Spontaneous immune complex orchitis in Brown Norway rats

Immune complexes occur spontaneously in the testis of Brown-Norway (BN) inbred rats between the basal lamina of the seminiferous tubules and the outer lamina of the myoid testicular cells. The deposits can be detected immunohistologically (IgG; C3) and by electron microscopy. The immune complexes appear between the 8th and 12th weeks of life, increase in amount up to the 30th week and decrease thereafter. After about the 20th week, of life, 15% of the animals show destruction of the germinal epithelium accompanied by an infiltration of lymphocytes and plasma cells. The final stage of this disease, which initially shows no signs of inflammation, is characterized by diffuse tubular atrophy. However, up to the 70th week of life, 85% of the animals with immune complexes show no pathological alterations. Antibodies eluated from the testes react with spermatocytes I and structures close to the lumen of the seminiferous tubules, but not with mature sperms. Serum antibodies to sperms occur in about 25% of the BN rats, but the presence of these antibodies shows no correlation with the immunohistological findings. This newly described spontaneous immune complex orchitis is regarded as a further example of an in-situ-induced immune complex disease. The observations made here can be compared with those in (peri-) membraneous glomerulonephritis, another example of a disorder resulting from in-situ-formation of immune deposits.     

Acute phase plasma proteins in kininogen-deficient Brown Norway rats

We examined whether Brown Norway rat plasma (BN/May Pfd f) contains alpha 1-cysteine proteinase inhibitor (alpha 1-CPI), also called major acute phase alpha 1-protein or T-kininogen. T-kininogen is a low molecular weight kininogen from which kinin can be released by trypsin but not by kallikreins. The BN plasma reacted with rabbit anti-alpha 1-CPI gamma globulins. Purified alpha 1-CPI released a kinin-like activity with trypsin and with homogenate of salivary glands, as Brown Norway rat plasma did. High concentration of added rat urine induced a small release (10%) of kinin from alpha 1-CPI. Preincubation of Brown Norway rat plasma with rabbit anti-rat alpha 1-CPI gamma-globulins nearly suppressed the kinin-forming substrate of trypsin in this plasma. These results indicated that plasma of our Brown Norway rats contains only alpha 1-CPI as kinin-forming substrate. This plasma contains low amount of alpha 2-macroglobulin, while its content in orosomucoid and haptoglobin was a little larger than that of Wistar rat plasma.     

Plasma prekallikrein deficiency in a strain of Brown Norway rats

Plasma of a strain of Brown Norway rats has a prolonged partial thromboplastine time while its Quick time is normal. With kaolin, this plasma does not form kinins. These results are the consequence of a lack of plasmatic prekallikrein-like activity.     

Airway remodeling in allergen-challenged Brown Norway rats: distribution of proteoglycans

Proteoglycans (PG) have important effects on the mechanical properties of tissues and the phenotype of various structural cells. Little is known about changes in PG deposition in the airways in animal models of asthma. We studied changes in PG in the airway wall of Brown Norway rats sensitized to ovalbumin (OA) and exposed to repeated OA challenge. Control (Sal) animals were sensitized and challenged with saline. After the 3rd challenge, animals were killed and lungs fixed in formalin. Tissue sections were incubated with antibodies to the small, leucine-rich PG, decorin, and biglycan and collagen type I. Airways were classified according to basement membrane perimeter length (< or =0.99, 1-2.99, and > or =3 mm). Decorin, biglycan, and collagen type I were increased in the airways of OA vs. Sal rats. Remodeling was most prominent in central airways. The distribution of PG differed with respect to the subepithelial vs. airway smooth muscle (ASM) vs. adventitial layer. Whereas biglycan was readily detected within the ASM, decorin and collagen were detected outside the ASM and especially in the adventitial layer. Differences in the distribution of these molecules within the layers of the airway wall may reflect their specific functional roles.     

Adverse effect of nano-silicon dioxide on lung function of rats with or without ovalbumin immunization

Background

The great advances of nanomaterials have brought out broad important applications, but their possible nanotoxicity and risks have not been fully understood. It is confirmed that exposure of environmental particulate matter (PM), especially ultrafine PM, are responsible for many lung function impairment and exacerbation of pre-existing lung diseases. However, the adverse effect of nanoparticles on allergic asthma is seldom investigated and the mechanism remains undefined. For the first time, this work investigates the relationship between allergic asthma and nanosized silicon dioxide (nano-SiO₂).

