Free flap transfer to the dorsum of the rat: a new technique to avoid autocannibalization in free flap studies

In this report the authors describe a new method that avoids autocannibalization by free transfer of a flap to the dorsum of the rat by means of a simple exposure technique. A total of 22 Wistar rats of both sexes (weight, 200-290 g) were used in this experiment. An anatomic study performed in 12 rats revealed that a wide exposure could be created in the axillary fossa by retracting the inferior tip of the scapular bone superiorly (after severing its attachments with the deep extrinsic back muscles), the latissimus dorsi muscle laterally, and the serratus anterior muscle medially. Furthermore, after obtaining vessel diameter measurements, it was ascertained that the subscapular and the lateral thoracic vessels could serve as the recipient vessels. Based on the anatomic study, a total of 10 conventional groin cutaneous flaps, measuring 2 x 3 cm in size, were harvested based on the femoral vessels and transferred to the dorsum of the same animal by the exposure method as just described, with microvascular anastomoses performed between the femoral vessels of the flap and either the subscapular artery and the lateral thoracic vein (N = 5) or the lateral thoracic artery and vein (N = 5). Results showed that 9 of the 10 transplanted flaps were totally viable on postoperative day 7, giving a success rate of 90%, with one failing flap belonging to the latter group. The authors conclude that by this simple method of recipient vessel exposure in the axillary fossa, free flap transfer to the dorsum of the rat is a simple and reproducible technique by microvascular anastomoses performed between the pedicle vessels of a flap and the subscapular artery and the lateral thoracic vein. This model offers the unique advantage of a dorsally located flap that is protected by autocannibalization. Moreover, daily observation and monitoring of the flap are easy and practical without the need to have the animal wear protective material such as vest.

Enhancing the effectiveness of drug-based cancer therapy by electroporation (electropermeabilization)

Many conventional chemotherapeutic drugs, as well as DNA for cancer gene therapy, require efficient access to the cell interior to be effective. The cell membrane is a formidable barrier to many of these drugs, including therapeutic DNA constructs. Electropermeabilization (EP, often used synonymously with "electroporation") has become a useful method to temporarily increase the permeability of the cell membrane, allowing a broad variety of molecules efficient access to the cell interior. EP is achieved by the application of short electrical pulses of relatively high local field strength to the target tissue of choice. In cancer therapy, EP can be applied in vivo directly to the tumor to be treated, in order to enhance intracellular uptake of drugs or DNA. Alternatively, EP can be used to deliver DNA into cells of healthy tissue to achieve longer-lasting expression of cancer-suppressing genes. In addition, EP has been used in ex vivo therapeutic approaches for the transfection of a variety of cells in suspension. In this paper, we communicate results related to the development of a treatment for squamous cell carcinomas of the head and neck, using electropermeabilization to deliver the drug bleomycin in vivo directly into the tumor cells. This drug, which is not particularly effective as a conventional therapeutic, becomes highly potent when the intracellular concentration is enhanced by EP treatment. In animal model experiments we found a drug dose of 1 U/cm(3) tumor tissue (delivered in 0.25 mL of an aqueous solution/cm3 tumor tissue) and an electrical field strength of 750 V/cm or higher to be optimal for the treatment of human squamous cell tumors grown subcutaneously in mice. Within 24-48 hours, the majority of tumor cells are rapidly destroyed by this bleomycin-electroporation therapy (B-EPT). This raises the concern that healthy tissue may be similarly affected. In studies with large animals we showed that normal muscle and skin tissue, normal tissue surrounding major blood vessels and nerves, as well as healthy blood vessels and nerves themselves, are much less affected than tumor tissue. Normal tissues did show acute, focal, and transitory effects after treatment, but these effects are relatively minor under standard treatment conditions. The severity of these effects increases with the number of electric pulse cycles and applied voltage. The observed histological changes resolved 20 to 40 days after treatment or sooner, even after excessive EP treatment. Thus, B-EPT is distinct from other ablative therapies, such as thermal, cryo, or photodynamic ablation, which equally affect healthy and tumor tissue. In comparison to surgical or radiation therapy, B-EPT also has potential as a tissue-sparing and function-preserving therapy. In clinical studies with over 50 late stage head and neck cancer patients, objective tumor response rates of 55-58%, and complete tumor response rates of 19-30% have been achieved.

