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PubMed2026

Dual recognition drives site-directed G-quadruplex stabilization: Oligonucleotide design in G4 ligand-oligonucleotide conjugates.

G-quadruplex (G4) DNA structures are increasingly recognized for their roles in transcriptional regulation and genome stability, making them attractive therapeutic targets. Selective recognition of individual G4s remains challenging due to the high structural similarity among G4 motifs. G4 Ligand-Oligonucleotides conjugates (GL-Os) address this challenge by combining small-molecule G4 ligands with the sequence specificity of oligonucleotides, targeting sequences flanking the intended G4 target. Here, we systematically investigate how oligonucleotide length, backbone composition, and sequence complementarity govern GL-O binding, selectivity, and G4 stabilization. We show that effective G4 recognition depends on the interdependence between oligonucleotide hybridization and G4 ligand binding, such that both elements cooperatively reinforce complex stability and site specificity. Longer oligonucleotides promote more stable complexes and stronger G4 stabilization, whereas central mismatches disrupt this dual-recognition mechanism. Replacement of DNA with peptide nucleic acids (PNAs) enhances binding strength, thermal stability, and metabolic stability. Importantly, ligand conjugation redirects PNA oligonucleotides from nonspecific polymerase stalling toward selective G4 stabilization. Finally, we demonstrate receptor-mediated cellular uptake of modified GL-Os, supporting the feasibility of cellular delivery while highlighting remaining delivery barriers. Together, these findings show the molecular design principles governing GL-O behavior and provide a foundation for the future development and evaluation of selective G4-targeting therapeutics.

G-quadruplex DNA↗
PubMed2005

Virion stability and aphid vector transmissibility of Cucumber mosaic virus mutants.

The physical stability of virions of Cucumber mosaic virus (CMV) mutants was investigated to determine if relative stability correlated with efficiency of aphid transmission. Virion stability was evaluated by a urea disruption assay and by testing the infectivity of virus following purifications. All viruses were infectious when purified using a low salt buffer without organic solvent, whereas two of seven viruses were less stable and inactivated following purification with a high salt buffer and chloroform. These two viruses were both reassortants derived from the spontaneous transmission-defective mutant CMV-M (F1F2M3 and F1F2M3-L129P). F1F2M3 was relatively unstable, being disrupted between 0 and 1 M urea versus the wild-type CMV-Fny (F1F2M3) that was destabilized at 3-4 M urea. Modifications of F1F2M3 at three amino acid positions (129, 162, 168), singly or in combination, increased the relative stability of virions. A second class of transmission-defective CMVs with engineered mutations in the betaH-betaI surface loop of the CMV-Fny capsid protein (CP) exhibited near wild-type levels of stability. Lastly, a single Pro to Leu substitution at CP position 129 of CMV-Fny (F1F2M3-P129L) conferred the induction of necrosis in tobacco plants and reduced aphid transmissibility, but did not markedly alter the physical stability of virions. Thus, only among CMV-M derivatives harboring the CP mutation of Thr to Ala at position 162 were increases in stability correlated with restoration of transmissibility by the aphid Aphis gossypii.

Amino Acid Substitution↗
PubMed2000

Pulmonary abnormalities after coronary arterial bypass grafting operation: cardiopulmonary bypass versus mechanical stabilization.

