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PubMedDate not supplied

Electron microscopic study of thymus and bone marrow derived mouse lymphocytes: morphological differences and evolution of surface markers before and after in vitro mitogenic stimulation.

T and B lymphocytes from spleen, lymph nodes, thymus and bone marrow of unstimulated CBA mice have distinct ultrastructural features: respectively the Th type (dense dark appearance, smooth margin, high nucleocytoplasmic ratio, rare cytoplasmic organelles) and the Bm type (low electronic density, villous margin, low nucleocytoplasmic ratio, numerous cytoplasmic organelles). Correlations between Th or Bm morphology and presence of specific T or B surface markers (theta antigen or surface Ig) have been established. The Th/T and Bm/B equivalence do not however hold in all circumstances: first, there are morphologically intermediate types termed In (less than 13%) that may be theta- or Ig-positive; second, some Bm lymphocytes are theta-positive in CBA thoracic duct and some Th lymphocytes are Ig-positive in Nude mice spleen. Purified T-or B lymphocyte populations stimulated by selective mitogens (ConA or LPS respectively) undergo ultrastructural modifications before their surface markers (theta or Ig respectively) disappear. A time, some theta-positive T lymphocytes show a Bm-like morphology. The results suggest that the basis for the usual T-B ultrastructural differences in unstimulated mice resides in the normally different functional state of metabolic activity of these two types of cells: the cell metabolism would be higher in Bm (the usual form of unstimulated B lymphocytes) than in Th (the usual form of unstimulated T lymphocytes). This view may explain the paradoxical results observed in thoracic duct and Nude mice spleen as well as conflicting data reported by several authors.

Animals↗
PubMed1992

Morphology, behavior, and evolution: comparative kinematics of aquatic feeding in salamanders.

The kinematics of aquatic prey capture were studied in species representing six salamander families (Ambystomatidae, Amphiumidae, Cryptobranchidae, Dicamptodontidae, Proteidae, and Sirenidae) to test the hypothesis that the process of aquatic prey capture is similar in these families. Seven variables were digitized from high-speed video records of prey capture, and a nested analysis of variance was performed to test for both significant individual within taxon and among taxa effects. The time-to-peak head angle and gape variables showed no taxon effect, while the other five variables exhibited highly significant differences among taxa. Cryptobranchus and Siren showed the most divergent kinematic pattern from the other taxa in a multivariate analysis of all variables, while Ambystoma, Dicamptodon, and Amphiuma tended to have similar overall patterns of head movement. These results show that kinematic patterns during aquatic feeding are not conserved across salamander taxa, and that phylogenetic differentiation in head morphology has been accompanied by novelties in feeding function. The feeding mechanisms of Cryptobranchus and Amphiuma have a bidirectional hydrodynamic design with kinematic correlates that are similar to kinematic characteristics of aquatic feeding in turtles and transformed ambystomatid salamanders. A general framework is presented as an aid to understanding the interrelationships among muscle activity patterns, morphology, and behavior (kinematic patterns). By considering the distribution of taxa in three multivariate spaces, corresponding to three of the levels at which one might analyze a behavior (kinematics, morphology, and motor pattern), it is possible to identify patterns of correspondence among the levels, which aid in understanding the evolution of behavior.

Animals↗
PubMed1994

Molecules vs. morphology in avian evolution: the case of the "pelecaniform" birds.

