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PubMed1996

Estimation of the position and orientation of the kinematic axis of the temporomandibular joint.

The kinematic axis refers to a theoretical intercondylar axis of the temporomandibular joint, which translates on a curved surface during all sagittal movements. In normal joints, the translation of this rotational axis is nearly reciprocal. Its estimation is arrived at in two steps: (i) axis points are estimated in several sagittal planes, using data of sagittal mandibular movements, and (ii) an axis is then fitted to them. Neither of them, however, takes into consideration any geometric constraints on the trajectories of the kinematic axis. To correct this theoretical inconsistency, this paper presents a technique capable of directly exploring the position and orientation of the axis. During exploration, the axis is evaluated by the extent of its motion range, which is approximated from trajectile data obtained at several points on the axis. The validity of this technique was verified, through experiments employing data of actual mandibular movements.

Adult↗
PubMed1997

Complete left bundle branch block with left QRS axis deviation: defining its clinical importance.

Aim of this study was to elucidate the diagnostic significance of left axis deviation (LAD) in patients (pts) with chronic (> 6 months) left bundle branch block (LBBB). We retrospectively studied 2094 consecutive pts who underwent cardiac catheterization. All pts had left heart catheterization and coronary angiography, whereas right heart catheterization or endomyocardial biopsy were performed on indication. Our study group consisted of 43 pts with LBBB (29 men, 14 women, mean age 60.3 +/- 7.9 years). Pts with acute myocardial infarction or prior high degree AV-block were excluded. Initial evaluation included history, physical examination, chest X-ray, serial ECGs, 2D-echo and Doppler studies. ECG-criteria for LBBB were a QRS duration of > 0.12 secs, a predominantly negative QRS deflection in V1 and a widened R-wave in V6. LAD was considered present when the mean frontal QRS axis was between -30 degrees and -90 degrees. The mean frontal QRS axis was considered normal if it was between -29 degrees and +90 degrees. Twenty-nine pts had normal axis and 14 had LAD. According to angiographic data, among coronary disease pts, 12 (31.48%) had normal axis and 4 (28.57%) LAD (p = 0.041). Among mitral valve disease pts, 3 (10.35%) had normal axis and none LAD. Among pts with aortic valve disease, I (3.45%) had normal axis and 8 (57.15%) LAD (p = 0.0001). Among pts with dilated cardiomyopathy, 2 (6.9%) had normal axis and 1 (7.14%) LAD. Among pts with no organic heart disease, 11 (37.93%) had normal axis and 1 (7.14%) LAD (p = 0.035). The presence of LAD had a 41.9% sensitivity and a 91.6% specificity for the presence of organic heart disease. These findings point towards a statistically significant difference in the presence of organic heart disease in LBBB pts with LAD compared to normals. Aortic valve disease in LBBB pts seems to be frequently accompanied by LAD.

Aged↗
PubMed2006

Two distinct events, section compression and loss of particles ("lost caps"), contribute to z-axis distortion and bias in optical disector counting.

Deformation of tissue sections in the z-axis can bias optical disector counting. When samples of particle densities are not representative for the entire tissue section, significant bias of estimated numbers can result. To assess the occurrence, prevalence, extent, sequence of events, and causes of z-axis distortion, the distribution of neuronal nucleoli in thick paraffin and vibratome sections was determined in chicken, rodent, and human brain tissues. When positions of neuronal nucleoli were measured in the z-axis, nucleoli were more frequent at the surfaces (bottom and top) of tissue sections than in the core. This nonlinear z-axis distribution was not lab-, equipment-, or investigator-specific, and was independent of age, fixation quality, coverslipping medium, or paraffin melting temperature, but in paraffin sections, was highly correlated with the tilt of the knife (cutting) angle. Manipulation of subsequent tissue processing steps revealed that two events contribute to z-axis distortion. Initially, a higher density of particles results at surfaces after sectioning, apparently due to section compression. Subsequently, particles can be lost to varying degrees from surfaces during floating or staining and dehydration, resulting in "lost caps." These results may explain different degrees of z-axis distortion between different types of sections and different labs, and reinforce the importance of checking z-axis distributions as a "quality control" prior to selection of guard zones in optical disector counting. Indirect approaches to assess section quality, such as resectioning in a perpendicular plane, yield additional artifacts, and should be replaced by a direct quantitative measurement of z-axis distribution of particles.

