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Biomedical subjects

C Martin

Publications and source records attributed to C Martin.

At least 757 records · Page 42Linked to original sources
PubMed1991

Improved chemiluminescent DNA sequencing.

A new chemiluminescent 1,2-dioxetane substrate, CSPD, shows improved performance over AMPPD when used in our nonisotopic method for DNA sequencing. CSPD differs from AMPPD by the addition of a chlorine atom to the adamantyl group that limits the amount of aggregation of the dioxetane and its dephosphorylated anion. This results in a shorter time elapsing before reaching steady state light emission when detecting nucleic acids on nylon membrane. An additional advantage of CSPD over AMPPD is that the resolution of imaged DNA bands does not degrade over time. These features of CSPD permit rapid acquisition of high-quality DNA sequence data.

Adamantane↗
PubMed1991

[Apparently primary cerebrospinal rhinorrhea. Apropos of 4 cases].

While rhino-liquorrhea is a severe condition, its incidence is not exceptionally rare, and it raises problems, namely etiopathogenic, diagnostic and therapeutical ones, which call for the close collaboration of ENT doctors, neuroradiologists and neurosurgeons. 4 relatively recent cases are reported here, whereby the diversity of the problems encountered is made apparent. ENT specialists must be aware of those when faced with refractory aqueous rhinorrhea, often triggered by forward head motion, Valsalva's maneuver... Screening for rhinorrhea is readily achieved by biochemical tests, or simply using a Labstix-type diagnostic strip. Rhinoscopic examination should be accurate and carried out optically to check for any congenital malformation (meningocele). Most of the times, but not always, a thorough radio-neurological workup (isotopic analysis, CT-scan with contrast medium, MR imaging) will provide precise data regarding the infraction site and its possible cause, invariably warranting surgical management. Surgery should be case-adapted (CSF derivation, filling of the gap via the extra- or intracranial approach).

Adolescent↗
PubMed1990

High-affinity binding sites for [3H]saxitoxin are associated with voltage-dependent sodium channels in portal vein smooth muscle.

Saturable, high-affinity binding sites for [3H]saxitoxin were identified in equine portal vein smooth muscle membranes. These sites had a dissociation constant of 0.29 nM and a maximal binding capacity of 115 fmol.mg-1 of protein. A similar dissociation constant was obtained with cells prepared from rat portal vein. Specific binding of [3H]saxitoxin was completely displaced by unlabelled saxitoxin and tetrodotoxin, with inhibition constants of 0.42 and 2.10 nM, respectively. Tetrodotoxin blocked the fast Na+ current in single cells of rat portal vein in a concentration-dependent manner, with an IC50 of 3.15 nM. These results suggest that the high-affinity binding sites for tetrodotoxin and saxitoxin may be associated with voltage-dependent Na+ channels in vascular myocytes.

Amphibian Proteins↗
PubMed1990

Transposition of an antibiotic resistance element in mycobacteria.

Bacterial resistance to antibiotics is often plasmid-mediated and the associated resistance genes encoded by transposable elements. Mycobacteria, including the human pathogens Mycobacterium tuberculosis and M. leprae, are resistant to many antibiotics, and their cell-surface structure is believed to be largely responsible for the wide range of resistance phenotypes. Antibiotic-resistance plasmids have so far not been implicated in resistance of mycobacteria to antibiotics. Nevertheless, antibiotic-modifying activities such as aminoglycoside acetyltransferases and phosphotransferases have been detected in fast-growing species. beta-lactamases have also been found in most fast- and slow-growing mycobacteria. To date no mycobacterial antibiotic-resistance genes have been isolated and characterized. We now report the isolation, cloning and sequencing of a genetic region responsible for resistance to sulphonamides in M. fortuitum. This region also contains an open reading frame homologous to one present in Tn1696 (member of the Tn21 family) which encodes a site-specific integrase. The mycobacterial resistance element is flanked by repeated sequences of 880 base pairs similar to the insertion elements of the IS6 family found in Gram+ and Gram- bacteria. The insertion element is shown to transpose to different sites in the chromosome of a related fast-growing species, M. smegmatis. The characterization of this element should permit transposon mutagenesis in the analysis of mycobacterial virulence and related problems.

