bluuebunny/crossref_metadata_2025 huggingface dataset:
Chest-lung statics: a realistic analog for student laboratory.
Authors: Chinet A E
Published: December 2017

A mechanical analog of the human lung-chest wall system was developed in Fribourg and Geneva Universities, Switzerland, to help students understand chest-lung statics. The equipment comprises a lung bellows, with upper airway connected to a three-way manifold, and a transparent chest whose lower part is another bellows that can be mobilized manually. Two water manometers measure intrapulmonary and intrathoracic pressures. The pressure-volume relationships of the lung-chest wall analog, which are essentially determined by the diameters of the bellows and the strains imposed by steel coils, closely parallel those of the human respiratory system. The chest can be opened to demonstrate pneumothorax. A first, guided manipulation of the model at the physiology laboratory provides excellent preparation for--or useful complement to--a human subject experiment on chest-lung statics. Unguided, further use of the model provides an opportunity for students to teach each other. Since the model is used, mean score on chest-lung statics at the practical examination is as good as that on other, more easy subjects.
Experience with a physiology workshop for high school and college teachers.
Authors: Randall D C , Engelberg J , Jackson B A , Ogilvy K A , Revelette W R , Speck D F , Vernon M W , Frazier D T
Published: December 2017

Science education in the United States at all academic levels is widely perceived to need direct assistance from professional scientists. The current dearth of quality applicants from this country to medical and graduate schools suggests that our existing undergraduate and high school science curriculum is failing to provide the necessary stimulus for gifted students to seek careers in the health sciences. Recognizing the need to become more directly helpful to high school and college science teachers, members of the faculty of the Department of Physiology and Biophysics at the University of Kentucky College of Medicine held a 5.5-day Physiology Summer Workshop during June, 1989. Participants included 25 college teachers from Kentucky and 5 other states plus 22 Kentucky high school teachers. The presence of the two levels of educators provided communication about curricular concerns that would be best addressed by mutual action and/or interaction. Each day's activities included morning lectures on selected aspects of organ system and cellular physiology, a series on integrative physiology, and afternoon laboratory sessions. The laboratory setting allowed the instructor to expand on principles covered in lecture as well as provided the opportunity for in-depth discussion. A selection of evening sessions was presented on 1) grants available for research projects, 2) obtaining funds for laboratory equipment, and 3) graduate education in physiology.
A survey of students' notions of body function as teleologic or mechanistic.
Authors: Richardson D R
Published: December 2017

The objectives of this study were to determine 1) the relative degrees to which students' notions of physiological functions are teleologic or mechanistic in nature, 2) whether these notions differ between students in elementary and advanced-level physiology courses, and 3) whether the degree of teleologic vs. mechanistic thinking can be modified by direct discussion of this topic. A questionnaire that determined whether students thought about body functions in a teleologic (why) or mechanistic (how) manner was administered to the following categories of students: 1) a class of high school biology students, 2) classes of students taking elementary college-level physiology courses, and 3) college students in advanced physiology courses. Overall, there was an average 61% teleologic response among the various classes, and differences between the classes were not statistically significant (P greater than 0.05). To address objective 3, one of the classes was presented the questionnaire after being given a lecture on teleology vs. mechanistic approaches to body function. The average teleological response of this class was only 12%, a value significantly lower in comparison, by a one-way analysis of variance, to any of the other groups (P less than 0.0001). These results indicate that the students have a strong tendency to think of body functions in teleological terms and that this tendency can be modified on a short-term basis by a direct discussion (by an instructor) of teleologic vs. mechanistic thinking.
Lectures in physiology: a three-phase evaluation plan.
Authors: Casteel C P , Mortillaro N A , Taylor A E
Published: December 2017

The initial phase of a voluntarily implemented multiphasic plan for improving faculty lectures was completed in 1988 and reported in 1989 [Am. J. Physiol. 256 (Adv. Physiol. Educ. 1): S3-S8, 1989]. That phase, conducted by a teaching consultant, included analysis of the teaching practices of each of seven faculty members. Following lecture observations, each faculty member received a written critique of his/her teaching, and individual as well as departmental strengths and weaknesses were identified. In the 1989 follow-up phase, faculty reviewed the feedback provided in their critiques and attended a seminar on developing effective lectures. Each faculty member was again observed during the presentation of a lecture; the same observation instrument was used in the follow-up phase as was used in the initial phase. A comparative analysis of the 1988 and 1989 teaching behaviors was completed for each faculty member and for the whole department. Results indicate that definitive changes had occurred in teaching methods employed since the initiation of the plan. Additional recommendations were made and specific target areas for ongoing improvement were identified.
Model to facilitate studying oxygen and carbon dioxide transport.
Authors: Gaar K A
Published: December 2017

