Deep neural network to locate and segment brain tumors outperformed the expert technicians who created the training data

Purpose: Deep learning (DL) algorithms have shown promising results for brain tumor segmentation in MRI. However, validation is required prior to routine clinical use. We report the first randomized and blinded comparison of DL and trained technician segmentations.

Approach: We compiled a multi-institutional database of 741 pretreatment MRI exams. Each contained a postcontrast T1-weighted exam, a T2-weighted fluid-attenuated inversion recovery exam, and at least one technician-derived tumor segmentation. The database included 729 unique patients (470 males and 259 females). Of these exams, 641 were used for training the DL system, and 100 were reserved for testing. We developed a platform to enable qualitative, blinded, controlled assessment of lesion segmentations made by technicians and the DL method. On this platform, 20 neuroradiologists performed 400 side-by-side comparisons of segmentations on 100 test cases. They scored each segmentation between 0 (poor) and 10 (perfect). Agreement between segmentations from technicians and the DL method was also evaluated quantitatively using the Dice coefficient, which produces values between 0 (no overlap) and 1 (perfect overlap).

Results: The neuroradiologists gave technician and DL segmentations mean scores of 6.97 and 7.31, respectively (p<0.00007). The DL method achieved a mean Dice coefficient of 0.87 on the test cases.

Conclusions: This was the first objective comparison of automated and human segmentation using a blinded controlled assessment study. Our DL system learned to outperform its “human teachers” and produced output that was better, on average, than its training data.

Magnetic Resonance Imaging Assessment of Vascular Contact of the Facial Nerve in the Asymptomatic Patient

Objective The objective of this study was to determine the prevalence of facial nerve vascular contact on magnetic resonance imaging (MRI) in patients without hemifacial spasm (HFS). Study Design Our radiology database was queried to identify consecutive adult patients without a history of HFS, intracranial tumor, brain radiation therapy, intracranial surgery, traumatic brain injury, or trigeminal nerve vascular compression. One hundred high-resolution MRIs of the posterior fossa were independently reviewed by two neuroradiologists for facial nerve vascular contact (200 sides). Main Outcome Measures The prevalence of vascular nerve contact in the non-HFS patient, the location of contact along the facial nerve, the culprit vessel, and severity of compression was recorded. Results The presence of vascular contact in the non-HFS patient may be as high as 53%. It is typically mild to moderate in severity, most commonly involves the cisternal portion, and usually caused by the anterior inferior cerebellar artery. Conclusion Vascular contact of the facial nerve is frequently identified in asymptomatic individuals but tends to be more peripheral and mild compared with previous descriptions of neurovascular contact in HFS patients. These results should be considered in assessing the candidacy of HFS patients for microvascular decompression.

Differential light-shift cancellation in a magnetic-field-insensitive transition of 87rb

The precise measurement of transition frequencies of trapped atomic samples is susceptible to inaccuracy arising from the inhomogeneous differential shift of the relevant energy levels in the presence of the trapping fields. We demonstrate near-complete cancellation of the differential ac Stark shift ("light shift") of a two-photon magnetic-field-insensitive microwave hyperfine (clock) transition in ^{87}Rb atoms trapped in an optical lattice. Up to 95(2)% of the differential light shift is cancelled while maintaining magnetic-field insensitivity. This technique should have applications in quantum information and frequency metrology.

Localization of a rapid CSF leak with digital subtraction myelography

A 53-year-old woman with superficial siderosis underwent spinal MR imaging, which demonstrated a large cervicothoracic epidural fluid collection compatible with a CSF leak. Conventional and dynamic CT myelography failed to localize the dural tear because of rapid equilibration of myelographic contrast between the thecal sac and the extradural collection. The superior temporal resolution of digital subtraction myelography precisely localized the CSF leak preoperatively and led to the successful surgical correction of the dural tear.

Refractory headaches due to multilevel thoracic cerebrospinal fluid leaks

BACKGROUND

Spontaneous cerebrospinal fluid leak is a well-documented cause of postural headache. We report a medically refractory headache due to multilevel thoracic cerebrospinal fluid leaks.

