scholarly journals Kinetic Studies on Uptake of Serotonin and Noradrenaline into Pial Arteries of Rats

1990 ◽  
Vol 10 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Jing-Yu Chang ◽  
J. E. Hardebo ◽  
Ch. Owman
Keyword(s):  
Kinetic Studies ◽  
Sympathetic Nerves ◽  
Substantial Effect ◽  
Nerve Fibers ◽  
Experimental Conditions ◽  
Pial Arteries ◽  
Uptake Process ◽  
5 Ht Uptake ◽  
Na Uptake

A population of cerebrovascular nerve fibers have recently been found to store serotonin (5-hydroxytryptamine; 5-HT). There is reason to assume that these 5-HT-containing fibers have a sympathetic rather than an intracerebral origin. This was further elucidated in the present study in which the uptake mechanisms of 5-HT and noradrenaline (NA) were characterized and compared in rat pial arteries by measuring the accumulation of [3H]5-HT and [14C]NA under various experimental conditions in vitro. Sympathectomized vessels served as blanks. The uptake into the perivascular sympathetic nerves was dependent on time as well as concentration and was saturable. The Km values were similar, 0.17 μ M for 5-HT and 0.15 μ M for NA, but the Vmax value was 10 times higher for NA (2.38 and 25 pmol/mg/15 min, respectively). The two amines competed with each other in the sympathetic uptake, as studied by inhibition of the accumulation of one labeled amine by the other nonlabeledamine. Corticosterone, acting on the extraneuronal process, significantly inhibited the 5-HT uptake but had no substantial effect on NA. Reserpine, blocking the intraaxonal vesicular stores, markedly attenuated the accumulation of NA, but not of 5-HT. The selective uptake blocker paroxetine reduced the 5-HT uptake with much higher potency than the NA uptake, whereas desipramine predominantly inhibited NA uptake. The pial 5-HT uptake was not significantly affected by lesion of the raphe complex, whereas it was reduced to half following superior cervical ganglionectomy. The results suggest that the 5-HT present in nerves associated with pial vessels at the base of the brain is taken up through an efficient axonal mechanism, functionally related but not identical to the uptake process for NA.

scholarly journals Effects of Kininase II Inhibitors on the Vasomotor Response to Bradykinin of Feline Intracranial and Extracranial Arteries in vitro and in situ

1983 ◽  
Vol 3 (3) ◽  
pp. 339-345 ◽  
Author(s):  
Michael Wahl ◽  
Alan R. Young ◽  
Lars Edvinsson ◽  
Franz Wagner
Keyword(s):  
Cerebral Arteries ◽  
Surrounding Tissue ◽  
Experimental Conditions ◽  
Pial Arteries ◽  
Simultaneous Application ◽  
Kininase Ii ◽  
Middle Cerebral Arteries ◽  
Prostaglandin F

Bradykinin is known to effect a vasodilatation of feline cerebral arteries in situ and of both human and feline pial arteries in vitro. In order to demonstrate whether kininase II (localized within the vessel wall or in the surrounding tissue or fluid) influences the response to bradykinin, two different inhibitors of this bradykinin degradation enzyme were tested. Perivascular microapplication of potentiator C (10−10–10−4 M) or captopril (10−10–10−3 M) did not, by itself, change the diameter of feline pial arteries (87–305 μm) in situ. In a similar investigation, the dilating action of bradykinin (10−8–10−5 M) was not modified by the simultaneous application of potentiator C or captopril (10−5 M). Furthermore, the relaxing effect of bradykinin (10−10–10−4 M) on isolated feline middle cerebral arteries (preconstricted with 5-hydroxytryptamine or prostaglandin F2α) was not influenced by the presence of captopril (10−7 M). In contrast, when studied on isolated extracranial vessel segments (feline sublingual artery), bradykinin caused a concentration-dependent constriction of the artery. This constriction was completely reversed to dilatation in the presence of captopril (10−7 M). Moreover, the characteristic effect of kininase II inhibition was demonstrated in the isolated guinea pig ileum preparation. In this instance, bradykinin induced a concentration-dependent contraction that was enhanced by potentiator C or captopril. We conclude, therefore, that bradykinin exerts variable responses on vascular smooth muscle, depending on the species used, the muscle location and experimental conditions. Finally, the in situ and in vitro findings for pial and middle cerebral arteries demonstrate that kininase II does not modify the dilating effect of bradykinin under our experimental conditions.

