Deep homologies in chordate caudal central nervous systems.

Invertebrate chordates, such as the tunicate Ciona, can offer insight into the evolution of the chordate phylum. Anatomical features that are shared between invertebrate chordates and vertebrates may be taken as evidence of their presence in a common chordate ancestor. The central nervous systems of Ciona larvae and vertebrates share a similar anatomy despite the Ciona CNS having ~180 neurons. However, the depth of conservation between the Ciona CNS and those in vertebrates is not resolved. The Ciona caudal CNS, while appearing spinal cord-like, has hitherto been thought to lack motor neurons, bringing into question its homology with the vertebrate spinal cord. We show here that the Ciona larval caudal CNS does, in fact, have functional motor neurons along its length, pointing to the presence of a spinal cord-like structure at the base of the chordates. We extend our analysis of shared CNS anatomy further to explore the Ciona "motor ganglion", which has been proposed to be a homolog of the vertebrate hindbrain, spinal cord, or both. We find that a cluster of neurons in the dorsal motor ganglion shares anatomical location, developmental pathway, neural circuit architecture, and gene expression with the vertebrate cerebellum. However, functionally, the Ciona cluster appears to have more in common with vertebrate cerebellum-like structures, insofar as it receives and processes direct sensory input. These findings are consistent with earlier speculation that the cerebellum evolved from a cerebellum-like structure, and suggest that the latter structure was present in the dorsal hindbrain of a common chordate ancestor.

Role of PLGA Variability in Controlled Drug Release from Dexamethasone Intravitreal Implants.

Long-acting injectable formulations based on poly(lactide-co-glycolide) (PLGA) have been commercialized for over 30 years in at least 20 FDA-approved products. These formulations offer several advantages, including reduced dosing frequency, improved patient compliance, and maintenance of therapeutic levels of drug. Despite extensive studies, the inherent complexity of the PLGA copolymer still poses significant challenges associated with the development of generic formulations having drug release profiles equivalent to those of the reference listed drugs. In addition, small changes to PLGA physicochemical properties or the drug product manufacturing process can have a major impact on the drug release profile of these long-acting formulations. This work seeks to better understand how variability in the physicochemical properties of similar PLGAs affects drug release from PLGA solid implants using Ozurdex (dexamethasone intravitreal implant) as the model system. Four 50:50, acid-terminated PLGAs of similar molecular weights were used to prepare four dexamethasone intravitreal implants structurally equivalent to Ozurdex. The PLGAs were extensively characterized by using a variety of analytical techniques prior to implant manufacture using a continuous, hot-melt extrusion process. In vitro release testing of the four structurally equivalent implants was performed in both normal saline and phosphate-buffered saline (PBS), yielding drastically different results between the two methods. In normal saline, no differences in the release profiles were observed. In PBS, the drug release profiles were sensitive to small changes in the residual monomer content, carboxylic acid end group content, and blockiness of the polymers. This finding further underscores the need for a physiologically relevant in vitro release testing method as part of a robust quality control strategy for PLGA-based solid implant formulations.

Manufacturing dexamethasone intravitreal implants: Process control and critical quality attributes.

Over 20 long-acting injectable formulations based on poly(lactide-co-glycolide) (PLGA) have been approved by the FDA to date. PLGA is a biodegradable polymer that can extend drug release from these dosage forms for up to six months after administration. Despite the commercial success of several of these formulations, there are still a limited number of products that utilize PLGA, and there are currently no generic counterparts of these products on the market. Significant technical challenges are associated with preparation of chemically and structurally equivalent formulations that yield an equivalent drug release profile to the reference listed drug (RLD) both in vitro and in vivo. In this work, Ozurdex (dexamethasone intravitreal implant) was used as a model system to explore how the manufacturing process of PLGA-based solid implants impacts the quality and performance of the dosage form. Control of implant structural characteristics, including diameter, internal porosity, and surface roughness, was required to maintain accurate unit dose potency. Implants were prepared by a continuous hot-melt extrusion process that was thoroughly characterized to show the importance of precise feeding control to meet dimensional specifications. Five extruder die designs were evaluated using the same hot-melt extrusion process to produce five structurally-distinct implants. The structural differences did not alter the in vitro drug release profile when tested in both normal saline and phosphate-buffered saline (pH 7.4); however, implant porosity was shown to impact the mechanical strength of the implants. This work seeks to provide insight into the manufacturing process of PLGA-based solid implants to support development of future novel and generic drug products.

