Magnetic resonance neurography in the management of peripheral trigeminal neuropathy: experience in a tertiary care centre.

OBJECTIVE: This tertiary care experience examines the utility of magnetic resonance neurography (MRN) in the management of peripheral trigeminal neuropathies. MATERIALS AND METHODS: Seventeen patients with clinically suspected peripheral trigeminal neuropathies (inferior alveolar nerve and lingual nerve) were imaged uniformly with 1.5-T examinations. MRN results were correlated with clinical and surgical findings in operated patients and the impact on clinical management was assessed. RESULTS: Clinical findings included pain (14/17), sensory changes (15/17), motor changes (2/17) and palpable masses (3/17). Inciting events included prior dental surgery (12/17), trauma (1/17) and idiopathic incidents (4/17). Non-affected side nerves and trigeminal nerves in the intracranial and skull base course were normal in all cases. Final diagnoses on affected sides were nerve inflammation (4/17), neuroma in continuity (2/17), LN transection (1/17), scar entrapment (3/17), infectious granuloma (1/17), low-grade injuries (3/17) and no abnormality (3/17). Associated submandibular gland and sublingual gland oedema-like changes were seen in 3/17 cases because of parasympathetic effects. Moderate-to-excellent MRN-surgical correlation was seen in operated (8/17) patients, and neuroma and nerve transection were prospectively identified in all cases. CONCLUSION: MRN is useful for the diagnostic work-up of suspected peripheral trigeminal neuropathy patients with significant impact on clinical management and moderate-to-excellent correlation with intra-operative findings. KEY POINTS: • MRN substantially impacts diagnostic thinking and management in peripheral trigeminal neuropathy. • MRN has moderate-to-excellent correlation with intra-operative findings. • MRN should be considered in pre-surgical planning of peripheral trigeminal neuropathy subjects.

Cells as strain-cued automata.

We argue in favor of representing living cells as automata and review demonstrations that autonomous cells can form patterns by responding to local variations in the strain fields that arise from their individual or collective motions. An autonomous cell's response to strain stimuli is assumed to be effected by internally-generated, internally-powered forces, which generally move the cell in directions other than those implied by external energy gradients. Evidence of cells acting as strain-cued automata have been inferred from patterns observed in nature and from experiments conducted in vitro. Simulations that mimic particular cases of pattern forming share the idealization that cells are assumed to pass information among themselves solely via mechanical boundary conditions, i.e., the tractions and displacements present at their membranes. This assumption opens three mechanisms for pattern formation in large cell populations: wavelike behavior, kinematic feedback in cell motility that can lead to sliding and rotational patterns, and directed migration during invasions. Wavelike behavior among ameloblast cells during amelogenesis (the formation of dental enamel) has been inferred from enamel microstructure, while strain waves in populations of epithelial cells have been observed in vitro. One hypothesized kinematic feedback mechanism, "enhanced shear motility", accounts successfully for the spontaneous formation of layered patterns during amelogenesis in the mouse incisor. Directed migration is exemplified by a theory of invader cells that sense and respond to the strains they themselves create in the host population as they invade it: analysis shows that the strain fields contain positional information that could aid the formation of cell network structures, stabilizing the slender geometry of branches and helping govern the frequency of branch bifurcation and branch coalescence (the formation of closed networks). In simulations of pattern formation in homogeneous populations and network formation by invaders, morphological outcomes are governed by the ratio of the rates of two competing time dependent processes, one a migration velocity and the other a relaxation velocity related to the propagation of strain information. Relaxation velocities are approximately constant for different species and organs, whereas cell migration rates vary by three orders of magnitude. We conjecture that developmental processes use rapid cell migration to achieve certain outcomes, and slow migration to achieve others. We infer from analysis of host relaxation during network formation that a transition exists in the mechanical response of a host cell from animate to inanimate behavior when its strain changes at a rate that exceeds 10-4-10-3s-1. The transition has previously been observed in experiments conducted in vitro.

Batch versus flow photochemistry: a revealing comparison of yield and productivity.

The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20% lower than that of batch, whereas three-layer reactors were 20% more productive. Finally, the utility of flow chemistry was demonstrated in the scale-up of the ring-opening reaction of a potentially explosive [1.1.1] propellane with butane-2,3-dione.

