Nasal tip sutures part II: the interplays

The achievement of consistently superior results in rhinoplasty is rendered difficult in part by a number of complex interplays between the anatomical structures of the nose and the techniques used for their alteration, such as tip sutures. The effects of sutures depend largely on the magnitude of suture tightening, the intrinsic forces on the cartilages, cartilage thickness, and the degree of soft-tissue undermining. The tip complex is perhaps the most intricate of the nasal structures, exhibiting subtle but evident responses to manipulations of the lower lateral cartilages. The three-dimensional effects of nine suture techniques that are frequently used in nasal tip surgical procedures are discussed and illustrated. (1) The medial crura suture approximates the medial crura and strengthens the support of the tip. The suture also has effects that are less conspicuous immediately. There is slight narrowing of the columella, caudal protrusion of the lobule, and minimal caudal rotation of the lateral crura. (2) The middle crura suture approximates the most anterior portion of the medial crura. There is greater strengthening of the tip and some approximation of the domes with this suture. (3) The interdomal suture approximates the domes and can equalize asymmetric domes. However, the entire tip may shift to the short side if there is a significant difference in the heights of the domes because of short lateral and medial crura. (4) Transdomal sutures narrow the domal arch while pulling the lateral crura medially. The net results are increased tip projection, alar rim concavity, and the potential need for an alar rim graft. In addition, depending on suture position, cephalic or caudal rotation of the lateral crura may be observed. (5) The lateral crura suture increases the concavity of the lateral crura, reduces the interdomal distance, and may retract the alar rims. Perhaps the most significant inadvertent results of this suture are caudal rotation of the tip and elongation of the nose. This is important because patients who undergo rhinoplasty would often benefit from cephalic, rather than caudal, rotation of the tip. (6) The medial crura-septal suture not only increases tip projection but also rotates the tip cephalically and retracts the columella. (7) The tip rotation suture shifts the tip cephalad while retracting the columella. (8) The medial crura footplate suture approximates the footplates, narrows the columella base, and improves undesirable nostril shape. (9) The lateral crura convexity control suture alters the degree of convexity of the lateral crura. The nuances of these sutures and their multiplanar effects on the nasal tip are discussed.     

Developmental genetics and arthropod evolution: part I, on legs

SUMMARY Developmental genetic information as it relates to the ontogeny of limbs can help evaluate various scenarios of arthropod evolution proposed in the past, as well as help frame other alternatives. First, the cascade of genetic expressions, which controls the development of the arthropod limb, suggests that a postulated evolution of the crustacean coxa from a proximal endite, a structure seen on certain Cambrian crustaceomorphs, might not be correct. Alternative hypotheses could explain the fossil anatomy, and the genetic patterns of expression demand that we at least be cautious in interpreting the Orsten material. Second, recognition of three distinct models of limb formation in arthropods would appear to preclude Rehbachiella , from the Cambrian Orsten, and Lepidocaris , from the Devonian Rhynie Chert, as members of the crown-group Branchiopoda. The recognition of a distinct Artemia Model of limb induction within living anostracans, notostracans, cladocerans, and conchostracans requires that such a model be part of the ground pattern of the Branchiopoda, a pattern that does not appear to have been possible in the fossil species. Finally, the suggestion that a large number of leg segments must be a plesiomorphic condition in arthropods should be considered cautiously. A sequential occurrence of mutations including, for example, a recessive loss-of-function mutant of a Hox -gene like Antennapedia could have resulted in the apomorphic evolution of long, multisegmented limbs within different groups of arthropods. The need for more comprehensive phylogenetic studies using as many taxa and characters possible is obvious both for the generation of scenarios of evolution, as well as in testing multiple alternative hypotheses of relationships.     

Nasal tip blood supply: confirming the safety of the transcolumellar incision in rhinoplasty

The transcolumellar incision in rhinoplasty has proven to be a safe and effective technique, even with simultaneous alar base resections. A sound appreciation of the blood supply to the nasal tip and adherence to the guidelines presented above will prevent vascular compromise of the nasal tip skin.     

