Underlying physiological control of reproduction in urban and forest-dwelling European blackbirds Turdus merula

The development and the continual expansion of urban areas have not only destroyed natural habitats, but also have drastically changed the environmental and ecological conditions of these areas. Consequently, species that have settled in these new man-made ecosystems are exposed to considerable alternations in environmental conditions compared to their 'wild' conspecifics. To understand the impact of human-induced environmental changes on life history events such as reproduction, we compared the timing of the reproductive season and its underlying endocrine control in free-living European blackbirds Turdus merula inhabiting urban and nearby forest areas. Body mass, fat score, gonadal size, luteinizing hormone (LH), testosterone (T), and estradiol (E₂) were measured. Urban blackbirds developed their gonads approximately three weeks earlier than forest birds, whereas the timing of gonadal regression did not differ. There are several factors (e.g. artificial light, temperature, food availability, and social cues) which may have caused the differences in the temporal organization of gonadal growth between the urban and forest-living populations. The advanced gonadal development of urban blackbirds did not coincide with an earlier secretion of reproductive hormones. In contrast, urban males had lower plasma LH and T levels during testicular growth than forest males. Differences in social interactions and environmental conditions may explain the contrast of gonadal development and the timing of hormone secretion between urban and forest blackbirds.     

Tn916-induced mutations in the hemolysin determinant affecting virulence of Listeria monocytogenes.

A genetic determinant essential for hemolysin production by Listeria monocytogenes has been inactivated by insertion of transposon Tn916 into L. monocytogenes DNA. The transposon was transferred by means of conjugation of a streptomycin-resistant L. monocytogenes recipient strain with Streptococcus faecalis CG110 on membrane filters. Among the tetracycline-resistant transconjugants, mutants were detected which had lost hemolytic activity. When tested in a mouse model, these mutants appeared to have lost the virulence that characterizes the parental strain. An extracellular protein of 58,000 apparent molecular weight was eliminated in the nonhemolytic mutants. In some of the mutants, the decrease in the production of the 58,000-dalton protein was accompanied by the production of a new protein of 49,000 apparent molecular weight. Hemolytic revertants regained the hemolytic phenotype and virulence and produced the extracellular protein that characterizes the recipient strain. Hybridization studies with Tn916 DNA indicated that the transposon is present in EcoRI and HindIII fragments of the nonhemolytic mutants. Single copies of Tn916 were detected in the chromosomal DNA of two of the three nonhemolytic mutants that were studied in detail. In hemolytic, tetracycline-sensitive revertants Tn916 appeared to be completely excised from the chromosome.     

Carbohydrates of influenza virus. Structure of the oligosaccharides linked to asparagines 406 and 478 in the hemagglutinin of fowl plague virus,strain dutch

Fowl plague virus, strain Dutch, was metabolically labeled withd-[2-³H]mannose, or withd-[6-³H]glucosamine, and the small subunit (HA₂; 0.8 mg in total) of the viral hemagglutinin was isolated by preparative sodium dodecylsulfate-polyacrylamide gel electrophoresis. After proteolytic digestion, the radioactive oligosaccharides were sequentially liberated from the glycopeptides by treatment with different endo--N-acetylglucosaminidases and with peptide:N-glycosidase or, finally, by hydrazinolysis. In this manner, four groups of glycans could be obtained by consecutive gel filtrations and were subfractionated by HPLC. The structures of the individual oligosaccharides were analyzed by micromethylation, by acetolysis or by digestion with exoglycosidases. The major species amongst the high mannose glycans at Ans-406 of the viral glycopolypeptide were found to be Man1-2Man1-3(Man1-2Man1-6)Man1-6(Man1-2Man1-2Man1-3)Man1-4GlcNac1-4GlcNAc and Man1-3(Man1-2Man1-6)Man1-6(Man1-2Man1-2Man1-3)Man1-4GlcNAc1-4GlcNAc, while the complex glycans at Asn-478 are predominantly GlcNAc1-2Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc (lacking, in part, one of the outerN-acetylglucosamine residues) and GlcNAc1-2Man1-3(Gal1-4GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc.Abbreviation BSA bovine serum albumin - endo D (F,H) endo--N-acetyl-d-glucosaminidase D (F,H) - HA hemagglutinin (HA₁, large subunit of HA - HA₂ small subunit - FPV fowl plague virus - PNGase F peptide:N-glycosidase F - SDS sodium dodecylsulfate     

