At what age do rat young stop responding to the maternal pheromone?

We tested postweanling rat young to see if they would continue to respond to the maternal pheromone when pheromone-containing feces were made available in the home cage. We found that they do, and that the consumption of pheromone-containing feces is important for such sustained responsiveness. Nonetheless, interest in the pheromone does not continue past 50 days of age. The possible adaptive significance of the continuation and cessation of pheromonal responsiveness was discussed.

The maternal pheromone and deoxycholic acid in the survival of preweanling rats

Preweanling rats selectively approach and consume pheromone-containing maternal feces. This selectivity suggests that the consumption of maternal feces might be important for the growing pup. We tested the hypothesis that such feces, because of their high deoxycholic acid content, may protect against acute enteritis. A series of experiments was carried out in which pups were denied access to maternal feces. These pups died more often from acute enteritis than control pups. Additional confirmation of the hypothesis was obtained when feces-denied young fed deoxycholic acid showed a significantly lower mortality than feces-denied young fed laboratory chow alone.

The maternal pheromone and deoxycholic acid in relation to brain myelin in the preweanling rat

We examined the lipid composition of blood and myelin in preweanling rats denied access to maternal feces. Levels of triglycerides and free fatty acids in the blood were reduced and in the brain the amount of myelin and the phospholipid concentration in myelin were also reduced. The addition of deoxycholic acid to ordinary laboratory chow prevented these deficiencies. We conclude that response to the maternal pheromone and the subsequent ingestion of deoxycholic acid through maternal feces promotes the deposition of normal brain myelin.

The maternal pheromone and brain development in the preweanling rat

Preweanling rats selectively approach and consume pheromone-containing maternal feces. This selectivity suggests that the consumption of maternal feces might be important for the growing pup. Previous research suggested that such feces might promote brain development. A series of experiments was carried out in which pups were denied access to maternal feces. These pups were clearly inferior to control pups in brain growth and neurobehavioral maturation, as well as in the quantity of brain myelin.

The relation between the internal phosphorylation potential and the proton motive force in mitochondria during ATP synthesis and hydrolysis

Using 31P NMR and a potassium ion distribution method, the internal phosphorylation potential and the transmembrane electrical potential of intact rat liver mitochondria were measured simultaneously during ATP synthesis and ATP hydrolysis. The ATPase was shown to quickly equilibrate the internal phosphorylation potential with the proton motive force across the mitochondrial membrane. Upon oxygenation of anaerobic mitochondria, there was a very fast increase of delta pH and a quick uptake of inorganic phosphate prior to the buildup of the internal ATP. Consistent with the chemiosmotic theory, these results showed the presence of proton pumping by the respiratory system from the bulk internal aqueous phase to the bulk external aqueous phase. There was, in the measured energetic parameters, no indication of direct energy coupling or short circuiting protons between the respiratory energy input and the ATP synthesis.

Altered bile acid physiology during lactation in the rat

There is evidence that the rate of bile acid secretion increases significantly during lactation in the rat. We show that this increase in secretion rate is accompanied by an expanded bile acid pool and that occasioning the enhancement of both pool size and secretion is an increase in bile acid synthesis. The hypothesis is advanced that maternal prolactin, promoted by suckling young, amplifies cholesterol-7-alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis, and perhaps HMG-CoA reductase, the rate-limiting enzyme in cholesterogenesis.

The maternal pheromone of the rat: testing some assumptions underlying a hypothesis

Herein we report four experiments relating to the maternal pheromone of the rat that show (a) preweanling young consume pheromone-containing feces most conspicuously between 14 and 27 days; (b) they consume those feces preferentially; (c) such feces contain high levels of deoxycholic acid; and (d) preweanling young are deficient in deoxycholic acid. The data of these experiments lend support to the hypothesis that in responding to the pheromone the young ingest deoxycholic acid, a steroid believed to promote gut immunocompetence and brain myelination.

Reduced prolactin binding to liver membranes during pheromonal emission in the rat

Between 14 and 27 days of lactation, female rats excrete a pheromone in their feces that is cholic-acid dependent and that strongly attracts young. Previous research has shown that high circulating levels of prolactin are necessary before the pheromone can be emitted. However, during the time of pheromonal emission prolactin in serum conspicuously declines, while in hepatic cytosol the hormone reaches peak levels. We were interested in the question of how the liver can show peak cytosolic concentrations of prolactin at a time of falling blood levels of prolactin. Accordingly, we examined the prolactin binding capacity of liver membrane fractions during selected periods of lactation. We also studied the livers of virgin and pregnant females for comparison. Three membrane fractions were separated: the cell membrane, the nuclear membrane and a fraction consisting of the cell membrane and large non-nuclear organelles. In all three fractions, there was an increase in available and total prolactin binding in the liver when pregnant females were compared with nulliparous females. However, during the time of pheromonal emission, when prolactin in hepatic cytosol was elevated, there was a significant reduction in the prolactin binding capacity of the liver. How such a reduction increases the cytosolic concentration of the hormone and in turn heightens cholic acid output and pheromonal emission remains unsolved.