A simple model has been constructed for microcomputer (PC) simulations involving basic cardiopulmonary principles of oxygen transport. Students can change parameters such as metabolic rate, blood hemoglobin concentration, barometric pressure, air composition, etc., and study parameter effects on blood gas concentrations and partial pressures. An important feature of the model program is that there are no negative feedback controls to maintain homeostasis. However, after a perturbation has been introduced, adjustments can be made to appropriate variables to correct for abnormal effects. For example, ventilation rate and blood hemoglobin concentration might be adjusted to compensate for low atmospheric oxygen. Because these do not change automatically in the model program, learning is enhanced when the student has to make the appropriate adjustments needed to correct disturbances in the blood gases that follow a perturbation.
A laboratory exercise in somesthesis that is expeditious, inexpensive, and suitable for large classes.
Authors: Greenspan J D
Published: December 2017

A teaching laboratory is described that demonstrates two principles of the somatosensory system: 1) the "spot-like" nature of skin sensitivity and 2) tactile acuity. This laboratory has been used for a large medical school class (140-160 students). One reason for the success of this laboratory is the ability to provide a sufficient number of stimulating apparatuses. The two-point discrimination device used to measure tactile acuity can be made easily and cheaply. In addition, two other demonstrations are described that are suitable for smaller classes or that students can do on their own. Although this lab was designed for medical students, the content makes it suitable for undergraduate or high school students.
Physiology laboratory experience for high school students.
Authors: Collins H L , DiCarlo S E
Published: December 2017

Recently, we were charged with providing a learning opportunity for high school students participating in the Upward Bound Regional Math and Science Program, a program designed to stimulate interest in mathematics and science for students from disadvantaged environments. Our challenge was to introduce students to the joys, excitement, and mystery of physiology and to stimulate their interest for future study. To this end, we developed a laboratory experience that examined basic physiological concepts in an animal model. This opportunity introduced students to how their bodies work and the importance of the use of animals in research. The students left the experience confident, motivated, and excited about learning.
Psychophysical determination of visual processing time by comparing depth seen in Pulfrich and Mach-Dvorak illusions.
Authors: Mojon D , Zhang W , Oetliker M , Oetliker H
Published: December 2017

A practical course for preclinical medical students was developed to illustrate aspects of binocular vision and mechanisms of primary visual transduction. It is based on a graphic analysis of two optical illusions, the Pulfrich and the Mach-Dvorak phenomena. A pendulum swinging in a plane perpendicular to the direction of observation appears to follow an elliptical path when viewed binocularly with a filter in front of one eye (Pulfrich illusion) or with alternating occlusion of the right and left eye above a critical frequency (Mach-Dvorak illusion). The Pulfrich phenomenon permits us to determine the relationship between perceived illusory depth and filter density. Analyzing the Mach-Dvorak phenomenon allows us to determine the dependence of illusory depth on interocular delay. Comparison of both determinations (depth against transmission and depth against time) permits us to establish, without complex calculations, the effect of luminescence on visual processing time. In addition, this course illustrates a general methodological concept mentioned by Popper: students make an unexpected observation, put forward a testable hypothesis, and try to falsify it.
Evaluation of a summer enrichment physiology course for matriculating medical students.
Authors: Carroll R G , Lee-Tyson M G
Published: December 2017

A summer enrichment physiology course for matriculating medical students has met a number of short-term goals, including bringing the students to the level of average medical student performance by the end of the summer. The long-term benefit of the program was evaluated by constructing a prospective expectation for each member of the medical class. Physiology grades obtained by past medical students were regressed on their undergraduate grades and MCAT scores. This regression model was used in a prospective manner to predict a physiology course grade for the entering class. Six of the seven summer program participants achieved scores equal to or higher than their predicted scores. Additionally, the regression model identified prospectively four of the six medical students who scored below 70% for the medical physiology course. This study suggests that a summer enrichment program can benefit participants.
Renal function in the laboratory rat: a student exercise.
Authors: Walker R L , Olson M E
Published: December 2017

Because of the increased concern over use of human body fluids in physiology teaching laboratories, we developed an exercise in renal function that utilizes laboratory rats. The purpose is to demonstrate the role of the kidneys in the homeostatic control of extracellular fluid volume, plasma ionic concentrations, and osmolarity. Three treatment groups are utilized: a volume-expanded (access to 1 g/100 ml sucrose) group, a volume-expanded and salt-loaded (access to 0.9 g/100 ml NaCl) group, and a volume-depleted (water-deprived) group. A normovolemic control group (access to tap water) is also included. Rats are housed individually in metabolic cages that allow accurate measurement of fluid intake and urine output. Blood samples are removed via cardiac puncture. The animals recover from this procedure and can be reutilized within 2-3 wk. When class data are pooled, clear trends are seen that demonstrate the volume-, osmo-, and ionoregulatory abilities of the kidneys.
Gregorc learning styles and achievement in anatomy and physiology.
Authors: Harasym P H , Leong E J , Lucier G E , Lorscheider F L
Published: December 2017

