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PubMed1985

The membrane skeleton of a unicellular organism consists of bridged, articulating strips.

In this paper we show that a membrane skeleton associated with the plasma membrane of the unicellular organism Euglena consists of approximately 40 individual S-shaped strips that overlap along their lateral margins. The region of strip overlap is occupied by a set of microtubule-associated bridges and microtubule-independent bridges. Both cell form and plasma membrane organization are dependent on the integrity of this membrane skeleton. Removal of the membrane skeleton with a low-molar base results in loss of membrane form and randomization of the paracrystalline membrane interior characteristic of untreated cells. Conversely, removal of the plasma membrane and residual cytoplasm with lithium 3,5-diiodosalicylate/Nonidet P-40 yields cell ghosts that retain the form of the original cell but consist only of the membrane skeleton. Two major polypeptides of 86 and 80 KD persist in the skeleton and two other major proteins of 68 and 39 kD are associated with the plasma membrane fraction. None of these components appears to be the same as the major polypeptides (spectrins, band 3) of the erythrocyte ghost, the other cell system in which a well-defined peripheral membrane skeleton has been identified. We suggest that the articulating strips of euglenoids are not only the basic unit of cell and surface form, but that they are also positioned to mediate or accommodate surface movements by sliding, and to permit surface replication by intussusception.

Animals↗

PubMed2002

Plakoglobin is required for maintenance of the cortical actin skeleton in early Xenopus embryos and for cdc42-mediated wound healing.

Early Xenopus embryos are large, and during the egg to gastrula stages, when there is little extracellular matrix, the cytoskeletons of the individual blastomeres are thought to maintain their spherical architecture and provide scaffolding for the cellular movements of gastrulation. We showed previously that depletion of plakoglobin protein during the egg to gastrula stages caused collapse of embryonic architecture. Here, we show that this is due to loss of the cortical actin skeleton after depletion of plakoglobin, whereas the microtubule and cytokeratin skeletons are still present. As a functional assay for the actin skeleton, we show that wound healing, an actin-based behavior in embryos, is also abrogated by plakoglobin depletion. Both wound healing and the amount of cortical actin are enhanced by overexpression of plakoglobin. To begin to identify links between plakoglobin and the cortical actin polymerization machinery, we show here that the Rho family GTPase cdc42, is required for wound healing in the Xenopus blastula. Myc-tagged cdc42 colocalizes with actin in purse-strings surrounding wounds. Overexpression of cdc42 dramatically enhances wound healing, whereas depletion of maternal cdc42 mRNA blocks it. In combinatorial experiments we show that cdc42 cannot rescue the effects of plakoglobin depletion, showing that plakoglobin is required for cdc42-mediated cortical actin assembly during wound healing. However, plakoglobin does rescue the effect of cdc42 depletion, suggesting that cdc42 somehow mediates the distribution or function of plakoglobin. Depletion of alpha-catenin does not remove the cortical actin skeleton, showing that plakoglobin does not mediate its effect by its known linkage through alpha-catenin to the actin skeleton. We conclude that in Xenopus, the actin skeleton is a major determinant of cell shape and overall architecture in the early embryo, and that plakoglobin plays an essential role in the assembly, maintenance, or organization of this cortical actin.

Actins↗

PubMed1992

Zinc deficiency alters the protein composition of the membrane skeleton but not the extractability or oligomeric form of spectrin in rat erythrocyte membranes.

We examined the effect of dietary Zn deficiency on the composition and structure of the rat erythrocyte membrane skeleton. Weanling rats were given free access to egg white-based diets (less than 1.0 mg Zn/kg) for 3 wk. Controls were fed diets (pair-fed or ad libitum) supplemented with 100 mg Zn/kg. Membrane skeleton proteins were extracted from isolated erythrocyte membranes in a low ionic strength buffer. Dietary Zn deficiency did not alter the content of spectrin, the major membrane skeleton protein, in the intact membranes or the percentage of spectrin extracted after 24 or 96 h. Zinc deficiency did not alter the oligomeric form of spectrin in the extracts that were analyzed in the presence or absence of EDTA. However, Zn deficiency resulted in a significant reduction in the relative content of protein R5 in the membrane skeleton extracts. The food restriction associated with dietary Zn deficiency was the major factor in the significant reduction in the relative content of RA (adducin) and R4 (protein 4.1) in the membrane skeleton extracts. Dietary Zn deficiency altered membrane skeleton protein composition but had no effect on the extractability or oligomeric form of spectrin.

