Biomedical subjects

A Bernd

Publications and source records attributed to A Bernd.

At least 37 records · Page 2Linked to original sources

PubMed1998

Lymphocyte transfer in streptozotocin-induced diabetes: adhesion of donor cells to islet endothelium.

The interaction between intravenously transferred lymphocytes derived from spleens of multiple low-dose streptozotocin-diabetic mice with islet, exocrine pancreatic, and gastric mucosal endothelium of nondiabetic recipient mice was investigated by in vivo microscopy. Donor lymphocytes were stained with acridine red in vitro. The adoptive transfer of these cells from diabetic donor animals resulted in significantly increased lymphocyte rolling (4.46 +/- 1.32%, P < 0.05) and adhesion (3.86 +/- 1.04%, P < 0.05) in islets of nondiabetic recipients that had been pretreated with a single subdiabetogenic dose of streptozotocin. No increased endothelial interaction was noted in nonpretreated recipients or in experiments with nondiabetic donors. Rolling (1.19 +/- 0.61 to 2.71 +/- 0.62%) and adhesion (0.61 +/- 0.33 to 2.80 +/- 0.97%) of donor lymphocytes were low in exocrine pancreatic and gastric mucosal control tissue. It is concluded that, in this animal model, lymphocytes from diabetic donors interact preferentially with recipient islet endothelium. However, additional stimulation of recipient islet endothelium by exogenous factors is necessary to enable transferred cells to adhere to pancreatic islets.

Animals↗

PubMed1997

Candida albicans suppresses transcription of melanogenesis enzymes in cultured melanocytes.

Human skin can be colonized by different yeasts that may have an impact on skin pigmentation. In order to study this effect normal human melanocytes were cultured with different yeasts. Reverse transcription polymerase chain reaction (RT-PCR) analysis gives evidence that Candida albicans suppresses the transcription of melanogenesis enzymes.

Aldose-Ketose Isomerases↗

PubMed1997

Measurement of anti-inflammatory effects of glucocorticoids on human keratinocytes in vitro. Comparison of normal human keratinocytes with the keratinocyte cell line HaCaT.

There are only few objective in vitro methods available for the testing of anti-inflammatory pharmaceutical products. One possibility is in the stimulation of cytokine production in cultivated human keratinocytes by UV light and the subsequent testing of suppressing activities. From the dermatological aspect the interleukins 6 and 8 are especially interesting because they are elevated in psoriatic skin. In the present work three glucocorticoids were tested in cultures of normal human keratinocytes and in the permanent keratinocyte cell line HaCaT. Both cell species produced IL-6 and IL-8 spontaneously, albeit in very small amounts. After UV irradiation the interleukin production increased in a dose dependent manner. The IL-6 and IL-8 induction could be suppressed by each of the glucocorticoids tested. The thymidine incorporation rate of the cells was not affected by the glucocorticoids indicating that the observed suppression of cytokine induction was not the result of a generalised cell damage. The response of both HaCaT keratinocytes and primary human keratinocytes to UV irradiation and glucocorticoid application was similar indicating the possible use of the generally available HaCaT cells for the pharmacological testing of anti-inflammatory activities in vitro.

Anti-Inflammatory Agents↗

PubMed1996

Transcription of melanogenesis enzymes in melanocytes: dependence upon culture conditions and co-cultivation with keratinocytes.

Eumelanogenesis of human skin melanocytes requires at least three enzymes: tyrosinase, TRP 1, and TRP 2. The regulation of these enzymes on transcriptional level was detected in a semiquantitative attempt. The total RNA of melanocytes was reverse-transcripted and followed by a PCR with degenerated primers for all three enzymes. The amplification products were related to each other densitometrically. We examined five different culture conditions: 1) melanocytes in a popular phorbolester containing F-10-medium, 2) melanocytes in a co-culture medium with EGF, 3) melanocytes in a co-culture medium with high calcium, 4) melanocytes co-cultured with keratinocytes in EGF containing co-culture medium, and 5) melanocytes co-cultured with keratinocytes in co-culture medium with high calcium. Melanocytes cultured in phorbolester containing F-10-medium featured transcripts of tyrosinase, TRP 1, and TRP 2 in the ratio 45:45:10. The same results were obtained for melanocytes co-cultured with keratinocytes under the two different culture conditions. In melanocytes cultured alone in co-culture media only TRP 1-transcripts were present. It is likely that under co-culture conditions a keratinocyte-derived factor supports the transcription of all three enzymes. For melanocytes in the phorbolester-containing melanocyte medium a proteinkinase C dependent regulation of transcription seems possible.

