Generation of an autologous tissue (matrix) flap by combining an arteriovenous shunt loop with artificial skin in rats: preliminary report.

The present experiment was designed to investigate the possibility of prefabricating a tissue flap in a rat by combining an arteriovenous (A-V) shunt loop with artificial skin dermis (AS). The A-V fistula loop was constructed between the right femoral artery and vein by the interposition of a vein graft and the loop was wrapped with a folded sheet of AS and buried beneath the inguinal skin. In the control group the folded sheet of AS was inserted without a vessel loop and embedded in the inguinal region as in the experimental group. There were three experiments. In experiment 1, the total volume of the generated tissue formed within the AS was calculated after 4 weeks in the experimental and control groups. In experiment 2, the AS in the experimental group was harvested at 2 (group 1) and 4 (group 2) weeks after insertion to assess the change in morphology over time. In experiment 3, full thickness skin grafts were placed over the generated tissue of the experimental groups to investigate the possibility of creating skin flaps. The total volume of tissue generated in the experimental group was significantly greater than in the control group (P< 0.01). Histological and carbon injection studies suggest that the new capillary bed is derived from the graft loop vessels and tissue generation and organisation of the AS were further advanced in group 2 than in group 1. The skin grafts placed over the tissues generated showed complete survival and could be raised as island flaps in both groups.

New source of vein graft for rabbit experimentation.

The present report introduces a new source of vein graft in rabbit experimentation which is long and of large caliber. The average length of available vein was 13.3+/-0.9 cm (mean+/-SD). The average external diameter of the vein was 1.8+/-0.2 mm (mean+/-SD), 1.4+/-0.4 mm (mean+/-SD), and 1.8+/-0.2 mm (mean+/-SD) at the proximal, middle, and distal portions, respectively. The average number of valves throughout the vein was 7+/-1. The vein is anatomically termed the lateral saphenous vein distally and the ischiadic vein proximally, and is superficially located on the lateral aspect of the pelvic limb. Therefore, this vein is easily harvested from the lower crus to the upper-thigh, providing a long length of vein graft for experimental study.

Long-term studies of cold-stored rabbit femoral artery and vein autografts.

UNLABELLED: In previous studies we have shown that 80-100% of rabbit femoral vascular autografts cold-stored at 4 degrees C for 3 weeks remain patent 3 weeks after reinsertion in the femoral artery. The present study reports the effect on graft patency of increasing either the period of cold storage prior to reinsertion or the duration of reperfusion to 6 months. Rabbit femoral blood vessels were cold-stored (CS) at 4 degrees C for varying periods. CS autografts were reinserted into the contralateral leg for 3 weeks or 6 months. Graft patency was determined and grafts examined by histological, immunohistochemical and electron microscopical techniques. Six months after reinsertion patency of 4-week CS arterial and 1-week CS venous grafts was 40% and 27% respectively, very much lower than the 80-100% seen after 3 weeks reperfusion. Arterial grafts CS for 6 months had a patency rate of 70% after 3 weeks reperfusion but 0% after 6 months. Morphological examination suggests that the delayed failure of cold-stored vascular grafts is caused by thrombus superimposed on intimal hyperplasia within the graft. CONCLUSIONS: Cold-stored vascular grafts are useful prostheses when only 3-4 weeks graft patency is required. They are not suitable for use when long-term graft patency is needed.

Fibroblast growth factor pretreatment of 1-mm PTFE grafts.

When using microvascular polytetrafluoroethylene (PTFE) vascular grafts, the best results in terms of patency rate and neoendothelialization are obtained with prostheses with thin walls and long fibril length (i.e., 90 microm). A complete internal neoendothelial lining is usually achieved at 12 weeks after implantation. Clinically, this period can be too long. In this study, 1-mm internal diameter PTFE prostheses with optimal physical characteristics were pretreated with basic fibroblast growth factor in fibrin glue, a potent endothelial cell mitogen, and chemoattractant. Rate, speed, extent, quality, and origin of neoendothelium were compared with two control groups, using Evans Blue dye, immunohistochemical localization of factor VIII von Willebrand factor protein, and scanning electron microscopy. Prostheses (8 mm long) were implanted in the infrarenal rat aorta and harvested after 3 weeks. In treated grafts, the amount of endothelial regeneration was greater than in untreated grafts (75% of the internal surface compared with 30%). However, patency rate in the experimental group was lower than in the control groups. This study provides new data on neoendothelial regeneration in small-diameter PTFE grafts.

