bluuebunny/crossref_metadata_2025 huggingface dataset:
THE BAND ENERGY ENGINEERING ON HIGH EPOXY (OR HYDROXYL) CONTENT GRAPHENE OXIDE
Authors: ARASHLOO BANAFSHEH ALIZADEH , AHMADI MOHAMMAD TAGHI , AFRANG SAEED
Published: December 2017

Nowadays, the superior properties of carbon-based materials especially nano structural derivation like graphene and graphene oxide (GO) spot light to the researchers. The GO has been suggested as an alternate material in device miniaturization due to its atomic structure. The memristors and nonvolatile memories are settled in these categories as a solution for the scaling limitation problem in the Moor’s law. Therefore, the GO can influence the memristor performance and characteristics. The current–voltage characteristics as the most significant parameter in the memristor design are considered. On the other hand [Formula: see text]–[Formula: see text] characteristic depends on the active layer (GO) bandgap energy in the metal/oxide/metal structure and therefore, needs to be explored. In the GO-based memristor, the bandgap energy can be changed by the percentage of the oxygen groups in comparison to the carbon on graphene sheets. Thus, the other parameters are overstated by the bandgap energy. In the presented work, the energy bandgap of a high epoxy group content of GO sheets is engineered. The opening of the bandgap in the graphene oxide by high epoxy groups content with the ratio of (O/C [Formula: see text] 50%) is studied. In other words, the oxygen adsorption effect on the Hamiltonian of the system is explored. For the proposed structure, the bandgap energy is modeled and the acceptable value (approximately equal to 2.799[Formula: see text]ev for epoxy groups) is obtained. Moreover, the hydroxyl group adsorption effect on the bandgap of the graphene oxide by high content hydroxyl group is considered (approximately equal to 2.647[Formula: see text]ev for epoxy groups). Consequently, the different absorption energy effects on the bandgap of the GO is participated and the opening bandgap in the range of 2[Formula: see text]ev to 3[Formula: see text]ev is obtained. The excitonic effect on the suggested model by epoxy groups and hydroxyl groups is explored and it is realized that the energy levels in the Dirac points of epoxy groups are closer than those of the hydroxyl groups.
Simulating the Effect of Contact Atomic Structure on the Spin-Dependent Transport Properties of Gold Nanowires
Authors: Ansarino Masoud , Ravan Bahram Abedi
Published: December 2017

Some experimental research works report on the superb magnetoresistance properties of magnetically contacted gold nanowires. With the intention of trying to understand the spin-dependent transport mechanism of these structures, in this work we have used first-principles density functional theory methods to investigate effects of interface structure on the spintronic characteristics of Au nanowires. Monatomic chains of gold are sandwiched between two ferromagnetic electrodes of Fe and by substituting the interfacial Fe atoms with some other transition metal elements (including Cr, Mn, Co and Ni) the occurrence of possible enhancement in the electronic conductance and magnetoresistance characteristics of the device are investigated. It is observed that replacing the interfacial atoms with Ni raises the junction’s magnetoresistance ratio to as high as 2000%.
Osmotic properties of cells: a computer laboratory.
Authors: Hempling H G
Published: December 2017

A computer laboratory has been designed to teach the osmotic properties of cells. One program, CELL.BA, is for the teacher to enter values for the volume of cell water and osmotically inactive material, the concentration of impermeant solute in the cell, and the permeability of the plasma membrane to water and a nonelectrolyte. When the program is protected, students use it as a cell with unknown osmotic properties. They run experiments on the computer with different concentrations of impermeant or permeant solutes or combinations of the two. Changes in cell volume or solute concentration are collected as data and analyzed with the program, PERMEABILITY LAB.BA. This program provides a parameter list, and students try to fit the data that are graphed on the screen by choosing values for the unknown cell parameters and generating model curves. Programs are written for the Macintosh computer.
Measurement of gastric secretion as a student teaching exercise.
Authors: Nicol S C , MacPherson R D , McLeod L J
Published: December 2017

Teaching gastrointestinal physiology to preclinical medical students presents problems in finding suitable practical exercises to demonstrate the physiology of gastric acid secretion. In our course, students measure their own gastric secretory activity by the use of nasogastric tubes. Gastric secretion can be stimulated by insulin-induced hypoglycemia or by pentagastrin, a synthetic gastrin analogue. The time course of the secretory responses, i.e., volume, acid output, and pH, are followed by collecting control and poststimulatory secretions into 15-min samples. The effect of antiulcer drugs, such as cimetidine, can be easily studied in such experiments. The results of these experiments are very reproducible, allowing year-to-year comparisons of treatments. Examples of results of various experimental protocols are shown. We believe this to be a useful class exercise not only because of the excellent results it yields but because of the experience and insights it produces.
The use of Apple Macintosh computers and Hypercard in teaching physiology laboratories.
Authors: Stephens P J , Doherty J A
Published: December 2017

A network of Apple Macintosh computers has been integrated into existing undergraduate physiology laboratories. Hypercard software programs replace the traditional laboratory handout; the text contains a number of buttons linked to cards that provide additional information on a particular subject. This additional information includes theory, the use of various instruments, expected results, and details on how to perform data analysis. This system of information layering allows students to work independently, at their own pace, and allows them to learn as much or as little as they consider necessary. Each computer is interfaced with a MacLab/4 data-acquisition unit, which permits the computer screen to display a four-channel chart recorder or a two-channel oscilloscope.
A novel interactive demonstration in clinical gastroenterology for first-year medical students.
Authors: Crass M F , Hodges D S
Published: December 2017

