Primary tumour growth in an orthotopic osteosarcoma mouse model is not influenced by analgesic treatment with buprenorphine and meloxicam.

Little is known about the treatment of bone pain in animal models of bone cancer. In the present study, the orthotopic 143-B human osteosarcoma xenotransplantation model was used to address the following questions: (1) Can repetitive analgesic treatment extend the experimental period by prolonging the time to reach humane endpoints and (2) Does repetitive analgesic treatment affect bone tumour development and metastasis? The analgesics, buprenorphine and meloxicam, were either applied individually or in combination at 12 h intervals as soon as the animals began to avoid using the tumour cell injected leg. While control mice treated with NaCl showed continuous body weight loss, the major criterion previously for terminating the experiments, animals treated with analgesic substances did not. The control mice had to be sacrificed 26 days after tumour cell injection, whereas the groups of animals with the different pain treatments were euthanized after an additional eight days. Importantly, primary intratibial tumour growth was not affected in any of the experimental groups by any of the pain treatment procedures. Between days 26 and 34 after tumour cell injection an increase of about 100% of the number of lung metastases was found for the groups treated with buprenorphine alone or together with meloxicam, but not for the group treated with meloxicam alone. In summary, the results indicated that both buprenorphine and meloxicam are suitable analgesics for prolonging the experimental periods in an experimental intratibial osteosarcoma mouse model.

Buprenorphine for pain relief in mice: repeated injections vs sustained-release depot formulation.

Sustained-release formulations of analgesic drugs are promising alternatives to repeated drug injections. Here, we compared a sustained-release formulation of buprenorphine (SB, 2.2 mg/kg) with a standard protocol of three injections of buprenorphine (Temgesic, 0.1 mg/kg/8 h) in mice. Buprenorphine serum concentration and analgesic action (thermal sensitivity) were determined in healthy mice. Additionally, the pain relief properties of both protocols were assessed after laparotomy using physiological and ethological measures of pain and recovery. Serum concentrations and thermal sensitivity tests indicated duration of action of at least 4 h (but less than 8 h) with the Temgesic protocol, and 24-48 h with SB. Behavioural and clinical parameters indicated at least partial pain relief after surgery for both protocols. Observed side-effects of buprenorphine independent of the protocol were increased activity, disturbed circadian rhythm and several abnormal behaviours. A tendency for decreased food and water intake as well as body weight reduction was also seen. Body weight decreased significantly in animals that received three injections of Temgesic, regardless of whether surgery was performed or not (P = 0.015; P = 0.023), hinting at a stress response towards this repeated intervention. In conclusion, an application interval of 8 h (Temgesic) appears too long and might lead to repeated periods with insufficient analgesia in animals undergoing lasting and/or substantial pain after surgery. In comparison to the standard protocol, SB provided a long-lasting, assured analgesia without possible stressful repeated injections in a standard surgical model, with only limited and acceptable behavioural side-effects.

Endogenous α-calcitonin-gene-related peptide promotes exercise-induced, physiological heart hypertrophy in mice.

AIM: It is unknown how the heart distinguishes various overloads, such as exercise or hypertension, causing either physiological or pathological hypertrophy. We hypothesize that alpha-calcitonin-gene-related peptide (αCGRP), known to be released from contracting skeletal muscles, is key at this remodelling. METHODS: The hypertrophic effect of αCGRP was measured in vitro (cultured cardiac myocytes) and in vivo (magnetic resonance imaging) in mice. Exercise performance was assessed by determination of maximum oxygen consumption and time to exhaustion. Cardiac phenotype was defined by transcriptional analysis, cardiac histology and morphometry. Finally, we measured spontaneous activity, body fat content, blood volume, haemoglobin mass and skeletal muscle capillarization and fibre composition. RESULTS: While αCGRP exposure yielded larger cultured cardiac myocytes, exercise-induced heart hypertrophy was completely abrogated by treatment with the peptide antagonist CGRP(8-37). Exercise performance was attenuated in αCGRP(-/-) mice or CGRP(8-37) treated wild-type mice but improved in animals with higher density of cardiac CGRP receptors (CLR-tg). Spontaneous activity, body fat content, blood volume, haemoglobin mass, muscle capillarization and fibre composition were unaffected, whereas heart index and ventricular myocyte volume were reduced in αCGRP(-/-) mice and elevated in CLR-tg. Transcriptional changes seen in αCGRP(-/-) (but not CLR-tg) hearts resembled maladaptive cardiac phenotype. CONCLUSIONS: Alpha-calcitonin-gene-related peptide released by skeletal muscles during exercise is a hitherto unrecognized effector directing the strained heart into physiological instead of pathological adaptation. Thus, αCGRP agonists might be beneficial in heart failure patients.

