Current leakage in bipolar electrocoagulation

Bipolar electrocoagulation has previously been shown to give a considerable amount of current leakage to ground from either of the two outputs. This might result in unwanted tissue destruction. Thus far, no standard has been proposed for current leakage to ground from the outputs of bipolar equipment. This study was performed to establish safe parameters for such leakage. To determine the limit for damage-no damage, monopolar stimulations were performed on the brain surface of dogs. Blood-brain barrier disturbance was used as an indicator of damage. The limit for acceptable current leakage was found to be about 10 to 15 mA. Most bipolar coagulators were found to exceed this value. The electrical data recorded in this study should be considered in the design of bipolar equipment for electrocoagulation.

Influence of bile acids on cholera toxin-induced secretion in mouse jejunum

The influence of bile acids on intestinal secretion induced by cholera toxin (CT) was studied in mice. The secretion was examined in ligated loops after the bile flow had been stopped by ligation of the common bile duct (CD). Bile depletion was found to inhibit both the secretion induced by CT, the degradation of CT, and the binding of CT to epithelial cells--all of which could be restored to normal by the application, before CT challenge, of bile acids in the loops of CD-ligated mice. Out of the nine bile acids tested, cholic acid, deoxycholic acid and chenodeoxycholic acid were the most potent, their ED50 values being 0.2, 0.2, and 0.6 mM respectively.

Electron microscopic analysis of the bone-titanium interface

Ten cylindrical implants, made of polycarbonate and covered with a 120-250-nm-thick layer of pure titanium, were implanted into each tibial metaphysis of five rabbits. Observation time was 12 weeks. The implants were surrounded by mature, living bone. No soft tissue intervened between bone and implant at any point. With TEM microscopy the titanium was shown to be bordered by a 20-nm-thick layer of proteoglycans, showing the characteristics of ground substance, and separating the collagen from the implant surface. Cells at the interface were likewise separated from the titanium by such a layer. Hydroxyapatite crystals were observed within the ground substance layer, occasionally seemingly in direct contact with the titanium. Normal mineralization was present 100-500 nm from the implant surface. While this study aims at defining interface anatomy, it also shows that macroscopically smooth-surfaced titanium can readily heal into bone without a soft tissue envelope. This could be of help for materials' choice and design of permanently fixed implants.

Mesothelial cell integrity of the subdural and arachnoid surfaces of the cat brain after exposure to neurosurgical irrigation fluids and air: a scanning electron microscopic study

The mesothelial cell integrity of the subdural and arachnoid surfaces in the cat was investigated by scanning electron microscopy after exposure to different irrigation fluids used in neurosurgery, as well as after drying by air. Irrigation for 3 hours with Elliott's Solution B and Ringer's solution retained the morphology of the cells. After exposure to saline for the same time, the mesothelial cells appeared perforated and were sometimes detached from the underlying connective tissue. Exposure to air for 15 minutes induced extensive, probably irreversible, cell damage. After 5 minutes of exposure to hydrogen peroxide, most cells disappeared, revealing the underlying collagenous connective tissue. These mesothelial cell changes might be one cause of the formation of postoperative subdural adhesions. In previous studies, disturbance of the blood-brain barrier was produced by those agents causing mesothelial cell damage. With hydrogen peroxide, widespread thrombosis occurred in leptomeningeal vessels supplying the cortex. Changes in these vessels can obviously be induced easily by fluids applied to the subdural space because of the close contact between the arachnoid and the adventitia of the vessels. This alternative should be considered in the treatment of cerebral vasospasm.

Nerve regeneration across an extended gap: a neurobiological view of nerve repair and the possible involvement of neuronotrophic factors

We have compared the anatomic and functional regeneration of a transected sciatic nerve following regrowth from its proximal stump through either preformed empty mesothelial chambers or autologous nerve grafts bridging a 10 mm gap. Within the mesothelial chambers an organized multifascicular nerve trunk forms between the proximal and distal stumps. After 3 months, distal segment cross sections from the mesothelial chamber and nerve graft groups did not differ with respect to axonal density or distribution of axonal diameters. Mean conduction velocities across the gaps were also similar, although the nerve graft group had a wider distribution of velocities. Little or no regeneration was evident when the gap between the nerve stumps was left empty. These results suggest that if the regrowing proximal stump is in an appropriate environment, it can form a well organized and oriented nerve trunk. In the mesothelial chambers, the regenerating nerve is surrounded by a loose cellular stroma and a small amount of interstitial fluid, which was found to contain trophic activity for cultured rodent sensory neurons. Such factors may also support nerve regeneration in vivo.

