Complex Sutures Research Articles

Assessment of the mechanical role of cranial sutures in the mammalian skull: Computational biomechanical modelling of the rat skull.

Cranial sutures are fibrocellular joints between the skull bones that are progressively replaced with bone throughout ontogeny, facilitating growth and cranial shape change. This transition from soft tissue to bone is reflected in the biomechanical properties of the craniofacial complex. However, the mechanical significance of cranial sutures has only been explored at a few localised areas within the mammalian skull, and as such our understanding of suture function in overall skull biomechanics is still limited. Here, we sought to determine how the overall strain environment is affected by the complex network of cranial sutures in the mammal skull. We combined two computational biomechanical methods, multibody dynamics analysis and finite element analysis, to simulate biting in a rat skull and compared models with and without cranial sutures. Our results show that including complex sutures in the rat model does not substantially change overall strain gradients across the cranium, particularly strain magnitudes in the bones overlying the brain. However, local variations in strain magnitudes and patterns can be observed in areas close to the sutures. These results show that, during feeding, sutures may be more important in some regions than others. Sutures should therefore be included in models that require accurate local strain magnitudes and patterns of cranial strain, particularly if models are developed for analysis of specific regions, such as the temporomandibular joint or zygomatic arch. Our results suggest that, for mammalian skulls, cranial sutures might be more important for allowing brain expansion during growth than redistributing biting loads across the cranium in adults.

Buoyancy control in ammonoid cephalopods refined by complex internal shell architecture

The internal architecture of chambered ammonoid conchs profoundly increased in complexity through geologic time, but the adaptive value of these structures is disputed. Specifically, these cephalopods developed fractal-like folds along the edges of their internal divider walls (septa). Traditionally, functional explanations for septal complexity have largely focused on biomechanical stress resistance. However, the impact of these structures on buoyancy manipulation deserves fresh scrutiny. We propose increased septal complexity conveyed comparable shifts in fluid retention capacity within each chamber. We test this interpretation by measuring the liquid retained by septa, and within entire chambers, in several 3D-printed cephalopod shell archetypes, treated with (and without) biomimetic hydrophilic coatings. Results show that surface tension regulates water retention capacity in the chambers, which positively scales with septal complexity and membrane capillarity, and negatively scales with size. A greater capacity for liquid retention in ammonoids may have improved buoyancy regulation, or compensated for mass changes during life. Increased liquid retention in our experiments demonstrate an increase in areas of greater surface tension potential, supporting improved chamber refilling. These findings support interpretations that ammonoids with complex sutures may have had more active buoyancy regulation compared to other groups of ectocochleate cephalopods. Overall, the relationship between septal complexity and liquid retention capacity through surface tension presents a robust yet simple functional explanation for the mechanisms driving this global biotic pattern.

The apical annuli of Toxoplasma gondii are composed of coiled-coil and signalling proteins embedded in the inner membrane complex sutures.

The apical annuli are among the most intriguing and understudied structures in the cytoskeleton of the apicomplexan parasite Toxoplasma gondii. We mapped the proteome of the annuli in Toxoplasma by reciprocal proximity biotinylation (BioID), and validated five apical annuli proteins (AAP1-5), Centrin2, and an apical annuli methyltransferase. Moreover, inner membrane complex (IMC) suture proteins connecting the alveolar vesicles were also detected and support annuli residence within the sutures. Super-resolution microscopy identified a concentric organisation comprising four rings with diameters ranging from 200 to 400 nm. The high prevalence of domain signatures shared with centrosomal proteins in the AAPs together with Centrin2 suggests that the annuli are related and/or derived from the centrosomes. Phylogenetic analysis revealed that the AAPs are conserved narrowly in coccidian, apicomplexan parasites that multiply by an internal budding mechanism. This suggests a role in replication, for example, to provide pores in the mother IMC permitting exchange of building blocks and waste products. However, presence of multiple signalling domains and proteins are suggestive of additional functions. Knockout of AAP4, the most conserved compound forming the largest ring-like structure, modestly decreased parasite fitness in vitro but had no significant impact on acute virulence in vivo. In conclusion, the apical annuli are composed of coiled-coil and signalling proteins assembled in a pore-like structure crossing the IMC barrier maintained during internal budding.

