Wearable airbag technology and machine learned models to mitigate falls after stroke

BACKGROUND

Falls are a common complication experienced after a stroke and can cause serious detriments to physical health and social mobility, necessitating a dire need for intervention. Among recent advancements, wearable airbag technology has been designed to detect and mitigate fall impact. However, these devices have not been designed nor validated for the stroke population and thus, may inadequately detect falls in individuals with stroke-related motor impairments. To address this gap, we investigated whether population-specific training data and modeling parameters are required to pre-detect falls in a chronic stroke population.

METHODS

We collected data from a wearable airbag's inertial measurement units (IMUs) from individuals with (n = 20 stroke) and without (n = 15 control) history of stroke while performing a series of falls (842 falls total) and non-falls (961 non-falls total) in a laboratory setting. A leave-one-subject-out crossvalidation was used to compare the performance of two identical machine learned models (adaptive boosting classifier) trained on cohort-dependent data (control or stroke) to pre-detect falls in the stroke cohort.

RESULTS

The average performance of the model trained on stroke data (recall = 0.905, precision = 0.900) had statistically significantly better recall (P = 0.0035) than the model trained on control data (recall = 0.800, precision = 0.944), while precision was not statistically significantly different. Stratifying models trained on specific fall types revealed differences in pre-detecting anterior-posterior (AP) falls (stroke-trained model's F₁-score was 35% higher, P = 0.019). Using activities of daily living as non-falls training data (compared to near-falls) significantly increased the AUC (Area under the receiver operating characteristic) for classifying AP falls for both models (P < 0.04). Preliminary analysis suggests that users with more severe stroke impairments benefit further from a stroke-trained model. The optimal lead time (time interval pre-impact to detect falls) differed between control- and stroke-trained models.

CONCLUSIONS

These results demonstrate the importance of population sensitivity, non-falls data, and optimal lead time for machine learned pre-impact fall detection specific to stroke. Existing fall mitigation technologies should be challenged to include data of neurologically impaired individuals in model development to adequately detect falls in other high fall risk populations. Trial registration https://clinicaltrials.gov/ct2/show/NCT05076565 ; Unique Identifier: NCT05076565. Retrospectively registered on 13 October 2021.

Effect of using real motion versus predicted motion as input for digital human modeling of back and shoulder loads during manual material handling

Digital human modeling (DHM) technology is considered the state of the art in designing and evaluating workstations. Previous studies examined the differences between DHM's posture and motion prediction relative to human experimental data. Yet, the effect the two different inputs on biomechanical loads was not assessed. Therefore, this study evaluates the differences in L4/L5 compression force and shoulder torques during a work process calculated using DHM with motion prediction (Jack by Siemens) and DHM with experimental data. The work process is a sequential removing, carrying, and depositing task performed by nine females and nine males and recorded using a motion capture system. The analysis shows that using experimental data results in larger back compression force during the removing task (average 15.4%), similar force during the depositing task (average 0.68%), and less force during the carrying task (19.875%). Using experimental data resulted in larger shoulder torque during all tasks (average 24.97%).

A smartphone-based online system for fall detection with alert notifications and contextual information of real-life falls

BACKGROUND

Falls are a leading cause of accidental deaths and injuries worldwide. The risk of falling is especially high for individuals suffering from balance impairments. Retrospective surveys and studies of simulated falling in lab conditions are frequently used and are informative, but prospective information about real-life falls remains sparse. Such data are essential to address fall risks and develop fall detection and alert systems. Here we present the results of a prospective study investigating a proof-of-concept, smartphone-based, online system for fall detection and notification.

METHODS

The system uses the smartphone's accelerometer and gyroscope to monitor the participants' motion, and falls are detected using a regularized logistic regression. Data on falls and near-fall events (i.e., stumbles) is stored in a cloud server and fall-related variables are logged onto a web portal developed for data exploration, including the event time and weather, fall probability, and the faller's location and activity before the fall.

RESULTS

In total, 23 individuals with an elevated risk of falling carried the phones for 2070 days in which the model classified 14,904,000 events. The system detected 27 of the 37 falls that occurred (sensitivity = 73.0 %) and resulted in one false alarm every 46 days (specificity > 99.9 %, precision = 37.5 %). 42.2 % of the events falsely classified as falls were validated as stumbles.

CONCLUSIONS

The system's performance shows the potential of using smartphones for fall detection and notification in real-life. Apart from functioning as a practical fall monitoring instrument, this system may serve as a valuable research tool, enable future studies to scale their ability to capture fall-related data, and help researchers and clinicians to investigate real-falls.

Shoulder moments and angles during single and combined manual material handling tasks

Shoulder musculoskeletal disorders due to manual material handling tasks are common workplace injuries. Here we investigated the difference in shoulder biomechanics (moments and angles) between a single task of removing a box from a shelf (or depositing a box on a shelf) and the equivalent part of a combined task that consisted of removing, carrying and depositing boxes; that is, a single removing [depositing] task was compared with the removing [depositing] part of a combined task. We found that the peak and cumulative shoulder moments were larger during the single-task paradigm than during the equivalent part of the combined task by 26.3 and 25.5%, respectively. The two paradigms also differed in terms of shoulder angles. It is likely that the main contributors to this overestimation were differences between the single and combined tasks in terms of the lever arm (i.e. horizontal distance), the shoulder angle, and the task duration. Practitioners' Summary: We investigated shoulder moments during single and combined manual material handling tasks. Shoulder moments were found to be smaller during combined tasks. Practitioners should consider that analysing combined tasks using estimations based on single tasks could result in an overestimation of 26.3 and 25.5% in peak and cumulative shoulder moments, respectively.Abbrevaitions: MSDs: musculoskeletal disorders; MMH: manual material handling; LMM: linear mixed model.

