Guinea Pig Lung Research Articles

Peroxynitrite Modulates Release of Inflammatory Mediators from Guinea Pig Lung Mast Cells Activated by Antigen-Antibody Reaction

Background: Peroxynitrite (ONOO^–), the product of the reaction between the superoxide anion (·O₂^–) and nitric oxide (NO), is produced during inflammatory disease and may be a major cytotoxic agent. No reports are available as to whether ONOO^– generates or modulates inflammatory mediator release from activated guinea pig lung mast cells. In this study, we explored the modulatory role of intracellular ONOO^– on inflammatory mediator release (histamine and leukotrienes) from activated mast cells. Methods: Guinea pig lung mast cells were purified by the enzyme digestion, and by using the rough and discontinuous Percoll density gradients. Mast cells were sensitized with IgG1 (anti-ovalbumin) antibody and challenged with ovalbumin (OVA). The intracellular ROS formation was determined by following the oxidative production of 2′, 7′-dichlorofluorescein diacetate (DCFH-DA), dihydrorhodamine 123 (DHR), and anti-nitrotyrosine antibody immunofluorescence. Histamine was assayed using a fluorometric analyzer, leukotrienes by radioimmunoassay, intracellular Ca²⁺ levels by confocal scanning microscopy, and PLA₂ activity using prelabeling of [³H]arachidonic acid. Results: ROS detected by DCFH-DA weakly increased in mast cells activated with OVA (1.0 g/ml), and the ROS so generated was inhibited by ebselen (50 µM). However, the ROS detected by DHR increased 3-fold under the same conditions. Peroxynitrite scavengers sL-MT, DMTU, and inhibitor FeTPPS inhibited ROS formation but the NADPH oxidase inhibitor diphenyleneiodonium (DPI) only partially inhibited this formation. Dimethyl thiourea (DMTU) and seleno-L-methionine (sL-MT) inhibited the tyrosine nitration of cytosolic proteins, the release of histamine and leukotrienes, Ca²⁺ influx, and the PLA₂ activity evoked by mast cell activation. Conclusion: The data obtained suggests that the ROS generated by the antigen/antibody reaction activated mast cells is ONOO^–, and that this modulates the release of inflammatory mediators via Ca²⁺-dependent PLA₂ activity.

Allergen-induced substance P synthesis in large-diameter sensory neurons innervating the lungs

Tachykinins such as substance P are localized in unmyelinated slow-conducting C fibers that can be activated by noxious stimuli and tissue inflammation. Substance P is seldom expressed in fast-conducting large-diameter (A-fiber) vagal sensory neurons. We have previously found that allergic inflammation causes a phenotypic change in tachykinergic innervation of the trachea such that the production of substance P is induced in large-diameter sensory neurons projecting mechanosensitive A fibers to the trachea. To evaluate whether allergic inflammation also induces substance P synthesis in large-diameter sensory stretch-receptor neurons innervating guinea pig lungs, and to investigate potential mechanisms by which this may occur. Sensitized guinea pigs were exposed to allergen (ovalbumin) aerosol. One day later, immunohistochemical analysis was performed on vagal sensory neurons that had been retrogradely labeled from the lungs. Ovalbumin inhalation caused a significant increase in substance P expression in large-diameter neurofilament-positive nodose ganglion neurons that innervate the lungs (P < .05). This effect was decreased by ipsilateral vagotomy. Exposing isolated nodose ganglia to the sensitizing antigen, ovalbumin, also significantly increased substance P expression compared with control. Allergic inflammation induces substance P synthesis in large-diameter (A-fiber) nodose ganglion neurons innervating guinea pig lungs. This could contribute to the hyperreflexia seen in allergic airway disease. The full expression of this phenotypic switch in vagus nodose ganglion neurons requires intact vagus nerve, but if allergen reached the systemic circulation in sufficient quantities, it could also affect substance P synthesis by local activation of vagal ganglionic mast cells.

PTHrP fragments 1-16 and 1-23 do not bind to either the ET A or the ET B endothelin receptors

Because of some isofunctional similarities with endothelin-1 (ET-1), it has been suggested that PTHrP(1-16) and PTHrP(1-23) could interact with osteoblast cells via ET A receptors. To document this interaction, we used the thoracic rat aorta and the guinea-pig lung parenchyma paradigms as ET A and ET B models, respectively. In addition, we also performed a series of competition experiments against [ 125I]ET-1, using transfected cells expressing the ET A or ET B receptor. So far, no agonistic nor antagonistic activities were observed in the ET A and ET B bioassays with the PTHrP fragments. Furthermore, both fragments were unable to displace [ 125I]ET-1 bound to cells expressing the ET A or ET B receptor.