Methodology/Principal Findings

Ovalbumin (OVA)-treated and saline-treated control rats were daily intratracheally administered 0.1 ml of 0, 40 and 80 µg/ml nano-SiO₂ solutions, respectively for 30 days. Increased nano-SiO₂ exposure results in adverse changes on inspiratory and expiratory resistance (Ri and Re), but shows insignificant effect on rat lung dynamic compliance (Cldyn). Lung histological observation reveals obvious airway remodeling in 80 µg/ml nano-SiO₂-introduced saline and OVA groups, but the latter is worse. Additionally, increased nano-SiO₂ exposure also leads to more severe inflammation. With increasing nano-SiO₂ exposure, IL-4 in lung homogenate increases and IFN-γ shows a reverse but insignificant change. Moreover, at a same nano-SiO₂ exposure concentration, OVA-treated rats exhibit higher (significant) IL-4 and lower (not significant) IFN-γ compared with the saline-treated rats. The percentages of eosinophil display an unexpected result, in which higher exposure results lower eosinophil percentages.

Conclusions/Significance

This was a preliminary study which for the first time involved the effect of nano-SiO₂ to OVA induced rat asthma model. The results suggested that intratracheal administration of nano-SiO₂ could lead to the airway hyperresponsiveness (AHR) and the airway remolding with or without OVA immunization. This occurrence may be due to the Th1/Th2 cytokine imbalance accelerated by the nano-SiO₂ through increasing the tissue IL-4 production.     

Ovalbumin sensitizes vagal pulmonary C-fiber afferents in Brown Norway rats.

Sensitization of vagal lung C fibers has been postulated to contribute to the development of asthma, but support for this notion is still lacking. We investigated the characteristics and function of pulmonary C fibers (PCFs) in ovalbumin (OVA)-sensitized Brown Norway rats, an established animal model of asthma. Rats were sensitized with intraperitoneal injection of OVA or were treated with saline (control). In study 1, with the use of open-chest and artificially ventilated rats, inhalation of 5% OVA aerosol evoked an augmented increase in total lung resistance in the OVA-sensitized rats, compared with the control rats. Bilateral vagotomy or subcutaneous pretreatment with a high-dose of capsaicin for blocking of C-fiber function equally attenuated this augmented total lung resistance response, suggesting the involvement of PCFs. In study 2, with the use of anesthetized, spontaneously breathing rats, right atrial injection of capsaicin (1 microg/kg; a PCF stimulant) evoked an augmented apneic response in the OVA-sensitized rats, compared with the control rats. In study 3, with the use of open-chest, paralyzed, and artificially ventilated rats, the afferent PCF responses to right atrial injection of capsaicin (0.5 and 1.0 microg/kg), phenylbiguanide (8 microg/kg; a PCF stimulant), or adenosine (0.2 mg/kg; a PCF stimulant) were enhanced in the OVA-sensitized rats, compared with the control rats. However, the baseline activities of PCFs and their afferent responses to mechanical stimulation by lung hyperinflation in the OVA-sensitized and control rats were comparable. Our results suggested that OVA-sensitized Brown Norway rats possess sensitized vagal PCFs, which may participate in the development of the airway hyperreactivity observed in these animals.     

Consumption of hypoallergenic flour prevents gluten-induced airway inflammation in Brown Norway rats

Brown Norway rats were immunized with gluten, and then fed a diet containing hypoallergenic flour or an amino acid mixture. The rats were then made to inhale a solubilized gluten to induce gluten-specific bronchial asthma. The antibody levels in the serum of rats were measured by ELISA, and cell counts were done on cytospin preparations of bronchoalveolar lavage fluid. Body weight was decreased after allergen challenge in rats fed the amino acid mixture but not in rats fed the hypoallergenic flour. Antibody levels in the serum were significantly lower in rats fed hypoallergenic flour than in those fed the amino acid mixture. Differential cell counts in the bronchoalveolar lavage fluid showed that the numbers of eosinophils, lymphocytes, and neutrophils were significantly lower in rats fed the hypoallergenic flour than in those fed the amino acid mixture. These results suggest that hypoallergenic flour actively suppresses the allergic reactions, probably by inducing oral tolerance.     

