Prostaglandin production in response to angiotensin-(1-7) in rabbit isolated vasa deferentia

Angiotensin-(1-7) is a predominant metabolite of angiotensin I in brain tissue. Its neuromodulatory and prostaglandin (PG) synthesizing capabilities were investigated in the rabbit isolated vas deferens. This metabolite had no significant effect as a neuromodulator, however it increased PGE synthesis in the vasa deferentia with a potency equivalent to that of angiotensin II. The angiotensin-(1-7) has a unique spectrum of activity among the angiotensin peptides to selectively increase PG synthesis. It could be useful in defining the relevance of angiotensin-induced PG synthesis in various systems, particularly in neuronal tissue. Angiotensin-(1-7) potentially could be useful in defining angiotensin receptor subtypes, as well.     

A male-specific nuclease-resistant chromatin fraction in the mealybug Planococcus lilacinus

In mealybugs, chromatin condensation is related to both genomic imprinting and sex determination. The paternal chromosomal complement is condensed and genetically inactive in sons but not in daughters. During a study of chromatin organization in Planococcus lilacinus, digestion with micrococcal nuclease showed that 3% to 5% of the male genome is resistant to the enzyme. This Nuclease Resistant Chromatin (NRC) apparently has a nucleosomal organization. Southern hybridization of genomic DNA suggests that NRC sequences are present in both sexes and occur throughout the genome. Cloned NRC DNA is A+T-rich with stretches of adenines similar to those present in mouse -satellite sequences. NRC DNA also contains sequence motifs that are typically associated with the nuclear matrix. Salt-fractionation experiments showed that NRC sequences are matrix associated. These observations are discussed in relation to the unusual cytological features of mealybug chromosomes, including the possible existence of multiple centres of inactivation.     

Increased expression of SIRT2 is a novel marker of cellular senescence and is dependent on wild type p53 status

Sirtuins (SIRT) belonging to the NAD+ dependent histone deacetylase III class of enzymes have emerged as master regulators of metabolism and longevity. However, their role in prevention of organismal aging and cellular senescence still remains controversial. In the present study, we now report upregulation of SIRT2 as a specific feature associated with stress induced premature senescence but not with either quiescence or cell death. Additionally, increase in SIRT2 expression was noted in different types of senescent conditions such as replicative and oncogene induced senescence using multiple cell lines. Induction of SIRT2 expression during senescence was dependent on p53 status as depletion of p53 by shRNA prevented its accumulation. Chromatin immunoprecipitation revealed the presence of p53 binding sites on the SIRT2 promoter suggesting its regulation by p53, which was also corroborated by the SEAP reporter assay. Overexpression or knockdown of SIRT2 had no effect on stress induced premature senescence, thereby indicating that SIRT2 increase is not a cause of senescence; rather it is an effect linked to senescence-associated changes. Overall, our results suggest SIRT2 as a promising marker of cellular senescence at least in cells with wild type p53 status.     

Biological activities of angiotensin II-(1-6)-hexapeptide and angiotensin II-(1-7)-heptapeptide in man

Biological activities of angiotensin II-(1-6)-hexapeptide [ANG-(1-6)] and angiotensin II-(1-7)-heptapeptide [ANG-(1-7)] were studied in 5 normal men and 3 patients with Bartter's syndrome. The angiotensins were infused iv in each subject from 0900 h to 0915 h at a rate of 21 nmol(16.8 micrograms)/kg X min and 18 nmol(16.2 micrograms)/kg X min for ANG-(1-6) and ANG-(1-7), respectively. In the normal men a significant rise in blood pressure was observed by the infusions of both peptides. Average increments of blood pressure for ANG-(1-6) were 17/14, 23/18, 22/15 and 17/14 mmHg at 2, 5, 10 and 15 min, respectively, and those for ANG-(1-7) were 19/15, 20/17, 13/13 and 15/13 mmHg at 2, 5, 10 and 15 min, respectively. The duration of pressor actions after the cessation of the infusions (T) was 10 min for ANG-(1-6) and 20 (for systolic) and 30 (for diastolic) min for ANG-(1-7). T for ANG-(1-6) was shorter than and T for ANG-(1-7) was similar to T for Ile5-angiotensin II (Ile5-ANG II) reported previously in 7 normal men 5 of whom were the same as examined in the present study. On the other hand, both peptides did not cause a rise in blood pressure in the 3 patients with Bartter's syndrome. Both angiotensins did not cause an increase in plasma aldosterone but did cause a significant decrease in plasma renin activity both in the normal men and in the patients. From these results and our previous observations of inactivity of angiotensin II-(5-8)-tetrapeptide, a pressor action of angiotensin II-(4-8)-pentapeptide, and pressor, renin-suppressing and steroidogenic actions of angiotensin II-(3-8)-hexapeptide in normal men, it is thought that ANG-(1-6) and ANG-(1-7) are bound to angiotensin II (ANG II) receptor in the peripheral arterioles and show pressor actions (less than 0.024% and less than 0.028% of Ile5-ANG II, respectively) and suppress renin mainly via short loop feedback and that the shortest biologically active ANG II molecules for pressor, renin-suppressing and steroidogenic actions are Tyr-Ile-His, Val-Tyr-Ile-His and Val-Tyr-Ile-His-Pro-Phe, respectively, in man. It is also evident that ANG-(1-6) is more rapidly metabolized than ANG-(1-7) or Ile5-ANG II in man.     

