Effects of CO2/HCO3- in perilymph on the endocochlear potential in guinea pigs

The effect of CO(2)/HCO(3)(-) on the endocochlear potential (EP) was examined by using both ion-selective and conventional microelectrodes and the endolymphatic or perilymphatic perfusion technique. The main findings were as follows: (i) A decrease in the EP from approximately +75 to approximately +35 mV was produced by perilymphatic perfusion with CO(2)/HCO(3)(-)-free solution, which decrease was accompanied by an increase in the endolymphatic pH (DeltapH(e), approximately 0.4). (ii) Perilymphatic perfusion with a solution containing 20 mM NH(4)Cl produced a decrease in the EP (DeltaEP, approximately 20 mV) with an increase in the pH(e) (DeltapH(e), approximately 0.2), whereas switching the perfusion solution from the NH(4)Cl solution to a 5% CO(2)/25 mM HCO(3)(-) solution produced a gradual increase in the EP to the control level with the concomitant recovery of the pH(e). (iii) The perfusion with a solution of high or low HCO(3)(-) with a constant CO(2) level within 10 min produced no significant changes in the EP. (iv) Perfusion of the perilymph with 10 microg/ml nifedipine suppressed the transient asphyxia-induced decrease in EP slightly, but not significantly. (v) By contrast, the administration of 1 microg/ml nifedipine via the endolymph inhibited significantly the reduction in the EP induced by transient asphyxia or perilymphatic perfusion with CO(2)/HCO(3)(-)-free or 20 mM NH(4)Cl solution. These findings suggest that the effect of CO(2) removal from perilymphatic perfusion solution on the EP may be mediated by an increase in cytosolic Ca(2+) concentration induced by an elevation of cytosolic pH in endolymphatic surface cells.     

Rapamycin inhibits airway leukocyte infiltration and hyperreactivity in guinea pigs

The effect of rapamycin on cell infiltration to the lung and on bronchial hyperreactivity induced by an intravenous injection of sephadex beads to guinea pigs was investigated. One day following the injection of sephadex the total cell number in bronchoalveolar lavage (BAL) fluid was significantly increased from 24.77 to 83.45×10⁶ cells. This was reflected in an increase in eosinophils, neutrophils, macrophages and lymphocytes. In addition, there was an increase in the reactivity of isolated bronchial strips to histamine. Rapamycin (5 mg/kg), administered two hours before the injection of sephadex, reduced the eosinophil, neutrophil, lymphocyte and macrophage number by 64%, 55%, 50% and 19%, respectively, and also inhibited the increased reactivity of isolated bronchial strips to histamine. These results suggest that rapamycin may reduce bronchial reactivity by the inhibition of leukocyte migration into the airways.

     

Sensitization potential of gold sodium thiosulfate in mice and guinea pigs

Since gold sodium thiosulfate (GST) has been included in a standard patch test series for diagnosis of allergic contact dermatitis from gold, the incidence of patients showing positive reactions to gold is increasing. However, there were little reports on induction of gold sensitization in animals. In this study, we have examined the sensitization potential of GST using mice and guinea pigs. In the guinea pig maximization test, 2 or 6 out of 10 animals showed positive skin responses, mainly edema, by challenge with 2% or 5% GST in 50% ethanol solution, respectively. In the mouse ear swelling test, positive ear swelling (20% greater increase in ear thickness) after challenge with GST was shown in 2 out of 6 mice those previously treated with GST. Topical exposure of mice to GST in 70% dimethylsulfoxide solution induced small increases in the lymph node weight and the lymph node cell (LNC) number in the murine local lymph node assay (LLNA). A greater degree of LNC responses were observed in the sensitive mouse lymph node assay (SLNA) compared with the LLNA, but the stimulation index of total lymph node response by GST was not so high. From these results, GST was identified as a contact allergen, but the sensitization potential was not so strong. In the mouse IgE test, treatment of mice with GST resulted in a statistically significant increase in the serum IgE antibody concentration that associated with immediate-type hypersensitivity reaction. It may suggest that the sensitization responses from gold would appear not only at the contact site but also systematically.     

