Evaluation Of Tissue Damage Research Articles

Histological evaluation of tissue damage caused by rotational needle insertion.

Needles used in percutaneous insertion must be as thin as possible to minimize invasiveness. However, using extra-thin needles with a diameter less than 25G (0.53 mm diameter) can cause needle deflection. Needle deflection can be minimized by insertion with axial rotation along the needle shaft; this rotation is also useful for steering the insertion direction of the needle tip. However, although high rotation speeds may decrease needle deflection, this may increase tissue damage. Therefore, the purpose of this study was to histologically evaluate tissue damage caused by the rotational needle-insertion method, and to verify the needle-tip deflection caused by tissue damage. In this paper, we evaluated tissue damage and needle deflection caused by needle insertion with no rotation, unidirectional rotation, and bidirectional rotation. The results suggest that percutaneous needle insertion under unidirectional rotation is potentially risky in humans, as this causes wound-up tissue and expansion of the area of the hole created by the needle path. In contrast, needle insertion under bidirectional rotation appeared to minimize deflection, and prevented winding of tissue and expansion of the hole created by the needle path.

Magnetic Resonance Imaging Allows the Evaluation of Tissue Damage and Regeneration in a Mouse Model of Critical Limb Ischemia.

Magnetic resonance imaging (MRI) provides non-invasive, repetitive measures in the same individual, allowing the study of a physio-pathological event over time. In this study, we tested the performance of 7 Tesla multi-parametric MRI to monitor the dynamic changes of mouse skeletal muscle injury and regeneration upon acute ischemia induced by femoral artery dissection. T2-mapping (T2 relaxation time), diffusion-tensor imaging (Fractional Anisotropy) and perfusion by Dynamic Contrast-Enhanced MRI (K-trans) were measured and imaging results were correlated with histological morphometric analysis in both Gastrocnemius and Tibialis anterior muscles. We found that tissue damage positively correlated with T2-relaxation time, while myofiber regeneration and capillary density positively correlated with Fractional Anisotropy. Interestingly, K-trans positively correlated with capillary density. Accordingly, repeated MRI measurements between day 1 and day 28 after surgery in ischemic muscles showed that: 1) T2-relaxation time rapidly increased upon ischemia and then gradually declined, returning almost to basal level in the last phases of the regeneration process; 2) Fractional Anisotropy dropped upon ischemic damage induction and then recovered along with muscle regeneration and neoangiogenesis; 3) K-trans reached a minimum upon ischemia, then progressively recovered. Overall, Gastrocnemius and Tibialis anterior muscles displayed similar patterns of MRI parameters dynamic, with more marked responses and less variability in Tibialis anterior. We conclude that MRI provides quantitative information about both tissue damage after ischemia and the subsequent vascular and muscle regeneration, accounting for the differences between subjects and, within the same individual, between different muscles.

Multiscale cartilage biomechanics: technical challenges in realizing a high-throughput modelling and simulation workflow.