Animals↗

PubMed2004

Analysis of the hemispheric asymmetry using fractal dimension of a skeletonized cerebral surface.

We investigated hemispheric asymmetry using the fractal dimension (FD) of the skeletonized cerebral surface. Sixty-two T1-weighted magnetic resonance imaging volumes from normal Korean adults were used. The skeletonization of binary volume data, which corresponded to the union of the gray matter and cerebrospinal flow classified by fuzzy clustering, was performed slice by slice in the sagittal direction, and then skeletonized slices were integrated into the three-dimensional (3-D) hemisphere. Finally, the FD of the 3-D skeletonized cerebral surface was calculated using the box-counting method. We measured the FD of the skeletonized cerebral surface and the volumes of intracranial gray matter and white matter for the whole hemispheres and obtained the hemispheric asymmetries of each measurement. The FD, the gray matter, and the white matter volumes for the whole hemispheres decreased in the old group. The asymmetry of the FD revealed a significant right-greater-than-left asymmetry showed rightward, but did not change according to age and gender. None of the intracranial gray matter or white matter volumes showed any significant asymmetric changes. It could be said that the FD of the skeletonized cerebral surface is a novel measure of cerebral asymmetry.

Adolescent↗

PubMed2000

Three-dimensional sonographic visualization of fetal skeleton in the second trimester of pregnancy.

PURPOSE: To demonstrate the potential of using three-dimensional (3D) sonography to reveal anomalies of fetal skeleton. MATERIALS AND METHODS: Forty-two normal fetuses and 3 anencephalic fetuses from 14 to 27 weeks' gestation were studied with a specially developed abdominal 3D transducer (3.5 MHz). This imaging system provided conventional two-dimensional (2D) sonographic images and also generated within seconds high-quality 3D images in the surface and transparent mode with no need for an external workstation. RESULTS: Using this imaging system, we obtained 2D and 3D images of fetal skeleton (skull, scapula, spine, rib, humerus, ulna/radius, pelvis, femur, and tibia/fibula) at two gestational ages. The percentages of fetal skeletal visualization at less than 20 weeks of gestation using 3D sonography were 78-100%, whereas those with 2D sonography were all 100%. The percentages of skeletal structures revealed after 20 weeks' gestation using 3D sonography were 82-100%, whereas those with 2D sonography were all 100%. We found no significant differences in detection rates of the fetal skeleton between 2D and 3D sonography. However, 3D sonographic images generally provided a more comprehensive view of the fetal skeleton than did conventional 2D sonography. In 2 cases with anencephaly, 3D sonography clearly revealed the defect of cranium. CONCLUSION: The new 3D sonographic technology can generate within seconds high-quality 3D images of the fetal skeleton. The 3D technology seems to perform at least as well as conventional 2D sonography. Our results suggest that 3D sonography has the potential to supplement 2D sonography and might be useful in identifying malformations of the fetal skeleton and chromosomal abnormalities in utero.

Anencephaly↗

PubMed2006

The internal thoracic artery skeletonization study: a paired, within-patient comparison [NCT00265499].

