Biochemical evidence associating membrane-encapsidated particles with reverse transcription in human gastric cancer.

We provide biochemical evidence demonstrating that membrane encapsidated structures present in terminal gastric patients share similar features with retrovirus-like particles. Purified particles reveal few polypeptides, one of them glycosylated. A ribonucleoprotein core-like component is recovered which retains the DNA-polymerizing activity and contains at least one RNA component which can be efficiently translated in vitro.

Exogenously added free phosphotyrosine induces aggregation of circulating platelets in rabbits.

When free phosphotyrosine is injected into rabbits, circulating aggregated platelets are readily observed in concomitance with altered electrocardiographic profiles. Since phosphotyrosine is also able to induce platelet aggregation in vitro, altogether these results suggest that free phosphotyrosine in blood could be meaningful for in vivo platelet activation.

Further characterization of RNA-dependent-DNA polymerase activity in human gastric cancer.

Based upon our previous report indicating the presence of retrovirus-like particles in human gastric cancer cells, we analyzed the putative endogenous reverse transcriptase activity these particles should have. To evaluate the specificity of reverse transcription over that displayed by normal cellular DNA polymerases, the following discriminatory criteria were used: 1) resistance to high concentrations of Actinomycin D; 2) sensitivity to preincubation with ribonuclease A; 3) behavior in cesium sulfate isopycnic gradients and 4) size-shifting of putative template-product complexes after RNase exposure in agarose gel electrophoresis. We report a significant endogenous reverse transcriptase activity associated with membrane-encapsidated particles from terminally-illed patients but not in normal counterparts. Although these structures closely resemble retro viruses, a new model is proposed to explain our findings.

Free L-phosphotyrosine activates human platelets: molecular evidence for a new signal transducer.

Human platelets, either purified or plasma-enriched, are activated when exposed to free L-phosphotyrosine. Physical aggregation is similar to that induced by collagen, although with distinctive biochemical features. Among these, a mobility shift of a GTP-binding protein specifically recognized by an anti-Ki-v-ras monoclonal antibody and an altered pattern of low molecular weight phosphorylated polypeptides are the most outstanding features. Since free phosphotyrosine is detected in platelets extracts, its role as a new signal transducer as well as its putative modulating action over protein phosphorylation are discussed.

Ageing-related changes in Mycoplasma canadense membranes.

Fluidity and composition of cell membranes during progression of Mycoplasma canadense cultures grown in a serum-free medium was assessed. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at 25 degrees C of intact cells and liposomes in the exponential and stationary phases of growth was compared. A decrease in fluidity and an increase in the ratio of saturated to unsaturated fatty acids was detected in cell membranes on aging. Nevertheless, membrane density remained unaltered although the molar ratio of cholesterol to phospholipids decreased. It is proposed that the increase in lipid order is primarily due to the increase in the ratio of saturated to unsaturated membrane fatty acids, being the diminished molar ratio of cholesterol to phospholipids involved in the reduced unsaturated fatty acid uptake.

Naturally occurring free phosphotyrosine in human liver.

We report an endogenous tyrosine-driven phosphorylating activity in human liver extracts. The detection is achieved after selective enrichment of soluble components present in a post-mitochondrial supernatant fraction (PMS) while measuring in vitro kinase activity. A putative functional role is inferred from the competence displayed by exogenous free target amino acids when added to the reaction. We demonstrate that exogenous tyrosine is specifically phosphorylated. In view of the close association between protein phosphorylation and cell function, our observations broader the scope of interpretation for the pivotal role phosphoamino acids might have in cell metabolism.

[Incidence of intrahepatic and subcapsular hematomas after percutaneous needle biopsy]. / Incidencia de hematomas intrahepáticos y subcapsulares post punción biopsia percutánea del hígado.

Intrahepatic and subcapsular hematomas are described as complications of percutaneous liver biopsy. Even though, its incidence is not clearly established. Through this study we try to set which is the real incidence of this complication in our medium. To comply with this, we control our patients by ultrasonography before, after, and even seven days after procedure has been carried out.

Incidencia de hematomas intrahepáticos y subcapsulares post punción biopsia percutánea del hígado. / [Incidence of intrahepatic and subcapsular hematomas after percutaneous needle biopsy]

Intrahepatic and subcapsular hematomas are described as complications of percutaneous liver biopsy. Even though, its incidence is not clearly established. Through this study we try to set which is the real incidence of this complication in our medium. To comply with this, we control our patients by ultrasonography before, after, and even seven days after procedure has been carried out.