Adreno- and cholinoreactivity of the vascular system under the influence of low temperature

The influence of low temperature results in the activation of a sympathetic division of the vegetative nervous system (mostly alpha2-artery adrenoreceptors). The data concerning the tone of the parasympathetic department are inconsistent. In studies carried out in experimental animals (rabbits), the cholinoreactivity of arterial vessels was investigated. After a single cooling the depressing action of acetylcholin on arterial vessels grows only because of an increase of the quantity of active (Pm) M-cholinoreceptors of vessels (by 66.6%) with a decrease of their sensitivity (1/K = 4) by 33.3%. By day 30 of cold depressing adaptation the action of acetylcholin grows (with doses 0.02-0.1 mkg/kg) only because of an increase of M-cholinoreceptors sensitivity by 233%. The reduction of the depressing action on arteries of acetylcholin with dozes of 0.2-0.8 mkg/kg is explained by a decrease of the quantity of active M-cholinoreceptors in these terms of the cold influence (by 41% as compared with a control group). According to the results the efficiency of the interaction (E = (Pm/2)*R)) of acetylcholin with M-cholinoreceptors of vessels grows by 96% (with E = 300 mm/m.c./1 mkg/kg in a control group up to E = 588 after 30 day's adaptation to cold).

Compartment syndromes

The compartment syndrome is defined as a condition in which high pressure within a closed fascial space (muscle compartment) reduces capillary blood perfusion below the level necessary for tissue viability'. This condition occurs in acute and chronic (exertional) forms, and may be secondary to a variety of causes. The end-result of an extended period of elevated intramuscular pressure may be the development of irreversible tissue injury and Volkmann's contracture. The goal of treatment of the compartment syndrome is the reduction of intracompartmental pressure thus facilitating reperfusion of ischaemic tissue and this goal may be achieved by decompressive fasciotomy. Controversy exists regarding the critical pressure-time thresholds for surgical decompression and the optimal diagnostic methods of measuring intracompartmental pressures. This paper will update and review some current knowledge regarding the pathophysiology, aetiology, diagnosis, and treatment of the acute compartment syndrome.

Effect of chronic ethanol ingestion and exercise training on skeletal muscle in rat

The aim of this study was to investigate the interactive effects of exercise training and chronic ethanol consumption on metabolism, capillarity, and myofibrillar composition in rat limb muscles. Male Wistar rats were treated in separate groups as follows: non exercised-control; ethanol (15%) in animals' drinking water for 12 weeks; exercise training in treadmill and ethanol administration plus exercise for 12 weeks. Ethanol administration decreased capillarity and increased piruvate kinase and lactate dehydrogenase activities in white gastrocnemius; in plantaris muscle, ethanol increased citrate synthase activity and decreased cross-sectional area of type I, IIa, and IIb fibres. Exercise increased capillarity in all four limb muscles and decreased type I fibre area in plantaris. The decreased capillarity effect induced by ethanol in some muscles, was ameliorated when alcohol was combined with exercise. While alcoholic myopathy affects predominantly type IIb fibres, ethanol administration and aerobic exercise in some cases can affect type I and type IIa fibre areas. The exercise can decrease some harmful effects produced by ethanol in the muscle, including the decrease in the fibre area and capillary density.

Delayed muscle injuries in arterial insufficiency: contrast-enhanced MR imaging and 31P spectroscopy in rats

PURPOSE

To evaluate whether the vascular system resulting from an arterial lesion shows differences in permeability to a tracer with respect to the normal vascular system and whether eventual differences are maintained for long periods.

MATERIALS AND METHODS

Permanent ischemia was induced in rats with femoral arterial removal, and magnetic resonance (MR) imaging was performed after 1, 7, 14, and 90 days. Gadopentetate dimeglumine was injected, and the kinetics of its penetration in the leg were studied. Phosphorus 31 spectroscopy was performed to determine the bioenergetic characteristics of the gastrocnemius muscle at rest and stimulation. Ischemic muscles were then processed for electron microscopy.

