Early Fetal Corpus Callosum: Demonstrating Normal Growth and Detecting Pathologies in Early Pregnancy

BACKGROUND AND PURPOSE

A malformed corpus callosum carries a risk for abnormal neurodevelopment. The advent of high-frequency transducers offers the opportunity to assess corpus callosum development in early pregnancy. The aim of the study was to construct a reference chart of the fetal corpus callosum length on ultrasound between 13 and 19 weeks of gestation and to prospectively examine growth patterns in pathologic cases.

MATERIALS AND METHODS

We performed a prospective cross-sectional study between 2020 and 2022 in well-dated, low-risk, singleton pregnancies between 13 and 19 weeks of gestation. A standardized image was obtained in the midsagittal plane. Imaging criteria were used as a confirmation of the early corpus callosum. Measurements were taken by 4 trained sonographers. Intra- and interobserver variability was assessed. Corpus callosum length in centiles were calculated for each gestational week.

RESULTS

One hundred eighty-seven fetuses were included in the study. All cases met inclusion criteria. At 13 weeks of gestation, the margins of the early corpus callosum were sufficiently clear to be measured in 80% (20/25) of fetuses. A cubic polynomial regression model best described the correlation between corpus length and gestational age. The correlation coefficient (r 2) was 0.929 (P < .001). Intra- and interobserver variability had high interclass correlation coefficients (>0.99). Presented is the earliest published case of agenesis of corpus callosum and a case of dysgenetic corpus callosum in Rubinstein-Taybi syndrome.

CONCLUSIONS

Provided is a nomogram of the early fetal corpus callosum. Applying imaging criteria helped to identify a case of complete agenesis of the corpus callosum as early as 14 weeks.

Co-mapping studies of QTLs for fruit acidity and candidate genes of organic acid metabolism and proton transport in sweet melon (Cucumis melo L.)

Sweet melon cultivars contain a low level of organic acids and, therefore, the quality and flavor of sweet melon fruit is determined almost exclusively by fruit sugar content. However, genetic variability for fruit acid levels in the Cucumis melo species exists and sour fruit accessions are characterized by acidic fruit pH of <5, compared to the sweet cultivars that are generally characterized by mature fruit pH values of >6. In this paper, we report results from a mapping population based on recombinant inbred lines (RILs) derived from the cross between the non-sour 'Dulce' variety and the sour PI 414323 accession. Results show that a single major QTL for pH co-localizes with major QTLs for the two predominant organic acids in melon fruit, citric and malic, together with an additional metabolite which we identified as uridine. While the acidic recombinants were characterized by higher citric and malic acid levels, the non-acidic recombinants had a higher uridine content than did the acidic recombinants. Additional minor QTLs for pH, citric acid and malic acid were also identified and for these the increased acidity was unexpectedly contributed by the non-sour parent. To test for co-localization of these QTLs with genes encoding organic acid metabolism and transport, we mapped the genes encoding structural enzymes and proteins involved in organic acid metabolism, transport and vacuolar H+ pumps. None of these genes co-localized with the major pH QTL, indicating that the gene determining melon fruit pH is not one of the candidate genes encoding this primary metabolic pathway. Linked markers were tested in two additional inter-varietal populations and shown to be linked to the pH trait. The presence of the same QTL in such diverse segregating populations suggests that the trait is determined throughout the species by variability in the same gene and is indicative of a major role of the evolution of this gene in determining the important domestication trait of fruit acidity within the species.

Organ transplantation from a donor colonized with a multidrug-resistant organism: a case report

The number of intensive care unit patients with infections caused by multidrug-resistant organisms is increasing in most developed countries. We report the case of a deceased multiorgan donor, who was an asymptomatic carrier of carbapenem-resistant Klebsiella pneumoniae (CR-KP) in the respiratory tract, a condition that was not diagnosed before organ harvesting and transplantation. The outcome of the 2 kidney recipients, the liver recipient, and 1 of the lung recipients was uneventful; in particular, no evidence of infection transmission or adverse graft outcomes was noted. The other lung recipient had a complicated postoperative course and, 4 weeks post transplantation, he developed a bacteremic pneumonia with CR-KP from which he subsequently died. These results suggest that, in well defined conditions, organs from donors who are CR-KP positive may be considered for transplantation.

