bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic AMP- and phorbol ester-regulated Cl- permeabilities in primary cultures of human and rabbit colonocytes
Authors: Sahi J. , Goldstein J. L. , Layden T. J. , Rao M. C.
Published: December 2017

Chloride transport in 24-h primary cultures of human and rabbit distal colonic crypt cells (90 +/- 5% viable) were characterized using the Cl(-)-sensitive fluorescent probe 6-methoxyquinolyl acetoethyl ester. To calculate the Cl- influx in millimolar per second, the Stern-Volmer quenching constant was determined to be 24.3 M-1 for human and 24.6 M-1 for rabbit colonocytes. Cl- influx was dependent on extracellular Cl- concentration ([Cl-]0), with maximal influx at [Cl-]0 > or = 20 mM. The adenosine 3',5'-cyclic monophosphate (cAMP)-dependent secretagogues forskolin (1 microM), prostaglandin E1 (1 microM), and 8-bromoadenosine 3',5'-cyclic monophosphate (100 microM) increased Cl- influx in human colonocytes from 0.35 +/- 0.08 to 2.14 +/- 0.65, 1.85 +/- 0.51, and 0.84 +/- 0.04 mM/s (n = 4), respectively, and in rabbit colonocytes from 0.22 +/- 0.03 to 1.04 +/- 0.11, 1.24 +/- 0.12, and 1.08 +/- 0.07 mM/s (n = 5), respectively. Depending on the secretagogue, this influx was inhibited 50-90% by the Cl- channel blocker diphenylamine-2-carboxylate (DPC; 50 microM) and > or = 65% by the Na-K-2Cl cotransport inhibitor furosemide (10 microM). Phorbol 12,13-dibutyrate, an activator of protein kinase C, increased Cl- permeability 3.8-fold in human and 2.4-fold in rabbit colonocytes. The phorbol 12,13-dibutyrate-stimulated Cl- permeabilities were sensitive to DPC and furosemide but not to indomethacin. These studies demonstrate DPC and furosemide-sensitive Cl- permeabilities in isolated cultured human and rabbit colonocytes, which can be activated by cAMP and protein kinase C stimulators.
Expression of protooncogenes c-fos and c-myc in healing of gastric mucosal stress ulcers
Authors: Wang J. Y. , Johnson L. R.
Published: December 2017

The current study determines the hypothesis that expression of protooncogenes c-fos and c-myc is involved in the mechanism of polyamine-stimulated healing in gastric mucosal stress ulcers. Rats were fasted 22 h, placed in restraint cages, and immersed in water to the xiphoid process for 2-6 h. Animals were killed either immediately after stress or at 2-h intervals up to 24 h after 6 h of stress. Stress caused both visible lesions and induction of ornithine decarboxylase (ODC) activity in the oxyntic gland mucosa after 2 h. Increased ODC activity was paralleled by increases in the mucosal polyamines putrescine, spermidine, and spermine. Exposure to stress led to appearance of c-fos mRNA and oncoprotein in the gastric oxyntic gland mucosa at 2 h and its disappearance by 4 h. Baseline expression of c-myc was enhanced significantly after 6 h of stress and remained elevated for 4 h. This change in the expression of c-fos and c-myc mRNA and oncoprotein preceded an increased rate of [3H]thymidine incorporation into mucosal DNA. Administration of alpha-difluoromethylornithine (DFMO, 500 mg/kg ip) totally prevented the marked increases in ODC activity and polyamine levels. DFMO also completely inhibited the expression of c-fos and significantly decreased c-myc mRNA and oncoprotein in the gastric mucosa of stressed rats. The healing process, which was significant by 12 h, was markedly inhibited by DFMO. These results show that 1) mucosa exposed to stress exhibits increased expression of c-fos and c-myc following increased polyamine synthesis and 2) inhibition of polyamine biosynthesis by DFMO decreases both protooncogene expression and mucosal healing.
Regulation of glucose-dependent insulinotropic peptide gene expression by a glucose meal
Authors: Tseng C. C. , Jarboe L. A. , Wolfe M. M.
Published: December 2017

Glucose-dependent insulinotropic peptide (GIP) enhances insulin secretion by pancreatic beta-islet cells. Its release has been demonstrated predominantly after the ingestion of carbohydrate and fat. We have recently cloned a rat intestinal GIP cDNA and in the present studies have used this cDNA as a probe for measuring rat duodenal GIP mRNA after nutrient administration. Rats were fasted overnight, after which they were permitted to drink water or 10% glucose. The duodenum was then removed, GIP mRNA was measured by Northern hybridization analysis, and duodenal mucosa and serum GIP levels were determined by radioimmunoassay. In response to oral 10% glucose, duodenal mucosal GIP mRNA concentrations increased from 2 to 4 h, and at the end of 4 h a threefold increase was detected. Serum and mucosal GIP concentrations increased earlier, starting at 60 min, and levels remained elevated at 4 h. In separate studies, nuclear run-on assays were performed to compare the effects of glucose and water ingestion on transcription of the GIP gene. Whereas no increase in GIP gene transcription was detected in rats ingesting water, the rate of transcription doubled in glucose-fed rats. Actin gene transcription was nearly identical in both groups, indicating genomic specificity. The results of these studies indicate that duodenal GIP gene expression is stimulated at both the pre- and posttranslational levels by glucose-containing meals. These studies further suggest that the release of GIP from cellular storage granules might account for the initial increase in serum GIP levels after oral glucose ingestion.
Effect of glucagon on plasma alanine and glutamine metabolism and hepatic gluconeogenesis in sheep
Authors: Brockman RP , Bergman EN
Published: December 2017

