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D L Lewis

Publications and source records attributed to D L Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Rat brain cannabinoid receptor modulates N-type Ca2+ channels in a neuronal expression system.

Modulation of neuronal ion channels by the cloned rat brain CB1 cannabinoid receptor was investigated with the use of a heterologous neuronal expression system. Transient expression of the rat brain CB1 cannabinoid receptor was accomplished through microinjection of in vitro transcribed cRNA into the cytoplasm of enzymatically dissociated adult rat superior cervical ganglion neurons. The cannabimimetic aminoalkylindole WIN 55,212-2 inhibited whole-cell Ca2+ currents in neurons injected 16-25 hr previously with rat brain CB1 cannabinoid receptor cRNA. Inhibition of the Ca2+ current was voltage and concentration dependent, with a maximal inhibition of 73% and an IC50 value of 47 nM. The synthetic cannabinoid analogue CP55,940 also inhibited Ca2+ currents, with a maximal inhibition of 38% and an IC50 value of 7 nM. Ca2+ current inhibition was blocked by inclusion of guanosine-5'-O-(2-thiodiphosphate) in the intracellular patch pipette solution or by pretreatment with pertussis toxin. Pretreatment with the N-type Ca2+ channel antagonist omega-conotoxin GVIA reduced the inhibition by 100 nM WIN 55,212-2 from 44% to 6%, indicating that N-type Ca2+ channels are a target of cannabinoid action. On washout of WIN 55,212-2, the Ca2+ current amplitude "overrecovered" in 47% of the neurons tested. Anandamide, the endogenous cannabimimetic compound, had an inconsistent effect on the voltage-dependent Ca2+ currents in the majority of neurons microinjected with cannabinoid receptor cRNA. Ca2+ channels were a specific effector target of the cannabinoid receptor, as two different K+ currents, the M current and the A current, were not modulated by the cannabimimetic WIN 55,212-2.

Animals↗
PubMed1995

L- and N-type Ca2+ channels in adult rat carotid body chemoreceptor type I cells.

1. Whole-cell voltage-dependent Ca2+ currents recorded from chemoreceptor type I cells of the adult rat carotid body had maximum amplitudes of -94 pA in 10 mM Ca2+ and were half-inactivated at a holding potential of -38 mV. Somatostatin and dopamine inhibited whole-cell Ca2+ current in type I cells. 2. The dihydropyridine agonist (+)202-791 increased the Ca2+ current amplitude by 106% at a step potential of -18 mV. The dihydropyridine antagonist nimodipine decreased the Ca2+ current amplitude by 40% from a holding potential of -80 mV, and by 74% from a holding potential of -60 mV. The nimodipine-sensitive current had a maximum amplitude at a membrane potential of -12 mV. omega-Conotoxin GVIA (omega-CgTX GVIA) blocked the whole-cell Ca2+ current by 40%. The omega-CgTX GVIA-sensitive current had a maximum amplitude at a membrane potential of +2 mV. 3. In summary, type I cells of the adult rat carotid body have dihydropyridine-sensitive L-type and omega-conotoxin GVIA-sensitive N-type voltage-dependent Ca2+ channels. These channels may play a role in the voltage-gated entry of Ca2+ necessary for stimulus-secretion coupling in response to changes in arterial PO2, PCO2 and pH. Inhibition of the Ca2+ currents by somatostatin and dopamine may alter the chemotransduction signal in type I cells.

Animals↗
PubMed1995

Heterologous expression of metabotropic glutamate receptors in adult rat sympathetic neurons: subtype-specific coupling to ion channels.

A novel heterologous expression system was used to examine the coupling of metabotropic glutamate receptors (mGluRs) to neuronal voltage-gated ion channels. Cytoplasmic injection of mGluR2 cRNA into adult rat sympathetic neurons resulted in the expression of receptors that negatively coupled to N-type Ca2+ channels through a pertussis toxin-sensitive pathway. Injection of mGluR1 alpha cRNA resulted in the expression of receptors that inhibited M-type K+ channels via a pertussis toxin-insensitive pathway. Coupling was restricted to specific transduction elements and effectors, since mGluR2 did not inhibit M channels and mGluR1 alpha had minimal effects on Ca2+ channels. These findings demonstrate that heterologously expressed, and thus unambiguously identified, mGluR subtypes modulate specific neuronal ion channels through discrete signal transduction pathways.

Animals↗
PubMed1995

Resistance of microorganisms to disinfection in dental and medical devices.

The U.S. Centers for Disease Control and Prevention (CDC) recommends that only heat sterilization be used for all reusable devices entering the oral cavity. However, chemical disinfection is still employed for reprocessing dental devices in many areas of the world. In an analysis of a Florida dental practice responsible for nosocomial human immunodeficiency virus (HIV) transmissions, the possible role of contaminated devices was deemed unlikely in part because they were subjected to high-level disinfection with 2% glutaraldehyde. Disease transmissions have, however, been documented for endoscopes used in diagnostic and surgical procedures even after this treatment. In some dental devices, lubricants mix with potentially infectious patient materials, and organic debris has been observed in endoscopes after cleaning. We have investigated whether lubricants can render high-level chemical disinfection procedures ineffective and have addressed the role that some common devices may play in disease transmission. We report here that HIV in whole-blood samples and Pseudomonas aeruginosa in blood and plasma survived high-level disinfection when entrapped in lubricants used in dental handpieces and endoscopes. We also found that lubricated dental devices used to clean and polish teeth (prophylaxis angles) have the potential to transfer sufficient amounts of blood to infect human lymphocyte cultures with HIV. These results emphasize the need to subject reusable dental devices to a heat-sterilization protocol that penetrates the lubricant.

