Persistence of High Lead Concentrations and Associated Effects in Tundra Swans Captured Near a Mining and Smelting Complex in Northern Idaho

Lead poisoning of waterfowl, particularly tundra swans (Cygnus columbianus), has been documented in the Coeur d'Alene River Basin in northern Idaho for nearly a century. Over 90% of the lead-poisoned tundra swans in this area that were necropsied have no ingested lead shot. Spent lead shot from hunting activities over the years is therefore a minor source of lead in these swans. The migrating swans accumulated lethal burdens of lead from ingestion of sediments and aquatic vegetation during a short stopover in the spring. The lead originated from mining and smelting activities. Lead concentrations and physiological characteristics of blood were compared in swans captured in swim-in traps, with moribund swans caught by hand in the lead-contaminated area in 1987 and 1994–1995 and with birds captured by night-lighting in reference areas in 1994–1995. Blood lead concentrations in swans were highest in moribund birds (3.3 g g^-1 in 1987 and 1995), intermediate in those trapped in the contaminated area (0.82 g g^-1 in 1987 and 1.8 g g^-1 in 1995), and lowest (0.11 g g^-1) in those trapped in the reference areas. -aminolevulinic acid dehydratase (ALAD) was significantly inhibited in swans from the contaminated area. Hematocrit and hemoglobin were significantly depressed only in moribund swans. Of the 19 swans found moribund and euthanized, 18 were classified as having lead toxicosis on the basis of lead levels in blood (1.3 to 9.6 g g^-1) and livers (6 to 40 g g^-1) and necropsy findings. The 19th swan had aspergillosis. There was no evidence that effects of lead on tundra swans had diminished from 1987 to 1995.     

Toxicity of Organic Compounds to Marine Invertebrate Embryos and Larvae: A Comparison Between the Sea Urchin Embryogenesis Bioassay and Alternative Test Species

This study investigated the toxic effects of the insecticides lindane and chlorpyrifos, the herbicide diuron, the organometallic antifoulant tributyltin (TBT), and the surfactant sodium dodecyl sulfate (SDS) on the early life stages of Paracentrotus lividus (Echinodermata, Euechinoidea), Ciona intestinalis (Chordata, Ascidiacea), Maja squinado and Palaemon serratus (Arthropoda, Crustacea) in laboratory acute toxicity tests. The assays studied embryogenesis success from fertilized egg to normal larvae in P. lividus (48 h incubation at 20 °C) and C. intestinalis (24 h incubation at 20 °C), and larval mortality at 24 and 48 h in M. squinado and P. serratus. For P. lividus, the median effective concentrations (EC₅₀) reducing percentages of normal larvae by 50% were: 350 g l^–1 for chlorpyrifos, 5500 g l^–1 for diuron, 4277 g l^–1 for SDS, and 0.309 g l^–1 for TBT. For C. intestinalis, the EC₅₀ values affecting embryogenesis success were 5666 g l^–1 for chlorpyrifos, 24,397 g l^–1 for diuron, 4412 g l^–1 for lindane, 5145 g l^–1 for SDS, and 7.1 g l^–1 for TBT. The median lethal concentrations (LC₅₀) for M. squinado larval survival were 0.84 g l^–1 (24 h) and 0.79 g l^–1 (48 h) for chlorpyrifos, 2.23 g l^–1 (24 h) and 2.18 g l^–1 (48 h) for lindane, and 687 g l^–1 (48 h) for SDS. For P. serratus the LC₅₀ values obtained were 0.35 g l^–1 (24 h) and 0.22 g l^–1 (48 h) for chlorpyrifos, 3011 g l^–1 (24 h) and 3044 g l^–1 (48 h) for diuron, 5.20 g l^–1 (24 h) and 5.59 g l^–1 (48 h) for lindane, and 22.30 g l^–1 (24 h) and 17.52 g l^–1 (48 h) for TBT. Decapod larvae, as expected, were markedly more sensitive to the insecticides than sea urchins and ascidians, and SDS was the least toxic compound tested for these organisms. Lowest observed effect concentrations (LOEC) of TBT for sea urchin and ascidian embryos, chlorpyrifos and lindane for crustacean larvae, and SDS, were similar to those found in many coastal areas indicating that there would be a risk to invertebrate embryos and larvae from exposure in the field to these pollutants.     