RESULTS

After ischemia induction, a hyperintense area that progressively decreased was present on T2-weighted images. Gadopentetate dimeglumine improved the signal intensity of the area. Three months after arterial occlusion, the contrast-enhanced images still showed microvessels highly permeable to the tracers. Spectroscopic data revealed that 3 months after arterial removal, the bioenergetic reserve of the gastrocnemius muscle was reduced, suggesting that the contrast-enhanced MR imaging-visible area is functionally relevant. Ultrastructural examination revealed persistent muscle damage and signs of chronic microangiopathy.

CONCLUSION

After ischemia induction, the restitutio ad integrum is not complete, and delayed muscle injuries can result from arterial insufficiency.

Monitoring blood oxygen state in muscle microcirculation with transverse relaxation

Oxygen uptake from the microcirculation is a direct measure of tissue function. Magnetic resonance is capable of detecting differences between oxygenated and deoxygenated blood due to the paramagnetic properties of deoxyhemoglobin. At the level of the microcirculation, however, imaging methods cannot directly visualize the vessels. Instead, bulk MR parameters are investigated for their ability to monitor blood oxygen saturation (%O(2)) changes in the microcirculation of tissue, specifically skeletal muscle. Experiments in an in vitro model verified the feasibility of detecting changes in exponential decay signals, and also verified the prediction of only two distinct decay components. Experiments in a rabbit model demonstrate that T(2)' and monoexponential T(2) decay are not sensitive to blood oxygen changes, but that the long-T(2) component in a biexponential fit is correlated to the blood oxygen state. Assuming a two-pool model for water protons in muscle, and with knowledge of the T(2)-%O(2) relation, estimates of the microcirculation blood oxygen state can be made with some reasonable assumptions. Magn Reson Med 45:662-672, 2001.

Assessment of peripheral arterial vascular disease with radionuclide techniques

Various radioisotopic imaging techniques for noninvasive detection of vessel stenosis and for functional investigation of reduced blood flow and follow-up have been developed during the last decade in peripheral vascular disease (PVD), with the aim of replacing invasive techniques and complementing standardized methods. Radionuclide assessment of PVD is divided into 2 major groups: imaging of perfusion and metabolic investigations. The measurement of arterial blood flow and muscle perfusion is intended to show the morphology, to evaluate the functional consequences of PVD, and to quantify the latter. The application of radiolabeled tracers was developed as a noninvasive alternative to angiography in morphologic imaging. Treadmill testing has been used to assess the functional effects of reduced blood flow in PVD where the onset of pain indicates the stage of disease, but the results can be confused by other symptoms. Scintigraphic measurement of muscle perfusion should detect insufficient nutritional blood flow in peripheral muscle and thus have a higher specificity for PVD than treadmill testing alone. Although there are very promising theoretical and experimental data in animals, the clinical use of radionuclide investigations is limited by different technical problems, such as methodologic differentiation between skin and muscle perfusion, the lack of controlled and prospective studies, and incomplete correlation with other standardized routine techniques. Among the great number of radioisotopic metabolic imaging techniques, only radiolabeled platelets and lipoproteins, to some extent, have shown a limited potential clinical use. Some other approaches seem to have a high potential from a theoretical point of view. They are limited, however, by a great number of problems. Correlation with sonographic or magnetic resonance imaging (MRI) findings may identify a potential metabolic value. Correlation with angiography reflecting the extent of the disease makes no sense. So far with PVD, neither radioisotopic perfusion studies nor metabolic imaging techniques are able to achieve a level of routine application or wider meaningful interpretation of the clinical condition of a specific patient. Competing techniques are easier to perform, less expensive, faster, more widely available, and do not carry the radiation burden. Positron emission tomography is still in its early stages of application, with great theoretical potential but at a high price. A great deal of work is still required to transform in vitro and experimental experience into more meaningful routine radioisotopic investigations in patients with PVD.

Non-invasive determination of muscle blood flow in the extremities from laser Doppler spectra

We investigate theoretically the non-invasive determination of blood flow in muscles of the extremities using laser Doppler measurements. Laser Doppler spectra are calculated using Monte Carlo simulations and solutions of the correlation diffusion equation. The extremities are modelled as a two-layered turbid medium. The first layer represents the skin and subcutaneous fat layer and the second layer the muscle. It is shown that the absolute root-mean-square velocity of the blood in the muscle layer can be accurately derived in many practical cases if the laser Doppler spectra are measured at a distance which is sufficiently far from the source, and if the optical properties of the muscle are simultaneously determined.

