Passive Mechanical Forces Control Cell-Shape Change during Drosophila Ventral Furrow Formation

During Drosophila gastrulation, the ventral mesodermal cells constrict their apices, undergo a series of coordinated cell-shape changes to form a ventral furrow (VF) and are subsequently internalized. Although it has been well documented that apical constriction is necessary for VF formation, the mechanism by which apical constriction transmits forces throughout the bulk tissue of the cell remains poorly understood. In this work, we develop a computational vertex model to investigate the role of the passive mechanical properties of the cellular blastoderm during gastrulation. We introduce to our knowledge novel data that confirm that the volume of apically constricting cells is conserved throughout the entire course of invagination. We show that maintenance of this constant volume is sufficient to generate invagination as a passive response to apical constriction when it is combined with region-specific elasticities in the membranes surrounding individual cells. We find that the specific sequence of cell-shape changes during VF formation is critically controlled by the stiffness of the lateral and basal membrane surfaces. In particular, our model demonstrates that a transition in basal rigidity is sufficient to drive VF formation along the same sequence of cell-shape change that we observed in the actual embryo, with no active force generation required other than apical constriction.     

Molecular phylogeny of Neotropical bioluminescent beetles (Coleoptera: Elateroidea) in southern and central Brazil

Bioluminescence in beetles is found mainly in the Elateroidea superfamily (Elateridae, Lampyridae and Phengodidae). The Neotropical region accounts for the richest diversity of bioluminescent species in the world with about 500 described species, most occurring in the Amazon, Atlantic rainforest and Cerrado (savanna) ecosystems in Brazil. The origin and evolution of bioluminescence, as well as the taxonomic status of several Neotropical taxa in these families remains unclear. In order to contribute to a better understanding of the phylogeny and evolution of bioluminescent Elateroidea we sequenced and analyzed sequences of mitochondrial NADH2 and the nuclear 28S genes and of the cloned luciferase sequences of Brazilian species belonging to the following genera: (Lampyridae) Macrolampis, Photuris, Amydetes, Bicellonycha, Aspisoma, Lucidota, Cratomorphus; (Elateridae) Conoderus, Pyrophorus, Hapsodrilus, Pyrearinus, Fulgeochlizus; and (Phengodidae) Pseudophengodes, Phrixothrix, Euryopa and Brasilocerus. Our study supports a closer phylogenetic relationship between Elateridae and Phengodidae as other molecular studies, in contrast with previous morphologic and molecular studies that clustered Lampyridae/Phengodidae. Molecular data also supported division of the Phengodinae subfamily into the tribes Phengodini and Mastinocerini. The position of the genus Amydetes supports the status of the Amydetinae as a subfamily. The genus Euryopa is included in the Mastinocerini tribe within the Phengodinae/Phengodidae. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,characterization, and molecular structure of a gallium(III) complex of an amine-phenol ligand with activity against chloroquine-sensitive Plasmodium falciparum strains

Emergence of chloroquine-resistant Plasmodium falciparum strains necessitates discovery of novel antimalarial drugs, especially if the agents can be synthesized from commercially available, inexpensive precursors via short synthetic routes. While exploring structure-activity relationships, we found a gallium(III) complex, [(1,12-bis(2-hydroxy-5-methoxybenzyl)-1,5,8,12-tetraazadodecane)-gallium(III)](+) [Ga-5-Madd](+), 1, that possessed antimalarial efficacy. Like previously reported complexes, the crystal structure of 1 revealed gallium(III) in a symmetrical octahedral environment surrounded by four secondary amine nitrogen atoms in equatorial plane and two axial oxygen atoms. In contrast to a previously reported complex, [Ga-3-Madd](+), this novel metallo-antimalarial 1 possessed modest efficacy against chloroquine-sensitive HB3 Plasmodium lines. Thus, slight variation in the positions of methoxy functionalities on the aromatic rings of the organic scaffold dramatically altered specificity thereby suggesting a targeted (e.g., transporter- or receptor-mediated) rather than non-specific (e.g., pH or other gradient-mediated) mechanism of action for these agents.     

Efficiency of body conduction of underwater sounds in the bottlenose dolphin

Hearing thresholds of the Black Sea bottlenose dolphin Tursiops truncatus for tonal and composite underwater sounds within 50 kHz were ascertained in fully or partly submerged (head out of water) animals (trained by operant conditioning with food reinforcement). Perception of sounds conducted through the body deteriorated in all cases (thresholds for 75%-correct response rose typically by 6-24 dB); the least changes were observed for 10 and 20 kHz tones. The aggregate data also suggested significant individual variations.     

