Overexpression of Androgen Receptors Masculinizes 2D:4D Digit Ratios in Mice.

Studying the role of the prenatal endocrine environment in humans is challenging due to the ethical and practical considerations of measuring hormone levels of the developing fetus. Because it has been difficult to ascertain whether prenatal androgens contribute to the brain and behavior in humans as it does in non-human species, retrospective markers of prenatal androgens, such as the second-to-fourth finger digit ratio (2D:4D), are of interest to the studying of human behavioral endocrinology. To assess the validity of such markers, laboratory animals have been studied. Some strains of mice have been reported to show a sex difference in 2D:4D, and pharmacological and genetic manipulation of the androgen and estrogen receptors (AR and ER) has implicated a role for prenatal androgens in mediating this sex difference, although there have been conflicting reports. Here, we compared mice with global AR overexpression to mice with wildtype (WT) littermates and mice with neural-specific AR overexpression. We found a sex difference in the right hind paw, such that males had larger digit ratios than females. Regardless of sex, mice with global AR overexpression showed an increase in the right hind 2D:4D ratio compared with both WT and neural-specific AR overexpression mice. These results support a role for non-neural AR in the development of 2D:4D and suggest that increased sensitivity to androgens via increased AR is sufficient to increase the masculinization of digit ratios. Future directions for confirming the validity of 2D:4D as a marker for prenatal androgen exposure are discussed.

Using 320-detector row computed tomography angiography to investigate the arterial anatomy of the toe flaps on living humans.

PURPOSE: Using 320-detector row computed tomography angiography (320-CTA) to investigate the arterial supply for the toe flaps, namely the anatomical characteristics of the dorsalis pedis artery (DPA), the first dorsal metatarsal artery (FDMA), and the arteries of the first toe web space (AsFTWS). METHODS: This was a prospective study on CTA of 72 intact feet of 36 Vietnamese adults who had sequelae of thumb or metacarpal hand amputation, from June 2017 to December 2019, then preoperative CTA images were compared with surgical findings on 31 feet of 29 patients. RESULTS: 320-CTA was able to investigate the DPA, FDMA, and AsFTWS in 100% of cases. DPA was absent in 6.9% of cases. The average diameters at its origin and termination were 3.22 and 2.56 mm, respectively. For FDMA, the rates of Gilbert type I, II, and III were 52.8%, 18.1%, and 29.2%; the average diameters at its origin and termination were 1.98 and 1.67 mm, respectively. At the first toe web space, FDMA was dominant in 54.2% of cases; the first plantar metatarsal artery (FPMA) was dominant in 29.2% of cases; both arteries were equally dominant in 16.6%. The average diameter at the origin of the lateral plantar digital artery of the great toe was 1.48 mm, of the medial plantar digital artery of the second toe was 1.21 mm. Preoperative CTA images resembled the surgical findings in all cases. The survival rate of toe flaps was 100%. CONCLUSION: The 320-CTA provided proper preoperative images in two and three dimensions, and helped surgeons to establish a preoperative surgical plan, thus increasing the success rate of toe transfer surgery.

Impact of intertendinous connections between the flexor digitorum brevis and longus on percutaneous tenotomy for the treatment of claw toes: an anatomic and ultrasound study.

PURPOSE: Selective percutaneous tenotomy of the flexor digitorum longus (FDL) is a treatment for claw toes that gives astonishingly good functional results despite tendon sacrifice. However, the involution of the FDL tendon stump after tenotomy is unknown. The aim of our study was to assess the involution of the tendon stump after selective percutaneous tenotomy of the FDL. METHODS: The study included two parts. In the clinical part, an ultrasound analysis of 15 FDL tenotomies in 7 patients was carried out 3 months post-surgery. In the anatomic part, the feet of 10 bodies donated to science were dissected and examined anatomically. RESULTS: The proximal stump of the FDL was located near the base of the proximal phalanx and moved synchronously with the flexor digitorum brevis (FDB).Separating the FDB and FDL revealed a large tissue connection between the plantar surface of the tendinous chiasm of the FDB and the dorsal part of the FDL. These connections had significant resistance ranging from 2 to 9 Newtons depending on the toe. Tenotomy of the FDL followed by proximal traction of it led to retraction of the stump up to the base of the proximal phalanx and transfer of its action to the FDB by tensioning the intertendinous structure. Histologically, these structures were mostly comprised of tendon connective tissue. Their vascular component was small. CONCLUSION: The presence of this intertendinous connection leads, in the case of isolated tenotomy of the FDL, to equivalent transfer of the latter to the FDB.