Function and structure of the nasal mucosa after 6 weeks' use of nose-drops

The nasal mucosa of 20 healthy subjects were examined before, during and after 6 weeks of regular use of xylometazoline nose-drops (1 mg/ml) 0.15 ml three times daily. The subjects, except those affected by common colds, did not suffer any diminished mucociliar function during or after the trial. The surface structures were not found to have changed when examined with scanning electron microscopy. No morphological changes were observed in the intercellular space, basal membrane or tunica propria when using transmission electron microscopy. During the test period 5 of the subjects developed upper respiratory infections which temporarily prolonged the mucociliar transport time tested with small particles of saccharin. In some of these subjects a reduction in the number of ciliated cells was observed as well as an inflammatory reaction close to the epithelial cells. It is concluded that the use of xylometazoline over a 6-week period does not provoke any major functional or structural changes in a normal nasal mucosa.

Identification and characterization of sulfhydryl-containing proteolytic fragments involved in the Ca2+-induced conformational change of beef brain S-100

The Ca2+-dependent conformational alteration of the brain-specific S-100 protein was studied by reacting the protein with N-ethyl[2,3-14C]maleimide in the absence and presence of Ca2+ and under denaturing conditions. Peptic hydrolysates of the 14C-labeled protein were analyzed and fractionated by high-performance liquid chromatography. Labeled peptide fractions were characterized by high-voltage electrophoresis and TLC. A clear distinction could be made between two classes of sulfhydryl-containing fragments: (a) neutral, hydrophobic, and (b) acidic. Ca2+ markedly favored 14C incorporation into the former components, whereas the latter were readily available only under denaturing conditions.

On the extensive contact between veins and arteries in the human ovarian pedicle

The human ovarian arteries and their anatomical relation to the utero-ovarian venous plexus were studied in surgical specimens using roentgen angiography and corrosion casts. The arteries were in close contact with the veins, had a tortuous shape and sometimes a helical folding of inner layers of the wall. The results obtained are similar to the findings in a number of animal species and may represent the morphological basis for a counter-current exchange mechanism.

Polytetrafluoroethylene and anodized aluminum surfaces in an extracorporeal circuit: scanning electron microscopic study

Tubes with polytetrafluoroethylene (PTFE) or anodized aluminum surfaces were inserted in an extracorporeal circuit which was connected to mongrel dogs. The tubes were removed at regular intervals during the perfusions and their inner surfaces were examined by scanning electron microscopy. The anodized aluminum tubes were covered with platelets, fibrin, and other blood elements in a thick layer. In contrast, the PTFE tubes were mainly uncovered.

Trichloroethylene: long-lasting changes in the brain after rehabilitation

The exposure of adult Mongolian gerbils to 60 or 320 ppm trichloroethylene (TCE) by continuous inhalation during 3 months, followed by a period of 4 months free of exposure, causes biochemical changes in the hippocampus, the posterior part of cerebellar vermis and in the brain stem, compatible with alterations comprising astroglial hypertrophy and/or proliferation. General and experimental neuropathology have been able to raise our knowledge of the glial cells, and a number of distinct tissue syndromes are characterized and pathogenetically determined by changes in the astroglial component of the nervous system. An astroglial reaction, comprising hypertrophy or proliferation, is known to be caused by exogenous and endogenous noxae. Ultrastructural evidences on neuronal cell alterations, such as decreased amounts of microtubules and increased content of lysosomes and myelin bodies, were observed. The biochemical and morphological data presented indicate that TCE is neurotoxic after moderate exposure levels and periods. Some brain areas seem to be more sensitive than others.

Pseudoendothelium formation in expanded polytetrafluoroethylene grafts implanted in the inferior vena cava of normal and defibrinogenated dogs

The outgrowth of endothelial cells in an expanded polytetrafluoroethylene graft implanted in the canine inferior vena cava was studied by scanning electron microscopy. The adjacent endothelial cells of the vena cava started to invade the anastomotic area three days after the implantation and reached approximately the central part of the 2-cm-long graft after 21 days. There was no obvious difference in the process of endothelialization between the control group and the moderately defibrinogenated group, in which the fibrinogen concentration was at most 0.72-0.87 gm/L. A slight delay in the outgrowth of endothelial cells was noted within the first seven days in the severely defibrinogenated group, in which the fibrinogen concentration was below 0.40 gm/L. After 70 days, all grafts were completely covered by endothelial cells. The structural difference of the mural thrombus resulting from reduced fibrin formation might be a major factor influencing the endothelium formation.

Absorbable or nonabsorbable suture materials for closure of the dura mater?

