1,720,966 research outputs found
Tidal breathing affects airway responsiveness to methacholine.
No full textAbstract
Asthma is characterized by increased airway responsiveness and airway inflammation. Airway hyperresponsiveness may be caused by increased airway smooth muscle contractility or by a decrease in the mechanical load that opposes airway smooth muscle contraction. Under static conditions, the equilibrium between contractility and load will determine the final airway smooth muscle length and therefore airway caliber. Because of tidal breathing, however, lungs normally function under dynamic conditions where both airway contractility and opposing load are affected. The capability of tidal breathing to appropriately modulate airway function might be the mechanism that differentiates airways of asthmatics from those of normal subjects
Improved diagnostic procedures in allergic RAST negative rhinitis.
No full textPatients affected by cutinegative, RAST negative, chronic hyperreactive rhinitis showed in 15/28 cases positive intradermal tests, nasal provocation test and RAST on nasal fluids. In 13/28 cases high IgE on nasal samples could be observed and seldom were the intradermal tests positive, but in no case were the nasal provocation or nasal RAST positive. Delayed and late positive provocation tests showed different features from early reactions. Criteria of positivity and checks during provocation tests look critical. The occurrence of sinusitis and polyposis can change clinical features. Mediators released from tissues lead to bronchial hyperreactivity
Effect of PEEP on induced constriction is enhanced in decorin-deficient mice
No full textDecorin (Dcn), a small leucinerich proteoglycan, is present in the extracellular matrix of the airways and lung tissues, contributes to lung mechanical properties, and its deposition is altered in asthma. The effect of Dcn deficiency on airway parenchymal interdependence was examined during induced bronchoconstriction. Studies were performed in C57Bl/6 mice in which the Dcn gene was disrupted by targeted deletion (Dcn_/_) and in wildtype controls (Dcn_/_). Mice were mechanically ventilated, and respiratory system impedance was measured during in vivo ventilation at positive end-expiratory pressure (PEEP) _ 2 and 10 cmH20, before and after aerosol delivery of methacholine (MCh). Length vs. tension curves in isolated tracheal rings were measured in vitro. Dcn distribution in _/_ mice airways was characterized by immunofluorescence; differences in collagen structure in Dcn_/_ and Dcn_/_ mouse lungs was examined by electron microscopy. MCh caused similar increases in airway resistance (Raw) and tissue elastance (H) in Dcn_/_ and Dcn_/_ mice. During MCh-induced constriction, increasing PEEP caused a decrease in Raw that was greater in Dcn_/_ mice and a decrease in H in Dcn_/_ mice only. Tracheal ring compliance was greater in Dcn _/_ mice. Imaging studies showed that Dcn was deposited primarily in the airway adventitial layer in Dcn_/_ mice; in Dcn_/_ mice, collagen had an irregular appearance, especially in the lung periphery. These results show that lack of Dcn alters the normal interaction between airways and lung parenchyma; in
asthma, changes in Dcn could potentially contribute to abnormal airway physiology
Attenuation of induced bronchoconstriction in healthy subjects: effects of breathing depth.
No full textThe effects of breathing depth in attenuating induced bronchoconstriction were studied in 12 healthy subjects. On four separate, randomized occasions, the depth of a series of five breaths taken soon (approximately 1 min) after methacholine (MCh) inhalation was varied from spontaneous tidal volume to lung volumes terminating at approximately 80, approximately 90, and 100% of total lung capacity (TLC). Partial forced expiratory flow at 40% of control forced vital capacity (V(part)) and residual volume (RV) were measured at control and again at 2, 7, and 11 min after MCh. The decrease in V(part) and the increase in RV were significantly less when the depth of the five-breath series was progressively increased (P < 0.001), with a linear relationship. The attenuating effects of deep breaths of any amplitude were significantly greater on RV than V(part) (P < 0.01) and lasted as long as 11 min, despite a slight decrease with time when the end-inspiratory lung volume was 100% of TLC. In conclusion, in healthy subjects exposed to MCh, a series of breaths of different depth up to TLC caused a progressive and sustained attenuation of bronchoconstriction. The effects of the depth of the five-breath series were more evident on the RV than on V(part), likely due to the different mechanisms that regulate airway closure and expiratory flow limitation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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