Changing the convexity and concavity of nasal cartilages and cartilage grafts with horizontal mattress sutures: part I. Experimental results

Prior studies indicated that horizontal mattress sutures can control the curvature of a convex lateral crus. This study undertook to ascertain the ideal spacing for mattress sutures, determine what effect they have on the subsequent strength of the cartilage, and compare that to the resultant strength after scoring procedures used to control curvature. Curved fresh cadaver septa of various thicknesses (0.5, 1, and 1.5 mm) were used. The ideal spacing (gap between suture purchases) for the mattress suture was sought in 15 specimens. The consequent change in stiffness (modulus) of the cartilage was measured in nine other specimens before and after suture placement and after scoring. If the spacing was too large, instability resulted. If it was too small, curvature correction could not be obtained. An ideal mattress spacing (6 to 8 mm for 0.5-mm specimens and 8 to 10 mm for 1.5-mm specimens) removed most curvature and provided stability. The mattress suture increased the stiffness (modulus) above normal and far above that when the curvature was removed by scoring. The mean composite modulus before suturing was 4.6 MPa. After ideally spaced sutures, it was 6.2 MPa, a 35 percent increase in stiffness. After scoring to improve curvature, it was 2.4 MPa, a 48 percent reduction in stiffness (p = 0.02, Wilcoxon signed rank test). The horizontal mattress suture technique corrects cartilage curvature if the appropriate spacing is used. The corrected cartilage is stiffer/stronger than normal cartilage and much stiffer/stronger than if scored.     

The evolution of myiasis in humans and other animals in the Old and New Worlds (part I): phylogenetic analyses

Myiasis, the infestation of live vertebrates with dipterous larvae, seems to take two distinct forms that, it has been suggested, evolved from two distinct phylogenetic roots: saprophagous and sanguinivorous. However, the convergent evolution of morphological and life-history traits seems to have had a major role in simplifying this overall assessment of the evolutionary routes by which myiasis arose. Moreover, this somewhat simplistic division is further complicated by the existence of both ectoparasitic and endoparasitic species of myiasis-causing Diptera, the evolutionary affinities of which remain to be resolved. To understand how different forms of parasitism arose, the evolution of the various groups of myiasis-causing flies must be separated from the evolution of the myiasis habit per se. Until recently, evolutionary studies of myiasis-causing flies were little more than discussions of morphology-based taxonomy. Since the mid-1990s, however, several formal phylogenies - based on both morphological and, increasingly, molecular data - have been published, enabling reassessment of the hypotheses concerning myiasis evolution. In part I of this review, we focus on some recent landmark studies in this often-neglected branch of parasitology and draw together phylogenetic studies based on molecular and morphological data to provide a framework for the subsequent analysis of biochemical, immunological, behavioural, biogeographical and fossil evidence relating to the evolution of myiasis.     

Clonality as a part of the evolution process inTaraxacum

A review is presented of various ecological and population aspects ofTaraxacum agamospermy. Agamospermy is compared with vegetative clonality, the former differeing in capability to generate variation, seed dispersal and often long evolutionary history. Clonal diversity of agamospermous taxa ranges from almost absolute uniclonality to high diversity of clones. Multiclonality is suggested to represent one of agamospecies' population characteristics. Biological individuality of clones allows coexistence of clones at a locality. Competition and other factors influencing number of clones at a locality are discussed. Geographical and ecological distribution of agamospermous and sexualTaraxacum taxa are evaluated, their coexistence and gene flow are addressed, and a hypothesis is presented concerning the population condition in mixed stands of sexual and asexualTaraxaca. Lastly, agamospermy is shown to significantly reduce recombination processes; it should not be considered an absolute evolutionary “blind alley”.     

