Physical and Clinical Evaluation of Hip Spica Cast applied with Three-slab Technique using Fibreglass Material.

Introduction: Hip spica casting is an important component of treatment for developmental dysplasia of the hip (DDH) and popular treatment method for femur fractures in children. Breakage at the hip region is a relatively common problem of this cast. We have developed a three-slab technique of hip spica application using fibreglass as the cast material. The purpose of this review was to evaluate the physical durability of the spica cast and skin complications with its use. Methodology: A retrospective review of children with various conditions requiring hip spica immobilisation which was applied using our method. Study duration was from 1st of January 2014 until 31st December 2015. Our main outcomes were cast breakage and skin complications. For children with hip instability, the first cast would be changed after one month, and the second cast about two months later. Results: Twenty-one children were included, with an average age of 2.2 years. The most common indication for spica immobilisation was developmental dysplasia of the hip. One child had skin irritation after spica application. No spica breakage was noted. Conclusion: This study showed that the three-slab method of hip spica cast application using fibreglass material was durable and safe with low risk of skin complications.

System approach to the transepithelial transport across rat jejunal enterocytes: effect of cytochalasin B, colchicine, and ethylenediaminetetraacetic acid on butyric acid transport.

A three-compartment physical model is devised for transepithelial passive transport across intestinal cells. The mathematical equations derived from the model allow the simultaneous and quantitative measurements, in the form of permeability coefficients, of solute transport across both the luminal-serosal and serosal-blood barriers. The proposed model is used to study the involvement of the cytoskeleton in butyric acid absorption by the rat jejunum. Alterations in cytoskeletal functions are introduced by the administration of microfilamentous and microtubular altering agents such as cytochalasin, colchicine, or EDTA. An isolated jejunal segment perfused with a buffer containing labeled butyric acid was homogenized at the end of the experiment and assayed for its butyric acid content. During the perfusion, portal blood samples, as well as perfusate samples collected 10 cm distal to the perfusion site were drawn at 5-min intervals and assayed for their radioactivity. Cytochalasin was found to decrease the permeability of the mucosal membrane to butyric acid and to increase that of the serosal membrane. Colchicine did not have any effect either on the mucosal or on the serosal side. Cytochalasin and colchicine, when given in the same experiment, increased the permeability of the serosal membrane to butyric acid, but were without any effect on the mucosal barrier. Also, EDTA had no effect on the mucosal side, but decreased significantly the permeability of the serosal membrane to the fatty acid.

Angiotensin II delivery and binding at the microvascular endothelium and cardiac myocyte surfaces in perfused rat hearts.

Peptide delivery toward its targets in an intact organ is equally as important as its routing from the systemic circulation to cell surface receptor sites. A physical model pertinent to a heart perfusion technique in Sprague-Dawley rats is presented describing reversible binding of angiotensin II and/or antagonist (DUP 753, losartan) with the microvascular endothelial receptor subtypes as well as with the cardiac myocyte receptor subtypes that are exposed to the perfusate by CHAPS-treatment. Analysis of the collected effluents are curve-fitted with a conservation equation and a first-order Bessel function. The results suggest that angiotensin II delivery and binding to the pool of receptor subtypes both at the level of the microvascular endothelium and cardiac myocyte sites differ marginally in binding affinities. The findings postulate that angiotensin II can have access to the myocyte site in an intact heart by an endothelial angiotensin II-receptor-internalization process. In addition, considering that the AT1- and AT2-receptor subtypes are present in equal proportions and have equal binding affinities with angiotensin II, the results of the 3H-DUP 753 binding indicated approximately 3-3.5 times higher affinity to the AT1-receptors subtype than angiotensin II at both the endothelial and myocyte sites. In the presence of losartan, angiotensin II binding showed higher affinity with the exposed unopposed AT2-receptor subtype than with the receptor pool, which could be due to alterations in the AT2-receptor structure and configuration. This increase in the binding affinity of angiotensin II with the AT2-receptor subtype may be categorized under the direct effect of the AT1-antagonist modality in producing cardioprotective effects.

Adsorption isotherms of ouabain on hepatocytes from normal and diabetic (streptozotocin-induced) rats.

