SEARCH · PubMed Health

Results for “DAMPs”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources

PubMed1990

Immunocytochemical evidence for the acidic nature of peroxisomes in methylotrophic yeasts.

The possible acidic nature of the peroxisomal matrix present in intact yeast cells was studied immunocytochemically, using the weak base DAMP as a probe. Spheroplasts of methanol-grown Candida boidinii and Hansenula polymorpha were regenerated and incubated with DAMP. After immunogold labelling, using antibodies against DAMP, a specific accumulation of gold particles was observed on the peroxisomal profiles. This labelling was absent in controls, performed in the presence of ionophores or chloroquine. These results support earlier observations, that in intact cells a pH-gradient exists across the peroxisomal membrane. Experiments, carried out on osmotically swollen spheroplasts indicated that maintenance of this pH-gradient is strongly related to the cell's integrity.

Candida↗

PubMed1989

Linear and nonlinear one-dimensional models of pulse wave transmission at high Womersley numbers.

The accuracy of nonlinear and linear one-dimensional models in describing pulse wave propagation in a uniform cylindrical viscoelastic tube, with Womersley's parameter alpha equal to 7.6 at 1 Hz, was evaluated. To this end calculations of wave propagation using these models were compared with the experimentally determined propagation of the pressure wave in the tube. The experimentally generated pressure pulse had an amplitude of 9.0 kPa and caused a relative radius change of about 17%. The static pressure vs cross-sectional area relation was found to be nonlinear for these pressure changes. Maximum fluid velocity was about 2.9 ms-1, while the phase velocity was about 5.4 ms-1. The radius change and the ratio of fluid and phase velocities violated the linear model assumptions. The nonlinear model with viscous fluid friction modelled on the basis of Poiseuille's law and treating the tube wall as purely elastic, underestimated the damping of the pulse wave and predicted the formation of shock waves, which were not found experimentally. In the linear models, the viscous friction of the blood was modelled according to either Poiseuille's law or Womersley's theory and the tube wall was treated as either linearly elastic or linearly viscoelastic. A description of the viscous friction of the blood based on Poiseuille's law underestimated damping. Disregarding the viscoelasticity of the tube wall resulted in an underestimation of both phase velocity and damping. In spite of the nonlinearity of the system, the linear viscoelastic Womersley model described the pulse wave propagation satisfactorily.

Animals↗

PubMed1992

Impedance response characteristics of the primate Mucaca mulatta exposed to seated whole-body gz vibration.

A mathematical model was used to quantify and describe the variability in the mechanical impedance response of the Rhesus monkey subjected to vibrations in the range 3-20 Hz at 0.5 g peak acceleration. Due to the similarities in response, a two-mass, one-degree-of-freedom (DOF) model was selected and the associated mechanical parameters determined using a nonlinear least-squares optimization program. For the six tests conducted on each of the four subjects, appreciable parameter variations were observed within a subject; however, the majority of the mean parameter values among different subjects and among the repeated tests on the population were within +/- 1 S.D. of each other. Significant differences were observed in the stiffness coefficient and the total mass among different subjects, and in the mass ratio (between inert and sprung masses) among the repeated tests. Variations in the profile shapes following resonance were described and limited by changes in the mass ratio and the damping factor. Higher mass ratios (greater than 1.0) were associated with lower damping factors (less than 0.50). The impedance response beyond resonance approached the response described by the impedance of the inert mass and the damper elements of the model combined in parallel, and supported the assumption that the lower torso was rigidly attached to the seat. Physically, the reactive force produced by the upper torso increasingly diminished following resonance, due to the load transmission/attenuation characteristics of the spinal structures at 0.5 g peak acceleration. The impedance measured at the seat becomes dominated by the transmitted damping force associated with the spine and the force generated by the rigid lower-torso mass.

Acceleration↗

PubMed1989

Transthoracic defibrillation threshold of sine and trapezoidal waveforms in defibrillation.

