Microenvironmental Modulation of Decorin and Lumican in Temozolomide-Resistant Glioblastoma and Neuroblastoma Cancer Stem-Like Cells

The presence of cancer stem cells (CSCs) or tumor-initiating cells can lead to cancer recurrence in a permissive cell–microenvironment interplay, promoting invasion in glioblastoma (GBM) and neuroblastoma (NB). Extracellular matrix (ECM) small leucine-rich proteoglycans (SLRPs) play multiple roles in tissue homeostasis by remodeling the extracellular matrix (ECM) components and modulating intracellular signaling pathways. Due to their pan-inhibitory properties against receptor tyrosine kinases (RTKs), SLRPs are reported to exert anticancer effects in vitro and in vivo. However, their roles seem to be tissue-specific and they are also involved in cancer cell migration and drug resistance, paving the way to complex different scenarios. The aim of this study was to determine whether the SLRPs decorin (DCN) and lumican (LUM) are recruited in cell plasticity and microenvironmental adaptation of differentiated cancer cells induced towards stem-like phenotype. Floating neurospheres were generated by applying CSC enrichment medium (neural stem cell serum-free medium, NSC SFM) to the established SF-268 and SK-N-SH cancer cell lines, cellular models of GBM and NB, respectively. In both models, the time-dependent synergistic activation of DCN and LUM was observed. The highest DCN and LUM mRNA/protein expression was detected after cell exposure to NSC SFM for 8/12 days, considering these cells as SLRP-expressing (SLRP+) CSC-like. Ultrastructural imaging showed the cellular heterogeneity of both the GBM and NB neurospheres and identified the inner living cells. Parental cell lines of both GBM and NB grew only in soft agar + NSC SFM, whereas the secondary neurospheres (originated from SLRP+ t8 CSC-like) showed lower proliferation rates than primary neurospheres. Interestingly, the SLRP+ CSC-like from the GBM and NB neurospheres were resistant to temozolomide (TMZ) at concentrations >750 μM. Our results suggest that GBM and NB CSC-like promote the activation of huge quantities of SLRP in response to CSC enrichment, simultaneously acquiring TMZ resistance, cellular heterogeneity, and a quiescent phenotype, suggesting a novel pivotal role for SLRP in drug resistance and cell plasticity of CSC-like, allowing cell survival and ECM/niche modulation potential.This study was supported by Fundació la Marató TV3, Project n° 111431

MUSCLE VIBRATION DOSAGE AND THE PATELLAR TENDON REFLEX RESPONSE

Zachary K. Pope & Jason M. DeFreitas Oklahoma State University, Stillwater, Oklahoma The physiological response to muscle vibration is complex. The repetitive length changes imposed by the mechanical oscillations strongly modulates proprioceptive activity, particularly the activity of the muscle spindles. Accordingly, vibration may represent a useful research tool to manipulate the sensitivity of the muscle spindle reflex arc. However, to truly understand its’ usefulness as a tool, the complex relationship between vibration dosage and spindle responsiveness requires a better understanding. PURPOSE: Thus, the purpose of this investigation was to examine the effects of acute and prolonged vibration on muscle spindle function. METHODS: A cross-over study design was utilized to determine the effects of vibration dosage on the patellar tendon reflexes of 20 volunteers (age 24.5 ± 4.6 years). A series of tendon taps were delivered using a custom reflex apparatus, during which surface electromyography, torque, and accelerometry signals were obtained. These signals were used to quantify reflex magnitude and latency for each of the following conditions: 1.) control, 2.) acute (i.e. 1-5 seconds) vibration and, 3.) prolonged (i.e. 20 minutes) vibration. The vibratory stimulus was applied perpendicularly to the distal quadriceps, just superior of the patella, using a percussion hammer set at a frequency of 66 Hz and was removed just prior to the reflex testing. RESULTS: When compared to the control condition, the results of the current study revealed that acute vibration did not significantly increase reflex torque magnitude (p = 0.461), but did significantly increase reflex latency (p = 0.022). Prolonged vibration, however, resulted in a significant depression of reflex magnitude (p = 0.001) and an increased reflex latency (p = 0.0002). CONCLUSIONS: The findings of the current study support the use of prolonged vibration as a means to suppress the muscle spindle reflex arc and lends credence to the contention of a peripheral origin for the altered motor response following prolonged vibration. The findings, in regards to the acute vibration condition, are less clear. It is speculated that the divergent responses for reflex magnitude and latency may indicate an altered composition of, or response to, the composite excitatory post-synaptic potential generated by the tendon tap. This research was made possible in total or in part by funding through the award for the project number HR-14-023, from the Oklahoma Center for the Advancement of Science and Technology

