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PubMed1990

Magnesium transport in ferret red cells.

1. Mg2+ efflux from ferret red cells into a nominally Mg2(+)-free medium is 41 +/- 2 mumol (l cell)-1 h-1. The properties of Mg2+ transport can be measured in these cells without the need for Mg2+ loading. 2. Amiloride, quinidine, imipramine and external divalent cations partially inhibit Mg2+ efflux. Maximal inhibition by these agents is about 60-70% suggesting that at least two Mg2+ transport pathways exist. 3. As external Na+ is replaced by choline or N-methyl-D-glucamine Mg2+ efflux is first stimulated, reaching a peak when external [Na+] ([Na+]o) is about 10 mM, and then inhibited. Mg2+ transport reverses direction so net Mg2+ uptake occurs when [Na+]o is reduced below 1 mM. 4. Mg2+ efflux is stimulated when 0.1 mM-EDTA is added to the medium only when [Na+]o is low. 5. Reduction of cell ATP content to about 20 mumol (l cell)-1 by treating cells with 2-deoxyglucose stimulates Mg2+ efflux measured over the 2 h period following depletion. 6. Substantial Mg2+ influx can be observed in ferret red cells when they are incubated in media containing 10 mM-Mg2+. Influx is stimulated by reducing [Na+]o to 10 mM. Further reduction of [Na+]o to below 1 mM reduces Mg2+ uptake. A component of uptake is inhibited by external Co2+. 7. Na(+)-Mg2+ antiport may account for a substantial component of Mg2+ transport in ferret red cells. The direction of transport can be reversed by sufficiently lowering [Na+]o or by increasing external [Mg2+]. Analysis of the conditions at which transport reverses direction suggests transport with a stoichiometry of 1 Na+:1 Mg2+. Antiport with this stoichiometry would also explain maintenance of the physiological level of intracellular ionized Mg2+ in these cells.

Amiloride↗
PubMed1991

The effects of pH changes on human and ferret detrusor muscle function.

1. The effects of altering extracellular pH on the electrically evoked contractions of ferret and human bladder (detrusor) smooth muscle have been investigated. pH was varied by changing superfusate PCO2 or NaHCO3 concentration. Acidosis increased force when superfusate PCO2 was raised but decreased force when the NaHCO3 concentration was reduced. 2. Intracellular pH (pHi) in isolated ferret detrusor cells was measured separately by epifluorescence microscopy. Extracellular pH changes caused by altering superfusate PCO2 were accompanied by similar changes of pHi, whereas variation of the NaHCO3 concentration had smaller effects on pHi. 3. It was proposed that intracellular acidosis increased contraction but extracellular acidosis depressed contraction. 4. Other interventions, such as addition and removal of NH4Cl, Cl- replacement, and NaHCO3 replacement with HEPES, changed pHi and had predictable effects on force. It was possible to describe unique relationships between tension and either intracellular or extracellular pH regardless of the means whereby pH changes were brought about. 5. Resting tension was reduced whether brought about by either intracellular or extracellular acidosis. K+ contractures were similarly affected by acidosis. Ferret preparations showed low levels of spontaneous activity, which was reduced by acidosis and enhanced by alkalosis.

Adult↗
PubMed1991

Sodium-dependent magnesium uptake by ferret red cells.

1. Magnesium uptake can be measured in ferret red cells incubated in media containing more than 1 mM-magnesium. Uptake is substantially increased if the sodium concentration in the medium is reduced. 2. Magnesium uptake is half-maximally activated by 0.37 mM-external magnesium when the external sodium concentration is 5 mM. Increasing the external sodium concentration increases the magnesium concentration needed to activate the system. 3. Magnesium uptake is increased by reducing the external sodium concentration. Uptake is half-maximum at sodium concentrations of 17, 22 and 62 nM when the external magnesium concentrations are 2, 5 and 10 mM respectively. 4. Replacement of external sodium with choline does not affect the membrane potential of ferret red cells over a 45 min period. 5. Magnesium uptake from media containing 5 mM-sodium is inhibited by amiloride, quinidine and imipramine. It is not affected by ouabain or bumetanide. Vanadate stimulates magnesium uptake but has no effect on magnesium efflux. 6. When cell ATP content is reduced to 19 mumol (1 cell)-1 by incubating cells for 3 h with 2-deoxyglucose, magnesium uptake falls by 50% in the presence of 5 mM-sodium and is completely abolished in the presence of 145 mM-sodium. Some of the inhibition may be due to the increase in intracellular ionized magnesium concentration ([Mg2+]i) from 0.7 to 1.0 mM which occurs under these conditions. 7. Magnesium uptake can be driven against a substantial electrochemical gradient if the external sodium concentration is reduced sufficiently. 8. These findings are discussed in terms of several possible models for magnesium transport. It is concluded that the majority of magnesium uptake observed in low-sodium media is via sodium-magnesium antiport. A small portion of uptake is through a parallel leak pathway. It is believed that the antiport is responsible for maintaining [Mg2+]i below electrochemical equilibrium in these cells at physiological external sodium concentration. Thus in ferret red cells the direction of magnesium transport can be reversed by reversing the sodium gradient.

