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Lester Packer

Publications and source records attributed to Lester Packer.

27 records · Page 2Linked to original sources
PubMed2002

Antioxidant activities of pomegranate fruit extract and its anthocyanidins: delphinidin, cyanidin, and pelargonidin.

Antioxidant activities of freeze-dried preparations of a 70% acetone extract of pomegranate (Punica granatum L.) and its three major anthocyanidins (delphinidin, cyanidin, and pelargonidin) were evaluated. Free radical scavenging activities were examined using an ESR technique with spin trapping; DMPO for hydroxyl (.OH) and superoxide (O(2)(.-) ) radicals; and [(MGD)(2)Fe(2+)] for nitric oxide (NO). Inhibitory effects on lipid peroxidation were estimated by the levels of malonaldehyde and 4-hydroxyalkenals in rat brain homogenates. Pomegranate extract exhibited scavenging activity against.OH and O(2)(.-). Anthocyanidins inhibited a Fenton reagent.OH generating system possibly by chelating with ferrous ion. Anthocyanidins scavenged O(2)(.)- in a dose-dependent manner. The ID(50) values of delphinidin, cyanidin, and pelargonidin were 2.4, 22, and 456 microM, respectively. In contrast, anthocyanidins did not effectively scavenge NO. Anthocyanidins inhibited H(2)O(2)-induced lipid peroxidation in the rat brain homogenates. The ID(50) values of delphinidin, cyanidin, and pelargonidin for them were 0.7, 3.5, and 85 microM, respectively. These findings suggest that the above anthocyanidins contribute to the antioxidant activity of pomegranate fruits.

Anthocyanins↗
PubMed2002

Impact of water-dispersible beadlets as a vehicle for the delivery of carotenoids to cultured cells.

Water-dispersible beadlets of carotenoids were used as supplements for human umbilical vein endothelial cells (HUVECs), human peripheral blood mononuclear cells (PBMCs) and human monocytes. Stability, cellular association and cytotoxicity of the carotenoid beadlets were compared with carotenoids delivered with tetrahydrofuran (THF). Incubations with lycopene, beta-carotene, lutein and astaxanthin dissolved in THF resulted in a lower stability in the medium, lower cellular association, and a higher standard deviation. Beadlets provided 60, 4, 6, and 2 times greater accumulation of lycopene, beta-carotene, lutein and astaxanthin, respectively, by PBMCs than THF. The cellular association of carotenoids delivered by THF seems to be more carotenoid-specific than when carotenoids are delivered by beadlets. After 48 h of incubation under cell culture conditions all of the four carotenoids (1 microM) delivered by beadlets to the medium showed a reduction less than 30%. In addition, no cytotoxic effect of the carotenoid beadlets or the vehicle alone was detected in a concentration range of 0.5-5 microM. The results show that beadlets are a non-toxic vehicle for supplementing and stabilizing carotenoids in culture media offering a reasonable compromise in term of cell accumulation efficiency.

Carotenoids↗
PubMed2002

S-Adenosylmethionine: molecular, biological, and clinical aspects--an introduction.

In clinical research, a novel approach has emerged: some of the essential nutrients are being used to treat pathologic conditions. Many of these nutrients, including methionine, must first be activated in the liver or in other tissues before they can exert their key functions. However, this activating process is impaired in disease states and, as a consequence, nutritional requirements change. For instance, for methionine to act as the main cellular methyl donor, it must first be activated to S-adenosylmethionine (SAMe; also known as ademethionine). SAMe is required and is of fundamental importance for the metabolism of nucleic acids and polyamines, the structure and function of membranes, and as a precursor of glutathione. These processes are often seriously altered in various pathologic states addressed in this symposium, but they cannot be restored by simply administering methionine. For instance, in liver disease associated with impairment of the enzyme that activates methionine to SAMe, supplementation with methionine is useless and may even become toxic as it accumulates because it is not used. Accordingly, one must correct the lack of SAMe by bypassing the deficiency in enzyme activation; this is done by providing the product of the defective reaction, namely SAMe. Under these pathologic conditions, SAMe becomes crucial for the functioning of the cell. Thus SAMe, which is found in all living organisms, becomes the essential nutrient instead of methionine. This symposium reviewed the biological and corresponding molecular aspects of SAMe metabolism and the clinical consequences of its deficiency or supplementation in various tissues.

Humans↗
PubMed2002

Bioflavonoid-rich botanical extracts show antioxidant and gene regulatory activity.

Reactive oxygen and nitrogen metabolites are obligatory and essential products of metabolism. Unregulated increase in their production is associated with a number of chronic illnesses. Diets rich in fruits, vegetables, and wines are implicated in the prevention of chronic diseases. Molecular mechanisms by which fruits and vegetables confer their disease-preventive actions are poorly defined. However, recent developments in the fields of genomics and bioinformatics provide powerful tools to investigate the mechanisms by which botanicals affect cellular functions. This monograph illustrates the potential of large-scale messenger RNA analysis to unravel the role of transcription in mediating the effects of botanical extracts with antioxidant properties. The application of microarrays and oligonucleotide arrays shows multiple effects of antioxidant extracts on the expression of a broad spectrum of genes.

