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Biomedical subjects

M Jobling

Publications and source records attributed to M Jobling.

11 recordsLinked to original sources
PubMed2001

Effects of Schistocephalus solidus infection on brain monoaminergic activity in female three-spined sticklebacks Gasterosteus aculeatus.

The three-spined stickleback Gasterosteus aculeatus is an intermediate host of the tapeworm Schistocephalus solidus. Changes in predator avoidance, foraging and shoaling behaviour have been reported in sticklebacks infested with S. solidus, but the mechanisms underlying parasite-induced behavioural changes are not understood. Monoamine neurotransmitters are involved in the control of behaviour and central monoaminergic systems are sensitive to various stressors. Thus, the behavioural effects of S. solidus infestation might be a reflection of changes in brain monoaminergic activity in the stickleback host. The concentrations of 5-hydroxytryptamine (5-HT), dopamine (DA), norepinephrine (NE) and their metabolites 5-hydroxy-indoleacetic acid (5-HIAA), homovanilic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured in the telencephalons, hypothalami and brainstems of parasitized and non-parasitized female sticklebacks held in the laboratory. The ratios of 5-HIAA:5-HT were significantly elevated in both the hypothalami and brainstems of infected sticklebacks. The concentrations of 5-HT and NE were significantly reduced in the telencephalons of infected fish as compared with controls, but there was no elevation of metabolite concentrations. The results are consistent with chronic stress in infected fish, but may also reflect other alterations of neuroendocrine status resulting from parasite infection.

Animals↗
PubMed2000

Astaxanthin and its metabolites idoxanthin and crustaxanthin in flesh, skin, and gonads of sexually immature and maturing Arctic charr (Salvelinus alpinus (L.)).

Carotenoid compositions of the flesh, skin, and ovaries were determined in sexually maturing and immature Arctic charr (Salvelinus alpinus) fed diets supplemented with astaxanthin (optical isomer ratio (3S,3'S):(3R,3'S; meso):(3R,3'R); 1:2:1). Astaxanthin comprised 64-79% of the flesh carotenoids, and the 3',4'-cis and 3',4'-trans glycolic isomers of idoxanthin, present in a 1:1 ratio, represented 20-35%. The flesh of the sexually maturing charr contained relatively more idoxanthin than that of sexually immature fish (20 vs 35% of total carotenoids), possibly being indicative of a higher metabolic turnover of astaxanthin in the latter. The relative proportions of flesh carotenoids were unaffected by sex. The relative carotenoid composition of ovaries was similar in sexually maturing and immature females. The 3',4'-cis and 3',4'-trans glycolic isomers of idoxanthin (ratio 0.7:1) were the major carotenoids (56% of total), followed by crustaxanthin (20%), and astaxanthin comprised less than 5% of ovarian carotenoids. Three glycolic isomers of crustaxanthin were detected (3,4,3',4'-di-cis-:3,4-cis-3',4'-trans-:3,4,3',4'-di-trans-glycolic isomer ratio 2.6:3.1:1) in the ovaries. Sex and maturity status had no apparent effect on the relative composition of skin carotenoids. The skin carotenoids consisted mainly of diesters (82-87% of total carotenoids) and monoesters (7-13% of total carotenoids). Saponification revealed that astaxanthin comprised 85% and idoxanthin 10% of total carotenoids, and minor amounts of tunaxanthin-, lutein-, and zeaxanthin-like metabolites were also present. Maturity status seems to be more important than sex in determining the relative carotenoid composition of the tissues of Arctic charr, with astaxanthin and its metabolites being selectively accumulated in different tissues.

Animals↗
PubMed2000

Floating cholera toxin into epithelial cells: functional association with caveolae-like detergent-insoluble membrane microdomains.

In polarized cells, signal transduction by cholera toxin (CT) requires apical endocytosis and retrograde transport into Golgi cisternae and likely endoplasmic reticulum (ER) (Lencer et al., J. Cell Biol. 131, 951-962 (1995)). We have recently found that the toxin's apical membrane receptor ganglioside GM1 acts specifically in this signal transduction pathway, likely by coupling CT with caveolae or caveolae-related membrane domains (lipid rafts) (Wolf et al., J. Cell Biol. 141, 917-927 (1998)). Work in progress shows that 1) cholesterol depletion uncouples the CT-GM1 receptor complex from signal transduction, a characteristic of lipid rafts; 2) the GM1 acyl chains rather than the carbohydrate head groups appear to account for the structural basis of ganglioside specificity in toxin trafficking; and 3) intestinal epithelial cells obtained from normal adult humans exhibit lipid rafts which differentiate between CT-GM1 and LTIIb-GD1a complexes and which contain caveolin 1.

Animals↗
PubMed1997

Evaluation of Y-chromosomal STRs: a multicenter study.

A multicenter study has been carried out to characterize 13 polymorphic short tandem repeat (STR) systems located on the male specific part of the human Y chromosome (DYS19, DYS288, DYS385, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393, YCAI, YCAII, YCAIII, DXYS156Y). Amplification parameters and electrophoresis protocols including multiplex approaches were compiled. The typing of non-recombining Y loci with uniparental inheritance requires special attention to population substructuring due to prevalent male lineages. To assess the extent of these subheterogeneities up to 3825 unrelated males were typed in up to 48 population samples for the respective loci. A consistent repeat based nomenclature for most of the loci has been introduced. Moreover we have estimated the average mutation rate for DYS19 in 626 confirmed fatherson pairs as 3.2 x 10(-3) (95% confidence interval limits of 0.00041-0.00677), a value which can also be expected for other Y-STR loci with similar repeat structure. Recommendations are given for the forensic application of a basic set of 7 STRs (DYS19, DYS3891, DYS389II, DYS390, DYS391, DYS392, DYS393) for standard Y-haplotyping in forensic and paternity casework. We recommend further the inclusion of the highly polymorphic bilocal Y-STRs DYS385, YCAII, YCAIII for a nearly complete individualisation of almost any given unrelated male individual. Together, these results suggest that Y-STR loci are useful markers to identify males and male lineages in forensic practice.