A genetic map of melon highly enriched with fruit quality QTLs and EST markers, including sugar and carotenoid metabolism genes

A genetic map of melon enriched for fruit traits was constructed, using a recombinant inbred (RI) population developed from a cross between representatives of the two subspecies of Cucumis melo L.: PI 414723 (subspecies agrestis) and 'Dulce' (subspecies melo). Phenotyping of 99 RI lines was conducted over three seasons in two locations in Israel and the US. The map includes 668 DNA markers (386 SSRs, 76 SNPs, six INDELs and 200 AFLPs), of which 160 were newly developed from fruit ESTs. These ESTs include candidate genes encoding for enzymes of sugar and carotenoid metabolic pathways that were cloned from melon cDNA or identified through mining of the International Cucurbit Genomics Initiative database (http://www.icugi.org/). The map covers 1,222 cM with an average of 2.672 cM between markers. In addition, a skeleton physical map was initiated and 29 melon BACs harboring fruit ESTs were localized to the 12 linkage groups of the map. Altogether, 44 fruit QTLs were identified: 25 confirming QTLs described using other populations and 19 newly described QTLs. The map includes QTLs for fruit sugar content, particularly sucrose, the major sugar affecting sweetness in melon fruit. Six QTLs interacting in an additive manner account for nearly all the difference in sugar content between the two genotypes. Three QTLs for fruit flesh color and carotenoid content were identified. Interestingly, no clear colocalization of QTLs for either sugar or carotenoid content was observed with over 40 genes encoding for enzymes involved in their metabolism. The RI population described here provides a useful resource for further genomics and metabolomics studies in melon, as well as useful markers for breeding for fruit quality.

Lipid homoeostasis and Golgi secretory function

The unique lipid composition of the Golgi membranes is critical for maintaining their structural and functional identity, and is regulated by local lipid metabolism, a variety of lipid-binding, -modifying, -sensing and -transfer proteins, and by selective lipid sorting mechanisms. A growing body of evidence suggests that certain lipids, such as phosphoinositides and diacylglycerol, regulate Golgi-mediated transport events. However, their exact role in this process, and the underlying mechanisms that maintain their critical levels in specific membrane domains of the Golgi apparatus, remain poorly understood. Nevertheless, recent advances have revealed key regulators of lipid homoeostasis in the Golgi complex and have demonstrated their role in Golgi secretory function.

Livedo reticularis is a marker for predicting multi-system thrombosis in antiphospholipid syndrome

OBJECTIVE

Livedo reticularis (LR) is a skin vasculopathy that has been frequently described in patients with anti-phospholipid syndrome (APS) and reported to be present in association with valvular heart pathology and strokes (i.e. Sneddon's syndrome).

METHODS

In a cohort of APS patients we investigated the possible association of LR with various clinical aspects of APS such as pregnancy morbidity, central nervous system (CNS) and cardiac manifestations.

RESULTS

Livedo reticularis was found in 50/308 (16%) of APS patients, and there was a significant association with cerebrovascular accidents (CVA), migraines and epilepsy (p = 0.01, 0.002, and 0.02 respectively). A similar association was also detected between LR, and the presence of cardiac valve thickening and vegetations (p = 0.001). No association with venous thrombosis, recurrent fetal loss, IUGR or toxemia was found.

CONCLUSION

Livedo reticularis is a frequent cutaneous manifestation in patients with APS. Its high association with cardiac and CNS thrombosis may suggest that LR-APS patients compose a subset at higher risk for thrombosis, and thus may require a closer follow-up and a more aggressive anticoagulation.

Close association between valvar heart disease and central nervous system manifestations in the antiphospholipid syndrome

BACKGROUND

Heart valves lesions and central nervous system involvement are among the most common manifestations of the antiphospholipid syndrome (APS).

OBJECTIVE

To evaluate possible interrelations between these manifestations in a large group of APS patients.

METHODS

284 APS patients were evaluated retrospectively, 159 of whom had primary APS. Cardiac-CNS associations were determined for the entire study population, and for subgroups of patients with primary APS or APS associated with systemic lupus erythematosus (SLE).

RESULTS

Significant associations where found between cardiac vegetations and epilepsy (p < 0.02), and between cardiac valve thickening or dysfunction and migraine (p = 0.002). Borderline association was found between valvar vegetations and migraine (p = 0.09). A significant association was also found between all valvar lesions and stroke or transient ischaemic attacks. Subanalyses showed that patients with primary APS had significant associations between cardiac valve pathology and all CNS manifestations, while patients with APS associated with SLE had no such associations.

