Muscle Patch Research Articles

Spontaneous release of acetylcholine affects the physiological nicotinic responses of rat retinal ganglion cells in culture

Nictonic cholinergic responses have been previously documented in mammalian retinal ganglion cells. In the present study, dissociated retinal cells were densely plated and grown in a specific batch of rat serum. When held at negative potentials during whole-cell recording with a patch electrode, the retinal ganglion cells located close to presumptive cholinergic amacrine cells in these cultures were found to respond to acetylcholine (ACh; 20-200 microM) with an apparent outward current in the presence of physiological salines on both sides of the membrane. Other nicotinic agonists (nicotine, carbachol) produced the same effect. Conductance measurements revealed that this apparent outward current was actually a decrease in a tonic inward current. Nicotinic antagonists such as d-turbocurarine (10 microM) and dihydro-beta-erythroidine (20 microM), when applied in dishes that had never been exposed to exogenous ACh, produced a similar decrease in a tonic inward current. The reversal potential of the tonic current suppressed by ACh was similar to the nicotinic current previously studied in these central neurons. Furthermore, purified acetylcholinesterase was capable of modulating the tonic inward current of the retinal ganglion cells. Lowering an excised patch of muscle into dense areas of the retinal cultures activated nicotinic channels in the muscle membrane, indicating the presence of endogenous ACh in the culture fluid. Divalent cations such as Co2+ blocked the tonic inward current of retinal ganglion cells in these cultures. Finally, direct biochemical measurements indicated that low levels of endogenous ACh (on the order of 0.5 microM near putative cholinergic amacrine cells) were present in the retinal cultures. Taken together, these results show that ACh was being spontaneously released into these cultures, resembling at least to some degree the tonic leakage of ACh found in the intact retina. This concentration of ACh was capable of tonically depolarizing the membrane potential of retinal ganglion cells exposed to this dosage. This culture system allows the study of trophic effects of ACh on a central mammalian neuron in a precisely controlled extracellular environment.

The Long-term Success of Skeletal Muscle in Aortic Repair

To determine the efficacy of skeletal muscle for aortic repair, 23 swine underwent repair of descending thoracic aortic defects. In one group, a vascularized muscle flap was used to patch a 2- to 3-cm aortic defect. In two other groups, a short segment of aorta was removed and a 2-cm tube graft of freshly harvested but devascularized skeletal muscle or Vicryl mesh was used to repair the aorta. Swine were followed for up to sixteen months after implantation. There were no deaths or graft-related complications in the vascularized muscle patch group, and after sixteen months, there were no stenoses or aneurysmal dilatations of the flaps. Histologically, a mature pseudointimal layer had been deposited under the muscle flap and was grossly indistinguishable from normal arterial wall. In the group that received devascularized muscle tube grafts, however, suture line dehiscences occurred in 3 of 7 animals within two weeks of operation. There were no dehiscences in the 9 recipients of a Vicryl tube graft, a finding suggesting that deposition of pseudointimal elements was rapid enough to ensure vascular integrity as the Vicryl was absorbed. Postmortem examination of these animals demonstrated stenoses ranging from 30 to 50%, thereby indicating a lack of growth in the new pseudointimal wall. These results demonstrate the long-term reliability of vascularized skeletal muscle for use in major vascular reconstruction, and suggest the beneficial effects of avoiding prosthetic material and promoting optimal pseudointimal formation.

Calcium dependent gating of thel-glutamate activated, excitatory synaptic channel on crayfish muscle

