A Small Scale Oxygenator for Cardiopulmonary Bypass in Rats

Cardiopulmonary bypass (CPB) devices replace transiently the function of both heart and lungs, allowing the investigator to work safely on a stopped heart. Although this technology has greatly improved since its first applications in the early 1950's there is still no definitive rat CPB model, various experiments reporting drawbacks like pulmonary edema, large priming volumes, etc. We present a new oxygenator that can be used in cardiopulmonary bypass experiments in rats, simple in design and efficient in function, in which the process of blood oxygenation takes place in a vertical cylinder filled up with air or oxygen, with blood being spread onto the wall and then trickling down in a thin layer that facilitates the oxygen transfer. The oxygenation is efficient, the pO2 reaches levels of almost 150 mmHg (physiological level is around 100 mmHg) in conditions of oxygen saturation of over 99% (normal levels 95%-98%).

Prefabrication and free transfer of a tissue engineered composite flap - An experimental model in the rat

BACKGROUND

The technique of flap-prefabrication has been successfully established in tissue engineering: missing intrinsic vascularisation of engineered tissue can be generated in vivo by microsurgical vesselloop construction. It is possible to move engineered tissue into a defect with microsurgery. In the literature, the combination of engineered tissue covered with skin is not widely reported.

OBJECTIVE

Aim of this study was to establish a model to investigate scaffold prefabrication with full thickness skin graft coverage with subsequent free tissue transfer.

METHODS

8 Wistar rats were operated in 2 separate steps: 1) after creating an arteriovenous loop with the femoral vessels, a porous scaffold was placed on the loop and covered with an inguinally based skin flap. A control was implanted without loop into the contralateral groin. 2) 6 weeks later the prefabricated composite flaps were microsurgically transferred to the cervical region. Skin-island monitoring was performed with Laser Doppler-scanner after the transfer.

RESULTS

Continuous loss of the skin islands was observed within 72 hours. Complications included wound-dehiscence, thrombosis and death from anaesthesia; in spite of consistent loop viability.

CONCLUSION

Evaluation showed that modifications are necessary to maintain the skin-island cove.

PREDISPOSANT FACTORS FOR INTIMAL HYPERPLASIA AND THEIR MECHANISMS OF ACTION IN OPEN VASCULAR SURGERY. A REVIEW

BACKGROUND

Intimal hyperplasia is a multifactorial process that determines local stenosis and subsequent ischemia after revascularisation procedures. It is controlled by a plethora of cytokines, growth factors and proteases that interact through multiple mechanisms, empowering or inhibiting their hyperplasic action. Although the elements involved are the same, the resulted degree of vascular stenosis varies.

METHODS

To highlight the predisposing conditions which enhance the vascular response to injury we consulted articles from Pubmed database, searching for the keywords "intimal hyperplasia", "neointimal hyperplasia" and "risk factor".

RESULTS

101 articles were included in the study. Risk factors analyzed are classified into local and systemic and the mechanisms by which they augment the process are explained.

CONCLUSION

Knowledge of risk factors and their control when possible is a key element in increasing revascularization patency.

Circular anastomotic experimental fibrin sealant protection in deep colorectal anastomosis in pigs in a randomized 9-day survival study

PURPOSE

The reported rate of clinically apparent anastomotic leakage (AL) in a low anterior resection of the rectum (LAR) (≤7 cm from the anal verge) using a circular double-stapled anastomosis (CDSA) without defunctioning stoma is up to 37.5 %. Since AL may result in life-threatening peritonitis, sepsis, and multiple organ failure, LAR and CDSA are regularly combined with defunctioning stoma. Accordingly, we now evaluated whether LAR and CDSA without defunctioning stoma but with extraluminal anastomotic application of an experimental fibrin sealant reduce the AL rate. This might prevent humans from defunctioning stoma increasing quality of life and decreasing surgical costs.

METHODS

Forty 8-week-old pigs underwent LAR and CDSA in an end-to-end technique (descendo-rectostomy). Animals were randomized into a therapy and control group (gr.). The therapy gr. (n = 20) received an additional extraluminal circular application of an experimental fibrin sealant to the anastomosis. The objective was to assess the incidence of clinically apparent and non-clinically apparent leakage through the ninth postoperative day. Double-contrast barium CT radiographs of the colorectal region were performed on the ninth postoperative day or earlier, in case there were clinical signs of AL. All remaining animals were sacrificed on the ninth postoperative day and the anastomotic region was histopathologically analyzed. In case of earlier diagnosed AL, animals were sacrificed immediately. Blood samples were taken for complete blood count, chemistry, and coagulation profile prior to surgery and on the first, third, fifth, seventh, and ninth postoperative day.

