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At least 217 records · Page 12Linked to original sources

PubMed2005

Anthropometric and physical abilities profiles: US National Skeleton Team.

The aim of this study was to characterize sprint ability, anthropometry, and lower extremity power in the US National Team Skeleton athletes. Fourteen athletes (male n = 7; mean +/- SD: height 1.794 +/- 0.063 m, body mass 81.2 +/- 3.7 kg, age 26.9 +/- 4.1 years; female n = 7; 1.642 +/- 0.055 m, 60.1 +/- 5.9 kg, 27.3 +/- 6.9 years) volunteered to participate. Sprinting ability was measured over multiple intervals using custom infrared timing gates in both an upright and a crouched sprint. The crouched sprint was performed while pushing a wheeled-simulated skeleton sled on rails on an outdoor skeleton and bobsleigh start track. Crouched skeleton sprint starts were able to achieve about 70% to 85% of the upright sprint times. The mean somatotype ratings for females were: 3.5-3.5-2.1, and males: 3.6-4.9-1.9. Lower extremity strength and power were measured via vertical jumps on a portable force platform using squat and countermovement jumps, and jumps with added mass. Jump height, power, rate offorce development and peak force were determined from force-time data. Lower extremity strength and power were strongly correlated with both upright and crouched sprint times. The results indicated that these athletes are strong sprinters with varying body structures, mostly mesomorphic, and that stronger and more powerful athletes tend to be better starters.

Adult↗

PubMedDate not supplied

Axial skeleton and pituitary gland in human fetuses with spina bifida and cranial encephalocele.

The purpose of this study was to investigate the axial skeleton and the pituitary gland in fetuses with spina bifida or cranial encephalocele in order to elucidate the pathogenesis of the conditions. The findings were related to former investigations performed on normal fetuses and on fetuses with anencephaly and rachischisis. Eight human fetuses from spontaneous or therapeutic abortions, 11-28 weeks of gestational age, were investigated. Radiographs were taken of the axial skeleton and histological investigation, including immunohistochemical marking for thyroid-stimulating hormone was performed on tissue blocks of the cranial base, including the sella turcica and the pituitary gland. Radiography revealed only minor malformations in the axial skeleton and not in all cases. The types of malformations resembled those seen in anencephaly and rachischisis. Histological investigations revealed severe malformations in the sella turcica region in spina bifida and minor ones in cranial encephalocele. Pharyngeally located adenopituitary gland tissue occurred in all fetuses. Anencephaly and cranial encephalocele seemingly are conditions resulting from different expressivity of the same multifactorial process of maldevelopment involving mesoderm (skeleton), neurectoderm (spinal cord and brain), and surface ectoderm (adenopituitary gland tissue). It is suggested that the molecular biological signaling between the notochord, the scleroderm, and the surface ectoderm is disturbed in spina bifida and cranial encephalocele.

Bone and Bones↗

PubMed1986

Control of erythroid differentiation: asynchronous expression of the anion transporter and the peripheral components of the membrane skeleton in AEV- and S13-transformed cells.

Chicken erythroblasts transformed with avian erythroblastosis virus or S13 virus provide suitable model systems with which to analyze the maturation of immature erythroblasts into erythrocytes. The transformed cells are blocked in differentiation at around the colony-forming unit-erythroid stage of development but can be induced to differentiate in vitro. Analysis of the expression and assembly of components of the membrane skeleton indicates that these cells simultaneously synthesize alpha-spectrin, beta-spectrin, ankyrin, and protein 4.1 at levels that are comparable to those of mature erythroblasts. However, they do not express any detectable amounts of anion transporter. The peripheral membrane skeleton components assemble transiently and are subsequently rapidly catabolized, resulting in 20-40-fold lower steady-state levels than are found in maturing erythrocytes. Upon spontaneous or chemically induced terminal differentiation of these cells expression of the anion transporter is initiated with a concommitant increase in the steady-state levels of the peripheral membrane-skeletal components. These results suggest that during erythropoiesis, expression of the peripheral components of the membrane skeleton is initiated earlier than that of the anion transporter. Furthermore, they point a key role for the anion transporter in conferring long-term stability to the assembled erythroid membrane skeleton during terminal differentiation.

