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Biomedical subjects

F Palma

Publications and source records attributed to F Palma.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

The age-dependent metabolic decline of the red blood cell.

The oxidative and non-oxidative utilization of glucose was evaluated in human erythrocytes of different ages, separated by density gradient ultracentrifugation. Young red blood cells are able to metabolize 2.5 times more glucose than old ones; on the other hand, the amount of glucose utilized via the hexose monophosphate shunt does not show any age dependence. Glucose metabolism evaluated during in vivo ageing of a rabbit red cell population shows results very similar to those obtained for human cells. Metabolic stimulation of glucose utilization by high phosphate in both young and old human red cells increases glucose utilization by 40%. In the same way young and old erythrocytes were able to increase the amount of glucose metabolized via the hexose monophosphate shunt when an oxidative stimulus (methylene blue) was introduced. Human erythrocytes of different age possess similar abilities to transport glucose so that an age-dependent defect in glucose transport can be excluded. The ATP content of human and rabbit red blood cells, as a function of cell age, follows the decrease in glucose metabolized via the Embden-Meyerhof pathway. Reduced glutathione, on the other hand, after a small decrease associated with the "maturation" of reticulocytes into red cells, remains constant like the rate of the hexose monophosphate shunt.

Adenosine Triphosphate↗
PubMedDate not supplied

Human erythrocyte phosphoglucomutase: comparison of the kinetic properties of PGM1 and PGM2 isoenzymes.

Kinetic properties of PGM1 and PGM2 phosphoglucomutase "primary" isoenzymes from human erythrocytes were studied. The two enzyme forms share a "ping-pong" kinetic mechanism and show similar Km for substrate (glucose 1-P) and cofactor (glucose 1,6-P2). Micromolar concentrations of fructose 1,6-P2 and glycerate 2,3-P2 inhibit both PGM1 and PGM2 isoenzymes to a similar extent. The sole PGM2 form is affected by ribose monophosphates (ribose 1-P and ribose 5-P) that act as mutase inhibitors vs. glucose 1,6-P2 and as apparent activators vs. glucose 1-P. The interaction between PGM2 isoenzyme and ribose monophosphates is discussed in the light of the ability of this form to also display phosphoribomutase activity.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

Membrane current of retinal rods of Caudiverbera caudiverbera (Amphibia: Leptodactylidae): dark noise, spectral and absolute light sensitivity.

We investigated the photocurrents from isolated rods of the South American anuran, Caudiverbera caudiverbera. Rod outer segments were on average 66.4 +/- 11.2 microm (mean +/- S.D., n = 104) in length and 6.6 +/- 0.9 microm (mean +/- S.D.) in diameter: 40 +/- 22 photoisomerizations (mean +/- S.D., range 10-99, n = 16) were required for eliciting a half-saturating photocurrent response. The time-to-peak was 911 +/- 217 ms (mean +/- S.D., n = 14, 20 degrees C) in the linear range of the response and the integration time of the current response was 1744 +/- 451 ms (mean +/- S.D., n = 14). The time-to-peak appears to be slower and the integration time shorter in Caudiverbera than in Ambystoma tigrinum, Rana pipiens or Xenopus laevis rods under similar experimental conditions. The a-band of rod spectral sensitivity has a lambda(max) at 520 +/- 2.1 nm (mean +/- S.D., range 516-525 nm, n = 24) and the bandwidth fits a porphyropsin visual pigment. The single-event response amplitude ranges from 0.31-0.51 pA, depending on the calculation method. The intrinsic dark current (variance at dark minus variance under bright light) was 0.045 +/- 0.040 pA2 (mean +/- S.D., n = 24). Our results support the presence of a dark-noise component below 1 Hz, with kinetics similar to the single-photon evoked response and a rate of 0.006 events s(-1) (n = 9).

Amphibians↗
PubMedDate not supplied

Management and outcome of liver recipients with post-transplant lymphoproliferative disease.

BACKGROUND/AIMS: The possibility of development of post-transplant lymphoproliferative disease by patients receiving immunosuppressive therapy is well known. However, elective treatment and outcome remain controversial. We reviewed the management and outcome of our patients with post-transplant lymphoproliferative disease. METHODOLOGY: Records of 457 patients who underwent orthotopic liver transplantation from 1986 to 1997 were analyzed. Patients who developed post-transplant lymphoproliferative disease were reviewed retrospectively. Incidence, clinical presentation, risk factors and outcomes were examined with special emphasis on ductopenic rejection and hilum involvement. RESULTS: Eleven patients developed a post-transplant lymphoproliferative disease (2.4%). These were B-cell non-Hodgkins lymphoma, Epstein-Barr virus-associated in all cases. Five patients (45.5%) received monoclonal antibodies or antithymocyte globulin. Seven patients (63.6%) developed a lymphoproliferative disease before 9 months post-transplant and 4 recipients (36.4%) after 20 months. No late lymphomas regressed after withdrawal from immunosuppression. Six patients (54.5%) were treated with chemotherapy. Eight patients (72.7%) had a tumoral remission. Five patients (45.5%) developed chronic rejection after immunosuppressant discontinuation. Four of them died as a consequence of ductopenic rejection and retransplantation was required in another; 2 died due to graft hilum infiltration. Five patients (45.5%) are alive after a follow-up of 36.5 +/- 32 months (range: 4-77 months). CONCLUSIONS: Patients with post-transplant lymphoproliferative disease require a close follow-up in order to promptly treat conditions that could lead to death. In our series, these were more closely associated with a failing transplanted organ than with the lymphoma itself.

Adolescent↗
PubMedDate not supplied

Rapid and sensitive detection of recombinant soluble proteins in the supernatant of transfected mammalian cells.

Cloning and expression of recombinant soluble proteins could be quite a difficult task, especially when it comes to reliably detect minute amounts of the soluble protein in the supernatant of transfected mammalian cells. Timing and sensitivity are of the essence in order to optimise the benefits/costs balance and to decide which clones to grow further and which ones to discard. Here we propose a modified inhibition assay. The key feature of this approach is the development of a sensitive and quantitative test to detect the presence of the recombinant soluble protein by exploiting its ability to compete with the binding of a specific monoclonal antibody to a target cell. The described procedure is a sensitive, efficient, dependable and low cost method.

3T3 Cells↗
PubMedDate not supplied

The relevance of glucose 1,6-bisphosphate formation and degradation to human red blood cell metabolism.

In human erythrocytes, in the absence of specific enzymes, G1,6P2 synthesis and degradation are carried out by phosphoglucomutase PGM2 isoenzymes. The results presented, obtained by using partially purified preparations of these enzyme forms, suggest that erythrocyte G1,6P2 may play a crucial role in the physiological interconversion of several important sugar monophosphates.

Erythrocytes↗
PubMedDate not supplied

Factors influencing the metabolic pathways of glucose in human erythrocytes.

The metabolic effect of a lactate or pyruvate load and methylene blue (Mb) on hexose monophosphate shunt (HMPS) and Embden-Meyerhof pathway (EMP) were investigated in intact erythrocytes in the presence of glucose. Pyruvate enhances glucose consumption and 14CO2 production, lactate reduces 14CO2 production but glucose consumption is unchanged. These effects are dependent on the lactate and pyruvate concentrations in the buffer. A pyruvate load does not results to influence the net production of pyruvate, which is conversely markedly increased by Mb. The lactate load raises slightly the total pyruvate level but its rate of production is unchanged, with respect to that of the control. A considerable effect on the intracellular to extracellular pyruvate ratio is observed in these different conditions, as well as modifications in the levels of inorganic phosphate (Pi).

Blood Glucose↗