In vivo three-dimensional intervertebral kinematics of the subaxial cervical spine during seated axial rotation and lateral bending via a fluoroscopy-to-CT registration approach

Accurate measurement of the coupled intervertebral motions is helpful for understanding the etiology and diagnosis of relevant diseases, and for assessing the subsequent treatment. No study has reported the in vivo, dynamic and three-dimensional (3D) intervertebral motion of the cervical spine during active axial rotation (AR) and lateral bending (LB) in the sitting position. The current study fills the gap by measuring the coupled intervertebral motions of the subaxial cervical spine in ten asymptomatic young adults in an upright sitting position during active head LB and AR using a volumetric model-based 2D-to-3D registration method via biplane fluoroscopy. Subject-specific models of the individual vertebrae were derived from each subject’s CT data and were registered to the fluoroscopic images for determining the 3D poses of the subaxial vertebrae that were used to obtain the intervertebral kinematics. The averaged ranges of motion to one side (ROM) during AR at C3/C4, C4/C5, C5/C6, and C6/C7 were 4.2°, 4.6°, 3.0° and 1.3°, respectively. The corresponding values were 6.4°, 5.2°, 6.1° and 6.1° during LB. Intervertebral LB (ILB) played an important role in both AR and LB tasks of the cervical spine, experiencing greater ROM than intervertebral AR (IAR) (ratio of coupled motion (IAR/ILB): 0.23–0.75 in LB, 0.34–0.95 in AR). Compared to the AR task, the ranges of ILB during the LB task were significantly greater at C5/6 (p=0.008) and C6/7 (p=0.001) but the range of IAR was significantly smaller at C4/5 (p=0.02), leading to significantly smaller ratios of coupled motions at C4/5 (p=0.0013), C5/6 (p<0.001) and C6/7 (p=0.0037). The observed coupling characteristics of the intervertebral kinematics were different from those in previous studies under discrete static conditions in a supine position without weight-bearing, suggesting that the testing conditions likely affect the kinematics of the subaxial cervical spine. While C1 and C2 were not included owing to technical limitations, the current results nonetheless provide baseline data of the intervertebral motion of the subaxial cervical spine in asymptomatic young subjects under physiological conditions, which may be helpful for further investigations into spine biomechanics.     

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0°, 10°, 20°, and 30° relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%,18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determine as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes — endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.     

The effect of aerobic exercise during the interset rest periods on kinematics, kinetics, and lactate clearance of two resistance loading schemes

It may be possible to enhance set and session kinematics and kinetics by engaging in low-intensity aerobic exercise during the interset rest period. The purpose of this study therefore was to quantify the change in session kinematics and kinetics of 35% 1RM and 70% 1RM loading schemes equated by volume, when aerobic exercise or passive rest was undertaken between sets. Twelve male student athletes were recruited for this study. Squat average force, peak force, average power, peak power, total work, and total impulse were quantified using a force plate and linear transducer. Blood lactate samples were taken before set 1, after set 1, after set 2, and after the last set performed. No significant (p < 0.05) differences (0.37-9.24%) were found in any of the kinematic and kinetic variables of interset after active or passive interset rest periods. Significant increases (64-76%) in blood lactate occurred from the inception of exercise to completion, for both the heavy and light loading schemes. However, no significant differences in lactate accumulation were noted, whether active or passive recovery was undertaken in the interest rest period. It was concluded that active recovery in the form of low-intensity cycling offered no additional benefits in terms of lactate clearance and enhancement of set and session kinematics and kinetics.     

Comparative study of observed actions,motor imagery and control therapeutic exercise on the conditioned pain modulation in the cervical spine: a randomized controlled trial

Abstract

Aim: The aim of this study was to compare the effects of cervical exercise, motor imagery (MI) and action observation (AO) of cervical exercise actions on conditioned pain modulation and pressure pain thresholds. The second objective was to assess the effects of these interventions on cervical motor activity (ranges of motion and muscle endurance), attention, and the ability to generate motor images.

Study design: Single-blinded randomized controlled trial.

