Karyological identification of two taxa of the Anopheles balabacensis complex from Burma

Giemsa and Hoechst staining of neuroblast chromosomes were used to identify two strains of the Anopheles balabacensis complex from Burma. The laboratory colony of Kwan-ka-thaung (KKT) strain is shown to correspond to A. dirus A, while the laboratory colony of Taikkyi (TKK) strain corresponds to A. dirus C as defined by earlier studies on material from Thailand.     

Studies on the transmission of simian malaria. VI. Mosquito infection and sporozoite transmission of Plasmodium fragile.

Anopheles b. balabacensis mosquitoes were infected with Plasmodium fragile when fed upon splenectomized Macaca mulatta monkeys. Highest level mosquito infections were obtained when feedings were made from 2 to 4 days prior to the peak in the parasitemia. Transmission to M. mulatta monkeys was obtained via mosquito bite on 2 occasions and via intrahepatic and intravenous inoculation of dissected infected salivary glands on 9 occasions. The prepatent periods ranged from 12 to 17 days with a median of 15 days.     

Pharmacological investigation on the neurohumoral transmission of the vasomotor regulation.

Renal efferent sympathetic activity and its changes due to stimulation of the central stump of the vagal, sciatic and ulnar nerves were investigated. In addition, the effect on basal activity and sympathetic reflexes of drugs with well defined site of action was studied (diazepam, tofizopam, phentolamine, dihydroergotamine, chlorpromazine, reserpine, clonidine, atropine, methysergide and phenindamine). The sympathetic efferent activity and the changes in sympathetic reflexes allowed conclusions to be drawn as to the functional state of the vasomotor centre. Neither methysergide nor phenindamine inhibited efferent sympathetic activity or influenced sympathetic reflexes. These findings exclude the possibility of serotonin or histamine being the transmitter substance in the vasomotor neurone. Experiments with atropine revealed that the muscarinic action of acetylcholine does not figure in the sympathetic inhibitory or excitatory reflex processes. Of the drugs investigated only diazepam and clonidine inhibited efferent sympathetic activity. Clonidine was more selective and acted in much lower doses (20 micrograms/kg) than diazepam (0.5--1 mg/kg). The alpha blocking agents inhibited the viscero-sympathetic inhibitory reflex arch more intensely than the somato-sympathetic inhibitory one. The transmitter is presumably noradrenaline. The sympathetic excitatory reflexes were decreased by diazepam and tofizopam and increased by clonidine and phentolamine. The other substances were ineffective. As to the transmitter substance figuring in the sympathetic excitatory reflexes no unequivocal answer could be obtained in the present experiments.     

Synaptic transmission in the retina.

A recent highlight in the study of the retina has been the publication of evidence that the response of the ON bipolar cells is generated by a cGMP-mediated second messenger system. This GTP-binding protein mechanism is activated by the binding of glutamate, the photoreceptor neurotransmitter, to the 2-amino-4-phosphonobutyrate (APB) class of receptor.     

Karyotype differentiation of three anopheline taxa in the balabacensis complex of Southeast Asia (Diptera: Culicidae)

Cytological studies of the mitotic and meiotic karyotypes and the polytene salivary chromosomes of Anopheles dirus, An. takasagoensis and An. balabacensis (Perlis form), have revealed significant differences in the sex chromosomes. These differences are largely due to the position of the centromere and different amounts of constitutive heterochromatin and euchromatin. The chromosomal data suggest that An. dirus and An. takasagoensis are more closely related to each other than either is to An. balabacensis (Perlis form). The karyological differences are very useful in differentiating these taxa, particularly the Perlis form, and lend support for their species status.     

The effect of cultural transmission on continuous variation.

Cultural transmission may depend on the non-genetic transfer of information from parent to offspring. The consequences of such cultural transmission for continuous variation are investigated theoretically for randomly mating populations. Cultural inheritance may act on genetical and environmental differences between individuals. The consequences for cultural inheritance of polygenic variation and variation due to chance environmental factors are considered. An equilibrium may occur in which the population variance and the covariances between relatives can be expressed as functions of estimable parameters of genetical and environmental variation. Whatever the ultimate origin of culturally inherited differences they are expected to lead to environmental differences between families ("E2" variation). In addition, if cultural transmission maintains differences due ultimately to segregation at many gene loci we may find genotype-environmental covariation is generated.     

Estimation of survival rate and oviposition interval of Anopheles balabacensis mosquitoes from mark-recapture experiments in Sabah, Malaysia

An exophilic population of the vector mosquito Anopheles balabacensis Baisas was investigated in two mark-recapture studies (16.ix-13.x.1986 and 6-26.i.1987) at an inland, foothill village in Sabah, Malaysia. Wild female mosquitoes were intercepted as they came to feed on man or buffalo, given a bloodmeal, marked with fluorescent dust and released. The recapture rate was about 12%. A new method of analysis is proposed which uses cross-correlation and a time series model. The estimated survival per oviposition cycle was 0.48-0.54 and the oviposition cycle interval 2-3 days.     

The effect of partial host immunity on the transmission of malaria parasites.

Experiments were carried out to determine the effect of partial host immunity against the rodent malaria parasite Plasmodium chabaudi on the transmission success of the parasite. There was a fourfold reduction in both the blood-stage, asexually replicating parasite density and the gametocyte (transmissable stage) density in immunized hosts. Some of the reduction in asexual parasite densities was due to strain-specific immunity, but there was no evidence that strain-specific immunity affected gametocyte densities. However, immunity did affect transmission in a strain-specific manner, with a fivefold reduction in gametocyte infectivity to mosquitoes in homologous challenges compared with heterologous challenges or non-immunized controls. This implies the existence of a mechanism of strain-specific infectivity-reducing immunity that does not affect the density of gametocytes circulating in peripheral blood. The proportion of asexual parasites that produced gametocytes increased during the course of infection in both non-immunized and in immunized hosts, but immunity increased gametocyte production early in the infection.     

Familial transmission of the FMR1 CGG repeat.

To better define the nature of FMR1 CGG-repeat expansions, changes in allele sizes for 191 families with fragile X and for 33 families with gray-zone repeats (40-60) were analyzed. Expansion of the fragile X chromosome to the full mutation was seen in 13.4% of offspring from premutation mothers with 56-59 repeats, 20.6% of those with 60-69 repeats, 57.8% of those with 70-79 repeats, 72.9% of those with 80-89 repeats, and 97.3% of those with 90-199 repeats. For premutation fathers, the majority (62%) of their daughters had a larger repeat number, while a few had either a smaller (22%) or the same (16%) repeat number, compared with their fathers' sizes. However, daughters with a smaller repeat number were observed only if their fathers had > or = 80 repeats. Fifteen (39.5%) of 38 such daughters carried a smaller repeat than did their fathers. We observed that a similar repeat number was inherited more often than expected by chance, among the members of a sibship segregating fragile X. This familial clustering, observed in the offspring of both males and females with a premutation, implies there may be an additional factor, independent of parental repeat size, that influences CGG-repeat instability. Instability in gray-zone allele transmissions was observed in 25% of alleles with 50-60 CGGs but in <8% of those with 40-49 CGGs. Examination of gray-zone allele organization revealed that long tracts of pure CGGs (>34) are not always unstably transmitted. These results raise new questions regarding the familial factors that may determine transmission expansions.