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Biomedical subjects

S Arnaud

Publications and source records attributed to S Arnaud.

70 records · Page 4Linked to original sources
PubMed1992

In vivo assessment of forearm bone mass and ulnar bending stiffness in healthy men.

The cross-sectional bending stiffness EI of the ulna was measured in vivo by mechanical resistance tissue analysis (MRTA) in 90 men aged 19-89 years. MRTA measures the impedance response of low-frequency vibrations to determine EI, which is a reflection of elastic modulus E and moment of inertia I for the whole ulna. EI was compared to conventional estimates of bone mineral content (BMC), bone width (BW), and BMC/BW, which were all measured by single-photon absorptiometry. Results obtained from the nondominant ulna indicate that BW increases (r = 0.27, p = 0.01) and ulnar BMC/BW decreases (r = -0.31, p < or = 0.005) with age. Neither BMC nor EI declined with age. The single best predictor of EI was BW (r2 = 0.47, p = 0.0001), and further small but significant contributions were made by BMC (r2 = 0.53, p = 0.0001) and grip strength (r2 = 0.55, p = 0.0001). These results suggest that the resistance of older men to forearm fracture is related to age-associated changes in the moment of inertia achieved by redistributing bone mineral farther from the bending axis. We conclude that the in vivo assessment of bone geometry offers important insights to the comprehensive evaluation of bone strength.

Absorptiometry, Photon↗
PubMed1991

Purification and characterization of the oxidase from the marine bacterium Pseudomonas nautica 617.

The aerobic respiratory system of the hydrocarbonoclastic marine bacterium Pseudomonas nautica 617 ends with a single terminal oxidase. It is a heme-containing membranous protein which has been demonstrated only to reduce molecular oxygen to hydrogen peroxide [Denis, M., Arnaud S. & Malatesta, F. (1989) FEBS Lett. 247, 475-479]. The purification of this oxidase was achieved in a single step through by DEAE-Trisacryl chromatography. SDS/PAGE showed the presence of four subunits. The pI was found to be 4.45 and a Mr of 130,000 was determined by gel filtration. The amino acid composition of the purified terminal oxidase has been determined. About 52% of the residues are hydrophobic, strengthening the membranous nature of this bacterial oxidase. Room temperature optical spectra are typical of heme b with a 560-nm band for the reduced form in the alpha range. The prosthetic group is made of two hemes b, one high-spin (S = 5/2, gl = 5.9, g parallel approximately 2.0), the other low-spin (S = 1/2, gz = 2.94, gy = 2.27). No other metal centre was detected by EPR. The two hemes remained unresolved in optical spectra, even at low temperature, and throughout redox titration. They behaved potentiometrically like a one-electron, single redox couple, with Em = 87 +/- 10 mV at pH 7.2 and 293 K. The purified oxidase did not oxidize ferrocytochrome c, but displayed quinol oxidase activity both with the native quinone (2419 nmol O2.min-1.mg protein-1 and commercially available coenzyme (101.74 nmol O2.min-1.mg protein-1). Exposure of the reduced enzyme to CO induced the collapse of alpha and beta bands as occurred during reoxidation. In contrast, NaCN and NaN3 fully inhibited the oxidase activity. Results are discussed with respect to other purified quinol oxidases.

Amino Acids↗
PubMed1991

Variations of vitamin D-like reactivity in the crustacean Orchestia cavimana during the molt cycle.

An investigation into vitamin D-like molecules has been performed on whole extracts of the terrestrial amphipod Orchestia cavimana, using a sensitive nonequilibrium assay employing 1,25-(OH)2 D receptor from calf thymus. Relatively large amounts of these secosteroid-like molecules were observed and they varied in concentration according to the stages of the molt cycle. The amplitude of these variations reaches a ratio of about 40 from the minimum in premolt to the intermolt sharp peak.

Animals↗
PubMed1990

Kidney cell lysates contain an activity that stimulates mature erythroid burst-forming-unit (mBFU-E) proliferation.

This study reports the detection of an activity that stimulates the development of a subclass of burst-forming unit-erythroid (BFU-E) progenitors giving rise to small bursts in semi-solid cultures established in the presence of saturating concentrations of erythropoietin. These progenitors are considered to be mature BFU-E. The activity is found in extracts from kidney cells and appears to be physiologically regulated as it was respectively enhanced and decreased in kidneys from anemic and polycythemic mice. The disappearance of activity in kidney-cell extracts during long-term polycythemia correlated with an accumulation of mature BFU-E in the spleen and bone marrow of polycythemic mice. Using specific neutralizing antibodies and in vitro tests, we also show that this activity is different from hemopoietins known to share burst promoting activity (Interleukin-3 [IL-3], granulocyte-macrophage colony-stimulating factor [GM-CSF], Interleukin-4 [IL-4], erythropoietin [EPO], human interleukin for DA cells [HILDA]) and that it can stimulate erythroid differentiation in long term bone marrow cell cultures.

