Guinea Pig Lung Research Articles

The relation between effects of adenosine, theophylline and enprofylline on the contractility of sensitized guinea-pig lung strips

Contractile responses of lung parenchymal strips from ovalbumin-sensitized guinea-pigs to cumulative addition of antigen were significantly potentiated by 10 min pretreatment with adenosine 10 microM. This potentiation was unaffected by the adenosine uptake inhibitor, dipyridamole, 2 microM. Cumulative addition of adenosine 0.1-100 microM to parenchymal strips without antigen produced variable responses, unrelated to sensitization, some contracting, some relaxing. Theophylline 100 microM caused relaxation of parenchymal strips and significantly inhibited the antigen-induced contraction with a parallel shift of the log concentration-response line. It also inhibited the adenosine-induced potentiation of contraction. Enprofylline 100 microM caused a greater relaxation of the tissue than theophylline. While it inhibited the adenosine-induced potentiation of the response, enprofylline, in contrast to theophylline, failed to inhibit the antigen-induced contraction of guinea-pig parenchyma. At these concentrations, theophylline and enprofylline each inhibited the antigen-induced release of SRSA (leukotrienes C4, D4 and E4), and of histamine, from sensitized guinea-pig lung fragments.

THE EFFECTS OF HISTAMINE RELEASE ON THE LIPID CONTENT OF THE ISOLATED PERFUSED LUNGS OF SENSITISED GUINEA-PIGS.

Abstract The histamine release induced in isolated perfused sensitised guinea-pig lungs by antigen, trypsin, Russell viper venom, and compound 48/80 has been compared. At equi-active dosage for histamine release, these four substances released varying amounts of slow reacting substances. Neither histamine release nor the release of slow reacting substances appeared to be responsible for the changes in cholesterol, glyceride or lipid phosphorus of the lung tissue observed in these experiments.

Differential relaxant responses of guinea-pig lung strips and bronchial rings to sodium nitroprusside: a mechanism independent of cGMP formation.

The biochemical mechanism subserving smooth muscle relaxant effects of sodium nitroprusside was examined on U46619, 9,11-dideoxy-9 alpha,11 alpha-methanoepoxy PGF2 alpha, precontracted guinea-pig lung strips and hilar bronchial rings. Lung strips were resistant to the relaxant action of sodium nitroprusside or sodium nitrite (NaNO2), whereas they markedly relaxed to 8-bromo-cyclic GMP (8-Br-cGMP), a membrane permeable analogue of cGMP. Precontracted bronchial rings completely relaxed to sodium nitroprusside, NaNO2, or 8-Br-cGMP in a concentration-dependent manner. Sodium nitroprusside (10 microM) substantially raised tissue cGMP level in lung strips. Conversely, sodium nitroprusside had no detectable effect on cGMP levels in bronchial rings. In the presence of 10 microM dipyridamole, an agent which preferentially inhibits cGMP-specific phosphodiesterase, cGMP levels in lung strips treated with sodium nitroprusside was significantly enhanced, but sodium nitroprusside demonstrated no relaxant effect on the preparations. However, dipyridamole potentiated sodium nitroprusside-induced precontracted bronchial ring relaxation without affecting the bronchial tissue cGMP level. In the presence of 10 microM LY83583 (6-anilino-5,8-quinoline-dione), a specific cGMP concentration-lowering agent, sodium nitroprusside-mediated elevation of cGMP level in lung strips was significantly reduced with no effect on the functional response. LY83583 demonstrated no inhibitory effect on either relaxation or cGMP level in bronchial rings treated with sodium nitroprusside. Our results suggest that precontracted smooth muscle in lung strips and in hilar bronchi respond distinctly to sodium nitroprusside. Furthermore, sodium nitroprusside mediates bronchial smooth muscle relaxation by mechanisms unrelated to cGMP.

Studies in the guinea-pig with ICI 185,282: a thromboxane A2 receptor antagonist.

