Flow cytometric detection of erythropoietic cytotoxicity in mouse bone marrow.

Erythroblast proliferation and maturation in bone marrow are the processes leading to the formation of polychromatic erythrocytes (PE) and normochromatic erythrocytes (NE), respectively. PE contain RNA but no DNA, and can therefore be distinguished both from NE (which lack both RNA and DNA) and from nucleated cells (which contain both DNA and RNA). Cytotoxic agents that induce impairment of the maturation process change the PE:NE ratio. We have developed a simple and rapid method of determining the PE:NE ratio, based on flow cytometric analysis of formaldehyde-fixed, acridine orange (AO)-stained cells. The effects of cyclophosphamide (CP), mitomycin C (MMC), and vincristine (VC) were tested and the PE:NE ratio was evaluated over 7 days of treatment. In this study we monitored the kinetics of these compounds and were able to demonstrate both a time- and a dose-dependent effect. We detected a difference between the effects of the alkylating agents tested and those induced by the spindle inhibitor tested. Flow cytometry of fixed bone marrow samples stained with AO provides more information, better and more rapid statistical analysis, than conventional microscopic methods for counting the PE:NE ratio.     

HGH20k species and variability of GH responses to long-duration exercise in male cyclists fed different food supplements.

Exercise studies dealing with hGH have always considered this hormone as a unique molecular entity. We postulated that the well-known variability in blood total hGH response could possibly be explained, at least in part, by concomitant changes in blood hGH20k levels, variant form possibly expressing some of the hGH anti-insulinic properties. Six male trained cyclists were imposed a 2-hr long ergocycle exercise. Food supplements were given prior to and/or during exertion to exacerbate a possible contribution from hGH20k to total hGH variability by modification of substrate availability. Both blood total hGH and hGH20k levels increased with exercise, the largest increases being observed in absence of supplementation. Large variability of responses were observed in both blood total hGH and hGH20k levels, the latter variant contributing minimally to total blood hGH response (4.3 +/- 0.8%), and being closely associated with the main species (r = 0.90; p less than 0.001). It was concluded that variations associated with hGH20k increases observed in response to prolonged exercise cannot explain the large intra-and inter-individual variability measured in blood total hGH response.     

Detection of ginkgolide A in Ginkgo biloba cell cultures

Ginkgo biloba cells were cultured in two 500 mL shake flasks and in 2 L and 6 L immobilization bioreactors using MS medium supplemented with 1 mg.L^–1 NAA, 0.1 mg.L^–1 K and 30 g.L^–1 sucrose. Specific growth rates were 0.06 d^–1, 0.11 d^–1 and 0.07 d^–1 for the 2 L and 6 L bioreactors and shake flask cultures, respectively. Extracellular phosphate, nitrate, ammonium and carbohydrate uptake rates of the bio reactor cultures were approximately 17 to 39% slower than those of shake flask cultures. The specific oxygen uptake and carbon dioxide transfer rates of immobilized Ginkgo biloba cells ranged from 0.027 to 0.041 mmol O₂.g^–1.d.w.hr^–1 (maximum uptake at 14 days) and 0.020 to 0.057 mmol CO₂g. ^–1.d.w.hr^–1 (maximum production at 14 days). Extracts from the biomass of the two immobilized and shake flask suspension cultures were analysed for ginkgolide A by GC-MS. Yields of 7, 17, 19 and 7 ng.g. ^–1d.w. of ginkgolide A were determined for shake flask 1, shake flask 2 and the 2 L and 6 L immobilized cultures, respectively. Traces of ginkgolide B were detected with the signal to noise ratio, however, being too low for positive confirmation of this last product.Abbreviations CTR Carbon dioxide transfer rate - DO Dissolved oxygen - g.d.w. Gram dry weight - GA Ginkgolide A - GB Ginkgolide B - GC Gas chromatography - GC-MS Gas chromatography-mass spectrometry - HPLC High performance liquid chromatography - K Kinetin - MS Murashige and Skoog salt medium - N₁K₁MS Complete Murashige and Skoog medium supplemented with 1 mg.L^–1 NAA, 0.1 mg.L^–1 K and 30g.L^–1 sucrose - NAA Naphthaleneacetic acid - OTR Oxygen transfer rate - PAF Platelet Aggregating Factor - q_CO2 Specific carbon dioxide production rate - q_O2 Specific oxygen uptake rate - u Specific growth rate     