Understanding the mechanical environment of articular cartilage and chondrocytes is of the utmost importance in evaluating tissue damage which is often related to failure of the fibre architecture and mechanical injury to the cells. This knowledge also has significant implications for understanding the mechanobiological response in healthy and diseased cartilage and can drive the development of intervention strategies, ranging from the design of tissue-engineered constructs to the establishment of rehabilitation protocols. Spanning multiple spatial scales, a wide range of biomechanical factors dictate this mechanical environment. Computational modelling and simulation provide descriptive and predictive tools to identify multiscale interactions, and can lead towards a greater comprehension of healthy and diseased cartilage function, possibly in an individualized manner. Cartilage and chondrocyte mechanics can be examined in silico, through post-processing or feed-forward approaches. First, joint-tissue level simulations, typically using the finite-element method, solve boundary value problems representing the joint articulation and underlying tissue, which can differentiate the role of compartmental joint loading in cartilage contact mechanics and macroscale cartilage field mechanics. Subsequently, tissue-cell scale simulations, driven by the macroscale cartilage mechanical field information, can predict chondrocyte deformation metrics along with the mechanics of the surrounding pericellular and extracellular matrices. A high-throughput modelling and simulation framework is necessary to develop models representative of regional and population-wide variations in cartilage and chondrocyte anatomy and mechanical properties, and to conduct large-scale analysis accommodating a multitude of loading scenarios. However, realization of such a framework is a daunting task, with technical difficulties hindering the processes of model development, scale coupling, simulation and interpretation of the results. This study aims to summarize various strategies to address the technical challenges of post-processing-based simulations of cartilage and chondrocyte mechanics with the ultimate goal of establishing the foundations of a high-throughput multiscale analysis framework. At the joint-tissue scale, rapid development of regional models of articular contact is possible by automating the process of generating parametric representations of cartilage boundaries and depth-dependent zonal delineation with associated constitutive relationships. At the tissue-cell scale, models descriptive of multicellular and fibrillar architecture of cartilage zones can also be generated in an automated fashion. Through post-processing, scripts can extract biphasic mechanical metrics at a desired point in the cartilage to assign loading and boundary conditions to models at the lower spatial scale of cells. Cell deformation metrics can be extracted from simulation results to provide a simplified description of individual chondrocyte responses. Simulations at the tissue-cell scale can be parallelized owing to the loosely coupled nature of the feed-forward approach. Verification studies illustrated the necessity of a second-order data passing scheme between scales and evaluated the role that the microscale representative volume size plays in appropriately predicting the mechanical response of the chondrocytes. The tools summarized in this study collectively provide a framework for high-throughput exploration of cartilage biomechanics, which includes minimally supervised model generation, and prediction of multiscale biomechanical metrics across a range of spatial scales, from joint regions and cartilage zones, down to that of the chondrocytes.

Synchrotron X-ray CT of rose peduncles – evaluation of tissue damage by radiation*

Abstract “Bent-neck” syndrome, an important postharvest problem of cut roses, is probably caused by water supply limitations and/or the structural weakness of vascular bundles of the peduncle tissue. For this reason, advanced knowledge about the microstructures of rose peduncles and their cultivar specific variations may lead to a better understanding of the underlying mechanisms. Synchrotron X-ray computed tomography (SXCT), especially phase-based CT, is a highly suitable technique to nondestructively investigate plants’ micro anatomy. SXCT with monochromatic X-ray beams of 30, 40 and 50 keV photon energy was used to evaluate the three-dimensional inner structures of the peduncles of 3 rose cultivars that differ greatly in their bent-neck susceptibility. Results indicated that this technique achieves sufficiently high spatial resolution to investigate complex tissues. However, further investigations with chlorophyll fluorescence analysis (CFA) and optical microscope imagery reveal different kinds of heavy damage of the irradiated regions induced by synchrotron X-rays; in a cultivar-specific manner, partial destruction of cell walls occurred a few hours after X-ray irradiation. Furthermore, a delayed inhibition of photosynthesis accompanied by the degradation of chlorophyll was obvious from CFA within hours and days after the end of CT measurements. Although SXCT is certainly well suited for three-dimensional anatomical analysis of rose peduncles, the applied technique is not nondestructive.

Pioglitazone attenuates lung injury by modulating adipose inflammation

BackgroundPioglitazone modulates adipocyte differentiation and enhances adiponectin promoter activity to increase plasma adiponectin levels. We investigated the effects of pioglitazone on cecal ligation and puncture (CLP)-induced visceral-adipose-tissue inflammation and lung injury in mice. Materials and methodsEight-wk-old male mice were assigned to three groups: (1) a sham-operated control group, (2) a CLP group, and (3) a pioglitazone-treated CLP group. Pioglitazone (10 mg/kg) was injected intraperitoneally for 7 d. Serum, lung, and visceral adipose tissue were collected 24 h after surgery. Tumor necrosis factor α (TNF-α) levels in peritoneal lavage fluid were measured by an enzyme-linked immunosorbent assay, and TNF-α and interleukin 6 messenger RNA (mRNA) expression levels in visceral adipose tissue were quantified by real-time polymerase chain reaction. Lung tissue specimens were stained with hematoxylin-eosin, and the terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling method was used to evaluate tissue damage. ResultsTNF-α levels in peritoneal lavage fluid were significantly higher in the CLP group than in the sham group. TNF-α levels in the pioglitazone-treated CLP group were significantly lower than those in the CLP group. TNF-α and interleukin 6 mRNA expression levels of visceral adipose tissue were significantly higher in the CLP group than in the sham group. Pioglitazone treatment decreased the mRNA expression levels of these cytokines compared with the respective values in the CLP group. Histopathologic analysis of lung tissue revealed significantly increased numbers of terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling–positive cells in the CLP group compared with the sham group. ConclusionsPioglitazone effectively prevents lung injury caused by CLP-induced sepsis by maintaining the anti-inflammatory status of visceral adipose tissue.

