The osmoregulatory system of birds with salt glands.
Explore the source record for details and available documents.
Adaptation, Physiological↗
Biomedical subjects
E Simon
Publications and source records attributed to E Simon.
Properties of high Q10 units in the conscious duck's hypothalamus responsive to changes of core temperature.
1. Five Pekin ducks were chronically implanted with a device allowing thermal stimulation of the hypothalamus and simultaneous recording of hypothalamic single unit activity on the conscious animals in repeated experiments. In addition, the core temperature of the animals could be lowered by means of a thermode tube which was placed in the colon and was perfused by a cold solution. Hypothalamic temperature was measured in the centre of the hypothalamic thermode array; core temperature was measured in the axillary pit.2. Each unit was tested in two periods of hypothalamic ramp cooling, one was performed at normal core temperature, and the other at a lowered core temperature during sustained intestinal cooling.3. Among forty-six neurones exhibiting a local Q(10) > 2 of their discharge rate, intestinal cooling was found to activate 26% (fall feed-back units), to inhibit 44% (rise feed-back units), and not to affect 30% (non-reactive units). The local Q(10) values of the fall feed-back units were, on average, significantly higher than those of the rise feed-back units.4. By multiple linear regression analysis the thermal coefficients (impulses/sec. degrees C) relating unit discharge to hypothalamic (local) and to core (remote) temperature changes were evaluated. The fall feed-back units exhibited average local temperature coefficients of 0.79+/-0.11 and remote coefficients of -2.75+/-0.56 (means+/-s.e. of mean); the corresponding coefficients of the rise feed-back units were determined as 0.44+/-0.08 and +2.33+/-0.41.5. The results of this study support the hypothesis that the activity of hypothalamic neurones conveying extrahypothalamic cold signals is depressed more by hypothalamic cooling than that of the neurons conveying extrahypothalamic warm signals. This would explain the paradoxical effects of hypothalamic cooling on thermoregulatory effector activity in birds.
Action Potentials↗
Opposing effects of hypothalamic cooling on threshold and sensitivity of metabolic response to body cooling in rabbits.
1. Extrahypothalamic thermosensitivity at normal (39 degrees C) and lowered (33.8 degrees C) hypothalamic clamp temperatures has been measured in cold exposed rabbits equipped with chronically implanted hypothalamic perfusion thermodes. The animals were subjected to body core cooling by means of cold perfused thermodes placed in the colon. 2. At lowered hypothalamic temperature the threshold core temperature for increased metabolic heat production due to body core cooling was significantly increased as compared to that at normal hypothalamic temperature. However, the slope of the response relating increased metabolic rate to body core temperature was significantly reduced. 3. The experimental results compare well with those predicted from a mathematical model, which takes into account the effect of temperature on synaptic transmission of afferent information in the hypothalamus.
Animals↗
Negative and positive feedback of central nervous system temperature in thermoregulation of pigeons.
Experimental alterations of spinal cord and hypothalamic temperature affecting behavioral and autonomic cold defense were investigated in pigeons under external cold load with access to instrumental heat reinforcement. Warming and cooling spinal cord resulted in negative-feedback effects on both instrumental and autonomic cold defense. Hypothalamic warming produced similar negative-feedback effects, whereas hypothalamic cooling produced either no effect or positive-feedback effects on both kinds of cold defense. As determined in previous studies, hypothalamic temperature displacements under heat-load conditions produced only negative-feedback effects on instrumental heat defense. However, only positive-feedback effects were observed on autonomic heat defense by panting. The diverse response patterns of autonomic and behavioral thermoregulatory effectors to changing hypothalamic temperature under heat- and cold-load conditions could be quantitatively described by a mathematical model that takes into account 1) a greater Q10 for intrahypothalamic transmission of the cold signal input than of the warm signal input, and 2) different weights of extra- and intrahypothalamic temperature signal inputs for the control of different effectors.
Animals↗
Effects of CNS temperature on generation and transmission of temperature signals in homeotherms. A common concept for mammalian and avian thermoregulation.