This study was undertaken to determine which suture material would give the best results for closure of the dura mater. Because there is no need for the suture to remain longer than until healing has occurred and as remaining foreign material will predispose to foreign body reactions and infection, it was considered important to test new absorbable materials like polyglactin 910 (Vicryl) and polyglycolic acid (Dexon) for closure of the dura mater. The reactions from these materials were compared to those of silk and polyester (Ethibond) in dogs 60 days after the suture of dural incisions. The quality of healing with respect to the smoothness of the subdural surface, the presence of adhesions between sutures and the brain surface, the degree of absorption of the material, and reactions around the sutures were evaluated. Vicryl gave the best results, providing a smooth subdural surface without adhesions. It was almost totally absorbed when healing was completed, in contrast to Dexon and the other materials. The cellular reaction around Vicryl was slight. Silk, Ethibond, and Dexon protruded from the subdural surface and adhesions to the arachnoid were common. When the dura mater was removed, these adhesions tore off the leptomeninges with their vascular supply to the cortex. The results of these experiments seem to justify the recommendation of Vicryl for suturing of the dura mater. Such an absorbable material decreases the risk of foreign body reactions, and infections will be more easily combated because of the absence of foreign material. The lack of subdural adhesions is an advantage if reoperation is necessary.

Lamellar bodies in Purkinje nerve cells experimentally induced by electric field

Rabbits reared from mating to the age of almost two months outdoors in a substation in an electric (E)-field of 14 kV/m (undisturbed field, 50 Hz AC) only gained about half the weight of their controls, either protected by a Faraday's cage or being kept outside measurable E-field. The Purkinje nerve cells of cerebellum showed important alterations of the endoplasmic reticulum with disintegration of Nissl bodies, disappearance of hypolemmal cisterns and formation of numerous lamellar bodies. Concomitantly, there was a reduction in number of microtubules and increase in neurofilaments. These structural neuronal changes were reflected by changes in the behaviour of the rabbits which become slow in movements.

Haemostatic clot formation at anastomosis of synthetic venous graft in defibrinogenated dogs: a scanning electron microscopic study

A segment of the inferior vena cava was replaced by an expanded polytetrafluoroethylene graft in 13 dogs. Five of them served as a control group, while the other 8 were moderately or severely defibrinogenated with subcutaneous batroxobin. Plasma fibrinogen decreased to extremely low values throughout the experiment in the defibrinogenated dogs except in the moderately treated group in which it temporarily rose to 0.72-0.87 g/l on the first postoperative day. Scanning electron microscopic observations of the haemostatic clot formed at the anastomoses of the graft revealed no significant morphological differences in platelet adhesion and/or aggregation between the three groups. These findings confirmed that platelets play a key role in primary haemostasis during defibrinogenation. The fibrin network was slightly diminished and only short fibrin filaments could be seen in the moderately and severely defibrinogenated groups respectively. These differences in composition of the clots are discussed in relation to their haemostatic capacity.

Pseudointima in expanded polytetrafluoroethylene graft implanted in the inferior vena cava of normal and defibrinogenated dogs

The pseudointimal formation in an expanded polytetrafluoroethylene graft implanted in the canine inferior vena cava was studied by light and transmission electron microscopy. Five of 6 grafts in the control group and all of the 10 grafts in the batroxobin-defibrinogenated group were patent, and provided for the investigation. The thickness of the mural thrombus formed within 3 days was significantly decreased in the severely defibrinogenated dogs, in which the fibrinogen concentration was below 0.40 gm/L, as compared to the controls and the moderately defibrinogenated dogs, in which the fibrinogen concentration was at highest 0.72-0.87 gm/L. In spite of reducing the fibrinogen concentration to unmeasurable levels after 3 days, there was no obvious difference in the process of pseudointimal formation between the moderately defibrinogenated dogs and the controls. In the severely defibrinogenated dogs, loose and spongoid mural thrombus required a longer time to be reorganized.

Purkinje nerve cell changes caused by electric fields - ultrastructural studies on long-term effects on rabbits

Albino rabbits exposed to E-field (50 Hz AC, 14 kV/m, undisturbed field) from foetal life period "in utero" up to 7.5 weeks postnatally gained only about half the weight of controls reared in a Faraday's cage or outside measurable E-field. The Purkinje nerve cells in the cerebellum of E-field-exposed rabbits were reduced in size and the number of Nissl's bodies was reduced, as were the profiles of endoplasmic reticulum. A new structure, not observed in the controls, appeared in large numbers, namely, lamellar bodies concomitant with loss of hypolemmal cisterns. These structures were shown to be derived from the endoplasmic reticulum. The structural changes observed are interpreted as reflecting effects of exposure to an E-field.

