Effects of exogenous guanosine on chromatophore differentiation in the axolotl

Guanosine is shown to dramatically alter the pigment phenotype of axolotls by suppressing melanization and enhancing the biosynthesis and deposition of purine-derived pigments. Phenotypic changes caused by guanosine are manifested by altered chromatophore differentiation patterns such that few black pigment cells (melanophores) differentiate (and those that do are punctate and necrotic in appearance), whereas the development of yellow (xanthophore) and reflecting (iridophore) pigment cells is enhanced. Mechanisms for changes in chromatophore differentiation, and thus pattern formation, are discussed, including the possibility that pigment cells may undergo transdifferentiation in vivo.     

Immunomagnetic separation as a final purification step of liver endothelial cells

Summary We describe a fast and reproducible method that can be used as a final step in obtaining pure populations of liver endothelial cells. This method employs endothelial cell specific lectin covalently bound to magnetic polystyrene beads (Dynabeads). Evonymus europaeus agglutinin (EEA)-coated Dynabeads were used to purify monkey liver endothelium from Percoll gradient separated nonparenchymal cells. EEA-coated beads were also successfully used to purify monkey aortic endothelial cells. The endothelial cells grew to confluence as a cobblestonelike monolayer, expressed Factor VIII related antigen, and incorporated acetylated-low density lipoprotein. The magnetic beads seemed not to modify the normal properties of the isolated endothelium, thus facilitating their use in experimental studies. This immunomagnetic separation technique may be applicable for purification of endothelial cells from a wide variety of tissue sources.     

Association of Variants at UMOD with Chronic Kidney Disease and Kidney Stones—Role of Age and Comorbid Diseases

Chronic kidney disease (CKD) is a worldwide public health problem that is associated with substantial morbidity and mortality. To search for sequence variants that associate with CKD, we conducted a genome-wide association study (GWAS) that included a total of 3,203 Icelandic cases and 38,782 controls. We observed an association between CKD and a variant with 80% population frequency, rs4293393-T, positioned next to the UMOD gene (GeneID: 7369) on chromosome 16p12 (OR = 1.25, P = 4.1×10⁻¹⁰). This gene encodes uromodulin (Tamm-Horsfall protein), the most abundant protein in mammalian urine. The variant also associates significantly with serum creatinine concentration (SCr) in Icelandic subjects (N = 24,635, P = 1.3×10⁻²³) but not in a smaller set of healthy Dutch controls (N = 1,819, P = 0.39). Our findings validate the association between the UMOD variant and both CKD and SCr recently discovered in a large GWAS. In the Icelandic dataset, we demonstrate that the effect on SCr increases substantially with both age (P = 3.0×10⁻¹⁷) and number of comorbid diseases (P = 0.008). The association with CKD is also stronger in the older age groups. These results suggest that the UMOD variant may influence the adaptation of the kidney to age-related risk factors of kidney disease such as hypertension and diabetes. The variant also associates with serum urea (P = 1.0×10⁻⁶), uric acid (P = 0.0064), and suggestively with gout. In contrast to CKD, the UMOD variant confers protection against kidney stones when studied in 3,617 Icelandic and Dutch kidney stone cases and 43,201 controls (OR = 0.88, P = 5.7×10⁻⁵).     

A Statistical Approach to Identify Ancient Template DNA

One of the key problems in the study of ancient DNA is that of authenticating sequences obtained from PCR amplifications of highly degraded samples. Contamination of ancient samples and postmortem damage to endogenous DNA templates are the major obstacles facing researchers in this task. In particular, the authentication of sequences obtained from ancient human remains is thought by many to be rather challenging. We propose a novel approach, based on the c statistic, that can be employed to help identify the sequence motif of an endogenous template, based on a sample of sequences that reflect the nucleotide composition of individual template molecules obtained from ancient tissues (such as cloned products from a PCR amplification). The c statistic exploits as information the most common form of postmortem damage observed among clone sequences in ancient DNA studies, namely, lesion-induced substitutions caused by cytosine deamination events. Analyses of simulated sets of templates with miscoding lesions and real sets of clone sequences from the literature indicate that the c-based approach is highly effective in identifying endogenous sequence motifs, even when they are not present among the sampled clones. The proposed approach is likely to be of general use to researchers working with DNA from ancient tissues, particularly from human remains, where authentication of results has been most challenging. [Reviewing Editor: Dr. Magnus Nordborg]     

