Triglyceride metabolism in the lung

Experiments were carried out to examine whether the lung acts as a depot for circulating lipid, especially that absorbed from the intestine. When 0.5 ml of triolein was administered orally to rats, the triglyceride content of the lung increased 2-3 hr later, but its increase in the lungs 2-3 hr later was only of about 1/10 of that in the liver. In the fed state the triglyceride content of the lung was only about 1/8 of that of the liver. When [3H]palmitic acid was administered orally to mice its uptake by the lung 1 and 2 hr later was 1/25-40 of that by the liver. In the lung, it was incorporated into phospholipid more than into triglyceride, but in the liver it was predominatly incorporated into triglyceride. Most of the lipase activity in both the microsomal and soluble fractions of rat lung appeared to be due to lipoprotein lipase. Fasting did not decrease the lipoprotein lipase activity in either fraction. It was concluded that the lung is not important in removal of triglyceride from the blood, even during fat absorption from the intestine, and that the lung takes up circulating lipid for its own metabolism rather than for storage.

[Determination of conjugated and free estrogen in male plasma (authors transl)]

Radioimmunoassay for conjugated and free estrone (E1), estradiol-17beta(E2) and estriol (E3) in male plasma was investigated, while no precise determination of conjugated estrogen in male plasma had been established. Each tritiated estrogen glucuronides for determining the recovery was added to 3 ml of plasma samples. These plasma samples were extracted with acetone, hydrolyzed with 15 vol% HCl at 100 degrees C for 60 minutes, and resulting free estrogens were extracted with ether. These extracts were washed with 1% NaOH and 1% NaHCO3, and applied to microcolumn of Sephadex LH-20. Then they were determined by the radioimmunoassay as the same method of evaluation for free estrogen. Each mean values of plasma free and conjugated estrogen in 10 normal adult males was as follows: 36.0 +/- 9.81 pg/ml(free E1), 29.5 +/- 11.0 pg/ml(free E2), 1.80 +/- 1.27 pg/ml (free E3), 31.0 +/- 12.6 pg/ml (conjugated E1), 36.0 +/- 14.2 pg/ml (conjugated E2), 30.6 +/- 8.35 pg/ml (conjugated E3). Conjugated estrogen to free estrogen ratio was 1.45.

Inhibition of hypoglossal motoneurons by stimulation of the jaw-opening muscle afferents

The synaptic linkage of jaw-opening muscle afferents with the retractive and the protrusive motoneurons (R-Mns and P-Mns) in the hypoglossal motor nucleus was explored in anesthetized cats. It was found that stimulation of low-threshold afferents arising in the jaw-opening muscles (m. mylohyoideus and m. digastricus) evoked IPSPs in both R-Mns and P-Mns with about 10 to 15 msec latencies. By injecting Cl ions into R-Mns or P-Mns, the hyperpolarizing postsynaptic potentials evoked by jaw-opening muscle afferent impulses were reversed to depolarizing potentials. The lingual-IPSPs of hypoglossal motoneurons were concluded to be dependent on increase of Cl conductance. Stimulation of low threshold lingual afferents evoked a reflex discharge in the retractive nerve fibers with a 6.0 msec latency and in the protrusive nerve fibers with a 5.5 msec latency. Inhibition of the linguohypoglossal reflex by stimulation of the jaw-opening muscle afferents was completely removed by an intravenous injection of strychnine (0.1 mg/kg) or picrotoxin (6 mg/kg). It is concluded that the low threshold afferents arising in the jaw-opening muscles are connected to both R-Mns and P-Mns and P-Mns through inhibitory synapses via a polysynaptic pathway.

Interrelation of afferent impluses from different bellies of the temporal muscle of the cat

A physiologic interaction of proprioceptive afferent impulses from the different muscle bellies of the temporal muscle were studied in the cat. The impulses from one belly of the temporal muscle modified the activities of the motoneurons innervating the different bellies of the muscle.

Ionic conductance changes in lobster axon membrane when lanthanum is substituted for calcium

The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.

Blockage of sodium conductance increase in lobster giant axon by tarichatoxin (tetrodotoxin)

Tarichatoxin, isolated from California newt eggs, has been found to selectively block the increase of sodium conductance associated with excitation in lobster giant axons at nanomolar concentrations. This resulted from a reduction in the amplitude of the conductance increase rather than a change in its temporal characteristics. The normal potassium conductance increase with depolarization is not altered. A high concentration of calcium applied concomitantly with the toxin significantly improves the reversibility of the sodium blocking. This toxin has recently been identified as chemically identical with tetrodotoxin from the puffer fish. Toxins from the two sources are equally effective and are shown to have an action which is distinctly different from that of procaine.