Lipopolysaccharide impairs fracture healing: an experimental study in rats

Background It has been shown that trauma causes translocation of lipopolysaccharide (LPS) endotoxins from the gut. LPS has been identified as a major bacterial bone resorbing factor. The effects of LPS on bone healing are therefore of clinical interest, as trauma involving fractures followed by sepsis is a clinical scenario. We investigated the effects of systemic and local administration of LPS on the healing of femoral fractures in rats.

Animals and methods In 3 groups, each consisting of 9 rats, a mid-diaphyseal osteotomy/fracture of the femoral bone was performed and then nailed. In one group of animals, LPS was applied intraperitoneally (systemically), and in another group, LPS was applied locally at the fracture site. The third group served as a control. The animals were killed after 6 weeks, and the mechanical characteristics of the healing osteotomies were evaluated.

Results We found that LPS induced a hypertrophic and immature callus, as evaluated by bone mineral content and density. In the rats given LPS intraperitoneally, the mechanical strength characteristics were reduced, as evaluated by bending moment, rigidity, and energy absorption.

Interpretation The rats given LPS intraperitoneally reflect a clinical situation with fracture trauma and endotoxinemia. Our findings indicate that endotoxinemia may impair the fracture healing processes.

        ▪     

Bone demineralization following ureterosigmoid anastomosis: an experimental study in rats

This study was designed to examine the renal and bony metabolic responses to urinary diversion through intestinal segments. Twenty rats underwent urinary diversion by ureterosigmoidostomy and were compared to twenty control rats with respect to renal excretion of electrolytes and bone mineralization after a 10-week period. Ureterosigmoidostomy rats demonstrated increased renal excretion of ammonium, sulfate, magnesium, and possibly phosphorus. Bone calcium content was decreased in ureterosigmoidostomy rats, while bone phosphorus content was slightly increased. These changes occurred in the absence of systemic acid-base alterations. We are unable to demonstrate an increased renal loss of calcium in the ureterosigmoidostomy rats compared to controls. This suggests that decreased renal reabsorption of urinary calcium is not the primary pathophysiologic process involved in this problem.     

Small-dose nitric oxide improves oxygenation during one-lung ventilation: an experimental study

Inhaled nitric oxide (NO) at 20 or 40 ppm does not improve arterial oxygenation during one-lung ventilation (OLV). The authors hypothesized that NO at smaller concentrations might improve oxygenation. Twelve piglets weighing 26 to 32 kg were studied. When PaO(2) had reached a plateau during OLV, NO at doses of 4, 8, 16, and 32 ppm were randomly administered for 30 min. Hemodynamic data were determined by invasive monitoring. Blood gas analysis and, in six animals, ventilation-perfusion analysis by the multiple inert gas elimination technique were used to characterize pulmonary gas exchange. NO at 4, 8, 16, and 32 ppm improved PaO(2) during OLV. NO at 4 ppm had a more intense effect on arterial oxygenation than doses of 8, 16, and 32 ppm (DeltaPaO(2), 42 +/- 35 mm Hg versus 22 +/- 20 mm Hg, 13 +/- 18 mm Hg, and 15 +/- 16 mm Hg; P < 0.05). NO at 4 ppm reduced intrapulmonary shunt flow, whereas a larger concentration exhibited no statistically significant effect. The authors conclude that NO improves arterial oxygenation more effectively at smaller doses than at larger doses. This dose-dependent effect remains to be confirmed in acute hypoxemia during OLV. IMPLICATIONS: Inhaled nitric oxide at 4 ppm improves arterial oxygenation during one-lung ventilation to a greater extent than larger doses, and this effect is caused by a reduction in intrapulmonary shunt.     

Staphylococcus aureus peptidoglycan impairs fracture healing: an experimental study in rats.

Staphylococcus aureus is the common organism causing musculoskeletal infections. Staphylococcus aureus peptidoglycan (SaPG) has been identified to increase the acute inflammatory response to wounding, increase reparative granulation tissue, and improve healing. The healing of bone fractures is a balanced process of granulation tissue that is calcified to obtain increasing stability. By increasing reparative collagen accumulation, however, SaPG may induce a shift towards immature fibrous callus production. Therefore, it was our hypothesis that SaPG would impair bone healing after fracture. In three groups, each of nine rats, a mid-diaphyseal osteotomy/fracture of the femoral bone was performed and then nailed. In one group of animals, SaPG was applied locally at the fracture site, and in another group SaPG was applied intraperitoneally (systemically). Control littermate received saline. The animals were sacrificed after 6 weeks, and the mechanical characteristics of the healing osteotomies were evaluated. We found that application of SaPG locally induced a hypertrophic and immature callus as evaluated by callus production, by bone mineral content and density, and by bending moment and rigidity. In the rats given SaPG intraperitoneally, bone healing went uneventful compared to the control rats. Collectively, these data show that SaPG induces an alteration in the normal bone healing response towards a less calcified callus production.     