CONCLUSIONS

The study suggests potential differences in biological behaviour between primary APS and APS associated with SLE. The presence of cardiac valve pathology may be a risk factor for several types of CNS involvement in PAPS.

Prevalence and clinical correlations of antibodies against six beta2-glycoprotein-I-related peptides in the antiphospholipid syndrome

Two-hundred ninety five patients with the antiphospholipid syndrome (APS) were studied for the presence of antibodies against six anti-beta2GPI-related peptides Abs. The prevalence of a wide spectrum of clinical and laboratory parameters of APS was evaluated in all patients, and correlated with the presence of each anti-beta2GPI peptide antibody. The rates of the various antipeptides Abs ranged from 18.0 to 63.7%. Altogether, 87.1% of the patients had antibody reactivity against at least one of the six beta2GPI-related peptides. A high degree of simultaneous reactivity against several beta2GPI-peptides was found. Positive and negative correlations were found between several antipeptides Abs and the rates of thrombosis and fetal loss. Our results point to a heterogeneous activity of antiphospholipid Abs in APS patients, directed, often concurrently, against various epitopes of the beta2GPI molecule. Evaluation of APS patients for the presence of specific antipeptides Abs may be of a value in predicting the risk for future thrombotic and obstetrical complication, as well as for specific therapeutic purposes.

Calcium, protease activation, and cytoskeleton remodeling underlie growth cone formation and neuronal regeneration

The cytoarchitecture, synaptic connectivity, and physiological properties of neurons are determined during their development by the interactions between the intrinsic properties of the neurons and signals provided by the microenvironment through which they grow. Many of these interactions are mediated and translated to specific growth patterns and connectivity by specialized compartments at the tips of the extending neurites: the growth cones (GCs). The mechanisms underlying GC formation at a specific time and location during development, regeneration, and some forms of learning processes, are therefore the subject of intense investigation. Using cultured Aplysia neurons we studied the cellular mechanisms that lead to the transformation of a differentiated axonal segment into a motile GC. We found that localized and transient elevation of the free intracellular calcium concentration ([Ca2+]i) to 200-300 microM induces GC formation in the form of a large lamellipodium that branches up into growing neurites. By using simultaneous on-line imaging of [Ca2+]i and of intraaxonal proteolytic activity, we found that the elevated [Ca2+]i activate proteases in the region in which a GC is formed. Inhibition of the calcium-activated proteases prior to the local elevation of the [Ca2+]i blocks the formation of GCs. Using retrospective immunofluorescent methods we imaged the proteolysis of the submembrane spectrin network, and the restructuring of the cytoskeleton at the site of GC formation. The restructuring of the actin and microtubule network leads to local accumulation of transported vesicles, which then fuse with the plasma membrane in support of the GC expansion.

Molecular aspects of retinal degenerative diseases

Retinal degeneration, either acquired or inherited, is a major cause of visual impairment and blindness in humans. Inherited retinal degeneration comprises a large group of diseases that result in the loss of photoreceptor cells. To date, 131 retinal disease loci have been identified, and 76 of the genes at these loci have been isolated (RetNet Web site). Several of these genes were first considered candidates because of their chromosomal localization or homology to genes involved in retinal degeneration in other organisms. In this review, I will discuss recent advances in the identification of genes that cause retinal degeneration, and I will describe the mechanisms of photoreceptor death and potential treatments for retinal degenerative diseases.

Coping with breast cancer: patient, spouse, and dyad models

OBJECTIVE

The objectives of this study were 1) to assess similarities and differences between patients with breast cancer and their spouses in terms of coping strategies and adjustment (psychosocial and psychological) to cancer and 2) to investigate the pattern of relationships between the patients' and spouses' coping strategies and between each of these strategies and the patient's adjustment to the illness using three types of models: patient, spousal, and dyadic coping.

METHODS

Seventy-three patients with breast cancer and their spouses completed questionnaires that measured distress (Brief Symptom Inventory), psychosocial adjustment, and coping strategies.

RESULTS

The patients' distress was greater than their spouses', but a similar level of psychosocial adjustment was reported. The patients used more strategies involving problem-focused coping than their spouses. The use of emotion-focused coping, which included ventilation and avoidance strategies, was highly related to distress and poor adjustment on the part of the patient. The spouses' emotion-focused coping and distress were related to that of the patients. Dyad emotion-focused coping measures were highly associated with the patients' distress and adjustment.

CONCLUSIONS

Spousal and dyad coping are important factors in a patient's adjustment to breast cancer.