Alpharetrovirus↗

PubMed1981

A nucleolar skeleton of protein filaments demonstrated in amplified nucleoli of Xenopus laevis.

The amplified, extrachromosomal nucleoli of Xenopus oocytes contain a meshwork of approximately 4-nm-thick filaments, which are densely coiled into higher-order fibrils of diameter 30-40 nm and are resistant to treatment with high- and low-salt concentrations, nucleases (DNase I, pancreatic RNase, micrococcal nuclease), sulfhydryl agents, and various nonionic detergents. This filamentous "skeleton" has been prepared from manually isolated nuclear contents and nucleoli as well as from nucleoli isolated by fluorescence-activated particle sorting. The nucleolar skeletons are observed in light and electron microscopy and are characterized by ravels of filaments that are especially densely packed in the nucleolar cortex. DNA as well as RNA are not constituents of this structure, and precursors to ribosomal RNAs are completely removed from the extraction-resistant filaments by treatment with high-salt buffer or RNase. Fractions of isolated nucleolar skeletons show specific enrichment of an acidic major protein of 145,000 mol wt and an apparent pI value of approximately 6.15, accompanied in some preparations by various amounts of minor proteins. The demonstration of this skeletal structure in "free" extrachromosomal nucleoli excludes the problem of contaminations by nonnucleolar material such as perinucleolar heterochromatin normally encountered in studies of nucleoli from somatic cells. It is suggested that this insoluble protein filament complex forms a skeleton specific to the nucleolus proper that is different from other extraction-resistant components of the nucleus such as matrix and lamina and is involved in the spatial organization of the nucleolar chromatin and its transcriptional products.

Animals↗

PubMed1984

A cell surface integral membrane glycoprotein of 85,000 mol wt (gp85) associated with triton X-100-insoluble cell skeleton.

The Triton X-100-insoluble skeleton of baby hamster kidney BHK cells consists of the nucleus, intermediate-size filaments, and actin fibers. By transmission electron microscopy, membrane fragments were found to be associated with these insoluble structures. When radioiodinated or [3H]glucosamine-labeled cells were extracted with 0.5% Triton, most plasma membrane glycoproteins were solubilized except for a glycoprotein with a molecular weight of 85,000 (gp85) that remained associated with the insoluble skeletons. Immunoprecipitation with a specific antiserum indicated that the gp85 is not a proteolytic degradation product of fibronectin, an extracellular matrix glycoprotein insoluble in detergent. A monoclonal antibody of BHK cells specific for gp85 was produced. Immunofluorescence analysis with this monoclonal antibody indicated that gp85 is not associated with the extracellular matrix, but is confined to the cell membrane. Both in fixed and unfixed intact cells, fluorescence was concentrated in dots preferentially aligned in streaks on the cell surface. Gp85 was found to behave as an integral membrane protein interacting with the hydrophobic core of the lipid bilayer since it was extracted from membrane preparations by ionic detergents such as SDS, but not by 0.1 N NaOH (pH 12) in the absence of detergents, a condition known to release peripheral molecules. Association of gp85 with the cell skeleton was unaffected by increasing the Triton concentration up to 5%, but it was affected when actin filaments were dissociated or when a protein-denaturing agent (6 M urea) was used in the presence of Triton, suggesting that protein-protein interactions are involved in the association of gp85 with the cell skeleton. We conclude that gp85 is an integral plasma membrane glycoprotein that might have a role in cell surface-cytoskeleton interaction.

Animals↗

PubMed1986

The distribution of blood flow to the whole skeleton in dogs, rabbits and rats measured with microspheres.

The distribution of blood flow to the skeleton was studied by injecting radioactive microspheres into the hearts of anaesthetised adult animals and measuring activity in individual bones and groups of bones. The mean proportion of the cardiac output delivered to the whole skeleton was 7.5% in dogs, 4.2% in rabbits and 4.5% in rats. The results throw doubt on the value for rats of 27% published by Brookes. There was a wide range of flow per unit mass of bone in different parts of the skeleton, demonstrating the inaccuracy of predicting total skeletal flow from measurements on a single bone. The relative distribution to different parts of the skeleton was similar in the three species, but there were quantitative differences.

