How reliable is the visual appraisal of a surgeon for diagnosing orbital fractures?

PURPOSE: The aim of this study was to evaluate the usefulness of intra-operative visualisation, endoscopic assistance, and CT measurements for estimating the orbital fracture size and complexity. METHODS: Ten human cadaver heads were subjected to thin-slice computed tomography (CT). Standardised fractures were created using piezoelectric surgery in accordance with the Jaquiéry classification system. Four surgeons and one anatomist used six different observation methods to visualise and describe the orbital defects. RESULTS: The intraclass correlation coefficients (ICCs) for the fracture length measurements were relatively low for all observation methods (range, 0.666-0.883). CT measurements of width showed high consistency (ICC, 0.910). The surface area of the defect was highly overestimated by all methods (range, 121-184%). None of the observers was able to accurately estimate the length or width of 95% of the defects within an error range of ±0.75 cm. CONCLUSION: CT measurements are the most consistent and accurate tool for estimating the critical size of orbital factures. In daily practice, a measurement tool in a DICOM viewer could be used, although software packages that allow manual adjustments are advisable. Direct intraoperative visualisation and surgeon experience are of limited value in the estimation of fracture size and complexity, and endoscopy provides no additional advantages.

Distinct regulation of developmental and heart disease-induced atrial natriuretic factor expression by two separate distal sequences.

Nppa, encoding atrial natriuretic factor, is expressed in fetal atrial and ventricular myocardium and is downregulated in the ventricles after birth. During hypertrophy and heart failure, Nppa expression is reactivated in the ventricles and serves as a highly conserved marker of heart disease. The Nppa promoter has become a frequently used model to study mechanisms of cardiac gene regulation. Nevertheless, the regulatory sequences that provide the correct developmental pattern and ventricular reactivation during cardiac disease remain to be defined. We found that proximal Nppa fragments ranging from 250 bp to 16 kbp provide robust reporter gene activity in the atria and correct repression in the atrioventricular canal and the nodes of the conduction system in vivo. However, depending on fragment size and site of integration into the genome of mice, the fetal ventricular activity was either absent or present in an incorrect pattern. Furthermore, these fragments did not provide ventricular reactivation in heart disease models. These results indicate that the proximal promoter does not provide a physiologically relevant model for ventricular gene activity. In contrast, 2 modified bacterial artificial chromosome clones with partially overlapping genomic Nppa sequences provided appropriate reactivation of the green fluorescent protein reporter during pressure overload-induced hypertrophy and heart failure in vivo. However, only 1 of these bacterial artificial chromosomes provided correct fetal ventricular green fluorescent protein activity. These results show that distinct distal regulatory sequences and divergent regulatory pathways control fetal ventricular activity and reactivation of Nppa during cardiac disease, respectively.

Cardiac expression of Gal4 causes cardiomyopathy in a dose-dependent manner.

Cardiac expression of a transgene is a common approach for determining the role of gene products in the processes underlying cardiomyopathy and heart failure (HF). We have generated transgenic mice that express the 'harmless' yeast transcription factor Gal4 in the heart under control of the alpha-myosin heavy chain promoter and found that expression of this gene causes cardiomyopathy and HF, the severity of which correlated with the number of copies of the transgene integrated into the genome and with the expression level. A line with a single copy of the transgene targeted to the hprt locus correctly expressed the transgene but did not develop cardiomyopathy. Our results indicate that expression of a transgene in the heart may non-specifically cause HF in a dose-dependent manner.

Regulatory modules in the developing heart.

Fragments of regulatory DNA of cardiac genes drive reporter gene expression in sometimes unexpected subdomains of the heart. These patterns have revealed that the regulatory DNA of genes consists of distinct subfragments (regulatory modules) that are active in different regions of the developing heart. In this review we give an overview of the activity of regulatory modules in vivo. Furthermore, we investigated the relationship between the activity domains of the regulatory modules, the building blocks of the heart and the developmental patterning of the myocardium. Most of the regulatory modules show a domain of activity broader than the morphological boundary of a cardiac compartment and seem to respond to a patterning program along the antero-posterior axis.

Species-specific differences of myosin content in the developing cardiac chambers of fish, birds, and mammals.

Key morphogenetic events during heart ontogenesis are similar in different vertebrate species. We report that in primitive vertebrates, i.e., cartilaginous fishes, both the embryonic and the adult heart show a segmental subdivision similar to that of the embryonic mammalian heart. Early morphogenetic events during cardiac development in the dogfish are long-lasting, providing a suitable model to study changes in pattern of gene expression during these stages. We performed a comparative study among dogfish, chicken, rat, and mouse to assess whether species-specific qualitative and/or quantitative differences in myosin heavy chain (MyHC) distribution arise during development, indicative of functional differences between species. MyHC RNA content was investigated by means of in situ hybridisation using an MyHC probe specific for a highly conserved domain, and MyHC protein content was assessed by immunohistochemistry. MyHC transcripts were found to be homogeneously distributed in the myocardium of the tubular and embryonic heart of dogfish and rodents. A difference between atrial and ventricular MyHC content (mRNA and protein) was observed in the adult stage. Interestingly, differences in the MyHC content were observed at the tubular heart stage in chicken. These differences in MyHC content illustrate the distinct developmental profiles of avian and mammalian species, which might be ascribed to distinct functional requirements of the myocardial segments during ontogenesis. The atrial myocardium showed the highest MyHC content in the adult heart of all species analysed (dogfish (S. canicula), mouse (M. musculus), rat (R. norvegicus), and chicken (G. gallus)). These observations indicate that in the adult heart of vertebrates the atrial myocardium contains more myosin than the ventricular myocardium.

Cooperative action of Tbx2 and Nkx2.5 inhibits ANF expression in the atrioventricular canal: implications for cardiac chamber formation.

During heart development, chamber myocardium forms locally from the embryonic myocardium of the tubular heart. The atrial natriuretic factor (ANF) gene is specifically expressed in this developing chamber myocardium and is one of the first hallmarks of chamber formation. We investigated the regulatory mechanism underlying this selective expression. Transgenic analysis shows that a small fragment of the ANF gene is responsible for the developmental pattern of endogenous ANF gene expression. Furthermore, this fragment is able to repress cardiac troponin I (cTnI) promoter activity selectively in the embryonic myocardium of the atrioventricular canal (AVC). In vivo inactivation of a T-box factor (TBE)- or NK2-homeobox factor binding element (NKE) within the ANF fragment removed the repression in the AVC without affecting its chamber activity. The T-box family member Tbx2, encoding a transcriptional repressor, is expressed in the embryonic myocardium in a pattern mutually exclusive to ANF, thus suggesting a role in the suppression of ANF. Tbx2 formed a complex with Nkx2.5 on the ANF TBE-NKE, and was able to repress ANF promoter activity. Our data provide a potential mechanism for chamber-restricted gene activity in which the cooperative action of Tbx2 and Nkx2.5 inhibits expression in the AVC.