Biomedical subjects

V Baimai

Publications and source records attributed to V Baimai.

At least 37 records · Page 2Linked to original sources

PubMed1994

Polytene chromosome arrangements in Drosophila bocki.

Cytological investigations of salivary gland polytene chromosomes of the Drosophila kikkawai complex in Thailand have revealed an interesting pattern of species divergence. Drosophila bocki, D. leontia and D. kikkawai share chromosome arrangement 3LB. However, additional gene arrangements of 3LA and 3LC have been observed in D. kikkawai and D. leontia, respectively, while D. bocki remains polymorphic for inversion 3LB. Chromosomal evidence seems to suggest that D. bocki is similar to a common ancestor of the D. kikkawai complex.

Animals↗

PubMed1993

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: I. The Hyrcanus Group.

Metaphase karyotypes of 6 species of the Hyrcanus Species Group of the subgenus Anopheles show constitutive heterochromatin variation in X and Y chromosomes. Anopheles peditaeniatus exhibits the most extensive variation in the size and shape of heterochromatic sex chromosomes, with 3 types of X and 5 types of Y chromosomes. Anopheles nitidus shows the least variation, with only 2 types of X chromosomes. Anopheles sinensis and An. crawfordi each have 2 forms of metaphase karyotype in the heterochromatin of the Y chromosome. It is not known whether the 2 forms of metaphase karyotype in these 2 species represent inter- or intraspecific differences. The 2 forms of heterochromatic sex chromosomes observed in An. argyropus and An. nigerrimus may suggest the existence of sibling species complexes within each of these species.

Animals↗

PubMed1992

Population genetic evidence for species A, B, C and D of the Anopheles dirus complex in Thailand and enzyme electromorphs for their identification.

Mixtures of chromosomal forms A, B, C and D in natural populations of Anopheles dirus Peyton & Harrison sensu lato in Thailand show significant positive values of Wright's fixation index for six enzyme-electromorph loci. The mean value of FIS over all loci was found to be +0.28 (SD 0.02), with a range of +0.57 (Odh) to +0.10 (Idh-2). Partitioning electromorph data for the chromosomal forms reduces the mean FIS to 0.03 (SD 0.01), which suggests that positive assortative mating is a characteristic of each form. This supports the hypothesis that the chromosomal/electrophoretic forms A, B, C and D represent four distinct biological species within the An. dirus complex. An example is given of the use of enzyme electromorphs as a means of vector identification during a malaria entomological field study involving a mixture of An. dirus species A and D. Electromorph identifications of 323 sp. A and 161 sp. D were more than 98% correct when cross-referenced to specific DNA probes.

Alleles↗

PubMed1990

Genetic linkage relationships of eight enzyme/electromorph loci in Anopheles minimus.

Two laboratory stocks of Anopheles minimus, each fixed for variant electromorphs of esterases, aspartate aminotransferase, hydroxyacid dehydrogenase, phosphogluconate dehydrogenase, mannose phosphate isomerase and glycerol dehydrogenase were used to assess linkage relationships between presumed gene loci controlling this variation. The two F1, which had been obtained from crossing the stocks, were backcrossed to a parental stock. Three loci controlled the esterases and one locus each of the other enzymes. Mpi is sex-linked. The rest are autosomal and suggested relationships are: Pgd 2.3% recombination from Aat and unlinked to any other loci; Est-1-33.8%-Est-3-31.5%-Est-2-21.0%-Had. Gcd is unlinked to any other locus. There was evidence of strong interaction between the X chromosome of one stock and autosomes of the other in which individuals bearing the X chromosome of the one suffered relatively greater mortality and had delayed development with respect to other genotypic classes.

Animals↗

PubMed1990

Population-genetic evidence for two species in Anopheles minimus in Thailand.

