Preclinical tissue distribution and metabolic correlations of vigabatrin, an antiepileptic drug associated with potential use-limiting visual field defects

Vigabatrin (VGB; (S)-(+)/(R)-(-) 4-aminohex-5-enoic acid), an antiepileptic irreversibly inactivating GABA transaminase (GABA-T), manifests use-limiting ocular toxicity. Hypothesizing that the active S enantiomer of VGB would preferentially accumulate in eye and visual cortex (VC) as one potential mechanism for ocular toxicity, we infused racemic VGB into mice via subcutaneous minipump at 35, 70, and 140 mg/kg/d (n = 6-8 animals/dose) for 12 days. VGB enantiomers, total GABA and β-alanine (BALA), 4-guanidinobutyrate (4-GBA), and creatine were quantified by mass spectrometry in eye, brain, liver, prefrontal cortex (PFC), and VC. Plasma VGB concentrations increased linearly by dose (3 ± 0.76 (35 mg/kg/d); 15.1 ± 1.4 (70 mg/kg/d); 34.6 ± 3.2 μmol/L (140 mg/kg/d); mean ± SEM) with an S/R ratio of 0.74 ± 0.02 (n = 14). Steady state S/R ratios (35, 70 mg/kg/d doses) were highest in eye (5.5 ± 0.2; P < 0.0001), followed by VC (3.9 ± 0.4), PFC (3.6 ± 0.3), liver (2.9 ± 0.1), and brain (1.5 ± 0.1; n = 13-14 each). Total VGB content of eye exceeded that of brain, PFC and VC at all doses. High-dose VGB diminished endogenous metabolite production, especially in PFC and VC. GABA significantly increased in all tissues (all doses) except brain; BALA increases were confined to liver and VC; and 4-GBA was prominently increased in brain, PFC and VC (and eye at high dose). Linear correlations between enantiomers and GABA were observed in all tissues, but only in PFC/VC for BALA, 4-GBA, and creatine. Preferential accumulation of the VGB S isomer in eye and VC may provide new insight into VGB ocular toxicity.

Time-on-Task Effect During Sleep Deprivation in Healthy Young Adults Is Modulated by Dopamine Transporter Genotype

Study Objectives

The time-on-task (TOT) effect and total sleep deprivation (TSD) have similar effects on neurobehavioral functioning, including increased performance instability during tasks requiring sustained attention. The TOT effect is exacerbated by TSD, suggesting potentially overlapping mechanisms. We probed these mechanisms by investigating genotype-phenotype relationships on psychomotor vigilance test (PVT) performance for 3 a-priori selected genes previously linked to the TOT effect and/or TSD: dopamine active transporter 1 (DAT1), catechol-O-methyltransferase (COMT), and tumor necrosis factor alpha (TNFα).

Methods

N = 82 healthy adults participated in 1 of 3 laboratory studies. A 10-min PVT was administered repeatedly during 38 h of TSD. We assessed changes in response time (RT) across each minute of the PVT as a function of time awake and genotype. Additionally, cumulative relative RT frequency distributions were constructed to examine changes in performance from the first to the second 5 min of the PVT as a function of genotype.

Results

DAT1, COMT, and TNFα were associated with differences in the build-up of the TOT effect across the 10-min PVT. DAT1 additionally modulated the interaction between TSD and the TOT effect. Subjects homozygous for the DAT1 10-repeat allele were relatively protected against TOT deficits on the PVT during TSD compared to carriers of the 9-repeat allele.

Conclusions

DAT1 is known to regulate dopamine reuptake and is highly expressed in the striatum. Our results implicate striatal dopamine in mechanisms involved in performance instability that appear to be common to TSD and the TOT effect. Furthermore, DAT1 may be a candidate biomarker of resilience to the build-up of performance impairment across TOT due to TSD.

Analytic Mode Normalization for the Kerr Nonlinearity Parameter: Prediction of Nonlinear Gain for Leaky Modes

Based on the resonant-state expansion with analytic mode normalization, we derive a general master equation for the nonlinear pulse propagation in waveguide geometries that is valid for bound and leaky modes. In the single-mode approximation, this equation transforms into the well-known nonlinear Schrödinger equation with a closed expression for the Kerr nonlinearity parameter. The expression for the Kerr nonlinearity parameter can be calculated on the minimal spatial domain that spans only across the regions of spatial inhomogeneities. It agrees with previous vectorial formulations for bound modes, while for leaky modes the Kerr nonlinearity parameter turns out to be a complex number with the imaginary part providing either nonlinear loss or even gain for the overall attenuating pulses. This nonlinear gain results in more intense pulse compression and stronger spectral broadening, which is demonstrated here on the example of liquid-filled capillary-type fibers.