The first record of Wormian bones in lizards

ABSTRACTWormian bones are accessory bones found between cranial elements. These rare bones vary greatly in size, shape and placement. Wormian bones are well-known in mammals, notably in humans and chimpanzees, but not in lizards. Here we examine the genus Zygaspis, a southern African amphisbaenian with complex cranial sutures, for the presence of Wormian bones. Skulls from seven of the eight species of Zygaspis were examined for the presence of Wormian bones. Because of their small size, complex sutures and delicate nature, high-resolution X-ray computed tomography was used to produce 3D models of the skulls. We discovered three Wormian bones in the interdigitated frontoparietal suture of Z. kafuensis. This discovery is the first known record of Wormian bones in a lizard and it is one of the few reports of them in the Squamata. The presence of Wormian bones in a head-first, burrowing squamate allows for a possible functional role to be hypothesised. Additional studies on a variety of squamate taxa are now needed, particularly in burrowing groups with interdigitated sutures, to improve our understanding of these rare cranial elements.

Suture line complexity as an adaptation to acceleration changes during ammonoid locomotion

Ammonoids had a great variety in shape of the suture septal lines in their shells that sparked a plethora of hypotheses about the reasons for their complexity; from strengthening the shell wall against implosion to improvement of muscle attachment onto the septal wall and increased retention of the cameral liquid in the phragmocone chambers. In the present study, simultaneous presence of air and water in the last chambers of the phragmocone and change in acceleration during jet propulsive movement were briefly reviewed. As both water and air were present in the same chamber, periodic alternation of acceleration and deceleration should induce subsequent water displacement (‘sloshing’) due to inertia. This would periodically displace the centre of gravity of the shell making the movement less stable and energy efficient. Analysis of complexity of the suture shape in the dorsal, flank and ventral sides of the shell chambers suggests yet another hypothesis of the suture line variety. More complex suture line in the flank should decrease the water movement at maximum torque when a chamber is half full of liquid. It was hypothesized that the ammonoids evolved a unique way to obstruct the water displacement in the chambers with their fluted septa acting as ‘wave breakers’ that dissipate the ‘wave’ on the boundary between water and air. Animals that moved slowly without sudden changes in acceleration had a simple suture line and were either planktonic or grazing predators cruising with more or less constant speed. Complex sutures in advanced ammonoids indicated their ability to sharply change the velocity of their movement when chasing their prey or escaping from predators.

Robot-assisted thoracic surgery for complex procedures.

As an option for minimally invasive thoracic surgery, robot-assisted thoracic surgery (RATS) has shown comparable perioperative outcomes to those achieved by traditional video-assisted thoracic surgery (VATS). It is unknown whether RATS might have any potential benefits in more complex thoracic surgical procedures, which usually require open surgery instead of VATS. The current study presents a preliminary result regarding the use of RATS in complex thoracic operations in an attempt to address this unresolved question. Data from a prospectively collected and maintained surgical database were collected on patients who underwent RATS between February 2012 and August 2014. We defined complex RATS as those operations involving difficult dissections, complex sutures or excision of very large tumors (>8 cm) which would have required open surgery in our hospital before the introduction of RATS. The characteristics and peri-operative outcomes of patients receiving complex RATS were reviewed. Of the 120 patients undergoing RATS, 30 of them were classified as having undergone complex RATS, 21 to remove lung tumors and 9 to remove mediastinal tumors. The indications for complex RATS included 21 difficult dissections, 10 complex sutures, and 7 very large tumors (8 patients had two indications). There are three conversions to thoracotomy for pulmonary arterial bleeding. There was one mortality resulted from post-pneumonectomy pulmonary hypertension and sepsis. Patients with difficult dissection had longer operative time and hospital stay, and more bleeding and postoperative morbidity. RATS for complex thoracic procedures is feasible, especially for complex suturing and excision of very large mediastinal tumors, but more attention is needed for patients needing difficult dissections. Advanced preparation for conversion is necessary during this difficult operation.

