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Biomedical subjects

P Raymond

Publications and source records attributed to P Raymond.

At least 55 records · Page 3Linked to original sources
PubMed1991

Study of glucose starvation in excised maize root tips.

Excised maize (Zea mays) root tips were used to follow the effects of a prolonged glucose starvation. Respiration rate began to decrease immediately after excision, reaching 30 to 40% of its initial value after 20 hours, and then declined more slowly until death of the tissues, which occurred after 200 hours of starvation. During the whole process, respiration could be uncoupled by 2,4-dinitrophenol and the energy charge remained high. These results suggest that in excised maize root tips, respiration rate is essentially limited by the rate of biosyntheses (ATP-utilizing processes) rather than mitochondrial number. During starvation the sugar content sharply decreased for the first 20 hours and reached zero at 120 hours. Following root excision, proteins and lipids were continuously degraded and were virtually the only substrates for respiration and biosyntheses after 20 hours of starvation. Over the first 90 hours of starvation, enzymic activities related to sugar metabolic pathways and the Krebs cycle decreased to 20% or less of their initial activity. Starvation was reversible only for the first 80 to 90 hours. Between 80 and 100 hours, there was a sharp fall in intracellular osmolarity and a 25% loss in the dry weight. The irreversibility may be due, as in senescence, to a change in membrane selective permeability.

Journal Article↗
PubMed1990

Mucoadhesion of hydroxypropylmethacrylate nanoparticles to rat intestinal ileal segments in vitro.

The purpose of this study was to evaluate the adhesion of HPMA nanoparticles to mucus using a perfused rat ileum test system. Radiolabeled nanoparticles were prepared and deposited onto rat ileal segments in vitro. The segments were perfused and the perfusate was collected in fractions and assayed for radioactivity. Between 10 and 50% of the radioactivity was eliminated over the first 120-sec perfusion, whereas the remaining activity was firmly attached to the ileum. Among the variables tested, the time interval between nanoparticle deposition and perfusion played the major role, indicating that the mucus-nanoparticle interaction is likely to result from the diffusion of polymers into the mucus and of mucin into the polymeric matrix.

Acrylates↗
PubMed1990

Radioimmunoassay for albuterol using a monoclonal antibody: application for direct quantification in horse urine.

A monoclonal antibody was synthesized in mouse against the O-(3-carboxypropionyl) derivative of albuterol linked to bovine serum albumin. Isotyping of this material revealed the IgG1 class characterized by an affinity constant of 1.03 nM-1 and a density of sites of 0.55 nM. This antibody was found specific as its cross-reactivity to structurally related molecules was less than 1% except for clenbuterol (75%). A radioimmunoassay was set up with culture supernatant (final dilution 1/1000) and [3H] albuterol. The calibration curve was characterized by a maximum binding of 28%, an ED50 of 1.15 pmol per tube, the detection limit was 28.8 fmol/tube and the linearity of the response was up to 39.8 pmol/tube. This RIA method has been used for direct quantitation of albuterol in horse urine without any clean-up or extraction step.

Albuterol↗
PubMed1989

Rheumatic syndromes and beta 2-microglobulin amyloidosis in patients receiving long-term peritoneal dialysis.

We studied 56 patients who had been receiving peritoneal dialysis for greater than 3 years, to investigate the prevalence of rheumatic diseases suggestive of beta 2-microglobulin (beta 2m) amyloid deposition. Eight patients were found to have carpal tunnel syndrome, 16 had chronic shoulder pain, 8 had subchondral bone cysts, and 13 had destructive arthropathies. Amyloid reacting with anti-beta 2m was demonstrated in the hip synovium of 1 patient. Serum beta 2m levels were elevated in all patients. These data suggest that peritoneal dialysis, like hemodialysis, may lead to the development of an arthropathy associated with beta 2m accumulation and beta 2m amyloid deposition.

Adult↗
PubMed1989

New method for the preparation of cyanoacrylic nanoparticles with improved colloidal properties.

The purpose of this study was to prepare nanoparticles with a size significantly smaller than 0.1 micron. It was shown that when sulphur dioxide was dissolved in the cyanoacrylic monomer at a high concentration, subsequent anionic polymerization in an aqueous phase produced particles as small as 10 nm. Moreover, the obtained particles displayed an important negative charge which improve their stability against aggregation. Finally, nanoparticles were successfully prepared in double-distilled water, thereby avoiding the use of dextran which can induce anaphylactoid reactions.

