Phosphatidylcholine and the CDP–choline cycle

The CDP–choline pathway of phosphatidylcholine (PtdCho) biosynthesis was first described more than 50 years ago. Investigation of the CDP–choline pathway in yeast provides a basis for understanding the CDP–choline pathway in mammals. PtdCho is considered as an intermediate in a cycle of synthesis and degradation, and the activity of a CDP–choline cycle is linked to subcellular membrane lipid movement. The components of the mammalian CDP–choline pathway include choline transport, choline kinase, phosphocholine cytidylyltransferase, and choline phosphotransferase activities. The protein isoforms and biochemical mechanisms of regulation of the pathway enzymes are related to their cell‐ and tissue-specific functions. Regulated PtdCho turnover mediated by phospholipases or neuropathy target esterase participates in the mammalian CDP–choline cycle. Knockout mouse models define the biological functions of the CDP–choline cycle in mammalian cells and tissues. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.     

Selenoprotein expression and function—Selenoprotein W

Selenoprotein W (SeW) is a small selenoprotein (85 to 88 amino acids) first identified in sheep suffering from selenium deficiency. The levels are highest in muscle, heart (except rodents) spleen and brain. The deduced amino acid sequence has been obtained for mice, rats, monkeys, humans, sheep, pigs, fish and chickens. The sequences of SeW are identical in rats and mice as well as monkeys and humans. In all eight species of animals cysteine is present at residue number 9 and selenocysteine at residue number 13. Residue number 37 is cysteine in six species of animal with fish and chickens as the exceptions. Of those examined, the rodent SeW is the only one containing four cysteines whereas the others contain only two cysteines. Glutathionylaltion has been shown for SeW from rats and monkeys but has not been confirmed for this selenoprotein from the other six animals. The biological function of SeW has not been definitely identified. Evidence has been obtained that it can serve as an antioxidant, responds to stress, involved in cell immunity, specific target for methylmercury, and has thioredoxin-like function.     

Differentiation of endoplasmic reticulum in the developing oocyte of the golden hamster (Mesocricetus auratus)

Summary The differentiation of the endoplasmic reticulum (ER) in the developing oocyte of the golden hamster is accompanied by changes in susceptibility to impregnation with a zinc iodide-osmium tetroxide (ZnOs) mixture. The staining of two of the three categories of oocyte ER is first seen at or about the time when rapid oocyte growth is initiated. Staining reaches a peak before antrum formation, then declines. A third category of ER remains unstained at all stages. Aberrant reactivity to ZnOs is seen in oocytes which become atretic, and differs with the stage of oocyte development at which atresia occurs.Relationships between the three categories are described, and an attempt made to relate changes in form and distribution to developmental processes. The frequent contact/continuity between ER and mitochondria is discussed with regard to its possible role in lipid metabolism.     

Comparison of Mandibular Phenotypic and Genetic Integration between Baboon and Mouse

In this study we compare patterns of mandibular integration between mice and baboons using both phenotypic and quantitative genetic data. Specifically, we test how well each species fits with the mosaic model of mandibular integration suggested by Atchley and Hall (Biol Rev Camb Philos Soc 66:101–157, 1991) based on developmental modules. We hypothesize that patterns of integration will be similar for mice and baboons and that both species will show strong integration within developmental modules and weaker integration between modules. Corresponding landmark data were collected from the hemi-mandibles of an advanced intercross mouse sample (N = 1239) and mandibles from a baboon sample of known pedigree from the Southwest Foundation for Biomedical Research (N = 430). We used four methods of analysis to quantify and compare the degree of mandibular integration between species including two methods based on a priori assumptions, and two a posteriori analyses. We found that patterns of integration are broadly similar for baboon and mouse mandibles, with both species displaying a modular pattern of integration. While there is a general trend of similarity in integration patterns between species, there were some marked differences. Mice are strongly correlated among distances within the coronoid process and the incisive alveolar region, whereas baboons are strongly integrated within the condylar process. We discuss the potential evolutionary implications of the similar patterns of integration between these species with an emphasis on the role of modularity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spatial organization of cell-adhesive ligands for advanced cell culture

