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L Turin

Publications and source records attributed to L Turin.

At least 19 recordsLinked to original sources
PubMed2002

A method for the calculation of odor character from molecular structure.

The relationship between molecular structure and odor character is one of the most complex structure-activity problems in biology. Despite over a century of effort, it remains unsolved, and synthesis of new odorants still proceeds largely by trial and error. In previous work, I have argued that the reason for this failure lies in a mistaken assumption, namely that molecular shape determines odor character. Instead, I have taken up and extended an old idea (Dyson, 1938) according to which vertebrate olfactory receptors detect odorants by their molecular vibrations. I propose that the detection mechanism is inelastic electron tunnelling. If this is correct, there should be a correlation between the tunnelling vibrational spectra of odorants and their odor character. Here, using semi-empirical quantum chemistry methods and a simple calculation method for tunnelling mode intensities, I calculate the spectra of structurally diverse odorants belonging to various odor categories. With few exceptions, the calculated spectra of bitter almonds, musks, ambers, woods, sandalwoods and violets strongly correlate with odor character.

Algorithms↗
PubMed2001

The hybridization-stabilization assay: a solution-based isothermal method for rapid screening and determination of sequence preference of ligands that bind to duplexed nucleic acids.

The gene-to-drug quest will be most directly served by the discovery and development of small molecules that bind to nucleic acids and modulate gene expression at the level of transcription and/or inhibit replication of infectious agents. Full realization of this potential will require implementation of a complete suite of modern drug discovery technologies. Towards this end, here we describe our initial results with a new assay for identification and characterization of novel nucleic acid binding ligands. It is based on the well recognized property of stabilization of hybridization of complementary oligonucleotides by groove and/or intercalation binding ligands. Unlike traditional thermal melt methodologies, this assay is isothermal and, unlike gel-based footprinting techniques, the assay also is performed in solution and detection can be by any number of highly sensitive, non-radioisotopic modalities, such as fluorescence resonance energy transfer, described herein. Thus, the assay is simple to perform, versatile in design and amenable to miniaturization and high throughput automation. Assay validation was performed using various permutations of direct and competitive binding formats and previously well studied ligands, including pyrrole polyamide and intercalator natural products, designed hairpin pyrrole-imidazole polyamides and furan-based non-polyamide dications. DNA specific ligands were identified and their DNA binding site size and sequence preference profiles were determined. A systematic approach to studying the relationship of binding sequence specificity with variation in ligand structure was demonstrated, and preferred binding sites in longer DNA sequences were found by pseudo-footprinting, with results that are in accord with established findings. This assay methodology should promote a more rapid discovery of novel nucleic acid ligands and potential drug candidates.

Base Pairing↗
PubMed2000

Fast, simple and highly sensitive double-rounded polymerase chain reaction assay to detect medically relevant fungi in dermatological specimens.

BACKGROUND: Early detection of fungal infection is essential for beginning of prompt and specific therapy. In this study we describe a rapid and sensitive procedure to detect, by polymerase chain reaction (PCR) assays, a wide range of medically important opportunistic and pathogenic fungi in dermal specimens from dermatomycoses-affected patients. MATERIALS AND METHODS: Three primer pairs, amplifying fragments of the highly conserved gene coding for small ribosomal RNA (18S rDNA) and the adjacent internal transcribed spacer (ITS) rDNA, previously published by others, were probed on DNA from pure cultures of medically relevant human and animal fungal species. In order to evaluate the specificity of the assay, amplifications of control DNAs from other eukaryotes and prokaryotes were also carried out, and they gave negative results. RESULTS: These primer sets, in single amplification or double-rounded PCR assays, allowed specific amplification when applied to a wide number of fungal DNA from human and animal tissue specimens, including dermatophytes (genera Trichophyton, Microsporum), several yeast species (Candida, Saccharomyces, Cryptococcus, Malassezia) and moulds (Aspergillus, Penicillium). The PCR assay was able to detect as little as 10 pg of fungal DNA, corresponding to approximately 25 fungal genomes per sample specimen. A small-scale DNA extraction method was also developed. This simple, time-saving and sensitive procedure was successfully applied to 40 human and veterinary specimens, and the diagnosis was confirmed with cultural techniques, being shown to work even in the presence of other lesions or contaminating organisms. CONCLUSIONS: This method allows early recognition of fungal pathogen cells in clinical samples as an alternative tool to conventional detection techniques.