A multi-scale, discrete-cell simulation of organogenesis: Application to the effects of strain stimulus on collective cell behavior during ameloblast migration.

A multi-scale strategy is presented for simulating organogenesis that uses a single cell response function to define the behavior of individual cells in an organ-scale simulation of a large cell population. The response function summarizes detailed information about the behavior of individual cells in a sufficiently economical way that the organ-scale model can be commensurate with the entire organ. The first application demonstrates the effects of strain stimulus on the migration of ameloblasts during enamel formation. Ameloblasts are an attractive study case because mineralization preserves a complete record of their migratory paths. The response function in this case specifies the motions of cells responding to strain stimuli that propagate through the population. The strain stimuli are related to the curvature of the surface from which the ameloblasts migrate (the dentin-enamel junction or DEJ). A single unknown rate parameter is calibrated by an independent datum from the human tooth. With no remaining adjustable parameters, the theory correctly predicts aspects of the fracture-resistant, wavy microstructure of enamel in the human molar, including wavelength variations and the rate of wave amplitude damping. At a critical value of curvature of the DEJ, a transition in the ordering of cells occurs, from invariant order over the whole population to self-assembly of the population into groups or gangs. The prediction of an ordering transition and the predicted critical curvature are consistent with gnarled enamel in the cusps of the human molar. The calibration of the model using human data also predicts waves in the mouse incisor and an ordering transition at the chimpanzee cingulum. Widespread compressive strain is predicted late in the migration for both the human molar and mouse incisor, providing a possible signal for the termination of amelogenesis.

Suicide by occupation: does access to means increase the risk?

OBJECTIVE: To examine suicide by identified occupational groups in New Zealand over a period of 30 years, focusing on groups predicted to have high suicide rates because of access to and familiarity with particular methods of suicide. METHOD: Suicide data (including open verdicts) for the period 1973-2004 were examined, excluding 1996 and 1997 for which occupational data were not available. Occupational groups of interest were dentists, doctors, farmers (including farm workers), hunters and cullers, military personnel, nurses, pharmacists, police and veterinarians. Crude mortality rates were calculated based on numbers in each occupational group at each quinquennial census, 1976-2001. Standardized mortality ratios were calculated using suicide rates in all employed groups (the standard population). RESULTS: Few of the occupations investigated had high risks of suicide as assessed by standardized mortality ratios, and some were at lower risk than the total employed population. Standardized mortality ratios were elevated for male nurses (1.7; 95% CI: 1.2-2.5), female nurses (1.3; 95% CI: 1.0-1.6), male hunters and cullers (3.0; 95% CI: 1.7-4.8), and female pharmacists (2.5; 95% CI: 0.8-5.9). Doctors, farmers and veterinarians were not at high risk, and men in the police and armed forces were at low risk. Access to means appeared to have influenced the method chosen. Nurses, doctors and pharmacists were more likely to use poisoning than were other employed people (3, 4 and 5 times respectively, compared with all others employed). Farmers and hunters and cullers were more than twice as likely as all others employed to use firearms. CONCLUSIONS: Access to means may be less important in some circumstances than in others, perhaps because of the presence of other factors that confer protection. Nevertheless, among the groups we studied with access to lethal means were three groups whose risk of suicide has so far received little attention in New Zealand: nurses, female pharmacists, and hunters and cullers.

Dissection and design of yeast prions.

Many proteins can misfold into beta-sheet-rich, self-seeding polymers (amyloids). Prions are exceptional among such aggregates in that they are also infectious. In fungi, prions are not pathogenic but rather act as epigenetic regulators of cell physiology, providing a powerful model for studying the mechanism of prion replication. We used prion-forming domains from two budding yeast proteins (Sup35p and New1p) to examine the requirements for prion formation and inheritance. In both proteins, a glutamine/asparagine-rich (Q/N-rich) tract mediates sequence-specific aggregation, while an adjacent motif, the oligopeptide repeat, is required for the replication and stable inheritance of these aggregates. Our findings help to explain why although Q/N-rich proteins are relatively common, few form heritable aggregates: prion inheritance requires both an aggregation sequence responsible for self-seeded growth and an element that permits chaperone-dependent replication of the aggregate. Using this knowledge, we have designed novel artificial prions by fusing the replication element of Sup35p to aggregation-prone sequences from other proteins, including pathogenically expanded polyglutamine.