BACKGROUND: Traditional harvesting of the internal thoracic artery (ITA) for use as a conduit in coronary bypass surgery involves the dissection of a rim of tissue surrounding the artery on either side. Recent studies, primarily observational, have suggested that skeletonization of the ITA can improve conduit flow, increase length, and reduce the risk of deep sternal infection in high risk patients. Furthermore, skeletonization of the ITA can potentially preserve intercostal nerves and reduce post-operative pain and dysesthesias associated with ITA harvesting. In order to assess the effects of ITA skeletonization, we report a prospective, randomized, within-patient study design that shares many features of a cross-over study. METHODS: Patients undergoing bilateral internal thoracic artery harvest will be randomized to having one side skeletonized and the other harvested in a non-skeletonized manner. Outcome measures include ITA flow and length measured intra-operatively, post-operative pain and dysesthesia, evaluated at discharge, four weeks, and three months post-operatively, and sternal perfusion assessed using single photon emission computed tomography. Harvest times as well as safety endpoints of ITA injury will be recorded. DISCUSSION: This study design, using within-patient comparisons and paired analyses, minimizes the variability of the outcome measures, which is seldom possible in the evaluation of surgical techniques, with minimal chance of carryover effects that can hamper the interpretation of traditional cross-over studies. This study will provide a valid evaluation of clinically relevant effects of internal thoracic artery skeletonization in improving outcomes following coronary artery bypass surgery.

Journal Article↗

PubMed2006

Relationship between push phase and final race time in skeleton performance.

The aim of this study was to examine the relationship between push-time and final race time in skeleton participants during a series of major international competitions to determine the importance of the push phase in skeleton performance. Correlations were computed from the first and second heat split data measured during 24 men and 24 women skeleton competitions. Body mass, height, age, and years of experience of the first 30 men and women athletes of the skeleton, bobsleigh and luge 2003-2004 World Cup ranking were used for the comparison between sliding sports. Moderate but significant correlations (p < 0.05) were found between push-time and final race time in men (r(mean) = 0.48) and women (r(mean) = 0.63). No correlations were found between changes in the individual push-time between the first and second heat with the corresponding changes in final race time. The bobsleigh sliders are heavier than the athletes of the other sliding disciplines. Luge athletes have more experience and are younger than bobsleigh and skeleton sliders. The results of this study suggest that a fast push phase is a prerequisite to success in competition and confirms that the selection of skeleton athletes based on the ability to accelerate to a maximum speed quickly could be valid. However, a good or improved push-time does not ensure a placement in the top finishing positions. On the basis of these results, we suggest that strength and power training is necessary to maintain a short push-time but additional physical training aimed to enhance the push phase might not reflect performance improvements. The recruitment of younger athletes and an increase of youthful competitive activity may be another effective way to reach international competitive results.

Acceleration↗

PubMedDate not supplied

Role of the skeleton in determination of the branching points in hydroid colonies.

Colonial hydroids of the suborder Thecaphora have rigid outer skeleton that possesses species-specific shape of the colony elements. Organisation of the elements within a colony shows strict spatial patterning. The points of branching (emergence of the new growing tip) within shoots are strictly determined and show positive correlation with the place of the most pronounced curvature of the elements skeleton. As it was shown earlier, the shoot growing tip, after emergence, performs its program of functioning independently from the colony condition. Several modifications of experiments with grafting of the growing tip together with rotation around its longitudinal axis were fulfilled. As the result of such grafting the normal orientation of the formed skeleton was altered. In overwhelming cases of further tip growth and shoot development the new growing tip emerged in correspondence with new orientation of the formed skeleton. The orientation of the hydranth of the maternal shoot element had no effect upon the orientation of the new tip emergence after grafting. It is supposed that the place of the new tip emergence is regulated hierarchically. At first level, the interaction of the soft tissues with the skeleton has priority. Anisotropy of mechanical tensions within cell layers due to interaction with the skeleton at the point of its most curvature serves as a primary stimulus in the chain of events leading to the initiation of the new growing tip. If this does not work the intrinsic tissue property (polarity) determines the place of the tip emergence. Such two-level mechanism of determination of the place of the new tip emergence in sympodial shoots stabilises spatial organisation of the entire shoot and decreases the probability of epigenetic mistakes.

Animals↗

PubMed2003

Pedicled or skeletonized? A review of the internal thoracic artery graft.