RESULTS

A circular extraluminal anastomotic application of an experimental fibrin protection decreased the rate of clinically and non-clinically apparent AL from 20 % (n = 4) in the control group to 5 % (n = 1) in the treatment group. Ulcerations were also observed in both gr. (control gr.-5 animals, therapy gr. -3 animals). All animals with AL showed necrosis surrounding the hole at the anastomoses. Three additional animals had a full wall defect at the anastomotic region that was blocked by the experimental fibrin sealant. The fibrin sealant was present at necropsy in all treated animals.

CONCLUSION

Circular anastomotic protection with the experimental fibrin sealant blocked anastomotic full wall defects, preventing peritonitis and significantly reducing the AL rate from 25 to 5 %.

Can an adipofascial flap be used to prevent adhesions after plating of the proximal phalanx? A case report

Tendon adhesions in zone IV after proximal phalangeal fractures are common and may lead to loss of range of motion at the proximal interphalangeal joint. The type of fracture, surgical technique and rehabilitation strategy also influence the final functional outcome. Plate fixation is a reliable solution in cases of comminuted phalangeal fracture. This article describes how adhesions between the plate and extensor apparatus in cases of comminuted fractures of the proximal phalanx can be reduced by using an adipofascial flap.

Meningococcal septic shock after IUD insertion, a case presentation

Neisseria meningitidis is a normal commensal of human mucous membranes that is no longer considered to be restricted to the nasopharynx. Due to the practice of oral sex, the mucous membranes of the cervix, urethra or anus have become a potential infection site for this bacterium. Inserting an intrauterine device (IUD), can alter the protective barrier of the endocervical mucosa, allowing for bacterial infection and systemic spread. We present a case report of a 40-year-old woman who presented with abdominal pain, spotting and fever after inserting an IUD and developed a fulminant septic shock. Blood cultures and cultures from ascites showed the presence of Neisseria meningitidis group Y. From our knowledge, there are a few cases presented in the literature of toxic shock syndrome after IUD insertion, caused by Staphylococcus aureus or Streptococcus group A, but this is the first case of meningococcal sepsis after IUD insertion described. So, even though IUDs rarely cause significant infection, physicians should consider this device as a possible source in reproductive-age women with the clinical features of sepsis.

A new anastomotic leakage model in circular double stapled colorectal anastomosis after low anterior rectum resection in pigs

BACKGROUND

A high incidence of anastomotic leakage (37.5%) is reported after low anterior rectal resection (LAR) and circular double-stapled anastomosis without protective ileostoma. Since the pathomechanism of anastomosis leakage is still unclear, a suitable animal model would be most desirable.

METHODS

The objective was to assess the incidence of clinically apparent and inapparent leakage after LAR in pigs (n = 20). Endpoints were radiological, clinical, macroscopic, and histologic proof of anastomotic leakage on the 9th postoperative day. Integrity of anastomosis was assessed by double-contrast barium examination on 9th postoperative day. Animals were sacrificed and anastomoses were resected for histopathological investigation. In case of earlier clinical apparent anastomotic leakage, radiologic double-contrast barium was performed immediately.

RESULTS

LAR with a circular double-stapled anastomosis without protective ileostoma was performed in 20 pigs (m:f = 8:12). Length of resection was 10-20 cm, anastomosis was performed 7 cm ab ano. Five animals (25%) developed clinical apparent anastomotic leakage (no appetite, fever, inactivity, tachypnea, discomfort, pain) between the 6th (n = 1) and 9th (n = 4) postoperative day, proven by double-contrast barium radiographs. Additionally in 1 animal clinical inapparent anastomotic insufficiency was observed radiologically. Total rate of leakage was 30% (n = 6). These results were confirmed by leucocytosis, low potassium levels, in two cases high ALT and AST and local peritonitis in all cases.

CONCLUSION

Including one additional case of clinical inapparent leakage, total rate of anastomotic leakage was 30% (6/20). Thus we managed to establish a new experimental model of anastomotic leakage after low rectal resection comparable to the human situation.

