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PubMed2001

[Analysis of cDNA and protein structure of tree shrew cholesterol ester transfer protein].

OBJECTIVE: To obtain the nucleotide sequence and deduced amino acid sequence of cholesteryl ester transfer protein (CETP) cDNA of tree shrew, mammalian insusceptible to atherosclerosis. METHODS: The first strand of cDNA of tree shrew was obtained from its liver. The sequence of tree shrew CETP cDNA was obtained by using techniques of switching mechanism at 5' end of RNA transcript (SMART) and rapid amplification of cDNA end (RACE), The CETP amino acid sequence was deduced from this cDNA and its primary and secondary structures were predicted by using DNAMAN, a software of molecular biology. Results The tree shrew CETP cDNA sequence covers 1636 bp, including a 178 bp fragment at the 3' of untranslated region and a 1458 bp fragment in the coding region, coding the complete sequence of mature tree shrew CETP except the initiator methionine. There are 477 amino acids in its mature protein, one amino acid more than that in human beings, with an extra Gly318. The homology of tree shrew CETP and human CETP and rabbit CETP is 88% and 82% respectively judged by comparing the amino acid sequence of tree shrew CETP and those of human beings and rabbit. The regions concerning the CETP function of binding and transferring neutral lipids in tree shrew CETP amino acid sequence are highly conservative. However, there is a deletion of N-linked glycosylation site at Asn342 in tree shrew protein that may increase the ability of removing peripheral cholesterol and cholesteryl ester. CONCLUSION: The glycosylation in tree shrew CETP may be one of the mechanisms of insusceptibility to atherosis of tree shrew.

Amino Acid Sequence↗

PubMed2000

Do the DSM decision trees improve diagnostic ability?

Experiment 1 examined whether the use of the DSM-III-R decision trees increased the accuracy of DSM-III-R diagnoses. Results indicated that the use of the decision trees interacted with the level of DSM-III-R experience to affect diagnostic accuracy. The use of the decision trees resulted in a modest increase in diagnostic accuracy for participants with less DSM-III-R experience; for participants with more DSM-III-R experience, the use of the decision trees had no significant effect on diagnostic accuracy. Experiment 2 examined whether the use of the DSM-III-R decision trees increased the accuracy and confidence and decreased the time of DSM-IlI-R diagnosis across participants with varying levels of DSM-III-R experience. The primary analyses consisted of a 3 x 2 x 2-multivariate analysis of variance (MANOVA) to determine whether the use of the decision trees increased diagnostic accuracy and diagnostic confidence and decreased diagnostic time. Results indicated (1) the experienced participants made more accurate diagnoses than the less-experienced and no-experience participants: (2) the decision trees, combined with practice, increased class diagnostic accuracy and decreased diagnostic time; and (3) participants were more confident in their diagnosis when they used the decision trees than when they did not use the decision trees. Supplementary analyses consisted of two one-way analysis of variance (ANOVA) procedures and indicated that participants' preference for and knowledge of how to use the decision trees did not significantly affect their diagnostic accuracy.

Adult↗

PubMed2003

Elevated CO2 reduces sap flux in mature deciduous forest trees.

We enriched in CO2 the canopy of 14 broad-leaved trees in a species-rich, ca. 30-m-tall forest in NW Switzerland to test whether elevated CO2 reduces water use in mature forest trees. Measurements of sap flux density (JS) were made prior to CO2 enrichment (summer 2000) and throughout the first whole growing season of CO2 exposure (2001) using the constant heat-flow technique. The short-term responses of sap flux to brief (1.5-3 h) interruptions of CO2 enrichment were also examined. There were no significant a priori differences in morphological and physiological traits between trees which were later exposed to elevated CO2 (n=14) and trees later used as controls (n=19). Over the entire growing season, CO2 enrichment resulted in an average 10.7% reduction in mean daily JS across all species compared to control trees. Responses were most pronounced in Carpinus, Acer, Prunus and Tilia, smaller in Quercus and close to zero in Fagus trees. The JS of treated trees significantly increased by 7% upon transient exposure to ambient CO2 concentrations at noon. Hence, responses of the different species were, in the short term, similar in magnitude to those observed over the whole season (though opposite because of the reversed treatment). The reductions in mean JS of CO2-enriched trees were high (22%) under conditions of low evaporative demand (vapour pressure deficit, VPD <5 hPa) and small (2%) when mean daily VPD was greater than 10 hPa. During a relatively dry period, the effect of elevated CO2 on JS even appeared to be reversed. These results suggest that daily water savings by CO2-enriched trees may have accumulated to a significantly improved water status by the time when control trees were short of soil moisture. Our data indicate that the magnitude of CO2 effects on stand transpiration will depend on rainfall regimes and the relative abundance of the different species, being more pronounced under humid conditions and in stands dominated by species such as Carpinus and negligible in mono-specific Fagus forests.

