Cell surface T3 expression requires the presence of both alpha- and beta-chains of the T cell receptor

We have identified a surface T3- Jurkat variant which has a defective alpha-chain but which possesses an intact beta-chain. The transfection of a functional mouse alpha-chain into this human T cell induces the expression of surface T3 molecules associated with mouse alpha-human beta-heterodimers detected by anticlonotypic antibodies. Treatment of the transfectant with anti-T3, anti-mouse Ti-alpha, or anti-human Ti-beta antibodies clears all Ti-T3 complexes from the surface. These results demonstrate that functional alpha- and beta-chains are both required for expression of T3 on the cell membrane, and that the Ti heterodimers present and associated with T3 on Jurkat cells involve only alpha- and beta-chains.     

Three-dimensional reconstruction of a human metaphase chromosome from electron micrographs

A complete human metaphase chromosome has been reconstructed from a series of electron microscopical projections obtained by tilting the specimen stage at 3 degree intervals from –60 to +60 degrees. The reconstructed structure is about 3.0 m long, 1.6 m wide, and 0.8 m thick. The mass distribution was fairly homogeneous within the chromatids and neither a hollow nor a dense core was observed. The distribution and course of fibers observed are most consistent with a looping model of chromosome structure.     

Die Bestandsentwicklung von Kleinv?geln in Mitteleuropa: Analyse von Fangzahlen

Zusammenfassung Im Mettnau-Reit-Illmitz-Programm (MRI-Programm) der Vogelwarte Radolfzell wurden von 1974–1983 auf drei Fangstationen in Süddeutschland, Norddeutschland und Ostösterreich (Abb. 1) 184 939 Vögel von 37 Kleinvogelarten gefangen. Die Fänge erfolgten jährlich während der gesamten Wegzugperiode von Ende Juni bis Anfang November an Durchzüglern in Japannetzen unter strikter und umfassender Standardisierung aller Fang- und Arbeitsmethoden. Die Fangzahlen (Tab. 1, Abb. 2–6) werden in fünf Regressionsanalysen (Tab. 2–9) auf systematische Änderungen untersucht.Von insgesamt 496 errechenbaren Koeffizienten waren 317 oder 63,9% negativ und nur 179 oder 38,1 % positiv. Bei 34 der 37 untersuchten Arten ließen sich signifikante Trends errechnen. Sie sind für 20 oder 54 % dieser Arten ausschließlich oder überwiegend negativ. 14 Arten zeigten mindestens auf zwei Stationen negative Trends. Nur für insgesamt 10 Arten ließen sich überwiegend positive Trends errechnen. Faßt man negative Trends und Tendenzen (Vorzeichen) zusammen, so ergibt sich für 26 oder 70 % der untersuchten Arten ein negatives Bild. Dieses stark negative Gewicht ist im statistischen Sinne keine zufällige Erscheinung. Da die Bestandszunahmen die Abnahmen nicht aufwiegen konnten, zeigten auch die jährlichen Gesamtfangzahlen aller drei Stationen negative Trends. Die mittlere jährliche Abnahme betrug auf den Stationen Mettnau, Reit und Illmitz etwa 1,6 %. Die Tendenzen und Trends der einzelnen Arten stimmen auf den drei Stationen weitgehend überein. Sie lassen für ihr Zustandekommen auf weitgehend gleichförmige Ursachen bei den durch Mitteleuropa wandernden Populationen schließen.Die Fangzahlen und Literaturdaten zeigen, daß beträchtliche Teile unserer Kleinvogelwelt von Rückgangserscheinungen betroffen sind, wie wir sie von vielen Großvogelarten seit langem kennen. Bei einer Reihe von Arten sind die Abnahmen gravierend und die jährlichen Fangzahlen inzwischen so niedrig, daß sich bei ihnen mit den in den 70er Jahren konzipierten Fanganlagen eine Reihe von Fragestellungen nicht mehr untersuchen lassen. Wir können der weiteren Entwicklung der Bestände unserer derzeit noch artenreichen Kleinvogelwelt — wie der vieler Großvögel — nur mit größter Sorge entgegensehen. Die Ursachen der Rückgänge sind weitgehend unbekannt, und demzufolge mangelt es fast vollständig an geeigneten Gegenmaßnahmen. Bisherige Schutzmaßnahmen haben die Rückgänge nicht aufhalten können. Künftiger Vogelschutz wird sich folglich weitergehender Maßnahmen bedienen müssen.

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The development of songbird populations in central Europe: Analysis of trapping data

