Neomorph and leaf differentiation as alternative morphogenetic pathways in soybean tissue culture.

Somatic embryogenesis and organogenesis were induced on immature cotyledons of different soybean cultivars. The anatomical investigation of morphogenesis proved neomorph differentiation instead of somatic embryos, and leaf formation instead of shoot development. While normal embryos were induced in 0-3.1% of the explants, neomorphs developed at a much higher rate i.e. in 10.5-78.9% depending on the genotype. Likewise organogenesis preferably followed the pathway of leaflet development (3.1-26.3%) than that of shoot tip formation (0-2.6%). Low plant regeneration frequency of soybean can partly be explained with these two alternative abortive pathways of morphogenesis probably induced with higher frequency than the normal pathways by the generally used in vitro methods.     

Plant regeneration from callus of Puccinellia distans (L.) Parl

Callus was induced from seeds of Puccinellia distans (L.) Parl. on MS medium supplemented with 2 mgl^-1 2,4-dichlorophenoxyacetic acid and 0.5 mgl^-1 kinetin. Morphogenesis initiation was achieved during subculture on medium containing 0.1 mgl^-1 2,4-D. From the point of morphogenetic capacity, 3 types of callus were selected. High frequency of plant regeneration was obtained by selection of embryogenic type of callus, and culture on N₆ medium and N₆ medium supplemented with kinetin (5–10 mgl^-1), or kinetin (2 mgl^-1) and IAA (0.5 mgl^-1). A high ratio of albinos among regenerants was observed.     

Localization of GABA-like immunoreactivity in the ectostriatum of domestic chicks: GABA immunocytochemistry combined with Golgi impregnation

Brain Cell Biology - The distribution of GABA-like immunoreactivity (GABA-LI) in the ectostriatal core (Ec) of domestic chicks (one to two days old) was investigated using (1) preembedding GABA...     

Plant regeneration of NaCl-pretreated cells from long-term suspension culture of rice (Oryza sativa L.) in high saline conditions

Cells of a 2-year-old suspension culture of rice (Oryza sativa L.), grown under 1.5% NaCl stress for 3 months, gave rise to plants through embryogenesis in different saline conditions. The high regeneration potential (59.6%) on salt-free medium decreased rapidly with increasing concentration of salt in the regeneration medium. At 1.25% NaCl, healthy shoots were developed in 14.9% of the cultures. Under 1.5% salt stress, embryo formation and embryo germination (6.1%) was observed but further development into plants was inhibited. Cells not pretreated with salt produced plants at a low frequency (2.6–4.2%) both in salt-free and low saline condition (0.75–1% NaCl). Cells pretreated for 3 months with 0.75% salt did not give rise to plants on all tested media. Plants regenerated from the salt-stressed cultures were transferred to soil and grew to maturity in a greenhouse.Abbreviations BA 6-benzyladenine - CH casein hydrolysate - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid     

Variations of matrix electrondensity in brain mitochondria.

The configuration of brain mitochondria was compared in situ, after aldehyde perfusion and/or osmium immersion fixation and in isolated fractions of different functional performance. After combined aldehyde perfusion osmium immersion fixation in situ, mitochondria were condensed having a dark matrix. Fractions capable of controlled respiration also consisted of condensed mitochondria. On the contrary, expanded mitochondria with light matrix were brought about by immersion fixation. Fractions consisting predominantly of light mitochondria displayed no controlled respiration. Light matrix and expanded form are therefore regarded as a functionally impaired state of brain mitochondria. The condensed form is thought to be a landmark of good fixation.     

Neuronal and Astroglial Correlates Underlying Spatiotemporal Intrinsic Optical Signal in the Rat Hippocampal Slice

