Age and segmental differences in 5-hydroxytryptamine-induced hypersecretion in the pig small intestine

5-Hydroxytryptamine is a mediator in cholera toxin-induced hypersecretion in the small intestine. Our hypothesis is that the hypersecretion induced by 5-hydroxytryptamine in the small intestine decreases with increasing age and in an aboral direction in the small intestine. In vivo, measuring accumulated fluid in ligated loops, the apparent maximal efficacy of the 5-hydroxytryptamine-induced jejunal secretion in pig neonates was 4.8±1.1 mg·mg^–1 dry loop·45 min^–1. The apparent maximal efficacy decreased by 23% and 63% in young and adult pigs, respectively, compared with neonates. In vitro, measuring changes in short-circuit current in Ussing chambers, the apparent maximal efficacy was 66.7±4.8 A·cm^–2 in neonates and was reduced by 30% and 57% in young and adult pigs, respectively. Young pigs were used in the segmental study. The apparent maximal efficacy in vivo was 3.7±0.5 mg·mg^–1 dry loop and decreased by 22% and 56% in the mid and distal small intestine, respectively. By contrast, in vitro the apparent maximal efficacy was elevated by 56% to 72.0±5.0 A·cm^–2 in the distal compared with the proximal part. In conclusion, the secretory response to 5-hydroxytryptamine in pig small intestine decreases with increasing age and in the aboral direction according to in vivo results. We suggest that the decrease in sensitivity to 5-hydroxytryptamine can explain a part of the reduced secretory response to cholera toxin with age and in the aboral direction of the small intestine.Abbreviations ASF pituitary peptide antisecretory factor - AMP cyclic adenosine monophosphate - CT cholera toxin - E _max apparent maximal efficacy - EC enterochromaffine ENS enteric nerve system - 5-HT 5-hydroxytryptamine serotonin - LT heat-labile - E. coli enterotoxin - PD electrical potential difference - R tissue resistance - SCC short-circuit current - VIP vasoactive intestinal peptide     

(4S)-4-amino-5,6-heptadienoic acid (MDL 72483): A potent anticonvulsant GABA-T inhibitor

(4S)-4-Amino-5,6-heptadienoic acid ((S)--allenyl-GABA; MDL 72483) is a potent inactivator of brain GABA-T in mice; (ED₅₀ (i.p.)=60 mg·kg^–1; ED₅₀ (oral)=70 mg·kg^–1). Its anticonvulsant effects against 3-mercaptopropionic acid (MPA)-induced seizures in mice is related to the elevation of whole brain GABA concentrations: The mentioned doses of MDL 72483 which cause a decrease of GABA-T activity by 50%, produce within 5 h after dosing an increase of GABA concentration by about 3 mol·g^–1, and protect 50% of the mice against seizures in this model of presynaptic GABA deficit. When given orally MDL 72483 is about five times more potent than vigabatrin ((4R/S)-4-amino-5-hexenoic acid) a known antiepileptic GABA-T inhibitor. Complete protection was achieved with a dose of 150 mg·kg^–1. Similar to vigabatrin, MDL 72483 does not protect significantly against metrazol-induced convulsions. However, at a dose of 300 mg·kg^–1, the time elapsing between metrazol administration and onset of convulsions was prolonged by a factor of 3.4. Oral administration of MDL 72483 for up to 19 days at a daily dose of 91–96 mg·kg^–1 did not produce any obvious behavioral changes in mice, nor was the ED₅₀ of the drug in MPA-seizure tests significantly altered by the pretreatment. These observations indicate that MDL 72483 is a promising drug for the treatment of certain epilepsies.Special issue dedicated to Dr. Eugene Roberts.     

Effects of serotonin on the cardio-circulatory system of the European eel (Anguilla anguilla) in vivo

The effects of serotonin on continuously recorded cardiac parameters (heart rate, cardiac output, cardiac stroke volume), ventral and dorsal aortic blood pressures, branchial and systemic vascular resistances were investigated in the European eel in vivo. Intravenous administration of serotonin (30 g · kg^–1) caused a marked bradycardia (45%) and a simultaneous decrease in cardiac output (50%), ventral (35%) and dorsal (50%) aortic blood pressures. Branchial resistance was markedly increased (60%) and systemic resistance decreased (30%). Cardiac stroke volume remained unchanged. The effects of serotonin on cardiac mained unchanged. The effects of serotonin on cardiac parameters were suppressed either by methysergide or a bilateral section of the cardiac vagus. Bradycardia could then be regarded as the consequence of a vagal mechanism triggered by serotonin action on central methysergide-sensitive serotonergic receptors. No inotropic effect of serotonin was observed. This lack of myocardiac contractility modification is discussed. The serotonin-mediated branchial vasoconstriction was attenuated by vagotomy, whereas the residual increase in branchial resistance (40%) was suppressed by methysergide. The serotonin-mediated branchial vasoconstriction could be the consequence of both a passive mechanism (compliance) caused by the decrease in cardiac output and an active mechanism involving methysergide-sensitive serotonergic receptors of the branchial vasculature. A possible involvement of this vasomotor effect in gill oxygen uptake is discussed. The serotonin-induced systemic vasodilation was insensitive either to cardiac vagotomy or to 5-HT_1/2, 5-HT₃ and 5-HT₄ receptor antagonists, suggesting the involvement of a local mechanism which remains to be assessed.Abbreviations CSV cardiac stroke volume - DAP dorsal aortic pressure - HR heart rate - QC cardiac output - VAP ventral aortic pressure - VR _b branchial vascular resistance - VR _s systemic vascular resistance - VR _t total vascular resistance - 5-HT 5-Hydroxytryptamine serotonin - RBI Research Biochemical Incorporated, metoclopramide HCl     

