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At least 397 records · Page 22Linked to original sources
PubMed1999

Evaluation of metastatic celiac axis lymph nodes in patients with esophageal carcinoma: accuracy of EUS.

BACKGROUND: Endosonography (EUS) is the most accurate modality for assessing depth of tumor invasion and local lymph node metastasis. However, its accuracy in the identification of metastatic (celiac axis) lymph nodes is less well defined. Our objective in this study was to determine the accuracy of Eus in detecting celiac axis lymph node metastasis in patients with esophageal carcinoma. METHODS: Two hundred fourteen patients with esophageal carcinoma underwent preoperative EUS. Of these, 145 underwent attempted surgical resection and staging, and 4 underwent EUS-guided fine-needle aspiration of mediastinal and celiac lymph nodes. Local (mediastinal) and distant (celiac axis) lymph nodes were assessed for malignancy on the basis of four criteria (larger than 1 cm, round, homogeneous echo pattern, sharp borders). Accuracy of EUS was determined by means of correlating histopathologic findings for the resected lymph nodes or results of EUS-guided fine-needle aspiration cytologic examination. RESULTS: Surgical exploration (n = 145) and fine-needle aspiration cytologic examination (n = 4) revealed metastatic celiac axis lymph nodes in 23 and metastatic mediastinal (local) lymph nodes in 93 of 149 patients with esophageal carcinoma. According to defined criteria for malignant lymph nodes, there were 19 true-positive and 4 falsenegative results. Sensitivity for the diagnosis of celiac lymph node metastasis with EUS was 83% with a 98% specificity. For the diagnosis of mediastinal lymph node metastasis, sensitivity was 79% and specificity was 63%. All patients with malignant celiac axis lymph nodes had local T3 (tumor breaching adventitia) or T4 (tumor invading adjacent organs) disease. CONCLUSION: EUS is an excellent modality in the evaluation of metastatic celiac axis lymph nodes in patients with esophageal carcinoma. These findings should be used in selecting options for treatment. Sensitivity for detecting malignancy is consistent with that of prior studies, and local and regional lymph nodes and specificity is significantly higher.

Aged↗
PubMed2003

The prototypic antidepressant drug, imipramine, but not Hypericum perforatum (St. John's Wort), reduces HPA-axis function in the rat.

Dysregulation in corticotropin-releasing hormone (CRH) secretion in the hypothalamus-pituitary-adrenal (HPA) axis may be involved in the etiology of major depressive disorder (MDD). Chronic therapy with standard antidepressant drugs, such as imipramine, can downregulate HPA axis function, indicating that the HPA axis may be an important target for antidepressant action. We tested several doses of a standardized commercial preparation of Hypericum perforatum plant extract (popularly known as St. John's Wort), a medicinal herb used for treating mild depressive symptoms, to determine whether it also modulated HPA axis function. Chronic imipramine treatment (daily injections for 8 weeks) of male Sprague-Dawley rats significantly downregulated circulating plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone compared to animals treated with saline. However, chronic St. John's Wort treatment (daily gavage for 8 weeks) had no effect on plasma ACTH or corticosterone, even at the highest doses tested. Our results confirm previous findings that imipramine may have significant peripheral HPA axis-mediated effects. However, our data does not support any role for H. perforatum in modulation of HPA axis function, suggesting that alternative pathways may be involved in mediating its antidepressant effects.

Adrenal Glands↗
PubMed2004

Flavonoids of St. John's Wort reduce HPA axis function in the rat.

