Using molecular markers to assess the effect of introgression on quantitative attributes of common bean in the Andean gene pool.

Progress in bean breeding programs requires the exploitation of genetic variation that is present among races or through introgression across gene pools of Phaseolus vulgaris L. Of the two major common bean gene pools, the Andean gene pool seems to have a narrow genetic base, with about 10% of the accessions in the CIAT core collection presenting evidence of introgression. The objective of this study was to quantify the degree of spontaneous introgression in a sample of common bean landraces from the Andean gene pool. The effects of introgression on morphological, economic and nutritional attributes were also investigated. Homogeneity analysis was performed on molecular marker data from 426 Andean-type accessions from the primary centres of origin of the CIAT common bean core collection and two check varieties. Quantitative attribute diversity for 15 traits was studied based on the groups found from the cluster analysis of marker prevalence indices computed for each accession. The two-group summary consisted of one group of 58 accessions (14%) with low prevalence indices and another group of 370 accessions (86%) with high prevalence indices. The smaller group occupied the outlying area of points displayed from homogeneity analysis, yet their geographic origin was widely distributed over the Andean region. This group was regarded as introgressed, since its accessions displayed traits that are associated with the Middle American gene pool: high resistance to Andean disease isolates but low resistance to Middle American disease isolates, low seed weight and high scores for all nutrient elements. Genotypes generated by spontaneous introgression can be helpful for breeders to overcome the difficulties in transferring traits between gene pools.

Advantage of single-trial models for response to selection in wheat breeding multi-environment trials.

An investigation was conducted to evaluate the impact of experimental designs and spatial analyses (single-trial models) of the response to selection for grain yield in the northern grains region of Australia (Queensland and northern New South Wales). Two sets of multi-environment experiments were considered. One set, based on 33 trials conducted from 1994 to 1996, was used to represent the testing system of the wheat breeding program and is referred to as the multi-environment trial (MET). The second set, based on 47 trials conducted from 1986 to 1993, sampled a more diverse set of years and management regimes and was used to represent the target population of environments (TPE). There were 18 genotypes in common between the MET and TPE sets of trials. From indirect selection theory, the phenotypic correlation coefficient between the MET and TPE single-trial adjusted genotype means [ r(p(MT))] was used to determine the effect of the single-trial model on the expected indirect response to selection for grain yield in the TPE based on selection in the MET. Five single-trial models were considered: randomised complete block (RCB), incomplete block (IB), spatial analysis (SS), spatial analysis with a measurement error (SSM) and a combination of spatial analysis and experimental design information to identify the preferred (PF) model. Bootstrap-resampling methodology was used to construct multiple MET data sets, ranging in size from 2 to 20 environments per MET sample. The size and environmental composition of the MET and the single-trial model influenced the r(p(MT)). On average, the PF model resulted in a higher r(p(MT)) than the IB, SS and SSM models, which were in turn superior to the RCB model for MET sizes based on fewer than ten environments. For METs based on ten or more environments, the r(p(MT)) was similar for all single-trial models.

Association between seed coat polyphenolics (tannins) and disease resistance in common bean.

Common beans (Phaseolus vulgaris L) contain a number of antinutritional factors such as condensed tannins. Reducing tannin concentration might contribute to improving the nutritional quality of common bean. But polyphenolics are involved in resistance to diseases and pests, and reducing tannin concentration may have a negative effect on plant resistance. Furthermore, the effects of tannin on disease resistance in different gene pools or in different seed colors are not defined. To investigate these effects, 790 accessions from a common bean core collection were investigated. Data were subjected to independent sample t-tests, and the calculation of correlation coefficients. The mean coat extracts of black and red bean classes were highest (with 0.129 g/g and 0.124 g/g of seed coat, respectively). Among the gene pools, the coat extract was greater in the Middle American gene pool (0.129 g/g) than in the Andean gene pool (0.108 g/g). Coat extract in the Andean gene pool was positively correlated with susceptibility to Middle American isolates of anthracnose and to common bacterial blight, but negatively correlated with susceptibility to Andean isolates of angular leaf spot and to empoasca. Only empoasca damage showed negative correlation with coat extract in the Middle American gene pool. However within gene pools, the coat extracts of different seed classes varied in correlations with reactions to disease and pest infestations. Significant correlations were particularly associated with the black seed class in both gene pools. The relationships between coat extract and disease reactions are complex. A better understanding will help breeders to select germplasm with improved nutritional quality without adversely affecting disease resistance.

