The role of exercise training and the endocannabinoid system in atherosclerotic plaque burden and composition in Apo-E-deficient mice

INTRODUCTION

We investigated the effect of combining exercise training and treatment with an endocannabinoid receptor 1 inhibitor (Rimonabant) on atherosclerosis burden and composition.

METHODS

Forty-eight apolipoprotein E-deficient (ApoE-/-) mice were kept on a 16-week high-fat diet. Mice were then placed on a normal diet and were randomized to the following groups with n=12 mice for 6 more weeks: 1) Control (Co) - no intervention; 2) Exercise (Ex) - exercise training on treadmill; 3) Rimonabant (Ri) - oral administration of rimonabant (10 mg/kg/day); or 4) Rimonabant+Exercise (RiEx) - combination of Ri and Ex groups treatment. At the end, all animals were sacrificed, and blood samples, as well as aortic root specimens, were obtained for histomorphometric analysis and quantification of the serum and plaque content of matrix metalloproteinases (MMPs).

RESULTS

The mean plaque area was significantly smaller (RiEx: 43.18±1.72%, Ri: 44.66±3.1%, Ex: 49±4.10%, Co: 70.43±2.83%) in all active treatment groups relative to the Co group (p<0.01). Conversely, the relative concentrations of collagen and elastin were increased significantly across all treatment groups compared to Co (p<0.05). Immunohistochemical analysis revealed significantly reduced macrophage content within plaques after all interventions, with the most pronounced effect observed after combined treatment (RiEx: 9.4±3.92%, Ri: 15±2.45%, Ex: 19.78±2.79%, Co: 34.25±4.99%; p<0.05). Within plaques, the TIMP-1 concentration was significantly upregulated in exercise-treated groups. MMP-3 and MMP-9 concentrations were equivalently decreased in all three active treatment groups compared to controls (p<0.001).

DISCUSSION

Both exercise and rimonabant treatments induced plaque regression and promoted plaque stability. The combined treatment failed to show additive or synergistic benefits relative to either intervention alone.

Adhesions and Healing of Intestinal Anastomoses

Background. Postoperative adhesions are the result of aberrant peritoneal healing. As they are the leading cause of postoperative bowel obstruction, anti-adherence barriers are advocated for their prevention. This study looks into the effect of these biomaterials on the healing of intestinal anastomoses. Materials and Methods. Thirty-three New Zealand White rabbits underwent laparotomy, transection of the terminal ileum, and creation of an end-to-end anastomosis. Animals were randomized into 3 groups: the Control group (n = 11); the Icodextrin group, receiving icodextrin 4% intraperitonealy (n = 11); and the HA/CMC group, having the anastomosis wrapped with a hyaluronic acid/carboxymethylcellulose film (n = 11). All animals were sacrificed on the seventh postoperative day. Macroscopic adhesions were graded and anastomotic strength was tested by the burst pressure. Histological healing was assessed in a semiquantitative way for the presence of ulceration, reepithelization, granulation tissue, inflammation, eosinophilic infiltration, serosal inflammation, and microscopic adhesions. Univariate and multivariate analysis was used. Results are given as medians with interquartile range. Results. The median adhesion scores were the following: Control 1 (0-3), Icodextrin 0 (0-1), HA/CMC 0 (0-0), P = .017. The burst pressure did not differ between the groups; however, all except one bowel segments tested burst away from the anastomosis. The macroscopic and histological anastomotic healing was comparable in all 3 groups. A poor histological anastomotic healing score was associated with a higher adhesion grade (odds ratio = 1.92; 95% confidence interval = 1.06-3.47; P = .032). Conclusion. Adhesion formation was inhibited by the materials tested without direct detrimental effects on anastomotic healing. Poor anastomotic healing provokes adhesions even in the presence of anti-adhesion barriers.

The complementary effects of atorvastatin and exercise treatment on the composition and stability of the atherosclerotic plaques in ApoE knockout mice

Aim

This study aimed to investigate the effects of combined atorvastatin and exercise treatment on the composition and stability of the atherosclerotic plaques in apolipoproteinE (apoE) knockout mice.

Methods

Forty male, apoE^−/− mice were fed a high-fat diet for 16 weeks. Thereafter, while maintained on high-fat diet, they were randomized into four (n = 10) groups for 8 additional weeks: Group CO: Control. Group AT: Atorvastatin treatment (10 mg/Kg/day). Group EX: Exercise-training on treadmill. Group AT+EX: Atorvastatin and simultaneous exercise training. At the study’s end, plasma cholesterol levels, lipids and triglycerides were measured, along with the circulating concentrations of matrix-metalloproteinases (MMP-2,3,8,9) and their inhibitors (TIMP-1,2,3). Plaque area and the relative concentrations of collagen, elastin, macrophages, smooth muscle cells, MMP-2,3,8,9 and TIMP-1,2,3 within plaques were determined. Lastly, MMP activity was assessed in the aortic arch.

Results

All intervention groups showed a lower degree of lumen stenosis, with atheromatous plaques containing more collagen and elastin. AT+EX group had less stenosis and more elastin compared to single intervention groups. MMP-3,-8 -9 and macrophage intra-plaque levels were reduced in all intervention groups. EX group had increased TIMP-1 levels within the lesions, while TIMP-2 was decreased in all intervention groups. The blood levels of the above molecules increased during atherosclerosis development, but they did not change after the therapeutic interventions in accordance to their intra-plaque levels.

Conclusion

The two therapeutic strategies act with synergy regarding the extent of the lesions and lumen stenosis. They stabilize the plaque, increasing its content in elastin and collagen, by influencing the MMP/TIMP equilibrium, which is mainly associated with the macrophage amount. While the increased MMP-2,-3,-8 -9, as well as TIMP-1 and TIMP-2 circulating levels are markers of atherosclerosis, they are not correlated with their corresponding concentrations within the lesions after the therapeutic interventions, and cannot serve as markers for the disease development/amelioration.

The anti-inflammatory effects of exercise training promote atherosclerotic plaque stabilization in apolipoprotein E knockout mice with diabetic atherosclerosis

Physical exercise is the cornerstone of cardiovascular disease treatment. The present study investigated whether exercise training affects atherosclerotic plaque composition through the modification of inflammatoryrelated pathways in apolipoprotein E knockout (apoE^−/−) mice with diabetic atherosclerosis. Forty-five male apoE^−/− mice were randomized into three equivalent (n=15) groups: control (CO), sedentary (SED), and exercise (EX). Diabetes was induced by streptozotocin administration. High-fat diet was administered to all groups for 12 weeks. Afterwards, CO mice were euthanatized, while the sedentary and exercise groups continued high-fat diet for 6 additional weeks. Exercising mice followed an exercise program on motorizedtreadmill (5 times/week, 60 min/session). Then, blood samples and atherosclerotic plaques in the aortic root were examined. A considerable (P<0.001) regression of the atherosclerotic lesions was observed in the exercise group (180.339±75.613×10³µm²) compared to the control (325.485±72.302×10³ µm²) and sedentary (340.188±159.108×10³µm²) groups. We found decreased macrophages, matrix metalloproteinase-2 (MMP-2), MMP-3, MMP-8 and interleukin-6 (IL-6) concentrations (P<0.05) in the atherosclerotic plaques of the exercise group. Compared to both control and sedentary groups, exercise training significantly increased collagen (P<0.05), elastin (P<0.001), and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) (P<0.001) content in the atherosclerotic plaques. Those effects paralleled with increased fibrous cap thickness and less internal elastic lamina ruptures after exercise training (P<0.05), while body-weight and lipid parameters did not significantly change. Plasma MMP-2 and MMP-3 concentrations in atherosclerotic tissues followed a similar trend. From our study we can conclude that exercise training reduces and stabilizes atherosclerotic lesions in apoE^−/− mice with diabetic atherosclerosis. A favorable modification of the inflammatory regulators seems to explain those beneficial effects.

