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Biomedical subjects

G Schwarz

Publications and source records attributed to G Schwarz.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Preoperative diagnosis of a patent foramen ovale: rational use of transthoracic and transesophageal contrast echocardiography].

BACKGROUND: The detection or ruling out of a patent foramen ovale (PFO) can be determined noninvasively by contrast echocardiography (CE). The transesophageal technique is superior to the transthoracic technique regarding sensitivity, whereas the specificity of both methods is equally high. This prospective study shows the rational use of transesophageal CE for the detection of a PFO, in patients without cardiovascular disorders. METHODS: 165 patients (92 female, 73 male, age 48 +/- 18 years) with planned neuro-surgery in a sitting position, underwent CE to rule out a PFO. If the CE was positive, an alternative position was selected in order to avoid a paradoxical air embolism. RESULTS: Initially, a transthoracic CE was performed in all patients resulting in 21 patients (13%) being positive and 39 patients (24%) being negative by sufficient image quality. A transesophageal CE was performed in 96 of the remaining 105 patients (63%). Here, further 25 patients showed a positive CE in the sense of a PFO. The combined use of transthoracic and transesophageal CE revealed a PFO in 46 of 165 patients (28%). CONCLUSION: The use of both, transthoracic and transesophageal CE is an efficient approach to the preoperative detection of a PFO in the sense of quality and economics. Depending upon the image quality, the use of a transesophageal examination could be avoided in one third of the cases.

Adolescent↗
PubMed1998

[Rhinomanometric studies of thermal modification of nasal ventilation].

Elevation of nasal resistance has been described as an effect of increased air temperature by different authors. The aim of this study was to evaluate the effect of high environmental temperature on congestion of the nasal mucosa. In all, 102 volunteers were studied and included normal controls, heart rehabilitation patients and high performance sportsmen. Rhinomanometric examinations were carried out before and after 10 min in a dry Finnish sauna at a 90 degrees C temperature. Computerized active anterior rhinomanometry was used. A uniform response pattern to the increased temperature could not be observed: i.e., some individuals had an elevated resistance immediately after the sauna while resistance was decreased in others. The relationship between the reaction of the nasal mucosa to body work and temperature is discussed.

Acclimatization↗
PubMed1998

Are allergic reactions to skin clips associated with delayed wound healing?

BACKGROUND: Metal skin clips are used in surgery. They may contain metals that might cause allergic reactions and delayed wound healing. METHODS: The metal composition of 18 different surgical clamps was examined. The allergy status of 184 patients was determined by patch tests and was correlated with the clinical outcome of wound healing after application of skin clips. RESULTS: Skin clips contained chromium, nickel, molybdenum, cobalt, and titanium in concentrations high enough to cause allergic reactions. Eighteen percent of the men and 23% of the women were sensitive to nickel and 16% of the men to chromium. We found a positive correlation between the grade of nickel allergy and the reaction to the skin clips. CONCLUSIONS: Our study suggests that allergic reactions and delayed wound healing can be caused by the use of surgical skin clips. Therefore skin clips are not recommended for patients with a history of contact dermatitis to metals and/or atopy.

Adolescent↗
PubMed1998

Xanthine dehydrogenase from the phototrophic purple bacterium Rhodobacter capsulatus is more similar to its eukaryotic counterparts than to prokaryotic molybdenum enzymes.

Fourteen Rhodobacter capsulatus mutants unable to grow with xanthine as sole nitrogen source were isolated by random Tn5 mutagenesis. Five of these Tn5 insertions were mapped within two adjacent chromosomal EcoRI fragments hybridizing to oligonucleotides synthesized according to conserved amino acid sequences of eukaryotic xanthine dehydrogenases. DNA sequence analysis of this region revealed two open reading frames, designated xdhA and xdhB, encoding xanthine dehydrogenase. The deduced amino acid sequence of XDHA contains binding sites for two [2Fe-2S] clusters and FAD, whereas XDHB is predicted to contain the molybdopterin cofactor. In contrast to R. capsulatus, these three cofactor binding sites reside within a single polypeptide chain in eukaryotic xanthine dehydrogenases. The amino acid sequence of xanthine dehydrogenase from R. capsulatus showed a higher degree of similarity to eukaryotic xanthine dehydrogenases than to the xanthine dehydrogenase-related aldehyde oxidoreductase from Desulphovibrio gigas. The expression of an xdhA-lacZ fusion was induced when hypoxanthine or xanthine was added as sole nitrogen source. Mutations in nifR1 (ntrC) and nifR4 (rpoN, encoding sigma54) had no influence on xdh gene expression. A putative activator sensing the availability of substrate seems to respond to xanthine but not to hypoxanthine. The transcriptional start site of xdhA was mapped by primer extension analysis. Comparison with known promoter elements revealed no significant homology. Xanthine dehydrogenase from R. capsulatus was purified to homogeneity. The enzyme consists of two subunits with molecular masses of 85 kDa and 50 kDa respectively. N-terminal amino acid sequencing of both subunits confirmed the predicted start codons. The molecular mass of the native enzyme was determined to be 275 kDa, indicating an alpha2beta2-subunit structure. Analysis of the molybdenum cofactor of xanthine dehydrogenase from R. capsulatus revealed that it contains the molybdopterin cofactor and not a molybdopterin dinucleotide derivative.

