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PubMed1963

CHEMICAL AND BIOLOGICAL BEHAVIOUR OF FENTHION RESIDUES.

Previous experiments at the University of California Citrus Research Center and Agricultural Experiment Station indicated that compounds incorporating the methylthiophenyl group-such as the insecticide fenthion-were highly susceptible to oxidation. Since the stability of fenthion and the properties of its degradation products have an important bearing not only on the efficacy of the insecticide but also on its toxicity to mammals under operating conditions, studies on the chemical and biological behaviour of fenthion and its residues have recently been carried out at the Center.The activity of fenthion against susceptible and resistant houseflies and mosquitos was compared with that of its principal oxidation products. Most of these products were similar to fenthion in their activity against houseflies, but appeared to be much less water-stable since they were considerably less effective against mosquito larvae. Stability tests showed that, in the presence of sunlight and air, fenthion was completely transformed into its sulfoxide and sulfone oxidation products within one to three days, and that these products were rapidly decomposed to non-insecticidal compounds. Upon heating, fenthion was rapidly isomerized to the S-methyl isomer.

Animals↗
PubMed1991

[Which structures in anti-vector control?].

The lack of efficient tools is often incriminated to explain the absence of anti-vectorial activities in control programmes of vector borne diseases. However, we must recognize that the available tools are under utilized due to the lack of appropriate structures. Existing structures are reviewed. So far, results achieved by the Primary Health Care System (PHCS) are scarce. In fact, even simple methods need specific know-how for execution and specialised knowledge for planning and supervision, which differ from those needed for medical care committed to the PHCS. To develop the use of simple methods, adequate structures have to be elaborated, maintaining a peripheral character but in direct connection with a central level, which provides expertise, supervision of the activities and evaluation of the results. The association of research and operational programmes is essential to face problems linked with epidemiological, environmental, socio-economical modifications or changes in sensitivity to insecticides and for the integration of new techniques. It is also this tandem "research-control operations" which will provide the best environment for training.

Animals↗
PubMed1990

A WHO global programme for monitoring vector resistance to pesticides.

This paper describes the programme for monitoring vector resistance to pesticides and how it was established. It presents a summary of the computer baseline data and the cumulative number of vector species developing resistance at intervals of 5 years, starting in 1956, as well as information derived from Expert Committee reports dating back to 1947. The problems and concerns of the programme and envisaged solutions are also discussed.

Animals↗
PubMed1969

The impact of insecticide-resistance on control of vectors and vector-borne diseases.

A questionnaire inquiring into the nature of schemes for the insecticidal control of disease vectors, the development of resistance in these vectors, and the effect of any such resistance on their control and on the extent of disease was sent to more than 100 health authorities throughout the world. The replies to the questionnaire are summarized in this paper.Until recently, the use of insecticides in public health has been largely based on three organochlorine compounds-DDT, HCH and dieldrin. However, in some countries resistance to these has now severely affected control both of many insect species and of the diseases they transmit (e.g., malaria, yellow fever, filariasis, typhus, plague). Certain other public health problems (onchocerciasis, Chagas' disease, trypanosomiasis, leishmaniasis) have not so far been greatly affected by resistance, but it is difficult to be sure of the continued reliability of the organochlorines.Research in the past 5 years, much of it sponsored by WHO, has shown the value of various organophosphorus and carbamate insecticides as replacements for the organochlorines, although resistance to them, too, can occur. Attention must therefore be focused on all facets of the use of these newer compounds and particular scrutiny made of possible instances of resistance to them.

Insect Control↗
PubMedDate not supplied

[Prevention and control of malaria in pregnant women in an urban setting (Yaoundé, Cameroun)].

