Biomechanical spinal growth modulation and progressive adolescent scoliosis – a test of the 'vicious cycle' pathogenetic hypothesis: Summary of an electronic focus group debate of the IBSE

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this debate was written by Dr Ian A Stokes. It evaluates the hypothesis that in progressive scoliosis vertebral body wedging during adolescent growth results from asymmetric muscular loading in a "vicious cycle" (vicious cycle hypothesis of pathogenesis) by affecting vertebral body growth plates (endplate physes). A frontal plane mathematical simulation tested whether the calculated loading asymmetry created by muscles in a scoliotic spine could explain the observed rate of scoliosis increase by measuring the vertebral growth modulation by altered compression. The model deals only with vertebral (not disc) wedging. It assumes that a pre-existing scoliosis curve initiates the mechanically-modulated alteration of vertebral body growth that in turn causes worsening of the scoliosis, while everything else is anatomically and physiologically 'normal' The results provide quantitative data consistent with the vicious cycle hypothesis. Dr Stokes' biomechanical research engenders controversy. A new speculative concept is proposed of vertebral symphyseal dysplasia with implications for Dr Stokes' research and the etiology of AIS. What is not controversial is the need to test this hypothesis using additional factors in his current model and in three-dimensional quantitative models that incorporate intervertebral discs and simulate thoracic as well as lumbar scoliosis. The growth modulation process in the vertebral body can be viewed as one type of the biologic phenomenon of mechanotransduction. In certain connective tissues this involves the effects of mechanical strain on chondrocytic metabolism a possible target for novel therapeutic intervention.     

Variation in protein levels obtained from human blood cells and biofluids for platelet, peripheral blood mononuclear cell, plasma, urine and saliva proteomics

Blood cells and biofluid proteomics are emerging as a valuable tool to assess effects of interventions on health and disease. This study is aimed to assess the amount and variability of proteins from platelets, peripheral blood mononuclear cells (PBMC), plasma, urine and saliva from ten healthy volunteers for proteomics analysis, and whether protein yield is affected by prolonged fasting. Volunteers provided blood, saliva and morning urine samples once a week for 4 weeks after an overnight fast. Volunteers were fasted for a further 24 h after the fourth sampling before providing their final samples. Each 10 mL whole blood provided 400–1,500 μg protein from platelets, and 100–600 μg from PBMC. 30 μL plasma depleted of albumin and IgG provided 350–650 μg protein. A sample of morning urine provided 0.9–8.6 mg protein/dL, and a sample of saliva provided 70–950 μg protein/mL. None of these yields were influenced by the degree of fasting (overnight or 36 h). In conclusion, in contrast to the yields from plasma, platelets and PBMC, the protein yields of urine and saliva samples were highly variable within and between subjects. Certain disease conditions may cause higher or lower PBMC counts and thus protein yields, or increased urinary protein levels.     

A high-resolution map of the <Emphasis Type="Italic">Grp1</Emphasis> locus on chromosome V of potato harbouring broad-spectrum resistance to the cyst nematode species <Emphasis Type="Italic">Globodera pallida</Emphasis> and <Emphasis Type="Italic">Globodera rostochiensis</Emphasis>

The Grp1 locus confers broad-spectrum resistance to the potato cyst nematode species Globodera pallida and Globodera rostochiensis and is located in the GP21-GP179 interval on the short arm of chromosome V of potato. A high-resolution map has been developed using the diploid mapping population RHAM026, comprising 1,536 genotypes. The flanking markers GP21 and GP179 have been used to screen the 1,536 genotypes for recombination events. Interval mapping of the resistances to G. pallida Pa2 and G. rostochiensis Ro5 resulted in two nearly identical LOD graphs with the highest LOD score just north of marker TG432. Detailed analysis of the 44 recombinant genotypes showed that G. pallida and G. rostochiensis resistance could not be separated and map to the same location between marker SPUD838 and TG432. It is suggested that the quantitative resistance to both nematode species at the Grp1 locus is mediated by one or more tightly linked R genes that might belong to the NBS-LRR class. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. A. Finkers-Tomczak and S. Danan contributed equally to this research.     

Habitat selection by blue swallows Hirundo atrocaerulea Sundevall, 1850 breeding in South Africa and its implications for conservation

This study investigated the utilization of mist‐belt grassland habitat by the threatened blue swallow and was conducted over three successive breeding seasons in the Blue Swallow Natural Heritage Site at Kaapsehoop, Mpumalanga, South Africa. Blue swallows significantly preferred wetlands over grasslands for foraging. Sufficient foraging habitat must be within a 1.5 km radius from an active nest site. The minimum size of a pair of blue swallows home range should be 333 ha, consisting at a minimum of grasslands (243 ha or 73%) and wetlands (90 ha or 27%). In order to conserve this threatened species, habitat transformation should not take place within a minimum radius of 1.5 km of any blue swallow nest. Due to the critical dependence of the blue swallow on wetland habitat for foraging, any development outside the 1.5 km radius that would affect hydrology and water quality within this range would need to be considered, and any adverse effect mitigated. Rehabilitation of areas to a grassland/wetland mosaic would rather quickly support foraging, and eventually breeding. Although a better understanding of the dynamics between wetlands and adjacent grasslands regarding blue swallow habitat requirements is needed, action can already be taken, based on our results.     

