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Food insecurity is an indicator of well-being in the United States. A high proportion of recipients of charitable food assistance (CFA) are women and are often in charge of specific household managerial responsibilities (e.g., childcare, transportation). Consequently, they frequently face choices between paying for food and paying for other basic need(s). This study aims to examine which hunger-coping economic tradeoffs place females with at least one dependent child in the house and females without a dependent child in the house at risk for experiencing food insecurity. Data was collected at 10 Houston-area and 10-Atlanta-area food pantries in 2022 (N = 883). Using USDA cutoff criteria, households were considered food insecure based on ≥3 affirmative responses to the 18-item Food Security Scale Module. Hunger-coping economic tradeoff experiences were based on affirmative responses to whether anyone in the household ever had to choose between food and six basic needs (i.e. childcare, medicine/medical care, utilities, rent/mortgage, transportation, education). Covariate-adjusted logistic regression models were conducted to understand the relationship between six hunger-coping economic tradeoffs and food insecurity for the entire analytic sample and stratified by whether the female participant had a child in house. Standard errors in all regression models were corrected to account for multiple observations within a pantry. Adults, on average, were 55 years old (58% food insecure; 47% Hispanic; 42% black). Four hunger-coping economic tradeoffs were related to experiencing food insecurity. Economic tradeoffs between food and a) medicine/medical care and b) transportation elevated the likelihood of food insecurity, regardless of child status. Tradeoffs between food and childcare increased the risk for experiencing food insecurity among females with a dependent child. Deciding to pay between food and utilities was related to food insecurity experiences among females without a dependent child. Increases in Supplemental Nutrition Assistance Program (SNAP) benefits and eligibility along with programs to enhance resources related to medical care, transportation, childcare and utilities could help reduce food insecurity, especially among CFA recipients., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Many channelrhodopsins are permeable to protons. We found that in neurons, activation of a high-current channelrhodopsin, CheRiff, led to significant acidification, with faster acidification in the dendrites than in the soma. Experiments with patterned optogenetic stimulation in monolayers of HEK cells established that the acidification was due to proton transport through the opsin, rather than through other voltage-dependent channels. We identified and characterized two opsins which showed large photocurrents, but small proton permeability, PsCatCh2.0 and ChR2-3M. PsCatCh2.0 showed excellent response kinetics and was also spectrally compatible with simultaneous voltage imaging with QuasAr6a. Stimulation-evoked acidification is a possible source of disruptions to cell health in scientific and prospective therapeutic applications of optogenetics. Channelrhodopsins with low proton permeability are a promising strategy for avoiding these problems., Competing Interests: RH, FB, SY, SG, AC No competing interests declared, (© 2023, Hayward et al.)

Presence has been studied in the context of virtual environments for nearly thirty years, but the field has yet to reach consensus on even basic issues of definition and measurement, and there are many open research questions. We gather many of these open research questions and systematically group them according to what we believe are five key constructs that inform user experience in virtual environments: immersion, coherence, Place Illusion, Plausibility Illusion, and presence. We also report on the design and results of a study that investigated the effects of immersion and coherence on user experience in a stressful virtual visual cliff environment. In this article, each participant experienced a given VE in one of four conditions chosen from a 2x2 design: high or low levels of immersion and high or low levels of coherence. We collected both questionnaire-based and physiological metrics. Several existing presence questionnaires could not reliably distinguish the effects of immersion from those of coherence. They did, however, indicate that high levels of both together result in higher presence, compared any of the other three conditions. This suggests that "breaks in PI" and "breaks in Psi" belong to a broader category of "breaks in experience," any of which result in a degraded user experience. Participants' heart rates responded markedly differently in the two coherence conditions; no such difference was observed across the immersion conditions. This indicates that a VE that exhibits unusual or confusing behavior can cause stress in a user that affects physiological responses, and that one must take care to eliminate such confusing behaviors if one is using physiological measurement as a proxy for subjective experience in a VE.

