Codon bias and plasticity in immunoglobulins

Immunoglobulin genes experience Darwinian evolution twice. In addition to the germline evolution all genes experience, immunoglobulins are subjected, upon exposure to antigen, to somatic hypermutation. This is accompanied by selection for high affinity to the eliciting antigen and frequently results in a significant increase in the specificity of the responding population. The hypermutation mechanism displays a strong sequence specificity. Thus arises the opportunity to manipulate codon bias in a site-specific manner so as to direct hypermutation to those parts of the gene that encode the antigen-binding portions of the molecule and away from those that encode the structurally conserved regions. This segregation of mutability would clearly be advantageous; it would enhance the generation of potentially useful variants while keeping mutational loss to acceptably low levels. But it is not clear that the advantage gained would be large enough to produce a measurable effect within the background stochasticity of the evolutionary process. I have performed a pair of statistical tests to determine whether site- specific codon bias in human immunoglobulin genes is correlated with the sequence specificity of the somatic mutation mechanism. The sequence specificity of the mutator was determined by analysis of a database of published immunoglobulin intron sequences that had experienced somatic mutation but not selection. The site-specific codon bias was determined by analysis of published sequences of human germline immunoglobulin V genes. Both tests strongly suggest that evolution has acted to enhance the plasticity of immunoglobulin genes under somatic hypermutation.      

Physiological and Ecological Correlates of Preferred Temperature in Fish

Fishes released from constraints of their previous thermal historytend to limit thermal exposure to a narrow range of temperatures.Thermoregulatory behavior (final preferendum) is a stable characteristicof each species studied, suggesting strong regulation by naturalselection. However, the adaptive significance of the final preferendumhas not been documented for most species. Species with widegeographic distributions, such as bluegill sunfish and largemouthbass exhibit constant laboratory final preferenda regardlessof their geographic origin or thermal histories. This apparentevolutionary anomaly of the final preferendum requires furtherstudy. It is no longer adequate to describe responses of fishto thermal gradients, rather falsifiable hypotheses concerningadaptive relations between thermoselection, and physiological,biochemical, life-history and genetic correlates must be developedand tested experimentally.     

Life History Patterns of Storage and Utilization of Lipids for Energy in Amphibians

Amphibians utilize lipids, principally triglycerides, storedin abdominal fat bodies and carcass depots for production ofgametes and for metabolic maintenance during dormancy. Storedlipids are maximal in early fall prior to winter dormancy andminimal after breeding in the spring and early summer in mostamphibians. Extirpation experiments show that fat bodies areessential for gonadal maintenance. Patterns of lipid compartmentalizationare discussed and quantified in a representative from the Salientiaand Urodela.     

An intraspecific gene duplication polymorphism of the urate oxidase gene of Drosophila virilis: a genetic and molecular analysis

Nineteen strains of Drosophila virilis from diverse geographic locations were examined by genetic and molecular analyses, revealing (a) 12 strains with a single copy of the urate oxidase (UO) gene per haploid genome and (b) 7 strains with a tandem duplication of the UO locus. The D. virilis strains with the UO duplication appear to have identical restriction maps of this region, implying either a single origin for the duplication or several similar events occurring at a hot spot. On the basis of the location of the duplication breakpoints and the restriction sites flanking these breakpoints, this duplication probably arose through nonhomologous recombination involving either a breakage and rejoining event or replication slippage. because documented cases of intraspecific gene duplication polymorphism are rare, the D. virilis UO duplication will be useful in identifying the molecular event giving rise to a gene duplication.      

Population differences in behaviour are explained by shared within‐population trait correlations

Correlations in behavioural traits across time, situation and ecological context (i.e. ‘behavioural syndromes’ or ‘personality’) have been documented for a variety of behaviours, and in diverse taxa. Perhaps the most controversial inference from the behavioural syndromes literature is that correlated behaviour may act as an evolutionary constraint and evolutionary change in one’s behaviour may necessarily involve shifts in others. We test the two predictions of this hypothesis using comparative data from eighteen populations of the socially polymorphic spider, Anelosimus studiosus (Araneae, Theriidae). First, we ask whether geographically distant populations share a common syndrome. Second, we test whether population differences in behaviour are correlated similarly to within‐population trait correlations. Our results reveal that populations separated by as much as 36° latitude shared similar syndromes. Furthermore, population differences in behaviour were correlated in the same manner as within‐population trait correlations. That is, population divergence tended to be along the same axes as within‐population covariance. Together, these results suggest a lack of evolutionary independence in the syndrome’s constituent traits.     

7th SOSORT consensus paper: conservative treatment of idiopathic & Scheuermann's kyphosis

Abstract

Thoracic hyperkyphosis is a frequent problem and can impact greatly on patient's quality of life during adolescence. This condition can be idiopathic or secondary to Scheuermann disease, a disease disturbing vertebral growth. To date, there is no sound scientific data available on the management of this condition. Some studies discuss the effects of bracing, however no guidelines, protocols or indication's of treatment for this condition were found. The aim of this paper was to develop and verify the consensus on managing thoracic hyperkyphosis patients treated with braces and/or physiotherapy.