Animals↗
PubMed1999

Eye-position dependence of three-dimensional ocular rotation-axis orientation during head impulses in humans.

If horizontal saccades or smooth-pursuit eye movements are made with the line-of-sight at different elevations, the three-dimensional (3D) angular rotation axis of the globe tilts by half the vertical eye eccentricity. This phenomenon is named "half-angle rule" and is a consequence of Listing's law. It was recently found that the ocular rotation axis during the horizontal vestibulo-ocular reflex (VOR) on a turntable also tilts in the direction of the line-of-sight by about a quarter of the eye's vertical eccentricity. This is surprising, since, in a "perfect" VOR, the angular rotation axis of the eye should be independent from the position of the eye to fully compensate for the 3D angular head rotation. We asked whether this quarter-angle strategy is a general property of the VOR or whether the 3D kinematics of ocular movements evoked by vestibular stimulation would be less eye-position dependent at higher stimulus frequencies. Nine healthy subjects were exposed to horizontal head impulses (peak velocity approximately 250 degrees /s). The line-of-sight was systematically changed along the vertical meridian of a tangent screen. Three-dimensional eye and head movements were monitored with dual search coils. The 3D orientation of the angular eye-in-head rotation axis was determined by calculating the average angular velocity vectors of the initial 10 degrees displacements. Then, the difference between the tilt angles of the ocular rotation axis during upward and downward viewing was determined and divided by the difference of vertical eccentricity ("tilt angle coefficient"). Control experiments included horizontal saccades, smooth-pursuit eye movements, and eye movements evoked by slow, passive head rotations at the same vertical eye eccentricities. On average, the ocular rotation axis during horizontal head-impulse testing at different elevations of the line-of-sight was closely aligned with the rotation axis of the head (tilt angle coefficient of pooled abducting and adducting eye movements: 0.11+/-0.17 SD). Values for slow head impulses, however, exceeded somewhat the quarter angle (0.33+/-0.12), while smooth-pursuit movements (0. 50+/-0.09) and saccades (0.44+/-0.11) were closest to the half angle. These results demonstrate that the 3D orientation of the ocular rotation axis during rapid head thrusts is relatively independent of the direction of the line-of-sight and that ocular rotations elicited by head impulses are kinematically different from saccades, despite similar movement dynamics.

Adult↗
PubMed2006

Axis of eye rotation changes with head-pitch orientation during head impulses about earth-vertical.

The goal of this study was to assess how the axis of head rotation, Listing's law, and eye position influence the axis of eye rotation during brief, rapid head rotations. We specifically asked how the axis of eye rotation during the initial angular vestibuloocular reflex (VOR) changed when the pitch orientation of the head relative to Earth-vertical was varied, but the initial position of the eye in the orbit and the orientation of Listing's plane with respect to the head were fixed. We measured three-dimensional eye and head rotation axes in eight normal humans using the search coil technique during head-and-trunk (whole-body) and head-on-trunk (head-only) "impulses" about an Earth-vertical axis. The head was initially oriented at one of five pitch angles (30 degrees nose down, 15 degrees nose down, 0 degrees, 15 degrees nose up, 30 degrees nose up). The fixation target was always aligned with the nasooccipital axis. Whole-body impulses were passive, unpredictable, manual, rotations with peak-amplitude of approximately 20 degrees , peak-velocity of approximately 80 degrees /s, and peak-acceleration of approximately 1000 degrees /s2. Head-only impulses were also passive, unpredictable, manual, rotations with peak-amplitude of approximately 20 degrees , peak-velocity of approximately 150 degrees /s, and peak-acceleration of approximately 3000 degrees /s2. During whole-body impulses, the axis of eye rotation tilted in the same direction, and by an amount proportional (0.51 +/- 0.09), to the starting pitch head orientation (P < 0.05). This proportionality constant decreased slightly to 0.39 +/- 0.08 (P < 0.05) during head-only impulses. Using the head-only impulse data, with the head pitched up, we showed that only 50% of the tilt in the axis of eye rotation could be predicted from vectorial summation of the gains (eye velocity/head velocity) obtained for rotations about the pure yaw and roll head axes. Thus, even when the orientation of Listing's plane and eye position in the orbit are fixed, the axis of eye rotation during the VOR reflects a compromise between the requirements of Listing's law and a perfectly compensatory VOR.

