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PubMed2000

Induction of emetic, pyrexic, and behavioral effects of Staphylococcus aureus enterotoxin B in the ferret.

Ferrets which had been orally dosed with 5 mg of Staphylococcal enterotoxin B (SEB) responded with an increase in subcutaneous temperature. At 75 min, the subcutaneous temperature was significantly higher (+ 0.9 degrees C +/- 0.38 degrees C, P < 0.007) than in control animals. Animals dosed with 1 or 2 mg of SEB responded with a small, but not significant, increase in subcutaneous temperature. All of the animals dosed with 5 mg of SEB retched and vomited. The mean latency for the onset of retching was 105 +/- 36 min, and the mean latency for the onset of vomiting was 106 +/- 34 min. The mean number of retches was 17.8 +/- 19.6, and the mean number of vomits was 2.0 +/- 1.5. These findings indicate that ferrets can be used as alternatives to primates for the study of the biological activities of SEB.

Administration, Oral↗

PubMed2000

Adherence of isogenic flagellum-negative mutants of Helicobacter pylori and Helicobacter mustelae to human and ferret gastric epithelial cells.

Isogenic flagellum-negative mutants of Helicobacter pylori and Helicobacter mustelae were screened for their ability to adhere to primary human and ferret gastric epithelial cells, respectively. We also evaluated the adherence of an H. pylori strain with a mutation in the flbA gene, a homologue of the flbF/lcrD family of genes known to be involved in the regulation of H. pylori flagellar biosynthesis. H. pylori and H. mustelae mutants deficient in production of FlaA or FlaB and mutants deficient in the production of both FlaA and FlaB showed no reduction in adherence to primary human or ferret gastric epithelial cells compared with the wild-type parental strains. However, adherence of the H. pylori flbA mutant to human gastric cells was significantly reduced compared to the adherence of the wild-type strain. These results show that flagella do not play a direct role in promoting adherence of H. pylori or H. mustelae to gastric epithelial cells. However, genes involved in the regulation of H. pylori flagellar biosynthesis may also regulate the production of an adhesin.

Adhesins, Bacterial↗

PubMed2004

Immunization with modified vaccinia virus Ankara-based recombinant vaccine against severe acute respiratory syndrome is associated with enhanced hepatitis in ferrets.

Severe acute respiratory syndrome (SARS) caused by a newly identified coronavirus (SARS-CoV) is a serious emerging human infectious disease. In this report, we immunized ferrets (Mustela putorius furo) with recombinant modified vaccinia virus Ankara (rMVA) expressing the SARS-CoV spike (S) protein. Immunized ferrets developed a more rapid and vigorous neutralizing antibody response than control animals after challenge with SARS-CoV; however, they also exhibited strong inflammatory responses in liver tissue. Inflammation in control animals exposed to SARS-CoV was relatively mild. Thus, our data suggest that vaccination with rMVA expressing SARS-CoV S protein is associated with enhanced hepatitis.

Animals↗

PubMed1980

Peripheral functional organisation of vagally evoked gastric motor responses in the ferret.

The aims of the present study were to determine the relative amplitudes of intragastric motor responses evoked by different vagal branches and to establish whether the effects of acute or chronic vagotomy could be predicted from these data. Intragastric pressure responses to electrical stimulation of the vagus were measured in urethane-anaesthetised ferrets and acute or chronic vagotomies were performed. The results show that the left and right cervical vagi were equipotential and fully overlaped each other. Their contributions to the dorsal trunk were equipotential and fully overlapping and so were their contributions to the ventral trunk. The dorsal trunk was more effective than the ventral trunk and there was total functional overlap between these two trunks. Vagal evoked gastric motor responses of the ferret are apparently organised in a different way from vagally induced acid secretion or hormone release in the cat. Acute removal of a trunk led to a reduction in evoked responses that was not linear function of the effect of stimulation of that trunk. In contrast, chronic removal caused a relative increase in evoked responses that ws inversely related to the decrease caused by acute removal. The implications of total functional overlap and neuromuscular reorganisation after chronic vagotomy are discussed.

Animals↗

PubMed1993

Development of a 14C-urea breath test in ferrets colonised with Helicobacter mustelae: effects of treatment with bismuth, antibiotics, and urease inhibitors.

