Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Beak”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed1997

Alterations in Msx 1 and Msx 2 expression correlate with inhibition of outgrowth of chick facial primordia induced by retinoic acid.

Spatially-restricted expression domains of Msx 1 and Msx 2 in the developing chick face suggest that they may play a role in epithelial-mesenchymal interactions governing outgrowth of facial primordia. Retinoid application to developing chick faces reproducibly inhibits upper beak outgrowth but the lower beak is unaffected. In the normal face, high levels of Msx gene transcripts in upper and lower beak primordia correlate with regions of outgrowth. Following retinoid treatment, Msx 1 and Msx 2 transcripts are rapidly down-regulated in upper beak primordia where outgrowth is inhibited, but remain largely unchanged in lower beak primordia, where outgrowth is unaffected. Decreases in gene expression precede retinoid-induced morphological changes in the upper beak, suggesting that Msx gene products are involved in mediating the effect of retinoids on facial development.

Abnormalities, Drug-Induced↗
PubMed2002

Keratinization and lipogenesis in epidermal derivatives of the zebrafinch, Taeniopygia guttata castanotis (Aves, Passeriformes, Ploecidae) during embryonic development.

Little is known of the lipid content of beta-keratin-producing cells such as those of feathers, scutate scales, and beak. The sequence of epidermal layers in some apteria and in interfollicular epidermis in the zebrafinch embryo (Taeniopygia guttata castanotis) was studied. Also, the production of beta-keratin in natal down feathers and beak was ultrastructurally analyzed in embryos from 3-4 to 17-18 days postdeposition, before hatching. Two layers of periderm initially cover the embryo, but there are eventually 6-8 over the epidermis of the beak. In the beak and sheath cells of feathers, peridermal granules are numerous at 12-14 days postdeposition but they are less frequent in apteria. These granules swell and disappear during sheath or peridermal degeneration at 15-17 days postdeposition. A thin beta-keratin layer forms under the periderm among feather germs of pterylous areas but is discontinuous or disappears in apteria. In differentiating cells of barbs, barbules, and calamus cells of natal down, electron-dense beta-keratin filaments form bundles oriented along the main axis of these cells. Cells of the pulp epidermis and collar, at the base of the follicle, contain lipids and bundles of alpha-keratin filaments. Degenerating pulp cells show vacuolization and nuclear pycnosis. During beta-keratin packing, keratin bundles turn electron-pale, perhaps due to the addition of lipids to produce the final, homogenous beta-keratin matrix. In contrast to the situation in feathers, in the cells of beak beta-keratin packets are irregularly oriented. In both feather and beak epidermal cells the Golgi apparatus and smooth endoplasmic reticulum produce vesicles containing lipid-like material which is also found among forming beta-keratin. The contribution of lipids or lipoprotein to the initial aggregation of beta-keratin molecules is discussed.

Animals↗
PubMed2007

Electromyography of the buccal musculature of octopus (Octopus bimaculoides): a test of the function of the muscle articulation in support and movement.

The buccal mass musculature of the octopus (Octopus bimaculoides) was studied with electromyography to test the predictions of a previous morphological study in which we suggested that the muscles of the buccal mass serve as both the effectors of movement and as the joint itself, forming a new category of flexible joint termed a ;muscle articulation'. The predictions of muscle function were tested by correlating muscle electrical activity in isolated buccal masses with spontaneous beak movements. Bipolar electromyography electrodes were implanted in the various beak muscles and beak position was recorded simultaneously with an electronic movement monitor (N=14). The results are consistent with the hypothesis that the lateral mandibular muscles produce opening movements of the beaks and provide the first definitive explanation of the opening mechanism. The results are also consistent with the hypothesis that the superior mandibular muscle functions primarily in closing. Co-contraction of the lateral mandibular muscles and the superior mandibular muscles was also observed, suggesting that these muscles may also stabilize the beaks during movement or provide a means of controlling the location of the pivot between the beaks. This study provides an important first test of the predictions of the role of the complex musculature found in muscle articulations such as the cephalopod buccal mass.

Animals↗
PubMed1997

Simulated Bennett fracture treated with closed reduction and percutaneous pinning. A biomechanical analysis of residual incongruity of the joint.