Materials and methods: Fifty-four healthy subjects were randomly assigned to each group. Response conditioned pain modulation, pressure pain threshold, were the main variables. The secondary outcome measures included, cervical range of motion, Neck flexor endurance test, mental movement representation associated and psychosocial variables.

Results: All groups showed significant differences in time factor for all evaluated variables (p?<?.01) except pressure pain threshold over the tibial region. The post hoc analysis revealed significant within-group differences in the AE and AO groups in conditioned pain modulation (p?<?.05), with medium effect size in time [AE (d –0.61); AO (d –0.74)].

Conclusion: The results showed that within-group changes in conditioned pain modulation, cervical muscle endurance, and attention where founded only in the AE and AO groups. Variations in pain thresholds at pressure in the trapezium area were also obtained in the three groups. Changes in the ranges of flexion-extension and rotation movement were presented exclusively in the exercise group, and in the capacity to generate motor images only in the AO group. However, there was no difference in the pressure pain threshold over the tibial region.     

Effect of load position on muscle forces,internal loads and stability of the human spine in upright postures

A novel kinematics-based approach coupled with a non-linear finite element model was used to investigate the effect of changes in the load position and posture on muscle activity, internal loads and stability margin of the human spine in upright standing postures. In addition to 397 N gravity, external loads of 195 and 380 N were considered at different lever arms and heights. Muscle forces, internal loads and stability margin substantially increased as loads displaced anteriorly away from the body. Under same load magnitude and location, adopting a kyphotic posture as compared with a lordotic one increased muscle forces, internal loads and stability margin. An increase in the height of a load held at a fixed lever arm substantially diminished system stability thus requiring additional muscle activations to maintain the same margin of stability. Results suggest the importance of the load position and lumbar posture in spinal biomechanics during various manual material handling operations.     

The effect of resistance level and stability demands on recruitment patterns and internal loading of spine in dynamic flexion and extension using a simple trunk model

The effects of external resistance on the recruitment of trunk muscles in sagittal movements and the coactivation mechanism to maintain spinal stability were investigated using a simple computational model of iso-resistive spine sagittal movements. Neural excitation of muscles was attained based on inverse dynamics approach along with a stability-based optimisation. The trunk flexion and extension movements between 60° flexion and the upright posture against various resistance levels were simulated. Incorporation of the stability constraint in the optimisation algorithm required higher antagonistic activities for all resistance levels mostly close to the upright position. Extension movements showed higher coactivation with higher resistance, whereas flexion movements demonstrated lower coactivation indicating a greater stability demand in backward extension movements against higher resistance at the neighbourhood of the upright posture. Optimal extension profiles based on minimum jerk, work and power had distinct kinematics profiles which led to recruitment patterns with different timing and amplitude of activation.     

The influence of different magnitudes and methods of applying preload on fusion and disc replacement constructs in the lumbar spine: a finite element analysis

In a finite element (FE) analysis of the lumbar spine, different preload application methods that are used in biomechanical studies may yield diverging results. To investigate how the biomechanical behaviour of a spinal implant is affected by the method of applying the preload, hybrid-controlled FE analysis was used to evaluate the biomechanical behaviour of the lumbar spine under different preload application methods. The FE models of anterior lumbar interbody fusion (ALIF) and artificial disc replacement (ADR) were tested under three different loading conditions: a 150 N pressure preload (PP) and 150 and 400 N follower loads (FLs). This study analysed the resulting range of motion (ROM), facet contact force (FCF), inlay contact pressure (ICP) and stress distribution of adjacent discs. The FE results indicated that the ROM of both surgical constructs was related to the preload application method and magnitude; differences in the ROM were within 7% for the ALIF model and 32% for the ADR model. Following the application of the FL and after increasing the FL magnitude, the FCF of the ADR model gradually increased, reaching 45% at the implanted level in torsion. The maximum ICP gradually decreased by 34.1% in torsion and 28.4% in lateral bending. This study concluded that the preload magnitude and application method affect the biomechanical behaviour of the lumbar spine. For the ADR, remarkable alteration was observed while increasing the FL magnitude, particularly in the ROM, FCF and ICP. However, for the ALIF, PP and FL methods had no remarkable alteration in terms of ROM and adjacent disc stress.     

