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Biomedical subjects

J L Robert

Publications and source records attributed to J L Robert.

At least 19 recordsLinked to original sources
PubMed2003

Natural and recombinant fungal laccases for paper pulp bleaching.

Three laccases, a natural form and two recombinant forms obtained from two different expression hosts, were characterized and compared for paper pulp bleaching. Laccase from Pycnoporus cinnabarinus, a well known lignolytic fungus, was selected as a reference for this study. The corresponding recombinant laccases were produced in Aspergillus oryzae and A. niger hosts using the lacI gene from P. cinnabarinus to develop a production process without using the expensive laccase inducers required by the native source. In flasks, production of recombinant enzymes by Aspergilli strains gave yields close to 80 mg l(-1). Each protein was purified to homogeneity and characterized, demonstrating that the three hosts produced proteins with similar physico-chemical properties, including electron paramagnetic resonance spectra and N-terminal sequences. However, the recombinant laccases have higher Michaelian (Km) constants, suggesting a decrease in substrate/enzyme affinity in comparison with the natural enzyme. Moreover, the natural laccase exhibited a higher redox potential (around 810 mV), compared with A. niger (760 mV) and A. oryzae (735 mV). Treatment of wheat straw Kraft pulp using laccases expressed in P. cinnabarinus or A. niger with 1-hydroxybenzotriazole as redox mediator achieved a delignification close to 75%, whereas the recombinant laccase from A. oryzae was not able to delignify pulp. These results were confirmed by thioacidolysis. Kinetic and redox potential data and pulp bleaching results were consistent, suggesting that the three enzymes are different and each fungal strain introduces differences during protein processing (folding and/or glycosylation).

Aspergillus niger↗
PubMed2003

Overproduction of laccase by a monokaryotic strain of Pycnoporus cinnabarinus using ethanol as inducer.

AIMS: Laccase production by the monokaryotic strain Pycnoporus cinnabarinus ss3 was studied using ethanol as inducer in the culture medium. METHODS AND RESULTS: The effect of ethanol was tested at 10, 20, 30, 35 and 45 g l-1 and compared with that of ferulic acid, known until now as the most efficient inducer for laccase expression by P. cinnabarinus ss3. In the presence of 35 g l-1 ethanol, laccase activity (266 600 U l-1) and productivity (19 000 U l-1 day-1) were nine and fivefold higher compared with ferulic acid-induced cultures, and 155- and 65-fold higher compared with non-induced cultures, respectively. In vivo, ethanol added to the culture medium of P. cinnabarinus ss3 favoured a continuous and high expression of laccase gene. Under these conditions, P. cinnabarinus ss3 produced preferentially the isoenzyme LAC I. Ethanol added in vitro to the purified P. cinnabarinus ss3 laccase typically inhibited the enzymatic activity. CONCLUSIONS: In spite of an initial inhibitory effect on mycelial growth, ethanol was shown to be a very strong inducer for laccase expression by P. cinnabarinus ss3 allowing an average yield of 1-1.5 g l-1 laccase. SIGNIFICANCE AND IMPACT OF THE STUDY: This study identified P. cinnabarinus ss3 as an outstanding producer of laccase in the presence of ethanol as inducer. Ethanol is an inexpensive agricultural by-product and the process is simple to scale-up for industrial production.

Basidiomycota↗
PubMed1998

[Long-term results of cobalt 60 curietherapy for uveal melanoma].

PURPOSE: To analyze 65 patients with uveal melanomas treated with cobalt plaque therapy with regards to mortality, visual results and complications. PATIENTS AND METHODS: Most of the melanomas were large (T3: 52.5%), with a mean largest dimension of the base of 11 mm, and a mean thickness of 6 mm. Most of the tumors were located in the choroid (95%), with an anterior margin behind the equator (65%), and a posterior margin at less than 3 mm of the disc and/or of the macula (69%). The plaque radiotherapy delivered a mean dose of 95 Gy to the tumor apex, either with a cobalt plaque alone (51 cases), or in association with a ruthenium plaque (14 cases). The mean follow up period was over 8 years. RESULTS: The local control was achieved initially in 86% of the eyes. The estimated melanoma specific survival rate was 83% after 5 years and 74% after 10 years. The main parameter associated with the metastases was the largest dimension of the base (p < 0.01). The eye was retained in 83% of the cases. The probability of keeping a vision better than or equal to 0,1 was 39% after 5 years and 27% after 10 years. The main parameter associated with the visual loss was the tumor size (p < 0.01). The complications included cataract (39%), radiation retinopathy (34%), with maculopathy (19%) and/or papillopathy (13.5%), vitreous hemorrhages (22%), neovascular glaucoma (15%) and retinal detachment (12%). CONCLUSION: These results supported the value of cobalt plaque radiotherapy in the management of uveal melanomas.