An animal model of ocular vestibular-evoked myogenic potential in guinea pigs

This study aimed to establish an animal model of ocular vestibular-evoked myogenic potential (oVEMP) in guinea pigs. Ten healthy and 10 gentamicin-treated guinea pigs underwent oVEMP test using a hand-held bone-conducted vibrator placed on the animal’s forehead. All 10 healthy animals exhibited bilateral oVEMPs at the stimulus intensity of 139 dB force level (FL), with a mean threshold and latencies of peak nI and pI of 130 ± 4 dBFL, 3.17 ± 0.37 ms and 4.72 ± 0.38 ms, respectively. Similar to response rate, the nI–pI amplitude decreased markedly in magnitude as stimulus intensity decreased. Another 10 animals administered with gentamicin (2 mg) on the left ear 1 week after surgery had 100% clear oVEMPs beneath the left eye (ipsilateral to the lesion side), whereas oVEMPs were absent and reduced beneath the right eye (opposite to the lesion side) in 7 and 3 animals, respectively. Morphological study of animals with absent oVEMPs identified substantial damage to the hair cells of the utricular macula. Quantitative analysis revealed that histological density of intact hair cells of the utricular macula from control and lesion ears were 194 ± 15 and 66 ± 9 per 130 × 130 μm² field, respectively, showing a 68% reduction in the latter. Further, the stereocilia of the residual hair cells were either fused or deformed, and pointed outward randomly. In conclusion, this study establishes the animal model of oVEMP in guinea pigs using bone-conducted vibration stimuli, which sets the stage for investigating the pathophysiology of the utricular disorders.     

Neurokinin-1 receptor antagonist inhibits short-term sulfuric-acid-induced airway hyperresponsiveness in sensitized guinea pigs

BACKGROUND: Tachykinins are involved in the development of bronchial inflammation and airway hyperresponsiveness (AHR); however, the role of the neurokinin-1 (NK(1)) receptor in acid-aerosol-induced bronchial impairment in asthmatic patients remains controversial. METHODS: To investigate the effects on the NK(1) receptor antagonist FK888 the neurokinin-2 (NK(2)) receptor antagonist SR48968 on sulfuric-acid (H(2)SO(4))-induced AHR in guinea pigs, specific airways resistance (sRaw) and airways responsiveness to methacholine (MCh) were measured before and after 6 h of exposure to H(2)SO(4) aerosol (pH 1.7, 82 mg/m(3)) in ovalbumin-sensitized guinea pigs. RESULTS: Airway responsiveness to MCh significantly increased (p<0. 05) after the exposure, however sRaw did not. Treatment with FK888 significantly inhibited (p<0.05) H(2)SO(4)-induced AHR in a dose-dependent manner, as did SR48968. CONCLUSIONS: These results suggest that not only NK(2) but also NK(1) receptors might have important roles in the development of acid-aerosol-induced AHR.     

Dependence of endocochlear potential on basolateral Na+ and Cl- concentration: a study using vascular and perilymph perfusion.

Inside-positive endocochlear potential (EP) and high potassium concentration in the endocochlear duct are generated by transepithelial K+ transport in marginal cells of the stria vascularis. In order to estimate the degree of involvement of Na+ and Cl- in K+ transport in marginal cells, EP in guinea pigs was measured under artificial vascular and perilymphatic perfusion in situ. Na+ depletion due to both vascular and perilymphatic perfusion decreased EP by -10.0 +/- 4.1 mV (delta EP = -86 +/- 5.2 mV, n = 5) from the control value of 78 +/- 4.3 mV (p < 0.01). Cl- depletion due to vascular and perilymphatic perfusion also decreased EP by -10.0 +/- 4.9 mV (delta EP = 8.5 +/- 4.8 mV, n = 6) from the control value of 77 +/- 5.1 mV (p < 0.01). However, under either vascular or perilymphatic perfusion, even lowering of Na+ or Cl- concentration in the perfusate decreased EP only slightly compared to the results under both vascular and perilymphatic perfusion. Furosemide, a blocker of Na+/K+/2Cl- symport, decreased EP under vascular perfusion. This dependency of EP on basolateral Na+ and Cl- concentration strongly suggests that K+ transport by the marginal cell is dependent on the basolateral Na+ and Cl- concentration, and that Na+/K+/2Cl- symport is raised as a possible mechanism for Na+ and Cl- dependency of EP.     

Adrenergic and cholinergic structures of the lungs in normal guinea pigs and in guinea pigs with experimental bronchial asthma

The morphological and functional state of the adrenergic and cholinergic innervation of the bronchopulmonary apparatus of guinea pigs was studied by luminescence and histochemical methods under normal conditions and during the course of sensitization (subcutaneous and inhalation methods) by the allergen of the miteDermatophagoides pteronyssinus. Considerable excitation of the adrenergic innervation and a fall in acetylcholinesterase activity were observed in the bronchopulmonary tissue during sensitization of the animals.Department of Pathological Physiology, Chuvash University. (Presented by Academician of the Academy of Medical Sciences of the USSR A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 4, pp. 446–448, April, 1977.     

