Incomplete Ossification Research Articles

Risk Assessment of the Plant Protection Product PROMAN – with the Active Ingredient Metobromuron

Proman is a new product containing the active substance metobromuron. The intended use is as a broad spectrum selective herbicide for potatoes grown outdoors.
 VKM’s Panel on Plant Protection Products has discussed the questions raised by The Norwegian Food Safety Authority in the Terms of reference and has stated the following opinion:
 On the relevance of the carcinogenic effects observed in the rat carcinogenicity study; fibrosarcomas in females and pheochromocytomas and Leydig cell tumours in males:
 It is the opinion of VKM’s Panel for Plant Protection Products that the relevance of the observed incidence in mammary gland tumours and Leydig cell tumours in the rat carcinogenicity study is strengthened by the fact that the tumours are observed in hormone responsive tissues. The panel concludes that the carcinogenic effects observed in the rat carcinogenicity study are likely to be relevant for tumours that are influenced by the endocrine system, also in humans.
 On the higher incidences of still dumbbell-shaped centres of thoracic vertebrae and nonossification of the 13th rib observed in the rat developmental toxicity study and whether these are considered to be malformations:
 VKM’s Panel on Plant Protection Products has discussed the classification of the different types of incomplete ossifications and concluded that incomplete ossification of sternebrae and non-ossification of the 13th rib in rats should by itself be considered to be variations, and not adverse developmental effects. On the other hand, the Panel agrees with ECHA that the “thoracic vertebral centres still dumbbell-shaped” should be considered as malformations, due to limited data and understanding of the mechanism underlying the observed slow reversal of these anomalies. Furthermore, it is the view of the Panel that the different types of retarded ossification induced by the exposure of metobromuron should be considered as a whole when assessing for developmental effects.
 On the establishment of the NOAEL for the developmental toxicity study in rats and the reference value (ARfD):
 VKM’s Panel on Plant Protection Products supports the proposal of an ADI value of 0.008 mg/kg bw/day based on a NOAEL of 0.8 mg/kg bw/day from the 2-year study in mouse, and VKM Report 2015: 03 5.
 AOEL of 0.016 mg/kg bw/day based on the NOAEL of 1.6 mg/kg bw/day from the 1-year feeding study in dog. An UF of 100 is applied. The panel suggests on the other hand an ARfD of 0.03 mg/kg bw based on a LOAEL of 10 mg/kg bw /day with the observations of incomplete ossification in the rat developmental study. An UF of 300 is applied.
 On the possible anti-androgenic potential of metobromuron:
 It is the view of the Panel that the rat carcinogenicity study suggests that metobromuron may possess endocrine disrupting potency. The data from the Hershberger in vivo rat study and the in vitro studies is also suggestive of a weak anti-androgenic effect. Thus, it is the opinion of the VKM Panel on Plant Protection Products that an anti-androgenic effect of metobromuron cannot be excluded.

Sternal elements of early dinosaurs fill a critical gap in the evolution of the sternum in Avemetatarsalia (Reptilia: Archosauria)

ABSTRACTThe sternum is a functionally important but poorly understood component of the pectoral girdle in both living and extinct dinosaurs. When ossified, the dinosaur sternum consists of paired plates situated just posterior to the clavicles and scapulocoracoid. In Avialae, the sternal plates are fused at the midline to form a single element, aiding in powered flight. Our understanding of the early evolutionary history of the theropod sternum is complicated by a lack of fossil material, especially outside Maniraptoriformes, both because of taphonomic biases and incomplete ossification. Here, we report the oldest-known dinosaur sternal plates from the Late Triassic taxon Tawa hallae recovered from the Hayden Quarry at Ghost Ranch, New Mexico, as well as an isolated sternal plate from just south of Petrified Forest National Park, Arizona. These specimens expand the fossil record and allow for reconstruction of early theropod sternal musculature. They bear morphological features that are surprisingly similar to sternal traits in avialans, including a sternocoracoidal process, costal processes, and possible homologs to the ‘coracoid facet’ and pila coracoidea. The presence of these features in T. hallae pushes their appearance back to the Late Triassic, well before the development of the modern avian sternum. The variable distribution of sternal character states across avemetatarsalians was previously recognized in later Cretaceous avialans and can now be shown to also characterize the early evolution of the theropod sternum.