Targeting of PYK2 to focal adhesions as a cellular mechanism for convergence between integrins and G protein-coupled receptor signaling cascades

The non-receptor tyrosine kinase PYK2 appears to function at a point of convergence of integrins and certain G protein-coupled receptor (GPCR) signaling cascades. In this study, we provide evidence that translocation of PYK2 to focal adhesions is triggered both by cell adhesion to extracellular matrix proteins and by activation of the histamine GPCR. By using different mutants of PYK2 as green fluorescent fusion proteins, we show that the translocation of PYK2 to focal adhesions is not dependent on its catalytic activity but rather is mediated by its carboxyl-terminal domain. Translocation of PYK2 to focal adhesions was attributed to enhanced tyrosine phosphorylation of PYK2 and its association with the focal adhesion proteins paxillin and p130(Cas). Translocation of PYK2 to focal adhesions, as well as its tyrosine phosphorylation in response to histamine treatment, was abolished in the presence of protein kinase C inhibitors or cytochalasin D treatment, whereas activation of protein kinase C by phorbol ester resulted in focal adhesion targeting of PYK2 and its tyrosine phosphorylation in an integrin-clustering dependent manner. Overexpression of a wild-type PYK2 enhanced ERK activation in response to histamine, whereas a kinase-deficient mutant substantially inhibited this response. Furthermore, inhibition of PYK2 translocation to focal adhesions abolished ERK activation in response to histamine treatment. These results suggest that PYK2 apparently links between GPCRs and focal adhesion-dependent ERK activation and can provide the molecular basis underlying PYK2 function at a point of convergence between signaling pathways triggered by extracellular matrix proteins and certain GPCR agonists.

Enhanced activity of a large conductance, calcium-sensitive K+ channel in the presence of Src tyrosine kinase

Large conductance, calcium-sensitive K(+) channels (BK(Ca) channels) contribute to the control of membrane potential in a variety of tissues, including smooth muscle, where they act as the target effector for intracellular "calcium sparks" and the endothelium-derived vasodilator nitric oxide. Various signal transduction pathways, including protein phosphorylation can regulate the activity of BK(Ca) channels, along with many other membrane ion channels. In our study, we have examined the regulation of BK(Ca) channels by the cellular Src gene product (cSrc), a soluble tyrosine kinase that has been implicated in the regulation of both voltage- and ligand-gated ion channels. Using a heterologous expression system, we observed that co-expression of murine BK(Ca) channel and the human cSrc tyrosine kinase in HEK 293 cells led to a calcium-sensitive enhancement of BK(Ca) channel activity in excised membrane patches. In contrast, co-expression with a catalytically inactive cSrc mutant produced no change in BK(Ca) channel activity, demonstrating the requirement for a functional cSrc molecule. Furthermore, we observed that BK(Ca) channels underwent direct tyrosine phosphorylation in cells co-transfected with BK(Ca) channels and active cSrc but not in cells co-transfected with the kinase inactive form of the enzyme. A single Tyr to Phe substitution in the C-terminal half of the channel largely prevented this observed phosphorylation. Given that cSrc may become activated by receptor tyrosine kinases or G-protein-coupled receptors, these findings suggest that cSrc-dependent tyrosine phosphorylation of BK(Ca) channels in situ may represent a novel regulatory mechanism for altering membrane potential and calcium entry.

Cerebral ischemia and seizures induce tyrosine phosphorylation of PYK2 in neurons and microglial cells

The nonreceptor tyrosine kinase PYK2 represents a stress-sensitive mediator of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) signaling pathways in many cell types. In the present study, we assessed the tyrosine phosphorylation of PYK2 under normal and pathological conditions in the CNS. We generated a polyclonal antibody that selectively recognizes tyrosine-phosphorylated PYK2 at its major autophosphorylation site. By using this antibody, we demonstrate that the phosphorylation profile of PYK2 after focal cerebral ischemia is biphasic. The first phase occurs within 1 hr, when most of the phospho-PYK2 immunoreactivity was observed in cortical neurons, whereas 24-72 hr after ischemia, a striking induction of phospho-PYK2 immunoreactivity was evident in microglia around the necrotic infarcted area. Double-immunostaining analysis using both anti-phospho-PYK2 antibody and antibody against the double-phosphorylated active form of p38MAPK revealed that the two phosphorylated protein kinases exhibit strikingly similar distribution patterns after ischemia. A short time after ischemia, phosphorylation of p38MAPK was evident in the cortical neurons as demonstrated by both immunohistochemistry and immunoblotting analysis, whereas 24-72 hr after ischemia, phospho-p38MAPK was found in activated microglia and colocalized with phospho-PYK2. In contrast to cortical neurons, basal phospho-PYK2 immunoreactivity was observed in hippocampal pyramidal neurons, which was markedly decreased after kainate acid-induced status epilepticus. However, 24 hr after the epileptic onset, a pronounced upregulation of PYK2 and phospho-PYK2 immunoreactivities was evident in microglial cells, as demonstrated by double-immunostaining with the microglial marker OX42. These results provide, for the first time, in situ localization of tyrosine-phosphorylated PYK2 in neuronal stress pathways in the adult rat brain and are consistent with the role of PYK2 as an upstream regulator of p38MAPK signaling cascades in response to stress signals.

