Expressions of visual pigments and synaptic proteins in neonatal chick retina exposed to light of variable photoperiods

Light causes damage to the retina, which is one of the supposed factors for age-related macular degeneration in human. Some animal species show drastic retinal changes when exposed to intense light (e.g. albino rats). Although birds have a pigmented retina, few reports indicated its susceptibility to light damage. To know how light influences a cone-dominated retina (as is the case with human), we examined the effects of moderate light intensity on the retina of white Leghorn chicks (Gallus g. domesticus). The newly hatched chicks were initially acclimatized at 500 lux for 7 days in 12 h light: 12 h dark cycles (12L:12D). From posthatch day (PH) 8 until PH 30, they were exposed to 2000 lux at 12L:12D, 18L:6D (prolonged light) and 24L:0D (constant light) conditions. The retinas were processed for transmission electron microscopy and the level of expressions of rhodopsin, S- and L/M cone opsins, and synaptic proteins (Synaptophysin and PSD-95) were determined by immunohistochemistry and Western blotting. Rearing in 24L:0D condition caused disorganization of photoreceptor outer segments. Consequently, there were significantly decreased expressions of opsins and synaptic proteins, compared to those seen in 12L:12D and 18L:6D conditions. Also, there were ultrastructural changes in outer and inner plexiform layer (OPL, IPL) of the retinas exposed to 24L:0D condition. Our data indicate that the cone-dominated chick retina is affected in constant light condition, with changes (decreased) in opsin levels. Also, photoreceptor alterations lead to an overall decrease in synaptic protein expressions in OPL and IPL and death of degenerated axonal processes in IPL.     

Detection of oestrous-related odour in bovine ( Bos taurus) saliva: bioassay of identified compounds

The present study was designed to identify the volatile constituents across the oestrous cycle of bovine in order to detect oestrous-specific chemical signal. The bovine saliva was extracted with diethyl ether (1 : 1 ratio, v/v) and analysed by gas chromatography-linked mass spectrometry. Numerous compounds were identified during oestrous cycle of bovine saliva. Among these, the compounds, namely, trimethylamine, acetic acid, phenol 4-propyl, pentanoic acid and propionic acid were specific to oestrous stage. The behaviour assay revealed that the compound, trimethylamine, is involved in attracting the male animal. The result concludes that the trimethylamine is considered as a putative oestrous-specific salivary chemo-signal in the bovine.     

Impact of chromate and dichromate on lysozyme stability: A spectroscopic and molecular docking investigation

A comparative study of interaction between chicken egg white lysozyme (Lyz) with two hexavalent chromate ions; chromate and dichromate; which are prevalently known for their toxicity, was investigated using different spectroscopic techniques along with a molecular docking study. Both steady-state and time-resolved studies revealed that the addition of chromate/dichromate is responsible for strong quenching of intrinsic fluorescence in Lyz and the quenching is caused by both static and dynamic quenching mechanisms. Different binding and thermodynamic parameters were also calculated at different temperatures from the intrinsic fluorescence of Lyz. The conformational change in Lyz and thermodynamic parameters obtained during the course of interaction with chromate/dichromate were well-supported by the molecular docking results.     

Cell culture and animal models of viral hepatitis. Part I: hepatitis B

Despite the existence of a preventative vaccine, HBV represents a substantial threat to public health, suggesting the need for research to develop new treatments to combat the disease. The authors review the available in vitro and in vivo models, including recently developed transgenic and chimeric mouse models.     

Protoporphyrin IX-induced structural and functional changes in human red blood cells,haemoglobin and myoglobin

Protoporphyrin IX and its derivatives are used as photosensitizers in the photodynamic therapy of cancer. Protoporphyrin IX penetrates into human red blood cells and releases oxygen from them. This leads to a change in the morphology of the cells. Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes. For both proteins, the binding affinity constant decreases, while the possible number of binding sites increases, as the aggregation state of the porphyrin is increased. The interactions lead to conformational changes of both haemoglobin and myoglobin as observed in circular dichroism studies. Upon binding with the proteins, protoporphyrin IX releases the heme-bound oxygen from the oxyproteins, which is dependent on the stoichiometric ratios of the porphyrin: protein. The peroxidase activities of haemoglobin and myoglobin are potentiated by the protein-porphyrin complexation. Possible mechanisms underlying the relation between the porphyrin-induced structural modifications of the heme proteins and alterations in their functional properties have been discussed. The findings may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.     

AP endonuclease-independent DNA base excision repair in human cells

The paradigm for repair of oxidized base lesions in genomes via the base excision repair (BER) pathway is based on studies in Escherichia coli, in which AP endonuclease (APE) removes all 3' blocking groups (including 3' phosphate) generated by DNA glycosylase/AP lyases after base excision. The recently discovered mammalian DNA glycosylase/AP lyases, NEIL1 and NEIL2, unlike the previously characterized OGG1 and NTH1, generate DNA strand breaks with 3' phosphate termini. Here we show that in mammalian cells, removal of the 3' phosphate is dependent on polynucleotide kinase (PNK), and not APE. NEIL1 stably interacts with other BER proteins, DNA polymerase beta (pol beta) and DNA ligase IIIalpha. The complex of NEIL1, pol beta, and DNA ligase IIIalpha together with PNK suggests coordination of NEIL1-initiated repair. That NEIL1/PNK could also repair the products of other DNA glycosylases suggests a broad role for this APE-independent BER pathway in mammals.     

In vitro nonenzymatic glycation enhances the role of myoglobin as a source of oxidative stress

Metmyoglobin (Mb) was glycated by glucose in a nonenzymatic in vitro reaction. Amount of iron release from the heme pocket of myoglobin was found to be directly related with the extent of glycation. After in vitro glycation, the unchanged Mb and glycated myoglobin (GMb) were separated by ion exchange (BioRex 70) chromatography, which eliminated free iron from the protein fractions. Separated fractions of Mb and GMb were converted to their oxy forms -MbO₂ and GMbO₂, respectively. H₂O₂-induced iron release was significantly higher from GMbO₂ than that from MbO₂. This free iron, acting as a Fenton reagent, might produce free radicals and degrade different cell constituents. To verify this possibility, degradation of different cell constituents catalyzed by these fractions in the presence of H₂O₂ was studied. GMbO₂ degraded arachidonic acid, deoxyribose and plasmid DNA more efficiently than MbO₂. Arachidonic acid peroxidation and deoxyribose degradation were significantly inhibited by desferrioxamine (DFO), mannitol and catalase. However, besides free iron-mediated free radical reactions, role of iron of higher oxidation states, formed during interaction of H₂O₂ with myoglobin might also be involved in oxidative degradation processes. Formation of carbonyl content, an index of oxidative stress, was higher by GMbO₂. Compared to MbO₂, GMbO₂ was rapidly auto-oxidized and co-oxidized with nitroblue tetrazolium, indicating increased rate of Mb and superoxide radical formation in GMbO₂. GMb exhibited more peroxidase activity than Mb, which was positively correlated with ferrylmyoglobin formation in the presence of H₂O₂. These findings correlate glycation-induced modification of myoglobin and a mechanism of increased formation of free radicals. Although myoglobin glycation is not significant within muscle cells, free myoglobin in circulation, if becomes glycated, may pose a serious threat by eliciting oxidative stress, particularly in diabetic patients.