The penetration of ciprofloxacin into bronchial mucosa,lung parenchyma,and pleural tissue after intravenous administration

Summary We have studied the concentrations of ciprofloxacin in serum, bronchial mucosa, lung parenchyma, and pleural tissue after a single intravenous dose of 200 mg in 20 patients subjected to lung surgery.The concentrations of ciprofloxacin in the tissues exceeded that in the serum by 3-fold to 7-fold: serum 0.6 g·ml^–1, bronchial mucosa 1.9 g·g^–1 lung parenchyma 3.4 g·g^–, and pleural tissue 1.7 g·g^–1.The achievable concentrations of ciprofloxacin in the tissues of the lower respiratory tract are above the MICs for most lung pathogens.     

Zinc,among a ‘cocktail’ of metal pollutants,is responsible for the absence of the terrestrial isopod Porcellio scaber from the vicinity of a primary smelting works

Porcellio scaber Latreille (Crustacea: Isopoda) of one month in age were reared for a year on leaf litter of field maple (Acer campestre) contaminated in the laboratory with a range of concentrations of cadmium, copper, lead or zinc. The metals were applied topically to the leaves as nitrates. Growth and survival, numbers of live offspring produced by females that matured, and concentrations of metals in adult isopods at the end of the experiment were measured.Critical concentrations of metals in food at which all the isopods died before producing offspring were 100 g Cd g^–1, 100 g Cu g^–1, 2000 g Pb g^–1 and 1000 g Zn g^–1 (on a dry weight basis). The relative toxicities of the four metals in the laboratory were compared with concentrations of cadmium, copper, lead and zinc in surface leaf litter in the vicinity of a primary smelting works at Avonmouth, South West England. The results support the hypothesis that the absence of Porcellio scaber from sites in the immediate vicinity of the factory is due to zinc poisoning. Although cadmium is approximately ten times more toxic to isopods than zinc in the laboratory, zinc is most likely to be killing isopods in the field because its concentration is always at least 30 times higher than cadmium in Avonmouth leaf litter, and more than 100 times higher at most sites.Populations of Porcellio scaber survive in field sites where surface leaf litter contains up to 5000 g Zn g^–1. This is at least five times higher than the critical concentration in laboratory experiments. Thus, the methodology for assessing metal toxicity described in this paper, exaggerates the potential effects of metals to isopods in the field. Such differences between laboratory and field toxicities of metals should be taken into account when environmental protection levels for metals are being proposed for soil invertebrates based on ecotoxicological tests conducted in the laboratory.     

Inhibition by ethanol of excitatory amino acid receptors and nicotinic acetylcholine receptors at rat locus coeruleus neurons

The frequency of spontaneous action potentials of locus coeruleus (LC) neurons was recorded extracellularly in pontine slices of the rat brain. Ethanol (1–100 mM) elevated the firing rate in most neurons; this effect was concentration-dependent. (S)--amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; 0.03–1 M), kainate ( 0.1–3 M), N-methyl-D-aspartate (NMDA; 1–30 M), substance P 0.01–1 M, nicotine 0.1–10 M and ,-methylene ATP ,-meATP; 0.3–30 M, all increased the firing. Application of ethanol g10–100 mM to the superfusion medium for 10 min, reproducibly and concentration-dependently inhibited the facilitatory effect of NMDA g10 M. However, the inhibitory effect of ethanol (100 mM) decreased during a 30-min superfusion period and after the washout of ethanol the sensitivity of LC neurons to NMDA (10 M) tended to overshoot above their initial level. Although NMDA was more potent in the absence than in the presence of external Mg²⁺, ethanol (100 mM) continued to depress the facilitatory effect of a low concentration of NMDA (EM) in a Mg²⁺-free medium. By contrast, in a medium containing normal Mg²⁺, ethanol (100 mM) failed to significantly interfere with the increase in firing rate induced by a high concentration of NMDA (30 M). The effects of kainate (0.5 M), AMPA (0.3 M) and nicotine (1 M) were also depressed by ethanol (100 M), while the effects of substance P (0.03 M) and ,-meATP (30 M) were not changed. In conclusion, ethanol selectively counteracts the opening of cationic channels caused by excitatory amino acid (EAA) receptor agonists and nicotinic acetylcholine receptor agonists. During a longer lasting incubation with ethanol, the inhibition of the NMDA-induced excitatory effect declines, indicating the development of tolerance. Correspondence to: P. Illes at the above address     