The internal thoracic artery is the gold-standard conduit for coronary artery bypass surgery. Until recently, it was used almost exclusively as a pedicle, with construction of 1 distal anastomosis. Skeletonization of the internal thoracic artery has recently been advocated in order to increase the number of arterial anastomoses and decrease the occurrence of sternal wound infections. When skeletonized, the vessel loses its "milieu" which raises the question of whether this technique sacrifices the superior longevity of the conduit. The current status of research on the effects of skeletonization (depriving the internal thoracic artery of vasa vasorum, innervation, and lymphatic and venous drainage, together with creating an imbalance between vasoconstricting and vasodilating substances) appears to support the superiority of the pedicled graft. Long-term patency studies of the skeletonized ITA, with meticulous follow-up and confirmation by angiography, are not currently available. Theoretically, skeletonization of the ITA might adversely affect its long-term resistance to atherosclerosis. More data are needed before this technique can be universally recommended. If the skeletonized ITA has decreased long-term patency, bypass surgery may be at a disadvantage when compared with the new generation of drug-eluting stents.

Coronary Artery Bypass↗

PubMed2004

[Skeletonized right gastroepiploic artery for coronary artery bypass grafting; evaluation of intraoperative graft flow and postoperative angiographic result].

We evaluated the efficacy of using the skeletonized right gastroepiploic artery (RGEA) in coronary artery bypass grafting (CABG). The RGEA was harvested either as a pedicle (group P, n = 14) or in a skeletonized fashion using a Harmonic Scalpel (group S, n = 14). The free flow of the RGEA was too small to be measured in some cases in group P. On the other hand, the free flow of the RGEA could be measured in all cases in group S, and that value obtained was comparable to the free flow of the left internal thoracic artery. The skeletonization of the RGEA also allowed us to directly visualize this vessel, and thus helped us to evaluate the quality of this artery. Postoperatively, all RGEAs were patent in both groups. The RGEA diameters on the postoperative angiography showed the RGEAs in group S to have a wider caliber, however, the differences in the values for each group did not reach statistic significance. Neither the operation time nor the postoperative hospital stay were substantially lengthened due to the skeletonization of the RGEA. In conclusion, the skeletonization of the RGEA using a Harmonic Scalpel is safe and effective modality which enables surgeons to directly visualize arteries in order to determine their quality and thereby making it easier to perform sequential bypass grafting. The method also demonstrated an excellent quality of the patent graft on postoperative angiography. We therefore consider the skeletonization of the RGEA to be a very useful method for harvesting the RGEA in CABG.

Aged↗

PubMed1991

A human skeleton from the Ohguruwa remains.

In 1941, the Ohguruwa remains were discovered at the Mizuho sports ground site in Nagoya. They date from about 3000 B.C., which is the early Jomon era. When the stadium was reconstructed in 1980, four human skeletons were found. Three of them, however, were in poor condition and moreover, were incomplete. However, the second skeleton was in good condition and could almost be reconstructed, and this skeleton (No. 2) was used for our study. It was found in the classic posture with arms and legs folded. Some pieces of a dog's skeleton were also discovered near the No. 2 skeleton's chest. This particular skeleton generally showed characteristics typical of the Jomon era. It had a stout structure and was judged to be a middle aged male because of the following features. There was considerable attrition of the occlusal surfaces on the remaining teeth. The teeth were worn flat, probably owing to the hard food and to their use as a tool. Both canines and first premolars of the upper and lower arches had been extracted in accordance with the custom of the time. Typical caries and localized periodontal breakdown were not observed, although there was horizontal alveolar bone loss, especially in the anterior regions. The mastoid process was extremely large and prominent. The lateral prominence of the mandible was developed. Analysis of lateral cephalogram revealed that the mandible was in the anterior position. The angles of SNA, SNB and ANB were 89.6 degrees, 89.2 degrees and 0.4 degrees, respectively. The skeletal pattern was definitive Class III. The adaptive changes in the teeth, their supporting tissues, temporomandibular joints and the related muscles--the harmonious masticatory system--were all estimated.

Cephalometry↗

PubMed1990

Effect of hemoglobin oxidation products on the stability of red cell membrane skeletons and the associations of skeletal proteins: correlation with a release of hemin.