The effect of propranolol on aortic structure and function in normotensive rats

INTRODUCTION

Beta-blocking agents are widely used for the treatment of many cardiovascular diseases. The effect of these agents, however, on the aortic wall structure and function has not been well defined. The present study was undertaken to investigate the effect of therapy with propranolol on wall structure and aortic function in rats.

METHODS

20 healthy Wistar rats (350-400 g) were assigned to a control group (n=8), with rats receiving only water and food, and an experimental group (n=12), in which 100 mg/kg/day propranolol was administered in the drinking water. Three months after initiation of treatment, aortic pressures and aortic pulse wave velocity (PWV) were measured using high-fidelity Millar catheters. Extensive histopathologic studies were performed in the wall of the descending thoracic aorta.

RESULTS

Systolic, mean, diastolic, and pulse pressure were significantly lower in the propranolol-treated rats compared to controls (p<0.05). For any given systolic, mean, and pulse pressure, PWV was greater in the propranolol-treated animals (p<0.05). The heart rate was lower and the response to isoproterenol infusion was less in the propranolol-treated animals. Smooth muscle content was decreased and collagen content was increased in the aortic wall of the propranolol-treated animals compared to controls.

CONCLUSIONS

Long-term propranolol administration elicits an increase in PWV adjusted for aortic pressure. This may be related to accumulation of collagen in the aortic wall at the expense of smooth muscle cells. The aortic stiffening may explain some of the reported data, suggesting that the effect of β-blockade therapy in patients with arterial hypertension may be inferior to other pharmacologic agents.

Effects of exercise training on the severity and composition of atherosclerotic plaque in apoE-deficient mice

AIM

To investigate the effects of exercise on atherosclerotic plaque composition, the concentration of matrix metalloproteinases (MMPs) in the atherosclerotic plaque and the systemic circulation.

METHODS

Ninety apolipoprotein E-deficient (apoE(-/-)) mice (45 male) were randomized to the following groups (n=15 each): control male/female; sedentary male/female; exercise male/female. Mice were kept on a 16-week high-fat diet. Subsequently, the control groups were sacrificed, while the rest of the animals were placed on a normal diet for 6 more weeks. During the latter period, the exercise groups were trained daily on treadmill. At the end of the study, mice were euthanized, and blood samples as well as aortic root specimens were obtained.

RESULTS

Compared to control and sedentary animals, exercise training reduced atherosclerotic plaques (-30%; p<0.01) and increased elastin and collagen content in both genders (p<0.05). Body weight or lipid profile did not change significantly. Decreased macrophages and MMP-9 as well as increased tissue inhibitor of metalloproteinases 1 (TIMP-1) levels were observed in the atherosclerotic plaques of the exercise-treated groups (p<0.05). Plasma concentrations of MMP-9 decreased, while plasma TIMP-1 levels increased in the exercise compared to control and sedentary groups (p < 0.05).

CONCLUSIONS

Exercise training had a favorable effect on the size and composition of the atherosclerotic plaque in apoE(-/-) mice, associated with suppressed MMP activity.

Exercise training ameliorates the effects of rosiglitazone on traditional and novel cardiovascular risk factors in patients with type 2 diabetes mellitus

The aim of the study was to investigate the effects of rosiglitazone and/or exercise training on novel cardiovascular risk factors in patients with type 2 diabetes mellitus. One hundred overweight/obese type 2 diabetes mellitus patients, with inadequate glycemic control (hemoglobin A(1c) >7%) despite combined treatment with gliclazide plus metformin, were randomized using a 2 x 2 factorial design to 4 equivalent (n = 25) groups, as follows: (1) CO: maintenance of habitual activities, (2) RSG: add-on therapy with rosiglitazone (8 mg/d), (3) EX: adjunctive exercise training, and (4) RSG + EX: supplementary administration of rosiglitazone (8 mg/d) plus exercise training. No participant had diabetic vascular complications or was receiving lipid-lowering therapy. Anthropometric parameters, cardiorespiratory capacity, glycemic and lipid profile, apolipoprotein (apo) A-I, apo B, interleukin (IL)-10, IL-18, insulin resistance, and blood pressure were measured before and after 12 months of intervention (P < .05). Both RSG and EX groups significantly reduced glycemic indexes, insulin resistance, blood pressure, and IL-18, whereas they significantly increased high-density lipoprotein, cardiorespiratory capacity, and IL-10, compared with CO group (P < .05). Besides this, exercise-treated patients conferred a remarkable down-regulation in the rest of lipid parameters (total cholesterol, low-density lipoprotein cholesterol, triglycerides, apo B) and body fat content (P < .05) in comparison with CO group. On the other hand, RSG group rather than CO group considerably increased apo A-I levels and body mass index (P < .05). Notably, the combined treatment group yielded pronounced beneficial changes in glycemic indexes, lipid profile, insulin resistance, blood pressure, IL-10, IL-18, apo A-I, and apo B (vs CO group, P < .05). Furthermore, the addition of exercise to rosiglitazone treatment counteracted the drug-related negative effects on body weight, low-density lipoprotein, and total cholesterol. Rosiglitazone plus exercise training elicited additive effects on body composition, glycemic control, and traditional and novel cardiovascular risk factors in type 2 diabetes mellitus patients, indicating complementary effects.

Effects of rosiglitazone and metformin treatment on apelin, visfatin, and ghrelin levels in patients with type 2 diabetes mellitus

Visfatin, ghrelin, and apelin are the most recently identified adipocytokines; but their response to insulin-sensitizing agents is poorly clarified. We aimed to assess the differential effects of either rosiglitazone or metformin monotherapy on the aforementioned adipocytokines in patients with type 2 diabetes mellitus (T2DM). One hundred T2DM patients (30 men, 70 women), with poor glycemic control (glycosylated hemoglobin >6.5%) while taking 850 mg of metformin daily, were enrolled. All participants were randomized to receive either adjunctive therapy with rosiglitazone (8 mg/d, n = 50) or the maximum dose (2550 mg/d) of metformin (MET group, n = 50). Anthropometric parameters, glycemic and lipid profile, high-sensitivity CRP (hs-CRP), insulin resistance (homeostasis model assessment of insulin resistance index [HOMA-IR]), visfatin, ghrelin, and apelin were assessed at baseline and after 14 weeks of therapy. Both rosiglitazone and metformin led to similar, significant improvement in glycemic profile and apelin levels, whereas lipid parameters, fat mass, and visfatin remained almost unaffected (P > .05). Insulin resistance was significantly attenuated in both groups, but to a lesser degree in the MET group (P = .045). Rosiglitazone-treated patients experienced a significant decrease in hs-CRP and systolic blood pressure compared with baseline values and those of the MET group (P < .05). Besides, rosiglitazone treatment considerably increased plasma ghrelin (3.74 +/- 1.52 ng/mL) in comparison with either baseline (P = .034) or metformin monotherapy values (-2.23 +/- 1.87 ng/mL, P = .008). On the other hand, the MET group, rather than the rosiglitazone group, had decreased body mass index (-0.79 +/- 0.47 vs 0.56 kg/m(2), P = .009). The aforementioned changes in apelin and ghrelin were independently associated with HOMA-IR changes. Both rosiglitazone and metformin favorably changed glycemic indexes and apelin levels. The addition of rosiglitazone seemed to confer greater benefits in ghrelin, hs-CRP, systolic blood pressure, and HOMA-IR regulation than metformin monotherapy. Although these results reflect improvement in cardiovascular risk profile, the overall clinical importance of insulin sensitizers must be further assessed.