How inaccuracies in protein structure models affect estimates of protein-ligand interactions: computational analysis of HIV-I protease inhibitor binding

The influence of possible inaccuracies that can arise during homology modeling of protein structures used for ligand binding studies were investigated with the molecular mechanics generalized Born surface area (MM-GBSA) method. For this, a family of well-characterized HIV-I protease-inhibitor complexes was used. Validation of MM-GBSA led to a correlation coefficient ranging from 0.72 to 0.93 between calculated and experimental binding free energies DeltaG. All calculated DeltaG values were based on molecular dynamics simulations with explicit solvent. Errors introduced into the protein structure through misplacement of side-chains during rotamer modeling led to a correlation coefficient between DeltaG(calc) and DeltaG(exp) of 0.75 compared with 0.90 for the correctly placed side chains. This is in contrast to homology models for members of the retroviral protease family with template structures ranging in sequence identity between 32% and 51%. For these protein models, the correlation coefficients vary between 0.84 and 0.87, which is considerably closer to the original protein (0.90). It is concluded that HIV-I low sequence identity with the template structure still allows creating sufficiently reliable homology models to be used for ligand-binding studies, although placement of the rotamers is a critical step during the modeling.     

The Oncoprotein E2A-Pbx1a Collaborates with Hoxa9 To Acutely Transform Primary Bone Marrow Cells

A recurrent translocation between chromosome 1 (Pbx1) and 19 (E2A) leading to the expression of the E2A-Pbx1 fusion oncoprotein occurs in approximately 5 to 10% of acute leukemias in humans. It has been proposed that some of the oncogenic potential of E2A-Pbx1 could be mediated through heterocomplex formation with Hox proteins, which are also involved in human and mouse leukemias. To directly test this possibility, mouse bone marrow cells were engineered by retroviral gene transfer to overexpress E2A-Pbx1a together with Hoxa9. The results obtained demonstrated a strong synergistic interaction between E2A-Pbx1a and Hoxa9 in inducing growth factor-independent proliferation of transduced bone marrow cells in vitro and leukemic growth in vivo in only 39 +/- 2 days. The leukemic blasts which coexpress E2A-Pbx1a and Hoxa9 showed little differentiation and produced cytokines such as interleukin-3, granulocyte colony-stimulating factor, and Steel. Together, these studies demonstrate that the Hoxa9 and E2A-Pbx1a gene products collaborate to produce a highly aggressive acute leukemic disease.     

Alterations in endothelial cell proteinase and inhibitor polarized secretion following treatment with interleukin-1, phorbol ester,and human melanoma cell conditioned medium

Polarized secretion of matrix metalloproteinases and plasminogen activators by monkey aortic endothelial cells was studied in vitro, using transwell inserts. The endothelial cells constitutively expressed matrix metalloproteinase-2, tissue inhibitors of metalloproteinases 1 and 2, urokinase, and tissue plasminogen activator, all with basal preference. Matrix metalloproteinase-9 activity was induced by phorbol 12-myristate 13-acetate (apical), interleukin-1α (basal), and by conditioned medium from DX3 human melanoma cells (basal). The DX3 melanoma conditioned medium also stimulated basal secretion of matrix metalloproteinase-2, urokinase, tissue plasminogen activator, and tissue inhibitors of metalloproteinases. The rise in proteolytic activity in the basal direction was reflected by increased capacity to degrade subendothelial basement membrane type IV collagen, shown immunohistologically, using monkey kidney tissue sections and basement membrane deposited by endothelial cells into the transwell membrane. Thus, IL-1α and DX3 melanoma conditioned medium can stimulate endothelial cells in vitro to concentrate secretion of proteinases spatially onto the underlying basement membrane. We suggest that the stimulation of endothelial cell proteinase activity by tumor cells may facilitate tumor cell extravasation. © 1996 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Psychotic Illness in First-Time Mothers with No Previous Psychiatric Hospitalizations: A Population-Based Study

