bluuebunny/crossref_metadata_2025 huggingface dataset:
Ventilatory control (Ventrol) simulation for education.
Authors: Boyle J
Published: December 2017

An educational microcomputer-based simulation of respiratory control has been developed. The program contains three major sections: tutorial, stimulation, and unknown testing. The tutorial section provides a brief discussion of the major factors involved in respiratory control. The simulation section provides a menu of variables to demonstrate the effects of altering inspired gases, changing compliance or airway resistance, metabolic acidosis, neural activity, and lesions (including vagotomy) or exercise. The last section of the program allows students to test their understanding of abnormal respiratory and blood gas values. The program has been used as a problem-solving exercise in a medical physiology course. Student groups were assigned to a microcomputer and given a specific problem during a regularly scheduled laboratory period. The students collected data using the program, analyzed and graphed or tabulated the results, and presented their findings in a minisymposium format to their fellow students. This approach has proven valuable and provides a number of pedagogical benefits that are lacking in a lecture-based basic science curriculum.
Keeping community college faculty current in physiology through utilization of health science center expertise.
Authors: Smith D S
Published: December 2017

The maintenance of current knowledge in physiology in community colleges is very difficult to accomplish. The absence of a research environment, limited library facilities, and heavy teaching loads often result in the instructor utilizing the teaching textbook as the primary source of information. A cooperative program between The University of Texas Health Science Center at San Antonio and San Antonio Community College has been developed in which the Health Science Center faculty present updated seminars in physiology topics for the community college faculty. This program has been in existence for three years and has proved to be very effective in improving the quality of the physiology curriculum at the community college.
Interactive videodisc calorimetry simulations for exercise physiology laboratories.
Authors: Misner J E , Geeseman R , Michael M E
Published: December 2017

Six interactive videodisc lessons for college-level exercise physiology classes were developed. The six lessons were written using TenCore for the IBM M-Motion technology. The focus of the laboratories is on exercise metabolism measured by indirect calorimetry. The six lessons are as follows. 1) Environmental measures: determines whether conditions are favorable for exercise. Dry bulb, wet bulb, and black globe temperatures are obtained to calculate relative humidity, STPD gas volumes, and the wet bulb-globe temperature index. 2) Basal metabolism: emphasizes the mechanics of calculating energy expenditure through indirect calorimetry. Lying, sitting, and exercise metabolism are compared. 3) Submaximal metabolism: compares the energy cost of walking a mile and running a mile. Steady-state exercise, oxygen debt, and oxygen deficit are explored. 4) Maximal metabolism: assesses maximal oxygen consumption using the Bruce protocol. 5) Hormonal responses to prolonged exercise: demonstrates the effect of hormonal levels on %fat and %carbohydrate utilization during 1 h of exercise. 6) Metabolic responses to supramaximal exercise: estimates anaerobic power using the Wingate test.
Looking forward to change
Authors: Hansen Penelope A.
Published: December 2017

This editorial outlines the changes in content and format for the journal over the next year.
Responsible conduct of scientific research: a one-semester course for graduate students.
Authors: Hoshiko T
Published: December 2017

This course was developed to satisfy in part the requirement that "a program in the principles of scientific integrity" be a part of any training program funded by the National Institutes of Health (NIH) or the Alcohol, Drug Abuse, and Mental Health Administration (NIH "Guide for Grants and Contracts," vol. 18, no. 45, 1989). The booklet On Being A Scientist (National Academy of Sciences, 1989) was chosen as required reading. The issues were presented in 15 1-h sessions. Public policy issues were not addressed. A danger was to be overly critical of scientific misconduct and stimulate a cynical skepticism of the integrity of the working scientist. One problem is that there are only general procedures a student can follow when encountering misconduct. Numerous guest speakers provided depth, objectivity, and authenticity to the discussion.
Educational puzzles for understanding gastrointestinal physiology.
Authors: Bailey C M , Hsu C T , DiCarlo S E
Published: December 2017

We developed four innovative, creative, and fun educational tools to promote active learning, enhance problem-solving skills, and encourage small group discussion. Furthermore, the tools encourage deductive reasoning and critical thinking rather than passive memorization of material. The tools include crossword puzzles, hidden messages, word scrambles, and word searches. These tools were developed using two computer programs: the Crossword Construction Kit and The New Puzzle Factory. Instructors are encouraged to optimize the value of the tools by using the additional options presented at the end of each of the puzzles. The additional options encourage students to become active learners by creating their own tools. Although the principles of these four tools can be adapted to many disciplines, these specific games focused on gastrointestinal physiology. Our goal was to create tools that can be used either inside or outside the classroom to complement and enhance the lecture.
Learning physiology through service.
Authors: Tong E Y
Published: December 2017

A service-learning component has been successfully incorporated into an introductory physiology course at Wheaton College. In addition to regular course work, each of the 24 students spent 12 hours shadowing and assisting staff at Sturdy Memorial Hospital, Attleboro, MA, with 4 hours in the emergency room and 8 hours in two other departments. Every student kept a log of his or her observations, reactions, and learning in the field and wrote a paper on a pathophysiological condition encountered in the hospital. To compare and contrast the real hospital experience with a fictional one, the students also studied patients from the television show ER. Each week in lab, two students showed a short videotape of one particular patient and discussed the diagnosis, symptoms, treatments, and surgical procedures involved. Questionnaire evaluations indicated that this program is effective in helping students learn more physiology and exposing them to community service. Health workers and patients also agreed that providing social support to patients while shadowing and assisting hospital staff was a valuable service.
Undergraduate students' misconceptions about respiratory physiology.
Authors: Michael J A , Richardson D , Rovick A , Modell H , Bruce D , Horwitz B , Hudson M , Silverthorn D , Whitescarver S , Williams S
Published: December 2017