Multiple Cervical Vertebral Malformations in a 21-Week-Old Kitten.

A 21 wk old, 2 kg neutered male domestic shorthair presented with a 24 hr history of acute-onset severe nonambulatory tetraparesis with no known inciting cause. Neurologic examination revealed a C1-C5 myelopathy. Computed tomography of the vertebral column and thorax revealed incomplete ossification of the C2 and C3 vertebrae and lung bullae. After 4 wk of conservative management, the client reported a return to normal ambulation with reluctance to jump up. To the authors' knowledge, this is the first report of a feline case of incomplete ossification of cervical vertebrae. The cervical malformations outlined in this report are differentials to consider in cases of acute-onset tetraparesis in cats.

Three-Dimensional Planning and Patient-Specific Drill Guides for Repair of Spondylolysis/L5 Pars Defect

Incomplete ossification of the pars interarticularis will result in a pars defect, a common cause of low back pain in youth and strongly associated with participation in high-impact sports. If left untreated, it can result in spondylolisthesis, causing dynamic canal stenosis, low back pain, and radiculopathy. The treatment of pars defect was first described by Bucks in 1970, who used screws in the lamina placed through an upward and outward direction. However, because of the multiple inclusion and exclusion criteria and narrow margin of error, the Bucks pars repair technique is not commonly performed. A 28-year-old woman had with low back pain that she had been experiencing since mid-adolescence. Computed tomography revealed a bilateral L5 pars defect without spondylolisthesis. Her L5 vertebra was reconstructed virtually. The screw trajectories, a 3-dimensional (3D) model of the vertebra, and a patient-specific drill guide (PSDG) were designed and printed using positioning guide software (MySpine MC Guides [Medacta International SA, Castel San Petro, Switzerland]). A modified Bucks procedure using cannulated compression screws and the PSDG was performed. Follow-up computed tomography revealed accurate placement of the compression screws, mirroring the planned trajectory. The patient was pain free at 3 months postoperatively, and early union across the defect was visualized on the 5-month radiographic imaging study. Using 3D planning software, complex surgical procedures can be planned using the patient's anatomy and computed tomography. With the aid of 3D-printed PSDGs, screw placement in narrow corridors, such as was shown in our case, is safe, efficient, and achievable.

Craniofacial abnormalities in a murine model of Saethre-Chotzen Syndrome

BackgroundSaethre-Chotzen Syndrome (SCS) is an autosomal dominant syndrome that occurs due to a mutation or deletion of the Twist1 gene at chromosome 7p21. Our aim was to conduct a morphometric analysis of the craniofacial features in the mouse associated with a Twist1+/− mutation. MethodsMicro-computed imaging was conducted for the skulls of forty skeletally mature mice, equally distributed by sex (male and female) and two genotypes (Twist1+/− or murine model of SCS; and Twist1+/+ or wild-type). A morphometric analysis was carried out for eight parameters for the maxillary-zygomatico-temporal region, 10 parameters for the mandible and three parameters for teeth from three-dimensional reconstructions. ResultsCompared with wild-type, the murine model of SCS showed these trends: (1) maxillary-zygomatico-temporal region, significantly shorter length and width posteriorly (p<0.05), (2) mandible, significantly reduced height and width (p<0.05), and (3) teeth, significantly shorter height, shorter mesio-distal width but longer bucco-lingual width (p<0.05). In the murine model of SCS, the key morphological variations included incomplete ossification of the temporal bone and zygomatic arch, twisting and/or incomplete ossification of the palatal process of the maxilla, premaxilla and the ventral nasal concha, as well as bifid coronoid processes. ConclusionsThe skeletal and dental alterations in the height, length and width provide a foundation for large-scale phenomics studies, which will improve existing knowledge of the Twist1 signalling cascade. This is relevant given the predicted shift towards minimally invasive molecular medical treatment for craniosynostosis.

Ossification of the pterygoalar and pterygospinous ligaments: a computed tomography analysis of infratemporal fossa anatomical variants relevant to percutaneous trigeminal rhizotomy.

