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Biomedical subjects

A Epple

Publications and source records attributed to A Epple.

At least 37 records · Page 2Linked to original sources
PubMed1993

Release of conjugated catecholamines by the adrenal medulla equivalent of the American eel, Anguilla rostrata.

The in vivo perfusate of the cardiovascular system of the American eel (Anguilla rostrata) contains both free and conjugated fractions of dopamine, norepinephrine, and epinephrine. In vitro perifusion revealed that conjugated catecholamines are released from the adrenal medulla equivalent. Together with similar reports on mammals, this suggests that conjugated catecholamines are phylogenetically wide-spread components of the secretory cocktail of chromaffin cells. The present findings are compatible with an "active" role of the catecholamine conjugates.

Adrenal Medulla↗
PubMed1993

Endogenous morphine and codeine: release by the chromaffin cells of the eel.

Both the adrenomedullary equivalent and the plasma of the American eel (Anguilla rostrata) contain endogenous morphine and codeine. The opiate concentrations are similar to those found in the rat adrenal and human plasma, respectively. The adrenal medulla equivalent of the eel was perifused in vitro and the levels of catecholamines and endogenous opiate alkaloids in the perfusate were measured. A strong correlation between the release of morphine and codeine and between the release of norepinephrine (NE) and epinephrine (E) was found. On the other hand, there was no significant correlation between the release of dopamine (DA) and that of the other catecholamines or opiate alkaloids, suggesting three different ways of release of these components of the secretory cocktail of the chromaffin cells. The plasma of eels stressed by urethane anesthesia showed a substantial increase in DA, NE, and E levels but there was no clear stress response of plasma morphine and codeine.

Adrenal Medulla↗
PubMed1993

Response of plasma cortisol to environmental cadmium in the eel, Anguilla rostrata LeSueur.

1. Long-term exposure (16 weeks) of the American eel, Anguilla rostrata, to an environmentally realistic concentration of cadmium (150 micrograms/l) causes a chronic elevation of plasma cortisol. During this time span, the eels retain the ability to respond to a weak additional stress (CO2 bubbles for 1 min) with a further increase in plasma cortisol. 2. Plasma glucose levels are significantly lowered after two weeks of exposure to cadmium (75 and 150 micrograms/l). However, subsequently they return close to control levels. 3. It is concluded that (a) a moderate cadmium pollution of the eel's habitat suffices to cause chronic stimulation of the eel's adrenocortical axis, and (b) the resulting continued hypercortisolemia must seriously affect the eel's metabolism, immunosystem, gonadal maturation, and ability to migrate to its spawning grounds.

Analysis of Variance↗
PubMed1993

Plasma catecholamines do not respond to insulin-induced hypoglycemia in a teleost, Anguilla rostrata.

The importance of epinephrine as a counterregulatory hormone in hypoglycemia is still debated. In the American eel (Anguilla rostrata), a species particularly sensitive to the hyperglycemic effect of exogenous epinephrine, insulin-induced hypoglycemia does not provoke an increase of plasma catecholamines; nor does a 35-fold rise of endogenous epinephrine within 5 min cause a statistically significant hyperglycemia. Together with findings in several other species of greatly varying phylogenetic position, these observations suggest that in vertebrates plasma epinephrine does not have significant, if any, glucoregulatory functions.

Animals↗
PubMed1992

The avian allantois: a depot for stress-released catecholamines.

Plasma and amniotic and allantoic fluid of 10- and 14-day-old chicken embryos contain free dopamine (DA), norepinephrine (NE), and epinephrine (E). Compared with postnatal chickens, concentrations of DA and E in the plasma are very high, and they are even higher in the allantoic fluid. In contrast, the allantoic concentration of NE is below the plasma level. In the amniotic fluid, the concentrations of all three catecholamines (CAs) are below the plasma levels. High concentrations of DA and E in the allantoic fluid after opening of the egg shell decline during the following 24 hr, which indicates that they are due to stress. Asphyxia, handling, disturbance of allantoic fluid, and cooling are also perceived as stress and are followed by immediate accumulation of CAs in the allantoic fluid. DA and E respond to stress in like manner, while NE often responds with an opposite trend. It appears that the avian allantois, in addition to its role in respiration and urea disposal, also serves the instant CA removal from the circulation. Both the amniotic and the allantoic membranes of the chicken should be ideal models for the study of CA transport mechanisms.

Allantois↗
PubMed1992

Impact of complete isletectomy on plasma glucose in the southern hemisphere lamprey Geotria australis.

The adult southern hemisphere lamprey Geotria australis is the only known vertebrate in which it is possible to remove all of the pancreatic islet tissue without damaging other organs. In the 24 hr after isletectomy, the plasma glucose of adult G. australis rose sharply from 5.0 to 11.6 mmol.liter-1 and remained at a similar elevated level throughout the subsequent 5 days of the experiment. The marked hyperglycemia that follows complete isletectomy parallels the results obtained after removal of the majority of the islet tissue from northern hemisphere lampreys and after pancreatectomy in mammals, but contrasts with observations recorded for some other groups of vertebrates.

