Eight human OPA1 isoforms,long and short: What are they for?

OPA1 is a dynamin-related GTPase that controls mitochondrial dynamics, cristae integrity, energetics and mtDNA maintenance. The exceptional complexity of this protein is determined by the presence, in humans, of eight different isoforms that, in turn, are proteolytically cleaved into combinations of membrane-anchored long forms and soluble short forms. Recent advances highlight how each OPA1 isoform is able to fulfill “essential” mitochondrial functions, whereas only some variants carry out “specialized” features. Long forms determine fusion, long or short forms alone build cristae, whereas long and short forms together tune mitochondrial morphology. These findings offer novel challenging therapeutic potential to gene therapy.     

Masting,mixtures and modes: are two models better than one?

A key hypothesis in population ecology is that synchronous and intermittent seed production, known as mast seeding, is driven by the alternating allocation of carbohydrates and mineral nutrients between growth and reproduction in different years, i.e. ‘resource switching’. Such behaviour may ultimately generate bimodal distributions of long‐term flower and seed production, and evidence of these patterns has been taken to support the resource switching hypothesis. Here, we show how a widely‐used statistical test of bimodality applied by many studies in different ecological contexts may fail to reject the null hypothesis that focal probability distributions are unimodal. Using data from five tussock grass species in South Island, New Zealand, we find clear evidence of bimodality only when flowering patterns are analyzed with probabilistic mixture models. Mixture models provide a theory oriented framework for testing hypotheses of mast seeding patterns, enabling the different responses underlying medium‐ and high‐ versus non‐ and low‐flowering years to be modelled more realistically by associating these with distinct probability distributions. Coupling theoretical expectations with more rigorous statistical approaches will empower ecologists to reject null hypotheses more often.     

Mimicry vs. similarity: which resemblances between brood parasites and their hosts are mimetic and which are not?

Mimicry is one of the most conspicuous and puzzling phenomena in nature. The best-known examples come from insects and brood parasitic birds. Unfortunately, the term 'mimicry' is used indiscriminately and inconsistently in the brood parasitic literature despite the obvious fact that similarities of eggs, nestlings and adults of brood parasites to their hosts could result from many different processes (phylogenetic constraint, predation, intraspecific arms-races, vocal imitation, exploitation of pre-existing preferences, etc.). In this note I wish to plead for a more careful use of the term. I review various processes leading to a similarity between propagules (both eggs and nestlings) of brood parasites and their hosts and stress that: (1) mimetic and non-mimetic similarities should be differentiated, (2) a mere similarity of host and parasite propagules provides no evidence for mimicry, (3) mimicry is more usefully understood as a (coevolutionary) process rather than an appearance, and (4) mimicry terminology should reflect the process which led to mimetic similarity. Accepting the mimicry hypothesis requires both the experimental approach and rejection of alternative hypotheses explaining similarities of host and parasite propagules.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 69–78.     

Dispersal and colonisation, long and short chronologies: how continuous is the Early Pleistocene record for hominids outside East Africa?

This paper examines the evidence for hominids outside East Africa during the Early Pleistocene. Most attention has focused recently on the evidence for or against a late Pliocene dispersal, ca. 1.8 Ma., of hominids out of Africa into Asia and possibly southern Europe. Here, the focus is widened to include North Africa as well as southern Asia and Europe, as well as the evidence in these regions for hominids after their first putative appearance ca. 1.8 Ma. It suggests that overall there is very little evidence for hominids in most of these regions before the Middle Pleistocene. Consequently, it concludes that the colonising capabilities of Homo erectus may have been seriously over-rated, and that even if hominids did occupy parts of North Africa, southern Europe and southern Asia shortly after 2 Ma, there is little evidence of colonisation. Whilst further fieldwork will doubtless slowly fill many gaps in a poorly documented Lower Pleistocene hominid record, it appears premature to conclude that the appearance of hominids in North Africa, Europe and Asia was automatically followed by permanent settlement. Rather, current data are more consistent with the view that Lower Pleistocene hominid populations outside East Africa were often spatially and temporally discontinuous, that hominid expansion was strongly constrained by latitude, and that occupation of temperate latitudes north of latitude 40 degrees was largely confined to interglacial periods.     