A 14C-urea breath test analogous to its clinical counterpart is described for use in ferrets naturally or experimentally infected with Helicobacter mustelae. The test is performed within a sealed glass metabolism chamber through which air is drawn at a constant rate and expired breath collected into sodium hydroxide. Peak 14CO2 production occurred approximately 1 hour after substrate administration. Both inter- and intra-animal responses were highly reproducible, with mean coefficients of variation less than 10%. Other than enhancing peak 14CO2 levels very slightly, fasting had little influence on the response. In infant animals challenged with H mustelae, breath test activity increased linearly with the total count of culturable bacteria isolated from the antrum. Treatment of established infections with colloidal bismuth subcitrate (DeNol) for 4 weeks resulted in clearance of all detectable bacteria but retention of some breath test activity. Subsequent regrowth of bacteria was parallelled by an increase in the breath test response. Inclusion of amoxycillin and metronidazole in the treatment regimen, however, eradicated all the bacteria and almost totally eliminated 14CO2 production. This response parallels the clinically observed suppressive effect on H pylori achieved with bismuth alone relative to the total eradication seen with triple therapy. A single oral dose of the urease inhibitor, flurofamide, inhibited over 90% of the response for at least 24 hours. Acetohydroxamic acid was less effective. These findings suggest that in the ferret H mustelae model, breath test analysis can be a useful, non-invasive alternative to endoscopy for evaluation of agents affecting either growth of the organism or urease activity.

Animals↗

PubMed2004

T cell lymphoma in the lumbar spine of a domestic ferret (Mustela putorius furo).

A 22-month-old castrated male ferret developed acute pelvic limb paresis. Radiographs and computed tomography revealed a soft tissue mass with associated bony lysis of L5, and ultrasound-guided fine needle aspirates suggested that it was a lymphoma. Treatment with prednisone at immunosuppressive doses did not produce any detectable improvement in the ferret's clinical signs and it became moribund less than two weeks after they developed. A postmortem biopsy confirmed the presence of a lymphoma which had invaded the vertebral bone. No viruses were detected by cell culture, or electron microscopy.

Animals↗

PubMed1982

Inhibition of ciliary activity in organ cultures of ferret trachea in reference to genetic and biological characters in influenza virus strains.

As reported previously, attenuated stable inhibitor-resistant influenza viruses can be screened by a 50% ciliary activity inhibition test in ferret tracheal organ cultures. This test was further applied to a 5 attenuated cold-adapted influenza strains and to 11 strains with known a percentage of RNA-RNA hybridization with the parental A/PR/8/34 (HON1) virus strain. Again, with one exception, attenuated strains could be clearly differentiated from virulent ones. It was concluded that virulence of influenza strains for man can be detected using this test regardless of the techniques used to prepare attenuated variants. A preliminary screening of attenuated candidates for live influenza vaccines can be achieved with confidence on ferret tracheal organ cultures.

Animals↗

PubMed1986

Neural control of jejunal and ileal motility and transmural potential difference in the ferret.

The aim of the present study was to examine the vagal control of motor activity and transmural potential difference in the anaesthetized ferret jejunum and ileum in vivo. The data suggest that in the jejunum fluctuations in transmural potential difference occur secondary to spontaneous bursts of contractions and both are controlled by activity in the vagus nerve. However, in the ileum, spontaneous contractile activity and transmural potential difference are not under the tonic influence of the vagus nerve, although transmural potential difference may be under tonic sympathetic control. Furthermore, it appears that vagally induced motor activity and transmural potential difference responses are independent phenomena. Finally the changes in transmural potential difference and the long latency motor responses to vagal nerve stimulation in the small intestine of the ferret are mediated at least in part by noncholinergic transmitters.

Adrenergic alpha-Agonists↗

PubMed1990

The inhibitory effect of halothane on the emetic response in the ferret.

Emesis and nausea are often associated with anaesthesia and continue to be a common clinical problem. Past clinical studies have demonstrated that halothane produces a higher incidence of vomiting compared with other anaesthetics, but some investigators have described an antiemetic effect. The purpose of this study was to investigate the effects of various doses of halothane on the emetic response in the decerebrate ferret. Following a control emetic response, a maximum of six increasing cumulative concentrations of halothane were delivered. At the end of each delivery period, the supradiaphragmatic vagal communicating branch, which has been shown to reproducibly elicit vomiting, was electrically stimulated and the emetic response was monitored. An increase in halothane concentration produced a marked depression of tongue, abdominal muscle, and diaphragm EMG activity as well as a decrease in central venous pressure. Licking, a prodromal response comparable to nausea in the human, appeared to be most sensitive. An increase in latency of the emetic response occurred as the concentration of halothane was increased. All phases of the response were observed at concentrations below 0.6 vol% halothane. At 0.6 vol% halothane, 75% of the animals vomited. At higher concentrations, the emetic response was completely abolished. One hour post-halothane, all latencies had returned to near control values. The methods utilized in this study provided a model that was not complicated by a large number of variables usually present in clinical studies. These data demonstrate that halothane exerts an inhibitory, concentration-dependent, and reversible effect on the emetic response in the ferret and provide further support that halothane alone does not possess emetic properties at clinical properties at clinical concentrations.

