Research in experimental medicine. Zeitschrift fur die gesamte experimentelle Medizin einschliesslich experimenteller Chirurgie最新文献

Few studies on treatment with inhaled nitric oxide (NOi) have been carried out in small laboratory animals yet, since commercially available dosing devices are not appropriate in this setting for technical or financial reasons. The aim of our study was to establish and validate a simple, cost-effective system for the application of NOi in small animals. The system mixes NOi with constant-flow inspiratory gas. A gas blender allows for a mixture of nitrogen, oxygen, and NO dissolved in nitrogen. A formula using the desired inspiratory oxygen fraction and the desired concentration of NOi as independent variables derives a somewhat higher inspiratory oxygen fraction, which is preset using an oximeter. Then the flow of NO in nitrogen is started, lowering the inspiratory oxygen fraction to the initially desired value, thereby adding NOi in the desired concentration. The method was validated by 153 adjustments, covering a variety of oxygen fractions and concentrations of NOi. NOi was measured by chemiluminescence as reference method. A close correlation (R = 0.994) was found, and the regression line was close to the line of identity with y = -0.0994 + 1.048x. No systematic errors could be identified. We conclude that the method described may serve as a simple, cost-effective way to administer NOi to small animals.

It has been demonstrated that intraperitoneal administration of proteolytic enzymes ameliorates the progression of renal diseases in various animal models. In the present study, we employed the rat remnant kidney model to study the effectiveness of oral administration of proteases. Twenty male Wistar rats underwent sham operation (CTRL), while 25 were subjected to 5/6 nephrectomy (5/6 NX). Rats were randomised into placebo (PL) (2 ml tap water/day by gavage), or Phlogenzym (E; fixed mixture of trypsin 2.42 mg, bromelain 4.54 mg, and rutozid 5.04 mg added as antioxidant, in 2 ml tap water daily by gavage) treated group. Duration of the study was 45 days. Rats were pair-fed. Enzyme treatment exerted salutary effects on various functional and morphological parameters. Proteinuria was higher in both 5/6 NX group rats throughout the study. Administration of proteases ameliorated its rise effectively (data at sacrifice: CTRL-PL 6.27 +/- 1.25, CTRL-E 9.27 +/- 0.99, 5/6 NX-PL 74.04 +/- 21.33, 5/6 NX-E 39.09 +/- 7.93 mg/24 h; P < 0.01). Increased urinary excretion of the fibrogenic cytokine transforming growth factor (TGF-beta 1) was improved, too (CTRL-PL 0.349 +/- 0.051, CTRL-E 0.693 +/- 0.230, 5/6 NX-PL 3.044 +/- 0.540, 5/6 NX-E 1.390 +/- 0.238 ng/mumol creatinine; P < 0.05). At sacrifice, tubulointerstitial fibrosis was less pronounced in E-treated rats. Correspondingly, the volume fraction of tubulointerstitial tissue in the renal cortex was improved in 5/6 NX-E rats (CTRL-PL 9.9 +/- 0.2, CTRL-E 10.0 +/- 0.2, 5/6 NX-PL 17.9 +/- 1.8, 5/6 NX-E 13.8 +/- 0.9%; P < 0.05). The protein/DNA ratio in isolated glomeruli and tubules, as an estimate of glomerular matrix accumulation and hypertrophy of tubules, was enhanced in 5/6 NX groups and a tendency towards lower values was observed after E treatment. Renal function as evaluated by serum creatinine and urea levels was not influenced by the enzyme therapy. No between-group differences in blood pressure were observed. In summary, oral administration of proteolytic enzymes improved proteinuria and urinary TGF-beta 1 excretion, as well as the severity of tubulointerstitial fibrosis without signs of toxicity.

The aim of this study was to implement the microdialysis method, a well-established technique for measuring the local concentration of neurotransmitters and metabolites in the brain, in the dorsal skinfold chamber of the awake hamster. First, the effects of implanted, nonperfused microdialysis probes on the microcirculation were examined. Skinfold chambers were prepared with and without probes. Two and 3 days later, the following parameters were assessed: diameter, red blood cell (RBC) velocity, macromolecular leakage, leukocyte rolling fraction, and adherent leukocytes in venules, diameter and macromolecular leakage in arterioles, and functional capillary density (FCD). No significant differences between the animals of the two groups were observed in any of the parameters on either day. Second, the interstitial lactate concentration was measured at two perfusion rates in groups with and without a 4-h tourniquet ischemia. The induction of ischemia resulted in a significant increase in lactate concentration over the control values in the tissue within 1 h to 8000 +/- 860 microM, where it remained until the reperfusion, at which point the concentration returned to control values within 1 h. The microdialysis method provides the opportunity to measure the concentration of metabolites in the extravascular space of the hamster dorsal skinfold chamber.

