bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exogenous pulmonary surfactant as a drug delivering agent: influence of antibiotics on surfactant activity
Authors: van ‘t Veen Annemarie , Gommers Diederik , Mouton Johan W. , Kluytmans Jan A.J.W. , Krijt Erik Jan , Lachmann Burkhard 
Published: July 2012

It has been proposed to use exogenous pulmonary surfactant as a drug delivery system for antibiotics to the alveolar compartment of the lung. Little, however, is known about interactions between pulmonary surfactant and antimicrobial agents. This study investigated the activity of a bovine pulmonary surfactant after mixture with amphotericin B, amoxicillin, ceftazidime, pentamidine or tobramycin.
Surfactant (1 mg ml−1 in vitro and 40 mg ml−1 in vivo) was mixed with 0.375 mg ml−1 amphotericin B, 50 mg ml−1 amoxicillin, 37.5 mg ml−1 ceftazidime, 1 mg ml−1 pentamidine and 2.5 mg ml−1 tobramycin. Minimal surface tension of 50 μl of the mixtures was measured in vitro by use of the Wilhelmy balance. In vivo surfactant activity was evaluated by its capacity to restore gas exchange in an established rat model for surfactant deficiency.
Surfactant deficiency was induced in ventilated rats by repeated lavage of the lung with warm saline until Pao2 dropped below 80 cmH2O with 100% inspired oxygen at standard ventilation settings. Subsequently an antibiotic‐surfactant mixture, saline, air, or surfactant alone was instilled intratracheally (4 ml kg−1 volume, n = 6 per treatment) and blood gas values were measured 5, 30, 60, 90 and 120 min after instillation.
The results showed that minimal surface tensions of the mixtures were comparable to that of surfactant alone. In vivo Pao2 levels in the animals receiving ceftazidime‐surfactant or pentamidine‐surfactant were unchanged when compared to the surfactant group. Pao2 levels in animals receiving amphotericin B‐surfactant, amoxicillin‐surfactant or tobramycin‐surfactant were significantly decreased compared to the surfactant group. For tobramycin it was further found that Pao2 levels were not affected when 0.2 m NaHCO3 (pH = 8.3) buffer was used for suspending surfactant instead of saline.
It is concluded that some antibiotics affect the in vivo activity of a bovine pulmonary surfactant. Therefore, before using surfactant‐antibiotic mixtures in clinical trials, interactions between the two agents should be carefully evaluated.
Selective and functional 5‐hydroxytryptamine4 receptor antagonism by SB 207266
Authors: Wardle K.A. , Bingham S. , Ellis E.S. , Gaster L.M. , Rushant B. , Smith M.I. , Sanger G.J. 
Published: July 2012

The pharmacology of a novel 5‐HT4 receptor antagonist, SB 207266 has been evaluated in vitro in the guinea‐pig distal colon longitudinal muscle myenteric plexus (LMMP) and in vivo in the dog Heidenhain pouch.
SB 207266 is a highly potent antagonist of 5‐HT‐evoked, cholinergically‐mediated contractions in the guinea‐pig distal colon. Low concentrations (0.1–10 nM) produced a parallel shift to the right of the concentration‐effect curve (apparent pA2 10.6±0.1) with no significant effect on the maximum response. With higher concentrations of SB 207266 (30 nM and above) the maximum response to 5‐HT was reduced.
The antagonism seen with SB 207266 cannot be attributed to a non‐selective effect since high concentrations (1 μm) had no effect on cholinergically‐mediated contractions evoked by the nicotinic receptor agonist DMPP in the same preparation.
SB 207266 is not an irreversible antagonist since the effects of the compound were reversible upon washing of the tissue.
In the dog Heidenhain pouch, oral (0.1–100 μg kg−1) and intravenous (0.1–100 μg kg−1) administration of SB 207266 produced a dose‐dependent antagonism of the contractions evoked by a bolus intravenous injection of 5‐HT. An ID50 for SB 207266 of 1.3 μg kg−1 was obtained following i.v. administration and 9.6 μg kg−1 following oral administration.