The transthoracic defibrillation threshold of trapezoidal (2.5-, 5-, 10-, 15-, 20-, 40-, and 55-msec duration) and damped sine waveforms were established in groups of anesthetized greyhounds. Of the seven trapezoidal waveforms, the threshold current was lowest for the 20-msec pulse but was not significantly different for the 5-20-msec pulses (p greater than 0.05). The threshold delivered energy was not significantly different for the 2.5-20-msec waveforms. The 40- and 55-msec pulses had significantly greater delivered energies than the shorter pulses (p less than 0.01). The transthoracic defibrillation threshold of two trapezoidal (5- and 20-msec) and three damped sine waves (Lown, Edmark, and Belfast) showed that the threshold transthoracic current and energy were not significantly different for the 5-msec trapezoid and three sine waves (p greater than 0.05). The threshold transthoracic energy for the 20-msec trapezoid was significantly greater than that of the four other waveforms. The threshold current for the 20-msec trapezoid was significantly less than that of the Belfast and Edmark waveforms only. Thus, none of the three damped sine waveforms was superior, with the 5-msec trapezoid producing similar results. Although the 20-msec trapezoid had the lowest threshold current, it had the highest delivery energy.

Animals↗

PubMed1992

Involvement of the muscarinic receptors in the postsynaptic potentiation of neurogenic twitch contraction in the mouse vas deferens.

Muscarinic agonists and three selective antagonists were used in an attempt to characterize the muscarinic receptor subtypes which regulate the electrically evoked, neurogenic twitch contraction of the mouse vas deferens. The neurogenic contraction was concentration-dependently potentiated by both carbachol and oxotremorine, but not McN-A-343. These agonists also potentiated the contraction of unstimulated preparations elicited by exogenous ATP. However, potentiation of the neurogenic twitch contraction was strongly antagonized by pretreatment with 4-DAMP (IC50 = 1.38 nM for carbachol, and 4.79 nM for oxotremorine). The inhibitory effects of methoctramine and pirenzepine (PRZ) were about 100 times lower than those of 4-DAMP; the descending order of antagonistic potencies was: 4-DAMP much greater than methoctramine approximately equal to PRZ. These results suggest that muscarinic receptors are involved in the postsynaptic potentiation of the neurogenic twitch contraction in the mouse vas deferens. Classifications for the muscarinic receptor subtypes were discussed.

Animals↗

PubMed1983

Misincorporation in DNA synthesis after modification of template or polymerase by MNNG, MMS and UV radiation.

The synthetic DNA polymers, poly(dG-dC), poly(dC), poly(dA-dT), poly(dA) and poly(dT), were treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl methanesulfonate (MMS) and UV irradiation. The modified polymers were used as templates to examine the incorporation of non-complementary nucleotides by E. coli DNA polymerase I. Methylation of poly(dG-dC) by MNNG predominantly induced the misincorporation of dTMP, whereas methylation by MMS induced that of dAMP. Treatment of poly(dT) with MNNG caused the misincorporation of dGMP to a considerable extent, but MMS did not enhance the error on poly(dT). The misincorporation of dAMP on poly(dC) and that of dGMP on poly(dA) were also increased by these chemicals. UV irradiation of poly(dT) and poly(dC) induced the error of dGMP and dAMP, respectively. These data on MNNG and MMS in vitro were in fair agreement with the directions of mutation in vivo. But the predominant induction of transitions by UV in vitro did not agree with the UV-induced transversions in E. coli. This inconsistency suggested the participation of other factors than direct mispairing in UV-induced transversion. Modification of DNA polymerase I by MNNG changed the ratio of polymerase to 3' leads to 5' exonuclease activity altering the fidelity of this enzyme, whereas MMS and UV-irradiation did not alter the fidelity of the enzyme.

DNA↗

PubMed1986

The effects of refuges on predator-prey interactions: a reconsideration.

Prey refuges are widely believed to prevent prey extinction and damp predator-prey oscillations. A review of the empirical evidence suggests that refuges are indeed capable of playing the former role. But the conditions under which they do so are not understood, nor is there any solid evidence for an effect on population fluctuations. The intuitive view that refuges act to stabilize equilibria and damp predator-prey oscillations is based in several theoretical studies of extremely simple models. Using a more realistic model, I show that several kinds of refuges can exert a locally destabilizing effect and create stable, large-amplitude oscillations which would damp out if no refuge was present. This finding contrasts sharply with the usual view. I argue that current evidence is tol weak, and the range of theoretically possible effects is too broad, to justify any simple characterization of refuge effects in nature. Manipulative empirical studies are an important first step toward correcting this situation, and I discuss some important factors to consider in their design.

