bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical adaptations in skeletal muscle of trained thyroidectomized rats
Authors: Terjung RL , Koerner JE
Published: December 2017

The cytochrome c concentrations of the different types of skeletal muscle of trained and nontrained normal and thyroidectomized rats were measured. Animals were trained by treadmill running 1 mph, at a 15% incline, 1 h/day, 5 days/wk for at least 12 wk. This training program induced an expected 50% increase in cytochrome c in the high-oxidative fast-twitch red (FTR) and slow-twitch red (STR) fibers and only a 25% increase in the low-oxidative fast-twitch white (FTW) fibers of the normal rats. This same training program caused a greater increase (100%) in the FTR and STR fibers of the thyroidectomized runners and a dramatic 243% increase in the FTW fiber. Even though the thyroidectomy procedure caused a reduction in oxidative capacity of all types of skeletal muscle fibers to about one-half normal, the absolute increase in cytochrome c in the muscles of the trained thyroidectomized animals was essentially the same or greater than that of the normal trained animals. These results indicate that the adaptive response to training of an increased oxidative capacity in skeletal muscle occurs in the absence of normal thyroid function. They also suggest that the exercise bouts of the thyroidectomized animals were performed with a relatively greater involvement of the FTW muscle fibers.
Evaluation of redox state of isolated perfused rat lung
Authors: Fisher AB , Furia L , Chance B
Published: December 2017

The metabolic responsiveness of lung tissue to inhibition of oxidative metabolism was determined by measurement of the redox state of the isolated perfused and ventilated rat lung. Changes in redox state were evaluated by fluorescence from the lung surface at wavelengths suitable for reduced pyridine nucleotides and by measurement of the ratios of redox couples in rapidly frozen lung tissue. Maximal change of redox state was observed during ventilation with carbon monoxide; surface fluorescence increased 6.6%, lactate/pyruvate increased 5.8 times, glycerol 3-P/dihydroxyacetone-P increased fourfold and glutamate/alpha-ketoglutarate doubled. KCN infusion resulted in similar changes. Hypoxia produced with N2 ventilation resulted in less than maximal changes in redox couple ratios until alveolar PO2 was reduced below 0.1 mmHg. Redox changes observed during infusion of 0.5 mM aminoxyacetic acid suggested that maintenance of cytoplasmic redox state depended on functioning of a malate-aspartate "shuttle." The isolated perfused lung appears suitable to study factors controlling pulmonary parenchymal oxidative metabolism. The results emphasize the need for ventilation with CO to establish intracellular anoxia.
Thyroid function in a hibernator, Spermophilus tridecemlineatus
Authors: Hulbert AJ , Hudson JW
Published: December 2017

Thyroid hormone secretion (assessed as thyroid 125I release rate) was monitored in Spermophilus tridecemlineatus from summer to winter (July-December) in 1973. The average release rate in July was 2.3% per day, but in August this rate decreased significantly and remained at an average 0.52% per day until December. This low rate (being similar to that of hypophysectomized rats), and the absence of any change in oxygen consumption following thyroidectomy, suggested hormone secretion was "turned off" during this period. During the period August-December, four S. tridecemlineatus showed normal thermoregulatory responses to anterior hypothalamic cooling but no thyroidal response whether restrained, unrestrained, or anesthetized. Thyroid 125I uptake (and presumably hormone manufacture) continued during the period August-December and 24-h uptake averaged 27.0% in December. Possible reasons for "turning off" thyroid hormone secretion are discussed, and it is concluded this is to allow the membrane fatty acids to revert to a less-saturated condition in preparation for low body temperatures during hibernation.
Compensatory adaptation of sodium and bicarbonate excretion: effect of diuretics
Authors: Guignard JP , Dirks JH
Published: December 2017

Complete clamping of the contralateral kidney results in a rapid and significant increase in the fractional excretion of Na, K, and bicarbonate by the remaining kidney during bicarbonate loading. Similar studies were performed in dogs after administration of diuretics with different major sites of action to localize the adaptive excretory response to acute reduction in renal mass. Volume expansion was carefully avoided. In experiments with the loop inhibitor, furosemide, contralateral kidney clamping rapidly and significantly increased fractional excretion of Na and bicarbonate. A more delayed and smaller response was observed in dogs given hydrochlorothiazide. Acetazolamide, a potent inhibitor of proximal Na bicarbonate reabsorption, completely blocked the excretory response to contralateral kidney clamping. The enhanced response with furosemide and its blockade with acetazolamide indicates a proximal site of adaptation to acute contralateral kidney exclusion. The overall natriuretic response depends on the level of inhibition of loop reabsorption.
Electrolyte transport in remnant kidney of the dog: effect of furosemide
Authors: Wen SF , Wong NL , Evanson RL , Lockhart EA , Dirks JH
Published: December 2017