Ribonucleotide reductases (RNRs) use a conserved radical-based mechanism to catalyze the conversion of ribonucleotides to deoxyribonucleotides. Within the RNR family, class Ib RNRs are notable for being largely restricted to bacteria, including many pathogens, and for lacking an evolutionarily mobile ATP-cone domain that allosterically controls overall activity. In this study, we report the emergence of a distinct and unexpected mechanism of activity regulation in the sole RNR of the model organism Bacillus subtilis. Using a hypothesis-driven structural approach that combines the strengths of small-angle X-ray scattering (SAXS), crystallography, and cryo-electron microscopy (cryo-EM), we describe the reversible interconversion of six unique structures, including a flexible active tetramer and two inhibited helical filaments. These structures reveal the conformational gymnastics necessary for RNR activity and the molecular basis for its control via an evolutionarily convergent form of allostery.

We report on the design and results of an experiment investigating factors influencing Slater's Plausibility Illusion (Psi) in virtual environments (VEs). Slater proposed Psi and Place Illusion (PI) as orthogonal components of virtual experience which contribute to realistic response in a VE. PI corresponds to the traditional conception of presence as "being there," so there exists a substantial body of previous research relating to PI, but very little relating to Psi. We developed this experiment to investigate the components of plausibility illusion using subjective matching techniques similar to those used in color science. Twenty-one participants each experienced a scenario with the highest level of coherence (the extent to which a scenario matches user expectations and is internally consistent), then in eight different trials chose transitions from lower-coherence to higher-coherence scenarios with the goal of matching the level of Psi they felt in the highest-coherence scenario. At each transition, participants could change one of the following coherence characteristics: the behavior of the other virtual humans in the environment, the behavior of their own body, the physical behavior of objects, or the appearance of the environment. Participants tended to choose improvements to the virtual body before any other improvements. This indicates that having an accurate and well-behaved representation of oneself in the virtual environment is the most important contributing factor to Psi. This study is the first to our knowledge to focus specifically on coherence factors in virtual environments.

A computer scientist was selected to prepare summary comments on the Faraday discussion. Much fine work was reported at the discussion. The tools and techniques reported at the conference have made radical improvements over past decades, and those are severally celebrated. Concerns and caveats about the papers are discussed.

Redirected Touching is a technique in which virtual space is warped to map many virtual objects onto one real object that serves as a passive haptic prop. Recent work suggests that this mapping can often be predictably unnoticeable and have little effect on task performance. We investigated training and adaptation on a rapid aiming task in a real environment, an unwarped virtual environment, and a warped virtual environment. Participants who experienced a warped virtual space reported an initial strange sensation, but adapted to the warped space after short repeated exposure. Our data indicate that all the virtual training was less effective than real-world training, but after adaptation, participants trained as well in a warped virtual space as in an unwarped one.

Background and Purpose: Persistent deficits in gait speed and spatiotemporal symmetry are prevalent following stroke and can limit the achievement of community mobility goals. Rehabilitation can improve gait speed, but has shown limited ability to improve spatiotemporal symmetry. The incorporation of combined visual and proprioceptive feedback regarding spatiotemporal symmetry has the potential to be effective at improving gait., Case Description: A 60-year-old man (18 months poststroke) and a 53-year-old woman (21 months poststroke) each participated in gait training to improve gait speed and spatiotemporal symmetry. Each patient performed 18 sessions (6 weeks) of combined treadmill-based gait training followed by overground practice. To assist with relearning spatiotemporal symmetry, treadmill-based training for both patients was augmented with continuous, real-time visual and proprioceptive feedback from an immersive virtual environment and a dual belt treadmill, respectively., Outcomes: Both patients improved gait speed (patient 1: 0.35 m/s improvement; patient 2: 0.26 m/s improvement) and spatiotemporal symmetry. Patient 1, who trained with step-length symmetry feedback, improved his step-length symmetry ratio, but not his stance-time symmetry ratio. Patient 2, who trained with stance-time symmetry feedback, improved her stance-time symmetry ratio. She had no step-length asymmetry before training., Discussion: Both patients made improvements in gait speed and spatiotemporal symmetry that exceeded those reported in the literature. Further work is needed to ascertain the role of combined visual and proprioceptive feedback for improving gait speed and spatiotemporal symmetry after chronic stroke.