The traditional avian Order Pelecaniformes is composed of birds with all four toes connected by a web. This "totipalmate" condition is found in ca. 66 living species: 8 pelicans (Pelecanus), 9 boobies and gannets (Sula, Papasula, Morus), ca. 37 cormorants (Phalacrocorax), 4 anhingas or darters (Anhinga), 5 frigatebirds (Fregata), and 3 tropicbirds (Phaethon). Several additional characters are shared by these genera, and their monophyly has been assumed since the beginning of modern zoological nomenclature. Most ornithologists classify these genera as an order, although tropicbirds have been viewed as related to terns, and frigatebirds as relatives of the petrels and albatrosses. DNA.DNA hybridization data indicated that the pelicans are most closely related to the Shoebill (Balaeniceps rex), a stork-like bird that lives in the swamps of central Africa; the boobies, gannets, cormorants, and anhingas form a closely related cluster; the tropicbirds are not closely related to the other taxa; and the frigatebirds are closest to the penguins, loons, petrels, shearwaters, and albatrosses (Procellarioidea). Most of these results are corroborated by DNA sequences of the 12S and 16S rRNA mitochondrial genes, and they provide another example of incongruence between classifications derived from morphological versus genetic traits.

Animals↗
PubMed1987

Evolution of P3 morphology in Australopithecus afarensis.

The Australopithecus afarensis dental sample exhibits a wide range of variation, which is most notable in the morphology of the lower third premolar (P3). P3 morphology in the A. afarensis sample ranges from the primitive sectorial extreme in AL 128-23 to the derived, bicuspid (molarized) extreme in AL 333w-1. In this paper, the degree and patterning of variation of the 20 known A. afarensis P3s are examined and the evolutionary implications are discussed. Initially, a series of dental and mandibular metric criteria are evaluated to determine whether this sample may be analyzed as a single species. From the metrics, it is clear that the single species hypothesis cannot be rejected. Next, a series of morphological criteria is devised to measure P3 molarization. Taken as a whole, the A. afarensis P3 sample displays more variation than a sample of modern hominoids (Pan troglodytes) and shows a slight trend toward increased molarization through time. When separated by sex, the A. afarensis sample still displays greater variation than the chimpanzee sample; however, only the male A. afarensis specimens show a trend toward increased molarization. Additionally, the male A. afarensis P3s are more molarized than the female, a pattern that is seen as well (though less markedly) in the chimpanzee sample. The trend toward increased molarization over time indicates selection for grinding in A. afarensis. The sexual differences parallel those seen in the postcrania (cf. Stern and Susman: Am. J. Phys. Anthropol. 60:279-318, 1983), as the females tend to retain the primitive condition, while the males display the derived morphology. Consequently, a model of sexual differences in niche exploitation, with the females exploiting a more arboreal environment, would seem to be supported by both the dental and postcranial evidence.

Africa↗
PubMed1983

[Evolution of a morphological variant and the prognosis in lymphogranulomatosis].

The authors present the results of a retrospective analysis of the clinical peculiarities of a course of Hodgkin's disease (HD) as compared to the results of histological examination of lymph node biopsies taken for diagnostic purposes and operative material from 235 patients after exploratory laparotomy with splenectomy. It was shown that rapid transformation (from the onset of disease) of the HD histological variant of the type of "lymphoid prevalence", "nodular sclerosis" or "mixed cellular" into the "lymphoid depletion" variant attests to high rates of the evolution of a tumor process and makes it possible to recognize the subacute nature of a course of disease before treatment. The above phenomenon points to poor prognosis and should be considered in the choice of therapeutic tactics.

Adult↗
PubMed1993

[Evolution and functional morphology of primate facial skulls].

Both ontogenetically and phylogenetically the facial skull of primates consists of two components: the endocranial nasal capsule, and the exocranial membrane bones. The cartilaginous nasal capsule of the fetal period constitutes the framework for the nasal cavity, and it also functions as an expansive basis for the developing facial skull. In adult animals, its ossified parts form the fragile ethmoid bone. The structure of the nasal capsule is determined on the one hand by the spatial requirements of the orbits and of the nasal cavity (with respiratory and olfactory components), and on the other hand by the biomechanical properties of the chewing apparatus. The interaction of these heterogeneous factors results in complex, species-specific compromises. Primates are characterized by a gradual reduction of their olfactory system throughout evolution and by binocular vision. Their chewing apparatus shows constructional adaptations to a varying herbivorous diet. Viewed within a phylogenetic-systematic framework, primate evolution may be taken as a natural experiment that demonstrates the influence of various factors on a complex structural system such as the nasal and facial skeleton.

