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S Meuser

Publications and source records attributed to S Meuser.

8 recordsLinked to original sources
PubMed2000

The retinal determination gene, dachshund, is required for mushroom body cell differentiation.

The dachshund gene of Drosophila encodes a putative transcriptional regulator required for eye and leg development. We show here that dachshund is also required for normal brain development. The mushroom bodies of dachshund mutants exhibit a marked reduction in the number of (&agr;) lobe axons, a disorganization of axons extending into horizontal lobes, and aberrant projections into brain areas normally unoccupied by mushroom body processes. The phenotypes become pronounced during pupariation, suggesting that dachshund function is required during this period. GAL4-mediated expression of dachshund in the mushroom bodies rescues the mushroom body phenotypes. Moreover, dachshund mutant mushroom body clones in an otherwise wild-type brain exhibit the phenotypes, indicating an autonomous role for dachshund. Although eyeless, like dachshund, is preferentially expressed in the mushroom body and is genetically upstream of dachshund for eye development, no interaction of these genes was detected for mushroom body development. Thus, dachshund functions in the developing mushroom body neurons to ensure their proper differentiation.

Animals↗
PubMed1998

Tandem repeat structure of the duplicated Y-chromosomal STR locus DYS385 and frequency studies in the German and three Asian populations.

The Y-chromosomal short tandem repeat (STR) locus DYS385 can be typed using PCR amplification and separation of the resulting polymorphic fragments by non-denaturing high resolution polyacrylamide gel electrophoresis followed by silver staining. The PCR primers amplify a duplicated repeat sequence on the Y chromosome revealing a two-band pattern in male individuals. To determine the internal repeat structure as a basis for a consensus nomenclature, DNA sequence analysis was carried out after subcloning of PCR-amplified fragments revealing the uniform 4-bp repeat structure 'GAAA'. The shortest allele observed consisted of 10 repeat units thus providing the basis for the designation 'allele 10'. Except for isolated point mutations, no systematic differences could be observed either in the repeat sequence or in the flanking regions between the two fragments of a given individual. Thus it was not possible to discriminate between the two loci of the DYS385 system. Four population samples of German (n = 146), Chinese (n = 100), Japanese (n = 100), and Thai (n = 95) origin were studied. In the four groups, alleles 10 to 24 could be observed and genotype frequencies differed significantly. In Germans only one common genotype was present (11-14; 33.8% frequency). In the Asian populations, the frequencies were more evenly distributed with the 13-13 genotype (9%) in Chinese, the 13-17 genotype (14%) in Japanese and the 14-18 genotype (7%) in Thai being the most common. Overall, 69 different genotypes were found, of these 36 were observed in Germans, 36 in Chinese, 33 in Japanese and 44 in Thai. No mutations were detected in 62 father-son pairs. Thus DYS385 is a highly polymorphic STR system with population-specific genotype distributions.

Asia, Southeastern↗
PubMed1998

Programmed cell death specifically eliminates one part of a locust pleuroaxillary muscle after the imaginal moult

In the hemimetabolous insect Locusta migratoria, fundamental restructuring occurs at the transition from flightless nymph to flight-capable adult. This transition involves all components of the flight circuit, which is present but not used for flight in nymphs. The meso- and metathoracic pleuroaxillary muscles, M85 and M114 respectively, constitute one component of this circuit. In the adult locust, these are flight-steering muscles, but their function in the nymph is as yet unknown. Our study reveals that adult and nymphal metathoracic pleuroaxillary muscles M114 differ profoundly. The nymphal muscle contains the distinct part M114c in addition to parts M114a and M114b characteristic of the adult. The contractions of M114c are slow and long-lasting, corresponding to its long sarcomeres and slow form of ATPase, and contrast with the adult muscle parts M114a and M114b in all of these features. We demonstrate a hormone-dependent degeneration of M114c after the adult moult. This degeneration can be blocked by actinomycin D and cycloheximide. It may thus be termed genetically programmed cell death, triggered after the adult moult and, as demonstrated here, functioning via the ATP-dependent ubiquitin pathway. Given the defined onset of degeneration after the adult moult, it is possible that M114c may fulfil a specific function in nymphs, during or shortly after moulting.

Journal Article↗
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↗
PubMed1997

Octopaminergic innervation and modulation of a locust flight steering muscle

We demonstrate that the meso- and metathoracic pleuroaxillary flight steering muscle (M85 mesothorax, M114 metathorax) of the migratory locust are each innervated by a single dorsal unpaired median neurone (DUM3,4,5a). The soma of this neurone can be localized by retrograde staining of the motor nerve with Neurobiotin, but not with cobalt salts. The primary neurite projects in the superficial DUM cell tract, and the axons run in nerve roots 3, 4 and 5 and in all their secondary branches. Other muscle targets include the second tergal remotor coxa (M120) and the posterior rotator coxae (M122, M123, M124), but not the first tergal remotor coxa (M119) and subalar (M129) flight muscles. Octopamine-like immunoreactive varicosities occur on the pleuroaxillary muscles. Stimulation of DUM3,4,5a and octopamine (10(-6) mol l-1) superfusion increased the amplitude and the relaxation velocity of neurally evoked twitch contractions of this muscle. Octopamine also significantly reduced the tonic tension that this muscle develops when stimulated at flight frequency (20 Hz), while increasing the amplitude of each phasic twitch. A catch-like tension is also reduced in the presence of octopamine. Simulations of the motor pattern experienced by the pleuroaxillary muscles during roll manoeuvres suggest that transient changes in tension underlying corrective steering could be doubled in the presence of octopamine.

Journal Article↗