Micropuncture studies were performed in 26 dogs with a unilateral remnant kidney to examine its response to modest extracellular volume expansion and furosemide administration in the presence (Stage II) and absence (Stage III) of an intact contralateral kidney. During hydropenia in 15 Stage II dogs, proximal and distal transport of sodium and potassium was comparable to that of normal dogs (Stage I). Following 3% volume expansion, fractional proximal reabsorption was reduced similarly in Stages I and II. Although a slightly greater reduction in fractional loop reabsorption of sodium in Stage II after volume expansion was not significant, it was significantly greater with furosemide administration. In 11 Stage III dogs, proximal fractional reabsorption was depressed during hydropenia, and the loop sodium response to both volume expansion and furosemide administration was exaggerated. In contrast, greater increase in distal potassium secretion was demonstrated mainly in Stage III but not in Stage II remnant kidneys both before and after the diuretic maneuvers. The observations of exaggerated sodium response to furosemide by the remnant kidney in both Stages II and III but greater potassium response only in Stage III suggest that independent factors are responsible for these adaptations when functioning renal mass is reduced.
Changes in body temperature produced by prostaglandins and pyrogens in the chicken
Authors: Pittman QJ , Veale WL , Cockeram AW , Cooper KE
Published: December 2017

Bacterial pyrogen from S. abortus equi (SAE) was injected into the wing veins of chickens. Following injection of 0.05-0.5 mug SAE, body temperatures did not change significantly, whereas 2.0 or 10 mug of pyrogen caused falls in body temperature of 0.56 +/- 0.10degrees C and 1.1 +/- 0.21degrees C (mean +/- SE, n=5). The temperature falls were accompanied by a flushing of the comb and an increase in respiratory rate and were not antagonized by 1.0 g of acetylsalicylic acid (ASA) given orally. The injection of SAE (0.1 mug in 1 mul) into the anterior hypothalamus produced fevers averaging 1.24 +/- 0.07 degrees C (n=9) which were antagonized by oral ASA. Injections of SAE at other brainstem loci produced no temperatur changes. Seven chickens were also injected with 0.1 mug PGE in 1.0 mul into the anterior hypothalamus, and they developed fevers averaging 0.90 +/- 0.16 degrees C. The results support the concept that prostaglandins may be involved in fever in chickens but suggest that the action of pyrogen injected intravenously may be different from that following its injection directly into the hypothalamus.
Michaelis-Menten kinetics of galactose elimination by the isolated perfused pig liver
Authors: Keiding S , Johansen S , Winkler K , Tonnesen K , Tygstrup N
Published: December 2017

The relation between galactose elimination rates and blood concentrations in the isolated perfused pig liver was analyzed by a mathematical kinetic model. It assumes that the substrate, under steady-state conditions, is removed from the blood that flows through the sinusoids by an irreversible process which follows Michaelis-Menten (i.e., saturation) kinetics. The experiments consisted of successive periods with constant infusions of galactose. The model fitted the data to within the experimental uncertainty. The estimated maximal rate (Vmax) ranged from 0.34 to 0.57 mmol-min(-1)-kg(-1) liver, and the Michaelis constant, Km, ranged from 0.12 to 0.30 mmol-liter(-1) plasma water in nine experiments. The ratio between the galactose concentration in hepatocyte water and plasma water was not significantly different from 1.0, indicating that membrane transport is not rate limiting for the elimination of galactose. In experiments with increasing concentrations of galactose in hepatocyte water and approximately saturated elimination rates, the concentrations of galactose 1-phosphate, UDPgalactose, and UDPglucose remained essentially constant. This indicates that the phosphorylation of galactose to galactose 1-phosphate is the rate-determining process.
Lateralized phrenic nerve responses to stimulating respiratory afferents in the cat
Authors: Berger AJ , Mitchell RA
Published: December 2017

We stimulated electrically pharyngeal branch of both glossopharyngeal nerves (PGLN), internal branch of superior laryngeal nerves (ISLN), and carotid sinus nerves (CSN) in anesthetized cats. We recorded simultaneously, averaged, and compared bilaterally evoked phrenic nerve (PHR) activity. Our objective was to demonstrate a short-latency evoked response in the PHR contralateral to the stimulus. Low-intensity stimulation of PGLN and ISLN during inspiration evoked a short-latency contralateral excitation with a latency of 5.2 ms +/- 0.2 SE (16 cats) for PGLN, and 3.8 ms +/- 0.1 SE (13 cats) for ISLN. This excitation could follow stimuli delivered at 100 Hz. Stimulation during expiration did not result in a lateralized excitation. The excitation is followed by bilateral inhibition. Neither strychnine nor picrotoxin prevented either the lateralized response or the inhibition, though strychnine diminished a delayed bilateral excitation following PGLN stimulation. This dalayed (latency 18.7 ms +/- 0.7 SE) bilateral excitation corresponds to the sniff reflex. CSN stimulation did not result in lateralized excitation. We suggest that the lateralized evoked response results from a gated paucisynaptic reflex pathway involving the PGLN and ISLN, ipsilateral inspiratory neurons, and contralateral PHR motoneurons.
Circadian distribution of bile acids in the enterohepatic circulatory system in rats
Authors: Ho KJ
Published: December 2017

The bile acid pool was first determined in six adult male rats to be 12.8 +/- 0.7 mg/100 g by comparing the total radioactivity of tritiated bile acid drained through the bile fistula and the initial bile acid specific activity. The distribution of bile acids in the enterohepatic circulatory system at various times of the day was then studied in 24 additional rats, each received a single dose of tritiated taurocholate intraperitoneally and was sacrificed 24 h later. The nearly complete recovery of the administered radioactivity from the serum, liver intestinal wall and content, and 24-h feces indicated the confinement of bile acids to the enterohepatic circulation. A remarkable circadian fluctuation of the bile acid content was observed in serum, liver, and intestinal contents. The patterns of such rhythmic change varied from each other in various segments of the intestinal tract but seemed to correlate with the time sequence of movement of bowel content and absorption of bile acids. The circadian rhythm of hepatic synthesis of bile acids but not cholesterol observed by others might be, in part, directly related to the circadian fluctuation of the amount of bile acids in the liver.
Factor VIII synthesis: hepatic and renal allografts in swine with von Willebrand's disease
Authors: Webster WP , Mandel SR , Strike LE , Penick GD , Griggs TR , Brinkhous KM
Published: December 2017