Oral cancer risk factors in New Zealand.

Oral cancer constitutes the majority of head and neck cancers, which are the fifth most common malignancy worldwide, accounting for an estimated 984,430 cases in 2012. Between 2000 and 2010, there were 1,916 cases of OSCC in New Zealand with a male to female ratio of 1.85:1, and an age-standardised incidence rate of 42 persons per 1,000,000 population. This article presents an overview of the main risk factors for oral and oropharyngeal cancers and their prevalence in New Zealand. Alcohol consumption is the most prevalent risk factor in New Zealand, followed by tobacco. Given the high prevalence of these two risk factors and their synergistic effect, it is important for doctors and dentists to encourage smoking cessation in smokers and to recommend judicious alcohol intake. Research is needed to determine the prevalence of use of oral preparations of tobacco and water-pipe smoking in New Zealand, especially due to changing demography and increases in migrant populations. UV radiation is also an important risk factor. Further investigations are also needed to determine the prevalence of oral and oropharyngeal cancers attributable to oncogenic HPV infection.

How the tooth got its stripes: patterning via strain-cued motility.

We hypothesize that a population of migrating cells can form patterns when changes in local strains owing to relative cell motions induce changes in cell motility. That the mechanism originates in competing rates of motion distinguishes it from mechanisms involving strain energy gradients, e.g. those generated by surface energy effects or eigenstrains among cells, and diffusion-reaction mechanisms involving chemical signalling factors. The theory is tested by its ability to reproduce the morphological characteristics of enamel in the mouse incisor. Dental enamel is formed during amelogenesis by a population of ameloblasts that move about laterally within an expanding curved sheet, subject to continuously evolving spatial and temporal gradients in strain. Discrete-cell simulations of this process compute the changing strain environment of all cells and predict cell trajectories by invoking simple rules for the motion of an individual cell in response to its strain environment. The rules balance a tendency for cells to enhance relative sliding motion against a tendency to maintain uniform cell-cell separation. The simulations account for observed waviness in the enamel microstructure, the speed and shape of the 'commencement front' that separates domains of migrating secretory-stage ameloblasts from those that are not yet migrating, the initiation and sustainment of layered, fracture-resistant decussation patterns (cross-plied microstructure) and the transition from decussating inner enamel to non-decussating outer enamel. All these characteristics can be correctly predicted with the use of a single scalar adjustable parameter.

Smoking-related Cancers in Maori and non-Maori in New Zealand, 1974-1993: Fewer Bladder Cancers among Maori.

Smoking is, and long has been, more prevalent among Maori than non-Maori in New Zealand. Lung cancer, but not other smoking-related cancers, is known to be markedly more common among Maori than non-Maori. Incidence and mortality data from the New Zealand Cancer Registry for cancers of the mouth/pharynx, oesophagus, pancreas, larynx, kidney and bladder, as well as lung/pleura, during the period 1974 to 1993 were analysed by sex to determine whether the rates of each of these smoking-related cancers were higher in Maori than in non-Maori. Truncated (35-64 yr) age-standardized incidence rates for 1974-93 were significantly higher in Maori than non-Maori for cancers of the pancreas, lung/pleura and kidney (both sexes), mouth/pharynx and oesophagus (males only). There was no difference between the Maori and non-Maori rates for cancer of the larynx, and bladder cancer incidence was significantly lower in Maori than non-Maori. Mortality rates followed a similar pattern as those for incidence for cancers of the pancreas, larynx, lung/pleura and kidney (both sexes) and bladder (males only). The pattern predicted by the higher prevalence of smoking in Maori than non-Maori was borne out for all smoking-related cancers except bladder and laryngeal cancer. Under-enumeration through lower access to health services may have contributed to the lower than expected rates of bladder cancer in Maori, but a role for a genetically or lifestyle related protective effect is suggested.