Gene and protein expressions of nitric oxide synthases in ischemia-reperfused peripheral nerve of the rat.

This study examined mRNA and protein expressions of neuronal (nNOS), inducible (iNOS), and endothelial nitric oxide synthases (eNOS) in peripheral nerve after ischemia-reperfusion (I/R). Sixty-six rats were divided into the ischemia only and I/R groups. One sciatic nerve of each animal was used as the experimental side and the opposite untreated nerve as the control. mRNA levels in the nerve were quantitatively measured by competitive PCR, and protein was determined by Western blotting and immunohistochemical staining. The results showed that, after ischemia (2 h), both nNOS and eNOS protein expressions decreased. After I/R (2 h of ischemia followed by 3 h of reperfusion), expression of both nNOS and eNOS mRNA and protein decreased further. In contrast, iNOS mRNA significantly increased after ischemia and was further upregulated (14-fold) after I/R, while iNOS protein was not detected. The results reveal the dynamic expression of individual NOS isoforms during the course of I/R injury. An understanding of this modulation on a cellular and molecular level may lead to understanding the mechanisms of I/R injury and to methods of ameliorating peripheral nerve injury.

Comparison of continuous and interrupted suture techniques in microvascular anastomosis.

We evaluated the efficacy of the continuous suture technique (CST) in arteries and veins with varying external diameters (ED). In study 1 a direct end-to-end anastomosis was performed in 5 groups of animals (n = 15 in each group): group 1, rabbit carotid artery (ED, 1.8-2.0 mm); group 2, rabbit femoral artery (ED, 1.4-1.6 mm); group 3, rat femoral artery (ED, 0.7-0.9 mm); group 4, rabbit femoral vein (ED, 2.0-2.2 mm); and group 5, rat femoral vein (ED, 1.0-1.2 mm). In study 2 a graft from the femoral vein was interposed into the carotid artery, with a ratio of the diameter of graft to artery of 1.3:1 in the rats (group 6, n = 12) and 1:1 in the rabbits (group 7, n = 12). In each animal the vessel on one side was repaired using CST and the opposite vessel using the interrupted suture technique. Vessel samples were harvested 1, 2, and 4 weeks after anastomosis. The CST significantly reduced anastomosis time by up to 47% in arteries and 41% in veins. Bleeding time and blood loss were also significantly reduced with CST. Similar results were found in study 2. The total thrombosis rate was 8%, but no significant patency difference was noted between the CST and the interrupted suture technique in any vessel category. We conclude that the CST is a reliable and time-saving procedure in microvascular anastomosis of arteries with diameters greater than 0.7 mm and of veins with diameters greater than 1.0 mm.

Hemorrhage and thrombus formation in early experimental osteonecrosis.

The aim of the current study was to test the hypothesis that the induction of an underlying immunologic condition in rabbits may enhance the development of steroid-induced osteonecrosis. Thirty-five adult rabbits were divided into four groups. Group I: 10 rabbits were immunized at 15-day intervals for 2 months by murine antibodies to deoxyribonucleic acid autoantibodies. Four weeks after the end of the immunization, the animals received injections of methylprednisolone for 7 days and then prednisolone per os for 8 months. Group II: 10 animals only received immunizations according to the protocol used in Group I. Group III: 10 animals only were treated with corticosteroids according to the protocol used in Group I. Group IV: five animals were used as controls. Various changes were observed in the proximal metaphysis and diaphysis of the femur in eight of 10 animals in Group I (80%) and in five of 10 animals in Group II (50%) when compared with the animals in Group III and Group IV. The most common feature was evidence of new and old hemorrhage through the sinusoids, exudative reaction and thrombus formation in veins and small arteries. Focal necrotic areas of bone marrow showed an accumulation of cell debris, residue of hemorrhage, and disappearance of marrow elements. These findings suggest that (1) corticosteroids may potentiate the effects of a preexisting condition to increase the risk of osteonecrosis; (2) immunologic reaction may be an important factor in the pathogenesis of necrotic lesions; and (3) repeated intramedullary hemorrhage and thrombus formation may represent early major pathologic findings in bone necrosis.