Assessing the influence of escalation during the Mesozoic Marine Revolution: Shell breakage and adaptation against enemies in Mesozoic ammonites

Escalation is evolution driven by interactions between individuals and their enemies. We examined escalation in ammonites using repair scars, which are indicative of sub-lethal predation. Because ornamentation is considered an antipredatory adaptation, we tested several hypotheses concerning the relationship between ornamentation and repair scars. We also investigated the possibility of complex sutures as a defensive trait. Ornamentation, suture complexity, and repair scar frequency (RF) data were collected from 26 Jurassic and Cretaceous ammonite genera from North America and Europe. Ornamentation was gauged as a ratio of rib thickness to shell diameter. RF was measured as percent individuals with scars and as average number of scars per individual. Suture complexity factor (CF) was calculated as a weighted count of suture features. Data on 1180 specimens revealed a significant inverse correlation between RF and shell ornament, contrary to our hypothesis that more highly ornamented shells will exhibit more repairs due to increased survivorship of attacks. Taxa exhibiting ornate ornamentation had fewer repair scars than expected, and taxa with ribs and nodes but no keel had more repair scars than expected. Repair frequencies of shells with different ornament types were found to differ between North American and European shells. No other geographic variation was found. Taxa with tightly spaced ribs were found to exhibit more repair scars. Rib size had no significant correlation with longitudinal scar size, disconfirming our hypothesis that scars on taxa with larger ribs were less able to propagate. Scars were concentrated on the first 90° of the shell, suggesting attacks at the aperture, and no right-left-medial selectivity of predatory attacks was found. Although some workers have suggested an antipredatory role for complex sutures, no relationship was found between CF and RF. Body size had a significant effect on repair scar occurrence in all but one of the taxa tested. Repair scar frequency and degree of ornamentation increased through the Jurassic and Cretaceous Periods. The data presented here support the traditionally held hypothesis that repair scars on ammonite shells represent interactions between ammonites and their enemies.

Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study

Introduction: Rapid palatal expansion of the midpalatal suture is an effective method for the correction of transverse malocclusions. This study was conducted to compare the reaction of circum-maxillary sutures and center of resistance of molar to the Hyrax appliance with different degrees of activations and the Spring jet appliance using laser holography on a freshly macerated skull. Materials and methods: A freshly macerated skull with well-aligned teeth and intact dental arches was used as the experimental model. The Hyrax appliance and Spring jet appliances were fabricated and analyzed qualitatively and quantitatively by using double exposure hologram. Hyrax was activated two 1⁄4 turns, four 1⁄4 turns and eight 1⁄4 turns. The Spring jet is activated and double exposure hologram was recorded. Results: Results were obtained qualitatively by observing the fringes, and quantitatively by counting the number of fringes. The Spring jet showed fringes only in the first molar area, whereas the Hyrax showed fringes along the circum-maxillary sutures and the first molar area; and the number of fringes increased with the number of turns. Conclusion: Hyrax appliance activation produced mechanical reactions on the teeth, alveolar bone, maxilla and the circum-maxillary bones and sutures. The displacement and fringes increased progressively with two, four and eight turns activation of hyrax. The pattern of the fringes was more circular around the nasomaxillary complex and zygomaticomaxillary sutures, suggesting rotational displacement of the maxilla. The number and pattern of fringes produced by the Spring jet appliances suggest that it produces only dentoalveolar changes and minimal orthopedic affects.

