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Biomedical subjects

C Koch

Publications and source records attributed to C Koch.

At least 235 records · Page 13Linked to original sources
PubMed1995

Extrinsic and intrinsic asthma from childhood to adult age: a 10-yr follow-up.

BACKGROUND: Asthma constitutes one of the most common chronic diseases in childhood, yet little is known about the factors that determine the outcome in childhood asthma. The purpose of this study was to describe various factors of potential importance for the outcome in children with intrinsic and extrinsic asthma. METHODS: Of 85 consecutive children, 5-15 years of age with asthma, 70 (82%) participated in a 10-yr follow-up examination. At the time of referral, all children underwent certain tests for asthma (case history, total IgE, skin prick tests, radioallergosorbent (RAST) tests and specific bronchial provocations). On the basis of these tests, 24 children had intrinsic asthma and 46 children had extrinsic asthma. RESULTS: At the follow-up examination, 60 of the 70 adults (86%, 20 with intrinsic asthma) had current symptoms; 54 of the 60(90%; 18 with intrinsic asthma) were receiving maintenance therapy. Both FEV1 %predicted and FEV1/FVC increased significantly (from 73% +/- 19% to 92% +/- 17% and from 75% +/- 13% to 80% +/- 12% respectively) from childhood to early adulthood (P < 0.0001 and P < 0.001), respectively); a matching amelioration of symptoms was observed (P < 0.0001). Adults with current symptoms had a significantly lower FEV1 %predicted at the time of follow-up (90% +/- 2% vs. 100% +/- 4%, P < 0.02) but not in childhood (73% +/- 20% vs. 71% +/- 10%) than adults who had ceased wheezing. CONCLUSIONS: In children with intrinsic asthma, the outcome seems to be predicted by a combination of the initial frequency of symptoms (P = 0.04), initial FEV1 (P = 0.002), active smoking (P = 0.001) and age at onset of respiratory symptoms (P = 0.001), whereas the initial FEV1 (P < 0.001) seems to be a strong predictor for the outcome in children with extrinsic asthma. These findings suggest that the pathogenic mechanisms underlying intrinsic and extrinsic asthma in children may differ.

Adolescent↗
PubMed1995

Trichostrongylus colubriformis infection in rabbits: persistence of the distal adaptive response to parasitism after anthelmintic treatment.

Mucosal changes associated with anthelmintic treatment in Trichostrongylus colubriformis-infected rabbits were assessed along the entire length of the small intestine. The following groups, each of five rabbits, were compared: infected (group I); infected and treated on day 21 with fenbendazole (group IT); uninfected but given fenbendazole on day 21 (group C, controls). All animals were killed on day 28. In the proximal part of the small intestine of group I rabbits, the worms were associated with shortening of the villi and a significant depletion in alkaline phosphatase activity, which differed significantly from the findings in groups C and IT. In the same region, no difference was found between groups C and IT. In the distal small intestine, hypertrophy of villi and crypts (an adaptive response to the infection), coupled with an increase in enzymic activity, were present in both groups I and IT, in contrast to group C. These results suggest that a complete mucosal restoration occurred within 7 days of anthelmintic treatment in the parasitized part of the intestine. In contrast, the adaptive response observed beyond the main site of parasitism was not abolished by treatment. The functional significance of these findings is discussed in relation to the compensatory growth commonly observed after anthelmintic treatment in ruminants.

Adaptation, Physiological↗
PubMed1995

[Clonidine increases the anesthetic effectiveness of thiopental].

