A computational model for previtamin D(3) production in skin.

Low levels of vitamin D have been implicated in a wide variety of health issues from calcemic diseases to cancer, diabetes and cardiovascular disease. For most humans, the majority of vitamin D(3) is derived from sunlight. How much vitamin D is produced under given exposure conditions is still widely discussed. We present a computational model for the production of (pre-)vitamin D within the skin. It accounts for spectral irradiance, optical properties of the skin and concentration profile of provitamin D. Results are computed for various sets of these parameters yielding the distribution of produced previtamin D in the skin.

Absorption spectra of human skin in vivo in the ultraviolet wavelength range measured by optoacoustics.

Knowledge of the optical properties of human skin in the ultraviolet range is fundamental for photobiologic research. However, optical properties of human skin in the ultraviolet spectral range have so far mainly been measured ex vivo. We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. In a study on 20 subjects belonging to phototypes I-IV, we studied the optical properties at the volar and dorsal aspect of the forearm as well as on the thenar. Analysis of the measured absorption spectra shows that comparable skin areas-like different sides of the forearm-have qualitatively similar optical characteristics. Still, the optical properties may vary substantially within the same area, probably due to the skin structure and inhomogeneities. Comparison of the spectra from different skin sites indicates that the spectral characteristics of the stratum corneum and its chromophores play an important role for the optical properties of human skin in vivo in the ultraviolet B range.

Wavelength-dependent penetration depths of ultraviolet radiation in human skin.

The wavelength-dependent penetration depth of ultraviolet radiation in human skin is a fundamental parameter for the estimation of the possible photobiological impact of ultraviolet (UV) radiation. We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3-nm steps using laser optoacoustics and calculated the respective penetration depths. Data were analyzed with respect to different skin regions and skin phototype of the 20 subjects in the study (phototype I: n=3; II: n=7; III: n=5; IV: n=5), revealing large variability between individuals. The penetration depth of UV radiation in human skin is highly dependent on wavelength and skin area, but no significant dependence on skin phototype could be found.

Effect of ultraviolet adaptation on the ultraviolet absorption spectra of human skin in vivo.

BACKGROUND: The absorption spectrum of human skin provides a basis for the estimation of the possible photobiological impact of ultraviolet (UV) radiation. The optical properties of human skin in the UV spectral range have so far mainly been measured ex vivo due to a lack of an appropriate in vivo technique and the change of optical properties during the course of adaptation to higher UV doses has hardly been addressed. METHODS: We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. Spectra from the volar and dorsal aspects of the forearm of 20 subjects were compared, i.e. sites with native and various facultative pigmentation. RESULTS: UV adaptation shows as an increase in absorption coefficients over the entire measured UV range and especially in short-range UVB. Subject groups with high vs. low UV exposure can be discriminated by analyzing the difference absorption spectra between dorsal and volar aspects of the forearm. No dependence on the subject's phototype was seen in the degree of adaptation. CONCLUSION: The difference between native and facultative pigmentation may be explained by the absorption properties of the two prime chromophores responsible for adaptation to higher UV exposure: melanin and keratin. Stronger pigmentation, i.e. a higher melanin concentration, is found as an increase of absorption coefficients over the entire UVA-II/UVB range. The thickening of the horny layer and accordingly, a higher influence of keratin on the absorption spectra is prominent especially in the UVB region.

Analysis of complex, multidimensional datasets.

Several exciting new technologies have been developed in the Biomedical and Life Sciences producing genome and proteome wide multidimensional datasets (see Glossary). However, discovery of the relevant information from this multidimensional data is still a very challenging task. This review examines the main analytic methodologies available to the practitioner. It considers their strengths and weaknesses from a practical standpoint and gives an application example for the classification of human health condition.:

Pilot study of capillary electrophoresis coupled to mass spectrometry as a tool to define potential prostate cancer biomarkers in urine.

We describe the use of capillary electrophoresis (CE) coupled with mass spectrometry (MS) to identify single polypeptides and patterns of polypeptides specific for prostate cancer (CaP) in human urine. Using improved sample preparation methods that enable enhanced comparability between different samples, we examined samples from 47 patients who underwent prostate biopsy. Of this group, 21 patients had benign pathology and 26 with CaP, and these were used to define potential biomarkers, which allow discrimination between these two states. In addition, CE-MS data from these 47 urine samples were compared to that of 41 young men (control) without known or suspected clinical CaP to further confirm the polypeptides indicative for CaP. Upon crossvalidation of the same samples, several polypeptides were selected that enabled correct classification of the CaP patients with 92% sensitivity and 96% specificity. We then examined an additional 474 samples from patients with renal disease enrolled in other studies and found that 14 (3%) had polypeptides suggestive of CaP possibly indicating that they harbor clinical CaP. In conclusion, this early pilot study suggests that CE-MS of urine warrants further investigation as a tool that can identify putative biomarkers for CaP.

Capillary electrophoresis coupled to mass spectrometer for automated and robust polypeptide determination in body fluids for clinical use.

