Contraction Delay Research Articles

Proprioception in the knee and reflex hamstring contraction latency

There are various methods of measuring proprioception at the knee. Beard et al (1993) have described a delay in reflex hamstring contraction in anterior cruciate deficient knees. We have repeated their experiment and were unable to detect any significant difference in reflex hamstring contraction between the injured and uninjured legs. We discuss possible neurophysiological and biomechanical causes for the conflicting results and conclude that this method may not be a valid measure of proprioception.

Ultraviolet-A induced delayed wound contraction and decreased collagen content in healing wounds and implant capsules.

Chronic exposure to ultraviolet-A radiation causes changes in the biochemistry of dermal connective tissue. To investigate its effects on wound healing, we irradiated Sprague-Dawley rats for 4 months using a black ray ultraviolet-A radiation source (560 J/cm2). Full thickness skin wounds of 2 cm in diameter were then created on the back of each animal and silicone cubes were implanted subcutaneously into the irradiated area of the back. Wound contraction in the irradiated animals (n = 28) was significantly slower than that of the controls (n = 29) (p < 0.001). Postoperatively, the hydroxyproline content of the contracted wounds and the implant capsules was assessed at 6 and 12 weeks, respectively. In the irradiated animals, it was found to be significantly less than that of the controls (p < 0.001). A delay in wound contraction and a decrease in hydroxyproline content of healing wounds and implant capsules, reflecting an alteration in collagen metabolism, are two effects of prolonged intermittent ultraviolet-A radiation pretreatment.

Reversal of gelatin-impaired wound healing in rats by exogenous fibronectin

Animal experiments have shown that administration of gelatin results in a deprivation of plasma fibronectin (FN) and impaired wound healing. For further elucidation of these findings a therapy study with purified human FN was performed in rats. Fifty animals received a standard burn injury of 1% body surface and were divided into five experimental groups. Positive controls given no further treatment or treated with solvent only served for estimation of normal healing. For a negative control, 10 animals received three intraperitoneal injections of gelatin (58 mg/kg body wt) on Days 0, 1, and 2 after injury. They exhibited a striking lack of plasma FN (Day 1) and a significant delay of wound contraction (Days 7 and 14). In the therapy groups each administration of gelatin was followed by an intraperitoneal or intracardiac injection of FN (58 mg/kg body wt) 1 hr later. In these animals the negative effect of gelatin upon plasma FN and wound contraction was prevented. According to this study wound healing is menaced by FN deficiency and can be optimized by substitution of exogenous FN.

Effects of tiropramide on the activity of lower urinary tract in dogs and its interpretation

The rhythmic contractions of urinary bladder under constant volume condition were evoked in decerebrate and de-anesthetized dogs, while various myogenic and nerve-mediated electrical and mechanical activities of smooth muscles were recorded from in vivo pelvic viscera. The vesical rhythmic contractions were transiently and partially blocked by intravenous application of tiropromide. This 'partial' block showed a good contrast to the 'complete' block of identical contractions, which was observed after application of oxybutynin, known as a potent anti-muscarinic drug. The bladder voiding cycles were observed in other decerebrate dogs, while the warmed Ringer solution was infused at a steady rate into the dome of the bladder until principal voiding contraction occurred in cystometric recordings. The initiation of voiding contraction was markedly delayed after intravenous injection of tiropramide. The delay of principal contraction was found to be due to successive appearance of falling waves in cystometric recordings. As a evident contrast, terodiline caused a significant reduction of voiding contraction height and shortening of clonic discharge phase of external urethral sphincters during voiding cycle. It is concluded that tiropramide does not reveal anti-muscarinic action which oxybutynin or terodiline does really show, instead tiropramide acts principally on bladder detrusor itself, especially on its relaxation phase of premature contraction to be prolonged. The evidences were also presented for electrophysiological identification of bladder detrusor and urethral smooth muscle.

Effects of right ventricular pacing rate on the pattern of left ventricular contraction and filling as assessed by radionuclide ventriculography.

