Evidence of ancillary trigeminal innervation of levator palpebrae in the general population.

The cranial synkineses are a group of disorders encompassing a variety of involuntary co-contractions of the facial, masticatory, or extraocular muscles that occur during a particular volitional movement. The neuroanatomical pathways for synkineses largely remain undefined. Our studies explored a normal synkinesis long observed in the general population - that of jaw opening during efforts to open the eyelids widely. To document this phenomenon, we observed 186 consecutive participants inserting or removing contact lenses to identify jaw opening. Seeking electrophysiological evidence, in a second study we enrolled individuals undergoing vascular decompression for trigeminal neuralgia or hemifacial spasm, without a history of jaw-winking, ptosis, or strabismus, to record any motor responses in levator palpebrae superioris (LPS) upon stimulation of the trigeminal motor root. Stimulus was applied to the trigeminal motor root while an electrode in levator recorded the response. We found that 37 participants (20%) opened their mouth partially or fully during contact lens manipulation. In the second study, contraction of LPS with trigeminal motor stimulation was documented in two of six patients, both undergoing surgery for trigeminal neuralgia. We speculate these results might provide evidence of an endogenous synkinesis, indicating that trigeminal-derived innervation of levator could exist in a significant minority of the general population. Our observations demonstrate plasticity in the human cranial nerve innervation pattern and may have implications for treating Marcus Gunn jaw-winking.

The adsorption and self-assembly of mixtures of alkylbenzene sulfonate isomers and the role of divalent electrolyte.

In this paper, the role of the different structural isomers of the anionic surfactant sodium para-dodecyl benzene sulfonate, LAS, on surface adsorption and solution self-assembly has been studied. Using a combination of neutron reflectivity, NR, and small angle neutron scattering, SANS, the effect of mixing an isomer with a short symmetric hydrocarbon chain with one which has an asymmetric hydrocarbon chain on both the equilibrium surface adsorption behavior and the solution microstructure of the mixtures, both in the presence and absence of a divalent cation (Ca(2+)), has been investigated. In the absence of electrolyte, the LAS isomer mixtures form small charged globular micelles throughout the composition range studied. The micelle aggregation number increases with the increase in the asymmetric isomer content, reflecting an increase in the packing efficiency within the micelle. The addition of calcium ions promotes the formation of planar aggregates, as multilamellar vesicles, but only when the symmetric LAS isomer is the major component of the mixture. At a surfactant concentration just above the critical micelle concentration, CMC, and in the absence of electrolyte, the variation in the surface composition is close to the solution composition. Regular solution theory, RST, calculations show that this variation is also close to what is expected for ideal mixing. The addition of Ca(2+) ions induces a different surface behavior, resulting in the formation of multilayer structures at the interface throughout the entire composition range.

Surface and solution properties of anionic/nonionic surfactant mixtures of alkylbenzene sulfonate and triethyleneglycol decyl ether.

The surface adsorption behavior and the solution microstructure of mixtures of the C(6) isomer of anionic surfactant sodium para-dodecyl benzene sulfonate, ABS, with nonionic surfactant monodecyl triethyleneglycol ether, C(10)E(3,) have been investigated using a combination of neutron reflectivity, NR, and small-angle neutron scattering, SANS. In solution, the mixing of C(10)E(3) and ABS results in the formation of small globular micelles over most of the composition range (100:0 to 20:80 ABS/C(10)E(3)). Planar aggregates (lamellar or unilamellar vesicles, ULV) are observed for solution compositions rich in the nonionic surfactant (>80 mol % nonionic). Prior to the transition to planar aggregates, the micelle aggregation number increases with increasing nonionic composition. The lamellar-phase region is preceded by a narrow range of composition over which mixtures of micelles and small unilamellar vesicles coexist. The variation in surface absorption behavior with solution composition shows a strong surface partitioning of the more surface-active component, C(10)E(3). This pronounced departure from ideal mixing is not readily explained by existing surfactant mixing theories. In the presence of Ca(2+) ions, a more complex evolution of solution phase behavior with solution composition is observed. The lamellar-phase region occurs over a broader range of solution compositions at the expense of the small-vesicle phase. The phase boundaries are shifted to lower nonionic compositions, and the extent to which the solution-phase diagrams are modified increases with increasing calcium ion concentration. The SANS data for the large planar aggregates are consistent with large polydisperse flexible unilamellar vesicles. In the presence of Ca(2+) ions, the surface adsorption patterns become more consistent with ideal mixing in the nonionic-rich region of the surface-phase diagram. However, in the ABS-rich regions the surface behavior is more complex because of the spontaneous formation of more complex surface microstructures (bilayers to multilayers). Both in water and in the presence of Ca(2+) ions the variations in the surface adsorption behavior and in the solution mesophase structure do not appear to be closely correlated.

