Standard Morphometric Parameters Research Articles

Accuracy of in vivo microCT imaging in assessing the microstructural properties of the mouse tibia subchondral bone.

Osteoarthritis (OA) is one of the most common musculoskeletal diseases. OA is characterized by degeneration of the articular cartilage as well as the underlying subchondral bone. Post-traumatic osteoarthritis (PTOA) is a subset of OA caused by mechanical trauma. Mouse models, such as destabilization of the medial meniscus (DMM), are useful to study PTOA. Ex vivo micro-Computed Tomography (microCT) imaging is the predominant technique used to scan the mouse knee in OA studies. Nevertheless, in vivo microCT enables the longitudinal assessment of bone microstructure, reducing measurement variability and number of animals required. The effect of image resolution in measuring subchondral bone parameters was previously evaluated only for a limited number of parameters. The aim of this study was to evaluate the ability of in vivo microCT imaging in measuring the microstructural properties of the mouse tibia trabecular and cortical subchondral bone, with respect to ex vivo high resolution imaging, in a DMM model of PTOA. Sixteen male C57BL/6J mice received DMM surgery or sham operation at 14 weeks of age (N=8 per group). The right knee of each mouse was microCT scanned in vivo (10.4μm voxel size) and ex vivo (4.35μm voxel size) at the age of 26 weeks. Each image was aligned to a reference image using rigid registration. The subchondral cortical bone plate thickness was measured at the lateral and medial condyles. Standard morphometric parameters were measured in the subchondral trabecular bone. In vivo microCT imaging led to significant underestimation of bone volume fraction (-14%), bone surface density (-3%) and trabecular number (-16%), whereas trabecular thickness (+3%) and separation (+5%) were significantly overestimated. Nevertheless, most trabecular parameters measured in vivo were well correlated with ex vivo measurements (R2 = 0.69-0.81). Degree of anisotropy, structure model index and connectivity density were measured in vivo with lower accuracy. Excellent accuracy was found for cortical thickness measurements. In conclusion, this study identified what bone morphological parameters can be reliably measured by in vivo microCT imaging of the subchondral bone in the mouse tibia. It highlights that this approach can be used to study longitudinal effects of diseases and treatments on the subchondral cortical bone and on most subchondral trabecular bone parameters, but systematic over- or under-estimations should be considered when interpreting the results.

Reproducibility of Densitometric and Biomechanical Assessment of the Mouse Tibia From In Vivo Micro-CT Images.

Interventions for bone diseases (e.g. osteoporosis) require testing in animal models before clinical translation and the mouse tibia is among the most common tested anatomical sites. In vivo micro-Computed Tomography (microCT) based measurements of the geometrical and densitometric properties are non-invasive and therefore constitute an important tool in preclinical studies. Moreover, validated micro-Finite Element (microFE) models can be used for predicting the bone mechanical properties non-invasively. However, considering that the image processing pipeline requires operator-dependant steps, the reproducibility of these measurements has to be assessed. The aim of this study was to evaluate the intra- and inter-operator reproducibility of several bone parameters measured from microCT images. Ten in vivo microCT images of the right tibia of five mice (at 18 and 22 weeks of age) were processed. One experienced operator (intra-operator analysis) and three different operators (inter-operator) aligned each image to a reference through a rigid registration and selected a volume of interest below the growth plate. From each image the following parameters were measured: total bone mineral content (BMC) and density (BMD), BMC in 40 subregions (ten longitudinal sections, four quadrants), microFE-based stiffness and failure load. Intra-operator reproducibility was acceptable for all parameters (precision error, PE < 3.71%), with lowest reproducibility for stiffness (3.06% at week 18, 3.71% at week 22). The inter-operator reproducibility was slightly lower (PE < 4.25%), although still acceptable for assessing the properties of most interventions. The lowest reproducibility was found for BMC in the lateral sector at the midshaft (PE = 4.25%). Densitometric parameters were more reproducible than most standard morphometric parameters calculated in the proximal trabecular bone. In conclusion, microCT and microFE models provide reproducible measurements for non-invasive assessment of the mouse tibia properties.

Age-Related Changes in the Gross Morphology and Morphometry of the Testis and Epididymis of the African Greater Cane Rat (Thryonomys swinderianus)

This study evaluated age-related changes in the gross morphology and morphometry of the testis and epididymis of the African Greater Cane Rat (AGCR). Twenty pathogen-free cane rats used for this study were randomly divided into 4 groups; Group I - prepubertal (≤4 months), Group II - pubertal (&gt;4≤12 months), Group III - adult (&gt;12≤30 months), and Group IV - aged (&gt;30 months) of 5 animals each. On day 8th of acclimatization, testis and epididymis were harvested from sedated cane rat, described grossly and standard morphometric parameters (length, width, circumference, weight, and relative weight) determined. Gross morphological observations in the testes of all the different age categories showed similar characteristically cream to milky-white coloration and ellipsoidal shape. The epididymis in the different AGCR group uniquely presents the same inverted S-shaped outline, loose attachment to the testis, and less distinct division into caput, corpus, and cauda segments. Testicular and epididymal morphometric parameters were significantly reduced in the prepubertal cane rat relative to other groups. The parameters consistently displayed an age-dependent increment with the advancing age of the animal. In conclusion, this study has shown that both testicular and epididymal gross morphometrics increase with age advancement and perhaps might be linked to the varying functional reproductive status of the different age groups of the African greater cane rat.

