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At least 1,117 records · Page 62Linked to original sources
PubMed1989

A temporary flagellate (mastigote) stage in the vahlkampfiid amoeba Willaertia magna and its possible evolutionary significance.

A temporary flagellate (mastigote) stage has been observed in several isolates of the vahlkampfiid amoeba Willaertia magna. In an Australian isolate studied in detail, flagellates appeared synchronously, although later than in Naegleria fowleri or N. lovaniensis under similar conditions (half-maximal time, t50 = 168 min at 37 degrees C). The flagellates initially have four flagella and lack a cytostome, but undergo several successive divisions, the first of them synchronous, resulting in progressive reduction in cell volume. New flagella appear during and after division, and the number of flagella in daughter cells of later divisions is rather variable. Comparison of these observations with descriptions of other amoeboflagellates confirms that Willaertia is a valid genus. A likely sequence of morphological changes in the evolution of Willaertia and Naegleria from a hypothetical ancestral vahlkampfiid is proposed.

Amoeba↗
PubMed1983

Ageing of hamster embryo fibroblasts as the result of both differentiation and stochastic mechanisms.

Fibroblasts from hamster embryos were serially cultivated in vitro and their evolution followed from a morphological, physiological and biochemical point of view. After an exponential growth for about 20 passages, cells entered the ageing phase which ended up after 29-34 passages. From our observations, it seems that the arrest of growth results from two different phenomena: first, the typically fibroblastic cells may undergo a stochastic ageing process; second, some of these cells evolve into a terminal differentiation process, characterized by a different non-fibroblastic phenotype.

Aging↗
PubMed2005

Formation of calcium crystallites in dry natural rubber particles.

In this paper, the effects of drying and aging of natural rubber particles of Hevea brasiliensis are studied. The evolutions of the particle morphology and of the elemental distribution are investigated using electron-energy-loss spectroscopy imaging in a low-energy transmission electron microscope (ESI-TEM). It is found that when the sample is aged, calcium salt crystallites are formed around the particles. Fusion of these crystallites with time to form larger crystals shows evidence of ion mobility in the dry rubber matrix. Electron diffraction patterns and elemental mapping analysis indicate the crystals to be calcium sulfate. These crystallites are closely associated with membrane materials of the rubber particle and are surprisingly compatible with the hydrocarbon matrix of the rubber particle. It is proposed that polar sites on the membrane materials provide nucleation sites for the crystallization of calcium and sulfate ions from the latex serum.

Ammonia↗
PubMed2006

Effects of activity pattern on eye size and orbital aperture size in primates.

Among primates, nocturnal species exhibit relatively larger orbital apertures than diurnal species. Most researchers have considered this disparity in orbital aperture size to reflect differences in eye size, with nocturnal primates having relatively large eyes in order to maximize visual sensitivity. Presumed changes in eye size due to shifts in activity pattern are an integral part of theoretical explanations for many derived features of anthropoids, including highly convergent orbits and a postorbital septum. Here I show that despite clear differences in relative orbital aperture size, many diurnal and nocturnal primates do not differ in relative eye size. Among nocturnal primates, relative eye size is influenced by diet. Nocturnal visual predators (e.g., Tarsius, Loris, and Galago moholi) tend to have larger relative eye sizes than diurnal primates. By contrast, nocturnal frugivores (e.g., Perodicticus, Nycticebus, and Cheirogaleus) have relative eye sizes that are comparable to those of diurnal primates. Although some variation in orbital aperture size can be attributed to variation in eye size, both cornea size and orbit orientation also exert a strong influence on orbital aperture size. These findings argue for caution in the use of relative orbital aperture size as an indicator of activity pattern in fossil primates. These findings further suggest that existing scenarios for the evolution of unique orbital morphologies in anthropoids must be modified to reflect the importance of ecological variables other than activity pattern.

Animals↗
PubMed2005

ventral veins lacking is required for specification of the tritocerebrum in embryonic brain development of Drosophila.