Investigation of 3D dynamic and quasistatic models for spinal moments during combined manual material handling tasks

Digital human modeling software uses biomechanical models to compute workers' risk of injury during industrial work processes. In many cases, the biomechanics are calculated using quasistatic models, which neglect the body's dynamics and therefore might be erroneous. This study investigated the differential effect of using a dynamic vs. a quasistatic model on spinal loading during combined manual material handling tasks that are prevalent in industry. An experiment was conducted involving nine male and nine female participants performing a total of 3402 cycles of a box-conveying task (removing, carrying and depositing) for different box masses and shelf heights. Using motion capture data, the peak and cumulative moments acting on the L5/S1 joint were calculated using 3D dynamic and quasistatic models. This revealed that neglecting the dynamic movements (i.e., using a quasistatic model) results in an on average underestimation of 19.7% in the peak spinal moment and 3.6% in the cumulative moment that in some cases exceeds the maximal limit for the compression forces acting on the lower back.

Inpatient stroke rehabilitation: prediction of clinical outcomes using a machine-learning approach

BACKGROUND

In clinical practice, therapists often rely on clinical outcome measures to quantify a patient's impairment and function. Predicting a patient's discharge outcome using baseline clinical information may help clinicians design more targeted treatment strategies and better anticipate the patient's assistive needs and discharge care plan. The objective of this study was to develop predictive models for four standardized clinical outcome measures (Functional Independence Measure, Ten-Meter Walk Test, Six-Minute Walk Test, Berg Balance Scale) during inpatient rehabilitation.

METHODS

Fifty stroke survivors admitted to a United States inpatient rehabilitation hospital participated in this study. Predictors chosen for the clinical discharge scores included demographics, stroke characteristics, and scores of clinical tests at admission. We used the Pearson product-moment and Spearman's rank correlation coefficients to calculate correlations among clinical outcome measures and predictors, a cross-validated Lasso regression to develop predictive equations for discharge scores of each clinical outcome measure, and a Random Forest based permutation analysis to compare the relative importance of the predictors.

RESULTS

The predictive equations explained 70-77% of the variance in discharge scores and resulted in a normalized error of 13-15% for predicting the outcomes of new patients. The most important predictors were clinical test scores at admission. Additional variables that affected the discharge score of at least one clinical outcome were time from stroke onset to rehabilitation admission, age, sex, body mass index, race, and diagnosis of dysphasia or speech impairment.

CONCLUSIONS

The models presented in this study could help clinicians and researchers to predict the discharge scores of clinical outcomes for individuals enrolled in an inpatient stroke rehabilitation program that adheres to U.S. Medicare standards.

Workers' biomechanical loads and kinematics during multiple-task manual material handling

This study investigated the biomechanical loads and kinematics of workers during multiple-task manual material handling (MMH) jobs, and developed prediction models for the moments acting on a worker's body and their peak joint angles. An experiment was conducted in which 20 subjects performed a total of 3780 repetitions of a box-conveying task. This task included continuous sequential removing, carrying and depositing of boxes weighing 2-12 kg. The subjects' motion was captured using motion-capture technology. The origin/destination height was the most influencing predictor of the spinal and shoulder moments and the peak trunk, shoulder and knee angles. The relationship between the origin/destination heights and the above parameters was nonlinear. The mass of the box, and the subject's height and mass, also influenced the spinal and shoulder moments. A tradeoff between the moments acting on the L5/S1 vertebrae and on the shoulder joint was found. Compared to the models developed in similar studies that focused on manual material handling (albeit under different conditions), the high-order prediction equation for peak spinal moment formulated in the present study was found to explain between 10% and 48% more variability in the moments. This suggests that using a high-order equation in future studies might improve the prediction.

Paramedic equipment bags: How their position during out-of-hospital cardiopulmonary resuscitation (CPR) affect paramedic ergonomics and performance

This study investigates how the positions of paramedic equipment bags affect paramedic performance and biomechanical loads during out-of-hospital Cardiopulmonary Resuscitation (CPR). An experiment was conducted in which 12 paramedic teams (each including two paramedics) performed in-situ simulations of a cardiac-arrest scenario. CPR quality was evaluated using five standard resuscitation measures (i.e., pre- and post-shock pauses, and compression rate, depth and fraction). The spinal loads while lifting, pulling and pushing the equipment bags were assessed using digital human modeling software (Jack) and prediction equation from previous studies. The results highlight where paramedics are currently choosing to position their equipment. They also demonstrate that the positions of the equipment bags affect CPR quality as well as the paramedics' work efficiency, physiological effort and biomechanical loads. The spinal loads ranged from 1901 to 4030N; furthermore, every occasion on which an equipment bag was lifted resulted in spinal forces higher than 3400N, thus exceeding the maximum threshold stipulated by the National Institute for Occupational Safety and Health. 72% of paramedics' postures were categorized as high or very high risk for musculoskeletal disorders by the Rapid Entire Body Assessment. Guidelines related to bag positioning and equipment handling might improve CPR quality and patient outcomes, and reduce paramedics' risk of injury.

Differences in spinal moments, kinematics and pace during single-task and combined manual material handling jobs

This study compared the spinal moments (i.e., peak and cumulative moments acting on the L5/S1 joint), kinematics (i.e., peak trunk and knee angles) and work pace of workers, when either removing a box from a shelf or depositing a box on a shelf, under two conditions: as a single task or as part of a combined task. An experiment was conducted, in which the subjects performed the tasks and were recorded using a motion capture system. An automated program was developed to process the motion capture data. The results showed that, when the removing and depositing tasks were performed as part of a combined task (rather than as single tasks), subjects experienced smaller peak and cumulative spinal moments and they performed the tasks faster. The results suggest that investigations into the separate tasks that comprise a combination have a limited ability to predict kinematics and kinetics during the combined job.

