Structural limits on force production and shortening of smooth muscle.

This study determined the factors that limit force production and shortening in two smooth muscles having very different relationships between active and passive force as a function of muscle length. The rat anococcygeus muscle develops active force over the range of lengths 0.2-2.

Calcium regulation of skeletal myogenesis. II. Extracellular and cell surface effects.

The process of myoblast fusion during skeletal myogenesis is calcium regulated. Suppression of fusion is obtained by lowering medium [Ca2+] and re-initiated by raising medium [Ca2+]. Previously, we showed that such changes in medium [Ca2+] produced concomitant changes in myoblast [Ca2+] and that a critical cellular concentration of calcium must be present in myoblasts for fusion to occur.

Differential regulation of glucose transport and transporters by glucose in vascular endothelial and smooth muscle cells.

Hyperglycemia has been implicated in the pathogenesis of both micro- and macrovascular complications in diabetes. Little is known, however, about glucose transporters and their regulation in the vascular system. In this study, the regulation of glucose transporters by glucose was examined in cultured BAECs and BSMCs, and in human arterial smooth muscle cells.

Insulin receptor number and binding affinity in newborn dogs.

The insulin resistance in newborn mammals may be caused by a receptor or postreceptor defect. Although liver and umbilical cord blood monocytes have increased numbers of insulin receptors, there is a paucity of information about other neonatal tissues. Glucose disposal takes place primarily in the skeletal muscle; therefore, it is important to evaluate this tissue for an insulin receptor defect.

Endogenous and exogenous plasma catecholamine levels in cardiac arrest in swine.

The use of epinephrine in cardiac arrest remains an area of continuing controversy. This study was undertaken to characterize the effect of endogenous and exogenous epinephrine on plasma epinephrine levels, and the relationship between plasma epinephrine and norepinephrine and mean arterial pressure and diastolic arterial pressure. Nineteen young swine were anesthetized with ketamine and alpha-chloralose and instrumented with arterial and central venous lines.

Efficacy of charcoal cathartic versus ipecac in reducing serum acetaminophen in a simulated overdose.

The traditional role of gastric emptying as the initial step in the management of the poisoned patient has recently been questioned; immediate activated charcoal administration has been recommended by some. In the setting of acetaminophen overdose, ipecac-induced emesis may interfere with subsequent oral antidotal therapy. Therefore, we conducted a study to compare the efficacy of initial therapy with ipecac with therapy with activated charcoal-cathartic in a simulated acetaminophen overdosage.

Intraosseous crystalloid and blood infusion in a swine model.

The technique of intraosseous infusion has attracted increasing interest in recent years, and has proven valuable for drug administration. This study was undertaken to determine whether it was also a potential route for fluid resuscitation. Thirteen- or eighteen-gauge tibial intraosseous needles were placed in eight "large" (mean weight, 14.

Fibre types in Limulus telson muscles: morphology and histochemistry.

Using a variety of techniques, we have demonstrated the presence of at least two fibre types in Limulus median telson levator muscle. By light and electron microscopy, large (2,156 microns 2 mean cross-sectional area) fibres have A-bands of 4.1 microns, one-half I bands of 2.

Post-traumatic neck pain: a prospective and follow-up study.

Three hundred fifty-one alert emergency department patients with post-traumatic neck pain were evaluated prospectively. Seven (2%) had proven fractures or ligament disruptions. The immediate onset of neck pain and the presence of posterior midline cervical tenderness each had 100% sensitivity, with specificity of 65% and 48%, respectively.

Sorbitol catharsis does not enhance efficacy of charcoal in a simulated acetaminophen overdose.

The use of a 70% sorbitol solution has recently been advocated as an adjunct to activated charcoal. This results in rapid and profuse catharsis that could possibly cause fluid and electrolyte imbalance. An investigation was undertaken to determine if sorbitol catharsis enhanced the antidotal efficacy of activated charcoal.

Effects of elevation of phosphocreatine on force and metabolism in rabbit aorta.

Rings of rabbit thoracic aorta were incubated in 40 mM creatine; both intracellular free creatine (Cr) and phosphocreatine (PCr) content increased 300% in 4 h, whereas tissue ATP content and PCr-to-Cr ratio remained constant. Exogenous Cr was taken up and metabolized by creatine kinase; the newly formed PCr was available for tissue metabolism. Compared with control tissue, muscle rings with markedly increased Cr and PCr content showed no difference in either the rate of contraction with norepinephrine or the amplitude of contraction.

Metabolic differences between norepinephrine- and K+-stimulated anococcygeus muscle.

The effects of norepinephrine (NE) and K+ stimulation on aerobic glycolysis (JLac), O2 utilization (JO2), and isometric force of isolated rat anococcygeus smooth muscle were investigated to determine the relationship between metabolism and contractility. A large sustained increase in JLac was measured during NE stimulation, but only a small rise in JLac occurred during high-KCl depolarization. JO2, in both cases, correlated with the force response.

Separation of aerobic glycolysis from oxidative metabolism and contractility in rat anococcygeus muscle.

The relationship of aerobic glycolysis (JLac) and O2 utilization (JO2) to contractility and the activity of the Na+-K+ pump was investigated in rat anococcygeus smooth muscle. Removal of extracellular potassium concentration ([K+]o) caused an initial increase followed by a decrease in JLac below the resting rate. Restoration of [K+]o caused JLac to increase, and this response, but not the initial one observed in zero [K+]o, was prevented by ouabain.

Structure of Limulus and other invertebrate thick filaments.

We have demonstrated remarkable similarity among the skeletal muscles of chelicerate arthropods with respect to the cross-bridge arrangement on the surface of their thick filaments. The latter, gently isolated from the muscles of three representative species (Limulus telson , tarantula leg and scorpion leg and tail) have been examined by electron microscopy and optical diffraction using both negatively stained and unidirectionally metal shadowed preparations. The filaments are highly periodic and produce clear and detailed diffraction patterns.

Energy utilization by Limulus telson muscle at different sarcomere and A-band lengths.

Phosphorylargnine utilization (delta PArg) was determined in isolated Limulus telson muscle during isometric and isovelocity contractions at long, intermediate, and short lengths when thick filaments were either long and staggered, long and aligned, or shortened. Muscles developed 30% of maximum force at a length of 0.5 Lo (Lo 7 micrometers sarcomere length) during isometric tetani of 5, 15, and 30 s; however, the rate of delta PArg was the same in both the 0.