Insights into sinus arrhythmia of the dog: Acetylcholine perfusion of canine right atrium results in beat-to-beat patterns that mimic sinus arrhythmia supporting exit block in the sinoatrial conduction pathways.

Sinus arrhythmia of the dog is unique because of the pronounced alternating beat-to-beat intervals. The clustering of these short (faster rates) and long (slower rates) intervals is not just influenced by autonomic input from breathing; sinus arrhythmia can persist in the panting or apneic dog. The multiplicity of central and peripheral influences on the sinus node complicates the unraveling of the mechanisms of sinus arrhythmia. Studies of the sinus node suggest that acetylcholine can slow cellular depolarization and block sinoatrial conduction. Electrocardiographic monitoring of the dog supports this notion in that abrupt bifurcation into short and long intervals develop at lower heart rates. We sought to determine whether this phenomenon could be recapitulated in canine atrial preparations perfused with acetylcholine and whether selective pharmacologic blockade of the voltage and calcium clocks could provide insight into its mechanism. Spontaneous beat to beat (A-A) intervals were obtained from monophasic action potential recordings of perfused canine right atrial preparations before and during perfusion with acetylcholine (2-5 µM). The calcium clock was blocked with ryanodine (2-3 µM). The membrane clock was blocked with diltiazem hydrochloride (ICa,L blocker; 0.25 µM) and ZD7288 (If blocker; 3 µM). Hyperpolarization was hindered by blockade of IK,Ado/IK,Ach with tertiapin Q (100 nM) before and during acetylcholine perfusion. Acetylcholine resulted in beat clusters similar to those seen in sinus arrhythmia of the dog. Beat clusters were consistent with intermittent 2:1 and 3:1 sinoatrial conduction block. Tertiapin Q abolished this patterning suggesting a role of IK,Ado/IK,ACh in the mechanism of these acetylcholine-induced beat-to-beat patterns.

Motivating landowners to recruit neighbors for private land conservation.

Encouraging motivated landowners to not only engage in conservation action on their own property but also to recruit others may enhance effectiveness of conservation on private lands. Landowners may only engage in such recruitment if they believe their neighbors care about the conservation issue, will positively respond to their conservation efforts, and are likely to take action for the conservation cause. We designed a series of microinterventions that can be added to community meetings to change these beliefs to encourage landowner engagement in recruitment of others. The microinterventions included neighbor discussion, public commitment making, collective goal setting, and increased observability of contributions to the conservation cause. In a field experiment, we tested whether adding microinterventions to traditional knowledge-transfer outreach meetings changed those beliefs so as to encourage landowners in Hawaii to recruit their neighbors for private lands conservation. We delivered a traditional outreach meeting about managing the invasive little fire ant (Wasmannia auropunctata) to 5 communities and a traditional outreach approach with added microinterventions to 5 other communities. Analysis of pre- and post-surveys of residents showed that compared with the traditional conservation outreach approach, the microinterventions altered a subset of beliefs that landowners had about others. These microinterventions motivated reputationally minded landowners to recruit and coordinate with other residents to control the invasive fire ant across property boundaries. Our results suggest integration of these microinterventions into existing outreach approaches will encourage some landowners to facilitate collective conservation action across property boundaries.