Endolymphatic and intracellular resting potential in the alligator lizard cochlea

Summary Endolymphatic potential (EP) and intracellular resting potentials (RPs) in the cochlea of the alligator lizard were measured with micropipets. The EP (defined as the dc electric potential recorded between the endolymph in scala media and the perilymph in scala tympani or scala vestibuli) had a mean value of +16 mV (in 96 ears). The RPs (defined as the de potentials recorded between the intracellular and perilymphatic spaces) were different in the distal portion of the cochlear nerve (range to-56 mV, mean of –23 mV in 158 cells) from those in the region of the basilar papilla (range to-154 mV, mean of-73 mV in 623 cells). In identified cells in the region of the basilar papilla, the mean values of RPs of hyaline epithelial cells (-113 mV in 7 cells) and supporting cells (-93 mV in 13 cells) were more negative than of hair cells (-73 mV in 5 cells). Differences in measured RPs could reflect differences in the resting potentials of these cells and/or their source resistances. RPs measured in the basilar papilla of the alligator lizard are compared with those obtained in other vertebrate hair cell organs.     

Circulatory basophilia in guinea pigs with delayed-type hypersensitivity

Circulatory basophilia could be induced in inbred guinea pigs systematically immunized with ovalbumin and consequently provoked repeatedly with dissolved ovalbumin applied onto the mucosa of the nares or the outer eye. The degree of the increase in circulatory basophil granulocytes depended on the adjuvant used and was significantly more pronounced after immunization with Freund's complete adjuvant than with alhydrogel (A1(OH)3). The degree of basophilia was also dependent on the animal strain, but different in two strains selected for high-asthma trait.     

Circulating connective tissue precursors: extreme rarity in humans and chondrogenic potential in guinea pigs

Using a variety of cell separation techniques and cultivation conditions, circulating, adherent, connective tissue, clonogenic cells were found in just 3 donors out of 66, demonstrating that these precursors are extremely rare in postnatal human blood. Contrary to humans, guinea pig blood shows much more reproducible connective tissue colony formation; it was therefore chosen to study the differentiation potential of adherent blood-derived clonogenic cells. Out of 22 single colony-derived strains of various morphologies, only 5 spindle-shaped strains showed extensive proliferative capacity in vitro. None of these strains formed bone upon in vivo transplantation, whereas two strains formed cartilage in high-density pellet cultures in vitro. Both chondrogenic strains included cells expressing aggrecan, whereas nonchondrogenic strains did not. Out of four polyclonal strains studied, one formed both cartilage and abundant bone accompanied by hematopoiesis-supporting stroma. Evidently, there are cells in adult guinea pig blood capable of both extensive proliferation and differentiation toward cartilage: circulating chondrogenic precursors. Although some of these cells lack osteogenic potential and therefore represent committed chondrogenic precursors, others may be multipotential and consequently belong to the family of skeletal stem cells. This is the first demonstration of postnatal circulating chondrogenic precursors, as well as of precursor cells with chondrogenic but not osteogenic potential. Disclosure of potential conflicts of interest is found at the end of this article.     

Hyperventilation-induced bronchoconstriction in guinea pigs

The purpose of this study was to investigate the pulmonary effects of hyperventilation in anesthetized, mechanically ventilated guinea pigs. Airway resistance (Raw), dynamic lung compliance (CDyn), blood pressure (BP), heart rate (HR), arterial blood gases (PaO2, PaCO2), pH and arterial plasma HCO3- were measured before and after a 10-min period of hyperventilation produced by increasing the respiratory rate from 60 to 120 breaths/min while maintaining tidal volume at 4 ml. There was a significant increase in Raw and decrease in CDyn lasting up to 20 min after hyperventilation was stopped with no change in BP and HR. PaO2 was reduced from 109 +/- 3 mm Hg before to 53 +/- 7 mm Hg at 5 min after hyperventilation. The Raw and CDyn changes were prevented and reversed with the bronchodilators salbutamol and aminophylline indicating that reversible bronchospasms are induced in guinea pigs following a period of hyperventilation. Additional studies demonstrated that the pulmonary mechanical responses to hyperventilation were not changed by vagotomy, ventilation with high CO2 or by pretreatment with chlorpheniramine, methysergide, atropine, indomethacin, FPL 55712 or calcium-influx blockers. These results indicate that neither vagal reflexes, airway hypocapnia, receptors of histamine, serotonin, acetylcholine nor the products of arachidonic acid metabolism were involved in hyperventilation-induced bronchospasm in guinea pigs.     

