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PubMed2003

Developmental morphology of the axial skeleton of the zebrafish, Danio rerio (Ostariophysi: Cyprinidae).

Before our rapidly increasing knowledge of gene interactions can be connected with the morphologic defects in mutant zebrafish, the normal course of skeletal development must be understood. Here, we describe the developmental morphology of the axial skeleton of zebrafish and review it in relation to the morphology of related species. The relative sequence of ossification in the skeleton is described. Two separate centers of development were found in the axial skeleton (Weberian apparatus and caudal fin) in contrast to tetrapods, which have a single anterior center. Slight variation was found in the overall relative timing of development. The extensive ichthyological literature on teleost anatomy and recent genetic data form the basis for our review and interpretation of homologies of various elements of the axial skeleton. Because homology forms the basis for all evolutionary comparisons, these data are critical for integration in evo-devo studies.

Animals↗

PubMed1994

Accuracy, precision, and utility of spine and whole-skeleton mineral measurements by DXA in rats.

We evaluated the precision and accuracy of dual-energy x-ray bone densitometry (DXA) in 38 male and female rats aged 1-10 months. The coefficients of variation (CV) estimated from same-day paired measurements of bone mineral content (BMC) were 1.26% at the lumbar spine and 0.69% at the whole skeleton, and the corresponding CV for BMC corrected for projected bone area (i.e., bone mineral density, BMD) were 0.57 and 0.66%. BMC, measured in vivo, correlated closely with the subsequently determined ash weights (spine r2 = 0.94, whole-skeleton r2 = 0.97). The long-term CV for BMC measurements, assessed by measuring a frozen animal daily for 4 weeks, were 1.28% for the spine and 1.03% for the whole skeleton; for BMD the corresponding CV were 0.88 and 1.15%. To examine the utility of serial DXA measurements we followed female rats subjected to ovariectomy (OVX) or sham operation at 10 months of age and male rats given daily subcutaneous injections of hPTH-(1-34) or vehicle starting at 10 months of age every 3 weeks for 15 weeks. In the OVX rats a progressive decrease in spine BMC was observed that was most rapid during the first 6 weeks. By 15 weeks the mean spine BMC decreased by 17% in the OVX rats (p < 0.007 versus sham operation). OVX did not affect the accuracy of DXA measurements as assessed by comparison with the ash weight at the end of the 15 week study. PTH treatment increased spine BMC by a mean of 32% and increased whole-skeleton BMC by a mean of 19% within 15 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed2001

Proteins and saccharides of the sea urchin organic matrix of mineralization: characterization and localization in the spine skeleton.

Properties of the echinoderm skeleton are under biological control, which is exerted in part by the organic matrix embedded in the mineralized part of the skeleton. This organic matrix consists of proteins and glycoproteins whose carbohydrate component is specifically involved in the control mechanisms. The saccharide moiety of the organic matrix of the spines of the echinoid Paracentrotus lividus was characterized using enzyme-linked lectin assays (ELLAs). O-glycoproteins, different types of complex N-glycoproteins, and terminal sialic acids were detected. Sialic acids are known to interact with Ca ions and could play an important role in the mineralization process. Some of the carbohydrate components detected by ELLAs as well as two organic matrix proteins (SM30 and SM50) were localized within different subregions of the spine skeleton using field-emission scanning electron microscopy. The mappings show that some of these components are not homogeneously distributed in the different skeletal subregions. For example, some N-glycoproteins were preferentially located in the putative amorphous subregion of the skeleton, whereas some O-glycoproteins were localized in the subregion where skeletal growth is inhibited. These results suggest that the biological control exerted on the skeletal properties can be partly modulated by local differences in the organic matrix composition.

Animals↗

PubMed1991

Morphological evidence for the association of plasma membrane glycoprotein IIb/IIIa with the membrane skeleton in human platelets.