Animals↗

PubMed2003

Natural marine sponge fiber skeleton: a biomimetic scaffold for human osteoprogenitor cell attachment, growth, and differentiation.

Identification of suitable scaffolds onto which human stem cells can be seeded to generate functional three-dimensional tissues is a major research goal. A natural marine sponge skeleton was selected as a potential scaffold on the basis of the hydration potential of the fiber, the presence of open interconnected channels created by the fiber network, the collagenous composition of the fiber, and the structural diversity of fiber architecture. The skeleton of an undetermined species of Spongia (Class Demospongiae: Order Dictyoceratida: Family Spongiidae), composed of spongin, supported growth of human osteoprogenitor cells. Cell attachment and invasion into the framework were observed within 16 h, followed by development into membranous sheets between the sponge fibers by concentric infilling. Histochemical staining for alkaline phosphatase and type I collagen indicated formation of bone matrix as confirmed by birefringence. At 9 and 14 days alkaline phosphatase-specific activity in sponge fiber-osteoprogenitor cell cultures was significantly greater than in control cultures on cell culture plastic. Adsorption with recombinant human bone morphogenetic protein 2 confirmed the potential of this sponge skeleton as a delivery scaffold for osteogenic factors. The abundance and structural diversity of natural marine sponge skeletons and their potential as multifunctional, cell conductive and inductive frameworks indicate a promising new source of scaffold for tissue regeneration.

Animals↗

PubMed1996

Frequency of throat-skeleton fractures in hanging.

A total of 109 cases of suicidal or accidental hanging were evaluated and the number of hyoid bone or thyroid cartilage fractures or both was investigated in relation to the highest point of the ligature mark. In 73 cases (67%), at least a single fracture of the throat skeleton was detectable, and the youngest individual with positive findings was aged 14 years. In 28 of the 73 positive cases (38%), a single fracture was found, whereas 27 individuals (37%) showed a twofold injury. Three fractures of the throat skeleton were observed in 11 cases (15%), and in seven individuals (10%), all the horns of the hyoid and thyroid cartilage were broken. The youngest individual with four fractures was 28 years old (elastic non-ossified throat skeleton). Even though a higher incidence of positive results and in particular of multiple fractures could be established in cases with a highest point of the ligature mark at or behind the ears, no clear correlation between frequency and number of throat-skeleton fractures was detectable in our series.

Adolescent↗

PubMed2001

Skeletonizing en bloc esophagectomy for cancer.

OBJECTIVE: To evaluate the long-term outcome of patients with esophageal cancer after resection of the extraesophageal component of the neoplastic process en bloc with the esophageal tube. SUMMARY BACKGROUND DATA: Opinions are conflicting about the addition of extended resection of locoregional lymph nodes and soft tissue to removal of the esophageal tube. METHODS: Esophagectomy performed en bloc with locoregional lymph nodes and resulting in a real skeletonization of the nonresectable anatomical structures adjacent to the esophagus was attempted in 324 patients. The esophagus was removed using a right thoracic (n = 208), transdiaphragmatic (n = 39), or left thoracic (n = 77) approach. Lymphadenectomy was performed in the upper abdomen and lower mediastinum in all patients. It was extended over the upper mediastinum when a right thoracic approach was used and up to the neck in 17 patients. Esophagectomy was carried out flush with the esophageal wall as soon as it became obvious that a macroscopically complete resection was not feasible. Neoplastic processes were classified according to completeness of the resection, depth of wall penetration, and lymph node involvement. RESULTS: Skeletonizing en bloc esophagectomy was feasible in 235 of the 324 patients (73%). The 5-year survival rate, including in-hospital deaths (5%), was 35% (324 patients); it was 64% in the 117 patients with an intramural neoplastic process versus 19% in the 207 patients having neoplastic tissue outside the esophageal wall or surgical margins (P <.0001). The latter 19% represented 12% of the whole series. The 5-year survival rate after skeletonizing en bloc esophagectomy was 49% (235 patients), 49% for squamous cell versus 47% for glandular carcinomas (P =.4599), 64% for patients with an intramural tumor versus 34% for those with extraesophageal neoplastic tissue (P <.0001), and 43% for patients with fewer than five metastatic nodes versus 11% for those with involvement of five or more lymph nodes (P =.0001). CONCLUSIONS: The strategy of attempting skeletonizing en bloc esophagectomy in all patients offers long-term survival to one third of the patients with resectable extraesophageal neoplastic tissues. These patients represent 12% of the patients with esophageal cancer suitable for esophagectomy and 19% of those having neoplastic tissue outside the esophageal wall or surgical margins.