Effect of Nicotine on Lung S-Adenosylmethionine and Development of Pneumocystis Pneumonia

Because S-adenosylmethionine (AdoMet) is required by Pneumocystis carinii in vitro, Pneumocystis infection depletes plasma AdoMet of rats and humans, nicotine reduces AdoMet of guinea pig lungs, and smoking correlates with reduced episodes of Pneumocystis pneumonia (PCP) in AIDS patients, we tested the effect of nicotine treatment on PCP using a rat model. Intraperitoneal infusion of 400 microg of R-(+) nicotine kg(-1) h(-1) intraperitoneal for 21 days caused a 15-fold reduction in lung AdoMet although neither plasma nor liver were changed. Infusion of 4 and 400 microg kg(-1) h(-1) into immunosuppressed rats, beginning when rats were inoculated with P. carinii, caused 85 and 99.88% reductions, respectively, in P. carinii cysts at sacrifice 21 days later; P. carinii nuclei were reduced by 91.2 and >99.99%, respectively. This effect was reversed by concomitant administration of AdoMet with nicotine. Treatment with AdoMet alone increased infection intensity. We conclude that AdoMet is a critical and limiting nutrient for Pneumocystis thus can serve as a therapeutic target for PCP. Regarding the mechanism, nicotine treatment caused no change in rat lung activity of AdoMet synthesizing methionine ATP transferase activity nor was there any evidence of increased AdoMet utilization for methylation reactions. Except of a doubling of putrescine, nicotine treatment also did not change lung polyamine content. However, key polyamine anabolic and catabolic enzymes were upregulated, and there were corresponding changes in polyamine metabolic intermediates. We conclude that chronic nicotine treatment increases lung polyamine catabolic/anabolic cycling and/or excretion leading to increased AdoMet-consuming polyamine biosynthesis and depletion of lung AdoMet.

The discovery of cromolyn sodium and its effect on research and practice in allergy and immunology

The discovery of cromolyn sodium and its effect on research and practice in allergy and immunology

Effect of propolis extract on guines pig lung mast cell

The direct effect of ethanolic extract of propolis on guinea pig lung cell suspension containing mast cells, as well as its influence on the histamine release induced by antigen (ovoalbumin 10 mg/ml) and ionophore A 23187 (3 mM) were investigated. Propolis ethanolic extract (300 mg/ml) increased the histamine release in guinea pig lung suspension containing mast cells by a cytotoxic effect. Lower concentrations of propolis had no effect on histamine release. Our results demonstrated that propolis (3, 10, 30, and 100 mg/ml) shows no significant effect on the histamine release induced by ionophore and antigen. Based on these results, we suggest that propolis could directly activate mast cells, promoting inflammatory mediators release by cytotoxic mechanisms, what could be related to allergic processes in propolis sensitive people.

Effect of 5-hydroxytryptamine on vagal C-fiber subtypes in guinea pig lungs

5-Hydroxytryptamine (5-HT, serotonin) evokes pulmonary reflexes partially by activating vagal bronchopulmonary C-fibers. In the guinea pig, vagal bronchopulmonary C-fibers arise from cell bodies situated in the nodose and the jugular ganglia. The nodose and the jugular C-fibers differ both pharmacologically and neurochemically, and may subserve different functions. In this study, we compared the effect of 5-HT on the nodose and jugular C-fibers with receptive fields within the guinea pig lungs. The nerve terminals of the vagal bronchopulmonary C-fibers were studied in an ex vivo isolated perfused lung nerve preparation using the extracellular recordings. All nodose C-fibers responded to transient administration of 5-HT (10 μM) and to the selective 5-HT 3 receptor agonist, 2-methyl-5-HT (10 μM), with the action potential discharge. The selective 5-HT 3 receptor antagonist ondansetron (10 μM) inhibited (by ∼90%) the activation of the nodose C-fibers evoked by 5-HT (10 μM). In contrast to the nodose C-fibers, the jugular C-fibers were unresponsive or poorly responsive to 5-HT ( n=9) and unresponsive to 2-methyl-5-HT ( n=11). A direct action of 5-HT on the C-fiber neurons was supported using the whole cell patch clamp recordings from the isolated vagal sensory neurons retrogradely labeled from the lungs. Consistently with the studies on the nerve terminals, 5-HT (10 μM) induced inward current in nodose lung-specific capsaicin-sensitive neurons. Conversely, 5-HT was inefficient to stimulate the lung-specific jugular neurons. We conclude that in the guinea pig lungs, 5-HT selectively stimulates vagal nodose, but not jugular C-fibers via the 5-HT 3 receptors in the neuronal membrane.