A common biological alteration in patients with major depression is the activation of the hypothalamic-pituitary-adrenal (HPA) axis, manifested as hypersecretion of adrenocorticotropic hormone (ACTH) and cortisol. The hyperactivity of the HPA axis in depressed patients can be corrected during clinically effective therapy with standard antidepressant drugs such as imipramine, indicating that the HPA axis may be an important target for antidepressant action. We previously showed that a methanolic extract of St. John's Wort (SJW) and hypericin, one of its active constituents, both have delayed effects on the expression of genes that are involved in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis , whereas the phloroglucinol derivative hyperforin was inactive in the same model . Since flavonoids of SJW are also discussed as active constituents it was of interest to determine whether these compounds can modulate HPA axis function. Imipramine (15 mg/kg), hypericin (0.2 mg/kg), hyperoside (0.6 mg/kg), isoquercitrin (0.6 mg/kg) and miquelianin (0.6 mg/kg) given daily by gavage for two weeks significantly down-regulated circulating plasma levels of ACTH and corticosterone by 40 - 70 %. However, none of the compounds tested had an effect on plasma ACTH and corticosterone levels after chronic treatment (daily gavage for 8 weeks). Our data suggest that besides hypericin, flavonoids of SJW play an important role in the modulation of HPA axis function. Furthermore, the results support the hypothesis that flavonoids are involved in the antidepressant effects of SJW.

Administration, Oral↗
PubMed2001

Effects of intranasal corticosteroids on the hypothalamic-pituitary-adrenal axis in children.

In adults, morning plasma cortisol levels are twice that of late afternoon and evening values. In children, a delay in the time of onset in peak cortisol levels has been observed in those treated with inhaled corticosteroids. Consequently, the single morning cortisol level has a low sensitivity for detecting adrenal insufficiency in children. It is not clear which test is best for detection of clinically relevant hypothalamic-pituitary-adrenal (HPA) axis suppression in children; 24-hour plasma cortisol is a good test because it measures biologically active, free cortisol levels for the entire day and is noninvasive. For research purposes, the 24-hour integrated concentration plasma cortisol test is preferred. Studies that have looked at HPA axis suppression with intranasal corticosteroids indicate that overall, intranasal corticosteroids have minimal effect on the HPA axis. A review of the literature reveals one study in which there was a decreased output of urinary cortisol during treatment with either budesonide or fluticasone propionate in adults. Other studies of fluticasone propionate or budesonide have shown no effect on the HPA axis in children. Beclomethasone dipropionate was shown to affect urinary cortisol output in one study of healthy volunteers. However, in a long-term study in children, no effect on the HPA axis was found. Mometasone furoate has been extensively studied in more than 20 trials of adults and children. No effects on the HPA axis were detected in either children or adults. It is unlikely that children are more sensitive to corticosteroids than are adults. There seems to be little point in performing routine monitoring of adrenal function in children who are treated with intranasal corticosteroid treatment.

Administration, Intranasal↗
PubMed2002

A role for biliverdin IXalpha in dorsal axis development of Xenopus laevis embryos.

The determinants of Xenopus laevis embryos that act before their first cell division are mandatory for the formation of mRNas required to establish the dorsal axis. Although their chemical identities are unknown, a number of their properties have long been recognized. One of the determinants is present in the cytoplasm and is sensitive to UV light. Thus, exposing stage 1 embryos to either standard 254-nm or, as shown here, to 366-nm UV light during the 0.3-0.4 time fraction of their first cycle inactivates the cytoplasmic determinant. As a consequence, both types of irradiated embryos fail to express dorsal markers, e.g., goosecoid and chordin, without affecting formation of ventral markers, e.g., Vent-1. The developmental outcome is dorsal axis-deficient morphology. We report here that biliverdin IXalpha, a normal constituent of cytoplasmic yolk platelets, is photo-transformed by irradiation with either 254- or 366-nm UV light and that the transformation triggers the dorsal axis deficiency. When the 254- or 366-nm UV-irradiated embryos, fated to dorsal axis deficiency, are incubated solely with microM amounts of biliverdin, they recover and form the axis. In contrast, incubation with either in vitro photo-transformed biliverdin or biliverdin IXalpha dimethyl ester does not induce recovery. The results define an approach to produce dorsal axis-deficient embryos by photo-transforming its biliverdin by irradiation with 366-nm UV light and identify an unsuspected role for biliverdin IXalpha in X. laevis embryogenesis.

Animals↗
PubMed1998

beta-Catenin is essential for patterning the maternally specified animal-vegetal axis in the sea urchin embryo.