We examined the association between glycoprotein (GP) IIb/IIIa, a receptor for fibrinogen, and membrane skeletons in both unstimulated and thrombin-activated human platelets. After a treatment with dithiobis succinimidyl propionate (DTSP), a cross-linker, unstimulated and activated platelets were simultaneously extracted and fixed with a fixing solution containing Triton X-100. Also, the localization of GPIIb/IIIa on the plasma membrane was observed by a preembedding staining method of unextracted platelets. In unstimulated platelets, 20-40% of the whole plasma membrane remained in the detergent-extracted samples. Amorphous structures with 10-70 nm in diameters are distributed at 20 to 100-nm intervals on the surface of plasma membrane. Similar structures also were identified in the intact platelets by the immunocytochemical method. By careful inspection, we found that most of the amorphous structures that contained gold particles were connected to the submembrane zone just beneath the plasma membrane. The submembrane zone was identified as the membrane skeleton because actin was detected in the zone. After activation, detergent-insoluble granules were surrounded by dense networks of microfilaments in the central part of platelets. The filaments were identified as actin and became associated with myosin. These results demonstrate that GPIIb/IIIa on the plasma membrane is connected to the membrane skeleton and suggest that, during activation, actin filaments which extend into the cytoplasm from the membrane skeleton increase and form dense networks around Triton-insoluble granules.

Actins↗

PubMed1992

Suppression of the osteogenic response in the aging skeleton.

The ability of physical stimuli demonstrated as potently osteogenic in the young adult skeleton were evaluated for their capacity to stimulate new bone formation in the aging skeleton. Using the externally loadable, functionally isolated turkey ulna preparation, the ulnae of 1-year-old (n = 5), and 3-year-old (n = 3) turkeys were subjected to 300 cycles per day of a load regimen generating a high but physiologic level of normal strain (3,000 microstrain). Following 8 weeks of loading, areal properties and histomorphometry were performed on both the experimental and intact control ulnae. Bone cross-sectional areas in the 1-year-old animal increased by 30.2% (+/- 7.8%) as compared with the intact contralateral control ulnae, whereas the areal properties of the older skeleton remained essentially unchanged (-3.3 +/- 7.5%). Renewed bone formation in the experimental ulnae of the 1-year-old animals was characterized by the activation of periosteal bone apposition (4.0 +/- 0.4 microns/day). In comparison, periosteal bone formation in the 3-year-old males was activated in only 1 animal, and this at a significantly attenuated level (less than 0.8 micron/day). The histomorphometric evaluation of intracortical bone remodeling revealed no significant differences between the control and experimental ulnae in either age group. However, osteon mean wall thickness and bone formation sigma were significantly increased in the 3-year-old males (P less than 0.05). In conclusion, these data suggest that a physical signal that is clearly osteogenic in the young adult skeleton is hardly acknowledged in older bone tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1993

Immunocytochemical study of membrane skeletons in abnormally shaped erythrocytes as revealed by a quick-freezing and deep-etching method.

Ultrastructures of membrane skeletons in spherocytic and elliptocytic erythrocytes were investigated immunocytochemically. Erythrocytes obtained from patients with hereditary spherocytosis (HS) and hereditary elliptocytosis (HE) were split open mechanically to obtain exposed cytoplasmic sides of erythrocyte membranes and were immunostained with anti-spectrin antibody. Replica membranes were prepared by a quick-freezing and deep-etching method and were checked by electron microscopy. The in situ membrane skeletons of normal erythrocytes consisted mainly of reticular patterns of spectrin filaments, which formed networks on the cytoplasmic sides of the cell membrane. In contrast, the membrane skeletons of abnormally shaped erythrocytes (HS and HE) were much less filamentous and more granular than those of normal erythrocytes. This abnormal organization in erythrocyte membrane skeletons may be one of the factors that induce abnormally shaped erythrocytes in HS and HE patients.

Adult↗

PubMed1998

Risk factors for the development of vertebral and total skeleton osteoporosis in patients with primary biliary cirrhosis.

