An extract of Commiphora erythraea: a repellent and toxicant against ticks

A hexane extract of the gum of an African plant, Commiphora erythraea Engler (Burseraceae), has larvicidal and repellent activity against the lone star tick, Amblyomma americanum (L.) and the American dog tick, Dermacentor variabilis (Say). Adult deer ticks, Ixodes dammini Spielman, Clifford, Piesman and Corwin, were also repelled by the extract. Concentrations of 0.02 mg/cm² of the extract impregnated onto filter paper killed 96.15 (±3.56)% of A. americanum larvae exposed to it for 24h. A concentration of 0.16 mg/cm² was needed to kill 80.3% of D. variabilis larvae. The extract was less effective as a larvicide against A. americanum and D. variabilis than permethrin. Less than 15.5% of A. americanum larvae and adults and D. variabilis and I. dammini adults entered and remained for 2 or 3 min on areas of cloth strips treated with the extract at the rate of 0.2 mg/cm². However, 73.3 to 83.3% of the ticks tested entered and remained in areas treated with hexane. Permethrin was about 1 or 2 orders of magnitude more effective against A. americanum larvae as a repellent than the extract.

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Résumé Un extrait à l'hexane de la gomme de la plante africaine, C. erythraea Engler (Burseraceae) a des effets larvicides et répulsifs contre les tiques, Amblyomma americanum L. et Dermacentor variabilis Say; les adultes de Ixodes dammini Spielman, Clifford, Piesman & Corwin, ont été aussi éloignés par l'extrait. Une concentration de 0,02 mg/cm² de l'extrait imprégnant du papier filtre a tué 96,15% (±3,56) larves de A. americanum exposées pendant 24 h. Une concentration de 0,16 mg/cm² a été nécessaire pour tuer 80,3% des larves de D. variabilis. L'extrait a été moins efficace que la perméthrine comme larvicide contre A. americanum et D. variabilis. Moins de 15,5% des larves et des adultes de A. americanum et des adultes de D. variabilis et de I. dammini pénétrèrent et séjournèrent 2 à 3 minutes dans des morceaux de tissu traités avec l'extrait à raison de 0,2 mg/cm², contre 73,3 et 83,3% qui pénétrèrent et restèrent lors de traitement avec de l'hexane. Contre A. americanum, la perméthrine est un répulsif d'un ordre de grandeur une à deux fois supérieur à l'extrait de C. erythraea.

     

Human testis cDNA for the regulatory subunit RII alpha of cAMP-dependent protein kinase encodes an alternate amino-terminal region

Phosphorylations catalyzed by cAMP-dependent protein kinase are essential for sperm motility, and type II cAMP-dependent protein kinase in mature sperm has been shown to be firmly bound to the flagellum via the regulatory subunit, RII. The present study documents high-levelled expression of a human, testis-specific RII alpha mRNA (2.0 kb) analogous to the rat mRNA which is induced in haploid germ cells [(1988) FEBS Lett. 229, 391-394]. We report the molecular cloning of a full-length human cDNA corresponding to this unique testis mRNA, and the presence of an alternative amino-terminal region (amino acids 45-75) of the predicted RII alpha protein (404 amino acids) compared with the previously published mouse and rat sequences. However, this alternate region is also shown to be present in RII alpha mRNA (7.0 kb) of human somatic cells. Our data indicate the divergent amino-terminal sequence to be due to species differences, suggesting an active evolutionary pressure on this particular region, which could be involved in subcellular attachment of RII alpha and thereby localization of kinase activity to certain targets within the cell.     

Specificity of Cellular DNA-Binding Sites of Microbial Populations in a Florida Reservoir

The substrate specificity of the DNA-binding mechanism(s) of bacteria in a Florida reservoir was investigated in short- and long-term uptake studies with radiolabeled DNA and unlabeled competitors. Thymine oligonucleotides ranging in size from 2 base pairs to 19 to 24 base pairs inhibited DNA binding in 20-min incubations by 43 to 77%. Deoxynucleoside monophosphates, thymidine, and thymine had little effect on short-term DNA binding, although several of these compounds inhibited the uptake of the radiolabel from DNA in 4-h incubations. Inorganic phosphate and glucose-1-phosphate inhibited neither short- nor long-term binding of [³H]- or [³²P]DNA, indicating that DNA was not utilized as a phosphorous source in this reservoir. RNA inhibited both short- and long-term radiolabeled DNA uptake as effectively as unlabeled DNA. Collectively these results indicate that aquatic bacteria possess a generalized nucleic acid uptake/binding mechanism specific for compounds containing phosphodiester bonds and capable of recognizing oligonucleotides as short as dinucleotides. This binding site is distinct from nucleoside-, nucleotide-, phosphomonoester-, and inorganic phosphate-binding sites. Such a nucleic acid-binding mechanism may have evolved for the utilization of extracellular DNA (and perhaps RNA), which is abundant in many marine and freshwater environments.     