State-Dependent Modulation of Visual Evoked Potentials in a Rodent Genetic Model of Electroencephalographic Instability

Despite normal sleep timing and duration, Egr3-deficient (Egr3^−/−) mice exhibit electroencephalographic (EEG) characteristics of reduced arousal, including elevated slow wave (1–4 Hz) activity during wakefulness. Here we show that these mice exhibit state-dependent instability in the EEG. Intermittent surges in EEG power were found in Egr3^−/− mice during wakefulness and rapid eye movement sleep, most prominently in the beta (15–35 Hz) range compared to wild type (Egr3^+/+) mice. Such surges did not coincide with sleep onset, as the surges were not associated with cessation of electromyographic tone. Cortical processing of sensory information by visual evoked responses (VEP) were found to vary as a function of vigilance state, being of higher magnitude during slow wave sleep (SWS) than wakefulness and rapid eye movement sleep. VEP responses were significantly larger during quiet wakefulness than active wakefulness, in both Egr3^−/− mice and Egr3^+/+ mice. EEG synchronization in the beta range, previously linked to the accumulation of sleep need over time, predicted VEP magnitude. Egr3^−/− mice not only displayed elevated beta activity, but in quiet wake, this elevated beta activity coincides with an elevated evoked response similar to that of animals in SWS. These data confirm that (a) VEPs vary as a function of vigilance state, and (b) beta activity in the EEG is a predictor of state-dependent modulation of visual information processing. The phenotype of Egr3^−/− mice indicates that Egr3 is a genetic regulator of these phenomena.

Analytical mode normalization and resonant state expansion for bound and leaky modes in optical fibers - an efficient tool to model transverse disorder

We adapt the resonant state expansion to optical fibers such as capillary and photonic crystal fibers. As a key requirement of the resonant state expansion and any related perturbative approach, we derive the correct analytical normalization for all modes of these fiber structures, including leaky modes that radiate energy perpendicular to the direction of propagation and have fields that grow with distance from the fiber core. Based on the normalized fiber modes, an eigenvalue equation is derived that allows for calculating the influence of small and large perturbations such as structural disorder on the guiding properties. This is demonstrated for two test systems: a capillary fiber and a photonic crystal fiber.

Sleep State Dependence of Optogenetically evoked Responses in Neuronal Nitric Oxide Synthase-positive Cells of the Cerebral Cortex

Slow-wave activity (SWA) in the electroencephalogram during slow-wave sleep (SWS) varies as a function of sleep-wake history. A putative sleep-active population of neuronal nitric oxide synthase (nNOS)-containing interneurons in the cerebral cortex, defined as such by the expression of Fos in animals euthanized after protracted deep sleep, may be a local regulator of SWA. We investigated whether electrophysiological responses to activation of these cells are consistent with their role of a local regulator of SWA. Using a Cre/loxP strategy, we targeted the population of nNOS interneurons to express the light-activated cation channel Channelrhodopsin2 and the histological marker tdTomato in mice. We then performed histochemical and optogenetic studies in these transgenic mice. Our studies provided histochemical evidence of transgene expression and electrophysiological evidence that the cerebral cortex was responsive to optogenetic manipulation of these cells in both anesthetized and behaving mice. Optogenetic stimulation of the cerebral cortex of animals expressing Channelrhodopsin2 in nNOS interneurons triggered an acute positive deflection of the local field potential that was followed by protracted oscillatory events only during quiet wake and slow wave sleep. The response during wake was maximal when the electroencephalogram (EEG) was in a negative polarization state and abolished when the EEG was in a positive polarization state. Since the polarization state of the EEG is a manifestation of slow-wave oscillations in the activity of underlying pyramidal neurons between the depolarized (LFP negative) and hyperpolarized (LFP positive) states, these data indicate that sleep-active cortical neurons expressing nNOS function in sleep slow-wave physiology.

