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21.
Isabel Walls J. J. Sheridean R. W. Welch D. A. McDowell 《Letters in applied microbiology》1990,10(1):23-26
A new method of separating bacteria from beef mince has been developed, in which an alkaline protease, Alcalase 0.6 L, was used to degrade the meat proteins, leaving micro-organisms in suspension. The organisms were then counted, using a membrane filtration-epifluorescent microscopy technique. A correlation coefficient of 0.97 was obtained between this method and the standard plate count, indicating its suitability for use in quality control. 相似文献
22.
Paulo E. Oliveira Peter E. Gibbs Ana Angélica Barbosa Salvador Talavera 《Plant Systematics and Evolution》1992,179(3-4):207-219
The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens. 相似文献
23.
Fernando G. de Mello Jan N. Hokoç Ana L. M. Ventura Patrícia F. Gardino 《Cellular and molecular neurobiology》1991,11(5):485-496
1. Retina-cell aggregate cultures expressed glutamate decarboxylase activity (L-glutamate 1-carboxylase; EC 4.1.1.15) as a function of culture differentiation. 2. Glutamic acid decarboxylase (GAD) activity was low in the initial phases of culture and increased eight-fold until culture day 7, remaining high up to day 13 (last stage studied). 3. The addition of GABA to the culture medium 24 h after cell seeding almost totally prevented the expression of GAD activity. 4. In association with decreased enzyme activity, aggregates exposed to GABA did not display immunoreactivity for GAD, suggesting that GAD molecules were either lost from GABAergic neurons or significantly altered with GABA treatment. 5. Control, untreated aggregates showed intense GAD immunoreactivity in neurons. Positive cell bodies were characterized by a thin rim of labeled cytoplasm with thickest labeling at the emergence of the main neurite. 6. Heavily labeled patches were also observed throughout the aggregates, possibly reflecting regions enriched in neurites. 7. The GABA-mediated reduction of GAD immunoreactivity was a reversible phenomenon and could be prevented by picrotoxin. 相似文献
24.
Influence of Calcium Ion on Ethanol Tolerance of Saccharomyces bayanus and Alcoholic Fermentation by Yeasts 总被引:1,自引:0,他引:1 下载免费PDF全文
Regina C. Nabais Isabel S-Correia Cristina A. Viegas Júlio M. Novais 《Applied microbiology》1988,54(10):2439-2446
The addition of Ca2+ (as CaCl2) in optimal concentrations (0.75 to 2.0 mM) to a fermentation medium with a trace contaminating concentration of Ca2+ (0.025 mM) led to the rapid production of higher concentrations of ethanol by Saccharomyces cerevisiae, Saccharomyces bayanus, and Kluyveromyces marxianus. The positive effect of calcium supplementation (0.75 mM) on alcoholic fermentation by S. bayanus was explained by the increase in its ethanol tolerance. The ethanol inhibition of growth and fermentation followed the equation μxi = μoi [1 - (X/Xmi)]ni, where μoi and μxi are, respectively, the specific growth (i = g) and fermentation (i = f) rates in the absence or presence of a concentration (X) of added ethanol, and Xmi is the maximal concentration of ethanol which allows growth or fermentation. The toxic power is given by ni. In Ca2+ - supplemented medium (0.75 mM), ng = 0.42 for growth and nf = 0.43 for fermentation compared with 0.52 and 0.55, respectively, in unsupplemented medium; for both media, Xmg = 10% (vol/vol) and Xmf = 13% (vol/vol). For lethal concentrations of ethanol, the specific death rates were minimal for cells that were grown and incubated with ethanol in medium with an optimal concentration of Ca2+, maximal for cells grown and incubated with ethanol in unsupplemented medium, and intermediate for cells grown in unsupplemented medium and incubated with ethanol in calcium-supplemented medium. The effect of Ca2+ on the acidification curve of energized cells in the presence of ethanol was found to be closely associated with its protective effect on growth, fermentation, and viability. 相似文献
25.
Isabel J. Wajda Miriam Banay-Schwartz Isaac Manigault Abel Lajtha 《Neurochemical research》1986,11(7):949-957
In vivo effects of chronic lithium administration on dopaminergic and serotonergic receptor binding were studied in the striatum and cerebral cortex of the rat. [3H]Domperidone was used as the ligand for the dopaminergic receptor, and [3H]ketanserin for the serotonergic system. Long-term ingestion of lithium (2–3 months) resulted in high levels of lithium in the cerebral cortex and significantly higher potassium levels; the sodium content remained at normal levels. The kinetic constants (K
d andB
max) of [3H]domperidone binding sites measured in the striatum did not show any deviation from control values, but the receptor concentration (B
max) of [3H]ketanserin binding sites was significantly reduced in the cerebral cortex of lithium-treated rats. The apparent dissociation constant (K
d) was not changed. The results indicate that the serotonergic component of the [3H]spiperone binding site, which we had previously found to be affected by chronic lithium treatment and which was shown by Peroutka and Snyder (1) to be the 5-HT2 receptor, is selectively affected by lithium.Special Issue dedicated to Prof. Eduardo De Robertis. 相似文献
26.