Interaction between biomaterials and cells is a critical aspect for successful application of tissue engineering research. Technological advances within the past decade have enabled a number of studies to investigate how the spatial organization of cell-adhesive ligands impacts complex and rich cell behaviors ranging from adhesion to differentiation. Cells in their native environment are surrounded by chemical and physical factors spanning a range of length scales from nanometers to hundreds of microns. Furthermore, signals in the form of cell-adhesive ligands presented from this environment in different size scales and/or geometrical arrangements can change how a cell senses and responds to its surroundings. Biology can thus convey information not only in the concentration of a ligand but through its ability to change the spatial organization of these cues, raising questions both on the mechanisms by which it patterns such information and on the means by which a cell interprets it. This review discusses major findings associated with various systems developed to study cell-adhesive ligand presentation as well as an overview of the important material systems used in these studies. Promising material systems to further investigations in this field are also examined. Future directions will likely include determining how cells sense local and global ligand concentrations, understanding underlying mechanisms that regulate cell behaviors, and investigating the function of more complex cell types and diverse ligands.     

Distribution,ontogeny and ultrastructure of the mammalian secretin cell

Summary Immunocytochemically, secretin cells have been demonstrated to occur in the duodenum and jejunum of several mammals. Calculations on the relative frequency of such cells indicate that the bulk of secretin occurs in the jejunum, a fact supporting the view that secretin may be released by physiological stimulants other than hydrochloric acid. Electron microscopical identification of cat and pig secretin cells confirmed their identity with the ultrastructurally defined S cells, and staining experiments revealed that secretin cells were argyrophilic both with the method of Grimelius and with that of Hellerström and Hellman. Secretin cells are detected already in the 17-day old fetal rat duodenum and show a developmental pattern similar to that displayed by the gastrin cells. It is suggested that secretin may play a role in the early regulation of growth of the fetal gastrointestinal tract. Acknowledgements: Supported by grants from the Danish and Swedish MRC     

Functional Analyses of Mammalian Reovirus Nonstructural Protein uNS

Genome replication of reovirus occurs in cytoplasmic inclusion bodies called viral factories or viroplasms. The viral nonstructural protein uNS, encoded by genome segment M3, is not a component of mature virions, but is expressed to high levels in infected cells and is concentrated in the infected cell factory matrix. Recent studies have demonstrated that uNS plays a central role in forming the matrix of these structures, as well as in recruiting other components to them for putative roles in genome replication and particle assembly.     

Interactions between terrestrial mammals and the fruits of two neotropical rainforest tree species

Mammalian frugivory is a distinctive biotic interaction of tropical forests; however, most efforts in the Neotropics have focused on cases of animals foraging in the forest canopy, in particular primates and bats. In contrast much less is known about this interaction when it involves fruits deposited on the forest floor and terrestrial mammals. We conducted a camera-trapping survey to analyze the characteristics of the mammalian ensembles visiting fruits of Licania platypus and Pouteria sapota deposited on the forest floor in a well preserved tropical rainforest of Mexico. Both tree species produce large fruits but contrast in their population densities and fruit chemical composition. In particular, we expected that more species of terrestrial mammals would consume P. sapota fruits due to its higher pulp:seed ratio, lower availability and greater carbohydrate content. We monitored fruits at the base of 13 trees (P. sapota, n = 4 and L. platypus, n = 9) using camera-traps. We recorded 13 mammal species from which we had evidence of 8 consuming or removing fruits. These eight species accounted for 70% of the species of mammalian frugivores active in the forest floor of our study area. The ensemble of frugivores associated with L. platypus (6 spp.) was a subset of that associated with P. sapota (8 spp). Large body-sized species such as Tapirus bairdii, Pecari tajacu and Cuniculus paca were the mammals more frequently interacting with fruits of the focal species. Our results further our understanding of the characteristics of the interaction between terrestrial mammalian frugivores and large-sized fruits, helping to gain a more balanced view of its importance across different tropical forests and providing a baseline to compare against defaunated forests.