Animals↗

PubMed1993

In vitro bond strength of two adhesives to enamel and dentin under normal and contaminated conditions.

In vitro bond strengths of human enamel and dentin treated with five contaminants were measured with air, water and damp conditions as controls. Two commercial bonding agents (a lower-viscosity, solvent-containing type, AB, and a higher-viscosity, hydrophilic monomer type, SB) and their composites were applied to tooth structure under two conditions (contaminated and re-etched). Samples were debonded in tension after 24 h using an inverted, truncated cone test. Among the controls, the highest bond strengths were obtained with damp conditions for AB (24 MPa) and damp conditions or air for SB (22 MPa) with small differences between enamel and dentin. Most contaminants lowered the bond strength. Re-etching without additional mechanical preparation resulted in bond strengths similar to controls. Bond strengths to tooth structure with the bonding agents tested may be less sensitive to common forms of contamination than typically assumed.

Acid Etching, Dental↗

PubMed1990

Preliminary report: hepatic vein Doppler in the early diagnosis of acute liver transplant rejection.

37 transplanted livers (in thirty patients) were assessed by serial doppler ultrasound examination. 18 of 23 biopsy-proved rejection episodes were associated with abrupt damping of the normally pulsatile blood flow of the hepatic veins. In the other 5 episodes, the waveforms were damped at the outset by perioperative ischaemia. There were no rejection episodes with normal traces. Another cause of damping was cholangitis (5 episodes), but this was distinguishable clinically and biochemically. There were no episodes of rejection with normal hepatic vein traces. Serial doppler examination, in combination with clinical evaluation, may allow earlier diagnosis and treatment of liver rejection.

Acute Disease↗

PubMed1988

Repetitive excitation of bursts of action potentials in the rat hippocampus following single shock stimulation.

1. Post-stimulus time (PST) histograms of rat hippocampal cells were recorded in vivo following single-shock stimulation of the fornix. 2. The PST histograms displayed a series of peaks of decreasing amplitude, similar to damped oscillatory responses previously recorded in cats and rabbits. 3. The effect of increased background activity was investigated by recording histograms with concurrent pulse train stimulation of the contralateral hippocampus. The histograms showed a decreased latency to the onset of the second peak. 4. Damped oscillatory activity seen in the in vivo rat preparation could not be elicited in the in vitro rat slice preparation. Thus species differences cannot account for the absence in slice studies of this type of damped oscillatory activity. 5. We conclude that the level of spontaneous activity is one factor contributing to the genesis of multiple peaks in histograms in the in vivo preparation.

Action Potentials↗

PubMed1992

The effects of selective matrix degradation on the short-term compressive properties of adult human articular cartilage.

The effects of proteoglycan and collagen digestion on the transient response of human articular cartilage when tested in unconfined compression were determined. Small cylindrical specimens of cartilage, isolated from the femoral head of the hip joint and from the femoral condyles of the knee joint, were subjected to a suddenly applied compressive load using a test apparatus designed to yield a transient oscillatory response. From this response values of the elastic stiffness and the viscous damping coefficient were determined. Cathepsin D and cathepsin B1 were used to digest the proteoglycan in some specimens, while in other specimens leukocyte elastase was used to attack the non-helical terminal regions of the Type II tropocollagen molecules and possibly the Type IX collagen molecule and thereby disturb the integrity of the collagen mesh. The results showed that proteoglycan digestion alone reduced the viscous damping coefficient but it did not significantly alter the elastic stiffness as determined from the oscillatory response. In contrast, the action of elastase reduced both the damping coefficient and the elastic stiffness of the cartilage. The results demonstrated the role of proteoglycans in regulating fluid transport in cartilage and hence controlling the time-dependent viscous properties. The elastic stiffness was shown to be dependent on the integrity of the collagen fibre network and not on the proteoglycans.

Aged↗

PubMed1987

Deoxyadenosine deamination and phosphorylation in rat liver mitochondria.