The effects of ICI 185,282 (5(Z)-7-([ 2,4,5-cis]-4-O-hydroxyphenyl-2-trifluoromethyl-1, 3-dioxan-5-yl)heptenoic acid) have been studied on guinea-pig platelets and pulmonary smooth muscle in-vitro and in-vivo. When tested on guinea-pig lung parenchyma in-vitro. ICI 185,282 (1 x 10(-7) M) produced a significant shift in U-46619 response curves (concentration ratio of 13:3); the antagonist (1 x 10(-5) M) did not modify histamine responses. When tested on guinea-pig trachea in-vitro ICI 185,282 (1 x 10(-7) M) caused significant inhibition of U-46619 and PGD2 responses (concentration ratios of 8.3 and 14.1, respectively); the antagonist (1 x 10(-5) M proved less effective against contractions of PGF2 alpha, LTD4 and histamine (concentration ratios of 7.0, 1.5 and 1.6). When added to guinea-pig platelet rich plasma in-vitro, ICI 185,282 (x 10(-6), 1 x 10(-5) M) caused concentration-dependent parallel shifts to the right of U-46619 aggregation curves, yielding concentration ratios of 13.6 and 141.9, respectively. In-vitro, addition of ICI 185,282 (x 10(-5) M) to indomethacin-treated pulmonary smooth muscle did not modify resting tone, neither did it induce aggregation or swelling in platelet-rich plasma preparations. When administered orally to guinea-pigs ICI 185,282 (0.1, 0.5 mg kg-1) caused a significant inhibition of U-46619-induced platelet aggregation ex-vivo which persisted greater than or equal to 8 h. In-vivo, a single oral dose of ICI 185,282 (1 mg kg-1) inhibited bronchospasm induced by U-46619, PGD2, PGF2 alpha, arachidonic acid, LTD4 and PAF; responses to histamine were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

The Anti-Anaphylactic Activity of Ethanolamine and Choline

Abstract Ethanolamine, N-methylethanolamine, N-dimethylethanolamine and choline have anti-anaphylactic activity in actively sensitised guinea-pigs. Administered alone their activity is slight, but they considerably potentiate the limited protection afforded by mepyramine. Ethanolamine has been shown to inhibit the release of the slow reacting substance of anaphylaxis in guinea-pig lung subjected to anaphylaxis in vitro.

Pharmacological antagonism of Anchietia salutaris extracts on the contraction induced by prostaglandin D2 and U46619 in guinea-pig lung parenchymal strips.

Anchietia salutaris tea is traditionally used in Brazil to treat allergies, suggesting it contains compounds with antagonistic activity on the allergic mediators. We have evaluated extracts and semi-purified fractions of Anchietia salutaris as a source of compounds having this type of antagonism on the contraction induced in guinea-pig lung parenchymal strips and on platelet aggregation and shape change. After 10 min pre-incubation dichloromethane extracts containing 30 or 100 microg mL(-1) inhibited the contraction induced by prostaglandin D2 (PGD2) in guinea-pig lung parenchymal strips with dose ratios (DR) of 0.76+/-0.14 and 0.93+/-0.19, respectively; the amount of inhibition depended both on the concentration and on the time of pre-incubation (DR after 30 min pre-incubation was 1.21+/-0.51). The dichloromethane extract and its semi-purified fractions also inhibited the contractions induced by U46619, a more potent, stable, synthetic agonist of thromboxane A2 (TxA2) prostanoid (TP) receptors, the receptors acted upon by PGD2 to produce lung contractions. The dichloromethane extract did not inhibit the lung parenchymal contractions induced by histamine, leukotriene D4 (LTD4) or platelet-activating factor (PAF). Platelet aggregation induced by U46619, adenosine 5'-diphosphate (ADP) or PAF was not inhibited by the dichloromethane extract. Indeed, the extract potentiated platelet aggregation induced by low concentrations of these agonists and also potentiated the shape change induced by U46619. These results imply that the dichloromethane extract of Anchietia salutaris and its semi-purified fractions contain an active principle that competitively inhibits TxA2 TP receptors, the stimulation of which causes lung parenchymal contraction. The inhibition seems to be selective for this receptor subtype, because the extract fails to inhibit platelet aggregation or shape change. This provides additional support of earlier reports suggesting the occurrence of TP receptor subtypes.

