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At least 739 records · Page 41Linked to original sources
PubMed1980

Effects of exogenous and endogenous opiates on the hypothalamic--pituitary--gonadal axis in the male.

Narcotics acutely depress serum testosterone levels in the male. Three mechanisms could be involved: an enhancement of the degradation of testosterone; a direct inhibition of testicular steroidogenesis; or, finally, an inhibition of the hypothalamic-pituitary-luteinizing hormone (LH) axis resulting in a reduction in LH-dependent testicular steroidogenesis. The currently available evidence indicates that narcotics do not affect the catabolism of testosterone by the liver or testicular steroidogenesis. Rather, the data favor a direct action on the hypothalamic--pituitary--LH axis, probably by inhibiting the secretion of LH-releasing hormone (LH-RH) from the hypothalamus. The effects of narcotics on serum LH appear to be mediated via specific opioid receptors, suggesting that a naturally occurring opioid-like substance exists that normally inhibits LH. In support of this conclusion, opiate receptor blockers markedly increase serum LH levels shortly after their subcutaneous administration. In addition, endogenous opioids also seem to participate in testosterone's negative feedback control of the hypothalamic--pituitary--LH axis. Thus, it appears that opiate drugs inhibit the function of the hypothalamic-pituitary-gonadal axis by occupying opiate receptors in the hypothalamus and, moreover, that endogenous opioids exist that normally bind to these receptors and regulate activity in this axis.

Animals↗
PubMed1981

A gradation of hyaluronate accumulation along the proximodistal axis of the embryonic chick limb bud.

We are currently investigating the mechanism by which the apical ectodermal ridge (AER) of the embryonic chick limb bud exerts its negative effect on the cytodifferentiation of limb mesenchymal cells directly subjacent to it, and the mechanism by which cytodifferentiation is triggered when the cells leave the influence of the AER. Since there is a gradation of differentiation along the proximodistal axis of the limb bud, we have dissected limb buds into discrete segments along the proximodistal axis, and biochemically examined the accumulation of hyaluronate (HA) and other glycosaminoglycans (GAG) in each segment. The unspecialized subridge region of stage-25 limb buds was separated into distal (segment 1) and proximal (segment 2) regions, and the remaining proximal portion of the limb was separated into four segments (segments 3, 4, 5 and 6) along the proximodistal axis. Stage-24 limb buds were separated into corresponding regions. Since in the proximal regions of the limb (segment 3 through 6), only the cells comprising the central cores of the limb are involved in chondrogenic differentiation, the central core tissue was surgically separated from the peripheral tissue. We have found that HA is by far the predominant GAG accumulated by cells comprising the distal subridge region (representing greater than 50% of the total GAG accumulated during a 90-min labelling period with [3H]glucosamine), and that there is a progressive decline in HA accumulation along the proximodistal axis. The relative and total amount of HA accumulated is highest in the distal subridge region (segment 1), intermediate in the proximal subridge region (segment 2) and lowest in the proximal central core regions of the limb (segments 3 through 6). The striking decrease in HA accumulation in the central core of segment 3 is accompanied by a striking increase in the accumulation of chondroitin sulphate, one of the major constituents of cartilage matrix. In contrast to the central core regions of segments 3 through 6, the relative and total amount of HA accumulated by the peripheral non-chondrogenic regions of these segments remains relatively high, being similar to the accumulation observed in the proximal subridge region. These results indicate that there is a gradation of HA accumulation along the proximodistal axis of both stages-24 and -25 limb buds which correlates with distance of cells from the AER and the state of differentiation of the cells.

Animals↗
PubMedDate not supplied

Effect of respiration of mean frontal P. QRS and T axis in normal young adults.

Deep inspiration shifted the mean frontal plane axis of P, QRS and T waves to the right in all the cases. Greater degree of shift in AP and AQRS was observed in cases where the resting axis had been 0 degrees to +30 degrees and minimum shift was observed where the resting axis was between +61 degrees to +90 degrees. Axis of the T wave though shifted to the right with deep inspiration in all the cases but there had been no statistically significant difference in the degree of shift in the three groups. In none of the case, axis changed from normal to abnormal degree.

Adolescent↗
PubMed1995

Axis I and personality comorbidity in adolescents with conduct disorder.