Bacterial Infections↗
PubMed1995

Drosophila melanogaster mitochondrial DNA: completion of the nucleotide sequence and evolutionary comparisons.

The nucleotide sequence of the regions flanking the A+T region of Drosophila melanogaster mitochondrial DNA (mtDNA) has been determined. Included are the genes encoding the transfer RNAs for valine, isoleucine, glutamine and methionine, the small ribosomal RNA and the 5'-coding sequences of the large ribosomal RNA and NADH dehydrogenase subunit II. This completes the nucleotide sequence of the D. melanogaster mitochondrial genome. The circular mtDNA of D. melanogaster varies in size among different populations largely due to length differences in the control region (Fauron & Wolstenholme, 1976; Fauron & Wolstenholme, 1980a, b); the mtDNA region we have sequenced, combined with those sequenced by others, yields a composite genome that is 19,517 bp in length as compared to 16,019 bp for the mtDNA of D. yakuba. D. melanogaster mtDNA exhibits an extreme bias in base composition; it comprises 82.2% deoxyadenylate and thymidylate residues as compared to 78.6% in D. yakuba mtDNA. All genes encoded in the mtDNA of both species are in identical locations and orientations. Nucleotide substitution analysis reveals that tRNA and rRNA genes evolve at less than half the rate of protein coding genes.

Amino Acid Sequence↗
PubMed1994

Sequence, organization, and evolution of the A+T region of Drosophila melanogaster mitochondrial DNA.

The long (4.6-kb) A+T region of Drosophila melanogaster mitochondrial DNA has been cloned and sequenced. The A+T region is organized in two large arrays of tandemly repeated DNA sequence elements, with nonrepetitive intervening and flanking sequences comprising only 22% of its length. The first repeat array consists of five repeats of 338-373 bp. The second consists of four intact 464-bp repeats and a fifth partial repeat of 137 bp. Three DNA sequence elements are found to be highly conserved in D. melanogaster and in several Drosophila species with short A+T regions. These include a 300-bp DNA sequence element that overlaps the DNA replication origin and two thymidylate stretches identified on opposite DNA strands. We conclude that the length heterogeneity observed in the A+T regulatory region in mitochondrial DNAs from the genus Drosophila results from the expansion (and contraction) of the number of repeated DNA sequence elements. We also propose that the 300-bp conserved DNA sequence element, in conjunction with another primary sequence determinant, perhaps the adjacent thymidylate stretch, functions in the regulation of mitochondrial DNA replication.

Animals↗
PubMed1993

Enhanced expression of Ca2+ channels by nerve growth factor and the v-src oncogene in rat phaeochromocytoma cells.

1. Rat phaeochromocytoma (PC12) cells were used to investigate the expression of Ca2+ channel types during neuronal differentiation. Neuronal differentiation was induced by treatment with nerve growth factor (NGF) or by activation of a temperature-sensitive tyrosine kinase (pp60v-src) in genetically modified PC12 (PC12/v-src) cells. PC12 cells differentiated morphologically in the presence of NGF. When grown at the permissive temperature of 37 degrees C which activates the kinase activity of pp60v-src, PC12/v-src cells differentiated morphologically with the extension of neurites. In contrast, PC12/v-src cells grown at the non-permissive temperature of 40 degrees C continued to divide and were morphologically indistinguishable from control PC12 cells. 2. Whole-cell Ca2+ currents were measured in PC12 cells using Ba2+ as the charge carrier. Ba2+ currents measured at the peak of the current-voltage curve from a holding potential of -80 mV were -0.28 +/- 0.04 nA (mean +/- S.E.M.) in control PC12 cells compared to -1.25 +/- 0.16 nA in NGF-differentiated cells. The current density increased from 9.4 +/- 0.7 pA/pF in control PC12 cells to 22.8 +/- 2.4 pA/pF in NGF-differentiated PC12 cells. Ba2+ currents were -0.24 +/- 0.04 nA in undifferentiated PC12/v-src cells grown at the non-permissive temperature of 40 degrees C compared to -0.95 +/- 0.16 nA in differentiated PC12/v-src cells grown at the permissive temperature of 37 degrees C. The current density increased from 4.5 +/- 0.5 pA/pF in PC12/v-src cells grown at the non-permissive temperature of 40 degrees C to 13.3 +/- 2.4 pA/pF in PC12/v-src cells grown at the permissive temperature of 37 degrees C. 3. The sensitivity of Ba2+ currents to omega-conotoxin GVIA (omega-CgTX) was determined for currents measured at the peak of the current-voltage curve (0 mV in 10 mM Ba2+) from a holding potential of -80 mV. In NGF-differentiated PC12 cells, 10 microM omega-CgTx inhibited 68.1 +/- 3.2% of the total Ba2+ current compared to 35.9 +/- 4.1% in control cells. The density of the omega-CgTX-sensitive current increased from 3.3 +/- 0.4 pA/pF in control cells to 15.7 +/- 2.0 pA/pF in NGF-differentiated cells. In differentiated PC12/v-src cells grown at 37 degrees C, omega-CgTX inhibited 52.2 +/- 4.2% of total Ba2+ current compared to 41.1 +/- 3.8% in PC12/v-src cells grown at 40 degrees C. The density of the omega-CgTX-sensitive current increased from 1.9 +/- 0.3 to 7.4 +/- 2.0 pA/pF with v-src-mediated differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Cross-contamination potential with dental equipment.

