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Biomedical subjects

A Bader

Publications and source records attributed to A Bader.

At least 37 records · Page 2Linked to original sources
PubMed2002

Ultraviolet protection factor of fabrics: comparison of laboratory and field-based measurements.

BACKGROUND/PURPOSE: Spectrophotometry has become an accepted laboratory-based method for the determination of the ultraviolet protection factor (UPF) of fabrics. However, the validity of the UPF determined in the laboratory has been a controversial issue with regard to its significance in the field. To compare UPF values obtained by spectrophotometry, determination of the minimal erythema dose (MED), and biological dosimetry, we conducted laboratory and field-based measurements on various fabric materials. METHODS: One cotton, two viscose, and two polyester fabrics were enrolled into the study. Spectrophotometric (SP) testing was performed in accordance with the European standard. In vivo "on skin" (IV) testing on human subjects was performed with and without fabric protection. For determination of MED, a solar-simulator was used. In another part of the study, biological dosimetry (BD) testing was employed for laboratory testing with solar-simulated radiation (laboratory BD testing) as well as field-based measurements with natural sunlight in stationary (stationary BD testing) and "real life" exposure situations (mobile subject BD testing). For field-based measurements one light-weight polyester fabric was selected. RESULTS: The differences of the mean UPF values obtained by the laboratory-based methods were significant (MANOVA; P = 0.05), except for fabric no. 2 (MANOVA; P = 0.097). In 4 of the 5 fabrics tested, UPF values obtained by IV testing were significantly lower than those obtained by SP testing (t-test; P = 0.05). In 3 fabrics, SP testing revealed significantly higher UPF values in comparison to laboratory BD testing (t-test; P = 0.05). The differences of UPF values obtained by the laboratory and field-based measurements employed for the light-weight polyester fabric were significant (ANOVA; P = 0.05). In comparison to SP testing (UPF 3.8), stationary BD testing resulted in significantly lower (UPF 3.5) and mobile subject BD testing in a significantly higher UPF of 4.4 (t-test; P = 0.05). The UPF obtained by mobile subject BD testing differed significantly from the UPF obtained by stationary BD testing (t-test; P = 0.05). CONCLUSIONS: Comparison of the presented methods indicates that IV testing generally results in lower UPF values. By contrast BD testing in "real life" exposure situations reveals relatively high UPF values. Although an overestimation of the spectrophotometrically measured UPF has been observed in comparative laboratory testing, UPF values obtained by field-based measurements are in relatively good agreement, or even surpass UPF values obtained by spectrophotometry. It is, therefore, suggested that SP testing provides "safe" UPF values which may be also valid in extreme real exposure situations. Biological UV dosimetry is, however, a promising alternative method for UPF testing: the test is easily performed in realistic exposure situations, the test is relatively inexpensive, and the measurements are valid.

Analysis of Variance↗
PubMed2002

A high-resolution comparative RH map of the proximal part of bovine chromosome 1.

Current comparative maps between human chromosome 21 and the proximal part of cattle chromosome 1 are insufficient to define chromosomal rearrangements because of the low density of mapped genes in the bovine genome. The recently completed sequence of human chromosome 21 facilitates the detailed comparative analysis of corresponding segments on BTA1. In this study eight bovine bacterial artificial chromosome (BAC) clones containing bovine orthologues of human chromosome 21 genes, i.e. GRIK1, CLDN8, TIAM1, HUNK, SYNJ1, OLIG2, IL10RB, and KCNE2 were physically assigned by fluorescence in situ hybridization (FISH) to BTA1q12.1-q12.2. Sequence tagged site (STS) markers derived from these clones were mapped on the 3000 rad Roslin/Cambridge bovine radiation hybrid (RH) panel. In addition to these eight novel markers, 17 known markers from previously published BTA1 linkage or RH maps were also mapped on the Roslin/Cambridge bovine RH panel resulting in an integrated map with 25 markers of 355.4 cR(3000) length. The human-cattle genome comparison revealed the existence of three chromosomal breakpoints and two probable inversions in this region.

Animals↗
PubMed2002

Plasma levels of opioid peptides after sunbed exposures.

