Effect of particle size on the anthelmintic efficacy of mebendazole against Nippostrongylus brasiliensis in the rat.

The effect of reduction in particle size on the anthelmintic efficacy of mebendazole (methyl 5 (6)- benzoyle 1–2 benzimidazole carbamate) was studied in rats undergoing a primary infection with N. brasiliensis. A single oral treatment with fine ground mebendazole (particle size spectrum—54·95 per cent of particles less than 10·62 μ dia.; 86·06 per cent less than 21·27 μ) removed more than 98 per cent of adult worms from the intestine at a dose rate of 12·5 mg/kg body wt. On the other hand the best result achieved with coarse ground mebendazole (18·47 per cent of particles less than 10·62 μ dia; 42·26 per cent less than 21·27 μ dia) was 58 per cent of adult worms removed at a dose rate of 100 mg/kg body wt. It was also shown that fine ground mebendazole adversely affected migrating third stage larvae of N. brasiliensis.     

Water exchange and effect of water vapour activity on metabolic rate in the dust mite, Dermatophagoides.

Oxygen consumption by Dermatophagoides farinae was found to vary with temperature and water vapour activity. The relationship between temperature and O₂ consumed/hr per mite was first order. Q₁₀'s were equal to exp (k 10°C) and were found to be 3·04 and 2·49 for 1 to 6 and 6 to 22 hr monitoring periods respectively. A significant difference between O₂ consumed/hr per mite for 1 to 6 and 6 to 22 hr monitoring periods was found. Inactivity of mites explained 29·6 and 31·8 per cent of this reduction. Dehydrating conditions and reduced permeability of the water and gas exchange surface explained a further reduction to 58·7 and 60·8 per cent.     

Rôle of labelled dietary fatty acids and acetate in phospholipids during the metamorphosis of Pieris brassicae

The incorporation of labelled dietary palmitic, linoleic, and linolenic acids into neutral (NL) and phospholipids (PL) during the metamorphosis of Pieris brassicae was studied, and the ability of the fat body to incorporate acetate into PL determined. Thirty-three per cent of total lipid in early fifth instar larvae (minus haemolymph) is PL, while the corresponding value in female 4-day pupae is 13·0 per cent and in the fat body of 4-day pupae 6·3 per cent. Incorporation of label into PL was studied more closely and in all cases the label was recovered from phosphatidylcholine (PTC) and phosphatidylethanolamine (PTE). The label from palmitate was also found in sphingomyelin and possibly phosphatidylserine. Specific activity of PL in the case of palmitic and linolenic acids was greatest in late fifth instar larvae. In early fifth instar larvae on palmitic acid-1-¹⁴C 39·0 per cent of label was in PTC, 52·8 per cent in PTE, and 2·0 per cent in sphingomyelin. In late fifth instar 45·0 per cent was in PTC, 45·5 per cent in PTE, and 6·5 per cent in sphingomyelin, while in 4-day female pupae 45·2 per cent was in PTC, 41·3 per cent in PTE, and 13·5 per cent in sphingomyelin. The label from linolenic acid only varied a little from early fifth instar to 4-day pupae, 51·8 per cent being in PTC and 48·2 per cent in PTE in early fifth instar larvae. The label from linoleic acid is incorporated in fat body PL almost exclusively in PTC and PTE, 55·8 and 43·2 per cent respectively in 4-day female pupae. Injected acetate is distributed after 1 hr between PTC (58·6 per cent), PTE (24·4 per cent), and sphingomyelin (17·0 per cent). It was concluded that the polyunsaturated acids are proportionately more common in PTE than in other PL types, and that the fatty acids of sphingomyelin are mainly those that the insect is capable of synthesizing from acetate. Palmitic acid is desaturated by Pieris to palmitoleic acid and the latter possibly utilized in PTE to compensate for a deficiency of linolenic acid in the artificial diet. No saturation of linoleic or linolenic acid was found. The rates of PL and NL synthesis during development and the rôle of the investigated fatty acids in the biosynthesis of PL are discussed.     

