Measuring the genetic contribution of a single locus to a multilocus disease

An increasing number of diseases are being demonstrated to be due to determinants at more than one genetic locus. It thus becomes of interest to determine the genetic contribution of a specific single locus. A method of estimating a "coefficient of genetic contribution" is described herein, based on a comparison of monozygotic twin concordance data for a specific disease, the empirical sibling recurrence risks, and the sharing of identical by descent genes at the specific locus of interest by pairs of siblings who are both affected. The value of the method is that it requires relatively few assumptions, and does not require knowledge of the mode of inheritance of disease susceptibility at the gene locus of interest. If there are major environmental determinants, this method will give a lower bound for the single locus of interest. To illustrate the method, it is applied to two specific diseases, insulin dependent diabetes mellitus (IDDM) and gluten-sensitive enteropathy (GSE), and a specific locus, the HLA gene complex. The best estimates would appear to be that the HLA "genes" provide a coefficient of 60% for IDDM susceptibility, but only 30% for GSE. A possible reason for these differences is the markedly increased disease susceptibility of the DR3/DR4 heterozygote for IDDM.     

Four-year persistence of a single Candida albicans genotype causing bloodstream infections in a surgical ward proven by multilocus sequence typing

The present study represents the first application of multilocus sequence typing to retrospectively investigate a suspected outbreak of Candida albicans bloodstream infection cases that occurred in the same hospital ward between July 1987 and October 1991. Results demonstrated that eight bloodstream infections were caused by the same strain, endemic in the ward, over a 4-year period.     

Development of a multilocus sequence typing scheme for Ureaplasma

Ureaplasma is a commensal of the human urogenital tract but is always associated with invasive diseases such as non-gonococcal urethritis and infertility adverse pregnancy outcomes. To better understand the molecular epidemiology and population structure of Ureaplasma, a multilocus sequence typing (MLST) scheme based on four housekeeping genes (ftsH, rpL22, valS, thrS) was developed and validated using 283 isolates, including 14 serovars of reference strains and 269 strains obtained from clinical patients. A total of 99 sequence types (STs) were revealed: the 14 type strains of the Ureaplasma serovars were assigned to 12 STs, and 87 novel and special STs appeared among the clinical isolates. ST1 and ST22 were the predominant STs, which contained 68 and 70 isolates, respectively. Two clonal lineages (CC1 and CC2) were shown by eBURST analysis, and linkage disequilibrium was revealed through a standardized index of association (I _A ^S). The neighbor-joining tree results of 14 Ureaplasma serovars showed two genetically significantly distant clusters, which was highly congruent with the species taxonomy of ureaplasmas [Ureaplasma parvum (UPA) and Ureaplasma urealyticum (UUR)]. Analysis of the biotypes of 269 clinical isolates revealed that all the isolates of CC1 were UPA and those of CC2 were UUR. Additionally, CC2 was found more often in symptomatic patients with vaginitis, tubal obstruction, and cervicitis. In conclusion, this MLST scheme is adequate for investigations of molecular epidemiology and population structure with highly discriminating capacity.     

Investigating Gata3 as a positional candidate gene for allergic asthma in a murine model

Gata3 is a positional candidate gene for allergic asthma. We determined allergen-induced GATA-3 mRNA and protein expression in asthma susceptible and resistant mice and generated Gata3 sequence data. Our data indicate that the Gata3 gene in isolation is not a causative agent of asthma susceptibility in our model.     

High rate of multilocus deletion in a human tumor cell line

The nature of recessive mutations at the autosomal locus encodingthe purine salvage enzyme adenine phosphoribosyl transferase(APRT) was analyzed in a highly malignant human tumor cell line(the colorectal carcinoma line SW620). Mutant strains resistantto the purine analog 8-azaadenine were obtained in two steps.The first step selection for partial drug resistance producedstrains hemizygous for APRT as a result of high frequency lossof one allele. In the second step selection, low frequency basesubstitutions, small deletions, or insertions produced completeazaadenine resistance. Luria-Delbruck fluctuation analysis ofeach step of this process indicated that the rate of mutationresulting from allele loss was over 100-fold greater than therate of mutation resulting from base substitution. There wasno reproducible difference in the rate of loss of either ofthe two APRT alleles even though one maps to a rearranged chromosome.Similarly base substitution rates for the two alleles were notsignificantly different. Polymorphic loci surrounding APRT onchromosome 16 band q24 were lost together with the selectedgene in all isolates while polymorphic loci on the short armof the chromosome were retained. Thus the high frequency lossof APRT in SW620 appears to be the result of multilocus deletions.SW620 derivatives behaving as heterozygotes were also obtainedin the first step selections, but these constituted only 5%of isolates.     

Investigating the role of implicit prototypes in the prototype willingness model

One useful theory to predict health behavior is the prototype-willingness model (PWM), which posits that people are more willing to engage in behavior to the extent that they have a positive view of the prototypical person who performs that behavior. The goal of the present research is to test whether adding an implicit measure of prototype favorability might improve explanatory power in the PWM. Two studies examined whether implicit prototype favorability uniquely predicted White women’s intentions to engage in healthy sun behavior over the next 3–6 months, and their willingness to engage in risky sun behavior, should the opportunity arise. The results suggested that implicit prototype favorability, particularly implicit prototypes of those who engage in risky UV-related behaviors, uniquely predicted intentions to engage in healthy sun behavior and willingness to engage in risky sun behavior in the PWM.     