Factors determining workers' pace while conducting continuous sequential lifting, carrying, and lowering tasks

To plan a new manual material handling work process, it is necessary to predict the times required to complete each task. Current time prediction models lack validity when the handled object's mass exceeds 2 kg. In this study, we investigated the effect of workplace design parameters on continuous sequential lifting, carrying, and lowering of boxes weighing from 2 kg to 14 kg. Both laboratory and field experiments were conducted. Results revealed that the box's weight and the lifting and lowering heights influenced the tasks' times. Further, the time to perform a task was influenced by the performance of other tasks in the same work process. New time prediction models were developed using the laboratory experiment data. Our models were found to be more accurate on average than the Maynard Operation Sequence Technique (MOST) and Methods Time Measurement (MTM-1) by 42% and 20%, respectively, for predicting the times of real workers at an actual workplace.

Resuscitation-induced gut edema and intestinal dysfunction

BACKGROUND

Mesenteric venous hypertension and subsequent gut edema play a pivotal role in the development of intra-abdominal hypertension. Although gut edema is one cause of intra-abdominal hypertension, its impact on gut function is unknown. The purpose of this study was to create a model of acute hydrostatic gut edema and to evaluate its effect on gut motility and barrier function.

METHODS

The first study, group A, evaluated the effect of gut edema on transit over time using 20 mL/kg 0.9% saline. The second study, group B, focused on the 12-hour time period using 80 mL/kg 0.9% saline. Rats were randomized to superior mesenteric vein partial occlusion (venous hypertension) or sham surgery. At 6, 12, and 24 hours, group A underwent intestinal transit and tissue water weight measurements. At 12 hours, group B underwent tissue water, transit, ileal permeability and resistance, lactate and myeloperoxidase activity, and mucosal injury measurements.

RESULTS

Venous hypertension with fluid resuscitation caused acute hydrostatic gut edema, delayed intestinal transit, increased mucosal permeability to macromolecules, and decreased tissue resistance over time. Mucosal injury was minimal in mesenteric venous hypertension.

CONCLUSION

Acute mesenteric venous hypertension and resuscitation-induced gut edema, in the absence of ischemia/reperfusion injury, is associated with delayed intestinal transit and altered gut barrier function.

Differential effects of prophylactic, concurrent and therapeutic lactoferrin treatment on LPS-induced inflammatory responses in mice

Mice injected with endotoxin develop endotoxaemia and endotoxin-induced death, accompanied by the oxidative burst and overproduction of inflammatory mediators. Lactoferrin, an iron binding protein, provides a natural feedback mechanism to control the development of such metabolic imbalance and protects against deleterious effects of endotoxin. We investigated the effects of intraperitoneal administration of human lactoferrin on lipopolysaccharide (LPS)-induced release of tumour necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), interleukin 10 (IL-10) and nitric oxide (NO) in vivo. Lactoferrin was administered as a prophylactic, concurrent or therapeutic event relative to endotoxic shock by intravenous injection of LPS. Inflammatory mediators were measured in serum at 2, 6 and 18 h post-shock induction. Administration of lactoferrin 1 h before LPS resulted in a rather uniform inhibition of all mediators; TNF by 82%, IL-6 by 43%, IL-10 by 47% at 2 h following LPS injection,and reduction in NO (80%) at 6 h post-shock. Prophylactic administration of lactoferrin at 18 h prior to LPS injection resulted in similar decreases in TNF-alpha (95%) and in NO (62%), but no statistical reduction in IL-6 or IL-10. Similarly, when lactoferrin was administered as a therapeutic post-induction of endotoxic shock, significant reductions were apparent in TNF-alpha and NO in serum, but no significant effect was seen on IL-6 and IL-10. These results suggest that the mechanism of action for lactoferrin contains a component for differential regulation of cellular immune responses during in vivo models of sepsis.

Down-regulation of inducible nitric-oxide synthase (NOS-2) during parasite-induced gut inflammation: a path to identify a selective NOS-2 inhibitor

Nitric oxide (NO) possesses potent anti-inflammatory properties; however, an over-production of NO will promote inflammation and induce cell and tissue dysfunction. Thus, the ability to precisely regulate NO production could prove beneficial in controlling damage. In this study, advantage was taken of the well characterized inflammatory response caused by an intestinal parasite, Trichinella spiralis, to study the relationship between intestinal inflammation and the regulation of nitric oxide synthase-type 2 (NOS-2) expression. Our study revealed that a specific gut inflammatory reaction results in inhibition of NOS-2 expression. Characteristics of this inhibition are: 1) local jejunal inflammation induced by T. spiralis systemically inhibits NOS-2 gene transcription, protein expression, and enzyme activity; 2) the inhibition blunts endotoxin-stimulated NOS-2 expression; 3) the inhibition does not extend to the expression of other isoforms of NOS, to paxillin, a housekeeper protein, or to cyclooxygenase-2, another protein induced by proinflammatory cytokines; 4) the inhibition is unlikely related to the formation of specific anti-parasite antibodies; and 5) the inhibition may involve substances other than stress-induced corticosteroids. Elucidation of such potent endogenous NOS-2 down-regulatory mechanisms could lead to the development of new strategies for the therapy of inflammatory conditions characterized by the overproduction of NO.

Intestinal anaphylaxis in chickens: epithelial ion secretion as a determinant and potential component of functional immunity

Immunity to secondary protozoan infections in chickens is accompanied by rapid onset of intestinal permeability to serum proteins, an event in mammals associated with local anaphylaxis. The permeability changes in the chicken intestine are hypothesized to be mediated by mast cell-derived paracrine factors. In a test of this hypothesis, we demonstrated, using an electrophysiological correlate of intestinal anaphylaxis (antigen-induced Cl(-) secretion), that the response of the chicken intestine to antigenic stimulation is consistent with type I hypersensitivity reactions. Day-old, single-comb-white-Leghorn chickens were sensitized to bovine serum albumin (BSA). At 3 weeks of age ileal segments were mounted in Ussing-type chambers. Serosal challenge with BSA elevated the transmural short circuit current (DeltaIsc) within 1min and was maximally expressed (DeltaIsc=50-60microA/cm(2)) within 2-3 min. The magnitude of the DeltaIsc was directly related to the concentration of antigen (10-200 microg antigen/ml), was only expressed in immunized chickens, and was blocked by the mucosal application of a Cl(-) channel blocker. Data obtained in the present investigation identify epithelial ion secretion as a potential mechanism of functional immunity in the mucosal immune system of the chicken small intestine.

