REVIEW | doi:10.20944/preprints202104.0738.v1
Subject: Medicine & Pharmacology, Allergology Keywords: posterior capsule opacification, experimental studies, cell cultures, tissue cultures, animal model of PCO
Online: 28 April 2021 (10:08:38 CEST)
Posterior capsule opacification (PCO) is the most common complication of cataract surgery. It causes a gradual deterioration of visual acuity, which would otherwise remain improved after a successful procedure. Despite recent advances in ophthalmology, this complication has not been eradicated and the incidence of PCO can be as high as 10%. This article reviews the literature concerning the pathomechanism of PCO and examines the biochemical pathways involved in its formation and methods to prevent this complication. We also review the reported tests performed in cell cultures under laboratory conditions, in experimental animal models, and in ex vivo human lens capsules. Finally, we describe research involving human eyes in the clinical setting and pharmacological methods that may reduce the frequency of PCO. Due to the multifactorial eti-ology of PCO, in vitro studies make it possible to assess the factors contributing to its complica-tions and search for new therapeutic targets. Not all pathways involved in cell proliferation, mi-gration, and contraction of the lens capsule are reproducible in laboratory conditions; moreover, PCO in humans and laboratory animals may be additionally stimulated by various degrees of postoperative reactions depending on the course of surgery. Therefore, further studies are necessary.
REVIEW | doi:10.20944/preprints201911.0084.v3
Subject: Biology, Anatomy & Morphology Keywords: brainstem sensory nuclei; somatosensation; secondary afferents; posterior column
Online: 8 March 2020 (17:17:31 CET)
The dorsal column nuclei complex (DCN-complex) includes the dorsal column nuclei (DCN, referring to the gracile and cuneate nuclei collectively), external cuneate, X, and Z nuclei, and the median accessory nucleus. The DCN are organised by both somatotopy and modality, and have a diverse range of afferent inputs and projection targets. The functional organisation and connectivity of the DCN implicate them in a variety of sensorimotor functions, beyond their commonly accepted role in processing and transmitting somatosensory information to the thalamus, yet this is largely underappreciated in the literature. To consolidate insights into their sensorimotor functions, this review examines the morphology, organisation, and connectivity of the DCN and their associated nuclei. First, we briefly discuss the receptors, afferent fibres, and pathways involved in conveying tactile and proprioceptive information to the DCN. Next, we review the modality and somatotopic arrangements of the remaining constituents of the DCN-complex. Finally, we examine and discuss the functional implications of the myriad of DCN-complex projection targets throughout the diencephalon, midbrain, and hindbrain, in addition to their modulatory inputs from the cortex. The organisation and connectivity of the DCN-complex suggest that these nuclei should be considered a complex integration and distribution hub for sensorimotor information.
ARTICLE | doi:10.20944/preprints202203.0317.v1
Subject: Medicine & Pharmacology, Dentistry Keywords: posterior edentulous maxilla; maxillary sinus; sinus floor elevation; tilted implants
Online: 23 March 2022 (12:49:55 CET)
The aim of this study was to evaluate implants survival rate, marginal bone loss, surgical and prosthetic complications of implants placed through sinus floor elevation and tilted implants en-gaged in basal bone in order to bypass maxillary sinus. 60 patients were enrolled for this study. According with residual bone height of posterior maxilla the sample was divided in three groups of 20 patients: Group A (lateral sinus floor elevation), Group B (transrectal sinus floor elevation) and Group C (tilted implants employed to bypass sinus floor). Follow-up visits were performed one week after surgery, at 3, 6 months and then once a year for next 4 years. The outcomes were implants survival rate, marginal bone loss and surgical and prosthetic complications. Although the Group A, B and C have demonstrated an implants survival rate of 83.3%, 86,7% and 98,3% respectively, the statistically analysis showed that there was no statistically significant difference between groups. Statistically significant differences between the groups were also not found con-cerning marginal bone loss, as recorded by intra-oral X-ray measurements during follow-up. About complications it wasn’t possible to perform a statistical analysis. To as to reduce potential surgical risks implants placement in basal bone should be preferred.
