Cobalt-Catalyzed Asymmetric Hydrogenation: Substrate Specificity and Mechanistic Variability

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area.

Synthesis of P-stereogenic 1-phosphanorbornane-derived phosphine-phosphite ligands and application in asymmetric catalysis

A convenient synthesis of enantiopure mixed donor phosphine-phosphite ligands has been developed incorporating P-stereogenic phosphanorbornane and axially chiral bisnaphthols into one ligand structure. The ligands were applied in Pd-catalyzed asymmetric allylic substitution of diphenylallyl acetate, Rh-catalyzed asymmetric hydroformylation of styrene and Rh-catalyzed asymmetric hydrogenation of an acetylated dehydroamino ester. Excellent branched selectivity was observed in the hydroformylation although low ee was found. Moderate ee's of up to 60% in allylic substitution and 50% in hydrogenation were obtained using bisnaphthol-derived ligands.

Access to Enantiomerically Pure P-Chiral 1-Phosphanorbornane Silyl Ethers

Sulfur-protected enantiopure P-chiral 1-phosphanorbornane silyl ethers 5a,b are obtained in high yields via the reaction of the hydroxy group of P-chiral 1-phosphanorbornane alcohol 4 with tert-butyldimethylsilyl chloride (TBDMSCl) and triphenylsilyl chloride (TPSCl). The corresponding optically pure silyl ethers 5a,b are purified via crystallization and fully structurally characterized. Desulfurization with excess Raney nickel gives access to bulky monodentate enantiopure phosphorus(III) 1-phosphanorbornane silyl ethers 6a,b which are subsequently applied as ligands in iridium-catalyzed asymmetric hydrogenation of a prochiral ketone and enamide. Better activity and selectivity were observed in the latter case.

Ru-Catalyzed Direct Asymmetric Reductive Amination of Bio-Based Levulinic Acid and Ester for the Synthesis of Chiral Pyrrolidinone

Direct asymmetric reductive amination of bio-based levulinic acid (LA) to the enantioenriched 5-methylpyrrolidinone is achieved by using a readily available chiral Ru/bisphosphine catalyst with excellent enantioselectivity (up to 96 % ee) and high isolated yield (up to 89 %). Methyl levulinate (ML), a byproduct from the industrial production of 2,5-furandicarboxylic acid (FDCA), can be used instead of LA with similar reactivity and selectivity. Mass spectrometry and isotope labelling studies indicate that the chiral lactam is formed via imine-enamine tautomerization/cyclization followed by asymmetric hydrogenation of the cyclic enamide.

Cobalt-catalyzed Enantioselective Hydrogenation of Trisubstituted Carbocyclic Olefins: An Access to Chiral Cyclic Amides

The enantioselective hydrogenation of cyclic enamides has been achieved using an earth-abundant cobalt-bisphosphine catalyst. Using CoCl2/(S,S)-Ph-BPE, several trisubstituted carbocyclic enamides were reduced with high activity and excellent enantioselectivity (up to 99%) to the corresponding saturated amides. The methodology can be extended to the synthesis of chiral amines by base hydrolysis of the hydrogenation products. Preliminary mechanistic investigations reveal the presence of a high spin cobalt (II) species in the catalytic cycle. We propose that the hydrogenation of the carbon-carbon double bond proceeds via a sigma-bond-metathesis pathway.

Betti base derived P-stereogenic phosphine-diamidophosphite ligands with a single atom spacer and their application in asymmetric catalysis

Small bite-angle P-chirogenic PNP ligands have been synthesized stereo-selectively and employed in Rh-catalyzed asymmetric hydrogenation and Pd-catalyzed asymmetric allylic substitution resulting in moderate to excellent enantioselectivities.

A Bis (BICAAC) Palladium(II) Complex: Synthesis and Implementation as Catalyst in Heck-Mizoroki and Suzuki-Miyaura Cross Coupling Reactions

Carbenes are one of the most appealing, well-explored, and exciting ligands in modern chemistry due to their tunable stereoelectronic properties and a wide area of applications. A palladium complex (BICAAC)₂PdCl₂ with a recently discovered cyclic (alkyl)(amino)carbene having bicyclo[2.2.2] octane skeleton (BICAAC) was synthesized and characterized. The enhanced σ-donating and π-accepting ability of this carbene lend a hand to form a robust Pd-carbene bond, which allowed us to probe its reactivity as a precatalyst in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions with low catalyst loading in open-air conditions. The diverse range of substrates was explored for both the cross-coupling reactions. To get a better understanding of the catalytic reactions, several analytical techniques such as field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and powder X-ray diffraction were employed in a conclusive manner.