Structure of partially fluorinated surfactant monolayers at the air-water interface.

Partially fluorinated cationic surfactants of the form C(n)F(2n+1)C(m)H(2m)N(CH3)Br have been prepared, and their behavior at the air-water interface has been studied using surface tension measurements and neutron reflectometry. The degree of fluorination has been varied while keeping the overall chain lengths similar. The results are compared with those previously obtained for C16H33N(CH3)Br (C16TAB). The structural studies show a decrease in molecular orientation with increasing fluorination. The mean tilt away from the surface normal varies from 55 degrees for C16TAB to 25 degrees for C8F17C6H12N(CH3)Br. The interfacial layer roughness is observed to be lower than that expected for a pure fluorocarbon surfactant.

Anomalous mandibular premolars: a mandibular first premolar with three roots and a mandibular second premolar with a C-shaped canal system.

AIM: To describe unusual variations in the root morphology and root canal systems of mandibular first and second premolar teeth extracted for orthodontic reasons. SUMMARY: Normally mandibular first and second premolar teeth have single roots with single canals. A 15-year-old patient presented for orthodontic treatment and two mandibular premolar teeth were examined post-extraction. The mandibular first premolar exhibited three distinct, separate roots and the mandibular second premolar exhibited a C-shaped root canal system. The coronal morphology of each of the mandibular premolars revealed dimensions and anatomy within normal limits. The incidence of a three-rooted mandibular first premolar is approximately 0.2%. KEY LEARNING POINTS: * Thorough clinical and radiographic interpretation is important in recognizing anomalous root and root canal systems. * The most common forms of root and canal systems and its aberrations must be understood to realize variations from normal do occur. * Successful root canal treatment requires an accurate diagnosis of the root canal system using all available aids. * Value of microcomputed tomography in the study of anatomy ex vivo and cone-beam tomography in clinical endodontics of complex premolar cases is increasing.

Equilibrium surface adsorption behavior in complex anionic/nonionic surfactant mixtures.

Neutron reflectivity (NR) and small angle neutron scattering (SANS) have been used to investigate the equilibrium surface adsorption behavior and the solution microstructure of mixtures of the anionic surfactant sodium 6-dodecyl benzene-4 sulfonate (SDBS) with the nonionic surfactants monododecyl octaethylene glycol (C12EO8) and monododecyl triiscosaethylene glycol (C12EO23). In the SDBS/C12EO8 and SDBS/C12EO23 solutions, small globular mixed micelles are formed. However, the addition of Ca2+ ions to SDBS/C12EO8 results in a transition to a vesicle phase or a mixed vesicle/micellar phase for SDBS rich compositions. In contrast, this transition hardly exists for the SDBS/C12EO23 mixture, and occurs only in a narrow composition region which is rich in SDBS. The adsorption of the SDBS/C12EO8 mixture at the air-solution interface is in the form of a mixed monolayer, with a composition variation that is not consistent with ideal mixing. In water and in the presence of NaCl, the nonideality can be broadly accounted for by regular solution theory (RST). At solution compositions rich in SDBS, the addition of Ca2+ ions results in the formation of multilayer structures at the interface. The composition range over which multilayer formation exists depends upon the Ca2+ concentration added. In comparison, the addition of a simple monovalent electrolyte, NaCl, at the same ionic strength does not have the same impact upon the adsorption, and the surface structure remains as a monolayer. Correspondingly, in solution, the mixed surfactant aggregates remain as relatively small globular micelles. In the presence of Ca2+ counterions, the variation in surface composition with solution composition is not well described by RST over the entire composition range. Furthermore, the mixing behavior is not strongly correlated with variations in the solution microstructure, as observed in other related systems.

The structure of mixed nonionic surfactant monolayers at the air-water interface: the effects of different alkyl chain lengths.

The structure of mixed nonionic surfactant monolayers of monodecyl hexaethylene glycol (C10E6) and monotetradecyl hexaethylene glycol (C14E6) adsorbed at the air-water interface has been determined by specular neutron reflectivity. Using partial isotopic labeling (deuterium for hydrogen) of the alkyl and ethylene oxide chains of each surfactant, the distribution and relative positions of the chains at the interface have been obtained. The packing of the two different alkyl chain lengths results in structural changes compared to the pure surfactant monolayers. This results in changes in the relative positions of the alkyl chains and of the ethylene oxide chains at the interface. The role of the alkyl chain length is contrasted with that of the ethylene oxide chain length, determined from results reported previously on the nonionic surfactant mixture of monododecyl triethylene glycol (C12E3) and monododecyl octaethylene glycol (C12E8).