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PubMed1988

Ca2+-induced lateral phase separation in ternary mixtures of phosphatidic acid, phosphatidylcholine, and phosphatidylethanolamine inferred by calorimetry.

Phase transition characteristics of ternary mixtures of dipalmitoylphosphatidic acid, dipalmitoylphosphatidylcholine, and phosphatidylethanolamine (dilauroyl-, dimyristoyl-, or dipalmitoyl-phosphatidylethanolamine) were examined by differential scanning calorimetry at various concentrations of calcium ions. In the absence of calcium ion, these ternary mixtures showed a broad phase transition, which suggested a high miscibility of these components. Addition of a low concentration of calcium ions showed a tendency to induce separation of the transition into a major one and a small one. As the concentration of calcium ions increased, the separation became more distinct and the transition enthalpy of the major transition decreased. At a Ca2+/dipalmitoylphosphatidic acid ratio (mol/mol) of 1.5, the major transition became similar to the transition of dipalmitoylphosphatidylcholine and the phosphatidylethanolamine binary mixture. On the other hand, in a binary mixture dipalmitoylphosphatidic acid and dipalmitoylphosphatidylcholine, the Ca2+-induced phase separation was distinct even at the lowest concentration of calcium ions used in the present experiment. The results indicate that a high concentration of calcium ion is required for inducing complete phase separation of the transition event in the ternary mixture because of its high miscibility. It is suggested that the phase separation revealed by spin-labeled phospholipid in ternary mixtures at a low Ca2+ concentration might be a phase separation in a local domain.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1997

Peripartum pubic symphysis separation: a case series and review of the literature.

Peripartum pubic symphysis separation is a recognized complication of pregnancy with incidence estimates ranging from 1:300 to 1:30,000. Characteristic symptoms of symphyseal separation include suprapubic pain and tenderness with radiation to the back of legs, difficulty ambulating, and occasionally, bladder dysfunction. Clinical history, presenting symptoms, and response to therapy are sufficient to make the diagnosis, although radiographic documentation of symphyseal separation by x-ray or ultrasound are frequently used to confirm the diagnosis. The underlying etiology of symptomatic symphyseal separation has not been fully elucidated. Associations with multiparity, macrosomia, pathological joint loosening, and increased force placed on the pelvic ring have been suggested as possible etiologies. Conservative therapy, including bedrest, pelvic binders, ambulation devices, and mild analgesics usually result in a complete recovery with 4 to 6 weeks. The occurrence of a symphyseal separation should not significantly alter the management of subsequent pregnancies, and conservative therapy is recommended for any recurrence of symptoms. A retrospective review of our experience with 5121 deliveries from 1994 to 1995 found 9 cases of peripartum symphyseal separation, resulting in an incidence of 1 of 569 deliveries. Details regarding this case series and a review of the literature are presented.

Biomechanical Phenomena↗

PubMed2000

Endoscopically assisted "components separation" for closure of abdominal wall defects.

The repair of ventral hernia defects of the abdominal wall challenges both general and plastic surgeons. Ventral herniation is a postoperative complication in 10 percent of abdominal surgeries; the repair of such defects has a recurrence rate as high as 50 percent. The "components separation" technique has successfully decreased the recurrence rates of ventral abdominal hernias. However, this technique has been associated with midline dehiscence and a prolonged postoperative stay at the authors' institutions. The purpose of this study was to determine whether endoscopically assisted components separation could minimize operative damage to the vasculature of the abdominal wall and decrease postoperative wound dehiscence. The study group consisted of seven patients who underwent endoscopically assisted components separation; the control group consisted of 30 patients who underwent open components separation. The two groups were similar regarding demographic data and defect size. The endoscopic group had a higher initial success rate than the open group (100 versus 77 percent). Recurrence rates were not significantly different between the two groups. However, the endoscopically assisted components separation patients had fewer postoperative and long-term complications. In the authors' experience, endoscopically assisted components separation has proved to be a safe and effective method for the repair of complicated and recurrent midline ventral hernias.

Abdominal Muscles↗

PubMed2003

Adhesion-induced phase separation of multiple species of membrane junctions.