Ossification of pterygoalar and pterygospinous ligaments traversing the superior aspect of the infratemporal fossa results in formation of osseous bars that can obstruct percutaneous needle access to the trigeminal ganglion through the foramen ovale (FO), interfere with lateral mandibular nerve block, and impede transzygomatic surgical approaches. Presence of these ligaments has been studied on dry skulls, but description of their radiological anatomy is scarce, in particular on cross-sectional imaging. The aim of this study was to describe visualization of pterygoalar and pterygospinous bars on computed tomography (CT) and to review their prevalence and clinical significance. The authors retrospectively reviewed 200 helical sinonasal CT scans by analyzing 0.75- to 1.0-mm axial images, maximum intensity projection (MIP) reconstructions, and volume rendered (VR) images, including views along the anticipated axis of the needle in percutaneous Hartel and submandibular approaches to the FO. Ossified pterygoalar and pterygospinous ligaments were readily identifiable on CT scans. An ossified pterygoalar ligament was demonstrated in 10 patients, including 1 individual with bilateral complete ossification (0.5%), 4 patients with unilateral complete ossification (2.0%), and 5 with incomplete unilateral ossification (2.5%). Nearly all patients with pterygoalar bars were male (90%, p < 0.01). An ossified pterygospinous ligament was seen in 35 patients, including 2 individuals with bilateral complete (1.0%), 8 with unilateral complete (4%), 8 with bilateral incomplete (4.0%), 12 with bilateral incomplete (6.0%) ossification, and 5 (2.5%) with mixed ossification (complete on one side and incomplete on the contralateral side). All pterygoalar bars interfered with a hypothetical needle access to the FO using the Hartel approach but not the submandibular approach. In contrast, 54% of complete and 24% of incomplete pterygospinous bars impeded the submandibular approach to the FO, without affecting the Hartel approach. This study provides the first detailed description of cross-sectional radiological and applied surgical anatomy of pterygoalar and pterygospinous bars. Our data are clinically useful during skull base imaging to predict potential obstacles to percutaneous cannulation of the FO and assist in the choice of approach, as these two variants differentially impede the Hartel and submandibular access routes. Our results can also be useful in planning surgical approaches to the skull base through the infratemporal fossa.

Customized fixation guide associated with bio-graft® to promote bone union and skeletal stability in mentoplasty

Background: Orthognathic surgery is the standard procedure to restore function and facial esthetics, correct skeletal and occlusal discrepancies in patients with facial deformities. Incomplete ossification between bone segments has proven to be a major problem when mentoplasty is performed, particularly if pseudarthrosis occurs. Bone grafts were introduced in recent years in order to promote bone union and prevent such complications. Among the biomaterials available, Geistlich Bio-Oss® has been used with success. The Bio-Graft® is a natural bone material of equine origin that emerges as a new bone graft alternative to prevent nonunion of the bone segments. Currently, simplified techniques are being developed for mentoplasty using customized guides manufactured with three-dimensional (3D) printing technology. The use of customized fixation guides allows the virtual surgical planning to be reproduced more accurately and reliably in unstable and surgical movements as clockwise rotations of the chin or vertical increasing.

Bone substitutes in Le Fort I osteotomy to promote bone union and skeletal stability

Background: Maxillary advancement by Le Fort I osteotomy has become the standard procedure to restore function and facial aesthetics, correct skeletal and occlusal discrepancies and treat obstructive sleep apnea in patients with facial deformities. Incomplete ossification between the bone segments at the jaw osteotomy site has proven to be a major problem in these cases. There are several studies in the literature that address orthognathic surgery, but only a limited number that discuss the use of graft materials in maxillary osteotomy. Bone grafts were introduced in recent decades in order to promote and improve bone union and prevent the formation of gaps.

Prenatal developmental toxicity evaluation of Verbena officinalis during gestation period in female Sprague-Dawley rats