The aim of this study was to evaluate the methods of preventing malaria (chemoprophylaxis, vector control) and of fever management (presumptive treatment of malaria) used for pregnant women in Yaounde, Cameroon and to identify the most important factors for assessing these practices. The 221 women studied were selected by cluster sampling. All had made extensive use of health services during pregnancy and 77% were using chemoprophylaxis. The number of febrile episodes in pregnant women who claimed to have used chemoprophylaxis was not significantly different to that in the women who did not use it. However, the mean birth weight of the babies of women who had used chemoprophylaxis was significantly higher. The women did not systematically use vector control measures; 21% used insect repellents (electric plaques, coil burners) and 20% used aerosol insecticides. Only 10% of the women slept under simple, untreated mosquito nets and none used mosquito nets impregnated with insecticide. Fifty per cent of the women had at least one episode of fever during pregnancy and 77% were treated for presumed malaria. However, the treatment was not standardized and was unsuitable in a third of cases. Possible changes in the chemoprophylaxis strategy are discussed.

Adult↗
PubMed2000

Biological control of an insect pest by gut-colonizing Enterobacter cloacae transformed with ice nucleation gene.

The ice nucleation (IN) gene inaA of epiphytic Erwinia (Pantoea) ananas IN10 was transformed into Enterobacter cloacae WBMH-3-CMr originated from the faeces of silkworms. The transformant designated as Ent. cloacae WBMH-3-CMr(pICE6S13) exhibited IN activity, unlike the parent strain. The transgenic strain was ingested by mulberry pyralid larvae, fed on detached mulberry leaves, and the supercooling capacity and cold hardiness of these larvae were examined. The mean supercooling point (SCP) of the larvae ingesting the transgenic strain was - 3.3 degrees C, 8 degrees C higher than that of larvae treated with distilled water (control) and 1.5 C higher than an ice nucleation active (INA) strain of Erw. ananas. The SCPs of the larvae were stably maintained over the 9 d after ingestion. The maintenance of these high SCPs was due to transgenic Ent. cloacae having a more stable and efficient gut colonization than Erw. ananas, which is identified by the distribution of a narrower range of SCPs (-2 to -5 degrees C) in larvae treated with the transgenic stain. Furthermore, most of the larvae ingesting the transgenic strain froze and died when they were exposed to cold conditions of -5 degrees C for 18 h, 3 or 7 d after ingestion. In contrast, most of the larvae ingesting no bacterium did not die under similar conditions. On the other hand, the growth ability of Ent. cloacae WBMH-3-CMr on mulberry leaves tended to be lower than that of epiphytic Erw. ananas, as assayed by pot tests. These findings would expand the possibility of biological control using INA bacteria since Ent. cloacae would harbour a broader host (insect) range for gut colonization and a smaller affinity to plants to benefit from prevention of plant frost injury.

Animals↗
PubMed2003

Control of flexor motoneuron activity during single leg walking of the stick insect on an electronically controlled treadwheel.

In the present study, motoneurons innervating the flexor tibiae muscle of the stick insect (Cuniculina impigra) middle leg were recorded intracellularly while the single leg performed walking-like movements on a treadwheel. Different levels of belt friction (equivalent to a change in load) were used to study the control of activity of flexor motoneurons. During slow leg movements no fast motoneurons were active, but a recruitment of these neurons could be observed during faster leg movements. The firing rate of slow and fast motoneurons increased with incremented belt friction. Also, the force applied to the treadwheel at different frictional levels was adapted closely to the friction of the treadwheel to be overcome. The motoneurons innervating the flexor tibiae were recruited progressively during the stance phase, with the slow motoneurons being active earlier than the fast (half-maximal spike frequency after 10-15% and 50-60% of the stance phase, respectively). The resting membrane potential was more hyperpolarized in fast motoneurons (64.6 +/- 6.5 mV) than in slow motoneurons (-52.9 +/- 5.4 mV). However, the threshold for the initiation of action potentials was not statistically significantly different in both types of flexor motoneurons. Therefore, action potentials were generated in fast motoneurons after a longer period of depolarization and thus later during the stance phase than in slow motoneurons. We show that motoneurons of the flexor tibiae receive substantial common excitatory inputs during the stance phase and that the difference in resting membrane potential between slow and fast motoneurons is likely to play a crucial role in their consecutive recruitment.

