Biomedical subjects

D D Branisteanu

Publications and source records attributed to D D Branisteanu.

At least 19 recordsLinked to original sources

PubMed2003

Combination of a 1,25-dihydroxyvitamin D3 analog and a bisphosphonate prevents experimental autoimmune encephalomyelitis and preserves bone.

The vitamin D analog TX527 (19-nor-14,20-bis epi-23-yne-1,25(OH)(2)D(3)), decreased disease severity (P < 0.001) and postponed disease onset (P < 0.0001) in SJL mice in which experimental autoimmune encephalomyelitis was induced. Levels of IFN-gamma and IL-2 mRNA were decreased in spinal cord and spleen in the analog-treated mice, suggesting a Th(1)-targeted effect. Adding the bisphosphonate pamidronate did not affect analog-protective efficacy, but completely prevented TX527-caused acceleration of bone turnover and increased total bone mineral content as well as femoral mineral and calcium content (P < 0.01). Less calcemic analogs of 1,25-dihydroxyvitamin D(3), in combination with bone sparing products such as bisphosphonates allow immune modulation in vivo without affecting bone.

Animals↗

PubMed2000

Analogs of 1,25-dihydroxyvitamin D3 as dose-reducing agents for classical immunosuppressants.

BACKGROUND: Most immunosuppressants have a narrow margin between efficacy and side effects. A major goal in the development of immunomodulatory strategies is the discovery of combinations of drugs exerting synergistic immunomodulatory effects. The active form of vitamin D, 1,25(OH)2D3, is an immunomodulator that interacts with T cells but mainly targets antigen-presenting cells. We have demonstrated synergism between 1,25(OH)2D3 and cyclosporine, rapamycin, and FK506. The aim of this study was to investigate whether this synergism could be observed with other immunosuppressants (mycophenolate mofetil, leflunomide, and the methylxanthine A802715) and whether analogs of 1,25(OH)2D3 share this synergistic capacity in vivo. METHODS: In vitro, the median effect analysis was applied to the inhibition of phytohemagglutinin A-induced lymphocyte proliferation. In vivo, synergism between analogs of 1,25(OH)2D3 and cyclosporine or mycophenolate mofetil was evaluated in experimental autoimmune encephalomyelitis. RESULTS: In vitro, all combinations with 1,25(OH)2D3 were synergistic. The strongest synergism was seen with the inhibitors of interleukin 2 secretion, cyclosporine and FK506 (indexes 0.16 and 0.27, respectively). The weakest synergism was observed in combinations using A802715, a second-signal inhibitor (index 0.52), or the nucleotide synthesis inhibitor mycophenolate mofetil (index 0.43). In vivo, analogs of 1,25(OH)2D3 share the in vitro-observed synergism with 1,25(OH)2D3. Moreover, the differences in synergism with different immunomodulators were also present in vivo, where the best synergism was again seen in combination with cyclosporine (up to 100% paralysis protection). CONCLUSIONS: These data confirm that 1,25(OH)2D3 and its analogs are potent dose-reducing drugs for other immunomodulators, making them potentially interesting for clinical use in autoimmunity and transplantation.

Animals↗

PubMed1998

D-myo-inositol derivatives alter liposomal membrane fluidity.

We investigated the effect on membrane fluidity induced by D-myo-inositol derivatives (IP3, IP4, IP5, IP6). Fluidity was determined as the anisotropy of fluorescence polarisation from liposome model membranes labelled with DPH (1,6-diphenyl-1,3,5 hexatriene). IP3 (10(-10) to 10(-5) M) increased the membrane fluidity with a maximum effect at 10(-5) M. For IP4, IP5 and IP6, at concentrations less than 10(-6) M these derivatives increased the membrane viscosity (i.e. reduced fluidity). This effect was enhanced when the derivatives were incorporated in the vesicles, rather than added to the vesicle suspension. In this case IP5 and IP6 increased viscosity over the reference values. We conclude that inositol derivatives directly modified membrane fluidity which could play a role in their effects in biological systems, beside the one mediated by binding to specific receptors.