Verbena officinalis is widely used by women for maintaining general health and treating various gynaecological disorders during pregnancy. A case report has indicated that the consumption of V. officinalis induced an abortifacient effect. Hence, this study aimed to investigate the prenatal developmental toxicity of this plant according to OECD guideline (no. 414). A total of 50 pregnant female rats (dams) were distributed into five groups (n = 10); 500 mg/kg 1000 mg/2000 mg/kg and 3000 mg/kg of V. offcinalis extracts and the fifth group served as a normal control. All dams received their respective oral single daily treatment from the 6th to the 20th day of gestation. Maternal clinical toxicity signs, body weight and weight gain were recorded. Caesarean sections were performed on day 21 to evaluate embryo–foetal developmental toxicity. For dams, ovaries were harvested and weighed. The number of corpora lutea, implantation sites, and resorptions were recorded. No mortality was observed in dams, but their body weight gain was significantly reduced particularly in dams treated with 2000 and 3000 mg/kg V. officinalis. Asymmetrical distribution of implantation sites and embryos were observed. Embryo-fetotoxicity retardation was observed as evident by the decrease in foetal weight, head cranium, tail length, and higher incidence in the pre-and post-implantation loss. Some foetal skeleton abnormalities such as incomplete ossification of skull, sternebrae, and metatarsal bones were observed in foetuses of the 2000 and 3000 mg/kg V. officinalis-treated dams. LC/MS analysis identified the major constituents including geniposidic acid, tuberonic acid glucoside, luteolin 7, 3′-digalacturonide, iridotrial and apigenin. The glycosylated flavonoids such as apigenin and luteolin could be responsible for the reported prenatal developmental toxicity. In conclusion, the use of V. officinalis during pregnancy is not safe indicating evidence-based toxic effects on the reproductive performance of dams and dose-dependent risk potentials to the foetuses.

Teratogenic Effect of Meloxicam on Pregnant Rats: Implication of Organogenesis Period

This study was carried out to detect the risk of meloxicam use on fetuses. It was given to pregnant rats orally by dose1.35 and 2.70 mg/kg b.wt, from 6th day until the 15th day of gestation daily. At 20th day of gestation female sacrified; morphological, visceral, skeletal, biochemical and histopathological studies were carried out to evaluate its harmful effect. Meloxicam increased abortion rate and fetal resorptions as well as growth retardation and external malformations as hematoma and paralysis of limbs. Visceral examination showed defects in internal organs. Weak and incomplete ossification in axial and appendicular system were observed by skeletal examination. Drug caused increased level of MDA meanwhile reduction of glutathione reduced in liver tissue of fetuses. The histopathological examination revealed presence of marked degenerative changes in liver and kidney of fetuses. This study support and proof the potential risks of the Meloxicam administration on fetuses.

Epidemiological and morphological characteristics of incomplete ossification of the dorsal neural arch of the atlas in dogs with atlantoaxial instability.

OBJECTIVE To retrospectively evaluate the epidemiological and morphological features and outcome of surgical treatment of incomplete ossification of the dorsal neural arch of the atlas (IODA) in dogs with atlantoaxial instability (AAI). ANIMALS 106 AAI-affected dogs that underwent ventral fixation of the atlantoaxial joint. PROCEDURES Medical records and CT images for each dog were reviewed. Dogs were allocated to 1 of 2 groups on the basis of the presence or absence of IODA or of dens abnormalities (DAs) in CT images. RESULTS Of the 106 dogs with AAI, 75 had and 31 did not have IODA; 70 had and 36 did not have DAs. Incomplete ossification was present in the cranialmost, central, or caudalmost portion of the dorsal neural arch of the atlas in 59, 39, and 28 dogs, respectively; 2 or 3 portions were affected in 29 and 11 dogs, respectively. The mean CT value (in Hounsfield units) for the midline of the dorsal neural arch of the atlas in dogs with IODA was significantly lower than that for the same site in the dogs without IODA. The mean age at surgery for dogs with central IODA was significantly higher than that of the non-IODA group. The severity of spinal cord injury before or after atlantoaxial ventral fixation did not differ between the IODA and non-IODA groups. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that concomitant DAs or IODA is common in dogs with AAI. In dogs with incomplete ossification in the central part of the dorsal neural arch of the atlas, surgical treatment of AAI generally occurs at a middle to advanced age.

