Breast-to-brain metastasis is exacerbated with chemotherapy through blood-cerebrospinal fluid barrier and induces Alzheimer's-like pathology.

Control of breast-to-brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have been shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through the formation of neurofibrillary tangles (NFT), independently. Now, in this study, we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies increase brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage and release of Tau from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer's-like tauopathy.

Improved Glioma Grading Using Deep Convolutional Neural Networks.

BACKGROUND AND PURPOSE: Accurate determination of glioma grade leads to improved treatment planning. The criterion standard for glioma grading is invasive tissue sampling. Recently, radiomic features have shown excellent potential in glioma-grade prediction. These features may not fully exploit the underlying information in MR images. The objective of this study was to investigate the performance of features learned by a convolutional neural network compared with standard radiomic features for grade prediction. MATERIALS AND METHODS: A total of 237 patients with gliomas were included in this study. All images were resampled, registered, skull-stripped, and segmented to extract the tumors. The learned features from the trained convolutional neural network were used for grade prediction. The performance of the proposed method was compared with standard machine learning approaches, support vector machine, random forests, and gradient boosting trained with radiomic features. RESULTS: The experimental results demonstrate that using learned features extracted from the convolutional neural network achieves an average accuracy of 87%, outperforming the methods considering radiomic features alone. The top-performing machine learning model is gradient boosting with an average accuracy of 64%. Thus, there is a 23% improvement in accuracy, and it is an efficient technique for grade prediction. CONCLUSIONS: Convolutional neural networks are able to learn discriminating features automatically, and these features provide added value for grading gliomas. The proposed framework may provide substantial improvement in glioma-grade prediction; however, further validation is needed.

Advanced ADC Histogram, Perfusion, and Permeability Metrics Show an Association with Survival and Pseudoprogression in Newly Diagnosed Diffuse Intrinsic Pontine Glioma: A Report from the Pediatric Brain Tumor Consortium.

BACKGROUND AND PURPOSE: Diffuse intrinsic pontine glioma is a lethal childhood brain cancer with dismal prognosis and MR imaging is the primary methodology used for diagnosis and monitoring. Our aim was to determine whether advanced diffusion, perfusion, and permeability MR imaging metrics predict survival and pseudoprogression in children with newly diagnosed diffuse intrinsic pontine glioma. MATERIALS AND METHODS: A clinical trial using the poly (adenosine diphosphate ribose) polymerase (PARP) inhibitor veliparib concurrently with radiation therapy, followed by maintenance therapy with veliparib + temozolomide, in children with diffuse intrinsic pontine glioma was conducted by the Pediatric Brain Tumor Consortium. Standard MR imaging, DWI, dynamic contrast-enhanced perfusion, and DSC perfusion were performed at baseline and approximately every 2 months throughout treatment. ADC histogram metrics of T2-weighted FLAIR and enhancing tumor volume, dynamic contrast-enhanced permeability metrics for enhancing tumors, and tumor relative CBV from DSC perfusion MR imaging were calculated. Baseline values, post-radiation therapy changes, and longitudinal trends for all metrics were evaluated for associations with survival and pseudoprogression. RESULTS: Fifty children were evaluable for survival analyses. Higher baseline relative CBV was associated with shorter progression-free survival (P = .02, Q = 0.089) and overall survival (P = .006, Q = 0.055). Associations of higher baseline mean transfer constant from the blood plasma into the extravascular extracellular space with shorter progression-free survival (P = .03, Q = 0.105) and overall survival (P = .03, Q = 0.102) trended toward significance. An increase in relative CBV with time was associated with shorter progression-free survival (P < .001, Q < 0.001) and overall survival (P = .004, Q = 0.043). Associations of longitudinal mean extravascular extracellular volume fraction with progression-free survival (P = .03, Q = 0.104) and overall survival (P = .03, Q = 0.105) and maximum transfer constant from the blood plasma into the extravascular extracellular space with progression-free survival (P = .03, Q = 0.102) trended toward significance. Greater increases with time were associated with worse outcomes. True radiologic progression showed greater post-radiation therapy decreases in mode_ADC_FLAIR compared with pseudoprogression (means, -268.15 versus -26.11, P = .01.) CONCLUSIONS: ADC histogram, perfusion, and permeability MR imaging metrics in diffuse intrinsic pontine glioma are useful in predicting survival and pseudoprogression.

ASFNR recommendations for clinical performance of MR dynamic susceptibility contrast perfusion imaging of the brain.