Animals↗

PubMed1989

Na-Ca exchange in ferret red blood cells.

Ferrets have high Na (140 mmol/l) red blood cells. To determine whether ferret red cells had a Na-Ca exchange system, Na effluxes via the Na + K + 2Cl cotransrpoter and Ca effluxes via the Ca pump had to be inhibited. This was accomplished by replacing cell chloride with nitrate and by loading the cells with vanadate that inhibits the Ca pump. Under these conditions, extracellular Na (Naout) inhibited Ca influx. Intracellular Na (Nain) was required for the large Ca influx as replacement of Na with Li reduced Ca influx to less than one-tenth of the original rate. Caout stimulated Na efflux by about twofold. The Ca efflux from cells depleted of Na was increased from 0.8 to 3.2 mmol.l packed cells-1.h-1 by the presence of Naout. Cells placed in a Na-free solution accumulated Ca: total intracellular Ca was 20-fold higher than free Caout. Most of this Ca was released on addition of the Ca ionophore, A23187. Because the Na gradient had driven net Ca uphill, the fluxes of Na and Ca are coupled. In a Na-free solution, the K1/2 for Ca influx was usually approximately 10 microM (occasionally approximately 100 microM), and the maximal velocity (Vmax was 1.5-4.4 mmol.l packed cells-1.h-1. At Naout = 150 mM, K1/2 increased 5- to 150-fold. In some cells, Naout decreased Vmax by approximately fourfold, suggesting that Naout does not always compete with Caout.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1993

Effects of extracellular ATP on ICa, [Ca2+]i, and contraction in isolated ferret ventricular myocytes.

The effects of extracellular ATP on the voltage-activated "L-type" Ca current (ICa), action potential, resting and transient intracellular Ca2+ levels, and cell contraction were examined in enzymatically isolated myocytes from the right ventricles of ferrets. With the use of the whole cell patch-clamp technique, extracellular ATP (10(-7) to 10(-3) M) inhibited ICa in a time- and concentration-dependent manner. ATP decreased the peak amplitude of ICa without altering the residual current at the end of 500-ms clamp steps. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half-maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Consistent with its inhibitory effect on ICa, ATP hyperpolarized the plateau phase and shortened the action potential duration. In fura-2-loaded myocytes, extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, when current was elicited under voltage-clamp conditions, ATP both decreased the myoplasmic intracellular Ca2+ transient and inhibited the degree of cell shortening. Our results suggest that ATP could be a genuine and potent extracellular modulator of cardiac function in ferret ventricular myocardium.

Action Potentials↗

PubMed1996

Na(+)-K(+)-2Cl- cotransport, Na+/H+ exchange, and cell volume in ferret erythrocytes.

Ferrets have high-Na+ and low-K+ erythrocytes (113 and 5.4 mmol/l cell water) due to the lack of Na(+)-K+ pumps. Because ferret erythrocytes have a high capacity for Na(+)-K(+)-2Cl- cotransport, the present study was undertaken to evaluate cell volume-related changes in cotransport activity and its role in volume regulation. With cell shrinkage, Na(+)-K(+)-2Cl- cotransport is activated about twofold. A large bumetanide-insensitive Na+ uptake component that has not yet been described is found in shrunken erythrocytes. Its inhibition by amiloride (concn inhibiting 50% of maximal response = 12 microM) and the Na+ dependence of amiloride-sensitive extracellular pH changes measured in cells suspended in hypertonic unbuffered medium indicate that this flux represents Na+/H+ exchange. Shrinkage activation of both transporters follows a time lag of approximately 3 min and also requires normal levels of ATP. ATP depletion inhibits Na(+)-K(+)-2Cl- cotransport even at normal cell volume. Both transporters are partially inhibited by the protein kinase inhibitors staurosporine and K252a, and activators of protein kinases A and C do not affect transport. Okadaic acid inhibition of protein phosphatases activates Na(+)-K(+)-2Cl- cotransport to its maximal activity (same after shrinkage), but shrinkage and okadaic acid activation are not additive. In contrast, okadaic acid activates Na+/H+ exchange even in shrunken cells. These results indicate that cell shrinkage activates Na(+)-K(+)-2Cl- cotransport and Na+/H+ exchange probably by phosphorylation processes.

