bluuebunny/crossref_metadata_2025 huggingface dataset:
Tyrphostins inhibit secretagogue-induced 1,4,5-IP3 production and amylase release in pancreatic acini
Authors: Piiper A. , Stryjek-Kaminska D. , Stein J. , Caspary W. F. , Zeuzem S.
Published: December 2017

We examined the role of protein tyrosine kinase inhibitors (tyrphostins) in secretagogue-induced inositol 1,4,5-trisphosphate (1,4,5-IP3) production and amylase secretion in rat pancreatic acinar cells. The data show that various specific cell-permeant tyrphostins (methyl 2,5-dihydroxycinnamate, tyrphostin 25, and genistein) inhibited the cholecystokinin octapeptide-, carbachol-, and bombesin-induced 1,4,5-IP3 production and amylase release. In digitonin-permeabilized cells, tyrphostins decreased 1,4,5-IP3 accumulation and amylase release generated by directly stimulating G proteins with the weakly hydrolyzable GTP analogue guanosine 5'-O-(3-thiotriphosphate). Tyrphostins had no effect on vasoactive intestinal peptide-induced amylase secretion. In isolated pancreatic acinar membranes, cholecystokinin octapeptide caused a rapid increase in tyrosine phosphorylation of a synthetic peptide containing the 12-amino acid sequence around a tyrosine phosphorylation site in pp6osrc. These results provide evidence that tyrosine kinases are involved in the activation of phospholipase C by G protein-coupled receptors in pancreatic acinar cells.
Unbound ligand drives hepatocyte taurocholate and BSP uptake at physiological albumin concentration
Authors: Sorrentino D. , Zifroni A. , van Ness K. , Berk P. D.
Published: December 2017

We have recently shown (D. Sorrentino, R.B. Robinson, C.-L. Kiang, and P.D. Berk. J. Clin. Invest. 84: 1325-1333, 1989) that, in a variety of isolated cell types, the uptake of oleate at physiological albumin concentrations is consistent with traditional pharmacokinetic theory (i.e., driven by unbound ligand). Lower albumin concentrations were associated with a deviant uptake pattern for which alternative theories have been proposed. Whether other classes of organic anions exhibit similar behavior is unknown. Therefore, we examined the effect of albumin on uptake of two widely studied organic anions, sulfobromophthalein (BSP) and taurocholate. Initial uptake velocity of [35S]BSP and [3H]taurocholate by isolated hepatocytes was studied employing a fixed albumin concentration and ligand-to-albumin molar ratios from 0.01:1 to 2:1 for taurocholate and 0.031:1 to 0.75:1 for BSP. In other experiments, albumin and ligand were altered in parallel, keeping their molar ratio constant. Unbound taurocholate concentrations were measured directly by equilibrium dialysis; unbound BSP concentrations were calculated from published data (K.J. Baker and S.E. Bradley. J. Clin. Invest. 45: 281-287, 1966). At 600 microM albumin, uptake of both ligands was a function of the unbound ligand concentration. At low ligand-to-albumin molar ratios and consequent unbound ligand concentrations this relationship was linear; over the entire range of unbound ligand concentrations studied, both ligands exhibited Michaelis-Menten kinetics, with definable maximal velocity and Michaelis constant values. At low albumin concentrations, the relationships between uptake and unbound ligand were unchanged for taurocholate; however, BSP exhibited altered kinetics similar to those observed with oleate. Nontraditional uptake kinetics at low albumin concentrations appear to correlate with very high affinity for albumin.
Rhythmic oscillating complex: characterization, induction, and relationship to MMC in chickens
Authors: Jimenez M. , Martinez V. , Rodriguez-Membrilla A. , Rodriguez-Sinovas A. , Gonalons E. , Vergara P.
Published: December 2017

Migrating myoelectrical complexes (MMCs) and rhythmic oscillating complexes (ROCs) have been investigated in chickens prepared for electromyography. Animals were chronically implanted with electrodes in stomach, duodenum, jejunum, ileum, ceca, and rectum. MMCs showing phases I-III were found in the jejunum and ileum both in fed and fasted states. Repetitive spike bursts were recorded in the duodenum (0.5-1/h), disrupting the gastroduodenal coordination and preceding a phase III in the jejunum. ROCs appeared spontaneously in fasted animals and in 75% of the recordings during the dark period. Four consecutive intestinal myoelectrical patterns have been described during a ROC. Briefly, they consisted in series of high-speed propagated abroad contractions of great amplitude that progressively changed into others of orad direction. In relation to the MMC, the ROC pattern appeared just after a phase III reached the distal ileum, and a pattern of duodenal repetitive spike bursts, followed by a migrating phase III in the jejunum, started at the duodenum after a ROC. No myoelectrical changes were recorded in cecorectal activity during ROC. Vagotomized animals showed the ROC pattern. Neither apomorphine (5-100 micrograms/kg iv) nor cholecystokinin (10(-9) mol/kg iv) induced ROCs. Naloxone (5 x 10(-7) mol/kg iv) and atropine (0.1 mg/kg iv) induced isolated orad contractions. Myoelectrical and functional similarities can be found between retrograde giant contractions, described in mammals, and ROCs. However, they differ in their origin and mechanism of induction.
Hepatic uptake of protein-bound ligands: extended sinusoidal perfusion model
Authors: Weisiger R. A. , Pond S. , Bass L.
Published: December 2017