L-NAME differentially alters ventilatory behavior in Sprague-Dawley and Brown Norway rats.

Nitric oxide (NO) is a regulating factor in respiration. The question was whether NO synthase (NOS) blockade would affect posthypoxic ventilatory behavior similarly in two rat strains with known differences in steady-state hypoxic and hypercapnic responses and in posthypoxic ventilatory behavior. Ventilatory behavior [respiratory frequency (f) and minute ventilation (VE)] was measured by body plethysmography on unanesthetized, unrestrained adult male Sprague-Dawley (SD; n = 8) and Brown Norway rats (BN; n = 8) at baseline and 1 min after rapid transition to 100% O(2) after 5 min of isocapnic hypoxia (10% O(2)-3% CO(2)-balance N(2)). Testing was performed 30 min after intraperitoneal injection of either saline (vehicle) or 100 mg/kg of N(G)-nitro-L-arginine methyl ester (L-NAME). Resting f and VE increased after L-NAME in both strains, more markedly in SD compared with BN (77 vs. 47% for f, and 42 vs. 16% for VE, respectively; P < 0.05). With vehicle, posthypoxic f and VE decline (Dejours phenomenon) was present only in BN and was absent in SD. With L-NAME, the Dejours phenomena were still present in BN but also were apparent in SD (f: 95.3 vs. 134.4 beats/min at baseline; VE: 66.3 vs. 88.8 ml/min at baseline; P < 0.05). Thus NOS blockade results in a strain-specific alteration in resting ventilation and uncovers the Dejours phenomenon in the SD strain.     

Thirst and salt appetite responses in young and old Brown Norway rats

Male Brown Norway rats aged 4 mo (young) and 20 mo (old) received a series of experimental challenges to body fluid homeostasis over approximately 3 mo. Water was available for drinking in some tests, and both water and 0.3 M NaCl were available in others. The series included three episodes of extracellular fluid depletion (i.e., furosemide + 20 h of sodium restriction), two tests involving intracellular fluid depletion (i.e., hypertonic saline: 1 or 2 M NaCl at 2 ml/kg body wt sc), one test involving overnight food and fluid restriction, and testing with captopril adulteration of the drinking water (0.1 mg/ml) for several days. Old rats were significantly heavier than young rats throughout testing. Old rats drank less water and 0.3 M NaCl after sodium deprivation than young rats, in terms of absolute and body weight-adjusted intakes. Old rats drank only half as much water as young rats in response to subcutaneous hypertonic NaCl when intakes were adjusted for body weight. Old rats drank less 0.3 M NaCl than young rats after overnight food and fluid restriction when intakes were adjusted for body weight. In response to captopril adulteration of the drinking water, young rats significantly increased daily ingestion of 0.3 M NaCl when it was available as an alternative to water and significantly increased daily water intakes when only water was available, in terms of absolute and body weight-adjusted intakes. Old rats had no response to captopril treatment. These results add important new information to previous reports that aging rats have diminished thirst and near-absent salt appetite responses to regulatory challenges.     

Impact of genetic background and aging on mesenteric collateral growth capacity in Fischer 344, Brown Norway, and Fischer 344 x Brown Norway hybrid rats

Available studies indicate that both genetic background and aging influence collateral growth capacity, but it is not known how their combination affects collateral growth. We evaluated collateral growth induced by ileal artery ligation in Fischer 344 (F344), Brown Norway (BN), and the first generation hybrid of F344 x BN (F1) rats available for aging research from the National Institute on Aging. Collateral growth was determined by paired diameter measurements in anesthetized rats immediately and 7 days postligation. In 3-mo-old rats, significant collateral growth occurred only in BN (35% +/- 11%, P < 0.001). The endothelial cell number in arterial cross sections was also determined, since this precedes shear-mediated luminal expansion. When compared with the same animal controls, the intimal cell number was increased only in BN rats (92% +/- 21%, P < 0.001). The increase in intimal cell number and the degree of collateral luminal expansion in BN rats was not affected by age from 3 to 24 mo. Immunohistochemical studies demonstrated that intimal cell proliferation was much greater in the collaterals of BN than of F1 rats. The remarkable difference between these three strains of rats used in aging research and the lack of an age-related impairment in the BN rats are novel observations. These rat strains mimic clinical observations of interindividual variation in collateral growth capacity and the impact of age on arteriogenesis and should be useful models to investigate the molecular mechanisms responsible for such differences.     

