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Biomedical subjects

F Millet

Publications and source records attributed to F Millet.

11 recordsLinked to original sources
PubMed1999

Vertical free-standing films of amphiphilic associating polyelectrolytes.

Hydrophobically modified poly(acrylic acid) sodium salt (HMPAANa) copolymers are known to provide a huge stabilization of oil in water macroemulsions. An interstitial HMPAANa film is formed between the oil droplets, thus creating repulsion between them. We present an x-ray reflectivity study of vertical free-standing films drawn from aqueous solutions of HMPAANa copolymers. The vertical HMPAANa films are model systems for the interstitial films between oil droplets and the description of their behavior provides information about the stabilization process. Their thickness was investigated as a function of various parameters such as the solution concentration, the degree of grafting, the length of the grafts, and the backbone molecular weight. Below a solution concentration threshold (C(t)), the film thickness scales like the square root of the molecular weight and is independent of the degree of grafting and the length of the grafts. Polyelectrolyte chains adopt a self-screened coil conformation within the films and the thickness is governed by the radius of gyration of the coils. Above C(t), a transition from a bimolecular film to a physical gel is observed and the thickness then increases with concentration. Finally, we propose an explanation for the stabilization of macroemulsions by HMPAANa copolymers.

Journal Article↗
PubMed1998

Benzene exposure in car mechanics and road tanker drivers.

The purpose of this study was to identify professional factors related to benzene exposure and to deduce suitable safety measures. Atmospheric benzene, urinary muconic acid (tt-MA) and leukocyte alkaline phosphatase activity (LAPA) were evaluated among 66 car mechanics, 34 road tanker drivers, and 28 nonexposed workers. Professional and medical questionnaires were filled in at the same time. Atmospheric benzene was significantly higher among road tanker drivers than among car mechanics. The arithmetic mean +/- SD, median, and geometric mean values were, respectively, 0.48 +/- 1.49, 0.14, and 0.06 mg/m3 among car mechanics and 1.88 +/- 4.18, 0.68, and 0.65 mg/m3 among road tanker drivers. In the latter case the increase was caused by transport of unleaded petrol and correlated with the volume of the tank. Among car mechanics, tobacco smoking, windy conditions, dismantling of petrol filters, and handling of petrol increased atmospheric benzene levels. Urinary muconic acid was increased significantly among car mechanics (148 +/- 137, 127, and 111 micrograms/g) and among road tanker drivers (309 +/- 420, 137, and 151 micrograms/g) as compared with the controls (49 +/- 46, 33, and 33 micrograms/g). Among road tanker drivers, alcohol intake and transportation of unleaded petrol increased the excretion of muconic acid, which was also directly related to the volume of the tank. Among car mechanics, professional factors (dismantling of petrol filters, handling of and washing of hands with petrol) and nonprofessional factors (tobacco smoking and damaged skin on the hands and forearms) increased muconic acid excretion. In the control group, tobacco smoking increased its excretion. LAPA was not significantly modified among exposed workers. There was a weak but significant linear correlation between LAPA and muconic acid. These results suggest that to reduce exposure to benzene in unleaded petrol, individual and collective safety measures should be imposed in both occupations.

Air Pollutants, Occupational↗
PubMed1995

Design of ruthenium-cytochrome c derivatives to measure electron transfer to cytochrome c peroxidase.

A new technique has been introduced to measure interprotein electron transfer which involves photoexcitation of a tris(bipyridine)ruthenium (Ru) complex covalently attached to one of the proteins. Four different strategies have been developed to specifically attach Ru to protein lysine amino groups, histidine imidazole groups, and cysteine sulhydryl groups. These strategies have been used to prepare more than 20 different singly-labeled Ru-cytochrome c derivatives. The new ruthenium photoexcitation technique has been used to study the mechanism for electron transfer between cytochrome c and cytochrome c peroxidase. Laser excitation of a complex between Ru-cytochrome c and cytochrome c peroxidase compound I results in formation of Ru(II*) which is a strong reducing agent, and rapidly transfers an electron to heme c Fe(III) to form Fe(II). The heme c Fe(II) then rapidly transfers an electron to the Trp-191 radical cation in CMPI. The rate constant for this reaction is 6 x 10(4) s-1 for a horse Ru-cytochrome c derivative labeled at lysine 27, and greater than 10(6) s-1 for yeast Ru-cytochrome c derivatives. A second laser flash results in electron transfer from heme c to the oxyferryl heme in cytochrome c peroxidase compound II with a rate constant of 350 s-1. The ruthenium photoreduction technique has been used to study the interaction domain between the two proteins, the pathway for electron transfer to the radical cation and the oxyferryl heme, and the specific residues in the heme crevice which control the electron transfer properties of the Trp-191 radical cation and the oxyferryl heme.

