Blue guaran (a chromophore-labeled galactomannan) as a reagent for lectins

A new reagent (blue guaran) for quantitative estimation of lectins, has been derived from a galactomannan (guaran). When the lectin solution is added to an aqueous solution of blue guaran, dye-bound guaran is precipitated from the solution. The difference in absorbance of the blue guaran solution before and after the addition of lectin solution is proportional to the amount of lectin present in the sample. The method of preparation of blue guaran, its spectral characteristics and effect of pH on precipitation have also been described. It gives a simple colorimetric method for the estimation of galactose-specific lectins.     

Arterial segmentation in the goat (Capra hircus) spleen. A study by corrosion cast.

50 corrosion casts of the splenic artery and its tree were studied to observe the arterial segmentation in the goat spleen on the basis of the intrasplenic distribution. The following observations were made: (i) 74% showed the presence of two arterial segments, a right and a left one; (ii) 10% revealed three arterial segments, a hilar, a right and a left one, and (iii) 16% showed the absence of arterial segmentation in the goat spleen.     

Structural variability of C3larvin toxin. Intrinsic dynamics of the α/β fold of the C3-like group of mono-ADP-ribosyltransferase toxins

C3larvin toxin is a new member of the C3 class of the mono-ADP-ribosyltransferase toxin family. The C3 toxins are known to covalently modify small G-proteins, e.g. RhoA, impairing their function, and serving as virulence factors for an offending pathogen. A full-length X-ray structure of C3larvin (2.3 Å) revealed that the characteristic mixed α/β fold consists of a central β-core flanked by two helical regions. Topologically, the protein can be separated into N and C lobes, each formed by a β-sheet and an α-motif, and connected by exposed loops involved in the recognition, binding, and catalysis of the toxin/enzyme, i.e. the ADP-ribosylation turn–turn and phosphate–nicotinamide PN loops. Herein, we provide two new C3larvin X-ray structures and present a systematic study of the toxin dynamics by first analyzing the experimental variability of the X-ray data-set followed by contrasting those results with theoretical predictions based on Elastic Network Models (GNM and ANM). We identify residues that participate in the stability of the N-lobe, putative hinges at loop residues, and energy-favored deformation vectors compatible with conformational changes of the key loops and 3D-subdomains (N/C-lobes), among the X-ray structures. We analyze a larger ensemble of known C3bot1 conformations and conclude that the characteristic ‘crab-claw’ movement may be driven by the main intrinsic modes of motion. Finally, via computational simulations, we identify harmonic and anharmonic fluctuations that might define the C3larvin ‘native state.’ Implications for docking protocols are derived.     

Human Pluripotent Stem Cells Have a Novel Mismatch Repair-dependent Damage Response

Human pluripotent stem cells (PSCs) are presumed to have robust DNA repair pathways to ensure genome stability. PSCs likely need to protect against mutations that would otherwise be propagated throughout all tissues of the developing embryo. How these cells respond to genotoxic stress has only recently begun to be investigated. Although PSCs appear to respond to certain forms of damage more efficiently than somatic cells, some DNA damage response pathways such as the replication stress response may be lacking. Not all DNA repair pathways, including the DNA mismatch repair (MMR) pathway, have been well characterized in PSCs to date. MMR maintains genomic stability by repairing DNA polymerase errors. MMR is also involved in the induction of cell cycle arrest and apoptosis in response to certain exogenous DNA-damaging agents. Here, we examined MMR function in PSCs. We have demonstrated that PSCs contain a robust MMR pathway and are highly sensitive to DNA alkylation damage in an MMR-dependent manner. Interestingly, the nature of this alkylation response differs from that previously reported in somatic cell types. In somatic cells, a permanent G₂/M cell cycle arrest is induced in the second cell cycle after DNA damage. The PSCs, however, directly undergo apoptosis in the first cell cycle. This response reveals that PSCs rely on apoptotic cell death as an important defense to avoid mutation accumulation. Our results also suggest an alternative molecular mechanism by which the MMR pathway can induce a response to DNA damage that may have implications for tumorigenesis.     

Seasonal changes in the oviduct of the pied myna (Aves: Sturnidae)

Study of the oviduct of the pied myna (Sturnus contra contra) throughout the year reveals that oviductal weight, length, surface epithelial height and glycogen content are low during August to January (nonbreeding phase), partially increase during February to April (pre-breeding phase), maximally increase in May (breeding phase) and decrease in June and July (post-breeding phase). In the nesting cycle, there is greatest growth in all the regions of the oviduct from early nest-building to the egg-laying period and this is followed by rapid involution during incubation and nestling periods. Some notable features in the oviduct of the pied myna are described: 1) All five regions of the oviduct (infundibulum, magnum, isthmus, uterus, and vagina) are clearly distinguishable when studied from serial sections of the oviduct even during the nonbreeding phase of the annual ovarian cycle. 2) There is a strong correlation between initiation of tubular gland formation and the onset of nestbuilding activity. 3) The distal part of the magnum is differentiated into a 'mucous region' having well developed basal nonciliated cells. 4) A sixth zone can be identified between the magnum and isthmus. Sperm hostlike glands exist at the cranial end of the zone. 5) Several circular epithelial invaginations are evident in the intermucosal folds and their size decreases in centripetal order in the vagina. 6) The pattern and degree of regression are different in various regions of the oviduct. A close synchrony between ovarian and oviducal cycles is indicated in the pied myna (Sturnus contra contra).     

Reproductive performance of four aphidophagous ladybirds on cowpea aphid, Aphis craccivora Koch

Abstract:  This study investigated prey consumption, egg production, percent progeny loss, reproductive, pre- and post-reproductive periods, reproductive time ratio, reproductive rate and bioconversion efficiency of four aphidophagous ladybirds, viz. Cheilomenes sexmaculata (Fabricius), Coccinella septempunctata Linnaeus, Coccinella transversalis Fabricius and Propylea dissecta (Mulsant) on Dolichos lablab Linnaeus infested with cowpea aphid, Aphis craccivora Koch. C. sexmaculata had the highest bioconversion efficiency, reproductive rate and reproductive time ratio followed in rank order by P. dissecta , C. transversalis and C. septempunctata . This study indicates that C. sexmaculata has a narrow ecological relationship with A. craccivora . The increased allocation of resources to reproduction as indicated through a high reproductive time ratio and high bioconversion efficiency of C. sexmaculata and P. dissecta suggest that they may be better adapted to compete for this prey with larger species like C. transversalis and C. septempunctata .