This study was undertaken to investigate psychiatric comorbidity in male and female adolescents with conduct disorder diagnoses. Twenty-five hospitalized adolescents (11 females, 14 males) with conduct disorder were evaluated using structured diagnostic interviews for Axis I and personality disorders. The most common Axis I comorbid diagnoses were: depressive disorders (major depression and/or dysthymia), 64 percent; anxiety disorders (separation anxiety disorder, overanxious disorder, panic disorder, obsessive-compulsive disorder, phobias, and/or posttraumatic stress disorder), 52 percent; substance abuse, 48 percent; and attention-deficit hyperactivity disorder, 28 percent. Common Axis II disorders included passive-aggressive personality disorder, 56 percent, and borderline personality disorder, 32 percent. When compared with the male subjects, the females had significantly more total Axis I disorders and a trend toward more total personality disorders, anxiety disorders, depression, and borderline personality disorders. These findings support conduct disorder as a complex illness with extensive Axis I and II involvement as well as some gender differences in presentation.

Adolescent↗
PubMed1994

The reproducibility of condylar hinge axis positions in patients, by different operators, using the electronic mandibular position indicator.

Three operators each made five recordings from 15 symptomatic patients using the electronic mandibular position indicator. The method consisted of measuring bilateral spatial changes of the hinge axis recalculated by the computer to an intercondylar distance of 110 mm and a third position, calculated from the rotation of the hinge axis, at the incisal guidance table. All individual patient recordings were related to the origin of the same coordinate system. This origin is designated and defined as the reference position, with purposeful elimination of any stated joint position for this definition. The measurements were in all planes of space at 10-millimicron increments, including the rotation of the transverse hinge axis in hundredths of degrees. These data showed that the reproducibility of hinge axis positions, ie, reference positions, to hinge axis condylar positions dictated by the maximum intercuspation of teeth was in average less than 0.2 mm for each record from all operators and patients.

Analysis of Variance↗
PubMed1993

Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis.

The posterior condylar surfaces of the femur are routinely used as the reference for the rotational orientation of the femoral component during most primary total knee arthroplasties. The purpose of this investigation was to identify a clearly discernible, reproducible secondary anatomic axis useful for determining the rotational orientation of the femoral component when the posterior condylar surfaces cannot be used. Seventy-five embalmed anatomic specimen femurs were studied. A surgical epicondylar axis was defined as the line connecting the lateral epicondylar prominence and the medial sulcus of the medial epicondyle. The posterior condylar angle was measured as the angle between the posterior condylar surfaces and the surgical epicondylar axis. Measurement of the posterior condylar angle referenced from the surgical epicondylar axis yielded a mean posterior condylar angle of 3.5 degrees (+/- 1.2 degrees) of internal rotation for males and a mean posterior condylar angle of 0.3 degree (+/- 1.2 degrees) of internal rotation for females. Thus, rotational alignment of the femoral component can be accurately estimated using the posterior condylar angle. The posterior condylar angle, referenced from the surgical epicondylar axis, provides a visual rotational alignment check during primary arthroplasty and may improve alignment of the femoral component at revision.

Biometry↗
PubMed1996

The kappa-opioid receptor agonist MR-2034 stimulates the rat hypothalamic-pituitary-adrenal axis: studies in vivo and in vitro.