Action Potentials↗
PubMed1988

Synthesis of functional bovine opsin in insect cells under control of the baculovirus polyhedrin promoter.

In vitro expression of cDNA encoding bovine opsin is accomplished using the baculovirus expression vector system. Full-length opsin was synthesized which was recognized by poly- and monoclonal antisera raised against bovine rhodopsin. Upon infection with a recombinant virus, 1 x 10(6) insect cells produced up to 3 micrograms opsin. Incubation of the in vitro synthesized opsin with 11-cis retinal produced a hydroxylamine-stable, photosensitive pigment.

Animals↗
PubMed1964

MERMITHID PARASITES OF BLACKFLIES.

Mermithid nematodes parasitize invertebrates only. A general account is given of their parasitism and the consequent mortality of blackflies. The author begins with a review of records of mermithid and blackfly association from different parts of the world and comments on the global distribution of the parasite. He discusses the life-histories of the parasites, stressing their adaptations to the moving environment of the aquatic stages of the blackfly and to the aerial environment of the adult. It is noted that the parasite usually kills its host upon emergence and has a restricted host range. Mermithids must be considered as selective mortality factors against blackfly populations. A survey of European and North American literature leads to conclusions concerning the role of the parasite in the natural regulation of blackflies. The possibility of utilizing these nematodes as biological control agents is discussed.

Animals↗
PubMed2000

Lysosomal neuraminidase. Catalytic activation in insect cells is controlled by the protective protein/cathepsin A.

Lysosomal N-Acetyl-alpha-neuraminidase is active in complex with the protective protein/cathepsin A (PPCA) and beta-galactosidase. The interaction with PPCA is essential for the correct intracellular routing and lysosomal localization of neuraminidase, but the mechanism of its catalytic activation is unclear. To investigate this process, we have used the baculovirus expression system to co-express neuraminidase and PPCA precursors in insect cells, which resulted in high enzymatic activity of neuraminidase. Both the 34- and 20-kDa PPCA subunits were required for the activation. We further demonstrated that when expressed alone, the neuraminidase precursor remained dimeric (114 kDa) and had low enzymatic activity, but when co-expressed with PPCA and beta-galactosidase, it multimerized in a complex of approximately 1350 kDa, together with the other two proteins. The fully active neuraminidase co-precipitated with full-length PPCA and beta-galactosidase precursors. However, when co-expressed with the individual PPCA subunits, neuraminidase co-precipitated only with the small 20-kDa polypeptide, which therefore must contain a neuraminidase-binding site. Our finding suggests a model of activation of neuraminidase dependent on its oligomerization at acidic pH that is mediated by interaction with PPCA.

Animals↗
PubMed1976

Entomopathogens: ecological manipulation of natural associations.

The control of insect pests with entomopathogens is unique, in that naturally occurring host-pathogen relations are manipulated to the benefit of man: protecting agricultural crops and forests or controlling insect vectors of disease. The isolation and identification of a virulent pathogen is the initial step in the development of a potential control agent. Production of the pathogen in adequate quantities must be possible either in vivo (insects) or in vitro (artificial medium). To insure usefulness, the pathogen must remain viable in the formulated form and after application in the field. Since inactivation rather than persistence is a problem, the pathogens must be formulated, protected, and applied to insure satisfactory pest control action. Studying the natural host--pathogen interactions will be necessary in order to manipulate the pathogen effectively, by introducing it at the most opportune time in the life cycle of the target pest. Generally, insect pathogens are more selective than conventional pesticides; this will limit their use and industrial development. Development, at least in part, by the public sector may be necessary and desirable. The most promising areas for the use of pathogens are in integrated pest management and in situations where pests have developed resistance to chemical control.

Animals↗