Conflicting demands on wetland ecosystem services: nutrient retention,biodiversity or both?

1. Wetland ecosystems may, besides having considerable economical value, increase landscape biodiversity and function as traps for nutrients from land to freshwater‐ and marine systems. As a result of these features, wetlands are nowadays often protected and restored, and many countries have even initiated wetland construction programmes. 2. In the present study, we aim at increasing the knowledge on how to improve the design of a wetland with respect to both biodiversity and nutrient retention, by analysing physical, chemical and biological features of a large set of constructed wetlands. 3. Our results show that a combination of the wetland features, namely shallow depth, large surface area and high shoreline complexity are likely to provide a high biodiversity of birds, benthic invertebrates and macrophytes and to have high nitrogen retention, whereas a small, deep wetland is likely to be more efficient in phosphorus retention, but less valuable in terms of biodiversity. 4. Hence, among the features used to design new wetlands, area, depth and shoreline complexity have fundamental, and sometimes conflicting, effects on nutrient retention and biodiversity. This means that there are, within limits, possibilities to direct the ecosystem function of a specific wetland in desired directions.     

The human mandible: Lever,link, or both?

Hylander ('78) recently published important new data on bite force in humans, and showed that the human mandible cannot function purely as a link during incisal biting. He concluded instead that the mandible acts as a lever. Reexamination of Hylander's data suggests that the mandible cannot function purely as a lever either, and in fact it probably functions simultaneously as both lever and link during incisal biting.     

Annual rhythm of human reproduction: I. Biology, sociology, or both?

The annual rhythm of human reproduction was analyzed on the basis of more than 3000 years of monthly birth rates covering 166 regions of the globe. The following variables were used to characterize the annual rhythm of human conception (birth minus 9 months): amplitude, phase of maximum and minimum, phase and length of the time span when rates are above the annual mean (alpha), and the steepest upward slope (delta max) of the curve fitted to the rates. The waveform of the annual rhythm is characteristic for geographical regions (e.g., unimodal or bimodal) and persists as such for many years. In most countries, the onset of alpha coincides with delta max and lies close to the spring equinox. This phase of the rhythm is the most stable over time. In many populations, the rhythm has changed in recent years, specifically in amplitude and phase. The phase of the rhythm depends on latitude, with a 6-month difference between the Northern and Southern Hemispheres. The latitudinal distribution of amplitudes is less systematic. In spite of the many social influences on timing of conceptions, we conclude that the seasonal component in human reproduction is based on biological factors.     

Nucleocytoplasmic trafficking of proteins: With or without Ran?

Proteins and RNAs move between the nucleus and cytoplasm by translocation through nuclear pore complexes in the nuclear envelope. To do this, they require specific targeting signals, energy, and a cellular apparatus that catalyzes their transport. Several of the factors involved in nucleocytoplasmic trafficking of proteins have been identified and characterized in some detail. The emerging picture for nuclear transport proposes a central role for the small GTPase Ran and proteins with which it interacts. In particular, asymmetric distribution of these proteins between nucleus and cytoplasm appears to be responsible for the vectorial nature of nucleocytoplasmic transport. Here, we summarize the role of Ran and Ran-binding proteins in nuclear trafficking of proteins with classical nuclear localisation signals. We also discuss examples of the growing number of alternative pathways that are involved in transport of proteins across the nuclear envelope. BioEssays 21:579–589, 1999. © 1999 John Wiley & Sons, Inc.     

Dental affinities of the C-group inhabitants of Hierakonpolis, Egypt: Nubian, Egyptian, or both?

By c. 2050 BC a small community of C-Group Nubians was present deep within Egyptian territory at the city of Hierakonpolis. Their descendants stayed for the next 400 years. Today, the site of Hierakonpolis, 113 km north of Aswan, is known for its Egyptian deposits; however, it also contains a C-Group cemetery, which documents the northernmost occurrence of this culture. Sixty skeletons were excavated. Tombs feature Nubian architecture and goods, including leather garments, although the use of Egyptian mortuary practices and artifacts increased through time. Dates range from the early 11th Dynasty into the Second Intermediate period. During this time the Egyptian empire occupied Lower Nubia, and their state ideology vilified Nubians. Yet, at least in death, the C-Group inhabitants of Hierakonpolis proudly displayed their cultural heritage.Beyond discerning the reason(s) for their presence at the site (e.g., mercenaries, leather-workers, entertainers?), the focus of this report is to estimate their biological affinity. Were they akin to other Nubians, Egyptians, or both? And, was increasing ‘Egyptianization’ evident in the mortuary ritual accompanied by concomitant genetic influence? To address these queries, up to 36 dental morphological traits in the recovered individuals were compared to those in 26 regional comparative samples. The most influential traits were identified and phenetic affinities were calculated using the mean measure of divergence and other multivariate analyses. Assuming phenetic similarity provides an estimate of genetic relatedness, these affinities suggest the individuals comprising the C-Group sample were, and remained Nubian during their tenure at Hierakonpolis.     

The inheritance of mitochondrial DNA heteroplasmy: random drift, selection or both?

