, or both, were recorded. RESULTS: Electrocardiographic or TEE evidence of intraoperative ischemia was present in 126 (36%) patients. The concordance between modalities was poor (positive concordance = 17%; Kappa statistic = 0.13). Myocardial infarction occurred in 62 (17%) patients, and 32 (52%) of them had previous intraoperative ischemia. Of these, 28 (88%) were identified by TEE, whereas 13 (41%) were identified by ECG. Prediction of MI was greater for TEE compared with ECG. CONCLUSIONS: Wall-motion abnormalities detected by TEE are more common than S-T segment changes detected by ECG, and concordance between the two modalities is low. One half of patients with MI had preceding ECG or TEE ischemia. Logistic regression revealed that TEE is twice as predictive as ECG in identifying patients who have MI.

Aged↗
PubMed1998

Decreased antitoxic activities among children with clinical episodes of malaria.

Healthy Gambian children, children with clinical Plasmodium falciparum malaria, and children with asymptomatic P. falciparum infections were studied to investigate whether antitoxic activities may contribute to protection against malarial symptoms. Markers of inflammatory reactions, soluble tumor necrosis factor receptor I, and C-reactive protein were found in high concentrations in children with symptomatic P. falciparum malaria compared with levels in children with asymptomatic P. falciparum infections or in healthy children, indicating that inflammatory reactions are induced only in children with clinical symptoms. Concentrations of soluble tumor necrosis factor receptor I and C-reactive protein were associated with levels of parasitemia. We detected antitoxic activities in sera as measured by their capacity to block toxin-induced Limulus amoebocyte lysate (LAL) activation. Symptomatic children had decreased capacity to block induction of LAL activation by P. falciparum exoantigen. The decreased blocking activity was restored in the following dry season, when the children had no clinical malaria. Symptomatic children also had the highest immunoglobulin G (IgG) reactivities to conserved P. falciparum erythrocyte membrane protein 1 and "Pfalhesin" (band #3) peptides, indicating that such IgG antibodies are stimulated by acute disease but are lost rapidly after the disease episode. Half of the children with symptomatic infections had low levels of haptoglobin, suggesting that these children had chronic P. falciparum infections which may have caused symptoms previously. Only a few of the children with asymptomatic P. falciparum infections had high parasite counts, and antitoxic immunity in the absence of antiparasite immunity appears to be rare among children in this community.

Amino Acid Sequence↗
PubMed1998

Identification of an erythrocyte binding peptide from the erythrocyte binding antigen, EBA-175, which blocks parasite multiplication and induces peptide-blocking antibodies.

A biotinylated peptide covering a sequence of 21 amino acids (aa) from the erythrocyte binding antigen (EBA-175) of Plasmodium falciparum bound to human glycophorin A, an erythrocyte receptor for merozoites, as demonstrated by enzyme-linked immunosorbent assay (ELISA) and to erythrocytes as demonstrated by flow cytometry analysis. The peptide, EBA(aa1076-96), also bound to desialylated glycophorin A and glycophorin B when tested by ELISA. The peptide blocked parasite multiplication in vitro. The glycophorin A binding sequence was further delineated to a 12-aa sequence, EBA(aa1085-96), by testing the binding of a range of truncated peptides to immobilized glycophorin A. Our data indicate that EBA(aa1085-96) is part of a ligand on the merozoite for binding to erythrocyte receptors. This binding suggests that the EBA(aa1085-96) peptide is involved in a second binding step, independent of sialic acid. Antibody recognition of this peptide sequence may protect against merozoite invasion, but only a small proportion of sera from adults from different areas of malaria transmission showed antibody reactivities to the EBA(aa1076-96) peptide, indicating that this sequence is only weakly immunogenic during P. falciparum infections in humans. However, Tanzanian children with acute clinical malaria showed high immunoglobulin G reactivity to the EBA(aa1076-96) peptide compared to children with asymptomatic P. falciparum infections. The EBA(aa1076-96) peptide sequence from EBA-175 induced antibody formation in mice after conjugation of the peptide with purified protein derivative. These murine sera inhibited EBA(aa1076-96) peptide binding to glycophorin A.

Adolescent↗
PubMed1998

Multimer formation is not essential for nuclear export of human T-cell leukemia virus type 1 Rex trans-activator protein.

The Rex trans-regulatory protein of human T-cell leukemia virus type 1 (HTLV-1) is required for the nuclear export of incompletely spliced and unspliced viral mRNAs and is therefore essential for virus replication. Rex is a nuclear phosphoprotein that directly binds to its cis-acting Rex response element RNA target sequence and constantly shuttles between the nucleus and cytoplasm. Moreover, Rex induces nuclear accumulation of unspliced viral RNA. Three protein domains which mediate nuclear import-RNA binding, nuclear export, and Rex oligomerization have been mapped within the 189-amino-acid Rex polypeptide. Here we identified a different region in the carboxy-terminal half of Rex which is also required for biological activity. In inactive mutants with mutations that map within this region, as well as in mutants that are deficient in Rex-specific multimerization, Rex trans activation could be reconstituted by fusion to a heterologous leucine zipper dimerization interface. The intracellular trafficking capabilities of wild-type and mutant Rex proteins reveal that biologically inactive and multimerization-deficient Rex mutants are still efficiently translocated from the nucleus to the cytoplasm. This observation indicates that multimerization is essential for Rex function but is not required for nuclear export. Finally, we are able to provide an improved model of the HTLV-1 Rex domain structure.