Motivaciones para que los Terratenientes Recluten a sus Vecinos para la Conservación Privada de Tierras Resumen Si se alienta a los propietarios motivados a no sólo participar con acciones de conservación en sus propiedades sino también a reclutar a otros, se podría mejorar la efectividad de la conservación en las propiedades privadas. Puede que los propietarios sólo se comprometan con el reclutamiento si consideran que a sus vecinos les importan los temas de conservación, si responderán positivamente a sus esfuerzos de conservación, y si tienen probabilidad de tomar acción por la causa de conservación. Diseñamos una serie de microintervenciones que pueden añadirse a las juntas comunitarias para cambiar estas creencias y así promover la participación de los propietarios en el reclutamiento de otros propietarios. Las microintervenciones incluyeron discusiones entre vecinos, firmas públicas de compromisos, el establecimiento de objetivos colectivos, y una observación incrementada de las contribuciones a la causa de la conservación. En un experimento de campo probamos si la suma de estas microintervenciones a las tradicionales juntas de participación con transferencia de conocimiento cambó dichas creencias de tal manera que alentara a los terratenientes en Hawái a reclutar a sus vecinos para la conservación de terrenos privados. Realizamos una junta tradicional de participación sobre el manejo de la hormiga de fuego (Wasmannia auropunctata), una especie invasora, para cinco comunidades y una estrategia tradicional de participación con la suma de microintervenciones para otras cinco comunidades. El análisis previo y posterior a las encuestas realizadas a los residentes mostró que, si se comparan con la estrategia tradicional de participación, las microintervenciones alteraron a un subconjunto de creencias que los propietarios tenían sobre los demás propietarios. Estas microintervenciones motivaron a los propietarios con una reputación de estar dispuestos a conservar a reclutar y coordinarse con otros residentes para controlar a la hormiga invasora atravesando los límites de las propiedades. Nuestros resultados sugieren que la integración de estas microintervenciones dentro de las estrategias existentes de participación alentará a algunos propietarios a facilitar las acciones de conservación colectiva a través de los límites de las propiedades.

A new formulation of selegiline: improved bioavailability and selectivity for MAO-B inhibition.

Seven randomised comparative studies were conducted in healthy volunteers to compare the pharmacokinetic and pharmacodynamic profiles of selegiline hydrochloride in a new formulation designed for buccal absorption "Zydis Selegiline" (1.25-10 mg) with conventional selegiline hydrochloride tablets "conventional selegiline tablets" (10 mg). A total of 156 healthy volunteers participated in these studies. Plasma concentrations of selegiline and its primary metabolites, N-desmethylselegiline (DMS), l-amphetamine (AMT), and l-methamphetamine (MET) were measured using Gas Chromatography Mass Spectrometry (GCMS) and gas liquid chromatography (GLC) assays. Inhibition of monoamine-oxidase type B (MAO-B) and monoamine oxidase type A (MAO-A) activity was determined by measurement of as beta-phenylethylamine (PEA) by GCMS and 5-hydroxyindoleacetic acid (5-HIAA) by High Performance Liquid Chromatography (HPLC) assays. Almost a third (2.96 mg) of a 10 mg selegiline dose in Zydis Selegiline was absorbed pre-gastrically (predominantly buccally) within 1 minute. Mean [SD] area-under-the curve (AUC(0- infinity)) values following Zydis Selegiline 10 mg (5.85 [7.31] ng.h/mL) were approximately five times higher than those following conventional selegiline tablets 10 mg (1.16 [1.05] ng.h/mL). In contrast, plasma concentrations of metabolites were significantly ( p<0.001) lower following Zydis Selegiline 10 mg than following conventional selegiline tablets 10 mg. Plasma concentrations of selegiline and its metabolites increased in a dose-dependent manner over the dose-range Zydis Selegiline 1.25-5 mg. Bioavailability was determined using AUC and peak plasma concentrations (C(max)). The C(max) of selegiline was similar following administration of Zydis Selegiline 1.25 mg (1.52 ng/mL) or conventional selegiline tablets 10 mg (1.14 mg/mL). The range of values for AUC(0- infinity) and C(max) following Zydis Selegiline 1.25 mg were entirely contained within the range following conventional selegiline tablets 10 mg, with a much higher variability of plasma selegiline concentrations occurring after conventional selegiline tablets than after Zydis Selegiline. As expected, peak plasma concentrations for DMS, AMT and MET were consistently lower after Zydis Selegiline 1.25 mg (1.19, 0.34, 0.93 ng/ml, respectively) than after conventional selegiline tablets 10 mg (18.37, 3.60, 12.92 ng/ml, respectively). A significant (r=0.0001) correlation between daily PEA excretion (a measure of brain MAO-B inhibition) and the log-transformed AUC((0-t)) for selegiline was demonstrated. Mean daily PEA excretion was similar following Zydis Selegiline 1.25 mg and conventional selegiline tablets 10 mg (13.0 microg versus 17.6 microg). In contrast, there was no correlation between PEA excretion and selegiline metabolites, indicating that selegiline metabolites do not significantly inhibit MAO-B. Urinary excretion of 5-HIAA (used as a marker for MAO-A inhibition) was unrelated to plasma concentrations of selegiline or DMS following single or repeat dosing of Zydis Selegiline 1.25 mg or conventional selegiline tablets 10 mg. However, comparison of treatment groups revealed a significantly lower excretion of 5-HIAA in the conventional selegiline tablets 10 mg group than in the Zydis Selegiline 1.25 mg group after repeated administration over 13 days. In summary, by reducing the opportunity for first-pass metabolism, the absorption of selegiline from Zydis Selegiline was more efficient and less variable than from conventional selegiline tablets. Compared with conventional selegiline tablets 10 mg, Zydis Selegiline 1.25 mg yielded similar plasma concentrations of selegiline and degree of MAO-B inhibition, but markedly reduced concentrations of the principal metabolites. Thus, the lower but equally MAO-B inhibitory dose of selegiline in Zydis Selegiline 1.25 mg, which is associated with lower concentrations of potentially harmful metabolites, could offer a safer and more predictable treatment in the management of patients with Parkinson's disease.