The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3 as catalyst precursor

RhCl3-catalysed hydrogenation/hydrodeoxygenation of aromatic ketones produced alkylcyclohexanes in TFE and cyclohexyl alkyl alcohols in water at moderate temperatures. Rh-nanoparticles were found to be the true catalysts.

Recent developments in asymmetric hydroformylation

This review describes the recent developments in the field of asymmetric hydroformylation. A large variety of ligands is now available, some of which are extremely effective in inducing high enantio- and regioselectivity.

Cation exchange synthesis of uniform PbSe/PbS core/shell tetra-pods and their use as near-infrared photodetectors

In this work we explore the preparation of complex-shaped semiconductor nanostructures composed of different materials via a cationic exchange process in which the cations of the original semiconductor nanostructure are replaced by cations of different metals with preservation of the shape and the anionic framework of the nanocrystals. Utilizing this cation exchange method, we synthesized two new tetrapods for the first time: Cu2-xSe/Cu2-xS and PbSe/PbS, both prepared from CdSe/CdS tetrapods as 'templates'. We also fabricated near-infrared (NIR) photodetectors with a very simple architecture comprising a PbSe/PbS tetrapod layer between two Au electrodes on a glass substrate. When illuminated by a NIR laser, these devices are capable of achieving a responsivity of 11.9 A W(-1) without the use of ligand-exchange processes, thermal annealing or hybrid device architecture. Transient absorption spectroscopy was carried out on these PbSe/PbS tetrapods, the results of which suggest that the branched morphology contributes in part to device performance. Investigation of the charge dynamics of the PbSe/PbS tetrapods revealed an extremely long-lived exciton recombination lifetime of ∼17 ms, which can result in enhanced photoconductive gain. Overall, these heterostructured tetrapods showcase simultaneously the importance of nanoparticle shape, band structure, and surface chemistry in the attainment of NIR photodetection.

A nanofiltration-coagulation integrated system for separation and stabilization of arsenic from groundwater

A membrane-integrated hybrid treatment system has been developed for continuous removal of arsenic from contaminated groundwater with simultaneous stabilization of arsenic rejects for safe disposal. Both trivalent and pentavalent arsenic could be removed by cross flow nanofiltration following a chemical pre-oxidation step for conversion of trivalent arsenic into pentavalent form. The very choice of the membrane module and its judicious integration with upstream oxidation and downstream stabilization resulted in continuous removal of more than 98% arsenic from water that contained around 190 mg L(-1) of total suspended solid, 205 mg L(-1) of total dissolved solid, 0.18 mg L(-1) of arsenic and 4.8 mg L(-1) of iron at a pH of 7.2. The used flat sheet cross flow membrane module yielded a high flux of 144-145 L m(-2) h(-1) at a transmembrane pressure of only 16 kgf·cm(-2) without the need for frequent replacement of the membranes. Transmembrane pressure, cross flow rate through the membrane module and oxidant dose were found to have pronounced effects on arsenic rejection and pure water flux. For the first time, an effective scheme for protection of the total environment has been ensured in this context where arsenic separated with high degree of efficiency has been stabilized in a solid matrix of iron and calcium under response surface optimized conditions. The study culminated in a total and sustainable solution to the problem of arsenic contamination of groundwater by offering arsenic-free water at a reasonably low price of only 1.41$·m(-3).

Arsenic removal from contaminated groundwater by membrane-integrated hybrid plant: optimization and control using Visual Basic platform

A simulation software (ARRPA) has been developed in Microsoft Visual Basic platform for optimization and control of a novel membrane-integrated arsenic separation plant in the backdrop of absence of such software. The user-friendly, menu-driven software is based on a dynamic linearized mathematical model, developed for the hybrid treatment scheme. The model captures the chemical kinetics in the pre-treating chemical reactor and the separation and transport phenomena involved in nanofiltration. The software has been validated through extensive experimental investigations. The agreement between the outputs from computer simulation program and the experimental findings are excellent and consistent under varying operating conditions reflecting high degree of accuracy and reliability of the software. High values of the overall correlation coefficient (R (2) = 0.989) and Willmott d-index (0.989) are indicators of the capability of the software in analyzing performance of the plant. The software permits pre-analysis, manipulation of input data, helps in optimization and exhibits performance of an integrated plant visually on a graphical platform. Performance analysis of the whole system as well as the individual units is possible using the tool. The software first of its kind in its domain and in the well-known Microsoft Excel environment is likely to be very useful in successful design, optimization and operation of an advanced hybrid treatment plant for removal of arsenic from contaminated groundwater.

