Expression of neurotrophin trk and p75 receptors in quail embryos undergoing gastrulation and neurulation

We have previously demonstrated the presence of mRNA for the full-length neurotrophin receptors trkA, trkB and trkC in quail embryos from stages 1 through 6 using reverse transcription followed by the polymerase chain reaction (RT-PCR; Yao et al. [1994] Dev. Biol. 165: 727-730). Furthermore, we showed that mRNA for the neurotrophins brain-derived neurotrophic factor and neurotrophin-3 was present from stage 1 onward, while nerve growth factor mRNA began to be expressed at stage 5. In the present study, wholemount in situ hybridization was used to localize full-length trk mRNA in embryos from stages 3 through 10. Structures expressing trkC mRNA included the primitive streak and Hensen's node, the neural plate or notochord, somites and the rostral neural tube. trkA and trkB mRNA were expressed at much lower levels than trkC mRNA; however, staining was detected on the primitive streak and Hensen's node. In addition to trk mRNA, we have also demonstrated the presence of full-length Trk protein in embryos from stages 3 through 11, suggesting that the trk mRNA detected at these early stages is translated into functional cell surface receptors. To support this hypothesis, we have shown that neurotrophins can induce phosphorylation of Trk on tyrosine residues, at least at stage 11. We also detected mRNA and protein for the nontyrosine kinase neurotrophin receptor, p75, at similar stages. The presence of neurotrophin receptors, as well as neurotrophin mRNA, in embryos undergoing gastrulation and neurulation leads to speculation that neurotrophins may be playing a role in these processes.

Nonparametric learning of decision regions via the genetic algorithm

A method for nonparametric (distribution-free) learning of complex decision regions in n-dimensional pattern space is introduced. Arbitrary n-dimensional decision regions are approximated by the union of a finite number of basic shapes. The primary examples introduced in this paper are parallelepipeds and ellipsoids. By explicitly parameterizing these shapes, the decision region can be determined by estimating the parameters associated with each shape. A structural random search type algorithm called the genetic algorithm is applied to estimate these parameters. Two complex decision regions are examined in detail. One is linearly inseparable, nonconvex and disconnected. The other one is linearly inseparable, nonconvex and connected. The scheme is highly resilient to misclassification errors. The number of parameters to be estimated only grows linearly with the dimension of the pattern space for simple version of the scheme.

Incidental magnetization transfer contrast in fast spin-echo imaging of cartilage

In this article, the authors illustrate the contributions of incidental magnetization transfer contrast (MTC) to the signal characteristics of patellar cartilage on routine, multiplanar fast spin-echo (FSE) images. Incidental MTC diminishes the signal of patellar cartilage by 30% on routine FSE scans. Spectral fat saturation does not significantly increase incidental MTC on multislice FSE acquisitions. By increasing the contrast between synovial fluid and patellar cartilage, incidental MTC may account for greater conspicuousness of chondromalacia on FSE as compared to conventional spin-echo images. Incidental MTC may also alter or obscure the normal, laminar appearance of hyaline cartilage on short-TE, FSE images.

Magnetic resonance imaging of plantar plate rupture

Degenerative plantar plate failure is an under-recognized cause of lesser metatarsalgia. We performed magnetic resonance imaging (MRI) with a small receiver coil in 13 patients in whom plantar plate ruptures of the second or third metatarsophalangeal joint were clinically suspected. In eight patients, MRI showed focal hyperintensity in the plantar plate that was interpreted as a rupture of the plate. Ruptures were confirmed in all five patients who underwent an operative procedure to treat the unstable, painful metatarsophalangeal joint. MRI is a noninvasive technique that can visualize plantar plate abnormalities and aid the clinical evaluation of problematic lesser metatarsalgia.

Locally focused MRI

Conventional magnetic resonance images are reconstructed by Fourier transformation and have uniform spatial resolution across the entire field of view (FOV). This paper describes a way of creating MR images that have higher spatial resolution in some areas than in others. High resolution imaging can be confined to just those areas where it is necessary to resolve strong edges without truncation artifact. Such locally focused images can be acquired in less scan time than that required to image the entire FOV with uniformly high resolution. Images are reconstructed from a subset of the usual phase-encoded signals required to create a uniformly well-resolved image. The measured signals are usually nonuniformly scattered in k-space. Functional and interventional imaging may benefit from this technique, which makes it possible to acquire a rapid series of dynamical images that have high resolution in areas of expected change and lower resolution elsewhere. Spectroscopic images may be improved by using high resolution in the neighborhood of sharp edges (e.g., scalp lipids) that might otherwise cause truncation artifacts.

Activation and interaction with protein kinase C of a cytoplasmic tyrosine kinase, Itk/Tsk/Emt, on Fc epsilon RI cross-linking on mast cells

Cross-linking of the high-affinity IgE receptor (Fc epsilon RI) on mast cells induces rapid phosphorylation on serine, threonine, and tyrosine residues and increases the enzymatic activity, of a Tec subfamily tyrosine kinase, Itk/Tsk/Emt (Emt). The pleckstrin homology domain of Emt at its amino-terminal interacts directly with multiple isoforms of protein kinase C (PKC) in vitro. In addition, a portion of Emt is physically associated with multiple isoforms of PKC in intact mast cells. PKC phosphorylates a bacterial fusion protein containing the pleckstrin homology domain of Emt in vitro. Coexpression of Emt in COS-7 cells with Ca(2+)-dependent PKC isoforms (alpha, beta I, or beta II) induces an enhancement in tyrosine phosphorylation of Emt. In vivo inhibition of PKC expression or activity attenuates tyrosine phosphorylation and enzymatic activity of Emt induced upon Fc epsilon RI cross-linking. These data collectively suggest that PKC phosphorylates Emt and activates its autophosphorylating activity. Alternatively, PKC could activate another tyrosine kinase that phosphorylates Emt, or PKC-mediated phosphorylation of Emt may render it a target for another tyrosine kinase. In any case, PKC appears to play a major role in the activation of Emt induced upon Fc epsilon RI cross-linking.