A bidirectional interface growth model for cranial interosseous suture morphogenesis

Interosseous sutures exhibit highly variable patterns of interdigitation and corrugation. Recent research has identified fundamental molecular mechanisms of suture formation, and computer models have been used to simulate suture morphogenesis. However, the role of bone strain in the development of complex sutures is largely unknown, and measuring suture morphologies beyond the evaluation of fractal dimensions remains a challenge. Here we propose a morphogenetic model of suture formation, which is based on the paradigm of Laplacian interface growth. Computer simulations of suture morphogenesis under various boundary conditions generate a wide variety of synthetic sutural forms. Their morphologies are quantified with a combination of Fourier analysis and principal components analysis, and compared with natural morphological variation in an ontogenetic sample of human interparietal suture lines. Morphometric analyses indicate that natural sutural shapes exhibit a complex distribution in morphospace. The distribution of synthetic sutures closely matches the natural distribution. In both natural and synthetic systems, sutural complexity increases during morphogenesis. Exploration of the parameter space of the simulation system indicates that variation in strain and/or morphogen sensitivity and viscosity of sutural tissue may be key factors in generating the large variability of natural suture complexity.

Trace/minor element:calcium ratios in cultured benthic foraminifera. Part II: Ontogenetic variation

Ontogenetic (developmental stage) measurements of Mg/Ca and Sr/Ca were made on the benthic foraminifer Bulimina aculeata, which were cultured under controlled physicochemical conditions of temperature, pH, alkalinity, salinity, and trace- and minor-element concentrations. We utilized two methods of ontogenetic sampling—whole specimens progressively increasing in length and laser microdissection of a single specimen with subsequent analysis of dissected portions. A novel high-resolution laser-microdissection (HRLM) method allowed for precise (10 μm) cuts of the foraminiferal tests (shells) along the geometrically complex sutures distinguishing individual chambers. This new microdissection method limited sample loss and cross-contamination between foraminiferal chambers. Little or no variation in D Sr was observed at different foraminiferal developmental stages. Conversely, D Mg was enriched during a mid-developmental stage of whole-specimen samples (150–225 μm D Mg = 1.6 × 10 −3) compared to earlier and later stages (<150 μm, >225 μm D Mg = 8.3 × 10 −4). Further analysis of HRLM ontogenetic samples showed a larger, age-dependent D Mg signature variation. This increase in shell Mg/Ca may contribute substantially to the measured inter-individual variability in Mg/Ca temperature prediction for cultured B. aculeata. Due to relatively large Mg/Ca inter- and intra-individual variability, measuring similar-size foraminiferal samples may improve the precision of paleotemperature prediction. Additionally, partial dissolution of the highest ontogenetically Mg-enriched calcite ( D Mg = 1.3 × 10 −2–1.6 × 10 −2) may occur in undersaturated bottom-water environments or during reductive cleaning procedures. Thus, the calcite phases remaining after partial dissolution by either natural or laboratory cleaning processes may not accurately represent the calcification environment.

Cranial suture complexity in white-tailed deer (Odocoileus virginianus)

Neurocranial expansion and mastication are commonly implicated as the two major biomechanical factors affecting suture morphology. In deer the antlers provide an additional source of biomechanical stress acting on the skull. Equivalent stresses are not found in females, who lack antlers. We analyzed the complexity and interdigitation of the interfrontal and coronal sutures that surround the antler-bearing frontal bones of (n = 67) white-tailed deer (Odocoileus virginianus) to 1) evaluate changes in suture morphology throughout ontogeny, and 2) test the hypothesis that male deer have more complex sutures than females. Two methods were used to quantify suture morphology: fractal analysis and length-ratios (actual suture length divided by direct straightline length). Both techniques produced similar results, although the two methods cannot be considered equivalent. Suture complexity increases markedly throughout ontogeny, but appears to level off after animals have reached adulthood. Cranial size in males, but not females, continues to increase in adults. No significant increase in suture complexity with age in the adult cohort was detected. While deer are highly dimorphic in size and the presence of antlers, no significant differences existed between males and females for any measure of suture complexity. No consistent patterns emerged between suture complexity and skull size or antler characteristics. The presence of antlers appears to have a minimal effect on suture complexity in white-tailed deer. Factors that may contribute to the lack of dimorphism in suture complexity are discussed.