A unique clinical correlation in gastroenterology for first-year medical students is described. This interactive demonstration is conducted in a clinical setting and is designed to introduce the student to a broad range of topics in clinical gastroenterology while complementing lecture material in gastrointestinal (GI) physiology. Faculty and fellows of the Department of Internal Medicine at Texas Tech University Health Sciences Center present minilectures and demonstrations at five different stations held in endoscopy rooms of the GI Diagnostic Center (GI Lab). The first-year class is divided into groups of 20 students or less. Each group visits a given station for 30 min, and each station has a specific topic. The topics are motility studies, esophagogastroduodenoscopy, gastric analysis, endoscopic retrograde cholangiopancreatography, and colonoscopy and sigmoidoscopy. At each station, physicians pose clinical questions related to the students' understanding of GI physiology and, in turn, respond to students' questions. For students who have been learning basic concepts of GI physiology, this clinical demonstration offers a more meaningful clinical correlation than standard clinical lectures could afford. In addition, the demonstration brings enhanced interest and enthusiasm for the subject matter.
Evaluation of vignette-type examination items for testing medical physiology.
Authors: Carroll R G
Published: December 2017

Step 1 of the United States Medical Licensing Examination has now replaced the National Board of Medical Examiners part 1 examination as the initial step in medical licensure. The new examination format places an increased emphasis on clinical vignettes to test basic physiological concepts. Suggestions from a question-writing workshop were incorporated into cardiovascular items in a midcourse physiology examination. Item analysis indicated that the overall examination difficulty was not different from examinations administered in the preceding years. Within the examination, however, the vignette questions had significantly higher discrimination indexes than other question types. The slope of the difficulty-to-discrimination relationship was significantly higher in 1992 than in previous years. This means that questions of equivalent difficulty were more discriminating in 1992 than in previous years. Finally, this report suggests a method of identifying questions with both high discrimination and high difficulty index for the development of an (informal) test item bank. The clinical vignette question types are a valuable method of examining basic physiological principles.
A laboratory demonstration for learning about mast cell degranulation.
Authors: Corado J , Eblen-Zajjur A
Published: December 2017

A simple experimental model of cell degranulation was implemented that exposed mast cells obtained from Sprague-Dawley rats to saponin. The model is flexible, asy, and low cost, is not very time-consuming to run, and needs a minimum of laboratory resources. It has been used for the last three years in our undergraduate medical physiology courses and has replaced the classic utilization of slides and drawings.
Use of course-embedded projects for program assessment.
Authors: Krilowicz B L , Downs T
Published: December 2017

There is increasing demand on science faculty to develop authentic assessment measures for both individual courses and undergraduate programs. We report here on a quarter-long group project used in a neurophysiology course that can be used for either purpose. Small groups of four to five students critically analyze at least 10 articles from the primary scientific literature. The end result of this process is the equivalent of a scientific review article that is presented in two formats, a 10-min oral presentation and a scientific poster presentation. Students perform better on application tasks than on analysis, synthesis, or evaluation tasks associated with the project (P < 0.025) and generally respond positively to process questions (59-82%) but less positively to task questions (36-76%) about group dynamics. The cognitive skills and basic content knowledge required to complete this project are developed throughout the undergraduate program. Thus the project is a type of culminating program experience. However, the project also assesses basic course proficiency, because students cannot analyze primary neuroscience research without an understanding of neurophysiological principles.
The beaver pond analogy of blood glucose control.
Authors: Swain D P
Published: December 2017

The concentration of glucose is tightly regulated in the blood by a complicated set of physiological variables. To provide students with a means to more readily understand these complex mechanisms, the control of the water level in a beaver pond is presented as an analogy. A beaver must maintain a constant water level in the pond for the proper functioning of the lodge, just as blood glucose is maintained for, among other reasons, brain function. The beaver controls the water level by changing outflow over the dam and inflow from stream beds. Water flow over the dam is analogous to glucose leaving the blood for tissues, which is controlled by insulin. Inflow of water from streams is analogous to glucose absorption from the gastrointestinal tract and glucose release from the liver, the latter being controlled by glucagon and other counterregulatory hormones. The analogy is extended by considering the effects of exercise in normal and diabetic individuals on blood glucose levels.
How accurate are our assumptions about our students' background knowledge?
Authors: Rovick A A , Michael J A , Modell H I , Bruce D S , Horwitz B , Adamson T , Richardson D R , Silverthorn D U , Whitescarver S A
Published: December 2017

Teachers establish prerequisites that students must meet before they are permitted to enter their courses. It is expected that having these prerequisites will provide students with the knowledge and skills they will need to successfully learn the course content. Also, the material that the students are expected to have previously learned need not be included in a course. We wanted to determine how accurate instructors' understanding of their students background knowledge actually was. To do this, we wrote a set of multiple-choice questions that could be used to test students' knowledge of concepts deemed to be essential for learning respiratory physiology. Instructors then selected 10 of these questions to be used as a prerequisite knowledge test. The instructors also predicted the performance they expected from the students on each of the questions they had selected. The resulting tests were administered in the first week of each of seven courses. The results of this study demonstrate that instructors are poor judges of what beginning students know. Instructors tended to both underestimate and overestimate students' knowledge by large margins on individual questions. Although on the average they tended to underestimate students' factual knowledge, they overestimated the students' abilities to apply this knowledge. Hence, the validity of decisions that instructors make, predicated on the basis of their students having the prerequisite knowledge that they expect, is open to question.
Basis for presentation of acid-base in two dimensions.
Authors: Gamble J L
Published: December 2017

