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Biomedical subjects

C Koch

Publications and source records attributed to C Koch.

At least 55 records · Page 3Linked to original sources
PubMed2001

Rainbow trout offspring with different resistance to viral haemorrhagic septicaemia.

To study immunological and immunogenetical parameters related to resistance against viral haemorrhagic septicaemia (VHS), attempts to make gynogenetic strains of rainbow trout selected for high and low resistance to VHS were initiated in 1988. The first gynogenetic generation of inbreeding resulted in the more resistant offspring E8 and the low resistance offspring K3; the K3 offspring having the same high mortality as the susceptible reference strain of outbred trout in infection trials. A second gynogenetic generation derived from the E8 strain resulted in some low resistance offspring, and two gynogenetic families in which all, or nearly all, fish survived challenge with VHS virus. In this study, an attempt to associate the distribution of different MHC class II genotypes with low and high resistance gynogenetic offspring was performed. Two different MHC haplotypes could be distinguished, and in both low and high resistance families all three genotypes were found, which could be explained by the fact that the mother fish carried the heterozygous genotype. Although no significant differences in MHC II genotypes were found between the high and low resistance offspring, a significantly different distribution of haplotypes in the low resistance offspring was observed, that could not be explained by a one- or two-locus model.

Animals↗
PubMed2001

[Development of a standardized instrument for quantitative and reproducible rehabilitation data assessment after polytrauma (HASPOC)].

INTRODUCTION: Previous scoring systems for measurement of the quality of outcome are based on scores regarding injuries to individual body regions. Known scores which describe several organ regions are of no importance for trauma patients. Therefore a new rehabilitation outcome evaluation score was developed at our hospital. METHODS: Based on a prospective reinvestigation, a score system was developed that allows a quantitative appraisal of the subjective and objective outcome. A complete physical examination was performed, including ROM, neurologic examination and strength analysis. Part I (113 questions) is to be filled out by the patient; part II (191 questions) focusses on different body regions, physical examination and functional scoring. Included are the MFA, FIM, GCO and Frankel score. A final score (HASPOC) was developed to give a quantitative result of the outcome. RESULTS: The new score has a range from 5 to 411 points. One hundred and fifty patients were re-examined. The mean follow-up time was 2.2 +/- 0.1 years. The SF 12 indicated an outcome more than satisfactory in 63% of cases. The MFA demonstrated moderate or severe restrictions in 41%, in the case of injuries of the lower extremity in 52% of patients. The HASPOC indicated a mean of 44.5 points. CONCLUSION: This paper describes the development, structure, and the quantitative outcome of rehabilitation in polytrauma patients. This standardized rehabilitation instrument deals with a very heterogeneous patient population and shows the rehabilitation deficits accurately. Implemented recognized evaluations allow comparison of these results with those of other scoring systems.

Data Collection↗
PubMed2001

Spatial aspects of object formation revealed by a new illusion, shine-through.

When a vernier stimulus is presented for a short time and followed by a grating comprising five straight lines, the vernier remains invisible but may bequeath its offset to the grating (feature inheritance). For more than seven grating elements, the vernier is rendered visible as a shine-through element. However, shine-through depends strongly on the spatio-temporal layout of the grating. Here, we show that spatially inhomogeneous gratings diminish shine-through and vernier discrimination. Even subtle deviations, in the range of a few minutes of arc, matter. However, longer presentation times of the vernier regenerate shine-through. Feature inheritance and shine-through may become a useful tool in investigating such different topics as time course of information processing, feature binding, attention, and masking.

Adult↗
PubMed2001

Shine-through: temporal aspects.

