Can ribs and septa provide an alternative standard for age in ammonite ontogenetic studies?

In ammonites, the time between two successive septal secretions is assumed to be almost stable during growth within homogeneous sets with regard to phylogeny and morphology. The number of septa (included in the adult phragmocone) is proposed as an alternative standard for age. At each moment of growth, the rate of shell secretion can be directly estimated by the measure of shell length between two septa. Equivalent results are obtained for ribs whose formation is also dependent on an almost stable rhythmical process. Results obtained from septa and size used as age standards are compared in the example of Liparoceratidae-Amaltheidae evolution. The two standards provide estimations of age which diverge from more than 1 to 2. For example, some small species previously seen as progenetic are now classified as dwarfed. These results emphasize the risk of using size as the only standard of age. Alternative standards not only in ammonites but also in other animal groups should be investigated.     

Looking for food in all the right places?

Examining a potential functional role for growth hormone secretagogue receptors in the hippocampus, Diano and colleagues (Diano et al., 2006), demonstrate novel actions of the orexigenic peptide ghrelin in hippocampal synaptic architecture, LTP, and learning and memory. These data suggest functional links between metabolic signaling and higher neural function.     

Could nested PCR be applicable for the study of microbial diversity?

PCR-based methods for rRNA gene analysis have been widely used to study diversity of microbiology. However, the analysis would be difficult when the DNA content in samples is too low to be amplified by conventional PCR. Nested PCR comes up with the advantage of higher sensitivity. It can detect target DNA at several-fold lower concentrations than conventional PCR. However, the amplification bias and factors that potentially affect measurement of sample diversity associated with nested PCR method has received little attention. Here, nested PCR was compared to reconditioning PCR which is based on conventional PCR and it would reduce the formation of heteroduplex. We investigated the use of both nested and reconditioning PCR methods to construct clone libraries of 16S rRNA genes from four swimming pool water samples. Abundances of OTUs (operational taxonomic units) were correlated between the libraries (r ² = 0.88, P < 0.0005), and some OTUs had equivalent abundances in the two libraries using the Chi-square test. Differences in taxonomic groups, as well as diversity and richness estimators, were compared by paired t-test and the Wilcoxon test, respectively. There were no significant differences between clone libraries using these two PCR methods. The results of ∫-Libshuff analysis suggested that nested PCR have no particular biases in revealing OTU diversity of a bacterial community. Thus, nested PCR produce congruent pictures with reconditioning PCR in the microbial community analysis.     

Is the bioavailability index applicable for trace elements in different types of soil?

Abstract

The bioavailability index (BI) is defined as the proportion of reduction in a plant’s accumulation of an element, caused by the removal of the extractable fraction of the element of interest from the soil. The BI and corresponding experimental methods were quantitatively applied to evaluate the bioavailability of trace elements in five Chinese soils. The soil was first extracted with various reagents (DTPA, HCl and NH₂OH.HCI) separately, to remove the extractable elements. The soil, after extraction, was washed with deionised water to eliminate the extractant used in the fractionation analysis. Then the pH of the soil was re-adjusted with CaO. The soil was then fertilised and incubated in a greenhouse for four weeks. Tests showed that after incubation the pH, cation exchange capacity (CEC) and organic matter (OM) of the treated soil were close to their original values. Wheat (Triticum aestivum L.) was planted in both the untreated and treated soil for eight weeks. After harvest the plant concentrations of the elements Cr, Mn, Co, Ni, Zn, Cu, Cd, and Pb were analysed by inductively coupled plasma mass spectrometry (ICPMS). Trace element accumulation by plants grown in the treated soil was reduced significantly compared with that of plants grown in the untreated soil. The results showed that BI values were in the order BI(DTPA)>BI(HCl)>BI(NH₂OH.HCl). This indicated that the DTPA-extractable fraction represented a highly available fraction of the total content. Variations of BI among different trace elements show that Cr, Mn, Zn and Co have a higher BI, in general for the elements tested, whereas, Cu, Cd and Pb have lower values. There are also slight differences in the BI among soils. However, no significant relationship could be found between the BI and the soil characteristics.     

The thymus and T-cell commitment: the right niche for Notch?

The current dogma is that the thymus is colonized by progenitors that retain the capacity to generate both T cells and B cells, and that intrathymic Notch signalling determines lineage choice so that T cells, rather than B cells, develop in the thymus. However, evidence is now accumulating to indicate that, at least during fetal life, this is not the case. Rather, it now seems that the fetal thymus is colonized by progenitors that have already made the T-cell versus B-cell lineage choice. We propose an alternative role for Notch signalling in the thymus, which is not to mediate this choice but instead to reveal it by supporting further T-cell differentiation in the thymic microenvironment.     