Conjugation of horseradish peroxidase to staphylococcal protein A with benzoquinone, glutaraldehyde, or periodate as cross-linking reagents

Horseradish peroxidase was conjugated to Staphylococcal protein A by three different two-step procedures using an increasing excess of peroxidase in the second step reaction. The yield of conjugated protein A was analyzed by SDS-polyacrylamide gel electrophoresis. Conjugation of peroxidase to protein A with benzoquinone or glutaraldehyde as cross-linking reagents at a 3- to 4-fold molar excess of peroxidase resulted in a high yield of coupled protein A with conjugates of low molecular size. Conjugation of peroxidase to protein A by the periodate method resulted in a high yield of coupled protein A with polymeric conjugates of large molecular size. Based on these results, conjugates produced with glutaraldehyde as cross-linking reagents were further analyzed. The capacity of the conjugates to precipitate human immunoglobulin evaluated by radial immunodiffusion was found to be reduced to about 50% of that of native protein A. Conjugates produced with glutaraldehyde as cross-linking reagent retained 70% of the enzyme activity of native peroxidase.

Reorganization and orientation of regenerating nerve fibres, perineurium, and epineurium in preformed mesothelial tubes - an experimental study on the sciatic nerve of rats

Regeneration of severed peripheral nerves is unfortunately often incomplete, due to loss of nerve fibers and neuroma formation. A new approach is presented with the intention of improving the conditions for nerve repair. In the first of the two stages, a pseudosynovial tube is formed around a silicone rubber rod, surrounded by a stainless steel spiral, which was placed in the backs of rats. This tube, in the second stage, is used as a free "tube graft" to bridge gaps of about 10-12 mm lengths in the severed sciatic nerve. The tube was kept open by the metal spiral. Regenerating nerve fibers with their sprouts grew into the initially open space in the tube. A new nerve trunk was formed, comprised of closely packed myelinated and unmyelinated axons, organized into fascicles. Demonstration by electron microscopy and by EMG recording of reinnervation of foot muscles supported successful long-term results. The fascicles were delimited by perineurial and epineurial sheaths and, furthermore, showed signs of maturation. It was also demonstrated that the nerve-fiber regeneration ceased after a few weeks if there was no distal nerve inserted into the tube. The importance of optimizing the interaction between local factors and regenerating nerve fibers for reestablishment of functionally valuable motor units is discussed.

Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man

A total of 2895 threaded, cylindrical titanium implants have been inserted into the mandible or the maxilla and 124 similar implants have been installed in the tibial, temporal or iliac bones in man for various bone restorative procedures. The titanium screws were implanted without the use of cement, using a meticulous technique aiming at osseointegration--a direct contact between living bone and implant. Thirty-eight stable and integrated screws were removed for various reasons from 18 patients. The interface zone between bone and implant was investigated using X-rays, SEM, TEM and histology. The SEM study showed a very close spatial relationship between titanium and bone. The pattern of the anchorage of collagen filaments to titanium appeared to be similar to that of Sharpey's fibres to bone. No wear products were seen in the bone or soft tissues in spite of implant loading times up to 90 months. The soft tissues were also closely adhered to the titanium implant, thereby forming a biological seal, preventing microorganism infiltration along the implant. The implants in many cases had been allowed to permanently penetrate the gingiva and skin. This caused no adverse tissue effects. An intact bone-implant interface was analyzed by TEM, revealing a direct bone-to-implant interface contact also at the electron microscopic level, thereby suggesting the possibility of a direct chemical bonding between bone and titanium. It is concluded that the technique of osseointegration is a reliable type of cement-free bone anchorage for permanent prosthetic tissue substitutes. At present, this technique is being tried in clinical joint reconstruction. In order to achieve and to maintain such a direct contact between living bone and implant, threaded, unalloyed titanium screws of defined finish and geometry were inserted using a delicate surgical technique and were allowed to heal in situ, without loading, for a period of at least 3--4 months.

Superficial repair of severed flexor tendons in synovial environment. An experimental, ultrastructural study on cellular mechanisms

Severed and subsequently sutured rabbit flexor tendons were kept free and isolated in the synovial cavity of the knee joint. In one series the tendon specimens were surrounded by a dialyzing membrane to avoid cell seeding from the synovial fluid. At different intervals of time over a period of 3 weeks, the tendons were studied morphologically with special reference to scanning electron microscopy. Adhesions were not observed and, with synovial fluid as the nutrient medium, the tendons showed an intrinsic ability to repair in the superficial layers, also bridging the suture gap. Moreover, cell seeding, mainly of macrophages, from the synovial fluid could be demonstrated on the very surface of the tendon. When this cell seeding was prevented, the fibroplasia in the superficial layer of the tendon did decrease slightly, but tendon cell morphology was that of active fibroblasts. The results support the concept that flexor tendons may show intrinsic fibroplasia when nourished by synovial fluid, while macrophages, mainly of extrinsic origin, contribute to restoration of the tendon surface.