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41.
The clinical, radiologic, cytopathologic and histologic features of a case of spermatocytic seminoma in a 56-year-old man are reported and discussed. The cytologic findings in fine needle aspiration (FNA) smears suggested a diagnosis of spermatocytic seminoma, which was confirmed by subsequent histopathologic studies. The case suggests that spermatocytic seminoma can be suspected and distinguished from other types of seminoma and germ cell neoplasms by FNA cytology. The following criteria appear to be the most useful in making the cytodiagnosis: the presence of three different types of cells (large, medium and small), a clean background, an absence of a lymphoid component and "tigroid" substances and the relative paucity and clumping tendency of the neoplastic cells in the smears. 相似文献
42.
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
43.
The influence of retinol and retinoic acid, two retinoids of major interest, on the main gel to liquid-crystalline phase transition of different phospholipid membranes has been studied by means of differential scanning calorimetry. Both compounds exerted perturbing effects on the phase transition of membranes composed of dipalmitoylphosphatidylcholine or dipalmitoylphosphatidylethanolamine. At concentrations up to 42.5 mol% of retinoid in the membrane, the delta H was not much affected with respect to the pure phospholipid, indicating a rather slight interaction. As the concentration of retinol was increased the Tc transition temperature decreased. A fluid-phase immiscibility was observed for the system DPPC/retinol at concentrations between 0 and 33 mol%. Almost ideal phase diagrams were obtained for the mixture DPPE/retinol. At concentrations of 33 mol% and higher retinol was able to induce phase separations in DPPC membranes, but not in DPPE. The effect of retinoic acid was much weaker, the Tc and delta H remaining almost unaltered and equal to that of the pure phospholipid up to concentrations of 30 mol%, at neutral pH. Retinoic acid exerted a pH-dependent effect. As the pH decreased, and therefore increased the extent of protonation of retinoic acid, the pertubation of the membrane induced by this compound was less. A strong effect, both on Tc and delta H, was observed at pH 10, where the retinoic acid moiety will be mainly unprotonated and the negative charge will generate repulsive forces thus destabilizing the membrane. The mixture DPPC/retinoic acid presents a region of fluid-phase immiscibility. At low pH, when the retinoic acid moiety was fully protonated, this fluid-immiscibility region extended from 0 to 36 mol% of retinoic acid, but its size decreased with increasing pH, and at pH 10 it was only found from 0 to 3 mol%. These results are discussed in terms of the possible retinoid/phospholipid interactions and the disposition of the retinoid moiety in the bilayer. 相似文献
44.
M D Perez L Sanchez P Aranda J M Ena R Oria M Calvo 《Biochimica et biophysica acta》1992,1123(2):151-155
The interaction of bovine beta-lactoglobulin with palmitic and oleic acids has been studied by a partition equilibrium method. Bovine beta-lactoglobulin displays only one high affinity binding site for fatty acids whose association constants for palmitic and oleic acids are 4.2 x 10(6) and 2.3 x 10(6) M-1, respectively. However, other binding sites with low affinity are also present. The existence of one high affinity binding site is in accordance with the amount of fatty acids naturally bound to beta-lactoglobulin isolated from milk. The effect of beta-lactoglobulin on ruminant pregastric lipases from a pharyngeal extract has been assayed. The activity of pharyngeal lipase on a triglyceride emulsion is increased about 200%, 250% and 190% in the presence of 10 mg/ml, 20 mg/ml and 40 mg/ml of beta-lactoglobulin, respectively, the last concentration representing that found physiologically in colostrum. Albumin, another ligand-binding protein, increases the activity of this enzyme to a lesser extent and high levels tend to inhibit enzyme action. These results indicate that beta-lactoglobulin could participate in the digestion of milk lipids during the neonatal period by enhancing the activity of pregastric lipase through removal of the fatty acids that inhibit this enzyme. 相似文献
45.
46.
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
47.
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
48.
The adsorption of 5′-AMP onto precipitated calcium phosphate (CaPi) requires the presence of soluble calcium and this dependence
exhibits a Michaelian-like behavior. This result suggests that the formation of a complex between 5′-AMP and free Ca2+ (CaAMP) is a prelude to the adsorption of the nucleotide in the solid matrix. At concentrations one order of magnitude higher,
Mn2+ and Mg2+ can substitute for soluble Ca2+ in the adsorption of 5′-AMP onto solid CaPi. However, when added simultaneously with 5′-AMP to a heterogeneous mixture that
contains CaPi and soluble Ca2+, Mn2+ and Mg2+ inhibit the adsorption of 5′-AMP in a concentration-dependent manner. This suggests the formation of complexes that are much
less effective for 5′-AMP adsorption than the CaAMP complex. On the other hand, Mn2+ and Mg2+ cannot promote desorption of the nucleotide attached to the precipitate in the presence of soluble Ca2+ if they are added after adsorption has attained equilibrium. Although desorption of 5′-AMP can be obtained by a sequential
dilution of the soluble phase with buffer and no nucleotide in a process that obeys a Langmuir equation, the lack of effect
of Mn2+ or Mg2+ when adsorption has attained its maximal value suggests strong interactions between the CaAMP complex and the solid matrix
when adsorption equilibrium is reached. The divalent cations present in the matrix also participate with different selectivity
in the attachment of the CaAMP complex, indicating that a cation-exchange mechanism could have acted in the modulation of
adsorptive/desorptive processes involving biomonomers and phosphate surfaces in primitive aqueous environments.
Received: 11 December 1995 / Accepted: 5 April 1996 相似文献
49.
Abstract: The relationship between elevations in intracellular free Ca2+ concentration ([Ca2+]i) by different mechanisms and tyrosine hydroxylase (TH) gene expression was examined. Depolarization by an elevated K+ concentration triggered rapid and sustained increases in [Ca2+]i from a basal level of ~50 to 110–150 nM and three- to fourfold elevations in TH mRNA levels, requiring extracellular calcium but not inositol 1,4,5-trisphosphate (IP3). On the other hand, bradykinin or thapsigargin, both of which induce release of intracellular calcium stores via IP3 or inhibition of Ca2+-ATPase, rapidly elevated [Ca2+]i to >200 nM and increased TH gene expression (three-to fivefold). Confocal imaging showed that the elevations in [Ca2+]i in each case occurred throughout the cyto- and nucleoplasm. The initial rise in [Ca2+]i due to either bradykinin or thapsigargin, which did not require extracellular calcium, was sufficient to initiate the events leading to increased TH expression. Consistent with this, the effects of bradykinin on TH expression were inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid or 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-octyl ester which chelates or inhibits the release of intracellular calcium, respectively. Bradykinin required a rise in [Ca2+]i for <10 min, as opposed to 10–30 min for depolarization to increase TH mRNA levels. These results demonstrate that although each of these treatments increased TH gene expression by raising [Ca2+]i, there are important differences among them in terms of the magnitude of elevated [Ca2+]i, requirements for extracellular calcium or release of intracellular calcium stores, and duration of elevated [Ca2+]i, indicating the involvement of different calcium signaling pathways leading to regulation of TH gene expression. 相似文献
50.
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