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Biomedical subjects

A Bernard

Publications and source records attributed to A Bernard.

At least 163 records · Page 9Linked to original sources
PubMed1997

In vivo mutational analysis of highly conserved amino acid residues of the small subunit Cpa1p of the carbamylphosphate synthetase of Saccharomyces cerevisiae.

The role of selected amino acid residues located in the putative catalytic domain and of two conserved histidine residues within the small subunit of the carbamylphosphate synthetase (CPS) specific to the arginine biosynthesis pathway of the yeast Saccharomyces cerevisiae was studied using site-directed mutagenesis to change all residues to aspartic acid. Carbamylphosphate synthesis catalysed by modified CPS was tested in vivo. The C264D, H307D and H349D mutants were unable to grow on minimal medium, indicating the importance of these three residues for efficient CPS activity, whereas, four other mutated residues located in the catalytic site (including a proline residue) do not affect the growth rate. These results in comparison to those obtained with the CPS of Escherichia coli, implicate residues Cys 264 and His 349 in the glutaminase catalytic activity, and His 307 in the binding of glutamine to the active site. Using these three defective mutants, we investigated the in vivo utilization of ammonia by CPS. C264D and H307D mutants are able to use ammonia as a substrate when provided in sufficiently high concentrations (up to 200 mM). The H349D mutant, however, did not grow even at ammonium sulfate concentrations above 400 mM, suggesting that this substitution is critical to NH3-dependent CPS activity although the ammonia binding site is presumably located within the large subunit of the enzyme.

Amino Acid Sequence↗
PubMed1997

Relationship between proliferation and susceptibility to CD95- and CD2-mediated apoptosis in stimulated primary T lymphocytes: T cells manifesting proliferative unresponsiveness are preferentially susceptible to CD95-mediated apoptosis.

We examined the relationship between proliferation and susceptibility to Fas- and CD2-mediated apoptosis of human peripheral T lymphocytes that had been exposed in primary culture to CD3- or CD2-derived mitogenic stimuli in the presence of monocytes and exogenous IL-2. After 5 days, activated T cells were fractionated into large (F2) and small (F6) cells on Percoll density gradients and analyzed for their susceptibility to apoptosis and for their position in the cell cycle. Most F6 cells displayed a CD45RA+, CD25-, CD2R- phenotype and were unable to incorporate bromodeoxyuridine (BrdUrd) during the entire culture period. However, they were activated to express Fas Ag and some cell cycle regulatory proteins specific to late G1 phase. T cells with proliferative unresponsiveness were sensitive to Fas-mediated apoptosis whether it was triggered by anti-Fas mAb or by Fas ligand, but were almost completely resistant to CD2 apoptotic signaling. In contrast, F2 cells exhibited classical activation markers (CD45RO, CD25, and CD2R), had crossed S phase at least once, and were sensitive to both Fas and CD2 apoptotic signals. In large cells harvested earlier (on day 3), the signals were operative in both BrdUrd+ and BrdUrd- cells. Thus, S phase entry is not required for Fas- and CD2-mediated apoptosis. The profound proliferative unresponsiveness of F6 cells to CD3 and CD2 stimuli (bypassed by ionomycin plus PMA) and the CD2R- conformation of their CD2 molecules suggest that they may be in vivo anergized cells whose elimination, upon restimulation, is highly dependent on the Fas death pathway.

Apoptosis↗
PubMed1997

Inhibition of Bax channel-forming activity by Bcl-2.

Proteins of the Bcl-2 family are intracellular membrane-associated proteins that regulate programmed cell death (apoptosis) either positively or negatively by as yet unknown mechanisms. Bax, a pro-apoptotic member of the Bcl-2 family, was shown to form channels in lipid membranes. Bax triggered the release of liposome-encapsulated carboxyfluorescein at both neutral and acidic pH. At physiological pH, release could be blocked by Bcl-2. Bcl-2, in contrast, triggered carboxyfluorescein release at acidic pH only. In planar lipid bilayers, Bax formed pH- and voltage-dependent ion-conducting channels. Thus, the pro-apoptotic effects of Bax may be elicited through an intrinsic pore-forming activity that can be antagonized by Bcl-2.

Animals↗
PubMed1997

Biomonitoring of early effects on the kidney or the lung.

