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 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because all the cell populations are capable of making switches between different genetic expression states in response to the environmental change, Thattai and van Oudenaarden (Genetics 167, 523-530, 2004) have raised a very interesting question: In a constantly fluctuating environment, which type of cell population (heterogeneous or homogeneous) is fitter in the long term? This problem is very important to development and evolution biology. We thus take an extensive analysis about how the cell population evolves in a periodically switching environment either with symmetrical time-span or asymmetrical time-span. A complete picture of the phase diagrams for both cases is obtained. Furthermore, we find that the systems with time-dependent cellular transitions all collapse to the same set of dynamical equations with the modified parameters. Furthermore, we also explain in detail how the fitness problem bears much resemblance to the phenomenon, stochastic resonance, in physical sciences. Our results could be helpful for the biologists to design artificial evolution experiments and unveil the mystery of development and evolution.
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PMID:On the long-term fitness of cells in periodically switching environments. 1770 70

Although right main bronchus intubation is associated with adverse consequences, the optimal endotracheal tube (ETT) tip position above the carina in neonates is not known. The aim of this study was to determine the association between ETT tip position and adverse pulmonary effects as assessed by chest radiographs (CXRs). Lung aeration was examined after masking ETT positions in the first two CXRs taken after birth in 74 consecutive ventilated premature infants <or= 28 weeks. All the CXRs of the infants during the first week were examined for predefined combined adverse pulmonary outcomes by two examiners (right upper lobe collapse, localized pulmonary interstitial emphysema [PIE], and pneumothorax). Infants who had ETT tips below T4 or in the right main bronchus were excluded. The ETT tip was above T1 in 4 (5.4%), at T1 in 11 (14.8%), at T2 in 19 (25.6%), at T3 in 27 (36.5%), and at T4 in 13 (17.6%) infants. The patients were categorized into group A (ETT tips at T1/2) or group B (ETT above T1 or below T2). The combined adverse pulmonary outcome of pneumothorax, localized PIE, and right upper lobe collapse was significantly higher in group B compared with group A ( P=0.03). On logistic regression analysis, the only independent association for adverse pulmonary outcome and asymmetrical lung aeration was the ETT position. The odds ratio for developing nonuniform lung aeration was 6 (95% confidence interval [CI] 1.8, 20) and for adverse pulmonary outcome was 8 (95% CI 1.1, 73) when the ETT tip was at T3/T4 compared with T1/2. We concluded that the ETT tip should be kept at the level of the first or second thoracic vertebrae in extremely premature babies to reduce the incidence of nonuniform lung aeration and adverse pulmonary outcomes.
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PMID:Optimal endotracheal tube tip position in extremely premature infants. 1802 11

An acute to chronic idiopathic necrotizing meningoencephalitis was diagnosed in 5 Chihuahua dogs aged between 1.5 and 10 years. Presenting neurologic signs included seizures, blindness, mentation changes, and postural deficits occurring from 5 days to 5.5 months prior to presentation. Cerebrospinal fluid analyses from 2 of 3 dogs sampled were consistent with an inflammatory disease. Magnetic resonance imaging of the brain of 2 dogs demonstrated multifocal loss or collapse of cortical gray/white matter demarcation hypointense on T1-weighted images, with T2-weighted hyperintensity and slight postcontrast enhancement. Multifocal asymmetrical areas of necrosis or collapse in both gray and white matter of the cerebral hemispheres was seen grossly in 4 brains. Microscopically in all dogs, there was a severe, asymmetrical, intensely cellular, nonsuppurative meningoencephalitis usually with cystic necrosis in subcortical white matter. There were no lesions in the mesencephalon or metencephalon except in 1 dog. Immunophenotyping defined populations of CD3, CD11d, CD18, CD20, CD45, CD45 RA, and CD79a immunoreactive inflammatory cells varying in density and location but common to acute and chronic lesions. In fresh frozen lesions, both CD1b,c and CD11c immunoreactive dendritic antigen-presenting cells were also identified. Immunoreactivity for canine distemper viral (CDV) antigen was negative in all dogs. The clinical signs, distribution pattern, and histologic type of lesions bear close similarities to necrotizing meningoencephalitis as described in series of both Pug and Maltese breed dogs and less commonly in other breeds.
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PMID:Necrotizing meningoencephalitis in five Chihuahua dogs. 1848 90

