Dog bone less osteogenetic than rat bone. Bone-matrix transplants in nude rats

Demineralized bone matrix and bone-matrix gelatin prepared from cortical rat bone, and from cortical and cancellous canine bone were implanted into muscle pouches of nude rats for 6 weeks. Evaluation was done by histology, histomorphometry, and determination of alkaline phosphatase. Rat matrix consistently induced new bone and high phosphatase levels. Canine matrix induced but small amounts of bone and lower phosphatase levels, with cortical matrix somewhat more inductive than cancellous matrix; demineralized cancellous bone matrix from the dog was the only material tested not showing any inductivity. Irrespective of bone type or species, gelatin had clearly higher induction capacity than demineralized bone matrix.     

Evidence that cyclosporine G is less deleterious to rat bone in vivo than cyclosporine A.

We have previously shown that CsA administration to rats causes a high turnover bone loss with bone resorption exceeding bone formation. Similar findings have been reported in renal and cardiac transplantation patients administered CsA. Cyclosporine-G (CsG), a natural equipotent immunosuppressive analogue of CsA, has been shown to be less nephrotoxic than CsA. We therefore compared the effects of CsG and CsA on bone mineral metabolism. Sixty male Sprague-Dawley rats were divided into 3 equal groups as follows: group A (n = 20) was the control; group B (n = 20) received CsA 15 mg/kg by daily gavage; and group C received CsG 15 mg/kg by daily gavage for 28 days. Rats were bled weekly for measurement of circulating biochemical parameters of bone mineral metabolism and after sacrifice on day 28, the tibiae were removed for histomorphometric analysis. The tibial bone histomorphometry revealed that the percentage of bone volume was significantly reduced, and the osteoclast count increased in both the CsA and CsG group, but significantly less so in the CsG than the CsA group. Parameters reflecting bone formation in the CsG group were similar to controls but significantly different from the CsA group. Bone Gla protein levels in the CsA group were significantly increased compared with the control and CsG groups from day 14. Serum 1,25 dihydroxyvitamin D was increased significantly in the CsA group on days 14 and 28 compared with both control and CsG groups, and was significantly elevated in the CsG group compared with controls on the same days. We conclude that CsG is significantly less deleterious to bone mineral metabolism than CsA in the rat in vivo.     

Anaesthetic management of bone marrow transplant recipients less than two years of age

The charts and anaesthetic records of 97 infants less than two years of age who underwent bone marrow transplantation at the University of Minnesota from 1978–1992 were retrospectively reviewed. These infants underwent 564 general anaesthetics. There were 48 perioperative complications, most (39) involving the airway. There were 20 difficult intubations occurring in 13 patients. The causes of the difficult intubations were anatomical abnormalities (12), mucositis (4), pharyngeal oedema (3) and emesis upon induction of anaesthesia (1). Four intraoperative deaths occurred. The deaths were caused by haemorrhage (2), pulmonary embolism (1) and myocardial ischaemia (1). Four patients died within 72 h of surgery; one from cerebral oedema following an intraoperative cardiac arrest, one from fungal septicaemia, one from haemorrhage and one from multiple organ failure following an intracerebral haematoma. Infants undergoing bone marrow transplantation are at high risk for perioperative morbidity and mortality, particularly from complications involving the airway, bleeding or sepsis.     

Systemic dextromethorphan and dextrorphan are less toxic in rats than bupivacaine at equianesthetic doses

Purpose

Dextrorphan, a major metabolite of dextromethorphan, produces the duration of spinal and cutaneous anesthesia similar to bupivacaine. The purpose of this study was to test the central nervous system and cardiovascular toxicity of bupivacaine, dextromethorphan, and dextrorphan.