REVIEW | doi:10.20944/preprints202212.0222.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: cerebellal mutism syndrome,; cerebello-cerebral diaschisis; posterior fossa tumor; vermis language impairment
Online: 13 December 2022 (02:35:01 CET)
Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, is encountered in a subset of children who have undergone an operative procedure of the posterior cranial fossa, mainly involving the vermis, and the most frequent underlying pathology is proved to be medulloblastoma. The most common characteristics of this syndrome include an often transient, although protracted, language impairment, emotional lability, along with cerebellar, and brainstem dysfunction. Nevertheless, a significant number of patients experience persistent neurological deficits and lasting neurocognitive impairment. A lot of research and clinical studies have been performed in order to better delineate this syndrome. The main obstacles in our way to highlight all aspects of this syndrome were related with an inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty surrounding risk factors and etiology. Currently, there is a combination of diagnostic criteria that are regarded as prerequisites in order to establish the diagnosis of CMS. These include language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement. Several risk factors are recognized as implicated in the pathogenesis of this syndrome, including midline tumor location, diagnosis of medulloblastoma, younger age at diagnosis, and preoperatively established language impairment. A proposed etiology of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Specific treatment for CMS is lacking, and it continues to be directed at symptom management. Our aim is to present a comprehensive narrative review of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. Moreover, we attempt to recognize the most widely recognized priorities of the research community in order to expand our knowledge in the era of diagnostics, prevention, and therapeutic options for patients suffering from CM, or who are at risk for development of this syndrome.
ARTICLE | doi:10.20944/preprints202108.0222.v1
Subject: Mathematics & Computer Science, Probability And Statistics Keywords: Maximum likelihood estimate; Bayes estimate; Gamma distribution; Squared error loss function; Posterior distribution
Online: 10 August 2021 (09:54:48 CEST)
The power function distribution is a flexible waiting time model that may provide better fit for some failure data. This paper presents the comparison of the maximum likelihood estimates and the Bayes estimates of two-parameter power function distribution. The Bayes estimates are obtained, using conjugate priors, under five loss functions consist of square error, precautionary, weighted, LINEX and DeGroot loss function. The Gibbs sampling algorithm is proposed to generate samples from posterior distributions and in result the Bayes estimates are computed. The comparison of the maximum likelihood estimates and the Bayes estimates are done through the root mean squared errors. One real-life data set is analyzed to illustrate the evaluation of proposed methods of estimation. Finally, results from the simulation are discussed to assess the performance behavior of the maximum likelihood estimates and the Bayes estimates.
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: Brain death; posterior fossa; brainstem death; ancillary tests; EEG; evoked potentials
Online: 3 August 2020 (01:22:49 CEST)
Background: New controversies have raised on brain death (BD) diagnosis when lesions are localized in the posterior fossa. Objective: To discuss the particularities of diagnosis BD in patients with posterior fossa lesions. Material and Methods. The author made a systematic review of literature on this topic. Results and Conclusions: A supratentorial brain lesion usually produces a rostrocaudal transtentorial brain herniation, resulting in forebrain and brainstem loss of function. In secondary brain lesions [i.e., cerebral hypoxia], the brainstem is also affected like the forebrain. Nevertheless, some cases complaining posterior fossa lesions [i.e., basilar artery thrombotic infarcts, or hemorrhages of the brainstem and/or cerebellum] may retain intracranial blood flow and EEG activity. In this article I discuss that if a posterior fossa lesion does not produce an enormous increment of intracranial pressure, a complete intracranial circulatory arrest does not occur, explaining the preservation of EEG activity, evoked potentials, and autonomic function. I also address Jahi McMath, who was declared braindead, but ancillary tests, performed 9 months after initial brain insult, showed conservation of intracranial structures, EEG activity, and autonomic reactivity to “Mother Talks” stimulus, rejecting the diagnosis of BD. Jahi McMath’s MRI study demonstrated a huge lesion in the pons. Some authors have argued that in patients with primary brainstem lesions it might be possible to find a in some cases partial recover of consciousness, even fulfilling clinical BD criteria. This was the case in Jahi McMath.