Catechol-O-methyltransferase (COMT) genotype affects cognitive control during total sleep deprivation

Adaptive decision making is profoundly impaired by total sleep deprivation (TSD). This suggests that TSD impacts fronto-striatal pathways involved in cognitive control, where dopamine is a key neuromodulator. In the prefrontal cortex (PFC), dopamine is catabolized by the enzyme catechol-O-methyltransferase (COMT). A functional polymorphism (Val158Met) influences COMT's enzymatic activity, resulting in markedly different levels of prefrontal dopamine. We investigated the effect of this polymorphism on adaptive decision making during TSD. Sixty-six healthy young adults participated in one of two in-laboratory studies. After a baseline day, subjects were randomized to either a TSD group (n = 32) with 38 h or 62 h of extended wakefulness or a well-rested control group (n = 34) with 10 h nighttime sleep opportunities. Subjects performed a go/no-go reversal learning (GNGr) task at well-rested baseline and again during TSD or equivalent control. During the task, subjects were required to learn stimulus-response relationships from accuracy feedback. The stimulus-response relationships were reversed halfway through the task, which required subjects to learn the new stimulus-response relationships from accuracy feedback. Performance on the GNGr task was quantified by discriminability (d') between go and no-go stimuli before and after the stimulus-response reversal. GNGr performance did not differ between COMT genotypes when subjects were well-rested. However, TSD exposed a significant vulnerability to adaptive decision making impairment in subjects with the Val allele. Our results indicate that sleep deprivation degrades cognitive control through a fronto-striatal, dopaminergic mechanism.

Stereotactic radiosurgery planning of vestibular schwannomas: Is MRI at 3 Tesla geometrically accurate?

Purpose

MRI is a mandatory requirement to accurately plan Stereotactic Radiosurgery (SRS) for Vestibular Schwannomas. However, MRI may be distorted due not only to inhomogeneity of the static magnetic field and gradients but also due to susceptibility‐induced effects, which are more prominent at higher magnetic fields. We assess geometrical distortions around air spaces and consider MRI protocol requirements for SRS planning at 3 T.

Methods

Hardware‐related distortion and the effect of incorrect shimming were investigated with structured test objects. The magnetic field was mapped over the head on five volunteers to assess susceptibility‐related distortion in the naso‐oro‐pharyngeal cavities (NOPC) and around the internal ear canal (IAC).

Results

Hardware‐related geometric displacements were found to be less than 0.45 mm within the head volume, after distortion correction. Shimming errors can lead to displacements of up to 4 mm, but errors of this magnitude are unlikely to arise in practice. Susceptibility‐related field inhomogeneity was under 3.4 ppm, 2.8 ppm, and 2.7 ppm for the head, NOPC region and IAC region, respectively. For the SRS planning protocol (890 Hz/pixel, approximately 1 mm³ isotropic), susceptibility‐related displacements were less than 0.5 mm (head), and 0.4 mm (IAC and NOPC). Large displacements are possible in MRI examinations undertaken with lower receiver bandwidth values, commonly used in clinical MRI. Higher receiver bandwidth makes the protocol less vulnerable to sub‐optimal shimming. The shimming volume and the CT‐MR co‐registration must be considered jointly.

Conclusion

Geometric displacements can be kept under 1 mm in the vicinity of air spaces within the head at 3 T with appropriate setting of the receiver bandwidth, correct shimming and employing distortion correction.

[Diffusion tensor imaging of the visual pathway in glaucomatous optic nerve atrophy]

In Germany more than one million inhabitants suffer from glaucoma, more than 100,000 are threatened with blindness because glaucoma is often diagnosed too late or not at all. Diagnosis and monitoring is usually carried out "only" by examination of the retina and not the whole visual pathway. However, the eye is just "the tip of the iceberg" of the actual visual pathway, which extends through the brain to the visual cortex. The interdisciplinary holistic assessment of the whole visual pathway in glaucoma is of crucial importance because glaucoma is a complex neurodegenerative disease. Subtypes, such as normal tension glaucoma (NTG), seem to originate from primary damage to the intracranial visual pathway with secondary retrograde retinal degeneration. Recent studies including glaucoma patients and healthy controls could show that diffusion tensor imaging with calculation of diffusion coefficients, i.e. fractional anisotropy (FA), mean and radial diffusivity (MD and RD) as markers of axonal integrity, provide the potential to assess the intracranial visual pathway with a high correlation to established ophthalmological examinations. In particular, calculation of FA maps of the visual pathway and accompanying voxel-based approaches, can be integrated into clinical routine. Thus, detection of glaucoma-related intracranial alterations, even in early stages of the disease, as well as differentiation of different glaucoma subtypes, is made possible. Furthermore, the diagnosis of normal tension glaucoma seems to be possible much earlier with these new imaging techniques compared to established ophthalmological work-up. Moreover, holistic imaging provides new insights into the pathophysiology of this form of glaucoma. This review article gives an overview of these novel magnetic resonance imaging techniques for assessment of the visual pathway in glaucomatous optic nerve atrophy and reveals the potential of an interdisciplinary approach.

