Posterior Bundle Research Articles

Comparison of diffusion tensor imaging and proton MR spectroscopy in the posterior cingulate of patients with Alzheimer disease

Objective To compare 1HMRS and DTI findings of Alzheimer disease (AD) patients and normal elderly controls. Methods Fifteen mild AD patients, 20 moderate to severe AD patients and 20 aging controlled normal subjects (CN) were recruited. MRS imaging and DTI were performed on a 1.5 T MRI scanner. A ROI was positioned in the posterior part of the cingulate. MRS data were processed and the metabolite ratios were estimated, including the ratios of NAA/Cr, Cho/Cr, mI/Cr. Comparing with the axial MRS location, we chose the same level to posit the ROIs on both sides of the posterior cingulated fibers on fractional anisotropy map (FA) and mean diffusivity map (MD). Mean spectroscopy data and DTI values for each groups were analysed with Mann-Whitney U non parametric test. Correlations between MRS and DTI values for AD groups were estimated using partial correlations test controlling for the age related bias. Results Compared to normal aging groups, mild AD group showed a significantly lower FA value in the left side of posterior cingulum bundle (0. 549±0. 056 vs 0. 517±0. 058,Z =2. 014,P <0. 05). Whereas, moderate to severe group versus mild AD group revealed significantly elevated MI) value and a decrease in FA value in the right side of posterior cingulate ( FA 0. 517 ± 0. 059 vs 0. 432 ± 0. 073, Z = 3. 216, P < 0. 01 ; MD (0.726±0.041) × 10-3 mm2/s vs (0.761±0.057) × 10-3 mm2/s,Z = 1.970,P <0.05) . Obvious increasing mI/Cr ratio was found in mild AD group ( 0. 61 ± 0. 07 vs 0. 68 ± 0. 12, Z = 2. 911, P < 0. 01 ). NAA/Cr ratio showed gradually decrease in AD groups. Partial correlations analysis revealed a positive correlation between ml/Cr ratio and left posterior cingulated FA value in mild AD group ( r = 0. 586, P < 0. 05) and negative correlation between NAA/Cr and MD value in the right side of posterior cingulated region ( r = - 0. 505, P < 0. 05 ). Conclusions These findings suggested that there were different regional and temporal pattern in different course of AD disease, resulting from axonal loss or gliosis. Combining MRS with DTI alternations could be a better potential indicator and could better explain the pathological changes in AD progression. Key words: Alzheimer disease; Magnetic resonance imaging; Magnetic resonance spectroscopy

In vivo anterior cruciate ligament elongation in response to axial tibial loads

BackgroundThe knowledge of in vivo anterior cruciate ligament (ACL) deformation is fundamental for understanding ACL injury mechanisms and for improving surgical reconstruction of the injured ACL. This study investigated the relative elongation of the ACL when the knee is subject to no load (<10 N) and then to full body weight (axial tibial load) at various flexion angles using a combined dual fluoroscopic and magnetic resonance imaging (MRI) technique. MethodsNine healthy subjects were scanned with MRI and imaged when one knee was subject to no load and then to full body weight using a dual fluoroscopic system (0°-45° flexion angles). The ACL was analyzed using three models: a single central bundle; an anteromedial and posterolateral (double functional) bundle; and multiple (eight) surface fiber bundles. ResultsThe anteromedial bundle had a peak relative elongation of 4.4% ± 3.4% at 30° and that of the posterolateral bundle was 5.9% ± 3.4% at 15°. The ACL surface fiber bundles at the posterior portion of the ACL were shorter in length than those at the anterior portion. However, the peak relative elongation of one posterolateral fiber bundle reached more than 13% whereas one anteromedial fiber bundle reached a peak relative elongation of only about 3% at 30° of flexion by increasing the axial tibial load from no load to full body weight. ConclusionsThe data quantitatively demonstrated that under external loading the ACL experiences nonhomogeneous elongation, with the posterior fiber bundles stretching more than the anterior fiber bundles.