The antagonistic effects of SB 207266 (0.1–100 μg kg−1) in the dog Heidenhain pouch were long lasting since, following oral administration, the response to 5‐HT was reduced for at least 135 min.
SB 207266 is a highly potent, highly selective and orally active 5‐HT4 receptor antagonist. This compound is the first orally active amide to be identified in this class of antagonists and as such is an important new tool in the evaluation of 5‐HT4 receptor function both in vitro and in vivo.
Intraplantar morphine depresses spinal c‐Fos expression induced by carrageenin inflammation but not by noxious heat
Authors: Honoré Prisca , Buritova Jaroslava , Besson Jean‐Marie 
Published: July 2012

We have studied the effects of intraplantar administration of the same doses of morphine on intraplantar carrageenin (6 mg 150 μ***l−1 of saline) and noxious heat (52°C for 15 s) induced spinal c‐Fos expression and inflammation.
Intraplantar carrageenin, in awake rats, induced numerous Fos‐like immunoreactive (Fos‐LI) neurones in the dorsal horn of L4‐L5 lumbar segments of the spinal cord and extensive peripheral oedema. At 1 h 30 min, Fos‐LI neurones were preferentially located in the superficial laminae (74 ± 2%) whereas at 3 h, Fos‐LI neurones were observed both in the superficial (45 ± 2%) and deep (37 ± 1%) laminae of the spinal dorsal horn.
Intraplantar morphine dose‐dependently reduced c‐Fos expression induced 1 h 30 min after carrageenin (r = 0.605, P < 0.02), these effects were completely blocked by intraplantar methiodide naloxone (20 μg) (121 ± 22% of control carrageenin expression). The systemic injection of the highest dose of intraplantar morphine (50 μg) had no significant effect on the number of Fos‐LI neurones (88 ± 9% of control carrageenin expression). None of the drugs influenced unilateral peripheral oedema observed 1 h 30 min after carrageenin.
In the second series of experiments, intraplantar morphine dose‐dependently reduced the number of superficial and deep Fos‐LI neurones induced 3 h after carrageenin (r = 0.794, P < 0.0004 and r = 0.698, P < 0.004, respectively). Furthermore, the effects of the highest dose of intraplantar morphine were completely blocked by co‐administration of intraplantar methiodide naloxone (20 μg).
In addition, intraplantar morphine dose‐dependently reduced the ankle (r = 0.747, P < 0.002) and paw (r = 0.682, P < 0.005) oedema observed 3 h after carrageenin, with the effect of the highest dose of intraplantar morphine being completely blocked by co‐administration of methiodide naloxone (98 ± 4% and 102 ± 8% of control paw and ankle oedema, respectively).
Brief noxious heat stimulation, in urethane anaesthetized rats, induced, 2 h after the stimulation, numerous Fos‐LI neurones in the dorsal horn of L3‐L4 lumbar segments of the spinal cord but no detectable peripheral oedema. Fos‐LI neurones were preferentially located in superficial laminae (94 ± 2%) of the spinal dorsal horn. None of the drugs influenced the noxious heat induced c‐Fos expression.
Such results illustrate that peripheral effects of morphine preferentially occur during inflammatory states and outline the interest of extending clinical investigations of the possible use of local injection of morphine in various inflammatory pain states.
Mechanotransduction through the endothelial cytoskeleton: mediation of flow‐ but not agonist‐induced EDRF release
Authors: Hutcheson Iain R. , Griffith Tudor M. 
Published: July 2012

We have used a cascade bioassay system and isolated arterial ring preparations to investigate the contribution of the endothelial microfilament and microtubule cytoskeleton to EDRF release evoked by time‐averaged shear stress and by acetylcholine in rabbit abdominal aorta.
Cytochalasin B (1 μm) and phalloidin (100 nM) were used to depolymerize and stabilize, respectively, F‐actin microfilaments. Colchicine (500 nM) was used to inhibit tubulin dimerization and thus disrupt the microtubule network. Experiments were performed before or 1 h after administration of agents to the donor perfusate or organ bath.