mTOR Inhibition Mitigates Molecular and Biochemical Alterations of Vigabatrin-Induced Visual Field Toxicity in Mice

BACKGROUND

Gamma-vinyl-γ-aminobutyric acid (GABA) (vigabatrin) is an antiepileptic drug and irreversible GABA transaminase inhibitor associated with visual field impairment, which limits its clinical utility. We sought to relate altered visual evoked potentials associated with vigabatrin intake to transcriptional changes in the mechanistic target of rapamycin (mTOR) pathway and GABA receptors to expose further mechanisms of vigabatrin-induced visual field loss.

METHODS

Vigabatrin was administered to mice via an osmotic pump for two weeks to increase GABA levels. Visual evoked potentials were examined, eye samples were collected, and gene expression was measured by quantitative reverse transcription-polymerase chain reaction. Similarly, human retinal pigment epithelial cells (ARPE19) were exposed to vigabatrin and treated with mTOR inhibitors for mTOR pathway analysis and to assess alterations in organelle accumulation by microscopy.

RESULTS

Dysregulated expression of transcripts in the mTOR pathway, GABA_A/B receptors, metabotropic glutamate (Glu) receptors 1/6, and GABA/glutamate transporters in the eye were found in association with visual evoked potential changes during vigabatrin administration. Rrag genes were upregulated in both mouse eye and ARPE19 cells. Immunoblot of whole eye revealed greater than three fold upregulation of a 200 kDa band when immunoblotted for ras-related guanosine triphosphate binding D. Microscopy of ARPE19 cells revealed selective reversal of vigabatrin-induced organelle accumulation by autophagy-inducing drugs, notably Torin 2. Changes in the mTOR pathway gene expression, including Rrag genes, were corrected by Torin 2 in ARPE19 cells.

CONCLUSIONS

Our studies, indicating GABA-associated augmentation of RRAG and mTOR signaling, support further preclinical evaluation of mTOR inhibitors as a therapeutic strategy to potentially mitigate vigabatrin-induced ocular toxicity.

Sleep Homeostatic and Waking Behavioral Phenotypes in Egr3-Deficient Mice Associated with Serotonin Receptor 5-HT2 Deficits

STUDY OBJECTIVE

The expression of the immediate early gene early growth response 3 (Egr3) is a functional marker of brain activity including responses to novelty, sustained wakefulness, and sleep. We examined the role of this gene in regulating wakefulness and sleep.

METHODS

Electroencephalogram/electromyogram (EEG/EMG) were recorded in Egr3-/- and wild-type (WT) mice during 24 h baseline, 6 h sleep disruption and 6 h recovery. Serotonergic signaling was assessed with 6 h EEG/EMG recordings after injections of nonselective 5-HT2 antagonist (clozapine), selective 5-HT2 antagonists (5-HT2A; MDL100907 and 5-HT2BC; SB206553) and a cocktail of both selective antagonists, administered in a randomized order to each animal.

RESULTS

Egr3-/- mice did not exhibit abnormalities in the timing of wakefulness and slow wave sleep (SWS); however, EEG dynamics in SWS (suppressed 1-3 Hz power) and in quiet wakefulness (elevated 3-8 Hz and 15-35 Hz power) differed in comparison to WT-mice. Egr3-/- mice showed an exaggerated response to sleep disruption as measured by active wakefulness, but with a blunted increase in homeostatic sleep drive (elevated 1-4 Hz power) relative to WT-mice. Egr3-/-mice exhibit greatly reduced sedative effects of clozapine at the electroencephalographic level. In addition, clozapine induced a previously undescribed dissociated state (low amplitude, low frequency EEG and a stable, low muscle tone) lasting up to 2 h in WT-mice. Egr3-/- mice did not exhibit this phenomenon. Selective 5-HT2A antagonist, alone or in combination with selective 5-HT2BC antagonist, caused EEG slowing coincident with behavioral quiescence in WT-mice but not in Egr3-/- mice.