The skin of birds' feet: Morphological adaptations of the plantar surface.

The skin of the foot provides the interface between the bird and the substrate. The foot morphology involves the bone shape and the integument that is in contact with the substrate. The podotheca is a layer of keratinized epidermis forming scales that extends from the tarsometatarsus to the toe extremities. It varies in size, shape, amount of overlap and interacts with the degree of fusion of the toes (syndactyly). A study of toe shape and the podotheca provides insights on the adaptations of perching birds. Our analysis is based on micro-CT scans and scanning electron microscopy images of 21 species from 17 families, and includes examples with different orientations of the toes: zygodactyl (toes II and III forward), anisodactyl (toes II, III, and IV forward), and heterodactyl (toes III and IV forward). We show that in these three groups, the skin forms part of a perching adaptation that involves syndactyly to different degrees. However, syndactyly does not occur in Psittacidae that use their toes also for food manipulation. The syndactyly increases the sole surface and may reinforce adherence with the substrate. Scale shape and toe orientation are involved in functional adaptations to perch. Thus, both bone and skin features combine to form a pincer-like foot.

The same but different: setal arrays of anoles and geckos indicate alternative approaches to achieving similar adhesive effectiveness.

The functional morphology of squamate fibrillar adhesive systems has been extensively investigated and has indirectly and directly influenced the design of synthetic counterparts. Not surprisingly, the structure and geometry of exemplar fibrils (setae) have been the subject of the bulk of the attention in such research, although variation in setal morphology along the length of subdigital adhesive pads has been implicated to be important in the effective functioning of these systems. Adhesive setal field configuration has been described for several geckos, but that of the convergent Anolis lizards, comprised of morphologically simpler fibrils, remains largely unexplored. Here, we examine setal morphology along the proximodistal axis of the digits of Anolis equestris and compare our findings to those for a model gecko, Gekko gecko. Consistent with previous work, we found that the setae of A. equestris are generally thinner, shorter, and present at higher densities than those of G. gecko and terminate in a single spatulate tip. Contrastingly, the setae of G. gecko are hierarchically branched in structure and carry hundreds of spatulate tips. Although the splitting of contacts into multiple smaller tips is predicted to increase the adhesive performance of a fiber compared to an unbranched one, we posited that the adhesive performance of G. gecko and A. equestris would be relatively similar when the configuration of the setal fields of each was accounted for. We found that, as in geckos, setal morphology of A. equestris follows a predictable pattern along the proximodistal axis of the pad, although there are several critical differences in the configuration of the setal fields of these two groups. Most notably, the pattern of variation in setal length of A. equestris is effectively opposite to that exhibited by G. gecko. This difference in clinal variation mirrors the difference in the direction in which the setal fields of anoles and geckos are peeled from the substrate, consistent with the hypothesis that biomechanical factors are the chief determinants of these patterns of variation. Future empirical work, however, is needed to validate this. Our findings set the stage for future comparative studies investigating the functional morphology of these convergent adhesive apparatuses. Such investigations will lead to an enhanced understanding of the interactions between form, function, and environment of fibril-based biological adhesive systems.

Cellular and molecular mechanisms that regulate mammalian digit tip regeneration.

Digit tip regeneration is one of the few examples of true multi-tissue regeneration in an adult mammal. The key step in this process is the formation of the blastema, a transient proliferating cell mass that generates the different cell types of the digit to replicate the original structure. Failure to form the blastema results in a lack of regeneration and has been postulated to be the reason why mammalian limbs cannot regrow following amputation. Understanding how the blastema forms and functions will help us to determine what is required for mammalian regeneration to occur and will provide insights into potential therapies for mammalian tissue regeneration and repair. This review summarizes the cellular and molecular mechanisms that influence murine blastema formation and govern digit tip regeneration.