A new knee arthrometer, the GNRB ®: Experience in ACL complete and partial tears

Clinical diagnosis of anterior cruciate ligament (ACL) tears (Lachman test and Pivot shift test in valgus and internal rotation) is reliable in case of complete ACL tear but reveals elusive in case of partial tears. Quantitative assessment of anterior tibial translation proves to be imprecise, subjective and poorly reproducible especially with the KT-1000 arthrometer. We developed the GNRB, an alternative original anterior knee laxity measurement device. The lower limb is placed in a rigid support with the knee at 0 degrees of rotation, the restraining power being recorded. A 0-250 N thrust force is transmitted by a jack to the upper segment of the calf. This force is only applied in the absence of hamstring muscles contraction. Displacement of the anterior tibial tubercle is recorded using a sensor with a 0.1mm precision. We hypothesize that this knee laxity measurement device is more reliable and reproducible than other currently available arthrometers. During a first validation study, the GNRB was compared to the KT-1000 arthrometer, in 20 pairs of healthy knees, measurements being performed by two investigators. Variance analyses were carried out at 134 N. In a second clinical study, 21 complete ACL tears (the notch is devoid of ACL) and 24 partial ACL tears (anterior or posterior bundle tear and cicatricial ACL remnant in continuity) were tested with these arthrometers to exact a differential laxity threshold value between both knees at 250 N. Statistical analysis was subsequently performed using variance and ROC curves analysis. The GNRB arthrometer reveals to be significantly more reproducible than the KT-1000, irrespectively of the tester's experience level. Moreover, unlike the KT-1000, the achieved measurement is independent from the uninvolved side. Reproducibility of laximetry proves to be significantly better with the GNRB than with the KT-1000, wherever the examiner's experience stands and whatever the evaluated side condition could be. When differential laxity threshold value was 3mm in complete ACL tears, sensitivity was 70% and specificity 99% at 134 N. Using a 1.5mm threshold value in ACL partial tears, the arthrometer sensitivity was 80% and specificity was 87% at 134 N. Reproducibility of laximetry was significantly better with the GNRB than the KT-1000 device, wherever the examiner's experience stands and whatever the evaluated side-condition could be. The GNRB reports various supplementary advantages compared with other available laximeters. Good control of the investigated limb position in rotation, recording of translation in the absence of hamstring muscles contraction and in direct comparison with the KT-1000: reproducibility, constant pressure, arthrometry improved accuracy and automated measurements recording. The GNRB might be used for diagnosis of partial and complete ACL tears and during follow-up of reconstructed or not ACL tears. type II. Prospective comparative study.

Abnormal integrity of association fiber tracts in amnestic mild cognitive impairment

The association fiber tracts integrity of the inter-hemispheric and within-hemispheric communication was poor understood in amnestic type mild cognitive impairment (aMCI) patients by diffusion tensor imaging (DTI). A region of interest-based DTI approach was applied to explore fiber tract differences between 22 aMCI patients and 22 well-matched normal aging. Correlations were also sought between fractional anisotropy (FA) values and the cognitive performance scores in the aMCI patients. Extensive impairment of association fiber tracts integrity was observed in aMCI patients, including bilateral inferior fronto-occipital fascicles, the genu of corpus callosum, bilateral cingulate bundles and bilateral superior longitudinal fascicles II (SLE II) subcomponent. In addition, the FA value of right SLE II was significantly negatively correlated to the performance of Trail Making Test A and B, whilst the values of right posterior cingulate bundle was significantly positive correlation with MMSE score. As aMCI is a putative prodromal syndrome to Alzheimer's disease (AD), this study suggested that investigation of association fiber tracts between remote cortexes may yield important new data to predict whether a patient will eventually develop AD.