Time-course of mechanical changes of the rat aorta following chronic beta-blocker treatment

INTRODUCTION

The mechanical properties of the aorta play an important role in arterial homeostasis and constitute a prognostic factor in cardiovascular disease. This study determined the time-course of mechanical changes of the thoracic aorta following prolonged beta (beta)-blocker treatment.

METHODS

Sixty-six healthy male Wistar rats were randomized to 4 groups. Group A was divided into subgroups A1 (n=6), A2 (n=6), and A3 (n=6), with animals receiving only water. In groups B (n=16), C (n=16), and D (n=16), propranolol was added to the drinking water (100 mg/kg/day). Animals of groups A1 and B, A2 and C, and A3 and D were sacrificed after 1, 2, and 3 months. The effect of beta-blockade was assessed by heart rate changes in response to isoproterenol infusion. The thoracic aorta was excised and submitted to mechanical testing. Regression analysis was performed to evaluate the relationship between elastic modulus and stress for low (part I), physiologic (part II), and high (part III) stresses.

RESULTS

Data from subgroups A1, A2, and A3 were pooled together and were used as a control. Differences were found in the regression parameters of parts II and III between the propranolol-treated groups and controls, indicating that the aorta was stiffer in propranolol-treated rats compared to controls at physiologic stresses, and at physiologic and high strains. Changes developed progressively with the duration of treatment. No differences were found in the regression parameters of part I, indicative of non-varying elastic modulus, i.e. stiffness, at low stresses and strains.

CONCLUSIONS

Chronic blockade of beta-adrenergic receptors induces changes in the mechanical properties of the thoracic aorta. Aortic stiffening in response to beta-blocker treatment may be of great clinical significance.

Visfatin (nampt) and ghrelin as novel markers of carotid atherosclerosis in patients with type 2 diabetes

OBJECTIVE

Visfatin (nampt) and ghrelin are the most recently identified adipocytokines, but their role in atherosclerosis is poorly clarified. In our study we investigated their association with advanced carotid atherosclerosis and carotid intima-media thickness (CIMT) in patients with type 2 diabetes mellitus (T2DM).

METHODS

122 patients (50 males) with T2DM, aged 55-70 were enrolled. Sixty-four age- and sex-matched healthy individuals served as controls (group A). CIMT was assayed in all participants by ultrasound. Among diabetic patients, 47 appeared with carotid plaques (group B), while 75 without plaques (group C). Anthropometric parameters, blood pressure, glycemic and lipid profile, high-sensitivity CRP (hsCRP), insulin resistance (HOMA-IR), fibrinogen, nampt and ghrelin were measured.

RESULTS

Diabetic patients had a higher mean-CIMT, increased body-mass index, worse lipid profile, elevated blood pressure and higher levels of white blood cells count, nampt and hsCRP with respect to controls (p<0.01). Among diabetic patients, groups B and C were comparable in anthropometric, glycemic and lipid parameters. Serum nampt was significantly higher in group B rather than in groups A and C (p<0.05). On the other hand, ghrelin levels were considerably lower only in diabetic patients with carotid atherosclerosis compared with healthy individuals. In univariate analysis, mean-CIMT correlated with age (r=0.312; p=0.003), nampt (r=0.341; p<0.001) and ghrelin (r=-0.421; p=0.002) and the latter associations remained significant in multiple regression analysis.

CONCLUSIONS

High nampt and low ghrelin serum levels are significantly associated with advanced carotid atherosclerosis in patients with T2DM. Moreover these adipocytokines are independently associated with CIMT, implicating their role as novel atherosclerotic biomarkers and providing another important link between adiposity and atherosclerosis.

The effects of hypothyroidism on the mechanical properties and histomorphological structure of the thoracic aorta

This experimental study investigates the effects of hypothyroidism on the descending thoracic aorta. Hypothyroidism was induced in 20 male Wistar rats by administering 0.05% of 6-n propyl 2-thiouracil (PTU) in their drinking water for 8 weeks. Euthyroid rats were used as controls. Animals were sacrificed and longitudinal strips of the descending aorta were subjected to various preselected levels of stress in a uniaxial tensile-testing device. Analysis of stress-strain, elastic modulus-strain curves disclosed significant differences between groups, indicative of stiffer aortas in hypothyroid animals at the upper physiologic and higher levels of pressure. Remodeling of the aortic wall of hypothyroid animals revealed significant histological changes. The thoracic aorta of hypothyroid rats compared with that of euthyroid ones became stiffer at high strains, including the upper physiologic range, loosing part of its distensibility. Hypothyroidism was also associated with diameter enlargement and substantial lengthening of the aorta.

Segmental differences of aortic function and composition: clinical implications

INTRODUCTION

Aortic function is an important determinant of pressure and flow in the entire cardiovascular system. This study aimed at evaluating segmental differences of aortic function and composition, in order to understand their clinical implications.

METHODS

The thoracic aorta from each of 20 healthy pigs was divided into four and the abdominal into three segments. From the stress-strain curves, relationships between elastic modulus and stress were obtained for low (part I), physiologic (part II) and high (part III) stresses. Linear regression analysis was performed.

RESULTS

No differences were found in the intercepts and slopes for part I. Significant differences were found in the intercepts and slopes between the thoracic and abdominal segments for part II, and in the slopes for part III, suggesting that the distal segments became progressively stiffer. Histologic examination disclosed higher concentrations of elastin in the proximal and collagen in the distal aortic wall. Aortic wall thickness reduced from proximal to distal aorta. Multiple regression analysis showed good correlations between elastic moduli and either elastin in part I (r=0.640) or collagen in part III (r=0.803).

CONCLUSIONS

The elastic properties and composition vary in different aortic segments. These differences should be taken into consideration when aortic function is determined in clinical practice.

The mechanical performance and histomorphological structure of the descending aorta in hyperthyroidism

Thyroid hormones decrease systemic vascular resistance by directly affecting vascular smooth muscle relaxation. There is limited literature about their effect on the mechanical performance of the aortic wall. Therefore, the authors determined the influence of hyperthyroidism on the mechanical properties and histomorphological structure of the descending thoracic aorta in rats. Severe hyperthyroidism was induced in 20 male Wistar rats by administering L-thyroxine (T(4)) in their drinking water for 8 weeks; age-matched normal euthyroid rats acted as controls. Animals were sacrificed, and the mechanical and histomorphometrical characteristics of the descending thoracic aorta were studied. The aortic wall of hyperthyroid rats was stiffer than that of euthyroid animals at the upper physiologic levels of stress or strain (p < 0.05) but less stiff at the lower physiologic and lower levels (p < 0.05). The aorta of hyperthyroid animals compared with that of euthyroid ones showed an increase of the internal and external diameters (p < 0.05), the media area (p < 0.05), the number of smooth muscle cell nuclei (p < 0.05), and the collagen density (p < 0.05) and a decrease in the elastin laminae thickness (p < 0.001) and elastin density (p < 0.001). In hyperthyroid rats, the aortic wall was stiffer at the upper physiologic and higher levels of stress and strain. These changes correlated with microstructural changes of the aortic wall. The coexistence of hyperthyroidism with disease states or clinical conditions that predispose to increased arterial pressure may be associated with increased arterial stiffness and have undesirable consequences on the mechanical performance of the thoracic aorta and hemodynamic homeostasis. These changes could lead to an increased risk for developing vascular complications.

