Dual effects of endogenous DNases on transcriptionally active and inactive chromatin

Experiments on resting hepatocytes with inactive c-fos gene and active albumin gene. We revealed that DNA of the transcribed gene is less susceptible to the influence of endogenous Ca2+/Mg(2+)-dependent DNases in matrix-associated and highly soluble chromatin fractions. In the fraction of low soluble chromatin active gene was more accessible for DNases. Our results indicate that activity of endogenous DNases can change in the transcribed gene locus.     

Mechanisms of antagonistic action of internal Ca2+ on serotonin-induced potentiation of Ca2+ currents in Helix neurones

The influence of internal Ca²⁺ ions has been investigated during intracellular perfusion of isolated neurones from pedal ganglia of Helix pomatia in which serotonin (5-HT) induces a cyclic-adenosine-monophosphate-(cAMP)-dependent enhancement of high-threshold Ca²⁺ current (I _Ca). Internal free Ca²⁺ ([Ca²⁺]_i) was varied between 0.01 and 10 M by addition of Ca²⁺-EGTA [ethylenebis(oxonitrilo)tetraacetate] buffer. Elevation of [Ca²⁺]_i depressed the 5-HT effect. The dose/ effect curve for the Ca²⁺ blockade had a biphasic character and could be described by the sum of two Langmuir's isotherms for tetramolecular binding with dissociation constants K _d1=0.063 M and K _d2=1 M. Addition of calmodulin (CM) antagonists (50 M trifluoperazine or 50 M chlorpromazine), phosphodiesterase (PDE) antagonists [100 M isobutylmethylxanthine (IBMX) or 5 mM theophylline] and protein phosphatase antagonists [2 M okadaic acid (OA)] in the perfusion solution caused anticalcium action and modified the Ca²⁺ binding isotherm. Using the effect of OA and IBMX, two components of the total Ca²⁺ inhibition were separated and evaluated. In the presence of one of these blockers tetramolecular curves with K _d1=0.04 M and K _d2=0.69 M were obtained describing the activation of the retained unblocked enzyme — PDE or calcineurin (CN) correspondingly. The sum of these isotherms gave a biphasic curve similar to that in control. Leupeptin (100 M), a blocker of Ca²⁺-dependent proteases did not influence the amplitude of 5-HT effect, indicating that channel proteolysis is not involved in the depression. Our findings show that the molecular mechanism of Ca²⁺-induced suppression of the cAMP-dependent upregulation of Ca²⁺ channels is due to involvement of two Ca²⁺-CM-dependent enzymes: PDE reducing the cAMP level, and CN causing channel dephosphorylation. No other processes are involved in the investigated phenomenon at a Ca²⁺ concentration of less than or equal to 10 M.     

Parathyroid hormone enhances calcium current in snail neurones — Simulation of the effect by phorbol esters

Effects of parathyroid hormone substance (PTH) on the voltage-activated calcium current (I _Ca) were studied on intracellularly perfused neurones of the snail, Helix pomatia, under voltage-clamp conditions. Application of 0.1 nM PTH produced a marked potentiation of the current. The effect developed slowly (60–70 min) and remained after removal of PTH. Potentiation could be observed in most neurones, but varied considerably from cell to cell; in some neurones I _Ca was increased 2- to 3-fold. Addition of ethylenebis(oxonitrilo)tetraacetate (EGTA, 10 mM) to, or removal of adenosine 5-triphosphate (ATP, 2 mM) from the intracellular perfusing solution resulted in a suppression or attenuation of the potentiating effect. The effect could be reproduced by the synthetic 1–34 amino acid fragment of PTH. Extracellularly applied protein kinase-C (PK-C) activator phorbol ester phorbol 12-myristate 13-acetate (PMA, 0.1–10 M) produced a similar slow increase in I _Ca (up to 1.5- to 2-fold), while its inactive analogue (4-phorbol ester) had no effect on I_Ca. The effects of PTH and PMA were not additive. PK-C inhibitors [1-(5-isoquinoline-sulphonyl)-2-methylpiperazine hydrochloride] (H-7, 100 M) and staurosporine (100 M) as well as calcium channel antagonists Cd²⁺, verapamil, nifedipine and nimodipine depressed the effect of PTH. The chloride channel blocker 4,4-diisothiocyanato-stilbene-2,2-disulphonic acid (DIDS, 1 mM) did not affect the potentiating action of PTH. Activation of the adelylate cyclase system also potentiated I _Ca in some neurones, but this effect had a different time course and was additive to the effect of PTH. A conclusion is made that activation of PK-C may mediate the slowly developing enhancement of I _Ca by PTH.     

