bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of digitalis and calcium on papillary muscles in normal and hypoxic states
Authors: Taubert K , Templeton G , Willerson JT , Shapiro W
Published: December 2017

The effects of digoxin and ouabain in 2.5 and 4.0 mM extracellular calcium were studied in well-oxygenated and hypoxic isolated, isometrically contracting cat papillary muscles. Muscle digoxin content was measured at the conclusion of the digoxin experiments. In the well-oxygenated environment muscles in the higher Ca bathing media reached peak glycoside inotropic effect sooner and contained 2.7 times more digoxin. During hypoxia and reoxygenation muscles contracting with glycosides performed no differently than those without a glycoside present. Muscle digoxin content was lowered at the end of hypoxia (P less than 0.05) in 2.5 mM Ca; after reoxygenation digoxin content was significantly greater than either before or after hypoxia (P less than 0.001). Hypoxic depression of muscle performance was attenuated in 4.0 mM Ca but muscles in 2.5 mM Ca showed greater improvement during reoxygenation even though the muscles in 4.0 mM Ca had significantly greater digoxin content at the end of reoxygenation (P less than 0.02). It therefore is concluded that, although altered extracellular calcium can alter performance during hypoxia and reoxygenation, muscle performance is not aided by the presence of digitalis and under these conditions performance cannot be correlated with muscle digoxin levels.
Oral contraceptives, norethindrone and mestranol: effects on tissue levels of minerals
Authors: Lei KY , Prasad AS , Bowersox E , Oberleas D
Published: December 2017

The study involved three levels of dietary zinc (deficient, marginal, and adequate) and four hormonal conditions; namely, no steriods, norethindrone, mestranol, and norethindrone plus mestranol. The steroids were incorporated into diets and fed to 11-wk-old female Sprague-Dawley rats. After 10 wk of treatment, various tissues were excised for mineral assays by atomic-absorption spectrophotometry. Both steroids, reduced weight gain. Mestranol depressed plasma zinc, tibia copper and magnesium, and liver iron, but elevated the zinc levels in liver and erythrocytes, plasma copper, liver magnesium and calcium, and iron content of tibia and heart. In general, the effect was most prominent with adequate zinc but diminished in magnitude with the reduction of zinc intake. In addition, norethindrone increased heart iron and tibia calcium. Mestranol appeared to be the main causative factor and may have induced a possible shift of minerals from one pool to another. As expected, zinc deficiency resulted in the reduction of zinc concentrations of plasma, tibia, kidney, and pancreas, and the elevation of copper, iron, magnesium, and calcium concentrations of various tissues.
Permeability of renal peritubular capillaries to neutral dextrans dextrans and endogenous albumin
Authors: Deen WM , Ueki IF , Brenner BM
Published: December 2017

Renal lymph-to-renal vein concentration ratios (CL/CV) for neutral dextrans (18-42 A effective radii) and endogenous serum albumin were measured in rats before and during acute colume expansion with isoncotic plasma or Ringer solution. Under all conditions studied, CL/CV decreased with increasing dextran size, in normal hydropenia falling from 0.93 +/- 0.03 SE at 18 A to 0.24 +/- 0.02 a 42 A (n = 12). Albumin (36 A pradius) behaved in a manner similar to a 40 A dextran, CL/CV averaging 0.33 +/- 0.03 (n = 12) in hydropenia. For all dextran sizes studied and for albumin, CL/CV decreased markedly during either form of volume expansion. Ringer loading produced significantly greater decreases in CL/CV for the larger dextrans and albumin than did plasma loading, and also resulted in much greater increases in renal lymph flow, while causing increases in whole kidney fluid reabsorption similar to those with plasma loading. With a compartmental model in which diffusion of dextrans and albumin from capillary lumen to interstitium is opposed by capillary uptake of tubule reabsorbate, these results are interpreted to indicate that connective reflection coefficients for dextrans with radii great than or equal to 36 A and albumin are essentially equal to 1. Indirect evidence is therefore provided that albumin and the larger globulins exert their full osmotic pressures across the walls of peritubular capillaries.
Lactate production in isolated perfused rat lung
Authors: Longmore WJ , Mourning JT
Published: December 2017

The ability of the isolated perfused rat lung to produce lactate under aerobic and hypoxic conditions has been studied. The lung has been found capable of producing lactate at a rate of 53 mumol/g dry wt per h in the presence of as great as 1 mM extracellular lactate under aerobic conditions. Essentially 100% of the lactate synthesized was derived from [U-14C]glucose. When hypoxic, the rate of lactate production doubled, but only 60% was found to be derived from [U-14C]glucose. When the perfused lung was exposed to aerobic conditions following hypoxia, it was found that lactate production did not decrease. However, lactate production from [U-14C]glucose did increase. It is concluded that lung tissue possesses a high rate of lactate production under aerobic contitions from glucose in comparison to glucose oxidation to CO2. When the lung is hypoxic, lactate production increases as a probable result of amino acid catabolism with little anaerobic energy production occurring. The effect of hypoxia was not reversed within the duration of the performed experiments.
Core temperature in the female rat: effect of pinealectomy or altered lighting
Authors: Spencer F , Shirer HW , Yochim JM
Published: December 2017