Transplantation experiments were utilized to study the possible sites of synthesis of von Willebrand factor (vWF) and factor VIII (F VIII) activities. Three normal kidney and two normal liver allografts were implanted into five swine with von Willebrand's disease (vWD) that survived for 1,6, and 7, and 4 and 9 days, respectively. The correction of the multiple hemostatic defects of vWD by organ transplantation was evaluated using the F VIII procoagulant activity, bleeding time, and platelet aggregating factor (PAF) levels; i.e., vWF levels. Normal kidney allografts produced no changes in the bleeding times or increases in F VIII or PAF. Transfusions for surgical hemostasis produced transient increases in F VIII and PAF. In animals receiving normal liver allografts, the levels of F VIII exceeded 100%, PAF was increased, and sustained correction of the bleeding time and maintenance of hemostasis was observed. These data suggest that the kidney is incapable of synthesizing either the vWF or the F VIII and that cells contained in the liver, possibly the endothelial cells, are one of the sites of synthesis of these factors.
Genetic predisposition to stroke in spontaneously hypertensive rats
Authors: Nagaoka A , Iwatsuka H , Suzuoki Z , Okamoto K
Published: December 2017

Hypertension and stroke in spontaneously hypertensive rats (SHR) were investigated genetically using stroke-prone SHR (A3), stroke-resistant SHR (C) and their hybrids, hybrid of A3 and C (F1), offspring of F1 X F1 (F2), and those of backcrossing of F1 to the respective parental strains, BC(F1 X A3) and BC(F1 X C). The average blood pressure measured without anesthesia increased in the following order during the experimental period: C less than BC (F1 X C) less than F1 approximately F2 less than BC(F1 X A3) less than A3. The F2 represented a wider spread of variation than the F1, with some of the pressure extending into the range of both parental strains. When the drinking water was replaced with a 1% salt solution, the blood pressure increased and the onset of stroke markedly accelerated in all groups of SHR. Under the hypertensive conditions, the incidence of stroke was associated with A3-gene concentration rather than with the level of blood pressure. Similar but less dramatic effects of salt were observed in another series of hybrid groups derived from A3 and normal Wistar-Kyoto rats. These findings suggest that the genetic factors are of great importance in the development of stroke as well as hypertension in the SHR.
Direct effects of various catecholamines on liver circulation in dogs
Authors: Hirsch LJ , Ayabe T , Glick G
Published: December 2017

As measured by electromagnetic blood flow transducers, direct infusion of epinephrine, norepinephrine, and dopamine into the portal vein (PV) produced a 40-50% decrease in hepatic arterial (HA) blood flow; isoproterenol increased HA flow by about 69%. No changes in PV flow or pressure were observed. Direct HA infusion of the vasoconstrictors decreased HA flow by amounts comparable to those occurring after PV infusion. However, HA infusion of isoproterenol increased HA flow only 15% suggesting a difference in beta-receptor population in the two vessels. When infused directly into the superior mesenteric artery (SMA), epinephrine and norepinephrine reduced SMA flow by about 45% and PV flow by 20-25%; HA flow increased 6-8%. Infusion of isoproterenol and dopamine into SMA increased SMA flow by 115% and 206% and PV flow by 60% and 70%, respectively, whereas HA flow decreased by 25% and 50%. Portal vein pressure increased less than 3 mmHg. Alpha- and beta-receptor blockade of the liver did not change significantly the alterations in hepatic arterial blood flow that were secondary to changes in portal venous blood flow. It is likely that regulation of hepatic arterial flow resides in mechanisms located within the liver sinusoids.
ADP-induced inhibition of von Willebrand factor-mediated platelet agglutination
Authors: Grant RA , Zucker MB , McPherson J
Published: December 2017

Human plasma von Willebrand factor (vWF) plus the antibiotic ristocetin, or bovine or porcine vWF alone, agglutinates platelets in either normal human ethylenediaminetetraacetate (EDTA)-treated citrated platelet-rich plasma (PRP) or citrated PRP from patients with the congenital platelet defect thrombasthenia. The prior addition of 1-10 muM ADP, which causes platelet shape change but not aggregation under these conditions, inhibited vWF-mediated agglutination. Inhibition was prevented by 200 muM ATP. Addition of ADP caused prompt reversal of established vWF-mediated agglutination, which resumed when the ADP was enzymatically removed. EDTA-treated, Formalin-fixed, washed normal platelets also underwent vWF-mediated agglutination. ADP was inhibitory only when added before fixation. Epinephrine (40 muM), prostaglandin E1 (7 muM), or serotonin (2 muM) added before fixation caused slight to moderate inhibition but always less than ADP. Platelets from blood chilled before fixation were fully active. Platelets fixed in freshly prepared PRP did not agglutinate as well as those fixed after incubation of PRP, probably because centrifugation exposes the platelets to ADP. It concluded that ADP causes a reversible decrease in the accessibility of the membrane receptor to vWF.
Micropuncture evidence of rapid hydrolysis of bradykinin by rat proximal tubule
Authors: Carone FA , Pullman TN , Oparil S , Nakamura S
Published: December 2017

