Programmed T-cell death in experimental chagas disease

In mature T cells, programmed cell death is thought to serve a regulatory function by limiting both the duration and amplitude of immune responses. Programmed cell death might also be involved in immuno-pathogenesis of certain infectious diseases: recent evidence suggests that programmed T-cell death plays an important role in immune suppression during viral infections. In this article, George DosReis, Maria Evangelina Fonseca and Marcela Lopes review their findings on programmed T-cell death in experimental infection induced by the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. They also discuss the differential behavior of CD4(+) and CD8(+) T-cell subsets regarding programmed cell death, and same possible pathogenic aspects of host-parasite interaction, where abnormal or exaggerated programmed T-cell death could be involved.     

Spatial reconstruction of the human motion based on images of a single camera

The inverse dynamic analysis procedures used in the study of the human gait require that the kinematics of the supporting biomechanical model is known beforehand. The first step to obtain the kinematic data is the reconstruction of human spatial motion, i.e., the evaluation of the anatomic points positions that enables to uniquely define the position of all anatomical segments. In photogrammetry, the projection of each anatomical point is described by two linear equations relating its three spatial coordinates with the two coordinates of the projected point. The need for the image of two cameras arises from the fact that three equations are necessary to find the original spatial position of the anatomical point. It is shown here that the kinematic constraint equations associated with a biomechanical model can be used as the extra set of equations required for the reconstruction process, instead of the equations associated with the second camera. With this methodology, the system of equations arising from the point projections and biomechanical model kinematic constraints are solved simultaneously. Since the system of equations has multiple solutions for each image, a strategy based on the minimization of the cost function associated to the smoothness of the reconstructed motion is devised, leading to an automated computer procedure enabling a unique reconstruction.     

Protein kinase C-induced phosphorylation modulates the Na(+)-ATPase activity from proximal tubules

This study describes the modulation of the ouabain-insensitive Na(+)-ATPase activity from renal proximal tubule basolateral membranes (BLM) by protein kinase C (PKC). Two PKC isoforms were identified in BLM, one of 75 kDa and the other of 135 kDa. The former correlates with the PKC isoforms described in the literature but the latter seems to be a novel isoform, not yet identified. Both PKC isoforms of BLM are functional since a protein kinase C activator, TPA, increased the total hydroxylamine-resistant 32P(i) incorporation from [gamma-32P]ATP into the BLM. In parallel, TPA stimulated the Na(+)-ATPase activity from BLM in a dose-dependent manner, the effect being reversed by the PKC inhibitor sphingosine. The stimulatory effect of TPA on Na(+)-ATPase involved an increase in the V(max) (from 13.4+/-0.6 nmol P(i) mg(-1) min(-1) to 25.2+/-1.4 nmol P(i) mg(-1) min(-1), in the presence of TPA, P<0.05) but did not change the apparent affinity for Na(+) (K(0.5)=14.5+/-2.1 mM in control and 10.0+/-2.1 mM in the presence of TPA, P>0.07). PKC involvement was further confirmed by stimulation of the Na(+)-ATPase activity by the catalytic subunit of PKC (PKC-M). Finally, the phosphorylation of an approx. 100 kDa protein in the BLM (the suggested molecular mass of Na(+)-ATPase [1]) was induced by TPA. Taken together, these findings indicate that PKCs resident in BLM stimulate Na(+)-ATPase activity which could represent an important mechanism of regulation of proximal tubule Na(+) reabsorption.     

Trypanosoma cruzi-cardiomyocytes: new contributions regarding a better understanding of this interaction

The present paper summarizes new approaches regarding the progress done to the understanding of the interaction of Trypanosoma cruzi-cardiomyocytes. Mannose receptors localized at the surface of heart muscle cell are involved in binding and uptake of the parasite. One of the most striking events in the parasite-heart muscle cells interaction is the disruption of the actin cytoskeleton. We have investigated the regulation of the actin mRNA during the cytopathology induced in myocardial cells by the parasite. T. cruzi invasion increases calcium resting levels in cardiomyocytes. We have previously shown that Ca2+ ATPase of the sarcoplasmic reticulum (SERCA) is involved in the invasion of T. cruzi in cardiomyocytes. Treating the cells with thapsigargin, a drug that binds to all SERCA ATPases and causes depletion of intracellular calcium stores, we found a 75% inhibition in the T. cruzi-cardiomyocytes invasion.     

NADPH-oxidase activity and lipid peroxidation in neutrophils from rats fed fat-rich diets

In order to investigate the effect of fat-rich diets on neutrophil functions, 21 day-aged rats were fed for 6 weeks with a control diet consisting of a regular laboratory rodent chow (4 per cent final fat content), a control diet supplied with soybean oil (15 per cent final fat content), or a control diet supplied with coconut oil (15 per cent final fat content). Glycogen-elicited peritoneal neutrophils from rats fed soybean and coconut oil-enriched diets presented a reduction in spontaneous and PMA-stimulated H2O2 generation relative to neutrophils from rats fed the control diet. The activity of superoxide dismutase, glutathione peroxidase and catalase did not change in animals fed fat-rich diets. In addition, the capacity to generate O2-, spontaneously or in response to PMA, did not change in neutrophils from animals fed fat-rich diets. Values attained matched those observed in animals fed the control diet, regardless of the method used to measure O2-, the superoxide dismutase-inhibitable reduction of cytochrome c or the lucigenin-dependent chemiluminescence. However, the initial rate of O2- generation both in resting neutrophils and in PMA-stimulated cells was significantly reduced when animals were fed with coconut or soybean oil-enriched diets due, at least in part, to a reduction in the activity of glucose-6-phosphate dehydrogenase. The concentration of thiobarbituric acid reactive substances, an index of lipid peroxidation, was increased in animals fed both fat-rich diets. This was accompanied by an increase in arachidonic acid content in these cells. Results presented suggest that lipid peroxidation in neutrophils from animals fed fat-rich diets may be associated with a consumption of H2O2 yielding more reactive oxygen-derived species such as the hydroxyl radical.     