scholarly journals Heterogeneous ventricular sympathetic innervation, altered β-adrenergic receptor expression, and rhythm instability in mice lacking the p75 neurotrophin receptor

2010 ◽  
Vol 298 (6) ◽  
pp. H1652-H1660 ◽  
Author(s):  
Christina U. Lorentz ◽  
Eric N. Alston ◽  
Todd Belcik ◽  
Jonathan R. Lindner ◽  
George D. Giraud ◽  
...  
Keyword(s):  
Adrenergic Receptor ◽  
Sympathetic Neurons ◽  
Sympathetic Innervation ◽  
Sympathetic Nerves ◽  
Nerve Fibers ◽  
Receptor Expression ◽  
Neurotrophin Receptor ◽  
P75 Neurotrophin Receptor ◽  
Semaphorin 3A

Sympathetic nerves stimulate cardiac function through the release of norepinephrine and the activation of cardiac β1-adrenergic receptors. The sympathetic innervation of the heart is sculpted during development by chemoattractive factors including nerve growth factor (NGF) and the chemorepulsive factor semaphorin 3a. NGF acts through the TrkA receptor and the p75 neurotrophin receptor (p75NTR) in sympathetic neurons. NGF stimulates sympathetic axon extension into the heart through TrkA, but p75NTR modulates multiple coreceptors that can either stimulate or inhibit axon outgrowth. In mice lacking p75NTR, the sympathetic innervation density in target tissues ranges from denervation to hyperinnervation. Recent studies have revealed significant changes in the sympathetic innervation density of p75NTR-deficient (p75NTR−/−) atria between early postnatal development and adulthood. We examined the innervation of adult p75NTR−/− ventricles and discovered that the subendocardium of the p75NTR−/− left ventricle was essentially devoid of sympathetic nerve fibers, whereas the innervation density of the subepicardium was normal. This phenotype is similar to that seen in mice overexpressing semaphorin 3a, and we found that sympathetic axons lacking p75NTR are more sensitive to semaphorin 3a in vitro than control neurons. The lack of subendocardial innervation was associated with decreased dP/d t, altered cardiac β1-adrenergic receptor expression and sensitivity, and a significant increase in spontaneous ventricular arrhythmias. The lack of p75NTR also resulted in increased tyrosine hydroxylase content in cardiac sympathetic neurons and elevated norepinephrine in the right ventricle, where innervation density was normal.

Accumulation of 5-Hydroxytryptamine by Aging Platelets: Studies in a Model of Suppressed Thrombopoiesis in Dogs

1994 ◽  
Vol 71 (04) ◽  
pp. 488-492 ◽  
Author(s):  
Eduardo Aranda ◽  
Myriam Pizarro ◽  
Jaime Pereira ◽  
Diego Mezzano
Keyword(s):  
Platelet Count ◽  
Kinetic Studies ◽  
Blood Platelet ◽  
Mean Value ◽  
Estradiol Valerate ◽  
Survival Times ◽  
5 Ht Uptake ◽  
Linear Decay

