Linearity of canal-otolith interaction during eccentric rotation in humans

During natural behavior, the head may simultaneously undergo rotation, transduced by the semicircular canals, and translation, transduced by the otolith organs. It has been demonstrated in monkey that the vestibulo-ocular reflexes (VORs) elicited by both endorgans (i.e., the angular and linear VORs, or AVOR and LVOR) sum linearly during combined rotation and translation, but this finding has proven more elusive in humans. To investigate the combined AVOR/LVOR response, six human subjects underwent yaw eccentric rotation at 3 Hz in darkness while displaced from the axis of rotation. Responses to on-center yaw rotation (AVOR alone) and interaural translation (LVOR alone) were also recorded. During eccentric rotation with the subject facing away from the axis of rotation (i.e., nose out), in which a yaw to the right occurs simultaneously with a translation to the right (i.e., translation in phase with rotation), the AVOR and LVOR acted synergistically. Responses were always out of phase with rotation, and became larger in magnitude as vergence increased. For nose-in eccentric rotation, during which translation is out of phase with rotation, the LVOR acted antagonistically to the AVOR. During near viewing, the LVOR often dominated the overall response when eccentricity was sufficiently large, producing eye movements that were in phase with the rotational stimuli. As vergence decreased, the LVOR influence diminished, eventually resulting in responses that were out of phase with rotation at lowest vergence. When the response to pure yaw rotation was vectorially removed from the responses to eccentric rotation, the results proved statistically indistinguishable from the LVOR recorded during interaural translation, suggesting that the ocular response to combined angular and linear motion reflects the linear combination of the AVOR and LVOR.     

Bone adaptation changes mechanical stress in the femur--a prospective two years follow up after Hüft-TEP implantation

AIM: Periprosthetic adaptive bone remodeling after total hip arthroplasty (THA) has been frequently simulated in computer models, combining bone remodeling theory with finite element analysis. Unfortunately, there is still a lack of clinical validation data. The collection of prospective volumetric bone density data with a clinical computerized tomography study after THA was previously conducted. The objective of the study presented here is an additional evaluation of femoral strain. METHOD: In a prospective clinical trial with 7 female patients after THA computerized tomography (CT) and finite element (FE) modeling was patient specifically combined immediately after surgery, as well as at three and 24 months postoperatively. Mechanical strain was expressed by strain energy density. RESULTS: Corresponding to a bone density decrease, a decrease of the femoral strain energy density was observed during the two year follow-up after surgery (approximately 20 %). The predominant change occurred within the first three months and was found to be distally stronger than proximally. CONCLUSION: As far as we are aware, this is the first combination of fully prospective 3D CT density data in vivo with patient-specific finite element modeling. The assessment of mechanical strain data during a follow-up trial should be a new approach for analyzing hip stems in clinical biomechanics. A future confirmative study based on a statistical case number calculation would increase the evidence of the results presented here.     

Distal ureteral stenosis after early adjuvant intravesical mitomycin C application for superficial bladder cancer

We report a case of distal ureteral stenosis after transurethral resection of a small bladder tumor near the left ureteral orifice and early postoperative mitomycin C instillation for prevention of recurrence. The patient developed late recurrent stenosis of the ureteral orifice with histologic evidence of localized, severe benign inflammatory reaction. The recurrent stenosis was successfully managed by transurethral resection of the scar tissue and ureteric stenting. Although ureteral stenosis does occur after transurethral resection, the severity and time course of the stenosis in this case suggest an influence of the intravesical chemoprophylaxis used.     

ICAM-1 expression and leukocyte accumulation in inner stripe of outer medulla in early phase of ischemic compared to HgCl2-induced ARF

BACKGROUND: After ischemia/reperfusion (I/R), as well as after toxic insults, there is significant infiltration of leukocytes in the kidney. It is well known that antibodies against adhesion molecules [e.g., intercellular adhesion molecule-1 (ICAM-1)] protect the kidney against acute ischemic injury. In contrast, same antibody treatment did not protect the rat kidney against toxic acute renal failure (ARF) induced by HgCl2. Protection obtained by anti-adhesion treatment in I/R injury is an early phenomenon, since delaying the administration of anti-ICAM-1 for 8 hours did not protect the kidney anymore. The aim of this study was to compare the early ICAM-1 expression and leukocyte accumulation in different zones of ischemic and toxic injury. METHODS: Male Lewis rats were injected with HgCl2 (2 mg/kg, subcutaneously) or uninephrectomized Lewis rats were submitted to 30 degrees C warm ischemia (I/R injury). Rats were sacrificed at 2, 6, 12 and 24 hours. ICAM-1 (1A29) expression in kidney was evaluated morphometrically. Different subsets of leukocytes were stained by immunohistochemistry and counted in cortex, the outer stripe of the outer medulla (OSOM) and the level of the inner stripe of the outer medulla (ISOM). RESULTS: Although the functional and morphologic damage was comparable between the I/R and toxic ARF group, different ICAM-1 expression could be observed early after injury. ICAM-1 expression in the ISOM started already 2 hours after the onset of I/R injury, and was increased after 12 hours in the cortex and after 24 hours in the OSOM. In contrast, during the first 24 hours after injury, ICAM-1 expression in HgCl2-injured kidneys was not different from noninjured kidneys in the ISOM and the cortex, whereas in the OSOM, ICAM-1 expression increased. The number of polymononuclear cells (PMNs) was low in noninjured kidneys and did not increase in time after both I/R injury and after HgCl2-induced ARF. In the ISOM, significant monocyte and T-cell accumulation was observed early after I/R but not after HgCl2. There was no significant T-cell accumulation in the cortex or in the OSOM. CONCLUSION: After HgCl2, almost no leukocyte accumulation and up-regulation of ICAM-1 was observed the first 12 hours after injury. In contrast, very early after I/R injury, increased expression of ICAM-1 goes along with monocyte and T-cell accumulation in the ISOM, endorsing this particular zone as critical in renal I/R injury. These observations contribute to the understanding why anti-ICAM-1 treatment in acute I/R injury is successful, but fails in acute toxic injury induced by HgCl2.     