Activation and interaction with protein kinase C of a cytoplasmic tyrosine kinase, Itk/Tsk/Emt, on Fc epsilon RI cross-linking on mast cells

Cross-linking of the high-affinity IgE receptor (Fc epsilon RI) on mast cells induces rapid phosphorylation on serine, threonine, and tyrosine residues and increases the enzymatic activity, of a Tec subfamily tyrosine kinase, Itk/Tsk/Emt (Emt). The pleckstrin homology domain of Emt at its amino-terminal interacts directly with multiple isoforms of protein kinase C (PKC) in vitro. In addition, a portion of Emt is physically associated with multiple isoforms of PKC in intact mast cells. PKC phosphorylates a bacterial fusion protein containing the pleckstrin homology domain of Emt in vitro. Coexpression of Emt in COS-7 cells with Ca(2+)-dependent PKC isoforms (alpha, beta I, or beta II) induces an enhancement in tyrosine phosphorylation of Emt. In vivo inhibition of PKC expression or activity attenuates tyrosine phosphorylation and enzymatic activity of Emt induced upon Fc epsilon RI cross-linking. These data collectively suggest that PKC phosphorylates Emt and activates its autophosphorylating activity. Alternatively, PKC could activate another tyrosine kinase that phosphorylates Emt, or PKC-mediated phosphorylation of Emt may render it a target for another tyrosine kinase. In any case, PKC appears to play a major role in the activation of Emt induced upon Fc epsilon RI cross-linking.

Measurement of acetabular version on the axiolateral radiograph

There are 3 definitions of acetabular version: true (anatomic) version, planar (radiographic) version, and operative version. Although planar version can be measured on standard radiographs, the measurement may be inaccurate when applied to metal-backed acetabular components. However, another version angle is depicted clearly on an angled, cross-table lateral radiograph of the hip--the axiolateral view, and this angle readily distinguishes anteversion from retroversion. If the angle of the xray beam is known or is standardized, version measured on the axiolateral view can be converted to the other version angles. Nomograms for these conversions are presented. In most cases, acetabular version measured on the axiolateral radiograph closely approximates planar version.

Uncomplicated cat-scratch disease: findings at CT, MR imaging, and radiography

PURPOSE

To describe the epidemiologic, clinical, and imaging features of cat-scratch disease (CSD) to facilitate prompt recognition and noninvasive diagnosis of this condition.

MATERIALS AND METHODS

Eight otherwise healthy patients with pet cats presented with the subacute onset of epitrochlear, axillary, or groin masses. All underwent cross-sectional imaging with computed tomography (CT) (n = 1) or magnetic resonance (MR) imaging (n = 7). Five patients underwent radiography of the elbow.

RESULTS

In all patients, MR imaging and CT showed a poorly defined soft-tissue mass with extensive surrounding edema in an efferent lymphatic distribution. Radiography revealed only soft-tissue edema in two patients and an ill-defined soft-tissue mass with soft-tissue edema in three patients. Six patients underwent biopsy; the findings of all pathologic specimens supported the diagnosis of CSD. No patients underwent serologic evaluation. All patients were asymptomatic within 4 weeks of beginning antibiotic therapy.

CONCLUSION

CSD should be considered in all patients with upper extremity or head and neck adenopathy and a history of cat exposure. Although generally not required for diagnosis, cross-sectional imaging will reveal a mass with surrounding edema in an area of lymphatic drainage.

Partial ACL rupture: an MR diagnosis?

PURPOSE

We sought to clarify the ability of magnetic resonance imaging (MR) to show partial anterior cruciate ligament (ACL) ruptures and to allow distinction of partial from complete ACL ruptures.

MATERIALS AND METHODS

Eighty-eight patients were studied by arthroscopy and MR (36 with normal ACLs, 21 with partial ACL ruptures, and 31 with complete ACL ruptures). MR studies were interpreted by an experienced, blinded reader. MR examinations were also independently scored with respect to four primary and seven secondary signs, and these data were analyzed using discriminant analysis.

RESULTS

The sensitivity of MR is lower for partial than for complete ACL ruptures. Most detected partial ACL ruptures resemble complete ruptures on MR. Secondary signs do not significantly improve detection of partial ACL ruptures, but they do help to distinguish partial from complete ACL ruptures. Displacement of the posterior horn of the lateral meniscus and popliteus muscle injury are indicative of complete ACL rupture.

CONCLUSIONS

The majority of partial ACL ruptures are shown by MR, but MR is less sensitive for partial than for complete ACL rupture. The distinction of partial from complete ACL rupture on MR examination, while problematic, is slightly improved by assessment of secondary signs.

MR findings in peroneal tendonopathy

OBJECTIVE

The purpose of this presentation is to familiarize the reader with the often subtle findings of peroneal tendon derangement on MRI examination.

MATERIALS AND METHODS

We present four patients who were studied with MR (1.5 T) prior to surgical exploration of the peroneal tunnel. All patients had lateral ankle symptoms for > 6 months. Normal MR anatomy and an example of the peroneus quartus tendon are also shown.

RESULTS

Surgery revealed two peroneus brevis and three peroneus longus lesions. A "multipartite" appearance of the peroneus tendon on axial MR images, especially when paired with a "flame-shaped" appearance on more distal axial images, indicates a longitudinal tendon split. Both patients with peroneus brevis tendon splits had insufficient superior peroneal retinacula.

CONCLUSION

Partial ruptures of the peroneal tendons characteristically take the form of longitudinal tendon splits. Axial MR images through the ankle and hindfoot can help distinguish peroneal tendonitis from longitudinal tendon splits.

