Astrocytic infection in canine distemper virus-induced demyelination

Summary Acute canine distemper virus (CDV)-induced demyelinating lesions were examined with double-labelling immunocytochemistry simultaneously demonstrating CDV antigen and glial fibrillary acidid protein (GFAP) as marker for astrocytes. It was shown that 64% of all astrocytes within the demyelinating lesions were infected and that 95% of all infected cells counted in the lesions were astrocytes. These results suggest that the astrocyte ist the main target for CDV and that astroglial infection may play an important role in the mechanism of demyelination.Supported by the Swiss National Science Foundation (grant no. 3.956.87) and the Swiss Multiple Sclerosis Society     

Impaired function of mitochondrial electron transfer complex I in canine myocardial ischemia: loss of flavin mononucleotide

Regional myocardial ischemia was produced in anesthetized dogs by occluding the left branch of the circumflex coronary artery. After 30 or 60 min of occlusion, mitochondria were isolated from both non-ischemic (control) and ischemic transmural samples of the left ventricle and septum. Mitochondria from 60 min ischemic myocardium exhibited a drop in NAD-linked state 3 respiratory rates to 56 +/- 3% of controls and a parallel loss of NADH-CoQ reductase activity to 54 +/- 4% of controls. Analyses of two non-protein components of electron transfer complex I in mitochondria isolated from 60 min ischemic myocardium revealed a decrease in acid-extractable flavin mononucleotide (FMN) to 58 +/- 5% of controls and a small decrease in ubiquinone to 89 +/- 2% of controls. The observed dissociation and apparent washout of non-covalently-bound FMN from the ischemically damaged mitochondria thus accounted nearly quantitatively for the proportionate decrease seen in NADH-CoQ reductase activity and in state 3 respiration with NAD-linked substrates.     

Calcium mobilization induced by endothelins and sarafotoxin in cultured canine tracheal smooth muscle cells

Endothelins (ETs)- and sarafotoxin (S6b)-induced rises in intracellular Ca²⁺ concentration ([Ca²⁺]_i) were monitored in cultured canine tracheal smooth muscle cells by using a fluorescent Ca²⁺ indicator fura-2. ET-1, ET-2, ET-3 and S6b elicited an initial transient peak and followed by a sustained elevation of [Ca²⁺]_i, with half-maximal effect (EC₅₀) of 18, 20, 38 and 21 nM, respectively. BQ-123, an ET_A receptor antagonist, had a high affinity to block the rise in [Ca2⁺]_i response to ET-1, ET-2, and S6b, as well as a low affinity for ET-3. Removal of external Ca²⁺ by addition of EGTA during the sustained phase, caused a rapid decline in [Ca²⁺]_i to the resting level. In the absence of external Ca²⁺, only an initial transient peak of [Ca²⁺]_i was seen, the sustained elevation of [Ca²⁺]. could then be evoked by addition of 1.8 mM Ca²⁺. Ca²⁺ influx was required for the changes of [Ca²⁺]_i, since the Ca²⁺-channel blockers, diltiazem, verapamil, and Ni²⁺, decreased both the initial and sustained elevation of [Ca²⁺]_i response to these peptides. ETs exhibited homologous desensitization of the Ca²⁺ response, but partial heterologous desensitization of the Ca²⁺ response mediated by carbachol to different extents. In contrast, ETs did not desensitize the Ca²⁺ response induced by ATP or vice versa. These data demonstrate that the initial detectable increase in [Ca2⁺]_i stimulated by these peptides is due to the activation of ET_A receptors and subsequently the release of Ca²⁺ from internal stores, whereas the contribution of external Ca²⁺ follows and partially involves a diltiazem- and verapamil-sensitive process. There is a cross-regulation among ETs and other receptor-coupling signal transduction pathways through PI hydrolysis in canine tracheal smooth muscle cells. Correspondence to: C. Mao Yang at the above address     

Nitric oxide synthase-immunoreactive nerve fibers in dog cerebral and peripheral arteries