Approximately 700 undergraduates studying physiology at community colleges, a liberal arts college, and universities were surveyed to determine the prevalence of our misconceptions about respiratory phenomena. A misconception about the changes in breathing frequency and tidal volume (physiological variables whose changes can be directly sensed) that result in increased minute ventilation was found to be present in this population with comparable prevalence (approximately 60%) to that seen in a previous study. Three other misconceptions involving phenomena that cannot be experienced directly and therefore were most likely learned in some educational setting were found to be of varying prevalence. Nearly 90% of the students exhibited a misconception about the relationship between arterial oxygen partial pressure and hemoglobin saturation. Sixty-six percent of the students believed that increasing alveolar oxygen partial pressure leads to a decrease in alveolar carbon dioxide partial pressure. Nearly 33% of the population misunderstood the relationship between metabolism and ventilation. The possible origins of these respiratory misconceptions are discussed and suggestions for how to prevent and/or remediate them are proposed.
Integration of myofilament response to Ca2+ with cardiac pump regulation and pump dynamics.
Authors: Solaro R J
Published: December 2017

In this paper I present some ideas related to teaching cardiac pump dynamics and regulation to first-year medical students. I emphasize explicit presentation of the relation between the activity of the contractile machine in the myocytes to pump dynamics, pressure-volume relations, and cardiac output regulation, with matching oxygen supply to tissue demands serving as a focal point. Important ideas here are 1) the concept that regulation is at the cellular level of regulation; 2) that force and shortening properties of the cells are ultimately dependent on the number of cross bridges reacting with the thin filament and on the rate of cross-bridge cycling; 3) that the concepts of preload, aferload, and contractility originated in studies of muscle mechanics; 4) that there is a reserve of force-generating cross bridges, i.e., the myofilaments are not fully activated by Ca2+ in the basal state, and that force-generating cross bridges can themselves activate the thin filament; and 5) that length dependence of myofilament Ca2+ activation is important in the cellular basis of Starling's law of the heart. The elaboration of these processes serves to elucidate how these mechanisms play a role in coupling tissue oxygen demands to supply.
Learning the regulation of peripheral blood flow.
Authors: Sparks H V
Published: December 2017

Students can learn a great deal about the peripheral circulation when teaching is based on five building blocks: hemodynamic principles, neurohumoral control, and three elements of local control of blood flow (metabolic, myogenic, and paracrine). Study of a particular special circulation starts with the application of these building blocks in the context of the function of that tissue. For example, control of skin blood flow is largely concerned with regulation of body temperature (neurohumoral control) and the response to injury (paracrine control). Regulation of coronary blood flow is almost entirely a matter of meeting the metabolic needs of the myocardium (metabolic control). By mixing and matching the five building blocks and keeping in mind the special functions of a particular tissue, students can master the peripheral circulation efficiently.
Cardiovascular response to exercise.
Authors: Laughlin M H
Published: December 2017

This article is intended for instructors who teach cardiovascular physiology. In our physiology course exercise physiology is used as a tool to review and integrate cardiovascular and respiratory physiology. It is assumed that the students already have mastered the fundamentals of cardiovascular and respiratory physiology. Because this paper is part of a cardiovascular refresher course, I have deleted much of the respiratory physiology. The objectives of this presentation are for the student to 1) understand the relationship between maximal oxygen consumption and endurance during sustained exercise and be able to define "maximal oxygen consumption"; 2) understand the determinants of of maximal oxygen consumption; 3) understand the effects of dynamic exercise on the cardiovascular system and mechanisms for these effects; 4) understand the relationships between exercise intensity and major cardiorespiratory parameters, including heart rate, cardiac output, blood flow distribution, left ventricular stroke volume, arterial pressures, total peripheral resistance, and arterial and venous blood oxygen content; 5) be able to compare and contrast the cardiovascular effects of dynamic and isometric exercise in man and the mechanisms responsible for the major differences; and 6) be able to apply knowledge of the cardiovascular effects of exercise to understanding the causes of cardiovascular symptoms in disease and in diagnosis of disease states. This material contains many areas that stimulate discussion with students and allow exploration of concepts that are challenging for the student. This give and take between teachers and student is difficult to summarize in an article of this sort. Therefore, subjects that in my experience often stimulate questions and discussion with the students are indicated in the text.
Common misconceptions that arise in the first-year medical physiology curriculum concerning heart failure.
Authors: Hintze T M , Zhao G
Published: December 2017

