The HIV-1 Integrase Mutations Y143C/R Are an Alternative Pathway for Resistance to Raltegravir and Impact the Enzyme Functions

Resistance to HIV-1 integrase (IN) inhibitor raltegravir (RAL), is encoded by mutations in the IN region of the pol gene. The emergence of the N155H mutation was replaced by a pattern including the Y143R/C/H mutations in three patients with anti-HIV treatment failure. Cloning analysis of the IN gene showed an independent selection of the mutations at loci 155 and 143. Characterization of the phenotypic evolution showed that the switch from N155H to Y143C/R was linked to an increase in resistance to RAL. Wild-type (WT) IN and IN with mutations Y143C or Y143R were assayed in vitro in 3′end-processing, strand transfer and concerted integration assays. Activities of mutants were moderately impaired for 3′end-processing and severely affected for strand transfer. Concerted integration assay demonstrated a decrease in mutant activities using an uncleaved substrate. With 3′end-processing assay, IC₅₀ were 0.4 µM, 0.9 µM (FC = 2.25) and 1.2 µM (FC = 3) for WT, IN Y143C and IN Y143R, respectively. An FC of 2 was observed only for IN Y143R in the strand transfer assay. In concerted integration, integrases were less sensitive to RAL than in ST or 3′P but mutants were more resistant to RAL than WT.     

The Loss of Structural Integrity in Damaged Spruce Needles from Locations Exposed to Air Pollution I. Mesophyll and Central Cylinder

Abstract In connection with the new type of forest damage, the individual disease situation of two-year-old spruce ( Picea abies ) needles was analyzed histopathologically in forest areas exposed to different levels of O₃-, SO₂- and NO₃- pollution.
Early damage results from losses of chlorophyll in the mesophyll cells. The bleaching is more intensive towards the apex in severely damaged needles. The cytoplasm is aggregated at the cell wall and the chloroplasts show definite structural damage as well.
The mesophyll cells below the epidermis, or the cells adjacent to the vascular bundle sheath, appear to be particularly susceptible. Collapsed cells (bone cells), which increase in number with damage, can lead to tissue death in certain needle areas, (brown tips, transverse bands).
Necrotic spots are manifested as groups of dissociated cells in which hypertrophic and collapsed cells as well as abnormal proliferations can be observed.
Hypertrophy and cell collapse appear in the central cylinder in addition to severe phenol deposits.
Bone cells and chlorophyll losses can already be detected in the green needles of damaged trees, indicating latent damage, which becomes macroscopically visible only after more extensive damage.
Our results indicate that no biotic stress factors take part in the damage of the spruce needles investigated here. Anthropogenic air pollutants in addition to abiotic stress factors must be regarded as a main cause of damage.     

Structure and function of ferredoxin-NADP+-oxidoreductase

The redox-enzyme ferredoxin-NADP-oxidoreductase has been shown to be activated by light and inactivated in the dark. This review will summarize recent data concerning the biochemical characterization of the enzyme compared to its in-vivo activation. Further-more the mechanism of this activation process is discussed as a conformational change caused by the light-driven proton gradient.Abbreviations cyt cytochrome - fd ferredoxin - FNR1 large form of ferredoxin-NADP-oxidoreductase - FNRox oxidized FNR - FNRred reduced FNR - FNRs small form of FNR - FNRsq FNR-semiquinone     

Electron Microscopic Studies of Spruce Needles in Connection with the Occurrence of Novel Forest Decline

Needles of four spruce trees showing different degrees of novel kinds of forest decline were investigated by electron microscopy. Green needles appearing at least superficially still intact were selected for the present investigation. Most of the mesophyll appeared to be undamaged. However, groups of atypical mesophyll cells were found close to the endodermis or the hypodermis. The chloroplasts of the apparently damaged cells were particularly affected. Changes in the matrix of the chloroplasts, i.e,. increased affinity to osmium, occurrence of extensive nests of plastoglobuli, as well as damage to the membranes, i.e. lesions in the envelope and abnormal thylakoid membranes, were observed. Signs of decomposition of other cellular structures including mitochondria were also detectable. There appeared to be a close correlation between the degree of damage at the whole tree level and the degree of damage occurring at the cellular level. It is concluded that particularly the lipids and the proteinsof, the membranes are affected by anthropogenic air pollutants and natural stressors. The altered membrane structure may for instance cause abnormal osmotic conditions for the cellular compartments and may impair transport processes and thus lead to lossof function not only of the cells but also of the whole needle.     