Optimization of the failure criterion in micro-Finite Element models of the mouse tibia for the non-invasive prediction of its failure load in preclinical applications

New treatments against osteoporosis require testing in animal models and the mouse tibia is among the most common studied anatomical sites. In vivo micro-Computed Tomography (microCT) based micro-Finite Element (microFE) models can be used for predicting the bone strength non-invasively, after proper validation against experiments. The aim of this study was to evaluate the ability of different microCT-based bone parameters and microFE models to predict tibial structural mechanical properties in compression. Twenty tibiae were scanned at 10.4 μm voxel size and subsequently tested in uniaxial compression at 0.03 mm/s until failure. Stiffness and failure load were measured from the load-displacement curves. Standard morphometric parameters were measured from the microCT images. The spatial distribution of bone mineral content (BMC) was evaluated by dividing the tibia into 40 regions. MicroFE models were generated by converting each microCT image into a voxel-based mesh with homogeneous isotropic material properties. Failure load was estimated by using different failure criteria, and the optimized parameters were selected by minimising the errors with respect to experimental measurements. Experimental and predicted stiffness were moderately correlated (R2 = 0.65, error = 14% ± 8%). Normalized failure load was best predicted by microFE models (R2 = 0.81, error = 9% ± 6%). Failure load was not correlated to the morphometric parameters and weakly correlated with some geometrical parameters (R2 < 0.37). In conclusion, microFE models can improve the current estimation of the mouse tibia structural properties and in this study an optimal failure criterion has been defined. Since it is a non-invasive method, this approach can be applied longitudinally for evaluating temporal changes in the bone strength.

Differentiating characteristics among three new goat populations from northern India

Three non-descript goat populations, viz. Kumaoni and Garhwali of Uttarakhand hills, and Rohilkhandi of upper Ganges alluvial plain of Uttar Pradesh (India) were characterized phenotypically with standard morphometric parameters. The animals were also evaluated for their reproductive and production performance. The null hypothesis that Garhwali, Kumaoni and Rohilkhandi goat populations are same was tested using value of discriminant functions (D), Wilks’ Lambda and Box’s M statistics. The classification results revealed that 84.9% of all the goats were correctly classified to their own population. This could be used by livestock development agencies to take up appropriate breeding program for the improvement of native stock for future genetic conservation. The milk composition of Uttarakhand goats did not differ much due to geographic identities except for milk fat percentage. The study revealed that body height, body length, horn pattern, face length, and chest girth were the most discriminating and unique variables to separate Rohilkhandi, Kumaoni and Garhwali goat populations.

Cirques in the Sierra de Guadarrama and7 Somosierra Mountains (Iberian Central System): Shape, size and controlling factors

The Guadarrama and Somosierra mountain ranges form the eastern sector of the Iberian Central System and hosted numerous glaciers during the Late Pleistocene (MIS2). Glaciation was of low intensity with glaciers of small sizes, strongly controlled by the climatic context and the topography. This study analyses the shape, size, distribution and location of 96 cirques existing in these mountain ranges. In addition to the standard morphometric parameters and controlling factors (altitude, aspect and lithology) used in most studies, additional factors were considered here in relation to the pre-glacial relief and fracture network. The data were obtained and processed using ArcGIS 10.4 and relations between the parameters and controlling factors were evaluated using statistical methods. The results indicate that most are simple cirques, tending to isometry, with low vertical incision capacity, considerable variation in size and predominantly east-facing. In the context of the Iberian Peninsula and other European mountains, these cirques are among the most isometric, the lowest in height and present the least overdeepening. The development of these cirques has generally been the result of random combination of various factors. Thus: (i) the largest cirques are located at intermediate altitudes, with the headwall located on the main divides, at former torrential valley heads or at the headwalls of fracture corridor valleys, and are north-facing; (ii) the longest cirques are located at former torrential valley heads, on metamorphic bedrock (i.e. schists, slates) and on uniform slopes. Finally, the prevailing eastern aspects are explained by topoclimatic factors and are in agreement with previous studies, which have proposed a Circulation Weather Type (CWT) model throughout the Iberian Peninsula during the Last Glacial Period, similar to its current configuration.

