Biomedical subjects

V Ceña

Publications and source records attributed to V Ceña.

46 records · Page 3Linked to original sources

PubMed1984

Uptake of [3H]-nicotine and [3H]-noradrenaline by cultured chromaffin cells.

Three day-old cultured bovine adrenal chromaffin cells incubated at room temperature with Krebs-HEPES solution containing different concentrations of [3H]-nicotine, took up and retained increasing amounts of the drug by a mechanism that did not saturate. Concentrations of cold nicotine as high as 100 microM did not alter the amount of [3H]-nicotine retained by cells. Imipramine, cocaine, tetracaine or mecamylamine, at concentrations (10 microM) that blocked the catecholamine secretory effects of nicotine completely, did not modify the uptake of [3H]-nicotine. Both imipramine and cocaine drastically inhibited [3H]-noradrenaline uptake by cells in a concentration-dependent manner (IC50S of 0.08 and 1 microM, respectively). These data indicate that the secretory effects of nicotine are not coupled to its previous uptake into cells, and are evidence in favour of a site of action for nicotine located in or at the surface of the chromaffin cell membrane.

Adrenal Medulla↗

PubMed1984

Orthograde and retrograde axonal transport of calmodulin in a cat noradrenergic neurone.

Subcellular distribution studies of calmodulin in cat sympathetic ganglia demonstrated that about 90% of the protein remained in the 27,000 g supernatant, suggesting that it is a cytosolic protein. Only 4.5% was recovered in the microsomal fraction pellet. The inferior mesenteric ganglia contained 93.3 +/- 3 ng calmodulin per ganglion, and segments of unligated cat hypogastric nerves had 6.53 +/- 0.32 ng per 5 mm segment. When the nerve was ligated in the middle and left in the cat for 1-6 days, substantial amounts of calmodulin accumulated in segments of nerve immediately proximal (P1) and distal (D1) to the ligature. The amounts found in P1 amounted to 15.3, 20, 30.4 and 39.4 ng calmodulin per 5 mm segment 1, 2, 3 and 6 days after ligation, respectively. The average rate of transport was 5.5 mm per day, which corresponds to a slow component b of axonal transport (SCb). The accumulation of calmodulin in D1 was also increased with the time of ligation. After 1, 2, 3 and 6 days, the amounts of the protein found in D1 were 14.4, 17.7, 19 and 21 ng per 5 mm segment, respectively. The calculated mean rate for the retrograde transport was 3.9 mm per day. Decentralization of the inferior mesenteric ganglia did not affect the rate of accumulation of calmodulin or the basal amounts found in ganglia and nerves. Local injection inhibited the orthograde, but not the retrograde axonal transport of the protein. It is concluded that calmodulin undergoes a process of slow orthograde axonal transport probably incorporated into the axoplasmic matrix of a network of actin microfilaments. The protein is also transported in a retrograde manner.

Animals↗

PubMed1983

Pharmacological dissection of receptor-associated and voltage-sensitive ionic channels involved in catecholamine release.

The experiments were designed to quantify pharmacologically the degree of participation of channels associated with the nicotinic cholinoceptor compared with voltage-sensitive channels during the evoked release of [3H]noradrenaline from prelabelled 3-7-day old cultured bovine adrenal chromaffin cells. To achieve this purpose we studied (a) the release of [3H]noradrenaline evoked by secretagogues known to trigger the secretory response through activation of receptor-associated channels (acetylcholine, nicotine), voltage-sensitive Na+ (veratridine) and Ca2+ (high [K+] ) channels or direct, channel-independent promotion of Ca2+ entry (ionomycin); and (b) the selective blockade of some of those responses using ionic manipulations (Na+ deprivation, high Mg2+) or drugs known to block the activity of receptor-operated channels (imipramine, cocaine), voltage-dependent Na+ (tetrodotoxin) or Ca2+ (nitrendipine) channels. Inhibition by nitrendipine, a potent Ca2+ antagonist, of the secretory responses to both nicotine and high [K+] indicates a preferential Ca2+ entry through voltage-sensitive channels during the secretory process. Blockade by cocaine and imipramine of the release of [3H]noradrenaline evoked by acetylcholine and nicotine, without alteration of the responses to high [K+], veratridine or ionomycin, speaks in favor of a selective inactivation of the nicotinic receptor-associated channel. Since Na+ deprivation abolished [3H]noradrenaline release produced by nicotine, it seems that Na+ entry through the receptor-linked ionophore might be a primary event in the initiation of the secretory process; the fact that tetrodotoxin did not affect the release favors this view. However, veratridine induced a tetrodotoxin-sensitive secretory response, suggesting the presence of voltage-sensitive Na+ channels which might physiologically be used to propagate action potentials through gap junctions between adjacent chromaffin cells, only in the intact gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1982

Effects of the cardiotonic drug ARL-115 on the release of noradrenaline from the cat atrium, the binding of 3H-ouabain to plasma membranes and the movements of calcium in mitochondria.

