Comparative biochemistry and physiology. C: Comparative pharmacology最新文献

1. The pneumatic pressure ejection of achatin-I (Gly-d-Phe-l-Ala-l-Asp), an endogenous tetrapeptide having a d-phenylalanine residue, produced an inward current (I_in) in an identifiable giant neuron, PON (periodically oscillating neuron), of an African giant snail, Achatina fulica Férussac. The influence of the drugs for membrane excitability modification, applied by perfusion, on the PON excitation caused by achatin-I was examined under voltage clamp.

2. The four channel blocking drugs, tetrodotoxin (TTX), tetraethylammonium chloride (TEA), verapamil and picrotoxin, at 10,⁻⁴ M did not affect significantly the PON excitation caused by the peptide.

3. $\text{N-β-}\text{phenylpropionyl-}\text{L}\text{-tyrosine}$ (BPLT), a membrane hyperpolarizant, at 10⁻⁶ M and concanavalin A (Con A), which altered the response to l-glutamate, at 100 $\text{μg}\text{ml}{}^{\mathrm{-1}}$ were considered to hardly influence the PON excitation caused by achatin-I.

1. Various biogenic amines including octopamine, dopamine and serotonin, and their precursors and metabolites in haemolymph and the central nervous system from American cockroaches (Periplaneta americana L.) were measured using electrochemical detection.

2. Octopamine was found in similar high relative abundances in haemolymph and the central nervous system.

3. The amount of octopamine was much higher than that of tyramine and synephrine in haemolymph and thoracic nerve cord, whereas tyramine was at the highest level followed by octopamine and synephrine in the brain.

4. Insects were stressed by vibrating at 100 or 1000 Hz, visually by flashing light at 4 Hz for 15 min or by immersing the insect in water at 60°C for 30 sec, which resulted in the elevation of octopamine, tyramine, synephrine and tyrosine levels in thoracic nerve cord.

1. Changes in the amounts of mucus secreted by the epidermis of the slug in response to an irritant chemical substance (NaCl) and the effect of mechanical stimulation on high-energy phosphorylation metabolism were studied.

2. ³¹P signals obtained from the slug with in vivo³¹P nuclear magnetic resonance (NMR) spectroscopy included phosphonate, sugar phosphate (SP), inorganic phosphate (Pi), arginine phosphate (Arg-P), and ATP (γ, α and β).

3. When the slug epidermis came into contact with NaCl or was exposed to mechanical stimulation, the concentration of Arg-P decreased and that of Pi increased along with mucus secretion.

4. The change of ³¹P signals in response to chemical stimulation was much more variable than that in response to mechanical stimulation.

5. The β-ATP concentration was dependent on the amount of mucus secreted.

1. The camel erythrocyte membrane bound acetylcholinesterase (AChE) was extracted with the non-ionic detergent Triton X-100 and some of its kinetics parameters were studied. In addition the effect of tetracaine hydrochloride on AChE was also investigated.

2. The Michaelis-Menten constant (K_m) for the hydrolysis of acetylthiocholine iodide was found to be 7 × 10⁻⁵M and the V_max was 21.2 μmol/hr/mg protein.

3. Tetracaine (0.025–0.80 mM) reversibly inhibited the AChE activity (25–82%) in a concentration-dependent manner, the ic₅₀ being about 0.12 mM.

4. The Lineweaver-Burk plot and its secondary plots indicated that the nature of this inhibition is of the linear mixed type. This mixed type inhibition system is considered to be composed of partial competitive and pure non-competitive in nature.

5. The values of K_i(slope) and K_{ii(intercept)} were estimated as 0.127 mM and 0.263 mM, respectively, by a secondary replot of primary double reciprocal plot of Lineweaver-Burk plot and Dixon plot.

6. $\text{K}{}_{\mathrm{<mtext>ii</mtext>}}\text{K}{}_{\mathrm{<mtext>i</mtext>}}$ ratio shows that tetracaine has a greater affinity of binding to the active site than to a peripheral site.