Physicians in health care management: 2. Managing performance: who,what, how and when?

Physicians are becoming more involved in performance management as hospitals restructure to increase effectiveness. Although physicians are not hospital employees, they are subject to performance appraisals because the hospitals are accountable to patients and the community for the quality of hospital services. The performance of a health care professional may be appraised by the appropriate departmental manager, by other professionals in a team or program or by peers, based on prior agreement on expectations. Appraisal approaches vary. They include behavioural approaches such as rating scales, peer rating, ranking or nomination and outcome approaches such as management by objectives and goal setting. Professionals should give and receive timely feedback on a flexible schedule. Feedback can be provided one-on-one, by a group assessing quality of care or through an anonymous survey.     

Do sibling tits (<Emphasis Type="Italic">Parus major,P. caeruleus</Emphasis>) disperse over similar distances and in similar directions?

We studied dispersal movements by sibling pairs of great tits, Parus major, and blue tits, P. caeruleus, in a patchy environment, in order to test whether siblings are more similar in dispersal than expected by chance. Because of possible common environmental effects due to the heterogeneity and finiteness of the study area, we compared the similarity among siblings with the similarity between each sibling and an unrelated bird that fledged in the same patch and year, as close to the siblings nest as possible. Siblings of both species were not more similar in dispersal distance than they were to control birds. However, great tit siblings dispersed in similar directions compared to control birds, and this result was not affected by the degree of matching between sibling and control birds. As a consequence, siblings ended up breeding at closer distances from one another than control birds. Heritability values calculated from parent-offspring regressions were close to zero, suggesting that there is no additive genetic variance for dispersal distance or dispersal direction. We propose that similarity in dispersal direction originates from association of siblings during dispersal or during activities that influence the choice of direction, such as postfledging family movements. Our results show that non-independence in the choice of dispersal direction by siblings may influence small-scale kin structure in this population with high local recruitment.     

Chiropterophily in Sinningieae (Gesneriaceae): Sinningia brasiliensis and Paliavana prasinata are bat-pollinated,but P. sericiflora is not. Not yet?

BACKGROUND AND AIMS: Based on the bell shape and greenish colour of the flowers, bat-pollination was suggested for some Sinningieae species (Gesneriaceae). Actually, there are no reports on pollination biology and visitors for these species. This paper reports on pollination biology of Sinningia brasiliensis, Paliavana prasinata and P. sericiflora in south-eastern Brazil. METHODS: Flowers were observed in situ to determine phases of anthesis, colour patterns and scent intensity. Corolla measures were taken from fresh flowers. Nectar production and concentration were measured in flowers bagged at the pre-anthesis phases. Direct visual observations of visitors were made during the day and night, and photographs were taken to analyse their visiting behaviour. KEY RESULTS: Some floral features of the three species fit the bat-pollination syndrome: large, robust and gullet-shaped corollas, colour patterns and large amount of nectar. However, other floral features-such as onset of anthesis, nectar attributes and odour intensity-differ among the species. Nectar volume and total sugar production increased significantly at midnight in S. brasiliensis and P. prasinata, but in P. sericiflora there were no significant differences in the total nectar and sugar production during anthesis. Scent intensity is much higher in S. brasiliensis and P. prasinata than P. sericiflora. Flowers of S. brasiliensis and P. prasinata, whose features fit the chiropterophilous syndrome, are pollinated by glossophagine bat species. Paliavana sericiflora, on the other hand, presents floral features intermediate between bat and hummingbird syndromes, but is visited and pollinated only by hummingbirds. CONCLUSIONS: These data strengthen the statement that the bat syndrome in Sinningieae originated independently in Sinningia brasiliensis and in Paliavana species. Paliavana sericiflora may be another example of a plant 'in transition' from the hummingbird to the bat pollination, but a reversion in the direction of bat to hummingbird might not be excluded. It is also possible that this is a case of speciation on both bat and hummingbird pollination. Studies on Paliavana sister species may provide insights about origins and the evolutionary directions of the pollination systems of these species.