Effect of dietary selenium and vitamin E on the biomechanical properties of rabbit bones

It is generally agreed that combined deficiency of selenium and vitamin E leads to several abnormalities including Kashin-Beck disease which is an endemic and chronic degenerative osteoarthrosis. The abnormalities can be reversed by the administration of various forms of selenium and vitamin E. The present study was designed to investigate the effects of dietary selenium and vitamin E on bone tissue and on the biomechanical properties of bone. Young rabbits of both sexes were fed with either a selenium- and vitamin E-adequate diet (control group), or a selenium- and vitamin E-deficient diet or a selenium-excess diet. The selenium-deficient diet resulted in a significant decrease in plasma selenium level and the selenium-excess diet resulted in a significant increase in the plasma selenium level with respect to the corresponding control values (p < 0.05). The diets did not affect the blood cell counts considerably but erythrocyte glutathione peroxidase activity increased (decreased) relatively when the plasma selenium level increased (decreased) (p < 0.05). The light microscopic investigations of the bone tissues of the two experimental groups indicate that the findings of the present work are compatible with osteomalacia. The biomechanical properties of the bones from the three groups were determined experimentally with bending tests. Both the Se- and vitamin E-deficient diet and the Se-excess diet decreased the biomechanical strength of the bones significantly while the bones belonging to the control group always had the largest modulus of elasticity (p < 0.05).     

Biocompatibility of heparin and low-molecular mass heparin in a new implantable medication pump

The present paper deals with the evaluation of normal heparin and low-molecular mass heparin as to their use in a new implantable medication pump. Latest versions of different Pharmacopoeias recommend techniques, which require large sample volumes for aqueous injectable drug solutions. Therefore, a commercially available enzymatic kit was used to determine heparin activity. As this test is designed for heparin plasma levels, transformation of the chromophore occurred only after adding heparin AT III complex, which is usually present in plasma. The applied test was found to be suitable regarding reproducibility, selectivity and sensitivity. There was no loss of enzyme activity of both normal heparin and low-molecular mass heparin within an investigation period of 8 weeks; thus, no decomposition products are to be expected and the biocompatibility of pump materials with both tested heparin preparations is evident.     

Prevention of glucocorticoid induced osteoporosis

INTRODUCTION: It is generally accepted that moderate to high dose glucocorticoid therapy is associated with bone loss and increased fracture risk. The degree of bone loss is closely related to the cumulative corticosteroid dose and the highest rate of bone loss is observed in the first 3 to 6 months of therapy. CURRENT KNOWLEDGE AND KEY POINTS: Optimal management strategies to prevent bone loss should include the use of the lowest efficacious dose of glucocorticoid. Alternate day dosing and bolus do not provide effective protection. Prevention should basically include adequate calcium intakes and additional vitamin D. All patients should be encouraged to modify their lifestyles, including smoking cessation and limitation of alcohol consumption; physical exercise for 30 minutes to 1 hour every day should also be recommended. Sodium restriction and thiazide diuretics have been shown to improve hypercalciuria that sometimes accompanies glucocorticoid therapy. Hormone replacement therapy should be recommended in postmenopausal women, while estrogen-containing oral contraceptives should be advocated in young women with menstrual irregularities, except for patients with systemic lupus erythematosus. FUTURE PROSPECTS AND PROJECTS: Dual-energy X-ray absorptiometry may be useful in patient with high risk of glucocorticoid-induced osteoporosis, as it allows accurate measurements of bone mineral density. Etidronate recently proved to be efficacious in preventing bone loss and decreasing the number of vertebral fractures in menopausal women.     

Effect of sodium naproxen on inflammatory response induced by anterior chamber paracentesis in the rabbit

