The control of cellular motility and the role of gelsolin.

Solation of actin gel by gelsolin is much less efficient in the presence of a high concentration of macromolecular solutes. The rigidity of the gel formed by 12 microM actin is lowered from 4 to 0.33 dynes/cm2 by 15 nM gelsolin, while in 6% (w/v) polyethylene glycol, rigidity is lowered only from 20 to 11 dynes/cm2 by 64 nM gelsolin. Owing to the large concentration of protein, transitions in the fluid- and gel-like properties of the cytoplasm are expected to be problematic when promoted by gelsolin alone.     

Proteome analysis of X-ray irradiated human erythroleukemia cells

In order to discover molecular biomarkers in radiation response we investigated the effects of X-radiation on radioresistant K562 cells by using a comparative proteomic analysis. In treated cells 29 up-regulated and 10 down-regulated proteins were detected by image analysis and identified by mass spectrometry. Elongation factor 1 alpha 1 and stress-70 protein showed a 6.2 and 5.4 fold increase respectively in treated cells. Additional proteins such us pi and omega classes glutathione transferases, ATP synthase D chain, were also found to be up-regulated, suggesting that the enzyme belonging to the cellular detoxification system against oxidative stress and energetic metabolism may have a key role in the cellular response to radiation injury. This data set may provide a useful tool to design a combined chemo- and radiotherapic strategy against leukemia disease.     

The nuclear ceramide/diacylglycerol balance depends on the physiological state of thyroid cells and changes during UV-C radiation-induced apoptosis

Intranuclear lipid metabolism modifications in relation to cell proliferation and/or apoptosis were demonstrated in hepatocytes. The aim of this study was to establish whether nuclear lipid metabolites influence cell function in different experimental models using a rat thyroid cell line (FRTL-5) treated with UV-C radiation. After UV-C irradiation cells proliferate and undergo apoptosis in the presence of thyrotropin, are quiescent and resistant to radiation-induced apoptosis in its absence and finally are proapoptotic for nutrition withdrawal. In nuclei purified from proliferating cells, irradiation stimulates neutral-sphingomyelinase activity and inhibits sphingomyelin-synthase, phosphatidylcholine-specific phospholipase C and phosphatidylinositol-specific phospholipase C activity with a consequent increase in the ceramide/diacylglycerol ratio. This effect is marked in proapoptotic cell nuclei and low in quiescent cell nuclei. In conclusion, UV-C radiation induces apoptosis, modifying nuclear lipid metabolism in relation to the physiological state of cells.     

Changes in water status and osmolyte contents in leaves and roots of olive plants (Olea europaea L.) subjected to water deficit

Two-year-old olive trees (Olea europaea L., cv. Coratina) were subjected to a 15-day period of water deficit, followed by 12 days of rewatering. Water deficit caused decreases in predawn leaf water potential (Ψ_w), relative water content and osmotic potential at full turgor (Ψ _π100) of leaves and roots, which were normally restored upon the subsequent rewatering. Extracts of leaves and roots of well-watered olive plants revealed that the most predominant sugars are mannitol and glucose, which account for more than 80% of non-structural carbohydrates and polyols. A marked increase in mannitol content occurred in tissues of water-stressed plants. During water deficit, the levels of glucose, sucrose and stachyose decreased in thin roots (with a diameter <1 mm), whereas medium roots (diameter of 1–5 mm) exhibited no differences. Inorganic cations largely contribute to Ψ _π100 and remained stable during the period of water deficit, except for the level of Ca²⁺, which increased of 25% in water-stressed plants. The amount of malate increased in both leaves and roots during the dry period, whereas citrate and oxalate decreased. Thin roots seem to be more sensitive to water deficit and its consequent effects, while medium roots present more reactivity and a higher osmotic adjustment. The results support the hypothesis that the observed decreases in Ψ_w and active osmotic adjustment in leaves and roots of water-stressed olive plants may be physiological responses to tolerate water deficit.     

