Linear phase-and-frequency-modulated photonic links using optical discriminators.

We report our experimental results for linear analog optical links that use phase or frequency modulation and optical discrimination. The discriminators are based on two architectures: a cascaded MZI FIR lattice filter and a ring assisted MZI (RAMZI) IIR filter. For both types of discriminators, we demonstrate > 6 dB improvement in the link's third-order output intercept point (OIP3) over a MZM link. We show that the links have low second-order distortion when using balanced detection. Using high optical power, we demonstrate an OIP3 of 39.2 dBm. We also demonstrate 4.3dB improvement in signal compression.

Perspectives on Systematic Analyses of Gene Function in Arabidopsis thaliana: New Tools, Topics and Trends.

Since the sequencing of the nuclear genome of Arabidopsis thaliana ten years ago, various large-scale analyses of gene function have been performed in this model species. In particular, the availability of collections of lines harbouring random T-DNA or transposon insertions, which include mutants for almost all of the ~27,000 A. thaliana genes, has been crucial for the success of forward and reverse genetic approaches. In the foreseeable future, genome-wide phenotypic data from mutant analyses will become available for Arabidopsis, and will stimulate a flood of novel in-depth gene-function analyses. In this review, we consider the present status of resources and concepts for systematic studies of gene function in A. thaliana. Current perspectives on the utility of loss-of-function and gain-of-function mutants will be discussed in light of the genetic and functional redundancy of many A. thaliana genes.

[A strategy for therapy of depressive disorders and anxiety disorders by a health education intervention in medical consultations: the results of the APRAND program]. / Prévention des troubles anxieux et dépressifs par une action d'éducation pour la santé en consultation: résultats du programme APRAND.

BACKGROUND: Studies devoted to the detection and treatment of anxiety and depression in adult populations show that at least 10% meet ICD10 criteria for an anxiety or a depressive disorder, but only half are diagnosed as such and only one third of those receive appropriate treatment. The goal of the APRAND program was to explore the possibility of improving management strategies via health education during doctors' visits. METHODS: In 2001, EDF-GDF conducted an experimental program in which 21 physicians from its in-house health insurance program used the MINI mental state examination to screen for ICD10 criteria for anxiety and depressive disorders in 9743 employees on sick leave. A "here-elsewhere" epidemiologic study evaluated the program, recording the initial diagnoses and studying a year later the outcome of the persons identified with these disorders in 8 active centers (with prevention activities) and in 13 control centers (without prevention activities). The activities consisted of explanations of the disorders identified, delivery of the test results, delivery of leaflets based on the WHO guidelines, and strong recommendations to see a general practitioner, or a psychiatrist, or the occupational physician, if necessary. Logistic regressions compared the two groups, taking into account sex, age, geographic region, comorbidity, and medical care at screening. RESULTS: Preventive activities were significantly associated with the disappearance at 1 year of depressive episodes (OR=1.93; CI 95%; 1.3-2.84) and of phobic or panic disorders (OR=1.98; CI 95%; 1.14-3.44). The only other variables affecting prognosis were age and sex. The probability of recovery or remission increased by 10 to 20% at active centers, according to age, sex and disorder. Moreover, the physicians reported that they learned a great deal from the program, which thus also improved their practices. CONCLUSION: Diagnosis and prognosis of depressive episodes and phobic and panic disorders in adult populations can be improved by a preventive diagnostic and educational approach of the type used by APRAND during doctor's visits.

The phytochrome A specific signaling component PAT3 is a positive regulator of Arabidopsis photomorphogenesis.

Phytochrome A plays a major role in early seedling development by triggering the transition from etiolated growth to greening. Seedlings germinated under constant far-red (FR) light show a partially de-etiolated phenotype that is not seen in phyA mutants. This phytochrome A specific response was used to screen a population of T-DNA mutagenized Arabidopsis seedlings. One mutant line, pat3 (phytochrome A signal transduction3), which showed no inhibition of hypocotyl elongation under FR light conditions and no FR-induced killing response, contained a T-DNA insertion in a 609-bp ORF. The recessive mutation co-segregated with the T-DNA resistance marker and could be allelic to fhy1. A 2,248-bp genomic fragment of the PAT3 locus can complement the pat3 mutant phenotype. PAT3 transcript peaked 3 d after germination and was downregulated by light. PAT3 has no significant homology to any known protein and shows no preferential cellular localization. The protein can activate transcription in yeast when fused to the GAL4 DNA-binding domain. Our results show that PAT3 is a positive regulator of phytochrome A signal transduction.