Comparison of tissue damage, cleansing and cross‐contamination potential during wound cleansing via two methods: lavage and negative pressure wound therapy with instillation

The use of lavage was compared to negative pressure wound therapy (NPWT) with instillation (NPWTi) to assess extent of soft tissue damage, debris removal and environmental cross-contamination susceptibility in three distinct models. Scanning electron microscopy in an ex vivo model showed increased visible tissue trauma from lavage treatment at low and high pressures versus NPWTi, with the degree of trauma relative to the pressure of the irrigant. These results were corroborated in granulating full-thickness excisional swine wounds coated with dextran solution to simulate wound debris. Both low-pressure lavage and NPWTi demonstrated effective cleansing in this model, reducing debris by >90%. However, using three-dimensional photography to evaluate tissue damage by measuring immediate tissue swelling (changes in wound volume and depth) showed significantly greater (P < 0.05) swelling in low-pressure lavage-treated wounds compared with NPWTi-treated wounds. Lastly, bench top wound models were inoculated with fluorescent bacterial particles to assess environmental cross-contamination potential and collected at measured distances after treatment with low-pressure lavage and NPWTi. No evidence of cross-contamination was found with NPWTi, whereas one-half of the particles became 'aerosolised' during low-pressure lavage (P < 0.05). Collectively, these studies demonstrate the effective wound cleansing capabilities of NPWTi without the tissue damage and environmental contamination associated with lavage.

Anisakis pegreffii experimental challenge in Dicentrarchus labrax: An endoscopic study

To validate the use of imaging techniques to evaluate tissue damage in vivo, ten European sea bass (Dicentrarchus labrax) were anesthetized with MS-222 and experimentally infected with nematode larvae collected from three Lepidopus caudatus. Live nematode larvae were introduced by gastroscopy into the stomach of ten fish. Another challenge was performed 15days later. After a 60day period, an explorative celioscopy was carried out. Fish were examined for Anisakis larvae and biopsy samples were collected. Parasites sampled from L. caudatus and D. labrax were morphologically identified at genus level. Biopsy samples were routinely processed for histopathology. Some larvae were sampled for PCR. At gastroscopic exam 15days after the first challenge some live nematode larvae were found within the lumen of the stomach in four fish. Two months later, at celioscopy, four sea bass showed hemorrhages and/or irregular neoformations within the celomic cavity. Within each of these changes a single nematode larva was detected. Histopathology showed hemorrhagic lesions with a cystic aspect. Parasite larvae were identified as L3 stages Anisakis Type I. PCR-RFLP analysis has allowed the identification of larvae isolated as Anisakis pegreffii. Endoscopy is a suitable noninvasive procedure for evaluation of experimental challenges in sea bass using live Anisakis larvae. The evidence of tissue change is an unusual occurrence in fish parasitized by Anisakis. The paper sets out to assess the damage anisakid nematodes induce in infected fish by imaging techniques.