Amino Acid Sequence↗
PubMed1998

The predictive value of early CT and angiography for fatal hemispheric swelling in acute stroke.

PURPOSE: Our goal was to analyze the predictive value of early CT and arteriographic morphologic criteria to achieve a more reliable prediction of fatal outcome in patients undergoing fibrinolytic stroke treatment. METHODS: In 74 patients with acute carotid artery stroke, early signs of cerebral ischemia were determined by CT. The site of vascular occlusion was identified by digital subtraction angiography (DSA). The patients were subsequently treated by intraarterial (n = 68) or intravenous (n = 6) fibrinolysis by means of recombinant tissue plasminogen activator (rt-PA), urokinase, or rt-PA combined with lys-plasminogen and followed-up for a period of 3 months. CT and DSA data were compared with the clinical course, with special emphasis on signs of early fatal deterioration (ie, death by intracranial mass effect) as determined by corresponding CT and clinical observations, occurring within 7 days after stroke. RESULTS: Seventeen patients died, all of intracranial mass effect, and all within a week after stroke. In nine of these fatalities, DSA revealed carotid "T" occlusion (CTO), which affected 19 patients. In five of the fatalities, a major early sign of ischemia (MESI, referring to cortical hypodensity in more than a third of the territory of the middle cerebral artery, as seen in 14 patients) was recognizable on the initial CT scan. This led to a higher predictive value and sensitivity of CTO relative to MESI for estimating early fatality. CONCLUSION: CTO as determined by DSA is a substantially better predictor of fatal outcome in patients undergoing intraarterial thrombolytic therapy than is MESI as determined by CT.

Acute Disease↗
PubMed1998

[Cystic fibrosis].

Cystic fibrosis (CF), the most common life-threatening autosomal recessive disorder in Causcasian populations, is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7, which encodes a protein that functions as a chloride channel in the apical membrane of epithelial cells. The clinical manifestations comprise recurrent and chronic bronchopulmonary infections, pancreatic insufficiency, and hidrotic salt depletion. Such complications as diabetes, cirrhosis, and respiratory insufficiency develop, resulting in death in the absence of lung transplantation. Treatment is aggressive and comprehensive from the time of diagnosis. Early and intensive treatment of bacterial colonisation and lung infection is correlated with improved prognosis, and monthly follow-up at a CF Centre is mandatory. Mean survival among CF patients at the Danish CF Centre i Copenhagen is more than 40 years. Clinical trials of gene therapy are under way, but results to date have been disappointing.

Chromosome Aberrations↗
PubMed1997

[Improved prognosis for patients with cystic fibrosis. A result of aggressive center-based treatment].

We report survival data for Danish centre-treated cystic fibrosis (CF) patients, covering the period 1974-1993 using cross-sectional cumulative survival probability based on annual age-specific mortality rates. No significant differences were noted in the survival probability when patients were grouped according to sex or absence/presence of meconium ileus. The annual mortality rate for 1989-1993 was 0-1.2%. Using the age-specific mortality rate for 1989-1993, we were unable to calculate the median survival probability because the curve did not fall below 50% (age up to 45 years). It was, however, possible to show that the survival probability for a CF child born after 1989 to reach his or hers 45th birthday was 80.4% (95% confidence interval 76.5-84.6%). The probability of surviving 40 years after the diagnosis of CF is made was 83.3% (95% confidence interval 80.1%-86.6%). This is considerably higher than any other published survival probability. An aggressive anti-Pseudomonas aeruginosa treatment regimen seemed important in achieving the observed improved survival.

Adolescent↗
PubMed1997

Conjugation to preadsorbed preactivated proteins and efficient generation of anti peptide antibodies.

A solid phase conjugation method is described based on the preadsorption of proteins to aluminium hydroxide adjuvant followed by activation of the adsorbed carrier proteins with iodoacetic acid N-hydroxysuccinimidester or other conjugation reagents. Cysteine-containing peptides were coupled to the iodoacetic acid-activated carrier-adjuvant particles through their SH groups. No dialysis is required since the reaction product is isolated at each step of the procedure by a simple centrifugation and can easily be extensively washed between individual manipulations. The method generates peptide-carrier-adjuvant particles with sterically defined presentation of the peptides at the surface of the particles. When used for immunization of mice and rabbits the conjugates elicited high-titered specific anti-peptide sera, which reacted well with the parent protein in ELISA. The strongest reactions were with the denatured form of the parent protein. On immunoblots antisera to the N- and C-terminus of calreticulin recognized the same M, 52,000 protein.

Adsorption↗
PubMed1997

Shunting inhibition does not have a divisive effect on firing rates.