Ileal mucosal response to bacterial toxin challenge

BACKGROUND

The cause of postinjury intestinal mucosal barrier disruption remains obscure. The present study examines the hypothesis that the bacterial toxin formyl-methionyl leucyl phenylalanine (FMLP) plays an initial role in this process.

METHODS

Mucosal permeability to fluorescein isothiocyanate-labeled dextran (4,400 molecular weight) was measured in perfused distal rat ileum with and without FMLP. Dextran and myeloperoxidase appearance in the lumenal perfusate was assessed in response to surrogates of traumatic stress: ischemia/reperfusion, total abdominal irradiation, and total parenteral nutrition. Recovery of FMLP in the effluent of static closed and perfused ileal loops was determined by mass spectrometry. Release of mast cell mediators in the presence of FMLP was determined in ileal everted sacs.

RESULTS

Seventy-five percent of FMLP was recovered in perfusion effluent in contrast to 5% in closed loops. There was a transient increase in ileal permeability in FMLP/perfused, untreated rats, and in ischemia/reperfusion and total parenteral nutrition treated rats that was recorded with a concomitant increment in myeloperoxidase (inflammatory marker) in all experimental models except irradiated rats, which were unresponsive to FMLP. FMLP responsiveness was associ. ated with a significant rise in release of serotonin (mast cell mediator).

CONCLUSION

These results suggest that mast cells and other resident inflammatory cells within the gut wall are involved in FMLP-induced changes in mucosal barrier permeability and raise the possibility that under conditions of traumatic stress, proinflammatory mediators within the gut wall might be activated by toxic factors in the gut lumen.

Lactoferrin protects gut mucosal integrity during endotoxemia induced by lipopolysaccharide in mice

The hypothesis that lactoferrin protects mice against lethal effects of bacterial lipopolysaccharide (LPS) is the subject of experimental investigations described in this article. Lipopolysaccharide is a powerful toxin produced by gram negative bacteria that when injected into humans or experimental animals reproduce many of the pathophysiologic and immune responses caused by live bacteria. Lactoferrin administered intraperitoneally 1 hr prior to injection of LPS significantly enhanced the survival of mice, reducing LPS-induced mortality from 83.3% to 16.7%. Changes in locomotor and other behavioral activities resulting from LPS injection were not present in mice treated with lactoferrin. Also, histological examination of intestine revealed remarkable resistance to injury produced by LPS if mice were pretreated with lactoferrin. Severe villus atrophy, edema and epithelial vacuolation were observed in LPS-treated animals but not in lactoferrin-treated counterparts. Electrophysiological parameters were used to assess secretory and absorptive functions in the small intestine. In mice treated with LPS, transmural electrical resistance was reduced and absorption of glucose was increased. Lactoferrin treatment had no significant influence on basal electrophysiological correlates of net ion secretion or glucose absorption nor on changes induced by LPS. Collectively, these results suggest that lactoferrin attenuates the lethal effect of LPS and modulates behavioral and histopathological sequela of endotoxemia.

Fish oil supplementation does not impair the gut immune response to Trichinella spiralis infection in rats

BACKGROUND

Fish oil has been recommended as a source of omega-3 fatty acids for preterm infants and for therapy of some inflammatory diseases.

METHODS

Because fish oil supplementation could downregulate the host's immune response, we studied the gut inflammatory response to an enteric infection in 72 rats assigned to three dietary groups with differing fatty acid profile: 1) fish oil, rich in eicosapentaenoic and docosahexaenoic acid; 2) olive oil, containing 71% monounsaturated fat; and 3) rat chow, containing 57% saturated fat. One half (n = 36) of the rats were infected with Trichinella spiralis larvae; the other half served as controls. The inflammatory response to initial infection (study 1), and type I hypersensitivity response to a subsequent parasite-derived antigenic challenge (study 2) were assessed. Jejunal inflammatory cell infiltrate, mean villus height, disaccharidase levels, changes in short-circuit current in response to glucose absorption, and chloride secretagogues (study 1) were measured 9 days after infection. Short-circuit current changes induced by chloride secretion were measured when the proximal jejunum was challenged with T. spiralis-derived antigen 40 days after infection (study 2).

RESULTS

In study 1, jejunal tissue from infected animals had more eosinophilic infiltrate, lower disaccharidase levels, and less glucose absorptive and chloride secretory capacity than tissue from noninfected animals. In study 2, the jejunum of infected animals showed an antigen-induced chloride secretory response, whereas no response was obtained from jejunal tissue from noninfected animals. Type of diet did not affect the response in either study.

CONCLUSION

Under the conditions of this experiment, fish oil supplementation did not interfere with the local intestinal inflammatory response after T. spiralis infection.

The gut. A key metabolic organ protected by lactoferrin during experimental systemic inflammation in mice

The gastrointestinal tract may be viewed as an ecologic system in which a balance between the host and bacterial flora exists. Two major host components appear to be involved in maintaining this balance. The first is a non-specific structural barrier provided by the epithelial layer of the gastrointestinal mucosae. The second component involves functional immunological elements found in the mucosal and submucosal compartments, e.g., gut associated lymphoid tissue. When gut integrity is disrupted by invasive pathogens or by trauma, a myriad of pro-inflammatory mediators are released from cells in the gut wall that exert actions in the tissue or gut lumen. One of these mediators is lactoferrin, and iron binding protein found in high concentration in most human exocrine secretions. Despite controversies on its physiological role, evidence is emerging that lactoferrin plays an important role in host defense against toxic metabolites and antigenic components of potential pathogens2-4. This manuscript is intended to provide an overview of work related to lactoferrin's modulatory roles in inflammation, and to present observations from experimental studies on the preservation of intestinal structure and function by lactoferrin during intestinal inflammation. The possibility that lactoferrin limits the autodestructive inflammatory responses presents a new alternative for the future management of systemic inflammation.