Animals↗
PubMed2005

Gonadogenesis in Pristionchus pacificus and organ evolution: development, adult morphology and cell-cell interactions in the hermaphrodite gonad.

The nematode gonad is an exemplary system for the study of organogenesis and fundamental problems in developmental and cellular biology. Nematode gonads vary dramatically across species (Chitwood, B.G., Chitwood, M.B., 1950. Introduction to Nematology." University Park Press, Baltimore; Felix, M.A., Sternberg, P.W., 1996. Symmetry breakage in the development of one-armed gonads in nematodes. Development 122, 2129-2142). As such, comparative developmental biology of gonadogenesis offers the potential to investigate changes in developmental and cellular processes that result in novel organ morphologies and thus may give insights into how these changes can affect animal bauplane. Pristionchus pacificus is a free-living nematode that diverged from the model nematode Caenorhabditis elegans around 200-300 million years ago. The morphology and development of P. pacificus is highly homologous to that of C. elegans. However, many differences in morphology and the underlying molecular signaling networks are easy to identify, making P. pacificus ideal for a comparative approach. Here, we report a detailed description of the P. pacificus hermaphrodite gonad using electron and fluorescent microscopy that will provide a basis for both phenotypic studies of genetic mutations and in vivo molecular studies of cloned genes involved in P. pacificus gonad development. We report that the morphology of the P. pacificus gonad is distinct from that of C. elegans. Among these differences are germ line patterning differences, heterochronic differences, novel gonadal arm-migrations, novel cellular composition of some somatic tissues (e.g., the number of cells that comprise the sheath and different spermathecal regions are different), the absence of a somatic tissue (e.g., the spermathecal valve cells), a novel architecture for the sheath, and changes in the cellular and sub-cellular morphology of the individual sheath cells. Additionally, we report a set of cell ablations in P. pacificus that indicate extensive cell communication between the somatic gonadal tissues and the germ line. Individual ablation experiments in P. pacificus show significant differences in the effects of individual somatic tissues on germ line patterning in comparison to C. elegans.

Animals↗
PubMed2001

Healing of acute myocarditis with left ventricular assist device: morphological recovery and evolution to the aspecific features of dilated cardiomyopathy.

Dilated cardiomyopathy may result from an acute myocarditis. Little is reported in vivo documenting the progression from the acute inflammatory disease to the healing phase. We describe the consecutive light and electron microscopy studies performed on five myocardial sample series in a 47-year-old female patient who was referred to our hospital with acute myocarditis. She was sustained with left ventricular assist device (LVAD) for 63 days, and then she died of cerebral hemorrhage. The first three consecutive endomyocardial biopsies (days 2, 4, 36 from onset) documented the acute and early healing phase of the inflammatory disease. In the last two biopsies (days 50 and 64 from onset) active inflammation and myocyte necrosis were absent. The histopathological features were those commonly observed in most patients diagnosed with dilated cardiomyopathy, namely myocyte hypertrophy, nuclear size and shape irregularities, and interstitial fibrosis. Overall, the myocyte morphology significantly improved and LVAD support likely contributed to the structural recovery. The major conclusions to be drawn from this case are: 1) the aspecific pathologic findings of dilated cardiomyopathy patients may result from an acute myocardial inflammation; 2) immediate endomyocardial biopsy in patients with clinically diagnosed myocarditis minimizes the risk of missing the diagnosis of inflammatory disease; to this aim a precise definition of "early onset" is especially needed; 3) LVAD support may contribute to the morphological recovery of severely damaged myocytes.

Biopsy↗
PubMed2002

The evolution of tendon--morphology and material properties.