Sympatric occurrence of homozygotes for two electromorphs controlled by a locus for octanol dehydrogenase, and the absence of heterozygotes, at two localities, indicates two isomorphic species within the taxon Anopheles minimus Theobald in Thailand. This view is supported by significant, relative deficiencies of heterozygotes at other electromorphic loci. Gene frequency data are reported for seven electromorphic loci in An. minimus sensu lato from eleven localities: one of the newly recognized species predominated in all but one locality and the second was confined to two localities. This species pair of An. minimus s.l. was clearly distinguished from An. aconitus Dönitz, An. pampanai Büttiker & Beales and An. varuna Iyengar, three species closely related to An. minimus s.l. in the series Myzomyia of Anopheles subgenus Cellia.

Alcohol Oxidoreductases↗

PubMed1990

Anopheles dirus species E: chromosomal and crossing evidence for another member of the dirus complex.

Cytogenetic and crossing data provide strong evidence for the existence of another species, dirus E in southwestern India, within the Dirus Complex of Anopheles. These findings are in accord with unpublished morphological observations. Our data suggest a significant genetic divergence between species E and its close relatives, An. dirus A, B and C in Thailand. These data also suggest that dirus E is an incipient sibling species of its geographically nearest relative, dirus D, and that it seemingly co-evolved through the process of allopatric speciation.

Animals↗

PubMed1989

Scanning electron microscopic observations and differentiation of eggs of the Anopheles dirus complex.

Microscopic observations have revealed differences among the eggs of species A, B, C and D of the Anopheles dirus complex. The eggs of species A and C are similar in size and shape. They are intermediate in size between the eggs of species B, which is the largest, and that of species D, which is the smallest. The pattern of outer chorionic cells between the frill and the float is species specific. The pattern consists of rows of irregularly shaped cells in species D and different numbers of rows of regularly shaped cells in species A, B and C. Scanning electron microscopy revealed that the deck tubercles are arranged in aggregates which are more widely spaced in species A than in species B. The aggregates are large in species C, of moderate size in species A and B, and small in species D. The egg characters may be useful in separating species A, B, C and D of the An. dirus complex.

Animals↗

PubMed1988

Cytological differences and chromosomal rearrangements in four members of the Anopheles dirus complex (Diptera: Culicidae).

A reference photomap of the larval salivary gland, polytene chromosomes of the Anopheles dirus complex (species A) is presented. Samples of species A, B, C, and D from natural populations in Thailand were compared to this standard map using the larval progeny of wild-caught females. All species show differences in their chromosome banding patterns involving band size, number, and shape, particularly at the free ends of the X, 2R, and 2L. These differences provide useful diagnostic characters for separating members of the species complex. However, overall banding patterns are conservative in the group: species A, B, and C are virtually homosequential. Species D is highly polymorphic for a single paracentric inversion in each of the four autosomal arms and has a fixed inversion on the X chromosome. This same X chromosome inversion occurs at low frequency in species A.

Animals↗

PubMed1988

Identification of isomorphic malaria vectors using a DNA probe.

About 7,000 recombinant clones, derived from chromosomally-identified families of wild-caught females of Anopheles dirus species D, were screened. The most promising clone was totally specific to species D when tested against single F1 females of all four species of the complex. In fresh specimens the clone was positive for DNA levels 150 times less than the normal DNA content of single individuals. Fresh adult males and females, larvae, and dried specimens have been successfully identified. The clone was sequenced; it is 124 bp long and appears to be repeated in the genome about 1.8 x 10(4) times.

Animals↗

PubMed1988

Cytogenetic evidence for two species within the current concept of the malaria vector Anopheles leucosphyrus in Southeast Asia.

Karyotypes and crossing relationships were investigated for three allopatric populations of Anopheles leucosphyrus in Southeast Asia: South Kalimantan, Sumatra and Thailand. The mitotic karyotypes of these populations were similar to those previously observed in other species of the An. leucosphyrus group. Populations from Thailand and South Kalimantan exhibited telocentric and subtelocentric sex chromosomes, respectively, with a distinctive band of intercalary heterochromatin in the X chromosome. Strikingly different submetacentric X and Y chromosomes were observed in the population from Sumatra, and it seems likely that the evolution of these chromosomes occurred through the acquisition of constitutive heterochromatin. Sterile F1 males were observed in crosses between the Sumatra population and the populations from South Kalimantan and Thailand. No genetic incompatibility was observed in crosses between the latter two populations. We believe that the present concept of An. leucosphyrus includes two allopatric species, one inhabiting Borneo, West Malaysia and southern Thailand and one confined to Sumatra.

