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Biomedical subjects

V Berger

Publications and source records attributed to V Berger.

At least 19 recordsLinked to original sources
PubMed2006

Semiconductor waveguide source of counterpropagating twin photons.

We experimentally demonstrate an integrated semiconductor source of counterpropagating twin photons in the telecom range. A pump beam impinging on top of an AlGaAs waveguide generates parametrically two counterpropagating, orthogonally polarized signal/idler guided modes. A 2 mm long waveguide emits at room temperature one average photon pair per pump pulse, with a spectral linewidth of 0.15 nm. The twin character of the emitted photons is ascertained through a time-correlation measurement. This work opens a route towards new guided-wave semiconductor quantum devices.

Journal Article↗
PubMed2004

Clinical experience with 99mTc-MIBI scintimammography in patients with breast microcalcifications.

The aim of this study was to evaluate whether 99mTc-MIBI scintimammography can improve the diagnostic value of mammography for the differentiation of benign and malignant breast microcalcifications. In 41 women presenting 45 clusters of microcalcifications, a 99mTc-MIBI scintimammography was performed before open biopsy. There were 24 malignant lesions (53%). The sensitivity (SE) and specificity (SP) of 99mTc-MIBI scintimammography were 58.3% and 81%, and the positive and negative predictive values (PPV, NPV) were 78% and 63%, respectively. SE and PPV increased for lesions over 10 mm and for the younger patients (under 50 years). No correlation was found between true positive uptake and breast cancer invasiveness: 69% (9/13) for invasive lesions and 45% (5/11) for noninvasive lesions (P = 0.48). 99mTc-MIBI scintimammography was more often positive in high grade than in low- or intermediate-grade ductal carcinoma in situ (P = 0.03). The results were analysed according to the morphologic aspect of the microcalcifications. 99mTc-MIBI scintimammography could not be used for routine evaluation of all the microcalcifications detected by mammography.

Adult↗
PubMed2002

Counterpropagating twin photons by parametric fluorescence.

An original geometry for parametric fluorescence is proposed and analyzed theoretically, in which counterpropagating twin photons are emitted in a thin waveguide. In this original down-conversion process, a dramatic decrease of the spectral signal bandwidth at degeneracy is expected, as compared to usual parametric fluorescence processes. The possibility of using the counterpropagating twin photons for quantum cryptography is emphasized. It is shown that the realization of a fibered semiconductor source of Einstein-Podolsky-Rosen photons is possible by this method.

Journal Article↗
PubMed2001

A three-stage clinical trial design for rare disorders.

Many clinical trials of uncommon diseases are underpowered because of the difficulty of recruiting adequate numbers of subjects. We propose a clinical trial design with improved statistical power compared to the traditional randomized trial for use in clinical trials of rare diseases. The three-stage clinical trial design consists of an initial randomized placebo-controlled stage, a randomized withdrawal stage for subjects who responded, and a third randomized stage for placebo non-responders who subsequently respond to treatment. Test level and power were assessed by computer-intensive exact calculations. The three-stage clinical trial design was found to be consistently superior to the traditional randomized trial design in all cases examined, with sample sizes typically reduced by 20 per cent to 30 per cent while maintaining comparable power. When a treatment clearly superior to placebo was considered, our design reached a power of 75 per cent with a sample of 21 patients compared with the 52 needed to attain this power when only a randomized controlled trial was used. In situations where patient numbers are limited, a three-stage clinical trial design may be a more powerful design than the traditional randomized trial for detecting clinical benefits.

Clinical Trials as Topic↗
PubMed2000

Transport mechanisms of the imino acid L-proline in the human intestinal epithelial caco-2 cell line.