Phylogenetically, tendinous tissue first appears in the invertebrate chordate Branchiostoma as myosepta. This two-dimensional array of collagen fibers is highly organized, with fibers running along two primary axes. In hagfish the first linear tendons appear and the myosepta have developed specialized regions with unidirectional fiber orientation-a linear tendon within the flat sheet of myoseptum. Tendons react to compressive load by first forming a fibrocartilaginous pad, and under severe stress, sesamoid bones. Evidence for this ability to react to load first arises in the cartilaginous fish, here documented in a tendon from the jaw of a hard-prey crushing stingray. Sesamoid bones are common in bony fish and also in tetrapods. Tendons will also calcify under tensile loads in some groups of birds, and this reaction to load is seen in no other vertebrates. We conclude that the evolutionary history of tendon gives us insight into the use of model systems for investigating tendon biology. Using mammal and fish models may be more appropriate than avian models because of the apparent evolution of a novel reaction to tensile loads in birds.

Animals↗
PubMed2006

In silico evolution of functional morphology: A test on bone tissue biomechanics.

Evolutionary algorithms (EAs) use Darwinian principles--selection among random variation and heredity--to find solutions to complex problems. Mostly used in engineering, EAs gain growing interest in ecology and genetics. Here, we assess their usefulness in functional morphology, introducing finite element modelling (FEM) as a simulated mechanical environment for evaluating the 'fitness' of randomly varying structures. We used this method to identify biomechanical adaptations in bone tissue, a long-lasting problem in skeletal morphology. The algorithm started with a bone tissue model containing randomly distributed vascular spaces. The EA randomly mutated the distribution of vascular spaces, and selected the new structure if its mechanical resistance was increased. After some thousands of generations, organized phenotypes emerged, containing vascular canals and sinuses, mimicking real bone tissue organizations. This supported the hypothesis that natural bone microstructures can result from biomechanical adaptation. Despite its limited faithfulness to reality, we discuss the ability of the EA+FEM method to assess adaptation in a dynamic evolutionary framework, which is not possible in the real world because of the generation times of macro-organisms. We also point out the interesting potential of EAs to simulate not only adaptation, but also concurrent evolutionary phenomenons such as historical contingency.

Algorithms↗
PubMed2000

Variation in mandible shape in Thrichomys apereoides (Mammalia: Rodentia): geometric analysis of a complex morphological structure.

The model of development and evolution of complex morphological structures conceived by Atchley and Hall in 1991 (Biol. Rev. 66:101-157), which establishes that changes at the macroscopic, morphogenetic level can be statistically detected as variation in skeletal units at distinct scales, was applied in combination with the formalism of geometric morphometrics to study variation in mandible shape among populations of the rodent species Thrichomys apereoides. The thin-plate spline technique produced geometric descriptors of shape derived from anatomical landmarks in the mandible, which we used with graphical and inferential approaches to partition the contribution of global and localized components to the observed differentiation in mandible shape. A major pattern of morphological differentiation in T. apereoides is attributable to localized components of shape at smaller geometric scales associated with specific morphogenetic units of the mandible. On the other hand, a clinical trend of variation is associated primarily with localized components of shape at larger geometric scales. Morphogenetic mechanisms assumed to be operating to produce the observed differentiation in the specific units of the mandible include mesenchymal condensation differentiation, muscle hypertrophy, and tooth growth. Perspectives for the application of models of morphological evolution and geometric morphometrics to morphologically based systematic biology are considered.

Animals↗
PubMed2001

Colony dispersal and the evolution of queen morphology in social Hymenoptera.