The two Early Toarcian (Early Jurassic) extinction events in ammonoids

The Early Toarcian (Early Jurassic) biological crisis was one of the ‘minor’ mass extinctions. It is linked with an oceanic anoxic event. Fossil data from sections located in northwestern European (epicontinental platforms and basins) and Tethyan (distal, epioceanic) areas indicate that Late Pliensbachian–Early Toarcian ammonoids experienced two extinction events during the Early Toarcian. The older one is linked with disruption of the Tethyan–Boreal provinciality, whereas the younger event correlates with the onset of anoxia and corresponds with the Early Toarcian mass-extinction event. These two extinctions cannot be interpreted as episodes of a single, stepwise, event. Values of the net diversification, more than the number of extinctions, allow the two extinction events to be clearly recognized and distinguished. Values of regional net diversification for northwestern European and Tethyan faunas point to greater evolutionary dynamics in the epioceanic areas. The inclusion of Mediterranean faunas in the database proves that the ammonite turnover at the Early Toarcian mass-extinction event was more important than previously thought. Progenitor (evolute Neolioceratoides), survivor (Dactylioceras, Polyplectus pluricostatus) and Lazarus (Procliviceras) taxa have been recognized. Different selectivity patterns are shown for the two events. The first one, linked to the disruption of the Tethyan–Boreal provinciality, has mainly affected ammonites adapted to epicontinental platforms. In the mass-extinction event, no selectivity is recognized, because also Phylloceratina and Lytoceratina were deeply affected at species level, although their wide biogeographical distribution at clade level was a significant buffer against extinction. In contrast to Palaeozoic mass extinctions, ammonoid survivors and Lazarus taxa are characterized by complex sutures: Phylloceratina (long-ranging ammonoids) and Polyplectus (relatively long-ranging compared to other Ammonitina).

Morphostructural constraints and phylogenetic overprint on sutural frilling in Late Jurassic ammonites

The functional significance of frilled septa and complex sutures in ammonoids has generated ongoing debate. The ‘classic’ hypothesis envisages ammonoid shells and septa as designed for resisting ambient hydrostatic pressure, complex sutures being the evidence of strength in shells for colonization of deep habitats. Here we address the ‘suture problem’, focusing on the analysis and interpretation of variables in our database of Late Jurassic ammonites not included in previous studies, such as whorl height (W h), whorl shape (S), shell coiling (WD), taxonomic grouping and basic planispiral shell shape. The results indicate that sutural complexity, as measured by the fractal dimension (D f) value of the suture line, is positively correlated with W h, and that the sutures of oceanic shells tend to provide, for a given W h value, lower D f estimates than do those of neritic shells. No general trend of increase in sutural complexity was noted for specimens recovered from swell areas belonging to oceanic fringes with respect to those that inhabited epicontinental shelves. In fact, Perisphinctoidea, the clade best represented in the database analysed, shows a higher D f mean value in neritic species than in epioceanic ones. Significant differences in sutural complexity were detected for groups of ammonites classified according to shell shapes (WD, S). Oxycones and discocones, streamlined potential swimmers, show the highest D f mean values, while spherocones and cadicones, which were presumably vertical vagrants, present the lowest ones. This indicates that sutural complexity was more related to shell geometry than to bathymetry.

Finite-element analysis of simulated ammonoid septa (extinct Cephalopoda): septal and sutural complexities do not reduce strength

Finite-element analysis of circular septum models indicates that (1) anticlastic fluting weakened the last septa of the same radius of curvature by a factor of about 2.5 relative to the tensile stresses in a sphere of nacre, (2) septa with ammonitic sutures were stronger than those with goniatitic sutures of the same thickness, and (3) septa with more “complex” ammonitic sutures were stronger at the edge between lobes and saddles than “simple” ones. These results contradict recent claims that ammonoid septa became weaker as sutural complexity increased from goniatitic through ammonitic, so that the most complex sutures were limited to the shallowest habitats. The smaller marginal flutes of complex septa were relatively strong, allowing them to be thinner than the central septum and still act as elastic wall supports. Many Mesozoic ammonoids with highly sinuous sutures occurred in deep epeiric and open-ocean habitats, whereas it is those with secondarily reduced, ceratitic sutures that were typically associated with restricted shallow basins.