Histological quantification of the tissue damage caused by PlasmaJet™ coagulator

The purpose of this study was to evaluate tissue damage caused by the PlasmaJetTM coagulator in the uterus, ovary, and fallopian tube at different power settings in vitro and then to examine the damage caused in vivo. In vitro evaluation included prospective recruitment of six subjects undergoing hysterectomy with or without salpingo-oophorectomy. Tissue damage was evaluated histologically for power levels at 10%, 15%, and 20%, and for duration of 2 and 5 s at a clinically acceptable distance of 0.5 to 1 cm between the tip of probe and tissue. In vivo evaluation included 15 subjects undergoing hysterectomy with or without salpingo-oophorectomy. The most suitable power setting and duration of diathermy was decided from in vitro examination and applied on in vivo setting. Tissue damage was evaluated histologically. There was no significant difference seen in the depth and width of tissue damage in the in vitro specimens at different low power levels and duration of diathermy (P > 0.05). A setting of 20% power and duration of 5 s of diathermy was used therefore for in vivo setting. Mean ± SD depth (millimetres) of tissue damage in uterus, ovary, and fallopian tube were 0.63 ± 0.19, 0.61 ± 0.14, and 0.63 ± 0.18, respectively. Mean ± SD width (millimetres) of tissue damage in uterus, ovary, and fallopian tube were 4.66 ± 0.05, 4.05 ± 0.61, and 4.51 ± 0.77, respectively. Irrespective of tissue type, the average depth and width of tissue damage with application of PlasmajetTM coagulator for 5 s at low power is 0.62 and 4.24 mm, respectively. It therefore appears to be a safe method of coagulation in vitro and in vivo at 20% power on gynaecological tissues.

Monitoring prostate thermal therapy with diffusion‐weighted MRI

For MR-guided minimally invasive therapies, it is important to have a repeatable and reliable tissue viability evaluation method. The use of diffusion-weighted MRI (DWI) to evaluate tissue damage was assessed in 19 canine prostates with cryoablation or high-intensity ultrasound (HIU) ablation. The apparent diffusion coefficient (ADC) trace value was measured in the treated tissue immediately upon the procedure and on the posttreatment follow-up. For the acute lesions, the ADC value decreased to (1.05+/-0.25)x10(-3) mm2/s, as compared to (1.64+/-0.24)x10(-3) mm2/s before the treatment. There was no statistical difference between previously frozen or previously ultrasound-heated lesions in terms of the 36% ADC reduction (P=0.66). The ADC decrease occurred early during the course of the treatment, which appears to complicate DWI-based thermometry. Over time, the ADC value increased as the tissue recovered and regenerated. This study shows that DWI could be a promising method to monitor prostate thermal therapies and to provide insight on tissue damage and tissue remodeling after injury.

Isothermal calorimetry approach to evaluate tissue damage in carrot slices upon thermal processing

The purpose of this investigation was to test calorimetry as a means of quantifying cell damage occurring at various stages of mild blanching treatments. Calorimetric measurements were carried out on cores taken from carrot slices blanched at 100 °C for 5–45 s. The calorimetric data were corrected for the influence of wounding stress due to slicing and coring. The validity of calorimetry to measure cell damage was assessed by simulating inactivation of cell metabolism based on bibliographic data on thermal inactivation kinetics of plasma membrane H +-ATPase, used as a marker of overall cell membrane damage. Calorimetric data paralleled the simulated decrease of actively metabolizing cells only in the first 20 s of blanching but diverged at higher blanching times. Our results suggest that inactivation of enzymes responsible for quality-related changes during frozen storage (e.g. blanching at 100 °C for 20 s) may be accompanied by cell damage in about 70% of the tissue.

A 7‐Day Mouse Model to Assess Protection from Sulfur Mustard (SM) Skin Injury

The mouse ear vesicant model (MEVM) is a screening tool used to identify protective compounds against acute sulfur mustard (SM)‐induced skin injury. It provides endpoints of edema and histopathology 24 h following a topical SM exposure to assess protection against inflammation and tissue damage. To further evaluate successful compounds, the MEVM was modified for use as a 7‐day model. Dose response studies were conducted with SM to select an optimal challenge dose for the new model. Due to severity of SM‐induced tissue damage by Day 7, edema and histopathology were determined unreliable endpoints. Therefore, a modified Draize scoring system (no damage to extensive necrosis) was incorporated as an endpoint to evaluate tissue damage out to Day 7. To aid in optimal SM dose selection, retro synthetic capsaicin (RSCAP), a protective compound in the MEVM, was evaluated as a treatment 15 min before exposure to 0.06, 0.08, and 0.16 mg SM. The RSCAP compound provided similar significant protection at Day 7 against ...