Results from the Gregorc Style Delineator (GSD), administered to 260 undergraduate nursing students, were compared with achievement scores in a human anatomy and physiology course. Factor analysis and VARIMAX rotation demonstrate that there is no relationship between any of the four learning styles allegedly identified by the GSD and achievement in anatomy and physiology. Factor analysis also shows that the GSD measures only a single bipolar scale of sequential vs. random ability rather than two bipolar scales comprising four learning styles, as suggested by Gregorc. These findings question the validity of the GSD and recommend discontinuing its use as an indicator of learning styles.
Hearts, lungs, and children: a physiologist returns to kindergarten.
Authors: Curran-Everett D
Published: December 2017

Scientific illiteracy is a prevalent problem: between kindergarten and high school, most children progressively lose their inherent affinity for science exploration. The correction of this deficiency requires vigorous participation by the scientific community. This paper details my experiences introducing kindergartners to the basics of cardiorespiratory physiology: pulmonary ventilation and circulatory transport of oxygen. More important, my presentation gives children an opportunity to participate in the process of scientific inquiry and to discover and explore the mystique of real hearts and lungs. The children and their teachers truly enjoy the demonstration. In particular, my use of animal organs meets with phenomenal success: the children are enchanted by my inflation and their exploration of pig lungs, and one teacher told me weeks afterward that her students were still "bragging of how they touched a real heart and lung." Young children delight in science exploration and marvel at the wonder inherent to physiology. Armed with an intriguing hands-on presentation and a spirit of adventure and fun, any scientist can return to kindergarten. The rewards are likely to be profound.
Starting a neuroscience research laboratory in a developing country: a Fulbright experience in Honduras.
Authors: Quirk G J
Published: December 2017

The first laboratory of neurophysiology was installed in the medical school of the University of Honduras during the 1992-1993 academic year. The goal of the project was to improve the teaching of physiology in the medical curriculum and to establish a neuroscience research laboratory able to address Honduran needs. In addition to a computer learning facility and wet labs in neurophysiology for medical students, an independent research program that focused on social problems in the country (for example, the effects of malnutrition on the developing central nervous system) was developed, paving the way for the first graduate program in physiology in Honduras. Funded by a Fulbright Lectureship Grant, the shoe-string budget was augmented by donations of equipment by colleagues. This first-hand account describes the planning and implementation of the project, covering both expected and unexpected problems and successes. An update on the progress of the lab after two years of independent operation is also described.
Using situational physiology in a didactic lecture setting.
Authors: Richardson D
Published: December 2017

This project used the approach of "human situations" to teach about the cardiovascular system within an undergraduate physiology course (PGY 412). About two-thirds of the students had previously taken a college-level physiology course (sophisticated), whereas one-third had not (naive). Nine didactic lectures were organized around the common human situations of orthostasis, blood donation, and exercise. For acceptance evaluation, the students were given a questionnaire consisting of six expectation statements (e.g., compared with other life science courses, I expect that I will better understand the material) and asked to rate the degree to which they agreed with each statement on a scale of 1 to 5. On completion of the lectures, the students were given a questionnaire asking them to compare experiences with expectations. Experiences were significantly less than expectations for naive (P < 0.05) but not for sophisticated students. On a scale of 1 to 5, sophisticated students preferred the situations approach more than did naive students (3.1 vs 2.4; P < 0.066). For performance evaluation, the students were given a set of questions used by the author in a previous PGY 412 course presented by traditional didactic lectures. There were no significant differences between present and previous scores (77 vs. 79%; P > 0.16). Furthermore, there were no significant differences between naive and sophisticated students in cardiovascular examination scores (P > 0.608) or in total course scores (P > 0.523). These results indicate that didactic lectures based on situational physiology will yield a performance outcome equivalent to traditional lectures. However, naive students may have difficulty with the procedure and require extra attention.
Philosophy of science and physiology education.
Authors: Refinetti R
Published: December 2017

Since the mid-1960s, philosophy of science [particularly that derived from Kuhn's work (The Structure of Scientific Revolutions, Chicago: University of Chicago Press, 1962)] has become an informal part of the education of scientists worldwide, including physiologists. However, recent postmodernist developments have enraged a number of scientists, who would like to sever any ties with philosophy of science. The author contends that the perceived conflict is due mainly to a misunderstanding of the implications of constructivist assertions and partially to flawed reasoning in a few constructivist approaches. There is no fundamental conflict that would justify the elimination of philosophy of science from science education.
A new PhD training track: a proposal to improve basic science teaching.
Authors: Smith J J , Koethe S M , Forster H V
Published: December 2017

There has been increasing criticism of medical basic science teaching; much of this has focused on overcrowding of the curriculum, inadequate application to clinical medicine, and the limited commitment of the faculty to teach. We have analyzed some of the factors that may contribute to these complaints, such as the fragmentation of physiology and the conflicting roles of the medical basic scientist. We have also reviewed some previous suggestions for improving basic science teaching. We suggest that a basic scientist with a background of integrative physiology, pharmacology, anatomy, and pathology, with a special emphasis on pathophysiology, would be well qualified to assume an important role in the medical education of the future. Because there is at present no established training program of this type, we have proposed a PhD training track with this objective and have listed some of the advantages and disadvantages of such a program.
Involving students in experimental design: three approaches.
Authors: McNeal A P , Silverthorn D U , Stratton D B
Published: December 2017

