Differing features of proteins in membranes may result in antioxidant or prooxidant action: opposite effects on lipid peroxidation of alcohol dehydrogenase and albumin in liposomal systems

SUMMARY

The influence of 3 thiol-containing compounds, bovine serum albumin (fatty acid free: BSA), glutathione (GSH) and yeast alcohol dehydrogenase (YADH) on lipid peroxidation in multilamellar liposomes, prepared from ox-brain phospholipid, was investigated. Thiol-compounds were added either before liposome formation, or after liposome formation; and their effects compared to a positive control. Bovine serum albumin (BSA), an acidic hydrophilic protein, displays a small, concentration dependent, antioxidant effect when added to preformed liposomes. A much larger antioxidant effect was observed when the BSA was entrapped inside the liposome, by adding BSA just prior to liposome preparation. In contrast, a Zn²⁺ containing redox enzyme, YADH, a basic hydrophobic membrane-associating protein, displays a large pro-oxidant effect at much lower concentrations especially when entrapped inside the liposome. This was observed also with GSH; but per mole of -SH, YADH was about 18 times as powerful a pro-oxidant perhaps because of structural changes to the membrane. Oxidized glutathione and N-acetylcysteine were also pro-oxidant (cysteine and cystine showed little effect). Formation of thiyl radicals may occur in the presence of iron ions with these pro-oxidant sulphur-containing compounds. Partial protection against lipid peroxidation was observed with EDTA, desferrioxamine and protoporphyrin (IX), potent iron-chelating agents.     

Population biology and assessment of the white-spotted spinefoot, Siganus canaliculatus (Park, 1797), in the southern Arabian Gulf

The age, growth, mortality, reproduction and resource status of Siganus canaliculatus in the southern Arabian Gulf were investigated using a combination of size frequency, biological and size‐at‐age data. Defined structural increments consisting of alternating translucent and opaque bands in transverse sections of sagittal otoliths were validated as annuli. The maximum absolute age estimate was 7.8 years. Parameter values of the von Bertalanffy growth function fit to size‐at‐age data (males and females combined) were: k = 1.0, L_∞ = 24.8 cm (L_F), t_o = −0.1 years. Fish in spawning condition were only observed between April and July although patterns in gonadosomatic indices suggested a second but less well defined spawning event in November. The mean sizes and ages at first sexual maturity were 21.5 cm L_F (1.9 years) for males and 25.7 cm L_F (2.1 years) for females. Fish were fully recruited to the fishery at a size (L₁₀₀ = 19.7 cm L_F) that was smaller than the sizes at which sexual maturity was attained. The annual instantaneous rate of fishing mortality (F = 0.85 year⁻¹) (0.26–1.44 year⁻¹ 95% CI) was considerably greater than the target (F_opt = 0.33 year⁻¹) and limit (F_limit = 0.44 year⁻¹) biological reference points, indicating that the stock is overexploited.     

Demographic parameters and status assessments of Lutjanus ehrenbergii,Lethrinus lentjan,Plectorhinchus sordidus and Rhabdosargus sarba in the southern Arabian Gulf

Demographic parameters and status assessments for L. ehrenbergii, L. lentjan, P. sordidus and R. sarba in the southern Arabian Gulf were established using a combination of size frequency, biological and size‐at‐age data. Defined structural increments consisting of alternating translucent and opaque bands in transverse sections of sagittal otoliths were validated as annuli. The maximum age estimates ranged from 5 years for R. sarba to 14 years for P. sordidus. Growth trajectories were significantly different between sexes for L. ehrenbergii and L. lentjan with females achieving a larger asymptotic size than males. Estimates of fishing mortality rates were less than the target (F_SB40) and limit (F_SB30) biological reference points for L. ehrenbergii, L. lentjan and P. sordidus indicating that these species were exploited within sustainable limits. Conversely, R. sarba was found to be heavily overexploited and recruitment overfishing may have occurred as the fishing mortality rate was considerably greater than the limit reference point and the relative spawner biomass per recruit was 6.4% of the theoretical unexploited level. Due to restrictions in the available data set, the presented results require confirmation from specific studies on natural mortalities and from growth estimates based on more extended size spectra, avoiding any size selective sampling method.     

Reproductive biology and implications for management of the orange-spotted grouper Epinephelus coioides in the southern Arabian Gulf

The reproductive biology of Epinephelus coioides was determined from the examination of 1455 individuals collected between July 2005 and June 2007 in the southern Arabian Gulf. Histological preparations of gonads indicated that males were either derived from a juvenile phase or the transition of postspawning females, confirming a diandric protogynous sexual pattern. The spawning season was well defined, occurring once a year during April and early May. Peaks in spawning occurred after the full and new moons and was completed within a single lunar cycle. The presence of mature males over the entire size and age range and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. While specimens undergoing sexual transition were only observed in size and age ranges of 335–685 mm total length ( L _T) and 5–6 years, patterns in the proportion of males in size and age classes suggested that sex change occurred at a relatively constant rate after female maturation up to the maximum size (1002 mm L _T) and age (11 years). Relationships between reproductive output and capacity with size and age indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of E. coioides . The maximum age, small size and young age at sexual maturation ( L _min= 320 mm L _T, 2 years, for females and 242 mm L _T, 1 year, for males) conflict with the general pattern for large epinepheline groupers and may be a direct result of the intensive demersal fishery in the southern Arabian Gulf.     