Influence of sampling conditions on blood chemistry values of Adriatic sturgeon Acipenser naccarii (Bonaparte, 1836)

Data on the blood chemistry of a chondrostean fish, the Adriatic sturgeon ( Acipenser naccarii ), are reported as measured with different sampling procedures, and as related to rearing conditions and age. Serum Cortisol, glucose, osmolality, Na⁺, Cl^-, Ca²⁺ and total protein concentrations were measured. Reference values for the blood chemistry of farmed sturgeon were measured on samples from resting undisturbed animals collected via a chronic indwelling catheter in the dorsal aorta that was implanted under anaesthesia. Following 24h recovery from catheterization, serum Cortisol, glucose and osmolality levels were 9.4 ng/ml, 58.8 mg/dl and 261.4 mOsm/kg, respectively. Furthermore, blood samples collected with the chronic indwelling catheters indicated that the surgical procedure of cannulation caused a stress response, with physiological changes that followed a pattern like that described in teleosts. Cortisol, glucose and osmolality were more sensitive to stress than the other variables measured. Sampling by cardiac puncture tended to be associated with elevated serum Cortisol levels in older, larger sturgeon, but not in young fish. Greater capture, confinement and handling stress in older, larger, sturgeon may have been responsible for this and other age-related differences in blood chemistry values measured following cardiac puncture. Within the same age class, both rearing conditions and temperature affected Cortisol, sodium and total protein concentrations significantly. Anaesthesia did not appear to reduce the degree of stress associated with cardiac puncture but altered serum ion concentrations.     

Differences in apparent pore sizes of low and high voltage-activated Ca2+ channels

Pore size is of considerable interest in voltage-gated Ca(2+) channels because they exemplify a fundamental ability of certain ion channels: to display large pore diameter, but also great selectivity for their ion of choice. We determined the pore size of several voltage-dependent Ca(2+) channels of known molecular composition with large organic cations as probes. T-type channels supported by the Ca(V)3.1, Ca(V)3.2, and Ca(V)3.3 subunits; L-type channels encoded by the Ca(V)1.2, beta(1), and alpha(2)delta(1) subunits; and R-type channels encoded by the Ca(V)2.3 and beta(3) subunits were each studied using a Xenopus oocyte expression system. The weak permeabilities to organic cations were resolved by looking at inward tails generated upon repolarization after a large depolarizing pulse. Large inward NH(4)(+) currents and sizable methylammonium and dimethylammonium currents were observed in all of the channels tested, whereas trimethylammonium permeated only through L- and R-type channels, and tetramethylammonium currents were observed only in L-type channels. Thus, our experiments revealed an unexpected heterogeneity in pore size among different Ca(2+) channels, with L-type channels having the largest pore (effective diameter = 6.2 A), T-type channels having the tiniest pore (effective diameter = 5.1 A), and R-type channels having a pore size intermediate between these extremes. These findings ran counter to first-order expectations for these channels based simply on their degree of selectivity among inorganic cations or on the bulkiness of their acidic side chains at the locus of selectivity.     

A fragment of 21 ORFs around the direct repeat (DR) region of Mycobacterium tuberculosis is absent from the other sequenced mycobacterial genomes: implications for the evolution of the DR region

The direct repeat (DR) region is a singular locus of the Mycobacterium tuberculosis complex genome. This region consists of 36 bp repetitive sequences separated by non-repetitive unique spacer sequences. Around this region there are several genes coding for proteins of unknown function. To determine whether the M. smegmatis, M. avium, M. marinum and M. leprae genomes contain sequences and ORFs similar to those of the DR locus of the M. tuberculosis complex, we analysed the corresponding regions in these species. As a first step, some conserved genes that flank the DR genes [Rv2785c (rpsO), Rv2786c (ribF), Rv2790c (ltp1 ), Rv2793c (truB), Rv2800, Rv2825, Rv2828, Rv2831 (echA16 ), Rv2838 (rbfA) and Rv2845 (proS )] were used as markers to locate the corresponding orthologues in M. smegmatis, M. avium, M. marinum and M. leprae in silico. Most of these M. tuberculosis marker genes have highly similar orthologues located in the same order and orientation in the other mycobacteria. In contrast, no orthologues were found for ORFs Rv2801-Rv2824, suggesting that these genes are unique to M. tuberculosis within the genus Mycobacterium.We observed that in M. smegmatis and M. avium, Rv2800 and Rv2825 are adjacent. This observation was experimentally confirmed by PCR. In conclusion, as the DR locus and the ORFs around it are absent in M. smegmatis and M. avium and, as it is possible that these species are older than M. tuberculosis, we postulated that the DR locus was acquired by the M. tuberculosis complex species or by an ancestor bacterium.