3H-labeled bradykinin ([3H]BKN) and 14C-labeled inulin ([14C]In) were simultaneously microinfused into proximal or distal tubules in Inactin-anesthetized rats, and urinary excretion and tubular transit times were measured. In other experiments higher doses of [3H]BKN were microinfused and intact peptide and its metabolites identified and quantified by two-dimensional peptide mapping. The site of infusion was identified by neoprene injection and microdissection. Urinary recovery of 3H label was 24.1% when proximal tubules were infused and 98.0% when distal tubules were infused. For proximal tubules, 85% of 3H activity recovered from urine consisted of metabolites (81%[3H]Pro and 4% [3H]Arg1-Phe5) and 15% was intact BKN. Urinary recoveries of [3H]BKN and metabolites were unrelated to tubular length. With distal tubules all 3H activity appeared as intact BKN. Excretion curves of simultaneously infused [3H]BKN and [14C]In showed no marked differences in configuration for either proximal or distal or distal tubules. We suggested that removal of [3H]BKN by proximal tubular cells occurs by rapid enzymatic cleavage at the luminal surface with reabsorption of most of the products and excretion of the remainder.
Gallbladder pressure-volume response to gastrointestinal hormones
Authors: Ryan J , Cohen S
Published: December 2017

The pressure-volume (PV) response of the opossum gallbladder was studied under basal conditions and after the continuous intravenous infusion of gastrin I, secretin, and cholecystokinin (CCK). The hormone effects were examined individually and in combination. The unstimulated gallbladder was capable of accommodating increases in intraluminal volume with only slight changes in intraluminal pressure. Cholecystokinin significantly increased the pressure recorded from the gallbladder. The pressure generated depended on the concentration of CCK and the intraluminal volume. Gastrin I had no independent effect on the PV response of the gallbladder but reduced the stimulatory affect of CCK. Secretin, alone, decreased the PV response of the gallbladder. Secretin also antagonized the stimulatory response to CCK. These findings suggest that the regulation of gallbaldder motor function and pressure generation exclusive of neural input, may depend on the interaction of CCK with gastrin and secretin and the intraluminal volume of the organ at the time of stimulation.
Temporal relationships of barosensory attenuation in conscious rabbits
Authors: Gimpl MP , Brickman AL , Kaufman MP , Schneiderman N
Published: December 2017

Electrical stimulation of anterior or posterior hypothalamus with 10-s trains elicited heart rate and blood pressure decreases. Presentation of anterior hypothalamic stimulation coincident with or 5, 10, or 15 s prior to 5-s train stimulation of aortic nerve (AN) summated with depressor-decelerator responses to AN stimulation. The summating effect was more pronounced for heart rate than for blood pressure. Simultaneous onset of AN and posterior hypothalamic stimulation did not influence AN responses. In contrast, when AN stimulation was delayed until 5, 10, or 15 s after onset of posterior hypothalamic stimulation, small, moderate, and full attenuation of AN responses occurred, respectively. Since AN and posterior hypothalamic stimulation each led to depressor-decelerator responses, attenuation of AN responses cannot be attributed to simple summation of cardiovascular responses elicited by intracranial and aortic nerve stimulation.
Secretion of new digestive enzyme by pancreas with minimal transit time
Authors: Rothman SS
Published: December 2017

A small amount of labeled digestive enzyme is secreted within 5 min of adding radioactive leucine to whole rabbit pancreas in vitro. This rapid secretion of labeled protein suggests that some new protein is able to bypass intracellular storage pools and is secreted immediately. The amount of protein secreted this way varies inversely with overall protein secretion in the unstimulated state and is decreased as the result of cholinergic stimulation of protein secretion as well. Under the conditions studied, a mean of 2.5% of secreted protein is apparently not stored prior to secretion.
Gastrointestinal control of sodium excretion in sodium-depleted conscious rabbits
Authors: Carey RM , Smith  , Ortt EM
Published: December 2017

Recent studies of sodium-depleted rabbits have shown that oral sodium loading is followed by greater natriuresis than intravenous sodium loading. The present study was undertaken to determine if this is dependent on differences in aldosterone excretion. Rabbits in balance on a low-sodium diet were given bolus doses of sodium either orally or intravenously. Those receiving oral sodium responded with a greater natriuresis than those receiving it intravenously. No differences in aldosterone excretion were demonstrated after oral or intravenous sodium repletion. Rabbits given large doses of exogenous aldosterone continued to excrete more sodium after oral than after intravenous repletion. This study demonstrates that in rabbits the gastrointestinal tract functions to regulate renal sodium excretion and that the mechanism is independent of aldosterone.
PAH transport and fluid absorption by isolated perfused frog proximal renal tubules
Authors: Irish JM  , Dantzler WH
Published: December 2017

