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Biomedical subjects

O Siddiqi

Publications and source records attributed to O Siddiqi.

At least 19 recordsLinked to original sources
PubMed2002

Guido Pontecorvo, 29 November 1907 - 25 September 1999.

Guido Pontecorvo was elected a Fellow of The Royal Society in 1955 for his contributions to the genetics of Drosophilia and the fungus Aspergillus nidulans. Pontecorvo was a leading British geneticist, prominent in the decade preceding the discovery of DNA, who enriched our understanding of genes and whose pioneering work on the parasexual cycle in fungi found application in human somatic cell genetics. Known to friends as Ponte, he had a strong personality. Somewhat irascible but warm, with a wry sense of humor, he made many lifelong friends and acquired a large body of admirers.

Genetics↗
PubMed2000

Genetic analysis of olfC demonstrates a role for the position-specific integrins in the olfactory system of Drosophila melanogaster.

Genetic analysis of olfC provides evidence for a role for integrins in the development and/or function of the olfactory system of Drosophila. The olfC gene was identified on the basis of mutations that result in specific defects in behavioural responses to acetate esters, and has been mapped to the cytogenetic interval 7D1;D5-6 on the X chromosome. The myospheroid (mys) gene maps to this region and encodes a beta subunit of integrins. Integrins are alpha(beta) heterodimers which are present on the cell surface and have been implicated in a variety of signalling roles. Mutations in mys fail to complement the olfactory deficits of olfC mutants. These defects can be rescued by misexpression of the mys+ gene under control of a hsp70 promoter. Mutations that affect the alpha subunit of the position-specific integrin PS2 show a dominant interaction with olfC. These results suggest that olfC is allelic to mys and functions together with alphaPS2 integrins in the olfactory pathway in Drosophila.

Acetates↗
PubMed1993

Olfaction in invertebrates.

Olfactory transduction in invertebrates seems to be similar to that in vertebrates. Three signalling systems involving activation of adenylate cyclase, phospholipase C and guanylate cyclase are present. A variety of second messengers, including cAMP, inositol 1,4,5-trisphosphate, diacylglycerol, nitric oxide and Ca2+, have been identified but their target sites and mode of action are not yet fully understood. The central projections of olfactory signals in invertebrates are relatively simple and perhaps more hard-wired than in vertebrates. Information about circuitry and functional mapping in the olfactory pathway is lacking. This is essential for understanding the sensory code and higher olfactory functions. Neurogenetic analysis has provided useful insights into olfaction and olfactory learning.

Animals↗
PubMed1991

Closely linked lesions in a region of the X chromosome affect central and peripheral steps in gustatory processing in Drosophila.

We have analyzed a set of closely linked mutations on the X chromosome of Drosophila that lead to defects in gustatory behavior. The mutations map to a small region of the X chromosome between 10E1-4. Two distinct complementation groups, gustB and gustD, map to the ends of this region. These groups show complex complementation patterns with the mutations gustC and GT-1, which also map to this region. We describe the behavioral and electrophysiological properties of the mutants. These mutations affect peripheral receptor properties as well as more central processing steps in the gustatory pathway.

Animals↗
PubMed1990

Genetics of olfactory behavior in Drosophila melanogaster.

We have used a behavioral genetic approach to identify six X-linked loci which specify olfaction in Drosophila melanogaster. Mutations in five of these genes lead to partial anosmias affecting responses either to aldehydes (olfA, olfB, olfE and olfF) or to acetate esters (olfC). Only one of the mutants obtained in our screening (olfD) resulted in a insensitivity to several different odorants. olfA, olfE and olfC map close together in a small region of the chromosome between 7C and 7D. The alleles at the olfC locus fall into two phenotypic classes according to their responses to different acetate esters. The two groups of olfC alleles interact in-trans.

Animals↗
PubMed1983

Projection patterns of different types of antennal sensilla in the antennal glomeruli of Drosophila melanogaster.

Cobalt fills from small, defined regions of the antenna in D. melanogaster show that the three types of sensilla on the third segment, the flagellum, and a fourth sensillum located in the arista, project into the glomeruli of the antennal lobe. We have identified 19 glomeruli in each lobe, according to their location, shape, and size. At least ten of these represent major projection areas of flagellar or aristal sensilla. The large majority of glomeruli is innervated from both antennae, but a small group of five receive exclusively ipsilateral input. A particular sensory fiber appears to terminate only in one specific glomerulus, either in the ipsilateral or in both lobes. Fills from flagellar regions bearing a single type of sensillum, yield a specific pattern of glomeruli containing stained terminals. Aristal projections remain strictly ipsilateral, whereas those from the other sensilla consist of an ipsilateral and a bilateral component. When filling from different points in an area bearing one type of sensillum, similar projections are produced, suggesting that projection patterns observed reflect predominantly the type of sensillum rather than its location on the flagellum. Accordingly, individual glomeruli might represent functional units, each receiving antennal input in a characteristic combination.

Animals↗
PubMed1981

torpid a new sex-linked paralytic mutation in Drosophila melanogaster.

A new temperature-sensitive paralytic locus on the X chromosome of Drosophila melanogaster called torpid is described. Mosaic analysis shows that the focus of defect in torp lies in the presumptive neural region of the blastoderm. Electrophysiological tests indicate that the excitability of the cervical axons is lowered at elevated temperatures.

Blastoderm↗
PubMed1981

A gustatory mutant of Drosophila defective in pyranose receptors.

Mutations in an X-linked gene, gust-A, block the responses of Drosophila melanogaster to a group of pyranose sugars. It is shown that the behavioural effects of this mutation are correlated with a loss of electrical responses in taste receptors. The mutation affects the chemoacceptors for pyranose sugars leaving the furanose acceptors intact.

Animals↗
PubMed1976

Neurophysiological defects in temperature-sensitive paralytic mutants of Drosophila melanogaster.

A new temperature-sensitive paralytic mutant of Drosophila, comatose, is compared behaviorally and physiologically with the previously known types, para and shi. All three have different properties with respect to kinetics of paralysis at high temperature and recovery from paralysis; com is hypersensitive to paralysis by cooling. Neurophysiological experimeents indicate different mechanisms for paralysis in each of the mutants.

Animals↗