Investigation of Dopamine Content, Synthesis, and Release in the Rabbit Retina In Vitro: I. Effects of Dopamine Precursors, Reserpine, Amphetamine, and l-DOPA Decarboxylase and Monoamine Oxidase Inhibitors

The basal catecholamine content of rabbit retina was determined by liquid chromatography with electrochemical detection (LC-EC) and 3,4-dihydroxyphenylethylamine (dopamine, DA) found to be the major catecholamine. The immediate DA precursor, 3,4-dihydroxyphenylalanine (L-DOPA), and the metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were also detected at about 2.8% and 17% of DA levels, respectively. When added exogenously, L-tyrosine did not increase the rate of DA synthesis over the basal level. In contrast, exogenous L-DOPA led to a 3.5-fold increase in DA, and to a 20-fold increase in DOPAC content. The monoamine oxidase inhibitors pargyline and (-)-deprenyl differentially affected the degradation of DA, since 100 microM pargyline was apparently more effective than 100 microM (-)-deprenyl. Reserpine and (+/-)-amphetamine each induced a Ca2+-independent decrease of DA stores. The separate actions of reserpine and (+/-)-amphetamine in lowering tissue DA levels were additive, suggesting two separate pools of DA available for release from presynaptic stores. The present study demonstrates that the LC-EC technique may be used to investigate the modulation of the synthesis and release of retinal DA in vitro, without the prior uptake of radiolabelled transmitter.     

Steady-state response of quadriplegic subjects to inspiratory resistive load

Normal subjects preserve tidal volume (VT) in the face of added inspiratory resistance by increasing maximal amplitude and duration of the rising phase of respiratory driving pressure (DP) and by changing the shape of this phase to one that is more concave to the time axis. To explore the possible role of chest wall afferents in mediating these responses, we determined averaged DP in eight quadriplegic subjects during steady-state unloaded breathing and while breathing through an inspiratory resistance (8.5 cmH2O X 1(-1) X s). As with normal subjects, quadriplegics preserved VT (loaded VT = 106% control) by utilizing all three mechanisms. However, prolongation of the inspiratory duration derived from the DP waveform (+22% vs. +42%) and shape response were significantly less in the quadriplegic subjects. Shape response was completely absent in subjects with C4 lesions. The results provide strong evidence that respiratory muscle spindles are responsible for shape response and that changes in afferent feedback from the chest wall play an important role in mediating inspiratory prolongation.     

A smooth muscle cell line suitable for the study of voltage sensitive calcium channels

A cell line originating from the fetal rat aorta has been studied with respect to 45Ca2+ uptake. Kinetic experiments showed an initial rapid uptake followed by a slow linear phase; both the initial rate and the maximum uptake were increased in the presence of 55 mM potassium chloride. The calcium channel antagonists, darodipine (PY 108-068) and verapamil, inhibited both the basal and the potassium chloride stimulated uptake. Neither tetrodotoxin nor furosemide affected either basal or depolarisation induced 45Ca2+ uptake. Blockade of the Na+/K+ ATPase by ouabain and of the Ca2+ ATPase by vanadate caused a net increase in cellular 45Ca2+ accumulation.     

On the Phospholipid Metabolism of Glial Cell Primary Cultures.

Abstract: Primary cultures were prepared from newborn rat brain. After 16-18 days, they consisted mainly of mature and immature astrocytes and oligodendrocytes, as judged by immunohistochemistry. To study the metabolism of ethanolamine glycerophospholipids, the cells were incubated with 1-[1-³H]alkyl- sn -glycero-3-phosphoethanolamine (1-alkyl-GPE), for 1–20 h. Five main products were formed: 1-alkyl-2-acyl-GPE; 1-alkyl-2-acyksn-glycero-3-phosphocholine (1-alkyl-2-acyl-GPC); 1-alkenyl-2-acyl-GPE (ethanolamine plasmalogen); 1-alkenyl-2-acyl-GPC (choline plasmalogen); and 1-alkyl-glycerol. Acylation of the substrate was the main reaction during the first 3 h of incubation, whereas desaturation to plasmaiogen reached a maximum after 12 h. Greater amounts of radioactivity were observed in the phosphatidylcholine fraction after longer incubation times. Only small amounts of choline plasmalogen were observed. The phosphatidylethanolamine fraction consisted of 26.5% diacyl-, 27.5% alkyl-acyl-, and 46.0% alkenyl-acyl- compounds, whereas the corresponding data for the phosphatidylcholine fraction were 78.5, 16.4, and 5.1%, respectively, after 20 h of incubation. Hydrolysis of the substrate to 1-alkyl-glycerol was a minor reaction.     

