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121.
Luis Rodríguez Teresa Ruiz Julio R. Villanueva Rafael Sentandreu 《Current microbiology》1978,1(1):41-44
The intracellular invertase ofSaccharomyces cerevisiae is mainly found in a soluble form (91–95%), while only minor amounts are found bound to the internal (4–8%) and plasma membranes
(less than 1%). In the processes of derepression or repression, inhibition of RNA or protein synthesis, or in the presence
of 2-deoxy-d-glucose, the levels of the membrane-bound and external activities are modified in a way in which their relation is clear,
while the soluble enzyme does not change at all. These results, together with the fact that the membrane-bound and the external
enzymes are glycoproteins, suggest a precursor-product relationship between the enzymic forms. 相似文献
122.
R Prasquier C Gibert S Witchitz P Valere P Beaufils F Vachon 《BMJ (Clinical research ed.)》1978,1(6104):9-11
Five patients were found during surgery or at necropsy to have the mitral valve orifice obstructed by vegetations. They had had unexplained severe and recurrent episodes of acute febrile pulmonary oedema, and four had few cardiac ausculatory findings. Three patients died suddenly and unexpectedly; the other two were operated on and survived. In view of its ominous prognosis, acute mitral valve obstruction should be considered in patients whose pulmonary symptoms are compatible with endocarditis and are not adequately explained by the findings on examination of the heart. The condition, which should be confirmed by echocardiography, requires emergency surgery. 相似文献
123.
Summary Microelectrode techniques were employed to study the mechanisms of the transepithelial voltage transients (V
ms
) observed during transmural current clamps in the isolatedNecturus gallbladder. The results indicate that: a) part of V
ms
is due to a transepithelial resistance change (R
t
), and part to a tissue emf change. b) R
t
is entirely caused by changes of the resistance of the paracellular pathway. At all current densities employed, the measured changes are probably due to changes in both fluid conductivity and width of the lateral intercellular spaces. At high currents, in addition to the effects on the lateral spaces, the resistance of other elements of the pathway (probably the limiting junction) drops, regardless of the direction of the current. c) The magnitude and polarity of the R
t
-independent transepithelial and cell membrane potential transients indicate that the largest emf change takes place at the basolateral membrane (E
b
), with smaller changes at the luminal membrane (E
a
) and the paracellular (shunt) pathway (E
s
). It is shown that two-thirds of the transient are caused by E
s
, and one-third by (E
b
–E
a
). E
s
can be explained by a diffusion potential generated by a current-dependent NaCl concentration gradient across the tissue. E
a
and E
b
are caused by [K] changes, mainly at the unstirred layer in contact with the basolateral membrane. 相似文献
124.
The cell-cell adhesion characteristic of C-6 astrocytoma cells changes as a function of cell density. Cell suspensions prepared from monolayers having a density lower than 1 × 105 cells/cm2 show maximal affinity for plasma membranes and cells obtained from monolayers at densities greater than 1 × 106 cells/cm2 shows minimal affinity for plasma membranes. The adhesive component retained on plasma membranes is present at essentially equal levels in membranes prepared from cells at different density. This modulation in cell surface affinity appears to be due to cell-cell contact and appears to represent a suitable model for the study of the modulation of cell-cell adhesion as a result of cell contact. 相似文献
125.
Luis A. Quesada Allue 《Molecular and cellular biochemistry》1980,33(3):149-155
Summary Microsome enriched Ceratitis capitata extracts synthesized a glucosylated lipid linked oligosaccharide. Its properties were closely related to those of the previously described insect mannosylated dolichyl diphosphate oligosaccharides and almost the same as those of the rat liver dolichyl-diphosphate-(GlcNAc)2-(Man)9-(Glc)1–3. The saccharide moiety of, the latter was transferred to an unknown endogenous protein-like acceptor by the fly extracts. These represent the first evidence of a protein glycosylation in a pluricellular invertebrate through dolichyl derivatives.Abbreviations Dol-P
dolichyl phosphate
- Dol-P-P
dolichyl diphosphate 相似文献
126.
