Structure and function of hemoglobin in antarctic fishes and evolutionary implications

Summary The hematological features of cold-adapted, red-blooded Antarctic teleosts has prompted this study on the relationship between hemoglobin molecular structure and oxygen-binding properties. The hemolysates from 21 species of 5 families contained one component (Hb 1), often accompanied by an additional, minor one (Hb 2, 5%–10% of total). On the other hand, 3 species of Zoarcidae, a non-endemic family, had 4–5 components. All purified hemoglobins from the former group, but only 1–2 of the 4–5 hemoglobins of Zoarcidae, showed a strong Root effect (pH regulation of oxygen binding). Globins from each hemoglobin have been purified and characterised with respect to molecular structure in several species. The similarity between the complete amino acid sequence of one -chain and those of non-Antarctic -chains is lower than that among the latter sequences, suggesting independent pathways of evolution.Presented at the 5th SCAR Symposium on Antarctic Biology, Hobart, Australia (August 29th-September 3rd, 1988)     

Competition for pollination influences selection on floral traits of Ipomopsis aggregata

Although rarely tested, it is often assumed that interspecific competition results in the divergence of traits related to resource use. Using a plant-pollinator system as a model, I tested the prediction the presence of a competitor for pollination influences the strength and/or direction of pollinator-mediated selection on floral traits. I measured phenotypic selection via female fitness on five floral traits of Ipomopsis aggregata in seven populations. Four contained only conspecifics (I only) and three also contained the competitor Castilleja linariaefolia (C + I). Directional selection via fruits/plant and conspecific pollen deposited/flower on corolla length was positive and significantly stronger in C + I populations. This difference in selection was apparently driven by interpopulation variation in the degree to which reproduction of I. aggregata was pollen limited. Consistent with expectations of interspecific competition, I. aggregata plants in C + I populations received less conspecific pollen per flower and set fewer seeds per fruit and fruits per plant than those in I only populations. Ipomopsis aggregata's corollas were also significantly longer in C + I populations, suggesting that there had been a response to a similar selective regime in past generations. Phenotypic correlations between corolla length and width, which determine the variation in I. aggregata's flower shape, were significantly weaker in C + I populations. These data suggest that competition for pollination can influence the strength of selection on and patterns of correlations among floral traits of I. aggregata. If I. aggregata populations with and without competitors for pollination are linked by gene flow, then measuring selection in competitive and noncompetitive environments maybe necessary to accurately predict how floral traits will evolve.     

Genetic polymorphisms of Fas (CD95) and Fas ligand (CD178) influence the rise in CD4+ T cell count after antiretroviral therapy in drug-naïve HIV-positive patients

Fas and Fas ligand (FasL) are the main genes that control cell death in the immune system. Indeed, they are crucial for the regulation of T lymphocyte homeostasis because they can influence cell proliferation. A strong debate exists on the importance of Fas/FasL system during HIV infection, which is characterized by the loss of CD4+ T cells directly, or indirectly, caused by the virus. To investigate whether the genetic background of the host plays a role in the immunoreconstitution, we studied the influence of different Fas and FasL polymorphisms on CD4+ T lymphocyte count and plasma viral load following initiation of highly active antiretroviral therapy (HAART) in drug-naïve HIV+ patients. We studied 131 individuals, who were compared to 136 healthy donors. Statistical analysis was performed by using X ² test, Fischer's Exact Test, and analysis for repeated measurements. The group of HIV+ patients had an unexpected lower frequency of FasLnt169 polymorphism (delT allele) than healthy controls (p=0.039). We then observed no significant differences in the immune reconstitution, in terms of CD4+ T cell increase, when the influence of single alleles of the gene Fas or FasL was considered. However, the combination of some polymorphisms of Fas or FasL significantly influenced CD4+ T cell production and viral load decrease, showing that these genes can play a role in the immunoreconstitution triggered by antiretroviral therapy.     