Coculture Techniques↗

PubMed1996

[Autologous keratinocyte culture on hyaluronic acid ester membranes: an alternative in complicated wound management?].

Cultivation and transplantation of autologous keratinocytes has been used in the last 15 years to treat complicated wounds of different origin. In spite of excellent technical advancements and clinical experiences cultured keratinocyte grafting still is associated with practical limitations. Application of hyaluronic acid ester membranes as carrier substrate for the transfer of keratinocytes allows improved graft handling: reduces total time required for tissue cultivation and furthermore enhances vitality of the keratinocytes because of possible grafting at semiconfluence.

Aged↗

PubMed1995

In vitro studies on the immunomodulating effects of polypodium leucotomos extract on human leukocyte fractions.

The in vitro effect of Anapsos, a water based extract of the naturally occurring fern Polypodium leucotomos (calagualine), on human leukocyte fractions was investigated. Calagualine inhibited interleukin-2 secretion and concanavalin A (Con A) stimulated proliferation of T-lymphocytes in a concentration dependent manner. In contrast, a greatly enhanced secretion of IL-1 alpha, IL-1 beta and tumor necrosis factor alpha was induced suggesting a stimulation of monocytes and dendritic cells also present in this system. Endotoxin induced stimulation was excluded. Also in the absence of Con A, calagualine stimulated cytokine production. The presented data show for the first time that calagualine exerts an immunomodulating effect on leukocyte fractions, paving the way for further detailed studies related to possible clinical efficacy.

Adjuvants, Immunologic↗

PubMed1994

Influence of suction cup oculopression on corneal astigmatism.

In 11 (right) eyes of 11 ocularly healthy subjects an artificial stepwise intraocular pressure (IOP) elevation was applied by suction cup oculopression. The initial negative pressure in the suction cup was 80 mmHg; it was raised in steps of 40 mmHg. The median of the corneal astigmatism, measured with a Zeiss ophthalmometer, was 0.50 D before oculopression (the values of the 10th and 90th percentiles were 0.30 and 1.10 D, respectively). Corneal astigmatism increased to 2.00 (0.00-5.10) D, 2.25 (1.00-5.55) D, 2.63 (0.63-7.00) D, 3.38 (1.88-6.88) D, 3.38 (2.83-7.25) D, and 4.38 (2.85-5.63) D with 80, 120, 160, 200, 240, and 280 mmHg oculopression, respectively. The astigmatism dropped to 0.75 (0.00-2.30) D immediately after removal of the suction cup. Thus, suction cup oculopression not only influenced IOP but also ocular refraction. This is of particular importance since visual evoked potential (VEP) amplitude is to a high degree dependent on refractive changes. This fact has to be considered if changes in VEP amplitude during suction cup oculopression are used as a tolerance test in glaucoma diagnosis.

Adult↗

PubMed1994

[Cell and tissue culture models in dermatology. The Frankfurt Center of Dermatology establishes models].

In the course of the Third Frankfurt Talks, for the first time a congress in dermatology was dedicated exclusively to cell and tissue culture models. The complexity of a whole organ, in this case the skin, could be reduced to single aspects without losing the holistic context. Ways of managing this were discussed on an interdisciplinary level by dermatologists, physiologists, pharmacologists and biologists. The results are also expected to be useful to the clinician. Focus points of in vitro investigations for dermatology are wound closure models and the use of in vitro skin for transplantation in the therapy of non-healing ulcers and vitiligo. As an alternative to animal experiments, cultures of human cells are gaining increasing influence in drug testing. The effect of glucocorticosteroids on normal skin fibroblasts, keratinocytes and permanent cell lines is discussed as an example, and in vitro models of diseases such as psoriasis are established. Additionally, basic events such as differentiation and ageing have been modelled in cell cultures of melanocytes and keratinocytes. Mechanical stress, UV radiation and nicotine are discussed as inductors.

