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Biomedical subjects

M Kohl

Publications and source records attributed to M Kohl.

At least 37 records · Page 2Linked to original sources
PubMed1999

Mercury intoxication presenting with hypertension and tachycardia.

An 11 year old girl presented with hypertension and tachycardia. Excess urinary catecholamine excretion suggested phaeochromocytoma but imaging studies failed to demonstrate a tumour. Other symptoms included insomnia and weight loss, and she was found to have a raised concentration of mercury in blood and urine. Mercury intoxication should be considered in the differential diagnosis of hypertension with tachycardia even in patients presenting without the skin lesions typical of mercury intoxication and without a history of exposure.

Adrenal Gland Neoplasms↗
PubMed1999

Saline lavage with substitution of bovine surfactant in term neonates with meconium aspiration syndrome (MAS) transferred for extracorporeal membrane oxygenation (ECMO): a pilot study.

BACKGROUND: Meconium aspiration syndrome (MAS) is still a condition associated with a high mortality, and many patients require extracorporeal membrane oxygenation (ECMO) as rescue therapy. Beneficial effects of surfactant and perflubron lavage have been reported. However, pure surfactant supplementation has not been proven to be beneficial in the most severe forms of MAS. This study was performed to demonstrate an improvement in oxygenation in neonates transferred for ECMO and fulfilling ECMO criteria with a saline lavage and surfactant resupplementation. METHODS: Twelve newborns with MAS [gestational age 36-40 weeks, mean birth weight 3200 g, age 4-16 h, oxygenation index (OI) > 40] transferred for ECMO therapy were treated with saline lavage (5-10 cm3/kg body weight, as long as green colored retrieval was observed) and resupplementation with bovine surfactant (Alveofact, Boehringer, Ingelheim, Germany). The OI at admission and 3 h after this procedure was compared using the t-test for paired samples. ECMO was available as rescue therapy at all times. RESULTS: The OI decreased from 49.4 (SD +/- 13.3) to 27.4 (SD +/- 7.3), P < 0.01. The decrease was sustained in nine patients, three patients required ECMO and all patients survived. CONCLUSIONS: As MAS is a condition with parenchymal damage, pulmonary hypertension and obstructive airway disease, no simple causative therapy is possible. Surfactant application after removal of meconium by extensive lavage is feasible as long as 16 h after birth even in infants considered for ECMO therapy; it might reduce the necessity of ECMO.

Journal Article↗
PubMed1999

Oxygenation and lung morphology in a rabbit pediatric ARDS- model under high peak pressure ventilation plus nitric oxide and surfactant compared with veno-venous ECMO.

UNLABELLED: The aim of the study is to investigate which of two treatment options of saline lavage induced ARDS in rabbits is better in terms of oxygenation and prevention of barotrauma: combined high peak pressure ventilation with surfactant administration and inhaled nitric oxide or veno-venous ECMO combined with low peak inspiratory pressure ventilation. MATERIALS AND METHODS: After saline lavage (10 cc/kg repeated as long as foamy retrieval was observed) two combined therapeutic strategies were examined: ventilation with high inspiratory pressures (35 cm H2O) with additional exogenous surfactant administration (100 mg/kg) and inhaled nitric oxide (10 PPM) (n=5, group 1) and low inspiratory pressure (20 cm H2O) ventilation under veno-venous ECMO support (n=5, group 2). The FiO2 was maintained at 1.0 in both groups. The paO2/FiO2 ratio was calculated in 30 minute intervals for 4 hours. After that the animals were sacrificed and the lungs examined macro- and microscopically. Aeration was described in a semiquantitative method using the alveolar expansion index. Oxygenation in group 1 was significantly better than in group 2, it increased significantly after surfactant but not after additional nitric oxide administration. However, the lungs in group 1 showed severe signs of baro/ergotrauma (Hyaline membranes, air leaks, infiltration of polymorphonuclear (PMN) granulocytes and macrophages, break down of alveolar capillary membranes) after 4 hrs of combined therapy, whereas the lungs in group 2 appeared normal. Adding surfactant and NO to a high tidal volume ventilation improved oxygenation, but did not prevent baro/ergotrauma. Ventilation with low inspiratory pressures combined with ECMO caused little baro/ergotrauma but adequate oxygenation could not be achieved, probably due to anatomical features of the rabbit which do not allow appropriate blood flow within the ECMO-circuit.