Adenocarcinoma↗

PubMed1998

Alternative techniques in rigid fixation of the craniomaxillofacial skeleton.

Rigid fixation techniques in pediatric craniofacial surgery have enhanced our clinical results by offering greater stabilization and control of bone grafts and osteotomized free segments of the craniofacial skeleton. A potential disadvantage of rigid fixation techniques in the growing craniofacial skeleton includes possible long-term growth restrictions, which have been demonstrated in various animal models. Our goal was to evaluate alternative fixation techniques in the growing craniofacial skeleton of the rabbit to study how altering fixation techniques affects craniofacial development. Eighty New Zealand White rabbits were used in this study. Rabbits were divided into eight groups of 10 each, and seven variant fixation techniques were used to stabilize the frontal bones after bifrontal craniectomies. In all groups except Group 1, the animals underwent a bifrontal craniectomy with orthotopic replacement of the frontal bones. Fixation for each group was as follows: Group 2, wire; Group 3, full microplate; Group 4, suture; Group 5, microplate removal at 4 weeks; Group 6, anterior plate; Group 7, posterior plate; Group 8, soft plate. It was demonstrated that long-term effects on craniofacial development in this animal model are significantly influenced by the type and location of rigid fixation hardware. Significant differences in growth of the craniofacial skeleton for the different fixation groups are presented and discussed.

Animals↗

PubMed2004

Distraction Osteogenesis of the Craniofacial Skeleton.

LEARNING OBJECTIVES:: After studying this article, the participant should be able to: 1. Review the biomechanical principles and pertinent cellular and molecular biology of distraction osteogenesis of the craniofacial skeleton. 2. Describe the clinical indications and applications of distraction osteogenesis of the craniofacial skeleton. 3. Describe maxillary, mandibular, midface, and calvarial procedures in distraction osteogenesis. 4. Discuss the clinical outcomes and complications of distraction osteogenesis of the craniofacial skeleton.The year 2002 marked the end of the first decade in clinical distraction osteogenesis of the craniofacial skeleton. In this short period, its application has increased exponentially. More than 3000 cases have been performed according to a recent survey, and more than 700 articles have been written on this subject in the MEDLINE database since 1996. It is a powerful surgical tool and enables surgeons to achieve results not previously attainable. Despite all this, distraction osteogenesis is practiced by only a small number of plastic surgeons. This article reviews the biomechanical principles; the pertinent cellular and molecular biology; and the clinical indications, applications, controversies, and complications of distraction osteogenesis of the craniofacial skeleton.

Journal Article↗

PubMed2003

Influence of bilateral skeletonized harvesting on occurrence of deep sternal wound infection in 1,000 consecutive patients undergoing bilateral internal thoracic artery grafting.

OBJECTIVE: To evaluate the risk of deep sternal infection in a large patient cohort following bilateral internal thoracic artery (BITA) grafting using skeletonized BITA dissection. SUMMARY BACKGROUND DATA: Complete myocardial revascularization using BITAs improves long-term survival and lowers the rate of repeat operations. Harvesting of ITAs as skeletonized vessels preserves sternal collateral blood supply, thus enabling rapid sternal healing with less risk of deep sternal infection. METHODS: One thousand consecutive patients (763 men, 340 patients >70 years old, 304 diabetics) underwent skeletonized BITA grafting from April 1996 to July 1999. RESULTS: The 30-day mortality rate was 3.4%. There were 10 perioperative infarcts, 16 strokes, and 22 deep sternal infections. There was an increased risk of deep sternal infection in repeat coronary artery bypass grafting (CABG) operations (15%), chronic obstructive pulmonary disease (COPD) (6.2%), congestive heart failure (4.7%), left ventricular dysfunction (ejection fraction < 35%, 4.5%), and longer aortic cross-clamping time. After adjustment for other demographic, clinical, and surgical predictors, the only independent predictors of deep sternal infection were repeat operations, COPD, and duration of aortic cross-clamping. No patients in the reoperation subgroup died, but three of six COPD patients with deep sternal infection died, and COPD was an independent predictor of overall (early + late) mortality. CONCLUSIONS: Skeletonized BITA grafting carries an acceptable risk of deep sternal infection but is not recommended for repeat CABG or for patients with COPD.