CASE REPORT

A 44-year-old male with an acute onset of postural headache failed to respond to bed rest, hydration, and analgesics. Magnetic resonance imaging demonstrated a large cerebrospinal fluid leak centered at the right T4 and left T11 to 12 levels, with bony pathology evident at the lower thoracic level. Lumbar (L4 to 5) and computed tomography guided T4 to 5 level epidural blood patches provided minimal pain relief. Percutaneous epidural fibrin glue injection at T4 followed by a repeat computed tomography guided epidural blood patch led to significant but incomplete symptom relief. Subsequent imaging demonstrated persistent fluid at the T11 to 12 level. Fibrin glue and epidural blood patches at this level reduced but did not eliminate the leak and residual symptoms. Extensive corrective surgery was offered but declined by the patient.

CONCLUSION

Treatment of multifocal cerebrospinal fluid leaks can be challenging, particularly when at least part of the underlying etiology is fixed structural bony pathology.

Release of bovine serum albumin from a hydrogel-cored biodegradable polymer fiber

We have developed a novel biodegradable, polymeric fiber construct that is coextruded using a wet-spinning process into a core-sheath format with a polysaccharide pre-hydrogel solution as the core fluid and poly(L-lactic acid) (PLLA) as the sheath. The biodegradable, biocompatible fibers were extruded from polymeric emulsions comprised of solutions of various molecular weights of PLLA dissolved in chloroform and containing dispersed, protein-free aqueous phases comprising up to 10% of the emulsion volume. Biologically sensitive agents can be loaded via a dispersed aqueous phase in the polymer, and/or directly into the polysaccharide. We show that this core-sheath fiber format will load a model protein that can be delivered for extended periods in vitro. Bovine serum albumin (BSA) was loaded into the fiber core as a model protein. We have shown that the greater the volume of the protein-free aqueous phase dispersed into the polymeric continuous-phase emulsion, the greater the total release of BSA encapsulated by a core gel comprised of 1% sodium alginate solution. We conclude this fiber format provides a promising vehicle for in vivo delivery of biological molecules. Its biocompatibility and biodegradability also allow for its use as a possible substrate for tissue engineering applications.

Metastatic Prostate Carcinoma Mimicking Meningioma

BACKGROUND

Intracranial dural-based lesions can be due to benign or malignant processes. Imaging characteristics cannot always discern between different pathologic conditions. A thorough clinical evaluation may reveal likely diagnostic possibilities. However, in certain cases, the etiology of the underlying lesion may require biopsy or resection to appropriately treat the patient.

REVIEW SUMMARY

We report the case of a large dural-based adenocarcinoma of the prostate clinically and radiographically mimicking a meningioma. We review the history and physical evaluation of the patient and subsequent treatment and response. We discuss the implications of dural-based intracranial lesions in patients with prostate cancer and review the literature of dural metastases, including the pathogenesis, tumor types, and clinical presentations.

CONCLUSION

The differential diagnosis of dural-based lesions in the brain varies from incidental and benign to symptomatic and malignant. Careful vigilance in patients with a history of cancer and presenting with new symptoms or imaging evidence of dural-based lesions is critically important to provide timely intervention.

Evaluation of in Vitro Drug Release, pH Change, and Molecular Weight Degradation of Poly(L-lactic acid) and Poly(D,L-lactide-co-glycolide) Fibers

Biodegradable fibers of poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) that encapsulated a water-soluble drug were created by a patented technique consisting of wet-spinning a water-in-oil emulsion. These fibers are 2.4% by mass drug, which is slowly released, making these fibers potential candidates for implantation as drug delivery devices and/or tissue-engineering substrates. Drug release kinetics and changes in molecular weight were investigated over time. This study demonstrated that drug release rates and molecular weight degradation are a function of the amount of aqueous phase added as an emulsion during fabrication. The type of polymer used (PLLA or PLGA) determines the molecular weight degradation rates, but has little effect on drug release kinetics.