Animals↗
PubMed1998

Characterization of the pulse signal over the human head by near infrared spectroscopy.

In this study we examine and describe the changes in the hemoglobin oxygenation and the Cytochrome-C-Oxidase redox state that are caused by the pulsatile character of the blood flow in the human head. We used near-infrared spectroscopy (NIRS) in combination with simultaneously recorded ECG and Transcranial Doppler sonography of arteries and veins and show that there is a distinct time lag between heart activity, arterial blood flow, hemoglobin concentration as measured by NIRS and venous blood flow. NIRS has intensively been used to measure functional activation of the brain. When measuring cortical activation by functional stimulation, the pulse signal interferes with the acquired activation signal. We demonstrate that a filter algorithm can remove the pulse artifact and therefore improves the data acquired during visual stimulation.

Adult↗
PubMed1998

Genetic rearrangements in the pathogenicity locus of Clostridium difficile strain 8864--implications for transcription, expression and enzymatic activity of toxins A and B.

The pathogenicity locus (PaLoc) of Clostridium difficile isolate 8864 was investigated to locate genetic rearrangements that would explain the exceptional pathogenicity of this particular isolate. Two major changes were defined: an insertion of 1.1 kb between the two genes tcdA and tcdE, coding for the enterotoxin and an accessory protein of unknown function, respectively, and a deletion of 5.9 kb encompassing the 3' ends of tcdA and tcdC. Transcription of the tcdA-E genes is severely affected by both rearrangements, explaining the demonstrated complete lack of TcdA polypeptide. We present a model of coordinate, growth-related transcription of the tcdA-E genes that confirms our previous findings in strain 10463. Recombinant TcdA-8864 had UDP-glucose-glucosyltransferase activity, proving that the N-terminal 698 amino acids of the polypeptide represent the catalytic domain. However, this truncated TcdA molecule lacks a ligand and translocation domain. To assess the catalytic domain of TcdB-8864, the sequence of the 5' end of its gene was determined. TcdB-8864 shows high homology to TcdB-1470 but lower homology to TcdB-10463 within this domain. This fits well with the altered glucosylation specificity of TcdB-8864 (Rac1, Rap2 and Ra1). Having defined the variations of transcription, expression and enzymatic activity of toxins A and B, implications for the pathogenic potential of strain 8864 are discussed.

Amino Acid Sequence↗
PubMed1998

Determination of the wavelength dependence of the differential pathlength factor from near-infrared pulse signals.

For the calculation of changes in oxyhaemoglobin, deoxyhaemoglobin and the redox state of cytochrome-c-oxidase from attenuation data via a modified Beer-Lambert equation the wavelength dependence of the differential pathlength factor (DPF(lambda)) has to be taken into account. The DPF, i.e. the ratio of the mean optical pathlength and the physical light source-detector separation at each wavelength, determines the crosstalk between the different concentrations and is therefore essential for a sensitive detection of chromophore changes. Here a simple method is suggested to estimate the wavelength dependence of the DPF(lambda) from pulse-induced attenuation changes measured on the head of adult humans. The essence is that the DPF is the ratio of the attenuation changes over absorption coefficient changes, and that the spectral form of the pulse correlated absorption coefficient change can be assumed to be proportional to the extinction coefficient of blood. Indicators for the validity of the DPF(lambda) derived for wavelengths between 700 and 970 nm are the stability of the calculated haemoglobin and cytochrome signals with variations of the wavelength range included for their calculation and its overall agreement with the data available from the literature.

Adult↗
PubMed1998

Near-infrared optical properties of ex vivo human skin and subcutaneous tissues measured using the Monte Carlo inversion technique.

