The generation of tetrahedral mesh models for neuroanatomical MRI

In this article, we describe a detailed method for automatically generating tetrahedral meshes from 3D images having multiple region labels. An adaptively sized tetrahedral mesh modeling approach is described that is capable of producing meshes conforming precisely to the voxelized regions in the image. Efficient tetrahedral mesh improvement is then performed minimizing an energy function containing three terms: a smoothing term to remove the voxelization, a fidelity term to maintain continuity with the image data, and a novel elasticity term to prevent the tetrahedra from becoming flattened or inverted as the mesh deforms while allowing the voxelization to be removed entirely. The meshing algorithm is applied to structural MR image data that has been automatically segmented into 56 neuroanatomical sub-divisions as well as on two other examples. The resulting tetrahedral representation has several desirable properties such as tetrahedra with dihedral angles away from 0 and 180 degrees, smoothness, and a high resolution. Tetrahedral modeling via the approach described here has applications in modeling brain structure in normal as well as diseased brain in human and non-human data and facilitates examination of 3D object deformations resulting from neurological illness (e.g. Alzheimer's disease), development, and/or aging.     

Bias in estimation of transporter kinetic parameters from overexpression systems: Interplay of transporter expression level and substrate affinity.

The objective was to investigate the interplay between transporter expression levels and substrate affinity in controlling the influence of aqueous boundary layer (ABL) resistance on transporter kinetics in an over-expression system. Taurocholate flux was measured across human apical sodium-dependent bile acid transporter (hASBT)-Madin-Darby canine kidney monolayers on different occasions and kinetic parameters estimated with and without considering ABL. In error-free simulation/regression studies, flux values were generated across a range of J max, Kt, and substrate concentrations. Similar evaluation was performed for transport inhibition studies. Additionally, simulation/regression studies were performed, incorporating 15% random error to estimate the probability of successfully estimating Kt. Across different occasions, experimental J max and Kt estimates for taurocholate were strongly associated (p < 0.001; r2 = 0.82) when ABL was not considered. Simulation/regression results indicate that not considering ABL caused this association, such that Kt estimates were highly positively biased at high hASBT expression. In reanalyzing taurocholate flux data using the ABL-present model, Kt was relatively constant across occasions (approximately 5 microM) and not associated with J max (p = 0.24; r2 = 0.13). Simulations suggest that J max and Kt collectively determined ABL influence, which is most prominent under conditions of low monolayer resistance. Additionally, not considering ABL lead to negatively biased Ki estimates, especially at high J max. Error-inclusive simulation/regression studies indicated that the probability of successfully estimating Kt depended on the contribution of ABL resistance to flux; when flux became increasingly ABL-limited, probability of success decreased. Results indicate that ABL resistance can bias Kt and Ki estimates from overexpression systems, where the extent of bias is determined by transporter expression level and substrate affinity.     

Outcomes of combined phacoemulsification and deep sclerectomy: a 10-year UK single-centre study

Purpose

To report the outcomes of combined phacoemulsification and -deep sclerectomy (phaco-DS) from a single UK centre over a 10-year period.

Methods

Retrospective analysis of phaco-DS data extracted from an ongoing glaucoma surgery database within Calderdale and Huddersfield NHS Trust. Two hundred and ninety-six eyes of 282 patients were included. Data included patient demographics, pre- and postoperative intraocular pressure (IOP), use of mitomycin C (MMC), spacer device implantation, and follow-up details including surgical success rates. IOP success criteria were: (A) IOP <19 mm Hg and/or 20% decrease from baseline and (B) IOP <16 mm Hg and/or 30% drop from baseline.

Results

Mean follow-up was 63.5±35.3 months. MMC was applied in 145 eyes (49%). Kaplan–Meier success rates in all eyes for criteria A were 89.1% and 80% with glaucoma medications (qualified success) and 81.2% and 68.3% without medications (unqualified success) at 2 and 5 years, respectively. Qualified success for criteria B was 72.4 and 61.4% and unqualified rates were 67.2 and 55.2% for the same time periods. Repeated-measures ANOVA showed significantly lower IOP in the phaco-DS with MMC group up to 3 years postoperatively (P=0.002). Cox''s proportional hazards for criteria B, however, showed no significant effect of MMC application in the long term (P=0.2). Increasing age and laser goniopuncture were positively associated with success, whereas the absence of spacer devices was negatively associated. At last follow-up, 20% of eyes were on glaucoma medications. Complication rates were low with hypotony rates of 0.68%.

Conclusions

This study confirms the long-term safety and efficacy of phaco-DS as a primary glaucoma procedure.     

Cordoplasty: A New Technique for Managing Bilateral Vocal Cord Paralysis and Its Comparison with Posterior Cordotomy and External Procedure in a Large Study Group

To compare the functional results between posterior cordotomy, cordoplasty and external procedure in managing bilateral vocal cord paralysis in one of the largest published study group. Retrospective and comparative study. 54 patients with bilateral vocal cord paralysis who underwent posterior cordotomy (Group-I), cordoplasty (Group-II) and external procedure (Group-III) from 2001 to 2013 were compared for functional outcomes. Successful decannulation was achieved more in Group-I and II than in Group-III. Voice outcome was better in Group-II patients compared to other groups. Outcomes of cordoplasty was better than posterior cordotomy and external procedures, with acceptable airway and good quality of voice. Posterior cordotomy is preferred in patients without tracheostomy and in pediatric patients. In patients with tracheostomy or who accept temporary tracheostomy, a cordoplasty is preferred for favorable voice. External procedure is preferred for patients not fit for general anesthesia.     

