Differing Characteristics of Human-Shaped Visual Stimuli Affect Clinicians' Dosage of a Spinal Manipulative Thrust on a Low-Fidelity Model: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to determine whether chiropractic clinicians modulate spinal manipulation (SM) thrust characteristics based on visual perception of simulated human silhouette attributes.

METHODS

We performed a cross-sectional within-participant design with 8 experienced chiropractors. During each trial, participants observed a human-shaped life-sized silhouette of a mock patient and delivered an SM thrust on a low-fidelity thoracic spine model based on their visual perception. Silhouettes varied on the following 3 factors: apparent sex (male or female silhouette), height (short, average, tall), and body mass index (BMI) (underweight, healthy, obese). Each combination was presented 6 times for a total of 108 trials in random order. Outcome measures included peak thrust force, thrust duration, peak preload force, peak acceleration, time to peak acceleration, and rate of force application. A 3-way repeated measures analysis of variance model was used to for each variable, followed by Tukey's honestly significant difference on significant interactions.

RESULTS

Peak thrust force was reduced when apparent sex of the presented silhouette was female (F_1,7 = 5.70, P = .048). Thrust duration was largely invariant, except that a BMI by height interaction revealed a longer duration occurred for healthy tall participants than healthy short participants (F_4,28 = 4.34, P = .007). Compared to an image depicting obese BMI, an image appearing underweight lead to reduced peak acceleration (F_2,5 = 6.756, P = .009). Clinician time to peak acceleration was reduced in short compared to tall silhouettes (t₇ = 2.20, P = .032).

CONCLUSION

Visual perception of simulated human silhouette attributes, including apparent sex, height, and BMI, influenced SM dose characteristics through both kinetic and kinematic measures. The results suggest that visual information from mock patients affects the decision-making of chiropractic clinicians delivering SM thrusts.

The role of dorsal root ganglia activation and brain-derived neurotrophic factor in multiple sclerosis

Multiple sclerosis (MS) is characterized by focal destruction of the white matter of the brain and spinal cord. The exact mechanisms underlying the pathophysiology of the disease are unknown. Many studies have shown that MS is predominantly an autoimmune disease with an inflammatory phase followed by a demyelinating phase. Recent studies alongside current treatment strategies, including glatiramer acetate, have revealed a potential role for brain-derived neurotrophic factor (BDNF) in MS. However, the exact role of BDNF is not fully understood. We used the experimental autoimmune encephalomyelitis (EAE) model of MS in adolescent female Lewis rats to identify the role of BDNF in disease progression. Dorsal root ganglia (DRG) and spinal cords were harvested for protein and gene expression analysis every 3 days post-disease induction (pdi) up to 15 days. We show significant increases in BDNF protein and gene expression in the DRG of EAE animals at 12 dpi, which correlates with peak neurological disability. BDNF protein expression in the spinal cord was significantly increased at 12 dpi, and maintained at 15 dpi. However, there was no significant change in mRNA levels. We show evidence for the anterograde transport of BDNF protein from the DRG to the dorsal horn of the spinal cord via the dorsal roots. Increased levels of BDNF within the DRG and spinal cord in EAE may facilitate myelin repair and neuroprotection in the CNS. The anterograde transport of DRG-derived BDNF to the spinal cord may have potential implications in facilitating central myelin repair and neuroprotection.

Increased GAD67 mRNA levels are correlated with in vivo GABA synthesis in the MPTP-treated catecholamine-depleted goldfish brain