Burrowing is a sensitive behavioural assay for monitoring general wellbeing during dextran sulfate sodium colitis in laboratory mice.

An impaired intestinal epithelial barrier is thought to be a major factor in the pathogenesis of human inflammatory bowel disease (IBD). IBD is frequently investigated by inducing a damaged barrier in murine models of colitis. This can be done by feeding mice with dextran sulfate sodium (DSS) polymers in their drinking water. Refinement measures should focus on alleviating unnecessary suffering during this probably painful condition. Appropriate parameters are needed to decide when to terminate the experiments. Our aim was to investigate whether a change in burrowing behaviour is a sensitive measure of animal welfare in murine models of colitis. Acute colitis was induced in C57BL/6 mice with 2.0% DSS over nine days. The burrowing test is based on the species-typical behaviour of mice to spontaneously displace items from tubes within their home cage. As a burrowing apparatus, a water bottle (250 mL, 150 mm length, 55 mm diameter) filled with 138-142 g of pellets of the animal's diet was used. The presence of intestinal inflammation as a result of acute DSS-induced colitis was confirmed by a decrease in body weight, colon length and an increase of murine endoscopic index of colitis severity, histological score and spleen weight in the group receiving DSS as compared with the control group. An onset of intestinal inflammation correlated with a significant decrease in burrowing behaviour (P < 0.05). Altered adrenal gland histology indicated stress as a result of acute colitis. Our findings provide evidence that changes of spontaneous burrowing behaviour correlate with the onset of inflammation in acute DSS-induced colitis.

In vitro ovine articular chondrocyte proliferation: experiments and modelling.

This study focuses on analysis of in vitro cultures of chondrocytes from ovine articular cartilage. Isolated cells were seeded in Petri dishes, then expanded to confluence and phenotypically characterized by flow cytometry. The sigmoidal temporal profile of total counts was obtained by classic haemocytometry and corresponding cell size distributions were measured electronically using a Coulter Counter. A mathematical model recently proposed (1) was adopted for quantitative interpretation of these experimental data. The model is based on a 1-D (that is, mass-structured), single-staged population balance approach capable of taking into account contact inhibition at confluence. The model's parameters were determined by fitting measured total cell counts and size distributions. Model reliability was verified by predicting cell proliferation counts and corresponding size distributions at culture times longer than those used when tuning the model's parameters. It was found that adoption of cell mass as the intrinsic characteristic of a growing chondrocyte population enables sigmoidal temporal profiles of total counts in the Petri dish, as well as cell size distributions at 'balanced growth', to be adequately predicted.

Experimental analysis and modelling of in vitro proliferation of mesenchymal stem cells.

OBJECTIVES: Stem cell therapies based on differentiation of adult or embryonic stem cells into specialized ones appear to be effective for treating several human diseases. This work addresses the mathematical simulation of proliferation kinetics of stem cells. MATERIALS AND METHODS: Sheep bone marrow mesenchymal stem cells (phenotype characterized by flow cytometry analysis) seeded at different initial concentrations in Petri dishes were expanded to confluence. Sigmoid temporal profiles of total counts obtained through classic haemocytometry were quantitatively interpreted by both a phenomenological logistic equation and a novel model based on a one-dimensional, single-staged population balance approach capable of taking into account contact inhibition at confluence. The models' parameters were determined by comparison with experimental data on population expansion starting from single seeding concentration. Reliability of the models was tested by predicting cell proliferation carried out starting from different seeding concentrations. RESULTS AND DISCUSSION: It was found that the proposed population balance modelling approach was successful in predicting the experimental data over the whole range of initial cell numbers investigated, while prediction capability of phenomenological logistic equation was more limited.