Noradrenalin antagonizes effects of serotonin and acetylcholine in the seawater eel intestine

After inhibiting ion and water transport with 10^-6 mol·l^-1 serotonin and 10^-6 mol·l^-1 methacholine, a muscarinic agonist of acetylcholine, 10^-5 mol·l^-1 (±)noradrenaline restored the serosa-negative transepithelial potential difference and short-circuit current in a step-like manner, accompanied by an increase in water absorption across the seawater eel intestine. Such recovery by noradrenalin was not obtained after pretreatment with 10^-7 mol·l^-1 eel atrial natriuretic peptide. This means that the inhibitory mechanisms of serotonin and acetylcholine are different from those of atrial natriuretic peptide. Similarly, 10^-7 mol·l^-1 clonidine and guanabenz (₂-agonists) also reversed the inhibitory action of serotonin and methacholine, but 10^-7 mol·l^-1 phenylephrine (₁-agonists) and 10^-7 mol·l^-1 isoproterenol (-agonist) did not antagonize serotonin and methacholine actions. Further, the enhancement by 10^-5 mol·l^-1 noradrenalin was blocked by 10^-4 mol·l^-1 yohimbine (₂-agonists) and 10^-4 mol·l^-1 prazosin (₁-agonists), but not by 10^-4 mol·l^-1 propranolol (-antagonist). Although relatively high dosage is required to obtain a significant effect, and discrimination between ₁- and ₂- is not successful in the present study, these results suggest that noradrenalin acts on an -type receptor. The -type receptor may exist on the enterocytes, since the effects of noradrenalin are observed even in the presence of 10^-6 mol·l^-1 tetrodotoxin. Interestingly, the tissue resistance also increased in parallel with increase in the short-circuit current after treatment with noradrenalin in the posterior part of the seawater eel intestine.Abbreviations ACh acetylcholine - 5-HT serotonin - eANP eel atrial natriuretic peptide - I _sc short-circuit current - MCh methacholine - NA noradrenalin - PD transepithelial potential difference - R _t tissue resistance - TTX tetrodotoxin - VIP vasoactive intestinal peptide     

Basal oxygen consumption,ventilatory frequency,and heart rate during the protracted spawning run of the Southern Hemisphere lamprey Geotria australis

Summary Basal oxygen consumption, ventilatory frequency, and heart rate were recorded at four different times during the unusually protracted 15–16-month spawning run of the Southern Hemisphere lamprey Geotria australis. At 15°C, the mean basal oxygen consumption of G. australis caught immediately after they had left the sea and embarked on the spawning run (45 l · g^-1 · h^-1) was less than in young adults about to commence their marine feeding phase (64 l · g^-1 · h^-1), but greater than in large ammocoetes (26.5 l · g^-1 · h^-1). Basal oxygen consumption fell progressively during the spawning-run of to 33 l · g^-1 · h^-1 after 5 months and 25 l · g^-1 · h^-1 after 10 months, before rising to 35 l · g^-1 · h^-1 after 15 months when the animals were approaching sexual maturity. The downwards trend in basal oxygen consumption contrasts with that recorded during the spawning run of Lampetra fluviatilis. Furthermore, these values for spawning-run of G. australis are far lower than those measured at any time during the upstream migration of L. fluviatilis or during the parasitic phase of landlocked Petromyzon marinus. A low and declining metabolic rate during much of the spawning run of G. australis would facilitate the conservation of energy reserves during this very long non-feeding period. Trends shown by ventilatory frequency and heart rate essentially parallel those of basal oxygen consumption. The Q₁₀s for basal oxygen consumption, ventilatory frequency and heart rate over the temperature range 5–25°C were 1.6, 1.6, and 1.7, respectively. The trends shown by basal oxygen consumption during metamorphosis and the upstream migration did not parallel those exhibited by circulating thyroid hormones.     