A role for ATP in the mechanical activation of nodose C‐fibers in guinea pig lungs

Activation of vagal afferent sensory C-fibers in the lungs leads to reflex responses that produce many of the symptoms associated with airway allergy. There are two subtypes of respiratory C-fibers whose cell bodies reside within two distinct ganglia, the nodose and jugular, and whose properties allow for differing responses to stimuli. We here used extracellular recording of action potentials in an ex vivo isolated, perfused lung-nerve preparation to study the electrical activity of nodose C-fibers in response to mechanical stimulati in guinea pig lung. We used smooth muscle agonists to induce bronchoconstriction, thereby producing a mechanical stimulus, and found that treatment with both histamine (HA; 30 μM; n=15) and methacholine (MCh; 10 μM; n=4) caused strong action potential discharge in nodose C-fibers (10 ± 2 Hz and 15 ± 8 Hz respectively), but not in jugular C-fibers (n=8). Responses to HA were significantly reduced (P<0.05) by blockade of smooth muscle contraction with isoproterenol (100 μM), suggesting that a component of the response is mechanical in nature. The HA-induced activation of the nodose C-fibers was blocked by pretreatment the H1 receptor antagonist pyrilamine (1 μM; n=5). As ATP activation of P2X3 receptors has been found to play a role in mechanosensory transduction, we examined the effect of P2X3 receptor inhibition on the mechanical activation of nodose C-fibers and found that pretreatment with the P2X3 receptor antagonist AF353 (100 μM; n=5) blocked the response to HA. These results suggest that ATP released within the tissues in response to rapid smooth muscle contraction may play a role in the mechanical activation of nodose C-fibers.

Kv7 Channels in Airway Smooth Muscle Cells as Targets for Asthma Therapy

Asthma is commonly associated with airway hyperresponsiveness (AHR) involving hypercontraction of airway smooth muscle cells (ASMCs). The mechanisms underlying this process are, however, not well understood. Here we test the hypothesis that bronchoconstrictor agonists suppress Kv7 potassium currents leading to ASMC contraction. We detected Kv7.1–7.5 mRNAs in guinea pig lung by RT‐PCR and Kv7.3–7.5 proteins by immunostaining of isolated ASMCs. Function of Kv7 channels was demonstrated in freshly isolated guinea pig ASMCs: currents measured by perforated patch whole cell voltage clamp displayed electrophysiological characteristics (slow voltage‐dependent non‐inactivating Kv currents with a very negative activation threshold (~−60mV) and a V0.5 ~ −31 mV) and pharmacological characteristics (enhancement by selective activators, suppression by selective blockers) of Kv7 currents. Bronchoconstrictor agonists methacholine (100 nM) and histamine (30 μM), significantly suppressed Kv7 currents and this effect was reversed by Kv7 channel activators. Our results provide the first evidence that Kv7 channels are present in ASMCs, that their activity is suppressed by bronchoconstrictor agonists, and that this effect can be reversed by Kv7 channel activators. Our findings reveal novel mechanisms for ASMC hypercontraction and identify a potential new therapeutic strategy for the treatment of AHR in asthma.

