Signaling induced by hop/STI-1 depends on endocytosis

The co-chaperone hop/STI-1 is a ligand of the cell surface prion protein (PrP(C)), and their interaction leads to signaling and biological effects. Among these, hop/STI-1 induces proliferation of A172 glioblastoma cells, dependent on both PrP(C) and activation of the Erk pathway. We tested whether clathrin-mediated endocytosis affects signaling induced by hop/STI-1. Both hyperosmolarity induced by sucrose and monodansyl-cadaverine blocked Erk activity induced by hop/STI-1, without affecting the high basal Akt activity typical of A172. The endocytosis inhibitors also affected the sub-cellular distribution of phosphorylated Erk, consistent with blockade of the latter's activity. The data indicate that signaling induced by hop/STI-1 depends on endocytosis. These findings are consistent with a role of sub-cellular trafficking in signal transduction following engagement by PrP(C) by ligands such as hop/STI-1, and may help help unravel both the functions of the prion protein, as well as possible loss-of-function components of prion diseases.     

Opuntia micropropagation by axillary proliferation

Cladode explants of Opuntia amyclaea were cultivated in Murashige and Skoog medium with different supplements. Benzyladenine was necessary for shoot development from pre-existing buds. Axillary proliferation was also stimulated in subsequent subcultures in the presence of benzyladenine and when the apical meristem was not present in the explant. The number of shoots and the total dry weight were maximum with 5% of sucrose in the medium. It was found that satisfactory rooting occurred when 5×10^-5 M indole butyric acid was added to the medium. Vascular contact between roots and shoots was clearly shown by histological observations. The micropropagation system developed here allows the production in 100 days of 25 000 rooted plantlets from a single cladode, by the stimulation of axillary proliferation in the absence of apical dominance.     

Phenotypical changes during in vitro cultivation of monocytes derived immature dendritic cells

Dendritic cells (DC) form a link between the first line of host defence and cellular immunity. In the present study we investigated the effect of cultivation time in generation of immature dendritic cells (iDCs) in vitro from human peripheral blood (PB) monocytes and the influence of iDCs on the oxygen free radicals (OFR) release by polymorphonuclear granulocytes (PMN) stimulated with opsonized zymozan (OZ) and concanavalin A (ConA). Our data suggest that the differentiation in vitro of PB monocytes in iDCs is influenced by the health status of the cell donor, and more by the concentration of cytokines GM-CSF and IL-4 in the system than by the time of cultivation. The in vitro experiments performed demonstrated the interactions between iDC and PMN granulocytes, evaluated by enhanced release of OFR.     

Acmella oppositifolia micropropagation by single-node culture

Acmella oppositifolia plantlet formation was achieved by subculturing single-node explants on Murashige and Skoog medium without growth regulators. The explants from 1-month-old in vitro plantlets produced shoots over a 7-day culture period. From these in vitro cultured nodes readily rooted shoots elongated on auxin-free MS medium. Plants produced were easily acclimatized and subsequently flowered in a greenhouse. This species is of medicinal value in tropical America from Mexico to Colombia.     

Morphological changes induced by ampicillin in Campylobacter

Morphologic changes in Campylobacter fetus ssp. jejuni were evaluated as cultivated on thioglycollute broth, containing minimum of 0.1, 1.3 and 10 Ampicillin minimal inhibitory concentration (MIC). During the first four hours of incubation, no changes occurred in the presence of 0.1 MIC; but with the rest of the ampicillin doses, even at the first hour, a proportion larger than 5% of filament-policurved forms was found, and it increased with the incubation time. The greatest number of altered bacteria was found with the use of 10 MIC. No other morphologic changes were observed.     

Morphological changes induced in fungi by antibiotics

In tests of 31 antibiotics, 29 inhibited growth ofBotrytis cinerea and of these, 18 induced morphological changes. Terminal and lateral branching of the hyphae was induced by actinomycin D, aspergillic acid, citrinin, cyanein, cycloheximide, desertomycin and polyene antibiotics. Curling of the hyphae was induced by griseofulvin and narrowing of the hyphae by citrinin. Some antibiotics at different concentrations produced several types of morphological changes. For example, aspergillic acid, desertomycin and flavofungin also induced terminal bulging of the hyphae. Growth of the dimorphic fungusPaecilomyces viridis was inhibited by 24 antibioties, nine of which induced morphological changes. Branching of the hyphae was induced by azalomycin F, citrinin, eyanein, desertomycin, patulin, rugulosin and trichothecin. Griseofulvin had a curling effect. Except for rugulosin, the above antibiotics, in higher concentrations, induced yeast-like growth ofPaecilomyces viridis. Morphological changes were also induced by inhibitors of RNA and protein synthesis and by antibiotics injuring the cell membranes. Antibiotics with different mechanisms of action induced similar morphological changes.     

Adaptive changes in photosynthetic performance and secondary metabolites during white dead nettle micropropagation

The white dead nettle, Lamium album L., is an herb that has been successfully cultivated under in vitro conditions. The L. album micropropagation system offers a combination of factors (light intensity, temperature, carbon dioxide (CO₂) level, humidity) that are limiting for plant growth and bioactive capacity. To get a better understanding of the mechanism of plant acclimation towards environmental changes, we performed a comparative investigation on primary and secondary metabolism in fully expanded L. album leaves during the consecutive growth in in situ, in vitro, and ex vitro conditions. Although the genetic identity was not affected, structural and physiological deviations were observed, and the level of bioactive compounds was modified. During in vitro cultivation, the L. album leaves became thinner with unaffected overall leaf organization, but with a reduced number of palisade mesophyll layers. Structural deviation of the thylakoid membrane system was detected. In addition, the photosystem 2 (PS2) electron transport was retarded, and the plants were more vulnerable to light damage as indicated by the decreased photoprotection ability estimated by fluorescence parameters. The related CO₂ assimilation and transpiration rates were subsequently reduced, as were the content of essential oils and phenolics. Transfer of the plants ex vitro did not increase the number of palisade numbers, but the chloroplast structure and PS2 functionality were recovered. Strikingly, the rates of CO₂ assimilation and transpiration were increased compared to in situ control plants. While the phenolics content reached normal levels during ex vitro growth, the essential oils remained low. Overall, our study broadens the understanding about the nature of plant responses towards environmental conditions.     