Defective membrane systems in dystrophic skeletal muscle of the UM-X7.1 strain of genetically myopathic hamster.

1. The function of mitochondria, sarcotubular membranes (heavy microsomes), sarcolemma and myofibrils from the hind-leg skeletal muscle of about 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters was examined. 2. The mitochondrial calcium uptake as well as mitochondrial phosphorylation and respiratory rates were lower in 60-day-old myopathic skeletal muscle, unlike 150-day-old myopathic animals, when pyruvate-malate and glutamate-malate were used as substrates. However, mitochondria from 150-day-old myopathic animals showed depressed glutamate-dependent respiratory and phosphorylation rates and succinate-supported initial rate of calcium uptake. 3. The microsomal calcium-uptake, but not calcium-binding, and Ca2+-stimulated adenosine triphosphatase (ATPase) activity of the 150-day-old myopathic skeletal muscle were lower than the control values. Although microsomal calcium-binding, calcium-uptake and ATPase activities of the 60-day-old myopathic muscle were not depressed significantly, the initial rate of calcium uptake was less than the control. 4. The sarcolemmal Ca2+-ATPase, but not Mg2+-ATPase or Na+ +K+-ATPase, activity was higher in 60-day-old myopathic muscle whereas the activities of all these enzymes from 150-day-old myopathic animals were higher than the control. On the other hand, the Na+ +K+-ATPase activities from 60- and 150-day-old myopathic animals were inhibited by ouabain to a lesser extent in comparison with the respective control values. 5. The myofibrillar Ca2+-ATPase and Mg2+-ATPase activities as well as inhibition of Mg2+-ATPase due to Na+ and K+ in myopathic muscle were no different from the control values. 6. The results reported here give further support to the view that different membrane systems of the dystrophic muscle are defective.     

When nouns and verbs degrade: Facilitating communication in semantic dementia

Background: Little is known about how to maintain communicative effectiveness in semantic dementia as the disease progresses from impairment in word retrieval to a loss of conceptual knowledge.

Aim: The purpose of this study is twofold. The first objective is to characterise communicative effectiveness using a modified framework derived from Chapman and Ulatowska (1997 Chapman, S. B. and Ulatowska, H. K. 1997. “Discourse in dementia: Consideration of consciousness.”. In Language structure, discourse and the access to consciousness, Edited by: Stamenov, M. I. 155–188. Philadelphia: John Benjamin Publishing Company.  [Google Scholar]) that integrates two components: codification of ideas (falling on a continuum from verbal to nonverbal and generative to automatic forms) and functions of communication (imaginative, heuristic, informative, personal, interactional, regulatory, and instrumental). The second objective is to outline principles of a discourse intervention that focuses on communicative effectiveness.

Method & Procedures: The participant was Mr Bobby V, a man with semantic dementia. His communication abilities were characterised at diagnosis and 24 months later using the framework of communicative effectiveness, based on discourse samples, clinical observation, and caregiver report. From the time of diagnosis, Bobby V received discourse intervention, which focused on maintaining his communication abilities using all available communication resources. We outline principles of discourse intervention in semantic dementia based on our experience of delivering individual and group intervention to Bobby V.

Outcomes and Results: The communicative effectiveness framework described here could be used to characterise communication skills, set therapy goals, and monitor progress in semantic dementia. Discourse intervention likely facilitated Bobby V's continued success in maintaining communication despite progressive loss of nouns and verbs.

Conclusions: Targeting conversational effectiveness in terms of communicative functions offers a promising and ecologically valuable intervention for people with semantic dementia, as it allows individuals with this form of dementia to connect meaningfully with people in their immediate surroundings well into the later stages of the disease.     

Hyperexcitability of inferior colliculus neurons caused by acute noise exposure

Noise exposure is one of the most common causes of hearing loss. Recent studies found that noise exposure‐induced cochlear damage may change the excitability and tonotopic organization of the central auditory system (CAS). This plasticity was suspected to be related to tinnitus and hyperacusis. However, how cochlear damage affects CAS function and causes these neurologic diseases is still not clear. CAS function is activity dependent, so we hypothesize that a restricted cochlear lesion might disrupt the balance of excitation and inhibition in the CAS and thereby affect its neural activity. To test this hypothesis, we studied the effects of narrow‐band noise exposure on the firing properties of neurons in the inferior colliculus (IC), which has complex neural circuits and plays an important role in sound processing. We found that noise exposure (20 kHz, 105 dB SPL, 30 min) caused a dramatic decrease of the characteristic frequency in about two‐thirds of high‐frequency neurons with/without causing a significant threshold shift. The noise exposure also caused an increase in firing rate of the low‐frequency neurons at suprathreshold levels, whereas it dramatically decreased the firing rate of the high‐frequency neurons. Our results suggest that acute high‐frequency noise exposure may increase low‐frequency responsiveness by causing hyperexcitability of low‐frequency neurons. The functional change of the low‐frequency neurons may be related to the disruption of side‐band inhibition at the noise exposure frequencies caused by cochlear damage. © 2012 Wiley Periodicals, Inc.     

Gastric Ultrasound: POCUSing an Intolerant GUT!

How to cite this article: Kothekar AT, Joshi AV. Gastric Ultrasound: POCUSing an Intolerant GUT! Indian J Crit Care Med 2022;26(9):981–982.