Nitric oxide synthase (NOS)-immunoreactive fibers innervating the dog arterial wall were histochemically determined by the use of NOS antiserum. NOS-immunoreactive fibers were consistently found in every arterial wall examined. In a whole-mount preparation, NOS-positive fibers were detectable in the small pial artery having a diameter of about 100 μm as well as the proximal middle cerebral artery. Further detailed analyses in thin cryostat sections indicated that in middle cerebral, basilar, temporal, mesenteric and femoral arteries, fine NOS-positive fibers were detected in outer zones of the media in addition to many thicker fibers in the adventitia. However, in the coronary artery, many thick fibers ere situated in the adventitia, and fine NOS-positive fibers were not the media. Injection of ethanol to the pterygopalatine ganglion markedly decreased or abolished the NOS immunoreactivity in nerve cells and fibers and abolished the innervation of NOS-positive fibers in the wall of middle cerebral artery of the ipsilateral side. Together with findings in our previous publications concerning the functional role of nitroxidergic nerve in the control of arterial tone, we conclude that perivascular nerves containing NOS are crucial in eliciting the neurally induced, NO-mediated arterial relaxation.     

Investigation of epidermotropism in canine mycosis fungoides: Expression of intercellular adhesion molecule-1 (ICAM-1) and beta-2 integrins

In human mycosis fungoides (MF), interactions between LFA-1 (CD11a/CD18) and ICAM-1 (CD54) are involved in lymphocyte adhesion to keratinocytes. The purpose of this study was to evaluate the expression of ICAM-1, beta-2 integrins and class II major histocompatibility complex molecules (MHC II) on keratinocytes and infiltrating lymphocytes in canine MF. Sections of frozen skin biopsy specimens from normal dogs (n=3) and dogs with MF (n=17) were evaluated by immunohistochemistry for expression of ICAM-1, beta-2 integrins, and class II MHC molecules. Our results demonstrated that in canine MF, ICAM-1 was expressed variably on epidermal and follicular keratinocytes. The extent of keratinocyte ICAM-1 expression did not correlate with the degree of lymphocyte epithelial infiltration, nor with lymphocyte LFA-1 expression. This was especially evident in cases of Pagetoid reticulosis-like disease in which prominent lymphocyte epidermotropism was not accompanied by keratinocyte ICAM-1 expression. Keratinocyte class II MHC molecule expression did not correlate with keratinocyte ICAM-1 expression. In conclusion, in canine MF, the lack of statistically significant correlations between epithelial lymphocyte infiltration and keratinocyte ICAM-1 expression, and between keratinocyte ICAM-1 and lymphocyte LFA-1 staining, suggests that the LFA-1/ICAM-1 pathway is not the major adhesion mechanism between lymphocytes and keratinocytes. It is suspected that different ligands of the LFA-1 integrin (e.g. ICAM-2) or other adhesion molecules (e.g. CD2/LFA-3, VLA-1) might be involved in the epitheliotropism phenomenon in canine MF. These hypotheses cannot be evaluated in the dog at this time owing to the lack of specific monoclonal antibodies.     

Epidemiology of canine leishmaniasis in the Madrid region,Spain

A cross-sectional serological survey was carried out in the Madrid Autonomous Region (Comunidad de Madrid) in order to study and describe canine leishmaniasis epidemiology. The presence of leishmaniasis-specific antibodies was ascertained by immunofluorescence testing. 591 dogs were screened, revealing a prevalence of 5.25% (95% confidence interval 7.4–3.6), with no difference being encountered between rural and periurban areas. Age-specific prevalence exhibits a peak at 2–3 years and another at 7–8 years. Incidence or force of infection by occupation is as follows: pet dogs 0.059 (95% confidence interval 0.009–0.108) and working dogs 0.035 (95% confidence interval 0.012–0.057), there being a ratio between infection rates of 1.7, viz., indicating a 70% greater risk of infection among pet than among working dogs. The basic case reproduction numberR ₀ is 1.06, suggesting that very intense control measures would not be needed for a drop in prevalence and incidence of infection to be achieved.     

Demyelination in experimental canine distemper virus infection: Immunological,pathologic, and immunohistological studies

Summary White matter lesions were induced in the brains of eight of nine dogs by means of experimental canine distemper virus (CDV) infection. Dogs were killed at 21, 24, 31, and 42 days after infection. Lymphocyte responsiveness to Con A and PHA stimulation in vitro was severely suppressed up to 31 days post infection (p.i.), followed by partial recovery as tested at 42 days p.i. Anti-CDV neutralizing antibody response was very weak in most dogs. There was a weak increase in antimyelin and antimyelin basic protein antibodies in most dogs during the course of the experiment. Dogs killed up to 31 days p.i. developed non-inflammatory demyclinating lesions in which no immunoglobulin could be detected. One of the three dogs that were killed at 42 days p.i. developed severe inflammatory demyelination. This was the only dog with a strong anti-MBP antibody response in the CSF and immunoglobulin demonstrated in demyelinating lesions. The present study supports previous observations that demyelination in acute CDV infection is not an immune mediated lesion but that these lesions may progress as a result of the local immune response. It is uncertain at this stage whether the local immune reaction specifically causes myelin destruction or whether bystander demyelination occurs in chronic CDE.Supported by Schweizer Nationalfonds grant no. 3.809.81 (to M.V.) and grant no. 3.957.0.80 (to A.J.S.)     

