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Biomedical subjects

U Frey

Publications and source records attributed to U Frey.

At least 37 records · Page 2Linked to original sources
PubMed2001

Hyperferritinemia as indicator for intravenous immunoglobulin treatment in reactive macrophage activation syndromes.

The underlying mechanisms of reactive macrophage activation syndromes (rMAS) are not understood in detail, and there is no specific treatment. This observational study was prompted by intravenous immunoglobulin (IVIG), dramatically halting two distinct rMAS episodes in the same patient. We evaluated the potential benefits of IVIG administration in treating fulminant rMAS and the usefulness of monitoring serum ferritin levels as an indication for emergency treatment with IVIG. Ten females and 10 males experiencing 22 episodes of rMAS were recruited on the basis of serum ferritin levels >or=10,000 microg/l and/or direct evidence of haemophagocytosis in 11 intensive care units in secondary and tertiary care hospitals in Switzerland between October 1993 and May 2000. In individual patients, serially measured ferritin was closely related to disease activity. Abrupt increases of up to >100,000 microg/l could be observed within hours. Rapid and profound beneficial effects of emergency IVIG treatment were seen in 12 episodes of rMAS accompanied by a prompt decrease of serum ferritin. IVIG produced partial or delayed improvements in 5 patients. No apparent effects were seen in 5 patients. IVIG was only successful if started early during the ferritin run-up to peak values. In conclusion, IVIG is effective in at least a subgroup of adult rMAS when started at the beginning of the macrophage activation process. The monitoring of serum ferritin levels might be helpful in detecting macrophage activation in order to commence IVIG treatment early enough.

Adolescent↗
PubMed2001

Clinical applications of infant lung function testing: does it contribute to clinical decision making?

Infant lung function testing is important in clinical research and recent standardisation efforts have enabled measurements to be made in infants in different laboratories throughout the world. Thus, the theoretical conditions are now fulfilled for use of these techniques in clinical practice. This review discusses the usefulness of various infant lung function techniques in a clinical setting and their potential present or future clinical application. It will focus on the role of infant lung function in the clinical management of infants with respiratory disease.

Age Factors↗
PubMed2001

[Frozen shoulder--MRI-verified continuous block of suprascapular nerve].

Suprascapular nerve block may provide sufficient analgesia in painful immobilisation of the shoulder joint. In the following case report a 41 year old male presenting with adhesive capsulitis (frozen shoulder) has been treated successfully by performing continuous delivery of local anesthetics to the suprascapular nerve via catheter. The location of the catheter has been verified using MRI examination. Pain relief was quantified by using visual analog scale (VAS 1 - 10) and showed decretion from VAS 8 - 10 pre treatment to VAS 1 - 2 after insertion of the catheter and throughout five days of intensive physiotherapy, respectively. The technique of catheterization using a nerve stimulator and alternative peripheral nerve blocks are discussed. In summary, continuous suprascapular nerve block offers an advantageous alternative for pain relief in patients with frozen shoulder. It may provide better pain control and earlier discharge in the ambulatory setting than repetetive single dose blocks.

Adult↗
PubMed2001

[Psychoactive mushrooms - an update].

Psychoactive mushrooms ("magic mushrooms") have been consumed in northern Europe since the late seventies. Recently, the use of hallucinogenic fungi has become popular among young people again. In autumn, psychoactive mushrooms can be collected from their natural habitats throughout Europe. Some species are cultivated in the Netherlands and are sold in "smart-shops" or via Internet. In Germany, dried specimens are sold as "Duftkissen" (aroma pads). The article reviews the common psychoactive species and illustrates medical risks.

Agaricales↗
PubMed2001

Cellular processes in the amygdala: gates to emotional memory?

The amygdala is considered a core structure of the so-called limbic system and has been implicated in a variety of functions, including emotional interpretation of sensory information, emotional arousal, emotional memory, fear and anxiety, and related clinical disorders. Despite the clinical and functional importance of the amygdala, it is only recently that some general principles of intra-amygdaloid mechanisms of signal processing that are relevant for fear behavior and memory have emerged from behavioral, anatomical, electrophysiological, and neurochemical studies performed in the amygdala of various mammalian species in vivo, in situ and in vitro.