If a vernier stimulus precedes a grating for a very short time, the vernier either remains invisible, but may bequeath some of its properties to the grating (feature inheritance), or might shine through keeping its features - depending on the number of grating elements [Herzog, M. H. & Koch, C., 2001. Seeing properties of an invisible element: feature inheritance and shine-through. Proceedings of the National Academy of Science USA 98, 4271-4275]. Feature inheritance and shine-through represent two different states of feature binding [Herzog, M. H., Koch, C., & Fahle, M., Switching binding states. Visual Cognition (in press)], whereas shine-through depends in subtle ways on the spatial layout of the grating [Herzog, M. H., Fahle, M., & Koch, C., (2001). Spatial aspects of object formation revealed by a new illusion, shine-through Vision Research]. Here, we show that also temporal parameters of the grating influence shine-through. For example, a delayed presentation of certain grating elements can deteriorate performance dramatically.

Afterimage↗
PubMed2001

Flanker effects in peripheral contrast discrimination--psychophysics and modeling.

We studied lateral interactions in the periphery by measuring how contrast discrimination of a peripheral Gabor patch is affected by flankers. In the psychophysical experiments, two Gabor targets appeared simultaneously to the left and right of fixation (4 degrees eccentricity). Observers reported which contrast was higher (spatial 2-alternative-forced-choice). In different conditions, Gabor flankers of different orientation, phase, and contrast were present above and below the two targets, at a distance of three times the spatial Gabor period. The data show that collinear flanks impair discrimination performance for low pedestal contrasts but have no effect for high pedestal contrasts. The transition between these two result patterns occurs typically at a pedestal contrast which is similar to the flanker contrast. For orthogonal flanks, we find facilitation at low pedestal contrasts, and suppression at intermediate contrasts. We account for this complex interaction pattern by a model that assumes that flankers can provide additive input to the target unit, and that they further contribute to the target's gain control, but only in a limited range of pedestal contrasts; once the target contrast exceeds a critical value, inhibition becomes subtractive rather than divisive. We further make specific propositions on how this model could be implemented at the neuronal level and show that a simple integrate and fire unit that receives time-modulated inhibition behaves in a fashion strikingly similar to the model inferred from the psychophysical data.

Contrast Sensitivity↗
PubMed2001

Computational modelling of visual attention.

Five important trends have emerged from recent work on computational models of focal visual attention that emphasize the bottom-up, image-based control of attentional deployment. First, the perceptual saliency of stimuli critically depends on the surrounding context. Second, a unique 'saliency map' that topographically encodes for stimulus conspicuity over the visual scene has proved to be an efficient and plausible bottom-up control strategy. Third, inhibition of return, the process by which the currently attended location is prevented from being attended again, is a crucial element of attentional deployment. Fourth, attention and eye movements tightly interplay, posing computational challenges with respect to the coordinate system used to control attention. And last, scene understanding and object recognition strongly constrain the selection of attended locations. Insights from these five key areas provide a framework for a computational and neurobiological understanding of visual attention.

Animals↗
PubMed2001

[Thermal effects of ultrasound].

AIM: Diagnostic ultrasound is a powerful, versatile and safe investigation tool in modern medicine. Methods are described, and conclusions are drawn and recommendations given for a responsible use of diagnostic ultrasound. METHOD AND RESULTS: Because of the increasing ultrasonic power penetrating the body, diagnostic techniques cannot always be applied without risk. The increase in temperature induced by ultrasound absorption should be considered a potential hazard in certain applications. The paper presents the physical basis for a quantitative estimation of the risk of a specific treatment plan. Mathematical models and the thermal index are described. CONCLUSION: Our findings and recommendations form a viable basis for the responsible use of diagnostic ultrasound.

Animals↗
PubMed2001

[Optimized logistics in the prehospital management of acute stroke].

