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At least 811 records · Page 45Linked to original sources
PubMed1970

The multi-axis vibration environment and man.

Many investigations into the effects of vibration on man have been performed since Mallock's first study of London Underground vibrations in 1902. The vibration research has tended to be confined to the vertical (heave) axis, yet recent experiments have indicated that low frequency vibration along the lateral (sway) axis has a greater adverse effect upon comfort and performance. Measurements of the vibration environments in current forms of transport including motor vehicles, hovercraft and aircraft etc have shown that appreciable quantities of vibration along all three axes exist. Further vibration research should consider the effects of multi-axis vibrations upon man rather than limit tests to single axis vibration.

Journal Article↗
PubMed1992

Activity of the hypothalamic-pituitary-adrenal axis in mice selected for left- or right-handedness.

Asymmetry in brain modulation of the immune system has been previously described. In mice, paw preference has been shown to be associated with immune reactivity but the mechanisms involved in such an association are not yet known. The autonomic nervous system and the neuroendocrine system are considered as major candidates for neural influences on the immune system. In the present study, the activity of the hypothalamic-pituitary-adrenal (HPA) axis of adult female mice selected for paw preference (left-handers vs. right-handers) was assessed by measuring both adrenocorticotropic hormone (ACTH) and corticosterone plasma levels, as well as the in vitro responses of hypothalamus and adrenocortical cells to various hormone releasing stimuli. The results reported here showed no difference in the activity of the HPA axis between left- and right-handed mice, suggesting that this neuroendocrine axis is not implicated in the association between functional brain asymmetry and immune reactivity. However, our results do not exclude the possibility that the HPA axis could play a role in such an association under other circumstances, such as during development or stressful situations.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Axis II comorbidity of normal-weight bulimia.

The axis II comorbidity of 34 women with active bulimia, 18 women with remitted bulimia, and 20 women with a history of major depression was assessed blind to axis I diagnosis using the Diagnostic Interview for Personality Disorders (DIPD), a semistructured interview of demonstrated reliability. Fifty percent of the active bulimic subjects, 44% of the remitted bulimic subjects, and 35% of the depressed controls met DSM-III criteria for at least one axis II disorder. Despite the generally higher prevalence of axis II pathology in both bulimic groups than depressed controls, these between-group differences did not reach significance. The clinical implications of these findings are discussed.

Adolescent↗
PubMed1983

Axis determination in eggs of Xenopus laevis: a critical period before first cleavage, identified by the common effects of cold, pressure and ultraviolet irradiation.

Exposure of eggs of Xenopus laevis to a temperature of 1.0 degree C for 4 min or a pressure of 8000 psi for 5 min in a critical period before first cleavage results in embryos exhibiting a reduction and loss of structures of the body axis. The deficiencies occur in a craniocaudal progression which is dose dependent. In the extreme, totally axis-deficient embryos with radial symmetry are formed. Maximum sensitivity to cold and pressure occurs at 0.6 of the time from fertilization to first cleavage and extends from approximately 0.4 to 0.8, the period between pronuclear contact and mitosis, and the approximate period of gray crescent formation. The effects of cold and pressure resemble those previously reported for uv irradiation in that (1) the types of axis-deficient embryos produced are morphologically indistinguishable; (2) sensitivity in all cases ends before 0.8; (3) cold and uv effects, although not those of pressure, can be prevented by cotreatment with D2O; and (4) impaired eggs can be rescued by oblique orientation. We interpret these results as follows: during the 0.4-0.8 period the egg reorganizes its contents in a manner critical for subsequent development of the embryonic body axis. The reorganization process involves cytoskeletal elements, some of which are sensitive to cold, pressure, and uv, and protected by D2O. Rescue by oblique orientation can be understood as the result of a gravity-driven reorganization of the egg's contents, supplanting the normal mechanochemical process impaired in treated eggs.

Animals↗
PubMed1988

Determination of dorso-ventral axis in early embryos of the sea urchin, Hemicentrotus pulcherrimus.