Methods

First, dose-response curves for dextromethorphan, dextrorphan, and bupivacaine (n = 8 at each testing point) were determined for cutaneous analgesia on the rat back, and equipotent doses were calculated. Next, during continuous intravenous infusion of equipotent doses of bupivacaine, dextromethorphan, and dextrorphan (n = 8 in each group), we observed the time to seizure, apnea, and complete cardiac arrest. A saline group (n = 7) was used for comparison. Mean arterial blood pressure (MAP), heart rate (HR), stroke volume (SV), and cardiac output (CO) were also monitored.

Results

Bupivacaine, dextromethorphan, and dextrorphan produced dose-dependent cutaneous anesthesia. A longer duration of equipotent infusion doses was required to produce seizures in the dextromethorphan group (10.6 ± 1.3 min) than in the bupivacaine group (7.6 ± 2.1 min) (P = 0.005). Dextrorphan did not produce any seizures. Compared with bupivacaine, time to apnea and complete cardiac arrest was longer with dextrorphan (P < 0.001) and with dextromethorphan (P = 0.001). Cardiovascular collapse, defined as a decline in MAP, HR, CO, and SV, was slower in the dextromethorphan and dextrorphan groups than in the bupivacaine group (P < 0.001 for both comparisons).

Conclusion

At equipotent doses for local anesthesia, dextromethorphan and dextrorphan were less likely than bupivacaine to induce central nervous system and cardiovascular toxicity.     

Intrathecal mepivacaine and prilocaine are less neurotoxic than lidocaine in a rat intrathecal model

BACKGROUND AND OBJECTIVES: Histologic evidence of the comparative neurotoxicity of lidocaine, mepivacaine, and prilocaine is incomplete. We compared the intrathecal neurotoxicity in rats among these 3 drugs based on morphologic and neurofunctional findings. METHODS: Rats (n=169) randomly received 0.12 microL/g of 0%, 2%, 5%, 7.5%, 10%, or 20% lidocaine, mepivacaine, or prilocaine or 25% glucose dissolved in distilled water via a chronically implanted intrathecal catheter. The effect of the agents on neurofunction was evaluated by movement of the hind limb (behavior test) and by sensory threshold (paw-stimulation test). The L1 spinal cord, the posterior and anterior roots, and the cauda equina were removed en bloc 5 days later and examined by light and electron microscopy. RESULTS: A significant decrease in sensory threshold or irreversible hind-limb limitation was observed only in rats receiving 20% lidocaine. Morphologic abnormalities characterized by axonal degeneration were observed in rats receiving > or =7.5% lidocaine, 20% mepivacaine, and 20% prilocaine, at the posterior white matter and the proximal portion of the posterior root just at the entrance into the spinal cord. The incidence of lesions was significantly higher in rats receiving lidocaine than mepivacaine and prilocaine. CONCLUSION: It is suggested that intrathecal mepivacaine and prilocaine are less neurotoxic than highly concentrated lidocaine in a rat intrathecal model.     

(Nva2)-cyclosporine--less potent than cyclosporine A in rats with lung and heart transplants

The ability of a new cyclosporine (Cs) derivative, (Nva2)-Cs (CsG), to suppress rejection of lung and heart allografts in rats was determined and compared with that of CsA. Left lungs were transplanted orthotopically; hearts were transplanted heterotopically into the abdomen. (Nva2)-Cs was used in three experimental protocols: (1) single or three (Nva2)-Cs injections given to lung-transplanted rats, (2) daily oral (Nva2)-Cs treatment at different doses compared with similar CsA treatments in heart allografted rats, and (3) An 11-day (Nva2)-Cs treatment starting at increasing intervals after transplantation of hearts. (Nva2)-Cs was found to be immunosuppressive, and effective even when the treatment started as late as four days after transplantation. However, (Nva2)-Cs was less effective than CsA in suppressing rejection of lung and heart allografts at low doses. Because (Nva2)-Cs is possibly not nephrotoxic, it might be a useful drug if used in higher doses than CsA or in combination with other immunosuppressive agents.     