The effect of cold ischemia on the patency of microvascular repair following arterial avulsion injury.

UNLABELLED: Avulsion injuries have a poor prognosis for survival in clinical replantation surgery. Arterial thrombosis is the most significant factor contributing to avulsion replant failure, and severe arterial damage has been observed with this injury. However, patency rates of experimentally avulsed arteries repaired immediately are much higher than in the clinical situation. This paper evaluates the effect of an added component--ischemia--on the patency of experimentally avulsed arteries. All avulsions seen clinically are subject to some degree of ischemia prior to replantation. Ninety rabbits had both femoral arteries avulsed under general anesthesia. A 6.5-cm graft was harvested from the left distal femoral artery. In 20 rabbits (group 1: 0 hours of ischemia) the graft was immediately inserted into the defect in the right femoral artery. Sixty rabbits (20 grafts per group) had their grafts stored at 4 degrees C for either 10 hours (group 2), 18 hours (group 3), or 24 hours (group 4) and reinserted into the right femoral artery in a second operation. Patency was assessed 3 weeks after reinsertion. Groups 1 and 2 maintained high patency rates (85 percent); however, group 3 (70 percent) and group 4 (45 percent) had lower patency rates than group 1, with a significant difference between groups 1 and 4 (p < 0.01). In a fifth group (10 grafts), avulsed 24-hour ischemic grafts were hydrodilated prior to reinsertion. The patency rate of this group increased significantly (90 percent) compared with group 4 (p < 0.005). CONCLUSION: These experiments suggest that a combination of avulsion injury and ischemia time is responsible for the poor clinical results of avulsion replantations.

Effects of cold storage on the subsequent structure and function of microvenous autografts.

A study was undertaken to evaluate the structure and patency of cold stored rabbit femoral veins following reinsertion as autografts for 3 weeks. The periods of cold ischaemic storage were 1, 2, 3 and 4 weeks (n = 10/gp) and 6 and 10 weeks (n = 6/gp). All rabbits were subject to 3 operations under general anaesthesia. In the first, a 4 cm segment of left femoral vein was harvested and stored at 4 degrees C for the specified ischaemic interval. Following storage the graft was microsurgically reinserted at a second operation into the right femoral artery of the donor rabbit. Three weeks later, graft patency was assessed by surgical exploration and the graft processed for light and electron microscopy. Patency rates remained over 80% after 3 weeks in all groups except the 10 week storage group where only 1 of 6 (17%) grafts was patent at 3 weeks. In all groups normal vein structure was absent, being replaced by thin walled necrotic areas or by neointimal ingrowth. The excellent patency rates achieved indicate it is possible to cold preserve extra lengths of vein grafts harvested at initial operation for reuse should regrafting be necessary.

Cold stored femoral vessels as microvascular allografts: a preliminary study.

Cold stored femoral arteries or veins have been reinserted successfully as autografts into rabbits. The present study examines whether grafting with cold stored vascular allografts is equally successful. Rabbit femoral arteries and veins were stored at 4 degrees C for 4 weeks before insertion as allografts into unrelated animals. Three weeks after insertion into the femoral artery all venous allografts and 80% of arterial allografts were patent, but patency of both graft types declined over the next few weeks. A small number of cold stored venous allografts when inserted into the femoral vein occluded within 3 weeks. No histological evidence of rejection was apparent. The findings suggest that cold stored vascular allografts could be used successfully as an arterial "prosthesis" to support free flaps where relatively short term patency is required until the flap can establish sufficient peripheral inset to survive in its own right. This technique could be applied when autologous veins are not available or not justified.

The functional and structural effects of hypothermic storage on ischaemic arterial grafts.

The effects of hypothermic ischaemia on blood vessels are unknown. This study aimed to determine the 3 week patency rate and the pathology of 9 experimental groups of hypothermically stored ischaemic arteries and one control group in a rabbit femoral artery model. Ischaemia times were 0 h, 24 h, 1, 2, 4, 6, 8 and 10 weeks (Groups 1-8). Patency was over 80% in all groups after 3 weeks reinsertion. Following reinsertion control grafts maintained normal arterial structure, but cellular degeneration had occurred in all ischaemic grafts and appeared complete after 4 weeks ischaemia. The graft connective tissue framework frequently remained intact. Repair was evident in central graft regions after 2 weeks ischaemia and 3 weeks reinsertion, but occurred only adjacent to the anastomosis in 4-10 week ischaemic arteries. Four week ischaemic arteries (Groups 9 and 10) reinserted for 6 and 12 weeks respectively exhibited near complete repair but patency dropped to 60% in the 12 week group.

