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At least 523 records · Page 29Linked to original sources
PubMed1995

Effects of HSV-1, a neurotropic virus, on the hypothalamic-pituitary-adrenocortical axis in rats.

It is well established that the hypothalamic-pituitary-adrenocortical (HPA) axis is activated during systemic viral diseases. In this study we examined the effects of a neurotropic virus, herpes simplex virus type 1 (HSV-1), on the HPA axis in male rats. Following corneal inoculation with HSV-1, the virus invaded the nervous system and replicated in the brainstem without clinical signs of disease. During this asymptomatic brainstem infection with HSV-1, significant changes were found in the function of the HPA axis: On days 3, 7 and 14 post-infection (p.i.) basal ACTH and corticosterone (CS) levels were markedly elevated, and photic stressful stimulation failed to further increase the levels of these hormones. In addition, the elevated basal serum levels of ACTH and CS could not be suppressed by pretreatment with dexamethasone. The content of CRF-41 in the paraventricular nucleus of the hypothalamus and in the median eminence measured at 6 days p.i. was similar to that of vehicle inoculated rats. By 4 weeks p.i. the basal levels of ACTH and CS returned to normal and these animals responded to photic stimulation and dexamethasone similar to vehicle inoculated rats. Systemic (intraperitoneal) inoculation of HSV-1 did not induce any changes in the HPA axis responses. We therefore suggest that asymptomatic acute infection of the brainstem with HSV-1 may affect brain regions involved in the regulation of the HPA axis, and that those effects are mediated centrally and not by a systemic mechanism.

Adrenal Glands↗
PubMed1985

Finite centroid and helical axis estimation from noisy landmark measurements in the study of human joint kinematics.

Recent work on joint kinematics indicates that the finite centroid (centre of rotation) and the finite helical axis (axis of rotation, screw axis, twist axis) are highly susceptible to measurement errors when they are experimentally determined from landmark position data. This paper presents an analytical model to describe these effects, under isotropic conditions for the measurement errors and for the spatial landmark distribution. It appears that the position and direction errors are inversely proportional to the rotation magnitude, and that they are much more error-prone than the relatively well-determined rotation and translation magnitudes. Furthermore, the direction and rotation magnitude errors are inversely proportional to the landmark distribution radius, and the position and translation magnitude errors are minimal if the mean position of the landmarks coincides with the centroid or helical axis. For the planar centroid, the use of rigid-body constraints results in considerable precision improvement relative to the classical, finite Reuleaux method for centroid reconstruction. These analytical results can be used to define suitable measurement configurations, and they are used in this paper to explain experimental results on Röntgenphotogrammetrically acquired in vitro wrist joint movement.

Biomechanical Phenomena↗
PubMed1992

The effect of a deprogrammer on the position of the terminal transverse horizontal axis of the mandible.

This study measured the amount of positional change in the terminal transverse horizontal axis of the mandible that results from altering undesirable neuromuscular influence. Centric relation records were made on 19 healthy subjects before and after deprogramming. The axis was located with a computerized axiograph, and the centric relation records were compared in vivo at the axis location. The positional change of the axis was quantified in three dimensions at an accuracy of +/- 0.05 mm. The net amount of positional change was compared to scores from the temporomandibular joint scale to test for correlation with the potential for developing a temporomandibular disorder. The findings showed that the amount of positional change in the terminal transverse horizontal axis in 18 of 19 healthy patients after 12 hours of deprogramming was less than 0.5 mm and did not correlate with scores from the TMJ Scale.

Adolescent↗
PubMed1995

Levorotation of the fetal cardiac axis: a clue for the presence of congenital heart disease.

OBJECTIVE: To evaluate the use of the cardiac axis within the chest for the prenatal detection of congenital heart defects. METHODS: We reviewed retrospectively the sonographic findings of all fetuses scanned between 17 and 40 weeks' gestation and diagnosed prenatally as having heart defects. The cardiac diagnoses were confirmed postnatally. The control group consisted of 75 consecutive fetuses with normal fetal surveys and newborn follow-up examinations. The cardiac axes were measured retrospectively using an image of the four-chamber view of the heart and measuring the angle between the interventricular septum and a line bisecting the chest. Mean and standard deviations (SDs) of the axis measurements in normal and abnormal fetuses were compared by Student t test. RESULTS: The 75 fetuses with heart defects diagnosed by prenatal sonogram had a mean cardiac axis of 56 +/- 13 degrees, compared with 43 +/- 7 degrees in normal fetuses (P < .001). Using 57 degrees (two SDs above the mean for normal fetuses) as the upper limit of normal, 33 of 75 (44%) abnormal fetuses versus none of 75 normal fetuses were identified. The frequency of cardiac rotation was greater in fetuses with truncus arteriosus, Ebstein's anomaly, pulmonic stenosis, coarctation of the aorta, and tetralogy of Fallot. CONCLUSION: The presence of a cardiac axis exceeding 57 degrees in the fetal chest is associated with a substantial risk of congenital heart defects. The finding of an abnormal axis should prompt further evaluation of the fetal heart.