Buffering of "metabolic" acid in tissues other than blood correlates closely with a change in extracellular bicarbonate concentration rather than with a change in extracellular pH. Of particular importance is the evidence for an absence of relation to change in pH. Questions are raised with respect to buffering mechanism, but simplification is offered for diagnosis. A clearer focus can be given to the guidepost changes in PCO2 and bicarbonate concentration. Basic relationships of buffering in the whole body are reviewed, and a modified diagnostic rationale is offered, based on a two-rather than a three-dimensional analysis.
Physiology teaching in the developing world: models for quality learning.
Authors: Siddiqui A
Published: December 2017

An important initiative to develop higher education and physiology teaching was launched when recommendations were deliberated at the concluding session of a four-day international workshop, Physiology Teaching in the Developing World: Models for Quality Learning, held April 5-8, 1999, at the Aga Khan University, Karachi, Pakistan. The event was organized under the auspices of the International Union of Physiological Sciences (IUPS), Pakistan Physiological Society, and Aga Khan University. Among other major sponsors, the Islamic Development Bank, Islamic Educational Science and Cultural Organization. Third World Academy of Sciences, and Pakistan Science Foundation were prominent.
Electrophysiology of the undergraduate neuroscience student: a laboratory exercise in human electromyography.
Authors: Lennartz R C
Published: December 2017

A laboratory exercise is described in which students in a neuroscience, psychobiology, or similar laboratory course record the electromyogram (EMG) from themselves, using surface electrodes (placed on the skin). This exercise is intended to give students a firsthand demonstration that electrical activity is produced within them and to allow the students to use this activity to study biological and psychological concepts. The students study the nature of the EMG (changes with tension and the temporal relationship with limb movement) and the concepts of flexion and extension, reaction time, and patellar ("knee jerk") reflex. In postlaboratory evaluations, undergraduate introductory neuroscience students indicated that they appreciated the opportunity to record electrical activity from their own bodies. The students found the exercise enjoyable, believed that they had learned from it, and indicated that it should be a regular part of the course. If electrophysiology in animal preparations is already part of the course, this exercise requires minimal additional equipment, some of which is easily constructed and the reminder of which is available inexpensively.
A potassium gradient in smooth muscle segment of the opossum esophagus.
Authors: Schulze K , Conklin J L , Christensen J
Published: December 2017

Sodium and potassium content were determined in the smooth muscle segment of the opossum esophagus. Extracellular space measurements were also made using inulin and mannitol as markers. The muscle also made using inulin and mannitol as markers. The muscle was sampled at five sites spaced equally along the esophageal segment. On site in the stomach was also examined. The mean tissue sodium content was 36.6 +/- 10.7 meg/kg, and the mean tissue sodium content was 83.5 +/- 2.9 meg/kg wet wt. The mean inulin space was 184 +/- 34 ml/kg, and the mean mannitol space was 249 +/- 20 ml wet wt. The tissue potassium content was found to decline from 48.4 /- 10.1 meg/kg at the proximal site to 23.6 +/- 8.0 meg k/g at the distal site. The slope of electrolyte values from sites 1 through 5 was significant for both potassium and sodium. Extracellular space volume did not differ significantly from one end of the smooth muscle segment to the other.
New method of quantifying ligand binding based on measurement of an induced response.
Authors: Moyle W R , Lee E Y , Bahl O P , Garfink J E , Rodbard D
Published: December 2017

A new general method is proposed for quantifying ligand-receptor interactions using the biological response induced by the ligand as an index of ligand binding. With this method the binding of human chorionic gonadotropin (hCG), several hCG derivatives, and luteinizing hormone (LH) to rat Leydig cells was measured by analysis of the ability of these materials to stimulate testosterone formation. As applied here, hormone dose-response curves were generated in the presence of increasing numbers of cells incubated in vitro in a successful attempt to alter the concentrations of bound and free hormone in the incubation mixture. Measurements of testosterone synthesis as a function of the total amounts of hormone and numbers of cells enabled us to evaluate the concentrations of both bound and free hormone at any constant fractional response (i.e. quarter-, half-, or three-quarter-maximal). We were thus able to measure hormone binding at the extremely low hormone concentrations (1 pM) within the steroidogenic dose-response range under conditions that would not have been possible using currently available radioiodinated hCG preparations. The results obrained confirmed the presence of spare functional receptors. Specific quantitative results are discussed in the text.
Consequences of ventromedial hypothalamic lesions on metabolism of perfused rat liver.
Authors: Karakash C , Hustvedt B E , Lovo A , Le Marchand Y , Jeanrenaud B
Published: December 2017

