Effect of growth regulators on microspore embryogenesis in coconut anthers

The effect of growth regulators on induction of androgenesis in coconut was investigated using seven different growth regulators at various concentrations and combinations. Three auxins (1-naphthalene acetic acid—NAA, indoleacetic acid—IAA, picloram) and three cytokinins (2-isopentyl adenine-2-iP, kinetin, zeatin) were tested either alone or in combination with 2,4-dichlorophenoxyacetic acid (2,4-D), using modified Eeuwens Y3 liquid medium as the basal medium. Among the tested auxins, 100 μM NAA in combination with 100 μM 2,4-D enhanced the production of calli/embryos (123) whereas IAA and picloram showed negative and detrimental effects, respectively, for androgenesis induction over 100 μM 2,4-D alone. Kinetin and 2-iP enhanced the production of calli/embryos when 100 μM 2,4-D was present in the culture medium. Both cytokinins at 10 μM yielded the highest frequencies of embryos (113 and 93, respectively) whereas zeatin (1 or 2.5 μM) had no impact on microspore embryogenesis. When calli/embryos (produced from different treatments in different experiments) were sub-cultured in somatic embryo induction medium (Y₃ medium containing 66 μM 2,4-D), followed by maturation medium (Y₃ medium without growth regulators) and germination medium (Y₃ medium containing 5 μM-6-benzyladenine—BA and 0.35 μM gibberellic acid—GA₃), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%).     

Accelerated clearance of plasma triglycerides and free fatty acids in omega3-depleted rats.

The present study aims mainly at exploring the effects of a severe depletion in polyunsaturated long-chain omega3 fatty acids upon the fate of circulating lipids. The plasma concentration and fatty acid pattern of triglycerides, diglycerides, free fatty acids, and phospholipids were measured in omega3-depleted and control rats injected intravenously one hour before sacrifice with either saline, a control medium-chain triglyceride:olive oil emulsion or a medium-chain triglyceride:fish oil emulsion recently found to rapidly increase the phospholipid content of C20:5omega3 and C22:6omega3 in different cell types. The estimated fractional removal rate of the injected triglycerides and the clearance of free fatty acids from circulation were both higher in omega3-depleted rats than in control animals. The injection of the lipid emulsions apparently inhibited intracellular lipolysis, this being least pronounced in omega3-depleted rats. The increased clearance of circulating triglycerides and unesterified fatty acids in omega3-depleted rats may favor the cellular accumulation of lipids. In turn, such an accumulation and the lesser regulatory inhibition of tissular lipolysis may match the increased clearance of circulating unesterified fatty acids and, hence, account for the lack of any significant difference in plasma unesterified fatty acid concentration between these and control animals.     

Phosphorylation of neurofilament subunit NF-M is regulated by activation of NMDA receptors and modulates cytoskeleton stability and neuronal shape

The cytoskeleton is essential for the structural organization of neurons and is influenced during development by excitatory stimuli such as activation of glutamate receptors. In particular, NMDA receptors are known to modulate the function of several cytoskeletal proteins and to influence cell morphology, but the underlying molecular and cellular mechanisms remain unclear. Here, we characterized the neurofilament subunit NF-M in cultures of developing mouse cortical neurons chronically exposed to NMDA receptor antagonists. Western blots analysis showed that treatment of cortical neurons with MK801 or AP5 shifted the size of NF-M towards higher molecular weights. Dephosphorylation assay revealed that this increased size of NF-M observed after chronic exposure to NMDA receptor antagonists was due to phosphorylation. Neurons treated with cyclosporin, an inhibitor of the Ca(2+)-dependent phosphatase calcineurin, also showed increased levels of phosphorylated NF-M. Moreover, analysis of neurofilament stability revealed that the phosphorylation of NF-M, resulting from NMDA receptor inhibition, enhanced the solubility of NF-M. Finally, cortical neurons cultured in the presence of the NMDA receptor antagonists MK801 and AP5 grew longer neurites. Together, these data indicate that a blockade of NMDA receptors during development of cortical neurons increases the phosphorylation state and the solubility of NF-M, thereby favoring neurite outgrowth. This also underlines that dynamics of the neurofilament and microtubule cytoskeleton is fundamental for growth processes.     

Plasticity of GABAergic synapses in the neonatal rat hippocampus

While the development and plasticity of excitatory synaptic connections have been studied into detail, little is known about the development of inhibitory synapses. As proposed for excitatory synapses, recent studies have indicated that activity-dependent forms of synaptic plasticity, such as long-term potentiation and long-term depression, may play a role in the establishment of functional inhibitory synaptic connections. Here, I review these different forms of plasticity and focus on their possible role in the developing neuronal network.     

High-potentiality preliminary selection criteria and transformation time-dependent factors analysis for establishing Epstein-Barr virus transformed human lymphoblastoid cell lines

Infection of freshly isolated and cryopreserved lymphocytes with Epstein-Barr virus (EBV) leads to the establishment of human B lymphoblastoid cell lines (LCLs). Techniques for optimal infection of the lymphocytes are vital for the establishment of a human biobank. The present study found that more than half (58-86%) of such established LCLs had transport times of less than 48 h, cell densities exceeding 10(6) cells/ml and cell viabilities greater than 90%. After EBV infection, 3306 freshly isolated lymphocytes required 30.0 +/- 0.1 days to become LCLs. Conversely, 1210 cryopreserved lymphocytes required 36.2 +/- 0.4 days. Cell density and viability of the culture affected transformation time in freshly isolated lymphocytes. On the other hand, blood transport time, cryopreservation time and initial cell viability were major factors in cryopreserved specimens. These results contribute to general information concerning the establishment of a human biobank for EBV infected cells.     