Biphasic changes in leukocytes induced by strenuous exercise

Seven healthy male volunteers participated in short- (STR, 1.7 km), middle- (MTR, 4.8 km) and long- (LTR, 10.5 km) term runs at a speed close to their maximum. A prompt mobilization of white cells, and lymphocytes in particular, appeared following the exercise. The initial increase in the number of lymphocytes was succeeded by a significant decrease [(P less than 0.03) lymphopenial], which on average was 32%-39% of the pre-exercise values in all groups. A close correlation was found between the initial increase in plasma cortisol concentration after exercise and the subsequent lymphopenia. A modest enhancement in the number of granulocytes immediately after the exercise was accompanied by a comprehensive increase in polymorphonuclear (PMN) elastase concentration accounting for 78.6%, SEM 16.3%, 140.7%, SEM 31.8% and 241.3%, SEM 48.1% in the STR, MTR and LTR groups. No correlation was found between granulocyte number and the plasma PMN elastase concentration. A delayed granulocytosis was noted in all subjects, reaching a peak between 2 and 4 h after the exercise. The magnitude of the granulocytosis varied among subjects and peak values of the number of circulating granulocytes were found to be 5.7 x 10(9) cells.l-1, SEM 0.5, 6.7 x 10(9) cells.l-1, SEM 0.6 and 8.8 x 10(9) cells.l-1, SEM 0.5 in STR, MTR and LTR respectively, whereas the mean baseline value was 3.6 x 10(9) cells.l-1, SEM 0.4. The neutrophilic granulocytosis was not accompanied by a corresponding enhancement in PMN elastase concentration. The plasma cortisol concentration reached a peak 30 min after exercise and declined below the control level in 4 h. Neither the initial increase, nor the subsequent decrease in plasma cortisol concentration were found to be essential for the magnitude of the delayed leukocytosis.     

Pigmentation changes in Brevibecteria induced by mutagenic treatment

Inducible pigmentation changes were observed in pigmented strains of Brevibacterium sp. M27 and B. flavum treated with N-methyl-N'-nitro-N-nitrosoguanidine. The highest frequency of induction was reached already at a survival of 30-40% with the maximal yield of 6-10%. As compared with the initial yellow colour, three new pigmentation types, viz. white, pink and orange, were observed. The yellow pigmented parent strains are most resistant to the lethal effects of UV radiation. By selecting pigmented mutants of all types on media containing antibiotics it was possible to obtain strains that were resistant either to tetracycline or to streptomycin. Auxotrophic pigmented mutants were also isolated. In multiple mutant strains of Brevibacterium sp. M27 a number of strainsexhibited a changed L-lysine production. In some strains the production was variable, whereasother strains did not produce L-lysine at all and stains with a limited production of other amino acids were also detected.     

Permeability changes induced by polylysines in rat spermatids

High molecular weight (HMW, >15 kDa) but not low molecular weight (LMW, <15 kDa) polylysines (PLs) bound and induced permeability changes in rat spermatid plasma membranes, estimated by Mn2+ quenching of intracellular indo-1 fluorescence (K(1/2) = 3.3 +/- 0.5 microg/ml) and Co2+ quenching of intracellular calcein. The pharmacology of the Mn2+ entry pathway activated by HMW PL does not suggest that Ca2+ channels are involved in this phenomenon. Concentrations of HMW PL that induced divalent ion entry did not induce the entry of ethidium bromide, suggesting that HMW PL first bound and perturbed the plasma membrane structure inducing a non-specific increase in membrane permeability. High concentrations of HMW PL induced cell lysis (K(1/2) = 23 microg/ml). The binding of HMW PL, initially homogenous on the cell surface, subsequently progressed to a segregated pattern resembling a clustering phenomenon.     

Morphological changes in erythrocytes induced by malarial parasites

Host cell alterations induced by Plasmodium falciparum, P. brasilianum, P. vivax and P. malariae were described by electron microscopy and post-embedding immunoelectron microscopy. P. falciparum infection induces knobs, electron-dense material and clefts in the erythrocyte. Clefts are involved in exporting P. falciparum antigen from the parasite to the erythrocyte membrane. P. falciparum antigen is present in knobs which adhere to endothelial cells causing the blockage of cerebral capillaries and ensuing pathological changes in cerebral tissues. P. brasilianum infection induces knobs, short and long clefts and electron-dense material. These structures appear to contain different P. brasilianum antigens. This indicates that each structure functions independently in trafficking P. brasilianum protein to the erythrocyte surface. P. vivax infection induces caveola-vesicle complexes and clefts in the erythrocyte. These structures are also involved in trafficking P. vivax protein from the parasite to the erythrocyte membrane. P. malariae induces caveolae, electron-dense material, vesicles, clefts and knobs in the erythrocyte. Although vesicles and caveolae are seen in the erythrocyte cytoplasm, they do not form caveola-vesicle complexes as seen in P. vivax-infected erythrocytes. They also appear to be involved in trafficking of malaria antigens. These studies, therefore, indicate that host cell changes occur in order to facilitate the transport of malarial antigens to the host cell membrane. The significance of these phenomena is still not clear.