Some types of reused dental equipment, especially handpieces and their attachments for drilling and cleaning teeth, might be responsible for cross-contamination if patient material were to lodge temporarily in difficult-to-disinfect internal mechanisms. This possibility is worrisome with respect to transmission of hepatitis B and human immunodeficiency viruses (HBV, HIV). Previous cross-contamination studies have relied on laboratory experiments with bacteria or dye tracers. To assess possible risk more thoroughly, we tested 30 new prophylaxis angles and 12 new high-speed handpieces to see whether they would take up and expel contaminants in laboratory and clinical trials. In treatments of three patients, including two infected with HIV, human-specific DNA (beta-globin, HLA DQ alpha) and HIV proviral DNA were detected inside or coming back from the devices. Similarly, when handpieces were operated in contact with blood pooled from HBV-infected patients, HBV DNA was detected in samples taken from inside the equipment and from their attached air/water hoses. When we used bacteriophage phi X174 as a model virus in laboratory tests, many infective viral particles were recovered from internal mechanisms of handpieces, their connecting air/water hoses, and from water spray expelled when the equipment was reused. We recommend that reused high-speed, air-driven handpieces and prophylaxis angles should be cleaned and heat-treated between patients. Further studies are needed to determine ways of eliminating the risks associated with exhaust hoses and air/water input lines.

Bacteriophages↗
PubMed1992

Heterologous expression of the human potassium channel Kv2.1 in clonal mammalian cells by direct cytoplasmic microinjection of cRNA.

The cloned human delayed rectifying K+ channel Kv2.1 (drk1) was expressed in clonal mouse fibroblasts (L-cells) and rat basophilic leukemia cells (RBL-1) by direct cytoplasmic microinjection of complementary RNA (cRNA). Within six hours, cells microinjected with Kv2.1 cRNA expressed a large sustained outward current as determined from whole-cell patch-clamp recordings. Nearly 100% of cells injected with cRNA expressed outward current. Current density was 30-70 pA/pF when measured at a potential of +50 mV. Steady-state activation and inactivation parameters for Kv2.1 were similar when expressed in either L-cells or RBL-1 cells. These results are the first to demonstrate that functional ion channel proteins can be expressed in mammalian clonal cell lines by direct cytoplasmic microinjection of cRNA.

Animals↗
PubMed1992

The prevalence of recurrent herpes labialis during an army hot weather exercise.

A survey was performed on 1,062 of 2,500 (42%) Army personnel participating in a desert training exercise at Fort Irwin, California, in September 1983. The prevalence of recurrent herpes labialis (RHL) and chapped lips was observed during the third week of a four-week training period. Complexion, sex, lip protectant use, age, and time spent outdoors were obtained by observation and interview. Recurrent herpes labialis was found in 46 subjects (4%). Stratified analysis and stepwise logistic regression were used to identify risk factors associated with RHL and to determine the prevalence odds ratios (POR). Risk factors with statistically significant associations with RHL were lip protectant use (POR = 0.19), chapped lips (POR = 2.87), being female (POR = 5.00), and light complexion (POR = 2.48). These findings strongly support the use of lip protectants during prolonged exposure to hot, dry climates as a prophylaxis against recurrent herpes labialis. Additional studies should focus on excitatory factors of RHL; and clinical trials of the efficacy of the lip protectants to protect against RHL and chapped lips should be undertaken.

Adolescent↗
PubMed1992

Treating soil solution samplers to prevent microbial removal of analytes.

Soil microorganisms colonizing soil water sampling devices (lysimeters) reduced concentrations of biodegradable organic chemicals, including 2,4-dichlorophenoxyacetic acid methyl ester, alachlor, methyl m-chlorobenzoate, and metolachlor as water entered through porous ceramic cups. In some cases, losses exceeded 99%. Additions of either a biocide (sodium hypochlorite) or a bacteriostat (copper salt) prevented microbial activity so that concentrations of test chemicals inside lysimeters equaled those outside. Field studies further indicated that treating lysimeters with a copper salt effectively prevented microbial activity. Thus, chemically treating soil water samplers could improve the accuracy of soil water data for a wide variety of analytes, including environmentally important organics, such as pesticides and industrial wastes, and inorganics, such as ammonia and nitrate.

Journal Article↗