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Penaeidins are members of a new family of antimicrobial peptides isolated from a crustacean, which present both Gram-positive antibacterial and antifungal activities. We have studied the localization of synthesis and storage of penaeidins in the shrimp Penaeus vannamei. The distribution of penaeidin transcripts and peptides in various tissues reveals that penaeidins are constitutively synthesized and stored in the shrimp haemocytes. It was shown by immunocytochemistry, at both optical and ultrastructural levels, that the peptides are localized in granulocyte cytoplasmic granules. The expression and localization of penaeidins were further analysed in shrimp subjected to microbial challenge. We found that (1) penaeidin mRNA levels decrease in circulating haemocytes in the first 3 hours following stimulation and (2) an increase in plasma penaeidin concentration occurs after microbial challenge, together with (3) a penaeidin immunoreactivity in cuticular tissue, which can be related to the chitin-binding activity we demonstrate here for penaeidins.

kappa-Opioid receptor agonists (niravoline) or nonpeptide antidiuretic hormone (ADH) V2 receptor antagonists (OPC-31260) possess aquaretic activity in cirrhosis; however, there is no information concerning the effects induced by the chronic administration of these drugs under this condition. To compare the renal and hormonal effects induced by the long-term oral administration of niravoline, OPC-31260, or vehicle, urine volume, urinary osmolality, sodium excretion, and urinary excretion of aldosterone (ALD) and ADH were measured in basal conditions and for 10 days after the daily oral administration of niravoline, OPC-31260, or vehicle to cirrhotic rats with ascites and water retention. Creatinine clearance, serum osmolality, ADH mRNA expression, and systemic hemodynamics were also measured at the end of the study. Niravoline increased water excretion, peripheral resistance, serum osmolality, and sodium excretion and reduced creatinine clearance, ALD and ADH excretion, and mRNA expression of ADH. OPC-31260 also increased water metabolism and sodium excretion and reduced urinary ALD, although the aquaretic effect was only evident during the first 2 days, and no effects on serum osmolality, renal filtration, and systemic hemodynamics were observed. Therefore, both agents have aquaretic efficacy, but the beneficial therapeutic effects of the long-term oral administration of niravoline are more consistent than those of OPC-31260 in cirrhotic rats with ascites and water retention.

Platelet hyperactivity has been one of the mechanisms implicated in the pathogenesis of diabetic retinopathy. Antiplatelet agents have been shown, in experimental models, to prevent the development of retinal vascular abnormalities when given from the first day after the onset of diabetes. We assessed the effect of aspirin plus dipyridamole (6 + 12 mg/kg daily) on the retinal vascular pattern in experimental streptozotocin-induced diabetes in rats, when the treatment was given at different intervals after the induction of diabetes, over a 3-month study period. Saline-pretreated diabetic rats showed a time-dependent increases in the platelet production of thromboxane B2 (r = 0.981, P < .0001) and a decrease in the aortic production of 6-keto-PGF1 alpha. The percentage of retinal area occupied by horseradish peroxidase-labeled vessels decreased progressively in relation to the length of time of the evolution of diabetes (r = 0.983, P < .00001) and the thromboxane/prostacyclin ratio. Treatment with aspirin plus dipyridamole caused an inhibition of the platelet production of thromboxane B2 and a decrease in the vascular synthesis of prostacyclin. Treatment with antiplatelet agents slowed down the decrease in the percentage of retinal area occupied by horseradish peroxidase-labeled vessels. These data provide further evidence to support the results of previous clinical trials in which antiplatelet agents had a beneficial effect on the evolution of retinal lesions in early diabetic retinopathy.