Nutritional support for adaptation to radiation-induced suppression of mucosal immunity in the intestine of the rat

Appropriate enteral nutrition provided immediately after injury or trauma to the gastrointestinal tract may limit or reverse damage to the mucosal barrier. In this regard, diets containing amino acids, such as arginine and glutamine, or fish oil have been identified as beneficial. This report assesses the role of amino acids as "essential nutrients" in the repair of intestinal mucosa damaged by gamma radiation. Rats were used experimentally to test the hypothesis that the recovery of the immune responses in the intestinal mucosa, which are suppressed by radiation, can be improved by feeding an elemental amino acid diet, referred to hereafter as the diet, immediately after irradiation. The objective was to assess the impact of the diet on the expression of type I hypersensitivity or anaphylaxis in the jejunal mucosa. The local expression of this immunological response, which involves several radiosensitive cell types, was studied in rats immunized by oral infection with the nematode parasite, Trichinella spiralis. Rats that recover from infection become immunized and their small intestine undergoes anaphylaxis when subsequently challenged with parasite-derived antigen. This hypersensitivity response is expressed, in part, as Cl- secretion and can be observed in vitro or in vivo. When challenge is provided by a secondary inoculum of infective T. spiralis larvae, Cl- secretion is accompanied by fluid secretion and by the rapid expulsion of the parasite from the intestine. Immunized rats maintained on a stock diet and exposed to 7 Gy of total-abdominal irradiation from a cobalt-60 gamma-ray source failed to express antigen-induced Cl- secretion fully for up to 14 days postirradiation, and rejection of the parasite was suppressed for at least 30 days postirradiation. The suppression of immune responsiveness is associated with the disappearance of intestinal mucosal mast cells, which normally trigger the anaphylactic response. When rats are maintained on the diet after irradiation, the capacity to reject the parasite remains suppressed. However, the ability to express anaphylaxis-mediated Cl- secretion returns by 3 days postirradiation. The quick, diet-supported recovery of antigen-induced Cl- secretion occurs despite the continued absence of mast cells. Although the recovery of anaphylaxis-mediated responses suppressed by irradiation is only partial, our experimental results underscore the potential for enhancing the recovery process through nutritional support.

Relative allergenicity of cow's milk and cow's milk-based formulas in an animal model

Human infants fed cow's milk or cow's milk-based formula may become intolerant to milk proteins partially because of allergic reactions. However, the relative allergenicity of these diets has not been clearly determined at the intestinal level. In this study, the allergenicity of cow's milk and milk-based formula was evaluated by examining intestinal anaphylaxis caused by challenge with a milk protein fraction, beta-lactoglobulin (beta LG), in guinea pigs orally sensitized to these diets. Colonic segments were removed and challenged with beta LG. An antigen-induced, anaphylactically mediated elevation of transmural short circuit current, which is caused by net chloride (Cl-) secretion, was measured in Ussing chambers as an index of local immune responsiveness. After removal of the colon, all guinea pigs were challenged by intracardiac injection with beta LG to examine the onset of bronchospasm, a test for systemic anaphylaxis. Whereas colonic segments from all guinea pigs fed whole cow's milk responded to challenge with beta LG, segments from only 60% of animals fed cow's milk formula responded to the challenge. In addition, the responders in the latter group had a significantly lower magnitude of beta LG-induced Cl- secretion compared with animals sensitized to whole cow's milk. In parallel, bronchospasm developed in all guinea pigs fed whole cow's milk. In the group of animals fed cow's milk formula, bronchospasm developed only in those who responded to the intestinal challenge. On the basis of these results, cow's milk-based formula has less sensitizing power than whole cow's milk in our animal model, and our approach is effective in testing allergenicity at the intestinal level.

Progesterone modulation of anaphylactically induced ion transport in uterus and intestine

The objective of this study was to investigate the role of progesterone in modulating electrophysiological responses to antigenic challenge that are reflective of immune functions in uterine and jejunal mucosae. In the rat-Trichinella spiralis, host-parasite system, an enteric infection with a microscopic nematode sensitizes both the jejunum and uterus. Electrophysiological correlates of local anaphylaxis or type I hypersensitivity were monitored in vitro throughout the estrus cycle and during pregnancy. The magnitude of the anaphylactic response was correlated with serum levels of progesterone. Functional immunity was measured directly in the intestine by assessing the development of acquired resistance to reinfection with T. spiralis. Results support the conclusion that high progesterone output, as occurs during metestrus and pregnancy, and exogenously administered hormone suppress uterine responsiveness. However, the reduced uterine sensitivity to challenge could be attributed to nonspecific physiological effects of progesterone rather than direct effects on immunological components involved in the transduction of the antigenic signal. The electrophysiological response to antigen in the intestine was relatively refractory to effects of progesterone. These observations add to our understanding of endocrine control of mucosal responses to antigenic challenge and underscore site selectively of hormonal action.

