The effects of a low dose of caffeine on cognitive performance

There is little evidence concerning the effects of caffeine in doses typical of one cup of tea. The present study investigated the effect of 60 mg caffeine, consumed in either tea or hot water, on performance on a subset of the CANTAB test battery. Eight males participated in a practice session and four test sessions. In each test session, the participant consumed a different hot beverage and then, over approximately 90 min, completed nine tests from the CANTAB battery. The four beverages were created by crossing beverage identity (tea or hot water) and caffeine dose (0 or 60 mg). Significant speeding of reaction time by caffeine consumption was found in pattern recognition, delayed match to sample, and match to sample visual search. The effect on reaction time of 60 mg caffeine can be detected, and may be evident within minutes of consumption. Received: 16 March 1998/Final version: 27 July 1998     

Haplotype diversity and somatic instability in normal and expanded SCA8 alleles.

Spinocerebellar ataxia type 8 (SCA8) is an autosomal dominant late-onset neurodegenerative disorder, belonging to the group of diseases caused by trinucleotide repeat expansions. SCA8 remains one of the most intriguing SCAs, regarding the reduced disease penetrance, and the high instability and poorly understood functional meaning of the (CTA)(n)(CTG)(n) expansion. We performed haplotype and sequencing analysis in a large region, encompassing the repeat, in four SCA8 and 20 control Portuguese families. The results from the haplotype study including the combined repeat and six SNP markers showed two different haplotypes, AG-Exp-GTTG and AG-Exp-CTTG, in the SCA8 families. Among the control population, these were also the most frequent, in a total of five haplotypes found unequally distributed throughout repeat sizes. From cloning fragments of control, unstable normal and expanded chromosomes, eleven different base substitutions were identified in exon A of the SCA8 gene. In some instances, somatic variability in repeat size or base composition was found for a same chromosome, regardless of its normal or expanded nature. In conclusion, our results in Portuguese families with ataxia show that SCA8 expansions arose in common backgrounds; in addition, this region seems to be unstable beyond the repeat.     

Ontogenetic profile of glutamate uptake in brain structures slices from rats: sensitivity to guanosine

The excitotoxicity of the neurotransmitter glutamate has been shown to be connected with many acute and chronic diseases of the CNS. High affinity sodium-dependent glutamate transporters play a key role in maintaining adequate levels of extracellular glutamate. In the present study, we used slices of striatum, hippocampus and cortex from rat brain to describe the in vitro profile of glutamate uptake during development and ageing, and its sensitivity to guanosine. In all structures, glutamate uptake was higher in immature animals. There was a maximum decrease in glutamate uptake in striatum and hippocampus in 15-month-old rats, which later increased, while in cortex there was a significant decrease in rats aged 60 days old. The effect of guanosine seems to be age and structure dependent since the increase in basal glutamate uptake was only seen in slices of cortex from 10-day-old animals.     

Inhibins are the major activin ligands expressed during early thymocyte development.

Activins are members of the transforming growth factor-beta (TGFbeta) superfamily, which regulate cell differentiation processes. Here we report the first quantitative analysis of the expression of Activin/Inhibin ligands, type I and II receptors, as well as Smad proteins in fetal (E14-E16) and adult thymic subpopulations. Our data showed that Alk4, ActRIIA, ActRIIB, and Smads 2, 3, and 4, are expressed in fetal thymus (E14 > E15 > E16) and in thymocytes from adult mice (mostly in the double negative [DN] subpopulation). Ligand expression analysis showed that betaA, betaB, and alpha subunits were mainly detected in thymic stromal cells. Interestingly, alpha subunits were expressed at much higher levels compared to betaA and betaB subunits, demonstrating for the first time the potential role of Inhibins as important mediators during early T cell development. Our data indicate that Activin/Inhibin signaling could regulate the process of thymus organogenesis and early thymocyte differentiation, as it has been demonstrated for other members of the TGF-beta superfamily.     

Life cycle of the moss,Physcomitrella patens,in culture

Summary A method employing tissue culture techniques for growth of mosses is described. This method allows for the completion of the sexual life cycle of the mossPhyscomitrella patens (Hedw.) BSG under controlled conditions in a two month period. The moss system is useful for class demonstration or for research in the areas of development, genetics and plant physiology.     

Circulating inflammatory mediators during start of fever in differential diagnosis of gram-negative and gram-positive infections in leukopenic rats

Gram-negative and gram-positive infections have been considered the most important causes of morbidity and mortality in patients with leukopenia following chemotherapy. However, discrimination between bacterial infections and harmless fever episodes is difficult. Because classical inflammatory signs of infection are often absent and fever is frequently the only sign of infection, the aim of this study was to assess the significance of serum interleukin-6 (IL-6), IL-10, macrophage inflammatory protein-2 (MIP-2), procalcitonin (PCT), and C-reactive protein (CRP) patterns in identifying bacterial infections during start of fever in normal and cyclophosphamide-treated (leukopenic) rats following an injection of lipopolysaccharide (LPS) or muramyl dipeptide (MDP) as a model for gram-negative and gram-positive bacterial infections. We found that, compared to normal rats, immunosuppressed animals exhibited significantly higher fevers and lesser production of all mediators, except IL-6, after toxin challenge. Moreover, compared to rats that received MDP, both groups of animals that received an equivalent dose of LPS showed significantly higher fevers and greater increase in serum cytokine levels. Furthermore, in contrast to those in immunocompetent rats, serum levels of IL-6 and MIP-2 were not significantly changed in leukopenic animals after MDP injection. Other serum markers such as PCT and CRP failed to discriminate between bacterial stimuli in both groups of animals. These results suggest that the use of the analyzed serum markers at an early stage of fever could give useful information for the clinician for excluding gram-negative from gram-positive infections.     

