THE SEPARATION OF DIFFERENT CELL CLASSES FROM LYMPHOID ORGANS : III. The Purification of Erythroid Cells by pH-Induced Density Changes

1. Mammalian erythrocytes swell as the pH of the isotonic suspending medium is lowered, as a direct consequence of the specialized permeability properties of the erythrocyte membrane. Lymphocytes and granulocytes from a variety of sources did not exhibit this property. 2. The behaviour of mouse bone marrow erythroid cells at various stages of differentiation was studied by using a change in buoyant density with pH as an index of swelling. The ability to swell with a pH drop was acquired while the cell was still nucleated. All non-nucleated cells showed swelling. Most small erythroblasts shared this property, whereas most large erythroblasts did not. 3. The density shift with pH was used to provide a purification scheme specific for erythroid cells. The bone marrow cells were first centrifuged to equilibrium in an isotonic albumin density gradient at neutral pH. Regions of the gradient containing the erythroid cells were collected, and the cells were recovered and redistributed in an albumin gradient at acid pH. The erythroid cells showed a specific density shift which removed them from contaminants. Preparations containing 90–97% erythroblasts were obtained by this technique. 4. Differentiation within the erythroid series was accompanied by a general increase in cell buoyant density at neutral pH. This density increase may have been a discontinuous process, since erythroid cells appeared to form a number of density peaks. 5. The pH shift technique, in association with established density distribution and sedimentation velocity procedures, provides a range of cell separation techniques for biological or biochemical studies of erythroid cell differentiation in the complex cell mixtures in bone marrow or spleen.     

Cancer of the Nasopharynx

Of 75 consecutive patients with nasopharyngeal cancer treated at UCLA Center for Health Sciences, 42 were eligible for long-term study. Fourteen (33 percent) survived five years, and one survived ten years. Since the management of nasopharyngeal cancer is primarily irradiation, a well-planned aggressive treatment program using supravoltage therapy is recommended. In spite of cranial nerve involvement or skull erosion, radiation therapy occasionally may offer long term control of the disease.     

Zur Biologie,Morphologie und Verhaltensweise von Apion virens Hrbst. (Col., Curculionidae)

Zusammenfassung Die vorliegende Arbeit soll einen Beitrag zur Monographie von Apion virens liefern. Von den einzelnen Stadien werden die Entwicklungsdauer sowie verschiedene morphologische Einzelheiten angegeben. Die Lebensdauer der Imagines beträgt 11–12 Monate, wobei die Käfer allerdings während der Überwinterung Nahrung aufnehmen müssen.Die Ausfärbung der Puppen und Imagines erfolgt progressiv. Der Fortgang dieser Prozesse wird im einzelnen beschrieben.Die Zahl der abgelegten Eier betrug maximal 166/.Untersuchungen zur Phänologie ergaben verschiedene gut abtrennbare Phasen im Laufe des Jahres.Im Wirtspflanzenspektrum der Art spielen Trifolium-Arten die wichtigste Rolle.Die Vorzugstemperatur- und-lichtbereiche zeigen charakteristische Veränderungen ihrer Lage im Laufe des Jahres. Dabei ergeben sich hinsichtlich der Temperatur auch Unterschiede zwischen und .Von den Verhaltensweisen der Imagines werden Kopulation, Eiablage und Putzhandlungen eingehend beschrieben.

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On the biology, morphology and behaviour of apion virens Hrbst. (Col., Curculionidae)

Summary This paper intends to give a contribution to a monography of Apion virens. From the different stages the duration of development and some details of the morphology are presented. The longevity of the adults reaches 11 to 12 months when uptake of food during hibernation is possible.The pigmentation of pupae and adults, which is described in detail, takes place progressively.The maximum number of eggs per female was 166.Investigations about the phenology showed several well separated phases in the course of one year. Trifolium species are the most suitable host plants of A. virens.The range of preference of temperature and humidity changes characteristically during the year. — Between and there exist also differences in the optimum temperature range.Copulation, egg-laying and cleaning behaviour are described in detail.

     

The Information Capacity of Nerve Cells Using a Frequency Code

Approximate equations are derived for the amount of information a nerve cell or group of nerve cells can transmit about a stimulus of a given duration using a frequency code (i.e., assuming the mean frequency of nerve impulses measures the intensity of a maintained stimulus). The equations take into account the variability of successive interspike intervals, and any serial correlations between successive intervals, but do not require detailed assumptions about the mechanism of impulse initiation. The errors involved in using these approximations are evaluated for neurons which discharge either completely regularly, completely at random (Poisson process) or show a particular type of intermediate variability (gamma distribution model). The errors become negligibly small as the stimulus duration or the number of functionally similar nerve cells increases. The conditions for applying these equations to experimental data are discussed. The application of these equations should help considerably in eliminating the enormous discrepancies between some earlier estimates for the information processing capabilities of single nerve cells and systems of nerve cells.     

The binding of cupric ions to bovine pancreatic ribonuclease studied with diligand metal-ion buffers

A procedure has been developed for the use of metal-ion buffers that depends on the formation of 2:1 complexes between suitable chelators and metal ions. beta-Alanine has been used as the chelator for Cu(2+) ions in a study of Cu(2+) binding by bovine pancreatic ribonuclease by the equilibrium-dialysis technique at pH7.0, 6.1 and 5.2. The results indicated the presence of two avid binding sites, the more avid group being implicated in the inhibition of enzyme activity by Cu(2+) ions.The binding constants of the more avid site were 2.97x10(7), 7.97x10(5) and 1.25x10(4) at pH7.0, 6.1 and 5.2 respectively, and the binding constants of the less avid site were 5.27x10(6) and 1.71x10(5) at pH7.0 and 6.1 respectively.The data show that the Cu(2+) is chelated to the protein through at least two ligand groups on the ribonuclease molecule.