mardi 21 avril 2009
par   G. Grégori

Boto WM, Brown L, Chrest J, Adler WH (1991) Distinct modulatory effects of bryostatin 1 and staurosporine on the biosynthesis and expression of the HIV receptor protein (CD4) by T cells. Cell Regul 2 :95-103


A family of structurally related macrocyclic lactones, bryostatins, have recently been shown to display several intriguing pharmacologic properties. Bryostatins are biosynthetic products of bryozoa phyllum of marine animals. To extend the analyses of the biological activities of these highly unusual biosynthetic animal products, we have examined the effect of bryostatin 1 (bryo-1) on the steady-state expression of the human immunodeficiency virus receptor, CD4, by normal peripheral blood T lymphocytes. Incubation of the cells with 5 nM bryo-1 caused a substantial loss of CD4 from the cell surface, as analyzed by flow cytometry using anti-CD4 monoclonal antibody. The modulation of CD4 expression by bryo-1 was not due to a cytotoxicity effect : in the culture conditions where it modulated CD4, bryo-1 also stimulated the expression of the interleukin 2 gene, as indicated by northern blot hybridization. In addition, incubation of the lymphocytes with nanomolar amounts of protein kinase C antagonist, staurosporine, resulted in the inhibition of the bryo-1-induced modulation of CD4 expression. The results of radioimmunoprecipitation analysis of detergent lysates of [35S] methionine-labeled lymphocytes strongly suggest that bryo-1 inhibits the glycosylation and expression of CD4 in a manner similar to that of tunicamycin.

Boucher N, Vaulot D, Partensky F (1991) Flow Cytometric Determination of Phytoplankton DNA in Cultures and Oceanic Populations. Marine Ecology-Progress Series 71 :75-84

<Go to ISI> ://WOS:A1991FE68000008

A method to measure DNA and chlorophyll fluorescence simultaneously in single phytoplankton cells was developed and tested on cultured and natural populations. Samples were stored at -80-degrees-C following fixation with 1% glutaraldehyde and freezing in liquid nitrogen, stained with DAPI (4’,6-diamino-2-phenylindole), and analyzed by flow cytometry. In cultures, cell DAPI-DNA fluorescence measured by flow cytometry was related to cell DNA content measured by fluorometry with DAPI, over almost 4 orders of magnitude. In natural populations, the method easily discriminated photosynthetic cells from other living and non-living particles and permitted computation of the fraction of particulate DNA contained in photosynthetic picoplankton. In the northwestern Mediterranean Sea in summer, this fraction was higher at neritic than at pelagic stations, and at the latter was maximum at mid-depth. In the future, this method should permit (1) better estimates of biomass partitioning among the different trophic compartments, and (2) studies of cell cycling of oceanic plankton populations.

Javanmardian M, Palsson BO (1991) High-Density Photoautotrophic Algal Cultures - Design, Construction, and Operation of a Novel Photobioreactor System. Biotechnology and Bioengineering 38 :1182-1189

<Go to ISI> ://A1991GR43100009

A photobioreactor system has been designed, constructed, and implemented to achieve high photosynthetic rates in high-density photoautotrophic algal cell suspensions. This unit is designed for efficient oxygen and biomass production rates, and it also can be used for the production of secreted products. A fiber-optic based optical transmission system that is coupled to an internal light distribution system illuminates the culture volume uniformly, at light intensities of 1.7 mW/cm2 over a specific surface area of 3.2 cm2/cm3. Uniform light distribution is achieved throughout the reactor without interfering with the flow pattern required to keep the cells in suspension. An on-line ultrafiltration unit exchanges spent with fresh medium, and its use results in very high cell densities, up to 10(9) cells/mL [3% (w/v)] for eukaryotic green alga Chlorella vulgaris. DNA histograms obtained from flow cytometric analysis reveal that on-line ultrafiltration influences the growth pattern. Prior to ultrafiltration the cells seem to have halted at a particular point in the cell cycle where they contain multiple chromosomal equivalents. Following ultrafiltration, these cells divide, and the new cells are committed to division so that cell growth resumes. The prototype photobioreactor system was operated both in batch and in continuous mode for over 2 months. The measured oxygen production rate of 4-6 mmol/L culture h under continuous operation is consistent with the predicted performance of the unit for the provided light intensity.