1. Most of the components of the mixed function oxidase (MFO) in hepatic microsomes were reduced by corticosterone implants, and the degree of the reduction in females and at an older age was greater than those in males and at a younger age.

2. Ascorbic acid (AA) prevented the reduction in the MFO caused by corticosterone implants.

3. The activities of aniline hydroxylase and aminopyrine N-demethylase were enhanced by corticosterone implants regardless of AA supplementation.

4. The activity of NADPH-cytochrome c reductase in male broiler was greater than that in females under normal conditions.

5. Corticosterone implants and dietary AA had less influence on the antibody production, especially to T-cell dependent antigen.

1. Three strains of Saccharomyces cerevisiae have been exposed to methanol both in the presence and absence of heavy metal ions. The growth curves and the Superoxide dismutase activity were determined.

2. The presence of alcohol, copper or cadmium alone did not give strong cytotoxic effects, while methanol plus cadmium yielded a growth inhibition in two strains.

3. SOD levels were stimulated by copper, while methanol did not affect SOD in this non-methylotrophic yeast, indicating the need of alcohol assimilation to stimulate SOD. Cadmium had no inducing effects on SOD levels.

1. The adenylate cyclase activity present in the particulate fraction of planaria homogenates has been characterized.

2. The enzyme requires divalent cations (Mg²⁺), and a K_m for ATP of 0.58 at 30°C was measured.

3. GTP and Gpp(NH)p, in an optimal range of 10⁻⁴–10⁻⁵M, increase the enzymatic activity.

4. In the presence of GTP, dopamine stimulates the adenylate cyclase and its action is inhibited by dopaminergic antagonist.

5. Both D-1 and D-2 selective dopaminergic agonists stimulate the enzymatic activity and their action is selectively antagonized by D-1 and D-2 antagonists.

6. The high concentrations required for some D-1 and D-2 agents to be effective, suggest an only partial consistency with mammalian dopaminergic receptors.

1. The effects of temperature on the topical toxicity of cypermethrin and fenvalerate to fifth-instar larvae of the fall annyworm, Spodoptera frugiperda, were investigated, as well as their effects on ataxia and prostration. Activities of carboxylesterase and glutathione S-transferase were also assessed.

2. Pyrethroid toxicities were characterized by a negative temperature coefficient (TC) between 15 and 27°C, and a positive TC between 27 and 38°C. Fenvalerate was more toxic at all test temperatures.

3. The median time for the onset of ataxia and prostration decreased as temperature increased.

4. Activity (μmol/min/mg protein) of carboxylesterase and glutathione S-transferase was significantly lower for fenvalerate-treated insects (217.4 and 17.2, respectively) than for cypermethrin (344.7, 39.7).

1. Exposure of the estuarine shrimp, Palaemonetes pugio, to a juvenile hormone analogue (⩾8 μg methoprene 1⁻¹) throughout larval development inhibited successful completion of metamorphosis.

2. Methoprene exposure retarded growth in early larval stages and postlarvae, but enhanced growth in premetamorphic larvae.

3. Respiration rates of early larvae were elevated by methoprene exposure, but not so older larvae or post larvae.

4. Lower net growth efficiency (K₂ values) in methoprene-exposed early larvae suggests that increased metabolic demands reduced assimilated energy available for growth.

5. Modifications in O:N ratios of premetamorphic larvae and postlarvae suggest that methoprene altered substrate utilization patterns during metamorphosis.

1. Hb, MCHC, Na, Ca, Mg and Cu in plasma decreased with atypical Aeromonas salmonicida infection. Whilst plasma K and NPN increased.

2. Plasma Fe decreased markedly with infection. No statistically significant change in UIBC was found, though moribund eels showed slightly lower values compared to that of the control. The rate of decrease in TIBC is similar to that in most elements in plasma.

3. Fe content in most tissues decreased with infection. It increased in the gills and head muscle (infection site). No significant change was found in the intestine.

4. Water content in various tissues increased with infection.