To elucidate a relationship between early cleavage planes and dorso-ventral (DV)-axis of sea urchin embryos, a fluorescent dye, Lucifer Yellow CH, was iontophoretically introduced into one blastomere at the 2-cell stage, and the location of the progeny cells was determined in the half-labeled prism larvae by examining the embryos from the animal pole. The boundary plane which divides the embryonic tissue into the labeled and nonlabeled parts was (1) coincident with, (2) perpendicular to, or (3) obliquely crossing the larval plane of bilateral symmetry. The oblique boundaries took only two angles mutually symmetrical with regard to the DV-axis of embryos. Combining these labeling patterns, the tissue of prism larvae could be divided into 8 sectors around the animal-vegetal axis. When the 2-cell stage embryos with different diameters of sister blastomeres were labeled with the dye, one end of the boundary plane was again found at one of the 8 boundary points noticed in equally cleaved embryos, while the other was observed to fall in the middle of a sector. These results indicate that the DV-axis of the embryo is established according to the spatial arrangement of blastomeres during the 5-6th cleavage stages when blastomeres align in 8 rows in meridional direction. It was also suggested that intercellular communication takes part in the determination of the fate of individual founder blastomeres during the two subsequent cleavages, i.e., 7-8th cleavage stages.

Animals↗
PubMed1988

Polarization of ooplasmic segregation and dorsal-ventral axis determination in ascidian embryos.

During ooplasmic segregation in ascidians, the myoplasm moves from its original location in the periphery of the unfertilized egg to the vegetal pole of the zygote. The vegetal cap of myoplasm marks the future site of gastrulation and the dorsal side of the embryo. The purpose of this investigation was to determine the mechanism for polarizing the myoplasm during ooplasmic segregation. To test the possibility that the myoplasm moves toward the sperm and that the vegetal pole is the exclusive site of sperm entry, we examined fertilization in egg fragments of the ascidians Styela plicata and Ciona savignyi. Similar frequencies of fertilization were exhibited by various egg fragments, including animal and vegetal fragments or multiple fragments prepared from the same egg. These results indicate that sperm do not enter the egg exclusively at the vegetal pole. Experiments with egg fragments and constricted eggs, combined with chalk marking of the animal pole, demonstrated that after fertilization the myoplasm segregates parallel to the animal-vegetal axis, usually toward the vegetal end of the cell. Activation of primary oocytes with the Ca2+ ionophore A23187 caused the myoplasm to segregate independently of the animal-vegetal axis. This confirms previous experiments in which eggs aligned along a glass fiber coated with A23187 segregated their myoplasm toward the fiber (W.R. Jeffery, 1982, Science 216, 545-547) and suggests that the intrinsic cue for polarization is a release of sequestered Ca2+ at fertilization. Therefore, it appears that ooplasmic segregation and the dorsal-ventral axis are polarized by maternal factors distributed in a concentration gradient along the animal-vegetal axis of the ascidian egg.

Animals↗
PubMed1991

A gradient of gap junctional communication along the anterior-posterior axis of the developing chick limb bud.

A modification of the scrape-loading/dye transfer technique was used to study gap junctional communication along the anterior-posterior (A-P) axis of embryonic chick wing buds at an early stage of development (stage 20/21) when positional values along the A-P axis are being specified. Extensive intercellular transfer of the gap junction-permeable dye, lucifer yellow, from scrape-loaded mesenchymal cells to contiguous cells occurs in the posterior mesenchymal tissue of the wing bud adjacent to the zone of polarizing activity, which is thought to be the source of a diffusible morphogen that specifies A-P positional identity according to its local concentration. Considerably less transfer of lucifer yellow dye occurs in scrape-loaded mesenchymal tissue in the middle of the limb bud compared to posterior mesenchymal tissue, and little or no transfer of lucifer yellow is observed in the mesenchymal tissue in the anterior portion of the limb bud. No intercellular transfer of the gap junction-impermeable dye, rhodamine dextran, occurs in any region of the limb bud. These results indicate that there is a gradient of gap junctional communication along the A-P axis of the developing chick wing bud. This gradient of gap junctional communication along the A-P axis might generate a graded distribution of a relatively low molecular weight intracellular regulatory molecule involved in specifying A-P positional identities.

Animals↗
PubMed1992

Crystal and molecular structure of the A-DNA dodecamer d(CCGTACGTACGG). Choice of fragment helical axis.