From medical imaging to image-guided therapy

This survey on medical imaging provides a look into three major components. The first one deals with the full steps through which it must be apprehended: from the sensors to the reconstruction, from the image analysis up to its interpretation. The second aspect describes the physical principles used for imaging (magnetic resonance, acoustic, optics, etc.). The last section shows how imaging is involved in therapeutic procedures and in particular the new physical therapies. All along this paper, the research perspectives are sketched.     

Variation of cytosine methylation in 57 sweet orange cultivars

Sweet orange is an important group of citrus cultivars, which includes a number of bud sport cultivars. Little is known about the CpG methylation status of the CCGG sequences in the orange genome. In this study, methylation-sensitive amplification polymorphism (MSAP), based on the application of isoschizomers (Hpa II and Msp I), was first used to analyze cytosine methylation patterns in 57 orange cultivars that were not fully differentiated by regular DNA molecular markers. Three types of bands were generated from ten primer pairs. Type I bands were present following restriction with Eco RI + Hpa II and Eco RI + Msp I; type II or type III were present only following restriction with either Eco RI + Hpa II or with Eco RI + Msp I. The total number of these three types of bands was 802, 72, and 157, respectively. Among these, the number of polymorphic bands were 244 (30.2%), 23 (31.9%), and 32 (20.4%), in type I, II and III, respectively. The methylation patterns of these 57 cultivars are discussed and assessed by dendrograms derived from the analysis of polymorphic MSAP bands. The distribution of polymorphic bands of the above three types demonstrate the methylation patterns and frequency at the cytosine loci. We suggest that methylation events could be more frequent than demethylation events, and that the methylation patterns maybe associated with phenotypic traits.     

Syphacia obvelata infections and reproduction of male domestic mice Mus musculus domesticus on a sub-Antarctic Island

The reproductive activity of feral male mice on an island of the sub-Antarctic Kerguelen archipelago was influenced by biological factors depending on periods within the breeding season. After having controlled host reproductive activity indices for body size, i.e. age, and body condition effects, Syphacia obvelata prevalence did not vary with host reproductive status or age either during the beginning or the middle-end of the reproductive season. Considering the beginning of the breeding season, worm abundance was more pronounced in males the year following a strong winter crash of the population than in years when high over wintering survival occurred. During the middle-end of the breeding season, males with the highest reproductive status were more infected than males with a lower reproductive status in years when oldest individuals dominated the population. It is suggested that this situation was due to an endocrine related increased host susceptibility partly influenced by a change in the age structure of the population, and that an increase in worm transmission was not directly related to male activity concurrent with reproductive status, nor to population density.     

The incidence and diversity of Wolbachia in gallwasps (Hymenoptera; Cynipidae) on oak

Wolbachia bacteria infect approximately 20% of all insect species, and cause a range of alterations to host reproduction, including imposition of thelytoky. The incidence and phenotypic impact of Wolbachia remains to be established in many insect taxa, and considerable research effort is currently focused on its association with particular reproductive modes and the relative importance of the various pathways via which infection occurs. Gallwasps represent an attractive system for addressing these issues for two reasons. First, they show a diversity of reproductive modes (including arrhenotoky, thelytoky and cyclical parthenogenesis) in which the impact of Wolbachia infection can be examined. Second, they occupy two intimately linked trophic niches (gall-inducers and inquilines) between which there is potential for the horizontal exchange of Wolbachia infection. In the arrhenotokous gallwasp lineages screened to date (the herb-galling 'Aylacini' and the rose-galling Diplolepidini), Wolbachia infection always induces thelytoky. The impact of Wolbachia in other arrhenotokous clades, and in the cyclically parthenogenetic clades remains unknown. Here we use polymerase chain reaction (PCR) screening and sequence data for two Wolbachia genes (wsp and ftsZ) to examine the prevalence and incidence of Wolbachia infection in 64 species (a total of 609 individuals) in two further tribes: the arrhenotokous inquilines (tribe Synergini), and the cyclically parthenogenetic oak gallwasps (tribe Cynipini). We ask: (i) whether Wolbachia infection has any apparent impact on host reproduction in the two tribes and (ii) whether there is any correlation between Wolbachia infection and the apparent lack of an arrhenotokous generation in many oak gallwasp life cycles. We show: (i) that Wolbachia infection is rare in the Cynipini. Infected species show no deviation from cyclical parthenogenesis, and infection is no more common in species known only from a thelytokous generation; (ii) that there is a higher incidence of infection within the arrhenotokous inquilines, and generally in gallwasp tribes without cyclical parthenogensis; (iii) all Wolbachia-positive inquiline species are known to possess males, implying either that Wolbachia infection does not result in loss of sex in this tribe or, more probably, that (as for some rose gallwasps) Wolbachia infection leads to loss of sex in specific populations; and (iv) although we find some inquilines and gall inducers to be infected with Wolbachia having the same wsp sequence, these hosts are not members of the same gall communities, arguing against frequent horizontal transmission between these two trophic groups. We suggest that exchange may be mediated by the generalist parasitoids common in oak galls.     

Recovery and regeneration of embryogenic cultures from female flowers of False Horn Plantain

Somatic embryogenesis from immature male flowers in Musa is only suitable for genotypes with a male bud. Six friable embryogenic cultures were obtained from 28 cultured buds of female flowers of the AAB False Horn Plantains, ‘Curraré’ and ‘Curraré Enano’. Embryogenic suspensions were established from these embryogenic cultures. Somatic embryogenesis was demonstrated histologicaly. Regeneration of plants was obtained either from somatic embryos directly isolated from embryogenic cultures or from suspensions after plating on a semi-solid medium. This study demonstrates that somatic embryogenesis from immature flowers is suitable for genotypes of Musa with or without male buds. This revised version was published online in June 2006 with corrections to the Cover Date.