Electrical stimulation of nerve regeneration in the rat: the early effects evaluated by a vibrating probe and electron microscopy.

This study examines the effect of applied d.c. electric fields on nerve regeneration following injury to the rat sciatic nerve using the circularly vibrating probe and electron microscopy. The transected and treated nerve which received a d.c. electrical stimulator (0.6 mu A) was compared with untreated transected and crushed nerves. At one week postoperative, the probe was used to measure in vivo the current density along the nerve length. All nerves studied had a proximal peak at the lesion site and a second peak at varying distal locations: crushed/untreated (13.3 mm), transected/untreated (9.7 mm) and transected/treated (16.3 mm). A significant difference (69%) between the distal peak distances in the two transection groups suggests that the electrical treatment enhanced the progress of nerve regeneration. There were no significant differences between the mean peak amplitudes (1.6-2.2 mu A/cm2). Applied verapamil reduced the peaks, suggesting they are associated in part with a calcium-dependent current. Electron microscopy at selected nerve regions indicated that the peaks correspond to regenerating axonal growth cones. The results suggest the potential clinical application of d.c. electric fields in the treatment of nerve injuries.

Effects of danazol, gonadotropin-releasing hormone agonist, and estrogen/progestogen combination on experimental endometriosis in the ovariectomized rat.

Direct effects of a gonadotropin-releasing hormone agonist (GnRHa), danazol, or estrogen/progestogen (E/P) on experimental endometriosis were evaluated in castrated female rats. Endometrial explants decreased in size following castration, but there was no further change in the treatment groups. Histologic examination indicated atrophy and regression of experimental endometriosis in all groups of castrated animals. As expected, following castration, serum estradiol (E2) became undetectable, serum progesterone (P4) decreased, and cytosolic E2 and P4 binding capacity in the endometrial explants was lower. However, in danazol-treated animals, serum P4 and E2 receptor concentrations were significantly higher than in all other castrated groups, and in both danazol and E/P treated animals, concentrations of P4 receptor were significantly higher than in castrated controls. In contrast, GnRHa treatment had no effect on serum E2 and P4 levels nor on E2 or P4 receptors. The authors conclude that danazol and E/P preparations may have a direct effect on the ectopic endometrium through interaction with steroid receptors.

New method for cardiac transplantation.

Rat cardiac transplantation into the femoral region has several advantages compared to cardiac transplantation into the peritoneal cavity. These advantages include increased speed, decreased hypothermia of the recipient, and easier-access palpation. However, there is a major discrepancy in the size of the donor and recipient vessels. The donor aorta is two to three times larger than the recipient's femoral artery and thus could be a contraindication to the transplant. To circumvent this problem, we anastomosed the donor's aorta with the recipient's femoral artery by an end-in-end technique whereas the donor's pulmonary artery was anastomosed by conventional end-to-end technique with the recipient's femoral vein. The excess wall of the donor's vessel was plicated on a slant for each anastomosis. Our results compare favorably to those of techniques established previously. We suggest that this new method of cardiac transplantation will be of great value in the study of immunological events involved in graft rejection.

Microwave irradiation of peripheral nerve following injury: a structural analysis of degeneration and regeneration.

Studies of the enhancement effect of pulsed energy irradiation on nerve regeneration following injury have produced variable results. The effect of microwave treatment on the rat peroneal nerve after transection and anastomosis was analyzed by light and electron microscopy. The hindquarters were irradiated 1 h/day during the first 10 days postoperative (dpo). The nerves were fixed in situ and prepared for microscopic analysis. At 10 dpo the distal segment of the degenerating nerve had several enlarged myelin sheath profiles devoid of axoplasm. The swelling was not significantly altered by microwave treatment, but the number and density of the empty myelin sheath profiles were three to four times greater in the treatment group. At 49 dpo the regenerating nerve segment had a 43% decrease in the nerve fiber diameter compared with a normal mean of 7 microns. The number and density of remyelinated fibers showed a 50% increase in both treatment and control groups. Histologic evidence indicated no permanent enhancement on nerve regeneration by microwave treatment, even though the treatment may have delayed Wallerian degeneration.

Absorbable external rings for anastomosis of the fallopian tubes: a feasibility study.

A novel approach to tubotubal anastomosis with external, absorbable, ring-shaped devices was evaluated. Fallopian tubes of female Sprague-Dawley rats were transected and coagulated and either left divided or anastomosed with microsurgical technique, with or without external rings. Postoperative patency and pregnancy rates were used to evaluate the procedures. Transected and coagulated fallopian tubes remained occluded at the time of repeated surgery, and no implantations were observed in the corresponding uterine horns. Of ten fallopian tubes anastomosed without the ring, five were patent and five were partially blocked. All ten fallopian tubes anastomosed with the external rings were fully open. Implantation sites were observed in four of ten uterine horns corresponding to fallopian tubes anastomosed without the ring and in eight of ten horns anastomosed with the external ring. The difference was statistically significant, P = to 0.03. All external rings were completely absorbed 7 weeks after anastomosis. The new technique was simpler to perform and was less time-consuming. We conclude that tubotubal anastomosis with external rings may offer advantages over the conventional technique.

The ring technique for end-to-side microvascular anastomosis.

The ring technique for end-to-side microvascular anastomosis employs a resorbable polyglycolic acid ring to prevent stenosis and spasm at the anastomotic site. In 20 rats, the ring technique was compared with the conventional technique for constructing end-to-side anastomoses between the femoral (0.9-1.1 mm) and superficial epigastric (0.3-0.4 mm) arteries. The ring technique proved superior to the conventional end-to-side technique both in speed of execution and in patency at 3-4 weeks (100% vs 70%). Grossly and microscopically, the ring was completely resorbed at 3 wk.

Rotational technique and microsurgery.

A rotational technique to manipulate microsurgical instruments has several advantages. Tremor is suppressed, the hands remain relaxed for long periods of time, and the nondominant hand is able to play a more active role in the operation. The fundamentals of rotational technique are discussed.