Adenosine Triphosphate↗
PubMed1992

Phenylephrine-induced translocation of protein kinase C and shortening of two types of vascular cells of the ferret.

1. The relationship between phenylephrine-induced smooth muscle contraction and the subcellular distribution of protein kinase C (PKC) was investigated. 2. Cell shortening induced by phenylephrine (10(-5) M) was measured in single vascular cells freshly isolated from ferret portal vein and aorta. 3. At various time points during phenylephrine activation, single cells were fixed with paraformaldehyde and the distribution of PKC was imaged in cells labelled with the fluorescent PKC probe 12-(1,3,5,7-tetramethylBODIPY-2-propionyl)phorbol-13-acetate. 4. The PKC probe located to a perinuclear region, the cytosol and surface membrane. The amplitude and time course of the phenylephrine-induced changes in the surface membrane/cytosol fluorescence ratio were measured and compared with the amplitude and time course of phenylephrine-induced cell shortening. 5. In portal vein cells incubated in 1 mM-external Ca2+, phenylephrine caused significant shortening and time-dependent translocation of the PKC probe to the surface membrane, but cell shortening preceded PKC translocation. In Ca2+free solution both cell shortening and translocation of the probe were completely inhibited. 6. Verapamil (3 x 10(-7) M) partially, but significantly, inhibited the magnitude of cell shortening and delayed the onset and time to peak shortening. Translocation of PKC in verapamil preceded or coincided with cell shortening. 7. In aorta cells incubated in 1 mM-extracellular Ca2+, phenylephrine induced significant shortening and time-dependent translocation of the PKC probe. Cell shortening preceded PKC translocation. In Ca(2+)-free solution, shortening was only partially, but significantly, inhibited and PKC translocation preceded the fraction of the shortening response that remained. 8. These data are consistent with a role for PKC in the maintenance of the phenylephrine-induced contraction in both portal vein and aorta. The data also suggest that phenylephrine-induced contraction may involve activation of a Ca(2+)-dependent PKC isoform in ferret portal vein but a Ca(2+)-independent isoform in ferret aorta.

Animals↗
PubMed2002

Heterogeneous expression of KChIP2 isoforms in the ferret heart.

Kv4 channels are believed to underlie the rapidly recovering cardiac transient outward current (I(to)) phenotype. However, heterologously expressed Kv4 channels fail to fully reconstitute the native current. Kv channel interacting proteins (KChIPs) have been shown to modulate Kv4 channel function. To determine the potential involvement of KChIPs in the rapidly recovering I(to), we cloned three KChIP2 isoforms (designated fKChIP2, 2a and 2b) from the ferret heart. Based upon immunoblot data suggesting the presence of a potential endogenous KChIP-like protein in HEK 293, CHO and COS cells but absence in Xenopus oocytes, we coexpressed Kv4.3 and the fKChIP2 isoforms in Xenopus oocytes. Functional analysis showed that while all fKChIP2 isoforms produced a fourfold acceleration of recovery kinetics compared to Kv4.3 expressed alone, only fKChIP2a produced large depolarizing shifts in the V(1/2) of steady-state activation and inactivation as seen for the native rapidly recovering I(to). Analysis of RNA and protein expression of the three fKChIP2 isoforms in ferret ventricles showed that fKChIP2b was most abundant and was expressed in a gradient paralleling the rapidly recovering I(to) distribution. Ferret KChIP2 and 2a were expressed at very low levels. The ventricular expression distribution suggests that fKChIP2 isoforms are involved in modulation of the rapidly recovering I(to); however, additional regulatory factors are also likely to be involved in generating the native current.