Case-Control Studies↗
PubMed1991

Injected Wnt RNA induces a complete body axis in Xenopus embryos.

Studies in Xenopus have shown that growth factors of the TGF beta and Wnt oncogene families can mimic aspects of dorsal axis formation. Here we directly compare the inductive properties of two Wnt proteins by injecting synthetic mRNA into developing embryos. The results show that Wnt-1 and Xwnt-8 can induce a new and complete dorsal axis and can rescue the development of axis-deficient, UV-irradiated embryos. In contrast, activin mRNA injection induces only a partial dorsal axis that lacks anterior structures. These studies demonstrate that the mechanism of Wnt-induced axis duplication results from the creation of an independent Spemann organizer. The relationship between the properties of the endogenous dorsal inducer and the effects of Wnts and activins is discussed.

Activins↗
PubMed1993

Axis specification in the developing Drosophila appendage: the role of wingless, decapentaplegic, and the homeobox gene aristaless.

The wingless (wg) and decapentaplegic (dpp) genes of Drosophila encode homologs of secreted growth factors and are required for the correct patterning of the appendages. We show that the presumptive tips of both the leg and wing, the distal extreme of the proximodistal axis, are characterized by the close association of cells expressing wg, dpp, and the homeobox gene aristaless (al). Ectopic expression of wg can induce both ectopic al expression and a duplication of the proximodistal axis (the development of supernumerary legs), but only in regions expressing high levels of dpp. Ectopic al expression can induce a duplication of the proximodistal axis in the wing, suggesting that it may be directly involved in axis specification. The proximodistal axis may be specified via a mechanism involving a direct interaction between cells expressing wg, dpp, and possibly al.

Animals↗
PubMed1992

Influence of position along the medial-lateral axis of the superior colliculus on the topographic targeting and survival of retinal axons.

Topographic order in the rat retinocollicular projection emerges from an initially diffuse projection during an early postnatal remodeling period that is coincident with the period of naturally occurring ganglion cell death. Here, we examine the relationship between a retinal axon's position along the medial-lateral axis as it enters the superior colliculus (SC) and its ability to form an appropriately positioned arbor and survive the remodeling period. At E18-E19, prior to map remodeling, axons labeled with focal DiI injections in the periphery of temporal, nasal, superior or inferior retina are widespread along the medial-lateral SC axis. At P12, after remodeling, the distributions of axons remain widespread over the medial-lateral SC axis relative to the positioning of their terminal arborizations, and resemble the distributions labeled at E18-E19, with the exception that the small proportion of axons most widely mispositioned along the medial-lateral SC axis are less frequent. These data indicate that the most widely mispositioned retinal axons are preferentially eliminated, but that a high proportion of retinal axons mispositioned along the medial-lateral axis as they enter the SC can correct their position, form topographically appropriate arbors, and survive the remodeling period.

Aging↗
PubMed1989

Neuroendocrine aspects of primary endogenous depression VIII. Pituitary-gonadal axis activity in male patients and matched control subjects.

To determine the extent of hypothalamo-pituitary-gonadal (HPG) axis dysfunction in endogenous depressed men, we measured nocturnal and diurnal serum luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), and estradiol (E2) concentrations, and their responses to gonadotropin releasing hormone (LHRH) and dexamethasone administration, in 16 Research Diagnostic Criteria primary, definite endogenous male depressives and 16 individually matched male normal controls. Compared to their controls, the patients showed no differences in basal nocturnal or diurnal gonadotropin or gonadal steroid hormone concentrations, and no differences in hormone concentrations either post-LHRH or post-dexamethasone. Age was negatively correlated with baseline serum T in the patients but not in the controls, and it was modestly positively correlated with baseline serum LH in both groups of subjects. In the patients, the presence of DSM-III melancholia was modestly negatively correlated with baseline and post-LHRH concentrations of both LH and FSH and was positively correlated with baseline serum T, but it bore no relation to serum E2. None of the other subject characteristics or specific dimensions of depressive symptomatology were significantly related to the HPG axis measures. The HPG axis measures also were unrelated to pre- and post-dexamethasone cortisol concentrations in both groups of subjects. The results of this study suggest that, in contrast to the hypothalamo-pituitary-adrenal cortical and thyroid axis abnormalities frequently found in endogenous depressives, HPG axis function in male depressives is relatively normal.