Pages G872–G884: R. A. Weisiger, S. Pond, and L. Bass. “Hepatic uptake of protein-bound ligands: extended sinusoidal perfusion model.” Page G879 (2nd column, 1st line): the sentence that reads “As for the standard model, the only fitted parameter was Pm, (resulting value 0.248 ± 0.051 cm/s)” should read “As for the standard model, the only fitted parameter was Pm, (resulting value 0.082 ± 0.004 cm/s).” The only effect of this error on the results and conclusions of this study is that the best-fit line in Fig. 3 is very slightly different in shape, with a correlation coefficient (r2) that still exceeds 0.999. The corrected figure is provided below.
Structural and molecular changes in intestinal smooth muscle induced by Trichinella spiralis infection
Authors: Weisbrodt N. W. , Lai M. , Bowers R. L. , Harari Y. , Castro G. A.
Published: December 2017

Infection with Trichinella spiralis in the rat causes altered intestinal motility and jejunal smooth muscle contractility by day 6 postinoculation. The purpose of this study was to determine structural and molecular changes in the smooth muscle that could account for the functional changes that have been reported. By day 6 postinoculation, there was an increase in thickness of both muscle layers of the jejunum. This increase in mass was accompanied by an increase in total protein content of the seromuscular tissues. When specific proteins were analyzed, increases in actin and myosin heavy chain contents were found. On the other hand, there was no increase in collagen content. Alterations in gene expression at the pretranslational level were determined by monitoring total RNA and the proportion of mRNA that codes for alpha-smooth muscle actin. There was an increase in both parameters in longitudinal muscle from the jejunum of infected animals. The increase appeared to be site selective because there were no increases in either parameter in longitudinal muscle of the distal intestine. These results indicate that pretranslational upregulation of gene expression for actin isoforms occurs in smooth muscle of the proximal but not distal intestine during the early enteric phase of infection with T. spiralis. Thus the altered smooth muscle contractility that has been reported in experimental trichinosis may be related in part to an increased expression of smooth muscle protein.
Amino acid imbalance protein intake, and changes in rat brain and plasma amino acids
Authors: Peng Y. , Tews J. K. , Harper A. E.
Published: December 2017

Page 314: Y. Peng, J. K. Tews, and A. E. Harper. "Amino acid imbalance protein intake, and changes in rat brain and plasma amino acids." Page 317, Fig. 5: the top section should carry the heading "HISTIDINE IMBALANCE (liver)."
Evidence for complexing of transcobalamin-2 in canine and human plasma and serum
Authors: Cooper B. A. , Dirks J.
Published: December 2017

Page 758: B. A. Cooper and J. Dirks. "Evidence for complexing of transcobalamin-2 in canine and human plasma and serum." Page 761: column 1, line 22, " T1/2 of 22 hr" should read, " T1/2 of 2.2 hr."
Temperature effects of the electrical characteristics of the barnacle muscle fiber
Authors: Rothberg J.
Published: December 2017

Page 240: J. Rothberg. "Temperature effects of the electrical characteristics of the barnacle muscle fiber." Page 240: the abstract, line 13, "rates up to 23 mV/°C" should read, "rates up to 2.3 mV/°C." Page 241: column 1, line 21 should read, "476 mM; K+, 8 mM; Ca++, 20 mM; Mg++, 12 mM; Cl–, 538 mM; and HCO3–, 10 mM ..."; line 26, "K+, 625 mM" should read, "K+, 652 mM."
Influence of reversible obesity on eating behavior, blood glucose, and insulin in the rat
Authors: Steffens AB
Published: December 2017

Excessive food intake, resulting in extreme obesity, was induced in rats by electrical stimulation (three 30-min sessions per day for 3 wk) of the lateral hypothalamus (LH). Outside the stimulation sessions no voluntary food intake occurred duringthese weeks. In the subsequent recovery period, accurate records of spontaneous feeding were made. Blood levels of glucose, insulin, and free fatty acids (FFA)were determined during the stimulation period as well as the recovery period. Duringfeeding elicited by electrical stimulation of the LH in the obese phase, there was alarge increase in the glucose level. The insulin level, very high in the intervals between the stimulation sessions, showed no change, a small decline, or a large decrease,respectively, during stimulation in the morning, the afternoon, or the night. If food was withheld during stimulation, there was a large increase in the glucose level and alarge decrease in the insulin level. The first spontaneous meal after the termination of stimulation was extremely postponed, viz, until the glucose and insulin levels returned to normal for the first time. The insulin response to the first spontaneous mealwas exaggerated. Although in the following period (about 10 days) a rapid decrease inbody weight occurred, food intake was only minimal. The insulin level was high and the glucose levelsubnormal during that period. The insulin and glucose levels were normal again only after recovery of normal body weight and food intake. It is tentatively concluded that the regulation of body energy stores (body weight) is achieved through the control of food intake by circulating insulin and glucose levels.
Escape from vasoconstriction in the gastric microcirculation
Authors: Guth PH , Smith E
Published: December 2017

Escape of splanchic resistance vessels from vasconstriction due to adrenergic stimulation has been attributed to increasing submucosal blood flow due to dilation of submucosal arteriovenous anastomes (shunts). This postulate, as applied to the rat gastric microcirculation, was studied by in vivo microscopy. Using an image-splittingTV microscope recording system, response of gastric submucosal arterioles (13-33 mum)to 3 min of left splanchnic nerve stimulation, norepinephrine superfision, and vasopressin superfission was measured. All stimuli produced initial vasoconstriction.Escape occurred in all rats with nerve stimulation and norepinephrine, but in onlyone of five with vasopressin. No shunts were seen. The study demonstrates that thegastric submucosal arterioles exhibit an escape phenomenon, suggesting that "autoregulatory escape" in other splanchic beds also may be due to relaxation of constricted vessels and not to opening of shunts.
Effects of diuretic states on collecting duct fluid flow resistance in the hamster kidney
Authors: Marsh DJ , Martin CM
Published: December 2017

