Head lice in Norwegian households: actions taken, costs and knowledge

Introduction

Head lice infestations cause distress in many families. A well-founded strategy to reduce head lice prevalence must shorten the infectious period of individual hosts. To develop such a strategy, information about the actions taken (inspection, treatment and informing others about own infestations), level of knowledge and costs is needed. The present study is the first to consider all these elements combined.

Materials and Methods

A questionnaire was answered by 6203 households from five geographically separated municipalities in Norway.

Results

94% of the households treated members with pediculicides when head lice were discovered. Nearly half of the households checked biannually or not at all. Previous occurrence of head lice and multiple children in a household improved both checking frequency and method. More than 90% of the households informed close contacts about their own pediculosis. Direct costs of pediculosis were low (less than €6.25 yearly) for 70% of the households, but the ability to pay for pediculicides decreased with the number of head lice infestations experienced. One in three households kept children from school because of pediculosis. Other widespread misconceptions, such as that excessive cleaning is necessary to fight head lice, may also add unnecessary burden to households. School affiliation had a significant effect on checking frequency and method, knowledge and willingness to inform others about own pediculosis.

Conclusions

Increased checking frequencies appear to be the most important element to reduce head lice prevalence in Norway and should be a primary focus of future strategies. National campaigns directed through schools to individual households, might be an important tool to achieve this goal. In addition to improving actions taken, such campaigns should also provide accurate information to reduce costs and enhance the level of knowledge about head lice in households.     

Questing activity in bed bug populations: male and female responses to host signals

A large‐arena bioassay is used to examine sex differences in spatiotemporal patterns of bed bug Cimex lectularius L. behavioural responses to either a human host or CO₂ gas. After release in the centre of the arena, 90% of newly‐fed bed bugs move to hiding places in the corners within 24 h. They require 3 days to settle down completely in the arena, with generally low activity levels and the absence of responses to human stimuli for 5 days. After 8–9 days, persistent responses can be recorded. Sex differences are observed, in which females are more active during establishment, respond faster after feeding, expose themselves more than males during the daytime, and respond more strongly to the host signal. The number of bed bugs that rest in harbourages is found to vary significantly according to light setting and sex. Both sexes stay inside harbourages more in daylight compared with night, and males hide more than females during the daytime but not during the night. The spatial distribution of the bed bugs is also found to change with the presence of CO₂, and peak aggregation around the odour source is observed after 24 min. Both male and female bed bugs move from hiding places or the border of the arena toward the centre where CO₂ is released. Peak responses are always highest during the night. Bed bug behaviour and behaviour‐regulating features are discussed in the context of control methods.     

Feasibility and limits of an orthotopic human colon cancer model in nude mice

We sought to develop an accurate colorectal cancer model in nude mice with stable local growth, tumor cell dissemination, and reproducible metastatic capacity. To this end, we orthotopically transplanted histologically intact human colorectal cancer tissue from 10 human patients into nude mice. After successful local tumor growth, tumor tissues were retransplanted as many as 9 times in serial passage. All specimens were transplanted using microsurgical techniques. Histologic, immunohistochemical, and polymerase chain reaction techniques were used to determine tumor growth rates and kinetics, development of regional lymph node and distant hepatic metastases, and the induction of minimal residual disease (MRD). Stable local tumor growth rates with variable growth kinetics were detected in 73.4% of all mice. The lymph node and hepatic metastasis rates were low, at 18.4% and 4.9%, respectively. MRD, as reflected by CK20 positivity of the bone marrow in animals with lymph node and hepatic metastases, was present in 22.2%. The orthotopic colorectal cancer model described here is feasible for the induction of reproducible local tumor growth but is limited by variable growth kinetics and the low rate of lymph node and hepatic metastases. Cytokeratin-positive cells indicative of MRD could be detected in the bone marrow of approximately 25% of the nude mice with metastases. The observed induction of MRD after orthotopic implantation of intact human colon cancer in animals with lymph node and hepatic metastases might be improved if established colon cancer cell lines were used.     

