Date Palm DNA Mini-Preparation without Liquid Nitrogen

We have developed a new mini-procedure for isolation of total cellular DNA from date palm (Phoenix dactylifera L.). The procedure, which does not use liquid nitrogen, has proved useful due to temporary disruptions in supplies of liquid nitrogen that occur in countries where date palm trees are cultivated. DNA suitable for RFLP and PCR analyses is obtained.     

A comparative study of chromatin from lymphocyte nuclei upon activation of transcription by irradiation from an He-Ne-laser or phytohemagglutinin]

The influence of He-Ne laser radiation (632.8 nm, 56 J/m2, t = 10 s) and phytohaemagglutinin (PHA, 2 micrograms/ml) on chromatin structure in human lymphocytes was studied by electron microscopy using ultrathin cell sections. Morphometric analysis of extranuclear condensed chromatin masses was performed 1 h after the irradiation or after the beginning of PHA treatment. In the irradiated cells the following insignificant changes were revealed: decrease in the relative area of the nucleoplasmic chromatin, increase in the relative area of decondensation zones as well as increase in the number of clumps of nucleoplasmic chromatin and relative length at their boundary with nucleoplasma. The tendency of these morphological changes may be interpreted as functional activation of extranucleolar RNA synthesis in response to irradiation by red laser light. Action of PHA results in significant changes of the surfaces of chromatin clumps, namely increase in relative length of nucleoplasmic chromatin boundary and decrease in relative length of perimembranous chromatin boundary with nucleoplasma as well as some less expressed delamination of the chromatin masses from the nuclear membrane. These essential changes may reflect chromatin activation by proliferative stimulus. Peculiarities of the ultrastructural reorganisation in the condensed chromatin after irradiation and PHA-treatment probably reflect the differences in the processes of gene activation caused by the two agents.     

Polarity reversal of inside-out thyroid follicles cultured within collagen gel: an ultrastructural study

Inside-out porcine thyroid follicles in culture undergo polarity reversal after being embedded in collagen gel. The newly-formed follicles reexpress some specific thyroid functions lost in inside-out follicles (Chambard et al., 1984. We present here an ultrastructural study of the inversion of polarity in this model system. This process takes place within 24 to 48 hr, without any opening of the original tight junctions, as shown by fixation in the presence of ruthenium red. A general shrinkage of cellular aggregates was noted soon after embedding. At the apical pole, three different modifications were observed: structural changes appeared in the kinocilium, microvilli and underlying cytoskeleton as early as 10 min after embedding, mainly when the apical pole of the cells was in close contact with the collagen fibers; large cytoplasmic lamellipod- or pseudopod-like extensions, covering the adjacent apical domain, protruded from outer apical regions; some other apical areas invaginated and formed channels inside the aggregates. The last two processes prevented close contact between apical cell surfaces and collagen fibers and allowed a persistence of the initial polarity in some of the cells. Newly-formed lumens were closed 24 hr after embedding in gel and the outer surface of the cellular aggregates in close contact with collagen fibers looked like a basal membrane. These mechanisms proceeded at different rates and involved different numbers of cells, but they all appeared to be related to the transformation of inside-out follicles into follicular structures.     

Evidence for probenecid-sensitive organic anion transporters on polarized thyroid cells in culture

Epithelial thyroid cells in primary cultures loaded with BCECF/AM rapidly released the impermeant fluorescent dye BCECF (bis(carboxyethyl)carboxyfluorescein) in the incubation medium. Cells organized into follicles rapidly cleared BCECF (80% within 10 min) whereas fluorescence microscopy did not show any fluorescence in the follicular cavity. Cells organized into monolayers on plastic exported BCECF into the medium (70% within 40 min) whereas fluorescence microscopy showed intense fluorescence under the domes. BCECF efflux was blocked by probenecid, one of the known inhibitors of organic anion transporters, with similar efficiency in both structures. Maximal and half-maximal effects were respectively observed for 5 mM and 0.4 mM probenecid. The polarity of BCECF efflux was studied by using monolayers on collagen-coated Nuclepore filters: 85% of BCECF released was found in the basal compartment and 15% in the apical compartment. These findings suggested that thyroid cells in culture expressed a transport mechanism for the anionic form of BCECF. Furthermore, the observed activation of the Na+/H+ exchanger by probenecid suggested that the presence of this blocker did not overcome problems arising in the use of BCECF as intracellular pH indicator for thyroid cells.     

