Arterioles within the microcirculation control organ blood flow and represent the main peripheral resistance within the circulation. However, larger vessels with a diameter of more than 150 microm are mostly used to study vascular behavior. Although arterioles have features in common with these conducting vessels, they exhibit distinct properties and the contribution of different pathways to constriction or relaxation varies with vessel size. This is especially the case for endothelium-dependent relaxations, which occur in response to mechanical stimuli (e.g. blood flow) and agonists. Autacoids released from the endothelium include nitric oxide, prostaglandins and an endothelium-derived hyperpolarizing factor (EDHF). Whereas nitric oxide is dominant in larger vessels, the importance of EDHF increases with decreasing vessel size. Its chemical nature is still a matter of debate and different substances have been identified to act as an EDHF in different vascular beds, e.g. epoxyeicosanoids, potassium ions, anandamide, hydrogen peroxide or C-type natriuretic peptide. Despite this heterogeneity of proposed factors it is unclear if such a factor indeed exists in all vessels since the hyperpolarization of vascular smooth muscle has been proposed to be induced by simple current transfer from the adjacent endothelium. For this to occur the cells need to be electrically coupled and this requirement is fulfilled by gap junctions which are composed of connexins forming intercellular channels. Aside from myoendothelial coupling gap junctions also interconnect endothelial cells thus creating a functional unit, which efficiently synchronizes cellular behavior within the arteriolar tree of the microcirculation.
It may be possible to describe and diagnose 4 lung diseases of the group CNSLD by laboratory data only, by computer, apart and separated from physician’s diagnosis. Recording of concentration curves of expired gases yield 4 lung parameter values: He1•5, MHe, RHe, RCO2. These, together with 8 other parameter values: FEVC, FEV1 % FEVC, M1 (= FEV1%FIV1%), MVV30/ FIVC, FRC % TLC, RV % TLC, DLCO/body surface area, reversibility of FEV1, and 3 administrative data: age, season and sex, form 15 ‘symptoms’, used together with ‘a priori probability’ to compute diagnosis of (A) asthma bronchiale, (B) bronchitis asthmatica, (C) bronchitis chronica and (E) emphysema pulmonum, from 703 patients in one clinic. The numerical values of the symptoms are grouped in symptom classes. By using chi-square test, Wilcoxon test, and T (=Δ/SE/Δ) test with and without classes, each disease (A, B, C or E) significantly differed in at least 7, 8, 8 and 10 symptoms, respectively, (on the average 12) from the other and in at least 11 symptoms from normal condition. Rank lists for discriminative properties of the symptoms show the importance of the gas concentration curve parameters RCO2, RHe, MHe and He1•5 and also of the parameters: reversibility and M1.
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