Net hepatic uptakes of plasma alanine (Ala), glutamate (Glu), and glutamine (Gln) were measured before and during intraportal glucagon infusions in five normaland four insulin-and alloxan-treated (ITA), conscious, fed sheep. Since hyperinsulinemia is associated with glucagon administration, ITA sheep were used so that constant plasma insulin levels could be maintained. Glucose turnover was determined by a vena caval infusion of glucose-6-'3H. In addition, in ITA sheep, Ala-'14C wasinfused for measurement of plasma Ala turnover, its unidirectional organ metabolism, and contribution to glucose synthesis. During infusion of glucagon, the net hepatic uptake of Ala increased significantly (P is less than 0.01) from control values of 3.8 plus or minus 0.5 and 2.7 plus or minus 0.6 mmol/h to 5.9 plus or minus 1.0 and 5.5 plus or minus 0.8 mmol/h in normal and ITA sheep, respectively. Similarly, Gin uptake increased from 4.3 plus or minus 1.4 and 1.6 plus or minus 0.5 to 5.5 plus or minus1.6 and 3.7 plus or minus 1.0 mmol/h, respectively. The conversion of Ala to glucose increased from control values of 1.7 plus or minus 0.5 to 3.0 plus or minus 0.5 mmol/h.Arterial plasma Ala and Gin concentrations decreased about 25% during glucagon administration, presumably as a result of their increased hepatic uptakes. A decreasein utilization of plasma Ala, but no change in production was calculated for the nonhepatic tissues, indicating that glucagon increased gluconeogenesis from Ala at the expense of muscle protein synthesis. Glucagon thus has a direct effect on the liver butonly an indirect effect on other tissues.
In vivo and in vitro miniature end-plate potentials at various external K concentrations
Authors: Muchnik S , Kotsias BA , Arrizurieta de Muchnik EE
Published: December 2017

In order to obtain a nore reliable picture of transmitter release, spontaneous synaptic activity was studied in vivo in the rat soleus neuromuscular junction. The in vivo miniature end-plate potential (MEPP) recordings were compared with those obtained in vitro and, in both circumstances, MEPP frequency was measured at external potassiumconcentrations ranging from 5 to 15 mM. The influence of external potassium loading on intra- and extracellular potassium concentration also estimated by measuring the muscle ionic composition and water distribution at normal and high plasma potassium concentrations. The MEPP frequencies recorded in vivo were consistently lower than those observed in vitro for all external potassium concentrations studied (P less than0.01). These data suggest that better experimental conditions are maintained in thein vivo preparations, since the intracellular potassium increase that follows the external potassium loading can only partially justify the observed differnce and other factors, such as anesthetic effects, etc, may be ruled out.
Secretin effect on gastrin, gastric secretion in dogs with chronic antral stimulation
Authors: Nasca S , Mignon M , Gramatica L , Accary J-P , Bonfils S
Published: December 2017

Antrocolic transposition in four dogs with Heidenhain pouch and gastrojejunostomyresulted in a marked increase in fasting plasma gastrin concentration and sustained highacid secretion, closely related to gastrin levels. A marked production of pepsin output could not be correlated with plasma gastrin. Reduction in plasma gastrin concentration was more than twofold less pronounced than the reduction in acid output for 1 and 2 U/kg-h, while the 0.5 U/kg-h no effect was noted. For both acid output and gastrin concentrations, close correlations were noted between presecretion level and remaining level upon secretin infusion. Despite the reduction in the secretory volume of the pouch, 0.5 and 1 U/kg-h of secretin induced a 1.5- and 2-fold increase in pepsin output, respectively. Two untis per kilagram-hour decreased the secretory volume as well as the pepsin output. If the physiological release of secretin in dogs does not exceed the equivalent of the lowest dose studied, our results would indicate that acid inhibition is a physiological activity of secretin, while the effect on circulating gastrin concentration seems to be phamacological.
Relationship between adenosine concentration and oxygen supply in rat brain
Authors: Rubio R , Berne RM , Bockman EL , CURNISH RR
Published: December 2017

Since adenosine is present in normal brain tissue and cerebrosipinal fluid and since it dilates the pial vessels, it is possible that adenosine, in addition to H-+, is also a mediator of the metabolic regulation of cerebral blood flow. Evidence supporting this hypothesis was obtained under various experimental conditions characterized by achange in brain oxygen supply. The brain was frozen in situ by means of a small bonerongeur precooled in liquid N2 and the tissue was processed for adenosine determination (nmol/g of tissue). Electrical stimulation of the cortex at 0, 15, 30, and 45 Hz yielded adenosine levels of 5.4 plus or minus 0.7, 10.5 plus or minus 1.7, 13.0 plusor minus 1.2, and 9.0 plus or minus 2.1 nmol/g. Arterial pressures of 87, 60, and 40mmHg gave adenosine levels of 7.5 plus or minus 0.76, 13 plus or minus 2.6, and 26.6plus or minus 3.3, respectively. Ventilation with 29.7, 20, 10.7, and5.5% O2 significantly increased the adenosine levels to 9.4 plus or minus 3.0, 6.4 plus or minus 1.2, 30.0 plus or minus 9.3, and 63.3 plus or minus 18.2 nmol/g, respectively. Hyperventilation significantly increased adenosine form 6.7 plus or minus 1.0 to 11.8 plus or minus 1.4 nmol/g. This increased adenosine level was reduced by additionof CO2 to the ventilating gas mixture. Lactate, the main H-+ donor, pyruvate, and cAMP changed in a fashion parallel to adenosine. However, cAMP showedonly a small increase in adenosine. These findings are in accordance with the concept that adenosine and H-+ may act synergistally to regulate cerebral blood flow and that endogenous adenosine may exert a small effect on cAMP formation.
Whole-brain blood flow and oxygen metabolism in the rat during nitrous oxide anesthesia
Authors: Gjedde A , Caronna JJ , Hindfelt B , Plum F
Published: December 2017