Neurophysiological studies on avian hypothalamic thermosensitivity have presented evidence for a higher Q10 of cold than of warm signal transmission in the CNS of birds. An identical temperature dependence of central cold and warm signal transmission in mammals is suggested by considerations on the phylogeny of temperature regulation. By taking into account the experimental evidence for the existence of thermosensory afferents in the CNS of mammals and birds, being differently developed in the various sections of the neural axis and exerting quantitatively different influences on the various thermoregulatory effectors, a common concept of homeothermic thermoregulation is proposed resting on the same basic assumptions for mammals and birds. The great diversity of negative as well as positive feedback effects of CNS temperature displacements on homeothermic thermoregulation, which is particularly expressed in avian autonomic and behavioral thermoregulation and, further, certain pathophysiological conditions of disturbed thermoregulation could be accounted for by assuming quantitatively different contributions of the central thermosensory inputs of thermoregulatory effector control, but maintaining the Q10 values of hypothalamic warn and cold signal transmission constant. The proposed model, while basically additive in its mathematical design, meets a number of properties described by multiplicative models of thermoregulation. In additionally generalizes these models of predicting that changes of hypothalamic temperature modify the sensitivities with which any thermoregulatory effector responds to any thermosensory input.
Animals↗
Central nervous versus total body thermosensitivity of the duck.
Explore the source record for details and available documents.
Animals↗
Temperature-sensitive mutant of Newcastle disease virus which has an altered nucleocapsid-associated protein.
Analysis of six temperature-sensitive (ts) mutants of Newcastle disease virus (NDV) representing each of six complementation groups by both SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis revealed that in only one mutant was there an alteration in the isoelectric point of a protein. This altered protein was the nucleocapsid-associated protein, NAP. In addition, the mobility of the haemagglutinin-neuraminidase protein, HN, was decreased on non-reduced SDS-PAGE in this mutant. All independent ts+ clones derived from this mutant had normal NAP but HN protein migrated at the decreased rate. Haemagglutinating activity of wide-type (ts+) and ts virions was equally thermostable. Wild-type and ts+ clones derived from this ts mutant were RNA(+) at both permissive and non-permissive temperatures, whereas the ts mutant was RNA(-) at the non-permissive temperature. This ts mutant appears to be a double mutant in both HN and NAP genes, the latter only being a temperature-sensitive lesion which affects virus-directed RNA synthesis.
Capsid↗
Brain stem sites mediating specific and non-specific temperature effects on thermoregulation in the pekin duck.
1. Thermodes were chronically implanted into various levels of the brain stem of sixteen Pekin ducks. The effects of local thermal stimulation on metabolic heat production, core temperature, peripheral skin temperature and respiratory frequency were investigated. 2. Four areas of thermode positions were determined according to the responses observed and were histologically identified at the end of the investigation. 3. Thermal stimulation of the lower mid-brain/upper pontine brain stem (Pos. III) elicited an increase in metabolic heat production, cutaneous vasoconstriction and rises in core temperature in response to cooling at thermoneutral and cold ambient conditions and, further, inhibition of panting by cooling and activation of panting by heating at warm ambient conditions. The metabolic response to cooling this brain stem section amounted to -0.1 W/kg. degrees C as compared with -7 W/kg. degrees C in response to total body cooling. 4. Cooling of the anterior and middle hypothalamus (Pos. II) caused vasodilatation in the skin and did not elicit shivering. The resulting drop in core temperature at a given degree of cooling was greater than the rise in core temperature in response to equivalent cooling of the lower mid-brain/upper pontine brain stem. 5. Cooling of the preoptic forebrain (Pos. I) and of the myelencephalon (Pos. IV) did not elicit thermoregulatory reactions. 6. It is concluded that the duck's brain stem contains thermoreceptive structures in the lower mid-brain/upper pontine section. However, the brain stem as a whole appears to contribute little to cold defence during general hypothermia because of the inhibitory effects originating in the anterior and middle hypothalamus. Cold defence in the duck, which is comparable in strength to that in mammals, has to rely on extracerebral thermosensory structures.
Animals↗
Extracerebral deep-body cold sensitivity in the Pekin duck.