Interaction between clonidine and physostigmine in normal rats and in rats after sinoaortic denervation

Summary Clonidine (3–30 g · kg^–1, i.v.) induced a fall in mean arterial pressure in rats after sinoaortic denervation but not in sham-operated animals. Moreover, sinoaortic denervation reduced the bradycardic action of this antihypertensive drug. Pressor and tachycardic response to physostigmine (60 g · kg^–1, i.v.) were greater in denervated than in sham-operated rats. The increase of mean arterial pressure was 26.2 ± 2.2 mm Hg in sham-operated rats (n = 12) and 53.8 ± 2.0 mm Hg in denervated rats (n = 12, P < 0.005).Pretreatment with 3 g · kg^–1 (i. v.) of clonidine did not alter the pressor response to physostigmine (60 g · kg^–1) in either of the two groups; 10 and 30 g · kg^–1 of clonidine reduced the physostigmine-induced increase of mean arterial pressure in sham-operated rats but enhanced the pressor response in denervated animals. Furthermore, an ineffective dose of physostigmine (30 g - kg^–1 i.v.) induced a pressor response after pretreatment with clonidine (10 gg · kg^–1) in denervated rats.Clonidine (10 g · kg^–1) did not affect the pressor effect of 1,1 dimethyl-4-phenylpiperazinium iodide (DMPP: 50 g · kg^–1 i.v.) or phenylephrine (4 g · kg ^–1, i.v.) in either group.The anticholinergic effect of clonidine in sham-operated rats may be explained by an inhibitory action on the release of acetylcholine in several brain structures but the facilitatory effect of clonidine observed in denervated animals is not clear. The results did not suggest a peripheral involvement in this facilitatory effect. Send offprint requests to M. A. Enero at the above address     

The Potential Use of the South African River Crab,Potamonautes warreni,as a Bioindicator Species for Heavy Metal Contamination

In 1995, preliminary water and sediment analyses of the river bed and burrow sediments from 9 locations along the Mooi River, NW Province, South Africa had shown cadmium concentrations up to 0.009 mg l^–1±0.003 and up to 0.33 and 0.89 weight % with scanning electron microscopy (SEM) and x-ray microanalysis. Samples of the adult river crab (Potamonautes warreni) were collected from the Mooi River at Noordbrug (26°40S/27°05E), 1 km north of Potchefstroom Town, and exposed to 0.2 or 2.0 mg Cd²⁺ l^–1 in situ to determine tolerance, uptake and bioaccumulation of cadmium. Using flame atomic absorption spectroscopy (FAAS) the gills, haemolymph and digestive gland of naturally exposed P. warreni showed wet mass values of 0.74±0.27 g Cd²⁺ g^–1, 0.007±0.007 g ml^–1 and 0.12±0.09 g g^–1 respectively. The tolerance of crabs to aqueous Cd reached its limit (ET₅₀=42 hours) at 2.0 mg l^–1 aqueous Cd exposure. At an exposure to 0.2 mg Cd²⁺ l^–1 for 21 days, the greatest Cd (n=11; 9.99±5.09 g g^–1 wet mass) and Cu concentrations (n=11; 17.90±4.66 g g^–1 wet mass) were associated with the gills, and to a lesser extent the digestive gland (n=11; 0.38±0.20 g g^–1 wet mass), whereas concentrations of Zn were variable in both organs. In the haemolymph Cd levels were relatively small (n=11; 0.012–0.006 g ml^–1) with exposure and time and Cu, Zn concentrations varied. Changes in the uptake of Cd in P. warreni indicated that transport, storage and possibly regulatory mechanisms are likely to operate in adult crabs. The potential of P. warreni as a bioindicator species of pollution is also discussed.     