Induction of candidicidal activity in mice by immunization with Candida albicans ribosomes

Abstract Mice immunized with ribosomes from Candida albicans are protected against experimental systemic candidiasis. In this study we investigated the candidacidal activity of spleen cells from immunized animals as measured by ⁵¹Cr release from pre-labelled yeast cells. It was found that the anti-candidal cytotoxic activity of splenocytes from immunized mice was significantly higher than that of spleen cells from non-immunized controls with various effector to target (E:T) ratios, but optimal results were obtained with an E:T ratio of 10:1. The cytotoxic activity of splenocytes as measured by the ⁵¹Cr release assay correlated well with the capacity of the cells to inhibit candidal growth as determined by quantitative plating. This candidacidal activity was not antibody dependent but increased killing was obtained by adding fresh (but not heat inactivated) mouse serum. The enhanced candidicidal activity was inhibited by removal of plastic- or nylon-adherent cells from the cell suspension but not by treatment with anti-Thy 1.2 serum and complement. The data indicate that a candidacidal cell population is induced in the spleens of animals immunized with C. albicans ribosomes.     

Renal epithelial proliferation and its clinical expression in Brown Norway (BN) rats

Renal epithelial proliferation has previously been found to be a common condition in a colony of Lewis x Brown Norway (BN) F2 hybrid rats. The aim of this study was to investigate the prevalence and clinical consequences of this condition in pure inbred BN and Lewis rats. Renal epithelial proliferation was found in 29 of 49 BN rats (59%) examined and in four of 50 Lewis rats (8%) examined. Serum creatinine and serum corticosterone was not influenced by the condition. Haematuria was more common in BN rats with (74%) than without renal papillary proliferation (35%, P < 0.05), but it may not be used to diagnose renal epithelial proliferation, as we found rats having renal epithelial proliferation without showing haematuria and rats showing haematuria without having renal epithelial proliferation. Haematuria was also common in Lewis rats (16-56% dependent of age and gender), in which renal epithelial proliferation were found in only 8%. Fluctuating asymmetry, which was used as a measure of developmental instability, was found to be increased in rats with renal epithelial proliferation (P < 0.05). Haematuria was also found to be related to the degree of fluctuating asymmetry (P < 0.01). Although the prevalence of renal epithelial proliferation is clearly higher in BN rats than in Lewis rats (P < 0.01), and although in previous reports the condition was found in F2 BN x Lewis hybrids and not in F1 BN x Lewis hybrids it cannot clearly be defined as having been caused by a single Mendelian gene, as we found it in both inbred strains. Futhermore, we found that morphologically the proliferations could be placed on the papillary as well as the medullary wall of the renal pelvis, while previously it has only been described on the papillary wall.     

Effects of aging on single cardiac myocyte function in Fischer 344 x Brown Norway rats

The Fischer 344 x Brown Norway (F344xBN) rat has been demonstrated to have a lower incidence of age-related pathology than other rat strains. Therefore, to elucidate the effects of aging on cardiac function, uncomplicated by compensatory effects caused by age-related pathology, cardiac myocytes were isolated from female F344xBN rats at 6 (young) and 32-33 (old) mo of age. Myocytes showed an increase in the relative amount of beta-myosin heavy chain with advanced age and a significant rightward shift in the tension-pCa curve from 5.78 +/- 0.02 pCa units in young adult myocytes to 5.66 +/- 0.03 pCa units. Consistent with a shift to a slower myosin isoform, the time from stimulation to peak sarcomere shortening increased with age from 50.5 +/- 1.3 to 58.9 +/- 1.0 ms. In contrast, no age-related difference was found in either the relengthening parameters or the Ca(2+) transient, indicating that relaxation is not directly altered by aging. This latter finding is at variance with previous studies in rat strains with higher rates of pathology. We conclude, therefore, that the primary effect of aging in isolated cardiac myocytes from the F344xBN rat model is a shift in the myosin heavy chain isoform. Changes in relaxation seen in other rat strains may result from compensatory mechanisms induced by pathological conditions.     