Animals↗
PubMed1999

BHV-1: new molecular approaches to control a common and widespread infection.

BACKGROUND: Herpesviruses are widespread viruses, causing severe infections in both humans and animals. Eradication of herpesviruses is extremely difficult because of their ability to establish latent and life-long infections. However, latency is only one tool that has evolved in herpesviruses to successfully infect their hosts; such viruses display a wide (and still incompletely known) panoply of genes and proteins that are able to counteract immune responses of their hosts. Envelope glycoproteins and cytokine inhibitors are two examples of such weapons. All of these factors make it difficult to develop diagnostics and vaccines, unless they are based on molecular techniques. MATERIALS AND METHODS: Animal herpesviruses, because of their striking similarity to human ones, are suitable models to study the molecular biology of herpesviruses and develop strategies aimed at designing neurotropic live vectors for gene therapy as well as engineered attenuated vaccines. RESULTS: BHV-1 is a neurotropic herpesvirus causing infectious rhinotracheitis (IBR) in cattle. It is a major plague in zootechnics and commercial trade, because of its ability to spread through asymptomatic carrier animals, frozen semen, and embryos. Such portals of infections are also important for human herpesviruses, which mainly cause systemic, eye, and genital tract infections, leading even to the development of cancer. CONCLUSIONS: This review covers both the genetics and molecular biology of BHV-1 and its related herpesviruses. Epidemiology and diagnostic approaches to herpesvirus infections are presented. The role of herpesviruses in gene therapy and a broad introduction to classic and engineered vaccines against herpesviruses are also provided. http://link.springer-ny. com/link/service/journals/00020/bibs/5n5p261.html

Animals↗
PubMed1998

ATP is a potent stimulator of the activation and formation of rodent osteoclasts.

1. There is increasing evidence that extracellular ATP acts directly on bone cells via P2 receptors. In normal rat osteoclasts, ATP activates both non-selective cation channels and Ca2+-dependent K+ channels. In this study we investigated the action of ATP on the formation of osteoclasts and on the ultimate function of these cells, namely resorption pit formation. 2. We found that ATP stimulated resorption pit formation up to 5.6-fold when osteoclast-containing bone cell populations from neonatal rats were cultured for 26 h on ivory discs, with a maximum effect occurring at relatively low concentrations (0.2-2 microM). The stimulatory effect of ATP was amplified greatly when osteoclasts were activated by culture in acidified media (pH 6.9-7.0). Pit formation by acid-activated osteoclasts in the absence of ATP was inhibited by apyrase, an ecto-ATPase and by suramin, an antagonist of P2 receptors. 3. Over the same concentration range at which rat osteoclast activation occurred (0.2-2 microM), ATP also enhanced osteoclast formation in 10 day mouse marrow cultures, by up to 3.3-fold, with corresponding increases in resorption pit formation. Higher concentrations of ATP (20-200 microM) reduced or blocked osteoclast formation. Adenosine, a P1 receptor agonist, was without effect on either osteoclast activation or formation. 4. These results suggest that low levels of extracellular ATP may play a fundamental role in modulating both the resorptive function and formation of mammalian osteoclasts.

Adenosine Triphosphate↗
PubMed1996

Reactivity of monoclonal antibodies of the B cell panel on PBM from BLV-infected and lymphocytotic cows.