In sea urchin embryos, the animal-vegetal axis is specified during oogenesis. After fertilization, this axis is patterned to produce five distinct territories by the 60-cell stage. Territorial specification is thought to occur by a signal transduction cascade that is initiated by the large micromeres located at the vegetal pole. The molecular mechanisms that mediate the specification events along the animal-vegetal axis in sea urchin embryos are largely unknown. Nuclear beta-catenin is seen in vegetal cells of the early embryo, suggesting that this protein plays a role in specifying vegetal cell fates. Here, we test this hypothesis and show that beta-catenin is necessary for vegetal plate specification and is also sufficient for endoderm formation. In addition, we show that beta-catenin has pronounced effects on animal blastomeres and is critical for specification of aboral ectoderm and for ectoderm patterning, presumably via a noncell-autonomous mechanism. These results support a model in which a Wnt-like signal released by vegetal cells patterns the early embryo along the animal-vegetal axis. Our results also reveal similarities between the sea urchin animal-vegetal axis and the vertebrate dorsal-ventral axis, suggesting that these axes share a common evolutionary origin.

Animals↗
PubMed2000

Contrast thresholds and fixation disparity during 5-Hz sinusoidal single- and dual-axis (vertical and lateral) whole-body vibration.

The present study assumed that whole-body vibration, transmitted through the seat, impairs spatial retinal resolution and oculomotor alignment parallel to the vibration axis. More specifically, that the decrement increases gradually from single-axis lateral via single-axis vertical and dual-axis linear to dual-axis circular motion. Twenty participants (19-26 years of age) with good vision volunteered for the experiment where in three sessions one of the following three conditions, contrast threshold, nonius bias or fixation disparity, for vertically and horizontally oriented test patterns was determined during five experimental conditions. The latter comprised a control (a(z) = a(y) = 0) and four conditions where 5-Hz sinusoidal motion of 1.2 ms(-2) rms were applied separately, either in the vertical or in the lateral direction, or simultaneously in both directions, once without and once with a phase shift of 90 degrees, thus causing dual-axis linear or circular motion. Contrast thresholds for horizontal gratings and the variability of vertical fixation disparity increased significantly whenever the participants were exposed to vertical motion (alone or combined with lateral motion). These effects may result in an increased difficulty in properly recognizing characters and graphic patterns containing horizontal lines and in the development of asthenopic complaints.

Adult↗
PubMed1997

Effects of endothelin-1 on the rat pituitary-adrenocortical axis under basal and stressful conditions.

Endothelins (ETs) and their receptor subtypes A and B (ETA and ETB) are expressed in the various components of the mammalian hypothalamo-pituitary-adrenal (HPA) axis, but their involvement in the functional regulation of HPA is controversial. To gain insight into this topic, we have investigated the effects of ET-1 and/or the specific antagonists of ETA and ETB receptors (BQ-123 and BQ-788, respectively) on the plasma concentrations of ACTH, corticosterone and aldosterone of non-stressed (control) and ether- or cold-stressed rats. The study of the effects of the administration of the two ET-receptor antagonists alone could provide informations about the possible action of endogenous ETs on the HPA axis. Exogenous ET-1 increased ACTH, corticosterone and aldosterone blood levels in control rats, as well as evoked a sizable enhancement of the HPA axis response to ether stress and a marked depression of the response to cold stress. BQ-123 and BQ-788 did not prevent the stimulatory effect of exogenous ET-1 in control rats, but when administered alone, raised the plasma concentrations of ACTH, corticosterone and aldosterone. Both ET-receptor antagonists magnified the HPA axis response to ether and cold stresses, but their effect was not counteracted by exogenous ET-1. Although very difficult to interpret, our present findings allow us to conclude that endogenous ETs play a role in the maintenance of the basal activity of rat HPA axis acting through ETA and ETB receptor subtypes, which are partially insensitive to BQ-123 and BQ-788. Conversely, the involvement of ETs in the modulation of the HPA axis responses to various stresses is very doubtful.