SummaryThrombocytopenia was induced in healthy, male mongrel dogs by intramuscular injection of a single dose of estradiol valerate (1 mg/kg). A steady, almost linear decay of the blood platelet count starting about day 6 post-estradiol and attaining a mean value of 14 × 103 platelets/pi one week later was observed. Thrombocytopenia is explained mainly by suppression- of thrombocytopoiesis, as established by two independent ways: 1. Megakaryocytes in the bone marrow were markedly reduced. 2. Kinetic studies with 11‘In labeled autologous platelets revealed a nearly linear decay of the radioactivity and mean survival times within the expected range. The progressive reduction in the platelet count is associated with an increase in the mean age of the platelets still circulating. Following estradiol injection, platelet 5-hydroxytryptamine (5-HT) increased from a basal value of 130 ± 30 ng/108 platelets (platelet count of 351 ± 53 × 103 platelets/p.1) to 343 ± 100 ng/108platelets eleven days latter, when the platelet count dropped to 32 ± 18 × 103 platelets/pi No significant changes in the number or affinity of the 5-HT uptake receptors could be demonstrated in platelets exposed in vitro and in vivo to estradiol. Our results indicate that aging platelets accumulate 5-HT, probably by a sustained exposure to the monoamine in plasma, confirming previous observations based on models in which thrombopenia was induced by immune and mechanical means.

scholarly journals Evidence for a novel ATP-dependent membrane-associated protease in spinach leaf mitochondria

1995 ◽  
Vol 310 (2) ◽  
pp. 527-531 ◽  
Author(s):  
C Knorpp ◽  
C Szigyarto ◽  
E Glaser
Keyword(s):  
Proteolytic Activity ◽  
Spinacia Oleracea ◽  
Plant Mitochondria ◽  
Kinetic Studies ◽  
Thiol Group ◽  
Nicotiana Plumbaginifolia ◽  
Experimental Conditions ◽  
Spinach Leaf ◽  
Membrane Bound

We report the presence of an ATP-dependent proteolytic activity in spinach (Spinacia oleracea) leaf mitochondria. The proteolysis was observed as degradation of newly imported precursor protein. The precursor studied was that of the ATP synthase F1 beta subunit of Nicotiana plumbaginifolia, transcribed and translated in vitro. Degradation of pre-F1 beta was observed during kinetic studies of import in vitro. The degradation was characterized in chase experiments in which the precursor was imported into mitochondria. The import reaction was subsequently stopped by the addition of valinomycin and oligomycin. The fate of the imported precursor inside the mitochondria was monitored under different experimental conditions. There was no proteolytic degradation of the newly imported precursor at 15 degrees C, whereas 50% of the precursor was degraded after a 45 min incubation at 25 degrees C. The proteolytic activity was found to be ATP-dependent and was partially inhibited by a metal chelator, o-phenanthroline. Fractionation of mitochondria prior to degradation showed that all the ATP-dependent degradative activity was associated with the mitochondrial membrane fraction. The membrane-bound protease was inhibited by Pefabloc [4-(2-aminoethyl)-benzenesulphonyl fluoride hypochloride], an inhibitor of serine-type proteases and by N-ethylmaleimide, a thiol group reagent. Our studies thus describe a novel ATP-dependent membrane-associated serine-type protease in plant mitochondria that is capable of degrading newly imported non-assembled proteins.

scholarly journals Effects of altered tonicity by sodium chloride onl-tryptophan binding to hepatic nuclei

2000 ◽  
Vol 278 (6) ◽  
pp. C1237-C1245 ◽  
Author(s):  
Herschel Sidransky ◽  
Ethel Verney ◽  
Jan Orenstein
Keyword(s):  
Kinetic Studies ◽  
Significant Inhibition ◽  
Inhibitory Effects ◽  
Experimental Conditions ◽  
Isolated Nuclei ◽  
Hepatic Cells ◽  
In Vitro Incubation ◽  
Nacl Concentration

