Skin Responses to Micro Scale Field Size of Solar‐Simulated Radiation – Preliminary Evaluation by Reflectance Confocal Microscopy in vivo

Erythema and pigment responses of human skin following an acute exposure to ultraviolet radiation (UVR) are frequently used to determine the photosensitivity of the skin. In this study we investigated the responses of the skin to a micro‐scale area of UVR exposure (MiR) and compared the responses to a macro‐scale area of exposure (MaR). Ten human volunteers were tested with solar‐simulated radiation on their upper arm or back using a beam size of 8 mm and 0.2 mm in diameter. The fluence required to produce a minimally perceptible erythema (MED) using the MiR was found to be higher than that for the MaR. The erythema response extended beyond the exposed area and this became pronounced when the beam size was microscopic. Reflectance confocal microscopy in vivo revealed that MiR induced cellular alterations within a confined area of smaller dimensions than the area of exposure. Pigment responses were confined within the areas of cellular damage. The erythema expression of exposed skin recovered faster for the sites receiving MiR even when the applied fluence was higher than the MED for the MaR. Through the use of MiR we were able to visualize spatially dissimilar skin responses of erythema and pigmentation suggesting different cellular mechanisms.     

Pseudo-Raman broad band of stacked benzene molecules

The broad band displayed by pilled-up benzene molecules in Raman-like scale has the same nature as the one produced by chain polymers as BSA and PGA.     

Laser-induced stimulation of chymotrypsin activity

Experimental evidence supporting Frölich's conjecture of a metastable state in enzymes is provided.     

AN EXPERIMENTAL STUDY OF THE CHANGES IN PIGMENTATION IN HUMAN SKIN IN VIVO WITH VISIBLE AND NEAR INFRARED LIGHT

Abstract— The skin of the lower inner arm of volunteers was irradiated, with a 390–1700 nm light source, through a fiber optic bundle for times of up to 1.2 × 10⁴ s and with powers of up to 0.35 W/cm². Simultaneously with the irradiation, spectra (390–720 nm) of the remitted intensity were measured, while a 5.0 cm in diameter area of the skin around the fiber bundle was maintained at constant temperature, within 0.2°C. The generation of a photoproduct was observed and measured as changes in the remitted intensity within 600 s (10 min) of the start of irradiation.
The photoproduct formed was characterized by a weak absorption in the blue part of the spectrum (400–450 nm), leading to a bluish appearance in the irradiated area only. The color change appears as a two step process. It starts with a "soluble" photoproduct, which disappears, within 24 h after irradiation, and an "insoluble" photoproduct which appears with irradiation greater than 3 ×10³ s (50 min). No spectral differences were detected between the two photoproducts. The "insoluble" photoproduct persists for periods of up to 8 weeks. The color change in the skin is immediate and there is no erythema associated with this color change.     

In vivo fluorescence spectroscopy of nonmelanoma skin cancer

In vivo and ex vivo tissue autofluorescence (endogenous fluorescence) have been employed to investigate the presence of markers that could be used to detect tissue abnormalities and/or malignancies. We present a study of the autofluorescence of normal skin and tumor in vivo, conducted on 18 patients diagnosed with nonmelanoma skin cancers (NMSC). We observed that both in basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) the endogenous fluorescence due to tryptophan residues was more intense in tumor than in normal tissue, probably due to epidermal thickening and/or hyperproliferation. Conversely, the fluorescence intensity associated with dermal collagen crosslinks was generally lower in tumors than in the surrounding normal tissue, probably because of degradation or erosion of the connective tissue due to enzymes released by the tumor. The decrease of collagen fluorescence in the connective tissue adjacent to the tumor loci was validated by fluorescence imaging on fresh-frozen tissue sections obtained from 33 NMSC excised specimens. Our results suggest that endogenous fluorescence of NMSC, excited in the UV region of the spectrum, has characteristic features that are different from normal tissue and may be exploited for noninvasive diagnostics and for the detection of tumor margins.     