Journal Article↗
PubMed2001

Analysis of the harmonic content of the tidal flow waveforms in infants.

The aim of this study was to examine whether the spectral characteristics of tidal flow waveform reflect the interaction between the control of breathing and lung mechanics in 10 healthy infants (H), 10 infants with a history of wheezing disorders (W), and 10 infants with chronic lung disease (CLD). From the flow waveform, we calculated a shape index, the harmonic distortion (k(d)), which quantifies the extent to which a periodic signal deviates from a sine wave. The k(d) of the entire tidal flow waveform did not significantly discriminate between diagnostic groups. However, k(d) was sensitive to maturation: it increased from 0.26 at 1 mo to 0.37 at 6 mo of age (P < 0.002). Furthermore, the frequency (f) spectra of the flow (V) amplitudes between 0.13 and 10 Hz followed a power law: V(f) approximately f(-s), where s (slope) is the exponent in the power law. The exponent of the healthy infants s(H) was 4.24 [95% confidence interval (CI) = 0.2] at 1 mo, 4.39 (CI = 0.16) at 6 mo, and 4.35 (CI = 0.19) at 12 mo and not significantly changing with age. The mean value of s(W) was marginally lower (4.09 +/- 0.28; P < 0.05) than that of s(H). The mean s(CLD) was significantly lower (3.04 +/- 0.31; P < 0.001). Lower values of s and higher values of k(d) indicate an increased complexity of the feedback mechanisms determining tidal flow waveform and may be associated with disease.

Algorithms↗
PubMed2001

An isoflow-volume technique for assessing airway dynamics in children and adults.

BACKGROUND: We propose a new approach to the measurement of small airway function as an alternative to recordings of maximal expiratory flow-volume (MEFV) curves. OBJECTIVES: A newly developed technique to record isoflow-volume (IFV) curves to be tested against maximal respiratory flow curves. METHODS: An isoflow whistle (IFW; Iflopen) measures the length of a constant expiration after full inspiration. The note of the whistle enables a subject to generate an even expiration, and the isoflow maintenance times at 1 l x s(-1) (IFMT1) and 2 l x s(-1) (IFMT2) are recorded. The accuracy and reproducibility of the IFV technique were evaluated in 17 healthy adults (age 17-55 years) and in 14 asthmatic children (age 6-14 years). Comparisons with standard lung function parameters, such as forced expiratory volume in 1 s (FEV1), maximal expiratory flow at 50% (MEF50) and 25% (MEF25) vital capacity and peak expiratory flow (PEF), obtained with a Wright Peakflow Meter were undertaken in 102 healthy (aged 8-14 years) and 101 asthmatic children (aged 6-17 years). A bronchial challenge test was performed in 13 asthmatic children. RESULTS: The expired volume measured by the IFW showed an acceptable agreement with that of a pneumotachograph (mean error of 4.32% for IFMT1 and 5.93% for IFMT2). In healthy and in asthmatic children, the correlations between FEV1 and IFMT1 or IFMT2 (r = 0.92 and 0.94, respectively) were found to be greater than that between FEV1 and PEF (r = 0.68). During bronchial challenge tests in 13 asthmatic children, the FEV1 decreased to 69% of baseline and IFMT1 to 58% of baseline. CONCLUSIONS: The IFV technique accurately measured airway obstruction and closely followed changes in standard parameters of the MEFV curve.

Adolescent↗
PubMed2001

Evaluation of the interrupter technique in healthy, unsedated infants.

