A redundant oncogenic potential of the retinoic receptor (RAR) alpha, beta and gamma isoforms in acute promyelocytic leukemia.

Alterations of the retinoic acid receptor (RAR)alpha locus are found in 100% of acute promyelocytic leukemia patients, where chromosomal translocations generate the promyelocytic leukemia (PML)-RARalpha chimeric protein. Here, we have investigated the biological properties of the other RAR isoforms (RARbeta and RARgamma), through the generation and characterization of artificial PML-RAR'x' fusion proteins. Surprisingly, we found that all of the RAR isoforms share an identical oncogenic potential in vitro, thus implying that the selection of the RARalpha locus in leukemia patients must occur--rather than through functional differences among the various RAR isoforms-as the consequence of the nuclear architecture of the different RAR loci.

Blood parasites, total plasma protein and packed cell volume of small wild mammals trapped in three mountain ranges of the Atlantic Forest in Southeastern Brazil.

A study of blood parasites in small wild non-flying mammals was undertaken in three areas of the Atlantic Forest in Southeastern Brazil: Serra de Itatiaia, RJ, Serra da Bocaina, SP and Serra da Fartura, SP, from June 1999 to May 2001. A total of 450 animals (15 species) were captured in traps and it was observed in 15.5% of the blood smears the presence of Haemobartonella sp. and Babesia sp. in red blood cells. There was no statistically significant difference between parasited and non-parasited specimens regarding total plasma protein, packed cell volume and body weight, which strongly suggests that these specimens might be parasite reservoirs.

Calcium metabolism in Ehrlich Ascites tumour cells.

Ehrlich ascites tumour cells are able, under the proper experimental conditions, to extrude a substantial amount of Ca2+ from the intracellular space. The Ca2+ extrusion mechanism, probably located at the plasma membrane level, appears to be similar to that found in red blood cells. It is energy-dependent and both respiration and glycolysis are able to drive it. The use of some inhibitors and uncouplers, besides showing that this activity is different from that linked to the mitochondrial Ca2+ pump which acts in the opposite direction, proposes some speculations on the energy compartmentation in the Ehrlich ascites tumour cells.

Calcium permeability of Ehrlich ascites tumour cell plasma membrane in vivo.

Passive Ca2+ entry into Ehrlich ascites tumour cells has been investigated. Passive equilibrium of Ca2+ takes place in ascites tumour cells only under conditions of exhaustive energy depletion. The specific Ca2+ ionophore A23187 does not affect Ca2+ entry into ascites tumour cells under active metabolic conditions, but it increases the rate of Ca2+ equilibration in ascites tumour cells in the early stages of energy depletion. The results of the present experiments lead to the conclusion that in ascites tumour cell plasma membrane Ca2+ permeability is not a limiting step in the regulation of intracellular calcium content, while the energy-dependent Ca2+ extrusion is the main mechanism that prevents uncontrolled intracellular Ca2+ increase. The results taken together support the hypothesis that increased Ca2+ influx into the cell, caused by plasma membrane alteration, is responsible for permanently elevated mitotic activity and for deranged metabolic behavior of these neoplastic cells.

Lack of effect of the Ca2+ ionophore A23187 on tumour cells.

The Ca2+ ionophore A23187 increases intracellular calcium content in normal thymic cells, while it is without effect on the corresponding neoplastic cell (Ascites thymoma) and on Ehrlich ascites tumour cells. The A23187-induced total cell calcium increase in normal thymocytes takes place both in control and energy-depleted cells, while it is lacking in neoplastic cells. In addition the ionophore stimulates aerobic glycolysis of normal thymocytes, whereas it is ineffective on neoplastic cells. The study of intracellular calcium exchange properties reveals that in normal cells the ionophore A23187 provokes a 60% increase of the exchangeable pool together with a more significant, 4-fold enlargement of the unexchangeable pool. These effects are lacking in cancer cells. The data give rise to interesting considerations concerning the regulation and compartmentalization of calcium in neoplastic cells. The results will be also discussed in relation to the models that predict altered cell calcium metabolism as a cause of cancer cell high aerobic glycolysis and uncontrolled growth.