In order to better understand how scene motion is perceived in immersive virtual environments, we measured scene-motion thresholds under different conditions across three experiments. Thresholds were measured during quasi-sinusoidal head yaw, single left-to-right or right-to-left head yaw, different phases of head yaw, slow to fast head yaw, scene motion relative to head yaw, and two scene illumination levels. We found that across various conditions 1) thresholds are greater when the scene moves with head yaw (corresponding to gain < 1:0) than when the scene moves against head yaw (corresponding to gain > 1:0), and 2) thresholds increase as head motion increases.

Slow gait speed and interlimb asymmetry are prevalent in a variety of disorders. Current approaches to locomotor retraining emphasize the need for appropriate feedback during intensive, task-specific practice. This paper describes the design and feasibility testing of the integrated virtual environment rehabilitation treadmill (IVERT) system intended to provide real-time, intuitive feedback regarding gait speed and asymmetry during training. The IVERT system integrates an instrumented, split-belt treadmill with a front-projection, immersive virtual environment. The novel adaptive control system uses only ground reaction force data from the treadmill to continuously update the speeds of the two treadmill belts independently, as well as to control the speed and heading in the virtual environment in real time. Feedback regarding gait asymmetry is presented 1) visually as walking a curved trajectory through the virtual environment and 2) proprioceptively in the form of different belt speeds on the split-belt treadmill. A feasibility study involving five individuals with asymmetric gait found that these individuals could effectively control the speed of locomotion and perceive gait asymmetry during the training session. Although minimal changes in overground gait symmetry were observed immediately following a single training session, further studies should be done to determine the IVERT's potential as a tool for rehabilitation of asymmetric gait by providing patients with congruent visual and proprioceptive feedback.

Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model - called Gait-Understanding-Driven Walking-In-Place (GUD WIP) - creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system - Low-Latency, Continuous-Motion (LLCM) WIP - while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency - LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

A common measure of effectiveness of a virtual environment (VE) is the amount of presence it evokes in users. Presence is commonly defined as the sense of being there in a VE. There has been much debate about the best way to measure presence, and presence researchers need and have sought a measure that is reliable, valid, sensitive, and objective. We hypothesized that to the degree that a VE seems real, it would evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence would evoke a greater response. To examine this, we conducted four experiments, each of which built upon findings that physiological measures in general, and heart rate in particular, are reliable, valid, sensitive, and objective presence measures. The experiments compare participants' physiological reactions to a nonthreatening virtual room and their reactions to a stressful virtual height situation. We found that change in heart rate satisfied our requirements for a measure of presence, change in skin conductance did to a lesser extent, and that change in skin temperature did not. Moreover, the results showed that significant increases in heart rate measures of presence appeared with the inclusion of a passive haptic element in the VE, with increasing frame rate (30 FPS > 20 FPS > 15 FPS) and when end-to-end latency was reduced (50 ms > 90 ms).

The nanoManipulator system adds a virtual reality interface to an atomic force microscope (AFM), thus providing a tool that enables the user not only to image but also to manipulate nanometer-sized molecular structures. As the AFM tip scans the surface of these structures, the tip-sample interaction forces are monitored, which in turn provide information about the frictional, mechanical, and topological properties of the sample. Computer graphics are used to reconstruct the surface for the user, with color or contours overlaid to indicate additional data sets. Moreover, by means of a force-feedback pen, which is connected to the scanning tip via software, the user can touch the surface under investigation to feel it and to manipulate objects on it. This system has been used to investigate carbon nanotubes, fibrin, DNA, adenovirus, and tobacco mosaic virus. Nanotubes have been bent, translated, and rotated to understand their mechanical properties and to investigate friction on the molecular level. AFM lithography is being combined with the nanoManipulator to investigate the electromechanical properties of carbon nanotubes. The rupture forces of fibrin and DNA have been measured. This article discusses how some of the graphics and interface features of the nanoManipulator made these novel investigations possible. Visitors have used the system to examine chromosomes, bacterial pili fibers, and nanochain aggregates (NCAs). Investigators are invited to apply to use the system as described on the web at http:@www.cs.unc.edu/Research/nano/doc/biovis it.html.