In cascade bioassay studies, time‐averaged shear stress was manipulated with dextran (1–4% w/v, 80,000 MW), to increase perfusate viscosity. EDRF release induced by increased perfusate viscosity was significantly (P < 0.01) attenuated by cytochalasin B, phalloidin and colchicine.
Endothelium‐dependent relaxations to acetylcholine (0.01–30 μm) in cascade bioassay and in isolated aortic ring preparations were unaffected by pretreatment with any of these agents both in terms of their EC50 and maximal responses. Endothelium‐independent relaxations to sodium nitroprusside (0.001–10 μm) were similarly unaffected.
We conclude that the endothelial F‐actin microfilament and microtubule networks are involved in the mechanotransduction pathway for flow‐evoked EDRF release in rabbit abdominal aorta. However, these cytoskeletal elements appear to play no role in acetylcholine‐induced EDRF release in this tissue.
Studies on the pharmacology of the inward transport of L‐DOPA in rat renal tubules
Authors: Pinto‐do‐Ó P.C. , Soares‐da‐Silva P. 
Published: July 2012

The accumulation of L‐DOPA in suspensions of renal tubules obtained from male Wistar rats occurred through non‐saturable and saturable mechanisms. The kinetics of the saturable component of L‐DOPA uptake in renal tubules was as follows: Vmax = 46.3 ± 2.8 nmol mg−1 protein h−1 and Km = 114.4 (95% confidence limits; 83.8, 156.2) μm (n = 5). The diffusion constant (in nmol−1) of the non‐saturable component for the accumulation of L‐DOPA was 1.3 (1.1, 1.6; n = 8).
The effect of 2, 4‐dinitrophenol was a marked reduction in the tubular uptake of L‐DOPA, with an IC50 value of 12.1 (4.0, 36.9) μm. Cocaine produced a slight (P = 0.08) decrease (22% reduction at 50 μm) in the tubular uptake of L‐DOPA. Corticosterone produced a considerable inhibitory effect on the uptake of L‐DOPA with an IC50 value of 11.0 (3.6, 33.5) μm. The maximal inhibitory effect of probenecid was a 24% decrease in the uptake of L‐DOPA; however, the more selective organic anion transport inhibitor 4, 4′‐diisothiocyantostilbene‐2, 2′‐disulphonic acid (DIDS) was, found not to affect the tubular uptake of L‐DOPA. The organic cation transport inhibitor, cyanine 863, was found to produce a marked decrease in the uptake of L‐DOPA (IC50 = 2.02 [1.07, 3.79]). The cyanine derivatives 1, 1′‐diethyl‐2, 2′‐cyanine (decynium 22) and 1, 1′‐diethyl‐2, 4′‐cyanine (decynium 24) also potently inhibited L‐DOPA uptake with IC50 values (in μm) of 0.63 (0.39, 1.01) and 0.10 (0.08, 0.13), respectively, both compounds were found to be more potent than cyanine 863.
The inhibitory effect of decynium 24 (0.2 μm) on the tubular uptake of L‐DOPA was dependent on the pH of the incubation medium; at pH = 6.5 the accumulation of L‐DOPA was reduced up to 37 ± 2% of control values, whereas at pH = 7.4 and pH = 8.2 the accumulation of L‐DOPA was reduced by 56 ± 1% and 60 ± 6%, respectively. Cyanine 863 (2 μm), decynium 22 (1 μm) and decynium 24 (0.2 μm) were found to decrease the Vmax values for the saturable component of L‐DOPA uptake without changes in Km values.
It is concluded that the tubular uptake of L‐DOPA might be promoted through a mechanism which is dependent on the activity of the organic cation transport system.
