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

1. Transmitter plasticity, the ability to alter transmitter expression, has been demonstrated in a wide range of neurons in the vertebrates and invertebrates.

2. One preparation where this issue has been investigated in detail is a set of four neurosecretory neurons in the tobacco hawkmoth Manduca sexta.

3. These neurons undergo a transmitter switch during the transition from caterpillar to moth.

4. In larvae these neurons, known as the lateral neurosecretory cells (LNCs), express CAP₂, a myomodulatory neuropeptide involved in the neuroregulation of the activity of visceral muscles.

5. By the adult moth stage, however, the LNCs are no longer producing CAP₂ and instead are expressing a different peptide, bursicon, which is involved in tanning of the cuticle at adult emergence.

6. Here I review the evidence for this transmitter switch and discuss its regulation by steroids.

1. The concentrations of zinc in the pyloric caeca and body wall were c. 10-fold greater than lead and nickel and c. 100-fold greater than cadmium and silver.

2. The concentration of metal in the pyloric caeca to that in the body wall was equal or significantly greater for cadmium, equal or significantly less for silver and zinc, and significantly less for lead and nickel.

3. The profiles of the metal concentrations in the organs were site specific, but the concentrations in the pyloric caeca and body wall were usually greater in the populations in the Bay than those in the Gulf of Mexico.

4. The concentrations of metals in the body wall were less in small than large L. clathrata, and in proximal than distal parts of the arms of L. senegalensis.

1. Administration of biogenic amines into intact Carcinus maenas induces dose- and timedependent elevation of hemolymph glucose level.

2. Removal of the neurosecretory centre containing the crustacean hyperglycemic hormone (CHH) by ablation of the eyestalks did not induce hypoglycemia.

3. Injection of dopamine (DA) into eyestalkless crabs showed no hyperglycemic effect, while serotonin (5-HT), epinephrine (E), norepinephrine (NE), and octopamine (OA) elevated glucose levels.

4. The dopaminergic effect was significantly reduced by administration of trifluoperazine (TFP).

5. 5-HT and OA were found to be strong elevators of glucose levels, while the other biogenic amines had moderate effects only.

6. The results indicate, that DA exerts its hyperglycemic effect by stimulating the release of CHH from the eyestalk neurosecretory centre. Elevation of hemolymph glucose level by 5-HT, OA, E, and NE, occurs independently of CHH.

1. The sublethal effects of Folidol 600, an organophosphate containing methyl parathion as its active principle, were analysed in the fish Callichthys callichthys.

2. After an intracoelomatic application of 500 mg/kg of Folidol 600, the behavior and the levels of plasmatic cholinesterase were analysed along the time, in acute experiments.

3. Plasma cholinesterase activity was inhibited by 90% after 4 hr from the initial time, keeping this level of inhibition for 4 days.

4. It recovered slowly in the next 8 to 10 days, reaching about 80–90% of the normal levels around the 35th day after the beginning of the experiment.

5. Many behavioral changes were observed in the first 96 hr, such as: lowering of motility with loss of equilibrium and frequent unnatural body positions; uncoordinated movements leading to incapacity of food intake; and increase in the levels of respiratory frequency.

1. Lindane was generally more toxic when ingested than when applied topically to similar sized larvae of Mamestra brassicae (L) (4th-instar), Spodoptera littoralis (Boisd) (4th-instar), Pieris brassicae (L) (3rd-instar), and Bombyx mori (L) (2nd-instar).

2. In vivo metabolism of ingested ¹⁴C-lindane decreased in order of S. littoralis > P. brassicae > B. mori (based on the recovery of metabolised ¹⁴C-lindane form the larva and frass) and followed the order of increasing susceptibility.

3. ¹⁴C-lindane was regurgitated after ingestion; its effects on insecticidal action are discussed.

4. The causes of variation in interspecies susceptibility with particular reference to concepts of resistance as influenced by polyphagy versus monophagy are discussed.

1. Collation of the data presented in the preceding papers (references 4,5) showed a significant correlation (r = 0.83; P < 0.001) between the molecular mass (and hence the extent of halosubstitution) of halogenated biphenyls and their rate of hydroxylation by hepatic microsomal monooxygenases.

2. There was no relationship between the extent of polyortho halosubstitution of biphenyl and the rate of metabolism.

3. A marginal correlation (r = 0.33; P < 0.001) was found when the number of adjacent unsubstituted meta-para positions were linked to the rate of metabolism of PCBs. This structural feature facilitates microsomal oxidation.

4. The results support the proposal that PCBs with meta-para hydrogen atoms are less enriched in tissues of animals and humans as this structural feature favours their metabolism by P450 isoenzymes.

1. Male CD-1 mice had about 1.6-fold higher glutathione (GSH), 2-fold higher glutathione S-transferase (GST) activity and 2.8-fold higher GST protein in their livers as compared to the female mice.

2. When mice were fed a diet containing 0.75% BHA for 2 weeks, a 1.8-fold increase was observed in GSH levels of female mice liver as opposed to only 1.2-fold increase in male mice. BHA caused 10-fold increase in GST activity and protein in livers of female mice as compared to only about 3–4-fold increase in livers of males. Differential induction of GSH and GST in males and females was also observed in other tissue besides liver but was not as remarkable.

3. Sex-related differences were also observed in the induction of the α- and μ- and π-classes ofGSTs by BHA; most noticeable being GST π, which was induced to about 10-fold in female liver as opposed to only 3.4-fold in male liver.

1. The effects of long-term starvation and isolation on biogenic amine contents of the central nervous system of the male cockroach Blaberus craniifer Burm. were investigated.

2. Levels of tryptophan, 5-hydroxytryptophan, 5-hydroxytryptamine, a 5-hydroxyindolacetic acid-like substance, N-acetyl-5-hydroxytryptamine, dopamine, N-acetyldopamine and octopamine were measured by HPLC with electrochemical detection in fasted-isolated and fed-crowded insects from day 0 (imaginal molt) to day 30.

3. Isolation and fasting resulted in general lower levels, except for serotoninergic pathway at day 10.

4. From these data, by comparison with the isolation effect registered in females: (i) it is hypothesized that fasting exerts an inhibitory influence; and (ii) it is speculated that this effect is convergent with that of the loss of mechanical feeding stimuli on neurosecretory cells, as described in other male cockroaches.

1. Dimethoate was generally more toxic when ingested than when applied topically to similar sized larvae of Mamestra brassicae (L) (4th-instar), Spodoptera littoralis (Boisd) (4th-instar), Pieris brassicae (L) (3rd-instar) and Bombyx mori (L) (2nd-instar).

2. In vivo oxidation of ingested ¹⁴C-dimethoate to omethoate decreased in the order of S. littoralis > P. brassicae > B. mori and followed the order of decreasing susceptibility.

3. ¹⁴C-dimethoate was regurgitated and excreted and was related to feeding rates of the species.

4. The implications of the above data in relation to causes of variation in interspecies susceptibility with particular reference to concepts of resistance as influenced by polyphagy versus monophagy are discussed.

1. The potential influence of sub-chronic ethanol treatment on the ability of three chemical classes of insecticide to interact with their neuronal sites of action has been investigated in mouse brain.

2. Ethanol administration did not influence the inhibitory effects of either the cyclodiene dieldrin or the avermectin abamectin as determined by inhibition of GABA-stimulated chloride uptake.

3. Likewise there was also no discernable change in the sensitivity of sodium channels to inhibition by dihydropyrazole RH-3421 with sub-chronic ethanol treatment as assessed indirectly using a membrane potential assay.

4. The results of this study indicate that short term dietary exposure to ethanol fails to cause functional changes to the primary target sites of cyclodienes, avennectins and dihydropyrazoles in the mammalian central nervous system.