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.     

The effects of abscisic acid on growth and respiratory characteristics of potato tuber tissue discs

Incubation of potato tuber tissue discs on B5 medium supplemented with 1-naphtyl-acetic acid (NAA) led to callus formation, irrespective of the presence of kinetin; without NAA no callus formation occurred. Incubation in the presence of abscisic acid (ABA) reduced the increases in fresh weight and dry weight both in callus-forming and in non-callus-forming tissue. Mitochondrial respiration was lowered by ABA as well. The induction of the alternative, CN-resistant pathway was inhibited by the presence of ABA, especially in mitochondria from non-callus-forming tissue.The in vivo respiration of the callus-forming tissue was higher than that of the non-callus-forming tissue. Total respiration, cytochrome pathway activity and the capacity of the alternative pathway were all lowered in callus-forming tissue by treatment with ABA. The in vivo activity of the alternative pathway was low in all tissue types, especially after ABA-treatment. The slight stimulation by hydroxamates of the oxygen uptake of callus-forming tissue incubated on medium with NAA and ABA indicates the involvement of a hydroxamate-activated peroxidase in the oxygen uptake of this tissue; this peroxidase seemed not to participate in the oxygen uptake of the other tissues types.In non-callus-forming tissue the oxygen uptake of ABA-treated tissue was very low and almost completely resistant to the combined addition of inhibitors of both the cytochrome and the alternative pathway, indicating that the in vivo activity of the mitochondria in the oxygen uptake of the tissue was very low. The possible causes for this ABA-effect are discussed. In non-callus-forming tissue the treatment with ABA creates a situation which is comparable with that observed in intact potato tubers. This situation is characterized by a tissue respiration lower than that of the isolated mitochondria and an alternative pathway capacity that is low or absent.     

Enzyme stability in downstream processing. Part 1: enzyme inactivation, stability and stabilization

In biotechnological recovery processes the instability of the product can lead to large losses in the sequence of recovery processes needed to purify the product. As the cost of the final active product is strongly dependent on the recovery yield, this will lead to an increase in product cost. Therefore knowledge of factors that influence stability is important. This Part 1 contains a review on the factors that influence stability. As stability is very important in enzyme purification this review deals about enzymes and their ability to retain catalytic activity. Inactivation mechanisms and agents are discussed. A short review is given of enzyme structure and stability. This is followed by stabilization strategies and methods.     

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.     

Technetium-99m in the Diagnosis of Thyrotoxicosis

The thyroid uptake at 20 minutes of intravenously administered Technetium-99^m (^99mTc) was measured in 117 patients with a standard scintillation counter. Patients were divided into three groups on the basis of clinical assessment, four-hour ¹³¹I uptake, triiodothyronine (T-3) resin uptake, and protein-bound iodine measurements.In 31 patients with no evidence of thyroid disease the mean ^99m Tc uptake was 1·8% ±S.D. 1·1%. In 32 patients with thyroid enlargement who were euthyroid the mean uptake was 2·5% ±S.D. 2·2%. In 54 thyrotoxic patients the mean uptake was 17·7% with a range of 4·1 to 44%, all cases having an uptake above the upper limit of normal (4·0%). These results agree closely with reported uptake studies using scanning techniques. In seven patients the extrathyroidal neck activity was measured by using a scanner, and the mean was 6·3% of the extrathyroidal total body radioactivity comparing favourably with an assumed 6% used in our calculations.We have shown that the measurement of the thyroid uptake of ^99mTc with a scintillation counter is of value, and that it is not necessary to use scanning techniques in the diagnosis of thyrotoxicosis. Advantages of ^99m Tc are minimal radiation, reduction in patient and laboratory time, and low cost.     

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.     

