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Articles 1 - 14 of 14
Full-Text Articles in Social and Behavioral Sciences
Role Of The Epididymis In Sperm Competition, Russell Jones, Jl Dacheux, Brett Nixon, Heath Ecroyd
Role Of The Epididymis In Sperm Competition, Russell Jones, Jl Dacheux, Brett Nixon, Heath Ecroyd
Heath Ecroyd
Although it is generally understood that the testes recruited kidney ducts for reproductive function during the evolution of vertebrates, little is understood of the biological significance of the adaptation. In the context of the evolution of the mammalian epididymis, this report provides evidence that a major role of the epididymis is to enhance a male's chance of achieving paternity in a competitive mating system. A unique example of sperm cooperation, in monotremes is used as evidence that the epididymis produces sperm competition proteins to form groups of 100 sperm into bundles that have a forward motility nearly thrice that of …
Tyrosine Phosphorylation Of Hsp-90 During Mammalian Sperm Capacitation, Heath Ecroyd, Russell Jones, Robert Aitken
Tyrosine Phosphorylation Of Hsp-90 During Mammalian Sperm Capacitation, Heath Ecroyd, Russell Jones, Robert Aitken
Heath Ecroyd
The process of sperm capacitation is correlated with activation of a signal transduction pathway leading to protein tyrosine phosphorylation. Whereas phosphotyrosine expression is an essential prerequisite for fertilization, the proteins that are phosphorylated during capacitation have not yet been identified. In the present study, we observed that a major target of this signaling pathway is the molecular chaperone protein, heat shock protein (HSP)-86, a member of the HSP-90 family of HSPs. We used cross-immunoprecipitation experiments to confirm the tyrosine phosphorylation of HSP-86, a process that is not inhibited by the ansamycin antibiotic, geldanamycin. The general significance of these findings was …
Dissociation From The Oligomeric State Is The Rate-Limiting Step In Fibril Formation By Kappa-Casein, Heath Ecroyd, Tomas Koudelka, David Thorn, Danielle Williams, Glyn Devlin, Peter Hoffmann, John Carver
Dissociation From The Oligomeric State Is The Rate-Limiting Step In Fibril Formation By Kappa-Casein, Heath Ecroyd, Tomas Koudelka, David Thorn, Danielle Williams, Glyn Devlin, Peter Hoffmann, John Carver
Heath Ecroyd
Amyloid fibrils are aggregated and precipitated forms of protein in which the protein exists in highly ordered, long, unbranching threadlike formations that are stable and resistant to degradation by proteases. Fibril formation is an ordered process that typically involves the unfolding of a protein to partially folded states that subsequently interact and aggregate through a nucleation-dependent mechanism. Here we report on studies investigating the molecular basis of the inherent propensity of the milk protein, kappa-casein, to form amyloid fibrils. Using reduced and carboxymethylated kappa-casein ( RCM kappa-CN), we show that fibril formation is accompanied by a characteristic increase in thioflavin …
The Effect Of Small Molecules In Modulating The Chaperone Activity Of Alpha B-Crystallin Against Ordered And Disordered Protein Aggregation, Heath Ecroyd, John Carver
The Effect Of Small Molecules In Modulating The Chaperone Activity Of Alpha B-Crystallin Against Ordered And Disordered Protein Aggregation, Heath Ecroyd, John Carver
Heath Ecroyd
Protein aggregation can proceed via disordered or ordered mechanisms, with the latter being associated with amyloid fibril formation, which has been linked to a number of debilitating conditions including Alzheimer's, Parkinson's and Creutzfeldt-Jakob diseases. Small heat-shock proteins (sHsps), such as alpha B-crystallin, act as chaperones to prevent protein aggregation and are thought to play a key role in the prevention of protein-misfolding diseases. In this study, we have explored the potential for small molecules such as arginine and guanidine to affect the chaperone activity of alpha B-crystallin against disordered (amorphous) and ordered (amyloid fibril) forms of protein aggregation. The effect …