MR perfusion imaging is becoming an increasingly common means of evaluating a variety of cerebral pathologies, including tumors and ischemia. In particular, there has been great interest in the use of MR perfusion imaging for both assessing brain tumor grade and for monitoring for tumor recurrence in previously treated patients. Of the various techniques devised for evaluating cerebral perfusion imaging, the dynamic susceptibility contrast method has been employed most widely among clinical MR imaging practitioners. However, when implementing DSC MR perfusion imaging in a contemporary radiology practice, a neuroradiologist is confronted with a large number of decisions. These include choices surrounding appropriate patient selection, scan-acquisition parameters, data-postprocessing methods, image interpretation, and reporting. Throughout the imaging literature, there is conflicting advice on these issues. In an effort to provide guidance to neuroradiologists struggling to implement DSC perfusion imaging in their MR imaging practice, the Clinical Practice Committee of the American Society of Functional Neuroradiology has provided the following recommendations. This guidance is based on review of the literature coupled with the practice experience of the authors. While the ASFNR acknowledges that alternate means of carrying out DSC perfusion imaging may yield clinically acceptable results, the following recommendations should provide a framework for achieving routine success in this complicated-but-rewarding aspect of neuroradiology MR imaging practice.

Perfusion and permeability MR imaging of gliomas.

Conventional contrast-enhanced MR imaging is the current standard technique for the diagnosis and treatment evaluation of gliomas and other brain neoplasms. However, this method is quite limited in its ability to characterize the complex biology of gliomas and so there is a need to develop more quantitative imaging methods. Perfusion and permeability MR imaging are two such techniques that have shown promise in this regard. This review will highlight the underlying principles, applications, and pitfalls of these evolving advanced MRI methods.

Multiphase evaluation of myocardial bridging with dual-source computed tomography.

BACKGROUND: Myocardial bridging (MB), also known as a tunneled artery, is a congenital anomaly that can be readily diagnosed with multidetector-row computed tomography (MDCT). With the advent of dual-source CT (DSCT), it may be feasible to evaluate dynamic changes of MB throughout the entire cardiac cycle. PURPOSE: To determine the feasibility of dynamic evaluation of MB using DSCT. MATERIAL AND METHODS: Forty-eight patients with MB of the left anterior descending artery diagnosed with multiplanar reconstruction on DSCT were included in this study. Multiphase reconstructions were performed for every subject. Image quality was assessed using a four-point scale (4 = excellent; 3 = good; 2 = adequate; 1 = not assessable). Systolic and diastolic images with optimal image quality were selected. Milking effect, defined as the narrowing of the tunneled artery during systole and its dilatation during diastole, was recorded. The stenosis rate of MB was computed. RESULTS: The optimal systolic and diastolic phases occurred between 40% and 70% of the R-R interval (range 20-80% of R-R interval). The image quality scores of all segments in systole and diastole were higher than or equal to 3. Diameter changes of tunneled vessel under MB in systole and diastole indicated milking effect, visualized on conventional coronary angiography (CAG). Average percentage of narrowing of the MB was 36+/-14%. CONCLUSION: High-quality systolic and diastolic images can be acquired using DSCT. Dynamic visualization of MB is possible, and milking effect can be quantified using DSCT.

Structural evidence for entropic contribution of salt bridge formation to a protein antigen-antibody interaction: the case of hen lysozyme-HyHEL-10 Fv complex.

A structural and thermodynamic study of the entropic contribution of salt bridge formation to the interaction between hen egg white lysozyme (HEL) and the variable domain fragment (Fv) of anti-HEL antibody, HyHEL-10, was carried out. Three Fv mutants (HD32A, HD96A, and HD32AD96A) were prepared, and the interactions between the mutant Fvs and HEL were investigated. Crystallography revealed that the overall structures of these mutant complexes were almost identical to that of wild-type Fv. Little structural changes were observed in the HD32AD96A mutant-HEL complex, and two water molecules were introduced into the mutation site, indicating that the two water molecules structurally compensated for the complete removal of the salt bridges. This result suggests that the entropic contribution of the salt bridge originates from dehydration. In the singly mutated complexes, one water molecule was also introduced into the mutated site, bridging the antigen-antibody interface. However, a local structural difference was observed in the HD32A Fv-HEL complex, and conformational changes occurred due to changes in the relative orientation of the heavy chain to the light chain upon complexation in HD96A Fv-HEL complexes. The reduced affinity of these single mutants for the antigen originates from the increase in entropy loss, indicating that these structural changes also introduced an increase in entropy loss. These results suggest that salt bridge formation makes an entropic contribution to the protein antigen-antibody interaction through reduction of entropy loss due to dehydration and structural changes.