White matter T 1 relaxation time histograms and cerebral atrophy in multiple sclerosis

T 1 relaxation time (T 1) provides a quantitative magnetic resonance imaging (MRI) parameter for evaluating tissue damage in the brain. We aimed to measure T 1 in the white matter of patients with multiple sclerosis (MS) and study relationships with cerebral atrophy, T 2 lesion load and clinical parameters. Twenty-six patients with relapsing–remitting MS and sixteen healthy controls were scanned with dual-echo T 2-weighted, 3-dimensional (3-D) magnetization-prepared rapid acquisition gradient echo and whole brain, multi-slice inversion recovery (IR) sequences. White matter masks were defined on axial T 1 map slices using semi-automated seed growing and normalized ‘total white matter’ T 1 histograms generated. Atrophy data was obtained using the Cavalieri method of modern design stereology. T 2 lesion volume was also determined using seed growing. T 1 histogram-derived measures (median, peak height, peak position and standard deviation) in MS patients were significantly different ( p<0.0001) from controls. Median T 1 correlated significantly with supratentorial ( r=0.42, p=0.036), lateral ventricle ( r=0.55, p=0.004), and T 2 lesion volumes ( r=0.84, p<0.0001), but not with clinical parameters. Total white matter T 1 provides a robust, quantitative measure of global disease burden in MS, and also correlates significantly with cerebral atrophy. Serial studies are required to determine its potential role as a surrogate marker of disease progression.

Magnetic Resonance Imaging of Experimental Microinfarctions in the Rabbit Brain

Small hyperintense lesions are frequently found with T2-weighted magnetic resonance imaging (MRI) of the human brain. A significant number of these lesions are probably infarctions. Because there is often a long delay between the microischemic impact and the autopsy, if any, and as the specificity of the MRI is low for detecting ischemic lesions, it is difficult to draw conclusions about the clinicotopographic correlations. This work concerns the usefulness of MRI in detecting experimental microischemic lesions in the rabbit brain about 24 h after the impact. It seems that the sensitivity of T2-weighted MRI in detecting foci of damaged areas in the rabbit brain is good enough to make it useful for evaluating tissue damage when screening for potential neuroprotective drugs and that the experimental model should be useful for developing diagnostically valuable MRI techniques.

Preservation of bladder tissue in different solutions for varying times.

To evaluate three popular storage media and the effect of 24-hour cold storage on bladder tissue. Guinea pig bladders were stored in three solutions: UW solution (a media used for transplant organs), Reznikoff solution [cell culture medium], and Krebs' solution with and without aeration. Cell potassium and sodium concentrations and total tissue water (a measurement of cell swelling) are important parameters for evaluating tissue damage. Reznikoff solution and Krebs' solution without gases maintained tissues for 24 hours with the least tissue damage; these solutions require no special equipment or attention. Twenty-four hour uniterrupted aeration of Krebs' solution caused the greatest degree of cell swelling with possible redistribution of receptors and required adjustment and regulation of the preservation apparatus. UW solution induced dehydration of cells, required the longest recovery period after cold storage, and is far more expensive than the other solutions. Reznikoff solution caused consistent relative changes in smooth muscle receptors and was superior to aerated Krebs' and UW solutions for 24-hour bladder tissue storage. It is unnecessary to aerate Krebs' solution during 24-hour cold storage.

A comparison of mucosal incisions made by scalpel, CO 2 laser, electrocautery, and constant-voltage electrocautery

