The unusual reproductive system of head and body lice (Pediculus humanus)

Insect reproduction is extremely variable, but the implications of alternative genetic systems are often overlooked in studies on the evolution of insecticide resistance. Both ecotypes of Pediculus humanus (Phthiraptera: Pediculidae), the human head and body lice, are human ectoparasites, the control of which is challenged by the recent spread of resistance alleles. The present study conclusively establishes for the first time that both head and body lice reproduce through paternal genome elimination (PGE), an unusual genetic system in which males transmit only their maternally derived chromosomes. Here, we investigate inheritance patterns of parental genomes using a genotyping approach across families of both ecotypes and show that heterozygous males exclusively or preferentially pass on one allele only, whereas females transmit both in a Mendelian fashion. We do however observe occasional transmission of paternal chromosomes through males, representing the first known case of PGE in which whole‐genome meiotic drive is incomplete. Finally, we discuss the potential implications of this finding for the evolution of resistance and invite the development of new theoretical models of how this knowledge might contribute to increasing the success of pediculicide‐based management schemes.     

Engorgement response of human body lice Pediculus humanus (Insecta: Anoplura) to blood fractions and their components

ABSTRACT. Fed through a synthetic membrane, 80% of females of the human body louse, Pediculus humanus de Geer, engorged on whole human blood compared to 30% on platelet poor plasma. Both the plasma albumin and small molecular weight components of the cellular fraction seemed to stimulate engorgement by lice. Known haemo-phagostimulants such as adenosine triphosphate and diphosphoglyceric acid when added to plasma, did not replace the small molecular weight components of the cellular fraction as feeding stimuli. Nymphs discriminated less than adults in selecting blood fractions.     

Partial characterization and post-feeding activity of midgut aminopeptidase in the human body louse, Pediculus humanus humanus

Abstract. A leucine aminopeptidase was found in the midgut of the human body louse, Pediculus humanus humanus L. (Anoplura: Pediculidae). The enzyme is activated by the bloodmeal with a pH optimum at 8. The enzyme is soluble in both aqueous and detergent-containing solutions. The two forms of the enzyme had the same Km but exhibited different catalytic activities with regard to Vmax values in these solutions. The enzyme is inhibited competitively by a substrate analogue 1,10-phenanthroline and by Mn²⁺ ions in the presence and absence of detergent.     

DNA barcoding of endoparasitoid wasps in the genus Anicetus reveals high levels of host specificity (Hymenoptera: Encyrtidae)

The genus Anicetus includes economically important biocontrol agents that are introduced for control of soft and wax scale insect agricultural pests (Ceroplastes spp.). Understanding of host–parasitoid associations is critical to the successful outcome of their utilization in biological control projects. However, identification of these parasitoids is often difficult because of their small size and generally similar morphological features, and hence, studies on the host–parasitoid associations. Here, nucleotide sequence data were generated from the mitochondrial COI gene and the D2 region of 28S rRNA to assess genetic variation within and between species of Anicetus occurring in China. The results of this study support the use of the COI and the D2 region of 28S rRNA gene as useful markers in separating species of Anicetus, even in cases where morphological differences are subtle. On the other hand, the COI gene is also useful in recognizing species with much variation in morphology. DNA barcoding reveals high levels of host specificity of endoparasitoids wasps in the genus Anicetus. Our results indicate that each Anicetus species is adapted to a limited set of host species, or even are monospecific in their host choice.     

Reduction of Cr(VI) by cysteine: Significance in human lymphocytes and formation of DNA damage in reactions with variable reduction rates