Differentiation of choroid plexus ependymal cells into astrocytes after grafting into the pre-lesioned spinal cord in mice

Choroid plexus epithelial cells represent a continuation of, and have the same origin as, ventricular ependymal cells, and are regarded as modified ependymal cells. To extend previous studies of the use of choroid plexus ependymal cell (CPEC) grafting for nerve regeneration in the spinal cord, we investigated the capacity of cultured choroid plexus ependymal cells to differentiate into other types of glial cells in the spinal cord tissue. The choroid plexuses were excised from the fourth ventricle of green fluorescent protein (GFP)-transgenic mice and the cells were dissociated and cultured for 4-6 weeks. CPECs were harvested from the monolayer cultures and injected into the pre-lesioned spinal cords of wild-type mice of the same strain using a Hamilton syringe. One week after injection, some GFP-positive transplanted cells became immunohistochemically positive for glial fibrillary acidic protein (GFAP) but negative for neurofilament and myelin basic protein. All the GFAP-positive transplanted cells were negative for vimentin. Two weeks after grafting, immunoelectron microscopy showed that the GFP-positive transplanted cells that had gained GFAP immunoreactivity contained numerous bundles of intermediate filaments, a morphological characteristic similar to that of astrocytes, and were in close contact with adjacent host tissue. These results indicate that, when grafted into the spinal cord, at least some cultured choroid plexus ependymal cells have the capacity to differentiate into astrocytes.

Grafting of choroid plexus ependymal cells promotes the growth of regenerating axons in the dorsal funiculus of rat spinal cord: a preliminary report

Nerve regeneration in the central nervous system has been studied by grafting various tissues and cells. In the present study, we demonstrated that choroid plexus ependymal cells can promote nerve regeneration when grafted into spinal cord lesions. The choroid plexus was excised from the fourth ventricle of adult rats (Wistar), minced into small fragments, and grafted into the dorsal funiculus at the C2 level in adult rat spinal cord from the same strain. Electron microscopy and fluorescence histochemistry showed that ependymal cells of the grafted choroid plexus intimately interacted with growing axons, serving to support the massive growth of regenerating axons. CGRP-positive fibers closely interacted with grafted ependymal cells. HRP injection at the sciatic nerve showed that numerous HRP-labeled regenerating fibers from the fasciculus gracilis extended into the graft 7 days after grafting. This regenerating axons from the fasciculus gracilis was maintained for at least 10 months, with some axons elongating rostrally into the dorsal funiculus. Evoked potentials of long duration were recorded at a level ca. 5 mm rostral to the lesion in the rats 8 to 10 months after grafting. These findings indicate that choroid plexus ependymal cells have the ability to facilitate axonal growth in vivo, suggesting that they may be a promising candidate as graft for the promotion of nerve regeneration in the spinal cord.

Choroid plexus ependymal cells enhance neurite outgrowth from dorsal root ganglion neurons in vitro

The epithelial cells of the choroid plexus are a continuation of the ventricular ependymal cells and are regarded as modified ependymal cells. The present study was carried out to determine the influence of choroid plexus ependymal cells (CPECs) on axonal growth in vitro. Choroid plexuses were dissected from the fourth ventricle of postnatal day-1-10 mice, mechanically dissociated, and plated in fibronectin-coated culture dishes. CPECs had spread into monolayers with few endothelial cells in 3-week cultures. Some macrophages were scattered on the monolayer of CPECs. Dorsal root ganglia (DRG) were excised from mouse fetuses of 14-day gestation, dissociated with trypsin and cocultured on the CPEC monolayers. For comparison, dissociated DRG neurons were cocultured on astrocyte monolayers or cultured on laminin-coated plates. After 4.5 h culturing, the cultures were fixed and immunohistochemically double-stained for neurites and CPECs using antibodies against beta-tubulin III and S-100 beta, respectively. It was demonstrated that neurons extended many long neurites with elaborate branching on the surface of S-100-stained CPECs. In contrast, DRG neurons cultured on the astrocytes and on the laminin-coated plates had much shorter primary neurites with fewer branches than those cultured on the CPECs. The total length of neurites including primary neurites and their branches, of a single DRG neuron was 285 +/- 14, 395 +/- 15 and 565 +/- 12 microM on the laminin-coated plates, on astrocytes and on CPECs, respectively. Scanning electron microscopy revealed extension of neurites with well-developed growth cones on the ependymal cells. These results suggest that CPECs have a great capacity to promote neurite outgrowth from DRG neurons in vitro.