This study compares the histologic effects of scalpel, CO 2 laser, electrosurgery, and constant-voltage electrosurgery incisions on the mucosal tissue of swine. Tissue studies comparing the CO 2 laser with the scalpel and electrosurgery have been done. However, a gross and histologic comparison of the effects of all three techniques on oral mucosal tissue has not been reported. A swine model of both tongue and buccal mucosa was used to compare the scalpel, CO 2 laser, electrosurgery unit, and constant-voltage electrosurgery unit in an effort to assess their value in oral surgery. Tissue samples of tongue and buccal mucosal incisions and excisions were histologically examined at 0, 3, 7, 14, 28, and 42 days after surgery to evaluate tissue damage and wound healing properties induced by the four instruments. The instruments were also evaluated for performance and ease of use. On subjective evaluation of ease of use, constant-voltage electrosurgery scored highest ( p < 0.05) on a scale of 0 to 4, followed by the CO 2 laser. Speed of incisions and excisions, measured in seconds, was fastest with the scalpel ( p < 0.001) and electrosurgery unit ( p < 0.05). The amount of bleeding, as evaluated on a scale of 0 to 4, was least for electrosurgery ( p < 0.001) and CO 2 laser ( p < 0.001). Histologic damage, as expected, was least with a scalpel. The extent of epithelial damage lateral to the wound edge and the extent of collagen denaturation were the lowest with the scalpel ( p < 0.001), followed by constant-voltage electrosurgery. The wounds created by all four instruments displayed intact epithelium by 4 weeks, and granulation tissue peaked at 4 weeks with all methods except constant-voltage electrosurgery, where granulation tissue was still prevalent at week 6. Constant-voltage electrosurgery and the CO 2 laser provided the best combination of ease of use, hemostasis, and lack of tissue injury among the instruments compared. Incisions and excisions made with constant-voltage electrosurgery required less time than those made with the laser, but constant-voltage electrosurgery wounds also had significantly more granulation tissue in later weeks of the study, suggesting that wound healing may be delayed. (Otolaryngol Head Neck Surg 1997;116:379-85.)

Role of endogenous and exogenous nitric oxide on intestinal mucosa and microflora in the rat.

In the present study the effects of exogenous and endogenous nitric oxide (NO) on intestinal bacteria and on the intestinal tissue integrity have been investigated in healthy rats and in rats receiving bacterial endotoxin (LPS). A segment of jejunum was taken in order to evaluate tissue damage and hematoxylin-eosin staining; microbiological studies were carried out collecting stool samples. Administration of LPS (5 mg kg-1 i.v.) induced a moderate jejunal damage, which was completely prevented by NG-nitro-L-arginine methyl ester (L-NAME), 5 mg kg-1 s.c.), thus suggesting a damage of endogenous NO on the intestinal mucosa; sodium nitroprusside (SNP, 10 mg kg-1 os) reduced significantly jejunal damage induced by LPS. Endogenous NO produced by the administration of LPS resulted to be cytotoxic for all examined aerobic and anaerobic bacteria, while exogenous NO, released from SNP, showed an inhibitory effect only on Entero. faecalis and E. coli growth. From our data, it seems reasonable to conclude that high local levels of NO are required in order to observe jejunal damage and cytotoxic effects on aerobic and anaerobic faecal flora.

The kinetics of copper-zinc superoxide dismutase in experimentally induced ischemia-reperfusion injury of the canine jejunum.

In this study, the kinetics of copper-zinc superoxide dismutase (CuZn-SOD) in experimentally induced ischemia-reperfusion injury of the canine jejunum were examined using immunohistochemical procedures, and evaluated as an index for the viability of transplants. A pedicled jejunal graft was subjected to arterial reperfusion after clamping the supplying blood vessels for 30 min. Under nonischemic conditions, some of the goblets in the goblet cells and the mucin covering the surface of the villi were stained positively with luxol fast blue, von Kossa, and immunohistochemistry for CuZn-SOD. Between 5 and 30 min after reperfusion, the appearance of goblets with positive immunoreaction for CuZn-SOD in the intestinal glands and the disappearance of these goblets in the villi were observed in the grafts of animals that received arterial reperfusion after 30 min of clamping of the arteries and veins at room temperature. Thereafter, the former disappeared gradually and the latter returned toward the nonischemic condition. The administration of allopurinol led to a decrease in tissue damage and a significantly higher number of goblets with positive immunoreaction for CuZn-SOD than in untreated animals. Furthermore, the goblets in the intestinal glands showed a negative reaction for CuZn-SOD 5 to 30 min after reperfusion. Preservation at 4 degrees C during ischemia revealed similar results to those observed in the animals given allopurinol. Thus, the distribution and intensity of CuZn-SOD positive goblets seems to be a useful indicator for the evaluation of tissue damage induced by free radicals mediating ischemia-reperfusion injury.

