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At least 505 records · Page 28Linked to original sources
PubMed1974

Self-damping mechanism in blood coagulation.

Two reactions of the extrinsic pathway of coagulation, the activations of Factor X and prothrombin, have been studied in purified systems and shown to be self-damping. Factor X was activated by the tissue factor-Factor VII complex, and prothrombin by two systems: the coagulant protein of Taipan venom, and the physiological complex of activated Factor X, Factor V, lipid, and calcium ions. In each case the yield of enzyme, activated Factor X or thrombin, is a function of the concentration of activator. These and other observations are considered as a basis for a control mechanism in coagulation.

Blood Coagulation↗
PubMedDate not supplied

Cardiac damage produced by transchest damped sine wave shocks.

High-energy transchest damped wave sine defibrillation shocks have been shown to produce cardiac damage when applied in rapid sequence. However, there are no reports as to whether single, threshold-intensity shocks produce damage. In this study, nonfibrillating dogs were subjected either to a single, threshold-intensity (1 A/kg) shock, or to a series of 6 shocks with high intensity (3 to 4.8 A/kg). Electrodes of 8 cm diameter were used to apply the shock through the chest wall. Dogs receiving shocks of adequate (but not excessive) strength to defibrillate showed no cardiac damage, although they exhibited transient ventricular arrhythmias after the shock was applied. All dogs receiving the higher intensity, multiple shocks showed gross and microscopic evidence of cardiac damage. Ventricular lesions were observed in both right and left ventricular free walls and were sometimes transmural in extent. ECG analysis of the records from the dogs receiving multiple, high-intensity shocks showed second and third degree A-V block, ventricular ectopic beats, ventricular tachycardia, S-T segment changes, and T-wave inversion. Although multiple, high-energy, high-current defibrillation shocks produce permanent cardiac damage in dogs, threshold shocks do not produce morphologic changes.

Animals↗
PubMedDate not supplied

Evaluation of the operating internal resistance, inductance, and capacitance of intact damped sine wave defibrillators.

A method is developed for determing actual values of circuit elements in a damped sine wave (Lown waveform) defibrillator solely from measurements of the output, using two or more power resistors and a storage oscilloscope. If a defibrillator containing capacitance C, inductance L, and internal resistance RI, is discharged into increasing 5- to 100-ohm resistive loads R, it is shown for underdamped output waveforms that â = RI/2L + R/2L and ĉ = CRI + CR, where â = pi[t2tan(pit1/t2)], ĉ = 2â/[â2 + (pi/t2)2], t1 = time from onset to peak, and t2 = time from onset to first zero crossing of the output waveform on the oscilloscope trace. Linear plots of â vs R are constructed for seven defibrillators, and values of RI and L computed as intercept/slope and 1/(2 slope) respectively. C is given by the slope of a linear plot of ĉ vs R. Delivered energy is accurately predicted as stored energy X R/(RI + R).

Electric Conductivity↗
PubMed1984

The action of caffeine on X-irradiated HeLa cells. VI. Damping of the structured age-survival function.

Postirradiation treatment of synchronous HeLa S3 cultures with 4 mM caffeine until greater than or equal to 32 hr after mitotic collection, following exposure to 220-kV X rays at various times during interphase, severely damps the fluctuations in the age-survival curve. Not only does the dose-survival curve essentially lose its shoulder, as reported previously, but it becomes steeper and displays a virtually age-independent terminal slope (D0 congruent to 0.5 Gy). It becomes multicomponent, at least early in the cycle. The residual structure in the interphase age-survival curve, if any, appears to reflect mainly an age-dependent fluctuation in the size of a subpopulation of cells having marked sensitivity to X rays (D0 congruent to 0.25 Gy), though there might be small residual fluctuations in the size of the shoulder and the slope. Mitotic cells also respond to postirradiation treatment with caffeine; they yield a dose-survival curve whose slope is similar to that of the sensitive subpopulation seen in interphase. These findings indicate that most of the structure in the unperturbed age-survival function derives from repair of potentially lethal radiation damage.

Caffeine↗
PubMedDate not supplied

[Conformational mobility and theory of the Mössbauer effect in biological systems. (Model of a Brownian oscillator strongly damped for conformational modes)].