Intestinal anaphylaxis: radiation-induced suppression

The gastrointestinal tract is highly sensitive to ionizing radiation. Some of the most radiosensitive cells in this system are mast cells and epithelium. This article describes experiments that test the hypothesis that irradiation suppresses mucosal immune responses in which mast cells and epithelium are involved. The hypothesis was tested by examining the impact of ionizing radiation on anaphylactically mediated Cl- secretion in jejunum of rats sensitized by Trichinella spiralis infection and challenged with antigen derived from the parasite. Antigen-induced Cl- secretion was measured electrophysiologically in vitro. Rats were immunized by inoculation with 3 x 10(3) T. spiralis larvae and, 30-50 days later, exposed to total abdominal irradiation from a cobalt-60 gamma source. Doses were 5, 7, and 9 Gy. At 1, 3, 5, 7, 14, and 21 days postirradiation (DPI), jejunal segments were assessed for immune responsiveness. (Duration of suppression to antigenic challenge was directly related to radiation dose). Recovery of response to antigenic challenge after irradiation with 5 Gy was complete by 5 DPI. At 7 Gy, responsiveness was totally suppressed from 1 to 5 DPI, was partially expressed from 5 to 14 DPI, and was completely restored by 21 DPI. A dose of 9 Gy completely suppressed immune responsiveness throughout the 21-day period. Full responsiveness of jejunum to exogenous Cl- secretagogues at 1-5 DPI indicates that the immunosuppressive effect of radiation was not due to a breakdown in the secretory process at the epithelium level.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural and molecular changes in intestinal smooth muscle induced by Trichinella spiralis infection

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

Use of a modified Ussing chamber to monitor intestinal epithelial and smooth muscle functions

A technique that allows the simultaneous monitoring of epithelial and smooth muscle function was developed and used to study rat small intestine in vitro. A Ussing chamber was modified so that a strain gauge force transducer could be sewn to the serosal surface of an intestinal segment clamped in the chamber. The apparatus was used to monitor short-circuit current, potential difference, and resistance across the segment, and contractions of the longitudinal layer of the muscularis externa. Both spontaneous activity and responses to the application of carbachol were recorded. Carbachol applied to the serosal side induced dose-dependent increases in both short-circuit current and contractile force. The median effective doses of the two responses differed, with contractions being more sensitive to the drug. Carbachol applied to the mucosal side induced no changes in either epithelial or contractile activities. The ability of the serosal strain gauge transducer to monitor contractions faithfully was tested in an organ bath in which the gut segment was attached to an external force-displacement transducer. There was a close correlation between the dose-dependent increase in force in response to carbachol measured by the serosal transducer and that measured by the force-displacement transducer (r = 0.988). Thus our technique can be used to study simultaneously epithelial and smooth muscle functions of the intestine.

Reconstruction of immune-mediated ion secretion in gut mucosa of the athymic rat

A defect in an immune-mediated, physiological reaction in the small intestine of congenitally immunosuppressed rats has been identified and corrected by recoupling the immunological trigger in the mucosa with epithelial effector cells. Antigenic challenge of jejunum from euthymic rats sensitized by infection with Trichinella spiralis evoked an anaphylactic response in vitro that was characterized by an elevation in transmural short-circuit current (Isc) and caused by net Cl- secretion. In contrast, jejunum from previously infected athymic counterparts failed to respond electrophysiologically to antigenic stimulation. Passive immunization of athymic rats with anti-Trichinella serum restored jejunal responsiveness to antigen. Jejunal unresponsiveness to antigenic challenge in the athymic rat compared with the euthymic rat was not due to a difference in the duration of exposure to the sensitizing antigens, mast cell numbers, inflammation-related histological changes nor to reduced responsiveness of epithelium to Cl- secretagogues. Because the transduction of the antigenic signal into epithelial ion transport changes in euthymic rats requires IgE, mucosal mast cells, mast cell-derived mediators and enteric nerves, the results support the conclusion that an antibody deficiency is the only functional defect preventing the antigen-induced change in mucosal ion transport in the athymic host.

Immunological sensitization of opossum gallbladder by naturally acquired stomach roundworm infection

1. The opossum gallbladder develops an immediate type hypersensitivity as a result of chronic infection with the gastric nematode, Physaloptera turgida. 2. Hypersensitization is evident from a change in net transepithelial ion transport in response to parasite-derived antigen. 3. The antigen-induced change in ion transport involves mediation by histamine and possibly prostaglandins and is independent of intrinsic neural modulation. 4. The functions of the gallbladder epithelium are influenced by reactions of local immune elements that are part of the common mucosal immune system.

Immunoregulation of endometrial and jejunal epithelia sensitized by infection

The hypothesis was tested that the uterus of the rat orally infected with the parasite Trichinella spiralis becomes hypersensitized and that subsequent antigenic challenge affects functions in the endometrial epithelium. Results of experiments comparing the immunological responsiveness of isolated rat uterus with that of the jejunum supports our hypothesis. Antigenic challenge of uterus mounted in Ussing-type chambers causes an elevation in transuterine short circuit current (Isc) of 6.4 +/- 0.8 microA/cm2. The transduction of the antigenic signal to elicit the electrophysiological response involves 5-hydroxytryptamine (5-HT) working through a nerve-independent pathway. The antigen-stimulated rise in Isc peaks approximately 3 min after challenge. The uterine response is blocked by diisothiocyanostilbene-2,2'-disulfonic acid, an inhibitor of bicarbonate-chloride exchange. The antigen-evoked change in jejunal Isc is biphasic, peaking at 1.5 and approximately 4.0 min after challenge, and is about 10-fold greater in magnitude than the Isc in the uterus. The transductive pathway in the jejunum involves 5-HT, histamine and prostaglandin acting partly through intrinsic nerves. The jejunal response to antigen is inhibited by diphenylamine-2-carboxylate, a chloride channel blocker. Changes in net ion transport which are primed by infection and evoked by antigen are apparently triggered by local anaphylaxis in both the uterus and jejunum.

Biliary and gut function following shock

The aim of this study was to characterize the alterations in gallbladder and intestinal function after hemorrhagic shock and blood reperfusion in opossums. Animals were subjected to a shock of 30 mm Hg of arterial blood pressure for 60 minutes and resuscitated with blood reinfusion. Gallbladder epithelial ion transport, gallbladder motility in vitro and in vivo, gastrointestinal motility, and flora of the stomach and small bowel were studied 2 and 24 hours after shock. Changes at 2 hours included decreased gallbladder contractility in vitro and decreased emptying in vivo, loss of coordination with intestinal motor activity, decrease in frequency of intestinal electrical slow waves, and reduced duration of the intestinal migrating motor complex cycle. By 24 hours, gallbladder epithelial permeability was increased and in vitro contractility remained reduced but the in vivo functions showed partial recovery. Gastrointestinal flora was not affected by these changes. These data demonstrate that hemorrhagic shock and reperfusion affect digestive motility. The early timing of the alterations observed and the partial recovery 24 hours post shock suggest an ischemia-hypoxia mechanism of injury.