Adrenocorticotropic Hormone↗
PubMed1999

The relationship of Axis II personality disorders to other known predictors of addiction treatment outcome.

This study evaluated the prevalence of Axis II disorders in substance abuse patients and the relationship between Axis II psychopathology and two other known predictors of adverse addiction treatment outcomes, i.e., Axis I psychiatric comorbidity and illegal drug use, specifically cocaine. 232 patients with cocaine and/or alcohol dependence were admitted to either inpatient or outpatient addiction recovery programs at Carrier Foundation, a nonprofit, private-pay hospital in New Jersey. Axis II disorders were more prevalent in cocaine than alcohol dependence and in patients with Axis I psychiatric comorbidity. When all three predictors were evaluated in one prediction model, the combination of Axis I and II psychopathology was the best predictor of a return to substance use at one year post-treatment, compared to the three factors alone. These findings highlighted the importance of the interrelationship of the relative prognostic value of three known predictors of addiction treatment.

Adolescent↗
PubMed2006

Stress, the hippocampus and the hypothalamic-pituitary-adrenal axis: implications for the development of psychotic disorders.

OBJECTIVE: The experience of stress is commonly implicated in models of the onset of psychotic disorders. However, prospective studies investigating associations between biological markers of stress and the emergence of psychotic disorders are limited and inconclusive. One biological system proposed as the link between the psychological experience of stress and the development of psychosis is the Hypothalamic-Pituitary-Adrenal (HPA) axis. This paper summarizes and discusses evidence supporting a role for HPA-axis dysfunction in the early phase of schizophrenia and related disorders. METHOD: A selective review of psychiatric and psychological research on stress, coping, HPA-axis, the hippocampus and psychotic disorders was performed, with a particular focus on the relationship between HPA-axis dysfunction and the onset of psychotic disorders. RESULTS: Individual strands of past research have suggested that the HPA-axis is dysfunctional in at least some individuals with established psychotic disorders; that the hippocampus is an area of the brain that appears to be implicated in the onset and maintenance of psychotic disorders; and that an increase in the experience of stress precedes the onset of a psychotic episode in some individuals. Models of the onset and maintenance of psychotic disorders that link these individual strands of research and strategies for examining these models are proposed in this paper. CONCLUSIONS: The current literature provides some evidence that the onset of psychotic disorders may be associated with a higher rate of stress and changes to the hippocampus. It is suggested that future research should investigate whether a relationship exists between psychological stress, HPA-axis functioning and the hippocampus in the onset of these disorders. Longitudinal assessment of these factors in young people at 'ultra' high risk of psychosis and first-episode psychosis cohorts may enhance understanding of the possible interaction between them in the early phases of illness.

Animals↗
PubMed2002

The role of gibberellins in embryo axis development.

The role of gibberellins (GAs) during early embryo development was examined using microspore-derived embryos (MDEs) of Brassica napus. At the globular stage of development, 10 d after initial culture (DAC) when endogenous GA(1) levels are increasing rapidly, a triazole, uniconazole, was used at 1, 33 and 100 microM to inhibit GA biosynthesis. Within this dose range there was no apparent effect of the inhibitor on embryo growth through to the early torpedo stage. However, by 25 DAC uniconazole-treated MDEs showed significantly reduced (50%) axis elongation. Addition of GA(1) at 33 microM on 14 DAC to embryos pretreated with 1 microM uniconazole on 10 DAC prevented this reduction in axis length, giving axis elongation equivalent to untreated MDEs. Application of GA(1) alone, however, did not significantly increase axis elongation. The reduced axis growth seen with uniconazole treatment was due to reduced cell elongation, but not cell number, and the co-applied GA(1) thus prevented the uniconazole-induced reduction in cell length. The elongating axis of MDEs may thus be a useful tool for examining the role of GAs in cell elongation.

Brassica napus↗
PubMed1997

The apical long-axis rather than the two-chamber view should be used in combination with the four-chamber view for accurate assessment of left ventricular volumes and function.