Kell DB, Ryder HM, Kaprelyants AS, Westerhoff HV (1991) Quantifying Heterogeneity - Flow-Cytometry of Bacterial Cultures. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology 60 :145-158

<Go to ISI> ://A1991HC95100004

Flow cytometry is a technique which permits the characterisation of individual cells in populations, in terms of distributions in their properties such as DNA content, protein content, viability, enzyme activities and so on. We review the technique, and some of its recent applications to microbiological problems. It is concluded that cellular heterogeneity, in both batch and continuous axenic cultures, is far greater than is normally assumed. This has important implications for the quantitative analysis of microbial processes.

Li WKW, Dickie PM (1991) Light and Dark C-14 Uptake in Dimly-Lit Oligotrophic Waters - Relation to Bacterial-Activity. Journal of Plankton Research 13 :S29-S44

<Go to ISI> ://A1991EW23200004

For plankton near the base of the euphotic zone in the oligotrophic Atlantic Ocean, the specific rates of increase for H-3-amino acid uptake and [H-3]thymidine incorporation were roughly equivalent to that for the fixation of inorganic C-14 in the dark. The observed net increase in bacterial abundance was of a magnitude appropriate to account for the measured fixation of C-14 in the dark. Growth of non-photosynthetic bacteria may therefore have a significant influence on values of C-14 measured in the light and dark. The interpretation of primary productivity experiments would be least difficult if incubations do not extend beyond a few hours so as to minimize the complications of declining chlorophyll a and increasing bacterial abundance.

Martin JM, Moreiraturcq P (1991) A New Methodology for Characterizing Organic Coatings of Aquatic Particles. Marine Pollution Bulletin 22 :287-290

<Go to ISI> ://A1991FY04800019

This paper describes a new method to study organic coatings which are associated with most aquatic particles. The method is based on the staining of different organic compounds such as polysaccharides with fluorescent dyes and their subsequent counting by flow cytometry. The method is shown to be selective. It allows qualitative discrimination between different polysaccharides such as mannose, glucose and galactose. Preliminary results show that the method should provide quantitative estimates of the investigated polysaccharides.

Morgan JAW, Cranwell PA, Pickup RW (1991) Survival of Aeromonas-Salmonicida in Lake Water. Applied and Environmental Microbiology 57 :1777-1782

<Go to ISI> ://A1991FP56400032

The survival of Aeromonas salmonicida subsp. salmonicida in lake water was investigated by using a variety of techniques. They included acridine orange epifluorescence, respiration, cell culture, cell revival, flow cytometry, plasmid maintenance, and membrance fatty acid analysis. During a 21-day study, A. salmonicida became nonculturable in sterile lake water samples. Flow cytometry and direct microscopy indicated that cells were present. Although the nonculturable cells could not be revived, the recovery method did indicate that the presence of low numbers of culturable cells within samples could produce misleading results. Plasmid DNA, genomic DNA, and RNA were maintained in the nonculturable cells ; in addition, changes in the fatty acid profiles were also detected. Although viability could not be proven, it was shown that the morphological integrity of nonculturable cells was maintained.

Ong LJ, Glazer AN (1991) Phycoerythrins of Marine Unicellular Cyanobacteria .1. Bilin Types and Locations and Energy-Transfer Pathways in Synechococcus-Spp Phycoerythrins. Journal of Biological Chemistry 266 :9515-9527

<Go to ISI> ://A1991FM45900031

Marine Synechococcus strains WH8103, WH8020, and WH7803 each possess two different phycoerythrins, PE(II) and PE(I), in a weight ratio of 2-4:1. PE(II) and PE(I) differ in amino acid sequence and in bilin composition and content. Studies with strain WH7803 indicated that both PE(II) and PE(I) were present in the same phycobilisome rod substructures and that energy absorbed by PE(II) was transferred to PE(I).
Strain WH8103 and WH8020 PE(I)s carried five bilin chromophores thioether-linked to cysteine residues in sequences homologous to those previously characterized in C-, B-, and R-PEs. In contrast, six bilins were attached to strain WH8103 and WH8020 PE(II)s. Five of these were at positions homologous to bilin attachment sites in other phycoerythrins. The additional bilin attachment site was on the alpha-subunit. The locations and bilin types in these PE(s) and in the marine Synechocystis strain WH8501 PE(I) (Swanson, R. V., Ong, L. J., Wilbanks, S. M., and Glazer, A. N. (1991) J. Biol. Chem. 266, 9528-9534) are :
Since phycourobilin (PUB) (lambda-max approximately 495 nm) transfers energy to phycoerythrobilin (PEB) (lambda-max approximately 550 nm), inspection of these data shows that the invariant PEB group at beta-82 is the terminal energy acceptor in phycoerythrins. The adaptations to blue-green light, high PUB content and the presence of an additional bilin on the alpha-subunit, increase the efficiency of light absorption by PE(II)s at approximately 500 nm.