Arterio-venous fistula using nonpenetrating titanium clips (VCS)

Vascular access in haemodialysis is still accompanied by a high morbidity rate. Neointimal hyperplasia due to thrombosis is one of the main causes of vascular access failure. The purpose of this paper is to present the use of non-penetrating titanium clips (VCS) for the creation of an arteriovenous fistula and its outcome.

MATERIALS AND METHODS

A male patient, 47 years old, with end-stage renal disease - ESRD - (2005) was addressed to our service, for a vascular access reintervention, after a failed forearm radio-cephalic fistula performed 3 months before. In January 2007, an arteriovenous fistula between the brachial artery and the median cubital vein using non-penetrating titanium clips (Anastoclip VCS) was created.

RESULTS

The vascular anastomosis was performed in 17 min. After unclamping the artery, a solid pulse and consistent thrill were obtained at the level of the cubital fossa. The postoperative course was uneventful. The arteriovenous fistula remains functional 60 months post-surgery.

CONCLUSIONS

The Anastoclip VCS system is versatile, safe to manipulate and enables fast anastomosis. Arteriovenous anastomosis performed with non-penetrating clips may be a solution with the potential to reduce postoperative complications and extend arteriovenous fistula patency in ESRD.

Infrarenal abdominal aorta approach through median minilaparotomy

Classically, infrarenal aortic exposure is achieved by xyphopubic or xypho-infraumbilical laparotomy, in transperitoneal approach, or through a left abdominal incision, in retroperitoneal approach. The transperitoneal approach is associated with longer intestinal activity resumption time and incisional hernias on long term, due to intestinal extracavitary mobilization and long incision. These disadvantages disappear in laparoscopic approach, but this method is extremely laborious, requires an extended period for dissection, and elicits increased difficulty in performing the anastomosis on the aorta. The purpose of the study is to evaluate the infrarenal abdominal aorta approach through median minilaparotomy, a method that combines the excellent exposure of xypho-pubic incision with the low morbidity of laparoscopic approach. Between 07.01.2010 - 07.01.2011, we performed 37 revascularization surgeries in 36 patients with aorto-iliac occlusive disease (one patient required reintervention due to graft thrombosis), approaching the infrarenal aorta through median minilaparotomy. The sex distribution was 35 men and one woman. The average age was 61.1 years. There have been 25 aorto-bifemoral bypasses, 11 aorto-unifemoral bypasses, and one aorto-biiliac bypass. The mean aorta clamping time was 15 minutes. Average operating time was 150 minutes. We used 26 bifurcated Dacron prostheses and 11 linear ePTFEprostheses. The average intestinal activity resumption time was 32 hours. All patients included in the study were mobilized 24 hours after surgery. The average length of hospitalization was 7.7 days. 5 patients experienced complications during hospitalization and 3 patients suffered long term complications. Infrarenal abdominal aorta approach through median minilaparotomy is a viable alternative to conventional surgical techniques used in aortoiliac occlusive disease.

Does VEGF have an effect on the survival of a long random skin flap by its application at the recipient area?

BACKGROUND

Vascular endothelial growth factor (VEGF) is a hormone-like molecule which has been shown to act on a specific receptor system and in this way to be the basic regulator of angiogenesis. The effect on the survival of a long random skin flap was examined by exogenous administration of this cytokine, at flap's recipient site.

MATERIALS & METHODS

A standard dorsal skin flap measuring 1.5 x 7.5cm was elevated in eighteen wistar rats with the pedicle centered and attached between the lower angles of the scapulae. The length to width ratio was relatively high (5:1). The rats were divided in two groups of nine. In group A, flap was elevated and a skin defect was created next to it. Normal saline was injected into the fascia of the defect and the flap was transposed and secured over the previously created recipient site. In group B, flap was elevated and transposed to a previous created defect, as before, where, this time, injections of VEGF were applied into the fascia of the recipient bed. Seven days later the rats were euthanized and the flaps were excised. The underlying fascias of the recipient beds were also excised in the same dimensions. The specimens were measured, photographed and put into formalin 10%. Immunohistochemical staining and histological analysis followed.

RESULTS

The differentiation between the surviving and the necrotic skin was macroscopically clear within seven days time. In group A, the mean flap survival percentage was 36.8%. In group B the percentage was 56.3%, respectively. Neovascularization of the fascia of the recipient bed was also demonstrated when VEGF had been injected.

