Identification of angiotensin I in a cyclostome, Lampetra fluviatilis

Angiotensin I (ANG I) was isolated from incubates of plasma and kidney extracts of the river lamprey, Lampetra fluviatilis, using eel vasopressor activity as an assay during purification. Its sequence was Asn-Arg-Val-Tyr-Val-His-Pro-Phe-Thr-Leu as determined by the sequence analysis and mass spectrometry. The sequence was confirmed by identity of the elution profile with the synthetic peptide in two different reverse-phase columns of high-performance liquid chromatography. Lamprey ANG I produced dorsal-aortic pressor responses in L. fluviatilis but the rise was very small in comparison to that produced by angiotensin II. Angiotensin III produced an even bigger increase. It was not possible to demonstrate a difference in response to Asn(1) (lamprey) ANG I and Asp(1) (human) ANG I. The present study directly demonstrated the presence and biological activity of the renin-angiotensin system in the most primitive extant vertebrates, the cyclostomes. Thus the renin-angiotensin system is a phylogenetically old hormonal system that is present throughout the vertebrates.     

Bicarbonate secretion plays a role in chloride and water absorption of the European flounder intestine

Experiments performed on isolated intestinal segments from the marine teleost fish, the European flounder (Platichthys flesus), revealed that the intestinal epithelium is capable of secondary active HCO3(-) secretion in the order of 0.2-0.3 micromol x cm(-2) x h(-1) against apparent electrochemical gradient. The HCO3(-) secretion occurs via anion exchange, is dependent on mucosal Cl(-), results in very high mucosal HCO3(-) concentrations, and contributes significantly to Cl(-) and fluid absorption. This present study was conducted under in vivo-like conditions, with mucosal saline resembling intestinal fluids in vivo. These conditions result in a transepithelial potential of -16.2 mV (serosal side negative), which is very different from the -2.2 mV observed under symmetrical conditions. Under these conditions, we found a significant part of the HCO3(-) secretion is fueled by endogenous epithelial CO2 hydration mediated by carbonic anhydrase because acetazolamide (10(-4) M) was found to inhibit HCO3(-) secretion and removal of serosal CO(2) was found not to influence HCO3(-) secretion. Reversal of the epithelial electrochemical gradient for Cl(-) (removal of serosal Cl(-)) and elevation of serosal HCO3(-) resulted in enhanced HCO3(-) secretion and enhanced Cl(-) and fluid absorption. Cl(-) absorption via an anion exchange system appears to partly drive fluid absorption across the intestine in the absence of net Na(+) absorption.     

Effects of diet and mating status upon corpus allatum activity, oocyte growth, and salivary gland size in the ring-legged earwig

The effect of diet on mating behavior and the subsequent effects of diet and mating status on the biosynthesis of juvenile hormone III, basal follicle length, salivary gland size and total body weight were assessed in the ring-legged earwig, Euborellia annulipes (Lucas) (Family Carcinophoridae; subfamily Carcinophorinae) during the first 15 days of adult life (the first gonadotrophic cycle of those fed presumably near-optimal diets of catfood) and again on day 25 (late vitellogenesis of the second gonadotrophic cycle of those fed catfood). Diets of catfood, honey, fructose and total starvation, respectively, imposed on 0-day adult females did not affect sexual receptivity, mating success or duration of mating as assessed on day 7. With the addition of a group of virgin, catfood fed females, we noted that only those females maintained on catfood oviposited within 25 days; enforced virginity virtually abolished oviposition. Total food deprivation of females as well as diets of honey or fructose abolished the cycles in total body weight, basal follicle length, salivary gland size and juvenile hormone production. Thus, starvation decreased the reproductive success of these insects, and carbohydrates only (fructose) or in combination with trace amounts of nutrients and protein (honey) were not sufficient to promote reproduction and associated cycles in this insect. Furthermore, virgins failed to undergo the decreases in salivary gland size that were characteristic of mated females. Among mated, catfood-fed females, the second cycle in juvenile hormone production appeared to be smaller than the first.