Concerning the sensitivity of Acinetobacter calcoaceticus

The strains of Acinetobacter calcoaceticus, var. anitratus (A. c. a.) were isolated in the nosocomial environment as an opportune pathogen. The therapy of choice may be determined after in vitro tests. Our results show following therapeutical possibilities: beta-lactam antibiotics--cephalosporins of IIIrd generation (cefotaxime), also combinations of antimicrobials have shown good results: amoxycillin or ticarcillin with clavulanic acid. Best synergistic effect was found in combination ticarcillin-amikacin.     

Angular sensitivity of the bee ommatidium

Summary Light propagation within the worker bee ommatidium is analyzed. The angular sensitivity of the ommatidium can be separated into a product of the bee's dioptric apparatus and rhabdom angular sensitivities. The discrepancy in angular sensitivity between recent electrophysiological measurements and ray tracing procedures for the worker bee arises because the field of view of the rhabdom is smaller than that of the optical system in front of it.I thank G. A. Horridge for suggesting this research, Simon Laughlin for providing the results of his recordings from the worker bee and J. W. Blamey for helpful discussion on optical systems.     

Understanding the pollution sensitivity of lichens

RICHARDSON, D. H. S. 1988. Understanding the pollution sensitivity of lichens. Lichens have been widely used to monitor air quality in urban and industrial situations. This review summarizes the effects of the various components of air pollution including metals, sulphur dioxide and acid rain. The mechanisms leading to the accumulation of elements by lichens or induction of damage by air pollutants are discussed.     

Mechanisms of the gravitational sensitivity of cells

It is well known that specialized gravireceptory cells have been formed in the course of evolution in the majority of multicellular organisms. These are statosytes (statenchyme cells) in higher plants and otolith apparatus cells in animals. The mechanisms of gravity reception and the generation of gravitational stimuli in these cells are well understood. Therefore, our attention was focused on cells devoid of special gravireceptory mechanisms, namely cell cultures grown in vitro (fibroblasts and osteoblasts) and unicellular free-swimming (i.e. possessing a locomotor apparatus) organisms. These were mainly representatives of two classes: Ciliata and Flagellata. The choice of the objects of study was mainly determined by their ecological and physiological characteristics with the main goals of this work.     

Radiation sensitivity and the status of some radiation sensitivity markers in relatively sensitive lymphoid cells

The most commonly used indicators of ionizing radiation exposure are cytogenetic measures and survival parameters. All these methods have their advantages, disadvantages and uncertainties, such that better biological estimators of the absorbed dose, especially in the low dose range, are being sought. In this study we analyzed apoptosis and several proteins involved in the regulation of apoptosis as possible indicators of irradiation after relatively small doses (0.1-2 Gy) of X-rays. The studies were carried out in seven lymphoid cell lines: two mouse lymphoma L5178Y, the human pre-B cell leukemia Reh, and four human Epstein-Barr virus-transformed lymphoid cell lines (two apparently normal and two Ataxia-telangiectasia (AT)). We detected apoptosis with the in situ terminal deoxynucleotidyl transferase assay and flow cytometry, and measured the expression of several apoptotic-regulatory proteins (Bcl-2, Bax, Bclx, NF kappa B) with Western blotting. The cytokinesis-block micronucleus assay, comet assay as a measure of DNA damage, and trypan blue survival test were also done for comparison Although for the most of examined parameters of radiation sensitivity: i.e. micronucleus assay, trypan blue test and percentage of apoptosis--there were observed clear dose-effect relationships for all cell lines examined, we did not find agreement between values for these measured parameters. There are marked differences in both timing of apoptosis and percentage of apoptotic cells. Variation in the apoptotic fraction in the controls for different sets of experiments is not very pronounced. There is however considerable variation for the same parameters in irradiated cells, possibly due to their cell cycle status during irradiation, as the cultures were not synchronized. Overall, neither the numbers of apoptotic cells nor the expression of apoptosis-related proteins, nor DNA repair can serve as dose estimators or sensors for these lines, but still these parameters can give valuable supplementary information about radiation sensitivity.     

