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Biomedical subjects

J Orehek

Publications and source records attributed to J Orehek.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

[Allergen-induced bronchoconstriction in asthma: antagonistic effect of a synthetic anticholinergic drug (author's transl)].

In ten allergic patients, the effect of inhaltion of increasing quantities of grass pollen on specific airways resistance (SRaw, measured by plethysmography) was estimated after preliminary inhalation of a placebo and of a synthetic anticholinergic drug (SCH 10000). After placebo, the inhalation of grass pollen induced in all cases a bronchoconstriction (mean increase of SRaw : 170 %). After SCH 1000, and for the same quantity of pollen inhaled, seven patients were entirely protected against the bronchoconstrictor effect of the allergen ; for the whole group, the observed bronchoconstriction was significantly lower (p less than 0.01, mean increase of SRaw : 60 %). The possible mechanisms of this protection are discussed. The results suggest that SCH 1000 could be used as a preventive drug in pollinic asthma.

Adult↗
PubMedDate not supplied

[Bronchial asthma and the beta adrenergic system].

The relationship between bronchial asthma and the beta adrenergic system is considered both from the physiopathologic and therapeutic point of view. A brief analysis of the sympathetic system is performed. The sympathetic nervous system is responsible for bronchodilation mediated through its beta-receptors. To evaluate this activity, beta adrenergic blockers such as propanolol are used. When this agent is administered, a descent of conductance is observed. On this condition, vagal stimulation brings about bronchoconstriction. At bronchial level, it seems that the beta-adrenergic system antagonizes vagal effect. From the physiopathologic point of view, Szentivanyi (1968) suggested a spontaneous beta block in the asthmatic. Other theories refer to a pathologic sensitivity of the peripheral bronchial receptors. The natural beta-adrenergics and the beta-adrenergic drugs enhance the synthesis of cAMP by stimulating the adenil cyclase system. This effect brings about relaxation of the bronchial smooth muscle. Considering the therapeutic effects, a comparative study of bronchodilators is performed. From all, Salbutamol has an intense broncholytic effect with little effect on heart dynamics. When sympathomimetics are bound to use in asthma, drugs such as Salbutamol and Terbutalina should be preferred because of its low cardiogenic effects. Its administration per os has rendered doubtful results.

Adenylyl Cyclases↗
PubMedDate not supplied

[Effect of hydrocortisone injections on bronchial obstruction in asthma (author's transl)].

In 14 asthmatic subjects with bronchial obstruction reversible by beta-sympathomimetic drug inhalation (salbutamol), the effect of intravenous injections of placebo and of 2, 4 and 8 mg/kg of hemisuccinate hydrocortisone (HSHC) has been measured by determining the forced expiratory volume in one second (FEV1) every two hours for eight hours. In four patients, FEV1 was not significantly altered by HSHC injection. It was improved in the ten other patients. The latency period lasted at least four hours and the peak action was observed between the sixth and the eighth hour. These two factors were related to the HSHC dose. The improvement obtained with 8 mg/kg HSHC was similar to that of salbutamol. The effect of the latter was potentiated by 8 mg/kg HSHC. These results suggest that HSHC should not be used when a fast reaction is wanted, on the one hand, and that the efficacy of the product must be controlled by objective measurements, on the other hand since not every subject is responsive.

Adult↗
PubMedDate not supplied

Dose-response curves to inhaled carbachol in asthma and chronic bronchitis.

Dose-response curves were established in 19 asthmatic and 19 bronchitic patients by measuring changes in specific airway resistance (sRaw) induced by graded doses of aerosolized carbachol. The shape of the individual curves was classified by the least-square method according to four models: hyperbolic, exponential, linear and logarithmic (with a plateau). The dose-response curves were hyperbolic in 9 asthmatics, exponential in 9, and linear in 1; they were hyperbolic in 2 bronchitics, exponential in 4, linear in 5 and logarithmic in 5. No response could be elicited in 3 bronchitics. Carbachol responsiveness of the bronchitics who had baseline sRaw values in the same range as the asthmatics was much less than that of the asthmatics, i.e. a given dose of carbachol yielded a smaller sRaw increase in the former group. Increased responsiveness to carbachol, resembling that found in the asthmatic group, was observed in most bronchitics whose baseline sRaw values were elevated. These data suggest that bronchitics and asthmatics have different bronchial responses to carbachol, quantitatively and, in some instances, qualitatively.