Impairment of microsomal calcium sequestration activity upon superoxide dismutase depletion in rat liver.

We have studied the Ca2+-accumulation activity of microsomal vesicles isolated from the liver of rats held for from 2 to 8 weeks on a copper-deficient diet. With this treatment that deeply modifies fatty acid composition, microsomal membranes show progressively lower Ca2+ sequestration. The activity can be fully restored upon physiological copper supply to the depleted animals. The determination of kinetic parameters of microsomal Ca2+ uptake shows that copper deficiency affects mainly the apparent velocity, leaving unaffected the apparent affinity of the pump for Ca2+. Many similarities were found between this model and the Morris hepatomas with different growth rate. The data support the hypothesis that the oxidative stress imposed on the cell by the loss of superoxide dismutase can influence many cell features, with different implications in the regulation of several biological and biochemical functions.

Red cell physiology.

The erythrocyte, the ultimate product of mammalian erythroid maturation, appears as a highly specialized and, paradoxically, a very simplified cell. In fact it lacks a nucleus and the intracellular organelles are essentially designed to transport oxygen from the outer environment to respiring tissues through the sophisticated functional properties of intraerythrocytic hemoglobin. In this respect, since oxygen transport is such a vital process, the red cell has often been considered, in an excess of oversimplification, as merely a "biological bag' enveloping a viscous solution of concentrated hemoglobin and containing only those few enzymes which are needed to maintain the cell functionally active. However, within the cell a number of different processes are contemporaneously going on, hemoglobin acts as an oxygen and carbon dioxide transporter, glycolysis and the pentose phosphate shunt are devoted to the production of ATP and NADPH, respectively, and membrane organization provides the cell with a good deformability, allowing it to cross narrow splenic capillaries and channels without any appreciable damage for several weeks of activity. All these processes are, indeed, highly integrated and concur to define a complex scenery centered on the oxygenation-deoxygenation cycle of hemoglobin. Within this emerging scheme, hemoglobin appears to display, besides the basic function of oxygen transport, several other biological functions which are driven by the oxygen-linked conformational transition and whose relative importance, in the economy of the cell and of the organism, is not easy to qualify. Some of these aspects are described and discussed.

Hemolytic anemias due to disorders of red cell membrane skeleton.

During the past 10 years, knowledge of the composition, function and supramolecular assembly of the red cell membrane has been greatly expanded by progress in molecular and cell biology. Detailed information on the organization of membrane cytoskeletal proteins and their molecular characterization has allowed us to correlate a number of protein abnormalities with clinical symptoms that are peculiar to hereditary hemolytic anemias (HHA). In particular, three general principles emerge that can help us to understand the pathogenetic mechanisms of HHA: (a) protein-protein and protein-lipid interactions greatly influence the correct assembly of the membrane skeleton; (b) the red blood cell (RBC) membrane skeleton mostly determines the shape (discocyte), deformability (rheologic properties) and durability (half-life and resistence to shear stress) of the erythrocytes; (c) changes in cytoskeletal composition and/or organization can produce alterations in all of the above properties, and therefore they are responsible for the onset of the hemolytic damage.

The influence of extracellular calcium on the distribution of protein kinase C in non-neoplastic and neoplastic rat liver cells.

Non-neoplastic T51B rat liver epithelial cells cannot proliferate in Ca2+-deficient medium. This proliferative inhibition in Ca2+-deficient medium is accompanied by a large reduction in the amount of cellular EDTA-extractable Ca2+/phospholipid-dependent protein kinase (protein kinase C) activity. By contrast, tumorigenic epithelial cells from several Morris hepatomas proliferate in Ca2+-deficient medium and either maintain or greatly increase their content of EDTA-extractable protein kinase C.

A functional assessment methodology for alcohol dependent patients undergoing rehabilitative treatments.

