Septal Margins Research Articles

Ventricular premature beats in a pregnant woman originating from trabeculae carneae in the right ventricle treated with radiofrequency ablation without X-ray guidance: a case report

BackgroundPremature ventricular beats increase the cardiac load in pregnant women, leading to symptoms, such as palpitations. In severe instances, they may reduce placental perfusion, potentially causing intrauterine distress and developmental delays in the fetus, which could result in miscarriage or stillbirth. Fluoroscopy-less ablation offers significant advantages for pregnant women, including reduced radiation exposure, enhanced treatment precision, and a lower incidence of postprocedure complications.Case PresentationThis case describes how radiofrequency catheter ablation was used on a pregnant Chinese woman who was identified with frequent ventricular premature beats originating from the high septal margin trabeculae carneae of the right ventricle. The rarity of this premature beat focus poses challenges for electrophysiology mapping and ablation; however, the ablation ultimately succeeded. In this case report, the clinical manifestations, electrocardiogram, ablation procedure, and patient prognosis are reported and discussed.ConclusionX-ray free ablation clearly reduces radiation exposure while maintaining a high success rate and safety of the ablation procedure.

Did shell-crushing predators drive the evolution of ammonoid septal shape?

AbstractFor centuries, paleontologists have sought functional explanations for the uniquely complex internal walls (septa) of ammonoids, extinct shelled cephalopods. Ammonoid septa developed increasingly complex fractal margins, unlike any modern shell morphologies, throughout more than 300 million years of evolution. Some have suggested these morphologies provided increased resistance to shell-crushing predators. We perform the first physical compression experiments on model ammonoid septa using controlled, theoretical morphologies generated by computer-aided design and 3D printing. These biomechanical experiments reveal that increasing complexity of septal margins does not increase compression resistance. Our results raise the question of whether the evolution of septal shape may be tied closely to the placement of the siphuncle foramen (anatomic septal hole). Our tests demonstrate weakness in the centers of uniformly thick septa, supporting work suggesting reinforcement by shell thickening at the center of septa. These experiments highlight the importance of 3D reconstruction using idealized theoretical morphologies that permit the testing of long-held hypotheses of functional evolutionary drivers by recreating extinct morphologies once rendered physically untestable by the fossil record.

Left ventricular summit arrhythmias with an abrupt V3 transition: Anatomy of the aortic interleaflet triangle vantage point

While early precordial electrocardiographic (ECG) characteristics are useful to differentiate left-sided from the right-sided outflow tract ventricular arrhythmia (OTVA), few patterns predict an origin from the septal margin of the left ventricular (LV) summit. The purpose of this study was to report mapping and ablation characteristics of a new ECG pattern with left bundle branch morphology and an abrupt R-wave transition in lead V3 (ATV3). Over a 3-year period, 78 consecutive patients (mean age 57±15 years; 35% female) with OTVA were referred for mapping and ablation. Twenty patients (26%) exhibited an ATV3 pattern, of whom 65% failed prior ablation. Ninety-two percent of patients with ATV3 that underwent simultaneous epicardial and endocardial mapping demonstrated an intramural or epicardial site of origin. Eighty percent of OTVA with ATV3 was eliminated by ablation from the vantage point of the interleaflet triangle below the right-left coronary junction. The ATV3 pattern showed higher sensitivity, specificity, predictive value, and accuracy than validated ECG criteria (notch or "w" pattern in lead V1, qrS pattern in leads V1 through V3, and pattern break V2) for predicting successful ablation in the region of the anterior LV ostium. At 12±11 months, freedom from ventricular arrhythmia recurrence was 89% and 82% in the ATV3 and control groups, respectively. ATV3 is a simple and distinct ECG pattern indicative of a site of origin from the septal margin of the LV summit. The right-left aortic interleaflet triangle vantage point was effective to eliminate OTVA with ATV3 that overwhelmingly exhibited the earliest activation from the epicardium or mid-myocardium. Test characteristics for ATV3 were superior to ECG patterns validated for the anterior LV ostium.