There is increasing evidence that opiates not only have analgesic properties, but also regulate mechanisms activated during the stress response, such as the hypothalamic-pituitary-adrenal (HPA) axis. Indeed, opioid-containing neurons innervate the paraventricular nucleus and the median eminence, thus modulating inputs to ACTH-controlling neurons. In addition, dynorphin (the endogenous ligand of the kappa-opioid receptor)-like peptides have been found co-localized with corticotrophin-releasing hormone (CRH) and are believed to be co-secreted with it in the hypophyseal portal circulation to modulate ACTH release. In this study, we evaluated the effects of the selective kappa-opioid receptor agonist MR-2034 [(-)-N-(2-tetrahydrofurfuryl)-normetazocine] on the HPA axis in vivo and in vitro. MR-2034 was given intravenously to catheterized, freely moving, male Sprague-Dawley rats and serial blood samples were collected for ACTH and corticosterone (B) measurements. We evaluated also the site of MR-2034 action on the HPA axis in vivo, after the administration of alpha-helical CRH9-41, a CRH receptor antagonist, on hypothalamic CRH, pituitary ACTH, and B release in vitro. MR-2034 increased plasma ACTH and B levels in a dose-related fashion and this effect was antagonized by the selective kappa-opioid receptor antagonist MR-1452. In the presence of alpha-helical CRH9-41, the responses of plasma ACTH and B to MR-2034 were blunted significantly, suggesting that this compound activates the HPA axis through a CRH-dependent mechanism. Accordingly, MR-2034 stimulated hypothalamic CRH release in vitro in a concentration-dependent fashion and this effect was antagonized dose-dependently by MR-1452. However, the stimulatory effect of MR-2034 on plasma ACTH and B in vivo was not completely abolished by alpha-helical CRH9-41, suggesting that an additional, CRH-independent, mechanism was involved. Indeed, MR-2034 was able to stimulate basal ACTH output in a dose-dependent manner and this effect was antagonized by MR-1452 in vitro. On the other hand, MR-2034 did not have any effect on B release from adrenocortical cells or adrenal quarters in vitro. These results show that the benzomorphan MR-2034 stimulates the HPA axis in the rat by acting at the hypothalamic and the pituitary level. We hypothesize that endogenous kappa-opioid peptides not only act at the pituitary level to increase ACTH output, but may also act at the hypothalamic level to increase CRH release through an autocrine and/or ultrashort positive feedback mechanism.

Adrenocorticotropic Hormone↗
PubMed1976

[Axis divergence in electrocardiography as a sign of heart disease].

In the ecgs of 3433 patients the QRS- and T-vectors were determined. The borderline between physiological and pathological ranges of axis-divergence is found to show fluctuations. The younger the patient and the steeper the electrical heart axis, the greater is the physiological axis-divergence. Ignoring this fact many young people by mistake are taken to suffer from a cardiac disease on account of a great axis-divergence. On the other hand the same setting often is the only sign of a heart disease. The axis-divergence can be a useful factor for the computer-analyzed ecg, although the evaluation of a tenfold of ecgs seems to be necessary to achieve a statistically significant statement.

Adult↗
PubMed1997

[Effect of three kinds (tonifying kidney, invigorating spleen, promoting blood circulation) recipes on the hypothalamus-pituitary-adrenal-thymus (HPAT) axis and CRF gene expression].

OBJECTIVE: To observe the effect of tonifying Kidney (TK), invigorating Spleen (IS) and promoting blood circulation (PBC) recipes on the hypothalamus-pituitary-adrenal-thymus (HPAT) axis. METHODS: Reverse-transcription polymerase chain reaction, radioimmunoassay and cellular immunity techniques were used to observe the effects of TH, IS, PBC on the neuroendocrine and immune system of this experimental model which HPAT axis was inhibited by corticosterone. RESULTS: Only TK could avoid the depression of exogenous corticosterone, which by enhancing the expression of CRFmRNA in hypothalamus, and following the improvement of function of HPAT axis, that IS might have direct promotion on immune system, whereas without any effect of PBC on HPAT axis was observed. CONCLUSION: TK, IS and PBC recipes have different effects on HPAT axis.

Animals↗
PubMedDate not supplied

[Two-leaflet artificial heart valve with the common turn axis for leaflets].

The paper describes the main results of calculations and studies of a basically new model of a two-leaflet valve which greatly differs from the St. Jude two-leaflet valves used in clinical setting. The main difference is that the two leaflets are fixed on one turn axis displaced from the axis of symmetry of the ring-carrying valve. The paper calculates the values of displacement (eccentricity) of the leaflet turn axis against the axis of symmetry of the ring-carrying valve. The new model of the valve is conventionally called Butterfly. The eccentricity of the new valve for the whole dimensional series is calculated by using experimental findings and the conditions for optimizing an effective valve opening. The strength of the axis of leaflet turning and attaching is also calculated. The results of experimental studies of the hydrodynamics of two models of the Butterfly valve by employing photochromic imaging are presented. The results of rapid filming were used to determine the time of closure and opening of the two models of valves.

Heart Valve Prosthesis↗
PubMed1999

Corrected formula for the calculation of the electrical heart axis.