Changes in the pattern of the global left ventricular (LV) time-activity curve with increasing pacing rates were evaluated using radionuclide ventriculography in 15 patients with chronically implanted right ventricular VVI pacemakers. The variables obtained were correlated with the conventional systolic time intervals recorded immediately after radionuclide ventriculography in 8 of the 15 patients. Increasing the pacing rate from 50 to 110 beats per minute (bpm) altered the pattern and timing of LV contraction and filling dramatically. It produced progressive delay and reduction of LV contraction, thus shortening the LV diastolic filling time, and sometimes resulting in LV filing even during early systole. Despite these profound alterations, relative cardiac output increased progressively, peaking at a pacing rate of 110 bpm in most patients. In paced patients, filling parameters and diastolic timing intervals require careful attention, since they may be difficult to determine from the altered LV time-activity curve at higher pacing rates.

Emulation of Conduction System Functions in the Hearts of Early Mammalian Embryos

The conduction system functions of atrioventricular sequential contractions, atrioventricular delay, and coordination of ventricular contraction were examined in rat embryos at the earliest functional stage of cardiac development (before cardiac looping, n = 6) and shortly after looping (n = 15). Atrioventricular sequential contractions were observed in all embryos, and contractions appeared to originate in the left sinus horn. Atrioventricular delay was present in both prelooped (132 +/- 32 ms) and looped (141 +/- 15 ms) hearts. Before looping, contractions traveled from proximal ventricle to bulbus cordis, a distance of 253 +/- 27 microns, in 72 +/- 22 ms. After looping, contractions crossed an increased intraventricular distance (520 +/- 28 microns, p less than 0.005) in substantially less time (16 +/- 7 ms, p less than 0.005). Sinoatrial and atrioventricular nodal functions are emulated in both prelooped and looped hearts of early mammalian embryos, and His-Purkinje system function is emulated in looped hearts.

Electromechanical delay in the vastus lateralis muscle during dynamic isometric contractions

Electromechanical delay (EMD) values were obtained using a cross-correlation technique for a series of 14 repetitive submaximal dynamic isometric contractions of the vastus lateralis performed by five subjects. To avoid a phase lag, which is introduced with one-way filtering, the EMG was processed with a bi-directional application of a second-order Butterworth filter. A mean EMD value of 86 ms (SD = 5.1 ms) was found. Moreover, contraction and relaxation delays were computed and compared. There was a significant difference between the contraction and relaxation delays (P less than 0.005). The mean contraction delay was 81.9 ms and the mean relaxation delay was 88.8 ms. Despite this significant difference, the computed contraction and relaxation delay values lie in the same range as the total phase lag, calculated with the cross-correlation technique. The magnitude of EMD values found supports the need to account for this delay when interpreting temporal aspects of patterns of intermuscular coordination.

The Effect of Topical Dexamethasone and Preoperative Beta Irradiation on a Model of Glaucoma Fistulizing Surgery in the Rabbit

We studied the effect of topical dexamethasone (1%) and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit. Intraocular pressure and gross facility of aqueous outflow following surgery were not influenced by either treatment, although blebs persisted longer in the irradiated eyes. Steroids reduced clinically observable inflammation as well as the number of inflammatory cells identifiable by microscopy. Fibroblast production temporarily slowed, and ultra-structural examination demonstrated lipid-filled vacuoles and dilated mitochondria in these eyes. Also, the scar was thinner at 24 days. Beta irradiation delayed wound healing and the scar was thinner in the early postoperative stages, but the light microscopic appearance of the scar was unaltered at 59 days. Inflammation was more pronounced initially, with abundant fibrin in the wound. Recovery of the conjunctival epithelium was delayed. The delay in fibroblast recruitment and wound contraction, the thinner scar tissue, and the increased survival of the bleb are all factors that suggest that beta irradiation may be a useful adjunct to glaucoma surgery.