This study evaluated the effect of sodium naproxen (a reversible competitive inhibitor of cyclo-oxygenase) and phenylephrine (a mydriatic alpha-adrenergic agent) eye drops in maintaining atropine mydriasis in the rabbit after paracentesis. Moreover, to assess the influence of these treatments on vascular and cellular inflammatory responses in the rabbit eye, several biochemical parameters were considered. Anterior chamber paracentesis significantly reduced atropine-induced mydriasis and a parallel elevation of proteins, polymorphonuclear leucocytes (PMNs), prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels in the secondary aqueous humour (obtained 120 min later) was observed. A significant increase in PMNs in the aqueous humour and a parallel increase in myeloperoxidase activity, a measure of PMN infiltration, in the iris-ciliary body were detected. Atropine-induced mydriasis was maintained in rabbits treated with either sodium naproxen or phenylephrine eye drops. However, only in the former group were the inflammatory parameters significantly reduced, with the exception of aqueous LTB4 levels. The inhibition of the protein influx in the aqueous humour and of the miosis produced by sodium naproxen can be related to the high drug levels in the aqueous humour that were effective in inhibiting the cyclo-oxygenase pathway of arachidonic acid metabolism, whereas the effects on PMN infiltration appear to be independent of significant release of the potent chemotactic agent LTB4, synthesized via the 5-lipoxygenase pathway.     

Steroid induced avascular necrosis of bones in eighteen sites: a case report

A patient with idiopathic thrombocytopenia purpura who was treated with high dosage corticosteroids for ten years, developed 18 separate lesions of avascular necrosis in 12 different bones. Despite spontaneous revascularization of many of the lesions, subchrondral collapse caused symptomatic secondary degenerative arthritis in many joints. Pathological examination of both resected femoral heads showed no intravascular thrombosis.     

Bilateral symmetry of biomechanical properties in rat femora

In many studies, bone healing and remodeling have been examined in various animal models using one femur as a control for the contralateral femur based on the assumption that they are bilaterally symmetrical. Symmetry studies have been limited mainly to geometrical properties. The purpose of this study was to determine whether or not there is symmetry in the mechanical properties of rat femora. Two strain gauges were attached to the anterior surface parallel to the long axis of explanted femora of retired female breeder and 120-day-old male Sprague Dawley rats. Femora were mechanically tested in cantilever bending and the strain values were recorded. Moments of inertia, cortical areas, and moduli of elasticity were determined from strains and cross-sectional properties. Female femora showed a bilateral strain difference of less than 2.2% and an elastic modulus difference of less than 8.7%. Males had less than 2.0% and 7.9% differences for strain and elastic moduli, respectively. Statistical analysis showed no significant difference between left and right femoral strain values for the females, but modulus differences were significant different at the p = 0.05 level. There was no significant difference in strain and modulus values for the males, indicating mechanical and geometrical symmetry of their femora.     

Effect of heparin on dextran sulfate sodium-induced colitis

Heparin has been shown to ameliorate inflammatory bowel disease in several series. In addition to its anticoagulant properties, heparin has numerous other effects that may be beneficial in inflammatory bowel disease. Other sulfated polysaccharides, such as dextran sulfate, cause colitis in mice through unknown mechanisms. We postulate that dextran sulfate and heparin may act via similar pathways with opposite effects. To examine this thesis, the effect of heparin on dextran sulfate-induced colitis was studied. Swiss-Webster mice were given 5% dextran sulfate in their drinking water for five days to induce colitis. Heparin was given both therapeutically after the induction of colitis and prophylactically by subcutaneous injections, with saline injections given in controls. Histologic sections of colon were randomized and graded for colitis. Heparinized animals showed no significant difference in the pattern or severity of colitis when compared to control animals. It is concluded that heparin does not ameliorate the murine colitis induced by dextran sulfate in the doses given.     

Effect of heparin on lecithin: cholesterol acyltransferase and lipids in cholestasis

Injury to the hippocamp disturbs learning processes and short-term memory in 20-, 50- and 110-day rats. In 50-day rats, hippocampectomy results in lesser changes in learning and memory than in 20- and 110-day animals. Anatomo-physiological characteristics of the hippocamp in 20-day rats presumably indicate a particular importance of this structure at early stages of ontogenesis, when the brain cortex is not yet sufficiently mature and its connections with other structures are not completely formed. Non-linear dependence of learning disturbance in rats of varying age after hippocampectomy suggests that in rat hippocampal function undergoes changes during individual development of animals.     

High-resolution magnetic resonance imaging: three-dimensional trabecular bone architecture and biomechanical properties

The development of vectors that are capable of efficient gene delivery is crucial to the success of gene therapy. We have developed both recombinant viral and nonviral vectors with the goal of correcting genetic abnormalities in cancer cells that are responsible for malignant transformation. Infection of cancer cells by recombinant adenovirus (Adv) indicates that the level of transduction is variable and dependent on the virus-to-cell ratio. Infection of cells with Adv/p53 resulted in levels of tumor suppressor p53 gene expression that could mediate tumor cell growth suppression and apoptosis, both in vitro and in vivo. The treatment of cancer cells with cisplatin prior to Adv transduction resulted in a higher level of therapeutic gene expression. Epidermal growth factor (EGF)/DNA complexes targeted to cancer cells overexpressing the EGF receptor resulted in efficient transduction of several lung cancer cell lines in vitro. As a result, these vectors provide improved methods with which to treat cancer in the clinical setting with gene therapy.     