The objectives of this work was to (1) study the bone mineral density (BMD) of the lumbar spine, total skeleton, and body composition in patients with primary biliary cirrhosis (PBC) and (2) evaluate the risk factors (premature menopause, stages of the disease, hyperbilirubinemia) and bone and liver biochemical parameters for the development of osteoporosis. We studied 23 women with a compatible diagnosis of PBC. The BMD and body composition were evaluated by X-ray absorptiometry (Lunar DPX-L). The average age of the population was 56.7 +/- 10.2 years. The BMD of the lumbar spine and of the total skeleton was 1.3 SDs below the normal population matched for sex and age. In the total skeleton, the legs were the most severely affected area (Z score -1.5). The body composition showed no significant difference compared with the normal population. The BMD of 56% of the patients was less than -2.5 SDs from the average normal young values. Patients with a history of vertebral fractures had diminished mineral density of the lumbar spine, as did those who had had no fractures. Of the risk factors studied, patients with premature menopause had a lower bone mass compared with patients with normal menopausal age (Z score of the total skeleton was -2.1 +/- 1.8 versus -1.1 +/- 1.0) but the difference did not reach statistical significance. The bone mass was not affected in patients with regular menstrual cycles. There were no statistically significant differences in high levels of bilirubin, advanced stages of the disease, or the biochemical variables studied. It is concluded that patients with primary biliary cirrhosis present diminished cortical and trabecular bone mass, whereas body composition was unaffected. Premature hormone deficit, possibly triggered by the chronic hepatic pathology, is a contributing factor to the osteoporosis in this population.

Adult↗

PubMed1995

Wheat germ agglutinin stabilization of erythrocyte shape: role of bilayer balance and the membrane skeleton.

The effects of wheat germ agglutinin (WGA), Limulus lectin, and concanavalin A on cell shape changes were examined in human erythrocytes. These agents inhibited echinocytosis in cells having elevated cytosolic Ca2+ or incorporated foreign phosphatidylcholine, but had no effect on cell stomatocytosis in response to incorporated phosphatidylserine. The role of the membrane skeleton in this selective membrane fixation was examined. WGA inhibited echinocytosis in cells previously depleted of polyphosphoinositides to reduce membrane skeleton binding to transmembrane proteins, treated with phorbol ester to enhance protein 4.1 phosphorylation, heat-treated to denature spectrin, alkylated with p-chloromercuribenzoate to dissociate glycophorin from the membrane skeleton, or subjected to elevated cell 2,3-diphosphoglycerate to alter organization of the spectrin-actin-protein 4.1 complex. Limulus lectin and increased concentrations of WGA also stabilized discoid shape in pronase-digested cells containing no detectable intact glycophorin. In contrast, cell digestion with sialidase abolished the shape-stabilizing effect of WGA. The results suggest that the membrane skeleton is not involved in WGA shape stabilization. Rather, they suggest that glycoproteins and glycolipids interact with the lectin to stabilize cell surface molecular associations, forming a superficial calyx that inhibits outward, but not inward, membrane bending.

Adult↗

PubMed1986

Computing the skeleton of coronary arteries in cineangiograms.

In this paper we describe techniques to determine the skeleton of coronary arteries and to measure their medically significant geometric properties (such as boundaries and orientations) in cineangiograms. We use these geometric properties for segmentation, i.e., for separating the image of the arteries from the background. The purpose of this segmentation is to produce a structural description of the arterial tree for high-level processing. Our technique is completely automatic, efficient, and reliable. Our technique starts with the detection of skeleton points from a local ridge detector using density profiles of the arteries. Local orientations of skeleton points are obtained directly from the ridge detection or from local edge directions. Boundaries of the arteries are computed from the density profile along a straight line perpendicular to the skeleton. From this, a sequential and raster-scan tracking procedure is applied to obtain segments of the arteries from two scanning directions. The final segments are generated by merging all the segments.

Algorithms↗

PubMed1989

The spectrin-actin junction of erythrocyte membrane skeletons.