The role of catecholamine neuronal input on GABAergic activity in the hypothalamus, telencephalon, optic tectum, and cerebellum was investigated in early recrudescent female goldfish (Carassius auratus). A new quantitative technique was developed and validated, permitting concomitant quantification and correlational analysis of glutamic acid decarboxylase 65 (GAD65), GAD67, and GAD3 mRNA levels and in vivo GABA synthesis. Catecholamine depletion was achieved by the administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 50 microg/g body weight) and dopamine (DA) depletion verified by HPLC. Endogenous GABA levels were increased by intraperitoneal administration of gamma-vinyl GABA (GVG; 300 microg/g body weight), an inhibitor of the GABA catabolic enzyme GABA transaminase. Treatment with MPTP resulted in a greater than twofold increase in GABA synthesis rate in the optic tectum and telencephalon. The increase in GABA synthesis rate was highly correlated with an increase in GAD67, but not GAD65 or GAD3 mRNA levels. These results suggest that catecholaminergic input exerts inhibitory effects on GABA synthesis rates through the modulation of GAD67 in the optic tectum and telencephalon. Together with previously published observations in rodents and primates, it is suggested that catecholaminergic control of GABA synthesis must have evolved more than 200 million years ago, before the emergence of the teleost fishes.

Regulation of B16F1 melanoma cell metastasis by inducible functions of the hepatic microvasculature

We have previously shown that circulating intravascular cells generally arrest by mechanical restriction in the hepatic sinusoids, causing rapid release of nitric oxide (NO) which is cytotoxic to these cells and inhibits their growth into metastatic tumours. Here, we present evidence that these NO-dependent cytotoxic mechanisms are susceptible to upregulation by lipopolysaccharide (LPS). Five x 10(5) fluorescently labelled melanoma cells were injected into the mesenteric vein of C57BL/6 mice to effect their localisation in the hepatic microvasculature. Test mice were then given 1 mg/kg LPS intraperitoneally (i.p.) to activate the microvascular cells. By electron paramagnetic resonance (EPR) spectroscopy, the expression of NO in the liver was significantly increased by 8 h in the LPS-treated mice. The non-selective NO synthase inhibitor L-NAME inhibited the induction of NO by LPS, while its inactive enantiomer D-NAME had no significant effect. Using immunohistochemistry (IHC), iNOS-positive microvascular cells were detected in the terminal portal venule (TPV) region of the liver 8 h after LPS stimulation. LPS treatment also increased the retention of melanoma cells in the liver between 8 and 24 h, especially in the TPV region. Eight hours after cell injection, local expression of VCAM-1 and ICAM-1 was detected by double-label immunohistochemistry at the sites of tumour cell arrest. Expression of these adhesion molecules was enhanced in mice treated with LPS. Using flow cytometry, 98% of the B16F1 melanoma cells expressed VLA-4, the counter receptor of VCAM-1, and approximately 1.5% expressed LFA-1, the counter receptor of ICAM-1. LPS did not significantly alter the expression of either counter receptor on melanoma cells in vitro or in vivo. By DNA end-labelling, the rates of melanoma cell apoptosis were significantly increased from 8 to 24 h in the TPV region (but not in the sinusoids) of LPS-treated mice. Fourteen days after tumour cell injection, the LPS-treated mice had a significantly smaller hepatic metastatic tumour burden than the control mice. These data suggest that LPS can inhibit the metastasis of melanoma cells in the liver by inducing the expression of NO and adhesion molecules by the hepatic endothelium. The induction of iNOS and the inducible cytotoxic effect of LPS appear to be primarily located within the TPV region of the liver acinus.

Tissue distribution of radiolabelled tumor cells in wheel exercised and sedentary mice

During the process of metastasis tumor cells must interact with vascular endothelial cells, basement membrane, and extracellular matrix. Specifically, tumor cells must bind to adhesion molecules to extravasate from the circulation into the tissue. Expression of adhesion molecules is altered by cytokines, such as tumor necrosis factor and interleukin-1. Exercise has been reported to alter circulatory levels of these cytokines. We have recently shown that exercise training reduces the number of experimental metastases in mice following intravenous (i.v.) injection of tumor cells. Thus, it was of interest to determine if one possible mechanism of reduced metastasis in exercised mice was a reduction in the initial retention of tumor cells in the pulmonary circulation. C3H/He and (C3H/H3XBALB/c)F1 mice were given access to running wheels or remained sedentary for nine weeks after which 51Cr labelled CIRAS 1 tumor cells (5 x 10(5) cells) were injected into a tail vein. Recovery of radioactivity in lungs, liver, spleen and kidney was assessed 5 min, 30 min, 90 min, 3 h and 24 h after injection. Wheel running mice displayed a lower retention of radioactivity in the lungs relative to sedentary mice 5 min (F1,34 = 11.91, p < 0.002; W = 59.1 +/- 3.6%, S = 75.0 +/- 2.9%; Mean +/- S.E.) and 30 min (F1,18 = 64.00, p < 0.001; W = 32.4 +/- 3.4%, S = 68.5 +/- 3.0%) post-injection. Radioactivity recovered in the lungs from wheel and sedentary mice was not significantly different at the other time points.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise training and tumour metastasis in mice: influence of time of exercise onset