Radiotelemetry of core temperature in unrestrained, mature female rats revealed the existence of a 24-h rhythm that was bimodal. The principal peak occurred during the night under control conditions of 14 h light and 10 h darkness, and a less pronounced, secondary peak occurred 3-4 h after the onset of the light phase. Shifts in the phase of the photoperiod or alteration of the proportion of light per day revealed that the temperature rhythm was entrained by light, but that the two component peaks were governed by different aspects of the lighting regimen. Exposure of rats to continuous darkness, continuous light, or to a 20-h photoperiod revealed that the primary rhythm was endogenous, entrained by circadian photoperiods only, whereas the secondary rhythm was exogenous, requiring a circadian light/dark rhythm. A relationship between mean core temperature and ttion pressure, end-systolic L was constant, despite variations in filling and therefore independent of initial L and delta L; moreover, the L to which the ventricle shortened was determined by the course of the systolic force L-relation. Thus, irrespective of loading, delta L occurs within the confines of the contractile state-depdendent isovolumic force-L relation and where the latter is equivalent to the end-systolic force-length relation.
Core temperature in the female rat: effect of ovariectomy and induction of pseudopregnancy
Authors: Yochim JM , Spencer F
Published: December 2017

Nocturnal peaks in core body temperature of rats during the estrous cycle were highest during the night of ovulation (2300-0200 h, proestrus-estrus) and lowest during the night before (diestrus 2-proestrus). Less dramatic diurnal secondary peaks, absent only during estrus, occurred 3-4 h after the onset of daylight. After induction of pseudopregnancy, mean temperature declined, but both daily peaks persisted until the first postluteal estrus, when the secondary peak was again absent transiently. Ovariectomy reduced mean core temperature and abolished all secondary peaks. In contrast, castration during pseudopregnancy did not abolish the secondary peaks. When cyclic rats were gonadectomized (abolishing the secondary rhythm) it was possible to re-establish this rhythm by stimulating the uterine cervix (as if to induce pseudopregnancy). However, in animals exposed to darkness (which also abolishes the secondary rhythm) reinduction by cervical stimulation was ineffective. These results indicated that the integrity of the secondary peak, though dependent on photoperiod, nevertheless was influenced by a neuroendocrine reflex arc.
Glucagon, insulin, and gluconeogenesis in fasted odd carbon fatty acid-enriched rats
Authors: Pi-Sunyer FX , Conway JM , Lavau M , Campbell G , Eisenstein AB
Published: December 2017

Forty-eight male rats were fed a nutritionally complete diet containing 30% of dietary energy as fat. For 24 animals (control) the fat source was corn oil, for the remaining 24 rats (experimental) the fat source was a triundecanoin-corn oil mixture (7:3, wt/wt). After 6 wk, groups of control and experimental rats were killed after 0, 24, and 48 h of fasting. In the experimental group, adipose tissue fatty acids contained, on average, 280 mmol undecanoate/mol fatty acid. In the control group, no odd-numbered fatty acids were present. During fasting, the experimental groups had higher plasma glucose and alanine levels, higher plasma insulin-to-glucagon ration, and lower liver phosphenol pyruvate caboxykinase. The results suggest that the terminal propionate residues generated when odd carbon fatty acids are oxidized become gluconeogenic precursors and cause a reduced need for gluconeogenesis from protein.
DDE feeding and plasma osmoregulation in ducks, guillemots, and puffins
Authors: Miller DS , Kinter WB , Peakall DB , Risebrough RW
Published: December 2017

To assess the possibility that organochlorine pesticide disruption of osmoregulation is responsible for recent large kills of young seabirds, we have studied the effects of DDE feeding (10-250 ppm) on plasma osmoregulation and nasal gland function in the following species: mallared and white Pekin ducks (both Anas platyrhynchos), black guillemot (Cepphus grylle), and common (Fratercula arctica). Other investigators have recently reported that dietary DDE (10-1,000 ppm) inhibits nasal gland secretion in freshwater-maintained mallards; our initial experiments with white Pekins showed no such inhibition during either freshwater or seawater maintainance. Moreover, DDE had minimal effects on plasma electrolyte levels and total nasal gland Na-K-ATPase activities in all species studied. Liver DDE levels in experimental ducks and guillemots were comparable to those reported for seabirds found dead after kills; levels in starved experimental puffins were much higher. Thus DDE at environmental levels does not affect osmoregulation or nasal gland Na-K-ATPase either in ducks or in two species of oceanic birds.
Gastrointestinal metabolism of cadmium in experimental iron deficiency;
Authors: Valberg LS , Sorbie J , Hamilton DL
Published: December 2017

The average gastrointestinal uptake 4 h after an intragastric dose of 400 nmol of cadmium chloride labeled with 109CdCl2 in iron-deficient mice, 25%, was significantly greater than the result, 16%, in iron-normal animals, and more cadmium entered the body of the former, 3.8%, than the latter, 2% (P less than 0.05). Between 4 and 72 h, gastrointestinal radioactivity declined without further increase in body activity; however, more radiocadmium remained in the duodenum of iron-deficient than iron-normal animals (P less than 0.05). The radiocadmium sequestered in the duodenum was bound to a protein with a molecular weight of about 12,000. After subcutaneous injection of radiocadmium, the rate of excretion of radioactivity from the body was similar in iron-normal and iron-deficient mice; however, a greater proportion of the injected dose accumulated in the duodenum of the iron-deficient animals (P less than 0.05). Thus, the intestinal adapative response to iron deficiency may enhance cadmium toxicity, whereas sequestration and subsequent excretion of cadmium by the intestinal mucosa serves to protect the body against toxic effects. The duodenum, particularly in iron-deficient mice, is especially vulnerable to the toxic effects of cadmium.
Protein metabolism in burned rats
Authors: Brown WL , Bowler EG , Mason AD  , pruitt BA
Published: December 2017

