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PubMed1983

Irrigation treatment of leg ulcers.

Wound healing produced by isotonic saline irrigation via a special dressing was compared with that produced by conventional saline dressings in 12 inpatients with 18 leg ulcers. Patients served as their own controls. Wound cleansing was estimated by fibrin crust disappearance and granulation tissue formation. Both occurred earlier during irrigation. Wound contraction was similar during the two treatments. Wound blood flow, estimated by means of a laser Doppler flowmeter, increased earlier with irrigation.

Adult↗
PubMed1999

Differences between mouse and rat myocardial contractile responsiveness to calcium.

Genetically altered mice have become an increasingly important tool for the study of mechanisms of cardiac function, and therefore it is vital to characterize the basic contractile properties of the mouse heart. As a first approach to this goal, we first optimized perfusion conditions and characterized the effect of incremental left ventricular balloon inflation on end-diastolic, systolic and developed pressures in the isovolumically-contracting mouse heart. Under constant loading conditions, we determined developed pressure in response to changing perfusate calcium (1.25, 2.5, 3.75 and 5.0 mM) and perfusate temperature (30 and 37 degrees C). We then compared the intrinsic inotropic responsiveness to changes in extracellular calcium of left ventricular myocardium from mouse to that from the rat. In the baseline state (1.25 mM extracellular calcium; [Ca2+]o), both isometric contraction duration and normalized active force at the peak of the active force-length relationship (Lmax) were less in mouse than in rat myocardium. Under isotonic conditions, temporal parameters of shortening and the relative shortening were less in mouse vs rat myocardium. Increasing [Ca2+]o from 1.25 to 2.5 mM markedly increased active isometric force and rate of force development (+dF/dt) in the mouse. However, rat myocardium responded to a lesser extent. Under isotonic conditions, peak shortening and the rate of shortening also increased to a greater extent in mouse relative to rat myocardium. Increasing the bath calcium concentration to 5.0 mM increased isometric force and +dF/dt further in the rat but not the mouse, suggesting that two species operate at different points on the force vs [Ca2+]o relationship. We conclude that mouse myocardium exhibits increased sensitivity to changes in [Ca2+]o within the physiologic range in comparison to rat. These differences do not appear to be due to differences in loading conditions. The data suggest that differences in inotropic responsiveness to calcium may reflect intrinsic differences in myocardial calcium sensitivity between species.

Animals↗
PubMed1985

Force generated by non-cycling crossbridges at low ionic strength in skinned smooth muscle from Taenia coli.

In skinned smooth muscle preparations of Taenia coli from guinea pig the cyclic actin-myosin-interaction is inhibited to resting levels whereas the force remains high when in the contracted muscle the ionic strength of the incubation solutions is lowered from 65 mM to 18 mM. In accordance with a strongly depressed ATPase activity under these conditions the isotonic shortening velocity is drastically decreased suggesting that crossbridges are not cycling (latch-state). Since the Ca2+ concentration is kept constant (4 X 10(-5) M) and the phosphorylation of the myosin light chain (LC) is found to be unchanged it must be concluded that the formation of latch-bridges is not necessarily dependent on a change in the Ca2+ concentration or the state of phosphorylation.

Adenosine Triphosphatases↗
PubMed1989

Regional and species differences in vascular reactivity to extracellular potassium.

In-vitro vasoreactivity to extracellular potassium (Ko+) was tested in isolated human pial and mesenteric arteries as well as basilar and mesenteric arteries from rabbits and rats. Contractions were induced by stepwise increases in [K+]o and were measured isometrically with a force-displacement transducer, in small-volume organ baths. Significant differences between species as well as between regions were found. The threshold of [K+]o for eliciting contraction in human cerebral arteries in hyperosmotic solutions was 10 mM, in rabbit cerebral arteries 17 mM and in rat cerebral arteries 27 mM. The threshold concentration for contraction in mesenteric arteries was significantly higher compared to cerebral arteries in humans and rabbits, but lower in rats: 20 mM in humans, 26 mM in rabbits and 25 mM in rats. In all species the contractile amplitudes were significantly higher in both cerebral and mesenteric arteries when [K+]o was increased under isotonic conditions in the buffer solution than when hyperosomolality was created. This difference increased with increasing hyperosmolality. In hyperosmotic solutions, the EC50 for [K+]o was lower in cerebral and mesenteric arteries from man than in vessels from rabbit and rat. When the solutions were isotonic, this pattern was seen only in mesenteric arteries. It is concluded that significant species and regional differences in vascular responses to [K+]o exist. Considering that [K+]o is increased in cerebral ischaemia, the observed significantly lower threshold for K+-induced contractions in human cerebral arteries may be of importance, especially in human cerebral ischaemic events.

Animals↗
PubMed1990

Development of motilin receptors and of motilin- and erythromycin-induced contractility in rabbits.