ARTICLE | doi:10.20944/preprints201905.0321.v1
Subject: Keywords: Hox genes, Hox collinearity, Noether’s Theory, Anterior Posterior axis, Rotational symmetry
Online: 27 May 2019 (14:14:36 CEST)
Hox Gene Collinearity (HGC) is a fundamental property that determines the development of many animal clades including Vertebrates. In the Hox gene clusters the genes are located in a sequence Hox1, Hox2, Hox3,… along the 3’ to 5’ direction of the cluster in the chromosome. During Hox cluster activation the Hox genes are expressed sequentially in the ontogenetic units D1, D2, D3,… along the anterior (A)- Posterior (P) axis of the early embryo. This collinearity, first observed by E.B. Lewis, is surprising because the spatial extent of these structures (Hox clusters and embryos) differ by about 4 orders of magnitude. Biomolecular mechanisms alone cannot explain this correlation. Long range physical interactions like diffusion or electric attractions should be involved. A biophysical model (BM) has been formulated which cooperates with the biomolecular processes and describes the data successfully. Hundred years ago E. Noether made a fundamental discovery in Mathematics and Physics. She proved rigorously that a physical system obeying a symmetry law (e.g.rotations or self similarity) is linked to a conserved physical quantity. It is argued here that HGC obeys a ‘primitive’ self similarity symmetry of the genes of a Hox cluster along a finite straight line. In the case of Vertebrates, the associated partially conserved quantity is the ever increasing ‘ratchet’- like gene ordering where some Hox genes are missing. Another application of Noether’s Theory is performed to rotationally symmetric embryos like the sea urchin.
Subject: Medicine & Pharmacology, Pediatrics Keywords: body posture defects; the shape of anterior-posterior spinal curvatures; body composition; school-children
Online: 11 April 2020 (05:38:01 CEST)
The aim of the study was to assess the relationship between the shape of the anterior-posterior curvature of the spine and body composition in school-children. The study included 257 children, aged 11-12. Correct spinal curvature was established in 106 (41.08%) subjects. Other types included: decreased kyphosis and correct lordosis - 40 participants (15.50%), correct kyphosis and decreased lordosis - 24 individuals (9.30%), increased kyphosis and correct lordosis - 17 subjects (6.59%), correct kyphosis and increased lordosis - 22 children (8.53%), decreased kyphosis and decreased lordosis - 32 people (12.40%), decreased kyphosis and increased lordosis - 4 of the examined subjects (1.55%), increased kyphosis and lordosis - 13 people (5.04%). In addition, 134 (51.94%) demonstrated scoliotic posture and 8 (3.10%) scoliosis. There were significant relationships between the shape of the anterior-posterior curvatures and body composition in school-children. Those with a strong body build (predominance of mesomorphs) were generally characterised by the correct formation of these curvatures. In contrast, lean people (with the predominance of ectomorphic factors) were more likely to experience abnormalities. No correlations with body composition were observed in the group with scoliotic posture or scoliosis.
ARTICLE | doi:10.20944/preprints201806.0084.v1
Subject: Behavioral Sciences, Cognitive & Experimental Psychology Keywords: qualia; consciousness; emission theories; perception; event-related brain potentials; P600 or late posterior positivity; N400
Online: 6 June 2018 (10:51:03 CEST)
We take what we see, hear, smell and feel for the reality. However, as neuroscientists, we know that this reality, that is, our perceptual world, is in fact made up by the brain from the processing of the nerve impulses coming from receptors. Ancient Greeks used to think that this perceptual world, sometimes called our 3D movie (Chalmers), is emitted and has its own physical nature. Given how real the 3D movie looks to us, it is still difficult today to consider that all we would be dealing with would be patterns of brain activity The present study thus aimed at testing whether the perceptual world could have some physical existence in addition to that of the neural patterns responsible for it. To achieve that goal, we tried to see whether brains could be sensitive to the 3D movie of others. This, admittedly unusual, operational hypothesis was based on two assumptions. First, brains are sensitive to the 3D movie, as our experience includes reactions to our perceptual world. Second, the physicality at stake does not differ across individuals. We recorded the event-related brain potentials (ERPs) evoked by stimuli of the international affective picture system in pairs of closely-related participants. Most importantly, they could neither see the stimuli simultaneously presented to their partners nor their reactions to them. As in Bouten et al. (2015), around 400 ms after the onset of the stimuli, ERPs started being more positive in inconsistent conditions. Namely, when the two subjects of each pair were presented with the same stimulus whereas they were told it would be a different one and vice-versa (i.e., different-stimuli expected to be same). ERPs were less positive when the two subjects of a pair were presented with the same stimuli and were told they were the same and conversely (i.e., different-stimuli expected to be different). The same experiment was then run in pairs of strangers. No significant effect of consistency on ERPs was observed even though participants could, this time, see, in the very periphery of their visual field, the reactions of their partner to the stimuli. We thus use the results of both studies to support a new version of the emission theory of consciousness and to suggest that the sensitivity to the perceptual world of others may depend on their prior familiarity with it.