OBJECTIVE: Current management of acute stroke is characterised by an aggressive approach including specific therapy i. e. reperfusion therapy. However currently stroke patients often arrive too late in hospitals offering adequate treatment. Therefore optimized logistics play a predominant role in modern stroke management. AIMS OF THE STUDY: 1. Does teaching of EMS staff and the public result in reduced prehospital latencies 2. Will EMS personnel be able to effectively screen patients potentially suitable for thrombolysis? METHODS: During a six week-period all EMS patients presenting with possible signs of an acute stroke were prospectively registered (period 1). Data of interest were age, mode of primary contact, prehospital latencies, mode of transportation, destination and final diagnosis. Next an algorithm was established allowing EMS personnel to transfer patients with an assumed stroke to the best suitable hospital. Teaching comprised clinical signs, indication of CT scanning, pathophysiology, specific therapeutic options (thrombolysis), and criteria to identify patients suitable for thrombolysis. In a second step the public was continuously taught about stroke symptoms and the necessity to instantly seek EMS assistance. After 12 months data were compared to baseline (period 2). RESULTS: (period 2 vs. Period 1): Rate of patients transferred to a stroke center: 60 % vs. 54 %; rate of those transported to hospitals not offering CT scans: 17 % vs. 26 % (p < 0.05). Percentage of patients primarily contacting the EMS system: 33 % vs. 24 %. Median interval between onset of symptoms and emergency call: 54 vs. 263 minutes Median interval between the emergency call and arrival at the emergency department: 44 vs. 58 minutes (p < 0.01). Rate of patients admitted with a diagnosis other than stroke: 18 % vs. 25 % (n. s.). Median interval between onset of symptoms and hospital admission: 140 vs. 368 minutes (p < 0.001). Median age: 69 vs. 75 years (p < 0.01). CONCLUSION: This study demonstrates the efficacy of educational efforts in reducing latencies and in screening patients potentially suitable for thrombolysis. Future efforts will comprise more intense education of a high risk subpopulation.

Age Factors↗
PubMed2001

Characterization of paired mucoid/non-mucoid Pseudomonas aeruginosa isolates from Danish cystic fibrosis patients: antibiotic resistance, beta-lactamase activity and RiboPrinting.

The purpose of this study was to characterize 42 paired mucoid and non-mucoid Danish cystic fibrosis (CF) Pseudomonas aeruginosa isolates collected in 1997, by RiboPrinting, antibiotic susceptibility and beta-lactamase activity. Eight P. aeruginosa isolates collected before 1991 were included for comparison. Eighteen of the 42 paired mucoid and non-mucoid isolates showed the same ribotype; the remaining 24 belonged to different ribogroups. Mucoid isolates showed higher susceptibility to antibiotics and lower beta-lactamase activity compared with non-mucoid isolates. Significant differences (P < or = 0.01) between mucoid and non-mucoid isolates were found for the meropenem and colistin MICs for the isolates with the same ribotype, and for the MICs of ceftazidime, piperacillin, aztreonam, meropenem, tobramycin, ciprofloxacin and in the basal levels of beta-lactamase for the paired isolates belonging to different ribogroups. A dominant ribotype 73-S2 with hyperinducible beta-lactamase production and significantly higher MICs of piperacillin, meropenem and tobramycin compared with the other major ribotypes (73-S1, 207-S3 and 227-S8) was present among the 84 CF isolates. The isolates collected before 1991 had an antibiotic susceptibility pattern similar to the 1997 isolates. Despite prolonged and intensive antibiotic treatment, susceptible mucoid isolates were isolated from the CF sputum, possibly because these bacteria are protected from the selective pressure of antibiotics by the resistant non-mucoid isolates co-existing in the biofilm in the lungs of CF patients.

Adolescent↗
PubMed2001

Efficacy and drug interactions of the new HMG-CoA reductase inhibitors cerivastatin and atorvastatin in CsA-treated renal transplant recipients.

