An auxin-auxotrophic mutant of Nicotiana plumbaginifolia

Summary Auxin (indole-3-acetic acid) is considered to be an important signalling molecule in the regulation of plant growth and development but neither auxin synthesis nor its mode of action is clearly understood. To identify genes involved in these processes, mutations were sought that altered the auxin requirement of plant tissues for growth. For the first time mutant plants were obtained that carry a recessive mutation at a single nuclear locus (auxl) which results in an absolute requirement for exogenous auxin for normal growth. In the absence of auxin treatment, mutant plants undergo premature senescence and die.Abbreviations BAP 6-benzylaminopurine - BUdR 5-bromodeoxyuridine - 2,4-D 2,4-dichlorophenoxyacetic acid - FUdR 5-fluorodeoxyuridine - IAA-EE indole-3-acetic acid ethyl ester - IMS indole-3-methanesulfonic acid     

Trichinosis: Thiabendazole in the Treatment of 11 Cases

We have studied 11 cases of acute human trichinosis; five of these patients were treated with thiabendazole. We have reviewed the laboratory data for these patients and described their course. This study has failed to show any definite effect of thiabendazole on the course of human trichinosis at the doses used. However, thiabendazole may have decreased the infectivity of the larvae which were embedded in the muscles of our patients.     

Influence ofl-thyroxine,l-triiodothyronine,thyroid stimulating hormone,or estradiol on the cell kinetics of cultured mammary cancer cells

Summary We describe the in vitro influence of 3,5,3′-triiodo-l-thyronine (T₃),l-thyroxine (T₄), a thyroid-stimulating hormone (TSH), and/or estradiol (E₂: chosen as the control of the methodology) on the cell kinetics (cell distribution in the S+G₂+M phases) of mouse MXT and human MCF-7 mammary cancer cells. Experiments were performed by means of a cell image processor, analyzing MCF-7 or MXT cells that had been grown on glass cover slips and whose nuclei had been stained by the Feulgen reaction, which is selective and quantitative (stoichiometric) with respect to DNA. We show that T₃, T₄, and TSH at 0.01 μM dramatically stimulate the cell kinetics of the MXT mouse and the MCF-7 human mammary cancer cell lines. Indeed, the three hormones bring about a significant transient increase in the S+G₂+M fraction as does E₂. Furthermore, our data indicate that E₂ and TSH are antagonistic with regards to MXT or MCF-7 cell kinetics. This work is supported by grants awarded by the IRSIA and the Fonds de la Recherche Scientifique Médicale (FRSM, Belgium).     

Increased intracellular Ca2+ is necessary for maximal expression of the proto-oncogene c-jun in the Jurkat T-cell line.

The time course and signal-transduction requirements for proto-oncogene c-jun expression in T-cells were investigated. Expression of c-jun mRNA was evident at 30 min after stimulation. Both the activation of Ca2+/phospholipid-dependent kinase as well as an increased intracellular free Ca2+ concentration were necessary for the maximal induction of c-jun mRNA and synthesis of Jun protein 1 h after stimulation.     

Analysis of phytochrome- and ABA-deficient mutants suggests that ABA degradation is controlled by light in Nicotiana plumbaginifolia

The phytochrome chromophore-deficient mutant, pew1, of Nicotiana plumbaginifolia exhibited decreased germination and slower dehydration of detached leaves during water stress as compared with the wild-type. These physiological processes are controlled by abscisic acid (ABA) and we examined, therefore, whether phytochrome plays a specific role in the regulation of ABA metabolism using the pew1 mutant. The ABA contents of mature seeds and young leaves were analysed and in both cases mutant material was found to contain higher amounts of ABA as compared with the wild-type. This indicates that the phytochrome activation can lead to a decrease of the ABA level in the wild-type plant. The role of phytochromes was investigated in greater detail using the ABA-deficient mutant aba1 of N. plumbaginifolia exhibiting an early and synchronous germination. This mutant accumulates at very high levels a metabolite derived from a precursor (ABA-aldehyde) in the ABA biosynthetic pathway. The first biochemical characterization of this molecule, which corresponds to the glucose-conjugated ABA-alcohol (ABA-AG) is described. A pew1-aba1 double mutant exhibiting both an etiolated growth and early germination was also obtained. The comparable accumulation of ABA-AG in the pew1-aba1 double mutant as compared with the aba1 mutant allowed the proposition that, in a wild-type plant, the phytochrome-mediated light signal enhances ABA degradation rather than inhibits its biosynthesis.     