Internalization of Staphylococcus aureus by endothelial cells induces cytokine gene expression

The ability of the vascular endothelium to elaborate cytokines in response to gram-positive sepsis has received limited attention. This study examined cytokine expression by human umbilical vein endothelial cells (EC) following infection with a gram-positive bacterial pathogen, Staphylococcus aureus. S. aureus infection of EC resulted in the production of interleukin-6 (IL-6) and IL-1 beta. For IL-6, message was detected at 3 h after infection, protein was present at 24 h, and both message and protein persisted for 72 h. IL-1 beta message was detected at 12 h, IL-1 beta protein was detected at 24 h, and both persisted for 72 h. Message for colony-stimulating factor 1 remained unaltered. UV-killed S. aureus also elicited IL-1 beta and IL-6 message and protein expression at 24 and 48 h. Twenty-one clinical isolates of S. aureus were tested, and all induced IL-6 release by 48 h. However, the laboratory strain 8325-4 did not induce cytokine expression at any time point and was internalized by EC 1,000-fold less than other strains were. Internalization of latex beads by EC did not induce IL-6 gene expression. Furthermore, cytochalasin D treatment of the EC prevented IL-1 and IL-6 induction by S. aureus but not by tumor necrosis factor alpha or lipopolysaccharide. These results indicate that S. aureus is a potent inducer of IL-1 and IL-6 in EC and that internalization of S. aureus by EC is necessary for their cytokine expression. Thus, our data suggest that the vascular endothelium may play an important role in the pathogenesis of septicemia caused by gram-positive organisms.

The identification of proliferating cell nuclear antigen (PCNA) on rat tissue cryosections and its application to double immunostaining with other markers

Proliferating cell nuclear antigen (PCNA) in a useful marker for monitoring cell proliferation in most species. The immunostaining of PCNA on tissue cryosections, however, has been hampered by a loss of PCNA immunoreactivity during the staining process. The need for both identifying the actual phenotypes of proliferating cells and differentiating them from other tissue components prompted us to establish reliable techniques for PCNA immunostaining on cryosections and to apply these to double immunostainings with other markers. We tested various fixing conditions for rat tissue cryosections and the effect derived from unmasking with pepsin digestion to restore PCNA immunoreactivity after fixation. For single immunostainings, the unmasking was effective in most fixing conditions tested. Particularly, 4% paraformaldehyde/0.05% glutaraldehyde fixation followed by 0.001% pepsin digestion resulted in the strongest immunoreactivity for PCNA and the best morphology, and was the first choice for double immunostainings with relatively stable second antigens. Alternatively, periodate-lysine-paraformaldehyde fixation was also applicable to other second antigens which are labile to the former treatment. These techniques can serve in the collection of important information from frozen tissues regarding the relationship between PCNA and other markers of interest which are usually susceptible to routine formalin and/or paraffin embedding.

Anterior cruciate ligament tear: indirect signs at MR imaging

PURPOSE

To establish the sensitivity and specificity of indirect signs at magnetic resonance (MR) imaging of anterior cruciate ligament (ACL) tear.

MATERIALS AND METHODS

MR images of the knees of 89 consecutive patients (54 with torn and 35 with normal ACLs) were reviewed.

RESULTS

The indirect signs were as follows (first percentage is sensitivity; the second, specificity): angle between lateral tibial plateau and ACL less than 45 degrees (90%, 97%); angle between Blumenstaat line and ACL more than 15 degrees (89%, 100%); bone contusions in lateral compartment (54%, 100%); position of posterior cruciate ligament (PCL) line (52%, 91%); PCL angle less than 107 degrees (52%, 94%); PCL bowing ratio more than 0.39 (34%, 100%); posterior displacement of lateral meniscus more than 3.5 mm (44%, 94%); anterior displacement of tibia more than 7 mm (41%, 91%); and lateral femoral sulcus deeper than 1.5 mm (19%, 100%).

CONCLUSION

Because the specificity is high, the presence of indirect signs corroborates the diagnosis of ACL tear. Because the sensitivity is low, the absence of these signs does not exclude the diagnosis of ACL tear.

The potential role of nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 in avian cochlear and vestibular ganglia development

The role of the nerve growth factor family of neurotrophins in the development of cochlear and vestibular ganglia is unclear. In order to predict the potential importance of nerve growth factor, brain-derived neurotrophic factor or neurotrophin-3, we examined the expression of neurotrophin mRNA and full-length neurotrophin receptor mRNA by in-situ hybridization and reverse transcription-polymerase chain reaction, as well as whether high affinity 125I-nerve growth factor binding was present, in cochlear and vestibular ganglia of the quail at several stages of development (stages 26, 31 and 36). Nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 mRNA was detected at all ages examined, suggesting that these neurotrophins may serve an autocrine or paracrine function, especially prior to target contact. In addition, we found full-length trkA and trkC mRNA was expressed, the products of which are the functional neuronal receptors for nerve growth factor and neurotrophin-3, respectively. Although full-length trkA mRNA was found, physiologically important high affinity 125I-nerve growth factor binding was not detected. Since nerve growth factor's effects on survival and neurite outgrowth are mediated through high affinity binding, nerve growth factor may serve an as yet unidentified role in this system. Full-length trkB mRNA, the product of which is the functional neuronal receptor for brain-derived neurotrophic factor, was not detected using reverse transcription-polymerase chain reaction, however, truncated (non-catalytic) trkB was present, at least in cochlear ganglia at stage 31. It is not known what function may be subserved by these truncated receptors.

Expression of trk and neurotrophin mRNA in dorsal root and sympathetic ganglia of the quail during development

The nerve growth factor (NGF) family of neurotrophins exerts effects by binding to products of the trk family of proto-oncogenes. We examined the expression of both trk and neurotrophin mRNA during the entire range of development of quail dorsal root ganglia (DRG) and sympathetic ganglia (SG) using in situ hybridization and reverse transcriptase-polymerase chain reaction (RT-PCR). TrkC mRNA was present in neurons or their precursors from the time of formation of DRG (stage 18, embryonic day 2.5 [E2.5]) and throughout development. The number of labeled cells changed, however, from a majority to a minority at later developmental stages. Expression of trkA mRNA was not detected in DRG until stage 30 (E6) by in situ hybridization, although results with RT-PCR were positive at stage 23 (E3.5). Labeling was always detected on a majority of neurons or their precursors. SG exhibited low levels of trkC mRNA during the later stages of development, whereas trkA mRNA was present from stage 34 onward in most neurons. We have also shown that NGF, neurotrophin-3 (NT-3), and brain-derived neurotrophic factor (BDNF) mRNA were present at all stages examined (stages 23 through 45 for DRG, stages 35-36 and 45 for SG). In DRG, NGF mRNA expression was limited to support cells, whereas NT-3 and BDNF mRNA were detected in both neurons and support cells. These results suggest that neurotrophins could serve a local function in developing ganglia, which can be correlated with the presence of their respective receptors.

