Elektronenmikroskopische Autoradiographie mit H3-Thymidin an der Thymusrinde der Maus

Zusammenfassung Ultradünnschnitte durch die Thymusrinde erwachsener männlicher Mäuse wurden mit einer Einkristallschicht von Ilford-L 4-Photoemulsion überzogen. In elektronenmikroskopischen Autoradiogrammen können die mit H³-Thymidin markierten Zelltypen besser erkannt werden als in lichtmikroskopisch-autoradiographischen Untersuchungen am gleichen Gewebe.Den größten Anteil der freien Zellen stellen die kleinen Lymphocyten mit dichten, von wenigen Ausnahmen abgesehen, unmarkierten Kernen und schmalem Zytoplasmasaum. In der subkapsulären Zone finden sich gehäuft große Lymphozyten und ihre Vorstufen mit einem umfangreichen, nicht so dichten Kern und einem breiteren, freie Ribosomen enthaltenden Zytoplasmasaum. 83% der Kerne dieser Zellen sind deutlich markiert. Die epithelialen Retikulumzellen im Inneren der Rinde und das Randepithel haben unmarkierte Kerne. Nur vereinzelt werden markierte Retikulumzellen unmittelbar unter dem Randsaum gefunden. Plasmazellen sind in der Rinde nur selten zu finden. Ihre Kerne weisen keine Markierung auf. Die lichtmikroskopisch-autoradiographisch erhobenen Befunde von Hinrichsen (1963, 1965) werden elektronenmikroskopisch bestätigt: Bei der Maus stellt die unmittelbar unter der Kapsel liegende Randzone des Thymus die Keimschicht zur Bildung von Thymuslymphozyten dar.

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Summary Sections of the thymus of adult male mice were covered with Ilford-L 4 photographic emulsion. In electron microscopic autoradiograms, the labelled cell types after H³-thymidine injection — can be more easily identified than with light microscopic autoradiographic methods.Most of the free cells are small lymphocytes with dense, mostly unlabelled nuclei and scanty cytoplasm. In the sub-capsular zone larger lymphocytes with a bigger, but not so condensed nucleus and more extensive cytoplasm containing free ribosomes can be found. 83% of their nuclei are labelled with tritiated thymidine. The nuclei of epithelial reticulum cells in the inner cortex and the surface epithelium are unlabelled. Only very few labelled reticulum cells can be found immediately under the connective tissue layer. Plasma cells are rarely found in the cortex. Their nuclei are not labelled. The light microscopic autoradiographic findings by Hinrichsen (1963, 1965) are electronmicroscopically confirmed: the lymphocytes of the mouse thymus originate in the immediately sub-capsular cortex of the thymus.

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Herrn Professor Bargmann zum 60. Geburtstag gewidmet.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Loss of Central Auditory Processing in a Mouse Model of Canavan Disease

Canavan Disease (CD) is a leukodystrophy caused by homozygous null mutations in the gene encoding aspartoacylase (ASPA). ASPA-deficiency is characterized by severe psychomotor retardation, and excessive levels of the ASPA substrate N-acetylaspartate (NAA). ASPA is an oligodendrocyte marker and it is believed that CD has a central etiology. However, ASPA is also expressed by Schwann cells and ASPA-deficiency in the periphery might therefore contribute to the complex CD pathology. In this study, we assessed peripheral and central auditory function in the Aspa^lacZ/lacZ rodent model of CD using auditory brainstem response (ABR). Increased ABR thresholds and the virtual loss of waveform peaks 4 and 5 from Aspa^lacZ/lacZ mice, indicated altered central auditory processing in mutant mice compared with Aspa^wt/wt controls and altered central auditory processing. Analysis of ABR latencies recorded from Aspa^lacZ/lacZ mice revealed that the speed of nerve conduction was unchanged in the peripheral part of the auditory pathway, and impaired in the CNS. Histological analyses confirmed that ASPA was expressed in oligodendrocytes and Schwann cells of the auditory system. In keeping with our physiological results, the cellular organization of the cochlea, including the organ of Corti, was preserved and the spiral ganglion nerve fibres were normal in ASPA-deficient mice. In contrast, we detected substantial hypomyelination in the central auditory system of Aspa^lacZ/lacZ mice. In summary, our data suggest that the lack of ASPA in the CNS is responsible for the observed hearing deficits, while ASPA-deficiency in the cochlear nerve fibres is tolerated both morphologically and functionally.     