Plasma glucose kinetics and tissue uptake in brown trout in vivo: effect of an intravascular glucose load

The object of the present study was to elucidate whether a glucose load modifies glucose uptake by tissues in brown trout in vivo. By the use of 2-[1,2-³H]-deoxyglucose, plasma glucose disappearance rate and tissue glucose uptake were measured after an intraaortic glucose load of 500 mg·kg^-1 (glucose load group) and under normoglycemic conditions (control). We also attempted to determine whether fasting modifies the glucose load disposal (fasted glucose load group). The procedure used to calculate 2-deoxyglucose uptake by tissues was evaluated, and the levels of 2-deoxyglucose uptake were compared with those of 2-deoxyglucose phosphorylation. Uptake and phosphorylation rates were similar in all tissues, except in brain and heart. In all the groups glucose uptake rates were highest in spleen, kidney, brain and gills, and lowest in red muscle, heart and white muscle. However, white muscle was the main site of glucose uptake on a whole tissue basis. The glucose load led to strong, long-lasting hyperglycemia, in spite of the increases observed in plasma insulin levels and in glucose uptake rate by the whole body (control: 4.9 mol·min^-1·kg^-1; glucose load group: 6.5 mol·min^-1·kg^-1). This higher rate was due to the higher glucose uptake only in white and red muscles (four- and threefold, respectively). Fasting halved the uptake of glucose by both red and white muscles in the load condition. In consequence the use of exogenous glucose decreased with fasting (fasted glucose load group: 5.1 mol·min^-1·kg^-1), causing still longer hyperglycemia.Abbreviations bw body weight - 2DG 2-[1,2-³H]-deoxyglucose - 2DG-P 2-[1,2-³H]-deoxyglucose phosphate - dpm disintegrations per min - FGL fasted glucose load group - GL glucose load group - G-6-Pase glucose-6-phosphatase - LG L-[1-¹⁴C]-glucose - MS-222 3-aminobenzoic acid ethyl ester methanesulphonate salt     

Penicillin recovery from aqueous solutions by continuous foam flotation

Summary Penicillin G recovery is investigated in a continuous flotation column in the presence of different collectors which form a complex with penicillin. The performance of the penicillin recovery was investigated as a function of the mole ratio () of collector-to-penicillin and the aliphatic chain length of the collector. At =1 and low penicillin concentrations (e.g., 20 mg·1^-1), high foam liquid concentrations (680 mg·l^-1), low residue concentrations (12 mg·l^-1) and high penicillin separation (56) can be attained. At =4 the separation increases to 150, and 95% of the penicillin can be recovered.Symbols C_p penicillin concentration in feed (mg·l^-1) - C_R penicillin concentration in outlet liquid (mg·l^-1) - C_S penicillin concentration in foam liquid (mg·l^-1) - C_S/C_P penicillin enrichment (-) - C_S/C_R penicillin separation (-) - % Pen in S penicillin yield in foam liquid (%) - VV}_S foam liquid volume flow (ml·min^-1) - VV}_P feed (ml·min^-1) - VV_{N 2} nitrogen flow rate (ml·s^-1) - temperature     

Organic reduction of tapioca wastewaters using modified RBC

A modified Rotating Biological Contactor (RBC) was used for the treatability studies of synthetic tapioca wastewaters. The RBC used was a four stage laboratory model and the discs were modified by attaching porous nechlon sheets to enhance biofilm area. Synthetic tapioca wastewaters were prepared with influent concentrations from 927 to 3600 mg/l of COD. Three hydraulic loads were used in the range of 0.03 to 0.09 m³·m^–2·d^–1 and the organic loads used were in the range of 28 to 306 g COD· m^–2·d^–1. The percentage COD removal were in the range from 97.4 to 68. RBC was operated at a rotating speed of 18 rpm which was found to be the optimal rotating speed. Biokinetic coefficients based on Kornegay and Hudson models were obtained using linear analysis. Also, a mathematical model was proposed using regression analysis.List of Symbols A m² total surface area of discs - d m active depth of microbial film onany rotating disc - K _s mg ·l^–1 saturation constant - P mg·m^–2·^–1 area capacity - Q l·d^–1 hydraulic flow rate - q m³·m^–2·d^–1 hydraulic loading rate - S ₀ mg·l^–1 influent substrate concentration - S _e mg·l^–1 effluent substrate concentration - w rpm rotational speed - V m³ volume of the reactor - X _f mg·l^–1 active biomass per unit volume ofattached growth - X _s mg·l^–1 active biomass per unit volume ofsuspended growth - X mg·l^–1 active biomass per unit volume - Y _s yield coefficient for attachedgrowth - Y _A yield coefficient for suspendedgrowth - Y yield coefficient, mass of biomass/mass of substrate removed Greek Symbols hr mean hydraulic detention time - (_max)_A d^–1 maximum specific growth rate forattached growth - (_max)_s d^–1 maximum specific growth rate forsuspended growth - _max d^–1 maximum specific growth rate - d^–1 specific growth rate - _v mg·l^–1·hr^–1 maximum volumetric substrateutilization rate coefficient     