Hydrostatic pressures were measured in cortical tubules, long loops of Henle, terminal collecting ducts, and in vasa recta in hamsters. In hydropenia, the loops of Henle and terminal collecting ducts provided the major fluid flow resistances, as judged by the location of hydrostatic pressure drops. In mannitol or saline diuresis, hydrostatic pressures in all tubular segments increased, but pressure drops in loops of Henle disappeared, indicating dilatation of loops. The major pressure drop was in terminal collecting ducts, especially in ducts of Bellini, even though these tubular segments also dilated. At highest urine flows, cortical tubule pressures were higher with the ureter and renal pelvis intact than when they were excised, suggesting laminar flow in the ureter adds a flow resistance at high flows. The pressure drop across the medullary capillary bed was 1-2 mmHg. The summation of medullary capillary hydrostatic and colloid osmotic pressures favored fluid uptake from the interstitium, a relationship enhanced by vasa recta geometry which ensures that descending vasa recta offer 4 times the flow resistance of ascending vessels.
Microelectrophoresis of PGE1 onto single units in the rabbit hypothalamus
Authors: Stitt JT , Hardy JD
Published: December 2017

Prostaglandin E1 (PGE1) when micro-injected into the preoptic anterior hypothalamus (PO/AH) of conscious rabbits is a potent pyrogenic agent. We have investigated the action of PGE1 on the activity of single units of the PO/AH area using the microelectrophoretic technique. One hundred and thirty-eight PO/AH units were tested both for their response to changes in local PO/AH temperature and for their response to PGE1 application. Less than 9.0% of the total population of units tested showed any response to PGE1 application. When present, the response was invariably one of mild facilitation. No specific unit type (thermally sensitive or insensitive) appeared to be selectively affected by PGE1. Thus, the proportion of units affected by PGE1 was constant at 8-10% for warm-sensitive, cold-sensitive, or thermally insensitive units. There was no evidence to support an antagonistic role for PGE1 on the effects on norepinephrine on PO/AH units. On the basis of these results, we cannot predicate any simple neuronal basis for the action of PGE1 in producing fever in conscious rabbits. However, it is suggested that the action of PGE1 might be the modulation of presynaptic release of neurotransmitter onto the units of the PO/AH area.
Effects of dehydration on body-water distribution in desert kangaroos
Authors: Denny MJ , Dawson TJ
Published: December 2017

The effect of dehydration on the distribution of water in the bodies of two species of desert kangaroos, the red kangaroo Megaleia rufa and the euro Macropus robustus, has been examined. The volumes of various body-fluid compartments were determined in normally hydrated animals and then after the kangaroos had been dehydrated until body weight declined to 80% of the initial weight. The fluid compartments examined were total body water, plasma volume, intracellular volume (cellular and gut water), and extracellular volume. Both species were camel-like in their response to dehydration in that plasma volume was maintained in both species, falling by only 8.3% in red kangaroos and 7.4% in euros. The pattern of water loss from other compartments differed between species, particularly gut water loss. This compartment, which includes the large rumenlike fore stomach, contributed 56% of the total water loss of red kangaroos but only 22% of the loss from euros. The ecological implications of the preferential maintenance of gut water by the sedentary, cave-dwelling euros have been discussed.
Prolonged vasodilation following fatiguing exercise of dog skeletal muscle
Authors: Morganroth ML , Mohrman DE , Sparks HV
Published: December 2017

Prolonged vasodilation follows 20- and 60-min periods of stimulation (4 twitches/s) of dog skeletal muscle with blood flow held constant at 23 plus or minus 2 ml/100 g per min. During stimulation isometric tension development fell 61 plus or minus 3%, and we have operationally defined this as fatiguing exercise. During stimulation vasodilation was maximum. Following stimulation vascular resistance returned to control with average half-times of 6.9 plus or minus 0.6 and 5.8 plus or minus 0.4 min after 20 and 60 min of stimulation, respectively. This prolonged vascular recovery following fatiguing exercise is an order of magnitude slower than vascular recovery following less severe exercise. The pressor response to an intra-arterial bolus of angiotensin (0.5 mug) is not depressed during prolonged vasodilation. Prolonged vasodilation does not appear to be closely linked to changes in tissue oxygen consumption. In addition, the changes in resistance can be dissociated from changes in K+, osmolality, and lactate production following fatiguing exercise. We conclude that prolonged vasodilation following fatiguing exercise is caused by a metabolic vasodilator substance which is yet to be identified.
Use of diphenylhydantoin and diazoxide to investigate insulin secretory mechanisms
Authors: Levin SR , Charles MA , O'connor M , Grodsky GM
Published: December 2017