A theory is presented for the intermembrane junction separation induced by the adhesion between two biomimetic membranes that contain two different types of anchored intermembrane junctions (receptor-ligand complexes). The analysis shows that several mechanisms contribute to the phase separation of the membrane junctions. These mechanisms include the following. (i) The elasticity of the membranes mediates a short-ranged nonlocal interaction between the junctions due to the height difference between type-1 and type-2 junctions. This is the main factor that drives the phase separation. (ii) When type-1 and type-2 junctions have different flexibilities against stretch and compression, the "softer" junctions are the "favored" species, and aggregation of the softer junctions can occur. (iii) The thermally activated shape fluctuations of the membranes also contribute to the phase separation by inducing another nonlocal interaction between the junctions and renormalizing the binding energy of the junctions. The combined effect of these mechanisms is that when phase separation occurs, the system separates into two domains with different relative and total junction densities.

Biophysical Phenomena↗

PubMed2004

Entropy-induced microphase separation in hard diblock copolymers.

Whereas entropy can induce phase behavior that is as rich as seen in energetic systems, microphase separation remains a very rare phenomenon in entropic systems. In this paper, we present a density functional approach to study the possibility of entropy-driven microphase separation in diblock copolymers. Our model system consists of copolymers composed of freely jointed slender hard rods. The two types of monomeric segments have comparable lengths, but a significantly different diameter, the latter difference providing the driving force for the phase separation. At the same time this system can also exhibit liquid crystalline phases. We treat this system in the appropriate generalization of the Onsager approximation to chain-like particles. Using a linear stability (bifurcation) analysis, we analytically determine the onset of the microseparated and the nematic phases for long chains. We find that for very long chains the microseparated phase always pre-empts the nematic. In the limit of infinitely long chains, the correlations within the chain become Gaussian and the approach becomes exact. This allows us to define a Gaussian limit in which the theory strongly simplifies and the competition between microphase separation and liquid crystal formation can be studied essentially analytically. Our main results are phase diagrams as a function of the remaining model parameters: i.e., the diameter ratio, the length ratio, and the number ratio of the two types of segments. We also determine the amplitude of the inhomogeneous order as a function of position along the chain at the onset of the microphase separation instability. Finally, we give suggestions as to how this type of entropy-induced microphase separation could be observed experimentally.

Journal Article↗

PubMed2006

Novel approach for modeling separation forces between deformable bodies.

Many minimally invasive surgeries (MISs) involve removing whole organs or tumors that are connected to other organs. Development of haptic simulators that reproduce separation forces between organs can help surgeons learn MIS procedures. Powerful computational approaches such as finite-element methods generally cannot simulate separation in real time. This paper presents a novel approach for real-time computation of separation forces between deformable bodies. Separation occurs either due to fracture when a tool applies extensive forces to the bodies or due to evaporation when a laser beam burns the connection between the bodies. The separation forces are generated online from precalculated force-displacement functions that depend on the local adhesion/separation states between bodies. The precalculated functions are accurately synthesized from a large number of force responses obtained through either offline simulation, measurement, or analytical approximation during the preprocessing step. The approach does not require online computation of force versus global deformation to obtain separation forces. Only online interpolation of precalculated responses is required. The state of adhesion/separation during fracture and evaporation are updated by computationally simple models, which are derived based on the law of conservation of energy. An implementation of the approach for the haptic simulation of the removal of a diseased organ is presented, showing the fidelity of the simulation.

Animals↗

PubMed2003

Genotype-environment interaction in children's adjustment to parental separation.

BACKGROUND: Understanding the processes by which genetic risks lead to psychopathology is a key conceptual and methodological task for research. The current study, based on an at-risk adoption design, examines the hypothesis that the effect of genetic risk on children's behavioral/emotional problems and social adjustment is moderated by psychosocial risk, specifically parental separation. METHOD: Data are based on the Colorado Adoption Project. One hundred and seventy-one adoptees, all of whom were placed in the adoptive home in early infancy, were assessed using a multi-method strategy at 12 years of age. Adoptees' adjustment was measured using parent and 'teacher reports on the Child Behavioral Checklist as well as observer ratings of social competence; all raters were blind to the biological background of the adoptee. Genetic risk was indexed by biological parents' self-reports of negative emotionality, which was completed prior to the adoption. RESULTS: By age 12 years, 23 of the 171 adoptees experienced a separation in the adoptive home. Correlation and regression analyses indicated that the association between genetic risk and child adjustment was moderated by parental separation. In the absence of parental separation, genetic risk was uncorrelated with adoptee adjustment; however, there were substantial and significant associations between individual differences in genetic diathesis and poor adjustment among the adoptees who experienced parental separation. CONCLUSIONS: The association between parental separation and children's behavioral/ emotional and social adjustment may not be entirely environmental in origin. Genetic vulnerability is accentuated by major psychosocial stresses, and this may partly explain the wide individual differences in children's adjustment to family transitions.

