PubMed Health⌕ Search

Biomedical subjects

L Richard

Publications and source records attributed to L Richard.

At least 19 recordsLinked to original sources
PubMed1992

Picosecond phase grating spectroscopy of hemoglobin and myoglobin: energetics and dynamics of global protein motion.

Phase grating spectroscopy has been used to follow the optically triggered tertiary structural changes of carboxymyoglobin (MbCO) and carboxyhemoglobin (HbCO). Probe wavelength and temperature dependencies have shown that the grating signal arises from nonthermal density changes induced by the protein structural changes. The material displaced through the protein structural changes leads to the excitation of coherent acoustic modes of the surrounding water. The coupling of the structural changes to the fluid hydrodynamics demonstrates that a global change in the protein structure is occurring in less than 30 ps. The global relaxation is on the same time scale as the local changes in structure in the vicinity of the heme pocket. The observed dynamics for global relaxation and correspondence between the local and global structural changes provides evidence for the involvement of collective modes in the propagation of the initial tertiary conformational changes. The energetics can also be derived from the acoustic signal. For MbCO, the photodissociation process is endothermic by 21 +/- 2 kcal/mol, which corresponds closely to the expected Fe-CO bond enthalpy. In contrast, HbCO dissipates approximately 10 kcal/mol more energy relative to myoglobin during its initial tertiary structural relaxation. The difference in energetics indicates that significantly more energy is stored in the hemoglobin structure and is believed to be related to the quaternary structure of hemoglobin not present in the monomeric form of myoglobin. These findings provide new insight into the biomechanics of conformational changes in proteins and lend support to theoretical models invoking stored strain energy as the driving force for large amplitude correlated motions.

Carboxyhemoglobin↗
PubMed1992

[Pathology of unstable sequence of genome: fragile-X-syndrome].

Fragile X syndrome is the most frequent form of inherited mental retardation and is associated with a fragile site at Xq27-3. This fragile site is an unstable microsatellite repeat, p(CCG). In fragile X syndrome families, this sequence exhibits variable amplification, the length of which correlates with phenotype. Affected persons have both a "full mutation" and abnormal DNA methylation. Subjects with smaller increase of this sequence, called "premutation", have little or no risk retardation, but are at high risk of having affected children or grandchildren. The passage from "premutation" to "full mutation" status occurs only with transmission from the mother. The unusual segregation patterns in fragile X pedigrees is referred to as the Sherman paradox, now elucidated by genotypic analysis. We present here a brief review of this pathology and illustrate the use of this new diagnostic test in our laboratory.

DNA↗
PubMed1991

Direct observation of global protein motion in hemoglobin and myoglobin on picosecond time scales.

Picosecond phase-grating spectroscopy is highly sensitive to density changes and provides a new holographic approach to the study of protein dynamics. Photodissociation of carbon monoxide from heme proteins induces a well-defined transition from a ligated to a deoxy structure that is important to hemoglobin and myoglobin functionality. Grating spectroscopy was used to observe protein-driven density waves on a picosecond time scale after carbon monoxide dissociation. This result demonstrates that global tertiary structure changes of proteins occur on an extremely fast time scale and provides new insight into the biomechanics of deterministic protein motion.

Animals↗
PubMed1991

Isolation and primary structure of the ERG9 gene of Saccharomyces cerevisiae encoding squalene synthetase.

The ERG9 gene of Saccharomyces cerevisiae has been cloned by complementation of the erg9-1 mutation which affects squalene synthetase. From the 5 kb insert isolated, the functional gene has been localized on a DNA fragment of 2.5 kb. The presence of squalene synthetase activity in E. coli bearing the yeast DNA fragment isolated, indicates that the structural gene encoding squalene synthetase has been cloned. The sequence of the 2.5 kb fragment contains an open reading frame which could encode a protein of 444 amino acids with a deduced relative molecular mass of 51,600. The amino acid sequence reveals one to four potential transmembrane domains with a hydrophobic segment in the C-terminal region. The N-terminus of the deduced protein strongly resembles the signal sequence of yeast invertase suggesting a specific mechanism of integration into the membranes of the endoplasmic reticulum.

Amino Acid Sequence↗
PubMed1991

A role for gamma interferon, tumor necrosis factors, and soluble T-cell receptors in the depressed blastogenic response of spleen cells of Mycobacterium lepraemurium-infected mice.

Spleen cells of Mycobacterium lepraemurium-infected mice were cultured on petri dishes coated with mycobacterial antigens, and antigen-reactive cells were isolated. Upon incubation in mitogen- or antigen-free culture medium, these cells released mediators capable of depressing the in vitro proliferative response of normal splenocytes to specific antigen and to concanavalin A and lipopolysaccharide. One of these mediators was identified with gamma interferon (IFN-gamma), mainly on the basis that treatment of supernatants with monoclonal anti-IFN-gamma antibodies markedly reduced the suppressive activity contained therein. Detectable levels of tumor necrosis factor alpha (TNF-alpha) and TNF-beta were present in spleen cell culture supernatants of infected mice. Moreover, low doses of recombinant TNF-alpha and TNF-beta were found to potentiate the suppressive activity of exogenous IFN-gamma. Soluble T-cell receptors beta were also detected in the culture supernatants. The elimination of these molecules with monoclonal anti-T-cell receptor beta (F23.1) antibodies immobilized on a plastic surface partially reversed the depression of the response to mycobacterial antigen but did not affect the response to mitogens. These results revealed the complex nature of suppressor mediators that are produced by mycobacterial antigen-reactive cells and that regulate the in vitro proliferative response.