Decreased Defect Size and Partial Restoration of Subchondral Bone on Computed Tomography After Arthroscopic Debridement and Microfracture for Osteochondritis Dissecans of the Capitellum

Background: Arthroscopic debridement and microfracture are considered the primary surgical treatment for capitellar osteochondritis dissecans (OCD). Healing of the subchondral bone plays an essential role in cartilage repair, while lack of healing is related to the development of osteoarthritis. To date, it is unknown to what extent healing of the subchondral bone occurs after this technique in the elbow. Purpose: To analyze defect size changes and subchondral bone healing with computed tomography (CT) after arthroscopic debridement and microfracture for advanced capitellar OCD. Study Design: Case series; Level of evidence, 4. Methods: Between 2009 and 2016, 67 patients underwent arthroscopic debridement and microfracture for advanced capitellar OCD. Fifty-four patients (81% follow-up rate) with CT scans were included (mean ± SD: preoperative, 4.0 ± 1.7 months; postoperative, 29 ± 9.0 months). OCD defect size was assessed by measuring the largest diameter in 3 directions: medial-lateral direction (coronal plane) and anterior-posterior direction and depth (both in sagittal plane). Healing of the OCD was divided into 3 categories: good—complete osseous union or ossification; fair—incomplete osseous union or ossification but improved; poor—no changes between pre- and postoperative scans. Postoperative clinical outcome was assessed with the Oxford Elbow Score (OES) at the same time as the postoperative CT scan. Results: There were 30 female and 24 male patients (age, 15.7 ± 3.2 years). Defect size decreased (P < .001) in all 3 directions (medial-lateral × anterior-posterior × depth) at 29 ± 9.0 months: preoperatively, 7.9 ± 2.8 × 8.0 ± 3.2 × 4.1 ± 1.5 mm; postoperatively, 3.5 ± 3.3 × 4.0 ± 3.5 × 1.6 ± 1.4 mm. Healing of the subchondral bone was graded as good in 19 defects (35%), fair in 27 (50%), and poor in 8 (15%). The mean postoperative OES score was 40 ± 8.4. Neither postoperative defect size nor healing grade correlated with the OES (P > .05). Conclusion: Arthroscopic debridement and microfracture for advanced capitellar OCD result in improved (ie, decreased) defect size at a mean follow-up of 29 months, both in width and in depth. Healing of the subchondral bone was either good or fair in 85%. Interestingly, CT findings did not correlate with clinical outcomes.

The incidence of Civinini’s bar in adult Anatolian dry skulls: An anatomical study

IntroductionCivinini’s ligament is among the intrinsic ligaments of sphenoid bone that may occasionally ossify. The ossification may be complete or incomplete and unilateral or bilateral. It may lead entrapment of neighboring neurovascular structures and may cause difficulties during surgical procedures through infratemporal fossa. Therefore, the aim of the present study was to demonstrate the incidence and types of Civinini’s bar and discuss its clinical relevance. MethodsSixty-six adult human Anatolian dry skulls with unknown age and sex were obtained from the Department of Anatomy. All skulls were examined and classified with regard to presence or absence, side and ossification degree of Civinini’s bar. ResultsA total incidence of 31.81% of different types of Civinini’s bars was observed, out of which 1.51% were Type I, 18.18% Type II, 1.51% Type III, 0% Type IV and 10.60% were of Type V variety. DiscussionComplete or incomplete ossification of Civinini’s ligament have significant relation with blockage and entrapment of important neurovascular structures. A thorough knowledge of the anatomy and incidence of Civinini’s bar and related clinical situations could be important for radiologists, neurosurgeons, maxillofacial surgeons, anaesthetists, anatomists and anthropologists.

Effect of azithromycin on fetal development in rats

This study was designed to evaluate the potential risks of the Azithromycin administration on fetuses. Therefore pregnant rats were received Azithromycin orally (90 and 180 mg/kg b.wt, daily) from sixth day until the fifteenth day of gestation. At 20th day of gestation female sacrificed; abortion, fetal resorptions, visceral examination, skeletal examination, Oxidative stress markers and histopathological examination for fetuses were recorded. Azithromycin caused abortion, fetal resorptions, growth retardation, hematoma and paralysis of limbs. Also caused cerebral dilatation, microcephaly, perforation of hard palate and hemorrhage around internal organs. By skeletal examination; weak and incomplete ossification were observed in bones .Biochemical studies showed that Azithromycin administration resulted in decreased glutathione reduced but increased malonaldahyde compared to control groups. Fetal kidney revealed degeneration and necrosis in the tubular lining epithelium and fibrosis in between the atrophied renal tubules. This study supports and proofs the potential risks of the azithromycin administration on fetuses. Â

Bupropion promotes alterations in the spermatogenesis of mice and congenital malformations in the offspring.