Adaptation, Psychological↗

PubMed1984

Differentiating anti-lamina lucida and anti-sublamina densa anti-BMZ antibodies by indirect immunofluorescence on 1.0 M sodium chloride-separated skin.

Sixty-one bullous disease sera containing IgG anti-BMZ antibodies were examined by indirect immunofluorescence on intact skin and skin separated through the lamina lucida by incubation in 1.0 M NaCl. All sera produced an indistinguishable pattern of linear immunofluorescence on intact skin at dilutions of 1:10 or higher. On separated skin, antibodies bound to either the epidermal (epidermal pattern), dermal (dermal pattern), or epidermal and dermal (combined pattern) sides of the separation. The binding patterns were consistent on separated skin from several donors and titers of anti-basement membrane zone antibodies on separated skin were comparable to those on intact skin. Sera from 3 patients with herpes gestationis (HG), 36 patients with bullous pemphigoid (BP), and 1 patient with clinical and histologic features of epidermolysis bullosa acquisita (EBA) showed an epidermal pattern. Sera from 9 patients with BP showed a combined pattern and sera from 6 patients with EBA and 6 patients with clinical and histologic features of BP showed a dermal pattern. Indirect immunoelectron microscopy of selected sera showed antibodies producing the epidermal and combined patterns were anti-lamina lucida antibodies and those producing the dermal pattern were anti-sublamina densa antibodies. These results show indirect immunofluorescence on separated skin is a dependable method for differentiating bullous disease anti-lamina lucida and anti-sublamina densa antibodies and that differentiating between the antibodies is essential for accurate diagnosis in some patients. The results also suggest BP anti-lamina lucida antibodies may have more than one antigenic specificity.

Antigens↗

PubMed2006

Characterization of induced mucosal connective tissue separation--a comparison of six different techniques.

BACKGROUND: Artificial separation of oral mucosa into epithelium and connective tissue represents the first step in investigating both the basement membrane zone and its two components (epithelium and connective tissue) separately. It is a useful tool in analysing the possible role of hepatitis C virus in the pathogenesis of oral lichen planus (OLP). The aim of the present study was to test different methods to separate the epithelium from the connective tissue of oral mucosa affected by OLP as a preliminary step for further immunohistochemical or molecular investigations. PATIENTS AND METHODS: Fourteen tissue biopsies of the oral mucosa of clinically and histopathologically confirmed OLP lesions underwent epithelial connective separation (ECS) using six different reagents. RESULTS AND CONCLUSIONS: Among the separation methods tested, CaCl2 1 M at 37 degrees C for 30 min, NaCl 1 M at 4 degrees C for 26 h and elastase at 4 degrees C for 22 h allowed good ECS without structural alteration or tissue loss. The present study provides useful information regarding techniques to separate the epithelium from the connective tissue as a preliminary step to investigate oral mucosa affected by OLP from an immunohistochemical or molecular viewpoint.

Aged↗

PubMed1979

Mode of cell separation and arrangement of Staphylococcus.

The process of cell separation and arrangement of Staphylococcus was investigated using a scanning electron microscope. After two cycles of cell division, the Staphylococcal cells cultured on an agar medium were generally observed to be arranged in three morphological types: linear, square, and crooked arrangements. Results of the examination of cell surface structure revealed that separations had occurred in these clustered cells following two patterns. One type of second separation occurred parallel to the transversal axis of the preceding pair of the parental cells (X-type) and the other occurred tangential to it (Y-type). In the former type, the four daughter cells were usually arranged tetragonally after the separations, and in the latter type they were arranged either linearly or crookedly depending on the direction of the second separation. The final pattern of the cell arrangement was thus determined by the type of septal wall formation and the direction of cell separation. After several cycles of cell divisions, the cells were finally arranged in an irregular grape-like cluster, even though the cross walls were formed regularly at the rectangular face of the preceding cross walls.

Cell Division↗

PubMed1987

Comparison between a swim-up and a Percoll gradient technique for the separation of human spermatozoa.

Two methods of separating human sperm were compared using twenty-two semen samples. The sperm were separated by a swim-up technique or by self-migration on a Percoll gradient followed by medium change. After separation, the sperm obtained were assessed for progressive motility, ATP content, energy charge index ([ATP + 0.5 ADP]/[ATP + ADP + AMP]) and morphology. In general, and especially for semen samples containing less than 20 X 10(6) sperm/ml, separation by Percoll gradient selected sperm that were superior to those separated by the swim-up technique. The relatively high energy charge index (greater than 0.8) showed that the sperm tolerated the separation conditions well. It is suggested that self-migration on a Percoll gradient should prove useful for obtaining sperm of high quality.