Wound healing in foetal sheep: a histological and electron microscope study.

A study was made of the healing of excised, unsutured and sutured skin wounds in foetal sheep of 75, 90 and 120 days gestation and of wounds in newborn lambs and adult ewes. Foetal and postnatal wounds were found to heal in a very similar way. At each stage of development studied, excised wounds contract rapidly and histological and electron microscope examination demonstrates formation of granulation tissue and its maturation to scar tissue in all types of wound. Examination of polyvinyl sponges 7 and 14 days after subcutaneous implantation confirms the ability of foetal sheep to form vascularised scar tissue. The cellular inflammatory response to wounding is much less prominent in foetal than in postnatal sheep, the number and type of extravascular cells reflecting the changes in blood leucocyte content during development. From a very early stage foetal sheep react to insoluble irritants by the formation of multinucleate giant cells.

Periosteal response in translation-induced bone remodelling.

Translation of transplanted bones induces strain in the periosteum and subsequent bone remodelling. This study examines the periosteal response on the leading and trailing sides of translated bones using an in vivo model where internal bone strain is virtually eliminated. Caudal vertebrae from 4 days old rats were threaded onto the arms of pre-stressed helical torsion springs and transplanted subcutaneously. In the experimental rats, the appliances were activated seven days later causing the bones to translate. Tissues were examined both optically and by transmission electron microscopy. A connective tissue sheath or capsule forms around the bones and, as the arms of the appliance move apart, traction on the enveloping soft tissues produces compression of the periosteum on the leading side and tension on the trailing side with remodelling occurring in a direction opposite to translation. The control periosteum has an ordered structure with well-delineated osteogenic, mid- and fibrous zones. During translation the periosteum on the leading side is consistently narrower than on the trailing side and shows a gradual reduction in formative activity followed by resorption in select areas. Cells and fibres are aligned predominantly parallel to the bone surface. Accelerated formation characterises the trailing side during the translation phase with increased activity and widening of all three periosteal layers. The fibrous layer merges with the connective tissue sheath which frequently is oriented approximately perpendicular to the bone surface. The direction of remodelling is reversed when translation ceases with corresponding changes visible in the periosteum, the osteoblastic layer being the last to show changes. A normal periosteal structure and remodelling pattern is regained when equilibrium of the bones within the soft tissues is attained. This study shows that the enveloping soft tissues profoundly influence the nature and rate of bone remodelling. The changes are reflected in the periosteum which functions as an integrated unit modulating the signal transmitted to the osteoblasts which play a key role in events occurring at the bone surface. Changes are not attributable to internal bone strain.

Objective measurement of surfactant irritation by fiber optic spectroscopy.

Erythema caused by occlusion of 3 concentrations of surfactant was quantified in vivo using a modified spectrophotometer. Standard chamber irritation test sites were evaluated objectively using the spectrophotometer and subjectively by trained observers. There was a good relationship between the instrumental and visual evaluations. The spectrum was analyzed and a region was chosen to optimize the sensitivity of the method.

The use of transepidermal water loss to measure and predict the irritation response to surfactants.

Synopsis The ability of baseline transepidermal water loss (TEWL) measurements to predict the response of healthy subjects to a standard soap chamber irritation insult was evaluated. Chambers containing surfactant solutions were applied to the forearms of normal volunteers for five consecutive days. TEWL was measured using a Servo Med Evaporimeter. TEWL measurements were made prior to the first application of the chambers and following the removal of the second set of chambers (the afternoon of Day 1). The correlation between the TEWL values obtained on Day 1 and the subjective evaluation of irritation resulting from the application of two different toilet soaps was statistically significant. This result indicates that damage to the skin is reflected by an increase in TEWL. Interestingly, there was also a statistically significant correlation between TEWL values obtained on the untreated skin at Time 0 and the five-day average irritation score for these two cleansing products. The results of this study indicate that a high baseline TEWL value may be predictive of a high susceptibility to soap irritation as measured by the chamber test. Le role des pertes en eau transepidermique pour mesurer et prevoir l'irritation due aux tensio-actifs.