Oxidative injury to hemoglobin (Hb) leads to formation of methemoglobin (MetHb), reversible hemichromes (rHCRs), and irreversible hemichromes (iHCRs). iHCRs precipitate and form Heinz bodies that attach to the red cell membrane causing injury that leads to hemolysis. The molecular mechanisms of this membrane damage have not been fully elucidated. We have studied the effect of Hb oxidation products on the mechanical stability of red cell membrane skeletons and the associations of membrane skeletal proteins. Hb and MetHb stabilized the isolated membrane skeletons, whereas further oxidation to rHCRs abolished this stabilizing effect. Crude iHCRs prepared by phenylhydrazine oxidation of Hb destabilized membrane skeletons by decreasing formation of the spectrin-protein 4.1-actin complex, the effect similar to that of pure hemin. Whereas virtually no hemin was released from Hb and MetHb, high concentrations of hemin were released from crude iHCR preparations. After removal of this hemin fraction by Dowex resin, the iHCRs lost their destabilizing effect. We conclude that as the oxidation of Hb proceeds, the stabilizing effect of Hb on the membrane skeleton is gradually lost and the deleterious effect increases. The destabilization of the red cell membrane skeleton in the presence of crude iHCR is caused by release of hemin, which lowers the stability of membrane skeleton by weakening the spectrin-protein 4.1-actin interaction.

Actins↗

PubMed2002

Osteobiographic analysis of skeleton I, Sítio Toca dos Coqueiros, Serra da Capivara National Park, Brazil, 11,060 BP: first results.

This paper presents an osteobiographic analysis of a single skeleton found in a small rock shelter known as Toca dos Coqueiros, Piauí, Brazil. This find is of interest because of an exceptionally old radiocarbon date associated with it. The date (11,060 BP) was obtained from charcoal associated directly with the skeleton. This is an interesting find because of the rarity of osteobiographic studies of skeletons of such antiquity. Despite the existence of two projectile points in association with the burial, the morphological and molecular analyses of the skeleton demonstrated that this was a female. She was about 35-45 years of age at death. The skeleton exhibited acute and chronic bone lesions. Oral pathology was also observed, including an interproximal dental groove, probably caused by the therapeutic use of a cactus thorn. This could be one of the oldest cases of an analgesic plant used in the prehistoric Americas.

Adult↗

PubMed1998

Growth patterns in the modern human skeleton.

This study investigates cross sectional growth patterns in the human skeleton using a recent skeletal sample of known age and sex. Measurements were selected to reflect different functional regions of the cranium, mandible and post cranial skeleton, and growth is evaluated using a single phase Gompertz curve. Different parts of the skeleton vary in the proportion of adult size attained at birth and in their subsequent rate of attainment of adult size. The paper introduces a method for the objective and quantitative comparison of the growth of different samples, and is used in this instance to analyze sexual differences in the growth of the post cranial skeleton. The development of sexual dimorphism is evaluated in terms of differences in the rate and duration of male and female growth. Adult sexual dimorphism is generally lower in early growing variables than in later-growing variables. There is considerable diversity in the ontogenetic basis of sexual dimorphism in the human skeleton demonstrating that the development of sexual dimorphism within a species should not be regarded as a uniform phenomenon.

Adolescent↗

PubMed2006

Lamprey type II collagen and Sox9 reveal an ancient origin of the vertebrate collagenous skeleton.

Type II collagen is the major cartilage matrix protein in the jawed vertebrate skeleton. Lampreys and hagfishes, by contrast, are thought to have noncollagenous cartilage. This difference in skeletal structure has led to the hypothesis that the vertebrate common ancestor had a noncollagenous skeleton, with type II collagen becoming the predominant cartilage matrix protein after the divergence of jawless fish from the jawed vertebrates approximately 500 million years ago. Here we report that lampreys have two type II collagen (Col2alpha1) genes that are expressed during development of the cartilaginous skeleton. We also demonstrate that the adult lamprey skeleton is rich in Col2alpha1 protein. Furthermore, we have isolated a lamprey orthologue of Sox9, a direct transcriptional regulator of Col2alpha1 in jawed vertebrates, and show that it is coexpressed with both Col2alpha1 genes during skeletal development. These results reveal that the genetic pathway for chondrogenesis in lampreys and gnathostomes is conserved through the activation of cartilage matrix molecules and suggest that a collagenous skeleton evolved surprisingly early in vertebrate evolution.