Observation of a narrow charm-strange meson D(+)(sJ)(2632)-->D(+)(s)eta and D(0)K(+)

We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.

Odd-Parity Superconductivity in Sr 2 RuO 4

Phase-sensitive measurements were made on Sr2RuO4 to establish unambiguously the odd-parity pairing in this material. The critical current of Au(0.5)In(0.5)-Sr2RuO4 superconducting quantum interference devices prepared on Sr2RuO4 single crystals was found to be a maximum for devices with junctions on the same side of the crystal and a minimum for devices with junctions on opposite sides, in the limit of zero magnetic flux; these findings indicate that the phase of the superconducting order parameter in Sr2RuO4 changes by pi under inversion. This result verifies the odd-parity pairing symmetry and the formation of spin-triplet Cooper pairs in Sr2RuO4.

Carotid pseudostring sign from vasa vasorum collaterals

OBJECTIVE

To describe the spectral and color Doppler imaging findings in 2 cases of internal carotid artery occlusion with vasa vasorum collateral flow, which we term the "pseudostring sign."

METHODS

Spectral and color Doppler imaging findings in both cases were reviewed. Magnetic resonance angiography in 2 cases and conventional angiography in 1 case were also reviewed.

RESULTS

Both patients had color Doppler images showing that the internal carotid artery was a narrow, stringlike vessel with arterial flow that had normal spectral Doppler features (velocity < 125 cm/s with a normal waveform). Magnetic resonance angiography in 1 patient showed total occlusion of the proximal internal carotid artery with patent vasa vasorum collaterals reconstituting the lumen distally. In the second patient, magnetic resonance angiography showed total occlusion of the proximal internal carotid artery, and conventional angiography showed proximal occlusion with collateral flow through the vasa vasorum.

CONCLUSION

Proximal internal carotid artery occlusion with vasa vasorum collateral flow should be considered when color Doppler imaging shows a seemingly narrow internal carotid artery with tortuosity and normal spectral Doppler features. Patients with these features should not undergo carotid endarterectomy directly on the basis of only the Doppler findings.

Quantum phase transition in quasi-one-dimensional BaRu6O12

We report the first systematic study of the electrical transport and magnetic properties of BaRu6O12, which has a quasi-one-dimensional (quasi-1D) hollandite structure. We show that BaRu6O12 is quasi-1D electronically as well. Its physical properties were found to be extremely sensitive to disorder. Furthermore, a transition from being metallic with a resistance drop around 2 K to being weakly insulating as the applied magnetic field was increased was also found. We propose that these two features are related to the possible presence of a quantum phase transition in this material system.

First observation of the doubly charmed baryon Xi(+)(cc)

We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.

Orthostatic headache syndrome with CSF leak secondary to bony pathology of the cervical spine

The syndrome of orthostatic (low pressure) headaches is well described and most commonly occurs following deliberate violation of the dura (e.g. lumbar puncture). This syndrome can also occur spontaneously and results from the leakage of CSF. We describe three patients who suffered from spontaneous CSF leaks secondary to bony pathology of the cervical spine, and propose that this may be a more common aetiology than originally thought. Often these patients are difficult to manage medically, and surgery may be necessary for symptomatic relief.

Observation of Andreev surface bound states in the 3-K phase region of Sr2RuO4

The tunneling spectrum of the superconducting phase with Tc approximately 3.0 K has been measured in the Ru-embedded region of Sr2RuO4 using cleaved junctions. A sharp zero-bias conductance peak (ZBCP) has been observed below 3 K. All characteristics of this ZBCP suggest that it originates from Andreev surface bound states, indicating that the pairing in the 3-K phase is also non- s-wave. Below the bulk Tc of Sr2RuO4 (approximately 1.5 K), a crossover from sharp to bell-shaped ZBCP was found. This supports the theory that there is a phase transition in the 3-K phase region near the bulk Tc.

