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Biomedical subjects

A Bernd

Publications and source records attributed to A Bernd.

At least 19 recordsLinked to original sources
PubMed2006

Elastin expression in a newly developed full-thickness skin equivalent.

The resilience of the human skin is mediated by elastic fibres mainly consisting of fibrillins and elastin. In order to establish a model system to study the impact of cosmetic and pharmaceutical compounds on the elastic system in vitro, we analyzed the expression of elastin in a newly developed full-thickness skin model. After a 5-week cultivation period the skin model developed a fully differentiated epidermis including a stratum corneum. The dermis contains fibroblasts embedded in extracellular matrix proteins. The models were viable until at least 51 days at the air-liquid interface (ALI) culture. Using immunohistochemistry we detected elastin first on day 7 of ALI. With proceeding culture time, elastin-positive fibres of different lengths and distribution patterns accumulated in the dermal compartment. Elastin mRNA expression started on day 7 of ALI, increased until day 10 and then dropped to a level comparable to that of day 7. Our results demonstrate that in our full-thickness skin model an in vivo-like elastic system, which clearly mimics at least two subsets of dermal elastic fibres, is generated. This physiological property favours the model as a promising animal-free approach to study those processes leading to an environment- and age-dependent decrease in skin elasticity.

Animals↗
PubMed2002

The curcuma antioxidants: pharmacological effects and prospects for future clinical use. A review.

In agreement with the predictions of the oxygen-stress theory of aging and age-related degenerative diseases, diet supplementation with a number of phenolic or thiolic antioxidants has been able to increase the life span of laboratory animals, protect against senescent immune decline and preserve the respiratory function of aged mitochondria. In addition to the above, more recent data reviewed here suggest that the polyphenolic compound curcumin and related non-toxic antioxidants from the rhizome of the spice plant Curcuma longa have a favorable effect on experimental mouse tumorigenesis as well as on inflammatory processes such as psoriasis and ethanol-caused hepatic injury. Our own research has focused on the effects of diet supplementation with an antioxidant-rich hydroalcoholic extract of the curcuma rhizome on key risk factors of atherogenesis and related cardiovascular disease. Our reviewed data show that, in human healthy subjects, the daily intake of 200 mg of the above extract results in a decrease in total blood lipid peroxides as well as in HDL and LDL-lipid peroxidation. This anti-atherogenic effect was accompanied by a curcuma antioxidant-induced normalization of the plasma levels of fibrinogen and of the apo B/apo A ratio, that may also decrease the cardiovascular risk. The reviewed literature indicates that curcumin and related plant co-antioxidants are powerful anti-inflammatory agents. Further, since they potentiate the anti-atherogenic effect of alpha-tocopherol, more extensive clinical testing of their probable usefulness in cardiovascular risk reduction seems justified.

Journal Article↗
PubMed2001

Activators of peroxisome proliferator-activated receptors protect human skin from ultraviolet-B-light-induced inflammation.

Peroxisome proliferator-activated receptors (PPAR) are members of a nuclear receptor superfamily, which were initially described in the context of fatty acid degradation and adipocyte differentiation. In this study we tested the hypothesis that peroxisome proliferator-activated receptor activation also controls inflammation. In an in vitro model with human keratinocytes inflammation was mimicked by irradiation with ultraviolet B light (150 mJ per cm(2)). Activators for PPAR-alpha (WY-14,643, clofibrate) were shown to reverse ultraviolet-B-light-mediated expression of inflammatory cytokines (interleukin-6, interleukin-8). An activator preferentially for PPAR-beta (bezafibrate) did not show prominent effects on interleukin-6 and interleukin-8 expression. The anti-inflammatory action of WY-14,643 on skin cells was further demonstrated by in vivo testings in which topically applied WY-14,643 markedly increased the minimal erythema dose in ultraviolet-B-irradiated skin. Additionally, it was shown that ultraviolet B irradiation led to a decrease of all three peroxisome proliferator-activated receptor subsets at the mRNA level. Also transactivation of peroxisome proliferator response element was attenuated by ultraviolet B irradiation. The downregulation of peroxisome proliferator-activated receptors by ultraviolet B irradiation provides a possible mechanism that leads to exaggerated and prolonged inflammation. This work suggests the possibility of PPAR-alpha activators as novel nonsteroidal anti-inflammatory drugs in the topical treatment of common inflammatory skin diseases such as atopic dermatitis, psoriasis, and photodermatitis.

Cell Division↗
PubMed2001

Effects of mechanical force on primary human fibroblasts derived from the gingiva and the periodontal ligament.

