The APPswe/PS1A246E mutations in an astrocytic cell line leads to increased vulnerability to oxygen and glucose deprivation,Ca2+ dysregulation,and mitochondrial abnormalities

Growing evidence suggests a close relationship between Alzheimer′s Disease (AD ) and cerebral hypoxia. Astrocytes play a key role in brain homeostasis and disease states, while some of the earliest changes in AD occur in astrocytes. We have therefore investigated whether mutations associated with AD increase astrocyte vulnerability to ischemia. Two astroglioma cell lines derived from APP_SWE /PS 1A246E (APP , amyloid precursor protein; PS 1, presenilin 1) transgenic mice and controls from normal mice were subjected to oxygen and glucose deprivation (OGD ), an in vitro model of ischemia. Cell death was increased in the APP_SWE /PS 1A246E line compared to the control. Increasing extracellular calcium concentration ([Ca²⁺]) exacerbated cell death in the mutant but not in the control cells. In order to explore cellular Ca²⁺ homeostasis, the cells were challenged with ATP or thapsigargin and [Ca²⁺] was measured by fluorescence microscopy. Changes in cytosolic Ca²⁺ concentration ([Ca²⁺]_c) were potentiated in the APP_SWE /PS 1A246E transgenic line. Mitochondrial function was also altered in the APP_SWE /PS 1A246E astroglioma cells; mitochondrial membrane potential and production of reactive oxygen species were increased, while mitochondrial basal respiratory rate and ATP production were decreased compared to control astroglioma cells. These results suggest that AD mutations in astrocytes make them more sensitive to ischemia; Ca²⁺ dysregulation and mitochondrial dysfunction may contribute to this increased vulnerability. Our results also highlight the role of astrocyte dyshomeostasis in the pathophysiology of neurodegenerative brain disorders.

     

Salmonella exploits host Rho GTPase signalling pathways through the phosphatase activity of SopB

Salmonella uses Type 3 secretion systems (T3SSs) to deliver virulence factors, called effectors, into host cells during infection. The T3SS effectors promote invasion into host cells and the generation of a replicative niche. SopB is a T3SS effector that plays an important role in Salmonella pathogenesis through its lipid phosphatase activity. Here, we show that SopB mediates the recruitment of Rho GTPases (RhoB, RhoD, RhoH, and RhoJ) to bacterial invasion sites. RhoJ contributes to Salmonella invasion, and RhoB and RhoH play an important role in Akt activation. R‐Ras1 also contributes to SopB‐dependent Akt activation by promoting the localised production of PI(3,4)P₂/PI(3,4,5)P₃. Our studies reveal new signalling factors involved in SopB‐dependent Salmonella infection.     

Juvenility and endogenous rooting substances inCastanea sativa Mill

The rooting response to exogenous auxin of cuttings in a juvenile phase of growth from plants ofCastanea sativa Mill. was determined and simultaneously the rooting potential of the water extracts was evaluated in presence of IAA by a bean rooting test. The level of the extractable rooting promoters was high in the cuttings which exhibited the highest percentage of rooting. An inhibition of the effect of IAA on rooting was detected in the cuttings which showed the lowest rooting response, the histogram differing not much from that of the adult plant. The results indicate that in chestnut the juvenile condition, easy rooting, is associated with high levels of endogenous rooting promoters.     

Effects of 5-fluoro-2′-deoxyuridine on bacterial growth its use for DNA labelling

Experiments on the action of 5-fluoro-2′-deoxyuridine on growth ofEscherichia coli B, CECT 101;Pseudomonas fluorescens, CECT 318;Pseudomonas savastanoi, CECT 93;Micrococcus luteus, ATCC 4698;Bacillus cereus, CIP 52.58;Bacillus macerans, ClP 52.58 andBacillus subtilis, ATCC 6633, are described. The inhibition of growth is reversed by thymine plus uracil in all cases except inPseudomonas strains in which uracil alone is active, and in which no exogenous thymine is taken up, not even in the presece of 2′-deoxyguanosine. Growth conditions for improved labelling of bacterial DNA are discussed in the light of the results.     