Adult↗
PubMed1993

Anatomy of the celiac axis and superior mesenteric artery and its significance in radiation therapy.

PURPOSE: In the radiation therapy of upper gastrointestinal malignancies, treatment of lymph nodes in the region of the celiac axis and superior mesenteric axis is often mandated. This study was undertaken to determine the relationship of the celiac axis and superior mesenteric arteries to the vertebral bodies--the radiographically visualized reference structures during simulation. METHODS AND MATERIALS: Twenty-three celiac angiograms and 24 superior mesenteric angiograms performed preoperatively in 24 patients treated at the University of Pennsylvania from 1984 to 1989 for pancreatic carcinoma were examined. The location of the origin of the celiac and superior mesenteric arteries was determined in each case. RESULTS: In 48% of the celiac angiograms, the celiac axis arose from the aorta high at the pedicle of the T-12 vertebral body, contrary to the common belief that the celiac axis arises near the T12-L1 interspace. The superior mesenteric artery arose at the level of L-1 in 83% of the 24 angiograms and below the pedicle of L-1 in 5 (21%). However, none arose below the L1-2 interspace. CONCLUSION: The variability demonstrated in the levels from which these vessels arise strongly suggests individualized treatment planning, including angiographic, CT or MRI data should be performed if tight margins are used. These studies would additionally optimize treatment of the tumor bed. Consideration for dose at field edges (i.e., "buildup") and day to day variation in set-up is required in determining the field borders. Treatment volumes tightly encompassing T12 and L1 could risk undertreating regional lymph nodes associated with these vessels.

Angiography↗
PubMed1992

Left ventricular volume determined echocardiographically by assuming a constant left ventricular epicardial long-axis/short-axis dimension ratio throughout the cardiac cycle.

OBJECTIVES: The purpose of this study was to develop and test a simplified echocardiographic method to calculate left ventricular volume. BACKGROUND: This method was based on the assumption that the ratio of the left ventricular epicardial long-axis dimension to the epicardial short-axis dimension was constant throughout the cardiac cycle. With use of this constant ratio, the method developed to calculate left ventricular volume at a given point in the cardiac cycle required the left ventricular endocardial long-axis dimension to be measured at only one point in the cardiac cycle. METHODS: Studies were performed in 13 normal dogs, 8 normal puppies, 9 normal pigs, 12 dogs with aortic stenosis, 13 dogs with acute mitral regurgitation, 12 dogs with chronic mitral regurgitation, 7 dogs that had undergone mitral valve replacement and 6 pigs that had had chronic supraventricular tachycardia. Animals with aortic stenosis developed left ventricular pressure overload hypertrophy with a 60% increase in left ventricular mass; chronic mitral regurgitation caused left ventricular volume overload hypertrophy with a 46% increase in left ventricular volume; supraventricular tachycardia caused a dilated cardiomyopathy with a 55% decrease in left ventricular ejection fraction. RESULTS: The left ventricular epicardial long-axis/short-axis dimension ratio remained constant throughout the cardiac cycle in each animal group. End-diastolic and end-systolic volumes calculated with the simplified echocardiographic method correlated closely with angiographically measured volumes; for end-diastolic volume, echocardiographic end-diastolic volume = 1.0 (angiographic end-diastolic volume) -1.8 ml, r = 0.96; for end-systolic volume, echocardiographic end-systolic volume = 0.98 (angiographic end-systolic volume) -0.7 ml, r = 0.95. CONCLUSIONS: Thus the left ventricular epicardial long-axis/short-axis dimension ratio was constant throughout the cardiac cycle in a variety of animal species and age groups and in the presence of cardiac diseases that significantly altered left ventricular geometry and function. The simplified echocardiographic method examined provided an accurate determination of left ventricular volumes.

Animals↗
PubMed1991

Cytokines as modulators of the hypothalamus-pituitary-adrenal axis.

The hypothalamus-pituitary-adrenal (HPA) axis is stimulated during the course of certain immune, inflammatory and neoplastic processes. IL-1 is an important immunologically derived cytokine mediating the stimulation of this axis, although not the only one. We have compared the relative potencies of the cytokines IL-1, IL-6 and tumor necrosis factor (TNF), which share several biological actions, for stimulating ACTH and corticosterone output in freely-moving rats. Although all three cytokines can stimulate the HPA axis, IL-1 was the most potent. This effect of IL-1 was also present during the neonatal period, when the response of the HPA axis to acute stress is reduced in rodents. The results support the existence of an immune-HPA axis circuit. The biological and clinical relevance of this circuit is discussed.