Blockade of L-selectin attenuates reperfusion injury in a rat model.

Ischemia/reperfusion (I/R) injury appears to be a significant neutrophil-dependent component and may be ameliorated by blocking leukocyte-endothelial adhesion. Using a rat extensor digitorum longus (EDL) muscle model, the present study tested the hypothesis that in vivo administration of the function-blocking monoclonal antibody (mAb) LAM1-116 which recognizes L-selectin, a cell-surface adhesion receptor, could decrease I/R injury. In 46 rats, one EDL served as a normal control and the opposite EDL underwent 3 hr of ischemia followed by 3 hr of reperfusion after pretreatment with LAM1-116 mAb, control IgG, or saline. Myeloperoxidase (MPO) activity showed only a two-fold increase from normal in LAM1-116-treated I/R EDL while a 27-fold increase occurred in the IgG2a and saline groups, with a statistically significant (p < 0.001) difference. A significantly (p < 0.05) lower wet weight ratio, improved fatigue contractile force, and less neutrophil infiltration were found in LAM1-116-treated EDL, when compared to those in control IgG- or saline-treated EDL. The results indicate that blockade of L-selectin by LAM1-116 mAb can effectively reduce neutrophil infiltration in reperfused skeletal muscle, thereby decreasing tissue edema and improving muscle fatigue contractile force. These findings may be important in understanding I/R injury.

Interleukin-1 beta promotes functional recovery of crushed peripheral nerve.

This study was conducted to elucidate the role of the cytokine interleukin-1 beta on peripheral nerve recovery following crush injuries of two different magnitudes. Eighty-eight female rats were divided into four groups. A 5-mm segment of the right sciatic nerve was subjected to a 100-g crush load for 2 hours in the rats in Groups A1 and B1 or to a 15,000-g crush load for 10 minutes in the rats in Groups A2 and B2. The rats in Groups A1 and A2 received 10 microg/100 g body weight human recombinant interleukin-1 beta intraperitoneally 48, 24, and 1 hours before the nerve injury. The rats in Groups B1 and B2 were treated with an equal volume of normal saline solution with identical schedule guidelines. Walking-track tests (sciatic functional index) performed at intervals until 56 days after the crush and measurements of the contractile force of the extensor digitorum longus muscle made until 28 days were used to evaluate functional recovery of the nerve. During the second week after injury, the rats treated with interleukin-1 beta (A1) had an earlier recovery on the walking track than did those treated with saline solution (B1); this difference reached significance (p < 0.05) at day 11. Although Group A2 demonstrated a trend toward earlier recovery compared with Group B2, there was no significant difference between the two groups. After low or high-load crush injury, tetanic contractile forces were greater in the rats treated with human recombinant interleukin-1 beta than in those treated with saline solution. The results suggest that treatment with human recombinant interleukin-1 beta before crush injury can promote function in the peripheral nerve after the injury. However, the mechanisms that underlie the observed beneficial effects are not completely understood and only speculations can be made.

Influences of inflation rate and duration on vasodilatory effect by intermittent pneumatic compression in distant skeletal muscle.

Previous study has demonstrated that application of intermittent pneumatic compression on legs can cause vasodilation in distant skeletal muscle at the microcirculation level. This study evaluated the influence of inflation rate and peak-pressure duration on the vasodilatory effects of intermittent pneumatic compression. The cremaster muscles of 50 male rats were exposed and divided into five groups of 10 each. A specially designed intermittent pneumatic-compression device was applied in a medial-lateral fashion to both legs of all rats for 60 minutes, with an inflation rate and peak-pressure duration of 0.5 and 5 seconds, respectively, in group A, 5 and 0 seconds in group B, 5 and 5 seconds in group C, 10 and 0 seconds in group D, and 10 and 5 seconds in group E. Diameters of arterial segments were measured in vessels of three size categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed that the greatest increase in diameter was produced by intermittent pneumatic compression with the shortest inflation rate (0.5 seconds). A moderate increase resulted from compression with an inflation rate of 5 seconds, and no effective vasodilation occurred during compression with the longest inflation rate (10 seconds). When the groups with different inflation rates but the same peak-pressure duration were compared, there was a significant difference between any two groups among groups A, C, and E and between groups B and D. When the groups with different peak-pressure durations but the same inflation rate were compared, compression with a peak-pressure duration of 5 seconds caused a generally similar degree of diameter change as did compression without inflation at peak pressure. The findings suggest that inflation rate plays an important role in the modulation of distant microcirculation induced by intermittent pneumatic compression whereas peak-pressure duration does not significantly influence the vasodilatory effects of the compression. This may be due to the fact that rapid inflation produces a significant increase in shear stress on the vascular wall, which stimulates vascular endothelium to release nitric oxide, causing systemic vasodilation.

