A sensitive assay employing a solid-phase metal chelator to estimate rates of iron accumulation by ferritin

To minimize the contribution by the appreciable rates of extraferritin Fe(II) autoxidation/polymerization which proceed concomitant with the accumulation of iron by ferritin, a simple discontinuous, spectrophotometric kinetic assay was developed. This assay procedure utilizes a commercial metal chelator to complex the substrate and thus quench the reaction. Because operation is between 0 and 20°C and below 1.5 mm Fe(II), interference by autoxidation is negligible. Rates are observed to be first order with respect to apoferritin concentration and first order with respect to Fe(II) concentration at substrate-to-protein ratios as great as 2 × 10⁴. Between 0 and 20°C, the temperature dependence of the rate yielded a linear Arrhenius plot with an activation energy of + 15.2 kcal mol^?1. The advantages offered by this assay procedure over existing assays are (i) the assay can be up to an order of magnitude more sensitive, and (ii) the interference by extraferritin Fe(II) autoxidation is insignificant.     

Purine metabolism in Trypanosoma brucei gambiense

The procyclic forms of Trypanosoma brucei gambiense do not incorporate glycine or serine into ribonucleotides. Although de novo purine synthesis does not occur, all purine bases and ribonucleotides are interconverted, indicating the presence of active salvage pathways. Guanine is actively deaminated to xanthine by guanase activity. Purine ribonucleosides are cleaved to their respective free bases. The order of salvage efficiency for purine bases and their respective ribonucleotides is: adenine > hypoxanthine > guanine > xanthine.     

Morphology of the core fibrous layer of the cetacean tail fluke

The cetacean tail fluke blades are not supported by any vertebral elements. Instead, the majority of the blades are composed of a densely packed collagenous fiber matrix known as the core layer. Fluke blades from six species of odontocete cetaceans were examined to compare the morphology and orientation of fibers at different locations along the spanwise and chordwise fluke blade axes. The general fiber morphology was consistent with a three‐dimensional structure comprised of two‐dimensional sheets of fibers aligned tightly in a laminated configuration along the spanwise axis. The laminated configuration of the fluke blades helps to maintain spanwise rigidity while allowing partial flexibility during swimming. When viewing the chordwise sectional face at the leading edge and mid‐chord regions, fibers displayed a crossing pattern. This configuration relates to bending and structural support of the fluke blade. The trailing edge core was found to have parallel fibers arranged more dorso‐ventrally. The fiber morphology of the fluke blades was dorso‐ventrally symmetrical and similar in all species except the pygmy sperm whale (Kogia breviceps), which was found to have additional core layer fiber bundles running along the span of the fluke blade. These additional fibers may increase stiffness of the structure by resisting tension along their long spanwise axis.     

On the empirical choice of the time window for restricted mean survival time

The t-year mean survival or restricted mean survival time (RMST) has been used as an appealing summary of the survival distribution within a time window [0, t]. RMST is the patient's life expectancy until time t and can be estimated nonparametrically by the area under the Kaplan-Meier curve up to t. In a comparative study, the difference or ratio of two RMSTs has been utilized to quantify the between-group-difference as a clinically interpretable alternative summary to the hazard ratio. The choice of the time window [0, t] may be prespecified at the design stage of the study based on clinical considerations. On the other hand, after the survival data have been collected, the choice of time point t could be data-dependent. The standard inferential procedures for the corresponding RMST, which is also data-dependent, ignore this subtle yet important issue. In this paper, we clarify how to make inference about a random “parameter.” Moreover, we demonstrate that under a rather mild condition on the censoring distribution, one can make inference about the RMST up to t, where t is less than or even equal to the largest follow-up time (either observed or censored) in the study. This finding reduces the subjectivity of the choice of t empirically. The proposal is illustrated with the survival data from a primary biliary cirrhosis study, and its finite sample properties are investigated via an extensive simulation study.     