Adolescent↗
PubMedDate not supplied

[Reversibility of airway obstruction in asthma and chronic bronchitis (author transl)].

Our purpose was to determine whether, in patients with airway obstruction, the change in the forced expiratory volume in one second (FEV1) which occurs after a bronchodilator drug, is helpful in differentiating asthma from chronic bronchitis. Two groups of patients (48 with asthma and 42 with chronic bronchitis) having a comparable level of initial airway obstruction were selected according to clinical criteria. After salbutamol (200 microgram inhaled) the number of subjects showing a change in FEV1 of at least 20 percent of its initial value or 10 percent of its predicted value was significantly greater (p less than 0.01) in the asthmatic than in the bronchitic group. Lesser changes in FEV1 did not significantly separate the two groups. When the changes in FEV1 were expressed as percentages of both initial and predicted values, the number of positive responses increased in the asthmatic group. However, there were still 20 asthmatics with little or no change in FEV1 after salbutamol who could not be distinguished from the patients with chronic bronchitis. From these data we conclude that, in patients with airway obstruction, a large bronchodilator-induced change in FEV1 strongly suggests the diagnosis of asthma but that the presence of "irreversible" airway obstruction does not disprove it.

Adult↗
PubMedDate not supplied

[Bronchial response to carbachol and isocapnic hyperventilation in asthma].

Bronchial challenge tests with carbachol and isocapnic voluntary hyperventilation (IVH) were performed in 15 asthmatics on two separate occasions. For the IVH test, the subject inhaled dry air at 20-21 degrees C; respiratory frequency and tidal volume were controlled in order to obtain various 3 min levels of ventilation; isocapnia was maintained by adding CO2 to the inspired air. Bronchial response was assessed by measuring airway conductance (Gaw) with a plethysmograph. Individual dose-response curves were constructed, allowing the calculation of two indices: the slope of the dose-response curve and the value of the minute-ventilation (V25, expressed as percent of predicted maximal minute-ventilation), or the dose of carbachol (D25) causing a 25% decrease in Gaw. There was no significant correlation between the slopes of carbachol and IVH dose-response curves and between the values of V25 and D25. These data demonstrate that the IVH and carbachol tests cannot be used indifferently to assess bronchial responsiveness.

Adolescent↗
PubMedDate not supplied

Comparative reflex action of histamine, acetylcholine and serotonin on dog airways.

To dissociate airway stimulation from airway response, a segment of the cervical trachea was isolated from the rest of the bronchial tree in 15 anesthetized dogs; nerve and blood supplies of the segment were preserved. Patency of the intrathoracic airways was assessed with lung resistance (RL) measurements. When doses of aerosolized histamine (His), acetylcholine (ACh) and serotonin (Ser) causing comparable increases in RL were delivered into the intrathoracic airways, concomitant increases in pressure were recorded in the tracheal segment (indicating constriction) with His being the most effective. When the hypoxemia accompanying His- and ACh-induced bronchoconstriction was prevented by inhaling an air-oxygen mixture, the tracheal response persisted (2 dogs). Vagotomy decreased the RL response to His, ACh and Ser and abolished tracheal response (13 dogs). The tracheal response was still abolished when larger doses of His and ACh were given in order to induce an increase in RL similar to that observed before vagotomy (7 dogs). These data suggest the existence of a positive feed-back mechanism in the airways, pharmacological bronchoconstriction causing vagally mediated reflex bronchoconstriction. Direct stimulation of lung irritant receptors by histamine may explain the larger degree of reflex bronchoconstriction observed with this agent.

Acetylcholine↗