Microscopic wire guide-based orotracheal mouse intubation: description, evaluation and comparison with transillumination.

Airway access is needed for a number of experimental animal models, and the majority of animal research is based on mouse models. Anatomical conditions in mice are small, and the narrow glottic opening allows intubation only with a subtle technique. We therefore developed a microscopic endotracheal intubation method with a wire guide technique in mice anaesthetized with halothane in oxygen. The mouse is hung perpendicularly with its incisors on a thread fixed on a vertical plate. The tongue is placed with a pair of forceps between the left hand's thumb and forefinger and slightly pulled, while the neck and thorax are positioned using the third and fourth fingers. By doing so, the neck can be slightly stretched, which allows optimal visualization of the larynx and the vocal cords. To ensure a safe intubation, a fine wire guide is placed under vision between the vocal cords and advanced about 5 mm into the trachea. An intravenous 22G x 1 in. plastic or Teflon catheter is guided over this wire. In a series of 41 mice, between 21 and 38 g, the success rate for the first intubation attempt was >95%. Certainty of the judgement procedure was 100% and success rate was higher using the described method when compared with a transillumination method in a further series. The technique is safe, less invasive than tracheostomy and suitable for controlled ventilation and pulmonary substance application.

Inhibitory ligand-gated ion channels as substrates for general anesthetic actions.

General anesthetics have been in clinical use for more than 160 years. Nevertheless, their mechanism of action is still only poorly understood. In this review, we describe studies suggesting that inhibitory ligand-gated ion channels are potential targets for general anesthetics in vitro and describe how the involvement of y-aminobutyric acid (GABA)(A) receptor subtypes in anesthetic actions could be demonstrated by genetic studies in vivo.

Higher heart rate of laboratory mice housed individually vs in pairs.

Many studies have shown that housing mice individually over a long period significantly alters their physiology, but in most cases measurement has required human interference and restraint for sampling. Using a radio-telemetry system with implantable transmitters, we recorded heart rate (HR), motor activity (ACT) and body temperature (BT) of freely moving male mice (NMRI) housed either individually or in pairs with an ovarectomized female. Data for each parameter were collected at 5 min intervals for two consecutive 24 h periods. Even after several weeks of habituation to the social conditions, HR was increased in mice housed individually compared with mice housed in pairs, although their measured ACT did not differ. Additionally, BT tended to be reduced in individually-housed mice. When the data were analysed according to different ACT levels, HR was increased in individually-housed mice during phases of low and high, but not intermediate, motor activity. Furthermore, individually-housed mice had more, but shorter, resting bouts, indicating disruption of the normal circadian sleep pattern. Enhanced HR in individually-housed mice does not necessarily indicate stress, but might be an important physiological indicator of discomfort. The fact that individual housing alters basic physiological parameters in laboratory mice highlights the need to control for housing-dependent variation, especially in experiments that are sensitive to changes in these parameters.

Synthesis and in vivo studies of the stereoisomers of N-[11C]methyl-homoepibatidine.

The carbon-11 labeled enantiomers of nicotinic acetylcholine receptor (nAChR) ligand N-[11C]methyl-homoepibatidine have been synthesized to study the neuronal nicotinic acetylcholine receptors (nAChRs). In vivo evaluations were performed in mice and pig using positron emission tomography (PET). The radioligands displayed a strong enantioselectivity. The (-)-enantiomer showed high uptake in the brain while the (+)-enantiomer was rapidly washed out. In metabolite studies in mice >65% unchanged ligand was found in the blood after 60 minutes. No metabolites were found in the brain. After intravenous application of N-[11C]methyl-(-)-homoepibatidine in the pig specific accumulation in the thalamus was seen. Blocking experiments with cytisine showed specific binding consistent with labeling of the alpha4beta2-nAChR-subtype in the brain. Quantitative kinetic modeling of radiotracers in the pig brain was performed using the arterial input function. The brain uptake of the (-)-isomer was best fitted by a three-compartment model. High distribution volumes were found in the thalamus (DV(TOT) = 66.617, DV(S) = 59.910) versus a low uptake in the cerebellum (DV(TOT) = 8.605m, DV(S) = 1.898). The binding characteristics suggest N-[11C]methyl-(-)-homoepibatidine to be suited for PET imaging studies, but high toxicity prevents routine use in humans.

