Shortening of rat teeth prevents autocannibalization of surgical flaps.

Self-biting in laboratory rats is an irritating problem that can impede progress and affect the credibility of experimental interventions. Autocannibalization frequently complicates the epigastric skin flap model that is often used to evaluate flaps. In one of the authors' studies, the autocannibalization rate of 55.6 percent in nine rats with unprotected skin flaps of the entire abdominal wall necessitated the application of previously reported plastic collars and protective vests to hinder self-biting. Because the use of these devices resulted in distress symptoms in nine of 11 rats with collars and flap congestion in five of five rats with vests, rat incisor teeth shortening was introduced as a stress-free method to prevent chewing. Careful teeth cutting obviated autocannibalization in 19 of 20 rats (p<0.01) during a 5-day follow-up. Rat incisor teeth shortening performed every 3 or 4 days is a simple, inexpensive, and reliable method to prevent autocannibalization in the rat, while maintaining the well-being of the animal.

Transfer of the rat tail: an experimental model for free osteocutaneous transfer.

A new experimental model for free transfer of the rat tail has been developed. The vascular and nerve anatomy of the tail was studied in ten Wistar rats. The caudal artery (average diameter: 0.8 mm) provides the principal arterial supply to the tail. The main venous drainage is from bilateral dorsolateral subcutaneous veins (average diameter: 1.2 mm). The inferior caudal trunk establishes the cutaneous nerve branches to the skin of the tail. Free transfer of the tail to the carotid artery and external jugular vein, with the attachment of the tail to the dorsum, allows for clinical monitoring of the transfer, without risk of autophagia. This transfer is easy to perform, simple to monitor, and provides consistent yet challenging microsurgery for the beginning microvascular surgeon. In addition to its utility as a training model, it may also have an application as an easy research model for composite tissue transfer.

A new heart failure model in rat by an end-to-side femoral vessel anastomosis.

OBJECTIVE: The aim of this study was to develop a new shunting procedure for producing heart failure in the rat incorporating microvascular techniques and avoiding an abdominal operation. METHOD: We performed an end-to-side anastomosis between the femoral vein and the femoral artery just proximal to their trifurcation into the saphenous, epigastric, and distal femoral vessels. RESULTS: Of the 15 rats which underwent this procedure, six died within 48 h. The nine surviving animals were sacrificed and examined six weeks following surgery. All nine had developed cardiac hypertrophy and cardiac failure. CONCLUSION: This model provides a relatively simple and reproducible means of creating high output heart failure and cardiac hypertrophy in the rat without necessitating abdominal surgery.

Arterialization of the venous system in a rat lower limb model.

Creation of alternative vascular conduits has been one of the most challenging subjects in the history of vascular surgery. In the past, afferent arteriovenous fistulas have been used by vascular surgeons to rescue ischaemic extremities. We have undertaken a comprehensive investigation to characterize arterialization of the venous system at different levels of the rat lower limb. In Group 1 (n = 28), we performed an end-to-end anastomosis between the proximal saphenous artery and the distal saphenous vein (Superficial venous system), and ligated all other branches of the femoral artery. In Group 2 (n = 28), we performed an end-to-end anastomosis between the proximal saphenous artery and the distal femoral vein (Deep venous system). In Group 3 (n = 24), the control group, the femoral artery was ligated proximal to its trifurcation into the saphenous, epigastric, and distal femoral vessels. Group 4 (n = 10), the normal group, underwent no surgery. Animals were sacrificed at the first, third, and eighth postoperative weeks. Arteriographic, India ink injection, latex injection, and histological studies were performed on all groups. Successful arterialization of veins, significant neovascularization, and less ischaemic injury of muscles were noted in the arterialized vein groups (Groups 1 and 2) when compared with the ligated group (Group 3). This model appears to depict successfully arterialization of the lower limb venous system in a small animal model.

New simplified radio-opaque injection technique for visualization of rat arteries.

We have developed a new and simplified injection technique based on a mixture of latex and lead oxide. This injection technique is unique in its possession of both color and radio-opacity. We have developed and refined this methodology in rats, and have demonstrated it to possess superior qualities of injectability. Depiction of small vessels is highly detailed both radiographically and grossly.

Experimental microvenous thrombosis following anastomosis with a knotted suture.