Eupatilin blocks mediator release via tyrosine kinase inhibition of initial stage in activated guinea pig lung mast cells

Eupatilin blocks mediator release via tyrosine kinase inhibition of initial stage in activated guinea pig lung mast cells

100 Met-enkephalin modifies respiratory function in guinea-pigs

Aim: Met-enkephalin is an endogenous opioid pentapeptide with cytokine properties that has been investigated in many in vitro and in vivo models of inflammation. This study was conducted in order to examine the possible effect of met- enkephalin on changes in pulmonary function provoked by histamine. Methods: Experimental animals were Hartley guinea-pigs (6 animals per group, male-female 1:1, weight 500-700g). Classic Konzett and Rossler’ s method of whole body plethysmography modified by Gjuris was applied to monitor changes in the respiratory rate, type of respirations or amplitude of respirations. Bronchoconstriction was induced in anesthetized animals by i.v. histamine (10 μ g/kg) and the protective effect of met-enkephalin was defined as the percentage of histamine blockade (the reduction of histamine-induced bronchoconstriction ; each animal its own control). Three doses of met-enkephalin were applied: 0.1 mg/kg, 1 mg/kg, and 10 mg/kg. Data were compared by t-test. Results: Met-enkephalin doses of 1 mg/kg and 10 mg/kg caused significant reduction of the histamine induced bronchoconstriction (p<0.059 and p<0.009, respectively), while the dose of 0.1 mg/kg was ineffective (p=0.141). Conclusion: Results implicate that met-enkephalin modulates histamine effects in guinea-pig lungs in a dose-dependent way. Histamine is not only a bronchoconstrictor ; it is nowadays recognized as a mediator of inflammation and part of a complex, not fully understood network of cytokines and chemokines. This fact, together with our results and the previously demonstrated regulating effect of met-enkephalin on growth of P. aeruginosa and S. aureus, justify further investigation of met- enkephalin as a potential drug in treatment of cystic fibrosis. Aim: Met-enkephalin is an endogenous opioid pentapeptide with cytokine properties that has been investigated in many in vitro and in vivo models of inflammation. This study was conducted in order to examine the possible effect of met- enkephalin on changes in pulmonary function provoked by histamine. Methods: Experimental animals were Hartley guinea-pigs (6 animals per group, male-female 1:1, weight 500-700g). Classic Konzett and Rossler’ s method of whole body plethysmography modified by Gjuris was applied to monitor changes in the respiratory rate, type of respirations or amplitude of respirations. Bronchoconstriction was induced in anesthetized animals by i.v. histamine (10 μ g/kg) and the protective effect of met-enkephalin was defined as the percentage of histamine blockade (the reduction of histamine-induced bronchoconstriction ; each animal its own control). Three doses of met-enkephalin were applied: 0.1 mg/kg, 1 mg/kg, and 10 mg/kg. Data were compared by t-test. Results: Met-enkephalin doses of 1 mg/kg and 10 mg/kg caused significant reduction of the histamine induced bronchoconstriction (p<0.059 and p<0.009, respectively), while the dose of 0.1 mg/kg was ineffective (p=0.141). Conclusion: Results implicate that met-enkephalin modulates histamine effects in guinea-pig lungs in a dose-dependent way. Histamine is not only a bronchoconstrictor ; it is nowadays recognized as a mediator of inflammation and part of a complex, not fully understood network of cytokines and chemokines. This fact, together with our results and the previously demonstrated regulating effect of met-enkephalin on growth of P. aeruginosa and S. aureus, justify further investigation of met- enkephalin as a potential drug in treatment of cystic fibrosis.

