Proteolytic activity of proteasome on myofibrillar structures

The physiologic function of proteasome remains unclear. Evidence suggests a role in degradation of ubiquitin-protein conjugates, MHC antigen presentation, and some specificity of substrate within certain cell types. To explore further the properties of proteasome we have examined its effect on a well defined structure, the myofibril. We find that despite its large size (20S) proteasome is able to degrade myofibrils and intact, permeabilized muscle fibrils. The proteins degraded showed some specificity because actin, myosin and desmin were degraded faster than -actinin, troponin T and tropomyosin. Changes in ultrastructure were slow and included a general loss of structure with Z and I bands effected before the M band and costameres.     

Changes in organic solutes,volume, energy state,and metabolism associated with osmotic stress in a glial cell line: A multinuclear NMR study

Diffusion-weighted in vivo¹H-NMR spectroscopy of F98 glioma cells embedded in basement membrane gel threads showed that the initial cell swelling to about 180% of the original volume induced under hypotonic stress was followed by a regulatory volume decrease to nearly 100% of the control volume in Dulbecco's modified Eagle's medium (DMEM) but only to 130% in Krebs-Henseleit buffer (KHB, containing only glucose as a substrate) after 7 h. The initial cell shrinkage to approx. 70% induced by the hypertonic stress was compensated by a regulatory volume increase which after 7 h reached almost 100% of the control value in KHB and 75% in DMEM.¹H-,¹³C-and³¹P-NMR spectroscopy of perchloric acid extracts showed that these volume regulatory processes were accompanied by pronounced changes in the content of organic osmolytes. Adaptation of intra- to extracellular osmolarity was preferentially mediated by a decrease in the cytosolic taurine level under hypotonic stress and by an intracellular accumulation of amino acids under hypertonic stress. If these solutes were not available in sufficient quantities (as in KHB), the osmolarity of the cytosol was increasingly modified by biosynthesis of products and intermediates of essential metabolic pathways, such as alanine, glutamate and glycerophosphocholine in addition to ethanolamine. The cellular nucleoside triphosphate level measured by in vivo³¹P-NMR spectroscopy indicated that the energy state of the cells was more easily sustained under hypotonic than hypertonic conditions.To whom to address reprint requests.     

A new monoclonal antibody (3D3) generated with human respiratory mucins and directed against Lewis determinants

We have prepared a monoclonal antibody (MAb), 3D3, raised againstpurified human respiratory mucins. This antibody recognizedmucins and proteolytically derived glycopeptides. The epitoperecognized by the antibody was destroyed by -L-fucosidase, indicatingthat it was present on the carbohydrate moieties. Structuralspecificity was determined by adsorption on a variety of synthetic,insolubilized oligosaccharides. Several lines of evidence indicatethat the 3D3 MAb reacted strongly with the Lewis (Le^b) antigen,but also recognized Le^a and Le^y determinants. This antibodymight be useful to study mucin secretion. human bronchial mucins Lewis b     

Glucosylenamines as glycosyl acceptors: synthesis of gentiobiosylenamines.

The preparation of 2,3,4-tri-O-benzyl- (3), 2,3,4-tri-O-acetyl- (4), and 2,3,4-tri-O-benzoyl-N-(2,2-diethoxycarbonylvinyl)-6-O-trityl-beta- D-glucopyranosylamine (5) is described. The reaction of 3-5 with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide yields 2,3,4-tri-O-benzyl- (9), 2,3,4-tri-O-acetyl- (10), and 2,3,4-tri-O-benzoyl-N-(2,2-diethoxycarbonylvinyl)-6-O-(2,3,4,6-tet ra-O- acetyl-beta-D-glucopyranosyl)-beta-D-glucopyranosylamine (11), respectively. 2,3,4-Tri-O-benzyl- (6), 2,3,4-tri-O-acetyl- (7), and 2,3,4-tri-O- benzoyl-N-(2,2-diethoxycarbonylvinyl)-beta-D-glucopyranosylamine (8) are also described.     

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     

A comparison of the Xenopus laevis oocyte acetylcholinesterase with the muscle and brain enzyme suggests variations at the post-translational level.

1. Xenopus laevis oocytes express endogenously two components of the cholinergic system: the muscarinic receptors and the acetylcholinesterase (AChE). 2. A biochemical characterization of this enzyme was carried out. 3. The results established that the activity found in the oocytes correspond to 'true' AChE with a molecular weight of 65,000 Da and a sedimentation coefficient of 3-4 S. 4. The enzyme aggregates in the absence of detergent suggesting that it possess an hydrophobic character; despite that, it is not sensitive to PIPLC. 5. A comparison with the Xenopus brain and muscle AChE shows different post-translational modifications and catalytic properties with the oocyte AChE.     

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.     

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.