Betulaceae↗

PubMed2003

Fire survival of lowland tropical rain forest trees in relation to stem diameter and topographic position.

The objective of this study was to relate patterns in forest structure, tree species diversity, and tree species composition to stem diameters and topography in unburned, once burned and twice burned lowland dipterocarp rain forests in East Kalimantan, Indonesia. To do this four unburned old growth forests were compared with three forests that burned once (1997/1998) and three forests that burned twice (1982/1983 and 1997/1998). Fire resulted in a strong reduction of climax tree density which was negatively related to tree diameter. However, a disproportionate reduction in small diameter understorey climax tree species occurred only after repeated fires. Climax tree species in both burned forest types were most common in swamps, river valleys and on lower slopes, while their density was much lower on places higher along hillsides. In unburned forest the opposite was observed, with climax tree density increasing steadily from swamp and river valleys to upper slopes and ridges. In contrast to climax trees, pioneer trees were abundant throughout the burned forest, with highest numbers on hill sides and ridges. Our results indicate that both diameter and topographic position of trees strongly affect their fire survival chances in tropical lowland forests.

Fires↗

PubMed2004

Response of tree biomass and wood litter to disturbance in a Central Amazon forest.

We developed an individual-based stochastic-empirical model to simulate the carbon dynamics of live and dead trees in a Central Amazon forest near Manaus, Brazil. The model is based on analyses of extensive field studies carried out on permanent forest inventory plots, and syntheses of published studies. New analyses included: (1) growth suppression of small trees, (2) maximum size (trunk base diameter) for 220 tree species, (3) the relationship between growth rate and wood density, and (4) the growth response of surviving trees to catastrophic mortality (from logging). The model simulates a forest inventory plot, and tracks recruitment, growth, and mortality of live trees, decomposition of dead trees (coarse litter), and how these processes vary with changing environmental conditions. Model predictions were tested against aggregated field data, and also compared with independent measurements including maximum tree age and coarse litter standing stocks. Spatial analyses demonstrated that a plot size of approximately 10 ha was required to accurately measure wood (live and dead) carbon balance. With the model accurately predicting relevant pools and fluxes, a number of model experiments were performed to predict forest carbon balance response to perturbations including: (1) increased productivity due to CO2 fertilization, (2) a single semi-catastrophic (10%) mortality event, (3) increased recruitment and mortality (turnover) rates, and (4) the combined effects of increased turnover, increased tree growth rates, and decreased mean wood density of new recruits. Results demonstrated that carbon accumulation over the past few decades observed on tropical forest inventory plots (approximately 0.5 Mg C ha(-1) year(-1)) is not likely caused by CO2 fertilization. A maximum 25% increase in woody tissue productivity with a doubling of atmospheric CO2 only resulted in an accumulation rate of 0.05 Mg C ha(-1) year(-1) for the period 1980-2020 for a Central Amazon forest, or an order of magnitude less than observed on the inventory plots. In contrast, model parameterization based on extensive data from a logging experiment demonstrated a rapid increase in tree growth following disturbance, which could be misinterpreted as carbon sequestration if changes in coarse litter stocks were not considered. Combined results demonstrated that predictions of changes in forest carbon balance during the twenty-first century are highly dependent on assumptions of tree response to various perturbations, and underscores the importance of a close coupling of model and field investigations.

Biomass↗

PubMed2005

Environmental sensitivity of gas exchange in different-sized trees.