The interrupter technique may be used to monitor respiratory resistance and does not require active patient cooperation, but has yet to be applied in unsedated, spontaneously breathing infants. The aim of this study was to determine if the interrupter technique is feasible in spontaneously breathing infants and to investigate the influence of facemask types and analysis techniques on the interrupter resistance (Rint). Rint was measured in 14 healthy, unsedated, sleeping infants (aged 38.4 (31-56) days (mean (range)). Paired measurements were made using large volume, compliant (Mcomp) and small volume, rigid (Mrigid) facemasks. Flow and pressure were measured at the airway opening prior to- and following a brief airway occlusion (500 ms). Rint was calculated using four previously reported analysis techniques. Rint could be measured in all infants. Mcomp, independent of the analysis method significantly underestimated Rint (p<0.001). The variability and magnitude of Rint were significantly influenced by the choice of analysis method. The conclusion is that the interrupter technique is feasible in spontaneously breathing, unsedated infants. Equipment design and analysis method significantly influences interrupter resistance. Studies standardizing equipment and identifying the most appropriate analysis technique in this age group are needed.

Airway Resistance↗
PubMed2001

The infant lung function model: a mechanical analogue to test infant lung function equipment.

To facilitate international multicentre studies and quality control of infant pulmonary function measurements, the European Respiratory Society-American Thoracic Society (ERS-ATS) working group for infant lung function testing aims to develop specifications for standardized infant lung function equipment and software. However, a standardized test device is also needed to test whether existing infant lung function equipment is able to meet these requirements. The authors have built a "mechanical model baby" consisting of a linear pump which can reproduce prerecorded tidal flow waveforms with a precision of 0.5% (full stroke), enabling the simulation of tidal and forced flow patterns. This linear pump can be connected to a series of copper lung volumes (range 50-300 mL) with known time constants, so that lung volumes can be reproduced with a precision of +/-1% at frequencies 10-120bpm. Five airflow resistors were built using sinter material. When assessed using flows 0-300 mL.s(-1) all resistors showed a quasilinear pressure/ flow relationship, with slopes 1.0-5.6 kPa.L(-1).s. These resistances could be reproduced with a precision of +/-2.5%. The infant lung model can also be used to assess frequency responses of infant lung function equipment, since the pump is capable of delivering low amplitude volumes up to 20 Hz in a pseudorandom noise manner. In summary, based on error estimations, this infant lung model is able to test whether or not infant lung function equipment meets the requirements suggested by the European Respiratory Society-American Thoracic Society standardization group, that is: flow measurements within +/-2.5%, volume and resistance measurements within +/-5%, frequency response: magnitude attenuation <+/-10% and phase shift <+/-3 degrees at 10 Hz.

Airway Resistance↗
PubMed2001

Assessment of an infant whole-body plethysmograph using an infant lung function model.

In order to facilitate international multicentre studies and improve the quality control of infant pulmonary function measurements, the European Respiratory Society-American Thoracic Society Task Force for infant lung function testing has recently developed specifications for standardized infant lung function equipment and software. A mechanical infant lung model analogue has been developed to assess whether infant lung function equipment is able to meet these requirements. However, the practical testing of infant lung function equipment using such models is highly complex because of the need to use very small pressure and flow changes, and the numerous potentially confounding factors associated with both the design of the device and the testing procedure. The aim of this study was to determine whether the infant lung model is capable of assessing the overall function of an whole-body infant- plethysmograph, using the only infant plethysmograph that was commercially available at the time as an example. The mechanical characteristics of the model such as vibrations or noise did not disturb the delicate plethysmographic measurements and thereby allowed a reliable assessment of the system. A series of tests revealed that the plethysmograph was able to measure airway resistance 1-3.5 kPa.L(-1).s with an accuracy of +/-2.5% and lung volumes 75-300 mL with an accuracy of +/-2.5% under in vitro conditions. To conclude, the infant lung model is a useful means of assessing the overall in vitro performance of infant whole-body plethysmographs, but thermal, mechanical and frequency response characteristics of such a device must be taken into account when interpreting the results of such assessments.

Airway Resistance↗
PubMed2000

Interaction of the G protein beta 3 subunit T825 allele and the IRS-1 Arg972 variant in type 2 diabetes.

