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Biomedical subjects

R Fuchs

Publications and source records attributed to R Fuchs.

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

Reconstructed skin equivalents for assessing percutaneous drug absorption from pharmaceutical formulations.

Excised human skin has so far been considered to be one of the most suitable in vitro methods to evaluate the penetration of dermatologically applied substances. The limited supply and the relatively high donor variability stimulated many research groups to use animal skin as a substitute for human skin. Since nowadays reconstructed skin equivalents are commercially available, we examined these cultures for their suitability as a percutaneous absorption model for different pharmaceutical formulations. One such equivalent is EpiDerm (EPI-606, MatTek corporation, Ashland Massachusetts) which was investigated using the lipophilic model drug flufenamic acid. Permeation studies with the Franz diffusion cell were undertaken to evaluate the model for the establishment of a new in vitro method to study the percutaneous absorption of different dosage forms. The drug was applied in two pharmaceutical formulations to the intact surface of the skin disk: dissolved in wool alcohol ointment (0.1125 %), and dissolved in Soerensen phosphate buffer pH 7.4 (0.1125% solution). HPLC was used for the analysis of drug content. It was shown that the model forms a barrier towards diffusion by comparing the permeation across the tissue-free inserts to the equivalents. Flux values were calculated and the permeation across the skin equivalent from the solution was noted to be almost forty times higher than from the ointment. Two different batches of the skin equivalent showed no statistically significant difference. Finally the permeability of the reconstructed skin was compared to human epidermis, and a five times higher flux value was found for the skin equivalent model. Our results suggest that reconstructed skin equivalents based on human keratinocytes have potential as a pharmaceutical test system to study dermal drug transport from topical formulations.

Administration, Cutaneous↗
PubMed2000

Inhibition of clathrin-dependent endocytosis has multiple effects on human rhinovirus serotype 2 cell entry.

Minor group human rhinoviruses (exemplified by human rhinovirus serotype 2 (HRV2)) use members of the low density lipoprotein receptor family for cell entry; all these receptors possess clathrin-coated pit localization signals. Viral infection should thus be inhibited under conditions of impaired clathrin-mediated endocytosis. However, Madshus et al. reported an increase in the cytopathic effect of HRV2 infection in HEp-2 cells upon suppression of clathrin-dependent endocytosis by hypotonic shock and potassium depletion (Madshus, I. H., Sandvig, K., Olsnes, S., and van Deurs, B. (1987) J. Cell. Physiol. 131, 14-22.) To resolve this apparent contradiction, we investigated the binding, internalization, conformational changes, and productive uncoating of HRV2 in HeLa cells subjected to hypotonic shock and potassium depletion. This treatment led to an increase in HRV2 binding, with internalization being barely affected. The generation of C-antigenic particles requiring pH </=5.6 was strongly reduced due to an elevation of the pH in endosomal compartments. However, K(+) depletion only slightly affected de novo viral protein synthesis, suggesting that productivity of viral RNA in the cytoplasm is enhanced and thus compensates for the reduction in C-antigenic particles. The distinct steps in the entry pathway of HRV2 are thus differently influenced by potassium depletion. Viral internalization under conditions of inhibited clathrin-dependent endocytosis without the need to disturb the ionic milieu was confirmed in HeLa cells overexpressing the nonfunctional dynamin-1 mutant K44A. Unexpectedly, overexpression of dynamin-1 K44A resulted in elevated endosomal pH compared with overexpression of wild-type dynamin.

Cell Membrane↗
PubMed2000

Contribution to the Determination of Kinetic Parameters of the Sol-Gel Transformation by Rheological Measurements.

The system tetraethoxysilane(TEOS)-water-ethanol has been studied by rheological measurements. Different molar ratios of TEOS : water (1 : 4, 1 : 10, and 1 : 20) are studied at different temperatures (30, 40, and 50 degrees C). The dynamic viscosity (rotating mode) at a constant shear rate (100 s(-1)) and the elastic and viscous moduli (oscillating mode) at a constant frequency (1 Hz) are determined. The viscosity-time curves are evaluated by application of a nucleation and particle growth model. Good agreement between experiments and theory is observed. The model allows the determination of the complex rate constant of silica precipitation. The temperature-dependent measurements gave the possibility to determine the apparent energy of activation by common methods. The results are in agreement with data from the literature. The gel time defined as intersection point of elastic and plastic moduli and its dependence on temperature are evaluated by the Smoluchowski model. The energy of activation for the coagulation was determined and found to be in the correct order of magnitude. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

[Analysis of a blood use list for orthopedic operations].