The crystal structure of the dodecamer d(CCGTACGTACGG) has been determined at 2.5 A resolution. The crystals grow in the hexagonal space group P6(1)22, a = b = 46.2 A, c = 71.5 A with one strand as the asymmetric unit. Diffraction data were collected by the oscillation film method yielding 1664 unique reflections with an Rmerge of 0.04. The structure was solved by real-space rotational translational searches with idealized helical models of A, B and Z-DNA. The best agreement was given by an A-DNA model with its dyad axis along the diagonal crystallographic dyad axis, with an R-factor 0.43 and correlation coefficient of 0.59 for data between 10 and 5 A. Iterative map fitting and restrained least-squares refinement and addition of 40 solvent molecules brought the R-factor to 0.15 and the correlation coefficient to 0.97 for all data between 8.0 and 2.5 A. The stereochemistry of the atomic model is good, with a root-mean-square deviation in bond distances of 0.006 A. This is the first example of an A-DNA containing a full helical turn. The dodecamer displays a novel packing motif. In addition to the characteristic contacts between the terminal base-pairs and the minor grooves of symmetry-related molecules, there are also minor groove to minor groove interactions not previously observed. The packing leaves an approximately 25 A diameter solvent channel around the origin, along the c-axis. The presence of a prominent 3.4 A meridional reflection and other diffuse features in the diffraction pattern provided evidence for the presence of disordered B-DNA along the c-axis, which can be accommodated in these solvent channels. The molecular conformation of the dodecamer also displays novel features. The dyad-related halves of the molecule are bent at an angle of 20 degrees, and the helical parameters are affected by this bend. Unlike the shorter A-DNA octamers, the dimensions of the major groove can be directly measured. Novel correlations between local helical parameters and global conformational features are presented. Most of the solvent molecules are associated with the major groove and the sugar-phosphate backbone.

Base Sequence↗
PubMed1988

Application of a geometric principle for locating the mandibular hinge axis through the use of a double recording stylus.

The hinge axis of the mandible has been determined by using double recording styli at a distance of 2 to 4 inches from the estimated axis area. Visible arcs in pairs on a plain recording surface become the basis for a geometric construction by which the true axis of rotation can be identified. The theoretical basis for this method of axis location is sound and practical as applied and the clinical results indicate that the procedure is accurate.

Dental Equipment↗
PubMed1989

The hinge axis: evaluation of current arbitrary determination methods and a proposal for a new recording method.

A proposed arbitrary method of recording the hinge axis based on the correlation between the profile width of the face and the kinematic axis was compared with three commonly used arbitrary methods. The investigation was carried out on 51 individuals. The kinematic point was recorded by the use of a kinematic locator. The different points of emerging axes were photographed at a fixed distance by using a magnification photoapparatus. The proposed method showed a regular distribution around the kinematic axis. Furthermore, this method clearly illustrated that its highest concentration was in the posteriosuperior quarter around the true axis. The proposed technique was found to be more accurate than the other techniques.

Adult↗
PubMed1992

Evaluation of variables associated with the transverse horizontal axis.

The effect of transverse horizontal axis deviations on the vertical and horizontal orientation of maxillary and mandibular members was investigated on a laboratory articulator model. Twelve axis deviations (+30, +25, +20, +15, +10, +5, -5, -10, -15, -20, -25, and -30 mm groups) within a 55 mm dimension model were evaluated. Three trials at each transverse horizontal axis deviation demonstrated significant changes in maxillomandibular orientation after mounting the mandibular member with a standardized intermember mounting record. A linear regression analysis produced an equation for predictive interpolation of anterior-posterior shift as a result of axis deviations from +30 to -30 mm.

Analysis of Variance↗
PubMedDate not supplied

Hypothalamic-pituitary-adrenal axis activity in panic disorder: effects of alprazolam on 24 h secretion of adrenocorticotropin and cortisol.

Pre-clinical and some clinical evidence suggests that central overdrive within the hypothalamic-pituitary-adrenal (HPA) axis may play a role in panic disorder, and that the anti-panic efficacy of alprazolam may involve its ability to inhibit this drive. Detailed examination of 24 h secretion of adrenocorticotropin (ACTH) and cortisol in 20 panic patients had revealed subtle HPA axis abnormalities prior to treatment. In order to determine whether these abnormalities resolve with alprazolam therapy, these patients were re-studied over a full circadian cycle after 12 weeks on alprazolam. Alprazolam produced substantial improvement in clinical status which was accompanied by nearly full resolution of pre-treatment hypercortisolemia. The impact of treatment on ACTH was more complex and influenced by symptom severity. The results are consistent with the hypotheses that HPA axis regulation is subtly disturbed in panic disorder and that impact on the HPA axis may play a role in alprazolam's mechanism of efficacy.

Adrenocorticotropic Hormone↗
PubMed1994

Axis-based neglect of visual shapes.

