Regional selectivity to ochratoxin A, distribution and cytotoxicity in rat brain

Ochratoxin A (OTA) a chlorodihydro-isocoumarin linked through an amide bond to phenylalanine, is a mycotoxin found as a contaminant in foodstuffs and shown to be nephrotoxic, teratogenic, immunosuppressive, genotoxic, mutagenic and carcinogenic in rodents. Ochratoxin A is known to induce teratogenic effects in neonates (rats and mice) exposed in utero, characterised by microcephaly and modification of the brain levels of free amino acids. Since OTA has been found to accumulate in the brain according to the duration of exposure to doses in the range of natural contamination of feedstuffs, experiments were designed to determine more precisely the structural target of OTA in the brain. After intracerebral injection, OTA (403 ng/10 microl) was not found in the following parts of the brain: the frontal cortex (FC), striatum (ST), ventral mesencephalon (VM) and the cerebellum (CB) in contrast to the rest of the brain, probably due to the detection limit of 0.1 ng/g of tissue. However lactate dehydrogenase (LDH) was increased in extracellular space in the VM to a greater extent than in the rest of the brain, indicating that this structure could be one of the targets of OTA in the brain. Contents of free amino acids were morever similarly modified in the VM and in the rest of the brain. Male rats were given OTA (289 microg/kg per 24 h) by gastric intubation for 8 days and the main brain structures analysed for OTA content and cytotoxicity. OTA was found in the following structures in decreasing order: rest of the brain (50.3%), cerebellum (34.4%), VM (5.1%), striatum (3.3%) and hippocampus (2.9%) of the total OTA amount found in the brain, which represents 0.022% to 0.028% of the given dose. Interestingly cytotoxicity as measured by lactate dehydrogenase (LDH) release in the extracellular space was much more pronounced in the VM, hippocampus, and striatum than in the cerebellum, whereas no cytotoxicity was observed in the rest of the brain. Similarly deoxyribonuclease (DNase) activity in relation to possible necrotic cells was increased in the VM and cerebellum. Altogether these results designated the ventral mesencephalon, hippocampus, striatum and cerebellum as the main OTA-targets in the brain of adult rats and excluded the rest of the brain.     

The molecular chaperone Hsp90 can negatively regulate the activity of a glucocorticosteroid-dependent promoter

Hsp90, a molecular chaperone required for the functioning of glucocorticosteroid receptor (GR), ensures, by direct interaction, the conformational competence of the steroid-binding pocket. In addition to having this positive function, Hsp90 maintains steroid receptors in an inactive form in the absence of hormone. However, neither the participation of Hsp90 once the pathway has been activated by the ligand nor the importance of increased Hsp90 levels in determining the amplitude of the response has ever been assessed directly. Here, by increasing the Hsp90/GR ratio in the nuclear compartment, we found an attenuation of the response to glucocorticosteroids that was not due to a nonspecific or toxic effect of the Hsp90 modified by nuclear targeting. Since this negative effect was more pronounced at high levels of hormone, when receptor and Hsp90 are maximally dissociated, the possibility of an interaction between Hsp90 and GR, already activated to a DNA-binding form, was directly investigated. Indeed GR, after in vivo activation by ligand, was still able to reassociate with Hsp90, suggesting that this interaction plays a role in vivo, possibly in receptor recycling. Moreover, the GR binding to its DNA response element was inhibited by an excess of Hsp90, pointing to a function of Hsp90 in the nuclear compartment. It is thus proposed that an increased Hsp90/GR ratio influences the responsiveness to ligand at a step that is after receptor activation. This increased ratio may be of pathophysiological relevance in the different circumstances that lead to an elevated level of nuclear Hsp90.     

Ultrafast Spectroscopy and Red Emission from β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>/β-Ga<Subscript>2</Subscript>S<Subscript>3</Subscript> Nanowires

Ultrafast pump-probe and transient photoluminescence spectroscopy were used to investigate carrier dynamics in β-Ga₂O₃ nanowires converted to β-Ga₂O₃/Ga₂S₃ under H₂S between 400 to 600 °C. The β-Ga₂O₃ nanowires exhibited broad blue emission with a lifetime of 2.4 ns which was strongly suppressed after processing at 500–600 °C giving rise to red emission centered at 680 nm with a lifetime of 19 μs. Differential absorption spectroscopy reveals that state filling occurs in states located below the conduction band edge before sulfurization, but free carrier absorption is dominant in the β-Ga₂O₃/Ga₂S₃ nanowires processed at 500 to 600 °C for probing wavelengths >500 nm related to secondary excitation of the photo-generated carriers from the mid-gap states into the conduction band of Ga₂S₃.     