The Kety-Schmidt washout technique has been modified to measure whole-brain blood flow and metabolism in the rat. During nitrous oxide anesthesia, 14 rats exhaled (133)Xe, and continuous and simultaneous arterial and cerebral venous samples were drawn from a femoral artery and the transverse sinus of the brain. Extracerebral contamination of the venous sample was minimal, and equilibration of (133)Xe in brain tissue and blood was obtained after 10-24 min of inhalation. Cerebral blood flow was calculated from the total activity of the mechanically integrated arterial and venous samples according to the principle of Scheinberg and Stead. At a mean Paco2 of 40 mmHg, CBF averaged 98 +/- 6 (SEM) ml/100 g-min and CMRO2 averaged 5.4 +/- 0.7 (SEM) ml/100 g-min. CBF changed 2.4% with each millimeter Hg change of Paco2 while CMRO2 changed only insignificantly. The values obtained for CBF are higher than reported for man and large laboratory animals bur reflect the proportionately greater amount of gray matter in the rat brain.
Effect of histamine on microvasculature of isolated dog gracilis muscle
Authors: McNamee JE , Grodins FS
Published: December 2017

Isogravimetric capillary pressure (Pci), capillary filtration coefficient (CFC), and plasma protein concentration were measured before and during adminisistration of histamine in an isolated, independently perfused canine gracilis muscle. Histamine produced an average decrease in Pci of 14.1 mmHg, an increase in CFC of 36-fold, and an increased rate of plasma protein escape of at least 24-fold. These results suggest that histamine reduces the reflection coefficient for protein at the capillary wall and are consistent with predictions of the theory of restricted diffusion assuming that 1-2.5% of available pores increase in radious from 40 to 240 A.
Ganglion cells in arterioles of skeletal muscle: role in sympathetic vasodilation
Authors: Myers HA , Schenk EA , Honig CR
Published: December 2017

Ganglion cells were found in arterioles of gracilis muscles of dogs 2 wk after complete extrinsic denervation. We tested the possibility that they function in active sympathetic vasodilation (SVD) induced in isolated gracilis muscles by hypothalamic stimulation. To this end various drugs were injected into the gracilis perfusate. (Drugs did not reach the systemic circulation, and exerted their effects within the gracilis itself). C6 had no effect. Submaximal doses of atropine or l-hyoscyamine delayed and slowed SVD; higher doses blocked completely. d-Hyoscyamine did not change SVD or acetylcholine vasodilation, but when administered prior to l-hyoscyamine, threshold for blockade of SVD by the l-isomer increased 10,000-fold. Blockade by l-hyoscyamine of acetylcholine vasodilation was unaltered by d-hyoscyamine. Eserine partly blocked SVD, but enhanced and prolonged acetylcholine vasodilation. The foregoing and certain features of the time course of SVD are interpreted to mean that: a) atropine blocks SVD at muscarinic sites on peripheral ganglion cells; b) transmission at the ganglion cells depends on slow excitatory postsynaptic potentials; c) the final mediator of SVD at the vascular muscle cell is unknown.
Anion effects on cation movements during correction of potassium depletion
Authors: Villamil MF , Deland EC , Henney RP , Maloney JV
Published: December 2017

The differential effects of KCl vs. KHCO3 for intravenous K+ repletion were evaluated in a series of nephrectomized dogs previously depleted of 20% of total-body K by a 2-wk regimen consisting of K-free diet plus DOCA plus chlorothiazide. Twenty-four percent of K losses (5% of original TBK) were replaced by a 2-h infusion of either CKl or KHCO3. Blood pH was maintained at normal levels by controlling the rate of respiration. Skeletal muscle biopsies were taken before and 2 h after repletion, and blood samples were taken at intervals throughout. The following differences resulting from KHCO3 compared to KCl repletion were found: a) a greater cellular K uptake, a lower rate of increase, and a lower steady-state extracellular K+ concentration; b) a less increase in intracellular K+ concentration and a less decrease in intracellular Na+ concentration. These differences, which were independent of extracellular pH or kidney function, are thought to be secondary to unequal distribution of Cl- and HCO3-ions.
Leukocytic pyrogen and sodium acetylsalicylate on hypothalamic neurons in the cat
Authors: Schoener EP , Wang SC
Published: December 2017

Leukocytic pyrogen and sodium acetylsalicyclate (NaASA) were microinjected into the preoptic/anterior hypothalamic (PO/AH) area of cats to examine the direct effects of these agents on identified thermoregulatory neurons. The pyrogen and NaASA were administered under thermoneutral conditions to preparations that displayed peripheral or peripheral and central thermoreceptor input. The majority of neurons studied with proximate injection of pyrogen responded in a manner consistent with the set-point hypothesis; i.e., units responding to heating with increased activity were depressed and those showing a decreased discharge with the heat test were excited by the pyretic agent. Injection of NaASA without pyrogen pretreatment caused no significant modification of thermoregulatory neuron discharge in most cases. However, when NaASA was administered after pyrogen, it uniformly antagonized the pyretic effect causing a return of the discharge to the control rate. It may be concluded that pyrogen and NaASA act directly in the PO/AH area to produce fever and antipyresis, respectively, by appropriately offsetting the activity of thermoregulatory neurons.
Effect of epinephrine on automaticity of the canine atrioventricular node
Authors: Tse WW
Published: December 2017

