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1.
Emma Bricchi Marco Fornaciari Claudia Giannoni Francesca Greco Daniela Fascini Giuseppe Frenguelli Gianfranco Mincigrucci Bruno Romano 《Aerobiologia》1992,8(3):401-406
Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria. 相似文献
2.
Regulation of beta-galactoside transport and accumulation in heterofermentative lactic acid bacteria. 总被引:13,自引:5,他引:8 下载免费PDF全文
Galactose-grown cells of the heterofermentative lactic acid bacteria Lactobacillus brevis and Lactobacillus buchneri transported methyl-beta-D-thiogalactopyranoside (TMG) by an active transport mechanism and accumulated intracellular free TMG when provided with an exogenous source of energy, such as arginine. The intracellular concentration of TMG resultant under these conditions was approximately 20-fold higher than that in the medium. In contrast, the provision of energy by metabolism of glucose, gluconate, or glucosamine promoted a rapid but transient uptake of TMG followed by efflux that established a low cellular concentration of the galactoside, i.e., only two- to fourfold higher than that in the medium. Furthermore, the addition of glucose to cells preloaded with TMG in the presence of arginine elicited a rapid efflux of the intracellular galactoside. The extent of cellular TMG displacement and the duration of the transient effect of glucose on TMG transport were related to the initial concentration of glucose in the medium. Exhaustion of glucose from the medium restored uptake and accumulation of TMG, providing arginine was available for ATP generation. The nonmetabolizable sugar 2-deoxyglucose elicited efflux of TMG from preloaded cells of L. buchneri but not from those of L. brevis. Phosphorylation of this glucose analog was catalyzed by cell extracts of L. buchneri but not by those of L. brevis. Iodoacetate, at a concentration that inhibits growth and ATP production from glucose, did not prevent efflux of cellular TMG elicited by glucose. The results suggested that a phosphorylated metabolite(s) at or above the level of glyceraldehyde-3-phosphate was required to evoke displacement of intracellular TMG from the cells. Counterflow experiments suggested that glucose converted the active uptake of TMG in L. brevis to a facilitated diffusion mechanism that allowed equilibrium of TMG between the extra- and intracellular milieux. The means by which glucose metabolites elicited this vectorial regulation is not known, but similarities to the inducer expulsion that has been described for homofermentative Streptococcus and Lactobacillus species suggested the involvement of HPr, a protein that functions as a phosphocarrier protein in the phosphotransferase system, as well as a presumptive regulator of sugar transport. Indeed, complementation assays wit extracts of Staphylococcus aureus ptsH mutant revealed the presence of HPr in L. brevis, although this lactobacillus lacked a functional phaosphoenolpyruvate-dependent phosphortransferase system for glucose, 2-deoxyglucose, or TMG. 相似文献
3.
4.
The rheological properties of aqueous solutions of hydroxyethyl guar gum, a synthetic derivative of guar gum, have been studied under continuous and oscillatory shear flow conditions. Data obtained from both experimental techniques were satisfactorily fitted according to Cross-type models. The effect of polymer concentration, molecular weight and temperature on the rheological behavior of hydroxyethyl guar gum systems have been investigated and discussed in terms of rheological parameters like the zero-shear viscosity η0 and the characteristic times λ and λ′. 相似文献
5.
R. M. Alvarez B. Rodríguez J. M. Romano A. O. Díaz E. Gómez D. Miró L. Navarro G. Saura J. L. García 《World journal of microbiology & biotechnology》1992,8(2):214-215
Microbial lipids produced byRhodotorula glutinis grown in continuous culture with molasses under nitrogen-limiting conditions were evaluated and the effects of growth rate on fatty acid composition were studied. As the growth rate decreased, cell biomass, lipid content and lipid yield gradually increased. The maximum lipid content recorded was 39% (w/w) of dry cell biomass at a dilution rate of 0.04 h–1. The growth rate also affected fatty acid composition: oleic acid decreased with decreasing growth rate while stearic acid increased. 相似文献
6.
A morphological and morphometrical study has been carried out on glomerular lesions in mink with spontaneous Aleutian disease, using the WHO classification for Systemic Lupus Erytematous Nefritis. 154 renal samples from sick animals and 10 samples from uninfected mink were processed by routine histopathological techniques and metacrylate inclusions. The samples were studied quantitatively with an automatic image analyzer. 5 forms of glomerulonephritis (GN) were identified: mesangial glomerulonephritis (n = 13), focal and segmental GN (n = 10), diffuse GN (n = 99), membranous GN (n = 12) and advanced sclerosing GN (n = 10) and were associated with the degree of interstitial plasmocytosis. Glomerule morphometry was shown to be an excellent method for identifying the type of lesion, while it quantified the participation of various glomerular elements in the lesion. 相似文献
7.