Amino Acid Sequence↗
PubMed1994

Efficacy of 2'-deoxy-2'-fluororibosides against influenza A and B viruses in ferrets.

Single-dose treatments (5 to 40 mg/kg of body weight given intraperitoneally) of ferrets with 2'-deoxy-2'-fluoroguanosine or its prodrug, 2,6-diamino-purine-2'-fluororiboside, 1 h after infection with influenza A virus significantly inhibited replication of virus in the upper respiratory tract, resulting in amelioration of fever and nasal inflammation. Replication of virus in the lower respiratory tract was also reduced > 100-fold, but three doses were required to prevent replication in the lungs. In ferrets infected with influenza B virus, single-dose treatment (40 mg/kg given intraperitoneally) produced a similar but reduced response in comparison with that in ferrets infected with influenza A virus, indicating that dosing was not optimal for this virus.

Adenosine↗
PubMed2002

Oral administration of cyclopentane neuraminidase inhibitors protects ferrets against influenza virus infection.

Several cyclopentane inhibitors of influenza virus neuraminidase that have inhibitory activities in tissue culture similar to those of zanamivir and oseltamivir have recently been described. These new inhibitors have been examined for efficacy against a virulent H3N2 influenza virus when administered orally to infected ferrets. Preliminary studies indicated that oral administration of BCX-1923, BCX-1827, or BCX-1812 (RWJ-270201) at a dose of 5 or 25 mg/kg of body weight was active in ferrets in reducing respiratory and constitutional signs and symptoms, but these antivirals affected virus titers in the upper and lower respiratory tracts only marginally. Of the three compounds, BCX-1812 seemed to be the most efficacious and was examined further at higher doses of 30 and 100 mg/kg. These doses significantly reduced peak virus titers in nasal washes and total virus shedding as measured by areas under the curve. Virus titers in lung homogenates were also reduced compared to those in controls, but the difference was not statistically significant. As was observed with BCX-1812 at lower doses, the nasal inflammatory cellular response, fever, and nasal signs were reduced while ferret activity was not, with activity remaining similar to uninfected animals.

Acetamides↗
PubMed1990

A domestic ferret model of immunity to Campylobacter jejuni-induced enteric disease.

Oral or intravenous inoculation of previously unexposed juvenile and adult ferrets with Campylobacter jejuni uniformly resulted in intestinal colonization lasting 2 to 12 days. Disease varied from mild to moderate diarrhea, which resolved in 2 to 3 days. Orally infected animals developed agglutinin titers of 8 to 256 within 3 weeks, while those infected intravenously developed titers of 256 to 2,048. Ferrets which had recovered from campylobacteriosis all developed high titers of agglutinating and bacterial antibodies but were readily colonized by subsequent oral inoculation with the same strain of C. jejuni. Orally infected ferret kits 3 to 6 weeks of age exhibited the same general pattern of infection and disease as adults, but diarrhea was somewhat more severe. Kits resolved their diarrhea in 1 to 6 days and developed agglutinin titers in serum of 16 to 32 within 3 weeks. A series of five oral or rectal inoculations of kits during the 5- to 9-week age interval resulted in progressively shorter clearance times and eventual strain-specific resistance against infection, as well as disease. Gnotobiotic adults showed the same pattern of strain-specific accelerated clearance and resistance to disease. Kits born to immune dams with high levels of whey antibodies had passively acquired serum agglutinin titers of 256 to 2,048. These kits showed no resistance to colonization with the homologous strain of C. jejuni but were completely refractory to diarrhea. These observations suggest that (i) some form(s) of specific immunity, rather than factors relating solely to age or normal flora, is responsible for resistance to C. jejuni colonization and disease production and (ii) humoral immunity at a level that does not prevent colonization can protect against enteric disease caused by this organism.

Administration, Oral↗
PubMed1997

Infection of the ferret stomach by isogenic flagellar mutant strains of Helicobacter mustelae.