A structural basis for the aortic stress–strain relation in uniaxial tension

A constitutive law that includes three analytical expressions was recently proposed to approximate the low, physiologic, and high-stress parts of the aortic stress-strain relation in uniaxial tension, consistent with the biphasic nature of the aortic wall under passive conditions. This consistency, and the fact that previous phenomenological uniaxial laws have only indirectly been related to vessel wall structure, motivates the investigation of the structural basis underlying the newly proposed three-part constitutive law. For this purpose, longitudinally oriented aortic strips were fixed in Karnovsky's solution, while subjected to various pre-selected levels of uniaxial tensile stress. Light microscopy examination disclosed that the elastic lamellae gradually unfolded at low and were almost straight at physiologic and high stresses, while collagen fibers reoriented in the longitudinal axis at low, started uncoiling at physiologic, and straightened massively at high stresses. In the circumferential sections, the elastic lamellae and the circumferentially distributed collagen bundles remained wavy at all levels of longitudinally applied stress. These microstructural changes suggest that elastin becomes load-bearing at low, and collagen at physiologic but mostly at high stresses, so that the first and third parts of the constitutive law are in turn due to the presence of elastin and collagen alone, and the second due to both elastin and collagen. The structural basis of this constitutive law allows physically significant interpretation of its parameters, offering insight into how the aortic microstructure determines the macromechanical response.

Post-Vagotomy Mechanical Characteristics and Structure of the Thoracic Aortic Wall

This study assessed the long-term effect of vagotomy on the structure and passive mechanical characteristics of the thoracic aorta under a wide range of stresses in vitro. Eight healthy Landrace pigs underwent bilateral vagotomy distal to the origin of the recurrent laryngeal nerve, and 10 pigs were sham-operated. Three months post-surgery, the aorta was excised and specimens from the ascending aorta, arch, and descending thoracic aorta were subjected to histomorphometrical evaluation and uniaxial tensile-testing until failure. Elastic modulus-stress data were plotted and submitted to regression analysis. Structural remodeling after vagotomy was characterized as vascular growth in the ascending aorta and arch, and as thinning in the descending thoracic aorta. In the aortic segments of vagotomized animals, the area density of elastin and collagen was increased, but smooth muscle density was decreased. Similar differences in regression parameters and failure strength between groups were found in all aortic segments, indicating that the vessel wall was stiffer and stronger in vagotomized animals. In the clinical setting, disease states or drugs blocking the regulatory role of the vagi nerves on the aortic wall may have undesirable consequences on the mechanical performance of the thoracic aorta, and therefore on hemodynamic homeostasis.

Immunomodulatory intervention in sepsis by multidrug-resistant Pseudomonas aeruginosa with thalidomide: an experimental study

Background

Thalidomide is an inhibitor of tumour necrosis factor-alpha (TNFα) that has been proven effective for the treatment of experimental sepsis by Escherichia coli. It was tested whether it might behave as an effective immunomodulator in experimental sepsis by multidrug-resistant (MDR) Pseudomonas aeruginosa.

Methods

Sepsis was induced by the intraperitoneal injection of 1 × 10⁸ cfu/kg inoculum of the test isolate in a total of 109 Wistar rats divided in three groups as follows: group A controls; group B administered seed oil 30 minutes before bacterial challenge; and group C administered 50 mg/kg of thalidomide diluted in seed oil 30 minutes before bacterial challenge. Blood was sampled for estimation of endotoxins (LPS), TNFα, interferon-gamma (IFNγ), nitric oxide (NO) and malondialdehyde (MDA). LPS was measured by the QCL-1000 LAL assay, TNFα and IFNγ by ELISA, NO by a colorimetric assay and MDA by the thiobarbiturate assay.

Results

Mean (± SE) survival of groups A, B and C were 18.60 ± 1.84, 12.60 ± 0.60 and 30.50 ± 6.62 hours (p of comparisons A to C equal to 0.043 and B to C equal to 0.002). Decreased TNFα and NO levels were found in sera of animals of group C compared to group A. Plasma levels of LPS, MDA and IFNγ did not differ between groups.

Conclusion

Intake of thalidomide considerably prolonged survival in experimental sepsis by MDR P.aeruginosa an effect probably attributed to decrease of serum TNFα.

n-6 polyunsaturated fatty acids enhance the activities of ceftazidime and amikacin in experimental sepsis caused by multidrug-resistant Pseudomonas aeruginosa

Recent in vitro and ex vivo studies disclosed an enhancement of the activity of antimicrobials on multidrug-resistant Pseudomonas aeruginosa by n-6 polyunsaturated fatty acids (PUFAS); therefore their effect was evaluated in experimental sepsis in 60 rabbits. Solutions of gamma-linolenic acid (GLA) and arachidonic acid (AA) were administered intravenously with ceftazidime and amikacin in rabbits with sepsis caused by one multidrug-resistant isolate. Therapy was started after bacterial challenge in five groups comprising 12 animals in each group: A, normal saline; B, antimicrobials; C, 99% ethanol and antimicrobials; D, GLA and antimicrobials; and E, AA and antimicrobials. Blood was sampled for the estimation of levels of endotoxins in serum (lipopolysaccharide), leukocytes, tumor necrosis factor alpha (TNF-alpha) and antimicrobials. Animals were sacrificed 210 min after bacterial challenge for tissue cultures. All animals had considerable endotoxemia and evolved leukopenia. The number of viable cells in blood, lung, and mesenteric lymph nodes was significantly reduced in groups D and E compared to that in other groups. Levels of antimicrobials in serum were inadequate to achieve bacterial killing due to the level of resistance. n-6 PUFAs did not influence TNF-alpha. It is concluded that intravenous coadministration of n-6 PUFAs and antimicrobials enhanced antimicrobial bacterial killing in experimental sepsis caused by multidrug-resistant P. aeruginosa.

Rapid alterations of serum fatty acids with the intravenous administration of an arachidonate solution

Polyunsaturated fatty acids (PUFAs) have been shown to possess a considerable anti-tumor and anti-bacterial effect in vitro. In an attempt to achieve serum concentrations of these acids similar to those applied in vitro, a solution of ethyl ester of arachidonic acid (AA) was administered intravenously at 25 mg/kg within 10 min in six male rabbits. Blood samples were collected before and 60 min after infusion from catheters inserted in the hepatic veins and in the carotid artery. Analysis of serum fatty acids was performed by gas chromatography mass spectrometry. Elevated concentrations of elongated fatty acids were detected in the hepatic veins after infusion. Mean concentrations of arachidonate in the hepatic veins and the carotid arteries after infusion of AA were 2.77 and 3.73 microM, respectively. It is concluded that the intravenous administration of a solution of AA might result in increased hepatic biosynthesis of serum saturated and unsaturated fatty acids of elongated carbon chains. The increasing interest for the application of PUFAs in therapeutics renders further study mandatory to clarify the significance of these findings.

The influence of indomethacin co-administration on ofloxacin levels in plasma and cerebrospinal fluid in rats

The possible increase of ofloxacin levels in serum and cerebrospinal fluid (CSF) by concomitant indomethacin administration was investigated in 120 healthy adult rats. The animals were administered intramuscular doses of ofloxacin 30 mg/kg alone (Group A, n = 60) or with indomethacin 2 mg/kg (Group B, n = 60). Blood and CSF samples were obtained from both groups at 30, 45, 60 and 90 min post-administration. Concentrations of ofloxacin were estimated using a microbiological assay. Co-administration of indomethacin did not affect plasma levels of ofloxacin significantly; however, higher levels were found in all CSF samples after co-administration with indomethacin, particularly after 90 min with 0.59 microg/ml versus zero median values when only ofloxacin was administered (P = 0.05). No central nervous system adverse effects were observed clinically. No correlation between levels of ofloxacin in plasma and CSF could be established either in rats administered only ofloxacin or in rats administered both drugs. The presented pharmacokinetic findings revealed that co-administration of ofloxacin and indomethacin may result in protracted quinolone levels in the CSF. However, the absence of significant correlation between concentrations of ofloxacin in plasma and CSF upon co-administration of indomethacin, as well as of central nervous system adverse effects, make the probability of an epileptogenic interaction between them unlikely. These results merit further clinical evaluation.