Teleradiology and eLearning

Purpose  

Clinical workflows and user interfaces of image-based computer-aided diagnosis (CAD) for interstitial lung diseases in high-resolution computed tomography are introduced and discussed.     

Two distinct receptors operate the cAMP cascade to up-regulate L-type Ca channels

Previously we have reported that serotonin’s (5-hydroxytryptamine or 5-HT) potentiating action on L-type Ca channels is present only in definite neurones from pedal ganglia of the mollusc Helix pomatia [Kostyuk PG, Lu kyanetz EA, Doroshenko PA (1992) Effects of serotonin and cAMP on calcium currents in different nevrones of Helix pomatia. Pflügers Arch 420:9–15]. The potentiation is mediated by the cAMP second messenger system and is triggered by 5-HT₁-like type receptors. To understand the physiological and pharmacological significance of this phenomenon, we analysed the comparative effects of dopamine (DA) and 5-HT on voltage-operated Ca currents (I _ca) in isolated, intracellularly perfused H. pomatia neurones in whole- cell patch-clamp experiments. Two types of effects of DA (1–10 μM) and 5-HT (1–10 μM) on I _ca were observed in different neurones: reversible inhibition (by about 40% and 20% respectively) or reversible potentiation (up to 65% and 40% respectively) of current amplitude. Neurones insensitive to neurotransmitter application were also observed. DA could induce potentiation of I _ca only in the same neurones that were similarly sensitive to 5-HT. However, a similar correlation between inhibitory action of neurotransmitters on I _ca was not observed. The potentiating effects of 5-HT and DA on I _ca were not additive and were mimicked by intracellular cAMP (100 μM) or 20 μg/ml of the catalytic subunit of protein kinase A. We established that the potentiating effects of neurotransmitters were mediated by two distinct receptors, as the DA receptor antagonist ergometrin (1 μM) selectively inhibited the enhancement of I _ca by DA and did not affect the action of 5-HT in the same cell. A similar specificity was observed for the dopaminergic compound, 5-chlortryptamine (10 μM), whereas the classical neuroleptic fluphenazine (10 μM) effectively blocked the 5-HT-evoked effect without significantly changing the action of DA. Methiothepin, an antagonist of 5-HT₁ and 5-HT₂ receptors, blocked both 5-HT-and DA-evoked effects. The results point out a possible convergence of the two different receptors (5-HT₁-like and D₁) on the same cAMP-dependent system of phosphorylation in the up-regulation of L-type Ca channel activity in mollusc neurones. Received: 14 September 1995/Received after revision and accepted: 8 January 1995     

Décider en cancérologie dans les situations médicosociales complexes: les réunions de concertation pluriprofessionnelles médicosociales et éthiques à l’hôpital Saint-Louis de Paris

Within the scheme of access to healthcare for destitute people, regulated by the French law of July 29 1998, the PASS (permanence d’accès aux soins de santé) Verlaine in Saint-Louis hospital sees many patients with high social instability, without financial social coverage, or strangers with linguistic barrier, without stable housing, social or familial environment, often penniless and with severe diseases such as advanced cancer or end-stage renal failure. It became obvious to the doctors responsible of the PASS that a strictly medical standardized proposal such as palliative chemotherapy could not by itself represent a useful solution, considering the multiple vulnerabilities of these patients. The “Réunions de concertation pluridisciplinaires médicosociales et éthiques (RCP MSE)” organised in Saint-Louis hospital put together the referring doctor, various specialists according to considered pathology, doctor(s) from the PASS itself, nursing staff, social workers, the coordinator of cancer care in the hospital, representatives of administration and service users. These meetings allow to consider and take into account, in order to establish the care program, all the vulnerabilities and constraints, to which are submitted the patient as well as the healthcare system, in order to make a proposal as adequate as possible in these highly complex situations.