Measuring foraging activity in bumblebee nests: a simple nest‐entrance trip recorder

We describe a new, electronic, apparatus for measuring the activity of bumblebees as they fly from and to their nests. The bee activity recorder (BAR) works on the principle that bees leaving and returning to their nest crawl through a tube equipped with infrared emitters and detectors so that when the beam is interrupted by the passage of a bee, the event is recorded as either an exit or an entry. Tests of BARs indicate that they are highly accurate, BAR counts and visual counts highly correlated with an almost one‐to‐one correspondence. We suggest that BARs can be used for recording the foraging activities of bumblebees through nest exit and entry counts in many practical and research applications.     

Sex-specific organisation of middle repetitive DNA sequences in the mealybug Planococcus lilacinus.

Differential organisation of homologous chromosomes is related to both sex determination and genomic imprinting in coccid insects, the mealybugs. We report here the identification of two middle repetitive sequences that are differentially organised between the two sexes and also within the same diploid nucleus. These two sequences form a part of the male-specific nuclease-resistant chromatin (NRC) fraction of a mealybug Planococcus lilacinus. To understand the phenomenon of differential organisation we have analysed the components of NRC by cloning the DNA sequences present, deciphering their primary sequence, nucleosomal organisation, genomic distri-bution and cytological localisation. Our observations suggest that the middle repetitive sequences within NRC are functionally significant and we discuss their probable involvement in male-specific chromatin organisation.     

Regulation of the activities of the mammalian transglutaminase family of enzymes

Mammalian transglutaminases catalyze post‐translational modifications of glutamine residues on proteins and peptides through transamidation or deamidation reactions. Their catalytic mechanism resembles that of cysteine proteases. In virtually every case, their enzymatic activity is modulated by elaborate strategies including controlled gene expression, allostery, covalent modification, and proteolysis. In this review, we focus on our current knowledge of post‐translational regulation of transglutaminase activity by physiological as well as synthetic allosteric agents. Our discussion will primarily focus on transglutaminase 2, but will also compare and contrast its regulation with Factor XIIIa as well as transglutaminases 1 and 3. Potential structure–function relationships of known mutations in human transglutaminases are analyzed.     

A secondary disruption of the dmpA gene encoding a large membrane protein allows aggregation defective Dictyostelium rasC- cells to form multicellular structures

The disruption of the gene encoding the Dictyostelium Ras subfamily protein, RasC, results in a strain that does not aggregate and has defects in both cAMP signal relay and cAMP chemotaxis. Disruption of a second gene in the rasC(-) strain by Restriction Enzyme Mediated Integration produced cells that were capable of forming multicellular structures in plaques on bacterial lawns. The disrupted gene (dmpA) encoded a novel membrane protein that was designated Dmp1. Although the rasC(-)/dmpA(-) cells progressed through early development, they did not form aggregation streams on a plastic surface under submerged starvation conditions. Phosphorylation of PKB in response to cAMP, which is significantly reduced in rasC(-) cells, remained low in the rasC(-)/dmpA(-) cells. However, in spite of this low PKB phosphorylation, the rasC(-)/dmpA(-) cells underwent efficient chemotaxis to cAMP in a spatial gradient. Cyclic AMP accumulation, which was greatly reduced in the rasC(-) cells, was restored in the rasC(-)/dmpA(-) strain, but cAMP relay in these cells was not apparent. These data indicate that although the rasC(-)/dmpA(-) cells were capable of associating to form multicellular structures, normal aggregative cell signaling was clearly not restored. Disruption of the dmpA gene in a wild-type background resulted in cells that exhibited a slight defect in aggregation and a more substantial defect in late development. These results indicate that, in addition to the role played by Dmp1 in aggregation, it is also involved in late development.