Rachel Galun

Permethrin resistance in the head louse Pediculus capitis from Israel

Head lice, Pediculus capitis, were collected from children aged 3–12 years in Maale Adumin, a town near Jerusalem, after reports of control failure with the pyrethroid insecticide permethrin. A total of 1516 children were examined: living lice and eggs were found on 12.1% of the children; or another 22.8% of the children only nits were found. Twice as many girls as boys (8.1% v 4%) were infested with lice and or nits. Head lice collected from infested children were exposed to permethrin impregnated filter‐papers. Log time probit mortality (ltp) regression lines were calculated for mortality data and compared to ltp lines for a similar collection of head lice made in 1989. The regression lines for the two years were significantly different, with a 4‐fold decrease in susceptibility at the LT50 level between 1989 and 1994. The slopes of the lines also suggested that the 1994 population was more heterogenous in its response to permethrin than the 1989 population. In contrast, a laboratory population of body lice (Pediculus humanus) tested with the same batch of permethrin‐impregnated papers showed a slight but non‐significant increase in susceptibility between 1989 and 1994. The results suggest that resistance to pyrethroids has developed rapidly among head lice since permethrin was introduced in 1991 as a pediculicide in Israel.

Antibacterial substances of low molecular weight isolated from the blowfly, Lucilia sericata.

Abstract Low molecular weight compounds were isolated by high‐performance liquid chromatography from the maggot or haemolymph extracts of Lucilia sericata (Meigen) (Diptera: Calliphoridae). Using gas chromatography‐mass spectrometry analysis, three compounds were obtained: p‐hydroxybenzoic acid (molecular weight 138 Da), p‐hydroxyphenylacetic acid (molecular weight 152 Da) and octahydro‐dipyrrolo[1,2‐a;1′,2′‐d] pyrazine‐5,10‐dione (molecular weight 194 Da), also known as the cyclic dimer of proline (or proline diketopiperazine or cyclo[Pro,Pro]). All three molecules revealed antibacterial activity when tested against Micrococcus luteus and/or Pseudomonas aeruginosa, and the effect was even more pronounced when these molecules were tested in combination and caused lysis of these bacteria.

The saliva of the medicinal leech Hirudo medicinalis—1. Biochemical characterization of the high molecular weight fraction

1. A method is described for obtaining dilute Hirudo medicinalis saliva by feeding leeches through a membrane on arginine/saline and squeezing them immediately after from the posterior end forwards. The process can be repeated at intervals. Yields are considerably higher than from salivary gland extracts. 2. Hirudo saliva contains hirudin, eglin, hyaluronidase, collagenase and apyrase. Leech collagenase and apyrase are here reported for the first time. 3. On gel filtration of lyophilized saliva, activity peaks were well defined. Approximate molecular weights were determined. Apyrase appears in two forms with optimum activity around pH 7.5. Collagenase was identified as belonging to the mammalian type.

Repellency of essential oils and their components to the human body louse, Pediculus humanus humanus

Five essential oils and nine of their components were compared to diethyl toluamide (DEET) for their repellent activity against the human body louse, Pediculus humanus humanus. The absolute or intrinsic repellency of the compounds was tested by applying the repellent to corduroy patches and comparing them with untreated patches. It was found that the most effective repellents were DEET and citronella, whose activity lasted at least 29 days. The activity of rosemary lasted at least 18 days and that of eucalyptus more than 8 days. The repellent activity of the oil components such as citronellal and geraniol lasted more than 15 and 8 days, respectively. DEET remained effective at a dilution of 1:32, geraniol at 1:8, citronella at 1:4 and rosemary and citronellal at 1:1. The comparative or standard repellency of the candidate repellents was examined with the aid of a new screening technique using hairs treated with ammonium bicarbonate which is attractive to lice. Using this technique it could be shown that the repellent activity of citronella and geraniol lasted 2 days and that of rosemary and citronellal for only one day. DEET was active for less than one day. Serial dilutions of these substances also revealed that citronella was the most potent repellent for lice, followed by citronellal, rosemary, geraniol and DEET. The differences however, were not significant.