Asymmetrical Flow Field Flow Fractionation for Molar Mass Characterization of Polyethylene Oxide in Abuse-Deterrent Formulations.

High molar mass polyethylene oxide (HM-PEO) is commonly used to enhance the mechanical strength of solid oral opioid drug products to deter abuse. Because the properties of PEO depend on molar mass distribution, accurately determining the molar mass distribution is a necessary part of understanding PEO's role in abuse-deterrent formulations (ADF). In this study, an asymmetrical flow field-flow fractionation (AF4) analytical procedure was developed to characterize PEO polymers with nominal molar masses of 1, 4 or 7 MDa as well as those from in-house prepared placebo ADF. The placebo ADF were manufactured using direct compress or hot-melt-extrusion methods, and subjected to physical manipulation, such as heating and grinding before measurement by AF4 were performed. The molar mass distribution characterized by AF4 revealed that PEO was sensitive to thermal stress, exhibiting decreased molar mass with increased heat exposure. The optimized AF4 method was deemed suitable for characterizing HM-PEO, offering adequate dynamic separation range for PEO with molar mass from 100 kDa to approximately 10 MDa.

A single oscillating proto-hypothalamic neuron gates taxis behavior in the primitive chordate Ciona.

Ciona larvae display a number of behaviors, including negative phototaxis. In negative phototaxis, the larvae first perform short spontaneous rhythmic casting swims. As larvae are cast in a light field, their photoreceptors are directionally shaded by an associated pigment cell, providing a phototactic cue. This then evokes an extended negative taxis swim. We report here that the larval forebrain of Ciona has a previously uncharacterized single slow-oscillating inhibitory neuron (neuron cor-assBVIN78) that projects to the midbrain, where it targets key interneurons of the phototaxis circuit known as the photoreceptor relay neurons. The anatomical location, gene expression, and oscillation of cor-assBVIN78 suggest homology to oscillating neurons of the vertebrate hypothalamus. Ablation of cor-assBVIN78 results in larvae showing extended phototaxis-like swims, even in the absence of phototactic cues. These results indicate that cor-assBVIN78 has a gating activity on phototaxis by projecting temporally oscillating inhibition to the photoreceptor relay neurons. However, in intact larvae, the frequency of cor-assBVIN78 oscillation does not match that of the rhythmic spontaneous swims, indicating that the troughs in oscillations do not themselves initiate swims but rather that cor-assBVIN78 may modulate the phototaxis circuit by filtering out low-level inputs while restricting them temporally to the troughs in inhibition.

A single oscillating proto-hypothalamic neuron gates taxis behavior in the primitive chordate Ciona.

Ciona larvae display a number of behaviors, including negative phototaxis. In negative phototaxis, the larvae first perform short spontaneous rhythmic casting swims. As larvae cast in a light field, their photoreceptors are directionally shaded by an associated pigment cell, providing a phototactic cue. This then evokes an extended negative taxis swim. We report here that the larval forebrain of Ciona has a previously uncharacterized single slow-oscillating inhibitory neuron (neuron cor-assBVIN78 ) that projects to the midbrain, where it targets key interneurons of the phototaxis circuit known as the photoreceptor relay neurons . The anatomical location, gene expression and oscillation of cor-assBVIN78 suggest homology to oscillating neurons of the vertebrate hypothalamus. Ablation of cor-assBVIN78 results in larvae showing extended phototaxis-like swims, but which occur in the absence of phototactic cues. These results indicate that cor-assBVIN78 has a gating activity on phototaxis by projecting temporally-oscillating inhibition to the photoreceptor relay neurons. However, in intact larvae the frequency of cor-assBVIN78 oscillation does not match that of the rhythmic spontaneous swims, indicating that the troughs in oscillations do not themselves initiate swims, but rather that cor-assBVIN78 may modulate the phototaxis circuit by filtering out low level inputs while restricting them temporally to the troughs in inhibition.

Identifying Radiographic and Clinical Indicators to Reduce the Occurrence of Nontherapeutic Laparotomy for Blunt Bowel and Mesenteric Injury.