OBJECTIVE: Treatment with alpha 2-agonists has been demonstrated to improve intra- and postoperative haemodynamic stability. After administration of alpha 2-agonists anaesthetic requirements have been shown to be reduced up to 90% for volatile anaesthetics as well as for intravenous anaesthetics like barbiturates. This study was designed to determine the effect of the alpha 2-agonist clonidine on the anaesthetic potency of the intravenous anaesthetic thiopental in absence of pharmacokinetic influences. METHODS: With approval by the local animal care committee all experiments were performed using Xenopus laevis tadpoles in the early pre-limb-bud stage. The animals were exposed to thiopental (0.1-250 microM) or a combination of thiopental (0.1-250 microM) + clonidine (100 microM) for up to 120 min. For each concentration at least ten animals were used. Anaesthesia was defined as loss of righting reflex for 10 s. Based on the response of the tadpoles at different concentrations of the anaesthetic a concentration-response curve was generated according to a method for quantal biologic data and halfmaximal concentrations (EC50) as well as slopes of the curves were calculated. All values are reported as mean +/- sem. Statistical significance was determined by Student's t-test (p < 0.05). RESULTS: The fraction of anaesthetised animals increased with increasing concentrations of thiopental. The logistic concentration-response plots showed a sigmoidal curve with a slope of 2.14 +/- 0.3. Calculation of the EC50 resulted in a value of 25.5 +/- 2.0 microM. In presence of clonidine thiopental exhibited a left shift of the concentration-response curve with an EC50 of 12.3 +/- 1.6 microM (Slope: 2.75 +/- 0.3). CONCLUSION: The presented data confirm the clinical impression that clonidine exercises an anaesthetic sparing effect. Clonidine enhances the anaesthetic potency of thiopental under equilibrium conditions, thus allowing to exclude pharmacokinetic influences as well as excluding effects of adjuvants. It is concluded that the reduction of requirement of anaesthetics by clonidine is due to a pharmacodynamic effect.

Adrenergic alpha-Agonists↗
PubMed1995

Taxonomic dissection of the genus Micrococcus: Kocuria gen. nov., Nesterenkonia gen. nov., Kytococcus gen. nov., Dermacoccus gen. nov., and Micrococcus Cohn 1872 gen. emend.

The results of a phylogenetic and chemotaxonomic analysis of the genus Micrococcus indicated that it is significantly heterogeneous. Except for Micrococcus lylae, no species groups phylogenetically with the type species of the genus, Micrococcus luteus. The other members of the genus form three separate phylogenetic lines which on the basis of chemotaxonomic properties can be assigned to four genera. These genera are the genus Kocuria gen. nov. for Micrococcus roseus, Micrococcus varians, and Micrococcus kristinae, described as Kocuria rosea comb. nov., Kocuria varians comb. nov., and Kocuria kristinae comb. nov., respectively; the genus Nesterenkonia gen. nov. for Micrococcus halobius, described as Nesterenkonia halobia comb. nov.; the genus Nesterenkonia gen. nov. for Micrococcus halobius, described as Nesterenkonia halobia comb. nov.; the genus Dermacoccus gen. nov. for Micrococcus nishinomiyaensis, described as Dermacoccus nishinomiyaensis comb. nov.; and the genus Kytocossus gen. nov. for Micrococcus sedentarius, described as Kytococcus sedentarius comb. nov. M. luteus and M. lylae, which are closely related phylogenetically but differ in some chemotaxonomic properties, are the only species that remain in the genus Micrococcus Cohn 1872. An emended description of the genus Micrococcus is given [corrected].

Base Sequence↗
PubMed1995

Reclassification of Micrococcus agilis (Ali-Cohen 1889) to the genus Arthrobacter as Arthrobacter agilis comb. nov. and emendation of the genus Arthrobacter.

Phylogenetic evidence derived from a 16S ribosomal DNA analysis indicated that the type strain of Micrococcus agilis, DSM 20550 (= ATCC 966 = CCM 2390), is less closely related to the type species of the genus Micrococcus, Micrococcus luteus, than to the type species of the genus Arthrobacter, Arthrobacter globiformis, and related Arthrobacter species. The phylogenetic position of M. agilis is supported by the presence of peptidoglycan variation A3 alpha and by the presence of MK-9(H2) as the major isoprenolog, a characteristic also found in strains of A. globiformis, Arthrobacter crystallopoietes, Arthrobacter atrocyaneus, Arthrobacter citreus, Arthrobacter aurescens, Arthrobacter ilicis, Arthrobacter ureafaciens, Arthrobacter oxydans, Arthrobacter histidinolovorans, and Arthrobacter nicotinovorans. The last six species and M. agilis are characterized by the presence of threonine in the interpeptide bridge of the peptidoglycan. Threonine has not been found in the peptidoglycans of other Arthrobacter species or in members of the genus Micrococcus. Despite the fact that a morphological life cycle is not known, these data support the proposal that M. agilis should be transferred to the genus Arthrobacter as Arthrobacter agilis comb. nov.

Arthrobacter↗
PubMed1995

Biochemical identification of the bovine blood group M' antigen as a major histocompatibility complex class I-like molecule.