Bupropion hydrochloride (BUP) has been associated with male sexual dysfunction. The aim of this study was to evaluate the effects of BUP on the reproductive function of male mice and to evaluate offspring development. The mice were distributed into BUP group (40mgkg-1) and control group (saline). On Day 35 of treatment the males were placed to mate with females and then killed on Day 46 for evaluation of reproductive function. On Day 18 of pregnancy, pregnant females were killed for evaluation of congenital malformations in the offspring. The BUP group showed a decrease in the Johnsen score (Control, 9.354±0.092; BUP, 7.615±0.147), Sertoli (Control, 5.623±0.184; BUP, 4.215±0.097) and Leydig (Control, 11.430±0.817; BUP, 7.531±0.213) cell counts, testosterone levels (Control, 783.5±154.2ngdL-1; BUP, 201.4±54.8ngdL-1) and sperm production (Control, 2.852±0.211; BUP, 1.988±0.116) and increased morphological alterations of the sperm head (Control, 8.134%; BUP, 10.423%) and tail (Control, 4.96%; BUP, 16.211%). The congenital malformations observed in BUP-derived offspring were: kyphosis (Control, 0.00%; BUP, 5.26%), retroverted rear legs (Control, 14.43%; BUP, 53.68%), incomplete ossification of the supraoccipital and exoccipital (Control, 21.82%; BUP, 86.00%) and sternum (Control, 25.45%; BUP, 82.00%). BUP had toxic effects on testicular function and teratogenic potential.

Equine gestational length and location: is there more that the research could be telling us?

Clear definitions of 'normal' equine gestation length (GL) are elusive, with GL being subject to a considerable number of internal and external variables that have confounded interpretation and estimation of GL for over 50 years. Consequently, the mean GL of 340 days first established by Rossdale in 1967 for Thoroughbred horses in northern Europe continues to be the benchmark value referenced by veterinarians, breeders and researchers worldwide. Application of a 95% confidence limit to reported GL range values indicates a possible connection between geographic location and GL. Improved knowledge of this variable may help in assessing the degree of the neonate's prematurity and dysmaturity at or soon after birth, and identification of conditions such as incomplete ossification of the carpal and tarsal bones. Associated pathologies such as bone malformation and fracture, angular limb deformity and degenerative joint disease can cause chronic unsoundness, rendering horses unsuitable for athletic purpose and shortening ridden careers. This review will examine both the factors contributing to GL variation and the published data to determine whether there is potential to refine our understanding of GL by establishing a more accurate and regionally relevant GL range based on a 95% confidence limit. This may benefit both equine industry economics and equine welfare by improving early identification of skeletally immature neonates, so that appropriate intervention may be considered.

EMBRYOTOXICITY AND TERATOGENICITY OF FIPRONIL IN RATS (Rattus norvegicus)

Teratogenic and embryotoxic effects of fipronil insecticide were studied following orally intubation of pregnant female rats. The animals were treated with different doses 1/10 LD50 (2.1 mg/kg b.wt) and 1/30 LD50 (0.7 mg/kg b.wt) at the 6th to 15th days of pregnancy (time of organogenesis). At the 20th days of pregnancy, pregnant females were subjected to a caesarean section. The effect of the fipronil on fetal development was evaluated. Maternal weight gain decreased at 1/10 and 1/30 LD50 of fipronil. The body weight and length of viable fetuses significantly decreased with both tested doses. Visceral examination revealed cleft palate, heart and lungs hypoplasia, liver and kidneys atrophy increased with fipronil treatments at different doses. Skeletal examination showed incomplete ossification of the skull bones, short ribs, coccygeal absences, sternbrae abscence and digits of fore and hind limbs.

Gestation length and racing performance in 115 Thoroughbred foals with incomplete tarsal ossification.

