Acétolyse d'une diazocétone derivée d'octose: synthése d'une N-acétyllincosamine protégée, de ses epiméres en c-6 et c-7, et d'une 3-oxétanone á chane latérale glucidique

The acetolysis with anhydrous acetic acid of the diazoketone 1, prepared from potassium 1,2:3,4-di-O-isopropylidene-α-D-galacturonate, gave ketoacetates having the D-glycero (3)and L-glycero (5)configuration at C-7, together with the 3-oxetanone 7, a product of pyranose-ring opening. Starting from the ketoacetates 3 and 5, the lincosamine derivative, 6-acetamido-6,8-dideoxy-1,2:,4-di-O-isopropylidene -α-D-erythro-D-galacto-octopyranose (8), and its three diastereoisomers at C-6 and C-7 (9, 10, and 11) were obtained by oximation, reduction, and N-acetylation.

Résumé

L'acétolyse par l'acide acétique anhydre de la diazocétone 1 dérivée du 1,2:3,4-di-O-isopropylidéne-α-D-galacturonate de potassium, donne les céto-acétates deconfiguration D-glycéro (3) et L-glycéro (5) sur C-7, ainsi que la 3-oxétanone 7 qui résulte de l'ouverture du cycle pyranosique. A partir des céto-acétates 3 et 5, on a obtenu, par oximation, réduction et N-acétylation, le dérivé de la lincosamine, 6-acétamido-6,8-didésoxy-1,2:3,4-di-O-isopropylidéne-α-D-érythro-D-galacto-octo-pyranose (8), et ses trois diastéréoisoméres en C-6 et C-7 (9, 10 et 11).     

Cartographie de restriction comparée de la séquence d''ADN hautement répétée coupée par Bam HI chez Papio papio et P. cynocephalus

Highly repeated DNA sequences from two baboon species (Papio papio and P. cynocephalus) have been compared using restriction endonucleases. The two species share a 343 base pairs tandemly repeated DNA, that is cut once by Bam HI. Papio cynocephalus differs from P. papio by loss of an EcoRI star site in the repeated sequence.     

Caractérisation de la membrane liée au chromosome replié isolé de Escherichia coli

Phospholipid analysis of the membranes associated with fast sedimenting folded chromosomes prepared by lysis of E. coli CR 34 shows that both inner and outer membranes are parts of the complex, in proportions not very different from that found in the whole bacteria.During the preparation of the folded chromosomes, the most recently synthesized molecules of phosphatidylglycerol and phosphatidylethanoamine are more sensitive to solubilisation, particularly those from the cytoplasmic membrane. Identification of a dominant fraction, the outer membrane, in some complexes, results from a preferential solubilization of the inner membrane.These results do not favor any specific association between the folded chromosome and the membranes.     

Productivité comparée des deux étangs situés à proximité du lac Saint-Jean,au Québec

The Comparative Productivity of Two Ponds in the Vicinity of Lake St-John, Québec In 1980 and 1981, the productivity of two ponds near Lake St. John were evaluated. One, the pond of Desbiens, did not communicate with Lake St. John and the other, the pond of St-Gédéon, was connected to the lake. The aim of this study was to evaluate the contribution that a pond could make to the increase in productivity of Lake St. John which is a reservoir. The pond of Desbiens is more productive than Lake St. John but two to three times less than the pond of St-Gédéon. The pond of Desbiens shows an advanced degree of eutrophication whereas the pond of St-Gédéon is similar to the northern lakes by its physico-chemistry, zooplankton, sediments and benthic fauna. If we want to create artificial ponds, for a better productivity of reservoirs, it is important that they be connected to each other.     

Biosynthèse de cellulose bactérienne à pertir de glycérol sélectivement deutérié en position 1, 2, ou 3: Etude par résonance magnétique nucléaire

Glycerol specifically deuterated at C-1, C-2, or C-3 was prepared and used for the biosynthesis of bacterial cellulose with Acetobacter xylinum.The material obtained were converted into glucitol hexaacetate and analyzed by 250-MHz nuclear magnetic resonance and mass spectrometry. The spectra indicated that the protons of the C-3 position of the starting glycerol were incorporated as substituents of the C-6 and C-1 positions of the cellulose. Similarly, protons of the C-2 and C-5 positions of the cellulose came essentially from water and the protons bonded at the C-3 and C-4 positions of the cellulose from protons bonded to C-1 of the starting glycerol.     

Composés glucidiques et azotés et résistance à la sécheresse chez Ailanthus altissima

In Ailanthus altissima, carbohydrate and protein reserves are mainly localized in the tap-root. Under drought stress they are very quickly hydrolysed. Despite the water deficiency, an increase in starch synthesis is observed in the leaves and stem during the first stages of stress. Stimulation of the cambial activity of the stems and an increase in protein content have also been observed. Chemical analyses have shown a high proline content which increases markedly following drought stress, especially in the tap-root.     