CONCLUSION

Egr3 has an essential role in regulating cortical arousal, wakefulness, and sleep, presumably by its regulation of 5-HT2 receptors.

Distribution of disease phase, treatment prescription and severe liver disease among 1598 patients with chronic hepatitis B in the Chronic Hepatitis Cohort Study, 2006-2013

BACKGROUND

Limited information exists regarding the distribution of disease phases, treatment prescription and severe liver disease among patients with chronic hepatitis B (CHB) in US general healthcare settings.

AIM

To determine the distribution of disease phases, treatment prescription and severe liver disease among patients with CHB in general US healthcare settings.

METHODS

We analysed demographic and clinical data collected during 2006-2013 from patients with confirmed CHB in the Chronic Hepatitis Cohort Study, an observational cohort study involving patients from healthcare organisations in Michigan, Pennsylvania, Oregon and Hawaii. CHB phases were classified according to American Association for the Study of Liver Disease guidelines.

RESULTS

Of 1598 CHB patients with ≥12 months of follow-up (median 6.3 years), 457 (29%) were immune active during follow-up [11% hepatitis B e antigen (HBeAg)-positive, 16% HBeAg-negative, and 2% HBeAg status unknown], 10 (0.6%) were immune tolerant, 112 (7%) were inactive through the duration of follow-up and 886 (55%) were phase indeterminate. Patients with cirrhosis were identified within each group (among 21% of immune active, 3% of inactive and 9% of indeterminate phase patients) except among those with immune-tolerant CHB. Prescription of treatment was 59% among immune active patients and 84% among patients with cirrhosis and hepatitis B virus (HBV) DNA >2000 IU/mL.

CONCLUSIONS

Approximately, one-third of the cohort had active disease during follow-up; 60% of eligible patients were prescribed treatment. Our findings underscore the importance of ascertainment of fibrosis status in addition to regular assessment of ALT and HBV DNA levels.

Higher all-cause hospitalization among patients with chronic hepatitis C: the Chronic Hepatitis Cohort Study (CHeCS), 2006-2013

In the United States, hospitalization among patients with chronic hepatitis C virus (HCV) infection is high. The healthcare burden associated with hospitalization is not clearly known. We analysed data from the Chronic Hepatitis Cohort Study, an observational cohort of patients receiving care at four integrated healthcare systems, collected from 2006 to 2013 to determine all-cause hospitalization rates of patients with chronic HCV infection and the other health system patients. To compare the hospitalization rates, we selected two health system patients for each chronic HCV patient using their propensity score (PS). Propensity score matching was conducted by site, gender, race, age and household income to minimize differences attributable to these characteristics. We also compared primary reason for hospitalization between chronic HCV patients and the other health system patients. Overall, 10 131 patients with chronic HCV infection and 20 262 health system patients were selected from the 1 867 802 health system patients and were matched by PS. All-cause hospitalization rates were 27.4 (27.0-27.8) and 7.4 (7.2-7.5) per 100 persons-year (PY) for chronic HCV patients and for the other health system patients, respectively. Compared to health system patients, hospitalization rates were significantly higher by site, gender, age group, race and household income among chronic HCV patients (P < 0.001). Compared to health system patients, chronic HCV patients were more likely to be hospitalized from liver-related conditions (RR = 24.8, P < 0.001). Hence, patients with chronic HCV infection had approximately 3.7-fold higher all-cause hospitalization rate than other health system patients. These findings highlight the incremental costs and healthcare burden of patients with chronic HCV infection associated with hospitalization.

