Enzyme induction in rat liver: The effects of Be2+ in vivo

Rats given an LD₅₀ dose of Be²⁺ showed reduced activities of ornithine decarboxytase and tyrosine aminotransferase in liver in response to dexamethasone induction. Control fed animals showed superinduction. Be²⁺ also inhibited the uptake of [³H]orotic acid into rapidly labelled RNA of ribonucleoprotein particles extracted from liver nuclei in isomolar solutions at pH 8.0. Consistent with inhibition of cytoplasmic protein kinase reported previously (Kaseret at., 1980), the uptake of [³²P]P_i into proteins in the ribonucleoprotein particles was also diminished.     

Structural Characteristics of the Short-Tail Fibers of T4 Bacteriophage

The characteristics of pure preparations of short-tail fibers of bacteriophage T4 have been studied in the optical and electron microscope. Three main structures were observed: 1) spheres of 8.1 nm diameter; 2) fibers 43 nm long and 3.8 nm thick; and 3) fibers 54 nm long and 3.2 nm thick. Both types of fibers exhibited a regular beaded appearance. The 43-nm fibers were the most abundant structure. During the process of purification of the short-tail fibers, the formation of aggregates was observed each time the material containing the short-tail fibers was dialyzed against saline solutions. These aggregates became increasingly fibrous (as observed in the optical microscope) as the material used was increasingly enriched in short-tail fibers. Finally, most of the aggregates were of the fibrous type when they were formed from a purified preparation of short-tail fibers. In the electron microscope, it was found that the filamentous aggregates were organized in well-defined bundles. The amino acid composition of the highly purified short-tail fibers was also determined. Among the known fibrous proteins, the ones that most resemble the amino acid composition of the short-tail fibers are actin and fibrinogen. These observations are discussed in relation to the T4 short-tail fiber structure and their localization on the hexagonal baseplate of the T4 tail structure.     

The Receptor-Mediated Activation of Tyrosine Hydroxylation in the Superior Cervical Ganglion of the Rat

The addition of carbachol to superior cervical ganglia causes a rapid increase in tyrosine hydroxylation in situ. The increase occurs in ganglia from both newborn and adult animals, and in ganglia from animals pretreated with reserpine. The increase is not due to increased transport of the substrate. The increase is dependent upon the presence of calcium, and is additive to the stimulation produced by dibutyryl cyclic AMP. The stimulation seems specific for tyrosine hydroxylation; dopamine beta-hydroxylation is not increased. Preincubation experiments suggest that the carbachol-induced stimulation is due to a change in the availability of, or the affinity of the enzyme for, reduced pterin cofactor. The stimulation is inhibited by atropine and also by low concentrations of phenoxybenzamine or haloperidol, which suggests that it is caused by an action of carbachol on the interneurons in the ganglia.     

Biosynthesis of candicidin by phosphate-limited resting cells ofStreptomyces griseus

Summary A phosphate-limited resting cell system ofStreptomyces griseus in a synthetic medium has been developed in which biosynthesis of the polyene macrolide, candicidin, is linear for at least 36 h without cell growth. Glucose and to a lesser degree sucrose, but not lactose, support antibiotic synthesis. Glucose is utilized at a constant rate for antibiotic synthesis without affecting mycelial dry weight. Acetate and propionate, the building units of the macrolide aglycone, stimulate candicidin biosynthesis in cultures supplemented with glucose but do not support its synthesis in the absence of glucose. Maximal stimulation of candicidin biosynthesis was produced by 40 mM propionate or 250 mM acetate. The biosynthetic intermediate, methyl malonate, and the analog, 1-propanol, were more stimulatory than propionate at the same concentration.     

X-ray microanalysis of chlorine and phosphorus content in biguanide-treated Acanthamoeba castellanii

Energy dispersive analysis of X-rays (EDAX) was used to study the effects of chlorhexidine diacetate (CHA) and polyhexamethylene biguanide (PHMB) on Acanthamoeba castellanii. A high variation of elements occurred in untreated individual cells and only two elements, Cl (a biocide marker) and P, were investigated. X-ray dot mapping of untreated trophozoites and cysts revealed that Cl in cells was uniformly distributed throughout the cytoplasm, whereas P was less dense in the vacuoles. X-ray dots of Cl in biocide-treated trophozoites and cysts appeared denser and evenly distributed within the cells as the biguanide concentration increased. Quantitative analysis of either CHA or PHMB within the cells using Cl as an elemental marker was unsatisfactory because of the high Cl levels in untreated cells. The apparent increases of P in some experiments with treated cells might be associated with reduced permeability, protein coagulation or aggregation of phospholipids.