Specific features of the Mössbauer effect on proteins are discussed. It is found that the temperature dependence of recoilless gammaquantum absorption, f'(T), cannot be explained in terms of solid effects or diffusion spectrum broadening in liquids. A sharp decrease in f'(T) at temperature above 200 degrees K that has been found is due to the specificity of the conformational mobility of proteins and due to a smaller correlation time for spacially-confined diffusion of a Mössbauer label tracer below a critical value of tau approximately 10(-7) s (the lifetime of 57Fe excitation). Protein conformational mobility is described by a Brownian, strongly damped oscillator. For this model, a new formula for the Mössbauer effect probability is derived. Calculations by the formula and corresponding experimental data are in good accord. By the formula for f'(T), a theoretical temperature dependence of medium microviscosity (with an activation energy of 5 kcal/mol) and estimates for some parameters are obtained.

Bacterial Chromatophores↗
PubMed1982

The reliability of MCLs with pure tones and damped wave trains.

Most Comfortable Loudness (MCL) was determined for each of 10 normal-hearing young adults using pulsed pure-tone trains and damped wave trains (DWTs) each at 2.5/sec, at frequencies of .25 and 2 kc/s; 4 MCLs were determined for each of the 4 signal type/frequency combinations. In a bracketing procedure employing steps of 20, 10, and finally 5 db, Ss were permitted to respond only "loud" or "soft" to each short train. Group mean test-retest differences within each stimulus type/frequency combination were only 1-2.5 db for all possible test-to-contiguous-test comparisons, i.e., better than with most other MCL procedures except the descending series in the Method of Limits. However, individual Ss differed by from 15-35 db within the 16 distributions (2 stimulus types X 2 frequencies X 4 replications). No statistical or practical differences were found between pure tones or DWTs, or across frequency. It was suggested that the range of individual differences renders any group mean MCL too imprecise a measure for selecting and prescribing a hearing aid, or for determining the effect that aid may have on an individual's performance.

Acoustics↗
PubMed1980

[Problems of a frequency-specific threshold measurement with the brainstem potentials using the otometric sound pressure signal (damped wavetrain) (author's transl)].

This study aimes at investigating if the damped wavetrain stimulus (Victoreen) may be used in the evaluation of frequency specific thresholds using brainstem potentials. Stimulus frequencies were 1, 4, and 8 kHz. Starting with a control group (10 persons) latency curves for the brainstem potentials were established. The test group included patients with various forms of sensorineural hearing loss in the audiogram. Threshold measurements at the three stimulus frequencies were done with these patients using the potential IV (Jewet V). The latency curves of the normal hearing control group reveal a frequency-specific information being present in the brainstem potentials. This can be derived from latency shifts at different stimulus frequencies. However, investigating patients with a steep slope or a notch in the pure-tone audiogram introduces some difficulties in the ERA-threshold evaluation.

Audiometry, Evoked Response↗
PubMedDate not supplied

Examination of the damping behavior of IMZ implants.

The damping behavior of 392 IMZ implants with a diameter of 4 mm was examined by performing Periotest measurements during regular implant follow-up. The results were correlated with radiographically assessed peri-implant bone reduction. To guarantee statistical independence, only one randomly chosen implant per patient was considered in the examination. In 167 implants, the difference between the mean mandibular and maxillary Periotest values proved to be statistically significant. Age, sex, and radiographic length of the endosseous part of the abutment had no influence on the Periotest values. Assessment of the Periotest values can thus be considered an additional parameter for objective determination of IMZ implant success. However, exclusive use of the Periotest method without additional radiographic examinations does not seem to be justified.

Adult↗
PubMed1995

[A study on relationship between balance of serum lipoprotein and the phlegm damp-blood stasis syndrome differentiation of coronary heart diseases].

75 patients were divided into A,B and C group. The LDL-C was 2.97 +/- 0.67, 4.05 +/- 0.38 and 5.25 +/- 0.98 mmol/L respectively (P > 0.01); but comparing group A or B with the normal group (D), it had no significant difference (P > 0.05). An abnormal coronary arteriography (CAG) was found in the group A in 62.1% and the group B in 57.6% (P > 0.05), while the group C in 84.6% (P < 0.01). There was unusual serum lipoprotein electrophoretogram (SLPG) in group A 75.9%, group B 84.8% and group C 100%, but it had no change in group D (P < 0.001). Five types of Syndrome Differentiation about the Phlegm damp and blood stasis (PDBS) could be found in the group A,B and C. The incidence (51.5%-55.2%) and abnormality of the SLPG (66.7%-92.5%) and CAG (68.8%-100%) of PDBS type were the highest among them. 82.7% CHD patient's clinical comprehensive diagnosis was in accordance with the SLPG and that of the CAG were 64.0%. As to the abnormal SLPG, the sensitivity and rate of coincidence of CAG was 91.7% and 69.3% (P < 0.05-0.01) respectively. The Syndrome Differentiation of PDBS was valuable in differentiating CHD. The SLPG is a good criterion for the study of CHD in TCM.