Non-Fermi-liquid behaviour in La4Ru6O19

Understanding the complexities of electronic and magnetic ground states in solids is one of the main goals of solid-state physics. Transition-metal oxides have proved to be particularly fruitful in this regard, especially for those materials with the perovskite structure, where the special characteristics of transition-metal-oxygen orbital hybridization determine their properties. Ruthenates have recently emerged as an important family of perovskites because of the unexpected evolution from high-temperature ferromagnetism in SrRuO3 to low-temperature superconductivity in Sr2RuO4 (refs 1, 2). Here we show that a ruthenate in a different structural family, La4Ru6O19, displays a number of highly unusual properties, most notably non-Fermi-liquid behaviour. The properties of La4Ru6O19 have no analogy among the thousands of previously characterized transition-metal oxides. Instead, they resemble those of CeCu6-xAux-a widely studied f-electron-based heavy fermion intermetallic compound that is often considered as providing the best example of non-Fermi-liquid behaviour. In the ruthenate, non-Fermi-liquid behaviour appears to arise from just the right balance between the interactions of localized electronic states derived from Ru-Ru bonding and delocalized states derived from Ru-O hybridization.

Precision measurements of the lambda(+)(c) and D0 lifetimes

We report new precision measurements of the lifetimes of the Lambda(+)(c) and D0 from SELEX, the charm hadroproduction experiment at Fermilab. Based upon 1630 Lambda(+)(c) and 10 210 D0 decays we observe lifetimes of tau[Lambda(+)(c)] = 198.1+/-7.0+/-5.6 fs and tau[D0] = 407.9+/-6.0+/-4.3 fs.

Laminin-coated poly(L-lactide) filaments induce robust neurite growth while providing directional orientation

Cellular channels during development and after peripheral nerve injury are thought to provide guidance cues to growing axons. In tissue culture where these cues are absent, neurites from dorsal root ganglion neurons grow with a radial distribution. To induce directional axonal growth and to enhance the rate of axonal growth after injury, we have designed microfilaments of poly(L-lactide). We demonstrate that dorsal root ganglia grown on these filaments in vitro extend longitudinally oriented neurites in a manner similar to native peripheral nerves. The extent of neurite growth was significantly higher on laminin-coated filaments compared with uncoated and poly-L-lysine-coated filaments. As high as 5.8 +/- 0.2 mm growth was observed on laminin-coated filaments compared with 2.0 +/- 0.2 mm on uncoated and 2.2 +/- 0.3 mm on poly-L-lysine-coated filaments within 8 days. Schwann cells were found to grow on all types of filaments. They were, however, absent in the leading edges of growth on laminin-coated filaments. Photolysis of Schwann cells caused a significant reduction in the neurite length on all types of filaments. Laminin-coated filaments, however, induced significantly longer neurites compared with uncoated and/or poly-L-lysine-coated filaments even in the absence of Schwann cells. Our results suggest that laminin-coated poly(L-lactide) filaments are suitable for inducing directional and enhanced axonal growth. Implants designed by arranging these microfilaments into bundles should aid regenerating axons by providing guidance cues and channels to organize matrix deposition, cell migration, axon growth, and improve functional recovery.

Controlled release from a composite silicone/hydrogel membrane

To enhance the drug uptake and release capacity of silicone rubber (SR), N-isopropylacrylamide (NIPA) hydrogel particles have been incorporated into a SR membrane. The NIPA particles were thoroughly blended with uncured SR with a certain ratio at room temperature. The mixture was then cast in a Petri dish to 1 mm thickness and cured 10 hours at 90 degrees C. The SR/NIPA composite gel can absorb water approximately equal to its dry weight. Brilliant blue, used as a mock drug, was loaded into the composite gel. Drug release increased exponentially to a final value that is temperature dependent: low at T> =34 degrees C, and high at T< 34 degrees C. This finding is because the hydrophobicity of NIPA changes with temperature. Pulsed release in response to temperature switching between 20 and 39 degrees C has been achieved. Drug uptake and release capability strongly depends upon the structure of the composite gel. The optimal range of NIPA composition is between 75 and 87% by volume. In the cited range, the NIPA particles form an interconnected network that provides a channel for diffusion of drug solution. The SR/NIPA composite gel has promising attributes as a wound dressing and other uses.