A comparison of Kodak Ultraspeed and Ektaspeed plus dental X-ray films for the detection of dental caries.

BACKGROUND: Using the fastest dental X-ray film available is an easy way of reducing exposure to ionizing radiation. However, the diagnostic ability of fast films for the detection of proximal surface caries must be demonstrated before these films will become universally accepted. METHODS: Extracted premolar and molar teeth were arranged to simulate a bitewing examination and radiographed using Ultraspeed and Ektaspeed Plus dental X-ray films. Three different exposure times were used for each film type. Six general dentists were used to determine the presence and depth of the decay in the proximal surfaces of the teeth radiographed. The actual extent of the decay in the teeth was determined by sectioning the teeth and examining them under a microscope. RESULTS: There was no significant difference between the two films for the mean correct diagnosis. However, there was a significant difference between the means for the three exposure times used for Ultraspeed film. The practitioners used were not consistent in their ability to make a correct diagnosis, or for the film for which they got the highest correct diagnosis. CONCLUSIONS: Ektaspeed Plus dental X-ray film is just as reliable as Ultraspeed dental X-ray film for the detection of proximal surface decay. The effect of underexposure was significant for Ultraspeed, but not for Ektaspeed Plus. Patient exposure can be reduced significantly with no loss of diagnostic ability by changing from Ultraspeed X-ray film to Ektaspeed Plus X-ray film.

A comparison of Kodak Ultraspeed and Ektaspeed Plus dental X-ray films for use in endodontics.

BACKGROUND: The advantage of using a faster film for length determination in endodontic therapy is obvious. However, for such a film to be generally accepted, it must demonstrate comparable diagnostic quality to traditionally used films. METHODS: The comparative accuracy of canal length determination of Ultraspeed and Ektaspeed Plus dental X-ray films was assessed in maxillary first and second molars; for different canals, for different teeth, for different exposures, and for different examiners (five general dentists and three endodontic specialists). RESULTS: In general, there were no significant differences between films, among examiners, or any interaction between films and exposures. That is, an assessor's ability to estimate lengths was not significantly influenced by the film type or by exposure used. There was a wide divergence in the individual assessor's ability to estimate lengths. Specialists estimated lengths more accurately than general practitioners and estimated lengths more accurately with Ektaspeed Plus film. Length determination in distobuccal and mesiobuccal canals was more accurate than in palatal canals. Most palatal canals were underestimated in length by more than 1mm. The use of file sizes larger in number than size 15 is recommended in these canals. CONCLUSION: For length determination, Ektaspeed Plus dental X-ray film is as effective as Ultraspeed film. Given the acceptable quality and accuracy of Ektaspeed Plus film, there seems to be no clinical reason to subject patients to greater radiation by using a slower film during endodontic therapy.

A laboratory study of dimensional changes for three elastomeric impression materials using custom and stock trays.

Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. Three elastomeric impression materials were used in custom and stock trays to determine the accuracy of impressions taken from an experimental stainless steel model representing premolar and molar bridge abutment preparations. Horizontal and vertical individual abutment and interabutment dimensions were measured on die stone replicas, and the measurements compared with those obtained from stainless steel master models. The results of this study demonstrate polysulphide is the least accurate impression material for both vertical and horizontal individual abutment dimensions. However, for interabutment horizontal dimensions, no statistical differences were noted between impression material types when using a custom tray. Stock trays produced unreliable results for all the materials tested.

Classifying infants in the Strange Situation with three-way mixture method of clustering.

The quality of the attachment relationship between mother and infant is typically determined in the Strange Situation. The assignments of infants to the A (avoidant), B (secure), and C (resistant) attachment classes are largely but not exclusively based on measurements during the reunion episodes. In this paper, the measurements in the reunion episodes are used to derive a clustering of the infants via three-way mixture method of clustering, a technique especially designed for clustering three-way mixture method of clustering, a technique especially designed for clustering three-way data (here: infants, variables and episodes). The results are compared with the A-B-C classification, and the relevance of the outcomes for attachment research are discussed. At the same time, the paper aims to demonstrate the use and usefulness of the three-way clustering procedure for data from the social and behavioural sciences.

