PubMed Health⌕ Search

Biomedical subjects

Christian Heinemann

Publications and source records attributed to Christian Heinemann.

7 recordsLinked to original sources
PubMed2007

Measurements of membrane patch capacitance using a software-based lock-in system.

On-cell patch-clamp capacitance measurements can resolve the fusion of individual vesicles to a membrane patch and the accompanying dilation of the fusion pore. So far, these measurements have used a patch-clamp amplifier in combination with a hardware lock-in amplifier. Usually, solely the capacitance and conductance outputs of hardware lock-in amplifiers were recorded, which needed to be filtered rather heavily to suppress spectral components at the stimulus frequency. Therefore, the temporal resolution was limited, and information carried in the patch current was not utilized. In this paper, we describe an alternative and more versatile approach for measuring patch capacitance and conductance, using a digitally controlled patch-clamp amplifier. The software lock-in system showed better bandwidth and identical signal-to-noise performance needing less instrumentation. High temporal resolution measurements on patches of chromaffin cells showed that vesicle fission can be completed in only tens of microseconds. Capacitance calculation based on the patch current allows for straightforward offline phase correction. Moreover, the close inspection of direct current for the first time revealed small current changes accompanying the fusion and fission of large secretory vesicles, promising new insights into the vesicles' membrane properties. A practical guide to high-resolution on-cell patch-clamp capacitance measurements using the software lock-in is provided.

Algorithms↗
PubMed2005

Induction of a hardening phenomenon by repeated application of SLS: analysis of lipid changes in the stratum corneum.

Adaptation of the skin to repeated influence of exogenous irritants is called the hardening phenomenon. We investigated the stratum corneum lipid composition before and after induction of a hardening phenomenon. Irritant contact dermatitis was induced in 23 non-atopic volunteers by repeated occlusive application of 0.5% sodium lauryl sulfate (SLS) over 3 weeks. At 3, 6 and 9 weeks after irritation, the SLS responses of pre-irritated skin and normal skin were compared. The horny layer lipid composition (ceramides 1-7, cholesterol and free fatty acids) was assessed before irritation and 3, 6 and 9 weeks after irritation. During the first 2 weeks of irritation the transepidermal water loss increased continuously and seemed to decrease during the third week (effect of adaptation). The barrier function of pre-irritated sites was more stable to SLS challenge. Three weeks after irritation, there was a significant increase of ceramide 1 (p<0.001). The only volunteer without hardening phenomenon showed no increase of ceramide 1. Ceramide 1 seems to play a key role as a protection mechanism against repeated irritation.

Administration, Cutaneous↗
PubMed2004

[Relapsing polychondritis as a rare different diagnosis of erysipelas].

A 76-year old patient with painful erythematous swelling of the right ear was initially treated with antibiotics under the suspected diagnosis of erysipelas. Her failure to respond and a history of previous laryngeal and nasal swelling suggested the possibility of relapsing polychondritis. High dose prednisolone therapy produced marked improvement. Relapsing polychondritis should be considered as a rare, but important differential diagnostic consideration for erysipelas.

Aged↗
PubMed2004

Prevention of experimentally induced irritant contact dermatitis by extracts of Isatis tinctoria compared to pure tryptanthrin and its impact on UVB-induced erythema.

Lipophilic extracts of Isatis tinctoria L. exhibit significant activity against several clinically relevant targets of inflammation. The alkaloid tryptanthrin was identified as one of the active principles in woad and characterised as a potent dual inhibitor of COX-2 and 5-LOX. Here, the anti-inflammatory efficacy of topical application of three different Isatis extracts and tryptanthrin was investigated in human volunteers. Two different models were used, namely the sodium lauryl sulphate (SLS)-induced irritant contact dermatitis (ICD) and UVB-induced erythema. Twenty healthy volunteers without any skin disease participated in the study. Cumulative irritant contact dermatitis was induced on test fields on the volunteers' backs by twice daily application of 0.5 % sodium lauryl sulphate over a period of four days. Half of the test fields were treated with the test substances during the eliciting phase, while the remaining test fields were treated over a period of 4 days after induction of dermatitis. In the second model, a UVB erythema on the volunteers' lower backs was induced using the double minimal erythema dose (MED). Twenty-four hours after irradiation the test fields were treated with the test substances over a period of 3 days. All reactions were assessed visually and by non-invasive bioengineering methods (evaporimetry and chromametry). Treatment with extracts during the ICD eliciting phase led to a significantly smaller increase of visual scores and transepidermal water loss compared to the untreated test field. For tryptanthrin this benefit was also observed, but the improvement was not statistically significant. When treatment was performed after completing the eliciting phase, accelerated resolution of the irritant reaction could not be observed. In the UVB erythema model anti-inflammatory effects of the test substances were not observed.

Adolescent↗
PubMed2003

A comparative study on the skin penetration of pure tryptanthrin and tryptanthrin in Isatis tinctoria extract by dermal microdialysis coupled with isotope dilution ESI-LC-MS.

The indolo[2,1- b]quinazoline alkaloid tryptanthrin has recently been identified as a pharmacologically active compound in Isatis tinctoria, with potent dual inhibitory activity on prostaglandin and leukotriene synthesis. To investigate the skin penetration of tryptanthrin from solutions of pure compound and Isatis extracts, we developed and validated a cutaneous microdialysis model using ex vivo pig foreleg. Microdialysis was performed by placing linear probes in the dermis of the skin in situ, and tryptanthrin concentrations in the dialysates were determined by isotope dilution electrospray ionization LC-MS in the selected ion mode. Measurable concentrations of tryptanthrin were detected 30 min after application. A dose-dependent increase in tryptanthrin concentrations in the dialysate was observed for the Isatis extracts, but not for pure tryptanthrin. Microscopic analysis showed that the pure compound crystallized from the solution but remained in an amorphous state in the extracts.

Animals↗