The effects of FMRFamide, 5-hydroxytryptamine and phorbol esters on the heart of the mussel Geukensia demissa

Summary The ventricle of the mussel Geukensia demissa is inhibited by 5-hydroxytryptamine and excited by the molluscan neuropeptide FMRFamide. Supra-threshold doses of amide result in marked positive chronotropy and inotropy within 5–15 s. 5-Hydroxytryptamine at 10^-8 M produces diastolic arrest within 10 s. A 1-min exposure to FMRFamide (5 · 10^-8 M) results in a small increase in the cytoplasmic levels of adenosine 3,5-cyclic monophosphate; shorter or longer exposures have no effect. The cAMP content of ventricles incubated in 5 · 10^-8 M 5-hydroxytryptamine for 1 min decreases by 2.3 pmol/mg protein; longer or shorter incubations have no effect. Treatment with forskolin results in 3-or 4-fold increases in adenosine 3,5-cyclic monophosphate, but forskolin has no effect on the mechanical activity of the ventricle. The levels of inositol monophosphate, inositol 1,4-diphosphate, and inositol 1,4,5-triphosphate in tissues exposed to 5-hydroxytryptamine are not different from levels in control tissues. FMRFamide decreases the levels of these phosphoinositides by 50% or more. Lower concentrations of phorbol 12,13-diacetate (10^-8 to 10^-7 M) and phorbol 12-myristate, 13-acetate (10^-6 M) cause positive chronotropy in the isolated ventricle; higher concentrations induce systolic arrest. These results suggest that the effects of 5HT on the ventricle are not mediated by adenosine 3,5-cyclic monophosphate or inositol 1,4,5-triphosphate. The effects of FMRFamide may involve a decrease in inositol 1,4,5-triphosphate. The effects of amide may involve a decrease in inositol 1,4,5-triphosphate. The response of the ventricles to phorbol esters suggest that protein kinase C may be involved in the regulation of cardiac contractility.Abbreviations cAMP adenosine 3,5-cyclic monophosphate - DMA dimethylformamide - DMSO dimethylsulfoxide - FMRFamide Phenylalanyl-methionyl-arginyl-phenylalanylamide - 5HT 5-hydroxytryptamine - IP inositol monophosphate - IP₂ inositol 1,4-diphosphate - IP₃ inositol 1,4,5-triphosphate - PDA phorbol 12,13-diacetate - PMA phorbol 12-myristate, 13-acetate - SW sea water Present address: MSU; E.M. Center, Memphis, TN 38152, USA     

Purification and characterization of glycogen phosphorylase A and B from the freeze-avoiding gall moth larvae Epiblema scudderiana

The active a and inactive b forms of glycogen phosphorylase from cold-hardy larvae of the gall moth, Epiblema scudderiana, were purified using DEAE⁺ ion exchange and 3-5-AMP-agarose affinity chromatography. Maximum activities for glycogen phosphorylases a and b were 6.3±0.74 and 2.7±0.87 mol glucose-1-P·min^-1·g wet weight^-1, respectively, in -4°C-acclimated larvae. Final specific activities of the purified enzymes were 396 and 82 units·mg protein^-1, respectively. Both enzymes were dimers with native molecular weights of 215000±18000 for glycogen phosphorylase a and 209000±15000 for glycogen phosphorylase b; the subunit molecular weight of both forms was 87000±2000. Both enzymes showed pH optima of 7.5 at 22°C and a break in the Arrhenius relationship with a two- to four-fold increase in activation energy below 10°C. Michaelis constant values for glycogen at 22°C were 0.12±0.004 mg·ml^-1 for glycogen phosphorylase a and 0.87±0.034 mg·ml^-1 for glycogen phosphorylase b; the Michaelis constant for inorganic phosphate was 6.5±0.07 mmol·l^-1 for glycogen phosphorylase a and 23.6 mmol·l^-1 for glycogen phosphorylase b. Glycogen phosphorylase b was activated by adenosine monophosphate with a K _a of 0.176±0.004 mmol·l^-1. Michaelis constant and K _a values decreased by two- to fivefold at 5°C compared with 22°C. Glycerol had a positive effect on the Michaelis constant for glycogen for glycogen phosphorylase a at intermediate concentrations (0.5 mol·l^-1) but was inhibitory to both enzyme forms at high concentrations (2 mol·l^-1). Glycerol production as a cryoprotectant in E. scudderiana larvae is facilitated by the low temperature-simulated glycogen phosphorylase b to glycogen phosphorylase a conversion and by positive effects of low temperature on the kinetic properties of glycogen phosphorylase a. Enzyme shut-down when polyol synthesis is complete appears to be aided by strong inhibitory effects of glycerol and KCl on glycogen phosphorylase b.Abbreviations E _a activation energy - GPa glycogen phosphorylase a - GPb glycogen phosphorylase b - h Hill coefficient - I ₅₀ concentration of inhibitor that reduces enzymes velocity by 50% - K _a concentration of activator that produces half-maximal activation of enzyme activity - K _m Michaelis-Menten substrate affinity constant - MW molecular weight - PEG polyethylene glycol - P_i morganic phosphate - SDS PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - V _max enzyme maximal velocity     