单钉固定股骨颈骨折的应力分析

本文对单钉同定股骨颈骨折的模型进行应力计算,考虑中空钉和股骨之间的接触以及摩擦作用,分析了不同摩擦系数的影响.有限元计算结果表明:摩擦系数对计算结果有一定的影响,采用不同的摩擦系数,计算结果最大相差7.16%;中空钉和股骨之间按接触计算,计算的结果更精确;如果是进行定性的分析,为了节省计算时间,可以用节点位移耦合代替接触,二者计算结果最大相差8.58%.     

Analysis of a uropathogenic Escherichia coli clonal group by multilocus sequence typing

Although many strain typing methods exist for pathogenic Escherichia coli, most have drawbacks in terms of resolving power, interpretability, or scalability. For this reason, multilocus sequence typing (MLST) is an appealing alternative. However, its applicability to different pathogens in specific epidemiologic contexts is not well understood. Here, we applied a previously established MLST method based on housekeeping genes to a well-characterized collection of uropathogenic E. coli isolates to compare the discriminatory ability of this procedure with that of enterobacterial repeat intergenic consensus (ERIC2) PCR, serogrouping, and pulsed-field gel electrophoresis (PFGE). Among 45 E. coli isolates studied, 17 different multilocus sequence types (ST) were identified. One MLST group (designated ST69 complex) was comprised of 22 isolates, all belonging to uropathogenic and bacteremic E. coli strains previously defined as clonal group A (CgA) by ERIC2 PCR. The ST69 strains contained five different serogroups and 14 PFGE types. ERIC2 PCR CgA strains belonging to different MLST groups were also identified. Interestingly, one cow E. coli isolate, previously shown by PFGE to be closely related to a human uropathogenic CgA strain, was found to cluster with the ST69 strains. All of the other animal and environmental CgA isolates had different MLST profiles. The discriminatory power of this MLST method based on housekeeping genes appears to be higher than that of ERIC2 PCR but lower than that of PFGE for epidemiologic study of uropathogenic E. coli.     

腰椎小关节不对称与椎间盘及小关节退变的关系

背景：腰椎小关节不对称与椎间盘退变程度之间的关系一直存在争议,并且国内在下腰痛患者中对小关节不对称与小关节退变程度之间关系的研究较少。 目的：调查分析腰椎小关节不对称在腰椎间盘退变与小关节退变过程中的作用。 方法：测量312例下腰痛患者共936个脊柱功能单位的小关节角度差值,差值<7°定义为小关节对称,差值≥7°定义为小关节不对称。对936个脊柱节段的椎间盘退变程度及小关节退变程度进行分级。 结果与结论：①小关节是否对称在年龄及性别上差异无显著性(P > 0.05)。②小关节不对称与椎间盘退变程度之间无显著关联(P > 0.05)。③在L4~L5节段小关节不对称组比小关节对称组的小关节退变程度更重(P < 0.01)。提示小关节不对称与椎间盘退变无明显影响,但在腰椎活动度最大的L4~L5节段,小关节不对称可能会引起小关节的退变。     

Development of a multilocus sequence typing method for analysis of Listeria monocytogenes clones

This study is a first step in the development of multilocus sequence typing (MLST) method for Listeria monocytogenes. Nine housekeeping genes were analyzed in a set of 62 strains isolated from different sources and geographic locations in Spain. These strains were previously characterized by pulsed-field gel electrophoresis (PFGE). Because of low diversity, two loci were discarded from the study. The sequence analysis of the seven remaining genes showed 29 different allelic combinations, with 22 of them represented by only one strain. The results of this sequence analysis were generally consistent with those of PFGE. Because MLST allows the easy comparison and exchange of results obtained in different laboratories, the future application of this new molecular method could be a useful tool for the listeriosis surveillance systems that will allow the identification and distribution of analysis of L. monocytogenes clones in the environment.     

Development of a multilocus sequence tool for typing Cryptosporidium muris and Cryptosporidium andersoni

Although widely used for the characterization of the transmission of intestinal Cryptosporidium spp., genotyping tools are not available for C. muris and C. andersoni, two of the most common gastric Cryptosporidium spp. infecting mammals. In this study, we screened the C. muris whole-genome sequencing data for microsatellite and minisatellite sequences. Among the 13 potential loci (6 microsatellite and 7 minisatellite loci) evaluated by PCR and DNA sequencing, 4 were eventually chosen. DNA sequence analyses of 27 C. muris and 17 C. andersoni DNA preparations showed the presence of 5 to 10 subtypes of C. muris and 1 to 4 subtypes of C. andersoni at each locus. Altogether, 11 C. muris and 7 C. andersoni multilocus sequence typing (MLST) subtypes were detected among the 16 C. muris and 12 C. andersoni specimens successfully sequenced at all four loci. In all analyses, the C. muris isolate (TS03) that originated from an East African mole rat differed significantly from other C. muris isolates, approaching the extent of genetic differences between C. muris and C. andersoni. Thus, an MLST technique was developed for the high-resolution typing of C. muris and C. andersoni. It should be useful for the characterization of the population genetics and transmission of gastric Cryptosporidium spp.     

