Bending Drosophila larva using a microfluidic device enables imaging of its brain and nervous system at single neuronal resolution.

Single neuronal imaging of a fully intact Drosophila larva is a difficult challenge for neurosciences due to the robust digging/burrowing behaviour of the Drosophila larva and the lack of intact immobilization methods at single-neuron resolution. In this paper, for the first time, a simple microfluidic device to completely immobilize the brain and the CNS of a live, fully-functioning Drosophila larva for single neuronal imaging has been demonstrated. The design of the microfluidic device contains a unique clamping feature which pins and bends the body of the larva at 1/3rd of its length from the head. This simple twist combined with the pinning mechanism not only could stop the locomotion of the larva but also could immobilize the major movement of internal organs including the CNS. The results showed that the bent trap could keep the single neuron completely inside the field of view (FOV) (50 µm × 50 µm) over 10 min of confocal imaging. The range of motion in the x- and y-axis was approximately 8 µm and 2.5 µm, respectively. This corresponds to a range of 16% and 6% along the axis of the channel and across it compared to the size of the FOV (50 µm × 50 µm). The calcium activity of the single neurons in a 3rd instar GCaMP5 larva (Cha-Gal4/CyO; UAS-GCaMP5G/TM3) was measured while its mouth region was exposed to 20 mM sodium azide (NaN3) for 5 s. The results showed that the activity of the neurons has been statistically (p < 0.0005) increased (∼60%).

Ten-year-old boy with atypical COVID-19 symptom presentation: A case report.

Since reactive arthritis (ReA) and urticaria could be seen in this age group along with atypical COVID-19 symptom presentation, pediatrics should be familiar with urticarial rashes and ReA in COVID-19 to enable early diagnoses of infected individuals.

Microfluidic Device for Microinjection of Caenorhabditis elegans.

Microinjection is an established and reliable method to deliver transgenic constructs and other reagents to specific locations in C. elegans worms. Specifically, microinjection of a desired DNA construct into the distal gonad is the most widely used method to generate germ-line transformation of C. elegans. Although, current C. elegans microinjection method is effective to produce transgenic worms, it requires expensive multi degree of freedom (DOF) micromanipulator, careful injection alignment procedure and skilled operator, all of which make it slow and not suitable for scaling to high throughput. A few microfabricated microinjectors have been developed recently to address these issues. However, none of them are capable of immobilizing a freely mobile animal such as C. elegans worm using a passive immobilization mechanism. Here, a microfluidic microinjector was developed to passively immobilize a freely mobile animal such as C. elegans and simultaneously perform microinjection by using a simple and fast mechanism for needle actuation. The entire process of the microinjection takes ~30 s which includes 10 s for worm loading and aligning, 5 s needle penetration, 5 s reagent injection and 5 s worm unloading. The device is suitable for high-throughput and can be potentially used for creating transgenic C. elegans.

Rapid Desensitization for Hypersensitivity Reactions to Chemotherapeutic Drugs; A Case Series.

Usage of cancer chemotherapeutics drugs can be associated with adverse drug reactions. When IgE-mediated drug reactions are formed following administration of a chemotherapeutics drug that is a drug of choice, drug desensitization protocols can be helpful. HSR can be allergic or nonallergic, but the clinical manifestations are similar. RDD is effective when used appropriately, however it is often over utilized instead of performing a drug challenge. RDD is both an acceptable approach and a high-risk treatment modality in patients, in whom the offending agent is the first choice in chemotherapy. The safety of this modality has been acceptable in large studies. The side effects are often less frequent and less severe by repeating the protocol. We present 4 cases of successful desensitization in cancer patients, who have developed IgE- mediated reactions to their major chemotherapy drug.

Chloroform and desflurane immobilization with recovery of viable Drosophila larvae for confocal imaging.

Imaging of living, intact Drosophila larvae is challenged if normal bodily function must be observed or when healthy larvae must be recovered for subsequent studies. Here, we describe a simple and short protocol that employs transient airborne chloroform or desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) to efficiently immobilize larvae without the use of manipulation devices, vaporizers or imaging chambers. This non-lethal method allows the use of anesthetics while allowing tracking of individual Drosophila into adulthood for follow-up experiments. At dosages sufficient to immobilize larvae, Desflurane, but not chloroform reduced the central nervous system response to auditory stimulus. Desflurane doses were sufficient to arrest the heart, however significant rapid recovery was observed. With our method, chloroform provided more rapid anesthesia but slower recovery than Desflurane. Without specialized hardware, this technique allows for repeated imaging of living Drosophila larvae.

A microfluidic microinjector for toxicological and developmental studies in Drosophila embryos.

Microinjection is an established and reliable method to deliver biological reagents such as transgenic constructs and drugs, to specific locations inside organisms such as the Drosophila embryo and C. elegans worm. In this paper, a simple compliant mechanism based PDMS-microinjection system has been demonstrated. Unlike conventional microinjectors, this unique system could allow one to precisely insert a long taper microneedle laterally and at various positions inside the length of the Drosophila embryo (up to 250 µm) with the resolution of 5 µm. Volumes as low as 30 pL with accuracy of ±10 pL were delivered inside the embryo via pressure pulses. The device has been used to study the effect of toxins on cardiogenesis in Drosophila embryos. Using this device, we demonstrate that the cardioblast (CB) migration velocity is modified in a dose sensitive manner to varying doses of injected sodium azide (NaN3) and, for the first time, quantify the effect of the toxin on heart assembly. Injection with 40 pL of NaN3 was shown to decrease CB migration velocity and filopodia number at concentrations above 10 mM, while embryos injected with the tracer Rhodamine B (0 mM NaN3) displayed no significant difference when compared to uninjected embryos. This device can be potentially used for other embryonic assays, which require accurate delivery of the reagents to a specific location within the embryo.

