Are Hyperglycemia-Induced Changes in the Retina Associated with Diabetes-Correlated Changes in the Brain? A Review from Zebrafish and Rodent Type 2 Diabetes Models.

Diabetes is prevalent worldwide, with >90% of the cases identified as Type 2 diabetes. High blood sugar (hyperglycemia) is the hallmark symptom of diabetes, with prolonged and uncontrolled levels contributing to subsequent complications. Animal models have been used to study these complications, which include retinopathy, nephropathy, and peripheral neuropathy.

Ethanol and caffeine age-dependently alter brain and retinal neurochemical levels without affecting morphology of juvenile and adult zebrafish (Danio rerio).

Adolescent alcohol exposure in humans is predictive of adult development of alcoholism. In rodents, caffeine pre-exposure enhances adult responsiveness to ethanol via a pathway targeted by both compounds. Embryonic exposure to either compound adversely affects development, and both compounds can alter zebrafish behaviors.

Prolonged Hyperglycemia Causes Visual and Cognitive Deficits in .

The present study induced prolonged hyperglycemia (a hallmark symptom of Type 2 diabetes [T2DM]) in (zebrafish) for eight or twelve weeks. The goal of this research was to study cognitive decline as well as vision loss in hyperglycemic zebrafish. Fish were submerged in glucose for eight or twelve weeks, after which they were assessed with both a cognitive assay (three-chamber choice) and a visual assay (optomotor response (OMR)).

Time dependent effects of prolonged hyperglycemia in zebrafish brain and retina.

Prolonged hyperglycemia causes long-term vision complications and an increased risk of cognitive deficits. High blood sugar also confers an osmotic load/stress to cells. We assessed behavioral and neurochemical changes in zebrafish brain and retina following prolonged hyperglycemia for 4-weeks or 8-weeks.

Developmental effects of siloxane exposure in zebrafish: A comparison study using laboratory-mixed and environmental water samples.

Siloxanes are used in personal care, biomedical, and industrial products. Their worldwide use and persistence in the environment cause consistent exposure for both humans and aquatic animals. Two siloxane congeners, decamethylcyclopentasiloxane (D5; CAS 541-02-6) and octamethylcyclotetrasiloxane (D4; CAS 556-67-2), are among the most prevalent, with measurable levels in air, sediment, water, and biological samples.

Differential effects of fluoxetine on the phototactic behavior of 3 amphipod species (Crustacea; Amphipoda).

We document phototactic responses in different amphipod populations of Gammarus minus, Stygobromus tenuis, and Crangonyx shoemakeri, each collected at 2-3 sites within the Washington DC area. We then assessed how baseline phototaxis was altered following either short-term (3-week) or long-term (6-week) exposure to 0.05 µg/L or 0.

The Role of Estrogen and Thyroid Hormones in Zebrafish Visual System Function.

Visual system development is a highly complex process involving coordination of environmental cues, cell pathways, and integration of functional circuits. Consequently, a change to any step, due to a mutation or chemical exposure, can lead to deleterious consequences. One class of chemicals known to have both overt and subtle effects on the visual system is endocrine disrupting compounds (EDCs).

Transient developmental exposure to tributyltin reduces optomotor responses in larval zebrafish (Danio rerio).

This study determined the effects of transient developmental exposure to tributyltin (TBT), a well-known anti-estrogenic environmental endocrine disrupting compound, on visual system development of larval zebrafish (Danio rerio). Zebrafish were exposed to either 0.2 μg/L or 20 μg/L TBT for 24 h when they were aged 24 h postfertilization (hpf), 72 hpf, or 7 days (d)pf.

Neurochemical and Behavioral Consequences of Ethanol and/or Caffeine Exposure: Effects in Zebrafish and Rodents.

Zebrafish are increasingly being utilized to model the behavioral and neurochemical effects of pharmaceuticals and, more recently, pharmaceutical interactions. Zebrafish models of stress establish that both caffeine and ethanol influence anxiety, though few studies have implemented coadministration to assess the interaction of anxiety and reward-seeking. Caffeine exposure in zebrafish is teratogenic, causing developmental abnormalities in the cardiovascular, neuromuscular, and nervous systems of embryos and larvae.

Ganglion cells in larval zebrafish retina integrate inputs from multiple cone types.

We recently showed the presence of seven physiological cone opsins-R1 (575 nm), R2 (556 nm), G1 (460 nm), G3 (480 nm), B1 (415 nm), B2 (440 nm), and UV (358 nm)-in electroretinogram (ERG) recordings of larval zebrafish () retina. Larval ganglion cells (GCs) are generally thought to integrate only four cone opsin signals (red, green, blue, and UV). We address the question as to whether they may integrate seven cone spectral signals.

Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish.

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This alternate immersion protocol is a noninvasive, step-wise method of inducing hyperglycemia for up to eight weeks. Adult zebrafish are alternately exposed to sugar (glucose) and water for 24 hours each.

The Three-Chamber Choice Behavioral Task using Zebrafish as a Model System.

Neurodegenerative diseases are age-dependent, debilitating, and incurable. Recent reports have also correlated hyperglycemia with changes in memory and/or cognitive impairment. We have modified and developed a three-chamber choice cognitive task similar to that used with rodents for use with hyperglycemic zebrafish.

Timed Electrodeposition of PEDOT:Nafion onto Carbon Fiber-Microelectrodes Enhances Dopamine Detection in Zebrafish Retina.