Adult↗
PubMed1994

Pulpal response to adhesive resin systems applied to acid-etched vital dentin: damp versus dry primer application.

A number of studies have reported that acid etching of dentin is toxic to the cells of the odontoblastic layer and dental pulp. Other studies report that pulpal inflammation is a consequence of bacterial microleakage. The purpose of this study was to observe the degree of pulpal healing after pretreatment of vital dentin prior to placement of All-Bond and Scotch-bond 2 composite resin adhesives. Zinc oxide-eugenol cement and an acidic cement were employed as controls. One hundred twelve Class V nonexposed cavity preparations were placed throughout the dentitions of five healthy adult rhesus monkeys and observed at 3, 25, and 80 days. Various dentinal pretreatment procedures were employed. The All-Bond Universal primer system was placed on air-dried vital dentin in 23 cavities and on damp vital dentin in 27 cavities. Scotchbond 2 was placed as per manufacturer's instructions. All treatment procedures, materials, and times were represented in all animals. Placement of silicate cement resulted in the most severe pulpal responses at all time periods. Stained bacterial profiles in the remaining dentin on the axial walls of inflamed control pulps were associated with severe pulpal inflammation. These results indicate that acid etching of vital dentin does not impair pulpal healing in deep Class V cavities.

Acid Etching, Dental↗
PubMed1976

Damped pendular rotation nystagmus after unilateral labyrinthectomy or unilateral lateral semicircular canal block in squirrel monkeys.

Using a damped pendular rotation table, which provided an oscillation of 15.5 sec, per-rotatory nystagmus, was evaluated in six squirrel monkeys that underwent unilateral labyrinthectomy and five that underwent unilateral lateral semicircular canal block, both pre- and postoperatively. The bidirectional summation of the nystagmic slow-phase eye speed after unilateral labyrinthectomy and after unilateral lateral semicircular canal block showed similar reduction to about 60 per cent of the values obtained in the pre-operative status. Under the present test situation, both slow-phase eye speed and number of nystagmic beats in the monkeys after unilateral lateral semicircular canal block were larger by the ampullopetal stimulation than those evoked by ampullofugal stimulation. The relation between slow-phase eye speed and number of beats showed similar tendency when we compared pre-operative controls and the group after unilateral lateral semicircular canal block, but the monkeys after unilateral labyrinthectomy depicted different tendencies.

Animals↗
PubMed1995

[The damped torsion swing test in guinea pigs].

The damped torsion swing test (DTST) was carried out for assessing the vestibular function in guinea pigs. Twenty guinea pigs which had normal pinna reflexes and normal tympanic membranes were used. In the formula, L represented the number of the left nystagmus, and R the right nystagmus during DTST. The symmetric rate [formula: see text] between left and right nystagmus was calculated. Then the animals were randomly divided into two groups: (1) Gentamicin group (n = 10): DTST was reexamined, Animals were injected with gentamicin (250 mg/kg) for three days. (2) Endolymphatic hydrops group (n = 10): Surgical obliteration of the right endolymphatic sac and duct was done, 30 days later DTST was carried out again. The results showed: (1) The normal value [formula: see text] of DTST in the 20 healthy guinea pigs is less than 8.25%. (2) Both of left and right nystagmus were reduced (P < 0.01) in gentamicin group. (3) The number of the right nystagmus was reduced in endolymphatic hydrops group (P < 0.01) and the symmetric rate of 6 animals was more than 8.25%. It is concluded that DTST is an important method of evaluating vestibular function in guinea pigs.

Animals↗
PubMed1985

Relief of pressure damping during coronary angioplasty: a device for creating side holes in PTCA guiding catheters.

Percutaneous coronary angioplasty guiding catheters occasionally wedge in the coronary orifice and obstruct blood flow, making completion of the balloon dilatation difficult. Side holes may be made in the catheter, but when created free-hand may not be ideal. This report describes a device for creating side holes of small size, with uniform shape, and without rough edges. The disadvantages of dye extravasation and loss of strength in the catheter are minimized.

Angina Pectoris↗