UNLABELLED: Contact area and contact pressure within the trapeziometacarpal joint were measured during static and dynamic loading in a cadaver model. The measurements were repeated after a Bennett fracture had been simulated with use of an osteotomy of the metacarpal base. The beak fragment was recessed two millimeters and was fixed in close apposition to maintain the integrity of the palmar beak ligament, and contact area and contact pressure were measured during lateral pinch. Despite the resulting articular incongruity, the mean total contact area of the joint surface increased from 15.8 to 25.8 square millimeters (63 per cent) in all specimens after simulation of the Bennett fracture (p = 0.02), and it shifted dorsally in moderately osteoarthrotic and non-osteoarthrotic specimens. The mean contact area in the palmar region of the joint surface decreased, from 58 to 25 per cent of the total area (p = 0.04); that in the central region increased, from 28 to 52 per cent (p = 0.05); and that in the dorsal region increased, but not significantly with the numbers available, from 14 to 24 per cent (p = 0.18). No pathological concentration of contact pressure was seen at the margin of the articular step-off. The changes in area and pressure reflect an unloading of the metacarpal beak, where osteoarthrotic degeneration most commonly occurs. CLINICAL RELEVANCE: There is no biomechanical basis for predisposition to post-traumatic osteoarthrosis after a Bennett fracture with a small palmar-beak component and a residual two-millimeter articular step-off, provided that the fragments of the shaft and the beak heal in close apposition. This suggests that reduction of the metacarpal shaft relative to the trapezium and the beak fragment, rather than strict anatomical restoration of the joint surface, should be the priority of treatment. Bennett fractures that can be reduced with articular incongruity of no more than two millimeters may be treated satisfactorily with closed reduction and percutaneous pinning without the need for open anatomical reduction and internal fixation of the joint surface.

Carpal Bones↗
PubMed2006

Sex steroid dependence of carotenoid-based coloration in female zebra finches.

Compared to male secondary sexual traits, the effect of testosterone (T) on female ornaments is understudied. In particular, it is unclear whether females experience different costs of T elevation than do males and how this affects the relationship between T and ornamentation in the two sexes. I experimentally and correlationally investigated the effect of T on the color of the carotenoid-based beak in female zebra finches (Taeniopygia guttata). Exogenous T administration elevated beak redness, indicative of sex-steroid sensitivity for this ornament. However, unlike in males, the relationship between T and color among unmanipulated birds was inversely U-shaped, with the most colorful females circulating intermediate T levels. This is consistent with the idea that females bear high costs of elevated T levels that weaken color intensity. Likely mechanisms for such an effect include: (1) the need to traffic carotenoids away from the beak to combat the immunosuppressive effects of high T, and (2) the loss of carotenoid stores in the body (e.g. from adipose tissue) due to a T-dependent increase in lipid metabolism (T-implanted females in this study decreased in body mass). Moreover, unlike what occurs in male zebra finches, T did not upregulate levels of plasma lipoproteins (carotenoid transporters) or plasma carotenoids in females; this provides further support that T controls beak-color intensity by different physiological mechanisms in the two sexes, with perhaps more of a localized role of sex-steroids at the beak in females.

Animals↗
PubMed1998

TGFbeta3 promotes transformation of chicken palate medial edge epithelium to mesenchyme in vitro.

Epithelial-mesenchymal transformation plays an important role in the disappearance of the midline line epithelial seam in rodent palate, leading to confluence of the palate. The aim of this study was to test the potential of the naturally cleft chicken palate to become confluent under the influence of growth factors, such as TGFbeta3, which are known to promote epithelial-mesenchymal transformation. After labeling medial edge epithelia with carboxyfluorescein, palatal shelves (E8-9) with or without beak were dissected and cultured on agar gels. TGFbeta1, TGFbeta2 or TGFbeta3 was added to the chemically defined medium. By 24 hours in culture, medial edge epithelia form adherent midline seams in all paired groups without intact beaks. After 72 hours, seams in the TGFbeta3 groups disappear and palates become confluent due to epithelial-mesenchymal transformation, while seams remain mainly epithelial in control, TGFbeta1 and TGFbeta2 groups. Epithelium-derived mesenchymal cells are identified by carboxyfluorescein fluorescence with confocal microscopy and by membrane-bound carboxyfluorescein isolation bodies with electron microscopy. Labeled fibroblasts completely replace the labeled epithelia of origin in TGFbeta3-treated palates without beaks. Single palates are unable to undergo transformation, and paired palatal shelves with intact beaks do not adhere or undergo transformation, even when treated with TGFbeta3. Thus, physical contact of medial edge epithelia and formation of the midline seam are necessary for epithelial-mesenchymal transformation to be triggered. We conclude that there may be no fundamental difference in developmental potential of the medial edge epithelium for transformation to mesenchyme among reptiles, birds and mammals. The bird differs from other amniotes in having developed a beak and associated craniofacial structures that seemingly keep palatal processes separated in vivo. Even control medial edge epithelia partly transform to mesenchyme if placed in close contact. However, exogenous TGFbeta3 is required to achieve complete confluence of the chicken palate.