Animals↗
PubMed1992

Impact of cadmium on the mummichog Fundulus heteroclitus and the role of calcium in suppressing heavy metal toxicity.

1. Freshwater adapted mummichogs (Fundulus heteroclitus) were exposed to cadmium. In soft water (less than or equal to 5 mg/l CaCO3), the 4-day safe (TL100) and sublethal (TL50) tolerance limits (TLs) for cadmium were 0.14 microgram/l and 12.2 micrograms/l, respectively. 2. Survival declined with increasing cadmium concentration and the length of exposure. The toxicity of cadmium was reduced in water with high calcium concentration (200 mg/l CaCO3). Pre-exposure to calcium also prolonged the survival in cadmium-containing water. 3. The mummichog appears to be extremely well suited for monitoring environmental cadmium poisoning.

Animals↗
PubMed1992

Trace metal (Cu and Zn) adaptation of organ systems of the American eel, Anguilla rostrata, to external concentrations of cadmium.

1. The impact of external cadmium on the concentrations of cadmium (Cd), copper (Cu) and zinc (Zn) in seven tissues of the American eel, Anguilla rostrata was investigated. Even after a week in freshwater with undetectable levels of Cd, the tissues of eels caught in fresh and/or brackish waters of the United States east coast contained Cd in kidney, liver, gut, and brain. 2. When the eels were exposed up to 16 weeks to low and high sublethal concentrations of Cd (75 and 150 micrograms/l, respectively), the highest tissue concentrations of Cd were found after two weeks of exposure. The accumulation was dose-related in all tissues studied except for the kidney. After 8 weeks of Cd exposure, the tissue levels of Cd were markedly reduced, and they were in a similarly low range after 16 weeks. At this time, the highest Cd concentrations were found in the gills and kidney. 3. After two weeks of Cd exposure, there was a drop of the tissue concentrations of Cu in liver and heart, and of Zn in gut and liver. The low concentrations of the two metals in other organs did not allow an evaluation of the Cd impact. After 16 weeks, the Cu concentrations in all tissues, with the exception of the liver, were similar to, or even higher than control levels. At the same time, Zn concentrations exceeded the control levels in heart and kidney of eels exposed to 75 and 150 micrograms Cd/l, respectively. 4. It is clear that some tissues of the eel are able to maintain or restore normal levels of Cu and Zn, up to 16 weeks, despite concomitant Cd accumulation.

Adaptation, Physiological↗
PubMed1990

Catecholamines, opioid peptides, and true opiates in the chromaffin cells of the eel: immunohistochemical evidence.

An immunohistological analysis of the chromaffin cell system of the American eel revealed the presence of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) in all cells. However, phenylethanolamine-N-methyltransferase (PNMT) was seen only in a fraction of the chromaffin cells. This suggests the presence of both norepinephrine and epinephrine cells and the absence of specific dopamine cells. The chromaffin cells are most numerous in the anterior region of the posterior cardinal vein, where they occupy a subendothelial position. Their number decreases caudally, and a relatively small number are present in the larger veins of the opisthonephric kidney. No PNMT-positive cells were identified in this region, although a radioenzymatic assay had previously shown the presence of epinephrine. Methionine-enkephalin immunoreactivity seems to be restricted to the chromaffin cells. However, particularly large amounts of leucine immunoreactivity occur in the interrenal cells, with smaller quantities in the chromaffin cells. The chromaffin cells of the eel also contain morphine immunoreactivity.

Animals↗
PubMed1989

Catecholamine release by catecholamines in the eel does not require the presence of brain or anterior spinal cord.

The catecholamine-producing chromaffin cells of the American eel are strongly innervated by fibers, which, by ultrastructural criteria, seem to be cholinergic. However, neither removal of the brain nor removal of the brain combined with extirpation of the anterior spinal cord prevents the release of catecholamines into the circulation by catecholamines. It appears that the chromaffin cells are controlled by both nervous and humoral stimuli, and that at least some of the latter do not require the presence of "preganglionic" innervation.

Anguilla↗
PubMed1989

Physiological doses of epinephrine in the human: chronotropic but not hyperglycemic or catecholaminotropic.

Single physiological doses of epinephrine did not affect the blood sugar level of human volunteers though they caused a marked tachycardia that was accompanied by a strong transient sensation, typically described as fullness in the chest. Epinephrine did not cause the release of norepinephrine and/or dopamine in man, in contrast to three other vertebrates (lamprey, eel, and rat). In the human, as in the rat and cyclostomes, the glycemic effect of epinephrine occurs only during stress and/or unphysiological conditions, while the chronotropic effects are probably physiological from cyclostomes to man.

Adult↗
PubMed1989

The sources of plasma catecholamines in the American eel, Anguilla rostrata.