Helicobacter mustelae, like Helicobacter pylori, possesses two flagellin proteins, FlaA and FlaB. Isogenic mutant strains of H. mustelae have been constructed by disruption of the flaA or flaB gene with a kanamycin resistance cassette or by introduction of both a kanamycin and a chloramphenicol resistance gene to produce a double mutant. To determine whether one or both flagellin proteins are necessary for colonization and persistence of infection with H. mustelae, 19 ferrets, specific pathogen free for H. mustelae, were given either the HMF1 flaA::km (weakly motile), ATCC 43772 flaB::km (moderately motile), or HMF1 flaA::cat flaB::km (non-motile) mutant strain, the wild-type parent strains, or sterile broth. Gastric tissue samples were obtained during sequential gastric biopsies beginning at 3 weeks postinoculation and ending at necropsy at 3 months postinoculation. H. mustelae infection status was determined by culture, histology, and serology. The wild-type parent strains of H. mustelae infected all ferrets at all time points. The double-mutant strain was unable to colonize; the flaA and flaB single-mutant strains were able to initially colonize at a low level and establish persistent infection with increasing numbers of organisms over time. The severity of gastritis produced by infection with these strains of H. mustelae correlated with the number of organisms present in the gastric mucosa. Flagellar motility is an important virulence factor for colonization and pathogenesis in the H. mustelae ferret model.

Animals↗
PubMed2006

Bacterial sinusitis and otitis media following influenza virus infection in ferrets.

Streptococcus pneumoniae is the leading cause of otitis media, sinusitis, and pneumonia. Many of these infections result from antecedent influenza virus infections. In this study we sought to determine whether the frequency and character of secondary pneumococcal infections differed depending on the strain of influenza virus that preceded bacterial challenge. In young ferrets infected with influenza virus and then challenged with pneumococcus, influenza viruses of any subtype increased bacterial colonization of the nasopharynx. Nine out of 10 ferrets infected with H3N2 subtype influenza A viruses developed either sinusitis or otitis media, while only 1 out of 11 ferrets infected with either an H1N1 influenza A virus or an influenza B virus did so. These data may partially explain why bacterial complication rates are higher during seasons when H3N2 viruses predominate. This animal model will be useful for further study of the mechanisms that underlie viral-bacterial synergism.

Animals↗
PubMed2003

A ferret model of canine distemper virus virulence and immunosuppression.

Canine distemper virus (CDV) infects many carnivores, including ferrets and dogs, and is the member of the Morbillivirus genus most easily amenable to experimentation in a homologous small-animal system. To gain insights into the determinants of CDV pathogenesis, we isolated a strain highly virulent for ferrets by repeated passaging in these animals. Sequence comparison of the genome of this strain with that of its highly attenuated precursor revealed 19 mutations distributed almost evenly in the six genes. We then recovered a virus from a cDNA copy of the virulent CDV strain's consensus sequence by using a modified reverse genetics system based on B cells. We infected ferrets with this virus and showed that it fully retained virulence as measured by the timing of rash appearance, disease onset, and death. Body temperature, leukocyte number, lymphocyte proliferation activity, and cell-associated viremia also had similar kinetics. We then addressed the question of the relative importance of the envelope and other viral constituents for virulence. Viruses in which the envelope genes (matrix, fusion, and hemagglutinin) of the virulent strain were combined with the other genes of the attenuated strain caused severe rash and fever even if the disease onset was delayed. Viruses in which the nucleocapsid, polymerase, and phosphoprotein genes (coding also for the V and C proteins) of the virulent strain were combined with the envelope genes of the attenuated strain caused milder signs of disease. Thus, virulence-inducing mutations have accumulated throughout the genome.

Animals↗
PubMed1993

Aleutian disease in domestic ferrets: diagnostic findings and survey results.

Aleutian disease was diagnosed as the cause of posterior ataxia and paresis in domestic ferrets. Six serologically positive animals (four clinically affected and two unaffected) were investigated in detail and seven other clinically affected ferrets were also identified. The diagnostic findings included hypergammaglobulinaemia, histological lesions in the central nervous system and parvovirus-like particles in mesenteric lymph nodes. A wider serological survey of 446 animals owned by members of a ferret club revealed an incidence of 8.5 per cent seropositive animals.

Aleutian Mink Disease↗
PubMed2003

Effects of anaesthesia and manual restraint on the plasma concentrations of pituitary and adrenocortical hormones in ferrets.