Cell Differentiation↗

PubMed1994

Levels of dopachrome tautomerase in human melanocytes cultured in vitro.

Several reports have been published about the level of activity and possible functions of dopachrome tautomerase (DCT) in mouse melanoma cells. Data about the levels of this activity in human melanocytes in culture are still scarce, and, as far as we know, a comparison between mouse and human melanocytes, or between normal and malignant melanocytes, has never been published. We have measured the tyrosinase and DCT activities, as well as the melanin content, in mouse Cloudman melanoma cells, two lines of human melanoma, and three lines of normal human melanocytes obtained from fetal skin. Although more cell lines should be tested to draw a general conclusion, our results suggest that normal melanocytes contained much higher tyrosinase activity and melanin content but lower DCT activity than malignant melanocytes. The two lines of human melanoma cells tested had lower levels of DCT activity than Cloudman melanoma cells. Finally, the low level of DCT activity found in normal human melanocytes cultured in vitro cannot be explained by any of the necessary stimulatory factors added to the cell culture media.

Animals↗

PubMed1994

Reactions of human keratinocytes in vitro after application of nicotine.

Nicotine is rapidly taken up by human keratinocytes (HaCaT cells) and after 3 h the uptake is approximately 50% of maximum. Cotinine, a metabolite of nicotine, was detected, thus demonstrating the metabolism of nicotine in HaCaT cells. Low nicotine concentrations (0.1-200 micrograms/ml) did not influence the incorporation rate of thymidine into DNA or amino acids into proteins. Inhibition of DNA and protein synthesis was only observed at concentrations > 200 micrograms/ml. After application of 400 micrograms/ml nicotine, the cells were vacuolated. This process was reversed after nicotine withdrawal. At low nicotine concentrations, no changes in microtubules and actin filaments could be detected. However, in the presence of nicotine (1-10 micrograms/ml), keratin filaments showed a more orderly pattern that controls, and the expression of the suprabasal keratins 1 and 10/11 was induced and increased according to the concentration of nicotine. The number of cornified envelopes also increased markedly. Nicotine concentrations > 100 micrograms/ml led to a disarrangement of keratin filaments and to a decrease in keratin expression and cornified envelope formation. Our results suggest that nicotine at concentrations up to 100 micrograms/ml is not an irritant but may induce cornification of the skin.

Cell Differentiation↗

PubMed1994

Effect of minoxidil on the mobility and differentiation of cultivated human keratinocytes.

The mode of topical action of minoxidil (U-10,858, CAS 38304-91-5) ist not entirely clear. The influence of minoxidil on the ultimate differentiation of keratinocytes was investigated. Human keratinocytes (HaCaT-cells) were incubated with minoxidil containing culture medium (10-250 micrograms/ml). Minoxidil inhibited in a concentration dependent manner cell mobility whereas the adhesion area and the cell circumference were increased. The minoxidil treated cultures had a higher desmosome density compared to parallel control cultures and they expressed the suprabasal keratins 1 and 10 (indicating progress in differentiation) earlier and to a larger extent than the controls. Keratins were revealed immunohistochemically and by two-dimensional polyacrylamide gel electrophoresis. The results suggest that minoxidil supports the differentiation of human keratinocytes.

Cell Adhesion↗

PubMed1994

[Effect of change in refraction by increasing intraocular pressure with the suction cup method on pattern reversal VECP].

