Dgp1 and Dfp1 are closely related plasmids in the Dictyostelium Ddp2 plasmid family.

Dictyostelium plasmids Dgp1 and Dfp1, two members of the Ddp2 plasmid family, are 86% identical in nucleotide sequence. These small (4481 and 5015 bp), high copy number, nuclear plasmids carry both a gene homologous to the Ddp2 rep gene and a long 0.47- to 0. 48-kb inverted repeat region. Their Rep proteins are 82.8% identical in amino acid sequence and carry all 10 of the conserved peptide sequence motifs found in the Ddp2 family Rep proteins. Unlike other members of this family, Dgp1 carries two copies and Dfp1 carries four copies of a 162- to 166-bp direct repeat element. Both the direct and inverted repeat elements, as well as the promoter of the rep gene, are highly conserved (81 to 90% identical) between Dgp1 and Dfp1. In contrast, these regions are not highly conserved and the Rep proteins are only about 40% identical among the other known members of the plasmid family.

Dictyostelium discoideum nuclear plasmid Ddp6 is a new member of the Ddp2 plasmid family.

Ddp6 is a high-copy number, circular plasmid found in the nucleus of the simple eukaryote Dictyostelium discoideum wild isolate NC47.2. The complete nucleotide sequence, 5257 bp, shows that Ddp6 has a structure similar to that of other members of the Ddp2 plasmid family: a single long 2.8-kb open reading frame (rep gene) and an inverted repeat containing a pair of 654-bp elements. A single constitutively expressed 3.3-kb transcript of the rep gene was detected in RNA prepared from vegetative and developmental cells. Maintenance assays revealed that sequences within the inverted repeat and the intact Ddp6 ORF are essential for maintenance of the plasmid. Mutation of the inverted repeat, or of the rep gene, lowered the plasmid copy number but did not affect autonomous replication of shuttle-vector constructs. Comparisons of the predicted protein products of the rep genes of five members of the Ddp2 plasmid family identified a set of ten conserved features distributed throughout the peptides.

Dictyostelium discoideum nuclear plasmid Ddp5 is a chimera related to the Ddp1 and Ddp2 plasmid families.

The 14,955-bp Dictyostelium discoideum nuclear plasmid Ddp5 contains six transcribed open reading frames. One of these is related to the rep gene of the Ddp2 plasmid, and the other five are related to genes present on the Ddp1 plasmid. The absence of a homolog of the Ddp1 G1 gene, coupled with the presence of the Ddp2 rep gene homolog and of a 1.6-kb inverted repeat analogous to the inverted repeats on members of the Ddp2 plasmid family, suggests that Ddp5 uses Ddp2-like replication and copy number control mechanisms and that it should be assigned to the Ddp2 plasmid family. Ddp5 carries genes homologous to the D1/D3 and D2 genes of the Ddp1 plasmid as well as the Ddp1 G2/G3/D4, G5/D6, and G6/G4/D5 genes. The products of the Ddp5 G2-like, G5-like, and G6-like genes are likely to be transcription factors regulating the expression of themselves and of the other Ddp5 genes. The D1-like and D2-like genes may confer a selective advantage to plasmid-bearing cells, because they can be deleted from plasmid-based shuttle vectors with no apparent effect on vector maintenance. Updated sequence information for the Ddp1 G5/D6, D1/D3, and D2 genes as well as the Dmp1 and Dmp2 G5-like genes is presented. The locations of introns in the G5-like and D1-like genes of Ddp5 and in the homologous genes of the Ddp1, Dmp1, and Dmp2 plasmids were identified. These introns all have GU at the 5' intron border and AG at the 3' intron border, are short (59 to 71 nucleotides), and are AT-rich. A conserved HHCC domain was identified in the G5 proteins; this is a putative zinc binding domain and may be involved in protein-DNA interaction.

Biological study of triterpenequinones from celastraceae.

The cytostatic activity of several triterpenequinone methides isolated from Rzedowskia tolantonguensis and Maytenus horrida (Celastraceae) was evaluated against HeLa cell cultures. Their ID50 were determined and compared with those of other related compounds. A preliminary study of the antibacterial activity of the above triterpenequinone methides was also carried out.

Occurrence of big renin in human plasma, amniotic fluid and kidney extracts.

Big renin, a relatively inactive renin which possesses a molecular weight larger than that of normal plasma or renal renin, has been demonstrated by gel filtration in certain human plasma, tumor extracts, and amniotic fluid. Big renin was not present in normal plasma or kidney extracts. Plasma from 3 hypertensive patients with nephropathy contained chiefly big renin. Varying proportions of both big and normal renin activity were present in plasma of other patients with hypertension and proteinuria. The renin present in amniotic fluid, which increased in activity following exposure to acid pH, was shown to be big renin in two patients. Large amounts of circulating big renin apparently can cause hypertension in patients with Wilms' tumors. Furthermore, the relatively inactive big renin may replace normal plasma renin in some patients, resulting in low plasma renin activity.

Abnormally sustained aldosterone secretion during salt loading in patients with various forms of benign hypertension; relation to plasma renin activity.

Among 25 patients with benign, essential hypertension, and an equal number with other benign forms of hypertension, without serious cardiac, renal, or cerebrovascular impairment, 41 cases failed to reduce aldosterone excretion rates into the normal range (less than 5 mug/day) on a daily intake of 300 mEq of sodium. The hypertensive patients excreted slightly less than the normal fraction of labeled aldosterone as acid-hydrolyzable conjugate. Secretion rates were significantly higher in the hypertensive patients than in normotensive controls taking the high-sodium intake. On a 10 mEq sodium intake, the increase in excretion and secretion rates of aldosterone in the hypertensive patients could be correlated with plasma renin activity (PRA). The patients with the least increase in PRA had subnormal increase in aldosterone secretion and excretion, while unusually large rises in aldosterone secretion accompanied high PRA, especially in the cases with increased plasma angiotensinogen induced by oral contraceptives. The persistence of inappropriately high aldosterone secretion in most hypertensive patients during sodium loading could be related to a higher PRA than that found in normotensive controls under comparable conditions. In other hypertensives, whose PRA was unresponsive to sodium depletion, there was no significant correlation between PRA and aldosterone output, and no known stimulus to aldosterone production was detected. Five obvious cases of hyperaldosteronism were found among the 16 low-renin patients. The cause of the nonsuppressible aldosterone production in the other low-renin cases remains to be determined.