In the isolated, perfused rat pancreas, we contrasted effects of diphenylhydantoin (DPH) and diazoxide on glucose-induced biphasic insulin secretion. Either drug partially inhibited the first phase. However, DPH completely inhibited the second phase, whereas diazoxide produced inhibition, then escape and post-inhibitory overshoot. Exposure to DPH prior to glucose further inhibited the first phase, and increasing the dose had no additional effects, whereas only raising the diazoxide dose intensified inhibition of early release. DPH sequentially suppressed early response to a series of two, short, glucose pulses. In contrast, no additional effects of diazoxide were noted after its initial inhibition of the first pulse. A computer analysis was programmed from hypotheses based on these experiments. It suggests that DPH inhibits release from a labile compartment and provision of insulin to that compartment, whereas diazoxide divides the labile compartment into two sequential subcompartments. Further, the computer analysis indicates that, with diazoxide, insulin (or substances on which secretion depends) accumulates not at the final release step but at a proximal portion of the labile compartment.
Contractile repriming of single muscle fibers: inactivation and tubular diffusion
Authors: Stuesse SC , Lindley BD
Published: December 2017

Following maximal potassium contractures of isolated single fibers from Rana pipiens, a brief recovery period is required to restore the ability to produce maximal tension by subsequent depolarization. At normal potassium concentration (2.5 mM), there is a minimal lag time of 5 s before any tension is produced by a second exposure to elevated K+; half-maximal tension can be produced in 13 s. The rate of repriming is directly related to the square of the fiber radius and is slowed by lowering external calcium concentration (1.5-0.4 mM). There is no significant difference in any of these respects between normal fibers and fibers dissected from semitendinosus muscles which had been chronically denervated for periods of up to 8 wk. Increased potassium concentration (5-20 mM) in the recovery solution decreased the steady-state repriming level, affecting denervated fibers more than controls. No repriming occurred at concentrations above 20 mM (-48 mV membrane potential.) At these intermediate concentrations, repriming was less complete in denervated muscle, reflecting the increased speed of delayed contractile inactivation. From the times to 50% repriming, which were proportional to the square of fiber radius, we estimated an upper limit for the diffusion coefficient for K+ in the transverse tubular system of 0.3 X 10(-6) cm2/s for both control and chronically denervated fibers.
Negative inotropic influence of hyperosmotic solutions on cardiac muscle
Authors: Wildenthal K , Adcock RC , Crie JS , Templeton GH , Willerson JT
Published: December 2017

In cardiac muscle, moderate degrees of hyperosmolality of the type encountered physiologically or clinically (i.e., less than 200 mosM above control) characteristically exert a positive inotropic effect, which presumably is mediated by increased Ca2+ availability for binding to troponin. In contrast, skeletal muscle displays significant contractile depression on exposure to hyperosmotic solutions, even at mild degrees of hypertonicity. To determine whether a similar potential for hyperosmolarity-induced depression also exists in cardiac muscle, right ventricular papillary muscles from cats were exposed to hypertonic solutions of mannitol or sucrose under circumstances in which positive inotropic effects were precluded by prior exposure to a bathing solution of 4.0 mM Ca2+ and paired electrical stimulation to maximize intracellular Ca2+ before addition of the hyperosmotic substances. In contrast to their usual positive inotropic effects, hypertonic solutions under these conditions caused cardiac depression at all osmolarities tested. Developed tension and its maximal rate of development (dT/dt) decreased by 18% at 50 mosM above control, by 30% at 100 mosM, by 36% at 150 mosM, and by 42% at 200 mosM (P less than 0.01 for all). Time to peak tension and resting tension were not changed significantly. When the muscles were returned to control solutions, tension development also returned toward normal. The data are compatible with the hypothesis that, within the range tested, all degrees of hyperosmolarity exert a significant negative inotropic influence on cardiac muscle, as is true in skeletal muscle; manifestation of this effect of increased tonicity normally would be obscured at low degrees of hyperosmolality, however, by an overriding positive influence that is absent in skeletal muscle.
Mesenteric baroreceptors
Authors: Tuttle RS , McCleary M
Published: December 2017

Occlusion of the mesenteric vessels in the cat and injection of catecholamines produced significant changes in skin and muscle blood flows. These were abolished by cutting the mesenteric nerves. The occurrence of systemic pressure and peripheral resistance changes in cross-perfused mesenteric preparations indicates that hemodynamic factors alone, such as might result from occlusion of a large vascular region, were not initiating the reflex. This also excludes extramesenteric receptors within the heart and large vessels from the reflex. Since both intravascular pressure and catecholamines have been shown to modify Pacinian receptor discharge in vivo, the evidence suggests that the mesenteric Pacinian corpuscle is the baroreceptor probably initiating the vasomotor reflexes in skin and muscle. The net effect of mesenteric receptor activity appears to be an inhibition of vasomotor neurons supplying skin and muscle.
Effects of amphotericin B on ionic transport and sodium permeability of the toad lens
Authors: Bentley PJ , Candia OA
Published: December 2017

The polyene antibiotic amphotericin B decreases the PD and short-circuit current (SCC) across the amphibian lens in vitro. It was only effective when placed in the solution at the anterior side and its effect was reversible. Amphotericin B caused a large decline in the PD across the anterior surface of the lens and a smaller reduction in the PD across the posterior side. This seems to be due to a direct decrease of the electrical resistance of the anterior face. The effects required the presence of sodium in the Ringer solution bathing the anterior surface. The translenticular Na fluxes were increased in both directions so that the net flux changed little. Amphotericin B produced a considerable increase in the rate of accumulation of sodium and loss of potassium by the lens. The oxygen consumption of the lens was unchanged by amphotericin B. Amphotericin B appears to act on the lens epithelium by selectively increasing its passive sodium permeability.
Nutritional effects on heart acetylcholinesterase and butyrocholinesterase activity
Authors: Eckhert C , Barnes RH , Levitsky DA
Published: December 2017