Creation of sutures with antimicrobial properties

It was found that Decamethoxin, as a broad-spectrum antiseptic with a pronounced antibacterial and fungicidal action, and BF-6 phenol-polyvinylacetal adhesive, which gives complex sutures the structure of a pseudomonofilament, are best as antimicrobial additives in a modifying composite for giving surgical sutures antimicrobial properties. A Decamethoxin content in the modifying composite of 10% of the weight of BF-6 (1.7–2.0% in the suture) is sufficient for manifestation of the antimicrobial effect with respect to Staphylococcus aureus, E. coli, and yeast-like fungi. The antimicrobial activity of a suture with a 1.7–2.0 wt. % decamethoxin content in the period from 2 to 24 h increases by 4 times with respect to E. coli and by 8 times with respect to Staphylococcus aureus and yeast-like fungi. Application of a coating of BF-6 adhesive with Decamethoxin has almost no effect on the physicomechanical properties of the sutures, but the capillarity decreases significantly (by ∼86%), which also decreases the probability of wound infection. The kinetics of release of Decamethoxin does not change after radiation sterilization of the sutures, i.e., the composition and content of the antimicrobial additive in the modified sutures and its antimicrobial activity are preserved. The optimum medium for storage of sterile modified sutures is 1% Decamethoxin solution. After 12 days of storage, the sutures remain sterile and lose a maximum of 6% of the breaking strength.

Mechanical significance of ammonoid septa with complex sutures

Pre- and post-19th century hypotheses relating hydrostatic pressure to the mechanical function of sutural complexity are compared. The old ideas gave rise to the 19th century ‘Buckland hypothesis’, which is in turn largely synonymous with the ‘Westermann model’. Buckland (1836) postulated that fluted septa buttressed the weak flanks of the phragmocone wall. Two new parameters are introduced to define the covariation between the strength of cylindrical segments of the wall flank bounded by the distance between adjacent lobe and saddle-flutes in transverse sections. The product of the index of wall strength (IWS) and this inverse support angle (ISA) predicts the buckling pressure in a cylinder of infinite length, and it implies that coiled nautiloids were more likely to be imploded via their whorl flanks than the apparently weaker oxyconic ammonoids. The widely used index of sutural complexity (ISC) measures the marginal corrugation which obscures this trend and acts as an elastic bed for both strong and weak walls. However, the ISC is more proportional to habitat depth than the buckling pressure when all other factors are constant. The central thickness of each fluted septum was increased in direct proportion to the distance spanned by the septum and the hydrostatic pressure on it in the ‘last septum’ position. The marginal thickness was maintained at a more constant value, which permitted the suture to increasingly act like a spring or shock absorber, as the wall thickness was enlarged during ontogeny. Both the ratios, between the central and marginal thicknesses and the closely related ISC, therefore, increased with shell diameter and habitat depth.

Fractal geometry of ammonoid sutures

Interior chamber walls of ammonites range from smoothly undulating surfaces in some taxa to complex surfaces, corrugated on many scales, in others. The ammonite suture, which is the expression of the intersection of these walls on the exterior of the shell, has been used to assess anatomical complexity. We used the fractal dimension to measure sutural complexity and to investigate complexity over evolutionary time and showed that the range of variation in sutural complexity increased through time. In this paper we extend our analyses and consider two new parameters that measure the range of scales over which fractal geometry is a satisfactory metric of a suture. We use a principal components analysis of these parameters and the fractal dimension to establish a two-dimensional morphospace in which the shapes of sutures can be plotted and in which variations and evolution of suture morphology can be investigated. Our results show that morphospace coordinates of ammonitic sutures correspond to visually perceptible differences in suture shape. However, three main classes of sutures (goniatitic, ceratitic, and ammonitic) are not unambiguously discriminated in this morphospace. Interestingly, ammonitic sutures occupy a smaller morphospace than other suture types (roughly one-half of the morphospace of goniatitic and ceratitic sutures combined), and the space they occupied did not change dimensions from the Jurassic to the late Cretaceous.We also compare two methods commonly used to measure the fractal dimension of linear features: the Box method and the Richardson (or divider) method. Both methods yield comparable results for ammonitic sutures but the Richardson method yields more precise results for less complex sutures.