Adult↗
PubMed1976

Lesions in the ribosomes of non-viable pea (Pisum arvense) embryonic axis tissue.

Ribosomes isolated from either dry viable or non-viable pea embryonic axis tissue were equally effective in the support of polyphenylalanine synthesis in a poly(U)-directed cell-free protein-synthesising system. Ribosomes isolated from imbibed non-viable axis tissue were impaired in their ability to support polyphenylalanine synthesis in the cell-free system. RNA isolated from ribosomes and 40-S ribosomal subunits of dry or imbibed viable axis tissue was found not to be degraded, whereas the equivalent RNA species isolated from non-viable axis tissue showed an increased degree of breakdown as imbibition proceeded. Even though rRNA of imbibed non-viable axis tissue was degraded, the ribosomes and ribosomal subunits of these embryos appeared intact. In viable embryonic axis tissue the percentage of ribosomes present in the cell in the form of polysomes increased during imbibition whereas no polysomes could be detected in ribosomal preparations from dry or imbibed non-viable axis tissue. The breakdown of rRNA in ribosomal particles from non-viable axis tissue may be a contributory factor to senescence and loss of viability in Pisum arvense.

Cell Fractionation↗
PubMed1996

Vestibulo-ocular reflex of the squirrel monkey during eccentric rotation with centripetal acceleration along the naso-occipital axis.

The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in four male squirrel monkeys. Monkeys were rotated in the dark at 200 degrees/s, centrally or 79 cm off-axis, with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's position relative to the centripetal acceleration (facing center or back to center) had a dramatic influence on the VOR. These studies show that a torsional response was always elicited that acted to shift the axis of eye rotation toward alignment with gravito-inertial force. On the other hand, a slow phase downward vertical response usually existed, which shifted the axis of eye rotation away from the gravito-inertial force. These findings were consistent across all monkeys. In another set of tests, the same monkeys were rapidly tilted about their interaural (pitch) axis. Tilt orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the rotation, no consistent eye velocity response was ever observed during or following the tilt. The absence of any response following tilt proves that the observed torsional and vertical responses were not a positional nystagmus. Model simulations qualitatively predict all components of these eccentric rotation and tilt responses. These simulations support the conclusion that the VOR during eccentric rotation may consist of two components: a linear VOR and a rotational VOR. The model predicts a slow phase downward, vertical, linear VOR during eccentric rotation even though there was never a change in the force aligned with monkey's spinal (Z) axis. The model also predicts the torsional components of the response that shift the rotation axis of the angular VOR toward alignment with gravito-inertial force.

Animals↗
PubMed2004

The effect of off-the-visual-axis retinoscopy on objective refractive measurement.

PURPOSE: To determine the effect of off-axis retinoscopy on objective refractive measurement. DESIGN: Prospective experimental study. METHODS: Eight volunteers underwent cycloplegic retinoscopy of their right eye on-the-visual-axis, and 5, 10, 15, and 20 degrees off-the-visual-axis in adduction. A single masked examiner performed all retinoscopy with random order of the patient and axis refracted. RESULTS: The average spherical retinoscopic value at 0, 5,10,15, and 20 degrees of off-axis alignment was -0.40, -0.90, -1.00, -1.38, and -1.80 diopters, respectively. The average spherical equivalent retinoscopic value obtained for each of the above positions of eye alignment was -0.02, -0.59, -0.45, -0.64, and -0.98 diopters, respectively. The induced cylinder power increased by an average of 3% for each degree of off-axis retinoscopy, though the axis of the cylinder was not predictable. CONCLUSION: Objective refractive measurement by retinoscopy is significantly altered by off-the visual-axis retinoscopy. The induced error may be clinically important even with small degrees of eccentricity.