Diurnal rhythms of leptin and ghrelin in the systemic circulation and in the gastric mucosa are related to food intake in rats

We investigated diurnal changes in leptin and ghrelin levels in the stomach and in the systemic circulation and their relation to food intake rhythms in Wistar rats housed at 22 °C with a 12-h light/dark cycle and free access to food and water. Animals were sacrificed every 3 h over a 24-h period. Leptin and ghrelin levels in serum and in the gastric mucosa were analysed by immunoassay. Leptin mRNA levels were determined in the gastric mucosa by RT-PCR and in different adipose tissue depots (epididymal, retroperitoneal and mesenteric) by Northern blot. Ghrelin mRNA levels were determined by Northern blot. Gastric and serum leptin levels displayed similar diurnal rhythms, rising during the dark phase and decreasing gradually during the light phase. Leptin expression in the different adipose tissue depots correlated positively with circulating leptin levels (P<0.05), although there were some depot-associated differences. Leptin mRNA levels in the mesenteric depot correlated positively with food intake (P<0.05). In blood, ghrelin levels rose sharply just before the onset of the dark phase and dropped suddenly just after. In the stomach, ghrelin levels were high during the fasting period of light and low during the night, and correlated inversely with food intake, gastric contents and serum leptin levels (P<0.05). Leptin and ghrelin in the stomach and in the systemic circulation thus show diurnal variations that are influenced by food intake rhythms. The results agree with a role for ghrelin as a stimulant of meal initiation.     

Predictive factors of virologic success in HIV-1-infected children treated with lopinavir/ritonavir

Predictive factors of the virologic success of the use of lopinavir/ritonavir (LPV/r) in HIV-infected children are unknown, especially in children who have been pretreated with protease inhibitors (PIs). This longitudinal, single-center, observational study included 69 children (21 PI-naive and 48 PI-experienced) who had received LPV/r for at least 3 months. The mean (+/- SD) age was 10.3 +/- 4.8 years, and the mean baseline of CD4 percentage and HIV-1 RNA was 14.9% +/- 9.8% and 4.8 +/- 1.05 log10 copies/mL, respectively. The mean duration of follow-up was 16.5 +/- 8.3 months. At 6, 12, and 18 months, 52%, 57%, and 49% of all children, respectively, had a viral load less than 50 copies/mL. The risk of virologic failure, defined as 2 consecutive viral loads greater than 1000 copies/mL, was significantly higher when the children were previously treated with PIs and when the baseline LPV mutation score exceeded 3 mutations. In the pretreated children, the ratio of the plasma LPV maximal concentration to the baseline LPV score mutation was also associated with failure, independently of resistance score. Finally, in children failing an LPV-containing regimen, accumulation of additional PI-associated resistance mutations was evidenced in viral isolates from children with prior PI treatment, even with viral replication levels less than 10,000 copies/mL. In pretreated children, LPV plasma levels should be optimized in an attempt to achieve sufficient drug concentrations to overcome the resistance level.     

Vascular endothelial growth factor C is required for sprouting of the first lymphatic vessels from embryonic veins

Lymphatic vessels are essential for immune surveillance, tissue fluid homeostasis and fat absorption. Defects in lymphatic vessel formation or function cause lymphedema. Here we show that the vascular endothelial growth factor C (VEGF-C) is required for the initial steps in lymphatic development. In Vegfc-/- mice, endothelial cells commit to the lymphatic lineage but do not sprout to form lymph vessels. Sprouting was rescued by VEGF-C and VEGF-D but not by VEGF, indicating VEGF receptor 3 specificity. The lack of lymphatic vessels resulted in prenatal death due to fluid accumulation in tissues, and Vegfc+/- mice developed cutaneous lymphatic hypoplasia and lymphedema. Our results indicate that VEGF-C is the paracrine factor essential for lymphangiogenesis, and show that both Vegfc alleles are required for normal lymphatic development.     

Genomic analysis of the nuclear receptor family: new insights into structure, regulation, and evolution from the rat genome

Completion of the Rattus norvegicus genome sequence enabled a global inventory and analysis of the nuclear receptors (NRs) in three mammalian species. Forty-nine NR members were found in mouse, 48 in human. Forty-seven were found in the rat, with gaps at the locations expected for the other two. Pairwise comparisons of their distribution in rat, mouse, and human identified 11 syntenic NR gene blocks, including three small clusters of two or three closely related genes, each spanning 40 kb to 1700 kb. The exon structure of the ligand-binding domain suggests that exon shuffling has played a role in the evolution of this family. An invariant splice junction in all members of the NR family except LXRbeta suggests a functional role for the intron. The ligand-binding domains of PXR and CAR are among the most divergent in the family. Their higher nucleotide substitution rates may be related to the central role played by these two NRs in the metabolism of the foreign compounds and may have resulted from limited positive selection.