Absence of fodrin (spectrin-like protein) under the pseudopod membrane in stimulated thyroid cells

A fodrin-like protein purified from porcine thyroid cells and characterized by its properties identical to those of pig brain spectrin (F. Regnouf et al., Eur. J. Biochem. 153, 313-319 (1985)) has been localized by immunofluorescence and electron immunocytochemistry in porcine and rat thyroid. Fodrin-like polypeptides were detected in subplasmalemmal meshworks of microfilaments attached to isolated or in situ plasma membranes. In resting cells, fodrin was found under apical and basolateral membrane domains, whereas it was always absent under the pseudopod membrane domain induced by acute TSH stimulation in vitro, using monolayers of porcine cultured cells attached to collagen permeable substrates, as well as in vivo, using rats intravenously treated with TSH. Thyroid fodrin could be involved in exocytosis and membrane stabilization which occurs during the formation of pseudopods induced by TSH stimulation.     

Modeling of adaptations to physical training by using a recursive least squares algorithm

Busso, Thierry, Christian Denis, Régis Bonnefoy,André Geyssant, and Jean-René Lacour. Modeling ofadaptations to physical training by using a recursive least squaresalgorithm. J. Appl. Physiol. 82(5):1685-1693, 1997.The present study assesses the usefulnessof a systems model with time-varying parameters for describing theresponses of physical performance to training. Data for two subjectswho undertook a 14-wk training on a cycle ergometer were used to testthe proposed model, and the results were compared with a model withtime-invariant parameters. Two 4-wk periods of intensive training wereseparated by a 2-wk period of reduced training and followed by a 4-wkperiod of reduced training. The systems input ascribed to the trainingdoses was made up of interval exercises and computed in arbitraryunits. The systems output was evaluated one to five times per week byusing the endurance time at a constant workload. The time-invariantparameters were fitted from actual performances by using the leastsquares method. The time-varying parameters were fitted by using arecursive least squares algorithm. The coefficients of determinationr² were 0.875 and0.879 for the two subjects using the time-varying model, higher thanthe values of 0.682 and 0.666, respectively, obtained with thetime-invariant model. The variations over time in the model parametersresulting from the expected reduction in the residuals appearedgenerally to account for changes in responses to training. Such a modelwould be useful for investigating the underlying mechanisms ofadaptation and fatigue.

     

Occurrence of 28- and 27-Carbon ecdysteroids and sterols in developing worker pupae of the leaf-cutting ant acromyrmex octospinosus (reich) (hymenoptera,formicidae: Attini)

The major ecdysteroids in large worker pupae of the leaf-cutting ant Acromyrmex octospinosus were characterized at the peak ecdysteroid concentration by using high-performance liquid chromatography, enzyme immunoassay, and mass spectrometry. In decreasing amounts, they were determined to be makisterone A, an unidentified C₂₈ ecdysteroid bearing a molecular weight of 494, 20-hydroxyecdysone (ratio of 1 to 6 as compared to makisterone A), and putative but negligible ecdysone. The presence of both C₂₈ and C₂₇ ecdysteroids is discussed in relation to the content of 4-desmethylsterols determined by gas chromatography and mass spectrometry to be ergosta-5,7,24 (28)-trien-3β-ol, ergosterol, ergosta-5,7-dien-3β-ol and ergosta-7,24(28)-dien-3β-ol for the main sterols, and with a small amount of cholesterol.