OBJECTIVE: Is the documentation of blood utilisation, as demanded in the guidelines of serology and transfusion medicine, a proper instrument of quality control for the use of homologous blood saving techniques? PATIENTS AND METHODS: We analysed retrospectively a list of blood utilisation based on 12,482 surgical procedures in orthopaedic surgery. This list included the type of operation, the number of transfused packed red cell units and, if applicable, the type of homologous blood saving technique (preoperative blood donation, mechanical autotransfusion and isovolaemic haemodilution). Total hip and knee replacement patients were divided in two groups according to base line haemoglobin (A: Hb > 13 mg%, B: hB < or = 13 mg%). RESULTS: The increase of the percentage of patients not receiving homologous blood achieved by blood saving techniques is more pronounced in group B. Preoperative blood donation seems to be the most effective technique with a percentage of patients not receiving homologous blood of 93% in group A and 80% in group B of total hip replacement. This high percentage cannot be improved when preoperative blood donation is combined with mechanical autotransfusion or isovolaemic haemodilution. The efficiency of mechanical autotransfusion and isovolaemic haemodilution can be improved by combination of the two techniques. CONCLUSIONS: A list of blood utilisation as presented can serve as a basis for guidelines regarding the use of homologous blood saving techniques. Moreover such a simple statistic provides a means of quality control and provides information about the likelihood of transfusion.

Adult↗
PubMed2000

Growth factor-induced morphological, physiological and molecular characteristics in cerebral endothelial cells.

The capacity of vascular endothelial cells to modulate their phenotype in response to changes in environmental conditions is one of the most important characteristics of this cell type. Since different growth factors may play an important signalling role in this adaptive process we have investigated the effect of endothelial cell growth factor (ECGF) on morphological, physiological and molecular characteristics of cerebral endothelial cells (CECs). CECs grown in the presence of ECGF and its cofactor heparin exhibit an epithelial-like morphology (type I CECs). Upon removal of growth factors, CECs develop an elongated spindle-like shape (type II CECs) which is accompanied by the reorganization of actin filaments and the induction of alpha-actin expression. Since one of the most important functions of CECs is the creation of a selective diffusion barrier between the blood and the central nervous system (CNS), we have studied the expression of junction-related proteins in both cell types. We have found that removal of growth factors from endothelial cultures leads to the downregulation of cadherin and occludin protein levels. The loss of junctional proteins was accompanied by a significant increase in the migratory activity and an altered protease activity profile of the cells. TGF-beta1 suppressed endothelial migration in all experiments. Our data provide evidence to suggest that particular endothelial functions are largely controlled by the presence of growth factors. The differences in adhesiveness and migration may play a role in important physiological and pathological processes of endothelial cells such as vasculogenesis or tumor progression.

Actins↗
PubMed2000

[Painfulness of transvaginal follicle aspiration for oocyte retrieval in in-vitro-fertilization].

OBJECTIVE: The aim of this study was to analyze the painfulness of a transvaginal ultrasound-guided follicle punction. MATERIAL AND METHODS: Patients could choose to have either a neuroleptanalgesia or to be supported by the partner or a psychotherapist during the oocyte pick up. Based on a questionnaire, 277 patients tried to describe their level of pain in a horizontal alphanumeric scale divided in 15 categories, while other painful physical interacts could be quantified, too. Furthermore, patients were asked for the cause of sterility, former IVF-ET treatments and whether the partner or the psychotherapist looked after them during the oocyte retrieval. Statistical analysis was performed using a standardized computer program (Stat View, Abacus Concepts, USA). RESULTS: The neuroleptanalgesia reduced the intensity of pain (average value of pain: 1.21 vs 9.26 without analgesia) in a significant way (p = 0.0001). Some patients compared the pain at oocyte retrieval with a bone fracture (8.08) or surgeries (10.12). More painful was a colic (13.67), infections (13.5), some diagnostic surgeries (12.09) or a delivery (11.91). Younger woman and patients with dysmenorrhea felt significantly more pain than others. Neither the presence of the partner or psychotherapist during punction nor the indication, number of previous IVF-ET treatments or a following pregnancy had any influence on the statistics. CONCLUSION: Age as well as the rate of problems with menstruation should help the patient to decide on whether to have the follicle punction with or without anesthesia.

Adult↗
PubMed1999

Human rhinovirus HRV14 uncoats from early endosomes in the presence of bafilomycin.