Kidney transplants in cyclosporine-treated Sprague-Dawley rats

Previous studies by others have shown that transplanted rat kidneys have abnormally low clearances of paraaminohippuric acid, inulin, and creatinine, due to rejection and/or to warm-ischemia-induced injury. In the present studies, randomly bred Sprague-Dawley rats were used as donors and recipients. The left kidneys of recipients were removed, and the right kidneys were left intact. Donor kidneys were flushed with an ice-cold hypertonic solution (150 mM NaCl, 200 mM mannitol, pH 6.4), and the kidneys were kept cold during surgery. Renal function was assessed 1 week later. The left transplanted kidneys in untreated recipients exhibited morphologic evidence of rejection, and the clearances of PAH and inulin were approximately 50% of those of the right native kidneys. CsA-treated rats did not reject the transplants, and the PAH and inulin clearances of the left transplanted kidneys were identical to those of the right native kidneys. Untreated and CsA-treated rats with both native kidneys intact served as controls. The amount of CsA given during the 7-day period produced no measurable change in renal function. This is the first demonstration of virtually normal hemodynamics in transplanted rat kidneys when randomly bred animals are used as donors and recipients. Moreover, the results indicate that if both rejection and warm ischemia are avoided, the presence of a functioning native kidney does not have a detrimental effect on the function of a transplanted kidney.     

Cortical bone is more sensitive to alcohol dose effects than trabecular bone in the rat

ObjectiveWhile chronic alcohol consumption is known to decrease bone mineral content (BMC), bone mineral density (BMD), and negatively modify trabecular bone microarchitecture, the impact of alcohol on cortical microarchitecture is still unclear. The aim of this study was to investigate the effects of various doses of alcohol on bone density, trabecular and cortical parameters and bone strength in rats.MethodsForty-eight male Wistar rats were divided into four groups: control (C), alcohol 25% v/v (A25), alcohol 30% v/v (A30) and alcohol 35% v/v (A35). Rats in the alcohol groups were fed a solution composed of ethanol and water for 17 weeks while the control group drank only water. Bone quality and quantity were evaluated through the analysis of density, trabecular and cortical bone microarchitectural parameters, osteocalcin and N-Telopeptide concentrations and a 3-point bending test.ResultsBone density along with trabecular and cortical thickness were lower in alcohol groups compared to C. BMD was lower in A35 vs. A30 and cortical thickness was lower in A35 vs. A25 and A30. Pore number was increased by alcohol and the porosity was greater in A35 compared to C. N-Telopeptide concentration was decreased in alcohol groups compared to control whereas no differences were observed in osteocalcin concentrations. Maximal energy to failure was lower in A25 and A35 compared to C.ConclusionChronic ethanol consumption increases cortical bone damage in rats and may have detrimental effects on bone strength. These effects were dose-dependent, with greater negative effects proportionate to greater alcohol doses.     

Elastic modulus of calcified cartilage is an order of magnitude less than that of subchondral bone

The elastic moduli of calcified cartilage and subchondral bone tissues were measured experimentally with use of a three-point bending test. Specimens were obtained from a bovine patella and the distal end of a bovine femur, from two different animals. Fifteen specimens were tested as “pure” subchondral bone beams, and 15 were tested as composite calcified cartilage/subchondral bone beams. A least-squares optimization scheme was used to obtain modulus values from the composite beams. The elastic modulus for subchondral bone calculated from the “pure” subchondral bone beams was 2.3 ± 1.5 GPa (3.9 ± 1.5 GPa for specimens from the femur and 1.6 ± 0.7 GPa for specimens from the patella). The composite beam optimization resulted in a modulus for subchondral bone of 5.7 ± 1.9 GPa and a modulus for calcified cartilage of 0.32 ± 0.25 GPa. The modulus for the calcified cartilage was more than an order of magnitude lower than the modulus of the underlying subchondral bone. This supports the idea that the zone of calcified cartilage forms a transitional zone of intermediate stiffness between the articular cartilage and the subchondral bone.     