The intestinal transport of L-proline (L-Pro) has been investigated in various animal species with the use of different tissue preparations. Because major qualitative differences have been observed among the species, it is difficult to extent the results obtained with animal models to humans. In addition, studies on human tissue are lacking because of difficulties in obtaining material for experiments. To characterize the mechanisms involved in the intestinal absorption of L-Pro in humans, the transport of this nonessential imino acid was studied in monolayers of human intestinal Caco-2 cells that were cultivated on microporous membranes. In this model, L-Pro was transported selectively in the apical (AP)-to-basolateral (BL) direction. This transport was significantly reduced by metabolic inhibitors and by an incubation at 4 degrees C; it was Na(+) dependent and showed competition with (methylamino)-alpha-isobutyric acid and L-hydroxyproline. By contrast, transport in the BL-to-AP direction resulted to a large extent from passive movement (paracellular passage and transcellular diffusion). L-Pro accumulation by Caco-2 cells was significantly greater from the AP pole than from the BL pole. About 30-50% of the accumulated molecules were incorporated into newly synthesized proteins in a process inhibited by cycloheximide, whereas the remainder were extensively metabolized into non-amino acid compounds. L-Pro accumulations from the AP and BL poles were both Na(+) dependent, but they exhibited different characteristics. AP accumulation was inhibited by competition with (methylamino)-alpha-isobutyric acid, L-hydroxyproline and, to a lesser extent, D-Pro, whereas BL accumulation was inhibited by competition with L-hydroxyproline, (methylamino)-alpha-isobutyric acid, alpha-aminoisobutyric acid, L-histidine and small neutral amino acids. The results indicate that AP-to-BL transport and AP accumulation of L-Pro exhibited very different characteristics than BL-to-AP transport and BL accumulation.

Amino Acids↗
PubMed2000

Transport mechanisms of the large neutral amino acid L-phenylalanine in the human intestinal epithelial caco-2 cell line.

The transepithelial transport and the intracellular accumulation of the large neutral amino acid L-phenylalanine (L-Phe) were studied in monolayers of Caco-2 cells, cultivated in a bicameral insert system, to characterize the mechanisms involved in the absorption of this essential amino acid by the human intestinal mucosa. In our model, L-Phe was transported selectively in the apical (AP)-to-basolateral (BL) direction. AP-to-BL transport of L-Phe was temperature dependent and Na(+) independent, increased in the absence of protein synthesis and showed competition with large neutral and cationic amino acids. By contrast, transport in the BL-to-AP direction mainly resulted from passive movement (probably paracellular passage and transcellular diffusion). L-Phe accumulation into Caco-2 cells was higher from the BL pole than from the AP pole and characterized by the incorporation of most of the accumulated molecules into newly synthesized proteins. In addition, L-Phe accumulation was Na(+) dependent from both poles, whereas only accumulation from the AP pole was sensitive to inhibition by both large neutral and cationic amino acids. These results suggest that the processes involved in AP-to-BL transport and AP accumulation of this amino acid are very different from those involved in BL-to-AP transport and BL accumulation.

Biological Transport↗
PubMed1999

[Abdominal and pelvic segmented T1-weighted echo-planar imaging and MRI. Comparison with T1-TSE and T2-UTSE sequences].

PURPOSE: To assess, quantitatively and qualitatively, the diagnostic value of a segmented EPI T1W sequence compared to T1W and T2W TSE sequences. MATERIAL AND METHODS: A prospective analysis of abdominal and pelvic MRI examinations of 70 patients (44 women, 26 men, mean age of 61 years), was performed on a 0.5 T supraconductive magnet with 15 mT/m gradients. The sequences were randomized and compared in a blinded fashion by 3 independent reviewers: TSE T1W (TR/TE = 500/12 ms, NSA = 6, turbo factor 5, 3:49 min), EPI T1W (TR/TE = 500/30 ms, NSA = 6, EPI factor = 7, 2:13 min) and UTSE T2W (TR/TE = 1600-2500/100, NSA = 6, turbo factor = 31, 2:20 min). RESULTS: Quantitatively, no significant difference was found between T1W sequences for signal to noise ratio. The EPI T1W sequence had lower signal but stronger enhancement after gadolinium injection. Qualitatively, EPI T1W had significantly less flow artefacts (p < 0.001, wilcoxon test), and more chemical shift artifact (p < 0.01). For lesion detection, differences were not statistically significant between T1W sequences or between paired T1W and T2W sequences (sensitivity and specificity 84 and 86% for TSE T1W 76 and 86% for EPI T1W, 78 and 79% for UTSE T2W, 90 and 65% for TSE T1W-UTSE T2W, 88 and 65% for EPI T1W-UTSE T2W). Kappa concordance test (0.686) and Mac Nemar symmetry test (3.55) were high between T1W sequences. CONCLUSION: The segmented EPI T1W sequence used had equivalent results compared to the TSE T1W sequence, it allows a 40% reduction in acquisition time and this without difference in the diagnostic performances of the reviewers.