Two experiments were carried out to investigate the effect of sampling techniques on the plasma concentrations of pituitary and adrenocortical hormones in ferrets (Mustela putorius furo). In the first experiment blood was collected on two occasions from 29 ferrets which were either manually restrained or anaesthetised with isoflurane. In the second experiment eight intact ferrets were fitted with jugular catheters and blood was collected on four occasions, just before and as soon as possible after they had been manually restrained or anaesthetised with medetomidine or isoflurane; blood was also collected 10 and 30 minutes after the induction of anaesthesia. Medetomidine anaesthesia had no effect on the plasma concentrations of pituitary and adrenocortical hormones. Isoflurane anaesthesia resulted in a significant increase in the plasma concentration of alpha-melanocyte-stimulating hormone (alpha-MSH) directly after the induction of anaesthesia. Manual restraint resulted in a significant increase in the plasma concentrations of cortisol and adrenocorticotrophic hormone (ACTH) and a decrease in the plasma concentration of alpha-MSH.

Adrenocorticotropic Hormone↗
PubMed1992

Effects of reduced external sodium concentration and multivalent cations on caffeine contractures in young ferret atrial trabeculae.

The characteristics of caffeine (1.25-80 mM) transient contractures have been examined in small atrial trabeculae (diameters 50-250 microns) isolated from young (1-1.5 months) ferret hearts. In the control medium, the half-saturation constant and the maximum contracture strength (at infinite caffeine concentration) were 37.8 +/- 10.2 mM and 0.9 +/- 0.2 kN.kg-1 (n = 11), respectively. The contractile response to caffeine was markedly enhanced following reduction of external sodium (70-0 mM). The perfusion of young ferret trabeculae with the sodium-free medium (up to 3 min) decreased the half-saturation constant by a factor of three (12.4 +/- 1.6 mM, n = 8) with an increase in maximum contracture strength (1.09 +/- 0.3 kN.kg-1, n = 8). The effects of various divalent and trivalent cations have been tested on the 10 mM caffeine contracture in trabeculae perfused with Na-containing (140 mM) solution. The order of cation effectiveness is Gd3+ (half effect 0.04-0.07 mM) greater than Cd2+ (0.15-0.25 mM) greater than Ni2+ (2-2.5 mM) greater than Co2+ (7-7.5 mM) much greater than Mn2+. In conclusion, the present work has shown that in atrial trabeculae isolated from young ferret hearts, the strength of the caffeine contracture was markedly affected by the activity of the sarcolemmal Na-Ca exchange.

Animals↗
PubMed1994

Cloning and characterization of an Ito-like potassium channel from ferret ventricle.

FK1, a ferret ventricular full-length cDNA clone, encodes a 654-amino acid protein with 98% identity to human K+ transient outward current (Ito)-like HK1 (Tamkun et al. FASEB J.5: 331-337, 1991). FK1 is detectable in ferret brain, atrium, left and right ventricle, and kidney but not in skeletal muscle, endothelial cells, aorta, and liver. In Xenopus oocytes, FK1 cRNA gives rise to a rapidly activating and inactivating Ito-like current, which is highly K+ selective (Na(+)-to-K+ permeability ratio = 0.003). Activation occurs over an approximately 50-mV range (-40 to +10 mV) and displays a sigmoid delay in onset with potential-dependent time constants that decrease with depolarization. Steady-state activation can be described with either a simple Boltzmann relationship [half-activation potential (V1/2) = -25 mV, slope (k) = 10 mV] or a Boltzmann relationship raised to either the third or fourth power (alpha 3: V1/2 = -43 mV, kappa = 13.1 mV; alpha 4: V1/2 = -48 mV, kappa = 13.6 mV, where alpha is the activation variable). Inactivation kinetics are biexponential, with the main fast time constant becoming independent of membrane potential depolarized to 0 mV. Steady-state inactivation can be described with a single Boltzmann relationship (V1/2 = -57 mV, kappa = 5.0 mV). Fast inactivation is removed by NH2-terminal deletions. Recovery from inactivation (-90 mV) is quite slow (half-time = 4.8 +/- 2.5 s). In 2 mM extracellular K+ concentration ([K+]o), FK1 tail currents display conventional deactivation behavior; however, in 98 mM [K+]o the tail currents display "reopening" behavior. These results suggest a molecular basis for the electrophysiological similarities between ferret and human ventricular Ito (Campbell et al. J. Gen. Physiol. 101: 571-601, 1993; Näbauer et al. Circ. Res. 73: 386-394, 1993).