BACKGROUND: Type 2 diabetes mellitus is a common late-onset disease with a strong genetic component. It is characterized by insulin resistance which results from alterations in insulin signal transduction. The G protein beta 3 subunit 825T allele was recently found to be associated with hypertension and obesity which makes it a sensible candidate gene for type 2 diabetes. METHODS: In a case-control study on 320 male patients and 962 male healthy controls we investigated the association of two candidate genes with diabetes, i.e. (i) the GNB3 825T allele, associated with a G protein beta 3 subunit splice variant and enhanced intracellular signal transduction, and (ii) the insulin receptor substrate-1 (IRS-1) 972Arg variant, which encodes a protein variant associated with cellular insulin resistance. RESULTS: The GNB3 825T allele and the IRS-1 972Arg variant were significantly associated with diabetes (odds ratios for either variant 1.4 1.8). Odds ratios were 3 4 in males carrying both alleles. CONCLUSIONS: The results document an association of a hypertension susceptibility gene with type 2 diabetes which may partially explain the frequent coexistence of both disorders.

Adult↗
PubMed2000

Speciation and kinetics related to catalytic carbonylation in the presence of cis-[Ir(CO)2I2]P(C6H5)4 under CO and H2 pressures.

The differences in the reactivities of the square-planar complexes cis-[Rh(CO)2I2]- (1) and cis-[Ir(CO)2I2]- (2), involved in the catalytic carbonylation of olefins, are investigated, with P(C6H5)4+ as the counterion, by ambient- and high-pressure NMR and IR spectroscopy. Under an elevated pressure of CO, 1 and 2 form the [M(CO)3I] complexes with the equilibrium constants KIr approximately 1.8 x 10(-3) and KRh approximately 4 x 10(-5). The ratio KIr/KRh close to 50 shows that, under catalytic conditions (a few megapascals), only complex 1 remains in the anionic form, while a major amount of the iridium analogue 2 is converted to a neutral species. The oxidative addition reactions of HI with 1 and 2 give two monohydrides of different geometries, mer,trans-[HRh(CO)2I3]- (3) and fac,cis-[HIr(CO)2I3]- (4), respectively. Both hydrides are unstable at ambient temperature and form, within minutes for Rh and within hours for Ir, the corresponding cis-[M(CO)2I2]- (1 or 2) and [M(CO)2I4]- (5 or 6) species and H2. When an H2 pressure of 5.5 MPa is applied to a nitromethane solution of complex 2, ca. 50% of 2 is transformed to cis-dihydride complexes. The formation of cis,cis,cis-[IrH2(CO)2I2]- (8a) is followed by intermolecular rearrangements to form cis,trans,cis-[IrH2(CO)2I2]- (8b) and cis,cis,trans-[IrH2(CO)2I2]- (8c). A small amount of a dinuclear species, [Ir2H(CO)4I4]x- (9), is also observed. The formation rate constants for 8a and 8b at 262 K are k1(262) = (4.42 +/- 0.18) x 10(-4) M-1 s-1, k-1(262) = (1.49 +/- 0.07) x 10(-4) s-1, k2(262) = (2.81 +/- 0.04) x 10(-5) s-1, and k-2(262) = (5.47 +/- 0.16) x 10(-6) s-1. The two equilibrium constants K1(262) = [8a]/([2][H2]) = 2.97 +/- 0.03 M-1 and K2(262) = [8b]/[8a] = 5.13 +/- 0.10 show that complex 8b is the thermodynamically stable addition product. However, no similar H2 addition products of the rhodium analogue 1 are observed. The pressurization with H2 of a solution containing 2 and 6 give the monohydride 4, the dihydrides 8a and 8b, the dinuclear complex 9, and the two new complexes [Ir(CO)2I3] (10) and [HIr(CO)2I2] (11). The reactions of the iridium complexes with H2 and HI are summarized in a single scheme.