The mammalian mitochondrial genome (mtDNA) is a small double-stranded DNA molecule that is exclusively transmitted down the maternal line. Pathogenic mtDNA mutations are usually heteroplasmic, with a mixture of mutant and wild-type mtDNA within the same organism. A woman harbouring one of these mutations transmits a variable amount of mutant mtDNA to each offspring. This can result in a healthy child or an infant with a devastating and fatal neurological disorder. Understanding the biological basis of this uncertainty is one of the principal challenges facing scientists and clinicians in the field of mitochondrial genetics.     

Single versus serial assessment of skeletal age: Either,both or neither?

Assessments of skeletal age are a valuable adjunct to the clinical evaluation of physical maturity but are more meaningful when considered in relation to chronological age, especially over time, than as separate entities. Data on 51 girls from the Child Research Council study series gave a correlation coefficient of 0.51 between skeletal age (SA) at menarche and chronological age (CA) at menarche — a value in close agreement with data reported from other studies. With a range in SA of 11.58 to 14.89 years, these data were examined further for changes in SA related to timing of adolescence. SA was greater than CA in each of the nine girls whose menarche occurred between 10.5 and 12 years of age. SA was equal to CA in one girl, greater than CA in eight girls and less than CA in 11 girls with menarche between 12.15 and 13.4 years. Of the 22 girls with menarche after 13.5 years, one had SA = CA at 14.89 years and the other 21 all had SA less than CA. An r of 0.84 was calculated between the values of CA minus SA at menarche and CA at menarche. Similar relationships were found between SA and CA at age of maximum increment in growth in height for these girls and for 53 boys in the study series. Longitudinal data for height, weight and SA for four boys and five girls demonstrate the problems of prediction of the timing of adolescence and of adult size from skeletal ages in the childhood years.     

Bcl-2 proteins: regulators of apoptosis or of mitochondrial homeostasis?

Programmed cell death (apoptosis) is used by multicellular organisms during development and to maintain homeostasis within mature tissues. One of the first genes shown to regulate apoptosis was bcl-2. Subsequently, a number of Bcl-2-related proteins have been identified. Despite overwhelming evidence that Bcl-2 proteins are evolutionarily conserved regulators of apoptosis, their precise biochemical function remains controversial. Three biochemical properties of Bcl-2 proteins have been identified: their ability to localize constitutively and/or inducibly to the outer mitochondrial, outer nuclear and endoplasmic reticular membranes, their ability to form heterodimers with proteins bearing an amphipathic helical BH3 domain, and their ability to form ion-conducting channels in synthetic membranes. The discovery that mitochondria can play a key part in the induction of apoptosis has focused attention on the role that Bcl-2 proteins may have in regulating either mitochondrial physiology or mitochondria-dependent caspase activation. Here we attempt to synthesize our current understanding of the part played by mitochondria in apoptosis with a consideration of how Bcl-2 proteins might control cell death through an ability to regulate mitochondrial physiology.     

Conchodontus,Mitrellataxis and Fungulodus: Conodonts,fish or both?

Conchodontus, Mitrellataxis and Fungulodus are phosphatic microfossils from the Late Devonian of China and North America, alternatively interpreted as conodont elements or fish scales. The histology and microornament of these sclerites have been studied in an attempt to resolve their affinity, and to determine characters for distinguishing between conodont elements and the ichthyoliths of other lower vertebrates. The histology of all three genera is directly comparable to conodont elements, dispelling the notion that conodonts are histologically indistinguishable from the teeth and scales of other vertebrates. Microornament is found not to be useful in discriminating between high-level taxonomic groupings. White matter and thickness of prismless enamel are suggested as apomorphies of the Conodonta.     

The roles of interleukin-15 receptor alpha: trans-presentation, receptor component, or both?

Interleukin-15 receptor alpha (IL-15R alpha) is a high affinity IL-15 binding protein that is crucial for mediating IL-15 functions such as memory CD8 T cell proliferation and NK, NK/T cell, and intestinal intraepithelial lymphocyte development. However, the mechanism by which IL-15R alpha mediates IL-15 functions is unique among cytokines. Originally, IL-15R alpha was thought to be a component of a heterotrimeric receptor complex containing the IL-2/IL-15R beta and common gamma chains (gammaC) that were required for mediating signaling. Although IL-15R alpha may in some cases act as a component of this receptor complex, more recent evidence indicates that IL-15R alpha predominately functions by presenting IL-15 to opposing cells expressing the IL-15R betagamma signaling components. This theory is consistent with the broad, non-lymphoid expression pattern of IL-15R alpha and the evidence that IL-15R alpha expression by lymphocytes is dispensable for IL-15 action in vivo. This new concept of cytokine delivery will allow us to better understand the regulation and function IL-15.     

Denatured bactericidal proteins: Active per se,or reservoirs of active peptides?

According to the structure-to-function paradigm proteins fold into a 3D structure for exerting their functions. Intrinsically destructured proteins with important biological functions have been identified and studied, but they assume a structure when interacting in the cell with their partners. There are instead bactericidal proteins, endowed also with other diverse activities (glycoside hydrolases, RNases, a defensin), which are lost when the proteins are denatured or inactivated, whereas the bactericidal activity is surprisingly conserved.The hypothesis is advanced that these proteins are not bactericidal per se, but because they store in their amino acid sequences peptide segments that display bactericidal activity when cut out as free peptides from the proteins. These bactericidal proteins would thus be merely containers of bactericidal peptides.