CONCLUSIONS

Exogenous administration of VEGF into the recipient bed of a skin flap improved the survival rate even though the flap's length was relatively high compared to its width.

[Accessory renal allotransplantation with internal or external urinary drainage. An experimental model in pig]

This study describes an experimental model of accessory renal allotransplantation in the big laboratory animal (pig). A total of 24 common-breed pigs were used. All allografts were transplanted in an accessory manner and revascularized at the level of the infrarenal abdominal aorta and inferior vena cava. The urinary drainage was performed either through a nexternal uretheroneostomy at the ipsilateral lumbar region (Group A--n=8) or by internal uretheroneocystostomy (Group B--n=8). All transplants were monitored for 8 days postoperatively using translumbar ultrasound-guided biopsies at 1, 4, 7 days. A total of 16 transplants were performed. 1 ectopic donor kidney was found and transplanted in the same fashion. Mean operative time was 125 minutes, immediate postoperative survival was 100% and at 72 hours, 87.5%. The onset of acute rejection was at day 4, by massive lymphocyte infiltration and was directly correlated with the abrupt decrease of the allograft diuresis in Group A, at day 3. At day 7, the rejection was complete. Both methods of urinary drainage are functional and can be employed. This experimental model is a useful tool for training of the transplant surgeons or for transplantation research. The surgical technique for accessory renal allotransplantation in pig is easy to learn and offers the possibility for allograft monitoring until complete rejection without influencing the receptor health condition.

[The electroacupuncture in patients recently operated for peripheral arterial disease. A comparative study of the two electrostimulation techniques]

Possible hemodynamic effects of electro acupuncture (A), by two electro stimulation techniques, were studied at patients with femuro - popliteal bypass revascularization. MMATERIAL AND METHOD:In a prospective study, we evaluated two EA techniques, by calculating the ankle-brachial index (ABI) and by estimating the pain with Numeric Rating Scale (NRS: 0 - 10). The patients were grouped in lot A (30 patients) and B (50 patients) according with the EA technique used. In both lots were used the same acupuncture points (acupoint): Pc6, P9, St36 and Sp6. These acupoints are adjacent to peripheral nerves median, radial, peroneal and safenous nerve. Needles, after insertion, were kept in place for 30 minutes. The electro stimulation (2 Hz) was only for 2 minutes in the lot A and for 30 minutes in the lot B.

RESULTS

The blood pressure data and ABI shows a significant increase of ABI (between 0.033 and 0.052) after EA at 5 minutes in the both lots (p < 0.05). At 30 minutes, ABI is increased in lot B, but in the lot A the ABI is elevated only at the non surgical leg (p < 0.05). The decrease of pain post EA is better in the lot B (NRS: initially 2.48--post EA pain decreased to 1.46 and remained 1.66 at 2 hours; p < 0.001), than lot A.

CONCLUSIONS

The electro stimulation of certain acupoints, at the operated peripheral arterial disease patients, interfere with tissular perfusion and increase temporally ABI. The pain is diminished more significantly by the 30 minutes electro stimulating technique.

[The first NOTE (Natural Orifice Translumenal Endoscopic) cholecystectomy in Romania: an experimental model in pig]

NOTES (Natural Orifice Translumenal Endoscopic Surgery) represents a very new acquisition in the field of gastrointestinal endoscopy, which uses common flexible endoscopes in order to perform intraperitoneal surgical procedures. This procedure offers a very good visualisation of the peritoneal cavity, as well as the possibility of performing surgical procedures. The aim of the study is to report our experience--the first of its kind in Romania--in performing per os, transgastric procedures, emphasizing the technical challenges and the possible complications associated with this method. This is an experimental study, using pigs (tri-hybrid PIC strain), in which peritoneoscopy and cholecystectomy were performed via a hybrid-NOTES approach (a 5 mm laparoscopic port has been used, placed in the right upper quadrant). The transgastric approach of the peritoneal cavity proved to be easy, allowing simple surgical procedures. The results of the study show the feasibility of the method. During surgery, no serious complications occurred, the minor incidents being managed without conversion to classical or laparoscopic surgery.

