Biomedical subjects

F Rakotosihanaka

Publications and source records attributed to F Rakotosihanaka.

3 recordsLinked to original sources

PubMed1988

Local cellular and humoral responses to antigenic and distilled water challenge in subjects with allergic rhinitis.

We studied nasal responses to allergen, saline, and distilled water aerosol in 7 subjects with allergic rhinitis to determine whether they caused a similar release of mediators and influx of inflammatory cells into the nasal lumen. The subjects were challenged first with allergen and then with aerosols of distilled water and of normal saline in random order on separate days. We measured nasal airway resistance (Rn) by posterior rhinomanometry, measured the concentrations of protein, histamine, leukotrienes (LT) B4, C4, and D4, and platelet-activating factor (PAF-acether) and performed total and differential cell counts in nasal lavage fluid obtained before and after each challenge. Allergen challenge provoked a 2-fold or greater increase in nasal airway resistance in all subjects (mean increase = 12.2-fold). This response was associated with significant increases in protein, histamine, LTB4, and sulfidopeptide leukotrienes. 2-lyso-PAF-acether increased significantly, indicating activation of phospholipase A2, but PAF-acether was detected in only one subject. The total cell count increased from 55 +/- 44 x 10(3)/ml to 200 +/- 168 x 10(3)/ml; polymorphonuclear neutrophils increased from 11 +/- 22 x 10(3)/ml to 108 +/- 96 x 10(3)/ml, and eosinophils increased from 1.3 +/- 1.8 x 10(3)/ml to 10.6 +/- 15.3 x 10(3)/ml (p less than 0.05). Saline insufflation provoked insignificant changes in mean Rn, in the levels of protein and all inflammatory mediators, and in the number and types of cells in nasal lavage fluid. Distilled water insufflation also provoked an insignificant increase in mean Rn, but there was a 14-fold increase in one subject.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Nasal response to substance P and methacholine in subjects with and without allergic rhinitis.

We compared the rise in nasal airway resistance (NAR) provoked by topical application of substance P (SP) and of methacholine (MCH) in seventeen patients suffering from rhinitis and fourteen control subjects. Challenges with SP or MCH were separated by a week or more. NAR was measured by posterior rhinomanometry before and 10 min after intranasal administration of SP (10-40 nmol) or MCH (3-12 mumol). The two groups of subjects had similar baseline levels of NAR and similar small responses to buffered saline. Substance P but not MCH provoked cutaneous flushing in all subjects. Both SP and MCH provoked a significantly greater increase in NAR in patients suffering from rhinitis than in control subjects. The increase in NAR was dose-dependent, and on a molar basis, SP was 375-500-fold more potent than MCH. Pretreatment with 200 micrograms of a topically active anticholinergic agent, oxytropium bromide, prevented the rise in NAR caused by 12 mumol of MCH but not that caused by 40 nmol of SP in six patients suffering from rhinitis. We conclude that SP is absorbed across the nasal mucosa and causes cutaneous vasodilation, that MCH and SP cause a greater rise in NAR in patients suffering from rhinitis than in control subjects, that SP is about 500-fold more potent than MCH in increasing NAR, and that the rise in NAR caused by SP is not mediated by postganglionic parasympathetic mechanisms.

Administration, Intranasal↗

PubMedDate not supplied

Refractoriness after hyperventilation-induced asthma.

It is still debated as to whether the bronchospasm induced by hyperpnoea in asthmatic subjects is followed by a period of refractoriness to a subsequent challenge. We studied, therefore, the effect of repeated challenges with eucapnic hyperpnoea in asthmatic subjects and compared it to that in normal subjects. Ten normal and 34 asthmatic subjects were challenged twice with a steady isocapnic hyperventilation (25 l X min-1 X m-2 BSA for 6 min) of dry air at room temperature. The interval between challenges was 30 min in the normal subjects and was 30-60 min in asthmatic subjects to allow for full recovery of FEV1 before the second challenge. In the normal subjects, neither the first nor the second challenge caused a detectable change in FEV1. In the asthmatic subjects, the fall in FEV1 was on average less marked at 5, 8 and 10 min after the second challenge than after the first one (p less than 0.05 by analysis of variance). Analysis of data from individuals showed partial to full refractoriness in 14 of the 34 subjects. In no instance was the fall in FEV1 significantly greater after the second challenge than after the first one. Thirteen other asthmatic subjects were challenged twice at a 30-60 min interval with stepwise increases in ventilation of dry air at room temperature until wheezing or chest tightness occurred or a ventilation of 50 l X min-1 X m-2 BSA was reached.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