一氧化氮对术后腹膜粘连作用的实验研究

目的研究一氧化氮 (NO)在预防大鼠术后腹膜粘连中的作用。方法 40只大鼠统一制作腹膜粘连模型 ,随机分为对照组和左旋精氨酸组。术后分别腹腔内注射 0 9%NaCl和左旋精氨酸 ,连续 3d。术后 3d随机抽取部分大鼠血样测定NO ,同时取材作病理检查。其余大鼠 2周后乙醚处死开腹观察并记录粘连情况。结果对照组的粘连分级 (3 7± 0 7)重于左旋精氨酸组 (0 9±1 1) ,t=8 6 ,P <0 0 1。对照组血中NO的水平为 (13 9± 1 1) μmol/L ,低于左旋精氨酸组 (32 2± 2 8)μmol/L ,t=2 0 4,P <0 0 1。左旋精氨酸组粘连组织中诱导型一氧化氮合酶 (iNOS)的免疫组化染色分级为 2 5± 0 7强度高于对照组 (0 8± 0 4) ,t=11 1,P <0 0 1。结论一氧化氮在腹膜粘连的预防中起重要作用     

Torsional stiffness in healing fractures: influence of ossification: an experimental study in rats

BACKGROUND: Different fracture fixation techniques and fracture environment influence bone formation in healing fractures. However, the influence on the development of biomechanical properties has not been clear described. We evaluated the influence of fracture fixation stability and fracture environment on mechanical properties in healing femoral fractures in rats. METHODS: Animals were treated surgically with external fixation: 1 group (27 rats) with 0-mm fracture gap size with bone ends touching, corresponding to an axial stiffness of 265 (SD 34) N/mm, and a second group (27 rats) with 2-mm fracture gap size corresponding to an axial stiffness of 30 (SD 2.1) N/mm. From each group, 6-7 animals were killed at 2, 4, 6 and 12 weeks. Torsional test revealed a delay in torsional stiffness in fractures in group 2 compared to group 1. In group 2, the torsional stiffness of the contralateral femora was found to be greater at 12 weeks than the torsional stiffness in group 1. INTERPRETATION: We found that during fracture healing, the development of torsional stiffness corresponds to the magnitude of endochondral ossification and late response of bone formation. A significantly increased torsional stiffness in the non-fractured leg of rats with delayed fracture healing was also found, possibly indicating a response to loading conditions or a systemic stimulation of bone mass.     

Effects of botulinum toxin A on fracture healing in rats: an experimental study

Introduction

Fracture healing is a complex process influenced by intrinsic and extrinsic factors. The aim of the present study was to evaluate the effects of botulinum toxin (BTX) A on fracture healing.

Materials and methods

Following the induction of bilateral standard closed femoral fractures and relative fixation in 18 Wistar albino rats, 8 IU of BTX A were injected into the right femoral region. After 28 days, all of the rats were sacrificed, the diameter of the callus was measured, and fracture healing was assessed by biomechanical and histopathologic evaluation.

Results

While an increase in biomechanical and histopathologic healing was noted on the side injected with BTX A, a decrease in callus diameter was observed.

Conclusion

Botulinum toxin A administration increases the healing power in a relatively fixated fracture and decreases the callus diameter, just as if rigid fixation had been performed. The beneficial effect of BTX A on fracture healing might be associated with increased fixation rigidity.     

The healing of colonic anastomoses after early intraperitoneal chemotherapy: an experimental study in rats

Early postoperative intraperitoneal administration of 5-fluorouracil (5-Fu) is a logical adjuvant treatment of patients with resectable colonic cancers. It is easier and less invasive than the intraportal administration of the drug. However, before applying the procedure to humans it must be demonstrated than it does not disturb the healing of recent colonic anastomoses. Colonic sutures were performed in 78 male Wistar rats. The animals then either served as controls or received intraperitoneal 5-Fu during 5 days starting on the first, third, or seventh postoperative day. No statistical difference was observed between treated and control groups when observing the incidence of anastomotic spontaneous disruptures, anastomotic healing strength, or the weight of the animals. It is concluded that early intraperitoneal 5-Fu administration does not impair the healing of recent colonic anastomoses in rats.     

Importance of dehydration in anastomotic and subcutaneous wound healing: an experimental study in rats.

