Cytotoxic Peptides: Naphthoquinonyl Derivatives of Luteinizing Hormone-Releasing Hormone

In an attempt to produce efficient cytotoxic derivatives of luteinizing hormone-releasing hormone (LH-RH), two novel 1,4-naphthoquinone derivatives of [D-Lys⁶]-LH-RH were synthesized primarily by solid-phase peptide synthesis, in good yield and high purity. The ability of each analog to produce reactive oxygen species using enzymatic reduction, i.e. NADPH-cytochrome P-450 reductase, was evaluated employing electron spin resonance (ESR) spectroscopy and spin-trapping techniques. The ESR results suggest that the novel cytotoxic analogs are extremely effective in generating oxygen radicals.     

The Aspartate-Less Receiver (ALR) Domains: Distribution,Structure and Function

Two-component signaling systems are ubiquitous in bacteria, Archaea and plants and play important roles in sensing and responding to environmental stimuli. To propagate a signaling response the typical system employs a sensory histidine kinase that phosphorylates a Receiver (REC) domain on a conserved aspartate (Asp) residue. Although it is known that some REC domains are missing this Asp residue, it remains unclear as to how many of these divergent REC domains exist, what their functional roles are and how they are regulated in the absence of the conserved Asp. Here we have compiled all deposited REC domains missing their phosphorylatable Asp residue, renamed here as the Aspartate-Less Receiver (ALR) domains. Our data show that ALRs are surprisingly common and are enriched for when attached to more rare effector outputs. Analysis of our informatics and the available ALR atomic structures, combined with structural, biochemical and genetic data of the ALR archetype RitR from Streptococcus pneumoniae presented here suggest that ALRs have reorganized their active pockets to instead take on a constitutive regulatory role or accommodate input signals other than Asp phosphorylation, while largely retaining the canonical post-phosphorylation mechanisms and dimeric interface. This work defines ALRs as an atypical REC subclass and provides insights into shared mechanisms of activation between ALR and REC domains.     

Human U1 small nuclear RNA genes: extensive conservation of flanking sequences suggests cycles of gene amplification and transposition.

The DNA immediately flanking the 164-base-pair U1 RNA coding region is highly conserved among the approximately 30 human U1 genes. The U1 multigene family also contains many U1 pseudogenes (designated class I) with striking although imperfect flanking homology to the true U1 genes. Using cosmid vectors, we now have cloned, characterized, and partially sequenced three 35-kilobase (kb) regions of the human genome spanning U1 homologies. Two clones contain one true U1 gene each, and the third bears two class I pseudogenes 9 kb apart in the opposite orientation. We show by genomic blotting and by direct DNA sequence determination that the conserved sequences surrounding U1 genes are much more extensive than previously estimated: nearly perfect sequence homology between many true U1 genes extends for at least 24 kb upstream and at least 20 kb downstream from the U1 coding region. In addition, the sequences of the two new pseudogenes provide evidence that class I U1 pseudogenes are more closely related to each other than to true genes. Finally, it is demonstrated elsewhere (Lindgren et al., Mol. Cell. Biol. 5:2190-2196, 1985) that both true U1 genes and class I U1 pseudogenes map to chromosome 1, but in separate clusters located far apart on opposite sides of the centromere. Taken together, these results suggest a model for the evolution of the U1 multigene family. We speculate that the contemporary family of true U1 genes was derived from a more ancient family of U1 genes (now class I U1 pseudogenes) by gene amplification and transposition. Gene amplification provides the simplest explanation for the clustering of both U1 genes and class I pseudogenes and for the conservation of at least 44 kb of DNA flanking the U1 coding region in a large fraction of the 30 true U1 genes.     

Enhanced Phosphorylation of Tyrosine Hydroxylase at More Than One Site Is Induced by 56 mM K+ in Rat Pheochromocytoma PC 12 Cells in Culture

Incubation of rat pheochromocytoma PC12 cells with dibutyryl cyclic AMP or 56 mM K+ is associated with increased activity and enhanced phosphorylation of tyrosine hydroxylase in situ. Following incubation of the PC12 cells with 32Pi, rapid isolation of the tyrosine hydroxylase, and tryptic digestion of the enzyme, two distinct 32P-peptides can be identified after paper electrophoresis. 56 mM K+ increases 32Pi incorporation into both of these peptides, whereas dibutyryl cyclic AMP increases 32Pi incorporation into only one of these peptides. The rate of increase in the incorporation of 32Pi into these two peptides in cells treated with 56 mM K+ is similar. The phosphorylation of tyrosine hydroxylase in PC12 cells occurs exclusively on serine residues. These results suggest that tyrosine hydroxylase in PC12 cells is phosphorylated on serine residues at two or more distinct sites after 56 mM K+ -induced depolarization. Since only one of these sites is phosphorylated by cyclic AMP-dependent protein kinase, activation of tyrosine hydroxylase by 56 mM K+ may involve phosphorylation by multiple protein kinases in rat pheochromocytoma PC12 cells.     