Expansion strategies for human mesenchymal stromal cells culture under xeno‐free conditions

Choosing the culture system and culture medium used to produce cells are key steps toward a safe, scalable, and cost‐effective expansion bioprocess for cell therapy purposes. The use of AB human serum (AB HS) as an alternative xeno‐free supplement for mesenchymal stromal cells (MSC) cultivation has increasingly gained relevance due to safety and efficiency aspects. Here we have evaluated different scalable culture systems to produce a meaningful number of umbilical cord matrix‐derived MSC (UCM MSC) using AB HS for culture medium supplementation during expansion and cryopreservation to enable a xeno‐free bioprocess. UCM MSC were cultured in a scalable planar (compact 10‐layer flasks and roller bottles) and 3‐D microcarrier‐based culture systems (spinner flasks and stirred tank bioreactor). Ten layer flasks and roller bottles enabled the production of 2.6 ± 0.6 × 10⁴ and 1.4 ± 0.3 × 10⁴ cells/cm². UCM MSC‐based microcarrier expansion in the stirred conditions has enabled the production of higher cell densities (5.5–23.0 × 10⁴ cells/cm²) when compared to planar systems. Nevertheless, due to the moderate harvesting efficiency attained, (80% for spinner flasks and 46.6% for bioreactor) the total cell number recovered was lower than expected. Cells maintained the functional properties after expansion in all the culture systems evaluated. The cryopreservation of cells (using AB HS) was also successfully carried out. Establishing scalable xeno‐free expansion processes represents an important step toward a GMP compliant large‐scale production platform for MSC‐based clinical applications. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1358–1367, 2017     

Lipid droplets fusion in adipocyte differentiated 3T3-L1 cells: A Monte Carlo simulation

Several human worldwide diseases like obesity, type 2 diabetes, hepatic steatosis, atherosclerosis and other metabolic pathologies are related to the excessive accumulation of lipids in cells. Lipids accumulate in spherical cellular inclusions called lipid droplets (LDs) whose sizes range from fraction to one hundred of micrometers in adipocytes. It has been suggested that LDs can grow in size due to a fusion process by which a larger LD is obtained with spherical shape and volume equal to the sum of the progenitors’ ones. In this study, the size distribution of two populations of LDs was analyzed in immature and mature (5-days differentiated) 3T3-L1 adipocytes (first and second populations, respectively) after Oil Red O staining. A Monte Carlo simulation of interaction between LDs has been developed in order to quantify the size distribution and the number of fusion events needed to obtain the distribution of the second population size starting from the first one. Four models are presented here based on different kinds of interaction: a surface weighted interaction (R2 Model), a volume weighted interaction (R3 Model), a random interaction (Random model) and an interaction related to the place where the LDs are born (Nearest Model). The last two models mimic quite well the behavior found in the experimental data. This work represents a first step in developing numerical simulations of the LDs growth process. Due to the complex phenomena involving LDs (absorption, growth through additional neutral lipid deposition in existing droplets, de novo formation and catabolism) the study focuses on the fusion process. The results suggest that, to obtain the observed size distribution, a number of fusion events comparable with the number of LDs themselves is needed. Moreover the MC approach results a powerful tool for investigating the LDs growth process.     

Pollen and non-pollen palynomorph evidence of medieval farming activities in southwestern Greenland

Radiocarbon dating, pollen and non-pollen palynomorph analyses from a lake core were used to establish the timing and effects of farming activities around Lake Igaliku, Eastern Settlement, Greenland. The absence of agro-pastoral impact before the medieval colonization by Europeans provides an opportunity to understand the development of farming activity in a pristine landscape. The results show that the first phase of clearance and grazing pressure, without the expansion of the Norse apophyte (native plant, in habitats created by humans) Rumex acetosa type, could have occurred in the 9–10th century a.d. The presence of Norse settlers and livestock is clearly recorded from the 11–12th century a.d. with increasing frequencies of the Norse apophytes Rumex acetosa type and Ranunculus acris type, and coprophilous fungi. This colonization phase is followed by a period of decreasing human impact at the beginning of the 14th century, with a decrease in weeds, apophytes and coprophilous fungi suggesting a reduced grazing pressure. The regrowth of Salix and Betula and the disappearance of anthropogenic indicators except Rumex acetosa type between the 15th and 18th century demonstrate the abandonment of the settlement, until the development of contemporary agriculture in the 20th century.