BACKGROUND: Roughly 5% of patients with blunt abdominal trauma (BAT) have a blunt bowel and/or mesenteric injury (BBMI). Determining the need for operative management in these patients can be challenging when hemodynamically stable. Single center studies have proposed scoring systems based on CT findings to guide management. Our study aimed to determine the predictability of abdominopelvic CT scan (CT A/P) findings in conjunction with clinical exam to determine the necessity of operative intervention for BBMI. METHODS: Patients presenting from 2017 to 2022 to the University of South Alabama Level 1 Trauma Center after motor vehicle collision were retrospectively reviewed. Patients with CT findings suggestive of BBMI were further analyzed, noting CT findings, Glasgow coma scale (GCS), shock index, abdominal exam, operative or nonoperative management, and intraoperative intervention. RESULTS: 1098 patients with BAT underwent CT A/P. 139 patients had ≥1 finding suggestive of BBMI. 38 patients underwent surgical exploration and 30 had surgically confirmed BBMI. 27 patients required intervention for BBMI. Univariate analysis indicated that pneumoperitoneum (p < 0.0001), active extravasation of contrast (p = 0.0001), hemoperitoneum without solid organ injury (SOI) (p < 0.0001), peritonitis (p < 0.0001), and mesenteric stranding(p < 0.05) were significantly associated with intervention. CONCLUSION: In total, 30 patients had surgically confirmed BBMI. Active extravasation, pneumoperitoneum, hemoperitoneum without SOI, mesenteric stranding, and peritonitis were significant indicators of BBMI requiring intervention. CT and clinical findings cannot reliably predict the need for surgical intervention without ≥1 of these findings. Initial nonoperative management with serial clinical exams should be strongly considered to reduce incidence of nontherapeutic laparotomies.

Determining critical overlap concentration of polyethylene oxide to support excipient safety assessment of opioid products.

Intravenous administration of abuse-deterrent opioid products poses high safety risks, in part due to the presence of high molecular weight polymeric excipients. Previous in vivo studies in animal models have shown that the higher molecular weight (Mw) polymeric excipients like polyethylene oxide (PEO) were directly linked to such adverse responses as intravenous hemolysis and kidney damage. PEO polymers have been widely used in abuse-deterrent formulations (ADF) of opioid products, adding to concerns over the general safety of the opioid category due to the unknown safety risk from abuse via unintended routes. The current study focused on the determination of the critical overlap concentration (c*) at various PEO molecular weights to aid in explaining differences in observed adverse responses from previous animal studies on the intravenous administration of PEO solutions. Adverse in vivo responses may be related to the viscoelastic regime of the polymer solution, which depends not only on Mw but also on concentration. Having a localized polymer concentration in the blood above the c*, i.e., the transition from the dilute to semi-dilute entangled viscoelastic regime, may influence the flow behavior and interactions of cells in the blood. The relationship of c* to this combination of physical, chemical, and rheological effects is a possible driving force behind adverse in vivo responses.

Using open-source data to construct 20 metre resolution maps of children's travel time to the nearest health facility.

Physical access to health facilities is an important factor in determining treatment seeking behaviour and has implications for targets within the Sustainable Development Goals, including the right to health. The increased availability of high-resolution land cover and road data from satellite imagery offers opportunities for fine-grained estimations of physical access which can support delivery planning through the provision of more realistic estimates of travel times. The data presented here is of travel time to health facilities in Uganda, Zimbabwe, Tanzania, and Mozambique. Travel times have been calculated for different facility types in each country such as Dispensaries, Health Centres, Clinics and Hospitals. Cost allocation surfaces and travel times are provided for child walking speeds but can be altered easily to account for adult walking speeds and motorised transport. With a focus on Uganda, we describe the data and method and provide the travel maps, software and intermediate datasets for Uganda, Tanzania, Zimbabwe and Mozambique.

Fold Change Detection in Visual Processing.