Effects of epinephrine on the automaticity of canine AV nodal fibers were studied on spontaneously beating AV node-His bundle preparations. Transmembrane potentials of single fibers of the AV node or His bundle were recorded with microelectrode techniques. Action potentials of most AV nodal fibers were characterized by steep phase-4 depolarization and smooth transition from phases 4 to 0. Epinephrine (0.1-0.2 mug/ml) increased the spontaneous rate of the AV nodal fibers. The slope of phase 4 depolarization was increased and the threshold shifted to a more negative level. These changes probably accounted for the increase in the automaticity of the node. Also, in the presence of epinephrine, the pacemaker of the preparation was consistently located at the AV node had a higher degree of automaticity than the His bundle. The findings of the present experiment, therefore, further support the view that the AV node is automatic.
Effect of cyanide on renal metabolic rate and glomerulotubular balance
Authors: Lie M , Johannesen J , Kiil F
Published: December 2017

Measurements of anesthetized dogs by the heat-accumulation technique showed that cyanide reduced equally the metabolic rates of outer medulla and cortex, whereas combined infusion of ethacrynic acid and chlorothiazide reduced mainly the metabolic rate of the outer medulla. During ethacrynic acid and chlorothiazide infusion, cyanide reduced the remaining sodium reabsorption by an average of 19% and the remaining cortical metabolic rate by 43%, but had no additional effect on the outer medullary metabolism. Metabolic rates remained essentially constant when glomerular filtration rate (GFR) was raised during cyanide infusion from 63 plus or minus 3 to 135 plus or minus 7% of control by carotid constriction or intravenous infusion of angiotensin. Glomerulotubular balance, defined as proportional relationship between sodium reabsorption and GFR during infusion of ethacrynic acid and chlorothiazide, was present only at GFR less than 80% of control in experiments with and without cyanide infusion. We conclude that cyanide inhibits proximal energy-requiring sodium transport which cannot be inhibited by ethacrynic acid and chlorothiazide, but does not alter the range of GFR over which glomerulotubular balance applies.
Renal neuroadrenergic transmission
Authors: Slick GL , Aguilera AJ , Zambraski EJ , DiBona GF , Kaloyanides GJ
Published: December 2017

To study the role of the renal sympathetic nerves in the regulation of sodium excretion, we examined the renal functional response to left renal nerve stimulation before (group I) and after (group II) left renal adrenergic blockade with guanethidine. In group I dogs, absolute sodium excretion from the left kidney fell markedly after left renal nerve stimulation; the decreases in glomerular filtration rate and renal blood flow were of a similar magnitude. Using the radiolabeled microsphere technique, distribution of renal blood flow to the outer cortex was diminished after left renal nerve stimulation. In group II dogs, guanethidine blocked all of these effects of left renal nerve stimulation. In group iii studies, a low level of left renal nerve stimulation was used which resulted in a decrease in sodium excretion in the absence of changes in glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow; this effect was blocked by renal adrenergic blockade with guanethidine in group iv studies. These data support a role for the renal sympathetic nerves to directly influence renal tubular sodium transport in the absence of alterations in renal hemodynamics.
Catecholamine release: mechanism of mercury-induced vascular smooth muscle contraction
Authors: Solomon HS , Hollenberg NK
Published: December 2017

The mechanism by which mercuric ion (HgCl2) induces contraction of vascular smooth muscle was defined in the kidney of anesthetized dogs and in rabbit aortic strips. In vivo, HgCl2 injected into the renal artery induced a dose-related reduction in renal blood flow (electromagnetic flowmeter) and glomerular filtration rate (creatinine clearance). An intra-arterial infusion of phenoxybenzamine (POB) significantly reduced the vascular response to HgCl2 (P less than 0.001). In vitro, alpha-adrenergic blockade with phentolamine and POB prevented mercury-induced contraction, whereas agents that block serotonin, histamine, acetylcholine, and angiotensin did not do so. Norepinephrine receptor "protection" from phenoxybenzamine blockade sustained the response to HgCl2. Reserpine pretreatment produced a parallel reduction in the response of the aorta to tyramine and mercury. The results are consistent with an indirect action of mercuric ion via release of endogenous catecholamines.
Physiological temperature response and embryonic mortality in stressed swine
Authors: Wildt DE , Riegle GD , Dukelow WR
Published: December 2017

Physiological responses and some aspects of reproductive function were examined in mated female pigs subjected to a short-term heat stress during two intervals of early gestation. Trial 1 control and treated animals experienced temperatures of 24.0 and 40.2 degrees C, respectively, from days 2 through 13 of pregnancy. Trial 2 control and treated pigs were exposed to 23.3 and 40.4 degrees C, respectively, from days 14 through 25 of pregnancy. Both high thermal exposures caused significant increases (P less than 0.05) in rectal temperature. At body temperatures of 41.1 degrees C or above, animals became more active and behavioral patterns erratic. Stressed pigs in both trials exhibited adaptation to the short-term high thermal environment as treatment days progressed. Embryonic mortality in the stressed animals in trial 1 was greater than in controls, with the animals in the former group retaining a normal size litter or losing the entire litter by day of slaughter. A significant proportion (P less than 0.01) of litters from stressed animals contained degenerating fetuses at day 42 of gestation, suggesting a continuous or delayed effect of thermal stress on embryo survival.
Effect of glucagon on secretin-stimulated bile flow
Authors: Kaminski DL , Ruwart MJ , Jellinek M
Published: December 2017