Noradrenaline release from rat sympathetic neurons evoked by P2-purinoceptor activation

The effects of ATP and analogues on the release of previously incorporated ³H-noradrenaline were studied in cultured sympathetic neurons derived from superior cervical ganglia of neonatal rats. Electrical field stimulation (40 mA at 3 Hz) of the neurons for 10 s markedly enhanced the outflow of tritium. ATP applied for 5 s to 2 min at concentrations of 0.01 to 1 mmol/l caused a time- and concentration-dependent overflow with half maximal effects at about 10 s and 100 mol/l, respectively. 2-Methylthio-ATP was equipotent to ATP in inducing ³H-overflow. ADP (100 mol/l), when applied for 2 min, also caused a small ³H-overflow, but , -methylene-ATP (100 mol/l), AMP (100 mol/l), R(–)N⁶-(2-phenylsiopropyl)-adenosine (R(–)-PIA; 10 mol/l) and 5-N-ethylcarboxamidoadenosine (NECA; 1 mol/l) did not. The ³H-overflow induced by 10 s applications of 100 mol/l ATP was abolished by suramin (100 mol/l) and reduced by about 70% by reactive blue 2 (3 mol/l). Electrically evoked overflow, in contrast, was slightly enhanced by suramin, but not modified by reactive blue 2. Xanthine amine congener (10 mol/l) and hexamethonium (10 mol/l) did not alter ATP-evoked release. Removal of extracellular Ca²⁺ from the medium reduced ATP- and electrically induced overflow by about 95%. Tetrodotoxin (1 mol/l) abolished electrically evoked ³H-overflow but inhibited ATP-induced overflow by only 70%. The ₂-adrenoceptor agonist UK 14,304 at a concentration of 1 mol/l diminished both electrically and ATP-evoked tritium overflow by approximately 70%. These results indicate that activation of P₂-purinoceptors stimulates noradrenaline release from rat sympathetic neurons. The release resembles electrically induced transmitter release, but additional mechanisms may contribute. Correspondence to: S. Boehm at the above address     

Photoelectric measurement of neurogenic vasoconstriction in jejunal branches of the rabbit mesenteric artery reveals the presence of presynaptic opioid δ-eceptors

Summary The perivascular nerves of rabbit mesenteric arteries were stimulated with 15 pulses at 2 Hz, and decreases in external diameter were measured by means of a photoelectric device. Both extra- and intraluminally added [Met⁵]-enkephalin 1 mol/l depressed vasoconstriction, although with the second mode of application a larger inhibition occurred. Therefore, in the subsequent experiments all opioids were added into the lumen. [Met⁵]enkephalin 0.1 mol/l had no effect. [d-Pen², l-Pen⁵]enkephalin 3 mol/l was less potent than [Met⁵]enkephalin 1 mol/l. ICI 174864 1 mol/l was also without effect when given alone, but antagonized the action of [Met⁵]enkephalin 1 mol/l.Ethylketocyclazocine, dynorphin A(1–13), normorphine and DAGO, all 1 mol/l, were ineffective. [Met⁵]enkephalin 1 mol/l did not change the vasoconstriction evoked by the application of noradrenaline (0.1 –3 mol/l). It is concluded that in the mesenteric artery action potential-induced transmitter release, and in consequence vasoconstriction can be inhibited by the activation of presynaptic opioid -receptors. Send offprint requests to P. Illes at the above address     

Pharmacokinetics of cefradine, sulfamethoxazole and trimethoprim and their metabolites in a patient with peritonitis undergoing continuous ambulatory peritoneal dialysis

Cefradine and co-trimoxazole pharmacokinetics were studied in a patient with peritonitis that complicated continuous ambulatory peritoneal dialysis (CAPD). Concentrations in the plasma reached after oral administration of 500 mg cefradine four times daily and 400/80 mg co-trimoxazole four times daily were for cefradine 100g/ml, for trimethoprim 15g/ml, and for sulfamethoxazole 100/ml, respectively. In the dialysate concentrations were reached of 35–70/ml cefradine, 2–5/ml trimethoprim and 8–17g/ml sulfamethoxazole. The values for sulfamethoxazole are regarded too low to be clinically effective. Half-lives protein binding values and CAPD clearances are presented. Low CAPD clearances were obtained during the night and high values during the day. The dosage yielded too high plasma trimethoprim concentrations, while sulfamethoxazole dialysate concentrations were too low. It seems questionable therefore whether co-trimoxazole can be used orally for the treatment of CAPD peritonitis.     