A cell surface adsorption isotherm approach is investigated with normal and diabetic (streptozotocin-induced) rat hepatocytes utilizing mathematical modeling. Freshly prepared monodispersed viable rat hepatocytes in Ca(2+)- and Mg(2+)-free phosphate buffer are obtained by collagenase perfusion and used in this study. [3H]ouabain is used as a ligand that specifically binds with the alpha 1 and alpha 2 isoforms of the alpha-protein subunit of the hepatocyte-membrane-incorporated Na-K-ATPase. The model that fits the experimental data assumes the presence of multiple receptors on the cell surface, and only when a specific fraction of the total number of one receptor have effectively reacted will the other receptor initiate reaction with the ligand. The results suggest the existence of two receptors, in normal and diabetic hepatocytes, interacting with ouabain and having different equilibrium constants. The alpha 2 isoform interacts more strongly with ouabain than the alpha 1 isoform in both types of cells. The alpha 1 isoform of the diabetic hepatocytes has stronger affinity with the glycoside than the alpha 1 isoform of the normal hepatocytes, while alpha 2 of the diabetics shows weaker affinity than alpha 2 of the normal hepatocytes. Therefore, the alpha 1 and alpha 2 isoforms of Na-K-ATPase in hepatocyte-cell-membrane have different affinities for ouabain and have been conformationally and/or structurally altered in chronic diabetes.

Angiotensin II binding and extracellular matrix remodelling in a rat model of myocardial infarction.

Clinical evidence points to a role for angiotensin II (Ang II) in the post-infarction remodelling of cardiac hypertrophy. The present study was designed to investigate the remodelling process in an animal model of myocardial infarction (MI) using the following criteria: 1) histological studies to examine the re-vascularisation process and collagen deposition in different regions of the myocardium; 2) histological evidence to investigate the cell type distribution using cell-specific markers; 3) histological and Western blot analysis to localise Ang II receptor subtypes (AT(1)-receptor and AT(2)-receptor) and to study their regulation; 4) kinetics of the binding of Ang II to its receptors in a heart perfusion model; and 5) to assess the effect of the Ang II antagonist (losartan) on these parameters. MI was induced by ligation of the left anterior descending coronary artery of Sprague-Dawley rats. Four different animal groups were established: 1) sham-operated, non-treated; 2) sham-operated, treated with losartan; 3) myocardial infarct, non-treated; and 4) myocardial infarct, treated with losartan. In infarcted rat hearts, fibroblasts and collagen types I and III increased in the remnant viable region of the left ventricle compared with sham-operated rats. One month of losartan treatment in myocardial infarcted rats revealed insignificant changes in fibroblasts and collagen types I and III compared with sham controls. Also, myocardial infarction increased AT(1)-receptor protein levels compared with sham-operated controls, as judged by Western blotting. In losartan-treated myocardial infarct animals, no changes were detected at the level of AT(1)-receptor expression compared with non-treated myocardial infarct rats. Binding studies of Ang II on endothelial cell lining and directly on myocytes in sham-operated and infarcted perfused rat hearts revealed that, in myocardial infarcted-animals, Ang II binding affinity increased both in the endothelium and in myofibres. This may be considered a major putative effect of the peptide in potentiating the pharmacodynamics of hypertrophy. In losartan-treated myocardial infarcted-animals, a marked increase in the binding affinities of Ang II for the AT(2)-receptor subtype was observed. Hence, potential cardioprotective effects of the AT(1)-receptor antagonist are proposed.

Characterization of insulin-resistance: role of receptor alteration in insulin-dependent diabetes mellitus, essential hypertension and cardiac hypertrophy.

Insulin-resistance is associated with a number of disease states such as diabetes, syndrome X, and hypertension. These situations may be coupled to insulin-resistance through the insulin signaling system as a common pathway. The purpose of this study was to investigate the receptor binding alterations in streptozotocin-induced diabetic rats, spontaneously hypertensive rats and aortocaval shunted rats (eccentric cardiac hypertrophy). A physical model describing a 1:1 stoichiometry of ligand binding with its receptor is proposed describing reversible binding of [(125)I]insulin or [(125)I]IGF-1 at the microvascular endothelial as well as with the cardiac myocytes after CHAPS-treatment. Analysis of the collected effluents are curve-fitted with a conservation equation and a first-order Bessel function which allowed the calculation of the forward binding constants (k(n)), the reversible constants (k(-n)), the dissociation constants (k(d)) and the residency time constants (tau). The results showed that streptozotocin-induced diabetic rats showed insulin-resistance through alterations in the kinetics of insulin receptor binding. The normotensive controls of the spontaneously hypertension rats (SHR) carry themselves insulin-resistant receptors whose binding to insulin worsens in the hypertensive SHR. Negative cooperativity between insulin-like growth factor IGF-1 and insulin receptors could be a causative factor predisposing for insulin-resistance in the aortocaval shunted rats to insulin resistance. The defects may be occurring at the receptor level in insulin-dependent diabetes mellitus, Wistar-Kyoto rats and spontaneously hypertensive rats. In conclusion, alterations in the kinetics of insulin binding to its receptor seem to play a central role for the initiation of insulin-resistance during the various pathophysiological states.