Aged↗

PubMed2002

Luminescence intensity in coral skeletons from Mona Island in the Caribbean Sea and its link to precipitation and wind speed.

This study investigates the potential of using changes of interannual luminescence intensity in hermatypic Montastraea coral skeletons in the northeastern Caribbean as a proxy of precipitation and (trade) wind speed. In order to find wavelength pairs that are well suited to detect variations in the concentration of incorporated terrestrial humic substances in coral skeletons, and thus to reconstruct past run-off and rainfall, three-dimensional excitation-emission matrix fluorescence spectra of seawater samples were investigated on their relationships to local precipitation. Three prominent excitation-emission peaks at 310/430, 425/480 and 390/530 nm were identified. The fluorescence intensities of the wavelength pair 310/430 nm showed a weak relationship, while the wavelength pairs at 425/480 and 390/530 nm showed strong relationships with local precipitation. Variations in luminescence intensities from scans on the coral surface along the growth axis using the wavelengths identified were then compared with instrumental records of regional precipitation and wind speed. In the coral skeleton as well, the wavelength pairs at 425/480 and 390/530 nm were more strongly correlated with regional precipitation and wind speed. This indicates that these two wavelength pairs are well suited to reconstruct past precipitation and wind speed. In order to evaluate the use as a proxy of trade wind variability in the Caribbean, tropical Atlantic region, variations in luminescence intensity were compared with a record of trade wind variability from the southern Caribbean. The two records are strongly correlated, which suggests that luminescence intensity in coral skeletons, at least from Mona Island, can be used as proxy of trade wind variability and precipitation.

Anthozoa↗

PubMed1982

Photoperiodic Control of Flowering in Dark-Grown Seedlings of Pharbitis nil Choisy : The Effect of Skeleton and Continuous Light Photoperiods.

The control of night-break timing was studied in dark-grown seedlings of Pharbitis nil (Choisy cv. Violet) following a single continuous or skeleton photoperiod. There was a rhythmic response to a red (R) interruption of an inductive dark period, and the phasing of the rhythm was influenced by the preceding light treatment.Following a continuous white light photoperiod of 6 hours or less, the points of maximum inhibition of flowering were constant in real time. Following a continuous photoperiod of more than 6 hours, maximum inhibition occurred at 9 and 32.5 hours after the end of the light period. The amplitude of the rhythm during the second circadian cycle was much reduced following prolonged photoperiods.Following a skeleton photoperiod, the time of maximum sensitivity to a R interruption was always related to the second pulse of the skeleton, R(2), with the first point of maximum inhibition of flowering occurring after 12 to 18 hours and the second after 39 hours. Without a second R pulse, the time of maximum sensitivity to a R interruption was related to the initial R(1) pulse. A ;light-off' or dusk signal was not mimicked by a R pulse ending a skeleton photoperiod; such a pulse only generated a ;light-on' signal and initiated a new rhythm.It is concluded that the timing of sensitivity to a R interruption of an inductive dark period in Pharbitis nil is controlled by a single circadian rhythm initiated by a light-on signal. After 6 hours in continuous white light, the phase of this rhythm is determined by the transition to darkness. Following an extended photoperiod, the timing characteristics were those of an hourglass; this seemed to be due to an effect on the coupling or expression of a single circadian timer during the second and subsequent cycles, rather than to the operation of a different timing mechanism.In addition to the effects on timing, the photoperiod affected the magnitude of the flowering response.

Journal Article↗

PubMed2006

Correcting curvature-density effects in the Hamilton-Jacobi skeleton.