BACKGROUND: Most biplane methods for the echocardiographic calculation of left ventricular volumes assume orthogonality between paired views from the apical window. Our aim was to study the accuracy of biplane left ventricular volume calculations when either the apical two-chamber or long-axis views are combined with the four-chamber view. The left ventricular volumes calculated from three-dimensional echocardiographic data sets were used as a reference. Twenty-seven patients underwent precordial three-dimensional echocardiography using rotational acquisition of planes at 2-degree intervals, with ECG and respiratory gating. End-diastolic and end-systolic left ventricular volumes and ejection fraction on three-dimensional echocardiography were calculated by (1) Simpson's methods (3DS) at 3 mm short-axis slice thickness (reference method) and by (2) biplane ellipse from paired views using either apical four- and two-chamber views (BE-A) or apical four- and long-axis views (BE-B). Observer variabilities were studied by the standard error of the estimate % (SEE) in 19 patients for all methods. RESULTS: The spatial angles (mean +/- SD) between the apical two-chamber, long-axis and four-chamber views were 63.3 degrees +/- 19.7 and 99.1 degrees +/- 25.6, respectively. The mean +/- SD of end-diastolic and end-systolic left ventricular volumes (ml) and ejection fraction (%) by 3DS were 142.2 +/- 60.9, 91.8 +/- 59.6 and 39.6 +/- 17.5, while that by BE-A were 126.7 +/- 60.4, 84.0 +/- 57.9 and 39 +/- 17 and by BE-B were 134.3 +/- 62.4, 88.6 +/- 59.7 and 39.1 +/- 16.7, respectively. BE-B intra-observer (8.4, 6.7 and 3.5) and inter-observer (9.8, 11.5 and 5.4) SEE for end-diastolic and end-systolic left ventricular volumes (ml) and ejection fraction (%), respectively, were smaller than that for BE-A (10.8, 8.8 and 4.1 and 11.4, 14.7 and 6.1, respectively). There was excellent correlation between 3DS and BE-A (r = 0.99, 0.98 and 0.98) and BE-B (0.98, 0.98 and 0.98) for calculating end-diastolic and end-systolic left ventricular volume and ejection fractions, respectively. There were no significant differences between BE-A and BE-B with 3DS for end-diastolic and end-systolic left ventricular volume and ejection fraction calculations (P = 0.2, 0.3 and 0.4 and P = 0.5, 0.5 and 0.4, respectively). There were closer limits of agreement (mean +/- 2 SD) between 3DS and BE-B 7.9 +/- 18.8, 3.2 +/- 14.2 and 0.8 +/- 5.8 than that between 3DS and BE-A 15.5 +/- 19.6, 7.8 +/- 16.2 and 1.1 +/- 7.4 for calculating end-diastolic and end-systolic left ventricular volume and ejection fractions, respectively. CONCLUSION: Both apical two-chamber and apical long-axis views are not orthogonal to the apical four-chamber view. Observer variabilities of BE-B were smaller than that for BE-A. BE-A and BE-B have excellent correlation and non-significant differences with 3DS for left ventricular volume and ejection fraction calculations. There were closer limits of agreement between BE-B with 3DS for left ventricular volume and ejection fraction calculations than that between BE-A and 3DS. Therefore, we recommend the use of the apical long-axis rather than the two-chamber view in combination with the four-chamber view for accurate biplane left ventricular volume and ejection fraction calculations.

Adult↗
PubMed2005

Relationship between hypothalamic-pituitary-adrenal axis responsiveness and age, sexual maturity status, and sex in Japanese quail selected for long or short duration of tonic immobility.

