How are climate and marine biological outbreaks functionally linked?

Since the mid-1970s, large-scale episodic events such as disease epidemics, mass mortalities, harmful algal blooms and other population explosions have been occurring in marine environments at an historically unprecedented rate. The variety of organisms involved (host, pathogens and other opportunists) and the absolute number of episodes have also increased during this period. Are these changes coincidental? Between 1972 and 1976, a global climate regime shift took place, and it is manifest most clearly by a change in strength of the North Pacific and North Atlantic pressure systems. Consequences of this regime shift are: (1) prolonged drought conditions in the Sahel region of Africa; (2) increased dust supply to the global atmosphere, by a factor of approximately four; (3) increased easterly trade winds across the Atlantic; (4) increased eolian transport of dust to the Atlantic and Caribbean basins; and (5) increased deposition of iron-rich eolian dust to typically iron-poor marine regions. On the basis of well-documented climate and dust observations and the widely accepted increase in marine outbreak rates, this paper proposes that the increased iron supply has altered the micronutrient factors limiting growth of opportunistic organisms and virulence of pathogenic microbes, particularly in macronutrient-rich coastal systems.     

How do biological systems discriminate among physically similar ions?

This paper reviews the history of understanding how biological systems can discriminate so strikingly among physically similar ions, especially alkali cations. Appreciation of qualitative regularities ("permitted sequences") and quantitative regularities ("selectivity isotherms") in ion selectivity grew first from studies of ion exchangers and glass electrodes, then of biological systems such as enzymes and cell membranes, and most recently of lipid bilayers doped with model pores and carriers. Discrimination of ions depends on both electrostatic and steric forces. "Black-box" studies on intact biological membranes have in some cases yielded molecular clues to the structure of the actual biological pores and carriers. Major current problems involve the extraction of these molecules; how to do it, what to do when it is achieved, and how (and if) it is relevant to the central problems of membrane function. Further advances are expected soon from studies of rate barriers within membranes, of voltage-dependent ("excitable") conducting channels, and of increasingly complex model systems and biological membranes.     

How similar are nut-cracking and stone-flaking? A functional approach to percussive technology

Various authors have suggested similarities between tool use in early hominins and chimpanzees. This has been particularly evident in studies of nut-cracking which is considered to be the most complex skill exhibited by wild apes, and has also been interpreted as a precursor of more complex stone-flaking abilities. It has been argued that there is no major qualitative difference between what the chimpanzee does when he cracks a nut and what early hominins did when they detached a flake from a core. In this paper, similarities and differences between skills involved in stone-flaking and nut-cracking are explored through an experimental protocol with human subjects performing both tasks. We suggest that a ‘functional’ approach to percussive action, based on the distinction between functional parameters that characterize each task and parameters that characterize the agent''s actions and movements, is a fruitful method for understanding those constraints which need to be mastered to perform each task successfully, and subsequently, the nature of skill involved in both tasks.     

How similar are P450s and what can their differences teach us?

Cytochromes P450 form a very large superfamily of proteins which metabolize substrates from steroids to fatty acids to drugs and are found in organisms from protists to mammals. P450s all appear to take on a similar structural fold, yet frequently having less than 20% sequence identity and having vastly different substrates. Within the structural fold there appears to be a highly conserved core, as determined from the comparison of the structures of the six crystallized, soluble P450s. There are also variable regions which by and large appear to be associated with substrate recognition, substrate binding, and redox partner binding. Molecular dynamics simulations of motion in P450cam and P450BM-3 indicate that substrate binding and product release require substantial motion around the "substrate access channel." Additionally, at the 11th International Conference on Cytochrome P450 Biochemistry, Biophysics, and Molecular Biology and briefly here, the first structure of a microsomal eukaryotic P450 will be presented and compared to the already determined structures by Drs. Johnson and McRee. Finally, with a better understanding of the structure/function relationship of P450s, one will be better able to modify P450s to metabolize the substrates of choice or produce needed valuable chemicals.     

Regulated exocytosis in chromaffin cells and cytotoxic T lymphocytes: How similar are they?

Chromaffin cells from the adrenal medulla secrete catecholamines into the blood stream as part of the fight-or-flight response. Cytotoxic T lymphocytes from the immune system release cytotoxic substances to kill antigen-presenting cells. While at first glance these two cell types do not seem to have much in common, evidence from human diseases indicates that the molecular mechanisms of exocytosis of the respective granules share many similar features. In this review we highlight the similarities and differences of individual aspects of granule maturation and release in both cell types. In addition, we discuss established and putative molecules involved in distinct steps and suggest technical approaches which might facilitate future studies in chromaffin cells and cytotoxic T lymphocytes.     