Incorporation of [2-14C]glycine was used to estimate serum protein synthesis in four groups of rats. These were the control (group C); 20% body surface burn (group B); 20% burn, seeded with Pseudomonas aeruginosa (group BI); and burned-infected treated topically with mafenide (alpha-amino-p-toluenesulfonamide) acetate (group BIS), a treatment which controls P, aeruginosa burn-wound infection in humans. On the 6th day postburn the relative specific activities of all fractions were increased in the order BI greater than BIS greater than B greater than C, as were the concentrations of the globulins; Serum albumin concentration fell, being lowest in BI. Tissue albumin contents, measured by radioimmunoassay, of eviscerated blood-free bodies of rats were (mg/100 g rat wt): C, 207; B, 294; BI, 256. Analyses of individual tissues showed that the difference was due to increased albumin content in the burn-wound area. The tissue albumin was of normal molecular size and was immunologically reactive. We conclude that the prolonged hypoalbuminemia following burn injury is not a consequence of impaired albumin synthesis, but a result of altered compartmentation.
Cerebral circulation and norepinephrine: relevance of the blood-brain barrier
Authors: MacKenzie ET , McCulloch J , O'Kean M , Pickard JD , Harper AM
Published: December 2017

The systemic administration of norepinephrine has minimal effects on the cerebral circulation, perhaps due to blood-brain barrier mechanisms. To test hypothesis, the cerebrovascular effects of norepinephrine beyond the blood-brain barrier were studied in anesthetized baboons, Intraventricular norepinephrine (40 mug/kg) resulted in significant increases in cerebral blood flow (40%), cerebral oxygen consumption (21%), and cerebral glucose uptake (153%). Intracarotid hypertonic urea opens the blood-brain barrier by osmotic disruption; Consequent to hypertonic urea, the intracarotid infusion of norepinephrine, 50 ng/kg-min, significantly increase cerebral blood flow (49%), cerebral oxygen consumption (21%), and cerebral glucose uptake (76%), It appears probable that the cerebrovascular responses to norepinephrine are dependent on the integrity of the blood-brain barrier; It is likely that the increase in cerebral blood flow, associated with norepinephrine when it bypasses the barrier, is secondary to an increase in cerebral metabolism.
Influence of endogenous norepinephrine on cerebral blood flow and metabolism
Authors: MacKenzie ET , McCulloch J , Harper AM
Published: December 2017

The influence of brain norepinephrine on cerebral metabolism and blood flow was examined because exogenous norepinephrine, administered in a way that the blood-brain barrier is bypassed, has been shown to effect pronounced changes in the cerebral circulation. Reserpine (40 mug/kg, by intracarotid infusion) was administered in order to release brain norepinephrine in five anesthetized baboons. Reserpine significantly increased cerebral oxygen consumption (23%) and cerebral blood flow (50%). This response lasted for approximately 60 min. In a further five animals, effects of central beta-adrenoreceptor blockade were studied. Pro pranolol (12 mug/kg-min) produced an immediate, significant reduction in both cerebral oxygen consumption (40%) and cerebral glucose uptake (39%). Cerebral blood flow was reduced minimally. However, the responsiveness of the cerebral circulation to induced hypercapnia was severely attenuated from a gradient of 3.22 before, to 1,11 after, administration. These experiments suggest that central norepinephrine can influence the cerebral circulation primarily through noradrenergic effects on brain metabolism.
Renal sugar transport in the winter flounder. II. Galactose transport system
Authors: Kleinzeller A , Dubyak GR , Mullin JM
Published: December 2017

The structural specificity of the transport of 0.5 mM D-galactose and 2-deoxy-D-galactose by teased renal tubules of the winter flounder Pseudopleuronectes americanus was investigated. The sugar uptake reflects preponderantly transport at the antiluminal membrane of tubular cells. Both sugars compete for the transport sites, indicating the sharing of a common carrier. 1) The structural requirements for the hexose-carrier interaction were defined by an inhibiton analysis using 12 structurally analogous sugars (5 mM): a (pyranose) ring structure; a free hydroxyl on C1; free hydroxyls (equatorial configuration) on C3 and C4; an oxygen on C6. Close packing in the vicinity of C2 is indicated. 2) Consonant with the requirement of a free C1-OH, beta-methyl-D-galactoside is not transported 3) Increasing concentrations (0.05-0.5 mM) of phlorizin and phloretin inhibit sugar uptake by lowering cellular levels of phosphorylated hexoses, whereas the levels of free sugars are not depressed. The possibility of an interaction of the sugar at C1-0H with a phosphorylated group at the carrier as the first step in the translocation process of both hexoses across the basal membrane is raised.
Skeletal muscle glycogen content: diurnal variation and effects of fasting
Authors: Conlee RK , Rennie MJ , Winder WW
Published: December 2017

