Structural changes in the innercortex cells of soybean root nodules are induced by short-term exposure to high salt or oxygen concentrations

After a 2 h exposure of intact soybean nodules to high concentrations of NaCl (100mol m_?3) or oxygen (8OkPa O₂), morphometric computations carried out using an image analysis technique on semi-thin sections showed that both treatments induced a decrease in the area of the inner-cortex cells, which were then characterized by a tangential elongation. In contrast, no significant change in area occurred in the middle-cortex cells although their elongation decreased. Electron microscopic observations showed that in the inner-cortex cells changes included the presence of wall infoldings, an enlarged periplasmic space and a lobate nucleus whose chromatin distribution differed from that of the control. Structural changes also occurred in the endoplasmic reticulum, microbodies, mitochondria and plastids. From several of these changes, which are similar to those noted in osmocontractil cells in response to external stimuli, it can be hypothesized that the inner cortex may provide a potential mechanism for the control of oxygen diffusion through the nodules.     

Effect of externally added carnitine on the synthesis of acetylcholine in rat cerebral cortex cells

Acetylcholine synthesis from radiolabelled glucose was monitored in cerebral cortex cells isolated from brains of suckling and adult rats. Acetylcholine synthesis was found much higher in suckling animals, both in the absence and presence of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) inhibitor, paraoxon. Together with choline (20 μM), carnitine was found to stimulate acetylcholine synthesis in a synergistic way in cortex cells from adult rats (18%). Choline, however, was incapable of reversing an inhibitory effect exerted by carnitine on acetylcholine synthesis in cortex cells from suckling animals. Distribution of carnitine derivatives was found significantly different in the cells from young and old animals, the content of acetylcarnitine decreased with age with a corresponding increase of free carnitine. The observed differences in carnitine effect on acetylcholine synthesis suggested that high acetylcarnitine in cells capable of β-oxidation might be correlated with the lower level of acetylcholine synthesis.     

Discovery of isoquinolinone and naphthyridinone-based inhibitors of poly(ADP-ribose) polymerase-1 (PARP1) as anticancer agents: Structure activity relationship and preclinical characterization

The exploitation of GLU988 and LYS903 residues in PARP1 as targets to design isoquinolinone (I & II) and naphthyridinone (III) analogues is described. Compounds of structure I have good biochemical and cellular potency but suffered from inferior PK. Constraining the linear propylene linker of structure I into a cyclopentene ring (II) offered improved PK parameters, while maintaining potency for PARP1. Finally, to avoid potential issues that may arise from the presence of an anilinic moiety, the nitrogen substituent on the isoquinolinone ring was incorporated as part of the bicyclic ring. This afforded a naphthyridinone scaffold, as shown in structure III. Further optimization of naphthyridinone series led to identification of a novel and highly potent PARP1 inhibitor 34, which was further characterized as preclinical candidate molecule. Compound 34 is orally bioavailable and displayed favorable pharmacokinetic (PK) properties. Compound 34 demonstrated remarkable antitumor efficacy both as a single-agent as well as in combination with chemotherapeutic agents in the BRCA1 mutant MDA-MB-436 breast cancer xenograft model. Additionally, compound 34 also potentiated the effect of agents such as temozolomide in breast cancer, pancreatic cancer and Ewing’s sarcoma models.     

Oral water ingestion in the pulmonate freshwater snail,Lymnaea stagnalis

InLymnaea stagnalis, oral uptake of ambient medium was studied using⁵¹Cr-ethylenediaminetetra-acetic acid. In normal snails Cr-ethylenediaminetetra-acetic acid uptake showed two components: a high uptake rate within the first hour followed by moderate uptake proportional with time. The tracer accumulated mainly in the digestive system. All animals showed initial, transient uptake. Moderate uptake proportional with time did not occur in snails in which the buccal ganglia had been extirpated, in which both the buccal ganglia had been extirpated and the oesophagus was sectioned, or in snails provided with an oesophageal fistula. These snails did not accumulate tracer in the intestinal system. This type of tracer accumulation clearly represented oral ingestion of surrounding water. The oral water ingestion rate ranged from 8 to 12 μl·h⁻¹·g⁻¹. Assuming complete absorption, this accounts for 20–30% of the urine production rate. At low external concentrations the contribution of oral water ingestion to Na⁺ balance is negligible. However, its importance will grow with increasing external concentrations and becomes a major factor at higher concentrations. The ingestion rate increased almost sixfold when starving snails were allowed to feed. It is suggested that oral water ingestion is a consequence of making bite cycles and swallowing.     

Transferring sediment containing intact seed banks: a method for studying plant community ecology

The experimental study of the ecology of natural plant communities is necessary to demonstrate the effects of environmental factors on plant growth. It allows one to make predictions of the likely effects of environmental changes on plant communities. Manipulating an entire ecosystem is complicated, and is rarely attempted. An alternative method is applied here for the submerged plant communities of the seasonally-flooded oligohaline marshes of the Camargue. It consists of collecting undisturbed sediment samples with their contained intact seed bank, and submitting them to different salinities. The study of total biomass and of the biomass of the more frequent species was carried out using parametric tests. The precision of the results depended on the frequency of the species in the replicates. When the frequency was low, non-parametric statistics were necessary. The method seems to be particularly suitable for the study of communities of annual species in aquatic environments.