High-resolution electron microscopy of erythrocyte membrane skeletons has provided striking images of a regular lattice-like organization with five or six spectrin molecules attached to short actin filaments to form a sheet of five- and six-sided polygons. Visualization of the membrane skeletons has focused attention on the (spectrin)5,6-actin oligomers, which form the vertices of the polygons, as basic structural units of the lattice. Membrane skeletons and isolated junctional complexes contain four proteins that are stable components of this structure in the following ratios: 1 mol of spectrin dimer, 2-3 mol of actin, 1 mol of protein 4.1 and 0.1-0.5 mol of protein 4.9 (numbers refer to mobility on SDS gels). Additional proteins have been identified that are candidates to interact with the junction, based on in vitro assays, although they have not yet been localized to this structure and include: tropomyosin, tropomyosin-binding protein and adducin. The spectrin-actin complex with its associated proteins has a key structural role in mediating cross-linking of spectrin into the network of the membrane skeleton, and is a potential site for regulation of membrane properties. The purpose of this article is to review properties of known and potential constituent proteins of the spectrin-actin junction, regulation of their interactions, the role of junction proteins in erythrocyte membrane dysfunction, and to consider aspects of assembly of the junctions.

Actins↗

PubMed1995

Autosomal dominant osteopetrosis: bone mineral measurements of the entire skeleton of adults in two different subtypes.

Bone mineral content (BMC) and density (BMD) were measured by dual-energy X-ray absorptiometry in two subtypes of autosomal dominant osteopetrosis (ADO). Both types have been radiologically characterized by diffuse symmetrical osteosclerosis, but with characteristic differences. Increased thickness of the cranial vault is a typical finding in type I ADO, whereas endobones in the pelvis and end-plate thickening in the spine are obligate findings in type II. Eleven patients with type I from three kindreds, and seven patients with type II, one family participated in the study, and were compared with 18 age- and sex-matched normal controls. Whole-body BMC and BMD were measured, and regions of special interest were selected: head, axial, and appendicular skeleton. Moreover, lumbar spine and femoral neck scans were performed. Whole-body BMC and BMD, mostly reflecting cortical bone, were markedly increased in both types compared with normals. A pronounced osteosclerosis was present in the axial as well as the appendicular skeleton. Median BMD was markedly increased in the axial skeleton by 51% (44-56) and 42% (33-56), (median differences with 95% CI), respectively, for types I and II compared to normal controls, and in the appendicular skeleton by 48% (37-59) and 38% (16-45). No overlap between observed ranges of patients and controls was observed. A positive correlation between age and whole-body BMD was demonstrated in ADO, but not in the control group, indicating progressive osteosclerosis with age. Median BMD of the lumbar spine, which mostly reflects trabecular bone, showed increased densities in both types, 71% (51-84) and 59% (37-93), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed2004

Should the internal thoracic artery be skeletonized?

Traditionally, the internal thoracic artery is harvested as a pedicle. In contemporary cardiac surgical practice, however, certain surgeons practice the internal thoracic artery-skeletonization technique. A systematic review of clinical studies reporting on the use of skeletonized internal thoracic arteries (SKT-ITA) has not yet been performed. The primary aim of this review article is to examine comprehensively the entire body of evidence regarding the use of SKT-ITA. In particular, we aimed to analyze the effects of skeletonization on sternal blood supply, wall damage and blood flow in the harvested vessel, postoperative graft patency, and clinical outcome. Advantages and disadvantages of the skeletonization technique are highlighted and discussed.

Coronary Artery Bypass↗

PubMed2004

The cooperative role of membrane skeleton and bilayer in the mechanical behaviour of red blood cells.

Red blood cell (RBC) shape, behaviour and deformability can be consistently accounted for by a model for the elastic properties of the RBC membrane that includes the elasticity of the membrane skeleton in dilation and shear, and the local and nonlocal resistance of the bilayer to bending. The role of the corresponding energy terms in different RBC shape and deformation situations is analyzed. RBC shape transformations are compared to the shape transformations of phospholipid vesicles that are driven by the difference between the equilibrium areas of the bilayer leaflets (DeltaA0). It is deduced that the skeleton energy contributions play a crucial role in the formation of an echinocyte. The effect of a transformation of the natural biconcave RBC shape into an echinocyte on its resistance to entry into capillary-sized cylindrical tubes is analyzed. It is shown that, during the aspiration of an echinocyte into a pipette, there are two competing skeleton deformation effects, which arise due to skeleton density changes, one due to spicule formation and the other due to deformation induced by micropipette aspiration. Furthermore, the shift of the observed dependence of the projection length on the aspiration pressure of more crenated cells towards higher aspiration pressures can be accounted for by an increase of the equilibrium area difference DeltaA0 and consequent modification of the nonlocal contribution to the cell elastic energy.