Adenosine Triphosphate↗

PubMed2006

Metabolic signals modulate hypothalamic-pituitary-adrenal axis activation during maternal separation of the neonatal mouse.

The postnatal development of the mouse is characterised by a period of hypo-responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to moderate stressors. Maternal separation disinhibits this blockade of the HPA axis, but the mechanism responsible is not clear. The present study examined the influence of metabolic signals on the central and peripheral components of the HPA axis in neonatal mice aged 8 days in absence or presence of the mother. Reductions in plasma glucose and leptin as well as rapid increases in plasma ghrelin were apparent in the neonate 4 h following maternal deprivation and maximal at 8 h. In addition, maternal separation induced an increase of neuropeptide Y (NPY) mRNA expression in the arcuate nucleus, a decrease of corticotrophin-releasing hormone (CRH) mRNA expression in the paraventricular nucleus and a rise in serum corticosterone. Pharmacological manipulation of the metabolic signals attenuated the HPA response to maternal separation. Thus, the rise in plasma corticosterone induced by maternal separation was ameliorated by prevention of reduction in blood glucose or blockade of the ghrelin signalling pathway, as were the hypothalamic changes in NPY and CRH mRNAs. By contrast, leptin treatment did not affect the HPA axis response to maternal separation. Together these results suggest that metabolic signals play an important role in triggering the HPA response of the neonate to maternal separation.

Analysis of Variance↗

PubMed2005

Identification and molecular characterization of an N-acetylmuramyl-L-alanine amidase Sle1 involved in cell separation of Staphylococcus aureus.

We purified a peptidoglycan hydrolase involved in cell separation from a Staphylococcus aureus atl null mutant and identified its gene. Characterization of the gene product shows a 32 kDa N-acetylmuramyl-L-alanine amidase that we designated Sle1. Analysis of peptidoglycan digests showed Sle1 preferentially cleaved N-acetylmuramyl-L-Ala bonds in dimeric cross-bridges that interlink the two murein strands in the peptidoglycan. An insertion mutation of sle1 impaired cell separation and induced S. aureus to form clusters suggesting Sle1 is involved in cell separation of S. aureus. The Sle1 mutant revealed a significant decrease in pathogenesis using an acute infection mouse model. Atl is the major autolysin of S. aureus, which has been implicated in cell separation of S. aureus. Generation of an atl/sle1 double mutant revealed that the mutant cell separation was heavily impaired suggesting that S. aureus uses two peptidoglycan hydrolases, Atl and Sle1, for cell separation. Unlike Atl, Sle1 is not directly involved in autolysis of S. aureus.

Amino Acid Motifs↗

PubMed1994

Double-pulse defibrillation using pulse separation based on the fibrillation cycle length.

INTRODUCTION: We investigated a method of defibrillation in which two shocks were delivered to the same electrodes with a separation based on the cycle length of the fibrillation event (FCL). METHODS AND RESULTS: In pentobarbital anesthetized dogs, a computerized system determined the FCL from the fibrillation event, computed the desired double-pulse (DP) shock separation, and immediately delivered the DP shocks. In group 1, energy for 50% success at defibrillation (E50) was measured using separations from 55% to 95% of the FCL and remeasured after administration of flecainide, clofilium, or vehicle to change the FCL. Both drugs increased FCL by approximately 25%. Plots of E50 versus %FCL aligned before and after drug showed that the optimum pulse separation followed the FCL. In group 2, E50s were measured for 55% to 185% FCL separations in clofilium or vehicle-treated animals. The optimum DP E50 was at 85% FCL and was not significantly different from the single-shock E50. In group 3, no differences were found when comparing the probability of success versus total energy relationships for single and optimum DP shocks. Group 4 compared E50s for single and DP shocks using a single-catheter configuration and three-electrode configurations (catheter-subdermal patch). E50s for single and DP shocks were equal using the single-catheter configuration but DP shocks required approximately 20% more energy in the three-electrode configurations. CONCLUSION: In single-pathway lead configurations, two shocks with 85% FCL separation can be reliably combined to defibrillate using the same total energy as a larger single shock. Since the energy is unchanged but the total duration is doubled, DP shock currents are reduced by 20% to 30%.