The absorption and transport scattering coefficients of caucasian and negroid dermis, subdermal fat and muscle have been measured for all wavelengths between 620 and 1000 nm. Samples of tissue 2 mm thick were measured ex vivo to determine their reflectance and transmittance. A Monte Carlo model of the measurement system and light transport in tissue was then used to recover the optical coefficients. The sample reflectance and transmittance were measured using a single integrating sphere 'comparison' method. This has the advantage over conventional double-sphere techniques in that no corrections are required for sphere properties, and so measurements sufficiently accurate to recover the absorption coefficient reliably could be made. The optical properties of caucasian dermis were found to be approximately twice those of the underlying fat layer. At 633 nm, the mean optical properties over 12 samples were 0.033 mm(-1) and 0.013 mm(-1) for absorption coefficient and 2.73 mm(-1) and 1.26 mm(-1) for transport scattering coefficient for caucasian dermis and the underlying fat layer respectively. The transport scattering coefficient for all biological samples showed a monotonic decrease with increasing wavelength. The method was calibrated using solid tissue phantoms and by comparison with a temporally resolved technique.

Biophysical Phenomena↗
PubMed1998

Effect of temperature on the optical properties of ex vivo human dermis and subdermis.

The effect of temperature on the optical properties of human dermis and subdermis as a function of near-infrared wavelength has been studied between 25 degrees C and 40 degrees C. Measurements were performed ex vivo on a total of nine skin samples taken from the abdomen of three individuals. The results show a reproducible effect of temperature on the transport scattering coefficient of dermis and subdermis. The relative change of the transport scattering coefficient showed an increase for dermis ((4.7+/-0.5) x 10(-3) degrees C(-1)) and a decrease for subdermis ((-1.4+/-0.28) x 10(-3) degrees C(-1)). Note that the magnitude of the temperature coefficient of scattering was greater for dermis than subdermis. A reproducible effect of temperature on the absorption coefficient could not be found within experimental errors. System reproducibility in transport scattering coefficient with repeated removal and repositioning of the same tissue sample at the same temperature was excellent at +/-0.35% for all measurements. This reproducibility enabled such small changes in scattering coefficient to be detected.

Biophysical Phenomena↗
PubMed1998

Value of myocardial hypoxia markers (creatine kinase and its MB-fraction, troponin-T, QT-intervals) and serum creatinine for the retrospective diagnosis of perinatal asphyxia.

Neonatal asphyxia is a major topic of neonatal research. However, no clear-cut physiologic parameters exist which enable an early identification of neonatal infants who are either at risk to develop brain damage or posthypoxic heart failure. Parameters indicating dysfunction of the heart and kidneys as creatinine and creatinine kinase have been evaluated. In our study, 47 asphyxiated infants (umbilical artery pH < 7.18 and either a 1-min Apgar score < 4 or a 5-min Apgar score < 7) were compared to 27 nonasphyxiated controls regarding significant differences in creatinine, creatinine kinase, its MB fraction, and a newly introduced myocardial hypoxia indicator -- troponin T -- to establish the value of these parameters in the retrospective diagnosis of asphyxia. Further we evaluated two subsets of these 47 asphyxiated infants with either subsequent signs of encephalopathy (seizures) or heart failure. Creatinine, creatinine kinase and troponin T were significantly elevated in asphyxiated infants compared with controls; no differences were found in creatinine kinase and its MB fraction. In asphyxiated infants with heart failure, troponin T was significantly higher than in the other asphyxiated infants. However, none of the parameters studied was significantly different in patients with brain damage compared with asphyxiated infants without neurological sequelae. Troponin T has a high positive predictive value in the postnatal diagnosis of asphyxia. The diagnostic power of troponin T equals that of creatinine. However, troponin T is more sensitive in the identification of infants with asphyxia and cardiocirculatory failure than creatinine. Creatinine kinase and its MB fraction have no diagnostic value.

Asphyxia↗
PubMed1997

Comparison of vancomycin and teicoplanin for prophylaxis of sepsis with coagulase negative staphylococci (CONS) in very low birth weight (VLBW) infants.