Invited review: Genomic selection for small ruminants in developed countries: how applicable for the rest of the world?

Improved management and use of estimated breeding values in breeding programmes, have resulted in rapid genetic progress for small ruminants (SR) in Europe and other developed countries. The development of single nucleotide polymorphisms chips opened opportunities for genomic selection (GS) in SR in these countries. Initially focused on production traits (growth and milk), GS has been extended to functional traits (reproductive performance, disease resistance and meat quality). The GS systems have been characterized by smaller reference populations compared with those of dairy cattle and consisting mostly of cross- or multi-breed populations. Molecular information has resulted in gains in accuracy of between 0.05 and 0.27 and proved useful in parentage verification and the identification of QTLs for economically important traits. Except for a few established breeds with some degree of infrastructure, the basic building blocks to support conventional breeding programmes in small holder systems are lacking in most developing countries. In these systems, molecular data could offer quick wins in undertaking parentage verification and genetic evaluations using G matrix, and determination of breed composition. The development of next-generation molecular tools has prompted investigations on genome-wide signatures of selection for mainly adaptive and reproduction traits in SR in developing countries. Here, the relevance of the developments and application of GS and other molecular tools in developed countries to developing countries context is examined. Worth noting is that in the latter, the application of GS in SR will not be a ‘one-size fits all’ scenario. For breeds with some degree of conventional genetic improvement, classical GS may be feasible. In small holder systems, where production is key, community-based breeding programmes can provide the framework to implement GS. However, in fragile growth systems, for example those found in marginal environments, innovative GS to maximize adaptive diversity will be required. A cost-benefit analysis should accompany any strategy of implementing GS in these systems.     

Death receptor agonist therapies for cancer,which is the right TRAIL?

The activation of cell-surface death receptors represents an attractive therapeutic strategy to promote apoptosis of tumor cells. Several investigational therapeutics that target this extrinsic pathway, including recombinant human Apo2L/TRAIL and monoclonal agonist antibodies directed against death receptors-4 (DR4) or -5 (DR5), have been evaluated in the clinic. Although Phase 1/1b studies provided encouraging preliminary results, findings from randomized Phase 2 studies failed to demonstrate significant clinical benefit. This has raised multiple questions as to why pre-clinical data were not predictive of clinical response. Results from clinical studies and insight into why current agents have failed to yield robust responses are discussed. In addition, new strategies for the development of next generation death receptor agonists are reviewed.     

Is selection responsible for the low level of variation in the last intron of the ZFY locus?

DNA variability was investigated in the last intron of the Y-chromosome-specific zinc finger gene, ZFY, and its X homolog on Xp21.3, ZFX. No polymorphisms were found in the 676-bp ZFY segment in a sample of 205 world-wide-distributed Y chromosomes, other than a solitary nucleotide variant in one individual (nucleotide diversity pi = 0.0014%). In contrast, 10 segregating sites (pi = 0.082%) were identified within 1,089 bp of the ZFX sequence in a sample of 336 X chromosomes. Four of these polymorphisms, which contributed most of the diversity, were located within an Alu insert disrupting the ZFY-ZFX homology (pi Alu = 0.24%). The diversity in the homologous portion of the ZFX intron, although higher than that in ZFY, was lower than that found in genomic segments believed to evolve neutrally; interspecies divergence in both segments was also reduced. Although this suggests that the evolution of both ZFY and ZFX homologs may not be entirely neutral, both Tajima and HKA tests did not reject neutrality. The lack of statistical significance may be attributed to a lack of power in these tests (the low divergence and variability values reduce the power of the HKA and Tajima tests, respectively); furthermore, Homo sapiens has recently undergone a rapid population growth, and selection is more difficult to detect in an expanding population. Therefore, the failure to reject neutrality does not necessarily indicate the absence of selection. In this context, the phylogenetic argument was given more weight in out interpretations. The high level of sequence identity in ZFY and ZFX segments, in spite of their separation 80-130 MYA, reflects a lower mutation rate as compared with other segments believed to undergo unconstrained evolution. Thus, the possibility of weak selection contributing to the low level of nucleotide diversity in the last ZFY intron cannot be excluded and should be kept in mind in the population genetics studies based on Y chromosome variability.     

Prominent ears in children younger than 4 years of age: what is the appropriate timing for otoplasty?