Biomechanical Phenomena↗

PubMed2006

Low-level mechanical vibrations can influence bone resorption and bone formation in the growing skeleton.

Short durations of extremely small magnitude, high-frequency, mechanical stimuli can promote anabolic activity in the adult skeleton. Here, it is determined if such signals can influence trabecular and cortical formative and resorptive activity in the growing skeleton, if the newly formed bone is of high quality, and if the insertion of rest periods during the loading phase would enhance the efficacy of the mechanical regimen. Eight-week-old female BALB/cByJ mice were divided into four groups, baseline control (n = 8), age-matched control (n = 10), whole-body vibration (WBV) at 45 Hz (0.3 g) for 15 min day(-1) (n = 10), and WBV that were interrupted every second by 10 of rest (WBV-R, n = 10). In vivo strain gaging of two additional mice indicated that the mechanical signal induced strain oscillations of approximately 10 microstrain on the periosteal surface of the proximal tibia. After 3 weeks of WBV, applied for 15 min each day, osteoclastic activity in the trabecular metaphysis and epiphysis of the tibia was 33% and 31% lower (P <0.05) than in age-matched controls. Bone formation rates (BFR.BS(-1)) on the endocortical surface of the metaphysis were 30% greater (P <0.05) in WBV than in age-matched control mice but trabecular and middiaphyseal BFR were not significantly altered. The insertion of rest periods (WBV-R) failed to potentiate the cellular effects. Three weeks of either WBV or WBV-R did not negatively influence body mass, bone length, or chemical bone matrix properties of the tibia. These data indicate that in the growing skeleton, short daily periods of extremely small, high-frequency mechanical signals can inhibit trabecular bone resorption, site specifically attenuate the declining levels of bone formation, and maintain a high level of matrix quality. If WBV prove to be efficacious in the growing human skeleton, they may be able to provide the basis for a non-pharmacological and safe means to increase peak bone mass and, ultimately, reduce the incidence of osteoporosis or stress fractures later in life.

Animals↗

PubMed2005

Determining protein topology from skeletons of secondary structures.

We report a novel computational procedure for determining protein native topology, or fold, by defining loop connectivity based on skeletons of secondary structures that can usually be obtained from low to intermediate-resolution density maps. The procedure primarily involves a knowledge-based geometry filter followed by an energetics-based evaluation. It was tested on a large set of skeletons covering a wide range of protein architecture, including one modeled from an experimentally determined 7.6A cryo-electron microscopy (cryo-EM) density map. The results showed that the new procedure could effectively deduce protein folds without high-resolution structural data, a feature that could also be used to recognize native fold in structure prediction and to interpret data in fields like structure genomics. Most importantly, in the energetics-based evaluation, it was revealed that, despite the inevitable errors in the artificially constructed structures and limited accuracy of knowledge-based potential functions, the average energy of an ensemble of structures with slightly different configurations around the native skeleton is a much more robust parameter for marking native topology than the energy of individual structures in the ensemble. This result implies that, among all the possible topology candidates for a given skeleton, evolution has selected the native topology as the one that can accommodate the largest structural variations, not the one rigidly trapped in a deep, but narrow, conformational energy well.

Algorithms↗

PubMed2004

Finite element growth analysis for the craniofacial skeleton in patients with cleft lip and palate.

The purpose of this study was to clarify the differences in the nature of craniofacial growth between subjects with normal occlusion and patients with unilateral cleft lip and palate (CLP) in terms of the size, shape and principal growth direction of craniofacial skeleton using finite element method (FEM). Lateral cephalograms were taken of 40 subjects as normal group and 178 patients as CLP group. These subjects were divided into seven developmental ages of 4-, 6-, 8-, 10-, 12-, 14- and 18-year-old. For the finite element analysis, the craniofacial complex was discretized into seven structures or elements with three nodal points in each after tracing each lateral cephalogram on acetate paper. For each stage, the growth parameters in CLP group were compared to those in normal group. The growth of upper facial skeleton and maxillary complex was more remarkably inhibited in CLP than in normal group. Especially, the growth inhibition of posterior maxillary complex in a vertical direction was remarkable in CLP group at any ages. Difference in the size and shape of entire mandibular skeleton between CLP and normal groups was not apparent. It is suggested that grow timing and peak velocity, an essential and key determinant to the success in orthodontic treatment, have been clarified in this study more clearly than in previous studies. It is hopefully anticipated to explore some key determinants to predict individual growth of the craniofacial skeleton near future.