EFFECTS OF UNILATERAL LOW-VELOCITY RESISTANCE TRAINING WITH BALLISTIC-INTENT ON MAXIMAL AND RAPID TORQUE DEVELOPMENT OF THE TRAINED AND UNTRAINED KNEE EXTENSORS

Cameron S. Mackey, Garrett M. Hester, Zachary K. Pope, Frank M. Benik, and Jason M. DeFreitas. Oklahoma State University, Stillwater, OK; e-mail: [email protected] It has been suggested that regardless of contraction velocity, the intent to contract in a ballistic manner during resistance training (RT) is responsible for the training-related increase in rate of torque development (RTD). However, little evidence exists regarding the effects of low-velocity RT involving a ballistic-intent on RTD. Furthermore, it is unknown whether or not low-velocity RT performed with a ballistic-intent increases RTD of the contralateral limb during the early-phase (i.e., ≤4 weeks) of training. PURPOSE: To examine the short-term maximal and rapid-strength adaptations of the trained and untrained knee extensors during 4 weeks of unilateral isokinetic RT performed with a ballistic intent. METHODS: Twenty-three healthy, college-aged males who had not performed RT within the past 6 months volunteered to participate in this study. A training group (TG; n = 14, age = 22 ± 1.89 yrs., body mass = 80.42 ± 14.21 kg) performed 3 sessions per week of unilateral isokinetic RT of the dominant leg for 4 weeks and 3 testing sessions. The control group (CG; n = 9, age = 23 ± 4.30 yrs., body mass = 88.71 ± 17.61 kg) only participated in the testing. RT sessions consisted of maximal concentric contractions of the knee extensors at 45°·s-1 for 4 sets of 10 repetitions with 2-3 s of rest between repetitions and a 2 min rest between sets. During each RT session, subjects were instructed to “kick out as hard and fast as possible”. Subjects performed two maximal voluntary isometric contractions (MVCs) of the knee extensors for the trained (TL) and untrained (UL) leg before (pre), at week 2 (mid), and after week 4 (post) of RT. Maximal strength (peak torque; PT) as well as RTD at its peak (RTDPK), at 30 ms (RTD0-30), and at 200 ms (RTD0-200) after the onset of contraction were recorded for subsequent analysis. Independent-samples t-testes were used to compare all dependent variables at pre for the TG and CG. One-way repeated measures ANOVAs were used to compare all dependent variables at pre, mid, and post for the TL and UL in the TG and CG. RESULTS: There were no differences between the TG and CG at pre (p \u3e 0.05). All dependent variables remained unchanged at mid and post for both legs in the CG (p \u3e 0.05). For the TG, there was a significant increase in PT from pre to post (p = 0.001) and mid to post (p = 0.021) for the TL, while no differences were found for the UL across time (p = 0.070). All RTD measures remained unchanged for the TL and UL (p \u3e 0.05). CONCLUSION: The results of the present study revealed that short-term, low-velocity RT performed with a ballistic intent led to an increase in PT of the TL but not the UL. In addition, all RTD measures for the TL and UL remained unchanged during the 4 week training protocol