The present study was designed to investigate the factor of timing of activity onset in determining the effects of exercise on experimental metastases. After 9 weeks of wheel running activity (W) or remaining sedentary (S), male C3H/He mice received an i.v. injection of CIRAS 1 tumor cells. Mice were then randomized into sedentary and wheel running groups (SS, SW, WS, WW) for a further 3 weeks. Although the average number of lung tumours did not differ by activity condition, the groups exercised prior to tumour injection had a greater incidence in the lowest tertile of tumour distribution relative to sedentary controls (SS = 8/20 vs. WS = 16/19, p < 0.005; SS vs. WW = 14/18, p < 0.05). In a replication trial, a similar outcome was present in the lowest tertile: increased incidence of animals exercised prior to injection (SS = 3/9 vs. WW = 7/9: p < 0.05). These data suggest that exercise training before, but not after, i.v. exposure to tumour reduces the number of lung metastases and that the timing of exercise onset influences the extent of experimental metastasis in this model.

Effect of exercise on natural cytotoxicity and pulmonary tumor metastases in mice

Exercise has been demonstrated to reduce experimental tumor formation in rodents when the exercise is present during the tumor initiation or promotion phases. This study evaluated whether exercise influenced the process of tumor metastasis and subsequent growth in a secondary implant site. Male C3H mice remained sedentary, were given free access to running wheels, ran on a treadmill (15 m.min-1, 30 min.d-1), or walked on a treadmill (5 m.min-1, 5 min.d-1)(N = 20/group). Following 9 wk of this protocol, exercise was discontinued. At this time all animals received a tumor cell dose (CIRAS 1, 3 x 10(5)) i.v., and remained sedentary until sacrificed 3 wk later. Splenic natural killer (NK) cell activity was elevated in the wheel running mice compared with sedentary controls 3 wk after cessation of exercise (F(3,74) = 6.266, P < 0.002). Exercised mice displayed lower tumor cell retention in the lungs relative to nonexercised mice (F(1,37) = 6.593, P < 0.02). Tumor incidence was not different across activity groups whereas tumor multiplicity was higher in mice that had been previously exposed to exercise. (However, it should be noted that the significant exercise-tumor effect was due to a small number of exercised mice with extreme multiplicity, > 200 foci/lung.) More extensive tumor colony formation was present in wheel-trained mice that displayed the greatest volumes of daily running. The results from this study suggest that exercise was able to augment natural immune cytotoxic function for up to 3 wk after cessation of activity. However, this augmentation of natural immune function was not associated with reduced tumor incidence in the exercised animals.

Chronic exercise enhances in vivo and in vitro cytotoxic mechanisms of natural immunity in mice