Effect of the Posterior Bundle of the Medial Collateral Ligament on Elbow Stability

The role of the posterior bundle of the medial collateral ligament in stability of the elbow remains poorly defined. The purpose of this study was to determine the effect of sectioning the posterior bundle of the medial collateral ligament on the stability of the elbow. Varus and valgus gravity-loaded passive motion and simulated active vertical motion were performed on 11 cadaveric arms using an in vitro elbow motion simulator. Varus/valgus angle and internal/external rotation of the ulna with respect to the humerus were recorded using an electromagnetic tracking system in varus, valgus, and vertical orientations. Testing was performed on the intact elbow and after sectioning of the posterior bundle of the medial collateral ligament. With active flexion in the vertical position, the varus/valgus kinematics were unchanged after sectioning of the posterior bundle of the medial collateral ligament. However, in pronation, there was an increase in internal rotation after sectioning of the posterior bundle of the medial collateral ligament compared with that of the intact elbow. This rotational difference was not detected with the forearm in supination. During supinated passive flexion in the varus position, sectioning of the posterior bundle of the medial collateral ligament resulted in increased varus angulation at all flexion angles. In pronation, varus angulation and internal rotation both increased. In supination, sectioning of the posterior bundle of the medial collateral ligament had no effect on maximum varus-valgus laxity or maximum internal rotation. However, in pronation, the maximum varus-valgus laxity increased by 3.5 degrees (30%) and maximum internal rotation increased by 1.0 degrees (29%). These results indicate that isolated sectioning of the posterior bundle of the medial collateral ligament causes a small increase in varus angulation and internal rotation during both passive varus and active vertical flexion. This study suggests that isolated sectioning of the posterior bundle of the medial collateral ligament may not be completely benign and may contribute to varus and rotation instability of the elbow. In patients with insufficiency of the posterior bundle of the medial collateral ligament, appropriate rehabilitation protocols (avoiding forearm pronation and shoulder abduction) should be followed when other injuries permit.

Successful radio frequency catheter ablation of trigger PVC of idiopathic ventricular fibrillation originated from Purkinje fiber in the left anterior and posterior bundle branch ; A case report

Successful radio frequency catheter ablation of trigger PVC of idiopathic ventricular fibrillation originated from Purkinje fiber in the left anterior and posterior bundle branch ; A case report

Effect of the Posterior Bundle of the Medial Collateral Ligament on Elbow Stability

Effect of the Posterior Bundle of the Medial Collateral Ligament on Elbow Stability

Degradation of Association and Projection White Matter Systems in Alcoholism Detected with Quantitative Fiber Tracking

Excessive alcohol use can cause macrostructural tissue shrinkage with regional preference for frontal systems. The extent and locus of alcoholism's effect on white matter microstructure is less known. Quantitative fiber tracking derived from diffusion tensor imaging (DTI) assessed the integrity of samples of 11 major white matter bundles in 87 alcoholics (59 men, 28 women) and 88 healthy control subjects (42 men, 46 women). Fiber integrity was expressed as fractional anisotropy (FA) and apparent diffusion coefficient (ADC), quantified separately for longitudinal diffusivity (lambdaL), a putative index of axonal integrity, and transverse diffusivity (lambdaT), a putative index of myelin integrity. Alcoholism affected FA and diffusivity, particularly lambdaT, of several fiber bundles. Frontal and superior sites (frontal forceps, internal and external capsules, fornix, and superior cingulate and longitudinal fasciculi) showed greatest abnormalities in alcoholics relative to control subjects. More posterior and inferior bundles were relatively spared. Lifetime alcohol consumption correlated with regional DTI measures in alcoholic men but not women. When matched for alcohol exposure, alcoholic women showed more DTI signs of white matter degradation than alcoholic men in several fiber bundles. Among all alcoholics, poorer performance on speeded tests correlated with DTI signs of regional white matter degradation. This survey of multiple brain fiber systems revealed a differential pattern of alcoholism's effect on regional FA and diffusivity with functional consequences attributable in part to compromised fiber microstructure with prominence in signs of myelin degradation. Sex-based differences suggest that women are at enhanced risk for alcoholism-related degradation in selective white matter systems.