Simulation of parasite-induced gut hypersensitivity: implications for vaccination

Antigenic challenge of jejunum from rats infected with Trichinella spiralis evokes a biphasic pattern of epithelial Cl- secretion, as measured in vitro by electrophysiological methods. Peaks of secretion occur at approximately 1.5 and approximately 5.0 min post-challenge. Challenge of jejunum from hosts passively immunized with serum containing anti-Trichinella anaphylactic antibody evokes the late phase but not the early phase of Cl- secretion. Since the early phase is mediated by 5-hydroxytryptamine and histamine from mast cells, we hypothesized that the failure to express that phase was due to a decrease in mast cell-derived mediators secondary to a deficiency in mucosal mast cell numbers. The hypothesis was tested by correlating mast cell numbers with patterns of antigen-induced Cl- secretion using several immunization regimes. Rats actively immunized by infection produced anti-Trichinella IgE and had a mucosal mastocytosis. Rats passively sensitized with serum containing anti-Trichinella IgE had normal numbers of mast cells in their mucosa. Inducing mastocytosis in rats, by infecting them with Nippostrongylus brasiliensis prior to passive sensitization with anti-Trichinella serum, primed for the expression of a biphasic Cl- secretory response upon subsequent challenge with Trichinella antigen. Rats actively sensitized by injection with Trichinella antigen elicited an IgE response without mastocytosis and expressed only the late phase of antigen-induced Cl- secretion. Results (i) support our hypothesis, (ii) emphasize the importance of the cellular state of the mucosa in the functional expression of local anaphylaxis; and (iii) provide a physiological explanation for the general failure of vaccination and passive sensitization to induce functional immunity equivalent to that induced by natural infection.

Evaluation of a possible functional relationship between chemical structure of intestinal brush border and immunity to Trichinella spiralis in the rat

Primary exposure to Trichinella spiralis in the rat, while immunizing against reinfection, induces changes in the carbohydrate structure of intestinal brush border membranes. Immunity is expressed in heightened resistance to mucosal invasion by L1 larvae, and the change in structure is evident in reduced membrane binding of the lectin, wheat germ agglutinin. The possibility that altered membrane composition is a requisite for expression of immunity was hypothesized and this was evaluated by correlating the maximum, specific binding of wheat germ agglutinin by isolated brush border membranes with (1) the expression of immunity acquired passively through serum transfer, and (2) the loss of immunity acquired from serial infections terminated in the intestinal phase. The hypothesis was further evaluated by determining whether the change in membrane structure represents a stimulus-specific response. We observed that (1) passively acquired immunity was not associated with a reduction in lectin binding and (2) short-term exposure to the intestinal stages of T. spiralis led to a reduction in lectin binding that was detectable at a time when rats were incapable of resisting reinfection. The change in lectin binding associated with trichinosis also accompanied infection with Nippostrongylus brasiliensis. Results uniformly support the conclusion that immunity to T. spiralis is independent of brush border membrane changes reflected in reduced binding of wheat germ agglutinin.

Mediators of anaphylaxis-induced ion transport changes in small intestine

Net ion transport by jejunum of rats immunized against Trichinella spiralis on challenge with parasite-derived antigen was measured in Ussing chambers as a rapidly expressed, biphasic rise and fall (phase I and II) in short-circuit current (delta Isc). This delta Isc is triggered by mucosal anaphylaxis. Our objective is to identify mast cell-derived substances that mediate the epithelial response. Antigenic challenge of sensitized jejunum caused the release of 5-hydroxytryptamine (5-HT), histamine, and prostaglandin E2 (PGE2). The antigen-induced phase I response was mimicked by exogenous 5-HT or histamine and blocked by pretreatment of tissue with 5-HT and histamine H1-antagonists; the phase II response was mimicked by exogenous PGE2 and blocked by an inhibitor of prostaglandin synthesis. Atropine and tetrodotoxin significantly blunted the phase I response as well as the delta Isc caused by exogenous 5-HT or histamine while only slightly reducing the phase II response and not affecting the delta Isc induced by PGE2. Results support the conclusion that 5-HT, histamine, and PGE2 mediate the antigen-induced change in Isc through direct and neurally mediated stimulation of jejunal epithelium.

Anaphylaxis-mediated epithelial Cl- secretion and parasite rejection in rat intestine

Immunologically mediated expulsion of Trichinella spiralis infective larvae in the rat was used as a model to test the hypothesis that intestinal anaphylaxis induced by parasite antigen causes ion transport alterations in small intestinal epithelium, and that the small intestinal epithelium, by altering its physiologic state in response to mast cell-derived mediators, functions as an effector tissue in the expulsion process. Experimental results demonstrated that the rapid rejection response and antigen-inducible changes in net intestinal ion transport acquired through active immunization were transferable with serum containing a high titer of anti-trichinella homocytotropic antibody, as measured by the PCA test. Neither response was expressed in nonimmune hosts nor in recipients of serum in which the PCA-detectable antibody was reduced by heat treatment. Net ion transport by jejunal epithelium of both actively and passively immunized rats was measured in Ussing chambers by using the electrical correlate, short circuit current (Isc). Involvement of chloride secretion in antigen-induced alterations in Isc was deduced from the use of chemical agents that effectively and specifically blocked the antigen-induced Cl- secretory response. The results implicate anaphylaxis in both rapid worm rejection and altered epithelial ion transport.

