摘要:

AbstractBy means of a pitot‐static tube airway compliance curves describing the cross‐sectional area (A) as a function of transmural pressure (Ptm) were constructed for several locations in the elastic airway of a mechanical model of the lung. From these curves local relations between elastic recoil pressure of the lung (Pel) and maximal expiratory flow (V̇max) were calculated and compared with the experimentally determined Pel‐V̇max curve for the entire airway,i.e.all parts in series. Theory and experiments showed that the latter was the lower borderline of all the local Pel‐v̇max curves. This means that the maximal flow through the entire airway at a given Pel is determined by the segment of the airway, having the smallest v̇max, just as the maximal strength of a chain is determined by its weakest link. The relation between the critical transmural pressure (Ptm‘) and the corresponding cross‐sectional area (A’) was derived from theexperimental Pel‐V̇max curve. This Ptm‘‐A’ curve had a composed appearance, which was found to reflect parts of the different local Ptm‐A curves and transitions between them because of movement of the flow limiting site within the airway. The Ptm‘‐A’ curve depends on the elastic properties of the flow limiting segment, and the slope of this curve (dA‘/dPtm’) is the compliance of the flow limiting segment. Significant frictional pressure losses upstream from the site of flow limitation caused underestimation of both A‘ and dA’/dPtm“, but downstream pressure

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10392.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of the polyene antibiotic filipin on the electrical properties and the passive permeability of the cell membranes was investigated. The addition of filipin to the outside bathing solution has the following effects: 1. it results in a drastic reduction in the transepithelial resistance and potential, 2. it causes a 10–20 times increase in the passive transepithelial chloride, sodium and sucrose flux, 3. it results in the formation of an amiloride insensitive sodium pathway in the outward facing membrane, 4. it results in an active outward transport of potassium, 5. it results in a highly significant swelling of all the cells in the epithelium. The addition of filipin to the inside bathing solution has the following effects 1. it results in an activation of the active sodium transport, 2. it causes a slight increase in the passive transepithelial chloride and sodium permeabilities but has no effect on the sucrose permeability, 3. it has no effect on the amiloride inhibition of the short‐circuit current, 4. it has no effect on the volume of the cells in the epithelium. It is suggested that the addition of filipin to the outside bathing solution increases the direct sodium flow from cell to cell in neighbour layers. Furthermore these experiments indicate that the outward facing membrane of the isolated frog skin has a high cholesterol content as compared with the cholesterol content of the inward facing membr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10393.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe extracellular K concentration, ([K]e), in the brain cortex of rats at different ages was measured by means of K+‐sensitive microelectrodes. [K]ewas between 3 and 5 mM at all ages. Following nitrogen inhalation there was an increase in [K]ewhich exhibited a sigmoid pattern in every age group: Firstly, there was a slow rate of rise which was followed by a sudden, steep increase where the [K]erose to about 70 mM. During the subsequent 5–10 min a plateau value of about 90 mM was reached. The prominent difference between the age groups was the time until the steep rise began. The time to the steep increase in [K]eand the [K]eat the start of the steep increase was inversely related to the age of the animal. A close relation was found between the time to the start of the steep increase and the time to the last gasp during nitrogen breathing (r ‐ 0.98). It is suggested that the different resistence to anoxia in young and adult animals is related to differences in the ability to keep near normal potassium gradients across the cells in the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10394.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution of coronary blood flow was estimated in anesthetized dogs by counting the activity in tissue blocks of the left ventricular free wall immediately after bolus injection of Xe‐133 into the aortic root. No differences in the uptake of isotope were observed between the apex and the base of the heart; between areas supplied by the anterior descending and circumflex branches of the left coronary artery; or between the endo‐ and epicardial halves of the wall. In most experiments a bolus injection of the isotope into the left coronary artery was followed by a difference in activity between areas supplied by the left anterior descending and left circumflex branches. This indicated inadequate mixing of blood and isotope in the main stem of the artery. The uneven distribution did not result in differences between the epi‐ and endocardial activity concentrations. The results from one normal, anesthetized dog in which tissue activities were measured after constant rate infusion of Xe‐133 into the left coronary artery for 8 min were in accordance with the general assumption of equal epiand endocardial volumes of distribution (values