An experimental model for producing venous thrombosis was developed in end-to-end anastomoses of femoral veins in rats. The anastomoses were performed using a suture (9-0 suture-70 microns needle) with a knot 1 cm from the needle. The knot was formed by making either six or eight half-hitches in one throw of the suture. Vessel patency was assessed through the direct "milking test" at 20 min and 24 hrs. The incidence of thrombosis when using one knot with six half-hitches ranged from 20% to 40% and with eight half-hitches, from 50% to 70%. The incidence of femoral vein thrombosis varied directly with the presence and size of the knot. In this model, thrombosis was induced by exaggerating vessel injuries that may occur when performing routine microvascular anastomoses. This study demonstrates a reproducible thrombogenic model which mimics clinical practice and may be used to study the effects of local and systemic antithrombogenic agents.

Advanced non-animal microsurgical exercises.

For the novice microsurgeon, suturing simple lines on a static model ill prepares them for the technically difficult live model that is to follow. A practice card was therefore designed to make the transition easier. The basic building block is rubber glove sutured to form a simple tube. From this point, progressive exercises are carried out. These are (1) simple suturing, (2) tube anastomosis, (3) end-to-end anastomosis, (4) end-to-side anastomosis, (5) side-to-side anastomosis, (6) inequality of diameters, and (7) free graft placement. Since the student is faced with problems that are challenging and progressively complex, a noticeable improvement is seen in their skills. These models introduce the student to planning and instrumentation that they would deal with in the clinical situation. Once the student has mastered these exercises, he/she is ready to advance to the rat model.

Microvascular vein-graft patency in the rat model.

This study establishes a controlled model, to examine the patency rates of simple, arterial and venous anastomoses, compared to vessel repairs performed with 10-mm, size-matched, interpositional, vein grafts in the rat femoral artery and vein. Patency rates in two control groups, consisting of 68 Sprague-Dawley rats in which simple, femoral-vessel repairs were performed, were compared to three experimental groups, consisting of 94 animals in which the femoral vessels were repaired with interpositional vein grafts. No statistically significant difference was found in the patency rates of arterial (p = 0.487) or venous repairs (p = 0.472) in the control groups. Nor was a significant difference found in arterial vein-graft patency (p = 0.560) or venous vein-graft patency (p = 0.862), when compared to the control groups. This study illustrates that, in the controlled laboratory setting, 10-mm, size-matched, interpositional, vein grafts have statistically the same patency rates as simple repairs of the rat femoral artery and vein.

Microvascular vein grafts in the rat cutaneous free-flap model.

This study utilizes the rat free groin-flap model to evaluate the survival of free flaps following revascularization with interpositional vein grafts. One hundred and fifty-three Sprague-Dawley rats were divided into a control group in which the groin flap was revascularized by simple end-to-end anastomosis, and three experimental groups revascularized with 10-mm, size-matched, interpositional, vein grafts to the femoral artery (Experimental Group 1), to the femoral vein (Experimental Group 2), and to both arterial and venous femoral vessels (Experimental Group 3). No statistically significant difference was noted in survival rates, when the experimental groups were compared to the control group (p1 = 0.619, p2 = 0.677, p3 = 0.666). As demonstrated by this study, free-tissue transfers in the rat, utilizing 10-mm, interpositional, vein grafts that are size-matched, and performed in a controlled laboratory setting, have the same survival rates as those revascularized by primary arterial and venous repairs.

Primary common bile duct anastomosis in the rat using microsurgical techniques.

In a rat model, we attempted to describe the natural healing course of the common bile duct (CBD) after primary microsurgical repair. Fifty-three rats were divided into experimental groups with CBD microsurgical anastomoses and control groups with CBD mobilization and ligation. Examination of three experimental groups at 1 week, 1 month, and 3 months showed evolving inflammation and stricture changes with eventual patent, healed ducts in 92% of animals at the end of 3 months following transection and repair. There were no histologic abnormalities in the livers. There were fibrotic ducts and hepatic stasis and cirrhosis changes in the control group with CBD ligation. This study demonstrates that microsurgical techniques can achieve successful primary biliary repair in the rat.

The greater omentum transplantation model in the rat.

Dissection of the rat omentum were performed to study the feasibility of rat omental free transfer. The right epiploic vessels were found to be adequate for anastomosis in transfer. Twelve omental free flaps were transferred to the groin, with 100% survival of flaps in the 10 animals that survived the operation. The artery and vein averaged 0.3 and 0.4 mm in diameter, respectively. The average pedicle length was 5 mm, and the average flap weight was 136.9 mg. This omental transplant offers a new experimental means of studying lymphedema, neovascularization, and tissue revascularization.

Microvascular transplant of the gastrocnemius muscle in rats.

