Biomedical subjects

J Robert

Publications and source records attributed to J Robert.

At least 379 records · Page 21Linked to original sources

PubMed1986

Sensitivity and specificity of radionuclide equilibrium angiocardiography for detection of hemodynamically significant secundum atrial septal defect.

To determine the value of gated equilibrium angiography in secundum atrial septal defect (ASD) in children, the first pass pulmonic/systemic flow ratio (Qp/Qs) was compared with diastolic count ratio (DCR) and stroke count ratio (SCR) of the two ventricles. In 50 children we have found a correlation between Qp/Qs and DCR (r = 0.71) and between Qp/Qs and SCR (r = 0.66). For detection of significant atrial shunt (QP/Qs greater than 1.5) the sensitivity of DCR greater than 2 was 0.81 and the specificity 0.75. For SCR greater than 1.5 we sensitivity and specificity values of 0.87 and 0.71 respectively. Left and right ventricular ejection fractions were normal (0.67 +/- 0.08 and 0.50 +/- 0.07).

Adolescent↗

PubMed1986

Experimental evidence for the probable involvement of calcium ion transport in 67Ga uptake by tumour cells.

The study of 67Ga-citrate uptake and calcium transport in Ehrlich ascites tumour cells seems to indicate that their peculiar characteristic of increased permeability to extracellular calcium ion might be responsible for their 67Ga accumulation. Experiments performed under different conditions of extracellular calcium, temperature, and presence of ionophore and other plasma membrane modifying agents such as lanthanum appear to corroborate this hypothesis.

Animals↗

PubMed1986

Fluorescence anisotropy of kidney lipids and membranes of a hibernating mammal.

The fluorescence anisotropy of lipids and membranes isolated from kidneys of European hamsters (Cricetus cricetus L.) has been estimated using 1,6-diphenyl-1,3,5-hexatriene as a probe. We have compared in this study the results obtained for two critical periods for a hibernator: winter (torpid state), and summer (active state). The differences were of very low magnitude. A slight increase in anisotropy was noticed in the kidney lipids and microsomal membrane preparations from torpid animals. In contrast, a small decrease in anisotropy was observed in the microsomal lipid extracts of torpid animals. A difference in triglyceride content of winter and summer total kidney lipids was detected, as well as a difference in microsomal protein content between winter and summer membrane preparations. It is hypothesized that the latter observations may explain why the behavior of kidney total lipids and microsomal preparations were different from that presented by kidney microsomal lipids in respect to fluorescence anisotropy. Therefore, only a little, if any, homeoviscous adaptation is exhibited by kidney membranes during hibernation of this mammal.

Animals↗

PubMed1986

Metabolism of doxorubicin and epirubicin in adult human hepatocytes in culture.

Epirubicin is the only anthracycline to be metabolized in humans through a glucuronidation pathway which is not observed in laboratory animals. In search of a model for the experimental study of this metabolism, we have observed that human hepatocytes in culture exhibited this pathway and could be of interest for the understanding of the metabolism of this new drug.

Cells, Cultured↗

PubMed1986

Cellular pharmacology of doxorubicin in sensitive and resistant rat glioblastoma cells in culture.

We have studied the incorporation and cytotoxicity of doxorubicin in cultured rat C6 glioma cells grown as monolayers. Net incorporation was linear up to high extracellular concentrations of drug (10 micrograms/ml). Cytotoxicity was evaluated both by tritiated thymidine incorporation inhibition and cloning efficiency inhibition. For similar total drug exposures, cytotoxicity was very different according to the exposure time and the exposure dose; incubation with a low dose for a long time was much less cytotoxic than that performed with a high dose for a short period of time. We have obtained several clones of doxorubicin-resistant cells. As compared to the wild strain, these cells were characterized by a larger size, a slower growth, a reduced cloning efficiency and a differential sensitivity of 100-1,000 to doxorubicin. Net incorporation of doxorubicin was 5-fold reduced in these cells, due to an increased efflux of the drug. These cells provide an interesting model of doxorubicin-resistant solid tumor in culture.

Animals↗

PubMed1986

Hyperthermia inhibition of tumor cells growth in the presence of ruthenium red.

Ruthenium red (RR) is taken up by DS sarcoma cells as a linear function of its concentration. Higher temperatures produce a higher uptake. This increased uptake is coincident with an augmentation of Trypan blue inclusion. A diminution of calcium transport in the presence of RR is observed at hyperthermia, and its uptake is not linear but presents a plateau for all temperatures and concentrations. RR-cell membrane interaction seems to produce two different effects: an early blocking of calcium transport, and a later change of the physicochemical characteristics of the plasma membrane. On the colony forming ability of CA1 cell RR shows clearly an intrinsic toxic effect, and when present during hyperthermia a low but significant enhancement of tumor cells mortality.

Animals↗

PubMed1986

Calcium and ATPase activity during hepatic intoxication with thioacetamide.