Immunomodulatory clarithromycin treatment of experimental sepsis and acute pyelonephritis caused by multidrug-resistant Pseudomonas aeruginosa

Clarithromycin was administered intravenously to 55 rabbits to evaluate its effect on experimental sepsis caused by multidrug-resistant Pseudomonas aeruginosa. Acute pyelonephritis was induced after ligation of the right ureter and injection of 10(8) CFU of the test isolate per kg of body weight into the renal pelvis. The animals were divided into six groups: group A, controls; group B, rabbits that received one intravenous dose of 80 mg of clarithromycin per kg concomitantly with bacterial challenge; group C, rabbits that received two doses of clarithromycin, the second one of which was given 2 h after the first one; group D, rabbits that received 15 mg of amikacin per kg; group E, rabbits that received one dose of clarithromycin and amikacin; and group F, rabbits that received two doses of clarithromycin and amikacin. Serum endotoxin levels were estimated by the QCL-1000 Limulus amoebocyte lysate assay, tumor necrosis factor alpha (TNF-alpha) levels were measured by a bioassay, and malondialdehyde (MDA) levels were measured by the thiobarbiturate assay. Viable bacterial counts in various tissue samples were also assessed. The mean survival times of the animals in groups A, B, C, D, E, and F were 4.50, 7.69, 4.07, 4.55, 11.55, and 11.60 days, respectively (P = 0.033 for group D versus group F, P = 0.006 for group D versus group E, P = not significant for group B versus group E, P = 0.042 for group C versus group F). Serum endotoxin levels were similar between groups at all sampling times; TNF-alpha and MDA levels in groups B, C, E, and F decreased significantly over follow-up. The numbers of viable bacterial cells in the infected kidney were similar among the groups; those in the liver, spleen, lungs, and mesenteral lymph nodes were significantly decreased in groups B, E, and F compared to those in groups A and D. It is concluded that a prolongation of survival in animals with experimental sepsis caused by multidrug-resistant P. aeruginosa was achieved after coadministration of clarithromycin and amikacin and that the increased survival was probably attributable to the immunomodulatory properties of clarithromycin.

Effective immunomodulatory treatment of Escherichia coli experimental sepsis with thalidomide

Thalidomide, an agent which inhibits biosynthesis of tumor necrosis factor alpha (TNF-alpha) and which is used to treat a variety of chronic inflammatory conditions, was investigated as therapy for experimental sepsis. Sepsis was induced by intraperitoneal injection of 10(7) CFU of Escherichia coli per kg of body weight to 80 Wistar rats divided into four groups. Group A consisted of 24 control animals that did not receive any pretreatment, group B consisted of 18 vehicle-treated control animals pretreated with seed oil, group C consisted of 30 rats administered thalidomide diluted in seed oil at a dose of 50 mg/kg 30 min before bacterial challenge, and group D consisted of eight animals that were not challenged with E. coli but that were used for white blood cell count determination. Sepsis was determined by measurement of vital signs before and 6 h after bacterial challenge. After 6 h the animals were killed and blood was sampled for culture; white blood cell count determination; and determination of endotoxin (lipopolysaccharide), TNF-alpha, interleukin-1beta (IL-1beta), and IL-6 levels. The levels of these cytokines were also estimated in the supernatants of human monocytes pretreated with thalidomide after exposure to the isolate. Sepsis developed in all vehicle-treated control animals and controls by 6 h after bacterial challenge but in only 10 animals (33.3%) pretreated with thalidomide (P < 0.0001). Six hours after bacterial challenge all animals had similar levels of endotoxemia, IL-1beta, and IL-6. The mean white blood cell count for groups A, B, and C were 5,631.1, 2,638.9, and 8,169.3 cells/ micro l, respectively (P value between groups, <0.0001); the TNF-alpha levels were 77.3, 107.2, and 26.1 pg/ml, respectively (P values between groups, <0.0001). Pretreatment of human monocytes with thalidomide prevented the secretion of TNF-alpha and IL-1beta but not that of IL-6. It is concluded that thalidomide exerts a considerable anti-inflammatory effect by preventing evolution to sepsis and by decreasing the level of production of TNF-alpha and therefore deserves to be further evaluated in research for the therapy of sepsis.

Dietary L-aspartate and L-glutamate inhibit fatty streak initiation in cholesterol-fed rabbit

BACKGROUND AND AIM

Low-density lipoprotein (LDL) oxidation is a potential atherogenic agent, and protecting LDL from oxidation prevents atherogenesis. It has been shown that L-aspartate and L-glutamate decrease lipid peroxidation after reoxygenation by means of the initiation of the cardiopulmonary bypass circuit (CPB), when supplemented to the CPB prime, and so they may protect against atherogenesis. The aim of this study was to evaluate the effect of the dietary administration of L-aspartate and L-glutamate on fatty streak onset in cholesterol-fed rabbit.

METHODS AND RESULTS

Male New Zealand white rabbits were fed for four weeks with either a high-cholesterol plus corn oil diet (control group) or the same diet supplemented with 12.5 mM L-aspartate and 12.5 mM L-glutamate in drinking water (Asp + Glu group). The mononuclear cells adhering to the endothelium and the intimal foam cells of the thoracic aorta were used to quantify the extent of atherosclerosis. Total serum cholesterol and lipid peroxidation activity, measured as thiobarbituric acid reactive substances (TBARS), were determined 0, 1 and 4 weeks after a 2-week adaptation period. There were no between-group differences in body weight or food intake during the intervention. Serum TBARS were significantly increased in both groups during the experimental period but without any statistical difference between groups. At the end of the dietary intervention, there was a ten-fold increase in total serum cholesterol concentration in both groups vs baseline. The numbers of adherent mononuclear cells and intimal foam cells were both significantly lower in the Asp + Glu group.

CONCLUSIONS

Our results suggest that dietary supplementation with L-aspartate and L-glutamate seems to protect the arterial wall from atherogenesis in an experimental animal.

Ex vivo synergy of arachidonate-enriched serum with ceftazidime and amikacin on multidrug-resistant Pseudomonas aeruginosa

Three multidrug-resistant strains of Pseudomonas aeruginosa were incubated ex vivo with sera sampled after a 10 min intravenous infusion of 25 mg/kg of arachidonic acid (AA) in 10 rabbits in the presence of ceftazidime and amikacin. Lipid peroxidation was assessed during bacterial growth. A statistically significant decrease in bacterial cells was found by the interaction of antimicrobials and serum sampled in the middle of infusion and 15 and 30 min after infusion of AA and was accompanied by elevated levels of malonodialdehyde. This effect of AA is probably attributed to lipid peroxidation and raises the possibility of its application in experimental infections.

Assessment of the aortic stress-strain relation in uniaxial tension

The passive elastic characteristics of the abdominal aorta were investigated in two experimental animal models, aiming at assessing the stress-strain relation of the aortic wall. Twenty porcine and 15 rabbit healthy abdominal aortas were subjected to uniaxial stress-strain analysis, performed on a tensile-testing device, while immersed in a physiologic saline bath at body temperature. Measured parameters included original length, width and thickness, as well as axial force and extension. Based on these data, Kirchhoff stress and Green-St.Venant strain were computed and one-dimensional constitutive equations were defined, comprising of a power function and two exponential ones, in turn, for the low, physiologic and high-stress regions. The stress-strain curves were plotted as elastic modulus versus stress, displaying nonlinear part I and linear parts II and III. These were regressed, yielding parameters k, q (part I), a, b (part II) and c, d (part III). A detailed comparison of these constitutive parameters was undertaken between the two species, demonstrating variations in d (p<0.05). No statistical differences were found in parameters a, b, c, k and q, implying that the two aortas were equally stiff under low and physiologic stresses, whereas the porcine aorta was stiffer at higher stresses. In conclusion, a bi-exponential in addition to a power law was established, relating stress and strain in the aorta, which is advantageous in comparison with previous constitutive equations. Under passive conditions, the nonlinear nature of this constitutive law may account for the low, part I, physiologic, part II, and high-stress, part III of the stress-strain relationship, supporting the concept of the aortic wall as a biphasic material.