There are a number of misconceptions that first-year medical students have concerning the pathophysiology of heart failure. These stem from 1) a poor definition of heart failure, 2) a lack of care in distinguishing between similar but distinct concepts, and 3) the inability to recognize the relationship between the various stages of heart failure and the clinical manifestation of the disease. In this paper we provide a list of some of the misconceptions that we have encountered, some explanations of the distinctions to be made, and some of the rationale behind current surgical procedures and drug treatment. The misconceptions include failing to differentiate between the Frank-Starling mechanism and cardiac dilation as well as not grasping the significance that changes in cardiac beta-receptor function have in limiting the positive inotropic actions of circulating catecholamines. Finally, we review some of the altered neurohumoral mechanisms in heart failure and explain the basis for some common therapeutic approaches, including the use of angiotensin-converting enzyme inhibitors, in this disease.
Teaching critical thinking skills in physiology.
Authors: McNeal A P , Mierson S
Published: December 2017

This is a report of a workshop presented at Experimental Biology '99 on April 18, 1999, in Washington, DC.
A simple, inexpensive method for teaching how membrane potentials are generated.
Authors: Moran W M , Denton J , Wilson K , Williams M , Runge S W
Published: December 2017

We have developed a simple laboratory exercise that uses an inexpensive dialysis membrane (molecular weight cutoff = 100) to illustrate the generation of membrane potentials (Vm) across plasma membranes of animal cells. A piece of membrane approximately 2.0 cm2 is mounted in an Ussing-like chamber. One chamber half is designated cytosol and the other half external. Chamber sidedness helps students relate their findings to those of real cells. As in real cells, outward directed K+ concentration gradients [high cytosolic K+ concentration ([K+]c) and low extracellular K+ concentration] generate cytosol electrically negative Vm with a slope of approximately -45 mV/decade change in [K+]c. The polarity of Vm reflects the outward flow of potassium ions because flow of the larger counterion, H2PO4-, is restricted to the pores in the membrane. A slope less than Nernstian (<59 mV/decade) suggests that the membrane is slightly permeable to H2PO4-. Importantly, this facilitates teaching the use of the Nernst equation to quantify the relationship between ion concentration ratios across membranes and magnitude of Vm. For example, students use their data and calculate a permeability ratio PK/PH2PO4 that corresponds to a slope of approximately 24% less than Nernstian. This calculation shows that Nernstian slopes are achieved only when permeability to the counterion is zero. Finally, students use the concept of membrane capacitance to calculate the number of ions that cross the membrane. They learn where these ions are located and why the bulk solutions conform to the principle of electroneutrality.
Report of the worldwide survey on teaching physiology.
Authors: Somjen G G
Published: December 2017

This report by George G. Somjen, for the Commission on Teaching Physiology, International Union of Physiological Sciences, presents a summary of answers received to a questionnaire concerning the state of Physiology Teaching. One hundred seventeen responses have been received from fifty countries. The results have been tabulated and contain information about the teaching methods and resources as well as the commitment in time and effort by the teaching staff. Free-ranging, sometimes pithy, comments made by the respondents have been excerpted and are included.
Involving students in question writing: a unique feedback with fringe benefits.
Authors: Sircar S S , Tandon O P
Published: December 2017

A contest on question writing was organized during the undergraduate medical physiology teaching program. Students were asked to write and submit multiple-choice questions of the assertion-reasoning type (type E) in physiology. The winners were decided after the questions submitted were graded on a six-point scale (0-5) that considered both thematic novelty and construct correctness. Of the 100 students in the class, 37 participated in the contest, and a total of 912 questions was received. The contest encouraged the students to go through their subjects critically. The questions provided the instructor with insight into the learning habits and misconceptions of the students and provided the grist for animated discussions in tutorial classes. Although several types of errors were deciphered in these questions, with suitable modifications the questions helped the faculty build up a sizable question bank.
Fatty acid oxidation by isolated perfused working hearts of aged rats.
Authors: Abu-Erreish G M , Neely J R , Whitmer J T , Whitman V , Sanadi D R
Published: December 2017

It has been reported that mitochondria isolated from hearts of old rats have lower respiratory activity than mitochondria from young rats. In order to determine the physiological correlates of these changes, the metabolism of hearts from young and old rats has been compared in a perfused working heart preparation. The oxidation of [14C]palmitate to 14CO2, oxygen consumption, and nucleotide levels were measured under different cardiac workloads. The hearts from old animals performed less cardiac work and utilized less oxygen and palmitate in proportion to tissue mass, but the ratio of oxygen consumed to pressure developed was unaltered. There was a small but significant decrease in cardiac efficiency expressed as the ratio between the rate of oxygen consumed and ventricular pressure development. Tissue levels of total carnitine and long-chain acylcarnitine derivatives were greatly reduced in the older heart without significant change in free CoA, acetyl-CoA, or long-chain acyl-CoA. The adenine nucleotide levels were not significantly different in the two groups. The results appear consistent with the in vitro studies on isolated mitochondria.
Uptake of K+ by frog gastric mucosa from submucosal side and acid secretory rate.
Authors: Takeguchi N , Horikoshi I , Hattori M
Published: December 2017

The K+ content in frog gastric mucosa (K+) was measured as a function of the submucosal K+ concentration ([K+sm]) in the absence of K+ on the mucosal side. The (K+) in HCO3- buffer with 95% O2-5% CO2 gas showed that the removal of external K+ induced a 27% K+ loss from the control value of 5 mM K+sm, that there was no linear relation between (K+) and [K+sm, and that the change in the (K+) versus the [K+sm] was hyperbolic, indicating that there are two different types of K+ in the mucosa: bound and free K+.
Adaptation to calcium deprivation in the rat: effects of parathyroidectomy.
Authors: Pento J T , Waite L C , Tracy P J , Kenny A D
Published: December 2017