Motor functional and morphological findings following end-to-side neurorrhaphy in the rat model.

Nerve repair cannot always be achieved by the conventional end-to-end technique. This study evaluated the functional recovery of nerves repaired with end-to-side neurorrhaphy in a rat model. The right peroneal nerves of 80 female rats were transected and divided into four groups. In group A, the nerve ends were separated and remained unrepaired; in group B, the distal peroneal ends were directly sutured to the epineurium of the tibial nerves in end-to-side fashion; in group C, the distal ends were sutured through an epineurial window at the repair site in end-to-side fashion; and in group D, the nerve ends were reconnected by the traditional end-to-end technique. Evaluation included gait analysis by calculation of a peroneal functional index, measurement of contractile function of the extensor digitorum longus muscle, wet weight of the extensor digitorum longus, and histological examination. The findings of this study suggested the following: (a) end-to-side neurorrhaphy allows effective motor functional recovery, demonstrated by earlier improvement of the peroneal functional index, stronger muscle contractile function, greater muscle weight, and higher density of regenerated axons compared with unrepaired nerves; (b) removal of the epineurium of the donor nerve at the nerve coaptation site increases the effectiveness of end-to-side neurorrhaphy, but the epineurium appears to be a partial barrier to axonal regeneration; (c) removal of the epineurium does not affect the structure and function of the donor nerve; and (d) end-to-end repair achieved the best functional recovery among the four groups; therefore, end-to-side repair should be considered as a potential alternative only when no proximal nerve is available.

Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle.

Intermittent pneumatic compression has been established as a method of clinically preventing deep vein thrombosis, but the mechanism has not been documented. This study observed the effects of intermittent pneumatic compression of legs on the microcirculation of distant skeletal muscle. The cremaster muscles of 80 male rats were exposed, a specially designed intermittent pneumatic-compression device was applied to both legs for 60 minutes, and the microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed significant vasodilation in arterial and venous vessels during the application of intermittent pneumatic compression, which disappeared after termination of the compression. The vasodilation reached a maximum 30 minutes after initiation of the compression and could be completely blocked by an inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine (10 micromol/min). A 120-minute infusion of NG-monomethyl-L-arginine, beginning coincident with 60 minutes of intermittent pneumatic compression, resulted in a significant decrease in arterial diameter that remained at almost the same level after termination of the compression. The magnitude of the decrease in diameter in the group treated with intermittent pneumatic compression and NG-monomethyl-L-arginine was comparable with that in the group treated with NG-monomethyl-L-arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermittent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilation.

Effect of a NOS inhibitor, L-NMMA, on the contractile function of reperfused skeletal muscle.