Amino Acid Sequence↗
PubMed1998

Effects of acupuncture on the oxygenation of cerebral tissue.

Monitoring of regional cerebral oxygen saturation (r. cereb. O2 satn.) was carried out continuously in 12 healthy subjects (mean age 35.2 +/- 4.4 years; range 26-41 years; 4 women, 8 men), prior to, during and following acupuncture. Measurements were obtained with the INVOS 3100 cerebral oximeter (Somanetics Corp., Troy, USA). In addition new robotic transcranial Doppler sonography (TCD) probes enabling three-dimensional imaging of the middle cerebral artery by the use of multi-scan techniques were used simultaneously. The results showed small increases in r. cereb. O2 satn. mean values (69.9% before, 70.3% during and 70.2% after acupuncture) and a significant (p < 0.01; ANOVA, Tukey test) increase in mean bloodflow velocity during acupuncture measured simultaneously at different depths within the right middle cerebral artery. There are reports in the literature about the effects of acupuncture on the oxygenation of cerebral tissue in a study with animals. An increase in the cerebral oxygen saturation could be registered with the help of microelectrodes in the cortex. This is parallel evidence to the present results with near infrared spectroscopy and transcranial Doppler sonography. Quantifiable changes in the physiological effects of acupuncture may contribute to improved acceptance of this unconventional complementary medical procedure.

Acupuncture Therapy↗
PubMed1998

[The artificial heart and neuromonitoring? Technical and clinical aspects].

There is a steady progress in the development of artificial heart and circulatory assist devices. There is also no doubt that further advances in energy systems, materials, and electronics will provide for smaller and more reliable electrically driven blood pumps, but the present engineering design appears to be adequate to provide devices satisfactory for initial clinical use. Due to problems in the availability of suitable donor hearts, the concept of replacing the natural heart with an artificial heart as a "bridge to transplantation" has gained attention in recent years. The present paper shows technical and clinical aspects of multivariable electrophysiologic neuromonitoring in a patient with an artificial heart assist device in the intensive care unit. The data (EEG, 40 Hz brain oscillations, brainstem auditory- and somatosensory evoked potentials) are discussed with respect to the influence of the artificial heart on their quality and reliability. Reasons for artifacts and problems of interpretation are shown.

Artifacts↗
PubMed1998

Robotic transcranial Doppler sonography probes and acupuncture.

The present study shows with a sophisticated quantitative method a change in blood flow velocity in a cerebral artery in response to acupuncture. Monitoring of transcranial Doppler sonography (TCD) was examined in 12 healthy volunteers (mean age: 35.2+/-4.4 years; 26-41 years; 4 female, 8 male) before, during and after acupuncture. In all persons the same unspecific scheme of acupuncture with a "general increase of Qi-energy" was used. The measurements were performed with new robotic TCD-probes allowing three-dimensional imaging by using multi-scan methods. The results showed a significant (p < 0.01; ANOVA; Tukey test) increase in mean blood flow velocity, which was measured at different depths of the right middle cerebral artery. Quantitative determination of the physiological effects during acupuncture can lead to a better acceptance of this unconventional complementary medical method.

Acupuncture Therapy↗
PubMed1998

Doppler color-flow imaging: screening of a patent foramen ovale in children scheduled for neurosurgery in the sitting position.