OBJECTIVE: To find out if preoperative and postoperative dehydration adversely affect anastomotic and subcutaneous healing. DESIGN: Randomized study. MATERIAL: 18 Wistar rats. INTERVENTIONS: Dehydration established in nine rats by withdrawal of food and water for 24 hours before operation, and by injections of frusemide twice daily. Laparotomy and division of intestine 5-8 cm from the ileocaecal valve. Implantation of expanded polytetrafluoroethylene (ePTFE) tubes in the backs of the necks. All rats killed after five days. MAIN OUTCOME MEASURES: Measurements of weight loss and of hydroxyproline per centimetre in the ePTFE tubes and standardized biopsy specimens of the intestine. Presence of anastomotic dehiscence at necropsy. RESULTS: Preoperative and postoperative dehydration caused a 24% weight loss in the experimental group on day 5 compared with 8% in the control group. Dehydrated animals accumulated less collagen in the ePTFE tubes than control animals (p less than 0.05). There were three anastomotic breakdowns in the dehydrated group compared with one in the control group. There was a loose but significant correlation between collagen accumulation in the anastomoses and the weight of the animal (r = 0.5, p less than 0.05). CONCLUSION: Preoperative and postoperative dehydration has a deleterious effect on subcutaneous, and to a lesser extent on anastomotic healing in rats.     

Bone flap prefabrication: an experimental study in rabbits

The usual method to prefabricate a bone flap is to harvest a nonvascularized bone graft and to implant the artery and vein bundle between segments of bone graft. The basic problem of this method is sacrificing an artery for prefabrication. Another method for creating flap donor sites without using an artery is venous flap prefabrication. There are a few articles describing bone flap prefabrication, and these include implantation of both artery and vein as a vascular bundle. Also, there is no experimental study in the literature using a vein or an arterialized vein pedicle for bone flap prefabrication. As an experimental model for bone flap prefabrication, the rabbit ear vascular model was chosen. For the experiments 3 groups were formed. Each group contained 5 rabbits. In the first experimental group a vein was implanted between the halves of bone graft. In the second experimental group an arterialized vein was implanted between the halves of bone graft. To compare the viability of the bone graft of the 2 prefabrication groups, a bone graft was implanted into the subcutaneous pocket of the posterior auricular area in the third group. The authors examined 5 rabbits in each group by microangiography at the end of 6 weeks except for group 3. On microangiographic analysis, groups 1 and 2 showed patency of the vascular pedicle. There was no difference between these 2 groups from the point of view of vascular patency and bone appearance. Bone scintigraphy was performed for 5 rabbits in each group. On bone scintigraphic scans, the bone component of the flaps was visualized in groups 1 and 2, but not in group 3. A quantitative analysis of images was performed by drawing symmetric spherical regions of interest (ROIs) over both the implanted area and cranial bone. The uptake ratios were computed by dividing the mean counts in the implanted ROI by mean counts in the cranial bone ROI. The mean value was 0.86 +/- 0.02 in group 1 and 0.86 +/- 0.04 in group 2. A statistically significant uptake difference was not seen between venous and arterialized venous groups (P < 0.01). Histologic examination was performed all rabbits in each group, and demonstrated that the bony component was viable, showing osteocytes containing lacunae, osteoblasts along bony trabeculae, and vascular channels in groups 1 and 2. In group 3, the bony architecture of the graft was still apparent, but all bone within it was dead. There were no significant microangiographic, histologic, and scintigraphic differences between the 2 experimental methods.     

Jaundice and wound healing: an experimental study.

Obstructive jaundice was induced in rats by ligation and division of the common bile duct. The healing of a standard gastric incision and a parietal peritoneal defect in these animals showed histological evidence of delayed healing compared with controls. The bursting strength of the abdominal incision was also lowered, but not that of the stomach, probably because of the adhesions which reinforced the gastric incisions. Angiography did, however, reveal delay in angiogenesis in the gastric wounds of jaundiced animals. The possible causes of this delay in healing and its clinical implications require further investigations.     

An experimental study on fracture healing in paraplegic rats

Fracture healing in denervated limbs was studied using paraplegic rats of Wistar stain. Femoral fractures were made at the same time as spinal cord injury or at regular intervals after spinal cord injury, for roentgenological and histological observation. In the former, proliferation and differentiation of osteogenic cells derived from the periosteum was almost the same as controls, with earlier bone union than controls. In the latter, with longer intervals between spinal cord injury and fracture, osteogenic cells were less proliferated and differentiated resulting in scant callus or delayed union. The environment of paralytic limbs was evidently altered substantially from 2 to 3 weeks after spinal cord injury, because thereafter fracture healing seemed to become poor. Circulatory disturbance plays a major role in fracture healing in paralytic limbs. Although healing is accelerated by increased circulatory volume at the acute phase of spinal cord injury, this potentiality is gradually decreased because of the regressive degeneration of long-term vasomotor nerve insufficiency.     