Endogenous calcium channels in human embryonic kidney (HEK293) cells
Authors: Berjukow Stanislav , Döring Frank , Froschmayr Monika , Grabner Manfred , Glossmann Hartmut , Hering Steffen 
Published: July 2012

We have identified endogenous calcium channel currents in HEK293 cells. Whole cell endogenous currents (ISr‐HEK) were studied in single HEK293 cells with 10 mM strontium as the charge carrier by the patch clamp technique. The kinetic properties and pharmacological features of ISr‐HEK were characterized and compared with the properties of a heterologously expressed chimeric L‐type calcium channel construct.
ISr‐HEK activated on depolarization to voltages positive of −40 mV. It had transient current kinetics with a time to peak of 16 ± 1.4 ms (n = 7) and an inactivation times constant of 52 ± 5 ms (n = 7) at a test potential of 0 mV. The voltage for half maximal activation was −19.0 ± 1.5 mV (n = 7) and the voltage for half maximal steady‐state inactivation was −39.7 ± 2.3 mV (n = 7).
Block of ISr‐HEK by the dihydropyridine isradipine was not stereoselective; 1 μm (+) and (−)−isradipine inhibited the current by 30 ± 4% (n = 3) and 29 ± 2% (n = 4) respectively. (+)‐Isradipine and (−)−isradipine (10 μm) inhibited ISr‐HEK by 89 ± 4% (n = 5) and 88 ± 8% (n = 3) respectively. The 7‐bromo substituted (±)‐isradipine (VO2605, 10 μm) which is almost inactive on L‐type calcium channels also inhibited ISr‐HEK (83 ± 9%, n = 3) as was observed for 10 μm (−)−nimodipine (78 ± 6%, n = 5). Interestingly, 10 μm (±)‐Bay K 8644 (n = 5) had no effect on the current. ISr‐HEK was only slightly inhibited by the cone snail toxins ω‐CTx GVIA (1 μm, inhibition by 17 ± 3%, n = 4) and ω‐CTx MVIIC (1 μm, inhibition by 20 ± 3%, n = 4). The funnel web spider toxin ω‐Aga IVA (200 nM) inhibited ISr‐HEK by 19 ± 2%, n = 4).
In cells expressing ISr‐HEK, maximum inward current densities of 0.24 ± 0.03 pA/pF and 0.39 ± 0.7 pA/pF (at a test potential of −10 mV) were estimated in two different batches of HEK293 cells. The current density increased to 0.88 ± 0.18 pA/pF or 1.11 ± 0.2 pA/pF respectively, if the cells were cultured for 4 days in serum‐free medium.
Co‐expression of a chimeric L‐type calcium channel construct revealed that ISr‐HEK and L‐type calcium channel currents could be distinguished by their different voltage‐dependencies and current kinetics. The current density after heterologous expression of the L‐type α1 subunit chimera was estimated to be about ten times higher in serum containing medium (2.14 ± 0.45 pA/pF) than that of ISr‐HEK under the same conditions.
Desensitization of glucagon‐like peptide 1 receptors in insulininsulinsecreting βTC3 cells: role of PKA‐independent mechanisms
Authors: Gromada Jesper , Dissing Steen , Rorsman Patrik 
Published: July 2012

The cellular processes involved in the desensitization of the glucagon‐like peptide 1 receptors were investigated by measurements of the glucagon‐like peptide 1(7–36)amide (GLP‐1(7–36)amide)‐induced increases in intracellular free Ca2+ concentration ([Ca2+]i) in insulin‐secreting βTC3 cells.
In the presence of 11.2 mM glucose, stimulation with GLP‐1(7–36)amide led to a small membrane depolarization (< 10 mV), induction of electrical activity and a rapid increase in [Ca2+]i. The increase in [Ca2+]i was not observed in the presence of the L‐type Ca2+‐channel antagonist nifedipine. However, nifedipine was ineffective when applied after addition of GLP‐1(7–36)amide.
The increase in [Ca2+]i evoked by GLP‐1‐(7–36)amide was transient and even in the continued presence of the agonist, [Ca2+]i returned to the basal value within 4–5 min. The latter process was slowed, but not prevented, by inhibition of protein kinase C (PKC) by staurosporine and Ro31‐8220.