Metabolism of perfused livers from control and ventromedial hypothalamus (VMH)-lesioned rats has been studied. To eliminate the possibility that observed metabolic abnormalities could be realted to hyperphagia, VMH-lesioned rats were placed on restricted diet matching that of controls. Ten days postoperatively, VMH-lesioned rats had hyperinsulinemia, hypertriglyceridemia, increased blood urea nitrogen levels, together with decreased plasma free fatty acid (FFA) and glucose levels. Insulin release produced in vivo by a glucose load was much higher in VMH-lesioned than in control rats. Perfused livers from VMH-lesioned rats secreted more triglycerides and produced more urea than controls, whereas production of glucose and ketone bodies was reduced. Lipogenesis, newly synthesized triglyceride secretion, and the activity of acetyl-CoA carboxylase and fatty acid synthetase were greatest in livers from VMH-lesioned rats. Fasting abolished hyperinsulinemia and most of these observed metabolic alterations. After treatment with anti-insulin serum, the high rate of lipogenesis observed in livers from VMH-lesioned rats was restored toward normal. It is suggested that hyperinsulinemia may be partly responsible for the metabolic disorders observed in livers from nonhyperphagic VMH-lesioned rats.
Relation between bone mineralization, Ca absorption, and plasma Ca in phosphonate-treated rats.
Authors: Trechsel U , Schenk R , Bonjour J P , Russell R G , Fleisch H
Published: December 2017

Disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) is known to inhibit the crystallization of calcium phosphate salts in vitro. Large doses of EHDP administered in vivo inhibit skeletal mineralization, decrease intestinal calcium absorption, and produce hypercalcemia. In the present study, EHDP or one of 13 other phosphonates were given to rats at 10 mg P/kg-day sc for 7 days in order to better define the nature of the relationship between bone mineralization, intestinal absorption, and plasma calcium in the regulation of calcium homeostasis. Each of the phosphonates which inhibited skeletal mineralization in vivo also inhibited crystallization in vitro, but the converse was not true. A very close correlation was found between inhibition of skeletal mineralization, decreased intestinal calcium absorption, and slight hypercalcemia. A dose-response study with two compounds also revealed the same close correlation. It is argued that the impairment of intestinal calcium absorption in phosphonate-treated rats may represent a secondary homeostatic response to the primary effect of the drugs on bone mineralization. This response may be mediated by an elevation of a fraction of plasma calcium.
Actions of cholecystokinin octapeptide on smooth muscle of isolated dog intestine.
Authors: Stewart J J , Burks T F
Published: December 2017

Adult dogs were anesthetized and segments of small intestine were isolated and perfused via a mesenteric artery with Krebs-bicarbonate solution. Muscle responses along the circular and longitudinal axes were monitored with extraluminal strain gauge transducers. Agonists were administered as intraarterial bolus injections in volumes not exceeding 0.1 ml. Antagonists were dissolved in the Krebs perfusion solution. The C-terminal octapeptide of cholecystokinin (CCK-OP) produced dose-related tonic and phasic contractions of smooth muscle along the transverse axis and tonic and phasic relaxations along the longitudinal axis of the muscle segments. Smooth muscle responses to CCK-OP were reduced by atropine sulfate (0.1 mug/ml) and minimally affected by hexamethonium (10 mug/ml) perfusion. Tetrodotoxin (TTX, 5 ng/ml) selectively reduced muscle responses to dimethylphenylpiperazinium (0.5 mug) and CCK-OP (0.2 mug) but failed to alter responses to bethanechol (BeCh, 5 mug). Higher concentrations of TTX (10 ng/ml) abolished responses to CCK-OP. Depolarizing doses of nicotine (500 mug) selectively antagonized responses to 5-hydroxytryptamine (5HT, 5 mug) and CCK-OP (0.2 mug) but did not alter responses to BeCh (5 mug). Perfusion with tetraethylammonium (1 mg/ml) reduced muscle responses to depolarizing doses of nicotine and abolished the nicotine-induced antagonism of 5HT and CCK-OP. The intestinal smooth muscle response to CCK-OP in the dog is mediated through a neurogenic mechanism. CCK-OP interacts with a nonnicotinic receptor on postganglionic cholinergic neural elements in this preparation.
Bovine pancreatic peptide: action on gastric and pancreatic secretion in dogs.
Authors: Lin T M , Evans D C , Chance R E , Spray G F
Published: December 2017

Bovine pancreatic peptide (BPP) is a straight chain peptide containing 36 amino acid residues that has recently been isolated from pancreatic tissue. At a dose of 40 mug/kg-h intravenously, it stimulated gastric acid secretion when given alone but inhibited the submaximal secretion induced by the C-terminal pentapeptide of gastrin. Basal pancreatic secretion of dogs was inhibited by BPP (1-10 mug/kg-h) inhibited pancreatic protein secretion but often showed a biphasic action on water-bicarbonate response, an initial augmentation followed by reduction. BPP (2-5 mug/kg-h) inhibited pancreatic water-bicarbonate and protein secretions induced by an infusion of secretin plus cholecystokinin. Des-tyrosyl-NH2 BPP lacking the C-terminal tyrosyl amide, failed to inhibit gastric acid induced by C-terminal pentapeptide of gastrin or pancreatic secretion induced by secretin. BPP had no hyper- or hypoglycemic, hyperkalemic, or diuretic actions in the dog.
Regulatory mechanisms of hepatic phosphorylase in fetal and neonatal livers of rats.
Authors: Biondi R , Viola-Magni M P
Published: December 2017