Adult↗
PubMed1996

Interlaboratory study of the analysis of ampicillin by liquid chromatography.

A liquid chromatographic method for the analysis of ampicillin was examined in a collaborative study involving seven laboratories. The method included an isocratic part, which is used in the assay. The isocratic part is similar to the assay method for ampicillin of the US Pharmacopeia XXIII Revision. When the isocratic part is combined with gradient elution, the method is suitable for purity control. Six samples of ampicillin (anhydrous, trihydrate and sodium salt) with varying purity were analysed. The main component and related substances were determined. An analysis of variance proved the absence of consistent laboratory bias. The laboratory-sample interaction was significant. Estimates of the repeatability and reproducibility of the method, expressed as standard deviations of the result of the determination of ampicillin, were calculated to be about 0.9 and 1.1 respectively.

Ampicillin↗
PubMed1992

[Giant cell tumors of the ribs. Apropos of a case].

The authors report a case of grade I-II giant-cell tumour of the ribs extending to the thorax and the vertebral column. The tumour was treated by surgical resection followed by vertebral curettage in two stages and adjuvant regional radiotherapy. Giant-cell tumours of the ribs are exceptional and rarely found in the literature. They raise a therapeutic problem (surgery is essential, but radiotherapy is controverted), and a prognostic problem (there is always a potential risk of recurrent malignancy).

Adult↗
PubMed1989

Multiple myeloma: a case of a cure?

It is exceptional to obtain a cure in multiple myeloma. We report a case of a 54-year old man with stage III, IgA K multiple myeloma in complete remission 12 years after the diagnosis. The patient was treated for 4 years with Melphalan-Prednisone. Eight years after the end of treatment the patient fulfilled the criteria of cure as defined by the "Chronic Leukemia Task Group" (no measurable myeloma protein and normal bone marrow) associated with the disappearance of some osteolytic lesions.

Humans↗
PubMed1987

Cellular behaviour in epithelial root sheath following vinblastine administration in mouse.

After injection of vinblastine sulfate (VLB) cells of the epithelial root sheath (ERS) showed accumulation of phagosomes lysosomes and, in particular, of exocytosis vesicles facing the basal lamina. An unusual frequency of cell contacts was also noted between pulp mesenchyme and ERS. In the periradicular zone the cells showed accentuated signs of a squamous-like evolution. In addition, numerous mitotic figures were seen arrested at prometaphase all along the tissue: the mitotic arrest index was higher at the tip of the sheath and decreased more coronally. These findings strongly suggest that ERS participates actively to the formation of the basal lamina. They show that heterogenous cell relations frequently occur during root morphogenesis; however they put into question the role of ERS in cementogenesis. The existence of a high mitotic potential in ERS can explain its consistent morphology and might reflect a process of differential mitotic sequences involved in odontoblast differentiation.

Animals↗
PubMed1979

Metastatic chordoma.

The authors present two cases of vertebral chordomas with widespread metastases. The literature is reviewed and the metastatic potential of chordomas is analysed.

Adult↗
PubMed1978

[Surgical treatment of chronic pain].

In view of negative experience and the disappointing long-term results, most of the classic surgical methods for treating chronic pain are no longer indicated. Only in cancer pain is dissection of the spino-thalamic tract at the cervical or upper thoracic level frequently helpful. In selected cases the same may be said of rhizotomy. Controlled thermocoagulation of the Gasserian ganglion provides the best results in typical trigeminal pain. Other methods of surgical treatment (e.g. commissural myelotomy, thalamotomy) mentioned in this article are things of the past which are no longer used.

Cordotomy↗