Male reed buntings do not adjust parental effort in relation to extrapair paternity

Parental effort is considered to be costly; therefore, malesare expected to provide less care to unrelated offspring. Theoreticalmodels suggest that males should either reduce their care tothe entire brood or alternatively distinguish between relatedand unrelated nestlings and direct provisioning to kin whenpaternity is in doubt. Reed buntings (Emberiza schoeniclus)have been found to have high levels of extrapair paternity (EPP,i.e., offspring of a male other than the male attending thenest; 55% of offspring), and males are therefore under strongselection pressure to adjust their parental effort accordingto the proportion of EPP in their brood. In this study, we investigatedwhether male reed buntings exhibit a reduction in paternal care(incubation and provisioning nestlings) in relation to decreasedpaternity. We also assess whether males bias their provisioningtoward kin. We measured incubation time, provisioning rates,and food allocation to individual nestlings using video recordingsat the nests. Microsatellite DNA analysis was used to analyzethe paternity of offspring. In direct contrast to a previousstudy on the same species, our results provided no indicationthat males lowered their effort with decreased paternity. Furthermore,in nests of mixed paternity, males did not bias their provisioningbehavior to kin. It remains to be investigated whether the absenceof a relationship between paternity and paternal care can beascribed to absence of reliable paternity cues or whether thebenefits of reducing paternal care did not outweigh the costsin our study population. We found no evidence that the levelof paternal care affected male survival or offspring mass, suggestingthat both the benefits and costs of any reduction in paternalcare would have been low.     

Manganese(II) complexes of a set of 2-aminomethylpyridine-derived ligands bearing a methoxyalkyl arm: syntheses, structures and magnetism

Four new ligands, N-(2-methoxyethyl)-N-(pyridin-2-ylmethyl)amine (mepma), N-(3-methoxypropyl)-N,N-bis(pyridin-2-ylmethyl)amine (mpbpa), N-(2-methoxyethyl)-N,N-bis(pyridin-2-ylmethyl)amine (mebpa) and 2-{[(2-methoxyethyl)(pyridin-2-ylmethyl)amino]methyl} phenol (Hmepap), and four of their complexes with manganese(II) halides, [MnCl₂(mepma)₂] (1), [MnCl(μ-Cl)(mpbpa)]₂ (2), [MnBr₂(mebpa)] (3) and [MnBr₂(MeOH)(Hmepap)] (4) have been synthesized and characterized. Single-crystal Xray studies revealed that in all four complexes, the Mn(II) coordination spheres are distorted octahedral. In 1 and 2, the ether oxygen atom does not coordinate to the Mn(II) centre, but in 3 and 4 it does. The mononuclear molecules of 1 are linked by double hydrogen bonds to form linear chains. Temperature dependent magnetic susceptibility measurements revealed that the Mn(II) ions in 1 interact antiferromagnetically, with J=−1.06 cm⁻¹. Compound 2 crystallizes as a double chloride-bridged dimer in which there is a weak ferromagnetic interaction (J=0.55 cm⁻¹) between the Mn(II) pair. The solution EPR spectrum of 2 suggests that in methanol compound 2 decomposes to a great extent to mononuclear species. In compound 3, mebpa acts as a tetradentate ligand with all of its nitrogen and oxygen atoms coordinated to the Mn(II) ion. Unexpectedly, in complex 4, the phenolic oxygen of Hmepap remains protonated and does not coordinate to the metal ion. Instead the oxygen from a methanol molecule coordinates the manganese centre. Hydrogen bonds between one of the two bromide ions, and the methanol and phenol hydroxyl groups, respectively, connect the mononuclear molecules of 4 into chains. No magnetic interactions were observed between the Mn(II) ions in 3 or 4.     