The calculation of the heart axis in the frontal plane can be performed with the combination of any two leads. The use of combination of bipolar (I, II, III) and unipolar leads (aVR, aVL and aVF) can produce wrong results. Calculation of the electrical axis from leads I and aVF without correction (sometimes used in ECG recorders): EA= Arctan (aVF/I) results in lower values (in our study: 34 4 , n = 48) as compared to the values obtained with formula that uses leads I and II: EA= Arctan ((2*II-I)/(Sqr(3)*I)) (axis = 33+/-7 degrees, n=48; p<0.005, paired t-test with Bonferroni correction) or with corrected formula which uses leads I and aVF: EA=+/-Arctan ((2*aVF)/(Sqr(3)*I)) (axis = 374 degrees, n=48; p<0.005, paired t-test with Bonferroni correction). The correction factor 2/Sqr(3) is required because the unipolar and bipolar leads have different strengths. Although the difference rarely reach clinical significance, our results suggests that the ECG recorders should be proofed on formulas used for the calculation of the electrical axis.

Electrocardiography↗
PubMed1999

Three-dimensional organization of vestibular-related eye movements to off-vertical axis rotation and linear translation in pigeons.

During linear accelerations, compensatory reflexes should continually occur in order to maintain objects of visual interest as stable images on the retina. In the present study, the three-dimensional organization of the vestibulo-ocular reflex in pigeons was quantitatively examined during linear accelerations produced by constant velocity off-vertical axis yaw rotations and translational motion in darkness. With off-vertical axis rotations, sinusoidally modulated eye-position and velocity responses were observed in all three components, with the vertical and torsional eye movements predominating the response. Peak torsional and vertical eye positions occurred when the head was oriented with the lateral visual axis of the right eye directed orthogonal to or aligned with the gravity vector, respectively. No steady-state horizontal nystagmus was obtained with any of the rotational velocities (8-58 degrees /s) tested. During translational motion, delivered along or perpendicular to the lateral visual axis, vertical and torsional eye movements were elicited. No significant horizontal eye movements were observed during lateral translation at frequencies up to 3 Hz. These responses suggest that, in pigeons, all linear accelerations generate eye movements that are compensatory to the direction of actual or perceived tilt of the head relative to gravity. In contrast, no translational horizontal eye movements, which are known to be compensatory to lateral translational motion in primates, were observed under the present experimental conditions.

Animals↗
PubMed1975

Lesions of the atlas and axis.

The atlas and axis support the head on the lower cervical spine while providing for considerable mobility in flexion, extension, rotation and lateral bending. The first two vertebrae also function as conduits for the cervical cord and vertebral arteries. Lesions of the atlas and axis, therefore, can cause instability with loss of support and encroachment on the upper cord and vertebral arteries, or less often stiffness with restricted motion. Congenital lesions of the occipito-cervical spine such as occipitalization of the atlas or accessory occipital vertebrae can constrict the upper cord with osseous, dural, or fibrous compression. Such encroachment on the cord at this level produces a varying array of clinical complaints and findings frequently difficult to interpret. Instability of the upper cervical spine can result from congenital, traumatic, inflammatory or neoplastic disruptions of the interlocking mechanism of the atlas and axis. Such factors as the loss of structural integrity of the dens or stretching or tearing of the transverse ligament can permit instability with cord involvement. Because of the serious potential of these lesions, patients with abnormalities of the atlas and axis require prompt recognition and treatment.

Adolescent↗
PubMed2004

Structural properties of the axis studied in cadaveric specimens.

Peripheral quantitative computed tomography scans of the axis in 20 fresh cadaveric specimens obtained at autopsy were studied to investigate the internal structural properties of the axis. In all specimens, serial scans were done in three planes. The area of the dens consisted of dense cortical and trabecular bone (Region 1, above the base of the dens) and showed statistically significantly greater peripheral quantitative computed tomography values when compared with the anterior part of the body of the axis (Region 2, below the base of the dens). An age-related progressive decrease of peripheral quantitative computed tomography values was observed, with specimens from subjects younger than 40 years showing statistically significantly greater peripheral quantitative computed tomography values when compared with those from subjects older than 40 years. A small area of trabecular bone with decreased density was found close to the anteroinferior edge of the body of the axis in the specimens from younger subjects. In contrast, a large area of trabecular bone with decreased density extending anteroinferiorly to superoposteriorly to the base of the dens was found in the specimens from older subjects. Based on these findings, we think that dens fracture classification systems and fixation techniques should be reconsidered.