Abdomen↗
PubMed1998

Dietary specific sugars for serum protein enzymatic glycosylation in man.

All glycoprotein sugars can theoretically derive from glucose. However, dietary specific sugars could represent preferential substrates or have regulatory roles in enzymatic glycosylation. This hypothesis was tested in man using stable isotopes. Healthy subjects ingested different amounts (150, 300, or 550 mg) of artificially 13C-enriched sugar (galactose, mannose, or glucose) diluted in 200 mL water containing 50 g 13C-poor sucrose. 13C enrichment of expired CO2 was monitored for 8 hours during indirect calorimetry. Serum glycoproteins were precipitated and delipidated at various intervals. Glycoprotein neutral sugars were obtained by acidic hydrolysis, purified by ion-exchange chromatography, derivatized to alditol acetates, and analyzed by gas chromatography-isotope ratio mass spectrometry. The oxidation rate for galactose and mannose was slower than the rate for glucose. Total oxidation over the 8-hour period was less than 10% of the ingested amount of galactose or mannose. Galactose and mannose were readily incorporated into glycoprotein glycans, in the native form or after interconversion, despite ingestion of a large excess of sucrose: glycoprotein sugar 13C enrichment was strongly higher after 13C-galactose or 13C-mannose than after 13C-glucose. Thus, the metabolism of these three sugars appears to be different. Specific dietary sugars could represent a new class of non essential nutrients displaying interesting metabolic roles. This could have practical consequences especially in parenteral nutrition, where glucose is currently the only sugar available for metabolism.

Adult↗
PubMed1998

Adhesion of mammalian cells to polymer surfaces: from physical chemistry of surfaces to selective adhesion on defined patterns.

The study of the adsorption of type I collagen from a solution containing Pluronic F68 has shown that the latter prevents collagen adsorption on polystyrene and does not prevent it on surface-oxidized polystyrene. This explains the control of mammalian cell adhesion by substrate surface hydrophobicity and composition of pre-conditioning solution. On that basis, selective adhesion of different types of mammalian cells (PC12 pheochromocytoma, MSC80 schwannoma, Hep G2 hepatoblastoma, rat hepatocytes) on patterned surfaces was achieved. Therefore tracks (width in the range of a few tens of microm) of reduced hydrophobicity were produced on polystyrene by photolithography and oxygen plasma treatment. After conditioning by a solution containing both Pluronic F68 and extracellular matrix protein (collagen, fibronectin), the latter adsorbed selectively on these paths thus allowing selective adhesion of the cells.

Adsorption↗
PubMed1998

Availability of specific sugars for glycoconjugate biosynthesis: a need for further investigations in man.

We review the metabolism of specific sugars used for protein glycosylation, focusing on the fate of exogenously provided sugars. Theoretically, all glycoprotein sugars can derive from glucose, but previous studies show that other exogenous sugars can be incorporated into glycoproteins. From data obtained in congenital galactosemia, exogenous galactose may be important for correct glycosylation. Contrary to galactose, the metabolism of other sugars seems to depend on insulin regulation: stimulation of their endogenous production in diabetic subjects might participate in some diabetic complications, precluding the need for an exogenous supply. The metabolic fate of these sugars is different according to the administration route and exogenous supply may be important either in enteral nutrition or in some clinical situations as has been suggested for sialic acid in the newborn. Data in man are too sparse to reach firm conclusions, implying a need for further investigations. Our preliminary results in animals and man demonstrate that stable isotope methodology allows one to trace glycoprotein sugar metabolism in nutritionally relevant conditions with accuracy and sensitivity, using doses of specific sugars well below toxic levels.

Animals↗
PubMed1998

Emergency room visits of asthmatic children, relation to air pollution, weather, and airborne allergens.