Embryonic stem cells differentiate into oligodendrocytes and myelinate in culture and after spinal cord transplantation

Demyelination contributes to the loss of function consequent to central nervous system (CNS) injury. Enhanced remyelination through transplantation of myelin-producing cells may offer a pragmatic approach to restoring meaningful neurological function. An unlimited source of cells suitable for such transplantation therapy can be derived from embryonic stem (ES) cells, which are both pluripotent and genetically flexible. In this paper we show that oligodendrocyte cultures can be reliably produced from retinoic acid-induced ES cells and that these oligodendrocytes can myelinate axons in vitro. Methods were further developed for generating highly enriched cultures of oligodendrocytes through an additional culturing step, producing an intermediate "oligosphere" stage. To test whether ES cells can survive, migrate, and differentiate into mature myelin-producing cells in areas of demyelination in the adult CNS, ES cells were transplanted into the dorsal columns of adult rat spinal cord 3 days after chemical demyelination. In the demyelination site, large numbers of ES cells survived and differentiated primarily into mature oligodendrocytes that were capable of myelinating axons. Furthermore, when oligosphere cells were transplanted into the spinal cords of myelin-deficient shiverer (shi/shi) mutant mice, the ES cell-derived oligodendrocytes migrated into the host tissue, produced myelin and myelinated host axons. These studies demonstrate the ability of ES cell-derived oligodendrocytes to myelinate axons in culture and to replace lost myelin in the injured adult CNS. Transplantation of ES cells may be a practical approach to treatment of primary and secondary demyelinating diseases in the adult CNS.

Functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia of adult rat with kaolin-induced hydrocephalus

Structural and/or functional injury of the basal ganglia can lead to motor functional disabilities, abnormal gait and posture, and intellectual/emotional impairment, disorders also frequently seen in hydrocephalus. Previous reports have documented changes in dopamine levels in the neostriatum in experimental hydrocephalus. The present study was designed to investigate possible functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia immunohistochemically in a model of kaolin-induced hydrocephalus. Hydrocephalus was induced in 12 Wistar rats by intracisternal injection of 0.05 ml volume of 25% kaolin solution under microscopic guidance. Four controls received an equal volume of sterile saline. The animals were killed at 2, 4 and 8 weeks after injection. The numbers of choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive (IR) neostriatal neurons and tyrosine hydroxylase (TH)-IR nigral neurons, were counted in 60-micron thick representative sections and the IR cellular densities (counted cell number/neostriatal area) were calculated in the neostriatum. The number of total neostriatal neurons was also counted in 15-micron thick sections stained by cresyl violet (Nissl staining) to calculate the cellular density. The number and cellular density of neostriatal ChAT-IR neurons were significantly reduced at 2, 4, and 8 weeks after injection (P < 0.05), while those of GAD-IR neurons decreased at 4 and 8 weeks (P < 0.05). There was a linear correlation between degree of ventricular enlargement, and reduction in number of ChAT- and GAD-IR neurons (P < 0.001) as well as in the cellular density (P < 0.001). However, Nissl staining revealed no reduction in the cellular density of total neostriatal neurons (P < 0.001). TH immunoreactivity was reduced in neostriatal axons and in nigral compacta neurons, particularly in the medial portion of the dopaminergic nigrostriatal pathway. These findings suggest that progressive hydrocephalus results in functional injuries of cholinergic and GABAergic neurons in the neostriatum and dopaminergic neurons in the substantia nigra compacta by mechanical distortion. The disturbance in balance of these neurotransmitter systems in the basal ganglia may explain some of motor functional disabilities in hydrocephalus.

Experimental syringomyelia: late ultrastructural changes of spinal cord tissue and magnetic resonance imaging evaluation

BACKGROUND

In human hydrosyringomyelia and in the late stage of experimental syringomyelia, the spinal cord tissue adjacent to the syrinx is exposed to a similar pathophysiologic condition. We investigated the ultrastructural changes in the late stages of kaolin-induced syringomyelia, and in addition, we presented magnetic resonance imaging (MRI) findings of the cervicomedullary junction and syrinx, and the nature of edema in the spinal cord of this experimental model.

