Size of the pores created by an electric pulse: Microsecond vs millisecond pulses

Here, the sizes of the pores created by square-wave electric pulses with the duration of 100μs and 2ms are compared for pulses with the amplitudes close to the threshold of electroporation. Experiments were carried out with three types of cells: mouse hepatoma MH-22A cells, Chinese hamster ovary (CHO) cells, and human erythrocytes. In the case of a short pulse (square-wave with the duration of 100μs or exponential with the time constant of 22μs), in the large portion (30-60%) of electroporated (permeable to potassium ions) cells, an electric pulse created only the pores, which were smaller than the molecule of bleomycin (molecular mass of 1450Da, r≈0.8nm) or sucrose (molecular mass of 342.3Da, radius-0.44-0.52nm). In the case of a long 2-ms duration pulse, in almost all cells, which were electroporated, there were the pores larger than the molecules of bleomycin and/or sucrose. Kinetics of pore resealing depended on the pulse duration and was faster after the shorter pulse. After a short 100-μs duration pulse, the disappearance of the pores permeable to bleomycin was completed after 6-7min at 24-26°C, while after a long 2-ms duration pulse, this process was slower and lasted 15-20min. Thus, it can be concluded that a short 100-μs duration pulse created smaller pores than the longer 2-ms duration pulse. This could be attributed to the time inadequacy for pores to grow and expand during the pulse, in the case of short pulses.     

DNA marker based identification of spontaneous hybrids between Pinus mugo and P. sylvestris at the Lithuanian sea‐side

The objective was to identify spontaneous hybrids between P. mugo and P. sylvestris using organelle DNA markers in sympatric zones at the sea‐side spit of Kursiu Nerija in western Lithuania. A field inventory was carried out over the entire Lithuanian part of the spit and 203 individuals morphologically intermediate between P. sylvestris and P. mugo were tested for their male parent with chloroplast DNA PCR‐RFLP markers and for their female parent with mitochondrial DNA PCR markers. Unfortunately, the mitochondrial DNA Nad7 marker failed to identify the female parent species in our study. However, the chloroplast DNA PCR‐RFLP marker revealed that out of 203 tested individuals only 23 had a paternity different than that indicated by morphology. Of these, 13 individuals were morphologically identified as P. sylvestris but possessed cpDNA of P. mugo (putative hybrids with P. sylvestris (female) ×P. mugo (male parent), and 10 individuals morphologically identified as P. mugo possessed cpDNA of P. sylvestris and may be hybrids with P. mugo (female) ×P. sylvestris (male parent). The remainder of the 177 individuals identified in the field inventory were were considered as pure species. In conclusion, our study indicates ongoing spontaneous hybridization between P. mugo and P. syvestris in Kursiu Nerija. Human impact via seed transfer on altered hybridization rates as well as evolutionary consequences are discussed.     

Comparative cytogenetics of Diphyllobothrium ditremum (Creplin, 1925) and Ligula intestinalis (Linnaeus, 1758) (Cestoda: Pseudophyllidea)

An investigation carried out on two species of pseudophyllidean cestodes belonging to different families showed very close karyological affinity between them. The karyotypes of Diphyllobothrium ditremum and Ligula intestinalis both consist of 18 bi-armed chromosomes and are almost identical with respect to the relative length and the centromeric indices of corresponding chromosomes. Statistically significant differences exist in the morphology of chromosomes 2 and 4, but they are not striking and may be due in part to errors of measurement. Differences in the absolute length of the chromosomes were noted: the chromosomes of D. ditremum are somewhat larger (from 2.7 to 8.5 μm) than those of L. intestinalis (from 1.9 to 5.4 μm). The results obtained were compared with data existing for other pseudophyllidean cestodes and preliminary conclusions on the karyotypic evolution in that group of helminths were made.     

Floral meristems as a source of enhanced yield and quality of DNA in grasses

Floral meristems of Lolium and Festuca grasses give a 5- to 19-fold enhancement in yield of extracted DNA in comparison with leaves. Meristems also provide highly pure DNA samples. The method could be useful for applications in molecular genetics in many species of the Gramineae. Received: 14 April 1998 / Revision received: 8 June 1998 / Accepted: 10 July 1998     

Current state of purification,isolation and analysis of bacteriocins produced by lactic acid bacteria

Applied Microbiology and Biotechnology - The scientific interest for the search of natural means of microbial inhibitors has not faded for several years. A search of natural antibiotics, so-called...     

Formic Acid and Acetic Acid Induce a Programmed Cell Death in Pathogenic Candida Species

Cutaneous fungal infections are common and widespread. Antifungal agents used for the treatment of these infections often have undesirable side effects. Furthermore, increased resistance of the microorganisms to the antifungal drugs becomes the growing problem. Accordingly, the search for natural antifungal compounds continues to receive attention. Apoptosis is highly regulated programmed cell death. During yeast cell apoptosis, amino acids and peptides are released and can stimulate regeneration of human epithelium cells. Thus, detection of chemical compounds inducing apoptosis in yeast and nontoxic for humans is of great medical relevance. The aim of this study was to detect chemical compound inducing apoptosis in pathogenic Candida species with the lowest toxicity to the mammalian cells. Five chemical compounds—acetic acid, sodium bicarbonate, potassium carbonate, lithium acetate, and formic acid—were tested for evaluation of antifungal activity on C. albicans, C. guilliermondii, and C. lusitaniae. The results showed that acetic acid and formic acid at the lowest concentrations induced yeast cells death. Apoptosis analysis revealed that cells death was accompanied by activation of caspase. Minimal inhibitory concentrations of potassium carbonate and sodium bicarbonate induced Candida cells necrosis. Toxicity test with mammalian cell cultures showed that formic acid has the lowest effect on the growth of Jurkat and NIH 3T3 cells. In conclusion, our results show that a low concentration of formic acid induces apoptosis-like programmed cell death in the Candida yeast and has a minimal effect on the survivability of mammalian cells, suggesting potential applications in the treatment of these infections.     

Ragweed plants and airborne pollen in the Baltic states

Presence of pollen in the atmosphere was determined inTartu in 1989–1997, in Kuressaare in 1996–1997 and iniauliai in 1997. Ragweed airpollen was found in latesummer in three years. The distribution, abundance andflowering of local ragweed plants were estimated. Itappeared that the number of local sources did notexceed twenty per country per year. Majority of thesesources consisted of a small number of pollinating A. artemisiifolia individuals. The largest localsources, consisting of several hundreds ofindividuals, were exclusively rare. Transport ofragweed pollen by air masses from distant sources wasstudied. It was found that incursions of ragweedpollen were determined by air fluxes originating fromthe Ukraine as well as from the southeastern andsouthern regions of the European part of Russia. Theseincursions occurred in extensive high-pressure areaswhose centre was located in the central region of theEuropean part of Russia with a periphery extending tothe Baltic countries.