Insulin-receptor binding characteristics in perfused SHR and WKY rat hearts.

This work uses a new heart-perfusion technique to measure 125I-insulin binding on capillary endothelium and myofiber cell membranes in Wistar-Kyoto and spontaneously hypertensive rats. Ringer-Lock buffer was infused at a rate of 1 ml min-1 in the presence of 20 meq l-1 K+ and 125I-insulin through an aortic cannula. The effluent was collected through a catheter introduced into the right atrium. The capillary endothelial lining was removed by detergent treatment to expose the cardiac myocyte surfaces. A physical model describing a 1:1 binding stoichiometry of 125I-insulin with its receptors is proposed and the derived mathematical equations allow for the calculation of binding constants (kn), unbinding constants (k-n), dissociation constants (kd), and residency time constants (tau). The results showed that in the spontaneously hypertensive rats' hearts significant alterations were not noticed in the kinetics of insulin binding with its receptor at the capillary endothelial site compared to hearts of the normotensive control Wistar-Kyoto rats. However, at the myocyte site and in the spontaneously hypertensive rats, steric, configurational, and/or structural modifications for insulin binding with the receptor were observed as indicated by changes in insulin affinity for its receptor. Hence, alterations in insulin binding rather than reduction in insulin receptor number due to hyperinsulinemia, can be considered among the peculiarities of insulin resistance in the spontaneously hypertensive rats. Hyperinsulinemia, therefore, may be considered an upregulatory process as a consequence of insulin-resistance. The results support the hypothesis that insulin-resistance on the myocytes could be a pathophysiologic defect in insulin-receptor structure, function and affinity, and therefore myocardial function.

Adsorption of concanavalin A on human platelets.

A physiological cell surface adsorption system approach is investigated on human platelets utilizing mathematical modeling. Monodispersed washed platelets are freshly collected in an isotonic buffer as a suspension utilizing a gel filtration technique. Concanavalin A is used as a glycoprotein receptor adsorbate in the adsorption studies. Three mathematical models are proposed based on simple chemical equilibrium reactions between adsorbate and cell surface receptors in an effort to explain concanavalin A - platelet surface glycoprotein interaction. Model I assumes that all receptors are undergoing simultaneous surface reactions with the adsorbate and without correlation. Model II reflects a strong correlation between the receptors, when only one receptor is active and the second receptor(s) is nothing but the combination of first receptor-adsorbate complex. Model III assumes the presence of multiple receptors on the cell surface. Only when a specific fraction of the total number of one receptor have reacted, will the other receptor(s) initiate reaction with the adsorbate. The results suggest the existence of at least three major glycoprotein receptors interacting with the lectin, and having different equilibrium constants as indicated in the adsorption isotherm. Model III seems to support best the experimental data of concanavalin A interaction with platelet surface glycoproteins.

Binding and distribution of three prototype calcium channel blockers in perfused rat liver.

This work represents a study of the binding and distribution of three different calcium channel blockers in the Sprague-Dawley rat liver, using an in situ perfusion technique. For this purpose, [3H] desmethoxyverapamil, [3H] PN200-110 (isradipine) and [3H] azidopine were used as binding probes interacting with calcium channels. The perfusion steps of the liver involved both portal vein and thoracic inferior vena cava cannulations as inlet and outlet respectively. The subhepatic inferior vena cava was ligated to prevent leakage of the perfusate. Buffer, containing the tracer drug, was administered via the portal vein at a rate of 1 mL/min and perfusate collected at the same rate within specified time intervals during 50 min. The concentration of the tracer solutes in the perfusate's outlet increased with time, and steady state was observed for all tracers at > or = 40 min. The effect of adding cold isradipine to tracer desmethoxyverapamil, or cold verapamil to tracer PN200-110 were also assessed. First order rate constants for hepatocellular influx, efflux and calcium channel binding of the tracer substances were obtained using a simplified model from Goresky et al. These constants were mathematically manipulated and changed into permeability constants, second order binding constants, and residency times. Tracer solute influx across hepatocellular membranes is solubility-diffusion controlled, is inversely related to the molecular weights and is different in value from the efflux constants. Cold isradipine reduced the binding constant of desmethoxyverapamil by 36%, while cold verapamil reduced the binding constant of PN200-110 by 23%. Azidopine cellular distribution was low, however, binding to its receptor was analogous to desmethoxyverapamil and PN200-110. Moreover, PN200-110 had the highest residency time with no effect of cold verapamil on its receptor binding, while desmethoxyverapamil had the lowest residency time which significantly increased in the presence of cold isradipine.