The carbon isotope signature (delta13C) of foliar cellulose from sunlit tops of trees typically becomes enriched as trees of the same species in similar environments grow taller, indicative of size-related changes in leaf gas exchange. However, direct measurements of gas exchange in common environmental conditions do not always reveal size-related differences, even when there is a distinct size-related trend in delta13C of the very foliage used for the gas exchange measurements. Since delta13C of foliage predominately reflects gas exchange during spring when carbon is incorporated into leaf cellulose, this implies that gas exchange differences in different-sized trees are most likely to occur in favorable environmental conditions during spring. If gas exchange differs with tree size during wet but not dry conditions, then this further implies that environmental sensitivity of leaf gas exchange varies as a function of tree size. These implications are consistent with theoretical relationships among height, hydraulic conductance and gas exchange. We investigated the environmental sensitivity of gas exchange in different-sized Douglas-fir (Pseudotsuga menziesii) via a detailed process model that specifically incorporates size-related hydraulic conductance [soil-plant-atmosphere (SPA)], and empirical measurements from both wet and dry periods. SPA predicted, and the empirical measurements verified, that differences in gas exchange associated with tree size are greatest in wet and mild environmental conditions and minimal during drought. The results support the hypothesis that annual net carbon assimilation and transpiration of trees are limited by hydraulic capacity as tree size increases, even though at particular points in time there may be no difference in gas exchange between different-sized trees. Maximum net ecosystem exchange occurs in spring in Pacific Northwest forests; therefore, the presence of hydraulic limitations during this period may play a large role in carbon uptake differences with stand-age. The results also imply that the impacts of climate change on the growth and physiology of forest trees will vary depending on the age and size of the forest.

Carbon Dioxide↗

PubMed2006

Tree height and age-related decline in growth in Scots pine (Pinus sylvestris L.).

Growth and seasonal water use was measured amongst trees growing in an old growth Scots pine forest in the Scottish Highlands. Three sites which differed in their recent management history and contained old and naturally regenerated young trees growing together were monitored in the field. Our results showed a clear decrease in growth efficiency with age, from values of around 0.25 kg m(-2) leaves year(-1) in approximately 25-year-old trees to less than 0.1 kg m(-2) leaves year(-1) in trees over 200 years old. When the old trees in one of the field sites were released from competition by thinning, their growth efficiency reverted to that of coexisting young trees, indicating that the decline in growth was reversible. This is consistent with the results of a parallel study showing that cambial age had no effect on the physiology or growth of grafted seedlings originating from the same population studied here (Mencuccini et al. 2005). Our detailed study of tree water use in the field showed an overall decrease in whole-tree hydraulic conductance and stomatal canopy conductance with tree height in the unthinned stands, in agreement with the hydraulic limitation hypothesis. However, the effect of this reduction in hydraulic efficiency on growth was comparatively small, and old trees also showed consistently lower nitrogen concentrations in needles, suggesting that hydraulic and nutritional factors combined to produce the decline in growth efficiency with age observed in the studied populations.

Pinus sylvestris↗

PubMed2007

Water source partitioning among trees growing on shallow karst soils in a seasonally dry tropical climate.

The sources of water used by woody vegetation growing on karst soils in seasonally dry tropical regions are little known. In northern Yucatan (Mexico), trees withstand 4-6 months of annual drought in spite of the small water storage capacity of the shallow karst soil. We hypothesized that adult evergreen trees in Yucatan tap the aquifer for a reliable supply of water during the prolonged dry season. The naturally occurring concentration gradients in oxygen and hydrogen stable isotopes in soil, bedrock, groundwater and plant stem water were used to determine the sources of water used by native evergreen and drought-deciduous tree species. While the trees studied grew over a permanent water table (9-20 m depth), pit excavation showed that roots were largely restricted to the upper 2 m of the soil/bedrock profile. At the peak of the dry season, the delta(18)O signatures of potential water sources for the vegetation ranged from 4.1 +/- 1.1 per thousand in topsoil to -4.3 +/- 0.1 per thousand in groundwater. The delta(18)O values of tree stem water ranged from -2.8 +/- 0.3 per thousand in Talisia olivaeformis to 0.8 +/- 1 per thousand in Ficus cotinifolia, demonstrating vertical partitioning of soil/bedrock water among tree species. Stem water delta(18)O values were significantly different from that of groundwater for all the tree species investigated. Stem water samples plotted to the right of the meteoric water line, indicating utilization of water sources subject to evaporative isotopic enrichment. Foliar delta(13)C in adult trees varied widely among species, ranging from -25.3 +/- 0.3 per thousand in Enterolobium cyclocarpum to -28.7 +/- 0.4 per thousand in T. olivaeformis. Contrary to initial expectations, data indicate that native trees growing on shallow karst soils in northern Yucatan use little or no groundwater and depend mostly on water stored within the upper 2-3 m of the soil/bedrock profile. Water storage in subsurface soil-filled cavities and in the porous limestone bedrock is apparently sufficient to sustain adult evergreen trees throughout the pronounced dry season.

Carbon Isotopes↗

PubMed2005

Floristics, performance and prognosis of historical trees in the urban forest of Guangzhou city (China).

