Dopamine receptor subtypes expressed in vertebrate (carp and eel) retinae: cloning, sequencing and comparison of five D1-like and three D2-like receptors

Eight dopamine receptor-like cDNA clones were isolated from the carp (Cyprinus carpio) retina and four dopamine receptor-like cDNA clones were isolated from the European eel (Anguilla anguilla) retina. These cDNA clones show high sequence and structural homology to the known dopamine receptor subtypes. The sequence similarity and phylogenetic analysis revealed that five subtypes (D1A3, D1A4, D1B, D1C and D1X) in the carp retina and four subtypes (D1A1, D1A2, D1B and D1C) in the eel retina are D1-like receptor subtypes, and three (D2, D4A and D4B) in the carp retina are D2-like receptor subtypes; no D2-like receptor was found in the eel. Carp D1A3 and D1A4, carp D4A and D4B, and eel D1A1 and D1A2 are highly homologous pairs of receptors which show significant, domain-specific differences to each other and to their species homologues. The structure of the third cytoplasmic loop in the carp D1X receptor was particularly different from the other D1-like receptors. The implications of these structural differences in terms of dopamine receptor activation and signalling are discussed. It is suggested that the known diverse physiological and pharmacological effects of dopamine on the retinal neurones are likely to be mediated through these multiple receptor subtypes which may be coupled to different signal transduction pathways.     

The nondigestible fat sucrose polyester does not stimulate gallbladder emptying in humans

BACKGROUND: We determined the effect of oral ingestion of sucrose polyester, which was approved as a fat replacer in the United States, on gallbladder motility and on the release of cholecystokinin, the hormone that mediates gallbladder emptying. OBJECTIVE: Our objective was to measure effects of sucrose polyester on gallbladder emptying and cholecystokinin release. DESIGN: Eight healthy volunteers (3 men and 5 women) drank 60 mL sucrose polyester, digestible fat, or saline solution in a balanced crossover design on 3 separate days. RESULTS: Mean (+/-SEM) gallbladder emptying, when integrated over time, was low in response to both sucrose polyester (-150 +/- 214 mL x 120 min) and saline solution (-89 +/- 123 mL x 120 min). In contrast, there was marked emptying in response to digestible fat (1069 +/- 253 mL x 120 min). Sucrose polyester did not affect plasma cholecystokinin concentrations (-9.3 +/- 15.0 pmol x 120 min/L), whereas digestible fat resulted in a significant increase (89.5 +/- 44.8 pmol x 120 min/L, P = 0.014) compared with saline solution (-3.0 +/- 13.8 pmol x 120 min/L). CONCLUSIONS: Ingestion of sucrose polyester, in contrast with digestible fat, did not stimulate gallbladder emptying or release of cholecystokinin.     

The evaluation of argon laser photocoagulation in a series of animal models of upper gastrointestinal bleeding

During the past five years we have evaluated argon laser photocoagulation in various canine models of upper gastrointestinal hemorrhage. In gastric erosions, the eight-watt argon laser was uniformly effective in stopping bleeding. In our standard acute ulcer model the seven-watt argon laser was effective in stopping bleeding from most ulcers and only occasionally produced deep injury. With the addition of a jet of CO2 exiting the laser catheter coaxial to the laser beam, the argon laser was 100% effective and no deep injury resulted. The application of the argon laser in a more physiologic canine bleeding model using a single bleeding vessel in an ulcer base is currently under study. The development of improved animal models of gastrointestinal bleeding should contribute to the identification of effective and safe endoscopic hemostatic methods.     

An unusual case of large right atrial myxoma

A case of right atrial myxoma is described. The patient had vague and variable symptoms and it was not until five years after first presentation that she had developed clinical and electrocardiographic evidence of right atrial hypertrophy, and angiocardiographic evidence of a fist-sized myxoma which was subsequently removed surgically.