BACKGROUND: Cardiopulmonary bypass has been implicated in causing poor pulmonary gas exchange postoperatively in patients undergoing coronary artery bypass grafting procedures. This randomized prospective study was conducted to determine whether patients undergoing coronary artery bypass grafting operations using cardiac stabilization and thereby avoiding cardiopulmonary bypass will have improved pulmonary function postoperatively. METHODS: Fifty-eight patients were randomized to one of two groups: coronary artery bypass grafting operation with stabilization or coronary artery bypass grafting operation with cardiopulmonary bypass. Preoperative and postoperative pulmonary gas exchange measurements were performed on intubated patients, including the arterial partial pressure of oxygen on 100% inspired oxygen, the alveolar-arterial oxygen gradient, and pulmonary shunt. Static and dynamic lung compliance measurements were performed postoperatively. Hemodynamic variables (including creatine kinase-MB and troponin levels), intubation time, postoperative bleeding, and blood transfusions were compared. RESULTS: Both study groups had a large decrease in arterial partial pressure of oxygen on 100% inspired oxygen (p < 0.0001) and a significant postoperative increase in the alveolar-arterial oxygen gradient (p < 0.0001). There was no statistical difference in the postoperative gas exchange between the two groups; however, the postoperative pulmonary shunt was significantly better in the stabilization group (24% versus 31%, p = 0.03). The patients were extubated in the intensive care unit earlier in the stabilization group (8.2 hours versus 9.2 hours, not significant). The mean static and dynamic lung compliance postoperatively was lower in the stabilization group, although not statistically significant (p = 0.06). CONCLUSIONS: Coronary artery bypass grafting operation using cardiac stabilization technique is safe and avoids the risk of cardiopulmonary bypass. The pulmonary gas exchange postoperatively is comparable to standard cardiopulmonary bypass procedures, but a reduced postoperative pulmonary shunt was seen in the stabilization group.

Blood Transfusion↗
PubMed1999

Clinical measurement of the static rear stability of occupied wheelchairs.

OBJECTIVE: To evaluate a new clinical test, platform testing of the static rear stability of wheelchairs occupied by their users (using methods adapted from the International Organization for Standardization [ISO]), from the perspective of its measurement properties, safety, and comfort. DESIGN: Within-subject comparisons. SETTING: Rehabilitation center. PATIENTS: Ninety-seven wheelchair users. MAIN OUTCOME MEASURES: Static stability (with the brakes locked and unlocked, the occupant leaning forward and back, and with antitip devices in place), dynamic stability (the criterion measure), reliability, validity, sensitivity, specificity, predictive values, and likelihood ratios. RESULTS: Test-retest reliabilities (n = 18 to 24) were all >.93. The test's construct validity was demonstrated by the finding that static stability was appropriately affected by locking the brakes, body position, and antitip devices (p < .0001). Spearman's rank correlations between static and dynamic stability ranged from .29 to .65. Sensitivity ranged from 46% to 85%, specificity from 59% to 78%, positive predictive values from 76% to 86%, negative predictive values from 42% to 69%, positive likelihood ratios from 1.56 to 2.95, and negative likelihood ratios from .22 to .71. There were no adverse events, and the subjects tolerated the tests well. CONCLUSIONS: In the clinical setting, the ISO platform test of static rear stability has good to excellent measurement properties, is safe, and is well tolerated. Static-stability testing in this setting should be performed in the context of a comprehensive evaluation of wheelchair safety and performance.

Adolescent↗
PubMed2003

Role of backbone hydration and salt-bridge formation in stability of alpha-helix in solution.

We test molecular level hypotheses for the high thermal stability of alpha-helical conformations of alanine-based peptides by performing detailed atomistic simulations of a 20-amino-acid peptide with explicit treatment of water. To assess the contribution of large side chains to alpha-helix stability through backbone desolvation and salt-bridge formation, we simulate the alanine-rich peptide, Ac-YAEAAKAAEAAKAAEAAKAF-Nme, referred to as the EK peptide, that has three pairs of "i, i + 3" glutamic acid(-) and lysine(+) substitutions. Efficient configurational sampling of the EK peptide over a wide temperature range enabled by the replica exchange molecular dynamics technique allows characterization of the stability of alpha-helix with respect to heat-induced unfolding. We find that near ambient temperatures, the EK peptide predominately samples alpha-helical configurations with 80% fractional helicity at 300 K. The helix melts over a broad range of temperatures with melting temperature, T(m), equal to 350 K, that is significantly higher than the T(m) of a 21-residue polyalanine peptide, A(21). Salt-bridges between oppositely charged Glu(-) and Lys(+) side chains can, in principle, provide thermal stability to alpha-helical conformers. For the specific EK peptide sequence, we observe infrequent formation of Glu-Lys salt-bridges (with approximately 10-20% probability) and therefore we conclude that salt-bridge formation does not contribute significantly to the EK peptide's helical stability. However, lysine side chains are found to shield specific "i, i + 4" backbone hydrogen bonds from water, indicating that large side-chain substituents can play an important role in stabilizing alpha-helical configurations of short peptides in aqueous solution through mediation of water access to backbone hydrogen bonds. These observations have implications on molecular engineering of peptides and biomolecules in the design of their thermostable variants where the shielding mechanism can act in concert with other factors such as salt-bridge formation, thereby increasing thermal stability considerably.