雷公藤对哮喘豚鼠外周血淋巴细胞IL—5,粒细胞—巨噬细胞 …

目的探讨哮喘豚鼠白介素-5(IL-5)、粒细胞-巨噬细胞集落刺激因子(GM-CSF)及CD4+和CD8+T细胞在哮喘发病中的作用及雷公藤的干预作用.方法实验分为哮喘组、雷公藤治疗组(处理组)和对照组,每组各10只豚鼠,采用原位杂交方法检测豚鼠外周血淋巴细胞的IL-5、GM-CSFmRNA表达;应用免疫细胞化学方法检测外周血淋巴细胞CD4+和CD8+的表达.结果哮喘组外周血淋巴细胞IL-5、GM-CSF-mRNA表达均明显高于处理组和对照组(P＜0.01),而处理组和对照组无显著差异.哮喘组外周血淋巴细胞CD4+表达明显高于对照组和处理组(P＜0.01),CD8+表达低于对照组和处理组(P＜0.05).结论哮喘豚鼠外周血淋巴细胞IL-5、GM-CSFmRNA表达增高、CD4+表达增高,CD8+表达降低,而雷公藤甲素可降低外周血淋巴细胞IL-5、GM-CSFmRNA表达,并可提高CD8+表达,降低CD4+表达.表明雷公藤可能在抗哮喘气道炎症中发挥一定作用.     

Congenital and perinatal infection with Junin virus in guinea pigs

Junin virus infection in guinea pigs is known to be similar to human Argentine hemorrhagic fever (AHF). The guinea pig was chosen as a model for transplacental transmission of Junin virus, as both guinea pig and man have a similar placental structure. Pregnant guinea pigs were infected with the pathogenic XJ strain of Junin virus intramuscularly route at different stages of pregnancy. The group infected during the last third of pregnancy produced 16 newborn, but mortality reached 100%: 18% were born with typical AHF hemorrhagic signs, 54% without signs, and the remainder were stillborn. Virus was recovered from organs of newborns, as well as placental tissues. A second group, infected in the second third of pregnancy, died with intrauterine fetuses, all of which showed hemorrhagic signs and virus present. In a last group, infected in the first third of pregnancy, fetuses were free from macroscopic lesions. In order to determine whether lactation may be an alternative infection route in guinea pigs, mother guinea pigs were infected with Junin virus at different times postparturition. The 84% noninfected newborn housed together with their infected mothers died during the suckling period, half with typical AHF signs. Junin virus transmission from mother to fetus was thus proved, and lactation may be considered as an alternative perinatal infection route.     

Supporting sensory transduction: cochlear fluid homeostasis and the endocochlear potential

The exquisite sensitivity of the cochlea, which mediates the transduction of sound waves into nerve impulses, depends on the endocochlear potential and requires a highly specialized environment that enables and sustains sensory function. Disturbance of cochlear homeostasis is the cause of many forms of hearing loss including the most frequently occurring syndromic and non-syndromic forms of hereditary hearing loss, Pendred syndrome and Cx26 -related deafness. The occurrence of these and other monogenetic disorders illustrates that cochlear fluid homeostasis and the generation of the endocochlear potential are poorly secured by functional redundancy. This review summarizes the most prominent aspects of cochlear fluid homeostasis. It covers cochlear fluid composition, the generation of the endocochlear potential, K⁺ secretion and cycling and its regulation, the role of gap junctions, mechanisms of acid–base homeostasis, and Ca²⁺ transport.     

A 5-lipoxygenase inhibitor,FR110302, inhibits ozone-induced airway hyperresponsiveness in guinea pigs and dogs

Airway hyperresponsiveness is a key feature of asthma, and attenuating airway hyperresponsiveness is an important part of asthma therapy. In the present study we examined the inhibitory effect of a potent 5-lipoxygenase inhibitor, FR 110302, on airway hyperresponsiveness induced by ozone exposure in guinea pigs and dogs. Respiratory resistance (R _rs) was measured by a forced oscillation method. Airway responsiveness was determined from the dose-response curve ofR _rs to acetylcholine. Guinea pigs were exposed to 2.5 ppm ozone for 1 h. In a control group of guinea pigs, log PC100 (the index of the ozone-induced airway hyperresponsiveness) was 0.58±0.04 (log mg/ml). Treatment with FR110302 (10 or 100 mg/kg p.o.) significantly diminished log PC100 (10 mg/kg; 0.22±0.10; 100 mg/kg; 0.11±0.06). Dogs were exposed to 3 ppm ozone for 2 h. In a control group of dogs, logD _min (another index of the ozone-induced airway hyperresponsiveness) was 1.24±0.15 (log unit). Treatment with FR110302 (1 or 3.2 mg/kg p.o.) significantly diminished logD _min (1 mg/kg: 0.60±0.18; 3.2 mg/kg: 0.27±0.12). These results suggest that FR110302 may be a useful drug for attenuating airway hyperresponsiveness in asthmatic patients.