DNA Mutational Analysis↗
PubMed1997

Chromosome Y microsatellites: population genetic and evolutionary aspects.

By means of a multicenter study, a large number of males have been characterized for Y-chromosome specific short tandem repeats (STRs) or microsatellites. A complete summary of the allele frequency distributions for these Y-STRs is presented in the Appendix. This manuscript describes in more detail some of the population genetic and evolutionary aspects for a restricted set of seven chromosome Y STRs in a selected number of population samples. For all the chromosome Y STRs markedly different region-specific allele frequency distributions were observed, also when closely related populations were compared. Haplotype analyses using AMOVA showed that when four different European male groups (Germans, Dutch, Swiss, Italians) were compared, less than 10% of the total genetic variability was due to differences between these populations. Nevertheless, these pairwise comparisons revealed significant differences between most population pairs. Assuming a step-wise mutation model and a mutation frequency of 0.21%, it was estimated that chromosome Y STR-based evolutionary lines of descent can be reliably inferred over a time-span of only 1950 generations (or about 49,000 years). This reduces the reliability of the inference of population affinities to a historical, rather than evolutionary time scale. This is best illustrated by the construction of a human evolutionary tree based on chromosome Y STRs in which most of the branches connect in a markedly different way compared with trees based on classical protein polymorphisms and/or mtDNA sequence variation. Thus, the chromosome Y STRs seem to be very useful in comparing closely related populations which cannot probably be separated by e.g. autosomal STRs. However, in order to be used in an evolutionary context they need to be combined with more stable Y-polymorphisms e.g. base-substitutions.

Biological Evolution↗
PubMed1995

Mutation processes at human minisatellites.

Minisatellites provide one of the most experimentally tractable systems for studying tandem repeat instability in man. Analysis of mutation processes has been greatly aided by the development of single molecule methods for recovering de novo mutants, and of techniques for exploring allele structure in detail. Application of these approaches to man has shown that minisatellites do not primarily mutate by processes such as replication slippage and unequal crossover intrinsic to the tandem repeat array. Instead, germline repeat instability is largely regulated by cis-acting elements near the array and involves unexpectedly complex processes of gene conversion, of potential relevance to the biology of meiosis. These processes can be explored both in humans and, in principle, in transgenic mouse models of human repeat instability.

Alleles↗
PubMed1993

A Y chromosome gene family with RNA-binding protein homology: candidates for the azoospermia factor AZF controlling human spermatogenesis.

We have previously mapped the human azoospermia factor to a deletion in Y chromosome interval 6 (subinterval XII-XIV). We now report the isolation and characterization of a gene family located within this deletion. Analysis of the predicted protein products suggests a possible role in RNA processing or translational control during early spermatogenesis. The Y chromosome RNA recognition motif (YRRM) family includes a minimum of three members expressed specifically in the testis. Interphase in situ results and Southern blot analysis indicate that several further YRRM sequences map within interval 6. Several mammalian species show Y chromosome conservation of YRRM sequences. We have detected deletions of YRRM sequences in two oligospermic patients with no previously detectable mutation.

Amino Acid Sequence↗
PubMed1993

Minisatellite variant repeat mapping: application to DNA typing and mutation analysis.

Most DNA typing systems assay allele length variation at tandemly repeated loci such as minisatellites and microsatellites. Allele length measurements are approximate, which impedes the use of such loci in forensic analysis and in studies of allelic variability at hypervariable loci. We now review progress in the development of alternative DNA typing systems based on allelic variation in the interspersion patterns of variant repeat units along minisatellite alleles. Minisatellite variant repeat mapping by PCR (MVR-PCR) not only provides a powerful new digital approach to DNA typing, but also for the first time allows investigation of the true level of allelic variability at minisatellite loci and of the mutational mechanisms that generate ultravariability.

Alleles↗
PubMed1993

Large arrays of tandemly repeated DNA sequences in the green alga Chlamydomonas reinhardtii.

We describe the characterization of tandemly repeated DNA sequences, which resemble the satellite DNA sequences of multicellular eucaryotes, in the unicellular green alga Chlamydomonas reinhardtii. Restriction enzymes that cleave C. reinhardtii DNA relatively frequently produce a number of high molecular weight DNA fragments in addition to the bulk of low molecular weight DNA fragments. pTANC 1.5 contains a 1.5 kb Sau3A fragment cloned from one of these large bands. pTANC 1.5 hybridized to at least three large arrays (200 to 700 kb) of tandemly repeated DNA sequences in the cell-wall-deficient strain cw1.5. These arrays are composed of repeat units that are each cleaved once by BamHl into bands of 1.5, 1.9, 2.0 and 2.5 kb in size. The copy numbers of the 1.5, 1.9, 2.0 and 2.5 kb BamHl bands vary between different C. reinhardtii strains. Chlamydomonas smithii and a number of C. reinhardtii strains are deficient in all four BamHl bands. Genetic analysis of wild-type strain 137c, which is deficient in the 2.0 kb BamHl band, indicates that the 1.5, 1.9 and 2.5 kb BamHl bands derive from at least five loci. The 1.5, 1.9 and 2.5 kb repeat units are not extensively interspersed with each other in strain 137c. Pulsed-field gel electrophoresis of intact C. reinhardtii chromosomes indicates that TANC arrays are present on more than one chromosome.

Animals↗