The millennium ecosystem assessment: what is it all about?

Hundreds of scientists from over 70 nations are now engaged in an intensive effort to assess what we know about the status of the world's ecosystems. Here, we describe the fundamental nature of this assessment, what it hopes to accomplish and how it will go about its work. The results of the Millennium Ecosystem Assessment will serve as a baseline for future assessments, as well as a blueprint for action for sustaining the ecosystem services upon which we all depend for our well being.     

Optimization of energy coupling: what is all the argument about?

Although it may be asked how effective glycolysis is in retaining the chemical energy in the bonds of glucose during its breakdown in the formation of ATP, the reasons for the coupled pathway of glycolysis having evolved as it has are probably as much as a consequence of the need to find reactions that can lead to formation of phosphoryl groups able to transfer to ADP as to the overall thermodynamics of the pathway. It is not meaningful to talk of optimization of energy coupling solely in terms of free energy changes.     

Phosphorothioate oligodeoxynucleotides: what is their origin and what is unique about them?

The development of nucleoside phosphorothioates is described in its historical context. Examples of the interaction of phosphorothioate groups, present either in oligodeoxynucleotides or in DNA, with nucleases are presented. The structural features responsible for the resistance of the phosphorothioates toward degradation by nucleases are discussed, as are the possible reasons for the high-affinity interaction of phosphorothioate oligodeoxynucleotides with certain proteins.     

Mitochondria in cancer cells: what is so special about them?

The past decade has revealed a new role for the mitochondria in cell metabolism--regulation of cell death pathways. Considering that most tumor cells are resistant to apoptosis, one might question whether such resistance is related to the particular properties of mitochondria in cancer cells that are distinct from those of mitochondria in non-malignant cells. This scenario was originally suggested by Otto Warburg, who put forward the hypothesis that a decrease in mitochondrial energy metabolism might lead to development of cancer. This review is devoted to the analysis of mitochondrial function in cancer cells, including the mechanisms underlying the upregulation of glycolysis, and how intervention with cellular bioenergetic pathways might make tumor cells more susceptible to anticancer treatment and induction of apoptosis.     

What is all the noise about in interval timing?

Cognitive processes such as decision-making, rate calculation and planning require an accurate estimation of durations in the supra-second range—interval timing. In addition to being accurate, interval timing is scale invariant: the time-estimation errors are proportional to the estimated duration. The origin and mechanisms of this fundamental property are unknown. We discuss the computational properties of a circuit consisting of a large number of (input) neural oscillators projecting on a small number of (output) coincidence detector neurons, which allows time to be coded by the pattern of coincidental activation of its inputs. We showed analytically and checked numerically that time-scale invariance emerges from the neural noise. In particular, we found that errors or noise during storing or retrieving information regarding the memorized criterion time produce symmetric, Gaussian-like output whose width increases linearly with the criterion time. In contrast, frequency variability produces an asymmetric, long-tailed Gaussian-like output, that also obeys scale invariant property. In this architecture, time-scale invariance depends neither on the details of the input population, nor on the distribution probability of noise.     

Too much teaching, not enough learning: what is the solution?

The curriculum is packed with so much content that teachers resort to telling students what they know and students simply commit facts to memory. The packed curriculum leaves little time for students to acquire a deep understanding of the subject or to develop life-long skills such as critical thinking, problem solving, and communication. However, learning is not committing a set of facts to memory, but the ability to use resources to find, evaluate, and apply information. This paper addresses these concerns by discussing \"how we learn\" and reviewing the literature on what works to improve learning. It is clear that active processing of information, not passive reception of information, leads to learning. That is, students must construct their own understanding of concepts, relationships, and procedures. Teachers can encourage this process by carefully considering the type and organization of information as well as instructional strategies. Specifically, teachers should reduce the total amount of factual information students are expected to memorize, reduce our use of the passive lecture format, and devote much more effort to helping students become active, independent learners and problem solvers. Collaborative learning activities, interactive models, educational games, and establishing a culture of inquiry/scholarship are critical for achieving these goals.     

Venous ulcer: what is new?

The pathophysiology of venous dermal abnormality in chronic venous ulcers is reflective of a complex interplay that involves sustained venous hypertension, inflammation, changes in the microcirculation, cytokine and matrix metalloproteinase activation, and altered cellular function. Red blood cells and macromolecules extravasate into the interstitium and activate endothelial cells. Endothelial expression of specific adhesion molecules recruits leukocytes and causes diapedesis of these cells into the dermal microvasculature, promoting an inflammatory response with activation of cytokines and proteinases. Altered cell function enhances a state of vulnerability in the surrounding tissues, initiating specific changes associated with venous disease. Ultimately, the persistent inflammatory-proteinase activity leads to advanced chronic venous insufficiency and ulcer formation. The mainstay of therapy in venous ulcer abnormality is correction of the underlying venous hypertension through compression therapy and/or surgery. Understanding the science involved in the pathophysiology of venous ulcer formation has led to the development of adjunctive treatment directed at the dysregulated molecular pathways. Randomized clinical trials are critical for determining the most effective evidence-based treatments for venous ulcer, and this review discusses important trials that have had a significant impact on venous ulcer healing. In addition, the authors have included subsections referred to as "Translational Implications for Therapy" in the basic science sections of the review to help bridge the basic science knowledge with clinical applications that may help to modulate the molecular abnormalities in the pathophysiologic cascade leading to venous ulcers.     

Speciation on islands: what are we learning?

Systematics and the Origin of Species from the Viewpoint of a Zoologist has remained an essential text on the bookshelves of evolutionary biologists since it was first published. Here, I expand upon several topics touched upon by Ernst Mayr to look at how our thinking has evolved, and is evolving, with particular reference to molecular phylogenetic studies on islands. At the time of publication, apart from the fossil record, inferences of temporal trends or patterns could only be speculative, deduced from the distributions of species and the patterns that these present. Much like the subject material itself, evolutionary biology evolves as a discipline, with an increasing availability of tools and resources. The development of molecular phylogenetics and molecular markers has given biologists a new window on the past and, as such, the ideas and explanations of Mayr have become more accessible to testing. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 47–52.     

Invertebrate learning: what can't a worm learn?

The nematode worm Caenorhabditis elegans can learn and remember the stimuli it encounters, the environment it is in, and its own physiological state. Analyses of mutations in C. elegans that affect different aspects of experience are beginning to address the nature of learning.     

Population ageing: what should we worry about?

Approximately half the world''s population now has replacement-level fertility or below. The UK experience in accommodating to a changing dependency ratio provides some generalizable insights. A mechanistic approach assuming a fixed retirement age and a need to raise fertility or increase immigration in order to maintain pensions at a fixed proportion of the gross domestic product (GDP) is overstated and wrong. It needs to be replaced by a welfare optimizing model, which takes into account the increasing years of healthy life, a slow rise in the pensionable age, capital inheritance and wider welfare considerations of population density that are not reflected in GDP measures. A combined replacement ratio (CRR) is suggested for developed countries combining the impact of the fertility rate and immigration rate. A CRR above 2 implies continued population growth. The current UK CRR of 2.48 is higher than needed for pension reasons, and it is suggested that it exceeds the welfare maximizing level.