Understanding the relative motion of objects in contact is essential for controlling macroscopic lubrication and adhesion, for comprehending biological macromolecular interfaces, and for developing submicrometre-scale electromechanical devices. An object undergoing lateral motion while in contact with a second object can either roll or slide. The resulting energy loss and mechanical wear depend largely on which mode of motion occurs. At the macroscopic scale, rolling is preferred over sliding, and it is expected to have an equally important role in the microscopic domain. Although progress has been made in our understanding of the dynamics of sliding at the atomic level, we have no comparable insight into rolling owing to a lack of experimental data on microscopic length scales. Here we produce controlled rolling of carbon nanotubes on graphite surfaces using an atomic force microscope. We measure the accompanying energy loss and compare this with sliding. Moreover, by reproducibly rolling a nanotube to expose different faces to the substrate and to an external probe, we are able to study the object over its complete surface.

: In many cases in experimental science, the instrument interface becomes a limiting factor in the efficacy of carrying out unusual experiments or prevents the complete understanding of the acquired data. We have developed an advanced interface for scanning probe microscopy (SPM) that allows intuitive rendering of data sets and natural instrument control, all in real time. The interface, called the nanoManipulator, combines a high-performance graphics engine for real-time data rendering with a haptic interface that places the human operator directly into the feedback loop that controls surface manipulations. Using a hand-held stylus, the operator moves the stylus laterally, directing the movement of the SPM tip across the sample. The haptic interface enables the user to "feel" the surface by forcing the stylus to move up and down in response to the surface topography. In this way the user understands the immediate location of the tip on the sample and can quickly and precisely maneuver nanometer-scale objects. We have applied this interface to studies of the mechanical properties of nanotubes and to substrate-nanotube interactions. The mechanical properties of carbon nanotubes have been demonstrated to be extraordinary. They have an elastic modulus rivaling that of the stiffest material known, diamond, while maintaining a remarkable resistance to fracture. We have used atomic-force microscopy (AFM) to manipulate the nanotubes through a series of configuration that reveal buckling behavior and high-strain resilience. Nanotubes also serve as test objects for nanometer-scale contact mechanics. We have found that nanotubes will roll under certain conditions. This has been determined through changes in the images and through the acquisition of lateral force during manipulation. The lateral force data show periodic stick-slip behavior with a periodicity matching the perimeter of the nanotube.

The curling of a graphitic sheet to form carbon nanotubes produces a class of materials that seem to have extraordinary electrical and mechanical properties. In particular, the high elastic modulus of the graphite sheets means that the nanotubes might be stiffer and stronger than any other known material, with beneficial consequences for their application in composite bulk materials and as individual elements of nanometre-scale devices and sensors. The mechanical properties are predicted to be sensitive to details of their structure and to the presence of defects, which means that measurements on individual nanotubes are essential to establish these properties. Here we show that multiwalled carbon nanotubes can be bent repeatedly through large angles using the tip of an atomic force microscope, without undergoing catastrophic failure. We observe a range of responses to this high-strain deformation, which together suggest that nanotubes are remarkably flexible and resilient.

We present our results on the manipulation of individual viruses using an advanced interface for atomic force microscopes (AFMs). We show that the viruses can be dissected, rotated, and translated with great facility. We interpret the behavior of tobacco mosaic virus with a mechanical model that makes explicit the competition between sample-substrate lateral friction and the flexural rigidity of the manipulated object. The manipulation behavior of tobacco mosaic virus on graphite is shown to be consistent with values of lateral friction observed on similar interfaces and the flexural rigidity expected for macromolecular assemblies. The ability to manipulate individual samples broadens the scope of possible studies by providing a means for positioning samples at specific binding sites or predefined measuring devices. The mechanical model provides a framework for interpreting quantitative measurements of virus binding and mechanical properties and for understanding the constraints on the successful, nondestructive AFM manipulation of delicate samples.