Quantification of tissue damage in the feline small intestine during ischaemia‐reperfusion: the importance of free radicals

Intestinal ischaemia is accompanied by characteristic mucosal lesions, which can be graded according to a six-grade system proposed by Chiu et al. (1970). This report describes a continuous grading system which makes it possible to quantify the intestinal damage in connection with ischaemia-reperfusion. The present morphometric method is based on quantitative histological analysis of intestinal biopsies performed on 200 histological sections from 44 cat experiments. Radical formation was quantified by infusing close i.a. a spin trap, OXANOH, which produces a secondary stable radical, OXANO., after reacting with radicals in the tissue. OXANO. concentration was determined in venous blood samples with electron spin resonance. We demonstrate a highly significant correlation between the grading system of Chiu et al. (1970) and the morphometric analysis of this study. The tissue damage was located exclusively in the intestinal villi. Comparing the mucosal damage that occurs during 60 min of intestinal ischaemia (superior mesenteric artery pressure 15-25 mmHg) with that seen during the first 30 min reperfusion this study shows that the villus damage occurring during ischaemia is at least twice as large as the aggravation seen upon reperfusion. Furthermore, the authors demonstrate a significant correlation between rate of radical formation and villus tissue damage particularly during the first 30 min after ischaemia. It is concluded that the proposed quantitative morphological method represents a non-discrete grading system for evaluating tissue damage in connection with ischaemia-reperfusion in the small intestine. The ischaemia itself inflicted a more severe damage to the intestine than reperfusion. A significant correlation between damage and radical formation was demonstrated during the reperfusion. However, the results suggest that factors other than radical formation are of importance in explaining the tissue damage upon reperfusion. The nature of these factors is presently unknown.

Somatosensory evoked potentials and intracranial pressure during chronic dilatation of an artificial extraparenchymal space-occupying lesion in cats.

Somatosensory evoked potentials (SEP) and intracranial pressure (ICP) were studied in cats, suffering from a chronic space-occupying lesion produced by enlargement of an epidural balloon over the left sensomotory cortex. Our study shows that latency alterations of SEP are not dependent on the degree of ICP. Additionally, the results obtained demonstrate that chronic space-occupying lesions cause continuous prolongation of SEP latencies, probably produced by atrophy of the compressed tissue. Regarding the clinical importance of SEP measurements, we concluded that they are not suitable for estimating the degree of ICP. However, they are useful to evaluate tissue damage caused by mass effects in the acute and chronic phase of various space-occupying processes.

Muscle injury induced beneath and distal to a pneumatic tourniquet: A quantitative animal study of effects of tourniquet pressure and duration

Previous recommendations regarding the “safe” period of tourniquet hemostasis were based largely on studies of ischemia distal to the tourniquet. This study quantitatively analyzed skeletal muscle injury induced beneath and distal to a pneumatic tourniquet applied to the hindlimbs of rabbits for 1, 2, or 4 hours with a cuff inflation pressure of 125, 200, or 350 mm Hg. Technetium Tc 99m pyrophosphate incorporation after systemic injection (Tc 99 uptake) and correlative histology were used to evaluate tissue damage 2 days after tourniquet application. Compared with the contralateral control limbs, compression and ischemia induced statistically significant increases in Tc 99 uptake in the thigh and leg regions of all groups. Pyrophosphate incorporation was significantly greater in the thigh region than in the leg region after 2 hours of compression in the 200 and 350 mm Hg pressure groups and following 4 hours of compression in all pressure groups. Focal and regional fiber necrosis and degeneration were observed in thigh muscles after 2 hours of tourniquet compression. Two hours of continuous tourniquet application at clinically relevant cuff inflation pressures induced significant skeletal muscle necrosis beneath the tourniquet. Use of the lowest possible inflation pressure for a limited duration should minimize the degree of tissue injury caused by tourniquet application.