When IOP is increased by the suction cup method, refraction changes will occur, depending on the shape of the cup and the height of the IOP increase. Similar refraction changes were simulated in six healthy volunteers by employing spherical and cylindrical glasses during pattern-reversal visual evoked cortical potential (VECP) with various check sizes and amount of contrast. While the pattern-reversal VECP latencies were not influenced, the amplitudes were reduced considerably. By using contact lenses and a suitably shaped suction cup, refraction changes could be compensated for. In 22 healthy volunteers pattern-reversal VECPs were derived with and without the application of contact lenses with artificially raised IOP. A comparison showed that the amplitudes differed significantly. Without contact lenses a negative pressure of more than 40 mmHg resulted in a drop in the amplitudes with a plateau formed between 80 and 120 mmHg. With compensation by contact lenses the amplitudes are found to be unaltered or even slightly increased until a negative pressure of 120 mmHg is reached in the suction cup, after which they drop. Plotting the pattern-reversal VECP amplitudes (obtained with refraction changes being compensated for by contact lenses) against ciliary perfusion pressure, one finds the characteristic curve described by Ulrich et al., suggesting an autoregulative capacity between 15 and 20 mmHg in healthy persons. The latencies, which remain uninfluenced by refraction changes, are also not altered within an IOP increase of 15-20 mmHg.

Adult↗

PubMed1993

Refraction changes during elevation of intraocular pressure by suction cup, their reflection in the pattern visual evoked cortical potential and their compensation.

Visual evoked cortical potential studies using pattern stimuli with the intraocular pressure raised artificially by the suction cup method have been reported. Possible changes in the refraction of the eye due to the method employed and their influence on the pattern visual evoked cortical potential have not been considered. Changes in the refraction of the eye during artificial intraocular pressure elevation and the influence of such changes on pattern visual evoked cortical potentials were studied. The refraction changes were found to depend on the shape of the suction cup. They could be compensated for by employing properly shaped suction cups and contact lenses. The behavior of amplitude and latency of the pattern visual evoked cortical potential at artificially elevated intraocular pressure with compensation for refraction changes has been studied and found to depend in a characteristic manner on ocular perfusion pressure.

Adult↗

PubMed1992

Effect of the dose of ultraviolet radiation on the pigment formation by human melanocytes in vitro.

Human melanocytes were cultivated under different conditions with phorbol ester (TPA), or with bovine pituitary extract (BPE). The cells altered their morphology with the different culture conditions. With TPA they were predominantly bipolar, while with BPE most of the cells had a dendritic cell shape. In order to investigate the effect of UV irradiation, the cells were irradiated with 50, 100 and 200 mJ/cm2 UVA/B. After irradiation with 200 mJ/cm2 UVA/B the cells cultured with TPA also showed a dendritic shape. We determined the tyrosinase activity, the cellular melanin content and the cell number 3 days after irradiation. In all cases the number of cells decreased depending on the UVA/B doses. In melanocytes we found a marked increase in tyrosinase activity and melanin content after irradiation with 200 mJ/cm2. The UV-induced effect on tyrosinase activity was higher in melanocytes cultured with BPE than in those cultured with TPA. The results were compared with two human melanoma cell lines. Only little pigment formation could be measured in the tested melanoma cell lines without change after UV irradiation.

Adult↗

PubMed1992

Pr VECPs related to ciliary perfusion pressure in primary open angle glaucoma. A study using contact lenses to compensate for refraction changes during artificially raised IOP.

Pr VECP studies in glaucoma patients with the IOP raised artificially by the suction cup method have recently been performed by several authors, who arrived at different results. The reason for those differences may be the changes employed. The refraction changes depend on the shape of the suction cup and the height of the artificial IOP raise. By using contact lenses and a suitably shaped suction cup refraction changes could be compensated for. Studies of the pr VECP with suction cup IOP elevation and simultaneous compensation for refraction changes by applying contact lenses were made on 17 patients with primary open angle glaucoma and 21 healthy volunteers. In healthy subjects pr VECP amplitudes were found unaltered or even slightly increased until 120 mmHg of negative pressure were reached in the cup. Beyond that range they dropped. Latencies remained unaltered over that range of negative pressures. Plotting the pr VECP amplitudes and latencies against ciliary perfusion pressure we obtained unaltered potentials over a range of ca. 20 mmHg, which we interpreted as autoregulative capacity. In the 17 glaucoma patients various degrees of impaired autoregulation were found corresponding to the progression of glaucoma damage.

