An empirical test of convergent evolution in rhodopsins.

Rhodopsins are photochemically reactive membrane proteins that covalently bind retinal chromophores. Type I rhodopsins are found in both prokaryotes and eukaryotic microbes, whereas type II rhodopsins function as photoactivated G-protein coupled receptors (GPCRs) in animal vision. Both rhodopsin families share the seven transmembrane α-helix GPCR fold and a Schiff base linkage from a conserved lysine to retinal in helix G. Nevertheless, rhodopsins are widely cited as a striking example of evolutionary convergence, largely because the two families lack detectable sequence similarity and differ in many structural and mechanistic details. Convergence entails that the shared rhodopsin fold is so especially suited to photosensitive function that proteins from separate origins were selected for this architecture twice. Here we show, however, that the rhodopsin fold is not required for photosensitive activity. We engineered functional bacteriorhodopsin variants with novel folds, including radical noncircular permutations of the α-helices, circular permutations of an eight-helix construct, and retinal linkages relocated to other helices. These results contradict a key prediction of convergence and thereby provide an experimental attack on one of the most intractable problems in molecular evolution: how to establish structural homology for proteins devoid of discernible sequence similarity.

Comparison of paraspinal cutaneous temperature measurements between subjects with and without chronic low back pain.

OBJECTIVE: The purpose of this study was to evaluate the effects of chiropractic manipulative treatment on paraspinal cutaneous temperature (PCT) for subjects with chronic low back pain and compare these PCT findings to subjects without chronic low back pain. METHODS: Two groups were created, a symptomatic treatment group (subjects with chronic low back pain, n = 11, 7 males, 4 females) and an asymptomatic, nontreatment group (asymptomatic subjects, n = 10, 6 males, 4 females). Outcomes included the modified Oswestry questionnaire and PCT measurements in the prone position after an 8-minute acclimation period. The treatment group received 9 chiropractic spinal instrument-based manipulative treatments over 2 weeks. Reevaluation was done 2 weeks after the initial evaluation for both groups. RESULTS: The preintervention Oswestry results (29.8% ± 11.8%) for the treatment group were higher than the asymptomatic group (10.2% ± 10.6%). The postintervention Oswestry results for the treatment group were 14.20 % ± 11.5%. The resulting Cohen's effect size of the spinal manipulation on the Oswestry evaluation is 0.58. The preintervention PCT showed higher temperature for the nontreatment group compared with the treatment group. Comparing the levels associated with low back pain, the nontreatment group PCT was stable, varying from 0.01°C to 0.02°C, whereas the treatment group PCT varied from 0.10°C to 0.18°C. The treatment group postintervention PCT showed an increase in temperature after the 9 visits; however, this did not reach the values of the asymptomatic group. CONCLUSION: The PCT readings for subjects with chronic low back pain were lower than the asymptomatic, nontreatment group. The PCT temperature of the treatment group increased after 9 treatments.

Consistency of cutaneous thermal scanning measures using prone and standing protocols: a pilot study.

OBJECTIVE: The goal of this pilot study was to measure paraspinal cutaneous temperature (PCT) in the prone vs standing position. METHODS: Ten symptom-free participants were evaluated. Paraspinal cutaneous temperature was recorded. Subjects were acclimated to the treatment room in a prone position for 8 minutes before the PCT was measured. After the prone PCT reading, patients stood. A standing PCT measurement was then taken. RESULTS: Paraspinal cutaneous temperature was marginally warmer when subjects were standing vs prone (PCT difference, 0.25 degrees C +/- 0.64 degrees C and 0.62 degrees C +/- 0.67 degrees C for left and right sides, respectively). The right and left side differential was the same in the prone and standing positions. There was a positive Pearson correlation (0.802-0.803; P < .000) between the standing and prone positions for both left and right sides. CONCLUSION: There are no differences between the prone or standing PCT measures if symptom-free subjects are given 8 minutes to acclimate before recording PCT measures.

Paraspinal cutaneous temperature modification after spinal manipulation at L5.

OBJECTIVE: The purpose of this study was to investigate local paraspinal cutaneous temperature (CT) modifications after spinal manipulative therapy at L5. METHODS: Twenty subjects with acute low back symptoms were randomly assigned to either a treatment or a sham group (n = 10 per group). Subjects underwent an 8-minute acclimatizing period. Temperature was measured bilaterally with infrared cameras at the L5 level. In the treatment group, a traditional chiropractic manipulation (lumbar roll technique with a pisiform contact on the ipsilateral mamillary of L5) was delivered, whereas with the sham group, the same technique was used, but no thrust was applied. Cutaneous temperature control measurements were taken 2 minutes before (t(-2)) and immediately after the intervention (t(0)) and at 1, 3, 5, and 10 minutes postintervention (t(1), t(3), t(5), and t(10), respectively). RESULTS: At t(0), CT in the treatment group on the treatment side (ipsilateral side) warmed up by 0.2 degrees F, whereas in the sham group, there were no significant temperature modifications on either side. At t(3) relative to t(0), CT in the treatment group on the treatment side warmed by approximately 0.6 degrees F, whereas the contralateral side (nontreatment side) cooled. In the treatment group, significant differences were noted between sides (F = 13.36, P = .002, P = .932) and sides x times (F = 2.97, P = .016, P = .838). CONCLUSION: The effects of a lumbar spine manipulation appear noticeable by changes in paraspinal CT measurements at the level of L5. However, the meaning and mechanisms of CT modifications at L5 are still being investigated.

