MamA as a Model Protein for Structure-Based Insight into the Evolutionary Origins of Magnetotactic Bacteria

MamA is a highly conserved protein found in magnetotactic bacteria (MTB), a diverse group of prokaryotes capable of navigating according to magnetic fields – an ability known as magnetotaxis. Questions surround the acquisition of this magnetic navigation ability; namely, whether it arose through horizontal or vertical gene transfer. Though its exact function is unknown, MamA surrounds the magnetosome, the magnetic organelle embedding a biomineralised nanoparticle and responsible for magnetotaxis. Several structures for MamA from a variety of species have been determined and show a high degree of structural similarity. By determining the structure of MamA from Desulfovibrio magneticus RS-1 using X-ray crystallography, we have opened up the structure-sequence landscape. As such, this allows us to perform structural- and phylogenetic-based analyses using a variety of previously determined MamA from a diverse range of MTB species across various phylogenetic groups. We found that MamA has remained remarkably constant throughout evolution with minimal change between different taxa despite sequence variations. These findings, coupled with the generation of phylogenetic trees using both amino acid sequences and 16S rRNA, indicate that magnetotaxis likely did not spread via horizontal gene transfer and instead has a significantly earlier, primordial origin.     

The Anabolic Androgenic Steroid Nandrolone Decanoate Disrupts Redox Homeostasis in Liver,Heart and Kidney of Male Wistar Rats

The abuse of anabolic androgenic steroids (AAS) may cause side effects in several tissues. Oxidative stress is linked to the pathophysiology of most of these alterations, being involved in fibrosis, cellular proliferation, tumorigenesis, amongst others. Thus, the aim of this study was to determine the impact of supraphysiological doses of nandrolone decanoate (DECA) on the redox balance of liver, heart and kidney. Wistar male rats were treated with intramuscular injections of vehicle or DECA (1 mg.100 g⁻¹ body weight) once a week for 8 weeks. The activity and mRNA levels of NADPH Oxidase (NOX), and the activity of catalase, glutathione peroxidase (GPx) and total superoxide dismutase (SOD), as well as the reduced thiol and carbonyl residue proteins, were measured in liver, heart and kidney. DECA treatment increased NOX activity in heart and liver, but NOX2 mRNA levels were only increased in heart. Liver catalase and SOD activities were decreased in the DECA-treated group, but only catalase activity was decreased in the kidney. No differences were detected in GPx activity. Thiol residues were decreased in the liver and kidney of treated animals in comparison to the control group, while carbonyl residues were increased in the kidney after the treatment. Taken together, our results show that chronically administered DECA is able to disrupt the cellular redox balance, leading to an oxidative stress state.     

Phospholipid metabolism and prolactin secretion in vitro

The possible mechanisms by which phospholipid metabolism may be involved in the biochemical events underlying pituitary hormone secretion in basal and stimulated conditions were examined. Particular emphasis was given to the role of changes in the turnover of specific membrane phospholipids, the polyphosphoinositides, in the stimulatory effect of TRH and neurotensin on prolactin release in vitro. Finally, some comments on the involvement of arachidonate and/or its metabolites in the mechanisms of release of the hormone have been reported. In this respect, the possibility that a specific diacylglycerol lipase may represent a link between the 'phosphatidylinositol effect' and the production of arachidonate from mammotroph membranal phospholipids was examined using the rather selective inhibitor of diacylglycerol lipase RHC80267.     

NO EVIDENCE OF ACCOMMODATION IN THE EYES OF THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS

Bottlenose dolphins ( Tursiops truncatus ) are aquatic mammals that must come to the surface to breathe. As a result, it might be expected that their eyes are adapted for both aerial and underwater vision. Earlier studies suggest that dolphins are emmetropic ( i. e. , focused at infinity) in water, and in some cases, emmetropic in air, although the mechanisms that permit these animals to see well in both media are not well understood. Nor is it known whether they can accommodate to focus sharply on objects at different distances. We employed video photoretinoscopy to investigate the possibility of an active accommodative mechanism in the eyes of the bottlenose dolphin in water. Measurements of the refractive state in water indicated near emmetropia for two individuals and slight myopia (nearsightedness) for the third individual. No clear cases of accommodation were observed underwater in any of the subjects examined. Vision underwater may be used to supplement echolocation. If so, such a role might not require an accommodative mechanism.     

Melanin coloration in New World orioles I: carotenoid masking and pigment dichromatism in the orchard oriole complex

Carotenoids produce the brilliant red, orange, and yellow colors of many animals. However, melanin pigments can also confer some of these same hues. Because carotenoid and melanin colors are produced in different ways and may serve different signaling functions, either within or between species, it is important to establish whether one or both types of pigment are responsible for coloration. We have discovered what appears to be an evolutionary switch from carotenoid- to melanin-based color in two sexually dichromatic New World orioles. Using a combination of reflectance spectrometry and chromatographic analyses of plumage pigments, we found that the chestnut plumage of adult male orchard orioles Icterus spurius is produced predominantly by phaeomelanins. Orchard oriole feathers also contain carotenoids, which appear to be masked by the high concentration of phaeomelanins. In contrast, both carotenoids and phaeomelanins appear to contribute to color in adult male Fuertes's orioles I. fuertesi . Moreover, yellow yearling male and female plumage in both species is produced by carotenoids alone. The masking of carotenoids with phaeomelanins in orchard orioles is interesting in light of the signaling roles that carotenoids are thought to play. In addition, these plumage differences produce a unique case of age and sexual pigment dimorphism in orchard and Fuertes's orioles.     

Melioidosis in imported non-human primates

In 1969, five cases of melioidosis in three separate outbreaks were diagnosed in nonhuman primates in the United States. In the first outbreak, two stump-tailed macaque monkeys (Macaca arctoides) developed signs of the disease approximately 6 months after purchase. A third animal, a chimpanzee (Pan troglodytes), probably acquired its infection from one of these monkeys. Two other unrelated cases involving a pig-tailed monkey (Macaca nemestrina) and a rhesus monkey (Macaca mulatta) were diagnosed. These monkeys had been imported 3 years and 6 months, respectively, prior to the recognized onset of their disease. These cases represent the first known occurrences of spontaneous melioidosis in nonhuman primates in the United States.