Airways that collapse during deflation generate a crackle sound when they reopen during subsequent reinflation. Since each crackle is associated with the reopening of a collapsed airway, the likelihood of an airway to be a crackle source is identical to its vulnerability to collapse. To investigate this vulnerability of airways to collapse, crackles were recorded during the first inflation of six excised rabbit lungs from the collapsed state, and subsequent reinflations from 5, 2, 1, and 0 cmH(2)O end-expiratory pressure levels. We derived a relationship between the amplitude of a crackle sound at the trachea and the generation number (n) of the source airway where the crackle was generated. Using an asymmetrical tree model of the rabbit airways with elastic walls, airway vulnerability to collapse was also determined in terms of airway diameter D. During the reinflation from end-expiratory pressure = 0 cmH(2)O, the most vulnerable airways were estimated to be centered at n = 12 with a peak. Vulnerability in terms of D ranged between 0.1 and 1.3 mm, with a peak at 0.3 mm. During the inflation from the collapsed state, however, vulnerability was much less localized to a particular n or D, with maximum values of n = 8 and D = 0.75 mm. Numerical simulations using a tree model that incorporates airway opening and closing support these conclusions. Thus our results indicate that there are airways of a given range of diameters that can become unstable during deflation and vulnerable to collapse and subsequent injury.
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PMID:Estimating the diameter of airways susceptible for collapse using crackle sound. 1972 87

(1) Definite changes in the radiographic appearance of the bones are found in renal infantilism.(2) The radiographs show two distinct types of change which I have called the "rachitic" and the "woolly" types.(3) The rachitic type is practically identical with ordinary rickets.(4) The woolly type is characteristic, and is sufficiently typical to be of diagnostic value.(5) The lesions found in this woolly type are asymmetrical, and may be much more marked in one bone than another.(6) The marked deformities in renal infantilism are produced by a collapse of the bone in the metaphysis, which throws the end of the bone out of line.
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PMID:A Radiological Study of the Bone Changes in Renal Infantilism. 1998 64

A unilateral transtibial amputation causes a disruption to the musculoskeletal system, which results in asymmetrical biomechanics. The current study aimed to assess the movement asymmetry and compensations that occur as a consequence of an amputation when performing a countermovement vertical jump. Six unilateral transtibial amputees and 10 able-bodied (AB) participants completed 10 maximal vertical jumps, and the highest jump was analyzed further. Three-dimensional lower limb kinematics and normalized (body mass) kinetic variables were quantified for the intact and prosthetic sides. Symmetry was assessed through the symmetry index (SI) for each individual and statistically using the Mann-Whitney U test between the intact and prosthetic sides for the amputee group. A descriptive analysis between the amputee and AB participants was conducted to explore the mechanisms of amputee jumping. The amputee jump height ranged from 0.09 to 0.24 m. In the countermovement, all ankle variables were asymmetrical (SI > 10%) and statistically different (p < .05) for the amputees. At the knee and hip, there was no statistical difference between the intact and prosthetic sides range of motion, although there was evidence of individual asymmetry. The knees remained more extended compared with the AB participants to prevent collapse. In propulsion, the prosthesis did not contribute to the work done and the ankle variables were asymmetrical (p < .05). The knee and hip variables were not statistically different between the intact and prosthetic sides, although there was evidence of functional asymmetry and the contribution tended to be greater on the intact compared with the prosthetic side. The lack of kinetic involvement of the prosthetic ankle and both knees due to the limitation of the prosthesis and the altered musculoskeletal mechanics of the joints were the reason for the reduced height jumped.
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PMID:Kinetic and kinematic compensations in amputee vertical jumping. 2208 22

A previously well 59-year-old lady with 70 kg weight loss and chronic diarrhoea over a 28-month period presented following collapse and subsequent diagnosis of pulmonary embolism. Previous investigations for this weight loss included normal gastroscopy and colonoscopy, CT and MRI abdomen, barium follow through and octreotide scan. She underwent echocardiogram which revealed myocardial speckling and asymmetrical left ventricular hypertrophy. Repeat oesophago-gastro-duodenoscopy and colonoscopy for rectal bleeding was performed. Colonoscopy revealed intramucosal haematomas and electron microscopy (EM) of the gastric biopsies confirmed amyloid deposition. Amyloidosis of the gastrointestinal (GI) tract and heart were confirmed on serum amyloid protein scan. GI amyloid is rare and symptoms include weight loss, diarrhoea, GI bleeding and gut dysmotility.1 GI amyloidosis should be considered as a diagnosis and sought when other common causes have been excluded. The greatest yield is by Congo red staining or EM of rectal specimens.
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PMID:Gastric amyloidosis presenting with severe weight loss. 2276 88