Methods

The Delphi process was utilised in four steps gradually modified according to the results of a set of recommendations: we involved the SOSORT Board twice, then all SOSORT members twice, with a Pre-Meeting Questionnaire (PMQ), and during a Consensus Session at the SOSORT Lyon Meeting with a Meeting Questionnaire (MQ).

Results

There was an unanimous agreement on the general efficacy of bracing and physiotherapy for this condition. Most experts suggested the use of 4-5 point bracing systems, however there was some controversy with regards to physiotherapeutic aims and modalities.

Conclusion

The SOSORT panel of experts suggest the use of rigid braces and physiotherapy to correct thoracic hyperkyphosis during adolescence. The evaluation of specific braces and physiotherapy techniques has been recommended.     

Geographical variation in genetic structure of an Atlantic Coastal Forest frog reveals regional differences in habitat stability

Climatic oscillations throughout the Pleistocene combined with geological and topographic complexity resulted in extreme habitat heterogeneity along the Atlantic coast of Brazil. Inferring how these historic landscape patterns have structured the current diversity of the region's biota is important both for our understanding of the factors promoting diversification, as well as the conservation of this biodiversity hotspot. Here we evaluate potential historical scenarios of diversification in the Atlantic Coastal Forest of Brazil by investigating the population genetic structure of a frog endemic to the region. Using mitochondrial and nuclear sequences, we generated a Bayesian population-level phylogeny of the Thoropa miliaris species complex. We found deep genetic divergences among five geographically distinct clades. Southern clades were monophyletic and nested within paraphyletic northern clades. Analyses of historical demographic patterns suggest an overall north to south population expansion, likely associated with regional differences in habitat stability during the Pliocene and early Pleistocene. However, genetic structure among southern populations is less pronounced and likely represents more recent vicariant events resulting from Holocenic sea-level oscillations. Our analyses corroborate that the Atlantic Coastal Forest has been a biogeographically dynamic landscape and suggest that the high diversity of its fauna and flora resulted from a combination of climatic and geologic events from the Pliocene to the present.     

Patterns of differential introgression in a salamander hybrid zone: inferences from genetic data and ecological niche modelling

Hybrid zones have yielded considerable insight into many evolutionary processes, including speciation and the maintenance of species boundaries. Presented here are analyses from a hybrid zone that occurs among three salamanders –Plethodon jordani, Plethodon metcalfi and Plethodon teyahalee– from the southern Appalachian Mountains. Using a novel statistical approach for analysis of non‐clinal, multispecies hybrid zones, we examined spatial patterns of variation at four markers: single‐nucleotide polymorphisms (SNPs) located in the mtDNA ND2 gene and the nuclear DNA ILF3 gene, and the morphological markers of red cheek pigmentation and white flecks. Concordance of the ILF3 marker and both morphological markers across four transects is observed. In three of the four transects, however, the pattern of mtDNA is discordant from all other markers, with a higher representation of P. metcalfi mtDNA in the northern and lower elevation localities than is expected given the ILF3 marker and morphology. To explore whether climate plays a role in the position of the hybrid zone, we created ecological niche models for P. jordani and P. metcalfi. Modelling results suggest that hybrid zone position is not determined by steep gradients in climatic suitability for either species. Instead, the hybrid zone lies in a climatically homogenous region that is broadly suitable for both P. jordani and P. metcalfi. We discuss various selective (natural selection associated with climate) and behavioural processes (sex‐biased dispersal, asymmetric reproductive isolation) that might explain the discordance in the extent to which mtDNA and nuclear DNA and colour‐pattern traits have moved across this hybrid zone.     

Characterisation of <Emphasis Type="Italic">mycobacteria</Emphasis> isolated from slaughter cattle in pastoral regions of Uganda

Background  

Bovine tuberculosis is a zoonotic problem in pastoral cattle and communities in Uganda. Tuberculin tests in pastoral cattle had shown a high herd but low animal prevalence, with a high proportion of avian reactors. No work had been done to identify the mycobacterial species involved. The objective of the study was to isolate and characterise Mycobacterial species causing tuberculous lesions in slaughtered animals. Lesioned organs compatible with bovine tuberculosis in slaughtered cattle from pastoral areas in Uganda were collected and cultured to isolate mycobacteria. AccuProbe culture identification kits for the Mycobacterium tuberculosis complex, M. avium complex and M. avium were used to identify the isolates. Spoligotyping and Insertion Sequence (IS) 1311 and IS1245 Restriction Fragment Length Polymorphism analysis (RFLP) were used to further characterise the isolates.