摘要:

AbstractThe rate of85Kr absorption from the feline gut was studied at varying intestinal blood flows induced by i.a. infusions of a vasodilator drug or by lowering arterial inflow pressure. The effects on rate of absorption of distending the intestine by increasing intraluminal pressure from 0–1 to 5–7 cm H2O as well as of augmenting the rate of luminal perfusion of the85Kr solution were also investigated. Distending the small bowel increased rate of85Kr absorption at all levels of intestinal blood flow except at the very low and the very high blood flow rates. Decreasing blood flow by lowering of arterial perfusion pressure decreased the rate of absorption from the distended gut while it had no effect in the collapsed small intestine. Increasing the rate of luminal perfusion enhanced the rate of85Kr absorption at all blood flow levels except at the lowest ones. The results are discussed with regard to villous hemodynamics, intestinal countercurrent exchange and intraluminal concentration gradients in the lumen. It is concluded that the countercurrent exchanger represents, under physiological conditions, the major limiting factor for the absorption of lipophilic solutes such as8

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05965.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIn enzymic preparations from mouse kidney stimulated with the anabolic steroid Durabolin (nandrolone phenpropionate) lysine and ornithine were shown to inhibit the decarboxylation of each other competitively. The Michaelis constants for the decarboxylations were approximately equal to the inhibition constants of the two amino acids. The pH optima of the decarboxylation of lysine and ornithine were found to be identical. Chromatographic studies of the enzyme preparation on a Sephadex G‐150 Superfine column did not bring about a separation of the two enzyme activities. The ratio of the decarboxylating activities was practically the same during the elution. Lysine decarboxylating activity was also shown to be present in growth hormone stimulated rat liver. The results are in agreement with the assumption that the decarboxylation of lysine and ornithine is carried out by the same enzym

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05966.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractCapillary permeability in adipose tissue for57Co‐cyanocobalamin (57Co‐B12) was determined by the single injection, external registration method. The capillary diffusion capacity, CDC, (the permeability‐surface area product, PS) was 1.1 ml/100 g·min at a capillary extraction of 0.21 and a plasma flow of 6.7 ml/100 g·min. Results were compared to51Cr‐EDTA data from a previous study with similar method and preparation. As CDC(51Cr‐EDTA)/CDC (57Co‐B 12) was 1.81 and as D(51Cr‐EDTA)/D(57Co‐B 12), the ratio between the free diffusion coefficients in water at 37°C, was 1.79, it is concluded that restricted diffusion does not occur in cutaneous tissue for57Co‐B 12 as compared to51Cr‐EDTA,i.e.,51Cr‐EDTA and57Co‐B 12 diffuse across the capillary membrane of adipose tissue at rates proportional to their respective free diffusion coefficients in water. The Pappenheimer equivalent pore radius estimate of 30 Å and the Karnovsky interendothelial 40 Å slit width are both defective in explaining the experimental data. The transendothelial channel system of fused vesicles (Simionescu, Simionescu and Palade 1975) is a possible structural equivalent for the present findings. The results support the hypothesis that capillaries of continuous type exhibit similar permeation characteristics regardless of the tiss

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05967.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractCapillary permeability for the extracellular, hydrophilic indicator,14C‐inulin, was determined in the autoperfused cat gastrocnemius muscle by bolus injection, venous sampling expts. The capillary diffusion capacity, CDC (the permeability‐surface are product, PS), was 0.84 ml/100 g·min, and capillary extraction, E, was 0.307 at a plasma flow of 4.0 ml/100 g·min as average values of 7 expts. Results were compared with51Cr‐EDTA and57Co‐B12 data of previous studies. The findings imply that14C‐inulin is not subject to restricted diffusion across the continuous capillary membranes of skeletal muscle as compared to51Cr‐EDTA as well as57Co‐B12. These hydrophilic indicators pass the capillary barrier at rates proportional to their respective free diffusion coefficients in water. The Pappenheimer equivalent pore radius estimate of 30 Å (or slit width of 37 Å) and the Karnovsky 40 Å interendothelial slit width are inconsistent with the present data which imply a much larger pore size. The transendothelial channel system of fused vesicles is a possible morphological equivalent for the present findings which support the general theory that capillaries of continuous type exhibit similar permeation characteristics regardless of the tissue in which they are located. By kinetic black‐box analysis the extravascular distribution volume for14C‐inulin in skeletal muscle was found to be 13.0 ml/100 g. The data indicate that51Cr‐EDTA, which has about the same molecular radius as sucrose, and14C‐inulin have identical extravascular volumes of distribution and that both molecules presumably enter