Character displacement in the midst of background evolution in island populations of Anolis lizards: A spatiotemporal perspective.

Negative interactions between species can generate divergent selection that causes character displacement. However, other processes cause similar divergence. We use spatial and temporal replication across island populations of Anolis lizards to assess the importance of negative interactions in driving trait shifts. Previous work showed that the establishment of Anolis sagrei on islands drove resident Anolis carolinensis to perch higher and evolve larger toepads. To further test the interaction's causality and predictability, we resurveyed a subset of islands nine years later. Anolis sagrei had established on one island between surveys. We found that A. carolinensis on this island now perch higher and have larger toepads. However, toepad morphology change on this island was not distinct from shifts on six other islands whose Anolis community composition had not changed. Thus, the presence of A. sagrei only partly explains A. carolinensis trait variation across space and time. We also found that A. carolinensis on islands with previously established A. sagrei now perch higher than a decade ago, and that current A. carolinensis perch height is correlated with A. sagrei density. Our results suggest that character displacement likely interacts with other evolutionary processes in this system, and that temporal data are key to detecting such interactions.

Biometría de los músculos extensor corto de los dedos y extensor corto del hallux en individuos brasileños: análisis anatómico para su uso como colgajo muscular en cirugías reconstructivas / Biometry of the extensor digitorum brevis and extensor hallucis brevis muscles in Brazilian individuals: anatomical analysis for use as a muscle flap in reconstructive surgeries

RESUMEN: El músculo extensor corto de los dedos (ECD) se sitúa junto con el músculo extensor corto del hallux (ECH) en la región dorsal del pie y están encargados de colaborar con la acción agonista de los músculos extensor largo de los dedos (ELD) y extensor largo del hallux (ELH), en la extensión de los cuatro dedos mediales en las articulaciones metatarsofalángicas. Esta condición complementaria permite su transferencia quirúrgica hacia otras regiones receptoras sin afectar la funcionalidad extensora de los dedos del pie motivo por el cual durante las últimas décadas se ha convertido en un tejido importante para la reconstrucción de lesiones tisulares, sin embargo, son escasos los estudios biométricos que lo describan en detalle. El objetivo de esta investigación fue establecer la longitud, ancho y área de extensión de estos músculos acompañada de la determinación de las distancias de éstos respecto a la cuña medial y la base del quinto metatarsiano para su uso quirúrgico. Sumado a lo anterior y posterior a la descripción de las variantes musculares encontradas se determinó los puntos motores de inervación de estos dos músculos. Para ello se estudiaron 36 miembros inferiores formolizados de individuos adultos brasileños pertenecientes a la Universidad Federal de Alagoas (UFAL), Maceió, Brasil. Las mediciones se realizaron con un cáliper marca Mitutoyo de 0,01 mm de precisión obteniendo una longitud, ancho y área de 6,89 ± 1,64 cm, 3,81 ± 0,42 cm y 31,98 ± 7,60 cm2 en el lado derecho de 6,91 ± 1,64 cm, 3,68 ± 0,46 cm y 30,75 ± 7,61 cm2 en el izquierdo respectivamente. En el 17 % de los casos hay presencia de tendones accesorios para el músculo ECD. La distancia desde el margen medial del músculo ECH respecto a la cuña medial y del margen lateral del músculo ECD a la base del quinto metatarsiano fue de 1,97 ± 0,43 y 1,72 ± 0,41 al lado derecho y de 2,01 ± 0,62 y 1,87 ± 0,36 al lado izquierdo respectivamente. Los puntos motores (Pm) predominaron en un 64 % en el tercio medio del músculo ECH y en un 64 % en el tercio proximal del músculo ECD. Estos resultados son un aporte significativo, tanto para quienes realizan cirugía ortopédica como para el conocimiento detallado de la anatomía dorsal del pie.

SUMMARY: The extensor digitorum brevis muscle (EDB) is located along with the extensor hallucis brevis (EHD) in the dorsal region of the foot and are responsible for collaborating with the agonist action of the extensor digitorum longus muscles (EDL) and extensor hallucis longus (EHL) in the extension of the four medial fingers in the metatarsophalangeal joints. This complementary condition allows its surgical transfer to other receptor regions without affecting the extensor functionality of the toes, which is why during the last decades it has become an important tissue for the reconstruction of tissue injuries, however, there are few studies biometrics that describe it in detail. The objective of this investigation was to establish the length, width and area of extension of these muscles accompanied by the determination of their distances from the medial wedge and the base of the fifth metatarsal for surgical use. In addition to the above and after the description of the muscle variants found, the innervation motor points of these two muscles were determined. To do this, 36 formalized lower limbs of Brazilian adult individuals belonging to the Federal University of Alagoas (UFAL), Maceió, Brazil, were studied. Measurements were made with a 0.01 mm precision Mitutoyo caliper obtaining a length, width and area of 6.89 ± 1.64 cm, 3.81 ± 0.42 cm and 31.98 ± 7.60 cm2 on the right side of 6.91 ± 1.64 cm, 3.68 ± 0.46 cm and 30.75 ± 7.61 cm2 on the left, respectively. In 17 % of cases there is presence of accessory tendons for the EDB muscle. The distance from the medial margin of the EHB muscle with respect to the medial wedge and the lateral margin of the EDB muscle to the base of the fifth metatarsal was 1.97 ± 0.43 and 1.72 ± 0.41 on the right side and 2,01 ± 0.62 and 1.87 ± 0.36 on the left side respectively. Motor points (Pm) predominated in 64 % in the middle third of the EHB muscle and in 64 % in the proximal third of the EDB muscle. These results are a significant contribution both for those who perform orthopedic surgery and for detailed knowledge of the dorsal foot anatomy.

Risk factors for infection following ingrowing toenail surgery: a retrospective cohort study.

BACKGROUND: Ingrowing toenails are a common and painful condition often requiring surgical management. Practitioners who perform surgery on ingrowing toenails include orthopaedic surgeons, general practitioners, podiatrists and podiatric surgeons. There has been limited investigation into the specific surgical approaches used by Australian podiatric surgeons for ingrowing toenails, or the associated infection rates for these procedures. The aim of this study was to assess the frequency and type of ingrowing toenail surgery performed by podiatric surgeons, and identify risk factors for post-operative infection. METHODS: Data was entered into the Australian College Podiatric Surgeons (ACPS) National Audit Tool for all patients who underwent foot and ankle surgery performed by podiatric surgeons in Australia between January 2014 and December 2017. Infection within the first 30 days following surgery was recorded according to the ACPS national audit descriptors. Infection rates, risk ratios (RR) and 95% Confidence Intervals (CI) were calculated to determine postoperative infection risk. RESULTS: Of 7682 records, 1831 reported 2712 diagnoses of ingrowing nails. Patients with a diagnosis of ingrowing toenails were younger, less likely to have systemic disease, and a lower proportion were female compared to those without ingrowing toenails. Furthermore, they were more likely to be diagnosed with a post-operative infection than those without ingrowing toenails (RR = 2.72; CI = 2.00-3.69; P < 0.01). Univariate risk factors for post-operative infection following ingrowing toenail surgery include age greater than 60 years (RR = 3.16; CI = 1.53-6.51; P < 0.01), surgery performed in an office setting (RR = 1.77; CI = 1.05-2.98; P = 0.04), and radical excision of toenail bed procedure (RR = 2.35; CI = 1.08-5.01; P = 0.04). Patients that underwent radical excision or office based procedures were on average older, and more likely to have systemic disease. Further, radical excision procedures were more likely to be performed in office base settings. CONCLUSIONS: Ingrowing toenail surgery carries a greater risk of postoperative infection than other procedures performed by podiatric surgeons. Radical excision of toenail bed was associated with higher postoperative infection rates compared to other ingrowing toenail procedures. Procedures performed in an office setting carry a higher risk of infection. Further research into these associations is recommended.

Study on bio-inspired feet based on the cushioning and shock absorption characteristics of the ostrich foot.