Aging↗

PubMed2006

Bayesian estimation of the shape skeleton.

Skeletal representations of shape have attracted enormous interest ever since their introduction by Blum [Blum H (1973) J Theor Biol 38:205-287], because of their potential to provide a compact, but meaningful, shape representation, suitable for both neural modeling and computational applications. But effective computation of the shape skeleton remains a notorious unsolved problem; existing approaches are extremely sensitive to noise and give counterintuitive results with simple shapes. In conventional approaches, the skeleton is defined by a geometric construction and computed by a deterministic procedure. We introduce a Bayesian probabilistic approach, in which a shape is assumed to have "grown" from a skeleton by a stochastic generative process. Bayesian estimation is used to identify the skeleton most likely to have produced the shape, i.e., that best "explains" it, called the maximum a posteriori skeleton. Even with natural shapes with substantial contour noise, this approach provides a robust skeletal representation whose branches correspond to the natural parts of the shape.

Algorithms↗

PubMed1996

Regulation of the disassembly/assembly of the membrane skeleton in Madin-Darby canine kidney cells.

The effects of pH, temperature, block of energy production, calcium/calmodulin, protein phosphorylation, and cytoskeleton-disrupting agents (cytochalasin D, nocodazole) on the integrity of the membrane skeleton were studied in polarized MDCK cells. The intracellular distributions of alpha-fodrin, actin, and ankyrin were monitored by immunofluorescence microscopy. The membrane skeleton, once assembled, seemed to be quite stable; the only factors releasing alpha-fodrin from the lateral walls were the acidification of the cytoplasm and the depletion of extracellular calcium ions. Upon cellular acidification, some actin was also released from its normal location along the lateral walls and was seen in colocalization with alpha-fodrin in the cytoplasm, whereas ankyrin remained associated with the lateral walls. No accumulation of plasma membrane lipids was observed in the cytoplasm of acidified cells, as visualized by TMA-DPH. These results suggest that the linkages between the fodrin-actin complex and its membrane association sites are broken upon acidification. The pH-induced change in alpha-fodrin localization was reversible upon restoring the normal pH. Reassembly of the membrane skeleton, however, required temperatures above +20 degrees C, normal energy production, proper cell-cell contacts, and polymerized actin. Release of alpha-fodrin from the lateral walls to the cytoplasm was also observed upon depletion of extracellular calcium ions. This change was accompanied by the disruption of cell-cell contacts, supporting the role of proper cell-cell contacts in the maintenance of the membrane skeleton polarity. These results suggest that local alterations of the cytoplasmic pH and calcium ion concentration may be important in regulating the integrity of the membrane skeleton.

Actins↗

PubMed2000

Possible case of spondylo-epiphyseal dysplasia in a medieval skeleton.

Multiple anomalies of vertebral and long bone growth were observed in the incomplete skeleton of an adult male from a collection of 693 medieval skeletons excavated at Abingdon, Oxfordshire. The skeleton consists of a fragmented skull, right scapula and humerus, left humerus, radius, ulna and partial hand, vertebrae from C1 to T11, and fragments of the ribs and sternum. The bones were examined, measured, and radiographed. The humeri are abnormally short and thick, with exaggerated muscle attachments. Both shoulder joints show extensive osteoarthritic destruction. Some vertebrae show slight flattening of the bodies, and there is possible evidence of both kyphosis and scoliosis. Skull, forearm, and hand bones are of normal size and morphology. Lack of lower limb bones and abnormal proportions in the upper limbs prevent meaningful estimation of stature. However, the other features of the skeleton are consistent with a diagnosis of spondylo-epiphyseal dysplasia. No other skeletons displaying similar anomalies were observed.

Arm↗