Microrheological characterisation of Cyanoflan in human blood plasma.

Naturally occurring polysaccharidic biopolymers released by marine cyanobacteria are of great interest for numerous biomedical applications, such as wound healing and drug delivery. Such polymers generally exhibit high molecular weight and an entangled structure that impact the rheology of biological fluids. However, biocompatibility tests focus not so much on rheological properties as on immune response. In the present study, the rheological behaviour of native blood plasma as a function of the concentration of a cyanobacterium biopolymer is investigated via multiple particle tracking microrheology, which measures the Brownian motion of probes embedded in a sample, and cryogenic scanning electron microscope microstructural characterisation. We use Cyanoflan as the biopolymer of choice, and profit from our knowledge of its chemical structure and its exciting potential for biotechnological applications. A sol-gel transition is identified using time-concentration superposition and the power-law behaviour of the incipient network's viscoelastic response is observed in a variety of microrheological data. Our results point to rheology-based principles for blood compatibility tests by facilitating the assignment of quantitative values to specific properties, as opposed to more heuristic approaches.

Selectivity in the heavy metal removal by exopolysaccharide-producing cyanobacteria.

AIMS: The aim of this study was to assess the selective removal of Cu(II), Cr(III) and Ni(II) by strains of exopolysaccharide (EPS)-producing cyanobacteria, and to investigate the interaction of sorption in solutions with multiple-metals. METHODS AND RESULTS: Nine EPS-producing cyanobacteria were tested for their ability to remove Cr, Cu and Ni in both single- and multiple-metal solutions. In the single-metal solutions, some of the strains showed very high values of metal uptake, however, only two of them showed the capability to selectively remove one or two of the metals present in the multiple-metal solutions. In multi-metal systems, the binding process was either noninteractive, synergistic or competitive between metal ions for different strains of cyanobacteria. CONCLUSIONS: Cyanothece 16Som 2 showed significantly greater sorptive capacity for Cu (1.5-20x) and Cr (2-50x) than all other strains tested. The Nostoc PCC 7936 strain showed high specific and almost exclusive selectivity towards Cu, which suggests its use aimed at recovering this metal from multiple-metal solutions. SIGNIFICANCE AND IMPACT OF THE STUDY: To find out microbial sorbents with good metal selectivity may be very useful for building up processes aimed to recover valuable metals from industrial wastewaters.

Uptake hydrogenase in cyanobacteria: novel input from non-heterocystous strains.

Most of the research to date on cyanobacterial uptake hydrogenases has been performed on filamentous heterocystous strains. However, recent results on the hup gene cluster organization and its transcriptional regulation in non-heterocystous strains has contributed to the widening of knowledge in this field. In the present study, we outline the recent findings on uptake hydrogenases from non-heterocystous cyanobacteria, comparing it with the presently available data from heterocystous strains, and draw attention to potential areas for future research.

Lymph node involvement in macroscopic medullary thyroid carcinoma.

BACKGROUND: Medullary thyroid carcinoma (MTC) is a rare disease, with variable tendency to lymphatic spread. The aim of this retrospective study was to identify distinctive features of large MTC with and without nodal metastases. METHODS: Between 1993 and 2003, 28 consecutive patients underwent total thyroidectomy and neck node dissection for sporadic MTC larger than 10 mm in diameter. RESULTS: All tumours were confirmed to be malignant with a locally invasive pattern of growth. Lymph node metastases were present in 16 patients (N1) and absent in 12 (N0). There were no statistically significant differences between patients with N0 and N1 tumours concerning age (mean 52.1 versus 53.4 years), male:female ratio (0.7 versus 1.0), basal preoperative calcitonin concentration (mean 3238 versus 3076 pg/ml) and tumour size (23.3 versus 23.9 mm). There were differences in the incidence of tumour invasion (P < 0.001), vascular embolism (P = 0.011) and peritumoral thyroiditis (P = 0.039). Measurement of basal and stimulated calcitonin levels after surgery confirmed biochemical cure in all patients with N0 tumours and half of those with N1 disease (P = 0.006). CONCLUSION: There were no preoperative factors that predicted node status for MTC larger than 1 cm in this series. Total thyroidectomy and nodal dissection remains the optimal treatment.