As the main actuator of high-speed running, the ostrich feet are highly capable of cushioning and shock absorption. In this study, based on the elastic modulus scales and assembly order of the 3rd toe soft tissues and the functions of the metatarsophalangeal (MTP) joint, we designed fourteen bio-inspired feet. The impact process on loose sand was simulated on the finite element software Abaqus. Also the stress distributions and deformations of each component of the bio-inspired feet were clarified. With the peak acceleration as the index, the cushioning performances of the bio-inspired feet were compared on both loose sand and solid ground through height-variable impact tests. The 15-15-15 HA (hardness unit) bio-inspired foot showed lower peak acceleration and thereby better cushioning performance, but larger deformation, less-uniform stress distribution and thereby lower stability than the 15-35-55 HA bio-inspired foot. In fact, the silicon rubbers with different hardness degrees (which simulate the elasticity modulus scales of the digital cushions, fascia and skin) and the spring mechanism (which simulates the functions of the MTP joint) work as an "integrated system" of cushioning and shock absorption.

Hurricane effects on Neotropical lizards span geographic and phylogenetic scales.

Extreme climate events such as droughts, cold snaps, and hurricanes can be powerful agents of natural selection, producing acute selective pressures very different from the everyday pressures acting on organisms. However, it remains unknown whether these infrequent but severe disruptions are quickly erased by quotidian selective forces, or whether they have the potential to durably shape biodiversity patterns across regions and clades. Here, we show that hurricanes have enduring evolutionary impacts on the morphology of anoles, a diverse Neotropical lizard clade. We first demonstrate a transgenerational effect of extreme selection on toepad area for two populations struck by hurricanes in 2017. Given this short-term effect of hurricanes, we then asked whether populations and species that more frequently experienced hurricanes have larger toepads. Using 70 y of historical hurricane data, we demonstrate that, indeed, toepad area positively correlates with hurricane activity for both 12 island populations of Anolis sagrei and 188 Anolis species throughout the Neotropics. Extreme climate events are intensifying due to climate change and may represent overlooked drivers of biogeographic and large-scale biodiversity patterns.

Three-dimensional modelling of computed tomography images of limb bones in gazelles (Gazella subgutturosa).

The objective of the present study was to model in 3D the detailed morphometric features of the thoracic and pelvic limb bones of the gazelle (Gazella subgutturosa), whose natural habitat is only in the Sanliurfa province, by using multidetector computerized tomography (MDCT) images. Materials from 14 (7 male and 7 female) dead gazelles were collected from the Harran University Veterinary Medicine Faculty clinics during or after treatment. MDCT images of the gazelles were taken and saved as DICOM (Digital Imaging and Communications in Medicine) files. MIMICS 20.1 software was used to generate a 3D reconstruction of the data, and morphological and morphometrical evaluation was performed. In respect of morphological features, the combined metacarpus (Mc) III and metacarpus Mc IV were the main weight-bearing metacarpal bone, while Mc II and Mc V were rudimentary. On the femur, the lateral condyle was bigger than the medial condyle at the caudodistal end and the medial wing of the trochlea femoris was larger than the lateral. As with the thoracic limb, the combined metatarsus (Mt) III and metatarsus Mt IV were the main weight-bearing metacarpal bone and they displayed a synostosis structure. There was no secondary metatarsus in the gazelles' pelvic limb. Based on digital measurements, the tibia was the longest bone of the gazelles' skeletal system, and there was a statistically significant sexual dimorphism throughout the skeleton at the levels of p < .05, p < .01 and p < .001. As a result, the present study's findings are useful as reference data for further studies on anatomy, surgery and archaezoology, while also being useful for classifying species and for forensic sciences.

Digit ratio and length asymmetry in calves' limbs.