Modern Breeding and Biotechnological Approaches to Enhance Carotenoid Accumulation in Seeds

There is an increasing demand for carotenoids, which are fundamental components of the human diet, for example as precursors of vitamin A. Carotenoids are also potent antioxidants and their health benefits are becoming increasingly evident. Protective effects against prostate cancer and age-related macular degeneration have been proposed for lycopene and lutein/zeaxanthin, respectively. Additionally, β-carotene, astaxanthin and canthaxanthin are high-value carotenoids used by the food industry as feed supplements and colorants. The production and consumption of these carotenoids from natural sources, especially from seeds, constitutes an important step towards fortifying the diet of malnourished people in developing nations. Therefore, attempts to metabolically manipulate β-carotene production in plants have received global attention, especially after the generation of Golden Rice (Oryza sativa). The endosperms of Golden Rice seeds synthesize and accumulate large quantities of β-carotene (provitamin A), yielding a characteristic yellow color in the polished grains. Classical breeding efforts have also focused in the development of cultivars with elevated seed carotenoid content, with maize and other cereals leading the way. In this communication we will summarize transgenic efforts and modern breeding strategies to fortify various crop seeds with nutraceutical carotenoids.

TNFα G308A polymorphism is associated with resilience to sleep deprivation-induced psychomotor vigilance performance impairment in healthy young adults

Cytokines such as TNFα play an integral role in sleep/wake regulation and have recently been hypothesized to be involved in cognitive impairment due to sleep deprivation. We examined the effect of a guanine to adenine substitution at position 308 in the TNFα gene (TNFα G308A) on psychomotor vigilance performance impairment during total sleep deprivation. A total of 88 healthy women and men (ages 22-40) participated in one of five laboratory total sleep deprivation experiments. Performance on a psychomotor vigilance test (PVT) was measured every 2-3h. The TNFα 308A allele, which is less common than the 308G allele, was associated with greater resilience to psychomotor vigilance performance impairment during total sleep deprivation (regardless of time of day), and also provided a small performance benefit at baseline. The effect of genotype on resilience persisted when controlling for between-subjects differences in age, gender, race/ethnicity, and baseline sleep duration. The TNFα G308A polymorphism predicted less than 10% of the overall between-subjects variance in performance impairment during sleep deprivation. Nonetheless, the differential effect of the polymorphism at the peak of performance impairment was more than 50% of median performance impairment at that time, which is sizeable compared to the effects of other genotypes reported in the literature. Our findings provided evidence for a role of TNFα in the effects of sleep deprivation on psychomotor vigilance performance. Furthermore, the TNFα G308A polymorphism may have predictive potential in a biomarker panel for the assessment of resilience to psychomotor vigilance performance impairment due to sleep deprivation.

An ion trap built with photonic crystal fibre technology

We demonstrate a surface-electrode ion trap fabricated using techniques transferred from the manufacture of photonic-crystal fibres. This provides a relatively straightforward route for realizing traps with an electrode structure on the 100 micron scale with high optical access. We demonstrate the basic functionality of the trap by cooling a single ion to the quantum ground state, allowing us to measure a heating rate from the ground state of 787 ± 24 quanta/s. Variation of the fabrication procedure used here may provide access to traps in this geometry with trap scales between 100 μm and 10 μm.

APRI and FIB-4 are good predictors of the stage of liver fibrosis in chronic hepatitis B: the Chronic Hepatitis Cohort Study (CHeCS)

We aim to determine the predictive ability of APRI, FIB-4 and AST/ALT ratio for staging of liver fibrosis and to differentiate significant fibrosis (F2-F4) from none to minimal fibrosis (F0-F1) in chronic hepatitis B (CHB). Liver biopsy results were mapped to an F0-4 equivalent fibrosis stage. Mean APRI and FIB-4 scores were significantly higher for each successive fibrosis level from F1 to F4 (P < 0.05). Based on optimized cut-offs, the AUROCs in distinguishing F2-F4 from F0 to F1 were 0.81 (0.76-0.87) for APRI, 0.81 (0.75-0.86) for FIB-4 and 0.56 (0.49-0.64) for AST/ALT ratio. APRI and FIB-4 distinguished F2-F4 from F0 to F1 with good sensitivity and specificity and can be useful for treatment decisions and monitoring progression of fibrosis.