[Reoperation of medullary thyroid carcinoma: long-term results]. / Réintervention pour carcinome médullaire de la thyroïde: résultats à long terme.

STUDY AIM: The impact of iterative surgery in medullary thyroid carcinoma is still debated. The study aim was to evaluate long-term results following reoperation for residual or recurrent medullary thyroid carcinoma. PATIENTS AND METHOD: Among the 136 patients operated on in our centre for medullary thyroid carcinoma (MTC) between 1970 and 2000, 25 patients (10 men and 15 women) were reoperated on for locoregional residual or recurrent lesions. Their mean age was 46 years (range: 19-73 years). The MTC was sporadic in 21 patients and familial in 4: NEM 2A (n = 3), NEM 2B (n = 1). In 11 patients (44%) operated in another centre, the first procedure was a total thyroidectomy; in 2 patients (8%) a total thyroidectomy with central lymphadenectomy was performed, and in 12 patients (48%) a total thyroidectomy with central and jugulo-carotid lymphadenectomy. After the first operation, 6 patients (24%) were classified stage II, 15 (60%) stage III and 4 (16%) stage IV. Basal and post-stimulation calcitonin dosages were performed for all the patients before and after reoperation. RESULTS: Thirty three reoperations were performed. In 24 cases, the recurrence was located in the laterocervical site; in 5 cases, the lymph node involvement was both central and laterocervical, in 2 cases, there was a mediastinal involvement and in 2 cases a spinal involvement. After reoperation, the calcitonin rate became normal in 4 patients (16%); in the other 21 (84%), the calcitonin rate was still high. With a mean 110 month--follow-up (range: 320-12 months), 4 patients (16%) were alive without disease, 2 (8%) died of their disease, 19 (76%) were alive with their disease, five of them with hypercalcitonemia without detectable metastasis. In addition to patients having metastasis at the time of reoperation, seven developed metastases secondarily (liver, bone, lung). CONCLUSION: Biological cure of medullary thyroid carcinoma is rarely obtained with reoperation. Reoperations may reduce progression of the disease in selected patients. Complete removal of the lesions at the time of the first procedure must be the ideal treatment for medullary thyroid carcinoma.

Identification of the green alga, Chlorella vulgaris (SDC1) using cyanobacteria derived 16S rDNA primers: targeting the chloroplast.

We have tested a set of oligonucleotide primers originally developed for the specific amplification of 16S rRNA gene segments from cyanobacteria, in order to determine their versatility as an identification tool for phototrophic eucaryotes. Using web-based bioinformatics tools we determined that these primers not only targeted cyanobacterium sequences as previously described, but also 87% of sequences derived from phototrophic eucaryotes. In order to qualify our finding, a type culture and environmental strain from the freshwater unicellular, green algae genus Chlorella Beijerinck, were selected for further study. Subsequently, we sequenced a 578-bp fragment of the 16S rRNA gene, which proved to be present within the chloroplast genome, performed sequence analysis and positively identified our solvent-degrading environmental strain (SDC1) as Chlorella vulgaris.

Diversity of cyanobacterial hydrogenases, a molecular approach.

In an effort to elucidate the diversity of cyanobacterial hydrogenases, we used a molecular approach. Filamentous strains from a broad range of sources were screened for the presence of hup (uptake hydrogenase), xisC (rearrangement within hupL), and hox (bidirectional hydrogenase) genes. As expected, an uptake hydrogenase seems to be present in all N(2)-fixing cyanobacteria. On the other hand, no evidence was found for the presence of a conventional bidirectional enzyme in several strains. Similarly, the presence of xisC is not a characteristic shared by all the heterocyst-forming cyanobacteria. Although tempting, it is not possible to establish a correlation between the presence/absence of the bidirectional hydrogenase and the occurrence of xisC. The natural molecular variation of hydrogenases in cyanobacteria is certainly a field to explore, both to understand the physiological functions of the respective enzymes and to identify a genetic background to be used when constructing a strain for photobiological H(2) production in a bioreactor.