Organogenesis at the shoot apex: An attempt at modelization

A geometrical model of the emergence of a primordium at the shoot apex in dicotyledons is proposed. It is based on recent fundamental results on plant morphogenesis, i.e.:

1. the emergence is preceded by the reorganization of the microtubules of the cortical cytoskeleton, leading to a new orientation of the synthesis of the cell wall microfibrils;
2. the resulting global stress is related to the general orientation of the cell growth.

So the model sums up the continuous interactions linking the microtubules, the microfibrils and the cell growth axis. This paper tries to answer three questions which are essential from a botanical point of view:

1. Why does the principal stem shift its growth direction after each lateral emergence?
2. Why do the three axes involved in any ramification (namely the old and the new principal stems and the lateral emergence) exhibit a plane configuration whereas this is an essentially three dimensional phenomenon?
3. Does phyllotaxis exclusively depend upon the local emergence of a primordium?

A come and go between the botanical knowledge and the mathematical model leads to an integrated view of the compatibility mechanisms linking the different microtubules and microfibrils networks, without forgetting the apical dome restoration. A geometrical formalism allows a modern redefinition of both the “generating centre” and the “organizing centre” and their field effects.     

Correlation between structure of polyoxotungstates and their inhibitory activity on polymerases

The 21-tungsto-9-antimonate (TA, HPA 23), a polyoxotungstate, has shown a significant antiviral activity in vivo and in vitro. It inhibits viral and bacterial DNA polymerases. In this paper, several compounds of two polyoxotungstic families, tungstoantimonates and tungstoarsenates, have been used to specify the mechanism of polymerase inhibition. It has been demonstrated that the inhibitory activity of polyoxotungstates is not related to the occupation of their coordinative sites by cations, nor to the nature of these bound cations. Kinetic studies and binding assays have shown that polyoxotungstates bind to the polymerases in competition with the nucleic acid template. This result seems to be related to their polyanionic nature. Furthermore, the size and charge of these compounds may play a prominent part in their affinity for the polymerases.     

Studies on the mechanism of photosystem II photoinhibition I. A two-step degradation of D1-protein

The role of D1-protein in photoinhibition was examined. Photoinhibition of spinach thylakoids at 20°C caused considerable degradation of D1-protein and a parallel loss of variable fluorescence, Q_B-independent electron flow and Q_B-dependent electron flow. The breakdown of D1-protein as well as the loss of variable fluorescence and Q_B-independent electron flow were largely prevented when thylakoids were photoinhibited at 0°C. The Q_B-dependent electron flow markedly decreased under the same conditions. This inactivation may represent the primary event in photoinhibition and could be the result of some modification at the Q_B-site of D1-protein. Evidence for this comes from fluorescence relaxation kinetics following photoinhibition at 0°C which indicate a partial inactivation of Q_A ^--reoxidation. These results support the idea of D1-protein breakdown during photoinhibition as a two step process consisting of an initial inactivation at the Q_B-site of the protein followed by its degradation. The latter is accompanied by the loss of PS II-reaction centre function.Abbreviations Asc ascorbate - p-BQ 1, 4-benzoquinone - DAD diaminodurene - DPC diphenylcarbazide - DQH₂ duroquinole - Fecy ferricyanide - MV methylviologen - Q_A primary quinone acceptor of PS II - Q_B secondary quinone acceptor of PS II - SiMo silicomolybdate     

