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Validity, reliability, and calibration of the Tritrac accelerometer as a measure of physical activity.

PURPOSE: The purposes of this study were to assess the validity and reliability of the Tritrac R3D accelerometer during treadmill walking and running and then to calibrate the instrument. METHODS: The Tritrac was assessed on 60 young adults (23.4 +/- 2.9 yr) during treadmill walking and running at 3.2, 6.4, and 9.7 km x h(-1). The calibration was carried out by identifying ranges of Tritrac raw data (vector magnitude) values corresponding to light (2-3.9 MET), moderate (4-7 MET), and vigorous (>7 MET) physical activity. Energy expenditure (EE), measured by indirect calorimetry, served as the criterion measure. RESULTS: Interinstrument intraclass reliability coefficients for Tritracs worn on the right and left hip ranged from 0.73-0.87, while intersession coefficients demonstrated high reliability for all speeds (R = 0.87-0.92). Paired t-tests comparing mean accelerometer counts at 6.4 km x h(-1), 0% grade (2647 +/- 456), and 6.4 km x h(-1), 5% grade (2635 +/- 435) demonstrated no significant difference (P > 0.05). Mean differences between EE measured by indirect calorimetry and that estimated by the Tritrac ranged from 0.0082 kcal x kg(-1) x min(-1) at 3.2 km x h(-1) to 0.0320 kcal x kg(-1) x min(-1) at 9.7 km x h(-1), with the Tritrac consistently overestimating EE during horizontal treadmill walking. The relationship between vector magnitude and EE across all speeds was highly linear (R2 = 0.90, SEE = 0.014 kcal x kg(-1) x min(-1)), with little overlap between light, moderate, and vigorous categories. The mean vector magnitudes at 2, 4, and 7 MET were 650, 1772, and 3455, respectively. CONCLUSIONS: These data indicate that the Tritrac is highly reliable from day to day and is sensitive to changes in speed but not grade. Furthermore, the Tritrac accurately distinguishes various intensities of walking and jogging on level ground. With limitations, these cut-points can be used to categorize light, moderate, and vigorous physical activity and to estimate EE.

Adolescent↗

Levels of physical activity and inactivity in children and adults in the United States: current evidence and research issues.

PURPOSE: The purpose was to describe current levels of physical activity and inactivity among adults and young people in the United States. METHODS: Estimates of participation in regular physical activity were derived from three national surveys for adults (National Health Interview Survey, National Health and Nutrition Examination Survey, and the Behavioral Risk Factor Surveillance System) and from the Youth Risk Behavior Survey for high school students. RESULTS: Overall, 63.8% of high school students surveyed on the 1997 YRBS reported participating in vigorous physical activity for at least 20 min on 3 or more days per week. Participation in vigorous activity was higher for boys (72.3%) than girls (53.5%), whites (66.8%) compared with blacks (53.9%) and Hispanics (60.4%), and decreased with advancing grade. Among adults, 27.7% meet recommended levels of either moderate or vigorous physical activity, whereas 29.2% report no regular physical activity outside of their work. Gender differences in participation in physical activity are less pronounced than in youth, and age-related patterns were complex. Whites are more active than blacks and Hispanics, and persons with higher family incomes and more education report being more physically active. There have been only minor changes in reported participation in leisure time physical activity over the past 15 yr. CONCLUSION: National estimates of physical activity appear to be reliable and valid for adults but may be less so for adolescents and are poor measures for children. Research is needed to determine the role that objective monitoring with accelerometers may play in surveillance. Reliable and valid measures of occupational, household, and transportation-related physical activity and sedentary behaviors are needed to better characterize the range of activity that is associated with health.

Adult↗

Changes in common activities of 3rd through 10th graders: the CHIC study.

PURPOSE: This study was a longitudinal examination of the change in both the activities done and the intensity of those activities from childhood to adolescence. METHODS: Common activities were assessed by questionnaire initially on 656 subjects from 21 elementary schools; 50.5% were female, 83.4% were Caucasian, 20.6% African-American, and 6.0% were other races. RESULTS: Girls more often reported sedentary activities overall. Weighted least squares analyses showed boys consistently reported more vigorous activities than girls (P < 0.0008). African-American girls reported fewer vigorous activities than Caucasian or other race girls (P = 0.027). Sedentary activities were more frequently reported with increasing age (X2 P < 0.001). The youngest African-American and Caucasian boys reported similar activity patterns. However, boys from other races reported more intense activities until sixth and seventh grades when African-American boys began reporting more sedentary activities than Caucasians or other races (P = 0.004). During sixth-eighth grades, Generalized Estimating Equations (GEE) models show that girls with more advanced pubertal status reported more sedentary activities than girls who were less developed (P < 0.0001). For high school girls, race was a marginally significant predictor (P = 0.05) of activity status. Neither race nor pubertal status were significant factors in activities chosen by middle school boys. However, for male high school students, Caucasians were more likely than African-Americans to report vigorous activities (P = 0.005). CONCLUSIONS: Variation in activities by race within gender suggests that establishing activity patterns in youth may be race-specific as well as gender-specific and must be accounted for in designing physical activity interventions. Also, pubertal maturation is a factor in activity choices in middle school girls.