Active phosphorylase was determined in rat livers during the end of the fetal period and the first days of life. This enzyme increases between the 16th day of gestation and birth. After birth, another increase in observed that takes place with 6 h. In the neonatal liver, the rapid increase in active phosphorylase, is inhibited by high levels of blood glucose, but is unaffected by actinomycin D. In fetal liver glucagon administration is followed after 5 h by an increase in total phosphorylase with only a small increase in active phosphorylase; this effect is blocked by actinomycin D. The fetal changes are interpreted as de novo synthesis, whereas the neonatal increase is due to an activation of inactive phosphorylase. Both enzymatic changes appear to be regulated by glycogen. The role of phosphorylase in the regulation of glycogen metabolism in neonatal liver is discussed.
Effects of calcium on renin and aldosterone in the rat.
Authors: Kotchen T A , Galla J H , Luke R G
Published: December 2017

CaCl2 suppresses the plasma renin activity (PRA) response to Na+ deprivation in the rat. The purpose of the present study is:1) to determine if the effect of Ca2+ on PRA is modified by the anion delivered with Ca2+, and 2) to evaluate the effect of Ca2+ loading on aldosterone production. PRA and in vitro aldosterone production by adrenal quarters were measured after a 7-day balance study. On a low Na+ diet, PRA of animals drinking 1% CaCl2 (13.1 ng/ml per h +/- 1.3 SE), but not of animals drinking 1% calcium gluconate, was suppressed (P less than 0.05) compared to that of water-drinking controls (20.9 ng/ml per h +/- 2.1 SE). Aldosterone production of calcium gluconate and CaCl2-loaded animals was greater than that of controls (P less than 0.01). K+ balance of CaCl2 and calcium gluconate-drinking animals was more positive than that of controls (P less than 0.05). In conclusion, inhibition of PRA by CaCl2 but not by calcium gluconate indicates that the effect of Ca2+ on PRA is modified by the accompanying anion. Both CaCl2 and calcium gluconate stimulate aldosterone production, independent of changes in PRA, possibly due to an effect of Ca2+ on K+ balance.
Epithelial cell extrusion during fluid transport in canine small intestine.
Authors: Lee J S
Published: December 2017

Epithelial cell extrusion during fluid transport was studied under both in vitro and in vivo conditions. The rate of cell extrusion from the villus tips in vitro increased by about onefold in the villi with obstruction of lymph flow associated with the increase of lymph and tissue fluid pressure. When lymph pressure in the jejunal and ileal villi was increased to 6.4 +/- .2 and 12.3 +/- .5 mmHg, respectively, by injection of Ringer solution into the central lacteals, fluid leaked out of the villi and a shedding of epithelium occurred. Vigorous villus spasmodic contraction induced by cocaine or atropine also caused a shedding of epithelium. Cells always appeared in the lumen of intestine in vivo either during fluid absorption or secretion. A copious secretion of fluid, increase of cell loss, and congestion of blood in the villi occurred by the action of cholera toxin, MgSO4, and choline chloride. The rate of cell loss was highest during fluid secretion induced by an elevation of tissue fluid pressure such as at high venous pressure or during intra-arterial histamine infusion. It is thus concluded that elevated tissue fluid pressure is involved in epithelial cell extrusion during fluid transport.
Glucose and lactate kinetics in burn shock.
Authors: Wolfe R R , Miller H I , Spitzer J J
Published: December 2017

We studied the glucose and lactate kinetics during burn shock by means of the primed constant infusion of [6-3H]glucose and Na-L-(+)-[U-14C]lactate. We found an early postburn hyperglycemia that was due to an increased rate of appearance (Ra) of glucose. Later, the ability of the tissues to extract glucose became impaired, and the plasma glucose concentration increased even more in spite of the return of Ra of glucose to the control level. The Ra of lactate rose rapidly postburn, whereas the rate of disappearance (Rd) of lactate stayed at the control level for 30 min. Consequently, plasma lactate rose approximately 350%. After 30 min, Rd of lactate increased to the same level as Ra; and Ra, Rd, plasma lactate concentration, and the percent of glucose derived from lactate remained elevated for the duration of the experiment. These results indicate an important role of lactate in burn shock metabolism and substrate kinetics.
Temperature dependence of responses of esophageal smooth muscle to electrical field stimulation.
Authors: De Carle D J , Szabo A C , Christensen J
Published: December 2017

Strips of smooth muscle, cut transversely from the smooth-muscle segment of opossum esophagus, were superfused with oxygenated Krebs-Ringer solution at 37 degrees C in a system that allowed electrical field stimulation of the intrinsic nerves. Three-to-five-second trains of rectangular pulses (0.5 ms long at 10 Hz) were delivered at 30-s intervals at supramaximal maximal current strength. In strips from the esophageal body, each train resulted in a twitch which followed after the end of train with a particular latency, the off-response. Strips from the esophagogastric sphincter relaxed during the train. Temperature was varied above and below 37 degrees C to observe the temperature dependence of the responses. Latency of the off-response varied exponentially with temperature. Amplitude of the off-response showed a linear decline with changes in temperature, both above and below 35 degrees C, the zero-intercepts being 19.6 and 42.3 degrees C, respectively. Amplitude of relaxation of strips from the junction varied little between 20 and 37 degree C but declined sharply beyond those limits, the zero-intercepts being 14.2 and 42 degrees C, respectively.
Effect of glucagon on thermogenesis in the pigeon.
Authors: Hohtola E , Hissa R , Saarela S
Published: December 2017