Purification and properties of an extra cellular xylanase enzyme ofClostridium strain SAIV

An extracellular xylanase enzyme fraction A from a mesophilicClostridium strain SAIV was purified by ammonium sulfate precipitation, Sephadex G-50 gel filtration and DEAE-Sephadex A-50 ion exchange. The xylanase exhibited a molecular weight of 30,000 and it was stable upto 55° C with an optimum temperature of 50° C. It was most stable between pH 5–7, with an optimum pH of around 6. The Km value was 7.0 mg·xylan ml^-1 and V_max was 36 mol·xylose liberated mg^-1 min^-1. Carboxymethyl cellulose, filter paper cellulose and 4-p-nitrophenyl -D-xylopyranoside were not hydrolysed. The specific activity of xylanase fraction A (9.8 U mg^-1) is 2–10 fold higher than the specific activity of xylanase in other mesophilic, xylanolytic, obligate anaerobic bacteria. A minor fraction of xylanase activity designated as xylanase B was also obtained supporting the view that the multiplicity of xylanases is common in microorganisms.     

Differential responses to copper in rainbow trout (Oncorhynchus mykiss) acclimated to sea water and brackish water

Rainbow trout, Oncorhynchus mykiss, acclimated to 33% sea water (12 mg·ml^-1 salinity) experienced significant (10 meq·1^-1) increases in plasma [Na⁺] and [Cl^-] within 5 h of exposure to 6.3 mol copper·1^-1 indicating severe impairment of branchial ionoregulatory capacity. All plasma ion levels subsequently stabilised once the transbranchial [Na⁺] gradient was reduced to zero. The similar ionic strength of the external medium and their body fluids appeared to protect trout maintained in 33% sea water from further ionoregulatory stress and any secondary physiological disturbances during exposure to copper. Despite three- and fourfold greater transbranchial [Na⁺] and [Cl^-] gradients, trout acclimated to full-strength sea water (35 mg·ml^-1 salinity) suffered no major changes in plasma Na⁺, Cl^-, K⁺, or Ca²⁺, blood gases or haematology during 24 h exposure to 6.3 mol copper·1^-1. This reduction in toxicity in full strength sea water cannot be explained by differences in copper speciation. We suggest that during acute exposure to waterborne copper, active NaCl extrusion is unaffected due to the basolateral location of the gill Na⁺/K⁺-ATPase, but that ionoregulatory disturbances can occur due to gill permeability changes secondary to the displacement of surface-bound Ca²⁺. However, in full strength sea water the three-fold higher ambient [Ca²⁺] and [Mg²⁺] appear to be sufficient to prevent any detrimental permeability changes in the presence of 6.3 mol copper·1^-1. Plasma [NH ₊ ⁴ ] and [HCO _- ³ ] were both significantly elevated during exposure to copper, indicating that some aspects of gill ion transport (specifically the apical Na⁺/NH ₊ ⁴ and Cl^-/HCO _- ³ exchanges involved in acid/base regulation and nitrogenous waste excretion) are vulnerable to inhibition in the presence of waterborne copper.Abbreviations C _aO₂ arterial oxygen content - Hb haemoglobin - Hct haematocrit - MABP mean arterial blood pressure - MCHC mean cell haemoglobin content - MO₂ rate of oxygen consumption - P _a CO₂ arterial carbon dioxide tension - P _aO₂ arterial oxygen partial pressure - S salinity - SW sea water - T _Amm total ammonia (=NH₃+NH ₊ ⁴ ) - T _{CO 2} total carbon dioxide - TEP transepithelial potential - TOC total organic carbon - %Hb-O₂ percentage of haemoglobin saturated with oxygen     

Anaerobic acetate oxidation to CO2 by Desulfotomaculum acetoxidans

Desulfotomaculum acetoxidans has been proposed to oxidize acetate to CO₂ via an oxidative acetyl-CoA/carbon monoxide dehydrogenase pathway rather than via the citric acid cycle. We report here the presence of the enzyme activities required for the operation of the novel pathway. In cell extracts the following activities were found (values in brackets=specific activities and apparent K _m; 1 U·mg^-1=1 mol·min^-1·mg protein^-1 at 37°C): Acetate kinase (6.3 U·mg^-1; 2 mM acetate; 2.4 mM ATP); phosphate acetyltransferase (60 U·mg^-1, 0.4 mM acetylphosphate; 0.1 mM CoA); carbon monoxide dehydrogenase (29 U·mg^-1; 13% carbon monoxide; 1.3 mM methyl viologen); 5,10-methylenetetrahydrofolate reductase (3 U·mg^-1, 0.06 mM CH₃–FH₄); methylenetetrahydrofolate dehydrogenase (3.6 U·mg^-1, 0.9 mM NAD, 0.1 mM CH₂=FH₄); methenyltetrahydrofolate cyclohydrolase (0.3 U·mg^-1); formyltetrahydrofolate synthetase (3 U·mg^-1, 1.4 mM FH₄, 0.4 mM ATP, 13 mM formate); and formate dehydrogenase (10 U·mg^-1, 0.4 mM formate, 0.5 mM NAD). The specific activities are sufficient to account for the in vivo acetate oxidation rate of 0.26 U·mg^-1.Non-standard abbreviations FH₄ Tetrahydrofolate - CHO-FH₄ N¹⁰-formyltetrahydrofolate - CHFH₄ N⁵,N¹⁰-methenyltetrahydrofolate - CH₂=FH₄ N⁵,N¹⁰-methylenetetrahydrofolate - CH₃–FH₄ N⁵-methyltetrahydrofolate - MOPS morpholinopropane sulfonic acid - DTT d,l-1,4-dithiothreitol - TRIS tris-(hydroxymethyl)-aminomethane - Ap₅A p¹,P⁵-di(adenosine-5)pentaphosphate - MV methyl viologen     

Effects of eel atrial natriuretic peptide on NaCl and water transport across the intestine of the seawater eel

Summary Eel atrial natriuretic peptide inhibited the serosa-negative transepithelial potential difference and short-circuit current, accompanied by a decrease in NaCl and water absorption across the seawater eel intestine. Similar effects were obtained after treatment with N-terminally truncated eel atrial natriuretic peptide (5–27), indicating that N-terminal amino acids are not essential for the action of eel atrial natriuretic peptide. Although mammalian atrial natriuretic peptides also inhibited the short-circuit current, a 100-fold higher concentration was reuired to obtain the same effect as with eel atrial natriuretic peptide, indicating that eel atrial natriuretic peptide is 100 times as potent in eel intestine as the mammalian atrial natriuretic peptides. Similarly, in mammalian atrial natriuretic peptide, the four N-terminal amino acids had no significant effects. However, when the C-terminal tyrosine was removed, the potency of rat atrial natriuretic peptide was lowered. Compared with the effects of acetylcholine, serotonin and histamine, eel atrial natriuretic peptide was the most potent inhibitor, with 100% inhibition at 10^-7 M; 50% inhibition was obtained at 10^-2 M in acetylcholine, and 30% inhibition in serotonin (10^-5 M) and histamine (10^-3 M). These inhibitory effects of eel atrial natriuretic peptide were not diminished even in the presence of tetradoxin, and were mimicked by 8-bromoguanosine 3,5-cyclic monophosphate. Based on these results, structure-activity relationships of eel atrial natriuretic peptide and a possible mechanism of action of eel atrial natriuretic peptide are discussed.Abbreviations 8BrcGMP 8-bromoguanosine 3,5-cyclic monophosphate - eANP eel atrial natriuretic peptide - hANP human atrial natriuretic peptide - 5-HT 5-hydroxytryptamine creatine sulphate - I _sc short-circuit current - PD transepithelial potential difference - rANP rat atrial natriuretic peptide - R _t tissue resistance - TTX tetrodotoxin     

Characterization of esophageal desalination in the seawater eel,Anguilla japonica

To characterize mechanisms of esophageal desalination, osmotic water permeability and ion fluxes were measured in the isolated esophagus of the seawater eel. The osmotic permeability coefficient in the seawater eel esophagus was 2·10^-4 cm·s^-1. This value was much lower than those in tight epithelial, although the eel esophagus is a leaky epithelium with a tissue resistance of 77 ohm·cm^-2. When the esophagus was bathed in normal Ringer solutions on both sides no net ion and water fluxes were observed. However, when mucosal NaCl concentration was increased by a factor of 3, Na⁺ und Cl^- ions were transferred from mucosa to serosa (desalination). If only Na⁺ or Cl^- concentration in the mucosal fluid was increased by a factor of 3, net Na⁺ and Cl^- fluxes were reduced to 30–40%, indicating that 60–70% of the net Na⁺ and Cl^- fluxes are coupled mutually. The coupled NaCl transport seems to be effective in desalting the luminal high NaCl. The remaining 30–40% of the total Na⁺ and Cl^- fluxes seems to be due to a simple diffusion, because these components are independent of each other and follow their electrochemical gradients, and also because these fluxes remain even after treatment with NaCN or ouabain. A half of the coupled NaCl transport could be explained by a Na⁺/H⁺–Cl^-/HCO ₃ ^- double exchanger on the apical membrane of the esophageal epithelium, because mucosal amiloride and 4.4-diisothiocyanatostilbene-2,2-disulphonic acid inhibited the net Na⁺ and Cl^- fluxes by approximately 30%. The other half of the coupled NaCl transport, which follows their electrochemical gradients, still remains to be explained.Abbreviations DIDS 4,4-diisothiocyanatostilbene-2,2-disulphonic acid - NMDG N-methyl-d-glucosamine - P _Cl Cl^- permeability coefficient - PD transepithelial potential difference - P _Na Na⁺ permeability coefficient - P _osm osinotic permeability coefficient - TALH thick ascending limb of Henle's loop     