The homeotic or Hox genes encode a network of conserved transcription factors which provide axial positional information and control segment morphology in development and evolution. During embryonic brain development of Drosophila, the Hox gene labial (lab) is essential for tritocerebral neuromere specification; lab loss of function results in tritocerebral cells that fail to adopt a neuronal identity, causing axonal pathfinding defects. Here we present evidence that the POU-homeodomain DNA-binding protein ventral veins lacking (vvl) acts genetically downstream of lab in the specification of the tritocerebral neuromere. In the embryonic brain, vvl expression is seen in all brain neuromeres, including the tritocerebral lab domain. Lab mutant analysis shows that vvl expression in the tritocerebrum is dependent on lab activity. Loss-of-function analysis focussed on the tritocerebrum reveals that inactivation of vvl results in patterning defects which are comparable to the brain phenotype caused by null mutation of lab. In the absence of vvl, mutant tritocerebral cells are generated and positioned correctly, but these cells fail to express neuronal markers indicating defects in neuronal differentiation. Moreover, longitudinal axon pathways in the tritocerebrum are severely reduced or absent and the tritocerebral commissure is missing in the vvl mutant brain. Genetic rescue experiments show that vvl is able to partially replace lab in the specification of the tritocerebral neuromere. Our results indicate that vvl acts downstream of the Hox gene lab and regulates specific aspects of neuronal differentiation within the tritocerebral neuromere during embryonic brain development of Drosophila.

Animals↗
PubMed2004

Candidate genes for behavioural ecology.

In spite of millions of years of evolutionary divergence, the conservation of gene function is common across distant lineages. As such, genes that are known to influence behaviour in one organism are likely to influence similar behaviours in other organisms. Recent studies of the evolution of behaviour and morphological adaptation support this notion. Thus, the candidate gene approach offers great potential to expand our understanding of behavioural ecology. Changes in the expression of candidate genes can reveal their contribution to behavioural variation and/or phenotypic plasticity. Knowledge of gene function also enables experimental manipulation of behaviour in the lab and in the field. The candidate gene approach provides an accessible and useful tool for generating insights about animals that are not typically associated with genetic experimentation.

Journal Article↗
PubMed2004

Zebrafish gcm2 is required for gill filament budding from pharyngeal ectoderm.

The pharyngeal arches give rise to multiple organs critical for diverse processes, including the thymus, thyroid and parathyroids. Several molecular regulators of thymus and thyroid organogenesis are strikingly conserved between mammals and zebrafish. However, land animals have parathyroids whereas fish have gills. The murine transcription factor Glial cells missing 2 (Gcm2) is expressed specifically in the parathyroid primordium in the endodermal epithelium of the third pharyngeal pouch, and in both mice and humans is required for normal development of parathyroid glands. The molecular regulation of fish gill organogenesis remains to be described. We report the expression of gcm2 in the zebrafish pharyngeal epithelium and a requirement for Hox group 3 paralogs for gcm2 expression. Strikingly, zebrafish gcm2 is expressed in the ectodermal portion of the pharyngeal epithelium and is required for the development of the gill filament buds, precursors of fish-specific gill filaments. This study identifies yet another role for a GCM gene in embryonic development and indicates a role for gcm2 during the evolution of divergent pharyngeal morphologies.

Amino Acid Sequence↗
PubMed1993

Aggregation of hapten-bearing liposomes mediated by specific antibodies.

We studied specific membrane-membrane interactions mediated by ligand-receptor binding in a model system, which consisted of (a) FG3P, the fluorescein hapten attached to a phospholipid by a peptidyl spacer as described previously (Petrossian, A., A.B. Kantor, and J.C. Owicki. 1985. J. Lipid Res. 26:767-773), (b) antifluorescein monoclonal antibodies (MAbs), and (c) phospholipid vesicles (liposomes) into which the FG3P was incorporated. The aggregation of the hapten-bearing liposomes by four MAbs was studied by differential centrifugation. The ability of the MAbs to induce vesicle aggregation varied considerably and correlated inversely with affinity. Aggregation by one of the MAbs was studied in more detail by turbidimetry and freeze-fracture electron microscopy of samples frozen throughout the course of the aggregation. Rapid freezing was achieved with a double propane-jet apparatus. The aggregate morphologies and the time evolution of the aggregate size distribution were obtained from the two-dimensional fracture views with a stereological correction. The aggregation kinetics were simulated by considering dynamical aggregation according to a mass-action model with two parameters, the rate constants for antibody-mediated vesicle aggregation and disaggregation. Both rate constants were orders of magnitude lower than the rate constants for the corresponding interactions of antibodies with haptens either in solution or on vesicles under nonaggregating conditions.