PURPOSE: We propose a functional assessment approach for patients with alcoholic dependence of working age undergoing aerobic training. The background is the WHO indication (ICIDH-2) to use measurable 'activities' as a means to assess the individual 'participation' in social life which also implies work capacity. Defining sustainable energetic levels for the individual is an important issue for both the quantification of an effective training and the evaluation of possible improvements following training. METHODS: Fifty-six 'alcohol dependent' patients, as defined by DSM IV (Diagnostic and Statistical Manual of Mental Disorders), admitted to our Unit in a 16 month-period participated in the study. Eighteen healthy subjects served as controls (Group C). Out of all the 56 patients, 33 (Group A) underwent an aerobic training and 23 subjects (Group N) underwent the same pharmacological and psychological therapy but without aerobic training. Patients were assigned to the treatment (A) or no treatment (N) group according to a 'quasi-experimental' design (i.e. temporal selection criteria). The evaluation protocol consisted of submaximal symptom-limited tests. The tests consisted of bouts of 'basic' activities (walking, lifting, arm-work) to be performed at different intensities. We estimated the total energetic work (TW) performed in the tests by means of formulas available in the literature. The maximal energetic intensity (EI) reached during the tests was also estimated and expressed in MET (multiple of the basal metabolism). RESULTS: Significant differences in work capacity were observed between patients and healthy subjects at baseline. Group A significantly increased TW after rehabilitation, while Group N did not increment their performance at the re-test. CONCLUSIONS: The proposed approach could be useful in the functional assessment of deconditioned subjects with alcohol dependence in working age, and could monitor the changes in work capacity following training.

Magnesium in normal and neoplastic cell proliferation: state of the art on in vitro data.

Information about the involvement of Mg2+ in all biochemical processes that participate in cell proliferation is reviewed in order to define the role of this divalent cation in normal and pathological growth. The lack of conclusive data about cell Mg2+ homeostasis does not suggest any definitive model for its role in the control of cell proliferation. On the other hand, new important information about its absolute requirement in crucial steps of cell activation that can, beside other functions, trigger cell division, strongly support the involvement of Mg2+ in the control of cell proliferation. Studies on the growth of cells in vitro, however, while confirming the indispensible requirement for Mg2+ in extracellular media, do not completely clarify the mechanism(s) or the exact phase/point of the cell cycle where Mg2+ exerts its regulation. Furthermore, the observation that tumour cells grown in culture are influenced by external divalent cations confirms the involvement of Mg2+ in cancer as well as in normal cell proliferation. The proposed explanations (theories, hypotheses) are described and discussed.

Pattern of elevational distribution and richness of non volant mammals in Itatiaia National Park and its surroundings, in southeastern Brazil.

Itatiaia National Park (PNI) and its surroundings present a unique fauna due to different forest formations with well-defined climatic and vegetation bands. The Itatiaia massif has four vegetation types that follow an altitudinal gradient: lower montane forest, montane forest, upper montane forest, and Campos de Altitude. Hence, this region is ideal for studying geographical variation in biological diversity. The main objectives of this study were to report on nonvolant mammal species known to occur in Itatiaia National Park and its surroundings and to determine if their distributional pattern is related to elevation. A review of the literature and a complete survey of specimens deposited in museums, as well as small-mammal trapping were carried out in order to obtain a complete record of the species from the region. Precise locality data were obtained for all specimens recorded, allowing the inclusion of each collected or observed individual in an altitude and vegetational class. We made a direct ordination gradient of marsupial, primate, and rodent species abundance with the altitude. Sixty-nine mammal species were collected or reported for the Itatiaia massif, belonging to seven orders and 20 families. Of these, 33 species (47.8%) are included in the official list of threatened or believed-to-be threatened species in Rio de Janeiro State. The orders Rodentia, Carnivora, and Didelphimorphia had the highest species richness, with 25, 14, and 13 species respectively. When species were grouped according to the vegetation, 16 species occured in the lower montane, 56 in the montane forest, five in the upper montane, and 21 in the high-altitude fields (Campos de Altitude). The communities of marsupials, primates, and rodents have an ordination pattern related to the altitude. Species richness was higher between 500 m and 1,500 m above sea level in montane forest, which is in agreement with recent studies showing that species richness can reach its maximum at mid-elevations.