Outstanding historical trees embedded in cities constitute pertinent environmental assets, yet they are widely threatened in third-world cities. Inadequate understanding of this valuable natural-cum-cultural heritage hinders proper conservation. A case study of Guangzhou in south China evaluated floristic composition, age profile and biomass structure of historical trees, assessed their performance in major habitats (institutional, park and roadside), and established a prognosis for future growth and management. The 348 historical trees examined belonged to only 25 species, vis-à-vis 254 trees in the entire urban forest, dominated by five species and native members. Roadside had more trees, followed by institutional and park, with merely the most common four species shared by all habitats. The limited commonality reflected tree-performance differentiation by habitats exerting selection pressure on species. The institutional growth-regime was more conducive to nurturing high-caliber specimens, whereas park is less capable. Individual species achievement by habitats, derived from tree-count ranking and relative-abundance indices, could inform species choice and tree conservation. Few trees exceeded 300 years of age in the millennium-old city, echoing a history of intense tree-city conflicts. Potential life-span, trunk and crown diameters indicated ample opportunities for further expansion of biomass and landscape impacts, which would be straitjacketed by the tightening urban fabric.

Biomass↗

PubMed1986

Branching ratio and growth of tree-like structures.

Dichotomously branching trees were generated by computer using random terminal and random segmental growth. The branching ratio (Rb) of such a tree during growth oscillates periodically as new branches are added. The magnitude of the oscillations diminishes as the tree enlarges and Rb converges towards an expected value. This phenomenon was investigated using the reverse of the growth process, that is by terminal or segmental subtraction of branches from existing trees. These were either computer generated trees or mammalian bronchial tree data. The oscillations of Rb thus obtained were similar to those obtained during growth and were used to calculate convergent values of Rb. In addition, an estimate of convergent Rb was obtained from the mean of the maximum and minimum Rb of the first oscillation occurring when the least number of branches had been subtracted. Values of Rb obtained by these methods were compared with those obtained by taking the antilogarithm of the slope of the regression of log number of branches against order. With large trees the results are similar, but with smaller trees a more reliable Rb is given by the means of the oscillations. We find that Rb values from the bronchial trees are different from those generated by random segmental growth and are not always in good agreement with random terminal growth. Some other growth process must therefore be operative in the bronchial tree.

Animals↗

PubMed2005

Regeneration of Nothofagus pumilio [Poepp. et Endl.] Krasser forests after five years of seed tree cutting.

Nothofagus pumilio [Poepp. et Endl.] Krasser is a deciduous tree species that grows in Chile and adjacent Argentina between 36 and 56 degrees S, often forming the Andean tree line. Silvicultural systems proposed for this species integrate both regeneration and intermediate level operations in an orderly process for managing forest stands. The seed-tree method of regeneration has been used to manage even-aged stands of this species. This paper investigates the effect of seed tree cuttings on the regeneration of Nothofagus pumilio [Poepp. et Endl.] Krasser forest located in the Magallanes region (Chile). The studied forest was managed on an even-aged basis using a seed tree silvicultural system for regeneration with an intensity of cutting of 65-70% of the basal area and a minimum of 15 dominant lenga trees per hectare retained. A regeneration inventory sampling was used to quantify regeneration attributes in the study area. Regeneration was found to be significantly affected by the seed tree cuttings. In fact, the number of established individuals rose from 0.39 to 26.7 plants m(-2) pre-harvest to 9.2-21.5 plants m(-2) post-harvest, depending on the particular development stage. Total regeneration ranged from 9.5 to 48.2 plants m(-2). The number of plants established over the period 1992-1997 was related to the residual basal area, coverage and number of trees. However, mean tree height was not significantly related to any regeneration variable. Significant variables were used to establish a regeneration prediction model using single and multiple linear equations (R2<0.418). Consequently, the seed tree method of regeneration can be considered feasible for commercially valuable lenga forests, although this method, in its strictest application, will create many large, irregularly shaped, even-aged groups.

Chile↗

PubMed2001

Limitations and perspectives about scaling ozone impacts in trees.