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05968.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA rapid and sensitive radioenzymatic method for analysis of choline (Ch) and acetylcholine (ACh) concentrations in rat brain regions is described. The ACh content is obtained as the difference in Ch concentration between a hydrolysed and an unhydrolysed tissue sample. The ACh content was 16 ± 1.0 nmol/g in the cortex and 76 ± 2.4 nmol/g in the striatum, and the corresponding Ch values were 23 ± 2.5 and 33 ±

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05969.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe Falck‐Hillarp fluorescence technique was employed in an attempt to determine the distribution of sympathetic innervation in frog skin. No evidence was found of a direct monoaminergic nerve supply to the cells of the non‐glandular epithelium in the epidermis. Instead, specific fluorescence was mainly confined to the vicinity of the skin glands. Fluorescent fibers were observed surrounding the mucous type of gland. The secretory content of this gland was not fluorescent. In the granular type of gland the main source of fluorescence was the secretory granules filling the lumen. These developed a fluorescence in the spectral range of 5‐hydroxytryptamine. The brightness of the fluorescence indicated a very high content of this amine. Fluorimetric analysis showed that no catecholamines were present in the secretion. In glands devoid of secretory granules there were some indications of a monoaminergic innervation of the secretory epithelium, but this was hard to determine because of the abundant nonspecific fluorescence. Sparse dots of specific fluorescence were found close to the surrounding smooth muscle cells. — These findings rule out the possibility of a direct sympathetic nervous control of the non‐glandular epithelium in frog skin but indicate that this is instead confined to the sk

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05970.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe ionic outflow, mainly consisting of Na+and Cl‐, from the mucous glands in an excised nerve‐skin preparation of frog has been determined by recording the conductance changes occurring in a fluid layer covering a small area of the skin surface. In the main series of experiments the glands were activated by stimulation of sympathetic nerve fibers in the skin nerve. The relationship between the ionic outflow and the number of nerve volleys was studied over a wide range. The outflow per impulse was found to be fairly constant during the first tens of impulses but diminished gradually with increasing number of stimuli up to a certain maximum value—varying in different preparations—after which the outflow ceased completely. During the initial phase of stimulation the outflow is most likely caused by an ejection of preformed secretion due to the contractions of the glandular myoepithelium. The continued outflow in the later stages of the stimulation periods must be due to production of new secretion. Since the glandular epithelium is devoid of nerve terminals a nervous control of the ionic secretion can only be explained by an indirect influence mediated either by transmitter diffusion from the myoepithelial nerve endings or by a close electric coupling between the contractile and the secretory gland cells. Adrenaline and noradrenaline induce ionic outflows which like those evoked by nerve stimulation are inhibited by the β‐adrenoreceptor blocker propranolol, α‐adrenoreceptor blockers being without effect. A serendipitous finding of tonus changes in the frog skin during nerve stimulation is a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05971.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIndividual mucous glands in the toe web were studied in curarized decerebrate frogs using vital microscopy in combination with still or motion photomicrography. By changing the focus position to different levels various structures in the gland could be identified and their changes during glandular activation studied. The first visible effect of nerve stimulation was a contraction of the myoepithelium and probably also structural changes of the secretory epithelium resulting in a narrowing of the glandular lumen. Following this, the tricuspid valve opened and secretion was ejected. The latency and time course of the contractile response to nerve stimulation were determined and the influence of the number of stimuli on the duration of the contraction and relaxation phases was analyzed. Comparisons were made with reflex activation of the gland as well as with neurohormonal stimulation. The myoepithelial contraction was found to be under adrenergic control. Of the smooth‐muscle stimulants tested only Substance P induced contractions. The time course of the ionic outflow from the toe web was determined by conductance measurements in the fluid surrounding the web and compared with the visually observed phenomena. The initial outflow was concomitant with the phasic myoepithelial contraction but a continued secretion could also be observed and recorded from glands kept in a steady state of contraction by iterative nerve stimulation. The functions of the toe web glands were found to be critically dependent on a maintained circulation in the surrounding capillary networ

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05972.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05973.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb05974.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY