Memory for relational information across eye movements.

Structural descriptions are hierarchical representations of a visual stimulus in terms of its parts and their relations. Previous research in which the retention of parts was examined has shown that structural descriptions can be used to represent information in transsaccadic memory. In three experiments, this idea was tested further by examining whether relational information is also maintained across saccades.

Catecholaminergic regulation of venous function in the rainbow trout.

The significance of the sympathetic nervous system (SNS) in regulating peripheral vascular resistance and cardiac function in fish has been well established, whereas its effect on venous function in vivo is unknown. Two protocols were employed in the present study to evaluate SNS effects on the venous system in intact, unanesthetized trout. In the first, trout were instrumented with pressure cannulas in the ventral (PVA) and dorsal (PDA) aortas and ductus Cuvier (PVEN), and cardiac output (CO) was measured with a flow probe around the ventral aorta.

Effects of natriuretic peptides and nitroprusside on venous function in trout.

Active venous regulation of cardiovascular function is well known in mammals but has not been demonstrated in fish. In the present studies, the natriuretic peptides (NP) rat atrial natriuretic peptide (ANP) and trout ventricular natriuretic peptide (VNP), clearance receptor inhibitor SC-46542, and sodium nitroprusside (SNP) were infused into unanesthetized trout fitted with pressure cannulas in the ventral aorta, dorsal aorta, and ductus Cuvier, and a ventral aorta (VA) flow probe was used to measure cardiac output (CO). In another group, in vivo vascular (venous) capacitance curves were obtained during ANP or SNP infusion.

Anatomy, histology, and development of the cardiac valvular system in elasmobranchs.

We report here on the anatomy, histology, and development of the three sets of cardiac valves in embryonic and adult elasmobranch fishes. The sinus venosus is the first segment of the heart to receive blood, and a pair of sinoatrial (SA) valves prevent backward flow of blood into the sinus venosus. The SA valves derive from two dorsolateral infoldings of the cardiac wall and consist of a simple endocardium covering transverse sheets rich in collagen.

Microcirculation of gills and accessory respiratory organs from the air-breathing snakehead fish, Channa punctata, C. gachua, and C. marulius.

Snakehead fish of the genus Channa have well-developed air-breathing organs (ABO) yet retain their gill arches for respiratory and non-respiratory functions. Alterations in the macrocirculation accompany inclusion of the ABO and appear to enhance gas exchange efficiency (Munshi et al., 1994.

Single-pass gill extraction and tissue distribution of atrial natriuretic peptide in trout.

A new method is described in the present experiments to quantify atrial natriuretic peptide (125I-ANP) extraction from plasma in a single transit through the gill vasculature of an unanesthetized trout. Tissue distribution of 125I relative to an inert extracellular space marker, 58Co-EDTA, was also measured 1 h after injection of 125I-ANP. Single-pass extraction of 125I-ANP by the gill was 60% in control fish; it fell to 18% in fish previously injected with saline and became negative (relative to 58Co-EDTA) after treatment with the clearance (C-type) receptor inhibitor SC 46542.

Cardiovascular and renal effects of eel and rat atrial natriuretic peptide in rainbow trout, Salmo gairdneri.

The renal and in vitro vascular effects of atrial natriuretic peptides have been examined in several species of fish. However, comparatively few investigations have described the effects of these peptides on the cardiovascular system in vivo. In the present experiments the dorsal aorta and urinary bladder were cannulated and the effects of atrial natriuretic peptides from rat and eel were monitored in conscious trout during bolus injection or continuous atrial natriuretic peptide infusion.

Vasculature of the fish gill: anatomical correlates of physiological functions.

The fish gill is a multifunctional organ responsible for respiration, osmoregulation, acid base balance, nitrogen excretion, and metabolism of circulating hormones. Two or more microcirculatory systems subserve these activities and form one of the most complex vascular networks found in any vertebrate. In this article the vascular anatomy of the teleost gill and the role of gill vessels in mediating physiological function are examined.

Evidence against nonprostanoid endothelium-derived relaxing factor(s) in trout vessels.

Bradykinin (BK)- or acetylcholine (ACh)-mediated vasodilation has only rarely been observed in fish. This suggests that many fish vessels lack the endothelium-dependent relaxing mechanisms recently identified in mammals. To examine this hypothesis, isolated vascular rings were prepared from trout ventral aortas (VA), efferent branchial and celiacomesenteric (CM) arteries, and anterior cardinal veins (CV) and examined for endothelium-mediated responses.

Effects of atrial natriuretic factor on isolated arteries and perfused organs of trout.

Atrial natriuretic factor (ANF) increases blood pressure when injected into conscious trout [Duff and Olson, Am. J. Physiol.

Angiotensin-converting enzyme in organs of air-breathing fish.

Angiotensin-converting enzyme (ACE) was measured in tissue homogenates from the African lungfish and six species of air-breathing teleosts (Heteropneustes fossilis, Clarias batrachus, Channa gachua, Anabas testudineus, Notopterus chitala, and Monopterus cuchia) using a standard spectrophotometric assay. In most species, the highest levels of ACE activity were found in the respiratory organs (gills and/or accessory respiratory organs). ACE was also found in heart and kidney tissues from most species and occasionally in liver.