[Endoscopy-assisted harvesting and free latissimus dorsi muscle flap transfer in reconstructive microsurgery]

Because of their generous dimensions, constant anatomy, great plasticity and well defined vascularization, muscles remain the preferred choice when approaching reconstruction of complex tissue defects resulting after trauma or oncological resections. The latissimus dorsi, represents a widely used flap when performing reconstructive microsurgery using free tissue transfer, but with important postoperative complications like seroma, donor-site hematoma and large scars. Along with the development of video assisted harvesting of muscular free flaps, the minimal invasive approach brings an important decrease of the donor site morbidity, followed by a faster healing. This article presents the case of a patient diagnosed with chronic osteomyelitis fistula, on the site of an older posttraumatic fracture at the level of the tibial diaphysis, where a large debridement of soft tissues and the involved bone was performed, followed by microsurgical reconstruction of the left over defect, using a free latissimus dorsi muscular flap harvested by endoscopic-assisted technique.

[Reparation of the parcel defect of duodenum with pediculated jejunal patch by laparoscopy. Experimental study]

The objectives were to evaluate the intraoperative aspects of the repairing by laparoscopy of a parcel duodenal defect, using a pediculated jejunal patch and to emphasize the intraoperative complications. The research has been made on 6 pigs. The pediculated jejunal patch was been achieved by excluding from the intestinal tract of a 2-4 cm segment with nutritional pedicle and the cut of intestinal tube on the anti-mesenteric border. The suture of the duodenal defect has been accomplished in one layer manner. The animals were followed 2 hours, under anesthesia. There was not intraoperative mortality, wether conversion to laparotomy. There was been a good cover of the defect, without any leakage. We did not notice intraperitoneal blood or bile. The duodenoplasty with pediculated jejunal patch is effective. The laparoscopic accomplishing of this procedure has no complications and it can be applied in clinical activity for selected cases.

[Experimental model of pancreas transplantation with portal or systemic drainage in laboratory rats]

The aim of this study was to develop an experimental model of pancreas transplantation in rats as a standardized tool for research in transplant immunobiology. Brown Norway (donors) and Lewis (receptors) rats, males, with an average weight of 220 grams, were used. The diabetes was induced in recipients using streptozocin. The pancreas was harvested with a duodenal stump, a segment of aorta containing the celiac and superior mesenteric artery and the portal vein and transplanted as follows: Group A (n=8) - systemic venous drainage; Group B (n=8) - portal venous drainage. The exocrine drainage of the pancreatic graft was established by para-topic reintegration of the graft duodenal stump in the recipient. Postoperative follow-up consisted of daily measurement of glycemia and macroscopic evaluation of the proximal duodenal stump mounted as a cutaneous stoma. Overall postoperative survival at 8 days was 87,5% for Group A and 75% for Group B. Glycemia levels started to regain normal values in both groups, at 2 days postoperatively. Rejection started at 9 and 10 days postoperatively for Group A and B respectively, being expressed by the gradual re-appraisal of hyperglycemia that followed necrosis of the proximal duodenal stump. The experimental model described is functional and has the advantage of being used either with portal or systemic drainage of the pancreatic graft. The results obtained show no significant difference between the time-points of normal postoperative glycemia when either systemic or portal venous drainage were used.

[Complex microsurgical reconstruction of diabetic foot]

Microsurgical techniques increased the operability of patients with critical limb ischemia to more than 95%. However, the percentage of ischemic limb salvage remains limited, especially in diabetic patients with associated tissue gangrene and neuropathy. The study presents a 67 years old female patient with type II diabetes mellitus and critical limb ischemia, complicated with progressive gangrene of the pre-calcaneal region and thus representing a classical indication for thigh amputation. A sequential femur-popliteal-tibial anterior by-pass was performed, followed by soft tissue reconstruction using a latissimus-dorsi musculo-cutaneous free flap. Two years postoperatively, the patient developed clinical signs of symmetrical peripheral distal neuropathy, managed by bilateral posterior tibial nerve decompression. The patient follow-up was of 3 years. Through the entire period, distal pulse (ram of posterior tibial artery) remained present with a good integration of the flap and with absent clinical and paraclinical signs of neuropathy. The patient regained full ambulation. Morphologically and functionally the affected limb is entirely salvaged. Using microsurgical techniques, a more complex and complete approach of the diabetic patient with ischemic-neuropathic syndrome can be considered. This includes revascularization, soft tissue reconstruction and nerve decompression. In selected patients with indication of major amputation these methods offer a salvage option, with excellent long-term results.