Interleukin-9 reduces lung fibrosis and type 2 immune polarization induced by silica particles in a murine model.

We examined the effect of interleukin (IL)-9, a cytokine active on B and T lymphocytes and associated with bronchial asthma, on the development of lung fibrosis induced by crystalline silica particles. Therefore, we compared the response to silica (1 and 5 mg/animal, intratracheally) in transgenic mice that constitutively express high levels of IL-9 (Tg5) and their wild-type counterparts (FVB). At 2 and 4 mo after treatment with silica, histologic examination and measurement of lung hydroxyproline content showed that the severity of fibrosis was significantly less important in Tg5 mice than in their wild-type counterparts. Intraperitoneal injection of IL-9 in C57BL/6 mice also reduced the amplitude of silica-induced lung fibrosis. The reduction of lung fibrosis by IL-9 was associated with a significant expansion of the B-lymphocyte population, both in bronchoalveolar lavage (BAL) and in the pulmonary parenchyma. In wild-type animals, silica-induced fibrosis correlated with markers of a T helper 2-like response such as upregulation of IL-4 levels in lung tissue and an increased immunoglobulin (Ig) G1/IgG2a ratio in BAL. Immunohistochemical studies demonstrated that the upregulation of IL-4 associated with the development of fibrosis was mainly localized in inflammatory alveolar macrophages. In transgenic mice, the level of IL-4 in lung homogenates was not significantly affected by silica treatment, and a reduced IgG1/IgG2a ratio was observed upon treatment with silica. The levels of interferon-gamma were significantly decreased after silica treatment in both strains. Together, these observations point to an antifibrotic effect of IL-9 in pulmonary fibrosis associated with a limitation of the type 2 polarization which accompanies lung fibrosis.

Neuroserpin, a neuroprotective factor in focal ischemic stroke.

Because recent studies have indicated that tissue plasminogen activator (tPA) aggravates neurodegenerative processes in many neural pathologies, we studied whether the endogenous tPA antagonist neuroserpin has a neuroprotective effect in an animal model of focal ischemic stroke. After induction of a focal ischemic stroke in the mouse by occlusion of the middle cerebral artery, we found that microglial cells accumulated in the marginal zone of the infarct are the most important source for both plasminogen activators, tPA and uPA. To investigate the effect of neuroserpin on the size and the histology of the infarct we produced transgenic mice overexpressing neuroserpin approximately sixfold in the nervous system. In the brain of these mice the total tPA activity in the uninjured tissue was strongly reduced. After induction of a focal ischemic stroke in the transgenic mice by a permanent occlusion of the middle cerebral artery (MCA), the infarcts were 30% smaller than in the wild-type mice. Immunohistochemical analyses and in situ hybridization revealed an attenuation of the microglial activation in the reactive zone. Concomitantly, the microglial production of tPA and uPA, as well as the PA-activity in the infarct region was markedly reduced. Thus, our results indicate that neuroserpin reduces microglial activation and, therefore, the PA activity and has a neuroprotective role after focal ischemic stroke.

Optimization of intraperitoneal injection anesthesia in mice: drugs, dosages, adverse effects, and anesthesia depth.

PURPOSE: The goals of the study were to find a safe intraperitoneal injection anesthesia protocol for medium-duration surgery in mice (e.g., embryo transfer/vasectomy) coupled with a simple method to assess anesthesia depth under routine laboratory conditions. METHODS: Eight anesthetic protocols consisting of combinations of dissociative anesthetics (ketamine, tiletamine), alpha2-agonists (xylazine, medetomidine), and/or sedatives (acepromazine, azaperone, zolazepam) were compared for their safety and efficacy (death rate, surgical tolerance), using observations and reflex tests. The four best protocols were further evaluated during vasectomy: physiologic measurements (respiratory rate, electrocardiogram, arterial blood pressure, body temperature, blood gas tensions, and acid-base balance) were used to characterize the quality of anesthesia. The reactions of physiologic parameters to surgical stimuli were used to determine anesthesia depth, and were correlated with reflex test results. RESULTS: The protocol with the highest safety margin and the longest time of surgical tolerance (54 min) was ketamine/ xylazine/acepromazine. Three further anesthetic combinations were associated with surgical tolerance: ketamine/ xylazine, ketamine/xylazinelazaperone, and tiletamine/xylazine/zolazepam (Telazol/xylazine). The protocols consisting of ketamine/medetomidine and ketamine/azaperone were not associated with clearly detectable surgical tolerance. The most reliable parameter of surgical tolerance under routine laboratory conditions was the pedal withdrawal reflex. CONCLUSIONS: The best intraperitoneal injection anesthesia regimen consisted of ketamine/xylazine/acepromazine. The dose must be adapted to the particulars of each experimental design (mouse strain, sex, age, mutation). This is best done by measuring surgical tolerance, using the pedal withdrawal reflex.