Absorption and elution experiments showed that it was impossible to separate antibodies against blood group factor M' from antibodies against bovine lymphocyte antigen (BoLA) A16 in an antiserum showing haemolytic activity against M' as well as lymphocytotoxic activity against BoLA-A16. To elucidate the structural relationship between BoLA-A16 and blood group antigen M', immunoprecipitation experiments on red and white cell lysates isolated from M'-A16 positive and negative cattle were carried out. These results showed that M(r) 44,000 and M(r) 12000 polypeptides can be precipitated from both red and white cells isolated from M'-A16 positive animals, whereas no bands were seen in M'-A16 negative animals in precipitations with the same antibody. Precipitation with a crossreacting human beta 2-microglobulin (beta 2-m) specific antibody confirmed a class-I-like structure associated with beta 2-m on M' positive red cells and the absence of such a structure on M' negative red cells. Sequential precipitations gave analogous results. Proteolytic degradation by papain and V8 protease did not reveal any substantial difference between red and white M'-A16 positive cells, but a slight difference in the pI of the immunoprecipitable components of red and white cells was observed. All together, this indicates that either the blood group antigen M' is the BoLA-A16 class I antigen or M' and BoLA-A16 are two different class I polypeptides with the same relative mass, sharing identical epitopes and both associated with beta 2-m. Comparable results were obtained with M1 and BoLA-A24.

Animals↗
PubMed1995

The level of the serum opsonin, mannan-binding protein in HIV-1 antibody-positive patients.

The concentrations of mannan-binding protein (MBP) in consecutive samples from 10 HIV+ persons were estimated using an ELISA based on polyclonal rabbit anti-MBP. The changes in MBP with time were similar in HIV+ and HIV- persons, and did not appear to be of clinical significance. MBP was determined in a further 70 persons found HIV-1+ during a period of 2.5 years (1984-1986). Out of the total of 80 patients, 32 have by now died from AIDS. According to the serum level of MBP the HIV-infected persons were grouped into high (> 650 ng MBP/ml), intermediate (101-650 ng/ml), and low MBP (< 101 ng/ml). At the termination of the study the frequency of deaths/total in each of the groups were: high MBP, 14/39 (36%); intermediate MBP, 12/26 (46%); and low MBP, 6/14 (43%). There was no association between the MBP level of the individual and the progressive loss of CD4+ T cells, and the level of MBP was not predictive for the length of time between the detection of HIV antibodies and development of AIDS, nor for the duration of AIDS before death occurred. The number of HIV+ persons without detectable MBP (10%) was significantly higher than previously reported for healthy persons (2.4%, P = 0.027). The course of HIV infection does not seem to be influenced by the level of MBP, nor does the antimicrobial activity of MBP appear to affect the progression of AIDS. Further studies are required to substantiate the significance of absence of MBP in the susceptibility to HIV.

Adult↗
PubMed1995

Quantification of the endotoxin-neutralizing capacity of serum and plasma.

A new procedure for quantifying the endotoxin-neutralizing capacity (ENC) of plasma or serum is described. Serially diluted samples were preincubated with endotoxin (lipopolysaccharide; LPS) and the sample dilution producing 50% inhibition of Tachypleus amebocyte lysate activation was measured by a Limulus peptide C enzyme-linked immunosorbent assay. The assay was not subject to interference from plasma or serum at a 500-fold dilution. The ENC of fresh sera from 120 healthy human donors, determined with Salmonella abortus LPS, had a median value of 7.7 kEU/ml (95% confidence limits 3-24 kEU/ml). Values for heparinized fresh plasma were close to those for the corresponding sera. Serum ENC varied greatly with different types of LPS. Neutralization of LPS by serum was rapid, heat-labile, and fully reversed by acidification. Addition of 2 mM EDTA to the serum diluent or pretreatment of LPS with 0.5% deoxycholate enhanced the ENC of serum about 25-fold or 10-fold respectively. The neutralization of LPS by polymyxin B or lysozyme could be demonstrated by the ENC assay, while that by human serum albumin, fibronectin or anti-LPS immunoglobulins was only detected in the presence of 2 mM EDTA. The kinetic changes of LPS and ENC during rabbit endotoxemia were also determined. The ENC assay may be used to study the significance of plasma ENC in Gram-negative infections and to identify the components contributing to plasma ENC.

Animals↗
PubMed1995

Diminished concentrations of insulin-like growth factor I in cystic fibrosis.