Enzymatic Measurement of Tryptase-Like Protease Release from Isolated Perfused Guinea Pig Heart during Ischemia-Reperfusion

To elucidate the details of tryptase release from the heart during ischemia-reperfusion (I/R), we attempted the enzymatic measurement of tryptase release from the isolated guinea pig heart perfused by the Langendorff mode I/R model. Tryptase-like activity in the effluent was monitored by the hydrolysis of L-Pyr-Gly-Arg-MCA. Tryptase-like protease and histamine were rapidly released from heart during ischemia within 10 min. After reperfusion, tryptase-like protease levels decreased, achieving stabilization. The tryptase-like protease activity in the effluent was inactivated by serine protease inhibitors. The pattern of inhibition was similar to those of guinea pig and human lung tryptase. In conclusion, tryptase was released into the coronary effluent during ischemia, but not during reperfusion in guinea pig heart.

Newly Designed Primer Sets Available for Evaluating Various Cytokines and iNOS mRNA Expression in Guinea Pig Lung Tissues by RT-PCR

Guinea pigs are often used as an animal model of human tuberculosis (TB). However, there are few methods available for pursuing the immunological processes involved in guinea pig TB. In this study, we developed for the first time systematic reverse transcription (RT)-PCR for evaluation of guinea pig mRNA expression. RT-PCR primer sets were newly designed for detection of cytokines and inducible nitric oxide synthase (iNOS) mRNA in guinea pig TB. Interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, interleukin (IL)-1beta, IL-2, IL-10, IL-12p40, granulocyte-macrophage-colony stimulating factor (GM-CSF) and iNOS mRNA expression were detected significantly and reproducibly when these primer sets were used. The data by real-time PCR were comparable with those of RT-PCR. We showed that these RT-PCR primer sets could be used to examine mRNA expression semi-quantitatively in guinea pig tissues, and conclude that these newly designed primer sets for conventional RT-PCR will be useful for studying the immunological processes in guinea pig tuberculosis experiments to investigate and evaluate efficacy of new vaccines or anti-mycobacterial drugs.

The efficacy of live tuberculosis vaccines after presensitization with Mycobacterium avium

The variable efficacy of BCG in humans has been extensively documented but its cause is still not well understood. One possible reason for this variation is the effect of presensitization with environmental mycobacteria. To investigate in guinea pigs the effects of presensitization with well characterized Mycobacterium avium strains on the vaccine efficacy of BCG and of two recently developed, avirulent strains of Mycobacterium bovis. Two strains of M. avium containing the DNA insertion element IS901 (M. avium+) and two strains not containing this element (M. avium-) were inoculated subcutaneously or by oral administration into guinea pigs to assess their virulence in these animals and their ability to induce delayed type hypersensitivity to tuberculins. Subsequently, groups of guinea pigs presensitized with orally administered M. avium+ and M. avium- and a control group were vaccinated with BCG, or one of two newly attenuated strains of M. bovis. All groups were then challenged by the aerosol route with virulent M. bovis. Vaccine efficacy was assessed 5 weeks later by the presence of macroscopic lesions and bacterial counts of spleen and lung. No macroscopic lesions were observed in any of the guinea pigs inoculated with strains of M. avium+ or M. avium- and all animals gave delayed-type hypersensitivity skin-test reactions to avian PPD. In the vaccine experiment, presensitization with orally administered M. avium+ alone produced a low level of protection against subsequent challenge with virulent M. bovis. In the absence of presensitization with M. avium or after presensitization with an M. avium- strain, BCG and two attenuated strains of M. bovis produced significant levels of protection. No additional protection was observed in lungs of guinea pigs presensitized with M. avium+ and subsequently vaccinated with BCG. In contrast, both newly attenuated strains of M. bovis induced significant protection in lungs after such presensitization. Presensitization of guinea pigs by the oral administration of M. avium+ provides a model for testing vaccines under conditions where the efficacy of BCG has been compromised by prior sensitization with environmental mycobacteria.