Preliminary results of orthotopic en bloc uterus and ovary transplantation in the laboratory rat

A new experimental model of whole uterus and ovary transplantation in the laboratory rat was achieved. The main goals of this study were concerned with developing and standardizing the microsurgical technique of uterus transplantation in rats and observing the particular cellular patterns of acute allograft rejection at the level of the transplanted graft. Thirty-five orthotopic uterus transplantations were performed. An additional 20 female rats were used for dissection training sessions. Recipients were euthanasied at 24 hours, 48 hours and 72 hours. Immediate postoperative survival was 100%. Patency of the microsurgical anastomoses, checked at 24 hours, was 100%. At 72 hours thrombosis occurred in all anastomoses. The explanted uterine grafts were fixed in formaline and analyzed under light microscopy and specific imunohistochemical analysis. The acute allograft rejection has a particular cellular reaction pattern, probably due to the unique diversity of the tissues that compose it. Inflammatory cells like LTCD8+, LBCD20+ and mastocytes tend to agglomerate in the vicinity of nervous and vascular structures, showing no signs of lymphoid tissue disposition like in typical acute rejection. Uterus transplantation in rats has proven to be a valid experiment that allows us to express hope that by further research on transplantation of the uterus gynecologists will be able to introduce an adapted technique in the treatment of specific cases of human female infertility.

[Experimental model of orthotopic uterus transplantation in the laboratory rat]

This study develops and standardizes an experimental model of uterus transplantation in the laboratory rat. Twelve orthotropic uterus transplantation were done. Animals were randomized in three groups. Postoperative survival was 100% and 75% at 72 hours. Recipients were euthanased at 24 hours, 48 hours and 72 hours and the grafts were harvested. Patency of the microsurgical anastomoses was 100% at 24 hours, 63% at 48 hours and 0% at 72 hours. The explanted uterine grafts were fixed in formalize and analyzed under light microscopy. The acute allograft rejection starts during the second day after transplantation. In additional dissection, anatomy of the pelvic region with regard to the topography of the uterus, tube and ovarian vessels was studied. This model of uterus transplantation in rats proposes a standardized tool for further research regarding cellular mechanisms of the acute allograft rejection and, for future, pregnancy of the transplanted uterus.

Thromboxane A2 release in ischemia and reperfusion of free flaps in rats, studied by microdialysis

Several studies have implicated enhanced eicosanoid production in reperfusion injury. The reported study investigated the use of microdialysis in the in vivo measurement of thromboxane levels during reperfusion in ischemic and reperfused experimental free muscle flaps. Microdialysis probes were inserted, via a guide, into the gracilis and semitendinosus free flap in the rat. The probe was perfused at a flow of 5 microl/min, with samples collected at intervals of 20 min, and analyzed by the ELISA technique. Animals were randomly distributed into three groups. After ischemic periods of 2, 4, and 6 hr, respectively, the free muscle flaps were revascularized on the contralateral femoral vessels. The mean thromboxane level during ischemia was 1785.34 +/- 124.81 pg/ml. The mean levels of thromboxane rose significantly (p < 0.05), compared to base level, with 151.65 percent in the 2-hr ischemia group, 192.33 percent in the 4-hr ischemia group, and 294.69 percent in the 6-hr ischemia group, and correlated well with histologic observations. The results suggest that a microdialysis technique, combined with a sensitive assay for measuring thromboxane, is a useful method for in vivo monitoring of inflammatory processes during ischemia and reperfusion. The evolution of thromboxane release following 6 hr of ischemia indicates that this mediator may be involved in facilitation of cell death, following ischemia and reperfusion, since its tissue level correlates with histologic tissue damage.

[Experimental model of heterotopic renal transplantation in rat]

This study describes the experience with a new technique for heterotopic kidney transplantation in the laboratory rat. This technique combines already known aspects in renal experimental transplantation, with technical improvements added to each surgical step. Ten heterotopic kidney transplantation were performed. Immediate postoperative survival was 100% and at 48 hours was 90%. The patency of the vascular anastomosis checked at 72 hours in survivors was 100%. As a preliminary study, 20 renal hilum dissections were done, noting the topographical aspects of the renal vessels. Representing a standardized and easy to use model, this solid organ transplantation technique is a valuable tool for studying the immunological and physiopathological aspects of transplantation and for refining the microsurgical skills.

