Evolution of heterospecific attraction: using other species as cues in habitat selection

We analyzed the ecological conditions that may favor a habitat selection process in which later arriving individuals (colonists) use the presence of earlier established species (residents) as a cue to profitable breeding sites (heterospecific attraction). In our model, colonists assessing potential breeding patches could select between high-quality source and low-quality sink patches. A proportion of the source patches were occupied by residents. Colonists could either directly sample the relative quality of the patches (termed samplers) or, alternatively, they could also use residents as a cue of patch quality (cue-users). Cue-users gained benefit from lowered costs when assessing occupied source patches. The cue-using strategy is an efficient way to choose the best possible patch not only when interspecific competition is intense, but also when benefits from social aggregation exceed the effects of competition. High relative cost of sampling empty patches increases the fitness of the cue-using strategy relative to samplers. The strongest attraction to heterospecifics was predicted when the benefit from aggregating with residents exceeded the effects of competition, and approximately half of the landscape consisted of occupied, high-quality source patches.     

Subfamily III of mammalian oxysterol-binding protein (OSBP) homologues: the expression and intracellular localization of ORP3, ORP6, and ORP7

The human OSBP related protein (ORP) family consists of 12 members, which can be divided into six subfamilies based on the genomic organization and amino acid homology. Here we performed basic characterization of subfamily III, which consists of three members: ORP3, ORP6, and ORP7. According to cDNA hybridization, the three genes are expressed in a tissue-specific manner. While ORP3 mRNA is most abundant in kidney, lymph nodes, and thymus, ORP6 shows highest expression in brain and skeletal muscle, and ORP7 in the gastrointestinal tract. Using monospecific peptide antibodies, we confirmed the presence of the three proteins in human and mouse tissues. ORP6 gene expression was induced upon differentiation of F9 embryonic carcinoma cells into parietal endoderm, while ORP3 and ORP7 mRNA levels were unchanged. In the F9 cells, endogenous ORP6 associated predominantly with the nuclear envelope. When expressed from the cDNA in cultured cells, the three proteins were distributed between the cytosol and endoplasmic reticulum (ER) membranes, with a minor portion found at the plasma membrane. Experiments with truncated constructs showed that the N-terminal portion of the proteins, containing a pleckstrin homology (PH) domain, has markedly strong plasma membrane targeting specificity, while the C-terminal half remains largely cytosolic. The expression data demonstrates that ORP3, -6, and -7 are not merely redundant gene products but show marked quantitative differences in tissue expression, suggesting tissue-specific aspects in their function. The dual targeting of the proteins indicates a putative role in communication between the ER and the plasma membrane.This study was supported by the Clinical Research Fund of Helsinki University Central Hospital (J.T.), the Academy of Finland (grant 51883 to M.L.; grants 49987, 50641, and 54301 to V.M.O.), the Sigrid Juselius Foundation, and the Finnish Cultural Foundation     

BAPS 2: enhanced possibilities for the analysis of genetic population structure

Bayesian statistical methods based on simulation techniques have recently been shown to provide powerful tools for the analysis of genetic population structure. We have previously developed a Markov chain Monte Carlo (MCMC) algorithm for characterizing genetically divergent groups based on molecular markers and geographical sampling design of the dataset. However, for large-scale datasets such algorithms may get stuck to local maxima in the parameter space. Therefore, we have modified our earlier algorithm to support multiple parallel MCMC chains, with enhanced features that enable considerably faster and more reliable estimation compared to the earlier version of the algorithm. We consider also a hierarchical tree representation, from which a Bayesian model-averaged structure estimate can be extracted. The algorithm is implemented in a computer program that features a user-friendly interface and built-in graphics. The enhanced features are illustrated by analyses of simulated data and an extensive human molecular dataset. AVAILABILITY: Freely available at http://www.rni.helsinki.fi/~jic/bapspage.html.     

PLTP secreted by HepG2 cells resembles the high-activity PLTP form in human plasma

Plasma phospholipid transfer protein (PLTP) is an important regulator of plasma HDL levels and HDL particle distribution. PLTP is present in plasma in two forms, one with high and the other with low phospholipid transfer activity. We have used the human hepatoma cell line, HepG2, as a model to study PLTP secreted from hepatic cells. PLTP activity was secreted by the cells into serum-free culture medium as a function of time. However, modification of a previously established ELISA assay to include a denaturing sample pretreatment with the anionic detergent sodium dodecyl sulphate was required for the detection of the secreted PLTP protein. The HepG2 PLTP could be enriched by Heparin-Sepharose affinity chromatography and eluted in size-exclusion chromatography at a position corresponding to the size of 160 kDa. PLTP coeluted with apolipoprotein E (apoE) but not with apoB-100 or apoA-I. A portion of PLTP was retained by an anti-apoE immunoaffinity column together with apoE, suggesting an interaction between these two proteins. Furthermore, antibodies against apoE but not those against apoB-100 or apoA-I were capable of inhibiting PLTP activity. These results show that the HepG2-derived PLTP resembles in several aspects the high-activity form of PLTP found in human plasma.     