The origin of the catecholamines (CAs) in the systemic blood of the American eel, Anguilla rostrata, was studied by three approaches: (1) determination of the CA content of tissues suspected to release large quantities of dopamine, norepinephrine, and/or epinephrine into the circulation; (2) measurement of local CA titers in selected regions of the cardiovascular system; and (3) removal of tissues with high CA concentrations, followed by determination of its impact on stimulated CA release. Large quantities of all three CAs were found in the walls of the posterior cardinal veins, from their caudal origin within the opisthonephric kidney to their termination in the ductus Cuvieri. Near the ductus Cuvieri, the CA concentration was 1-3 orders of magnitude above that in other tissues. In this region, which contains the presumed adrenal medulla equivalent, occur the highest plasma levels of the CAs. Strong CA release also in the opisthonephric kidney region raises the question if these CAs affect locally the kidney functions, and/or via the hepatic portal vein (which originates in this region), the liver. Other organs (especially brain and heart) contain CA concentrations high enough to potentially affect the CA level in the systemic blood, if instantly released. However, neither partial removal of the brain nor hypophysectomy, "adrenomedullectomy," Stanniectomy, or urophysectomy had an appreciable impact on stimulated CA release. Together with previous data, these findings show that in the eel (a) the region of the presumed adrenal medulla equivalent is the most important source of all three CAs in systemic plasma; (b) that strong CA-stimulated CA release also occurs outside this region; and (c) that the pituitary, forebrain, and midbrain are not necessary for the CA-stimulated CA release.

Anguilla↗
PubMed1988

Single doses of catecholamines in the rat: catecholaminotropic, but not hyperglycemic.

1. As in two "lower" vertebrates, the lamprey and the eel, single intravascular injections of physiological doses (2.5 micrograms/kg) of epinephrine (E) into the rat immediately increased levels of plasma dopamine (DA) and norepinephrine (NE). 2. Single doses of DA (5 micrograms/kg) enhanced circulating NE and E, while NE (5 micrograms/kg) had no clear impact on the plasma levels of the other two catecholamines (CAs). 3. These data are at variance with findings in the eel, where all three CAs are mutually stimulatory; and in the lamprey, where only E stimulates release of the other two CAs. 4. It appears that E-stimulated CA release is widespread or ubiquitous among vertebrates, and that complex interactions between circulating CAs must be considered under experimental, physiological, and clinical conditions. 5. None of the injections had a significant hyperglycemic effect.

Anguilla↗
PubMed1985

The morphology and histology of the endocrine pancreas of the southern hemisphere lamprey, Geotria australis gray.

The location and arrangement of the pancreatic endocrine tissue in larval and adult Geotria australis (Geotriidae) differ markedly from those exhibited by the comparable stages of Northern Hemisphere lampreys (Petromyzontidae). In larval Geotria australis, the main zones of islet proliferation are located laterally between the oesophagus and the inner edge of the two large intestinal diverticula unique to this species rather than dorsal and ventral to the oesophagus. In adult Geotria australis, the islet follicles are closely packed into a single discrete capsule which could be easily removed surgically, rather than into cranial, intermediate, and caudal cords. The differences in the adult can be related to a lack of involvement of the bile duct in islet formation during metamorphosis. While B cells were found in both larval and adult islet follicles, the PI acidophilic cells and argyrophilic cells, which appeared respectively at stages 3 and 4 in metamorphosis, were present in all adult stages.

Aging↗
PubMed1985

Catecholaminotropic effects of catecholamines in a teleost fish, Anguilla rostrata.

Injections of physiological and supraphysiological doses of epinephrine (E) into cardiac-cannulated eels cause a dose-related increase of plasma dopamine (DA) and norepinephrine (NE) within 3 min. Likewise, both exogenous DA and NE increase the plasma titers of the respective other two catecholamines (CAs). The baseline titers of NE and E are closely correlated. Lack of a correlation of the baseline titers of NE and E with that of DA appears to be due to a faster disappearance rate of DA from the circulation. E is strongly hyperglycemic, and the weaker glycemic action of NE may be mediated via E release. The effects of E seem to depend on a spurt-like increase rather than its titer per se. The ability of the eel to cope with very fast, excessive increases of plasma CAs raises the question of the underlying mechanisms.

Animals↗
PubMed1985

Plasma catecholamines in the lamprey: intrinsic cardiovascular messengers?

The widely scattered cardiovascular chromaffin cells of Petromyzon marinus appear to form an intrinsic control system of circulatory function. In response to blood-borne stimuli, a checkpoint-like accumulation of epinephrine cells in the heart releases its hormone; epinephrine, in turn, stimulates the release of norepinephrine, and probably also of dopamine, from other cardiovascular chromaffin cells. The myocardium seems to be a major target of norepinephrine. On the other hand, high disappearance rates of epinephrine and dopamine in the gills point to these organs as possible major targets of the latter two secretions. Carbon dioxide and hypovolemia are strong stimuli of catecholamine release.

Animals↗