Early population differentiation in extinct aborigines from Tierra del Fuego-Patagonia: ancient mtDNA sequences and Y-chromosome STR characterization

Ancient mtDNA was successfully recovered from 24 skeletal samples of a total of 60 ancient individuals from Patagonia-Tierra del Fuego, dated to 100-400 years BP, for which consistent amplifications and two-strand sequences were obtained. Y-chromosome STRs (DYS434, DYS437, DYS439, DYS393, DYS391, DYS390, DYS19, DYS389I, DYS389II, and DYS388) and the biallelic system DYS199 were also amplified, Y-STR alleles could be characterized in nine cases, with an average of 4.1 loci per sample correctly typed. In two samples of the same ethnic group (Aonikenk), an identical and complete eight-loci haplotype was recovered. The DYS199 biallelic system was used as a control of contamination by modern DNA and, along with DYS19, as a marker of American origin. The analysis of both mtDNA and Y-STRs revealed DNA from Amerindian ancestry. The observed polymorphisms are consistent with the hypothesis that the ancient Fuegians are close to populations from south-central Chile and Argentina, but their high nucleotide diversity and the frequency of single lineages strongly support early genetic differentiation of the Fuegians through combined processes of population bottleneck, isolation, and/or migration, followed by strong genetic drift. This suggests an early genetic diversification of the Fuegians right after their arrival at the southernmost extreme of South America.     

5,6-Epoxyeicosatrienoic acid mobilizes Ca2+ in anterior pituitary cells

Luteinizing hormone releasing hormone stimulates the concomitant release of luteinizing hormone and 45Ca2+ from prelabeled anterior pituitary cells. Indomethacin (10 microM) and nordihydroguaiaretic acid (10 microM) had no effect on the luteinizing hormone releasing hormone-stimulated release of either luteinizing hormone or 45Ca2+. Eicosatetraynoic acid (10 microM) blocked both luteinizing hormone releasing hormone-stimulated luteinizing hormone secretion and luteinizing hormone releasing hormone-stimulated 45Ca2+ efflux. 5,6-Epoxyeicosatrienoic acid stimulated both luteinizing hormone secretion and 45Ca2+ efflux from anterior pituitary cells. Additionally, 5,6-epoxyeicosatrienoic acid closely mimics the ability of luteinizing hormone releasing hormone to increase intracellular free calcium. These results are consistent with the hypothesis that 5,6-EET alters calcium homeostasis in a manner similar to that observed during luteinizing hormone releasing hormone stimulation of luteinizing hormone release.     

The freshwater planarian Dugesia (G.) tigrina contains a great diversity of homeobox genes

To identify potential pattern control and cell determination and/or differentiation genes in the freshwater planarian Dugesial (G.) tigrina, we searched for homeobox genes of different types in the genome of this primitive metazoan. We applied two basic approaches: 1) Screening the cDNA library with degenerate oligonucleotides corresponding to the most conserved amino acid sequence from helix-3 of the homeodomain of each family; and 2) PCR amplification of genomic DNA or cDNA, using two sets of degenerated oligonucleotides corresponding to helices 1 and 3 of the homeodomain or two specific domains of the POU family. Using the first strategy we have identified and characterized two tissue-specific cell determination and/or differentiation NK-type homeobox genes. Using the second strategy we have identified several homeobox genes that belong to the HOM/Hox, paired (prd) or POU families.     

Thermodynamic concepts in the study of microbial populations: age structure in Plasmodium falciparum infected red blood cells

Variability is a hallmark of microbial systems. On the one hand, microbes are subject to environmental heterogeneity and undergo changeable conditions in their immediate surroundings. On the other hand, microbial populations exhibit high cellular diversity. The relation between microbial diversity and variability of population dynamics is difficult to assess. This connection can be quantitatively studied from a perspective that combines in silico models and thermodynamic methods and interpretations. The infection process of Plasmodium falciparum parasitizing human red blood cells under laboratory cultivation conditions is used to illustrate the potential of Individual-based models in the context of predictive microbiology and parasitology. Experimental data from several in vitro cultures are compared to the outcome of an individual-based model and analysed from a thermodynamic perspective. This approach allows distinguishing between intrinsic and external constraints that give rise to the diversity in the infection forms, and it provides a criterion to quantitatively define transient and stationary regimes in the culture. Increasing the ability of models to discriminate between different states of microbial populations enhances their predictive capability which finally leads to a better the control over culture systems. The strategy here presented is of general application and it can substantially improve modelling of other types of microbial communities.     