Short-term effects of herbicides on primary productivity of periphyton in lotic environments

Freshwater algae are quite sensitive to herbicides that enter running water ecosystems through direct application, aerial drift, and/or watershed run-off. However, due to a lack of suitable methodologies, few studies examine the effects of such contamination on naturally occurring attached algal communities under field conditions (i. e., exposure regimes using pulsed doses or brief episodes of peak concentrations to simulate surface run-off during storm events). This paper describes a method for determining the acute short-term effects of four herbicides (hexazinone, atrazine, tebuthiuron and metolachlor) on the net primary productivity (NPP) of periphytic algae in the field using a portable bankside incubator; NPP was measured by monitoring changes in oxygen production (mg O₂ per m²) upper surface of rock substrate per h and mg O₂ h per mg chlorophyll using the light-dark technique. All herbicides with photosynthetic inhibition as a mode of action significantly reduced NPP. The lowest observed effect concentrations (LOECs) for the herbicides were 43 g hexazinone l^–1, 109 g atrazine l^–1 and 137 g tebuthiuron l^–1. The no observed effect concentrations (NOECs) for these chemicals were <43 g hexazinone l^–1, 93 g atrazine l^–1 and 52 g tebuthiuron l^–1. Metolachlor did not significantly reduce NPP at the concentrations that were tested (range 19.6–274 g l^–1). However, community respiration (which included respiration by invertebrates) was significantly reduced at the highest metolachlor concentration (274 g l^–1). Community respiration was not significantly affected by any concentration of the other three herbicides used.     

Steady-state concentrations of choline and acetylcholine in rat brain parts during a constant rate infusion of deuterated choline

Summary An intravenous infusion of deuterated choline at constant rate for 6 min (5 or 25 moles kg^–1 min^–1) significantly increases the concentration of choline in plasma, occipital cortex and striatum. Both 5 and 25 moles kg^–1 min^–1 increase the concentration of acetylcholine in cortex but only 25 moles kg^–1 min^–1 increases the acetylcholine content in striatum. In contrast, 1 mole kg^–1 min^–1 does not change the choline or acetylcholine content in cortex or striatum. A single pulse injection of choline (200 moles kg^–1) causes a significant increase in the concentration of choline in striatum 30 sec following injection. The choline content returns to normal values within 2 min. These studies show that when a pulse injection of a non-tracer dose of radioactive choline is used to measure brain acetylcholine turnover rate the maintenance of steady state must be verified within seconds after the pulse injection of radioactive choline. When constant infusion of deuterated choline is used to measure turnover rate of acetylcholine in the brain of rats, a dose of 1 mole kg^–1 min^–1 appears to be a maximal infusion rate.     

Effects of the calmodulin antagonists fendiline and calmidazolium on aggregation,secretion of ATP,and internal calcium in washed human platelets

Summary Ca²⁺-calmodulin dependent phosphorylation of myosin is essential for the induction of platelet shape change and subsequent reactions. Therefore, we studied the effects of the calmodulin antagonists fendiline and calmidazolium on the thrombin-induced aggregation, secretion of ATP, and increases in the intracellular free calcium concentration ([Ca²⁺]_i) in washed human platelets in the absence and presence of extracellular Ca²⁺. In Ca²⁺ free medium, fendiline (10–100 M) and calmidazolium (3–30 M) concentration-dependently inhibited aggregation. The effect of fendiline could be partly reversed by extracellular Ca²⁺ and higher thrombin concentrations. Furthermore, aggregations induced by the calcium ionophore ionomycin and by the protein kinase C-activator 4--phorbol 12-myristate 13-acetate were inhibited by fendiline, although to a smaller degree than the thrombin-induced aggregation. Thrombin-induced secretion of ATP was attenuated by low concentrations of fendiline (1–30 M) and calmidazolium (1 M) but enhanced by higher concentrations (10–30 and 3–10 M, respectively), independently of extracellular Ca²⁺. Fendiline (1–10 M) did not affect [Ca²⁺]_i in resting and thrombin-stimulated platelets. At higher concentrations (30–100 M), it induced increases in [Ca²⁺]_i in unstimulated platelets and attenuated the response to thrombin in Ca²⁺ free medium, whereas thrombin-induced Ca²⁺ influx was markedly enhanced. Similar results were obtained with calmidazolium (1–3 M). These stimulating effects on ATP secretion and on [Ca²⁺]_i of fendiline and calmidazolium may be attributed to interactions with platelet membranes by which the permeability of small cations is increased. In contrast to these actions that would be normally considered platelet-activating, our study demonstrates that the two calmodulin antagonists effectively antagonize [Ca²⁺]_i ^– mediated induction of platelet aggregation. Send offprint requests to A. Lückhoff at the above address     