The induction of genotoxicity by Cr (VI) is dependent on its reductive activation inside the cell. Our recent studies have found that reduction of Cr (VI) by cysteine resulted in the formation of mutagenic Cr (III)-DNA adducts in the absence of oxidative DNA damage. In this work, we examined the formation of oxidative and Cr (III)-dependent types of DNA damage under a broader range of Cr (VI) and cysteine concentrations and investigated a potential role of this reducer in intracellular metabolism of Cr (VI). Peripheral lymphocytes from unexposed humans had 7.8-fold excess of glutathione over cysteine, whereas lymphocytes from stainless steel welders contained only 3 times higher amount of glutathione (p = 0.0009) which was entirely caused by the decrease in the concentration of glutathione. A strong correlation (r = 0.72) between the levels of both thiols was found in lymphocytes from controls. The number of DNA-protein crosslinks in lymphocytes from welders was 4.1 times higher than among controls, indicating the presence of Cr (VI)-dependent DNA damage. The average rate of Cr (VI) reduction by cysteine was approximately 5 times faster than that by glutathione. Higher reduction rate combined with the decrease in the intracellular concentration of glutathione should make cysteine a predominant Cr (VI)-reducing thiol in lymphocytes of welders. Analysis of the initial rates of Cr (VI) reduction by different concentrations of cysteine suggested the presence of one- and two-electron pathways, with one-electron mechanism dominating in the physiological range of concentrations. There was no detectable formation of DNA breaks or abasic sites under a broad range of Cr (VI) and cysteine concentrations, resulting in up to 68-fold differences in the rates of reduction and the production of as many as 3 Cr (III)-DNA adducts per 10 bp. The reactions with slow reduction rates (low concentrations of cysteine) led to the most extensive formation of Cr (III)DNA adducts. In summary, these results further establish Cr (III)-DNA adducts as the major form of DNA damage resulting from Cr (VI) metabolism by cysteine. The role of cysteine in reduction of Cr (VI) becomes more significant under conditions of occupational exposure to Cr (VI)-containing welding fumes.     

Design and validation of a new method to detect and quantify residual host cell DNA in human recombinant erythropoietin (rEPO)

During the purification of human recombinant erythropoietin (rEPO) from host cells, residual DNA may remain in final products. This contamination is a risk factor for patients and may result in the inactivation of some tumor suppressor genes or activation of oncogenes if its concentration is more than the standard defined by WHO. Based on WHO’s criteria, acceptable level of residual DNA in biopharmaceuticals is less than 10–100?pg/dose. In this study, we have designed a sensitive and specific quantitative real-time polymerase chain reaction (PCR) assay for the detection of residual DNA in human rEPO products. All reported sequences of CHO’s GAPDH gene were retrieved from GenBank, and a multiple alignment was performed using Mega 6 software to find conserved regions of the gene. Primers and probe were designed by AlleleID7 software for the highly conserved region. Quantitative real-time PCR showed an R² value more than 0.99 and the efficiency equal to 101% indicating a highly accurate and efficiency of the reaction, respectively. Based on the standard curve, the limit of detection of the assay was determined to be 10?copies/µL (0.00967?fg/µL). In addition, the inter- and intra-assay of the test were determined to be 1.14% and 0.65%, respectively, which are in acceptable range according to the WHO’s guidelines.     

Characterization of geographically isolated accessions in five Alstroemeria L. species (Chile) using FISH of tandemly repeated DNA sequences and RAPD analysis

In fifteen geographically isolated populations of five species of Alstroemeria L. (A. aurea, A. hookeri, A. ligtu, A. pelegrina and A. presliana) collected in Chile, karyotypes and variation of RAPD markers were investigated. Tandemly repeated DNA sequences - 5S and 18/25S rDNA genes and the sequence A001-1 (De Jeu et al. 1997) were used to characterize karyotypes by fluorescence in situ hybridization (FISH). Ten somatic metaphases per population were used for measurement of chromosome length. Differences in RAPD marker bands were used for characterization of populations, creating a similarity index. FISH with all three DNA probes shows a high degree of polymorphism between and sometimes also within accessions of A. aurea, A. hookeri and A. ligtu. The number of chromosome pairs showing 5S rDNA signals is more different for the investigated species A. aurea, A. hookeri, A. ligtu, A. pelegrina and A. presliana with 5, 7, 5, 3 and 7, respectively, than the number of 18/25S rDNA signals in this succession with 7, 7, 6, 5 and 7 chromosome pairs, showing a high evolutionary dynamics within the genus. Furthermore, among the four populations of A. hookeri, accession 4181 was different in arm length of chromosome 3. RAPD markers (index of similarity) also showed a greater genetic distance of accession 4181 from the other three accessions of A. hookeri. The possible evolutionary mechanisms providing these polymorphisms were discussed.