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PubMed1997

The application of three-dimensional quantitative computed tomography to the maxillofacial skeleton.

OBJECTIVES: To develop a method for three-dimensional quantitative computed tomography (QCT) of the maxillofacial skeleton. METHODS: The linearity of reference phantom consisting of five hydroxyapatite (HA) rods was tested under various conditions, including the size of field of view, the position of object, and reconstruction algorithm, on three different scanners. The calibrated HA concentration value and the absolute Ca content of the mandible removed from fresh cadaver was compared in order to evaluate the calibration error. RESULTS: There was a high correlation between average CT number and HA concentration in the phantom rods. There was a 4-5% difference in results from the three scanners. High density areas, corresponding to more than 75% HA, were extracted from the original image. Data were reconstructed three-dimensionally and combined using a 32-bit computer system. A three-dimensional distribution of bone density superimposed on the maxillofacial skeleton was produced. CONCLUSION: Three-dimensional QCT of the maxillofacial skeleton has potential as a means of analysing bone density. Difference in performance of different CT scanners should be considered when comparing results.

Adolescent↗

PubMed2000

A new method for three-dimensional skeleton graph analysis of porous media: application to trabecular bone microarchitecture.

This paper introduces a new three-dimensional analysis of complex disordered porous media. Skeleton graph analysis is described and applied to trabecular bone images obtained by high resolution magnetic resonance imaging. This technique was developed bearing in mind topological considerations. The correspondence between vertices and branches of the skeleton graph and trabeculae is used in order to get local information on trabecular bone microarchitecture. In addition to real topological parameters, local structural information about trabeculae, such as length and volume distributions, are obtained. This method is applied to two sets of samples: six osteoporosis and six osteoarthritis bone samples. We demonstrate that skeleton graph analysis is a powerful technique to describe trabecular bone microarchitecture.

Femur Head↗

PubMed2001

Three-dimensional finite element analysis of the facial skeleton on simulated occlusal loading.

Development of predictive models of occlusal loading of the facial skeleton will be of value for prosthetic design in oral rehabilitation. A 3-D finite element (FE) model of a human skull, based on CT scans, was constructed to analyse strain and stress distribution in the facial skeleton caused by simulated occlusal loading. Vertical loads were applied simulating loading of the full maxillary arch and unilateral single point occlusal loading of maxillary molar, pre-molar, canine and incisor sites. Strain and stress regimes from Von Mises (VM) failure criteria and extension and compression diagrams showed even distribution of strain following loading of the full maxillary arch throughout the facial elements. For individual points, the highest VM concentrations were consistently located on the facial aspect several mm above the loading site. Strain trajectories divided into a 'V-shaped' pattern, from the loading point into medial and lateral branches with higher VM values in the medial. As the same load was applied from the posterior to anterior region, VM values increased on all facial areas. Strain patterns were less symmetric and there was an increase in strain in the alveolar arch and around the rim of the nasal cavity. The overall picture of the facial skeleton is of a vertical plate enabling it to withstand occlusal stresses by in-plane loading and bending in its own plane. The most efficient distribution of load was on maxillary full arch loading with the most unfavourable strain concentrations occurring on loading in the anterior region.

Adult↗

PubMed1988

Responses of market lambs and Suffolk rams to a stimulatory skeleton photoperiod.

Young crossbred lambs and Suffolk rams were exposed to photoperiods stimulatory to growth or reproduction respectively. Whereas long days are known to facilitate rate of gain, feed efficiency and carcass yield in young market lambs, exposure to decreasing daylengths or short days is necessary for successful reproduction of the species. Successful substitution of a "skeleton" long photoperiod (7L:9D:1L:7D) for long photoperiod (16L:8D) exposure to growing lambs to improve performance provides strong support for the conclusion that long-day stimulation is not the result of the interval of day being illuminated but rather the time interval between two periods within a day which is illuminated. The same "skeleton" long photoperiod (7L:9D:1:7D) is shown to substitute effectively for a long (16L:8D) photoperiod when used alternately with a short (8L:16D) photoperiod in eight-week light cycle exposure of mature Suffolk rams. Light cycles of this duration entrain LH, testosterone and testicular weight and stimulate reproductive activity to a level comparable to that observed in rams during the normal breeding season. Evidence is presented that the relatively short eight-week light cycles prevent photorefractoriness from occurring and thereby can maintain indefinitely the behavioral and gametogenic activities required of the breeding ram. Implementation of short days combined with alternating "skeleton" long days should be energy efficient and may prove useful for application to sire management.