Effect of antiparkinsonian medication on plasma levels of chlorpromazine

Twenty-one chronic schizophrenics were stabilized with chlorpromazine therapy at their therapeutic dosage for one month. Trihexyphenidyl hydrochloride or identical placebo was then added according to a double-blind, split crossover design. The duration of each half of the crossover was 15 days. Steady state blood samples were drawn three times weekly during the experimental period and the amount of chlorpromazine was determined. The results indicated there were no differences in the levels obtained between the trihexyphenidyl and the placebo phases. A two-hour postdrug blood sample was also drawn at the end of each phase and again, there were no differences between the two conditions. The importance of these results is discussed.     

Changes in biomechanical properties of biological and synthetic prostheses

Arterial compliance which is an expression of the structural properties of the vessel wall is defined as the fractional change in diameter in response to a unit change in pressure. It is likely to play an important role as a predictive parameter for maintenance of arterial reconstruction. Usually, vascular grafts are implanted with an arbitrarily applied longitudinal tension. The current study was designed to evaluate in vitro the effects of longitudinal tension on the dynamic circumferential compliance of different Dacron, Polytetrafluorethylene, Polyurethane and newly developed synthetic vascular grafts as well as arteries and veins. Longitudinal tensions between 0 and 1000 g were applied. Different grafts showed characteristic peak compliance values due to the used graft material, fabrication and extent of tension. Concerning their different compliance-tension profiles two groups of vascular grafts could be differentiated: 1) grafts which develop best compliance values after implementation of longitudinal traction and 2) prostheses which gain optimal biomechanical properties without any traction. There is strong evidence for modulation of compliance by implementation of longitudinal tension which suggests that it is useful to improve long term patency of arterial reconstruction.     

Effect of heparin on the interaction between platelets with collagen

An effect of a standard heparin preparation on the interaction between blood platelets and collagen has been investigated. The experiments have shown, that the addition of heparin in the concentration of 0.3; 0.6 or 0.9 IU/mL did not change the interaction between blood platelets and collagen. Such interaction increased, when heparin concentration was 1,2 IU/mL, and remained unchanged despite the further increase in heparin concentration. The authors suggest that such a course of this interaction results from the stimulating action of heparin added in adequate concentration on protein release from platelet alpha granulations--which bound GP II b/III a complex with collagen.     

The effects of dietary-induced obesity on the biomechanical properties of femora in male rats

OBJECTIVE: To assess the effects of diet-induced obesity (DIO), on the biomechanical and biochemical properties of the femur in mature male rats. DESIGN AND SUBJECTS: Two groups of male rats were studied. The DIO experimental group was fed a high caloric diet and a 31% sucrose solution as drinking fluid for a month, whereas the control group was fed lab chow and tap water. MEASUREMENT: Body weight; body water; lean body mass; femoral length; average cortical thickness; outer anteroposterior diameter; outer mediolateral diameter; cortex area; moment of inertia; cortical and cancellous bone hydration; tendon and muscle hydration; ash content of cortical and cancellous bone; ultimate load; deflection at ultimate load; ultimate strength; stiffness; elastic modulus and energy absorption capacity. RESULTS: 'Gainers' (final body weight in excess of three standard error of mean of the controls) were 19.1% heavier, with higher body fat, whereas body water, lean body mass, hydration of cancellous bone and ash content of cortical bone were lower, when compared to controls. Rats that failed to gain weight, despite the high caloric diet, were termed 'resisters' (weight gain less than three standard error of mean of the controls). Ultimate load, deflection at ultimate load and femoral energy absorption capacity were significantly higher in the experimental group when compared to the controls. However, no differences were found among the groups with respect to ultimate stress and stiffness. CONCLUSION: The weight gain produced by DIO may lead to bone adaptation and improved biomechanics.     