Signification of the unusual delineation of the anterior meniscofemoral ligament of Humphrey during knee arthro-CT

Meniscofemoral ligaments (MFLs) are recognized as stabilizing and protective structures for the posterolateral meniscocondylar compartment of the knee, and as secondary restraints to tibial posterior translation. We report the 64-row arthro-MDCT findings of 10 patients (8 males, 2 females; mean age 43.8 years) in which the anterior MFL of Humphrey (aMLF) was atypically well delineated by an unusual circumferential effusion of iodine contrast. We discuss a possible physiopathologic mechanism for this effusion, describe the MDCT anatomy of the aMLF and review the literature about the anatomy and physiology of the MFLs. In each of our ten patients an unusual effusion of articular contrast was found delineating a posterior oblique ligamentar bundle, which was running in front of the posterior cruciate ligament (PCL). This bundle was best appreciated on posterior coronal oblique and sagital MPR views, and was recognized as the aMFL. The finding was associated with a partial tear of the tibial insertion of the posterior horn (PH) of the lateral meniscus (LM) in three patients, and with a partial (two cases) or subtotal (three cases) tear of the PCL in five patients. A swollen-probably oedematous-PCL was found in another patient and in the last case the anomaly was minimal and remained isolated. All patients were treated conservatively. Since the aMFL inserts inferiorly into the posterior horn of the LM and runs in very close anatomic and functional relation with the PCL, we hypothesize that a trauma producing a tear in these structures may also occasionally sufficiently stretch the aMFL to produce a peripheral loosening allowing a circumferential effusion of opacified synovial fluid around the ligament. Our report offers the opportunity to illustrate the "in vivo" anatomy of the aMFL through original unpublished figures. It also contributes to reinforce the literature data concerning the potential fine mechanical role played by the LM-MFLs-PCL complex, in which the centrally located MFLs act laterally as stabilizing and protective structures for the posterolateral meniscocondylar compartment and medially as secondary restraints to tibial posterior translation.

Brain Structural Changes in Obstructive Sleep Apnea

Determine whether obstructive sleep apnea (OSA) subjects show indications of axonal injury. We assessed fiber integrity in OSA and control subjects with diffusion tensor imaging (DTI). We acquired four whole-brain DTI series from each subject. The four series were realigned, and the diffusion tensor calculated at each voxel. Fractional anisotropy (FA), a measure of fiber integrity, was derived from the diffusion tensor, resulting in a whole brain FA "map." The FA maps were spatially normalized, smoothed, and compared using voxel-based statistics to determine differences between OSA and control groups, with age as a covariate (P < 0.05, corrected for multiple comparisons). University medical center. We studied 41 patients with untreated OSA (mean age +/- SD: 46.3 +/- 8.9 years; female/male: 7/34) with apnea-hypopnea index 15 to 101 (mean +/- SD: 35.7 +/- 18.1 events/hour), and 69 control subjects (mean age +/- SD: 47.5 +/- 8.79 years; female/male: 25/44). Multiple regions of lower FA appeared within white matter in the OSA group, and included fibers of the anterior corpus callosum, anterior and posterior cingulate cortex and cingulum bundle, right column of the fornix, portions of the frontal, ventral prefrontal, parietal and insular cortices, bilateral internal capsule, left cerebral peduncle, middle cerebellar peduncle and corticospinal tract, and deep cerebellar nuclei. White matter is extensively affected in OSA patients; the alterations include axons linking major structures within the limbic system, pons, frontal, temporal and parietal cortices, and projections to and from the cerebellum.

Double-bundle PCL and Posterolateral Corner Reconstruction Components are Codominant