Excitatory, glutamate-activated single channel currents were measured in outside-out patches of crayfish muscle. The open times of single channel openings, and the durations and rates of bursts were evaluated. These kinetic parameters were not appreciably affected by replacement of extracellular Na+ by Li+ or choline. Changes in extracellular Ca2+ concentration Cao also did not influence the duration of single openings. However the mean burst duration decreased for Cao less than 13.5 mM and the rate of bursts declined with a power of almost 2 in low Cao. At Cao less than 1 mM practically no channel openings were observed in presence of glutamate. In order to exclude more rapid desensitization of the glutamate receptors in low Cao as the cause of disappearance of channel openings, glutamate was applied in short pulses with a liquid-filament switch. In 0 Cao also a glutamate pulse did not trigger channel openings. In presence of 13.5mM Cao, the inorganic Ca-channel blockers La3+ and Cd2+ diminished the duration and rate of bursts of channel openings in a similar manner as low Cao. The effects of low Cao and of Cd2+ were tested also on quantal postsynaptic currents, EPSCs, which were recorded through a perfused macro-patch-clamp electrode. At 1.4 mM Cao in the perfused electrode tip, spontaneous EPSCs were reduced at least by a factor of 4, and elicited EPSCs by a factor of 16. Application of Cd2+ had similarly strong effects on the EPSCs. Also the decay of EPSCs was shortened substantially in 1.4 mM Cao or 5 mM Cd2+. The inhibitory Cl(-)-channel of crayfish muscle, activated by glutamate or GABA, also was studied in outside-out patches. The openings of this channel persisted in 0 Cao solutions; the block of channel openings in low Cao thus is a specific property of the excitatory channel. The action of Cao on the excitatory channel may be described as that of a cofactor to glutamate. A possible reaction scheme is proposed.

Conductance properties and voltage dependence of an anion channel in amphibian skeletal muscle

Single anion-selective channels were studied in excised membrane patches of adult frog toe muscle. The conductance gamma and the probability po of the main open state were determined for various ionic compositions of the extra- and intracellular solutions. gamma = 280 pS in symmetrical 110 mM NaCl, pH 7.4 solutions at 15 degrees C. Higher gamma values were found at elevated internal or external NaCl concentrations, in 70 mM external CaCl2 and at lower extracellular pH. The po(E) curve declined steeply with hyperpolarization and was shifted towards more negative potentials at increased internal ionic strength and at higher external pH. Positive shifts were induced by extracellular Ca. The results show that the anion channel saturates at Cl concentrations greater than 110 mM, that the potential profile of an open channel is almost symmetrical and that channel gating is affected by neighboring channels. It is suggested that the anion channel has a voltage sensor (effective gating charge 4.3) and a similar collection of local fixed charges on the extra- and intracellular sides as voltage-gated cation channels.

The use of muscle flaps in the repair of aortic defects

The successful repair of an infected arterial anastomosis is often hampered by the need to leave prosthetic material at the site of infection. To determine whether an aortic defect could be repaired by direct closure with a muscle flap, thereby eliminating the need for prosthetic material, we subjected 33 young pigs weighing 17 to 19 kg to a left lateral thoracotomy under sterile conditions. An aortic defect 2 cm in diameter was created in the descending thoracic aorta just distal to the origin of the left subclavian artery. In one group (n = 11), this defect was patched with a freshly harvested but devascularized segment of chest wall muscle. In another group (n = 22), the aortic defect was patched with a vascularized chest wall muscle flap. Pigs were followed for up to 12 weeks and evaluated by arteriography and postmortem examination. There were no deaths or vascular complications attributable to the muscle flap repair in any pig. Pseudointimal formation began within 24 hours postoperatively and was of comparable thickness to the original arterial wall by 12 weeks. No aneurysmal changes were noted in any animal, and normal aortic luminal dimensions were preserved despite a tripling in mean body weight over the 12 week period. The loss of flap viability appeared to offer no threat to vascular integrity, as the free muscle patches, although undergoing cell necrosis and substantial remodeling, remained intact. These results demonstrate the short-term feasibility of using viable muscle flaps to patch aortic defects in situations wherein the use of prosthetic material would be undesirable.