The development of the motilin receptor was studied through contraction and binding studies of groups of three rabbits aged between 2 and 289 days. The contractility of small intestinal smooth muscle strips was measured isotonically. The aborally decreasing gradient in response to motilin, known to exist in adult rabbits, was already present at day 8 (maximum contractile responses expressed as a percent of the maximal response to acetylcholine were 77% +/- 9%, 34% +/- 10%, and 25% +/- 8% for duodenal, jejunal, and ileal strips, respectively). Throughout the observation period, the doses of motilin and its agonist erythromycin that were required to induce 50% of the response remained constant and were not significantly different from doses required for adults (their negative logarithms were 8.55 +/- 0.35 and 5.70 +/- 0.25, respectively). The correlation between the maximum contractile response toward motilin and erythromycin was almost perfect (r2 = 0.82). Binding studies with iodinated norleucine13-porcine motilin were performed using antral smooth muscle tissue homogenates. The maximum number of binding sites increased rapidly after 8 days (3.3 +/- 0.4 fmol/mg protein) and reached a peak at 21 days (20.7 +/- 1.4 fmol/mg protein), but decreased at that point toward the adult value (40 days, 10.6 +/- 1.3; 289 days, 9.8 +/- 1.1 fmol/mg protein). The dissociation constant, however, remained unchanged. The peak value of receptor density occurred at about the time that the rate of increase of the length of the intestine and of the weight of the antrum were at maximum levels (at 18 and 27 days, respectively). Motilin receptors are expressed early postnatally, and the regional gradient in sensitivity towards motilin is also established soon after birth. If applicable to humans, an early response to erythromycin may have therapeutic value.

Acetylcholine↗
PubMed1995

Motor unit activity during isometric and concentric-eccentric contractions of the human first dorsal interosseus muscle.

1. Motor unit activity was recorded with intramuscular fine wire electrodes during isometric, concentric, and eccentric activity in the human first dorsal interosseus muscle. Twenty-one units from 11 subjects were sampled. 2. During isotonic cycles of shortening and lengthening, 18 of 21 units were recruited during the concentric phase, increased their discharge rates as the concentric movement progressed, then decreased their discharge rate during the eccentric phase, and were derecruited. 3. A different pattern of recruitment was observed in recordings from three units. These units were recruited during the eccentric phase, at a time when other units were decreasing their discharge rate or being derecruited. In two of the units selectively recruited during the eccentric phase, it was possible to determine their isometric thresholds, which were higher than those of units exhibiting the more common pattern of recruitment. 4. For two of the three units exhibiting selective recruitment during eccentric contraction, the unit was recorded simultaneously with different pairs of recording wires separated by 5-10 mm. Each discharge of these units was detected by both electrodes, making it unlikely that movement artifact was responsible for the initiation or cessation of discharge. 5. The recruitment patterns observed suggest that changes in the type or distribution of synaptic inputs to motoneurons during movement can, in some instances, override pre- and postsynaptic factors that shape recruitment order in isometric conditions.

Adolescent↗
PubMed1993

Measurements of duodenal wall motility, mucosal fluid transport and alkaline secretion. Description and evaluation of a methodological approach in the anaesthetized cat.

This paper describes and evaluates a method for simultaneous recordings of duodenal motility and mucosal secretions in chloralose-anaesthetized cats. Biliary and pancreatic secretions were diverted by separate cannulation of each duct. A 2 cm segment of the proximal duodenum was isolated between two luminally situated balloons (the proximal balloon being positioned immediately distal to the pylorus). Each balloon was connected to a barostatic device maintaining a constant pressure within the balloon independent of the degree of contraction. Motor activity in the duodenal wall was recorded as changes in balloon volume. The duodenal segment was perfused at a constant rate with isotonic saline containing [14C]PEG 4000 as a non-absorbable marker. The recovered perfusate was sampled in 5 min fractions and analysed with regard to alkalinity (back titration) and concentration of marker (liquid scintillation). Net alkalinization and net fluid transport was calculated with conventional equations. The sensitivity of the analytical procedures was tested bench-side. The technique was evaluated in vivo during basal conditions and during acid exposure of the mucosa. Exposing the duodenal segment to 30 mM HCl induced a marked change in the duodenal functional state with the occurrence of a polarized duodenal motility pattern, net fluid secretion and an increased alkaline secretion.

Anesthesia↗
PubMed2005

Cd2+-induced swelling-contraction dynamics in isolated kidney cortex mitochondria: role of Ca2+ uniporter, K+ cycling, and protonmotive force.

