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81.
To identify those glycoproteins whose synthesis or modification is necessary for memory formation, we have studied the uptake of radiolabelled fucose into synaptic plasma membranes (SPMs) and postsynaptic densities (PSDs) derived from two specific left and right forebrain loci, at two different times after training of 1-day-old chicks on a one-trial passive avoidance learning task. To increase the reliability of the comparison, a double-labelling method was used. Tissue samples from intermediate medial hyperstriatum ventrale (IMHV) and lobus parolfactorius (LPO) were isolated at 6 and 24 h after training. At both times, training resulted in region-specific changes, both increases and decreases, in incorporated radioactivity into pre- and postsynaptic glycoproteins. After 6 h, there was a relative decline in incorporation into both SPMs and PSDs of the right IMHV of trained chicks, a decline that persisted in the PSDs until 24 h. A small decline in incorporation in SPMs from the right LPO of trained chicks at 6 h was reversed by 24 h, by which time there was a 64% increase in incorporation into SPMs and a 24% increase into PSDs of the left LPO. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of left and right hemisphere samples containing LPO revealed that 6 h after training the main effect was presynaptic, including a reduction of incorporation into high molecular mass glycoproteins, of 150-180 kDa, and an increase in a lower molecular mass (41 kDa) fraction. By 24 h after training, a left hemisphere presynaptic glycoprotein of molecular mass approximately 50 kDa showed the biggest increase in fucosylation. In addition, a wide group of postsynaptic glycoproteins of both hemispheres, in the ranges 150-180, 100-120, and 33 kDa now showed increases in incorporation. Some other fractions showed decreases. These results are in accord with previous data on incorporation obtained using the amnesic agent 2-deoxygalactose. They also support the hypothesis that memory formation involves the strengthening of connections between pre- and postsynaptic neurons of the LPO by growth or modulation of pre- and postsynaptic structures. 相似文献
82.
83.
Three strains of Bradyrhizobium, 280A, 2209A and 32H1, that nodulated peanuts (Arachis hypogaea L.), were tested for their ability to grow and survive at elevated temperatures of up to 42°C in laboratory culture. Strain 32H1 was unable to grow at 37°C and was more sensitive to elevated temperatures than the other two strains. All three produced heat-shock proteins of molecular weights 17 kDa and 18 kDa. Two greenhouse experiments were conducted to determine the effect of high root temperature on nodulation, growth and nitrogen fixation of peanut. Two peanut varieties (Virginia cv NC7 and Spanish cv Pronto) were inoculated and exposed to root temperatures of 30°, 37° and 40°C. Nodulation and nitrogen fixation were strongly affected by root temperature but there was no variety × temperature interaction. At a constant 40°C root temperature no nodules were formed. Nodules were formed when roots were exposed to this temperature with diurnal cycling but no nitrogen fixation occurred. Highest plant dry weight, shoot nitrogen content and total nitrogen were observed at a constant root temperature of 30°C. Increasing root temperature to 37°C reduced average nitrogen content by 37% and total nitrogen by 49% but did not reduce nodulation. The symbiotic performance of the strains corresponded to their abilities to grow and survive at high temperature in culture. 相似文献
84.
