In vitro propagation of <Emphasis Type="Italic">Pimelea spicata</Emphasis> R.Br (Thymelaeaceae), an endangered species of the Sydney region,Australia

Micropropagation was assessed as an ex situ conservation strategy for the endangered Australian plant Pimelea spicata (Thymelaeaceae). Although regeneration of this species was achieved, several physiological problems were observed and examined. Explants of P. spicata had a higher multiplication rate on MS medium, than on ½ MS, but there was a significantly higher percentage of necrotic shoot tips on the higher salt medium. Increasing calcium concentration and gas exchange exacerbated shoot-tip necrosis. A number of hyperhydrated shoots were produced in all treatments, the cause of which could not be determined, although less hyperhydicity was observed in the ½ MS treatment. Shoots, rooted in vitro on ½ MS in the absence of plant growth regulators, were successfully acclimatised to greenhouse conditions, while direct rooting of microshoots using IBA gel treatment proved unsuccessful. This is the first report of tissue culture propagation of this endangered species.     

Preapoptotic chromatin changes induced by ultraviolet B irradiation in human erythroleukemia K562 cells

Exponentially growing human erythroleukemia K562 cells were permeabilized and the dose dependent decrease of DNA synthesis rate was measured after ultraviolet (UV B, 290 nm) irradiation. Cells were able to overcome 2 and 5 J/m2 UV doses, partial recovery was observed at 15 J/m2, while at high (25 J/m2) UV dose replicative DNA synthesis remained suppressed. K562 cells were subjected to synchronization prior to and after UV irradiation (24 J/m2) and 18 fractions were collected by centrifugal elutriation. Cell cycle analysis by flow cytometry did not show early apoptotic cells after UV irradiation. The gradual increase in DNA content typical for non-irradiated cells was contrasted by an early S phase block between 2.2 and 2.4 C-values after UV irradiation. Cell cycle dependent chromatin changes after ultraviolet irradiation were seen as a fine fibrillary network covering the mainly fibrous chromatin structures and incompletely folded primitive chromosomes. Based on observations after UV irradiation and on earlier results with cadmium treatment and gamma irradiation, we confirm that typical chromatin changes characteristic to genotoxic agents can be recognized and classified.     

Pulmonary type II cell hypertrophy and pulmonary lipoproteinosis are features of chronic IL-13 exposure

Interleukin (IL)-13, a key mediator of Th2-mediated immunity, contributes to the pathogenesis of asthma and other pulmonary diseases via its ability to generate fibrosis, mucus metaplasia, eosinophilic inflammation, and airway hyperresponsiveness. In these studies, we compared surfactant accumulation in wild-type mice and mice in which IL-13 was overexpressed in the lung. When compared with littermate controls, transgenic animals showed alveolar type II cell hypertrophy under light and electron microscopy. Over time, their alveoli also filled with surfactant in a pulmonary alveolar proteinosis pattern. At the same time, prominent interstitial fibrosis occurs. Bronchoalveolar lavage fluid from these mice had a three- to sixfold increase in surfactant phospholipids. Surfactant proteins (SP)-A, -B, and -C showed two- to threefold increases, whereas SP-D increased 70-fold. These results indicate that IL-13 is a potent stimulator of surfactant phospholipid and surfactant accumulation in the lung. IL-13 may therefore play a central role in the broad range of chronic pulmonary conditions in which fibrosis, type II cell hypertrophy, and surfactant accumulation occur.     

Temporal properties of dual-peak responses of mouse retinal ganglion cells and effects of inhibitory pathways

Dual-peak responses of retinal ganglion cells (RGCs) are observed in various species, previous researches suggested that both response peaks were involved in retinal information coding. In the present study, we investigated the temporal properties of the dual-peak responses recorded in mouse RGCs elicited by spatially homogeneous light flashes and the effect of the inhibitory inputs mediated by GABAergic and/or glycinergic pathways. We found that the two peaks in the dual-peak responses exhibited distinct temporal dynamics, similar to that of short-latency and long-latency single-peak responses respectively. Pharmacological studies demonstrated that the application of exogenous GABA or glycine greatly suppressed or even eliminated the second peak of the cells’ firing activities, while little change was induced in the first peak. Co-application of glycine and GABA led to complete elimination of the second peak. Moreover, application of picrotoxin or strychnine induced dual-peak responses in some cells with transient responses by unmasking a second response phase. These results suggest that both GABAergic and glycinergic pathways are involved in the dual-peak responses of the mouse RGCs, and the two response peaks may arise from distinct pathways that would converge on the ganglion cells.     

A genetic map of tetraploid <Emphasis Type="Italic">Paspalum notatum</Emphasis> Flügge (bahiagrass) based on single-dose molecular markers

Paspalum notatum Flügge is a warm-season forage grass with mainly diploid (2n = 20) and autotetraploid (2n = 40) representatives. Diploid races reproduce sexually and require crosspollination due to a self-incompatible mating system, while autotetraploids reproduce by aposporous apomixis. The objectives of this work were to develop a genetic linkage map of Paspalum notatum Flügge at the tetraploid level, identify the linkage/s group/s associated with apomixis and carry out a general characterization of its mode of inheritance. A pseudo test-cross F₁ family of 113 individuals segregating for the mode of reproduction was obtained by crossing a synthetic completely sexual tetraploid plant (Q4188) as female parent with a natural aposporous individual (Q4117) as pollen donor. Map construction was based on single-dose markers (SDAFs) segregating from both parents. Two linkage maps (female and male) were constructed. Within each map, homologous groups were assembled by detecting repulsion-phase linked SDAFs. Putative Q4188 and Q4117 homolog groups were identified by mapping shared single dose markers (BSDF). The Q4188 map consisted of 263 markers distributed on 26 co-segregation groups over a total genetic distance of 1.590.6 cM, while the Q4117 map contained 216 loci dispersed on 39 co-segregation groups along 2.265.7 cM, giving an estimated genome coverage of 88% and 83%, respectively. Seven and 12 putative homologous chromosomes were detected within Q4188 and Q4117 maps, respectively. Afterward, ten female and male homologous chromosomes were identified by mapping BSDFs. In the Q4117 map, a single linkage group was associated with apospory. It was characterized by restriction in recombination and preferential chromosome pairing. A BPSD marker mapping within this group allowed the detection of the female homolog and the putative four male groups of the set carrying apospory.