Measurement of blood flow in rabbit bone transplants

Summary The rate of blood flow in free bone grafts in rabbits was monitored for 8 weeks after transplantation using the hydrogen washout technique. Blood flow was present at 2 weeks in both autografts and allografts, although the rate was significantly lower in the allograft compared to the autograft. Autografts showed a rapid increase from 2 to 3 weeks and a maximum flow 4 weeks after transplantation, whereas in allografts the rate of increase was slower. This study has demonstrated that the hydrogen washout technique is a useful method of monitoring blood flow and can be applied to clinical investigations.

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Résumé Le degré de vascularisation des greffes osseuses libres pratiquées ches le lapin a été contrôlé pendant 8 semaines après la transplantation en utilisant la technique de lavage à l'hydrogène. La vascularisation était présente à 2 semaines aussi bien dans les autogreffes que dans les allogreffes. Mais le degré de vascularisation était significativement plus bas dans les allogreffes que dans les autogreffes. La vascularisation des autogreffes augmente rapidement entre la 3ème et la 4ème semaine avec un maximum 4 semaines après la transplantation. Le degré d'accroissement de la vascularisation est plus lent dans les allogreffes. Cette étude démontre que la technique du lavage à l'hydrogène est une méthode utile pour contrôler la vascularisation et qu'elle peut être appliquée en clinique.

     

Osteogenicity of autologous bone transplants in the goat

BACKGROUND: Little is known about the specific mechanisms that make autologous graft bone (AG) superior to the current alternatives. A potential mechanism is the active bone formation by the osteoprogenitor cells within the AG. However, whether these cells survive the transplantation is questionable, especially in nonvascularized, clinically sized grafts. In the present study, we investigated the role of viability in AG implanted ectopically and orthotopically in the goat. METHODS: Eight goats were operated on twice. At the first operation, pieces of vital or devitalized autologous cortical bone were implanted in the paraspinal muscles. Eight weeks later, corticocancellous plugs were taken from the femoral condyles, morselized, and reimplanted as either vital or devitalized orthotopic grafts. The goats received fluorochrome labels at 5, 7, and 9 weeks after the first operation. At 12 weeks, the goats were killed, and the samples were examined histologically. RESULTS: Ectopically, new bone had formed in both the vital and devitalized grafts. In the vital grafts, all three fluorochrome labels were present, indicating an early osteogenic mechanism. Within the devitalized grafts, only the 9-week label was observed. Histomorphometry indicated significantly more new bone in the vital grafts (10.3% vs. 1.7% in the devitalized grafts, P <0.01). Orthotopically, both vital and devitalized grafts showed new bone. Again, graft viability was advantageous in terms of new bone formation (14.5% vs. 9.3%, P <0.02). CONCLUSION: The cells inside the autologous bone transplants most likely survived transplantation and were capable of initiating and sustaining new bone formation.     

Cancer of the tongue in patients less than forty

INTRODUCTION: It is the opinion of many surgeons that the biologic potential of cancer that develops in young people is different compared with older patients. Prior reports on small series of patients addressing this issue have inadequate statistical power to resolve the question. METHODS: By use of the techniques of meta-analysis, patients less than 40 years old who had undergone treatment of squamous cell carcinoma (SCC) of the oral tongue were examined. Twenty-eight patients who were encountered in the Department of Otolaryngology, University of Pittsburgh School of Medicine, and 94 patients were identified in the literature for a total of 122 patients <40 years old. A control group of 150 patients, aged 40 years and older treated for SCC of the oral tongue between 1982 and 1994 was identified. RESULTS: Three-year disease-free survival in the group of patients aged less than 40 was 53.3% compared with 3-year disease free survivorship of 55.0% in the older cohort of patients. CONCLUSION: These data strongly suggest that the outcomes of treatment for SCC of the oral tongue in young patients are similar compared with patients older than 40 with similar extent of disease.