Bibliothek

Notizen: The hardware necessary for the electro-optic study of conducting polyelectrolyte solutions is frequently not commercially available or financially practical. The designs of an electrical rectangular pulse switch and polarity-reversing relay switch capable of producing 3 kV 5 A direct current pulses lasting longer than 100 μs are presented. As an example of the operation of this equipment, the electric birefringence of an aqueous solution of the Pseudomonas bacteriophage Pf1 in tris/EDTA buffer is presented. © 2002 American Institute of Physics.

Notizen: The sign and magnitude of Landé gF factors for single NO2 rovibronic (J=3/2) eigenstates in the 15 cm−1 region below dissociation threshold (D0=25 128.57 cm−1) were investigated using Zeeman quantum-beat spectroscopy. The derived Landé gF factors exhibit pronounced fluctuations about an average much smaller than expected in the absence of rovibronic perturbations, which destroy the goodness of the N and K quantum numbers and the J=N+S coupling scheme. The F=J+I coupling scheme was found to be valid near D0 to within the uncertainty of our measurements, and the average Landé gF factors near dissociation threshold are in good agreement with those calculated under the assumption of complete rovibronic mixing. Our findings do not provide evidence for the participation of repulsive quartet states near dissociation threshold. © 2002 American Institute of Physics.

Notizen: The bacterial septum appears to comprise a macromolecular assembly of essential cell division proteins (the ‘septasome’) that are responsible for physically dividing the cell during cytokinesis. FtsL and DivIC are essential components of this division machinery in Bacillus subtilis. We used yeast two-hybrid analysis as well as a variety of biochemical and biophysical methods to examine the proposed interaction between Bacillus subtilis FtsL and DivIC. We show that FtsL and DivIC are thermodynamically unstable proteins that are likely to be unfolded and therefore targeted for degradation unless stabilized by interactions with other components of the septasome. However, we show that this stabilization does not result from a direct interaction between FtsL and DivIC. We propose that the observed interdepend-ence of DivIC and FtsL stability is a result of indirect interactions that are mediated by other septasomal proteins.

Notizen: Yersinia species utilize a type III secretion system to inject toxins, called Yops (Yersinia outer proteins), into eukaryotic cells. The N-termini of the Yops serve as type III secretion signals, but they do not share a consensus sequence. To simplify the analysis of type III secretion signals, we replaced amino acids 2–8 of the secreted protein YopE with all permutations (27 or 128) of synthetic serine/isoleucine sequences. The results demonstrate that amphipathic N-terminal sequences, containing four or five serine residues, have a much greater probability than hydrophobic or hydrophilic sequences to target YopE for secretion. Multiple linear regression analysis of the synthetic sequences was used to obtain a model for N-terminal secretion signals. The model accurately classifies the N-terminal sequences of native type III substrates as efficient secretion signals.

Notizen: This study examined the association between the therapeutic alliance in family therapy and changes in symptom distress, interpersonal relationships, and family coping. The participants (N = 81) were members of low socioeconomic status families referred to a university clinic for in-home family therapy. Participants completed the Outcome Questionnaire, Family Crisis Oriented Personal Evaluation, and the Family Therapy Alliance questionnaires. Regression analyses revealed that the therapeutic alliance explained 19% of the variance in symptom distress changes for mother, 55% for fathers, and 39% for adolescents. The implications of these findings for practicing and researching family therapy are presented.