1. Deoxyadenosine metabolism was measured in freshly isolated mitochondria; these organelles took up the deoxynucleoside and formed three detectable products: deoxyinosine, dAMP and dIMP. 2. Enzyme extracts prepared from sonicated mitochondria exhibited deoxyadenosine deaminase, deoxyadenosine kinase, dAMP deaminase and deoxyinosine kinase activities. 3. These data suggest that deoxyadenosine was initially altered in mitochondria by at least two metabolic reactions--deamination and phosphorylation. Deoxyinosine and dAMP were produced. 4. These two products were subsequently phosphorylated and deaminated, respectively to produce dIMP.

Adenosine Deaminase↗

PubMed1985

Visual circadian rhythmicity in splitbrain crayfish: a plastic behavioral expression of symmetric circadian pacemakers.

Electroretinographic evoked potentials (ERG's) were continuously recorded in dark-adapted, splitbrain crayfishes Procambarus bouvieri. Pulses of light (0.95 cd/m2) illuminating the left or the right eyes were alternatively applied every 15 or 30 min. As compared to intact crayfish, uni or bilateral damping or suppression of circadian retinal sensitivity rhythm could be caused by surgical bisection of cerebral ganglion in these crustaceans. The damped ERG circadian rhythm was rapidly reversed by reduction or elimination of the test light stimulus to the contralateral eye. Given the redundant processing of pacemaking information coming from bilaterally positioned cephalic circadian pacemakers to the central nervous system in splitbrain crayfish, photodependent damping of ERG rhythm revealed a plastic potential of central circadian pacemakers. The possibility that a strong but reversible inhibitory influence acts simultaneously upon the left and right protocerebral circadian pacemakers while receiving bilateral photic stimulation is considered.

Animals↗

PubMed2005

Gender and age effects on elbow joint stiffness in healthy subjects.

OBJECTIVE: To investigate the effect of demographic factors on upper-limb pendulum tests in healthy subjects. DESIGN: Experimental. Upper-limb pendulum tests were performed on healthy subjects. Biomechanical parameters of the elbow joint were estimated. The body weight, forearm length, gender, and age of subjects were recorded. The relationships among the biomechanical parameters and demographic factors were investigated. SETTING: A referral medical center in Taiwan. PARTICIPANTS: Healthy subjects (N=192). INTERVENTION: Upper-limb pendulum test. MAIN OUTCOME MEASURES: Number of swings, relaxation indices calculated from the angle trajectories, and stiffness constants and damping coefficients estimated from the elbow model were used as the biomechanic parameters of elbow joints. RESULTS: Age had little effect on the biomechanic parameters. Both mean stiffness constant and damping coefficient were larger in men. However, when the influence of body weight was corrected, the biomechanic parameters were the same for both genders. Forearm length had similar but weaker effects on stiffness constant and damping coefficient. CONCLUSIONS: In healthy subjects, the mechanical properties of the elbow joints were similar in men and women of comparable body weights and did not deteriorate significantly until subjects reached the age of 70 years.

Adult↗

PubMed2004

The mono-exponential pattern of phosphocreatine recovery after muscle exercise is a particular case of a more complex behaviour.

A mathematical model is proposed showing that the mono-exponential recovery of phosphocreatine (PCr) after exercise is an approximation of a more complex pattern, which is identified by a second-order differential equation. The model predicts the possibility of three different patterns of PCr recovery: bi-exponential, oscillatory damped, and critically damped; the mono-exponential pattern being a particular case of the functions which are solutions of the differential equation. The model was tested on a sample of recovery data from 50 volunteers, checking whether the recovery patterns predicted by the model lead to a significant improvement of fit (IF) compared with the mono-exponential pattern. Results show that the IF is linked to pH. Bi-exponential solutions showed an IF in the pH range 6.65-6.85, and the oscillatory solutions at pH>6.9. Critically damped solutions displayed a poor IF. Oscillation frequencies found in the oscillatory recoveries increase at increasing pH. These results show that pH has a pivotal role on the pattern of PCr recovery and implications on the regulation of oxidative phosphorylation are discussed.

