ONTOGENETIC DEVELOPMENT OF ADENYL CYCLASE AND PHOSPHODIESTERASE IN RAT BRAIN

Abstract— The activities of adenyl cyclase and phosphodiesterase were determined in homogenates of cerebrum, cerebellum and brain stem of rats of 1 day to 9 weeks of postnatal age. The activity of cerebral and brain stem adenyl cyclase measured either in the absence or presence of sodium fluoride increased rapidly for 2 weeks, reached at 20 days a maximum about three times (brain stem) or six times (cerebrum) that seen on day 1 and then declined slightly during the next several weeks. In contrast, activity of cerebrellar adenyl cyclase increased more slowly and reached a maximum at about 32 days. Activity of phosphodiesterase in cerebrum and brain stem increased several-fold during brain maturation; however, enzymic activity in the cerebellum decreased during the entire 9 week period.
In the pineal gland, adenyl cyclase activity measured in the absence of norepinephrine or sodium fluoride did not change significantly with age. However, enzymic activity measured in the presence of these agents increased with the age of the rat. Bilateral removal of the superior cervical ganglia at 1 day of age is known to arrest the sympathetic innervation of the pineal gland but did not prevent the development of this adenyl cyclase system activated by catecholamines or fluoride.     

PROTEIN METABOLISM AND AMINO ACID ACCUMULATION IN THE RAT SUBMAXILLARY GLAND DURING REDUCED SYMPATHETIC ACTIVITY

Abstract— Unilateral sympathetic decentralization of the superior cervical ganglion of rats was performed 3 days prior to the experiments. A two-compartment kinetic model was proposed to describe the effect of decentralization on (1) the uptake of a nonphysiological amino acid from plasma to the submaxillary gland and (2) the incorporation of a physiological amino acid from precursor pool into protein. The calculations based on the model showed that the fractional rate constant for efflux of the nonphysiological amino acid, α-[3-¹⁴C] aminoisobutyric acid, was greater in the decentralized than in the normal gland. However, efflux rate was equal in the two glands because the extrapolated zero time value of the initial concentration was greater in the normal gland.
The labelled physiological amino acid, [¹⁴C]leucine, was used in initial experiments to assess turnover rate of the gland proteins but it was rapidly metabolized to many other radioactive compounds. Therefore, arginine[¹⁴C]guanido was employed-arginine being the only labelled amino acid found after injection. Since the steady state content of submaxillary gland proteins was not changed but the fractional rate constant of conversion of free arginine into protein (k_p) was greater in the decentralized gland (k_p= 0-40 h^_l) than in the normal (k_p= 0-27 h⁻¹), we can conclude that decentralization increases protein turnover rate; thus, assuming that arginine[¹⁴C]guanido is homogeneously distributed in the tissue pools of free arginine, the rate of protein turnover is greater in the sympathetically decentralized gland than in the normal.     

Equations for the age structure of growing populations

Generalized equations are developed for the age structure of growing cell populations when other parameters besides chronological age are taken into account. These are summarized in a parameter which we call “chronological age”. The theory is Markovian in spirit and leads to an integro-differential equation for population density which generalizes several equations now appearing in the literature. Approximations to the fundamental equation are suggested.     

A new method for the quantitative determination of monosaccharides, amino sugars and N-acetylneuraminic acid and of 6-deoxyhexose (fucose) in the presence of other sugars

1. Monosaccharides, amino sugars and N-acetylneuraminic acid were determined by using an original colorimetric assay procedure, based on the detection of formaldehyde released after periodate oxidation. A range of these compounds was investigated by this method and they were all found to obey Beer's law within the concentration range 0-0.6mumole/ml. 2. A simple method for the determination of 6-deoxyhexose concentration in the presence of other monosaccharides is also described. 3. The optimum pH for the release of formaldehyde from sugars by periodate oxidation was 7.0-7.5. 4. The methods described have considerable advantages over existing assay systems and their particlar value in automatic colorimetry, where the use of concentrated acids is undesirable, is discussed.     

Dynamic adhesion and separation of cells in vitro. II. Interactions of cells with hydrophilic and hydrophobic surfaces

Experiments made on the passage of cells through untreated and siliconized glass beads, and on the adhesion and spread of cultured cells on glass and Teflon surfaces show that, in the absence of serum and in its presence in low concentrations, cell adhesion and spread is sensitive to substratum wettability. On the other hand, in the presence of 100% serum, no differences in adhesive parameters are detectable. It is concluded that arguments correlating cell adhesion to surface wettability, and, by inference, surface free energy, are unsubstantiated in 100% serum, which may well approximate to the in vivo situation. The results also show no correlation between parameters of cell adhesion and cell separation, and thereby support the hypothesis that these are different processes.