Paracrine erythropoietin (EPO) signaling and anti‐apoptosis in the lungs of guinea pigs exposed to high altitude (HA)

HA residence stimulates erythropoiesis as well as lung growth and remodeling in young animals, suggesting parallel upregulation of endocrine and paracrine/autocrine EPO signaling. To examine this possibility, we exposed weanling male guinea pigs to 3,800 m HA for 3 d, 7 d or 1 mo compared to matched controls at sea level (SL) (n = 5–8 each), and measured mRNA and/or protein expression of hypoxia‐inducible factors (HIF‐1alpha and ‐2alpha), EPO and its receptor (EPOR), Jak2, VEGF and its receptors (−R1, −R2), endothelin‐1 (ET‐1), proliferation marker (PCNA), and an apoptotic suppressor (Bcl‐2) and a promoter (BAD). Compared to SL, HA‐exposed lungs showed 100% and 50% higher HIF‐1alpha mRNA at 3 and 7 d and 55% lower HIF‐2alpha mRNA at 3 d, although HIF‐2alpha protein was 120% higher. Lung EPO mRNA and cytoplasmic EPOR protein increased 150% and 25% at 3 d without significant changes in membrane EPOR or Jak2. Plasma and urine EPO protein increased 56% and 160% at 3 d. Lung VEGF‐R2 protein increased 72% at 3 d while VEGF increased 27% at 7 d. ET‐1 mRNA increased 3‐fold at 3 and 7 d. BAD was 50% lower and Bcl‐2 100% higher at 3 d. PCNA was unaltered. All changes resolved by 1 mo. Thus, short‐term HA exposure stimulates both endocrine and paracrine/autocrine EPO signaling. Enhanced EPO signaling in the lung occurs primarily at the ligand but not the receptor level and is associated with anti‐apoptosis. Support: NIH R01 HL045716.

Location of intra- and extracellular M. tuberculosis populations in lungs of mice and guinea pigs during disease progression and after drug treatment.

The lengthy treatment regimen for tuberculosis is necessary to eradicate a small sub-population of M. tuberculosis that persists in certain host locations under drug pressure. Limited information is available on persisting bacilli and their location within the lung during disease progression and after drug treatment. Here we provide a comprehensive histopathological and microscopic evaluation to elucidate the location of bacterial populations in animal models for TB drug development.To detect bacilli in tissues, a new combination staining method was optimized using auramine O and rhodamine B for staining acid-fast bacilli, hematoxylin QS for staining tissue and DAPI for staining nuclei. Bacillary location was studied in three animal models used in-house for TB drug evaluations: C57BL/6 mice, immunocompromised GKO mice and guinea pigs. In both mouse models, the bacilli were found primarily intracellularly in inflammatory lesions at most stages of disease, except for late stage GKO mice, which showed significant necrosis and extracellular bacilli after 25 days of infection. This is also the time when hypoxia was initially visualized in GKO mice by 2-piminidazole. In guinea pigs, the majority of bacteria in lungs are extracellular organisms in necrotic lesions and only few, if any, were ever visualized in inflammatory lesions. Following drug treatment in mice a homogenous bacillary reduction across lung granulomas was observed, whereas in guinea pigs the remaining extracellular bacilli persisted in lesions with residual necrosis.In summary, differences in pathogenesis between animal models infected with M. tuberculosis result in various granulomatous lesion types, which affect the location, environment and state of bacilli. The majority of M. tuberculosis bacilli in an advanced disease state were found to be extracellular in necrotic lesions with an acellular rim of residual necrosis. Drug development should be designed to target this bacillary population and should evaluate drug regimens in the appropriate animal models.