Exercise↗

PubMed2004

Excitation of vibrations in microtubules in living cells.

Microtubules, which are thought to be the primary organizers of the cytoskeleton, are electrical polar structures with extraordinary elastic deformability at low stress and with energy supply from hydrolysis of guanosine triphosphate (GTP) to guanosine diphosphate (GDP). At least a part of the energy supplied from hydrolysis can excite vibrations. Energy is mainly lost by viscous damping of the surrounding cytosol. Viscous damping is diminished by a slip layer which is formed by an attracted ionic charge layer and by a thin surface layer of the microtubule. Relaxation time caused by viscous damping may be several orders of magnitude greater than period of vibrations at 10 MHz. Energy supplied to the microtubule is of the order of magnitude of 10(-14) W cm(-1) (per unit length of the microtubule).

Animals↗

PubMed2004

The relations among upper-extremity loading characteristics and bone mineral density changes in young women.

The relations among the reaction forces engendered during an upper-extremity dynamic impact-loading exercise (DILE) program and bone mineral density adaptations (DeltaBMD) in the radius were investigated in 24 healthy premenopausal women (mean age = 29 +/- 6 years). Subjects performed DILE 36 cycles/day, 3 days/week for 24 weeks. The exercised arm was allocated randomly to either the dominant or the nondominant limb. In addition, subjects were assigned randomly into either damped or nondamped treatment arms to examine the effects of both higher- and lower-magnitude loading prescriptions. Measurements including anthropometrics, self-reported physical activity levels, hand-grip strength, radial BMD (DEXA, Hologic QDR1500, MA) at the ultradistal radius (UD), distal 1/3 radius (DR), and total distal radius (TOTAL), and exercise-related loading characteristics (impact load, loading rate, and impulse) were recorded at baseline and at 6 months. Simple linear regression models were used to fit the regional BMD changes to the reaction force, changes in hand-grip strength (DeltaGRIP), and changes in body weight (DeltaBW). Findings demonstrated that the damping condition utilized during DILE influenced the relations between loading events and BMD changes. Specifically, none of the reaction-force characteristics significantly predicted changes in BMD in participants performing DILE using the damped condition, whereas, in the nondamped condition, impact load accounted for 58% of the variance in BMD change at DR and 66% of the variance in BMD change at TOTAL. Thresholds of 345 and 285 N of impact force to promote BMD increases at DR and TOTAL, respectively, were obtained from the regression models in the nondamped group. Impulse was also an independent predictor of BMD changes at TOTAL, accounting for 56% of the variance. Neither DeltaGRIP nor DeltaBW significantly predicted DeltaBMD at any radial site. These findings, in young adult women, parallel previous reports identifying significant, regionally specific relations among external loading events and BMD changes in both animal and human models.

Adult↗

PubMed2005

Comparison of vertebral artery velocity and flow volume measurements for diagnosis of vertebrobasilar insufficiency using color duplex sonography.

INTRODUCTION: The aim of this study was to compare the measurements of vertebral artery (VA) systolic flow velocity and flow volume for diagnosis of vertebrobasilar insufficiency (VBI). MATERIAL AND METHODS: We examined 96 patients who were referred for evaluation of VBI. Net vertebral artery flow volume and mean systolic flow velocity were determined by using color duplex sonography. We had grouped the patients into three according to VA flow volume: group 1 was consisted of patients with severely damped VA flow volume (lower than 120 mL/min), group 2 was consisted of patients with moderately damped VA flow volume (120-200 mL/min), group 3 was consisted of patients with normal VA flow volume (>200 mL/min). The mean systolic flow velocities in each group were compared by one-way ANOVA. RESULTS: Mean VA systolic flow velocities of groups 1, 2 and 3 were 32 +/- 12, 42 +/- 10 and 46 +/- 8 cm/s, respectively. Mean VA systolic flow velocity in group 1 was significantly lower than that of group 2 (P = 0.001). However, there were no significant differences between VA systolic flow velocities in groups 2 and 3 (P = 0.2). CONCLUSIONS: According to our findings, measurement of volume in addition to velocity is more valuable in detection of moderately damped VA flow volumes in diagnosis of VBI.

Adolescent↗