BACKGROUND: Previous studies have indicated that solar and artificial ultraviolet (UV) radiation have a positive influence on psychological variables such as mood and emotional state. Circulating opioid peptides have been suggested as being important in this effect. OBJECTIVES: To investigate in a controlled trial the influence of UVA radiation on opioid peptide levels. METHODS: We determined plasma levels of beta-endorphin immunoreactive material (IRM) and met-enkephalin in UV-exposed (n = 35) and non-exposed (n = 9) healthy volunteers. On the first day of the study, blood samples were taken from the volunteers (time A). UVA irradiation was subsequently administered with an air-conditioned tanning device. During the UV exposures the volunteers wore opaque goggles. Twenty minutes after UV exposure, blood samples were collected again (time B). Within the following 3 weeks the volunteers had a series of five UV exposures. On the last day of the study (24 h after the sixth UV exposure) blood samples were collected (time C). The cumulative UVA doses were 96 J cm-2 for skin type II and 126 J cm-2 for skin type III. The controls had no UV exposures. Plasma beta-endorphin IRM and met-enkephalin levels were determined using radioimmunoassays. RESULTS: At all times of blood collection (A, B, C), there were no significant differences in plasma levels of beta-endorphin IRM and met-enkephalin between UV-exposed and non-exposed volunteers (P > 0.05). CONCLUSIONS: UVA irradiation does not significantly elevate plasma levels of beta-endorphin IRM and met-enkephalin. Therefore we suggest that psychological benefits claimed to occur after UV exposure are unlikely to be mediated by the types of circulating opioid peptides measured in this study.

Adolescent↗
PubMed2002

Preservative properties of Calamintha officinalis essential oil with and without EDTA.

AIMS: This study was focused on the preserving properties of Calamintha officinalis essential oil, a plant known for its diaphoretic, expectorant and aromatic properties. METHODS AND RESULTS: The commercial aerial parts of C. officinalis Moench were hydrodistilled and the essential oil analysed by Gas chromatography/Electron impact mass spectrometry (GC/EIMS). The inhibition efficacy of this essence, alone (0.5 and 1.0% v/v) and in combination with 2.0 mM EDTA, was assayed, in culture medium and in cetomacrogol cream, using preservative efficacy testing against standard microrganisms (E. coli ATCC 25922, Ps. aeruginosa ATCC 9027, Staph. aureus ATCC 6538P, C. albicans ATCC 10231 and A. niger ATCC 16404). C. officinalis essential oil in cetomacrogol cream with EDTA showed long-lasting antimicrobial activity, satisfying the European Pharmacopoeia Commission (E. P.) criteria. CONCLUSION: C. officinalis essential oil could have a potential for a future use as a cosmetic preservative. IMPACT OF THE STUDY: To find natural compounds with antimicrobial activity which could be alternatives to the synthetic chemical preservatives.

Aspergillus niger↗
PubMed2002

Permissive and suppressive effects of dexamethasone on enzyme induction in hepatocyte co-cultures.

1. Steroids are known to act as permissive factors in hepatocytes. This study shows that dexamethasone (DEX) is a permissive factor for induction of CYP2B1/2, CYP3A1, CYP2A1 and probably also CYP2C11 in cultures with primary rat hepatocytes. 2. The induction factor of phenobarbital (PB)-induced formation of 16beta-hydroxytestosterone (OHT), a testosterone biotransformation product predominantly formed by CYP2B1, is increased 18-fold by the addition of 32 nM DEX to the culture medium. Interestingly, higher concentrations of DEX up to 1000 nM led to a concentration-dependent maximally 5-fold decrease (p = 0.002) of phenobarbital-induced 16beta-OHT formation compared with the effect observed with 32 nM DEX. Thus, DEX shows permissive and suppressive effects on enzyme induction depending on the concentration of the glucocorticoid. 3. Qualitatively similar but smaller permissive and suppressive effects of DEX were observed for PB-induced CYP3A1 activity as evidenced by formation of 2beta-, 6beta- and 15beta-OHT. 4. DEX is a permissive factor for induction of CYP2A1 activity by 3-methylcholanthrene (3MC), as evidenced by the formation of 7alpha-OHT. Without addition of DEX, 3MC did not induce formation of 7alpha-OHT, whereas an almost 3-fold induction occurred in the presence of DEX. In contrast to CYP2B and CYP3A, concentrations up to 1000 nM DEX were not suppressive for the induction of CYP2A1. 5. We described recently a technique that allows preparation of cultures from cryopreserved hepatocytes. An almost identical influence of dexamethasone on enzyme induction was observed here in cultures from cryopreserved compared with freshly isolated hepatocytes. 6. Cultures with primary hepatocyte cultures represent a well-established technique for the study of drug-drug interactions. However, a large interlaboratory variation is known. Our study provides evidence that differences in glucocorticoid concentration in the culture medium contribute to this variation.