---

Résumé L'étude expérimentale de l'écologie des communautés naturelles de plantes est nécessaire pour démontrer les relations de cause à effet entre les facteurs environnementaux et l'abondance des plantes. Elle l'est également pour faire des prédictions réalistes sur les effets de modifications envisagées de l'environnement sur des communautés de plantes. La manipulation de l'écosystème complet est complexe, ce qui rend son utilisation rare. Une méthode alternative a été utilisée pour l'étude de la composition spécifique des communautés de plantes submergées des marais temporaires de Camargue. Elle consiste à prélever des échantillons non perturbés de sédiment, avec leur stock de semences intact, et à les soumettre à des conditions de salinité. L'étude de la biomasse totale et de la biomasse des espèces les plus fréquentes est faite au moyen de test paramétriques. La précision attendue des résultats dépend de la fréquence de l'espèce dans les réplicats. Lorsque la fréquence n'est pas élevée l'emploi de statistiques non paramétriques est indispensable. La méthode se révéle particulièrement bien adaptée à l'étude des communautés d'annuelles en milieu aquatique.

     

Purification and Some Properties of Nucleases from Shii-take,Lentinus edodes

Three kinds of nuclease preparations, each of which having both endonuclease activity that formed 5′-mononucleotides and 3′-nucleotidase activity, were separated and partially purified from Shii-take, Lentinus edodes. Both enzyme activities of each preparation showed a similar thermostability and electrophoretic mobility on Polyacrylamide gel, and a competitive relationship was observed between RNA and 3′-AMP in their enzyme reactions. From these results, it is concluded that both enzyme activities of these three preparations reside in a single protein, respectively. They resemble one another in substrate specificity, cleavage pattern of RNA and thermostability, but are distinguishable from one another by molecular weight, electrophoretic mobility and optimum pH for degradation of RNA.     

Membrane lipid composition and susceptibility to bile salt damage

Erythrocyte membranes with low sphingomyelin: choline-containing phospholipid ratios haemolyse at low concentrations of the bile salt, glycocholate. Erythrocytes with higher sphingomyelin: choline-containing phospholipid ratios require progessively greater concentrations of the bile salt for lysis.Sublytic concentrations of glycocholate remove phospholipid and acetylcholinesterase from the membranes. Membranes with low sphingomyelin: choline-containing phospholipid ratios lose both particulate (microvesicles of distinct composition) and ‘solubilized’ material, the particulate form predominating. The proportion of particulate material falls with increase of the membrane sphingomyelin: choline-containing phospholipid ratio and those membranes of highest sphingomyelin: choline-containing phospholipid ratio lose material predominantly in ‘solubilized’ form.Sheep erythrocytes treated to increase their content of phosphatidylcholine (and thereby reduce their membrane sphingomyelin: choline-containing phospholipid ratio) become more susceptible to lysis by glycocholate.These observations indicate a correlation between membrane lipid composition and the perturbation of membranes with bile salt; they also point to possible features of membranes capable of surviving exposure to the high bile salt concentrations of the biliary tract.     

Induction of unscheduled DNA synthesis by the carcinogen 7-bromomethylbenz(a)anthracene and its removal from the DNA of normal and xeroderma pigmentosum lymphocytes

The carcinogen 7-bromomethylbenz(a)anthracene (BBA), which can bind strongly to DNA, induces unscheduled DNA synthesis (DNA repair) in normal lymphocytes but almost none in lymphocytes from patients with Xeroderma pigmentosum (XP), and inherited disease known to be defective in excision repair of ultraviolet-damaged DNA. We studied [³H]BBA's ability to bind to DNA of normal and XP lymphocytes, its influence on unscheduled DNA synthesis, and its removal from the DNA of both cell types. We found that 20–30% of the BBA is bound to macromolecules other than DNA and that its binding to DNA is essentially complete after 30 min. The induction of unscheduled DNA synthesis by the carcinogen in XP lymphocytes was approximately 10% of that induced in normal lymphocytes. While 15–20% of the BBA was removed from the DNA of normal cells 6 h after treatment, only 1–2% was removed from the DNA of XP cells. Thus, XP cells not only are defective in repairing ultraviolet-damaged DNA and excising thymine dimers but also fail to repair DNA damaged by certain carcinogens, and, most importantly, fail to remove the DNA-bound carcinogen, BBA.     

Modeling productivity of a salt marsh

A model of primary productivity in a salt marsh is developed and compared to a regression analysis study of data showing dependence of growth on growing season, mean tidal height, and average monthly temperatures for several grass species.     

The stimulating effects of NaCl on root growth of Rhodes grass (Chloris gayana)

Rhodes grass ( Chloris gayana Kunth. cv. common) is a halophytic forage grass. Like most halophyles, its growth is positively affected by low levels of salinity but is inhibited by high salinity. However, such a definition is not clear and not unmistakable: NaCl concentrations which inhibit the growth of the whole plant stimulate the growth of single roots when applied to them individually.