Animals↗
PubMed1984

An immunochemical procedure to evaluate the degree of desialylation of alpha 1-acid glycoprotein in rat serum.

When radial immunodiffusion (RID) and electroimmunodiffusion (EID) were used for the determination of rat alpha 1-acid glycoprotein (alpha 1-AGP) a significant discrepancy in the results was encountered depending on the degree of sialylation. When alpha 1-AGP was desialylated, the amounts estimated by EID were much lower than those actually present as assayed by the RID method. The relationship between the percentage of desialylation of alpha 1-AGP and the percentage of its underestimation by EID relative to RID was determined and a calibration curve was plotted to evaluate the degree of desialylation of rat alpha 1-AGP. When compared to other procedures (rat membrane inhibition assay and isoelectrofocusing), the proposed method was easier to perform and allowed the specific evaluation of the degree of undersialylation of the glycoprotein.

Animals↗
PubMed1984

[Biological stigmata of lead poisoning from water and their peculiarities. Application to the choice of diagnostic tests].

We have studied the diagnostic efficiency of some biological tests in 59 consecutive patients whom we suspected to be poisoned by lead from drinking water. This diagnosis was confirmed in 30 patients in whom EDTA-promoted urinary excretion of lead was greater than 800 micrograms/24 hr. The measurement of delta-ALA (delta-aminolevulinic acid) dehydrase was the most sensitive test (89.7 p. 100). Sensitivities of protoporphyrin blood level (64.7 p. 100), of serum lead level (46.2 p. 100), of the presence of erythrocytes with basophilic stippling in blood (44.4 p. 100) were lower. The determinations of urinary coproporphyrin and of delta-ALA levels in blood and urine had no practical diagnostic value. We conclude that the best screening test for the diagnosis of lead poisoning by drinking water is the measurement of delta-ALA dehydrase activity. An increase of the EDTA-promoted urinary excretion of lead is required for a final confirmation of the diagnosis.

Adult↗
PubMed1981

Reduction of bile salt secretion in children with coeliac disease in activity and in remission.

To assess the role of intestinal absorption in bile secretion, the effects of milk perfusion into the duodenum on bile salt secretion were studied in children with active coeliac disease. Bile secretion was evaluated by measuring the bile salt concentration and output in the duodenum in response to a perfusion with a milk containing a casein hydrolysate as the protein source (4 ml/min/m2) followed by i.v. injection of 2 U/kg cholecystokinine (CCK). Bile salt output was estimated taking into account the dilution of the BSP perfused into the first part of the duodenum and collected 15 cm further on. Results found in nine children with active coeliac disease (A) were compared both to results for seven control children (C) and to those for three children with coeliac disease in remission (CDR). The values obtained show: 1. a significant drop in bile salt concentration and output in response to Nutramigen perfusion in groups A and CDR compared to group C; 2. a diminution in bile salt output perfusion is groups A and CDR; 3. smaller variations in bile salt output (expressed in mumol/min m2) after i.v. stimulation by CCK in group A (from 25 +/- 3.5 to 36 +/- 8.5) than in group C (from 46 +/- 6 to 52 +/- 9) or group CDR (from 19.5 +/- 1.4 to 52 +/- 20.6). However, there was no significant difference between the groups, because responses were heterogeneous; 4. there was no correlation between bile salt output or intestinal concentration of bile salt and fat absorption. These results indicate a reduction in bile salt secretion during the active phase of coeliac disease. The mechanism controlling this anomaly is not clear, since reduced bile salt output persisted after histological restoration of the duodenum.

Bile Acids and Salts↗