Visual processing transforms the complexities of the visual world into useful information. Ciona, an invertebrate chordate and close relative of the vertebrates, has one of the simplest nervous systems known, yet has a range of visuomotor behaviors. This simplicity has facilitated studies linking behavior and neural circuitry. Ciona larvae have two distinct visuomotor behaviors - a looming shadow response and negative phototaxis. These are mediated by separate neural circuits that initiate from different clusters of photoreceptors, with both projecting to a CNS structure called the posterior brain vesicle (pBV). We report here that inputs from both circuits are processed to generate fold change detection (FCD) outputs. In FCD, the behavioral response scales with the relative fold change in input, but is invariant to the overall magnitude of the stimulus. Moreover, the two visuomotor behaviors have fundamentally different stimulus/response relationships - indicative of differing circuit strategies, with the looming shadow response showing a power relationship to fold change, while the navigation behavior responds linearly. Pharmacological modulation of the FCD response points to the FCD circuits lying outside of the visual organ (the ocellus), with the pBV being the most likely location. Consistent with these observations, the connectivity and properties of pBV interneurons conform to known FCD circuit motifs, but with different circuit architectures for the two circuits. The negative phototaxis circuit forms a putative incoherent feedforward loop that involves interconnecting cholinergic and GABAergic interneurons. The looming shadow circuit uses the same cholinergic and GABAergic interneurons, but with different synaptic inputs to create a putative non-linear integral feedback loop. These differing circuit architectures are consistent with the behavioral outputs of the two circuits. Finally, while some reports have highlighted parallels between the pBV and the vertebrate midbrain, suggesting a common origin for the two, others reports have disputed this, suggesting that invertebrate chordates lack a midbrain homolog. The convergence of visual inputs at the pBV, and its putative role in visual processing reported here and in previous publications, lends further support to the proposed common origin of the pBV and the vertebrate midbrain.

Misregulation of cell adhesion molecules in the Ciona neural tube closure mutant bugeye.

Neural tube closure (NTC) is a complex multi-step morphogenetic process that transforms the flat neural plate found on the surface of the post-gastrulation embryo into the hollow and subsurface central nervous system (CNS). Errors in this process underlie some of the most prevalent human birth defects, and occur in about 1 out of every 1000 births. Previously, we discovered a mutant in the basal chordate Ciona savignyi (named bugeye) that revealed a novel role for a T-Type Calcium Channel (Cav3) in this process. Moreover, the requirement for CAV3s in Xenopus NTC suggests a conserved function among the chordates. Loss of CAV3 leads to defects restricted to anterior NTC, with the brain apparently fully developed, but protruding from the head. Here we report first on a new Cav3 mutant in the related species C. robusta. RNAseq analysis of both C. robusta and C. savignyi bugeye mutants reveals misregulation of a number of transcripts including ones that are involved in cell-cell recognition and adhesion. Two in particular, Selectin and Fibronectin leucine-rich repeat transmembrane, which are aberrantly upregulated in the mutant, are expressed in the closing neural tube, and when disrupted by CRISPR gene editing lead to the open brain phenotype displayed in bugeye mutants. We speculate that these molecules play a transient role in tissue separation and adhesion during NTC and failure to downregulate them leads to an open neural tube.

Disruption of left-right axis specification in Ciona induces molecular, cellular, and functional defects in asymmetric brain structures.

BACKGROUND: Left-right asymmetries are a common feature of metazoans and can be found in a number of organs including the nervous system. These asymmetries are particularly pronounced in the simple central nervous system (CNS) of the swimming tadpole larva of the tunicate Ciona, which displays a chordate ground plan. While common pathway elements for specifying the left/right axis are found among chordates, particularly a requirement for Nodal signaling, Ciona differs temporally from its vertebrate cousins by specifying its axis at the neurula stage, rather than at gastrula. Additionally, Ciona and other ascidians require an intact chorionic membrane for proper left-right specification. Whether such differences underlie distinct specification mechanisms between tunicates and vertebrates will require broad understanding of their influence on CNS formation. Here, we explore the consequences of disrupting left-right axis specification on Ciona larval CNS cellular anatomy, gene expression, synaptic connectivity, and behavior. RESULTS: We show that left-right asymmetry disruptions caused by removal of the chorion (dechorionation) are highly variable and present throughout the Ciona larval nervous system. While previous studies have documented disruptions to the conspicuously asymmetric sensory systems in the anterior brain vesicle, we document asymmetries in seemingly symmetric structures such as the posterior brain vesicle and motor ganglion. Moreover, defects caused by dechorionation include misplaced or absent neuron classes, loss of asymmetric gene expression, aberrant synaptic projections, and abnormal behaviors. In the motor ganglion, a brain structure that has been equated with the vertebrate hindbrain, we find that despite the apparent left-right symmetric distribution of interneurons and motor neurons, AMPA receptors are expressed exclusively on the left side, which equates with asymmetric swimming behaviors. We also find that within a population of dechorionated larvae, there is a small percentage with apparently normal left-right specification and approximately equal population with inverted (mirror-image) asymmetry. We present a method based on a behavioral assay for isolating these larvae. When these two classes of larvae (normal and inverted) are assessed in a light dimming assay, they display mirror-image behaviors, with normal larvae responding with counterclockwise swims, while inverted larvae respond with clockwise swims. CONCLUSIONS: Our findings highlight the importance of left-right specification pathways not only for proper CNS anatomy, but also for correct synaptic connectivity and behavior.