Male rat pups were undernourished in energy and protein by assigning them at birth to lactating dams receiving a low-protein diet (12% casein) to decrease the maternal milk supply. A normal diet (25% casein) was fed to the dams of control pups. On day 21 the pups were killed and hearts were removed and examined from both groups. Hearts from the undernourished animals weighed less and contained less DNA, RNA, and protein. The chemical indices of cell number (DNA) and cell size (wt/DNA) were reduced in the hearts from undernourished animals. Assays of the cardiac tissue for the activity of acetylcholinesterase and butyrocholinesterase indicated that undernutrition altered the activities of both enzymes, but in opposite directions. Protein-energy undernutrition resulted in an increase in acetylcholinesterase activity and a decrease in butyrocholinesterase activity. The specific activities of choline acetyltransferase and cholinesterase were unchanged. The total activity of both cholinesterase and butyrocholinesterase was reduced in the hearts of the undernourished animals. The data indicate that nutritional status can alter the activity of cardiac enzymes which have been associated with controlling the rate and rhythmic contractions of the heart.
Evoked release of [14C]norepinephrine from the rat hypothalamus during feeding
Authors: Martin GE , Myers RD
Published: December 2017

The pattern of catecholamine release was studied at sites adjacent to the lateral ventricle or in the anterior, dorsomedial or ventromedial hypothalamus of the rat as it was feeding. Endogenous stores of norepinephrine (NE) were first labeled by the microinjection of [14C]NE into these circumscribed sites. Subsequently, [14C]NE release was examined by repeated perfusions of an artificial cerebrospinal fluid through a push-pull cannula at the rate of 23 mul/min for 5-10 min every 30 min. After successive control perfusates were collected, food or water was given to the animal. During an interval of feeding, a significant efflux of [14C]NE and its metabolites occurred reliably from midline structures of the hypothalamus at the level of the ventromedial nucleus. Although the feeding-related output of [14C]NE detected within the anterior hypothalamus was lower, [14C]NE was also released from this region when the rat pressed a lever to obtain food pellets. These results support the view that endogenous catecholamines underlie, at least partially, diencephalic mechanisms controlling food intake, including sensory, motor, or motivational components.
Influence of age on size and number of fat cells in the epididymal depot
Authors: Stiles JW , Francendese AA , Masoro EJ
Published: December 2017

The extensive literature on the effect of rat age on the size and number of adipocytes in adipose tissue depots relates solely to young developing rats and young adults. Therefore a study was carried out in our laboratory on the cellular characteristics of the epididymal depot of the Fisher 344 strain of rats through virtually the entire life-span. Collagenase digests of this depot prepared from rats of 9, 13, 26, 52, 104, and 130 wk of age yield a population of cells with diameters greater than 30 mum identified as adipocytes or "fat cells." A remarkably complex pattern of changes in both the size and the number of these fat cells in the epididymal depot occurred through the life-span of the rats. The epididymal depots also contain some cells with diameters around 10 mum which have a morphology similar to that of the classic adipocytes; such cells may be preadipocytes.
Impermeability of rabbit erythrocytes to prostaglandins
Authors: Bito LZ , Baroody RA
Published: December 2017

Washed rabbit erythrocytes were suspended in Tris-electrolyte buffer containing [3H]prostaglandin (PG) E1, F1alpha, F2alpha, or A1 and one 14C-labeled compound such as sucrose. After up to 24 h of incubation, aliquots of centrifuged, packed cells and supernatant were oxidized and the 3H and 14C samples were counted. The mean sucrose space of the packed cell was 7.4%. After 1 min the E1, F1alpha, and F2alpha spaces were 16, 15.4, and 10.0%, respectively, and showed no increase even after 24 h of incubation at either 23 or 5 degrees C. At 23 degrees C the initial (0.5 min) PGA1 and thiourea spaces were 94 and 75%, respectively, whence the PGA1, but not the thiourea, space declined, reaching 30% at 4 h. The large initial uptake of PGA1 was eliminated at 5 degrees C, while it was accentuated at pH 6.8 or at a PGA1, concentration of 10(-3) M. 14C-Labeled arachidonic, octanoic, and other non-PG fatty acids gave apparent distribution spaces of 140-300%. These results show that PG's can partition into rabbit erythrocyte membranes, but the intracellular volume of the erythrocytes is not freely accessible to these autacoids. The implications of the finding that some cell membranes are impermeable to prostaglandins are discussed.
Parasympathetic regulation of mitosis induced in rat parotid by dietary change
Authors: Schneyer CA , Hall HD
Published: December 2017

Mitotic activity of rat parotid was increased from levels near zero to 10-40 mitotic figures per 1,000 acinar cells (mean, 15/1,000) 2 days after glandular activity was increased from less than normal to normal by replacing liquid diet with a diet of solid chow. This frequency greatly exceeded the maximum (1-3/1,000 acinar cells) observed at any time during the diurnal mitotic fluctuations. This mitotic burst was virtually prevented if the auriculotemporal nerve was removed 2 days prior to introduction of solid chow, but was only somewhat reduced when the superior cervical ganglion was removed prior to the dietary substitution. The parasympathetic innervation also was chiefly responsible for the increased cell size that followed reintroduction of solid food.
Accumulation of some secretory enzymes in venom glands of Vipera palaestinae
Authors: Brown RS , Brown MB , Bdolah A , Kochva E
Published: December 2017