The rat gastrocnemius muscle can serve as a vascularized, innervated muscle transplant model. To establish the anatomic and technical details of this model, we performed ten gastrocnemius transplants and collected data on muscle weight, dimension, and vessel caliber from each muscle. The muscle, consisting of medial and lateral heads, is supplied by pairs of sural vessels averaging 0.2 mm in diameter. These vessels, however, can be taken in continuity with the femoral vessels (averaging 1.0-1.6 mm in diameter), which are used for transplantation. The muscles weighed an average of 2.8 g, and the average pedicle length was 24 mm. Eight of ten transplanted muscles were viable with intact circulation at 72 hr. The gastrocnemius transplant was technically reliable, and the muscle bulk and contour could allow biochemical and functional studies. Donor site morbidity limits this model to transplantation studies.

Microvascular transfer of the rectus abdominis muscle and myocutaneous flap in rats.

A rat microvascular free rectus myocutaneous flap model with a superior epigastric vessel pedicle is presented. The rectus muscle has a predictable "flow-through" axial vascular system consisting of superior and inferior epigastric vessels anastomosing under the fascial sheath, and six to seven musculocutaneous perforating branches to the skin. The superior epigastric artery and vein, averaging 0.45 mm and 0.5 mm in diameter, can be used as the vascular pedicle in muscle or myocutaneous flap transplantation. Eight muscle and 15 myocutaneous flaps were transplanted to the groin. The myocutaneous flaps averaged 3.5 cm by 1.2 cm in size; the pedicle length averaged 11 mm. The 5 day survival was 100% for muscle flaps and 67% for myocutaneous flaps. The rectus myocutaneous flap is believed to be the first true myocutaneous model in the rat.

Muscle flap monitoring in a rat model with a variable gain quantitative fluorometer.

A variable gain dermofluorometer with a wide range of sensitivities capable of quantifying fluorescein emission from both skin and muscle was tested in a rat latissimus dorsi island muscle flap model. Quantitative fluorometric readings directly from muscle and skin sites that did not undergo surgery were taken at intervals over 2 hours after intravenous fluorescein injection. Muscle flaps with intact pedicles gave an inflow-outflow pattern. A no-outflow pattern was seen in muscle flaps with ligated pedicle veins and a no-inflow pattern was seen in muscle flaps with ligated pedicle arteries. These patterns were similar to the flow pattern seen with quantitative fluorometric monitoring in flaps with cutaneous components. These results suggest that quantitative fluorometry may be applicable to circulation monitoring in muscle flaps.

Single pedicle microvascular transfers of the serratus anterior and latissimus dorsi muscles in rats.

In the rat, the serratus anterior and latissimus dorsi muscles receive axial vascular pedicles from the thoracodorsal artery. This anatomy was confirmed by dissections, and 10 microvascular transfers of the latissimus-serratus flap on a common pedicle were performed with a 90% success rate. The flaps had an average weight of 1.8 g. This flap is a reliable small animal model for microvascular muscle transplants and contains sufficient tissue to be used in multiple biochemical assays.

Customized prefabricated neovascularized free flaps.

Neovascularization of tissues into which a vascular pedicle has been implanted can result in the creation of a flap, or free flap, which is supported by those vessels as a neopedicle. This phenomenon allows the construction of customized prefabricated free flaps from tissue without restriction to naturally occurring vascular territories.

Strain of Escherichia coli with a temperature-sensitive mutation affecting ribosomal ribonucleic acid accumulation.

A mutant of Escherichia coli has been isolated that has a temperature-sensitive mutation that results in specific loss of ribosomal ribonucleic acid (RNA) synthesis and some reduction in messenger RNA synthesis. When the strain was grown in glucose medium at a restrictive temperature, RNA accumulation ceased, but both messenger RNA and protein synthesis continued for an extended time. Because carbon metabolism was slowed drastically when strain AA-157 was placed at the restrictive temperature, this phenotype can be compared with carbon depletion conditions present during diauxic lag. However, the phenotype of mutant AA-157 differs from shift-down conditions in that guanosine-3',5'-tetraphosphate levels are unaffected; therefore, a different site is affected. This mutant strain (AA-157) thus shows many characteristics similar to an aldolase mutant previously reported (Böck and Neidhardt, 1966). However, the mutation occurred in a different position on the E. coli genetic map, and furthermore, aldolase was not temperature sensitive in strain AA-157. In this paper we present a study of macromolecular biosynthesis in this mutant.