Mauricio Goihman-Yahr Leo Pine Maria Cecilia Albornoz Luis Yarzabal Maria Helena De Gomez Blanca San Martin Ana Ocanto Tulio Molina Jacinto Convit 《Mycopathologia》1980,71(2):73-83
Mild sonication was used to obtain single cell suspensions of Paracoccidioides brasiliensis. These cells were intact by microscopic criteria. Direct cell counts in a given inoculum and colony formation on various media were used to determine plating efficiency. Sonicated and nonsonicated cell suspensions were used to study plating efficiency and to estimate viability by means of vital dyes. Methylene blue, Erythrosin B, and Janus green were unreliable when used with P. brasiliensis, but vital dyes were accurate when tested with Candida albicans.Acridine orange gave more meaningful results of viability. Estimates of viability, however, changed significantly as a result of relatively minor alterations in the composition of the suspending medium.In initial experiments, the plating efficiency of P. brasiliensis was dismally low. It descended abruptly with increasing dilution of inoculum. Efficiency was much improved if horse serum was added to brain heart infusion plates or if glucose glycine yeast extract (GGY) plates were incubated at room temperature and mycelial colonies were counted. With the technique we report, current plating efficiency of sonicated suspensions is of the order of 25 %. Our results and procedures have an important bearing upon those studies concerned with in vitro killing of P. brasiliensis in suspensions or with isolating this fungus from clinical or environmental specimens. 相似文献
127.
Summary Conventional and Cl-selective liquid ion-exchanger intracellular microelectrodes were employed to study the effects of extracellular ionic substitutions on intracellular Cl activity (aCl
i
) inNecturus gallbladder epithelium. As shown previously (Reuss, L., Weinman, S.A., 1979;J. Membrane Biol.
49:345), when the tissue was exposed to NaCl-Ringer on both sidesaCl
i
was about 30mm, i.e., much higher than the activity predicted from equilibrium distribution (aCleq) across either membrane (5–9mm). Removal of Cl from the apical side caused a reversible decrease ofaCl
i
towards the equilibrium value across the basolateral membrane. A new steady-stateaCl
i
was reached in about 10 min. Removal of Na from the mucosal medium or from both media also caused reversible decreases ofaCl
i
when Li, choline, tetramethylammonium or N-methyl-d-glucamine (NMDG) were employed to replace Na. During bilateral Na substitutions with choline the cells depolarized significantly. However, no change of cell potential was observed when NMDG was employed as Na substitute. Na replacements with choline or NMDG on the serosal side only did not changeaCl
i
. When K substituted for mucosal Na, the cells depolarized andaCl
i
rose significantly. Combinations of K for Na and Cl for SO4 substitutions showed that net Cl entry during cell depolarization can take place across either membrane. The increase ofaCl
i
in depolarized cells exposed to K2SO4-Ringer on the mucosal side indicates that the basolateral membrane Cl permeability, (P
Cl) increased. These results support the hypothesis that NaCl entry at the apical membrane occurs by an electroneutral mechanism, driven by the Na electrochemical gradient. In addition, we suggest that Cl entry during cell depolarization is downhill and involves an increase of basolateral membraneP
Cl. 相似文献
128.
Summary Intracellular ion activities inNecturus gallbladder epithelium were measured with liquid ion-exchanger microelectrodes. Mean values for K, Cl and Na activities were 87, 35 and 22mm, respectively. The intracellular activities of both K and Cl are above their respective equilibrium values, whereas the Na activity is far below. This indicates that K and Cl are transported uphill toward the cell interior, whereas Na is extruded against its electrochemical gradient. The epithelium transports NaCl from mucosa to serosa. From the data presented and the known Na and Cl conductances of the cell membranes, we conclude that neutral transport driven by the Na electrochemical potential difference can account for NaCl entry at the apical membrane. At the basolateral membrane, Na is actively transported. Because of the low Cl conductance of the membrane, only a small fraction of Cl transport can be explained by diffusion. These data suggest that Cl transport across the basolateral membrane is a coupled process which involves a neutral NaCl pump, downhill KCl transport, or a Cl-anion exchange system. 相似文献
129.
Summary Cytogenetic studies on lymphocytes from a girl aged 3 years and 10 months revealed a ring chromosome 15. Several banding methods showed the r(15) chromosome not to have any apparent deletion of the long arm. The silver staining technique for nucleolar organizer regions showed an NOR positive region (band p12). In only a few cells was a chromosome 15 missing. The size of the r(15) was found to be constant. Comparison with 11 previous reported cases in the literature shows that the clinical manifestations in the different patients with ring chromosome 15 are constant although not clinically identifiable and it appears likely to attribute them to a significantly retarded intrauterine and postnatal growth instead of presumed deficiency in the long arm and mosaic configurations. 相似文献
130.
Axel Kahn Joelle Marie Juan Luis Vives-Corrons Pierre Maigret Albert Najman 《Human genetics》1981,57(2):172-175
Summary Anomalies of the mutant pyruvate kinase variants and clinical symptoms have been compared in 22 unrelated patients with congenital red cell pyruvate kinase deficiency. This study suggests that some characteristics of the mutant enzymes could play a role in the intensity of haemolysis, namely residual activity, affinity for the substrate phosphoenolpyruvate and for the allosteric activator fructose 1,6 diphosphate and inhibition by ATP. 相似文献