Facilitating Surveillance of Incidental Findings Using a Novel Reporting Template: Proof of Concept in Patients With Pancreatic Abnormalities.

OBJECTIVE: To determine the surveillance impact of utilizing a discrete field in structured radiology reports in patients with incidental pancreatic findings. METHODS: We implemented a dictation template containing a discrete structured field element to auto-trigger listing of patients with incidental pancreatic findings on a pancreas clinic registry in the electronic health record. We isolated CT and MRI reports with incidental pancreatic findings over a 24-month period. We stratified patients by presence or absence of the discrete field element in reports (flagged versus unflagged) and evaluated the impact of report flagging on likelihood of clinic follow-up, follow-up imaging, endoscopic ultrasound, surgical intervention, genetics referral, obtaining pathologic diagnosis, and time interval between index imaging to various outcomes. RESULTS: Patients with flagged reports were more likely to be seen or discussed in a pancreas clinic compared with those with unflagged reports (189 of 376, 50.3% versus 79 of 474, 16.7%; P <. 001). Patients with flagged reports were more likely to get follow-up imaging than patients with unflagged reports (188 of 376, 50.0% versus 121 of 474, 25.5%; P < .001) and were more likely to undergo appropriate management of actionable findings compared with patients in the unflagged group (23 of 62, 37.1% versus 28 of 129, 21.7%; P = .036). DISCUSSION: Implementation of a structured discrete field element for reporting of patients with incidental pancreatic findings had positive impact on surveillance measures and can be applied in other organ systems with established surveillance guidelines to standardize patient care.

Impact of particle flocculation on the dissolution and bioavailability of injectable suspensions.

Injectable suspensions occasionally exhibit variations in dissolution and bioavailability, which may impact the clinical outcome of the drug product. Here, variation in the injection method (i.e., applied shear) for triamcinolone acetonide (TA) injectable suspension (40 mg/mL) altered the flocculation state of the particles and subsequently their dissolution. Notably, TA suspensions contained primary particles of approximately 2 µm and secondary flocculates of tens of microns. The conversion between flocculated and deflocculated particles was rapid, reversible and highly shear dependent. As such, changing shear rates during laser diffraction (LD) measurement like stirring rate, sonication, and sample introduction method (micropipette vs 25-gauge needle) may result in variability in particle size distributions (PSD) that have the potential to alter drug dissolution. Furthermore, a non-sink, discriminatory in vitro release testing (IVRT) method was developed, which combined in-situ fiber optic UV with LD to simultaneously monitor the dissolution and changing PSD of the suspension. The simultaneously measured dissolution and PSD data showed that flocculated and deflocculated particles followed different dissolution pathways. Importantly, deflocculated particles dissolved up to six times faster than the flocculated particles. Similar shear-induced changes during injection could occur in a clinical setting and have implications for drug bioavailability.

Consequences of school closure on access to education: Lessons from the 2013-2016 Ebola pandemic.

The COVID-19 pandemic has seen an unprecedented shutdown of society. Among the various safety measures taken, much attention has been given to school closure as a non-pharmaceutical mitigation tool to curb the spread of the disease through ensuring "social" (physical) distancing. Nearly 1.725 billion children in over 95% of countries worldwide have been affected by school closures implemented in April 2020 as the virus continued to spread. In the field of education, policymakers' attention has been directed at keeping students on board through remote learning and addressing the immediate needs of schools upon reopening. The study presented in this article focuses on who remains absent after schools resume. Using publicly available survey data from the USAID Demographic Health Surveys Program and the UNICEF Multiple Indicator Cluster Survey from before and after the 2013-2016 Ebola pandemic in Guinea and Sierra Leone in West Africa, the author examined changes in school enrolment and dropout patterns, with targeted consideration given to traditionally marginalised groups. At the time, schools closed for between seven to nine months in the two countries; this length and intensity makes this Ebola pandemic the only health crisis in the recent past to come close to the pandemic-related school closures experienced in 2020. The author's findings suggest that post-Ebola, youth in the poorest households saw the largest increase in school dropout. Exceeding expected pre-Ebola dropout rates, an additional 17,400 of the poorest secondary-age youth were out of school. This evidence is important for minimising the likely post-COVID-19 expansion in inequality. The author's findings point to the need for sustainable planning that looks beyond the reopening of educational institutions to include comprehensive financial support packages for groups most likely to be affected.