METHODS

Syringomyelia was induced in rabbits by intracisternal injection of kaolin. MRI was performed at 6 weeks, and 6 and 12 months following injection, and the animals were killed by transcardial perfusion of formaldehyde solution and examined by transmission electron microscopy. Evans blue was injected intravenously in six rabbits, 6 weeks and 12 months following kaolin injection and was examined by confocal laser scanning microscopy.

RESULTS

MRI showed that the syrinx communicated with the fourth ventricle in most animals. Demyelination of varying degrees and slight edematous change were seen in the perisyrinx white matter. No extravasation of Evans blue was seen by confocal microscopy. Abundant astrocytic proliferation with a large number of glial filaments was seen at the margin of the syrinx and between the axons in the perisyringeal region. The perivascular space enlargement occurred in both the gray and white matter. The endothelial junctions appeared intact. Regenerating axons and remyelination by oligodendrocytes were seen occasionally.

CONCLUSIONS

The MRI confirmed the communication between the fourth ventricle and the syrinx. The ultrastructural changes were almost identical to those of the early stage syrinx, but the astrocytic proliferation was more severe, and the edema was less in the late stage. The perisyrinx edema appeared to be of the interstitial type, as in hydrocephalus. Axonal degeneration and demyelination continued with abortive attempt at regeneration and remyelination in the less edematous late stage, which might be the cellular basis for the persistence or worsening of clinical symptoms and signs in the chronic stage of syringomyelia even after surgical treatment.

Progressive loss of glutamic acid decarboxylase, parvalbumin, and calbindin D28K immunoreactive neurons in the cerebral cortex and hippocampus of adult rat with experimental hydrocephalus

The authors investigated functional neuronal changes in experimental hydrocephalus using immunohistochemical techniques for glutamic acid decarboxylase (GAD) and two neuronal calcium-binding proteins: parvalbumin (PV) and calbindin D28K (CaBP). Hydrocephalus was induced in 16 adult Wistar rats by intracisternal injection of a kaolin solution, which was confirmed microscopically via atlantooccipital dural puncture. Four control rats received the same volume of sterile saline. Immunohistochemical staining for GAD, PV, and CaBP, and Nissl staining were performed at 1, 2, 3, and 4 weeks after the injection. Hydrocephalus occurred in 90% of kaolin-injected animals with various degrees of ventricular dilation. In the cerebral cortex, GAD-, PV-, and CaBP-immunoreactive (IR) interneurons initially lost their stained processes together with a concomitant loss of homogeneous neuropil staining, followed by the reduction of their total number. With progressive ventricular dilation, GAD- and PV-IR axon terminals on the cortical pyramidal cells disappeared, whereas the number of CaBP-IR pyramidal cells decreased, and ultimately in the most severe cases of hydrocephalus, GAD, PV, and CaBP immunoreactivity were almost entirely diminished. In the hippocampus, GAD-, PV-, and CaBP-IR interneurons demonstrated a reduction of their processes and terminals surrounding the pyramidal cells, with secondary reduction of CaBP-IR pyramidal and granular cells. On the other hand, Nissl staining revealed almost no morphological changes induced by ischemia or neuronal degeneration even in the most severe cases of hydrocephalus. Hydrocephalus results in the progressive functional impairment of GAD-, PV-, and CaBP-IR neuronal systems in the cerebral cortex and hippocampus, often before there is evidence of morphological injury. The initial injury of cortical and hippocampal interneurons suggests that the functional deafferentation from intrinsic projection fibers may be the initial neuronal event in hydrocephalic brain injury. Although the mechanism of this impairment is still speculative, these findings emphasize the importance of investigating the neuronal pathophysiology in hydrocephalus.

Intracerebral ring-enhancing lesions in a patient with multiple sclerosis: a case report

BACKGROUND Intracerebral cystic lesions can easily be identified by computed tomography (CT) and magnetic resonance imaging (MRI). Cystic gliomas, brain abscesses, or metastatic carcinoma are the usual underlying causes for this neuroradiologic finding. CASE PRESENTATION We report here the case of a patient with multiple sclerosis who has two intracerebral cystic lesions. CONCLUSIONS Central nervous system (CNS) tissue destruction, necrosis, and cyst formation are very unusual in multiple sclerosis. Diagnostic difficulty therefore arises when patients suspected of having multiple sclerosis have radiologic evidence of cystic CNS lesions.