The effect of glucagon on secretin-stimulated bile flow was evaluated in dogs with chronic biliary and gastric fistulas. Evaluation of the effects of secretin and glucagon alone on hepatic bile flow indicated that the calculated maximal response (CMR) values of the two agents were similar. Secretin increased the bicarbonate concentration in hepatic bile whereas glucagon did not, suggesting basic differences in mechanism of action. Administration of glucagon to secretin-stimulated bile flow produced an increase in bile flow while decreasing the bicarbonate concentration in secretin-stimulated bile. Since the maximal response for bile flow to glucagon and secretin was significantly greater than the maximal response to either agent alone, glucagon produced potentiation of secretin-stimulated bile. Glucagon increased the CMR value of secretin-stimulated bile from 513 mul/min for secretin alone to 692 mul/min for secretin and glucagon. This was associated with no significant change in the values of the respective D50S. These data suggest that glucagon produced a noncompetitive augmentation of secretin-stimulated bile flow and suggest that the two agents do not utilize the same receptor to stimulate bile flow.
Oxygenation of frog gastric mucosa in vitro
Authors: Kidder GW , Montgomery CW
Published: December 2017

We have recently shown that 5% CO2/95% O2 in the serosal bathing solution, with 100% O2 in the mucosal solution, results in CO2-diffusion limitation of acid secretion in bullfrog gastric mucosa. Changing to 10% CO2/90% 02 on both surfaces doubles the acid secretory rate. We calculate that, were the rate of oxygen consumption to increase significantly as a result of secretory stimulation, the tissue would now be oxygen limited. This prediction is tested by raising the P02 by increasing the total pressure in a hyperbaric chamber. Since no change in acid secretory rate or potential difference was observed upon changing from PO2 = 0.9 to PO2 = 1.9 atm, we conclude that the tissue is not O2 limited at normal pressure. Decreasing PO2 below 0.9 atm, by contrast, decreases the acid secretory rate and raises both PD and resistance. We infer that the rate of oxygen consumption did not rise significantly when acid secretion was increased by supplying sufficient CO2.
Acute suppression of hepatic gluconeogenesis by glucose in the intact animal
Authors: McDaniel HG
Published: December 2017

Within 2 h after glucose administration to fasting rats the incorporation of radioactive lactate into blood glucose and liver glycogen is decreased. Using tryptophan, which facilitates the study of gluconeogenesis prior to the phosphoenolpyruvate (PEP) carboxykinase step by increasing the level of certain hepatic metabolites, we have found that in animals fasted for 24 h glucose markedly decreased hepatic malate and aspartate concentrations without a corresponding fall in that of pyruvate, suggesting a decrease in pyruvate carboxylase activity. An inhibitor of fatty acid oxidation, 4-pentenoic acid, similarly decreased the accumulation of these intermediates, and octanoic acid significantly lessened the fall in malate and aspartate with glucose. The changes in tissue metabolite levels were consistent with inhibition of the liver pyruvate carboxylase reaction by glucose treatment, and with abolition of this inhibition by octanoate administration. Alanine and glutamate levels in the liver of tryptophan-treated animals were decreased 90 and 32%, respectively, by glucose. Thus, glucose administration in the whole animal acutely decreases gluconeogenesis by apparently inhibiting the pyruvate carboxylase step and decreasing alanine levels in the liver.
Pentobarbital and contraction of vascular smooth muscle
Authors: Altura BT , Altura BM
Published: December 2017

This study, with isolated rat aortic strips and portal veins, was undertaken to : 1) study the effects, if any, of pentobarbital Na (PTB) (5 x 10(-5) to 2 X 10(-3) M) on reactivity to epinephrine, serotonin, and KCl; 2) determine whether certain concentrations of PTB induce direct actions on aortic strips and portal veins; and 3) gain some insight into how these effects are brought about. The results indicate that PTB can: a) inhibit development of spontaneous mechanical activity in these vessels in anesthetic concentrations; b) dose-dependently attenuate contractions induced by epinephrine, serotonin, and KC1; c) cause a noncompetitive type displacement of the dose response curves of these vasoactive agents; d) attenuate Ca2+- induced contractions of potassium-depolarized aortic strips and portal veins concomitant with a dose-dependent displacement of these dose-response curves to the right; and e) rapidly relax drug as well as Ca2+ -induced contractions of aortas and portal veins. In addition, the data indicate that rat portal venous smooth muscle is more sensitive to the inhibitory actions of PTB than rat aortic smooth muscle. Overall, these data suggest that concentrations of PTB used to induce surgical anesthesia can exert profound depressant effects on at least two different types of vascular smooth muscle that may be related to actions on movement and/or translocation of Ca2+.
Mechanics of guinea pig taenia coli smooth muscle during anoxia and rigor
Authors: Bose D. , Bose R.
Published: December 2017

Page 324: D. Bose and R. Bose. "Mechanics of guinea pig taenia coli smooth muscle during anoxia and rigor." Page 326: in legend to Fig. 4A, first line, "6%" should read "2.5%." In Fig. 6, on the isotonic scale on the ordinate, "2.3" and "3.3" should be interchanged.
Changed cholinergic receptor characteristics after vagotomy in gastric fistula dogs
Authors: Hirschowitz BI , Gibson R , Wright L , Hutchison G
Published: December 2017