Animals↗

PubMed1977

[Computerized tomography of the facial skeleton (part II). Pathological changes (author's transl)].

The value and main task of computerized tomography in the diagnosis of benign and malignant processes in the middle and upper facial skeleton lies in its accurate demonstration of the extent of the disease; this is important in relation to the planning of treatment, prognosis and to other complementary procedures. CT is a new and potent method for the TNM classification of tumours of the nose, paransal sinuses and nasal pharynx. The ability of the CT to demonstrate deeply situated structures in the face, without disturbing overlying shadows, makes precise staging of deep tumours possible, eg. stages T2-T4. The consequences in terms of pre-treatment TNM classification are discussed. In cases of fronto-basal fractures, the CT will show particularly trauma to the orbital contents, intracranial displacement of bone fragments and cerebral trauma with or without bleeding. Suspicion of orbital involvement by benign or malignant disease is a definite indication for a CT examination. As regards the middle and upper facial skeleton, computer tomography provides information of a morphological and quantitative nature and aids in the localisation of lesions. It should be properly integrated into the conventional clinical, endoscopic and tomographic methods employed in the diagnosis of lesions of the facial skeleton.

Facial Bones↗

PubMed1999

Three novel bicyclic taxane diterpenoids with verticillene skeleton from the needles of Chinese yew, Taxus chinensis var. mairei.

Three novel bicyclic taxane diterpenoids with the verticillene skeleton were isolated from the needles of Chinese yew, Taxus chinensis var. mairei. Their structures were established as (3E,7E)-2 alpha, 10 beta, 13 alpha, 20-tetraacetoxy-5 alpha-hydroxy-3,8-secotaxa-3,7,11-trien-9-one (1), (3E,7E)-2 alpha, 5 alpha, 10 beta, 13 alpha-tetraacetoxy-20-hydroxy-3,8-secotaxa-3,7,11-trien-9-one (2), and (3E,7E)-10 beta, 13 alpha-diacetoxy-2 alpha, 5 alpha, 20-trihydroxy-3,8-secotaxa-3,7,11-trien-9-one (3) on the basis of 1D, 2D NMR and HR-MS spectroscopic analysis. Verticillene skeleton was considered as the biogenetic intermediate of taxane diterpenoids, isolation of bicyclic taxane diterpenoids with verticillene skeleton from this plant provides direct proof for this hypothesis.

Bridged Bicyclo Compounds↗

PubMedDate not supplied

[Disorders of the membrane skeleton of erythrocytes in hereditary spherocytosis and elliptocytosis: significance of the molecular defect for pathogenesis and clinical severity].

During recent years an increasing number of inherited variants of erythrocyte membrane proteins and defects of the membrane skeleton could be described. Mostly these defects explain the pathogenesis of hemolytic anemias due to erythrocyte membrane defects. For hereditary spherocytosis and elliptocytosis a close correlation between the clinical severity and the biochemical defect was found; thus biochemical characterization can give valuable information about the expected course of the disease and the need for splenectomy. The erythrocyte membrane skeleton stretches along the inner surface of the membrane; it provides the stability of the erythrocyte under circulatory shear stress. The membrane skeleton consists of spectrin, actin, band 4.1 and band 4.9. Spectrin is the major component. In the membrane mostly all spectrin self-associates to the tetrameric form: one tetramer is formed by two alpha and two beta-chains. By denaturing SDS polyacrylamide gelelectrophoresis the composition of the membrane proteins can be analysed. The portion of tetrameric and dimeric spectrin is determined on native agarose gel electrophoresis. The concentration of spectrin in the membrane can be measured by an enzyme linked immunosorbent assay using monoclonal antibodies against human spectrin. By polymerase chain reaction and DNA sequencing the moleculargenetic cause of singular membrane defects was clarified. Hereditary spherocytosis was mostly due to a more or less diminished concentration of spectrin. Based on hematological, clinical' and biochemical observations, a new classification of spherocytosis (mild, moderate and severe form) is proposed. In addition to routine hematologic determinations and osmotic fragility, erythrocyte spectrin content is taken into account. The disease severity correlates with the diminution of spectrin. In hereditary elliptocytosis the concentration of tetrameric spectrin is reduced in about 30% of the patients. Defects of the N-terminal alpha I 80,000 dalton peptide are predominantly found. The defective alpha chain can be further studied by analysis of "tryptic" peptides after limited tryptic digestion of the spectrin. According to the reduced molecular weight of the anomalous tryptic alpha I peptide the variant spectrin alpha chains are designed as Spectrin alpha I/46, Sp alpha I/50, Sp alpha I/65, Sp alpha I/74 and Sp alpha I/78. In most cases a single amino acid substitution of the alpha chain could be proven. Until now only singular patients with hereditary elliptocytosis due to a shortened spectrin beta chain have been described. The shortening of the beta chain is due to a loss of the C-terminal phosphorylated peptide. The molecular cause is a defect at the 3' end of the beta spectrin gen, resulting in a premature termination of the peptide chain-synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Actins↗