Adult↗
PubMed2005

Normal hypothalamo-pituitary-adrenal axis function in a rat model of peripheral neuropathic pain.

Chronic pain conditions such as rheumatoid arthritis and fibromyalgia are associated with profound hypothalamo-pituitary-adrenal (HPA) axis dysfunction which may exacerbate symptoms of chronic pain. HPA axis dysfunction has also been well documented in animal models of chronic inflammatory pain. However, the role of the HPA axis in animal models of neuropathic pain is currently unknown. Rats with a chronic constriction injury (CCI) of the sciatic nerve that developed marked mechanical allodynia and hyperalgesia of the injured hindpaw were used to determine basal and stimulatory levels of HPA axis activity. Plasma ACTH and corticosterone levels were increased significantly (P < 0.05) in CCI rats after 20 min restraint stress compared with baseline; however, the magnitude of the increase was no different from sham rats. Furthermore, the temporal profile of ACTH release over the 60 min period after termination of restraint was similar between CCI and sham rats suggesting normal glucocorticoid-mediated feedback. Restraint stress also significantly increased (P < 0.05) expression of the immediate early genes c-Fos and FosB within the hypothalamic PVN to a similar extent in CCI and sham rats. Within the parvocellular PVN basal expression of both CRF and AVP mRNA was no different between CCI and sham rats; restraint stress induced a significant 2.5 fold increase (P < 0.05) in CRF mRNA expression in sham rats only. These results suggest that, in contrast to inflammatory immune-mediated pain models where HPA axis function is profoundly altered, in the CCI model of neuropathic pain, basal HPA axis function is unchanged. Furthermore, the HPA axis responds normally to a novel stressor in the face of ongoing nociceptive input, a stimulus known to activate the HPA axis.

Adrenocorticotropic Hormone↗
PubMed2006

From Malthus to motive: how the HPA axis engineers the phenotype, yoking needs to wants.

The hypothalamo-pituitary-adrenal (HPA) axis is the critical mediator of the vertebrate stress response system, responding to environmental stressors by maintaining internal homeostasis and coupling the needs of the body to the wants of the mind. The HPA axis has numerous complex drivers and highly flexible operating characterisitics. Major drivers include two circadian drivers, two extra-hypothalamic networks controlling top-down (psychogenic) and bottom-up (systemic) threats, and two intra-hypothalamic networks coordinating behavioral, autonomic, and neuroendocrine outflows. These various networks jointly and flexibly control HPA axis output of periodic (oscillatory) functions and a range of adventitious systemic or psychological threats, including predictable daily cycles of energy flow, actual metabolic deficits over many time scales, predicted metabolic deficits, and the state-dependent management of post-prandial responses to feeding. Evidence is provided that reparation of metabolic derangement by either food or glucocorticoids results in a metabolic signal that inhibits HPA activity. In short, the HPA axis is intimately involved in managing and remodeling peripheral energy fluxes, which appear to provide an unidentified metabolic inhibitory feedback signal to the HPA axis via glucocorticoids. In a complementary and perhaps a less appreciated role, adrenocortical hormones also act on brain to provide not only feedback, but feedforward control over the HPA axis itself and its various drivers, as well as coordinating behavioral and autonomic outflows, and mounting central incentive and memorial networks that are adaptive in both appetitive and aversive motivational modes. By centrally remodeling the phenotype, the HPA axis provides ballistic and predictive control over motor outflows relevant to the type of stressor. Evidence is examined concerning the global hypothesis that the HPA axis comprehensively induces integrative phenotypic plasticity, thus remodeling the body and its governor, the brain, to yoke the needs of the body to the wants of the mind. Adverse side effects of this yoking under conditions of glucocorticoid excess are discussed.

Animals↗
PubMed2005

Child maltreatment and HPA axis dysregulation: relationship to major depressive disorder and post traumatic stress disorder in females.