The potential fertility estimation capacity of the hypoosmotic swelling test, the thermal stress test and a modified cervical mucus penetration test in the bovine

In this study, hypoosmotic swelling (HOS), thermal stress (TS) and modified cervical mucus penetration (mCMP) tests have been used with routine tests for the assessment of semen quality. This is the first study in which the comparison of potential fertility estimation of fore-mention three tests was performed. Bull semen samples were divided into two fertility groups (high: n=3, low: n=3), according to their post-insemination NRR (non-return rate). Prior to the tests, post-thawed spermatological characteristics were assessed after which HOS, TS and mCMP tests were carried out. In the HOS test, the ratio of swollen cells, in the TS test the motility, and in the mCMP test the number of spermatozoa penetrating the cervical mucus, were examined. The relationship between the tests and fertility was also evaluated. HOS test was carried out according to different incubation times and temperatures (37 degrees C 60 min/41 degrees C 15 min/41 degrees C 30 min/46 degrees C 15 min/46 degrees C 30 min). For TS test, samples were subjected to various temperatures for different periods (no incubation (37 degrees C)/41 degrees C 15 min/41 degrees C 30 min/46 degrees C 15 min/46 degrees C 30 min). The mCMP test were subjected to various temperatures for the same period (37 degrees C 15 min/41 degrees C 15 min). In this study, post-thawed motility was found to be similar in high and low fertility groups. However, it has been determined that acrosomal (p<0.01) and other morphological defects (p<0.05) were low in the high fertility group. When HOS test was carried out at 37 degrees C, no difference was observed between the bulls with high and low fertility, but at 41 and 46 degrees C, results of high fertility group were significantly higher than those of low fertility group (p<0.01). Similarly in TS test, the progressive motility rates of high fertility bulls was higher after thermal practices at 41 and 46 degrees C (p<0.01). In mCMP test, at 37 degrees C, the number of cells that had penetrated was similar. However, significant differences were observed in the incubation at 41 degrees C (p<0.01). It has been concluded that for the estimation of potential fertility of bulls, HOS, TS and mCMP tests, in combination with routine spermatological tests can be used and the use of further penetration distance range (PDR2) in mCMP test and higher temperatures such as 41 degrees C instead of 37 degrees C, during the incubations in the afore-mentioned performance tests, is more determinative.     

The separate and combined effects of harmonic structure, phase, and FM on female preferences in the barking treefrog (Hyla gratiosa)

In natural advertisement calls of the barking treefrog, Hyla gratiosa, a small amount of incoherent frequency modulation (FM) is present. Incoherency in the FM of a call creates inharmonicity and phase changes between its frequency components. In this study, the combined and separate effects of the harmonic structure, phase spectrum, and FM of an advertisement call on female choice were tested. The harmonic structure of a call can have a direct effect on female preference; females showed a significant preference for static-inharmonic calls over static-harmonic calls. Neither differences in phase or FM alone conferred a preference in two choice tests. However, when FM is present in both calls it does influence female preference for harmonic structure -namely harmonic calls become preferable to inharmonic calls. This reversal of female preference for inharmonicity in a call by the presence of FM suggests that call parameters may interact, and thereby effect mate choice.Abbreviations AP amphibian papilla - BP basilar papilla - FM frequency modulation - PM phase modulation - HS harmonic structure - GB Gaussian Band     

The effect of decapitation on the levels of IAA and ABA in the lateral buds of Betula pendula roth

The level of IAA and ABA in lateral buds of birch shoots 24 h and 5 days after the decapitation of the apical bud was determined. Twenty four hours after decapitation, when visible signs of outgrowth of lateral buds were not observed yet, an increase in the level of IAA and a decrease of ABA, as compared with the buds of non-decapitated shoots, was found. Five days later, when lateral buds were in the period of intensive outgrowth, a decrease in the levels of IAA and ABA was observed. It has been suggested that removing the source of auxin, by the decapitation of the apical bud makes possible the lateral buds to undertake the synthesis of their own auxin. It could lead to the decrease in the content of ABA. These all events could create suitable conditions for the outgrowth of lateral shoots.     