UNC-11, a Caenorhabditis elegans AP180 homologue, regulates the size and protein composition of synaptic vesicles.

The unc-11 gene of Caenorhabditis elegans encodes multiple isoforms of a protein homologous to the mammalian brain-specific clathrin-adaptor protein AP180. The UNC-11 protein is expressed at high levels in the nervous system and at lower levels in other tissues. In neurons, UNC-11 is enriched at presynaptic terminals but is also present in cell bodies. unc-11 mutants are defective in two aspects of synaptic vesicle biogenesis. First, the SNARE protein synaptobrevin is mislocalized, no longer being exclusively localized to synaptic vesicles. The reduction of synaptobrevin at synaptic vesicles is the probable cause of the reduced neurotransmitter release observed in these mutants. Second, unc-11 mutants accumulate large vesicles at synapses. We propose that the UNC-11 protein mediates two functions during synaptic vesicle biogenesis: it recruits synaptobrevin to synaptic vesicle membranes and it regulates the size of the budded vesicle during clathrin coat assembly.

Antibodies to glutamate, aspartate and glycyl-D-aspartate reversibly suppress stimulus-evoked, extracellularly recorded responses in slices of rat neocortex.

Polyclonal antibodies raised against glutamate, aspartate and the dipeptide, glycyl-D-aspartate were dissolved in artificial cerebrospinal fluid (aCSF) and administered at concentrations as low as 0.05% to slices of prefrontal cortex maintained in vitro. These antisera caused a reversible attenuation of evoked field potentials and/or single-unit activity recorded extracellularly following the delivery of shocks to the underlying white matter, or to cortical layer IV. To the best of our knowledge, this result provides the first demonstration using electrophysiological recording of the use of a transmitter-specific antibody as a blocker of synaptic transmission in living slices of the central nervous system (CNS). The results lend support to the suggestion that glutamate, aspartate, and a molecule related closely to glycyl-D-aspartate, are involved in synaptic transmission at major pathways within prefrontal cortex.

Gel extenders in larval diet of Cochliomyia hominivorax (Diptera: Calliphoridae).

Larvae of the screwworm, Cochliomyia hominivorax (Coquerel), were reared on meridic diets containing ground corncob material (grit) in test 1 and the cob grit or sawdust in test 2 to reduce or replace the amount of an expensive synthetic copolymer gelling agent. Biological parameters for the tests included pupal yield (total number), pupal weight (size), pupal malformation, adult emergence, adult malformation, egg weight, and egg hatch to assess for any significant differences. In the first test, larval propagation was successful for five consecutive generations on 24 of an original 37 formulations. Results indicate that a minimum concentration of 4% of the cob grit is needed to reduce the gel by 50%; at least 8% concentration is needed to reduce the gel by 80%; and at least 12% concentration is needed to replace the gel completely. In the second test, the larvae were successfully propagated for five consecutive generations when the copolymer gel was reduced by 50 or 75% in the diet by using either sawdust or the no. 60 cob grit size. The cost savings and applications of use of sawdust or the cob grit incorporated into the larval diet can be beneficial to a mass-production screwworm program.

Electron spin echo envelope modulation studies of lectins: evidence for a conserved Mn(2+)-binding site.