To test whether skeletal muscle glycogen concentration is related to food consumption, glycogen content was determined in red (R) and white (W) vastus lateralis and in soleus (S) muscles from six groups of ad libitum-fed rats killed at 4-h intervals and from 24-h-fasted animals killed at 0800 and 1600 h. The animal quarters were illuminated between 0700 and 1900 h. Glycogen values exhibited a peak at 0800 h and a nadir at 2000 h. These changes bore no relationship to blood glucose and lactate or plasma free fatty acids, glucagon, insulin, and corticosterone concentrations. Fasting resulted in reductions of glycogen content of 49% (S), 47% (R), and 29% (W) in animals killed at 0800h, but at 1600h changes were only 23% (RY), 17% (W), and 8% (S). The smaller changes at 1600 h were apparently due to lower glycogen levels in the tissues of the fed animals. It was concluded that skeletal muscle exhibits a diurnal variation in glycogen content, and that, contrary to accepted belief, fating significantly alters muscle glycogen concentration.
Role of atrial receptors in the control of ACTH
Authors: Baertschi AJ , Ward DG , Gann DS
Published: December 2017

Sinusoidal volume changes (+/- 1 ml) were applied at 1 Hz to the right or left atrium of 25 anesthetized cats. Changes in firing rates of single vagal fibers and in plasma ACTH and cortisol were observed in response to start and stop of atrial pulsation. Decreased activity of right atrial and/or septal B-receptors was associated with increased ACTH. Changes in left atrial B-receptor activity were associated with a change in ACTH only if right atrial/septal receptors or baroreceptors also changed their activity in the same direction. The activity of atrial A-receptors did not change in response to atrial pulsation. A quantitative analysis suggested strongly that right atrial and/or septal B-receptors dominate in the response of ACTH to hemodynamic stimuli. Arterial receptors appear less effective, and left atrial B-receptors appear least effective in the hemodynamic control of ACTH.
Adrenergic receptors mediating depolarization in brown adipose tissue
Authors: Fink SA , Williams JA
Published: December 2017

Adrenergic receptors mediating depolarization in in vitro neonatal rat brown adipose tissue (BAT) have been characterized by use of adrenergic agonists and antagonists. Releasable endogenous catecholamine was present in BAT as demonstrated by tyramine- and 1,1-dimethyl-4-phenylpiperazinium iodide- (DMPP) induced depolarization in BAT from normal rats and its absence when BAT from reserpinized rats was used. In BAT from reserpinized rats l-norepinephrine, l-phenylephrine, and l-isoproterenol all similarly depolarized the bronw adipocytes over the concentration range of 10(-8) to 10(-6) M with a maximal depolarization of about 25 mV. Dopamine and d-norepinephrine were more than 100 times less potent. The beta-adrenergic blocker propranolol competitively inhibited isoproterenol-induced depolarization, whereas the alpha-adrenergic blackers, phentolamine and phenoxybenzamine, inhibited the phenylephrine-induced depolarization with much smaller inhibitory effects on the isoproterenol-induced depolarization. Both phenylephrine and isoproterenol elicited transient depolarizations when briefly added to the bathing medium while continuously recording from the same cell. Both the agonist and antagonist studies are interpreted as indicating the presence of both alpha- and beta-adrenergic receptors on BAT cells which mediate catecholamine-induced depolarization.
Identification and discharge patterns of spinal sympathetic interneurons
Authors: Gebber GL , McCall RB
Published: December 2017

Sympathetic interneurons, in the vicinity of the intermediolateral cell column of the cat thoracic spinal cord, were identified by determining whether the probability of spontaneously occurring unitary discharge was correlated in time with the R wave of the ECG. Fifteen units which could not be antidromically activated by stimulation of the cervical sympathetic nerve exhivited a positive post-R wave relationship. The discharge patterns of these cells were distinctly different from those of antidromically identified preganglionic neurons. The interneurons discharged spontaneously in bursts with short interspike intervals (less than 20 ms). Preganglionic neurons rarely discharged more than once during a cardiac cycle. Single shocks applied to medullary pressor sites evoked a train of spikes in the interneurons. Preganglionic units usually discharged only once to medullary pressor stimulation. Electrial activation of medullospinal inhibitory tracts suppressed the discharges of both interneurons and preganclionic units. This observation indicates that spinal inhibition is exerted at an interneuronal level within sympathoexictatory pathways. No evidence was found for the existence of inhibitory interneurons in the intermediolateral cell column. This study demonstrated that the post-R wave time interval histogram in combination with a test for antidromic activation can be used to differentiate between spinal sympathetic internuerons and preganglionic cells.
Elevation of plasma renin activity during avoidance performance in baboons
Authors: Blair ML , Feigl EO , Smith OA
Published: December 2017

The effect of a 3-h Sidman avoidance operant conditioning schedule (liver pressing to avoid an electric shock) on plasma renin activity and renin substrate concentration was examined in baboons (Papio cynocephalus). Plasma samples were drawn over a 24-h period on both the control and test days, and the avoidance session was presented on the morning of the test day. Plasma renin activity was significantly higher on the test day than at the corresponding hours of the control day at 1, 2, and 3 h after onset of the avoidance test and 30 min after its termination (P = .032). The magnitude of the increase in plasma renin activity was not correlated with either the rate of lever pressing or the number of shocks received. Renin substrate concentration was not changed during or after the avoidance session. These data demostrate that plasma renin activity can be increased by a psychological stimulus.
D-Glucose enhancement of water reabsorption in proximal tubule of the rat kidney
Authors: Weinman EJ , Suki WN , Eknoyan G
Published: December 2017