The role of parathyroid hormone (PTH) in the adaptive response in gut calcium transport to calcium deprivation has been studied in the rat using both the in vitro everted duodenal sac and the in situ ligated duodenal segment technique. Intact or parathyroidectomized (PTX) young rats were placed on a low calcium (0.01%) diet for 7-, 14-, or 21-day adaptation periods and compared with control rats maintained on a high calcium (1.5%) diet. Prior PTX (3 days before the start of the adaptation period) abolished the adaptive response (enhanced calcium transport) induced by calcium deprivation for a 7-day adaptation period, but did not abolish a response after a 21-day period. A 14-day adaptation period gave equivocal results. It is concluded that PTH appears to be necessary for short-term (7-day) adaptation, but not for long-term (21-day) adaptation to calcium deprivation. However, if accessory parathyroid tissue is present, the data could be interpreted differently: the essentiality of PTH for the adaptive response might be independent of the length of the adaptation period. The data also contribute to a possible resolution of the controversy concerning the involvement of PTH in the regulation of intestinal calcium transport in the rat.
Effects of hormones on 3', 5' -cyclic adenosine monophosphate in choroid plexus.
Authors: Rudman D , Hollins B M , Lewis N C , Scott J W
Published: December 2017

Choroid plexus of rabbit and rat was incubated for 2-30 min at 37 degrees C under 95% O2-5% CO2 in Tyrode solution containing 10 mM glucose and 1 mM theophylline with these agents: epinephrine, norepinephrine, isoproterenol, dopamine, histamine, serotonin, arginine, and lysine vasopressins, oxytocin, angiotensin, adrenocorticotropin (ACTH), beta-melanocyte-stimulating hormone, and choroid plexus peptide IIF. After incubation, tissue and medium were analyzed for 3', 5' -cyclic adenosine monophosphate (cAMP) content. Each amine or peptide was tested initially at 1,000 microng/ml. Only ACTH and serotonin affected cAMP content of rabbit choroid plexus. At 1,000 microng/ml, these agents caused a 10 and 4 times (respectively) increase in cAMP content of tissue + medium at 2-10 min with decline in content at 10-30 min. More than 90% of the increment was located in tissue, less than 10% in medium. Minimal effective dose (MED) to cause a significant (P less than .05) accumulation of cAMP was 0.1 microng/ml (2.2 x 10(-8) M) for ACTH and 10 microng/ml (5.7 x10(-3) M) for serotonin. Only isoproterenol, epinephrine, and norepinephrine influenced cAMP content of rat choroid plexus. MED's for this effect by isoproterenol, epinephrine, and norepinephrine were .001, .01, and 10 microng/ml (4.7 x 10(-9), 5.5 x 10(-8), and 5.9 x 10(-5) M), respectively.
Pulmonary fatty acid synthesis. II. Amino acids as fatty acid precursors in rat lung.
Authors: Scholz R W , Evans R M
Published: December 2017

The incorporation of various 14C-labeled amino acids into CO2 and lipids by rat lung slices was examined. Alanine, valine, leucine, isoleucine, aspartate, and glutamate were oxidized by lung tissue, whereas glycine and phenylalanine were not oxidized. Carbon originating from alanine, leucine, and glutamate was incorporated into pulmonary fatty acids by a mechanism indicative of de novo synthesis. Experiments with specifically labeled [14C]aspartate and [14C]glutamate revealed that the complete citrate-malate cycle described by Patel et al. (25) is of minor importance in pulmonary lipogenesis due to the extremely low activity of NADP-malate dehydrogenase. Glucose and pyruvate were also actively incorporated into fatty acids, and it is suggested that citrate in pulmonary tissue, as in other tissues, plays an important role in the transport of acetyl units from the mitochondria to the cell cytosol during lipogenesis from various carbohydrate and amino acid substrates.
Circadian rhythms of enzyme and running activity under ultradian lighting schedule.
Authors: Deguchi T
Published: December 2017

Serotonin N-acetyltransferase activity in the pineal gland and running acitvity of rats were measured under an ultradian lighting schedule (light/dark 6:6). When rats were moved from a diurnal lighting condition to the ultradian conditions, N-acetyltransferase activity showed a circadian rhythm, increasing once a day. N-acetyltransferase activity in the pups born and raised under the ultradian lighting conditions also exhibited a circadian change, the phase of which coincided with that of their mothers. When pups were raised by a foster mother with an inverted rhythmic phase from that of the original mother, the phase of the rhythm in N-acetyltransferase activity of the pups synchronized with that of the foster mother. When pups were separated from their mothers for 12 h/day, the circadian increase of N-acetyltransferase activity appeared during the dark period when they were separated from their mothers. The circadian rhythms of running acitvity were in phase with those of N-acetyltransferase activity in the pineal gland.
Body elemental composition: comparison between black and white adults.
Authors: Cohn S H , Abesamis C , Zanzi I , Aloia J F , Yasumura S , Ellis K J
Published: December 2017