Animals↗
PubMed1991

Congenital histiocytosis. A heterogeneous group of diseases, one presenting as so-called congenital self-healing histiocytosis.

Three cases of congenital histiocytic disorders--generalized Langerhans cell histiocytosis, generalized juvenile xanthogranuloma and so-called congenital self-healing histiocytosis are compared using histiochemical, immunohistochemical and ultrastructural methods. The results showed a typical morphological pattern of Langerhans cell histiocytosis (S 100+, CD 1+, alpha-mannosidase +) with an unusual self-healing cutaneous phenomenon. The congenital self-healing histiocytosis showed a non-Langerhans cell immunophenotype (CD 14+, CD 1-, S 100-) and morphological appearance resembling the evolutive "early" stage of juvenile xanthogranuloma. A diffuse cellular positivity of alpha-mannosidase in juvenile xanthogranuloma and congenital self-healing histiocytosis differed from a typical perinuclear globular positivity of this enzyme in Langerhans cell histiocytosis. It is concluded that congenital self-healing histiocytosis may in some cases be of non-Langerhans cell type and under this term a clinically characteristic syndrome of histiocytic proliferation of Langerhans cells or tissue histiocytes may be included.

Biomarkers↗
PubMed1983

Asplenia and polysplenia malformation complexes explained by abnormal embryonic body curvature.

Asplenia and polysplenia malformation complexes characteristically have severe cardiovascular defects and visceral heterotaxy. We examined the hypothesis that the conditions may arise from an altered timing of development of embryonic body curvature: delayed in asplenia, accelerated in polysplenia. The morphologic features of the 25 patients with asplenia and 15 with polysplenia autopsied at The Johns Hopkins Hospital were determined. The time of appearance of various morphologic features and the evolution of body curvature was studied in 351 staged serially sectioned human embryos of The Carnegie Embryological Collection. All asplenia patients had severe atrioventricular canal malformations. Bilateral trilobed lungs were found in 12 patients. The polysplenia patients had severe interatrial septal defects in 10 patients; but ventricular septal defects in only six. Bilateral bilobed lungs were seen in five patients. Comparison of the time of appearance of anatomic structures in normal embryos with the observed malformations suggest that asplenia and polysplenia complexes originate in stages 13 to 15. The observations are consistent with the concept that the malformations in asplenia and polysplenia can be explained by minor alterations in the sequence of development of embryonic body curvature relative to organ maturation.

Adult↗
PubMed2003

Cercopithecine Y-chromosome data provide a test of competing morphological evolutionary hypotheses.

We report here the results of the first molecular evolutionary analysis to include members of all 10 extant genera of cercopithecine monkeys. A total of 44 individuals were surveyed for approximately 2.2 kb of the testis-specific protein, Y-chromosome (TSPY). The TSPY sequences were subjected to parsimony analyses in PAUP 4.0, followed by tree comparison tests designed to assess existing morphological hypotheses of cercopithecine evolution. The results of these tests show that the present Y-chromosome dataset unambiguously supports: (1) monophyly of Macaca, (2) polyphyly of the mangabeys (Cercocebus and Lophocebus), (3) paraphyly of Cercopithecus, and (4) inclusion of Allenopithecus and Miopithecus in the tribe Cercopithecini. A number of unexpected Y-chromosome relationships are also discussed, including a pattern suggesting resurrection of the genus Chlorocebus for the guenons currently identified as Erythrocebus patas, Cercopithecus aethiops, and Cercopithecus lhoesti. Relative rate tests reveal significant difference in the TSPY substitution rate across numerous lineages in the tribe Cercopithecini. Because the rate differences follow no obvious phylogenetic pattern, "local" molecular clocks were not employed and divergence dates were not estimated for this tribe. In contrast, similar analysis of the Papionini reveals rate heterogeneity between a single pair of taxonomic groups: Macaca vs. the "African papionins." Divergence dates were therefore calculated for the tribe by calibrating TSPY clocks specific to each of these two clades.