The combined gracilis and semitendinosus free flap in the rat

A free-flap model in rats is presented, that consists of gracilis and semitendinosus muscles pedicled on the femoral vessels, in continuation with deep femoral and saphenous vessels. This flap was transferred to the contralateral side in 40 rats and yielded a 95 percent survival rate. The weight of the flaps averaged 1.65 gm, and the mean pedicle length was 20 mm. The flap is reliable, versatile, and may be used as a muscular, musculocutaneous, or osteomusculocutaneous free flap. The gracilis and semitendinosus muscles may be innervated independently as functioning muscle units. In the musculocutaneous flap, each pedicle may be monitored separately by raising two independently vascularized skin islands. The statistical distribution of the origins of the deep femoral vessels was established in 164 groin dissections; two origins of the vessels not previously described are reported here. The volume of the transferable tissue-about three times more than described in previous studies-and the reliability of the flap make it an ideal microsurgical, experimental model.

Improved technique for cannulation of the murine thoracic duct: a valuable tool for the dissection of immune responses

Several experimental approaches have been used in the past for the cannulation of the thoracic duct in mice. Most, however, are characterized by a modest reproducibility and a low lymph yield. Here, we describe a cannulation technique modified with respect to the anesthesia, the use of a silicone cannula and a simple and efficient intraabdominal fixation of the drain. Surgery averaged 45 min with an intra- and postoperative mortality rate of zero. Postoperatively, mice were given access to an exercise wheel allowing increased mobility and consequently a good lymph flow, thus maintaining the function of the cannula. The mice yielded a mean of 29.3 ml/24 h (range 8-40 ml) thoracic duct lymph, which contained a mean of 2.2 x 10(6) lymphocytes/ml during the first 24 h, decreasing to 0.1 x 10(6) lymphocytes/ml on the 2nd day after cannulation. Patency of the cannulae was 100% after 3 days. Interestingly, we have detected strain dependent differences in the anatomy of the thoracic duct in the mouse and these need to be considered when cannulation procedures are attempted.

Peripheral noxious stimulation releases spinal PGE2 during the first phase in the formalin assay of the rat

Injection of formalin (5%; 50 microl) into the dorsal surface of the hind paw of rats evoked a characteristic biphasic flinching behaviour of the injured paw accompanied by a significant increase in the interstitial prostaglandin E2 (PGE2) concentration of the dorsal lumbar spinal cord. Interestingly, the increase in PGE2 concentration was only observed during the first phase of the formalin behavioural response (during the 0-10 and 10-20 min microdialysis-sample). Saline paw injection did not have a significant effect on behaviour or on PGE2 concentration. These data suggest that spinal release of PGE2 is involved in nociceptive processing in the formalin-induced hyperalgesia model of the rat during the first but not second phase.

Transfer of different nonsteroidal antiinflammatory drugs via the lymphatic system in the rat

The motility of lymphatic vessels is regulated by arachidonate metabolites and can, therefore, be altered by cyclooxygenase blockers such as nonsteroidal antiinflammatory drugs (NSAIDs). To investigate the transfer of different NSAIDs via the lymphatic system, pharmacokinetics in plasma and lymph after peroral administration of three model compounds (namely, racemic ibuprofen, tenoxicam, and nabumetone) were investigated in rats. Microsurgical cannulation of the thoracic duct allowed cumulative sampling of lymph fluid up to 48 hr (N = 16). Pharmacokinetic parameters in plasma were determined in a control group (N = 12). Concentrations of R-ibuprofen, S-ibuprofen, tenoxicam, nabumetone, and the metabolites OH-ibuprofen, COOH-ibuprofen and 6-methoxy-2-naphthylacetic acid (6MNA; a metabolite of nabumetone) were monitored in lymph and plasma by HPLC. The observed peak concentrations in lymph of the investigated drugs are likely to produce different biological effects with regard to cyclooxygenase-1 inhibition. To quantify the appearance in lymph fluid, a "lymphatic clearance" of the investigated compounds was defined by dividing the amount recovered in lymph by the corresponding area under the plasma concentration-time curve. The "lymphatic clearance" differed substantially between the investigated compounds (mean +/- SD: R-ibuprofen, 19.8 +/- 9.4; S-ibuprofen, 9.6 +/- 3.6; tenoxicam, 32.5 +/- 31.3; nabumetone, 133.6 +/- 75.2; 6MNA, 18.3 +/- 8.5 microliters/min/kg). Overall recovery of the investigated compounds in lymph did not exceed 5% of the doses given. The known fact that lymphatic drainage is regulated by arachidonate metabolites suggests that NSAIDs differing in their transfer via the lymphatic system could result in different responses of lymphatic vessels to an inflammatory fluid load.