The validity of serum markers for fibrosis staging in chronic hepatitis B and C

Assessment of liver fibrosis is critical for successful individualized disease management in persons with chronic hepatitis B (CHB) or chronic hepatitis C (CHC). We expanded and validated serum marker indices to provide accurate, reproducible and easily applied methods of fibrosis assessment. Liver biopsy results from over 284 CHB and 2304 CHC patients in the Chronic Hepatitis Cohort Study ('CHeCS') were mapped to a F0-F4 equivalent scale. APRI and FIB-4 scores within a 6-month window of biopsy were mapped to the same scale. A novel algorithm was applied to derive and validate optimal cut-offs for differentiating fibrosis levels. For the prediction of advanced fibrosis and cirrhosis, the FIB-4 score outperformed the other serum marker indices in the CHC cohort and was similar to APRI in the CHB cohort. The area under the receiver operating characteristic curves (AUROC) for FIB-4 in differentiating F3-F4 from F0-F2 was 0.86 (95% CI: 0.80-0.92) for CHB and 0.83 (95% CI: 0.81-0.85) for CHC. The suggested cut-offs based on FIB-4 model produced high positive predictive values [CHB: 90.0% for F0-F2, 100.0% for cirrhosis (F4); CHC: 89.7% for F0-F2; 82.9% for cirrhosis (F4)]. In this large observational cohort, FIB-4 predicted the upper and lower end of liver fibrosis stage (cirrhosis and F0-F2, respectively) with a high degree of accuracy in both CHB and CHC patients.

Reflectivity enhanced refractive index sensor based on a fiber-integrated Fabry-Perot microresonator

We discuss a fiber-integrated refractive index sensor with strongly improved detection performance. The resonator has been implemented by means of focused-ion beam milling of a step index fiber and shows a sensitivity of about 1.15µm/RIU. Coating the resonator walls led to a strongly improved mirror reflectivity by a factor of about 26. Design rules for device optimization and a detailed mathematical analysis are discussed, revealing that the sensor operates as an optimized Fabry-Perot resonator. We also show that the performance of such kind of Fabry-Perot sensors is, in general, limited by the detection limit function - a quantity depending on the cavitiy's finesse and on the measurement capabilities used.

Midinfrared frequency combs from coherent supercontinuum in chalcogenide and optical parametric oscillation

We observe the coherence of the supercontinuum generated in a nanospike chalcogenide-silica hybrid waveguide pumped at 2 μm. The supercontinuum is shown to be coherent with the pump by interfering it with a doubly resonant optical parametric oscillator (OPO) that is itself coherent with the shared pump laser. This enables coherent locking of the OPO to the optically referenced pump frequency comb, resulting in a composite frequency comb with wavelengths from 1 to 6 μm.

Influencing surgical management in patients with carcinoma of the cervix using a T2- and ZOOM-diffusion-weighted endovaginal MRI technique

BACKGROUND

Endovaginal MRI (evMRI) at 3.0-T with T2-weighted (T2-W) and ZOnal Oblique Multislice (ZOOM)-diffusion-weighted imaging (DWI) potentially improves the detection of stage Ia/Ib1 cervical cancer. We aimed to determine its sensitivity/specificity, document tumour-to-stromal contrast and establish the effect of imaging on surgical management.

METHODS

Following ethical approval and written informed consent, 57 consecutive patients with suspected stage Ia/Ib1 cervical cancer underwent evMRI at 3.0-T using T2-W and ZOOM-DWI. Sensitivity/specificity were calculated against histopathology for two independent observers. Tumour-to-stromal contrast was determined on T2-W, and diffusion-weighted (b=800 s mm(-2)) images and apparent diffusion coefficients (ADCs) were recorded. In patients due for radical vaginal trachelectomy (RVT), change of surgical management based on imaging findings was documented.

RESULTS

Sensitivity/specificity for detecting tumour was the following: reporting read 88.0/81.8%, anonymised read 92.0/81.8% (observer 1); 84.0/72.7% (observer2; median tumour volume=1.7 cm(3)). Intraobserver agreement was excellent (kappa=0.89) and the interobserver agreement was good (kappa=0.65). Tumour-to-stromal contrast was greater on ZOOM-DWI compared with T2-W images (3.35±2.36 vs 1.39±0.95; P<0.0004). Tumour and stromal ADCs were significantly different (P<0.00001). In 31 patients due for RVT, evMRI altered surgical management in 12 (38.7%) cases (10 cone-biopsy, 2 chemoradiotherapy).

CONCLUSION

T2-W+ZOOM-DWI evMRI has high sensitivity/specificity for detecting stage Ia/Ib1 cervical tumours; in patients due for RVT, the surgical management was altered in ∼39%.