Animals↗
PubMed1992

Is behavior analysis undergoing selection by consequences?

The legacy of B. F. Skinner's life is a natural science of behavior. The generality of its basic functional relations has led, by induction, to the unifying principle of selection by consequences, which accounts for morphological, behavioral, and cultural evolution. This principle both predicts and explains the observation that the science itself is becoming the object of differential selection in our culture. Public policy is increasingly being framed in terms of the effects of consequences on behavior, as illustrated by examples from education, economics, and politics. Survival of our culture may depend on our skill in managing this process.

Behavior Therapy↗
PubMed1995

Hox gene expression in teleost fins and the origin of vertebrate digits.

Hox genes are essential for growth and patterning of the tetrapod limb skeleton. Mice mutant for the Hoxd-13 gene have an important delay in morphogenesis owing to reduced proliferation. Based on the appearance of atavisms in such mice, we suggested that modifications of Hox gene regulation may have been a source of morphological variation during the evolution of tetrapod limbs. Pectoral and pelvic fins are homologous to fore- and hindlimbs, respectively. To compare the relative importance of Hox genes during fin versus limb morphogenesis, we cloned zebrafish (Danio rerio) HoxD and HoxA complex genes and analysed their expression during fin development. The results suggest a scheme for the fin-limb transition in which the distal autopods (digits) are neomorphic structures produced by unequal proliferation of the posterior part of an ancestral appendix.

Animals↗
PubMed2004

Divergence dates for Malagasy lemurs estimated from multiple gene loci: geological and evolutionary context.

The lemurs of Madagascar are a unique radiation of primates that show an extraordinary diversity of lifestyles, morphologies and behaviours. However, very little is known about the relative antiquity of lemuriform clades due to the lack of terrestrial fossils for the Tertiary of Madagascar. Here, we employ a Bayesian method to estimate divergence dates within the lemuriform radiation using several unlinked gene loci and multiple fossil calibrations outside the lemuriform clade. Two mitochondrial genes (cytochrome oxidase II and cytochrome b), two nuclear introns (transthyretin intron 1 and von Willebrand factor gene intron 11) and one nuclear exon (interphotoreceptor retinoid binding protein, exon 1) are used in separate and combined analyses. The genes differ in taxon sampling and evolutionary characteristics but produce congruent date estimates. Credibility intervals narrow considerably in combined analyses relative to separate analyses due to the increased amount of data. We also test the relative effects of multiple vs. single calibration points, finding that, when only single calibration points are employed, divergence dates are systematically underestimated. For the mitochondrial DNA data set, we investigate the effects of sampling density within the mouse lemur radiation (genus Microcebus). When only two representative species are included, estimated dates throughout the phylogeny are more recent than with the complete-species sample, with basal nodes less affected than recent nodes. The difference appears to be due to the manner in which priors on node ages are constructed in the two analyses. In nearly all analyses, the age of the lemuriform clade is estimated to be approximately 62-65 Ma, with initial radiation of mouse lemurs and true lemurs (genus Eulemur) occurring approximately 8-12 Ma. The antiquity of the mouse lemur radiation is surprising given the near uniform morphology among species. Moreover, the observation that mouse lemurs and true lemurs are of similar ages suggests discrepancies in rates of morphological, behavioural and physiological evolution in the two clades, particularly with regard to characteristics of sexual signalling. These differences appear to correlate with the nocturnal vs. diurnal lifestyles, respectively, of these two primate groups.

Animals↗
PubMed2000

Early events leading to renal injury in obese Zucker (fatty) rats with type II diabetes.