Para-aminohippurate (PAH) transport and fluid absorption were studied in isolated perfused frog (Rana catesbeiana) proximal renal tubules. With 2 X 10(-5) M PAH in the bath, tubule fluid-to-bath (TF/B) concentration ratios averaged 3.0 and net secretion averaged 746 X 10(-15) mol min(-1) mm(-1) in the proximal tubule. Net PAH secretion did not vary with perfusion rate. During PAH secretion, cell water PAH concentration exceeded that in the tubular fluid or bath, suggesting active transport into cells and subsequent diffusion into lumen. In accordance with this concept, luminal membrane permeability (3.8 X 10(-5) cm s(-1) calculated from perfusion studies was about 6 times greater than peritubular membrane permeability (0.66 X 10(-5) cm s(-1)) determined from studies of PAH efflux from tubules with oil-filled lumens. Net transepithelial PAH transport saturated at bath concentration of about 6 X 10(-5) M. Addition of 20 mM urea to PAH bath concentration of 2 X 10(-5) M reduced net PAH secretion by 32%. Fluid absorption in proximal tubules averaged 0.34 nl min(-1) mm(-1). Ouabain (10(-4), 10(-5), or 10(-6) M) added to bath blocked fluid absorption. Fluid absorption was partially restored following removal of ouabain.
Mechanism of decrease in plasma renin activity during volume expansion
Authors: Stitzer SO , Martinez-Maldonado M
Published: December 2017

The importance of filtered load of sodium and extracellular volume expansion (ECVE( per se on plasma renin activity (PRA) was studied in two groups of hydropenic dogs. Group I protocol consisted of bilateral ureteral obstruction (UO) followed by isotonic ECVE and finally UO release. During UO, PRA rose significantly above control (15.4 leads to 41.7 ng/ml per h). Superimposition of ECVE did not significantly alter PRA, but UO release returned PRA toward control (24.8 ng/ml per h). Fractional sodium excretion (FE(Na)) after UO release was higher than control (0.6 leads to 12.6%). In group II, ECVE preceded UO and caused a fall in PRA below control (16.8 leads to 4.8 ng/ml per h). FE(Na) was significantly increased over control (0.3 leads to 14.7%). Superimposition of UO reversed the fall in PRA to a value not significantly different from control. On release of UO PRA fell, but not significantly, whereas FE(Na) fell to 12.6%, a value not different from that during ECVE alone. The results indicate that filtration is required for ECVE to elicit a fall in PRA, under the present experimental condition.
Age-dependent mechanical and biochemical responses to glucagon
Authors: Ahumada G , Sobel BE , Friedman WF
Published: December 2017

The age-dependent relationships between glucagon-induced alterations in myocardial mechanics and adenylate cyclase activity in fetal and newborn lambs and adult sheep were evaluated. Glucagon substantially augmented the force of contraction of ventricular myocardium isolated from the adult but not from the fetus or newborn. Similarly, substantial increases in the spontaneous frequency of contraction and tension were observed in adult atrial strips, but not in the fetus or newborn. Comparable activities of phosphodiesterase were observed in extracts from fetal and adult myocardium and were unaltered by the addition of glucagon. Adenylate cyclase activity in adult myocardial homogenate and particulate fractions was comparable to that of fetal tissue. Glucagon stimulation of the particulate fraction produced no change in fetal adenylate cyclase activity whereas a 43% increase in activity was observed in preparations from adult tissue. Sodium fluoride and epinephrine augmented adenylate cyclase activity in both fetal and adult myocardium. Thus, glucagon produced age-dependent, parallel changes in heart rate, active tension development, and particulate fraction adenylate cyclase activity, suggesting that these chronotropic and inotropic responses are indeed mediated by adenylate cyclase and that lack of response in the fetus reflects the absence of mature glucagon receptor sites.
Selective transfer of plasma proteins across mammary gland in lactating mouse
Authors: Gitlin JD , Gitlin JI , Gitlin D
Published: December 2017

Specific plasma proteins were labeled with 131I, and their half-lives in lactating and nonlactating mice were determined. The proteins included mouse IgF and IgM, mouse, bovine, rabbit, and human IgG, human serum and salivary IgA, human transferrin and albumin, and mouse and human immunoglobin light chains. The rates at which these proteins are transferred across the mammary gland in mice suckling their young were calculated: transmammary protein transfer was found to be highly selective. The G-class immunoglobulins readily traversed the mammary gland, the rate being dependent on the IgG load presented to the transport system. Immunoglobulin lambda-chains and human serum IgA crossed the mammary gland even more rapidly than did the G immunoglobulins. Human IgA without secretory piece was transported into milk more rapidly than IgA with secretory piece attached. Protein transport across the mouse mammary gland was found to be similar to and yet different from protein transport across either the suckling mouse intestine or the mouse placenta as to which proteins crossed and at what relative rates.
Aldosterone and insulin effects on driving force of Na+ pump in toad bladder
Authors: Siegel B , Civan MM
Published: December 2017

Both aldosterone and insulin increase active Na+ transport across the urinary bladder of the toad. Recent data have provided further support to the concept that aldosterone acts primarily to increase Na+ entry from the mucosal medium into the transporting cells, whereas insulin acts to increase active Na+ extrusion into the serosal medium. To examine this concept further, the driving force (E(Na)) of the Na+ pump was measured, by the technique described by Yonath and Civan (48), before and after hormonal administration. Both hormones increased short-circuit current, but only insulin increased E(Na). The validity of the technique was further explored by imposing periods of hypoxia upon a series of experimental hemibladders; as expected, hypoxia reversibly decreased E(Na). The data indicate that insulin stimulates Na+ transport, in part by directly stimulating the Na+ pump. The results are also consistent with the concept that aldosterone stimulates net Na+ movement solely by enhancing Na+ entry into the transporting cells, but are subject to alternative interpretations.
Fluorometric studies of recovery metabolism of rat fast- and slow-twitch muscles
Authors: Wendt IR , Chapman JB
Published: December 2017