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10395.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractTo reveal a possible rate‐sensitive component in the myogenic control, changes of total and segmental vascular resistances in sympathectomized skeletal muscle in response to alteration of vascular transmural pressure (extravascular pressure) by 40 mmHg were compared when the pressure change was applied at two distinctly different rates (15 and 120 s). The papaverine‐dilated vascular bed showed an entirely passive behaviour, whereas the normal, myogenically reactive vascular bed responded with active constriction upon transmural pressure increase and active dilation upon pressure decrease. These responses were especially pronounced in the microvessels where a clearcut two‐component effector response was observed. The magnitude of the initial component was distinctly correlated to the rate at which the transmural pressure stimulus was applied, whereas the later steady state component during the static pressure change was rate‐independent. At the high rate of pressure increase, the initial rate‐dependent microvascular constrictor response was some ten times larger than the steady state response. These observations indicate the existence of a rate‐sensitive as well as a static component in the myogenic response to changed transmural pressure, an interpretation strongly supported by a previous analogous study on isolated single‐unit vascular smooth muscle (Johansson and Mellander 1975). It is concluded that the microvessels in skeletal muscle are highly responsive to myogenic stimuli and that emphasis should be placed on the dynamic rather than the static characteristics of the stimulus. Such rate‐sensitivity in myogenic control would seem to facilitate prompt and proper vascular adjustments, for instance in myogenic

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10396.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe characteristics of 40 C‐fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between 0.5‐1.8 m/s (0.91±0.05, mean ± S.E.). The activation threshold for all the fibres lay between 70–140 mmHg. 32 medullated fibres from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C‐fibres occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C‐fibres. The mean activity at 100 mmHg was, for the C‐fibres 5.0 Hz and for the medullated fibres 34 Hz. At 130 mmHg the activity in the C‐fibres was 13 Hz and in the medullated fibres 68 Hz. Thus C‐fibres from the aortic baroreceptor regions are activated at higher pressures than the medullated fibres and have lower discharge frequencies. Noradrenaline did not influence the pressure response curves of the C‐fibres. It is concluded that the arterial baroreceptor C‐fibres may exert a weak tonic influence on the vasomotor centre at normal pressures but are likely to be of greater importance when the arterial p

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10397.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractDecreased chronotropic and inotropic sensitivity of isolated atria to phenylephrine but not to isoprenaline was found in rats following repeated physical training by swimming or repeated ACTH‐injections. These changes were induced within a week of subjection of animals to these treatments. It is concluded, that these effects are mediated by increased adrenergic activity which results in this subsensitivity of alpha‐recept

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10398.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractCytochrome concentrations of rat heart and liver mitochondria were measured postnatally from newborn animals to young adults. Mitochondrial cytochrome aa3concentration increased shortly after birth in both tissues, this concentration being in a newborn animal 0.149 ± 0.027 nmol/mg protein in liver and 0.333 ± 0.082 nmol/mg protein in heart. The respective values from a two week old animal were 0.216±0.031 and 0.583 10.100. Postnatally cytochromes c±c1and b increased markedly in the heart, but in the liver of newborn animals the cytochrome content was more close to the adult values. The amount of mitochondrial protein increased after birth, too. In a newborn animal the mitochondrial protein values were 39.7 ± 3.6 mg/g wet weight in liver and 26.6± 6.5 mg/g wet weight in heart. In adult animals the respective values were 71.5 ± 4.8 and 80.7± 13.1. The effect of postnatal hypoxia (10% O2, 24 h and 48 h) on liver and heart mitochondrial cytochrome concentration and protein values of newborn animals were investigated. During hypoxia the amount of mitochondrial protein remained about at the level of a newborn animal. The postnatal increase in the mitochondrial cytochrome concentration, which was smaller in the liver than in the heart, was also inhibited by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10399.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect on tissue catecholamines of blockade of the pentose phosphate pathway with 6‐aminonicotinamide (6‐AN) was studied in the rat. 6‐AN at 35–50 mg kg‐1persistently lowered the adrenaline content in the adrenal gland to less than 10% of control values and caused a 50% loss of noradrenaline, which recovered. When the amine turnover rate was increased by a preceding period of drum stress, 6‐AN also consistently depressed noradrenaline in the gland. 6‐AN was without significant effect on the noradrenaline concentration in heart tissue, hypothalamus and superior cervical ganglion and did not affect the uptake or release of catecholaminesin vitro.The possibility is discussed that 6‐AN interferes with the biosynthesis of catecholamines, when it blocks the pentose phosphate pathway, by decreasing the supply of reducing equivalents in the form of NADPH which are necessary for the tetrahydropteridine cofactors of tyros

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10400.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractBovine adrenal medullary granules isolated by miliipore filtration were depleted of CA and ATP by dialysis. The resulting material showed an ability to bind inorganic cations and biogenic amines in a concentration‐dependent manner. The similarity of the uptake curves, the identical uptake maxima and the narrow pH range (between 4–7) over which the uptake of the inorganic and organic cations took place indicated a binding of these ions to common sites. In addition, the fact that all the uptake curves fitted the Rothmund‐Kornfeld equation for cation exchangers corroborated the cation exchanger properties of the dialyzed granule material. The CA binding capacity corresponded to 20–30% of the normal CA content of bovine medullary g

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb10401.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY