Serotonin or electrical optic nerve stimulation increases the photosensitivity of the Aplysia eye

• 1.1. Exposure of isolated Aplysia eyes to serotonin (10⁻⁷ M) produces large and long-lasting (hours) increases in the ERG recorded from the surface of the eye.
• 2.2. Dopamine, octopamine, or acetylcholine do not mimic the effect of 5-HT on the ERG.
• 3.3. Brief electrical optic nerve stimulation (2 Hz, 2 min) also increases the ERG and this effect also lasts a long period of time (0.5–2 hr).
• 4.4. Our results suggest that serotonin increases the response of photoreceptor cells to light and that efferent optic nerve activity may modulate photosensitivity through release of serotonin in the eye.

     

The digestive enzymes of the pacific brown shrimp Penaeus californiensis.: I—Properties of amylase activity in the digestive tract

• 1.1. Crude extract of the whole digestive tract from the brown shrimp (P. californiensis) was investigated for digestive amylase activity.
• 2.2. Considerable amylase activity was found at pH 6.5–8.0, with optimum pH at around 7.5.
• 3.3. Optimum temperature was found between 30–40°C, similar to amylases from other crustaceans.
• 4.4. Amylase activity was highly halotolerant, having 50% maximum activity at 3 M NaCl.
• 5.5. Maximum amylase activity was found at 0.01 M NaCl.
• 6.6. Amylase activity was partially inhibited by the divalent ions Hg²⁺, Zn²⁺, Cu²⁺ and Cr²⁺.
• 7.7. Mg²⁺ and Ca²⁺ ions seemed to enhance amylase activity.

     

Time-dependent cadmium-neurotoxicity in rat brain synaptosomal plasma membranes

• 1.1. The modulation of lipid dynamics and lipid protein interactions were studied in rat brain synaptosomal plasma membranes (SPM) up to 24 hr after exposure to cadmium (Cd).
• 2.2. The activity of acetylcholinesterase and adenylate cyclase showed a considerable decrease after 6 hr of Cd exposure, followed by a progressive increase up to 24 hr.
• 3.3. SPM chemiluminescence showed a maximum decrease at 12 hr, demonstrating a considerable increase in lipid peroxidation.
• 4.4. SPM of Cd-exposed animals showed a statistical significant increase in fluorescence anisotropy parameter [(r₀/r) — 1]⁻¹ at 18 and 24 hr compared to SPM of the control, indicating a decrease of membrane fluidity.

     

Intestinal l-methionine transport in the cultured gilthead bream (Sparus aurata)

• 1.1. The influx and transepithelial movements of l-methionine and its effects on the electrophysiology and Na-Cl-transport in upper and lower intestine of the cultured fish, Spanis aurata, were measured.
• 2.2. The K_m and V_max of l-methionine influx into the tissues were higher in lower intestine than in upper intestine. A prominent diffusion-like transport component was also measured in both segments during influx experiments.
• 3.3. Net transepithelial fluxes of l-methionine (1 mM) were observed in both upper and lower intestine, this transport being Na⁺-dependent.
• 4.4. The two intestinal segments exhibited an electrical potential difference (PD) and a short circuit current (I_sc) serosa negative or near zero. Tissue conductance (G_t) was higher in posterior than in lower intestine.
• 5.5. Addition of l-methionine to the mucosal side of lower or upper intestine did not induce changes in PD in either part.
• 6.6. Isotopic fluxes of Cl⁻ or Na⁺ measurements under short circuit conditions showed that there were no net Cl⁻ or Na⁺ transport in either part.
• 7.7. l-Methionine additions to the mucosa did not induce changes in unidirectional fluxes of Cl⁻ or Na⁺ or in the (I_sc) in either the anterior or posterior intestine.

     

A study of visual pigments in the two antarctic crustaceans Orchomene plebs (Amphipoda) and Glyptonotus antarcticus (Isopoda)

• 1.1. Total chromophore contents as well as the contributions made by 11-cis retinal were determined by high pressure liquid chromatography in light- and dark-adapted eyes of Orchomene plebs and Glyptonotus antarcticus (Amphipoda and Isopoda, respectively).
• 2.2. In O. plebs the highest amount of total chromophore in pmol/eye was found to be 18.5 in 36 hr dark-adapted animals. The lowest amount (11.6 pmol/eye) was recorded in 24 hr light-adapted individuals.
• 3.3. In dark-adapted O. plebs, irrespective of whether dark-adapted for 36 or 60 hr, the percentage of 11-cis retinal was maximally 96.6%. In the light-adapted material it reached 71.2%
• 4.4. In eyes of 20 hr dark-adapted Glyptonotous antarcticus, possibly because of insufficient dark adaptation, a total chromophore content of only 3.2 pmol/eye was found. The percentage of 11-cis retinal was 55.8.
• 5.5. Porphyropsin with its testable 3-dehydroretinal (vitamin A₂-aldehyde) was not encountered in any of our samples.
• 6.6. Calculations of photopigment per gram body weight and a comparison with data from freshwater crayfish show that dark-adapted O. plebs possess approximately 20 times the relative photopigment amount of the crayfish. Absolute sensitivity of the eye of O. plebs is, therefore, expected to be very high.

     

Detection of 180 kDa proteins in electroplax sodium channel preparations

• 1.1. Co-isolating proteins (M_r 170,000–220,000) from sodium channel preparations made from the electric organ of the electric eel (Electrophorus electricus) were detected on Western blots using monoclonal a antibodies.
• 2.2. Similar protein patterns were seen on immunoblots containing immunoprecipitated protein from eel muscle and brain tissues but not heart.
• 3.3. These co-isolating proteins could be separated from the mature TTX-sensitive channel protein (M_r 280,000) using a lentil lectin-Sepharose column.
• 4.4. The 180 kDa proteins do not appear to be channel-related and can be detected as contaminants in electroplax sodium channel preparations using the monoclonal antibodies described here.

     

The pattern and influential factors of aquatic pharyngeal movements of Trionyx sinensis

• 1.1. The pharyngeal movements of Trionyx sinensis during submersion where recorded with physiological instruments.
• 2.2. Anoxia or hypercapnia caused a marked increase in breathing rate of tested turtles during voluntary diving, and in anoxia there was a significant increase in the frequency of aquatic pharyngeal movements while hypercapnia had a slight or no effect on the frequency of these movements.
• 3.3. During voluntary diving when turtles could easily extend their heads out of water to breathe air, the frequency of rhythmic pharyngeal movements was lower; but during forced submersion, the frequency was higher and the movements were continuous.
• 4.4. The frequency increased more rapidly and greatly when turtles were in forced submersion than when they dived freely and could easily surface to breathe in N₂.
• 5.5. The frequency of pharyngeal movements of T. sinensis during diving in an aquarium with water depth of 30 or 45 cm was markedly higher than that at a water depth of 15 cm. Disturbing stimuli also influenced the aquatic rhythmic pharyngeal movements of T. sinensis.

     

Modulation of active potassium transport by aldosterone

• 1.1. The role of aldosterone on active potassium transport across lizard colon under voltage-clamped conditions has been investigated.
• 2.2. Control colons exhibited no net potassium flux (J^k_net) despite of the existence of active opposite unidi ectional fluxes.
• 3.3. An important net secretory potassium flux was found in short-circuited aldosterone-stimulated colons.
• 4.4. Mucosal amiloride did not change (J^k_net) either in control or aldosterone-stimulated colons.
• 5.5. Luminal barium alters K ⁺ transport in a manner consistent with the presence of barium-sensitive conductances at the apical membrane of both control and aldosterone-treated colons.
• 6.6. The effects of ouabain and barium on control and aldosterone-induced potassium flows were consistent with a model involving basolateral uptake by an Na ⁺-K ⁺-ATPase and conductive exit across the apical membrane.
• 7.7. The stimulatory effect of aldosterone on potassium secretion is associated with parallel increases of both basolateral K ⁺ entry and the apical conductive pathway.

     

The effect of reduced salinity on tissue and plasma composition of the dogfish,Squalus acanthias

• 1.1. Dogfish (Squalus acanthias) were acclimated to reduced salinities and their plasma, muscle tissue and erythrocytes subsequently analysed.
• 2.2. Decrease in the osmolarity of the plasma was principally due to a fall in urea concentration and a significant fall in the concentrations of sodium and chloride.
• 3.3. Changes in the muscle and erythrocytes in dilute media were a decrease in urea, potassium, sodium and chloride concentrations.
• 4.4. The concentrations of the free amino acids in the muscle and the red blood cells decreased more than would be expected by the movements of water only.
• 5.5. The results were discussed in relation to the regulation of cellular volume and the involvement of the free amino acid pool of the tissues in this process.

     

An alkaline phosphatase from Thermus sp strain Rt41A

• 1.1. A thermostable orthophosphoric monoester phosphohydrolase (EC 3.1.3.1) from Thermus sp strain Rt41A has been purified 400-fold to give a specific activity of 25 U/mg at 60°C in IM diethanolamine (pH 11.1).
• 2.2. The enzyme has a M_r of 160,000 and is trimeric.
• 3.3. The half-life of the enzyme is 5 min at 85°C.
• 4.4. The enzyme has a wide specificity for a number of phosphate monoesters.
• 5.5. The H_m of the enzyme is pH dependent, so the pH optimum of the enzyme is affected by the substrate concentration.
• 6.6. The enzyme is inhibited 50% by 20 mM Ca²⁺ or Mg²⁺.
• 7.7. The K_i for phosphate, EDTA-di sodium salt and arsenate (in 1 M diethanolamine, pH 11.1) is approx 1.2, 1.6 and 4mM respectively.
• 8.8. Urea (200 mM) is not inhibitory.

     

Electrical transport characteristics of Aplysia californica intestinal epithelium

• 1.1. Replacing chloride (Cl⁻) with sulfate (SO₄²⁻) in the bathing medium drastically reduced the mucosal membrane potential difference (ψ_m).
• 2.2. The voltage divider ratio was significantly greater than one.
• 3.3. Mucosal ^d-glucose decreased the input resistance of the intestinal epithelium.
• 4.4. Addition of furosemide to the mucosal bathing medium inhibited transepithelial potential difference and short-circuit current.
• 5.5. Addition of SITS to the mucosal bathing medium partially inhibited transepithelial potential difference and short-circuit current.
• 6.6. Diffusion potentials in the intestinal epithelium were symmetrical.

     

Osmoregulation in the brook trout,Salvelinus fontinalis—II. Effects of size,age and photoperiod on seawater survival and ionic regulation

• 1.1. Brook trout (Salvelinus fontinalis) of a single genetic stock, and hatched at the same time, were raised under two photoperiod and two feeding regimes to obtain fish of the same age but with different sizes and photoperiod experiences. In 11 experiments over 1.5 firs, fish were gradually exposed to 32 ppt seawater for 20 days to investigate the ontogeny of salinity tolerance.
• 2.2. Daily changes in plasma osmolarity, [Na⁺], [Cl⁻], [K⁺], [Mg²⁺], thyroxine, hematocrit and gill Na⁺,K⁺-ATPase during adaptation to 10, 20 and 32 ppt were examined in one experiment.
• 3.3. Size was the primary determinant of seawater survival (r² = 0.77) the effect of size on seawater survival slowed after fish reached a fork length of 14 cm. The effect of age on seawater survival (r² = 0.65) was through its covariance with size.
• 4.4. Photoperiod affected seawater survival only through its influence on the timing of male maturation, which decreased salinity tolerance.
• 5.5. Regulation of plasma osmolarity, [Na⁺], [Cl⁻], [K²⁺], [Mg²⁺] and hematocrit in sea water increased linearly with size over the entire range of sizes (6–32 em).
• 6.6. Gill Na⁺,K⁺-ATPase activity after 20 days in seawater decreased with increasing size of brook trout, possibly reflecting decreased demand for active ion transport in larger fish.
• 7.7. Plasma thyroxine concentrations declined in seawater, but no definitive role of this hormone in seawater adaptation was found.
• 8.8. Size dependent survival and osmoregulatory ability of brook trout is compared to other salmonids and a conceptual model is developed.

     

The measurement of glutamate dehydrogenase activity in Praunus flexuosus and its role in the regulation of ammonium excretion

• 1.1. A strong correlation (r² = 0.916) was found between glutamate dehydrogenase (GDH) activity and ammonium excretion in Praunus flexuosus suggesting a key regulatory role for this enzyme.
• 2.2. The high level of GDH activity found in this mysid was sufficient to account for all the ammonium excreted.
• 3.3. Activator-inhibitor studies imply that GDH may regulate energy production and growth, in addition to ammonium excretion.
• 4.4. The GDH assay presented here appears useful as a technique for quantifying zooplankton ammonium excretion impacts in the world oceans.

     

Purification and properties of an ld-dipeptidase FROM Bacillus sphaericus

• 1.1. An ld-dipeptidase (EC 3.4.13.-) that hydrolyzes the unrelated dipeptides l-Ala-d-Glu (sp. act. 0.85 μmol·min⁻¹·mg⁻¹) and l-Lys-d-Ala (sp. act. 11 μmol · min⁻¹·mg⁻¹) has been purified 250-fold from the sporulation medium of Bacillus sphaericus with a 4% recovery of lytic activity.
• 2.2. Throughout the purification steps, followed with both substrates, the enzyme peaks of activities were congruent and the ratios of activities were constant. Both activities were activated 50-fold by cobalt. Polyacrylamide gel electrophoresis of the final preparation showed the two enzyme activities to be coincident. The data are consistent with those activities being due to a single enzyme.
• 3.3. Sodium dodecylsulfate polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band (M_r 38,000).
• 4.4. This dipeptidase hydrolyzes some other ld-dipeptides with a free amino and carboxyl group. Although dipeptides having a di-amino acid as the amino terminus are the best of the substrates tested, the hydrolysis occurs also when neutral amino acids are N-terminal. The activity is higher with neutral C-terminal residues such as Gly or d-Ala than with a di-acid residue such as d-Glu.
• 5.5. This enzyme may have a function in peptidoglycan metabolism.

     

Osmoregulation in the brook trout,Salvelinus fontinalis—I. Diel,photoperiod and growth related physiological changes in freshwater

• 1.1. Brook trout (Salvelinus fontinalis) raised from eggs under two photoperiod and two feeding regimes were tested for physiological changes preparatory for transition from freshwater to seawater. Size, age, growth rate, photoperiod, and diel rhythms were examined for possible influences on plasma osmolarity, [Na⁺], [Cl⁻], [K⁺], [Mg²⁺], thyroxine concentration, hematocrit, and gill Na⁺, K⁺-ATPase activity of brook trout in freshwater.
• 2.2. Significant diel cycles were found in plasma osmolarity, [Na⁺] and thyroxine concentration.
• 3.3. Significant size and/or age related changes occurred for plasma osmolarity, Na⁺], [K⁺] and hematocrit, but could explain little of their total variation (0.02 < r² < 0.18).
• 4.4. A sexually dimorphic response to photoperiod was observed in hematocrit for both mature and immature fish, with hematocrit of mature females declining in autumn and hematocrit of immature males increasing in autumn.
• 5.5. Gill Na⁺, K⁺-ATPase activity did not respond to photoperiod or feeding treatment and showed no change with size or age.
• 6.6. Plasma thyroxine levels responded to feeding and photoperiod treatment. There was a significant correlation between the percent mean difference in plasma thyroxine and the mean difference in growth rate between high and low feed fish (r² =0.51), suggesting a relationship between thyroxine and growth.

     

Ionic dependence and vanadate sensitivity of (Na+, K+)-ATPase isolated from branchial sac of ascidians

• 1.1. Ion dependence and vanadium-induced inhibition on branchial sac ATPase in five species of ascidian Phlebobranchiata (vanadium-accumulating) and Stolidobranchiata (iron-accumulating) were studied.
• 2.2. The ATPase was obtained from the microsomal fraction, which was prepared from each ascidian branchial sac.
• 3.3. The ATPase was dependent on Mg²⁺ and activated by exogenous Na⁺ + K⁺.
• 4.4. Ouabain inhibited the ATPase activity in vitro, 10 μM to 100 μM vanadate, in vitro, suppressed the (Na⁺, K⁺)-ATPase.

     

DNase-I-like enzyme from the carp liver—Inhibition by muscle and endogenous actin

• 1.1. DNase-I-like activity occurs in the carp (Cyprinus carpio) liver cytosol (supernatant 105,000g).
• 2.2. The enzyme resembles DNase I from bovine pancreas in respect to the molecular mass (~31 kDa), pH (7.4) and ion requirements (Mg²⁺, Ca²⁺) and the ability to degrade native as well as denatured DNA.
• 3.3. As judged by comparison of DNase zymograms obtained after native- and SDS-PAGE, the enzyme occurs in the three molecular forms of similar molecular weight and different charges.
• 4.4. All these forms are inhibited by rabbit skeletal muscle actin as well as by endogenous actin isolated from the carp liver cytosol.
• 5.5. DNase from the carp liver cytosol does not interact with the antibodies directed against DNase I from bovine pancreas and against DNase I from the rat and bovine parotid glands.

     

Preparation of two neurotoxic esterases from the chick central nervous system

• 1.1. A standard procedure for lipid-extraction of lyophilized hen brain material is decribed.
• 2.2. Nine carboxylesterase isoenzymes (EC 3.1.1.1) are identified in lipid-extracted lyophilized material (LELM) using kinetic analysis of organophosphate inhibition. Total phenyl valerate (PV) hydrolysing carboxylesterase activity in LELM is 43.3U.g⁻¹
• 3.3. Two carboxylesterase isoenzymes of LELM are classified as neurotoxic esterases (NTE_A and NTEg_B).
• 4.4. Using n-octylglucoside 51% of the water-insoluble neurotoxic esterase activity from LELM are solubilized.
• 5.5. Six carboxylesterase isoenzymes including NTE_A (6.5 U-l⁻¹) and NTE_B (4.2 U-l⁻¹) are present in the solubilized preparation.
• 6.6. Throughout purification and separation steps carboxylesterase isoenzymes are identified by their rate constants for the reaction with organophosphorus inhibitors.

     

Allozyme variation in a wild african elephant (Loxodonta africana) population from the Kruger National Park,South Africa

• 1.1. Blood, liver, heart, testis, skin, eye, muscle and kidney samples were obtained from elephants (Loxodonta africana) in the Kruger National Park during a culling programme in April 1992.
• 2.2. Gene products of 25 protein coding loci in L. africana were examined by horizontal starch-gel electrophoresis.
• 3.3. Eighteen protein coding loci (72%) displayed monomorphic gel banding patterns whereas only seven (28%) displayed polymorphic gel banding patterns.
• 4.4. Average heterozygosity values for adults, youngsters and the total population are respectively 0.058, 0.024 and 0.047.
• 5.5. Relative gene diversities within and between populations are 84% and 16% respectively.
• 6.6. Two population simulation programmes were utilized to predict the duration of the current variability present in this species, based on current genetic variation and gene transfer from one generation to the next.

     

Changes in high-energy phosphate metabolism in the water scorpion,Ranatra chinensis,under cold water-warm water stress

• 1.1. To evaluate changes in high-energy phosphate metabolism in the water scorpion (Ranatra chinensis) under restraint and cold water-warm water stresses, in vivo [³¹P]NMR spectra were obtained.
• 2.2. Under restraint stress, arginine phosphate (Arg-P) decreased by 10% after 1 hr and remained at that level thereafter, while β-ATP showed negligible changes over 6 hr.
• 3.3. As the water temperature gradually increased or decreased, the relative concentration of Arg-P decreased due to enzyme regulation.
• 4.4. Repeated cold water-warm water stress, which consisted of repeated 15 min exposures to cold water (5°C) followed by 15 min exposures to warm water (30°C) caused distinct decreases in Arg-P and β-ATP concentration. These decreases were dependent on the frequency of exposure.
• 5.5. Phosphomonoesters (PME) increased not only with restraint stress but also with cold water-warm water stress.
• 6.6. The effect of cold water-warm water stress on high-energy phosphate metabolism was greater than that of restraint stress.