Task‐Dependent Differences in Learning by Subordinate and Dominant Wild Arabian Babblers

Learning and innovation abilities have been studied extensively in flocking birds, but their importance and relevance in cooperatively breeding birds have been relatively unexplored. We studied the acquisition of novel foraging skills in 14 groups of wild, cooperatively breeding Arabian babblers (Turdoides squamiceps). While in a previous study we found that subordinate individuals were usually the first to learn to remove black rubber lids from a foraging grid, here we show that dominant individuals were the first to succeed in shifting from these black rubber lids to newly introduced white rubber lids. We also found that in all groups where one forager learned to shift to the white lids, the rest of the foragers also learned to do so, suggesting that this behaviour may be transmitted among group members. Although dominant individuals were almost always the first to remove white lids, once starting to remove white lids, dominants and subordinates learned equally well to prefer white over black lids based on differential reinforcement (food was provided only under white lids). Together with our previous study, our results suggest that differences in learning between dominants and subordinates may be task‐specific, which may represent different cognitive strategies: subordinates may explore a more diverse range of foraging opportunities, while dominants may be better at generalizing from familiar tasks to similar ones.     

Some regulatory properties of purine biosynthesis de novo in long-term cultures of epithelial-like rat liver cells

De novo synthesis of purine nucleotides and some regulatory properties of this pathway were studied in cultured epithelial-like rat liver cells. It was found that the physiological 5-phosphoribosyl 1-pyrophosphate (P-Rib-PP) concentration in these cells is limiting for purine synthesis de novo. Increase of P-Rib-PP availability, achieved by activation of P-Rib-PP synthetase at high P_i concentration, resulted in acceleration of purine synthesis. The effects of increasing cellular ribose 5-phosphate (Rib-5-P availability, by methylene blue-induced acceleration of the oxidative pentose phosphate pathway, on P-Rib-PP availability and on the rate of the novo purine synthesis were also studied. It was found that at the P_i concentration prevailing in the tissue at extracellular physiological P_i concentration, Rib-5-P availability is saturating for P-Rib-PP generation and therefore also for purine synthesis.     

Maturation of the neonatal oral mucosa involves unique epithelium-microbiota interactions

1. Download : Download high-res image (181KB)
2. Download : Download full-size image

     

Evaluation of gene-expression clustering via mutual information distance measure

Background  

The definition of a distance measure plays a key role in the evaluation of different clustering solutions of gene expression profiles. In this empirical study we compare different clustering solutions when using the Mutual Information (MI) measure versus the use of the well known Euclidean distance and Pearson correlation coefficient.     

The B regulatory subunit of protein phosphatase 2A is required for completion of macroconidiation and other developmental processes in Neurospora crassa

rgb-1 , encoding the tentative B regulatory subunit of the type 2A Ser/Thr phosphatase in Neurospora crassa , was isolated from cDNA and genomic libraries. Based on analysis of cDNA and genomic clones, rgb-1 is 3387 nucleotides in length, contains seven putative introns and encodes a 461-amino-acid polypeptide. Intron I, which is 5' to the presumed translation initiation codon, contains a uORF encoding 34 amino acids. Intron VI undergoes alternative splicing. Inactivation of rgb-1 by the repeat-induced point (RIP) mutation procedure produced progeny that grow slowly, have abnormal hyphal morphology, are female sterile and produce abundant amounts of arthroconidia. The rgb-1 ^RIP strain does not produce major constriction chains or mature macroconidia. Minor constriction chains are formed, yet the growth process reverts to hyphal elongation. Microscopic and genetic analyses indicate that rgb-1 is a regulator of the budding subroutine of the macroconidiation process and that arthroconidiation, which shares common early and late events with macroconidiation, is induced as a default mechanism for asexual reproduction in this fungus.     

Involvement of Endomannanase in the Control of Tomato Seed Germination under Low Temperature Conditions

The cause of differences in germination rates in a cold-toleranttomato line (PI341988), a control line (UC82B), and six progenylines stemming from crosses and backcrosses between the twoparent lines was investigated. Pursuant to earlier work showingthat differences in germination ability at 12°C are dueto the barrier imposed by the endosperm layer, we analysed theactivity of cell-wall-hydrolysing enzymes extracted from theselines. A significant increase in endomannanase activity wasfound in plant line PI341988 prior to germination at 12°C.Extracts of PI341988 seeds that had imbibed at either 12 or25°C exhibited higher endomannanase activity than theircounterparts from plant line UC82B. Moreover, a positive relationshipwas found between germination ability at low temperature andendomannanase activity in the six progeny lines. Analysis ofendomannanase activity in sub-regions of the seed indicatedthat the increase in activity prior to germination was higherin the micropylar endosperm cap than in the rest of the seed.Exogenous application of mannanase originating from soil-bornebacteria increased germination rates under both moderate andlow temperature conditions. Cellulase (endo-1,4-ß-glucanase)activity was also found to be higher in plant line PI341988.However, the activity of this enzyme probably increases aftergermination and it is therefore not considered as a key enzymecontrolling germination at low temperatures.Copyright 1995,1999 Academic Press Lycopersicon esculentum, tomato, seed germination, cell wall     

Cardiomyocytes cultured in serum-free medium: Growth and creatine kinase activity

Primary cultures of newborn rat heart cells were grown for up to 3 weeks in serum-free medium supplemented by insulin, hydrocortisone, transferrin and fetuin. The cells resumed spontaneous beating at 20 h post plating. Mean rates of beating on the second and third day were 79.5 and 94 beats per min, respectively. Cell proliferation occurred during the first 3 days of culture with maximal rates of DNA and protein synthesis on the second day. The highest values of creatine kinase activity were observed on days 2–5 and the three cytoplasmic isozymes, MM, MB and BB, were present in the cultures in proportions similar to those of the newborn heart, indicating stability of the differentiated state of the cells. The relative amount of each isozyme remained unchanged throughout the experiments, MM constituted 70–90% of enzyme activity, MB contributed up to 30% and BB did not exceed 15% of activity. The very low proportion of BB and the lack of increase in this isozyme with age of culture support our earlier morphological observations that non-myocytes do not overgrow the culture.     

Trem2 restrains the enhancement of tau accumulation and neurodegeneration by β-amyloid pathology

1. Download : Download high-res image (349KB)
2. Download : Download full-size image

     

Multiple sclerosis risk gene Mertk is required for microglial activation and subsequent remyelination

1. Download : Download high-res image (155KB)
2. Download : Download full-size image