Animals↗
PubMed1994

Feeding behavior and growth of turkey poults fed larvae of the darkling beetle, Alphitobius diaperinus.

Experiments were conducted to determine the effects of feeding larvae of the darkling beetle (lesser mealworm), Alphitobius diaperinus (Panzer) [Coleoptera:Tenebrionidae], to turkey poults on poult growth and of beak trimming on poult feeding on the larvae. Young turkey poults readily fed on the larvae and exhibited reduced growth in the absence of other feed. Poults 3 to 5 d old restricted to a diet of only larvae consumed 259 +/- 99 (+/- SD) larvae per poult per day and their body weights were significantly lower (mean = 30 g) at the end of the 3 d than for poults on starter feed during the same time. After return to starter feed for 16 d after feeding on larvae for 3 d, the poults did not compensate for the weight loss although weight gains were normal. Poults from 2 through 10 d of age were given a choice between starter turkey feed and darkling beetle larvae. The numbers of larvae consumed per poult per day were: 174 +/- 8 for Days 2 to 4, 221 +/- 3 for Days 5 to 7, and 189 +/- 80 for Days 8 to 10. There was no significant difference between the body weight of poults feeding on larvae and starter feed compared with that of poults consuming feed only. In the presence of larvae, the mean feed consumption per poult was lower than for poults provided with only starter feed. The beetle larvae were 68% crude protein and 21% fat (DM basis) and had higher amounts of 18 amino acids than the starter feed. Poults that were beak trimmed consumed only about one-third as many larvae as poults with intact beaks. Poults (1 to 3 d old) with intact beaks consumed 169 +/- 20 larvae per poult per day; poults with trimmed beaks consumed 58 +/- 23 larvae per poult per day.

Animal Feed↗
PubMed1991

Osteoarthritis of the trapeziometacarpal joint: the pathophysiology of articular cartilage degeneration. I. Anatomy and pathology of the aging joint.

An anatomic study of the trapeziometacarpal joint was conducted on 47 cadaver thumb specimens. The superficial capsule restrained only metacarpal rotation about its long axis. Intracapsular anatomy was notable for a large anterior subthenar recess limited dorsally by the abductor pollicis longus insertion and palmarly by the deep palmar or "beak" ligament. This beak ligament was essential for translational stability of the metacarpal on the trapezium with flexion of the thumb ray. There was a direct correlation between the status of the articular surfaces and the integrity of the beak ligament. Normal surfaces were associated with an intact ligament confluent with the hyaline cartilage of the palmar lip of the metacarpal; degeneration of the palmar lip cartilage was always associated with attritional detachment of the beak ligament. Advanced articular disease occurred only in the palmar contact areas and was predicted by degeneration of the adjacent beak ligament; only nonprogressive chondromalacia was found on the dorsal portions of the articular surfaces.

Aged↗
PubMed1997

Effects of plastic anti-pecking devices on food intake and behaviour of laying hens fed on pellets or mash.