Water reabsorption in the proximal convoluted tubule of the rat kidney was examined by in vivo microperfusion techniques in order to examine the effect of D-glucose within the tubular lumen. When tubules were perfused with a balanced artificial solution containing Na, K, Cl, HCO3, urea, and D-glucose, absolute reabsorption averaged 4.01 +/- 0.24 nl/min per mm. Addition of D-glucose to the NaCl perfusate enhanced water reabsorption to values similar to those obtained with the balanced artificial perfusate. The enhanced water reabsorption consequent to the addition of D-glucose to the NaCl perfusion solution was completely inhibited by addition of phloridzin to the perfusate. The addition of an unabsorbed hexose, 2-deoxy-D-glucose, to the NaCl perfusate failed to enhance water reabsorption, whereas the addition of an incompletely reabsorbed sugar that is not metabolized, 3-O-methyl-D-glucose, resulted in partial enhancement of theabsolute rate of water reabsorption. These studies demonstrate that D-glucose has the specific effect of augmenting water reabsorption in the proximal tubule of the rat kidney.
Effect of histamine on intestinal fluid secretion in the dog
Authors: Lee JS , Silverberg JW
Published: December 2017

Intra-arterial infusion of histamine into the small intestine caused about a onefold increase of blood flow, edema of the intestinal tissues and mesentery, and produced a copious secretion of fluid. The jejunal secretions had an ionic composition similar to that of plasma, whereas ileal secretions contained high concentrations of HCO3 with relative low concentrations of Cl. The secretions contained protein (1.5 +/- .2 g/100 ml, range 0.5-2.4) with a similar electrophoretic pattern of plasma protein. When lissamine green was present in the blood, it also appeared in the secretion to a considerable concentration. It is inferred from these findings that a major mechanism of fluid secretion by the action of histamine involves a filtration process across the mucosal epithelium by the incrreased tissue fluid pressure due to extensive capillary leak.
Correlation of plasma corticosterone levels with running activity in the blinded rat
Authors: Gibbs FP
Published: December 2017

Blinded female reats were placed in running-wheel cages to monitor the phase of their activity cycle.After approximately a month of adaptation to the wheels, jugular vein blood samples were withdrawn at the beginning and end of the running phase of activity and analyzed for plasma corticosterone. By the time blood samples were obtained, the blined rats' activity cycles had desynchronized from the lighting cycle of the room in an apparently free-running fashion, and were out of phase with each other. The corticosterone levels were high at the beginning of the running phase and low at the end: begin run corticosterone was 34.5 +/- 13, end run corticosteronewas 14.2 +/- 10 (mean +/-SD in mug/100 ml of plasma; t = 7.93, df = 82, P less than 0.001). It was concluded that blinded rats do have an adrenocortical rhythm and that it is in phase with the activity cycle of each individual rat.
Early postglomerular plasma concentrations of chloride, sodium, and inulin in the rat kidney
Authors: Weinstein SW , Szyjewicz J
Published: December 2017

Sodium, chloride, and inulin concentrations were measured in plasma collected from the terminal portions of long efferent vessels at the subcapsular surface of the rat kidney. Sodium concentration equaled and the concentrations of chloride and inulin were less than those in peripheral plasma. During benzolamide infusion, chloride concentration equaled while inulin concentration remained less than in peripheral plasma. In free-flow micropuncture samples collected randomly during control conditions, chloride concentration rose rapidly in the early proximal tubule and then remained elevated and constant throughout the remainder of the proximal tubule accessible to micropuncture. These experiments indicate that normally tubular reabsorbate low in chloride and inulin is added to the blood traversing the early postglomerular vessels before reaching the kidney surface. Bases on the analyses of proximal tubular fluid, this type of reabsorbate appears available only from the early proximal tubular segment. We conclude that a close functional relationship exists between the first segment of the proximal tubule and the early postglomerular blood supply characteristic of the superficial cortical nephron.
Effect of rapid temperature change on mean body temperature and gill ventilation in carp
Authors: Crawshaw LI
Published: December 2017

Carp were transferred from 25 degrees C water to a calorimeter at 15 degrees C or from 15 degrees C water to a calorimeter at 25 degrees C. During cooling, dorsal muscle temperature (Tdm) and mean body temperature (Tb) were continuously monitored. During the first minutes Tb changed rapidly, while Tdm changed only slightly. In a 0.468-dg fish, Tdm decreased to two-thirds of the final value in 8.05 min, while Tb attained this value in 3.6 min. Tdm changed faster during heating than during cooling. Carp were also placed in a device where gill ventilation (VG) could be continuously monitored while rapid shifts in the temperature of the inspired water (TPINSP) AND/OR BODY SURFACE (Tbs) were effected. Changing Tinsp and Tbs both effected rate-sensitive changes in VG, although Tinsp was more effective. Decreases in Tinsp or Tbs produced decreases in VG; increases in Tinsp or Tbs had an opposite effect. The fish respiratory system is sensitive to the rate of change of external temperature. This sensitivity provides evidence for the existence of peripheral thermal input to the systems regulating respiration in teleost fish.
Osmoltye and tryptophan receptors controlling gastric emptying in the dog
Authors: Stephens  , Woolson RF , Cooke AR
Published: December 2017