Adrenocorticotropic Hormone↗
PubMed2006

Extended pancreatectomy with resection of the celiac axis: the modified Appleby operation.

BACKGROUND: Celiac axis invasion by central and distal pancreatic cancers has been considered a contraindication to resection. Appleby first described en-bloc celiac axis resection with total gastrectomy for locally advanced gastric cancer. We present our experience with a modification of this procedure in central pancreatic cancers involving the celiac trunk. METHODS: Three patients with central pancreatic cancers invading the celiac axis are reviewed. All patients underwent extended pancreatectomy with en-bloc resection of the celiac axis. RESULTS: Margins were grossly clear of tumor in all patients. The mean length of stay was 8.3+/-1.1 days. There was no evidence of clinically significant gastric or hepatic ischemia. All 3 patients remain disease free at 34, 14, and 14 months from surgery, respectively. COMMENTS: Extended pancreatectomy with celiac axis resection can result in prolonged survival and should be considered in central and distal pancreatic cancers invading the celiac trunk.

Adenocarcinoma↗
PubMed2004

Psychiatric challenges in the first 6 years after traumatic brain injury: cross-sequential analyses of Axis I disorders.

OBJECTIVE: To examine the preinjury rates of Axis I disorders and the prospective rates within the first 6 years after traumatic brain injury (TBI). DESIGN: Cross-sectional, longitudinal, and cross-sequential. SETTING: Community-based research and training center. PARTICIPANTS: Persons (N=188) who had sustained TBI within 4 years of enrollment into the project were interviewed at either 2 and 3 assessments. Each assessment was approximately 1 year apart. Several Axis I diagnoses were analyzed to detect cross-sectional differences (by age and time postinjury) and average individual changes over the multiple measurement time points. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders. RESULTS: The odds ratios changed longitudinally within each subject, indicating a decreased probability of having an Axis I diagnosis over time. There were few cross-sectional differences in age; therefore, age at the time of injury had little impact on Axis I diagnoses. Cross-sectional time since injury was not associated with more psychiatric disorders, whereas cross-sectional preinjury history of psychiatric disorders was predictive of postinjury psychiatric disorders. After controlling for cross-sectional effects, the frequencies of Axis I disorders increased in depression, anxiety, and posttraumatic stress disorders in the first assessment postinjury and declined in subsequent assessments. CONCLUSIONS: Cross-sequential analyses that control for cross-sectional and longitudinal differences produced a more complete description of psychiatric disorders after TBI.

Adult↗
PubMed2006

Do neonatal bilateral ibotenic acid lesions of the hippocampal formation or of the amygdala impair HPA axis responsiveness and regulation in infant rhesus macaques (Macaca mulatta)?

In response to stressful events, the HPA axis is activated triggering the successive release of CRF, ACTH, and glucocorticoids. The glucocorticoids in turn provide a negative feedback signal to terminate the stress response. The amygdala and the hippocampus are involved in the regulation of the HPA axis. In rodents, their respective roles have been identified; the amygdala exerts a stimulatory effect, whereas the hippocampus provides negative feedback control. In primates, however, their regulatory roles are still not well defined. The present study compared HPA axis responsiveness and regulation in 3- to 5-month-old rhesus macaques that received neonatal (15 +/- 3 days old) bilateral ibotenic acid lesions of the hippocampus or amygdala, or sham lesions. Group differences in plasma cortisol response to separation from the mother and relocation in a novel environment were assessed as well as response to dexamethasone suppression and ACTH challenge. Results revealed that the initial cortisol levels after separation/relocation did not differ between groups. Subjects with hippocampus lesions did not show a suppression of cortisol in response to dexamethasone, suggesting a loss of negative feedback control of HPA regulation. Subjects with amygdala and sham lesions did not differ in response to dexamethasone. Indeed, bilateral neonatal lesions of the amygdala have little impact on HPA axis responsiveness and regulation in contrast to lesions in adult monkeys. Finally, females displayed higher cortisol levels than males, independently of their lesion, indicating that the development of sex differences in the regulation of the HPA axis does not involve the amygdala or hippocampus.

Adrenocorticotropic Hormone↗
PubMed2004

[Effect of dehydration on nitric oxide, corticotropic and vasopressinergic axis in rat].

