Muscarinic M3-receptors mediate cholinergic synergism of mitogenesis in airway smooth muscle

Muscarinic receptor agonists have been considered to act synergistically in combination with growth facors on airway smooth muscle growth. Characterization of the proliferative responses and of the receptor subtype(s) involved has not yet been studied. Therefore, we investigated mitogenesis induced by stimulation of muscarinic receptors, alone and in combination with stimulation by platelet-derived growth factor (PDGF). For this purpose, [(3)H]thymidine-incorporation was measured at different culture stages in bovine tracheal smooth muscle cells. Functional muscarinic M(3)-receptors, as measured by formation of inositol phosphates, were present in unpassaged cells, but were lacking in passage 2 cells. Methacholine (10 microM) by itself was not able to induce a proliferative response in both cell culture stages. However, methacholine interacted synergistically with PDGF in a dose-dependent fashion (0.1-10 microM), but only in cells having functional muscarinic M(3)-receptors. This synergism could be suppressed significantly by the selective M(3)-receptor antagonists DAU 5884 (0.1 microM) and 4-DAMP (10 nM), but not at all by the M(2)-subtype selective antagonist gallamine (10 microM). These results show that methacholine potentiates mitogenesis induced by PDGF solely through stimulation of muscarinic M(3)-receptors in bovine tracheal smooth muscle cells.     

Patient characteristics and resource utilisation in paediatric intensive care.

To determine the relation between basic clinical characteristics and resource utilisation in paediatric intensive care, an open prospective study was performed. Resource utilisation was expressed using the therapeutic intervention score system (TISS) and length of stay (LOS), from which total resource utilisation per admission (TISSTOT) and average daily resource utilisation (TISSMEAN = TISSTOT/LOS) were obtained. Overall 593 admissions, totalling 3130 days, were included. Mortality was 8.4% and non-survivors accounted for 14.1% of overall resource utilisation. In non-survivors, TISSTOT and TISSMEAN were higher, whereas LOS was not different from survivors'. Severity of illness, surgical status, significant chronic comorbidity, emergency admission, and transfer status constituted the major predictive determinants of TISSTOT (r2 = 0.19) and TISSMEAN (r2 = 0.45) in multiple regression analysis. High resource utilisation in high risk patients was probably warranted, as effectiveness of prolonged intensive treatment was demonstrated. It is concluded that TISSTOT and TISSMEAN are appropriate, non-monetary measures of resource utilisation, a considerable proportion of which are determined by a concise set of basic clinical characteristics.     

Congenital laryngeal stenosis; a rare cause of dyspnea in the newborn infant

Congenital laryngeal obstruction is a rare but serious cause of severe, often fatal, post partum asphyxia. The condition should be recognized and in most cases an artificial airway has to be established immediately because hypoxia allows little time for extensive evaluation. Thereafter a further diagnostic procedure by means of laryngobronchoscopy and contrast laryngography should be performed. The clinical picture of two cases with a congenital laryngeal stenosis is described and the initial therapeutic approach is discussed.     

Long-term consequences of lung injuries in flax scutchers

A female patient, 60 years old, had been working as a flax scutcher for 20 years. Sectional investigation showed fissural thin-walled caverns in the superior lobe of the lung. Histologic investigation revealed granulomas of epithelioid and lymphoid cells in the lungs, pleura, spleen, and silicon dioxide crystals in the lung tissue. The clinical picture resulted from a combined action of flax dust particles and silicon dioxide, and was similar to those of allergic exogenous alveolitis and late stages of silicosis, which attributed it to the occupational diseases of flax scutchers.     

Minimal sampling protocol for accurate estimation of urea production: a study with oral [13C]urea in fed and fasted piglets

BACKGROUND & AIMS: An oral [13C]urea protocol may provide a simple method for measurement of urea production. The validity of single pool calculations in relation to a reduced sampling protocol was assessed. METHODS: In eight fed and five fasted piglets, plasma urea enrichments from a 10 h sampling protocol were measured following an intragastric [13C]urea bolus. Blood [13C]bicarbonate was measured to trace gut [13C]urea oxidation. Two-compartment and regression (single pool) computations were performed. Pool sizes were compared to urea distribution over total body water (TBW). Shorter protocol duration was tested in regression simulations. RESULTS: Differences in urea kinetics between fed and fasted piglets did not reach statistical significance. Mean (+/-SE) urea pool from TBW times plasma urea concentration was 2.2+/-0.16 mmol kg(-1). Two-compartment modelling yielded similar results for pool size (despite the oxidation of a small amount of urea tracer). Urea appearance rate was 306+/-18 micromol kg(-1)h(-1). Regression calculations overestimated urea appearance rate vs. compartmental model (P<0.05). When samples <2 h were discarded, results were comparable to compartmental calculations even if protocol length was 6 h (325+/-24 micromol kg(-1)h(-1), NS). CONCLUSIONS: Regression calculations using plasma enrichments sampled between 2 and 6 h after oral [13C]urea administration provide accurate rates of urea production, and are not affected by tracer oxidation.     

Insulin induces a hypercontractile airway smooth muscle phenotype

This study aims to investigate the effects of insulin on bovine tracheal smooth muscle phenotype in vitro. Contractility of muscle strips and DNA-synthesis ([3H]thymidine incorporation) of isolated cells were used as parameters for smooth muscle phenotyping. Insulin (1 microM) was mitogenic for bovine tracheal smooth muscle and potentiated DNA-synthesis induced by other growth factors. In contrast, after pretreatment of unpassaged bovine tracheal smooth muscle cells in culture, the mitogenic response induced by growth factors was strongly diminished, with no difference in the basal incorporation. Pretreatment of bovine tracheal smooth muscle strips in organ culture with insulin increased maximal contraction to methacholine and KCl. These results show that insulin acutely augments DNA-synthesis in the presence of other growth factors. In contrast, insulin pretreatment induces a hypercontractile phenotype with a decreased mitogenic capacity. This mechanism may be involved in the putative negative association between asthma and type I diabetes. In addition, these findings may have implications for the use of aerosolized insulin in diabetes mellitus.     

5-HT1A receptor knockout mice and mice overexpressing corticotropin-releasing hormone in models of anxiety

Pharmacological experiments have implicated a role for serotonin (5-HT)(1A) receptors in the modulation of anxiety. More recent is the interest in corticotropin-releasing hormone (CRH) system as a potential target for the treatment of anxiety disorders. However, selective pharmacological tools for the CRH system are limited, hampering research in this field. Gene targeting is a relatively new approach to study mechanisms underlying anxiety disorders. 5-HT(1A) receptor knockout (1AKO) mice have been created on three different background strains, and two different lines of mice, overexpressing CRH (CRH-OE), have been generated. In the present review, behavioural and physiological findings reported for 1AKO mice and CRH-OE mice will be reviewed. As behavioural phenotyping is often limited to one or two approach avoidance paradigms, we extended these observations and also tested 1AKO and CRH-OE mice in a conditioned fear paradigm. This paradigm reflects essentially different aspect of anxiety than approach avoidance paradigms. 1AKO mice on a 129/Sv background strain showed similar freezing as wild-type (WT) mice. In CRH-OE mice, less freezing was observed than in the corresponding wild-type mice. The fact that the anxious phenotype of these genetically altered mice seems less clear than initially reported will be discussed. Rather than studying the direct consequences of alterations in the targeted gene, 1AKO and CRH-OE mice seem very valuable to study compensatory processes that seem to have taken place in reaction to life-long changes in gene expression.