We review the need for scaling effects of ozone (O3) from juvenile to mature forest trees, identify the knowledge presently available, and discuss limitations in scaling efforts. Recent findings on O3/soil nutrient and O3/CO2 interactions from controlled experiments suggest consistent scaling patterns for physiological responses of individual leaves to whole-plant growth, carbon allocation, and water use efficiency of juvenile trees. These findings on juvenile trees are used to develop hypotheses that are relevant to scaling O3 effects to mature trees, and these hypotheses are examined with respect to existing research on differences in response to O3 between juvenile and mature trees. Scaling patterns of leaf-level physiological response to O3 have not been consistent in previous comparisons between juvenile and mature trees. We review and synthesize current understanding of factors that may cause such inconsistent scaling patterns, including tree-size related changes in environment, stomatal conductance, O3 uptake and exposure. carbon allocation to defense, repair, and compensation mechanisms, and leaf production phenology. These factors should be considered in efforts to scale O3 responses during tree ontogeny. Free-air O3 fumigation experiments of forest canopies allow direct assessments of O3 impacts on physiological processes of mature trees, and provide the opportunity to test current hypotheses about ontogenetic variation in O3 sensitivity by comparing O3 responses across tree-internal scales and ontogeny.

Air Pollutants↗

PubMed2001

The paradox of great longevity in a short-lived tree species.

Thuja occidentalis is a tree species that was once thought to be relatively short-lived (80 years). Up until 10 years ago maximum ages were considered to be near 400 years, but such trees were thought to be rare. Research along the cliffs of the Niagara Escarpment has altered this view. Exceptionally slow-growing trees of this species have been found with ring counts to 1653 years and estimated ages to 1890 years. Senescence is slow or absent. Injury and death is due to rockfall and sporadic severe drought that kills small sectors of the trees by exposing and killing the roots. Experiments in which colored dyes are infused into roots show that each tree is composed of hydraulically independent units that allow mortality in one part of the 'individual' with little negative effect on the remaining parts of the tree. The trees are small, so environmental loadings of ice, snow, and wind are low. Slow growth of the trees results in a much greater mechanical strength in the wood. Together these properties increase the ability of the cedars to persist on cliffs for long periods of time. The paradox of great longevity in this 'short-lived' tree species is explained by slow growth that minimizes maintenance and repair costs while maximizing durability and strength, combined with an internal architecture that creates functionally independent units within each tree.

Aging↗

PubMed1997

The limitations of decision trees and automatic learning in real world medical decision making.

The decision tree approach is one of the most common approaches in automatic learning and decision making. The automatic learning of decision trees and their use usually show very good results in various "theoretical" environments. But in real life it is often impossible to find the desired number of representative training objects for various reasons. The lack of possibilities to measure attribute values, high cost and complexity of such measurements, and unavailability of all attributes at the same time are the typical representatives. For this reason we decided to use the decision trees not for their primary task--the decision making--but for outlining the most important attributes. This was possible by using a well-known property of the decision trees--their knowledge representation, which can be easily understood by humans. In a delicate field of medical decision making, we cannot allow ourselves to make any inaccurate decisions and the "tips," provided by the decision trees, can be of a great assistance. Our main interest was to discover a predisposition to two forms of acidosis: the metabolic acidosis and respiratory acidosis, which can both have serious effects on child's health. We decided to construct different decision trees from a set of training objects. Instead of using a test set for evaluation of a decision tree, we asked medical experts to take a closer look at the generated trees. They examined and evaluated the decision trees branch by branch. Their comments show that trees generated from the available training set mainly have surprisingly good branches, but on the other hand, for some, no medical explanation could be found.

Acidosis↗

PubMed2003

The small-world dynamics of tree networks and data mining in phyloinformatics.

MOTIVATION: A noble and ultimate objective of phyloinformatic research is to assemble, synthesize, and explore the evolutionary history of life on earth. Data mining methods for performing these tasks are not yet well developed, but one avenue of research suggests that network connectivity dynamics will play an important role in future methods. Analysis of disordered networks, such as small-world networks, has applications as diverse as disease propagation, collaborative networks, and power grids. Here we apply similar analyses to networks of phylogenetic trees in order to understand how synthetic information can emerge from a database of phylogenies. RESULTS: Analyses of tree network connectivity in TreeBASE show that a collection of phylogenetic trees behaves as a small-world network-while on the one hand the trees are clustered, like a non-random lattice, on the other hand they have short characteristic path lengths, like a random graph. Tree connectivities follow a dual-scale power-law distribution (first power-law exponent approximately 1.87; second approximately 4.82). This unusual pattern is due, in part, to the presence of alternative tree topologies that enter the database with each published study. As expected, small collections of trees decrease connectivity as new trees are added, while large collections of trees increase connectivity. However, the inflection point is surprisingly low: after about 600 trees the network suddenly jumps to a higher level of coherence. More stringent definitions of 'neighbour' greatly delay the threshold whence a database achieves sufficient maturity for a coherent network to emerge. However, more stringent definitions of 'neighbour' would also likely show improved focus in data mining. AVAILABILITY: http://treebase.org

Algorithms↗

PubMed1994

Using allele frequencies and geographic subdivision to reconstruct gene trees within a species: molecular variance parsimony.