Cadmium-induced stress on the seed germination and seedling growth of <Emphasis Type="Italic">Brassica napus</Emphasis> L., and its alleviation through exogenous plant growth regulators

Because of its prolific growth, oilseed rape (Brassica napus L.) can be grown advantageously for phytoremediation of the lands contaminated by industrial wastes. Therefore, toxic effect of cadmium on the germination of oilseed rape, the capability of plants for cadmium phytoextraction, and the effect of exogenous application of plant growth regulators to mitigate phytotoxicity of cadmium were investigated. For the lab study of seedlings at early stage, seeds were grown on filter papers soaked in different solutions of Cd²⁺ (0, 10, 50, 100, 200 and 400 μM). In greenhouse study, seedlings were grown in soil for 8 weeks, transferred to hydroponic pots for another 6 weeks growth, and then treated with plant growth regulators and cadmium. Four plant growth regulators viz. jasmonic acid (12.5 μM), abscisic acid (10 μM), gibberellin (50 μM) and salicylic acid (50 μM); and three levels of Cd²⁺ (0, 50 and 100 μM) were applied. Data indicated that lower concentration of Cd²⁺ (10 μM) promoted the root growth, whereas the severe stresses (200 or 400 μM) had negative effect on the establishment of germinating seedlings. Plants treated with any of the tested plant growth regulators alleviated cadmium toxicity symptoms, which were reflected by more fresh weight, less malondialdehyde concentration in leaves and lower antioxidant enzyme activities. The application of abscisic acid to the plants cultivated in the medium containing 100 μM Cd²⁺ resulted in significantly lower plant internal cadmium accumulation. Huabing Meng and Shujin Hua contributed equally to this paper.     

The morphology and genetic characterization of Iheringascaris goai n. sp. (Nematoda: Raphidascarididae) from the intestine of the silver whiting and spotted catfish off the central west coast of India

In this study a new species of nematode, Iheringascaris goai n. sp., is reported from two fish hosts, including silver whiting, Sillago sihama, and spotted catfish, Arius maculatus, caught off the Central West Coast of India at Goa. The new species can be differentiated morphologically from I. inquies, the most closely related species collected from cohabiting marine fish. The distinguishing characteristics are distinct cuticular striations, a unilateral excretory system, the presence of dentigerous ridges on the inner margin of the lips and the ratio of oesophagus to body length. In males, the ratio of spicules to body length is higher and the number of pre-anal papillae is less in comparison to those in I. inquies. In addition, the tail curves ventrad in males, while in females, the vulva is post-equatorial. The sequence alignment of 18S rDNA and cytochrome c oxidase subunit I with sequences of known species selected from the same superfamily shows a significant difference. The morphological and molecular differences reported here can, therefore, be used to assign the specimen to a new species.     

Blue light induces mitochondrial DNA damage and free radical production in epithelial cells

Exposure of biological chromophores to ultraviolet radiation can lead to photochemical damage. However, the role of visible light, particularly in the blue region of the spectrum, has been largely ignored. To test the hypothesis that blue light is toxic to non-pigmented epithelial cells, confluent cultures of human primary retinal epithelial cells were exposed to visible light (390-550 nm at 2.8 milliwatts/cm2) for up to 6 h. A small loss of mitochondrial respiratory activity was observed at 6 h compared with dark-maintained cells, and this loss became greater with increasing time. To investigate the mechanism of cell loss, the damage to mitochondrial and nuclear genes was assessed using the quantitative PCR. Light exposure significantly damaged mitochondrial DNA at 3 h (0.7 lesion/10 kb DNA) compared with dark-maintained controls. However, by 6 h of light exposure, the number of lesions was decreased in the surviving cells, indicating DNA repair. Isolated mitochondria exposed to light generated singlet oxygen, superoxide anion, and the hydroxyl radical. Antioxidants confirmed the superoxide anion to be the primary species responsible for the mitochondrial DNA lesions. The effect of lipofuscin, a photoinducible intracellular generator of reactive oxygen intermediates, was investigated for comparison. Exposure of lipofuscin-containing cells to visible light caused an increase in both mitochondrial and nuclear DNA lesions compared with non-pigmented cells. We conclude that visible light can cause cell dysfunction through the action of reactive oxygen species on DNA and that this may contribute to cellular aging, age-related pathologies, and tumorigenesis.     

Preliminary report of histopathology associated with infection with tongue worms in Australian dogs and cattle

Tongue worms utilise herbivorous mammals as intermediate hosts and reside in the nasopharynx of carnivores as their definitive hosts. A recent study in south eastern Australia showed an unexpectedly high infection (67%) of wild dogs with these parasites. The present study aimed at determining the pathogenicity of the parasite in both definitive (dog) and intermediate (cattle) hosts by histopathology. The definitive host showed multifocal haemorrhage of the interstitium of the nasal mucosa, multifocal mucosal erosion, congestion and haemorrhage, with haemosiderin laden macrophages present in those foci and distortion and destruction of the nasal mucosa. Histopathologic examination of lymph nodes from an infected cow showed diffuse eosinophilic granulomatous necrotising lymphadenitis and perinodal panniculitis with intralesional parasitic remnants and comparatively large numbers of eosinophils. A large, ~300–500?μm diameter, area of necrosis was also observed in one lymph node. This is the first time a study has been undertaken in Australia to determine the pathogenicity of tongue worms in both their definitive and intermediate hosts. This is a preliminary study and to properly estimate the health impact of infection with this pathogenic parasites on Australian production and companion animals more studies are necessary.