Uptake of phosphate by symbiotic and free-living dinoflagellates

Uptake of phosphate in the light by Amphidinium carterae, Amphidinium klebsii, cultured and symbiotic Gymnodinium microadriaticum conformed to Michaelis-Menten type saturation kinetics with all organisms showing similar K _m values, namely 0.005 to 0.016 M phosphorus. V _max values were 0.009–0.32 nmol phosphorus · 10⁵ cells^-1 · 10 min^-1. Phosphate uptake by all the dinoflagellates was greater in the dark than in the light. The metabolic inhibitor 3-(3,4-dichlorophenyl) 1,1-dimethylurea stimulated phosphate uptake in the light by A. carterae and A. klebsii, but inhibited uptake by cultured and symbiotic G. microadriaticum. Carbonylcyanide 3-chlorophenylhydrazone (CCCP) inhibited phosphate uptake by A. carterae and A. klebsii under both light and dark conditions. Uptake of phosphate by cultured and symbiotic G. microadriaticum in the light, but not in the dark, was inhibited by CCCP. Low concentrations of arsenate (5 g As · l^-1) stimulated phosphate by A. carterae and A. klebsii, but inhibited uptake by cultured and symbiotic G. microadriaticum. High concentrations of arsenate (100 g As · l^-1) did not affect uptake of phosphate by A. carterae and A. klebsii.     

High-affinity amylolytic enzymes produced by the mould Trichoderma harzianum

Summary The apparent substrate constants of the amylolytic enzymes produced by the mould Trichoderma harzianum CBS 354.33 were measured. The value for -amylase was 64 mg starch·1^-1 which is very low as compared with those of other -amylases. The substrate constant for glucoamylase was 78 mg starch·l^-1. Both enzymes were sensitive to Acarbose; 50% inhibition was observed at 2.5 mg·l^-1 (-amylase) and 0.10 mg·l^-1 (glucoamylase).     

Oxygen transport and cardiovascular responses in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) exposed to acute hypoxia

Summary Responses to acute hypoxia were measured in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) (1–3 kg body weight). Fish were prevented from making swimming movements by a spinal injection of lidocaine and were placed in front of a seawater delivery pipe to provide ram ventilation of the gills. Fish could set their own ventilation volumes by adjusting mouth gape. Heart rate, dorsal and ventral aortic blood pressures, and cardiac output were continuously monitored during normoxia (inhalant water (PO ₂>150 mmHg) and three levels of hypoxia (inhalant water PO ₂130, 90, and 50 mmHg). Water and blood samples were taken for oxygen measurements in fluids afferent and efferent to the gills. From these data, various measures of the effectiveness of oxygen transfer, and branchial and systemic vascular resistance were calculated. Despite high ventilation volumes (4–71·min^-1·kg^-1), tunas extract approximately 50% of the oxygen from the inhalant water, in part because high cardiac outputs (115–132 ml·min^-1·kg^-1) result in ventilation/perfusion conductance ratios (0.75–1.1) close to the theoretically ideal value of 1.0. Therefore, tunas have oxygen transfer factors (ml O₂·min^-1·mmHg^-1·kg^-1) that are 10–50 times greater than those of other fishes. The efficiency of oxygen transfer from water in tunas (65%) matches that measured in teleosts with ventilation volumes and order of magnitude lower. The high oxygen transfer factors of tunas are made possible, in part, by a large gill surface area; however, this appears to carry a considerable osmoregulatory cost as the metabolic rate of gills may account for up 70% of the total metabolism in spinally blocked (i.e., non-swimming) fish. During hypoxia, skipjack and yellowfin tunas show a decrease in heart rate and increase in ventilation volume, as do other teleosts. However, in tunas hypoxic bradycardia is not accompanied by equivalent increases, in stroke volume, and cardiac output falls as HR decreases. In both tuna species, oxygen consumption eventually must be maintained by drawing on substantial venous oxygen reserves. This occurs at a higher inhalant water PO₂ (between 130 and 90 mmHg) in skipjack tuna than in yellowfin tuna (between 90 and 50 mmHg). The need to draw on venous oxygen reserves would make it difficult to meet the oxygen demand of increasing swimming speed, which is a common response to hypoxia in both species. Because yellowfin tuna can maintain oxygen consumption at a seawater oxygen tension of 90 mmHg without drawing on venous oxygen reserves, they could probably survive for extended periods at this level of hypoxia.Abbreviations BP_da, BP_va dorsal, ventral aortic blood pressure - C _aO₂, C _vO₂ oxygen content of arterial, venous blood - DO₂ diffusion capacity - E_b, E_w effectiveness of O₂ uptake by blood, and from water, respectively - Hct hematocrit - HR heart rate - PCO₂ carbon dioxide tension - P _aCO₂, P _vCO₂ carbon dioxide tension of arterial and venous blood, respectively - PO₂ oxygen tension - P _aO₂, P _vO₂, P _iO₂, P _cO₂ oxygen tension of arterial blood, venous blood, and inspired and expired water, respectively - pHa, pHv pH of arterial and venous blood, respectively - P_w—b effective water to blood oxygen partial pressure difference - Pg partial pressure (tension) gradient - cardiac output - R vascular resistance - SV stroke volume - SEM standard error of mean - TO₂ transfer factor - U utilization - _g ventilation volume - O₂ oxygen consumption     