Effect of dehydration on nitric oxide, corticotropic and vasopressinergic axis in rat. The purpose of our work is to study, in the male 'Wistar' rat, the effects of a chronic dehydration, by deprivation of water for three days out of four, during four repeated cycles, on the evolution of certain blood variables, on the activities of both corticotropic and vasopressinergic axis and on the synthesis of nitric oxide. The chronic dehydration causes a considerable reduction of the body weight, an activation of the vasopressinergic axis and an increase in the circulating rates of the nitrates/nitrites, which represent the final metabolites of the reaction of oxidation of nitric oxide. The pituitary-adrenal axis is not statistically affected by the chronic dehydration. This seems to be in favour of a possible adaptation of corticotropic axis to chronic water deprivation. The activation of synthesis of nitric oxide shows its implication in the regulation of the water balance and its buffer effect on vasoconstriction and hypertension induced by water stress.

Adrenocorticotropic Hormone↗
PubMed2005

Canonical Wnt signaling and its antagonist regulate anterior-posterior axis polarization by guiding cell migration in mouse visceral endoderm.

The mouse embryonic axis is initially formed with a proximal-distal orientation followed by subsequent conversion to a prospective anterior-posterior (A-P) polarity with directional migration of visceral endoderm cells. Importantly, Otx2, a homeobox gene, is essential to this developmental process. However, the genetic regulatory mechanism governing axis conversion is poorly understood. Here, defective axis conversion due to Otx2 deficiency can be rescued by expression of Dkk1, a Wnt antagonist, or following removal of one copy of the beta-catenin gene. Misexpression of a canonical Wnt ligand can also inhibit correct A-P axis rotation. Moreover, asymmetrical distribution of beta-catenin localization is impaired in the Otx2-deficient and Wnt-misexpressing visceral endoderm. Concurrently, canonical Wnt and Dkk1 function as repulsive and attractive guidance cues, respectively, in the migration of visceral endoderm cells. We propose that Wnt/beta-catenin signaling mediates A-P axis polarization by guiding cell migration toward the prospective anterior in the pregastrula mouse embryo.

Animals↗
PubMed2005

Defining the knee joint flexion-extension axis for purposes of quantitative gait analysis: an evaluation of methods.

Minimising measurement variability associated with hip axial rotation and avoiding knee joint angle cross-talk are two fundamental objectives of any method used to define the knee joint flexion-extension axis for purposes of quantitative gait analysis. The aim of this experiment was to compare three different methods of defining this axis: the knee alignment device (KAD) method, a method based on the transepicondylar axis (TEA) and an alternative numerical method (Dynamic). The former two methods are common approaches that have been applied clinically in many quantitative gait analysis laboratories; the latter is an optimisation procedure. A cohort of 20 subjects performed three different functional tasks (normal gait; squat; non-weight bearing knee flexion) on repeated occasions. Three-dimensional hip and knee angles were computed using the three alternative methods of defining the knee joint flexion-extension axis. The repeatability of hip axial rotation measurements during normal gait was found to be significantly better for the Dynamic method (p<0.01). Furthermore, both the variance in the knee varus-valgus kinematic profile and the degree of knee joint angle cross-talk were smallest for the Dynamic method across all functional tasks. The Dynamic method therefore provided superior results in comparison to the KAD and TEA-based methods and thus represents an attractive solution for orientating the knee joint flexion-extension axis for purposes of quantitative gait analysis.

Adult↗
PubMed2005

Comparison of modified short axis view and apical four chamber view in evaluating right ventricular function after repair of tetralogy of Fallot.

BACKGROUND: In clinical settings an easy and reliable method for following up right ventricular (RV) function in patients after repair of tetralogy of Fallot (TOF) is needed. It is, however, unclear whether the novel modified short axis view from echocardiography is superior to the apical four chamber view in this aspect. MATERIALS AND METHODS: Thirty postoperative TOF patients with median age 17 years (range 6-45 years) and follow up period of 10 years (range 0.5-40 years) were examined echocardiographically using the apical four chamber view and the novel modified short axis view. RV areas in end-systole (Amin) and end-diastole (Amax) were measured and an area fraction [(Amax - Amin)/Amax * 100%] was calculated from the respective view. RV ejection fraction was assessed through magnetic resonance imaging (MRI). The RV area fractions from echocardiography were compared to the RV ejection fraction. RESULTS: The right ventricular area fraction derived from the modified short axis view was significantly lower than that from the apical four chamber view (34.3+/-9.1% vs. 42.5+/-10.2%, p=0.007). Both the RV area fractions obtained from the modified short axis view (r=0.674, p<0.001) and from the apical four chamber view (r=0.512, p=0.025) correlated significantly with the MRI derived RV ejection fraction. CONCLUSION: The novel modified short axis view from echocardiography may be superior to the apical four chamber view for routine follow up of patients after TOF repair, in whom the right ventricular outflow tract plays an important role in the right ventricular systolic function.

Adolescent↗