Haematological cell proliferation and differentiation responses to perturbations of polyamine biosynthesis

Combined administration of methylglyoxal-bis-guanylhydrazone (MGBG) (25 mg/kg) with difluoromethylornithine (DFMO), or MGBG alone at a higher dose (50 mg/kg), to mice resulted in a decreased white cell count (WBC) in the peripheral blood while DFMO or MGBG alone at a lower dose (25 mg/kg) had no effect. As expected, DFMO alone increased the number of colony forming units spleen (CFU-s), colony forming units diffusion chamber granulocyte (CFU-dg) and colony forming units culture (CFU-c) in the bone marrow. MGBG treatment led to an increase in CFU-dg alone. Combined treatment seemingly had no effect on marrow stem cells. Total tibial and differential counts were not affected by any of the treatments. Cell proliferation in diffusion chamber cultures, as judged by CFU-dg colony formation, was impaired by MGBG alone or in combination with DFMO, at dose levels which had no effect or increased the precursor cell number in the bone marrow. This effect was partially reversed with either putrescine or spermidine. Determination of intracellular polyamine concentrations, demonstrated decreased putrescine and spermidine levels after DFMO administration. As expected, MGBG treatment resulted in decreased spermidine and spermine levels, concomitant with an increase in putrescine. In mice which received both agents, rather than only MGBG, after 3 days higher intracellular polyamine concentrations were observed. After 11 days, however, there was no significant difference between the two groups.     

HEMOPOIETIC STEM CELL PROLIFERATION AND MIGRATION FOLLOWING BORDETELLA PERTUSSIS VACCINE

The ability of a single injection of killed, intact bacteria to effect an increase in the proliferative rate of hemopoietic stem cells was studied. The total numbers of colony forming units in bone marrow, spleen and peripheral blood as well as the proportion of CFU in cycle was assessed. Splenic CFU were observed to rise exponentially due initially to in situ proliferation and later to proliferation in bone marrow with migration via the blood to the spleen. The results are discussed in the light of current concepts of stem cell regulation.     

Growth of mouse and human bone marrow in diffusion chambers in mice. Development of myeloid and erythroid colonies and proliferation of myeloid stem cells in cyclophosphamide- and erythropoietin-treated mice.

Both murine and human bone marrow cells were cultured in plasma clots which were formed inside diffusion chambers implanted into cyclophosphamide- and saline-treated mice. After an initial fall, the number of mouse bone marrow cells and numbers of mouse myeloid stem cells (CFU-C) and agar cluster-forming units rose faster in the cyclophosphamide-treated animals. These hosts also favored formation of myeloid (CFU-D-G) and erythroid (CFR-D-E) colonies and myeloid higher than those of CFU-C from the same marrow population. These observations suggest the existence of humoral factors stimulating granulocyte progenitor cell replication and differentiation. At its best the increment of CFU-D-E number was equivalent to that caused by a single 0.1 unit erythropoietin dose. Culture of normal human marrow cells resulted in colonies in the plasma clot containing only granulocytes and macrophages. Cyclophosphamide-treated host animals were essential for human CFU-D-G development. Plating efficiency for human marrow myeloid colonies was better in the conventional in vitro agar cultures than in diffusion chambers.     

A genome‐wide linkage map for the house sparrow (Passer domesticus) provides insights into the evolutionary history of the avian genome

The house sparrow is an important model species for studying physiological, ecological and evolutionary processes in wild populations. Here, we present a medium density, genome wide linkage map for house sparrow (Passer domesticus) that has aided the assembly of the house sparrow reference genome, and that will provide an important resource for ongoing mapping of genes controlling important traits in the ecology and evolution of this species. Using a custom house sparrow 10 K iSelect Illumina SNP chip we have assigned 6,498 SNPs to 29 autosomal linkage groups, based on a mean of 430 informative meioses per SNP. The map was constructed by combining the information from linkage with that of the physical position of SNPs within scaffold sequences in an iterative process. Averaged between the sexes; the linkage map had a total length of 2,004 cM, with a longer map for females (2,240 cM) than males (1,801 cM). Additionally, recombination rates also varied along the chromosomes. Comparison of the linkage map to the reference genomes of zebra finch, collared flycatcher and chicken, showed a chromosome fusion of the two avian chromosomes 8 and 4A in house sparrow. Lastly, information from the linkage map was utilized to conduct analysis of linkage disequilibrium (LD) in eight populations with different effective population sizes (N_e) in order to quantify the background level LD. Together, these results aid the design of future association studies, facilitate the development of new genomic tools and support the body of research that describes the evolution of the avian genome.     

