Amplified somatic embryogenesis from male flowers of triploid banana and plantain cultivars (Musa spp.)

Summary Somatic embryogenesis and plant regeneration of banana and plantain cultivars (Musa spp.) were obtained by culturing young male flowers. Multiplication and maintenance of embryogenic cultures were achieved by culturing somatic embryos in a temporary immersion system (SIT). A multiplication rate of 40 allowed us to obtain more than 6000 somatic embryos after 6 mo. of subculture. Plant recovery frequencies were 60 to 70%. This method was expanded to different banana and plantain genomic groups.     

Anti-idiotypic mimicry of a neutralizing epitope on the glycoprotein B complex of human cytomegalovirus.

Experiments were carried out to investigate the ability of rabbit anti-idiotype antibodies (Ab2), directed against an anti-human cytomegalovirus monoclonal antibody (Ab1), to induce neutralizing antibodies specific for the immunodominant glycoprotein B viral complex. Mice immunized with Ab2 produced anti-Ab2 (Ab3) that was both antigen and idiotype specific with regard to Ab1. We conclude that the Ab2 antibodies mimicked a neutralizing epitope and acted as a network antigen for inducing a specific anti-human cytomegalovirus antibody response in this experimental system.     

Dialysable leukocyte extracts modify the course of experimental paracoccidioidomycosis in the Syrian hamster

The effect of dialysable leukocyte extracts (DLE) obtained from hamsters immunized withParacoccidioides brasiliensis (immune DLE) and from non-immunized hamsters (non-immune DLE) was studied in hamsters inoculated withP. brasiliensis by the intratesticular route. Treatment with immune or non-immune DLE was started during the third week of infection and was repeated at 7, 11, 15 and 19 weeks. A group of untreated infected animals was used as control. Animals were submitted to the delayed hypersensitivity skin test toP. brasiliensis antigen (PbAg) in vivo and assayed in vitro by the macrophage migration inhibition test in the presence of Phytohemagglutinin (PHA) and PbAg and by immunodiffusion for specific antibody. The animals were sacrificed at 4, 8, 12, 16 and 20 weeks. The morphology and extension of the lesions were studied at the inoculation site, and in lymph nodes, lungs, liver, spleen and kidneys. In contrast to the controls, animals treated with both DLEs maintained a positive cell-mediated immune response throughout the experiment and developed less extensive infection with a significantly lower number of fungi in the lesions. The results suggest that immune and non-immune DLE preparations modified the evolution of experimental paracoccidioidomycosis with equal efficiency. This similarity may be explained by the immunoregulatory activities of both extracts.     

Prospects for the genetics of human longevity

Longevity varies between and within species. The existence of species-specific limit to human life-span and its partial heritability indicate the existence of genetic factors that influence the ageing process. Insight into the nature of these genetic factors is provided by evolutionary studies, notably the disposable soma theory, which suggests a central role of energy metabolism in determining life-span. Energy is important in two ways. First, the disposable soma theory indicates that the optimum energy investment in cell maintenance and repair processes will be tuned through natural selection to provide adequate, but not excessive, protection against random molecular damages (e.g. to DNA, proteins). All that is required is that the organism remains in a sound condition through its natural expectation of life in the wild environment, where accidents are the predominant cause of mortality. Secondly, energy is implicated because of the intrinsic vulnerability of mitochondria to damage that may interfere with the normal supply of energy to the cell via the oxidative phosphorylation pathways. Oxidative phosphorylation produces ATP, and as a by-product also produces highly reactive oxygen radicals that can damage many cell structures, including the mitochondria themselves. Several lines of evidence link, on the one hand, oxidative damage to cell ageing, and on the other hand, energy-dependent antioxidant defences to the preservation of cellular homeostasis, and hence, longevity. Models of cellular ageing in vitro allow direct investigation of mechanisms, such as oxidative damage, that contribute to limiting human life-span. The genetic substratum of inter-individual differences in longevity may be unraveled by a two-pronged reverse genetics approach: sibling pair analysis applied to nonagenarian and centenarian siblings, combined with association studies of centenarians, may lead to the identification of genetic influences upon human longevity. These studies have become practicable thanks to recent progress in human genome mapping, especially to the development of microsatellite markers and the integration of genetic and physical maps.     

Counterselection on sex chromosomes in the Mus musculus European hybrid zone

The extent to which alleles can disperse across a hybrid zone depends on the selection they are subjected to in the hybrid genetic background or, for those that are selectively neutral, on their ability to escape from the unfavourable environment by recombination. Three markers spanning a 45 cM segment in the center of the X chromosome were used to investigate the degree to which selection against X chromosome linked genes helps to maintain the barrier to gene flow in the hybrid zone between Mus musculus domesticus and M. m. musculus in Denmark. The introgression of all the sex chromosome specific markers was more limited than that of the autosomal enzymes (Idh1, Amy, Gpd1, Pgm1, Es1, Es2, Mpi, Np1, Es10, Sod1) and the mitochondrial DNA. The cline for DXPas2, which is in the center of the X chromosome, is extremely steep and shows that certain genes located in this region are strongly selected against in the hybrid background. The clines of the other two X-linked markers, Hprt and DXPas1, and of the Y chromosome are not as abrupt and all three have similar asymmetric introgression patterns. Although the musculus variants appear to behave in much the same way as those of the autosomal genes, the domesticus variants do not introgress. The results show that X-linked and to a lesser extent Y-linked genes are more strongly selected against in the hybrid genome than the mitochondrial genome or the different autosomal loci. This suggests that co-adapted gene systems involving the sex chromosomes may play an important role in the hybrid breakdown between the two subspecies.     