Background

Psychotic illness following childbirth is a relatively rare but severe condition with unexplained etiology. The aim of this study was to investigate the impact of maternal background characteristics and obstetric factors on the risk of postpartum psychosis, specifically among mothers with no previous psychiatric hospitalizations.

Methods and Findings

We investigated incidence rates and potential maternal and obstetric risk factors of psychoses after childbirth in a national cohort of women who were first-time mothers from 1983 through 2000 (n = 745,596). Proportional hazard regression models were used to estimate relative risks of psychoses during and after the first 90 d postpartum, among mothers without any previous psychiatric hospitalization and among all mothers. Within 90 d after delivery, 892 women (1.2 per 1,000 births; 4.84 per 1,000 person-years) were hospitalized due to psychoses and 436 of these (0.6 per 1,000 births; 2.38 per 1,000 person-years) had not previously been hospitalized for any psychiatric disorder. During follow-up after the 90 d postpartum period, the corresponding incidence rates per 1,000 person-years were reduced to 0.65 for all women and 0.49 for women not previously hospitalized. During (but not after) the first 90 d postpartum the risk of psychoses among women without any previous psychiatric hospitalization was independently affected by: maternal age (35 y or older versus 19 y or younger; hazard ratio 2.4, 95% confidence interval [CI] 1.2 to 4.7); high birth weight (≥ 4,500 g; hazard ratio 0.3, 95% CI 0.1 to 1.0); and diabetes (hazard ratio 0).

Conclusions

The incidence of psychotic illness peaks immediately following a first childbirth, and almost 50% of the cases are women without any previous psychiatric hospitalization. High maternal age increases the risk while diabetes and high birth weight are associated with reduced risk of first-onset psychoses, distinctly during the postpartum period.     

Abdominal aortic aneurysm is associated with a variant in low-density lipoprotein receptor-related protein 1

Abdominal aortic aneurysm (AAA) is a common cause of morbidity and mortality and has a significant heritability. We carried out a genome-wide association discovery study of 1866 patients with AAA and 5435 controls and replication of promising signals (lead SNP with a p value < 1 × 10⁻⁵) in 2871 additional cases and 32,687 controls and performed further follow-up in 1491 AAA and 11,060 controls. In the discovery study, nine loci demonstrated association with AAA (p < 1 × 10⁻⁵). In the replication sample, the lead SNP at one of these loci, rs1466535, located within intron 1 of low-density-lipoprotein receptor-related protein 1 (LRP1) demonstrated significant association (p = 0.0042). We confirmed the association of rs1466535 and AAA in our follow-up study (p = 0.035). In a combined analysis (6228 AAA and 49182 controls), rs1466535 had a consistent effect size and direction in all sample sets (combined p = 4.52 × 10⁻¹⁰, odds ratio 1.15 [1.10–1.21]). No associations were seen for either rs1466535 or the 12q13.3 locus in independent association studies of coronary artery disease, blood pressure, diabetes, or hyperlipidaemia, suggesting that this locus is specific to AAA. Gene-expression studies demonstrated a trend toward increased LRP1 expression for the rs1466535 CC genotype in arterial tissues; there was a significant (p = 0.029) 1.19-fold (1.04–1.36) increase in LRP1 expression in CC homozygotes compared to TT homozygotes in aortic adventitia. Functional studies demonstrated that rs1466535 might alter a SREBP-1 binding site and influence enhancer activity at the locus. In conclusion, this study has identified a biologically plausible genetic variant associated specifically with AAA, and we suggest that this variant has a possible functional role in LRP1 expression.