Echocardiographic Assessment of Cardiac Changes during Normal Pregnancy among Nigerians

BACKGROUNDPregnancy is a physiological process associated with an increased hemodynamic load and cardiac structural remodeling. Limited echocardiographic information exists on cardiac chambers, left ventricular (LV) systolic and diastolic functions, and LV mass during trimesters of normal pregnancy among African women.MATERIALS AND METHODSEchocardiography was done at the beginning of the second trimester, beginning of the third trimester, and middle of the third trimester for 100 normal pregnant women and at one visit for age-matched 100 nonpregnant women. The data were analyzed using the Statistical Package for Social Sciences (SPSS) version 17 software. Analysis of variance was used to compare within trimesters, and a P value of <0.05 was considered significant.RESULTSThe mean (SD) ages of the patients and controls were 28.20 (±5.91) and 28.35 (±6.06) years, respectively (age range = 19–44 years, P = 0.86). Cardiac chambers, LV systolic function, and LV mass and its index increased significantly during pregnancy. A significant increase in A-wave velocity but slight increase in E-wave velocity and a reduction in tissue e′ velocity at the septal margin but a progressive increase in a′ velocity were also observed (P < 0.05).CONCLUSIONCardiac chamber dimensions, LV wall thickness, and mass, most indices of LV systolic and diastolic function, though within normal range, were significantly higher in pregnant than in nonpregnant Nigerian women.

Forgotten in the taxonomic literature: resurrection of the scleractinian coral genus Sclerophyllia (Scleractinia, Lobophylliidae) from the Arabian Peninsula and its phylogenetic relationships

The monospecific scleractinian coral genus Sclerophyllia Klunzinger, 1879 was originally described from Al-Qusayr (Egypt) in the Red Sea based on a series of solitary specimens. Thenceforth, it has been considered a junior synonym of Symphyllia and Cynarina based on corallum macromorphology. In this study, several specimens of Sclerophyllia margariticola were collected on the coasts of Saudi Arabia in the northern and central Red Sea. Four molecular markers were sequenced, COI and the intergenic spacer between COI and l-rRNA from mitochondrial DNA and Histone H3 and ribosomal ITS2 from nuclear DNA. Phylogenetic trees and haplotype network analyses show that S. margariticola belongs to the family Lobophylliidae and that it is closely related to Acanthastrea maxima, an uncommon species from waters around the Arabian peninsula (the Gulf of Aden, Arabian Sea, Gulf of Oman and Persian Gulf). Sclerophyllia margariticola and A. maxima share several macro- and micromorphological characters, such as the presence of free septa, high elliptical septal teeth perpendicular to the septal margin, irregular lobate tips, very wide tooth spacing, a very strong granulation with granules scattered all along the septal sides, and a palisade interarea structure, and their micromorphology differs substantially from that of Acanthastrea echinata, the type species of Acanthastrea. Therefore, we formally resurrect Sclerophyllia, provide a revised diagnosis for the genus, and move A. maxima into Sclerophyllia.

Minimally invasive atrial septal defect closure: what is that?

