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At least 865 records · Page 48Linked to original sources
PubMed2003

The placenta in Monoclea forsteri Hook. and Treubia lacunosa (Col.) Prosk: insights into placental evolution in liverworts.

Placental morphology is remarkably diverse between major bryophyte groups, especially with regard to the presence and distribution of transfer cells in the sporophyte and gametophyte. In contrast, with the exception of metzgerialean liverworts, placental morphology is highly conserved within major bryophyte groups. Here we examine the ultrastructure of the placenta in Monoclea forsteri and Treubia lacunosa, basal members of the marchantialean and metzgerialean liverwort lineages, respectively. In both species several layers of transfer cells are found on both sides of the placenta, with sporophytic transfer cells exhibiting prominent wall labyrinths. Consistent with previous reports of a similar placenta in other putatively basal and isolated liverwort genera such as Fossombronia, Haplomitrium, Blasia and Sphaerocarpos, this finding suggests that this type of placenta represents the plesiomorphic (primitive) condition in liverworts. Distinctive ultrastructural features of placental cells in Monoclea include branched plasmodesmata in the sporophyte and prominent arrays of smooth endoplasmic reticulum, seemingly active in secretion in the gametophyte. These arrays contain a core of narrow tubules interconnected by electron-opaque rods, structures with no precedent in plants. Analysis of the distribution of different types of placenta in major bryophyte groups provides valuable insights into their inter-relationships and possible phylogeny.

Biological Evolution↗
PubMed2003

Developmental gene regulatory network architecture across 500 million years of echinoderm evolution.

Evolutionary change in morphological features must depend on architectural reorganization of developmental gene regulatory networks (GRNs), just as true conservation of morphological features must imply retention of ancestral developmental GRN features. Key elements of the provisional GRN for embryonic endomesoderm development in the sea urchin are here compared with those operating in embryos of a distantly related echinoderm, a starfish. These animals diverged from their common ancestor 520-480 million years ago. Their endomesodermal fate maps are similar, except that sea urchins generate a skeletogenic cell lineage that produces a prominent skeleton lacking entirely in starfish larvae. A relevant set of regulatory genes was isolated from the starfish Asterina miniata, their expression patterns determined, and effects on the other genes of perturbing the expression of each were demonstrated. A three-gene feedback loop that is a fundamental feature of the sea urchin GRN for endoderm specification is found in almost identical form in the starfish: a detailed element of GRN architecture has been retained since the Cambrian Period in both echinoderm lineages. The significance of this retention is highlighted by the observation of numerous specific differences in the GRN connections as well. A regulatory gene used to drive skeletogenesis in the sea urchin is used entirely differently in the starfish, where it responds to endomesodermal inputs that do not affect it in the sea urchin embryo. Evolutionary changes in the GRNs since divergence are limited sharply to certain cis-regulatory elements, whereas others have persisted unaltered.

Animals↗
PubMed1997

Evolution and development--the nematode vulva as a case study.

To understand how morphological characters change during evolution, we need insight into the evolution of developmental processes. Comparative developmental approaches that make use of our fundamental understanding of development in certain model organisms have been initiated for different animal systems and flowering plants. Nematodes provide a useful experimental system with which to investigate the genetic and molecular alterations underlying evolutionary changes of cell fate specification in development, by comparing different species to the genetic model system Caenorhabditis elegans. In this review, I will first discuss the different types of evolutionary alterations seen at the cellular level by focusing mainly on the analysis of vulva development in different species. The observed alterations involve changes in cell lineage, cell migration and cell death, as well as induction and cell competence. I then describe a genetic approach in the nematode Pristionchus pacificus that might identify those genetic and molecular processes that cause evolutionary changes of cell fate specification.

Animals↗
PubMed2000

Formation of insulin amyloid fibrils followed by FTIR simultaneously with CD and electron microscopy.

Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and electron microscopy (EM) have been used simultaneously to follow the temperature-induced formation of amyloid fibrils by bovine insulin at acidic pH. The FTIR and CD data confirm that, before heating, insulin molecules in solution at pH 2.3 have a predominantly native-like alpha-helical structure. On heating to 70 degrees C, partial unfolding occurs and results initially in aggregates that are shown by CD and FT-IR spectra to retain a predominantly helical structure. Following this step, changes in the CD and FTIR spectra occur that are indicative of the extensive conversion of the molecular conformation from alpha-helical to beta-sheet structure. At later stages, EM shows the development of fibrils with well-defined repetitive morphologies including structures with a periodic helical twist of approximately 450 A. The results indicate that formation of fibrils by insulin requires substantial unfolding of the native protein, and that the most highly ordered structures result from a slow evolution of the morphology of the initially formed fibrillar species.

Animals↗
PubMed2006

A matter of measurements: challenges and approaches in the comparative analysis of static allometries.

Comparisons of static allometries are frequently used to gain insights into patterns and processes underlying morphological and developmental evolution. A study by J. L. Tomkins and coworkers, recently published in the American Naturalist, examined complex nonlinear allometries in three insect species in which males are dimorphic in the expression of secondary sexual traits. Employing a novel approach to analyzing male allometries in these organisms, the authors were able to show that developmental reprogramming of trait primordia is not necessary to explain allometric scaling in two of the species examined, contrary to several previous studies on the same species. Instead, male dimorphisms could be explained by simple exponential growth, an important result that carries with it major evolutionary and developmental implications. Using this study as an example, I highlight some of the methodological challenges involved in analyzing and comparing static allometries and in inferring the developmental processes that underlie them. I end by discussing how correct application of hypothesis testing, on one side, and basic anatomy and developmental biology, on the other, should guide how morphology is measured.

Anatomy↗
PubMed1996

Acquired homozygosity (isodisomy) of chromosome 3 during clonal evolution of a uveal melanoma: association with morphologic heterogeneity.

Cytogenetic investigation of untreated uveal melanoma has shown that the most frequent abnormality is monosomy 3, which occurs in approximately 60% of cases. One of our cases showed distinct pigmented and nonpigmented areas at gross dissection; representative tissue was collected separately from each area, cultured, and harvested using standard cytogenetic techniques. On histologic examination, the pigmented area was found to be composed of small epithelioid cells, whereas the nonpigmented area contained large, pleomorphic epithelioid cells. The karyotype of the pigmented tumor revealed monosomy 3, whereas the nonpigmented tumor showed two apparently normal chromosomes 3. Our purpose in the present study was to investigate the two tumor areas by molecular techniques to determine whether the karyotype of the nonpigmented tumor evolved directly from the pigmented tumor with duplication of the remaining chromosome 3 or whether the two sublines evolved in a divergent fashion from a common precursor stemline. DNA was extracted from normal lymphocytes and separately from both areas of the tumor. The DNA was analyzed using the polymerase chain reaction for polymorphic dinucleotide and tetranucleotide repeat sequences on chromosome 3. Both pigmented and nonpigmented areas of the tumor showed loss of heterozygosity at all informative loci on chromosome 3 that were tested. These results support our hypothesis that an abnormality on chromosome 3 plays a central role in the molecular pathogenesis of uveal melanoma and that some melanomas develop acquired homozygosity (isodisomy) by loss and duplication of the remaining, presumably abnormal, chromosome 3.

Aged↗
PubMed1989

Auditory primary afferents in the starling: correlation of function and morphology.

Despite the independent evolution of birds and mammals, a number of structural similarities of their hearing organs have developed in parallel. By tracing the peripheral origin of functionally-characterized primary neurons, the present study demonstrates functional similarities between the respective hair cell populations of the hearing organs of birds and mammals. The space devoted to one octave on the starling's basilar papilla is not constant over the whole length; rather it increases from the apical low- to the basal high-frequency end. The finding that (with the exception of a specialized area near the apical end) only tall hair cells situated on the neural limbus receive active afferent innervation is a functional parallel to the mammalian inner hair cells. The thresholds of afferents increase with distance of the related hair cells from the neural side of the papilla and cover a range of more than 50 dB within the area of tall hair cells.