Adolescent↗

Age-related differences in physical activity levels of young adults.

PURPOSE: To examine age-related differences in the physical activity behaviors of young adults. METHODS: We examined rates of participation in vigorous- and moderate-intensity leisure-time activity and walking, as well as an index of physical activity sufficient for health benefits in three Australian cross-sectional samples, for the age ranges of 18--19, 20--24, and 25--29 yr. Data were collected in 1991, 1996, and 1997/8. RESULTS: There was at least a 15% difference in vigorous-intensity leisure-time physical activity from the 18--19 yr to the 25--29 yr age groups, and at least a 10% difference in moderate-intensity leisure-time physical activity. For the index of sufficient activity there was a difference between 9 and 21% across age groups. Differences in rates of walking were less than 8%. For all age groups, males had higher rates of participation for vigorous and moderate-intensity activity than did females, but females had much higher rates of participation in walking than males. Age-associated differences in activity levels were more apparent for males. CONCLUSIONS: Promoting walking and various forms of moderate-intensity physical activities to young adult males, and encouraging young adult females to adopt other forms of moderate-intensity activity to complement walking may help to ameliorate decreases in physical activity over the adult lifespan.

Activities of Daily Living↗

Validity of a physical activity questionnaire among African-American Seventh-day Adventists.

INTRODUCTION: Physical activity has been identified as an important predictor of chronic disease risk in numerous studies in which activity levels were measured by questionnaire. Although the validity of physical activity questionnaires has been documented in a number of studies of U.S. adults, few have included a validation analysis among blacks. We have examined the validity and reliability of a physical activity questionnaire that was administered to 165 black Seventh-day Adventists from Southern California. METHODS: Subjects completed a self-administered physical activity questionnaire and then "reference" measures of activity (7-d activity recalls, pedometer readings) and fitness (treadmill test) were completed in subsets of this population. RESULTS: The authors found that 7-d recall activity levels correlated well with the corresponding questionnaire indices among women (total activity, r = 0.65; vigorous, r = 0.85; moderate, r = 0.44; inactivity, r = 0.59; sleep duration, r = 0.52) and men (total activity, r = 0.51; vigorous, r = 0.65; moderate, r = 0.53; inactivity, r = 0.69; sleep duration, r = 0.39). Vigorous activity from 7-d recalls was best measured by gender-specific indices that included only recreational activities among men and emphasized nonrecreational activities among women. Correlations between questionnaire data and the other "reference" measures were lower. Test-retest correlations of questionnaire items over a 6-wk interval were high (r = 0.4-0.9). CONCLUSION: Simple questions can measure activities of different intensity with good validity and reliability among black Adventist men and women.

Adult↗

A comparison of the Yale Physical Activity Survey with other physical activity measures.

PURPOSE: The purpose of this study was to determine associations of the Yale Physical Activity Survey (YPAS) with the Stanford 7-d physical activity recall (PAR) and several physiologic measures, both cross-sectionally and longitudinally. METHODS: Participants were 59 individuals (45% African-American, 79% women) between the ages of 60 and 80 yr who were enrolled in a clinical trial. From the YPAS, total time in activity, estimated weekly energy expenditure, and indices of vigorous activity, leisurely walking, moving, standing, sitting, and an overall summary index were determined. From the PAR, daily energy expenditure, and hours spent in light, moderate, and hard/very hard activities were estimated. Physiologic measurements included estimated VO2max, resting pulse rate, and body mass index (BMI). RESULTS: Weekly energy expenditure, total time in activity, and the summary index correlated with daily energy expenditure at baseline (Spearman correlations = 0.37, 0.30, 0.33, respectively, Ps < 0.01) and time in moderate activity (r = 0.37, 0.29, 0.39, Ps < 0.01). The vigorous index was also significantly correlated with daily energy expenditure and time in light, moderate, and hard/very hard activity. The summary, moving, and standing indices correlated with VO2max (Ps < 0.05) and BMI (Ps < 0.05). Change in physical activity determined from the PAR correlated with change in most YPAS dimensions, although few correlations were statistically significant. CONCLUSIONS: The global activities and the vigorous activity index determined from the YPAS correlated with corresponding measures of the PAR. The validity of the YPAS for light-intensity activities is less clear, although optimal validation measures for light-intensity activity are yet to be defined. The ability of the YPAS to detect change in physical activity shows some promise, but data from this study are insufficient to be conclusive.