The effects of glucagon injection on temperature regulation and some metabolic parameters were studied in the pigeon. Glucagon (100 microng/kg) always inhibited shivering and caused a fall in the oxygen consumption and body temperature of the unanesthetized pigeon at + 6 degrees C. At + 34 degrees C, the same dose of glucagon had no effect on these parameters. At 22 degrees C, glucagon produced an elevation in plasma free fatty acid (FFA) and blood glucose levels. The rise in FFA at 22 degrees C coincided with the suppression of shivering at 6 degrees C. The glucagon-mediated rise in plasma FFA, but not glucose level, was potentiated by cold ambient temperature. Adrenergic blocking agents given prior to glucagon did not abolish its effects. Phentolamine even prolonged the absence and accelerated the suppression of shivering. A dissociation in the mechanisms by which catecholamines and glucagon suppress shivering is suggested. Although mobilizing energy reserves, glucagon does not seem to be calorigenic in the pigeon at this dose. The interpretation of the changes in plasma FFA levels is discussed in relation to fuel consumption during shivering.
Compartment analysis of metabolism of chromium(III) in rats of various ages.
Authors: Onkelinx C
Published: December 2017

The metabolism of chromium(III) was studied in groups of female Wistar rats of various ages (35, 60, and 120 days) after a single intravenous injection of 51CrCl3 in trace amounts. In all the animals, the plasma disappearance curve could be adequately described by a sum of three exponential terms between 0 and 265 h postinjection. A three-compartment mammillary model is proposed that permits the description of Cr(III) metabolism in quantitative terms. The model defines compartment volumes, clearances by exchange, and clearances by excretion. The total excretory clearance is the sum of three components: urinary clearance (fu), fecal clearance (fd), and a residual clearance (fs), corresponding to an apparently irreversible deposition of chromium into long term body reservoirs. The parameters of the model are reported for each age group; when their values are expressed per 100 g of body wt, all the components of the excretory clearance decrease with age. In all cases elimination takes place primarily via the urine and fs accounts for 31-41% of the total excretory clearance. Consistent with the model, 51Cr was found to accumulate with time in several organs such as bone, kidney, spleen, and liver after a single intravenous injection of 51CrCl3.
Migrating action potential complex of cholera: a possible prostaglandin-induced response.
Authors: Mathias J R , Carlson G M , Bertiger G , Martin J L , Cohen S
Published: December 2017

Distal ileal loops of New Zealand white rabbits exposed to cholera toxin demonstrated the presence of a highly organized myoelectric pattern defined as the migrating action potential complex (MAPC). We investigated the mechanism by which cholera enterotoxin stimulates MAPC activity. Certain anti-inflammatory drugs have altered the secretory component of cholera diarrhea. We investigated effects of these anti-inflammatory drugs on the MAPC. Indomethacin, 5.0 mg/kg iv, abolished all MAPC activity. Indomethacin, 1.5 mg/kg iv, or acetylsalicylic acid, 150 mg/kg given intragastrically, altered propagation velocity and at times its direction of propagation, but did not abolish the MAPC. An infusion of prostaglandin F2alpha, 2 microng/kg per min intraluminally, induced MAPC activity similar to that of the cholera complex. Indomethacin, 5.0 mg/kg iv, produced no significant changes in number of complexes or propagation velocity. These observations suggested that inhibition of the cholera complex by indomethacin may result from the alteration of prostaglandin synthesis and that prostaglandins may initiate the motility component of cholera diarrhea.
Longitudinal force and stress of rat's esophagus: age-related changes.
Authors: Zabinski M P , Biancani P
Published: December 2017

Longitudinal force-length relationship of the rat esophagus was studied in vitro in three age groups: 1 mo, 3 mo, and 12 mo. The length of maximum force development (MFD) occurs at 1.4-1.5 times the in vivo length for all age groups. The active force developed at MFD increases markedly with age. The difference in the active forces in the 3-mo and 12-mo age groups is due to differences in cross section because the active stress of the esophagus in the longitudinal direction is approximately equal for the two age groups. The active stress in the 1-mo-old rats is lower than in the 3-mo-old rats, suggesting an increased contractility of the esophagus with age in this period of development.
Neural control of glycogen content and its diurnal rhythm in mouse pineal cell.
Authors: Kachi T , Ito T
Published: December 2017

In adult male dd mice, possible mechanisms regulating the glycogen content in the pineal cell were investigated by a semiquantitative histochemical method, with particular reference to the role of the sympathetic innervation. Reserpine, superior cervical ganglionectomy (SCGX), or decentralization of the ganglia (DC), as well as continuous light, prevented the nocturnal decrease in the glycogen content, causing a marked increase, and caused a gradual decrease in the size of the pineal cell. In the SCGX or DC group, the glycogen content reached a peak at 2 days and then decreased gradually. The nocturnal decrease was also prevented by propranolol. Noradrenaline caused a marked decrease in the glycogen content. These findings support the hypothesis that the glycogen metabolism and its diurnal rhythm in the pineal cell are regulated by the sympathetic nerve terminals innervating the pineal gland, presumably by the release of noradrenaline. In addition, the nature of the internal mechanism in the organism generating the pineal glycogen rhythm was examined. Light was considered to induce a phase shift in such a mechanism, but reserpine was not.
A comparison of effect of insulin on hepatic metabolites, gluconeogenesis, and ketogenesis.
Authors: McDaniel H G
Published: December 2017