A New Method to Compare Statistical Tree Growth Curves: The PL-GMANOVA Model and Its Application with Dendrochronological Data

Growth curves are monotonically increasing functions that measure repeatedly the same subjects over time. The classical growth curve model in the statistical literature is the Generalized Multivariate Analysis of Variance (GMANOVA) model. In order to model the tree trunk radius (r) over time (t) of trees on different sites, GMANOVA is combined here with the adapted PL regression model Q = A·T+E, where for and for , A =  initial relative growth to be estimated, , and E is an error term for each tree and time point. Furthermore, Ei[–b·r]  = , , with TPR being the turning point radius in a sigmoid curve, and at is an estimated calibrating time-radius point. Advantages of the approach are that growth rates can be compared among growth curves with different turning point radiuses and different starting points, hidden outliers are easily detectable, the method is statistically robust, and heteroscedasticity of the residuals among time points is allowed. The model was implemented with dendrochronological data of 235 Pinus montezumae trees on ten Mexican volcano sites to calculate comparison intervals for the estimated initial relative growth . One site (at the Popocatépetl volcano) stood out, with being 3.9 times the value of the site with the slowest-growing trees. Calculating variance components for the initial relative growth, 34% of the growth variation was found among sites, 31% among trees, and 35% over time. Without the Popocatépetl site, the numbers changed to 7%, 42%, and 51%. Further explanation of differences in growth would need to focus on factors that vary within sites and over time.     

Shifts in an invasive rodent community favoring Black rats (Rattus rattus) following restoration of native forest

One potential, unintended ecological consequence accompanying forest restoration is a shift in invasive animal populations, potentially impacting conservation targets. Eighteen years after initial restoration (ungulate exclusion, invasive plant control, and out planting native species) at a 4 ha site on Maui, Hawai'i, we compared invasive rodent communities in a restored native dry forest and adjacent non‐native grassland. Quarterly for 1 year, we trapped rodents on three replicate transects (107 rodent traps) in each habitat type for three consecutive nights. While repeated trapping may have reduced the rat (Black rat, Rattus rattus) population in the forest, it did not appear to reduce the mouse (House mouse, Mus musculus) population in the grassland. In unrestored grassland, mouse captures outnumbered rat captures 220:1, with mice averaging 54.9 indiv./night versus rats averaging 0.25 indiv./night. In contrast, in restored native forest, rat captures outnumbered mouse captures by nearly 5:1, averaging 9.0 indiv./night versus 1.9 indiv./night for mice. Therefore, relatively recent native forest restoration increased Black rat abundance and also increased their total biomass in the restored ecosystem 36‐fold while reducing House mouse biomass 35‐fold. Such a community shift is worrisome because Black rats pose a much greater threat than do mice to native birds and plants, perhaps especially to large‐seeded tree species. Land managers should be aware that forest restoration (i.e. converting grassland to native forest) can invoke shifts in invasive rodent populations, potentially favoring Black rats. Without intervention, this shift may pose risks for intended conservation targets and modify future forest restoration trajectories.     

Linkage to Xq28 in a family with nonspecific X-linked mental retardation

Linkage analysis was performed in a family with nonspecific X-linked mental retardation (MRX). Affected individuals had no clinical characteristics other than mental retardation. Linkage was detected to the marker loci DXS477, DXS465, DXS52, DXS15 and F8C with maximum lod scores of 1.70, 1.32, 2.52, 1.70, and 1.09, respectively ( = 0.0). The results strongly indicate that the gene for mental retardation in the family studied maps close to DXS52.     

Removal of Mercury from Chloralkali Electrolysis Wastewater by a Mercury-Resistant Pseudomonas putida Strain

A mercury-resistant bacterial strain which is able to reduce ionic mercury to metallic mercury was used to remediate in laboratory columns mercury-containing wastewater produced during electrolytic production of chlorine. Factory effluents from several chloralkali plants in Europe were analyzed, and these effluents contained total mercury concentrations between 1.6 and 7.6 mg/liter and high chloride concentrations (up to 25 g/liter) and had pH values which were either acidic (pH 2.4) or alkaline (pH 13.0). A mercury-resistant bacterial strain, Pseudomonas putida Spi3, was isolated from polluted river sediments. Biofilms of P. putida Spi3 were grown on porous carrier material in laboratory column bioreactors. The bioreactors were continuously fed with sterile synthetic model wastewater or nonsterile, neutralized, aerated chloralkali wastewater. We found that sodium chloride concentrations up to 24 g/liter did not inhibit microbial mercury retention and that mercury concentrations up to 7 mg/liter could be treated with the bacterial biofilm with no loss of activity. When wastewater samples from three different chloralkali plants in Europe were used, levels of mercury retention efficiency between 90 and 98% were obtained. Thus, microbial mercury removal is a potential biological treatment for chloralkali electrolysis wastewater.