Cystic fibrosis is frequently accompanied by a catabolic condition with low body mass index caused by a number of disease complications. Insulin-like growth factor-I (IGF-I) is an anabolic hormone and an important marker of nutritional status, liver function, and linear growth. Available data on IGF-I in cystic fibrosis are sparse and conflicting. From 1990-3, 235 of our 240 patients (114 males, 121 females, median age 16.2 years, ranged 0.1-44.0 years) had IGF-I measured once by radioimmunoassay. IGF-I was significantly reduced compared with a healthy Scandinavian control population: mean (-2 SD to +2 SD) IGF-I SD score was -0.97 (-3.7 to 1.7) in males and -0.67 (-3.2 to 1.9) in females. Height SD score was -0.95 (-3.3 to 1.4) in males and -0.81 (-3.2 to 1.6) in females. In patients who were still in the growth period a significant correlation of IGF-I SD score to height SD score (r = 0.28, p < 0.001) was found. The low IGF-I concentrations may reflect the catabolic state of many patients with cystic fibrosis and play a part in their abnormal growth pattern.

Adolescent↗
PubMed1995

Transplantation of a lobe of lung from mother to child following previous transplantation with maternal bone marrow.

A left lower lobe of the lung was transplanted from a mother to her child, who had previously received a maternal bone marrow transplant for an immune defect. Following the bone marrow transplantation, the child had developed severe pulmonary fibrosis. Surgery and the early postoperative course have been uncomplicated. Immunosuppression with corticosteroids was administered for a short period, after which all immunosuppressive treatment was discontinued. The operation and the outcome are described both in the donor and recipient. Rehabilitation was slow, but one year later the patient is doing well.

Adult↗
PubMed1995

Reexamining the Snodgrass and Corwin 1988 picture identification norms.

Snodgrass and Corwin (1988) provided a database of 150 fragmented pictures identified by subjects only 35% of the time. However, recent research by Koch, Abbey, and Schmidt in 1995 with these pictures has yielded higher identification rates. The present study examined the difference in identification rates between Koch, et al., 1995 and Snodgrass and Corwin in 1988. 85 subjects were given 25 min. to identify all 150 pictures from Snodgrass and Corwin. Of the 150 pictures, 95 were identified more than 35% of the time. Since Snodgrass and Corwin used an implicit-learning task while the present study used an object-identification task, the present findings suggest that identification rates may be specific to the type of object-recognition task employed.

Adult↗
PubMed1995

Modeling direction selectivity of simple cells in striate visual cortex within the framework of the canonical microcircuit.

Nearly all models of direction selectivity (DS) in visual cortex are based on feedforward connection schemes, where geniculate input provides all excitatory synaptic input to both pyramidal and inhibitory neurons. Feedforward inhibition then suppresses feedforward excitation for nonoptimal stimuli. Anatomically, however, the majority of asymmetric, excitatory, synaptic contacts onto cortical cells is provided by other cortical neurons, as embodied in the Canonical Microcircuit of Douglas and Martin (1991). In this view, weak geniculate input is strongly amplified in the preferred direction by the action of intracortical excitatory connections, while in the null direction inhibition reduces geniculate-induced excitation. We investigate analytically and through biologically realistic computer simulations the functioning of a cortical network based on massive excitatory, cortico-cortical feedback. The behavior of this network is compared to physiological data as well as to the behavior of a purely feedforward model of DS based on nonlagged input. Our model explains a number of puzzling features of direction selective simple cells, including the small somatic input conductance changes that have been measured experimentally during stimulation in the null direction, and the persistence of DS while fully blocking inhibition in a single cell. Although the operation at the heart of our network is amplification, the network passes the linearity test of (Jagadeesh et al., 1993). We make specific predictions concerning the effect of selective blockade of cortical inhibition on the velocity-response curve.

Animals↗
PubMed1994

[Biofilm, foreign bodies and chronic infections].