Free radicals are thought to be the most important cause of the reperfusion injury subsequent to ischemia. The antioxidant status of the tissue affected by ischemia-reperfusion is of great importance for the primary endogenous defense against the free radical induced injury. This investigation was performed to evaluate the antioxidant enzyme capacity of the brain tissue in the ischemia-reperfusion period using an experimental global moderate (penumbral) ischemia model on rat brains. Experiments were performed on 45 male Sprague Dawley rats. Ischemia was induced by bilateral vertebral arteries cauterization and temporary bilateral carotid arteries occlusion and sustained for 10 minutes. At the end of ischemia (0 min reperfusion) and various reperfusion periods (20 min, 60 min, 240 min), rats were decapitated and brains were frozen in liquid nitrogen. Changes in the intracellular antioxidant enzyme (superoxide dismutase, glutathione peroxidase and catalase) activities were assessed in the rat brain tissues, by spectrophotometric methods. In all moderate ischemia-reperfusion groups, superoxide dismutase activities were found to have decreased significantly compared to the sham operated controls (P < 0.05). During ischemia superoxide dismutase activity was lowered to 31% of that of the control group. The decreases were more significant in reperfusion groups, particularly in 60 min reperfusion (40%). Relatively smaller but still significant diminution was observed in glutathione peroxidase activities (P < 0.05). The ratio of diminution was striking in 20 min and 60 min reperfusion groups with 26% of the sham operated rats. Conversely, moderate ischemia-reperfusion caused significant increase in catalase activities (P < 0.05). The increment was 63% of the preischemic level with 10 min of moderate ischemia. In conclusion, activities of the major antioxidant enzymes were changed significantly in moderate brain ischemia-reperfusion. These results suggest that the disturbance in oxidant-antioxidant balance might play a part in rendering the tissue more vulnerable to free radical induced injuries.

One-sided fluid flooding of the lung after intubation with a double-lumen tube facilitates pulmonary sonography during surgery. Arterial blood pressure, cardiac index, and heart rate remained unchanged during one-lung fluid flooding in healthy animals. The arterial PO(2) was greater by about 100 mmHg after flooding one lung with 15 ml/kg fluid and ventilation with a FiO(2) of 1.0 compared with total atelectasis. This seems to be identical to a continuos positive airway pressure level of 5 cm H(2)O with pure oxygen on the nonventilated lung. The one-sided fluid flooding induced a statistically significant increase in pulmonary artery pressures and pulmonary capillary wedge pressure. In comparison with total atelectasis, fluid flooding in tendency reduced the pulmonary right-left shunt and increased the arterial PO(2).

In 35 anaesthetised human subjects, we examined the effect of cardioventilatory coupling on R-R interval and ventilatory period time series. We observed that, in the presence of coupling: (a) ventilatory period fluctuated in a quantal manner, each quantal step corresponding to a multiple (or a little less) of the heart period; (b) heart period fluctuations, associated with respiratory sinus arrythmia, were identical for consecutive ventilatory periods. The regularity of heart period variation lead to geometric patterning of raw R-R time series, R-R consecutive difference time series, the phase portrait (R-R(n) vs R-R(n+1)) and the map of R-R interval variation (DeltaR-R(n) vs DeltaR-R(n+1)). These geometric features may be useful for the determination of cardioventilatory coupling from heart rate time series.

Heterotopic pancreas transplantation in type I diabetic patients does not correct hyperglucagonemia, which is thought to be due to insufficiently suppressed glucagon release by the host pancreas. The diabetogenic effects of glucagon then have to be corrected by higher than normal insulin secretion from the transplant, with the attendant risk of earlier loss of islet cell function, and development of atherosclerosis. To establish whether this situation can be prevented, we investigated glucose homeostasis and blood lipids, as well as fecal fat and chymotrypsin as indicators for pancreatic exocrine function 14 weeks after orthotopic pancreas transplantation in inbred rats. The pancreas was resected before orthotopic transplantation of the donor pancreas with portal venous drainage (n=8). Laparotomized animals served as controls (n=8). Basal plasma glucagon, basal plasma insulin to glucagon molar ratio, and basal and integrated incremental responses of plasma glucose, insulin, and C-peptide after an oral glucose load (2 g/kg body weight) were similar in both groups. However, hepatic insulin clearance was slightly but significantly lower in the transplanted group (1.1+/- 0.1 vs 1.6+/-0.2; P<0.05). Basal plasma levels of free fatty acids, phospholipids, triglycerides, cholesterol, low-density lipoproteins, and high-density lipoproteins were unchanged after transplantation. Also unchanged were fecal fat and chymotrypsin levels, thus indicating preserved pancreatic exocrine function. We concluded that orthotopic pancreas transplantation with portal venous drainage achieves almost optimal metabolic control with respect to endocrine and exocrine pancreatic function as well as blood lipids. This technique could therefore be used to treat combined endocrine and exocrine insufficiency in chronic pancreatitis and thus enlarges the spectrum of indications for pancreas transplantation.