The authors investigated the effect of NG-monomethyl-L-arginine acetate (L-NMMA), a nitric oxide synthase (NOS) inhibitor, on the contractile function of skeletal muscle following ischemia/reperfusion (I/R) injury. The extensor digitorum longus (EDL) muscles of 50 rats were divided into seven groups. Contractile function in non-ischemic EDL did not change statistically significantly with L-NMMA infusion. I/R (1.5 hr I and 3 hr R) significantly decreased EDL contractile function, with an average maximal twitch force of 56 percent of the contralateral normal muscle force and isometric tetanic contractile forces between 47 and 84 percent at four different stimulation frequencies. Following L-NMMA administration at three different dosages, contractile function of I/R muscle decreased in a dose-dependent manner. The highest dosage of L-NMMA (10 micromol/min) reduced the average maximal twitch force to 15 percent and the isometric tetanic contractile forces to between 10 to 23 percent. Histologic evaluation revealed increased edema, neutrophil infiltration, and muscle-fiber necrosis in L-NMMA-infused EDL, compared to the controls. 1) Skeletal muscle contractile function was dose-dependently decreased with the administration of L-NMMA during I/R. 2) The concentrations of L-NMMA used in this study did not influence the function of non-ischemic EDL. These findings suggest that reduction of NO production during I/R is damaging to skeletal muscle function and would impair successful functional outcomes in microsurgical replantation.

Recombinant human glial growth factor 2 (rhGGF2) improves functional recovery of crushed peripheral nerve (a double-blind study).

This in vivo double-blind study evaluated the effect of recombinant human glial growth factor 2 (rhGGF2), a Schwann cell mitogen, on the recovery of motor function of rat sciatic nerve following crush injury. Seventy three rats were divided into three groups. Group I (n=5), sham operated; Groups II (n=34) and III (n=34) received a 100 g crush load for 2 h over a 5 mm segment of the sciatic nerve. Group III was treated with 1 mg/kg rhGGF2, via subcutaneous injection one day before nerve crush and daily for the following four days. Group II received an equivalent volume of saline as a control. Motor functional recovery was assessed by calculating the sciatic functional index (SFI) and the recovery rate of tetanic contractile force of the extensor digitorum longus (EDL) muscle. Recovery of nerve function was evident at day 11 after crush in the rhGGF2-treated animals, whereas the nerves in controls were still paralyzed. The rhGGF2-treated animals showed a significant improvement of the SFI between days 11-21 postoperatively when compared to controls. The isometric tetanic contractile force was stronger in the rhGGF2-treated group than in controls, with a significant difference at 40 to 70 Hz stimulus frequencies on day 4. Correlation analysis showed that tetanic contractile force had a linear correlation with the SFI. Histologic assessment indicated that the rhGGF2-treated animals showed less severe degeneration and earlier robust remyelination of axons than controls. The results suggest that treatment with rhGGF2 is effective in promoting nerve regeneration as seen in measurements of functional recovery and qualitative assessment of nerve morphology. The mechanism of GGF's protective effect may be related to its direct action on Schwann cells, stimulating their mitosis as well as inducing neurotrophic factors essential to neuronal maintenance and repair.

S-nitroso-N-acetylcysteine protects skeletal muscle against reperfusion injury.

The effects of a nitric oxide (NO) donor on microcirculation and contractile function of reperfused skeletal muscle were studied. Rat cremaster muscles underwent 5 hours of ischemia and 90 minutes of reperfusion and were divided into two groups systemically infused with S-nitroso-N-acetylcysteine (SNAC, 100 nmol/min) and phosphate-buffered saline (PBS), respectively. The results showed that the vessels in the SNAC group had more rapid and complete recovery than that in controls. A significant difference was found from 10 to 40 minutes and at 90 minutes in 10-20-microm arterioles, from 10 to 90 minutes in 20-40-microm arterioles, and at 10 and 90 minutes in 40-70-microm arteries. When compared to controls, SNAC-treated muscles showed larger fluorescein filling areas at 15, 30, 60, and 90 minutes and greater isometric tetanic contractile forces in response to stimulation frequencies of 40, 70, 100, and 120 Hz. The data indicate that supplementation of exogenous NO could effectively improve microcirculation and contractile function of skeletal muscle during early reperfusion.

Effect of increased compartment pressure on the microcirculation of skeletal muscle.