Amino Acid Sequence↗
PubMed1975

Effect of amygaloid lesions on gonadal maturation in male and female ferrets.

Two experiments were performed to determine whether the amygdala is involved in theregulation of gonadal maturation in the ferret. In an experiment with prepuberal males it was found that testicular and epididymal wieghts, seminiferous tubule diameters, Leydid cell number, and ratings of spermatogenic development were the samein animals autopsied 4 wk after either the placement of a platinum-elctrode lesion in the amygdala or a sham operation. Testosterone concentrations both in testis and in blood tended to be lower, and body growth was significantly retarded in males with amygdaloid lesions. In a second experiment with prepuberal females it was found that the first estrus occurred significantly earlier in ferrets that had received amygdaloidlesions than in sham-operated controls. Neither body growth nor fertility of femaleswas affected. These findings suggest that the amygdala exerts an inhibitory influence on the hypothalamic mechanism which controls the secretion of gonadotropins required for initial estrus in female ferrets, but not for the initail masturation of the testes in males.

Amygdala↗
PubMed2006

Secretory phospholipases A2 stimulate mucus secretion, induce airway inflammation, and produce secretory hyperresponsiveness to neutrophil elastase in ferret trachea.

Secretory phospholipases A(2) (sPLA(2)) are increased in the bronchoalveolar lavage fluid of patients with asthma and acute respiratory distress syndrome. Intratracheal sPLA(2) instillation induces acute lung injury in the rat and guinea pig. We hypothesized that sPLA(2) would stimulate mucus secretion in vitro and that intratracheal sPLA(2) exposure would induce mucus hypersecretion and airway inflammation in the ferret trachea in vivo. In vitro, porcine pancreatic sPLA(2) at a concentration of 0.5 or 5 U/ml significantly increased mucous glycoconjugate (MG) secretion from the excised ferret trachea. P-bromophenacylbromide (a sPLA(2) inhibitor), quercetin (a lipoxygenase inhibitor), or MK-886 (a 5-lipoxygenase inhibitor), each at 10(-4) M, significantly reduced sPLA(2)-induced MG secretion. sPLA(2)-stimulated MG secretion was decreased in Ca(2+)-free medium. In vivo, ferrets were intubated for 30 min once per day for 3 days using an ETT coated with 20 units of porcine pancreatic sPLA(2) mixed in water-soluble jelly. Constitutive MG secretion increased 1 day after sPLA(2) exposure and returned to control 5 days later. Human neutrophil elastase (HNE) at 10(-8) M increased MG secretion in the sPLA(2)-exposed trachea compared with that in the control trachea, but methacholine at 10(-7) M did not. sPLA(2)-induced secretory hyperresponsiveness continued for at least 5 days after sPLA(2) exposure ended. sPLA(2) increased tracheal inflammation, MG secretion, and secretory hyperresponsiveness to HNE probably through enzymatic action rather than by activation of its receptor.

Animals↗
PubMed1993

Calcium sensitivity of skinned ferret EDL, soleus, and cremaster fibers.

The properties of the contractile system at different times of the year in the ferret extensor digitorum longus (EDL), soleus and cremaster muscles were examined by using chemically skinned (Triton X-100) preparations. The results show clear differences in calcium sensitivity between these skeletal muscles. The apparent calcium threshold for activation was lower in soleus than in EDL, while calcium concentrations ([Ca2+]) required to obtain the half-maximal tension, expressed as pCa50 (-log[Ca2+]), was lower in EDL than in soleus muscle. In fact, pCa50 obtained in fast and slow fibers by fitting the experimental data points by a modified Hill equation was 5.92 +/- 0.02 (n = 9) and 6.09 +/- 0.03 (n = 11) respectively. So EDL appears to be a typical fast-twitch muscle and soleus a typical slow-twitch muscle. Adult ferret cremaster muscle was composed of two types of fibers during the quiescent period similar to EDL and soleus, and only one type that was intermediate between EDL and soleus in the breeding period, as assessed by pCa50 values. These annual modifications in calcium activation of adult ferret cremaster muscle could be related to changes in the function of these muscles and may be correlated with seasonal variations of sexual activity.

Animals↗