The present study was conducted to determine whether otoplasty performed in children younger than 4 years of age has an acceptable long-term outcome. This two-part study consisted of (1) a questionnaire mailed to 481 members of the American Association of Plastic Surgeons to ask their opinion on the timing of otoplasty, and (2) a consecutive series of 12 patients who had otoplasty performed before the age of 4 years. The survey demonstrated that the majority (57 percent) of the respondents perform otoplasty on patients who are aged 5 years or older. The prospective series consisted of 12 patients ranging in age from 9 months to 3 years at the time of the procedure. Otoplasty was bilateral in nine patients and unilateral in three patients. Length of follow-up ranged from 21 months to 7(1/2) years, with a median follow-up of 41 months. Growth following otoplasty was evaluated in three patients who underwent unilateral otoplasty by measuring the length of both ears at the time of final follow-up. No difference in ear length was noted between the sides that were and were not operated on during a follow-up period of 46 to 63 months. Noticeable recurrence was noted in only one (8 percent) of 12 patients. In response to a follow-up questionnaire to the patients' families, all respondents (n = 10) stated that if again asked to choose the timing of otoplasty in their children, they would opt to have it performed at the same age of younger than 4 years. Otoplasty can be safely performed at ages younger than previously thought without interfering with growth of the operated ear.     

Is seasonal variation in leaf traits adaptive for the annual plant Dicerandra linearifolia?

Empirical studies of phenotypic plasticity have often relied on the plausibility that a plastic response to the environment would increase fitness in order to diagnose the response as adaptive. I conducted a test of the hypothesis that seasonal variation in leaf traits is an adaptive response to seasonal variation in environmental conditions faced by the annual plant Dicerandralinearifolia. This species exhibits variation in leaf morphology and anatomy in response to temperature that is consistent with the expectations for adaptive plasticity. I examined variation in the size, thickness and density of stomata of leaves that develop in summer and winter and used analysis of phenotypic selection during winter and summer seasons to test the hypothesis that seasonal variation in these traits is adaptive. Regression analyses of estimated dry mass (as a proxy for fitness) on leaf traits revealed no evidence supporting the adaptive hypothesis. Selection favoured individuals with large and thick leaves in both winter and summer, and density of stomata had little or no effect on estimated relative fitness in any season. Correspondence between seasonal variation in leaf thickness and density of stomata and expectations for adaptive plasticity appears to be purely fortuitous. Seasonal variation in leaf traits may persist simply because there is no selection against individuals in which these traits vary. My results underscore the importance of definitive tests of the hypothesis of adaptation to distinguish adaptive plasticity from neutral or nonadaptive phenotypic plasticity.     

Electronic particle counting for evaluating the quality of air in operating theatres: a potential basis for standards?

Airborne particle counting in eight size ranges (0.5- greater than 20 microns), by computerized electronic equipment, was compared with the numbers of bacteria-carrying particles (BCP) assessed by slit sampling in ultra-clean and turbulently ventilated operating theatres. In the ultra-clean theatre the number of particles of 5-7 microns size range correlated with BCP while peaks in the numbers of particles less than 3 microns and greater than 15 microns corresponded with activity. Comparative relationships also occurred in the turbulently ventilated theatre but the use of this equipment in that environment cannot yet replace counts of airborne bacteria. We consider that electronic particle counting in the 0-20 microns size range may be used to judge the performance of a clean air operating theatre distribution system, including efficiency and integrity of the filter/seal systems and the presence or absence of entrainment of bacteria and other particles. The sampling techniques and analysis of particle concentration results described here may be a suitable basis for standards.     

Are there mappable genes for family resemblance for the magnitude of intra-individual variation in systolic blood pressure?

Background

The genetic regulation of variation in intra-individual fluctuations in systolic blood pressure over time is poorly understood. Analysis of the magnitude of the average fluctuation of a person's systolic blood pressure around his or her age-adjusted trend line, however, shows moderate, albeit significant, family resemblance in Cohort 1 of the Framingham Heart Study. To determine whether genomic regions affecting this phenotype could be identified, we pursued a "model-free" multipoint quantitative linkage analysis.

Results

Two different linkage methods revealed multiple nominally significant signals, two to four of which are "replicated" in Cohort 2. When both cohorts are assembled into extended pedigrees, three linkage signals remain nominally significant by one or both methods.

Conclusion

Any or all of the genomic regions in the vicinity of D5S1456, D11S2359, and D20S470 may contain elements that regulate systolic blood pressure homeostasis.

     

Bone and cartilage in osteoarthritis: is what's best for one good or bad for the other?

The interest in the relationship between articular cartilage and the structural and functional properties of peri-articular bone relates to the intimate contact that exists between these tissues in joints that are susceptible to the development of osteoarthritis (OA). The demonstration in several animal models that osteoporosis and decreased bone tissue modulus leads to an increased propensity for the development of post-traumatic OA is paradoxical in light of the extensive epidemiological literature indicating that individuals with high systemic bone mass, assessed by bone mineral density, are at increased risk for OA. These observations underscore the need for further studies to define the pathophysiological mechanisms involved in the interaction between subchondral bone and articular cartilage and for applying this information to the development of therapeutic interventions to improve the outcomes in patients with OA.