Determination of infectious progeny virus and in vivo labelling with [(35)S]methionine followed by immunoprecipitation demonstrates that the major receptor group human rhinovirus HRV14 is able to infect HeLa cells in the presence of the V-ATPase inhibitor bafilomycin A1. However, host cell shut off is delayed and viral yield is decreased in the presence of the drug. Uncoating can thus take place under conditions that prevent endosomal acidification indicating that it is catalysed by the viral receptor alone. Since transport is arrested in early endosomes upon inhibition of vesicle acidification, the data also suggest that productive uncoating takes place from early endocytic compartments.

Anti-Bacterial Agents↗
PubMed1999

The occurrence of ochratoxin A in blood in general population of Croatia.

The exposure of general population in Croatia to mycotoxin ochratoxin A (OTA) was investigated in five cities: Split, Rijeka, Varazdin, Osijek, and Zagreb. In June 1997, blood donors from each of these cities gave 50 samples of 3 ml plasma each. The mean concentration of OTA, determined using high-pressure liquid chromatography (HPLC), was 0.39 ng/ml of plasma. The highest frequency of OTA-positive samples (>0.2 ng/ml plasma), and the highest number of samples with the concentration exceeding 1.0 ng/ml, were found in Osijek. This difference is probably due to the higher consumption of fresh and dried pork by population of Osijek. The calculated daily intake of OTA, estimated from the mean OTA concentration of all samples in each town (in the range from 0.24 to 0.91 ng/kg b.w. found in Rijeka and Osijek, respectively) is lower than the tolerable daily intake proposed by Joint FAO/WHO Expert Committee on Food Additives (1995) of 16.0 ng OTA/kg b.w.

Chromatography, High Pressure Liquid↗
PubMed1999

Astrocytes and neurons express the tight junction-specific protein occludin in vitro.

The expression of occludin, an integral plasma membrane protein specifically located at tight junctions, was studied in various epithelial and nonepithelial tissues by means of RT-PCR, Western blotting, and immunofluorescent staining. Besides detection in epithelial and endothelial tissue, expression of occludin was found in primary and secondary cultures of neurons and astrocytes. Differentiation of astrocytes in vitro led to a marked decrease in occludin expression. Extractability of occludin from plasma membranes differed considerably between epithelial and nonepithelial cells. Following treatment with Triton X-100, occludin was completely extracted from astrocytic membranes but not from membranes derived from MDCK cells, suggesting a difference in the cytoplasmic and/or plasma membrane anchoring of occludin between these cell types.

Animals↗
PubMed1999

Occurrence of an HIV-1 gp160 endoproteolytic activity in low-density vesicles and evidence for a distinct density distribution from endogenously expressed furin and PC7/LPC convertases.

Human immunodeficiency virus (HIV) glycoprotein (gp) 160 processing by host cell proteinases is an essential step for viral fusion and infectivity. We have identified a rat liver subcellular fraction which specifically processes gp160 into gp120 and gp41. Using equilibration of microsomes in sucrose gradients, the gp160 cleavage activity was associated with particles equilibrating at low densities, well-separated from the endoplasmic reticulum, cis-Golgi network, Golgi stacks, lysosomes and plasma membrane. Its density distribution was compatible with light secretory vesicles derived from the trans-Golgi network (TGN) or to endosomes, but association with endosomes was not supported by free flow electrophoresis. Although furin and pro-protein convertase (PC) 7/LPC have been proposed as the major gp160 processing convertases, the rat liver microsomal gp160 processing activity was essentially resolved from furin and only partially overlapped PC7/LPC. These data suggest that proteinase(s) other than furin and PC7/LPC, presumably located in TGN-derived vesicles, may participate in the gp160 processing into gp120 and gp41.

Amino Acid Sequence↗
PubMed1999

A fast screening method for the identification of siderophores from fluorescent Pseudomonas spp. by liquid chromatography/electrospray mass spectrometry.

A screening method was developed for the fast identification of known pyoverdin-type siderophores produced by fluorescent Pseudomonas spp. It is based on reversed-phase high-performance liquid chromatography interfaced with electrospray ionization mass spectrometry of the Sep-Pak RP-C18 culture supernatant extracts. The siderophores of five bacterial strains were characterized by their molecular masses obtained from their doubly protonated molecular ions [M + 2H]2+ and their UV/visible spectra recorded with a diode-array detector. Additional structural information was gained by skimmer collision-induced dissociation experiments. For all strains new minor siderophores were found. A table of fully or partially identified pyoverdins and related siderophores is provided which will be the basis for screening studies.

Chromatography, Liquid↗
PubMed1999

IgG transport across trophoblast-derived BeWo cells: a model system to study IgG transport in the placenta.