Previous experiments have shown that mechanical stress may alter the interactions between cells and extracellular matrix (ECM). The purpose of our study was to investigate the effects of mechanical load on metabolism and ECM expression of primary human periodontal cells. The influence of gravitational force on proliferation, lactate dehydrogenase (LDH) release, and tenascin expression of gingival (HGF) and periodontal ligament fibroblasts (HPDL), as well as their adhesion to various extracellular matrix (ECM) components, was determined. Cells were centrifuged in microplates or flat tubes for 16 hrs at 217 g. Neither an enhanced release of LDH nor an alteration of cell proliferation could be detected after centrifugation. However, the attachment of loaded gingival and periodontal ligament fibroblasts to all tested ECM components significantly decreased in comparison with controls (Wilcoxon-Mann-Whitney test; HGF, p < 0.05; HPDL, p < 0.01). Tenascin expression of mechanically stressed fibroblasts significantly increased in comparison with controls (p < 0.01).

Cell Adhesion↗
PubMed2000

An hydroalcoholic extract of curcuma longa lowers the apo B/apo A ratio. Implications for atherogenesis prevention.

It is generally accepted that free-radical induced blood lipid peroxidation and especially peroxidized LDL play a central role in the pathogenesis of atherosclerosis and related cardiovascular disease. Moreover, recent research highlights the key contribution of apolipoprotein B (apo B) to atherogenesis as the main inductor of one of its earlier steps, i.e. macrophage proliferation. This has led us to investigate the apo B response to a very effective phenolic lipid-antioxidant, namely an hydroalcoholic extract of Curcuma longa, which according to our previous work does not show any toxic effects and decreases the levels of blood lipid peroxides, oxidized lipoproteins and fibrinogen. The present study shows that a daily oral administration of the extract decreases significantly the LDL and apo B and increases the HDL and apo A of healthy subjects. This and recent data on the increased anti-atherogenic action of the physiological antioxidant tocopherol in the presence of phenolic co-antioxidants (which eliminate the tocopheroxyl radical), justifies planned clinical research to test the usefulness of the curcuma extract as a co-antioxidant complement to standard treatments to prevent or retard atherosclerosis.

Adult↗
PubMed2000

Melanocytes respond to mechanical stretch by activation of mitogen-activated protein kinases (MAPK).

Cells of human epidermis are permanently targeted by mechanical stimuli. Besides mechanical forces from external sources the body itself generates mechanical forces via muscle contractions and growth processes. Recently, it was demonstrated that mechanical stretch is connected to enhanced proliferation in epidermal cells. The underlying biochemical events are still a matter of debate. Here we show that mechanical stretch leads to activation of both ERK1/2 and SAPK/JNK in human melanocytes and keratinocytes. In response to a 5 min single stretch ERK1/2 becomes moderately induced in melanocytes and peaked 30 min after the stimulus. In keratinocytes strong activation of ERK1/2 is present directly after the stimulus. SAPK/JNK shows the same activation pattern in both cell species--a slow but steady activation. The different kinetics of both MAPK suggest that different signalling cascades were activated. Future studies should evaluate the relevance of stretch-dependent MAPK activation in triggering the cell proliferation.

Cell Line↗
PubMed2000

Signaling of mechanical stretch in human keratinocytes via MAP kinases.

Cells within human skin are permanently exposed to mechanical stretching. Here we present evidence that alterations in cell shape trigger biochemical signaling via MAP kinases in human keratinocytes. In an in vitro attempt we demonstrate a fast but transient activation of extracellular signal-regulated kinases 1/2 in response to cell stretch. This activation is reversed by preincubation with functional blocking antibodies directed towards beta1-integrins. As a second member of MAP kinases, stress-activated protein kinase/c-JUN NH2-terminal kinase was activated in a slower fashion, peaking at 1 h after the initial stimulus. The delay in signal transmission suggests that extracellular signal-regulated kinases 1/2 and stress-activated protein kinase/c-JUN NH2-terminal kinase do not share the same signaling pathway. p38 was not activated by cell stretching. The contribution of cytoskeletal elements in signal perception and transduction was evaluated by selective disruption of either actin filaments, microtubules, or keratin filaments but showed no clear effect on stretch-induced activation of extracellular signal-regulated kinases 1/2 and stress-activated protein kinase/c-JUN NH2-terminal kinase. In conclusion we found evidence of a cell-shape-dependent activation of MAP kinases in human keratinocytes disclosing beta1-integrins as putative mechano-transducers. It is likely that alterations of skin mechanics in vivo underlying pathogenic processes like wound formation and healing trigger physiologic responses via the MAP kinase pathway.