The effect of acoustic and visual priming stimuli on the reproductive behaviour of female zebra finches, <Emphasis Type="Italic">Taeniopygia guttata</Emphasis>

We investigated the influences of reproductive priming, using acoustic stimuli alone or a combination of acoustic and visual stimuli on egg-laying in female zebra finches (Taeniopygia guttata). One group of females was exposed during 6 days to both acoustic and visual stimuli from males while another was exposed only to acoustic stimuli; a control group was unable to see or hear males prior to the introduction of unfamiliar males for pairing. We also manipulated the amount of visual stimulation by presenting either: males with normal red bands, males with red bands without ultraviolet reflection or unadorned males. Females exposed to visual stimuli spent more time on perches near males than control females or those only hearing males. However, there were no statistically significant differences in subsequent total eggs produced, or the latency to egg-laying between females exposed to priming males with different visual characteristics; they did not significantly differ from the control females in these parameters either. Females that heard, but did not see, priming stimuli produced more eggs when paired with males than the controls. Thus, acoustic stimuli alone may have promoted reproductive condition while the acoustic and visual stimuli together did not. Our results contradict a previous report, and may reflect components of the experimental design we employed (i.e. by pairing females with unfamiliar males after their initial exposure to priming males, we may have suppressed their ability to advance their reproductive state). Females that only heard priming males may have been more willing to accept pairing males because of the absence of visual identifiers.     

The effect of training on the lateral musculature of O-group roach, Rutilus rutilus (L.), and their fatigue in subsequent exercise tests

First year roach from a Stillwater habitat were maintained in an'artificial stream for periods of up to 40 days and samples of the lateral musculature were subjected to histological examination. It was found that there was a highly significant increase in the percentage of red muscle present in the hindermost regions of the fish confined for 30 days or more in the stream. In subsequent exercise tests, it was shown that the FV₅₀ was higher for fish conditioned for 40 days, but it was considered unlikely that this increase in swimming ability was as a direct result of changes in muscle composition.     

The effect of axial ligands on the reactivity and stability of the oxoferryl moiety in model complexes of Compound I of heme-dependent enzymes

 The contribution of simple inorganic model complexes to the understanding of related processes in biomolecules is demonstrated by a series of Compound I analogs of heme-dependent enzymes. The oxoiron(IV) porphyrin cation radical state in these synthetic complexes is stable enough to be studied by spectroscopic methods as a function of only one variable, the axial ligand trans to the oxoiron bond. Complementary information from kinetic investigations of the reactivity in epoxidation of olefins enables the separation of the thermodynamic and kinetic effects of the axial ligands. The results clearly indicate that epoxidation by these complexes proceeds by two distinguishable steps, which are affected differently by the axial ligands. The first step is electron transfer from the olefin to the ferryl moiety, probably followed by intramolecular charge rearrangement and product release. It is proposed that part of the enhanced oxygenation activities of cytochrome P-450 monooxygenases and chloroperoxidases is due to a lowering of the energy barrier for the second step via participation of their redox-active cysteinate ligand in charge rearrangement. Received and accepted: 7 May 1996     

The effect of shoot-bending on the amount of diffusible indole-3-acetic acid and its transport in shoots of Japanese pear