Alanine↗
PubMed1997

Influence of low corrected seminal fructose levels on sperm chromatin stability in semen from men attending an infertility service.

OBJECTIVE: To determine any correlation between sperm chromatin stability under sodium dodecyl sulfate (SDS), and SDS-ethylendiamine tetraacetic acid (SDS and EDTA) conditions with levels of corrected seminal fructose, obtained multiplying logarithm of sperm count by seminal fructose concentration, in men attending an infertility service. DESIGN: Cross sectional study to compare semen parameters of two groups (control and experimental), one with normal levels of corrected fructose (control) and the second with low levels of corrected fructose (experimental). Subjects were also grouped according to number, motility and morphology of sperm, and according to results of hypo-osmotic test. SETTING: Andrology laboratory at the Instituto de Investigaciones de la Altura, Lima, Perú. PATIENT(S): Two hundred and twenty five male partners in infertile couples attending the Andrology Laboratory. INTERVENTION(S): None MAIN OUTCOME MEASURE(S): semen analysis, hypo-osmotic swelling test, sperm chromatin stability after SDS, and SDS and EDTA, and seminal fructose. RESULT(S): Seminal volume, sperm motility, and seminal fructose were significantly lower in samples from subjects with low levels of corrected fructose. Subjects with low levels of corrected fructose had also high sperm chromatin stability under SDS, and SDS and EDTA treatment. After SDS treatment, sperm chromatin stability was similar in normal samples and in those with oligozoospermia, asthenozoospermia, teratozoospermia, or abnormal hypo-osmotic swelling test. After SDS and EDTA treatment, a high sperm stability was observed in samples with asthenozoospermia. This hyper-stability is observed in asthenozoospermic samples with low corrected fructose levels, but not in asthenozoospermic samples with normal corrected fructose levels. The logistic regression analysis applied to asthenozoospermic data showed that chronological age, seminal volume, acid phosphatase per ejaculate and percent of stable sperm after SDS and EDTA treatment were significantly associated to levels of corrected fructose. CONCLUSION(S): Low levels of corrected fructose were associated to low seminal volume, low sperm motility, and high sperm chromatin stability under SDS and EDTA treatment.

Adult↗
PubMed2000

Slower speeds in patients with diabetic neuropathy lead to improved local dynamic stability of continuous overground walking.

Patients with diabetic peripheral neuropathy are significantly more likely to fall while walking than subjects with intact sensation. While it has been suggested that these patients walk slower to improve locomotor stability, slower speeds are also associated with increased locomotor variability, and increased variability has traditionally been equated with loss of stability. If the latter were true, this would suggest that slowing down, as a locomotor control strategy, should be completely antithetical to the goal of maintaining stability. The present study resolves these seemingly paradoxical findings by using methods from nonlinear time series analysis to directly quantify the sensitivity of the locomotor system to local perturbations that are manifested as natural kinematic variability. Fourteen patients with severe peripheral neuropathy and 12 gender-, age-, height-, and weight-matched non-diabetic controls participated. Sagittal plane angles of the right hip, knee, and ankle joints and tri-axial accelerations of the trunk were measured during 10 min of continuous overground walking at self-selected speeds. Maximum finite-time Lyapunov exponents were computed for each time series to quantify the local dynamic stability of these movements. Neuropathic patients exhibited slower walking speeds and better local dynamic stability of upper body movements in the horizontal plane than did control subjects. The differences in local dynamic stability were significantly predicted by differences in walking speed, but not by differences in sensory status. These results support the hypothesis that reductions in walking speed are a compensatory strategy used by neuropathic patients to maintain dynamic stability of the upper body during level walking.

Aged↗
PubMed2000

Stability criterion for controlling standing in able-bodied subjects.