Adenosine Triphosphate↗

PubMed1992

Intestinal uptake and lymphatic absorption of beta-carotene in ferrets: a model for human beta-carotene metabolism.

To determine the appropriateness of the ferret as a model for human beta-carotene (beta-C) metabolism, we have perfused both 15,15'-beta-[14C]C and unlabeled beta-C through the upper 30-cm portion of the small intestine of ferrets in vivo. The effluents of a mesenteric lymph duct cannulation and a common bile duct cannulation, as well as portal vein blood periodically sampled via an indwelling catheter, were collected. Ten percent (9.5 +/- 0.06%) of the total administered beta-C was taken up by the intestine after a 4-h perfusion. Of the radioactivity taken up, 68.6 +/- 6.5% remained in the intestinal mucosa, 3.2 +/- 0.2% was recovered in the lymph, and 28.2 +/- 6.5% (calculated) was absorbed via the portal system. The total uptake/absorption of beta-C was 12.9 +/- 6.8 nmol.h-1.30 cm intestine-1. Large amounts of unchanged beta-C and relatively small amounts of both beta-apo-12'-carotenal and beta-apo-10'-carotenal were isolated in the intestinal mucosa after a 4-h perfusion with beta-C. Considerable amounts of metabolites more polar than retinol were formed and comprised 35% of the total radioactivity recovered in the intestinal mucosa. Polar metabolites were absorbed mostly into the portal venous system, whereas retinol and retinyl esters were absorbed mainly into the mesenteric lymph. Of the total absorbed radioactivity in lymph, 10 +/- 1.0% appeared as unchanged beta-C, with peak absorption occurring at 3 h after beginning the perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗

PubMed1999

Inhibition of transient LES relaxations and reflux in ferrets by GABA receptor agonists.

Transient lower esophageal sphincter (LES) relaxation is the major mechanism of gastroesophageal reflux. This study uses an established ferret model to evaluate GABA(B) receptor agonists' ability to reduce triggering of transient LES relaxations. One hundred sixty manometric/pH studies were performed on 18 conscious ferrets. In untreated animals, intragastric infusion of 25 ml glucose (pH 3.5) led to 2.0 +/- 0.6 reflux episodes over the first 30 min. Twenty-nine of forty-seven reflux episodes occurred during transient LES relaxation, and 18 occurred after downward drifts (<1 mmHg/s) in basal LES pressure. The GABA(B) receptor agonists baclofen (7 micromol/kg ip), CGP-44532, and SKF-97541 (both ED(50) <0.3 micromol/kg) reduced reflux episodes and transient LES relaxations. The putative peripherally selective GABA(B) receptor agonist 3-aminopropylphosphinic acid (80-240 micromol/kg) was ineffective, as was the GABA(A) receptor agonist muscimol (5 micromol/kg). Baclofen's inhibition of transient LES relaxations and reflux was unaffected by low-affinity GABA(B) receptor antagonists CGP-35348 and CGP-36742 at 100 micromol/kg but was reversed by higher-affinity CGP-54626 and CGP-62349 (0.7 micromol/kg) or by CGP-36742 at 200 micromol/kg. Therefore, GABA(B) receptor inhibition of reflux shows complex pharmacology. Our and other data indicate the therapeutic potential for these drugs.

Animals↗

PubMed1989

Pressure response to quick volume changes in tetanized isolated ferret hearts.

Observed pressure responses to quick volume changes in the isolated tetanized heart of ferrets were compared with previously reported tension responses to quick length changes in isolated cardiac muscle. Hearts were isolated from ferrets, perfused with ryanodine solution, and stimulated rapidly (50 ms between stimulations) to produce repeated 4-s intervals of tetanus. During each tetanus interval, volume increments of different amplitudes were rapidly removed and then reinfused into the left ventricular chamber. The pressure responses to these volume changes were evaluated for differences between withdrawals and infusions and for dependence on the amplitude of the volume change. It was found for both withdrawal and infusion that the response could be divided into three phases: 1) an immediate phase coincident with volume change, 2) a fast-recovery phase, and 3) a slow-recovery phase. The amplitude of the immediate phase was linearly dependent on the volume change so that a single regression line fit all the data (withdrawal and infusion). The fast recovery phase was 2.5 times faster for infusion than for withdrawal and generated a rebound effect with the pressure going below the initial pressure in the response to infusion. The pressure never went above the initial pressure in the response to withdrawal. The slow-recovery phases in infusion and withdrawal did not differ. These responses in the isolated heart bear striking similarities to tension responses to quick length changes in isolated constantly activated cardiac muscle. We concluded that muscle fiber dynamics were being faithfully transformed to left ventricular (LV) chamber dynamics without appreciable distortion because of the many intervening factors between the wall muscle fiber and the LV chamber.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Effect of in vivo inhibition of neutrophil adherence on skeletal muscle function during ischemia in ferrets.