Short pretreatment of the cells with the phorbol ester, 4‐β‐phorbol‐12‐β‐myristate‐13‐α‐acetate (PMA), an activator of PKC, reduced the GLP‐1(7–36)amide‐evoked increase in [Ca2+]i by 75%. This effect of PMA was fully reversed by staurosporine and Ro31‐8220.
The ability of GLP‐1(7–36)amide to increase [Ca2+]i disappeared upon pre‐exposure of the cells to the hormone (desensitization). This process was maximal within 5 min of exposure to the agonist. Following removal of the agonist from the medium, the ability to respond to subsequent stimulation by GLP‐1(7–36)amide recovered gradually with time; half and complete recovery requiring > 20 min and 60 min, respectively. The desensitizing action of GLP‐1(7–36)amide persisted in the presence of either staurosporine or forskolin and did not require an elevation of [Ca2+]i.
Our data suggest that the GLP‐1(7–36)amide‐evoked increase in [Ca2+]i is initiated by Ca2+‐influx though voltage‐dependent and nifedipine‐sensitive L‐type Ca2+ channels but depends principally on Ca2+ mobilization from internal stores for its maintenance. The desensitization of the GLP‐1 receptors that occurs in the continued presence of the agonist does not result from the activation of protein kinase A or Ca2+‐dependent kinases/phosphatases. Our data indicate that activation of PKC may contribute to the desensitization of the GLP‐1 receptors but that other (PKC‐independent) mechanisms also participate in this process.
Inhibition of purinergic transmission by prostaglandin E1 and E2 in the guinea‐pig vas deferens: an electrophysiological study
Authors: Brock James A. , Cunnane Thomas C. 
Published: July 2012

The effects of prostaglandin E1 (PGE1) and E2 (PGE2) on postjunctional electrical activity in the guinea‐pig vas deferens evoked by sympathetic nerve stimulation were investigated using both intracellular and focal extracellular recording techniques in vitro.
Bath application of PGE1 (1–100 nM) or PGE2 (0.1–100 nM) concentration‐dependently inhibited the amplitudes of all excitatory junction potentials (e.j.ps) evoked during short trains of stimuli (10 stimuli at 1 Hz). Increasing the duration of nerve stimulation (100 stimuli at 1 Hz) did not overcome this inhibitory effect. At these concentrations PGE1 and PGE2 were without any apparent inhibitory effect on the amplitudes of spontaneous e.j.ps.
Local application of PGE1 (10–100 nM) or PGE2 (10–30 nM) markedly reduced the frequency of occurrence of excitatory junction currents (e.j.cs) evoked by trains of 20–100 stimuli at 1 to 4 Hz without changing the amplitudes of spontaneous e.j.cs or the configuration of the nerve terminal impulse.
In the presence of PGE1 or PGE2, raising the frequency of stimulation (from 1 to 4 Hz), increased the likelihood of e.j.c. occurrence.
The postjunctional electrical activity recorded in the guinea‐pig vas deferens is believed to be due to ATP released from the sympathetic nerve endings. Thus the present study demonstrates that both PGE1 and PGE2 powerfully inhibit quantal ATP release in the guinea‐pig vas deferens.
Transport and epithelial secretion of the cardiac glycoside, digoxin, by human intestinal epithelial (Caco‐2) cells
Authors: Cavet Megan E. , West Mike , Simmons Nicholas L. 
Published: July 2012

Human intestinal epithelial Caco‐2 cells have been used to investigate the transepithelial permeation of the cardiac glycoside, digoxin.
Transepithelial basal to apical [3H]‐digoxin flux exceeds apical to basal flux, a net secretion of [3H]‐digoxin being observed. At 200 μm digoxin, net secretory flux (Jnet) was 10.8 ± 0.6 nmol cm−2 h−1. Maximal secretory flux (Jmax) of vinblastine was 1.3 ± 0.1 nmol cm−2 h−1. Cellular uptake of digoxin was different across apical and basal cell boundaries. It was greatest across the basal surface at 1 μm, whereas at 200 μm, apical uptake exceeded basal uptake.
