Introns and gene evolution

In one scenario of gene evolution, exon shuffling has a fundamental role in increasing gene diversity. As DNA sequences accumulate in the databases, the picture of the intron/exon structures of genes becomes more and more clear. We discuss in this review some features of this picture that suggest that introns have been present since the early stages of evolution, and that exon shuffling was a fundamental process in the construction of ancient as well as modern genes.     

The immediate consequences of middle cerebral artery occlusion on GABA synthesis in mouse cortex and cerebellum.

The effect on gamma-aminobutyric acid (GABA) synthesis of focal ischaemia in the right cortex of the mouse was investigated by performing a right middle cerebral artery (MCA) occlusion. Synthesis of GABA was determined by measurement of the rate of GABA accumulation in tissue following injection of amino oxyacetic acid (AOAA; 30 mg/kg, i.p.). Five min following the MCA occlusion, the rate of GABA synthesis in the right (ischaemic) cortex was decreased by approximately 70% compared to either the left cortex or the right cortex of untreated controls. The basal GABA concentration was however unaffected. Four hours after the occlusion the rate of GABA synthesis was similar in the right and left cortex. The rate of GABA accumulation in the cerebellum was unchanged at both times after the right MCA occlusion compared with untreated control mice. The data suggest that there is a rapid but short lasting decrease in GABA synthesis following an ischaemic insult and it is suggested that this might be associated with the EEG spiking activity that occurs at this time.     

Variability of thoracic impedance cardiograms in man

The variability of thoracic impedance cardiogram signals was studied in a normal population with the objective of determining the effect of different respiratory manoeuvres and the optimal criteria for acquisition of this type of physiological signal. The variability of the first derivative of the thoracic impedance signal (dZ/dt) was determined at each 5ms intervals along the signal as the ensemble confidence limits of 3% and 97% around the coherent average. The results obtained indicate that: (a) signal variability is minimum during respiratory apnea (p<0.05) as compared with apneusis or normal respiration, (b) signal patterns are different during apnea and apneusis, and (c) during normal respiration the cardiac component of the thoracic impedance signal can be extracted from the respiratory noise by coherent average yielding a signal with the same pattern obtained during apnea.     

Group‐specific component (GC) in curiaú and pacoval,two african‐derived brazilian populations

The group‐specific component (GC) system is of interest in anthropological genetic studies because the distribution of its subtypes distinguishes among major ethnic groups. The GC system was analyzed in Curiaú and Pacoval, two remnant Quilombo populations (African‐derived populations) from the Brazilian Amazon. There was no significant statistical difference in allelic frequencies between the two populations or between them and three other African‐derived Brazilian populations (Mimbó, Sítio Velho, and Gaucinha in Northeastern Brazil). These populations share similarities among themselves and with African populations (high frequencies of GC*1F and lower frequencies of GC*1S), which may reflect the influence of a high level of African contribution to their formation, but there is a clear difference between them and Europeans and South American Indians. It is suggested that the GC system is a useful marker for studying relationships between single populations and major ethnic groups, but does not discriminate between populations which share the same parental stock. Am. J. Hum. Biol. 13:718–720, 2001. © 2001 Wiley‐Liss, Inc.     

Hepatitis B virus transmission in Brazilian hemodialysis units: serological and molecular follow-up

A serological and molecular study of hepatitis B virus (HBV) infection was carried out in dialysis units in Central Brazil. Between 1995 and 1999, serum samples from all HBsAg-positive hemodialysis patients (n = 43) were tested for HBeAg/anti-HBe and subtyping by monoclonal ELISA. HBV DNA was detected by PCR and positive samples were genotyped by restriction fragment polymorphism pattern (RFLP) methodology. TheHBsAg prevalence declined in this population during the survey period (12-5.8%). HBeAg and anti-HBe were detected in 23 (53.5%) and 18 (41.9%) sera, respectively. Thirty-six samples could be HBsAg subtyped: 21 were subtype ayw(3), 14 belonged to adw(2) and one was identified as adw(4). HBV DNA was present in 30 serum samples. Of these, 20 (66.7%) were genotype D, 9 (30%) genotype A, and 1 (3.3%) genotype F. In addition, the RFLP pattern could be determined in samples from 18/20 genotype D patients: D3 (10 strains), D7 (7 strains) and D4 (1 strain); from 8/9 genotype A patients: A1 (6 strains) and A3 (2 strains); and from the patient infected with genotype F: F1. Patterns D3 and D7 were associated closely with HBV infection in the two largest hemodialysis units studied. These findings confirm the value of the RFLP method as an effective molecular epidemiological tool for elucidating HBV transmission in hemodialysis units.     