Functional stability of the aristaless gene in appendage tip formation during evolution

The appendages of an insect are subdivided into distinct segments or podomeres. Many genes responsible for the regionalization of the growing limb into subdomains have been isolated from Drosophila. So far, only one gene is known in the leg that is solely required for specifying the distal-most pattern element—the pretarsal claw. In Drosophila, the gene aristaless is expressed in the centre of the antennal and leg imaginal disc that represents the most distal position of appendages, and in a proximal region. When Drosophila aristaless function is impaired, antennae and legs develop without their distal-most structures—the arista and the claw. We describe here the analysis of aristaless in the beetle Tribolium—an insect that shows a different, more ancestral mode of appendage formation than Drosophila. In Tribolium, appendages grow out continuously during embryogenesis, and no imaginal discs are formed. Tribolium aristaless (Tc-al) expression starts midway during appendage elongation, and is seen in a distal and a proximal position of head and trunk appendages. At the end of embryogenesis, Tc-al is seen in four expression domains in the leg, in the dorsal epidermis, and ventrally in every segment in lateral groups of cells, presumably the histoblasts. Like in the Drosophila adult, Tc-al is required in the larva for the formation of the most distal structures of the leg and the antenna as revealed by RNAi experiments. We conclude that aristaless is evolutionarily robust, meaning that it has retained its expressional and functional characteristics, although a heterochronic change of the process of appendage elongation took place towards the evolution of the highly derived diptera.Edited by D. Tautz     

About functional evolution of peripheral part of the auditory system

Functional evolution of the peripheral part of the auditory system is considered. The key point of the appearance of a possibility of analysis of sound waves is formation in the course of evolution of cells with protoplasmic processes (sensillae)--the hair cells--that are transformed into auditory receptors. The fundamental moment is the emergence in evolution of the specialized ionic medium (endolymph) surrounding the auditory receptors. This medium is necessary for generation of receptor potential due to mechanical deformations of the auditory receptor. The characteristic feature of functional evolution of the peripheral part of the auditory system is the many-time repetition in the course of evolution of the main devices to detect and to distinguish sounds. This indicates recapitulation in evolution not only of the central parts of the brain (including central regions of the auditory system), but also of its peripheral part.     

On the evolution of epistasis I: diploids under selection

One interpretation of recent literature on the evolution of phenotypic modularity is that evolution should act to decrease the degree of interaction between genes that contribute to different phenotypes. This issue is addressed directly here using a fitness scheme determined by two genetic loci and a third locus which modifies a measure of statistical interaction between the fitnesses due to the first two. The equilibrium structure of such an epistasis-modifying locus is studied. It is shown that under well-specified conditions a modifying allele that increases epistasis succeeds. In other words, genetic interactions tend to become stronger. It is speculated that this occurs because the mean fitness in such models is locally increasing as a function of the degree of epistasis.     

Computational studies of the farnesyltransferase ternary complex part I: substrate binding

Farnesyltransferase (FTase) catalyzes the transfer of farnesyl from farnesyl diphosphate (FPP) to cysteine residues at or near the C-terminus of protein acceptors with a CaaX motif (a, aliphatic; X, Met). Farnesylation is a critical modification to many switch proteins involved in the extracellular signal transduction pathway, which facilitates their fixation on the cell membrane where the extracellular signal is processed. The malfunction caused by mutations in these proteins often causes uncontrolled cell reproduction and leads to tumor formation. FTase inhibitors have been extensively studied as potential anticancer agents in recent years, several of which have advanced to different phases of clinical trials. However, the mechanism of this biologically important enzyme has not been firmly established. Understanding how FTase recruits the FPP substrate is the first and foremost step toward further mechanistic investigations and the design of effective FTase inhibitors. Molecular dynamic simulations were carried out on the ternary structure of FTase complexed with the FPP substrate and an acetyl-capped tetrapeptide (acetyl-CVIM), which revealed that the FPP substrate maintains an inactive conformation and the binding of the diphosphate group can be largely attributed to residues R291beta, K164alpha, K294beta, and H248beta. The FPP substrate assumes an extended conformation in the binding site with restricted rotation of the backbone dihedral angles; however, it does not have a well-defined conformation when unbound in solution. This is evident from multinanosecond MD simulations of the FPP substrate in a vacuum and solution. Our conclusion is further supported by theoretical J coupling calculations. Our results on the FPP binding are in good agreement with previous experimental kinetic studies on FTase mutants. The hypothetical conformational activation of the FPP substrate is currently under investigation.