The role of ammonia in the attraction of females of the Mediterranean fruit fly to protein hydrolysate baits

Attraction of female Mediterranean fruitfly (medfly) to ammonia and to protein baits was studied with an olfactometer. Ammonia bait (1 cc/trap) proved to be an effective lure. The maximum number of females was caught in traps loaded with 0.01 M ammonia solution with a release rate of 5.28 μg/cc/h.

Chemical basis of feeding in the tick Ornithodoros tholozani

Abstract Investigation of the factors which can induce feeding of Ornithodoros tholozani has shown that this tick imbibes saline containing reduced glutathione and glucose almost as readily as whole blood. The effect of these two compounds was synergistic when tested at concentrations found in blood. Glucose could not be replaced by fructose, galactose, arabinose, or sucrose. After prolonged starvation marked feeding response could be also elicited by isotonic saline containing glucose and one of the following amino acids: l -leucine, l -allo-isoleucine, l -proline, l -valine, l -serine, l -alanine, l -phenylalanine, and l -glutamine. Solutions containing ATP or DPNH in place of glutathione also induced maximal feeding response. l -Glutamate and the SH reagent DTNB inhibited feeding in presence of GSH, ATP, or DPNH. Addition of Mn2+ or one of the heavy metals Cd2+, Zn2+, and Ni2+ prevented feeding on all solutions. It is believed that feeding is mediated by at least two kinds of chemoreceptors; one specific for GSH, ATP, or DPNH, the other for amino acids. The identification of several compounds which, in certain combinations, induce feeding in O. tholozani can account completely for the taste-response to blood in chemical terms.

Glutathione as an inducer of feeding in ticks.

Ticks engorged solutions containing reduced glutathione as readily as blood, provided that the tonicity of the solutions was adjusted to that of plasma. Among substances tested this effect was specific for the tripeptide. Glutamic acid inhibited the feeding response.

Responses of freshwater prawn,Macrobrachium rosenbergii, to chemical attractants

Chemoreception in the adults of the freshwater prawnMacrobrachium rosenbergii was investigated under controlled laboratory conditions, using behavioral assays. Tests were carried out on groups, as well as on individuals, all at their intermolt stages of the molt cycle, and prestarved for three to four days. Of 28 different substances tested, the amino acids taurine, glycine, arginine, and betaine, as well as trimethylamine, elicited a positive behavioral response in at least 50% of the test animals when applied at a threshold concentration of 10−5-10−8 M. A positive response comprises enhanced antennular flicking and food search motion. Of the various nucleotides tested for chemoattraction, only adenosine monophosphate elicited a response similar to that of the above amino acids, although at a concentration of 10−4 M, whereas adenosine diphosphate required a dosage of 10−1 M.

Chemical specificity of the feeding response in Hirudo medicinalis (L.).

Abstract 1. 1. The specificity of substances which cause sucking response of H. medicinalis was examined by means of feeding through an artificial membrane. 2. 2. Blood could be substituted to a considerable extent by a solution of glucose in 0·15 NaCl. 3. 3. The following sugars: D -galactose, L -sorbose, L -arabinose and DL -glyceraldehyde showed similar activity to that of glucose while a large number of other mono- and di-saccharides had no effect. 4. 4. Sodium chloride could be replaced by sodium bromide, but not by sodium nitrate or lithium chloride. 5. 5. Potassium chloride abolished the sucking response when added before or during the feeding. 6. 6. Iodoacetate, potassium fluoride and ouabain were not inhibitory although causing eventual death of the leeches.

The presence of insulin in and some effects of exogenous insulin on hymenoptera tissues and body fluids

Abstract o 1. Radioimmunoassay technique has revealed the presence of insulin in the tissues of various Hymenopteran insects, including the honeybee Apis mellifera , the Oriental hornet Vespa orientalis and several other Paleoarctic social wasps, the Mason bee Chalicodoma sicula , the cuckoo wasp Chrysis sp. and the weaver ant Polyrachis simplex . 2. Laboratory determinations carried out in vivo and in vitro on several insects have shown that bovine insulin injected into insect hemolymph or incubated together with the hemolymph causes a significant drop in the glucose level of the fluid.