Perin L. Donnini M. Diomede L. Romano M. Tacconi M. T. Luisetti M. Salmona M. 《Cytotechnology》1991,7(1):25-32
An expression vector for G-CSF, pASLB3-3, was constructed and introduced into Namalwa KJM-1 cells (Hosoi et al., 1988), and cells resistant to 100 nM of methotrexate (MTX) were obtained. Among them, the highest producer, clone SC57, was selected and the productivity of this clone was further characterized. The maximal production of G-CSF was at the most 1.8 g/ml/day using a 25 cm2 tissue culture flask, even though the cell number was above 7×105 cells/ml. The limiting factors at high density were analyzed as the deficiency of nutrients, such as glucose, cysteine and serine, and pH control. The depression of specific G-CSF productivity per cell under the batch culture conditions was overcome by using a perfusion culture system, BiofermenterTM (Sato, 1983) with modifications of nutrients supplementation by a dialysis membrane and/or dissolved oxygen (DO) supplementation by microsilicone fibers. ITPSGF medium was modified to elevate concentrations of amino acids and glucose by 2.0- and 2.5-times, respectively. Under the control of pH at 7.4 and DO at 3 ppm, the specific G-CSF productivity was not depressed even at high cell density (above 1×107 cells/ml), and the amount of G-CSF reached 41 g/ml. These results indicated the possibility of finding the optimum culture conditions for the production of recombinant proteins by Namalwa KJM-1 cells.Abbreviations ABTS
2,2-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
- BSA
Bovine Serum Albumin
- BSA-PBS
Phosphate-buffered Saline without Ca2+ and Mg2+ containing Bovine Serum Albumin
- dhfr
Dihydrofolate Reductase
- DO
Dissolved Oxygen
- G-CSF
Granulocyte Colony-stimulating Factor
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethansulfonic Acid
- IFN
Interferon
- MTX
Methotrexate
- PBS(-)
Phosphate-buffered saline without Ca2+ and Mg2+
- Tween-PBS
Phosphate-buffered saline without Ca2+ and Mg2+ containing 0.05% of Tween 20 相似文献
85.
Jan E. M. Souren Chris Schneijdenberg Arie J. Verkleij Roeland van Wijk 《In vitro cellular & developmental biology. Animal》1992,28(3):199-204
Summary A floating collagen matrix culture of neonatal rat heart myocardial cells shows rhythmic contractions which are dependent
on localization of cells, cell density, and collagen concentration. The rhythmic contractions of the collagen matrix can be
registered by a device scanning the optical density at the edge of the gel and have been observed over a temperature range
from 9° to 40° C. The results of the present study underline the usefulness of myocardial cell populated collagen matrixes
for studies on coherent contractions of heart cell cultures. 相似文献
86.
We compared the feeding excavations on wood blocks of three species of subterranean termites, Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar), and R. virginicus (Banks). Feeding rate followed the order C. formosanus > R. flavipes > R. virginicus. Wood surface area (mm2) exposed per unit feeding was higher for C. formosanus and R. flavipes than for R. virginicus. This was caused by the tendency of C. formosanus and R. flavipes to make internally penetrating tunnels, thereby increasing surface area, whereas R. virginicus made trough- and bowl-like depressions on the outside of blocks, sometimes decreasing the size of blocks outwardly without a corresponding high increase in surface area typical with the tunnels of the other species. Consequently, wood surface area was sometimes reduced, rather than increased as a result of feeding by R. virginicus. Different patterns of wood excavation suggest that these termites have divergent roles in wood decay processes.
Résumé Les organismes pionniers qui modifient le bois et le rendent acceptable par les insectes qui le perforent sont généralement des champignons du bois pourri. Cependant, une fois que les termites ou autres insectes perforant le bois ont pénétré, leurs galeries favorisent les bactéries fixatrices d'azote, permettent l'invasion d'autres organismes décomposeurs, et de ce fait régularisent la décomposition du bois (Ausmus, 1977). L'exposition de la surface à l'intérieur des perforations jouant un rôle très important dans le processus de pourrissement, il est souhaitable de pouvoir quantifier la surface des galeries dues à l'alimentation des termites. Une courbe type permettant de prédire l'aire de la surface perforée a été construite en perçant 109 morceaux de bois de trous cylindriques de différents diamètres, en calculant l'aire de la surface des morceaux de bois, en appliquant et pesant une couche de vernis pour bois au polyuréthane, et en divisant la masse de polyuréthane par l'aire de la surface. Le modèle prédictif qui en découle est: Y=0,01443×-3,51825 (P=0,0001; r=0,68), y étant la masse de polyuréthane (en g) et x la surface (en mm2) du morceau de bois. En traitant de la même façon au polyuréthane les morceaux de bois perforés par les termites, nous pourrions déduire leur surface.Une expérience a été effectuée avec 3 espèces de rhinotermitides,- Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar) et R. virginicus (Banks). Des groupes de chaque espèce se sont alimentés pendant 11 ou 12 jours sur des morceaux de bois non contaminés par des champignons. Nous avons déterminé la survie, la consommation, la modification de la surface du morceau de bois (par utilisation du modèle prédictif) et le changement de surface par terminte.La survie est la même, mais la consommation est dans l'ordre suivant: C. formosanus > R. flavipes > R. virginicus. L'aire de la surface exposée par unité d'alimentation était plus élevée pour C. formosanus et R. flavipes que pour R. virginicus (Tab. 1). Ceci est dû à la tendance de C. formosanus et R. flavipes de creuser des galeries vers l'intérieur, tandis que R. virginicus fait des cuvettes à la surface du bois. Les attaques superficielles de R. virginicus réduisent parfois le volume du morceau de bois sans accroître proportionnellement la surface comme le font les espèces creusant des galeries. Ainsi, avec R. virginicus la surface peut être réduite au lieu d'augmenter. Des différences entre colonies s'observent avec toutes les variables (Tab. 2).Nos résultats suggèrent que C. formosanus et R. flavipes contribuent plus que R. virginicus à exposer le bois aux autres organismes décomposeurs. Cependant, ces résultats peuvent être modifiés par un conditionnement préalable du bois par des champignons.相似文献
87.
Louis Piovetti Christian Francisco Ginette Pauly Otmane Benchabane Colette Bernard-Dagan Anne Diara 《Phytochemistry》1981,20(6):1299-1302
Analysis of wood essential oil of Cupressus dupreziana revealed 26 components: 13 monoterpenes and 13 sesquiterpenes. The main components were carv 相似文献
88.
Peter F. Davies 《Journal of cellular biochemistry》1980,13(2):211-217
In sub-confluent cultures of Balb/c-3T3 cells, pinocytosis rates were increased after exposure to specific growth factors (serum; platelet-derived growth factor, PDGF; epidermal growth factor, EGF). Conversely, as cells became growth-inhibited with increasing culture density, there was a corresponding decline in pinocytosis rate per cell. In order to test whether density-inhibition of pinocytosis was influenced either by the growth cycle or by cell contact independently of growth, cells were induced into a quiescent state at a range of subconfluent and confluent densities. Under such conditions, cell density did not significantly inhibit pinocytosis rate. When confluent quiescent cultures in 2.5% serum were exposed to 10% serum, the resulting round of DNA synthesis was accompanied by enhanced pinocytosis per cell, even though the cells were incontact with one another. Furthermore, in a SV40-viral transformed 3T3 cell line, both the growth fraction and the pinocytosis rate per cell remained unchanged over a wide range of culture densities. These studies indicate that density-dependent inhibition of pinocytosis in 3T3 cells appears to be secondary to growth-inhibition rather than to any direct physical effects of cell–cell contact. 相似文献
89.
Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity (
), in accord with the culture cell density. At low cell density
poise, whereas at confluency it increases to
poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in
cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates
similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin
receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the
erythropoiesis pathway. 相似文献
90.
Takeshi Kawarabata Masako Funakoshi Yoshinobu Aratake 《Journal of invertebrate pathology》1980,35(1):34-42
Occluded virions of the Bombyx mori nuclear polyhedrosis virus were efficiently liberated from polyhedra by dissolution with the silkworm gut juice. The liberated virions were purified by sucrose density gradient centrifugation and the bands of enveloped virions were observed in the gradients. There was no functional difference between the gut juice-liberated and the carbonate-liberated virions. Disruption of enveloped virions by the gut juice was observed, but the formation of nucleocapsids from the degradation of the occluded virions was not detected. High yields of the enveloped virions from the polyhedra dissolved by the gut juice was obtained by separating the virions through sucrose density gradient centrifugation immediately after the dissolution of the polyhedra. Many factors, e.g., rearing seasons, silkworm strains, and rearing conditions, affect the polyhedra-dissolving property of the larval gut juice. 相似文献