Case report 878: Densely calcifying synovial sarcoma of the hip metastatic to the lungs

We discuss a patient with an occult, densely calcified synovial sarcoma of the hip who came to clinical attention because of pulmonary metastases. When synovial sarcomas present with dense and conglomerate calcification, they may be confused with benign processes such as myositis ossificans or tumoral calcinosis. Malignancies such as extraskeletal osteogenic sarcoma, extraskeletal chondrosarcoma, and mesenchymal chondrosarcoma must also be considered in the differential diagnosis.

Labrocapsular ligamentous complex of the shoulder: normal anatomy, anatomic variation, and pitfalls of MR imaging and MR arthrography

Magnetic resonance (MR) imaging is a useful modality for evaluating the labrocapsular ligamentous complex (LCLC) of the shoulder. MR arthrography is an important and occasionally indispensable supplementary modality for accurate differentiation between normal and deranged glenohumeral joints. Because of the joint distention that occurs during MR arthrography, it is especially helpful in detecting subtle capsular derangement, as occurs in patients with atraumatic instability. Also, some of the pitfalls associated with MR imaging of the LCLC are less likely to occur with MR arthrography. Radiologists should look for several key abnormalities when evaluating MR images of the shoulder: an anterior or posterior Bankart lesion; a Hill-Sachs defect; a tear of the rotator cuff, glenoid labrum, or superior labrum-biceps tendon attachment; and loose bodies. Knowledge of normal anatomy, normal variations, and pitfalls in image interpretation related to evaluation of the LCLC will help the radiologist accurately detect debilitating derangements associated with glenohumeral instability.

Statistical concepts in the interpretation of serial bone densitometry

The precision of a measurement can be expressed as the variance of multiple measurements. The coefficient of variation is a dimensionless expression of precision that is prevalent in the radiology literature. However, the coefficient of variation has important limitations. The question whether measured change is significant arises whenever any quantitative clinical parameter is followed over time. When serial bone mineral density measurements are made, change is commonly estimated as the slope of a line fitted to the serial data by linear regression. Confidence intervals for change based on this method usually assume that the precision error in measurement remains constant over time and that change is truly linear. Estimates of long-term precision may be elusive, and if constant, may vary for different individuals. If separate measurement precisions are known or are indeed constant, one can assess the level of statistical agreement of longitudinal data to linear, or other theoretical, models.

The onset of neurotrophin and trk mRNA expression in early embryonic tissues of the quail

To determine the role of neurotrophins on the initial development of the avian embryo, RT-PCR was used to detect when mRNA for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), as well as their respective receptors, trkA, trkB, and trkC, is first expressed in the avian embryo. trkA, BDNF, trkB, NT-3, and trkC mRNA were expressed as early as stage 1 ("prestreak" stage), while NGF mRNA was not expressed until later in development (stage 5, "notochord" stage). Microdissection of Embryonic Day 2 quail (stages 12 to 14) and RT-PCR analysis revealed that the neural crest, neural tube, somites, or notochord all expressed some neurotrophin or trk mRNA. Although a neurotrophin and its appropriate receptor were both often present or absent, in several cases they were present individually, suggesting that they might have either local or target-derived actions.

MR imaging of tibial collateral ligament injury: comparison with clinical examination

We sought to clarify the capability of routine magnetic resonance (MR) imaging of the knee to detect and grade tibial collateral ligament (TCL) injury. We also wanted to define the exact MR findings that were the most important for diagnosis. Sixty-three patients were clinically evaluated for TCL injury prior to MR imaging of the knee on a 1.5-tesla system. MR studies were scored with respect to multiple direct and indirect findings. By discriminant analysis, the overall accuracy of classification (into clinical grades 1, 2, 3 and normal) on the basis of MR was 65%. Accuracy for detection of abnormal TCLs was 87%. The most useful MR findings for detection and grading of TCL injury were direct signs: subcutaneous edema over the TCL, focal disruption of the TCL, increased signal in the TCL on T2-weighted images, and longitudinal striations within the TCL. Indirect signs such as trabecular trauma were less useful for TCL evaluation. The presence of a tear of the anterior cruciate ligament, however, correlated with TCL injury of a higher grade. T2-weighted coronal images, by better depicting intraligamentous edema and fiber disruption, improved the MR assessment of the TCL.

MAC of xenon and halothane in rhesus monkeys

Local cerebral blood flow (LCBF) maps produced by 33% xenon-enhanced computed tomographic scanning (Xe/CT LCBF) are useful in the clinical diagnosis and management of patients with cerebrovascular disorders. However, observations in humans that 25-35% xenon (Xe) inhalation increases cerebral blood flow (CBF) have raised concerns that Xe/CT LCBF measurements may be inaccurate and that Xe inhalation may be hazardous in patients with decreased intracranial compliance. In contrast, 33% Xe does not increase CBF in rhesus monkeys. To determine whether this interspecies difference in the effect of Xe on CBF correlates with an interspecies difference in the anesthetic potency of Xe, we measured the minimum alveolar concentration (MAC) of Xe preventing movement to a tail-clamp stimulus in rhesus monkeys. Using a standard protocol for the determination of MAC in animals, we first measured the MAC of halothane (n = 5), and then used a combination of halothane and Xe to measure the MAC of Xe (n = 7). The halothane MAC was 0.99 +/- 0.12% (M +/- SD), and the Xe MAC was 98 +/- 15%. These results suggest that the MAC of Xe in rhesus monkeys is higher than the reported human Xe MAC value of 71%. Thus the absence of an effect of 33% Xe on CBF in the rhesus monkey may be related to its lower anesthetic potency.