By the use of small doses of atropine (0.2-10 mug/kg-h) the kinetics of atropine antagonism to the gastric stimuli Urecholine and pentagastrin could be defined in intact dogs and in dogs after fundic vagotomy. Though pentagastrin was a much less effective stimulus after vagotomy, atropine had very similar effects on the pentagastrin response before and after vagotomy. Stimulation of both acid and pepsin by Urecholine remained unchanged by vagotomy but was uncompetitively inhibited by atropine in the intact dog, suggesting irreversible binding of atropine to gastric cholinergic receptors. After vagotomy, however, atropine inhibited Urecholine competitively, suggesting that atropine was now bound reversibly to cholinergic receptors. These changes are analogous to those occurring in muscle after denervation and suggest the growth of new cholinergic receptors with changed characteristics after denervation of the stomach.
Effects of acute metabolic acidosis on parathyroid hormone action and calcium mobilization
Authors: Beck N , Webster SK
Published: December 2017

Mechanisms through which metabolic acidosis increases calcium mobilization have been investigated in thyroparathyroidectomized rats with induction of acute metabolic acidosis by infusing NH4C1 intravenously. Acute metabolic acidosis directly raised serum calcium concentration and augmented the effect of parathyroid hormone (PTH) to raise serum calcium concentration. The same effects of metabolic acidosis were observed in rats with surgically removed intestines and bilateral nephrectomy, suggesting that acute metabolic acidosis directly increases calcium mobilization from bone and augments the effect of PTH to mobilize calcium from bone. In the kidney, acidosis directly inhibited the tubular reabsorption of calcium, but augmented the effect of PTH to increase tubular reabsorption of calcium. Acidosis had no measurable effect on calcitonin action.
Correlation of contractions and transit in rat small intestine
Authors: Scott LD , Summers RW
Published: December 2017

A single strain gauge was implanted chronically in the proximal jejunum of the rat to record contractions. FAsted pentobarbital-anesthetized animals received glucagon, caerulein, or isotonic saline control infusions intravenously while contractions were recorded. In control animals, the distribution of contractions in time showed clusters, with peaks at intervals of 14.24 +/-5.6 (SD) min. Glucagon produced dose-related inhibition of contractions. Caerulein at two lower doses produced a more uniform distribution of contractions in time; a higher dose caused inhibition. In other fasted rats, an isotopically labeled bolus was given through a chronically implanted duodenal cathether, and its distribution along the small intestine was examined in animals receiving the same doses of glucagon, caerulein, and saline. Glucagon caused a dose-related delay in transit. Those doses of caerulein that produced a uniform distribution of contractions accelerated transit; the dose that inhibited contractions delayed transit. Doses of glucagon and caerulein known to affect both motility and transit did not significantly affect water movement. The fasted rat resembles the fasted go in respect to the temporal distributions of jejunal contractions at a single point. Both quantitative and qualitative changes in contractions induce changes in transit.
Glucose utilization and recycling in ponies
Authors: Anwer MS , Chapman TE , Gronwall R
Published: December 2017

Variables of glucose metabolism determined by the use of [U-14C]glucose were compared in fed and fasted ponies. Relative recycling of glucose carbon with respect to tritium in fed animals was negligible for 6-T and 3-T and 16% for 2-T studies; in fasted animals relative recycling was 12 and 14% for 6-T and 3-T studies, respectively. Minimal mass of total-body glucose decreased significantly in the fasted ponies. Based on relative recycling of carbon to tritium, a negligible fraction of plasma glucose was produced via the Cori cycle or from glycerol in fed ponies; recycled tricarbon units contributed 12% of glucose produciton in ponies fasted 72 h. In fed ponies, 16% of plasma glucose carbon was recycled via a futile cycle at the glucose 6-phosphate stage. Glucose utilization was best estimated with the use of [6-T]glucose (or 3-T).
Effect of aging on bone mass in adult women
Authors: Cohn SH , Vaswani A , Zanzi I , Ellis KJ
Published: December 2017

Total-body calcium was measured in 40 adult women by total-body neutron activation analysis (TBNAA). Procedures for normalizing the absolute calcium measurements for the parameters of size and age were developed in order to effect a direct comparison of women of age 30-78 yr. The normal total-body calcium (TBCa) for an individual can be predicted by a formula developed in the present study to within +/- 11% (1.62 SD) at the 90% confidence level. The TBCa loss can be characterized by two components: one with a slower rate, 0.37%/yr, and the other with a faster rate, 1.08%/yr. The latter, a more rapid postmenopausal loss, started at 50-60 yr and was superimposed on the slower rate of loss that started in the fourth decade and continued throughout life. The bone mineral content (BMC) of the radius, measured by the absorptiometric technique, correlated well with the total-body skeletal calcium in this population (r = 0.813, P less than .001). However, for intercomparisons of the BMC values of individuals, normalization of the BMC values for size and age is required, as it is for the TBCa data. Normalization provided by the ratio of BMC to radius width is not adequate for comparative studies.
Ontogeny of thirst in the infant rat
Authors: Wirth JB , Epstein AN
Published: December 2017