Soluble tumor necrosis factor (TNF) receptors p55 and p75 and interleukin-10 downregulate TNF-alpha activity during the lung response to silica particles in NMRI mice.

We have found reduced activity of tumor necrosis factor (TNF)-alpha accompanying resolving and fibrosing alveolitis induced in NMRI mice by mineral particles (MnO2 and SiO2, respectively), which is in apparent contradiction to the well-recognized proinflammatory and profibrotic activities of this cytokine. The objective of this study was to examine the mechanisms involved in this paradoxical response in NMRI mice. Although lung tissue messenger RNA (mRNA) levels for TNF-alpha were transiently (up to 15 d) and persistently (up to 120 d) upregulated in the resolving and fibrosing models, respectively, these changes were not accompanied by a parallel release of TNF-alpha protein, which was respectively transiently and persistently downregulated in bronchoalveolar lavage fluid and bronchoalveolar lavage cell cultures. The downregulation of the TNF-alpha protein was concurrent with the accumulation of recruited polymorphonuclear neutrophils (PMNs) in alveoli, and coculture experiments showed that PMN explanted from the lungs of mice treated with silica particles were able to downregulate the expression of TNF-alpha protein by naive alveolar macrophages. In addition, PMN depletion prevented the downregulation of TNF-alpha induced by silica, further establishing the role of PMNs in the downregulation of TNF-alpha. The possible degradation of TNF-alpha by proteolytic enzymes could be excluded. Marked increases in soluble p55 and p75 TNF receptors (sTNF-R), as well as in interleukin (IL)-10, paralleled the downregulation of TNF-alpha protein. The role of these mediators in the observed reduction of TNF-alpha activity was confirmed by immunoneutralizing the activity of p55 and p75 sTNF-R and by using IL-10-deficient animals. Because IL-10 also exerts profibrotic activity in addition to its antiinflammatory activity, the protracted overproduction of IL-10 observed in fibrosing alveolitis may help the understanding of why, in NMRI mice treated with silica particles, lung fibrosis develops in association with a downregulation of TNF-alpha.

IL-9 induces chemokine expression in lung epithelial cells and baseline airway eosinophilia in transgenic mice.

Recent data have identified IL-9 as a key cytokine in determining susceptibility to asthma. These data are supported by the finding that allergen-exposed IL-9-transgenic mice exhibit many features that are characteristic of human asthma (airway eosinophilia, elevated serum IgE and bronchial hyperresponsiveness) as compared to the background strain. A striking feature of these animals is a robust peribronchial and perivascular eosinophilia after allergen challenge, suggesting that IL-9 is a potent factor in regulating this process. In an attempt to gain insights into the molecular mechanism governing IL-9 modulation of lung eosinophilia, we investigated the ability of this cytokine to induce the expression of CC-type chemokines in the lung because of their effect on stimulating eosinophil chemotaxis. Here we show that IL-9-transgenic mice in contrast to their congenic controls exhibit baseline lung eosinophilia that is associated with the up-regulation of CC-chemokine expression in the airway. This effect appears to be through a direct action of IL-9 because the addition of recombinant IL-9 to primary epithelial cultures and cell lines induced the expression of these chemokines in vitro. These data support a mechanism for IL-9 in regulating the expression of eosinophil chemotactic factors in lung epithelial cells.