PubMed1994

[3-D CT reconstruction of fractures of the skull base and the facial skeleton].

3-D reconstructions of the skull base, temporal bone, and skull fractures were compared to 2-D- CT to evaluate the diagnostic value in traumatized patients. 38 patients with 22 fractures of the facial skeleton (orbita, zygomatic, Le Fort), 12 temporal bone, and 4 skull fractures were investigated. Subjective grading was performed by two physicians (ENT/RAD) in respect of quality diagnostic validity and estimated clinical impact. The average image validity and quality were graded good. In the temporal bone the average information supplied by 3-D was of inferior value; here, the lack of information regarding the inner ear structures was responsible for the lack of clinical impact. In fractures of the facial skeleton and the skull base a good to very good image quality was seen and clinical relevance was high. 3-D CT is capable of demonstrating fractures, which is of little value in the temporal bone, but of high value in the skull base and the facial skeleton, especially if surfaces are involved or fragments are displaced.

Facial Bones↗

PubMed2000

Bilateral skeletonized internal thoracic artery grafting in 303 patients seventy years and older.

OBJECTIVES: Higher patency rates of the internal thoracic artery have led myocardial revascularization with bilateral internal thoracic arteries to be a procedure designated primarily for young patients. Fewer leg wound complications and sternal collateral flow preservation with the skeletonizing dissection technique can make bilateral internal thoracic artery grafting attractive also for elderly patients. METHODS: Between May 1996 and May 1998, 303 consecutive patients aged 70 years or older (mean age 75.5 years; range 70-92 years) underwent coronary artery bypass grafting with double skeletonized internal thoracic arteries. Forty-four (14.5%) patients were 80 years or older, and 89 (28%) had diabetes. The mean number of grafts was 3.1 per patient (2-6). RESULTS: Operative mortality was 2.6% (n = 8): it was higher for octogenarians (6.8%) than for younger patients (1.9%) (P =.06). The only significant preoperative predictors of early mortality were complicated percutaneous transluminal coronary angioplasty (P =.03) and preoperative use of intra-aortic balloon pumping (P =.03). Six patients (2%) had sternal wound infections for which chronic lung disease (P =.02) and emergency operation (P =.006) were the only significant predictors. Twenty-two (7.2%) late deaths occurred, and 1- and 3-year survivals were 93% and 90%, respectively. The 3-year survival of patients 80 years old or older was 92%. CONCLUSIONS: Bilateral grafting of the skeletonized internal thoracic artery carries relatively low morbidity and mortality in elderly patients and can be recommended for selected patients including octogenarians.

Aged↗

PubMed2000

Histologic and physiologic evaluation of skeletonized internal thoracic artery harvesting with an ultrasonic scalpel.