Animals↗
PubMed1989

Mouse serum contains two erythroid progenitor-stimulating activities, one being highly increased in serum from anemic mice.

We previously observed that the addition of normal mouse serum to mouse bone marrow cell cultures increases the number of erythroid colonies arising from erythroid colony-forming units (CFU-E). In this paper, we show that the stimulating activity could be divided into two active fractions with 110 kd and 50 kd apparent molecular weight by gel filtration. The 50-kd fraction, in addition to its stimulating activity, increased the sensitivity of CFU-E to erythropoietin. The 110-kd activity was hardly detectable in normal mouse serum but was greatly increased in anemic mouse serum. This renders this activity of interest and suggests that it may play a regulatory role in mouse erythropoiesis.

Anemia↗
PubMed1988

Erythroid colony formation by human CFU-E is stimulated by compatible human serum but impaired by blood group antibodies.

Normal human serum was shown to stimulate the proliferation of human CFU-E when added into in vitro cultures of bone marrow cells. However, this was observed only when donors of serum and bone marrow cells were compatible on the basis of their blood groups. Absorption of incompatible sera removed the inhibition. Monoclonal anti-blood group antibodies exhibited the same pattern of CFU-E inhibition. The inhibition was complement-independent. Using suspension bone marrow cultures, it was shown that this blockage took place at an earlier differentiation step than the CFU-E level. This effect should be taken into account in studies of the inhibiting activities present in human anaemic sera.

ABO Blood-Group System↗
PubMed1988

Temporal interrelationships between the circadian rhythms of serum parathyroid hormone and calcium concentrations.

The temporal relationships between the circadian rhythms of serum PTH, total calcium (Cat), and phosphate (Pi) and plasma ionized calcium (Cai) concentrations were determined in 9 normal men. Blood samples were collected every half hour for 24 h. Serum PTH was measured by an RIA specific for the midregion of the molecule. The mean circadian pattern for each variable was derived by calculating the average value across all men at concurrent time points. After the data were smoothed by the method of running means, the correlations between PTH and mineral values from concurrent time points were calculated, as were cross-correlations to 12 lag periods (6 h). Spectral and cross-spectral analyses were performed on the same data set. Both statistical methods yielded consistent results: 1) at concurrent time points (0 lag), high correlations were found between serum PTH and Cat (r = -0.74), PTH and Pi (r = 0.79), and PTH and Cai (r = -0.53); and 2) when the PTH series was lagged by 2 h, the PTH/Cai correlation improved to -0.70. A direct PTH/Cai correlation of 0.50 was found when the Cai series was lagged about 4.5 h. No improvement in the correlations were found when the other series were lagged. Spectral analyses also detected significant interrelations between PTH and Cai at 2 and 3.5 h. These data describe the timing of the bidirectional interaction between serum PTH and plasma Cai under steady state conditions in normal adult men; changes in Cai concentrations precede inverse changes in PTH levels by 2 h, whereas changes in PTH precede similar directional alterations in Cai by about 4 h.

Adolescent↗
PubMed1987

Normal human serum stimulates murine erythroid precursor growth in in vitro culture.

When introduced into cultures of murine CFU-E human sera inhibited the formation of erythroid colonies. However, after absorbtion on murine cells and heating all tested sera became stimulatory. Crude sera were separated into two fractions by DEAE chromatography: the first fraction was stimulatory. The second was toxic but the toxicity could be eliminated by heating; the fraction then became slightly stimulatory. Attempts at characterizing the molecular weight of the stimulatory activity led to variable results, suggesting either that the stimulatory activity(ies) could polymerize or be fixed on different serum proteins. All sera from 11 different anemic patients were also shown to be stimulatory.

Anemia↗
PubMed1986

The erythropoietic stimulating activity of normal mouse serum: effect on erythroid precursors from different haematopoietic tissues and suggested role of accessory cells.

