Do male hoots betray parasite loads in Tawny Owls?

Bird song structure may honestly reveal the health and vigour of individual males to potential mates and competitors. If this is the case then song may reflect the level of parasitic infections in males. We initially examined the relationship between blood parasite infections and the time taken to respond by 22 male Tawny Owls to a broadcast hoot. We then examined the call structure (total length and frequency) in relation to parasite infection, an index of owl condition and an index of food abundance. Owls with higher parasite loads responded more slowly to an intruder, although this relationship was not significant once condition and vole abundance were controlled for. We found no relationship between call length and any of the measured variables. However, the high frequency and the range of frequencies used in calls decreased with increasing parasite load. Thus, there was the potential for individuals to assess male parasite load from the speed of response and the structure of the call. Experimental tests of these relationships are now required.     

Comparative development of Cryptosporidium parvum (Apicomplexa) in 11 continuous host cell lines

Abstract Using standardized media, incubation, and parasite inoculating procedures, we compared development of Crytosporidium parvum between Madin-Darby bovine kidney (MDBK) cells and 10 additional host cell lines available through the American Type Culture Collection. Parasite development was assessed by counting parasite numbers atop monlayers in 25 random oil fields 68 h post-infection using Nomarski interference-contrast optics. Results revealed that the human ileocecal adenocarcinoma (HCT-8) cell line supported nearly twice the number of parasite developmental stages than MDBK cells or any of the other host cell types.     

Decrease in ribosomal proteins 1, 2/3, L4, and L7 in Drosophila melanogaster in the absence of X rDNA

Summary The rRNA genes (rDNA) in Drosophila melanogaster are found in two clusters, one on the X and one on the Y chromosome. We have compared the ribosomal protein composition of wild-type Oregon-R flies containing both X-linked and Y-linked rDNA with that of flies containing only the Y-linked rDNA by two-dimensional polyacrylamide gel electrophoresis. Four basic proteins (1, 2/3, L4, and L7) normally present in wild-type flies were either electrophoretically not detectable (1, 2/3, and L4) or marginally detectable (L7) in flies with only Y-linked rDNA. No additional proteins were observed in these flies. However, immunodiffusion assays using specific antibodies raised against purified protein L4 confirmed that L4 was present but in relatively lower amounts in these Y-linked rDNA flies. An investigation was carried out to determine whether these electrophoretically undetectable proteins were more readily lost during ribosome preparation and hence were not readily detectable in the 80S particles by gel electrophoresis or whether they had been modified. Thus the proteins in the post-ribosomal cell supernatant and the high salt sucrose gradient were analyzed by two-dimensional gel electrophoresis and immunochemical assays with antibodies raised against protein L4 and total 80S ribosomal proteins. The experimental evidence indicates that there is a small amount of protein L4 and probably proteins 1, 2/3, and L7 in flies with only Y-linked rDNA but significantly less of these proteins than in wild-type flies.     

The effects of Cu on the adenylate energy charge of open ocean phytoplankton

The effects of short-term, acute Cu exposure (6 h) on the adenylateenergy charge (EC_A) of open-ocean phytoplankton populations(northeastern equatorial Pacific) were investigated. Energycharge remained at {small tilde}0.77 over the range of Cu additions(0.025 – 5.µg l^–1), even though ¹⁴C uptakeand total adenylate levels (ATP + ADP + AMP) were reduced byas much as 60%. These findings suggest that EC_A alone is nota sensitive indicator of acute sublethal metal effects on phytoplankton. ¹This research was supported by the NSF Biological OceanographyProgram grant #OCE 81-17286.     

An allied reprogramming,selection, expansion and differentiation platform for creating hiPSC on microcarriers

ObjectivesInduced pluripotent stem cells (iPSCs) generated by monolayer cultures is plagued by low efficiencies, high levels of manipulation and operator unpredictability. We have developed a platform, reprogramming, expansion, and differentiation on Microcarriers, to solve these challenges.Materials and MethodsFive sources of human somatic cells were reprogrammed, selected, expanded and differentiated in microcarriers suspension cultures.ResultsImprovement of transduction efficiencies up to 2 times was observed. Accelerated reprogramming in microcarrier cultures was 7 days faster than monolayer, providing between 30 and 50‐fold more clones to choose from fibroblasts, peripheral blood mononuclear cells, T cells and CD34+ stem cells. This was observed to be due to an earlier induction of genes (β‐catenin, E‐cadherin and EpCAM) on day 4 versus monolayer cultures which occurred on days 14 or later. Following that, faster induction and earlier stabilization of pluripotency genes occurred during the maturation phase of reprogramming. Integrated expansion without trypsinization and efficient differentiation, without embryoid bodies formation, to the three germ‐layers, cardiomyocytes and haematopoietic stem cells were further demonstrated.ConclusionsOur method can solve the inherent problems of conventional monolayer cultures. It is highly efficient, cell dissociation free, can be operated with lower labor, and allows testing of differentiation efficiency without trypsinization and generation of embryoid bodies. It is also amenable to automation for processing more samples in a small footprint, alleviating many challenges of manual monolayer selection.

We have developed an allied protocol for reprogramming, selecting, expanding and differentiating human pluripotent stem cells on Microcarriers (designated as RepMC). This method allows faster reprogramming, selecting 30‐50‐fold more candidates for characterization and also allows us to find high quality candidates that differentiate to cardiomyocytes and blood lineages. Mechanistically, this method appears to accelerate the induction, maturation and stabilization phases of reprogramming. Our findings help simplify the process of deriving and expanding iPSCs for therapeutic applications, offering a robust and scalable suspension platform for large‐scale generation of clinical grade iPSCs.     

Identification of low frequency knockout mutants in Dictyostelium discoideum created by single or double homologous recombination

Generation and characterization of knockout clones is a widely used approach to evaluate the specific function of a gene product in Dictyostelium discoideum. The mutant clones are generally obtained by double homologous recombination in the target gene. A frequent limitation to obtaining mutants is the low frequency of homologous recombination. Here we present an easy method to identify rare mutants, based on PCR analysis of pools of clones. This method also allows the isolation of functional knockout mutants created by a single homologous recombination event, which can be more frequent than a double recombination event.