Glucose metabolism and internal pH of Lactococcus lactis subsp. lactis cells utilizing NMR spectroscopy

The metabolism of glucose was studied in Lactococcus lactis subsp. lactis CNRZ 125 by ¹³C NMR. The initial rate of glucose utilization was higher for exponential phase cells than for stationary phase cells [150 vs 85 nmol g (dry wt)^-1 s^-1]. ³¹P NMR was used to determine changes in glycolytic phosphorylated intermediates (fructose-1,6-diphosphate, dihydroxyacetone phosphate and phosphoglycerate). The internal pHs of L. lactis subsp. lactis CNRZ 141 and CNRZ 125 were also measured by ³¹P NMR as a function of the external pH during growth. When the external pH was 6·8, the internal pHs of strain CNRZ 141 and CNRZ 125 were similar, 7·4. After the external pH had decreased to 5·5, the internal pH of strain CNRZ 141 had declined by 0·6 unit, whereas that of strain CNRZ 125 had decreased by only 0·2 unit of pH.     

Structure-function relationship in hemoproteins: The role of cytochrome c 3 in the reduction of colloidal sulfur by sulfate-reducing bacteria

Cytochromes c ₃ of different strains of sulfatereducing bacteria have been purified and tested for their capacity to reduce colloidal sulfur to hydrogen sulfide. The results are in good agreement with the activities reported for the whole cells. Cytochrome c ₃ is the sulfur reductase of some strains of sulfate-reducing bacteria such as Desulfovibrio desulfuricans Norway 4 and sulfate-reducing bacterium strain 9974 from which the sulfur reductase activity can be purified with the cytochrome c ₃. In contrast, Desulfovibrio vulgaris Hildenborough cytochrome c ₃ is inhibited by the product of the reaction namely hydrogen sulfide. Chloramphenicol has no effect on the sulfur reductase activity of D. desulfuricans Norway 4 when resting cells grown on lactate-sulfate medium are put in the presence of colloidal sulfur. This shows that the sulfur reductase activity is constitutive and corresponds to the fact that colloidal sulfur grown cells do not contain more cytochrome c ₃ (or another sulfur reductase) than lactate-sulfate-grown cells.     

WOLBACHIA INFECTION IN DROSOPHILA SIMULANS: DOES THE FEMALE HOST BEAR A PHYSIOLOGICAL COST?

Fitness traits of three Drosophila simulans strains infected by endocellular bacteria belonging to the genus Wolbachia have been compared with those of replicate stocks previously cured from the infection by an antibiotic treatment. The traits measured were development time, egg-to-adult viability, egg hatch, productivity, fecundity, and the number of functional ovarioles. Individuals of the first strain were bi-infected by two Wolbachia variants, wHa and wNo. The second strain was infected by wHa, the third one by wNo. The Wolbachia studied here cause cytoplasmic incompatibility (CI), a high embryonic mortality (70% to > 90%) when an infected male is crossed with an uninfected female. Three generations after antibiotic treatment, we observed in all strains a significant drop in productivity in the cured stocks. This drop was not due to antibiotic toxicity and was associated with the loss of the Wolbachia. However the effect had disappeared in two of the three strains five generations after treatment, and could not be found in the third strain in a third measurement carried out 14 generations after treatment. The temporary nature of the productivity difference indicates that Wolbachia do not enhance productivity in infected strains. On the other hand, in all traits measured, our results show the absence of any negative effects of the Wolbachia on their host. This could be explained when considering Wolbachia evolution, as maternally transmitted parasites bear a strong selective pressure not to harm their female host. However, CI would allow the bacteria to be maintained even when harming the female. The apparent absence of deleterious effects caused by these Wolbachia might result from a trade-off, where a relatively low bacteria density would advantage the Wolbachia by suppressing any deleterious effects on the female host, at the cost of a weaker maternal transmission rate of the infection.