The rabbit as an experimental model for regional chemotherapy. 2. Isolated perfusion of hindlimbs

Regional chemotherapy to a tumour is most commonly delivered by intra-arterial infusion. An alternative method of regional drug delivery, isolated perfusion, may be used where anatomical considerations permit. The technique of isolated perfusion in the rabbit hindlimb is described. The use of this model with the implantable rabbit VX2 carcinoma allows estimation of drug uptake by normal tissues, primary tumour and popliteal lymph node metastases. Correlation of such data with blood flow measurements enables targeting of new cytotoxic agents to be evaluated. The effect of perfusate composition on tissue uptake of such an agent, the plant toxin ricin, has been determined.     

The goat as an experimental ruminant model for tuberculosis infection

Young goats were inoculated intratracheally with a low dose of Mycobacterium bovis to determine if they develop lesions similar to those seen in the natural disease in cattle. After 3 months, the challenge induced small lesions (<1 cm diameter) localized in the lungs and pulmonary lymph nodes, similar to those seen in the natural cattle disease. All of the M. bovis-inoculated young goats showed strong cellular immune responses to bovine PPD. Results of the present study suggest that young goats can be used as animal models since a low dose challenge mimics the natural pathogenesis and pathology processes caused by M. bovis in cattle.     

The rabbit as an animal model of hepatic lipase deficiency

A natural deficiency of hepatic lipase in rabbits has been exploited to gain insights into the physiological role of this enzyme in the metabolism of plasma lipoproteins. A comparison of human and rabbit lipoproteins revealed obvious species differences in both low-density lipoproteins (LDL) and high-density lipoproteins (HDL), with the rabbit lipoproteins being relatively enlarged, enriched in triacylglycerol and depleted of cholesteryl ester. To test whether these differences related to the low level of hepatic lipase in rabbits, whole plasma or the total lipoprotein fraction from rabbits was either kept at 4 degrees C or incubated at 37 degrees C for 7 h in (i) the absence of lipase, (ii) the presence of hepatic lipase and (iii) the presence of lipoprotein lipase. Following incubation, the lipoproteins were recovered and subjected to gel permeation chromatography to determine the distribution of lipoprotein components across the entire lipoprotein spectrum. An aliquot of the lipoproteins was subjected also to gradient gel electrophoresis to determine the particle size distribution of the LDL and HDL. Both hepatic lipase and lipoprotein lipase hydrolysed lipoprotein triacylglycerol and to a much lesser extent, also phospholipid. There were, however, obvious differences between the enzymes in terms of substrate specificity. In incubations containing hepatic lipase, there was a preferential hydrolysis of HDL triacylglycerol and a lesser hydrolysis of VLDL triacylglycerol. By contrast, lipoprotein lipase acted primarily on VLDL triacylglycerol. When more enzyme was added, both lipases also acted on LDL triacylglycerol, but in no experiment did lipoprotein lipase hydrolyse the triacylglycerol in HDL. Coincident with the hepatic lipase-induced hydrolysis of LDL and HDL triacylglycerol, there were marked reductions in the particle size of both lipoprotein fractions, which were now comparable to those of human LDL and HDL3, respectively.     

The rabbit as an animal model for haemoperfusion: surgical preparation and use

In this paper the authors describe the surgical procedure to prepare rabbits for haemoperfusion experiments. The carotid artery and jugular vein are cannulated and a simple shunt device inserted to maintain patency of the vessels over a period of time. The cannulas and shunt remain patent and free of infection for some months. Specially designed outflow and inflow extracorporeal tubing sets minimize blood volume outside the body of the rabbit. The authors also illustrate the efficacy of this system in haemoperfusion trials to remove specific antibodies. Recently a system was described to remove mercury from the bloodstream of poisoned animals. The rabbit is a useful experimental animal for this type of haemoperfusion trial.     

In vivo rabbit hindquarter model for assessment of regional burn hypermetabolism.

Severe burn injury evokes hypermetabolism and muscle wasting, despite nominally adequate nutrition. Although there is much information on whole organism and isolated tissue metabolism after burn injury, data examining regional burn hypermetabolism in vivo are lacking. Using surgically implanted (general anesthesia) regional vascular catheters and primed constant infusion of l-[1-(13)C]phenylalanine tracer, we have determined in vivo burn-induced alterations in rabbit hindquarter protein and energy metabolism. Burn injury evokes increased whole body resting energy expenditure and phenylalanine turnover, accompanied by significantly increased hindquarter proteolysis, creating a negative protein balance in burned rabbit hindquarter. Hindquarter oxygen consumption showed an increase after burn injury, but it did not reach statistical significance. Burn-induced changes in hindquarter protein turnover account for approximately one-third of the whole animal hypermetabolism. This model offers a system for regional manipulation of postburn hypermetabolism.     