Secretion of venom in the venom glands of Vipera palaestinae was studied by measuring the protein content and enzymatic activities of L-amino acid oxidase (LAO), phosphodiesterase (PDE), and benzoylarginine ethyl esterase (BAEE). These were tested in the accumulating venom and gland homogenates at 0, 2, 3, 4,6, and 15 days after an intitial emptying of the venom glands by milking. Changes in the total activities of the enzymes and in the protein concentration were found in the venom samples, but not in the homogenates, at the different intervals after milking. In the venom the total activities of LAO, PDE, and BAEE were higher the longer the time intervals from the initial milking. When the data were fit by a straight line, the fluctuations from the line were of opposite signs for LAO and PDE at the 3- and the 4-day intervals. There were no significant correlations between the specific activities or between the changes in the specific activities of any two of the enzymes at any time interval. It is concluded that each of the enzymes is secreted at a rate independent of the other two; this pattern of secretion can best be described as nonparallel.
Embryonic and placental development during prolonged inanition in the pig
Authors: Anderson LL
Published: December 2017

Pregnancy is maintained in a high percentage (79%) of pigs subjected to inanition for periods up to 37 days, but few (25%) remain pregnant when inanition continues beyond 41 days. All remain pregnant during prolonged inanition (45 days) when exogenous progesterone and estradiol benzoate are given daily. Embryo survival rates in animals on inanition remain high (88%) and similar to those (89%) found in pigs given a full diet. Nitrogen content of embryos increases at a decreasing rate after 41 and 45 days inanition; placental nitrogen is markedly reduced at those times. By 45 days of inanition, nitrogen contents of embryos and placentas are less (P less than 0.01) than found in dams receiving a full diet. During prolonged inanition, exogenous progesterone (80 mg/100 kg) and estradiol benzoate (500 mug/100 kg) maintain embryonic and placental development at levels similar to those found in animals on a full diet. Maternal stores of protein and energy are made available for embryonic and placental developement in the presence of adequate levels of progesterone and estrogen, in spite of severe body weight loss during prolonged inanition of the dam.
Myocardial contractile force as a function of coronary blood flow
Authors: Downey JM
Published: December 2017

The contractile force of the deep and superficial myocardial fibers was examined in the open-chest anesthetized dog as a function of coronary blood flow (CBF). When 1) dogs that failed to demonstrate coronary autoregulation were eliminated from the data base and 2) CBF and contractile force data were both normalized as a percent of their vaues when perfusion was from aortic pressure (autoperfusion), the relationship between them became very reproducible. Contractile force was highly dependent on the flow rate when the CBF was below that chosen by autoregulation (the rate during autoperfusion). Conversely contractile force was relatively independent of flow at higher CBF. The contractile force-CBF curve thus was found to break precisely at the autoperfused CBF. When myocardial metabolism was elevated by paired electrical stimulation this relationship was unchanged. It was concluded that coronary blood flow is tightly regulated to match metabolic needs over a range of metabolic rates.
Endogenous prostaglandin in guinea pig taenia coli
Authors: Yamaguchi T , Hitzig B , Coburn RF
Published: December 2017

Prostaglandin (PGE) is synthesized in the guinea pig taenia coli. A low threshold concentration for an effect of exogenous PGE1 or PGE2 on spontaneous mechanical activity was demonstrated. The PG synthetase inhibitors aspirin, indomethacin, and 5,8,11,14-eicosatetraynoic acid, at concentrations that inhibited PGE efflux, had effects on spontaneous mechanical activity, membrane potential, membrane resistance, and evoked and spontaneous action potentials (single and double sucrose-gap methods) that were consistent with an action due to inhibition of membrane PGE concentration. The threshold concentration of indomethacin, which inhibited PGE efflux, was the same as the concentration that inhibited spontaneous mechanical activity. Pretreatment with ouabain (10(-6)-10(-5) g/ml) or elevated extracellular K+ (29 and 126 mM) made the guinea pig taenia coli entirely refractory to exogenous PGE1 or PGE2; the mechanical effects of the three prostaglandin synthetase inhibitors also were absent in the presence of elevated K+ or ouabain. The data are consistent with a hypothesis that, under conditions of our experiments, endogenous PGE has an effect on resting tension and spontaneous mechanical activity and on properties of the surface membrane of the guinea pig taenia coli.
Effect of ionic environment on oxygen uptake and lactate production of myometrium
Authors: Kroeger EA
Published: December 2017

The present studies were designed to measure the metabolic cost, in terms of oxygen consumption (QO2) and lactate production, of membrane ion transport, and activation of the contractile apparatus of rat myometrium. The normal QO2 of 16.98 +/- 0.84 mumol/g wet tissue per h was reduced to 15.42 +/- 0.66 in the presence of high-K (127 mM) solution. This was further reduced to 14.05 +/- 0.77 and 13.53 +/- 0.76 by the addition of D-600 (10(-5) M), which inhibits Ca influx or in the presence of Ca-deficient high-K solutions, respectively. Ouabain (10(-3) M) reduced QO2 by an amount similar to that produced by high K. Addition of K+ to Na-rich preparations produced an immediate ouabain-sensitive increase of QO2 whose rate was a linear function of [K+]o up to 30 mM in Ca-deficient solution. In all of the above conditions, changes in lactate release paralleled those in QO2. Isoproterenol (10(-6) M), which causes mechanical inhibition of myometrium, had no effect on the QO2 of muscles in normal solution but reduced the QO2 of muscles in Ca-deficient solution. Lactate release was increased by isoproterenol in both normal and Ca-deficient solutions. These results show that the Na pump is an important site of energy utilization in myometrium. Components which can be interpreted in terms of energy utilization for Ca pumping and the contractile apparatus were also demonstrated.
Carbohydrate metabolism in perfused livers of adrenalectomized and steroid-replaced rats
Authors: Exton JH , Miller TB , Harper SC , Park CR
Published: December 2017

