The effect of larval selection on adult resistance to DDT in two strains of the mosquito Aedes aegypti (L)

Evidence is presented which confirms the influence of linkage group II on adult DDT-resistance in one strain of Aedes aegypti (Bangkok-MR) but not in another strain (Bangkok-HR).

Linkage of the genes for DDT and dieldrin resistance in larvae of the mosquito Aedes aegypti

The DDT resistance gene RDDT1, and the dieldrin resistance gene Rd1 have been mapped on linkage group II with respect to visible markers, in the mosquito Aedes argypti L. The best interpretation of the data gives the order wa - Rdl - ds RDDT1 - s - y but was - Rdl -ds - y - s - RDDT1 is also possible. h is very loosely linked with RDDT1. The length of the linkage group has been considerably extended from previous studies.

Application of the single radial diffusion test for assay of antibody to influenza type A viruses

Single radial diffusion (SRD) tests for antibodies to influenza type A hemagglutinin, neuraminidase, nucleoprotein, and matrix protein antigens were compared with conventional hemagglutination inhibition, neuraminidase inhibition, and complement fixation tests. Sera used in this study were obtained in 1968-1969 from volunteers before and after vaccination and before and after an ensuing epidemic of Hong Kong influenza. The SRD test compared favorably with conventional tests for assessment of vaccine- or infection-induced rises in antibody titers to influenza type A viruses. Little linear relationshiip was seen between zone areas with SRD and titers with conventional tests, suggesting that the SRD test may detect antibody of different quality or specificity. The SRD seemed equal to the hemagglutination inhibition test for predicting susceptibility to influenza. SRD is a simple test for the recognition of antibody to various antigenic components of the influenza virus and could prove to be a valuable epidemiological tool.

Linkage of a gene for DDT-resistance in adults of the mosquito Aedes aegypti

The gene RDDT2, which gives resistance to DDT in the imago of Aedes aegypti L. has been mapped on linkage group III with respect to six visible markers. The best interpretation of the order of the genes is:- blp - blt - co - fz - wi -RDDT2 - min, but the order blp - blt - co - fz -RDDT2 - wi - min is also possible.

A genetical study of DDT resistance in the mosquito Aedes aegypti

Crosses have been carried out to determine the relationship between adult DDT resistance and the three linkage groups of the mosquito Aedes aegypti. Two linkage groups were implicated in the control of DDT resistance. In the Bangkok-HR strain resistance derived mainly from linkage group III, probably with the maor effect from the gene R-DDT2. When resistance was transferred into a susceptible background, by outcrossing Bangkok-HR to strain 64 and reselecting, resistance in the resulting Bangkok-MR strain came from both linkage groups II and III.

Proceedings: Osmoreception and thirst in the dog

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The relationship between elevated water intake and oedema associated with congestive cardiac failure in the dog

1. In the dog constriction of the thoracic region of the inferior vena cava increases water intake and extracellular and plasma fluid volumes. 2. Restriction of water intake to the pre-operative level for 2 weeks reduces the measured extracellular fluid volume to the pre-operative level. 3. Administration of the competitive angiotensin inhibitor, saralasin acetate, to two dogs in congestive cardiac failure following thoracic caval constriction markedly reduced their water intake. 4. These results suggest that increased fluid intake is probably important in the aetiology of the oedema associated with congestive cardiac failure, probably through the renin-angiotensin system.

Colorimetric analysis of hexachlorophene in topical formulations

The commonly used 4-aminoantipyrine dye formation procedure for hexachlorophene analysis in topical formulations was modified to overcome interference due to other components. Bar soaps and nonemulsion formulations are analyzed directly, employing a chloroform back-extraction stage of the dye prior to quantitation. Hexachlorophene in emulsions and liquid soaps is determined using a TLC separation prior to dye formation.

The production of a DDT-resistant strain of Aedes aegypti marked on all three linkage groups

DDT-resistant strains marked on all three linkage groups have been produced by selection at the adult stage after outcrossing a resistant strain (BANGKOK-HR) to a marked susceptible strain (64). The most resistant and viable line (BANGKOK-MR) was kept for linkage studies. The production of a marked resistant strain was not entirely straightforward. In the absence of a suitable genetic background, major resistance genes conferred little or no DDT tolerance and could not be selected. Selection at the adult stage produced resistance in larvae as well as in adults. Resistance was achieved more rapidly in larvae than in adults

A genetical investigation of resistance to "knockdown" and "kill" by DDT in adults of the mosquito Aedes aegypti L

A genetical investigation of DDT resistance in Aedes aegypti has provided similar values of recombination between the gene for DDT resistance and visible markers, whether the response to DDT was scored as knockdown or as kill, indicating that resistance to knockdown and resistance to kill are controlled at the same gene locus.