Three-dimensional coronary MR angiography performed with subject-specific cardiac acquisition windows and motion-adapted respiratory gating

OBJECTIVE: In coronary MR angiography, data are conventionally accepted in only short and fixed periods of the cardiac and respiratory cycles. We hypothesized that a more flexible and subject-specific approach to cardiac and respiratory gating may shorten scanning times while maintaining image quality. SUBJECTS AND METHODS: We implemented an acquisition technique that uses subject-specific acquisition windows in the cardiac cycle and a motion-adapted gating window for respiratory navigator gating. Cardiac acquisition windows and trigger delays were determined individually from a coronary motion scan. Motion-adapted gating used a 2-mm acceptance window for the central 35% of k-space and a 6-mm window for the outer 65% of k-space. In 10 subjects, three-dimensional coronary MR angiograms of the right and left coronary systems were acquired with this technique (the "adaptive technique") as well as a conventional acquisition method, and the scanning times and image quality were compared. The adaptive technique was then applied prospectively to 40 patients who underwent coronary radiographic angiography. RESULTS: Scanning times with the adaptive technique were reduced by a factor of 2.3 for the right coronary artery and by a factor of 2.2 for the left coronary artery system compared with the conventional technique, mainly because we were able to use longer subject-specific acquisition windows in patients with low heart rates. Subjective and objective measurements of image quality showed no significant differences between the two techniques. Prospective evaluation of MR angiograms yielded a sensitivity and specificity of 74.3% and 88.2%, respectively, to detect significant coronary artery stenoses. CONCLUSION: Coronary MR angiography with subject-specific acquisition windows and motion-adapted respiratory gating reduces scanning times while maintaining image quality and provides high diagnostic accuracy for the detection of coronary artery stenosis.     

Analysis of injuries in long-distance triathletes

Triathlon is an individual sport consisting of three disciplines - swimming, cycling and running. Triathlon has changed from a novel appearance to a very popular Olympic sport within the last fifteen years. Nevertheless, there is not sufficient data about injuries in triathlon. The aim of this retrospective survey was to investigate the incidence of injuries according to class of injuries, anatomical sites and disciplines. Relations to age, sex, performance level, training habits and medical care were analysed. Questionnaires were sent to all German speaking participants of the Ironman Europe 2000. With a response rate of 35 %, 656 questionnaires met the inclusion criteria. At least one injury was experienced by 74.8 % (95 %-CI: 71.3-78.1) of all respondents during their active time in triathlon. 51.1 % (95 %-CI: 47.2-55.0) suffered one or more contusion/skin-abrasions, 33.1 % (95 %-CI: 29.5-36.8) muscle-/tendon-injuries, 29.0 % (95 %-CI: 25.5-32.6) ligament-/capsule-injuries and 11.9 % (95 %-CI: 9.5-14.6) fractures. Most of the injuries happened during cycling (54.8 % [95 %-CI: 51.9-57.8]) within training sessions. 18.7 % (95 %-CI: 16.4-21.2) of all injuries occurred while the athletes were competing. Considering the low number of competition hours per year, the incidence of injuries during competition was higher than during training session. Significant relations were found considering the age, performance level and weekly training hours of the triathletes. Older athletes sustained more fractures (p = 0.024), high performance athletes suffered more contusions/abrasions (p = 0.003) and muscle-tendon-injuries (p = 0.001) and athletes with a large number of weekly training hours suffered more muscle-tendon-injuries (p = 0.014). To summarize, injuries in triathlon seem to be related to age, performance level and weekly training hours, but not to sex, presence of training coach and medical care.     

Modulation of peripheral endogenous opioid analgesia by central afferent blockade

BACKGROUND: Peripheral tissue injury causes a migration of opioid peptide-containing immune cells to the inflamed site. The subsequent release and action of these peptides on opioid receptors localized on peripheral sensory nerve terminals causes endogenous analgesia. The spinal application of opioid drugs blocks the transmission of nociceptive information from peripheral injury. This study investigates the influence of exogenous spinal opioid analgesia on peripheral endogenous opioid analgesia. METHODS: Six and forty-eight hours after initiation of continuous intrathecal morphine infusion and administration of Freund's complete adjuvant into the hind paw of rats, antinociceptive and antiinflammatory effects were measured by paw pressure threshold, paw volume, and paw temperature, respectively. Inflammation and quantity of opioid-containing cells were evaluated by immunocytochemistry and flow cytometry. Cold water swim stress-induced endogenous analgesia was examined 24 h after discontinuation of intrathecal morphine administration. RESULTS: Intrathecal morphine (10 micro g/h) resulted in a significant and stable increase of paw pressure threshold ( P< 0.05) without changing inflammation, as evaluated by paw volume, paw temperature, and flow cytometry ( P> 0.05). At 48 but not at 6 h after Freund's complete adjuvant, the number of beta-endorphin-containing cells and cold water swim-induced antinociception were significantly reduced in intrathecal morphine-treated rats compared with those treated with intrathecal vehicle ( P< 0.05). CONCLUSIONS: These findings suggest an interplay of central and peripheral mechanisms of pain control. An effective central inhibition of pain apparently signals a reduced need for recruitment of opioid-containing immune cells to injured sites.