First insight into the genome of an uncultivated crenarchaeote from soil

Molecular phylogenetic surveys based on the characterization of 16S rRNA genes have revealed that soil is an environment particularly rich in microbial diversity. A clade of crenarchaeota (archaea) has frequently been detected among many other novel lineages of uncultivated bacteria. In this study we have initiated a genomic approach for the characterization of uncultivated microorganisms from soil. We have developed a procedure based on a two-phase electrophoresis technique that allows the fast and reliable purification of concentrated and clonable, high molecular weight DNA. From this DNA we have constructed complex large-insert genomic libraries. Using archaea-specific 16S rRNA probes we have isolated a 34 kbp fragment from a 900 Mbp fosmid library of soil DNA. The clone contained a complete 16S/23S rRNA operon and 17 genes encoding putative proteins. Phylogenetic analyses of the rRNA genes and of several protein encoding genes (e.g. DNA polymerase, FixAB, glycosyl transferase) confirmed the specific affiliation of the genomic fragment with the non-thermophilic clade of the crenarchaeota. Content and structure of the genomic fragment indicated that the archaea from soil differ significantly from their previously studied uncultivated marine relatives. The protein encoding genes gave the first insights into the physiological potential of these organisms and can serve as a basis for future genomic and functional genomic studies.     

Effect of Free Malonate on the Utilization of Glutamate by Rat Brain Mitochondria

Malonate is an effective inhibitor of succinate dehydrogenase in preparations from brain and other organs. This property was reexamined in isolated rat brain mitochondria during incubation with L-glutamate. The biosynthesis of aspartate was determined by a standard spectrofluorometric method and a radiometric technique. The latter was suitable for aspartate assay after very brief incubations of mitochondria with glutamate. At a concentration of 1 mM or higher, malonate totally inhibited aspartate biosynthesis. At 0.2 mM, the inhibitory effect was still present. It is thus possible that the natural concentration of free malonate in adult rat brain of 192 nmol/g wet weight exerts an effect on citric acid cycle reactions in vivo. The inhibition of glutamate utilization by malonate was readily overcome by the addition of malate which provided oxaloacetate for the transamination of glutamate. The reaction was accompanied by the accumulation of 2-oxoglutarate. The metabolism of glutamate was also blocked by inclusion of arsenite and gamma-vinyl-gamma-aminobutyric acid but again added malate allowed transamination to resume. When arsenite and gamma-vinyl-gamma-aminobutyric acid were present, the role of malonate as an inhibitor of malate entry into the mitochondrial interior could be determined without considering the inhibition of succinate dehydrogenase. The apparent Km and Vmax values for uninhibited malate entry were 0.01 mM and 100 nmol/mg protein/min, respectively. Malonate was a competitive inhibitor of malate transport (Ki = 0.75 mM).     

Probing lymphoma infiltration in spleen of AKR/J mice chronically exposed to electromagnetic fields for risk assessment – toward noninvasive modeling

Using the AKR/J mouse model, the potential of Raman spectroscopy for monitoring lymphoma in predisposed subjects is demonstrated by discriminating lymphoma infiltration in spleens; the relevance of different excitation profiles is shown. Under green excitation with optimal fluorescence bleaching, stronger DNA bands, intensity variations at amide‐III and phenylalanine bands, and the behavior of the 1606/1639 cm^–1 doublet correlate with tumorigenesis. Under red excitation, Raman fingerprints with multivariate models help to discriminate AKR/J‐mouse histological subtypes: Lymphoblastic lymphoma (LB) is found significantly distant from both separated lymphocytic lymphoma (LL) and healthy spleen; this agrees with histology since LB has well differentiated large lymphoma cells, while LL, with smaller cells similar to normal lymphocytes, usually cannot be discriminated from normal tissue without histoimmunoassays. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)