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Biomedical subjects

G Tarasidis

Publications and source records attributed to G Tarasidis.

9 recordsLinked to original sources
PubMed1999

Strain differences in peripheral-nerve regeneration in rats.

Currently, several strains of rats are used for studies of peripheral-nerve injury and repair. The purpose of this study was to determine if significant differences in regeneration between strains exist that might influence comparison of results and interpretation of scientific conclusions. One outbred (Sprague-Dawley) and four inbred stains (ACI, Wistar-Furth, Lewis, Brown-Norway) were studied. Animals were randomized to one of two experimental conditions, undergoing either posterior tibial nerve transection and repair, or Silastic conduit repair of the posterior tibial nerve (n=6/group). Endpoint evaluations at 6 and 13 weeks included histomorphometry and walking-track analysis. Evidence of excellent regeneration was noted in all rat strains undergoing primary repair. Generally, no statistically significant differences between strains were noted, regardless of endpoint evaluation used in the primary repair group. Nerve regeneration across the conduits was either poor or not present at 6 weeks, with no regeneration at all noted in any animals in the ACI and Brown-Norway groups, and regeneration in only one or two animals in the other strains. At 13 weeks, between three and five animals in each strain showed regeneration, but functional recovery was poor. Overall, few differences in peripheral-nerve recovery appear to exist between rat strains. It seems that uniform conclusions may be drawn regardless of strain used.

Analysis of Variance↗
PubMed1998

End-to-side neurorraphy: a long-term study of neural regeneration in a rat model.

This study evaluated long-term reinnervation of an end-to-side neurorraphy and the resultant functional recovery in a rat model. The divided distal posterior tibial nerve was repaired to the side of an intact peroneal nerve. Control groups included a cut-and-repair of the posterior tibial nerve and an end-to-end repair of the peroneal nerve to the posterior tibial nerve. Evaluations included walking-track analysis, nerve conduction studies, muscle mass measurements, retrograde nerve tracing, and histologic evaluation. Walking tracks indicated poor recovery of posterior tibial nerve function in the experimental group. No significant difference in nerve conduction velocities was seen between the experimental and control groups. Gastrocnemius muscle mass measurements revealed no functional recovery in the experimental group. Similarly, retrograde nerve tracing revealed minimal motor neuron staining in the experimental group. However, some sensory staining was seen within the dorsal root ganglia of the end-to-side group. Histologic study revealed minimal myelinated axonal regeneration in the experimental group as compared with findings in the other groups. These results suggest that predominantly sensory regeneration occurs in an end-to-side neurorraphy at an end point of 6 months.

Action Potentials↗
PubMed1998

Long-term observation of the effect of peripheral nerve injury in neonatal and young rats.

The purpose of this study was to observe functional recovery and motoneuron death after nerve transection-and-repair in neonatal versus young animals. One hundred nine Lewis rats underwent posterior tibial nerve transection-and-repair at 6 or 22 days of age. Fifty-two and fifty-seven nerves at the 6- and 22-day times were used for endpoint analysis at 1, 3, 10, and 14 months. These assessments included serial functional walking track analysis, electrophysiologic studies, muscle mass evaluation, motoneuron counts with retrograde horseradish peroxidase tracing, and histologic and morphometric nerve analysis. Walking track analysis and nerve conduction velocity indicated significantly poorer functional regeneration in the 6-day-old group than in the 22-day-old group. Muscle mass in the 6-day-old group did not recover as well as in the 22-day-old group. Motoneuron numbers stained with horseradish peroxidase were less in the 6-day-old group than in the 22-day-old group. In contrast, morphometric analysis did not reach significance. This study suggests that the same nerve injury sustained in a neonatal rat is less likely to demonstrate functional recovery than one sustained in a young rat.

Animals↗
PubMed1997

The effect of ammonium sulfate injection on peripheral nerve.

Local anesthetic drugs with prolonged nerve-block effect would have clinical application for postoperative or neuromatous pain relief. This study evaluated the possibility of peripheral nerve neurotoxicity by injection of 10 percent ammonium sulfate. Both intrafascicular and extrafascicular injection of 10 percent ammonium sulfate were tested in the rat sciatic nerve model. One percent lidocaine HCl, 5 percent phenol, and normal saline were similarly injected for comparison. Using histologic studies and motor function evaluation with walking-track analysis, 10 percent ammonium sulfate was found to be neurotoxic when it is injected intrafascicularly; however, extrafascicular injection of this drug did not cause significant nerve injury. The neurotoxicity of the 10 percent ammonium sulfate solution was intermediate between the neurotoxicity of 0.1 percent lidocaine hydrochloride and the marked neurotoxicity of 5 percent phenol solution.

Ammonium Sulfate↗
PubMed1997

End-to-side neurorrhaphy resulting in limited sensory axonal regeneration in a rat model.

This study evaluated reinnervation of an end-to-side neurorrhaphy and the resultant functional recovery in a rat model. The cut distal posterior tibial nerve was repaired to the side of an intact peroneal nerve. In one group, the epineurium of the peroneal nerve was left intact; in another group, the epineurium was stripped; in the third experimental group, a perineurial slit was created. Evaluations included walking track analysis, nerve conduction studies, muscle mass measurements, retrograde nerve tracing, and histologic evaluation. Walking tracks indicated poor functional recovery. No significant difference in nerve conduction between the experimental and control groups was seen. Gastrocnemius muscle mass measurements revealed no functional recovery in the end-to-side groups. Retrograde nerve tracing revealed minimal staining of motor neurons. However, sensory neuronal staining of the dorsal root ganglia occurred in all groups. Histology revealed minimal myelinated axonal regeneration. These results suggest that predominantly sensory neural regeneration occurs in an end-to-side neurorrhaphy at an end point of 16 weeks.