The protective effect of arbutin against potassium bromate-induced oxidative damage in the rat brain

This study aimed to investigate the protective effects of arbutin (ARB) against brain injury induced in rats with potassium bromate (KBrO₃). The rats were divided into four groups as Group 1: Control (0.9% NaCl ml/kg/day p.), Group 2: KBrO₃ (100 mg/kg (gavage), Group 3: ARB (50 mg/kg/day p.), and Group 4: KBrO₃ + ARB (100 mg/kg (gavage) + 50 mg/kg/day p.). At the end of the fifth day of the study, the rats in all groups were killed, and their brain tissues were collected. In the collected brain tissues, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were measured, and routine histopathological examinations were made. The MDA levels in the group that was exposed to KBrO₃ were significantly higher than those in the control group (p ˂ 0.001). In comparison to the KBrO₃ group, the MDA levels in the KBrO₃ + ARB group were significantly lower (p ˂ 0.001). It was observed that SOD and CAT enzyme activity levels were significantly lower in the KBrO₃ group compared to the control group (p ˂ 0.001), while these levels were significantly higher in the KBrO₃ + ARB group than in the KBrO₃ group (p ˂ 0.001). Additionally, the group that was subjected to KBrO₃ toxicity, as well as ARB administration, had much lower levels of histopathologic signs than the group that was subjected to KBrO₃ toxicity only. Consequently, it was found that KBrO₃ exposure led to injury in the brain tissues of the rats, and using ARB was effective in preventing this injury.     

Coevolution of species colonisation rates controls food-chain length in spatially structured food webs

How the complexity of food webs depends on environmental variables is a long-standing ecological question. It is unclear though how food-chain length should vary with adaptive evolution of the constitutive species. Here we model the evolution of species colonisation rates and its consequences on occupancies and food-chain length in metacommunities. When colonisation rates can evolve, longer food-chains can persist. Extinction, perturbation and habitat loss all affect evolutionarily stable colonisation rates, but the strength of the competition-colonisation trade-off has a major role: weaker trade-offs yield longer chains. Although such eco-evo dynamics partly alleviates the spatial constraint on food-chain length, it is no magic bullet: the highest, most vulnerable, trophic levels are also those that least benefit from evolution. We provide qualitative predictions regarding how trait evolution affects the response of communities to disturbance and habitat loss. This highlights the importance of eco-evolutionary dynamics at metacommunity level in determining food-chain length.     

Three major mesoplanktonic communities resolved by in situ imaging in the upper 500 m of the global ocean

Aim

The distribution of mesoplankton communities has been poorly studied at global scale, especially from in situ instruments. This study aims to (1) describe the global distribution of mesoplankton communities in relation to their environment and (2) assess the ability of various environmental-based ocean regionalizations to explain the distribution of these communities.

Location

Global ocean, 0–500 m depth.

Time Period

2008–2019.

Major Taxa Studied

Twenty-eight groups of large mesoplanktonic and macroplanktonic organisms, covering Metazoa, Rhizaria and Cyanobacteria.

Methods

From a global data set of 2500 vertical profiles making use of the Underwater Vision Profiler 5 (UVP5), an in situ imaging instrument, we studied the global distribution of large (>600 μm) mesoplanktonic organisms. Among the 6.8 million imaged objects, 330,000 were large zooplanktonic organisms and phytoplankton colonies, the rest consisting of marine snow particles. Multivariate ordination (PCA) and clustering were used to describe patterns in community composition, while comparison with existing regionalizations was performed with regression methods (RDA).

Results

Within the observed size range, epipelagic plankton communities were Trichodesmium-enriched in the intertropical Atlantic, Copepoda-enriched at high latitudes and in upwelling areas, and Rhizaria-enriched in oligotrophic areas. In the mesopelagic layer, Copepoda-enriched communities were also found at high latitudes and in the Atlantic Ocean, while Rhizaria-enriched communities prevailed in the Peruvian upwelling system and a few mixed communities were found elsewhere. The comparison between the distribution of these communities and a set of existing regionalizations of the ocean suggested that the structure of plankton communities described above is mostly driven by basin-level environmental conditions.

Main Conclusions

In both layers, three types of plankton communities emerged and seemed to be mostly driven by regional environmental conditions. This work sheds light on the role not only of metazoans, but also of unexpected large protists and cyanobacteria in structuring large mesoplankton communities.