Population genomics and morphometric assignment of western honey bees (Apis mellifera L.) in the Republic of South Africa

BackgroundsApis mellifera scutellata and A.m. capensis (the Cape honey bee) are western honey bee subspecies indigenous to the Republic of South Africa (RSA). Both bees are important for biological and economic reasons. First, A.m. scutellata is the invasive “African honey bee” of the Americas and exhibits a number of traits that beekeepers consider undesirable. They swarm excessively, are prone to absconding (vacating the nest entirely), usurp other honey bee colonies, and exhibit heightened defensiveness. Second, Cape honey bees are socially parasitic bees; the workers can reproduce thelytokously. Both bees are indistinguishable visually. Therefore, we employed Genotyping-by-Sequencing (GBS), wing geometry and standard morphometric approaches to assess the genetic diversity and population structure of these bees to search for diagnostic markers that can be employed to distinguish between the two subspecies.ResultsApis mellifera scutellata possessed the highest mean number of polymorphic SNPs (among 2449 informative SNPs) with minor allele frequencies > 0.05 (Np = 88%). The RSA honey bees generated a high level of expected heterozygosity (Hexp = 0.24). The mean genetic differentiation (FST; 6.5%) among the RSA honey bees revealed that approximately 93% of the genetic variation was accounted for within individuals of these subspecies. Two genetically distinct clusters (K = 2) corresponding to both subspecies were detected by Model-based Bayesian clustering and supported by Principal Coordinates Analysis (PCoA) inferences. Selected highly divergent loci (n = 83) further reinforced a distinctive clustering of two subspecies across geographical origins, accounting for approximately 83% of the total variation in the PCoA plot. The significant correlation of allele frequencies at divergent loci with environmental variables suggested that these populations are adapted to local conditions. Only 17 of 48 wing geometry and standard morphometric parameters were useful for clustering A.m. capensis, A.m. scutellata, and hybrid individuals.ConclusionsWe produced a minimal set of 83 SNP loci and 17 wing geometry and standard morphometric parameters useful for identifying the two RSA honey bee subspecies by genotype and phenotype. We found that genes involved in neurology/behavior and development/growth are the most prominent heritable traits evolved in the functional evolution of honey bee populations in RSA. These findings provide a starting point for understanding the functional basis of morphological differentiations and ecological adaptations of the two honey bee subspecies in RSA.

Sexual dimorphism in tooth morphometrics: An evaluation of the parameters.

Aims and Objectives:Sexual dimorphism refers to the variations in tooth size and shape between the sexes. The consistency of these variations is valuable in the identification of the sex of an individual in times of mass disaster when whole body parts get destroyed or are unavailable. There exist differences in the expression of these variables across races and regions. This study aims to tabulate and identify the variations in tooth measurements using standarized reference points in an attempt to establish parameters of sexual dimorphism.Materials and Methods:100 individuals (50 of each sex) in the age group 19-23 years were assessed for standard morphometric parameters of the maxillary central incisor, canine, premolar and molar. Odontometric measurements of established parameters were recorded from impression casts of the maxillary jaws. The mesiodistal width (MDW), the bucco-ligual width (BLW), the crown length (CL) and the cervical angle (CA) were charted among the teeth. The consistency of the variations was statistically analyzed and a logistic regression table was prepared to identify the sex of the individual from the tooth measurements.Results and Conclusions:The BLW, MDW and CL reflected significant variations among all the teeth to be effective in establishing sexual dimorphism. CA as a parameter was inadequate across all the teeth. The permanent maxillary canine was the most important tooth to be reflective of the gender and statistically significant to be utilized for gender determination.

Differences Exist in the Left and Right Sciatic Nerves of Naïve Rats and Cats

The sciatic nerve of rats and cats is commonly used in experimental models of peripheral nerve injury and repair, as well as experiments involving peripheral nerve electrode implantation. In such experiments, morphometric parameters from the implanted nerve are commonly evaluated and compared to control values obtained from the contralateral nerves. However, this may not be an appropriate approach as differences may naturally exist in the structure of the two nerves owing to developmental or behavioral asymmetry. Additionally, in the cat, baseline values for standard morphometric parameters are not well established. In this study, we characterized fascicle area, fiber count, fiber density, fiber packing, mean g-ratio, and fiber diameter distributions in the rat and cat, as well as investigated the potential for naturally occurring sided differences in these parameters in both species. We also investigated whether animal age or location along the nerve influenced these parameters. We found that sided or left/right leg differences exist in some parameters in both the rat and the cat, calling into question the validity of using the contralateral nerve as a control. We also found that animal age and location along the nerve can make significant differences in the parameters tested, establishing the importance of using control nerves from age- and behaviorally matched animals whose morphometric parameters are collected and compared from the same location.

INFLUENCE OF ARBUSCULAR MYCORRHYZAL FUNGI ON FRUIT ROOTSTOCKS

ISHS XXVII International Horticultural Congress - IHC2006: International Symposium on Sustainability through Integrated and Organic Horticulture INFLUENCE OF ARBUSCULAR MYCORRHYZAL FUNGI ON FRUIT ROOTSTOCKS