A history of child maltreatment increases the vulnerability to the development of Major Depressive Disorder (MDD) and/or Posttraumatic Stress Disorder (PTSD), especially in females. Both MDD and PTSD are associated with a dysregulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis. Dysregulation of the HPA axis may be an important etiological link between child maltreatment and subsequent psychiatric disorder, yet little is known about the relationship between exposure and outcome. The aim of this review is to explore the role of HPA axis dysregulation in the link between child maltreatment and MDD/PTSD among women. Studies of females with MDD frequently indicate a hyperactivity of the HPA axis, and contribute to our understanding of the underlying mechanisms involved in mood dysregulation. Evidence for HPA axis dysregulation in PTSD is less convincing and suggests that timing of the stressful experience as well as the type of the trauma may influence the outcome. The strongest evidence to date suggesting that the development of the HPA axis may be affected by early life stressful experiences comes from pre-clinical animal studies. Together these studies add to our understanding of the role of the HPA axis in psychiatric disorders in relation to stress. The literature on HPA axis function in both children and adults following child maltreatment further highlights the potential relevance of early stress to later onset of major psychiatric disorders. Such knowledge may also contribute to the development of early interventions targeted at primary prevention.

Adolescent↗
PubMedDate not supplied

Axis I diagnostic comorbidity and borderline personality disorder.

Borderline personality disorder (PD) has been the most studied PD. Research has examined the relationship between borderline PD and most axis I diagnostic classes such as eating disorders, mood disorders, and substance use disorders. However, there is little information regarding the relationship of borderline PD and overall comorbidity with all classes of axis I disorders assessed simultaneously. In the present study, 409 patients were evaluated with semistructured diagnostic interviews for axis I and axis II disorders. Patients with a diagnosis of borderline PD versus those who did not receive the diagnosis were assigned significantly more current axis I diagnoses (3.4 v 2.0). Borderline PD patients were twice as likely to receive a diagnosis of three or more current axis I disorders (69.5% v 31.1%) and nearly four times as likely to have a diagnosis of four or more disorders 147.5% v 13.7%). In comparison to nonborderline PD patients, borderline PD patients more frequently received a diagnosis of current major depressive disorder (MDD), bipolar I and II disorder, panic disorder with agoraphobia, social and specific phobia, posttraumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), eating disorder NOS, and any somatoform disorder. Similar results were observed for lifetime diagnoses. Overall, borderline PD patients were more likely to have multiple axis I disorders than nonborderline PD patients, and the differences between the two groups were present across mood, anxiety, substance use, eating, and somatoform disorder categories. These findings highlight the importance of performing thorough evaluations of axis I pathology in patients with borderline PD in order not to overlook syndromes that are potentially treatment-responsive.

Adult↗
PubMed1997

Adrenal axis activation by chronic social stress fails to inhibit gonadal function in male rats.

Stress in males via the hypothalamic-pituitary-adrenal (HPA) axis may set into motion varied physiological alterations, including dysfunction of the hypothalamic-pituitary-gonadal (HPG) axis. However, the influence of the HPA on the HPG axis may not always be inhibitory. Presence or absence of stimuli of sexual significance that typically activates the HPG axis may alter the influence of the adrenal axis on gonadal axes. In this project, we used male rats and chronic social stimulation that included brief or extended periods with female rats to examine HPA-HPG axes interactions. In experiment 1, we used intact males and a 'chronic social stress' paradigm developed in our previous research that induces social instability by daily changing the membership of group-housed males with females. Thymus weight was reduced and corticosterone levels were marginally increased by chronic social stress, indicating a HPA axis hyperactivity. The HPG axis was also activated as shown by the increased weight of the androgen-sensitive sex structures. These results indicate that when these two axes are stimulated together, neither interferes with nor suppresses activities of the other. Implants of corticosterone pellets to adrenalectomized animals that maintained constant, high corticosterone levels failed to reverse the gonadal hyperactivity induced by sexual stimulation. In a second experiment, we studied the influence of different intensity of sexual stimulations on HPA-HPG axes interactions. Increased corticosterone levels and adrenal weight, indicating a HPA hyperactivity, failed to inhibit HPG hyperactivity as measured by the increased sexual organs weight, whatever the sexual intensity of the stimulation. This work demonstrates that the gonadal axis is freed from suppression when sexual stimulation occurs together with stress. The general conclusion is that the nature of complex social settings is important in determining interactions between the two neuroendocrine axes.