The age-related changes in body chemical composition were measured in a normal black population ranging in age from 30 to 80 yr. The levels of total-body calcium, phosphorus, sodium, and chlorine were measured by in vivo neutron activation. In addition, the lean body mass (total-body potassium) was measured by whole-body counting of 40K. These data were compared with the same data obtained on a normal white population in a previous study. Although there were no significant differences in the height of the two groups, black men and women had significantly higher total-body calcium, phosphorus, sodium, chlorine, and potassium than the sex-and age-matched white population. The increased levels of total-body calcium and potassium when normalized for the weight and height of the subjects were reduced but still remained significantly higher than those of the white population. Clearly specific reference standards for skeletal and muscle mass as well as for sodium and chlorine need to be established for black populations.
Effect of ovarian hormones on lysosomal acid hydrolase activities in rat myometrium.
Authors: Sloane B F , Bird J W
Published: December 2017

The activities of the lysosomal acid hydrolases-cathespin D, acid phosphatase, beta-N-acetylglucosaminidase, and beta-glucuronidase-were measured in rat myometrium under the following hormonal conditions: during the estrus stage of the estrous cycle (NE); at 1,2, and 3 wk after ovariectomy; and in 3-wk postovariectomized females after hormone replacement therapy with 17 beta-estradiol (E2), progesterone (P), or E2 + P. Activities per milligram protein and per milligram DNA of the enzymes were significantly decreased after ovariectomy and were restored to the NE level or above after injecting E2 or E2 + P. Lysosomal enzyme activities did not change with hormonal state in hypophysectomized rats, suggesting that other hormones are required for mediation of enzyme activity. Acid hydrolase activities in other tissues and nonlysosomal enzyme activites in the myometrium did not fluctuate with hormonal state. Studies of lysosomal membrane integrity suggested that one population of lysosomes richer in cathepsin D and acid phosphatase and another rich in beta-N-acetylglucosaminidase and beta-glucuronidase may be present in rat myometrium. Estrogen seemed to labilize the lysosomal membrane of at least the latter of the two proposed populations of myometrial lysosomes.
Fetal metabolic response to maternal fasting in the rat.
Authors: Girard J R , Ferré P , Gilbert M , Kervran A , Assan R , Marliss E B
Published: December 2017

To determine the fetal response to altered maternal fuel supply, the effects of prolonged maternal fasting, begun 24-96 h before term, were examined and compared with values from normally fed term animals. Fetal weight decreased only after 48 h of maternal fasting. Prolonged maternal fasting was associated with low blood glucose, high blood ketone bodies, and decreased gluconeogenic substrate in the fetus. Plasma insulin was decreased, whereas plasma glucagon was increased in the fetus of fasted mothers. Infusion of [2-3H]glucose into the mother to constant specific activity gave a ratio of maternal to fetal glucose activity of 1.0 in fed and 1.56 in fasted mothers. Fetal liver from fasted mothers showed both increase in activity of key gluconeogenic enzymes (glucose-6-phosphatase and phosphoenolpyruvate carboxykinase) and increased conversion in vitro of lactate, alanine, serine, and glycerol in glucose by liver slices. It is inferred that maternal fasting induces fetal substrate alterations and hormonal changes appropriate to premature appearance of hepatic gluconeogenesis. The priority for endogenous fuel provision in this state leads to impaired fetal growth.
Role of glucagon in mediating metabolic effects of epinephrine.
Authors: Chideckel E W , Goodner C J , Koerker D J , Johnson D G , Ensinck J W
Published: December 2017

In order to separate direct effects of epinephrine on fuel metabolism from those mediated by glucagon, epinephrine (0.1 microng/kg-min) was infused for 120 min in 18- and 65-h fasted, nonanesthetized baboons with and without a concomitant somatostatin infusion. At both stages of fasting, epinephrine stimulated glucagon, secretion, and this was blocked by somatostatin. At 18 h, with epinephrine alone, glucose rose early and remained elevated throughout the infusion. In the glycogen-depleted 65-h fasted animals, there was attenuation of the early glucose rise, with glucose reaching a maximum level at 100-120 min. With somatostatin blockade of glucagon release in the 18-h fasted animals, a pattern of attenuated early glucose rise similar to that of the 65-h fasted animals occurred. Somatostatin also inhibited this early glycogenolytic response when the epinephrine dose was increased fivefold. The behavior of FFA, glycerol, and beta-hydroxybutyrate was unchanged by the addition of somatostatin to epinephrine at either stage of fasting. Thus, glucagon mediates the early glycogenolytic response to epinephrine, but not the delayed hyperglycemia and probably not the lipolysis.
Vitamin A1 intestinal absorption in vivo: influence of luminal factors on transport.
Authors: Hollander D , Muralidhara K S
Published: December 2017

Intestinal absorption of [3H]retinol was studied in the unanesthetized rat. Luminal perfusate was recirculated through isolated intestinal segments with intact vascular and lymphatic circulation. Apparent saturation kinetics were found in physiological concentrations of retinol, whereas a linear relationship between the concentration and absorption rate was found at pharmacological concentrations of retinol in the perfusate. In physiological concentrations, retinol uptake in vitro by everted gut sacs was unaffected by anoxia or metabolic inhibitors and uncouplers. In vivo retinol absorption rate was decreased when sodium taurocholate concentration was raised above 5 mM, or when 2.5 mM linoleic or linolenic acids were added to the perfusate. Absorption increased markedly as the thickness of the unstirred water layer was diminished. Variations in perfusate pH from 4.5 to 8.6 did not change the retinol absorption rate. In vivo absorption of retinol in physiological concentrations is mediated by a saturable, carrier-mediated passive absorption mechanism modified by the presence of fatty acids of varying chain length.
Effects of cholecystokinin, gastrin, and related peptides on coho salmon gallbladder contraction in vitro.
Authors: Vigna S R , Gorbman A
Published: December 2017