We describe a new paradigm for modeling proteins in interactive computer graphics systems--continual maintenance of a physically valid representation, combined with direct user control and visualization. This is achieved by a fast algorithm for energy minimization, capable of real-time performance on all atoms of a small protein, plus graphically specified user tugs. The modeling system, called Sculpt, rigidly constrains bond lengths, bond angles, and planar groups (similar to existing interactive modeling programs), while it applies elastic restraints to minimize the potential energy due to torsions, hydrogen bonds, and van der Waals and electrostatic interactions (similar to existing batch minimization programs), and user-specified springs. The graphical interface can show bad and/or favorable contacts, and individual energy terms can be turned on or off to determine their effects and interactions. Sculpt finds a local minimum of the total energy that satisfies all the constraints using an augmented Lagrange-multiplier method; calculation time increases only linearly with the number of atoms because the matrix of constraint gradients is sparse and banded. On a 100-MHz MIPS R4000 processor (Silicon Graphics Indigo), Sculpt achieves 11 updates per second on a 20-residue fragment and 2 updates per second on an 80-residue protein, using all atoms except non-H-bonding hydrogens, and without electrostatic interactions. Applications of Sculpt are described: to reverse the direction of bundle packing in a designed 4-helix bundle protein, to fold up a 2-stranded beta-ribbon into an approximate beta-barrel, and to design the sequence and conformation of a 30-residue peptide that mimics one partner of a protein subunit interaction. Computer models that are both interactive and physically realistic (within the limitations of a given force field) have 2 significant advantages: (1) they make feasible the modeling of very large changes (such as needed for de novo design), and (2) they help the user understand how different energy terms interact to stabilize a given conformation. The Sculpt paradigm combines many of the best features of interactive graphical modeling, energy minimization, and actual physical models, and we propose it as an especially productive way to use current and future increases in computer speed.

We investigated the gastric acid secretory and motility responses to microinjection of thyrotropin-releasing hormone (TRH) into the dorsal motor nucleus of the vagus (DMV) in anesthetized cats. Gastric acid output was collected every 15 min through a gastric cannula after saline flush and titrated to pH 7.0. Antral and corpus contractions were continuously recorded by extraluminal force transducers. TRH dissolved in 200 nl of saline and microinjected unilaterally into the DMV induced a dose-dependent (50-200 ng) increase in gastric acid secretion. The acid secretory response began in the first 15 min collection and lasted 45 min. TRH frequently increased the force of contractions of the antrum and corpus within one minute of microinjection. The minimal effective dose for eliciting increased motility was lower than for inducing acid secretion. These results demonstrate that TRH acts in the DMV of cats to stimulate gastric acid secretion and contractions.

We investigated the gastric acid secretory and motility responses to microinjection into the dorsal motor nucleus of the vagus (DMV) of RX 77368, a stable thyrotropin-releasing hormone (TRH) analogue, and bicuculline, a gamma-aminobutyric acid (GABAA) receptor antagonist in ketamine-chloralose-anesthetized cats. Gastric acid output was collected every 15 min through a gastric cannula after saline flush and titrated to pH 7.0. Antral contractions were continuously recorded by an extraluminal strain gauge force transducer. The chemicals were dissolved in saline and unilaterally microinjected in volumes of 200 nl. RX 77368 or bicuculline microinjected into the DMV induced significant dose-dependent (50-500 ng) increases in gastric acid secretion and significant dose-dependent (50-200 ng) increases in the force of antral contractions. In response to both chemicals the gastric acid output increased in the first 15 min and peaked in the second and third collections. RX 77368 (500 ng) had a second greater peak 90 min after microinjection. The motility responses were rapid in onset and lasted 60 min for RX 77368 and 30 min for bicuculline. The minimal effective dose for eliciting increased motility was consistently lower than inducing acid secretion. Electrical stimulation of the DMV with 100 microA, 50-Hz, and 0.2-ms pulse duration increased the force of antral contractions but had no effect on gastric acid secretion. Our results demonstrate that the DMV exerts important control over both gastric acid secretion and motility in cats. TRH exerts a stimulatory influence, while GABAA receptors mediate an inhibitory influence on this vagal control.