A new stability criterion that can be used to assess the standing condition of a subject from center of pressure (CoP) measurements is presented. This criterion can be applied, for example, to control a standing prosthesis, which should allow a paraplegic subject to stand up, sit down and stand safely without using hands for support. Experiments conducted with able-bodied subjects enabled us to establish a relationship between its stability and the subject's CoP position. Four CoP stability zones were identified: high preference, low preference, undesirable and unstable zones. The high preference zone is defined as the area where the CoP is found 99% of the time during quiet standing. The area where the CoP is found during the remaining 1% of the time is called the low preference zone. The undesirable zone is defined as the CoP area where the subject is forced to change posture in order to maintain balance, and the unstable zone is defined as the CoP area in which the subject is forced to step forward, backward or sideways to maintain stability. A general model of the proposed four stability zones was derived, which can be used to compute stability zones a priori for any subject and thus allows one to assess the subject's stability condition from the CoP measurements.

Adult↗
PubMed1999

Intra-abdominal pressure mechanism for stabilizing the lumbar spine.

Currently, intra-abdominal pressure (IAP) is thought to provide stability to the lumbar spine but the exact principles have yet to be specified. A simplified physical model was constructed and theoretical calculations performed to illustrate a possible intra-abdominal pressure mechanism for stabilizing the spine. The model consisted of an inverted pendulum with linear springs representing abdominal and erector spinae muscle groups. The IAP force was simulated with a pneumatic piston activated with compressed air. The critical load of the model was calculated theoretically based on the minimum potential energy principle and obtained experimentally by increasing weight on the model until the point of buckling. Two distinct mechanisms were simulated separately and in combination. One was antagonistic flexor extensor muscle coactivation and the second was abdominal muscle activation along with generation of IAP. Both mechanisms were effective in stabilizing the model of a lumbar spine. The critical load and therefore the stability of the spine model increased with either increased antagonistic muscle coactivation forces or increased IAP along with increased abdominal spring force. Both mechanisms were also effective in providing mechanical stability to the spine model when activated simultaneously. Theoretical calculation of the critical load agreed very well with experimental results (95.5% average error). The IAP mechanism for stabilizing the lumbar spine appears preferable in tasks that demand trunk extensor moment such as lifting or jumping. This mechanism can increase spine stability without the additional coactivation of erector spinae muscles.

Abdomen↗
PubMed2000

Dependence of cyano bonded phase hydrolytic stability on ligand structure and solution pH.

As part of our program to develop more stable cyano (CN) high-performance liquid chromatography (HPLC) column packings, we have evaluated hydrolytic stability as a function of ligand connectivity, chain length, and side group steric protection and the pH of the mobile phase. Three accelerated tests were used to evaluate stability: (1) A non-HPLC screening test measuring carbon loss in refluxing MeOH-100 mM KH2PO4 pH 4.5 (1:1, v/v) solution; (2) a continuous flow HPLC test measuring capacity factor maintenance in 1% trifluoroacetic acid in water (pH 1.02) at 80 degrees C; and (3) a continuous flow HPLC test measuring column efficiency maintenance in 50 mM triethylamine in water (pH 10.00) at 50 degrees C. The stability of the CN phases was found to be dependent on both ligand chemical structure and the pH of the test conditions. The starting screen test of intermediate pH was least able to differentiate the CN phases based on structure, because two different degradation mechanisms appear to offset each other (acid induced siloxane bond cleavage vs. base induced silica dissolution). A trifunctional and a sterically protected CN phase were notably stable under the acidic test conditions, but had poor stability under basic conditions. Conversely, chain extension afforded poor stability under acidic conditions, but did afford improved stability at higher pH. In total, the data indicate that good CN column stability can be achieved by using a trifunctional or a sterically protected phase in acidic mobile phases. However, as mobile phases of intermediate or higher pH are employed, shorter column lifetimes can be expected due to an accelerated dissolution of the underlying silica substrate. Materials were also compared chromatographically using a mixture of non-polar, polar, and basic analytes under reversed-phase conditions.

Chromatography, High Pressure Liquid↗
PubMed1999

Fetal stabilization for antenatally diagnosed diaphragmatic hernia.