Pekin ducks, in which cerebral cold sensitivity is negligible, were submitted to general body cooling at warm, thermoneutral, and cold ambient temperature (Ta) with an intestinal thermode. In some animals, hypothermia was enhanced by additional hypothalamic cooling that suppressed cold defense. In other animals, the spinal cord was cooled, either selectively or during intestinal cooling. From core temperature (Tc) and metabolic heat production (M) an overall cold sensitivity of about -5 to -6 W . kg-1 . degrees C-1 was determined at thermoneutrality. Maximum M amounted to four to five times the resting M of 3.8 W . kg-1 and was attained when Tc fell by 2.5 degrees C or more. In the cold, threshold Tc for the activation of M was elevated; overall cold sensitivity remained constant. In the warmth, threshold Tc was lowered; overall cold sensitivity was reduced, if mean skin temperature (Tsk) remained at aout 39 degrees C or higher. Spinal cold sensitivity amounted to about -0.25 W . kg-1 . degrees C-1 at normal Tc and thermoneutral and warm Ta; it increased to aout -0.50 W . kg-1 . degrees C-1 in the cold and during hypothermia. Peripheral cold sensitivity was estimated from Tsk and M as -0.4 to -0.8 W . kg-1 . degrees C-1. It is concluded that overall cold sensitivity in ducks mainly depends on deep-body temperature sensors outside of the central nervous system.
Animals↗
Pullout threatens N.Y. plan.
Explore the source record for details and available documents.
Government Agencies↗
Radioautography of binding of tritiated diprenorphine to opiate receptors in the rat.
Explore the source record for details and available documents.
Animals↗
Intracerebroventricular osmosensitivity in the Pekin Duck. Properties and functions in salt and water balance.
Pekin ducks were implanted with devices allowing intracerebroventricular (i.c.v.) microinfusions at rates of 0.1--0.4 mul/min during 15 min in the conscious animals. When hydrated by intragastric infusion of 1 ml/min tap water, i.c.v. infusion of hypertonic NaCl solutions reduced urine flow and increased osmolality, presumably due to increased ADH release. Osmotically equivalent Li+ salts (Cl-, Br-, So24-) caused a slightly prolonged antidiuresis, while Ca2+ and Mg2+ salts caused a more protracted antidiuresis. Urea solution osmotically equivalent to 4.8% NaCl had no effect on diuresis, while osmotically equivalent mannitol solution slightly enhanced diuresis. Angiotensin II (0.5--2.5 pmol in 15 min) and Carbachol (3.0 pmol in 15 min) infused in 0.9% saline caused antidiuresis. The results suggest that the central control of ADH release in birds is similarly organized as in mammals, with receptive elements reacting to ionic rather than osmotic changes and with Na+ as the naturally involved cation. In ducks with their salt glands activated by i.v. infusion of 800 mosmol NaCl/kg H2O at 0.2 ml/min, salt gland secretion was not augmented by i.c.v. microinfusion of hypertonic NaCl but inhibited by i.c.v. infusion of osmotically equivalent mannitol solution. The supraorbital salt glands, when activated appear to be little stimulated further by a rise but may be inhibited by a fall of i.c.v. Na+ concentration.
Angiotensin II↗
Radioimmunoassay for arginine-vasotocin (AVT) in serum of Pekin ducks: AVT concentrations after adaptation to fresh water and salt water.
A radioimmunoassay for arginine-vasotocin (AVT), the antidiuretic principle in birds, was developed using the high cross-reactivity of AVT with an AVP antiserum raised in rabbits. This assay is specific for the measurement of AVT in serum of birds. The sensitivity and precision is such that serum AVT concentrations above 0.5 fmol/ml can be measured quantitatively. A serum AVT concentration of 5.1 +/- 1.4 fmol/ml was found in normally hydrated, fresh water adapted ducks with a serum osmolality of 293.7 +/- 2.2 mosmol/kg. When the same animals were acutely hydrated, no or < 0.5 fmol/ml AVT was present at an osmolality of 289.8 +/- 2.4 mosmol/kg. In salt water adapted ducks with a serum osmolality of 333.0 +/- 7.6 mosmol/kg, a serum AVT of 22.7 +/- 3.0 fmol/ml was found. When fresh water adapted ducks were hydrated and infused with different doses of AVT, a linear relationship between serum AVT and the amount infused was obtained. During AVT infusions, serum osmolality and urine flow rate were negatively correlated and urine osmolality was positively correlated with serum AVT.