Many faculty want to involve students more actively in laboratories and in experimental design. However, just "turning them loose in the lab" is time-consuming and can be frustrating for both students and faculty. We describe three different ways of providing structures for labs that require students to design their own experiments but guide the choices. One approach emphasizes invertebrate preparations and classic techniques that students can learn fairly easily. Students must read relevant primary literature and learn each technique in one week, and then design and carry out their own experiments in the next week. Another approach provides a "design framework" for the experiments so that all students are using the same technique and the same statistical comparisons, whereas their experimental questions differ widely. The third approach involves assigning the questions or problems but challenging students to design good protocols to answer these questions. In each case, there is a mixture of structure and freedom that works for the level of the students, the resources available, and our particular aims.
The role of a scientific society in physiology education: current and future perspectives.
Authors: Matyas M L
Published: December 2017

As a professional society of physiologists involved in research and teaching, the American Physiological Society (APS) is "...devoted to fostering education, scientific research, and the dissemination of information in the physiological sciences." Established long-range goals for education guide the development of current and future programs at all education levels. K-12 outreach programs develop working relationships between physiologists and K-12 teachers within local communities and improve the quality of precollege science education. At the undergraduate level, APS programs foster excellence in physiology education and promote student interest in physiology careers. At the graduate level, activities promote excellence in graduate training and the professional development of students, including a focus on underrepresented groups. At each of these levels, the Society includes activities for the continuing education of its members. Looking to the future, the Society plans to expand the programs and resources offered to researchers and educators at all levels. On-line programs, resources, and communications have been initiated and will play an even more important role in the future.
The future of teaching physiology: an international viewpoint.
Authors: Sefton A J
Published: December 2017

The discipline of physiology is challenging to teach. It has ill-defined boundaries and no agreed sequence for learning; students' needs depend on the goals of the specific degree programs in which they are enrolled. Internationally, it is taught under many different conditions, using a range of strategies, to a wide variety of groups. All teachers are subject to local constraints and the availability of resources. Newer educational methods emphasizing active and integrated learning provide novel challenges. Computer-based educational strategies offer promise but do not represent easy solutions, particularly when they are unaffordable in many parts of the world. Particular difficulties in teaching arise for some when they are not themselves broadly educated in physiology and related disciplines and for others when they have only limited access to up-to-date knowledge and resources. Sessions and workshops on modern physiology and educational issues should be included in national, regional, and international conferences at which the participation of teachers is encouraged and supported.
Measurement of human nasal potential difference to teach the theory of transepithelial fluid transport.
Authors: Kersting U , Schwab A , Hebestreit A
Published: December 2017

We describe a novel student course in membrane physiology in which students record their own nasal potential difference, i.e., the transepithelial potential difference of the respiratory mucosa in the nose. The nasal potential difference monitors directly, and in vivo, changes in the apical cell membrane potential of the respiratory mucosa induced by activators and inhibitors of ion channel activities. Basic principles of transepithelial fluid transport are taught by applying an appropriate perfusion protocol to the respiratory epithelium to either depolarize or hyperpolarize the membrane potential of the luminal cell side, thereby increasing or decreasing the nasal potential difference. This course was given at the Department of Physiology at the University of Würzburg in 1997, and responses of the students as reported on questionnaires were mainly positive.
Student test scores are improved in a virtual learning environment.
Authors: Goldberg H R , McKhann G M
Published: December 2017

This study evaluates the effectiveness of delivering the core curriculum of an introductory neuroscience course using a software application referred to as a virtual learning interface (VLI). The performance of students in a virtual learning environment (VLE) is compared with that of students in a conventional lecture hall in which the same lecturer presented the same material. This study was not designed to determine whether grades are improved by augmenting a lecture with other information. The VLI takes advantage of audio, video, animation, and text in a multimedia computer environment. Our results indicate that raw average scores on weekly examinations were 14 percentage points higher for students in the VLE compared with those for students in a conventional lecture hall setting. Moreover, normalized test scores were over 5 points higher for students in the VLE. This analysis suggest that a core curriculum can be effectively presented to students using the VLE, thereby making it possible for faculty to spend less class time relaying facts and more time engaging students in discussion of scientific theory.
The water-tower analogy of the cardiovascular system.
Authors: Swain D P
Published: December 2017