Animals↗

PubMed1997

Vasorelaxant properties of brefeldin A in rat aorta.

The effects of brefeldin A, a putative specific agent that disassembles the Golgi apparatus were assessed on the contractility of de-endothelised rat aorta. Brefeldin A inhibited, either as pre- or as post-treatment, the contractions elicited by K+ (75 mM) or phenylephrine (10 microM), being significantly more potent upon the latter. The thapsigargin (1 microM)-induced rat aorta contraction was less sensitive to brefeldin A inhibition. Pre-treatment with brefeldin A (30-100 microM) did not affect phenylephrine-induced transient contractions in Ca2+-free medium, but strongly inhibited the phenylephrine-induced sustained contractions upon re-admission of Ca2+ to the medium. Brefeldin A was unable to prevent Ca2+ stores refilling. We concluded that brefeldin A inhibits Ca2+ entry but not the pathways activated after Ca2+ stores depletion or the pathways responsible for replenishment of these stores in rat aorta, presumably by disassembling the Golgi apparatus network.

Adrenergic alpha-Agonists↗

PubMed1997

Synergism between sirolimus and 1,25-dihydroxyvitamin D3 in vitro and in vivo.

The active form of vitamin D, 1 alpha, 25-(OH)2D3, displays immunomodulatory effects in vitro and in vivo at pharmacological levels. We evaluated the dose-effect relationship of 1,25(OH)2D3 and sirolimus (rapamycin, RAP) in vitro, on the inhibition of PHA-stimulated PBMC proliferation, by using the median effect analysis. Pharmacological concentrations of 1,25(OH)2D3 (between 10(-9) and 3 x 10(-6) M) interacted synergistically with RAP (combination index value of 0.01 for 50% suppression of PBMC proliferation). In vivo, the effect of 1,25(OH)2D3 and RAP combinations on the evolution of experimental allergic encephalomyelitis in SJL mice was analyzed. 1,25(OH)2D3, given i.p., in monotherapy, at a dose of 2 micrograms/kg every two days, from day -3 until day +19 after disease induction, or RAP, injected daily at a dose of 0.3 mg/kg for the same period, decreased EAE incidence (paralysis in 70 and 55% of the animals, respectively, versus 98% in the placebo treated group, p < 0.001). The combination treatment using the two drugs in these subtherapeutical doses provided near-total clinical (8% paralysis, p < 0.001 compared to monotherapy with 1,25(OH)2D3 or RAP) and histological protection, comparable to that obtained with RAP in monotherapy at a threefold higher dose (1 mg/kg/d). When the two drugs were given using an alternate day administration schedule (RAP at 0.6 mg/kg and 1,25(OH)2D3 at 2 micrograms/kg, each given on alternate days from day -3 to 19), near total protection was again obtained (13% paralysis, p < 0.001 versus control). These in vitro and in vivo data support the existence of synergistic interactions between 1,25(OH)2D3 and RAP. Considering the narrow therapeutic windows of both RAP and vitamin D-related compounds in autoimmune disease models, combinations of these drugs could find clinical application in reducing their individual therapeutically efficient doses to non-toxic levels.

Animals↗

PubMed1995

Effects of alpha-trinositol administered extra- and intracellularly (using liposomes) on rat aorta rings.

The effects of alpha-trinositol, a D-myo-inositol [1,2,6]trisphosphate derivative, were studied on de-endothelised rat aorta rings. The substance was applied extracellularly as well as intracellularly (by using liposomes as drug carriers). Upon extracellular administration, the drug reduced the level of contraction induced by 40 mM K+ or by phenylephrine (10(-5) M). No effects were observed on relaxed preparations. Liposomes containing alpha-trinositol induced a dose-dependent contraction of the preparations under resting tension with a threshold of 10(-5) M in the aqueous phase. These contractions were heparin-insensitive but were significantly blocked by D-600 (10(-5) M) (an L-type Ca2+ channel blocker) or in Ca(2+)-free medium. Our data suggest that alpha-trinositol has a plasmalemmal mechanism of action which could involve Ca2+ influx from the extracellular space.