LAF1, a MYB transcription activator for phytochrome A signaling.

The photoreceptor phytochrome (phy) A has a well-defined role in regulating gene expression in response to specific light signals. Here, we describe a new Arabidopsis mutant, laf1 (long after far-red light 1) that has an elongated hypocotyl specifically under far-red light. Gene expression studies showed that laf1 has reduced responsiveness to continuous far-red light but retains wild-type responses to other light wavelengths. As far-red light is only perceived by phyA, our results suggest that LAF1 is specifically involved in phyA signal transduction. Further analyses revealed that laf1 is affected in a subset of phyA-dependent responses and the phenotype is more severe at low far-red fluence rates. LAF1 encodes a nuclear protein with strong homology with the R2R3-MYB family of DNA-binding proteins. Experiments using yeast cells identified a transactivation domain in the C-terminal portion of the protein. LAF1 is constitutively targeted to the nucleus by signals in its N-terminal portion, and the full-length protein accumulates in distinct nuclear speckles. This accumulation in speckles is abolished by a point mutation in a lysine residue (K258R), which might serve as a modification site by a small ubiquitin-like protein (SUMO).

PAT1, a new member of the GRAS family, is involved in phytochrome A signal transduction.

Light signaling via the phytochrome A (phyA) photoreceptor controls basic plant developmental processes including de-etiolation and hypocotyl elongation. We have identified a new Arabidopsis mutant, pat (phytochrome A signal transduction)1-1, which shows strongly reduced responses in continuous far-red light. Physiological and molecular data indicate that this mutant is disrupted at an early step of phyA signal transduction. The PAT1 gene encodes a cytoplasmic protein of 490 amino acids with sequence homologies to the plant-specific GRAS regulatory protein family. In the pat1-1 mutant, a T-DNA insertion introduces a premature stop codon, which likely results in the production of a truncated PAT1 protein of 341 amino acids. The semidominant phenotype of this mutant can be recapitulated by overexpression of an appropriately truncated PAT1 gene in the wild type. The results indicate that the truncated PAT1 protein acts in a dominant-negative fashion to inhibit phyA signaling.

Overexpression of rice phytochrome A partially complements phytochrome B deficiency in Arabidopsis.

The red/far-red reversible phytochromes play a central role in regulating the development of plants in relation to their light environment. Studies on the roles of different members of the phytochrome family have mainly focused on light-labile, phytochrome A and light-stable, phytochrome B. Although these two phytochromes often regulate identical responses, they appear to have discrete photosensory functions. Thus, phytochrome A predominantly mediates responses to prolonged far-red light, as well as acting in a non-red/far-red-reversible manner in controlling responses to light pulses. In contrast, phytochrome B mediates responses to prolonged red light and acts photoreversibly under light-pulse conditions. However, it has been reported that rice (Oryza sativa L.) phytochrome A operates in a classical red/far-red reversible fashion following its expression in transgenic tobacco plants. Thus, it was of interest to determine whether transgenic rice phytochrome A could substitute for loss of phytochrome B in phyB mutants of Arabidopsis thaliana (L.) Heynh. We have observed that ectopic expression of rice phytochrome A can correct the reduced sensitivity of phyB hypocotyls to red light and restore their response to end-of-day far-red treatments. The latter is widely regarded as a hallmark of phytochrome B action. However, although transgenic rice phytochrome A can correct other aspects of elongation growth in the phyB mutant it does not restore other responses to end-of-day far-red treatments nor does it restore responses to low red:far-red ratio. Furthermore, transgenic rice phytochrome A does not correct the early-flowering phenotype of phyB seedlings.

Different sequences for 5'-untranslated leaders of nuclear genes for plastid proteins affect the expression of the beta-glucuronidase gene.