Widely used for mapping afferent activated brain areas in vivo, the label-free intrinsic optical signal (IOS) is mainly ascribed to blood volume changes subsequent to glial glutamate uptake. By contrast, IOS imaged in vitro is generally attributed to neuronal and glial cell swelling, however the relative contribution of different cell types and molecular players remained largely unknown. We characterized IOS to Schaffer collateral stimulation in the rat hippocampal slice using a 464-element photodiode-array device that enables IOS monitoring at 0.6 ms time-resolution in combination with simultaneous field potential recordings. We used brief half-maximal stimuli by applying a medium intensity 50 Volt-stimulus train within 50 ms (20 Hz). IOS was primarily observed in the str. pyramidale and proximal region of the str. radiatum of the hippocampus. It was eliminated by tetrodotoxin blockade of voltage-gated Na⁺ channels and was significantly enhanced by suppressing inhibitory signaling with gamma-aminobutyric acid(A) receptor antagonist picrotoxin. We found that IOS was predominantly initiated by postsynaptic Glu receptor activation and progressed by the activation of astroglial Glu transporters and Mg²⁺-independent astroglial N-methyl-D-aspartate receptors. Under control conditions, role for neuronal K⁺/Cl⁻ cotransporter KCC2, but not for glial Na⁺/K⁺/Cl⁻ cotransporter NKCC1 was observed. Slight enhancement and inhibition of IOS through non-specific Cl⁻ and volume-regulated anion channels, respectively, were also depicted. High-frequency IOS imaging, evoked by brief afferent stimulation in brain slices provide a new paradigm for studying mechanisms underlying IOS genesis. Major players disclosed this way imply that spatiotemporal IOS reflects glutamatergic neuronal activation and astroglial response, as observed within the hippocampus. Our model may help to better interpret in vivo IOS and support diagnosis in the future.     

Conformational Preferences of the CalliFMRFamides and their Free-Acid Analogues

Abstract

A molecular dynamics study was undertaken to determine the conformational basis for the differing activities of the insect neuropeptide hormones calliFMRFamide 3 (SPSQDFMRF-NH₂), calliFMRFamide 5 (APGQDFMRF-NH₂) and their corresponding free-acid analogues (SPSQDFM- RF-OH and APGQDFMRF-OH) in two insect bioassays. A simulated annealing protocol was used to determine the range of conformers available to the linear peptides. Analysis of the conformers obtained indicated that all the peptides exhibited distinct secondary structure preferences. These, when correlated with their biological activities, enabled the formulation of putative conformation- activity relationships for the peptides.     

Characterisation of an uridine-specific binding site in rat cerebrocortical homogenates

Parameters of [3H]uridine binding to synaptic membranes isolated from rat brain cortex (K(D)=71+/-4 nM, B(max)=1.37+/-0.13 pmol/mg protein) were obtained. Pyrimidine and purine analogues displayed different rank order of potency in displacement of specifically bound [3H]uridine (uridine>5-F-uridine>5-Br-uridine approximately adenosine>5-ethyl-uridine approximately suramin>theophylline) and in the inhibition of [14C]uridine uptake (adenosine>uridine>5-Br-uridine approximately 5-F-uridine approximately 5-ethyl-uridine) into purified cerebrocortical synaptosomes. Furthermore, the effective ligand concentration for the inhibition of [14C]uridine uptake was about two order of magnitude higher than that for the displacement of specifically bound [3H]uridine. Adenosine evoked the transmembrane Na(+) ion influx, whereas uridine the transmembrane Ca(2+) ion influx much more effectively. Also, uridine was shown to increase free intracellular Ca(2+) ion levels in hippocampal slices by measuring Calcium-Green fluorescence. Uridine analogues were found to be ineffective in displacing radioligands that were bound to various glutamate and adenosine-recognition and modulatory-binding sites, however, increased [35S]GTPgammaS binding to membranes isolated from the rat cerebral cortex. These findings provide evidence for a rather specific, G-protein-coupled site of excitatory action for uridine in the brain.     

Sildenafil,N-desmethyl-sildenafil and Zaprinast enhance photoreceptor response in the isolated rat retina

Here we report that the active component of Viagra, Sildenafil and the first metabolite, N-desmethyl-sildenafil (UK-103, 320) increased the amplitude of flash-evoked electroretinogram (ERG) of dark-adapted albino rat retina. Effects of Sildenafil and N-desmethyl-sildenafil were comparable to those of the known phosphodiesterase inhibitor, Zaprinast. The photoreceptor cell response was isolated by blocking the glial K(+) ion-buffering and the on-bipolar components of the ERG with the use of BaCl(2) (500 microM) and the specific type VI metabotropic glutamate receptor agonist, DL-2-amino-4-phosphonobutyric acid (25 microM), respectively. Zaprinast, Sildenafil and N-desmethyl-sildenafil (1 microM each) increased the amplitude of photoreceptor cell response either. Besides, Sildenafil was significantly more effective than N-desmethyl-sildenafil. These findings suggest an increased sensitivity of photoreceptor cells in the presence of Sildenafil and it is metabolite.