Dr. María Cristina Maldonado Ana María Strasser de Saad Danley Callieri 《Current microbiology》1989,18(5):303-306
Several recent reports have described large numbers of monoclonal antibodies that cross-react with toxins A and B ofClostridium difficile; this suggests that the toxins share major epitopes. Our results show that monoclonal antibodies (MAb) against other antigens bind nonspecifically to both toxins. Therefore, we believe that the cross-reacting MAb bind by this manner and not by a true immune reaction. 相似文献
27.
Marcelo Hermes-Lima Ana Claudia Tessis Adalberto Vieyra 《Origins of life and evolution of the biosphere》1990,20(1):27-41
In this paper it is shown that the adsorption of 5-adenosine monophosphate (5-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 °C. This result indicates a cooperative behavior in the adsorption of 5-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the adsorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5-AMP interacts with a positively charged site (possibly Ca2+) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed. 相似文献
28.
Ana M. Moura-da-Silva R. David G. Theakston Julian M. Cramptonl 《Journal of molecular evolution》1996,43(3):263-269
The evolution of the Metalloproteinase Disintegrin Cysteine-rich (MDC) gene family and that of the mammalian Matrix-degrading
Metalloproteinases (MMPs) are compared. The alignment of snake venom and mammalian MDC and MMP precursor sequences generated
a phylogenetic tree that grouped these proteins mainly according to their function. Based on this observation, a common ancestry
is suggested for mammalian and snake venom MDCs; it is also possible that gene duplication of the already-assembled domain
structure, followed by divergence of the copies, may have significantly contributed to the evolution of the functionally diverse
MDC proteins. The data also suggest that the structural resemblance of the zinc-binding motif of venom MDCs and MMPs may best
be explained by common ancestry and conservation of the proteolytic motifs during the divergence of the proteins rather than
through convergent evolution.
Correspondence to: J.M. Crampton 相似文献
29.
Claudia Gaspar Iscia Lopes-Cendes Anita L. DeStefano Patrícia Maciel Isabel Silveira Paula Coutinho Patrick MacLeod Jorge Sequeiros Lindsay A. Farrer G. A. Rouleau 《Human genetics》1996,98(5):620-624
Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar degeneration originally described in families of Portuguese-Azorean
ancestry. The hypothesis that its present world distribution could result from the spread of an original founder mutation
has been raised. To test this possibility we have conducted a linkage disequilibrium study of markers segregating with the
MJD1 locus in a total of 64 unrelated families of different geographical origins. Significant association was detected between
the MJD1 locus and marker alleles at loci D14S280, D14S1050 and D14S81. All affected individuals, except one Chinese family, had allele
3 (237 bp) at D14S280. This finding is consistent with a founder effect in our MJD population. However, distinct haplotypes
were observed in patients originating from the two Azorean islands showing the highest disease prevalence; therefore, the
possible existence of more than one founder mutation can not be excluded with the markers currently available.
Received: 27 February 1996 / Revised: 4 June 1996 相似文献
30.
Márcia Camargo-De-Morais Marta De Freitas Angela G. De Mattos Nádia Schröder Ana C. Zilles Carla S. F. Lisboa Nice Arteni Armando Barlem Rejane Schierholt Guilherme Zwetsch Carlos A. B. Souza Regina Pessoa-Pureur Carlos A. Netto 《Neurochemical research》1996,21(5):595-602
Neurofilaments subunits (NF-H, NF-M, NF-L) and glial fibrillary acidic protein (GFAP) were investigated in the hippocampus
of rats after distinct periods of reperfusion (1 to 15 days) following 20 min of transient global forebrain ischemia in the
rat. In vitro [14Ca]leucine incorporation was not altered until 48 h after the ischemic insult, however concentration of intermediate filament
subunits significantly decreased in this period. Three days after the insult, leucine incorporation significantly increased
while the concentration NF-H, NF-M, and NF-L were still diminished after 15 days of reperfusion. In vitro incorporation of32P into NF-M and NF-L suffered immediately after ischemia, but returned to control values after two days of reperfusion. GFAP
levels decreased immediately after ischemia but quickly recovered and significantly peaked from 7 to 10 days after the insult.
These results suggest that transient ischemia followed by reperfusion causes proteolysis of intermediate filaments in the
hippocampus, and that proteolysis could be facilitated by diminished phosphorylation levels of NF-M and NF-L. 相似文献