Acoustic Stimulation↗
PubMed2003

Species-specific activation of EGF receptor signaling underlies evolutionary diversity in the dorsal appendage number of the genus Drosophila eggshells.

In Drosophila melanogaster, the patterning of dorsal appendages on the eggshell is strictly controlled by EGFR signaling. However, the number of dorsal appendages is remarkably diverse among Drosophila species. For example, D. melanogaster and D. virilis have two and four dorsal appendages, respectively. Here we show that during oogenesis the expression patterns of rhomboid (rho) and argos (aos), positive and negative regulators of EGFR signaling, respectively, were substantially different between D. melanogaster and D. virilis. Importantly, the number and position of both the rho expression and MAPK activation were consistent with those of the dorsal appendages in each species. Despite the differences in the spatial expression, these results suggest that the function of EGFR signaling in dorsal appendage formation is largely conserved between these two species. Thus, our results link the species-specific activation of EGFR signaling and the evolution of eggshell morphology in Drosophila.

Acute-Phase Proteins↗
PubMed2005

Evolution of the interface and metal film morphology in the vapor deposition of Ti on hexadecanethiolate hydrocarbon monolayers on Au.

The combination of in situ X-ray photoelectron spectroscopy, infrared reflection spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry are used to probe the nature of the evolving interface chemistry and metal morphology arising from Ti vapor deposition onto the surface of a CH(3)(CH(2))(15)S/Au{111} self-assembled monolayer (SAM) at ambient temperature. The results show that for a deposition rate of approximately 0.15 Ti atom.nm(-2).s(-1) a highly nonuniform Ti overlayer is produced via a process in which a large fraction of impinging Ti atoms do not stick to the bare SAM surface. The adsorbed atoms form isolated Ti clusters and react with CH(3) groups to form carbide products at the cluster-SAM interfaces. Further growth of Ti clusters appears to be concentrated at these scattered reaction centers. The SAM molecules in the local vicinity are subsequently degraded to inorganic products, progressing deeper into the monolayer as the deposition proceeds to give an inorganic/organic nanocomposite. A continuous overlayer does not form until metal coverage approaches approximately 50 Ti atoms per SAM molecule. These data indicate that for applications such as molecular device contacts the use of Ti may be highly problematic, suffering from both a highly nonuniform contact area and the presence of extensive inorganic products such as nonstoichiometric carbides and hydrides.

Journal Article↗
PubMed2006

[Fatty hepatosis. Non-alcoholic steatohepatitis (evolution of the knowledge about clinico-morphological features, prognosis, treatment)].

AIM: To study histological, clinical features and prognosis in patients with fatty hepatosis (FH) and non-alcoholic steatohepatitis (NASH). MATERIAL AND METHODS: Clinical and laboratory data on 74 patients with FH of non-alcoholic origin were studied. All the patients have undergone puncture biopsy of the liver (a total of 91 biopsies). Patients with fatty dystrophy of the first, second and third degree and fibrosis of the first and second degree entered the group of fatty hepatosis without inflammation (group 1, n = 54), patients with fatty dystrophy of the second and third degree and fibrosis of the third degree were assigned to group 2 (n = 20), i.e. to the group of FH with inflammation. The latter group by modern histological characteristics belongs to NASH. RESULTS: Functional disorders of the liver were insignificant, urobilinogenuria, delayed retention of bromsulphalein, hypertriglyceridemia were observed. AlAT activity was insignificantly elevated in FH patients. It was elevated 1.5-2.5-fold in NASH, the activity of AsAT, gamma-GTP was high in half of the patients. NASH has no specific clinico-biochemical signs and its diagnosis is based on the data of puncture biopsy of the liver. Long-term follow-up of 42 patients with FH and NASH discovered stabilization of the process in 34 patients. Cirrhosis of the liver occurred in 5 patients. Repeated biopsies established association of fatty dystrophy with developing micronodular cirrhosis. CONCLUSION: NASH is an independent disease. This should be taken into consideration in differential diagnosis in patients with a stable rise of serum activity of AlAT and AsAT, especially in obesity, diabetes, hyperlipidemia. The diagnosis is verified at biopsy of the liver. In spite of scare symptoms, long-term follow-up detects progression of the disease in more than 1/3 of the patients. Cirrhosis arose in 1/6 of the patients. Standard NASH treatment is absent, though elimination of the provoking factors, therapy with antioxidant drugs and ursodesoxycholic acid produce a favourable effect.