Recovery metabolism of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat has been investigated using fluorometric monitoring of reduction of nicotinamide adenine dinucleotide (NAD). In both EDL and SOL, groups of twitch contractions produced a decrease in fluorescence (oxidation of NADH) which returned to the resting base line after contraction ceased. These responses proceeded more quickly in EDL than SOL and were abolished by anoxia. A 1-s tetanus of SOL produced an initial reduction which could be abolished with iodoacetate followed by a prolonged oxidation which could be blocked by anoxia. The fluorescence of EDL was decreased immediately following a 1-s tetanus but then rapidly increased well beyond the resting level of reduction and persisted throughout the recovery period. This reduction was largely depressed by iodoacetate. The results indicate marked differences in the recovery metabolism of these muscles, consistent with predominantly mitochondrial oxidative activity in the slow-twitch muscles and predominantly glycolytic activity in the fast-twitch muscles.
Pig reticulocytes: I. Transitory glucose permeability and metabolism
Authors: Kim HD , Luthra MG
Published: December 2017

Glucose permeability and metabolism were examined in the reticulocytes of pigs made anemic by daily administration of phenylhydrazine for 5-7 days. Blood samples containing 70-90% reticulocytes were fractionated according to their density by centrifugation. The most immature reticulocytes obtained from the top centrifugal fractions possessed a glucose permeation mechanism. The salient features of glucose transport include a) saturable kinetics with Vm ranging from 0.1 to 0.4 mumol/ml cell X min and with Km ranging from 6.6 to 12 mM, b) inhibition by phloretin, and c) countertransport characteristics suggesting that the glucose entry was mediated by a mechanism involving membrane carrier-type transport. In the course of reticulocyte maturation leading to mature red cells, the glucose carrier mechanism was discarded or rendered ineffective, resulting in nonglycolytic mature red cells. Glucose and ribose consumptions in the most immature reticulocytes were 2.5 and 0.75 mumol/ml cell X h, respectively. Concomitant with the diminishing glycolytic ability, ribose consumption was enhanced slightly as the reticulocytes matured to red cells. Dihydroxyacetone, a potent metabolic substrate for the mature pig red cell, was utilized readily by the reticulocytes.
Reduced high-energy phosphate levels in rat hearts. II. Effects of sodium cyanate
Authors: Allison TB , Pieper GM , Clayton FC , Eliot RS
Published: December 2017

The effects of increased blood-oxygen affinity, due to carbamylation of hemoglobin in vivo, on aerobic metabolism in the heart were studied in rats. Adult male rats were injected intraperitoneally 3 times weekly for 10 wk with sodium cyanate (60 mg/kg). Significant derangement of blood-oxygen interaction was observed. Oxygen-dissociation curves were left shifted by 13 mmHg (35.1-21.8), and the overall deoxygenation rate (k) was reduced 41% (6.142-3.624; s(-1)); P is less than 0.001 for each parameter. Heart ATP and PCr levels were reduced (ATP: 19.4-16.7; PCr: 15.0-11.0, mum/g dry wt; P is less than 0.001 for each). In addition, glycogen levels fell (161.4-112.9, mum C6/g dry wt; P is less than 0.001). Myocardial lactate levels increased 54% (2.6-4.0, mum/g dry wt; P is less than 0.01) in the cyanate-treated group. These findings strongly suggest a hypoxia-induced activation of glycolysis as a consequence of altered oxidative metabolism in rats treated with sodium cyanate.
Ionic requirements of proximal tubular sodium transport. II. Hydrogen ion
Authors: Green R. , Giebisch G.
Published: December 2017

Page 1216: R. Green and G. Giebisch. "Ionic requirements of proximal tubular sodium transport. II. Hydrogen ion." Page 1218: Table 1, the sixth column, NaH2,PO4, should read "1.55"; the seventh column, Na2HPO4, should read "7.25." Pages 1220–1223: In Figs. 1–7, the phosphate composition of the fluids, given on the insets, should read "8.25."
Accumulation of some secretory enzymes in venom glands of Vipera palaestinae
Authors: Brown R. S. , Brown M. B. , Bdolah A. , Kochva E.
Published: December 2017

Page 1675: R. S. Brown and M. B. Brown, A. Bdolah, and E. Kochva. "Accumulation of some secretory enzymes in venom glands of Vipera palaestinae." Page 1677: in Table 4, the values in the first line of the fourth, fifth, and sixth columns should read "440 ± 190," "3,040 ± 1,460," "1,750 ± 720," respectively.
Pineal multiunit activity in conscious quail: effects of light, blinding, ganglionectomy
Authors: Herbute S , Bayle JD
Published: December 2017

Multiunit activity (MUA) was recorded from thr pineal gland in unanesthetized male Japenese quail. The influence of light regimen on spontaneous and flash-evoked firing patterns of pineal cells was investigated. Shortening the day length from 18 to 6 h/24 h resulted in a marked increase in pineal MUA. Pineal firing rate was higher during the dark than during the light fraction of the photoperiod. Flashlight stimulation always led to a marked inhibition of the pineal MUA. Cutting the optic nerves bilaterally resulted in a marked increase in the level of MUA. None of the experimental conditions altered the elevated MUA in blinded birds. Thus, photoperiod and light stimulation appeared to be important for pineal activity; however, no direct photosended quail. Superior cervical ganglionectomy resulted in slightly increased spontaneous MUA but did not inhibit pineal responses to flashlight stimulations.
Metabolic adaptations in brown adipose tissue of the hamster in extreme ambient temperatures
Authors: Rabi T , Cassuto Y
Published: December 2017