BACKGROUND: Hyperlipidaemia is an important risk factor for cardiovascular disease in renal transplant recipients. The aim of this study was to test the efficacy and possible drug-drug interactions of the new HMG-CoA reductase inhibitors (statins) atorvastatin and cerivastatin in cyclosporin A (CsA)-treated renal transplant patients. Subjects and methods. Thirty patients with stable graft function and LDL cholesterol of 130 mg/dl were randomly assigned to active treatment groups (10 mg atorvastatin or 0.2 mg cerivastatin), or a control group. CsA blood trough levels were controlled on a weekly basis and adapted if they changed more than 25% from baseline values (100-150 ng/ml). Lipid levels and routine laboratory parameters before and after a treatment period of 3 months were compared. RESULTS: In the group treated with cerivastatin no significant changes in CsA blood trough levels occurred (CsA 116+/-21 ng/ml vs 110+/-20 ng/ml). In contrast, in the group treated with atorvastatin, four of 10 patients had a rise in CsA blood trough levels of more than 25% within 7-14 days of starting therapy. In the remaining patients no significant changes in CsA drug levels occurred. After therapy with atorvastatin or cerivastatin, total cholesterol, LDL cholesterol, and triglycerides were significantly lower compared with baseline conditions. No changes of CsA or lipoprotein levels were present in the control group. CONCLUSION: In our study population both statins were very effective in lowering elevated LDL cholesterol levels. Cerivastatin did not influence CsA blood trough levels, whereas atorvastatin increased CsA levels in four of 10 patients. Further research in a larger study is necessary in order to confirm these results and to investigate the possible reasons for this drug interaction.

Adult↗
PubMed2001

Isolation of a lysogenic bacteriophage carrying the stx(1(OX3)) gene, which is closely associated with Shiga toxin-producing Escherichia coli strains from sheep and humans.

A specific PCR for the detection of a variant of the gene encoding Shiga toxin 1 (stx(1)) called stx(1(OX3)) (GenBank accession no. Z36901) was developed. The PCR was used to investigate 148 Stx(1)-producing Escherichia coli strains from human patients (n = 72), cattle (n = 27), sheep (n = 48), and a goat (n = 1) for the presence of the stx(1(OX3)) gene. The stx(1(OX3)) gene was present in 38 Shiga toxin-producing E. coli (STEC) strains from sheep belonging to serogroups O5, O125, O128, O146, and OX3 but was absent from Stx(1)-positive ovine STEC O91 strains. The stx(1(OX3)) gene was also detected in 22 STEC strains from humans with nonbloody diarrhea and from asymptomatic excreters. Serotypes O146:H21 and O128:H2 were most frequently associated with stx(1(OX3))-carrying STEC from sheep and humans. In contrast, Stx(1)-producing STEC strains from cattle and goats and 50 STEC strains from humans were all negative for the stx(1(OX3)) gene. The stx(1(OX3))-negative strains belonged to 13 serotypes which were different from those of the stx(1(OX3))-positive STEC strains. Moreover, the stx(1(OX3)) gene was not associated with STEC belonging to enterohemorrhagic E. coli (EHEC) serogroups O26, O103, O111, O118, O145, and O157. A bacteriophage carrying the stx(1(OX3)) gene (phage 6220) was isolated from a human STEC O146:H21 strain. The phage was able to lysogenize laboratory E. coli K-12 strain C600. Phage 6220 shared a similar morphology and a high degree of DNA homology with Stx(2)-encoding phage 933W, which originates from EHEC O157. In contrast, few similarities were found between phage 6220 and Stx(1)-encoding bacteriophage H-19B from EHEC O26.

Animals↗
PubMed2001

Detecting and estimating signals over noisy and unreliable synapses: information-theoretic analysis.

The temporal precision with which neurons respond to synaptic inputs has a direct bearing on the nature of the neural code. A characterization of the neuronal noise sources associated with different sub-cellular components (synapse, dendrite, soma, axon, and so on) is needed to understand the relationship between noise and information transfer. Here we study the effect of the unreliable, probabilistic nature of synaptic transmission on information transfer in the absence of interaction among presynaptic inputs. We derive theoretical lower bounds on the capacity of a simple model of a cortical synapse under two different paradigms. In signal estimation, the signal is assumed to be encoded in the mean firing rate of the presynaptic neuron, and the objective is to estimate the continuous input signal from the postsynaptic voltage. In signal detection, the input is binary, and the presence or absence of a presynaptic action potential is to be detected from the postsynaptic voltage. The efficacy of information transfer in synaptic transmission is characterized by deriving optimal strategies under these two paradigms. On the basis of parameter values derived from neocortex, we find that single cortical synapses cannot transmit information reliably, but redundancy obtained using a small number of multiple synapses leads to a significant improvement in the information capacity of synaptic transmission.