Expression of chimeric uidA gene fusions (for bacterial beta-glucuronidase) with 5'-flanking sequences of the spinach AtpC and PetE genes (encoding the subunit gamma of the chloroplast ATP synthase and plastocyanin, respectively) requires sequences for the 5'-untranslated leaders. The sequence for the PetE leader does not exhibit significant similarities to those of other leader sequences. Closer inspection of PetE uncovered that the crucial region is located in the vicinity of the transcription start site (+5/+15, TTGTCATTTCT). In contrast, 3' deletions of sequences for the AtpC leader revealed that the region in the vicinity of the translation initiation codon is essential for uidA gene expression (+103/+176). This segment contains a CT-rich sequence (TTCTCTCTCCT), which is found identically or in a slightly modified form in sequences for 85 plant leaders deposited in the EMBL data bank. Site-directed mutagenesis of the CT-rich sequence resulted in a three-fold reduction of the transcription of the transgene. It is concluded (1) that different elements in the sequences for the spinach PetE and AtpC leaders control the expression of the uidA gene, (2) that these elements operate transcriptionally rather than post-transcriptionally and (3) that a CT-rich sequence represents a crucial cis element for the transcription of the AtpC::uidA gene fusion.

Intron sequences are involved in the plastid- and light-dependent expression of the spinach PsaD gene.

Plastid- and light-regulated expression of the spinach PsaD gene in transgenic tobacco requires sequences downstream of the transcription start site, sand promoter sequences alone are not sufficient to respond to these stimuli. The spinach PsaD mRNA level in transgenic tobacco is still plastid- and light-responsive when the expression of the intron-containing transcription unit is driven by the 35S RNA CaMV promoter indicating that PsaD contains (a) gene-internal control element(s). If the genomic PsaD sequence in the latter construct was replaced by the cDNA, a constitutive expression of the PsaD transcript level was observed. It is concluded that the intron sequence contributes to the plastid- and light-dependent expression of the spinach PsaD gene.

Evidence that the plastid signal and light operate via the same cis-acting elements in the promoters of nuclear genes for plastid proteins.

Nuclear-encoded genes for proteins of the photosynthetic machinery represent a particular subset of genes. Their expression is cooperatively stimulated by discrete factors including the developmental stage of plastids and light. We have analyzed in transgenic tobacco the plastid- and light-dependent expression of a series of 5' promoter deletions of various nuclear genes from spinach, of fusions of defined promoter segments with the 90-bp 35S RNA CaMV minimal promoter, as well as with mutations in sequences with homologies to characterized cis-elements, to address the question of whether the plastid signal and light operate via the same or different cis-acting elements. In none of the 160 different transgenic lines (representing 32 promoter constructs from seven genes) analyzed, could significant differences be identified in the responses to the two regulatory pathways. The data are compatible with the idea that both signals control the expression of nuclear genes for plastid proteins via the same cis-acting elements.

The spinach AtpC and AtpD genes contain elements for light-regulated, plastid-dependent and organ-specific expression in the vicinity of the transcription start sites.

Run-on assays with isolated nuclei demonstrate that the transcription rates of AtpC and AtpD (gene products: the CF1 subunits gamma and delta of the chloroplast ATP synthase) are comparable in spinach seedlings. However, chimeric GUS gene fusions with 5'-flanking regions of the AtpC gene direct an approximately 10-fold lower GUS level in transgenic tobacco compared with equivalent fragments from the AtpD gene. Both promoters contain sequences in the vicinity of the respective TATA boxes, which are sufficient to direct light-regulated, plastid-dependent and organ-specific expression of the GUS gene. In contrast, the upstream regions of both promoters differ the higher GUS level directed by the AtpD promoter is caused by enhancer-like elements located upstream of the region involved in the regulated expression, while nucleotides upstream of -73 in the AtpC promoter contribute relatively little to the promoter activity. 5'-Deletion analyses and site-directed mutagenesis studies indicated that the -73/-48 bp AtpC region contains cis-elements crucial for this regulated expression. If five nucleotides within this region (-59/-55) are exchanged, the GUS gene is constitutively expressed and the activity in etiolated seedlings, in seedlings with photobleached plastids and in roots increases to the level detectable in green cotyledons. It is concluded that signal transduction pathways from different regulators converge prior to gene regulation and that these five nucleotides are part of a cis-element which functions as a repressor in darkness, in tissues with impaired plastids and in roots.

