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1.
Josef Stingl Petr Zach Josef Sach Jana Vranova Zdenek Suchomel Vaclav Kudrna Jana Mrzilkova David Kachlik Vladimir Musil 《Journal of morphology》2020,281(11):1476-1485
The aim of this study was to perform a pilot histological and quantitative analysis of the blood vessels accompanying the epicardial nerves (vasa nervorum) in the porcine hearts. Twenty healthy porcine hearts were used in this study. The blood vessels were analyzed by light microscopy using four different staining techniques in transverse sections taken from the upper, middle, and lower segments of the anterior part of the interventricular region and the adjacent parts of the right and left ventricles containing epicardial nerves and the endocardial peripheral parts of the Purkinje fibers. In total, 317 epicardial nerves were detected. The vasa nervorum were present in 75.7% of these nerves. The vasa nervorum resembled arterioles and postcapillary and collecting venules. One hundred and forty nine epicardial nerves were perivascular, located in the adventitia of the anterior interventricular artery and vein. The remaining 168 nerves ran freely through the epicardial interstitium. The presence of the vasa nervorum was not related to topographical location or nerve diameter. Additionally, from a total of 33 analyzed ventricular complexes of Purkinje fibers small blood vessels located in their proximity were identified in only two cases. It can be concluded that the majority of the anterior epicardial nerves of porcine heart possess well-developed vasa nervorum. In contrast, similar blood vessels are rarely present in the vicinity of the Purkinje fibers. The data obtained contribute to a better understanding of the nutrition of the cardiac nerves. 相似文献
2.
Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose-free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long-distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long-distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure-chamber technique was cardenolide-free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue. 相似文献
3.
《Developmental cell》2022,57(22):2533-2549.e7
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4.
A. Coulombe H. Duclohier E. Coraboeuf N. Touzet 《European biophysics journal : EBJ》1987,14(3):155-162
Large conductance channels were observed in the membrane of cultured cardiac cells of newborn rats studied with the patch-clamp technique in cell-attached and inside-out configurations. These channels were observed in 4% of the patches. In the cell-attached configuration they exhibited outward rectification and partial inactivation. In the inside-out configuration no rectification occurred but inactivation was present, mainly during hyperpolarizations. Two channels with large single unit conductances (400–450 pS) and one with a smaller conductance (200–250 pS) were frequently observed in the same patch. The two large channels generally had different kinetics. Under steady-state conditions the opening probability of the faster channel appeared to be voltage-independent. The slower channel was activated by depolarization. In asymmetrical solutions the permeability ratios P
Na/P
Cl were 0.03 and 0.24 for the larger and smaller channels, respectively; corresponding values for P
Ba/P
Cl were 0.04 and 0.09. It is proposed that in cardiac membranes the chloride permeability system is composed of widely dispersed microclusters forming grouped channels of different types and sizes. 相似文献
5.
Grant N. Pierce 《Molecular and cellular biochemistry》1987,78(1):89-94
Na+-H+ exchange and passive Na+ flux were investigated in cardiac sarcolemmal vesicles as a function of changing the ionic composition of the reaction media. The inclusion of EGTA in the reaction medium resulted in a potent stumulation of Na+ uptake by Na+-H+ exchange. It was found that millimolar concentrations of Mg2+ and Li+ were capable of inhibiting Na+-H+ exchange by 80%. One mechanism by which these ions may inhibit intravesicular Na+ accumulation by Na+-H+ exchange is via an increase in Na+ efflux. An examination of Na+ efflux kinetics from vesicles pre-loaded with Na+ revealed that Na+, Ca2+, Mg2+ and Li+ could stimulate Na+ efflux. Na+-H+ exchange was potently inhibited by an organic divalent cation, dimenthonium, which screens membrane surface charge. This would suggest that Na+-H+ exchange occurs in the diffuse double layer region of cardiac sarcolemma and this phenomenon is distinctly different from other Na+ transport processes. The results in this study indicate that in addition to a stimulation of Na+ efflux, the inhibitory effects of Mg2+, Ca2+ and Li+ on Na+-H+ exchange may also involve a charge dependent screening of Na+ interactions with the membrane. 相似文献
6.