Studies on the control of mitotic activity

Summary A tetraploid cell population was produced in the primary root meristem of Pisum sativum by one-half hour treatments with various concentrations of colchicine. The tetraploid population so produced was found to be reasonably synchronous in its passage through successive mitotic cycles with the degree of synchrony being more or less proportional to the concentration of colchicine used. The average time between mitoses appears to be of the order of 12 hours which agrees well with previous estimates. Treatments of roots containing tetraploid populations with 2.52 × 10^–5 M. actidione for 15 minutes were used to demonstrate the possibility of using the system for studies on the differential susceptibility of cells at different stages of the mitotic cycle.This work was carried out under contract number RG-4835 of the National Institutes of Health, United States Public Health Service, and an Institutional Grant from the American Cancer Society.Contribution number 59-26 of the Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan.Predoctoral Fellow (CF-9871) of the National Cancer Institute, United States Public Health Service     

Rapid Plasma Membrane Anchoring of Newly Synthesized p59 fyn: Selective Requirement for NH2-Terminal Myristoylation and Palmitoylation at Cysteine-3

The trafficking of Src family proteins after biosynthesis is poorly defined. Here we studied the role of dual fatty acylation with myristate and palmitate in biosynthetic transport of p59^fyn. Metabolic labeling of transfected COS or NIH 3T3 cells with [³⁵S]methionine followed by analysis of cytosolic and total membrane fractions showed that Fyn became membrane bound within 5 min after biosynthesis. Newly synthesized Src, however, accumulated in the membranes between 20– 60 min. Northern blotting detected Fyn mRNA specifically in soluble polyribosomes and soluble Fyn protein was only detected shortly (1–2 min) after radiolabeling. Use of chimeric Fyn and Src constructs showed that rapid membrane targeting was mediated by the myristoylated NH₂-terminal sequence of Fyn and that a cysteine at position 3, but not 6, was essential. Examination of Gα_o-, Gα_s-, or GAP43-Fyn fusion constructs indicated that rapid membrane anchoring is exclusively conferred by the combination of N-myristoylation plus palmitoylation of cysteine-3. Density gradient analysis colocalized newly synthesized Fyn with plasma membranes. Interestingly, a 10–20-min lag phase was observed between plasma membrane binding and the acquisition of non-ionic detergent insolubility. We propose a model in which synthesis and myristoylation of Fyn occurs on soluble ribosomes, followed by rapid palmitoylation and plasma membrane anchoring, and a slower partitioning into detergent-insoluble membrane subdomains. These results serve to define a novel trafficking pathway for Src family proteins that are regulated by dual fatty acylation.     

Cells of pea (Pisum sativum) that differentiate from G2 phase have extrachromosomal DNA.

Velocity sedimentation in an alkaline sucrose gradient of newly replicated chromosomal DNA revealed the presence of extrachromosomal DNA that was not replicated by differentiating cells in the elongation zone. The extrachromosomal DNA had a number average molecular weight of 12 X 10(6) to 15 X 10(6) and a weight average molecular weight of 25 X 10(6), corresponding to about 26 X 10(6) and 50 X 10(6) daltons, respectively, of double-stranded DNA. The molecules were stable, lasting at least 72 h after being formed. Concurrent measurements by velocity sedimentation, autoradiography, and cytophotometry of isolated nuclei indicated that the extrachromosomal molecules were associated with root-tip cells that stopped dividing and differentiated from G2 phase but not with those that stopped dividing and differentiated from G1 phase.     

Developmental Changes in Glycolipid Synthesizing Enzymes in the Brain of a Myelin-Deficient Mutant Wistar Rat

Changes in the activities of UDP-galactose:ceramide galactosyltransferase (CGalT, EC 2.4.1.45), UDP-glucose:ceramide glucosyltransferase (CGlcT, EC 2.4.1.80) and 3'-phosphoadenosine-5'-phosphosulfate (PAPS): galactosylceramide 3'-sulfotransferase (EC 2.8.2.11) over the myelinating period between 12 and 25 days were studied in the brains of control and myelin-deficient rats. Although the activity of galactosyltransferase with ceramides containing hydroxy fatty acids quadrupled in normal male littermates between 14 and 20 days, hardly any increase was observed in the mutant and the activity was less than 10% of control above 20 days of age. With normal fatty acid containing ceramides as acceptors, the activity decreased from 83% of the control at 12 days to approximately 30% after 20 days. Sulfotransferase activity also did not show the normal increase during the 3rd week of life and declined from 60% to 22%. Glucosyltransferase and lysosomal hydrolases in brain and ceramide galactosyltransferase in sciatic nerves appeared to be normal. These results suggest close similarities to the jimpy mutant mouse in which myelin deficiency is also inherited as an x-linked recessive trait.