Regeneration of the enteric nervous system in the sea cucumber Holothuria glaberrima.

Among higher metazoans, echinoderms exhibit the most impressive capacity for regeneration. Holothurians, or sea cucumbers, respond to adverse stimuli by autotomizing and ejecting their visceral organs, which are then regenerated. Neuronal fibers and cell bodies are present within the viscera, but previous regeneration studies have not accounted for the nervous component. We used light microscopic immunocytochemistry and ultrastructural studies to describe the regeneration of the enteric nervous system in the sea cucumber Holothuria glaberrima. This study provides evidence that the enteric nervous system of this echinoderm regenerates after evisceration and that in 3-5 weeks the regenerated system is virtually identical to that of noneviscerated animals. The regeneration of the enteric nervous system occurs parallel to the regeneration of other organ components. Nerve fibers and cells are observed within the mesenterial thickenings that give rise to the new intestine and within the internal connective tissue prior to lumen formation. We also used bromodeoxyuridine incorporation to show that proliferation of the neuronal population occurs in the regenerating intestine. The regeneration of the nervous system commands high interest because members of the closely related phylum Chordata either lack or have a very limited capacity to regenerate their nervous system. Thus, holothurians provide a model system to study enteric nervous system regeneration in deuterostomes.

Fasciotomy, chronic venous insufficiency, and the calf muscle pump.

OBJECTIVE: To test the hypothesis that fasciotomy may impair the function of the calf muscle pump, which in turn could result in the development of chronic venous insufficiency. DESIGN: A cohort study of patients with a history of lower extremity fasciotomy. SETTING: An urban trauma center. PATIENTS: Seventeen of the 83 patients identified through trauma, vascular, and/or orthopedic registries consented to participation in this study. INTERVENTIONS: Participating patients completed a study questionnaire, and then underwent a complete vascular examination, including air plethysmographic (APG) assessment. Patients with a history of venous injuries were also studied with color flow duplex venous imaging. MAIN OUTCOME MEASURES: Function of the calf muscle pump as measured by APG, and evidence of chronic venous insufficiency as measured by APG, findings on clinical examination, and by venous ultrasonography. RESULTS: Seventeen patients completed the study, including 8 with a history of vascular injuries, 6 with old fractures, and 3 who had undergone fasciotomy for soft tissue infections. The time from injury to examination ranged from 5 months to 20 years. Eight patients had signs or symptoms of venous insufficiency, the severity of which appeared to be time dependent. The APG data showed significant mean differences between fasciotomy and control extremities in ejection fraction (P<.001) and residual volume fraction (P<.001), both measures of calf muscle pump function. There were no significant changes in venous filling index, a measure of venous reflux, or in outflow fraction, which correlates with venous obstruction. There were no differences in APG variables between patients with vascular injuries vs those with orthopedic or soft tissue injuries. CONCLUSIONS: Lower extremity fasciotomy impairs long-term calf muscle pump function, as measured by APG, in patients with and without vascular injuries. These patients are at risk for the long-term development of chronic venous insufficiency following lower extremity trauma.

Long-term results of lower-extremity venous injuries.

OBJECTIVES: To compare the long-term venous function of ligated, simple, and complex repairs and to assess long-term patency in repaired veins. DESIGN: A cohort study of patients with lower-extremity venous injuries treated during a 7-year period. SETTING: A level I urban trauma center. PATIENTS: Twenty-one of the 79 patients with a history of lower-extremity venous injury identified via the trauma registry consented to outpatient evaluation. INTERVENTION: Participating patients underwent a through vascular examination that included color flow duplex venous imaging and air plethysmographic assessment. MAIN OUTCOME MEASURES: The patency of venous repairs, the incidence of chronic deep venous thrombosis, and evidence of chronic venous insufficiency. RESULTS: The venous injuries included 5 iliac, 10 femoral, and 6 popliteal. Six of these injuries were ligated, 11 injuries were simply repaired (lateral venorrhaphy or end-to-end), and 4 were repaired with complex interposition grafts. All repairs were patent, with no evidence of deep venous thrombosis by color flow duplex venous imaging. Seventeen of the 21 patients had symptoms, color flow duplex venous imaging findings, and air plethysmographic data consistent with chronic venous insufficiency, including significant mean differences (P < .03) in outflow fraction, outflow fraction with compression, venous filling index, and residual volume fraction, when compared with the uninjured extremity. The most profound changes followed complex repairs and perioperative fasciotomies. CONCLUSIONS: While the long-term patency of venous repairs is excellent, most patients demonstrate evidence of chronic venous insufficiency after either ligation or repair. Complex venous repairs and fasciotomy are associated with the most severe functional changes.

Use of tissue oxygen tension measurements during resuscitation from hemorrhagic shock.

BACKGROUND: Tissue oxygen tension can be measured directly in selected organ beds, and these measurements may be more sensitive in assessing the adequacy of resuscitation than global physiologic parameters. We hypothesized that heart tissue oxygen tension would be an important marker for the severity of ischemic insult to the heart during hemorrhagic shock. We further hypothesized that gut oxygen tension measured in the jejunum would prove to be a better measure of splanchnic hypoperfusion than intramucosal pH (pHi). METHODS: Tissue oxygen probes were inserted directly into the myocardium of the left ventricle and into the lumen of the proximal jejunum in 10 anesthetized swine. A pHi catheter was introduced into the stomach. The animals were subjected to a controlled hemorrhage of 50% of estimated blood volume. Gut and cardiac oxygen were monitored continuously during hemorrhage and resuscitation, which was performed with shed blood and crystalloid. RESULTS: While gut O2 and pHi trended together, we were unable to establish a correlation between changes in these two variables during hemorrhage and resuscitation. Heart PO2 decreased significantly during hemorrhage, but surpassed baseline values after resuscitation, a finding not seen in gut PO2. No standard physiologic variables reliably predicted changes in heart PO2 during these experiments. CONCLUSIONS: Tissue oxygen tensions measurements are highly responsive to changes induced during graded hemorrhagic shock and resuscitation. Gut PO2 and pHi appear to be measuring different physiologic processes in the gastrointestinal tract. The compensatory ability of the heart far exceeds that of the gut after ischemic insult. This hemorrhagic shock model appears feasible for the study of various methods of resuscitation.