Animals↗
PubMed2002

Antioxidant supplementation decreases lipid peroxidation biomarker F(2)-isoprostanes in plasma of smokers.

Free radicals in cigarette smoke (CS) cause oxidative damage to proteins, DNA, and lipids, contributing to the pathobiology of atherosclerosis, heart disease, and cancer. In vitro studies have shown that antioxidants quench free radicals and ameliorate certain aspects of biomolecular damage caused by CS. It is hypothesized that a combination of antioxidants is more effective than a single antioxidant, due to their interactions. To investigate whether supplemental antioxidants reduce CS-related lipid peroxidation in vivo and whether they are more effective in combination, we conducted an intervention study in smokers. In a randomized double-blind placebo-controlled trial, we investigated whether vitamin C or an antioxidant mixture containing vitamin C, alpha-lipoic acid, and vitamin E decreases plasma F(2)-isoprostane levels, an index of oxidant stress, in smokers. Plasma of 126 smokers (mean age, 46 years; age range, 20-78 years) was analyzed for F(2)-isoprostanes at baseline and after intervention with antioxidants and placebo. In smokers with a body mass index (BMI) above the median, 2 months of daily supplementation with 500 mg of vitamin C decreased plasma F(2)-isoprostane levels by 28.8 pmol/liter when compared with the placebo group (P = 0.001); levels in the mixture group were 7.45 pmol/liter lower after treatment, but this difference was not statistically significant (P = 0.14). There was no treatment effect in smokers with a low BMI. BMI was significantly positively associated with plasma F(2)-isoprostane levels (trend P = 0.001). Antioxidants decrease smoking-related lipid peroxidation markers of oxidative stress in humans with high BMI. Our results do not indicate that an antioxidant combination is more effective than vitamin C alone. The intake of antioxidants may help prevent smoking-related diseases. Smoking cessation should still be considered the most effective way to prevent smoking-related diseases.

Adult↗
PubMed2002

Egb 761 in the postgenomic era: new tools from molecular biology for the study of complex products such as Ginkgo biloba extract.

The decoding of the human genome has completely changed our views on medicine. Beyond sequencing, tools of the postgenomic era may lead to a better understanding of various therapies, especially those with a complex effect on numerous cellular components and functions. The development of high-density oligonucleotide microarrays led to pioneer studies on the multiple gene expression effects exhibited by Ginkgo biloba extract EGb 761, changing traditional pharmacology and medicine concepts. Instead of studying a simple gene or protein, a global investigation of all genes or proteins at once can give insights of the complexity of biological systems.

Gene Expression Regulation↗
PubMed2002

Global gene expression analysis identifies cell and tissue specific actions of Ginkgo biloba extract, EGb 761.

Clinical and pre-clinical uses of Ginkgo biloba extract encompass a broad spectrum of pathologies that include peripheral arterial disorders, cardiovascular and neuronal dysfunctions and resolution of ischemia-reperfusion injuries. Many of these pathologies develop over time and recruit multiple cell types and molecular pathways that alter the cellular a nd molecular profiles of the failing targetorgans. Transcriptional processes are important determinants of the pathogenesis of these chronic disease states. Therefore the potential therapeutic and preventive actions of a standardized Ginkgo biloba extract, EGb 761, may be affected through modulation of transcriptional processes. We have used various techniques for large-scale mRNA expression analysis, including differential display of mRNAs, cDNA arrays and high-density oligonucleotide arrays, to evaluate the actions of EGb 761 on the activities of the genomes in vitro and in vivo. The results show broad but cell specific actions of Ginkgo biloba extract that may enhance antioxidant defenses in vitro in cancer cells and modulate neuronal functions in cortex and hippocampus in brain in vivo. The large scale analysis of mRNAs in response to Ginkgo biloba extract in vitro and in vivo show that the standardized extract affects the activities of the mammalian genome. The data provide some support for the concept that the actions of EGb 761 are mediated through it effects on the process of gene transcription which plays a causative role in chronic diseases.

Animals↗
PubMedDate not supplied

Antioxidants and the response of skin to oxidative stress: vitamin E as a key indicator.

As the outermost barrier of the body, the skin is directly and frequently exposed to a prooxidative environment, including solar UVA and UVB radiation, and air pollution. The skin is equipped with an elaborate system of antioxidant substances and enzymes that includes a network of redox active antioxidants. Among these, vitamin E has been identified as the predominant antioxidant both in murine and human skin and shows a characteristic gradient with lower levels towards the outer stratum corneum layers. Skin exposure to UV and ozone alone and in combination resulted in a significant potentiation of the UV-induced vitamin E depletion. Oxidants and antioxidants play an important role in maintaining a balance between free radicals produced by metabolism or derived from environmental sources. Cellular antioxidants may change their redox state, be targeted for destruction, regulate oxidative process involved in signal transduction, affect gene expression and pathways of cell proliferation and death. Here we provide an overview of the antioxidant system with a special relevance to skin.

Animals↗