CASE REPORT | doi:10.20944/preprints202103.0466.v1
Subject: Behavioral Sciences, Applied Psychology Keywords: anarchic hand syndrome; DTI; white matter disconnection; lesion mapping; sense of agency; posterior lesions.
Online: 18 March 2021 (10:09:37 CET)
The anarchic hand syndrome refers to an inability to control the movements of one’s own hand which acts as if it had a will of its own. The symptoms may differ depending on whether the brain lesion is anterior, posterior, callosal or subcortical, but the relative classifications are not conclusive. This study investigates the role of white matter disconnections in a patient whose symptoms are inconsistent with the mapping of the lesion site. A repeated neuropsychological investigation was associated with a review of the literature on the topic to identify the frequency of various different symptoms relating to this syndrome. Furthermore, an analysis of the neuroimaging regarding structural connectivity allowed us to investigate the grey matter lesions and white matter disconnections. The results indicated that some of the patient’s symptoms were associated with structures that, although not directly damaged, were dysfunctional due to a disconnection in their networks. This suggests that the anarchic hand may be considered as a disconnection syndrome involving the integration of multiple antero-posterior, insular and interhemispheric networks. In order to comprehend this rare syndrome better, the clinical and neuroimaging data need to be integrated with the clinical reports available in the literature on the topic.
ARTICLE | doi:10.20944/preprints201810.0704.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: inferior vena cava (IVC); ultrasound imaging; anterior posterior (AP) diameter; active ellipse; active rectangle; volume status
Online: 30 October 2018 (05:14:43 CET)
Medical research has suggested that the anterior-posterior (AP)-diameter of the inferior vena cava (IVC) and its associated temporal variation as imaged by bedside ultrasound is useful in guiding fluid resuscitation of the critically-ill patients. This paper develops semi-automatic active ellipse and rectangle algorithms for measurement and tracking of the AP-diameter. The proposed algorithms are compared with an expert manual measurement and the previous work based on active circle model. It is shown that regardless of the shape of the IVC, the rectangle model always outperforms the two other models and performs very close to manual measurement.
REVIEW | doi:10.20944/preprints202212.0208.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: Proliferative diabetic retinopathy; recurrent vitreous hemorrhage; diabetes duration; anemia; posterior vitreous; retinal laser photocoagulation
Online: 12 December 2022 (14:59:08 CET)
(Background) the aim was to determine related factors to recurrent vitreous hemorrhage (RVH) in a sample of proliferative diabetic retinopathy (PDR) patients. (Methods) A retrospective, review-based study. We studied 183 eyes from 121 type 2 diabetes patients with PDR. We recorded diabetes duration, history of hypertension, retinal photocoagulation status, the posterior vitreous status, the mean HbA1c, mean hemoglobin, the renal function, and the systemic complications related to diabetes. We also recorded the use of ranibizumab prior to vitrectomy and the following surgical variables: the application of segmentation and diathermy on fibrovascular proliferative tissue, the use of silicone oil, and the occurrence of surgical complications, to study which independent variables were significantly related to the presence of RVH. (Results) Duration of diabetes (P= 0.028), hemoglobin (P=0.02), status of the posterior vitreous (P=0.03), retinal photocoagulation (P=0.002) and use of segmentation surgery technique (P=0.003) have significant link to the presence of RVH. In addition, patients with diabetic polyneuropathy, myocardial infarction and ischemia in lower limbs had more vitreous hemorrhage events (p<0.001). (Conclusions) Patients with PDR and with longer diabetes duration, anemia, attached posterior vitreous, deficient retinal photocoagulation, and previously cardiovascular events, were more prone to RVH.