Dynamics of the pregnancy cycle in the tsetse Glossina morsitans

A normal pregnancy in tsetse involves the successful integration of larval development with maternal activity. At 25°C, ovulation in Glossina morsitans occurs 1 hr after the previous larviposition, the egg hatches on day 3·8 (1·57 mm length, 0·09 mg dry wt.), ecdysis to second instar occurs on day 4·9 (2·3 mm, 0·30 mg), the third instar cuticle is formed on day 6·8 (4·5 mm, 5·0 mg), and parturition occurs on day 9·0 (6·0 mm, 10·0 mg). Melanization of the in utero third instar follows a regular sequence over a 2 day period. Parturition follows a circadian pattern with a peak 9 hr after lights on (12 hr daily photophase). All instars receive nutriment from the female's milk gland. During early pregnancy the rate of milk synthesis is greater than rate of uptake by the larva, thus causing expansion of the secretory reservoirs. After day 6, the volume of the secretory reservoirs decreases, but as is indicated by nuclear volume and larval growth the rate of synthesis remains high until day 8. Feeding activity of the adult female is maximal on day 1, levels off at 60 per cent up to day 6, and then declines sharply towards the end of pregnancy. Oöcyte development proceeds in phase with larval development and thus minimizes a lag period between successive pregnancies.     

‘Hunger’ in the tsetse fly: The nutritional correlates of behaviour

The spontaneous activity and visual responsiveness of starved tsetse flies, Glossina morsitans, increase exponentially for about 5 days after feeding until a pre-moribund decline sets in. Evidently the depletion of food reserves affects the behaviour of the fly. The causal relationship in this interaction was sought in two ways: (a) by looking for changes in nutritional parameters that follow the same trend and time course as the behavioural change, (b) by calculating the correlations between behaviour and these various parameters from concurrent data on individual flies. None of the three factors traditionally measured in tsetse (per cent hydration, lipid content, and residual blood meal) changed along a course similar to that followed by behaviour, nor did any expression of them correlate as well with behaviour (r = 0·75, 0·74, and 0·71, respectively) as did the duration of starvation alone (r = 0·79). On the other hand, abdominal weight and total body weight both changed in parallel with behaviour and correlated substantially better with it than did starvation time (r = 0·85 and 0·89, respectively); they also correlated very strongly with each other (r = 0·98). It is suggested that the mean levels of the fly's behavioural thresholds are modulated on the basis of information about its overall nutritional state derived from monitoring its weight or abdominal volume, or perhaps some third variable with which these two are closely correlated.     

A chemical modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolyethylene glycol)-4,6-dichloro-s-triazine (activated PEG1)

The modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolethylene glycol)-4, 6-dichloro-s-triazine, an activated polyethylene glycol (PEG₁), was investigated. The modification caused a shift of the Soret band in the light absorption spectrum, from 430 nm to 418 nm in the case of myeloperoxidase (native ferric form), and from 412 nm to 406 nm in the case of lactoperoxidase (native ferric form). PEG₁-modified myeloperoxidase and PEG₁-modified lactoperoxidase both failed to bind with antiserum to the respective native enzyme, but both retained respectively 4·5±0·3 per cent (mean±SE, n=5) and 0·6±0·2 per cent (mean±SE, n=5) of the activities of peroxidation of the hydrogen donor o-methoxyphenol in comparison with the native enzyme, and 1·5±0·2 per cent (mean±SE, n=5) and 1·2±0·2 per cent (mean±SE, n=5) of the activities of destruction of fuchsin basic in the presence of hydrogen peroxide and a halide, bromide. The pH dependencies of the peroxidating activities were almost the same as those of the corresponding native enzymes, but both the optimal pHs of the reactions involving the destruction of fuchsin basic were shifted by approximately 1·0 pH unit toward neutral pH compared with the respective native enzymes. © 1998 John Wiley & Sons, Ltd.     

RNA synthesis in imaginal disks of Galleria mellonella: Effects of alpha- and beta-ecdysone and fat body in vitro

The effects of alpha-ecdysone (α-E), beta-ecdysone (β-E), and larval fat body on morphogenesis and total RNA synthesis in wing imaginal disks of Galleria mellonella were studied. Both ecdysones induce morphogenesis of disks in vitro. Alpha-ecdysone and β-E (0·3–3·0 μg/ml) stimulate RNA synthesis 30 and 60 per cent above control levels, respectively. While less α-E (0·3 μg/ml) is required to increase RNA synthesis than to induce morphogenesis, the reverse is true for β-E. Morphogenesis (i.e. tracheole migration and evagination) can proceed in the presence of concentrations of β-E (0·03 μg/ml) that are subthreshold for the induction of RNA synthesis (0·3 μg/ml). We conclude, therefore, that the increase in total RNA (presumbly ribosomal) is unrelated to and not a prerequisite for tracheole migration or evagination. If morphogenically active preconditioned medium (i.e. medium in which α-E and fat body have been incubated for 48 hr and the fat body then removed) is added to disk cultures, RNA synthesis is not stimulated. Apparently, increases in total RNA caused by both ecdysones may not be necessary for early in vitro disk development. The independent nature of some ecdysone-induced events and implications of our conclusions are discussed.     