The cardiovascular system is a complex arrangement of hydraulic, yet living, components. The complexity of this system may make it difficult for students to see the "forest" instead of the "trees." To better explain the dynamics of cardiovascular function and control, an analogy has been drawn to the operation of a city water supply. In cities that use a water tower, fresh water is pumped up into the tower from a river or other source. The tower serves as a pressure reservoir for providing water to homes through a largely parallel arrangement of distribution pipes. Local homeowners control their own water usage through faucets, whereas the city maintains water pressure by monitoring the level in the tower. Key analogous points with the cardiovascular system are the heart as the city pump, the aorta as the water tower, arteries as parallel distribution pipes, and arterioles as faucets. Baroreceptor reflex control is discussed as well as such features as the capacitance role of veins, the skeletal muscle pump, and the competition between locally mediated vasodilation and sympathetically mediated vasoconstriction. Subjective student and peer evaluations have indicated that this analogy is effective in improving student comprehension of the cardiovascular system.
TOWARD CONSISTENT DEFINITIONS FOR PRELOAD AND AFTERLOAD
Authors: Norton James M.
Published: December 2017

Significant differences exist among textbook definitions for the terms preload and afterload, leading to confusion and frustration among students and faculty alike. Many faculty also chose to use in their teaching simple terms such as “end-diastolic volume” or “aortic pressure” as common-usage approximations of preload and afterload, respectively, but these are only partial representations of these important concepts. Straightforward definitions both of preload and afterload that are concise yet still comprehensive can be developed using the Law of LaPlace to describe the relationships among chamber pressure, chamber radius, and wall thickness. Within this context, the term “preload” can be defined as all of the factors that contribute to passive ventricular wall stress (or tension) at the end of diastole, and the term “afterload” can be defined as all of the factors that contribute to total myocardial wall stress (or tension) during systolic ejection. The inclusion of “wall stress” in both definitions helps the student appreciate both the complexities of cardiac pathophysiology and the rationale for therapeutic intervention.
IN PURSUIT OF MEANINGFUL LEARNING
Authors: Michael Joel
Published: December 2017

The Bernard Distinguished Lecturers are individuals who have a history of experience and expertise in teaching that impacts multiple levels of health science education. Dr. Joel Michael more than meets these criteria. Joel earned a BS in biology from CalTech and a PhD in physiology from MIT following which he vigorously pursued his fascination with the mammalian central nervous system under continuous National Institutes of Health funding for a 15-yr period.

At the same time, he became increasingly involved in teaching physiology, with the computer being his bridge between laboratory science and classroom teaching. Soon after incorporating computers into his laboratory, he began developing computer-based learning resources for his students. Observing students using these resources to solve problems led to an interest in the learning process itself. This in turn led to a research and development program, funded by the Office of Naval Research (ONR), that applied artificial intelligence to develop smart computer tutors. The impact of problem solving on student learning became the defining theme of National Science Foundation (NSF)-supported research in health science education that gradually moved all of Dr. Michael’s academic efforts from neurophysiology to physiology education by the early 1980’s. More recently, Joel has been instrumental in developing and maintaining the Physiology Education Research Consortium, a group of physiology teachers from around the nation who collaborate on diverse projects designed to enhance learning of the life sciences.

In addition to research in education and learning science, Dr. Michael has devoted much of his time to helping physiology teachers adopt modern approaches to helping students learn. He has organized and presented faculty development workshops at many national and international venues. The topics for these workshops have included computer-based education, active learning, problem-based learning, and the use of general models in teaching physiology.
ATP utilization associated with recovery metabolism in anaerobic frog muscle
Authors: DeFuria R. R. , Kushmerick M. J.
Published: December 2017

The ATP turnover during single isometric 0.5-, 1-, and 3-s tetani in anaerobic frog sartorii was measured at 20 degrees C. In parallel experiments, we measured the lactate production by sartorii during their metabolic recovery from such tetani. From these measurements, we obtained an experimental P/lactate ratio which was less than 1.5, the expected value for simple Embden-Meyerhof glycolysis when glycogen is metabolized to lactate. We interpreted these results as indicating a substantial amount of suprabasal ATP breakdown occurred during metabolic recovery. The operation of the fructose phosphate substrate cycle is suggested as a cause of this additional ATP breakdown.
Sodium in smooth muscle relaxation
Authors: Ma T. S. , Bose D.
Published: December 2017

The contraction of guinea-pig taenia coli due to high K+ could not be reversed by washing when Na+ was absent from the medium. Reintroduction of Na+ (7 mM or more) caused relaxation. Similar results were obtained with rat uterus. The effect of sodium replacement was not due to change in ionic strength because equal or higher osmoles of choline, Ca++, K+, Mn++, or Mg++ had little or no effect. Persistence of contraction in the Na+-free medium was not due to a “catch state” of the contractile apparatus. Impairment of Ca+ removal from the cytoplasm rather than persistent increase in Ca+ influx seemed to sustain the mechanical response. This was because D600 (a calcium influx blocker) failed to completely relax K+-induced contraction in the absence of Na+ and also because the ability of EGTA to produce relaxation was reduced in the absence of Na+. Measurement of tissue calcium content using the lanthanum method revealed coincident decrease in tissue calcium and tension to control level during Na+-mediated relaxation. The results suggest a role for transmembrane Na+-Ca++ exchange in causing the Na+-mediated relaxation of taenia undergoing Na+-free contracture.
Potassium and chloride conductances in normal and denervated rat muscles
Authors: Lorkovic H. , Tomanek R. J.
Published: December 2017