To determine the changes in capillary perfusion, which occur with elevated tissue pressure, and to highlight the relationship between systemic blood pressure and compartment pressure, we designed an experiment that allowed direct observation of the microcirculation of skeletal muscle under normal and increased compartment pressures. In each of 10 anesthetized rats, the cremaster muscle was exposed and suspended in a transparent pressure chamber. In vivo videomicroscopy was then performed and blood pressure was monitored via left carotid artery cannulation. Two sets of data for each animal were obtained: deltaP (mean arterial pressure compartment pressure) at which the muscle capillary blood flow was completely arrested, and the number of capillaries per 10,000 square micrometers of skeletal muscle with blood flowing at compartment pressures of 0, 15, 30, 45, and 60 mm Hg. Capillary blood flow stopped at a deltaP of 25.5 mm Hg +/- 14.3 SD. We found that capillary blood flow, as measured by the number of capillaries with blood flow per 10,000 square micrometers, decreased significantly (P < 0.05) as compartment pressure reached 15, 30, 45, and 60 mm Hg, when compared to 0 mm Hg; there was no vessel collapse at these pressures. These data show that increasing compartment pressure reduces the number of perfused capillaries per unit area, and that there is complete cessation of muscle capillary blood flow when the compartment pressure is within about 25 mm Hg of the mean arterial pressure.

Pharmacokinetics of a degradable drug delivery system in bone.

Local delivery of antibiotics via a degradable carrier has the potential for high local antibiotic levels and avoids systemic toxicity. Intravenous access, renal function monitoring, and later surgical removal may not be required when degradable local delivery modalities are used. This study examined the in vivo elution of gentamicin from processed bovine collagen (Type I). Gentamicin impregnated collagen (3 mg/kg) was implanted into the femoral medullary canal of 45 adult white rabbits. The gentamicin was released into the bone and averaged greater than 600 micrograms/ml during the initial 48 hours. Local bone levels fell to 144.40 +/- 229.84 micrograms/ml at 5 days and were subsequently greater than or equal to 10.30 +/- 5.02 micrograms/ml through Day 28. Serum levels reached an average peak of 1.25 +/- 0.29 micrograms/ml 5 hours after implantation and fell below 1.0 microgram/ml at 12 hours after implantation. Serum levels subsequently averaged less than or equal to 0.63 +/- 0.09 microgram/ml through Day 28. Collagen impregnated with gentamicin proved to be an effective degradable carrier of gentamicin in the healthy rabbit; it provided local bone concentrations above the minimum inhibitory concentration of gentamicin and serum concentrations below levels associated with systemic toxicity as long as 28 days after implantation.

Effects of S-nitroso-N-acetylcysteine on contractile function of reperfused skeletal muscle.

The ultimate goal of replantation and microsurgical reconstructive operations is to regain or improve impaired function of the tissue. However, the data related to the influence of NO on tissue function are limited. This study evaluated the effects of the NO donor S-nitroso-N-acetylcysteine (SNAC) on contractile function of skeletal muscle during reperfusion. Forty-nine rats were divided into six groups. The extensor digitorum longus (EDL) muscles in groups I and II were not subjected to ischemia-reperfusion but were treated with a low (100 nmol/min) or high (1 mumol/min) dose of SNAC. In groups III-V, the EDL underwent 3 h of ischemia and 3 h of reperfusion and was also treated with low (100 nmol/min) or high doses (1 or 5 mumol/min) of SNAC. Group VI was a phosphate-buffered saline (PBS)-treated control group. Twenty additional animals were used to document systemic effects of SNAC and PBS only. SNAC or PBS was infused for 6.5 h, beginning 30 min before ischemia and continuing throughout the duration of reperfusion. Contractile testing compared the maximal twitch force, isometric tetanic contractile forces, fatigue, and fatigue half time of the experimental EDL and the contralateral nontreated EDL. The findings indicate that 1) SNAC does not influence contractile function of EDL muscle not subjected to ischemia-reperfusion, 2) SNAC significantly protects the contractile function of ischemic skeletal muscle against reperfusion injury in the early reperfusion period, and 3) the protective role of SNAC is critically dosage dependent; protection is lost at higher doses. The conclusion from this study is that supplementation with exogenous NO exerts a protective effect on the tissue against reperfusion injury.