BACKGROUND/PURPOSE: Infants with congenital diaphragmatic hernia have pulmonary hypoplasia resulting in persistent pulmonary hypertension of neonates (PPHN), which is the main contributor to both high mortality and morbidity. The pulmonary artery bed in patients with congenital diaphragmatic hernia (CDH) is underdeveloped and is very sensitive to slight stimuli. It is, therefore, vital to avoid any factors that might increase pulmonary vascular resistance during the perinatal treatment of these patients. Recently, fetal anesthesia for perinatal stabilization in patients with CDH has been reported. However, the efficacy of this method remains controversial. The aim of this study is to analyze the benefits of fetal stabilization using fetal anesthesia in patients with CDH. METHODS: The authors have seen 9 cases of antenatally diagnosed CDH and attempted fetal stabilization. The indication for fetal stabilization was a lung thoracic ratio of less than 0.2, without any severe associated anomalies. The protocol for fetal stabilization was (1) monitoring the fetal respiratory movement and heart beat by ultrasonography, (2) the administration of morphine (20 to 30 mg) and diazepam (5 mg) to the mother, (3) the confirmation of any interruptions in fetal movement followed by a cesarean section, (4) pancuronimum (0.5 mg) was given through the umbilical vessels, (5) intubation before clamping of the umbilical cord, and (6) high-frequency oscillatory ventilation (HFO) without bagging. RESULTS: The lung-thratic ratio (LTR) was between 0.06 to 0.17 (average, 0.10+/-0.04). Operation was performed in 7 of 9 patients at between 2.5 and 27 hours after birth. The overall survival rate was 66.7% (6 of 9). All of the patients who underwent operation within 5 hours after birth survived. CONCLUSIONS: Perinatal stabilization using fetal anesthesia was found to be effective in preventing PPHN and shortening the period of preoperative stabilization. It also improved the survival rate of patients with severe CDH.

Female↗
PubMed2002

Comparison of the effects of Mg(OH)2 and sucrose on the stability of bovine serum albumin encapsulated in injectable poly(D,L-lactide-co-glycolide) implants.

Incomplete release and poor stability of encapsulated proteins are common hurdles to overcome when developing poly(lactide-co-glycolide) (PLGA) controlled-release systems. Antacid excipients such as Mg(OH)2, which increase both microclimate pH and polymer water uptake, have been shown to prevent acid-induced instability of proteins encapsulated in PLGA. The purpose of this study was to delineate the effects of microclimate pH and polymer water content on the stability of encapsulated bovine serum albumin (BSA) by comparing the effects of Mg(OH)2 with those of another excipient, sucrose, which increases polymer water content without significantly affecting acid-base chemistry of the polymer. These two excipients, when encapsulated in PLGA at appropriate levels (3% Mg(OH)2 vs. 10% sucrose), were found to cause identical water sorption kinetics, thus allowing the effect of the two microclimate parameters to be determined. In contrast to their similar effects on polymer water sorption, Mg(OH)2 afforded a much greater stabilization effect on encapsulated BSA than did sucrose, with less than 7% aggregates for 3% Mg(OH)2 compared to 51% for 10% sucrose and 81% without either excipient after 4 weeks of incubation at 37 degrees C. When the protein stabilization rationale of neutralizing the acidic microenvironment by adding Mg(OH)2 was applied to the delivery of an important therapeutic protein, tissue plasminogen activator (t-PA), t-PA stability was also improved and the active protein was completely recovered during a one month period of in vitro release. These data demonstrated that although increased water uptake induced by antacid excipients may improve the stability of the encapsulated proteins, the homogeneous acid neutralization effect is unique to antacid excipients such as Mg(OH)2, which is necessary to maintain the stability of proteins in acidic PLGA specimens.

Drug Implants↗
PubMed1998

Knee flexion and base of support in asymmetrical handling: effects on the worker's dynamic stability and the moments of the L(5)/S(1) and knee joints.