Guinea-pig lung adenylyl and guanylyl cyclase and PDE activities associated with airway hyper- and hypo-reactivity following LPS inhalation

The relationships between changes in in vivo airway reactivity and levels cyclicAMP and cyclicGMP were determined in guinea-pig lungs after exposure to inhaled lipopolysaccharide (LPS). After LPS (30 μg.ml −1, 1 h), guinea-pigs displayed in vivo airway hyperreactivity (AHR) at 1 h and hyporeactivity (AHOR) at 48 h, to inhaled (20 s) histamine (1 or 3 mM, respectively). Isoprenaline-stimulated cAMP or SNAP-stimulated cGMP were determined in the lungs isolated from guinea-pigs exposed to LPS inhalation to determine whether there was a relationship between AHR or AHOR and adenylyl/guanylyl cyclase and phosphodiesterase (PDE) activities. Assays were performed in the absence and presence of the non-selective PDE inhibitor, 3-isobutyl-1-methylxanthine (IBMX). Levels of cAMP and cGMP in its presence indicated adenylyl and guanylyl cyclase activities, respectively. The difference between cAMP and cGMP levels, in the absence and presence of IBMX, reflected relevant PDE activity. In vivo AHR was associated with increased PDE activity towards cAMP and cGMP (67 and 278%, respectively) and also increased adenylyl (47%) and guanylyl (210%) cyclase activities. In vivo AHOR at 48 h after LPS inhalation was also associated with raised cyclase activity ( p < 0.05), whereas relevant PDE activity declined by 79 and 68%, compared with 48 h after vehicle. Although net stimulated cGMP levels increased during AHR and AHOR and net stimulated cAMP increased during AHOR, our index of PDE activity increased during AHR and decreased during AHOR. These results therefore support the rationale for the use of PDE-inhibitors in the treatment of respiratory diseases associated with AHR.

Pharmacological profile of CR3465, a new leukotriene CysLT 1 receptor antagonist with broad anti-inflammatory activity

CR3465 ( l-Tyrosine, N-[(2-quinolinyl)carbonyl]- O-(7-fluoro-2-quinolinylmethyl) sodium salt) is a potent antagonist of [ 3H]leukotriene D 4 ([ 3H]LTD 4) binding to guinea pig lung preparations, its K i (4.7±0.7 nM) being comparable with that of montelukast (5.6±0.6 nM). In tracheal strips from standard or ovalbumin-sensitized guinea pigs, CR3465 caused parallel rightward shifts in the concentration–response curves obtained with either LTD 4 or antigen (p A 2, 8.74 and 8.15). Intravenous (i.v.) administration of the agent both antagonized (ED 50, 9.9±1.9 μg/kg) and reverted LTD 4-induced bronchoconstriction of anesthetized guinea pigs. CR3465 reduced inflammatory infiltrates in the bronchoalveolar lavage fluid after antigen challenge of sensitized animals, and proved also active in inhibiting phosphodiesterase 3 (PDE3) and phosphodiesterase 4 (PDE4) activities exhibited by human platelets and neutrophils (IC 50, 2.01±0.07 and 4.7±0.5 μM). In line with properties shown by phosphodiesterase inhibitors, CR3465 reduced the contractile response of guinea pig airways to histamine and decreased N-formyl-Met-Leu-Phe (fMLP)-induced degranulation of human neutrophils (IC 50, 13.8 μM). Oral administration (20 mg/kg) of the compound in rats produced a significant (37%) ex vivo inhibition of tumor necrosis factor-alpha (TNF-α) release from lipopolysaccharide-stimulated whole blood. Pharmacokinetic data in the rat demonstrated approximately 100% bioavailability of the agent. We conclude that CR3465 represents a potent leukotriene CysLT 1 receptor antagonist with enhanced effects, being also useful for counteracting spasmogenic and inflammatory stimuli other than those elicited by cysteinyl–leukotrienes (Cys-LTs).

Magnetic resonance imaging of pulmonary lesions in guinea pigs infected with Mycobacterium tuberculosis.

We utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected by low-dose aerosol exposure to Mycobacterium tuberculosis. Lesions were prominent in such images, and colorized three-dimensional reconstructions of images revealed a very uniform distribution in the lungs. Lesion numbers after 1 month were approximately similar to the aerosol exposure algorithm, suggesting that each was established by a single bacterium. Numbers of lesions in unprotected and vaccinated animals were similar over the first month but increased thereafter in the control animals, indicating secondary lesion development. Whereas lesion sizes increased progressively in control guinea pigs, lesions remained small in BCG-vaccinated animals. A prominent feature of the disease pathology in unprotected animals was rapid and severe lymphadenopathy of the mediastinal lymph node cluster, which is paradoxical given the strong state of cellular immunity at this time. Further development of this technical approach could be very useful in tracking lesion size, number, and progression in the search for new tuberculosis vaccines.

