The mesopneumonia and the post-hepatic septum of the Teiioidea (Reptilia: Squamata)

Klein, W., Böhme, W. and Perry, S. F. 2000. The mesopneumonia and the post‐hepatic septum of the Teiioidea (Reptilia: Squamata). —Acta Zoologica (Stockholm) 81 : 109–119 This study investigates the structure of the pleuroperitoneal cavity of Teiioidea. Seven of nine genera of Teiidae and eight of 35 genera of Gymnophthalmidae were dissected and the results are presented in a highly schematic two‐dimensional representation. The main anatomical differences between the two families are (1) the presence of a hepatic ligament which fuses with the pericardiaco‐peritoneal septum in the Gymnophthalmidae but not in the Teiidae; (2) the presence of a ventral mesopneumonium on the right side in the Gymnophthalmidae, while this structure is secondarily lacking in the Teiidae; (3) that the post‐hepatic septum of Teiidae consists of a bipartite hepatic ligament and the ventral mesentery, while in gymnophthalmids the hepatic ligament remains undivided. Neusticurus and Echinosaura completely lack a post‐hepatic septum. The results are consistent with the hypothesis that the Gymnophthalmidae are primitive within the Teiioidea and that the Tupinambinae are the most highly derived teiids. We propose that the post‐hepatic septum may restrict passive visceral movement during breathing, thereby increasing the efficiency of respiratory effort; a modification that could benefit the fitness of active, predatory teiids.     

Interaction of RecBCD Enzyme with DNA at Double-Strand Breaks Produced in UV-Irradiated Escherichia coli: Requirement for DNA End Processing

The RecBCD enzyme has a powerful duplex DNA exonuclease activity in vivo. We found that this activity decreased strongly when cells were irradiated with UV light (135 J/m²). The activity decrease was seen by an increase in survival of phage T4 2⁻ of about 200-fold (phage T4 2⁻ has defective duplex DNA end-protecting gene 2 protein). The activity decrease depended on excision repair proficiency of the cells and a postirradiation incubation. During this time, chromosome fragmentation occurred as demonstrated by pulsed-field gel electrophoresis. In accord with previous observations, it was concluded that the RecBCD enzyme is silenced during interaction with duplex DNA fragments containing Chi nucleotide sequences. The silencing was suppressed by induction or permanent derepression of the SOS system or by the overproduction of single-strand DNA binding protein (from a plasmid with ssb⁺) which is known to inhibit degradation of chromosomal DNA by cellular DNases. Further, mutations in xonA, recJ, and sbcCD, particularly in the recJ sbcCD and xonA recJ sbcCD combinations, impeded RecBCD silencing. The findings suggest that the DNA fragments had single-stranded tails of a length which prevents loading of RecBCD. It is concluded that in wild-type cells the tails are effectively removed by single-strand-specific DNases including exonuclease I, RecJ DNase, and SbcCD DNase. By this, tailed DNA ends are processed to entry sites for RecBCD. It is proposed that end blunting functions to direct DNA ends into the RecABCD pathway. This pathway specifically activates Chi-containing regions for recombination and recombinational repair.     

Synthesis of highly potent and selective hetaryl ureas as integrin alpha(V)beta3-receptor antagonists

Solid-phase synthesis and SAR of integrin alpha(V)beta3-receptor antagonists containing a urea moiety as non-basic guanidine mimetic are described. The most potent compounds exhibited IC(50) values towards alpha(V)beta3 in the nanomolar range and high selectivity versus related integrins like alpha(IIb)beta3. For selected examples efficacy in functional cellular assays is demonstrated.     

Somatic embryogenesis from pea embryos and shoot apices

Conditions were defined for plant regeneration via somatic embryogenesis in pea, using explants from immature zygotic embryos or from shoot apices. For the induction of somatic embryos, an auxin (picloram or 2,4-dichlorophenoxyacetic acid) was required. Embryogenic callus originated from embryonic axis tissue of immature embryos and from the axillary-bud region and the plumula of shoot apices. A clear effect of embryo size on somatic embryogenesis was shown. There were differences in frequency of somatic embryogenesis among the five genotypes used in the study. Additions of BA to auxin-containing medium reduced embryo production. Histological examinations confirmed the embryogenic nature of the immature embryo cultures and revealed that somatic embryos originated from the meristematic areas near the callus surface.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid     