In this issue, Nezafati et al. [1] present their centre’s experience on off-pump atrial septal defect closure. Interestingly, they opted for caval inflow occlusion. Technological advances enable treatment for a wide range of congenital defects with often excellent results. As a result, both children and adults with congenital heart defects can now expect better outcomes. In recent years, however, surgical techniques have also centred around reduction of trauma and postoperative recovery time and also improvement of cosmetic results. However, these techniques have had selective application in congenital cardiac surgery when compared with adults. Open heart procedures for congenital lesions have been largely confined to operations where an intracardiac repair is carried out through the right atrium. A conventional full sternotomy approach for treatment of ‘simple’ lesions can now largely be avoided; instead, approaches vary from an anterior thoracotomy, inframammary thoracotomy and posterior thoracotomy to a limited inferior sternotomy. Nowadays, Atrial septal communications can usually be closed by an interventional cardiologist, unless morphological features are unfavourable. I would call this a true minimally invasive method. Any other attempt is rather ‘minimal access’ surgery. For the latter, a range of approaches are currently used: cardiopulmonary bypass (CPB)-assisted operations with minimal thoracotomies or ‘hybrid procedures’. The term ‘hybrid procedures’ refers to the combined use of direct surgical access to cardiac structures and catheterbased techniques to treat cardiac defects [2]. Nezafati et al. [1] describe a technique that lies somewhat in between. Even though any percutaneous programme is costly and requires a specific setup, Butera et al. [3] showed in a summary of data from studies comparing surgical versus percutaneous closure of atrial septal defects that treatment by a percutaneous approach has a significantly lower rate of either total or major early post-procedural complications compared with surgery. Economical issues are, however, a concern in many countries. In part, this seemed to have led the colleagues to aim for avoidance of CPB. Even though they report on a low overall complication rate, I would personally not advocate the use of this approach unless patients are carefully informed and selected, and all team members are acquainted in detail with all procedural steps. It is of note, however, that, for instance, mitral valve surgery is occasionally done on the beating heart too [4]. Personally, potential neurological sequelae and assurance of 100% closure of any interatrial connection would be my major concern. The described technique must be carried out within a limited time, both for visualizing the atrial septal defect margins and subsequent closure. It is of note that none of the defects could be closed with a patch. With regard to the surgical approach, I am in favour of staying well away from future breast tissue in prepubescent patients, especially in female patients. We have highlighted this issue and have since only opted for a midaxillary incision in young patients [5]. Beyond puberty, we cannulate the jugular vein and the femoral vessels, and perform only a very limited anterolateral thoracotomy. It will be interesting to see whether the described contribution triggers further applications. If cardiologists fail to close an atrial septal defect, a surgeon ought to offer the patient a safe and reliable treatment, keeping cosmetic aspects in mind.

Atrial septal defects: Pattern, clinical profile, surgical techniques and outcome at Innova heart hospital: A 4-year review.

Background:Atrial septal defect (ASD) is a congenital heart defect that leads to shunting of blood between left and right atria. It may be asymptomatic and sometimes may present with heart failure. Surgical repair is definitive, but currently non-surgical procedure is used to close the defect.Materials and Methods:It is a retrospective study of patients who underwent transcatheter closure of ASD at Innova Heart Hospital, Hyderabad, India. Echocardiography was repeated at intervals of 24 hours, then at 1, 3 and 6 months after the procedure to assess complications. The morphological characteristics of the ASD, including its diameter, location, shape and the width of surrounding septal margins, were also evaluated.Results:From April 2007 to June 2011, 69 consecutive children (29 males, 40 females) with a median age of 9.0 years (range = 3.2–19 years) registered with diagnosis of ASD. The median weight was 31.5 kg (range = 7.5–39.0 kg). Five patients (7.2%) were young children aged 3–5 years. Forty-four (63.8%) of these children presented with symptoms of heart failure, whereas 47 (68.1%) of the cases repaired with device were large-sized ASD. The most common interventional procedures done were Searcare Heart® and Amplatzer® technique with a highest success rate obtained in 2010.Conclusions:ASD is a common congenital heart disease with a high success rate for those who undergo intervention.

Revision of the family Felixaraeidae (Scleractinia; Cretaceous)

The Late Cretaceous coral family Felixaraeidae (suborder Fungiina) is revised on the basis of its type genus and respective type species. The family encompasses solitary and colonial forms with very strong and perforated radial elements with a subregular radial symmetry. Radial elements are composed of large trabeculae expressed in a strongly ornamented upper septal margin and septal lateral face. Synapticulae are present. Together with the name-giving genus Felixaraea Beauvais, 1982, the Tethyan coral genera Brachycaulia Beauvais, 1982, Pseudofavia Oppenheim, 1930, and ThecoseriopsisAlloiteau, 1957, aswellasthe Western Atlantic genera Filkornia Löser, 2012, Paracycloseris Wells, 1934, and Trechmannaria Wells, 1935, are assigned to the family. The new genus Marcelohelia n. gen. from the Maastrichtian of Mexico is established. It differs from all known member of the family by its phaceloid growth form. All genera are revised on the basis of the types of their respective type species. Possible species of all genera are presented. The palaeobiogeography of the genera is discussed. The family occurs from the Turonian to Maastrichtian or, possible, Danian.