The pleckstrin homology domain of Bruton tyrosine kinase interacts with protein kinase C

Bruton tyrosine kinase (EC 2.7.1.112) [Btk, encoded by Btk in mice and BTK in humans (formerly known as atk, BPK, or emb)], which is variously mutated in chromosome X-linked agammaglobulinemia patients and X-linked immunodeficient (xid) mice, has the pleckstrin homology (PH) domain at its amino terminus. The PH domain of Btk expressed as a bacterial fusion protein directly interacts with protein kinase C in mast cell lysates. Evidence was obtained that Btk is physically associated with protein kinase C in intact murine mast cells as well. Both Ca(2+)-dependent (alpha, beta I, and beta II) and Ca(2+)-independent protein kinase C isoforms (epsilon and zeta) in mast cells interact with the PH domain of Btk in vitro, and protein kinase C beta I is associated with Btk in vivo. Btk served as a substrate of protein kinase C, and its enzymatic activity was down-regulated by protein kinase C-mediated phosphorylation. Furthermore, depletion or inhibition of protein kinase C with pharmacological agents resulted in an enhancement of the tyrosine phosphorylation of Btk induced by mast cell activation.

Plantar plate of the foot: findings on conventional arthrography and MR imaging

The plantar plate of the foot is formed by the plantar aponeurosis and plantar capsule. The plantar plate arises from the distal plantar aspect of the metatarsal neck and inserts on the plantar aspect of the proximal phalangeal base. This thick plate supports the undersurface of the metatarsal head and resists hyperextension of the metatarsophalangeal joint (MTPJ) [1]. Plantar plate rupture may present as lesser metatarsalgia (the lesser metatarsals are the second through fifth), occasionally with exuberant synovitis. Plantar plate derangement also plays a central role in the genesis of the common hammertoe [2, 3]. Rupture or degeneration of the plantar plate destabilizes the MTPJ, allowing dorsal subluxation of the proximal phalanx. The resulting "cock-up" deformity at the MTPJ shortens and compromises the action of the extensor digitorum longus tendon, contributing over time to a flexion deformity at the interphalangeal joints.

Tyrosine phosphorylation and activation of Bruton tyrosine kinase upon Fc epsilon RI cross-linking

Tyrosine phosphorylation of several cellular proteins is one of the earliest signaling events induced by cross-linking of the high-affinity receptor for immunoglobulin E (Fc epsilon RI) on mast cells or basophils. Tyrosine kinases activated during this process include the Src family kinases, Lyn, c-Yes, and c-Src, and members of another subfamily, Syk and PTK72 (identical or highly related to Syk). Recently, some of us described two novel tyrosine kinases, Emb and Emt, whose expression was limited to subsets of hematopoietic cells, including mast cells. Emb turned out to be identical to Btk, a gene product defective in human X-linked agammaglobulinemia and in X-linked immunodeficient (xid) mice. Here we report that Fc epsilon RI cross-linking induced rapid phosphorylation on tyrosine, serine, and threonine residues and activation of Btk in mouse bone marrow-derived mast cells. A small fraction of Btk translocated from the cytosol to the membrane compartment following receptor cross-linking. Tyrosine phosphorylation of Btk was not induced by either a Ca2+ ionophore (A23187), phorbol 12-myristate 13-acetate, or a combination of the two reagents. Co-immunoprecipitation between Btk and receptor subunit beta or gamma was not detected. The data collectively suggest that Btk is not associated with Fc epsilon but that its activation takes place prior to protein kinase C activation and plays a novel role in the Fc epsilon RI signaling pathway.

Development of a digital duplication system for portable chest radiographs

To provide high-quality duplicate chest images for the intensive care units, we have developed a digital duplication system in which film digitization is performed in conjunction with nonlinear density correction, contrast adjustment, and unsharp mask filtering. This system provides consistent image densities over a wide exposure range and enhancement of structures in the mediastinum and upper abdominal areas, improving visibility of catheters and tubes. The image quality is often superior to that of the original radiograph and is more consistent from day to day. Repeat rates for portable chest radiographs have been reduced by more than a factor of two since implementation of digitization in December 1991, and the number of repeat examinations caused by exposure errors have been substantially reduced.

Compartmentation of whole brain blood flow and oxygen and glucose metabolism in monkeys

The cerebral metabolic rate of oxygen (CMRO2) has been functionally compartmentalized using the barbiturate thiopental into active CMRO2, associated with electroencephalographic (EEG) activity, and the balance, basal CMRO2, associated with the maintenance of neuronal viability. Previous measurements of these CMRO2 compartments were made in anesthetized animals. Our aim was to determine whether the same proportions for these compartments applied in unanesthetized monkeys. The active: basal distribution of the cerebral metabolic rate of glucose (CMRG) and cerebral flood flow (CBF) were also determined. Three measurements of whole-brain CBF (H2 clearance), CMRO2, and CMRG were made in six unanesthetized rhesus monkeys (Macaca mulatta). Thereafter, thiopental anesthesia was induced and maintained until an isoelectric EEG was obtained. Three additional measurements of CBF, CMRO2, and CMRG were made. Arterial blood pressure, end-tidal CO2, and arterial blood gas were measured with each set of measurements. Thiopental-induced isoelectric EEG resulted in a 47% reduction in CMRO2 from 5.95 +/- 0.54 to 3.10 +/- 0.51 ml/100 g/min (mean +/- SD); a 36% reduction in CBF from 76 +/- 21 to 48 +/- 14 ml/100 g/min; and a 61% reduction in CMRG from 8.09 +/- 2.78 to 3.13 +/- 0.77 mg/100 g/min. The oxygen-glucose index was 0.99 +/- 0.10 for the whole brain, 0.87 +/- 0.15 for the active, and 1.27 +/- 0.25 for the basal compartments. These results indicated an active:basal distribution of approximately 50:50 for CMRO2, 40:60 for CBF, and 60:40 for CMRG. The active:basal CMRO2 distribution corroborates earlier data and shows that relative to CMRO2, the active compartment is underperfused with a lower oxygen-glucose index compared with the basal compartment.