Biomarkers of toxicity are usually altered before the onset of functional changes or clinical manifestations. Peripheral biomarkers of toxicity present an additional advantage in that they can be applied on easily accessible biological materials (blood or urine). They represent useful tools that can be used for identifying subjects or groups at risk in the industry or environment, or for establishing acceptable exposure levels. In the case of the kidney, for instance, a relatively large battery of peripheral markers has been developed during the last decade. These markers are either constituents of the renal parenchyma whose urinary excretion can signal lesions or an abnormal secretion, or plasma proteins reflecting the integrity of nephron structures involved in their selective filtration or reabsorption. The epidemiological application of these tests has revealed that widespread occupational or environmental pollutants such as lead, cadmium, crystalline silica or perchloroethylene may cause very early effects on different segments of the nephron. In the case of the lung, we have recently identified a lung toxicity biomarker applicable not only on bronchoalveolar lavage fluid but also or sputum provided some precautions are taken. This biomarker called Clara cell protein (CC16) is a kDa protein secreted in the respiratory tract by the non-ciliated Clara cells known for their vulnerability to toxic insult. Studies on occupationally exposed workers and experimental animals indicate that the assay of CC16 in serum is a sensitive and a relatively specific test to detect early acute or chronic effects of toxicants on the tracheobronchial tree. The ultimate goal, however, is the development and validation of biomarkers that have a sufficient toxicological relevance to be used for health risk assessment. It is thus of premier importance to establish in health significance of early biomarkers of toxicity by determining to what extent they reflect critical steps in, and are predictive of the development of a chronic and irreversible disease.

Biomarkers↗
PubMed1997

Patterned delivery of immunoglobulins to surfaces using microfluidic networks.

Microfluidic networks (microFNs) were used to pattern biomolecules with high resolution on a variety of substrates (gold, glass, or polystyrene). Elastomeric microFNs localized chemical reactions between the biomolecules and the surface, requiring only microliters of reagent to cover square millimeter-sized areas. The networks were designed to ensure stability and filling of the microFN and allowed a homogeneous distribution and robust attachment of material to the substrate along the conduits in the microFN. Immunoglobulins patterned on substrates by means of microFNs remained strictly confined to areas enclosed by the network with submicron resolution and were viable for subsequent use in assays. The approach is simple and general enough to suggest a practical way to incorporate biological material on technological substrates.

Adhesiveness↗
PubMed1997

Apoptosis of immature thymocytes mediated by E2/CD99.

E2/CD99 is a 32-kDa transmembrane molecule that does not belong to any known family of proteins. It appears to regulate adhesion properties of T cells as previously reported, in particular, the induction of homotypic adhesion in CD4+ CD8+ thymocytes. Apoptosis induced via E2/CD99 displays characteristic morphologic features, but includes early mitochondrial alterations and phosphatidylserine exposure at the outer leaflet of the plasma membrane. It is not followed by detectable DNA fragmentation, and its time course is much longer than apoptosis induced via the Fas/CD95 pathway. It requires 18 h for completion. E2/CD99-induced apoptosis does not require any RNA or protein synthesis and still occurs following blockage of the Fas pathway. It is, however, dependent on CPP32 and IL-1beta-converting enzyme-type cysteine proteases, as shown by blockade with their respective specific inhibitors. This effect is restricted to double-positive thymocytes carrying an intermediate density of CD3 and including all CD69+ cells. Thus, E2/CD99 apears to mediate a distinctive apoptotic signal at a critical stage of thymocyte differentiation, i.e., when positive selection is known to occur.

12E7 Antigen↗
PubMed1997

Integrin-associated protein (CD47) is a comitogenic molecule on CD3-activated human T cells.

IAP is a glycoprotein functionally and physically associated with some integrins, i.e., the leukocyte response integrin and the beta3 integrin chain on placenta, platelets, and polymorphonuclear cells. IAP may act as a transducer element in activation mediated via these integrins. Since IAP is present at high density on peripheral T lymphocytes we have investigated its involvement in T cell activation. We tested three mAbs against IAP, namely B6H12, BRIC126, and 2D3, which recognize two distinct epitopes. IAP cross-linking with B6H12 or BRIC126, but not 2D3, transduces costimulatory signals within highly purified CD3-activated T lymphocytes, i.e., enhancement of proliferation, CD25 expression, and IL-2 secretion, while no effect was observed upon CD2 stimulation. However, we could not observe any functional association between IAP and integrins on peripheral T cells. In an attempt to explore further the activation signal delivered by IAP, we show here that IAP cross-linking with the comitogenic B6H12 mAb induces the phosphorylation on tyrosine of several proteins, one of which is identified as p56(lck) protein tyrosine kinase. Moreover, we observed that IAP is associated with p56(lck) on PMA-activated, but not on resting, T cells. These data suggest that on T cells, IAP may be involved directly via a specific ligand in cell-matrix or cell-cell interactions. Such interactions could trigger protein tyrosine phosphorylation pathways, which play an important role in both maturation and activation of T cells.

Antibodies, Monoclonal↗
PubMed1997

Changes in astrocytic glutamate catabolism enzymes following neuronal degeneration or viral infection.