In 12-h fasted rats given tryptophan, insulin decreased the hepatic content of alanine and the three precursors of oxalacetate-malate, citrate, and aspartate-while elevating hepatic pyruvate. These changes are consistent with suppression of the pyruvate carboxylase step. Animals fasted for 24 h lose the effect on oxalacetate precursors, and this correlates with a loss of suppression of hepatic ketones. The decrease in hepatic alanine and oxalacetate precursors is more sensitive than the blood sugar. However, the conversion of labeled lactate to glucose is not inhibited by insulin in 12-h fasted animals. (+)-Decanoylcarnitine also produces a decrease in oxalacetate precursors comparable to insulin and a lowering of the blood sugar. However, in fasted animals not given tryptophan it does not alter the blood sugar. Therefore, in tryptophan-treated animals alterations of fatty acid oxidation by insulin or (+)-decanoylcarnitine produce a fall in oxalacetate precursors consistent with inhibition of pyruvate carboxylase but this does not equate with overall suppression of gluconeogenesis by either of these agents in the absence of tryptophan.
Uptake of amino acids by islet of Langerhans and other tissues of the toadfish.
Authors: Cooperstein S J , Lazarow A
Published: December 2017

The uptake of injected radioactive amino acids by the isolated islet and other tissues of the toadfish has been examined. The islet and most other tissues appear to actively transport most amino acids and, of the tissues studied, the islet is one of the most active in this regard. Most tissues accumulated the dicarboxylic acids to the greatest extent, with the basic amino acids and the neutral amino acids with unbranched side chains also being taken up well. However, each tissue showed a unique pattern of uptake of the different amino acids, and islet was distinguished by its high uptake of glycine 15 min after injection. The pattern of uptake of amino acids by toadfish islet does not appear to be related to their relative ability to stimulate insulin release from islets of other species or to their relative rates of metabolism, but does correlate well with the content of free amino acids in mouse islets and with the sum of the amino acid contents of anglerfish proinsulin and proglucagon.
Log linear relationship between plasma arginine vasopressin and plasma osmolality.
Authors: Weitzman R E , Fisher D A
Published: December 2017

The integrated plasma arginine vasopressin concentration (IpAVP) was determined by pooling the results of single samples collected every 3 min for 0.5 h in dehydrated, randomly hydrated, and water-loaded sheep. A linear relationship was observed between the log of the integrated AVP concentration and plasma osmolality. This relationship was tested by the bolus injection of 20 g/100 ml NaCl to both water-loaded and randomly hydrated sheep. The rise in the log of IpAVP divided by the rise in plasma osmolality was similar in both groups (P greater than 0.5) and was superimposable upon the regression line derived from steady-state observations. The data would suggest that AVP is released as an exponential function of plasma osmolality rather than as a threshold phenomenon.
Protein degradation in muscle: response to feeding and fasting in growing rats.
Authors: Wassner S J , Orloff S , Holliday M A
Published: December 2017

Degradation rates of muscle proteins were determined in young rats allowed access to standard rat chow 12 h/day. degradation was assessed by determination of 3-methylhistidine (3MH) excretion rates. 3MH is a nonreutilized amino acid produced almost exclusively within the actin and myosin of skeletal and cardiac muscle. Because plasma levels of 3MH are low and renal clearance is high, excretion reflects myofibrillar degradative rates. Excretion of 3MH was determined for 4-h periods beginning 12 and 20 h after initiation of feeding and after 24-and 48-h fasts. Excretion of 3MH per 4-h period increased with time after the last feeding. Because creatinine excretion is a function of muscle mass dividing 3MH excretion by creatinine excretion represents myofibrillar degradation per unit muscle mass, the fractional degradative rate. Degradation rates rose from 4.6 to 14.5%/day between 12 and 16 and 60 and 64 h after the beginning of the last meal. These results support the presence of a diurnal pattern of protein degradation as well as increased muscle degradation during starvation.
Functional abnormalities of islets of Langerhans of obese hyperglycemic mouse.
Authors: Lavine R L , Voyles N , Perrino P V , Recant L
Published: December 2017

Glucose-induced insulin release was studied in vitro with isolated islets of Langerhans obtained from obese hyperglycemic C57Bl/6J-ob/ob (ob/ob) and lean C57Bl/6J-+/+ (control) mice. The threshold concentrations of glucose for insulin release were determined. In addition, the effect of total fast and of chronic food restriction on in vitro insulin release were studied. The following was observed: 1) with fasting, islet volume decreased. Islets obtained from ob/ob mice were larger than control islets, except for the chronic food restricted group. 2) Ob/ob islets were more sensitive to glucose than were controls in that the threshold for glucose-induced insulin release occured at lower glucose concentrations. 3) Fasting for 48 h completely abolished glucose-induced insulin release in control islets, whereas glucose-induced insulin release was maintained in 48-h and 7-day fasted ob/ob islets. 4) The increased glucose sensitivity of the ob/ob islets was maintained despite chronic food restriction.
Mechanism of triiodothyronine-induced creatinuria in the rat.
Authors: Kurahashi M , Kuroshima A
Published: December 2017