A more complete biomechanical understanding of a combined posterior cruciate ligament and posterolateral corner knee reconstruction may help surgeons develop uniformly accepted clinical surgical techniques that restore normal anatomy and protect the knee from premature arthritic changes. We identified the in situ force patterns of the individual components of a combined double-bundle posterior cruciate ligament and posterolateral corner knee reconstruction. We tested 10 human cadaveric knees using a robotic testing system by sequentially cutting and reconstructing the posterior cruciate ligament and posterolateral corner. The knees were subjected to a 134-N posterior tibial load and 5-Nm external tibial torque. The posterior cruciate ligament was reconstructed with a double-bundle technique. The posterolateral corner reconstruction included reattaching the popliteus tendon to its femoral origin and reconstructing the popliteofibular ligament. The in situ forces in the anterolateral bundle were greater in the posterolateral corner-deficient state than in the posterolateral corner-reconstructed state at 30 degrees under the posterior tibial load and at 90 degrees under the external tibial torque. We observed no differences in the in situ forces between the anterolateral and posteromedial bundles under any loading condition. The popliteus tendon and popliteofibular ligament had similar in situ forces at all flexion angles. The data suggest the two bundles protect each other by functioning in a load-sharing, codominant fashion, with no component dominating at any flexion angle. We believe the findings support reconstructing both posterior cruciate ligament bundles and both posterolateral corner components.

A Concerted Action of Engrailed and Gooseberry-Neuro in Neuroblast 6-4 Is Triggering the Formation of Embryonic Posterior Commissure Bundles

One challenging question in neurogenesis concerns the identification of cues that trigger axonal growth and pathfinding to form stereotypic neuronal networks during the construction of a nervous system. Here, we show that in Drosophila, Engrailed (EN) and Gooseberry-Neuro (GsbN) act together as cofactors to build the posterior commissures (PCs), which shapes the ventral nerve cord. Indeed, we show that these two proteins are acting together in axon growth and midline crossing, and that this concerted action occurs at early development, in neuroblasts. More precisely, we identified that their expressions in NB 6-4 are necessary and sufficient to trigger the formation of the PCs, demonstrating that segmentation genes such as EN and GsbN play a crucial role in the determination of NB 6-4 in a way that will later influence growth and guidance of all the axons that form the PCs. We also demonstrate a more specific function of GsbN in differentiated neurons, leading to fasciculations between axons, which might be required to obtain PC mature axon bundles.

Release of the medial collateral ligament to improve flexion in post-traumatic elbow stiffness

Contracture of the collateral ligaments is considered to be an important factor in post-traumatic stiffness of the elbow. We reviewed the results of isolated release of the medial collateral ligament in a series of 14 patients with post-traumatic loss of elbow flexion treated between 1998 and 2002. There were nine women and five men with a mean age of 45 years (17 to 76). They were reviewed at a mean follow-up of 25 months (9 to 48). The operation was performed through a longitudinal posteromedial incision centred over the ulnar nerve. After decompression of the ulnar nerve, release of the medial collateral ligament was done sequentially starting with the posterior bundle and the transverse component of the ligament, with measurement of the arc of movement after each step. If full flexion was not achieved the posterior half of the anterior bundle of the medial collateral ligament was released. At the latest follow-up, the mean flexion of the elbow improved significantly from 96 degrees (85 degrees to 115 degrees ) pre-operatively to 130 degrees (110 degrees to 150 degrees ) at final follow-up (p = 0.001). The mean extension improved significantly from 43 degrees (5 degrees to 90 degrees ) pre-operatively to 22 degrees (5 degrees to 40 degrees ) at final follow-up (p = 0.003). There was a significant improvement in the functional outcome. The mean Broberg and Morrey score increased from a mean of 54 points (29.5 to 85) pre-operatively to 87 points (57 to 99) at final follow-up (p < 0.001). All the patients had normal elbow stability. Our results indicate that partial surgical release of the medial collateral ligament is associated with improved range of movement of the elbow in patients with post-traumatic stiffness, but was less effective in controlling pain.