OBJECTIVES: The safety and reliability of a method of skeletonized internal thoracic artery harvesting with an ultrasonic scalpel (Harmonic Scalpel; Ethicon Endo-Surgery, CVG, Cincinnati, Ohio) were evaluated. METHODS: The mural branches of the internal thoracic artery were cut by means of 3 methods, differentiated by distance from the site of application of the Harmonic Scalpel blade to the internal thoracic artery. A total of 15 branches were cut from the internal thoracic artery at (0 mm) the origin (group I) or at 1 mm (group II) or 2 mm (group III) distal to the origin. Tissue preparations were examined for successful vessel closure and severity of tissue damage. The length of stump (L) and the length of tissue damage from the stump (D) were determined by a computer image analysis system, and pressure testing was performed to evaluate the physical strength of vessel closure. RESULTS: In group I, 8 of the 15 branches exhibited discontinuity of the vascular wall structure, probably because of insufficient sealing of the divided section, and 12 of the 15 branches exhibited tissue denaturation on the internal thoracic artery wall adjacent to areas of origin, which was probably caused by the heat transferred from the branches during the process of coagulation. In groups II and III, continuity of wall structure of stumps suggestive of stable closure of branches was confirmed. The lengths of tissue damage from the stump (D) were 0.96, 0.58, and 0.63 mm in groups I, II, and III, respectively, and the lengths of intact area (L - D) in the corresponding groups were -0.78, 0.61, and 1.51 mm. The negative figure in group I indicates the presence of tissue damage in the internal thoracic artery itself. By contrast, in groups II and III the internal thoracic arteries were intact, with a safety margin of greater than 0.5 mm. On physiologic evaluation of vessel closure, 2 of the 24 (8.3%) branches burst under a pressure lower than 350 mm Hg because of insufficient vessel coagulation, but the remaining 22 branches (91.7%) remained intact under pressures up to 350 mm Hg. CONCLUSION: The internal thoracic artery skeletonization method with an ultrasonic scalpel (Harmonic Scalpel: output level 2) appears to be a safe and reliable method of skeletonized internal thoracic artery harvesting when branches are sectioned at least 1 mm distal to their origin at a sufficiently slow speed.

Animals↗

PubMed2006

Naked corals: skeleton loss in Scleractinia.

Stony corals, which form the framework for modern reefs, are classified as Scleractinia (Cnidaria, Anthozoa, and Hexacorallia) in reference to their external aragonitic skeletons. However, persistent notions, collectively known as the "naked coral" hypothesis, hold that the scleractinian skeleton does not define a natural group. Three main lines of evidence have suggested that some stony corals are more closely related to one or more of the soft-bodied hexacorallian groups than they are to other scleractinians: (i) morphological similarities; (ii) lack of phylogenetic resolution in molecular analyses of scleractinians; and (iii) discrepancy between the commencement of a diverse scleractinian fossil record at 240 million years ago (Ma) and a molecule-based origination of at least 300 Ma. No molecular evidence has been able to clearly reveal relationships at the base of a well supported clade composed of scleractinian lineages and the nonskeletonized Corallimorpharia. We present complete mitochondrial genome data that provide strong evidence that one clade of scleractinians is more closely related to Corallimorpharia than it is to a another clade of scleractinians. Thus, the scleractinian skeleton, which we estimate to have originated between 240 and 288 Ma, was likely lost in the ancestry of Corallimorpharia. We estimate that Corallimorpharia originated between 110 and 132 Ma during the late- to mid-Cretaceous, coinciding with high levels of oceanic CO(2), which would have impacted aragonite solubility. Corallimorpharians escaped extinction from aragonite skeletal dissolution, but some modern stony corals may not have such fortunate fates under the pressure of increased anthropogenic CO(2) in the ocean.

Animals↗

PubMed1999

The early Upper Paleolithic human skeleton from the Abrigo do Lagar Velho (Portugal) and modern human emergence in Iberia.

The discovery of an early Upper Paleolithic human burial at the Abrigo do Lagar Velho, Portugal, has provided evidence of early modern humans from southern Iberia. The remains, the largely complete skeleton of a approximately 4-year-old child buried with pierced shell and red ochre, is dated to ca. 24,500 years B.P. The cranium, mandible, dentition, and postcrania present a mosaic of European early modern human and Neandertal features. The temporal bone has an intermediate-sized juxtamastoid eminence. The mandibular mentum osseum and the dental size and proportions, supported by mandibular ramal features, radial tuberosity orientation, and diaphyseal curvature, as well as the pubic proportions align the skeleton with early modern humans. Body proportions, reflected in femorotibial lengths and diaphyseal robusticity plus tibial condylar displacement, as well as mandibular symphyseal retreat and thoracohumeral muscle insertions, align the skeleton with the Neandertals. This morphological mosaic indicates admixture between regional Neandertals and early modern humans dispersing into southern Iberia. It establishes the complexities of the Late Pleistocene emergence of modern humans and refutes strict replacement models of modern human origins.

