Viability and acrosome integrity of rabbit spermatozoa processed in a gelatin-supplemented extender

The effect of gelatin addition to the semen extender on the viability and acrosome integrity of rabbit spermatozoa was studied. Pooled semen samples were processed in a boar semen extender with or without gelatin addition. Semen samples were stored at 5 °C for 72 h. Viability and acrosome integrity was evaluated by light microscope. Results showed that gelatin addition had a significant positive effect on the quality of the stored semen.     

Glandular hairs of Sigesbeckia jorullensis Kunth (Asteraceae): morphology,histochemistry and composition of essential oil

Long-stalked glandular hairs of outer and inner involucral bracts of Sigesbeckia jorullensis, which are important for epizoic fruit propagation, were investigated using light and scanning electron microscopy. The essential oil secreted by the hairs was analysed by chromatographic methods including gas chromatography/mass spectrometry and with a laser microprobe mass analyser. The glandular hairs consisted of a large multicellular stalk and a multicellular secreting head. The apical layer of glandular head cells was characterized by leucoplasts and calcium oxalate crystals. Below the apical cells there were up to six layers of cells containing many chloroplasts around the nucleus and surrounded by vacuoles filled with flavonoids and tannins. The essential oil originating in the head cells was secreted into the subcuticular space and may be liberated by rupture of the cuticle. It was mainly composed of sesqui- and diterpenes, with the sesquiterpene hydrocarbon germacrene-D as the main component. Monoterpenes, n-alkanes and their derivatives as well as flavonoid aglycones were also detected. The stickiness of the essential oil is probably associated with the high content of oxygenated sesqui- and diterpenes. In addition to long-stalked trichomes, small biseriate trichomes occurred, secreting small quantities of essential oil into a subcuticular space.     

Rolling properties of rGPIbalpha-conjugated phospholipid vesicles with different membrane flexibilities on vWf surface under flow conditions

The recombinant fragment of the platelet membrane glycoprotein, rGPIbalpha, was conjugated to phospholipid vesicles with the average diameter of ca. 1 microm using N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP). We used five kinds of rGPIbalpha-vesicles with different fluorescent anisotropies of 1,6-diphenyl-1,3,5-hexatriene (DPH) to study the rolling properties of the vesicles on the von Willebrand factor (vWf)-immobilized surface. Under flow conditions, the rolling velocity of the rGPIbalpha-vesicles decreased with the increasing membrane flexibility. It is considered that the vesicles with a high membrane flexibility have a high deformability and can be flattened to a high degree during rolling on the vWf surface, thus resulting in the large contact area. We obtained a recipe to control the rolling velocity of artificial platelets by membrane flexibility.     

Mapping candidate hotspots of meiotic recombination in segments of human DNA cloned in the yeast<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis>

The hotspots of meiotic recombination in the human genome can be localized by genetic techniques. The resolution of these techniques is in the range of kilobases and depends on the density of the physical markers identifying allelic variants of the chromosomal loci. We thought it would be interesting to localize these sites with higher resolution. Assuming that some human chromosomal sites conserve their propensity for recombination when cloned in yeast, we localized the hotspots of recombination in several yeast artificial chromosomes (YACs) carrying human DNA. A number of potential recombination hotspots could be identified in the clones studied. Among them there are two classes of sites that are particularly recombination prone also in human meiotic cells: sites associated with CpG islands and sites located in the vicinity of long minisatellite sequences.Communicated by G. P. Georgiev     

Micropropagation of calla lily (<Emphasis Type="Italic">Zantedeschia albomaculata</Emphasis>) via <Emphasis Type="Italic">in vitro</Emphasis> shoot tip proliferation

Summary A method for the micropropagation of Zantedeschia albomaculata is presented using shoot tip proliferation onto Murashige and Skoog (MS) medium supplemented with different plant growth regulator concentrations and combinations. Of the four cytokinins tested, 6-benzyladenine (BA) and thidiazuron (TDZ) were found to be more effective. An optimal concentration of BA (8.87 μM) or TDZ (4.54 μM) developed an average of 3.8 and 3.2 shoots per explant, respectively, but increasing concentrations of cytokinins often led to lower proliferation rate and stunted growth. Addition of auxins to the MS medium supplemented with 8.87 μM BA slightly enhanced multiple shoot formation in the explants. Multiplication of six cultivars of Zantedeschia genus comprising different flower types and colors were tested and achieved using only one regeneration medium (MS+8.87 μMBA+2.46 μM IBA). Different MS medium strength, air temperature (15, 20, 25, and 30°C) and light quality [fluorescent, red + blue, red and blue light provided by a LED (light-emitting diode) system] were used (without phytohormone) with the aim of stimulating in vitro shoot and root development. Half-strength MS or MS and cultures maintained at 25°C were found to be equally suitable for shoot tip culture of Z. albomaculata. Shoot elongation as well as fresh and dry weight were significantly increased when cultures were kept under red or blue light.     

Micropropagation of chinese redbud (<Emphasis Type="Italic">Cercis yunnanensis</Emphasis>) through axillary bud breaking and induction of adventitious shoots from leaf pieces

Summary Factors affecting in vitro shoot production and regeneration of Cercis yunnanensis Hu et Cheng were investigated by comparing various growth regulators and explant types. For optimum shoot production from axillary buds, Murashige and Skoog (MS) media containing 6-benzyladenine, either alone or in combination with a low concentration of thidiazuron, resulted in the greatest number of shoots formed per explant (>3). Explants (2 mm long) containing one axillary bud placed in directcontact with the medium yielded the most shoots per bud (1.6) when grown on growth regulator-free medium. Root formation on 70–80% of shoot explants was accomplished using either indole-3-butyric acid or α-naphthaleneacetic acid in the medium, with significantly more roots formed on explants possessing and apical bud than those without the bud. Direct shoot organogenesis from leaf explants occurred on MS medium containing 10–30 μM thidiazuron, with up to 42% of leaf explants producing shoots.     

Measuring tolerance to herbivory: accuracy and precision of estimates made using natural versus imposed damage

Abstract.— Tolerance to herbivory (the ability of a plant to incur herbivore damage without a corresponding reduction in fitness) can be measured using either naturally occurring or imposed herbivore damage. After briefly reviewing some of the advantages and disadvantages of these approaches, we present calculations describing the degree to which estimates of tolerance will be biased by environmental variables that affect both herbivory and fitness. With naturally occurring herbivory the presence of environmental variables that are correlated with herbivory and fitness will result in biased estimates of tolerance. In contrast, estimates obtained from experiments in which herbivory is artificially imposed will be unbiased; however, under a wide range of parameter values these estimates will be less precise than estimates obtained from experiments in which herbivory is not manipulated.