Ultrasound indentation of bovine knee articular cartilage in situ

We have earlier developed a handheld ultrasound indentation instrument for the diagnosis of articular cartilage degeneration. In ultrasound indentation, cartilage is compressed with the ultrasound transducer. Tissue thickness and deformation are calculated from the A-mode ultrasound signal and the stress applied is registered with the strain gauges. In this study, the applicability of the ultrasound indentation instrument to quantify site-dependent variation in the mechano-acoustic properties of bovine knee cartilage was investigated. Osteochondral blocks (n=6 per site) were prepared from the femoral medial condyle (FMC), the lateral facet of the patello-femoral groove (LPG) and the medial tibial plateau (MTP). Cartilage stiffness (dynamic modulus, E(dyn)), as obtained with the ultrasound indentation instrument in situ, correlated highly linearly (r=0.913, p<0.01) with the values obtained using the reference material-testing device in vitro. Reproducibility (standardized coefficient of variation) of the ultrasound indentation measurements was 5.2%, 1.7% and 3.1% for E(dyn), ultrasound reflection coefficient of articular surface (R) and thickness, respectively. E(dyn) and R were site dependent (p<0.05, Kruskall-Wallis H test). E(dyn) was significantly higher (p<0.05, Kruskall-Wallis Post Hoc test) in LPG (mean+/-SD: 10.1+/-3.1MPa) than in MTP (2.9+/-1.4MPa). In FMC, E(dyn) was 4.6+/-1.3MPa. R was significantly (p<0.05) lower at MTP (2.0+/-0.7%) than at other sites (FMC: 4.2+/-0.9%; LPG: 4.4+/-0.8%). Cartilage glycosaminoglycan concentration, as quantified with the digital densitometry, correlated positively with E(dyn) (r=0.678, p<0.01) and especially with the equilibrium Young's modulus (reference device, r=0.874, p<0.01) but it was not associated with R (r=0.294, p=0.24). We conclude that manual measurements are reproducible and the instrument may be used for detection of cartilage quality in situ. Especially, combined measurement of thickness, E(dyn) and R provides valuable diagnostic information on cartilage status.     

Genetic polymorphism of the human ICOS gene

Inducible costimulator (ICOS) is a novel receptor belonging to the same family as CD28 and CTLA4, which regulate T-lymphocyte activation in the immune response. The genes for these molecules are located adjacent to each other on Chromosome 2q33. Many autoimmune diseases have been found to be genetically linked to or associated with genetic markers near the CTLA4 gene. However, as all three genes are closely linked and have related functions, it is possible that the findings could be explained by variation in CD28 or ICOS. Few data on genetic variation in the ICOS gene are available. We sequenced the ICOS gene in 13 healthy unrelated individuals and found eight single nucleotide polymorphisms. One was located in the first intron, and the others in the untranslated region of the last exon. The allele frequencies and linkage disequilibrium were determined from a population sample of 63 Finnish individuals. The results show that the ICOS gene is polymorphic, but no variation in the coding sequence was detected, implying that the genetic linkage of this gene region to autoimmune diseases may not result from structural variation in the ICOS molecule. These polymorphisms, however, should be useful in genetic studies of this candidate gene.     

Effects of ovariectomy and estrogen treatment on learning and hippocampal neurotransmitters in mice

This study examined the effects of long-term estrogen treatment (sc 17 beta-estradiol minipellets) on learning in C57BL/6J female and male mice using a position discrimination task in the T-maze and a win-stay task (1/8 arms baited) in the radial arm maze (RAM). In addition, hippocampal monoamines and ChAT activity were measured at the end of the study and correlated to task performance. Female sham-operated (gonadally intact) and ovariectomized (OVX) mice were treated with estrogen either for 7 or 40 days before the behavioral tests and intact male mice for 7 days before the behavioral tests. In sham-operated mice the 40-day estrogen treatment improved RAM performance and in OVX mice both the 7- and 40-day estrogen treatments improved the performance in both maze tasks. The estrogen treatment also improved RAM performance in males. The hippocampal ChAT, NA, 5-HIAA, and DOPAC levels were decreased in OVX mice. Furthermore, the effects of estrogen treatment on the levels of hippocampal 5-HT and its metabolite 5-HIAA were different in sham-operated than in OVX mice. We could find no correlation between cognitive measures and neurochemical variables. This study gives new information about the effects of estrogen on learning and hippocampal neurotransmitters in mice.     

FGFR1 is required for the development of the auditory sensory epithelium

The mammalian auditory sensory epithelium, the organ of Corti, comprises the hair cells and supporting cells that are pivotal for hearing function. The origin and development of their precursors are poorly understood. Here we show that loss-of-function mutations in mouse fibroblast growth factor receptor 1 (Fgfr1) cause a dose-dependent disruption of the organ of Corti. Full inactivation of Fgfr1 in the inner ear epithelium by Foxg1-Cre-mediated deletion leads to an 85% reduction in the number of auditory hair cells. The primary cause appears to be reduced precursor cell proliferation in the early cochlear duct. Thus, during development, FGFR1 is required for the generation of the precursor pool, which gives rise to the auditory sensory epithelium. Our data also suggest that FGFR1 might have a distinct later role in intercellular signaling within the differentiating auditory sensory epithelium.     

Development of an automation system for a tablet coater

An instrumentation and automation system for a side-vented pan coater with a novel air-flow rate measurement system for monitoring the film-coating process of tablets was designed and tested. The instrumented coating system was tested and validated by film-coating over 20 pilot-scale batches of tablets with aqueous-based hydroxypropyl methylcellulose (HPMC). Thirteen different process parameters were continuously measured and monitored, and the most significant ones were logged for analysis. Laser profilometry was used to measure the surface roughness of the coated tablets. The instrumentation system provided comprehensive and quantitative information on the process parameters monitored. The measured process parameters and the responses of the film-coated tablet batches showed that the coating process is reproducible. The inlet air-flow rate influenced the coating process and the subsequent quality of the coated tablets. Increasing the inlet flow rate accelerated the drying of the tablet surface. At high inlet flow rate, obvious film-coating defects (ie, unacceptable surface roughness of the coated tablets) were observed and the loss of coating material increased. The instrumented and automated pancoating system described, including historical data storage capability and a novel air-flow measurement system, is a useful tool for controlling and characterizing the tablet film-coating process. Monitoring of critical process parameters increases the overall coating process efficiency and predictability.