The cardiotonic pyridine derivative ARL-115 increased the spontaneous and electrically-evoked release of 3H-noradrenaline from the cat right atrium superfused with oxygenated Krebs-bicarbonate solution at 37 degrees C. On the contrary, ouabain inhibited the evoked release while it also enhanced the spontaneous release of the transmitter. Vanadate did not affect either spontaneous or evoked release. Tetraethylammonium chloride (TEA) and 4-aminopyridine (4-AP) greatly potentiated 3H-noradrenaline release induced by electrical stimulation; when applied in addition to each agent, ARL-115 failed to further increase the secretory response. 3H-ouabain specific binding to partially purified bovine adrenal medulla plasma membranes was very efficiently antagonized by cold ouabain, but not by vanadate or ARL-115, even at concentrations as high as 10(-3) mol/l. 45Ca uptake into isolated bovine adrenal medulla mitochondria was prevented by dinitrophenol (DNP) but unchanged in the presence of ARL-115. 45Ca release from preloaded mitochondria was, again, markedly increased by DNP, but not affected by ARL-115. The results suggest that ARL-115 enhances the release of noradrenaline from cardiac sympathetic nerves by a TEA- and 4-AP-like action. In this manner, ARL-115 would inactivate the K+ current in the nerve terminals, thereby prolonging the duration of the action potential, allowing the Ca2+ channels to remain open longer and more Ca2+ to enter the terminal. ARL-115 is not acting like digitalis.

Adrenal Medulla↗

PubMed1982

Presence and axonal transport of cholinoceptor, but not adrenoceptor sites on a cat noradrenergic neurone.

1. Noradrenaline release and radioligand binding studies were carried out in the cat hypogastric nerve ligated in vito 2 cm distal to the inferior mesenteric ganglion for different time periods, and in different effector organs.2. Large quantities of noradrenaline and dopamine beta-hydroxylase (DBH) accumulated in the segments of nerve immediately proximal (P(1)) and distal (D(1)) to the ligation, with rates of about 100 and 25 mm/24 hr for the orthograde and retrograde transport, respectively.3. Nicotine evoked the release of noradrenaline from P(1) and atrial slices; the secretory response to nicotine was completely antagonized by mecamylamine. [(3)H]alpha-bungarotoxin biding to membranes from P(1) allowed the estimation of a K(D) of 2.97 nm and a B(max) of 1639 f-mole/mg protein.4. Acetylcholine inhibited the release of endogenous noradrenaline evoked by high K(+) stimulation in atrial slices, but not in P(1) segments. Similarly, carbachol decreased [(3)H]noradrenaline release induced by electrical stimulation (twenty-six shocks, 2 Hz, 5 msec) in the atrium but not in P(1).5. [(3)H]Quinuclydinilbenzylate ([(3)H]QNB) specifically binds to membranes from P(1) and vas deferens, following a saturation curve. In the case of P(1) segments taken 48 hr after ligation a K(D) of 0.35 nm and a B(max) of 129 f-mole/mg protein were found.6. The fact that the B(max) in P(1) and D(1) increased with the time of ligation suggests that orthograde and retrograde axonal transports of muscarinic binding sites exist in this nerve, with approximate rates of transport of 15 and 8 mm/24 hr, respectively.7. As far as adrenoceptors are concerned, we observed that yohimbine or phentholamine did not modify transmitter release from P(1), evoked by high K(+) or electrical stimulation. However, yohimbine enhanced the release of [(3)H]noradrenaline induced by electrical stimulation from splenic slices of the same animals.8. [(3)H]Clonidine, [(3)H]dihydroergocryptine or [(3)H]dihydroalprenolol ([(3)H]DHA) did not specifically bind to membranes from P(1), in spite of the fact that they showed typical saturation curves for specific binding in cortex and atrial membranes from the same cats.9. In conclusion, these data (a) further show that the ligated hypogastric nerve is a good model of noradrenergic nerve terminal free of effector cell; (b) provide direct evidence for the neural location of nicotinic receptors whose activation trigger noradrenaline release from noradrenergic neurones; (c) demonstrate the neural location and axonal transport of muscarinic receptor sites, but leave certain doubts about its functional role in this noradrenergic neurone; and (d) do not support the hypothesis that alpha and beta-adrenoceptors which modulate noradrenaline release from peripheral noradrenergic nerve terminals are neurally (or prejunctionally) located.

Animals↗

PubMed1980

Release of noradrenaline from the ligated cat hypogastric nerve.

After in vivo ligation for 24 of the cat hypogastric nerve, large amounts of noradrenaline (NA) and dopamine beta-hydroxylase (DBH) accumulated in the nerve segment immediately proximal to the ligature (P 1). In vitro incubation of 24-h-ligated nerves ((segments P1 and P2) in oxygenated Krebs solution at 37 degrees C in the presence of the ionophore X537A or high K+ concentrations caused a marked release of endogenously accumulated NA into the incubation medium. High-K+-evoked release was entirely dependent on extracellular Ca2+. Electrical nerve stimulation caused an 80% tissue NA loss, but the transmitter could not be found in the medium as intact NA. These results suggest that the in vivo ligated cat hypogastric nerve may serve as a useful model of adrenergic nerve terminals free of effector cells.

Animals↗

PubMedDate not supplied

[Cysteine proteinase and neurodegeneration].