A method for assessing the microfloral status of the human intestines by the quantity of adhesion-active bacteria and by the type of adhesins

The method for the evaluation of the state of intestinal microflora in the diagnosis of enteric diseases by the determination of the number of actively adhesive bacteria and the type of adhesins in the primary culture of human microflora has been developed. This method permits the simultaneous analysis of all colonies grown in a given Petri dish by the sign of their adhesion, which eliminates the possibility of mistakes due to the occasional choice of colonies, as it may happen in the agglutination test. The time necessary for the study of adhesive properties is reduced, as the result is evaluated as early as on day 2 after the inoculation of the seed material. It is also of importance that the method is simple in realization, needs no special equipment, preparation and staining of the material. To determine the type of adhesins, a series of identical inoculations may be obtained by replication with the use of red blood cells of different animals. The proposed method may be used for the confirmation of the etiological role of enterobacteria as evidenced by the presence of high percentage of their actively adhesive colonies.     

An investigation of playful behaviour in Rattus norvegicus and Mus musculus (Mammalia)

The playful behaviour of laboratory rats ( Rattus norvegicus ) was investigated in litters of five individuals with the mother present; parallel observations were made on mice ( Mus musculus ). Seven mixed litters containing four young rats and a young mouse fostered at birth were also observed.
Solitary play was recorded in both species and took a similar form but social play was only observed in rats. In rats, solitary play frequently preceeded social play.
The behavioural elements involved in the social play of Rattus norvegicus were described, and the majority of these were the playful equivalent of adult agonistic behaviour elements. These social play elements were found to be organized into definite sequences which differed from those of adult aggression. Each behavioural element was found to act as a social releaser.
Young mice did not respond playfully to social play from a rat litter mate; mice were less attractive to rats as playmates in comparison with fellow rats.     

Morphological and histochemical characterization of the pectoral fin muscle of batoids

Batoids differ from other elasmobranch fishes in that they possess dorsoventrally flattened bodies with enlarged muscled pectoral fins. Most batoids also swim using either of two modes of locomotion: undulation or oscillation of the pectoral fins. In other elasmobranchs (e.g., sharks), the main locomotory muscle is located in the axial myotome; in contrast, the main locomotory muscle in batoids is found in the enlarged pectoral fins. The pectoral fin muscles of sharks have a simple structure, confined to the base of the fin; however, little to no data are available on the more complex musculature within the pectoral fins of batoids. Understanding the types of fibers and their arrangement within the pectoral fins may elucidate how batoid fishes are able to utilize such unique swimming modes. In the present study, histochemical methods including succinate dehydrogenase (SDH) and immunofluoresence were used to determine the different fiber types comprising these muscles in three batoid species: Atlantic stingray (Dasyatis sabina), ocellate river stingray (Potamotrygon motoro) and cownose ray (Rhinoptera bonasus). All three species had muscles comprised of two muscle fiber types (slow-red and fast-white). The undulatory species, D. sabina and P. motoro, had a larger proportion of fast-white muscle fibers compared to the oscillatory species, R. bonasus. The muscle fiber sizes were similar between each species, though generally smaller compared to the axial musculature in other elasmobranch fishes. These results suggest that batoid locomotion can be distinguished using muscle fiber type proportions. Undulatory species are more benthic with fast-white fibers allowing them to contract their muscles quickly, as a possible means of escape from potential predators. Oscillatory species are pelagic and are known to migrate long distances with muscles using slow-red fibers to aid in sustained swimming.     

Hydrodynamic design of the humpback whale flipper

The humpback whale (Megaptera novaeangliae) is reported to use its elongate pectoral flippers during swimming maneuvers. The morphology of the flipper from a 9.02-m whale was evaluated with regard to this hydrodynamic function. The flipper had a wing-like, high aspect ratio plan-form. Rounded tubercles were regularly interspersed along the flipper's leading edge. The flipper was cut into 71 2.5-cm cross-sections and photographed. Except for sections near the distal tip, flipper sections were symmetrical with no camber. Flipper sections had a blunt, rounded leading edge and a highly tapered trailing edge. Placement of the maximum thickness placement for each cross-section varied from 49% of chord at the tip to 19% at mid-span. Section thickness ratio averaged 0.23 with a range of 0.20–0.28. The humpback whale flipper had a cross-sectional design typical of manufactured aerodynamic foils for lift generation. The morphology and placement of leading edge tubercles sugges that they function as enhanced lift devices to control flow over the flipper and maintain lift at high angles of attack. The morphology of the humpback whale flipper suggests that it is adapted for high maneuverability associated with the whale's unique feeding behavior. © 1995 Wiley-Liss, Inc.