Distribution of cytoskeletal structures and organelles of the host cell during evolution of the intracellular parasitism by Trypanosoma cruzi

The distribution of microtubules, microfilaments, mitochondria, Golgi complex and endosomes/lysosomes was analyzed in Vero cells allowed to interact for different periods of time with the pathogenic protozoan Trypanosoma cruzi and observed by confocal laser scanning microscopy. Microtubules were revealed using a mouse monoclonal anti-alpha-tubulin antibody. Actin filaments were revealed using phalloidin-rhodamine. To identify mitochondria, endosomes/lysosomes and the Golgi complex the cells were labelled with Rhodamine 123, Lucifer yellow and C6-NBD-ceramide, respectively. During cell invasion actin filaments concentrate at the site of parasite penetration in some, but not in all cells, probably depending upon the mechanism used by the trypomastigote form to penetrate into the host cells. Following internalization the trypomastigote form gradually changes into the amastigote form, disruption of the parasitophorous vacuole membrane takes place and the amastigote form enters in direct contact with host cell structures and organelles, and starts to divide. The presence of the parasite in the cytoplasm of the host cell did not induce significant changes in the distribution of actin filaments, microtubules, the Golgi complex, mitochondria and endosomes/lysosomes during the first 48 h of infection. Amastigote forms were seen close to the microtubules. After 72 h of interaction, the number of microtubules and microfilaments around the parasites was reduced and lysosomes and mitochondria were seen in between the parasites.     

Upregulation of TGF-beta, FOXP3, and CD4+CD25+ regulatory T cells correlates with more rapid parasite growth in human malaria infection

Understanding the regulation of immune responses is central for control of autoimmune and infectious disease. In murine models of autoimmunity and chronic inflammatory disease, potent regulatory T lymphocytes have recently been characterized. Despite an explosion of interest in these cells, their relevance to human disease has been uncertain. In a longitudinal study of malaria sporozoite infection via the natural route, we provide evidence that regulatory T cells have modifying effects on blood-stage infection in vivo in humans. Cells with the characteristics of regulatory T cells are rapidly induced following blood-stage infection and are associated with a burst of TGF-beta production, decreased proinflammatory cytokine production, and decreased antigen-specific immune responses. Both the production of TGF-beta and the presence of CD4+CD25+FOXP3+ regulatory T cells are associated with higher rates of parasite growth in vivo. P. falciparum-mediated induction of regulatory T cells may represent a parasite-specific virulence factor.     

Vagotomy reduces obesity in MSG-treated rats

In order to study the role of vagus nerve activity at the onset of obesity induced by monosodium glutamate (MSG), 30-day-old MSG-rats were vagotomized or sham operated. Body weight and food intake were recorded until animals were 90 days old and then sacrificed. Naso-anal length was recorded for all animals. Periepididymal and retroperitoneal fat pads were isolated and weighed. Reduction of body weight and naso-anal length were registered in 30-day-old MSG-rats. Obesity could also be observed, as increase of Lee index indicated. Results were most evident in 90-day-old MSG-rats. In both groups neither body weight gain nor food intake was changed by vagotomy. However, fat accumulation on tissues was reduced by vagotomy in MSG-rats. The results showed that MSG-obesity is not related to an increment in food intake behavior. Vagotonia might play a role at the onset of MSG-obesity.