Aspirin

> Among the many useful discoveries which this age has made, there are very few which better deserve the attention of the public that what I am going to lay before your Lordship. > > —Reverend Edward Stone –Chipping-Norton, Oxfordshire –April 25, 1763 These prophetic words, written by Reverend Edward Stone in a 1763 letter to George Parker, the second Earl of Macclesfield, describe the results of the first clinical trial recorded in medical history.1 Stone's report on the rediscovery of the medicinal value of willow bark among subjects suffering from malarial symptoms is considered a significant milestone in the development of aspirin. Although society now takes many of its beneficial effects for granted, aspirin did not suddenly appear for medicinal use after Reverend Stone's discovery. Instead, its tumultuous journey was fueled by individual scientific curiosity, accidental discoveries, and intense business rivalry.1 No other drug is used by a greater number of people worldwide than aspirin, the benefits of which span centuries, beginning with the very first uses of willow bark by Egyptian physicians (Figure 1). Aspirin single-handedly transformed a coal-dye company into a pharmaceutical giant and has emerged as a cornerstone in the present-day therapies available for treating cardiovascular disease (CVD), pain, and inflammation. This article discusses the sentinel historical aspects of the discovery and clinical cardiovascular developments of aspirin, as well as its contemporary use in today's medical arena. Figure 1. Timeline of historical events in the development of aspirin. ### Historical Developments of Salicylates On January 20, 1862, Edwin Smith made one of the most historically important purchases of his life. Well-regarded among his peers for his keen scholarship and intricate knowledge of Egyptology, Smith purchased, for £12, 2 worn papyrus scrolls in a local Luxor street market1 that later turned out to be a formative medical textbook unlocking ancient Egyptian's practice of medicine. Although authorless, the Ebers Papyrus is 110 pages …

Comparison Between Perfadex and Locally Manufactured Low-Potassium Dextran Solution for Pulmonary Preservation in an Ex Vivo Isolated Lung Perfusion Model

Introduction Lung tranplantation, a consolidated treatment for end-stage lung disease, utilizes preservation solutions, such as low potassium dextran (LPD), to mitigate ischemia–reperfusion injury. We sought the local development of LPD solutions in an attempt to facilitate access and enhance usage. We also sought to evaluate the effectiveness of a locally manufactured LPD solution in a rat model of ex vivo lung perfusion. Methods We randomized the following groups \\?\\adult of male Wistar rats ( n = 25 each): Perfadex (LPD; Vitrolife, Sweden); locally manufactured LPD-glucose (LPDnac) (Farmoterapica, Brazil), and normal saline solution (SAL) with 3 ischemic times (6, 12, and 24 hours). The harvested heart–lung blocks were flushed with solution at 4°C. After storage, the blocks were connected to an IL-2 Isolated Perfused Rat or Guinea Pig Lung System (Harvard Apparatus) and reperfused with homologous blood for 60 minutes. Respiratory mechanics, pulmonary artery pressure, perfusate blood gas analysis, and lung weight were measured at 10-minute intervals. Comparisons between groups and among ischemic times were performed using analysis of variance with a 5% level of significance. Results Lungs preserved for 24 hours were nonviable and therefore excluded from the analysis. Those preserved for 6 hours showed better ventilatory mechanics when compared with 12 hours. The oxygenation capacity was not different between lungs flushed with LPD or LPDnac, regardless of the ischemic time. SAL lungs showed higher P co 2 values than the other solutions. Lung weight increased over time during perfusion; however, there were no significant differences among the tested solutions (LPD, P = .23; LPDnac, P = .41; SAL, P = .26). We concluded that the LPDnac solution results in gas exchange were comparable to the original LPD (Perfadex); however ventilatory mechanics and edema formation were better with LPD, particularly among lungs undergoing 6 hours of cold ischemia.