A patent foramen ovale (PFO) is the most common cause of paradoxical air embolism during neurosurgical procedures in the posterior fossa in the sitting position in both adults and children. To detect right-to-left shunting, we performed Doppler color-flow imaging preoperatively in 30 children scheduled for neurosurgical procedures in the sitting position. A PFO was diagnosed on the basis of color alterations indicating an immediate blood shunt through a PFO. Six of 30 children (20%) had a PFO; in 4 of these children the sitting position then was avoided, and 2 children were operated on in a special supine position with minimal elevation of the head. Venous air embolism occurred in 9 of 24 (37%) children operated on in the sitting position and in none of the 6 children operated on in a nonsitting position. We conclude that Doppler color-flow mapping could be a useful noninvasive technique to screen children scheduled for neurosurgery in the sitting position for the presence of a PFO.

Adolescent↗
PubMed1998

Quantification of the dermal vascular response to hyperbaric oxygen with laser-Doppler flowmetry.

The vasoconstrictive response to hyperbaric oxygen (HBO2) therapy was non-invasively quantified in eight healthy volunteers at 1.95 and 2.5 atm abs (197.5 and 253.2 kPa; multiplace chamber, air environment) by laser-Doppler flowmetry (LDF). The sensors for continuous measurement of microvascular perfusion (flux) and skin temperature were localized on the thenar eminence. Transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) tensions, blood pressure, heart rate, respiration rate, peripheral oxygen saturation, and temperature of the hyperbaric chamber were recorded at five conditions: 1) baseline--air breathing at 1.0 atm abs, 2) after 15 min of HBO2 at 2.5 atm abs, 3) after 15 min of HBO2 at 1.95 atm abs, 4) 1 min after decompression with oxygen breathing at 1.0 atm abs, and 5) after 15 min of breathing air at 1.0 atm abs. Flux decreased continuously at conditions 2 (76.5%), 3 (50.6%), and 4 (37% of baseline, P < 0.05; Tukey test). Skin temperature fell below baseline at conditions 2, 3, 4 (P < 0.01, Tukey test), and 5 (P < 0.05, Tukey test, P < 0.001, analysis of variance). Range of correlation between inspired gas PO2 (PIO2) and alteration of flux 0.91 to 0.72, median -0.41. Correlation between PIO2 and tcPO2, r = 0.98. Chamber temperature and tcPCO2 remained stable. HBO2 reduced dermal microcirculation and temperature disproportionate to PIO2. LDF is suitable for use under hyperbaric conditions.

Adult↗
PubMed1997

Pores formed by influenza hemagglutinin.

Low pH-induced fusion mediated by the hemagglutinin (HA) of influenza virus involves a conformational change in the protein that leads to the insertion of a "fusion peptide" of the protein into the target membrane. It has been suggested that this insertion, aided by the formation of a complex of multiple HA trimers, would lead to perturbation of the bilayer structure of the membrane, initiating fusion. Here we present data showing that the interaction of the bromelain released ectodomain of the protein (BHA) with liposomal membranes at low pH leads to pore formation, at least at low temperatures. Strongly temperature-dependent low pH-induced inactivation of BHA resulted in a complete lack of activity of BHA above 10 degrees C. Even at 0 degrees C, only about 5% of the BHA participated in pore formation. Viral HA was less rapidly inactivated and still induced pores at 37 degrees C. BHA-induced pore formation showed a sigmoidal time course. Once BHA had formed a pore in one liposome, it did not form a pore in a further liposome. Quantitative analysis of pore formation indicated that one single BHA trimer sufficed to produce a pore. These data indicate that fusion peptide insertion perturbs the membrane and that the formation of a complex of trimers is not a prerequisite for the perturbation.

Cold Temperature↗
PubMed1997

Molybdenum cofactor biosynthesis. The plant protein Cnx1 binds molybdopterin with high affinity.

The molybdenum cofactor is an essential part of all eukaryotic molybdoenzymes. It is a molybdopterin (MPT) revealing the same core structure in all organisms. The plant protein Cnx1 from Arabidopsis thaliana is involved in the multi-step biosynthesis of molybdenum cofactor. Previous studies (Stallmeyer, B., Nerlich, A., Schiemann, J., Brinkmann, H., and Mendel, R. R. (1995) Plant J. 8, 751-762) suggested a function of Cnx1 in a late step of cofactor biosynthesis distal to the formation of MPT, i.e. conversion of MPT into molybdenum cofactor. Here we present the first biochemical evidences confirming this assumption. The protein Cnx1 consists of two domains (E and G) homologous to two distinct Escherichia coli proteins involved in cofactor synthesis. Binding studies with recombinantly expressed and purified Cnx1 and with its single domains revealed a high affinity of the G domain to MPT (kD = 0.1 microM) with equimolar binding. In contrast, the E domain of Cnx1 binds MPT with lower affinity (kD = 1.6 microM) and in a cooperative manner (nH = 1. 5). The entire Cnx1 showed a tight and cooperative MPT binding. Based on these data providing a common link between both domains that matches the previous characterization of plant and bacterial Cnx1 homologous mutants, we present a model for the function of Cnx1.