Characterization of microfluidic clamps for immobilizing and imaging of Drosophila melanogaster larva's central nervous system.

Drosophila melanogaster is a well-established model organism to understand biological processes and study human diseases at the molecular-genetic level. The central nervous system (CNS) of Drosophila larvae is widely used as a model to study neuron development and network formation. This has been achieved by using various genetic manipulation tools such as microinjection to knock down certain genes or over-express proteins for visualizing the cellular activities. However, visualization of an intact-live neuronal response in larva's Central Nervous System (CNS) is challenging due to robust digging/burrowing behaviour that impedes neuroimaging. To address this problem, dissection is used to isolate and immobilize the CNS from the rest of the body. In order to obtain a true physiological response from the Drosophila CNS, it is important to avoid dissection, while the larva should be kept immobilized. In this paper, a series of microfluidic clamps were investigated for intact immobilization of the larva. As a result, an optimized structure for rapid mechanical immobilization of Drosophila larvae for CNS imaging was determined. The clamping and immobilization processes were characterized by imaging and movement measurement of the CNS through the expression of genetically encoded Calcium sensor GCaMP5 in all sensory and cholinergic interneurons. The optimal structure that included two 3D constrictions inside a narrowed channel considerably reduced the internal CNS capsule movements. It restricts the CNS movement to 10% of the motion from a glued larva and allows motion of only 10 ± 30 µm over 350 s immobilization which was sufficient for CNS imaging. These larva-on-a-chip platforms can be useful for studying CNS responses to sensory cues such as sound, light, chemosensory, tactile, and electric/magnetic fields.

Microfluidic Devices for Automation of Assays on Drosophila Melanogaster for Applications in Drug Discovery and Biological Studies.

Drug discovery is a long and expensive process, which usually takes 12-15 years and could cost up to ~$1 billion. Conventional drug discovery process starts with high throughput screening and selection of drug candidates that bind to specific target associated with a disease condition. However, this process does not consider whether the chosen candidate is optimal not only for binding but also for ease of administration, distribution in the body, effect of metabolism and associated toxicity if any. A holistic approach, using model organisms early in the drug discovery process to select drug candidates that are optimal not only in binding but also suitable for administration, distribution and are not toxic is now considered as a viable way for lowering the cost and time associated with the drug discovery process. However, the conventional drug discovery assays using Drosophila are manual and required skill operator, which makes them expensive and not suitable for high-throughput screening. Recently, microfluidics has been used to automate many of the operations (e.g. sorting, positioning, drug delivery) associated with the Drosophila drug discovery assays and thereby increase their throughput. This review highlights recent microfluidic devices that have been developed for Drosophila assays with primary application towards drug discovery for human diseases. The microfluidic devices that have been reviewed in this paper are categorized based on the stage of the Drosophila that have been used. In each category, the microfluidic technologies behind each device are described and their potential biological applications are discussed.

Microfluidic devices for imaging neurological response of Drosophila melanogaster larva to auditory stimulus.

Two microfluidic devices (pneumatic chip and FlexiChip) have been developed for immobilization and live-intact fluorescence functional imaging of Drosophila larva's Central Nervous System (CNS) in response to controlled acoustic stimulation. The pneumatic chip is suited for automated loading/unloading and potentially allows high throughput operation for studies with a large number of larvae while the FlexiChip provides a simple and quick manual option for animal loading and is suited for smaller studies. Both chips were capable of significantly reducing the endogenous CNS movement while still allowing the study of sound-stimulated CNS activities of Drosophila 3rd instar larvae using genetically encoded calcium indicator GCaMP5. Temporal effects of sound frequency (50-5000 Hz) and intensity (95-115 dB) on CNS activities were investigated and a peak neuronal response of 200 Hz was identified. Our lab-on-chip devices can not only aid further studies of Drosophila larva's auditory responses but can be also adopted for functional imaging of CNS activities in response to other sensory cues. Auditory stimuli and the corresponding response of the CNS can potentially be used as a tool to study the effect of chemicals on the neurophysiology of this model organism.

A method for determining the robustness of bio-molecular oscillator models.

BACKGROUND: Quantifying the robustness of biochemical models is important both for determining the validity of a natural system model and for designing reliable and robust synthetic biochemical networks. Several tools have been proposed in the literature. Unfortunately, multiparameter robustness analysis suffers from computational limitations. RESULTS: A novel method for quantifying the robustness of oscillatory behavior to parameter perturbations is presented in this paper. This method relies on the combination of Hopf bifurcation and Routh-Hurwitz stability criterion, which is widely applied in control system design. The proposed method is employed to calculate the robustness of two oscillating biochemical network models previously analyzed in the literature. The robustness bounds here obtained are tighter than what was previously obtained in the literature for both models. CONCLUSION: The method here proposed for quantifying the robustness of biochemical oscillator models is computationally less demanding than similar multiparamter variation techniques available in the literature. It also provides tighter bounds on two models previously analyzed in the literature.