Effect of calcaneal osteotomy and lateral column lengthening on the plantar fascia: a biomechanical investigation

OBJECTIVES: To evaluate the efficacy and safety of one single intravenous methylprednisolone (IVMP) pulse therapy in myasthenia gravis. MATERIAL AND METHODS: We performed a double blind placebo controlled study (2+2 g IVMP vs placebo) in patients with moderate MG. RESULTS: A mean increase in muscle function of 27 points was found in the treatment group after one IVMP pulse as compared with a 0.7 point increase in the placebo group (P<0.01). In the IVMP group 8 of 10 patients showed a positive treatment response. The mean duration of improvement after IVMP was 8 weeks (range 4-14 weeks). No severe side effects were found. Acetylcholine receptor antibody concentrations were unchanged in spite of the positive treatment response. CONCLUSIONS: We conclude that a single IVMP treatment is efficacious and safe in the treatment of moderate MG.     

Sustained local delivery of heparin to the rabbit arterial wall with an electroporation catheter

Since the rapid expansion of managed care coupled with dramatic reductions in lengths of inpatient stay, there is widespread concern that the emphasis on cost containment is eclipsing attention to patient care. The present study was undertaken to evaluate speculations that the majority of short-stay (less than 48 hours) admissions to a psychiatric inpatient service at a large teaching hospital in the midwestern United States consisted of public pay patients who were rapidly transferred to area state hospitals. Using two cases mix measures, severity of illness and changes in acuity and clinical outcomes of a sample of short-stay (n = 77) and longer stay (n = 145) admissions were compared. Short-stay admissions, although similar to longer stay patients in terms of demographics, Axis I diagnosis, payer status, and appropriateness of admission, are clinically distinct. The use of nonhospital alternatives in treating a subsample of suicidal patients and the implications for improved mental health services delivery are discussed.     

Experimental meningococcal septicemia. Effect of heparin therapy

The pathogenesis of experimental meningococcal septicemia and the efficacy of heparin sodium therapy were evaluated by inoculating rabbits intraperitoneally with type B meningococci in mucin. Half the rabbits died, and the respiratory distress and circulatory failure that occurred during the terminal phase of the disease were associated with diffuse pulmonary capillary and venular thrombosis and with renal glomerular fibrin deposition. Platelet and leukocyte counts and plasma fibrinogen levels decreased in all rabbits, and prothrombin and partial thromboplastin times were prolonged. Pretreatment with heparin sodium diminished intravascular fibrin deposition but failed to prevent the pulmonary microthrombi and did not either reduce the mortality or improve the survival time. We conclude that death in meningococcal septicemia is due to widespread thrombosis of the pulmonary microcirculation. The disease is complicated by diffuse intravascular coagulation, which can be controlled with heparin sodium but which is not immediately life-threatening.     

Comparison of biomechanical properties of the incisor periodontal ligament among different species

BACKGROUND: The aim of this study was to obtain a more precise understanding of the mechanical properties of the periodontal ligament in continuously erupting incisors by comparing the shear stress-strain relations among teeth from four closely related species. METHODS: Four species of experimental animals (mice, hamsters, rats, and rabbits) were used. Transverse sections of the left mandibular incisors were cut from the incisal, middle, and basal regions of each incisor. The tooth was pushed out of the alveolar bone in an extrusive direction at 5 mm/min using a materials testing machine. The maximum shear stress, maximum shear strain, tangent modulus, and failure strain energy density were estimated from the resulting stress-strain curve. Polarized light microscopic observations of collagen fibers were also made. RESULTS: All the biomechanical measures tended to decrease from the incisal toward the basal regions in all species. There were large species differences, especially in the incisal region, with the greatest maximum shear stress and failure strain energy density in hamsters. The greatest tangent modulus and the smallest maximum shear strain were observed in mice. The birefringent fiber architectures of the periodontal ligaments in the four species appeared to be similarly organized; the incisal periodontal ligament appeared to have more organized and thicker collagen fibres than did the middle and basal ligaments in the four species. CONCLUSIONS: These results suggest that the regional differences in the biomechanical properties of the periodontal ligament depend upon the developmental stages of the periodontal collagen fibers that may be related to the general arrangement, diameters, and densities of the collagen fiber bundles and the fiber insertions into the alveolar bone and cementum. The species differences in the biomechanical properties may be due to differences in the width of the periodontal ligament and the waviness as well as the strength and stiffness of the periodontal collagen fibers.