Anaphylaxis-mediated epithelial Cl- secretion and parasite rejection in rat intestine

Immunologically mediated expulsion of Trichinella spiralis infective larvae in the rat was used as a model to test the hypothesis that intestinal anaphylaxis induced by parasite antigen causes ion transport alterations in small intestinal epithelium, and that the small intestinal epithelium, by altering its physiologic state in response to mast cell-derived mediators, functions as an effector tissue in the expulsion process. Experimental results demonstrated that the rapid rejection response and antigen-inducible changes in net intestinal ion transport acquired through active immunization were transferable with serum containing a high titer of anti-trichinella homocytotropic antibody, as measured by the PCA test. Neither response was expressed in nonimmune hosts nor in recipients of serum in which the PCA-detectable antibody was reduced by heat treatment. Net ion transport by jejunal epithelium of both actively and passively immunized rats was measured in Ussing chambers by using the electrical correlate, short circuit current (Isc). Involvement of chloride secretion in antigen-induced alterations in Isc was deduced from the use of chemical agents that effectively and specifically blocked the antigen-induced Cl- secretory response. The results implicate anaphylaxis in both rapid worm rejection and altered epithelial ion transport.

Phosphatidylethanolamine methylation in intestinal brush border membranes from rats resistant to Trichinella spiralis

Methylation of phospholipids is proposed as a mechanism to explain changes in properties of intestinal brush border membrane that coincide with development of immunity to the intraepithelial parasite, Trichinella spiralis. Methylation was measured by the incorporation of the [3H]methyl group from S-adenosyl-L-[3H]methyl methionine into phospholipids. At least two enzymatic components were detected that converted phosphatidylethanolamine to phosphatidylcholine. The first, designated methyltransferase I, catalyzed the formation of phosphatidylmonomethylethanolamine from phosphatidylethanolamine and had a low Km for S-adenosyl-L-methyl-methionine (5 microM). The second, designated methyltransferase II, which catalyzed the methylation of phosphatidylmonomethylethanolamine to phosphatidyldimethylethanolamine and phosphatidyldimethylethanolamine to phosphatidylcholine, had a high Km for S-adenosyl-L-methyl methionine (167 microM). Both enzymes had two pH optima, were most active at 37 degrees C and were Mg2+ dependent. A decrease in methylation activity was present in brush border membranes from rats immunized against T. spiralis. Although the synthesis of phosphatidylcholine was not significantly altered there was a substantial decrease in the formation of phosphatidylmonomethylethanolamine and phosphatidyldimethylethanolamine as compared with nonimmunized rats. Since phospholipid composition influences membrane fluidity and cell function, it is proposed that altered methylation activity may influence the characteristics of brush border membrane in the immune host.

Sialic acid deficiency in lectin-resistant intestinal brush border membranes from rats following the intestinal phase of trichinellosis

Maximal binding (Bmax) of the lectin, wheat germ agglutinin, by small intestinal brush border membrane is significantly reduced in rats infected with Trichinella spiralis. Wheat germ agglutinin specificity is for N-acetylglucosamine and sialic acid. Whereas total hexosamine and N-acetylglucosaminidase-labile N-acetylglucosamine were comparable in membranes from uninfected as compared with infected rats, the total sialic acid content and neuraminidase-released sialic acid were significantly higher in BBM from uninfected hosts. N-Acetylglucosaminidase treatment of membranes reduced Bmax for wheat germ agglutinin in both hosts. Neuraminidase treatment reduced Bmax in uninfected hosts, but tended to increase it in infected rats. Membranes from uninfected rats incorporated more N-acetylglucosamine from UDP-N-[14C]acetylglucosamine into oligosaccharide-lipid than did membranes from infected hosts. However, lipid and protein fractions were labeled at the same rate in both sets of membranes. Sialic acid was incorporated into protein at a slightly faster rate in brush border membrane from uninfected rats, indicative of a higher level of sialotransferase activity. These results suggest that the reduction in Bmax for wheat germ agglutinin in gut epithelial cell membranes from infected rats is related to a reduced level of sialic acid available for lectin binding as well as specific interactions between N-acetylglucosamine and sialic acid.

Intestinal epithelial membrane changes in rats immune to Trichinella spiralis

Establishment of Trichinella spiralis infective larvae is blocked to a large degree in the immune rat as compared with the nonimmune host. The rapidity with which this response occurs indicates that most worms are either prevented from penetrating the intestinal epithelium or are rejected immediately after cell entry. It is proposed that interference with larval infectivity is due to alterations in the epithelial cell apical or brush border membrane. Alterations may result from prior infection or may reflect an acute change induced by challenge infection. In either case the establishment of normal populations of larvae in the mucosa is disturbed. Lectin binding capacity of brush border membranes was used to assess possible membrane alterations. This parameter in uninfected (control) rats was compared with that in infected rats, which acquire resistance to subsequent challenge, and in infected rats immediately after a challenge inoculum. Enriched brush border membrane preparations were characterized for their binding of wheat germ agglutinin, which attaches specifically to the carbohydrate, N-acetylglucosamine. Maximum specific binding of 125I-labeled wheat germ agglutinin occurred within 20 min. The spontaneous rate of dissociation was negligible for 90 min. Highest specific binding resulted at 24 degrees C, pH 6.0 and with 75 micrograms brush border membrane protein per assay tube. Results suggested the existence of multiple binding sites. 1 mg of membrane protein from uninfected rats and rats immunized by primary infection maximally bound 9.8 X 10(10) and 4.3 X 10(10) molecules of wheat germ agglutinin, respectively. Binding for the 'immune' brush border membrane, as compared with the 'uninfected' brush border membrane was reduced during the first 3 weeks of infection and remained low for at least 3 months. No further reduction in binding was observed for brush border membrane isolated within minutes after a secondary infection. These results reveal the induction by a primary infection of changes in brush border membrane structure and the persistence of these changes in the immune host. In view of the rapid turnover time of epithelial tissue the mechanism by which this change is perpetuated speculatively involves immune elements in the lamina propria.