Segments encoding 5'-untranslated leaders of genes for thylakoid proteins contain cis-elements essential for transcription.

The promoter region -118/-29 of the spinach PetH gene encoding the ferredoxin-NADP(+)-oxidoreductase contains crucial cis-elements for the regulated expression, while sequences for the 5'-untranslated leader determine the quantitative expression of chimeric GUS gene fusions in transgenic tobacco. Deletion of leader sequences in chimeric GUS gene fusions of the spinach PetE and PsaF genes (for plastocyanin and the subunit III of photosystem I, respectively) results also in a decline in the GUS activity. Appropriate gene constructs and run-on transcription assays demonstrate unambiguously that the leaders of all three genes are involved in transcription rather than in post-transcriptional processes. They appear to contain gene-specific control elements rather than cis-determinants for general initiation factors. Expression-relevant segments in the PsaF and PetH leaders contain two CT-rich sequences, designated CT-LB and CT-B, of which at least the former binds to a protein factor in gel mobility shift assays. These motifs are not found in the PetE leader. The findings imply that leader sequences may contain cis-elements that are essential for the transcription, that they influence GUS gene expression quantitatively rather than qualitatively, and that these elements, as those of promoters, can be quite variable in sequence.

The Role of Plastids in the Expression of Nuclear Genes for Thylakoid Proteins Studied with Chimeric [beta]-Glucuronidase Gene Fusions.

We have analyzed plastid and nuclear gene expression in tobacco seedlings using the carotenoid biosynthesis inhibitor nor-flurazon. mRNA levels for three nuclear-encoded chlorophyll-binding proteins of photosystem I and photosystem II (CAB I and II and the CP 24 apoprotein) are no longer detectable in photobleached seedlings, whereas those for other components of the thylakoid membrane (the 33- and 23-kD polypeptides and Rieske Fe/S polypeptide) accumulate to some extent. Transgenic tobacco seedlings with promoter fusions from genes for thylakoid membrane proteins exhibit a similar expression behavior: a CAB-[beta]-glucuronidase (GUS) gene fusion is not expressed in herbicide-treated seedlings, whereas PC-, FNR-, PSAF-, and ATPC-promoter fusions are expressed, although at reduced levels. All identified segments in nuclear promoters analyzed that have been shown to respond to light also respond to photodamage to the plastids. Thus, the regulatory signal pathways either merge prior to gene regulation or interact with closely neighboring cis elements. These results indicate that plastids control nuclear gene expression via different and gene-specific cis-regulatory elements and that CAB gene expression is different from the expression of the other genes tested. Finally, a plastid-directing import sequence from the maize Waxy gene is capable of directing the GUS protein into the photodamaged organelle. Therefore, plastid import seems to be functional in photobleached organelles.

Promoters from genes for plastid proteins possess regions with different sensitivities toward red and blue light.

The light-regulated expression of eight nuclear-encoded genes for plastid proteins from spinach (Spinacia oleracea) (RBCS-1 and CAB-1; ATPC and ATPD, encoding the subunits gamma and delta of the ATP synthase; PC and FNR; PSAD and PSAF, encoding the subunits II and III of photosystem I reaction center) was analyzed with promoter/beta-glucuronidase (GUS) gene fusions in transgenic tobacco (Nicotiana tabacum and Nicotiana plumbaginifolia) seedlings and mature plants under standardized light and growth conditions. Unique response patterns were found for each of these promoters. GUS activities differed more than 30-fold. Strong promoters were found for the PC and PSAD genes. On the other hand, the ATPC promoter was relatively weak. Expression of the CAB/GUS gene fusion in etiolated material was at the detection limit; all other chimeric genes were expressed in the dark as well. Light stimulation of GUS activities ranged from 3- (FNR promoter) to more than 100-fold (CAB-1 promoter). The FNR promoter responded only to red light (RL) and not significantly to blue light (BL), whereas the PC promoter contained regions with different sensitivities toward RL and BL. Furthermore, different RNA accumulation kinetics were observed for the PSAF, CAB, FNR, and PC promoter/GUS gene fusions during de-etiolation, which, at least in the case of the PSAF gene, differed from the regulation of the corresponding endogenous genes in spinach and tobacco. The results suggest either that not all cis elements determining light-regulated and quantitative expression are present on the spinach promoter fragments used or that the spinach cis-regulatory elements respond differently to the host (tobacco) regulatory pathway(s). Furthermore, as in tobacco, but not in spinach, the trans-gene hardly responds to single light pulses that operate through phytochrome. Taken together, the results suggest that the genes have been independently translocated from the organelle to the nucleus during phylogeny. Furthermore, each gene seems to have acquired a unique set of regulatory elements.