This study considered possible sexual dimorphism in the relative lengths of the second, third and fourth digits (digit ratio), in calves. Furthermore, a different length of the bone structures of the third (3D) and of the fourth (4D) digits has been examined as an evolutionary adaptation to locomotion on soft ground. The length of the digital bones of the right fore-limb of 33 females and 15 male calves was measured in vivo using a portable X-ray machine. The vestigial structure of the second digit (2D), and 3D and 4D, from metacarpus to the third phalanx were considered in a mixed model, as well as some ratios between 2D and different parts of 3D or 4D (2D:3D and 2D:4D). A covariate for the mean finger length was considered for digit ratios to control for possible biases due to shape allometry. Shorter first phalanx and trotter were found in 3D than in 4D, and the reverse for the third phalanx. The 2D was significantly shorter in females, as well as the second phalanges of 3D and 4D. Significant sex differences in 2D:3D and 2D:4D were found for some digit parts of 3D and 4D and for the first phalanges of 3D:4D. These ratios were always shorter in females, in contrast to that found in most mammals. The asymmetry between 3D and 4D could mean a functional adaptation for locomotion. Sex differences in 2D:4D and 3D:4D were found, but with a reverse pattern than in most mammal species (males > females rather than males < females). In this regard digit ratio in calves was similar to that of Old World monkeys. This study is the first investigation of digit ratio in Ungulates, whose limbs differ from the limbs of most mammals, maintaining five digits. The reverse pattern of sex differences (digit ratios: males> females) could be due to the peculiar nature of the vestigial dewclaw of 2D and to the hormone patterns acting on this digit during development, but further research is required around this topic.

Effects of toe length, foot arch length and toe joint axis on walking biomechanics.

Toe joint articulation has been shown to affect gait mechanics, as evidenced by walking simulations, biped robots, and foot prostheses. However, it is not known how parameters such as toe length, foot arch length (i.e., heel-to-toe-joint length) or toe joint axis angle affect human walking. We utilized a previously developed adjustable ankle-toe prosthesis to systematically examine these three foot parameters. We tested ten able-bodied persons walking on a force instrumented-treadmill while wearing a pair of adjustable prostheses attached bilaterally below simulator boots (which fixated their biological ankles). We collected motion and ground reaction force data to compute lower-limb kinematics and kinetics as well as COM power and work. We observed that increasing the foot arch length by 60 mm (35%) increased COM Push-off work by ~5 J, due to increased energy storage and return by the ankle spring. Increasing the toe length by 40 mm (80%) and changing the toe joint axis by ±9° from a neutral angle resulted in negligible effects on COM mechanics and lower limb kinetics. This study provides further insights regarding toe joint function; knowledge which may benefit the design/integration of toe joints into prostheses, exoskeletons and legged robots.

Flexor hallucis longus tendon branch test: Development and validation of a new method to assess anatomical variation of the tendinous slip.

BACKGROUND: The flexor hallucis longus (FHL) muscle often has a tendinous slip with a variable number of branches. We aimed at developing the FHL branch test to determine the number of FHL branches. METHODS: In anatomical validation study, 6 intact cadavers were used. The toe flexion angles were measured while the FHL and flexor digitorum longus (FDL) were manually pulled individually. For electrophysiological studies, 4 healthy men participated. The FHL was electrically stimulated, and electromyography (EMG) of the FHL and FDL were recorded during the FHL branch test. RESULTS: The toe flexion angles' changes in the FHL pulling condition were equivalent with pulling FDL in toes with FHL branching. The electrical stimulation of the FHL produced similar flexion as the FHL branch test. EMG of the FHL was higher than FDL during the FHL branch test (p=0.036). CONCLUSIONS: The FHL branch test could be used to evaluate the number of FHL branches.

Anatomical Differences Between Foot and Hand Web Space Reconstruction.

The differences in the anatomy of the foot and the hand may affect the dorsal flap design for web space reconstruction. In this study, the authors aimed to identify the differences in web space anatomy of the foot and the hand and provide a guideline of flap design for web space reconstruction in the foot and the hand. The right hands and right feet of adult volunteers were measured, including surgical landmarks (i.e., the dorsal prominence of proximal interphalangeal and metacarpophalangeal joints [or metatarsophalangeal joints]), proximal phalangeal length, tip of the web space, and width of web space. The web spaces and other parameters were analyzed and compared between the foot and the hand by using a paired t test with p < .05 to indicate statistical significance. A total of 108 web spaces of the foot and hand from 18 adult volunteers were analyzed. The parameters that were significantly different between the foot and the hand included (1) proximal phalangeal length (34.63 vs 60.16 mm), (2) average web height ratio (0.72 vs 0.51), (3) average web width ratio (0.69 vs 0.81), (4) mean slope angle (4.89° vs 19.26°), and (5) average abduction angle (25.33° vs 31.07°). In conclusion, the foot web space had a higher slope angle, less abduction angle, and shorter proximal phalangeal length. Therefore, the flap design for foot web space reconstruction requires a longer and narrower flap than the design for the hand. The recommended flap design length should be at least 72% of proximal phalangeal length for the foot versus 51% for the hand, and the width should be at least 69% of the distance between the tips of adjacent metatarsophalangeal joints for the foot versus 81% for the hand.