The effect of three monosaccharides, three disaccharides, two dipeptides, combinations of tryptophan with two hexoses, one hexitol, and two amino acids ongastric emptying was studied in dogs to further define the samll intestinal receptors responsive to osmolytes and tryptophan. On a molar basis the disacchardies and dipeptides were almost twice as potent as their respective constituent monosaccharides or amino acids implying that the osmoreceptor is deep to the brush border disaccharidases and cytosol dipeptidases. Tryptophan probably acts by a mechanism different from the osmoreceptor since slowing of gastric emptying by tryptophan was inhibited by methionine which has no effect on a stimulant of the osmoreceptor mechanism. Lysine unlike methionine does not share the neutral amino acid transport pathway with tryptophan. Lysine did not change the inhibitory effect of tryptophan on gastric emptying. This imples that transport of tryptophan into the intestinal cell is necessary for its slowing effect. Glucose and galactose also inhibited the tryptophan effect whereas a nonabsorbed hexitor, mannitol, was without effect. Interference by the hexoses was also probably by competition with tryptophan for transport into the cell. These studies further indicate that the tryptophan receptor is different from the osmoreceptor.
Duodenal and ileal adaptation to dietary calcium restriction: in vivo studies in the rat
Authors: Petith MM , Schedl HP
Published: December 2017

Intestinal adaptation by the growing rat to a low-calcium diet was studied by in situ perfusion of duodenum and ileum in vivo. Rats were fed diets containing either 1.2 or 0.02% Ca for 17-24 days. To study plasma-to-lumen flux and net calcium absorption, rats were loaded parenterally with 45Ca and perfused intraluminally with 3.4 mM calcium. Calcium restriction caused net absorption in ileum to increase fourfold, in duodenum almost twofold. With calcium restriction, plasma-to-lumen flux decreased in duodenum but not in ileum and was small relative to absorption. However, net calcium secretion, when measured in a separate set of animals by inraluminal perfusion of NaCl, decreased in ileum but not in duodenum in response to clacium restirction. The magnitude of adaptation is greater in ileum than duodenum and is largely the result of increased lumen-to-plasma flux. The distal small intestine is probably crucial for calcium homeostasis in dietary calcium deficiency.
Stimulation of rat lung metabolism with 2,4-dinitrophenol and phenazine methosulfate
Authors: Bassett DJ , Fisher AB
Published: December 2017

Glucose metabolism was stimulated in isolated perfused rat lungs by perfusion with 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation or phenazine methosulfate (PMS), an artificial hydrogen acceptor. Lungs were ventilated with 95% O2:5% CO2 and perfused with Krebs-Ringer bicarbonate buffer pH 7.4 containing 5.5 mM [U-14C, 5-3H]glucose for 100 min. In control lungs, 45% of total glucose 14C was recovered as perfusate lactate plus pyruvate (L+P) and 24% as 14CO2. Perfuson with 0.8 mM DNP resulted in a 102% increase in 14CO2 production and a 98% increase in L+P, associated with a fall in tissue ATP/ADP ratio and decreased incorporation of glucose carbons into lipids. Perfusion with 8 muM PMS resulted in a 116% increase in 14CO2 production but no change in L+P; the lactate-to-pyruvate ratio in the perfusate was reduced to 4 from a control value of 10, and tissue adenine nucleotide levels were unchanged. In all experiments, 3H was mainly recovered as 3H2O in the perfusate. These data demonstrate the pattern of response of the isolated lung preparation to uncoupling of oxidative phosphorylation and to alterations in cytoplasmic redox state. The results suggest that the isolated lung preparation is metabolically intact and suitable for study of metabolic control processes.
Energy expenditure for thermoregulation and locomotion in emperor penguins
Authors: Pinshow B , Fedak MA , Battles DR , Schmidt-Nielsen K
Published: December 2017

During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting while they breed at rookeries 80 km or more from the sea, huddling close together in the cold. This breeding cycle makes exceptional demands on their energy reserves, and we therefore studied their thermoregulation and locomotion. Rates of metabolism were measured in five birds (mean body mass, 23.37 kg) at ambient temperatures ranging from 25 to -47 degrees C. Between 20 and -10 degrees C the metabolic rate (standard metabolic rate (SMR)) remained neraly constant, about 42.9 W. Below -10 degrees C metabolic rate increased lineraly with decreasing ambient temperature and at -47 degrees C it was 70% above the SMR. Mean thermal conductance below -10 degrees C was 1.57 W m-2 degrees C-1. Metabolic rate during treadmill walking increased linearly with increasing speed. Our data suggest that walking 200 km (from the sea to the rookery and back) requires less than 15% of the energy reserves of a breeding male emperor penguin initially weighing 35 kg. The high energy requirement for thermoregulation (about 85%) would, in the absence of huddling, probably exceed the total energy reserves.
Stretch receptor model for renin release with evidence from perfused rat kidney
Authors: Fray JC
Published: December 2017