Animals↗

PubMed2004

Melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Melatonin in mammals, produced by the pineal gland and elsewhere, has shown antioxidant and neuroprotective properties in neuronal cells. We investigated whether melatonin would increase newly born cells (cell proliferation) in the dentate gyrus of maternally separated rats. To examine the effect of melatonin on cell proliferation of the dentate gyrus in maternally separated rats, 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry was performed. Rat pups were separated from their mothers and socially isolated on postnatal day 14. Melatonin (10 mg/kg, i.p.) and BrdU (50 mg/kg, i.p.) were given to them for 7 days. The number of BrdU-positive cells was significantly increased in the dentate gyrus of maternally separated pups with melatonin administration (P < 0.001). In addition, the expression of glucocorticoid receptor was significantly decreased in the dentate gyrus compared with maternally separated pups not given melatonin (P < 0.001). This is the first report that melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Animals↗

PubMed1990

Separation and identification of growth hormone variants with high performance liquid chromatography techniques.

Liquid chromatography techniques were used to separate and identify human growth hormone (hGH) variants. N-terminal modified forms, such as des-Phe (2-191) and methionyl-hGH (met-1-191), were separated from recombinant human growth hormone (rhGH (1-191] by hydrophobic interaction chromatography (HIC). A proteolytically cleaved ('clip') form of rhGH which has a break in the polypeptide chain between Thr(142) and Tyr(143), also proved to be separable from rhGH by HIC. In addition, a mutated form of rhGH with only two amino acid substitutions, Glu(65) to Val(65) and Glu(66) to Lys(66), on a random coil domain of the molecule, was separated from rhGH by HIC, indicating that these substitutions altered the hydrophobicity of the molecule. Treatment of rhGH with hydrogen peroxide led to sulphoxide formation in two methionine residues Met(14) and Met(125); it was not possible to oxidize Met(170). The oxidized forms of rhGH were readily separated from rhGH(1-191) by reversed-phase chromatography. Analyses of rhGH batches showed very low levels (less than 0.3%) of oxidized rhGH, indicating that rhGH is highly resistant to oxidative reactions. Deamidations were induced in rhGH by heat treatment. The primary deamidation site was found to be Asn(149). Monodesamido rhGH and didesamido rhGH were efficiently separated from rhGH(1-191) by anion-exchange chromatography.

Chromatography, High Pressure Liquid↗

PubMed2003

The use of conducting polymers in membrane-based separations: a review and recent developments.

As a material family, pi-conjugated polymers (also known as intrinsically conductive polymers) elicit the possibility of both exploiting the chemical and physical attributes of the polymer for membrane-based separations and incorporating its electronic and electrochemical properties to enhance the separation figures-of-merit. This review article, although by no means comprehensive, provides a current snapshot of the investigations from many research laboratories in the use of conducting polymers for membrane-based separations. The review focuses primarily on polyaniline, polypyrrole, and substituted-polythiophene and includes applications in gas separations, liquid (and/or vapor) separations, and ion separations. Additionally, we discuss the broad challenges and accomplishments in membrane formation from conducting polymers.

Aniline Compounds↗

PubMed1998

Decreased glucose metabolism causes separation of hoof lamellae in vitro: a trigger for laminitis?

Explants of horses' hooves remained intact for up to 8 days when incubated in Dulbecco's modified Eagle medium (D-MEM) containing 25 mmol/l glucose but separated within 36 h when incubated in saline. The separation occurred between the basal epidermal cells and their basement membrane which is characteristic of the hoof separation that occurs in laminitis. Separation of hoof explants was prevented by addition of glucose to saline and was induced by adding 2-deoxyglucose or aminophenylmercuric acetate to D-MEM. Glucose consumption by the hoof explants was inhibited by 2-deoxyglucose and aminophenylmercuric acetate. The explants consumed relatively large amounts of glucose during the first 2 days of incubation and then little over the next 6 days. Despite the reduced glucose consumption, the hoof explants did not separate over 8 days of incubation. The results indicated that the integrity of the hoof explants was initially dependent on consumption of glucose and provide a possible explanation for the development of laminitis caused by conditions such as carbohydrate overload, acute inflammatory conditions, corticosteroid therapy and hyperlipidaemia. It would be expected that these conditions would induce a major hormonally-mediated metabolic shift away from glucose consumption by many peripheral tissues. It is suggested, therefore, that if the metabolic change occurred faster than the hoof tissue could adapt to an alternative energy substrate, then hoof separation and laminitis would occur.

Analysis of Variance↗