Chicken or the Egg?

The age-old question persists: which came first, the chicken or the egg? Approximately 24 hr after fertilization occurs in a chicken, the egg is laid. The newly formed single cell begins to divide; tissue begins to form on the yolk by the end of day 1. By the end of day 2, the heart begins to beat. On day 14, claws begin to form and the embryo is moving into position to hatch. On the 21st day, the chick finishes its escape from the shell.

Image: This image depicts a 13-day-old chicken embryo. The networks of chorioallantoic membrane blood vessels used for gas exchange and the yolk sack blood vessels used for nutrient uptake can easily be seen. By day 8, the beak and feathers are also visible. The allantois (sac involved in gas exchange and excretion) shrinks to become the chorioallantoic membrane (vascular membrane). And so begins the appearance of claws and leg scales. Inset: Photo of two fully developed chicks with their mother.

This image shows the development of a chicken embryo from day 0 to day 21. Approximately 24 hr after fertilization occurs, the egg is laid. The newly formed single cell begins to divide; tissue begins to form on the yolk by the end of day 1. By the end of day 2, the heart begins beating. On day 14, claws begin to form and the embryo is moving into position to hatch. On the 21st day, the chick finishes its escape from the shell.

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What is preclinical testing?

In the process of preclinical testing of a compound or biological agent into a drug, the compound involved must go through the testing phase. First, we need to identify potential targets that can treat the disease. Then, a variety of compounds or preparations are screened out. Any compound that has shown potential as a drug for the treatment of this disease needs to be tested for toxicity before clinical testing to reduce the possibility of injury. preclinical testing What is the basis of preclinical testing? According to US Food and Drug Administration (FDA) regulations, a series of tests are required before a new drug is approved for use. In the first stage, basic research determines a hypothetical target for the treatment of a certain disease, and then screens small molecules or biological compounds to discover any substance with the potential to treat the disease. Then, a preclinical research phase followed, before which, as described above, the potential toxicity of the compou

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Inventory of the three major in vitro pharmacokinetic research methods

The metabolic properties of a compound are an essential factor in whether or not it can be used as a drug in the clinical setting, so pharmacokinetic studies of newly synthesized compounds are required in drug development. In vitro incubation with liver microsomes, recombinant CYP450 enzyme lines, and in vitro incubation with hepatocytes are some of the more common in vitro drug metabolism methods. 1. In vitro incubation method with liver microsomes The metabolic stability and metabolic phenotypes of candidate compounds in different species of liver microsomes are good predictors of the metabolic properties of compounds in vivo. They are practical tools for evaluating candidate compounds in the pre-development phase of drug development. Liver microsomes include rat liver microsomes, human liver microsomes, canine liver microsomes, monkey liver microsomes, and mouse liver microsomes. In in vitro incubation of the liver, microsomes are the "gold standard" for in vitro d

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Novel Parkinson’s Therapies Possible with New Mouse Model

Parkinson's disease (PD) is a neurodegenerative disorder that is marked by the accumulation of the protein, α-synuclein (αS), into clumps known as Lewy bodies, which diminish neural health. Now, researchers from Brigham and Women's Hospital (BWH) report the development of a mouse model to induce PD-like αS aggregation, leading to resting tremor and abnormal movement control. The mouse responds to L-DOPA, similarly to patients with PD. The team's study (“Abrogating Native α-Synuclein Tetramers in Mice Causes a L-DOPA-Responsive Motor Syndrome Closely Resembling Parkinson’s Disease”) on the use of this transgenic mouse model appears in Neuron . “α-Synuclein (αS) regulates vesicle exocytosis but forms insoluble deposits in PD. Developing disease-modifying therapies requires animal models that reproduce cardinal features of PD. We recently described a previously unrecognized physiological form of αS, α-helical tetramers, and showed that familial PD-causing missense mutati

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