Orthodontic treatment need and the dental aesthetic index.

The Dental Aesthetic (DAI) was devised as a measure of dental appearance and based on lay opinions as opposed to professional assessments of need. The DAI is calculated from the weighted scores of ten occlusal variables. These same variables have been used in other malocclusion indices intended to measure morphological deviations from normality. It is, therefore, important to ask if the DAI might be used to screen both deviations of dental appearance and deviations of occlusion from accepted norms. The original DAI design was based on analysis data from permanent dentitions. However, a large percentage of orthodontic assessments are carried out in the mixed dentition. Therefore, the present study includes a sample of mixed dentitions to test the effectiveness of the DAI in this group. The DAI was tested against the subjective assessments of severity made by orthodontists. Sensitivity and negative predictive power were high. Performance in the mixed dentition group was slightly lower than the permanent dentition group. It is concluded that while the DAI is not sufficiently reliable for assessment of treatment need in the individual, its sensitivity and negative predictive power might provide a useful screening mechanism which reflects both the concerns of patients regarding appearance and the general treatment recommendations of orthodontists. Testing on much larger samples is now required.

Phenotypic and functional analysis of peripheral blood lymphocytes in oral lichen planus.

To assess cellular immunity in oral lichen planus (OLP), peripheral blood mononuclear cells (PBMC) were obtained from 19 OLP patients and 30 control subjects. The proportions of circulating CD45RA+ and CD29+ lymphocyte subsets were determined. The proliferative activity of PBMC to the non-specific plant mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) was examined together with the spontaneous proliferative response and the response in the autologous mixed lymphocyte reaction (AMLR). In the OLP group, the proportion of CD4+ CD45RA+ T lymphocytes was significantly less than control subjects and the proportion of CD4+ CD29+ T lymphocytes was increased significantly. The proliferative response to PHA was similar in OLP and controls subjects. Con A-stimulated PBMC proliferation was decreased significantly in the OLP group. Spontaneous PBMC proliferation in patients with non-reticular lesions was significantly less than control subjects. Despite a mildly depressed response in the AMLR in OLP patients, this result was not statistically significant. Results of the phenotypic analysis of peripheral blood lymphocytes indicate a decreased proportion of naive T cells and an increased proportion of primed memory T cells, although the antigen specificity of these memory cells remains to be determined. Results of the functional assays would seem to reflect this phenotypic shift, and as T cells responding to Con A stimulation and in the AMLR possess suppressor-inducer activity, these results may also suggest an association between OLP and defective innate T cell-mediated suppressor circuits.

Automated microdensitometry of nucleolar organizer regions using microspectrophoto-microscopy.

Nucleolar organizer regions (NORs) are major sites of ribosomal RNA synthesis, providing an index of transcriptional activity and possibly determining the malignant status of cells. Difficulties lie in quantifying them. This study reports a methodology to assist in the standardization of the assessment of interphase NORs. Regenerating hepatocytes, which have increased rRNA synthesis, were chosen as a model to test automated microdensitometry for silver-stained NORs. Quantification employed a microspectrophoto-microscope as a microdensitometer. Significant differences in silver-stained NORs in hepatocytes were recorded among treatment/fixative groups. As the quantitative method avoids subjective observer error and thus improves the accuracy of measurement, it would potentially have routine application to diagnostic pathology.

Classifying genotypic data from plant breeding trials: a preliminary investigation using repeated checks.

Several subjective choices must be made when classifying genotypes based on data from plant breeding trials. One choice involves the method used to weight the contribution each environment makes to the classification. A second involves the use of either genotype-means for each environment or genotypevalues for each block, i.e., considering each block to be a different environment. Another involves whether environments (or blocks) in which genotypes are nonsignificantly different should be included or excluded from such classifications. An alternative to the use of raw or standardized data, is proposed in which each environment is weighted by a discrimination index (DI) that is based on the concept of repeatability. In this study the effect of three weighting methods (raw, standardized and DI), the choice of using environments or blocks, and the choice of including or excluding environments or blocks in which genotypic effects were not significant, were considered in factorial combination to give 12 options. A data set comprised of five check cultivars each repeated six times in each of three blocks at six environments was used. The effect of these options on the ability of a hierarchical clustering technique to correctly classify the repeats into five groups, each consisting of all the six repeats of a particular check cultivar, was investigated. It was found that the DI weighting method generally led to better recovery of the known structure. Using block data rather than environmental data also improved structure recovery for each of the three weighting methods. The exclusive use of environments in which genotypic effects were significant decreased structure recovery while the contrary generally occurred for blocks. The best structure recovery was obtained from the DI weighting applied to blocks (whether genotypes were significant or not).

