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Biomedical subjects

G Burkhardt

Publications and source records attributed to G Burkhardt.

At least 19 recordsLinked to original sources
PubMed1998

Inhibition of oxidant-induced lipid peroxidation in cultured renal tubular epithelial cells (LLC-PK1) by quercetin.

The protective effect of quercetin against oxidant-induced cell injury (hypoxanthine/xanthine oxidase system) was studied in the renal tubular epithelial cell line LLC-PK1. Pretreatment with quercetin provided protection from structural and functional cell damage in a concentration-dependent manner (10-100 microM). Comparison with structural variants revealed that the protective property of quercetin depends on the number of hydroxyl substituents in the B-ring, the presence of an extended C-ring chromophore, 3-D-planarity and lipophilicity, indicating that membrane affinity is essential for protection. The hypothesis that quercetin exerts its protective effects via inhibition of lipid peroxidation was further examined. Protection by quercetin was found when lipid peroxidation, assessed by the release of malondialdehyde, was initiated by H2O2 or by the combination of 1-chloro-2,4-dinitrobenzene and aminotriazole. In contrast, the bioflavonoid was not protective when oxidative cell damage was induced by menadione and occurred in the absence of lipid peroxidation. These data suggest that cytoprotective effects of quercetin are related to membrane affinity and may be explained by interruption of membrane lipid peroxidation rather than by intracellular scavenging of oxygen free radicals.

Animals↗
PubMed1997

Insights into potential cellular mechanisms of cisplatin nephrotoxicity and their clinical application.

Cisplatin preferentially accumulates in cells of the S3 segment of the renal proximal tubule and is toxified intracellularly by hydration. The earliest manifestation of toxicity is inhibition of protein synthesis. GSH depletion is another important mechanism causing CP toxicity. Intracellular binding to SH groups leads to GSH depletion, resulting in lipid peroxidation and eventually mitochondrial damage. New measures to prevent GSH depletion and scavenge intracellular free oxygen radicals have been tried in clinical studies. Promising results indicate that cisplatin nephrotoxicity can be further reduced in the future.

Antineoplastic Agents↗
PubMed1995

Proportionate mortality among construction laborers.

This report presents the results of proportionate mortality ratio (PMR) analyses and proportionate cancer mortality ratio (PCMR) analyses among the 11,685 members of the Laborers' International Union of North America (LIUNA), who died between 1985-1988, using U.S. proportionate mortality rates as the comparison population. Statistically significant elevated mortality risks were observed for all malignant neoplasms (N = 3285, PMR = 1.13, CI = 1.09-1.17), as well as for site-specific neoplasms of the lung (N = 1208, PCMR = 1.06, CI = 1.00-1.12), stomach (N = 170, PCMR = 1.44, CI = 1.23-1.68), and thyroid gland (N = 10, PCMR = 2.24, CI = 1.07-4.12). The PCMRs for these malignant neoplasms were elevated among both white and non-white males, regardless of length of union membership, in most 10-year categories of age at death above 40 and for the three largest LIUNA regions examined. The study also observed 20 mesothelioma deaths, which indicated that some LIUNA members had been previously exposed to asbestos. Statistically significant elevated risks were also observed for deaths from transportation injuries (N = 448, PMR = 1.37, CI = 1.25-1.51), falls (N = 85, PMR = 1.34, CI = 1.07-1.66), and other types of injuries (N = 245, PMR = 1.61, CI = 1.42-1.83). The deaths due to injuries were most often observed among those members who had the shortest amount of time within the union, were younger, and first entered the union after 1955. This is the first study that has examined the general mortality experience limited to construction laborers only (Bureau of Census code 869).

Accidents, Occupational↗
PubMed1995

Community based dengue control in Columbia: people's knowledge and practice and the potential contribution of the biological larvicide Bti (Bacillus thuringiensis israelensis).

A study on dengue control was undertaken in a poor urban area in Cúcuta, Colombia. The first objective was to describe people's knowledge, attitudes and practices regarding dengue fever, the transmission of the disease and possible preventive measures. The second objective was to analyse the infestation of the community with Aedes aegypti larvae, and the third objective to test the efficacy of Bti (Bacillus thuringiensis israelensis) with respect to the level and duration of reduction of Ae. aegypti larvae in water tanks. It was found that people had a very fragmentary knowledge about dengue and about the necessary protective measures which did not lead them to any action. The infestation of water containers, particularly the larger tanks, was very high (house index = 61; Breteau index = 96). The application of Bti in water tanks led to satisfactory results: For one month and longer, the water tanks treated with Bti were free of mosquito larvae. The effect was reduced by a lower dose, washing the tanks and a less potent formulation. People's acceptance of Bti was higher than that of temephos. Further studies are necessary to confirm the utility of Bti in dengue control.

Aedes↗
PubMed1994

Bioactive chromenes from Rhyncholacis penicillata.

Investigation of the aerial parts of Rhyncholacis penicillata afforded the new chromenes, 7-hydroxy-6-(3-methylbutyryl)-5-oxymethyl-chromene (rhynchonin A) and 7-hydroxy-6-(2-methylbutyryl)-6-oxymethylchromene (rhynchonin B). Structures were elucidated by spectroscopic methods and independent synthesis. Rhynchonin A showed broad insecticidal, acaricidal and nematicidal potency including strong biological activity against Heliothis zea.

Animals↗
PubMed1986

Terpene hydrocarbons in Pimpinella anisum L.

The essential oil of anise (fruits and shoots) was investigated focusing on the composition of the hydrocarbon fraction. Several sesquiterpenes were identified by GC-MS and the relative composition of the fractions was established by GC analysis. gamma-Himachalene and the diterpene neophytadiene were isolated by TLC and column chromatography at low temperatures. Their structures were determined by MS and NMR including 1H-1H correlated COSY and NOE experiments.

Chromatography, Gas↗
PubMed1984

Assessment of in situ host immunity to syngeneic tumors utilizing the multicellular spheroid model.

In situ host immunity to the EMT6/Ro mammary sarcoma tumor was evaluated by implanting multicellular spheroids of this tumor into the peritoneal cavity of syngeneic BALB/cKa mice and determining the kinetics of host cell infiltration and tumor cell killing. Spheroids grown in vitro and implanted into unsensitized mice continued to grow resulting in peritoneal tumor masses and eventual death of the animal. However, in mice previously sensitized with a single injection of heavily irradiated EMT6/Ro cells, spheroids implanted intraperitoneally were rapidly infiltrated by host immune cells (macrophages, lymphocytes, and granulocytes), tumor cell killing was detectable within 1 day and by Day 6 essentially no clonogenic tumor cells were recoverable. Despite this marked loss of both total and clonogenic tumor cells, there was little decrease in the diameter of the spheroids recovered during this time period. Physical size thus does not provide a reliable estimation of tumor cell killing. The tumor cell killing was immunologically specific in that little killing was observed when EMT6/Ro spheroids were implanted into mice sensitized with other allogeneic or syngeneic tumor cells. Host cells from within the spheroids were found to be cytotoxic for EMT6/Ro tumor cells in a 51Cr release assay. A major portion of these cytotoxic cells appear to be T lymphocytes. However, other host cell types may also be involved in the in vivo tumor cell killing.

Animals↗