Journal Article↗
PubMed2000

Mechanism of CO exchange on cis-[M(CO)2X2]- complexes (M=Rh,Ir;X=Cl, Br, or I).

The CO exchange on cis-[M(CO)2X2]- with M = Ir (X = Cl, la; X = Br, 1b; X = I, 1c) and M = Rh (X = Cl, 2a; X = Br, 2b; X = I, 2c) was studied in dichloromethane. The exchange reaction [cis-[M(CO)2X2]- + 2*CO is in equilibrium cis-[M(*CO)2X2]- + 2CO (exchange rate constant: kobs)] was followed as a function of temperature and carbon monoxide concentration (up to 6 MPa) using homemade high gas pressure NMR sapphire tubes. The reaction is first order for both CO and cis-[M(CO)2X2]- concentrations. The second-order rate constant, k2(298) (=kobs)[CO]), the enthalpy, deltaH*, and the entropy of activation, deltaS*, obtained for the six complexes are respectively as follows: la, (1.08 +/- 0.01) x 10(3) L mol(-1) s(-1), 15.37 +/- 0.3 kJ mol(-1), -135.3 +/- 1 J mol(-1) K(-1); 1b, (12.7 +/- 0.2) x 10(3) L mol(-1) s(-1), 13.26 +/- 0.5 kJ mol(-1), -121.9 +/- 2 J mol(-1) K(-1); 1c, (98.9 +/- 1.4) x 10(3) L mol(-1) s(-1), 12.50 +/- 0.6 kJ mol(-1), -107.4 +/- 2 J mol(-1) K(-1); 2a, (1.62 +/- 0.02) x 10(3) L mol(-1) s(-1), 17.47 +/- 0.4 kJ mol(-1), -124.9 +/- 1 J mol(-1) K(-1); 2b, (24.8 +/- 0.2) x 10(3) L mol(-1) s(-1), 11.35 +/- 0.4 kJ mol(-1), -122.7 +/- 1 J mol(-1) K(-1); 2c, (850 +/- 120) x 10(3) L mol(-1), s(-1), 9.87 +/- 0.8 kJ mol(-1), -98.3 +/- 4 J mol(-1) K(-1). For complexes la and 2a, the volumes of activation were measured and are -20.9 +/- 1.2 cm3 mol(-1) (332.0 K) and -17.2 +/- 1.0 cm3 mol(-1) (330.8 K), respectively. The second-order kinetics and the large negative values of the entropies and volumes of activation point to a limiting associative, A, exchange mechanism. The reactivity of CO exchange follows the increasing trans effect of the halogens (Cl < Br << I), and this is observed on both metal centers. For the same halogen, the rhodium complex is more reactive than the iridium complex. This reactivity difference between rhodium and iridium is less marked for chloride (1.5: 1) than for iodide (8.6:1) at 298 K.

Journal Article↗
PubMed2000

Elevation of soluble Fas and soluble Fas ligand in reactive macrophage activation syndromes.

Derailed T-cell activation can give rise to life-threatening macrophage activation, the final common pathway of the different forms of reactive macrophage activation syndromes (rMAS). Besides inappropriate activation of the immune system, impaired termination of immune responses might be another mechanism leading to rMAS. The Fas (CD95)/Fas ligand (CD95 ligand) system functions in turning off immune responses by executing activation-induced cell death (AICD). Soluble Fas (sFas) and Fas ligand (sFasL) can interfere with their corresponding membrane-bound counterparts, qualifying them as potential parameters of impaired immune termination. Hence, sFas and sFasL were analyzed in sera of rMAS patients. We show that soluble Fas/CD95 (sFas) is elevated >2 SD over the mean of controls in all 8 rMAS episodes studied (mean 12.08 +/- 6.12 ng/mL, range 3.7-20.2; controls 2.46 +/- 0.49, range 1.5-2.9). sFasL was detected during five rMAS episodes (0.70 +/- 0.49 ng/mL, range 0.16-1.28; controls all below the limit of detection of 0.1). In addition, both parameters decrease during convalescence, reflecting clinical evolution. In conclusion, sFas seems to be consistently elevated during acute rMAS. sFasL is detected only in a subgroup of our adult rMAS patients extending the recent finding of sFasL elevation in a majority of children with macrophage activation syndromes (Hasegawa et al. Blood 1998;91(8):2793-2799). By interfering with AICD, sFas and sFasL might contribute to the pathogenesis of at least a subset of rMAS.