ECG left anterior fascicular block reveals diverse patterns on scintigraphic phase analysis

Left anterior fascicular block (LAFB) remains an uncertain diagnosis by scalar ECG, particularly with coexisting inferlor infarction. To assess the use of phase analysis in LAFB, left ventricular phase and amplitude maps were evaluated in the 70-degree left anterior oblique projection in eight control patients and 13 patients with LAFB who met the ECG criteria of Warner et al. The left ventricular region was divided into anterior (A) and inferior (I) segments. Contraction patterns were assessed by examination of the sequence of phase angies (φ), relative contraction time of the anterior versus inferior segments was assessed from the difference between segment mean phase angles, Δ φ A−1, determined from the phase histogram, and duration of contraction was assessed by histogram width. Relative stroke volume was assessed on the amplitude image. Eight control subjects had normal amplitude, contraction of the anterior before inferior segment, narrow histrogram width, and a normal ECG. Among the 13 patients with ECG LAFB, seven were concordant, with phase analysis demonstrating anterior contraction delay. Two of seven patients had narrow histograms and normal amplitude, which were compatible with isolated anterior conduction delay, and five of seven patients had broad histograms and reduced anterior amplitude, compatible with anterior infarction. Phase analysis was discordant with ECG LAFB diagnosis in six patients. All showed contraction of anterior segments before inferior segments as in normal subjects. Four had broad histograms and reduced inferior amplitude, compatibie with prior inferior infarction without LAFB, and two had normal phase and amplitude maps. Phase patterns appear characteristic of LAFB with or without associated infarction. Phase and amplitude analysis may ciarify the ECG diagnosis of LAFB and provide etiologic insight.

線維芽細胞を用いた皮膚賦活剤評価法の開発 ＩＩ コラーゲンゲル収縮と細胞形態との相関

Fibroblast like cells (swiss 3T3 cells) treated by trypsin under various conditions were cultured within collagen gel. Contraction of collagen gel was more retarded with cells treated as increasing concentration of trypsin or as increasing time of trypsin treatment. Number of spherical cells within collagen gel observed by phase-contrast micrography 6hr after culture increased with increasing concentration of trypsin or time of trypsin treatment, while bipolar cells decreased. These results suggest that cell surface contains a membrane protein which is trypsin-sensitive and which interacts with collagen, ultimately contributing to contraction of collagen gel. Correlation between contraction of collagen gel and morphological change of cells might be realized by the membrane protein assumed to exist. It seems that the delay of contraction by trypsin treatment of cells is related to a prolonged period during which the shape of cells changes from sphere to bipolar.

The effect of systemic isotretinoin on wound contraction in guinea pigs.

An experimental study was designed using Hartley guinea pigs to evaluate wound contraction on animals receiving systemic isotretinoin at a dose of 10 mg/kg. Half the animals received isotretinoin for 4 weeks before the surgery and for 2 weeks after the surgical procedure. A square of skin and panniculus carnosus measuring 200 mm2 was excised from the back of each animal, and the amount of wound contraction was determined by a computer program from the drawings on celluloid overlays done weekly. The animals on systemic isotretinoin had a significant delay in wound contraction when compared to control animals (p less than 0.001). When the medication was discontinued, all the animals had complete wound healing within a week.

Skeletal muscle contraction characteristics in vivo in malignant hyperthermia susceptible subjects.

Ten malignant hyperthermia susceptible (MHS) subjects were investigated, all of them positive in in vitro tests. As a control group 12 healthy subjects were investigated. The investigation was done in a blind fashion during strictly standardized conditions. Electromechanical delay of contraction and half contraction time to tetanus were faster (P less than 0.05) while half relaxation time was shorter in the MHS subjects (P less than 0.05). Skin and intramuscular temperature were significantly higher in the MHS subjects (P less than 0.05). This indicates that MHS subjects differ in various skeletal muscle characteristics during "normal" conditions. Further studies to define the temperature level at which the test of muscle function is most discriminating are needed before it can be used for diagnostic purposes.