Animals↗

PubMed2001

Regulation of the glycophorin C-protein 4.1 membrane-to-skeleton bridge and evaluation of its contribution to erythrocyte membrane stability.

The band 3-ankyrin-spectrin bridge and the glycophorin C-protein 4.1-spectrin/actin bridge constitute the two major tethers between the erythrocyte membrane and its spectrin skeleton. Although a structural requirement for the band 3-ankyrin bridge is well established, the contribution of the glycophorin C-protein 4.1 bridge to red cell function remains to be defined. In order to explore this latter bridge further, we have identified and/or characterized five stimuli that sever the linkage in intact erythrocytes and have examined the impact of this rupture on membrane mechanical properties. We report here that elevation of cytosolic 2,3-bisphosphoglycerate, an increase in intracellular Ca(2+), removal of cell O(2), a decrease in intracellular pH, and activation of erythrocyte protein kinase C all promote dissociation of protein 4.1 from glycophorin C, leading to reduced retention of glycophorin C in detergent-extracted spectrin/actin skeletons. Significantly, where mechanical studies could be performed, we also observe that rupture of the membrane-to-skeleton bridge has little or no impact on the mechanical properties of the cell, as assayed by ektacytometry and nickel mesh filtration. We, therefore, suggest that, although regulation of the glycophorin C-protein 4.1-spectrin/actin bridge likely occurs physiologically, the role of the tether and the associated regulatory changes remain to be established.

2,3-Diphosphoglycerate↗

PubMed2003

Rh-RhAG/ankyrin-R, a new interaction site between the membrane bilayer and the red cell skeleton, is impaired by Rh(null)-associated mutation.

Several studies suggest that the Rh complex represents a major interaction site between the membrane lipid bilayer and the red cell skeleton, but little is known about the molecular basis of this interaction. We report here that ankyrin-R is capable of interacting directly with the C-terminal cytoplasmic domain of Rh and RhAG polypeptides. We first show that the primary defect of ankyrin-R in normoblastosis (nb/nb) spherocytosis mutant mice is associated with a sharp reduction of RhAG and Rh polypeptides. Secondly, our flow cytometric analysis of the Triton X-100 extractability of recombinant fusion proteins expressed in erythroleukemic cell lines suggests that the C-terminal cytoplasmic domains of Rh and RhAG are sufficient to mediate interaction with the erythroid membrane skeleton. Using the yeast two-hybrid system, we demonstrate a direct interaction between the cytoplasmic tails of Rh and RhAG and the second repeat domain (D2) of ankyrin-R. This finding is supported by the demonstration that the substitution of Asp-399 in the cytoplasmic tail of RhAG, a mutation associated with the deficiency of the Rh complex in one Rhnull patient, totally impaired interaction with domain D2 of ankyrin-R. These results identify the Rh/RhAG-ankyrin complex as a new interaction site between the red cell membrane and the spectrin-based skeleton, the disruption of which might result in the stomato-spherocytosis typical of Rhnull red cells.

Animals↗

PubMed1987

Distribution of 239Pu in the skeleton of the tree shrew (Tupaia belangeri) between 15 and 50 months after injection.

The macroscopic and microscopic distribution of intramuscularly injected, essentially monomeric, 239Pu was studied in the skeleton of the adult tree shrew (Tupaia belangeri). Data for the period between 15 and 50 months after injection are presented and compared with the data from earlier time points. Between 83 and 500 days after injection the nuclide content and the wet weight of the skeleton decreased to a constant level at about 55 per cent of the maximum values. The microscopic distribution has been analysed in distal femora, proximal humerus, proximal tibia and lumbar vertebra over the whole observation time; additionally at some selected time points proximal femur, femur shaft, distal humerus and distal tibia were analysed. The initial endosteal surface activity ranged from 3.8 to 5.3 Bq/cm2 and decreased to a minimum at about 1000 days after injection and increased thereafter. A similar behaviour was found for the dose rate near bone surfaces which was initially about 0.075 Gy/day on endosteal surfaces. In the deep bone and the deep marrow the dose rate was negligible, about 0.008 Gy/day and 0.001 Gy/day, respectively. The average cumulative dose 1500 days after injection was about 67 Gy on the endosteum, six times greater than the cumulative dose calculated from the mean concentration of plutonium in the whole skeleton. All values are normalized to an injected activity of 37 kBq/kg body weight. The tupaia data are discussed in relation to the available data from monkeys, dogs and rats.