Adrenal Glands↗
PubMed1998

Evaluation of axis alignment system for correction of myopic astigmatism with the excimer laser.

PURPOSE: To evaluate the efficacy of in situ axis alignment for the treatment of myopic astigmatism with an excimer laser. METHODS: In this prospective clinical trial, 71 eyes with stable astigmatism of -1.00 to -6.00 diopters (D) with or without stable myopia of up to 10.00 D were randomized to receive excimer treatment of their astigmatic component aligned to the axis determined by subjective refraction (control group) or to have the alignment verified and altered is necessary by in situ alignment (axis alignment group). A VISX Twenty-Twenty excimer laser was used for the treatment. Patients were followed for 6 months. RESULTS: In 85% of eyes in the axis alignment group, the axis of cylinder was different from that calculated by routine refraction. Pretreatment mean cylinder was -1.81 D +/- 0.91 (SD) in the axis alignment group and -1.75 +/- 0.60 D in the control group. At 6 months, an undercorrection of cylinder was seen in both groups; the mean residual cylinder was -0.70 +2- 0.56 D in the axis alignment group and -0.59 +/- 0.50 D in the control group. More than 80% of all eyes were within +/- 1.00 D of plano and achieved an uncorrected visual acuity of 6/12 or better. A loss of two or more lines of best corrected visual acuity was recorded in three eyes. CONCLUSION: The in situ alignment technique did not produce better results of photoastigmatic refractive keratectomy than the routine axis alignment technique.

Adult↗
PubMed2000

The hypothalamic-pituitary-adrenal axis activity as a predictor of cardiovascular disease, type 2 diabetes and stroke.

OBJECTIVES: The hypothalamic-pituitary-adrenal (HPA) axis, the mediator of cortisol, plays a central role in the homeostatic processes. In this study, we addressed the potential impact of HPA axis activity on established anthropometric, metabolic and haemodynamic risk factors for cardiovascular disease (CVD), type 2 diabetes mellitus and stroke. DESIGN: A cross-sectional study. SUBJECTS: A subgroup of 284 men from a population sample of 1040 at the age of 51 years. MAIN OUTCOME MEASURES: Anthropometric measurements included body mass index (BMI, kg m-2), waist/hip circumference ratio (WHR) and abdominal sagittal diameter (D). Overnight fasting values of blood glucose, serum insulin, triglycerides, total, low (LDL) and high density (HDL) lipoprotein cholesterol, as well as resting heart rate and blood pressure, were also determined. By using repeated diurnal salivary cortisol measurements during everyday conditions, methods were developed to characterize the status of the HPA axis, and set in relation to the anthropometric, metabolic and haemodynamic measurements. RESULTS: In bivariate analyses, risk factors intercorrelated in clusters of anthropometric (BMI, WHR, D), metabolic (insulin, glucose and their ratio, triglycerides, cholesterol [total and LDL], HDL cholesterol [negative]) and haemodynamic (systolic and diastolic blood pressure and heart rate) measurements. This was also the case in the two-dimensional scaling analysis, where, however, HDL separated out. A normal HPA axis status, characterized by high variability and morning cortisol values, as well as a clear response to a standardized lunch and dexamethasone suppression test, was then introduced by a statistical weighting procedure. This did not essentially change the results of either the bivariate correlation matrix or the two-dimensional scaling analysis. A similar introduction of a pathological HPA axis, characterized by low variability and morning cortisol values, a poor lunch-induced cortisol response and a blunted dexamethasone suppression of cortisol, changed the results markedly. Now strong and consistent correlations were found not only within but also between different clusters of risk factors, which also congregated into one distinct cluster, again except for HDL cholesterol. CONCLUSIONS: These results disclose the prospect of an overriding function of a pathological HPA axis on other, established risk factors for CVD, type 2 diabetes and stroke. Its close association to HPA axis dysfunction may explain the previously reported powerful risk indication of abdominal obesity for the diseases mentioned. The HPA axis abnormality has been reported to be a characteristic consequence of frequently repeated or chronic environmental stress challenges.