Adult↗

PubMed1991

Translocation of the nuclear autoantigen La to cell surface: assembly and disassembly with the extracellular matrix.

La (SS-B) protein is known as one major antigenic target for autoantibodies from patients with certain autoimmune diseases such as Sjogren's syndrome or Lupus Erythematosus. La protein belongs to the so called "extractable nuclear antigens". Here we report that La antigen is not restricted to the nucleus as one might deduce from the exclusive nuclear staining pattern of patient anti-La antibodies but after stimulation of serum-starved cells with 10% fetal calf serum (FCS) appears and stays for at least 45 min at the outer surface of CV-1 cells being available for binding of anti-La antibodies. In addition we found that a minor part of La antigen associates with the extracellular fibronectin network. After addition of 10% FCS to serum starved cells this extracellular autoantigen disassembled from the extracellular matrix and was taken up again by the cells. Incubation of serum starved cells with mercuric chloride, a known potent inducer of autoantibodies, also resulted in a detachment of the extracellular matrix associated La protein. From our studies it becomes likely that La protein itself is the antigen during autoimmunization. Moreover, once developed, anti-La antibodies might be able to bind to cell surface expressed La protein resulting in a damage of these cells leading to the inflammational events known to occur during disease.

Autoantigens↗

PubMed1991

[Porphyria cutanea uraemica: an obligate systemic disease in chronic kidney insufficiency?].

Patients with chronic renal failure, especially those receiving maintenance haemodialysis, have a number of dermatological alterations. Some of them are similar to those seen in porphyria cutanea tarda (PCT). Whereas early studies showed normal plasma porphyrin levels, a striking elevation of plasma porphyrins, and particularly of uroporphyrin, has recently been found. We measured the concentrations of porphyrins in the plasma and erythrocytes of 55 patients with chronic renal failure and receiving maintenance haemodialysis and also in 7 patients with PCT and 100 healthy volunteers. The mean concentration of porphyrins in plasma was 2.7-fold, and the maximum concentration, 6-fold the highest value measured in plasma of controls. The mean plasma concentration of uroporphyrin was 6-fold higher up to a maximum value of 37-fold the upper limit of the controls. The plasma porphyrin values of 3 of 7 patients with PCT were on the same high level as those measured in patients undergoing haemodialysis. The mean porphyrin concentration in the erythrocytes of haemodialysis patients were 1.5-fold the control values. Because of the known pathophysiological effect of uroporphyrin, especially its stimulation of the collagen synthesis and the activation of the complement system, we suppose that the porphyria cutanea tarda like skin lesions in patients with chronic renal failure are due to the highly increased uroporphyrin concentration.

Humans↗

PubMed1990

A new model of epidermal differentiation: induction by mechanical stimulation.

In vivo, epidermal cells are committed to terminal differentiation in which they undergo a series of morphological and biochemical changes. In vitro, keratinocytes are able to undergo some steps of this differentiation process only. In view of the fact that in vivo skin is continuously subjected to mechanical stress, we investigated the stimulation of differentiation of transformed keratinocytes by mechanical stimulation. The cells, grown in plastic culture dishes, were periodically treated with weights exerting a pressure of 0.015 Ncm-2. This stimulation lasted from 1 to 4 days. Then keratinocytes were examined using indirect immunofluorescence, 3H-thymidine and 14C-amino acid incorporation, SDS polyacrylamide gel electrophoresis, and Western blotting. Following pressure treatment, the previously monolayered keratinocytes locally grew up to several layers, the number of horny scales increased and, after 4 days, the pattern of cytokeratin was modified. The total amount of keratin increased, forming granular accumulations, while the proliferation rate of the cells decreased. Both the 67 kDa and 49.5 kDa keratin subunits increased in stimulated cells. Moreover, a weak keratin band of 44 kDa appeared that was not present in controls. The results demonstrate that cyclic pressure promotes differentiation of cultivated epidermal cells.

Amino Acids↗