The influence of alkyl pyridinium sponge toxins on membrane properties, cytotoxicity, transfection and protein expression in mammalian cells

The ability of two alkyl pyridinium sponge toxin preparations (poly-APS and halitoxin) to form transient pores/lesions in cell membranes and allow transfection of plasmid cDNA have been investigated using HEK 293 cells. Poly-APS and halitoxin preparations caused a collapse in membrane potential, reductions in input resistance and increased Ca²⁺ permeability. At least partial recovery was observed after poly-APS application but recovery was more rarely seen with halitoxin. The transfection with plasmid cDNAs for an enhanced green fluorescent protein (EGFP) and human tumour necrosis factor receptor 2 (TNFR2) was assessed for both toxin preparations and compared with lipofectamine. Stable transfection was achieved with poly-APS although it was less efficient than lipofectamine. These results show that viable cells transfected with alien cDNA can be obtained using novel transient pore-forming alkyl pyridinium sponge toxins and a simple pre-incubation protocol. This provides the first proof of principle that pore-forming alkyl pyridinium compounds can be used to deliver cDNA to the intracellular environment without permanently compromising the plasma membrane.     

Isolation of Actinomycetes synthesizing proteases with thrombolytic activity

Proteases with the thrombolytic activity were studied in 212 strains of actinomycetes isolated from different soils of the Soviet Union. The cultures belonged to the genera Micromonospora, Nocardia and Streptomyces. Proteases were synthesized by 41% of the studied actinomycetes and some of their strains completely dissolved in vitro artificially obtained blood thrombi within 120-240 min. In the Streptomyces genus, more active strains were found in the groups Flavus, Fradia and Globisporus. The groups Olivaceus, Violaceus and Viridis had less active strains.     

Effect of nitroammofoska on the aldolase activity of the normal hemolymph in the mollusk Planorbarius banaticus and in trematode invasion

The infection of Planorbarius banaticus with sporocysts of Cotylurus cornutus is accompanied by an increase in aldolase activity of molluscs' haemolymph of 1.2 fold. In solutions of nitroammofoska (0.1, 1 and 10 mg/1) the activity of this ferment in infected individuals increases much higher than in non-infected ones. This results in fast carbohydrate expenditures by molluscs, intermediate hosts of trematodes, and their death from exhaustion.     

Cytogenetic analysis of mouse metaphase II oocytes following exposure to tritiated water

Female mice were given different dosages (0, 3.0, 7.5, 15.0, or 30 muCi/ml) of tritium in their drinking water continuously from 3 to 7 weeks of age to assess the effects on germ cell chromosomes. At 8-9 weeks of age, mice were superovulated and metaphase II oocytes were processed and C-banded for cytogenetic analyses. Chromatid acentric fragments were the only type of structural aberration detected, and their incidence was higher in controls than in any of the tritiated water (HTO) groups. Analysis of numerical chromosomal aberrations revealed that the incidence of hypoploid (N = 19) oocytes was higher in oocytes from mice who drank HTO as compared with controls. However, the effects of HTO upon aneuploidy induction was not definitive due to the increase the incidence of aberrations in mouse oocytes can be related to the low dose rate resulting from chronic HTO exposure and possibly death of tritium-damaged cells.     

The effect of administering corticoliberin into the striatum on the open-field and shuttle-box behaviors of KHA and KLA strain rats]

The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress.     

Moult in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma

We recorded the age of individual wing and tail feathers of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma of known age and breeding status at Bird Island, South Georgia. Breeders and non-breeders of both species moult their rectrices annually. Non-breeders moult primaries biennially. In the first year of a cycle, the outer three and some inner primaries are moulted descendantly; in the next year the inner primaries are moulted ascendantly, starting from primary seven. There is a general progression to moulting equal numbers of primaries in each half of the cycle by the time breeding starts at about 10 years of age. Grey-headed Albatrosses usually moult fewer primaries than Black-browed Albatrosses, particularly as 3-year-olds, when they undertake substantial plumage change in body moult. Most secondaries in Black-browed Albatrosses have been replaced once by age 4 years. Breeding Black-browed Albatrosses continue the moult pattern established as immatures whether they fail or not, as do failed Grey-headed Albatrosses. Successful Grey-headed Albatrosses, which breed again 16 months later, moult their three innermost primaries after breeding in the remainder of the current year and, after a period when moult is interrupted, renew the remaining primaries the following year. Comparisons between species and between failed and successful birds within species indicate that moult rate is not closely linked to the length of the interval between breeding attempts. Interspecies differences are better explained by breeding latitude, with tropical albatrosses moulting twice as fast as sub-Antarctic species, possibly reflecting food availability outside the breeding season.     

Density-dependent inhibitory effect of transforming growth factor-β on human fibroblasts involves the down-regulation of platelet-derived growth factor α-receptors

We have previously found that transforming growth factor-β1 (TGF-β1) inhibits the mitogenic activity of platelet-derived growth factor (PDGF) in cultures of human neonatal fibroblasts in a density-dependent fashion. In the present investigation we determined the effect of TGF-β1 on the PDGF α-receptor, which binds all PDGF isoforms, as well as on the β-receptor, which binds only PDGF-BB with high affinity. We found that the inhibitory effect of TGF-β1 on PDGF-AA-induced mitogenesis was density-dependent; when dense cell cultures were preincubated with TGF-β1, there was an complete inhibition of ³H-thymidine incorporation, whereas the effect was less in sparse cultures. A similar density-dependent effect of TGF-β1 was seen in PDGF-BB treated cells, although less pronounced. The binding of ¹²⁵I-labeled PDGF-AA and PDGF-BB to the α-receptor was significantly reduced after treatment with TGF-β1 in dense cultures, whereas the sparse cultures were less affected. A decrease of α-receptor mRNA was also seen. The levels of β-receptor protein and mRNA were unaffected. We conclude that the growth inhibitory effect of TGF-β1 is cell density-dependent and involves down-regulation of PDGF α-receptors. © 1993 Wiley-Liss, Inc.