Animals↗

PubMed1995

Multiple effects of tyrosine kinase inhibitors on vascular smooth muscle contraction.

The effects of three tyrosine kinase inhibitors: genistein, quercetin and psi-tectorigenin, were investigated on contractions evoked in de-endothelised rat aortic rings, either by phenylephrine or 70 mM K+. A dose-dependent inhibition of both contractions by all three compounds was observed, the phenylephrine-mediated contractions being more sensitive to genistein. No differences between genistein or quercetin effects in pre-treatment or post-treatment protocols were found. Ca2+ store refilling, expressed in terms of phenylephrine-induced tension in Ca(2+)-free medium, was dose-dependently blocked by quercetin and genistein. Sodium orthovanadate, an inhibitor of tyrosine phosphatase, contracted the rat aortic rings with an IC50 of 0.66 microM. Its presence during the refilling period after exposure to Ca(2+)-free medium completely prevented the subsequent response to phenylephrine. One can conclude that the use of the above-mentioned protein tyrosine kinase inhibitors in the rat aorta blocks a step involved in Ca2+ entry and Ca2+ store refilling. A definite conclusion regarding the vanadate effects is not possible due to the fact that this compound also affects Ca2+ ATP-ases.

Animals↗

PubMed1995

Effects of liposome-entrapped platelet-activating factor in the isolated rat trachea.

The effects of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine)-filled liposomes upon rat tracheal rings in vitro were examined. The capture of liposomes by the smooth muscle cells of the isolated tracheal rings as well as the release of their content into the cytoplasm was shown by using Evans blue (5 x 10(-4) M)-loaded liposomes. Administration of PAF (10(-3) M)-filled liposomes contracted the preparations, in contrast with extracellular administration of PAF and control liposomes, which had no effect. Administration during the plateau or pretreatment with liposomes containing BN 52021 (3-t-butylhexahydro-4,7b-trihydroxy-8-methyl-9H-1,7a-epoxymethano- 1H,6aH- cyclopenta[c]furo(2,3-b)furo[3',2':3,4]cyclopental [1,2-d]furan-5,9,12(4H)-trione) ((10(-3) M, a selective PAF receptor antagonist) or heparin (5 x 10(-5) M) blocked this contraction. BN 52021 and heparin, not entrapped in liposomes, had no such effect. Our data suggest an intervention of PAF in the mechanisms of contraction of tracheal smooth muscle, involving a direct or indirect intervention (intracellular receptors for PAF cannot be excluded). At the same time, the rat trachea contraction induced by PAF-loaded liposomes could be linked to the PtdIns(1,4,5)P3-dependent Ca2+ channels from the endoplasmic reticulum and/or to the interaction with G proteins, as shown by the blocking effects of heparin-containing liposomes.

Animals↗

PubMed1995

Characteristics and possible mechanisms of low-Na+ induced contractions in rat aorta.