Animals↗
PubMed2001

High-throughput site-directed mutagenesis in ES cells.

Introduction of nonselectable mutations into the genome of embryonic stem cells by homologous recombination allows to investigate the function of genes at the molecular level and has been achieved, however, at very low efficiencies by the Hit and Run, Tag and Exchange, and Double Replacement strategies. Comparing those strategies at a single locus with vectors derived from a single fragment of the desmin gene led to the improvement of two strategies by employing a new selection cassette and modified selection procedures. Modified strategies resulted in the introduction of nonselectable point-mutations in 53% of the Hit and Run derived embryonic stem cell clones and in 0.7% of the Tag and Exchange clones. Efficiency of intrachromosomal recombination at Hit alleles outscored replacement-type recombination at the tagged alleles making the modified Hit and Run strategy the method of choice for the efficient introduction of nonselectable point mutations into the genome of embryonic stem cells.

Alleles↗
PubMed2001

Serum folate levels after UVA exposure: a two-group parallel randomised controlled trial.

BACKGROUND: Photodegradation of certain vitamins such as riboflavins, carotinoids, tocopherol, and folate has been well-documented. Previous observations suggest that ultraviolet (UV) radiation may cause folate deficiency. This is of great importance since folate deficiency is also known to be linked with the development of neural tube defects. To investigate the influence of UVA radiation on serum folate levels in vivo, we conducted a two-group randomised controlled trial on healthy subjects. MATERIAL AND METHODS: Twenty-four healthy volunteers with skin type II were enrolled into the study. Eight volunteers of the study population were randomly assigned to the control group. UVA irradiation was administered with an air-conditioned sunbed. Blood samples were taken from all volunteers at baseline (T1), 30 min after the first UVA exposure (T2), and at the end of the study 24 h after the sixth UV exposure (T3). The volunteers had two UVA exposures weekly within three weeks (cumulative UVA dose: 96 J/cm2). Volunteers of the control group had no UVA exposures. Serum folate was analysed with an automated immunoassay system. RESULTS: At all times of blood collection the differences between serum folate levels were insignificant (P > 0.05), except of the non-exposed controls at T2 (P < 0.05). We did not observed significant differences of folate levels between UVA exposed and non-exposed volunteers (P > 0.05). CONCLUSIONS: Our data suggest that both single and serial UVA exposures do not significantly influence serum folate levels of healthy subjects. Therefore, neural tube defects claimed to occur after periconceptual UVA exposure are probably not due to UVA induced folate deficiency.

Adult↗
PubMed2001

Longterm stability of phase I and phase II enzymes of porcine liver cells in flat membrane bioreactors.

Recently, researchers have focused on the use of bioartificial liver devices to support patients with fulminant hepatic failure. Our team developed a cell-based flat membrane bioreactor (FMB). In this, porcine liver cells were maintained in 3D-coculture between two gel layers in a sandwich configuration for 3 weeks to study the influence of this bioreactor technique on the preservation of basic, not induced activities of phase I and phase II enzymes. First, the time and substrate dependencies of the following enzymes were measured: ethoxyresorufin-O-deethylase (EROD, CYP 1A1/1A2) and ethoxycoumarin-O-deethylase (ECOD, CYP 2B6) as phase I enzymes, and glutathione-S-transferase (GST), UDP-glucuronosyltransferase (UGT) and sulfotransferase (ST) as phase II enzymes. To find optimal test conditions Michaelis-Menten kinetics were calculated. Next, different potential inducers were tested to find out the most effective compounds. Based on these results, the basic, not induced levels of the different enzymes were determined in the flat membrane bioreactor. Furthermore, the response of these enzyme activities to the chosen inducers was investigated to examine whether the cells keep their ability for drug-drug interactions. Basic, not induced activities of both phase I enzymes and the phase II enzymes GST and UGT were maintained at nearly the initial levels during the complete period of study. In addition, it was possible to induce these enzymes twice or three times in a weekly interval. In contrast, the basic, not induced activity of ST increased during the first 10 days of culture. It stabilized then and was maintained steady. As in short-term investigations, no reaction of the ST-activity towards any inducer could be obtained. These results prove that porcine liver cells preserve their phase I and phase II activities and respond to inducing drugs over 3 weeks in culture. Therefore, the flat membrane bioreactor is not only suitable for investigating drug metabolism, drug-drug interactions, and enzyme induction but also for supporting liver functions.