EFFECTS OF REST PERIOD DURATION ON MUSCLE ECHOGENICITY AND CROSS SECTIONAL AREA

Michelle M. Miller, Zachary K. Pope, Franklin M. Benik, Garrett M. Hester & Jason M. DeFreitas. Oklahoma State University, Stillwater, Oklahoma; e-mail: [email protected] Numerous studies have shown that resistance training can improve muscle size and quality over time; yet, it remains unknown how these muscle variables are influenced by the manipulation of training variables, such as rest period duration (i.e. time interval allotted between sets). PURPOSE: To determine the effects of rest period duration on muscle echogenicity and muscle cross-sectional area (CSA) following an 8 week (3 session/wk) resistance training program. METHODS: Twenty-one, college-aged males volunteered for, and completed, this IRB-approved research study. The participants were randomly assigned to 1 of 2 groups [SHORT (n=11); LONG (n=10)], before participating in 8 weeks of supervised, full-body, dynamic resistance training. All training variables were identical between groups (7 exercises, 3 sets, 10 reps, 10 RM load) with the only exception being rest period duration (SHORT = 1 min; LONG = 3 min). Before, and following, the resistance training program, ultrasound images were obtained from each participant’s dominant rectus femoris (RF) and vastus lateralis (VL) muscles. Using NIH Image-J software, CSA (cm2) and echogenicity (mean gray-scale value; 0 – 255) were calculated by carefully selecting as much of the muscle as possible, while avoiding any outer fascia. RESULTS: Following training, no significant differences were observed between groups (p\u3e.05). However, with both groups collapsed (n=21), significant improvements were seen for 3 of the 4 variables: CSA of the RF (+6.62%; p\u3c.05), CSA of the VL (+13.61%; p\u3c.05), and echogenicity of the VL (-7.73%; p\u3c.05). Echogenicity of the RF, however, was not significantly affected following training (-3.23%; p\u3e.05). CONCLUSION: Resistance training can increase muscle size and may positively affect echogenicity of the quadriceps muscles in college-aged males. However, our findings indicate that these adaptations were not specific to the rest period duration utilized. Therefore, it was concluded that the resistance training program described in this investigation can elicit positive muscular adaptations (size and quality) using either 1 or 3 minute rest periods

THE ACUTE EFFECTS OF A BALLISTIC AND HEAVY EXERCISE ON VERTICAL JUMP PERFORMANCE

Garrett M. Hester, Zachary K. Pope, John H. Sellers, Ryan M. Thiele & Jason M. DeFreitas Oklahoma State University, Stillwater, Oklahoma Post-activation potentiation (PAP) refers to the enhancement of muscular performance characteristics as a result of their contractile history. PAP may be elicited at an earlier time interval following ballistic exercise compared to heavy exercise. PURPOSE: The purpose of this study was to compare the temporal effects of a jump squat and back squat protocol on vertical jump performance. METHODS: Fourteen resistance-trained men (mean ± SD: age = 22 ± 2.1 yrs., body mass = 86.29 ± 9.95 kg, height = 175.39 ± 9.34 cm, back squat 1-RM = 173.05 ± 24.61 kg) with an average relative full squat of 2.02 ± 0.28 times their body mass participated in this study. In randomized, counter-balanced order subjects performed two countermovement vertical jumps (CMVJs) before and 1 min, 3 min, 5 min, and 10 min after either performing 10 rapid jump squats or 5 heavy back squats. Each subject visited the laboratory on 3 occasions; one familiarization session which comprised 1-RM testing, followed by two testing sessions, separated by at least 72 hours. The back squat protocol (BS) consisted of one set of 5 parallel back squats at 80% 1-RM, whereas the jump squat protocol (JS) consisted of one set of 10 jump squats at 20% 1-RM. Peak jump height (in) using a jump mat, along with power output (W) and velocity (m/s) via a linear transducer were recorded for each time interval. RESULTS: There was no significant condition × time interaction for any of the dependent variables (p = 0.066-0.127). There was no main effect of time for any of the dependent variables for the JS (p = 0.159-0.283) or BS (p = 0.119-0.121), except for jump height which was significantly lower at 1 min post BS compared to baseline (p = 0.014). CONCLUSION: Neither the JS nor BS induced PAP during the CMVJ. The BS significantly impaired CMVJ height at 1 min post (-3.74%), while the JS tended to have an insignificant positive effect (0.13-0.65%) during early time intervals (i.e., 1-5 min). Future research should investigate the effectiveness of other ballistic exercises to produce PAP at early time intervals