Aged↗

Arterial distensibility and physical activity in the ARIC study.

PURPOSE: Arterial distensibility decreases with age. This decrease may be associated with the initiation and/or progression of hypertension and atherosclerosis and may be attenuated by positive lifestyle habits, including habitual physical activity. We tested the hypothesis that self-reported sport, leisure, and work physical activity is associated with greater arterial distensibility (i.e., carotid artery pulsatile diameter changes). METHODS: The Atherosclerosis Risk in Communities (ARIC) study assessed left common carotid arterial diameters and intimal-medial wall thickness (IMT) using B-mode ultrasound techniques, in 10,644 African-American and white men and women aged 45-64 yr and free of cardiovascular disease. RESULTS: Work activity, but not sports or leisure activity, was weakly associated with greater arterial distensibility in an ANCOVA model adjusted for blood pressure and other covariates (diastolic arterial diameter, pulse pressure, pulse pressure squared, age, race, sex, smoking, dietary fat intake, height, education, and clinical center) (P for linear trend = 0.03). Vigorous sports activity was weakly positively associated with arterial distensibility (arterial diameter change (mean +/- SE in mm) 0.42 +/- 0.004 vs 0.41 +/- 0.002 for the 12.7% of participants reporting any vs no vigorous activity, P = 0.02), and this association was not attenuated by adjustment for IMT, body mass index, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, or diabetes. Repeated analyses with traditional arterial stiffness indices showed similar findings for vigorous but not work activity. CONCLUSION: In contrast to several smaller studies, these findings do not support the hypothesis that habitual physical activity has a strong, consistent positive effect on arterial distensibility.

Arteries↗

Validity and reproducibility of a physical activity questionnaire in women.

PURPOSE: To determine the validity and reproducibility of a self-administered physical activity questionnaire that assesses the frequency, intensity, and duration of recreational, household, and occupational activity in women. METHODS: The questionnaire was administered by mail twice to 131 participants 1 yr apart. During this interval, participants completed four 1-wk activity logs corresponding to different seasons throughout the year. RESULTS: The intraclass correlation coefficients used to measure reproducibility were 0.82 for total activity, 0.79 for moderate activity, 0.86 for vigorous activity, 0.80 for recreational activity, and 0.73 for household activity. The distribution of activity scores was similar between the questionnaires and the average of the four logs, indicating the participants' ability to incorporate seasonal variation into their recall on a questionnaire. The correlations between the questionnaire-based activity scores and log-based activity scores, indicating validity, were 0.26 for total activity, 0.15 for moderate activity, and 0.52 for vigorous activity. Women younger than age 50 tended to have higher validity scores than women aged 50 yr and older (r = 0.31 vs r = 0.19, respectively, for total activity). CONCLUSION: These data indicate that this physical activity questionnaire is reproducible and provides a useful measure of current activity, particularly vigorous activity, over a 1-yr period.

Adult↗

Physical activity, sports participation, and suicidal behavior among college students.

PURPOSE: To evaluate the relationship between physical activity, sports participation, and suicidal behavior among college students (N = 4,728). METHODS: Data from the 1995 National College Health Risk Behavior Survey were analyzed. Students were classified as engaging in frequent vigorous activity 6-7 d.wk-1, vigorous activity 3-5 d.wk-1, moderate activity, low activity, or no activity. Sports participation was dichotomized into "yes" or "no" participation. Suicidal behavior was defined as thoughts about, plans for, or attempts at suicide during the 12 months before completing the survey. Data were stratified by sex and multivariable logistic regression modeling, calculated odds ratios (ORs) (adjusted for age, race/ethnicity, Body Mass Index/weight perception, cigarette smoking, episodic heavy alcohol use, drug use, and either activity level or sport participation) for suicidal behavior as associated with physical activity and sports participation. RESULTS: Adjusted ORs show that men in the "low activity" group were at almost half the odds (adjusted OR = 0.54; P < 0.015) of reporting suicidal behavior than men in the "not active" group. Women who engaged in moderate or frequent vigorous activity were at greater odds of reporting suicidal behavior compared with inactive women; OR = 1.76 (P < 0.035) and 1.99 (P < 0.034) respectively. Sports participation was protective against suicidal behavior. Adjusted ORs show that men who did not participate in sports were 2.5 times (P < 0.0003) more likely to report suicidal behavior than men who were sports participants. Women not participating in sports had 1.67 times the odds of reporting suicidal behavior than women sports participants (P < 0.05). CONCLUSIONS: Associations were found between sports participation/selected patterns of physical activity and suicidal behavior. Causal factors mediating the relationships need to be identified.