Evidence that endo-1,4-beta-glucanases act on cellulose in suspension-cultured poplar cells.

Suspension-cultured poplar (Populus alba) cells produce two distinct endo-1,4-beta-glucanases, one of which is released in the extracellular culture medium and the other localized in their walls. Two cDNA clones, PopCel1 and PopCel2, isolated from a poplar cDNA library, encode the extracellular and the wall-bound endo-1, 4-beta-glucanases, respectively, based upon deduced amino acid sequences. The products of these two genes contained domains conserved in endo-1,4-beta-glucanase (family 9) and showed 91.5% amino acid identity. The levels of both PopCel1 and PopCel2 mRNAs increased during the lag phase of growth and decreased rapidly during the linear phase. After the levels had decreased, they were again increased by addition of sucrose to the culture medium and further enhanced by the addition of 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence of sucrose. The accumulation of the mRNAs was correlated with the solubilization of cello-oligosaccharides. Cello-oligosaccharides and xyloglucan were also solubilized from the wall preparations of poplar cells incubated with enzyme preparations from the extracellular culture medium and walls. An antibody against both PopCel proteins reduced the production of cello-oligosaccharides by the extracellular enzyme by 90% and that by the wall-bound enzyme by 55%, and also prevented xyloglucan solubilization. The results show that the accumulation of poplar endo-1,4-beta-glucanases is regulated indirectly by auxin in the presence of sucrose and can act on cellulose in suspension-cultured poplar cells.

Thermodynamic consequences of grafting enhanced affinity toward the mutated antigen onto an antibody. The case of anti-lysozyme antibody, HyHEL-10.

In order to address the mechanism of enhancement of the affinity of an antibody toward an antigen from a thermodynamic viewpoint, anti-hen lysozyme (HEL) antibody HyHEL-10, which also recognize the mutated antigen turkey lysozyme (TEL) with reduced affinity, was examined. Grafting high affinity toward TEL onto HyHEL-10 was performed by saturation mutagenesis into four residues (Tyr(53), Ser(54), Ser(56), and Tyr(58)) in complementarity-determining region 2 of the heavy chain (CDR-H2) followed by selection with affinity for TEL. Several clones enriched have a Phe residue at site 58. Thermodynamic analyses showed that the clones selected had experienced a greater than 3-fold affinity increase toward TEL in comparison with wild-type Fv, originating from an increase in negative enthalpy change. Substitution of HyHEL-10 HTyr(58) with Phe led to the increase in negative enthalpy change and to almost identical affinity for TEL in comparison with mutants selected, indicating that mutations at other sites decrease the entropy loss despite little contribution to the affinity for TEL. These results suggest that the affinity of an antibody toward the antigen is enhanced by the increase in enthalpy change by some limited mutation, and excess entropy loss due to the mutation is decreased by other energetically neutral mutations.

Crystal structure of anti-Hen egg white lysozyme antibody (HyHEL-10) Fv-antigen complex. Local structural changes in the protein antigen and water-mediated interactions of Fv-antigen and light chain-heavy chain interfaces.

In order to address the recognition mechanism of the fragments of antibody variable regions, termed Fv, toward their target antigen, an x-ray crystal structure of an anti-hen egg white lysozyme antibody (HyHEL-10) Fv fragment complexed with its cognate antigen, hen egg white lysozyme (HEL), was solved at 2.3 A. The overall structure of the complex is similar to that reported in a previous article dealing with the Fab fragment-HEL complex (PDB ID code,). However, the areas of Fv covered by HEL upon complex formation increased by about 100 A(2) in comparison with the Fab-HEL complex, and two local structural differences were observed in the heavy chain of the variable region (VH). In addition, small but significant local structural changes were observed in the antigen, HEL. The x-ray data permitted the identification of two water molecules between the VH and HEL and six water molecules retained in the interface between the antigen and the light chain complementarity determining regions (CDRs) 2 and 3 (CDR-L2 and CDR-L3). These water molecules bridge the antigen-antibody interface through hydrogen bond formation in the VL-HEL interface. Eleven water molecules were found to complete the imperfect VH-VL interface, suggesting that solvent molecules mediate the stabilization of interaction between variable regions. These results suggest that the unfavorable effect of deletion of constant regions on the antigen-antibody interaction is compensated by an increase in favorable interactions, including structural changes in the antigen-antibody interface and solvent-mediated hydrogen bond formation upon complex formation, which may lead to a minimum decreased affinity of the antibody Fv fragment toward its antigen.

Myocardial protection: the rebirth of potassium-based cardioplegia.