The influence of the y locus on DDT resistance in the mosquito Aedes aegypti L

The influence of the linkage group II locusyon DDT resistance inAedes aegyptihas been studied in crosses between the Trinidadresistant strain and QS susceptible strain. Theylocus influences DDT resistance in bothR/RandR/+ larvae. The effect ofymay be interpreted as reducing the penetrance ofR(RDDT1), which is also located on linkage group II.y+is partially dominant and incompletely penetrant in its resistance-enhancing role (although in its pleiotropic effect on larval colour it is dominant and fully penetrant). Penetrance ofy+is influenced by an environmental factor, probably associated with the larval diet.

The effect ofyon resistance is evaluated in relation to other genetic influences on the expression ofRDDT1.

The significance of polymorphism at theylocus is discussed.

Heterogeneity in the Trinidad DDT-resistant strain and the QS susceptible strain of Aedes aegypti L. The isolation of highly resistant and highly susceptible substrains

Investigating heterogeneity in response to DDT with 2 strains of Aedes aegypti, the author has compared DDT-resistance in the F(1) and F(2) progenies of single-pair matings of resistant with resistant (TRINIDAD) and susceptible with susceptible (QS) strains.Both strains showed heterogeneity; however, there was little overlap between the most tolerant QS progeny and the least resistant TRIN progeny. A substrain of very high resistance was isolated from a single TRIN progeny and one of very low tolerance from a single QS progeny.Between QS progenies there was wide variation in DDT-tolerance, due in part to an environmental component but in part also to a genetic component. Variation between progenies in the already very resistant TRIN strain was marked. However, a genetic component was shown by the fact that it was possible to select an exceptionally resistant TRIN substrain in one step by rearing from the most tolerant TRIN progeny.

A comparative genetical study of DDT resistance in adults and larvae of the mosquito Aedes aegypti L

Inheritance of DDT resistance has been studied in crosses between the highly resistant ‘T’ strain ofA. aegypti(constituted by inbreeding from the TRINIDAD DDT-resistant stock) and the ‘64’ susceptible strain.

Larval DDT resistance derives from a major geneRDDT1on linkage group II, the order beingRDDT1–s–y. Linkage group III may also contribute to larval resistance. Linkage group I makes no contribution.

Adult DDT resistance derives from a major geneRDDT2, 18·2 ± 2·1 units from the marketblton linkage group III. Linkage group II has no influence on adult resistance.

Selection with DDT to retain onlyRDDT1/+ segregants in larvae of backcrossesRDDT1/+×+/+ did not increase resistance in resulting adults, confirming the difference in genetic mechanism at the two stages.

The F1progenies from reciprocal crosses between ‘T’ and ‘64’ differed slightly but significantly in larval resistance, modifying the influence of the major geneRDDT1in the heterozygote.

The early developmental stages of theRDDT1/+ phenotype (up to the fourth larval stage) were more viable than the +/+ phenotype in backcross segregation. The difference in mortality probably exceeded 30%.

A COMPARISON OF THE CONCENTRATION OF C14 IN THE TISSUES OF PREGNANT AND NONPREGNANT FEMALE RATS FOLLOWING THE INTRAVENOUS ADMINISTRATION OF VITAMIN K1-C14 AND VITAMIN K3-C14

The C14 content was determined of the livers, spleens, skeletal muscle, blood, feces, and urine of both pregnant and nonpregnant female rats and of the placentas, fetal livers, fetuses, and amnionic fluids of pregnant rats following the intravenous administration of 5 mg./kg. of either vitamin K1-C14 or vitamin K3-C14. The C14 concentrations of the livers of the rats given vitamin Kt were about 24 times larger than those of animals that had received vitamin K3-C14. A fivefold difference in the same direction exists between the concentrations in the spleens of the two groups. The C14 levels for skeletal muscle, blood, placenta, fetal liver, and fetal tissue were of similar magnitude regardless of whether vitamin Kt or vitamin K3 was administered. Isotope dilution tests revealed that following intravenous administration of vitamin K1-C14 the amount of radioactivity present as unchanged vitamin Kt-C14 was 12% for fetal tissue, 59% for placenta, and 120% for the maternal liver. The dry weights of the livers of pregnant rats were larger than those of nonpregnant rats and the increase was proportional to the live weight of the pregnant rat. No significant difference could be demonstrated in the percentage of the injected dose of vitamin K1 deposited in the livers of pregnant or nonpregnant rats. The same was true for vitamin K3-C14. The results of this experiment indicate that vitamin K3-C14 is not concentrated in the liver of the rat whereas vitamin K1-C14 is. Furthermore, it would appear that both vitamin K1 and vitamin K3 can pass the placental barrier of the rat.