Adult↗
PubMed2005

Chance-type fractures of the axis.

STUDY DESIGN: A retrospective study was performed to identify horizontal fractures of the body of the axis, with special attention to their pattern, prevalence, and clinical outcome. OBJECTIVE: The prevalence of this type of injury and the long-term clinical behavior are examined. SUMMARY OF BACKGROUND DATA: Although isolated cases have been reported, horizontal Chance-type fractures of the body of the axis are not common cervical spine injuries. METHODS: The medical records of 674 consecutive patients with fractures of the cervical spine admitted to the authors' institute from 1970 to 2002 were reviewed. Of them, 2 (0.3%) had a horizontal Chance-type fracture of the body of the axis. Neurologic deficits were not diagnosed at admission. Mechanism of injury, treatment, and long-term follow-up were evaluated. RESULTS: Both patients were treated nonoperatively. At the latest follow-up, 3 and 12 years, respectively, both patients had a satisfactory clinical outcome. CONCLUSION: Horizontal fractures of the Chance-type of the body of the axis are rare. Conservative treatment proved to be effective.

Aged↗
PubMed2006

Simultaneous anterior arthrodesis C2-3 and anterior odontoid screw fixation for stabilization of a 4-part fracture of the axis--a technical description.

Multiple fractures of the axis are rare and present challenging patterns of instability in cervical spine surgery. Once a surgeon is faced with a combination of fractures in the axis vertebra, including stable and unstable components, a sound treatment concept must be worked out to achieve primary stability, early mobilization, and superior outcome. We demonstrate an operative technique for the stabilization of a 4-part fracture of the axis. Utilizing anterior odontoid screw fixation and C2-3 arthrodesis, an unstable traumatic spondylolisthesis with fracture of the odontoid type IIA, and lateral mass of C2 was successfully stabilized at once. The technique enabled early postoperative mobilization of our patient, who, after 1 year, showed a favorable outcome with a pain-free range of motion. The basic thoughts guiding to treatment options in multiple fractures of the axis are discussed and our therapy concept is presented.

Adult↗
PubMed1996

Management strategies for tumors of the axis vertebra.

Primary and metastatic tumors of the axis vertebra pose difficult surgical problems. The authors report 14 cases of patients with axis tumors who underwent surgery between 1970 and 1993. The eight male and six female patients ranged in age from 9 to 70 years (mean 46 years). Presenting symptoms and signs included pain in 12, myelopathy in nine, radiculopathy in four, and cranial nerve deficits in two patients. Preoperative instability of the cervical spine was present in eight patients. The goal of surgery was to achieve diagnosis, decompression, and stabilization; the choice of operative intervention was based on tumor location and patient prognosis. Six transoral-transpalatal resections, two lateral extrapharyngeal approaches, four posterolateral decompressions, and 11 dorsal decompressions were performed. Eleven fusion procedures were required to achieve spinal stability. Patients with aggressive tumors requiring concomitant radiotherapy underwent fusion using contoured loop instrumentation or methyl methacrylate, whereas those with benign lesions underwent fusion using traditional techniques. With maximum medical and surgical intervention, 10 patients are alive and their tumors are in remission. In eight of these 10 patients, gross-total resection was achieved. Four patients died from tumor progression, and in three of these cases gross-total resection was not possible. There were no operative deaths and morbidity was minimal. Development of new surgical approaches to the axis has allowed resection of previously inoperable tumors. The extent of resection correlated with the duration of survival. A classification system for axis tumors is proposed to facilitate selection of appropriate surgical approaches that will maximize the extent of resection while achieving or maintaining spinal stability.

Adolescent↗
PubMed1999

Anomaly of the axis causing cervical myelopathy. Case report.

Although the craniovertebral junction is one of the most common sites at which anomalies develop, spina bifida occulta of the axis (C-2) associated with cervical myelopathy is extremely rare. The authors present the case of a 46-year-old man who developed progressive tetraparesis caused by a cervical canal stenosis at the level of the axis. The spinal cord was compressed by an invaginated bifid lamina of the axis. The patient made a remarkable recovery after undergoing decompressive laminectomy of C-3 and removal of the bifid posterior arch of the axis.

Axis, Cervical Vertebra↗