左内側後頭頭頂葉病変で発症したｐｏｓｔｓｔｒｏｋｅ ｄｅｍｅｎｔｉａの１例

We report herein a patient of poststroke dementia (PSD) following left medial occipitoparietal hemorrhage triggered by drainage of an acute traumatic subdural hematoma. The patient, an independent 73-year-old man, became dependent due to dementia. Cognitive dysfunction was characterized by moderately decreased IQ, severe memory disturbances, topographical disorientation, executive dysfunction and loss of self-awareness. Cognitive dysfunction has not advanced for 3 years. Hypo-perfusion in the whole brain, particularly in the left temporal and parietal regions, was visible on 123I-IMP SPECT images. Magnetic resonance imaging demonstrated damage to the left posterior cingulate cortex, cingulate bundle, superior parietal lobule and subcortical region of the occipital lobe. The fornix was spared. Some subcortical small spotted lesions were detected, but periventricular lucency was not prominent. Structures known to be important in memory but spared by the lesion included the thalamus and basal forebrain. Small spotted subcortical lesions were detected in bilateral hippocampi, which are also known to be important in memory, but these were probably silent lesions. This case suggested that dementia is brought on by the lesion of the left posterior cingulate bundle and retrosplenial cortex causing amnesia by disrupting the cingulate-hippocampal connection or the retrosplenial cortex itself, with the lesion of the left occipitoparietal subcortex causing frontal dysfunction by disrupting the dorsal limbic pathway and occipitofrontal fasciculus of the prefrontal circuits.

Ligament fibre recruitment of the elbow joint during gravity-loaded passive motion: An experimental study

Background Knowledge of elbow collateral ligament length during passive motion is essential in understanding ligament physiology and pathology, such as tightness and instability. Methods Five anatomical unembalmed specimens were passively placed in six flexion positions together with three forearm rotations, using equipment with gravity as motion force. These 18 positions were recorded using CT-scan. Three-dimensional data of ligament insertions were obtained through anatomical millimetre sections. Ligament length was measured in each position. Findings In neutral rotation, the lateral collateral ligament was long between 0° and 30° as well as at 90°, and short between about 60° and 120° of flexion. In pronation, it was long at about 0° and between 60° and 120°, short at about 30° of flexion. In supination, it was long at about 30° and 90° and short between 120° and 150° of flexion. In any forearm rotation, the highest length of the anterior bundle of the ulnar collateral ligament was measured at about 90°, its smallest length between 120° and 150° of flexion, position at which the posterior bundle length was greatest. Interpretation At 60° of flexion, the collateral ligaments were slackened in any forearm rotations. Forearm rotation plays an indirect role in the posterolateral stability of elbow as it changes length of the lateral collateral ligament. This ligament can be tested passively at 90° of flexion in supination, the anterior bundle of the ulnar collateral ligament between 0° and 30° in neutral rotation and the posterior bundle between 120° and 150° in neutral rotation.

Function of Posterior Cruciate Ligament Bundles during in Vivo Knee Flexion

Background The biomechanical functions of the anterolateral and posteromedial bundles of the posterior cruciate ligament over the range of flexion of the knee joint remain unclear. Hypothesis The posterior cruciate ligament bundles have minimal length at low flexion angles and maximal length at high flexion angles. Study Design Descriptive laboratory study. Methods Seven knees from normal, healthy subjects were scanned with magnetic resonance, and 3-dimensional models of the femur, tibia, and posterior cruciate ligament attachment sites were created. The lines connecting the centroids of the corresponding bundle attachment sites on the femur and tibia represented the anterolateral and posteromedial bundles of the posterior cruciate ligament. Each knee was imaged during weightbearing flexion (from 0° to maximal flexion) using a dual-orthogonal fluoroscopic system. The length, elevation, deviation, and twist of the posterior cruciate ligament bundles were measured as a function of flexion. Results The lengths of the anterolateral and posteromedial bundles increased with flexion from 0° to 120° and decreased beyond 120° of flexion. The posteromedial bundle had a lower elevation angle than the anterolateral bundle beyond 60° of flexion. The anterolateral bundle had a larger deviation angle than the posteromedial bundle beyond 75° of flexion. The femoral attachment of the posterior cruciate ligament twisted externally with increasing flexion and reached a maximum of 86.4° ± 14.7° at 135° of flexion (P < .05). Conclusion These data suggest that there is no reciprocal function of the bundles with flexion, which is contrary to previous findings. The orientation of the anterolateral and posteromedial bundles suggests that at high flexion, the anterolateral bundle might play an important role in constraining the mediolateral translation, whereas the posteromedial bundle might play an important role in constraining the anteroposterior translation of the tibia. Clinical Relevance These data provide a better understanding of the biomechanical function of the posterior cruciate ligament bundles and may help to improve the design of the 2-bundle reconstruction techniques of the ruptured posterior cruciate ligament.

