Running rat experiment

The second study concerns the enzyme that catalyzes the synthesis of "2-6," fructase-6-phosphate 2-kinase. The liver is composed of several types of cells. The major cell, the hepatocyte, constitutes about S0% of the cell population and contains about 99% of the protein, Hepatocytes carry out most of the metabolic functions of the liver, Castenodd. (1979) added glucagon to hepatocytes in culture and found that fructo e-6-phosphate 2-kinase decreased within the first minute of addition of the hormone. Addition of the hormone was intended to simulate, in part, hormonal changes that occur in the body during exercise. The observed decrease in enzyme activity is consistent with the dramatic drop in "2-6" that occurred in the running rat experiment. The work described thus far shows that "2-6" levels in the liver Increase or decrease under certain conditions. These facts, though interesting, do not directly indicate a function for "2-6,"... 

Ruminants, dietary Rber digestion, 143 144 Running rat experiment, 191-193 RXR, 5S5,586, 583... 

The third study involves the purified enzymes fmctose-l,6-bisphosphatase and phosphofmctokinase. This study brings discussion of "2-6" to a conclusion by demonstrating its effects on these enzymes. Fmctose-l,6-bisphosphatase, an enzyme of the gluconeogenic pathway, catalyzes the conversion of F-l,6-P2 to F-6-P. Ekdahl and Ekman (1984) showed that the activity of this enzyme is maximal in the absence of or presence of low concentrations of "2-6." These researchers showed that its activity is inhibited by "2-6" at concentrations of 10 micromolar and higher. The running rat experiment showed that the resting rat liver contained "2-6" at a concentration of about 12 [iM. Their data also indicated that this level of "2-6" is sufficient to inhibit the activity of the enzyme, but that the levels found in the running rat would be expected to permit near-maximal activity. 

Net protein ratio (NPR) is used to correct PER values for the amount of protein required for cell maintenance. NPR is often run in conjunction with a PER. The experiment requires that one additional set of animals be added as a treatment group. This group of animals is fed a basal diet with no protein (zero protein or basal diet). Results from RNPR are similar to net protein utilization (NPU) and biological value (BV methods, see Alternate Protocol 4). A 2-week RNPR is thought to be the most appropriate rat test for routine assessment of protein quality. 

Surprisingly, individuals with hemoglobin levels as low as 20 to 30 mg Hb/ml can continue to be physically active. This is due to adaptive mechanisms involving an increase in the heart rate and an increase in efficiency of extraction of oxygen from the blood. Experiments with rats have revealed that the decreased work capacity of the iron-deficient animals, as determined by their ability to run, was due to a deficiency in the enzymes of the respiratory chain of muscle, as well as to anemia. In short, transfusion with normal blood failed to restore fully the running capacity of the deficient animals. 

FIG. 1. The four stages of a rat reasoning task are shown. First (A), the rat is given an exploratory experience in which it has the run of the maze in the absence of any food reinforcement. Second (B), the rat is fed in one of the arms and is prevented from re-entering the rest of the maze. In the test component the rat is removed to a separate start arm and the target arm rebaited (C). The rat can then combine his two prior experiences to chart a direct accurate course to the reward (solid line in D) or may enter another arm, which is scored as an error (dashed line in D). 

CatteraU We did experiments in cultured primary neurons from rat brain. The Na+ channels turn over with a half-life of about 48 h in pulse-chase experiments. But I don t imagine that a myelinated neuron that runs aU the way down to your foot turns over its Na+ channels in 48 h. 

In practice, the ability of large corporations to relocate tied the hands of state regulators. Louis Brandeis, the jurist who inspired many New Dealers, famously described the states as the laboratories of democracy. But—as a young Massachusetts legislator named Barney Frank would remark years later—Justice Brandeis s laboratories have a problem you can t run a good experiment if the rats are free to choose their own cages. 

Figure 3. Effect of Ca yCM-PKIl on CPT I activity. Rat liver mitochondria (l.S-2.0mg protein nil" ) were preincubated for 30 min in the absence (-) or in the presence (+) Of cytoskeletal Fraction 11 (0.05-0.06 mg protein ml ). Purified Ca VCM-PKII was subsequently added (+) or not (-) to the incubations, which were run for 10 additional min. Aliquots were subsequently taken to determine CPT 1 activity. Results correspond to 4 different experiments Significantly different (P < 0.01) from incubations with no additions.

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