The influence of reducing external Na+ concentration ([Na+]ex) upon vascular smooth muscle contractility was investigated using the rat isolated aorta. NaCl from the physiological saline solution (PSS) was replaced with either choline-Cl, sucrose, or LiCl to give the following [Na+]ex (mM): 115, 85, 55, and 25 (115NaPSS to 25NaPSS). Small reductions in [Na+]ex (115NaPSS) induced a biphasic contraction, comparable in amplitude with the control one induced by phenylephrine 10(-6) M. Elimination of the endogenous catecholamine participation using either phentolamine 10(-5) M or guanethidine 3.10(-6) M similarly reduces these contractions to 25% (sucrose replacement). A similar relaxing effect was obtained with D600 10(-5) M, an antagonist of the voltage operated Ca2+ channels (25-30% residual tension for all the substitutes). Large reductions in [Na+]ex (25NaPSS) induced contractions comparable in amplitude and shape, but less sensitive to phentolamine and guanethidine (residual tension 65-75%, sucrose replacement) and insensitive to D600 (all the substitutes). The Na+/K+ ATPase inhibitor ouabain (10(-4) M) elicited slowly developing contractions, the amplitude being 115% of the phenylephrine 10(-6) M control. Phenylephrine further contracted the 115NaPSS precontracted preparations, but was significantly less effective in 25NaPSS, although the precontraction levels were similar for the same substitute used. The amplitude of the superimposed phenylephrine contractions exhibited [Na+]ex dependence. Phenylephrine 10(-6) M failed to further contract the ouabain 10(-4) M precontracted rings. We conclude that relatively small reductions in [Na+]ex are able to induce contractions of rat aorta primarily through release of endogenous catecholamines, probably through neural Na+/Ca2+ exchange. Larger reductions in [Na+]ex appear to cause contraction through muscular Na+/Ca2+ exchange.

Animals↗

PubMed1995

Prevention of murine experimental allergic encephalomyelitis: cooperative effects of cyclosporine and 1 alpha, 25-(OH)2D3.

The hormone 1 alpha, 25-dihydroxyvitamin D3 (1,25(OH)2D3) has immune modulatory activities in vitro and in vivo, and can prevent or delay the onset of experimental or spontaneous autoimmune diseases. At therapeutical doses, however, hypercalcemic side effects are found. The present experiments examined the effects of combined treatment with subtherapeutic doses of cyclosporine A (CsA) and 1,25(OH)2D3 on the evolution of experimental autoimmune encephalomyelitis (EAE) in SJL mice. 1,25(OH)2D3 at 5 micrograms/kg body weight (given by i.p. injection every 2 days) prevented the appearance of paralysis in 70% of the treated mice. The treatment with 1,25(OH)2D3 at 2 micrograms/kg/2 days alone had less substantial protective effects (22% disease-free animals versus 5% in the control group). However, when this subtherapeutic dose was associated to treatment with a daily dose of CsA (2 or 5 mg/kg/day), which by itself was subtherapeutic (24 and 50% disease-free animals, respectively), the association of both drugs led to near-total protection (86% disease-free animals when combined with the highest dose of CsA). When an alternate day administration schedule (CsA at 10 mg/kg and 1,25(OH)2D3 at 2 micrograms/kg, each given on alternate days from day -3 to +19 after disease induction) was used, all treated mice were completely protected clinically and histologically. The two drugs also showed additive effects on serum osteocalcin and urinary calcium and desoxypyridinoline excretion, but not on serum calcium concentration. Our experiments demonstrate that 1,25(OH)2D3 might be a potential dose-reducing agent for CsA in immunosuppressive therapy.

Amino Acids↗

PubMed1993

Effects of liposome-entrapped adenosine in the isolated rat aorta.

This study examined the effects of adenosine- and adenosine deaminase-loaded liposomes upon the contractile activity of the vascular smooth muscle, using the isolated, de-endothelised rat aorta ring as in vitro model. While control liposomes had no effect, intraliposomal adenosine (5 x 10(-3) M) induced contraction of the preparation. Intraliposomal adenosine deaminase induced partial relaxation of high K(+)-precontracted rings. The adenosine-induced contraction seems to involve Ca2+ influx through L-type channels as an essential component, but protein kinase C may also have a modulatory role.

Adenosine↗

PubMed1993

Effects of liposome-entrapped D-myo-inositol 1,4,5-trisphosphate and D-myo-inositol 1,3,4,5-tetrakisphosphate in the isolated rat aorta.