EFFICACY OF A VENTILATORY TRAINING MASK TO IMPROVE ANAEROBIC CAPACITY IN RESERVE OFFICERS’ TRAINING CORPS CADETS

John H. Sellers, Taylor P. Monaghan, Bert H. Jacobson FACSM, Jessica A. Schnaiter, Garrett M. Hester & Zach K. Pope. Health & Human Performance, Oklahoma State University, Oklahoma; e-mail: [email protected] Present day military operations often require personnel to be deployed into high altitude locations without a sufficient acclimatization period, which may require 1-3 weeks for sufficient physiological changes to occur. Any decrement to performance as a result of environmental factors such as altitude increases the risk of the mission. Therefore seeking both cost effective and time efficient methods for providing adequate physiological altitude adaptations is of great importance. Intermittent hypoxic training (IHT), follows the “live low-train high” philosophy. One potential method is performing physical training (PT) while wearing a commercially available ventilatory training mask, which increases the energy costs of breathing and provides a small level of hypoxia in an attempt to simulate training at altitude. PURPOSE: The purpose of this study was to examine the efficacy of a ventilatory training mask to improve anaerobic fitness in ROTC cadets. METHODS: Nineteen ROTC cadets (age 19.47 ± 1.22 y, weight 73.2 ± 9.94 kg, height 174.79 ± 6.5 cm, body fat 7.85 ± 2.9%) from a Midwest university completed pre- and post-assessments consisting of anthropometry and a 30-sec Wingate Anaerobic Test (WAnT). A six week intervention training period was utilized during which time participants completed their mandatory physical training (PT) sessions. Participants were randomly assigned to either the experimental group (MASK; n = 9), or the control group (CON; n = 8). The ventilatory training masks were adjusted to simulate an altitude of 2750 m. RESULTS: There was no significant effect (p \u3c .05) between groups on fatigue index (FI), anaerobic capacity (AC), or peak power (PP). Based on the results from the paired samples t-test, there was a significant improvement in AC for the combined groups (p \u3c .001), while no significant difference was found for the combined group’s FI (p = .724) nor PP (p = .154). CONCLUSION: These results suggest that the use of the ventilatory training mask during mandatory PT did not elicit superior anaerobic adaptations in ROTC cadets. Therefore, it is recommended that more established simulated altitude training methods be utilized when incorporating intermittent hypoxic training

EFFECTIVENESS OF A VENTILATORY TRAINING MASK ON AEROBIC CAPACITY IN RESERVE OFFICERS’ TRAINING CORPS CADETS

Taylor P. Monaghan, John H. Sellers, Bert H. Jacobson FACSM, Jessica A. Schnaiter, Garrett M. Hester, & Zach K. Pope. Health & Human Performance, Oklahoma State University, Oklahoma; e-mail: [email protected] Exercise training at altitude is a well-established and commonly used method for increasing aerobic performance with endurance athletes. Currently, the military requires personal to be deployed into high altitude situations without sufficient time to acclimatize. This can result in altitude sickness and a decrease in performance, which in turn increases the risk of injury during an assignment. To reduce the detriments in performance due to altitude, hypoxic training during physical training (PT) may be an option. An economical solution could be to implement a commercially available ventilatory training mask during their PT sessions. Such a mask essentially causes breathing to become more difficult while creating slightly hypoxic conditions, thus roughly simulating altitude. PURPOSE: The purpose of this study was to observe the effects on aerobic performance after using the ventilatory training mask during PT for a 6 week period. METHODS: Nineteen ROTC cadets (age 19.47 ± 1.22 y, weight 73.2 ± 9.94 kg, height 174.79 ± 6.5 cm, body fat 7.85 ± 2.9%) from a Midwest university completed pre- and post-assessments consisting of anthropometry and a maximal aerobic capacity treadmill ergometer test. Participants underwent a six week intervention training program consisting of their ROTC mandatory PT sessions. The experimental (MASK; n = 9) and control (CON; n = 8) groups were randomly divided based on VO2max to create two groups of similar fitness. Ventilatory training masks were set to simulate an altitude of 2750 m. RESULTS There was no significant difference main effect between groups after the intervention period on VO2max nor Time to Exhaustion (TE), VO2max scores, F(1,15) = .598, p = .451, TE, F(1,15) = .327, p = .576 based on a repeated measures ANOVA. Although statistical significance was not reached for either group, mean VO2max for the MASK group displayed a slight increase of 1.81% and the mean VO2max CON group exhibited a marginally greater increase of 5.57% CONCLUSION: The results of the current study demonstrated that the ventilatory training masks did not yield any greater aerobic performances in ROTC cadets. We recommend further research to be conducted using other more established forms of altitude training to benefit future military operations