Comparative effects of combretastatin A-4 disodium phosphate and 5,6-dimethylxanthenone-4-acetic acid on blood perfusion in a murine tumour and normal tissues

PURPOSE

To compare the ability of combretastatin A-4 disodium phosphate (CA4DP) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) to change tissue blood perfusion.

MATERIALS AND METHODS

The tissues were a C3H mouse mammary carcinoma and various murine normal tissues, with perfusion measured using the 86RbCl extraction technique.

RESULTS

CA4DP (250mg/kg; i.p.) reduced tumour perfusion to 34% of that seen in controls within 1 h of injection. It was maintained at this for at least 6 h, returning to control levels by 24 h. This decrease was dose-dependent. DMXAA (25mg/kg; i.p.) caused a 79% reduction in tumour perfusion 6h after injection; no recovery was observed even after 24 h. DMXAA showed no changes at doses below 10 mg/kg. Both CA4DP and DMXAA increased perfusion in the gut, kidney, bladder and lung, while decreasing splenic perfusion. CA4DP tended to decrease perfusion in muscle, while DMXAA increased liver perfusion. These changes in normal tissue perfusion were generally less than those changes seen in tumours. No significant changes were seen in skin.

CONCLUSIONS

CA4DP and DMXAA produced a selective and significant reduction in tumour perfusion, but the pattern of change was different. These results suggest how these vascular targeting drugs should be combined with more conventional therapies.

Differential inhibition of functional dilation of small arterioles by indomethacin and glibenclamide

Indomethacin or glibenclamide treatments attenuate functional dilation of larger-diameter "feed" arterioles paired with venules in hamster cremaster muscle. We tested the hypothesis that release of cyclooxygenase products from venules is important for functional dilation of third- and fourth-order arterioles. We also tested whether ATP-sensitive potassium channels are important during functional dilation of smaller arterioles. The microcirculation of hamster cremaster muscle was visualized with in vivo video microscopy. We measured diameter responses of third- and fourth-order arterioles paired and unpaired with venules in response to 2 minutes of muscle field stimulation (40 microseconds, 10 V, 1 Hz). Control diameters of vessels were 31+/-2 (n=19), 13+/-1 (n=12), 12+/-2 (n=12), and 10+/-1 (n=12) for paired and unpaired third-order and paired and unpaired fourth-order arterioles, respectively. In all groups, field stimulation resulted in increases in mean control diameter of >80%. Indomethacin (28 micromol/L) superfused on the preparation was used to inhibit cyclooxygenase metabolism, or glibenclamide (10 micromol/L) was used to block ATP-sensitive potassium channels. Indomethacin attenuated arteriolar vasodilations to electrical stimulation in paired third-order vessels only, whereas glibenclamide attenuated this vasodilation in all 4 groups. These results support a role for ATP-sensitive potassium channels in functional dilation of arterioles of all sizes regardless of whether or not they are paired with venules. Conversely, a role for cyclooxygenase products is limited to larger "feed arterioles" paired with venules. This study provides further evidence that venules may be the source of prostaglandin release during functional hyperemia.

Review and case report of idiopathic lower extremity compartment syndrome and its treatment in diabetic patients

Diabetic muscle infarction is a rare complication of diabetes mellitus. However, idiopathic compartment syndrome in the diabetic patient is even a rarer disease, which has been reported only in three cases up to date. The disease seems to occur in patients affected by type 1 diabetes mellitus with a history of poorly controlled glucose levels. MRI aids in the diagnosis by delineating the edema of the muscle. However, definitive diagnosis is made using the Stryker needle unit. Treatment is accomplished by immediate two-incision fasciotomy. We present a case where a 34 yr-old female with a long standing history of poorly controlled Type 1 diabetes mellitus presented with a painful right lower extremity and was diagnosed with compartment syndrome. In our patient, a single incision fasciotomy to release the pressure was sufficient and might be considered as an alternative and less morbid procedure in the diabetic patient with already poorly healing tissues. We conclude that the muscle infarction in these patients is from diffuse microangiopathic disease leading to muscular infarction and fluid accumulation in the cells causing a decrease in the space in the compartment in question causing compartment syndrome.