A prospective randomized study was performed to evaluate the efficacy of a low dose (5 mg/kg/day bid) vancomycin compared with a low dose (5 mg/kg/day once daily) teicoplanin therapy to prevent CONS sepsis in VLBW-infants. All infants received this therapy after their 4th day of life or after an eventual therapy of early onset sepsis as long as an i.v. line was in place or 1500 g body weight. Twenty-seven infants were treated with vancomycin (birth weight 1103 +/- 286 g, gest. age 28.8 +/- 1.9 weeks), 28 with teicoplanin (birth weight 1133 +/- 226 g, gest. age 29.04 +/- 2.2 weeks). The infants were observed for clinical and laboratory signs of sepsis. On day 4 of therapy and every 3rd day during therapy serum creatinine levels, tracheal aspirates, stool cultures and vancomycin/teicoplanin peak and trough levels were obtained. We could not detect any case of blood culture positive sepsis and 1 case of suspected sepsis (neg. blood cultures) in both groups, as compared with a former CONS sepsis rate of 24% in our institution's VLBW infants without antibiotic prophylaxis. Nine patients in the vancomycin and five in the teicoplanin group had tracheal colonization with CONS. In both groups peak and trough levels of antibiotics were in the bactericidal range. Serum creatinine was not normal in both groups. We conclude that teicoplanin is preventing CONS sepsis as well is vancomycin. The minimal inhibitory concentrations of both antibiotics against grampositive isolates in units using this strategy have to be observed carefully to detect emerging resistance.

Anti-Bacterial Agents↗
PubMed1996

Comparison of circulating phagocyte oxidative activity measured by chemiluminescence in whole blood and isolated polymorphonuclear leukocytes.

The generation of reactive oxygen species (ROS) was measured by chemiluminescence (CL) in whole blood and isolated polymorphonuclear leukocytes (PMNLs) in 113 subjects. There were no differences in ROS production in males and females, smokers and non-smokers and no age dependency. A significant correlation was found between whole blood CL parameters and between parameters derived from isolated cells, but there was no correlation when these parameters were compared using isolated PMNLs and whole blood. Variations in serum lipid levels did not account for the variability of CL parameters in blood or PMNLs. Both methodologies had the same validity in demonstrating priming of phagocytes. Zymosan-induced CL was more sensitive in detecting distinct functional states of phagocytes than FMLP-induced CL.

Adult↗
PubMed1995

Endothelin-1 does not prime polymorphonuclear leukocytes for enhanced production of reactive oxygen metabolites.

UNLABELLED: The in vitro effect of endothelin-1 (ET-1) on the capacity of polymorphonuclear leukocytes (PMNLs) to generate reactive oxygen species (ROS) was investigated. Human PMNLs were separated from healthy volunteers and preincubated for 10 min. at 37 degrees C with varying concentrations (10(-7)-10(-12) M) of ET-1. After subsequent stimulation with FMLP (10(-7) M) or opsonized zymosan (0.5 mg/ml) the intra- and extracellular generation of ROS was assessed by luminol-amplified chemiluminescence, superoxide radical (.O2-) and hydrogen peroxide (H2O2) production. RESULTS: ET-1 alone failed to stimulate ROS generation. Neither the capacity for extracellular generation of oxygen metabolites nor the production of ROS with an intracellular origin was changed after preincubation of PMNLs with ET-1. ET-1 did not cause a shift of the .O2-/H2O2 production ratio after stimulation of PMNLs with FMLP. These findings suggest that ET-1 in vitro does not prime human PMNLs for enhanced production of ROS.

Endothelins↗
PubMed1995

The influence of glucose concentration upon the transport of light in tissue-simulating phantoms.

The effect of glucose upon the transport of light in tissue-simulating phantoms is shown and its possible application for non-invasive glucose monitoring in diabetic patients is discussed. The aim of this paper is to investigate the physical background of this effect. The presence of glucose in an aqueous solution increases its refractive index and therefore has an influence upon the scattering properties of particles suspended in solution. Experimental data on the effect of glucose upon the scattering coefficient and the phase function of aqueous suspensions of spherical polystyrene particles are presented for near-infrared wavelengths and compared to values predicted by Mie theory. The subsequent effect upon light transport in multiple scattering, tissue-simulating phantoms is demonstrated experimentally in a slab geometry and theoretically by applying diffusion theory. It is furthermore shown that optional measurements in the frequency domain allow changes of absorption and scattering coefficient to be separately determined. The possible magnitude of this glucose effect in tissue in vivo is discussed.

Glucose↗