Isometric contractions of coho salmon (Oncorhynchus kisutch) gallbladder longitudinal muscle strips were recorded in response to porcine cholecystokinin (CCK), octapeptide of CCK (OP-CCK), desulfated octapeptide of CCK (ds-OP-CCK), porcine heptadecapeptide gastrins I and II, and pentagastrin. Peak tonic contraction amplitude and peak rhythmic contraction frequency were used to construct concentration-response curves for each peptide. Observed maximal responses to each peptide were not significantly different; therefore, all peptides tested were equal in efficacy. CCK, OP-CCK, and gastrin II were equipotent, and ds-OP-CCK and gastrin I were equipotent. Conclusions: 1) porcine CCK can stimulate contraction of the coho salmon gallbladder; 2) tonic and rhythmic contractile responses are elicited in coho salmon gallbladder by agonists; 3) coho salmon gallbladder muscle cannot distinguish between agonists that differ in the location of a sulfated tyrosyl residue at position 6 versus position 7 from the C-terminus; and 4) the results of this study are consistent with the hypothesis that coho salmon gallbladder muscle contains a relatively primitive CCK receptor.
Vagotomy impairs pentagastrin-induced relaxation of canine gastric fundus.
Authors: Okike N , Kelly K A
Published: December 2017

In eight dogs, a separated, vagally innervated pouch was made from the gastric fundus. Electrodes were implanted on the pouch, and an antral gastric fistula was created through which gastric juice was drained externally during all tests. After recovery, the fasted, conscious dogs received intravenous infusions of 154 mM NaCl to which randomly selected doses of pentagastrin were intermittently added while intraluminal pressure and electric activity of the distended pouch were recorded. Transthoracic vagotomy was then performed, and the dogs were restudied. Before vagotomy, pentagastrin decreased the amplitude of the phasic changes in intraluminal pressure and of the bursts of spiking potentials of the pouch. The D50 for inhibition of mean intrapouch pressure was 4.2 ng/kg per min. After vagotomy, pentagastrin still decreased intrapouch pressure and inhibited fundal spikes, but larger doses were required to produce equivalent decreases in pressure. The D50 was 41.4 ng/kg per min after vagotomy. Our conclusion is that pentagastrin-induced relaxation of the canine gastric fundus is impaired, but not abolished, by vagotomy.
Food intake controls in the suckling pig: glucoprivation and gastrointestinal factors.
Authors: Houpt K A , Houpt T R , Pond W G
Published: December 2017

The energy balance of suckling Yorkshire pigs 1 day to 2 wk old was challenged by: food deprivation, glucoprivation, and caloric and noncaloric gastric loads delivered by intubation. tafter 2--4 h fasts, food intake greatly increased over nonfasted control intake during a 3-h refeeding period. This response occurred both when body weight gain was used as a measure of intake for pigs nursing on the sow and when intake was measured directly in bottle-fed pigs. Glucoprivation produced by 0.5--2 U/kg insulin did not stimulate food intake although plasma glucose fell to a mean of 49 mg/100 ml (43% of control) after 1 U/kg insulin. Gastric loads of water or 3% NACl depressed intake after 3-h fast, but 0.9% NaCl did not. All the caloric gastric loads depressed intake; in order of increasing effectiveness, they were: heavy cream, protein hydrolysate, corn oil, milk, 5% glucose, and 5% lactose. The carbohydrate loads were most effective, a result which indicates that the response was not to calories alone but to some specific nutrient, possibly glucose.
Role of parathyroid hormone in regulation of main calcium fluxes in rats.
Authors: Haldimann B , Bonjour J P , Fleisch H
Published: December 2017

The effect of calcium deprivation on the various calcium fluxes was studied in growing rats either sham-operated (SHAM), thyroparathyroidectomized (TPTX), or thyroparathyroidectomized and supplemented with parathyroid hormone (PTH) (TPTX + PTH). In SHAM rats a decrease in the net absorption of calcium (Vna) has no influence on calcemia or on bone formation (Vo+), but leads to an increase in bone resorption (Vo-). In TPTX rats a decrease in Vna induces a decrease in calcemia and in Vo+ but still causes an increase in Vo-. The same is true in TPTX + PTH rats although all the variables measured are increased. In TPTX rats, both without and with PTH, a linear correlation exists between calcemia and Vo+ suggesting that calcemia influences bone formation. Furthermore, it appears that PTH is important in regulating bone turnover, but that the adaptation of Vo- to a change in Vna can occur in the absence or in the presence of a constant amount of this hormone. The mechanism of regulating this adaptation of bone resorption is still unknown.
Thyroid cold acclimation influences on norepinephrine metabolism in brown fat.
Authors: Kennedy D R , Hammond R P , Hamolsky M W
Published: December 2017