Animals↗
PubMed1990

Biological properties of factors secreted by antigen-reactive suppressor cells in mice infected with Mycobacterium lepraemurium.

Antigen-reactive cells were isolated from the spleens of Mycobacterium lepraemurium-infected C57BL/6 mice on petri dishes coated with mycobacterial antigens. When adoptively transferred to syngeneic mice, the mycobacterial antigen-reactive cells were found to depress the induction and expression of the delayed-type hypersensitivity (DTH) reaction to M. lepraemurium antigens. The adoptive transfer of soluble suppressor factors (SF) secreted by these cells inhibited only the expression of DTH. The cells depressing the induction of DTH mainly belonged to the L3T4+ (CD4+) T-lymphocyte subset, whereas those depressing its expression differed from the L3T4+ and Lyt-2+ (CD8+) subsets. Treatment of M. lepraemurium-infected mice with SF reduced their mean survival time and enhanced the multiplication of bacilli at the site of infection and their dissemination to the spleen and liver. In vitro at least, SF appeared to interfere at the level of mycobacterial antigen recognition by T lymphocytes rather than at the levels of antigen processing and presentation by macrophages.

Animals↗
PubMed1990

[Current role of decortication in problems of bone healing].

The authors present the results of 101 osteo-periostal decortications. This technique was used in 72 cases of aseptic non-union, 15 cases of infected non-union and 14 cases with malunion. Stable fixation was carried out using a plate or an external Judet fixator. An autologous cancellous or cortico-cancellous bone graft was added in 12 cases. Union was achieved in 98 of 101 patients after an average of 45 days to 4 months, depending on the localisation and the etiology involved. The 3 failures were due to technical errors or presence of an unfilled bone defect. Osteoperiostal decortication is a reliable and reproductible solution to many problems of malunion or non-union. We consider bone grafting to be necessary only in patients with a major bone defect.

Bone Transplantation↗
PubMed1990

Methods of theophylline assay and therapeutic monitoring of this drug.

The purpose of this article is to review various analytical methods of monitoring plasma theophylline. This article was investigated by the "Drug Commission" of SFBC (Société Française de Biologie Clinique). The primary objective is to provide the "know-how", particular for this analysis, which allows the choice between various analytical methods available: immunochemical or physiochemical ones. The techniques described are not necessarily the best, they are approved and tested methods which are the most frequently used in routine practice. The proposed immunochemical methods are: absorption spectroscopy methods: Enzyme ImmunoAssay (EIA), Enzyme Multiplied ImmunoAssay Technique (EMIT); Reflectance spectroscopy method: Apoenzyme Reactivation Immunoassay System (ARIS); Fluorometry spectroscopy method: Substrate Labeled FluoroImmunoAssay (SLFIA); Fluorometry spectroscopy on solid base; Polarization fluorescence spectroscopy ImmunoAssay (FPIA); Turbidimetric measurements: Particle Enhanced Turbidimetric Inhibition ImmunoAssay (PETINIA); Nephelometric measurement: Nephelometric Inhibition ImmunoAssay (NIIA). And the proposed physicochemical methods are: High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC). The second objective is a review of pharmacological properties of theophylline, necessary for a good understanding of therapeutic drug monitoring: intestinal resorption, distribution, metabolism and elimination, drug interactions, dose/response relationship, physiopathological variations and proposed "predictive" "theophylline test". The authors conclude that because of the multiplicity of methodologies used in theophylline therapeutic monitoring the choice of one of them is not easy. The best way to compare different techniques available would be the use of a "reference material" for theophylline monitoring and a quality control network between different clinical pharmacological laboratories.

Chromatography, Gas↗
PubMed1989

Malignant germ cell sacrococcygeal tumors in children. Improved prognosis after introduction of cisplatin-containing multiple drug treatment.

The survival of children with malignant germ cell sacrococcygeal tumors has improved during the last few years after introduction of a multidrug protocol including cisplatinum. Treatment for 10 patients registered in 1965-1978 was not uniform and consisted of surgical resection or biopsy and radiotherapy with or without multiple drug chemotherapy (methotrexate + actinomycin D + cyclophosphamide). Only one of these patients is alive. Fifteen patients registered between 1978 and 1986 were treated with actinomycin D + cyclophosphamide + vincristine + doxorubicin + bleomycin + cisplatinum. Four patients also received radiotherapy. Seven out of these 15 children are alive without evidence of disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

[Plasma determination of 7 common drugs by high performance liquid chromatography].