The left vagal trunk of blood-perfused, isolated, canine stomach was continously stimulated electrically for periods of 30 min at 7 v and 5-msec duration; the frequency of stimulation was varied without interruption from 0.5 to 10 Hz. Plasma immunoreactive gastrin (IRG), total gastric blood flow (GBF), and gastric acid output (GAO) were monitored continuously. When the vagus was stimulated, gastrin concentrations and GBF increased rapidly, while GAO rose at a slower rate. Two Hertz appeared to be the optimal stimulus frequency for increasing plasma IGR levels, while 10 Hz was most effective for increasing GBF. Increasing the frequency from 0 to 0.5 Hz produced the maximum observed change in GAO; additional increments to 2 or 10 Hz produced no consistent additional increase in GAO. The results indicate that plasma IRG concentration and GBF increase in response to various frequencies of vagal stimulation. Vagal stimulation increases the output of immunoreactive gastrin, as well as acid, from the isolated canine stomach.

Heterogeneity is the most important consideration in the pathophysiology of peptic ulcer disease. Acute ulcers and erosions present clinically with gastrointestinal bleeding or perforation. If they heal there is no predictable recurrence. Factors concerned with mucosal defense are relatively more important than aggressive factors such as acid and pepsin. Local ischemia is the earliest recognizable gross lesion. The gastric mucosa is at least as vulnerable as the duodenal mucosa and probably more so. Most drug-induced ulcers occur in the stomach. Chronic or recurrent true peptic ulcers (penetrating the muscularis mucosae) usually present with abdominal pain. Many duodenal ulcer patients report that the pain occurs when the stomach is empty or is relieved by food, and follows a pattern of relatively long periods of freedom from symptoms between recurrences. Approximately 50% of patients experience a recurrence within a year if anti-ulcer medication is stopped. In most western countries recurrent duodenal ulcer is more common than gastric ulcer. Peptic ulcer disease is also more common in men. Recent evidence indicates genetic and familial factors in duodenal ulcer and increased acid-pepsin secretion in response to a variety of stimuli. However, it is also becoming clear that of all the abnormal functions noted, few are present in all subjects and many are clustered in subgroups. In chronic gastric ulcer of the corpus, defective defense mechanisms, such as duodenogastric reflux and atrophic gastritis, seem to be more important than aggressive factors. Nevertheless, antisecretory medications accelerate the healing of such ulcers. It remains to be seen whether prostaglandins, mucus secretion, or gastric mucosal blood flow are impaired in chronic ulcer disease.

A 26-year-old woman with enteric endometriosis presenting with cecocolic intussusception, a cecal mass on barium enema, and gastrointestinal hemorrhage is described. Laparotomy revealed cecocolic intussusception, ileocecal endometrial implants, and cecal mucosal ulceration presumed secondary to ischemia of the intussuscepted bowel. Histopathology showed serosal and subserosal endometrial implants without mucosal invasion. A review of the literature of endometrial bowel disease is presented.