In livers from fasted rats perfused with bicarbonate buffer containing bovine albumin and erythrocytes, adrenalectomy decreased glycogen levels and glucose production, impaired the incorporation of 14C from [14C]lactate into glucose or glycogen, and decreased the activity of the active (I) form of glycogen synthase. Cortisol treatment restored gluconeogenesis after 1 h and glycogen synthesis after 2 h. Adrenalectomy did not alter the production of glucose or lactate or the levels of gluconeogenic intermediates in livers from fasted rats perfused with fructose, but reduced the formation of glycogen from this substrate. Adrenalectomy increased the levels of lactate and decreased the levels of P-pyruvate and subsequent intermediates in the gluconeogenic pathway. These changes were reversed by cortisol treatment. It is concluded that glucocorticoids support gluconeogenesis and glycogen synthesis in livers from fasted rats primarily by facilitating a reaction(s) located between pyruvate and P-pyruvate in the gluconeogenic pathway and by promoting the conversion of inactive to active glycogen synthase.
Elastic modulus and stress relationships in stretched and shortened frog sartorii
Authors: Halpern W , Moss RL
Published: December 2017

The longitudinal dynamic elastic modulus (delta stress/delta strain) of 11 sartorius muscles (Rana pipiens; 3 degrees C) was measured at static strains, 0.57 less than L/Lo less than 1.53. Pseudorandom white-noise displacements less than +/-0.031% Lo (mean, peak to peak) were imposed on tetanically stimulated and resting muscles to obtain the isometric moduli. The active elastic modulus at each length was determined as the difference between the low-frequency (15-80 Hz) asymptotes of the tetanic and resting modulus functions. Resting moduli were found to increase with stretch at a declining rate, suggesting that some resting elasticity is attributable to active crossbridges. For isometric, tetanically stimulated muscles above L/Lo = 1.0, the ratio dynamic elastic modulus/active stress was nearly constant (65.4); the data predict zero modulus at a stretched length corresponding to zero active stress. Hence, the modulus per crossbridge exhibits sarcomere length invariance. On the other hand, active muscles below L/Lo = 0.77 manifest a significant (P less than or equal to 0.05) additional modulus beyond that found at the same active stress in the stretched muscle. Sarcomeric structural rearrangements are suggested as a possible source of this additional modulus.
Metabolism of histamine in secreting and isolated canine stomach
Authors: Code CF , Green WE , Kennedy JC , Ritchie HD , Schlegel JF
Published: December 2017

Total 14C activity in juice secreted by gastric pouches of six dogs and seven isolated canine stomachs was determined in response to intravenous and intra-arterial infusions of histamine and [14C]histamine. The proportions of 14C attributable to histamine, Nalpha-methylhistamine (NalphaMeH), Nalpha,Nalpha-dimethylhistamine (NalphaNalphaMe2H), N-telle-methylhistamine (NtauMeH), imidazole acetic acid (ImAA), N-methylimidazole acetic acid (NtauMeImAA), acetylhistamine (AcH), and histaminol (HOH) were defined using thin-layer chromatography. Similar estimates were made at the end of infusions on blood, gastric mucosa, and gastric muscle. Methylation was the major, or sole, route of metabolism of histamine in the gastric mucosa, and the major product was inactive NtauMeH. Small quantities of the active NalphaMe derivatives, particularly NalphaNalphaMe2H, were identified in both the juice and mucosa. Little or no ImAA, NtauMeImAA, AcH, and HOH were present in juice from isolated stomachs while they did occur in the juice from intact dogs, demonstrating they are extragastric metabolites of histamine. A major mucosal function of methylation of histamine is inactivation, although NalphaMe derivatives formed may play a role in the secretagogue action of histamine.
Intracellular bicarbonate of skeletal muscle under different metabolic states
Authors: Khuri RN , Agulian SK , Bogharian KK
Published: December 2017

Intracellular bicarbonate of single muscle fibers in vivo was measured by a direct electrometric method simultaneously with the membrane PD in rats under seven different metabolic states. From the measured intracellular bicarbonate values and the PCO2, the bicarbonate equilibrium potential and the intracellular pH were calculated. The mean intracellular [HCO3-] under normal control conditions was 10.3 +/- 0.7 mM (SE). The intracellular bicarbonate fell significantly in both chronic metabolic acidosis and chronic K+ depletion. In contrast, intracellular bicarbonate was elevated in chronic metabolic alkalosis, K+ loading, and Na+ depletion. Taking intracellular pH as an index of the acid-base status of cells, we find that whereas the calculated cell pH decreased along with the cell bicarbonate in both chronic metabolic acidosis and K+ depletion, cell pH increased along with the bicarbonate only in chronic metabolic alkalosis. Cell pH was unchanged in both chronic K+ loading and Na+ depletion.
Reflex sympathetic tachycardia during intravenous infusions in chronic spinal cats
Authors: Bishop VS , Lombardi F , Malliani A , Pagani M , Recordati G
Published: December 2017