Anterior cruciate ligament tear. A new diagnostic index on magnetic resonance imaging

An objective index of anterior cruciate ligament (ACL) tears based on posterior cruciate ligament (PCL) shape has been introduced. The PCL shapes on magnetic resonance imaging (MRI) were measured in 67 patients (31 normal ACL, 31 torn ACL, and five partial ACL tears, all confirmed by arthroscopy). All of the measurements were performed in a blinded manner, without previous knowledge of the MRI or arthroscopy diagnosis. The index consisted of the ratio B/A, with B equaling the length of the line between the posterior inferior tibial and the superior anterior femoral attachment of the PCL, and A equaling the maximum perpendicular distance from this line to the PCL. All measurements were performed twice, and the mean was used for statistical significance. The average index ratio was 5.4 and 3.9 for normal ACL and torn ACL, respectively. Using a cutoff value of 4.75, the sensitivity of the index was 87% and the specificity was 84%. An objective and reproducible index measurement of PCL shape for normal and injured ACL has been established. It provides additional information for both orthopaedic surgeons and radiologists in the diagnosis of ACL injury.

Case report 818: Pericapsular desmoid tumor of the knee

A case of pericapsular desmoid tumor is presented. The MR features of signal hypointensity and association with the joint capsule suggested the diagnosis of focal PVNS or giant cell tumor of tendon sheath. Arguing against the diagnosis of PVNS were the absence of significant joint effusion, the unifocality of a fairly large lesion, and the absence of bony erosion. While nonspecific, the MR features in some cases of desmoid tumor may help to suggest the correct diagnosis.

Case report 826: Physiological resorption of allograft simulating recurrent giant cell tumor

A case of focal resorption in a limb salvage/bone allograft is presented, illustrating that roentgenological differentiation from other causes for graft resorption may be very difficult. The possibilities of infection and tumor recurrence, as well as "physiologic" graft resorption, must be considered in the differential diagnosis of a lytic process in an allograft for limb salvage. To date, early biopsy remains mandatory for accurate diagnosis.

Fibrous dysplasia associated with cortical bony destruction: CT and MR findings

OBJECTIVE

Fibrous dysplasia is a benign disorder of bone that can cause cortical thinning as well as bony expansion. Full-thickness cortical bony destruction, however, typically characterizes more aggressive or malignant lesions of bone. We present three cases of fibrous dysplasia that illustrate this more aggressive and potentially confusing feature.

MATERIALS AND METHODS

The findings on radiography and cross-sectional imaging studies are reviewed in three surgically proven cases of fibrous dysplasia that exhibited full-thickness cortical bony destruction.

RESULTS

Well-defined cortical perforations without associated periosteal reaction were clearly seen on CT. This finding was suspected on plain radiography in only one of the three cases. A small associated soft tissue mass was detected by MR imaging in this case. Many cortical perforations were seen in the one case of polyostotic fibrous dysplasia.

CONCLUSION

Full-thickness cortical bony destruction can be seen in fibrous dysplasia. This finding, which may only be evident on cross-sectional imaging studies, should not by itself alter a diagnostic impression of fibrous dysplasia supported by other radiographic and clinical features.

Evaluation of an enhanced digital film-duplication system by receiver operating characteristic analysis

RATIONALE AND OBJECTIVES

Over- or underexposure often results in poor quality radiographs. Using receiver operating characteristic analysis, the authors investigated the potential utility of a system that corrects densities in such images to improve the accuracy of lung nodule detection.

METHODS

Chest radiographs were digitized by a laser film digitizer. Simulated nodules were superimposed on 36 improperly exposed chest radiographs. All images, with and without nodules, were then processed by a nonlinear density-correction technique. Hard-copy images were produced by a laser film printer. Eight radiologists evaluated the corrected and uncorrected images for the presence or absence of lung nodules using a continuous (0-100) confidence-rating scale.

RESULT

The detectability of lung nodules improved significantly in the retrocardiac/retrodiaphragmatic regions of underexposed images and in the peripheral lung region of overexposed images.

CONCLUSIONS

This system may increase diagnostic accuracy in detection of lung nodules in improperly exposed images.

Spring ligament of the ankle: normal MR anatomy

The plantar calcaneonavicular or spring ligament is visualized inconsistently and incompletely on routine MR images of the foot. This ligament is a vital stabilizer of the longitudinal arch of the foot, providing support for the head of the talus, which rests on the ligament's central portion. Laxity or rupture of the spring ligament permits plantar flexion of the talus. This motion results in valgus alignment of the calcaneus and a flatfoot deformity (pes planovalgus). Laxity or rupture of the spring ligament can develop in cases of chronic dysfunction of the posterior tibial tendon. In rupture of the posterior tibial tendon, surgical management may include plication of the spring ligament in addition to repair or reconstruction of the tendon to stabilize the medial column of the foot. Thus, the status of the spring ligament can be a significant consideration in preoperative planning. This pictorial essay illustrates the normal MR anatomy of the spring ligament, the planes of imaging required for optimal depiction of the ligament, and the neighboring structures with which the ligament can be confused.

Imaging shoulder impingement

Appropriate imaging and clinical examinations may lead to early diagnosis and treatment of the shoulder impingement syndrome, thus preventing progression to a complete tear of the rotator cuff. In this article, we discuss the anatomic and pathophysiologic bases of the syndrome, and the rationale for certain imaging tests to evaluate it. Special radiographic projections to show the supraspinatus outlet and inferior surface of the anterior third of the acromion, combined with magnetic resonance images, usually provide the most useful information regarding the causes of impingement.

Early embryonic quail dorsal root ganglia exhibit high affinity nerve growth factor binding and NGF responsiveness--absence of NGF receptors on migrating neural crest cells

Dorsal root ganglia (DRG) midway through development require nerve growth factor (NGF) for survival and differentiation. These studies investigated when avian neural crest cells or DRG first exhibit high affinity NGF receptors in situ, and whether early embryonic cells expressing high affinity NGF receptors are responsive to NGF. Unfixed cryostat sections of quail embryos were exposed to varying concentrations of [125I]NGF to distinguish between high and low affinity binding. Radioautography revealed an absence of [125I]NGF binding on migrating neural crest cells in situ. Both high and low affinity NGF receptors were first detected in differentiating DRG at E3.5 (stage 23). The presence of high affinity receptors was additionally confirmed by identification of a high molecular weight complex on radioautographs of gels following cross-linking of [125I]NGF to dissociated DRG. The presence of high affinity NGF receptors in E3.5 DRG was unexpected since DRG have been reported to be unresponsive to NGF prior to the midpoint of development. Exposure of E3.5 DRG neuron-enriched cultures to exogenous NGF resulted in approximately 30% more neurons after 24 h in vitro. The effect of NGF was blocked by anti-NGF and was shown to be dose dependent. It remains to be determined whether the increase in cell number is due to a survival or mitogenic effect.

Local cerebral blood flow measured by xenon-enhanced CT during cryogenic brain edema and intracranial hypertension in monkeys

We developed a closed-skull model of freeze injury-induced brain edema, a model classically thought to produce vasogenic edema, and observed the natural course of changes in edema and blood flow using xenon-enhanced computed tomography (CT) in five rhesus monkeys before and for up to 6 h post insult. Intracranial pressure (ICP) gradually rose throughout the duration of the experiment. CT scans and CBF images permitted direct observation of the evolution of the lesion and revealed early ischemia in the periphery of the injury zone that progressed over time in association with edema. Frequency histogram analysis of local CBF (ICBF) demonstrated subtle but potentially important changes in distribution of ICBF between and within hemispheres at various times post insult. Changes in ICBF distribution were phasic and dissociated from increases in ICP in the latter stages of injury. The Xe/CT CBF method can be used to evaluate the effects of injury and therapy on CBF in this and other models of acute brain injury.

Magnetic resonance imaging of a symptomatic meniscal ossicle

Meniscal ossicles are uncommon in humans. They are usually located in the posterior horn of the medial meniscus and are generally first observed on roentgenograms as intraarticular corticated bone densities. Many different entities appear similar to meniscal ossicles on roentgenography. Magnetic resonance imaging (MRI) can help to distinguish between these different entities and thereby assist in guiding treatment. Magnetic resonance imaging also can identify concurrent intraarticular pathology (e.g., meniscal tears), which may influence the choice of treatment. In a 29-year-old man, MRI confirmed the intrameniscal location of a corticated bone density seen in the posteromedial knee on roentgenograms. An associated medial meniscus tear was found at arthroscopy. The patient's symptoms were relieved after resection of the meniscal ossicle and the associated meniscal tear.

Experimental and clinical investigations of human insoluble bone matrix gelatin. A report of 24 cases

Human bone matrix gelatin (hBMG) was implanted into the quadriceps muscles of mice to determine its osteoinductive activity and immune responses. The host mouse muscle assay reacted positively to the hBMG, providing an experimental basis for clinical application. At two weeks after implantation, cartilage was produced in the mouse muscle, and new bone and bone marrow were formed at three to four weeks after implantation. Human bone matrix gelatin, which was thus shown to have osteoinductive activity, was subsequently implanted in 24 patients. Generally, the bone defects were filled with new bone tissue with increased density within two to four months after operation. Nonunion and delayed unions were healed at two to six months after surgery.

Clinical experience with an advanced laser digitizer for cost-effective digital radiography

Film digitization has not been widely pursued in clinical settings mainly because of perceived limitations involving film latitude and image quality. However, a high-quality laser digitizer can be combined with wide-latitude film and specially developed digital processing techniques to achieve image quality comparable or superior to that of storage phosphor computed radiography (SPR) over a wide range of exposure. This film digitization system provides the operational advantages of digital radiography, such as consistent image density, high-quality inexpensive duplicates, and digital storage and retrieval capability. The reliability and monetary costs of the system also compare favorably with those of SPR. In the long term, technologies that employ reusable plates and do not require chemical processing to produce diagnostic images may well replace screen-film systems. Presently, however, film digitization remains a practical and cost-effective approach to digital radiography.

Diagnosis of soft-tissue masses with MR imaging: can benign masses be differentiated from malignant ones?

A blinded, retrospective review of 83 soft-tissue masses (49 benign and 34 malignant) was performed to evaluate the ability to distinguish benign from malignant soft-tissue masses with magnetic resonance (MR) imaging. The correct histologic diagnosis was reached in 31% of cases by one reader and in 16% of cases by the second reader. Mean sensitivity was 50% for benign masses and 80% for malignant masses. The majority of both benign and malignant masses had inhomogeneous signal intensity and at least partially irregular borders. Malignant masses uncommonly had smooth borders and homogeneous signal intensity. MR imaging can be used to evaluate the extent of soft-tissue masses, but most masses will require biopsy to determine if they are benign or malignant.

Effects of Dobutamine and Dopamine on Whole Brain Blood Flow and Metabolism in Unanesthetized Monkeys

Dobutamine (DO) and dopamine (DA) are positive inotropic agents used clinically to improve cardiac output in patients in acute or chronic heart failure or to counteract intracranial vasospasm. These patients are also at risk for cerebrovascular disease, but studies on the effects of DA on cerebral blood flow (CBF) and metabolism are few and for DO nonexistent. We evaluated the effects on DO and DA on whole brain CBF and cerebral metabolic rates of oxygen (CMRO2) and glucose (CMRglc) in unanesthetized rhesus monkeys. Microelectrodes and catheters inserted in the superior sagittal sinus monitored H2 clearance and sampled cerebral venous blood. Studies were done at low and high doses with control measurements between doses. At 5.10, and 15 microg/kg/min (n = 6), neither systemic nor cerebral variables were affected by either drug. At doses of 50 and 100 microg/kg/min (n = 4), DO and DA increased arterial blood pressure and heart rate by 15 to 30%. Whereas CBF, CMRO2, and CMRglc were clearly unaffected by DO at high doses, they increased by 20-30% with DA, 100 microg/kg/min and although not significant (p >0.05), the consistency and magnitude of the increase along with the likelihood of a type II error led us to conclude that (a) both DO and DA are less effective in monkeys than in humans and (b) whereas DO at all doses tested showed no indication of affecting CBF and CMR, DA increased CBF and CMR by 20 to 30% at a dose of 100 microg/kg/min.