OBJECTIVE: To investigate the effects of knee flexion and of the variations of feet lateral spacing on dynamic stability and on the net joint moments distribution between the back and knees. BACKGROUND: The width of the base of support and knee flexion effects on joint moments in asymmetric handling and especially on the worker's stability have rarely been studied. METHODS: Fourteen healthy male subjects performed an asymmetrical lifting task, using four different techniques: two imposed lateral feet spacings (41 and 57 cm) and two knee flexion amplitudes (slightly and deeply flexed knees). A tridimensional dynamic rigid body model was used to estimate the triaxial net reaction moments at L(5)/S(1) and at the knees, using two force platforms. New developments have been undertaken to characterize workers' stability while handling: the horizontal force required to destabilize the worker was calculated as a measure of dynamic stability. RESULTS: The width of the base of support had little effect on L(5)/S(1) and knee moments; however, the subjects were less stable with the narrow base of support. Using the slightly flexed knees technique, trunk maximal resultant moments were slightly smaller (202 vs. 216 Nm), and maximal resultant knee moments were larger (96 vs. 62 Nm). Furthermore, asymmetric moments at the trunk and the asymmetric position of the knees were reduced with this technique, but subjects were less stable. CONCLUSIONS: The use of a slightly flexed knees technique in asymmetrical handling of low-lying loads appears advantageous because it reduces L(5)/S(1) moments while increasing the knees' flexing moments, although this may compromise workers' stability. RELEVANCE: Handling methods used by workers in asymmetrical handling have rarely been studied. Optimizing the safety of a handling method can involve many parameters, such as reducing joint moments and maximizing stability. The evaluation of the worker's stability while handling in conjunction with joint moments is an interesting alternative to study the safety of handling methods.

Journal Article↗
PubMed2000

MSW fly ash stabilized with coal ash for geotechnical application.

The solidification and stabilization of municipal solid waste (MSW) fly ash for the purpose of minimizing the geo-environmental impact caused by toxic heavy metals as well as ensuring engineering safety (strength and soaking durability) are experimentally evaluated. The mixtures of MSW fly ash stabilized with cement and fluidized bed combustion coal fly ash (FCA) were used for unconfined compressive strength tests, leachate tests, and soaking tests. The behavior of soluble salts contained in the MSW fly ash significantly affects strength development, soaking durability, and the hardening reaction of the stabilized MSW fly ash mixtures. The cement stabilization of the MSW fly ash does not have enough effect on strength development and soaking durability. The addition of cement only contributes to the containment of heavy metals due to the high level of alkalinity. When using FCA as a stabilizing agent for MSW fly ash, the mixture exhibits high strength and durability. However, the Cd leachate cannot be prevented in the early stages of curing. Using a combination of cement and FCA as a MSW fly ash stabilizer can attain high strength, high soaking durability, and the containment of heavy metals. The stabilized MSW fly ash with cement and FCA can be practically applied to embankments.

Alkalies↗
PubMed1998

Immunization against East Coast Fever in field cattle with low infectivity Theileria parva stabilate--preliminary assessment.

Two Theileria parva sporozoite stabilates stored at -196 degrees C, then at -70 degrees C for six weeks (stabilate 1) and more than six months (stabilate 2) were inoculated into four eight-month old male calves, 1 and 2 (stabilate 1), and 3 and 4 (stabilate 2). Calves 1 and 2 developed pyrexia, enlargement of lymph nodes, and the former died of East Coast Fever. Calves 3 and 4 showed slight enlargement of lymph nodes without fever. Lymph node smears from all calves (from day 10 to 20 post-inoculation) showed lymphoblasts, phagocytic macrophages, and schizonts. Piroplasms were detected in erythrocytes in blood smears from calves 1 and 2 but not in calves 3 and 4. Calves 2, 3 and 4 recovered without any treatment while calf 1 died of East Coast Fever on day 20. Serum samples from recovered calves taken on day 30 of the experiment were positive for antischizont antibodies to T. parva at 1:640 dilution, but pre-inoculation serum samples were negative. Stabilate 2 was used to immunize 64 Boran, Friesian, Ayrshire and crosses with Zebu cattle in four herds with 25% reduction of oxytetracycline dose. All the animals except one calf recovered without any severe reactions. The latter died of disease other than ECF after the monitoring period was over (day 24). Day 30 post-inoculation serum samples were positive for T. parva antischizont antibodies. A follow-up of the remaining animals for over one year revealed no further ECF incidences in these herds. This experiment shows the loss of infectivity of the vaccine stored at temperatures higher than -196 degrees C. dependent on the duration. However, despite the lack of clinical signs in calves 3 and 4, there was cellular response and antibody production, and the stabilate for vaccine against East Coast fever can thus be stored prior to use at higher than -196 degrees C and still maintain capability to produce antibodies in field cattle, eliminating the use of oxytetracycline and monitoring. The vaccine will be cheaper and easier to use and the requirement for liquid nitrogen in the field reduced and the scale of application of the vaccine widened.