Functional changes in astrocytes are among the earliest cellular responses to a wide variety of insults to the central nervous system (CNS). Such responses significantly contribute to maintaining CNS homeostasis. In this context, by controlling energetic metabolism and overall excitability of the CNS, the modulation of glutamate uptake and catabolism in astrocytes is crucial. Here, we review specific modulations of the expression of glutamate catabolizing enzymes (glutamate dehydrogenase and glutamine synthetase) in response to CNS insults (degeneration of serotonergic neurons or viral infection by a human retrovirus, HTLV-I). The cellular and molecular mechanisms involved in the control of the glutamate catabolism are discussed in relation to neurological disorders.

Animals↗
PubMed1997

Electronic States of Scandium Monoiodide

The many electronic transitions observed in high-resolution spectra of the fluorescence of scandium monoiodide following excitation by Ar+ and Kr+ laser lines have been extensively analyzed. Equilibrium vibrational and rotational constants are obtained for the six lowest electronic states. Spin-orbit constants in a3Delta and b3Pi are also determined. The laser-excited levels are regrouped into two electronic states, of 1Pi and 3Pi symmetries, for which molecular constants are derived. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Purification, characterization, and in vitro phosphorylation of the neuron-specific membrane-associated protein SCG10.

SCG10 is a neuron-specific, developmentally regulated protein which is highly enriched in growth cones. Sequence homology indicates that it is related to the phosphoprotein stathmin or Op18, an in vitro and in vivo substrate for several serine/threonine kinases which are involved in a variety of signaling pathways. As a first step to examine the biochemical properties of SCG10, the protein was expressed in Escherichia coli and purified to apparent homogeneity. The purified protein was used in in vitro phosphorylation assays. SCG10 was phosphorylated by MAP kinase, cAMP-dependent protein kinase, cGMP-dependent protein kinase, p34cdc2 kinase, DNA-dependent protein kinase, Ca2+/calmodulin kinase II, and casein kinase II. The protein was not a substrate for casein kinase I and protein kinase C. SCG10 was phosphorylated by src tyrosine kinase, which demonstrates that the protein can be phosphorylated in vitro on a tyrosine residue. Our data suggest that SCG10 is a phosphoprotein which might be involved in signal transduction in neurons.

Amino Acid Sequence↗
PubMed1997

Long-term pulmonary and systemic toxicity following intravenous mercury injection.

Long-term pulmonary and systemic toxicity following mercury intravenous injection has rarely been assessed. We present the results of a detailed investigation assessing pulmonary and systemic long-term toxic effects in a subject who had pulmonary and systemic mercury microembolism diagnosed more than 11 years previously. Radiographic examination showed the persistence of mercury microemboli in both lungs and elsewhere in the body. Lung function tests revealed a decreased diffusing capacity for carbon monoxide and PO2 probably indicative of microscopic inflammation of lung interstitium. Electroneuromyography showed signs of mild axonopathy in both legs. At semen analysis, a high proportion of motionless spermatozoa was present. Urinary excretion of mercury was high. Signs of interstitial lung impairment, peripheral axonopathy and asthenozoospermia in a subject who had mercury microembolism persisting for more than 11 years might be evidence of long-term mercury toxicity.

Adult↗
PubMed1997

Surgical management of invasive pulmonary aspergillosis in neutropenic patients.

BACKGROUND: The aim of our study was to clarify the indications for operation in invasive pulmonary aspergillosis. METHODS: Nineteen patients with hematologic malignancy, in whom invasive pulmonary aspergillosis developed during the course of neutropenia, had operations. Neutropenia lasted 28 days (range, 15 to 45 days). The preoperative diagnosis of invasive pulmonary aspergillosis was based on computed tomographic scan findings (halo or air crescent signs). RESULTS: Eight patients underwent emergency operations, before marrow recovery, for prevention of massive hemoptysis. The criterion for operation was an aspergillosis lesion that contacted the pulmonary artery on computed tomography. A lobectomy was performed in all cases. A sleeve resection of the pulmonary artery was necessary on two occasions. There was one postoperative death due to extensive aspergillosis. The length of hospitalization after operation was 13 days (range, 6 to 18 days). Seven patients were treated by elective resection of a residual mass (before hematologic therapy in 6 cases). The types of resection performed were lobectomy (n = 4), lingulectomy (n = 1), and wedge resection (n = 2). There were no postoperative deaths. The average length of stay before discharge from the hospital was 11 days (range, 7 to 20 days). The surgical resection was performed as a diagnostic procedure in the 4 remaining patients after an allotted time of 14 days (range, 4 to 24 days) from initiation of antifungal therapy. CONCLUSIONS: The combination of antifungal agents and surgical resection is an efficient strategy for the treatment of invasive pulmonary aspergillosis in patients with hematologic malignancy.