Studies of ischemia-reperfusion injury in skeletal muscle: efficacy of 21-aminosteroids on microcirculation and muscle contraction after an extended period of warm ischemia.

The present study was conducted to elucidate the effects of tirilazad mesylate (U-74006F), a potent inhibitor of lipid peroxidation, on vessel diameter, capillary perfusion, and contractile function of rat cremaster muscle during a 90-minute reperfusion period that followed 4 hours of warm ischemia. Two groups of 32 animals were treated with either 3 mg/kg U-74006F or the vehicle (citrate buffer) alone 30 minutes before ischemia, 90 minutes after ischemia, and immediately before reperfusion. With use of intravital videomicroscopy, the internal luminal diameters of preselected vessels were measured prior to ischemia and during reperfusion. The area that filled with fluorescein was determined at 15-minute intervals for as long as 90 minutes of reperfusion, and contractile function was examined in vitro in an organ bath at that point. In the U-74006F group, after 90 minutes of reperfusion the vessel diameters returned completely to baseline and the diameters of all three categories of vessels at every time point from 10 to 90 minutes of reperfusion had significantly more rapid recovery than the controls. Although some evidence of more rapid fluorescence was noted in the U-74006F group, the two groups did not differ significantly at any time period of reperfusion. In response to tetanic stimulation, the muscles treated with U-74006F had a significantly greater contractile force at all stimulation frequencies than the control muscles. Our findings indicate that pretreatment with U-74006F can effectively decrease the rise of vascular resistance and preserve the contractile function of skeletal muscle during early reperfusion, thereby attenuating ischemia-reperfusion injury.

Antithrombotic potencies of enoxaparin in microvascular surgery: influence of dose and administration methods on patency rate of crushed arterial anastomoses.

This study evaluated the influence of the dose and administration methods of enoxaparin, a low-molecular-weight heparin, on the patency rate of crushed rat femoral arteries following anastomosis. An impact crush with a 25-kg magnitude was applied to a 2-mm segment of 100 rat femoral arteries, followed by anastomosis. The arteries were divided into five groups: group 1 received systemic enoxaparin alone with a relatively high dose (45 IU) twice a day for 3 days; groups 2 and 3 received topical irrigation with a lower (15 IU/mL) concentration and a higher (45 IU/mL) concentration, respectively; group 4 received systemic and topical application at a lower (15 IU) dose and concentration (15 IU/mL); and group 5 received systemic and topical application at a higher (45 IU) dose and concentration (45 IU/mL). The results of this study demonstrate the following: (1) topical irrigation with enoxaparin at a concentration of 45 IU/mL-three times higher than that recommended for clinical use adjusted by body weight (15 IU/mL)-is effective for antithrombotic action; (2) a combination of systemic and local application does not offer additional benefit in the patency rate when compared to local irrigation alone; (3) systemic administration alone does not prevent thrombus formation; and (4) enoxaparin is potentially useful to enhance the patency rate in compromised microvessels.

Calcitonin gene-related peptide and reperfusion injury.

Calcitonin gene-related peptide is a potent intrinsic vasodilator, can induce prostacyclin release, and may inhibit membrane lipid peroxidation. This study examines the effect of calcitonin gene-related peptide on vessel diameters, capillary perfusion, and contractile function of skeletal muscle after 4 or 5 hours of ischemia and during immediate reperfusion using the rat cremaster muscle model. Forty-two male rats were used; half of these received 0.2 ml of 10(-7) M calcitonin gene-related peptide after 0, 15, and 30 minutes of reperfusion, while the other half received normal saline as a control. By means of intravital videomicroscopy, the diameters of 10 vessels per muscle were measured prior to ischemia and during reperfusion. The fluorescein filling area was determined at 15, 30, and 60 minutes of reperfusion. After 1 hour of reperfusion, muscle function was examined in vitro by quantifying the contractile response to electric field stimulation of the muscles in an organ bath system. There was a significant increase in the diameter of the arterioles, but not the small arteries, at every time point from 10 to 60 minutes of reperfusion. The fluorescein filling area was increased in treated muscles at every time point. Contractile function was not significantly preserved. In light of the ability of calcitonin gene-related peptide to relieve vasospasm and improve capillary perfusion, it may be useful in reducing reperfusion injury in the future.