The monoclonal antibodies included in the B cell panel of the Third Workshop on Ruminant Leukocyte Antigens were tested by flow cytometry for their reactivity with peripheral blood mononuclear cells (PBM) from normal, BLV (bovine leukemia virus)-infected but non-lymphocytotic and lymphocytotic cows. Three MoAbs probably detected pan-B cell antigens. They detected an increase in the B/T cell ratio in peripheral blood from lymphocytotic cattle. However, no changes were observed in the surface phenotypes of B cells from infected animals with MoAbs of the workshop panel.

Animals↗
PubMed1996

A spectroscopic mechanism for primary olfactory reception.

A novel theory of primary olfactory reception is described. It proposes that olfactory receptors respond not to the shape of the molecules but to their vibrations. It differs from previous vibrational theories (Dyson, Wright) in providing a detailed and plausible mechanism for biological transduction of molecular vibrations: inelastic electron tunnelling. Elements of the tunnelling spectroscope are identified in putative olfactory receptors and their associated G-protein. Means of calculating electron tunnelling spectra of odorant molecules are described. Several examples are given of correlations between tunnelling spectrum and odour in structurally unrelated molecules. As predicted, molecules of very similar shape but differing in vibrations smell different. The most striking instance is that of pure acetophenone and its fully deuterated analogue acetophenone-d8, which smell different despite being identical in structure. This fact cannot, it seems, be explained by structure-based theories of odour. The evidence presented here suggests instead that olfaction, like colour vision and hearing, is a spectral sense.

Amino Acid Sequence↗
PubMed1996

Surface analysis of IgM-expressing bovine lymphocytes in BLV-infected cattle by immuno-scanning electron microscopy.

Surface of IgM-expressing lymphocytes infected by bovine leukemia virus and with/without persistent lymphocytosis (BLV+PL-, BLV+PL+) in cattle is heterogenous. Three distinct morphological structures of B lymphocytes were found in these groups by immuno-scanning electron microscopy (ISEM). B lymphocytes with generally elongated and pleomorphic microvilli and sometimes short ruffles were observed in infected, and as well as in non-infected animals. A second morphological type endowed with a relatively small number of elongated villi-like veils, and a third morphological type characterized by a relatively small number of short microvilli or blunt stub-like microvilli covering the smooth surface were seen, mainly in BLV+PL+ and seldom in BLV+PL- Cells of the second type were more intensively labeled, than lymphocytes of the third type.

Animals↗
PubMed1991

Hydrophobic ion transfer between membranes of adjacent hepatocytes: a possible probe of tight junction structure.

The topology of the tight junction is probed by introducing dipicrylamine (dpa-), a lipid-soluble anion, into the membranes of hepatocyte pairs in culture. Once partitioned into the membrane, dpa- ions are free to move in the hydrophobic core of the membrane, where their mobile charges greatly increase membrane capacitance. If tight junctions are lines of membrane fusion, dpa- will cross the tight junction without traversing a polar headgroup layer. Furthermore, the electric potential across the tight junction will be equal to the difference in membrane potentials of the two cells. dpa- can therefore be expected to move electrophoretically from cell membrane to cell membrane across the junction in response to an intercellular voltage difference. Experiments performed under double whole-cell clamp show that this transfer occurs as follows: First, dpa- causes an intercellular current unrelated to gap junctions to flow in response to an intercellular voltage difference. Second, this electrophoretic removal or addition of dpa- from a cell's membrane through the tight junction must reduce or increase its dpa- content and thus its capacitance. Experiments confirm this prediction: We detect rapid, symmetric, and reversible changes in membrane capacitance in response to changes in the membrane potential of the neighboring cell. Finally, we find that hepatocyte membranes contain a negatively charged endogenous molecule that contain a negatively charged endogenous molecule that can move from cell to cell like dpa- under the influence of an intercellular potential difference. We conclude that membrane fusion occurs at tight junctions and that this hydrophobic intercellular pathway can play a role in intercellular communication.