Animals↗

PubMed1988

Cytogenetic evidence for a fifth species within the taxon Anopheles dirus in Thailand.

Crossbreeding and chromosomal evidence are presented for the existence of a fifth sibling species within the taxon of Anopheles dirus in Thailand. The new species is morphologically identifiable as Anopheles balabacensis "Fraser's Hill form." Structural differences in mitotic chromosomes and extensive asynapsis in hybrid polytene chromosomes indicate that significant genetic divergence exists between this species and its closest relatives, An. dirus species A, B, C and D and An. balabacensis.

Animals↗

PubMed1988

Distribution and chromosomal polymorphism of the malaria vector Anopheles dirus species D.

Preliminary results indicate that species D of the Anopheles dirus complex is widespread west of the Thai-Burma border in Burma and Bangladesh. A chromosomal study of An. dirus species D in these areas has revealed that this malaria vector is highly polymorphic for chromosomal rearrangements in salivary gland polytene chromosomes. The data from the limited number of wild-caught samples suggest that different geographically isolated populations may occur with respect to the frequency of inversions 2La, 3Ra and 3La. The distribution of chromosomal polymorphisms may be associated with the geography and epidemiology of human malaria in this region.

Animals↗

PubMed1988

Population cytogenetics of the malaria vector Anopheles leucosphyrus group.

Until recently, very little was known of Anopheles species complexes and their relationships to epidemiology and malaria transmission in Southeast Asia. During the past eight years, extensive studies on the genetics of natural populations of anopheline mosquitoes in this region, involving the interdisciplinary efforts of taxonomists, operational entomologists and biologists, have revealed groups of cryptic species of Anopheles vectors, particularly the An. leucos phyrus group. This species group comprise seventeen species and two subspecies widely distributed in the forested areas of Southeast Asia. Among these species. An. dirus Peyton and Harrison, has been shown by cytogenetic and morphological studies to be a complex of at least seven isomorphic species, provisionally designated species A, B, C, D, E, F and takasagoensis, on the Southeast Asian mainland. Cytological identification of these species is based on distinct banding patterns of salivary gland polytene chromosomes as well as heterochromatin differences in mitotic karyotypes. The five species found in Thailand (A-D, F) exhibit distinct geographic distributions. Species A is widespread throughout Thailand except in the south. Species B had been found in sympatry with species C in southern Thailand and both seem to show north-south clinal geographic variation. Species D is common on the west side of southern Thailand and along the Thai-Burmese border in sympatry with species A. Species F, An. nemophilous Peyton and Ramalingam, has been found in a population at the Thai-Malaysian border in this study although it was known to be common in southern and western Thailand and Peninsular Malaysia. Species E is known only from western India. The five species found in Thailand also exhibit seasonal variation in relative abundance and different nocturnal biting cycles. Chromosomal polymorphisms have been observed in mitotic and polytene chromosomes of An. dirus A and D. Species B and C also show heterochromatin variation in the sex chromosomes, but are monomorphic for the standard sequence in polytene chromosomes. These biological characteristics of the An. dirus complex may have implications for understanding the epidemiology of malaria in Southeast Asia. Recent cytogenetic studies of wild-caught samples of An. leucosphyrus from Sumatra, Kalimantan and southern Thailand have revealed the presence of two distinct species within this taxon. Species A is widely distributed in southern Thailand, East Malaysia and Kalimantan, while species B is confined to Sumatra. The two isomorphic species are vectors of human malaria within their range of distribution.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Geographic distribution and biting behaviour of four species of the Anopheles dirus complex (Diptera: Culicidae) in Thailand.