SHORT NOTE | doi:10.20944/preprints202206.0032.v1
Subject: Life Sciences, Other Keywords: Conformity assessment; lot inspection; acceptance sampling; Quality level; sample size; Bayesian statistics; prior distribution; posterior distribution; consumer risk; producer risk
Online: 2 June 2022 (10:59:47 CEST)
The ISO 2859 and ISO 3951 series provide acceptance sampling procedures for lot inspection, allowing both sample size and acceptance rule to be determined, starting from a specific value either for the consumer or producer risk. However, insufficient resources often make it difficult to implement “ISO sampling plans.” In cases where the sample size is determined by external constraints, the focus shifts from determining sample size to determining consumer and producer risks. Moreover, if the sample size is very low (e.g. one single item), prior information should be included in the statistical analysis. For this reason, it makes sense to work within a Bayesian theoretical framework, such as that described in JCGM 106. Accordingly, the approach from JCGM 106 is adopted and broadened so as to allow application to lot inspection. The discussion is based on a “real-life” example of lot inspection on the basis of a single item. Starting from simple assumptions, expressions for both the prior and posterior distributions are worked out, and it is shown how the concepts from JCGM 106 can be reinterpreted in the context of lot inspection. Conceptual differences regarding the definition of consumer and producer risks in JCGM 106 and in the ISO acceptance sampling standards are elucidated and a numerical example is provided.
ARTICLE | doi:10.20944/preprints202101.0478.v1
Subject: Medicine & Pharmacology, Allergology Keywords: ocular drug delivery system; topical liposomes; posterior segment of the eye; safety and toler-ability; biologic activity; diabetic macular edema
Online: 25 January 2021 (10:48:51 CET)
Intravitreal injections (IVTs) of corticosteroids as triamcinolone acetonide (TA) are frequently used for the treatment of many vitreous and retinal disorders. However, IVTs are related to severe ocular complications. Lately, a topical ophthalmic TA loaded liposomes formulation (TALF) was designed to transport TA into the posterior segment of the eye when instilled in the ocular surface. To evaluate the safety, tolerability, and biologic activity of TALF, an animal study and a phase I clinical assay was performed. Moreover, four patients with diabetic macular edema (DME) were treated with TALF in order to explore the biologic activity of the formulation. No inflammation, lens opacity, swelling or intraocular pressure rising were recorded after the instillation of TALF in any of the animal or clinical study. Mainly, mild and transient adverse events such as dry eye (30%) and burning (30%) were reported. TALF improves significantly visual acuity and diminishes central foveal thickness in patients with DME. The current data demonstrate the safety, tolerability, and biologic activity of TALF. It seems that TALF can be used topically to treat vitreous and retinal diseases that respond to TA such as DME, avoiding the use of corticosteroids IVTs and its associated hazards.
REVIEW | doi:10.20944/preprints202007.0053.v1
Subject: Life Sciences, Other Keywords: thalamocortical loop; thalamus; microcircuit; modeling; reticular nucleus; somatosensory system; ventral posteromedial nucleus; ventral posterolateral nucleus; posterior nucleus; thalamic relay cells; thalamic interneurons; rodent
Online: 5 July 2020 (07:45:16 CEST)
As our understanding of the thalamocortical system deepens, the questions we face become more complex. Their investigation requires the adoption of novel experimental approaches complemented with increasingly sophisticated computational modeling. In this review, we take stock of current data and knowledge about the circuitry of the somatosensory thalamocortical loop in rodents, discussing common principles across modalities and species whenever appropriate. We review the different levels of organization, including the cells, synapses, neuroanatomy, and network connectivity. We provide a complete overview of this system that should be accessible for newcomers to this field while nevertheless being comprehensive enough to serve as a reference for seasoned neuroscientists and computational modelers studying the thalamocortical system. We further highlight key gaps in data and knowledge that constitute pressing targets for future experimental work. Filling these gaps would provide invaluable information for systematically unveiling how this system supports behavioral and cognitive processes.