Chemistry, Pharmaceutical↗
PubMed1989

Diffusion of rat atrial natriuretic factor in thermoreversible poloxamer gels.

Concentrated poloxamer 407 solutions display a negative thermorheological behaviour, resulting in a higher viscosity at body temperature than below. This could be exploited for various controlled delivery applications including the nasal delivery of peptides. The rheology of the gel and the diffusion of ANF were studied as a function of temperature. A theory is proposed, according to which a temperature rise creates an intermicellar network resulting in a viscosity increase. The diffusion of the drug appears limited only by the presence of micelles which lengthens the diffusion pathways and is not significantly influenced by the formation of this network.

Atrial Natriuretic Factor↗
PubMed1989

Artefactual Origins of Cyclic AMP in Higher Plant Tissues.

A highly sensitive radioimmunoassay has been used to determine the levels of adenosine 3',5'-cyclic monophosphate (cAMP) in five higher plants (Lactuca sativa, Helianthus annuus, Oryza sativa, Pinus pinaster, Nicotiana tabacum). Particular attention was paid to the three main sources of errors in the characterization of cAMP in plants: presence of interfering substances in plant tissues; possible artefactual formation of cAMP from endogenous ATP during extraction, purification, and assay; and microbial origin of cAMP. In all the tested tissues, the cAMP level was below the detection limit of 0.5 picomole per gram fresh weight, a value much lower than those reported for similar materials of the same species in many previous studies. This result is not in favor of cAMP-dependent regulations in higher plants.

Journal Article↗
PubMed1988

Quantification of carbon fluxes through the tricarboxylic acid cycle in early germinating lettuce embryos.

A method involving labeling to isotopic steady state and modeling of the tricarboxylic acid cycle has been used to identify the respiratory substrates in lettuce embryos during the early steps of germination. We have compared the specific radioactivities of aspartate and glutamate and of glutamate C-1 and C-5 after labeling with different substrates. Labeling with [U-14C]acetate and 14CO2 was used to verify the validity of the model for this study; the relative labeling of aspartate and glutamate was that expected from the normal operation of the tricarboxylic acid cycle. After labeling with 14CO2, the label distribution in the glutamate molecule (95% of the label at glutamate C-1) was consistent with an input of carbon via the phosphoenolpyruvate carboxylase reaction, and the relative specific radioactivities of aspartate and glutamate permitted the quantification of the apparent rate of the fumarase reaction. CO2 and intermediates related to the tricarboxylic acid cycle were labeled with [U-14C]acetate, [1-14C] hexanoate, or [U-14C]palmitic acid. The ratios of specific radioactivities of asparate to glutamate and of glutamate C-1 to C-5 indicated that the fatty acids were degraded to acetyl units, suggesting the operation of beta-oxidation, and that the acety-CoA was incorporated directly into citrate. Short-term labeling with [1-14C]hexanoate showed that citrate and glutamate were labeled earlier than malate and aspartate, showing that this fatty acid was metabolized through the tricarboxylic acid cycle rather than the glyoxylate cycle. This was in agreement with the flux into gluconeogenesis compared to efflux as respiratory CO2. The fraction of labeled substrate incorporated into carbohydrates was only about 5% of that converted to CO2; the carbon flux into gluconeogenesis was determined after labeling with 14CO2 and [1-14C]hexanoate from the specific radioactivity of aspartate C-1 and the amount of label incorporated into the carbohydrate fraction. It was only 7.4% of the efflux of respiratory CO2. The labeling of alanine indicates a low activity of either a malic enzyme or the sequence phosphoenolpyruvate carboxykinase/pyruvate kinase. After labeling with [U-14C]glucose, the ratios of specific radioactivities indicated that the labeled carbohydrates contributed less than 10% to the flux of acetyl-CoA. The model indicated that the glycolytic flux is partitioned one-third to pyruvate and two-thirds to oxalacetate and is therefore mainly anaplerotic. The possible role of fatty acids as the main source of acetyl-CoA for respiration is discussed.