The amount of diffusible indole-3-acetic acid (IAA) in shoots ofJapanese pear (Pyrus pyrifolia) decreased when vertical shootswere bent at an angle of 45°. A significant decrease of diffusibleIAA was observed one day after shoot bending (DAB), and the degree ofthis decrease was larger in the apical region of the shoot than in thebasal region. The decrease caused by the shoot bending increased withthe duration of the treatment. The IAA amounts in the bent shoot in theapical, central, and basal segments on 1 DAB were58.2±6.4%, 92.6±7.6%, and79.1±7.1% of the control, while 43.7±4.1%,30.8±2.9%, and 39.4±2.5% on 14 DAB.Radiolabelled IAA transport velocity was also examined, but it was notinfluenced by the shoot angle in the apical region of the shoot.However, the IAA transport velocity in the basal region decreased. Itdropped first on 1 DAB, but it recovered to the control level 3 DAB,then it decreased again on 14 DAB. A large increase in ethyleneproduction was observed in the bent shoot, but it seemed transient anddid not continue for 14 days. These results suggest that the decrease ofdiffusible IAA amounts may be induced not by the decrease of IAAtransport velocity but by the production/supply of IAA in the apicalregion.     

The pattern of cervical penetration and the effect of topical treatment with prostaglandin and/or FSH and oxytocin on the depth of cervical penetration in the ewe during the peri-ovulatory period

Artificial insemination in sheep has two major limiting factors: the poor quality of frozen-thawed ram semen and the convoluted anatomy of the sheep cervix that does not allow transcervical passage of an inseminating catheter. It has been demonstrated that in the ewe during estrus, there is a degree of cervical relaxation mediated by ovarian and possibly gonadotrohic hormones, and we set out to investigate factors that might enhance cervical relaxation. Five experiments were conducted on ewes of different breeds to determine: 1) the pattern of cervical penetration during the periovulatory period in ewes of several breeds (Welsh Mountain, Île-de-France, Vendéenne, Romanov and Sarda); 2) the effect of the “ram effect” a socio-sexual stimulus, on cervical penetration; and 3) the effects of the intracervical administration of follicle-stimulating hormone (FSH), oxytocin and a prostaglandin E agonist (misoprostol) on the depth of cervical penetration during the periovulatory period. The results showed that during the periovulatory period in all breeds examined, there was increased penetration of the cervical canal (P < 0.05) by an inseminating catheter. Cervical penetration increased to a maximum 54 h after the removal of progestagen sponges and then gradually declined. Furthermore, the depth of cervical penetration but not its pattern, was affected (P < 0.05) by the breed of ewe. The maximum depth of cervical penetration was lower (P < 0.05) in the Vendéenne breed compared to the Île-de-France and Romanov breeds, which did not differ from one another. In the presence of rams, the depth of cervical penetration was increased at 48 and 54 h after removal of sponges (P < 0.05) and reduced at 72 h (P < 0.05). The local administration of hormones FSH, misoprostol (a PGE agonist) and oxytocin alone and in various combinations did not have any significant effect on the depth of cervical penetration during the periovulatory period. In conclusion, the natural relaxation of the cervix observed in ewes of several breeds occurs at a time during estrus, 54 h after the removal of progestagen sponges, which is the most suitable for artificial insemination. The effect was enhanced by the presence of a ram but not by the local intracervical administration of FSH, misoprostol and oxytocin even though oxytocin and PGE₂ are involved in cervical function. The time of maximum cervical penetration in the preovulatory period (54 h) coincides with high LH and estradiol concentrations suggesting they might be responsible for the relaxation of the cervix probably through an oxytocin-PGE mediated pathway.     

The effects of posterolateral spine length and body length on feeding rate in the rotifer,Brachionus calyciflorus

The length of the posterolateral spines in the rotifer, Brachionus calyciflorus, is variable. The effect of the length of these spines on the clearance rates of B. calyciflorus was examined under laboratory conditions using radioactively-labelled yeast (Rhodotorula) and bacteria (Aerobacter). The hypothesis that individuals with longer spines have higher clearance rates than those of similarly-sized individuals with shorter spines was rejected. The effect of body length (L) on the clearance rates (C) of short-spined and long-spined animals was also examined. Statistically significant linear regressions of the form log₁₀ C = aL + b, were derived for both types. The slopes of both regressions were similar and suggest that clearance rate in B. calyciflorus increases as a cube function of body length.     

