First detection of plastic microfibers in a wild population of South American fur seals (Arctocephalus australis) in the Chilean Northern Patagonia.

The dramatic increase of microplastics (plastic fragments <5 mm) in marine environments is a problem that has attracted public attention globally. Within the different types of microplastics, microfibres are the least studied (size <1 mm). We examined 51 female scats from a population in Northern Patagonia. Our results showed no presence of microplastic particles, however 67% of them showed a remarkable abundance of microfibers, which until now had only been reported in animals fed in captivity. As a result of this work we propose that the examination of scats from South American Fur Seal and also other pinnipeds could be an efficient tool to monitor environmental levels of microfibres and maybe microplastics in the environment due to the easy recognition of the animals and their scats.

Morphometrical and molecular evidence suggests cryptic diversity among hookworms (Nematoda: Uncinaria) that parasitize pinnipeds from the south-eastern Pacific coasts.

Hookworms of the genus Uncinaria parasitize pinniped pups in various locations worldwide. Four species have been described, two of which parasitize pinniped pups in the southern hemisphere: Uncinaria hamiltoni parasitizes Otaria flavescens and Arctocephalus australis from the South American coast, and Uncinaria sanguinis parasitizes Neophoca cinerea from the Australian coast. However, their geographical ranges and host specificity are unknown. Uncinaria spp. are morphologically similar, but molecular analyses have allowed the recognition of new species in the genus Uncinaria. We used nuclear genetic markers (internal transcribed spacer (ITS) and large subunit (LSU) rDNA) and a mitochondrial genetic marker (cytochrome c oxidase subunit I (COI)) to evaluate the phylogenetic relationships of Uncinaria spp. parasitizing A. australis and O. flavescens from South American coasts (Atlantic and Pacific coasts). We compared our sequences with published Uncinaria sequences. A Generalized Mixed Yule Coalescent (GMYC) analysis was also used to delimit species, and principal component analysis was used to compare morphometry among Uncinaria specimens. Parasites were sampled from A. australis from Peru (12°S), southern Chile (42°S), and the Uruguayan coast, and from O. flavescens from northern Chile (24°S) and the Uruguayan coast. Morphometric differences were observed between Uncinaria specimens from both South American coasts and between Uncinaria specimens from A. australis in Peru and southern Chile. Phylogenetic and GMYC analyses suggest that south-eastern Pacific otariid species harbour U. hamiltoni and an undescribed putative species of Uncinaria. However, more samples from A. australis and O. flavescens are necessary to understand the phylogenetic patterns of Uncinaria spp. across the South Pacific.

Coastal debris survey in a Remote Island of the Chilean Northern Patagonia.

Global marine litter pollution is increasing dramatically, and oceanic islands are one of the most vulnerable ecosystems due to their high debris accumulation rate compared to continental sites. Remote areas, such as inhabited islands, represent a perfect study case to track marine debris sources, due to the assumed low rates of local production of debris. Guafo Island is one of the largest islands of the Chilean Northern Patagonia and is considered a remote zone. The accessible coast of Guafo Island was monitored during four austral summers revealing higher levels of marine debris accumulation than continental Chile. Plastic was the most abundant type of debris constituting 50% of the total litter monitored. Our results suggest that most of the plastic identified is likely to be related to local fisheries activities. Mitigation measures including collaboration among fishing communities and scientists could contribute to reduce the coastal debris pollution in remote areas.

Pathological findings in South American fur seal pups (Arctocephalus australis gracilis) found dead at Guafo Island, Chile.