Experimental syringomyelia in the rabbit: an ultrastructural study of the spinal cord tissue

Hydrosyringomyelia was produced experimentally by the injection of kaolin into the cisterna magna of the rabbit, and the ultrastructural changes of the spinal cord surrounding the syrinx were investigated 2, 4, and 6 weeks after injection by transmission electron microscopy. The ependyma at the ventral part of the central canal was flat and stretched, whereas, in the dorsal part, it was split, and the syrinx extended through the dorsal median plane in most animals. Extracellular edema was found in the subependymal white matter and in and around the posterior median septum. Many nerve fibers surrounding the syrinx were in varying stages of axonal degeneration. Myelin sheaths were split, thinned, and completely lost in many nerve fibers. In some fibers, the axons were totally lost, leaving the myelin sheaths as empty tubes. Astrocytic processes containing a large number of glial filaments covered the nerve fibers adjacent to the syrinx and partially replaced the edematous area. The perivascular spaces were enlarged, especially near the syrinx and in the dorsal white matter. Oligodendrocytes remained undamaged, and the remyelination by oligodendrocytic processes was seen on some denuded axons. Sometimes, this further remyelination was abortive, especially where the edema was severe. The ultrastructural changes of the neural tissue and their sequences were identical, in most respects, to those of hydrocephalus and noncommunicating syringomyelia. The oligodendrocytic remyelination with ongoing demyelination found in this model has many similarities to those in experimental hydrocephalus.

Congenital frontal bone defect with intact overlying scalp

An unusual case of a congenital frontal bone defect with intact overlying scalp and intact underlying dura mater is reported. Although spontaneous healing by the intact underlying dura mater by regeneration was expected, it did not occur. Cranioplasty was done for protective and cosmetic purposes. A review of the literature of congenital skull defects shows that spontaneous regeneration does not occur in this rare anomaly.

Intraorbital arteriovenous malformation: case report

A case of intraorbital arteriovenous malformation presenting with visual loss, exophthalmos, and chemosis of the right eye is reported. Enhanced computer tomography and magnetic resonance imaging showed extraocular muscle enlargement and vascular abnormality in the right retrobulbar space. Angiography revealed an abnormal intraorbital vascular stain with an extremely dilated right ophthalmic artery. Total removal of the intraorbital contents was performed after unsuccessful endovascular and surgical treatment of arteriovenous malformation (AVM). Histopathological examination disclosed an AVM in the retrobulbar fatty tissue with extension into the extraocular muscles and optic nerve.

Myelomeningocele and thick filum terminale with tethered cord appearing as a human tail. Case report

Tail-like caudal appendages may be associated with spinal dysraphism, particularly with spinal lipomas or lipomyelomeningoceles. An unusual case is presented of a patient with a myelomeningocele and a thick filum terminale with tethered spinal cord, which presented with the external appearance of a human tail. A review of the literature reveals that human tails may be associated with dysraphic conditions. Extensive neuroradiological examinations should be performed for all such cases of apparent tails.

Growth hormone-producing pituitary adenomas: MR characteristics and pre- and postoperative evaluation

Twelve patients with growth hormone-producing pituitary adenomas were investigated to evaluate correlations between magnetic resonance (MR) appearance and tissue characteristics, sellar expansion, suprasellar tumor extension, and tumor consistency. MR imaging could detect microadenomas with a characteristic enhancement delay of gadolinium-diethylenetriaminepenta-acetic acid in the surrounding normal pituitary gland. Macroadenomas and giant tumors appeared on T2-weighted images as mostly high intensity, while varied greatly on T1-weighted images. The signal intensities of growth hormone-producing adenomas were more homogeneous (80%) than those of other functioning and non-functioning adenomas on T1-weighted images. However, there was no typical MR imaging for the tissue characteristics of the growth hormone-producing adenomas, and no particular correlation with suprasellar extension or consistency. Postoperative MR findings showed that the transcranial approach was superior for total or subtotal removal of large tumors, especially with suprasellar extension up to the upper third ventricle. The transsphenoidal approach can achieve a satisfactory decompressive effect on the optic chiasm, but more radical removal is required to achieve a normal hormone level.

Maffucci's syndrome associated with intracranial enchondroma and aneurysm: case report

Maffucci's syndrome is a rare, congenital mesodermal dysplasia combined with dyschondroplasia and hemangiomatosis. Enchondromatous involvement of the skull bones is rare in this syndrome. A rare case of Maffucci's syndrome associated with enchondroma at the skull base, left internal carotid artery aneurysm, and goiter is reported. Two other previously reported cases of Maffucci's syndrome with associated aneurysms and the present case suggest that Maffucci's syndrome may be associated with aneurysm.