The Hamilton-Jacobi approach has proven to be a powerful and elegant method for extracting the skeleton of two-dimensional (2-D) shapes. The approach is based on the observation that the normalized flux associated with the inward evolution of the object boundary at nonskeletal points tends to zero as the size of the integration area tends to zero, while the flux is negative at the locations of skeletal points. Nonetheless, the error in calculating the flux on the image lattice is both limited by the pixel resolution and also proportional to the curvature of the boundary evolution front and, hence, unbounded near endpoints. This makes the exact location of endpoints difficult and renders the performance of the skeleton extraction algorithm dependent on a threshold parameter. This problem can be overcome by using interpolation techniques to calculate the flux with subpixel precision. However, here, we develop a method for 2-D skeleton extraction that circumvents the problem by eliminating the curvature contribution to the error. This is done by taking into account variations of density due to boundary curvature. This yields a skeletonization algorithm that gives both better localization and less susceptibility to boundary noise and parameter choice than the Hamilton-Jacobi method.

Algorithms↗

PubMed2005

Skeleton photoperiods alter delayed-type hypersensitivity responses and reproductive function of Siberian hamsters (Phodopus sungorus).

Photoperiod (day length) can modulate immune function. Whether these photoperiodic effects on immune function are mediated directly by a circadian photoperiodic time measurement system or indirectly by nonspecific (e.g. stressful) effects of light is unknown. To discriminate between these two possibilities, Siberian hamsters (Phodopus sungorus) were housed in either long or short photoperiods (LD 16 : 8 h or LD 8 : 16 h) or in 'skeleton' long or short photoperiods (LD 1 : 14 h: LD 1 : 8 h or LD 1 : 6 h: LD 1 : 16 h). In the skeleton photoperiods, both long- and short-day animals received 2 h of light per day. After 10 weeks in their respective photoperiods, hamsters were tested for an antigen specific immune response using a delayed type hypersensitivity (DTH) model. Reproductive and endocrine responses of hamsters in each of the skeleton photoperiods were equivalent to those in standard long or short days, respectively. Hamsters in skeleton short days and LD 8 : 16 increased DTH responses compared to hamsters in both long-day groups. DTH responses were equivalent in both long-day groups. These results suggest that the influences of day length on immune function potentially are due to circadian photoperiodic time measurement systems.

Animals↗

PubMed1994

Mineral status of skeleton and advanced periodontal disease.

Studies of the effect of general bone loss on periodontal condition and on development of periodontal pockets suggest that there is no clear correlation between periodontal health or number of teeth and the general mineral status of the skeleton. In some reports, however, deep periodontal pockets have been correlated with good mineral status in the jawbones and skeleton. The purpose of this study of 227 healthy postmenopausal women aged 48 to 56 years was to determine whether advanced alveolar bone loss, diagnosed by panoramic radiographs, and periodontal probing depths or number of remaining teeth were correlated with the bone mineral status of the skeleton and cortical bone in the mandible. The results suggest that individuals with high mineral values in the skeleton seem to retain their teeth with deep periodontal pockets more easily than those with osteoporosis. This finding may especially motivate treatment of persons suffering from advanced periodontal disease but having good mineral status.

Alveolar Bone Loss↗

PubMed1993

Evidence that the middle T antigen of polyomavirus interacts with the membrane skeleton.

The transforming protein of polyomavirus, middle T antigen, is associated with cellular membranes. We have examined the subcellular location of the middle T antigen in two different cell types by fractionation and detergent phase partitioning. Middle T antigen expressed in human cells by a recombinant adenovirus was detected primarily in the membrane skeleton. Sucrose gradient fractionation revealed that the middle T antigen was associated with complexes with molecular weights of 500,000 to 1,000,000. Several markers for cytoskeleton cofractionate with these complexes, including actin, tubulin, and vimentin. Electron micrographs of membrane skeleton prepared from cells expressing middle T antigen demonstrated that this material contained primarily fibrous structures and was clearly devoid of bilayer membranes. These structures were distinct from the filamentous structures observed in fractions enriched for cytoskeleton. Consistent with a role for membrane skeleton localization in transformation, middle T antigen was detected exclusively in fractions enriched for membrane skeleton in middle T antigen-transformed Rat-2 cells. Our results may resolve the apparent difference between middle T antigen localization as determined by immunomicroscopy and that determined by subcellular fractionation.

Antigens, Polyomavirus Transforming↗