ABSTRACT
A study of the interaction of gramicidin A (gA), tert-butyloxycarbonyl-gramicidin (g-BOC), and desformyl gramicidin (g-des) with dioleoyl phosphatidylcholine (DOPC) and DOPC/phosphatidylserine (PS) mixed monolayers on a mercury electrode is reported in this paper. Experiments were carried out in electrolytes KCl (0.1 mol dm(-3)) and Mg(NO3)2 (0.05 mol dm(-3)). The channel-forming properties of the gramicidins were studied by following the reduction of Tl(I) to Tl(Hg). The frequency dependence of the complex impedance of coated electrode surfaces in the presence and absence of the gramicidins was estimated between 65,000 and 0.1 Hz at potentials of -0.4 V versus Ag/AgCl with 3.5 mol dm(-3) KCl. Epifluorescence microscopy was used to qualitatively correlate the interaction of the gramicidin peptides with dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG) at the air-water interface. gA was shown to form Tl+ conducting channels in a DOPC monolayer, while g-BOC and g-des did not. In DOPC-30% PS (DOPC-0.3PS) layers, there is a marked increase in channel activity of all three gramicidin derivatives. None of the peptides facilitate the permeability of the DOPC-0.3PS layer to Cd2+. All three peptides interact with the layer as shown by capacitance-potential curves and impedance spectroscopy indicated by penetration of the peptide into the dielectric, an increase in surface "roughness", and an increased significance of low-frequency relaxations. The order of interaction is gA > g-des > g-BOC. The epifluorescence study of DPPC and DPPG layers at the air-water interface shows a selective action of the different gramicidins.
Subject(s)
Gramicidin/analogs & derivatives , Gramicidin/chemistry , Phospholipids/chemistry , 1,2-Dipalmitoylphosphatidylcholine/chemistry , Air , Metals, Heavy/chemistry , Oxidation-Reduction , Particle Size , Phosphatidylglycerols/chemistry , Surface Properties , Water/chemistryABSTRACT
Amongst approximately 1 500 spastic children under treatment, the authors have seen three cases of fatigue fracture of the patella. One patient was spastic and two others were athetotic. The fatigue fractures can be explained by a flexed knee gait aggravated by a contracture of the hamstring tendons. No fracture was seen in patients treated by Egger's operation. It is concluded that this procedure both prevents and cures fatigue fracture of the patella.
Subject(s)
Cerebral Palsy/complications , Fatigue/complications , Fractures, Bone/etiology , Patella/injuries , Adolescent , Fatigue/physiopathology , Female , Fractures, Bone/physiopathology , Fractures, Bone/surgery , Humans , Leg , Male , Muscles/physiopathology , Tendons/physiopathologyABSTRACT
The authors have studied 1575 children treated by rehabilitation, splintage and eventually surgery. Some were followed up for 25 years and all were followed up for more than 4 years. The results are described for the upper limb in hemiplegics and quadriplegics and for the lower limb in paraplegics and quadriplegics. An analysis was made of the influence of I.Q., age at onset of treatment, and neurological features (spasticity, athetosis, sensory deficiency, anaesthesia). It is concluded that some attempts to treat must always be made. The authors describe the results that may be expected.