Carbon fiber-microelectrodes (CFMEs) are one of the standards for the detection of neurotransmitters such as dopamine (DA). In this study, we demonstrate that CFMEs electrodeposited with poly (3,4-ethylenedioxythiophene) (PEDOT) in the presence of Nafion exhibit enhanced sensitivity for DA detection. Scanning electron microscopy (SEM) revealed the smooth outer surface morphologies of polymer coatings, which filled in the ridges and grooves of the bare unmodified carbon electrode and energy-dispersive X-ray spectroscopy (EDX) confirmed PEDOT:Nafion incorporation.

Zebrafish Optomotor Response and Morphology Are Altered by Transient, Developmental Exposure to Bisphenol-A.

Estrogen-specific endocrine disrupting compounds (EDCs) are potent modulators of neural and visual development and common environmental contaminants. Using zebrafish, we examined the long-term impact of abnormal estrogenic signaling by testing the effects of acute, early exposure to bisphenol-A (BPA), a weak estrogen agonist, on later visually guided behaviors. Zebrafish aged 24 h postfertilization (hpf), 72 hpf, and 7 days postfertilization (dpf) were exposed to 0.

Using a variant of the optomotor response as a visual defect detection assay in zebrafish.

We describe a visual stimulus that can be used with both larval and adult zebrafish (Danio rerio). This protocol is a modification of a standard visual behavior analysis, the optomotor response (OMR). The OMR is often used to determine the spatial response or to detect directional visuomotor deficiencies.

Observational learning and irreversible starvation in first-feeding zebrafish larvae: is it okay to copy from your friends?

Starvation is one cause of high mortality during the early life stages of many fish species. If larvae do not learn to feed, or if no food is available during early stages, irreversible starvation occurs and larvae reach the Point of No Return (PNR), the developmental period/age when they will not feed even if food is available. Fish larvae may learn to how to feed by observing conspecifics or through personal/individual experience with prey items that are encountered.

Using zebrafish to assess the effect of chronic, early developmental exposure to environmentally relevant concentrations of 5-fluorouracil and leucovorin.

Environmental contaminants can deleteriously affect aquatic animals. One such contaminant is 5-fluorouracil (5-FU), a long-prescribed chemotherapeutic drug. Leucovorin (LV) is co-administered with 5-FU, potentiating its effects.

Anatomical and Behavioral Assessment of Larval Zebrafish (Danio rerio) Reared in Anacostia River Water Samples.

Rapid urbanization, industrial activity, and runoff have all played a role in transforming the Anacostia River from a biologically rich ecosystem to an ecologically threatened environment facing extensive pollution. In recent decades, numerous groups have worked to document and begin to address pollution in the waterway, but few have examined the biological impact of these contaminants. To assess water quality, the current study examined the effects of Anacostia water on early fish development and behavior using zebrafish (Danio rerio).

Acute exposure to 4-OH-A, not PCB, alters brain aromatase activity but does not adversely affect growth in zebrafish.

Acute developmental exposure to pharmaceuticals or environmental contaminants can have deleterious, long lasting effects. Many of these compounds are endocrine disruptors (EDCs) that target estrogen signaling, with effects on reproductive and non-reproductive tissues. We recently reported that zebrafish larvae transiently exposed to the pharmaceutical EDC 4-OH-A display visual deficits as adults.

Color Processing in Zebrafish Retina.

Zebrafish () is a model organism for vertebrate developmental processes and, through a variety of mutant and transgenic lines, various diseases and their complications. Some of these diseases relate to proper function of the visual system. In the US, the National Eye Institute indicates >140 million people over the age of 40 have some form of visual impairment.

One month of hyperglycemia alters spectral responses of the zebrafish photopic electroretinogram.

Prolonged hyperglycemia can alter retinal function, ultimately resulting in blindness. Adult zebrafish adults exposed to alternating conditions of 2% glucose/0% glucose display a 3× increase in blood sugar levels. After 4 weeks of treatment, electroretinograms (ERGs) were recorded from isolated, perfused, eyecups.

Developmental exposure to heavy metals alters visually-guided behaviors in zebrafish.

This laboratory-based study determined the consequences of heavy metal exposure using zebrafish . Embryos were transiently exposed to environmentally-relevant concentrations of cadmium or nickel until 72 h postfertilization (hpf), then they were returned to system water and allowed to grow until 7, 9, and 11 days postfertilization (dpf), when they were examined morphologically and behaviorally. Morphological measures of notochord length, eye diameter, and inter-eye distance were not different across treatments; however, significant differences in optomotor responses were observed in treated larvae at all ages tested.

Acute developmental exposure to 4-hydroxyandrostenedione has a long-term effect on visually-guided behaviors.

Estrogenic and anti-estrogenic endocrine disrupting compounds (EDCs) are recognized as critical modulators of neural development, including sensory system development. Using the zebrafish model, we tested the effect of transient developmental exposure to a known anti-estrogenic EDC on adult visually-guided behavior. In particular, we exposed zebrafish aged 24-hour post-fertilization (hpf), 72 hpf, or 7-days post-fertilization (dpf) to the aromatase inhibitor 4-hydroxyandrostenedione (4-OH-A) for 24h.

Differential behavioral effects of ethanol pre-exposure in male and female zebrafish (Danio rerio).

Alcohol exposure in adolescence is a contributing factor toward reward-seeking behavior in adulthood. This reward-seeking behavior is assessed in animal models using the conditioned place preference (CPP) paradigm. In this study, ethanol-induced change in time spent by zebrafish on the initially non-preferred tank side was studied by conditioning adult zebrafish to ethanol dissolved in water (0.