Animals↗
PubMed1991

Pharmacokinetics of GLQ223 in rats, monkeys, and patients with AIDS or AIDS-related complex.

The pharmacokinetics of GLQ223 administered as a single short intravenous infusion to rats, monkeys, and patients with AIDS or AIDS-related complex (ARC) are presented. GLQ223 was given at a dose of 3,500 micrograms/kg of body weight to five Sprague-Dawley rats; a dose of 300 micrograms/kg was given to three cynomolgus monkeys; and doses of 1, 8, 16, 24, and 36 micrograms/kg were given to 10 patients with AIDS and 8 patients with ARC in an escalating dose design. Plasma clearance was 0.85 +/- 0.24 liter/h/kg in rats, 0.16 +/- 0.08 liter/h/kg in monkeys, and 0.13 +/- 0.07 liter/h/kg in patients with AIDS or ARC. The volume of distribution at steady state was 0.42 +/- 0.12, 0.21 +/- 0.20, and 0.18 +/- 0.50 liter/kg in rats, monkeys, and patients, respectively. The elimination half-life was 1.3 +/- 0.4, 3.7 +/- 1.5, and 3.2 +/- 1.0 h in rats, monkeys, and patients, respectively. The disposition of GLQ223 was not dose dependent within the dose range tested in patients with AIDS or ARC. Interspecies pharmacokinetic scaling resulted in a good linear correlation for plasma clearance and the volume of distribution at steady state plotted versus species body weight on a log-log scale, indicating the predictability of elimination and distribution of GLQ223 among species. Allometric equations derived may be useful for the prediction of doses and dosage regimens to be used in animal models.

AIDS-Related Complex↗
PubMed1990

The safety and pharmacokinetics of GLQ223 in subjects with AIDS and AIDS-related complex: a phase I study.

A phase I dose-escalation study was performed to evaluate the safety and pharmacokinetics of a single intravenous infusion of GLQ223 in subjects with AIDS and AIDS-related complex (ARC). The active ingredient in GLQ223 is trichosanthin. Trichosanthin, imported from China, is the active drug in community-initiated treatment programs for patients with HIV infection. Eighteen subjects were enrolled, 10 with AIDS and eight with ARC. All subjects were monitored for tolerance and toxicity. Immunological and virological parameters were also followed. GLQ223 administration was not associated with notable toxicity with the exception of one subject who experienced a severe neurological adverse reaction. No consistent or sustained changes in CD4+ lymphocyte populations or HIV antigen levels were observed. Serum concentrations of GLQ223 that were comparable to concentrations shown to have antiviral activity in vitro were achieved transiently but may not have been maintained for a sufficient duration to exert antiretroviral effects. Further studies are indicated to determine pharmacodynamic properties of GLQ223, its optimal dosing schedule, and whether GLQ223 or related molecules will be useful in the treatment of HIV infection.

AIDS-Related Complex↗
PubMed1988

Patterns of junctional communication during development of the early amphibian embryo.

Cell-cell communication through gap junctions was examined in Xenopus laevis embryos between the 16-cell and early blastula stages using Lucifer Yellow, Fluorescein, lead EDTA and dicyanoargentate as probes of junctional permeability. Injections were made into cells whose position was identified with respect to the primary cleavage axis and the grey crescent. FITC dextrans revealed cytoplasmic bridges between the injected cell and its sister only. In the animal pole at the 16-cell stage at the future dorsal side of the embryo, Lucifer Yellow was frequently and extensively transferred between cells through gap junctions. At the future ventral side gap junctional transfer of Lucifer Yellow was significantly less frequent and less extensive. The asymmetry of transfer between future dorsal and ventral sides of the animal pole was more marked at the 32-cell stage. In the vegetal pole also at the 32-cell stage, a dorsoventral difference in junctional permeability to Lucifer Yellow was observed. At the 64-cell stage the transfer of Lucifer Yellow was relatively frequent between cells lying in the same radial segment in the animal pole; transfer into cells outside each segment was infrequent, except at the grey crescent. At the 128-cell stage, Lucifer transfer between future dorsal or future ventral cells in the equatorial region was infrequent. A high incidence of transfer was restored at the future dorsal side at the 256-cell stage. At the 32-cell stage, fluorescein was infrequently transferred between animal pole cells although lead EDTA moved from cell to cell with high, comparable frequency in future dorsal and ventral regions. Dicyanoargentate always transferred extensively, both at the 32- and 64-cell stages. Treatment of embryos with methylamine raised intracellular pH by 0.15 units, increased the electrical conductance of the gap junction and produced a 10-fold increase in the frequency of Lucifer Yellow transfer through gap junctions in future ventral regions of the animal pole at the 32-cell stage.