Bipedicle paraspinous muscle flaps for spinal wound closure: an anatomic and clinical study

The purpose of this study was to evaluate the vascular anatomy of the paraspinous muscles and review their clinical use as bipedicled flaps in spinal wound closure. Anatomically, through cadaver dissections, lead oxide injections, and radiographic imaging, the blood supply to the paraspinous muscles was determined. Clinically, 29 consecutive patients treated with spinal wounds and exposed bone or hardware were reviewed retrospectively. Of these patients, 19 underwent closure in delayed primary fashion, whereas 10 were referred to plastic surgery for reconstruction because of the complex nature of their wounds. The cadaver study demonstrated the paraspinous muscles to possess a segmental arterial supply through medial and lateral perforators. Division of the medial perforators allowed for medial advancement of the muscles. Lead oxide injection of the lateral perforators demonstrated adequate medial muscle perfusion with ligation of the medial perforators. Ten of the 29 patients (six women, four men, 32 to 62 years of age) were reconstructed with paraspinous (eight), latissimus (one), and trapezius (one) muscle flaps. A higher complication rate was found in wounds closed in delayed primary fashion (13 of 19 patients, 68 percent) than those reconstructed with muscle flaps (2 of 10 patients, 20 percent) (p = 0.021). Follow-up of the muscle flap reconstructed patients averaged 12 months (range, 3 to 27 months). Cadaver muscle injections predicted and clinical cases confirmed that the paraspinous muscles can be raised on lateral perforators and advanced medially to close lumbar spine wounds reliably with fewer complications.

Failure of laser Doppler signal to correlate with total flow in muscle: is this a question of vessel architecture?

The signal strength from LDF probes positioned in perfused muscle can be altered by vasoconstrictors despite total flow being maintained constant. Apart from redistribution of flow via collateral channels outside the region of measurement, the change in LDF signal may arise because the vasoconstrictors have switched flow to vessels of different architecture or altered the architecture of the blood vessels being perfused. Thus we have examined the effect of tube architecture on LDF signal using polymer tubes of 250, 100, and 50 microm internal diameter. At 3% hematocrit the LDF signal was linear for each of the three tube sizes from 10 to 80 microl/h. The signal strength was greatest from the smallest tube and least from the largest tube. For a single tube (100 microm) that doubled back on itself twice to cross the field of measurement three times, the LDF signal at any flow (10-80 microl/h, hematocrit 3%) was approx threefold greater than that for the same tube crossing the field of measurement once. The effect of progressively switching flow (constant at 120 microl/h, hematocrit 9%) from five to one tube in a manifold of five tubes (100 microm) gave rise to a progressive increase in signal. It is concluded that LDF signal derives predominantly from nonvectorial cell speed and less from cell number. Thus any agent that alters the architecture has the potential to alter the LDF signal.

Skeletal muscle kinetics of propofol in anaesthetized sheep: effect of altered muscle blood flow

1. The kinetics of propofol were studied in vivo in a skeletal muscle bed of the hindlimb of the anaesthetized sheep at normal and low rates of blood flow. 2. Propofol kinetics in muscle were determined during and after a 20-min i.v. infusion of propofol (10 mg min-1) via paired arteriofemoral venous blood sampling. One-and-a-half hours later, the study was repeated but with a concurrent left femoral artery infusion of adrenaline (0.004 mg min-1) to lower the muscle blood flow by vasoconstriction. 3. Muscle blood flow in the low flow state was 28% of that in the normal state. The kinetics were poorly described by a single flow-limited compartment model, but were better described by a model with a flow-limited component and a deeper distribution component. There were no significant differences in muscle retention of propofol between normal and low flow states. 4. There was an apparent arteriovenous shunt of approximately 24% of total muscle blood flow for the low flow state, but not for the normal blood flow state.

Important role of CD18 in TNF-alpha-induced leukocyte adhesion in muscle and skin venules in vivo

OBJECTIVE

To examine the role of CD 18 in tumor necrosis factor-alpha (TNF-alpha)-induced leukocyte adhesion and extravasation in vivo.

MATERIAL

Male wild-type (WT) and mutated mice with hypomorphic expression of CD 18.

METHODS

Intravital microscopy was used to quantitate leukocyte-endothelium interactions provoked by TNF-alpha (0.5 microg) in the cremaster muscle and dorsal skin microcirculation. Tissue recruitment of leukocytes was evaluated in wholemounts of the cremaster muscle and in air pouches in the dorsal skin after TNF-alpha stimulation.