Summary In the Mettnau-Reit-Illmitz-Program (MRI-Program) of the Vogelwarte Radolfzell 184 939 birds of 37 songbird species were caught in the period 1974–1983 on three trapping stations in S. and N. Germany and E. Austria (Fig. 1). Trapping of passage migrants in mist nets occurred annually from the end of June to the beginning of November, the entire autumn migratory period. All trapping and working methods were strictly and comprehensively standardized. The trapping figures (Tab. 1, Fig. 2–6) were analyzed with respect to systematic alterations to gain information about changes in the population levels of species migrating through central Europe. The investigation is based above all on five regression analyses (Tab. 2–9).The most important individual results are: out of a total of 496 coefficients which could be calculated 317 or 63.9 % were negative and only 179 or 38.1 % positive. For 34 of the 37 investigated species significant trends could be calculated. In 20 or 54 % of these species they were (exclusively or predominately) negative. 14 species showed negative trends at least at two stations. Mainly positive trends could be found in only 10 species. Taking negative trends and tendencies (negative signs) together, 26 or 70 % of the species were included. This strongly negative bias is not accidental in a statistical sense. Since the increases could not balance the declines, the annual trapping totals of all three stations also showed negative trends. The mean annual decline in the stations Mettnau, Reit and Illmitz was about 1.6 %. Trends and tendencies of the species show a high degree of agreement for the three stations. This suggests that in the species migrating through central Europe rather uniform factors control the population levels. From the most recent literature results, it appears that most of the species with declining trapping figures in the MRI-Program demonstrate decreases elsewhere.The trapping figures of the MRI-Program and data from the literature together clearly indicate that considerable parts of our small birds are affected by declines as have been known in many large bird species for long time. In a number of species the decreases have been quite dramatic and their annual trapping totals are now so low that a number of problems can no longer be studied. We should be alarmed when considering this negative development among our small birds as we must be with respect to many large bird species. The reasons for the declines are almost unkown and thus there is lack of appropriate counter-measures. Hitherto existing efforts for conservation which are briefly discussed have not been able to prevent the decline. Consequently, bird conservation in the future has to be based on more effective methods. Proposals, briefly raised, will be discussed in a forthcoming paper.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft und gefördert mit Hilfe von Forschungsmitteln des Landes Niedersachsen. 15. Mitteilung aus dem MRI-Programm     

STUDY OF MITOCHONDRIA IN RAT LIVER : Quantitative Electron Microscopy

The electron microscope has been used to determine the weight distribution of isolated subcellular particles from normal rat liver. The following results are reported: (1) There exist at least two well defined weight populations of subcellular particles; their respective median weights are 1.3 x 10^-14 and 11 x 10^-14 gm. The lighter fraction is considered to consist of lysosomes, the heavier of mitochondria. (2) The mitochondrial fraction shows a log-normal distribution of the particle weight. (3) By the introduction of morphologic criteria, the mitochondrial fraction is divided into two groups, one consisting of a spherical, the other of an oblong type of particle. The data found support the following concepts: (a) Mitochondria increase their weight from a certain size up by linear growth. (b) Mitochondria divide. The division is not necessarily symmetric; in all cases, however, one part of the division product is a spherical particle. It is felt that these results constitute a valuable demonstration of the general capabilities of quantitative electron microscopy and may stimulate many other useful applications of this technique in cytology, bacteriology, and virology.     

The carbonyl reactivity of 3-bromopyruvate and related compounds

The covalent hydration of β-halopyruvic acids and β-halopyruvamides has been investigated in the uv region by stopped-flow techniques. In aqueous solutions of β-bromopyruvate and related compounds, the geminal diol is the predominant form at all pH values. Kinetic investigations have also been carried out on these hydrations. General bases enhance the rate of approaching the equilibrium. Specific acid catalysis was not detected. In the water-catalyzed reaction of pyruvamides, the relationship between the equilibrium constants K and the rate constants of the forward reaction shows that the transition state is more productlike.     

An electron paramagnetic resonance study of Mn2+ uptake by the chick chorioallantoic membrane.

Mn2+ uptake in the chick chorioallantoic membrane, an embryonic epithelial tissue which transports Ca2+ in vivo was studied using electron paramagnetic resonance (EPR). Mn2+ was used as a paramagnetic analog for Ca2+, since there is evidence that Mn2+ is accumulated by the Ca2+ transport mechanism. After 1.5 h of uptake the EPR spectrum of the Mn2+ in the membrane indicated that 89% of the Mn2+ was in a spin-exchange form, indicating close packing of Mn2+. The Mn2+ spacing was estimated from the line width to be about 4.7 A. The remaining Mn2+ was very likely Mn2+ hexahydrate. At pH 7.4 the spin-exchange spectrum tended to broaden when uptake was inhibited, while at pH 5.0 the spin-exchange spectrum was completely abolished in the presence of inhibitors. The EPR spectrum of Mn2+ in the chorioallantoic membrane had a broader line width than that of Mn2+ in isolated mitochondria, suggesting that in this tissue mitochondria are not directly involved in divalent cation transport. These EPR studies support the concept that divalent cations are sequestered in high concentrations from the rest of the cell contents during transcellular active transport.     

Assessing sub-seafloor microbial activity by combined stable isotope probing with deuterated water and 13C-bicarbonate

Sub‐seafloor sediments are populated by large numbers of microbial cells but not much is known about their metabolic activities, growth rates and carbon assimilation pathways. Here we introduce a new method enabling the sensitive detection of microbial lipid production and the distinction of auto‐ and heterotrophic carbon assimilation. Application of this approach to anoxic sediments from a Swedish fjord allowed to compare the activity of different functional groups, the growth and turnover times of the bacterial and archaeal communities. The assay involves dual stable isotope probing (SIP) with deuterated water (D₂O) and ¹³C_DIC (d issolved i norganic c arbon). Culture experiments confirmed that the D content in newly synthesized lipids is in equilibrium with the D content in labelled water, independent of whether the culture grew hetero‐ or autotrophically. The ratio of ¹³C_DIC to D₂O incorporation enables distinction between these two carbon pathways in studies of microbial cultures and in environmental communities. Furthermore, D₂O‐SIP is sufficiently sensitive to detect the formation of few hundred cells per day in a gram of sediment. In anoxic sediments from a Swedish fjord, we found that > 99% of newly formed lipids were attributed to predominantly heterotrophic bacteria. The production rate of bacterial lipids was highest in the top 5 cm and decreased 60‐fold below this depth while the production rate of archaeal lipids was rather low throughout the top meter of seabed. The contrasting patterns in the rates of archaeal and bacterial lipid formation indicate that the factors controlling the presence of these two lipid groups must differ fundamentally.