Artifacts↗
PubMed2001

Factors associated with poor pulmonary function: cross-sectional analysis of data from the ERCF. European Epidemiologic Registry of Cystic Fibrosis.

The European Epidemiologic Registry of Cystic Fibrosis began collecting longitudinal data on European cystic fibrosis patients in 1994. A cross-sectional analysis was performed to identify the factors associated with low values of % predicted forced expiratory volume in one second (FEV1) upon patient enrollment. Data from 7,010 patients aged > or =6 yrs were included. Clinical conditions, microbiological isolates and medications reported at enrollment or within the following 180 days were analysed for age-specific associations. Factors associated with FEV1 that were lower by >10% of pred values were: lower weight for age percentiles, haemoptysis, pneumothorax, pulmonary symptoms at presentation, Pseudomonas aeruginosa, Burkholderia cepacia, oral corticosteroids, nonsteroid anti-inflammatory drugs, dornase alfa, oxygen and assisted ventilation and, in patients >12 yrs old only, use of airway clearance techniques, inhaled bronchodilators, oral nutritional supplements, pancreatic enzymes and insulin or oral hypoglycaemics. Slightly impaired lung function (5-10%) was associated with: diabetes (> or = 18-yrs-old), gastro-oesophageal reflux, allergic bronchopulmonary aspergillosis, asthma-like symptoms, portal hypertension, Aspergillus spp. and Candida spp. Sex, Haemophilus influenzae and Staphylococcus aureus were not associated with impaired pulmonary status. Regular exercise (especially in older patients) and nasal polyposis were associated with slightly better FEV1. The results confirm those of previous studies and suggest selective prescribing in sicker patients.

Adolescent↗
PubMed2001

Combined prostaglandin and nitric oxide inhibition produces anatomic remodeling and closure of the ductus arteriosus in the premature newborn baboon.

After birth, the full-term ductus arteriosus actively constricts and undergoes extensive histologic changes that prevent subsequent reopening. These changes are thought to occur only if a region of intense hypoxia develops within the ductus wall after the initial active constriction. In preterm infants, indomethacin-induced constriction of the ductus is often transient and is followed by reopening. Prostaglandins and nitric oxide both play a role in inhibiting ductus closure in vitro. We hypothesized that combined inhibition of both prostaglandin and nitric oxide production (with indomethacin and N-nitro-L-arginine (L-NA), respectively) may be required to produce the degree of functional closure that is needed to cause intense hypoxia. We used preterm (0.67 gestation) newborn baboons that were mechanically ventilated for 6 d: 6 received indomethacin alone, 7 received indomethacin plus L-NA, and 16 received no treatment (control). Just before necropsy, only 25% of control ductus and 33% of indomethacin-treated ductus were closed on Doppler examination; in contrast, 100% of the indomethacin-plus-L-NA-treated ductus were closed. Control and indomethacin-treated baboons developed negligible-to-mild ductus hypoxia (EF5 technique). Similarly, there was minimal evidence of ductus remodeling. In contrast, indomethacin-plus-L-NA-treated baboons developed intense hypoxia in regions where the ductus was most constricted. The hypoxic muscle strongly expressed vascular endothelial growth factor, and proliferating luminal endothelial cells filled and occluded the lumen. In addition, cells in the most hypoxic regions were undergoing DNA fragmentation. In conclusion, preterm newborns are capable of remodeling their ductus, just like the full-term newborn, if they can reduce their luminal blood flow to a point that produces intense ductus wall hypoxia. Combined prostaglandin and nitric oxide inhibition may be necessary to produce permanent closure of the ductus and prevent reopening in preterm infants.

Animals↗
PubMed2001

Stress, coping, and success among graduate students in clinical psychology.