Adult↗
PubMed2000

Moment ratio analysis of multiple breath nitrogen washout in infants with lung disease.

Measurement of lung volumes at end expiratory level and assessment of ventilation inhomogeneity is important for respiratory management in infants with lung disease. This study compared multiple breath nitrogen washout was compared with body plethysmography to measure functional residual capacity in infants and assessed ventilation inhomogeneity using mean dilution numbers and alveolar based gas dilution numbers. Measurements were performed in 23 infants with lung disorders, eleven had wheezing bronchitis, four bronchopulmonary disease, and eight cystic fibrosis. Mean age was 11.2+/-5.8 months. Functional residual capacity of nitrogen washout (29.8+/-11.4 mL x kg(-1)) was significantly (p<0.05) lower than the plethysmographically measured functional residual capacity (40.3+/-11.4 mL x kg(-1)). Tidal volumes before nitrogen washout (90.4+/-35.1 mL) were significantly larger than at the end of the washout (72.2+/-26.9 mL). Alveolar based gas dilution numbers (6.7+/-2.3) were significantly lower (p<0.001) than mean dilution numbers (10+/-5.7). Functional residual capacity determination by nitrogen washout and plethysmography in infants with lung disease showed evidence of air trapping and ventilation inhomogeneity. Ventilation inhomogeneities are best described by alveolar based dilution numbers, since rebreathing of 100% oxygen changes ventilation pattern.

Breath Tests↗
PubMed2000

Specifications for equipment used for infant pulmonary function testing. ERS/ATS Task Force on Standards for Infant Respiratory Function Testing. European Respiratory Society/ American Thoracic Society.

The aim of this position paper is to define minimal performance criteria for the separate items comprising equipment used to measure respiratory function in infants together with overall performance criteria for the assembled pieces of such equipment. These guidelines cover numerous aspects including: 1) safety, 2) documentation and maintenance of equipment, 3) physical characteristics of mechanical parts and signal transducers, and 4) data acquisition. Further, validation procedures for individual components as well as for the integrated equipment are recommended. Adherence to these guidelines should ensure that infant lung function measurements can be performed with an acceptable degree of safety, precision and reproducibility. They will also facilitate multicentre collection of data and performance of clinical investigations. Manufacturers of infant respiratory function equipment should make every effort to comply with these guidelines, which represent the current standards of paediatric health professionals in this field.

Data Collection↗
PubMed2000

Alterations in airway wall properties in infants with a history of wheezing disorders.

Airway diameter and airway wall mechanics (compliance) are important determinants of flow limitation and wheezing. We have previously used the high-speed interrupter technique (HIT) to measure input impedance (Zin) in infants at frequencies up to 900 Hz, including antiresonance phenomena, which are known to be related to wave propagation velocity, and have shown that the frequency at which the first antiresonance occurs (f(ar,1)) is a function of airway wall compliance. We aimed to determine whether f(ar,1) (and thus airway wall compliance) was different in infants with a history of wheezing disorders. We compared 23 asymptomatic infants (aged 36 to 81 wk) with a history of wheezing with an age-matched group of 19 healthy control infants. We found that f(ar,1) was significantly lower in infants with wheezing disorders than in the control group (p < 0. 005), implying differences in airway wall compliance, even when they were clinically asymptomatic. Developmental differences in airway wall mechanics may be important in the pathogenesis of wheezing disorders or, alternatively, alterations in airway wall mechanics might be a consequence of postinflammatory remodeling.

Airway Resistance↗