Human erythrocyte glucose-6-phosphate dehydrogenase. Identification of a reactive lysyl residue labelled with pyridoxal 5'-phosphate 总被引:5,自引:0,他引:5
L Camardella C Caruso B Rutigliano M Romano G Di Prisco F Descalzi-Cancedda 《European journal of biochemistry》1988,171(3):485-489
Human erythrocyte glucose-6-phosphate dehydrogenase contains a reactive lysyl residue, which can be labelled with pyridoxal 5'-phosphate. The binding of one mole of pyridoxal 5'-phosphate per mole of enzyme subunit produces substantial inactivation. The substrate glucose-6-phosphate prevents the loss of activity, suggesting that the reaction site is close to the substrate-binding site. A tryptic peptide containing the pyridoxal-5'-phosphate-binding lysyl residue has been isolated and characterised. The reactive lysyl residue has been identified in the glucose-6-phosphate dehydrogenase amino acid sequence. Comparison with glucose-6-phosphate dehydrogenase from other sources shows a high homology with a peptide containing a reactive lysyl residue, isolated from the enzyme from Saccharomyces cerevisiae; glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides also contains a region highly homologous with the sequence around the reactive lysyl residue in the human enzyme. The results of this communication provide the first direct evidence for the association of an essential catalytic function with a specific region of the molecule of human erythrocyte glucose-6-phosphate dehydrogenase. 相似文献
8.
Leishmania major and L. donovani: effects on proteolytic enzymes of Phlebotomus papatasi (Diptera, Psychodidae) 总被引:2,自引:0,他引:2
Phlebotomus papatasi is susceptible to Leishmania major which it transmits in nature, but is resistant to L. donovani. The present study compares the effect of L. major and L. donovani on the proteolytic activity of P. papatasi gut enzymes. The experiments measured digestion of C14-labeled globin by gut homogenates of flies. Homogenates were prepared from flies fed on serum only (controls) or from flies fed serum containing promastigotes or their dried culture overlayer. In other experiments, the promastigotes or dried culture overlayers were added in vitro to the gut homogenate of control flies. Proteolytic activity of gut homogenate from flies infected with L. major was about one-third less than that of controls, while that from flies infected with L. donovani was one-third greater. Ingestion of L. major dried culture overlayer had an effect on flies similar to that of the promastigotes, while L. donovani dried culture overlayer produced no significant effect. When added to gut homogenate in vitro, promastigotes of both species promoted proteolysis as did dried culture overlayer of L. major. Dried culture overlayer of L. donovani, however, had an opposite effect. It is suggested that the observed reduction in proteolytic activity caused by L. major infection may result from inhibition of enzyme production. 相似文献
9.
Hyla chrysoscelis (2n=24) and H. versicolor (2n=48) are a diploid-tetraploid species pair of treefrogs. Restriction endonuclease mapping of ribosomal RNA (rRNA) gene repeat units of diploids collected from eastern and western populations reveals no differences within rRNA gene coding regions but distinctive differences within the nontranscribed spacers. A minimum of two physical maps is required to construct an rRNA gene map for the tetraploid, whose repeat units appear to be a composite, with about 50% of the elements resembling the western diploid population and about 50% resembling the eastern population. These results imply that this population of the tetraploid species may have arisen from a genetically hybrid diploid. Alternatively, the dual level of sequence heterogeneity in H. versicolor may reflect some type of gene flow between the two species. The coding region of the rRNA genes in the tetraploid differs from that in either diploid in about 20% of all repeat units, as exemplified by a BamHI site located near the 5 terminus of the 28 S rRNA gene. If the 20% variant class of 28 S rRNA gene coding sequences is expressed, then there must be two structural classes of ribosomes; if only the 80% sequence class is expressed, then a genetic control mechanism must be capable of distinguishing between the two different sequence variants. It is postulated that the 20% variant sequence class may be correlated with a partial functional diploidization of rRNA genes in the tetraploid species.This research was supported, in part, by NSF Grants CDP-8002341 and PRM-8106947 and by faculty research grants from Miami University to J.C.V. 相似文献
10.
An interrelationship between immune and reproductive systems has been postulated, and involves, among others, bidirectional effects between gonads and thymus. To this effect a rat thymus fraction of about 28000 mol wt has been reported to inhibit the effect of hCG on in vitro suspension of Leydig cells. We have investigated the antigonadotropin activity of thymus extracts on rat testis receptors. Acetonic powder obtained from thymus of 14 day-old rats was separated by molecular sieve chromatography. The effect of the collected fractions on the 125I-hCG binding to receptor sites in rat testes was evaluated. A fraction corresponding to 27000-28000 mol wt named thymus factor (TF), was found to inhibit the binding activity of 125I-hCG to its testicular receptor. The inhibitory effect of TF on hCG binding is dose related. By Scatchard analysis a competitive interaction at the receptor level between TF and hCG was demonstrated. The Ka values of hCG binding were diminished in the presence of TF while no significative changes were detected in the number of receptor sites. Present results strongly suggest a modulation function of TF at the testis receptor level. 相似文献