A study on the exchange rate of magnesium with ATP

The exchange process of Mg2+ with ATP was found to be, in many cases, dominated by Mg2+ exchange between ATP and ATP-Mg (a bimolecular reaction) rather than the Mg2+ off-process from ATP-Mg to solution (a unimolecular reaction). The Mg2+ off-rate from ATP-Mg and the rate constant of the bimolecular reaction were determined at 10 and 25 degrees C at pH 7.3, using 31P-NMR at 145.7 MHz. At this resonance frequency intermediate to slow exchange phenomena with respect to the NMR time scale of 2.5 . 10(3) s-1 were observed in ATP resonances. Various implications of these results to studies of biological systems have been pointed out.

Two-dimensional TLC analysis of ginsenosides from root of dwarf ginseng (Panax trifolius L.) Araliaceae

A procedure is reported for the two-dimensional TLC separation of ginsenosides from the root of Panax trifolius L. The solvent systems and spray reagents described are useful for the identification of ginsenosides in various species of Panax. The results of the separation and identification with controls of at least four ginsenosides from the root of P. trifolius L. are reported. The total percentage of ginsenosides was 0.0061%.

Measurement of the internal pH of yeast spores by 31P nuclear magnetic resonance

The asci and single spores of the yeast Pichia pastoris were examined by using 31P NMR. The pH within the spores was determined from the pH-dependent chemical shifts of the internal orthophosphate (Pi) peaks. In spectra of asci, two internal Pi peaks corresponding to two compartments were observed. Only small variations in the internal pH values were found upon incubation of the asci in buffers ranging in pH from 3 to 10. For this range in external pH, the internal pH values calculated from the Pi chemical shifts were 5.5-6.3 and 5.1-5.9. The two internal Pi peaks, which have line widths of approximately 60 Hz, have been assigned to spore and epiplasmic compartments, respectively. Spectra of single spores revealed only one Pi peak, and, upon germination of either the single spores or asci, only this Pi peak disappeared. Peaks corresponding to ATP were not found in the dormant spores and asci but did appear upon germination. These NMR studies show the yeast spore to have a mobile and relatively acidic interior.

Effect of visceral afferent activation on leg extension induced by sciatic afferent stimulation

In cats under light chloralose and sodium pentobarbital anesthesia the effects of electrical stimulation of various visceral afferent nerves on leg extension induced by sciatic afferent stimulation were studied. Stimulation of the central end of the cervical vagus and stellate ganglion produced inhibition of induced leg extension while stimulation of the distal end of the thoracic vagus, coeliac ganglion, and splanchnic nerves produced facilitation. Decortication slightly reduced the inhibitory effect and greatly reduced the facilitatory effect. Additional decerebration greatly reduced the inhibitory effect and almost abolished the facilitatory effect. Spinal transection at C1 completely abolished the inhibitory and facilitatory effects on induced leg extension. These results suggest that visceral afferents facilitate sciatic induced leg extension principally through the cortex while they inhibit extension through the midbrain and hypothalamus.

Effects of diphenylhydantoin on cardiac arrhythmias induced by carotid occlusion in the cat

The effects of diphenylhydantoin (DPH) on cardiac arrhythmias induced by occlusion of the common carotid arteries were studied in vagotomized cats under light chloralose anesthesia. It was found that the mean effective dose of DPH via the i.v. route was 11.0 mg/kg. When DPH was injected into the vertebral artery, the carotid artery or the 4th cerebral ventricle, the mean effective dose was 0.8, 1.2 and 0.32 mg/kg, respectively, When DPH was injected directly into the posterior hypothalamic regions, the mean effective dose was even smaller, i.e., 0.14 mg/kg. On the other hand, when DPH was injected into the left ventricle of the heart, the mean effective dose was 1.7 mg/kg and the dose was significantly increased to 4.4 mg/kg when cerebral circulation was temporarily occluded. The data suggest that DPH exerts a potent antiarrhythmic effect through its action on the central nervous system. For the cardiac arrhythmias induced by occlusion of the common carotid arteries, it appears likely that DPH acts on the posterior hypothalamus.