Twice daily versus four times daily insulin dose regimens for diabetes in pregnancy: randomised controlled trial

ObjectiveTo compare perinatal outcome and glycaemic control in two groups of pregnant diabetic patients receiving two insulin regimens.DesignRandomised controlled open label study.SettingUniversity affiliated hospital, Israel.Participants138 patients with gestational diabetes mellitus and 58 patients with pregestational diabetes mellitus received insulin four times daily, and 136 patients with gestational diabetes and 60 patients with pregestational diabetes received insulin twice daily.InterventionThree doses of regular insulin before meals and an intermediate insulin dose before bedtime (four times daily regimen), and a combination of regular and intermediate insulin in the morning and evening (twice daily regimen).ResultsMean daily insulin concentration before birth was higher in the women receiving insulin four times daily compared with twice daily: by 22 units (95% confidence interval 12 to 32) in patients with gestational diabetes and by 28 units (15 to 41) in patients with pregestational diabetes. Glycaemic control was better with the four times daily regimen than with the twice daily regimen: in patients with gestational diabetes mean blood glucose concentrations decreased by 0.19 mmol/l (0.13 to 0.25), HbA_1c by 0.3% (0.2% to 0.4%), and fructosamine by 41 μmol/l (37 to 45), and adequate glycaemic control (mean blood glucose concentration <5.8 mmol/l) was achieved in 17% (8% to 26%) more women; in patients with pregestational diabetes mean blood glucose concentration decreased by 0.44 mmol/l (0.28 to 0.60), HbA_1c by 0.5% (0.2% to 0.8%), and fructosamine by 51 μmol/l (45 to 57), and adequate glycaemic control was achieved in 31% (15% to 47%) more women. Maternal severe hypoglycaemic events, caesarean section, preterm birth, macrosomia, and low Apgar scores were similar in both dose groups. In women with gestational diabetes the four times daily regimen resulted in a lower rate of overall neonatal morbidity than the twice daily regimen (relative risk 0.59, 0.38 to 0.92), and the relative risk for hyperbilirubinaemia and hypoglycaemia was lower (0.51, 0.29 to 0.91 and 0.12, 0.02 to 0.97 respectively). The relative risk of hypoglycaemia in newborn infants to mothers with pregestational diabetes was 0.17 (0.04 to 0.74).ConclusionsGiving insulin four times rather than twice daily in pregnancy improved glycaemic control and perinatal outcome without further risking the mother.

Key messages

• Improving maternal glycaemic control during pregnancy is the key to better perinatal outcome
• In pregnant diabetic women insulin four times daily achieved better glycaemic control and lower rate of perinatal complications (hypoglycaemia, hyperbilirubinaemia) than insulin twice daily
• Better glycaemic control resulted from a larger total daily insulin dose
• The intensified regimen did not lead to higher rate of severe maternal hypoglycaemia

     

Discovery and optimization of 3-(4-aryl/heteroarylsulfonyl)piperazin-1-yl)-6-(piperidin-1-yl)pyridazines as novel,CNS penetrant pan-muscarinic antagonists

This letter describes the synthesis and structure activity relationship (SAR) studies of structurally novel M₄ antagonists, based on a 3-(4-aryl/heteroarylsulfonyl)piperazin-1-yl)-6-(piperidin-1-yl)pyridazine core, identified from a high-throughput screening campaign. A multi-dimensional optimization effort enhanced potency at human M₄ (hM₄ IC₅₀s < 200 nM), with only moderate species differences noted, and with enantioselective inhibition. Moreover, CNS penetration proved attractive for this series (rat brain:plasma K_p = 2.1, K_p,uu = 1.1). Despite the absence of the prototypical mAChR antagonist basic or quaternary amine moiety, this series displayed pan-muscarinic antagonist activity across M_1-5 (with 9- to 16-fold functional selectivity at best). This series further expands the chemical diversity of mAChR antagonists.