Preoperative localization and surgical margins in conservative breast surgery.

Breast-conserving surgery (BCS) is the treatment of choice for early breast cancer. The adequacy of surgical margins (SM) is a crucial issue for adjusting the volume of excision and for avoiding local recurrences, although the precise definition of an adequate margins width remains controversial. Moreover, other factors such as the biological behaviour of the tumor and subsequent proper systemic therapies may influence the local recurrence rate (LRR). However, a successful BCS requires preoperative localization techniques or margin assessment techniques. Carbon marking, wire-guided, biopsy clips, radio-guided, ultrasound-guided, frozen section analysis, imprint cytology, and cavity shave margins are commonly used, but from the literature review, no single technique proved to be better among the various ones. Thus, an association of two or more methods could result in a decrease in rates of involved margins. Each institute should adopt its most congenial techniques, based on the senologic equipe experience, skills, and technologies.

Persistent hiccup after surgical resection of a brainstem arteriovenous malformation: a case successfully treated with gabapentin during rehabilitation. Case report.

Persistent hiccup rarely occurs during rehabilitation, but its management can prove to be very difficult, particularly in presence of associated dysphagia, requiring longer hospitalization and higher risk of severe clinical complications. We present a case of persistent hiccup after surgical resection of a brainstem arteriovenous malformation successfully treated with gabapentin during rehabilitation.

The self-association coiled-coil domain of PML is sufficient for the oncogenic conversion of the retinoic acid receptor (RAR) alpha.

In acute promyelocytic leukemia (APL) the retinoic acid receptor alpha (RARα) becomes an oncogene through the fusion with several partners, mostly with promyelocytic leukemia protein (PML), all of which have in common the presence of a self-association domain. The new fusion proteins, therefore, differently from the wild-type RARα, which forms only heterodimers with retinoic X receptor alpha, are also able to homo-oligomerize. The presence of such a domain has been suggested to be crucial for the leukemogenic potential of the chimeric proteins found in APL blasts. Whether or not any self-association domain is sufficient to bestow a leukemogenic activity on RARα is still under investigation. In this work, we address this question using two different X-RARα chimeras, where X represents the coiled-coil domain of PML (CC-RARα) or the oligomerization portion of the yeast transcription factor GCN4 (GCN4-RARα). We demonstrate that in vitro both proteins have transforming potential, and recapitulate the main PML-RARα biological properties, but CC-RARα is uniquely able to disrupt PML nuclear bodies. Indeed, in vivo only the CC-RARα chimera induces efficiently APL in a murine transplantation model. Thus, the PML CC domain represents the minimal structural determinant indispensable to transform RARα into an oncogenic protein.

Further observations on the effect of calcium ionophores on ascites tumor cells.

The effect of the Ca2+ ionophore ionomycin on neoplastic thymocytes in comparison to its effect on normal thymus cells was studied. Ionomycin increases intracellular Ca2+ in normal lymphocytes but fails to increase Ca2+ in neoplastic thymocytes. In these cells the ionophore causes a transient increase in cytosolic free Ca2+. The lack of effect of ionomycin reproduces that of A23187, but it does not depend on reduced availability of intracellular Mg2+ to exchange with Ca2+; it appears to depend on the strong activity of the plasma membrane Ca2+-extruding pump that counteracts ionomycin permeabilization and that can be partly inhibited by the calmodulin inhibitor R24571 (calmidazolium). Neoplastic thymocytes show a high content of magnesium, the intracellular binding of which is efficiently regulated by endogenous ATP. The data show also an interesting correlation between the regulation of energy metabolism (aerobic glycolysis) and cation homeostasis in the neoplastic cells studied.