Amino Acid Sequence↗
PubMed1990

[Treatment of deep wounds with loss of tissue. Value of a 3 percent boric acid solution].

Following the finding of dramatic improvement in a deep wound with loss of substance treated with a 3 percent boric acid solution, 31 patients hospitalized in a surgical intensive care unit and holding such a wound initially unimproved by classical treatments were subjected, in 1987-88, to a short-time use of this solution. A case-control study retrospectively performed with 12 of the patients demonstrated that after wound granulation was obtained they returned to a normal care unit about three times more rapidly than patients receiving conventional antiseptics (means: 20 and 55 days respectively). This reduction in intensive care duration of stay for these 12 patients saved approximately 2 millions francs. Thus, the 3 percent boric acid solution may be considered an efficient alternative in the treatment of deep wounds with loss of substance, but it is delicate to handle because of toxicity.

Adolescent↗
PubMed1990

Characterization of a B cell helper factor(s) derived from CD5+ B cell hybridomas.

Work from our laboratory suggests that the selective advantage of frequently autoreactive CD5+ B cells is to provide activation signals to CD5- antigen-specific B cells. This hypothesis is supported by the observation that supernatants from CD5+ B cell hybridomas replace CD5+ B cell populations in helping idiotypic B cell subsets respond to antigen plus anti-idiotype antibody. The present study was designed to initiate the characterization of CD5+ B hybridoma-derived helper factor(s) (BHF) and to compare BHF to previously described cytokines. Elution of BHF from a lectin column enabled significant enrichment of the apparently glycosylated helper factor(s) from serum-free hybridoma supernatant. Gel filtration of this enriched activity revealed two significant peaks of helper activity, one at approximately 19-22 kDa and a second at 29-32 kDa. BHF activity in each fraction was sensitive to protease treatment. To determine if some previously described cytokines of approximately the same molecular weights were responsible for BHF activity, BHF fractions were tested for cytokine activity in respective bioassays. At least 2000 units of BHF did not contain detectable levels of IL-1, IL-2, IL-3, IL-4, IL-6, GM-CSF, G-CSF, or IFN-gamma activity. Furthermore, three hybridomas which produced BHF did not transcribe detectable levels of mRNAs specific for IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, GM-CSF, or IFN-gamma. The results suggest that CD5+ B cell hybridomas produce a lymphokine(s) distinct from cytokines commonly associated with B cell activation. The potential roles of this lymphokine in immunity and disease are discussed.

Animals↗
PubMed1990

Rapid purification of the peptide toxins microcystin-LR and nodularin.

An isolation procedure was developed to provide within one day microcystin-LR, a cyclic heptapeptide toxin from Microcystis aeruginosa PCC 7806. After ODS (octadecylsilyl) solid phase extraction, the crude toxin fraction was chromatographed using a strong anion exchange column. The toxin was eluted with 0.02 M ammonium bicarbonate. An at least 95% purity was revealed on HPLC separation by monitoring at 214 nm. Application of the procedure to the cyclic pentapeptide toxin nodularin from Nodularia spumigena AV2 was examined.

Chromatography, Gel↗
PubMed1990

The wrinkled-seed character of pea described by Mendel is caused by a transposon-like insertion in a gene encoding starch-branching enzyme.

We describe the cloning of the r (rugosus) locus of pea (Pisum sativum L.), which determines whether the seed is round or wrinkled. Wrinkled (rr) seeds lack one isoform of starch-branching enzyme (SBEI), present in round (RR or Rr) seeds. A major polymorphism in the SBEI gene between near-isogenic RR and rr lines shows 100% cosegregation with the r locus, establishing that the SBEI gene is at the r locus. An aberrant transcript for SBEI is produced in rr embryos. In rr lines the SBEI gene is interrupted by a 0.8 kb insertion that is very similar to the Ac/Ds family of transposable elements from maize. Failure to produce SBEI has complex metabolic consequences on starch, lipid, and protein biosynthesis in the seed.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1990

Metabolic inhibitors distinguish cytolytic activity of CD4 and CD8 clones.

