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.     

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.     

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     

Prediction of the Reaction Equilibrium of Biocatalytic Reactions in Aqueous-Organic Two-Phase Systems

Biocatalytic reactions can be carried out in aqueous-organic two-phase systems. Several models to describe the thermodynamically-determined equilibrium position in such systems have appeared in the literature. Some of these models are only valid for dilute systems, whereas others can also be used for nondilute systems. In this paper, these models are described and compared. It is explained in what way the equilibrium constants of each model can be used to predict the product concentration in different organic solvents.     

Value of 1-alpha-hydroxy vitamin D3 in treatment of primary hyperparathyroidism before parathyroidectomy.

The postoperative course of six patients with primary hyperparathyroidism and obvious radiological evidence of bone disease pretreated with 1-alpha-hydroxy vitamin D3 (1 alpha HCC) was indistinguishable from that of six patients with a similar clinical and radiological picture who were not pretreated. 1alphaHCC may increase the hypercalcaemia in some cases and cannot be recommended for the routine preparation of such patients for surgery.     

The size and number of replicon families of chromosomal DNA of Arabidopsis thaliana

Analysis of the replicon properties and the cell cycle ofArabidopsis thaliana (col.) at 22° C were performed via autoradiography of isolated chromosomal DNA fibers and single cells of seedlings. The cell cycle was 8.5 h and G1, S, and G2+1/2 M were 1.7, 2.8, and 4 h respectively. The average single fork rate was 5.8 m/h and the average replicon size was 24 m. The data best support the hypothesis that A. thaliana has two replicon families, one with approximately 687 and another with 1888 members per genome and that the families initiate replication in sequence separated by a 36 min interval. Replication of an average single replicon required a little more than 2 h or 74% of S and the 36 min interval between the initiation of replication by the two families constituted 21% of S.     

Replicon properties of chromosomal DNA fibers and the duration of DNA synthesis of sunflower root-tip meristem cells at different temperatures

Chromosomal DNA fiber autoradiography was used to examine the replicon properties of root-tip meristem cells of Helianthus annuus intact seedlings grown at temperatures from 10 to 38° C and those of root-tip cells grown in vitro at 23°. The average replicon size was approximately 22 m and it did not change with temperature nor when the roots were grown in culture. The average fork rate was 6 m/h at 10° and it rose gradually to 12 m/h at 38°. The responses of replication fork movement and of the duration of S to temperature were of three types: those in which change in fork rate was primarily (more than 90%) responsible for change in the duration of S, those in which the fork rate remained constant while S increased nearly twofold, and those in which the duration of S increased even though the replication forks were moving faster. The first type of response listed was observed at temperatures from 20 to 35°, the second type listed was observed at 10 to 15°, and the third, was produced at 38°.     

CELL PROLIFERATION IN COMPLEX TISSUES: THE CONTROL OF THE MITOTIC CYCLE OF CELL POPULATIONS IN THE CULTURED ROOT MERISTEM OF SUNFLOWER (HELIANTHUS)

Experiments were performed with cultured primary root tips of sunflower (Helianthus annuus var. Russian Mammoth) to determine: (1) if progression in the mitotic cycle of meristematic cells was nutritionally controllable by carbohydrate starvation and replenishment; (2) where in the mitotic cycle control was effected; and (3) whether nutritional deprivation could be used to detect phenotypically different subpopulations in a complex tissue. Meristematic cells were rendered stationary by carbohydrate starvation, as indicated by the absence of cell division; this condition was reversed by carbohydrate provision. After 72 or 96 hr of starvation most cells stopped in G1 (80–90%) and G2 (10–20%), and a very few (“leaky” cells) continued to enter S. “Leaky” cells represent a small population with an S period of approximately 4.1 hr that either lack a principal control point in G1 or have an unusual metabolism whereby the control point requirements are met and have a carbohydrate dependence for mitosis. Though phenotypically different, no specific functions can be attributed to “leaky” cells at this time.