This study investigated the influence of 9 wk of chronic exercise on natural cytotoxicity in male C3H mice. Both in vivo cytotoxicity (pulmonary vasculature) and in vitro cytotoxicity (spleen) were determined for voluntary (wheel running; n = 30) and forced (treadmill running, 15 m/min, 30 min/day; n = 30) exercise protocols. A sedentary control group (n = 30) and a treadmill control group (5 m/min, 5 min/day; n = 30) were also included. After 9 wk of chronic exercise, submaximal exercise O2 uptake was reduced in the wheel-running group relative to that in sedentary or treadmill-trained mice. Maximal citrate synthase activity of soleus muscle was higher in treadmill-trained group compared with that in sedentary or wheel-running mice. Chronic exercise consistently reduced percent retention of CIRAS 3 tumor cells in the lungs of treadmill- (15.3 +/- 1.4) and wheel- (17.9 +/- 1.4) trained mice below that of sedentary (29.5 +/- 2.7) and treadmill control (25.8 +/- 1.8) groups (P < 0.001). Injection of anti-asialo GM1 (ASGM1) antibody increased tumor cell retention in the lungs for all groups but did not alter the differences between activity conditions. In vitro cytotoxicity was enhanced in treadmill- and wheel-trained mice relative to that in sedentary controls but was not elevated in the treadmill control group. Anti-ASGM1 injection eliminated in vitro cytotoxicity for all groups. Chronic exercise slightly increased the frequency of ASGM1-positive splenocytes in treadmill-trained mice only. These results indicate that chronic exercise enhances natural cytotoxic mechanisms in vivo and in vitro and that this enhancement is present for both forced and voluntary exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of differential housing in mice on natural killer cell activity, tumor growth, and plasma corticosterone

Various forms of stress have been shown to alter natural killer (NK) cell activity and tumorigenesis; however, few studies have measured these two variables simultaneously. Isolation of mice was utilized as a model of stress by which to study NK cell activity and pulmonary metastatic response following a tumor challenge. Male C3H mice were group or individually housed for 3 weeks, after which CIRAS 3 fibrosarcoma tumor cells or the tumor vehicle was injected intravenously (tail vein), NK cell activity, pulmonary metastasis, and plasma corticosterone were measured 1, 7, and 21 days following tumor cell inoculation. Individually housed mice, irrespective of tumor or vehicle condition, had a higher NK response on Day 1 relative to group-housed animals (P less than 0.001). By Day 21, tumor condition, rather than housing, was the major significant factor affecting NK activity (P less than 0.001). Nevertheless, individually housed, tumor-injected mice still had higher NK activity compared with the other treatment groups on Day 21. No effect of housing condition was present for the incidence of pulmonary metastases or frequency of metastases in affected animals. Plasma corticosterone levels generally increased over the study period, with no housing or injection effects at Days 1 and 7. Individually housed, vehicle-injected mice had higher corticosterone levels at Day 21 (P less than 0.01). These data suggest that in response to housing condition, NK cell activity differs in tumor-bearing mice and vehicle controls. Furthermore, CIRAS 3 pulmonary tumor formation is not affected by differences in NK activity consequent to housing condition. Plasma corticosterone does not appear to be a major in vivo regulator of NK activity in this experimental tumor system. Finally, the interpretation of housing effects on NK activity and plasma corticosterone levels depends on the temporal window in which sampling occurs.

Differential effects of exercise and housing condition on murine natural killer cell activity and tumor growth

Acute exercise and exercise conditioning have been shown to affect the activity of natural killer (NK) cells as well as the growth of experimentally induced tumors in animals. Since psychosocial factors are also known to alter NK activity and tumor growth, isolation, a known psychosocial stressor of mice, was also investigated to see if housing condition could alter exercise-induced changes in NK cell activity and tumor growth. NK cell activity and concentration of asialo GM1 (ASGM1) positive splenocytes were measured in male C3H mice inoculated i.v. with CIRAS 3 tumor cells. Mice were housed individually or in groups of four and trained to run for eight weeks on a rodent treadmill; controls remained sedentary throughout the experimental period. At four weeks into the training protocol, mice were injected with the tumor cells and continued to run for four weeks after tumor exposure. There was a significant effect of physical activity (p less than 0.019) but not of housing on splenic NK cytotoxicity against tumor targets in vitro. When the data were analyzed by presence or absence of lung metastases, only those animals without visible lung tumors had significantly higher NK activity as a function of exercise relative to sedentary controls. There were no significant differences in the frequency of ASGM1+ splenocytes between trained and untrained animals, irrespective of presence or absence of lung tumor colonies. There was a significant effect of housing (p less than 0.02), but not of physical activity, in mice with successful tumor takes with greater numbers of group housed animals (29/59) with tumor relative to individually housed animals (13/60).(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte proliferation responses after exercise in men: fitness, intensity, and duration effects