Imaging of cystic lesions

Cystic neck masses are varied in their histology and embryogenesis. Because neural, vascular, and lipomatous lesions may all appear cystic, a multimodality imaging approach can help identify these potential mimics. Developmental neck cysts include thyroglossal duct, thymic, and branchial cleft cysts, and teratomatous lesions or lymphangiomas. Although laryngoceles are acquired lesions, congenital anomalies (e.g., abnormally long saccules) may play a role in their formation. Lesion location is at least as important a determinant as morphology in formulating the differential diagnosis of a cystic neck mass. Midline cystic lesions are most commonly thyroglossal duct cysts, although dermoid tumors are also frequently midline. Squamous cell carcinoma metastatic to anterior triangle lymph nodes (Fig. 17), and cystic, necrotic schwanommas, can mimic the typical appearance of an infected second branchial cleft cyst. Posterior triangle lymphadenopathy and lipomatous lesions may resemble cystic hygromas. Cystic-appearing masses in the carotid space include neurogenic tumors, vascular thromboses, and carotid chain lymphadenopathy. Neural-based lesions typically occur posterolateral to the carotid artery. Necrotic lymphadenopathy may be suggested by lesion multiplicity, or by the presence of ancillary features, such as systemic symptoms, or the existence of a primary tumor. It must be emphasized that the primary role of the radiologist in head and neck imaging is to help stage disease and guide surgery. Despite clinical and radiographic analysis, the diagnosis of many lesions ultimately depends on image-guided or excisional biopsy.

A mitogen-activated protein kinase of the corn leaf pathogen Cochliobolus heterostrophus is involved in conidiation, appressorium formation, and pathogenicity: diverse roles for mitogen-activated protein kinase homologs in foliar pathogens

Fungal pathogens perceive and respond to molecules from the plant, triggering pathogenic development. Transduction of these signals may use heterotrimeric G proteins, and it is thought that protein phosphorylation cascades are also important. We have isolated a mitogen-activated protein kinase homolog from the corn pathogen Cochliobolus heterostrophus to test its role as a component of the transduction pathways. The new gene, CHK1, has a deduced amino acid sequence 90% identical to Pmk1 of the rice blast fungus Magnaporthe grisea and 59% identical to Fus3 of Saccharomyces cerevisiae. A series of chk1 deletion mutants has poorly developed aerial hyphae, autolysis, and no conidia. No pseudothecia are formed when a cross between two Deltachk1 mutants is attempted. The ability of Deltachk1 mutants to infect corn plants is reduced severely. The growth pattern of hyphae on a glass surface is strikingly altered from that of the wild type, forming coils or loops, but no appressoria. This set of phenotypes overlaps only partially with that of pmk1 mutants, the homologous gene of the rice blast fungus. In particular, sexual and asexual sporulation both require Chk1 function in Cochliobolus heterostrophus, in contrast to Pmk1, but perhaps more similar to yeast, where Fus3 transmits the mating signal. Chk1 is required for efficient colonization of leaf tissue, which can be compared with filamentous invasive growth of yeast, modulated through another closely related mitogen-activated protein kinase, Kss1. Ubiquitous signaling elements thus are used in diverse ways in different plant pathogens, perhaps the result of coevolution of the transducers and their targets.