Revision of the family Asteroseriidae (Anthozoa, Scleractinia, Cretaceous)

ABSTRACT The Cretaceous coral family Asteroseriidae (suborder Fungiina) is revised on the basis of its type genus and respective type species. The family encompasses small solitary patellate corals with compact septa in a regular hexameral symmetry. Septa are made of large trabeculae expressed in a regularly ornamented upper septal margin and septal lateral face. Synapticulae are present. In addition to the name-giving genus Asteroseris de Fromentel, 1867, the genera Actinoseris d'Orbigny, 1849 and Microseris de Fromentel, 1867, from the Cretaceous of France are assigned to the family. All genera are revised on the basis of the types of their respective type species, as far as available. Possible species of all three genera are presented. The family ranges from Hauterivian to Cenomanian of the Tethys.

Skeletal ontogeny in basal scleractinian micrabaciid corals

The skeletal ontogeny of the Micrabaciidae, one of two modern basal scleractinian lineages, is herein reconstructed based on serial micro-computed tomography sections and scanning electron micrographs. Similar to other scleractinians, skeletal growth of micrabaciids starts from the simultaneous formation of six primary septa. New septa of consecutive cycles arise between septa of the preceding cycles from unique wedge-shaped invaginations of the wall. The invagination of wall and formation of septa are accompanied by development of costae alternating in position with septa. During corallite growth, deepening invagination of the wall results in elevation of septa above the level of a horizontal base. The corallite wall is regularly perforated thus invaginated regions consist of pillars inclined downwardly and outwardly from the lower septal margins. Shortly after formation of septa (S2 and higher cycles) their upper margins bend and fuse with the neighboring members of a previous cycle, resulting in a unique septal pattern, formerly misinterpreted as "septal bifurcation." Septa as in other Scleractinia are hexamerally arranged in cycles. However, starting from the quaternaries, septa within single cycles do not appear simultaneously but are inserted in pairs and successively flank the members of a preceding cycle, invariably starting from those in the outermost parts of the septal system. In each pair, the septum adjacent to older septa arises first (e.g., the quinaries between S2 and S4 before quinaries between S3 and S4). Unique features of micrabaciid skeletal ontogeny are congruent with their basal position in scleractinian phylogeny, which was previously supported by microstructural and molecular data.

AORTIC VALVE AREA CAN DETERMINE MYOCARDIAL CONTRACTILE DETERIORATION IN SEVERE AORTIC STENOSIS: STUDY WITH TISSUE DOPPLER

Introduction: After‐load increase in aortic stenosis does not alter the left ventricular ejection fraction (LVEF), even in advanced stages of the illness. We analyzed the ventricular long‐axis velocities and amplitude using tissue Doppler (TD) imaging of the mitral annulus, as this perhaps provides a more sensitive index of systolic function than LVEF. Objectives: (1) To evaluate the left ventricular function in patients with chronically high afterload and (2) determine the effective aortic valve area able to produce changes in left ventricular contractility. Methods: We studied 111 subjects, mean age 68.7 years (range 29–90 years). Of these, 106 (88%) had a valvular area smaller that 1 cm2, and there were 18 age‐matched normal controls (mean age 63.9 years, range 71–81 years) representing the control group (C). The Doppler sample volume was placed at the lateral and septal margins of the mitral annulus. We measured the peak of the systolic apically directed (S‐wave), early diastolic (E), and late diastolic (A) myocardial velocities, the isovolumetric relaxation time (IVRT), and isovolumetric contraction time (IVCT). Patients were classified in groups representing valvular areas 1.1–1.5 cm2 (Group 1, n = 13), 0.71–1 cm2 (Group 2, n = 42),: and &lt;0.7 cm2 (Group 3, n = 64). Statistics: Data are expressed as mean (SD). Group data were compared using the unpaired Student's t test or analysis of variance (ANOVA) with Fisher's PLSD test where appropriate. Linear regression analysis was used (stepwise) to compare continuous variables. A probability value of p &lt; 0.05 was considered significant. Results: The only significant difference observed among groups C and 1 was an increase in the time of ventricular relaxation (103 ± 22 vs.137 ± 35, p &lt; 0.003). Group 2 had a significantly smaller S‐wave than group 1 (5.71 ± 1.15 vs. 6.9 ± 0.91, p &lt; 0.001). Group 3 had significantly smaller A‐wave (6.45 ± 2.5 vs. 8 ± 2.1, p &lt; 0.002), and S‐wave (5.06 ± 1.02 vs. 5.71 ± 1.15, p &lt; 0.005) velocities than group 2, as well as a significant increase in the E/A ratio compared to group 2 (1.00 ± 0.62 vs. 0.74 ± 0.35, p &lt; 0.018). In the regression analysis, we observed a moderate direct relationship between the aortic area and the S‐wave of the TD (r = 0.49, p &lt; 0.0001). LVEF diminished significantly more in group 3 than in group 2 (56 ± 16 vs. 63 ± 15, p &lt; 0.015) but were within normal values. Conclusions: (1) AS first deteriorates the left ventricular diastolic function, prolonging the IVRT. (2) Left ventricular contraction (S‐wave) deteriorates when the aortic valve area decreases below 1 cm2, and this deterioration has a direct relationship with aortic valve area. LVEF decreases when the valvular area is smaller than 1 cm2, but remains inside what is considered normal values.