Mechanism of triiodothyronine (T3)-induced creatinuria was studied in rats after a single injection of T3 (100 microgram/100 g per s). Urinary creatine excretion increased markedly during the 1st day after T3 injection. Peak of creatinuria was observed during the 2nd day after T3 injection. Excretions of nonprotein nitrogen and potassium were not different between control and T3-injected animals throughout the experimental period. Creatine reabsorption in the kidney was not influenced by T3 treatment. Radioactive creatines in both plasma and urine after [14C]creatine injection were higher in T3-injected animals than in controls, whereas the uptake of radioactive creatine by muscle was lower in the former. Creatine content in muscles decreased significantly 48 h after T3 injection. Moreover, T3 increased a fraction derived from muscle in urinary creatine, but it did not influence that derived from creatine synthesized de novo. These results suggest that both decreased creatine uptake by muscle and increased release of creatine from muscle play important roles in T3-induced creatinuria.
Adrenergic control of pineal N-acetyltransferase activity: developmental aspects.
Authors: Yuwiler A , Klein D C , Buda M , Weller J L
Published: December 2017

The activity of pineal N-acetyltransferase in the neonatal rat does not exhibit the large daily rhythm seen in the adult and is intermediate between the low day and high night adult values. These intermediate values appear to result from adrenergic stimulation. Blockade of adrenergic receptors or of catecholamine synthesis results in a decrease in enzyme activity in vivo. In vitro studies provide additional evidence of a completely developed postsynaptic adrenergic control system for pineal N-acetyltransferase activity at birth. Our observations indicate that the appearance of a circadian rhythm in pineal N-acetyltransferase at the end of the first week of life reflects the development of presynaptic mechanisms and structures necessary for the control of catecholamine release and uptake. These events follow the developmental appearance of the postsynaptic mechanisms required to mediate the adrenergic-cycle AMP regulation of pineal N-acetyltransferase activity, which can be detected prior to birth.
Esophageal manometry in the opossum.
Authors: Schulze K , Dodds W J , Christensen J , Wood J D
Published: December 2017

The opossum esophagus is commonly used as an animal model of the human esophagus. We used esophageal manometry in normal animals to provide basal data about normal esophageal motor functions in vivo in this species. At rest, separate and distinct high pressure zones can be recorded at the level of the lower esophageal sphincter, diaphragmatic hiatus, aortic arch, and upper esophageal sphincter. Each zone demonstrates a characteristic pattern of pressures in the radii of the coronal section and a characteristic response to swallowing. The hiatal and aortic zones can be mistaken for the esophageal sphincters. Pressures in the sphincters fall with swallowing. Peristalsis is not bolus-dependent and occurs with 98% of swallows. Pressures generated by peristalsis are greater in the middle of the esophagus than at the ends. Values for resting lower esophageal sphincter pressure and the characteristics of peristalsis were reproducible between different studies in the same animals.
Gluconeogenesis in the suckling rat.
Authors: Beaudry M A , Chiasson J L , Exton J H
Published: December 2017

Gluconeogenesis from lactate was increased more than twofold in perfused livers and isolated hepatocytes from 10- and 15-day-old suckling rats compared with adult rats and was not increased by fasting. Glucagon (10(-19)-10(-7) M) induced minimal activation of gluconeogenesis in hepatocytes from such animals even though it promoted accumulation of cAMP. Suckling rats had low plasma insulin levels and high plasma glucagon levels. The presented very low insulin/glucagon ratios were associated with high liver cAMP levels. Contrary to the situation in adult rats, glucagon levels fell with fasting. Insulin levels fell proportionally further so that the insulin/glucagon ratios declined. On the basis of these findings, it is proposed that the high glucagon and low insulin levels in young suckling rats result in high liver cAMP levels with resultant maximal stimulation of hepatic gluconeogenesis so that it cannot be further increased by fasting or exogenous glucagon. It is also suggested that milk is an important stimulus to the hyperglucagonemia of suckling rats in view of its high protein and low carbohydrate content.
Histamine H1- and H2-receptor vasodilation of canine intestinal circulation.
Authors: Pawlik W , Tague L L , Tepperman B L , Miller T A , Jacobson E D
Published: December 2017

Studies were conducted in anesthetized dogs to determine whether the mesenteric vasodilator response to histamine is mediated by H1 receptors alone or whether H2 receptors are also involved in the response. Evidence favoring a role for both receptors included: 1) the vasodilator response to histamine was inhibited by either the H1-receptor antagonist, tripelennamine, or the H2-receptor antagonist, metiamide; 2) both the H1 agonist, 2-methylhistamine, and the H2 agonist, 4-methylhistamine, induced dilator responses in the mesenteric circulation; and 3) two temporal patterns of vasodilation could be distinguished, namely a transient spike and subsequent fade of blood flow (seen with either the H1 agonist or with histamine after H2-receptor blockade) and a sustained and stable increase in flow (seen with either the H2 agonist or with histamine after H1 blockade). Metiamide appeared to be a potent inhibitor of the mesenteric vasodilator response to histamine at least equal to tripelennamine.