This study examined the effects of D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3)- and D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4)-loaded liposomes upon the contractile activity of vascular smooth muscle, using the isolated (endothelium removed) rat aortic ring as in vitro model. While control liposomes had no effect, the administration of Ins(1,4,5)P3-containing liposomes contracted the smooth muscle preparation. Furthermore, a similar effect was seen with the administration of Ins(1,3,4,5)P4-filled liposomes but, in this case, the rings developed a significantly higher level of active tension. Pretreatment of the aortic preparation with heparin-loaded liposomes blocked the contractions induced by both Ins(1,4,5)P3- and Ins(1,3,4,5)P4-containing liposomes.

Animals↗

PubMed1993

Partial prevention of active Heymann nephritis by 1 alpha, 25 dihydroxyvitamin D3.

The hormone 1 alpha, 25 dihydroxyvitamin D3 (1,25(OH)2D3) has potent immunosuppressive effects in vitro. Recent publications also described a protective effect of the hormone in various animal models of immune-mediated diseases. To test its in vivo activity we induced active Heymann nephritis in Lewis rats that were either untreated or treated with 1,25(OH)2D3 or its synthetic 20-epi analogue, KH1060. Treatment with cyclosporine A (CsA) was used as an immunosuppressive control. In this nephrotic model the administration of 1,25(OH)2D3 (0.5 microgram/kg body weight) given on alternate days during the first 13 days after active immunization significantly reduced the proteinuria as measured by weeks 7-9. This reduction was comparable to the reduction observed in rats treated with CsA (20 mg/kg) on alternate days. A second series of experiments with 1,25(OH)2D3 confirmed these findings. The level of autoantibodies was found to be significantly suppressed during the treatment time in the CsA (20 mg/kg) group, whereas the limit of significance (P = 0.06) was reached in the 1,25(OH)2D3 (0.5 microgram/kg) group. The size of the immune deposits also was found to be substantially smaller in the groups that developed less proteinuria. The administration of 1,25(OH)2D3 transiently increased the mean serum calcium concentration with 2.5 mg/dl above the pretreatment values, and the urinary calcium excretion by a factor of 3-5 during the short treatment time. Treatment with the analogue KH1060 did not reduce the proteinuria significantly. Our experiments add evidence to the hypothesis that 1,25(OH)2D3 in pharmacological doses has immunosuppressive potency.

Animals↗

PubMed1982

Ketamine and ditran block end-plate ion conductance and [3H]phencyclidine binding to electric organ membrane.

Alterations by ketamine (10-100 microM) and ditran (50-100 microM) of end-plate currents were studied using transected cutaneous pectoris muscles. Both drugs reduced peak current and shortened the time constant for end-plate current decay (tau). Ketamine was more effective at pH 5.3 than at 7.4 or 9.1. Recovery from blockade was asymmetrical in that tau recovered more quickly than did peak current when the drugs were removed from the bath. By contrast, 4-aminopyridine antagonized the depression of peak current by ketamine, but not the reduction of tau. Both ketamine and ditran disrupted the voltage dependence of tau. The binding to microsacs prepared from electric organs of [3H]phencyclidine ([3H]PCP) was blocked by ketamine and ditran. In microsacs treated with carbachol, the IC50 for ketamine block of [3H]PCP binding was 6.6 X 10(-6) M. For ditran, the IC50 for block of [3H]PCP binding in the presence of carbachol was 1.7 X 10(-6) M. The binding of [alpha-125I]bungarotoxin to the microsacs or to the cultured chick myotubes was reduced only slightly by ketamine. Because ketamine has no effect on transmitter release and little effect on [alpha-125I]bungarotoxin binding, it is concluded that, like PCP, ketamine and ditran block open channels in the end-plate. In addition, the asymmetrical recovery of end-plate current parameters suggests that ketamine may block closed channels. The recovery from block of closed channels (caused by either a direct action on closed channels or a very slow channel unblocking rate) proceeds more slowly than does the block of open channels.

Animals↗

PubMed1980

Effects of McN-A-343, a cholinomimetic drug, on endplate currents in the frog.