The function of the ammonite fluted septal margins

The fluted margins of ammonite septa were thought to resist the hydrostatic pressure upon the phragmocone while the ammonoid dived. However, ammonoids probably did not dive deeper than the extant nautilids, whose conchs, with the simple septa, sustain pressure correlative to depth of about 800 m. The backward and forward stretching lobes and saddles actually provide resistance to pressure perpendicular to the septum. Ammonoids lived for about three to five years, and septa were precipitated in intervals of nearly two weeks to two days, which explain the small dimensions of the scars of the adductor muscles, which were periodically detached and reattached. The weak hold between these small muscles and the buoyant conch was compensated for by the backward branching and expanding folds (forming the sutural lobes), into which the soft tissue penetrated and stiffened for a required period to firmly anchor the body to the conch throughout its whole circumference. The greater the complexity of the septa marginal fluting, the better the ammonoid could withstand the dragging force between the body and the buoyant conch, and hence the more aggressively the ammonoid predated and competed with other creatures.

Surgical validation and implications for transcatheter closure of quantitative echocardiographic evaluation of atrial septal defect

Accurate evaluation of secundum atrial septal defect (ASD) is important for the success of transcatheter closure. The purpose of this study was (1) to describe a quantitative evaluation by transthoracic (TTE) and transesophageal (TEE) echocardiography of the various morphologic features of ASD that might be important for patient selection for transcatheter closure, and (2) to assess the reliability of these 2 methods by surgical findings. Preoperative TTE and TEE were used to evaluate the ASD of 27 children undergoing surgical closure. Measurements included the diameters of ASD and the atrial septal lengths in the transverse and longitudiual axis, and the width of the superior, inferior, anteroinferior, and posterior septal margins. The shape and location of the ASD and the adequacy of the septal margins for anchoring occluding devices were determined. Echocardiographic data were compared with corresponding surgical measurements. No significant difference occurred in the means of all the parameters measured with the 3 methods, except for the transverse ASD diameter (p <0.05). Good agreement occurred between TTE and TEE and surgical data, except for the transverse ASD diameter, transverse atrial septal length, and the posterior septal margin on TTE. Intraclass correlations between TTE and TEE and surgical measurements of all parameters were good, except for the transverse ASD diameter. The accuracy in determining shape and location of the ASD by TTE and TEE were 100%, whereas that for determining the adequacy of septal margins was 98% and 97%, respectively. In conclusion, TTE and TEE are reliable methods for quantitative evaluation of ASD.

Remodeling of alveolar walls after elastase treatment of hamsters. Results of elastin and collagen mRNA in situ hybridization.