We formalize the use of allele frequency and geographic information for the construction of gene trees at the intraspecific level and extend the concept of evolutionary parsimony to molecular variance parsimony. The central principle is to consider a particular gene tree as a variable to be optimized in the estimation of a given population statistic. We propose three population statistics that are related to variance components and that are explicit functions of phylogenetic information. The methodology is applied in the context of minimum spanning trees (MSTs) and human mitochondrial DNA restriction data, but could be extended to accommodate other tree-making procedures, as well as other data types. We pursue optimal trees by heuristic optimization over a search space of more than 1.29 billion MSTs. This very large number of equally parsimonious trees underlines the lack of resolution of conventional parsimony procedures. This lack of resolution is highlighted by the observation that equally parsimonious trees yield very different estimates of population genetic diversity and genetic structure, as shown by null distributions of the population statistics, obtained by evaluation of 10,000 random MSTs. We propose a non-parametric test for the similarity between any two trees, based on the distribution of a weighted coevolutionary correlation. The ability to test for tree relatedness leads to the definition of a class of solutions instead of a single solution. Members of the class share virtually all of the critical internal structure of the tree but differ in the placement of singleton branch tips.

Alleles↗

PubMed2004

Dynamics of transpiration, sap flow and use of stored water in tropical forest canopy trees.

In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree. We measured time courses of sap flow, hydraulic resistance, plant water potential and stomatal resistance in co-occurring tropical forest canopy trees with trunk diameters ranging from 0.34-0.98 m, to determine how total daily water use and daily reliance on stored water scaled with size. We also examined the effects of scale and tree hydraulic properties on apparent time constants for changes in transpiration and water flow in response to fluctuating environmental variables. Time constants for water movement were estimated from whole-tree hydraulic resistance (R) and capacitance (C) using an electric circuit analogy, and from rates of change in water movement through intact trees. Total daily water use and reliance on stored water were strongly correlated with trunk diameter, independent of species. Although total daily withdrawal of water from internal storage increased with tree size, its relative contribution to the daily water budget (approximately 10%) remained constant. Net withdrawal of water from storage ceased when upper branch water potential corresponded to the sapwood water potential (Psi(sw)) at which further withdrawal of water from sapwood would have caused Psi(sw) to decline precipitously. Stomatal coordination of vapor and liquid phase resistances played a key role in limiting stored water use to a nearly constant fraction of total daily water use. Time constants for changes in transpiration, estimated as the product of whole- tree R and C, were similar among individuals (~0.53 h), indicating that R and C co-varied with tree size in an inverse manner. Similarly, time constants estimated from rates of change in crown and basal sap flux were nearly identical among individuals and therefore independent of tree size and species.

Panama↗

PubMedDate not supplied

Identifying diagnostic errors with induced decision trees.

OBJECTIVE: The purpose of this article is to compare the diagnostic accuracy of induced decision trees with that of pruned neural networks and to improve the accuracy and interpretation of breast cancer diagnosis from readings of thin-needle aspirate by identifying cases likely to be misclassified by induced decision rules. METHOD: Using an online database consisting of 699 cases of suspected breast cancer and their corresponding readings of fine-needle aspirate, decision trees were induced from half of the cases, randomly selected. Accuracy was determined for the remaining cases in successive partitions. The pattern of errors in the multiple decision trees was examined. A smaller data set was created with 2 classes: (1) correctly classified and (2) misclassified by a decision tree, rather than the original benign and malignant classes. From this data set, decision trees that describe the misclassified cases were induced. RESULTS: Larger, less severely pruned decision trees were more accurate in breast cancer diagnosis for both training and test data. The accuracy of the induced decision trees exceeded that reported for the smaller pruned neural networks. Combining classifications from 2 trees was effective in identifying malignancies missed by a single tree. Induced decision trees were able to identify patterns associated with misclassified cases, but the identification of errors inductively did not improve the overall error rate. CONCLUSION: In this application, a model that is too compact identifies fewer cases of the minority class, malignancy. New methods that combine models and examine classification errors can improve diagnosis by identifying more malignancies and by describing ambiguous cases.

Breast Neoplasms↗