The muscarinic ganglion stimulating agent, McN-A-343 has unusual blocking actions on endplate currents (EPCs) at frog neuromuscular junctions. McN-A-343 caused depolarization by a curare-sensitive process, blocked neuromuscular transmission, depressed EPCs and reduced the time for EPC decay. These results are explained best by a nicotinic agonist action of McN-A-343 on the acetylcholine receptor to cause ion flow and the blockade by McN-A-343 of the open ion channels. The actions of McN-A-343 are similar to those of decamethonium (C-10) described by others. Unlike C-10, however, McN-A-343 did not alter the exponential character of the EPC or alter the voltage dependency of the EPC. The prototypical nicotinic agonist, dimethylphenylpiperazinium had no effect on EPC parameters of endplate clamped at -90mV.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗

PubMed1976

Quantal parameters of transmission at the frog neuromuscular junction.

Estimates of quantal release parameters at frog neuromuscular junctions showed that alterations in [Ca2+]o affected m (number of quanta), p (probability of quantal release) and n (stores of quanta available for release). The effect of [Ca2+]o depended upon the initial value for p. When p was low, raising [Ca2+]o increased m and p, but not n. However, when p was large, raising [Ca2+]o had no further effect on p but increased m and n. During prolonged repetitive nerve stimulation to cause a decrease in m, n was decreased and p was increased. This finding was attributed to a failure of transmitter mobilization to maintain the stores of transmitter available for release.

Acetylcholine↗

PubMed1976

Effects of physiologic alterations on binomial transmitter release at magnesium-depressed neuromuscular junctions.

1. Transmitter release from Mg2+-treated frog neuromuscular junctions can be described by binomial statistics. Good agreement between the observed amplitude-frequency distribution of e.p.p.s. and that predicted by binomial statistics is observed with relatively low concentrations of Mg2+. Conversely, good agreement is found with Poisson predictions when higher concentrations of Mg2+ are used to depress transmission. 2. Binomial analysis at these junctions shows that Mg2+ reduces quantal content (m), the probability of release (p) and to a lesser extent the available stores of transmitter (n). Raising Ca2+ causes an increase in n and p and a small but significant increase in n. K+ increases m and p but not n. 3. During 'frequency-facilitation' (1-6 Hz), e.p.p.s., m and n are increased but p is unaffected. 4. It is concluded that binomial statistics can be used to estimate the quantal parameters of transmitter release and that these parameters can be identified as discrete entities.

Animals↗

PubMed1976

Statistical parameters of transmitter release at frog neuromuscular junctions treated with guanidine or tetraethylammonium.

Transmitter release at Mg++ -depressed frog neuromuscular junctions can be described using binomial statistics. The number of quanta (m) released by the nerve terminal action potential is directly proportional to the mean probability (p) that a quantum will be released and the number of quanta available for release (n). Guanidine or tetraethylammonium (TEA) increased m and n, but had no effect on p. At junctions depressed by d-tubocurarine, both compounds enhanced the amplitude of the initial end-plate potential, caused an accelerated rate of fade of end-plate potential amplitudes and raised the steady-state level of end-plate potential amplitude. This finding was interpreted to mean that guanidine and TEA increased transmitter mobilization and may be related to the increase by the compounds of the parameters n. If so, then the data support the idea that n represents the number of quanta available for release rather than the number of transmitter release sites in the terminal membrane. Neither compound affected the power relationship between [Ca++]o and transmitter release. When plotted on a double logarithmic basis, the slope of the line relating [Ca++]o to increased transmitter release was 3.7, a relationship not altered by the drugs. Thus, the compounds had no effect on the fundamental interaction between Ca++ and transmitter release sites. In contrast to [Ca++]o, the power relationship between increased transmitter release and the concentration of drug in the bathing solution was 0.69 for guanidine and 0.84 for TEA. Because of this finding, it was concluded that the compounds increased transmitter release by mechanisms other than or in addition to increasing Ca++ conductance.

Animals↗