A comparison of neutron rbe values for normal canine lung by densitometry,pulmonary function and radionuclide studies

Thirty-nine adult male beagles received either fast neutron or photon irradiation to the right thorax. there were two unirradiated control dogs. Twenty-four dogs received fast neutrons with a mean energy of 15 MeV to total doses of 1000, 1500, 2250, or 3375 rad delivered in four fractions per week for six weeks. Fifteen dogs received total doses of 3000, 4500, or 6750 rad of photons (⁶⁰Co) in the same fractionation pattern. Radionuclide evaluations of pulmonary function were performed pre-irradiation and every three months post-irradiation for two years. These included: (1) radioaerosol deposition of ^99mTc-phytate, an insoluble radiocolloid, (2) ¹³³Xe ventilation studies and (3) ^99mTc-macroaggregated albumin perfusion images. A chest radiograph taken prior to each radionuclide evaluation was measured for density changes. Mechanical properties of pulmonary function were studied pre-irradiation and at 3-month intervals post-irradiation for one year. Values for the relative biological effectiveness (RBE) of fast, neutrons in producing changes in these parameters were obtained by plotting the changes from pre-irradiation values in the right lung as a function of the total dose. The RBE for neutron damage to normal lung tissue was always greater than 4 in the clinical dose range of 4000–6000 rad of photons, regardless of the parameter that was used to generate the value.     

Multiple sclerosis and dog ownership: A case-control investigation

In 1977 and 1978 Cook and his associates demonstrated a positive association between ownership of small dogs and both familial and sporadic cases of multiple sclerosis in New Jersey. Because of the far reaching implications of this work, a similar study was carried out and 72 patients with clinically definite multiple sclerosis (MS) who were resident in the area covered by the Oxford Regional Health Authority, were interviewed to ascertain their past exposure to housepets and other animals. Two hospital controls were chosen for each patient matched for age and sex and area of residence, and these were interviewed in the same manner as the MS cases by the same interviewer, usually in the patients' homes.Similar proportions of cases and controls had resided in a household with a dog at some time prior to the onset of their disease and there was no evidence that cases had lived with more dogs or had lived with them for longer periods than had controls. There was no indication that cases had greater exposure than controls to dogs or any other housepet in the early years of their life or in the period immediately prior to disease onset. Our data suggest that exposure to housepets and other domestic animals is unlikely to be an aetiological factor in MS.     

Effects of fractionated doses of fast neutrons and photons on the normal canine lung: relative biological effectiveness values obtained by radionuclide studies.

Thirty nine adult male beagles received either fast neutron or photon irradiation to the right thorax. There were 2 unirradiated control dogs. Twenty four dogs received fast neutrons with a mean energy of 15 MeV to total doses of 1000, 1500, 2250 or 3375 rad delivered in 4 fx/wk for 6 weeks. Fifteen dogs received total doses of 3000, 4500 or 6750 rad of photons (⁶⁰Co) in the same fractionation pattern.Radionuclide evaluations of pulmonary function were performed pre-irradiation and every three months post-irradiation for 1 year. These included: (1) radioaerosol deposition of an insoluble radiocolloid, ^99mTc-phytate; (2) ¹³³Xe ventilation studies; and (3) ^99mTc-macroaggregated albumin perfusion images.Values for the relative biological effectiveness (RBE) of fast neutrons in producing changes in these parameters have been obtained by plotting the changes from pre-irradiation values in the right lung as a function of the total dose. RBE values for the relative deposition of aerosol and the relative distribution of volume and perfusion have been obtained at 3, 6, 9 and 12 months post-irradiation. The relative biological effectiveness (RBE) for neutron damage to normal lung tissue was always greater than 4 in the clinical dose range of 4000–6000 rad of photons.