Biomedical subjects

P J Caspers

Publications and source records attributed to P J Caspers.

6 recordsLinked to original sources

PubMed2003

Combined in vivo confocal Raman spectroscopy and confocal microscopy of human skin.

In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination allows the skin morphology to be visualized and (subsurface) structures in the skin to be targeted for Raman measurements. Novel results are presented that show detailed in vivo concentration profiles of water and of natural moisturizing factor for the stratum corneum that are directly related to the skin architecture by in vivo cross-sectional images of the skin. Targeting of skin structures is demonstrated by recording in vivo Raman spectra of sweat ducts and sebaceous glands in situ. In vivo measurements on dermal capillaries yielded high-quality Raman spectra of blood in a completely noninvasive manner. From the results of this exploratory study we conclude that the technique presented has great potential for fundamental skin research, pharmacology (percutaneous transport), clinical dermatology, and cosmetic research, as well as for noninvasive analysis of blood analytes, including glucose.

Arm↗

PubMed2003

A fast, digitally controlled flow proportional gas injection system for studies in lung function.

The aim of this paper is to describe a device for flow proportional injection of tracer gas in the lungs of mechanically ventilated patients. This device may then be used for the study of the multiple breath indicator gas washout technique to determine the end-expiratory lung volume. Such a tracer gas injection device may also be used in the study of other techniques that rely on uptake and elimination of tracer gas by the lungs. In this paper, an injector is described which enables injection of indicator gas at a predetermined concentration in a breathing circuit independent of the type of breathing. The presented setup uses a control computer to produce steering signals to a multivalve array in proportion to the input breathing signals. The multivalve array consists of ten circular valves, each with a different diameter, which can be opened or closed individually according to the input signal of the array. By opening of a certain combination of valves an amount of sulphur hexafluoride gas proportional to the inspiratory breathing signal is released. The rate of transmission between the components of the injection system was 80 Hz. The injector has a full flow range between 0-10 L/min. The delay time between the breathing signal and the flow response was 70 ms. The aimed washin gas concentration of 1% SF6 was achieved after 0.5 s. The study describes the results of tests to determine valve-flow ratios, step response and dynamic response of the injector. The flow output response of the injector system was shown to increase in input frequencies above 3 Hz. The valve flow ratios showed the largest relative deviation in the two smallest valves of the 10 valve array, respectively 0.005 L/min (25%) and 0.002 L/min (20%). We conclude that the injector can achieve a stable concentration of indicator gas in a breathing system with an accuracy of 0.005 L/min to execute the multiple breath indicator washout test in human subjects. The results of the study indicate that the injector may be of use in other application fields in respiratory physiology in which breathing circuit injection of indicator gas is required.

Algorithms↗

PubMed2001

In vivo confocal Raman microspectroscopy of the skin: noninvasive determination of molecular concentration profiles.

Confocal Raman spectroscopy is introduced as a noninvasive in vivo optical method to measure molecular concentration profiles in the skin. It is shown how it can be applied to determine the water concentration in the stratum corneum as a function of distance to the skin surface, with a depth resolution of 5 microm. The resulting in vivo concentration profiles are in qualitative and quantitative agreement with published data, obtained by in vitro X-ray microanalysis of skin samples. Semi-quantitative concentration profiles were determined for the major constituents of natural moisturizing factor (serine, glycine, pyrrolidone-5-carboxylic acid, arginine, ornithine, citrulline, alanine, histidine, urocanic acid) and for the sweat constituents lactate and urea. A detailed description is given of the signal analysis methodology that enables the extraction of this information from the skin Raman spectra. No other noninvasive in vivo method exists that enables an analysis of skin molecular composition as a function of distance to the skin surface with similar detail and spatial resolution. Therefore, it may be expected that in vivo confocal Raman spectroscopy will find many applications in basic and applied dermatologic research.

Adult↗

PubMed1998

In vitro and in vivo Raman spectroscopy of human skin.

Noninvasive techniques that provide detailed information about molecular composition, structure, and interactions are crucial to further our understanding of the relation between skin disease and biochemical changes in the skin, as well as for the development of penetration enhancers for transdermal drug administration. In this study we present in vitro and in vivo Raman spectra of human skin. Using a Raman microspectrometer, in vitro spectra were obtained of thin cross sections of human skin. They provided insight into the molecular composition of different skin layers. Evidence was found for the existence of a large variation in lipid content of the stratum corneum. A simple experimental setup for in vivo confocal Raman microspectroscopy of the skin was developed. In vivo Raman spectra of the stratum corneum were obtained at different positions of the arm and hand of three volunteers. They provided evidence for differences in the concentration of natural moisturizing factor at these positions.

Dermis↗

PubMed1994

Resonance Raman microspectroscopic characterization of eosinophil peroxidase in human eosinophilic granulocytes.

A resonance Raman microspectroscopic study is presented of eosinophil peroxidase (EPO) in human eosinophilic granulocytes. Experiments were carried out at the single cell level with laser excitation in Soret-, Qv-, and charge transfer absorption bands of the active site heme of the enzyme. The Raman signal obtained from the cells was almost exclusively due to EPO. Methods were developed to determine depolarization ratios and excitation profiles of Raman bands of EPO in situ. A number of Raman band assignments based on earlier experiments with isolated EPO have been revised. The results show that in agreement with literature on isolated eosinophil peroxidase, the prosthetic group of the enzyme in the (unactivated) cells is a high spin, 6-coordinated, ferric protoporphyrin IX. The core size of the heme is about 2.04 A. The proximal and distal axial ligands are most likely a histidine with the strong imidazolate character typical for peroxidases, and a weakly bound water molecule, respectively. The data furthermore indicate that the central iron is displaced from the plane of the heme ring. The unusual low wavenumber Raman spectrum of EPO, strongly resembling that of lactoperoxidase, intestinal peroxidase and myeloperoxidase, suggests that these mammalian peroxidases are closely related, and characterized by, as yet unspecified, interactions between the peripheral substituents and the protein, different from those found in other protoheme proteins.

Binding Sites↗

PubMedDate not supplied

Tissue characterization using high wave number Raman spectroscopy.

Raman spectroscopy is a powerful diagnostic tool, enabling tissue identification and classification. Mostly, the so-called fingerprint (approximately 400-1800 cm(-1)) spectral region is used. In vivo application often requires small flexible fiber-optic probes, and is hindered by the intense Raman signal that is generated in the fused silica core of the fiber. This necessitates filtering of laser light, which is guided to the tissue, and of the scattered light collected from the tissue, leading to complex and expensive designs. Fused silica has no Raman signal in the high wave number region (2400-3800 cm(-1)). This enables the use of a single unfiltered fiber to guide laser light to the tissue and to collect scattered light in this spectral region. We show, by means of a comparison of in vitro Raman microspectroscopic maps of thin tissue sections (brain tumors, bladder), measured both in the high wave number region and in the fingerprint region, that essentially the same diagnostic information is obtained in the two wave number regions. This suggests that for many clinical applications the technological hurdle of designing and constructing suitable fiber-optic probes may be eliminated by using the high wave number region and a simple piece of standard optical fiber.

Animals↗