Inhibitory effects of flavonoids on phosphodiesterase isozymes from guinea pig and their structure–activity relationships

The structure–activity relationships of flavonoids with regard to their inhibitory effects on phosphodiesterase (PDE) isozymes are little known. The activities of PDE1–5 were measured by a two-step procedure using cAMP with [ 3 H]-cAMP or cGMP with [ 3 H]-cGMP as substrates. In the present results, PDE1, 5, 2, and 4 isozymes were partially purified from guinea pig lungs in that order, and PDE3 was from the heart. The IC 50 values of PDE1–5 were greater than those reported previously for the reference drugs, vinpocetin, EHNA, milrinone, Ro 20-1724, and zaprinast, by 5-, 5-, 7-, 5-, and 3-fold, respectively. As shown in Table 2, luteolin revealed non-selective inhibition of PDE1–5 with IC 50 values in a range of 10–20 μM, as did genistein except with a low potency on PDE5. Daidzein, an inactive analogue of genistein in tyrosine kinase inhibition, showed selective inhibition of PDE3 with an IC 50 value of around 30 μM, as did eriodictyol with an IC 50 value of around 50 μM. Hesperetin and prunetin exhibited more-selective inhibition of PDE4 with IC 50 values of around 30 and 60 μM, respectively. Luteolin-7-glucoside exhibited dual inhibition of PDE2/PDE4 with an IC 50 value of around 40 μM. Diosmetin more-selectively inhibited PDE2 (IC 50 of 4.8 μM) than PDE1, PDE4, or PDE5. However, biochanin A more-selectively inhibited PDE4 (IC 50 of 8.5 μM) than PDE1 or PDE2. Apigenin inhibited PDE1–3 with IC 50 values of around 10–25 μM. Myricetin inhibited PDE1–4 with IC 50 values of around 10–40 μM. The same was true for quercetin, but we rather consider that it more-selectively inhibited PDE3 and PDE4 (IC 50 of <10 μM). In conclusion, it is possible to synthesize useful drugs through elucidating the structure–activity relationships of flavonoids with respect to inhibition of PDE isozymes at concentrations used in this in vitro study.

Intratracheal dosing with disodium cromoglycate inhibits late asthmatic response by attenuating eicosanoid production in guinea pigs

Disodium cromoglycate is an anti-asthmatic drug that has mast cell-stabilizing effects and other anti-inflammatory effects. However, the mechanisms of its anti-inflammatory effects are unclear. In this study, we evaluated effects of disodium cromoglycate on eosinophilia, early and late asthmatic responses, and production of arachidonic acid metabolites in guinea pig lungs. Guinea pigs were alternately sensitized and challenged by exposure to mists of ovalbumin+Al(OH) 3 and ovalbumin, respectively. Disodium cromoglycate (0.5–2 mg/0.1 ml/animal) administered intratracheally before the fifth challenge dose-dependently inhibited asthmatic response, but early asthmatic response was not affected. Disodium cromoglycate at 2 mg/animal potently suppressed increases in cysteinyl leukotrienes (CysLTs) and thromboxane A 2 in the lung during late asthmatic response. Eosinophilia was slightly reduced by disodium cromoglycate. The inhibitory effect of disodium cromoglycate on late asthmatic response is apparently due to inhibition of the release of arachidonic acid metabolites, some of which may be derived from eosinophils that infiltrate the lung.

A Czech researcher and Pneumocystis.

In 1909, two years after the birth of Otto Jirovec (figure 1) in Bohemia, Carlos Chagas described an organism in the lungs of infected guinea pigs that he named Schizotrypanum cruzi [1, 2]. In 1912, Antonio Carini noted these same organisms in the lungs of rats. Both researchers were convinced that what they had observed was a type of trypanosome. However, later that year, at the Pasteur Institute, the husband-and-wife team of Delanoe and Delanoe [3] demonstrated that the cysts observed in the lungs of Carini's rats were unrelated to trypanosomes and named the organism Pneumocystis carinii. In the 1930s and 1940s, an epidemic form of pneumonia was recognized in European infants who were born prematurely [1]. This called plasma cell pneumonia, was associated with death by the age of 6 months [4]. It was not until 1951 that Otto Jirovec, along with Joseph Vanek, demonstrated that the etiologic agent of interstitial plasma cell pneumonia was Pneumocystis. Otto Jirovec started out as a zoologist studying microsporidia and later contributed to the understanding of Trichomonas vaginalis, Toxoplasma, and Leptospira [5]. However, he is most famous for his work on Pneumocystis, both for his initial description of the species that infects humans and later for his studies of its development and epidemiology. In 1976, four years after Otto Jirovec's death, Jacob Frenkel proposed to use the name of Pneumocystis carinii for the species that infects rats and to use Pneumocystis jerovici for the species that infects humans, on the basis of the knowledge that interspecies infection was not experimentally possible [2]. In the late 1980s, RNA analysis demonstrated that Pneumocystis was a fungus, not a protozoa [6, 7]. Ironically, it was not until 1999, after this change in taxonomy, that the species of Pneumocystis that infects humans was renamed Pneumocystis jiroveci after the great Czech parasitologist [2].