Quantitative MR imaging study of intravitreal sustained release of VEGF in rabbits

PURPOSE

To determine whether sustained elevation of vascular endothelial growth factor (VEGF) in the vitreous cavity causes retinal hyperpermeability [blood-retinal barrier (BRB) breakdown] before the development of retinal neovascularization (NV) and to document the kinetics of the integrity of BRB breakdown versus time.

METHODS

Poly(L-lactide-co-glycolide)based devices loaded with VEGF were implanted intravitreally in rabbit eyes. Contrast-enhanced magnetic resonance imaging (MRI) methods were used to identify and quantitate the retinal permeability at various time points after implantation. This was done with the newly developed MR tracer AngioMARK (Epix Medical, Boston, MA). After the MRI measurements, fundus photography and fluorescein angiography (FA) also were performed on the same set of animals.

RESULTS

At 3 days after implantation, the MR images showed a significant retinal leakage into the vitreous cavity (BRB breakdown) of the VEGF-implanted eyes. To quantitate this leakage, the permeability surface area product (PS) was measured. At 3 days, the mean PS product was 1.25 +/-0.25 x 10(-5) cm3/min. Based on the VEGF in vitro release study, this 3-day BRB breakdown corresponded to a total sustained release of 7.42 +/- 0.54 microg/ml of VEGF. The fundus and FA photographs of these VEGF-implanted eyes taken at 4 days after implantation also showed a considerable level of retinal vascular dilation and tortuosity. By 12 days after implantation, the mean PS product decreased to 5.83 +/- 1.38 x 10(-6) cm3/min. However, the retinal NV was observed only after the second week after implantation. By this time, a total of 10.70 +/- 0.92 microg/ml of VEGF was released in a sustained fashion. Also, after the retinal NV development, retinal detachment also was observed. The control eyes, however, which were implanted with blank devices, remained unchanged and normal during the entire course of this study (PS = 5.57 +/- 0.66 x 10(-7) cm3/min). CONCLUSIONS. The findings indicate that sustained delivery of elevated amounts of VEGF in the vitreous cavity induces a BRB breakdown even earlier than 3 days after implantation. This was achieved after a total sustained release of 7.42 +/- 0.54 microg/ml of VEGF. This retinal leakage regressed by more than half by the time the retinal NV developed. Furthermore, a retinal detachment occurred after this retinal NV. These results are similar to proliferative diabetic retinopathy (PDR). The sustained elevation of VEGF in the vitreous cavity of rabbit eyes is potentially a good model to test VEGF antagonists to treat or prevent PDR in humans. The quantifiable change of BRB breakdown by the contrast-enhanced MRI method is ideal to assess the therapeutic intervention in vivo without killing the animal and may prove to be clinically useful in humans.

Enhancing hepatocyte adhesion by pulsed plasma deposition and polyethylene glycol coupling