On the directional sensitivity of motion detectors

The output of a motion detector depends on the direction of pattern motion, relative to the axis defined by its two input elements. Usually a cosine shaped directional sensitivity characteristics is assumed: The response is strongest for pattern motion along the detector axis, reversing its sign for motion in opposite direction; for motion perpendicular to the detector axis it is expected to be zero, with intermediate values for oblique motion directions. However, geometric considerations show that this expectation is by no means trivial. When a periodic pattern moves along a direction a relative to the detector axis, the spatiotemporal intensity distribution along the detector axis can be described by its apparent spatial wavelength and its apparent velocity, which both vary with 1/cos. In consequence, a motion detector depending exclusively on the apparent velocity of the stimulus would respond strongest to gratings moving perpendicular to the detector axis, whereas motion along the detector axis would yield the smallest response in such a detector. The response of a motion detector of the correlation type, on the other hand, is determined by the ratio between velocity and wavelength, the temporal frequency, which is not influenced by the direction of pattern motion, and by the ratio between sampling base and the wavelength. The latter feature leads to a cosine-shaped directional characteristics for large pattern wavelengths. However, for smaller wavelengths specific deviations from a simple harmonic are expected. These expectations were confirmed by the simulation of an elementary motion detector model and extended for a slightly more elaborated model. Representing a biological motion detecting unit of the correlation type, the directional characteristics of the H1 interneuron in the fly's brain was investigated electrophysiologically, and compared to the simulations.     

Rethinking temperature sensitivity of the suprachiasmatic nucleus

A report by Buhr et al. (2010) proposed that the suprachiasmatic nucleus (SCN) is resistant to phase shifts induced by heat pulses and to entrainment by temperature cycles. These findings are inconsistent with those from studies by other laboratories in which the SCN readily phase shifts in response to heat pulses. I propose that their negative findings are not due to the SCN being temperature insensitive but are based on an explant culture preparation that does not fully express the properties of the SCN that are present in other in vitro preparations.     

Increased sensitivity of the parapertussis diagnostic agent

The adsorption activity of formolated sheep red blood cells can be increased by their combined treatment with low-frequency ultrasound, tannin and Tween-40. The diagnosticums thus obtained have proved to be highly sensitive and specific and can be recommended for the detection of antibodies to Bordetella parapertussis in the sera of sick children.     

Enhanced sensitivity to noradrenaline of the Ainu

A small dose of noradrenaline, which was ineffective in non-Ainu Japanese subjects, caused marked elevations in energy metabolism and plasma levels of FFA and total ketone bodies in the Ainu. The striking sensitivity to noradrenaline of the Ainu is assumed to indicate a characteristic feature of cold adaptability of this ethnic group.

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Zusammenfassung Eine geringe Dosis Noradrenalin, die bei nicht-Ainu Japanern unwirksam war, bewirkte bei Ainus eine ausgeprägte Erhöhung des Stoffwechsels, des Plasmaspiegels, der freien Fettsäuren und der Gesamt-Ketonkörper. Die Noradrenalin-Empfindlichkeit der Ainus wird als Kennzeichen besonderer Kälteanpassungsfähigkeit erklärt, das für diesen Volksstamm kennzeichend ist.

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Resume Une faible dose de noradrénaline, dose qui reste sans effet sur les Japonais n'appartenant pas à la race des Ainous, provoque au contraire une nette élévation du métabolisme énergétique chez les natifs de cette race. Cette élévation se signale notamment par le relèvement du taux des acides gras libres et des masses de kétone dans le sérum sanguin. L'extrême sensibilité des Ainous à la noradrénaline explique la facilité avec laquelle les gens de cette race s'adaptent au froid. Cette facilité d'adaptation est d'ailleurs une des caractéristiques de cette race.

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This study was made as a part of J-IBP/HA.     

Possibilities of enhancing the sensitivity of the coagglutination reaction

The influence of heating Shigella suspension at 60 degrees C (for 3 minutes) and 100 degrees C (for 30 minutes), as well as adding extraneous microorganisms (Escherichia coli, Proteus) and homologous antibodies to these suspensions, on the sensitivity of the coagglutination test has been studied. The possibility of enhancing the sensitivity of this test 10 to 100 times by heating Shigella suspensions at 100 degrees C for 30 minutes has been shown.     

Increment-threshold spectral sensitivity in the rabbit

Summary Increment threshold measurements in wild rabbits give rise to spectral sensitivity curves that are unimodal or bimodal in nature, depending on the background luminance. We propose a model that explains the shape of these curves on the basis of synergistic and antagonistic interaction of blue cones (_max = 425 nm), green cones (_max = 523 nm) and rods (_max = 498 nm).