The effect of doxorubicin and its analogue mitoxantrone on cardiac muscle and on serum lipids: an experimental study

This experimental study compares the toxic effect of the two cytotoxic drugs, doxorubicin and mitoxantrone, on cardiac muscle and on serum lipids. The cardiotoxicity of doxorubicin due to the cumulative effect of repeated administration is known. A relative compound, mitoxantrone, is a member of the androstenedione class of synthetic antitumor agents and its chemical structure, based on a quinone ring, is similar to that of doxorubicin. Doxorubicin has wide application in cancer medicine but its dose-limited cardiac effect creates the need for a substitute compound. Mitoxantrone, also an effective agent, may be able to cover this need. Three groups of 35 Wistar rats were used during this experimental study of 12 weeks' duration. Drugs at a certain calculated dose were administered once weekly. Group A animals were treated with doxorubicin, Group B with mitoxantrone and Group C, the controls, with normal saline. Six animals per group were autopsied after euthanasia in the 3rd, 6th, 8th, 10th and 12th weeks. Cardiac muscle, liver and other organs, plus blood, were removed for macro- and microscopical, and biochemical tests. Our results showed that there was a cumulative toxic effect of doxorubicin (adriamycin) on cardiac muscle starting in the 6th week which gradually increased to Grade III lesions by the 10th and 12th weeks. In parallel, an increase in serum lipids, mainly cholesterol and triglycerides was observed. Mitoxantrone-treated animals showed moderate cardiotoxic lesions (but not cumulative) and no increase in serum lipids. In vitro testing of oxygen-free radical production showed high production by doxorubicin and very low production by mitoxantrone. Thus, mitoxantrone appears to be safer than doxorubicin.

A morphometric study of the structural characteristics of the aorta in pigs using an image analysis method

The objective of this study was to evaluate multiple structural characteristics, in addition to vasa vasorum density, in different aortic regions. The aorta of healthy Landrace pigs was divided into four thoracic and three abdominal segments. Transverse sections were reserved for morphometric analysis. Image analysis showed the aortic diameter, the thickness of the media, the number of elastic lamellae and the thickness of elastic membranes being reduced with increased distance from the heart (P < 0.05). The average thickness of lamellar units remained constant in the thoracic, but increased in the abdominal aorta (P < 0.05). The number of lamellar units, contained in the avascular zone of the media, and the density of vasa vasorum decreased peripherally (P < 0.05), still the average thickness of the avascular zone was invariant. In conclusion, the anatomical properties of the vessel wall alter through the aorta, being optimal for the varying stresses to which the aorta is subjected along its length. The distinct aortic parts may exhibit inherent morphological features, responsible for the various pathological processes that affect the aorta.

Investigation of doxorubicin tissue toxicity: does amifostine provide chemoprotection? An experimental study

This experimental animal study of 12-weeks' duration, involving Wistar rats, tested the possible chemoprotection of Doxorubicin (adriamycin), cardiomyopathy and other toxicities by Amifostine. One hundred and five animals were divided into 3 groups: Groups A, B and C, which had Doxorubicin, simultaneous Doxorubicin and Amifostine treatment and normal saline for control, respectively. Treatment was administered once weekly for 12 consecutive weeks. The doses of each drug were appropriately calculated on the basis of other experiments in the literature and given in analogous dosage to human kilograms of body weight. Euthanasias and autopsies of six animals at a time from each animal group were performed on weeks 3, 6, 8, 10 and 12. The blood, heart, lung, liver, aorta, thymus, spleen, kidneys, adrenals, testis and ovaries and muscle and lipoid tissue were examined macroscopically and microscopically. Biochemical liver and kidney examinations, full blood count and serum lipids were examined before and during the weeks of treatment and autopsies. Increased cholesterol and triglycerides from the 6th week towards the end of the experiment and a gradual increase in cardiomyopathy were found, particularly in Group A. The findings were similar in Group B, except for the timing (the increase of serum lipids and the serious cardiac lesions were delayed by two weeks). No abnormalities were detected in the controls, Group C. In conclusion, Amifostine does not seem to be cardioprotective when administered with Doxorubicin, since it only delays the onset of cardiac lesions. In in vitro testing, Amifostine was found to be a scavenger of the oxygen-free radicals which are produced by Doxorubicin.

Effect of impaired vasa vasorum flow on the structure and mechanics of the thoracic aorta: implications for the pathogenesis of aortic dissection

OBJECTIVE

To investigate the alterations of structure and mechanical properties of the aortic wall, resulting from impairment of vasa vasorum flow.

METHODS

Eight healthy Landrace pigs were subjected to interruption of vasa vasorum flow to the upper segment of their descending thoracic aorta. Under sterile conditions, the periaortic tissue was excised and the contiguous intercostal arteries were ligated. Ten sham-operated pigs were used as controls. Fifteen days postoperatively, the animals were sacrificed and their upper descending thoracic aortas were removed. Histology, and collagen and elastin content determination by image analysis technique were performed. Mechanical analysis of aortic strips was carried out with a uniaxial tension device and stress-strain curves were obtained.

RESULTS

In contrast to normal aortic walls of the control group, histology of the avascular aortas revealed severe ischemic necrosis of the outer media along with abnormal straightening of the elastin and collagen fibers, without significant collagen and elastin content changes. The borderline between the outer ischemic and inner non-ischemic media was sharp, and an outset of dissection was observed at this point. Mechanical analysis showed that at the same level of strain, the ischemic aorta was significantly stiffer at both low (P=0.03) and high strains (P=0. 003).

CONCLUSIONS

Impairment of blood supply to the thoracic aorta leads to abnormal morphology of elastin and collagen fibers of the outer media, resulting in increased aortic stiffness under a wide range of stresses. In the clinical setting, decreased vasa vasorum flow, reportedly occurring in arterial hypertension, may increase the stiffness of the outer media of the thoracic aorta and produce interlaminar shear stresses, contributing to the development of aortic dissection.

Inhibition of adriamycin cardiotoxicity by 5-fluorouracil: a potential free oxygen radical scavenger

Adriamycin (ADR), a broad spectrum anticancer agent, has a limit to total dose used, due to cumulative cardiotoxicity. This side effect has been tested in the present study in combined administration with 5-fluorouracil a cytotoxic drug that often is applied together with ADR in cancer treatment. The study was performed on Wistar rats, and the experiment consisted of weekly administration for 12 weeks of adriamycin alone, of 5-fluorouracil alone, a combination of both, and a control group (normal saline) in separate groups comprising 42 animals each. The histology of the cardiac muscle, large vessels and liver, biochemistry of serum cholesterol, triglycerides and HDL-C and oxygen free radical production were examined. It was found that addition of 5-FU to the ADR administration reduced significantly the cardiac lesions, delayed and reduced the increase of serum lipids, produced by ADR alone and oxygen free radical production was also reduced, indicating that 5-fluorouracil is acting as a scavenger of free radicals.