Antioxidants↗
PubMed1995

[Micro-morphology of the ovipositor in Hymenoptera and evolution from phytophagous Symphyta to parasitoid Apocrita].

The ovipositor of 1 Symphyta and 12 primitive parasitoid Apocrita belonging of the family of Ichneumonidae has been studied with the scanning electron microscope (SEM) and for 2 species, semi-thin sections were used. The study shows the presence of closed trachea in the 3 pairs of valvulae and a secretory system in the 2 pairs of valvulae interlocked into a piercing stylus. We discuss the role of trachea and a secretory system leading to excretory pores on the lancets of valvulae which occupy very precisely the site of sensory chemoreceptors known in more advanced species lacking this secretory system. The micromorphological data support the phylogeny within Hymenoptera, from Symphyta to primitive parasitoid Apocrita.

Animals↗
PubMed1998

[Early rheumatoid synovitis and its evolution].

The clinical and morphological evidence of rheumatoid synovitis of 3 months to 5 years duration was analyzed. Its early lesions were characterized by angiomatosis, vasculopathy, and proliferation of synoviocytes and fibroblasts. Protein infiltrates contained IgG and C3 complement. Herpes simplex was detected in the vessels and synoviocytes. Structural changes may be explained by immune mechanisms and by infectious agents as well. Chronic inflammation, vasculitis, and sclerosis were prevalent in late rheumatoid synovitis. Lymphoid follicles, macrophages, and endothelial proliferation can be markers for infectious persistence.

Adult↗
PubMed2004

Convergent evolution in mechanical design of lamnid sharks and tunas.

The evolution of 'thunniform' body shapes in several different groups of vertebrates, including whales, ichthyosaurs and several species of large pelagic fishes supports the view that physical and hydromechanical demands provided important selection pressures to optimize body design for locomotion during vertebrate evolution. Recognition of morphological similarities between lamnid sharks (the most well known being the great white and the mako) and tunas has led to a general expectation that they also have converged in their functional design; however, no quantitative data exist on the mechanical performance of the locomotor system in lamnid sharks. Here we examine the swimming kinematics, in vivo muscle dynamics and functional morphology of the force-transmission system in a lamnid shark, and show that the evolutionary convergence in body shape and mechanical design between the distantly related lamnids and tunas is much more than skin deep; it extends to the depths of the myotendinous architecture and the mechanical basis for propulsive movements. We demonstrate that not only have lamnids and tunas converged to a much greater extent than previously known, but they have also developed morphological and functional adaptations in their locomotor systems that are unlike virtually all other fishes.

Animals↗
PubMed2004

Escalation and trophic specialization drive adaptive radiation of freshwater gastropods in ancient lakes on Sulawesi, Indonesia.

Species flocks in ancient lakes have long been appreciated as ideal model systems for the study of speciation and adaptive processes. We here present data from a new invertebrate model system with intrinsic parameters distinct from those of other documented radiations. The ancient lakes on Sulawesi harbour an endemic species flock of at least 33 species of viviparous snails. Molecular data reveal multiple independent colonizations of the lakes by riverine ancestors. In each colonizing clade, parallel evolution of conspicuous shell morphologies, followed by a differentiation of trophic morphology and the development of habitat specificity can be observed. Extensive shell crushing experiments and strong dentition of the chelae observed in some lacustrine crab species suggest that coevolution with crabs, i.e. escalation, is the most likely cause of initial shell divergence. By contrast, repeated parallel evolution in radula morphology indicates that speciation within lineages is driven by divergent adaptation to different resources among sympatric taxa. The inclusion of coevolutionary processes is unique in this system compared with diversification models developed for vertebrate radiations.

Adaptation, Biological↗