Partensky F, Vaulot D, Videau C (1991) Growth and Cell-Cycle of 2 Closely Related Red Tide-Forming Dinoflagellates - Gymnodinium-Nagasakiense and G Cf Nagasakiense. Journal of Phycology 27 :733-742

<Go to ISI> ://A1991GY88100012

Small-sized vegetative cells were found to co-occur with normal-sized cells in populations of the European bloom-forming dinoflagellate Gymnodinium cf. nagasakiense Takayama et Adachi, currently known as Gyrodinium aureolum Hulburt, but not in populations of the closely related Japanese species Gymnodinium nagasakiense. We examined how cell size differentiation may influence growth and cell cycle progression under a 12:12-h light : dark cycle in the European taxon, as compared to the Japanese one. Cell number and volume and chlorophyll red fluorescence in both species varied widely during the photocycle. These variations generally appeared to be related to the division period, which occurred at night, as indicated by the variations of the fraction of binucleated cells (mitotic index) as well as the distribution of cellular DNA content. "Small" cells of G. cf. nagasakiense divided mainly during the first part of the dark period, although a second minor peak of dividing cells could occur shortly before light onset. In contrast, "large" cells displayed a sharp division peak that occurred 9 h after the beginning of the dark period. The lower degree of synchrony of "small" cells could be a consequence of their faster growth. Alternatively, these data may suggest that cell division is tightly controlled by an endogenous clock in "large" cells and much more loosely controlled in "small" cells. Cells of the Japanese species, which were morphologically similar to "large" cells of the European taxon, displayed an intermediate growth pattern between the two cell types of G. cf. nagasakiense, with a division period that extended to most of the dark period.

Rao DVS, Partensky F, Wohlgeschaffen G, Li WKW (1991) Flow-Cytometry and Microscopy of Gametogenesis in Nitzschia-Pungens, a Toxic, Bloom-Forming, Marine Diatom. Journal of Phycology 27 :21-26

<Go to ISI> ://A1991EY97600004

The domoic acid-producing diatom Nitzschia pungens Grunow f. multiseries Hasle, which is responsible for amnesic shellfish poisonings in Prince Edward Island, Canada, underwent gametogenesis when senescent cells (i.e. in stationary growth phase for more than 290 days) were subcultured into fresh FE medium and light intensity was increased from 33 to 530-mu-E.m-2.s-1. The number of gametes produced varied with the salinity of the medium, with a maximum at 23.5 parts per thousand. Cells in the exponential growth phase (0.8 div.d-1) did not produce gamates, nor did senescent cells when transferred without change in light intensity. Anisogamous gametes, probably haploid, were isolated by combining conventional microscopy with flow cytometry. Zygotes resulting from syngamy yielded cigar-shaped naviculoid cells, morphologically different from parent cells (heteromorphism). These cells, with a division rate of 1.9 div.d-1, could serve as a seed population and explain the origin and rapid progression of the toxic blooms of red-water proportions that have been a public health problem in Eastern Canada. Production of domoic acid by postexponential and moribund cells but not by gametes, zygotes, or immediately resulting cells, provides an insight into the dependence of toxicity on the developmental history of this diatom.

Sode K, Horikoshi K, Takeyama H, Nakamura N, Matsunaga T (1991) On-line monitoring of marine cyanobacterial cultivation based on phycocyanin fluorescence. J Biotechnol 21 :209-217


A novel on-line fluorescence monitoring system for marine cyanobacterial cultivation was developed. This method is based on the measurement of intracellular phycocyanin content, which is the major light harvesting protein. A fluorescence spectrophotometer, equipped with a flow cell connected with a culture liquid recycling tube was used. Experiments were carried out using a marine unicellular cyanobacteria Synechococcus sp. NKBG 042902 isolated from Japanese coastal sea water. We have optimized excitation wavelength to avoid the light scattering, using non-pigmented old cells which no longer contained phycocyanin. At an excitation wavelength of 590 nm, light scattering was minimized. Viable cell concentration could be measured in the range of 2 x 10(6) to 2 x 10(8) cells per ml, without pronounced light scattering. Continuous monitoring of marine cyanobacteria cultivation was performed. Cell concentrations were determined by both culture fluorescence and by using a hemacytometer. A good linear correlation was obtained. We conclude that on-line monitoring of cyanobacterial culture fluorescence based on phycocyanin is a rapid, efficient and also versatile method for determining viable cell concentration.