Doxorubicin cardiotoxicity and serum lipid increase is prevented by dextrazoxane (ICRF-187)

This study is related to the serious side effects of Doxorubicin-cardiotoxicity and serum lipid caused by the drug's cumulative effect. Studies were performed on experimental animals treated with intensive administration of Doxorubicin. Seventy five wistar rats were divided in two equal groups A and B. Group A was used for doxorubicin administration and B for doxorubicin and dextrazoxane. The drugs were administered weekly for twelve weeks at doses 0.2 mg/100 g BW for doxorubicin and 1.5 mg/100 g BW for dextrazoxane. Histological examination of the cardiac muscle, large vessels, liver and other organs and biochemical examination for serum lipids and liver enzymes were performed on certain weeks. Comparison of the findings of the two groups showed a) a reduction in doxorubicin cardiotoxicity by dextrazoxane and b) the addition of dextrazoxane to doxorubicin resulted in lowering the increase of serum lipids produced by doxorubicin. c) In vitro tests by chemiluminescence showed that dextrazoxane acts as a scavenger of oxygen free radicals.

An increase of serum lipids after cumulative doses of doxorubicin and epirubicin in experimental animals

A wide range of pharmacological actions has been attributed to the anthracyclins. In this study we examined their effect on serum lipids in experimental animals in parallel with histological alterations. Three Wistar rat groups were injected with doxorubicin, epirubicin or normal saline once a week for 12 weeks. Total serum lipids, cholesterol, triglycerides, HDL-cholesterol, transaminases, proteins and alkaline phosphatase were assayed weekly. A proportion of the animals were sacrificed at the same time points and the cardiac muscle, large vessels, liver and abdominal muscle were stained and examined under light microscopy. Serum lipids were found to increase gradually, starting after 8 weeks of drug administration, until the end of the experiment. Tissue damage was noted in the cardiac muscle, abdominal muscle and large vessels, also following an increasing trend. Doxorubicin had a more pronounced effect than epirubicin on both serum lipid increase and tissue destruction. These alterations may contribute to anthracyclin-related cardiac damage.

Low-dose heparin treatment does not inhibit SW480 human colon cancer growth and metastasis in vivo

We investigated heparin effects on the biological behavior of SW480 human colon adenocarcinoma cells in vivo. Tumor growth, pathological features, metastatic potential and karyotype, were studied after the twelve week low-dose heparin treatment of nude mice subcutaneously injected with SW480 cells. A non statistically significant increase in tumor growth was observed (0.05 < p < 0.1, compared to the control group). No differences in tumor histology and karyotype were detected. Two of the six heparin-treated animals exhibited an increase in tumor vascularization. Metastasis to the lungs and liver was not inhibited. These results do not support the role of heparin in the prevention of the in vivo growth and metastasis of SW 480 colon cancer cells.

In vitro effects of heparin on SW480 tumor cell-matrix interaction

We investigated the in vitro effects of heparin on the growth and interaction of SW480 colon adenocarcinoma cells with the extracellular matrix proteins laminin, fibronectin and collagen IV. Cell adhesion assays were performed in wells precoated with the proteins mentioned. Tumor cell migration and invasiveness were assayed in Transwell cell culture chambers. SW480 cell adhesion to the matrix proteins and migration to laminin/fibronectin precoated filters were inhibited by heparin in a dose- dependent manner, whereas cell growth and invasion through collagen IV gel were not affected. Our results suggest that heparin influences the SW480 cell-matrix interaction in vitro and inhibits crucial steps of the metastatic process in an experimental model.

Medial necrosis and acute alterations in aortic distensibility following removal of the vasa vasorum of canine ascending aorta

OBJECTIVE

It is known that the outer layers of the thoracic aorta receive substantial blood flow through vasa vasorum. This study was undertaken to test the hypothesis that removal of vasa vasorum flow will alter the elastic properties of the ascending aorta.

METHODS

Distensibility of the ascending aorta was determined before and 30 min after careful removal of the periaortic fat network which contains the vasa vasorum in 10 acutely instrumented dogs (experimental group) and the results were compared with those obtained from six weight matched sham operated control dogs. Aortic distensibility was measured using the formula: distensibility = 2 x pulsatile changes in aortic diameter divided by (diastolic aortic diameter x pulse pressure). Aortic pressures were measured directly from the ascending aorta by a pressure gauge. Aortic diameters were simultaneously determined by an elastic air filled ring connected to a transducer. The efficacy of the technique for the interruption of vasa vasorum blood supply to the aortic wall was proved in six additional animals by histology of transverse blocks of aortic wall from the area of interest. Histology was performed before vasa vasorum removal in two animals, 30 min after vasa vasorum removal in another two, and 15 d after vasa vasorum removal in the remainder.

RESULTS

At baseline, there was no difference in the measured variables between the two groups. Aortic distensibility decreased significantly in the experimental group after vasa vasorum removal by 0.90(SEM 0.17) 10(-6).cm2.dyn-1 (p < 0.001), while it remained unchanged in the control group during the experiment. Complete removal of vasa vasorum of the ascending aorta was found in experimental group animals which were killed 30 min after operation, while ischaemic medial necrosis was observed in those killed 15 d after operation.

CONCLUSIONS

Vasa vasorum removal led to an acute decrease in the distensibility of the ascending aorta. Lack of blood supply to the outer part of the aortic wall is most likely to have accounted for these findings.

Mechanism of growth retardation following chronic administration of beta-adrenoceptor antagonists to developing rats

A total of 112 3-week old Wistar rats were separated into eight groups: control groups I-IV (n = 62) and propranolol-treated groups V-VIII (n = 50). Propranolol hydrochloride (100 mg/kg) was present in the rats' drinking water until 26 weeks of age and growth rates of all groups were monitored daily until 53 days of age and thereafter every third day throughout the study. Chronic oral propranolol administration produced growth retardation (P less than 0.05) in both sexes that was reversible when treatment was discontinued. Organ weights were generally smaller in propranolol-treated rats; on the other hand, the ratio of most organ weights per 100 g of body weight was greater in propranolol-treated rats (especially females). The radio-immunological determination of plasma growth hormone showed increased concentrations of growth hormone in propranolol-treated rats (P less than 0.05), whereas hypothalamic somatostatin content was not significantly changed. The results showed that the retarded growth rate following chronic oral propranolol administration to growing rats was independent of changes in plasma growth hormone and hypothalamic somatostatin concentrations, and that retardation was entirely reversible when the beta-adrenoceptor antagonist was discontinued.

Pharmacokinetic interaction in beagle dogs of antiplatelet drugs: acetylsalicylic acid, dipyridamole and calcium dobesilate

In clinical practice, the co-administration of antiplatelet drugs, such as acetylsalicylic acid (ASA) and dipyridamole (DP) and calcium dobesilate, is often recommended in order to obtain secondary prophylaxis against certain ischaemic diseases. Therefore the possible pharmacokinetic interactions between these three drugs were studied after a single-dose in beagle dogs. The plasma concentrations of ASA, DP and CaDb were measured by HPLC. It was found that the DP and CaDb kinetics were unaffected by concurrent intake of ASA, DP or CaDb. However, concurrent DP or CaDb improved the bioavailability of ASA, particularly the increased Cmax and (AUC).

Creatine kinase (CK-BB) determination in cerebrospinal fluid after acute experimental head injury

Early changes of the activity of enzymes such as creatine kinase in the cerebrospinal fluid (CSF) or serum are often investigated after head injuries to assess the extent of brain damage and establish a reliable prognosis. The purpose of the present study was to determine levels of creatine kinase isoenzyme CK-BB in the CSF of rats after experimental head injuries. External head injuries of different severity were inflicted on rats, immediately after which CSF was collected for isoenzyme activity determination. It was found that the levels of CK-BB were significantly elevated immediately after the head injury and that the greater the degree of external cranial injury inflicted, the higher the isoenzyme activity was. The results seem to provide evidence that CK-BB activity is an early indicator of brain damage and that its level may reflect the extent of cerebral damage involved.

