Desert locusts, Schistocerca gregaria (Forskål) (Orthoptera, Acrididae), are generalist herbivores that, in the Sahara desert, may at times feed only on Schouwia purpurea (Forskål) (Brassicaceae), that is 10 times richer in thioglucosides than currently observed in other crucifers (>100 μmoles/g d.w.). Thioglucosides, when ingested, release products that are usually toxic to generalist insects. We studied the short‐term (8 days) and long‐term (21–26 days) consequences of a Schouwia‐only diet on the digestion of these insects. The response was compared to the effects of a diet of Brassica oleracea, a crucifer well consumed in laboratory rearing conditions (7 μmoles/g glucosinolates d.w.). We found that the production of a myrosinase was induced in the midgut as early as 8 days following exposure to glucosinolates. No negative short‐term effects were observed on the growth of the insect, but the activity of β‐glucosidases decreased in the midgut. The long‐term exposure to the Schouwia diet affected activities of β‐glucosidases and β‐galactosidases, growth and assimilation efficiency. The limited adaptation of the desert locust to plant glucosides is compensated by an ability to tolerate high concentrations of allelochemicals for a short period.

The mosquito C. p. pipiens L. never colonize sewerage water covered with duck weed. The Lemna minor vegetations affected the identification of the oviposition site by the females. The amputation of sensilla made the mosquito incapable of choosing the oviposition site. The immature stages of the mosquito are susceptible to the water borne synomones of the duck weed; the first instar larvae are most susceptible and have high mortality. Resume-La moustique C. p. pipiens L. ne colonize jamais dans les eaux d'egouts couvertes par Lemna minor (duck weed). Les eaux salees et leur pH n'ont pas d'effets sur les colonies des moustiques. Seule, la presence des colonizations, et non leur densite, affecte la discrimination des lieux de pondre par les femelles des moustiques, il semble que c'est un effet repugnant. L'amputation des tarses et des antennes fait perdre a la femelle la capacite de trouver les lieux de pondre, ce qui prouve la presence des synomones secretes par L. minor dans I'air et I'eau des marais. II semble aussi que les premieres larves du C. p. pipiens sont plus sensibles, aux synomones de I'eau, ques les dernieres larves.

The glucosinolates of a Saharan crucifer Schouwia purpurea (Forskfil) (Brassicaceae) were determined by liquid chromatography. Two of these glucosinolates and sinigrin were tested for their deterrent effect on Schistocerca gregaria (Forskfil) (Orthoptera: Acrididae). Glucobrassicin, three indolyls and epigoitrin were synthesized for this purpose. Epiprogoitrin was extracted from Crambe seeds. Choice tests on artificial substrate compared feeding responses to glucosinolates and to related breakdown products released when the plant is eaten. Breakdown products were more efficient in deterring the generalist locust than were glucosinolates. Two patterns of dose responses were recorded: glucosidic compounds deterred or stimulated feeding, depending on the concentration tested; aglycones did not stimulate feeding at any concentration. Allyl isothiocyanate, a volatile compound, was a 100-fold higher deterrent than its substrate (sinigrin).

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The effects of diet on quantitative nutritional indices were measured in fifth-instar female nymphs of the grasshopper, Euprepocnemis plorans. Analysis of the main and interactive effects of feeding on the host plants lupine (Lupinus termis), horsebean (Vicia faba) or clover (Trifolium alexandrinum) and some of the plants' allelochemicals indicated that nymph performance was adversely affected by the hydrogen cyanide (HCN) and quinolizidine in horsebean and lupine respectively. Assimilation of clover was higher than of lupine or horsebean. Relative growth rate (RGR) was significantly higher in grasshoppers fed on clover than in those fed on either lupine or horsebean. Relative consumption rate (RCR) was in the order lupine > clover > horsebean. The efficiency of the digested and ingested food conversion were significantly lower in grasshoppers fed on lupine or horsebean than those fed on clover. The duration of the fifth instar was in the order horsebean > lupine > clover. Grasshoppers fed on horsebean or lupine lost weight during the experiment, with a greater weight loss recorded in those fed on horsebean. Grasshoppers contained the highest concentration of haemolymph proteins when fed on clover. Short-term feeding on lupine and horsebean resulted in 10 and 20 % mortality respectively, and nymphs that died on a horsebean diet were malformed.

Background: The milk alkali syndrome has always been suspected when patients present with hypercalcemia, renal impairment and metabolic alkalosis. Nowadays, the occupational exposure to carbonate salts at the workplace is considered an environmental problem that seems to increase the possibility of the appearance of more cases of the syndrome. Objective: investigating the effects of exposure to lime stone dust among working population in the petrochemical industry and determining the importance of interpreting the unexplained abnormal kidney functions in the diagnosis of chronic form of milk alkali syndrome. Methods: Detailed assessment questionnaire and thorough clinical examination were used to study the health condition of 24 workers exposed to sodium and calcium carbonate during the processing of limestone and of 21 matched non-exposed workers. The cardiovascular changes were further evaluated using the electrocardiogram. The blood gases as well as sodium, potassium and chloride were estimated by the automated analyzer. Laboratory tests investigated the serum levels of ionized calcium and phosphorus calorimetrically and the 1,25-dihydroxyvitamin D (1,25-(OH) 2-D) 63 Gaballah I.F., et al., 64 by chromatography. As for the intact parathyroid hormone (PTH) and parathormone hormone related peptides (PTH-rP) in serum, estimation was carried out using the two-site immunoassay technique. Results: Urinary frequency was detected among exposed workers as sign of isotonic polyuria caused by increased stimulation of calcium-sensitive receptors in the collecting tubules. Elevation of ionized calcium levels (mean values 8.32 ± 0.72 mg/ dl) among exposed workers resulted in lowered glomerular filtration rate as evidenced by azotemia. A positive linear association was detected between urea and the ionized levels of calcium. At the renal tubules, hypercalcemia induced bicarbonate absorption that led to metabolic alkalosis as evidenced by elevation in blood pH (7.46 ± 0.03) and bicarbonate equivalent above 28 mEq/L, and by the positive correlation of calcium and PTH with blood gas parameters. The resulting decreased kidney activity appeared to be a major factor in derangement of the vitamin D metabolism and lowering of phosphorus levels. Deficiency of vitamin D stimulated the release of parathyroid hormone highly significantly to maintain calcium level via decreasing urinary excretion and increasing renal calcium re-absorption. PTH and calcium, which were positively associated together highly significantly, both showed negative correlations with the 1,25-(OH) 2-D level. The PTH-rP was significantly low among exposed workers excluding the possibility of any active role in the development of hypercalcemia. Age and smoking were not considered confounding factors in the study compared to the exposure duration which was significantly playing a positive role in the development of alkalemia and hypercalcemia. Conclusion: The obtained data suggested the presence of a relationship between the exposure to limestone and renal affection. ...