The reflex tachycardia elicited by rapid intravenous infusions of a blood substitute was studied in 21 chronic cats with spinal sections at C8. All animals could breath spontaneously. The day after section the average resting heart rate (HR) and arterial pressure (AP) were 109 beats/min and 98/67 mmHg, respectively. Vagal blockade with atropine (0.5-0.7 mg/kg iv) was performed prior to each infusion, increasing the average HR To 127 beats/min. In 39 infusions in 21 cats the average increase in HR was 10 beats/min (range from -6 to +22 beats/min). A tachycardia was observed in all but five trials, four of which were obtained in two cats that subsequently responded with a tachycardia. In seven animals the neural circuit mediating the response was partially or totally interrupted by section of several thoracic dorsal roots (T1-T4 or T1-T6) and of the spinal cord at the inferior level of these sections (between T6 and T7). The tachycardia response was progressively reduced and finally abolished by these procedures. These experiments indicate that spinal neural mechanisms are likely to contribute to the phenomenon first described by Bainbridge.
Preabsorptive insulin release and hypoglycemia in rats
Authors: Louis-Sylvestre J
Published: December 2017

Peripheral blood glucose and immunologically reactive insulin levels were determined in freely moving normal rats which were submitted either to a free oral glucose load or to a gastric administration of the glucose load. Identical determinations were performed in ventromedial hypothalamic nucleus-(VMH) lesioned and vagotomized rats after the same oral intake. It was demonstrated that: 1) a free oral glucose intake was immediately followed by two peaks of insulun release and a resultant decrease in blood glucose; 2) a gastric glucose load resulted in a single peak of insulin release and the concomitant decline in blood glucose; 3) the recorded blood glucose level was the resultant of the insulin-induced hypoglycemia and the postabsorptive hyperglycemia; and 4) the responses were largely exaggerated in VMH-lesioned rats and abolished by vagotomy. It is concluded that the early prandial insulin release reflexly induced by food-related stimuli temporarily enhances the metabolic conditions which provoke feeding.
Role of arterial baroreceptors in mediating cardiovascular response to exercise
Authors: McRitchie RJ , Vatner SF , Boettcher D , Heyndrickx GR , Patrick TA , Braunwald E
Published: December 2017

The role played by the major arterial baroreceptor reflexes in the cardiovascular response to exercise was examined by comparing the responses of untethered conscious dogs instrumented for the measurement of aortic pressure and cardiac output with those of dogs with total arterial barorecptor denervation (TABD). Moderately severe levels of exercise (12 mph) in intact dogs increased cardiac output from 111 +/- 17 ml/kg per min, increased heart rate from 101 +/- 5 to 265 +/- 8 beats/min, and reduced total peripheral resistance from 0.039 +/- 0.003 to 0.015 +/- 0.002 mmHg/ml per min. Dogs with TABD responded in a very similar fashion; exercise increased cardiac output from 119 +/- 8 to 356 /+- 23 ml/kg per min, increased heart rate from 122 +/- 7 to 256 +/- 5 beats/min, and decreased total peripheral resistance from 0.042 +/- 0.005 to +/- 0.015 +/- 0.001 mmHg/ml per min. The reflex heart rate responses to intravenous bolus doses of methoxamine were also examined in intact animals, both at rest and during exercise. Methoxamine caused striking bradycardia at rest, but little bradycardia during exercise. These results suggest that the arterial baroreceptor reflex is normally turned off during severe exercise and thus does not modify significantly the cardiovascular response to exercise.
Effect of adrenal steroids on bone resorption in rats
Authors: Yasumura S
Published: December 2017

Rats labeled with strontium-85 (85Sr) were rejected with adrenocortical steroids for 2 wk. The urinary-to-tibial (U/T) 85Sr ratio was used as an index of bone resorption. The glucocorticoids caused an inhibition of skeletal resorption, as judged by the 50% reduction in the U/T ratio, and decreased excretion of hydroxyproline. Thyroidal calcitonin levels were slightly elevated in glucocorticoid-treated animals, suggestive of a possible retardation of calcitonin release. The U/T ratios of thyroparathyroidectomized (TPTX) rats injected with corticosteroids were 50% of control values. The results indicate that glucocorticoids inhibit bone resorption independent of the action of calcitonin. Cortisol treatment increased the tibial density as measured by a radiographic technique. However, bone density was decreased and the U/T ratio increased in steroid-treated rats fed a low-calcium diet. In TPTX cortisol-treated rats, parathyroid extract (PTE) increased the U/T ratio and serum calcium but not to the degree observed in TPTX PTE-injected control animals. These experiments indicate that in rats glucocorticoids inhibit the rate of bone resorption but this effect can be overcome in part by PTE.
Effect of carbachol on 45Ca uptake and protein secretion in rat lacrimal gland
Authors: Keryer G , Rossignol B
Published: December 2017

Carbachol stimulates 45Ca uptake and protein secretion in rat lacrimal glands. At low concentration (10-8 M) atropine inhibits these effects but phentolamine and propranolol (10-5 M) are ineffective. The optimum response in both processes is obtained at the same concentration (10-6 M) of the cholinergic agonist. Vinblastine (10-4 M) reduces protein discharge induced by carbachol without modifying the uptake of 45Ca stimulated by the parasympathetic mediator. Calcium influx is proposed as the primary effect of cholinergic inducers in secretory processes.