Coaction of blue light and light absorbed by phytochrome in control of glutamine synthetase gene expression in Scots pine (Pinus sylvestris L.) seedlings.

The level of plastidic glutamine synthetase (GS; EC 6.3.1.2) in the cotyledonary whorl of the Scots pine (Pinus sylvestris L.) seedling was previously reported to be regulated by light. In the present paper we report on the control by light of the GS transcript level. A full-length GS cDNA clone of Scots pine was isolated (pGS1), sequenced and employed to measure GS transcript levels. Using dichromatic light treatments it was found that the transcript level is regulated by phytochrome. The strong specific effect of blue light is to be attributed to an increase of the responsiveness to phytochrome. Since no direct correlation between the transcript level and the rate of GS protein synthesis was observed, it was concluded that GS gene expression is only coarsely regulated at the level of transcript accumulation. Synthesis of GS protein is by itself light-dependent (light-mediated fine tuning of gene expression). This control at the translational level is also exerted via phytochrome with blue light determining the responsiveness of the process toward phytochrome. If the level of the far-red absorbing form of phytochrome (Pfr) is kept very low, blue light is not capable of bringing about synthesis of GS protein.

Characterization of the promoter from the single-copy gene encoding ferredoxin-NADP(+)-oxidoreductase from spinach.

We describe a genomic DNA segment from spinach that bears part of the single-copy gene for ferredoxin-NADP(+)-oxidoreductase (FNR) including a 3.4 kb promoter sequence. Dissection of this DNA segment and its analysis in GUS (beta-glucuronidase) gene fusions in transgenic tobacco demonstrated that the promoter differs in structure from all other promoters for thylakoid protein genes studied to date. Two regions with light-responsive elements were identified. One is located within the first 118 bp upstream of the transcription initiation site. A second fragment covering nucleotide positions -220 to -119 is capable of conferring light-dependent GUS gene expression on two different minimal promoters. The latter fragment binds a transacting factor in gel-shift assays. None of the fragments carries cis elements known from other genes to be involved in light-controlled expression. Comparison of the light responsiveness of GUS gene fusions controlled by the -753/+231 and -118/+231 regions indicates that they respond differentially to phytochrome-dependent signals and that their expression in tobacco is not restricted to tissue with functional chloroplasts.

Cause of death in squamous cell carcinoma of the head and neck. An autopsy study on 31 patients.

A series of 31 autopsied patients, with a history of head and neck squamous cell carcinoma is reported, with the emphasis on the cause of death. There were 26 males and 5 females; mean age being 64 years (range 44-88 years). Locoregional disease (LRD) was the cause of death in 19 patients (61%) and was present in 2 patients dying of an unrelated cause. Distant metastasis (DM) was found in 8 patients (26%) but had caused death in only 1 of them. A shorter survival time for patients with DM than for those without (8 months versus 13 months) indicates that DM is established early in the course of the disease. Therefore, a longer survival time will not result in an increase in DM and we infer that a better locoregional control will also not result in a real increase in DM but only in an apparent one, due to a shift of cause of death from LRD to DM in a group of patients that formerly would have died of LRD before the already present DM had become manifest.

Immunological rebound following cessation of chemotherapy in 15 acute lymphoid leukemia patients in complete remission.

The number of blood and bone marrow lymphocytes, the E-rosette forming cells, the Ig-bearing lymphocytes, the serum immunoglobulin levels were evaluated after discontinuation of 36 months of chemotherapy in 15 acute lymphocytic leukemia patients in complete remission. The study provides further information on the immunological rebound during the "off-therapy" period.