UNLABELLED: Early events leading to renal injury in obese Zucker (fatty) rats with type II diabetes. BACKGROUND: More than half of the new patients admitted to dialysis therapy in some centers are diagnosed with type IIb diabetes, that is, diabetes associated with obesity. This study searched for a common final pathway of renal damage in this progressive renal disease. METHODS: The evolution of biochemical and morphological renal changes was examined in 6- to 60-week-old Zucker rats (fa/fa-rats), a model of obesity associated with type II diabetes. RESULTS: fa/fa-rats exhibited pronounced hyperinsulinemia and hyperlipidemia at 6 weeks and became diabetic after 14 weeks of age. Significant focal segmental glomerulosclerosis was first noted in 18-week-old fa/fa-rats and tubulointerstitial damage and proteinuria in 40-week-old fa/fa-rats. A comparison of kidneys of six-week-old fa/fa-and lean control (Fa/?) rats by immunohistology revealed a 1.8-fold increase in glomerular monocyte/macrophage counts in fa/fa-rats and a significant increase in de novo desmin expression in podocytes. Electron microscopy demonstrated an increase in the number of podocyte mitochondria and intracytoplasmic protein and fat droplets. Podocyte desmin scores markedly increased until week 18 in fa/fa-rats, whereas glomerular monocyte/macrophage counts peaked at 3.2-fold at week 14. Podocyte desmin expression, but not glomerular macrophage infiltration, correlated with damage in adjacent tubular cells, as evidenced by their de novo expression of vimentin. Progressive glomerular hypertrophy was detected in fa/fa-rats after 10 weeks. GBM width was significantly increased in 14-week-old fa/fa-rats as compared with lean controls. Mesangial cell activation (de novo expression of alpha-smooth muscle actin) and proliferation was low to absent throughout the observation period in fa/fa-rats. Renal cell death counts (TUNEL) remained unchanged in 6- to 40-week-old fa/fa-rats. Tubulointerstitial myofibroblast formation and matrix accumulation occurred late during the study duration in fa/fa-rats. CONCLUSION: These data suggest that early progressive podocyte damage and macrophage infiltration is associated with hyperlipidemia and type IIb diabetes mellitus, and antedates both the development of glomerulosclerosis and tubulointerstitial damage.

Aging↗
PubMed2002

Diffuse lung disease in the immunocompromised non-HIV patient.

Physicians are encountering an increasing number of patients with various levels of immunosuppression, such as patients with AIDS, transplant recipients, patients on immunosuppressive therapy, and those with congenital immune defects and malignancy. This results in a greater diagnostic dilemma for the medical community because of the significant increased risk of opportunistic infections and noninfectious complications, as well as a more aggressive clinical course with typical pathogens. [figure: see text] Furthermore, it is not just the pathogens that are changing but also their clinical and radiographic presentations. The radiologist has a large role in not only detecting the presence of disease but also in narrowing the differential possibilities. This can be an overwhelming task given the wide variety of presentations of diseases on radiographs. However, by understanding the level and degree of the patient's immunosuppression, the radiologist may anticipate the most likely pulmonary complications. By using the radiographic morphology, distribution, and temporal evolution of the abnormalities, a manageable differential diagnosis can be created for referring clinicians.

Adolescent↗
PubMed2006

Differential actin-dependent localization modulates the evolutionarily conserved activity of Shroom family proteins.

Shroom is an actin-associated determinant of cell morphology that is required for neural tube closure in both mice and frogs. Shroom regulates this process by causing apical constriction of epithelial cells via a pathway involving myosin II. Here we report on characterization of the Shroom-related proteins Apxl and KIAA1202 and their role in cell architecture. Shroom, Apxl, and KIAA1202 exhibit differing abilities to interact with the actin cytoskeleton. In fibroblasts, Shroom readily associates with actin stress fibers and induces bundling, Apxl is found on cortical actin, and KIAA1202 is localized to a cytoplasmic population of F-actin. In epithelial cells, Apxl and KIAA1202 do not induce apical constriction as Shroom does, but have the capacity to do so if targeted to the apical junctional complex. To determine whether the activity of Shroom-like proteins is conserved in invertebrates, we have tested the ability of the lone Shroomrelated protein in Drosophila, CG8603, to activate the constriction pathway. A chimeric protein consisting of the Shroom targeting domain and the Drosophila protein elicits constriction. Finally, we show that Apxl is involved in regulating the cytoskeletal organization and architecture of endothelial cells. We predict that the ability of Shroom-like proteins to regulate cellular morphology is conserved in evolution and is regulated in part by subcellular localization.

Actins↗