The effect of various metabolic inhibitors on the expression of cytolytic activity of CD4 (TH1) and CD8 (CTL) clones was studied. The cytolytic activity of CD4 clones, but not CD8 clones, was sensitive to the RNA synthesis inhibitor actinomycin D and the protein synthesis inhibitor cycloheximide. Conversely, cholera toxin (CT) inhibited cytolytic activity of CD8, but not CD4 clones. Both mitomycin C, a DNA synthesis inhibitor, and cyclosporin A (CsA) failed to inhibit the cytolytic activity of either CD4 or CD8 clones. Although pretreatment with CsA or CT did not inhibit the cytolytic activity of CD4 clones, lymphokine (interleukin 2, IL2, interferon-gamma, IFN-gamma, and tumor necrosis factor, TNF) production was strongly inhibited. Similarly, pretreatment of a CD8 clone with actinomycin D or CsA inhibited lymphokine production without affecting cytolytic activity. The production of mRNA for TNF and IFN-gamma by concanavalin A-activated CD4 clones was also inhibited by CsA and CT. Moreover, perforin-specific mRNA was not detected in activated CD4 clones. Collectively, these observations demonstrated that de novo synthesis of RNA and protein is required for expression of cytolytic activity of CD4 clones, yet production of TNF, INF-gamma, IL 2 and perforin is not involved. In contrast, the cytolytic machinery of CD8 clones is present prior to activation and is quickly expressed following activation even when de novo synthesis of RNA, protein and lymphokines is blocked.

Animals↗
PubMed1990

Melatonin modulates the neural activity in photosensory pineal organ of the trout: evidence for endocrine-neuronal interactions.

Hormonal and neural signals transmitted from the pineal organ to the brain in cold-blooded vertebrates presumably convert information about the ambient illumination into signals which may be used to mediate photoperiodic and circadian responses. The possible intrapineal function of melatonin was investigated by recording intra- and extracellularly from photoreceptors and second-order neurons in the isolated superfused pineal organ of the trout (Salmo gairdneri). Melatonin added through the perfusion bath to the explanted pineal organ caused a dose-related and reversible inhibition of ganglion cells of the luminance type whereas the hormone did not significantly affect the membrane potential of photoreceptors and their light-evoked response. The observed effects seem to be independent from photoperiod and adaptation conditions. These results suggest that melatonin provides a feedforward signal to intrapineal neurons regulating the neural output of the organ.

Adaptation, Physiological↗
PubMed1990

Characterization of the light response in the pineal gland of intact and sympathectomized rats.

Electrophysiological recordings were performed in the pineal gland of pigmented rats BD9 to investigate the possible contribution of a direct neural connection of the gland with the central nervous system in the transmission of photic information. Extracellular potentials were recorded during brief photic stimulation of the eyes before and after bilateral sympathectomy. Two types of responses could be distinguished in intact as well as in sympathectomized rats: spontaneously active units which were unresponsive to light flashes and units responding to photic stimulation with ON and ON/OFF discharges. Spectral sensitivity curves recorded from the pineal organ of dark adapted rats showed a maximum at 500 nm. Interruption of the sympathetic innervation by bilateral denervation or removal of the superior cervical ganglia did not alter the spectral properties of pineal units. Additionally, response-intensity curves and response threshold (about 0.0017 microW/cm2) were not changed after sympathectomy. These results suggest that the pineal gland of the rat receives projections from the visual system via a central pinealopetal innervation.

Action Potentials↗
PubMed1990

Aldehyde dehydrogenase activity in xenografted human brain tumor in nude mice. Preliminary results in human glioma biopsies.

ALDH activity measured fluorimetrically using a high concentration of aliphatic aldehyde as substrate was studied in human glioblastomas grafted in nude mice. Compared with normal brain, ALDH activity is significantly increased in malignant glioma tissue, especially in the cytosolic subcellular fraction. Correlatively, in comparison with normal brain tissue, MDA levels were significantly reduced in whole homogenates and in cytosolic fractions of xenografted glioblastoma tissue. Preliminary results concerning human malignant glioma biopsies are in good agreement with our experimental data. In view of previous works, these results suggest a relationship between alterations in ALDH iso-enzymes activities and cytosolic aldehyde concentrations with respect to normal or tumoral cell growth.

Aldehyde Dehydrogenase↗
PubMed1990

[Risk of thrombosis in prolonged catheterization of the radial artery: comparison of 2 types of catheters].