Cold acclimation caused the following changes in the brown adipose tissue (BAT) of the hamster: the relative weight of the tissue increased, it color darkened, the multilocular structure predominated, and tissue protein content increased while fat content decreased. There was also an increase in the mitochondrial protein content. Heat acclimation had the opposite effects, i.e., the color became lighter, total and mitochondrial protein decreased, fat content increased, and tissue structure was mostly unilocular. Accordingly, cold acclimation was accompanied by increased tissue respiration in the presence of chi-glycerophosphate (chi-GP) and succinate, whereas heat acclimation reduced the respiratory activity of the tissue with these substrates. Isolated BAT mitochondria from cold-acclimated animals increased activities of chi-GP and NADH oxidase, whereas the activities of succinic and cytochrome oxidases and the amount of mitochondrial cytochromes were unchanged. The effects of heat acclimation were more pronounced: there was a decrease in the activities of chi-GP, succinic, NADH, and cytochrome oxidases, as well as in the cytochrome a and a3 content. When respiration of tissue slices on succinate was compared to the maximal potential respiration, as measured with mitochondria disrupted by freezing and thawing, it was found that the relative activity (slices vs. disrupted mitochondria) was highest in cold-acclimated animals and decreased progressively with increasing acclimation temperatures. It is suggested that the differences in the apparent activity of the mitochondria were due to changes in the conformation of the mitochondria as a result of acclimation.
Influence of vasopressin and amiloride on shunt pathways of frog skin
Authors: O'Neil R , Helman SI
Published: December 2017

Studies were done to determine the influence of vasopressin and amiloride on the sodium backflux of nonedge-damaged frog skin. As before, the bidirectional fluxes of sodium appeared to be limited primarily to the active transport pathways of control skins. When the skins were treated with vasopressin, the sodium backflux was increased selectively (over that of sucrose) and more so than was expected for the active transportpathway alone. In control skins, amiloride had no effect on the flux of the shunt pathway. However, with vasopressin-treated skins, amiloride at 10(-6) M decreased the sodium backflux of the shunt pathway to levels observed previously for the control skins. These observations are compatible with the idea that the shunt pathway may in part be cellular and in part extracellular. When the changes in open-circuit voltage and shunt resistance caused by vasopressin and amiloride (as determined from the I-V relationships) were examined, the data were also found to be compatible with the idea that vasopressin exerted an influence on the shunt pathway of the frog skin, and this effect of vasopressin could be reversed by amiloride.
Reversal of hypoxic bradycardia by halothane or midcollicular decerebration
Authors: Katzin DB , Rubinstein EH
Published: December 2017

Previous work suggests a primary vagal bradycardia during hypoxic excitation of the arterial chemoreceptors. In this study we examined whether tachycardia, resulting from withdrawal of vagal inhibition of the cardiac pacemaker, may also occur during hypoxia. Cats with cervical spinal section were ventilated with hypoxic gas mixtures or allowed to remain apneic in expiration while heart rate was continually monitored. During recovery from halothane anesthesia or following electrolytic midcollicular decerebration, the bradycardic response to hypoxic or asphyxic stimulation was reduced or was reversed to tachycardia. The extent of reduction or reversal of the bradycardia was positively correlated with the level of the arterial pressure which was adjusted by either hemorrhage or infusion of phenylephrine. These findings indicate a tachycardic component of the vagal response to hypoxia, integrated in the pontomedullary region of the brainstem and resulting from interaction between the chemoreceptor and baroreceptor reflexes.
Distribution of fetal cardiac output: importance of pacemaker location
Authors: Pitlick PT , Kirkpatrick SE , Friedman WF
Published: December 2017

Important questions exist about the relative roles of changes in heart rate versus extent of myocardial shortening in regulating fetal cardiac output, because increases in heart rate created by left atrial pacing have been shown to increase right ventricular output and decrease left ventricular output. Since the pacemaker site could importantly influence foramen ovale flow and, hence, each ventricle's output, changes in individual ventricular outputs were examined when both the right and left atria were paced at a rate of 270 beats/min in five acute and in eight chronically instrumented fetal lamb studies. With pacing of either atrium, total cardiac output was unchanged compared to control values. However, the right ventricle contributed more to total cardiac output with left atrial pacing (73% acute, 65% chronic) than with right atrial pacing (51% acute, 57% chronic). Converse changes were observed in left atrial pacing (27% acute, 35% chronic) as compared to right atrial pacing (49% acute, 43% chronic). Thus the disparity that exists normally in the contributions of the right and left ventricles to total cardiac output is accentuated with left atrial pacing and minimized with right atrial pacing. Pressure measurements demonstrated changes in the atrial pressure relations that would be expected to alter flow across the foramen ovale depending on the chamber initially activated. Previous experimental differences can, therefore, be attributed to changes in the magnitude of shunting across the foramen ovale and depend on pacemaker location.
Further studies on coupling between sodium transport and respiration in toad urinary bladder
Authors: Beauwens R , Al-Awqati Q
Published: December 2017