5-HT-induced neurogenic relaxations of the guinea-pig proximal colon: investigation into the role of ATP and VIP in addition to nitric oxide

In the guinea-pig proximal colon, 5-hydroxytryptamine (5-HT) relaxes the longitudinal muscle by stimulating neuronal 5-HT receptors, which induces the release of nitric oxide (NO). It was investigated whether the inhibitory neurotransmitters adenosine 5-triphosphate (ATP) and/or vasoactive intestinal polypeptide (VIP) could be involved as well.Antagonists to block the contractile response to 5-HT via 5-HT₂, 5-HT₃ or 5-HT₄ receptors were present throughout the experiments and methacholine was administered to precontract the strips. ATP, VIP and 5-HT induced concentration-dependent relaxations, in the case of 5-HT yielding a non-monophasic concentration-response curve. Tetrodotoxin (TTX; 300 nM), N^G-nitro-l-arginine (l-NNA, 100 M) and their combination did not inhibit the relaxations induced by VIP (up to 0.3 M) or 0.3–3 M ATP but reduced those by 10 M ATP. Suramin (300 M) strongly inhibited the relaxations to ATP and VIP. l-NNA and suramin also inhibited the relaxations to 5-HT. In the presence of l-NNA (100 M), suramin did not significantly inhibit the relaxations to 5-HT. Suramin did not affect the relaxations to isoprenaline, nitroglycerin or exogenous NO (1 M), demonstrating its specificity. Apamin (30 nM) inhibited both the relaxations to ATP (by 70–100%) and to 5-HT; relaxations to isoprenaline were partially inhibited, indicating a non-specific component in the inhibitory action of apamin. However, relaxations to exogenous VIP (up to 0.3 M), NO (1 ,M) and to nitroglycerin were not inhibit ed. In the presence of l-NNA (100 M), apamin inhibited the relaxations to 5-HT only at 30 M. ,\-methylene-ATP (,-Me-ATP; 100 M) did not desensitize the responses to ATP. Reactive blue 2 affected the relaxations to isoprenaline at concentrations necessary to significantly inhibit the relaxations to ATP (i.e. from 10 M onwards). Thus, it was not possible to test either ,-Me-ATP or reactive blue 2 against the relaxations to 5-HT. -Chymotrypsin (0.015 mg·ml^–1) and trypsin (0.005 mg·ml^–1) almost abolished the relaxations to VIP, but did not affect those to isoprenaline and 5-HT. The VIP receptor antagonists [p-Cl-d-Phe⁶, Leu¹⁷]VIP (1 M) and VIP_10–28 (1 and 3 M) did not affect the concentration-response curve to VIP and were hence not tested against 5-HT. Phosphoramidon (1 M) had no effect on the relaxations to VIP or 5-HT.It can be concluded that in the guinea-pig colon longitudinal muscle, VIP and ATP induce relaxation via a direct effect on the smooth muscle, not involving NO. 5-HT-induced relaxations are mediated by NO as well as by a substance which is sensitive to inhibition by suramin but not apamin. It is suggested that this substance is ATP and not a peptide.     

Antagonism by γ-aminobutyric acid of the stimulant effect of angiotensin II on cardiac sympathetic ganglia in spinal dogs

Summary The effects of angiotensin II and neuro-aminoacids administered through the right subclavian artery (i. a.) to the cardiac sympathetic ganglia were investigated in spinal dogs. Angiotensin II (1–8 g) elicited a dose-dependent positive chronotropic effect which was reduced after i. a. injection of saralasin (100g). The effect of angiotensin II was not reduced after combined treatment with either hexamethonium (10 mg/kg) plus atropine (0.1 mg/kg) or hemicholinium-3 (5 mg/kg) plus preganglionic stimulation. The dosedependent response to angiotensin II of heart rate was inhibited by GABA (50, 500g), GABOB (500g) and muscimol (50, 100g). The inhibition of the response to angiotensin II by a small dose of GABA (50g), but not by a high one (500g), was antagonized by i. a. injection of picrotoxin (2 mg). The positive chronotropism induced by bethanechol (25, 50g) and a small dose of acetylcholine (25g) were significantly inhibited by a high dose (500g) but not by a low dose (50g) of GABA. These results confirm that angiotensin II stimulates cardiac chronotropism by acting on the angiotensin II receptor located at the cardiac ganglia and show that this stimulant effect is antagonized by GABA.     