Treatment of hamster lungs with porcine pancreatic elastase (PPE) causes emphysema and a decrease in lung elastin content, which returns to control level by Day 30. To explore the mechanism of alveolar wall remodeling after elastolytic injury, we examined the expression of elastin and alpha1(I) collagen mRNAs by in situ hybridization at 1, 2, 3, 5, 7, and 30 d after intratracheal PPE. The lungs of control animals displayed weak signals for elastin and alpha1(I) collagen mRNA in pleura, large arteries, veins, and airways. There was little or no signal in respiratory air space walls. Increased expression of elastin and alpha1(I) collagen mRNA began by Day 1 after PPE and reached an asymptote by Day 3 that was maintained by elastin until Day 7; expression of alpha1(I) collagen mRNA waned earlier. Elastin and, to a lesser extent, alpha1(I) collagen mRNA were heavily expressed in pleura, blood vessels, and airways. Analysis of serial sections showed elastin message was minimal in the walls of respiratory air spaces and when present, at 3, 5, and 7 d, was primarily found at the free margins of alveolar septa. Collagen message was very sparse in respiratory air space walls. By 30 d, elastin mRNA expression was reduced but still above control levels and emphysema was widespread and severe. Rank score of elastin mRNA expression in individual subpleural air spaces showed a positive correlation with air space size. In conclusion, most expression of elastin and alpha1(I) collagen mRNA occurs in the pleura, airway, and vascular walls. In respiratory air space walls, expression of elastin mRNAs occurs in damaged tissue at free septal margins.

Three-dimensional keconstruction of ventricular septal defects: Validation studies and in vivo feasibility

Objectives. The purpose of this study was to demonstrate the feasibility of in vivo three-dimensional reconstruction of ventricular septal defects and to validate its quantitative accuracy for defect localization in excised hearts (used to permit comparison of three-dimensional and direct measurements without cardiac contraction).Background. Appreciating the three-dimensional spatial relations of ventricular septal defects could be useful in planning surgical and catheter approaches. Currently, however, echocardiography provides only two-dimensional views, requiring mental integration. A recently developed system automatically combines two-dimensional echocardiographic images with their spatial locations to produce a three-dimensional construct.Methods. Surgically created ventricular septal defects of varying size and location were imaged and reconstructed, along with the left and right ventricles, in the beating heart of six dogs to demonstrate the in vivo feasibility of producing a coherent image of the defect that portrays its relation to surrounding structures. Two additional gel-filled excised hearts with defects were completely reconstructed. Quantitative localization of the defects relative to other structures (ventricular apexes and valve insertions) was then validated for seven defects in excised hearts. The right septal margins of the exposed defects were also traced and compared with their reconstructed areas and circumferences.Results. The three-dimensional images provided coherent images and correct spatial appreciation of the defects (two inlet, two trabecular, one outlet and one membranous Gerbode in vivo; one inlet and one apical in excised hearts). The distances between defects and other structures in the excised hearts agreed well with direct measures (y = 1.05x − 0.18, r = 0.98, SEE = 0.30 cm), as did reconstructed areas (y = 1.0x − 0.23, r = 0.98, SEE = 0.21 cm2) and circumferences (y = 0.97s + 0.13, r = 0.97, SEE = 0.3 cm).Conclusions. Three-dimensional reconstruction of ventricular septal defects can be achieved in the beating heart and provides an accurate appreciation of defect size and location that could be of value in planning interventions.

Quantitation of the Motion of the Cardiac Base in Normal Subjects by Doppler Echocardiography

Because the motion of the base of the heart plays a central role in its filling and emptying, we developed an original method to characterize the base motion dynamics throughout each cycle by use of pulsed Doppler echocardiography. A 100 Hz wall filter and low gain settings were used to record the low-frequency, high-energy Doppler signals generated by the motion of the base. From the apical four-chamber view, the sample volume was placed at the lateral margin and at the common septal margin of the tricuspid and mitral annuli. These signals were differentiated from left and right atrioventricular flows by their opposite direction, higher energy, timing, and unique audio signal. The dynamics of the cardiac base were quantitated in 17 normal subjects (31 +/- 13 years). The time relationship between transvalvular flows and the motion of the base was studied in nine normal subjects by matching recordings at the same RR interval. The Doppler signal of the motion of the cardiac base showed a succession of positive (apically directed) and negative (atrially directed) velocity waves. Differences in the dynamics of the cardiac base were demonstrated between its left and right components, probably related to different loading conditions and different myocardial mechanical properties. The relationship between the motion of the base and mitral flow as shown in this study suggests that Doppler-measured mitral flow velocity underestimates relative left ventricular inflow velocity with respect to the atrium by about 17% at peak early flow and by 20% at peak late flow. The method reported in the present study allows a more informative noninvasive quantitation of the cardiac base motion derived from measurements of its velocity, excursion, and acceleration. This new method may provide unique information on the left ventricular and right ventricular performance in the meridional direction.