The Interrelationship of Lens Anatomy and Optical Quality II. Primate Lenses

We have quantified the influence of lens sutural anatomy on optical quality (focal length variability, i.e. spherical aberration) in adult monkeys (Macaque nemestrina). Adult lenses (n = 6) were initially scanned by a low-power helium-neon laser beam that was passed at a series of acute angles to, and/or directly through, lens sutures. Optical analysis showed that while the 'star' sutures of primate lenses exerted a quantifiable negative effect on focal length variability, this detrimental effect was far less significant than that attributable to 'line' and 'Y' sutures in non-primate lenses. Correlative morphological and 3-D computer-assisted drawing (CAD) analysis of the laser-scanned lenses areas, as well as of variably aged lenses (n = 30), revealed that primates have a more complex lens architecture than non-primates. Non-primate lenses feature suture planes, aligned along the visual axis that are responsible for a significant quantifiable increase in spherical aberration. Primate lenses are characterized by an absence of continuous suture planes aligned along the visual axis. Rather, 3-D-CADs of primate lenses demonstrate that distinct generations of progressively more complex sutures are produced as a function of development, growth, and age. In succession, 'Y' sutures (three branches) are formed throughout embryonic development, 'simple star' sutures (three-six branches) evolve after birth and through infancy, 'star' sutures (six-nine branches) are made in young adult lenses and, finally, 'complex star' sutures (nine-15 branches) are laid down from middle through old age. In view of the fact that slit-lamp evaluation of cataractous lenses often reveals abnormally thin zones of discontinuity, it is significant to note that the temporal development of the zones of discontinuity in normal human lenses is essentially identical to the progressive iteration of offset monkey lens sutures. In conclusion, these studies describe a specific structural aspect of lenses that adversely influences optical quality, and relates it to the most commonly employed clinical technique to identify and monitor the progress of cataracts.

Evolution of biological complexity and its relation to taxonomic longevity in the Ammonoidea

Research Article| November 01, 1992 Evolution of biological complexity and its relation to taxonomic longevity in the Ammonoidea George Boyajian; George Boyajian 1Department of Geology, University of Pennsylvania, 240 South 33rd Street, Philadelphia, Pennsylvania 19104-6316 Search for other works by this author on: GSW Google Scholar Tim Lutz Tim Lutz 2Department of Geology and Astronomy, West Chester University, West Chester, Pennsylvania 19383 Search for other works by this author on: GSW Google Scholar Author and Article Information George Boyajian 1Department of Geology, University of Pennsylvania, 240 South 33rd Street, Philadelphia, Pennsylvania 19104-6316 Tim Lutz 2Department of Geology and Astronomy, West Chester University, West Chester, Pennsylvania 19383 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1992) 20 (11): 983–986. https://doi.org/10.1130/0091-7613(1992)020<0983:EOBCAI>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation George Boyajian, Tim Lutz; Evolution of biological complexity and its relation to taxonomic longevity in the Ammonoidea. Geology 1992;; 20 (11): 983–986. doi: https://doi.org/10.1130/0091-7613(1992)020<0983:EOBCAI>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The increase in biological complexity over evolutionary time has been the subject of extensive study and many hypotheses, but there are few data to document the increase or how organisms may have benefited by becoming more complex. By measuring the fractal dimension of the sutures of >600 ammonoid genera, we document the increase in anatomical complexity of the Ammonoidea and show that there is no differential survival between simple and complex forms. Simple sutures are present throughout the entire history of the Ammonoidea, but the range of variation of suture complexity increased over time as more complex sutures evolved. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

全下顎堤形成術における糸かけ器の使用経験

In this paper we report about a suture holder for preprosthetic surgery.This inexpensive suture holder is easily made and can be sterilized by any method.Through its use, an oral surgeon can manage numerous complex sutures without any trouble and perform the operation quickly and systematically.We recommed this valuable suture holder.