Evidence for M1 muscarinic cholinoceptors mediating facilitation of noradrenaline release in guinea-pig carotid artery

Summary The muscarinic agonists acetylcholine (150 mol/l), carbachol (1–10 mol/l) and McN-A-343 (1–50 mol/l, selective for M₁ receptors) increased, in a concentration-dependent manner, the electrically-evoked tritium overflow from guinea-pig carotid arteries preincubated with [³H]-noradrenaline. The increase caused by acetylcholine was not modified by hexamethonium (300 mol/l) but was reduced by the muscarinic receptor antagonists methylatropinium (0.5 and 1 nmol/l, nonselective), pirenzepine (1 and 5 mol/l, M₁-selective), methoctramine (1 and 5 mol/l, M₂-selective) and pfluoro-hexahydro-sila-difenidol (0.1–1 mol/l, M₃-selective). The order of potencies (expressed as negative logarithms of concentrations that reduced by 50% the facilitatory effect of acetylcholine) was: methylatropinium (9.93) > pirenzepine (8.83) > p-fluoro-hexahydro-siladifenidol (6.81) methoctramine (6.20). These results demonstrate the existence of facilitatory M₁ receptors modulating noradrenaline release in blood vessels. Correspondence to M. Salaices at the above address     

Pharmacokinetic study of methotrexate,folinic acid and their serum metabolites in children treated with high-dose methotrexate and leucovorin rescue

Summary The pharmacokinetics of methotrexate (MTX), 7-hydroxymethotrexate (7-OHMTX), 2,4-diaminomethylpteroic acid (APA), folinic acid, and 5-methyltetrahydrofolate (5-MTHF) have been studied during 21 high-dose MTX (HDMTX) infusions (5 g·m^–2 in 24 h) with leucovorin (LCV) rescue, a component of the therapy of 5 children with acute lymphoblastic leukemia (ALL).The median steady-state concentration of MTX was 66 mol·l^–1. Three elimination half-lifes were determined for MTX: 1.8 h, 6.4 h and a terminal 15 h. The median systemic MTX clearance was 110 mg·m^–2·min^–1.The 7-OHMTX level increased during each infusion and a C_max of 19 mol·l^–1 was achieved at the end. Its initial half-life was 5 h and the terminal half-life was 12 h. Thus, the peak serum concentration ratio of 7-OHMTX to MTX was reached 24 h after the end of the infusion at a median ratio of 8.The MTX metabolite APA was detected in concentrations less than 0.06 mol·l^–1. The median folinic acid level during rescue, 48 h after starting the infusion, was 7.0 mol·l^–1 and 18 h following the last dose of LCV it was 0.44 mol·l^–1, leading to ratios of folinic acid to MTX of 31 and 6, respectively. The median 5-MTHF level during rescue was 0.44 mol·l^–1 with a median ratio of 5-MTHF to MTX of 2.Twenty infusions with 48 h MTX levels of less than 0.5 mol·l^–1 were without marked toxicity. Only one patient with a 48 h MTX concentration of 5.5 mol·l^–1 and a ratio of 5-MTHF to MTX of 0.08 suffered from ulcerating mucositis and septicaemia despite increased and prolonged LCV rescue.     

Opioid peptides decrease noradrenaline release and blood pressure in the rabbit at peripheral receptors