Lymph distribution of different non-steroidal anti-inflammatory drugs assessed by microsurgical cannulation of the thoracic duct in rat

The motility of lymphatic vessels is regulated by arachidonate metabolites and, therefore, can be altered by cyclo-oxygenase blockers such as non-steroidal anti-inflammatory drugs (NSAIDs). In order to investigate the lymphotropic properties of different NSAIDs, pharmacokinetics in plasma and lymph following intragastric administration of three model compounds, namely racemic ibuprofen, tenoxicam and nabumetone, were investigated in rats. Microsurgical cannulation of the thoracic duct allowed cumulative sampling of lymph fluid up to 48 hrs (n = 16). Pharmacokinetic parameters in plasma were determined in a control group (n = 12). Concentrations of R-, S-ibuprofen, tenoxicam, nabumetone and the metabolites OH-ibuprofen, COOH-ibuprofen and 6-methoxy-2-naphthyl-acetic acid (6MNA, metabolite of nabumetone) were monitored in lymph and plasma by HPLC. To quantify the lymphotropic properties of the investigated compounds, a "lymphatic clearance" was defined by dividing the amount recovered in lymph fluid by the corresponding area under the plasma concentration-time curve (AUCP). The "lymphatic clearance" substantially differed between the investigated compounds (mean +/- SD: R-ibuprofen 6.71 +/- 3.15 microliters/min, S-ibuprofen 3.24 +/- 1.20 microliters/min, tenoxicam 8.74 +/- 8.11 microliters/min, nabumetone 46.05 +/- 26.08 microliters/min and 6MNA 6.32 +/- 2.96 microliters/min). The overall recovery of the investigated compounds in lymph did not exceed 5% of the doses given. The known fact that lymphatic drainage is regulated by arachidonate metabolites might suggest that NSAIDs differing in their lymphotropic properties could result in different responses of lymphatic vessels to an inflammatory fluid load.

Oxaceprol, an atypical inhibitor of inflammation and joint damage

Oxaceprol, an established therapeutic agent for osteoarthritis, had no effect on macrophage prostaglandin E2 release in vitro and inhibited carrageenan paw oedema at high doses (18-150 mg/kg p.o.). In the same dose range, oxaceprol was comparable to indomethacin (3 mg/kg p.o.) as an inhibitor of yeast hyperalgaesia and at 6-50 mg/kg/day p.o. had a mild, variable inhibitory effect on cotton pellet granuloma formation. In adjuvant arthritic rats, oxaceprol (6-54 mg/kg/day p.o.) given therapeutically had no effect on the primary paw oedema response, but inhibited secondary lesions in the ears and tail. Histologically, oxaceprol markedly inhibited inflammatory cell infiltration and bone damage in the adjuvant-injected paw. In contrast to indomethacin, oxaceprol was more effective at inhibiting periarticular soft tissue inflammation but did not affect cartilage breakdown in this model. Oxaceprol has a clearly different spectrum of action to NSAIDs such as indomethacin and may act by inhibiting leucocyte infiltration and late connective tissue changes during inflammatory joint disease.

[A microsurgical approach to drainage of the thoracic duct in the rat]

Study of thoracic lymph flow is still of interest in gastrointestinal absorption and lymph distribution of different drugs or in immunological studies. A microsurgical experimental model for cannulation of the thoracic duct in rats is described. The principle of the method is the end fistula described by Bollman, allowing the sampling of the total thoracic duct lymph output. A simple method of collecting lymph under free moving conditions was used. The lymph cannulations were one with 0.9 mm outer diameter silicone tubing in 24 Sprague-Dawley rats with an average preoperative weight of 300 +/- 30 g. The daily lymph output measured for up to 10 days in the awake and unrestrained rats varied between 24.4 ml and 97.7 ml/day (average 45.6 ml/ day). The hourly lymph output varied between 0.55 ml and 5.8 ml (average 1.9 ml/h). Patency of the lymph fistulas was 87.5% at five days and 64.3% at the end of the experiment. The rats with failed fistulas presented various degrees of thickening of the lymphatic vessel wall. The average weight loss at the time of euthanasia was 72 g (24%). An accurate technique under the operation microscope and the use of silicone tubing may offer a reliable method in experiments requiring the sampling of the whole thoracic duct lymph output for limited periods of time.