7-Alkoxycoumarin O-Dealkylase↗
PubMed2001

Repeatability of in vitro measurements of the ultraviolet protection factor (UPF) by spectrophotometry with automatic sampling.

BACKGROUND/AIMS: Spectrophotometric assessment (in vitro) is the most established method for determining the ultraviolet protection factor (UPF) of textiles. Apart from stringent requirements for measurement precision, practical methods are required for the routine determination of the UPF. We report here spectrophotometric measurements of textiles using a newly developed autosampler. Measurement precision was evaluated under repeatable conditions. METHODS: Fifteen different textiles were spectrophotometrically assessed for the determination of the UPF. Sample handling inside the spectrophotometer was performed with a computer-controlled sampling device, capable of loading and unloading a textile sample from a magazine as well as rotating the sample perpendicular to the spectrometer beam. In order to evaluate the repeatability of measurements, one sample of each textile was assessed eight times under the same conditions in the same laboratory. RESULTS: A mean percentage of the standard error of 1% [E(UPF)] was calculated for the UPF measurements. For UPFs >30, a significantly higher E(UPF) was found (r=0.78; P<0.001). E(UV) (3.9%) of ultraviolet A (UVA) transmission differed significantly from E(UV) (1.1 %) of ultraviolet B (UVB) transmission (P<0.05). CONCLUSIONS: Though a slight decrease of repeatability was observed for UVA transmission measurements and UPFs higher than 30, our data indicate a high measurement precision under repeatable conditions. In conclusion, spectrophotometric measurements of textiles with the aid of the autosampler presented have been shown to be highly practical, time saving and precise.

Automation↗
PubMed2001

Ultraviolet protection by summer textiles. Ultraviolet transmission measurements verified by determination of the minimal erythema dose with solar-simulated radiation.

BACKGROUND: Apart from sunscreen lotions, clothing provides protection from acute and chronic sun damage. Therefore, it is very important to know the ultraviolet (UV) protection factor (UPF) of textiles, in particular of lightweight summer clothing. Usually, the UPF of a textile is determined by spectrophotometric assessment of the UV transmission (in vitro method). OBJECTIVES: To compare the relationship between in vitro tests and in vivo tests of UPF using solar simulators for determination of the minimal erythema dose (MED), applied to 30 different summer textiles. METHODS: Thirty summer textiles were spectrophotometrically assessed, and UPFs were calculated with respect to the International Commission on Illumination (CIE) erythemal action spectrum.1 Based on the in vitro UPFs 'on skin' and 'off skin', in vivo testing was performed using a solar simulator for the determination of the MEDunprotected and MEDprotected. RESULTS: The UPFs obtained from in vivo 'on skin' testing were significantly (r = 0.95; P < 0.001) lower than the predicted in vitro UPFs. This disparity was also confirmed by chromometric assessment of the MED testing; the erythemal responses measured after textile protection were significantly (P < 0.001) higher than those obtained without protection. However, the in vivo 'off skin' UPFs did not significantly (r = 0.98; P > 0.05) differ from the in vitro UPFs; comparison of the chromometrically assessed erythemal responses was also insignificant (P > 0.05). CONCLUSIONS: The different correlation between in vitro and in vivo measurements of the UPF may be due to the optical-geometrical properties of textiles and the different amount of direct and diffuse radiation passing through the spaces between the yarns. As spectrophotometric measurements of a textile may generally yield lower UPFs than those obtained under average field conditions, the in vitro test method provides 'safe' UPF values representing a 'worst-case scenario'. In contrast to in vitro testing, in vivo methods are much more expensive and time-consuming. Thus, with respect to practicality, spectrophotometric measurements seem to be most suitable for the evaluation of UV protection of textiles.

Adult↗
PubMed2001

Paracrine promotion of cardiomyogenesis in embryoid bodies by LIF modulated endoderm.

