Cholinergic control of the mechanical properties of the catch connective tissue in the holothurian body wall

Effects of acetylcholine (ACh), ACh-agonists and antagonists were studied on the viscosity of the dermis of the sea cucumber Holothuria leucospilota. ACh and nicotinic agonists caused an early increase in viscosity and late decrease. Muscarinic agonists produced a viscosity decrease. The viscosity increase elicited by nicotine was inhibited by tubocurarine. The viscosity decrease caused by methacholine was suppressed by atropine. The mechanical properties of this connective tissue are very likely controlled by both nicotinic and muscarinic cholinoreceptors.     

Stiffness of starfish arm and involvement of catch connective tissue in the stiffness change

• 1.1. Bending tests were performed on intact arms of two starfishes of different orders to obtain stiffness of the arm.
• 2.2. Linckia laevigata without stimulation showed a wide variety of arm stiffness of 2.24–51.3 MPa (average: 8.0 MPa). Mechanical stimulation increased the stiffness by 2.5 times.
• 3.3. In Asterias forbesii, isolated arms were 23 times stiffer than intact ones. Anesthesia with 0.1% MS-222 or menthol-saturated sea water increased the stiffness by 7–170 times.
• 4.4. Ion dependence of stiffness suggests that the catch connective tissue was involved in the stiffness change.

     

The glycosaminoglycans of pig colonic wall connective tissue

Colon wall from pig, stripped of most of the mucosal layer to leave material largely composed of muscle, basement membrane, and extracellular matrix, was subjected to procedures for isolation of glycosaminoglycans. A total ethanol precipitate from a papain digest was fractionated by selective ethanol precipitation in the presence of Ca²⁺. Glycosaminoglycan fractions, freed proteolytically from a high molecular weight glycoprotein component, were further purified by Sepharose CL-6B gel-filtration or DE-52 anion-exchange chromatography. Glycosaminoglycans were identified by chemical composition, ¹³C-NMR spectroscopy and response to chondroitinase and nitrous acid degradations. The content of glycosaminoglycan in the tissue is low (0.05% dry weight) being comprised of dermatan sulphate (38%), heparin (34%), heparan sulphate (18%) and chondroitin sulphates (10%) as a percentage of total glycosaminoglycan content. Hyaluronic acid and keratan sulphate have not been detected. The composition is generally typical of a high muscle content tissue.     

Effects of ionic environment on viscosity of Triton-extracted catch connective tissue of a sea cucumber body wall

Mechanical properties of catch connective tissue are greatly affected by its ionic environment. In order to understand the role of ions, a preparation was developed in which cellular activities were suppressed by treatment with 1% Triton X-100.The material used was body-wall dermis of the sea cucumber Holothuria leucospilota Brandt.The effects of the main cations in seawater (H⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺) on the creep viscosity of the Triton model were compared with those of intact dermis.The comparison distinguished the site of action of ions. K⁺ had its main effect on cells that control the catch mechanism, whereas Ca²⁺ worked directly on extracellular materials. H⁺, Na⁺ and Mg²⁺ had both effects.     

Mechanical properties of orbital fat and its encapsulating connective tissue

There is an increasing need to understand the mechanical properties of human orbital fat and its encapsulating connective tissue (OFCT), but such knowledge is not available in the current literature. The purpose of the present study is to examine the mechanical properties of the OFCT. From 5 pairs of 76- to 92-year-old Caucasian human eyes and 33 5- to 7-month-old porcine eyes, 5 human and 11 porcine OFCT samples were dissected at the posterior pole or adjacent to the pole in the vertical, horizontal, and radial directions. Sample dimensions were fixed or measured. Tensile tests were performed on the samples in body-temperature saline. The stress-strain relationship was first approximately linear and then became nonlinear. The linear, the neo-Hookean, and the Mooney-Rivlin constants are reported in Tables 1 and 2. No statistical difference was found among their properties in the different directions in either the human or the porcine samples. Statistical differences were found between the human and the porcine material constants in the horizontal and radial directions. Among our material models, only the Mooney-Rivlin model was able to capture the mechanical properties of the OFCT in large deformation properly. The Mooney-Rivlin model was especially adaptive to the human data. This is the first time the mechanical properties of the human and porcine OFCT have been examined in the literature. We believe our data will provide valuable information to others regarding designing implant biomaterials in orbital treatments and developing computer models to study orbital biomechanics.     

Development of the connective tissue in the wall of the rabbit aorta in experimental atherosclerosis

Structural and functional characteristics of cells involved in collagen synthesis have been studied in experimental hypercholesterolemia in rabbits. Autoradiographic studies, using 3H-proline and 14C-hydroxyproline have demonstrated that collagen synthesis takes place only in the intima in the area of cellular proliferation. At earlier stages of experimental atherosclerosis collagen synthesis predominantly involves synthetic GABA phenotype, while at progressing stages fibroblasts are predominantly involved.