Notizen: There is increasing public, governmental and commercial interest in the welfare of intensively farmed fish and stocking density has been highlighted as an area of particular concern. Here we draw scientific attention and debate to this emerging research field by reviewing the evidence for effects of density on rainbow trout. Although no explicit reference to ‘welfare’ has been made, there are 43 studies which have examined the effects of density on production and physiological parameters of rainbow trout. Increasing stocking density does not appear to cause prolonged crowding stress in rainbow trout. However, commonly reported effects of increasing density are reductions in food conversion efficiency, nutritional condition and growth, and an increase in fin erosion. Such changes are indicative of a reduced welfare status—although the magnitude of the effects has tended to be dependent upon study-specific conditions. Systematic observations on large scale commercial farms are therefore required, rather than extrapolation of these mainly small-scale experimental findings. There is dispute as to the cause of the observed effects of increasing density, with water quality deterioration and/or an increase in aggressive behaviour being variously proposed. Both causes can theoretically generate the observed effects of increasing density, and the relative contribution of the two causes may depend upon the specific conditions. However, documentation of the relationship between density and the effects of aggressive behaviour at relevant commercial densities is lacking. Consequently only inferential evidence exists that aggressive behaviour generates the observed effects of increasing density, whereas there is direct experimental evidence that water quality degradation is responsible. Nevertheless, there are contradictory recommendations in the literature for key water quality parameters to ensure adequate welfare status. The potential for welfare to be detrimentally affected by non-aggressive behavioural interactions (abrasion, collision, obstruction) and low densities (due to excessive aggressive behaviour and a poor feeding response) have been largely overlooked. Legislation directly limiting stocking density is likely to be unworkable, and a more practical option might be to prescribe acceptable levels of water quality, health, nutritional condition and behavioural indicators.

Notizen: The plasma concentrations of testosterone (T) of cultured jundiáRhamdia quelen increased progressively during spermatogenesis and reached a peak at the beginning of spermiation (e.g. fluidization of the sperm and production of milt). Plasma peaks of T occurred simultaneously to the highest production of T by the testis, however, both plasma concentrations and testis production of T decreased progressively during spermiation. Concentrations of 11-ketotestosterone (11-KT) peaked c. 1 month after the peak of T, concomitant with enhanced production of 11-KT by the testis. The concentrations of 11-KT during the first cycle were extremely high (〉 1 μg ml−1), but less during the second and third cycles, suggesting that this steroid is most important during the pubertal phase in male jundiá. Plasma concentrations of both 17-hydroxy-4-pregene-3,20-dione (17-P) and 17,20β-dihydroxy-4-pregen-3-one (17,20β-P) were significantly higher during spermiation than at any other times, and showed little variation. The pattern of steroid changes was cyclical and consistent with their proposed roles in male fish reproduction.

Notizen: : Many studies can be found in the literature pertaining to the effects of urbanization on surface runoff in small watersheds and the hydrologic response of undeveloped watersheds. However, an extensive literature review yielded few published studies that illustrate differing hydrologic responses from multiple source areas within a watershed. The concepts discussed here are not new, but the methods used provide a unique, basic procedure for investigating stormwater hydrology in topographically diverse basins. Six storm hydrographs from three small central Pennsylvania watersheds were analyzed for this paper; five are presented. Two important conclusions are deduced from this investigation. First, in all cases we found two distinct peaks in stream discharge, each representing different contributing areas to direct discharge with greatly differing curve numbers and lags representative of urban and rural source regions. Second, the direct discharge represents only a small fraction of the total drainage area with the urban peak becoming increasingly important with respect to the rural peak with the amount of urbanization and as the magnitude of the rain event decreases.

Notizen: 1. The development of atherosclerosis, including the role of the classical and new risk factors, is briefly reviewed an emphasis on the links between some of these risk factors and atherogenesis.2. While genetic factors are doubtlessly important, they contribute (from the population point of view) little to the overall burden of atherosclerosis.3. Our studies on the relationship between abdominal obesity and metabolic risk factors in two ethnic groups, namely individuals of Cantonese and European background, suggest that different ranges for at least some of the risk factors should be established for specific ethnic groups (e.g. waist circumference for individuals of Chinese and European background).4. Using the example of differences between Cantonese heterozygotes for familial hypercholesterolaemia living in Vancouver, Canada, and Canton, China, we demonstrate how the environment can modify a genetic predisposition for atherosclerosis.5. Gender differences are illustrated by a study of serum lipoprotein (a) as a risk factor in men and women.6. The principles of current Canadian recommendations for the assessment and treatment of atherosclerosis are outlined; they are based on knowledge gained from both basic and clinical research of atherosclerosis.