Analysis Of The Mechanism By Which Calcium Negatively Regulates The Tyrosine Phosphorylation Cascade Associated With Sperm Capacitation, Mark Baker, Louise Hethrington, Heath Ecroyd, Shaun Roman, Robert Aitken
Analysis Of The Mechanism By Which Calcium Negatively Regulates The Tyrosine Phosphorylation Cascade Associated With Sperm Capacitation, Mark Baker, Louise Hethrington, Heath Ecroyd, Shaun Roman, Robert Aitken
Heath Ecroyd
The capacitation of mammalian spermatozoa involves the activation of a cAMP-mediated signal transduction pathway that drives tyrosine phosphorylation via mechanisms that are unique to this cell type. Controversy surrounds the impact of extracellular calcium on this process, with positive and negative effects being recorded in independent publications. We clearly demonstrate that the presence of calcium in the external medium decreases tyrosine phosphorylation in both human and mouse spermatozoa. Under these conditions, a rise in intracellular pH was recorded, however, this event was not responsible for the observed changes in phosphotyrosine expression. Rather, the impact of calcium on tyrosine phosphorylation in …
The Two Faced Nature Of Milk Casein Proteins: Amyloid Fibril Formation And Chaperone-Like Activity, David Thorn, Heath Ecroyd, John Carver
The Two Faced Nature Of Milk Casein Proteins: Amyloid Fibril Formation And Chaperone-Like Activity, David Thorn, Heath Ecroyd, John Carver
Heath Ecroyd
Molecular chaperones are a diverse group of proteins that stabilise partially folded target proteins to prevent their misfolding, aggregation and potential precipitation under conditions of cellular stress, e.g. elevated temperature. Protein aggregation, particularly the formation of highly ordered protein aggregates termed amyloid fibrils, is of considerable research interest because of its intimate association with a wide range of debilitating diseases, including Alzheimer's, Parkinson's and Huntington's diseases and type II diabetes. In this review, we discuss the ability of the milk casein proteins to act in a chaperone-like manner. This property is of biological importance since at least two of the …
Post-Testicular Sperm Environment And Fertility, Jean-Luc Gatti, Sandrine Castella, Francoise Dacheux, Heath Ecroyd, S Metayer, Veronique Thimon, Jean-Louis Dacheux
Post-Testicular Sperm Environment And Fertility, Jean-Luc Gatti, Sandrine Castella, Francoise Dacheux, Heath Ecroyd, S Metayer, Veronique Thimon, Jean-Louis Dacheux
Heath Ecroyd
When mammalian spermatozoa exit the testis, they show a highly specialized morphology; however, they are not yet able to carry out their task: to fertilize an oocyte. This property, that includes the acquisition of motility and the ability to recognize and to fuse with the oocyte investments, is gained only after a transit through the epididymis during which the spermatozoa from the testis travel to the vas deferens. The exact molecular mechanisms that turn these cells into fertile gametes still remain mysterious, but surface-modifying events occurring in response to the external media are key steps in this process. Our laboratory …
Testicular Descent, Sperm Maturation And Capacitation. Lessons From Our Most Distant Relatives, The Monotremes, Russell Jones, Heath Ecroyd, Jean-Louis Dacheux, Brett Nixon
Testicular Descent, Sperm Maturation And Capacitation. Lessons From Our Most Distant Relatives, The Monotremes, Russell Jones, Heath Ecroyd, Jean-Louis Dacheux, Brett Nixon
Heath Ecroyd
The present review examines whether monotremes may help to resolve three questions relating to sperm production in mammals: why the testes descend into a scrotum in most mammals, why spermatozoa are infertile when they leave the testes and require a period of maturation in the specific milieu provided by the epididymides, and why ejaculated spermatozoa cannot immediately fertilise an ovum until they undergo capacitation within the female reproductive tract. Comparisons of monotremes with other mammals indicate that there is a need for considerable work on monotremes. It is hypothesised that testicular descent should be related to epididymal differentiation. Spermatozoa and …
Beyond Multiple Regression: Using Commonality Analysis To Better Understand R2 Results, Russell Warne