This study investigated the effects of intensity and duration of exercise on lymphocyte proliferation as a measure of immunologic function in men of defined fitness. Three fitness groups--low [maximal O2 uptake (VO2max) = 44.9 +/- 1.5 ml O2.kg-1.min-1 and sedentary], moderate (VO2max = 55.2 +/- 1.6 ml O2.kg-1.min-1 and recreationally active), and high (VO2max = 63.3 +/- 1.8 ml O2.kg-1.min-1 and endurance trained)--and a mixed control group (VO2max = 52.4 +/- 2.3 ml O2.kg-1.min-1) participated in the study. Subjects completed four randomly ordered cycle ergometer rides: ride 1, 30 min at 65% VO2max; ride 2, 60 min at 30% VO2max; ride 3, 60 min at 75% VO2max; and ride 4, 120 min at 65% VO2max. Blood samples were obtained at various times before and after the exercise sessions. Lymphocyte responses to the T cell mitogen concanavalin A were determined at each sample time through the incorporation of radiolabeled thymidine [( 3H]TdR). Despite differences in resting levels of [3H]TdR uptake, a consistent depression in mitogenesis was present 2 h after an exercise bout in all fitness groups. The magnitude of the reduction in T cell mitogenesis was not affected by an increase in exercise duration. A trend toward greater reduction was present in the highly fit group when exercise intensity was increased. The reduction in lymphocyte proliferation to the concanavalin A mitogen after exercise was a short-term phenomenon with recovery to resting (preexercise) values 24 h after cessation of the work bout. These data suggest that single sessions of submaximal exercise transiently reduce lymphocyte function in men and that this effect occurs irrespective of subject fitness level.

Exercise and blood lymphocyte subset responses: intensity, duration, and subject fitness effects

This study examined the effect of exercise intensity and duration on the percent blood lymphocytes in men of low [LF; maximal O2 uptake (VO2max) less than 50 ml.kg-1.min-1 and sedentary], moderate (MF; VO2max = 50-60 ml.kg-1.min-1 and recreationally active), and high (HF; VO2max greater than 60 ml.kg-1.min-1 and recent training history) fitness. Thirty healthy adult men (aged 20-31 yr) participated in four randomly ordered cycle ergometer rides: ride 1 (65% VO2max, 30 min), ride 2 (30% VO2max, 60 min), ride 3 (75% VO2max, 60 min), and ride 4 (65% VO2max, 120 min). Blood samples were drawn at various times before and after the exercise sessions. Lymphocyte subsets were determined by flow cytometry using monoclonal antibodies for total T (CD3+), T-helper (CD4+), and T-suppressor (CD8+) lymphocytes and for a subset of cells expressing a natural killer (NK) cell antigen (Leu7+). Plasma catecholamines were assayed to determine exercise stress. There were sharp reductions (P less than 0.01) in the percentage of pan-T and T-helper lymphocytes immediately after exercise across all fitness levels; the magnitude of this reduction was greatest after the highest intensity (ride 3) or longest duration (ride 4) work. In contrast, the absolute number of T and T-helper cells tended to increase after exercise and significantly so in the HF subjects (P less than 0.005). There was no significant effect of exercise or subject fitness category on the percentage of T-suppressor lymphocytes, although the absolute numbers of this subset increased significantly after exercise in LF subjects. Marked increases (P less than 0.01) in the percentage of NK cells occurred immediately after exercise at all intensities and durations tested; numerical increases in total NK cells were significant in all fitness groups after the highest intensity work (ride 3; P less than 0.005). Irrespective of whether the changes were expressed as percentage or total numbers, recovery to base line occurred at 30 min after exercise. The results suggest that the exercise effect on blood lymphocyte subset percentages in men is transient and occurs across all fitness levels. Concomitant changes in plasma catecholamine concentrations are only weakly associated with these lymphocyte subset percentage responses to exercise. Furthermore, this study shows that the exercise-induced changes in lymphocyte percentages do not consistently reflect changes in the absolute numbers of cells.