Most bacteria occur in the environment as sessile cells adhering to a surface, whereas a minority exists as free floating (planktonic) cells. Biofilms consist of microcolonies embedded in a polysaccharide matrix produced by the bacteria. This polysaccharide slime protects the bacteria against hostile environmental factors. Planktonic daughter cells are liberated from the surface of biofilms and may colonize new surfaces and subsequently produce new biofilms. Biofilms are often consortia of several different bacterial species. The normal microflora on the skin or on the mucous membranes in the human body occurs as a biofilm, which is removed by the shedding of old cells and by the excretion of mucus. Subsequently new cells and new mucus are colonized by biofilm forming bacteria without giving rise to any symptoms. When body surfaces with a normally occurring microflora (A) are connected by means of an implanted foreign body with body surfaces or tissue compartments without a microflora (B) e.g. bronchi, gall bladder, peritoneum, veins, then a translocation of the normal microflora from (A) to (B) may easily occur leading to acute infection, formation of new biofilms on the implanted foreign body and induction of inflammation in the environment of this biofilm. Chronic bacterial infections are frequently caused by biofilm producing bacteria and the pathogenesis of the tissue damage is dominated by a persistent immune complex mediated inflammation. Bacteria growing in biofilms cannot be eradicated by antibiotics and biofilms resist the immunological and non-specific defence mechanisms of the body.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1994

The influence of endosome-disruptive peptides on gene transfer using synthetic virus-like gene transfer systems.

The process by which viruses destabilize endosomal membranes in an acidification-dependent manner has been mimicked with synthetic peptides that are able to disrupt liposomes, erythrocytes, or endosomes of cultured cells. Peptides containing the 20 amino-terminal amino acid sequence of influenza virus hemagglutinin as well as acidic derivatives showed erythrocyte lysis activity only when peptides were elongated by an amphipathic helix or by carboxyl-terminal dimerization. Interestingly, peptides consisting of the 23 amino-terminal amino acids of influenza virus hemagglutinin were also active in erythrocyte lysis. When peptides were incorporated into DNA complexes that utilize a receptor-mediated endocytosis pathway for uptake into cultured cells, either by ionic interaction with positively charged polylysine-DNA complexes or by a streptavidin-biotin bridge, a strong correlation between pH-specific erythrocyte disruption activity and gene transfer was observed. A high-level expression of luciferase or interleukin-2 was obtained with optimized gene transfer complexes in human melanoma cells and several cell lines.

Amino Acid Sequence↗
PubMed1994

Correlation between specific IgG subclass antibodies to Pseudomonas aeruginosa and opsonic activity in serum from patients with cystic fibrosis.

Heat-stable opsonins from sera of patients with cystic fibrosis (CF) non-CF patients with chronic Pseudomonas aeruginosa infection, healthy children, and adults were investigated for their ability to promote phagocytosis of 35S-labeled P. aeruginosa by human polymorphonuclear neutrophils. Healthy children had significantly lower levels of opsonic activity than adults. Sera from patients with CF without chronic P. aeruginosa lung infection showed significantly higher levels of opsonic activity compared to healthy children. Sera from patients with CF in the early stage of chronic infection had similar opsonic activity as non-CF patients with chronic infection. Sera from patients with CF in the late stage of chronic infection had higher opsonic activity than other infected patients, but not different from adult controls. An inverse correlation was found between levels of specific antibodies to P. aeruginosa and opsonic activity in the group of patients in a late stage of infection. An inverse correlation was also found between levels of IgG1 and IgG3 to P. aeruginosa St-Ag and opsonic activity during the late stage of infection. Infection with P. aeruginosa in CF did not induce significantly increased opsonic activity. It seems that antibodies to P. aeruginosa may have inhibitory opsonic activity.

Adult↗
PubMed1994

A model for the neuronal implementation of selective visual attention based on temporal correlation among neurons.

We propose a model for the neuronal implementation of selective visual attention based on temporal correlation among groups of neurons. Neurons in primary visual cortex respond to visual stimuli with a Poisson distributed spike train with an appropriate, stimulus-dependent mean firing rate. The spike trains of neurons whose receptive fields do not overlap with the "focus of attention" are distributed according to homogeneous (time-independent) Poisson process with no correlation between action potentials of different neurons. In contrast, spike trains of neurons with receptive fields within the focus of attention are distributed according to non-homogeneous (time-dependent) Poisson processes. Since the short-term average spike rates of all neurons with receptive fields in the focus of attention covary, correlations between these spike trains are introduced which are detected by inhibitory interneurons in V4. These cells, modeled as modified integrate-and-fire neurons, function as coincidence detectors and suppress the response of V4 cells associated with non-attended visual stimuli. The model reproduces quantitatively experimental data obtained in cortical area V4 of monkey by Moran and Desimone (1985).

Animals↗