Acetates↗
PubMed1988

Radionuclide exploration of dialysis amyloidosis: preliminary experience.

The noninvasive diagnosis of amyloid arthropathy in dialysis patients is still uncertain. Therefore, we investigated the potential diagnostic value of the 99mTc-methylene diphosphonate scan in seven long-term hemodialysis patients suffering from chronic joint pain who had biopsy-proven osteoarticular amyloidosis of the recently discovered beta 2-microglobulin (beta 2-M) type. In six, but in none of five control patients on short-term hemodialysis, increased tracer uptake was found at the site of one or several articular and/or periarticular regions. Increased uptake at a given joint was often, but not always, associated with joint pain. It appeared to precede radiologically visible changes. In conclusion, the 99mTc-methylene diphosphonate scan may be of help in the early diagnosis of dialysis amyloidosis.

Adult↗
PubMed1985

ATP Production by Respiration and Fermentation, and Energy Charge during Aerobiosis and Anaerobiosis in Twelve Fatty and Starchy Germinating Seeds.

The respiration and fermentation rates were compared in germinating seeds of 12 different cultivated species from five families. In air, fermentation contributes significantly to the energy metabolism only in some species (pea, maize), but is generally negligible when compared to respiration. The fermentation rate under anoxia was related either to the metabolic activity under air or to the adenine nucleotide content of the seeds: it was generally higher in seeds which contain starchy reserves (rice, maize, sorghum, pea), than in seeds which do not contain starch (lettuce, sunflower, radish, turnip, cabbage, flax); however, it was similar in wheat, sorghum (starchy seeds), and soya (nonstarchy seeds). The value of the energy charge of all the seeds was lower under anoxia than in air: after 24 hours under anoxia, it was higher than 0.5 in the starchy seeds and in soya and it was around 0.25 in the other fatty seeds.

Journal Article↗
PubMed1985

Germination, respiration, and adenylate energy charge of seeds at various oxygen partial pressures.

The effect of O(2) partial pressure on the germination and the respiration of 12 cultivated species was studied. The reciprocal of the time necessary to observe rootlet emergence in 50% of the seeds was used to approach the germination rate. The maximum germination and respiration rates were reached in most seeds at O(2) pressures close to that of air. Decreasing the O(2) pressure produced a gradual decrease of the germination rate. The seeds could be classed in two groups according to their response to low O(2) pressures. Group I includes lettuce, sunflower, radish, turnip, cabbage, flax, and soybean: at O(2) pressures close to 2 kilopascals, the germination in this group was stopped and the adenylate energy charge was lower than 0.6. Group II includes rice, wheat, maize, sorghum, and pea. The germination rate of these seeds was also gradually decreased by lowering the O(2) partial pressure but germination still occured, very slowly, at 0.1 kilopascal; the adenylate energy charge remained higher than 0.6. These differences in the germination rates and adenylate energy charge values could not be explained by differences in the sensitivity of respiration to O(2).

Journal Article↗
PubMed1983

Oxygen Transport and Root Respiration of Maize Seedlings: A Quantitative Approach Using the Correlation between ATP/ADP and the Respiration Rate Controlled by Oxygen Tension.

Oxygen uptake and ATP/ADP ratio were simultaneously monitored during incubation of excised maize (Zea mays L. INRA 508) root tips under varying O(2) partial pressure. Both variables were independent of O(2) tension until a critical O(2) pressure was reached. Below this pressure, ATP/ADP ratio and respiratory rate declined. However, in tissues having a high glycolytic capacity, the correlation between the ATP/ADP ratio and the respiratory rate breaks down as O(2) tension decreases, due to the increasing contribution of fermentative processes.In presence of 2 millimolar NaF, the ATP/ADP ratio varied solely as a function of the O(2) tension, without interference by fermentative activity, and a close correlation links the ATP/ADP ratio and the respiratory rate of excised maize root tips over the whole range of O(2) tensions tested.Using this correlation, a method is proposed for the quantitative determination of the relative cellular respiratory rate permitted by O(2) transport from the aerial part of young maize seedlings along the seminal root placed in an anoxic environment.Data are presented which demonstrate the preeminent part played by the cortical air spaces in O(2) transport. Their contribution to respiration was high in the first few centimeters nearest the seed and decreased rapidly as the distance from the aerated source increased. It is concluded that O(2) transport might contribute to the survival or to adaptive responses of root tissues in flooded soils but that the ventilation of the apical growing zone was inadequate to sustain the growth.