Heart rate variability modulation after manipulation in pain-free patients vs patients in pain.

BACKGROUND: The purpose of this study was to examine heart rate variability (HRV) in the presence or the absence of pain in the lower back, while receiving one chiropractic treatment at L5 from either a manually assisted mechanical force (Activator) or a traditional diversified technique spinal manipulation. METHODS: A total of 51 participants were randomly assigned to a control (n = 11), 2 treatment, or 2 sham groups (n = 10 per group). Participants underwent an 8-minute acclimatizing period. The HRV tachygram (RR interval) data were recorded directly into a Suunto watch (model T6; FitzWright Company Ltd, Langley, British Columbia, Canada). We analyzed the 5-minute pretreatment and posttreatment intervals. The spectral analysis of the tachygram was performed with Kubios software. RESULTS: All groups decreased in value except the control group that reacted in the opposite direction, when comparing the pretests and posttests for the high-frequency component. The very low frequency increased in all groups except the control group. The low frequency decreased in all groups except the sham pain-free group. The low frequency-high frequency ratio decreased in the treatment pain group by 0.46 and in the sham pain-free group by 0.26. The low frequency-high frequency ratio increase was 0.13 for the sham pain group, 0.04 for the control group, and 0.34 for the treatment pain-free group. The mean RR increased by 11.89 milliseconds in the sham pain-free group, 18.65 milliseconds in the treatment pain group, and 13.14 milliseconds in the control group. The mean RR decreased in the treatment pain-free group by 1.75 milliseconds and by 0.01 milliseconds in the sham pain group. CONCLUSION: Adjusting the lumbar vertebrae affected the lumbar parasympathetic nervous system output for this group of participants. Adaptation in the parasympathetic output, reflected by changes in high frequency, low frequency, and very low frequency, may be independent of type of adjustment. Therefore, the group differences found in the modulation of the HRV would seem to be related to the presence or absence of pain. The autonomic nervous system response may be specific and sensitive to its effectors organ.

Effects of a manually assisted mechanical force on cutaneous temperature.

OBJECTIVE: Digitized infrared segmental thermometry (DIST) is a tool used for measuring cutaneous temperature (CT). This project ascertains the effect of a manually assisted mechanical force producing a chiropractic adjustment in the lumbar spine after the Activator Methods Chiropractic Technique on CT during 2 different time recording periods (TRPs). METHODS: Sixty-six healthy subjects (36 women and 30 men) without acute low back conditions or symptoms were recruited. Subjects were randomly divided into 2 groups based on the length of the acclimatization period (8 or 30 minutes; TRP(8) and TRP(30), respectively). In turn, each recording period group was divided into 3 subgroups (n = 11 per subgroup): treatment, sham, and control subgroups. Bilateral DIST was conducted at L-4 (TRP(30)) and L-5 (TRP(8)) using infrared cameras (Subluxation Station Insight 7000; Chiropractic Leadership Alliance, Mahwah, NJ). RESULTS: Before treatment (t(-0.5)), the TRP(8) CT was significantly different between the ipsilateral and the contralateral sides for all subgroups. At 10 minutes (t(10)) after intervention, CT increased significantly (P < .05) for the treatment group but not for the sham and control groups. In contrast, there were no significant differences in the TRP(30) CT before treatment between the ipsilateral and the contralateral sides; but at t(10), CT was significantly (P < .05) greater for all 3 subgroups compared with preintervention CT. CONCLUSION: Contacting the skin with the instrument with (treatment group TRP(30)) or without (sham group TRP(30)) a thrust with a sustained pressure stronger than the loading principle taught in the Activator Methods Chiropractic Technique protocol or a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument produced a CT cooling immediately after the adjustment. Furthermore, we observed that when contacting the skin with the instrument with a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument, it produced a secondary cooling at t(5) followed by a rewarming at t(10). Finally, contacting the skin with the instrument without a thrust and respecting the standard loading principle (sham TRP(8)) of the instrument did not produce a CT change.

Digitized infrared segmental thermometry: time requirements for stable recordings.

OBJECTIVES: Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body temperatures. The project evaluated the required length of time for patients to acclimatize their core body temperature to ambient conditions to obtain stable DIST readings. METHODS: Seventeen subjects were allowed a 20-minute acclimatizing period in a temperature-controlled room. The bilateral DIST temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC temperatures were recorded after a 20-minute stabilization period. The room temperature and relative humidity were recorded throughout all trials. The acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days. RESULTS: We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core temperature requirements. CONCLUSIONS: This study determined a core body temperature acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend acclimatization in a temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.

Inflammatory response following a short-term course of chiropractic treatment in subjects with and without chronic low back pain.

OBJECTIVE: Inflammatory markers interleukin-6 (IL-6) and C-reactive protein (CRP) have not been evaluated in response to a short course of lumbar spinal manipulation. The purpose of this study is to observe the responses of inflammatory markers (IL-6 and CRP) after a series of 9 chiropractic spinal manipulations. METHODS: Twenty-one participants were assigned to a treatment or a control group. Only the treatment group received 9 chiropractic interventions. Pre- and postintervention measures were recorded for blood samples for detection of proinflammatory cytokines IL-6 and CRP. RESULTS: Mediators of inflammation (IL-6 and high-sensitivity CRP) were modified by the intervention received in the treatment group, and the effect size demonstrated a tendency toward the control group values. CONCLUSION: A total of 9 chiropractic lower back manipulations caused the mediators of inflammation to present a normalization response in individuals suffering from chronic low back pain.