This study was concerned with the effects of NaCl administered in vivo or added in vitro to isolated nuclei on [3H]tryptophan binding to rat hepatic nuclei assayed in vitro. Hypertonic (10.7%) NaCl administered in vivo to rats caused at 10 min a marked decrease in in vitro binding (total and specific) of [3H]tryptophan to hepatic nuclei. In vitro incubation of isolated hepatic nuclei, but not of isolated nuclear envelopes, with added NaCl (particularly at 0.125 × 10−4 M and 0.25 × 10−4 M) revealed significant inhibition of [3H]tryptophan binding. However, isolated hepatic nuclear envelopes prepared after in vitro incubation of isolated nuclei with added NaCl did show inhibition of [3H]tryptophan binding (total and specific) compared with controls. Other salts (KCl, MgCl2, NaHCO3, NaC2H3O2, NaF, or Na2SO4), at similar concentrations to that of NaCl except for MgCl2, when added to isolated nuclei did not appreciably inhibit nuclear tryptophan binding. Kinetic studies of in vitro nuclear [3H]tryptophan binding in the presence of 0.125 × 10−4 M NaCl revealed that binding decreased at 0.5 h and continued to 2 h compared with nuclear [3H]tryptophan binding with controls (without NaCl addition). The results obtained in vivo in rats and those obtained in vitro with isolated hepatic nuclei revealed NaCl-induced inhibitory effects on [3H]tryptophan binding to hepatic nuclei. Although the inhibitory effects were similar under the two different experimental conditions, the mechanism for each may be different in that the NaCl concentration in hepatic cells after administration of NaCl in vivo was appreciably higher than the low levels added in vitro to the isolated hepatic nuclei.

Observations of Frozen-Hydrated Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 504-505
Author(s):  
D. Chrétien ◽  
D. Job ◽  
R.H. Wade
Keyword(s):  
Fourier Transforms ◽  
Structural Complexity ◽  
Image Contrast ◽  
Phase Behaviour ◽  
Experimental Conditions ◽  
Thin Sections ◽  
Surface Lattice ◽  
Cilia And Flagella ◽  
Outstanding Question

Microtubules are filamentary structures found in the cytoplasm of eukaryotic cells, where, together with actin and intermediate filaments, they form the components of the cytoskeleton. They have many functions and show various levels of structural complexity as witnessed by the singlet, doublet and triplet structures involved in the architecture of centrioles, basal bodies, cilia and flagella. The accepted microtubule model consists of a 25 nm diameter hollow tube with a wall made up of 13 paraxial protofilaments (pf). Each pf is a string of aligned tubulin dimers. Some results have suggested that the pfs follow a superhelix. To understand how microtubules function in the cell an accurate model of the surface lattice is one of the requirements. For example the 9x2 architecture of the axoneme will depend on the organisation of its component microtubules. We should also note that microtubules with different numbers of pfs have been observed in thin sections of cellular and of in-vitro material. An outstanding question is how does the surface lattice adjust to these different pf numbers?We have been using cryo-electron microscopy of frozen-hydrated samples to study in-vitro assembled microtubules. The experimental conditions are described in detail in this reference. The results obtained in conjunction with thin sections of similar specimens and with axoneme outer doublet fragments have already allowed us to characterise the image contrast of 13, 14 and 15 pf microtubules on the basis of the measured image widths, of the the image contrast symmetry and of the amplitude and phase behaviour along the equator in the computed Fourier transforms. The contrast variations along individual microtubule images can be interpreted in terms of the geometry of the microtubule surface lattice. We can extend these results and make some reasonable predictions about the probable surface lattices in the case of other pf numbers, see Table 1. Figure 1 shows observed images with which these predictions can be compared.