Social Hymenoptera show two contrasting strategies of colony reproduction. A reproductive female can raise the first generation of brood alone (independent foundation), or a colony can divide into autonomous parts in which the reproductive female is helped by sterile relatives (fission, budding, swarming). In independent-founding ants, queens can histolize their flight muscles after dispersal; in many species, large flight muscles and metabolic reserves reduce or eliminate the need for risky foraging trips during the vulnerable solitary stage. Colony division is a derived strategy, and we review the selective pressures leading to its occurrence in the different social taxa. In various ants, fission coexists with independent foundation, and alate queens are retained. However, in ants exhibiting obligate fission (e.g. all army ants and many Ponerinae), queens are permanently wingless (ergatoid), or the queen caste is missing altogether. When reproductive females are flightless, dispersal distances and colonization ability are reduced, and there are extensive modifications in mating behavior and resource allocation. We focus on the characteristics of fission in the phylogenetically primitive ants Ponerinae in which both ergatoid queens and gamergates occur. The ground-living habits of ants have permitted extensive changes in the phenotypes of their reproductive females, unlike in wasps and bees.

Animals↗
PubMed1998

Correlations of cranial morphology, ecology, and evolution in Australian suctorial tadpoles of the genera Litoria and Nyctimystes (Amphibia: Anura: Hylidae: Pelodryadinae).

Suctorial anuran larvae are highly specialized for living in fast-flowing waters, using their oral disks as adhesive organs to attach to the substrate. The cranial musculoskeletal structure of suctorial larvae of Litoria nannotis, L. rheocola, and Nyctimystes dayi (Hylidae: Pelodryadinae) were compared with congenerics with pond-type larvae (L. caerulea, L. genimaculata, L. xanthomera). Data from two other neobatrachian species with suctorial larvae (Boophis sp., Hyla armata) as well as published descriptions were taken into account. Suctorial tadpoles evolved several times independently in the Neobatrachia and share various features, irrespective of their phylogenetic position. These include the following. Cornua trabeculae are expanded anteriorly and sometimes fused. The lower jaws are robust. The greatest width of the skull is at the level of the jaw articulation. The upper jaw cartilages are partially or fully fused. The palatoquadrate is robust and connected to the skull by a wide commissura quadratocranialis anterior, processus oticus, processus basalis (in some species), and processus ascendens (vestigial or absent in some species). A processus ventralis quadrati provides an extended area of origin for the m. orbitohyoideus. The m. rectus abdominis inserts far anterior and acts on the cranium. The insertion of the epaxial musculature is shifted anteriorly to the anterior parts of the otic capsule. The mm. diaphragmatobranchialis and rectus cervicis cross at their origins. The origin of the m. levator mandibulae anterior has shifted posteriorly. The branchial basket is relatively small and the ceratohyal area is large. Multiple convergent evolution of these features suggests that they may be causally associated with the suctorial mode of larval life. Aside from these characters, however, the suctorial and pond-type neobatrachian species are remarkably similar in their jaw musculature and hyobranchial musculoskeletal composition. In some features, Ascaphus truei differs significantly from the neobatrachian suctorial species, indicating the influence of the historically distant separation of the two taxa. A novel modification of the upper jaw abduction mechanism has evolved in L. nannotis, L. rheocola, and N. dayi. It involves an adrostral cartilage as a pushing-rod element. This mechanism and unique structural similarities of the cartilago labialis superior gives support to the preliminary assumption that the nannotis species group is more closely related to the suctorial Nyctimystes dayi than it is to other Litoria species with pond-type larvae. Suctorial larvae presumably were present in the most recent common ancestor of the Litoria nannotis group and Nyctimystes dayi.

Animals↗
PubMed2006

Tumor morphology and phenotypic evolution driven by selective pressure from the microenvironment.

Emergence of invasive behavior in cancer is life-threatening, yet ill-defined due to its multifactorial nature. We present a multiscale mathematical model of cancer invasion, which considers cellular and microenvironmental factors simultaneously and interactively. Unexpectedly, the model simulations predict that harsh tumor microenvironment conditions (e.g., hypoxia, heterogenous extracellular matrix) exert a dramatic selective force on the tumor, which grows as an invasive mass with fingering margins, dominated by a few clones with aggressive traits. In contrast, mild microenvironment conditions (e.g., normoxia, homogeneous matrix) allow clones with similar aggressive traits to coexist with less aggressive phenotypes in a heterogeneous tumor mass with smooth, noninvasive margins. Thus, the genetic make-up of a cancer cell may realize its invasive potential through a clonal evolution process driven by definable microenvironmental selective forces. Our mathematical model provides a theoretical/experimental framework to quantitatively characterize this selective pressure for invasion and test ways to eliminate it.

Adaptation, Physiological↗
PubMed2005

Evolution of surface morphologies in multivariant assemblies of surface-tethered diblock copolymers after selective solvent treatment.

We study systematically the topography behavior of PHEMA-b-PMMA block as a function of the PHEMA and PMMA block lengths after selectively collapsing the top (PMMA) block by using surface-anchored assemblies of poly(2-hydroxyethyl methacrylate-b-methyl methacrylate), PHEMA-b-PMMA, block copolymer with orthogonally varying lengths of each block. Our experimental results are in excellent qualitative agreement with topology diagrams predicted by self-consistent field calculations of Zhulina and co-workers.

Polyhydroxyethyl Methacrylate↗
PubMedDate not supplied

The evolution of foot morphology in children between 6 and 17 years of age: a cross-sectional study based on footprints in a Mediterranean population.

Footprint evaluation is a widely used method for the determination of foot morphology, but its efficacy and validity are considered controversial. Dynamic footprints were obtained from both feet of 5,866 school-aged children (6-17 years old) to detect any foot changes during growth. The interpretation of the imprint was performed using a classification scheme consisting of 6 types of footprints. In this scheme, footprint types I and II represent the typical and intermediate high-arched foot, respectively. Types III and IV represent normal foot variants, while type V corresponds to the low-arched foot and type VI to the severe flat foot, the latter often encountered in pathological conditions. There was statistically significant difference (P<.05) in footprint-type frequencies between boys and girls of ages 7, 9, 11, 14, and 15, which probably indicates the difference in growth potential of the foot between sexes. The proportion of high- and low-arched foot types decreased with increasing age in both boys and girls. Even though critical changes of the foot are believed to occur during pre-school development, this study shows that considerable changes also take place during school age and until late adolescence.

Adolescent↗
PubMed1988

Prevalence, morphologic types, and evolution of cardiac valvular disease in systemic lupus erythematosus.

We performed echocardiography prospectively 4.9 +/- 0.7 years apart (mean +/- SD), in 74 patients with systemic lupus erythematosus. On the basis of the first study, the patients were distributed in four groups according to the type of valvular involvement: 7 patients had vegetations (Libman-Sacks endocarditis; group 1); 6 patients had rigid and thickened valves with stenosis, regurgitation, or both (group 2); 5 patients had miscellaneous forms of valvular involvement without valvular dysfunction (group 3), as did the 60 controls; and 56 patients had no valvular disease (group 4). The overall prevalence of clinically important valvular disease (groups 1 and 2) was 18 percent. Patients in group 1 were younger than those in group 2 (33.5 +/- 16.7 vs. 47.8 +/- 17.6 years; P less than 0.05), had a shorter mean duration of lupus (4.8 +/- 2.2 vs. 10.7 +/- 6.4 years; P less than 0.001), and had received a smaller cumulative dose of steroids (21.5 +/- 13.1 vs. 79.5 +/- 63.4 g of methylprednisolone or its equivalent; P less than 0.05). During the five-year follow-up, one patient in group 1 and five in group 2 required valve surgery, no patient in group 3 had valvular dysfunction, and five patients in group 4 had mild valvular lesions. We conclude that clinically important valvular involvement in systemic lupus is relatively frequent and sometimes requires surgery. Echocardiography can identify a subset of lesions (valvular thickening and dysfunction), other than verrucous (Libman-Sacks) endocarditis, that are prone to hemodynamic deterioration.

Adolescent↗