A new test of "object-centered" visual neglect uses equilateral triangles, with ambiguous principal axes that can be manipulated by context. Three left neglect patients detected gaps in such triangles. The location of the gap relative to the biased principal axis was varied, while maintaining the same egocentric locus. More gaps were missed on the left of the axis. This supports Driver and Halligan's (Cognit. Neuropsychol. 8, 475-496, 1991) claim that neglect can apply to the contralesional side of a shape's principal axis, while avoiding serious flaws in their method. The relation between axis-based neglect and other cases of object-centred neglect is discussed.

Attention↗
PubMed1992

Hypothalamic-pituitary-adrenal axis responsiveness to insulin-induced hypoglycaemia is modified by trypanosome infection in Boran (Bos indicus) cattle.

Ten Boran (Bos indicus) cattle were used to study the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis during trypanosome infection. Five cattle were infected with Trypanosoma congolense IL 1180 by tsetse challenge and five cattle served as controls. All infected animals developed acute trypanosomiasis. Insulin-induced hypoglycaemia (50 per cent of pre-insulin glucose concentration) was used as a stress factor. Acute hypoglycaemia was observed in three infected and three control animals after insulin challenge. Two animals from each group either did not respond or responded slowly. Hypoglycaemia in infected animals completely failed to induce an HPA axis response, while in control animals an HPA axis response was indicated by a significant increase in plasma adrenocorticotrophic hormone (ACTH) and cortisol concentrations (P less than 0.01). The results show that trypanosomiasis in Boran cattle can cause a decrease in the stress responsiveness of the HPA axis as indicated by a blunted ACTH/cortisol response to insulin-induced hypoglycaemia.

Adrenocorticotropic Hormone↗
PubMed1983

Renal axis deviation in the elderly.

Renal axis variations occurring in age-grouped populations are described. We discovered a significant difference in renal axis deviations between young and old population groups with a tendency for a more vertical axis as age increases. Possible reasons for these changes are proposed. We suggest that not all renal axis deviations in the elderly population require extensive evaluation.

Adolescent↗
PubMed1996

Algorithms for finding the axis of a helix: fast rotational and parametric least-squares methods.

Several methods for finding the axis of a helix are presented and compared. The most accurate determines the helix axis as the axis of rotation necessary to map point i to point i + 1 of the helix. The fastest method calculates the helix axis as the best-fit line through the coordinates by a three-dimensional parametric linear least-squares algorithm, taking advantage of the sequential nature of the data.

Algorithms↗
PubMed1989

Use of DSM-III Axis IV in clinical practice: rating the severity of psychosocial stressors.

This study investigates the usefulness of DSM-III Axis IV ratings of Severity of Psychosocial Stressors. Multiaxial evaluations were made on a diagnostically heterogeneous group of 362 psychiatric patients. Severity ratings on Axis IV were compared to a more extensive system for measuring life event stress, embedded in the Psychiatric Epidemiology Research Interview (PERI). The results indicate that Axis IV ratings are consistent with meaningful diagnostic and demographic group differences, and correlate significantly with PERI ratings of normative change or disruption associated with rated events. The Axis IV guideline that the stressor reflect the summed effect of all psychosocial stressors listed, however, appeared to be too complex to be incorporated into routine clinical practice, even by relatively well-trained evaluators with expert supervision.

Adaptation, Psychological↗
PubMed1981

The relationship of marked left axis deviation to the risk of ischemic heart disease.

The purpose of this study was to examine the value of marked left axis deviation in men without apparent heart disease in the assessment of ischemic heart disease risk. In the Manitoba Study, a cohort of 3983 men who were predominantly between 25 to 34 yr of age at entry in 1948, 247 cases of marked left axis deviation (mean frontal plane QRS vector of -45 degrees to -90 degrees) were identified at a mean age of 46.1 +/- 0.7 (+/- 1 SEM) yr with a mean follow-up of 12.1 +/- 0.6 yr. The results were that the development of left axis deviation in men 40 to 59 yr of age, independent of blood pressure is a significant predictor of ischemic heart disease events that are usually manifest 5 to 10 yr after the onset of this electrocardiographic abnormality. Subsets of QRS variables examined to identify cases with different degrees of ischemic heart disease risk revealed that neither Q waves in leads I or aVL, or QRS duration or actual frontal plane QRS vector identified groups with different ischemic heart disease risk. However, subsets of age (less than 40 and 60 yr or greater) perhaps reflecting different etiologies of marked left axis deviation and previous electrocardiographic findings (S1S2S3 pattern) identify a low risk group.

Adolescent↗