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11.
Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatura, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included. 相似文献
12.
The inheritance of duodenal alkaline phosphatase activity has been studied in two inbred strains of Swiss mice. These two strains consistently maintained a three- to fourfold difference in duodenal phosphatase activity for six generations before the start of the genetic studies. Males of both the high-activity strain (HAS) and the low-activity strain (LAS) were mated to females of the other strain to produce an F1 generation, members of which were sib-mated to produce an F2 generation. The frequency distributions of the parental, F1, and F2 generations reveal that the activity of the enzyme is under polygenic control. Distribution of activities in the F2's derived from HAS grandmothers differs from that of the F2's from LAS grandmothers, indicating that a maternally inherited factor, probably contained in the milk of one strain, influences the activity. Heritability estimates based on half-sib correlation coefficients show that additive genetic variance makes up about 50–70% of the total variance of duodenal phosphatase activity in LAS, and approximately 30–45% in HAS. The latter strain is the more variable, both within generations and within litters; its activity is also more strongly enhanced by injection of substrate into the stomach, and is more severely reduced by starvation. Chromatographic analysis of butanol extracts of phosphatase from 11-day-old mice of the two strains reveals that both contain the same two isozymes. HAS does, however, appear to have 6–8 times as much as LAS of an isozymic form of phosphatase having a relatively high phenylphosphate/-glycerophosphate ratio, and only about twice as much of a low PhP/bGP ratio form.Supported by Research Grant GM 03937 from the National Institutes of Health, U.S. Public Health Service. 相似文献
13.
Mark R. Olive John C. Walker Karambir Singh Elizabeth S. Dennis W. James Peacock 《Plant molecular biology》1990,15(4):593-604
The functional properties of the anaerobic responsive element (ARE) of the maize Adh1 gene have been analysed using a transient expression assay in electroporated maize protoplasts. The ARE functions in both orientations although inversion of the ARE sequence relative to the TATA box element produces slightly weaker promoter activity under anaerobic conditions and elevated expression under aerobic conditions. Promoter activity under anaerobic conditions is proportional to the number of complete ARE sequences in the Adh1 promotor. The ARE contains two sub-regions and dimers of sub-region II are as efficient as the wild-type sequence in activating gene expression under anaerobic conditions. However, sub-region I dimers do not appear capable of inducing gene expression in response to anaerobic stress. We conclude that sub-region II is essential for anaerobic induction of gene expression. Reporter gene expression remains constant when the spacing between sub-regions of the ARE is increased up to at least 64 bp, but increased spacing of 136 bp or greater abolishes expression in both aerobic and anaerobic conditions, indicating that a close association of the two sub-regions is required both for anaerobic responsiveness and for maximal levels of aerobic gene expression. When the ARE is placed upstream of position –90 of the CaMV 35S promoter, the ARE produces a high level of expression in both aerobic and anaerobic conditions. The general enhancement of gene expression driven by the hybrid ARE/35S promoter in aerobic conditions requires an intact sub-region II motif since mutation or deletion of sub-region II from the hybrid promoter reduces the level of expression to that observed for the truncated 35S promoter alone. In addition, mutation of the sub-region I sequences in the ARE/35S hybrid promoter does not significantly reduce expression in aerobic conditions, relative to pARE/35S(-90), suggesting that sub-region I does not contribute to this general enhancer function. 相似文献
14.
Book reviews
Improving vegetatively propagated cropsA.J. Abbott and R.K. Atkin (Eds.), London: Academic Press, 1987. xvii + 416 pages. £37.00. 0-12-041410-4 相似文献15.
The overlapping distribution of opioid and cholecystokinin (CCK) peptides and their receptors (μ and δ opioid receptors; CCK-A
and CCK-B receptors) in the central nervous system have led to a large number of studies aimed at clarifying the functional
relationships between these two neuropeptides. Most of the pharmacological studies devoted to the role of CCK and enkephalins
have been focused on the control of pain. Recently the existence of regulatory mechanisms between both systems have been proposed,
and the physiological antagonism between CCK and endogenous opioid systems has been definitely demonstrated by coadministration
of CCK-B selective antagonists with RB 101, a systemically active inhibitor, which fully protects enkephalins from their degradation.
Several studies have also been done to investigate the functional relationships between both systems in development of opioid
side-effects and in behavioral responses. This article will review the experimental pharmacology of association of enkephalin-degrading
enzyme inhibitors and CCK-B antagonists to demonstrate the interest of these molecules in the management of both pain and
opioid addiction.
Special issue dedicated to Dr. Eric J. Simon. 相似文献
16.
The mechanism(s) by which zinc is transported into cells has not been identified. Since zinc uptake is inhibited by reducing
the temperature, zinc uptake may depend on the movement of plasma membrane micoenvironments, such as endocytosis or potocytosis.