Flower development in Amelanchier alnifolia (Maloideae)

The development of the flower of Amelanchier alnifolia from initiation to the onset of anthesis is described. Sepals are formed sequentially, but interprimordial zonal growth results in the initiation of the hypanthium. Petals and stamens arise in whorls around the floral meristem as the hypanthium extends. They show neither coalescence nor adnation and do not appear to contribute to the development of the hypanthium. Gynoecial primordia arise individually, give rise to the styles and stigmas, and are joined basally by zonal growth to produce the roof of the ovary. The wall of the inferior ovary is interpreted as a gynoecial hypanthium. It is difficult to determine the extent to which the gynoecial primordia contribute to the development of the ovary. They do not give rise to most of its structure but may be responsible for the initiation of the ovules. There is evidence of postgenital fusion of the septal margins as they converge in the centre of the ovary. The timing of events in floral development is recorded for the locality of the study. The observations are discussed in relation to current theories concerning the nature of the inferior ovary. Key words: Amelanchier, flower, development, inferior ovary, hypanthium.

Functional and morphological organization of the guinea-pig sinoatrial node compared with the rabbit sinoatrial node

The primary pacemaker, i.e. the group of pacemaker cells discharging the sinoatrial node comprises less than 1000 cells in the guinea-pig and about 5000 cells in the rabbit. These primary pacemaker cells are described as 'central nodal' cells in light microscopy and as 'typical nodal' cells in electron microscopy. The action potential of the leading cells has a higher upstroke velocity in the guinea-pig than in the rabbit (6.2 v. 1.9 V/s). Gap junctions have been observed even in the very center of the node in both species. A zone of double-component action potentials at the septal margin of the node was observed in the rabbit, but not in the guinea-pig. Evidence is presented for abrupt transitions in electrophysiological as well as in ultrastructural characteristics in the guinea-pig sinoatrial node. The differences in intrinsic cycle length between both species but also between individuals of the same species are discussed.

Septum Primum Defect Repair

Two technical maneuvers in septum primum defect repair have resulted in improved mitral valve function and security against heart block. One maneuver, critical to restoring mitral competence, is accurate reconstruction of the leading edge of the mitral valve. A second maneuver, suturing the septal defect patch at its inferior aspect to the mitral valve near the annulus instead of to the inferior septal defect margin or to the tricuspid annulus, eliminates the hazard of atrioventricular node or bundle injury.

Biosystematic studies onMaianthemum (Liliaceae-Polygonatae)

A similar floral vascular anatomy involving a constant dimerous, bicarpellate plan for each of the threeMaianthemum species is reported. All of the tepal, stamen and ovary traces are derived via repeated radial division of two pedicel bundles. The four tepal and stamen traces are fusion products, as are the two dorsals. A third, smaller (vestigial) pedicel bundle which continues unbranched and uninvolved into the ovary was observed in all three species. It could indicate a past reduction from a trimerous, tricarpellate condition, and gives a basis for comparison to the closely related genusSmilacina. The gynoecial vasculature lacks peripheral laterals, septal axials and terminal cross-connections between the dorsal and ventral supplies. The placentation is only apparently axile, since the two septa divide at the mid-ovary level. Consistently the four co-lateral ovules which are anatropous and bitegmic are supplied by four free placentals. The placentals supplying the two ovules of a given carpel have had a common origin in a single pedicel bundle. Raphides characterize post-fertilization ovaries in all species. ADrusa-type of embyro sac formation shown forM. dilatatum corresponds with that known for the other species. An internal stigmoidal tissue system involving micropylar obturators extends from the base of each locule through the hollow stylar canal. Temporal separation occurs between male and female meiosis (protandry), and outbreeding is further promoted by terminal septal glands functioning as nectaries and the synchronized closure of the common carpellary cavity by inter-digitating papillae on the inner septal margins.