Beyond Multiple Regression: Using Commonality Analysis To Better Understand R2 Results, Russell Warne
Russell T Warne
Multiple regression is one of the most common statistical methods used in quantitative educational research. Despite the versatility and easy interpretability of multiple regression, it has some shortcomings in the detection of suppressor variables and for somewhat arbitrarily assigning values to the structure coefficients of correlated independent variables. Commonality analysis—heretofore rarely used in gifted education research—is a statistical method that partitions the explained variance of a dependent variable into nonoverlapping parts according to the independent variable(s) that are related to each portion. This Methodological Brief includes an example of commonality analysis and equations for researchers who wish to conduct their …
How Do Environmental And Natural Resource Economics Texts Deal With The Simple Model Of The Intertemporal Allocation Of A Nonrenewable Resource, Robert Main
Robert S. Main
Textbooks in Environmental and Natural Resource Economics invariably deal with the problem of allocating a non-renewable resource over time. The simplest version of that problem is the case of a resource that is to be allocated over two periods. The resource has a constant Marginal Extraction Cost (MEC). Most textbooks treat this case before moving on to more complex and realistic cases. This paper suggests the results that should be emphasized and the method that should be used to arrive at those results. It also points out the possible confusions that should be avoided. Finally, it examines how several well-known …
Publishing Survey Articles On Information Retrieval Topics, Douglas Oard, Fabrizio Sebastiani, Jonathan Furner, Gary Marchionini
Publishing Survey Articles On Information Retrieval Topics, Douglas Oard, Fabrizio Sebastiani, Jonathan Furner, Gary Marchionini
Jonathan Furner
Survey articles are an important way of sharing knowledge among interested researchers and contributing to the growth of a field. This brief note identifies several outlets for survey articles on information retrieval, and identifies some reasons to write articles of this type.
Hayek's Philosophical Psychology, Leslie Marsh
Hayek's Philosophical Psychology, Leslie Marsh
Leslie Marsh
Hayek's philosophical psychology as set out in his The Sensory Order (1952) has, for the most part, been neglected. Despite being lauded by computer scientist grandee Frank Rosenblatt and by Nobel prize-winning biologist Gerald Edelman, cognitive scientists -- with a few exceptions -- have yet to discover Hayek's philosophical psychology. On the other hand, social theorists, Hayek's traditional disciplinary constituency, have only recently begun to take note and examine the importance of psychology in the complete Hayek corpus. This volume brings together for the first time state-of-the-art contributions from neuroscientists and philosophers of mind as well as economists and social …
Business Ethics As Rational Choice, John Hooker
Gis And Paleoanthropology: Incorporating New Approaches From The Geospatial Sciences In The Analysis Of Primate And Human Evolution, Robert L. Anemone, Glenn C. Conroy, Charles W. Emerson
Gis And Paleoanthropology: Incorporating New Approaches From The Geospatial Sciences In The Analysis Of Primate And Human Evolution, Robert L. Anemone, Glenn C. Conroy, Charles W. Emerson
Robert L. Anemone
The incorporation of research tools and analytical approaches from the geospatial sciences is a welcome trend for the study of primate and human evolution. The use of remote sensing (RS) imagery and geographic information systems (GIS) allows vertebrate paleontologists, paleoanthropologists, and functional morphologists to study fossil localities, landscapes, and individual specimens in new and innovative ways that recognize and analyze the spatial nature of much paleoanthropological data. Whether one is interested in locating and mapping fossiliferous rock units in the field, creating a searchable and georeferenced database to catalog fossil localities and specimens, or studying the functional morphology of fossil …