Septum Primum Atrial Septal Defect in an Infant with Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a form of congenital heart disease characterized by severe underdevelopment of the left heart, leading to inadequate systemic blood flow. Several different atrial septal morphologies are observed in HLHS, most commonly a secundum atrial septal defect, patent foramen ovale, intact septum, and leftward displacement of the superior attachment of the septum primum. It has been postulated that atrial septal development is associated with the development of the left heart. We present a case of a newborn infant with HLHS and the unusual finding of a primum ASD.

Transcriptional regulation of tropoelastin expression in rat lung fibroblasts: changes with age and hyperoxia

Elastic fibers are thought to provide structural support for secondary septa as the lung undergoes the transition from the saccular to the alveolar stage. The synthesis of the soluble precursor of elastin, tropoelastin, occurs during a finite developmental period. We have investigated the developmental regulation of tropoelastin gene transcription and mRNA expression in fetal and postnatal rat lung fibroblasts and have assessed the changes in tropoelastin gene expression caused by hyperoxic exposure during secondary septal development. With the use of an RT-PCR assay and intron-specific primers to detect heterogeneous nuclear RNA (hnRNA) and intron-spanning primers to detect mRNA in freshly isolated rat lung fibroblasts, tropoelastin gene expression was found to be upregulated late in gestation. From days 18 to 21 of gestation, there was a 4.5-fold increase in tropoelastin hnRNA ( P < 0.0001) and a 6-fold increase in mRNA ( P = 0.002). After birth, tropoelastin expression was downregulated. Signals decreased from fetal day 21 to postnatal day 2 for both tropoelastin hnRNA ( P = 0.021) and mRNA ( P = 0.043). Tropoelastin hnRNA decreased further from days 2 to 6 ( P= 0.04). Both tropoelastin hnRNA and mRNA were again upregulated during alveolarization from days 9 to 11, indicating that, once upregulated, transcription of the tropoelastin gene is not constant but varies with fetal and postnatal age. Exposure to >95% oxygen, when initiated on postnatal day 2 or 3 and continued until day 11, significantly diminished the developmental increase in tropoelastin hnRNA ( P < 0.005) and mRNA ( P < 0.05) normally seen on days 9– 11, indicating that the postnatal upregulation of tropoelastin gene expression is inhibited by hyperoxic exposure in the early postnatal period.

Atrial Septal Defect in Cyanotic CL/Fr Mice

Objective It is widely known that some newborn CL/Fr mice with cleft lip and palate (CLP) also have cyanotic symptoms, which have been thought to depend on an atrial septal defect (ASD). In a previous study, we found that cyanotic mice tended to have more severe types of CLP. We hypothesize that the mechanical airway obstruction due to a poorly developed palatal shelf and unmoved tongue in CLP(+) mice might be related to the occurrence of cyanosis. The purpose of this study was to examine the relationships between ASD and cyanosis in CLP(+) newborns. Method The newborn hearts from CLP(-), noncyanotic CLP(+), cyanotic CLP(+), CL/Fr mice and ICR mice were examined histologically, and the incidence and size of ASD was determined on neonatal day (ND) 0. In CLP(-) newborns, similar procedures were performed from ND 1 to ND 4. Furthermore, in CLP(+) newborns, development of the palatal shelf was examined. Results While all the ICR mice had a well-developed atrial septum, and the incidence of ASD was 0%, about 80% of CL/Fr mice had ASD, irrespective of the presence or absence of CLP and cyanosis. On ND 0, the septum primum was significantly shorter in cyanotic CLP(+) mice than in CLP(-) mice. It also tended to be shorter in CLP(+) mice than in CLP(-) mice. Between the cyanotics and noncyanotics, there were no significant differences in the incidences of ASD and the rate of septal development. In CLP(-) mice, the septum primum developed well later and no ASD was observed on ND 4. Cyanotic newborns had significantly less developed palatal shelves than did noncyanotics. Conclusions Cyanosis may not be related to ASD and the rate of septal development, but may be related to the occurrence of CLP in this strain. Furthermore, we confirmed that some relationship exists between the development of the palatal shelf and cyanosis. The present study supports our hypothesis concerning the cause of cyanosis in CL/Fr mice.

Heliolitine corals of the upper Douro Formation (Upper Silurian), Canadian Arctic Islands

Heliolitine corals are closely associated with lithistid sponge-dominated reef mounds in Ludlow carbonate ramp facies on Somerset Island. The corals occur abundantly in argillaceous, fossiliferous wackestone immediately flanking and capping the reef mounds, less commonly in calcilutite mudstone within the reef mounds, and with sharply decreasing abundance in nodular argillaceous wackestone to mudstone away from the reef mounds. Exhaustive field collection, and systematic study that included biometric analysis of collected assemblages, indicates that ten heliolitine species are present, including the new species Heliolites furyi, H. garnieri, and H. greineri, and two unidentified species, Heliolites sp. A, and Podollites? sp. The occurrence of H. subdecipiens Klaamann, 1984, H. tchernyshevi Bondarenko, 1966, H. cf. H. rariformis Tchi, 1976, Stelliporella cf. S. podolica Bondarenko, 1971, and Squameolites anomalus Tchi, 1976 indicates an affinity with Eurasian rather than North American faunas of equivalent age. Many new species have been ascribed to Stelliporella since the mid-1970s; most lack the diagnostic axial structures of the genus and are more appropriately regarded as belonging to Heliolites. Newly defined structures termed septal florets occur commonly in H. garnieri and very rarely in three other species of Heliolites. Effective taxonomic use of septal development requires very careful study because of the degree of intraspecific and intracolony variation in some species.

Species definition in heliolitine corals of the lower Douro Formation (Upper Silurian), Canadian Arctic

Specimens representingHeliolites diligensBondarenko, 1966,H.aff.H. luxarboreusYang, 1978, andH. tchernysheviBondarenko, 1966, are common andHeliolitessp. andStelliporellasp. are rare in diverse coral assemblages associated with lithistid sponge reefs in deep shelf or ramp limestone facies of the Douro Formation.Heliolites diligens, a more widely adapted, possibly “opportunist” species, occurs abundantly in lower diversity stromatoporoid/coral assemblages from nonreefal, shallower shelf limestone facies. Detailed systematic study of approximately contemporaneous populations of these Ludlovian heliolitid species shows that all are morphologically variable; assessment of this variability qualitatively and quantitatively is critical to species definition and recognition.Heliolites diligensis the most variable, with wide intercolony variation in septal development, corallite wall configuration, and spacing of horizontal skeletal elements. This apparently represents morphological plasticity rather than differences that can be ascribed to distinct species. Conspecificity of the more extreme and dissimilar variants can be inferred from study of large assemblages of coeval specimens. The other species, with more narrowly defined, discrete variation fields, are more readily distinguished from each other.