EXPERIMENTAL EVALUATION OF 3-DIMENSIONAL KINEMATIC BEHAVIOR OF THE CRUCIATE LIGAMENTS

The purpose of this study was to evaluate a low-cost and easily reproducible technique for biomechanical studies in cadavers. In this kind of study, the natural effect of loading of the joint and shear forces are not taken into account. The objective is to describe the plastic deformation of the ligaments into 3-dimensional space. For 18 intact human cadaver knees, the cruciate ligaments were divided into 3 fiber bundles, the tibial or femoral fixation points were marked, and 2 perpendicular different x-ray exposures were performed, thus obtaining radiographs of spatial projections of the bundle in 3 anatomic planes (frontal, sagittal, and transversal). From the measurements made on the x-ray films, we obtained the average distance between the 2 fixation points of the cruciate ligaments on the tibia and the femur at 4 different flexion angles. The distance between the fixation points of the medial and lateral fiber bundles of the cruciate ligaments did not change significantly during movement. There were, however, significant variations (P < .05) in the distance between the fixation points of the posterior fiber bundles of the anterior cruciate ligament and the anterior fiber bundles of the posterior cruciate ligament. This technique was efficient for demonstrating the plastic deformability of the cruciate ligaments. The results proceeding from this type of study can assist in the planning of physical rehabilitation programs.

Dementia in Parkinson?s disease: diffusion tensor imaging

Dementia occurs frequently in patients with Parkinson's disease (PD). However, the nature of the dementing process remains controversial. We evaluated various cognitive functions in patients with PD, compared fractional anisotropy (FA) values between PD patients with and without dementia. Thirty-seven consecutive patients with Hoehn-Yahr stage III or IV PD participated in this study. Patients were divided into two groups: (i) PD with dementia group (PDD) and (ii) PD without dementia group (PDND). There were 11 PDD and 26 PDND cases. Ten controls were also studied. The PDD group showed significant FA reduction in the bilateral posterior cingulate bundles compared with PDND. FA values in the left posterior cingulate bundle showed significant correlations with many cognitive parameters. Our results showed that the posterior cingulate areas play some important roles in the dementing process in PDD. However, as the pathological processes responsible for dementia in PD patients may be multifaceted, further studies are necessary.

Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark

The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus. The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25 degrees C for Triakis and 15 to 28 degrees C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6-0.65 L) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20 degrees C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25 degrees C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28 degrees C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15 degrees C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.

The three-dimensional architecture of the human styloglossus especially its posterior muscle bundles

The arrangement of the lingual muscles in the interior of the human tongue, particularly the course of the posterior muscle bundles of the styloglossus, was studied by gross anatomical examination and SEM, and its relationship with tongue functions was considered. The styloglossus divided into anterior and posterior fiber bundles. The bilateral anterior fiber bundles ran anteriorly, and fused at the median region of the lower surface of the tongue, forming a large arched structure. The posterior bundles divided into 10 or more smaller bundles and entered the interior of the tongue. These muscle bundles passed through the spaces between the inferior longitudinal and genioglossus and inserted in the lingual septum, forming a small arched structure. These posterior muscle bundles passed near the midpoint between the central third and dorsal third of the line between the mental spine and the dorsal surface of the tongue in the upper half of the root of the tongue, showing a multilayer structure. In many of the areas in which posterior muscle bundles were distributed, muscle bundles in the tongue were arranged along the posterior muscle bundles of the styloglossus, glossopharyngeal bundles of the superior pharyngeal constrictor muscle, and transverse muscle of the tongue from the deep layer to the dorsal surface of the tongue.