Trypanosoma evansi: a comparative study of four diagnostic techniques for trypanosomosis using rabbit as an experimental model

The goal of this study was to compare two parasitological diagnostic techniques, such as by Micro-Haematocrit Centrifugation Technique (MHCT) and Direct Microscopic Examination (DME) with a serological method (iELISA), and a molecular procedure PCR, in rabbits experimentally infected with Trypanosoma evansi, in order to determine their sensitivity throughout the course of disease. The parasitological methods were not able of detecting the presence of the parasite during the phases of low parasitemia, the prepatency period and the chronic phase. In contrast, PCR detected T. evansi in the prepatency and chronic phase, when increase the amount of DNA from 100 to 300 ng. 100% detection was observed with iELISA only in the chronic stage of the disease. In the acute phase, all samples were positively diagnosed using either MHCT or PCR, whereas only few samples were diagnosed by DME. Samples obtained from day 15 post infection were also detected by iELISA. The highest diagnostic register during the course of infection was achieved by the PCR technique (93.8%), followed by iELISA (71.1%), MHCT (59%) and DME (13.6%). Therefore, we recommend the use of PCR in epidemiological studies in order to implement sanitary control plans for the improvement of livestock productivity in the country.     

Cytochrome c as an experimental model protein

Mitochondrial cytochrome c is among the most intensively studied of all proteins. Initial interest was in its role in the respiratory chain and as a model for studies of protein structure, folding and electron transfer. The function of cytochrome c in signalling apoptosis has brought a new wave of research into the protein. Bacterial cytochromes c are more complex and varied in function. This review highlights some of these roles and expands on systems for producing holocytochrome c proteins.     

The pathogenetic bases for chemotherapy in an experimental Salmonella infection]

The effect of etiotropic (polymyxin and adriblastin) and pathogenetic (levamisole and vitamin E) chemotherapy on lipid peroxidation (LPO), phagocyte functional activity and the process and outcomes of Salmonella infection was studied in rabbits. It was shown that development of salmonellosis was accompanied by activation of LPO which was phase-by-phase. There was synchronism in changing of LPO and neutrophilic phagocytic activity. Adriblastin and levamisole stimulated LPO and increased the neutrophilic phagocytic activity. Vitamin E inhibited LPO and had an unfavourable effect on the process and outcomes of the infection. The problem in differential use of the chemotherapeutic drugs with an account of their modulating effect on LPO is discussed.     

Cowhage-induced itch as an experimental model for pruritus. A comparative study with histamine-induced itch

Background

Histamine is the prototypical pruritogen used in experimental itch induction. However, in most chronic pruritic diseases, itch is not predominantly mediated by histamine. Cowhage-induced itch, on the other hand, seems more characteristic of itch occurring in chronic pruritic diseases.

Objectives

We tested the validity of cowhage as an itch-inducing agent by contrasting it with the classical itch inducer, histamine, in healthy subjects and atopic dermatitis (AD) patients. We also investigated whether there was a cumulative effect when both agents were combined.

Methods

Fifteen healthy individuals and fifteen AD patients were recruited. Experimental itch induction was performed in eczema-free areas on the volar aspects of the forearm, using different itch inducers: histamine, cowhage and their combination thereof. Itch intensity was assessed continuously for 5.5 minutes after stimulus application using a computer-assisted visual analogue scale (COVAS).

Results

In both healthy and AD subjects, the mean and peak intensity of itch were higher after the application of cowhage compared to histamine, and were higher after the combined application of cowhage and histamine, compared to histamine alone (p<0.0001 in all cases). Itch intensity ratings were not significantly different between healthy and AD subjects for the same itch inducer used; however AD subjects exhibited a prolonged itch response in comparison to healthy subjects ( p<0.001).

Conclusions

Cowhage induced a more intense itch sensation compared to histamine. Cowhage was the dominant factor in itch perception when both pathways were stimulated in the same time. Cowhage-induced itch is a suitable model for the study of itch in AD and other chronic pruritic diseases, and it can serve as a new model for testing antipruritic drugs in humans.     

The influence of antimetabolites on Trichomonas vaginalis as an experimental model]

The present study was concerned with the relationship between antimetabolites and Trichomonas vaginalis. In all of the strains (with p-nitrobenzylether of N-acetyldiiodtryrosine) tested, the growth of Trichomonas vaginalis was identical to that of the control series at concentrations up to 2 mg/ml. At higher concentrations a decrease in multiplication was noted. In the experimental series with antitrypsin, from 1 mg/ml produced an inhibiting effect upon the Trichomonas population. Further investigations on the combined inhibition test are envisaged.     

The VX2 carcinoma in the rabbit auricle as an experimental model for intra-arterial embolization of head and neck squamous cell carcinoma with dextran microspheres

A head and neck cancer model is developed using the VX2 carcinoma cell line injected s.c. in both ears of New Zealand White (NZW) rabbits. The study is focused on the effects of intraarterial embolization of the carcinomas with a new type of dextran hydrogel microspheres. During the phase of exponential growth the tumour-surface doubling-time was 7.1+/-2.0 days. Standard deviation in growth of the tumours was significantly larger between separate animals than between tumours growing in the left and right auricle of each individual animal (2.0 versus 0.65 days). A fresh cell suspension containing at least 10 x 10(6) vital tumour cells was necessary to yield a tumour-take of 85%. The caudal auricular artery perfuses the caudal half of the external ear and is very suitable for macroscopic cannulation. Histological evaluation shows, that the use of dextran hydrogel microspheres of at least 25 microm in combination with ligation of non-tumour perfusing branches of the central auricular artery yields diffuse embolization of the VX2 carcinoma. This tumour model can be of use in further studies to optimize particle size and dosage for embolization as well as to evaluate the effect of different anti-neoplastic drugs, slowly released by controlled degradation of dextran microspheres.