The membrane conductance of rat muscles (mainly gastrocnemius (G) and soleus (S)) was measured by using the two-microelectrode technique and the current point clamp method. Thin muscle bundles were washed in Tris chloride and Tris propionate solutions containing 6 mM K. The current strength was always 5 x 10–9 A and the steady-state membrane voltage was about 5 mV. The average chloride conductance (gcl, in mumho/cm2) of normal muscles was 845 (G) and 1,025 (S). The potassium conductance (gk) was 99 (G) and 161 (s). In separate measurements, the contribution of the chloride conductance (gcl) to the total membrane conductance (gm) was 89% for normal G and S. Two weeks after denervation the average gcl decreased to 440 in G and 191 in S; gk increased to 205 in G and to 364 in S in the presence of 0.1 mM Ca in solution; the increase in gk was less when measurements were made in the presence of 3mM Ca and 1 mM Mg. The contribution of gcl to gm was 60% in G and 30% in S in 14-day denervated muscles. The coefficient of variation for gcl/gk in 30 normal and 46 denervated muscles was 0.91 and 0.46, respectively. The curve representing the voltage-current relationship of muscles washed in Cl-free solutions containing 60 mM K was S-shaped in normal and in denervated muscles, but the changes in slope were less marked in the latter.
Effect of pulmonary edema on drug transport and binding in rat lung
Authors: Gardiner T. H. , Goodman F. R.
Published: December 2017

The pulmonary absorption and uptake of (35S)phenol red ((35S)PR was measured in anesthetized rats with alpha-naphthylthiourea- (ANTU) induced lung edema. When (35S)PR solution was injected through a tracheal cannula in control animals and the percentage of the tracheal cannula in control animals and the percentage of the dose unabsorbed plotted semilogarithmically against time, an apparent first-order absorption rate was obtained. In contrast, in rats with ANTU-induced edema, the absorption time curve showed at least two different first-order components. Increasing the concentration of (35S)PR from 0.01 to 3 mM resulted in a decrease in the percentage absorption of the compound in controls compared with a relatively constant percentage absorption in edematous lungs. (35S)PR uptake by lung slices from ANTU-treated rats was decreased in the presence of IAA and a N2 atmosphere, and the dye accumulated at a faster rate and to a greater extent than in controls. The results suggest that although energy-dependent drug transport mechanisms remain intact, the porosity of the absorbing membranes and the extent of drug binding in the lung are increased markedly in the presence of edema.
Effects of luminal hyperosmolality on electrical pathways of Necturas gallbladder
Authors: Reuss L. , Finn A. L.
Published: December 2017

The electrical properties of the transepithelial pathways of Necturaus gallbladder were studied with intracellular microelectrode techniques under control conditions and after exposure to hyperosmotic mucosal bathing media (addition of sucrose or other solutes). Doubling mucosal osmolality produces a large increase in the resistance of the intercellular shunt pathway (from 420 +/- 50 to 700 +/- 70 omega - cm2, P is less than 0.001) and a significant decrease in the resistance of the apical membrane of the cells (from 3,510 +/- 420 to 1,540 +/- 380 omega p cm2, P is less than 0.001). The basolateral membrane resistance remains unchanged. Both the apical and basolateral membranes depolarize (from 59.5 +/- 1.8 to 36.6 +/- 2.8 mV, P less than 0.0001, and from 61.8 +/- 1.7 to 32.2 +/- 3.0 mV,P is less than 0.001, respectively). The transepithelial diffusion potential resulting from NaCl concentration gradients due to the osmotic water flow does not explain the cell potential changes. Mucosal solution ion substitution experiments demonstrate increases of gk, gcl, and gna (ca. 2.5-fold, 4-fold, and 7-fold, respectively). Therefore, cell depolarization appears to be produced mainly by a reduction of apical membrane K permselectivity. The increase in the resistance of the shunt is attributable to reduction of the width of the lateral intercellular spaces, because of the osmotic serosa-to-mucosa water flow.
Na+-K+-ATPase inhibition stimulates PGE release in guinea pig taenia coli
Authors: Coburn R. F. , Soltoff S.
Published: December 2017

Inhibition of the plasma membrane enzyme Na+-K+-ATPase by ouabain zero extracellular K+, or low extracellular Na+, markedly augmented prostaglandin E release from the guinea pig taenia coli. Data suggest this phenomenon may be linked directly to Na+-K+-ATPase or Na+ pump activities, or changes in intracellular K+ concentration. The augmented prostaglandin E release was not due to changes in intracellular Na+, Ca2+, pH, or membrane potential, resulting from Na+ pump inhibition. The characteristics of the plasma membrane may exert a control on prostaglandin E release in this smooth muscle.
Protein transport across cerebral vessels during metrazole-induced convulsions
Authors: Hedley-Whyte E. T. , Lorenzo A. V. , Hsu D. W.
Published: December 2017