Decreased hepatocyte adhesion to polymeric constructs limits the function of tissue engineered hepatic assist devices. We grafted adhesion peptides (RGD and YIGSR) to polycaprolactone (PCL) and poly-L-lactic acid (PLLA) in order to mimic the in vivo extracellular matrix and thus enhance hepatocyte adhesion. Peptide grafting was done by a novel technique in which polyethylene glycol (PEG)-adhesion peptide was linked to allyl-amine coated on the surface of PCL and PLLA by pulsed plasma deposition (PPD). Peptide grafting density, quantified by radio-iodinated tyrosine in YIGSR, was 158 fmol/cm(2) on PLLA and 425 fmol/cm(2) on PCL surfaces. The adhesion of hepatocytes was determined by plating 250,000 hepatocytes/well (test substrates were coated on 12 well plates) and quantifying the percentage of adhered cells after 6 h by MTT assay. Adhesion on PCL surfaces was significantly enhanced (p < 0.05) by both YIGSR (percentage of adhered cells = 53 +/- 7%) and RGD (53 +/- 12%) when compared to control surfaces (31 +/- 8%). Hepatocyte adhesion on PLLA was significantly (p < 0.05) enhanced on PLLA-PEG-RGD surfaces (76 +/- 14%) compared to control surfaces (42 +/- 19%) and more (68 +/- 25%) but not statistically significant (p = 0.15) on PLLA-PEG-YIGSR surfaces compared to control surfaces. These results indicate that hepatocyte adhesion to PCL and PLLA based polymeric surfaces can be enhanced by a novel adhesion peptide grafting technique using pulsed plasma deposition and PEG cross-linking.

Quantitative determination of the peptide retention of polymeric substrates using matrix-assisted laser desorption/ionization mass spectrometry

Polymer surface-peptide binding interactions have been shown previously to lead to reductions in peptide matrix assisted laser desorption/ionization (MALDI) ion signals. In previous studies, increases in surface-peptide binding were characterized by the increases in both the initially adsorbed and retained quantities of 125I-radiolabeled peptides. The present studies establish a specific correlation between the peptide retention properties of the polymer surface and the reduction in the peptide MALDI ion signal. This correlation is demonstrated by obtaining MALDI mass spectra of angiotensin I applied to various polymer surfaces having a range of peptide adsorption and retention properties. In addition, the use of a MALDI based method of standard additions is shown to allow the quantitation of the polymer surface-peptide retention affinity for angiotensin I and porcine insulin. The MALDI standard additions method for measurement of surface-peptide retention affinities offers a number of significant advantages over conventional radiolabeled peptide binding methods and promises to be a valuable tool for the determination of this important biomaterial characteristic.

Effects of protein-surface interactions on protein ion signals in MALDI mass spectrometry

The influence of polymer surface-protein binding affinity on protein ion signals in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is examined. The surfaces of poly(vinylidene fluoride) and poly(ethylene terephthalate) polymer substrates are modified by pulsed rf plasma deposition of allylamine. By varying the on/off duty cycle of the pulsed rf plasma, the polymer substrate surfaces are coated with thin films having varying densities of surface amine groups. The varying surface amine density is shown to lead to systematic changes in the surface binding affinity for the 125I-radiolabeled peptides angiotensin I and porcine insulin. Unlabeled angiotensin I and porcine insulin are then deposited on the pulsed rf plasma-modified substrates and analyzed by MALDI mass spectrometry. The experimental approach involves applying the peptide to the modified polymer surface in an aqueous phosphate-buffered saline solution and allowing the peptide solution to dry completely under ambient conditions. Subsequently, the MALDI matrix alpha-cyano-4-hydroxycinnamic acid in methanol and 10% trifluoroacetic acid in water are added to the peptide-coated modified polymer surfaces. The results of these studies demonstrate that, for the sample preparation method employed, increases in the surface peptide binding affinity lead to decreases in the peptide MALDI ion signal.

Design of an oxygenator with enhanced gas transfer efficiency

Membrane oxygenator designs were examined with particular attention to the influence of radial and axial flow around windings of microporous polypropylene hollow fibers. Oxygen transfer performance was calculated, employing the Mockros-Leonard modified heat transfer analysis and Curtis-Eberhart normalization methods. Flow through an Avecor Affinity oxygenator was imaged by gamma scintigraphy using a bolus injection of 99mTc-DTPA. Experimental mass transfer correlations were developed for this oxygenator using saline. The oxygen exchange of the Avecor Affinity was slightly less than that for the Medtronic Maxima or COBE Optima models, which are based on similar designs.