Kinetics of lipopolysaccharide clearance by Kupffer and parenchyma cells in perfused rat liver.

We studied the kinetics of [3H]lipopolysaccharide ([3H]LPS) (endotoxin) binding to Kupffer cells and hepatocytes at the level of the microtubular system after treatment with gadolinium chloride (GdCl(3)) and colchicine. Liver perfusion in Sprague-Dawley rats involves both portal vein and thoracic inferior vena cava cannulations as inlet and outlet, respectively. The subhepatic inferior vena cava is ligated to prevent perfusate leakage. Buffer containing 2% serum and [3H]LPS is administered at 1 ml/min and collected for 50 min. Rate constants for hepatocellular clearance of [3H]LPS in controls, colchicine-treated rats, GdCl(3)-treated rats, and colchicine plus GdCl(3)-treated rats are assessed using a simplified mathematical model. Forward-binding, reversal-binding, residency time, and influx rate constants are estimated. Results show that in GdCl(3)-treated rats, the hepatocytes effectively clear endotoxin from the circulation, and its ultimate binding affinity at the hepatocyte site is somewhat reduced compared to the Kupffer cells. In colchicine-treated rats, the disruption of the microtubule network altered [3H]LPS binding with Kupffer cells, suggesting that the microfilament-microtubular network also affects Kupffer cell function. Simultaneous treatments with colchicine and GdCl(3) increased the influx rate constant, suggesting that the compiled morphological alterations up-regulated endotoxin clearance by the liver, as indicated by a drastic increase in cellular vacuolation. In conclusion, the kinetics of the trafficking process of [3H]LPS clearance are regulated by apical-sinusoidal endocytotic and canalicular routes.

Binding of 125I-insulin on capillary endothelial and myofiber cell membranes in normal and streptozotocin-induced diabetic perfused rat hearts.

A heart-perfusion technique was employed to measure 125I-insulin binding on capillary endothelial and myocyte cell membranes in Sprague-Dawley rats. Animals were anesthetized, and the anterior chest wall excised to expose the mediastinal contents. The right and left superior and inferior venae cavae were dissected and tied, and another tie was passed around the aorta. A polyethylene catheter was introduced into the aortic lumen from cephalad to caudad to sit with its tip above the aortic valve. Another catheter was introduced into the cavity of the right atrium and both were anchored by sutures. Oxygenated Ringer-Lock buffer containing 20 mM/L K+ and 125I-insulin was perfused at a rate of 1 mL/min via the aortic catheter. Concomitantly, the distal ascending aorta and venae cavae were ligated. The effluent was collected from the right atrial catheter at the same infusion rate. Animals were divided into two groups, the normal group and streptozotocin-induced diabetic group. Heart perfusion was done on both groups either without or after treatment with detergent (CHAPS) to remove the capillary endothelial lining. A physical model for 125I-insulin sequestration as a ligand to its receptors on endothelial and/or myocyte plasma membranes was proposed. The model described a reversible binding of ligand on cellular surface receptor concentration to fit a conservation equation and a first order Bessel function. The binding constants (kn), reversal constants (k-n), dissociation constants kd = k-n/kn, and residency time constants tau = 1/k-n of 125I-insulin in normal untreated, normal CHAPS-treated, diabetic untreated, and diabetic CHAPS-treated hearts were estimated using a theoretically generated curve-fit to the data. Since insulin receptor binding on the capillary endothelial cell surfaces may serve to transport insulin from the intravascular to the subendothelial space, and since streptozotocin-induced diabetes was shown to diminish receptor autophosphorylation and kinase activity and hence internalization of insulin, then one can conclude the following from the data. In the normal heart, removal of the capillary endothelial lining with CHAPS did not alter kn, k-n, kd, and tau of insulin binding as compared to the normal untreated, whereas in the diabetic untreated heart these constants were altered, compared to the diabetic treated. Furthermore, the kn and k-n values in the diabetic CHAPS-treated hearts were the same as for the normals untreated and CHAPS-treated, respectively. In conclusion, the dissociation constants and residency time constants of all groups indicated the possible existence of two types of insulin receptors: the capillary endothelial cell surface insulin receptors with lower residency time (low affinity receptor or combination of insulin and IGF-1 receptors) and the myocyte plasma membrane insulin receptors with higher residency times (high affinity).