Alpha-glycerophosphate dehydrogenase in Drosophila melanogaster: kinetic differences and developmental differentiation of the larval and adult isozymes

The isozymes of α-glycerophosphate dehydrogenase (α-GPDH) differ markedly with respect to their kinetic and stability parameters. Adult-limited GPDH-1 is stable at 50°C but decays at 57°C, while GPDH-3 is labile at 50°C under similar experimental conditions. By extrapolation of the thermal denaturation curves of crude adult extracts, we estimate GPDH-1 to constitute 76 per cent of the adult α-GPDH activity. Substrate kinetic studies revealed that, at pH 9·5, GPDH-3 exhibits an affinity for α-glycerophosphate which is twofold higher than that of GPDH-1, while K_m's for NAD⁺ are indistinguishable. The apparent K_m of GPDH-3 for dihydroxyacetone phosphate is consistently lower than that of GPDH-1 at pH 7·5, whereas at pH 6·7 the latter isozyme's apparent K_m approximates that of GPDH-3 at pH 7·5. Indistinguishable molecular weights of 66,000 were estimated by gel filtration for both GPDH-1 and 3. Gene dosage studies indicate that all three α-GPDH isozymes are simultaneously affected by dosage of the Gdh⁺ locus. These observations support a homomultimeric model of α-GPDH and the isozymes just discussed arise through epigenetic modification of the product of a single structural gene locus.     

Utilization of fatty acids by Pieris brassicae reared on artificial and natural diets

The fatty acid composition of Pieris brassicae was measured from larvae reared on four different diets. Pieris can alter the composition of fatty acids in the diet through selective incorporation and synthesis. Oleate is preferentially accumulated on artificial diets (15·9 per cent in diet, 43·8 per cent in neutral lipid (NL) of fifth instar larvae), but not equally on natural diets (18·1 per cent in Brassica napus, 25·6 per cent in the NL of fifth instar larvae). Incorporation of linolenate appears to depend on the concentration of both linolenate and linoleate in the diet. With dietary levels of 35·7% linolenate and 32·2% linoleate, fifth instar larvae contain 12·2 and 16·0 per cent, respectively, of these acids. With 45·8% linolenate and 12·5% linoleate in the diet, fifth instar larvae contain 44·1 and 11·6 per cent of these acids, respectively, in the NL. Palmitoleate is actively synthetized on the artificial diets; with trace amounts of dietary palmitoleate, fifth instar larvae have 9·3 per cent of this acid in the NL. Pieris regulates the uptake of linoleate from the diet at the intestinal wall as was shown by linoleic acid-1-¹⁴C, and is unable to convert dietary linoleate to any of the 18-carbon analogues. The female apparently accumulates linolenate into egg phospholipids on the artificial diet, but in general the fatty acid composition of the eggs resembles that of the fat body.     

Cultural ecology and the genetical structure of Nicobar island populations

The population of Nicobar is not a single random mating population but divided into a number of subpopulations within each of which essentially random mating takes place. Heterogeneity tests indicate that there is a significant difference among subpopulations for the ABO blood group system but not for the MN system. The overall gene frequencies of the ABO system were: r = 0·914; p = 0·033; q = 0·053. The gene frequencies of the MN system are much more consistent in the area as a whole than in the ABO system. The gene frequencies of the MN system were: M = 0·92 and N = 0·08. The Wahlund's principle yields the value of Ø = 0·0358 for the MN system and the unweighted mean value of Øs equals 0·0301 for the ABO system. The founder effect may have a far greater effect than the effects of chance in the genetical structure of Nicobar subpopulations.     

Double-helical structures for polyxanthylic acid

Polyxanthylic acid has been found to exist in two different duplex forms, A_I and A_II. a_I, formed at pH5·7, occurs in a compact lattice with nearest neighbor molecules spaced at 2.11 nm. It has an axial translation per residue, h = 0·301 nm, and a rotation per residue, t = 36·0 °. The intensity distribution in its X-ray fiber diffraction pattern is analogous to that of A-RNA (h = 0·281 nm, t = 32·7 °). On the other hand A_II, formed at pH 8·0, has a less compact, statistically disordered crystal packing with nearest neighbors 2·35 nm apart. It has h = 0·252 nm and t = 32·7 ° and gives an X-ray intensity distribution essentially identical to A-DNA (h = 0·256 nm, t = 32·7 °). Similar right-handed helical duplex models, with flexible C-3′-endo sugar rings, have been developed for each molecular structure. Both have purine purine base-pairs, possibly triply hydrogen-bonded, and certainly with the same symmetry as Watson-Crick pairs but with a 0·2 nm greater C-1′ … C-1′ separation.     