TRPA1 receptors in cough

In the early 1990’s ion channels of the Transient Receptor Potential (TRP) class were implicated in the afferent sensory loop of the cough reflex and in the heightened cough sensitivity seen in disease. Agonists of the TRPV1 capsaicin receptor such as vanilloids and protons were demonstrated to be amongst the most potent chemical stimuli which cause cough. However, more recently, the TRPA1 receptor (not activated by capsaicin) has become of interest in the cough field because it is known to be activated by ligands such as acrolein which is present in air pollution and the acrid smoke from organic material. TRPA1 is a Ca 2+-permeant non-selective cation channel with 14 ankyrin repeats in its amino terminus which belongs to the larger TRP family. TRPA1 has been characterised as a thermoreceptor which is activated by cold temperature, environmental irritants and reactive electrophilic molecules which can be generated by oxidant stress and inflammation. TRPA1 is primarily expressed in small diameter, nociceptive neurons where its activation probably contributes to the perception of noxious stimuli and the phenomena known as inflammatory hyperalgesia and neurogenic inflammation. The respiratory tract is innervated by primary sensory afferent nerves which are activated by mechanical and chemical stimuli. Activation of these vagal sensory afferents leads to central reflexes including dyspnoea, changes in breathing pattern and cough. Recently, it has been demonstrated that stimulating TRPA1 channels activates vagal bronchopulmonary C-fibres in the guinea pig and rodent lung, and recent data have shown that TRPA1 ligands cause cough in both animal models and normal volunteers. In summary, due to their activation by a wide range of irritant and chemical substances, either by exogenous agents, endogenously produced mediators during inflammation or by oxidant stress, we suggest TRPA1 channels should be considered as one of the most promising targets currently identified for the development of novel anti-tussive drugs.

The Stringent Response Is Required for Full Virulence ofMycobacterium tuberculosisin Guinea Pigs

During human latent tuberculosis infection, Mycobacterium tuberculosis likely resides within the nutrient‐starved environment of caseous lung granulomas. The stringent response alarmone (p)ppGpp is synthesized by Rel in response to nutrient starvation, thus enabling tubercle bacilli to restrict growth and shut down metabolism in a coordinated fashion. In this study, we investigated the virulence of a rel‐deficient M. tuberculosis mutant in the guinea pig model. Quantitative reverse‐transcription polymerase chain reaction was used to study the effect of (p)ppGpp deficiency on expression of key cytokine and chemokine genes in guinea pig lungs. The rel‐deficient mutant showed impaired initial growth and survival relative to the wild‐type strain. Loss of Rel was associated with the striking absence of tubercle lesions grossly and of caseous granulomas histologically. The attenuated phenotype of the rel‐deficient mutant was not associated with increased expression of genes encoding the proinflammatory cytokines interferon‐γ and tumor necrosis factor α in the lungs 28 days after infection.

Bronchoconstrictor effect of the tachykinin NK3-receptor agonists [MePhe7]-neurokinin B and senktide in the isolated guinea pig lung

ABSTRACTTo determine whether bronchoconstriction can be mediated via the tachykinin NK3 receptors, isolated guinea pig lungs were challenged with the exogenous tachykinin NK3-receptor agonists [MePhe7]-neurokinin B ([MePhe7]-NKB) and senktide. [MePhe7]-NKB induced bronchoconstriction (EC50 = 11.8 ± 1.7 μM) that was significantly inhibited by the tachykinin NK3-receptor antagonist SB 223412 at 10 μM (EC50 = 24.4 ± 4.5 μM). Senktide also induced bronchoconstriction (EC50 = 96.2 ± 20.3 μM) and the bronchoconstriction was significantly reduced by SB 223412 at 1 and 10 μM (EC50 = 270.8 ± 78.9 μM and 388.3 ± 105.5 μM, respectively). Although the authors demonstrated that SB 223412, [MePhe7]-NKB, and senktide are potent and selective for the tachykinin NK3 receptors in binding and functional (Ca2+ mobilization) assays, the tachykinin NK1-receptor antagonist CP 99,994 at 1 μM (EC50 = 32.7 ± 8.5 μM) produced inhibition of [MePhe7]-NKB–induced bronchoconstriction, whereas the tachykinin NK2-receptor antagonist SR 48968 at 0.1 μM (EC50 = 213.2 ± 42.9 μM) blocked senktide-induced bronchoconstriction. These data suggest that [MePhe7]-NKB and senktide caused bronchoconstriction in guinea pig through activation of the tachykinin NK3-receptors but the tachykinin NK1- and/or NK2-receptors are also involved in the response.