Animals↗
PubMed1998

Cardiorespiratory stability of premature boys and girls during kangaroo care.

The objective of the investigation was to study the stability of the cardiorespiratory system of 20 premature boys and girls during maternal kangaroo care (KC) and in the incubator. Stability of heart rate, respiration and oxygen saturation was compared in a pretest-test-posttest design by means of a stability score. The three stability items and the total stability did not change significantly during the three conditions. In some individuals the stability either increased or decreased markedly during Kangaroo Care. The boys showed significantly less cardiorespiratory stability both during kangaroo care and in the incubator compared to the girls.

Female↗
PubMed1999

Using entropies of reaction to predict changes in protein stability: tyrosine-67-phenylalanine variants of rat cytochrome c and yeast Iso-1 cytochromes c.

Using the voltammetric method of square-wave voltammetry, a direct electrochemical examination was made of the wild type and Tyr67Phe mutant of both rat cytochrome c and yeast iso-1-cytochrome c. In addition to determining the equilibrium reduction potential (E0') for each cytochrome, the entropy of reaction, deltaS0'(Rxn)(deltaS0'(Rxn) = S0'(Red) - S0'(Ox)), for the reduction process was determined via the non-isothermal method. Having determined deltaS0'(Rxn) and E0', deltaH0' was calculated. For rat cytochrome c, it was found that deltaS0'(Rxn) = -43 J mol(-1) K(-1) for the wild type and -53 J mol(-1) K(-1) for the Tyr67Phe variant, with the deltaH0' for both the wild type and variant nearly identical, indicating that the changes in reduction potential and probably stability are due to changes in deltaS0'(Rxn). In contrast the measured deltaS0'(Rxn) for yeast iso-1-cytochrome c demonstrated significant changes in both entropic and enthalpic contributions in going from wild type to mutant cytochrome c. The entropy of reaction provides information regarding the relative degree of solvation, and very likely the degree of compactness, of the oxidized state versus the reduced state of the redox protein. A thermodynamic scheme and stability derivation are presented that show how the entropies of reaction of wild type versus variant cytochromes contribute to and predict changes in stability in going from oxidized to reduced protein. For yeast iso-1-cytochrome c, the thermodynamically predicted change in stability was very close to the experimentally observed value, based on previous differential scanning calorimetric stability measurements. While such data is not available for rat cytochrome c, consideration of the enormously increased local stability of the rat oxidized cytochrome c variant predicts that the reduced rat variant will be even more stable than the already stabilized oxidized variant.

Algorithms↗
PubMed1998

Oculo-motor stabilization reflexes: integration of inertial and visual information.

STABILIZATION OF GAZE IS A FUNDAMENTAL REQUIREMENT OF AN ACTIVE VISUAL SYSTEM FOR AT LEAST TWO REASONS: (i) to increase the robustness of dynamic visual measures during observer's motion; (ii) to provide a reference with respect to the environment ([Ballard and Brown, 1992]). The aim of this paper is to address the former issue by investigating the role of integration of visuo-inertial information in gaze stabilization. The rationale comes from observations of how the stabilization problem is solved in biological systems and experimental results based on an artificial visual system equipped with space-variant visual sensors and an inertial sensor are presented. In particular the following issues are discussed: (i) the relations between eye-head geometry, fixation distance and stabilization performance; (ii) the computational requirements of the visuo-inertial stabilization approach compared to a visual stabilization approach; (iii) the evaluation of performance of the visuo-inertial strategy in a real-time monocular stabilization task. Experiments are performed to quantitatively describe the performance of the system with respect to different choices of the principal parameters. The results show that the integrated approach is indeed valuable: it makes use of visual computational resources more efficiently, extends the range of motions or external disturbances the system can effectively deal with, and reduces system complexity.

Journal Article↗