Subtypes of vagal afferent C-fibres in guinea-pig lungs.

An ex vivo, vagally innervated, lung preparation was used to address the hypothesis that vagal C-fibres comprise at least two distinct phenotypes. Histological and extracellular electrophysiological experiments revealed that vagal C-fibres innervating the pulmonary system are derived from cell bodies situated in two distinct vagal sensory ganglia. The jugular (superior) ganglion neurones project C-fibres to both the extrapulmonary airways (larynx, trachea and bronchus) and the lung parenchymal tissue. By contrast, C-fibres from nodose (inferior) neurones innervate primarily structures within the lungs. Histologically, nodose neurones projecting lung C-fibres were different from the jugular neurones in that they were significantly less likely to express neurokinins. The nerve terminals within the lungs of both nodose and jugular C-fibres responded with action potential discharge to capsaicin and bradykinin application, but only the nodose C-fibre population responded with action potential discharge to the P2X selective receptor agonist alpha,beta-methylene-ATP. Whole cell patch clamp recording of capsaicin-sensitive nodose and jugular ganglion neurones retrogradely labelled from the lung tissue revealed that, like the nerve terminals, lung specific nodose C-fibre neurones express functional P2X receptors, whereas lung specific jugular C-fibres do not. The data support the hypothesis that both neural crest-derived neurones (jugular ganglia) and placode-derived neurones (nodose ganglia) project C-fibres in the vagus, and that these two C-fibre populations represent distinct phenotypes.

Binding affinities of ocular hypotensive beta-blockers levobetaxolol, levobunolol, and timolol at endogenous guinea pig beta-adrenoceptors.

The current study determined the relative affinities and selectivities of numerous beta-adrenoceptor antagonists at the endogenous beta(1)- and beta(2)-adrenoceptors in guinea pig heart and lung, respectively, using [(3)H]-CGP12177. Specific binding of [(3)H]-CGP12177 comprised 80 +/- 0.2% (n = 11) and 94 +/- 0.2% (n = 16) of the total binding in washed heart and lung homogenates, respectively. Concentration-dependent displacement of [(3)H]-CGP12177 binding from beta-adrenoceptors in both preparations was observed with nine different beta-adrenoceptor antagonists. Levobetaxolol, betaxolol, CGP-20712A, levobunolol, and timolol yielded bi-phasic (two-site-fit) competition curves in the heart, while CGP-20712A, ICI-118551 and levobunolol produced bi-phasic curves in the lung preparation. The high-affinity component of [(3)H]-CGP12177 binding in the heart and lung reflected binding to beta(1)-receptors and beta(2)-receptors, respectively. The binding inhibition parameters (IC(50)s) for displacement of [(3)H]-CGP12177 from these predominantly high-affinity sites were: levobetaxolol (24.9 +/- 1.6 nM heart, 4810 +/- 367 nM lung), racemic betaxolol (37.9 +/- 8.7 mM heart; 8840 +/- 424 mM lung), CGP-20712A (4.6 +/- 0.9 nM heart; 171,000 +/- 109,000 nM lung), ICI-118551 (9230 +/- 3240 nM heart; 2.9 +/- 0.6 nM lung), levobunolol (42 +/- 15 nM heart, 0.3 +/- 0.2 nM lung), (l)-timolol (3.1 nM heart, 2.9 +/- 1.5 nM lung), ICI-215001 (5840 +/- 114 nM heart; 26100 +/- 3200 nM lung), BRL-37344 (83,300 +/- 2660 nM heart; 13,200 +/- 1250 lung). These data indicated that while levobetaxolol and betaxolol possessed a 193-233-fold selectivity for beta(1)-receptors, levobunolol exhibited a 140-fold beta(2)-receptor selectivity and (l)-timolol was essentially nonselective.