The addition of normal mouse serum (NMS) to mouse bone marrow cell cultures was found to stimulate the growth of late erythroid precursors (CFU-E). The stimulating activity was called Erythropoietic Stimulating Cofactor (ESCF) (Blanchet et al 1984). In this article, we report that CFU-Es from foetal liver are not sensitive to serum addition, in contrast to CFU-Es from bone marrow or spleen taken from the same foetuses. When foetal liver cells were co-cultured with irradiated adult bone marrow cells, addition of NMS stimulated the foetal liver CFU-Es, suggesting that ESCF acts via some accessory cells not present (or in too low a frequency) among foetal liver cells. Moreover, NMS should be added at onset of adult bone marrow cell culture to be fully stimulatory. In addition, a very large increase (by a factor of 5 to 7) was observed for CFU-Es from spleen and bone marrow from 6- to 20-d-old newborn mice. This high sensitivity was correlated with a post-natal anaemia. We propose the existence of two different CFU-E population, one stimulated by the accessory cells, the other not, the proportion of which could be modified in response to anaemia.

Anemia↗
PubMed1986

Mouse serum enables CFU-E to grow under physiologic concentration of erythropoietin in vitro.

Addition of normal mouse serum to cultures of mouse CFU-Es, not only increases the number of colonies as we recently reported (Blanchet et al. 1984), but also enhances the sensitivity of mouse CFU-Es to erythropoietin so that physiologic concentrations can be used with optimal colony development. These results were obtained as well with porcine or murine Epo. Thus, NMS exerts a stimulating and facilitating effect on CFU-E development. The stimulating activity was less resistant to heat treatment than was the facilitating one, an indication that both activities may be mediated by different molecules.

Animals↗
PubMed1984

A factor present in normal mouse serum stimulates late erythroid precursor proliferation.

A factor present in normal mouse serum stimulates proliferation of late erythroid precursors grown in cultures in vitro. This factor was shown not to have a corrective effect on culture conditions by the following criteria: (a) CFU-E frequency in the absence of NMS was at least as great as published data for various mouse strains, (b) an inhibitory effect of endotoxin was ruled out, (c) sensitivity of erythroid precursors to erythropoietin was similar in the presence or absence of NMS, and (d) the number of colonies was linearly related to the cell dose. The enhancing effect of NMS was independent of hemin, transferrin, or dexamethasone, products all known to be stimulators of erythropoiesis. It was shown to be specific for CFU-E. We propose that this material be termed erythropoietic stimulating cofactor (ESCF).

Animals↗
PubMed1983

Vitamin D3 production by cultured human keratinocytes and fibroblasts.

We have demonstrated that monolayers of human cultured newborn foreskin keratinocytes and fibroblasts elaborate vitamin D3 following exposure to UV-B. This in vitro system provides a new means to study those factors (hormones, ions, vitamin D3 metabolites, etc.) that regulate the production of vitamin D3 by human skin cells. Vitamin D3 production was enhanced greatly by using cells that were pre-treated with AY-9944, a non-toxic drug that inhibits cholesterologenesis while elevating cellular levels of 7-dehydrocholesterol, the sterol precursor of vitamin D3. The pre-D3 formed within viable, irradiated cells is transformed to D3 within a matter of hours at 37 degrees C, and keratinocytes proved to be more proficient sources of the vitamin and its metabolites than corresponding skin fibroblasts.

Acetates↗
PubMed1981

The pathogenesis of infantile malignant osteopetrosis: bone mineral metabolism and complications in five infants.

Bone mineral metabolism was studied in five infants aged 8 to 22 months with severe osteopetrosis. There were findings consistent with biochemical osteomalacia. These included hypocalcemia, hypophosphatemia, high serum acid phosphatase and alkaline phosphatase activity, high levels of serum parathyroid hormone, and high urinary cyclic AMP. Serum 1,25(OH)2 vitamin D3 level was high in the one patient tested. Radiographs in all infants revealed rachitic changes in the metaphyses. However, dense bones on radiographs, calcium balance studies, and radio-calcium absorption studies demonstrated markedly positive calcium balance. Iliac crest bone biopsies showed increased quantity of woven bone with abundant numbers of osteoclasts, excessive amounts of osteoid, myelofibrosis, and a decreased number of Howship's lacunae. The wide bands of unmineralized osteoid did not take up tetracycline. In vitro bone resorbing activity due to osteoclast activating factor from cultured stimulated leukocytes was normal. Bone turnover however, was now as evidenced by low urinary hydroxyproline levels. We interpret these findings as indicating there is decreased bone remodeling and resorption in spite of increased humoral stimuli and osteoclasts. Since calcitonin levels were normal for age, the most likely cause of the impaired bone remodeling sequence was defective osteoclast function. We postulate that there may be a common genetic defect in phagocyte cells, including monocytes, neutrophils and osteoclasts, which accounts for the abnormalities of mineral metabolism and previously reported hematologic, neurologic, and infectious complications.

Biopsy, Needle↗