Adénylate-cyclase/Lipase: Induction des récepteurs hormonaux

An adenylate cyclase activity (AC) was found in guinea pig brown adipose tissue (BAT), since the tissue's apparition. This enzymatic activity increased during the development and showed high values at the end of gestation. An increase of AC units per cell was observed, in addition to the cell multiplication. A norepinephrine stimulation of AC activity was observed at the end of gestation: this regulating action disappeared in the first days of extrauterine life. Neither glucagon nor ACTH had any regulating role upon AC activity during fetal and newborn life. The basal lipolytic activity which was observed in BAT of fetuses (61rst day) and neonate dramatically decreased around the 15th day. A potent lipolysis activation by norepinephrine was observed, but only after birth. The correlation observed between these enzymatic activities in presence of norepinephrine seems to indicate that the AC/lipase system was involved in the neonatal thermogenesis of guinea pigs.     

APC/C-Cdh1

Anaphase-promoting complex/cyclosome (APC/C) is a multifunctional ubiquitin-protein ligase that targets various substrates for proteolysis inside and outside of cell cycle. The activation of APC/C is depended on two WD-40 domain proteins, Cdc20 and Cdh1. While APC/Cdc20 principally regulates mitotic progression, APC/Cdh1 shows a broad spectrum of substrates in and beyond cell cycle. In past several years, numerous biochemical and mouse genetic studies have greatly attracted our attention to the emerging role of APC/Cdh1 in genomic integrity, cellular differentiation and human diseases. This review will aim to summarize the recent expended understanding of APC/Cdh1 in regulating biological function and how its dysfunction may lead to diseases.     

Sur la stéréospécificité de la ribonucléoside-diphosphate-réductase: préparation de désoxyribonucléosides pyrimidiques deutérés

Methyl 2-deoxy-3,5,6-tri-O-p-nitrobenzoyl- -ribo-hexofuranoside was converted into the glycosyl halide which was then condensed with 2,4-bis(trimethylsilyloxy)-pyrimidine in the presence of mercuric chloride to give, after alkaline methanolysis, 1-(2-deoxy-β- -ribo-hexofuranosyl)uracil, in a yield too low for the reaction to be applied to deuterated compounds. Methyl 2-deoxy- -allofuranoside-2-d was degraded into methyl 2-deoxy- -arabinofuranoside-2-d. Its di-p-nitrobenzoate was converted into the glycosyl halide which was coupled with 2,4-bis(trimethylsilyloxy)-pyrimidine to give, after alkaline hydrolysis, deuterated deoxyuridine. Thiationammonolysis of a mixture of the 3′,5′-di-p-nitrobenzoates of the latter compound and its anomer gave the corresponding deoxycytidines. Comparison of the n.m.r. spectra of these compounds to that of deuterated deoxycytidine, prepared by the enzymic reduction of cytidine 5′-pyrophosphate with the Escherichia coli system in the presence of deuterium oxide confirmed that the substitution of a hydroxyl group by a hydrogen atom proceeds with retention of configuration.     

Cas9 Cuts and Consequences; Detecting,Predicting, and Mitigating CRISPR/Cas9 On- and Off-Target Damage

Large deletions and genomic re-arrangements are increasingly recognized as common products of double-strand break repair at Clustered Regularly Interspaced, Short Palindromic Repeats - CRISPR associated protein 9 (CRISPR/Cas9) on-target sites. Together with well-known off-target editing products from Cas9 target misrecognition, these are important limitations, that need to be addressed. Rigorous assessment of Cas9-editing is necessary to ensure validity of observed phenotypes in Cas9-edited cell-lines and model organisms. Here the mechanisms of Cas9 specificity, and strategies to assess and mitigate unwanted effects of Cas9 editing are reviewed; covering guide-RNA design, RNA modifications, Cas9 modifications, control of Cas9 activity; computational prediction for off-targets, and experimental methods for detecting Cas9 cleavage. Although recognition of the prevalence of on- and off-target effects of Cas9 editing has increased in recent years, broader uptake across the gene editing community will be important in determining the specificity of Cas9 across diverse applications and organisms.     

Étude ultrastructurale du cycle nucléolaire de Physarum polycephalum après mise en évidence préférentielle des RNP par la réaction régressive à l''EDTA

Nucleolar cycle in Physarum polycephalum was studied using EDTA preferential stain for RNP. We have been able to establish the following.

1. 1. The nucleolar remnants that are observed during mitosis correspond to the fibrillar zones of the interphase nucleolus.

2. 2. In prometaphase and metaphase the nucleolar remnants lie peripherically around the chromosomal mass with which they are only superficially associated.

3. 3. Preribosomal granules appear 10–15 min after metaphase in the prenucleolar bodies.

The results shown that the interphase nucleolus is an assembly of multiple subunits. The relationship between the nucleolar remnants and chromosomes is discussed in the light of the recent understanding of the extrachromosomal nature of rDNA.Le cycle nucléolaire de Physarum polycephalum a été étudié en microscopie électronique après réaction régressive à l'EDTA qui met préférentiellement en évidence les RNP. Nous avons suivi ainsi la dispersion du nucléole en prophase, le devenir des restes nucléolaires au cours de la métaphase et de la télophase, puis l'apparition des corps prénucléolaires en début d'interphase.