A cytogenetic analysis of the species status of members of the Anopheles dirus group, from natural populations, over a six-year period has produced biogeographic and behavioural data which are presented herein. Species A, B, C and D have quite distinct geographic distributions in Thailand. Species A is the only species in most of the mainland but is absent from the southern half of the peninsula. Species B is dominant in the far south of the peninsula giving way to species C on the north-east side and rarely occurring on the west side of the peninsula; it is unknown from the northern half or the rest of the country. Species C is known from the middle eastern side of the peninsula and from a site far to the north along the Burmese border. Species D occurs down the mountains along the Burmese/Thai border and along the north half of the western peninsula. Each species appears to have distinct times of biting during the night. They also appear to have differential seasonal abundance. These data together with the differing geographic distributions suggest some implications for Plasmodium transmission and that care should be taken to identify these genetic species during malariometric studies.

Animals↗

PubMed1987

Intraspecific variation in sex heterochromatin of species B of the Anopheles dirus complex in Thailand.

Cytological examination of F1 larval mitotic chromosomes from a total of 126 families of Anopheles dirus species B from southern Thailand populations has revealed a pronounced quantitative variation of constitutive heterochromatin in the two sex chromosomes. Five types of X chromosomes and four types of Y chromosomes have been identified in this study. Such gross variation in sex chromosomes is most likely due to a gradual acquisition of extra heterochromatin.

Animals↗

PubMed1987

Some observations on sympatric populations of the malaria vectors Anopheles leucosphyrus and Anopheles balabacensis in a village-forest setting in South Kalimantan.

Human bait collections of biting anopheline mosquitoes were made on five consecutive nights during September 1986 in a remote village located in a heavily forested area of South Kalimantan, Indonesia. Anopheles leucosphyrus and An. balabacensis comprised 97.7% of the total number of specimens collected outside houses in the village. Anopheles balabacensis were slightly fewer in total numbers than leucosphyrus. Mosquitoes were collected simultaneously in the village and the forest on two nights. The numbers of leucosphyrus and balabacensis biting in the forest were small in comparison with the populations encountered in the village. Approximately 75% of the specimens were checked individually for sporozoite infections using ELISA for P. falciparum and P. vivax. Sporozoites of P. falciparum were detected in one specimen of leucosphyrus and one of balabacensis. The sporozoite infection rate was 1.0% for leucosphyrus and 1.3% for balabacensis.

Animals↗

PubMed1987

Monandry (monogamy) in natural populations of anopheline mosquitoes.

Polymorphic Y chromosomes within two species of anopheline mosquitoes provide markers for testing if females are inseminated by one or more males in nature. Wild-caught females of Anopheles dirus (sp. A) and An. maculatus s.s. produced 291 and 55 families, respectively, which showed a single type of Y chromosome. One family of the former species showed two types of Y chromosomes. These field data support the idea, established from laboratory studies, that female mosquitoes are largely monandrous (monogamous). Such information is important in interpretation of population biological data and, practically, in attempts to control insect pests by use of genetically designed males.

Animals↗

PubMed1986

Genetics of esterases and 6-phosphogluconate dehydrogenase in the Anopheles maculatus complex.

Electromorphic variation for some esterases and 6-phosphogluconate dehydrogenase enzymes in the Anopheles maculatus complex is controlled by four loci which are unlinked to sex. Esterase loci are linked to each other: Est-1-36%-Est-4-16.5%-Est-3; but unlinked to Pgd-2. Linkage data were obtained by selfing the F1 generation from selected parents and analysing genotypes in the F2; the classical dihybrid-cross. The analysis consists of testing observed data for goodness of fit to a) ratios expected from Mendelian ratios without linkage and b) if they do not fit then computing a likely degree of linkage and computing expected ratios with such linkage for further tests. Confidence limits are given for the most likely levels of linkage. This method can provide useful information for population-genetic studies on anopheline mosquitoes, whose laboratory rearing is generally difficult. Through indirect evidence, the enzyme loci are correlated to polytene chromosomes. The esterases probably lie on chromosome three (polytene arms 3 and 4) and Pgd-2 on the second chromosome (arms 2 and 5).

Animals↗