Acute Disease↗
PubMed1997

Intestinal lipid esterification and aging in mice and rats.

The effects of aging on lipid absorption, particularly on fatty acid glycerophospholipid and triacyl-glycerol esterification, were investigated in 2.5-, 12- and 24-month-old mice and rats. Two intestinal mucosa microsomal enzymes, involved in the dietary fatty acid absorption, were assayed: acylCoA:2-monoacylglycerol acyltransferase and acylCoA:1-lysophosphatidylcholine acyltransferase. In both mice and rats, the activities of both enzymes varied with the nature of the acyl-CoA. Indeed acylCoa:2-monoacylglycerol acyltransferase activities were significantly higher with oleoyl-CoA and linoleoyl-CoA than with palmitoyl-CoA and arachidonoyl-CoA, while acylCoA:1-lysophosphatidylcholine acyltransferase activities were highest with arachidonoyl-CoA. AcylCoA:2-monoacylglycerol acyltransferase activity did not decrease significantly with aging in mice or rats, whatever the acyl-CoA used. In contrast, acylCoA:1-lysophosphatidylcholine acyltransferase activity in the 24-month-old rats was significantly lower (-47%) than in 2.5-month-old rats, with oleoyl-CoA, linoleoyl-CoA and arachidonoyl-CoA. Simultaneously we observed that less glycerophospholipid esterification of oleic and linoleic acid occurs in older rats than in 2.5-month-old rats.

Aging↗
PubMed1997

Is the Parsonnet's score a good predictive score of mortality in adult cardiac surgery: assessment by a French multicentre study.

OBJECTIVE: Parsonnet proposed a preoperative score ("initial Parsonnet's score", which predicts the hospital mortality of adult cardiac surgery. This score was then modified by including several risk factors used in the 'SUMMIT' system ("modified Parsonnet's score", 44 variables). We wanted to assess the predictive value of these two scores in a French surgical population. METHODS: From December 1992 to April 1993, in France, we organised a prospective multicentre study on adult cardiac surgery mortality and morbidity. Data on 6649 patients were included. We analysed statistically the predictive value of each risk factor and of the two scores on mortality and morbidity at one month. RESULTS: Only 6 of the 15 variables of the initial Parsonnet's score and 19 of the 44 variables of the modified Parsonnet's score significantly influence hospital mortality. Both scores are able to predict hospital mortality and severe morbidity, but the modified Parsonnet's score has the best predictive value (initial Parsonnet's score: odds ratio by point of score = 1.01, area under the roc curve = 0.64; modified Parsonnet's score: odds ratio by point of score = 1.05, area under the roc curve = 0.70). CONCLUSIONS: This study shows that the Parsonnet's scores are predictive, but that these scores remain imperfect: many risk factors are non significant, the initial Parsonnet's score has a moderate predictive value, and the modified Parsonnet's score is too complex (44 variables). Thus, we have built a new score for cardiac surgery in French adults.

Adult↗
PubMed1997

Illudinic acid, a novel illudane sesquiterpene antibiotic.

A novel illudane sesquiterpene antibiotic (1) with activity against methicillin-resistant Staphylococcus aureus (MRSA), has been isolated. Its MIC against MRSA was found to be 16 micrograms/mL. It also shows L-1210 cytotoxicity with an IC50 of 10-15 micrograms/mL.

Animals↗
PubMed1997

Expression of oxidative phosphorylation genes in muscle cell cultures from patients with mitochondrial myopathies.

The expression of several mitochondrial and nuclear genes involved in ATP production was examined in cells cultured from muscle biopsies of patients harboring mitochondrial pathologies. The transcript patterns in muscle cells from the patients affected by carnitine palmitoyl transferase II or 2-ketoglutarate dehydrogenase deficiencies were almost similar to control patterns. In the opposite, patterns were strikingly abnormal in all the other cell cultures from patients with defects in enzymatic complexes involved in oxidative phosphorylation: mitochondrial complex II and III deficiencies, two MELAS syndromes (myopathy, encephalopathy, lactic acidosis and stroke like episodes), a case of Kearns-Sayre syndrome and a case of chronic progressive external ophthalmoplegia. In cultured muscle cells from patients with mtDNA mutations, the percentage of mutated mtDNA was low as compared with those determined in the corresponding skeletal muscle biopsy. Moreover, the complex II defect resulting of a nuclear mutation was not expressed in the cell cultures. Thus, an undetermined transcriptional event, transmitted from muscle biopsies to cultured muscle cells, should be involved to account for such abnormal transcript patterns.

Adolescent↗