Social and biological measures of hyperactivity and inattention: are they describing similar underlying constructs of child behavior?

The relationship between 27 different measures of hyperactive, impulsive, and inattentive behavior, including those considered to be more objective and those considered more influenced by social factors, is examined using a normal sample of 219 Mexican children, ages 6 to 12. Measures were based on activity monitoring by accelerometry, ethological observation of attentional and movements states in the classroom, cognitive testing using the TOVA continuous performance test (CPT), and parents' and teachers' reports on ratings scales and symptom checklists. Factor analysis was used to examine to what degree these different measures are reporting similar underlying constructs (factors) of hyperactivity and inattention. Parent and teacher ratings appear to be describing underlying constructs that are distinct from those described by the other measures, but measures based on CPT, observation, and activity monitoring did not factor together either, nor more highly correlate to each other. Analysis combining all the measures showed that parent and teacher ratings factored together based on who was reporting the behavior, rather than the behavior being reported. The findings underscore that each type of measurement of hyperactivity, impulsivity, and inattention measures a different aspect of a complex behavioral phenomenon, rather than some better measuring than others the same underlying factor.     

How are cohesin rings opened and closed?

The cohesin complex is proposed to embrace sister chromatids within its ring-like structure, in which two ATP-binding 'head' domains of an SMC (structural maintenance of chromosomes) heterodimer are linked by a kleisin subunit. Recent studies shed new light on the crucial functions of the 'hinge' domain of the SMC dimer, which is located approximately 50 nm from the head domains. An emerging idea is that the hinge and head domains cooperatively modulate cohesin-DNA interactions by opening and closing the ring in a highly regulated manner.     

How scalable and suitable are single-use bioreactors?

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How similar are protein folding and protein binding nuclei? Examination of vibrational motions of energy hot spots and conserved residues

The underlying physico-chemical principles of the interactions between domains in protein folding are similar to those between protein molecules in binding. Here we show that conserved residues and experimental hot spots at intermolecular binding interfaces overlap residues that vibrate with high frequencies. Similarly, conserved residues and hot spots are found in protein cores and are also observed to vibrate with high frequencies. In both cases, these residues contribute significantly to the stability. Hence, these observations validate the proposition that binding and folding are similar processes. In both packing plays a critical role, rationalizing the residue conservation and the experimental alanine scanning hot spots. We further show that high-frequency vibrating residues distinguish between protein binding sites and the remainder of the protein surface.     

Shapes of river networks and leaves: are they statistically similar?

The structure of river networks is compared with the vein structure of leaves. The two structures are visually similar at the smaller scales. The statistics of branching and side branching are nearly identical. The branching structure of diffusion-limited aggregation clusters is also similar and can provide an explanation for the structure of river networks. The origin of the self-similar branching and side branching of the vein structure in leaves is not clear but it appears to be an optimal network in terms of transporting nutrients to all parts of the leaf with the least total resistance.     

Two short, daily activity bouts vs. one long bout: are health and fitness improvements similar over twelve and twenty-four weeks?

This study sought to determine whether a 12-week intermittent (INT; 2 x 15 min.d(-1)) exercise program yielded similar improvements in cardiovascular health and fitness, compared with a traditional 12-week, 30-minute continuous (CON; 1 x 30 min.d(-1)) exercise program. A second purpose was to determine the effects of switching exercise programs and continuing training for an additional 12 weeks. Twenty women and 17 men, (age 48.8 +/- 9.0 years) were divided randomly into 2 groups: INT (n = 20) and CON (n = 17). Aerobic exercise was performed 4 d.wk(-1) for 12 weeks. Subjects then crossed over to the opposite training program for an additional 12 weeks of training. Subjects exercised incrementally for weeks 1-4 and training was conducted at 70-80% heart rate reserve for weeks 5-24. Both groups showed comparable exercise adherence, completing 96.6 +/- 12.2% (CON) and 96.3% +/- 17.7% (INT) of the prescribed exercise time. The INT walked at a lower percentage of Vo(2)max, maximum heart rate, systolic blood pressure, and diastolic blood pressure (p < 0.05). Maximal oxygen consumption increased by 4.5% in CON and by 8.7% in INT. Following the second 12 weeks, Vo(2)max increased by 3.6 and 7.7% in CON and INT, respectively. Treadmill test time increased by 41 seconds in CON (p < 0.05) and 71 seconds in INT (p < 0.05) after 12 weeks of training. High-density lipoproteins significantly increased in the INT group following the first 12 weeks of training. This study suggests that an INT exercise program, which is incremental in nature, provides comparable, and in some cases greater, health and fitness benefits than those expected following traditional CON exercise training.     

Cancer and diet: How are they related?