BACKGROUND: The worldwide increase in the incidence, prevalence, and severity of asthma may suggest that environmental factors play a role in these epidemiologic changes. OBJECTIVE: To examine the correlations between air pollutants, weather conditions, airborne allergens, and the incidence of emergency room (ER) visits of children with acute asthma attacks. DESIGN: One-year prospective study. Data of daily concentration of air pollutants, weather conditions, and selective airborne allergens were collected and compared with the number of ER visits of asthmatic children. SUBJECTS: 1076 asthmatic children (aged 1 to 18 years) who presented at the Pediatric ER between January 1 and December 31, 1993. RESULTS: Correlations between fluctuations in ER visits of asthmatic children and various environmental parameters were more relevant for weekly than for daily values. Emergency room visits correlated positively with concentrations of NOx, SO2 and with high barometric pressure; and negatively with O3 concentration and minimal and maximal temperature. There were no significant correlations with concentrations of particulates, humidity, or airborne pollen and spores. An exceptionally high incidence of ER visits of asthmatic children was observed during September. This peak coincided with the beginning of the school year and the Jewish holidays. The correlations between ER visits and the environmental factors increased significantly when the September peak was excluded, revealing that 61% of the variance in ER visits was explained by NOx, SO2, and 03 concentrations, 46% by weather parameters, 66% by NOx, SO2 and barometric pressure, and 69% by the combination of air pollutants and weather parameters. CONCLUSION: The major factors found to be associated with ER visits of asthmatic children were high NOx, high SO2, and high barometric pressure. Negative correlation was found between ER visits of asthmatic children and ozone concentrations. The particularly high number of ER visits at the beginning of the school year and the Jewish holidays was probably associated with an increase in the number of viral infections and/or emotional stress.

Adolescent↗
PubMed1998

Evidence for a role for bulbospinal pathways in the spinal antinociceptive effect of systemically administered vapreotide in normal rats.

Numerous neurotransmitters are involved in nociceptive transmission or regulation. Several reports have shown the analgesic effects of somatostatin and its analogues. Somatostatin, when given intrathecally, markedly reduced pain in cancer patients. Somatostatin analogues that possess a longer half-life time are more convenient for therapeutic use. Vapreotide, a somatostatin analogue, was shown to induce a long-lasting antinociceptive effect in rats. We studied the site and the mechanism of action of vapreotide in rats using the paw pressure test. Intrathecal administration of vapreotide induced no antinociception. Systemically administered vapreotide-induced antinociception was inhibited by several intrathecal (i.t.) administered antagonists (yohimbine, naloxone and to a lesser degree tropisetron). These results show a lack of spinal effect and suggest a supraspinal site of action with an involvement of noradrenergic and to a lesser degree serotonergic bulbospinal pathways. In addition, spinal opioid receptors also seen to be involved.

Adrenergic alpha-Antagonists↗
PubMed1997

Influence of Substrate Hydrophobicity on the Adsorption of Collagen in the Presence of Pluronic F68, Albumin, or Calf Serum

The influence of Pluronic F68 [a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer surfactant], serum albumin (HSA), and fetal calf serum (FCS) on the adsorption of type I collagen by polymer substrates was investigated using radiolabeling and XPS analysis. Three different kinds of polystyrene substrates with increasing level of hydrophobicity were used. Change in the state of hydration of the sorbent and protein surfaces appears to be the main driving force for collagen adsorption. Pluronic F68 strongly reduces collagen adsorption, the reduction being more pronounced with higher substrate hydrophobicity. This explains why epithelial cell adhesion on substrates preconditioned with a solution of Pluronic F68 and collagen is strongly influenced by substrate hydrophobicity. Collagen adsorption is also reduced in the presence of HSA and FCS, but the reduction and its sensitivity to substrate hydrophobicity are lower than with Pluronic F68.

Journal Article↗
PubMed1997

[Left ovarian vein syndrome].

Ovarian vein syndrome is classically described on the right side. Patients present with lumbar pain or renal colics due to a compression of the ureter between the external iliac artery and a dilated ovarian vein. We report an unusual case of left ovarian vein syndrome between a dilated ovarian vein and the psoas muscle, with a similar clinical presentation.

Dilatation, Pathologic↗