Dietary cholesterol requirements of housefly, Musca domestica, larvae.

Quantitative analyses have been made of the dietary cholesterol requirement for the growth of the larvae of Musca domestica. The larvae will not grow on diets to which no cholesterol is added, a few pupae and adults are obtained when the concentration of cholesterol is 0·05 μmol/g of diet, but the concentration has to be raised to 0·36 μmol/g of diet before the maximum numbers of pupae and adults are obtained. Further addition of cholesterol above 0·36 μmol/g diet did not have any significant effect on the weight and growth of the larvae. However, the ratios of the cholesterol to phospholipid fractions recovered from the larvae increased rapidly when the concentration of cholesterol in the diet was raised from 0·05 to 0·56 μmol/g of diet. Above this concentration only a slight increase in the ratios was observed. Larvae reared on diets containing 0·05 μmol cholesterol/g of diet contain only 25 per cent of the cholesterol content of the larvae reared on the diets containing more than 0·28 μmol of cholesterol/g of diet, the cholesterol content being expressed relative to the weight of the larvae,The absence of cholesterol synthesis has been demonstrated in the larvae by feeding [4-¹⁴C] cholesterol. The specific activity of the cholesterol recovered from the larvae is the same as that of cholesterol added to the diet. Irrespective of the cholesterol concentration of the larval diet, approximately 97 per cent of the radioactivity recovered from the larvae behaved as free cholesterol, less than 1 per cent as cholesterol esters and the rest as unidentified ‘polar sterols’. The results are compared with those from similar studies on other insects.     

Observational and experimental studies on the acquisition of Anisakis sp. larvae (nematoda: Ascaridida) by trout in fresh water

In the enclosed fresh-water environmsnt of Hanningfield Reservoir, Essex, England, Anisakis sp. larvae (parasites of marine fish) were found in 55 per cent of 40 brown trout and in 26·2 per cent of 61 rainbow trout. Experimental infection by intubating larvae into the stomach was more successful in brown trout (50·6 per cent recovery rate) than in rainbow trout (27 per cent recovery rate). Some larvae reached the body-cavity as early as 2 h after infection. They penetrated the region between the oesophagus and intestine immediately posterior to the caecal openings. Fewer larvae successfully penetrated the gut wall of brown trout within 24 h at 8°C than at 15 ± 1°C. It appears that the reservoir trout acquired Anisakis by being fed as juveniles on untreated marine fish offal containing live larvae.     

Size and number of nerve fibres in the central nervous system connectives of the cockroach Blaberus craniifer

The size and number of axons in the ventral cord connectives of the cockroach Blaberus craniifer were determined from montages constructed of electron micrographs of the left connective of each of the connective pairs examined. The fibres were grouped into three main diameter categories: fine fibres from 0·2 to 1 μm, small fibres from 1 to 6 μm, and large fibres from 6 to 24 μm. In the five different left connectives examined, the fine fibres numbered from 2006 to 8535 and composed from 56·5 to 83 per cent of the total fibres. The small fibres numbered from 1269 to 2361 and composed from 16·5 to 41 per cent of the total fibre number. The large axons ranged between 29 and 220 in number which represented from 0·5 to 2·5 per cent of the fibre population.     

Energy metabolism of reticulocytes: Two different sources of energy for Na+K+-ATPase activity

Total energy production in rabbit reticulocytes amounted to 136·52 ± 6·50μmol ATP h^?1ml^?1 of reticulocytes: 88·3 per cent was provided by oxidative phosphorylation, whereas only 11·7 per cent by aerobic glycolysis. Na⁺K⁺-ATPase accounted for 23 per cent, i.e. 27·65 ± 2·55μmol ATP h^?1ml^?1 of reticulocytes, in the overall energy consumption in reticulocytes of rabbits. Under basal conditions ATP for Na⁺K⁺-ATPase activity was derived exclusively from oxidative phosphorylation. However, when the activity of Na⁺K⁺-ATPase was increased due to the stimulation of adenylate cyclase by (?)-isoprenaline, the additional energy required was provided by aerobic glycolysis. These results indicate that two different compartments, one cytosolic and the other mitochondrial, provide energy for Na⁺K⁺-ATPase activity in reticulocytes.     