Net secretion of [3H]‐digoxin was subject to inhibition by digitoxin and bufalin but was not inhibited by ouabain, convallatoxin, and strophanthidin (all 100 μm). Inhibition was due to both a decrease in Jb‐a and an increase in Ja‐b. Uptake of [3H]‐digoxin at the apical surface was increased by digitoxin and bufalin. All cardiac glycosides decreased [3H]‐digoxin uptake at the basal cell surface (except for 100 μm digitoxin).
The competitive P‐glycoprotein inhibitors, verapamil (100 μm), nifedipine (50 μm) and vinblastine (50 μm) all abolished net secretion of [3H]‐digoxin due to both a decrease in Jb‐a and an increase in Ja‐b. Cellular accumulation of [3H]‐digoxin was also increased across both the apical and basal cell surfaces. 1‐Chloro‐2,4,‐dinitrobenzene (10 μm), a substrate for glutathione‐S‐transferase and subsequent ATP‐dependent glutathione‐S‐conjugate secretion, failed to inhibit net secretion of [3H]‐digoxin. The increase in absorptive permeability Pa‐b (= Ja‐b/Ca) and cellular [3H]‐digoxin uptake upon P‐glycoprotein inhibition, showed that the intestinal epithelium was rendered effectively impermeable by ATP‐dependent extrusion at the apical surface.
A model for [3H]‐digoxin secretion by the intestinal epithelium is likely to involve both diffusional uptake and Na+‐K+ pump‐mediated endocytosis, followed by active extrusion at the apical membrane.
Evidence for a P2‐purinoceptor mediating vasoconstriction by UTP, ATP and related nucleotides in the isolated pulmonary vascular bed of the rat
Authors: Rubino Annalisa , Burnstock Geoffrey 
Published: July 2012

The vasoconstrictor effects of uridine 5′‐triphosphate (UTP), uridine 5′‐diphosphate (UDP), uridine 5′‐monophosphate (UMP) and uridine were tested in the isolated pulmonary vascular bed of the rat. Comparison was made with the effects of adenine nucleotides, adenosine 5′‐triphosphate (ATP), adenosine 5′‐diphosphate (ADP), adenosine 5′‐monophosphate (AMP) and with adenosine. The effect of P2x‐purinoceptor desensitization and blockade was compared on the vascular responses to uracil and adenine nucleotides.
At doses ranging from 10−8 to 10−5 mol, UTP elicited dose‐dependent vasoconstriction. UDP was equiactive to UTP, while UMP and uridine did not show vasomotor activity. Similarly, ATP showed dose‐related vasoconstrictor activity. ADP was less potent than ATP in eliciting vasoconstriction, while AMP was active only at the higher doses tested and adenosine was ineffective.
Vasoconstriction was produced by ATP analogues with the following order of potency: α,β‐methylene ATP > ATPγS > β,γ‐methylene ATP > 2‐methylthio ATP ≥ ATP.
Desensitization of P2x‐purinoceptors by the selective agonist α,β‐methylene ATP did not modify the vasoconstrictor activity of UTP and UDP and only partially reduced vasoconstrictor responses to ATP, while it abolished vascular responses to α,β‐methylene ATP itself.
The antagonists of P2‐purinoceptors, suramin and pyridoxalphosphate‐6‐azophenyl‐2′, 4′‐disulphonic acid (PPADS), did not affect vascular responses to UTP and UDP, but reduced vasoconstriction evoked by β,γ‐methylene ATP and ATP by about 70 and 30%, respectively.
This study demonstrates that uracil nucleotides, UTP and UDP, elicit vasoconstriction in the rat pulmonary vascular bed. In addition to confirming the presence of classical P2x‐purinoceptors, these results also suggest the presence of a distinct purinoceptor subtype which mediates UTP‐ and ATP‐evoked vasoconstriction in the rat pulmonary circulation.