A high performance liquid-chromatographic procedure is reported for measuring the plasma concentration of 5 anticonvulsants: phenobarbital, phenytoin, carbamazepine, ethosuximide, valproic acid and 2 bronchodilators: theophylline and caffeine. Limits of detection of ethosuximide and valproic acid are 28 mumol/l, 5 mumol/l for the other drugs. Linearity limits are always very upper than the higher therapeutic dose concentration, the inter assay relative standard deviation are less than 8 p. cent for the 7 drugs at the 3 levels of concentration and the analytical recoveries ranged from 93 to 104 p. cent. The technique is simple and rapid: 4 anticonvulsants are simultaneously extracted and dosed, valproic acid, only has to be dosed lonely. Finally, comparatively to the other immunoassay technique, this method is cheaper.

Anticonvulsants↗
PubMed1989

[Advances in the treatment of acute myeloid leukemia in children. Experience of the Argentinian Group of Acute Leukemia Treatment and the Latin American Group of Malignant Hemopathies Treatment 1967-1987].

Three hundred and seventy-one children below 16 years, with newly diagnosed acute myeloid leukaemia, were included in six consecutive GATLA/GLATHEM protocols, from November 1967 to December 1987. The study was divided in three periods: 1967 to 1975, 1976 to 1982, and 1983 to 1987. Three induction schedules were used during the first two periods, and different maintenance schemes alternating with monthly consolidations were explored; the value of immunotherapy with C. Parvum and androgen therapy with stanozolol was also tested. Protocol 3-AML-83, representing the third period, included a four-week induction phase with vincristine, adriamycin, cytosine-arabinoside, prednisone and 6-mercaptopurine, followed by a consolidation phase with cyclophosphamide, cytosine-arabinoside and 6-mercaptopurine for four weeks. Maintenance phase included daily, oral 6-mercaptopurine, and monthly cytosine-arabinoside, both during two years, and adriamycin every eighth week, for one year. Complete remission rates for the first two periods of therapy were 40% and 55%, whereas that of the last period was 74%. The overall results of the period 1967-1982, showed actuarial duration rates of complete remission, event-free survival and survival, at 60 months, between 2% and 6%, their median duration being of 9, 8 and 10 months respectively. No significant difference was observed between the first two periods or protocols. Protocol 3-AML-83, activated in March 1983, achieved actuarial rates of continuous complete remission, event-free survival, and survival of 51%, 37% and 39% respectively, at 48 months. The difference between the first two periods and the last one was highly significant (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Femur lengthening in children and adolescents. Comparative study of a series of 82 cases].

The authors reviewed 82 cases of femur lengthenings performed in 71 children and adolescents during a period of 15 years. They successively used 6 technics, the one-stage lengthening 14 times, the Judet technic 20 times, the Wagner technic 13 times, a personal technic combining the transversal osteotomy and a grafting 11 times, the llizarov technic 4 times, the callotasis technic 20 times. They study the complications faced, according to the technic, the etiology, the importance of the shortening, the age, and the repetition of the procedure. If the previous lengthenings were always achieved, complications frequently occurred with the ancient technics. In the authors' experience, the callotasis technic is the best, since they had no serious complications out of 20 cases, and 85 p. 100 of the patients had none apart from the inevitable infection of the pins in progressive lengthenings. They provide explanations to this important improvement and recall the details of the technics.

Adolescent↗
PubMed1988

Partial characterization of suppressor factors in spleen cell culture supernatants of Mycobacterium lepraemurium-infected mice.

Suppressor factors (SF) were released into the culture supernatant when spleen cells from M. lepraemurium-infected C57BL/6 mice were incubated at 37 degrees C in the absence of any inducing agents. Some of the SF appeared to be specific in that they inhibited the blastogenic response to mycobacterial antigens by opposition to the others which inhibited the blastogenic responses to PHA, Con A and LPS. All SF seemed to be produced in a cyclic manner. In mice infected 9 weeks earlier, the release of "specific" SF occurred early (4-8 h) during the incubation period whereas, the nonspecific SF were released later on (12-32 h). Adoptive transfers of SF-containing culture supernatants depressed the expression of DTH to M.1m antigens but not its induction.

Animals↗
PubMed1987

Suppressor T cells for delayed-type hypersensitivity in susceptible mice infected with Mycobacterium lepraemurium.

Spleen cells from immunodepressed C3H mice, i.e., mice inoculated intravenously 4 months earlier with 1 X 10(7) Mycobacterium lepraemurium (Mlm) bacilli, were separated into different populations, and the T-cell-enriched population was treated further with gamma-irradiation or specific anti-Lyt antibodies plus complement. The cell populations obtained were then adoptively transferred to normal and Mlm-sensitized syngeneic mice in order to investigate whether or not suppressor cells regulate the delayed-type hypersensitivity (DTH) reaction to specific antigens. A radiosensitive cell population expressing the Lyt 1+, 2+ phenotype had the capacity to depress the induction (afferent phase) of DTH reaction. In contrast, a radioresistant cell population expressing the Lyt 1+, 2- phenotype possessed the capacity to depress the expression (efferent phase) of the cutaneous reaction. Thus, distinct populations of suppressor cells, each regulating a different phase of DTH, are induced in the spleen of Mlm-infected mice.

Animals↗