The thrombosis rate after long-term cannulation of the radial artery was assessed prospectively in 48 intensive care patients randomly assigned to groupe A (polyethylene Leader-Cath 115-09 catheter; n = 50, aged 55 +/- 20 years, 74% male patients) or groupe B (Teflon Viggo Floswitch 4441 catheter; n = 48, aged 58.6 +/- 16 years, 73% male patients). Bedside angiography was carried out with 10 to 15 ml Hexabrix before removal of the catheter. The two groups were similar with regard to anthropometric parameters, used drugs, pathological events during the stay in ICU, arterial cannulation technique and its duration. There was no case of clinically significant ischaemia. The rate of X-ray total arterial thrombosis was 20% in group A, and 2% in group B (p less than 0.01). There was no difference in the rate of partial thrombosis (54% vs. 41.7% respectively, NS) and of lack of thrombosis (26% vs. 56.3% respectively, NS). The overall rate of thrombosis was greater in group A than in group B, but not significantly (74% vs. 43.7% respectively). The duration of arterial cannulation did not influence the rate of thrombosis. However it was higher in males of Group A than in those of Group B (p less than 0.01), when heparin was not given (p less than 0.05); when vaso-active drugs were used (p less than 0.05); and when the time required for cannula insertion was greater than 5 min (p less than 0.01). It is concluded that Teflon catheters are more biocompatible than polyethylene catheters.

Adult↗
PubMed1990

Lower oesophageal reflux during priming with vecuronium.

We have studied the effects of vecuronium given in divided doses (priming principle) on the frequency of acid reflux into the oesophagus. Two groups of 16 patients were studied. After induction with thiopentone 6 mg kg-1 and fentanyl 3 micrograms kg-1, patients in one group were given vecuronium 0.01 mg kg-1 as a priming dose, followed by an intubation dose of 0.1 mg kg-1 4 min later. Patients in the other group were given no priming dose. Lower oesophageal pH was monitored continuously and acid reflux was defined as a decrease in pH to less than 4.0. One patient in each group had acid reflux during the time course of the induction. This study suggests that vecuronium 0.01 mg kg-1 given as a priming dose does not increase the risk of acid reflux into the oesophagus.

Anesthesia, Intravenous↗
PubMed1990

Evidence for peripheral mechanisms inducing tissue tolerance during ontogeny.

Tissue grafts from a histoincompatible donor of the same developmental stage were introduced into an early chick embryo host in order to probe the immune response to the graft after birth, when the host has reached immune maturity. Limb buds from B4 or B12 chicken strains were grafted in situ on (B15 x B21)F1 recipients that were allowed to hatch. The grafted wing grew normally and was tolerated in a nearly perfect way during the host's lifetime, although reversible rejection crises severely affected the fundamentally healthy state of the grafted tissues. Skin grafts of the same major histocompatibility complex haplotype as the wing were performed on the adult wing-chimera and were permanently tolerated. In contrast, host peripheral blood lymphocytes maintained their capacity to proliferate against donor cells in the mixed lymphocyte reaction. These results, while showing that in vitro and in vivo tolerance are separable phenomena, suggest the existence of a peripheral mechanism inducing tolerance to self that complements the elimination of self-reactive clones by the thymus.

Animals↗
PubMed1990

Pharmacokinetics of long-term propofol infusion used for sedation in ICU patients.

The pharmacokinetics of propofol were determined in nine patients (seven men, two women, (mean +/- SD) 55.8 +/- 21.2 yr, 65.2 +/- 8 kg) requiring prolonged mechanical ventilation of their lungs. After an initial dose of 1-3 mg/kg, propofol was administered iv at 3 mg/kg/h for 72 h. Arterial blood samples were collected at selected times during and up to 72 h after infusion. Propofol whole blood concentrations were determined by high-performance liquid chromatography with fluorescence detection. Individual pharmacokinetic parameters were estimated by noncompartmental analysis. Derived pharmacokinetic parameters showed a long terminal phase (T1/2 = 1878 +/- 672 min), a large volume of distribution at steady state (Vdss = 1666 +/- 756 l), and a high total body clearance (Cl = 1.57 +/- 0.56 l/min). While the propofol terminal elimination half-life is longer than that previously reported, emergence from sedation after prolonged administration will be governed by both redistribution mechanisms arising from the large distribution volumes and elimination from the body.

Adult↗