Occlusal contacts: comparison of orthodontic patients, posttreatment patients, and untreated controls.

Orthodontic treatment may severely alter tooth contacts during early treatment, but after its completion the number of contracts increases with settling of the occlusion. Long-term changes are sparsely documented and this investigation examined changes by comparing adequate control groups before treatment, during treatment, and several years after treatment. Although the number of contacts is gradually elevated after orthodontic treatment, the present data suggested that orthodontic patients may not realize the same number of contacts as untreated controls despite prolonged periods out of retention. The functional significance of this finding remains unknown and suggests the need for further research.

Dimensional change of impressions on sterilization.

The volume of impressions, before and after disinfection in a gluteraldehyde solution for longer than ten hours (that is, sterilization), was measured indirectly from dies produced from the impressions. Three elastomeric impression materials were used in both acrylic resin and poly-vinyl-chloride 'trays' to form the impressions. One impression material appeared to be practically superior to the others with respect to variability of volume. The effect of tray material on change in volume (calculated as after disinfection minus before disinfection) was significant for one impression material; acrylic trays produced the greatest effect. The change in volume was significant for two impression materials; acrylic trays were associated with greater increase in volume. It was concluded that if impressions are to be sterilized, a tray material having minimal potential to absorb disinfectant should be used.

Multiattribute evaluation of regional cotton variety trials.

The Australian Cotton Cultivar Trials (ACCT) are designed to investigate various cotton [Gossypium hirsutum (L.)] lines in several locations in New South Wales and Queensland each year. If these lines are to be assessed by the simultaneous use of yield and lint quality data, then a multivariate technique applicable to three-way data is desirable. Two such techniques, the mixture maximum likelihood method of clustering and three-mode principal component analysis, are described and used to analyze these data. Applied together, the methods enhance each other's usefulness in interpreting the information on the line response patterns across the locations. The methods provide a good integration of the responses across environments of the entries for the different attributes in the trials. For instance, using yield as the sole criterion, the excellence of the namcala and coker group for quality is overlooked. The analyses point to a decision in favor of either high yields of moderate to good quality lint or moderate yield but superior lint quality. The decisions indicated by the methods confirmed the selections made by the plant breeders. The procedures provide a less subjective, relatively easy to apply and interpret analytical method of describing the patterns of performance and associations in complex multiattribute and multilocation trials. This should lead to more efficient selection among lines in such trials.

Cement spacing for the one-step post-core and crown. A new laboratory technique.

A technique to provide cement spacing for cast post-cores prior to construction of their crowns is described. The axial lift of crowns cemented with zinc phosphate was greater, but not significantly, for crowns constructed on non-spaced post-cores compared with crowns constructed on spaced post-cores. Three materials were evaluated to determine their effectiveness in providing cement spacing for post-cores. The phenomenon of post-core 'wedging' during luting was identified.

Attitudes and knowledge of nursing staff in relation to management of postoperative pain.

The effectiveness of pain control following surgery is notoriously difficult to assess, but objective assessment by nursing staff has been found to correlate reasonably well with subjective patient assessment. A study was designed to investigate the attitudes and knowledge of 86 qualified nursing staff in relation to postoperative pain management. Overall knowledge was sound to a point, but there were some obvious deficiencies in practical application; for example, 25% of staff would wait until a patient was in severe pain before using a prescribed (charted) analgesic. Additionally, almost three-quarters of staff felt that, in general, postoperative patients received adequate pain relief, while the great majority felt that prescription writing could be improved, mainly by improved legibility and clarity of actual instructions. The results suggest that the aim of postoperative pain management--that is, the provision of adequate analgesia--may need to be more strongly defined in nursing education.