Shielding effects and hypoxia in photodynamic therapy

Photodynamic therapy (PDT) is a new modality to treat cancer. In clinical use, the procedure is limited by the poor penetration depth of the curative light, which ranges between 3 and 6 mm. The cause of this situation is not clear. Two hypotheses are discussed: shielding effect or hypoxia. To test both hypotheses, we designed an in vitro model. Suspensions and sediments of OAT-75 cells were incubated at 37 degrees C with pheophorbide a or 13(2)-hydroxy-bacteriopheophorbide a methyl ester, both second-generation sensitizers. Irradiation was done with laser light of suitable wavelength. In all experiments, cell death was seen on the surface of the sediment, i.e., near the border of the oxygen-containing atmosphere and opposite the site of the irradiation beam. Therefore, we should accept the hypoxia thesis.

Quantitative determination of urinary lipid metabolites by high pressure liquid chromatography as indicators of menadione-induced in vivo lipid peroxidation

The one- and two-electron-reduction reactions of menadione result in the generation of reactive oxygen species which are believed to mediate the cytotoxicity of this xenobiotic. The induction of lipid peroxidation in liver and isolated hepatocytes occurs in response to the menadione-mediated formation of reactive oxygen species. However, studies on the effects of menadione on the urinary excretion of lipid metabolites have not been conducted. The effect of a single oral dose of 60 mg menadione/kg to rats on the urinary excretion of the lipid metabolites malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) has been examined over 48 h post-treatment. The urinary metabolites were identified by gas chromatography-mass spectrometry and quantitated by high pressure liquid chromatography. Time-dependent increases in the urinary excretion of the four metabolites were observed after menadione administration. Over the 48 h of the study, the menadione-induced urinary excretion of MDA, FA, ACT, and ACON increased by approximately 1.5-, 2.0-, 1.7-, and 3.2-fold, respectively, relative to control animals. The data were expressed in nmoles/kg body weight/4.5 h. The results clearly demonstrate that menadione increases the urinary excretion of four lipid metabolites. These metabolites may have widespread applicability as biomarkers of altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics which induce enhanced lipid peroxidation. The non-invasive methods offer advantages over most other methods for assessing oxidative stress in vivo.

Effects of carbon tetrachloride, menadione, and paraquat on the urinary excretion of malondialdehyde, formaldehyde, acetaldehyde, and acetone in rats

Excretions of the lipid peroxidation products, formaldehyde (FA), acetaldehyde (ACT), malondialdehyde (MDA), and acetone (ACON), were simultaneously identified and quantitated in the urine of female Sprague-Dawley rats by gas chromatography-mass spectroscopy (GC-MS) and high pressure liquid chromatography (HPLC) following the acute administration of carbon tetrachloride, a model alkylating agent that does not induce glutathione depletion, and the redox cycling compounds paraquat and menadione. All three xenobiotics are well-known inducers of oxidative stress. Oxidative stress was induced by oral administration of single doses of 2.5 mL of carbon tetrachloride/kg, 60 mg menadione/kg, and 75 mg paraquat/kg. These doses are approximately 50% of the LD50's for the three xenobiotics. Urinary excretion of FA, ACT, MDA, and ACON increased relative to control animals following treatment with all xenobiotics. Over the 48 hours of the study, the greatest increases in the excretion of MDA, FA, ACT, and ACON occurred after paraquat administration, with increases of approximately 2.7-, 2.6-, 4.3-, and 11.0-fold, respectively. This technique may have wide-spread applicability as an effective biomarker for investigating altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics.

Excretion of malondialdehyde, formaldehyde, acetaldehyde and acetone in the urine of rats following acute and chronic administration of ethanol

Recent studies have shown that xenobiotics which induce oxidative stress result in an increased production and excretion of acetaldehyde (ACT), formaldehyde (FA), acetone (ACON) and malondialdehyde (MDA) in the urine of rats. We have therefore examined the effect of acute and chronic ethanol administration on the excretion of these four lipid metabolites in female Sprague-Dawley rats. Urine samples were collected over dry ice for 6 hr time periods. Aliquots of urine were derivatized with 2,4-dinitrophenylhydrazine HCl, and extracted with n-pentane. High pressure lipid chromatogrpahy (HPLC) was used to quantitate and the hydrazones of the four lipid metabolite products. Following a single, oral, acute dose of 5 g ethanol/kg, urinary excretion of ACT increased approximately 5.8-fold from 6 to 12 hr posttreatment, and decreased thereafter. FA excretion decreased by approximately 50% from 0 to 12 hr, returned to control values in the 18-24 hr urine samples, and was 1.3-fold greater than control values at 42-48 hr. ACON increased 3.1-fold over control values from 0 to 30 hr and remained elevated throughout the remaining 18 hr of the study. The excretion of MDA increased approximately 1.5-fold from 18 to 36 hr, then remained constant through the 48 hr time point. In a separate series of experiments, a chronic oral dose of 0.5 g ethanol/kg was administered to rats for 10 consecutive days and the urinary excretion of the lipid metabolites MDA, FA, ACT and ACON was examined for 11 days, beginning with the first day of ethanol administration.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prospective study of complications of central venous catheters]

The complications of central venous catheters used for immediate postoperative nutrition and monitoring were evaluated in 120 patients. Two patients had to be excluded due to an irregular protocol. 149 central venous catheters were placed in the remaining 118 patients. As to the access, the subclavian vein was used in 72.3%, the v. jugularis interna in 18.9%. The catheters were in average 11.7 days in place giving a total of 1392 catheter days. The end of therapy was the most frequent reason for removal of the catheter (81.6%) followed by septic (4.1%) and mechanical problems (8.8%). Venous thrombosis was observed in 2 patients, and embolisation of a catheter fragment and acute infusothorax each in 1 patient. 13% of the catheters were found to be malpositioned, and malposition was identified as a risk factor for thrombosis.--It is concluded from the comparison of these results with the literature, that the central venous catheter for parenteral nutrition has a risk of complication greater than 5% and therefore requires a clear indication. X-ray-control of catheter position is obligatory and malpositioned catheters are to be corrected. If the parenteral regimen is low in glucose concentration and osmolarity, blood sampling and monitoring via the same central venous line does not appear to increase the rate of complications.

A clinical evaluation of semiprecious alloys for dowels and cores

The semiprecious metals investigated and hard dental gold alloys may be manipulated in a similar manner. The semiprecious metals produced accurate and well-fitted dowels needing minimal adjustment. Being harder than type III gold alloy, they would be ideal for casting dowels and cores. Before considering these semiprecious alloys as final restorations, however, they must be further examined for resistance to tarnish and corrosion and their marginal adaptability and burnishability.