During four breeding seasons (2004-2008), 78 necropsy examinations were performed on South American fur seal pups (Arctocephalus australis gracilis) found dead on Guafo Island, southern Chile (43°36'S, 74°43'W). Tissue samples from 65 pups were examined microscopically. The primary causes of death were enteritis with microscopical lesions of bacteraemia (28.2%), starvation (23.1%), drowning (21.8%), trauma (19.2%) and stillbirth (2.6%). Those pups with enteritis and microscopical lesions of bacteraemia had haemorrhagic enteritis (100%), interstitial pneumonia (86%), periportal hepatitis (73%) and vasculitis (18%). The pups that died from starvation had atrophy of hepatocytes (61%) and cholestasis (61%). The pups that drowned had bronchoalveolar oedema (65%) and foreign bodies in the airways (65%). In animals that died from trauma, the main lesions were skull fractures (67%). This range of pathological findings is within what would be expected in a healthy otariid breeding colony.

Myosin inhibitors block accumulation movement of chloroplasts in Arabidopsis thaliana leaf cells.

Chloroplasts alter their distribution within plant cells depending on the external light conditions. Myosin inhibitors 2,3-butanedione monoxime (BDM), N-ethylmaleimide (NEM), and 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-7) were used to study the possible role of myosins in chloroplast photorelocation in Arabidopsis thaliana mesophyll cells. None of these agents had an effect on the chloroplast high-fluence-rate avoidance movement but all of the three myosin inhibitors blocked the accumulation movement of chloroplasts after a high-fluence-rate irradiation of the leaves. The results suggest that myosins have a role in A. thaliana chloroplast photorelocation.

Arabidopsis thaliana myosin XIK is involved in root hair as well as trichome morphogenesis on stems and leaves.

Myosins form a large superfamily of molecular motors that move along actin filaments. The functions of myosins in plant cells are thought to be related to various processes: cell division, movement of mitochondria and chloroplasts, cytoplasmic streaming, rearrangement of transvacuolar strands, and statolith positioning. Class VIII and XI myosins are represented in the Arabidopsis thaliana genome by 4 and 13 potential genes, respectively. The roles of individual class XI myosins and their cellular targets in A. thaliana are still unclear. In this work we implemented a reverse genetic approach to analyse the loss-of-function mutants of XIK, a representative of class XI myosins in A. thaliana. Three different T-DNA insertion mutants in the myosin XIK gene showed similar phenotypes: impaired growth of root hair cells, twisted shape of stem trichomes, and irregular size, branch positioning, and branch expansion of leaf trichomes. Morphometric analysis of mutant seedlings showed that the average length of root hairs was reduced up to 50% in comparison with wild-type root hairs, suggesting an involvement of the class XI myosin XIK in tip growth. On leaves, the proportion of trichomes with short branches was doubleed in mutant plants, and the mutant trichomes possessed a mildly twisted shape. Therefore, we concluded that myosin XIK is involved also in the elongation of stalks and branches of trichomes.

Neurotrophins as in vitro growth cone guidance molecules for embryonic sensory neurons.

Neurotrophins NGF, BDNF, NT-3, and NT-4/5 are members of the neurotrophin family of proteins, which support the survival and induce differentiation of vertebrate neurons. We have studied the effects of neurotrophins on growth cones of embryonic sensory neurons. BDNF and NT-4/5 cause growth cone collapse and transient neurite growth inhibition in NGF-dependent or NT-3-dependent rat dorsal root ganglion (DRG) neurons but not in BDNF-dependent or NT-4/5-dependent neurons, whereas NGF and NT-3 do not produce growth-cone collapse in these neurons. All neurotrophins show a chemoattractive effect on growth cones of embryonic DRG neurons: NGF and NT-3 are chemoattractants for all DRG neurons, except NT-3-dependent and NT-4/5-dependent neurons; BDNF and NT-4/5 are chemoattractants only for BDNF-dependent DRG neurons. BDNF-induced and NT-4/5-induced growth cone collapse is quantitatively characterized as a 50% decrease in F-actin content, total protein content, and area of growth cones of NGF-dependent or NT-3-dependent neurons, and a reorganization of microfilaments. BDNF induces a rapid transient 3-fold to 4-fold increase of F-actin concentration at the central part of growth cones of NGF-dependent neurons. Our results suggest that different neurotrophins have chemoattractive or inhibitory effects on the same growth cone, and that they may act as specific growth cone guidance cues.