Congenital cystic disease of the lung

In 19 cases of congenital cystic disease of the lung, the cysts were always multiple or multilocular and thin-walled. Their walls resembled those of bronchioles with surrounding patches of smooth muscle without cartilage. The cysts communicated with bronchi proximally and with alveoli distally suggesting bronchiolectasis. However, there was also proliferation of bronchiolar structures, shown by their increase in number and by papillary overgrowth of the lining epithelium. Bronchiolar proliferation is also a feature of adenomatoid malformation. The 2 terms therefore, may possibly apply to different degrees of the same anomaly, a severe one producing stillbirth or neonatal death, and a milder one allowing survival long enough for successful surgical resection. One third of the children were full-term neonates, one third were aged 1 to 12 mth, and one third 1 to 10 yr. Fifteen of the specimens were surgical and 4 were necropsies. Half also had emphysema in the affected lobe, and 4 had associated extra lobar sequestration. None was associated with cysts in other organs. Radiologically and macroscopically, the overdistended lobe sometimes mimicked congenital lobar emphysema. All cases with more than focal chronic inflammation were omitted, in order to exclude post inflammatory pneumatoceles. Intrapulmonary bronchogenic cysts and intrapulmonary sequestrations differed in being usually single, often having cartilage and inflammatory fibrosis in their walls, and not having alveoli budding off the cyst. In 19 cases of congenital cystic disease of the lung, the cysts were always multiple or multilocular and thin-walled. Their walls resembled those of bronchioles with surrounding patches of smooth muscle without cartilage. The cysts communicated with bronchi proximally and with alveoli distally suggesting bronchiolectasis. However, there was also proliferation of bronchiolar structures, shown by their increase in number and by papillary overgrowth of the lining epithelium. Bronchiolar proliferation is also a feature of adenomatoid malformation. The 2 terms therefore, may possibly apply to different degrees of the same anomaly, a severe one producing stillbirth or neonatal death, and a milder one allowing survival long enough for successful surgical resection. One third of the children were full-term neonates, one third were aged 1 to 12 mth, and one third 1 to 10 yr. Fifteen of the specimens were surgical and 4 were necropsies. Half also had emphysema in the affected lobe, and 4 had associated extra lobar sequestration. None was associated with cysts in other organs. Radiologically and macroscopically, the overdistended lobe sometimes mimicked congenital lobar emphysema. All cases with more than focal chronic inflammation were omitted, in order to exclude post inflammatory pneumatoceles. Intrapulmonary bronchogenic cysts and intrapulmonary sequestrations differed in being usually single, often having cartilage and inflammatory fibrosis in their walls, and not having alveoli budding off the cyst.

Electrical transmission of slow waves from longitudinal to circular intestinal muscle.

Circular muscle from cat intestine exhibits spontaneous rhythmical contractions only when it is attached to longitudinal muscle. Under these conditions electrical slow waves can be recorded from circular muscle, but they disappear following complete removal of the longitudinal layer. If a small patch of longitudinal muscle remains, slow waves can be recorded from adjacent circular muscle. Those recorded lateral to the longitudinal layer are synchronized with slow waves recorded directly from this layer. Their amplitude decreases exponentially with distance, approaching zero at about 12 mm from the lateral edges and about 3 mm from the oral or aboral edge of the longitudinal layer. Slow waves can also be recorded across the entire intestinal wall or across a longitudinal-circular muscle preparation. With this method of recording, the amplitude of the slow waves decreases as the thickness of the circular layer is reduced by stripping away its innermost layers. The amplitude is not increased by replacing these layers. These results indicate that slow waves may be transmitted electrotonically from longitudinal to circular muscle, implying the existence of electrical continuity between the two muscle layers. The transmission of slow waves can account for the coordinated spontaneous rhythmicity exhibited by circular muscle under normal conditions, i.e., when attached to the longitudinal layer.

INSTANT POLYMERIZATION OF PLASTIC MONOMER FOR TISSUE REPAIR. A PRELIMINARY REPORT.

Methyl 2-cyanoacrylate * polymerizes fairly rapidly in the presence of heat, pressure, slightly moist alkaline substances, ionizing radiation, etc. On polymerization it becomes densely adherent to glass, steel, wood, protein, and many other materials. Because of these qualities it has been used as an adhesive in a wide variety of adherend combinations.10In recent years it has been used experimentally in surgery for the cementing of the skin,2,3,11intestines,21kidney,19conjunctiva,4arteries,5-9, 12,14,20veins,13,14bronchi,15and bone.18. It has been used as an adhesive in cementing patches of muscle, vessel walls, and Teflon over defects in blood vessels, dura,1,5,8,9and so on. It causes rapid coagulation of the blood as well as adherence of the blood vessel walls to each other and, by virtue of this fact, it has also been used in experimental hemostasis.16,17 In most of the trials