Age-related changes in cardiac structure and function in Fischer 344 x Brown Norway hybrid rats

The effects of aging on cardiovascular function and cardiac structure were determined in a rat model recommended for gerontological studies. A cross-sectional analysis assessed cardiac changes in male Fischer 344 x Brown Norway F1 hybrid rats (FBN) from adulthood to the very aged (n = 6 per 12-, 18-, 21-, 24-, 27-, 30-, 33-, 36-, and 39-mo-old group). Rats underwent echocardiographic and hemodynamic analyses to determine standard values for left ventricular (LV) mass, LV wall thickness, LV chamber diameter, heart rate, LV fractional shortening, mitral inflow velocity, LV relaxation time, and aortic/LV pressures. Histological analyses were used to assess LV fibrotic infiltration and cardiomyocyte volume density over time. Aged rats had an increased LV mass-to-body weight ratio and deteriorated systolic function. LV systolic pressure declined with age. Histological analysis demonstrated a gradual increase in fibrosis and a decrease in cardiomyocyte volume density with age. We conclude that, although significant physiological and morphological changes occurred in heart function and structure between 12 and 39 mo of age, these changes did not likely contribute to mortality. We report reference values for cardiac function and structure in adult FBN male rats through very old age at 3-mo intervals.     

Bcl-2 in LPS- and allergen-induced hyperplastic mucous cells in airway epithelia of Brown Norway rats

Environmental toxins, infection, and allergens lead to a transient mucous cell hyperplasia (MCH) in airway epithelia; however, the mechanisms for reducing mucous cell numbers during recovery are largely unknown. This study investigated Bcl-2 expression in mucous cells induced by a neutrophilic or eosinophilic inflammatory response. Brown Norway rats intratracheally instilled with lipopolysaccharide (LPS) showed an inflammatory response characterized primarily by neutrophils. Secreted mucin was increased fourfold at 1 day, and the number of mucous cells was increased fivefold 2, 3, and 4 days post-LPS instillation compared with those in noninstilled rats. None of the mucous cells in non- or saline-instilled control animals expressed Bcl-2, whereas 20-30% of mucous cells were Bcl-2 positive 1 and 2 days post-LPS instillation. Brown Norway rats immunized and challenged with ovalbumin (OVA) for 2, 4, and 6 days showed an inflammatory response characterized primarily by eosinophils. Secreted mucin increased fivefold, and mucous cell number increased fivefold after 4 and 6 days of OVA exposure compared with water-immunized control rats challenged with OVA aerosols. Approximately 10-25% of mucous cells were Bcl-2 positive in OVA-immunized and -challenged rats. These data demonstrate Bcl-2 expression in hyperplastic mucous cells of Brown Norway rats regardless of the type of inflammatory response and indicate that apoptotic mechanisms may be involved in the resolution of MCHs.     

Brain aromatase in control versus castrated Norway Brown, Sprague-Dawley and Wistar adult rats.

Brain aromatase cytochrome P450 converts androgens to estrogens that play a critical role in the development of sexually dimorphic neural structures, the modulation of neuroendocrine function(s), and the regulation of sexual behavior. We characterized the influence of surgical castration on brain aromatase in Norway Brown and Wistar adult rats and compared their responses to Sprague-Dawley rats that were surgically or biochemically castrated (with flutamide, a known androgen receptor blocker). Aromata enzyme activity was measured by the tritiated water release assay in the medial basal hypothalmus/preoptic area (MBH/POA) and amygdala brain regions. The present results demonstrate that independent of the rat strain examined, MBH/POA aromatase is regulated by androgens (in Sprague-Dawley, Norway Brown and Wistar males). However, intact Wistar animals displayed significantly higher MBH/POA aromatase levels compared to Sprague-Dawley control values. Conversely, in the amygdala region, there was an apparent lack of androgen hormone action upon aromatase enzyme activity in some of the rat strains tested. The importance of brain aromatase regulating estrogen biosynthesis and influencing brain development and function is covered.