Neutrophils are reported to play an important role in the genesis of tissue damage during reperfusion after periods of ischemia in a variety of organs and may also be involved in loss of tissue function during ischemia. To test this hypothesis, the monoclonal antibody, MoAb 60.3, which prevents the adhesion of ferret neutrophils to cultured human endothelial cells at a concentration of 30 micrograms/ml, was tested in a model of peripheral vascular disease to determine whether it would preserve skeletal muscle function during ischemia. In an anesthetized ferret the muscles of the hindlimb were stimulated electrically to contract isometrically and the force of contraction was measured. Under normal perfusion conditions the contractile force peaked within 1 or 2 min of initiation of stimulation and gradually declined to approximately 80% of peak force after 20 min. When femoral arterial pressure was reduced to 45 mmHg by partial occlusion of the abdominal aorta, peak force was reduced by 25 +/- 7%, and within 5 min the force decayed to approximately 20% of the original peak, resulting in an area under the force-time curve (AUC) of 32 +/- 5% of that seen during the normal flow period. During ischemia after treatment with MoAb 60.3 (2 mg/kg iv), peak force was 94 +/- 3% and AUC was 49 +/- 5% of that observed during the normal flow period, a significant protective effect compared with the untreated control group (P = 0.0294). When the nonneutrophil-directed monoclonal antibody, L6, was tested in this model, no protective effects were evident.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

PAF induces relaxation of pulmonary arteries but contraction of pulmonary veins in the ferret.

The present study was designed to determine whether platelet-activating factor (PAF) has different effects on pulmonary arteries and veins. Third-order pulmonary arterial and venous rings of the ferret were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2, 37 degrees C) and their isometric tension was recorded. Under basal conditions, PAF had no effect on the resting tension of arteries but induced an endothelium-dependent contraction of veins. The contraction was not affected by BW-755C (an inhibitor of cyclooxygenase and lipoxygenase), BQ-123 [an antagonist of endothelin (ET) A (ETA) receptors)], or IRL-1038 (an antagonist of ETB receptors). PAF had no effect on veins during contraction to prostaglandin F2 alpha (PGF 2 alpha) but induced an endothelium-dependent relaxation of arteries. The relaxation was abolished by N omega-nitro-L-arginine. Incubation with PAF for 30 min augmented contractions of veins with endothelium to PGF 2 alpha. The augmentation was not affected by BW-755C, BQ-123, or IRL-1038. Pretreatment with PAF had no effect on the response of veins to phenylephrine or on the response of arteries to either PGF 2 alpha or phenylephrine. These observations demonstrated that, in the ferret, PAF affected differently the response of pulmonary arteries and veins and that the endothelium plays a critical role in the PAF-induced effects. Furthermore, the PAF-induced effects appear not to be mediated by metabolites of arachidonic acid and ET.

Animals↗

PubMed1996

Length-dependent activation in intact ferret hearts: study of steady-state Ca(2+)-stress-strain interrelations.

We examined the steady-state stress-strain relationships and the steady-state stress-intracellular calcium concentration ([Ca2+]i) relationship in intact ferret hearts and compared these to previously published analogous relationships in skinned and intact muscle. Langendorff-perfused ferret hearts were treated with ryanodine and tetanized by rapid stimulation to create steady-state conditions. [Ca2+]i was measured concurrently by macroinjected aequorin. Over a range of volumes corresponding to strains between 1.0 and 0.75, steady-state stress decreased by 33% when saturating levels of perfusate calcium were used, indicating the degree to which physical factors contribute to the Frank-Starling relationship. The steady-state stress-[Ca2+]i relationship was sigmoidal with a mean Hill coefficient (nH) of 4.91 +/- 0.29 at a strain of 1.0, and the [Ca2+]i required for half-maximal activation (K1/2) was 0.41 +/- 0.03 microM. K1/2 increased and nH decreased with decreasing strains. These results are similar to those observed in intact muscle but differ quantitatively from results obtained in isolated, skinned preparations. Based on these results, we suggest that whole heart function can be related to average sarcomere function without the need for complex models of ventricular structure.

Aequorin↗