Norepinephrine turnover rates and tyrosine hydroxylase activities were determined in the interscapular brown fat pad of the rat during cold acclimation, hyperthyroxinism, and after thyroidectomy. Rats were cold acclimated by placement in a cold room, one rat to a cage, for a period of 6 wk. Hyperthyroxinism was induced by daily subcutaneous injections of L-thyroxine (1 mg/kg) for 6 days. Norepinephrine turnover rate and enzyme activity were determined at the end of each experimental period and at 8 wk after thyroidectomy. The rate of norepinephrine turnover increased during cold acclimation and hyperthyroxinism and decreased after thyroidectomy. Cold acclimation resulted in a significant increase in tyrosine hydroxylase activity, whereas no significant effect on enzyme activity was observed in hyperthyroxinism or after thyroidectomy. None of the conditions produced a change compared to controls in the apparent Km of tyrosine hydroxylase for L-tyrosine. Cold acclimation resulted in a significant decrease in the apparent Km of tyrosine hydroxylase for pterin cofactor, whereas thyroxine treatment and thyroidectomy had no effect.
Aminergic and thermoregulatory mechanims in hypothalamic regulation of growth hormone in cats.
Authors: Ruch W , Mixter R C , Russell R M , Garcia J F , Gale C C
Published: December 2017

In conscious cats intravenous infusion of L-dopa (20 mg/kg) increased plasma growth hormone (GH), hydrocorticosterone (17-OHCS), and glucose while lowering midbrain (core) temperature (Tmb). Peripheral blockade of aromatic amino acid decarboxylase by L-alpha-hydrazino-methyldopa (MK 486) abolished only L-dopa hyperglycemia, indicating CNS stimulation by de novo catecholamines caused endocrine and temperature changes. Phenoxybenzamine but not pimozide pre-treatment abolished GH release after L-dopa. Apomorphine infusion alone did not alter basal GH. These data indicate central alpha-adrenergic mediation of GH release. Norepinephrine (NE) injected (5 or 10 microgram) into the preoptic anterior hypothalamus (POAH) (7 of 10 cases) and medial hypothalamus (17 of 30) raised GH while lowering Tmb, in agreement with alpha-adrenergic mediation. Responsive sites were distributed in ventral and dorsal medial hypothalamus and extended into the thalamus. Cooling of the POAH by implanted thermode raised GH in association with shivering, vasoconstriction, and rise in Tmb. Correlation between GH release and change in Tmb after L-dopa, central NE injection, and POAH cooling suggests hypothalamic integration of GH release with thermoregulation. Intravenous infusion of 5-hydroxytryptophan after MK 486 raised GH and 17-OHCS, suggesting serotonergic mechanisms also control GH and ACTH.
Insulin and growth hormone in lean and obese pigs.
Authors: Wangsness P J , Martin R J , Gahagan J H
Published: December 2017

Plasma glucose, immunoreactive insulin (IRI), and growth hormone (GH) were determined in fasted lean and genetically obese pigs at 1, 3, and 6 mo of age. Rate of glucose clearance and plasma IRI and GH response in provocative stimulation were also measured. Fasting glucose was similar in lean and obese pigs, whereas glucose clearance rate was more rapid in lean pigs. Obese pigs were not hyperinsulinemic but had lower plasma GH than lean pigs. At 1 mo of age, both lean and obese pigs had higher plasma IRI and GH as compared to 3 and 6 mo. Glucose infusion produced increases in plasma IRI at 1, 3, and 6 mo, respectively, with the greatest increases at 6 mo. Plasma IRI peaked at the same level in both pig types at a given age; but due to a more prolonged response in obese pigs, the overall IRI response to glucose infusion was greater in obese pigs. Arginine infusion caused much smaller IRI responses than glucose, but the response of obese pigs was significantly greater than that of lean pigs. Both provocative stimuli caused increases in plasma GH. The GH response to glucose infusion in obese pigs was considerably less than in lean pigs. These observations suggest mild insulin insensitivity and a reduced GH secretory potential in the obese as compared to lean pigs.
Serum total and free thyroxine and triiodothyronine during dynamic muscular exercise in man.
Authors: Caralis D G , Edwards L , Davis P J
Published: December 2017

The effect of strenuous dynamic muscular exercise on serum-free thyroxine (FT4) and free triiodothyronine (FT3) concentrations has been studied in 10 healthy subjects. In the course of 7.8-19 min of treadmill exercise (protocol of R. A. Bruce), the group showed a mean increase in serum albumin concentration of 11.4% (P less than 0.01). Five subjects demonstrated an increase in FT4 concentrations (x = +54%) and five showed decreased FT4 (x = -36%). The difference in FT4 concentrations was accounted for primarily by acute alterations in dialyzable fraction T4 (DFT4) rather than total serum T4. Mean changes in DFT4 were statistically significant (P less than 0.02) when increased FT4 and decreased FT4 groups were compared. Acute exercise was accompanied by a 9% decrease in dialyzable fraction T3 (DFT3) (P less than 0.02) in the 10 subjects, but the concomitant decrease in FT3 concentration was not significant. Changes in DFT4 and DFT3 and FT4 and FT3 concentrations were not correlated. Trends in double product (heart rate times blood pressure) with maximal exercise and in double-product recovery after exercise suggested that increased FT4 concentrations developed in subjects who were physically better trained.
Role of cyclic 3',5'-GMP in modulation of cellular uptake of phosphate.
Authors: Rosenberg E M , Fogel A J
Published: December 2017