Pulmonary Immunization of Guinea Pigs with Diphtheria CRM-197 Antigen as Nanoparticle Aggregate Dry Powders Enhance Local and Systemic Immune Responses

This study establishes the immune response elicited in guinea pigs after pulmonary and parenteral immunizations with diphtheria CRM-197 antigen (CrmAg). Several spray-dried powders of formalin-treated/untreated CrmAg nanoaggregates with L-leucine were delivered to the lungs of guinea pigs. A control group consisting of alum with adsorbed CrmAg in saline was administered by intramuscular injection. Animals received three doses of powder vaccines containing 20 or 40 μg of CrmAg. The serum IgG titers were measured for 16 weeks after the initial immunization; IgA titers were measured at the time of sacrifice in the broncho-alveolar lavage fluid. Further, toxin neutralization tests in naïve guinea pigs were performed for a few select serum samples. Histopathology of the lung tissues was conducted to evaluate inflammation or injury to the lung tissues. While the highest titer of serum IgG antibody was observed in guinea pigs immunized by the intramuscular route, those animals immunized with dry powder formulation by the pulmonary route, and without the adjuvant alum, exhibited high IgA titers. A pulmonary administered dry powder, compared to parenteral immunization, conferred complete protection in the toxin neutralization test. Mild inflammation was observed in lung tissues of animals receiving dry powder vaccines by the pulmonary route. Thus, administering novel CrmAg as dry powders to the lungs may be able to overcome some of the disadvantages observed with the existing diphtheria vaccine which is administered by the parenteral route. In addition, these powders will have the advantage of eliciting a high mucosal immune response in the lungs without using traditional adjuvants.

Allometry of the mammalian intracellular pulmonary surfactant system

Alveolar epithelial (AE) surface area is closely correlated with body mass (BM) in mammals. The AE is covered by a surfactant layer produced by alveolar epithelial type II (AE2) cells. We hypothesized that the total number of AE2 cells and the volume of intracellular surfactant-storing lamellar bodies (Lb) are correlated with BM with a similar slope as AE surface area. We used light and electron microscopic stereology to estimate the number and mean volume of AE2 cells and the total volume of Lb in 12 mammalian species ranging from 2 to 3 g (Etruscan shrew) to 400-500 kg (horse) BM. The mean size of Lb was evaluated using the volume-weighted mean volume and the volume-to-surface ratio of Lb. The mean volume of AE2 cells was 500-600 μm(3) in most species, but was higher in Etruscan shrew, guinea pig, and human lung. The mean volume of Lb per AE2 cell was 80-100 μm(3) in most species, with the same exceptions as above. However, the total number of AE2 cells and the total volume of Lb were closely correlated with BM and exhibited an allometric relationship similar to the slope of AE surface area. The mean size of Lb was similar in all investigated species. In conclusion, the mean volume of AE2 cells and their Lb are independent of BM but show some interspecific variations. The adaptation of the intracellular surfactant pool size to BM is obtained by the variation of the number of AE2 cells in the lung.