When sodium transport (JNa) and CO2 production (JCO2) were measured simultaneously in the toad urinary bladder in the absence of electrochemical gradients under conditions of spontaneous variation of JNa, the curve of JNa on JCO2, phiJNa/phiJCO2, was found to be highly linear in an individual epithelium. However, no unique value appeared to characterize a population of bladders. In an effort to investigate the nature of this variation, phiJNa/phiJCO2 was examined under a variety of conditions. It was found that agents that affect sodium entry into the active transport pool, e.g. vasopressin and amiloride, or those that influence the energy-linked exit step, e.g. ouabain and insulin, have no effect on the phiJNa/phiJCO2. To investigate the possibility of the presence of a significant backleak from the serosal side into the cell, the sodium concentration was changed to 75 and 160 mM. Neither of these maneuvers influenced phiJNa/phiJCO2 or (JCO2)JNa=O. Furthermore, in the absence of mucosal sodium, ouabain had no effect on JCO2, suggesting that no significant recirculation is occurring. It is concluded that for each individual epithelium JNa is coupled to JCO2, and their ratios appear, within experimental error, to be invariant. It is suggested that sodium traverses the active transport pathway largely or entirely in one direction.
Sensitivity of small subcutaneous vessels to altered respiratory gases and local pH
Authors: Harris PD , Longnecker DE , Miller FN , Wiegman DL
Published: December 2017

Television microscopy was used to quantitate the responses of small arteries and veins, in the wings of unanesthetized bats, to alterations in the inspired concentrations of O2 and CO2. Mean arterial pressure, heart rate, and the diameters of small arteries (28-54 mum) and veins (50-128 mum) were measured during a 90-min protocol--30 min with an inspiratory gas mixture of 20% O2 and 80% N2 (control period); 30 min with a gas mixture containing 5% O2 (hypoxic period) or 12, 20, or 28% CO2 (hypercapnic period); and 30 min with the original control gas. The hypoxic responses were dilatation of arteries and no change in the veins in both innervated and surgically denervated wings. Hypercapnia resulted in artery dilatation in innervated wings. Hypercapnia resulted in artery dilatation in innervated wings and constriction in denervated wings. The veins constricted in both innervated and denervated wings during the hypercapnia period. In another series, topical application of Krebs solutions (pH ranging from 7.7 to 6.7) to exposed segments of small arteries and veins produced dilatation of both vessels with decreasing pH. Artery dilatation during hypoxia and vein constriction during hypercapnia involve non-neural mechanisms, while both a neural stimulus for dilatation and a non-neural stimulus for constriction are components in the response of innervated arteries to hypercapnia. The non-neural stimulus for artery and vein constriction during hypercapnia is not a local decrease in pH.
Bioassay of endotoxin clearance in vivo and by perfused rat liver
Authors: Buchanan BJ , Filkins JP
Published: December 2017

Endotoxin clearances in vivo and by the isolated perfused rat liver were evaluated via bioassay in lead-sensitized rats. A linear relationship between the probit of shock lethality and the endotoxin dose in the probit range of 4-6 was validated. Endotoxin clearance in normal, fed rats displayed a linear relationship between the logarithm of the blood endotoxin concentration and time throughout the period of 15-240 min at doses of 500 and 1,000 mug/ rat; the half-time values were 58-63 min. Decreasing the endotoxin dose to 250 mug resulted in multiphasic clearance curves. Induction of tolerance to endotoxin resulted in marked acceleration of endotoxin clearance. Endotoxin clearance from the isolated perfused rat liver was not influenced by serum or rat blood as compared to clearance from a balanced salt solution. These data suggest that a physiologically stressful dose of endotoxin is slowly cleared from the blood and, therefore, circulates for prolonged periods.
Effect of vasopressin on sodium excretion and plasma antinatriferic activity in the dog
Authors: Buckalew VM , Dimond KA
Published: December 2017

Vasopressin (VP) was administered for 1 h intravenously to hydropenic, anesthetized dogs in doses of 1.0-1.25 mU/kg per min. In 14 experiments, sodium excretion (UNA V) increased from a mean of 13 +/- 5 to a peak of 96 +/- 21 mueq/min 40 min after beginning infusion (P less than .001). Urine flow and potassium excretion increased from 0.18 +/-.04 ml/min and 20 +/- 2 meuq/min to peak values of 0.6 +/- .08 ml/min and 61 +/- 9 mueq/min, respectively (P less than .001), with no significant increase in glomerular filtration rate. No significant changes in UNA V occurred in eight sham control experiments of in six experiments in which VP was given at 75 muU/kf per min. To test the hypothesis that VP might be natriuretic indirectly by releasing a natriuretic substance, plasms ultrafiltrates were tested for toad bladder antinatriferic activity(AA). During steady-state control, AA was -10 +/- 3%. Thirty and sixty minutes after beginning VP, AA increased to -24 +/- 3% (P less than .05) and -26 +/- 2% (P less than .001), respectiviely. No significant change in plasma AA occurred in either sham controls or in animals given the subnatriuretic VP dose. Incubation of plasma with 1,000 muU/ml VP caused no increase in AA. The data show that VP natriuresis is accompanied by an increase in plasms AA. The results suggest that vasopressin natriuresis in hydropenic dogs at least in part to the release of a humoral inhibitor of renal tubular sodium transport.