Variability of Positioning Accuracy following a Maximum Isometric Contraction

The purpose of this study was to examine the effects of different contraction times and delay times prior to a positioning task. While blindfolded, each of 25 subjects learned to produce elbow-extension movements to a short and a long target using a kinesthesiometer. The subject then produced 30 trials without feedback to each target. These control trials were preceded by a foreperiod of 0-, 3-, or 6-sec. delay. The 60 experimental trials were identical to control trials except the subject isometrically contracted elbow extensor muscles for 3 or 6 sec. prior to each trial. Following each isometric contraction the subject delayed movement for 0, 3, or 6 sec. The 3-sec. and 6-sec. prepositioning contractions produced greater undershooting and variability than no prepositioning contractions, and the 0-sec. delay produced less constant error than either the 3- or 6-sec. delay. It was concluded that following isometric contraction, undershooting a target occurred and this effect did not dissipate within a 6-sec. period.

Spatial and temporal variations in regional left ventricular function in isolated disease of the left anterior descending coronary artery.

The temporal and spatial pattern of left ventricular (LV) contraction and relaxation in 34 patients with isolated lesions of the left anterior descending artery (LAD) were studied from the LV cineangiogram in the right anterior oblique position using a computer interactive technique. The LV outline was divided into 100 equiangular radii from the center of the enddiastolic silhouette and the trajectory of contraction and relaxation of each radius measured and displayed. Patients were divided into different subsets. Classical anterior wall infarction caused impaired contraction of the distal two thirds of the anterior wall, the apex and the distal quarter of the inferior wall, with marked delay in contraction and relaxation of the border zones and hyperkinesis of the inferior wall. Spatial and temporal disturbances (akinesis and asynchrony) were marked in the other subsets. Left bundle branch block caused profound temporal delay particularly during relaxation.

Water relations of gas-vacuolate prokaryotes

Gas vesicles can be used to provide an instantaneous measurement of the hydrostatic pressure that exists inside the cells of prokaryotic organisms that possess them. Such measurements, carried out on the blue-green alga Anabaena flos-aquae , have been used to determine its cell-water relations. The cell turgor pressure is determined as the difference between the mean critical pressure required to collapse gas vesicles in cells' suspended in hypertonic sucrose solution and that for the cells suspended in water. The turgor pressure falls slightly as the gas vesicles are collapsed because the volume of the cell contents decreases. The relation between the cell turgor pressure and volume is described by the volumetric elastic modulus, e, which can be determined by measuring the turgor pressure of cells suspended in sucrose solutions of increasing concentration. As the external osmotic pressure is increased, the turgor pressure, which stretches the cell wall, falls and the cell shrinks by losing water. The cell water volume can be calculated from the internal osmotic pressure, which is equal to the sum of the external osmotic pressure and the turgor pressure. The elastic modulus of the A. flos-aquae . cell is quite low, about 11 bar, and constant over a range of turgor pressures down to 1.3 bar. W hen gas vesicles are collapsed inside cells, the turgor pressure suddenly drops, but it partially recovers as water enters to restore the osmotic balance. The rate of entry can be computed from the time course of gas vesicle collapse in cells held under moderate hydrostatic pressures, and from this the hydraulic conductivity, L p , of the cell wall and membrane can be calculated; it is estimated to be about 0.14 μm s -1 bar -1 in A . flos-aquae , with the assumption that there are no errors owing to delay in the elastic contraction of the cell wall. The permeability, k , of the cell to various solutes can be determined by following the rate of turgor pressure recovery as the solutes penetrate the cells from external solutions of 0.15 osm concentration. Two methods are described in which turgor pressure rise is monitored by gas vesicle collapse, one for slowly penetrating solutes (e.g., mannitol) and one for rapidly penetrating solutes (e.g., glycerol). Passive uptake is indicated by exponential kinetics of turgor pressure recovery to the initial value in water, as for sugar alcohols; active uptake results in turgor pressures exceeding the initial value, as observed for K + and glycine—betaine. The biological significance of cell—water relations in gas-vacuolate organisms is discussed.

Transaqueous diffusion of acetylcholine to denervated iris sphincter muscle: a mechanism for the tonic pupil syndrome (Adie syndrome).