The effects of pentylenetetrazole-induced convulsions on cerebrovascular permeability for horseradish peroxidase were studied in locally anesthetized, artificially respired, paralyzed cats. Horseradish peroxidase circulated for 1, 2.5, 5, 10, 30, and 60 min and accumulated in medium-size, i.e., arterial or venous, blood vessel walls. Cerebral neuropil was permeated earliest in thalamic nuclei including medial and lateral geniculate nuclei. No tight junctions containing horseradish peroxidase were found. With 1.0 and 2.5 min circulation of horseradish peroxidase, arterial adventitia and basement membranes contained more peroxidase than surrounding interstitial space in contrast to veins and capillaries. Convulsions increased the number of endothelial vesicles containing horseradish peroxidase in arteries, veins, and capillaries but total number (stained plus unstained) of endothelial vesicles was increased slightly only in capillaries. We conclude that increased permeability is initially at the arterial level, although veins may also become permeable. The role of the endothelial vesicles in transit or protein in and out of the nervous system is not clear.
Regulation of tension in skinned muscle fibers: effect of high concentrations of Mg-ATP
Authors: Orentlicher M. , Brandt P. W. , Reuben J. P.
Published: December 2017

The control of tension in skinned fibers by Mg-ATP and Ca described in previous publications has been studied at high substrate concentrations over a wide range of temperature and salt concentration. Curves of tension versus pCa shift systemically to the right as [Mg-ATP] increases. The maximum Ca-activated tension of a skinned fiber declines at sufficiently high substrate concentrations. This behavior is described by a generalization of the scheme given in the earlier reports.
Sodium ions, calcium ions, blood pressure regulation, and hypertension: a reassessment and a hypothesis
Authors: Blaustein M. P.
Published: December 2017

Page C165: M. P. Blaustein. “Sodium ions, calcium ions, blood pressure regulation, and hypertension: a reassessment and a hypothesis.” Page C169: left column, paragraph 2, line 9 should read (with Na rate coefficient k-1). Page C170: left column, top paragraph, lines 21–22 should read total cell Ca will increase by about 4–40 micromoles per liter fiber water. Left column, top paragraph, lines 23–24 should read 1,000–1,500 micromoles per liter fiber water.
Binding of 2,3-diphosphoglycerate by spectrin and its effect on oxygen affinity of hemoglobin
Authors: Shaklai N. , Benitez L. , Ranney H. M.
Published: December 2017

The relationships between spectrin, a structural protein of the red blood cell (RBC) membrane facing the cytoplasm, and hemoglobin were studied. The oxygen-binding properties of stripped hemoglobin were not altered by the presence of spectrin, but the interaction of hemoglobin with organic phosphates was reduced by the addition of spectrin. The presence of the enzyme glyceraldehyde 3-phosphate dehydrogenase (G3PD), another component of the RBC membrane used as a control, did not change the oxygen affinity of either stripped hemoglobin or of hemoglobin solutions containing phosphates. Binding studies using the gel filtration method at pH 7.3 indicated reversible binding of 2,3-diphosphoglycerate to spectrin. A unit of 220,000 daltons was calculated to have seven binding sites and a binding constant of 1.2 X 10(4) M-1. A mechanism is proposed in which spectrin may facilitate oxygen transport for hemoglobin molecules reaching the membrane.
Induction of cytochrome P-450 in a selective subpopulation of hepatocytes
Authors: Gumucio J. J. , DeMason L. J. , Miller D. L. , Krezoski S. O. , Keener M.
Published: December 2017

The objective of this study was to determine whether the inductive effect of phenobarbital (PB) on liver cytochrome P-450 was the result of the action of this drug on all or some hepatocytes. For this purpose, a light (cell band I) and a heavy (cell band II) subpopulation of hepatocytes were separated from rat liver in a continuous density gradient. To determine the location of these hepatocytes in tissue, [14C]bromobenzene, which binds covalently to centrilobular hepatocytes, was administered. The specific activity (14C dpm/mg protein) was greater in cells of band I than in cells of band II, suggesting a predominant contribution of centrilobular hepatocytes to the lighter cell band. Microsomes were separated from each cell subpopulation after 3 days of PB administration and cytochrome P-450 was measured. Although a fivefold increment in cytochrome P-450 content of light hepatocytes was noted, the content of heavy hepatocytes was similar to that of the respective subpopulation in controls. Concomitantly, PB administered for 3 days induced the smooth endoplasmic reticulum of centrilobular hepatocytes only, as revealed by electron microscopy of whole tissue. These results indicated that PB induces cytochrome P-450 in a selective subpopulation of hepatocytes, most likely located near the terminal hepatic venule.
Association of increased pHi with calcium ion release in skeletal muscle
Authors: Connett R. J.
Published: December 2017