A guinea pig model of latent Mycobacterium tuberculosis H₃₇Rv infection

To establish the guinea pig model of latent Mycobacterium tuberculosis (MTB) H₃₇Rv infection, and to study the multiplication dynamics of MTB in vivo, and the relationship between latent MTB infection and PPD skin test. Sixty-two guinea pigs were randomly divided into the model group (n = 42) and the control group (n = 20), and the model group was subdivided into a 4 weeks group (n = 12), an 8 weeks group (n = 21) and a 12 weeks group (n = 9), challenged by 500 CFU H₃₇Rv with restored toxicity. After 2 weeks challenge, the model groups were treated with isoniazid (INH, 10 mg/kg) + pyrazinamidum aldinamide (PZA, 40 mg/kg) for 4 weeks, 8 weeks and 12 weeks respectively. The natural recurrence of tuberculosis was observed in the model 4 weeks group, and the natural and induced recurrence by dexamethasone was observed in the model 8 weeks group and 12 weeks group. PPD skin test, the pathologic changes, and MTB quantity of organs were observed. In the control group, the average MTB quantity of spleen was 3.3 lg CFU after 2 weeks challenge, and the average MTB quantity of spleen and lung in guinea pigs were 4.5 lg CFU and 1.8 lg CFU respectively after 6 weeks challenge, and they reached 5.3 lg CFU and 5.4 lg CFU at 18 weeks respectively. The latent MTB infection of the model 4 weeks group recurred naturally 12 weeks after stopping treatment. The latent MTB infection of the model 8 weeks group recurred naturally and by dexamethasone treatment. The latent MTB infection of the model 12 weeks group did not recur naturally, but dexamethasone induced recurrence. The positive PPD response correlated with recurrence. A latent MTB infection model was established successfully by H₃₇Rv challenge and treatment with INH and PZA. The latent MTB infection may recur naturally or by induction. The PPD response was related to tuberculosis recurrence.

Multiple M. tuberculosis phenotypes in mouse and guinea pig lung tissue revealed by a dual-staining approach.

A unique hallmark of tuberculosis is the granulomatous lesions formed in the lung. Granulomas can be heterogeneous in nature and can develop a necrotic, hypoxic core which is surrounded by an acellular, fibrotic rim. Studying bacilli in this in vivo microenvironment is problematic as Mycobacterium tuberculosis can change its phenotype and also become acid-fast negative. Under in vitro models of differing environments, M. tuberculosis alters its metabolism, transcriptional profile and rate of replication. In this study, we investigated whether these phenotypic adaptations of M. tuberculosis are unique for certain environmental conditions and if they could therefore be used as differential markers. Bacilli were studied using fluorescent acid-fast auramine-rhodamine targeting the mycolic acid containing cell wall, and immunofluorescence targeting bacterial proteins using an anti-M. tuberculosis whole cell lysate polyclonal antibody. These techniques were combined and simultaneously applied to M. tuberculosis in vitro culture samples and to lung sections of M. tuberculosis infected mice and guinea pigs. Two phenotypically different subpopulations of M. tuberculosis were found in stationary culture whilst three subpopulations were found in hypoxic culture and in lung sections. Bacilli were either exclusively acid-fast positive, exclusively immunofluorescent positive or acid-fast and immunofluorescent positive. These results suggest that M. tuberculosis exists as multiple populations in most conditions, even within seemingly a single microenvironment. This is relevant information for approaches that study bacillary characteristics in pooled samples (using lipidomics and proteomics) as well as in M. tuberculosis drug development.

A Novel External Esophageal Perfusion Model for Reflux-Associated Respiratory Symptoms

Background and Objective: Gastroesophageal reflux disease (GERD) has been linked to a number of extra-esophageal symptoms and disorders, primarily in the respiratory tract. Current animal models of reflux esophagitis are adapted to diseases of the digestive system, rather than to reflux-associated respiratory symptoms. The aim of this study was to evaluate a novel external esophageal perfusion model to induce esophageal, tracheal and pneumonic histological injury similar to that associated with GERD. Methods: Twenty guinea pigs were randomized to the acid-treated or PBS-treated group. Esophageal catheters were used to perfuse the esophageal lumen of guinea pigs with hydrochloric acid containing 1 g/l pepsin or PBS for 14 days. The total cell number and cell differential counts in bronchoalveolar lavage fluid (BALF) were determined 24 h after the last perfusion. Histological changes in the esophageal, tracheal and pneumonic tissues were observed by hematoxylin-eosin staining. Results: The numbers of lymphocytes, eosinophils and total inflammatory cells in the BALF were significantly higher in acid-perfused than PBS-perfused animals. Histological evidence suggested esophageal and pneumonic inflammations were prominent in acid-treated animals. Conclusion: Repetitive, acid-perfused, esophageal events copied the animal models of reflux esophagitis, and elicited inflammatory responses in the airways and lungs of guinea pigs.