Adolescent↗

Sources of variance in daily physical activity levels as measured by an accelerometer.

PURPOSE: To examine sources of variance in objective measures of physical activity in a group of healthy adults (N = 92) participating in a physical activity measurement study. METHODS: Physical activity was assessed for up to 21 consecutive days using the Computer Science Applications (CSA) accelerometer. Day-of-the-week effects were evaluated for activity counts (ct.min(-1).d(-1), ct.d(-1)) and time (min.d(-1)) spent in inactivity (0-499 ct), moderate-1 (500-1951 ct), and moderate-2-vigorous activity (> or =1952 ct). Random effects models were employed to estimate variance components for subject, day of the week, and residual error from which the number of days of assessment required to achieve 80% reliability were estimated. RESULTS: Physical inactivity was lower on weekend days, and Saturday was the least inactive day of the week for both men and women. Inter-individual variation, or differences between subjects, was proportionally the largest source of variance (55-60% of total) in accelerometer counts and time spent in moderate to vigorous activity. Differences within subjects (intra-individual variation) accounted for 30-45% of the overall variance, and day-of-the-week effects accounted for 1-8%. For activity counts, and time spent in moderate to vigorous activity, at least 3-4 d of monitoring were required to achieve 80% reliability. Reliable measures of physical inactivity required at least 7 d of monitoring. CONCLUSION: These findings provide insight for understanding the behavioral variability in the activity patterns of adults and suggest that reliable measures of activity behaviors require at least 7 d of monitoring.

Acceleration↗

Leisure time activities of elementary school children.

The three most common leisure time activities of 2,200 third and fourth grade children (mean age 8.8 + 0.8; 50.7% girls) and the association of the intensity levels of those activities with demographic variables and risk factors for cardiovascular disease are reported. Activities reported most often by boys were playing video games (33%), playing football (32%), bicycling (31%), watching television (28%), and playing basketball (26%). The girls reported doing homework (39%), bicycling (31%), watching television (30%), dancing (27%), and reading (23%). Overall, the children, especially girls, reported fairly sedentary activities, with an average metabolic equivalent level of 4.2 for girls and 4.8 for boys. Among boys, African Americans reported more vigorous activities than Whites, but the activities reported by White girls were somewhat more vigorous than those reported by non-White girls. Children from a higher socioeconomic status (SES), especially boys, reported a greater proportion of sedentary activities than lower SES children. The risk factors of cholesterol, blood pressure, skinfold thickness, and body mass index were not significantly associated with total activity score. However, significantly more nonobese than obese children reported a vigorous (high-intensity) activity as one of their top three activities.

Black or African American↗

Levels of physical activity among school-age children in Taiwan: a comparison with international recommendations.

Few studies have investigated levels of physical activity among children in Taiwan. The purposes of this study were to explore levels of physical activity among children and examine their rates of compliance with various international recommendations. The sample was comprised 463 children (249 boys and 214 girls) , aged between nine and twelve from four cities in Taiwan. Three-day Physical Activity Logs (3-d PAL) were used as the instrument to measure physical activity in the previous seven days. The mean and percentile of average estimated energy expenditure (EE, kcal/kg/day), moderate-vigorous physical activity (MVPA, min/day) and vigorous physical activity (VPA, min/day) among boys and girls according to age group were reported. Four international physical activity recommendations were used, as the criteria with which were examined compliance rates. Results indicated no significant main effects of age or gender, and no interaction was found between EE and MVPA. VPA significantly increased between the aged nine and eleven. Girls aged 12 engaged less significantly VPA than boys. Over 90% of children met the Physical Activity Guidelines for Adolescents (PAGA) and the United States' Healthy People Objective No. 22.6; 80% met the United Kingdom Expert Consensus Group guideline; and 70% met the Healthy People Objective No. 22.7. These results indicated that physical activity among the majority of children complied with the international recommendations. The only significant difference came in participation rates for vigorous physical activity among children of different ages and gender. Our results provide important information for health policy in the field of children' s physical activity. We would recommend the setting up of national objectives for the physical activity of children and the conducting of a national surveillance study with a more precise and consistent measurement of physical activity for children to offer a comparable data in the future is suggested.