Cyclic nucleotides play a central role in the modulation of ion channels in a variety of tissues, including the heart. In order to determine the possible role of cyclic GMP (cGMP) in the regulation of the background K channel activity of cardiac cells, the effect of 8-Br-cGMP on the inwardly-rectifying K channels of cultured ventricular myocytes from embryonic chick hearts was examined. 8-Br-cGMP (10-4 to 10-3 M) inhibited these single channel currents within 3 to 10 min. Spontaneous recovery of the currents occurred with prolonged ( 15 min) exposure to 8-Br-cGMP, but this recovery was accompanied by altered channel behavior. Thus, a new long-lasting open state of the channel appeared, in addition to the open state observed prior to 8-Br-cGMP addition. Superfusion of the cells with the muscarinic agonist carbamylcholine (10-5 M) also resulted in inhibition of the currents, which suggests that the cGMP-mediated inhibition of these channels may occur under physiological conditions. Thus, it appears that cGMP may be an important modulator of the background K conductance (and excitability) of cardiac cells. 相似文献
7.
Gordon M. Wahler Dennis E. Coyle Nicholas Sperelakis 《Molecular and cellular biochemistry》1990,93(1):69-76
Platelet-activating factor (PAF) has been implicated as one of the mediators of cardiac anaphylaxis. This phospholipid has been shown to have numerous effects on a variety of tissues, including the heart. Among these effects are alterations in the resting potential and generation of arrhythmias at very low concentrations. This suggests that PAF may modulate the activity of the background, inwardly-rectifying potassium current (IK1). Thus, the effects of PAF on IK1 were examined at the single channel level. Ventricular cells were isolated from adult guinea pig hearts and single channel currents recorded from cell-attached patches. PAF had substantial effects on the single channel currents at sub-nanomolar concentrations (10–11 to 10–10 M). PAF initially caused flickering of the channels, followed by a gradual prolonged depression of channel activity. Since these potassium channels play a major role in determining the resting potential and excitability of the cardiac cell, the effects of PAF on IK1 may play a major role in the deleterious electrophysiological actions of PAF on the heart.Abbreviations IK1
Inwardly-rectifying background potassium current
- Lyso-PAF
Lyso-platelet-activating factor
- PAF
Platelet-activating factor 相似文献
8.
Nicholas Sperelakis 《Molecular and cellular biochemistry》1990,99(2):97-109
The voltage-dependent slow channels in the myocardial cell membrane are the major pathway by which Ca2+ ions enter the cell during excitation for initiation and regulation of the force of contraction of cardiac muscle. The slow channels have some special properties, including functional dependence on metabolic energy, selective blockade by acidosis, and regulation by the intracellular cyclic nucleotide levels. Because of these special properties of the slow channels, Ca2+ influx into the myocardial cell can be controlled by extrinsic factors (such as autonomic nerve stimulation or circulating hormones) and by intrinsic factors (such as cellular pH or ATP level). The slow Ca2+ channels of the heart are regulated by cAMP in a stimulatory fashion. Elevation of cAMP produces a very rapid increase in number of slow channels available for voltage activation during excitation. The probability of a slow channel opening and the mean open time of the channel are increased. Therefore, any agent that increases the cAMP level of the myocardial cell will tend to potentiate Isi, Ca2+ influx, and contraction. The myocardial slow Ca2+ channels are also regulated by cGMP, in a manner that is opposite to that of CAMP. The effect of cGMP is presumably mediated by means of phosphorylation of a protein, as for example, a regulatory protein (inhibitory-type) associated with the slow channel. Preliminary data suggest that calmodulin also may play a role in regulation of the myocardial slow Ca2+ channels, possibly mediated by the Ca2+-calmodulin-protein kinase and phosphorylation of some regulatory-type of protein. Thus, it appears that the slow Ca2+ channel is