Animals↗
PubMed1983

Muscle activity and the loss of electrical coupling between striated muscle cells in Xenopus embryos.

The gap junctions between embryonic striated muscle cells are lost during development. The time course of their elimination has been examined with electrophysiological techniques in myotomes of Xenopus laevis embryos. Gap junctions were detected by the passage of electronic current or the fluorescent dye, Lucifer Yellow, from one muscle cell to another. These tracers only spread to neighboring cells when injected intracellularly. All the muscle cells are electrically coupled at stage 24 when neuromuscular transmission begins, but normally many cells become uncoupled during the next 48 hr. In contrast, the muscle cells remain electrically coupled if neuromuscular transmission is blocked during that period with tricaine or alpha-bungarotoxin. When muscle activity recovers, the loss of coupling resumes. Once the coupling has disappeared, neuromuscular blockade does not restore it. Muscle contraction is blocked during development in a mutant of Xenopus, even though the muscle cells remain electrically excitable. After stage 32 in these immobile embryos, the muscle cells are stimulated repeatedly by regular bursts of neural activity. Although they never contract, the mutant muscle cells become uncoupled at the same time as the muscle cells in normal embryos. The results suggest that some consequence of repeated cholinergic activation, other than contraction, stimulates the loss of gap junctions between striated muscle cells during development. The elimination of gap junctions may be required for neural control of subsequent muscle differentiation.

Aminobenzoates↗
PubMed1980

Intracellular pH in early Xenopus embryos: its effect on current flow between blastomeres.

1. Electrophysiological techniques were used to monitor the flow of electric current from one cell to the next in Xenopus laevis embryos between the 4-cell and early blastula stages of development. Intracellular pH and blastocoel pH were determined using pH-sensitive micro-electrodes. 2. The resting intracellular pH was 7.74+/-0.02 (S.E. of mean, n = 29); there were no systematic differences between developmental stages. Blastocoel cavity pH was 8.4+/-0.06 (S.E. of mean, n = 10). The intracellular buffer value was 18 m-equiv. H+/pH unit per litre. 3. In embryos treated with bicarbonate buffered Holtfreter solution equilibrated with 100% CO2 the intracellular pH fell to 6.3+/-0.17 (S.D., n = 8). The membrane potential fell and the input resistance increased. The size of the effect on membrane potential and input resistance varied. 4. From the 32-cell stage onwards current flow from one cell to the next was abolished when the intracellular pH fell to below 6.5; the effect was rapid in onset and completely reversible. At cleavage stages of development lowering intracellular pH with CO2 had no effect on current flow from cell to cell. 5. The relationship between intracellular pH and current flow from cell to cell was sigmoid and covered between 0.2 and 0.4 pH units. The pH at which current flow was completely abolished ranged from 6.85 to 6.4. 6. Alterations in extraembryonic pH over the range 5.8-7.5 had no effect on any parameter measured. 7. We conclude that lowering the intracellular pH increases the resistance of both non-junctional junctional membranes. The data do not allow us to extract the pH junctional conductance relationship. 8. Variations in intracellular pH may provide a useful tool for the study of the functional role of direct cell to cell communication in both adult organs and early embryos.

Animals↗