The influences of age (4 to 12 wk), sexual maturity status, and sex on hypothalamic-pituitary-adrenal (HPA) axis responsiveness were investigated by measuring changes in peripheral basal levels of corticosterone (B) and responses to 10 min of physical restraint in a crush cage or injection of 1-24 adrenocorticotropic hormone (ACTH) in 2 genotypes of Japanese quail divergently selected for long (LTI) or short (STI) duration of tonic immobility (TI). Although gonad development was more advanced in male STI quail, most birds were still immature at 4 wk of age, but sexual maturity was fully acquired by 6 wk of age in both sexes and genotypes. This change was associated with increases in basal B levels in both genotypes and sexes. On the other hand, HPA axis responsiveness to restraint and adrenal responsiveness to 1-24 ACTH injection remained stable in STI quail, whatever the age. Conversely, significant responses to restraint compared with basal B levels were only observed at 4 and 6 wk of age, and adrenal responsiveness increased with age in LTI quail. Moreover, higher B levels were measured in response to restraint in STI than in LTI quail, whereas similar adrenal responses were measured at 9 and 12 wk of age. We concluded that an increase in basal B levels is associated with the stage of sexual maturity acquired, but it did not affect HPA axis responsiveness or adrenal B response capacity. On the other hand, age affected HPA axis responsiveness and adrenal B response capacity in LTI quail of both sexes but not in STI quail. It is hypothesized that functional HPA axis maturity occurs after 6 wk of age in the LTI genotype, but it is reached by 4 wk of age in the STI genotype. In conclusion, the divergent selection program for TI conducted on quail resulted in changes in HPA responsiveness that probably resulted from differences in development rate and function of the adrenal glands or other upstream structures of the HPA axis.

Aging↗
PubMed2003

Deviation of the blastocyst axis from the first cleavage plane does not affect the quality of mouse postimplantation development.

Several researchers have suggested recently that the embryonic-abembryonic (Em-Ab) axis of the mouse blastocyst is orthogonal to the first cleavage plane of the two-cell embryo. To determine the universality of this relationship, we used embryos of two different genotypes, F1 (C57BL/6 x DBA/2) and CD-1. The position of the first cleavage plane in the early blastocyst was determined by labeling a blastomere with the fluorescent lineage tracer DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) at the two-cell stage. Approximately one quarter of the blastocysts from both genotypes possessed an Em-Ab axis that respected the orthogonal relationship with the first cleavage plane. However, the remainder of the blastocysts deviated from the orthogonal relationship. This result indicates that the orthogonal orientation of the Em-Ab axis to the first cleavage plane is not a universal phenomenon. We also tested whether the angular relationship between the Em-Ab axis and first cleavage plane influences postimplantation embryo development. We sorted the blastocysts that had the Em-Ab axis orthogonal to the first cleavage plane from the ones that did not. These two types of blastocysts were transferred separately into surrogates, and fetal development was examined in late gestation. The results revealed that both types of blastocysts produced normal fetuses at a similar frequency. Thus, the relationship of the blastocyst axis to the first cleavage plane does not significantly influence later development.

Animals↗
PubMed1993

Hepatic ischemia, caused by celiac axis compression, complicating pancreaticoduodenectomy.

OBJECTIVE: In the course of pancreaticoduodenectomy, profound hepatic ischemia developed in two patients (one with ampullary carcinoma, the other with chronic pancreatitis). This article addresses the diagnosis and correction of the celiac axis compression responsible in this complication. SUMMARY BACKGROUND DATA: Since hepatic ischemia appeared immediately after division of the gastroduodenal--pancreaticoduodenal arcade, which provides mesenteric to celiac collateral circulation, celiac axis narrowing or occlusion was suspected. Previous reports have indicated that celiac axis disease may be present in about 10% of such patients. METHODS: Doppler flow studies, and in the second patient, intraoperative angiography were performed. The celiac axis was exposed and mobilized in both. RESULTS: Initially, no flow could be detected in the celiac axis. Dense fibrous tissue was found encasing it. Division of the entrapping tissue restored flow to the upper abdominal viscera. CONCLUSIONS: The anatomic deformation of the celiac axis predisposing to this complication is detectable on the lateral projection of a preoperative celiac angiogram. If, however, an angiogram has not been done, an initial test occlusion of the gastroduodenal artery before its division permits anticipation of the complication, correction of the celiac impingement, and hence, avoidance of hepatic ischemia.