Factor IXPortland: a nonsense mutation (CGA to TGA) resulting in hemophilia B

Male siblings with severe hemophilia b were studied for the molecular defect responsible for their disorder. To define the precise DNA alteration, a 362-bp fragment in the first part of exon VIII of the factor IX gene was amplified and sequenced. A single-base-pair substitution of C----T at the nucleotide sequence 30875 was found which resulted in a nonsense mutation (TGA) and terminated the protein synthesis of factor IX at amino acid residue 252. The single-base change occurred as a classic CG dinucleotide alteration to TG (or CA), a common mechanism for point mutations in mammals.     

Properties of several protein kinases that copurify with rat spinal cord neurofilaments

Several protein kinases that copurify with neurofilaments (NF) were identified and each kinase was assessed for its ability to phosphorylate NF proteins. NFs were isolated using an axonal flotation procedure and the kinases were extracted from NFs with 0.8 M KCl. NF kinases were incubated with peptide substrates for selected protein kinases, [32P]ATP and protein kinase cofactors and inhibitors to characterize the kinases. Using peptide substrates, three types of kinase were identified, and a fourth was identified using NF protein as substrate. The first three kinases were the catalytic subunit of cAMP-dependent protein kinase, calcium-calmodulin dependent protein kinase II and a cofactor-independent kinase that phosphorylated prepro VIP sequence 156-170 and was inhibited by heparin. Using NF proteins as substrate, a fourth kinase was identified which was cofactor-independent and was not inhibited by heparin. Neither cofactor-independent kinase was casein kinase II. NF proteins were phosphorylated in vitro on serine and threonine, primarily by the two cofactor-independent kinases. Using [alpha-32P]8-N3ATP for affinity labeling, one kinase of 43,800 Da was identified. Thus, in addition to cAMP-dependent protein kinase and calcium-calmodulin dependent protein kinase II, two kinases have been found which are primarily responsible for NF phosphorylation in vitro and are cofactor-independent.     

Interactions between Pesticide Genes: Model and Experiment

In response to years of intense selection pressure by organophosphate insecticides, several different insecticide resistance mechanisms have evolved in natural populations of the mosquito Culex pipiens. We examined interactions between two of the most important mechanisms using a four-compartment model of insecticide pharmacokinetics. The joint effect of different mechanisms of resistance can be expressed in terms of epistasis at the physiological level in this model. The type of epistasis predicted by the model depends on the particular physiological mechanisms of resistance involved. Resistance due to a reduced penetration of the insecticide combines multiplicatively with other resistance factors, but resistance due to detoxicative processes and to insensitivity of the target site combines additively. How the pattern of epistasis at the physiological level is translated into fitness epistasis in natural populations of this mosquito depends on the intensity and pattern of insecticide selection in the field.     

Effect of Moniliformis moniliformis density on distribution within the definitive host population (Rattus norvegicus)

The population dynamics of Moniliformis moniliformis was studied in ‘free-ranging’ laboratory rats, Rattus norvegicus, presented with different relative density levels of M. moniliformis in cockroaches, Periplaneta americana. Changes in selected population parameters of the negative binomial distribution were evaluated as indicators of changes in aggregation. A significant increase in the degree of aggregation of parasites occurred as a result of the increase in relative density of infective stages available to the rats. This increase in aggregation was due to the increase in over-dispersion that occurred in female rats only. The degree of aggregation in females was found to be significantly higher than that in males at both treatment levels. The best indicators of the degree of aggregation were found to be the ratio of the variance to the relative density and the ratio of the log-variance to log-relative density. Changes in k were not correlated with changes in over-dispersion or the relative density.     

Evidence for a stem cell-specific repressor of Moloney murine leukemia virus expression in embryonal carcinoma cells.

A negative regulatory element (NRE) spanning the tRNA primer-binding site (PBS) of Moloney murine leukemia virus (M-MuLV) mediates repression of M-MuLV expression specifically in embryonal carcinoma (EC) cells. We precisely defined the element by base-pair mutagenesis to an 18-base-pair segment of the tRNA PBS and showed that the element also restricted expression when moved upstream of the long terminal repeat. A DNA-binding activity specific for the M-MuLV NRE was detected in vitro by using crude EC nuclear extracts in exonuclease III protection assays. Binding was strongly correlated with repression in EC cells. Mutations within the NRE that relieved repression disrupted binding activity. Also, nuclear extracts prepared from permissive, differentiated EC cell cultures showed reduced binding activity for the NRE. These results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS.