Respiratory transfer impedance and derived mechanical properties of conscious rats.

A setup is described for measuring the respiratory transfer impedance of conscious rats in the frequency range 16-208 Hz. The rats were placed in a restraining tube in which head and body were separated by means of a dough neck collar. The restraining tube was placed in a body chamber, allowing the application of pseudorandom noise pressure variations to the chest and abdomen. The flow at the airway opening was measured in a small chamber connected to the body chamber. The short-term reproducibility of the transfer impedance was tested by repeated measurements in nine Wistar rats. The mean coefficient of variation for the impedance did not exceed 10%. The impedance data were analyzed using different models of the respiratory system of which a three-coefficient resistance-inertance-compliance model provided the most reliable estimates of respiratory resistance (Rrs) and inertance (Irs). The model response, however, departed systematically from the measured impedance. A nine-coefficient model best described the data. Optimization of this model provided estimates of the respiratory tissue coefficients and upper and lower airway coefficients. Rrs with this model was 13.6 +/- 1.0 (SD) kPa.l-1.s, Irs was 14.5 +/- 1.3 Pa.l-1.s2, and tissue compliance (Cti) was 2.5 +/- 0.5 ml/kPa. The intraindividual coefficient of variation for Rrs and Irs was 11 and 18%, respectively. Because most of the resistance and inertance was located in the airways (85 and 81% of Rrs and Irs, respectively), the partitioning in tissue and upper and lower airway components was rather poor. Our values for Rrs and Irs of conscious rats were much lower and our values for Cti were higher than previously reported values for anesthetized rats.     

Dermal cryptococcosis in a guinea pig

A case of cryptococcosis in a guinea pig with lesions confined to the dorsum of the nose is described. Results of clinical, postmortem and histological examination are discussed. The diagnostic and therapeutic possibilities and problems of cryptococcosis are mentioned.     

The Nobel Prize as a Reward Mechanism in the Genomics Era: Anonymous Researchers,Visible Managers and the Ethics of Excellence

The Human Genome Project (HGP) is regarded by many as one of the major scientific achievements in recent science history, a large-scale endeavour that is changing the way in which biomedical research is done and expected, moreover, to yield considerable benefit for society. Thus, since the completion of the human genome sequencing effort, a debate has emerged over the question whether this effort merits to be awarded a Nobel Prize and if so, who should be the one(s) to receive it, as (according to current procedures) no more than three individuals can be selected. In this article, the HGP is taken as a case study to consider the ethical question to what extent it is still possible, in an era of big science, of large-scale consortia and global team work, to acknowledge and reward individual contributions to important breakthroughs in biomedical fields. Is it still viable to single out individuals for their decisive contributions in order to reward them in a fair and convincing way? Whereas the concept of the Nobel prize as such seems to reflect an archetypical view of scientists as solitary researchers who, at a certain point in their careers, make their one decisive discovery, this vision has proven to be problematic from the very outset. Already during the first decade of the Nobel era, Ivan Pavlov was denied the Prize several times before finally receiving it, on the basis of the argument that he had been active as a research manager (a designer and supervisor of research projects) rather than as a researcher himself. The question then is whether, in the case of the HGP, a research effort that involved the contributions of hundreds or even thousands of researchers worldwide, it is still possible to “individualise” the Prize? The “HGP Nobel Prize problem” is regarded as an exemplary issue in current research ethics, highlighting a number of quandaries and trends involved in contemporary life science research practices more broadly.     

Synthesis of protoporphyrin IX induced by 5-aminolevulinic acid in yeast cells in the presence of 2,2;-dipyridyl

5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX.     

The physiology and ecology of a novel, obligate mycophagous flagellate

Abstract To determine if conidia of the nematophagous fungus Drechmeria coniospora are subject to predation by soil protozoa, several sandy soils were enriched with 10⁹ conidia of this fungus per g dry soil. After incubation of the samples at 20°C for three weeks, a flagellate was detected as the most dominant mycophagous protozoan. Conidia of several fungi, with minimum diameters between 2 and 16 μm, supported growth of this flagellate, irrespective of pigmentation. Bacteria however could not be used for growth, although bacteria and also latex beads of the same size were ingested. This is, to our knowledge, the first report of an obligate mycophagous soil-borne flagellate. The flagellate was able to grow at the expense of the conidia of D. coniospora in liquid culture, with a specific growth rate of about 0.1 h⁻¹; the optimum temperature was 20–24°C. Approximately 10 D. coniospora conidia were required for one flagellate division. In sterilized soil, enriched with 10⁸ D. coniospora conidia per g dry soil, the specific growth rate was 0.014 h⁻¹, when the soil was at 50 or 65% of its water-holding capacity (WHC). In drier soil, i.e. 25% WHC, no growth took place. During growth of the flagellate in soil, the number of D. coniospora was reduced by about 20%, which was in the same order of magnitude as expected on the basis of the requirement of 10 D. coniospora conidia for one flagellate division. Since many conidia remained in the soil after growth of the flagellate, we concluded that although the flagellate is an interesting organism, it does not play a very important role in the survival of D. coniospora conidia in the soil.