Expression of a gene encoding a ribosomal p40 protein and identification of an active promoter site

The promoter of a gene encoding a ribosome-associated protein of 40 kDa from Arabidopsis thaliana (A-p40) was sequenced and the expression of the gene studied. A-p40 was expressed in the same organs and with the same variations as the eukaryotic elongation factor 1 (eEF1A), another gene coding for a protein involved in translation Arabidopsis plants transformed with a -glucuronidase (GUS) gene driven by the A-p40 promoter confirm that A-p40 is expressed in actively dividing and growing cells. eEF1A promoter-GUS fusions have the same pattern of expression. Comparison of cis-acting elements from A-p40 and eEF1A revealed some common elements. A-p40 promoter deletions and transient gene expression in transfected Arabidopsis protopasts allowed the identification of trap40, a cis-acting element regulating gene expression. Gel retardation experiments indicate that eEF1A and A-p40 are regulated by different cis-acting elements. The role of such elements is discussed.     

Hand preferences in chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and orangutans (Pongo pygmaeus) in food-reaching and other daily activities

We observed 36 captive great apes [31 chimpanzees (Pan troglodytes),2 bonobos (Pan paniscus), and3 orangutans (Pongo pygmaeus)]reaching for items of food and engaging in other spontaneous behaviors. We consider circumstantial factors that could influence the preferred choice of one hand or the other. Most of the subjects (81%) showed a significant hand preference in food reaching that is consistent in directionality with the hand preferences that they showed during other spontaneous behaviors. The results show that the postural adjustment required when carrying out an action seems to influence directly the expression of manual laterality in individuals. Moreover, the results indicate the possible existence of a relationship between maturational factors and persistence in directionality of hand preferences.     

Peroxidase isoenzymes in the defense response of Capsicum annuum to Phytophthora capsici

Quantitative and qualitative changes in isoperoxidase patterns from stems of three cultivars of pepper ( Capsicum annuum L.). one susceptible, one intermediate and one resistant, were found upon inoculation with Phytophthora capsici using a decapitation method. The peroxidase activity was determined in the intercellular fluid as well as in the cytosolic fraction of the necrotic, healthy and intermediate zones of stems of the three cultivars, 6 days after inoculation. In the intercellular fluid, peroxidase activity of the susceptible cv. Yolo Wonder increased somewhat from 4.7 (healthy zone) to 12.9 (intermediate zone) μmol mg⁻¹ protein min⁻¹, whereas in the intermediate cv. Americano, the peroxidase activity decreased from 123 (healthy zone) to 78 (intermediate zone) μmol mg⁻¹ protein min⁻¹. The most dramatic increase (5.7 to 662 μmol mg⁻¹ protein min⁻¹) in intercellular peroxidase activity was found in the resistant cv. Smith-5. This, in conjunction with the appearance of an additional acidic isoperoxidase (pI 4.4) specific for the cv. Smith-5, could be the reason for the resistance of this cultivar against the fungus attack. The release of peroxidase into the intercellular space as a defense reaction was confirmed by histochemical analysis, showing that peroxidase activity occurred in the intercellular spaces of those stems of the resistant cultivar that had not yet been invaded by the fungus, but was detected neither in the other cultivars nor in the intercellular spaces of such stems of the intermediate and susceptible cultivars that contained growing mycelium of P. capsici. The lack of staining in the intercellular spaces of the susceptible cultivars could be attributed to their low content in peroxidase.     

EFFECTS OF ARSENATE ON GROWTH AND PHOSPHORUS METABOLISM OF PHYTOPLANKTON1,2

The response to arsenate in growth and phosphate uptake by five algae in culture varied considerably. The growth rates of Melosira granulata var. angustissima O. Müll, and Ochromonas vallesiaca Chodat were depressed by 1 μM arsenale. Chlamydomonas reinhardtii Dang. required 10 μM for the same degree of depression, while the growth rules of Cryptomonas eroasa Ehr. and Anabaena variabilis Kütz. were unaffeted up to 100 μM. However, following depletion of phosphate, cultures of the later two algae began to die at the higher concentrations of arsenale tested. Growth of C. reinhardtii in the presence of 35 μM arsenate resulted in characteristics of P deficiency. Comparison of rates of photosynthesis, respiration, and phosphate uptake between cultures of C. reinhardtii which had grown in the presence and absence of arsenate showed little evidence after 16 doublings that it had adapted to arsenale.