Anastomosis, Surgical↗
PubMed1996

Peripheral nerve allograft preservation improves regeneration and decreases systemic cyclosporin A requirements.

Peripheral nerve allografting is limited by the need for long-term systemic immunosuppression. The purpose of this study was to determine if nerve allograft preservation reduced the requirements for systemic Cyclosporin A (CsA) immunosuppression. One hundred twenty Lewis rats were randomized to one of seven experimental groups. Group 1 received a 2-cm Lewis posterior tibial nerve autograft. Groups 2-7 received 2-cm ACI posterior tibial nerve allografts. The allograft group was then further subdivided into three groups of two receiving daily subcutaneous injections of 0, 2.5, or 5.0 mg/kg of CsA for 12 weeks. Within each CsA dose, one group received a fresh while the other received a preserved allograft. Preserved grafts were stored in University of Wisconsin solution for 7 days at 5 degrees C prior to implantation. Animals from each group were sacrificed at 6, 12, and 20 weeks postoperatively. Evaluations included histomorphometry, electrophysiology, and serial walking track analysis. Histology revealed varying degrees of nerve regeneration in all groups at 6, 12, and 20 weeks. For a given CsA dose, the group receiving the preserved graft revealed evidence of better nerve regeneration by all histomorphometric parameters including fiber width and density, percentage neural tissue, and total fiber number. There was no statistical difference in walking track analysis between groups at 4 weeks. By 20 weeks, functional recovery statistically poorer than autograft was seen only in the fresh allograft groups receiving 0 or 2.5 mg/kg of CsA. Identical electrophysiologic findings were seen at 20 weeks. These results suggest that nerve graft preservation may decrease systemic immunosuppression requirements while improving functional recovery. As well, storage of nerve grafts is feasible and would facilitate elective surgery and less costly reconstructive repair.

Analysis of Variance↗
PubMed1996

Wire mesh as a post-operative physiotherapy assistive device following peripheral nerve graft repair in the rat.

Traditional methods of assessing nerve recovery following injury, including histomorphometry and electrophysiology, do not necessarily correlate with return of motor and sensory function. Accordingly, many investigators have used walking track analysis as an assessment of global functional recovery following sciatic, peroneal or tibial nerve injury. However, walking track reliability may be compromised by the development of flexion contractures secondary to neurologic loss. To prevent this, regular manual physiotherapy is recommended which is a time-consuming and often frustrating process for both the animal and investigator. We report the use of a wire mesh as a simple post-operative assistive device to provide constant physiotherapy. Twelve Lewis rats were randomized to one of two experimental groups. Each rat received a 2 cm posterior tibial nerve autograft. Postoperatively, animals in group 1 received manual physiotherapy, consisting of repeated flexion and extension exercises of the ankle, knee and hip every two weeks. Group 2 rats were permitted to climb freely on a 30 x 18 cm piece of wire mesh placed at a 45 degree angle within their cage. Group 2 rats received no manual physiotherapy throughout the course of the study. Serial walking tracks were performed every four weeks until sacrifice at sixteen weeks. There was no development of flexion contractures in the injured hind limbs of either group. There was no morbidity such as blisters associated with the use of the wire mesh. There was no statistical difference in walking track recovery between groups at any time period. However, a trend towards better functional recovery was seen in the group receiving constant physiotherapy via the wire mesh. The use of a wire mesh as a post-operative assistive device is an inexpensive, simple and reliable method to provide continuous physiotherapy to animals following denervation.

Animals↗
PubMed1991

Smooth muscle tumors of the rectum and anus: a collective review of the world literature.

In this collective review, we have compiled all the reported cases of smooth muscle tumors of the rectum/anus in the world literature from 1959 to 1989. Our goal was to increase the data pool of smooth muscle tumors by adding these new data to that previously collected from 1881 to 1959. We increased the pool for leiomyomas from 89 to 148 and that for leiomyosarcomas from 54 to 215. By doing this, we hoped to make more accurate conclusions about smooth muscle tumors based on this increased data pool. Some interesting findings included three cases in small children that were found in our recent review: a 2-year-old with a leiomyoma and two small infants, aged 12 days and 36 days, with leiomyosarcomas. Again, the findings were probably consistent with an increased data pool. We were also able to find several more cases involving the anal region. We found the highest incidence of leiomyomas to have increased by a decade from the 40-49 year age group to the 50-59 year age group, while among leiomyosarcomas, there was about equal incidence among the 50-59 and 60-69 age groups. We doubt that these represent actual changes in the demographics, but rather that these latter findings are more accurate based on the greater quantity of cases available to us. As a further example, we found no appreciable sex difference; however, we did find more cases reported in females. From our increased data pool, we were able to find 16 more cases that were described as dumbbell-shaped, compared to one that was reported before 1959. Palpable mass, hemorrhage, and pain/discomfort continued as the most common symptoms reported at presentation. With regard to size, the majority of leiomyomas were found to be less than 5 cm in diameter, closely followed by those 5-9 cm. The majority of leiomyosarcomas were 5-9 centimeters at discovery. Most cases of leiomyoma were treated by excision, while most cases of leiomyosarcoma were treated by abdominoperineal resection, a finding consistent with old data. We hope that this paper thoroughly reviews pertinent information about leiomyomas and leiomyosarcomas of the rectum/anus and, in doing so, serves to refresh a few memories, stimulate others, and teach a few.

Adolescent↗