Program specification: a precursor to program monitoring and quality improvement. A case study from Boysville of Michigan

The reaction of synthetic DOPA melanin (DM) with lactoperoxidase (LPO), hydrogen peroxide, and nitrite (NO2-) has been investigated using EPR. We observed that in the presence of nitrite LPO/H2O2 generated large amount of melanin radicals, as evidenced by a strong, up to 11-fold, increase in the intensity of the melanin EPR signal. In contrast, when nitrite was omitted the increase was much less, ca. 30%, which, nevertheless, indicates that DM can be metabolized directly by LPO/H2O2. When the nitrite was present, the concentration of melanin radicals was linearly dependent on [NO2-] (for [NO2-] <5 mM), and increased when [LPO] and [H2O2] increased (at constant [NO2-]). We propose that the mechanism for the generation of melanin radicals by the LPO/H2O2/nitrite system involves oxidation of NO2- by LPO/H2O2 to a reactive metabolite, most likely the nitrogen dioxide radical (.NO2), which subsequently reacts with melanin 5,6-dihydroxyindole subunits producing the respective semiquinone radicals. Because melanin and .NO2 generating systems (nitrite, peroxidase enzymes, hydrogen peroxide) may coexist in cells in vivo, our results suggest that melanin could function as a natural scavenger of this highly reactive nitrogen species. This property may be relevant to the physiological functions of the melanin pigments in vivo.     

PREPARATION OF CLOVE BUDS DEODORIZED AQUEOUS EXTRACT (CDAE) AND EVALUATION OF ITS POTENTIAL TO IMPROVE OXIDATIVE STABILITY OF CHICKEN MEATBALLS IN COMPARISON TO SYNTHETIC AND NATURAL FOOD ANTIOXIDANTS

ABSTRACT

Antioxidative properties of prepared clove buds deodorized aqueous extract (CDAE) in chicken meatballs are studied. Total phenolic and flavonoid contents were found to be 271.9 ± 12.0 mg gallic acid equivalent per gram and 161.6 ± 7.7 mg rutin equivalent per gram CDAE, respectively. Chicken meatball samples were: (1) C (control, i.e., without CDAE), and those supplemented with 200 ppm of; (2) T1 (CDAE); (3) T2 (ascorbic acid); and (4) T3 (butylated hydroxyanisole [BHA] : butylated hydroxytoluene [BHT] = 1:1). Oxidative stability was assessed by measuring peroxide value (PV) and 2‐thiobarbituric acid reactive substances (TBARS) besides determination of color and sensory acceptability, over 12 days of chilled storage (8 ± 1C). All the treated samples showed higher induction period as well as lower PV and TBARS values than “C” throughout 12 days of storage (*P < 0.05). Color analysis showed that CDAE greatly improved redness of meatballs as compared with ascorbic acid and BHA‐BHT (*P < 0.05). Meanwhile, hedonic test indicated that treatment T1 did not affect sensory acceptability of chicken meatballs for all the tested attributes (color, aroma, taste, texture and overall acceptance) (*P > 0.05) up to comparable extent with T2 and T3.

PRACTICAL APPLICATIONS

The study provides a valuable method for the preparation of meatballs by replacing harmful synthetic antioxidants with natural ones with promising antioxidant and shelf‐life potential besides maintaining sensory attributes. This adaptation may result in massively enhanced consumption of these meatballs with disease‐preventive and health‐promoting effects. The main hurdle in commercialization of spicy meatballs is the pungent smell of spices as well as use of toxic organic solvents for extraction. The problem has been overcome by developing a method for the preparation of deodorized extracts in aqueous medium, which may significantly enhance the commercialization potential of meatballs and meatball‐based functional foods.