Adaptation, Physiological↗
Serum arginine-vasotocin (AVT) and afferent and central control of osmoregulation in conscious Pekin ducks.
In conscious Pekin ducks adapted either to fresh water or to hypertonic saline (1.9%) as drinking fluid, urinary excretion, salt gland secretion and the serum concentration of radioimmunoassayable arginine-vasotocin (AVT) were examined with regard to their afferent and central control. The experiments were carried out under conditions of water diuresis, osmotic diuresis or supraorbital salt gland secretion, which were induced by continuous infusions of appropriate solutions. Temporary bilateral vagus blockade caused rises in AVT serum concentration accompanied by antidiuresis in hydrated ducks and by inhibition of salt gland secretion in salt-stressed ducks. Rostral brainstem cooling caused decreases of AVT serum concentration and water diuresis in ducks under osmotic diuresis and reduction of AVT serum concentration and inhibition of salt gland secretion in salt-stressed ducks. Cerebral osmotic stimulation in hydrated ducks by intracarotid injection or by intracerebroventricular microinfusion of hypertonic NaCl solutions caused antidiuretic reactions associated with rises of AVT serum concentration.
Animals↗
Effect of the aggregational state on the mitogenicity of lipoprotein from the outer membrane of Escherichia coli.
The effects of ultrasonication, electrodialysis, and centrifugation through sucrose gradients on the mitogenicity of the lipoprotein (LP) from the outer membrane of Escherichia coli were studied in several inbred mouse strains. LP is not readily soluble in aqueous solution. By ultrasonication for 1 minute we obtained LP aggregates which were fully mitogenic; prolonged sonification had no influence on activity. Solubilization in 4% sodium dodecyl sulphate (SDS) and centrifugation into sucrose gradients yielded different aggregation forms of LP, which were B-lymphocyte mitogens towards LPS non responder C3H/HeJ mouse splenocytes, and towards congenitally athymic nude mice. By electrodialysis, LP could be transformed into different salt forms. The TEA-salt of LP exhibited enhanced mitogenicity. The results suggest that the mitogenicity of lipoprotein is widely independent from the aggregational state in which it is offered to the cells.
Amino Acids↗
Mitogenicity of a lipid-deficient lipoprotein from a mutant Escherichia coli strain.
From the mutant bacterial strain Escherichia coli JE5511 lpp lpm, muropeptide-containing and muropeptide-free lipoproteins were prepared. By gas chromatography and by infrared spectroscopy we showed that the products were deficient in the two ester-bound N-terminal fatty acids, but still carried the amide-linked fatty acid. Mutant lipoproteins were tested for mitogenicity in lipopolysaccharide nonresponder C3H/HeJ mice by incorporation of [3H]thymidine and [3H]uridine and by hemolytic plaque assays for immunoglobulin-secreting plasma cells. Our results showed that the mutant lipoproteins still exhibited marked mitogenicity toward mouse B-lymphocytes, although the activity of the products was reduced in comparison to the wild-type lipoprotein. Thus, the presence of one fatty acid in the N-terminal part of lipoprotein is sufficient to bring about mitogenicity.
Animals↗
Properties of body fluids influencing salt gland secretion in Pekin ducks.
Pekin ducks were reared and maintained on 620 mosmol NaCl/kg H2O to enhance the secretory capability of their salt glands. When a control solution of 1,000 mosmol NaCl/kg H2O was infused intravenously at 0.2, 0.4, or 0.6 ml/min for 60-90 min, the infused loads were secreted in approximately equal quantities, indicating that the amount of NaCl in the extracellular fluid (ECF) before and after each infusion did not change. Salt and water secreted in response to experimental infusions of hyposmotic saline or blood were less than the solute and water infused. Thus, ECF volume increased and the Na+ concentration decreased. Infusions of control solution followed these experimental infusions. The salt and water secreted again equaled the amounts infused, indicating that the threshold concentration of Na+ ([Na+]th) for salt gland secretion was decreased by the increase in ECF volume. When the colloid dextran was added to the control solution, its infusion increased the colloid osmotic pressure of the blood and decreased nasal secretion. Because dextran increased the intravascular volume while the interstitial fluid volume (ISFV) decreased, we conclude that the [Na+]th was inversely correlated with ISFV.
Animals↗