This paper demonstrates membrane poration of a single suspension cell due to a fast liquid microjet. The jet is formed during the collapse of a laser induced bubble created at a variable stand-off distance from the target cell. The cell is trapped by a converging structure within a microfluidic chip. The asymmetrical growth and collapse of the cavitation bubble next to the cell lead to the microjetting, which deforms and porates the cell membrane. In the experiments, the membrane porations of myeloma cells are probed with the uptake of trypan blue. Time-resolved studies of the diffusion of trypan blue show a marked dependency on the bubble dynamics, i.e. the stand-off distance. The penetration length of the dye increases with shorter distances. Numerical simulations of the diffusion process agree with larger pores formed on the cell membrane. This method allows for a fast, repeatable, and localized rupture of membranes of individual cells in suspension.
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PMID:Single cell membrane poration by bubble-induced microjets in a microfluidic chip. 2336 62

A one-dimensional model of inertial pumping is introduced and solved. The pump is driven by a high-pressure vapor bubble generated by a microheater positioned asymmetrically in a microchannel. The bubble is approximated as a short-term impulse delivered to the two fluidic columns inside the channel. Fluid dynamics is described by a Newton-like equation with a variable mass, but without the mass derivative term. Because of smaller inertia, the short column refills the channel faster and accumulates a larger mechanical momentum. After bubble collapse the total fluid momentum is nonzero, resulting in a net flow. Two different versions of the model are analyzed in detail, analytically and numerically. In the symmetrical model, the pressure at the channel-reservoir connection plane is assumed constant, whereas in the asymmetrical model it is reduced by a Bernoulli term. For low and intermediate vapor bubble pressures, both models predict the existence of an optimal microheater location. The predicted net flow in the asymmetrical model is smaller by a factor of about 2. For unphysically large vapor pressures, the asymmetrical model predicts saturation of the effect, while in the symmetrical model net flow increases indefinitely. Pumping is reduced by nonzero viscosity, but to a different degree depending on the microheater location.
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PMID:One-dimensional model of inertial pumping. 2349 15

Lipids account for 16-19 percent dry platelet matter and includes 65 percent phospholipids, 25 percent neutral lipids and about 8 percent glycosphingolipids. The cell membrane that surrounds platelets is a bilayer that contains different types phospholipids symmetrically distributed in resting platelets, such as phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine, and sphingomyelin. The collapse of lipid asymmetry is exposure of phosphatidylserine in the external leaflet of the plasma bilayer, where it is known to serve at least two major functions: providing a platform for development of the blood coagulation cascade and presenting the signal that induces phagocytosis of apoptotic cells. During activation, this asymmetrical distribution becomes disrupted, and PS and PE become exposed on the cell surface. The transbilayer movement of phosphatidylserine is responsible for the platelet procoagulant activity. Exposure of phosphatidylserine is a flag for macrophage recognition and clearance from the circulation. Platelets, stored at room temperature for transfusion for more than 5 days, undergo changes collectively known as platelet storage lesions. Thus, the platelet lipid composition and its possible modifications over time are crucial for efficacy of platelet rich plasma therapy. Moreover, a number of substances derived from lipids are contained into platelets. Eicosanoids are lipid signaling mediators generated by the action of lipoxygenase and include prostaglandins, thromboxane A2, 12-hydroxyeicosatetraenoic acid. Isoprostanes have a chemical structure similar to this of prostanoids, but are differently produced into the particle, and are ligands for prostaglandins receptors, exhibiting biological activity like thromboxane A2. Endocannabinoids are derivatives from arachidonic acid which could reduce local pain. Phospholipids growth factors (sphingolipids, lysophosphatidic acid, platelet-activating factor) are involved in tissue regenerating process. Finally, a warning concerning the atherogenic role of platelets, although it should not be exerted in a local therapy, is mentioned. The lipid content of plaletets must be taken into account when these particles are concentrated and used for a local therapy, while the different categories of lipid derivatives could improve or affect the quality of the product.
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PMID:Platelet lipidomic. 2364 96


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