OBJECTIVE: This is a review of the part played by the cysteine proteases in different physiological and pathological processes. DEVELOPMENT: Apoptotic processes have a crucial function in control of the number of cells in multicellular organisms, both during development and throughout life. Alterations in these are closely related to different pathological processes, from cancer (with fewer apoptotic processes) to the degenerative disorders in which apoptosis is increased. Although the stimuli which may induce apoptosis are very varied, the apoptotic phenotypes are similar. Different metabolic routes are involved in apoptosis and in these changes, both in transcription and postranscription. The latter form the basis of this paper. We review the role of the cysteine protease family, in which the caspases and calpains are the best representatives, which have been related to different degenerative models. In this review we describe the stimuli and cascades of intracellular signalling which occur on activation. CONCLUSION: These proteases are involved in many situations involving the development and maintenance of the number of cells in the tissues, both physiological and pathological. They may be considered to be possible therapeutic targets in neurodegenerative diseases such as Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's chorea.

Apoptosis↗

PubMedDate not supplied

[The role of the mitochondrial permeability transition pore in neurodegenerative processes].

AIMS: To review the role played by the mitochondrial permeability transition pore (MPTP) in different physiological and pathological processes. METHOD: Both genetic and functional alterations in mitochondria can lead to errors that trigger programmed cell death, which in turn give rise to a number of diseases that affect the nervous system. Over the last few years the mitochondrion has been seen as the link between the different signalling pathways involved in some degenerative processes. The mitochondrion seems to play an important part in the cellular decision making that leads, irreversibly, toward the execution phase in cellular death processes. This being the case, the action would be mediated by the permeability of its membranes, through the formation of the mitochondrial permeability transition pore, and would involve phenomena such as the dissipation of the mitochondrial electrochemical potential and the release of substances from within it. These substances include apoptosis inducing factor (AIF), apoptosis protease activating factor 1 (apaf 1), cytochrome c and members of the protease family: the caspases. These alterations have been described in neurodegenerative pathologies such as Alzheimer s and Parkinson s disease, amyotrophic lateral sclerosis and transmissible spongiform encephalopaties. CONCLUSIONS: Designing pharmaceutical products capable of interfering with the functions of MPTP would allow a better therapeutic approach in neurological pathologies.

Animals↗

PubMedDate not supplied

[Pharmacological targets in neurodegenerative diseases].

The frequency, morbidity and complexity of neurodegenerative diseases (NDD) make them the greatest therapeutic challenge to Medicine today. These diseases are characterized by a decreased number of cells in certain neuronal populations, which is clinically reflected in the appearance of specific symptoms. In this study, we will centre our attention on the two fundamental lines of action that, from a pharmacological point of view, are available for the treatment of NDD. The first is aetiopathogenic, and is aimed at stopping cell death and promoting the recovery of cell populations. The second line is physiopathological and seeks to prevent, delay or palliate the appearance of the symptoms indicating an alteration in the levels of neurotransmitters, and its chief objective is to maintain them. Pharmacology has already provided neurologists with a wide range of tried and tested drugs, yet the results obtained in research laboratories in the last few years seem to indicate that the number of therapeutic possibilities are very likely to rise sharply in the future. Progress made in genomics and the better understanding of cellular biochemical cycles allow us to expect that this century will finally be that of the Neurosciences, and that Neurology, without losing its cognitive essence, will start to be considered to be a speciality that is as therapeutic as it is diagnostic.

Adjuvants, Immunologic↗

PubMedDate not supplied

[The serine proteases and their function in neuronal death processes].

AIMS: In this review we analyse the role played by the serine proteases in the nervous system and we focus on the role they play in degenerative processes. DEVELOPMENT: These proteolytic enzymes, together with the caspases, play a vital role in the processes regulating cell functioning, both in the development stages and following the response to a harmful stimulus. This family of proteases includes the granzymes and thrombin (TR). The former, which are closely related to proteases I and II and cathepsin G, are situated in the cytoplasmic granules of the activated T lymphocytes, together with other proteins such as perforin or cytolysin. Granzymes A and B are linked to degenerative processes. These enter the target cells thanks to the action of perforin and once inside they are translocated to the nucleus. Granzyme A has been isolated and identified as the agent responsible for the immediate and complete retraction of neurites in different models. Its physiological substrates include fibronectin, type IV collagen and the proteoglycans. Granzyme B is characterised by its being a cysteine protease with substrates such as prointerleukin 1 beta, TR receptor and poly(ADP ribose) polymerase. The family of TR type proteases includes proteases such as TR itself, plasmin, kallikrein, urokinase plasminogen activator and tissue plasminogen activator. TR is considered to be an early modulator in damaged tissues which acts as an extracellular signal of death, leading to the activation of intracellular mechanisms that appear to be mediated by calcium. Serine protease activity is regulated by endogenous inhibitors, such as plasminogen activator inhibitor, protease nexin 1 and neuroserpin. CONCLUSIONS: Upsets in the protease inhibitor balance are crucial in the processes involved in the neuronal plasticity and death induced by ischemia in the brain and by excitotoxins.

Animals↗