Pretreatment with endothelium-derived nitric oxide synthesis modulators on gastrointestinal microcirculation during NOTES: an experimental study

Background and study aims

On-demand endoscopic insufflation during natural orifice transluminal endoscopic surgery (NOTES) adversely affects microcirculatory blood flow (MBF), even with low mean intra-abdominal pressure, suggesting that shear stress caused by time-varying flow fluctuations has a great impact on microcirculation. As shear stress is inversely related to vascular diameter, nitric oxide (NO) production acts as a brake to vasoconstriction.

Objective

To assess whether pretreatment by NO synthesis modulators protects gastrointestinal MBF during transgastric peritoneoscopy.

Methods

Fourteen pigs submitted to cholecystectomy by endoscope CO₂ insufflation for 60 min were randomized into 2 groups: (1) 150 mg/kg of N-acetyl cysteine (NAC, n = 7) and (2) 4 ml/kg of hypertonic saline 7.5 % (HS, n = 7), and compared to a non-treated NOTES group (n = 7). Five animals made up a sham group. Colored microspheres were used to assess changes in MBF.

Results

The average level of intra-abdominal pressure was similar in all groups (9 mmHg). In NOTES group microcirculation decrease compared with baseline was greater in renal cortex, mesocolon, and mesentery (41, 42, 44 %, respectively, p < 0.01) than in renal medulla, colon, and small bowel (29, 32, 34, respectively, p < 0.05). NAC avoided the peritoneoscopy effect on renal medulla and cortex (4 and 14 % decrease, respectively) and reduced the impact on colon and small bowel (20 % decrease). HS eliminated MBF changes in colon and small bowel (14 % decrease) and modulated MBF in renal medulla and cortex (19 % decrease). Neither treatment influenced mesentery MBF decrease.

Conclusions

Both pretreatments can effectively attenuate peritoneoscopy-induced deleterious effects on gastrointestinal MBF.

     

Beneficial effects of Salvia miltiorrhiza in the healing of burn wounds: an experimental study in rats

Introduction: Burn healing is a complicated process and very few treatments can positively alter its effects. The aim of this study was to investigate the effects Salvia miltiorrhiza (SM -Danshen), a traditional Chinese medicine, on burn wound healing.

Material and methods: Twenty rats were included in this study and divided into two groups. 3?×?2?cm wide burn areas were created in the dorsal skin of all the animals with thermal contact. Intraoral 1?ml/day saline and 1?g/kg/day SM were given in control and experiment groups, respectively. Fourteen days following the burn injury burn zones were evaluated with indocyanine green-SPY imaging device, and multiple samples were collected for histopathological evaluation. Standard photographs were taken for the evaluation of necrotic skin areas.

Results: Neovascularization was increased in the SM group when compared with the control group (p?=?0.0406). SPY studies revealed a meaningful increase in the tissue perfusion in the SM group (p?=?0.0286). The average amount of necrotic area in the control and experiment group on the postoperative 14th day was 71.6% (±16.51) and 42.5% (±10.64) respectively (p?=?0.0002).

Conclusion: Our study shows that SM can decrease the amount of necrosis in burn wounds by increasing tissue perfusion and neovascularization.     

Effect of early wound excision on changes in plasma nitric oxide and endothelin-1 level after burn injury: an experimental study in rats

The purpose of this study was to evaluate effects of early wound excision on changes in NO and endothelin-1 (ET-1) level in the plasma after extensive burn injury. The effects on vascular permeability and hepatic blood flow (HBF) were also assessed. Male Wistar rats were used for this study. A 30% total body surface area (TBSA) third-degree burn was made on the back. Then animals were divided into four groups. Burn group (n = 13), burn alone; infusion group (n = 13), burn injury and fluid resuscitation; early excision group (n = 13), burn injury, total wound excision at 30 min after the injury followed with immediate allogenic skin graft and fluid resuscitation; and the sham group (n = 15). The sham group and the early excision group did not show significant changes in the NO and ET-1 level in plasma during experimental period, while the burn group and the infusion group showed significant increase in the NO and ET-1. The early excision group also did not show hypovolemia, and the significant decrease in the HBF. These data suggest that the increased NO and ET-1 in plasma following thermal injury were originated from burned tissue and the removal of these injured tissue has beneficial effect on the vascular permeability and the changes in HBF.     

NO在创伤愈合过程中的作用

创伤修复是损伤组织恢复其完好结构的必需过程，大致分为三个阶段：①局部炎症反应阶段：②细胞增殖分化及肉芽组织形成阶段：③组织重建阶段。有研究发现包括一氧化氮（nitric oxide，NO）在内的小分子自由基对伤口的良好愈合起到了关键作用。现就NO在创伤修复过程中的作用作以阐述。