Apical dominance in Phaseolus vulgaris. The triggering effect of shoot decapitation and leaf excision on growth of the lateral buds

It was postulated that the release of lateral buds from apical dominance is triggered by the immediate increase in apoplastic water potential (hydrostatic pressure) that is produced by shoot decapitation and that is rapidly transmitted throughout the plant. In experiments conducted to test this hypothesis the use of a strain gauge transducer capable of measuring bud growth with an accuracy of ± 0.1 μm, showed that growth of the inhibited lateral bud at the primary leaf node of Phaseolus vulgaris (L.) ev. Canadian Wonder was initiated within 1 to 5 s following shoot decapitation or excision of the primary leaves. When only the apical bud was excised the lateral bud showed a brief, transitory growth response of ca 1 min duration, but the axillary buds of the first and second trifoliate leaves were released from inhibition. Decapitation of the shoot just below the first trifoliate leaf induced a lateral bud response characterized by three distinct stages: a) a rapid initial growth response with a mean duration of 4.9 min b) a period of arrested growth, which varied in duration from 2 min to 4 h and c) the subsequent resumption of growth.
Excision of both primary leaves induced a rapid but transitory bud response of considerably greater duration than that induced by apical bud excision. Excision of the primary leaves prior to decapitation of the shoot eliminated the phase of arrested growth, which characterized the bud response to decapitation of the intact plant. The rapidity of the bud response to both shoot decapitation and leaf excision and the interaction between the effect of these two treatments are consistent with the hypothesis that competition for water plays a major role in the correlative inhibition of lateral buds.     

The effects of nitrate loading on the invasive macrophyte Hydrilla verticillata and two common, native macrophytes in Florida

Rising nitrate concentrations in the water column and the spread of invasive, non-native macrophytes are two major threats to Florida's oligotrophic, freshwater ecosystems. We used a replicated mesocosm experiment to test the effects of elevated nitrate concentrations in the water on the growth of the invasive macrophyte Hydrilla verticillata and two common, native submerged macrophytes Vallisneria americana and Sagittaria kurziana. Results from this study indicate that nitrate concentrations of 1.0 mg L⁻¹ NO₃-N in the water increased the final dry-weight biomass of H. verticillata by 2.75 times, while having no statistical effect on the growth of the two native species. Additionally, H. verticillata grew at a faster rate than the two native species in the low nitrate treatments accounting for 82% of the total biomass, indicating that it may have the capacity to invade relatively pristine communities. In waters where nitrate concentrations continue to rise, the cost of control efforts for H. verticillata may substantially increase in the future.     

The effect of monensin on gametogenesis and zoosporogenesis in the aquatic fungus,Allomyces macrogynus

Summary Cytoplasmic cleavage in the gametangia and zoosporangia ofA. macrogynus was studied using monensin, an ionophore known to disrupt several endomembrane functions in plant and animal cells. Monensin interfered with normal gamete and zoospore formation in a dose dependent manner such that at a 20 M concentration very abnormal cells were released from the reproductive structures. It was evident that monensin's effect was most pronounced during the first 25 minutes of gametogenesis and parallels in time the onset and continuation of the cytoplasmic cleavage events. Observations using fluorescence and differential interference contrast microscopy indicated that the ionophore inhibited normal cytoplasmic cleavage resulting in the production of multinucleate cells, many of which had either no flagella or multiple flagella. Transmission electron microscopy showed that the monensin-treated gametangia had many large vacuoles which contained amorphous electron-opaque material. X-ray microprobe analysis demonstrated that the elemental composition of the large vacuoles was identical to that of the dense globular inclusions seen in untreated gametangia, and morphological analysis confirmed the relationship between these endomembrane structures. Thus this swollen endomembrane component probably is not involved in the cleavage process. Single endomembrane cisternae which were very common in untreated gametangia were seldom seen in monensin-treated preparations. Instead, many smaller electron-transparent vacuoles were observed. These swollen cisternae may both represent monensin-modified Golgi apparatus equivalents and/or play a critical role during the process of gametogenesis and zoosporogenesis inA. macrogynus.