The effects of acute thioacetamide (TAA) intoxication on the calcium, magnesium, sodium and potassium content of liver and on its ATPase activities were studied in rats. Samples of liver were analyzed by atomic absorption spectrometry for their cationic content 6, 24 and 48 h after administration of TAA through a stomach tube. After sonification other samples were assayed for (Na+ + K+)-dependent, (Ca2+ + Mg2+)- and Ca2+-dependent ATPases. No apparent correlation has been found between the increased hepatic calcium after TAA treatment and the variations of ATPase activity. Both calcium movement and ATPase activity appear sex-determined. These results bring support to the hypothesis that an interaction between TAA or its metabolites with the cell membrane provokes an increased influx of extracellular calcium. The relationship between this calcium increase and the changes in ATPase activity with the events triggering the neoplastic transformation is discussed.

Acetamides↗

PubMed1986

[Evaluation of the Rapid-ATB system for testing the sensitivity of staphylococci to antibiotics. Comparison with the agar dilution reference method].

Rapid ATB Staph is a new, automated, four-hour procedure for testing the susceptibility to antibiotics of staphylococci. Results obtained with this method were compared to those recorded using agar dilution. For all tested antibiotics as a group (5 on 201 strains, 8 on 100 strains), overall agreement between the two sets of results was 96%. 1,809 susceptibility tests were performed, with only 24 minor discrepancies (1.3%) mainly involving cotrimoxazole, and 50 major discrepancies (2.7%) mainly involving doxycycline and chloramphenicol. Rapid ATB Staph clearly demonstrates the heterogeneous oxacillin-resistance of staphylococci as well as their inducible resistance to erythromycin. Our results show that this new system is a very accurate means for testing the susceptibility to antibiotics of staphylococci.

Anti-Bacterial Agents↗

PubMed1986

Fatty acid composition transport and metabolism in doxorubicin-sensitive and-resistant rat glioblastoma cells.

We have studied the lipid composition and the acyl group composition, transport, and metabolism of doxorubicin-sensitive and -resistant rat glioblastoma cells in monolayer cultures (C6 clone). No difference in lipid composition was evidenced; the acyl group composition was, in contrast, highly modified in resistant cells, and these modifications appeared progressively during the acquisition of the resistance. Resistant cells were characterized by a decrease of n-9 eicosatrienoic acid and by a 2-3-fold increase of the proportions of the polyunsaturated fatty acids of the n-6 and n-3 families, especially arachidonic acid and n-3 docosahexaenoic acid. These differences were probably due to a 2-fold increase of the uptake of fatty acids by resistant cells as compared to sensitive cells, this increase allowing the suppression of an essential fatty acid deficiency. Only small changes in the transformations of 16 and 18-carbon atoms' fatty acids to higher analogues were evidenced. A small reduction of the desaturation of stearic acid to oleic acid and of linoleic acid to arachidonic acid was the main characteristic of resistant cells; these differences can be explained as a consequence of the suppression of the essential fatty acid deficiency.

Animals↗

PubMed1986

[Isotopic exercise tests and selection of cases of inferior infarction requiring coronarography].

Exercise tests involving isotopes were evaluated in 38 subjects presenting inferior myocardial necrosis. Cardiographic data were used to calculate sensitivity and specificity of the method in detection of subjects requiring surgical treatment. Sensitivity was 90% and specificity 62% when three criteria were employed: ECG of positive exertion, reversible diminished accumulation of thallium 201 outside the necrotic site or decrease in the fraction of ejection force. Examination of the fraction of ejection force improved the results of myocardial scanning using thallium and increased detection of subjects requiring surgery from 61% to 90%.

Adult↗

PubMed1986

Fluorescence anisotropy of cell membranes of doxorubicin-sensitive and -resistant rodent tumoral cells.

We have studied the plasma membrane fluidity of rat C6 glioblastoma cells and simian virus 40-transformed mouse liver cells in culture that had been rendered resistant to doxorubicin. This was done by the evaluation of fluorescence anisotropy of two probes; diphenylhexatriene was used on membrane microsomal fractions, and trimethylammonium-diphenylhexatriene was used on whole cell suspensions as a plasma membrane-specific probe since it does not enter the cells. A higher degree of membrane fluidity was exhibited with both techniques by doxorubicin-resistant glioblastoma cells as compared to the doxorubicin-sensitive strain, but in the transformed liver cells no such alteration was seen in the physical properties of their plasma membranes. A higher degree of acyl group unsaturation was noticed in the glioblastoma cells but not in the transformed liver cells upon acquisition of doxorubicin resistance. A similar simultaneous increase in acyl group unsaturation and membrane fluidity can be obtained easily by growing the sensitive cells with a medium supplemented with exogenous polyunsaturated fatty acids. This alteration does not modify the sensitivity of the cells to doxorubicin. We conclude from our work that the increase in membrane fluidity, which is frequently associated with drug resistance, is neither necessary nor sufficient for the expression of the resistance. The reason for a link between cell resistance to doxorubicin and plasma membrane fluidity remains to be found.