Biology of peripheral blood cells in obstructive sleep apnea--the tip of the iceberg

Obstructive sleep apnea (OSA), a highly prevalent breathing disorder in sleep, characterized by intermittent and recurrent pauses in respiration, has emerged as an independent risk factor for cardiovascular morbidity and mortality. Accumulated evidence implicates Leukocyte-endothelial cell activation and adhesion as critical components that induce inflammation and injury to the vasculature resulting in the development of cardiovascular complications. Similar cellular interactions were described in conditions of ischemia/reperfusion, and various components of the metabolic syndrome as hypercholesterolemia and hypertension. The hallmark of sleep apnea--the multiple cycles of hypoxia/reoxygenation--promote oxidative stress and inflammation. These facilitate increased interactions of blood cells with endothelial cells, resulting in endothelial cell injury and dysfunction. Such events can promote atherosclerosis and the development of cardiovascular morbidities in OSA. However, inter-individual differences in response to intermittent hypoxia and activation of anti-inflammatory cytokine profiles in T lymphocytes can serve as protective mechanisms.     

Recombinant human erythropoietin with additional processable protein domains: Purification of protein synthesized in <Emphasis Type="Italic">Escherichia coli</Emphasis> heterologous expression system

Three variants of human recombinant erythropoietin (rhEPO) with additional N-terminal protein domains were obtained by synthesis in an Escherichia coli heterologous expression system. These domains included (i) maltose-binding protein (MBP), (ii) MBP with six histidine residues (6His) in N-terminal position, (iii) s-tag (15-a.a. oligopeptide derived from bovine pancreatic ribonuclease A) with N-terminal 6His. Both variants of the chimeric protein containing MBP domain were prone to aggregation under nondenaturing conditions, and further purification of EPO after the domain cleavage by enterokinase proved to be impossible. In the case of 6His-s-tag-EPO chimeric protein, the products obtained after cleavage with enterokinase were successfully separated by column chromatography, and rhEPO without additional domains was obtained. Results of MALDI-TOF mass spectrometry showed that after refolding 6His-s-tag-EPO formed a structure similar to that of one of native EPO with two disulfide bonds. Both 6His-s-tag-EPO and rhEPO without additional protein domains purified after proteolysis possessed the same biological activity in vitro in the cell culture.     

Results of molecular genetic testing in Russian patients with Pendred syndrome and allelic disorders

Pendred syndrome is an autosomal recessive inherited disorder characterized by a combination of sensorineural hearing impairment and euthyroid goiter; its clinical manifestation in children is hardly distinguishable from nonsyndromic hearing loss. Pendred syndrome is one of the most frequent types of syndromic hearing loss. Hearing impairment is accompanied by abnormal development of the bony labyrinth—enlarged vestibular aqueduct (EVA) and occasionally combined with Mondini dysplasia. Mutations in the SLC26A4 gene, which encodes the pendrin protein, are responsible for both Pendred syndrome and for allelic disorder (nonsyndromic enlarged vestibular aqueduct). The present study for the first time conducted molecular genetic analysis in 20 Russian patients with Pendred syndrome, EVA and/or Mondini dysplasia. As a result, six pathogenic mutations in the SLC26A4 gene were revealed in four patients. The mutation c.222G>T (p.Trp74Cys) was detected for the first time. Mutations were found in patients with Pendred syndrome and nonsyndromic EVA with or without Mondini dysplasia. Mutations were not detected in patients with isolated Mondini dysplasia. One proband with clinical diagnosis Pendred syndrome was homozygous for the c.35delG mutation in the GJB2 gene. The absence of frequent mutations, including well-known ones or “hot” exons in the SLC26A4 gene, was reported. Therefore, the optimal method to search for mutations in the SLC26A4 gene in Russian patients is Sanger sequencing of all exons and exon-intron boundaries in the SLC26A4 gene.     

Genotyping of patients with phenylketonuria from different regions of Russia for determining BH4 responsiveness

To date, the efficacy of the phenylalanine hydroxylase (PAH) cofactor is proved for the treatment of both BH4-dependent hyperphenylalaninemia and phenylketonuria patients with mutations in the PAH gene. Since the patient’s response depends on the presence of residual PAH enzyme activity, it is advisable to search for mutations in the PAH gene to identify the potential responders and nonresponders to therapy. Four hundred thirty-five phenylketonuria patients from 13 regions of the Russian Federation were genotyped in order to identify responders and nonresponders to tetrahydrobiopterin (BH4) therapy. According to the results of this study, the number of probable nonresponders to the BH4 treatment exceeds 50% owing to a higher overall allelic frequency of “severe” PAH gene mutations. Responder patients with two “mild” mutations in the PAH gene were identified (1.6%).     

Substrate Specificity of Thymidine Phosphorylase of E. Coli: Role of Hydroxyl Groups

Substrate specificity of E. coli thymidine phosphorylase to pyrimidine nucleoside modified at 5 ′-, 3 ′-, and 2 ′-positions of sugar moiety has been studied. Equilibrium (K_eq) and kinetics constants of phosphorolysis reaction of nucleosides were measured. The most important hydrogen bonds in enzyme-substrate complex have been determined.