Investigating tendon mineralisation in the avian hindlimb: a model for tendon ageing,injury and disease

Mineralisation of the tendon tissue has been described in various models of injury, ageing and disease. Often resulting in painful and debilitating conditions, the processes underlying this mechanism are poorly understood. To elucidate the progression from healthy tendon to mineralised tendon, an appropriate model is required. In this study, we describe the spontaneous and non‐pathological ossification and calcification of tendons of the hindlimb of the domestic chicken (Gallus gallus domesticus). The appearance of the ossified avian tendon has been described previously, although there have been no studies investigating the developmental processes and underlying mechanisms leading to the ossified avian tendon. The tissue and cells from three tendons – the ossifying extensor and flexor digitorum longus tendons and the non‐ossifying Achilles tendon – were analysed for markers of ageing and mineralisation using histology, immunohistochemistry, cytochemistry and molecular analysis. Histologically, the adult tissue showed a loss of healthy tendon crimp morphology as well as markers of calcium deposits and mineralisation. The tissue showed a lowered expression of collagens inherent to the tendon extracellular matrix and presented proteins expressed by bone. The cells from the ossified tendons showed a chondrogenic and osteogenic phenotype as well as tenogenic phenotype and expressed the same markers of ossification and calcification as the tissue. A molecular analysis of the gene expression of the cells confirmed these results. Tendon ossification within the ossified avian tendon seems to be the result of an endochondral process driven by its cells, although the roles of the different cell populations have yet to be elucidated. Understanding the role of the tenocyte within this tissue and the process behind tendon ossification may help us prevent or treat ossification that occurs in injured, ageing or diseased tendon.     

Development of a multilocus sequence typing scheme for the opportunistic pathogen Pseudomonas aeruginosa

A multilocus sequence typing (MLST) scheme has been developed for Pseudomonas aeruginosa which provides molecular typing data that are highly discriminatory and electronically portable between laboratories. MLST data confirm the data from previous studies that suggest that P. aeruginosa is best described as nonclonal but as having an epidemic population. The index of association was 0.17, indicating a freely recombining population; however, there was evidence of clusters of closely related strains or clonal complexes among the members of this population. It is apparent that the sequence types (STs) from single isolates, representing each of the present epidemic clones in the United Kingdom from Liverpool, Manchester, and the West Midlands, are not closely related to each other. This suggests distinct evolutionary origins for each of these epidemic clones in the United Kingdom. Furthermore, these clones are distinct from European clone C. Comparison of the results of MLST with those of toxA typing and serotyping revealed that strains with identical STs may possess different toxA types and diverse serotypes. Given that recombination is important in the population of P. aeruginosa, the lack of a linkage between toxA type and serotype is not surprising and reveals the strength of the MLST approach for obtaining a better understanding of the epidemiology of P. aeruginosa.     

A kinetic model of the transformation of a micropatterned amorphous precursor into a porous single crystal

Biogenic single crystals with complex shapes are believed to be generated by the crystallization of an amorphous precursor. Recent biomimetic experiments on the crystallization of calcite via amorphous-to-crystalline transition point to the fact that the transformation kinetics may be controlled by the micropattern and the macroscopic shape of the amorphous precursor phase. Here we analyse a simple kinetic model, based on thermodynamic considerations, showing that the presence of cavities in the micropatterned precursor phase might interfere with the transformation process and control its kinetics. The size of the cavities couples to the total surface energy and, hence, to crystal nucleation and growth, while the spacing of the cavities, as compared to the typical diffusion path, controls the possible nucleation of competing crystals.     

Clonal complexes of Campylobacter jejuni identified by multilocus sequence typing correlate with strain associations identified by multilocus enzyme electrophoresis

Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) with SmaI were used to subtype 55 isolates of Campylobacter jejuni from a diverse range of human and animal sources previously characterized by multilocus enzyme electrophoresis (MEE). MEE and MLST targeted 11 and 7 loci, respectively, and all loci were unique to each method. MEE, MLST, and PFGE identified 40, 37, and 48 discrete subtypes, respectively, with many of the subtypes occurring only once within the data set. Simpson's indices of diversity were calculated to be 0.979, 0.966, and 0.994 for MEE, MLST, and PFGE, respectively, demonstrating that MEE and MLST had similar discriminatory powers but that PFGE was more discriminatory. Allele diversity was higher in the MLST loci; individual single-locus diversities for the 11 MEE loci and the 7 MLST loci were 0.491 and 0.854, respectively. The clonal complexes recognized by MLST correlated with the strain associations previously recognized by MEE and contained some isolates indistinguishable by PFGE. Many clusters contained isolates from diverse geographical regions and from both humans and animals. These results demonstrate the usefulness of MLST for investigation of the global epidemiology of this important pathogen and illustrate its potential to identify indistinguishable strains or clones in geographically distinct regions.