Incomplete ossification of the cuboidal bones of the carpus and tarsus in foals has the potential for significant consequences including chronic lameness and decreased athletic ability. To determine if the degree of ossification of the cuboidal bones is associated with gestational length and if the diagnosis of incomplete ossification is a predictor of performance in Thoroughbred racehorses. Retrospective cohort study. The medical records of Thoroughbred foals less than 90 days of age from 1994 to 2011 were examined and records containing tarsal radiographs identified. Radiographs of the tarsus were examined for signs of incomplete ossification and those that were incompletely ossified graded on a scale of 1-4 using a modification of a previously reported index, with Grade 1 being the least ossified and Grade 4 being the most. Gestational length was determined by examining breeding records and foaling dates reported to the Jockey Club. Race records for 2- and 3-year-old affected foals and their maternal siblings were obtained and compared. Foals with Grades 1 and 2 ossification were usually premature (gestation length <325 days), but Grades 3 and 4 were not. Foals with Grades 2 and 3 ossification were significantly less likely to race than their maternal siblings and Grades 1, 2, 3 and 4 foals earned less money. A larger sample size of foals with Grade 1 ossification would increase the power of the study. Foals radiographed at an older age may have had lower ossification scores if radiographed earlier. Incomplete ossification, especially Grades 1 and 2, is associated with a short gestation length. Foals with Grades 2 and 3 incomplete ossification were less likely to race and Grades 1, 2 and 3 earned around $30,000 less than their maternal siblings.

Methyltransferase G9A Regulates Osteogenesis via Twist Gene Repression

Here we investigate the role of epigenetic factors in controlling the timing of cranial neural crest cell differentiation. The gene coding for histone H3 lysine 9 methyltransferase G9A was conditionally deleted in neural crest cells with Wnt1-Cre. The majority of homozygous-null animals survived to birth but thereafter failed to thrive. Phenotypic analysis of postnatal animals revealed that the mutants displayed incomplete ossification and 20% shorter jaws as compared to their wild-type littermates. At E13.5, patterns of expression of the osteogenic transcription factor RUNX2 and the mesenchymal transcription factor TWIST are similar in controls and mutants; both overlap in areas of future intramembranous bone formation. At E14.5, the nonosteogenic mesenchyme expressed TWIST, whereas the ossification center had strong RUNX2 and osteopontin expression. In the mutants, TWIST protein was present in the osteogenic mesenchyme, while osteopontin was not expressed until E15.5. In addition, in mutants, small regions of TWIST-positive osteogenic mesenchyme were visible until E15.5. The delay in ossification and reduction in size of the ossification centers were correlated with an earlier decrease in proliferation. We used micromass cultures of the face to investigate the direct effects of G9A inhibition on skeletal differentiation. Addition of a small molecule inhibitor for G9A, BIX-01294, to wild-type cells upregulated Twist genes similar to what was observed in vivo. The inhibitor also caused decreases in several osteogenic markers. Chromatin immunoprecipitation analysis of primary osteogenic mesenchyme from calvaria revealed that Twist1 and Twist2 regulatory regions contain the repressive H3K9me2 marks catalyzed by G9A, which are removed when BIX-01294 is added. Our results establish a role for G9A and H3K9me2 in the regulation of Twist genes and provide novel insights into the significance of epigenetic mechanisms in controlling temporal and tissue-specific gene expression during development.

A diagnostic pathologist's guide to carpal disease in racehorses.

As a pathologist, postmortem examination of the equine carpus can be daunting. The anatomy is complex and oftentimes, small or subtle lesions have significant impact on lameness and secondary lesions such as catastrophic musculoskeletal fractures and other injuries. In performance horses, particularly racehorses, the carpus is a common site of injury and source of lameness. Given the predisposition of racehorses to developing carpal disease, familiarity with clinically relevant anatomy and common developmental, degenerative, traumatic, and inflammatory processes are imperative for thorough postmortem examination. Our aim is (1) to provide a concise summary of clinically relevant anatomy and function that serves as a guide for postmortem evaluation of the equine carpus, and (2) to review common carpal injuries and diseases in actively training, racing, or retired racehorses, including developmental lesions (incomplete ossification, osteochondromata), infectious and inflammatory lesions (septic arthritis and tenosynovitis), and degenerative and traumatic lesions (degenerative and traumatic osteoarthritis, osteochondral fragmentation, and polyostotic catastrophic "breakdown" fractures). Representative gross and histologic images are presented along with corresponding antemortem and postmortem diagnostic images, and a review of current scientific literature pertaining to the pathogenesis of these equine carpal lesions.