Control of renin release was studied in isolated rat kidneys perfused with Krebs-Henseleit solution containing albumin. Cumulative perfusate renin activity (PRA) as measured by radioimmunoassay was increased by low perfusion pressure and suppressed by high pressure. Renal vasoconstriction induced by infusion of phenylephrine or methoxamine increased PRA, whereas vasodilatation by papaverine suppressed renin activity. The increased renin activity induced by phenylephrine was blocked by high pressure or papaverine. Changing sodium concentration in the perfusion medium had no effect on basal renin release. A mathematical analysis for an intrarenal stretch receptor indicates that renin release is related to the elastic modulus, the internal and external hydrostatic pressures, and the internal and external radii. Calculations based on this model also indicate that renin release is most sensitive to changes in the ratio of the radii. It is proposed that basodilatation or high perfusion pressure may increase the stretch of the afferent arteriole and depolarize the granular cell membrane, whereas vasoconstriction or low pressure may decrease stretch and thus hyperpolarize the cell.
Processing of hydrophobic pulmonary surfactant protein B in rat type II cells
Authors: Weaver T. E. , Whitsett J. A.
Published: December 2017

The amino acid sequence of surfactant protein B (SP-B), derived from human genomic and cDNA sequences, indicates that the active polypeptide is contained within the sequence of a preproprotein of 381 residues. Synthesis of mature SP-B, which requires proteolytic processing at both the NH2- and COOH-termini of the proprotein, was studied in primary cultures of rat alveolar type II epithelial cells. Type II cells were pulse labeled with [35S]methionine-cysteine for 15-30 min and chased for 0-18 h. SP-B proprotein (Mr = 42,000) accumulated in the medium at early time points but declined at later time points suggesting extracellular proteolysis of the proprotein. In contrast, surfactant protein A (SP-A), another surfactant protein, continued to accumulate extracellularly during this time period. A proteolytic fragment of SP-B (Mr = 25,000) accumulated in the medium with a slightly slower time course, consistent with extracellular proteolysis of the proprotein. Intracellular processing of SP-B was also detected. SP-B polypeptides of Mr 8,000 and 12,000 were detected intracellularly and in the medium at late time points. These forms of SP-B (Mr = 8,000 and 12,000) comigrated in two-dimensional isoelectric-focusing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with mature SP-B isolated from rat alveolar lavage fluid. The mature form of SP-B (Mr = 8,000), but not the Mr 42,000 and 25,000 SP-B precursors, was also detected in lamellar bodies isolated from rat lung homogenates. These experiments demonstrate complete proteolytic processing of prepro-SP-B to the alveolar Mr 8,000 form by type II epithelial cells in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
Pulmonary surfactant apoproteins: a review of protein and genomic structure
Authors: Hawgood S.
Published: December 2017

In recent years, as the complexity of the surfactant system has become more apparent, investigators with an increasingly diverse set of skills have been attracted to the study of this secretory product of the alveolar epithelium. In addition to advancing our knowledge of the mechanisms underlying the mechanical stability of the lung, recent studies of the surfactant system have also contributed information to less organ-specific biological phenomena such as exocytosis, endocytosis, cell differentiation and lipid-protein interactions in biomembranes. Pulmonary surfactant is not composed of a single class of molecules but, rather, is a collection of interrelated macromolecular lipoprotein complexes that differ in composition, structure, and function. The purpose of this review is to describe the structure of the lung-specific proteins that are associated with the phospholipids of surfactant in the alveolar space. The organization of the genes for the surfactant proteins is outlined and the affects of these proteins on the properties of phospholipid membranes are discussed.
Evidence for regulation of sodium transport from airspace to vascular space by cAMP
Authors: Goodman B. E. , Anderson J. L. , Clemens J. W.
Published: December 2017

Evidence has been accumulating that regulation of the rate of solute and fluid removal from the alveolar spaces may play an important role in the prevention and/or resolution of alveolar pulmonary edema. In this study, the isolated perfused rat lung was used to investigate the effects of an adenosine 3',5'-cyclic monophosphate (cAMP) analogue or a phosphodiesterase inhibitor on active sodium transport from airspace to vascular space. Three tracers were instilled into the airways of isolated Krebs-Ringer bicarbonate solution (KRB)-perfused rat lungs. The appearance of tracers in the single-pass perfusate was measured, and the apparent permeability-surface area products (PS) were calculated for each tracer at each sample time based on Fick's first law of diffusion. After steady-state PS values had been reached, a cAMP analogue or phosphodiesterase inhibitor was added to the perfusate. Both agents caused significant increases in the PS for 22Na. In another group of experiments, a cAMP analogue was added to the perfusate, followed by the subsequent addition of a sodium transport inhibitor and the resultant large decrease in the PS for 22Na. These data are consistent with the regulation of active sodium transport across the intact mammalian alveolar epithelium by a cAMP-mediated process leading to removal of sodium from the alveolar spaces, with anions and water following passively.
Thyroid inhibition and developmental increases in fetal rat lung antioxidant enzymes
Authors: Sosenko I. R. , Frank L.
Published: December 2017