Special communicationthe critical role of mechanical forces in blood vessel development, physiology and pathology

The following extended abstracts were presented at the Research Initiatives in Vascular Disease Conference, Movers and Shakers in the Vascular Tree-Hemodynamic and Biomechanical Factors in Blood Vessel Pathology, sponsored by The Lifeline Foundation and the Cardiovascular & Interventional Radiology Research and Educational Foundation; jointly sponsored by the International Society for Cardiovascular Surgery, North American Chapter, The Society for Vascular Surgery, and The Society of Cardiovascular and Interventional Radiology; in cooperation with the National Institutes of Health-National Heart, Lung &Blood Institute on Mar 11-12, 1999, in Bethesda, Md.

Lung fibrosis induced by silica particles in NMRI mice is associated with an upregulation of the p40 subunit of interleukin-12 and Th-2 manifestations.

Interleukin (IL)-12 is a cytokine produced principally by activated macrophages which is involved in control of the T-helper 1/T-helper 2 cell (Th1/Th2) polarization of immune responses. To examine its potential involvement in the development of lung fibrosis, we examined the expression (protein, messenger RNA [mRNA]) of IL-12 (p70) and of its subunits (p40 and p35) in lung homogenates, bronchoalveolar lavage fluid (BALF), and bronchoalveolar lavage (BAL) cell cultures in mouse models of resolutive alveolitis (RA) and fibrosing alveolitis (FA) induced by inorganic particles (manganese dioxide [MnO2] and crystalline silica, respectively). The administration of tungsten carbide (WC), which behaved as an innocuous dust for the lung, served as a negative control condition. The FA was specifically accompanied by a Th2-like polarization characterized by high levels of immunoglobulin (Ig)G1 in BALF and by a protracted overproduction of both p40 protein and mRNA, but not by the biologically active form of IL-12 (p70). In the RA model, the p40 response was only transient, and a Th1-like response was reflected by increased levels of interferon (IFN)-gamma and dominant levels of IgG2a in BALF. Taken together, these findings suggest that production of the p40 subunit of IL-12 and Th2 polarization play important roles in lung inflammatory and fibrotic responses to inhaled inorganic particles.

HLA-B35 frequency variations correlate with malaria infection in Sardinia.

The hypothesis of a possible selective role of malaria in HLA allele frequency variations was investigated in Sardinia by typing completely 1,039 individuals for HLA: 536 from six lowland villages exposed to malaria until 1948, and 503 from six highland villages with no history of malaria. Another 1,928 individuals from 136 villages scattered all over the island were studied to establish if the HLA allele frequencies among villages correlated with the malaria incidence and/or altitude above sea level. Only the HLA-B35 allele yielded significantly higher frequencies in the lowland versus the highland villages (P<1 x 10(-5)). The observed B35 variance was 9.5 times higher than expected in the absence of selection, showing an adaptive origin. The highly significant positive correlation found between HLA-B35 frequency and malaria in 136 villages suggests that malaria has been the selective factor for HLA-B35 in Sardinia.

Tumor necrosis factor-alpha is expressed by monocytes/macrophages following cardiac microembolization and is antagonized by cyclosporine.

The time course of expression of TNF-alpha in myocardial wound healing following ischemic injury was investigated in the porcine heart. Microembolization was used to induce focal ischemia and necrosis in hearts of 39 adult pigs. The animals were sacrificed after 3, 6, 12, 24 h, 3 and 7 days, and after 4 weeks, and the myocardial tissue was studied by immunofluorescence using specific antibodies. TNF-alpha containing cells were identified as monocytes/macrophages by double staining with a muramidase antibody. Monocytes/macrophages were the only source of TNF-alpha. Microembolization caused multiple necrotic foci with loss of myocytes in the left ventricular myocardium. These foci contained numerous monocytes/macrophages and showed an inflammatory reaction typical of wound healing followed by replacement with scar tissue. The number of TNF-alpha positive cells increased after 24 h, peaked between 3-7 days and slowly decreased thereafter. Expression of TNF-alpha in monocytes/macrophages was significantly reduced after pretreatment of pigs with cyclosporine or dexamethasone. It is concluded that 1.) in myocardial tissue monocytes/macrophages are the only cell type expressing TNF-alpha, 2.) TNF-alpha is involved in wound healing after ischemia, and 3.) synthesis of TNF-alpha and inflammatory angiogenesis can be inhibited be treatment with either cyclosporine or dexamethasone.