Thermodynamic analysis of nonelectrolyte sorption in plant cuticles: The effects of concentration and temperature on sorption of 4-nitrophenol

The sorption of 4-nitrophenol (4-NP) in enzymatically isolated cuticles ofLycopersicon esculentum fruits andFicus elastica leaves was studied as a function of temperature and solute concentration. Plots of the concentrations of 4-NP sorbed in the cuticle versus the equilibrium concentrations in the aqueous phase gave linear isotherms at low concentrations that tended to approach plateaus at higher sorbate concentrations ( 10 mmol·kg^-1). At low concentrations of sorbed 4-NP, cuticles have sorptive properties similar to those of organic solvents which are able to form intermolecular hydrogen bonds, while at higher concentrations their solid nature becomes apparent. During sorption of 4-NP the cutin matrix swells and new sorption sites are successively formed. The partition coefficients of 4-NP in the system cuticle/buffer are functions of temperature and concentration. At high sorbate concentrations (approx. 1 mol·kg^-1) they approach a value of 1. Different sorptive properties were observed for the cutin regions normally encrusted with soluble cuticular lipids (SCL) and those without SCL. Increasing temperature augmented the number of sorption sites in the cutin ofLycopersicon while no effect was observed withFicus. The changes of partial molar free energy (G ^o _tr), enthalpy (H ^o _tr), and entropy (S ^o _tr) for the phase transfer of 4-NP also depended on sorbate concentration: H ^o _tr and S ^o _tr were negative and steeply decreased at high sorbate concentrations. This is due to solute-solute interactions replacing solute-cutin interactions at high concentrations resulting in solid precipitates of solute within the cutin matrix. This formation of ordered solid domaines starting from a small number of nonelectrolyte molecules interacting with the cutin is proposed as a model for the intracuticular deposition of SCL.Abbreviations CM cuticular membrane - MX polymer matrix membrane - 4-NP 4-nitrophenol - SCL soluble cuticular lipids     

The distribution and turnover of tryptamine in the brain and spinal cord

Tryptamine levels have been determined in mouse brain regions and spinal cord and in rat spinal cord. They were; caudate nucleus 2.5 ng·g^–1, hypothalamus <0.5 ng·g^–1, hippocampus <0.7 ng·g^–1, olfactory bulb <0.7 ng·g^–1, olfactory tubercles <0.6 ng·g^–1, brain stem <0.4 ng·g^–1, cerebellum <1.0 ng·g^–1, and the rest 0.9 ng·g^–1. The mouse whole brain was found to have 0.5 ng·g^–1, the mouse spinal cord 0.3 ng·g^–1, and the rat spinal cord 0.3 ng·g^–1. These concentrations increased rapidly to 22.8 ng·g^–1, 14.2 ng·g^–1, and 6.6 ng·g^–1 respectively at 1 hr after 200 mg·kg^–1 pargyline. The turnover rates and half lives of tryptamine in the mouse brain and spinal cord and rat spinal cord were estimated to be 0.14 nmol·g^–1·h^–1 and 0.9 min; 0.054 nmol·g^–1·h^–1 and 1.5 min and 0.04 nmol·g^–1·h^–1 and 1.6 min respectively. The aromaticl-aminoacid decarboxylase inhibitors NSD 1034 and NSD 1055 reduced synthesis of tryptamine in controls and pargyline pretreated animals. Tryptophan increased the concentrations of mouse striatal tryptamine and 5-hydroxytryptamine and brain stem 5-hydroxyindole acetic acid.p-Chlorophenylalanine reduced formation of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid but did not change that of tryptamine.