Arabidopsis↗
PubMed1997

The molecular area characteristics of the HIV-1 gp41-fusion peptide at the air/water interface. Effect of pH.

The putative fusion peptide of HIV-1 is a highly surface active substance. Relevant measurements with the Langmuir monolayer technique have been carried out for a broad range of the pH in the aqueous subphase. The data are processed towards a quantitative analysis of the partitioning equilibrium between the interfacial and aqueous moieties. Our results reveal a pronounced decrease of the surface area per peptide molecule upon monolayer compression. This phenomenon could be interpreted in terms of an orientational transition experienced by an alpha-helical peptide structure. The area requirements at any fixed lateral pressure pass through a distinct minimum at a pH of 5.5 (+/-0.5). Such an apparent isoelectric point was confirmed by isoelectric focusing of peptide aggregates. Accordingly a drastic drop of the pK-values of the two basic amino acid residues in comparison with an aqueous medium is indicated. It can be readily explained based on an inherent decrease of the effective dielectric constant. The observed low pH in favor of an enhanced surface affinity of the peptide may be a significant factor concerning its function as a fusion promoting agent.

Amino Acid Sequence↗
PubMed1997

Inflammatory reactions of the skin caused by adhesive EEG electrodes.

The correct choice of electrodes for neurophysiologic monitoring is one of the unsolved problems in clinical practice and scientific research. In addition to the familiar electrodes, i.e., cup (silver-/silver-chloride, gold) and needle electrodes, adhesive electrodes (e.g., Zipprep electrodes) have been offered for rapid application and accurate signal recording. This case report indicates that adhesive electrodes can lead to superficial lesions of the skin or inflammatory infiltration.

Adhesives↗
PubMed1997

Transcranial cerebral oximetry in the hyperbaric environment.

Continuous monitoring of dynamic changes of transcranial regional cerebral oxygenation (rSO2) was performed in 7 healthy volunteers (mean age 40.9 +/- 12.6 years; range 25-62 years) during normo- and hyperbaric oxygenation (HBO at 2.5 and at 1.95 ATA) using an INVOS 3100 cerebral oximeter. A significant change between HBO and control phase could be found in rSO2, alterations (p < 0.05; ANOVA, Tukey test). The results suggest that the calculation of rSO2 may be a useful method to monitor changes of oxygen saturation under hyperbaric conditions. However, the absolute quantification of rSO2 is useless at the moment and needs further investigation.

Adult↗
PubMed1997

Transcranial cerebral oximetry--is it clinically useless at this moment to interpret absolute values obtained by the INVOS 3100 cerebral oximeter?

Dynamic changes of regional cerebral oxygenation (rSO2) were measured simultaneously to laser Doppler flowmetry in a 35-year-old female during cerebral aneurysm surgery. In addition, to demonstrate the uselessness of the absolute values obtained by the INVOS 3100, cerebral oximeter readings from a pumpkin ("Styrian Cucurbita") are demonstrated. The results of the present study and of other reports discussed in this paper demonstrate that the INVOS 3100 cerebral oximeter should not be used at this moment as a measure reflecting absolute rSO2 values. However, it seems to be relevant that the INVOS 3100 system can monitor the dynamic changes in rSO2, although limitations have to be taken into consideration.

Adult↗
PubMed1997

[Laser Doppler data analysis during interstitial laser thermotherapy with magnetic resonance control within the scope of an animal experiment study].

The aim of the present study was to investigate, using laser Doppler (LD) flowmetry, the phases immediately prior to and following experimental, neurosurgical laser therapy in animals. Two statistical models obtained on the basis of discriminant analysis are described. These models should enable the user to classify the sets of parameters calculated from the LD signals. With both models which contain 3 and 5 parameters, respectively. 100% discrimination of the two phases was attained. The usefulness of the models could be validated by results obtained with other models.

Animals↗