Mechanisms of cell differentiation: Affinity of a morphogenetic factor to DNA

Summary A morphogenetic factor which induces inTriturus gastrula ectoderm tissues which are derived from mesoderm and endoderm has been extracted from chicken and amphibian embryos. The factor which is protein in nature has been obtained from chicken embryos in a highly purified state.The biological activity of the chicken factor is partially inhibited when the factor is combined with chicken DNA or sonicated chicken DNA.When the 3H-labelled factor is combined with sonicated DNA and then centrifuged on a sucrose gradient the factor migrates in part with the DNA. This indicates that the factor is bound to DNA.The inferences from these results are discussed with regard to the possible mechanism of action of the factor and the molecular mechanism of differentiation.     

Genduplikation durch polyploide Evolution: die Isoenzyme der Sorbitdehydrogenase bei herings- und lachsartigen Fischen (Isospondyli)

Zusammenfassung Die elektrophoretische Analyse der Isoenzyme der Sorbitdehydrogenase (SDH) bei verschiedenen Säugerspecies unter Einschluß des Menschen läßt darauf schließen, daß bei Säugern nur 1 Genlocus für dieses Enzym existiert. Auch bei Knochenfischen läßt sich in der Regel nur 1 SDH-Gen nachweisen. Eine Ausnahme bilden einige Species der Fischordnung Isospondyli. Innerhalb dieser Ordnung findet sich eine Diploid-tetraploid-Beziehung. Arten mit diploiden Charakteristika wie der Hering (Clupea harengus) besitzen 1 SDH-locus, an dem 3 Allele zu beobachten waren. Bei einigen phylogenetisch tetraploiden lachsartigen Fischen läßt sich eine Duplikation des SDH-Gens nachweisen. Während bei der Bachforelle (Salmo trutta) die nach der Tetraploidisierung zunächst identischen loci sich divergent entwickelt haben und jetzt diploidisiert sind, zeigen Regenbogenforelle (Salmo irideus) und Blaufelchen (Coregonus lavaretus) tetrasome Phänotypen der SDH. Beim Blaufelchen findet sich ein Überschuß an Heterozygoten, der auf eine meiotische Vorzugspaarung der Chromosomen mit identischen Allelen schließen läßt. Diese Befunde geben Einblick in den Mechanismus der Diploidisierung, der in der Evolution der höheren Wirbeltiere eine wesentliche Rolle gespielt haben dürfte.

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Sorbitol dehydrogenase isozymes in clupeoid fish: a further example of gene duplication through polyploid evolution

Summary Electrophoretic analysis of the sorbitol dehydrogenase isozymes (SDH) in various mammalian species including man revealed the existence of only 1 gene locus for this enzyme. As a rule, the same is true for Teleostean fishes. Some species of the fish order Isospondyli, however, represent an exception. Within this order, a diploid-tetraploid relationship exists. Species exhibiting diploid characteristics as the herring (Clupea harengus), are endowed with a single SDH gene locus at which 3 different alleles were observed. In some Salmonoid fish having passed through tetraploid evolution, a duplication of the SDH gene can be demonstrated. While in Salmo trutta the duplicated genes evolved divergently and became diploidized, in Salmo irideus and Coregonus lavaretus tetrasomic phenotypes occur. In Coregonus, the predominance of heterozygotes is to be interpreted as the consequence of preferential pairing of meiotic chromosomes endowed with identical alleles. These findings give some insight in the diploidization mechanism which may have played an important role during evolution of higher vertebrates.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.