Optogenetic stimulation of escape behavior in Drosophila melanogaster.

A growing number of genetically encoded tools are becoming available that allow non-invasive manipulation of the neural activity of specific neurons in Drosophila melanogaster. Chief among these are optogenetic tools, which enable the activation or silencing of specific neurons in the intact and freely moving animal using bright light. Channelrhodopsin (ChR2) is a light-activated cation channel that, when activated by blue light, causes depolarization of neurons that express it. ChR2 has been effective for identifying neurons critical for specific behaviors, such as CO(2) avoidance, proboscis extension and giant-fiber mediated startle response. However, as the intense light sources used to stimulate ChR2 also stimulate photoreceptors, these optogenetic techniques have not previously been used in the visual system. Here, we combine an optogenetic approach with a mutation that impairs phototransduction to demonstrate that activation of a cluster of loom-sensitive neurons in the fly's optic lobe, Foma-1 neurons, can drive an escape behavior used to avoid collision. We used a null allele of a critical component of the phototransduction cascade, phospholipase C-ß, encoded by the norpA gene, to render the flies blind and also use the Gal4-UAS transcriptional activator system to drive expression of ChR2 in the Foma-1 neurons. Individual flies are placed on a small platform surrounded by blue LEDs. When the LEDs are illuminated, the flies quickly take-off into flight, in a manner similar to visually driven loom-escape behavior. We believe that this technique can be easily adapted to examine other behaviors in freely moving flies.

Ontogeny, growth and development of the small intestine: Understanding pediatric gastroenterology.

Throughout our lifetime, the intestine changes. Some alterations in its form and function may be genetically determined, and some are the result of adaptation to diet, temperature, or stress. The critical period programming of the intestine can be modified, such as from subtle differences in the types and ratios of n3:m6 fatty acids in the diet of the pregnant mother, or in the diet of the weanlings. This early forced adaptation may persist in later life, such as the unwanted increased intestinal absorption of sugars, fatty acids and cholesterol. Thus, the ontogeny, early growth and development of the intestine is important for the adult gastroenterologist to appreciate, because of the potential for these early life events to affect the responsiveness of the intestine to physiological or pathological challenges in later life.

Influence of dietary gangliosides on neonatal brain development.

Gangliosides are sialic acid-containing glycosphingolipids. Gangliosides are found in human milk; understanding of the potential role of gangliosides in infant development is emerging, with suggested roles in the brain and gut. Ganglioside accretion in the developing brain is highest in utero and in early neonatal life, during the periods of dendritic branching and new synapse formation. Further, brain contains the highest relative ganglioside content in the body, particularly in neuronal cell membranes concentrated in the area of the synaptic membrane. Gangliosides are known to play a role in neuronal growth, migration and maturation, neuritogenesis, synaptogenesis, and myelination. In addition to their roles in development and structure of the brain, gangliosides also play a functional role in nerve cell communication. It is less well known whether dietary gangliosides can influence the development of cognitive function. This review summarizes current knowledge on the role gangliosides play in brain development.

Dexamethasone plus glucagon-like peptide 2 given to lactating rat dams has a late effect on intestinal lipid uptake in the weanling offspring.

BACKGROUND: Glucagon-like peptide 2 (GLP-2) has a trophic effect on the intestine and enhances intestinal absorption in adult animals, but its effect in young rats is unknown. Glucocorticosteroids accelerate the ontogeny of the intestine, and in adult animals they increase the uptake of sugars and lipids. We hypothesized that GLP-2 and dexamethasone (DEX), when administrated to lactating rat dams, will enhance lipid uptake in the suckling and weanling offspring. METHODS: Eight nursing rats were treated during lactation, 19 to 21 days, with GLP-2 (0.1 microg/g/d subcutaneously [s.c.]), DEX (0.128 microg/g/d s.c.), GLP-2 + DEX (GLP-2 0.1 microg/g/d s.c. plus DEX 0.128 microg/g/d s.c.), or placebo. Half of the offspring ("sucklings") were killed at 19 to 21 days of age, and half were killed 4 weeks later ("weanlings"). The rate of intestinal uptake of fatty acids (12:0, lauric; 16:0, palmitic; 18:0, stearic; 18:1, oleic; 18:2, linoleic; and 18:3, linolenic) and cholesterol were assessed using an in vitro ring technique. RESULTS: GLP-2 and DEX resulted in loss of body weight in sucklings, which was prevented by giving the combination GLP-2 + DEX. The jejunal atrophy in sucklings given DEX was prevented by giving GLP-2 + DEX, but GLP-2 + DEX did not prevent the decline in jejunal and ileal villous height and crypt depth observed in weanlings given DEX. GLP-2 had little effect on lipid uptake in sucklings, whereas DEX or GLP-2 + DEX increased the uptake of lipids. In contrast, in weanlings there was malabsorption of several lipids with GLP-2 or GLP-2 + DEX, but not with DEX. Lipid uptake was lower in weanlings than in sucklings, and this age-associated decline was not altered by GLP-2 or DEX. CONCLUSIONS: The loss of body weight and the jejunal atrophy induced by DEX in sucklings is prevented by adding GLP-2. Giving DEX or GLP-2 + DEX to lactating mothers enhances lipid uptake in their suckling offspring. In marked contrast, a month after lactating dams were given GLP-2 or GLP-2 + DEX, there was reduced lipid absorption in the postweaning animals. Thus, giving GLP-2 + DEX during lactation may be useful to enhance lipid uptake in the suckling offspring, without adverse effects on body weight or intestinal characteristics. However, the late effects of this treatment on lipid absorption were of concern, and could be potentially deleterious to the nutritional well-being of the animal.