The role of cGMP in regulating renal cortical phosphate uptake was investigated in rats. Cyclic GMP (1 mM) produced a 27.7% +/- 1.4 (SE) increase in 32PO4 uptake by isolated renal cortical tubules (P less than 0.001) and cAMP (1 mM) a 28.7% +/- 1.4 increase (P less than 0.001), but their effects were not additive. Acetylcholine (Ach) (1 mM), in the presence of theophylline (T) (10 mM), increased cGMP in cortical slices from 24.1 pmol/g wet wt +/- 1.3 to 76.5 +/- 5.2 (P less than 0.001), but had no effect on cAMP, and Ach (1 mM) in the presence of T (1 mM) increased 32PO4 uptake 19.1% +/- 1.1 (P less than 0.001). Addition of Ca2+ to the incubation medium in the presence of T (10 mM) significantly increased cGMP in cortical slices from 7.4 pmol/g wet wt +/- 0.6 (0 Ca2+ plus EGTA, 0.5 mM) to 24.1 +/- 1.3 (1 mM Ca2+) and caused a 52.2% +/- 2.7 rise in 32PO4 uptake (P less than 0.001). Cyclic AMP was decreased by the addition of Ca2+. In summary, cGMP and cAMP stimulate 32PO4 uptake by renal cortex, and Ach and Ca2+ increase both cGMP and 32PO4 but do not increase cAMP. These data suggest that cGMP may play a role in regulating cellular uptake of phosphate.
Development-dependent responses of ovarian follicles to FSH and hCG.
Authors: Zeleznik A J , Keyes P L , Menon K M , Midgley A R , Reichert L E
Published: December 2017

Ovarian follicles removed from immature rats (preantral follicles) and immature rats treated in vivo with follicle stimulating hormone (FSH) (antral follicles) released progesterone in vitro in response to either human chorionic gonadotropin (hCG), hFSH, or DBcAMP in a time- and concentration-dependent fashion. Antral follicles produced approximately 20 times more progesterone than preantral follicles in response to both FSH and hCG at 10(-7) M and approximately 5 times more progesterone in response to 8 X 10(-3) M DBcAMP. After in vitro incubations, follicles were transplanted beneath the kidney capsules of recipient rats to assess their ability to luteinize after hormonal stimulation. Only antral follicles incubated with hCG, hFSH, and DBcAMP formed ectopic corpora lutea. Adenylate cyclase activity in preantral and antral follicle granulosa cells increased in response to both 10 mM KF and 10(-6) M hFSH with no major differences observed between membranes prepared from preantral or antral follicle granulosa cells. These results demonstrate that follicular maturation is associated with major changes in the ability of the granulosa cells to produce progesterone and luteinize in response to hormonal stimulation and that these changes may be, in part, independent of a functional hormone-responsive adenylate cyclase system.
Hypothalamic influence on insulin and glucagon release in the rat.
Authors: de Jong A , Strubbe J H , Steffens A B
Published: December 2017

Blood glucose, plasma insulin, and glucagon levels were measured in undisturbed and free-moving rats. The insulin and glucagon levels rise in the 1st min after the beginning of food ingestion, whereas the glucose level begins to increase only in the 3rd min if carbohydrate-rich food is eaten. This early rise in insulin and glucagon level is also observed under conditions in which carbohydrate-free food is eaten. A similar release of insulin and glucagon can be obtained by injection of 0.1 microgram of norepinephrine into the ventromedial hypothalamus, but the same injection made into the lateral hypothalamus causes release of insulin only, whereas injections in other hypothalamic areas are nearly without effect. Similar injections of isoproterenol did not cause changes in insulin, glucagon, and glucose levels. It is suggested that the early insulin and glucagon responses are of reflex origin and that the ventromedial and lateral hypothalamic areas are relay stations in the reflex pathways. The lack of effect of atropine to block the insulin and glucagon responses to noradrenergic stimulation of the ventromedial hypothalamus indicates that the efferent pathway is not cholinergic.
Kinetic differences between uterine and renal renins in the dog.
Authors: Potter D M , McDonald W J , Metcalfe J , Porter G
Published: December 2017

It has previously been reported that in the dog the Michaelis constant (Km) of renal renin with respect to homologous plasma substrate is the same as that for the angiotensin-generating enzyme extractable from the myometrium during pregnancy. We have reexamined the kinetics with a different methodology. Enzyme preparations from dog kidneys, the uterus of a nonnephrectomized pregnant bitch, and the uterus of a nephrectomized pregnant bitch were used. The substrate, prepared by diluting plasma from a nephrectomized, hysterectomized pregnant bitch, had a maximum endogenous substrate concentration of 1,750 ng/ml angiotensin I equivalents. Lineweaver-Burk kinetic analysis was used to calculate the Michaelis constants at pH 6.2. The Km of the renal enzyme was 720 ng/ml, of the enzyme prepared from the nonnephrectomized uterus 1,570 ng/ml, and of the nephrectomized dog uterus 1,500 ng/ml. The uterine enzyme was not activated by transient acid treatment, in contrast to renins reported from other sources. The data support the concept of biochemical heterogeneity of the two enzymes in the dog.