Identification of a novel family of targets of PYK2 related to Drosophila retinal degeneration B (rdgB) protein

The protein tyrosine kinase PYK2 has been implicated in signaling pathways activated by G-protein-coupled receptors, intracellular calcium, and stress signals. Here we describe the molecular cloning and characterization of a novel family of PYK2-binding proteins designated Nirs (PYK2 N-terminal domain-interacting receptors). The three Nir proteins (Nir1, Nir2, and Nir3) bind to the amino-terminal domain of PYK2 via a conserved sequence motif located in the carboxy terminus. The primary structures of Nirs reveal six putative transmembrane domains, a region homologous to phosphatidylinositol (PI) transfer protein, and an acidic domain. The Nir proteins are the human homologues of the Drosophila retinal degeneration B protein (rdgB), a protein implicated in the visual transduction pathway in flies. We demonstrate that Nirs are calcium-binding proteins that exhibit PI transfer activity in vivo. Activation of PYK2 by agents that elevate intracellular calcium or by phorbol ester induce tyrosine phosphorylation of Nirs. Moreover, PYK2 and Nirs exhibit similar expression patterns in several regions of the brain and retina. In addition, PYK2-Nir complexes are detected in lysates prepared from cultured cells or from brain tissues. Finally, the Nir1-encoding gene is located at human chromosome 17p13.1, in proximity to a locus responsible for several human retinal diseases. We propose that the Nir and rdgB proteins represent a new family of evolutionarily conserved PYK2-binding proteins that play a role in the control of calcium and phosphoinositide metabolism downstream of G-protein-coupled receptors.

Relationship of maternal and general self-acceptance to pre- and postpartum affective experience

Forty-nine married primiparous Israeli women responded to W. W. K. Zung's (1965) Self-Rating Depression Scale, N. M. Bradburn's (1969) Affect Balance Scale, and measures of general and maternal self-acceptance during the last trimester of pregnancy and again 6 to 8 weeks following childbirth. There was a significant decrease in depression from pre- to postpartum for the total group. Women high in general self-acceptance were less depressed and displayed less negative affect than those low in general self-acceptance. There were no corresponding differences between the high and low maternal self-acceptance groups. Both pre- and postpartum women tended to rate themselves significantly higher for maternal self-acceptance than for general self-acceptance.

Tumour necrosis factor alpha binding to human and mouse trophoblast

Tumour necrosis factor alpha (TNF-alpha) is a cytokine with pleiotropic effects, modulating cell growth, differentiation, and synthesis of various substances. Recent demonstration of TNF-alpha mRNA and protein in the uteroplacental unit suggests that this cytokine may be involved in the development of the embryo. To determine whether the embryo itself binds TNF-alpha, mouse blastocyst outgrowths and human first trimester villous trophoblast were analysed for TNF-alpha binding. Our experiments revealed that binding of TNF-alpha could be specifically detected on the trophectoderm of the outgrowing mouse embryos. They also show a complete disappearance of the colony-stimulating factor 1 (CSF-1) receptor that occurs shortly after the binding of TNF-alpha by the trophectoderm. In human first trimester villous trophoblast, TNF-alpha binding was found to be predominantly detectable on the syncytiotrophoblast and to a lesser extent on the cytotrophoblastic cells. Binding was not observed on adjacent embryonic or maternal cells. Our results further support the idea that TNF-alpha as well as other cytokines may modulate early embryonic development and implantation.

Tyrosine phosphorylation of Pyk2 is selectively regulated by Fyn during TCR signaling

The Src family protein tyrosine kinases (PTKs), Lck and Fyn, are coexpressed in T cells and perform crucial functions involved in the initiation of T cell antigen receptor (TCR) signal transduction. However, the mechanisms by which Lck and Fyn regulate TCR signaling are still not completely understood. One important question is whether Lck and Fyn have specific targets or only provide functional redundancy during TCR signaling. We have previously shown that Lck plays a major role in the tyrosine phosphorylation of the TCR-zeta chain and the ZAP-70 PTK. In an effort to identify the targets that are specifically regulated by Fyn, we have studied the tyrosine phosphorylation of Pyk2, a recently discovered new member of the focal adhesion kinase family PTK. We demonstrated that Pyk2 was rapidly tyrosine phosphorylated following TCR stimulation. TCR-induced tyrosine phosphorylation of Pyk2 was selectively dependent on Fyn but not Lck. Moreover, in heterologous COS-7 cells, coexpression of Pyk2 with Fyn but not Lck resulted in substantial increases in Pyk2 tyrosine phosphorylation. The selective regulation of Pyk2 tyrosine phosphorylation by Fyn in vivo correlated with the preferential phosphorylation of Pyk2 by Fyn in vitro. Our results demonstrate that Pyk2 is a specific target regulated by Fyn during TCR signaling.

Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements

Our purpose was to explore the utility of cine phase-contrast MRI velocity measurements in determining the functional status of third ventriculostomies, and to correlate the quantitative velocity data with clinical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI. The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of interest near the third ventricular floor, and in cerebrospinal fluid anterior to the upper pons and spinal cord on midline sagittal images. Ratios of the velocities of both the third ventricle and prepontine space to the space anterior to the spinal cord were obtained. The velocities near the third ventricular floor and in the pontine cistern were significantly higher in patients than in normal subjects, but the velocity anterior to the spinal cord was similar between the groups. The velocity ratios, used to normalize individual differences, were also higher in patients than in controls. Two patients had lower velocity ratios than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, who had a third ventricular/thalamic tumor, the lower values probably reflect distortion of the third ventricular floor. We conclude that phase-contrast MR velocity measurements, specifically the velocity ratio between the high pontine cistern and the space anterior to the spinal cord, can help determine the functional status of third ventriculostomies.

A role for Pyk2 and Src in linking G-protein-coupled receptors with MAP kinase activation

The mechanisms by which mitogenic G-protein-coupled receptors activate the MAP kinase signalling pathway are poorly understood. Candidate protein tyrosine kinases that link G-protein-coupled receptors with MAP kinase include Src family kinases, the epidermal growth factor receptor, Lyn and Syk. Here we show that lysophosphatidic acid (LPA) and bradykinin induce tyrosine phosphorylation of Pyk2 and complex formation between Pyk2 and activated Src. Moreover, tyrosine phosphorylation of Pyk2 leads to binding of the SH2 domain of Src to tyrosine 402 of Pyk2 and activation of Src. Transient overexpression of a dominant interfering mutant of Pyk2 or the protein tyrosine kinase Csk reduces LPA- or bradykinin-induced activation of MAP kinase. LPA- or bradykinin-induced MAP kinase activation was also inhibited by overexpression of dominant interfering mutants of Grb2 and Sos. We propose that Pyk2 acts with Src to link Gi- and Gq-coupled receptors with Grb2 and Sos to activate the MAP kinase signalling pathway in PC12 cells.

Activation of Pyk2 by stress signals and coupling with JNK signaling pathway

The c-Jun amino-terminal kinase (JNK) is activated by various heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors, inflammatory cytokines, and stress signals. Yet, upstream mediators that link extracellular signals with the JNK signaling pathway are currently unknown. The tyrosine kinase Pyk2 was activated by tumor necrosis factor alpha, by ultraviolet irradiation, and by changes in osmolarity. Overexpression of Pyk2 led to activation of JNK, and a dominant-negative mutant of Pyk2 interfered with ultraviolet light- or osmotic shock-induced activation of JNK. Pyk2 represents a cell type-specific, stress-sensitive mediator of the JNK signaling pathway.

Osteosarcoma: subtle, rare, and misleading plain film features

Osteosarcoma is a malignant, mesenchymal, osteoid, and bone-forming tumor [1-3]. In most cases, typical radiographic features clearly illustrate the aggressive bone-forming nature of the lesion. These features include long-bone metaphyseal location, mixed areas of lysis and sclerosis, cortical destruction, periosteal new bone, and soft-tissue mass. However, numerous factors contribute to misleading radiographic patterns of osteosarcoma. They include histologic low-grade, lytic, or minimally sclerotic lesions, early detection, confinement to the intramedullary canal, benign-appearing periosteal reaction, rare intraosseous locations (subchondral, diaphyseal, intracortical), and rare skeletal sites (e.g., soft tissues, skull, ribs, tarsal bones). Secondary osteosarcomas, such as those arising from infarcts or fibrous dysplasia, may also produce a confusing radiologic picture. The purpose of this pictorial essay is to illustrate cases of osteosarcoma that proved to be difficult diagnostic dilemmas because of their subtle, rare, or misleading plain film features.

Protein tyrosine kinase PYK2 involved in Ca(2+)-induced regulation of ion channel and MAP kinase functions

The protein tyrosine kinase PYK2, which is highly expressed in the central nervous system, is rapidly phosphorylated on tyrosine residues in response to various stimuli that elevate the intracellular calcium concentration, as well as by protein kinase C activation. Activation of PYK2 leads to modulation of ion channel function and activation of the MAP kinase signalling pathway. PYK2 activation may provide a mechanism for a variety of short- and long-term calcium-dependent signalling events in the nervous system.