The pH difference across the cell membrane of frog sartorius muscle cells was measured with the distribution of 5,5-dimethyl-2,4-oxazolidine-dione (DMO) as the marker. Depolarization of the muscles to values at or below the contraction threshold caused by elevating external potassium up to approximately 20 mM resulted in an internal alkalinization. The change was smaller with superthreshold depolarization (20--30 mM [K+]). The alkalinization was blocked by agents that block calcium release from the sarcoplasmic reticulum (procaine and dantrolene sodium). Other agents that cause calcium release (caffeine, theophylline, and quinine) were found to give alkalinization when tested at concentrations just below the contracture threshold. Increased acidification of the extracellular medium was associated with the internal alkalinization. The data were interpreted as indicating the presence of a calcium-stimulated H+ and/or OH- ion transport system in the muscle membrane.
Glucose metabolism by adult hepatocytes in primary culture and by cell lines from rat liver
Authors: Bissell D. M. , Levine G. A. , Bissell M. J.
Published: December 2017

The metabolic fate of [U-14C]glucose has been examined in detail in adult rat hepatocytes in primary monolayer culture, as well as in two permanent cell lines--Buffalo rat liver (BRL) and transplantable rat hepatoma (HTC) cells-derived from normal rat liver and from rat hepatoma, respectively. Under defined conditions of incubation, at a glucose concentration of 5.5 mM, the three types of cultured liver cells exhibited pronounced differences in glucose metabolism. Primary cultures, like the intact liver, differed from the cell lines in consuming relatively small amounts of glucose and converting approximately 50% of the total metabolized glucose to lactate. By contrast, the permantent cell lines consumed glucose at a 40-fold greater rate than did primary cultures, converting 80--90% of the carbohydrate to lactate. Oxidative metabolism of glucose carbon also differed among the three types of liver culture. Of the total [U-14C]glucose consumed, primary cultures converted approximately 30% to labeled CO2 per hour, whereas the liver cell lines converted 5--10%. Finally, glucose metabolism in primary culture exhibited adaptation as hepatocytes aged in culture, shifting progressively toward the pattern exhibited by the permanent cell lines. This change occurred over a time course similar to that for other kinds of functional change in hepatocytes in primary culture and thus may be relevant to the general problem of phenotypic alteration in liver cell culture.
Insulin effects on monovalent cation transport and Na-K-ATPase activity
Authors: Hougen T. J. , Hopkins B. E. , Smith T. W.
Published: December 2017

The effects of insulin on monovalent cation transport and on Na-K-ATPase activity from intact cells, tissue homogenates, and purified enzyme of the avian salt gland were studied. Monovalent cation active transport, measured by ouabain-inhibitable 86Rb+ uptake, was significantly increased (21.9 +/- 7.3% SE) in tissue slices exposed to insulin (100 mU/ml) for 15 min. A small but significant (12.2 +/- 1.9%) increase in Na-K-ATPase activity was similarly observed after salt gland tissue slices were exposed to insulin. This increase in enzymatic activity did not occur when broken-cell homogenates were exposed to insulin. Purified preparations of Na-K-ATPase showed no insulin enhancement of activity either in the presence of optimal or less than fully activating Na+ and ATP concentrations. Na-K-ATPase activity was the same in detergent-activated homogenates of both control and insulin-treated slices, consistent with insulin activation of existing enzyme sites. These data support the hypothesis that at least part of the increase in monovalent cation active transport produced by insulin is related to enhanced Na-K-ATPase activity and indicate that the latter phenomenon is dependent on some components or properties of the intact cell.
Homeostatic regulation of cellular energy metabolism: experimental characterization in vivo and fit to a model
Authors: Erecinska M. , Wilson D. F. , Nishiki K.
Published: December 2017

Measurements in isolated liver cells, cultured kidney cells, protozoa (Tetrahymena pyriformis), and yeast (Candida utilis) indicate that homeostatic regulation of cellular energy metabolism is of common origin. In every case near equilibrium is maintained between the transfer of reducing equivalents from the intramitochondrial NAD couple to cytochrome c and the phosphorylation of cytosolic ADP to ATP. Under conditions of constant energy demand, changes in the intracellular phosphate concentration cause an adjustment in the [ATP]/[ADP] to maintain a constant [ATP]/[ADP][Pi] and constant respiratory rate. The regulation of mitochondrial respiration occurs as part of the reactions by which reduced cytochrome c is oxidized by molecular oxygen. At similar values for the [ATP]/[ADP][Pi] the respiratory rate increases with increasing reduction of cytochrome c. A model for mitochondrial respiratory control is found to give a good fit to the data in all of the different types of cells tested.
A mechanism for minimizing temperature effects on repetitive firing frequency
Authors: Partridge L. D. , Connor J. A.
Published: December 2017

The magnitudes and time courses of conductance changes in molluscan neurons show marked temperature dependence. Interestingly, though, the relationship between repetitive firing frequency and stimulus current is not greatly affected by moderated temperature changes (6-8 degrees C). The transient potassium current, IA, is largely reponsible for the interspike voltage trajectory, hence, repetitive interval, in molluscan neurons. It is shown in this study that temperature dependencies of the rate constants and magnitude of the IA system are balanced in such a way that the observed temperature insensitivity of the repetitive response is predicted.