Animals↗

PubMed1985

Predictors of asymptomatic gonorrhea among patients seen by private practitioners.

Nineteen physicians participating in a program for detecting and treating gonorrhea and other sexually transmitted diseases (STD) in high-risk groups filled out encounter forms for the initial visits by the first 3144 patients. This information was used to describe the program users and, by means of logistic regression analysis, to identify predictors of gonorrhea in asymptomatic patients. Overall, 17.3% of the users had culture-proved gonorrhea. Of the symptomatic patients 24.5% had gonorrhea. Of the asymptomatic patients 20.4% of those with a history of contact with a known or suspected case of STD had the disease, and 5.3% of those without a history of contact had the disease. The independent predictors of gonorrhea identified were, in order of importance, a history of contact with a case of STD and being aged less than 30 years. These predictors underline the importance of contact tracing, an underused but productive method of gonorrhea control that can be used effectively in private practice.

Adolescent↗

PubMed1985

Enhancement of hematoporphyrin derivative uptake in vitro and in vivo by tumor cells in the presence of lanthanum.

Hematoporphyrin derivative is currently used as a photochemotherapeutic agent in the treatment of neoplasms. The uptake of hematoporphyrin derivative was determined in vitro and as a function of time with Ehrlich ascites cells in the presence of lanthanum and in vivo with VFM1, tumor-bearing mice pretreated by intratumoral injection of LaCl3. Our results indicate that the treatment with lanthanum increases the uptake of hematoporphyrin derivative by tumor cells.

Animals↗

PubMed1985

Placenta, embryo, and tumor uptake of 67Ga-citrate and 59Fe-citrate.

The uptake of gallium citrate Ga67 and ferrous citrate Fe59 was studied in pregnant rats with or without a 4-dimethylamino-stilben(DS)-induced sarcoma tumor. The liver and placenta of the mother concentrated 67Ga, while the uptake of 67Ga in the embryo was minimal. However, the embryo showed higher concentrations of 59Fe. Preloading with iron did not affect the 67Ga uptake of the placenta, but increased the uptake in the blood and liver of the mother. With regard to 59Fe uptake, iron loading only affected the embryo liver. Tumors and the placenta showed a similar 67Ga uptake but a different incorporation of 59Fe. The probable mechanisms involved are discussed.

Animals↗

PubMed1985

Molecular structures involved in 67Ga and 59Fe binding by placenta and tumors.

The binding of 67Ga and 59Fe by placenta and tumors was compared. After sonification, about 50% of the total radioactivity was present in the insoluble fraction consisting of heavy subcellular particles (mitochondria, fragments of membranes, nuclei, etc.) and known to be rich in lipo- and glycoproteins. Heat denaturation and gel filtration were used to study transferrin and ferritin distribution in the supernatant. The differences between 59Fe and 67Ga uptake in this supernatant seemed to indicate that the transferrin-ferritin system plays a less important role in 67Ga binding than in 59Fe binding.

Animals↗

PubMed1985

Tentative dose-monitoring of doxorubicin in lymphoma patients.

We have investigated the feasibility of individual dose-monitoring of doxorubicin in lymphoma patients. The purpose was to overcome the large variability of the early-phase kinetic parameters of the drug. We have used a test-dose and calculated for 32 patients a therapeutic dose which could allow us to obtain a predetermined early drug exposure. Such a predetermined drug exposure was obtained in 24 patients of the study. Important variations of the early clearance occurred in 8 patients.

Adolescent↗

PubMed1985

Incorporation and turnover of phospholipid precursors in normal and tumoral glial cells in culture.

The incorporation and turnover of phospholipid precursors in cultured normal and tumoral glial cells was investigated during the plateau phase of growth. Glycerol was incorporated similarly by all cell types, and was renewed with a half-life of 19-37 hr. Acetate had a much longer half-life in primary cultures (50-75 hr) than in proliferative tumor cells (20-40 hr). Phosphate had a more rapid turnover rate in primary cultures (25 hr) than in proliferative tumor cells (50 hr). For all precursors, inositol- and choline phosphoglycerides had a faster turnover rate than other phospholipids.

Acetates↗

PubMed1985

Effects of extracellular calcium on calcium transport during hyperthermia of tumor cells.

The effects of different concentrations of extracellular ion calcium on the transport of calcium by tumor cells have been studied by means of the uptake of radiocalcium. Tumor cells incubated at 45 degrees C take up 4-10 times the amount of radioactivity incorporated by cells incubated at 37 degrees C. The difference is still greater (up to 100 times) for the intracellular incorporation as assessed by elimination of the membrane-bound calcium by EGTA treatment. The possible mechanisms involved in this differential behavior are discussed.

Animals↗