113Cd nmr study of the metal cluster structure of human liver metallothionein

Cadmium-113 nuclear magnetic resonance (¹¹³Cd nmr) was used to elucidate the structural properties of the cadmium binding sites in human liver metallothionein. The isotopically labeled ¹¹³Cd-metallothionein was prepared by the in vitro exchange of the native metals (greater than 94% zinc) for ¹¹³CdCl₂ during isolation. The two isoproteins, MT-1 and MT-2, showed ¹¹³Cd nmr resonances in the chemical shift range 610–670 ppm. The multiplet structure of the resonances is due to two bond scalar interactions between adjacent ¹¹³Cd ions linked by cysteine thiolate ligands. Homonuclear ¹¹³Cd decoupling experiments allowed the determination of the metal cluster structure, which, similar to the rabbit liver metallothionein, consists of a four- and a three-metal cluster designated cluster A and cluster B, respectively. Chemical shift similarities in the ¹¹³Cd nmr spectra of the human, rabbit and calf liver MT-1 and MT-2 are observed, especially for cluster A. Small variations in chemical shifts are explained in terms of differences in the primary structure between the two human isoproteins.     

The connecting cilium inner scaffold provides a structural foundation that protects against retinal degeneration

Inherited retinal degeneration due to loss of photoreceptor cells is a leading cause of human blindness. These cells possess a photosensitive outer segment linked to the cell body through the connecting cilium (CC). While structural defects of the CC have been associated with retinal degeneration, its nanoscale molecular composition, assembly, and function are barely known. Here, using expansion microscopy and electron microscopy, we reveal the molecular architecture of the CC and demonstrate that microtubules are linked together by a CC inner scaffold containing POC5, CENTRIN, and FAM161A. Dissecting CC inner scaffold assembly during photoreceptor development in mouse revealed that it acts as a structural zipper, progressively bridging microtubule doublets and straightening the CC. Furthermore, we show that Fam161a disruption in mouse leads to specific CC inner scaffold loss and triggers microtubule doublet spreading, prior to outer segment collapse and photoreceptor degeneration, suggesting a molecular mechanism for a subtype of retinitis pigmentosa.

Inherited retinal degeneration due to loss of photoreceptor cells is a leading cause of human blindness. Ultrastructure expansion microscopy on mouse retina reveals the presence of a novel structure inside the photoreceptor connecting cilium, the inner scaffold, that protects the outer segment against degeneration.     

Development of a 16S rRNA gene-based prototype microarray for the detection of selected actinomycetes genera

Actinomycetes are known for their secondary metabolites, which have been successfully used as drugs in human and veterinary medicines. However, information on the distribution of this group of Gram-positive bacteria in diverse ecosystems and a comprehension of their activities in ecosystem processes are still scarce. We have developed a 16S rRNA-based taxonomic microarray that targets key actinomycetes at the genus level. In total, 113 actinomycete 16S rRNA probes, corresponding to 55 of the 202 described genera, were designed. The microarray accuracy was evaluated by comparing signal intensities with probe/target-weighted mismatch values and the Gibbs energy of the probe/target duplex formation by hybridizing 17 non-actinomycete and 29 actinomycete strains/clones with the probe set. The validation proved that the probe set was specific, with only 1.3% of false results. The incomplete coverage of actinomycetes by a genus-specific probe was caused by the limited number of 16S rRNA gene sequences in databases or insufficient 16S rRNA gene polymorphism. The microarray enabled discrimination between actinomycete communities from three forest soil samples collected at one site. Cloning and sequencing of 16S rRNA genes from one of the soil samples confirmed the microarray results. We propose that this newly constructed microarray will be a valuable tool for genus-level comparisons of actinomycete communities in various ecological conditions.