Cell Line↗
PubMed1999

Cyclic stretch up-regulates proliferation and heat shock protein 90 expression in human melanocytes.

Human skin is repeatedly exposed to mechanical stretching in vivo, but in an ordinary culture of skin cells this prominent feature has been neglected. In order to study whether mechanical stretching plays a role for human melanocytes, we have established a culture technique to mimic this physical stretching: primary cultures of human melanocytes were plated on silicon supports, which undergo a stretching of about 10% of the initial length. After application of repeated stretching and relaxation for 4 days, cell count was significantly (about 40%) enhanced. In addition, we found approximately 2-fold increase in heat shock protein (HSP) 90, both at the protein and mRNA level. HSP 90 is known to bind to Raf-1 and, therefore, may contribute to the Raf-1-MEK (mitogen-activated protein-kinase kinase)-MAPK (mitogen-activated protein-kinase) signaling pathway. Disruption of the Raf-1-HSP 90 multimolecular complex by geldanamycin lead to a considerable decrease in melanocyte cell count. However, geldanamycin did not reverse the stretch-induced growth stimulation. Therefore, the stretch-mediated up-regulation of HSP 90 expression in melanocytes appears to be independent of stretch-mediated growth stimulation. These findings have strong implications for the in vitro cultivation of melanocytes for transplantation purposes.

Cell Division↗
PubMed1999

Autologous keratinocytes cultured on benzylester hyaluronic acid membranes in the treatment of chronic full-thickness ulcers.

Keratinocytes were obtained from three patients with chronic full-thickness ulcers of different aetiologies. The cells were isolated, cultured and then seeded on to a membrane composed of benzylester hyaluronic acid. Once the keratinocytes had become subconfluent, the keratinocyte-containing matrix sheets were then applied as autologous grafts to the patients' ulcers. Results indicate that autologous grafting of keratinocytes cultured on benzylester hyaluronic acid membranes provides improved graft handling, reduces total time required for tissue cultivation and enhances cellular vitality because of the possibility of grafting at a subconfluent non-differentiated stage.

Aged↗
PubMed1999

Phototoxic effects of Hypericum extract in cultures of human keratinocytes compared with those of psoralen.

Extracts of Hypericum perforatum (St. John's wort) are used in the treatment of depression. They contain the plant pigment hypericin and hypericin derivates. These compounds have light-dependent activities. In order to estimate the potential risk of phototoxic skin damage during antidepressive therapy, we investigated the phototoxic activity of hypericin extract using cultures of human keratinocytes and compared it with the effect of the well-known phototoxic agent psoralen. The absorbance spectrum of our Hypericum extract revealed maxima in the whole UV range and in parts of the visible range. We cultivated human keratinocytes in the presence of different Hypericum concentrations and irradiated the cells with 150 mJ/cm2 UVB, 1 J/cm2 UVA or 3 h with a white light of photon flux density 2.6 mumol m-2 s-1. The determination of the bromodeoxyuridine incorporation rate showed a concentration- and light-dependent decrease in DNA synthesis with high hypericin concentrations (> or = 50 micrograms/mL) combined with UVA or visible light radiation. In the case of UVB irradiation a clear phototoxic cell reaction was not detected. We found phototoxic effects even with 10 ng/mL psoralen using UVA with the same study design as in the case of the Hypericum extract. These results confirm the phototoxic activity of Hypericum extract on human keratinocytes. However, the blood levels that are to be expected during antidepressive therapy are presumably too low to induce phototoxic skin reactions.

Antidepressive Agents↗
PubMed1998

Increase with age of serum lipid peroxides: implications for the prevention of atherosclerosis.

There is considerable support for the concept that oxygen free radicals and related lipid peroxides play a key role in the pathogenesis of normal senescence and of age-related chronic degenerative diseases, including atherosclerosis. This has led to a great deal of interest regarding peroxidized LDL, which seems to be more atherogenic than LDL. In contrast, the relationship of total serum or plasma lipid peroxides (which also have a marked atherogenic action) with both aging and atherogenesis are not well understood. In view of the above, we have determined the level of serum lipid peroxide (expressed as thiobarbituric acid reactive substances) in a sample of 100 healthy men and women ranging in age from 20 to 70 years. Our data show that there is an age related increase in the concentration of lipid peroxide, with men showing higher or about equal values than women until about 60 years, after which age women show the higher values. Our data also suggest that in certain men and women, aging is linked to a decline in the competence of the oxyradical-detoxifying mechanisms, which results in increased serum lipid peroxidation. Further research is needed to find out if lowering the serum peroxide levels of aging subjects by diet supplementation with antioxidants will decrease that risk. An adequate intake of antioxidants seems especially indicated in post-menopausal women because of their apparent greater sensitivity to age related oxygen stress.