The development of water drinking in response to thirst stimuli was found to be precocious and sequential in the neonatal rat. It was studied in suckling rats with a technique that took advantage of their vigorous consummatory reflexes and minimized appetitive responding. Responsiveness to the following thirst challenges appeared in the suckling rat with a clear timetable: cellular dehydration at 2 days of age, hypovolemia induced by colloid dialysis at 4 days, and beta-adrenergic activation at 6 days. Responsiveness to deprivation from mother's milk was vigorous at the earliest day tested (2 days) but could not be distinguished from hunger. Rats weaned, isolated, and tested as miniadults responded appetitively to thirst challenges as early as 16 days of age. But they required a warm environment, optimum access to the water source, and sufficient time to respond. As revealed by consummatory responding, the controls of water drinking mature weeks before they are required. They precede the maturation of capacities for sustained appetitive responding. These appear in the last week of the suckling period, yielding animals that are prepared for adult, thirst-motivated behavior at the onset of weaning.
Electrical off response of cat esophageal smooth muscle: an analog simulation
Authors: Chan WW , Diamant NE
Published: December 2017

This investigation was performed to define characteristics and to design an electrical model of the slow membrane depolarization, or "electrical off response," that follows stimulation of cat circular esophageal smooth muscle. The electrical off response showed the following characteristics: 1) the response was preceded by hyperpolarization of the muscle membrane; 2) the amplitude of the off-response depolarization increased directly with increasing amplitude of the preceding hyperpolarization; 3) the membrane potential showed varying degrees of oscillation around the resting point; 4) the oscillation period was constant (4-5 s) and was double the time from the point of maximum hyperpolarization to the peak of the electrical off response. These characteristics suggested that the electrical off response could be represented by a linear second-order differential equation with variable damping, and an analog simulation was constructed. By varying the damping ratio and/or the natural frequency of the analog model, the characteristics of the electrical off response of esophageal muscle could be reproduced. The model provides a means to explore the behavior of esophageal smooth muscle contraction under normal and pathological conditions.
Effect of acid lumen pH on potassium transport in renal cortical collecting tubules
Authors: Boudry JF , Stoner LC , Burg MB
Published: December 2017

In order to determine the effect of acid lumen pH on renal tubular potassium transport, cortical collecting tubules were dissected from rabbit kidneys and perfused in vitro. When the pH of the perfusate was lowered from 7.4 to 6.8, potassium secretion into the tubule lumen decreased by an average of 47%. The transepithelial voltage increased from a mean value of -32 mV (lumen negative) at pH 7.4 to -51 mV at PH 6.8. Net sodium absorption from the tubule lumen was essentially unchanged (5% mean decrease). Transepithelial voltage and potassium secretion returned to control values when the pH of the perfusate was raised to 7.4. Alterations in pH of the bath had no comparable effect on the transepithelial voltage, whether the bath pH was increased or decreased. We conclude that a decrease in the pH of the tubule fluid of itself inhibits active potassium secretion in this tubule segment, providing an additional explanation for the decrease in potassium excretion found in acidosis. The negative voltage (presumably caused by sodium absorption out of the lumen) is increased under these conditions, possibly because of reduction of a smaller counterbalancing positive voltage caused by potassium secretion into the lumen.
Humoral deficiency and reticuloendothelial depression after traumatic shock
Authors: Kaplan JE , Saba TM
Published: December 2017

Circulating opsonin levels and reticuloendothelial (RE) phagocytic activity were investigated in anesthetized rats subjected to Noble-Collip drum (NCD) trauma. Reticuloendothelial function was assessed by colloid clearance kinetics and circulating opsonin levels by in vitro tissue slice bioassay. After sublethal shock, both hepatic RE phagocytosis and plasma opsonic activity were significantly (P less than 0.001) depressed in the 0.5- to 6-h posttrauma period. Pulmonary and bone marrow localization of the blood-borne test microparticles significantly (P less than 0.05) increased during hepatic RES depression. Hepatic RE cells from animals during the interval of posttraumatic in vivo phagocytic depression exhibited normal phagocytosis when incubated in normal pretrauma plasma and decreased phagocytic activity when incubated in posttrauma plasma. After sublethal shock, restoration or opsonin levels by 24 h after shock resulted in hepatic RE recovery. Plasma opsonin levels declined in direct relationship to the degree of trauma. Progressive hepatic RE failure was correlated with the progressive decline in circulating plasma opsonic activity. The findings indicate that opsonic depletion may be involved in the etiology of hepatic reticuloendothelial depression after traumatic shock.
Amino acid assignment to one of three blood-brain barrier amino acid carriers
Authors: Oldendorf WH , Szabo J
Published: December 2017

The percentages of 22 14C-labeled amino acids remaining in rat brain 15 s after carotid injection were measured relative to a simultaneously injected diffusible internal standard, 3HOH. The injected solution also contained a nondiffusible internal standard, [113mIn]EDTA to correct for incomplete brain blood compartment washout. Self-inhibition and cross-inhibition was demonstrated by inclusion of unlabeled amino acids and carboxylic acids. All amino acids tested, excluding proline, alanine, and glycine, could be assigned to one, and only one, blood-brain barrier carrier system. The neutral carrier system transported phenylalanine, leucine, tyrosine, isoleucine, methionine, tryptophane, valine, DOPA, cysteine, histidine, threonine, glutamine, asparagine, and serine. Affinity for a basic amino acid carrier system was demonstrated for arginine, ornithine, and lysine. A third, low-capacity independent carrier system transporting aspartic and glutamic acids was demonstrated.
Colonic absorption of bacterially synthesized vitamin K2 in the rat
Authors: Hollander D , Muralidhara KS , Rim E
Published: December 2017