Aged↗
PubMed1980

Interstitial hyperosmolarity may cause axis cylinder shrinkage in streptozotocin diabetic nerve.

Maximal conduction velocity values of nerves of diabetic rats 20 weeks after streptozotocin intoxication were found to be intermediate between those of onset-control and those of end-control groups. The abnormality of conduction velocity of the streptozotocin group might therefore be attributed to a failure of maturation. Detailed electron microscopic morphometry of myelinated fibers (MFs) indicates that more than lack of maturation is involved. Whereas the number of lamellae and the perimeter of axis cylinders of myelinated fibers of the three study groups suggested that growth continues, cross-sectional area of the axis cylinders of the streptozotocin group was smaller than those of either control group. Scored evaluation of fiber shape and the measured index of circularity, which related perimeter and transverse axis cylinder area, also indicated that a selective shrinkage of axis cylinders had occurred. This selective alteration in size and shape of axis cylinders is identical to that described after hyperosmolar fixation. Compared with that of controls, the serum of streptozotocin rats is hyperosmolar. It would seem reasonable to attribute the axis cylinder changes to shrinkage. Whether an additional maturational effect is operative as well cannot be resolved from our data.

Animals↗
PubMed1991

Use of the Humphrey Lens Analyzer for off-axis measurements of spectacle lenses.

Automated focimeters can be used to make quick, precise measurements of off-axis power and prismatic effects corresponding to an eye rotating behind a spectacle lens. An automated focimeter, the Humphrey Lens Analyzer, was assessed in this regard. The Humphrey Lens Analyzer can be used to give a valid measure of off-axis power of lenses with low power, but not of lenses with moderate to higher power (greater than 3 D). For 3 D spherical lenses discrepancies of the order of 0.1 D occur at 30 degrees rotation, and 6 D spheres give discrepancies of 0.5 D at the same rotation. Small discrepancies were found for measurements of prism. The Humphrey Lens Analyzer was also used in a mode where the lens being tested is rotated about the center of curvature of its back surface. This is the mode often used to assess aberrations and prism of progressive-addition lenses. In this mode, the instrument provides reasonable accuracy in estimating off-axis power corresponding to eye rotation for lenses with low power, but not for lenses with moderate to higher power (greater than 3 D). However, it provides accurate values of the variation in off-axis surface power for low powered lenses with aspheric front surfaces. There were considerable systematic errors associated with the measurement of prism. A simple raytracing method was developed to predict the results of measurements with the Humphrey Lens Analyzer. Predictions of off-axis power were good when lenses were rotated about a position corresponding to the center-of-rotation of an eye, but were poorer when lenses were rotated about the center of curvature of their back surfaces. Predictions of primatic efforts were good in both situations. A method by which the Humphrey Lens Analyzer should provide an accurate measurement of off-axis powers corresponding to eye rotation behind a spectacle lens is described, but has not been tested.

Eyeglasses↗
PubMed1992

Instantaneous axis of rotation as a function of the three columns of the spine.

A knowledge of the rotatory motion of the vertebral bodies is needed to understand the normal biomechanical behavior of the spine. The aims of this investigation were 1) to define the instantaneous axis of rotation of the lumbar spine in rotation; and 2) to study the effect of the loss of the anulus, facet joints, and ligamentous structures on the location of the instantaneous axis of rotation. The instantaneous axis of rotation was found in 10 human cadaver thoracolumbar spines by the method of Reuleaux from superimposed serial photographs. Long-segment specimens were tested to minimize the effect of the imposed axis of the testing device. The instantaneous axis of rotation was consistently posterior to the anulus in the intact spine. With isolated destruction of the columns of the spine, the instantaneous axis of rotation migrated to the remaining intact structures. Anterior releases enhance derotation by removing the primary rotatory stabilizer. Ultimate control of a rotatory deformity or instability lies in the recognition that the anterior structures have a mechanical advantage in resisting torsion.

Biomechanical Phenomena↗