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.     

Hallmarks of cancer: of all cancer cells,all the time?

In two landmark articles, Hanahan and Weinberg synthesized into one conceptual framework 'the hallmarks of cancer', a massive amount of information describing the characteristics of a cancer cell. Although this is neither the intention nor the belief of the authors, hallmarks are often interpreted as applying to a canonic cancer cell, or equally to all cells within a cancer. In this article, we clarify the separate concepts of causes, oncogenic events, signal transduction programs, and hallmarks to show that there is no unimodal relation between these concepts but a complex network of interrelations that vary in different cells, between cells, and at different times in any given cell. We consider cancer as an evolving, dynamic, and heterogeneous system, explaining, at least in part, the difficulty of treating cancer and supporting the use of simultaneous, multitarget therapies.     

Genomic imprinting and kinship in the social Hymenoptera: what are the predictions?

The kinship theory of genomic imprinting predicts that conflicts of interest between parents can promote the evolution of opposed expression patterns of maternally and paternally derived alleles in the offspring. The social Hymenoptera (ants, some bees, and some wasps) are particularly suitable to test this theory, because a variety of social conflicts are predicted due to relatedness asymmetries between female and male nestmates that are a corollary of haplo-diploid sex determination. Here I argue that the kin-selection predictions for genomic imprinting in social Hymenoptera might in many cases be more complex than previously suggested, because the optimal strategy will have to take fitness effects in different castes and sexes into account.     

Recognition memory: what are the roles of the perirhinal cortex and hippocampus?

The hallmark of medial temporal lobe amnesia is a loss of episodic memory such that patients fail to remember new events that are set in an autobiographical context (an episode). A further symptom is a loss of recognition memory. The relationship between these two features has recently become contentious. Here, we focus on the central issue in this dispute--the relative contributions of the hippocampus and the perirhinal cortex to recognition memory. A resolution is vital not only for uncovering the neural substrates of these key aspects of memory, but also for understanding the processes disrupted in medial temporal lobe amnesia and the validity of animal models of this syndrome.     

The treatment of CIN: what are the risks?

The treatment of squamous cervical intraepithelial neoplasia is to remove or destroy the transformation zone (TZ). It is likely that no method of treatment is superior to another if it is performed properly and the limited available evidence supports this view. The significant advantages of excision (simplicity, cost, outpatient procedure, histological examination of the entire TZ) mean that treatment thresholds may have lowered over the last decade. Long-term pregnancy-related morbidity associated with excision has been reported recently. The evidence would suggest that this increase equates to a genuine increase in serious adverse outcome for cone biopsy but not large loop excision of the transformation zone (LLETZ). The available data also point to an increase in both incomplete excision and premature labour associated with the excision of large endocervical TZs. The clinical implications arising from this are firstly that women with large type 2 and 3 TZs need appropriate counselling before treatment and that the threshold for treating young women with mild abnormalities needs review.     

Spatial and temporal patterns of intertidal macrobenthic populations in the Oosterschelde: are they influenced by the construction of the storm-surge barrier?

The construction of a storm-surge barrier in the mouth of the Oosterschelde caused important hydrodynamical and morphological changes that could influence the macrobenthic populations. This paper is one in a series of five all dealing with the effects of the storm-surge barrier on macrozoobenthos and analyses the spatial and temporal distribution of macrozoobenthos in the Oosterschelde and its relationship with some environmental parameters, based on two large scale sampling campaigns, one before and one after the completion of the barrier.The sediment of the sampling stations was fine, well sorted sand, with an average mud content of about 2.5 %. Only in the Krabbenkreek the sediment was coarser in 1989. The tidal elevation of the sampling sites decreased significantly in 1989.The density of macrozoobenthos was significantly lower, the biomass higher in 1989. The density was dominated by deposit feeders, the biomass by filter feeders. The difference in biomass between both years was mainly due to a substantial increase of the biomass of filter feeders in 1989. The number of species per station was significantly smaller in 1989 than in 1985. Between 1985 and 1989, frequency of occurrence decreased in 34 versus 13 which increased, density increased in 13 species and decreased in 34 species, biomass increased in 18 species and decreased in 29 species.Based on TWINSPAN several clusters of stations, each with a different faunal composition, were identified. These clusters did not form distinct zones on the tidal flats but were dispersed widely.The relationship between density and biomass of different trophic groups and the mud content of the sediment and the depth was analysed. This relationship sometimes differed clearly between years. The correlation coefficient of a multiple regression between density and biomass of individual species and environmental factors, although significant in most cases, was very low, indicating that only a small proportion of the species variability was explained. The relationship between benthos and environmental factors was further analysed by canonical correlation analysis and multivariate discriminant analysis that gave different results for the 1985 and 1989 data. This is probably due to the broad tolerance of the species to the range of the environmental variables found in our study area. From a TWINSPAN of the density data of 1985 and 1989 together we could conclude that, although the environmental parameters in a group of stations, showing a large faunal similarity in one year, did not change, the faunal composition did. This indicates that faunal changes are not necessarily linked to changes in the measured environmental parameters.In the discussion the different factors affecting macrobenthic populations are situated and it is suggested that the macrobenthic populations are probably more towards the nonequilibrium end of the continuum between nonequilibrium and equilibrium communities as defined by Wiens (1984).Although the impact of the construction of the barrier on the macrobenthic community seems at present to be rather small this does not mean that on the long-term there will be no effect.