Journal Article↗
PubMed1980

Stabilization of adenine nucleotide ratios at various values by an oxygen limitation of respiration in germinating lettuce (Lactuca sativa) seeds.

The concentrations of adenine nucleotides were determined in germinating lettuce (Lactuca sativa) seeds after transitions from air to hypoxic or anoxic atmospheres. The ratio ATP/ADP and the energy charge were rapidly lowered after the transitions and remained stable at low values for hours. The energy charge in anoxia stabilized at a value close to 0.3. After 24 h in anoxia the energy charge rose rapidly to high values (0.9) when N2 was replaced by air. The metabolic properties of lettuce seeds had then been conversed for hours at low energy charge. In hypoxia the O2 uptake was decreased and the energy charge was stabilized at values intermediate between that in air and that in anoxia. When the O2 partial pressures (pO2) were 5 and 2kPa, the values of O2 uptake were one-third and one-sixth of that in air, and the energy charges were 0.7 and 0.5. These results show that the energy charge is regulated over a wide range of values. The ratio ATP/ADP and the energy charge are indicators of the limitation of metabolic activity by hypoxia.

Adenine Nucleotides↗
PubMed1980

Metabolic Activity and Energy Charge of Excised Maize Root Tips under Anoxia: CONTROL BY SOLUBLE SUGARS.

Energy charge and fermentative metabolism under anoxia were monitored in excised maize root tips after various times of aging in air and were related to their soluble sugar content. The energy charge value, which was 0.9 in air irrespective of the time of aging, dropped to a lower value within minutes of transfer to a nitrogen atmosphere. This value was dependent upon sugar content of the tissues which was itself a function of aging. The energy charge value after transfer to nitrogen was 0.6 in freshly excised tissue but only 0.2 in tissue aged for 4 hours. When aged tissues supplied with 0.2 molar glucose were transferred to nitrogen, the energy charge was 0.6, irrespective of the time of aging. When 0.2 molar glucose was added under nitrogen, energy charge rose to 0.6. This rise was faster in root tips aged for 8 hours than those aged for 24 hours.The rate of ethanol plus lactate production (representing 60 and 10%, respectively, of the total sugar consumption in anoxia) was closely correlated to the level of energy charge. It is concluded that, in anoxia, there is a quantitative relationship between the energy charge value and the level of metabolic activity via fermentative pathways.

Journal Article↗
PubMed1979

[Reversible dialytic encephalopathy after interruption of aluminium intake. 6 cases (author's transl)].

The cases presented with psychic troubles and repeated somnolence episodes accompanied by dysarthria in 5 cases, myoclonic jerks in 4 cases and epileptic seizures in 1 case. In all cases the EEG was disturbed. It showed symetrical, paroxystic, bilateral, monomorph slow activity with more or less frequent paroxysms. The average serum aluminium level was at 407 microgram/l in the acute phase, at 161 microgram/l in the remission phase and at 123 microgram/l three months later. After interruption of oral and dialytic aluminium intake the remission is maintained. However in 2 cases the transitory readministration of aluminium gel was followed by reversible recurrency. The role of both aluminium gel and dialysate aluminium as the origin of encephalopathy is discussed.

Aged↗
PubMed1978

[Prolonged and reversible encephalopathy in a chronic haemodialysis patient. Probable responsibility of aluminium salts (author's transl)].

A case of encephalopathy with elevation of plasma aluminium level in a patient treated by maintenance hemodialysis is reported. Clinical symptoms were made of moderate impairment of intellectual functions and of intermittent drowsiness. EEG after 3 minutes of hyperpnea evidenced bisynchronous anteriorly dominant intermittent delta waves. Plasma aluminium level, determined by atomic absorption spectrophotometry, was initially at 300 microgram/l (normal range greater than 40 microgram/l). After interruption of aluminium gels, clinical and EEG symptoms slowly subsided in 9 months, plasma aluminium level came down to 145 microgram/l. This picture of encephalopathy could preceede irreversible dialysis dementia in chronic dialysis patients.

Aluminum↗