In the vertebrate embryo the heart is the first organ to form. Embryonic and extra-embryonic tissues are supposed to contribute to cardiac lineage commitment before and during gastrulation in a paracrine fashion. Evidence has accumulated that factors secreted by the anterior lateral endoderm and extra-embryonic endoderm contribute to cardiomyogenesis. Here we exploit in vitro differentiation of embryonic stem cells in embryoid bodies to study differentiation of the extraembryonic endodermal lineage, gastrulation-like processes, and the influence of endoderm on cardiomyogenesis. We demonstrate that in embryoid bodies primitive endoderm differentiates to visceral and parietal endoderm and that parietal endoderm influences onset of cardiomyogenesis in a concentration-dependent manner. Both increased concentrations of leukemia inhibitory factor and its absence in lif-/- embryoid bodies hampered parietal endoderm formation. Reduced differentiation of parietal endoderm correlated with an attenuation of cardiomyogenesis even in the presence of LIE These and previous results suggest that leukemia inhibitory factor is directly and indirectly, via endoderm formation, involved in the regulation of cardiomyogenesis. Increased proliferation of parietal endoderm in lifr -/- embryoid bodies and addition of conditioned lif -/- cell culture supernatant promoted cardiomyogenesis, demonstrating for the first time that parietal endoderm also contributes to cardiomyogenesis in embryoid bodies in a paracrine and leukemia inhibitory factor and its receptor independent pathway. New factors signaling independently of the leukemia inhibitory-factor receptor pathway may sustain cardiomyocyte cell proliferation and thus be a future target for gene therapy of cardiomyopathies and cell therapy of the myocardium.

Cell Differentiation↗
PubMed2001

Heart valves from pigs and the porcine endogenous retrovirus: experimental and clinical data to assess the probability of porcine endogenous retrovirus infection in human subjects.

OBJECTIVE: Replacement of heart valves in human subjects has become a routine procedure in cardiac operations. We sought to investigate whether commercially available glutaraldehyde-fixed porcine heart valve prostheses cause porcine endogenous retrovirus infection in human subjects because recent studies revealed that human cells can be infected with porcine endogenous retrovirus. METHODS: Blood samples of 18 patients who underwent aortic or mitral valve replacement with porcine heart valves were collected 6 months to 3 years after operation and tested for porcine endogenous retrovirus by means of polymerase chain reaction and reverse transcriptase-polymerase chain reaction. In addition, we tried to trace porcine endogenous retrovirus in 3 commercially available, glutaraldehyde-fixed, porcine heart valves. RESULTS: Porcine endogenous retrovirus can be easily detected in native porcine heart valves and degrades completely within 1 week of fixation in glutaraldehyde. In all 3 commercially available porcine heart valves, no traces of porcine endogenous retrovirus were found. All blood samples showed negative test results for the porcine endogenous retrovirus genome. CONCLUSION: Our results indicate that glutaraldehyde fixation of porcine heart valves reliably prevents cross-species transmission of porcine endogenous retrovirus.

Aged↗
PubMed2001

Review of a flat membrane bioreactor as a bioartificial liver.

Recent developments in tissue engineering permit to use isolated hepatocytes in a bioreactor for the creation of a bioartificial liver which supports patients suffering from acute liver failure. In this study, the authors discuss the development of a flat membrane bioreactor using pig hepatocytes for the replacement of liver functions. The flat membrane bioreactor permits a high-density hepatocyte culture under sufficient oxygenation conditions, comparable to an in vivo microenvironment. In this bioreactor, built according to the in vivo organisation of the liver, pig hepatocytes are cultured with non-parenchymal cells within an extracellular matrix between oxygen-permeable flat-sheet membranes as individual plates. The performance of the "scale-up bioreactor" was tested in vitro for 18 days in static and flux conditions. Pig hepatocytes in the bioreactor were maintained in three-dimensional co-culture with non-parenchymal cells and are reorganised in a way similar to the liver cell plates in vivo: cells remained polarised in vitro clearly demonstrating biliary zones surrounding individual hepatocytes. The biochemical performance of the bioreactor was assessed by estimating its ability to remove two of the major toxins associated with hepatic encephalopathy: benzodiazepines and ammonia. The rates of ammonia elimination and drug biotransformation were maintained at constant high levels for almost two weeks. This "scaled-up bioreactor" provides conditions favourable for the formation of contiguous cell sheets, which allow to maintain constant liver specific functions.

Ammonia↗