Effects of planktivore abundance on chlorophyll-a and Secchi depth

We used two analyses to test the hypothesis that planktivore abundances contribute to the residual variations of Secchi depth or chlorophyll-a plotted with respect to mean summer epilimnetic total phosphorus. The first analysis involved 15 lake years of data from six lakes. The data set comprised mark-recapture assessments of piscivore and planktivore numbers and estimates of mean summer chlorophyll-a, total phosphorus and Secchi depth. We found that residual chlorophyll-a variation was not significantly (p>0.05) correlated with planktivore densities, but that planktivore densities did contribute (p<0.02) to the residual variation of Secchi depth on mean total phosphorus. The second analysis included all of the data used in the first plus an additional 13 lake years of data from the literature. These data showed that the percentage of the total fish community comprising planktivores did not significantly (p>0.05) contribute to the residual variation in chlorophyll-a with respect to mean summer total phosphorus. Together, our results suggest that planktivore abundance has a significant cascading impact on water clarity, but no long term statistically significant impact on mean summer chlorophyll-a concentration.     

Escherichia coli 4.5S RNA gene function can be complemented by heterologous bacterial RNA genes.

The essential 4.5S RNA gene of Escherichia coli can be complemented by 4.5S RNA-like genes from three other eubacteria, including both gram-positive and gram-negative organisms. Two of the genes encode RNAs similar in size to the E. coli species; the third, from Bacillus subtilis, specifies an RNA more than twice as large. The heterologous genes are expressed efficiently in E. coli, and the product RNAs resemble those produced by cognate cells. We conclude that the heterologous RNAs can replace E. coli 4.5S RNA and that the essential function of 4.5S RNA is evolutionarily conserved. A consensus structure is presented for the functionally related 4.5S RNA homologs.     

Characteristics of development and variations in ecdysteroid levels in Clitumnus embryos deprived of their cephalic endocrine glands

Microsurgical suppression of presumptive endocrine areas in very young embryos of Clitumnus resulted in an arrest in development, which occurred at different stages according to the operation. In most cases however. the duration of embryonic life was not reduced significanly. The repercussions of each operation type on the ecdysteroid content of the embryos were determined using a radioimmunoassay technique.Consideration of the experimental results provides some indication on the part played by each endocrine formation during the last part of embryonic development that is between dorsal closure and hatching time. Our experiments offer original evidence that the corpora allata of the embyro are of utmost importance at the stage VII_3t, in initiating the normal expression of larval characteristics.     

Modelling the Persistence of Quiescent Conidia of the Entomopathogenic Hyphomycete Paecilomyces fumosoroseus Exposed to Solar Radiation

Persistence of conidia of the entomopathogenic fungus Paecilomyces fumosoroseus exposed to artificial and solar radiation at a constant temperature was studied by monitoring the ability to germinate and to form colonies (colony - forming units , CFUs) . The photic effect of radiation on each of these variables was modelled by a decreasing function of UVB irradiation ( in J m 2) . Germination ability was represented by a logistic function and viability (log CFU) by an infinitely decreasing function . Experiments carried out under artificial conditions , at three different UVB irradiances ( from 0 . 3 to 1 . 6 W m 2) , similar to those observed in nature , confirmed the adequacy of the predictor variable and of the functions chosen for describing these data . The proposed models appeared to be irradiance independent . Under solar radiation , the models were able to describe data collected on three different summer days in France (48 o 51 N , 2 o 06 E) . However , it took a greater amount of solar UVB radiation to produce the same effect as that achieved indoors . This could be explained by differences in radiation spectra . For each model , one set of parameters was sufficient for representing all three sets of data: this constitutes an initial validation of the models proposed .     

Oribatid mites (Acari,Oribatida) from riverine environments of some islands in Oceania

A checklist of identified oribatid mite taxa from riverine freshwater environments from six islands in Polynesia (New Caledonia, Tahiti, Moorea, Rurutu, Tubuai, Raiatea) is presented; 18 species, 16 genera and eight families were recorded. Trhypochthoniellus longisetus (Berlese, 1904) and Trimalaconothrus albulus Hammer, 1972 prevailed on distribution. Fortuynia smiti sp. n. (Fortuyniidae) is described from New Caledonia. The new speciesis morphologically most similar to Fortuynia marina Hammen, 1960 from New Guinea, but it differs from the latter by the longer notogastral setae dm, lm, c₂, p₁, epimeral setae 3b and adanal setae ad₁ and the presence of prodorsal lateral ridges.