The accepted hypothesis for the pathophysiology of tonic pupil syndrome (Adie syndrome) was reexamined in light of recent developments concerning denervation supersensitivity of cholinergically innervated smooth muscle. Kinetic analysis suggests that enzymatic hydrolysis is unimportant relative to convective diffusion in the turnover of acetylcholine in the aqueous humor. We postulate that the greater response to near stimuli than to light stimuli and the delay in iris sphincter contraction and relaxation can be explained by release of acetylcholine from the neuromuscular junction of the ciliary muscle followed by transaqueous diffusion to receptor sites on denervated, supersensitive iris sphincter muscle.

The effect of PGE 2 on contraction delay and velocity of the field stimulated guinea-pig vas deferens

The shape of mechanical responses elicited by continuous field stimulation of the guinea-pig vas deferens depends on the frequency of stimulation. When the frequency was increased from 5 to 50 Hz, the maximum of contractions became higher and a shorter delay and a greater velocity of contractions could be observed. Prostaglandin E 2 (PGE 2) markedly retarded the onset and depressed the velocity of mechanical responses. Inhibition caused by this drug was inversely proportional to the nerve stimulation frequency. Above a certain concentration (10 ng/ml) PGE 2 failed to produce any further depression, even a reduction of the inhibitory effect could be observed. The action of PGE 2 on velocity and onset of contractions at a given frequency (5 or 10 Hz) increased with concentration up to 10 ng/ml. When the number of shocks was plotted semi-logarithmically against tension of the tissue a typical “S” shaped curve was obtained. This shock-number-effect curve could be shifted with PGE 2 to the right without a significant change in slope. The interaction between PGE 2 and number of shocks did not fulfill the criterion for competitive antagonism. The dual (pre- and postjunctional) action of PGE 2 may be the reason for the noncompetitive nature of antagonism. In the rat vas deferens, the shape of responses elicited by continuous stimulation with different frequencies (5, 10 and 50 Hz) was very similar. Prostaglandin E 2 was ineffective at any frequency of stimulation and in any concentration applied (10, 100 and 1000 ng/ml).

Temporal discrepancies in the electromyographic study of rapid movement.

Elbow flexor and extensor contraction and relaxation delays, relative to muscle action potentials are evaluated as 30-60 msec for contraction and 30-70 msec for relaxation, but with significant differences between subjects and between different muscles in the same subject. The contention that proper temporal interpretation of rapid movement EMGs is impossible without prior evaluation of the delays specific to the subject and muscles involved is supported by applying such evaluations to explain anomolies in rapid elbow movement EMGs. It is shown that apparent cocontraction of antagonist muscles may be an artifact explicable by these (subject and muscle specific) delay differences. The need for extensive study of muscle action delays is stressed.

Echocardiographic demonstration of abnormal motion of the interventricular septum in left bundle branch block.

A characteristic abnormality of motion of the interventricular septum was recorded by echocardiography in 17 of 18 patients with left bundle branch block. Early and abrupt contraction of the septum occurs during the pre-ejection period before the delayed commencement of contraction of the posterior wall of the left ventricle. This abnormality can be explained by asynchronous contraction of the left ventricle with early activation and contraction of the septum but delay in activation and contraction of the left ventricular free wall due to a block in the left bundle branch or its peripheral branches.

The first heart sound and the dynamic events in ventricular ectopic beats and in paced beats

The electrocardiograms and clinical phonocardiograms of 27 patients presenting ventricular ectopic beats were studied, as well as the electrocardiograms, intracardiac phonocardiograms and pressure tracings from both ventricles of 11 patients presenting ventricular ectopic beats during catheterization. The electrocardiograms and clinical phonocardiograms plus the carotid tracings of 5 patients with artificially paced hearts were also studied. It was demonstrated that both the ectopic origin of the impulse and pacing prolong the interval between the onset of the QRS complex and the first heart sound (QRS-I interval) and that right ventricular ectopic origin or right ventricular pacing prolongs this interval more than left ventricular ectopic origin or left ventricular pacing. These facts are discussed and related to (1) altered modality of left ventricular activation (ventricular ectopic beats, paced beats); and (2) additional delay in left ventricular contraction occurring in the case of either right ventricular ectopic beats or hearts paced from the right ventricle, because the left ventricle is the only chamber that causes the first heart sound. No difference was found in the interval between the first two components of the first sound.