Characterization of SrgA,a Salmonella enterica serovar Typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA,essential for biogenesis of plasmid-encoded fimbriae

Disulfide oxidoreductases are viewed as foldases that help to maintain proteins on productive folding pathways by enhancing the rate of protein folding through the catalytic incorporation of disulfide bonds. SrgA, encoded on the virulence plasmid pStSR100 of Salmonella enterica serovar Typhimurium and located downstream of the plasmid-borne fimbrial operon, is a disulfide oxidoreductase. Sequence analysis indicates that SrgA is similar to DsbA from, for example, Escherichia coli, but not as highly conserved as most of the chromosomally encoded disulfide oxidoreductases from members of the family Enterobacteriaceae. SrgA is localized to the periplasm, and its disulfide oxidoreductase activity is dependent upon the presence of functional DsbB, the protein that is also responsible for reoxidation of the major disulfide oxidoreductase, DsbA. A quantitative analysis of the disulfide oxidoreductase activity of SrgA showed that SrgA was less efficient than DsbA at introducing disulfide bonds into the substrate alkaline phosphatase, suggesting that SrgA is more substrate specific than DsbA. It was also demonstrated that the disulfide oxidoreductase activity of SrgA is necessary for the production of plasmid-encoded fimbriae. The major structural subunit of the plasmid-encoded fimbriae, PefA, contains a disulfide bond that must be oxidized in order for PefA stability to be maintained and for plasmid-encoded fimbriae to be assembled. SrgA efficiently oxidizes the disulfide bond of PefA, while the S. enterica serovar Typhimurium chromosomally encoded disulfide oxidoreductase DsbA does not. pefA and srgA were also specifically expressed at pH 5.1 but not at pH 7.0, suggesting that the regulatory mechanisms involved in pef gene expression are also involved in srgA expression. SrgA therefore appears to be a substrate-specific disulfide oxidoreductase, thus explaining the requirement for an additional catalyst of disulfide bond formation in addition to DsbA of S. enterica serovar Typhimurium.     

A combination of protein profiling and isotopomer analysis using matrix-assisted laser desorption/ionization-time of flight mass spectrometry reveals an active metabolism of the extracellular matrix of 3T3-L1 adipocytes

Differential gel electrophoresis followed by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) is a commonly used protein profiling method. However, observed changes can be explained in multiple ways, one of which is by the protein turnover rate. In order to easily and rapidly obtain information on both the identity and turnover of individual proteins, we applied a combination of protein labeling with L-(ring-2,3,4,5,6 2H5) phenylalanine and MALDI-TOF MS. While the spectrum reveals the identity of a protein, mass isotopomer analysis provides information about the rate of protein labeling as a measure of synthesis or turnover. Using this approach on mature 3T3-L1 adipocytes, we were able to discriminate between rapidly and slowly metabolised proteins. In our isolate, proteins of the cytoskeleton appeared to be slowly metabolised, whereas components of the extracellular matrix, in particular collagen type I alpha 1 (COL1A1) and collagen type I alpha 2 (COL1A2) showed rapid accumulation of newly synthesized proteins. Both proteins appeared to be metabolised in the same ratio as they are present in collagen fibers, i.e. 2:1 (COL1A1: COL1A2). In addition, functionally related proteins were also readily labeled. Taken together, we have shown that a combination of stable isotope labeling and protein profiling by gel electrophoresis and MALDI-TOF analysis can simultaneously provide information on the identity and relative metabolic rate of proteins in eukaryotic cells in a simple, nonhazardous and rapid-throughput way.     

New developments in developmental biology

A report on the 15th International Society of Developmental Biologists Congress, Sydney, Australia, 3-7 September 2005.     

Myometrial activity around estrus in sows: spontaneous activity and effects of estrogens,cloprostenol, seminal plasma and clenbuterol

A new, nonsurgical, open-end catheter technique was used to study spontaneous uterine activity around estrus in sows, and the effects of estrogens, seminal plasma, cloprostenol, and clenbuterol on uterine activity. In the first experiment, uterine activity was studied in 14 multiparous, cyclic sows, during one or more estrous cycles, from day -4 to day 4 of the cycle (day 0: first day of standing estrus). From a few days before estrus until estrus, the percentage of sows showing any uterine contractions increased from 55 to 100%, and frequency and mean amplitude of uterine contractions for these sows increased from 15 to 22/h, and from 20 to 40 mmHg on average. After estrus, uterine activity decreased. There were large differences between sows in uterine activity, which were consistent over the days of the cycle. In the second experiment, 11.5 microg of estrogens in 100 ml saline (n = 17), 100 ml seminal plasma (n = 5), 1 mg cloprostenol in 100 ml saline (n = 10), 0.30 mg clenbuterol in 100 ml saline (n = 11), or 100 ml saline (n = 5) was infused IU, after recording spontaneous activity. Infusion with saline or seminal plasma did not affect uterine activity. Estrogens increased frequency of contractions. Cloprostenol increased both frequency and amplitude of contractions. Clenbuterol reduced both frequency and amplitude of contractions. In conclusion, this study shows that spontaneous uterine activity in sows is increased around estrus, and it supports the role of estrogens in boar seminal plasma in affecting uterine activity around mating. Further, this study has yielded possible tools to study the relation between uterine activity and sperm transport.