Adipose Tissue↗
PubMed2001

Are changes in left ventricular volume as measured with the biplane Simpson's method predominantly related to changes in its area or long axis in the prognostic evaluation of remodelling following a myocardial infarction?

AIMS: Two-dimensional (2D) echocardiography has been widely applied to measure left ventricular volumes with the biplane Simpson's method in the assessment of left ventricular remodelling following an acute myocardial infarction. This volume formula is based upon tracings of endocardium and measurement of long axis on left ventricular images. In the present follow-up study of post-myocardial infarction patients we evaluated the prognostic impact of changes in left ventricular areas and geometry versus long axis to determine if only long-axis measurements may be used for prognostic purposes. METHODS AND RESULTS: Two-dimensional echocardiographic video recordings of the apical four-chamber and long-axis views were obtained in 756 patients 2--7 days and 3 months following an acute myocardial infarction. All videotapes were sent to a core laboratory and left ventricular volumes were measured with the biplane Simpson's method in end-diastole and end-systole. During the first 3 months 44 patients had suffered one of the following end-points and were excluded: cardiac death, recurrent myocardial infarction, heart failure or chronic arrhythmia. Over a period of 3--24 months 58 such end-points occurred. With the Cox proportional hazards model the increase in left ventricular systolic volume was the strongest predictor for such events (Chi-square 18.5, P<0.0001), followed by an increase in end-systolic area (Chi-square 17.0, P<0.0001) and end-systolic spherity index (Chi-square 8.74,P =0.003). The increase in end-systolic long axis had only a borderline predictive value (Chi-square 4.3, P=0.04). The change in long-axis shortening from end-diastole to end-systole had no significant predictive value at all. CONCLUSION: In the studied population changes in left ventricular area and geometry, but not in the long axis, were mainly related to cardiac morbidity. The proper assessment of changes in left ventricular dimensions should therefore be based upon tracings of the area and not on long axis measurements only.

Aged↗
PubMed2001

Occlusal plane discrepancies generated by transverse horizontal axis deviations.

STATEMENT OF PROBLEM: Any deviation from the patient's rotational axis of the mandible during closure and the arc of closure on an articulator has been reported to produce occlusal discrepancies. These discrepancies can affect diagnostic planning procedures and the occlusal relationships of restorations. PURPOSE: This study investigated the magnitude and types of occlusal errors produced by deviations between the patient's transverse horizontal axis and the axle on the articulator. MATERIAL AND METHODS: A simplified monoplane model was diagrammatically analyzed for deviations from the model's true transverse horizontal axis. Axis deviations of 5 mm were used in 8 different directions from the true transverse horizontal axis of the model. Changes in the orientation of the mandibular plane to the maxillary plane were illustrated diagrammatically. These changes were quantified by geometric and trigonometric assessments. RESULTS: All axis deviations produced mandibular plane orientation errors with angular plane malalignment to the maxillary plane on complete closure. These axis deviations also produced anterior-posterior shifting of the mandibular plane relative to the maxillary plane. CONCLUSION: Several different types of planar shifting and angular discrepancies were demonstrated from deviations away from the true transverse horizontal axis.

Computer Simulation↗
PubMed1990

Assessing the discomfort of the whole-body multi-axis vibration: laboratory and field experiments.

Laboratory and field experiments were conducted to determine the best procedure for predicting the discomfort caused by multi-axis vibration. In the laboratory experiment, 11 seated subjects compared single-axis vibration in one axis to single-axis vibration in another axis, and compared dual-axis vibration to single-axis vibration. In the field experiment, 22 lorry drivers rated the discomfort of 16 different rides. The results show that the best procedure for predicting the discomfort is to combine the vibration inputs by taking the square root of the sum of squares of the weighted r.m.s. values of the vibration in each axis.

Adult↗