Chemotherapy might damage intestinal barrier function (IBF). The aim of the study was to evaluate the effect of dietary fiber on IBF of 5-fluorouracil (5-Fu) stressed rats. Thirty Wistar rats after gastrostomy were assigned randomly to one of three groups (10 of each group), Chow, enteral nutrition (EN), or EN+Fiber (2 g/100 ml solution). They kept their diets respectively for 8 days. 5-Fu (75 mg/kg body weight) was injected intraperitoneally on day 4. Urinary recovery ratios of lactulose and mannitol (L%/M%) were measured on day 3 and day 7. The mesenteric lymph nodes were harvested for bacterial translocation (BT). On day 8, small intestine and colon were taken for wet weight, mucosal thickness of both small intestine and colon and villus height of small intestine. The BT rates of Chow and EN+Fiber groups (20% for both) were lower than that of EN group (70%) (P<0.05). The L%/M% of both EN+Fiber (from 0.0265+/-0.0073 to 0.0274+/-0.0068) and Chow groups (from 0.0268+/-0.0039 to 0.0281+/-0. 0044) were unchanged after stress (P>0.05 for both), whereas that of EN group significantly increased (from 0.0289+/-0.0070 to 0.0331+/-0. 0084) (P<0.01). Chow group gained body weight (4.9+/-4.3 g). EN+Fiber group lost less body weight (-3.1+/-3.4 g) than EN group (-6.6+/-5.2 g) (P<0.05). The intestinal structure of Chow and EN+Fiber groups was superior to that of EN group. In conclusion, dietary fiber could protect the IBF of 5-Fu stressed rats.

Under normal physiological conditions, chemical and antioxidant defenses protect tissues from the damaging effects of reactive oxygen metabolites (ROM). It has been proposed that ROMs are involved in the development of tissue injury in many inflammatory diseases and also in patients with colitis. In the present study we aimed to investigate the effects of antioxidant therapy on the extent of colonic inflammation and ROM levels in the injured tissues in a trinitrobenzene sulfonic acid-induced colitis model in the rat. Sprague-Dawley rats were pretreated with the antioxidants superoxide dismutase (30,000 U/kg s.c.) or catalase (400,000 U/kg s.c.) prior to induction of colitis and they were decapitated 24 h (acute group) or 6 days (chronic group) after the induction of colitis (each group consists of eight to ten rats). Pretreatment with the antioxidants reduced the macroscopic damage score significantly in both acute and chronic groups compared with untreated colitis groups, whereas they reduced the microscopic damage score and colonic wet weight only in the chronic group. The chemiluminescence assay - a technique to assess the presence of reactive oxygen species in the tissues - values of the groups pretreated with the antioxidants showed a tendency to decrease compared with the untreated colitis group, but they were not statistically significant. Based on these findings, pretreatment with the antioxidants superoxide dismutase or catalase has beneficial effects on the extent of colonic inflammation, particularly in the chronic period, and this may support the importance of antioxidant therapy to reduce the severity of inflammatory bowel disease in humans.

Background: Local hyperthermia has been shown to be an effective adjuvant therapy for cancer. However, progress in this treatment modality requires the non-invasive assessment of temperature distribution in the entire tumour to enable administration of an efficient thermal dose to all tumour areas. Magnetic resonance (MR) imaging offers a promising tool to quantify, non-invasively and three-dimensionally, temperature distribution within tumours. An animal model taking into account the complex interrelationship between pathophysiological changes within a tumour during hyperthermia and temperature-sensitive MR parameters is warranted for the development and validation of new MR thermometry technology.

Methods: An experimental set-up was implemented to allow simultaneous measurements of temperature, tumour blood flow and temperature-sensitive MR parameters under standardised conditions in vivo. Local hyperthermia was induced at 44 degrees C for 20 min under inhalation anaesthesia on seven Syrian Golden hamsters bearing an amelanotic melanoma. Fibreoptic probes were used for reference temperature measurements. Laser Doppler flowmetry served for on-line tumour blood flow determination, and MR thermometry was performed using longitudinal T1 relaxation time measurements.

Results: The experimental design enables multifunctional MR thermometry. T1 relaxation times of tumours were 1.44 s (1.36, 1.46) and 1.53 s (1. 48, 1.75) at 37 degrees C and during hyperthermia at 44 degrees C, respectively (median, 25% and 75% quartiles, respectively; P<0.05). At the end of 20 min of hyperthermic treatment at 44 degrees C, relative tumour blood flow was reduced to 40.5% (20.7, 43.3) compared to values before treatment (median, 25% and 75% quartiles, respectively; P<0.05). Imaging of T1 relaxation times revealed a heterogeneous distribution in temperature during hyperthermic treatment.

Conclusion: This novel in vivo model allows standardised investigations for the development and validation of MR thermography methods.