Characteristics of small cell colonies developing in primary cultures of adult rat hepatocytes

Phenotypes of the cells developing into small colonies after days of primary culture of adult rat hepatocytes in serum-free modified Dulbecco Modified Eagles’ medium containing 10 mM nicotinamide and 10 ng/ml epidermal growth factor were analyzed immunocytochemically, cytochemically and ultrastructurally. Albumin, cytokeratin 8 and 18 were seen by immunocytochemical techniques in the cells of the small colonies at Day 6. Transferrin, α-antitrypsin, ceruloplasmin, and haptoglobin, proteins secreted by mature hepatocytes, were faintly stained in these cells as was α-fetoprotein. These proteins were secreted into the culture medium as evidenced by immunoblot analysis. γ-Glutamyltransferase, alkaline phosphatase and glucose 6-phosphatase were not present in the cells of the small colonies as well as the surrounding hepatocytes at Day 6 of culture. In addition, ultrastructural examinations of the cells in the small colonies indicated that these cells not only had many characteristic mitochondria and desmosomes, but also a few small peroxisomes. Such cells, even after 20 days in culture were proliferating, as evidenced by the intranuclear presence of the proliferating cell nuclear antigen. The potential relation of these cells to hepatocytes which may serve as the principal reserve for replicating hepatocytes is discussed.     

Decisions,decisions, decisions: the host colony choices of a social parasite

Many factors contribute to the success of a socially parasitic strategy, especially the ability of the parasite to invade a host colony. However, little research has focused on the choices that may be made by an invading parasite, specifically whether parasites actively discriminate between different host colonies and if they have a preference for colonies of a particular size. When an allodapine social parasite, Inquilina schwarzi, was presented with colonies of their host species, Exoneura robusta, the parasites were found to invade the larger host colonies. However, it could not be ascertained from this study whether the parasites were making an active decision concerning which colony to invade, or whether they were simply more attracted to the larger colonies due to potentially stronger odour cues. Regardless of the cause, the larger host colonies are more at risk of being invaded by a social parasite, which would give parasites greater resources for exploitation and could also provide selection against the large host colony sizes.     

Caste differentiation and growth of laboratory colonies of Reticulitermes urbis (Isoptera, Rhinotermitidae)

A total of 280 laboratory colonies of Reticulitermes urbis were raised for 3 years, in order to observe caste differentiation and overall colony growth, and to investigate whether the initial composition (0, 2 or 4 nymphs; 0, 5, 10, 20 or 50 workers) affected colony survival, population growth and other colony dynamics. We also wanted to determine the minimum number of individuals needed to establish a vital colony. As a result, every colony beginning with less than 20 workers died within 60 weeks, while colonies beginning with at least 20 workers survived until the end of the tests, with varied survival rates dependent upon the initial size and the time of formation (summer or autumn). The number of nymphs did not affect colony survival and colony growth. Reproductives developed from nymphs within 2 weeks and later from workers. Many of the reproductives derived from nymphs were killed by workers. The majority of the colonies contained two reproductives 3 years after initiating the tests. In addition, a few individual workers were still alive at the end of the 3-year tests. At the end of the tests, the proportion of soldiers ranged anywhere from 5.23 to 7.69% of the total population. The number of viable “juveniles” from each colony was relatively low throughout the tests and the overall population growth was not sufficient enough to replace dead workers or increase the colony size considerably. These results indicate that the potential to establish viable and sustainable colonies for groups of R. urbis composed of 5–50 workers is very low.     

“Entombed Pollen”: A new condition in honey bee colonies associated with increased risk of colony mortality

Here we describe a new phenomenon, entombed pollen, which is highly associated with increased colony mortality. Entombed pollen is sunken, capped cells amidst “normal”, uncapped cells of stored pollen, and some of the pollen contained within these cells is brick red in color. There appears to be a lack of microbial agents in the pollen, and larvae and adult bees do not have an increased rate of mortality when they are fed diets supplemented with entombed pollen in vitro, suggesting that the pollen itself is not directly responsible for increased colony mortality. However, the increased incidence of entombed pollen in reused wax comb suggests that there is a transmittable factor common to the phenomenon and colony mortality. In addition, there were elevated pesticide levels, notably of the fungicide chlorothalonil, in entombed pollen. Additional studies are needed to determine if there is a causal relationship between entombed pollen, chemical residues, and colony mortality.     

Rapid immuno‐monitoring of inoculant plant growth‐promoting microorganisms

Rapid, specific techniques are essential to monitor the quality of inoculant plant growth‐promoting strains at all stages of manufacture from starter culture to the final product in its carrier medium. In this study, colony immunoblotting was evaluated for the specific detection and enumeration of Citrobacter freundii, one component of a Vietnamese commercial inoculant plant growth‐promoting product used to improve the yield and nutrient efficiency of paddy rice. For quality control of either sterilised or unsterilised carrier media in commercial products colony immunoblotting proved to be a promising tool. Furthermore, it was possible using this technique to measure the survival of this strain in soil and the rhizosphere.     