Differential net food utilization by larvae of Sitophilus oryzae and Sitophilus granarius

The net utilization of a meridic diet by Sitophilus oryzae from the newly hatched larva to the pupa was more efficient compared with that of S. granarius. The artificial diet was highly digestible to both species, but S. oryzae converted 24·1 per cent of the ingested food into body substance compared with 12·4 per cent converted by S. granarius. The mean pupal weight of S. granarius (1·402 mg) was greater than that of S. oryzae (1·012 mg); however, larvae of S. granarius consumed 2·6 times as much food and excreted 8·1 times as much faecal material to obtain that weight. Even though S. granarius consumed the diet at a greater rate, the relative growth rate of S. oryzae was faster. The intracellular symbiotes present in S. oryzae may have a rôle in the species' faster development and more efficient utilization of its food.     

Sex pheromone of the cabbage looper: Reactions with antennal proteins in vitro

In the presence of (Z)-7-dodecen-1-ol acetate, the sex attractant of the cabbage looper, Trichoplusia ni, soluble protein from male antennae showed a time-dependent difference spectral absorbance at 280 nm. The change was associated with the enzymatic conversion of the pheromone to (Z)-7-dodecen-1-ol, a potent inhibitor of behavioural responses to the pheromone. In contrast, the response obtained with the inhibitor was indicative of non-enzymatic binding to specific protein(s) in the fraction. GLC analyses of the relative rates of enzymatic hydrolysis of the pheromone by the antennae, haemolymph, and legs revealed 33·9, 10·1, and 6·5 per cent conversion per hour, respectively. These results may provide an insight into the fate of a pheromone in the olfactory process of this insect; however, the significance of the reaction with the inhibitor is not yet known.     

The viability and survival of sporozoites of Eimeria in vitro

Some factors affecting excystation and viability of sporozoites of several species of Eimeria from chickens were examined in vitro. Chicken embryos or cultured kidney cells were inoculated with sporozoites in order to assess viability.Sporozoites of E. tenella survived in phosphate buffer (P.B.S.) containing 0·9 per cent NaCl for 14 days. Some sporozoites survived in solutions containing up to 16 per cent NaCl for 3 days at +4°C. Sporozoites of E. maxima and E. acervulina survived for only 27 h in phosphate buffer containing 1 or 2 per cent NaCl.Sporozoites of E. brunetti, E. maxima, and E. acervulina var: mivati were released rapidly from sporocysts in vitro, but survived for relatively short periods in PBS at 4°C. However, the addition of serum or gelatine to these solutions increased survival to at least 96 h.The viability of sporozoites after freezing and storing in liquid nitrogen was best when 12 per cent dimethyl sulphoxide (DMSO) was added to the sporozoite suspensions. P.B.S. with DMSO was less suitable than the other solutions used and serum or gelatine with the DMSO, was needed to increase survival. Increasing the density of sporozoites in the frozen stabilates did not increase survival.     

Uric acid synthesis by rat liver supernatants from purine bases,nucleosides and nucleotides. Effect of allopurinol

The synthesis of uric acid from purine bases, nucleosides and nucleotides has been measured in reaction mixtures containing rat liver supernatant and each one of the following compounds at 1 mM concentration (except xanthine, 0·5 mM and guanosine and guanine, 0·1 mM). The rates of the reaction, expressed as nanomoles of uric acid synthesized g^?1 of wet liver min^?1 were: ATP, 10; ADP, 37; AMP, 62; adenosine, 108; adenine 6; adenylo-succinate, 9; IMP 32; inosine, 112; hypoxanthine, 50; GTP, 19; GDP, 19; GMP, 27; guanosine, 34; guanine, 72; XMP, 10; xanthosine, 24; xanthine, 144. These figures divided by 55 correspond to nanomoles of uric acid synthesized min^?1 per mg^?1 of protein. The rate of synthesis of uric acid obtained with each one of those compounds at 0·1 and 0·05 mM concentrations was also determined. ATP (1 nM) strongly inhibited uric acid synthesis from 0·05 mM AMP (91 per cent) and from 0·05 mM ADP (88 per cent), but not from adenosine. CTP or UTP (1 mM ) also inhibited (by more than 90 per cent) the synthesis of uric acid from 0·05 mM AMP. Xanthine oxidase was inhibited by concentrations of hypoxanthine higher than 0·012 mM. The results favour the view that the level of uric acid in plasma may be an index of the energetic state of the organism. Allopurinol, besides inhibiting uric acid synthesis, reduced the rate of degradation of AMP. The ability of crude extracts to catabolize purine nucleotides to uric acid is an important factor to be considered when some enzymes related to purine nucleotide metabolism, particularly CTP synthase, are measured in crude liver extracts.