Optimal data placement in two-headed disk systems

A problem inherent to the performance of disk systems is the data placement in cyinders in such a way that the seek time is minimized. If successive searchers are independent, then the optimal placement for conventional one-headed disk systems is the organ-pipe arrangement. According to this arrangement the most frequent cylinder is placed in the central location, while the less frequent cylinders are placed right and left alternatively. This paper proves that the optimal placement for two-headed disk systems is the camel arrangement, which may be viewed as two consecutive organ-pipe arrangements. It is also proved that, for a two-headed disk system withN=2(2n+1) cylinders, the total number of these optimal camel arrangements is exp₂ (N/2+1).Professor J. G. Kollias died untimely December 1989.     

Quantum Monte Carlo study of the reaction: Cl+CH3OH-->CH2OH+HCl

A theoretical study is reported of the Cl+CH3OH-->CH2OH+HCl reaction based on the diffusion Monte Carlo (DMC) variant of the quantum Monte Carlo method. Using a DMC trial function constructed as a product of Hartree-Fock and correlation functions, we have computed the barrier height, heat of reaction, atomization energies, and heats of formation of reagents and products. The DMC heat of reaction, atomization energies, and heats of formation are found to agree with experiment to within the error bounds of computation and experiment. M?ller-Plesset second order perturbation theory (MP2) and density functional theory, the latter in the B3LYP generalized gradient approximation, are found to overestimate the experimental heat of reaction. Intrinsic reaction coordinate calculations at the MP2 level of theory demonstrate that the reaction is predominantly direct, i.e., proceeds without formation of intermediates, which is consistent with a recent molecular beam experiment. The reaction barrier as determined from MP2 calculations is found to be 2.24 kcal/mol and by DMC it is computed to be 2.39(49) kcal/mol.     

Suppression of UVB-induced cutaneous erythema by a previous UVB exposure

People who vacation in sunny places are exposed to the sun on multiple occasions at least on a daily basis. The clinical assessment of sun exposure is erythema in the first 48 h after exposure and pigmentation at times greater than 3-5 days. The purpose of this investigations was to determine the extent to which consecutive erythemogenic exposures result in additive erythema responses. Studies were conducted in which volunteers were first exposed to a graded series of fluences of UVB radiation and then on subsequent days (1-3 days) the same sites along with the surrounding unexposed skin were challenged with varying fluences of UVB radiation. The erythema reactions were assessed clinically and were objectively documented with diffuse reflectance spectroscopy. The sites that received two exposures always showed a reduced erythema response compared to a single erythemogenic exposure. The suppression of erythema was more pronounced when the second exposure was given 48 h after the first. The erythema suppression was maximal when the first exposure was at 1.3 minimum erythema dose (MED). The pigment response to the first exposure was completely suppressed for fluences less than 1.5 MED. We thus provide evidence for a decoupling of the classical sequence of erythema-pigmentation response. We also show that the erythema induced by a second exposure may be substantially suppressed by an earlier exposure, and that this cannot be due to melanin photoprotection or due to substantial thickening of the stratum corneum. We propose that the cause may be some diffusible element of yet unknown origin.     

Protoporphyrin IX Fluorescence Induced in Basal Cell Carcinoma by Oral δ-Aminolevulinic Acid*

Limited depth of penetration significantly limits photodynamic therapy of nodular basal cell carcinoma (BCC) using topical δ(5)-aminolevulinic acid (ALA). To demonstrate safety and efficacy of orally administered ALA in inducing endogenous protoporphyrin IX (PpIX) production in BCC, 13 patients with BCC ingested ALA in a dose-escalation protocol. All dose ranges (10, 20 or 40 mg/kg single doses) resulted in formation of PpIX in human skin and BCC, measurable by in vivo fluorescence spectrophotometry. The PpIX fluorescence peaked in tumors before normal adjacent skin from 1 to 3 h after ALA ingestion. Gross fluorescence imaging of ex vivo specimens revealed greater PpIX fluorescence in tumor than normal skin only at the 40 mg/kg dose. Fluorescence microscopy confirmed this finding by showing distinct, full-thickness PpIX fluorescence in all subtypes of BCC only after ALA given at 40 mg/kg. Side effects were dose dependent and self limited. Photosensitivity lasting less than 24 h and nausea coinciding with peak skin PpIX fluorescence occurred at 20 and 40 mg/kg doses. After 40 mg/kg ALA, serum hepatic enzyme levels rose to a maximum within 24 h, then resolved over 1–3 weeks. Transient bilirubinuria occurred in two patients.