The cortico-thalamic theory for generalised spike-wave discharges

The origin of generalized absence epilepsy is still not known. In the last century, four theories have dominated the debate about the origin of the bilateral synchronous generalized spike-wave discharges associated with absence seizures: the "centrencephalic" theory [Penfield and Jasper], the "cortical" [Bancaud, Niedermeyer, Luders], the "cortico-reticular" theory [Gloor, Kostop[oulos, Avoli] and the "thalamic clock" theory [Buzsaki]. There is now some evidence that absence epilepsy, as studied in the WAG/Rij model, is a corticothalamic type of epilepsy. A new hypothesis is proposed which suggests that a cortical focus in the somatosensory cortex is driving the widespread corticothalamic networks during spontaneous absence seizures. This modern theory was given the name "hot spot' theory" [Meeren et al., 2002]. According to the present view three brain structures are critically involved and their integrity seems a minimal and sufficient condition for the occurrence of spike-wave discharges. Firstly, the reticular thalamic nucleus is involved and most likely its rostral pole. Secondly, the thalamocortical relay cells in the ventrobasal complex play a role and, thirdly and most importantly, the cerebral cortex with its epileptic zone. The zone in which the epileptic focus seems to be localised is located on the somato-sensory cortex, and more precisely in the area on which the peri-oral region including the upper lip, projects.     

Microsatellite variation and evolutionary history of PCDHX/Y gene pair within the Xq21.3/Yp11.2 hominid-specific homology block

To better understand the evolutionary dynamics of repetitive sequences in human sex chromosomes, we have analyzed seven new X/Y homologous microsatellites located within PCDHX/Y, one of the two recently described gene pairs in the Xq21.3/Yp11.2 hominid-specific homology block, in samples from Portugal and Mozambique. Sharp differences were observed on X/Y allele distributions, concerning both the presence of private alleles and a different modal repeat length for X-linked and Y-linked markers, and this difference was statistically significant. Higher diversity was found in X-linked microsatellites than in their Y chromosome counterparts; when comparing populations, Mozambicans showed more allele diversity for the X chromosome, but the contrary was true for the Y chromosome microsatellites. Evolutionary patterns, relying on intragenic PCDHX/Y SNPs, also revealed distinct scenarios for X and Y chromosomes. Greater microsatellite diversity was displayed by African X chromosomes within the most common haplotypes shared by both populations, whereas higher microsatellite diversity was found in Portugal for the ancestral Y chromosome haplotype. The most frequent PCDHY haplotype in Portuguese was the derived one, and it was not found in Mozambicans. TMRCA estimated by the rho parameter resulted in 13,700 years (7,500-20,000 years), which is consistent with a recent, post-Out-of-Africa origin for this haplotype. In conclusion, the newly described microsatellite loci generally displayed greater X-linked to Y-linked diversity and this pattern was also detected with slower evolving markers, with a remarkable differentiation between populations observed for Y chromosome haplotypes and, thus, greater divergence among Y chromosomes in human populations.     

Bone marrow stromal cells improve cardiac performance in healed infarcted rat hearts

Postinfarct congestive heart failure is one of the leading causes of morbidity and mortality in developed and developing countries. The main purpose of this study was to investigate whether transplantation of bone marrow stromal cells (BMSC) directly into the myocardium could improve the performance of healed infarcted rat hearts. Cell culture medium with or without BMSC was injected into borders of cardiac scar tissue 4 wk after experimental infarction. Cardiac performance was evaluated 2 wk after cellular (n = 10) or medium (n = 10) injection by electro- and echocardiography. Histological study was performed 3 wk after treatment. Electrocardiography of BMSC-treated infarcted rats showed electrical and mechanical parameters more similar to those in control than in medium-treated animals: a normal frontal QRS axis in 6 of 10 BMSC-treated and all control rats and a rightward deviation of the QRS axis in all 10 medium-treated animals. BMSC treatment, assessed by echocardiography, improved fractional shortening (39.00 +/- 4.03%) compared with medium-treated hearts (18.20 +/- 0.74%) and prevented additional changes in cardiac geometry. Immunofluorescence microscopy revealed colocalization of 4',6-diamidino-2-phenylindole-labeled nuclei of transplanted cells with cytoskeletal markers for cardiomyocytes and smooth muscle cells, indicating regeneration of damaged myocardium and angiogenesis. These data provide strong evidence that BMSC implantation can improve cardiac performance in healed infarctions and open new promising therapeutic opportunities for patients with postinfarction heart failure.     

Cholesterol modulates maculosin's orientation in model systems of biological membranes. Relevance towards putative molecular recognition

Fluorescence techniques were used to study (1) the extent of insertion of the bioactive cyclic dipeptide cyclo(l-tyrosyl-l-prolyl), maculosin, in model systems of membranes of 1, 2-palmitoyl-sn-glycero-3-phosphatidyl choline (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl choline (POPC), (2) its in-depth location in those lipidic membranes, and (3) the influence of cholesterol on the dipeptides's location and orientation. Partition into lipidic bilayers is extensive, mainly for liquid crystalline phase membranes (K(p)=1.3x10(4)). Maculosin locates at the lipid head groups level regardless of the membrane system. Nevertheless, its orientation is lipid phase dependent. When maculosin was inserted in liquid crystalline phase bilayers, its phenolic ring was perpendicular to the membrane surface, whereas it changed orientation when inserted in gel phase membranes. Cholesterol was able to reverse the lipid phase influence on maculosin's orientation.