Analysis of Variance↗

Recurrent senescence in axenic cultures of Physarum polycephalum.

When subcultures of the aux-2 and aux-4 strains of Physarum polycephalum, which had been grown for more than four years in axenic shake culture, were transferred to non-axenic surface culture they displayed progressively shorter lifespans (older axenic surface cultures yield shorter lived non-axenic cultures). Similar subcultures transferred to axenic agar medium also underwent senescent-like events. These subcultures, after a period of vigorous growth, displayed a slower growth rate, reduced cytoplasmic streaming, loss of yellow pigment, and eventually they fragmented into a number of small spherical structures with the concomitant lysis of most of the plasmodium. In non-axenic culture these structures quickly degenerated (and disappeared from the culture); however, in axenic culture they revived and after several days produced new vigorous plasmodia. Following a period of vigorous growth the plasmodium again underwent senescent-like events. This cycle of senescence and growth was repeated a number of times before death finally occurred.

Cell Cycle↗

Imbibitional chilling injury in pollen: involvement of the respiratory chain.

Chilling injury is sustained by dry pollen of Typha latifolia L. upon hydration in germination medium at 0 degrees C. This injury is evidenced as poor germination, low vigor, and depressed respiration. Isolated mitochondria showed multiple sites of impaired electron transport. Besides losses of cytochrome (Cyt) c and NAD(+), the activities of membrane-bound enzyme complexes such as Cyt oxidase, NADH-duroquinone oxidoreductase, succinate-duroquinone oxidoreductase, and malate-duroquinone oxidoreductase were severely affected.Similarly, as in isolated mitochondria, in situ tests of mitochondrial activity showed that Cyt c was partially lost from its site of action. Re-addition of the lost Cyt c to the grains restored the N,N,N',N'-tetramethyl p-phenylenediamine dihydrochloride plus ascorbate-mediated electron transport from Cyt c to O(2), but did not significantly accelerate the overall O(2) uptake. Electron flow to duroquinone in the injured grains was low, indicating that lesions at the substrate side of ubiquinone determine the rate of O(2) consumption. Leakage of NAD(+), and also of adenylate phosphates and Krebs cycle substrates out of the injured grains, was considerable.Increasing the initial moisture content of the grains strongly enhanced their resistance to cold hydration. Below 17% moisture content (fresh weight basis), the decrease in vigor closely matched the loss of NAD(+) and adenosine phosphates. Vitality was irreversibly lost by cold hydration below 10 to 12% initial moisture content.Injury to dry pollen was prevented by imbibition at 27 degrees C. Decrease of vigor and increased leakage, however, started below 20 degrees C, and complete loss of vitality occurred below 10 degrees C.These results are interpreted as evidence that loss of membrane integrity is the primary cause of imbibitional chilling injury.

Journal Article↗

Reversal of the effects of aging in soybean seeds.

Accelerated aging predisposed seeds to imbibition injury. Slowing the rate of hydration prevented the loss of germinability due to imbibition injury. Germinability of accelerated aged seeds (50 hours) was increased from 10 to 90% by controlling the rate of imbibition. Slow hydration also prevented seed electrolyte leakage. This may indicate that cell membrane permeability or rupture was a major factor contributing to the loss of germinability after aging.Reversal of the effects of aging (repair) was accomplished by slowly inbibing and then redrying seeds (priming). This treatment lowered steep water conductivity by a factor of 2 to 5. Priming also increased the per cent germination of low vigor seeds. The mechanism of this reversal was probably metabolic because it depended on temperature, seed moisture, and treatment duration.Priming doubled the survival of seeds in the accelerated aging vigor test. The ;rejuvenation' was accepted as evidence for metabolic repair. Since the ;vigor' of seeds was increased by priming, metabolic repair probably included other subcellular components as well as the plasma membrane.

Journal Article↗

The association between information and communication technology exposure and physical activity, musculoskeletal and visual symptoms and socio-economic status in 5-year-olds.