Effect of 80% Xe on Whole Brain Blood Flow and Metabolism in Awake Monkeys

We previously reported that 33% xenon (Xe) did not activate cerebral blood flow (CBF) and metabolism in monkeys as it appears to do in humans. However, monkeys may be less sensitive to Xe than humans are, which would explain the discrepancy in the results, but no one has studied the effects of higher concentrations of Xe on CBF and metabolism in monkeys. Therefore, we studied the effect of 80% Xe on whole-brain CBF, cerebral metabolic rate for oxygen (CMRO2) and glucose (CMRG) in five awake rhesus monkeys. Platinum microelectrodes and catheters inserted into the torcular Herophili were used to measure H2 clearance CBF, and to withdraw cerebral venous blood for O2 and glucose analysis. Cerebral variables were measured after 15 min exposure to 80% N2/20% O2 followed by 80% Xe/20% O2. Eighty percent Xe compared with 80% N2 increased (p <0.01) CBF by 52.7% from 74 +/- 16 to 113 +/- 25 (mean +/- SD) ml 100 g(-1)/min(-1), CBF/CMRO by 154% from 13 to 33, and decreased (p <0.05) CMRO2 by 39.3% from 6.1 +/- 0.9 to 3.7 +/- 0.8 ml 100 g(-1)/min(-1) and CMRG by 52.4% from 8.4 +/- 2.6 to 4.0 +/- 2.0 mg 100 g(-1)/min(-1). Electroencephalogram frequency decreased from a predominantly alpha to dagger rhythm in three of five monkeys. The 40 and 50% reduction in CMRO2 and CMRG, respectively, by 80% Xe suggests an anesthetic effect at this dose in the rhesus monkey but also activates CBF by 50%.

Rapid disruption of cochlear function and structure by trimethyltin in the guinea pig

Trimethyltin (TMT) is a potent ototoxicant which acutely disrupts generation of the action potential evoked by a broad range of tone frequencies and subsequently produces selective high frequency impairment and outer hair cell (OHC) damage in the extreme basal turn of the cochlea. We investigated the development of TMT ototoxicity in the guinea pig 6-48 h following treatment using the compound action potential (CAP), cochlear microphonic (CM), endocochlear potential (EP) and light and electron microscopic examinations. At all time intervals studied, TMT reduced CAP sensitivity and CM amplitude. The effect was relatively broad across test frequencies at 6 h and subsequently became restricted to higher frequencies. No disruption of the EP was observed between 6 and 24 h following TMT. OHC pathology in the basal turn of the cochlea 12 h following TMT consisted of vacuolization in the supranuclear region and disruption of the cuticular plate; some mitochondria exhibited dark inclusions. Type 1 spiral ganglion cells appeared swollen at 24 h with separation of myelin from the cell bodies. No pathological changes were observed in the inner hair cells (IHC). The present data identify the OHC as targets responsible for the loss of CM sensitivity after TMT as the EP was unaffected. These data suggest that CAP and CM recovery at low and middle frequencies following acute TMT administration is accompanied by recovery of neurotransmission at the IHC or Type 1 SGC level and OHC recovery at apical regions of the cochlea.

Case report 715. Necrotic giant cell tumor of the femur

We present a giant cell tumor of the distal end of the femur that exhibited unusual diaphyseal extension and atypical MRI features. MRI demonstrated differing zonal signal characteristics in the distal metaphyseal/epiphyseal versus the diaphyseal components of the tumor. It also depicted an irregular, proximal tumor margin with an unusual, enhancing, peripheral zone. The atypical MRI features may be related to the unusual finding at pathological examination of an almost entirely necrotic giant cell tumor. This massive necrosis may illustrate a stage in the evolution of some giant cell tumors to fibrous histiocytoma-like variants of giant cell tumor or to conventional, benign fibrous histiocytoma of bone.

MR imaging of joints: analytic optimization of GRE techniques at 1.5 T

To clarify the choice of imaging parameters for optimal gradient-recalled echo MR scanning of joints, we analyzed the behavior of contrast-to-noise and signal-to-noise ratios for spoiled (i.e., fast low-angle shot [FLASH] or spoiled GRASS) and steady-state (i.e., gradient-recalled acquisition in the steady state [GRASS] or fast imaging with steady precession) techniques at 1.5 T. The analysis is based on tissue characteristics derived from spin-echo measurements of hyaline cartilage and synovial fluid signal in the patellofemoral joints of 11 volunteers. Separate analysis of contrast-to-noise and signal-to-noise ratios for multiplanar (long TR) acquisitions shows that these parameters are each improved compared with single-slice methods. At TRs greater than 250 msec, there is no significant difference in the contrast behavior of FLASH and GRASS. For optimal contrast-to-noise ratio (synovial fluid-cartilage), the best multiplanar sequence (for TE less than 23 msec) is with a short TE and a large flip angle (e.g., 400/9/73 degrees [TR/TE/flip angle]). If a single-scan or three-dimensional technique is desired, than a GRASS sequence at minimal TR and TE and intermediate flip angle (18/9/32 degrees) is best. For optimal signal-to-noise ratio (for both synovial fluid and hyaline cartilage), the best multiplanar sequence uses a short TE and an intermediate flip angle (e.g., 400/9/30 degrees). If a short TR, high signal-to-noise technique is desired, then GRASS (18/9/13 degrees) is superior to FLASH.