Extensive research in the past decade has revealed cancer to be a multigenic disease caused by perturbation of multiple cell signalling pathways and dysregulation of numerous gene products, all of which have been linked to inflammation. It is also becoming evident that various lifestyle factors, such as tobacco and alcohol use, diet, environmental pollution, radiation and infections, can cause chronic inflammation and lead to tumourigenesis. Chronic diseases caused by ongoing inflammation therefore require chronic, not acute, treatment. Nutraceuticals, compounds derived from fruits, vegetables, spices and cereals, can be used chronically. This study discusses the molecular targets of some nutraceuticals that happen to be markers of chronic inflammation and how they can prevent or treat cancer. These naturally-occurring agents in the diet have great potential as anti-cancer drugs, thus proving Hippocrates, who proclaimed 25 centuries ago, 'Let food be thy medicine and medicine be thy food'.     

How cooperative are protein folding and unfolding transitions?

A thermodynamically and kinetically simple picture of protein folding envisages only two states, native (N) and unfolded (U), separated by a single activation free energy barrier, and interconverting by cooperative two‐state transitions. The folding/unfolding transitions of many proteins occur, however, in multiple discrete steps associated with the formation of intermediates, which is indicative of reduced cooperativity. Furthermore, much advancement in experimental and computational approaches has demonstrated entirely non‐cooperative (gradual) transitions via a continuum of states and a multitude of small energetic barriers between the N and U states of some proteins. These findings have been instrumental towards providing a structural rationale for cooperative versus noncooperative transitions, based on the coupling between interaction networks in proteins. The cooperativity inherent in a folding/unfolding reaction appears to be context dependent, and can be tuned via experimental conditions which change the stabilities of N and U. The evolution of cooperativity in protein folding transitions is linked closely to the evolution of function as well as the aggregation propensity of the protein. A large activation energy barrier in a fully cooperative transition can provide the kinetic control required to prevent the accumulation of partially unfolded forms, which may promote aggregation. Nevertheless, increasing evidence for barrier‐less “downhill” folding, as well as for continuous “uphill” unfolding transitions, indicate that gradual non‐cooperative processes may be ubiquitous features on the free energy landscape of protein folding.     

How are proliferation and differentiation of melanocytes regulated?

Coat colors are determined by melanin (eumelanin and pheomelanin). Melanin is synthesized in melanocytes and accumulates in special organelles, melanosomes, which upon maturation are transferred to keratinocytes. Melanocytes differentiate from undifferentiated precursors, called melanoblasts, which are derived from neural crest cells. Melanoblast/melanocyte proliferation and differentiation are regulated by the tissue environment, especially by keratinocytes, which synthesize endothelins, steel factor, hepatocyte growth factor, leukemia inhibitory factor and granulocyte-macrophage colony-stimulating factor. Melanocyte differentiation is also stimulated by alpha-melanocyte stimulating hormone; in the mouse, however, this hormone is likely carried through the bloodstream and not produced locally in the skin. Melanoblast migration, proliferation and differentiation are also regulated by many coat color genes otherwise known for their ability to regulate melanosome formation and maturation, pigment type switching and melanosome distribution and transfer. Thus, melanocyte proliferation and differentiation are not only regulated by genes encoding typical growth factors and their receptors but also by genes classically known for their role in pigment formation.     

How Tough are Sclerophylls?

Fracture toughness was estimated for a 'least tough' path inthe leaves of woody species from three sclerophyllous plantcommunities. Most of the species from Mediterranean, tropicalheath forest and lowland tropical rain forest habitats had verytough leaves, with toughness generally 600-1300 J m^-2, whichis two to four times higher than soft-leaved tropical pioneertrees. The toughest leaf (2032 J m^-2), Parishia insignis, camefrom the canopy of the lowland rain forest. Leaves from theshaded understorey of the rain forest did not appear any lesstough than those from the canopy.Copyright 1993, 1999 AcademicPress Leaf fracture toughness, sclerophylly, Mediterranean vegetation, tropical forest     

How reticulated are species?

Many groups of closely related species have reticulate phylogenies. Recent genomic analyses are showing this in many insects and vertebrates, as well as in microbes and plants. In microbes, lateral gene transfer is the dominant process that spoils strictly tree‐like phylogenies, but in multicellular eukaryotes hybridization and introgression among related species is probably more important. Because many species, including the ancestors of ancient major lineages, seem to evolve rapidly in adaptive radiations, some sexual compatibility may exist among them. Introgression and reticulation can thereby affect all parts of the tree of life, not just the recent species at the tips. Our understanding of adaptive evolution, speciation, phylogenetics, and comparative biology must adapt to these mostly recent findings. Introgression has important practical implications as well, not least for the management of genetically modified organisms in pest and disease control.