Protein synthesis by membrane-bound and free ribosomes of the developing rat cerebral cortex

1. Rates of RNA and protein synthesis were measured in rat cerebral-cortex slices, and compared with amino acid incorporation into protein by membrane-bound and free ribosomes from the same tissue, in the first 3 weeks of life. 2. A rapid age-dependent decline in the incorporation of labelled precursors into both RNA and protein was observed, which was more marked for amino acid incorporation into protein. 3. Although membrane-bound ribosomes comprise only a small fraction of total ribosomes, they were more active in incorporating amino acids into protein than were free ribosomes, especially immediately after birth. The decline in activity with age was more marked in the membrane-bound fraction than in free ribosomes. This loss of activity was largely independent of alterations in soluble factors or endogenous mRNA content and appeared to involve some alteration of the function of the ribosome itself, with relatively small alterations in the ratio of membrane-bound to free ribosomes. 4. Thyroidectomy, performed soon after birth, had no effect on the incorporation of radioactive precursors into RNA or protein by either slices or the cell-free preparations during the first 3-4 weeks of life.     

Isolation and characterisation of a cDNA clone for human apolipoprotein CI and assignment of the gene to chromosome 19

Summary We have synthesised a mixed oligonucleotide 17 bases long and used it to isolate cDNA clones for apolipoprotein CI (apo CI) from an adult liver cDNA library. The partial sequence of one of these clones confirms its identity. We have used this probe and Southern blotting techniques to identify the human apo CI gene in DNA from a series of rodent x human somatic cell hybrids. Our Results provide evidence for the assignment of this gene to human chromosome 19.     

Novel ketal ligands for the glucocorticoid receptor: in vitro and in vivo activity

A novel series of selective ligands for the human glucocorticoid receptor is described. Structure-activity studies focused on variation of B-ring size, ketal ring size, and ketal substitution. These analogs were found to be potent and selective ligands for GR and have partial agonist profiles in functional assays for transactivation (TAT, GS) and transrepression (IL-6). Of these compounds, 27, 28, and 35 were evaluated further in a mouse LPS-induced TNF-alpha secretion model. Compound 28 had an ED(50) of 14.1 mg/kg compared with 0.5 mg/kg for prednisolone in the same assay.     

The subcellular distribution of 32P-labelled phospholipids, 32P-labelled ribonucleic acid and 125I-labelled iodoprotein in pig thyroid slices. Effect in vitro of thyrotrophic hormone and dibutyryl-3′,5′-(cyclic)-adenosine monophosphate

1. The incorporation in vitro of [(32)P]phosphate into phospholipids and RNA and of [(125)I]iodide into protein-bound iodine by pig thyroid slices incubated for up to 6hr. was studied. The subcellular distribution of the labelled products formed after incubation with radioactive precursor in the nuclear, mitochondrial, smooth-microsomal, rough-microsomal and cell-sap fractions was also studied. 2. Pig thyroid slices actively took up [(32)P]phosphate from the medium during 6hr. of incubation; the rate of incorporation of (32)P into phospholipids was two to five times that into RNA. 3. The uptake of [(125)I]iodide by the slices from the medium was rapid for 4hr. of incubation, 6-10% of the label being incorporated into iodoprotein. 4. Much of the (32)P-labelled phospholipid accumulated in mitochondria and microsomes, whereas the nuclear fraction contained most of the (32)P-labelled RNA. After 2hr. of incubation most of the (32)P-labelled cytoplasmic RNA accumulated in the rough-microsomal fraction. The major site of localization of proteinbound (125)I was the smooth-microsomal fraction, and gradually increasing amounts appeared in the soluble cytoplasm fraction, suggesting a vectorial discharge of [(125)I]iodoprotein (presumably thyroglobulin) from smooth vesicles into the colloid. 5. The addition of 0.1-0.4 unit of thyrotrophic hormone/ml. of incubation medium markedly enhanced the accumulation of (32)P-labelled phospholipids in the microsomal fractions and to a much smaller extent that of (32)P-labelled RNA without any increase in the total uptake of the label. Almost simultaneously the hormone increased the uptake of [(125)I]iodide by the slices and enhanced the accumulation of protein-bound (125)I in the smooth-microsomal fraction. 6. As a function of time of incubation, thyrotrophic hormone had a biphasic effect on [(125)I]iodide uptake and protein-bound (125)I formation, the stimulatory effect being reversed after 4hr. of incubation. 7. 6-N-2'-O-Dibutyryl-3',5'-(cyclic)-AMP, but not 3',5'-(cyclic)-AMP or 5'-AMP, mimicked the action of thyrotrophic hormone on iodine uptake as well as on iodination of protein. On the other hand, the mimicry by 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP of the stimulatory effect of thyrotrophic hormone on the formation of labelled thyroid phospholipids and RNA was only an apparent one resulting from an enhanced uptake of [(32)P]phosphate. 8. It is concluded that thyrotrophic hormone causes a co-ordinated increase in the formation or accumulation of phospholipids, RNA and iodoprotein associated with the endoplasmic reticulum, and that 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP mimics the more rapid effects of thyrotrophic hormone on transport and metabolic functions of thyroid cells, but does not influence their slower biosynthetic responses to the hormone.     

PAHs,OCPs and PCBs in sediments from three catchments in Durban,South Africa

Polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analysed from sediment samples collected in 2012 from rivers, surface runoff canals and estuaries in three highly urbanised catchments in durban, KwaZulu-Natal, South Africa. PAHs were ubiquitous, at concentrations between 36–6 800 ng g^?1 dry mass (dm). Congener ratio diagnosis suggests the PAHs were derived predominantly from pyrogenic sources. Four OCPs and/or their metabolites were detected at varying frequencies and concentrations. Of these, dichlorodiphenyltrichloroethane (ddT) and metabolites were most frequently detected and were at a high concentration in sediment in some systems. Toxaphene was detected at a high concentration at some sites. The total PCB concentration varied widely, from below the method detection limit to 110 ng g^?1 (dm). Based on the comparison of chemical concentrations to international sediment quality guidelines, PAH, OCP and PCB concentrations in most sediment samples posed a low risk to sediment-dwelling organisms. However, in some instances the risk was moderate or high. It is recommended that these compounds be monitored more frequently and comprehensively in aquatic ecosystems to better understand the ecological and human health implications.