a complex structure, including perhaps several associated regulatory proteins, which can be regulated by a number of extrinsic and intrinsic factors.VSM cells contain two types of Ca2+ channels: slow (L-type) Ca2+ channels and fast (T-type) Ca2+ channels. Although regulation of voltage-dependent Ca2+ slow channels of VSM cells have not been fully clarified yet, we have made some progress towards answering this question. Slow (L-type, high-threshold) Ca2+ channels may be modified by phosphorylation of the channel protein or an associated regulatory protein. In contrast to cardiac muscle where cAMP and cGMP have antagonistic effects on Ca2+ slow channel activity, in VSM, cAMP and cGMP have similar effects, namely inhibition of the Ca2+ slow channels. Thus, any agent that elevates cAMP or cGMP will inhibit Ca2+ influx, and thereby act to produce vasodilation. The Ca2+ slow channels require ATP for activity, with a K0.5 of about 0.3 mM. C-kinase may stimulate the Ca2+ slow channels by phosphorylation. G-protein may have a direct action on the Ca2+ channels, and may mediate the effects of activation of some receptors. These mechanisms of Ca2+ channel regulation may be invoked during exposure to agonists or drugs, which change second messenger levels, thereby controlling vascular tone. 相似文献
9.
Kenneth S. Leonards 《Molecular and cellular biochemistry》1990,95(1):31-42
To ascertain the roles of the membrane proteins in cation/sarcolemmal membrane binding, isolated rat cardiac sarcolemmal vesicles were extensively treated with Protease (S. aureus strain V.8). SDS-gel electrophoresis, protein and phosphate analysis confirmed that at least 20–22% of the protein, but none of the phospholipid, was solubilized by this procedure, and that the remaining membrane proteins were extensively hydrolyzed into small fragments. The cation binding properties of the treated vesicles were then examined by analyzing their aggregation behavior. The results demonstrate that this procedure had no effect on the selectivity series for di- and trivalent cation binding, or the divalent cation-induced aggregation behavior of the sarcolemmal vesicles at different pHs, indicating that proteins are probably not involved in these interactions and cannot be the low affinity cation binding sites previously observed [21, 22]. It did, however, change the pH at which protons induced sarcolemmal vesicle aggregation, suggesting a possible role for proteins in these processes. Protease treatment also modified the effects of fluorescamine labelling on divalent cation-induced vesicle aggregation, indicating that the NH, groups being labelled with fluorescamine are located on the sarcolemmal proteins. Together, these results support the hypothesis that di- and trivalent cation binding to the sarcolemmal membrane is largely determined by lipid/lipid and/or lipid/carbohydrate interactions within the plane of the sarcolemmal membrane, and that membrane proteins may exert an influence on these interactions, but only under very specialized conditions.Abbreviations MES
2-(N-morpholino)ethanesulfonic acid
- MOPS
3-(N-morpholino) propanesulfonic acid
- HEPES
N-2-Hydroxyethylpiperizine-N-2- ethanesulfonic acid
- CHES
2(N-Cyclohexylamino) ethanesulfonic acid
- DTT
DL-Dithiothreitol
- PMSF
Phenylmethyl-sulfonyl fluoride 相似文献
10.
Knowledge of the diseases of great apes in captivity is essential for captive management of self-sustaining populations. This survey of medical and pathology records of orangutans, gorillas, and one chimpanzee at the National Zoological Park was conducted to provide a data base for improving health care of captive apes. Strongyloidiasis, balantidiasis, and entamoebiasis were recurrent problems in adult and juvenile apes of all species. Cardiac fibrosis also was prevalent in middle-aged apes and was a major cause of mortality. Bacterial infections were prevalent in perinatal orangutans and resulted in the death of two. For gorillas, rheumatoid arthritis associated with mycoplasma infections, and infertility were major problems. Because the pathogenesis of many of these lesions is unknown, survival of great ape populations in captivity may depend on future research on these problems. 相似文献