In Vivo Effect of Suloctidil as an Antiplatelet Agent

1979 ◽  
Vol 41 (03) ◽  
pp. 465-474 ◽  
Author(s):  
Marcia R Stelzer ◽  
Thomas S Burns ◽  
Robert N Saunders
Keyword(s):  
Ex Vivo ◽  
Antiplatelet Agent ◽  
Ratio Method ◽  
Platelet Aggregate ◽  
Permanent Effect ◽  
Platelet Aggregates ◽  
5 Ht Uptake ◽  
High Doses

SummaryThe relationship between the effects of suloctidil in vivo as an antiplatelet agent and in vitro as a modifier of platelet serotonin (5-HT) parameters was investigated. Suloctidil was found to be effective in reducing platelet aggregates formation in the retired breeder rat as determined using the platelet aggregate ratio method (PAR) with an ED50 of 16.1 mg/kg 24 hours post administration. In contrast to the hypothesis that 5-HT depletion is involved in the anti-aggregatory mechanism of suloctidil, no correlation was found between platelet 5- HT content and this antiplatelet activity. Reduction of platelet 5-HT content required multiple injections of high doses (100 mg/kg/day) of suloctidil. Suloctidil administration for 8 days at 100 mg/kg/day, which lowered platelet 5-HT content by 50%, resulted in no permanent effect on ex vivo platelet 5-HT uptake or thrombin-induced release, nor alteration in the plasma 5-HT level. However, these platelets exhibited a short-lived, significant increase in percent leakage of 5-HT after 30 minutes of incubation. Therefore, suloctidil treatment at high doses may with time result in platelet 5-HT depletion, however this effect is probably not related to the primary anti-aggregatory activity of the drug.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

Desmopressin (DDAVP) Enhances Platelet Adhesion to the Extracellular Matrix of Cultured Human Endothelial Cells through Increased Expression of Tissue Factor

1997 ◽  
Vol 77 (05) ◽  
pp. 0975-0980 ◽  
Author(s):  
Angel Gálvez ◽  
Goretti Gómez-Ortiz ◽  
Maribel Díaz-Ricart ◽  
Ginés Escolar ◽  
Rogelio González-Sarmiento ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Tissue Factor ◽  
Platelet Adhesion ◽  
Umbilical Vein ◽  
Procoagulant Activity ◽  
Experimental Conditions ◽  
Chromogenic Assay

SummaryThe effect of desmopressin (DDAVP) on thrombogenicity, expression of tissue factor and procoagulant activity (PCA) of extracellular matrix (ECM) generated by human umbilical vein endothelial cells cultures (HUVEC), was studied under different experimental conditions. HUVEC were incubated with DDAVP (1, 5 and 30 ng/ml) and then detached from their ECM. The reactivity towards platelets of this ECM was tested in a perfusion system. Coverslips covered with DD A VP-treated ECMs were inserted in a parallel-plate chamber and exposed to normal blood anticoagulated with low molecular weight heparin (Fragmin®, 20 U/ml). Perfusions were run for 5 min at a shear rate of 800 s1. Deposition of platelets on ECMs was significantly increased with respect to control ECMs when DDAVP was used at 5 and 30 ng/ml (p <0.05 and p <0.01 respectively). The increase in platelet deposition was prevented by incubation of ECMs with an antibody against human tissue factor prior to perfusion. Immunofluorescence studies positively detected tissue factor antigen on DDAVP derived ECMs. A chromogenic assay performed under standardized conditions revealed a statistically significant increase in the procoagulant activity of the ECMs produced by ECs incubated with 30 ng/ml DDAVP (p <0.01 vs. control samples). Northern blot analysis revealed increased levels of tissue factor mRNA in extracts from ECs exposed to DDAVP. Our data indicate that DDAVP in vitro enhances platelet adhesion to the ECMs through increased expression of tissue factor. A similar increase in the expression of tissue factor might contribute to the in vivo hemostatic effect of DDAVP.

Insulin secretion in the spiny mouse (Acomys cahirinus). Dose and time kinetic studies with glucose in vivo and in vitro

Diabetes ◽  
1975 ◽  
Vol 24 (12) ◽  
pp. 1094-1100 ◽  
Author(s):  
A. Rabinovitch ◽  
A. Gutzeit ◽  
A. E. Renold ◽  
E. Cerasi
Keyword(s):  
Insulin Secretion ◽  
Kinetic Studies ◽  
Spiny Mouse ◽  
Acomys Cahirinus
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