The introduction of open-heart surgery more than 4 decades ago signaled a new era in medicine. For the 1st time, previously untreatable cardiac anomalies became amenable to surgical therapy. The use of the heart-lung machine seemed to grant the surgeon unlimited time in which to operate inside the heart. Still frustrated by poor operating conditions and the threat of air embolism, Denis Melrose introduced elective cardiac arrest in 1955. His use of a potassium citrate solution seemed to offer a safe method to effect a quiet, bloodless field. However, a few years after its inception, numerous reports began to question the safety of this approach, and the Melrose technique was abandoned in the early 1960s. Nearly 15 years elapsed before potassium-based cardioplegia regained popularity. During this period, topical hypothermia, coronary perfusion with intermittent aortic occlusion, and normothermic ischemia were evaluated and discarded. A few European investigators like Hoelscher, Bretschneider, and Kirsch had maintained their interest in chemical cardioplegia, and it was through their efforts that future researchers like Hearse and Gay spearheaded the return to potassium-based cardioplegia, which today forms the core of the cardiac surgeon's myocardial protective armamentarium and has contributed towards lowering operative mortality rates.

Retrograde transvenous neuroperfusion: a back door treatment for stroke.

BACKGROUND AND PURPOSE: Stroke is the third leading cause of death and the leading cause of adult disability in the United States. The clot-lysis drug tissue plasminogen activator is the only treatment that has been effective for acute stroke patients, yet there are significant limitations to its use and effectiveness. In this study retrograde transvenous neuroperfusion (RTN) was evaluated for its efficacy in reversing acute ischemia, preventing paralysis, and limiting pathological evidence of infarction in baboons. METHODS: Ten adult male baboons underwent 3.5 hours of reversible middle cerebral artery occlusion (MCAO) under isoflurane (0.25% to 1.5%) anesthesia. Five randomly chosen animals received RTN treatment 1 hour after start of MCAO. Somatosensory evoked potentials were recorded during MCAO. Animals were assigned daily neurological scores. Animals were killed 6 days after MCAO, and brains were quantitatively analyzed for infarct volume. RESULTS: Within 1 hour after RTN was started, treated animals showed significantly improved somatosensory evoked potentials (103.3% versus 75% of baseline; P<0.01). Likewise, the combined neurological score for the RTN-treated group was 99.2, while the combined mean score for the untreated group was 66.4 (P<0.015). The mean infarction volume was 8.8+/-3.1% (of contralateral hemisphere) for the control group and 0.3+/-0.2% for the RTN-treated group (P<0.01). No increased mortality was seen in the RTN-treated group. CONCLUSIONS: We conclude that RTN treatment during MCAO effectively reverses the pathophysiological sequelae of ischemia, even when the treatment is initiated 1 hour after the onset of ischemia. Although the infarct volume in the control group was variable when quantitatively assessed 6 days after 3.5 hours of MCAO, virtually no evidence of infarcts was seen in the RTN-treated group.

Fine substrate specificities of four exo-type cellulases produced by Aspergillus niger, Trichoderma reesei, and Irpex lacteus on (1-->3), (1-->4)-beta-D-glucans and xyloglucan.

To investigate the fine substrate specificities of four highly purified exo-type cellulases (Exo-A from Aspergillus niger, CBHI and CBHII from Trichoderma reesei, and Ex-1 from Irpex lacteus), water-soluble substrates such as barley glucan, xyloglucan from tamarind (Tamarindus indica L.), and their oligosaccharides were employed. Four exo-type cellulases immediately hydrolyzed 3-O-beta-D-cellotriosylglucose to produce cellobiose and laminaribiose. In contrast, CBHII showed no hydrolytic activity towards 3(2)-O-beta-D-cello-biosylcellobiose, which was hydrolyzed to cellobiose by the other exo-type cellulases. These cellulases hydrolyzed the internal linkages of barley glucan and lichenan in an endo-type fashion to produce cellobiose and mix-linked oligosaccharides as main products. The DP-lowering activities of the four exo-type cellulases on barley glucan were in the order of Ex-1, CBHII, Exo-A, and CBHI. Based on gel permeation chromatography analysis of the hydrolysates, Ex-1 seemed to attack the internal cellobiosyl unit adjacent to beta-1,3-glucosidic linkages in barley glucan molecule more frequently than did the other cellulases. Xyloglucan was hydrolyzed only by CBHI and CBHII, and produced hepta-, octa-, and nona-saccharides. In addition, a xyloglucan tetradecasaccharide (XG14) was split only to heptasaccharide (XG7) by CBHI and CBHII.