The carbonic anhydrase domain of receptor tyrosine phosphatase beta is a functional ligand for the axonal cell recognition molecule contactin

Receptor-type protein tyrosine phosphatase beta (RPTP beta) is expressed in the developing nervous system and contains a carbonic anhydrase (CAH) domain as well as a fibronectin type III repeat in its extracellular domain. Fusion proteins containing these domains were used to search for ligands of RPTP beta. The CAH domain bound specifically to a 140 kDa protein expressed on the surface of neuronal cells. Expression cloning in COS7 cells revealed that this protein is contactin, a GPI membrane-anchored neuronal cell recognition molecule. The CAH domain of RPTP beta induced cell adhesion and neurite growth of primary tectal neurons, and differentiation of neuroblastoma cells. These responses were blocked by antibodies against contactin, demonstrating that contactin is a neuronal receptor for RPTP beta. These experiments show that an individual domain of RPTP beta acts as a functional ligand for the neuronal receptor contactin. The interaction between contactin and RPTP beta may generate unidirectional or bidirectional signals during neural development.

Cerebrospinal fluid flow waveforms: analysis in patients with Chiari I malformation by means of gated phase-contrast MR imaging velocity measurements

PURPOSE

To determine the features of the cardiac cycle-related cerebrospinal fluid (CSF) flow pulsations in with Chiari I malformation before and after decompressive surgery.

MATERIALS AND METHODS

Fifteen patients and 23 healthy subjects underwent cine phase-contrast magnetic resonance imaging. Ten patients were also examined after decompressive surgery. Four regions of interest were selected in the upper cervical subarachnoid space and premedullary cistern. Velocity and fraction of the cardiac cycle waveforms were plotted, and amplitude, temporal, and CSF displacement parameters were assessed.

RESULTS

In the Chiari I patients, impaired systolic and unaltered diastolic CSF flow pulsations immediately below the foramen magnum were identified. After surgery, the systolic flow pulsations immediately below the foramen magnum improved. Good correlation with post-surgical improvement was observed.

CONCLUSION

CSF flow waveform analysis helps demonstrate abnormalities in CSF flow at the foramen magnum and the benefits of decompressive surgery in patients with the Chiari I malformation.

The fourth immunoglobulin domain of the stem cell factor receptor couples ligand binding to signal transduction

Receptor dimerization is ubiquitous to the action of all receptor tyrosine kinases, and in the case of dimeric ligands, such as the stem cell factor (SCF), it was attributed to ligand bivalency. However, by using a dimerization-inhibitory monoclonal antibody to the SCF receptor, we confined a putative dimerization site to the nonstandard fourth immunoglobulin-like domain of the receptor. Deletion of this domain not only abolished ligand-induced dimerization and completely inhibited signal transduction, but also provided insights into the mechanism of the coupling of ligand binding to dimer formation. These results identify an intrinsic receptor dimerization site and suggest that similar sites may exist in other receptors.

Steel factor and c-kit protooncogene: genetic lessons in signal transduction

Despite extensive research on the molecular mechanisms of signal transduction by growth factors and their oncogenic receptor tyrosine kinases, the physiological relevance of these pathways, especially in mammals, remains largely unknown. A unique exception is the Steel factor (SLF) and its c-kit-encoded receptor, because many natural germ line mutations of both the ligand and the receptor exist in mice. The protooncogene c-kit encodes a cell surface receptor that belongs to the immunoglobulin gene family and carries an intrinsic tyrosine kinase activity in its cytoplasmic portion. The precursor of the Kit ligand, SLF, is also a transmembrane protein that exists as a soluble factor as well as a cell surface protein. The interaction of Kit with SLF leads to receptor dimerization, kinase activation, and tyrosine phosphorylation of cytoplasmic proteins that contain Src homology 2 motifs. Various mutations in Kit and SLF result in a defective signaling pathway and underly the complex phenotypes of W and Sl mice, respectively. The early development of at least four cell lineages is affected. These are erythrocytes, melanocytes, germ cells, and mast cells. Correlation between the behavior of these lineages and specific mutations uncovered interesting physiological aspects of the mechanism of signal transduction by a polypeptide growth factor. These include the different degrees of severity of affected lineages, indications for distinct functions during early embryonic development and at late phases, the significance of synergy between a growth factor and lymphokines, the interaction between mutant and wild-type proteins in heterozygous animals, and the possibility that a surface-anchored ligand may act differently than a soluble factor. Predictably, the lessons learned with Kit and Sl mice will be widely relevant to other pairs of ligands and receptors that control the function of different cell lineages and physiological processes.