Inhibition of protein synthesis by ricin: experiments with rat liver mitochondria and nuclei and with ribosomes from Escherichia coli (Short Communication)

1. Ricin, a toxic protein from the seeds of Ricinus communis which inhibits poly(U)-directed polyphenylalanine synthesis by rat liver ribosomes (Montanaro et al., 1973), does not affect protein synthesis by isolated rat liver mitochondria. 2. The toxin is ineffective also on poly(U)-directed polyphenylalanine synthesis in reconstituted systems with ribosomes isolated from rat liver mitochondria or from Escherichia coli. 3. Ricin inhibits protein synthesis by isolated rat liver nuclei, but at concentrations much higher than those affecting rat liver ribosomes.     

A COI Nonsynonymous Mutation as Diagnostic Tool for Intraspecific Discrimination in the European Anchovy Engraulis encrasicolus (Linnaeus)

The European anchovy, Engraulis encrasicolus, is currently one of the principal target species for commercial fisheries in Europe. In this study, the mitochondrial Control Region (CR) and the Cytochrome Oxidase I (COI) mitochondrial gene were analyzed in 74 specimens of E. encrasicolus from four localities in the central Mediterranean. In both populations, the two markers revealed the presence of two main haplogroups, A and B, already detected in previous investigations of different classes of molecular markers. Both CR and COI markers consistently identified two haplogroups. The COI sequence analysis identified a non-synonymous transversion (T to G) at position 116 of the translated sequence, resulting in an amino acid change. All COI sequences of haplogroup A had an amino acid sequence with alanine in this position, while serine was present in the same position in haplogroup B. The two haplogroups A and B were also discriminated by the variable number of TACA elements at the 5’-end of the mitochondrial CR. The selection tests applied to the COI dataset revealed that codon 116 was not under positive selection, that seven amino acid changes were under purifying selection, and that two amino acids were under episodic positive selection.     

Endothelin-1 induces contraction of human and Australian possum gallbladder in vitro

This study examined the role of the renin-angiotensin and vasopressin systems on systolic blood pressure (SBP) variability following subarachnoid haemorrhage (SAH) in conscious rats. Animals received no treatment, the angiotensin II AT1 receptor antagonist, losartan, or the vascular vasopressin receptor antagonist, AVPX. SAH resulted in a transient sympathetic activation as estimated from the increase in the mid-frequency oscillations of SBP (3.2 +/- 0.8 mm Hg2, 3 hours after the injury vs. 1.3 +/- 0.3 mm Hg2 in control conditions, p < 0.01). On the second and fourth day following SAH, a marked elevation in the low-frequency component of SBP was observed (7.1 +/- 1.0 mm Hg2 on day 2 vs. 2.6 +/- 0.3 mm Hg2 in control conditions, p < 0.001 and 6.3 +/- 1.1 mm Hg2 on day 4 vs. 2.6 +/- 0.3 mm Hg2 in control conditions, p < 0.01). Pre-treatment with losartan prevented the acute rise in the mid-frequency oscillations in SBP and partially reduced the low-frequency component observed at 2 and 4 days. Administration of AVPX on the second and fourth day following SAH normalised the elevated low-frequency oscillations in SBP. This study indicates that the modifications in SBP variability observed in the early and delayed stage after subarachnoid haemorrhage involve angiotensin II. Vasopressin seems to be implicated in the delayed development of low-frequency fluctuations of SBP.     

The pig genome: compositional analysis and identification of the gene-richest regions in chromosomes and nuclei

The isochore organization of the mammalian genome comprises a general pattern and some special patterns, the former being characterized by a wider compositional distribution of the DNA fragments. The large majority of the mammalian genomes belong to the former, and only some groups, such as the Myomorpha sub-order of Rodentia, belong to the latter. Here we describe the compositional organization of the pig (Sus scrofa) genome that belongs to the general mammalian pattern. We investigated (i) the compositional distribution of the genes by analysis of their GC3 levels (the GC levels at the third codon positions), and (ii) the correlation between the GC3 value of orthologous genes from pig and other vertebrates (human, calf, mouse, chicken, and Xenopus). As expected, the highest gene concentration corresponded to the H3 isochore family, and the highest GC3 correlations were observed in the pig/human and pig/calf comparisons. Then we identified, by in situ hybridization of the GC-richest H3 isochores, the pig chromosomal regions endowed by the highest gene-density that largely corresponded to the telomeric chromosomal bands. Moreover, we observed that these gene-rich bands are syntenic with the previously identified GC-richest/gene richest H3+ bands of the human chromosomes. At the cell nucleus level, we observed that the gene-dense region corresponded to the more internal compartment, as previously found in human and avian cell nuclei.