1. This study investigated effects of plastic anti-pecking devices on food intake and behaviour to assess their applicability in commercial layer flocks. 2. In experiment 1, 72 individually caged ISA Brown pullets were fitted at 16 weeks of age (point of lay) with either 'ring' or 'bumper' beak devices or no device (control), half being fed on pellets and half on mash. The devices were held in place by lugs inserted in the nares. 3. There was evidence of discomfort immediately after fitting the devices, but not thereafter. In the first week, the devices reduced food intake, and were removed from 7 (15%) birds that lost weight consistently. Between 16 and 21 weeks, however, there were no significant effects of beak treatment or food form on either total food intake or egg production with the 65 remaining birds. 4. Beak treatment did not affect feeding efficiency (food intake per minute of feeding). The only behaviour affected was pecking at birds in adjacent cages, which was reduced with the ring device. 5. At 21 weeks, the birds were placed together in groups of 4 to 6 in 12 pens, each group consisting of birds from one of the 6 original treatments, and their behaviour was observed in experiment 2 between 21 and 23 weeks. 6. The only effects of beak treatment on behaviour were that pecking at pen walls was increased with the ring device, while pulling and eating feathers from group mates was seen mainly with control birds fed on pellets. Two birds were cannibalised in a control group on pellets. 7. Devices came off 3 (7%) birds in experiment 1 and were replaced, and rings slipped over lower mandibles of 2 (5%) birds in experiment 2 and were corrected. 8. At 23 weeks, beak lengths were increased with ring and bumper treatments, and pecking damage scores were low with all treatments. 9. It is concluded that these devices are not applicable commercially, but further trials would be justified with new improved designs.

Animal Feed↗
PubMed2006

Phylogeography and alpha taxonomy of the common dolphin (Delphinus sp.).

The resolution of taxonomic classifications for delphinid cetaceans has been problematic, especially for species in the genera Delphinus, Tursiops and Stenella. The frequent lack of correspondence between morphological and genetic differentiation in these species raises questions about the mechanisms responsible for their evolution. In this study we focus on the genus Delphinus, and use molecular markers to address questions about speciation and the evolution of population structure. Delphinus species have a worldwide distribution and show a high degree of morphological variation. Two distinct morphotypes, long-beaked and short-beaked, have been considered different species named D. capensis and D. delphis, respectively. However, genetic differentiation between these two forms has only been demonstrated in the Pacific. We analysed samples from eight different geographical regions, including two morphologically defined long-beaked form populations, and compared these with the eastern North Pacific populations. We found high differentiation among the populations described as long-beaked instead of the expected monophyly, suggesting that these populations may have evolved from independent events converging on the same morphotype. We observed low genetic differentiation among the short-beaked populations across a large geographical scale. We interpret these phylogeographical patterns in the context of life history and population structure in related species.

Animal Migration↗
PubMed1988

Pattern formation in the facial primordia.

Pattern formation is the developmental process that leads to the spatial ordering of cell differentiation. We have explored the problem of pattern formation in the development of the face of chick embryos. At early stages, the developing face consists of a series of small buds of tissue, the facial primordia that encircle the primitive mouth. The concepts of positional information provide a framework for considering how the patterns of differentiated cells are generated in the face. We suggest that the cranial neural crest cells must first be informed to which facial primordium they belong and then of their position within that primordium. The cells of the early primordia appear indistinguishable. However, when the mesenchyme cells are placed in high-density culture, cartilage differentiates. The extent and pattern of cartilage differentiation is characteristic for the cell population of each facial primordium. Myogenic cells also differentiate in the cultures, but the proportion of myogenic cells is independent of the extent of chondrogenesis. Within the facial primordia, a set of epithelial-mesenchymal interactions appears to be required for outgrowth and pattern formation along the proximodistal axis of the chick beaks. In culture, face epithelium locally inhibits cartilage differentiation and suggests that another set of epithelial-mesenchymal interactions may be involved in cell patterning. The mechanisms involved in specifying the mediolateral axis of the face, for example, the midpoint of the upper beak, are not known. Vitamin A derivatives, collectively known as retinoids, affect the development of the face of chick embryos and lead to a specific facial defect. Upper beak development is inhibited but the lower beak develops normally. The response to retinoids could be related to the specification of cells to belong to the facial primordium that will form the upper beak. Alternatively, retinoids may interfere with positional cues that operate to inform cells of their position within that primordium.

Animals↗
PubMedDate not supplied

Anatomic measurements for the endoscopic modified Lothrop procedure.