We investigated the potential role of potocytosis in cellular zinc uptake by incubating normal and acrodermatitis enteropathica
fibroblasts with nystatin, a sterol-binding drug previously shown to inhibit potocytosis. Zinc uptake was determined during
initial rates of uptake (10 min) following incubation of the fibroblasts in 50 μg nystatin/mL or 0.1% dimethyl-sulfoxide for
10 min at 37°C. The cells were then incubated with 1 to 30 μM
65zinc. Michaelis-Menten kinetics were observed for zinc uptake. Nystatin inhibited zinc uptake in both the normal and AE fibroblasts.
Reduced cellular uptake of zinc was associated with its internalization, not its external binding. In normal fibroblasts,
nystatin significantly reduced theK
m 56% and theV
max 69%. In the AE fibroblasts, nystatin treatment significantly reduced theV
max 59%, but did not significantly affect theK
m. The AE mutation alone affected theV
max for cellular zinc uptake. The control AE fibroblasts exhibited a 40% reduction inV
max compared to control normal fibroblasts. We conclude that nystatin exerts its effect on zinc uptake by reducing the velocity
at which zinc traverses the cell membrane, possibly through potocytosis. Furthermore, the AE mutation also effects zinc transport
by reducing zinc transport. 相似文献
17.
Anne Imberty Florence Casset Colin V. Gegg Marilynn E. Etzler Serge Pérez 《Glycoconjugate journal》1994,11(5):400-413
The three-dimensional structure ofDolichos biflorus seed lectin has been constructed using five legume lectins for which high resolution crystal structures were available. The validity of the resulting model has been thoroughly investigated. Final structure optimization was conducted for the lectin complexed with GalNAc, providing thereby the first three-dimensional structure of lectin/GalNAc complex. The role of theN-acetyl group was clearly evidenced by the occurrence of a strong hydrogen bond between the protein and the carbonyl oxygen of the carbohydrate and by hydrophobic interaction between the methyl group and aromatic amino acids. Since the lectin specificity is maximum for the Forssman disaccharide GalNAc(1–3)GalNAc-O-Me and the blood group A trisaccharide GalNAc(1–3)[Fuc(1–2)]Gal-O-Me, the complexes with these oligosaccharides have been also modelled. 相似文献
18.
Lacker (1981) and Lacker & Akin (1988) developed a mathematical model of follicular maturation and ovulation; this model of only four parameters accounts for a large number of results obtained over the past decade or more on the control of follicular growth and ovulation in mammals. It establishes a single law of maturation for each follicle which describes the interactions between growing follicles. The function put forward is sufficient to explain the constancy of the number of ovulations or large follicles in a female as well as the variability of this number among strains or species and for either induced or spontaneous ovulators. According to the model, the number of ovulations or large follicles lies between two limits that are themselves simple functions of two parameters of the model. Moreover, Lacker's model exhibits interesting characteristics in agreement with results obtained by physiologists: in particular, it predicts that the number of ovulating or large follicles is independent of:
- the total number of maturing follicles,
- the process of recruitment of newly maturing follicles towards the terminal maturation (Poisson or other),
- the form of the LH or FSH secretion curves as functions of the systemic level of oestradiol. The model further predicts that
- selection and dominance of follicles result from the feedback between the ovary and the hypophysis through the interactions between follicles; these interactions are expressed by the maturation function of the model.
- recovery from atresia is possible for a follicle: from decreasing, the rate of secretion of oestradiol may increase.
- the revised model suggests a renewal of follicles during the sexual cycle, as “waves of follicular growth”.
19.
Florence Fèvre Jean-Pierre Henry Michel Thieffry 《Journal of bioenergetics and biomembranes》1993,25(1):55-60
In addition to the voltage-dependent anion channel (VDAC), mitochondrial outer membranes contain a cationic channel of large conductance, which is blocked by a mitochondrial addressing peptide (peptide-sensitive channel, PSC). Bovine adrenal cortex mitochondria were solubilized in 1.5% octyl -glucoside, and membrane vesicles were reconstituted by slow dilution with a low ionic strength buffer. The reconstituted vesicles contained a functional channel possessing the electrical characteristics of the cationic channel, including its sensitivity to the mitochondrial addressing peptide. Important features of the described protocol are the nature of the detergent, its concentration, and the addition of glycerol during the whole procedure. No solubilization could be observed in the presence of cholate. 相似文献
20.
Traditional regression analysis of body weight growth curvesencounters problems .when the data are extremely variable. Whiletransformations are often employed to meet the criteria of theanalysis, some transformations are inadequate for normalizingthe data. Regression analysis also requires presuppositionsregarding the model to be fit and the techniques to be usedin the analysis. An alternative approach using artificial neuralnetworks is presented which may be suitable for developing predictivemodels of growth. Neural networks are simulators of the processesthat occur in the biological brain during the learning process.They are trained on the data, developing the necessary algorithmswithin their internal architecture, and produce a predictivemodel based on the learned facts. A dataset of SpragueDawleyrat (Rattus norvegicus) weights is analyzed by both traditionalregression analysis and neural network training. Predictionsof body weight are made from both models. While both methodsproduce models that adequately predict the body weights, theneural network model is superior in that it combines accuracyand precision, being less influenced by longitudinal variabilityin the data. Thus, the neural network provides another toolfor researchers to analyze growth curve data. 相似文献