The nephrotoxic metal Cd(2+) causes mitochondrial damage and apoptosis of kidney proximal tubule cells. A K(+) cycle involving a K(+) uniporter and a K(+)/H(+) exchanger in the inner mitochondrial membrane (IMM) is thought to contribute to the maintenance of the structural and functional integrity of mitochondria. In the present study, we have investigated the effect of Cd(2+) on K(+) cycling in rat kidney cortex mitochondria. Cd(2+) (EC(50) approximately 19 microM) induced swelling of nonenergized mitochondria suspended in isotonic salt solutions according to the sequence KCl = NaCl > LiCl >> choline chloride. Cd(2+)-induced swelling of energized mitochondria had a similar EC(50) value and showed the same cation dependence but was followed by a spontaneous contraction. Mitochondrial Ca(2+) uniporter (MCU) blockers, but not permeability transition pore inhibitors, abolished swelling, suggesting the need for Cd(2+) influx through the MCU for swelling to occur. Complete loss of mitochondrial membrane potential (DeltaPsi(m)) induced by K(+) influx did not prevent contraction, but addition of the K(+)/H(+) exchanger blocker, quinine (1 mM), or the electroneutral protonophore nigericin (0.4 microM), abolished contraction, suggesting the mitochondrial pH gradient (DeltapH(m)) driving contraction. Accordingly, a quinine-sensitive partial dissipation of DeltapH(m) was coincident with the swelling-contraction phase. The data indicate that Cd(2+) enters the matrix through the MCU to activate a K(+) cycle. Initial K(+) load via a Cd(2+)-activated K(+) uniporter in the IMM causes osmotic swelling and breakdown of DeltaPsi(m) and triggers quinine-sensitive K(+)/H(+) exchange and contraction. Thus Cd(2+)-induced activation of a K(+) cycle contributes to the dissipation of the mitochondrial protonmotive force.

Animals↗
PubMed1984

Segmental chloride and fluid handling during correction of chloride-depletion alkalosis without volume expansion in the rat.

To determine whether chloride-depletion metabolic alkalosis (CDA) can be corrected by provision of chloride without volume expansion or intranephronal redistribution of fluid reabsorption, CDA was produced in Sprague-Dawley rats by peritoneal dialysis against 0.15 M NaHCO3; controls (CON) were dialyzed against Ringer's bicarbonate. Animals were infused with isotonic solutions containing the same Cl and total CO2 (tCO2) concentrations as in postdialysis plasma at rates shown to be associated with slight but stable volume contraction. During the subsequent 6 h, serum Cl and tCO2 concentrations remained stable and normal in CON and corrected towards normal in CDA; urinary chloride excretion was less and bicarbonate excretion greater than those in CON during this period. Micropuncture and microinjection studies were performed in the 3rd h after dialysis. Plasma volumes determined by 125I-albumin were not different. Inulin clearance and fractional chloride excretion were lower (P less than 0.05) in CDA. Superficial nephron glomerular filtration rate determined from distal puncture sites was lower (P less than 0.02) in CDA (27.9 +/- 2.3 nl/min) compared with that in CON (37.9 +/- 2.6). Fractional fluid and chloride reabsorption in the proximal convoluted tubule and within the loop segment did not differ. Fractional chloride delivery to the early distal convolution did not differ but that out of this segment was less (P less than 0.01) in group CDA. Urinary recovery of 36Cl injected into the collecting duct segment was lower (P less than 0.01) in CDA (CON 74 +/- 3; CDA 34 +/- 4%). These data show that CDA can be corrected by the provision of chloride without volume expansion or alterations in the intranephronal distribution of fluid reabsorption. Enhanced chloride reabsorption in the collecting duct segment, and possibly in the distal convoluted tubule, contributes importantly to this correction.

Absorption↗
PubMed2000

Biofeedback for fecal incontinence using transanal ultrasonography: novel approach.

PURPOSE: Neosphincter procedures may prove to be the treatment of choice for patients with neuropathic fecal incontinence but are rarely proposed for milder forms of the disease. Biofeedback may prove beneficial to these patients but is yet unproven. The objectives of this study were to develop a method of performing biofeedback using transanal ultrasound to teach the patient to contract repetitively and to determine biologic measures of sphincter function using transanal ultrasound in healthy and incontinent patients. METHODS: Initial uncontrolled studies were performed to determine the compliance, normal values, biologic measures of external sphincter strength (isotonic and isometric fatigue times), and early efficacy data using continence scores and visual analog scale scores. RESULTS: Forty-four patients were assessed during three months, with relative improvements in continence scores (St. Mark's Hospital, 40 percent; Pescatori, 20 percent) and patient and investigator visual analog scale scores (38 percent for both) and measurable increase in biologic fatigue times measured by transanal ultrasound. CONCLUSIONS: Transanal ultrasound seems to be a method of teaching external sphincter contraction and measuring sphincter strength with good initial compliance. Clinically and statistically significant improvements in incontinence scores, visual analog scale scores, and biologic strength of the external sphincter were detected in the short-term follow-up with uncontrolled data. The randomized, controlled trial that we have begun will either confirm or refute these results.

Adult↗