Circular dichroism spectra of human hemoglobin reveal a reversible structural transition at body temperature

Previously we have shown that human red blood cells (RBCs) undergo a sudden change from blocking to passing through a 1.3±0.2-µm micropipette when applying an aspiration pressure of 2.3 kPa at a critical transition temperature (T_c=36.4±0.3 °C). Low-shear viscosity measurements suggested that changes in the molecular properties of hemoglobin might be responsible for this effect. To evaluate structural changes in hemoglobin at the critical temperature, we have used circular dichroism (CD) spectroscopy. The thermal denaturation curves of human hemoglobin A (HbA) and hemoglobin S (HbS) upon heating between 25 and 60 °C were non-linear and showed accelerated denaturation between 35 and 39 °C with a midpoint at 37.2±0.6 °C. The transition was reversible below 39 °C and independent of solution pH (pH 6.8–7.8). It was also independent of the oxygenation state of hemoglobin, since a sample that was extensively deoxygenated with N₂ showed a similar transition by CD. These findings suggest that a structural change in hemoglobin may enable the cellular passage phenomenon as well as the temperature-dependent decrease in viscosity of RBC solutions.     

The Evolution of the Exponent of Zipf's Law in Language Ontogeny

It is well-known that word frequencies arrange themselves according to Zipf''s law. However, little is known about the dependency of the parameters of the law and the complexity of a communication system. Many models of the evolution of language assume that the exponent of the law remains constant as the complexity of a communication systems increases. Using longitudinal studies of child language, we analysed the word rank distribution for the speech of children and adults participating in conversations. The adults typically included family members (e.g., parents) or the investigators conducting the research. Our analysis of the evolution of Zipf''s law yields two main unexpected results. First, in children the exponent of the law tends to decrease over time while this tendency is weaker in adults, thus suggesting this is not a mere mirror effect of adult speech. Second, although the exponent of the law is more stable in adults, their exponents fall below 1 which is the typical value of the exponent assumed in both children and adults. Our analysis also shows a tendency of the mean length of utterances (MLU), a simple estimate of syntactic complexity, to increase as the exponent decreases. The parallel evolution of the exponent and a simple indicator of syntactic complexity (MLU) supports the hypothesis that the exponent of Zipf''s law and linguistic complexity are inter-related. The assumption that Zipf''s law for word ranks is a power-law with a constant exponent of one in both adults and children needs to be revised.     

Water relations,gas exchange,and growth of resprouts and mature plant shoots of Arbutus unedo L. and Quercus ilex L.

Resprout and mature plant shoot growth, leaf water status and gas exchange behavior, tissue nutrient content, flowering, and production were studied for co-occurring shallow-rooted (Arbutus unedo L.) and deeprooted (Quercus ilex L.) Mediterranean tree species at the Collserola Natural Park in Northeast Spain Resprouts showed higher growth rates than mature plant shoots. During fall, no differences in eco-physiological performance of leaves were found, but mobilization of carbohydrates from burls strongly stimulated growth of fall resprouts compared to spring resprouts, despite low exposed leaf area of the fall shoots. During summer drought, resprouts exhibited improved water status and carbon fixation compared to mature plant shoots. Shoot growth of Q. ilex was apparently extended due to deep rooting so that initial slower growth during spring and early summer as compared to A. unedo was compensated. Tissue nutrient contents varied only slightly and are postulated to be of minor importance in controlling rate of shoot growth, perhaps due to the relatively fertile soil of the site. Fall flowering appeared to inhibit fall shoot growth in A. unedo, but did not occur in Q. ilex. The results demonstrate that comparative examinations utilizing vegetation elements with differing morphological and physiological adaptations can be used to analyze relatively complex phenomena related to resprouting behavior. The studies provide an important multi-dimensional background framework for further studies of resprouting in the European Mediterranean region.     

In vitro antiprotozoal activity of alkaloids from Phaedranassa dubia (Amaryllidaceae)

The bulbs of Phaedranassa dubia (Amaryllidaceae) were found to contain the novel compound phaedranamine, together with seven known alkaloids. The structure and stereochemistry of the alkaloids were determined by physical and spectroscopic methods. An in vitro screening against four different parasitic protozoa was carried out using the isolated compounds. The alkaloids ungeremine, pseudolycorine and haemanthamine showed good activity in in vitro assays against Trypanosoma brucei rhodesiense, T. cruzi and Plasmodium falciparum with IC₅₀ values in the range of 3.66 μM or lower.