Electron spin echo envelope modulation (ESEEM) experiments have been used to investigate the Mn(2+)-binding site in a series of lectins including concanavalin A, pea lectin (Pisum sativum), isolectin A from lentil (Lens culinaris), soybean agglutinin (Glycine max), Erythrina indica lectin, and Lotus tetragonolobus isoelectin A. Together with model studies, the results provide direct evidence for a single nitrogen atom of a conserved residue bonded directly to Mn2+ in all of them. ESEEM measurements of the lectins exchanged with deuterium oxide, together with model studies, provide evidence for the presence of two water molecules coordinated to the Mn2+ in all of the proteins. In contrast to concanavalin A, the absence of solvent exchange at the Mn2+ site in the pea and lentil lectins demonstrated by nuclear magnetic relaxation dispersion measurements [Bhattacharyya, L., Brewer, C.F., Brown, R. D., III, & Koenig, S. H. (1985) Biochemistry 24, 4985-4990] must therefore be due to slow exchange of the water ligands of the bound Mn2+. Binding of saccharides was observed to have little effect on the structural features of the Mn2+ site in the lectins as determined by ESEEM.

Seasonal and annual variation of antibody to HIV-1 among male inmates entering Maryland prisons: update.

Previous serosurveys of antibody to HIV-1 among incoming male inmates in Maryland between April and June of 1985, 1986 and 1987 have shown a prevalence of 7.0, 7.7 and 7.0%, respectively, with stability persisting after multivariate adjustment. To investigate seasonality and update annual trends, excess sera were obtained from incoming male inmates between August 1987 and August 1988. Correctional personnel also provided demographic variables of age, race, offense, category, and jurisdiction. Once rendered anonymous, specimens were assayed for antibody to HIV-1 using enzyme-linked immunosorbent assay and Western blot. For the 12-month study period, 415 (7.9%) of 5262 consecutive male entrants were seropositive. On univariate and multivariate analyses, no significant change in seroprevalence or risk by subgroup was noted by month or season. For data from April to June 1988, 113 (8.1%) of 1398 consecutive entrants demonstrated anti-HIV-1; seropositivity was associated with age greater than 25 years, Black race, and Baltimore jurisdiction. No significant change was found over time in seroprevalence or risk of HIV-1 infection by subgroup in multivariate analysis combining data for 1985-1988. These data provide additional evidence to suggest stability of HIV-1 seroprevalence in Maryland male prison entrants.

Reexamination of the 1H NMR assignments and solution conformations of L-carnitine and O-acetyl-L-carnitine using C-2 stereospecifically labeled monodeuterated isomers.

The two C-2 monodeuterated isomers of L-carnitine were synthesized by enzymatic hydration of crotonobetaine in D2O and by enzymatic proton exchange of L-[2-2H2]carnitine in H2O. These reactions, catalyzed by an induced Escherichia coli carnitine hydrolyase proceed stereospecifically. The two isomers of L-[2-2H]carnitine were examined by 1H NMR at 500 MHz, which allowed us to independently monitor the pD dependence and coupling constants of the H-2 protons. The results obtained indicate that there is little effect of the carboxyl charge on the conformational state(s) of L-carnitine about the C-2/C-3 bond. The NMR data obtained in this study do not support previous solution studies of the pH-dependent conformational changes for DL-carnitine nor the proposed conformation of O-acetyl-DL-carnitine in the crystalline state.

Temporal trends of human immunodeficiency virus type 1 (HIV-1) infection among inmates entering a statewide prison system, 1985-1987.

Acquired immune deficiency syndrome (AIDS) became the leading cause of death among Maryland State prisoners in 1985. To identify the prevalence, risk factors, and temporal trends for infection with the human immunodeficiency virus type 1 (HIV-1) in the statewide prison system, excess sera were obtained from incoming male inmates during specified periods between April and June 1985, 1986, and 1987. Correctional medical personnel also provided demographic variables of age, race, offense category, sentence, jurisidiction, and an indicator of intravenous drug use. Once rendered anonymous, specimens were assayed for antibody to HIV-1, using ELISA and Western blot techniques. For data from April to June 1985, 1986, and 1987, the crude prevalence of anti-HIV-1 was 7.1, 7.7, and 7.0%, respectively. Although one-third of incoming inmates were identified as intravenous drug users (IVDUs), the drug use variable was missing for 70% of the 1985 sample, and 40% of the 1986 sample. Several strategies were used to examined temporal trends in the context of missing data. Univariate analyses suggested no substantial change over time for either HIV-1 seroprevalence or risk of infection among IVDUs.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding and precipitating activities of Erythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins from E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica.

