Peripheral oxidative stress biomarkers in mild cognitive impairment and Alzheimer's disease

Oxidative stress has been associated with normal aging and Alzheimer's disease (AD). However, little is known about oxidative stress in mild cognitive impairment (MCI) patients who present a high risk for developing AD. The aim of this study was to investigate plasma production of the lipid peroxidation marker, malonaldehyde (MDA) and to determine, in erythrocytes, the enzymatic antioxidant activity of catalase, glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST) in 33 individuals with MCI, 29 with mild probable AD and 26 healthy aged subjects. GR/GPx activity ratio was calculated to better assess antioxidant defenses. The relationship between oxidative stress and cognitive performance was also evaluated by the Mini Mental State Examination (MMSE). AD patients showed higher MDA levels than both MCI and healthy elderly subjects. MCI subjects also exhibited higher MDA levels compared to controls. Catalase and GPx activity were similar in MCI and healthy individuals but higher in AD. GR activity was lower in MCI and AD patients than in healthy aged subjects. Additionally, GR/GPx ratio was higher in healthy aged subjects, intermediate in MCI and lower in AD patients. No differences in GST activity were detected among the groups. MMSE was negatively associated with MDA levels (r = -0.31, p = 0.028) and positively correlated with GR/GPx ratio in AD patients (r = 0.68, p < 0.001). MDA levels were also negatively correlated to GR/GPx ratio (r = -0.31, p = 0.029) in the AD group. These results suggest that high lipid peroxidation and decreased antioxidant defenses may be present early in cognitive disorders.

Environmental tobacco smoke induces oxidative stress in distinct brain regions of infant mice

Environmental tobacco smoke (ETS) leads to the death of 600,000 nonsmokers annually and is associated with disturbances in antioxidant enzyme capacity in the adult rodent brain. However, little is known regarding the influence of ETS on brain development. The aim of this study was to determine levels of malonaldehyde (MDA) and 3-nitrotyrosine (3-NT), as well as enzymatic antioxidant activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD), in distinct brain structures. BALB/c mice were exposed to ETS twice daily for 1 h from postnatal day 5 through postnatal day 18. Acute exposure was performed for 1 h on postnatal day 18. Mice were euthanized either immediately (0) or 3 h after the last exposure. Immediately after an acute exposure there were higher GR and GST activities and MDA levels in the hippocampus, higher GPx and SOD activities in the prefrontal cortex, and higher GST activity and MDA levels in the striatum and cerebellum. Three hours later there was an increase in SOD activity and MDA levels in the hippocampus and a decrease in the activity of all enzymes in the prefrontal cortex. Immediately after final repeated exposure there were elevated levels of GST and GR activity and decreased GPx activity in the hippocampus. Moreover, a rise was found in GPx and GST activities in the prefrontal cortex and increased GST and GPx activity in the striatum and cerebellum, respectively. After 3 h the prefrontal cortex showed elevated GR and GST activities, and the striatum displayed enhanced GST activity. Data showed that enzymatic antioxidant system in the central nervous system responds to ETS differently in different regions of the brain and that a form of adaptation occurs after several days of exposure.

Raman, hyper-Raman, hyper-Rayleigh, two-photon luminescence and morphology-dependent resonance modes in a single optical tweezers system

We present a setup of optical tweezers combined with linear and nonlinear microspectroscopies that enhances the capabilities of capture and analysis of both techniques. We can use either a continuous-wave (cw) Ti:sapphire laser for Raman measurements or a pulsed femtosecond Ti:sapphire laser that permitted the observation of nonlinear results such as hyper-Raman, hyper-Rayleigh, and two-photon luminescence. Only the high peak intensity of the femtosecond laser allows the observation of all these nonlinear spectroscopies. The sensitivity of our system also permitted the observation of morphology-dependent resonance (MDR) modes of a single stained trapped microsphere of 6 microm. The possibility of performing spectroscopy in a living microorganism optically trapped in any desired neighborhood would mean that one can dynamically observe the chemical reactions and/or mechanical properties changing in real time.

[Utilization of lactic bacteria in the control of pathogenic microorganisms in food]

The lactic acid bacteria have the potential to inhibit the growth of pathogenic and spoilage bacteria and the possibility exists of using them to improve the hygienic quality and to extend the shelf-life of different foods. Among the many inhibitory substances produced by the lactic acid bacteria, the bacteriocins are of particular interest. It has been the objective of this work to review the bacteriocins produced by lactic acid bacteria from the genera Lactococcus, Lactobacillus and Pediococcus, as well as Leuconostoc and Carnobacterium to understand their relevant biochemical, immunological and genetic characteristics. The lactic acid bacteria may also express foreign genes codifying metabolites with antimicrobial activities against foodborne pathogens of interest, and this will also permit hypothesize about theoretical and experimental models of microbial antagonism mediated by the lactic acid bacteria.

Sakacin M, a bacteriocin-like substance from Lactobacillus sake 148

The antagonistic activity of Lactobacillus sake 148 was evaluated during its growth on complex broth media and in a semisynthetic defined medium (SDM) with various supplements. The antagonistic activity was a growth-associated property, being detected and quantified when L. sake 148 was grown at either 4, 8, 16, 25 or 32 degrees C. The concentrated culture supernatant of L. sake 148 was subjected to purification by lyophilization and gel filtration. The purification procedure resulted in a small increase in its specific activity (7-fold) and in a low recovery of the original inhibitory activity (8%). Gel filtration analysis of the partially purified activity on Sephadex G-50 revealed an apparent molecular weight of 4640. The partially purified antagonistic activity of L. sake 148 was destroyed by treatment with proteolytic enzymes. However, the antagonistic activity was resistant to heat, having D-values at 121, 135 and 150 degrees C of 23.8, 17.4 and 15.2 min, respectively.

Antibacterial activity of Lactobacillus sake isolated from dry fermented sausages

Lactic acid bacteria isolated from Spanish dry fermented sausages were screened for antagonistic activities under conditions that eliminated the effects of low pH and hydrogen peroxide. From 720 isolates tested 119 were inhibitory to Lactobacillus fermentum CECT285. The isolates showing the largest inhibitory activity exhibited an antagonistic effect against several other lactobacilli and the selected foodborne pathogens Staphylococcus aureus and Listeria monocytogenes. Comparison of the antimicrobial spectra of the supernatants suggested that the inhibitory compounds were not identical. The isolates were tentatively characterized as Lactobacillus sake. One of the isolates, L. sake 148 was chosen for further study. The compound excreted by L. sake 148 was active against various lactobacilli and several Gram-positive foodborne bacteria, but not against the Gram-negative bacteria tested. The antagonistic effects were almost eliminated by treatment with proteases, whereas they were heat resistant and bacteriostatic rather than bacteriocidal.