RESULTS

TNF-alpha markedly increased venular leukocyte adhesion and recruitment in the cremaster muscle and skin in WT. Notably, in CD 18-targeted animals, leukocyte adhesion triggered by TNF-alpha challenge was significantly reduced by 58% and 72% in venules of the cremaster muscle and skin, respectively. Moreover, in CD18-mutants, tissue accumulation of polymorphonuclear leukocytes (PMNLs) provoked by TNF-alpha in the muscle and skin was decreased by 84% and 70%, respectively. Interestingly, the observed level of reduction in TNF-alpha-induced neutrophil adhesion and recruitment in CD18 gene-targeted animals corresponded well with the decrease in CD 18 expression on neutrophils from these mice, i.e. the surface density of CD18 was reduced by 77% in mutants compared to WT. Differential analysis revealed that the extravascular leukocytes comprised more than 90% PMNLs, indicating that neutrophils were the main inflammatory cell responding to TNF-alpha activation. Notably, the expression of CD18 increased by more than two-fold on extravasated neutrophils compared to circulating neutrophils in the peripheral blood both in WT and mutant animals.

CONCLUSIONS

These findings suggest that CD18 is a dominant mediator of firm neutrophil adhesion to venular endothelial cells in the muscle and skin stimulated by TNF-alpha in vivo. In addition, this decreased adhesion in CD18-mutants attenuates leukocyte extravasation in response to TNF-alpha activation. Thus, inhibition of CD 18-function may provide an important strategy to inhibit leukocyte recruitment in cytokine-dependent diseases.

From the outside looking in. The surgical approach

This series of articles will draw on Physiology and Anatomy, a homeostatic approach (hereafter referred to as 'the reader'), written by John Clancy and Andrew McVicar. There will also be cross-references to the series of articles entitled 'Homeostasis--the key concept to physiological control' published in the British Journal of Theatre Nursing 1996-98. The articles will include some activities which the readers can carry out to test their understanding and deepen their knowledge base of the anatomy explored in each article. The introductory article will cover the common anatomical structures involved in the 'surgical approach', looking first at the anatomy and then relating it to surgical practice. Homeostasis is the key underlying principle to which the surgical practice will refer.

Congenital macroglossal angiodysplasia ("Lymphangioendotheliomatosis")

A case of congenital lingual angiodysplasia with macroglossia in a 5-year-old girl is presented. A diffusely enlarged tongue was present at birth and continued to grow as the child aged. It was accompanied by impaired speech, difficulty in eating and breathing, and sleep apnea, necessitating surgical intervention. The fundamental lesion represents a complex vascular malformation of the lymphangioma-hemangioma type, involving extensively the deep musculature of the tongue. Multifocal and multicentric cavernous lymphangioma-like and hemangioma-like areas merge with benign angioendotheliomatous-like foci in a background of variable muscle degeneration and marked fibrosis. Neither a borderline nor an overtly malignant vasoformative neoplasm was present. Because of its distinctively widespread, multicentric intramuscular distribution, this lesion may be construed as a diffuse variant of lingual lymphangioma-hemangioma malformation, closely resembling a previously described case of macroglossal lymphangioendotheliomatosis.

Clostridial gas gangrene. I. Cellular and molecular mechanisms of microvascular dysfunction induced by exotoxins of Clostridium perfringens

Mechanisms responsible for the rapid tissue destruction in gas gangrene are not well understood. To examine the early effects of Clostridium perfringens exotoxins on tissue perfusion, a rat model of muscle blood flow was developed. Intramuscular injection of a clostridial toxin preparation containing both phospholipase C (PLC) and theta-toxin caused a rapid (1-2 min) and irreversible decrease in blood flow that paralleled formation of activated platelet aggregates in venules and arterioles. Later (20-40 min), aggregates contained fibrin and leukocytes, and neutrophils accumulated along vascular walls. Flow cytometry confirmed that these clostridial toxins or recombinant PLC induced formation of P-selectin-positive platelet aggregates. Neutralization of PLC activity in the clostridial toxin preparation completely abrogated human platelet responses and reduced perfusion deficits. It is concluded that tissue destruction in gas gangrene is related to profound attenuation of blood flow initiated by activation of platelet responses by PLC.