Ultrastructure of the Genital Organs in the Interstitial Syllid Petitia amphophthalma (Annelida,Polychaeta)

Abstract The gonochoristic syllid Petitia amphophthalma is one of the truly interstitial polychaetes. P. amphophthalma does not show any epitokous modifications at maturity such as those that usually occur in syllids. The reproductive structures are unique: the male genital organs consist of a seminal vesicle in chaetigers 6–10, subdivided into a dorsal part tightly filled with spermatozoa and a ventral part with contents in different stages of spermatogenesis, one pair of sperm ducts and conspicuous gland cells situated in chaetigers 10 and 11. Their glandular secretions are discharged into the sperm duct together with those of other types of gland cells that form the duct. The oocytes develop freely within the body cavity of the females. Each of the fertile segments possesses a paired oviduct ending in a large ciliated funnel. Sperm ducts and oviducts are probably modifications of excretory organs; nephridia are absent in segments where gonoducts occur. A direct sperm transfer by lytic opening of the integument of the female and internal fertilization are inferred. Copyright © 1996 Published by Elsevier Science Ltd on behalf of the Royal Swedish Academy of Sciences     

Coaggregation of RNA-binding proteins in a model of TDP-43 proteinopathy with selective RGG motif methylation and a role for RRM1 ubiquitination

TAR DNA-binding protein 43 (TDP-43) is a major component within ubiquitin-positive inclusions of a number of neurodegenerative diseases that increasingly are considered as TDP-43 proteinopathies. Identities of other inclusion proteins associated with TDP-43 aggregation remain poorly defined. In this study, we identify and quantitate 35 co-aggregating proteins in the detergent-resistant fraction of HEK-293 cells in which TDP-43 or a particularly aggregate prone variant, TDP-S6, were enriched following overexpression, using stable isotope-labeled (SILAC) internal standards and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). We also searched for differential post-translational modification (PTM) sites of ubiquitination. Four sites of ubiquitin conjugation to TDP-43 or TDP-S6 were confirmed by dialkylated GST-TDP-43 external reference peptides, occurring on or near RNA binding motif (RRM) 1. RRM-containing proteins co-enriched in cytoplasmic granular structures in HEK-293 cells and primary motor neurons with insoluble TDP-S6, including cytoplasmic stress granule associated proteins G3BP, PABPC1, and eIF4A1. Proteomic evidence for TDP-43 co-aggregation with paraspeckle markers RBM14, PSF and NonO was also validated by western blot and by immunocytochemistry in HEK-293 cells. An increase in peptides from methylated arginine-glycine-glycine (RGG) RNA-binding motifs of FUS/TLS and hnRNPs was found in the detergent-insoluble fraction of TDP-overexpressing cells. Finally, TDP-43 and TDP-S6 detergent-insoluble species were reduced by mutagenesis of the identified ubiquitination sites, even following oxidative or proteolytic stress. Together, these findings define some of the aggregation partners of TDP-43, and suggest that TDP-43 ubiquitination influences TDP-43 oligomerization.     

The Strawberry Pathogenesis-related 10 (PR-10) Fra a Proteins Control Flavonoid Biosynthesis by Binding to Metabolic Intermediates

Pathogenesis-related 10 (PR-10) proteins are involved in many aspects of plant biology but their molecular function is still unclear. They are related by sequence and structural homology to mammalian lipid transport and plant abscisic acid receptor proteins and are predicted to have cavities for ligand binding. Recently, three new members of the PR-10 family, the Fra a proteins, have been identified in strawberry, where they are required for the activity of the flavonoid biosynthesis pathway, which is essential for the development of color and flavor in fruits. Here, we show that Fra a proteins bind natural flavonoids with different selectivity and affinities in the low μm range. The structural analysis of Fra a 1 E and a Fra a 3-catechin complex indicates that loops L3, L5, and L7 surrounding the ligand-binding cavity show significant flexibility in the apo forms but close over the ligand in the Fra a 3-catechin complex. Our findings provide mechanistic insight on the function of Fra a proteins and suggest that PR-10 proteins, which are widespread in plants, may play a role in the control of secondary metabolic pathways by binding to metabolic intermediates.