Forefoot Pain in the Lesser Toes: Anatomical Considerations and Magnetic Resonance Imaging Findings.

Various conditions may result in forefoot pain. Magnetic resonance (MR) imaging allows accurate assessment of many of these conditions. We provide an overview of forefoot disorders divided into bones, capsule and plantar plate, musculotendinous structures, neurovascular structures, and subcutaneous tissue. We review normal anatomical features as well as MR imaging findings of common disorders.

Does the 2nd and 4th digit ratio reflect prenatal androgen exposure?

OBJECTIVES:  The aim of our study was to describe the effect of prenatal testosterone exposure on 2D:4D in both sexes, and to determine whether this effect is mediated via the androgen receptor. In addition, the sex differences in lengths of 2D, 4D, and 2D:4D ratio were analyzed. BACKGROUND:  Clinical studies suggest a negative correlation between prenatal testosterone exposure and ratio of the lengths of the second and fourth digits (2D:4D). However, less is known about the underlying molecular mechanisms. METHODS:  Pregnant rats were treated with olive oil, testosterone, flutamide or testosterone with flutamide daily from the fourteenth day of pregnancy until delivery. The finger lengths of adult offspring were measured using both, digital scanning of the paws and µCT analysis of the phalanges. RESULTS:  None of the aforementioned methods revealed any effect of testosterone on 2D:4D. µCT measurements showed that prenatal hyperandrogenism in both sexes leads to shorter 2D compared to controls. Moreover, the testosterone treatment in males resulted in the shortening of 4D when compared to controls. CONCLUSION:  Prenatal hyperandrogenism leads to shorter lengths of 2D and 4D; however, it does not affect 2D:4D ratio. Whether other steroid hormones and/or testosterone metabolites affect the 2D:4D ratio requires further investigation (Tab. 5, Fig. 3, Ref. 32).

Comparing the toepads of Australian diurnal and nocturnal raptors with nonpredatory taxa: Insights into functional morphology.

The ventral structures of the avian digits are the critical interface between a bird and the item within its grasp (e.g., prey, landing substrate, or object), and as such are vital for ensuring the hunting success and survival of predatory birds. Here, we present the first descriptive analysis of the ventral structures of the toes, toepad morphology, and toepad surface area of several diurnal (Accipitriformes and Falconiformes) and nocturnal species (Strigiformes) of Australian raptors. We compare these with nonpredatory taxa (passeriform and psittaciform) to elucidate possible functional explanations for these differences. Although all groups shared the structural characters of joint, phalanx, ungual, and central (tarsal) pad features, the positioning of these structures in relation to the underlying skeletal framework and subsequent gross morphology differed markedly. Toepads overlying the phalangeal joints were much more developed in raptorial species with protrusional toepads only found on goshawks (Accipiter sp.), falcons, and owls. In contrast, the ventral surface of representative passeriform and parrot species showed overall uniformity in contact surface area, with much flatter toepads. There was only a very low phylogenetic signal in the data indicating that phylogenetic relationships did not have a significant effect on toepad surface area. Linear discriminant analysis indicated that functional prey sizes correlated positively with toepad surface areas. Generalized linear modelling showed that there was a positive, significant relationship between body mass and toepad surface area, and prey category significantly affected the toepad surface areas for Digit I and Digit IV. Overall, the ventral surface of the raptorial foot is subject to considerable variation, with active hunters showing the greatest differences in structures, specifically markedly developed toepads to protrusional toepads, potentially as a means to enable more efficient predatory behaviors and facilitate diet preferences for more difficult to catch prey items.