BACKGROUND: The aim of this study was to introduce preoperative radiographic frontal recess and sinus anatomic measurements to assist in the selection of patients considered for the modified Lothrop procedure. METHODS: Data were collected from sagittally reconstructed computed tomography (CT) scans of seven cadaver heads. Four anatomic parameters for measurement were defined as follows: (1) thickness of the nasal beak (desirable < 10 mm); (2) midsagittal distance from nasal beak to skull base (adding 1 and 2 provides the anterior-posterior (AP) space at the cephalad margin of the frontal recess; desirable, > or = 15 mm); (3) accessible dimension (in a parasagittal plane through the frontal ostium; the distance between two lines drawn parallel to the plane of the anterior skull base and perpendicular to the line of the insertion of the nasal endoscope during surgery; the posterior line is drawn at the skull base and the anterior line is drawn at the posterior margin of the nasal beak; the distance between the lines indicates the space available for instrumentation; desirable, > 5 mm); (4) AP dimension of each frontal sinus. RESULTS: The average and the range of each parameter measured were as follows: (1) nasal beak thickness = 8.0 mm (5.0-10.4 mm); (2) nasal beak-skull base = 7.9 mm (2.5-14.1 mm); (3) accessible dimension, 6.1 mm (0.9-9.6 mm); (4) AP diameter of the frontal sinus, 9.7 mm (5.2-14.1 mm). Four specimens were considered candidates for modified Lothrop and three were not. CONCLUSION: Preoperative radiographic frontal recess and sinus anatomic measurements may assist in the selection of patients considered for the endoscopic modified Lothrop procedure.

Cadaver↗
PubMed2005

A novel lipoprotein-mediated mechanism controlling sexual attractiveness in a colorful songbird.

Sexually selected traits like complex vocalizations or vibrant colors communicate reliable information about mate quality when they are costly to display. Although several general condition-dependent mechanisms underlying the acquisition of mating advertisements have been identified, we rarely know the precise physiological and molecular challenges that animals must meet to develop their sexual ornaments. The flashy pigment-based colors commonly displayed by birds are ideal candidates for investigating the pathways and demands of sexual-signal expression, because we know the biochemical currency with which the trait is produced. Carotenoid colors in birds, for example, are derived from pigments that are acquired from the diet and assimilated into feathers and bare parts. In previous work, we showed that variation in the sexually attractive red carotenoid-colored beak of male zebra finches (Taeniopygia guttata) was predicted not by the amount of food or pigments ingested, but by the levels of carotenoids that birds circulated in blood. Here we elucidate a novel physiological mechanism by which birds are able to accumulate high levels of carotenoids in the body and develop a colorful bill. Carotenoids are transported through the bloodstream bound to lipoproteins. We assayed a critical component of lipoprotein particles-cholesterol-and found that males with higher cholesterol levels circulated more carotenoids and displayed redder beaks. Experimental supplementation of dietary cholesterol elevated carotenoid levels in the blood and beak hue. Experimental reductions in blood cholesterol, using the human lipid-lowering agent atorvastatin, diminished blood carotenoids and faded the beak; carotenoid and cholesterol levels were restored, however, by subsequent addition of dietary cholesterol. These results suggest that the production of circulating lipoproteins critically regulates the development of a colorful sexually selected trait in zebra finches.

Animals↗
PubMed2001

Correlated evolution of morphology and vocal signal structure in Darwin's finches.

Speciation in many animal taxa is catalysed by the evolutionary diversification of mating signals. According to classical theories of speciation, mating signals diversify, in part, as an incidental byproduct of adaptation by natural selection to divergent ecologies, although empirical evidence in support of this hypothesis has been limited. Here I show, in Darwin's finches of the Galápagos Islands, that diversification of beak morphology and body size has shaped patterns of vocal signal evolution, such that birds with large beaks and body sizes have evolved songs with comparatively low rates of syllable repetition and narrow frequency bandwidths. The converse is true for small birds. Patterns of correlated evolution among morphology and song are consistent with the hypothesis that beak morphology constrains vocal evolution, with different beak morphologies differentially limiting a bird's ability to modulate vocal tract configurations during song production. These data illustrate how morphological adaptation may drive signal evolution and reproductive isolation, and furthermore identify a possible cause for rapid speciation in Darwin's finches.