Shunting inhibition, a conductance increase with a reversal potential close to the resting potential of the cell, has been shown to have a divisive effect on subthreshold excitatory postsynaptic potential amplitudes. It has therefore been assumed to have the same divisive effect on firing rates. We show that shunting inhibition actually has a subtractive effect on the firing rate in most circumstances. Averaged over several interspike intervals, the spiking mechanism effectively clamps the somatic membrane potential to a value significantly above the resting potential, so that the current through the shunting conductance is approximately independent of the firing rate. This leads to a subtractive rather than a divisive effect. In addition, at distal synapses, shunting inhibition will also have an approximately subtractive effect if the excitatory conductance is not small compared to the inhibitory conductance. Therefore regulating a cell's passive membrane conductance-for instance, via massive feedback-is not an adequate mechanism for normalizing or scaling its output.

Animals↗
PubMed1997

Isolation and characterization of a new member of the scavenger receptor superfamily, glycoprotein-340 (gp-340), as a lung surfactant protein-D binding molecule.

We have purified a previously unknown glycoprotein (designated gp-340) from human bronchioalveolar lung washings from a patient with alveolar proteinosis. gp-340 was identified by its calcium-dependent binding to lung surfactant protein D (SP-D) and by its molecular mass of 340 kDa in the reduced state on SDS-polyacrylamide gel electrophoresis (PAGE). gp-340 was purified from the 10,000 x g pellet of the lavage fluid by ion-exchange and gel permeation chromatography. On SDS-PAGE, gp-340 showed an apparent molecular mass of 290 kDa in the unreduced state. On gel chromatography under non-dissociating conditions, the apparent molecular mass of gp-340 was >1000 kDa. The presence of N-linked glycosylation was shown by digestion with N-glycosidase F, which reduced the apparent molecular mass of gp-340 under reducing condition to about 300 kDa. Partial amino acid sequence data showed the presence of scavenger-receptor type domains. Monoclonal and polyclonal antibodies were raised against gp-340, and their specificities were confirmed by Western blotting. The antibodies were used for immunohistochemical localization of gp-340 in the lung, where it was found on the surface of and within alveolar macrophages. Direct binding between gp-340 and SP-D took place at physiological ionic strength, required the presence of calcium, and was not inhibited by maltose. The binding between SP-D and mannan also required the presence of calcium, but this interaction was completely inhibited by maltose. The same binding pattern was seen between gp-340 and recombinant human SP-D composed of the trimeric neck region and three carbohydrate recognition domains. These findings indicate that the binding between gp-340 and SP-D is a protein-protein interaction rather than a lectin-carbohydrate interaction and that the binding to gp-340 takes place via the carbohydrate recognition domain of SP-D. We conclude that gp-340 is a new member of the scavenger-receptor superfamily and likely to be a truncated form of a receptor for SP-D.

Amino Acid Sequence↗
PubMed1997

Crystal structure of the DNA-binding domain of Mbp1, a transcription factor important in cell-cycle control of DNA synthesis.

BACKGROUND: During the cell cycle, cells progress through four distinct phases, G1, S, G2 and M; transcriptional controls play an important role at the transition between these phases. MCB-binding factor (MBF), a transcription factor from budding yeast, binds to the so-called MCB (MluI cell-cycle box) elements found in the promoters of many DNA synthesis genes, and activates the transcription of those at the G1-->S phase transition. MBF is comprised of two proteins, Mbp1 and Swi6. RESULTS: The three-dimensional structure of the N-terminal DNA-binding domain of Mbp1 has been determined by multiwavelength anomalous diffraction from crystals of the selenomethionyl variant of the protein. The structure is composed of a six-stranded beta sheet interspersed with two pairs of alpha helices. The most conserved core region among Mbp1-related transcription factors folds into a central helix-turn-helix motif with a short N-terminal beta strand and a C-terminal beta hairpin. CONCLUSIONS: Despite little sequence similarity, the structure within the core region of the Mbp1 N-terminal domain exhibits a similar fold to that of the DNA-binding domains of other proteins, such as hepatocyte nuclear factor-3gamma and histone H5 from eukaryotes, and the prokaryotic catabolite gene activator. However, the structure outside the core region defines Mbp1 as a larger entity with substructures that stabilize and display the helix-turn-helix motif.

Amino Acid Sequence↗
PubMed1997

Monoclonal antibodies against human tetranectin, epitope characterization and use in immunohistochemistry.

Two IgG2a/kappa- and three IgG1/kappa monoclonal antibodies (MAbs) were produced against human tetranectin (TN): this is the first report of stable hybridomas producing MAbs against TN. All the MAbs reacted with non-conformational epitopes located within amino acid residues 50-181 of the primary sequence. In relative epitope mapping with enzyme immunoassay and isotachophoresis the five MAbs defined two independent epitope groups. One of them is suggested to be immunodominant in rabbits, since MAbs inhibited binding of a polyclonal rabbit antibody. Several combinations of MAbs were suitable for TN-ELISA and two MAbs could be used for immunohistochemical detection of TN in both fresh frozen and paraffin-embedded tissues. The MAbs will facilitate future studies on structure, function, clinical significance and immunolocalization of TN.

Animals↗