We describe the application of capillary electrophoresis (CE) coupled on-line to an electrospray ionization-time of flight-mass spectrometer (ESI-TOF-MS) to the analysis of human urine and serum for the identification of biomarkers for clinical diagnostics. CE-MS led to display > 1000 polypeptides present in complex biological samples within 45-60 min in a single analysis run. To extract the information of the CE-MS spectra in a timely fashion, a software was designed to automatically deconvolute and normalize the spectra. Both urine and serum contain several hundred polypeptides in samples from healthy individuals. Hence, it is possible to establish typical "normal urine" or "normal serum" polypeptide patterns. Samples from patients with different diseases display polypeptide patterns that differ significantly from those obtained from healthy individuals. Examining series of patients with the same disease allowed the establishment of polypeptide patterns typical for specific diseases. This permits the search for marker peptides specific for diseases. The data indicate that a single polypeptide present in all patients with the same disease, but absent in all healthy control individuals does not exist. The combination of several polypeptides found in either urine or serum or both are forming a specific pattern, which is indicative not only for the particular disease, but also for the stage of disease. CE-MS detects many polypeptides in single samples and the application of the software to the search of identical polypeptides excreted in urine allows the unbiased diagnosis based on a pattern and does not rely on single disease markers.

Proteomic patterns established with capillary electrophoresis and mass spectrometry for diagnostic purposes.

BACKGROUND: Proteomics applied in large scale may provide a useful diagnostic tool. METHODS: We developed an online combination of capillary electrophoresis with mass spectrometry, allowing fast and sensitive evaluation of polypeptides found in body fluids. Utilizing this technology, polypeptide patterns from urine are established within 45 minutes. About 900 to 2500 polypeptides as well as their concentrations are detected in individual urine samples without the need for specific reagents such as antibodies. To test this method for clinical application, we examined spot urine samples from 57 healthy individuals, 16 patients with minimal change disease (MCD), 18 patients with membranous glomerulonephritis (MGN), and 10 patients with focal segmental glomerulosclerosis (FSGS). RESULTS: One-hundred seventy-three polypeptides were present in more than 90% of the urine samples obtained from healthy individuals, while 690 polypeptides were present with more than 50% probability. These data permitted the establishment of a "normal" polypeptide pattern in healthy individuals. Polypeptides found in the urine of patients differed significantly from the normal controls. These differences allowed the distinction of specific protein spectra in patients with different primary renal diseases. Abnormal pattern of proteins were found even in urine from patients in clinical remission. CONCLUSION: The data indicate that capillary electrophoresis with mass spectrometry coupling provides a promising tool that permits fast and accurate identification and differentiation of protein patterns in body fluids of healthy and diseased individuals, thus enabling diagnosis based on these patterns.

Mass spectrometry for the detection of differentially expressed proteins: a comparison of surface-enhanced laser desorption/ionization and capillary electrophoresis/mass spectrometry.

The discovery of biomarkers is currently attracting much interest as it harbors great potential for the diagnosis and monitoring of human diseases. Here we have used two advanced mass spectroscopy based technologies, surface enhanced laser desorption ionization (SELDI-MS) and capillary electrophoresis/mass spectrometry (CE/MS), to obtain proteomic patterns of urine samples from patients suffering from membranous glomerulonephritis (MGN) and healthy volunteers. The results indicate that CE/MS analysis is able to display a rich and complex pattern of polypeptides with high resolution and high mass accuracy. In order to analyze these patterns, the MosaiqueVisu software was developed for peak identification, deconvolution and the display of refined maps in a three-dimensional format. The polypeptide profiles obtained with SELDI-MS from the same samples are much sparser and show lower resolution and mass accuracy. The SELDI-MS profiles are further heavily dependent on analyte concentration. SELDI-MS analysis identified three differentially expressed polypeptides, which are potential biomarkers that can distinguish healthy donors from patients with MGN. In contrast, approximately 200 potential biomarkers could be identified by CE/MS. Thus, while SELDI-MS is easy to use and requires very little sample, CE/MS generates much richer data sets that enable an in-depth analysis.

Capillary electrophoresis coupled to mass spectrometry to establish polypeptide patterns in dialysis fluids.

Combination of capillary electrophoresis with mass spectrometry (CE-MS) allows generation of polypeptide patterns of body fluids. In a single CE-MS (45 min) run more than 600 polypeptides were analyzed in hemodialysis fluids obtained with different membranes (high-flux/low-flux). Larger polypeptides (M(r) > 10 000) were almost exclusively present in high-flux dialysates only, while in low-flux dialysates additional small polypeptides were detected. Comparison to the normal urine pattern yielded a surprisingly low consensus: a number of polypeptides present in urine were missing. We established a fast and sensitive technique, easily applicable to the monitoring of different modalities of dialyzers.

Determination of peptides and proteins in human urine with capillary electrophoresis-mass spectrometry, a suitable tool for the establishment of new diagnostic markers.

The on-line coupling of capillary electrophoresis (CE) with electrospray-time-of-flight mass spectrometry (MS) has been used to obtain patterns of peptides and proteins present in the urine of healthy human individuals. This led to the establishment of a "normal urine polypeptide pattern", consisting of 247 polypeptides, each of which was found in more than 50% of healthy individuals. Applying CE-MS to the analysis of urine of patients with kidney disease revealed differences in polypeptide pattern. Twenty-seven polypeptides were exclusively found in samples of patients. Another 13, present in controls, were missing. These data indicate that CE-MS can be applied as powerful tool in clinical diagnostics.