Different effects of carbohydrate binding modules on the viscoelasticity of nanocellulose gels

Many cellulose degrading and modifying enzymes have distinct parts called carbohydrate binding modules (CBMs). The CBMs have been shown to increase the concentration of enzymes on the insoluble substrate and thereby enhance catalytic activity. It has been suggested that CBMs also have a role in disrupting or dispersing the insoluble cellulose substrate, but dispute remains and explicit evidence of such a mechanism is lacking. We produced the isolated CBMs from two major cellulases (Cel6A and Cel7A) from Trichoderma reesei as recombinant proteins in Escherichia coli. We then studied the viscoelastic properties of native unmodified cellulose nanofibrils (CNF) in combination with the highly purified CBMs to detect possible functional effects of the CBMs on the CNF. The two CBMs showed clearly different effects on the viscoelastic properties of CNF. The difference in effects is noteworthy, yet it was not possible to conclude for example disruptive effects. We discuss here the alternative explanations for viscoelastic effects on CNF caused by CBMs, including the effect of ionic cosolutes.     

Risk Ranking of Antimicrobials in the Aquatic Environment from Human Consumption: An Irish Case Study

A mechanistic model is presented for determination of antimicrobial presence in the environment, using antimicrobial characteristics and Irish-specific usage data. The model simulates release of antimicrobials into the aquatic environment by integrating the effects of antimicrobial use, metabolism, degradation, and dilution. Predicted environmental concentrations (PECs) were ranked in relation to their potential to select for resistant bacteria, toxicity (chronic and acute), and hazard quotient (HQ). The simulated mean PECs of penicillins (PEN), β-lactams (BET), tetracyclines (TET), macrolides (MAC), quinolone/fluoroquinolones (Q/F), and sulphonamides/trimethoprim (S/T) were 1.05, 0.19, 0.06, 0.07, 0.02, and 0.08 mg/m³, respectively. All antimicrobials, excluding Q/F, showed a low HQ (<1) indicating low toxicity. Q/F had a HQ of 1.51 indicating moderate toxicity. All antimicrobial groups expressed varying resistance formation potential with Q/F having the highest. Q/F also exhibited the lowest degradation rate. A sensitivity analysis indicated a possible role for considering metabolism during regulation of new antimicrobials as this can significantly influence PEC values. The observed results suggest that current antimicrobial use can lead to levels in the environment that may increase resistance formation. The results and limitations presented here accentuate the need for further investigation into antimicrobials in the environment and contribution to resistant strains.     

Cleavage of the Phosphodiester Bond of Uridylyl-(3′,5′)-8-Carboxymethylaminoadenosine by Hydronium,Hydroxide and Zinc(Ii) Ions: A Model Study Aimed at Elucidating the Potential of a Carboxylate Function as an Intramolecular Catalyst

Abstract

Uridylyl-(3′,5′)-8-carboxymethylaminoadenosine has been synthesised, and its transesterification to uridine 2′,3′-cyclic phosphate in the presence and absence of Zn²⁺ ion has been studied. The results show that a carboxylate function in the vicinity of the phosphodiester bond accelerates the metal ion promoted cleavage but not the metal ion independent reaction. Under acidic conditions, the predominant reaction is the cleavage of the side chain, giving the 8-amino derivative.     

Variation in eggshell traits between geographically distant populations of pied flycatchers Ficedula hypoleuca

The expression and impact of maternal effects may vary greatly between populations and environments. However, little is known about large‐scale geographical patterns of variation in maternal deposition to eggs. In birds, as in other oviparous animals, the outermost maternal component of an egg is the shell, which protects the embryo, provides essential mineral resources and allows its interaction with the environment in the form of gas exchange. In this study, we explored variation of eggshell traits (mass, thickness, pore density and pigmentation) across 15 pied flycatcher populations at a large geographic scale. We found significant between‐population variation in all eggshell traits, except in pore density, suggesting spatial variation in their adaptive benefits or in the females’ physiological limitations during egg laying. Between‐ population variation in shell structure was not due to geographic location (latitude and longitude) or habitat type. However, eggshells were thicker in populations that experienced higher ambient temperature during egg laying. This could be a result of maternal resource allocation to the shell being constrained under low temperatures or of an adaptation to reduce egg water loss under high temperatures. We also found that eggshell colour intensity was positively associated with biliverdin pigment concentration, shell thickness and pore density. To conclude, our findings reveal large‐ scale between‐population variation of eggshell traits, although we found little environmental dependency in their expression. Our findings call for further studies that explore other environmental factors (e.g. calcium availability and pollution levels) and social factors like sexual selection intensity that may account for differences in shell structure between populations.