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certain Erythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 27:1034-41]. The present work describes a comparative study of the binding and precipitating activities of four Erythrina lectins, viz., E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, the Erythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.

Verapamil reversal of vincristine resistance and cross-resistance patterns of vincristine-resistant Chinese hamster ovary cells.

The phenotypic properties of a large number of low-level vincristine (VCR)-resistant Chinese hamster ovary cell lines have been studied. In particular, we examined the correlation between the reversal of VCR resistance by verapamil (VRP) and cross-resistance patterns to other drugs. Cross resistance to other vinca alkaloids developed in parallel with VCR resistance. Doxorubicin resistance was observed in many of the cell lines, occurring even at the lowest levels of VCR resistance. Increased sensitivity to taxol (TAX) was a feature of half of the lines tested and there was no increased resistance to 5-fluorouracil or chlorambucil. Two main groups of mutants have been identified: (a) those that are thought to be membrane mutants which are cross-resistant to TAX and whose VCR resistance is reversible by VRP; and (b) those that appear to be tubulin mutants, which have increased sensitivity to TAX and resistance to VCR in the presence of VRP. It was not possible to distinguish between the different mechanisms of low-level resistance by drug accumulation studies in unsupplemented medium. However, VCR accumulation in the presence of VRP did correlate with the cross-resistance results.

Verapamil hypersensitivity of vincristine resistant Chinese hamster ovary cell lines.

Vincristine resistant CHO cell lines, obtained by prolonged selection in semi-inhibitory drug concentrations show considerable hypersensitivity to verapamil. Their D10 values are around 0.2 micrograms/ml compared to 23 micrograms/ml for unselected controls. Reversion of vincristine resistance during growth in vincristine free medium is correlated with reversal of verapamil sensitivity indicating that the two aspects of the cells' phenotype have a common underlying cause. The rate of uptake of calcium in the absence and presence of verapamil is similar in the vincristine resistant cells and the controls. The correlation of verapamil sensitivity with vincristine resistance is not a universal feature of CHO cell lines resistant to antimicrotubular drugs, since it was found that other resistant cell lines which have been selected by short term exposure to high drug concentrations were not verapamil hypersensitive.

Interactions of concanavalin A with a trimannosyl oligosaccharide fragment of complex and high mannose type glycopeptides.

It has previously been reported that the binding interactions of concanavalin A with a purified high mannose type glycopeptide from ovalbumin differs from that with simple mono- and oligosaccharides (Brewer, C.F. (1979) Biochem. Biophys. Res. Commun. 90, 117-122). We now report studies with a synthetic analog of complex type glycopeptides, and a synthetic trimannosyl oligosaccharide fragment that is common to both complex and high mannose type glycopeptides. We find that both synthetic oligosacchardes undergo similar interactions with concanavalin A which mimic the effects of binding corresponding larger glycopeptides. Furthermore, the relative affinity of the trimannosyl oligosaccharide is 130-fold greater than the binding of methyl-alpha-D-mannopyranoside. The results indicate that the trimannosyl oligosaccharide is a unique structural element recognized by the lectin.

Resistance to the mitotic inhibitor NY 3170 in Chinese hamster ovary cells.

Mutant CHO cells have been isolated which are resistant to NY 3170, a member of the metahalone group of antimitotic drugs. One NY 3170 resistant mutant is hypersensitive to the microtubule-stabilising drug, taxol, but there is not a reciprocal relationship between levels of resistance to these drugs in CHO cells, since it was found that sixteen other mutants isolated on the basis of taxol resistance had wild type levels of NY 3170 resistance. Our NY 3170 resistant mutants are cross-resistant to vincristine and other mutants, selected on the basis of vincristine resistance, are cross-resistant to NY 3170.