Adaptation, Physiological↗
PubMed2003

Carotenoids, immunocompetence, and the information content of sexual colors: an experimental test.

Many male birds use carotenoid pigments to acquire brilliant colors that advertise their health and condition to prospective mates. The direct means by which the most colorful males achieve superior health has been debated, however. One hypothesis, based on studies of carotenoids as antioxidants in humans and other animals, is that carotenoids directly boost the immune system of colorful birds. We studied the relationship between carotenoid pigments, immune function, and sexual coloration in zebra finches (Taeniopygia guttata), a species in which males incorporate carotenoid pigments into their beak to attract mates. We tested the hypotheses that increased dietary carotenoid intake enhances immunocompetence in male zebra finches and that levels of carotenoids circulating in blood, which also determine beak coloration, directly predict the immune response of individuals. We experimentally supplemented captive finches with two common dietary carotenoid pigments (lutein and zeaxanthin) and measured cell-mediated and humoral immunity a month later. Supplemented males showed elevated blood-carotenoid levels, brighter beak coloration, and increased cell-mediated and humoral immune responses than did controls. Cell-mediated responses were predicted directly by changes in beak color and plasma carotenoid concentration of individual birds. These experimental findings suggest that carotenoid-based color signals in birds may directly signal male health via the immunostimulatory action of ingested and circulated carotenoid pigments.

Animal Nutritional Physiological Phenomena↗
PubMed2005

Evolution of bite force in Darwin's finches: a key role for head width.

Studies of Darwin's finches of the Galapagos Islands have provided pivotal insights into the interplay of ecological variation, natural selection, and morphological evolution. Here we document, across nine Darwin's finch species, correlations between morphological variation and bite force capacity. We find that bite force correlates strongly with beak depth and width but only weakly or not at all with beak length, a result that is consistent with prior demonstrations of natural selection on finch beak morphology. We also find that bite force is predicted even more strongly by head width, which exceeds all beak dimensions in predictive strength. To explain this result we suggest that head width determines the maximum size, and thus maximum force generation capacity of finch jaw adductor muscles. We suggest that head width is functionally relevant and may be a previously unrecognized locus of natural selection in these birds, because of its close relationship to bite force capacity.

Animals↗
PubMed2005

Developmental mechanisms facilitating the evolution of bills and quills.

Beaks and feathers epitomize inimitable avian traits. Within individuals and across species there exists astounding diversity in the size, shape, arrangement, and colour of beaks and feathers in association with various functional adaptations. What has enabled the concomitantly divergent evolution of beaks and feathers? The common denominator may lie in their developmental programmes. As revealed through recent transplant experiments using quail and duck embryos, the developmental programme for each structure utilizes mesenchyme as a dominant source of species-specific patterning information, acts as a module of closely coupled molecular and histogenic events, and operates with a high degree of spatial and temporal plasticity. By synergizing these three features, the developmental programmes underlying beaks and feathers likely have the essential potential to react spontaneously to novel conditions and new gene functions, and as a consequence are well equipped to generate and accommodate innovative phenotypes during the course of evolution.

Adaptation, Physiological↗
PubMed1976

Behaviour and aeration of the respiratory system in the domestic fowl embryo.

1. The monitoring of developmental stage and under-water dissection were used to examine the initial aeration of the respiratory system in domestic fowl embryos. 2. A virtually complete absence of free air within the chorioallantois was found before the beak had begun to make 'beak-clapping' movements, even when the membranes were already draped over its tip. 3. During the 'beak-clapping' stage, but before the membranes were pierced and before respiratory movements had begun, many embryos were found to contain free bubbles of air within the trachea and air sacs. 4. All embryos in which the respiratory system was aerated were found also to have froth in the crop or other parts of the digestive system. 5. Air was found in both the respiratory and digestive systems of all embryos examined after membrane penetration by the beak. 6. When air was injected into the chorioallantois before the stage of initial aeration it was recovered 5 min later from both the respiratory and digestive systems in under-water dissections. 7. It is suggested that lung ventilation takes place in the avian embryo in three distinct stages: the major air-ways become aerated, then respiratory movements begin and lastly the tertiary bronchi are slowly aerated. It is suggested also that movements involved in the imbibing of fluids play a part in aeration before the membranes are pierced.

Air↗