Colonic absorption of bacterially synthesized vitamin K2 ([3H]menaquinone-9) was studied with everted rat colonic sacs in vitro. The mean +/- SE rate of absorption of the vitamin by the colon was 20 +/- 1.45 pmol/min per 100 mg tissue at 300 nM mucosal concentration of the vitamin. The rate of absorption did not change (P greater than 0.10) with the addition of 2,4-dinitrophenol, Na azide, or KCN to the mucosal incubation medium. No evidence for transmural transport of the vitamin was detectable. When the concentration of the vitamin was increased in a stepwise fashion up to 900 nM, the absorption rate remained linear with respect to the mucosal fluid concentration (r = 0.98). Autoradiography indicated that the vitamin accumulated in the mucosal and submucosal layers of the large bowel. Absorption of the vitamin by the large bowel takes place via a passive, nonsaturable process that shows no evidence of energy dependence or carrier mediation. It was concluded that vitamin K2 (bacterial origin) is absorbable by the rat colon in amounts sufficient to meet the daily requirement of the animal and may explain the lack of bleeding problems in the face of episodic lack of dietary vitamin K.
Effects of temperature on cardiac transmembrane potentials in hibernation
Authors: Jacobs HK , South FE
Published: December 2017

Resting and action potential parameters were measured from papillary muscle isolated from hibernating and control hamsters and from rats. The temperature range of the study was 12-38 degrees C. The decrease in resting membrane potential (Em) with decreasing temperature was significantly less in the hibernation preparations (HH), down to 20 degrees C, than in either the control hamsters or rats. Below 20 degrees C the declines in Em of all preparations were indistinguishable. Action potential magnitude was adequately maintained in HH to 12 degrees C while both control hamster and rat action potentials declined markedly as temperatures were reduced. Both types of hamster preparations showed greatly prolonged action potentials with reduced temperatures as contrasted to a limited prolongation of rat action potentials. The data are suggestive of a membrane modication in hibernation.
Variability of skin temperature in the waking monkey
Authors: Baker MA , Cronin MJ , Mountjoy DG
Published: December 2017

Temperatures of the brain, skin, and nasal mucosa were recorded along with the cortical electroencephalogram (EEG) in chaired, conscious pigtail monkeys at 25 degrees C air temperature. In undisturbed animals, skin temperatures ranged from 34 to 37 degrees C. When the animal was alerted by visual or auditory stimuli, temperatures on the extremities, tail, nose, ears, and nasal mucosa dropped rapidly to 22-29 degrees C. Temperatures on the proximal limbs and trunk and most of the head remained steady at all times. Average hypothalamic temperature was 0.91 degrees C higher when the extremities, tail, nose, ears, and nasal mucosa were cool than when they were warm, the brain temperature change beginning 80-120 s after the change in peripheral temperatures. A slight decrease in EEG frequency, but no change in amplitude, occurred during skin warming. Anesthetic doses of barbiturate led to a rapid rise in temperature of the extremities, tail, nose, ears, and nasal mucosa and a drop in brain temperature. These large changes in skin temperature in conscious monkeys reflect changes in cutaneous blood flow, the resulting alteration in heat loss leading to a rapid change in deep body temperature. The experiments demonstrate the importance of the state of arousal on autonomic nervous control of peripheral vasomotor tone in the monkey.
Mechanics of canine iliac artery smooth muscle in vitro
Authors: Cox RH
Published: December 2017

Transmural pressure and external diameter were continuously recorded from intact segments of canine iliac artery and used to determine wall responses to maximal smooth muscle (SM) activation by norepinephrine (NE). Three different approaches were used:a) step inflations from low pressure following NE, B) slow, continuous inflation from low pressure following NE, and c) direct isometric and isobaric responses to NE. Passive pressure-diameter data were determined. The results show that active wall stress and diameter responses to NE determined using direct isometric and isobaric responses and from slow inflation responses (less than 1 mmHg/s) were not significantly different. Pressure-diameter and stress-strain curves determined using continuous (0.2 mmHg/s) and step pressure inflations after NE were not signficantly different. Pressure-diameter curves obtained at different inflation rates were not those expected from a simple viscoelastic material. The results suggest that slow inflation of iliac arteries with activated SM is a reasonable method for assessing contractile properties of SM. Furthermore, they also suggest that activation of iliac artery SM at high contractile element length (L greater than Lo) does not produce attenuated constriction responses.
Fluoride renal clearance: a pH-dependent event
Authors: Whitford GM , Pashley DH , Stringer GI
Published: December 2017

The renal clearance of fluoride (CF) was studied in pentobarbital-anesthetized rats. Urine flow rate and chloride clearance, previously thought to be the main determinants of CF, were readily dissociated from CF. Neither the clearance of sodium nor the excretion of potassium correlated consistently with CF. In experiments designed to manipulate urinary pH, viz., the administration of NaHCO3 or NH4Cl, acetazolamide, and mannitol, CF correlated closely with urinary pH. At a urinary pH of 5.0-k96, CF/GFR averaged less than 5%, while at a urinary pH of approximately 7.6, mean CF/GFR exceeded 65%. The data suggest that 35-45% of the filtered fluoride is reabsorbed in the proximal tubule, regardless of the final urinary pH, while in acidosis the majority of fluoride reabsorption occurs in the distal nephron. The results suggest that the tubular reabsorption of fluoride is inversely related to tubular fluid pH. Fluoride reabsorption seems to occur by nonionic diffusion, apparently as hydrogen fluoride. Depending on local pH gradients, it may occur along the entire nephron.