Research has indicated that coping styles and social support are moderating variables in the relationship between stress and distress. Few studies, however, have examined the relationship between these variables and the relative health and success of graduate students in clinical psychology. We administered measures of stress, psychological health, social support, and coping styles to 53 doctoral students in clinical psychology. Current grade point averages were used as a measure of academic success. We hypothesized that more successful students would likely be healthier and report less stress, more social support, and utilization of more positive and less negative coping styles. Results generally supported the hypothesis. Unexpected findings were that more successful students were likely to be women and to report increased use of focus on and venting of emotion as a coping style, increased utilization of medical care, and increased stress regarding scholastic coursework.

Adaptation, Psychological↗
PubMed2001

[Differences between management guidelines and global health strategies for arterial hypertension with metabolic disorders in France in 1999. Ohara study].

Taking into account all the risk factors and blood pressure levels, as indicated by several American and European recommendations available since 1997, is a leading strategy to reduce mortality and morbidity of hypertensive patients. The aim of this study was to quantify how, in 1999. French practitioners applied recommendations on hypertension (HTN), diabetes and hypercholesterolemia in recently diagnosed hypertensive patients and to evaluate whether or not the recommended targets were met. 1639 French GPs and cardiologists included 5831 recently diagnosed (7.5 +/- 3.6 months) hypertensives (57 +/- 12 years of age, M/F = 55/45%). Initial BP was 173 +/- 15/99 +/- 9 mmHg. 56% had no concomitant disease, 36% had either diabetes, dyslipidemia or coronary heart disease, 8% had at least two concomitant diseases. At the time of the study corresponding to 6.3 +/- 3.8 months after initiation of diet and/or medical treatment, their BP was 148 +/- 17/86 +/- 11 mmHg (-25/-19 mmHg). At that time only 37% of patients with stage 2 HTN were encouraged to adopt lifestyle modifications without any medical treatment as recommended by the JNC VI. Among these hypertensives, measurement of plasma cholesterol was performed in only 61%, HDL-C/LDL-C in 26% and blood glucose in 51%. In the patients with dyslipidemia, LDL-C was measured in only 47%. In the 677 diabetic patients only 27% had a glycated hemoglobin measurement. The percentage of patients reaching target BP was 59% as regard DBP < 90 mmHg, 25% as regard SBP < 140 mmHg, and 23% reached both target values of BP. In addition, 30% of patients with dyslipidemia reached the target LDL-C as defined by French recommendations (ANAES 1996) and 30% of the diabetic patients reached the target value for glycemia recommended by ADA (1997). In 1999 in France, a minority of patients reaches the national or international recommended target values for blood pressure, glycemia and plasma LDL-cholesterol. In spite of that, French practitioners do not implement all the available diagnostic tools to improve the treatment of metabolic disorders in hypertensive patients. As a conclusion, to improve the prognosis of hypertensive patients, it is mandatory to raise the awareness of physicians about multiple risk factor management and help them implement the recommendations in their daily practice.

Adult↗
PubMed2000

Imagery neurons in the human brain.

Vivid visual images can be voluntarily generated in our minds in the absence of simultaneous visual input. While trying to count the number of flowers in Van Gogh's Sunflowers, understanding a description or recalling a path, subjects report forming an image in their "mind's eye". Whether this process is accomplished by the same neuronal mechanisms as visual perception has long been a matter of debate. Evidence from functional imaging, psychophysics, neurological studies and monkey electrophysiology suggests a common process, yet there are patients with deficits in one but not the other. Here we directly investigated the neuronal substrates of visual recall by recording from single neurons in the human medial temporal lobe while the subjects were asked to imagine previously viewed images. We found single neurons in the hippocampus, amygdala, entorhinal cortex and parahippocampal gyrus that selectively altered their firing rates depending on the stimulus the subjects were imagining. Of the neurons that fired selectively during both vision and imagery, the majority (88%) had identical selectivity. Our study reveals single neuron correlates of volitional visual imagery in humans and suggests a common substrate for the processing of incoming visual information and visual recall.

Action Potentials↗