METHOD FOR COMBINED ULTRASTRUCTURAL AND BIOCHEMICAL ANALYSIS OF NEURAL TISSUE

No significant change was found in the electrolytes and lipids of the brain analyzed after glutaraldehyde fixation by perfusion of laboratory animals; such fixation also satisfactorily preserves neural tissues for electron microscopy. The brains of normal and tumor-bearing C3H mice, Wistar rats, and New Zealand rabbits were studied. Little difference was found in the dry weight and the content of sodium, potassium, total lipid and lipid fractions, and in the sulfate space (S³⁵O₄) between specimens from unperfused and perfused animals, whether normal or tumor-bearing. The results suggest the possibility of using selected regions of the nervous system, dissected after fixation, for chemical study and at the same time characterizing similar regions morphologically with the electron microscope.     

The settling of female Haematopota insidiatrix austen (Diptera, Tabanidae) on cloth screens

The response of female Haematopota insidiatrix towards cloth screens is considered as part of the host-finding behaviour. When black, dark grey, light grey and white cloths were compared as regards attractiveness, more flies settled on the black than on the other shades. When a screen was carried horizontally flies settled on the under surface but not on the upper surface and more flies were caught. A black screen with three white stripes was progressively less attractive as the width of these stripes was increased. Even narrow white stripes reduced the catch, particularly if they were horizontally arranged. When differently sized black screens were compared, fewer flies were caught on the smaller ones. Flies settled on the lower part of a screen, as they do on a host animal. When a screen was divided so that its lower half was white and its upper half black, fewer flies settled on it than on the all-black reverse side (control). Conversely, with black below white approximately the same number of flies were caught on this as on the black control side of the screen. At temperatures below 19°C and humidities above 77% R.H., more flies settled on the sunny than on the shaded side of the screen. At higher temperatures and lower humidities this preference was reversed.

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Zusammenfassung Die Reaktion der weiblichen Haematopota insidiatrix auf Stoffschirme wird als ein Teil des Verhaltens bei der Suche nach einem Wirtstier betrachtet. Beim Vergleich von schwarzen, dunkelgrauen, hellgrauen und weissen Stoffen in Beziehung auf ihre Anziehungskraft setzten sich mehr Fliegen auf die sxhwarzen Stoffe als auf anders getönten. Wenn ein Schirm horizontal getragen wurde, setzten sich die Fliegen auf die untere Seite doch nicht auf die obere Seite. Ausserdem stieg die Anzahl der gefangenen Fliegen. Ein schwarzer Schirm mit drei weissen Streifen versehen übte um so weniger Anziehungskraft aus, je breiter die Streifen gemacht wurden. Selbst enge weisse Streifen verminderten die Anzahl der gefangenen Fliegen, besonders wenn sie horizontal angebracht waren. Wenn Schirme von verschiedener Grösse herumgetragen wurden, fingen sich auf den kleineren Schirmen weniger Fliegen. Die Fliegen setzten sich auf den unteren Teil der Schirme genau wie sie es bei Wirtstieren machen. Wurde ein Schirm in eine untere Hälfte (weiss) und eine obere Hälfte (schwarz) geteilt, so liessen sich weniger Fliegen darauf nieder als auf der ganzschwarze Rückseite (Kontrolle). Im umgekehrten Falle, (untere Hälfte schwarz, obere Hälfte weiss) wurde ungefähr dieselbe Anzahl von Fliegen auf dieser Seite wie auf der völlig schwarzen Rückseite gefangen. Bei Temperaturen unter 19°C und einen relativen Feuchtigkeit von über 77% setzten sich mehr Fliegen auf die sonnige Seite als auf die beschattete Seite des Schirmes. Bei höheren Temperaturen und niedrigerem Luftfeuchtigkeitsgehalt war diese Vorliebe umgekehrt.

     

Some further comments on the DNA-protein coding problem: A correction and a note

An error appearing in the proof of Theorem 4 of a previous paper of the author’s (1959,Bull. Math. Biophysics,21, 289–97) is pointed out, and a new proof of the theorem is supplied. We also obtain a corollary from Theorem 3 ofloc. cit. which reveals the existence of a hitherto unrecognized class of codes.     

Some mathematical aspects of chemotherapy—II: The distribution of a drug in the body

In a previous paper (Bellman, Jacquez, and Kalaba,Bull. Math. Biophysics,22: 181–198, 1960) a model of the processes occurring in the exchange of a drug between capillary plasma, extracellular space and intracellular space was developed. This included the possibility of a reaction between the drug and a component of the intracellular space. The equations developed thus describe the events within a capillary bed. In the present paper, a simplified model of the body is set up. Each organ is treated as a single capillary bed and is linked to other organs via the circulation, in the parallel and/or series arrangements found in the body. Mixing in the circulation is included at the simplest possible level. The concentration of drug entering any one capillary bed is determined by the concentrations leaving all other capillary beds, the time lags, and mixing involved in the circulation. The equations describing these processes in conjunction with the equations of the processes occurring within each capillary bed lead to a large set of differential-difference equations.