Bright Spots, Structure, and Magmatism in Southern Tibet from INDEPTH Seismic Reflection Profiling

INDEPTH seismic reflection profiling shows that the decollement beneath which Indian lithosphere underthrusts the Himalaya extends at least 225 kilometers north of the Himalayan deformation front to a depth of approximately 50 kilometers. Prominent reflections appear at depths of 15 to 18 kilometers near where the decollement reflector apparently terminates. These reflections extend north of the Zangbo suture to the Damxung graben of the Tibet Plateau. Some of these reflections have locally anomalous amplitudes (bright spots) and coincident negative polarities implying that they are produced by fluids in the crust. The presence of geothermal activity and high heat flow in the regions of these reflections and the tectonic setting suggest that the bright spots mark granitic magmas derived by partial melting of the tectonically thickened crust.

Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results

INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.

High affinity polyethylene oxide for improved biocompatibility

Albumin passivation methods are based on the premise that a confluent layer of conformationally intact albumin will provide a biocompatible surface. However, albumin in contact with foreign surfaces tends to denature, and other proteins will adsorb to the surface, making the albumin passivation theory difficult to test. To overcome these two limitations, it was necessary to have a nondenaturing ligand specific for albumin attached to the surface by a long chain polyethylene oxide (PEO), which is known to have low protein binding. Clinical reports suggest no denaturation of albumin upon binding with warfarin, a drug known to have high albumin affinity. Thus, we tethered warfarin to glass.

Radiation-induced meningioma following radiation therapy for pituitary adenoma

The authors report the long-term result of treatment of a presumed pituitary adenoma with external-beam radiation therapy, which appears to be the development of a radiation-induced meningioma. Of the post radiation neoplasms that have been reported, meningiomas constitute a large proportion of these lesions.

Analysis of albumin deposits on hydroxylated siloxane films. Implications for surface treatment of medical devices

The authors have developed methods to enhance albumin binding to modified silicone rubber (SR) films. An intermediate bifunctional coupling agent, polyvinylmethyl siloxane-comethyl-1-ethanol siloxane (PVMS-CO-MES), is prepared from a cyclic tetramer, vinyl-methyl siloxane, by an oxymercuration-demercuration reaction, and cross-linked to silicone rubber under mild peroxide catalytic conditions. Free mercury on the surface was obtained under many reaction conditions and is shown to materially enhance 125I-labeled albumin binding. The mechanism most likely occurs via disulfide bond breakage, protein denaturation, and aggregation. The possible role of iodine-mercury bonds, an artefactual source, is ruled out with the aid of total internal reflectance-fluorescence measurements of the albumin adsorption rate constant. Although in situ albumin aggregation via disulfide bond breakage is a potentially attractive method for biocompatible protein gel formation, the toxicity of mercury makes the current method unfit for clinical practice.

Late juvenile-onset Krabbe's disease

Krabbe's disease is an autosomal recessive leukodystrophy characterized by a lack of galactocerebroside beta-galactosidase activity. In contrast to the classic early infantile-onset form of Krabbe's disease, less recognized, late-onset variants exist. The authors present a case of late juvenile-onset Krabbe's disease, including the associated magnetic resonance imaging (MRI) findings. Most patients with late-onset Krabbe's disease present with visual loss due to optic atrophy. Associated gait abnormalities and parental consanguinity should increase the clinician's suspicion that a child may have late-onset Krabbe's disease. Because of the prolonged survival in late-onset Krabbe's disease, the recent development of bone marrow transplantation for these patient makes diagnosis of this disorder particularly important.

Separation of epidermal cells by density centrifugation: a new technique for studies on normal and pathological differentiation

Murine keratinocytes, isolated by flotation trypsinization of skin, can be separated into five groups by centrifugation through Percoll, a colloidal silica gradient. Within each group a good correlation was found between density, plating efficiency, morphological appearance, DNA synthesis, and degree of keratinization/cornification. This method can be applied equally well to fetal, newborn, or adult keratinocytes and should be useful in a variety of studies including isolation of subpopulations of pathological cell types, work on chalones and hyperplastic diseases such as psoriasis, and in vitro transformation studies.