Assessment of ischemia and reperfusion injury.

Direct videomicroscopy of the rat cremaster muscle microcirculation supplemented by animal models of replantation, vascular crushing, and muscle function after injury and recovery were used to investigate the occurrence of reperfusion failure. It is evident that failure of blood reflow may be induced by multiple factors that can be grouped into categories of ischemia, intimal damage, and systemic or local responses, which are referred to as the no reflow triad. The components comprising the 3 sides of the no reflow triad can interact with one another in an intricate manner, and any single factor or combination of factors is capable of triggering the events leading to reperfusion failure. The pronounced regional nature of reperfusion injury and the direct relationship between the severity of the observed vascular alterations and increasing duration of ischemia have been documented. The dynamic changes and histopathology of the microcirculation included constriction of the arteries, swelling of endothelial and leukocytes, and erythrocyte rouleaux formation during ischemia. As ischemia duration was lengthened, the degree of these changes increased correspondingly. The changes on reperfusion were disruption of blood flow patterns, vortex formation, regional stasis, adhesion and migration of leukocytes, focal hemorrhage, edema, vasospasm, and platelet aggregation. The deleterious effects of systemic acidosis, interstitial hemorrhage, denervation, and prolonged venous occlusion were subsequently documented. The application of information gained from this series of laboratory experiments has resulted in continued improvement in the success rate in clinical microvascular surgery.

Meniscal fixation with an absorbable staple. An experimental study in dogs.

An absorbable staple for meniscal fixation was developed and evaluated in an in vivo canine study. The staple consisted of two rigid barbed legs, made of a copolymer of polyglycolic acid and polylactic acid, connected by a flexible suture made of the same absorbable material. The staple was developed for arthroscopic use, eliminating the risk of nerve or vascular injuries associated with suture fixation. Eighty-two mongrel dogs underwent meniscal repair in this study, which was performed in two sequential parts. An incision was made in the medial meniscus at the peripheral third and was fixed with either the staple or with a single 3-0 PDS suture. The animals from the first part of the study, in which the biocompatibility of a prototype staple design, was evaluated were sacrificed at 3 days, 2 weeks, 6 weeks, 3 months, and 9 months. Those from the second part of the study, in which an improved staple design of the same material, was evaluated were sacrificed at 6 weeks, 4 months, and 1 year. The operated menisci were either examined histologically or were mechanically tested for tensile strength. Absorption of the staple began by 3 months and was almost complete by 1 year. Mechanically, the staple provided greater tensile strength augmentation of the meniscus than suture fixation for up to 4 months. In the long term, there was no difference between the staple and suture in enhancement of healing.

Anticardiolipin antibodies and osteonecrosis of the femoral head.

The current study evaluated the prevalence of anticardiolipin antibodies, which have been associated with thrombotic phenomena, in patients with nontraumatic osteonecrosis of the hip and assessed whether the presence of such antibodies is associated with an increased risk for the development of bone necrosis. Forty consecutive patients (25 men and 15 women) with nontraumatic osteonecrosis of the hip were studied. Their ages ranged from 19 to 56 years (average, 34.3 years). Anticardiolipin antibodies were present in 37.5% (15 of 40) of the tested patients, a significantly higher rate than is seen in healthy subjects, of whom only one of 100 had low titer anticardiolipin antibodies (1%). Six of 40 patients tested positive for immunoglobulin M alone, and six of 40 patients tested positive for immunoglobulin A alone. Three of 40 patients tested positive for immunoglobulin M and immunoglobulin A isotype. The results of the current study indicate an increased incidence of anticardiolipin antibodies in patients with nontraumatic osteonecrosis of the femoral head, which may reflect that anticardiolipin antibodies play a role in the pathogenesis of bone necrosis by predisposing to thrombotic phenomena.