After demonstrating that prenatal exogenous thyroid hormone administration to pregnant rats produces decreases in fetal lung antioxidant enzyme (AOE) development despite increases in surfactant development, we examined the role of endogenous thyroid hormones on the development of these two lung systems. We administered the antithyroid drug methimazole (or diluent) to pregnant rats for the final 3 days before premature or term delivery; in a second series of experiments, propylthiouracil was administered for the 10 days before delivery. Both antithyroid drugs, known to cross the placenta, produced significantly decreased thyroid hormone levels in the pregnant dams. Fetal offspring from methimazole-, and propylthiouracil-treated dams demonstrated significant increases in pulmonary superoxide dismutase activity at 20 and 21 days of gestation and in catalase and glutathione peroxidase activities at 21 days compared with control offspring. Surfactant, measured as lung tissue disaturated phosphatidylcholine, was not different between either experimental group and controls. These results suggest that thyroid blockade increases AOE because the influence of thyroid hormone on AOE development may be one of depression. The findings confirm that certain hormonal regulators may influence different developing fetal lung systems in different ways.
Sublethal oxidant injury inhibits signal transduction in rat type II pneumocytes
Authors: Warburton D. , Buckley S. , Cosico L. , Forman H. J.
Published: December 2017

The production of reduced forms of O2 in oxidant injury can lead to lipid peroxidation, which would pose a threat to cell membrane integrity and therefore to signal transduction pathways located in the membrane. We studied the effects of oxidant injury with t-butyl hydroperoxide (tBOOH) on signal transduction in rat type II pneumocytes in culture. Exposure of 1 x 10(6) type II pneumocytes to tBOOH concentrations less than or equal to 100 microM did not cause significant release of lactate dehydrogenase and was therefore termed sublethal. Exposure to sublethal concentrations of tBOOH caused a dose-dependent inhibition of surfactant secretion stimulated both by terbutaline (10(-4)M) and by extracellular ATP (10(-5)M). Adenosine 3',5'-cyclic monophosphate production in response both to terbutaline and to extracellular ATP was also inhibited by exposure to 100 microM tBOOH. In addition, exposure to 100 microM tBOOH inhibited inositol phosphate formation in response to extracellular ATP. We conclude that sublethal oxidant injury inhibits not only receptor-mediated agonist stimulation of surfactant secretion but also receptor-mediated agonist stimulation of second messenger formation in type II pneumocytes in culture. Such inhibition may be important in the pathogenesis of both the adult and neonatal forms of respiratory distress syndrome, in which alveolar surfactant deficiency may be exacerbated by oxidant injury.
Increase in endothelial cell glutathione and precursor amino acid uptake by diethyl maleate and hyperoxia
Authors: Deneke S. M. , Baxter D. F. , Phelps D. T. , Fanburg B. L.
Published: December 2017

Diethyl maleate (DEM, 0.025-0.10 mM) increased glutathione (GSH) levels in calf pulmonary artery endothelial cells up to fivefold in 12-24 h of incubation. Parallel increases occurred in the rates of uptake of cystine and glutamate. The DEM-mediated increases in both GSH levels and glutamate-cystine uptake were inhibited by cycloheximide and actinomycin D, indicating a dependency on protein and RNA synthesis. The stimulatory effects of DEM on amino acid uptake and GSH levels were greater than those in endothelial cells exposed to 80% O2 for 24 h. The effect of hyperoxia on cellular transport processes was also less specific than that of DEM. Although the increase in glutamate uptake produced by hyperoxia appeared to be under the regulation of protein synthesis, the relationship with elevated GSH in the presence of hyperoxia was less clear because of elevation of control cellular GSH by cycloheximide or actinomycin D alone. Inhibition of GSH synthesis by buthionine sulfoximine also stimulated cystine and glutamate uptake. We conclude that elevation of endothelial intracellular GSH by both DEM and hyperoxia is associated with and may be produced by enhanced uptake of precursor amino acids; the effect of DEM is more pronounced and more specific than that of hyperoxia.
Lung accumulation of hyaluronan parallels pulmonary edema in experimental alveolitis
Authors: Nettelbladt O. , Tengblad A. , Hallgren R.
Published: December 2017

The glycosaminoglycan hyaluronan (HA, hyaluronate or hyaluronic acid) was quantified in rat lung during the development of bleomycin-induced lung injury. Extracted lung HA was measured by a radiometric assay. In control rats, the HA lung content was 95 +/- 5 (SE) micrograms/g of freeze-dried and homogenized lung tissue. After a single intratracheal instillation of bleomycin, the HA content of the lung increased significantly on day 1. Peak HA concentrations on days 3-7 averaged 70% higher than normal lung HA concentrations. From day 7 the HA concentrations progressively declined and had returned to normal by day 30. Qualitative assessment of lung HA has previously demonstrated that HA is accumulated in the edematous interstitial alveolar space during the alveolitis phase of bleomycin injury. Since high-molecular-weight HA has unique hydrophilic properties, another aim of the study was to elucidate the possible link between the increase in lung HA and the development of interstitial-alveolar edema postbleomycin. HA recovered by bronchoalveolar lavage from bleomycin-injured lungs increased with increasing total lung HA and had a mean molecular size of 220,000 +/- 50,000 (SE), indicating the minimum size of HA accumulated in the alveolar space. The relative lung water increased significantly on days 3-7 after bleomycin administration. A close relationship (P less than 0.001) and time dependence between the increase in relative lung water and the increase in lung HA were found.