The plasma-gastrin response to feeding and to insulin stimulation was determined before and after precise antrectomy in conscious rhesus monkeys (Macaca mulatta). Feeding resulted in a significant increase above basal gastrin levels (107 plus or minus 13 to 276 plus or minus 22 pg. per milliliter), as did stimulation with insulin (93 plus or minus 8 to 182 plus or minus 23 pg. per milliliter). Antrectomy reduced basal gastrin concentrations and abolished the gastrin response to both feeding and insulin. Antrectomy abolished the acid secretory response to histamine and insulin. In order to eliminate the problems of reflux gastritis and to study the time course of reduced acid secretory capacity, three monkeys were antrectomized and maintained by duodenal feedings. The histamine acid secretory response virtually was abolished within 24 hours and was not recovered over a 4 week period. Parietal cell architecture remained intact. In the monkey a major portion of basal circulating gastrin is antral in origin and the gastrin response to feeding and insulin is from the antrum exclusively. Loss of antral gastrin results in a virtual abolition of the acid secretory response to insulin and histamine. This decline is immediate in onset and is not related to parietal cell atrophy.

Perfusion of the jejunum with a mixture of amino acids (MAA) stimulates cholecystokinin-pancreozymin (CCK) release in man. Since gastrin is normally found in the small intestine, studies were conducted to determine if MAA perfusion had an effect on circulating serum gastrin levels in man. In man, endogenous stimulation of CCK had no effect on gastrin release; however, when CCK was given exogenously (10% pure form), serum gastrin levels were significantly increased. In dogs, the 10% pure CCK given exogenously also significantly increased gastrin concentrations, while the pure CCK octapeptide did not. Cross-reactivity between CCK and the gastrin antibody was minimal and could not be shown to be responsible for the serum gastrin elevations. Neither the physiological release of CCK in humans nor exogenous administration of CCK octapeptide in dogs at a dose equivalent to maximal stimulation of pancreatic secretion in humans significantly altered peripheral venous serum levels of immunoreactive gastrin. Therefore, we conclude that the gastrinemic response of exogenous CCK (10% pure) in man and dog is probably due to an impurity in the CCK preparation; when studying the effects of CCK on the gastrointestinal tract, only the pure CCK or the octapeptide should be used.

In 57% of the patients (12 of 25) seen with celiac sprue, as shown by clinical course and small bowel biopsy, peripheral blood thrombocytosis was present (range: 350,000 to 815,000 platelets per mm(3); mean: 546,000 +/- 44,060 SE). After clinical and histological remission, the platelet counts in these patients fell significantly (range: 188,000 to 300,0000 platelets per mm(3); mean 252,750 +/- 13,211 SE). There was no correlation between thrombocytosis and serum iron, folate, or vitamin B12 levels. Celiac sprue joins inflammatory bowel disease among gastrointestinal disorders as a consideration in the differential diagnosis of thrombocytosis. In these patients, thrombocytosis reflected active disease and was not present during remission. Evaluation of peripheral blood platelets may be useful in the assessment of patients with celiac sprue.

The emptying of a liquid test meal from the stomach was studied during, and in the absence of, electrical stimulation of cut ends of a thoracic branch of the vagus in anaesthetized cats. The test meal (154 mmol.1-1 NaCl and 30 mg.1-1 phenol red) was measured by collecting effluent from a duodenal fistula over a 30 min period. The stomach emptied about 60% of the meal under control conditions compared with over 90% during efferent stimulation of the vagus. The increased volumes emptied during efferent stimulation were not accounted for by secretion of gastric acid. Coincident with the vagally evoked antral contractions there was a gush of liquid from the duodenal cannula. Afferent vagal stimulation resulted in an initial marked delay of emptying followed by an acceleration so that the volume emptied after 30 min was similar to that in control experiments. Antral contractions, evoked by efferent vagal stimulation, accelerated the emptying of a liquid test meal from the stomach.

Research on the exocrine pancreas is showing signs of an accelerating rate of advance. After a period of relative inactivity, there is a prospect for major advances in both basic science and clinical areas. Isolated acinar cells and lobules can now be studied in vitro, and electrophysiologic techniques can be applied to individual cells. Hormones acting on the exocrine pancreas have been isolated and purified, and radioimmunoassays are available. "Candidate hormones" are under investigation. Controlled clinical trials of therapeutic agents are being carried out in pancreatic diseases, and a number of new diagnostic techniques are being evaluated. It remains for investigators to propose important new hypotheses that can be tested by these new techniques.