Conséquences de la fermeture des écoles sur l'accès à l'éducation : les enseignements de la pandémie d'Ebola de 2013 à 2016 ­ La pandémie de COVID-19 a infligé un arrêt sans précédent à la société. Parmi les diverses mesures de sécurité qui ont été prises, une attention particulière à été accordée à la fermeture des écoles devenue un outil non pharmaceutique pour freiner la propagation de la maladie par le biais d'une distanciation « sociale ¼ (physique) ainsi garantie. Près de 1,725 milliard d'enfants dans plus de 95 % des pays du monde entier ont été concernés par les fermetures d'établissements scolaires entrées en vigueur en avril 2020, alors que le virus continuait de se propager. Dans le domaine de l'éducation, les politiques se sont appliquées à permettre aux écoliers de continuer à étudier au moyen de l'apprentissage à distance et à répondre aux besoins immédiats des écoles lors de leur réouverture. L'étude présentée dans cet article est essentiellement consacrée à ceux qui restent absents une fois que l'école a repris. S'appuyant sur des données accessibles au public du Programme d'enquêtes démographiques et sanitaires de l'USAID (l'Agence des États-Unis pour le développement international) et l'Enquête par grappes à indicateurs multiples de l'UNICEF avant et après la pandémie d'Ebola de 2013­2016 en Guinée et en Sierra Leone, en Afrique de l'Ouest, l'auteur s'est penché sur les changements concernant les inscriptions dans les établissements scolaires et les schémas d'abandon de la scolarité en portant une attention particulière aux groupes traditionnellement marginalisés. À cette époque-là, les écoles ont fermé leurs portes pendant sept à neuf mois dans les deux pays. La durée et l'intensité de ces fermetures ont fait de la pandémie d'Ebola la seule crise sanitaire du passé récent à se rapprocher en la matière de celle de COVID-19 en 2020. Les conclusions de l'auteur indiquent qu'après la pandémie d'Ebola, la plus forte hausse des abandons scolaires a été enregistrée chez jeunes des foyers les plus démunis. Dépassant les taux d'abandon d'avant Ebola auxquels on s'attendait, 17 000 écoliers supplémentaires faisant partie des plus pauvres au niveau de l'enseignement secondaire ont abandonné l'école, une preuve importante pour œuvrer à réduire au minimum l'augmentation probable des inégalités après la pandémie de COVID-19. Les conclusions de l'auteur montrent qu'il est nécessaire de planifier durablement en se projetant au-delà de la réouverture des écoles afin d'inclure de vastes aides financières pour les groupes qui seront probablement touchés.

New Advances and Applications in Field-Flow Fractionation.

Field-flow fractionation (FFF) is a family of techniques that was created especially for separating and characterizing macromolecules, nanoparticles, and micrometer-sized analytes. It is coming of age as new nanomaterials, polymers, composites, and biohybrids with remarkable properties are introduced and new analytical challenges arise due to synthesis heterogeneities and the motivation to correlate analyte properties with observed performance. Appreciation of the complexity of biological, pharmaceutical, and food systems and the need to monitor multiple components across many size scales have also contributed to FFF's growth. This review highlights recent advances in FFF capabilities, instrumentation, and applications that feature the unique characteristics of different FFF techniques in determining a variety of information, such as averages and distributions in size, composition, shape, architecture, and microstructure and in investigating transformations and function.

Analyzing ophthalmic suspension particle size distributions using laser diffraction: Placebo background subtraction method.

