Biological role of endoreplication in the process of spermatogenesis inChara vulgaris L.

Summary During cell division in antheridial filaments ofChara vulgaris an increase in DNA content occurs in both shield cells and manubria within an antheridium, reaching 16C–64C and 8C–32C levels, respectively. Endoreplication ceases prior to the formation of spermatids and initiation of spermiogenesis, probably as a result of symplasmic isolation of the antheridium from the thallus. As the DNA content of the nuclei increases, the shield cells³H-leucine incorporation increases, and they grow intensively in the tangential plane. Translation decreases considerably after termination of shield cell growth. DNA content of mature manubria is half of that in shield cells, although their size is 10 times that of manubria. Translational activity of manubria also increases as DNA content rises and cells grow. However, during spermiogenesis, this activity remains at its maximum, which is associated with the secretory function of the manubria. Spermiogenesis is also accompanied by far-reaching ultrastructural changes within the manubrial cytoplasm.The level of endopolyploidy in both shield cells and manubria of antheridia formed in the spring is higher by one replication cycle, than in autumnal antheridia. AMO-1618, at a concentration of 10^–5M reduces the DNA content in the autumnal manubria. The higher the manubrial level of endopolyploidy in spermiogenesis, the greater their size, and the higher the translational activity and number of joined spermatids. The number of spermatozoids in the antheridium is also positively correlated with the internal volume of an antheridium, which is itself dependent on the endopolyploidy level of shield cells.The results obtained confirm the assumption that endoreplication favours the higher growth dynamics and potential translational activity, which occurs in the dynamic growth phase only in shield cells, while in manubria, i.e. cells producing substances necessary to spermatozoids development, it remains high until the end of spermiogenesis.     

The shikonin derivatives and pyrrolizidine alkaloids in hairy root cultures of Lithospermum canescens (Michx.) Lehm.

Hairy root cultures of Lithospermum canescens were established using three strains of Agrobacterium rhizogenes: ATCC 15834, LBA 9402 and NCIB 8196. Eight lines resulting from infection with A. rhizogenes ATCC 15834 demonstrated sufficient biomass increase and were submitted to further investigations. The contents of acetylshikonin (ACS) and isobutyrylshikonin (IBS) in transformed hairy roots made up ca. 10% of those observed in natural roots of L. canescens (24.35 and 14.48 mg g⁻¹ DW, respectively). One line, Lc1-D, produced the largest amounts of ACS (2.72 mg g⁻¹ DW) and IBS (0.307 mg g⁻¹ DW). Traces of pyrrolizidine alkaloids (PA), canescine and canescenine, were found in all lines of transformed hairy roots.     

On the inducibility of nitrate transport by tobacco cells

The question as to whether the nitrate transport system is induced by nitrate was addressed using a cell suspension of the XD line of Nicotiana tabacum L. cv. Xanthi as an experimental system. The cells were grown on area as the sole nitrogen source, and tungstate was used to render nitrate reductase non-functional. To avoid shock due to vacuum filtration, the cells, were harvested by gravity filtration. Nitrate uptake by cells, which were harvested, transferred to fresh medium, and immediately exposed to nitrate (freshly harvested cells), displayed a lag period of about 3 h.
In cells which were given incubation periods in fresh medium before exposure to nitrate (preincubated cells), the lag period was considerably shortened. After 3 h of preincubation in the absence of nitrate (recovered cells), the lag period was almost completely eliminated. Cycloheximide inhibited nitrate uptake by recovered cells within minutes, and prevented the development of nitrate uptake in freshly harvested cells. Cycloheximide did not affect uptake of α-aminoisobutyric acid (AIB) within the first 2 h after its addition. Recovery of the membrane potential from a low value just after the harvest of the cells to a maximal value 3 h later, was observed using the lipophilic cation methyltriphenylphosphonium (MTPP⁺), supplied at low concentrations, as a probe. Depolarization of the membrane potential by MTPP⁺, at the millimolar range, caused a rapid inhibition of nitrate uptake by recovered cells. The results indicate that nitrate transport by the XD cells depends on the membrane potential and on protein components with short half life. In addition, it requires a continuous protein synthesis. The effects of physical manipulation on nitrate uptake are discussed.     

Effect of nickel on antioxidative enzyme activities, proline and chlorophyll contents in wheat shoots

Effect of two Ni concentrations (10 and 200 μM) on growth, Ni accumulation, chlorophyll and proline contents, relative water content (RWC) as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione S-transferase (GST) were studied in shoots of wheat plants. Treatments caused a considerable accumulation of Ni in the shoots. However, exposure of plants to 10 μM Ni did not lead to significant alterations in shoot growth except for a slight increase in fresh mass. The other parameters studied were not affected by treatment of plants with 10 μM Ni. In contrast, 200 μM Ni caused inhibition of shoot growth, a decline in RWC and chlorophyll content, accumulation of proline and occurrence of visible symptoms of Ni toxicity. The activities of SOD and CAT decreased in response to 200 μM Ni. Conversely, several-fold enhancements of POD and GST activities were observed following the 3^rd day of 200 μM Ni treatment.     

Fatty acid efficiency profile in uncoupling of <Emphasis Type="Italic">Acanthamoeba castellanii</Emphasis> mitochondria

A profile of free fatty acid (FFA) specificity in Acanthamoeba castellanii mitochondrial uncoupling is described. The FFA uncoupling specificity was observed as different abilities to stimulate resting respiration, to decrease resting membrane potential, and to decrease oxidative phosphorylation efficiency. Tested unsaturated FFA (C18–20) were more effective as uncouplers and protonophores when compared to tested saturated FFA (C8–18), with palmitic acid (C16:0) as the most active. As FFA efficiency in mitochondrial uncoupling is related to physiological changes of fatty acid composition (and thereby FFA availability) during growth of amoeba cells, it could be a way to regulate the activity of an uncoupling protein and thereby the efficiency of oxidative phosphorylation during a cell life of this unicellular organism. Aleksandra Swida and Małgorzata Czarna contributed equally to this work.     

Chromosome C-banding patterns in isolated population of the grasshopper Podisma pedesis (L.) (Orthoptera,Acrididae) from the Altai Mts

The C-banding patterns in the embryo chromosomes of the grasshopper Podisma pedestris (L.) from the Altai Mts are reported. The additional second C-heterochromatic arms in at least five pairs of autosomes and in the X-chromosome were revealed. The paracentromeric, interstitial, and telomeric C-bands were observed. The studied population of P. pedestris shows some differences in the distribution and amount of the heterochromatin in comparison with European populations.     

Influence of exogenic salicylic acid on Fusarium seedling blight reduction in barley

Salicylic acid (SA) applied at concentrations from 1–10 μg·ml⁻¹ to germinating seeds of 8 barley cultivars reduced the disease rating of seedlings. Seedlings of barley not treated with SA and inoculated with Fusarium culmorum exhibited disease rating of root on avarage 76 %. Seedlings treated before inoculation with solution of SA 1, 2, 5 and 10 μg/ml exhibited significantly lower disease rating: on average 66, 58, 44 and 38 %. Disease score of leaf decreased in similar extent: from 30 % to 20, 11, 7 and 0 %.