Pentoxifylline in the treatment of experimental peritonitis in rats

The objective of this study was to determine the effect of pentoxifylline on the clinical and pathologic course of experimentally induced peritonitis in rats. This drug is a methyxanthine derivative that has vasodilating properties and may decrease platelet aggregation. Peritonitis was induced in 40 Wistar rats by creating a closed ileal loop 4 cm long 5 cm from the ileocecal valve. The animals were divided into two groups of 20 animals each. The first group served as controls, while each animal of the second group received 17 mg/kg/day of pentoxifylline intramuscularly from the day of operation until 30 days postoperatively. The survival rate was significantly increased in the group receiving pentoxifylline and adhesion or abscess formation was considerably reduced. We concluded that the administration of pentoxifylline prolongs significantly the survival of animals with experimental peritonitis and reduces the development of adhesions and abscesses in the peritoneal cavity. This beneficial effect may be attributed to decreased fibrinogen deposits and increased fibrinolytic activity within the peritoneal cavity, thus rendering the bacteria more susceptible to cellular and noncellular clearing mechanisms.

The effect of heparin upon fibrinopurulent peritonitis in rats

The effect of heparin upon the clinical and pathologic course of experimentally induced peritonitis in the rat was studied. Peritonitis was induced in 40 rats by creating a closed ileal loop 4 centimeters long at a distance of 5 centimeters from the ileocecal valve. The rats were divided into two groups of 20 each. The first group served as the control group while each rat of the second group received 30 units of heparin subcutaneously per day postoperatively. Survival was drastically increased in the group receiving heparin (p = 0.001). Adhesion or abscess formation was considerably reduced in this group. The results of peritoneal cultures showed decreased incidence of Escherichia coli and clostridia in the heparin-treated group. Blood cultures also showed decreased incidence of both aerobes and anaerobes in the treated group. It is concluded from this that the administration of heparin significantly prolongs survival time of animals with peritonitis and reduces the development of adhesions and abscesses in the peritoneal cavity. This beneficial effect could be attributed to decreased fibrinogen deposits within the peritoneal cavity, thus rendering the bacteria more susceptible to cellular and noncellular clearing mechanisms.

Effect of beta-adrenergic blockade on physiologic growth in the Wistar rat

The effect of propranolol (Pr) on body weight was studied in 144 Wistar rats of both sexes from weaning to 17 weeks of age. Pr was administered to 77 of these rats (chosen at random), in a dose of 100 mg/kg body weight daily. Body weights were monitored every third day throughout the study. During their 17th week of age, all the rats were weighed for the last time and then sacrificed. The following organs were carefully dissected and weighed: brain, thymus, lungs, heart, liver, kidneys, adrenals, testes and ovaries. Gain in body weight was significantly reduced in the propranolol treated animals compared to control in both sexes. Organ weights were also less in propranolol-treated rats except for the kidneys of both sexes and the heart and testes of the males. However, the ratio of most organ weights per body weight was greater, indicating that the inhibition of weight gain was less severe in those organs compared to that of total body weight.

Effect of afterload on left ventricular performance in experimental animals. Comparison of the pre-ejection period and other indices of left ventricular contractility

Afterload reduction has become a routine treatment of patients with severe heart failure. In order to investigate the effect of afterload changes on indices of left ventricular performance, seven anesthetized dogs were studied. Serial alterations of afterload were produced with sodium nitroprusside and methoxamine infusions while the heart rate was maintained constant with right atrial pacing (120/min). High fidelity left ventricular (LV) pressure, aortic pressure (AoP) and systolic time intervals (STI) were measured simultaneously as a control and each time with the AoP changes. LV max dp/dt was measured by an RC differentiation and DP/DT was calculated from the pressure pulses and systolic time intervals. Each change in AoP resulted in a significant change in isovolumic pressure (IP) and the changes were parallel. Changes in pre-ejection period (PEP) and LV max (dp/dt)/(IP) were parallel changes in IP. A significant direct relationship was found between changes in IP and PEP, and an inverse relationship existed between changes in PEP and LV max (dp/dt)/(IP). Changes in LV max dp/dt and calculated DP/DT were parallel and approached unity. Thus, afterload changes with resultant changes in IP directly alter PEP and inversely affect max (dp/dt)/(IP). These effects of pure afterload changes must be considered in clinical pharmacologic studies when LV contractility is evaluated. Furthermore, calculated DP/DT can be used to measure changes in max dp/dt because of the close relationship between these two parameters.

Potential role of velocity and wall tension in vein graft failure

The factors contributing to early thrombosis or late intimal proliferation in arterialized vein grafts were studied in seven dogs. Autologous jugular veins replaced a segment of the cervical carotid artery bilaterally. Thirty minutes after graft installation and six months later, graft and proximal artery diameter, arterial pressure and blood flow were measured and wall tension, vascular resistance, flow velocity and energy loss between proximal artery and graft were computed. The diameter ratio of proximal artery to graft increased by 37% (p less than 0.05). Velocity of flow within the graft averaged 87% less than that in the proximal artery (p less than 0.05) and decreased by 58% after six months (p less than 0.05). Graft wall tension at both experimental periods was significantly higher than that of the proximal artery (p less than 0.05), increasing over six months by 91% (p less than 0.05). These results support contentions that low flow velocity contributes to early thrombosis of the graft and, that increased wall tension is significant factor in the pathogenesis of intimal thickening.

Safety and rationale for continuation of propranolol therapy during coronary bypass operation

Thirty consecutive patients undergoing coronary bypass were studied. Oral propranolol therapy was maintained up to 4 to 10 hours before operation. Nineteen of the patients had a history of myocardial infarction (MI), 14 had hypoakinetic areas, and 8 had decreased ejection fraction indicating advanced coronary artery disease. Twenty-four-hour urinary epinephrine and norepinephrine obtained the day before operation were markedly increased at 136 +/- 12 microgram per 24 hours (normal, 39 +/- 4 microgram, rho less than 0.01). There were 4 perioperative MIs (13%) and no deaths. Plasma propranolol 1 hour before operation was 43.3 +/- 8 ng per milliliter, indicating good beta blockade. Propranolol was started within 24 hours postoperatively. There were no preoperative, intraoperative, or postoperative complications related to propranolol therapy. We conclude that because of markedly increased adrenergic tone the day before operation and transient hypersensitivity to adrenergic stimulation after withdrawal of propranolol, this agent should be continued through coronary bypass operation.

Late failure in vein grafts: mediating factors in subendothelial fibromuscular hyperplasia

Late failure of autologous vein grafts often results from excessive subendothelial fibromuscular hyperplasia. Varying factors have been implicated in this process, but the exact etiology remains unclear. In this study, three groups of animals were studied which had sections of common carotid artery replaced with autologous vein grafts. Group I had simple replacement, while Groups II and III had grafts supported by either tightly woven or loose mesh dacron prostheses. Thrombosis occurred only in the unsupported grafts. Unsupported grafts also had more subendothelial proliferation when compared to the loose mesh group. The combined thickness of the intima-media correlated inversely with the number of vasa present within the vein graft wall, i.e. significantly more vascularization was found in the mesh supported group when compared to the other groups. Grafts supported with the tightly woven prosthesis were relatively impervious to the ingrowth of vasa vasora. The data suggest that persistent distension of the graft wall by intra-arterial pressure influences the degree of subendothelial fibromuscular hyperplasia and may be interrelated to revascularization of the graft wall per se.