Summary Effects of dynorphin-(1–13), Leu⁵-enkephalin,d-Ala²,d-Leu⁵-enkephalin (DADLE), and for comparison bremazocine, on plasma noradrenaline concentration and mean arterial pressure (MAP) were studied in pithed rabbits. In the first series of experiments, the sympathetic outflow was stimulated electrically via the pithing rod at 2 Hz twice for 3 min each (S₁, S₂). Drugs were administered before S₂. Bremazocine 10 g/kg+2g/kg/h and 100 g/kg+20 g/kg/h, dynorphin 1 and 3 g/kg/min, Leu⁵-enkephalin 100 g/kg/min and DADLE 10 and 30 g/kg/min all diminished the electrically-evoked increase in plasma noradrenaline and MAP. The effects were antagonized by naloxone. In the second series, an infusion of noradrenaline (2 g/kg/min) was given twice for 3 min each (N₁, N₂). Drugs were administered before N₂. Bremazocine 100 g/kg+20 g/kg/h slightly enhanced the pressor effect of exogenous noradrenaline, whereas dynorphin 3 g/kg/min, Leu⁵-enkephalin 100 g/kg/min and DADLE 30 g/kg/min caused no significant change. In the third series, the sympathetic outflow was stimulated continuously at 2 Hz, and the interaction of dynorphin and DADLE was studied. Dynorphin 1 g/kg/min and DADLE 10g/kg/min initially decreased MAP to a similar extent. The effect of DADLE faded with time. When, during continuous infusion of DADLE 10 g/kg/min, and after return of MAP to the pre-DADLE level, dynorphin 1 g/kg/min or DADLE 10 g/kg/min was infused additionally, the effect of dynorphin was unchanged, whereas that of DADLE was almost abolished. We conclude that the opioid peptides as well as bremazocine decrease action potential-evoked release of noradrenaline and, secondarily, blood pressure. They act at peripheral sites, presumably prejunctional opioid receptors at postganglionic sympathetic axons. Dynorphin on the one hand, and Leu⁵-enkephalin and DADLE on the other hand, appear to act at different receptors, dynorphin probably at a - and DADLE and Leu⁵-enkephalin at a -receptor.     

Salivary nystatin concentrations after administration of an osmotic controlled release tablet and a pastille

Mucosal oral therapeutic system (MOTS) is a controlled-release osmotic system for oral cavity therapy. MOTS (nystatin) is designed to deliver approximately 200,000 units of nystatin over several hours. A crossover study was conducted in five healthy volunteers to evaluate the amount of nystatin released (based on residual drug content) when the system is held in the mouth for 30 min, 1 h, and 2 h, and to compare these concentrations with those achieved with a Mycostatin (nystatin) pastille.An average of 37% of the nystatin content was released intra-orally from MOTS during 2 h in the mouth, which was very similar to the percentage delivered in vitro. Mean salivary drug concentrations were as follows: 279 g·ml^–1 at 30 min; 654 g·ml^–1 after 1 h; and 532 g·ml^–1 at 2 h. These concentrations consistently exceeded those produced by the pastille at the same time points. Fifteen minutes after placement of the pastille in the mouth (i.e., immediately after its dissolution) mean nystatin concentrations reached 746 g·ml^–1 but fell rapidly to 13.2 g·ml^–1 at 30 min, 7.2 g·ml^–1 at 1 h, and 5.6 g·ml^–1 at 2 h.The study demonstrates that MOTS maintains high salivary nystatin concentrations throughout a 2 h dosing interval.     

The effect of some antidepressants on prejunctional muscarinic receptors on the sympathetic nerves of the isolated rabbit ear artery

Summary The antimuscarinic activity of amitriptyline, desipramine, iprindole, mianserin and viloxazine on prejunctional sympathetic nerve endings were compared in the isolated rabbit ear artery. In the presence of cocaine (10 M) and yohimbine (1 M), amitriptyline (0.5–1 M), desipramine (1–3 M) and iprindole (5–10 M), desipramine (1–3 M) and iprindole (5–10 M) produced parallel rightward shifts of the concentration-response curve for the inhibitory effect of carbachol (CCh) on responses to electrical stimulation of the preparation at 3 Hz. Mianserin (3 M) produced some inhibition but altered the slope of the concentration-responses curve to CCh while viloxazine (10 M) produced no inhibition.The depression of tritium efflux by CCh from arteries preincubated in ³H-noradrenaline was inhibited significantly (P<0.05) by amitriptyline (0.1 M) and desipramine (1 M) and not by iprindole (17 M), mianserin (3 M) or viloxazine (10 M). Amitriptyline was 10-fold more active than desipramine and at least 30-fold more active than the other antidepressants as a muscarine receptor blocking drug in this preparation.Thus, mianserin, viloxazine and iprindole exhibit much weaker antimuscarinic activity relative to amitriptyline on prejunctional muscarine receptors on sympathetic nerve endings compared with that observed by others for excitatory muscarine receptors in sympathetic ganglia. The findings support an earlier suggestion that these receptors differ.