ABSTRACT
Collagenase was injected into the ears of rabbits and the cheek-pouches of hamsters. The acute and long-term microvascular effects were studied by vital microscopy and microangiography. The enzyme was injected at three different concentrations: 120 units/ml, 600 units/ml and 3,000 units/ml. The medium (600 units/ml) and high (3,000 units/ml) concentrations induced effects on the microcirculation such as blood flow impairment and microbleedings. The magnitude of these effects was related to the concentration of the enzyme. Generally, these microvascular effects were of low magnitude as compared with other substances tested using the same experimental models.
Subject(s)
Microbial Collagenase/administration & dosage , Microcirculation/drug effects , Animals , Cheek/blood supply , Cheek/drug effects , Cicatrix , Cricetinae , Ear, External/blood supply , Ear, External/drug effects , Injections, Subcutaneous , Mesocricetus , Microbial Collagenase/pharmacology , Rabbits , Regional Blood FlowABSTRACT
Indomethacin can reduce the microvascular permeability induced by repeated ischemia. In this investigation the influence of histamine H1 and H2 receptor blockers was studied for comparison with indomethacin. Application of 60 mmHg pressure to the hamster cheek pouch for 5 min was repeated eight times, with 10-min restitution intervals. Altered permeability was evaluated with use of FITC-dextran and intravital microscopy. Progressive efflux of FITC-dextran was observed in the control group. When either diphenhydramine or indomethacin was used alone, a few spots of extravasated dye were seen. Combination of diphenhydramine with either indomethacin or cimetidine reduced the extravasation. Furthermore, the spots appeared significantly later than in the controls, and some faded. Increase in the efflux of macromolecules due to repeated ischemia seems to be mediated via H1 and H2 receptors in conjunction with other receptors and/or amines e.g. prostaglandins.
Subject(s)
Capillary Permeability/drug effects , Histamine H1 Antagonists/pharmacology , Histamine H2 Antagonists/pharmacology , Indomethacin/pharmacology , Microcirculation/drug effects , Animals , Cricetinae , Diphenhydramine/pharmacology , Ischemia , Mesocricetus , PressureABSTRACT
Effects of graded compression on nerve function were analyzed in order to evaluate the relative importance of pressure level and duration of compression for functional deterioration. The pressure was applied by means of a small inflatable cuff. The effects of two pressure levels, i.e., 80 mm Hg applied for 2 hr or 400 mm Hg applied for 15 min, were studied in rabbit tibial nerves. The lower pressure tested, which is known to induce ischemia of the compressed nerve segment, also causes some degree of mechanical deformation of the nerve trunk, which leads to incomplete recovery following pressure release. The duration of compression is of importance for the degree of nerve injury even at the higher pressure level tested.
Subject(s)
Nerve Compression Syndromes/physiopathology , Peripheral Nerves/physiopathology , Animals , Biomechanical Phenomena , Disease Models, Animal , Electric Conductivity , Peripheral Nerves/physiology , Rabbits , Stress, Mechanical , Tibial Nerve/physiology , Tibial Nerve/physiopathologyABSTRACT
Intradiscal injection of proteolytic enzymes implies a potential risk for exposure of nervous tissue to the enzyme solution. In the present study, the effects on peripheral nerve tissue of application of a solution containing a clinically recommended concentration of collagenase have been evaluated. Acute experiments showed that the enzyme induces transient swelling at the site of application and edema in the epineurium. There were, however, no detectable effects on the permeability of the perineurium or the endoneurial microvascular bed. Four and 8 weeks later, there was a slight fibrosis in the epineurium, but neurophysiologic tests did not reveal any impairment of the nerve function. The results are discussed in terms of the clinical use of collagenase for dissolution of herniated intervertebral discs.
Subject(s)
Microbial Collagenase/pharmacology , Peripheral Nerves/drug effects , Animals , Capillary Permeability/drug effects , Female , Male , Myelin Sheath/drug effects , Peripheral Nerves/blood supply , RabbitsABSTRACT
Pressure ulcer and tracheal injury occurring after endotracheal intubation are clinical examples of pressure-induced tissue damage where magnitude and duration of the applied pressure are of major importance. The objective of this study was to investigate the efflux of macromolecules caused by repeated short-time ischemia induced by a pressure of 60mmHg, which causes circulatory standstill. Pressure was applied to the hamster cheek pouch and the efflux of the macromolecules of the microvasculature was evaluated by using the fluorescein isothiocyanate (FITC) dextran dye and intravital microscopy. The pressure was applied for either 1 or 5 min and repeated 8 times with a 10min restitution period in between. The repeated 1min pressure caused almost no change in microvascular efflux of FITC-dextran while 5min repeated pressure did. The gross mechanical impact on the tissue seems to be equal in the 1 and 5min exposure and thus cannot explain the difference in the developed permeability. Ischemia of such short time as 1 and 5min does not alter the energy state of the tissue significantly. The reactive hyperemia and the mediating vasoactive amines can differ markedly after 1 and 5min ischemia and can thus contribute to the permeability alteration. However, the role of vasoactive amines is unclear and further experiments are needed to determine their role.