BACKGROUND: Increasing use of computers by children has raised concerns over the potential impact on their cognitive, social, educational, visual and physical development. Despite this concern, there are no large-scale studies relating the use of computers to specific health indicators in children as they reach school age. METHODS: A cross-sectional analysis of 1600 5-year-old Western Australian children participating in a longitudinal cohort study was conducted to ascertain their computer use, other activities (watching television and videos, playing electronic games, reading and looking at books, drawing on paper and moderate to vigorous physical activity), and specific health indicators. RESULTS: More than half (56%) of the children used computers each week. Computer use was significantly related to TV viewing (OR 1.97 weekday) and electronic game use (console games OR 2.48 weekday, 1.81 weekend; hand-held games OR 1.88 weekend) and negatively associated with vigorous physical activity on weekends (OR 0.72). Computer use was also significantly related to socio-economic indicators such as the mother being older (40+ years, OR 1.70 weekend, 1.73 weekday), tertiary educated (OR 1.63 weekend) and studying (OR 1.52 weekend, 1.41 weekday). Almost 1% children were reported to have complained of tired or sore muscles, and 2.2% had complained of tired or sore eyes, after watching television or using a computer. CONCLUSION: A substantial proportion of 5-year-old Western Australian children are using computers. Computer use was related to other sedentary activities and less vigorous activity. While musculoskeletal and vision problems are not widespread, their presence and the sedentary nature of computer use is of public health concern.

Child Behavior↗

Safety of sports participation in patients with implantable cardioverter defibrillators: a survey of heart rhythm society members.

UNLABELLED: Safety of Sports for ICD Patients. INTRODUCTION: The safety of sports participation for patients with implantable cardioverter defibrillators (ICDs) is unknown, and recommendations among physicians may vary widely. The purposes of this study were to determine current practice among patients with ICDs and their physicians regarding sports participation, and to determine how many physicians have cared for patients who have sustained adverse events during sports participation. METHODS AND RESULTS: A survey was mailed to all 1,687 U.S. physician members of the Heart Rhythm Society. Among 614 respondent physicians, recommendations varied widely. Only 10% recommended avoidance of all sports more vigorous than golf. Seventy-six percent recommended avoidance of contact, and 45% recommend avoidance of competitive sports. Most (71%) based restrictions on patients' underlying heart disease. Regardless of recommendations, most physicians (71%) reported caring for patients who participated in sports, including many citing vigorous, competitive sports, most commonly cited were basketball, running, and skiing. ICD shocks during sports were common, cited by 40% of physicians. However, few adverse consequences were reported. One percent of physicians reported known injury to patient (all but 3 minor); 5%, injury to the ICD system, and <1%, failure of shocks to terminate arrhythmia. The most common adverse event reported was lead damage attributed to repetitive-motion activities, most commonly weightlifting and golf. CONCLUSIONS: Physician recommendations for sports participation for patients with ICDs varies widely. Many patients with ICDs do participate in vigorous and even competitive sports. While shocks were common, significant adverse events were rare.

Awareness↗

Pathogenesis of Yersinia-triggered reactive arthritis: immunological, microbiological and clinical aspects.

When a patient develops reactive arthritis after Yersinia enteritis, the following conditions are often fulfilled: the patient is HLA-B27-positive; however, some B27-negative individuals develop severe arthritis and some positives do not, in the initial phase, the diarrhea is milder, the anti-Yersinia antibody response of IgG class is more vigorous and persists longer, the anti-Yersinia antibody response of IgA class is more vigorous and persists much longer, the anti-Yersinia antibodies of IgA1 and IgA2 subclass, those with J-chain and, especially, those with secretory piece are produced more vigorously, indicating local immunostimulation close to the intestinal epithelium, in the early phase, Yersinia-IgM immune complexes are found in the circulation, and the lymphocyte transformation response against not only Yersinia but also against other gram-negative enteric bacteria is weaker. When all these aspects are considered together a strong suspicion arises that the patients who are destined to develop reactive arthritis fail in their first line of defense against the invading organism when contracting a Yersinia enteritis. This may lead to persistence of the microorganism within the body, e.g., in the intestinal epithelium or in the mesenteric lymphoid tissues, maintaining a stimulus for a prolonged--apparently futile and perhaps harmful--antibody production. Finally, the initiating and decisive factor should not be forgotten: the Yersinia. Why and how it triggers the process is at present one of the enigmas of the pathogenesis of reactive arthritis.

Antibodies, Bacterial↗