The current study demonstrated that the presence of excipients can interfere with the measurement of particle size distribution (PSD), a critical quality attribute of ophthalmic suspensions, by laser diffraction (LD) and that a placebo background subtraction approach can eliminate the impact of excipients on the PSD measurement. Commercially available loteprednol etabonate and brinzolamide ophthalmic suspensions were used as model suspensions. The impact of excipients in these formulations on the LD measurements was determined using a one-factor-at-a-time experimental design approach, using National Institute of Standards and Technology (NIST) traceable polystyrene particle size standards as references. Among the evaluated excipients, polymers containing polyacrylic acid were found to interfere with the PSD analysis by creating the LD signals correspond to particles ranging from a few micrometers to a hundred micrometers in size. As a result, the measured PSD of active pharmaceutical ingredient (API) particles in the formulation overlapped with or superimposed on the excipient PSD signal, leading to erroneous interpretation of the API particle size. Additionally, dispersion of brinzolamide particles in unsaturated solutions led to rapid dissolution of brinzolamide particles during the measurement, resulting in underestimation of the particle size range. Here, a placebo background subtraction approach was developed to eliminate the interference of the excipients. This newly developed LD method was also evaluated using orthogonal methods, including polarized light microscopy and scanning electron microscopy (SEM). The strategy used in this study to eliminate the interference of excipients may also be useful for other heterogeneous dispersions where excipient interference may be of concern.

Antagonistic Inhibitory Circuits Integrate Visual and Gravitactic Behaviors.

Larvae of the tunicate Ciona intestinalis possess a central nervous system of 177 neurons. This simplicity has facilitated the generation of a complete synaptic connectome. As chordates and the closest relatives of vertebrates, tunicates promise insight into the organization and evolution of vertebrate nervous systems. Ciona larvae have several sensory systems, including the ocellus and otolith, which are sensitive to light and gravity, respectively. Here, we describe circuitry by which these two are integrated into a complex behavior: the rapid reorientation of the body followed by upward swimming in response to dimming. Significantly, the gravity response causes an orienting behavior consisting of curved swims in downward-facing larvae but only when triggered by dimming. In contrast, the majority of larvae facing upward do not respond to dimming with orientation swims-but instead swim directly upward. Under constant light conditions, the gravity circuit appears to be inoperable, and both upward and downward swims were observed. Using connectomic and neurotransmitter data, we propose a circuit model that can account for these behaviors. The otolith consists of a statocyst cell and projecting excitatory sensory neurons (antenna cells). Postsynaptic to the antenna cells are a group of inhibitory primary interneurons, the antenna relay neurons (antRNs), which then project asymmetrically to the right and left motor units, thereby mediating curved orientation swims. Also projecting to the antRNs are inhibitory photoreceptor relay interneurons. These interneurons appear to antagonize the otolith circuit until they themselves are inhibited by photoreceptors in response to dimming, thus providing a triggering circuit.

Tunicate gastrulation.

Tunicates are a diverse group of invertebrate marine chordates that includes the larvaceans, thaliaceans, and ascidians. Because of their unique evolutionary position as the sister group of the vertebrates, tunicates are invaluable as a comparative model and hold the promise of revealing both conserved and derived features of chordate gastrulation. Descriptive studies in a broad range of tunicates have revealed several important unifying traits that make them unique among the chordates, including invariant cell lineages through gastrula stages and an overall morphological simplicity. Gastrulation has only been studied in detail in ascidians such as Ciona and Phallusia, where it involves a simple cup-shaped gastrula driven primarily by endoderm invagination. This appears to differ significantly from vertebrate models, such as Xenopus, in which mesoderm convergent extension and epidermal epiboly are major contributors to involution. These differences may reflect the cellular simplicity of the ascidian embryo.

Thermal Field-Flow Fractionation for Characterization of Architecture in Hyperbranched Aromatic-Aliphatic Polyesters with Controlled Branching.

Thermal field-flow fractionation (ThFFF) was used to characterize the architecture of aromatic-aliphatic polyesters with varying degrees of branching. Thermal diffusion and Soret coefficients (DT and ST, respectively) provide a novel route to polymer architecture analysis. This paper demonstrates an innovative strategy to extract architecture information from the physicochemical separation parameters embedded in ThFFF retention times without explicit separation of linear and branched samples. A Soret contraction factor (g″), defined as the ratio of the ST of a branched polymer to the ST of a molecular weight equivalent linear analogue, is introduced as a metric to indicate degree of branching (DB). This approach circumvents several challenges associated with the analysis of high molar mass polymers with a high degree of branching. The g″ value is shown to be proportional to the degree of branching for linear (DB, 0%), gradually branched (DB, <50%), hyperbranched (DB, 50%), and pseudodendritic (DB, 100%) polyesters allowing the establishment of architecture calibration curves. Furthermore, positive log(g″) values (∼0.2) at low molar mass are attributed to cyclic subpopulations. This work demonstrates the usefulness of the Soret contraction factor for statistically and hyperbranched polymer systems and its sensitivity to cyclic polymers.