Hydrogen uptake in Nostoc sp. strain PCC 73102. Cloning and characterization of a hupSL homologue.

Structural genes encoding an uptake hydrogenase of Nostoc sp. strain PCC 73102 were isolated. From partial libraries of genomic DNA, two clones (pNfo01 and pNfo02) were selected and sequenced, revealing the complete sequence of both a hupS (960 bases) and a hupL (1,593 bases) homologue in Nostoc sp. strain PCC 73102. A comparison between the deduced amino acid sequences of HupS and HupL of Nostoc sp. strain PCC 73102 and Anabaena sp. strain PCC 7120 showed that the HupS proteins are 89% identical and the HupL proteins are 91% identical. However, the noncoding region between the genes in Nostoc sp. strain PCC 73102 (192 bases) is longer than that of Anabaena sp. strain PCC 7120 and of many other microorganisms. Southern hybridizations using DNA from both N2-fixing and non-N2-fixing cells of Nostoc sp. strain PCC 73102 and different probes from within hupL clearly demonstrated that, in contrast to Anabaena sp. strain PCC 7120, there is no rearrangement within hupL of Nostoc sp. strain PCC 73102. Indeed, 6 nucleotides out of 16 within the potential recombination site are different from those of Anabaena sp. strain PCC 7120. Furthermore, we have recently published evidence demonstrating the absence of the bidirectional/reversible hydrogenase in Nostoc sp. strain PCC 73102. The present knowledge, in combination with the unique characteristics, makes Nostoc sp. strain PCC 73102 an interesting candidate for the study of deletion mutants lacking the uptake-type enzyme.

Hydrogenases in Nostoc sp. Strain PCC 73102, a Strain Lacking a Bidirectional Enzyme.

The present study was carried out in order to examine and characterize the bidirectional hydrogenase in the cyanobacterium Nostoc sp. strain PCC 73102. Southern hybridizations with the probes Av1 and Av3 (hoxY and hoxH, bidirectional hydrogenase small and large subunits, respectively) revealed the occurrence of corresponding sequences in Anabaena variabilis (control), Anabaena sp. strain PCC 7120, and Nostoc muscorum but not in Nostoc sp. strain PCC 73102. As a control, hybridizations with the probe hup2 (hupL, uptake hydrogenase large subunit) demonstrated the presence of a corresponding gene in all the cyanobacteria tested, including Nostoc sp. strain PCC 73102. Moreover, with three different growth media, a bidirectional enzyme that was functional in vivo was observed in N. muscorum, Anabaena sp. strain PCC 7120, and A. variabilis, whereas Nostoc sp. strain PCC 73102 consistently lacked any detectable in vivo activity. Similar results were obtained when assaying for the presence of an enzyme that is functional in vitro. Native polyacrylamide gel electrophoresis followed by in situ hydrogenase activity staining was used to demonstrate the presence or absence of a functional enzyme. Again, bands corresponding to hydrogenase activity were observed for N. muscorum, Anabaena sp. strain PCC 7120, and A. variabilis but not for Nostoc sp. strain PCC 73102. In conclusion, we were unable to detect a bidirectional hydrogenase in Nostoc sp. strain PCC 73102 with specific physiological and molecular techniques. The same techniques clearly showed the presence of an inducible bidirectional enzyme and corresponding structural genes in N. muscorum, Anabaena sp. strain PCC 7120, and A. variabilis. Hence, Nostoc sp. strain PCC 73102 seems to be an unusual cyanobacterium and an interesting candidate for future biotechnological applications.