Animals↗

PubMed1988

Identification of a membrane skeleton in platelets.

Platelets have previously been shown to contain actin filaments that are linked, through actin-binding protein, to the glycoprotein (GP) Ib-IX complex, GP Ia, GP IIa, and an unidentified GP of Mr 250,000 on the plasma membrane. The objective of the present study was to use a morphological approach to examine the distribution of these membrane-bound filaments within platelets. Preliminary experiments showed that the Triton X-100 lysis buffers used previously to solubilize platelets completely disrupt the three-dimensional organization of the cytoskeletons. Conditions were established that minimized these postlysis changes. The cytoskeletons remained as platelet-shaped structures. These structures consisted of a network of long actin filaments and a more amorphous layer that outlined the periphery. When Ca2+ was present, the long actin filaments were lost but the amorphous layer at the periphery remained; conditions were established in which this amorphous layer retained the outline of the platelet from which it originated. Immunocytochemical experiments showed that the GP Ib-IX complex and actin-binding protein were associated with the amorphous layer. Analysis of the amorphous material on SDS-polyacrylamide gels showed that it contained actin, actin-binding protein, and all actin-bound GP Ib-IX. Although actin filaments could not be visualized in thin section, the actin presumably was in a filamentous form because it was solubilized by DNase I and bound phalloidin. These studies show that platelets contain a membrane skeleton and suggest that it is distinct from the network of cytoplasmic actin filaments. This membrane skeleton exists as a submembranous lining that, by analogy to the erythrocyte membrane skeleton, may stabilize the plasma membrane and contribute to determining its shape.

Actins↗

PubMed1998

Regulation mechanism of the lateral diffusion of band 3 in erythrocyte membranes by the membrane skeleton.

Mechanisms that regulate the movement of a membrane spanning protein band 3 in erythrocyte ghosts were investigated at the level of a single or small groups of molecules using single particle tracking with an enhanced time resolution (0.22 ms). Two-thirds of band 3 undergo macroscopic diffusion: a band 3 molecule is temporarily corralled in a mesh of 110 nm in diameter, and hops to an adjacent mesh an average of every 350 ms. The rest (one-third) of band 3 exhibited oscillatory motion similar to that of spectrin, suggesting that these band 3 molecules are bound to spectrin. When the membrane skeletal network was dragged and deformed/translated using optical tweezers, band 3 molecules that were undergoing hop diffusion were displaced toward the same direction as the skeleton. Mild trypsin treatment of ghosts, which cleaves off the cytoplasmic portion of band 3 without affecting spectrin, actin, and protein 4.1, increased the intercompartmental hop rate of band 3 by a factor of 6, whereas it did not change the corral size and the microscopic diffusion rate within a corral. These results indicate that the cytoplasmic portion of band 3 collides with the membrane skeleton, which causes temporal confinement of band 3 inside a mesh of the membrane skeleton.

Anion Exchange Protein 1, Erythrocyte↗

PubMed1978

Rat liver nuclear skeleton and small molecular weight RNA species.

Small molecular weight RNA species (smwRNAs) were studied in rat liver nuclei with and without chromatin as well as with and without nuclear envelope and nucleoplasm. From all the species identified, only two, N5 and 5Sb, were related to ribosomes. The others were localized exclusively in the nuclear skeleton or the spongelike network that was described in the preceding communication. This network or protein matrix contains a less abundant but exclusive set of molecules designated 5Sa, N1, and 4.5S, as well as other more abundant molecules which also exist in rat liver endoplasmic reticulum but not in polysomes or postribosomal RNP complexes. The smwRNAs behave like HnRNA; they remain located in the nuclear skeleton when nuclei are deprived of nucleoplasm and chromatin. With the information presently available, it is not possible to know whetherer both species are in the same or different RNP complexes and whether some of the smwRNAs contribute to the architecture of the nuclear skeleton. Distinct from any other nuclear RNA species, smwRNAs have two unique properties: facility of extraction, and resistance to nuclear ribonuclease digestion.

Animals↗