Adolescent↗

PubMed2002

Bilateral skeletonized internal thoracic artery graftings in off-pump coronary artery bypass: early result of Y versus in situ grafts.

BACKGROUND: Use of bilateral skeletonized internal thoracic arteries (ITAs) in off-pump coronary artery bypass (OPCAB) retains several advantages that may eventually result in better patient outcomes. We compared the early results of OPCAB using bilateral ITAs as Y grafts with results of OPCAB using bilateral ITAs as in situ grafts. METHODS: A total of 223 consecutive patients who underwent OPCAB using bilateral skeletonized ITAs as Y grafts (group I, n = 113) or in situ grafts (group II, n = 110) were studied. RESULTS: Both the number of distal anastomoses per patient and the number of distal anastomoses per bilateral ITA were higher in group I (3.5 +/- 1.0 and 2.9 +/- 0.7) than in group II (3.0 +/- 0.7 and 2.4 +/- 0.5) (p < 0.01). Hospital mortality was 1.8% (2/113) in group I and 0.9% (1/110) in group II (p = ns). There were no differences in postoperative complications including atrial fibrillation (13.3% vs 10.9%), perioperative myocardial infarction (0.9% vs 2.7%), mediastinitis (0.9% vs 1.8%), and hypoperfusion syndrome (0.9% vs 0%) between groups I and II (p = ns). Postoperative coronary angiographies performed in 110 patients in group I and 108 patients in group II showed 99.0% (382/386) overall patency and 99.4% (319/321) patency for distal anastomoses using ITAs in group I, and 98.1% (312/318) overall patency and 98.1% (258/263) patency for distal anastomoses using ITA in group II. There were no significant differences in graft patency rates between the two groups (p = ns). CONCLUSIONS: Our results demonstrate that OPCAB using bilateral skeletonized ITAs is technically feasible, with excellent graft patency. Using bilateral skeletonized ITAs as Y grafts increases the number of distal anastomoses that can be performed and does not cause additional postoperative morbidity.

Atrial Fibrillation↗

PubMed2002

Changing pattern in beating heart operations: use of skeletonized internal thoracic artery.

BACKGROUND: The use of skeletonized internal thoracic artery (ITA) was reported to be technically and hemodynamically beneficial in conventional coronary artery bypass grafting with cardiopulmonary bypass assistance. The purpose of this study is to evaluate the impact of changing from conventional to skeletonized ITA harvesting on early off-pump coronary artery bypass grafting outcome. METHODS: Between 1996 and 2001, 640 patients underwent systematic off-pump coronary artery bypass grafting (single surgeon experience). The ITA was pedicled (P) in the first consecutive 440 patients and skeletonized (S) in the subsequent 200 consecutive patients. Mean age, preoperative risk factors, sex, number of involved territories, and incidence of reoperations were similar in both groups. RESULTS: In group S, number of ITAs per patient (1.7 +/- 0.08 versus 1.2 +/- 0.05; p < 0.001), bilateral ITA (46% versus 27%; p < 0.001), ITA sequential grafts (27% versus 1%; p < 0.001), and T grafts (16% versus 3%; p < 0.001) were higher. Deep sternal infections were comparable in both groups (group S: 1%, group P: 1.2%; p = 0.38). Perioperative myocardial infarction, maximal creatinine kinase-MB level, and requirement for more than 24 hours of inotropic support were comparable in both groups. Thirty-day mortality was also similar (S: 1.7%, P: 1.6%). CONCLUSIONS: Changing to routine use of skeletonized ITA in off-pump coronary artery bypass grafting is a safe alternative to routine pedicled ITA. In our experience, this procedure has facilitated the use of ITA anastomosis without increasing sternal wound complications.

Aged↗