Ontogeny of hydrocarbon profiles in the ant Aphaenogaster senilis and effects of social isolation

In ants, cuticular hydrocarbons are used for nestmate recognition; they are stored in the postpharyngeal gland and shared among the individuals. Newly emerged ants have a very small quantity of hydrocarbons. We studied the ontogeny of the hydrocarbon profile in Aphaenogaster senilis. The total quantities of both cuticular and postpharyngeal gland (PPG) hydrocarbons increased with age from 0 to 20 days after emergence and then stabilised. These quantities are correlated with the development of the ovary. Under individual social isolation, cuticular hydrocarbons increased as normal, but the total quantity of PPG hydrocarbons never increased from the initial low level. This effect of social isolation on the PPG hydrocarbon level indicates the importance of hydrocarbon transfer between nestmates through the PPG and lends support to the gestalt model of nestmate recognition. To cite this article: K. Ichinose, A. Lenoir, C. R. Biologies 332 (2009).     

Improving post-transfer survival of bovine embryos produced in vitro: actions of insulin-like growth factor-1, colony stimulating factor-2 and hyaluronan

Technologies for in vitro embryo production have the potential to enhance the efficiency of cattle production systems. However, utilization of in vitro-produced embryos for transfer remains limited throughout much of the world. Despite improvements over the past two decades, problems associated with the production of bovine embryos in vitro still exist which limit the widespread commercial application of this technology. In particular, bovine embryos produced in vitro have a reduced capacity to establish and maintain pregnancy as compared with their in vivo-derived counterparts. Embryo competence for survival following transfer is improved by in vivo culture in the sheep oviduct, thus indicating that standard embryo culture conditions are sub-optimal. Therefore, one strategy to improve post-transfer survival is to modify embryo culture media to more closely mimic the in vivo microenvironment. The maternal environment in which the bovine embryo develops in vivo contains various growth factors, cytokines, hormones, and other regulatory molecules. In addition to affecting bovine embryo development in vitro, recent research indicates that embryo competence for survival following transfer can also be improved when such molecules are added to embryo culture medium. Among the specific molecules that can increase post-transfer embryo survival are insulin-like growth factor-1 (IGF-1), colony stimulating factor-2 (CSF-2) and hyaluronan. This paper will review the effects IGF-1, CSF-2 and hyaluronan on post-culture embryo viability and discuss the potential mechanisms through which each of these molecules improves post-transfer survival.     

Growth and decline of a penguin colony and the influence on nesting density and reproductive success

Colonial breeding is characteristic of seabirds but nesting at high density has both advantages and disadvantages and may reduce survival and fecundity. African penguins (Spheniscus demersus) initiated breeding at Robben Island, South Africa in 1983. The breeding population on the island increased in the late 1990s and early 2000s before decreasing rapidly until 2010. Before the number breeding peaked, local nest density in the areas where the colony was initiated plateaued, suggesting that preferred nests sites were mostly occupied, and the area used by breeding birds expanded. However, it did not contract again as the population decreased, so that nesting density varied substantially. Breeding success was related positively to the prey available to the breeding birds and negatively to local nest density, particularly during the chick-rearing period, suggesting a density-dependence operating through social interactions in the colony, possibly exacerbated by poor prey availability when the breeding population was large. Although nest density at Robben Island was not high, nesting burrows, which probably reduce the incidence of aggressive encounters in the colony, are scarce and our results suggest that habitat alteration has modified the strength of density-dependent relationships for African penguins. Gaining a better understanding of how density dependence affects fecundity and population growth rates in colonial breeders is important for informing conservation management of the African penguin and other threatened taxa.     

Design and synthesis of novel dasatinib derivatives as inhibitors of leukemia stem cells

We used the concept of bioisosteres to design and synthesize a novel series of dasatinib derivatives for the treatment of leukemia. Unfortunately, most of the dasatinib derivatives did not show appreciable inhibition against leukemia cell lines K562 and HL60. However, acrylamide compound 2c had comparable inhibitory activity with dasatinib against K562 cells (IC₅₀?=?0.039?nM vs. 0.069?nM). And amide compound 2a and acrylamide compound 2c also had comparable inhibitory activity with dasatinib against the leukemia cell line HL60 (IC₅₀?=?0.25?nM and 0.26?nM vs. 0.11?nM). Against the leukemia progenitor cell line KG1a, triazole compounds 15a and 15d–15f and oxadiazole compounds 24a–24d were more potent than dasatinib. In particular, the hydroxyl compounds 15a and 24a were about 64 and 180 fold more potent than dasatinib against KG1a cells (IC₅₀?=?0.14?μM and 0.05?μM vs. 8.98?μM). Compounds 15a and 24a also inhibited colony formation in MCF-7 cells and inhibited cell migration in the cell wound scratch assay in B16BL6 cells. Moreover, hydroxyl compounds 15a and 24a had low toxicity in vivo.