Adult↗
PubMed1998

Limitations of imaging choroidal tumors in vivo by optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) produces two-dimensional cross-sectional images with a longitudinal resolution of 10 microns. Its capacity for imaging retinal structure has been shown in a variety of diseases. There are no reports on its capacity and limitations in imaging choriocapillary and choroidal structures. METHODS: Twenty-two patients with the diagnosis of malignant melanoma of the choroid were submitted to OCT. We used a prototype and a commercial device, both with an 850-nm superluminescent diode with a band-width of 30 nm (reported longitudinal resolution 10 microns). The images were evaluated for retinal thickness, changes in retinal pigment epithelium, subretinal fluid accumulation and changes in choriocapillary or choroidal reflectivity. RESULTS: Retinal edema and detachment found on biomicroscopic examination for fluorescein angiography was detected by OCT in all such cases. In 2 of 22 cases small retinal detachments were detected only by OCT. Tumor extension through the retinal pigment epithelium was not seen in this series, either by biomicroscopy or by OCT. The pattern of choroidal or choriocapillary reflectivity was nonspecifically lower than that of normal choroid, but did not yield any additional information about tumor histology. When normal retina was present, the OCT appearance of a malignant melanoma resembled that of normal choroid. CONCLUSION: OCT may provide information about the retinal structure overlying prominent tumors and the extent of adjacent retinal detachment. In its present state of development, OCT is of little value in the differential diagnosis of choroidal tumors. Its potential value for the follow-up of shallow tumors needs further investigation.

Adult↗
PubMed1998

Quantification of tyrosinase, TRP-1, and Trp-2 transcripts in human melanocytes by reverse transcriptase-competitive multiplex PCR--regulation by steroid hormones.

We have introduced a reverse transcriptase polymerase chain reaction based method to measure mRNA levels of the melanogenesis enzymes tyrosinase, tyrosinase-related-protein 1 (TRP-1), and tyrosinase-related-protein 2 (TRP-2). Expression was determined by reverse transcriptase-competitive multiplex polymerase chain reaction of (i) melanogenesis enzyme transcripts and the "housekeeping" gene glyceraldehyde-3-phosphate dehydrogenase, and (ii) two internal standards consisting of mutated melanogenesis enzyme cDNA and mutated gene glyceraldehyde-3-phosphate dehydrogenase cDNA. This was investigated on in vitro cultured melanocytes in the presence of three different steroids; one glucocorticoid (betamethasone-17-valerate) and two sex steroids (diethylstilbestrol and estradiol). All three steroids lead to an increase of about 1.5-2.5-fold of tyrosinase transcripts. The amount of TRP-1 transcripts was likewise enhanced, but only moderately (approximately 1.5-fold). In contrast, TRP-2 transcripts were reduced by approximately 40% in number after betamethasone-17-valerate treatment, whereas the two sex steroids, diethylstilbestrol and estradiol, caused an upregulation of about 20-fold of the initial TRP-2 transcript level. We therefore suggest that hyperpigmentation during pregnancy or under contraceptive treatment is mediated by a direct induction of melanogenesis via sex steroids.

Betamethasone↗
PubMed1998

Grafting of in vitro cultured melanocytes onto laser-ablated lesions in vitiligo.

A variety of grafting procedures using autologous melanocytes have achieved promising results in the treatment of vitiligo. We here report on the preparation of an adequate graft recipient bed by pulsed Erbium-YAG laser skin ablation. In particular, for irregular lesions on delicate sites, which cannot be approached by utilization of suction blisters or dermabrasion, this technique may offer a distinct advantage.

Adult↗
PubMed1998

The mechanism of melanocyte dendrite formation: the impact of differentiating keratinocytes.

In human epidermis one dendritic melanocyte interacts with about 36 keratinocytes and supplies them with melanin. In contrast to the vivo situation melanocytes in culture are far less dendritic. In the present study different culture systems were tested in order to observe the mechanism of melanocyte dendrite formation. In particular, we focused on the role of keratinocytes in this process. Time lapse studies revealed that only differentiated keratinocytes enhance melanocyte dendricity. Differentiated keratinocytes form connected cell sheets, which attach to part of the melanocyte plasma membrane. By contraction and retraction of keratinocyte units, new dendrites were drawn out from the melanocytes. Melanocytes remain passive during this process, which is indicated by the observation that sometimes extended dendrites could not withstand the tension and shear.

Calcium↗