In primates, prenatal transfer of IgG from mother to offspring occurs predominantly across the placenta. Although a number of Fcgamma-receptors and IgG binding proteins have been detected in human placental tissue, an involvement of any of these receptors in IgG transport across the syncytiotrophoblast remains to be demonstrated. Therefore, we investigated the mechanism of IgG transcytosis in trophoblast-derived BeWo cells. BeWo cells were not only found to express the MHC class I-related IgG Fc receptor, human FcRn, but also specifically bound fluorescein isothiocyanate (FITC)-labeled human IgG (FITC-hIgG) at the apical surface at mildly acidic pH. The cells preferentially transcytosed FITC-hIgG from the apical to the basolateral side when compared to the fluid-phase marker FITC-dextran and to FITC-hIgG transcytosis in the opposite direction. However, endocytosis of FITC-hIgG at the apical plasma membrane at physiological pH required the continuous presence of FITC-hIgG at concentrations similar to those present in the maternal circulation. These results suggest a mechanism by which IgG is internalized by BeWo cells via fluid-phase endocytosis. Tight binding of IgG to hFcRn may then occur in acidic endosomes, followed by selective sorting into the transcytotic pathway. Thus, the main function of this receptor is to prevent entry of IgG into the degradative pathway in lysosomes.

Animals↗
PubMed1999

Ochratoxin A in blood of healthy population in Zagreb.

Healthy blood donors from the city of Zagreb were checked for the presence of a nephrotoxic mycotoxin ochratoxin A (OTA) in the plasma. Samples of blood were collected in June, September, and December 1997, and March 1998, totalling 200 or 50 in each round. The concentrations of OTA were measured using high pressure liquid chromatography (HPLC) method (detection limit 0.2 ng OTA/ml of plasma). The frequency of OTA-positive samples (> 0.2 ng/ml of plasma) showed significant seasonal variation (P < 0.001). The frequency of OTA-positive samples was the highest in March (65%) and it gradually decreased towards December (12%). The high frequency of positive samples coincided with seasons favouring growth of moulds and production of toxins. The daily intake of OTA by healthy persons in Zagreb was estimated from the mean concentration of OTA in samples collected during the whole year (0.19 ng OTA/ml plasma). The estimated daily intake was 0.26 ng/kg b.w., that is, substantially below the tolerable daily intake proposed by World Health Organization (16.0 ng/kg b.w.).

Chromatography, High Pressure Liquid↗
PubMed1998

Fluorescence in situ hybridization characterization of the chromosomal breakpoints in a case with ins(17;3)(q11.2;q21q26.3) and acute monocytic leukemia.

A 63-year-old patient with acute myeloid leukemia of FAB M5 subtype revealing chromosomal breakpoints in 3q21 and 3q26 is presented. Although rearrangements of 3q21 and 3q26 are relatively common in patients with myelocytic malignancies, this is the first report of ins(17;3)(q11.2;q21q26.3). We defined the chromosomal breakpoints and the extent of the insertion by fluorescence in situ hybridization (FISH) with yeast artificial chromosomes (YACs).

Chromosome Aberrations↗
PubMed1998

Detection of the bcr/abl gene in bone marrow macrophages in CML and alterations during interferon therapy--a fluorescence in situ hybridization study on trephine biopsies.

A fluorescence in situ hybridization (FISH) study was performed on trephine biopsies of the bone marrow in chronic myelogenous leukaemia (CML) to evaluate the bcr/abl translocation in macrophages before and during interferon (IFN) therapy. Mature macrophages and osteoclasts were identified by the monoclonal antibody PG-M1, which recognizes a fixative-resistant epitope of the CD68 molecule. In contrast to a control group, in 145 of 479 (30 per cent) macrophages of the CML bone marrow, a positive fusion signal was found, together with corresponding translocation sites in the surrounding myeloid cells. In patients following IFN treatment for approximately 12 months and with haematological/cytogenetic remission by clinical standards, this number was reduced to 10 of 136 (9 per cent) macrophages. In addition, the few multinucleated osteoclasts of the untreated CML bone marrow displayed positive translocation spots. This finding supports the hypothesis that stromal macrophages and osteoclasts are of haematogenic stem cell origin. Moreover, clinical remission and reduction of bcr/abl-positive macrophages under IFN therapy lend support to the hypothesis that the presence of malignant stromal macrophages may contribute to the selective expansion of leukaemic precursors and the suppression of normal haematopoiesis in CML.

Antigens, CD↗