The effect of 9,11-secosterol, a newly discovered compound from the soft coral Gersemia fruticosa, on the growth and cell cycle progression of various tumor cells in culture.

A new 9,11-secosterol, 24-nor-9,11-seco-11-acetoxy-3 beta,6 alpha-dihydroxycholest-7,22(E)-dien-9-one, was found to exhibit growth inhibitory (IC50 below 10 microM) and cytotoxic activities against human leukemia K562, human cervical cancer HeLa, and Ehrlich ascites tumor cells in vitro. The cytostatic concentrations of the compound generally caused the G2/M block in the cell cycle progression, but differences between the three tumor cell lines in the events leading to cell death were remarkable. While inhibiting cell proliferation, 9,11-secosterol caused accumulation of HeLa and K562 cells in the metaphase of mitosis. So, abnormal mitosis can play an important role in the cytotoxicity of 9,11-secosterol in these cell lines. In the Ehrlich ascites tumor cell line the increasing concentrations of the drug (up to 40 microM) did not cause an immediate cell killing. Instead, due to continued DNA synthesis without entry into mitosis, cells with high DNA ploidy were produced. It was shown that the cytoskeletal systems such as microtubules and microfilaments were not damaged by the action of 9,11-secosterol. Further studies are necessary to elucidate the mechanism of the cytotoxic effect of 9,11-secosterol.

Nerve growth factor-induced rapid reorganization of microfilaments in PC12 cells: possible roles of different second messenger systems.

Nerve growth factor (NGF) induces in 2 to 10 min the redistribution of F-actin in rat pheochromocytoma PC12 cells. The NGF specificity of this phenomenon was shown by blocking it with anti-NGF antibodies. We used the rapid F-actin redistribution as an assay to study NGF second messenger systems and their inhibition or activation by specific agents. The results show that the NGF-induced effect on the microfilament system of PC12 cells can be specifically inhibited by lithium chloride and neomycin, inhibitors of the phosphoinositol system, but cannot be mimicked by TPA and acetylcholine, the activators of the phosphoinositol system. An increase in the intracellular concentration of cyclic AMP by addition of dBcAMP (but not dBcGMP) caused rapid F-actin redistribution that nonetheless differed from the NGF-induced effect. Changes in the intracellular calcium level did not have any influence on the microfilament system of PC12 cells. The specificity of the inhibition of NGF-induced effects by methylase inhibitors was questionable, since MTA- or SAH-treated PC12 cells acquired an altered morphology even in the absence of NGF or dBcAMP. Using the microfilament- and microtubule-disrupting drugs cytochalasin B and colchicine, we showed that the microtubule system in PC12 cells is required for the initiation of neurite outgrowth and that microfilament-associated filopodial activity does not appear to be necessary.

Nerve growth factor increases the cyclic GMP level and activates the cyclic GMP phosphodiesterase in PC12 cells.

Nerve growth factor (NGF) rapidly increases the cyclic GMP (cGMP) level about 2-3-fold and enhances the cGMP phosphodiesterase (PDE) activity about 2-fold in rat pheochromocytoma PC12 cells. No changes in the level of cyclic AMP (cAMP) and in the activity of cAMP PDE were found. GTP and a nonhydrolysable analog of GTP, GMP-PCP, at 100 microM, were able to mimic the effect of NGF on the cGMP PDE activity. These results suggest that the cGMP system may be one of the second messengers of NGF action in PC12 cells.

Nerve growth factor induces rapid redistribution of F-actin in PC12 cells.

Nerve growth factor (NGF) induces the redistribution of F-actin in rat pheochromocytoma PC12 cells within 2-10 min, whereas epidermal growth factor (EGF) has no effect on microfilament organization. This redistribution of F-actin in PC12 cells is not protein synthesis dependent, but can be blocked by methyltransferase inhibitors.