Control by the extracellular environment of differentiation pathways in 1003 embryonal carcinoma cells: study at the level of specific intermediate filaments.

1003 is a multipotential embryonal carcinoma (EC) clonal cell line which can be induced to follow different developmental pathways by altering the composition of the culture medium. When grown in serum-containing medium the great majority of 1003 cells remain undifferentiated; they express the ECMA 7 cell-surface embryonic antigen and very low amounts of vimentin. In serum-free medium, most 1003 cells differentiate into neuroepithelial cells. The majority of these cells are still labelled with ECMA 7 antibodies. They contain higher amounts of vimentin than EC cells, but no neurofilament proteins. Neuroepithelial cells then differentiate into neurons through a stage of preneurons containing both vimentin and the 70-K neurofilament protein. Fully differentiated neurons contain 70-K neurofilament protein but no vimentin. The 200-K neurofilament protein is detected later in the neurons. Mesenchymal cells (induced by re-adding serum) express high amounts of vimentin organized in networks. Preneurons , neurons, and mesenchymal cells do not express ECMA 7 antigen.     

Well-identifiable human chromosomes Isolated from mitotic fibroblasts by a new method

Summary Metaphase chromosomes isolated from human fibroblasts by lysis of mitotic cells in the presence of the intercalating DNA-specific fluorochrome propidium iodide appear relatively long, even after exposure to vinblastine sulfate overnight. Therefore, they can be easily banded and thereby unequivocally identified. Chromosomes isolated in this way may be employed in flow analysis and sorting without loosing the inducibility of their band patterns.     

A model for the temporal organization of X- and Y-type receptive fields in the primate retina

A model is proposed for the temporal characteristics of X-and Y-type responses of ganglion cells in the primate retina. The main suggestions of the model are: (I) The X-type temporal response is determined primarily by the delay between center and surround contributions. (II) The Y-type response is generated in the inner plexiform layer by a derivativelike operation on the bipolar cell's input, followed by a rectification in the convergence of these inputs onto the Y-ganglion-cell. (III) The derivative-like operation is obtained by recurrent inhibition in the dyad synaptic structure.The X-and Y-type responses predicted by the model, for a variety of stimuli, were examined and compared with available electrophysiological recordings. Finally, certain predictions derived from the model are discussed.     

Die Wirkung von Beleuchtungsfaktoren und Lichtpunktmustern auf die n?chtliche Zugaktivit?t von Rotkehlchen(Erithacus rubecula)

Zusammenfassung 1. Die nächtliche Zugunruhe setzt auch unter konstanten Lichtbedingungen (Dauerdunkel 0,06 Lux, Dauerhell 250 Lux) etwa mit der Sonnenuntergangszeit ein und erreicht im Frühjahr etwa um 21^h ihr Maximum (etwas später bei Dauerhell).2. Während der Nacht werden vom zugaktiven Rotkehlchen in stärkerem Maße als bei Tag die dunkleren Abteilungen einer Lichtorgel aufgesucht.3. Die höchste Zugaktivität wird bei Beleuchtungsstärken von 1–10 Lux erreicht, aber auch bei völliger Dunkelheit wird noch etwa 7 % der Maximalaktivität gemessen. Sommer-Nachtaktivität erreicht ebenfalls bei ca. 5 Lux ein Maximum, erlischt aber fast völlig bei Beleuchtungsstärken unter 1 Lux.4. Bei dunklem Untergrund ist die gemessene Aktivität bei gleicher Beleuchtungsstärke deutlich geringer als bei hellem Untergrund.5. Niedrigere Tagesbeleuchtungsstärken im Versuchsraum (250 gegenüber 700 Lux) bewirken ein Ansteigen der Zugaktivität in der folgenden Nacht, bei gleichzeitig zunehmender Futteraufnahme während des Tages.6. Einzelne Lichtpunkte wirken aktivitätssteigernd unabhängig von der von ihnen bewirkten Beleuchtungsstärke. Eine größere Zahl von Lichtpunkten, gleichmäßig über die Decke verteilt, hemmt dagegen die Zugaktivität, auch wenn die dabei erreichte Beleuchtungsstärke höher ist als bei einer Diffusionsbeleuchtung, unter der dieselben Tiere eine höhere Aktivität zeigen.

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Nocturnal migratory restlessness in the robin under different light conditions and patterns of light spots

Summary 1. Nocturnal migratory restlessness even under constant LL or DD lighting conditions (250 Lux, 0,006 Lux) starts at the time of sunset, and in spring reaches a maximum at 9 pm under constant dark, and a little later in constant light (Fig. 1).2. At night, during nocturnal restlessness, the birds tend to be more active in the darker parts of a set of differently lighted chambers than during daytime (Fig. 3 b).3. Highest migratory restlessness in spring and autumn is recorded under an illumination of 1 to 10 Lux, though even in total darkness a high level of activity persists. Nocturnal activity in summer also reaches a maximum at an illumination level of 5 Lux, but drops to zero at intensities below 1 Lux (Fig. 4 a).4. In cages painted black the nocturnal activity is lower than in white cages with the same overhead illumination intensity (Fig. 5).5. Low illumination intensity during daytime (250 against 700 Lux) causes high activity during the following night and raises diurnal food consumption considerably.6. A few single light spots (stars) on the ceiling strongly activate migratory restlessness (almost independent of their brightness), while higher numbers of evenly spaced light spots lower the birds activity even though total illumination intensity is higher than under the diffuse control lighting under which the birds show a higher amount of activity (Fig. 7, 8).

     

Liver as a source of transformed cell growth factor

Isolated rat hepatocytes release an acidic glycoprotein(s) that can selectively promote the growth of transformed cells. This factor has a molecular weight of 60 000–70 000 D. Liver microsomal and cytosol fractions contain two species of stimulatory activity—44 000 and 3 500 D. Mitochondrial and nuclear fractions contain only the lower molecular weight factor.     

Distinctive properties of fucosyl glycopeptides on human teratoma cells

Fucose-labeled glycopeptides from four human teratoma cell lines of independent origin show similar elution profiles on Sephadex G-50 column chromatography. The fucosyl glycopeptides elute in two major regions: one near the void volume, the other in fractions corresponding to a molecular weight of 2500-3000. These elution profiles are very different from those obtained with the other human cell lines examined which included 3 lymphomas, 2 colon carcinomas, and HeLa. The elution profiles of the human teratomas, however, show remarkable similarities to those obtained with murine embryonal carcinoma cell culture and early mouse embryos. These results suggest that the excluded G-50 fraction may well contain glycopeptides playing a role in mammalian embryogenesis.     

Behavioural displays to gustatory stimuli in newborn rabbit pups

Motor displays in the face and head regions of 33 neonate rabbits(less than 24 hrs post partum) in response to taste stimulationwere examined. A droplet of taste solution was placed mediallyon the pup's lips and the ensuing behavioral repertoire wastallied over a 60 sec period in a double blind situation. Tastantsincluded 2 concentrations each of sucrose, saccharin, citricacid and quinine. Distilled water was used as a stimulant andfor intertrial rinses. Response characteristics to the varioustaste stimuli were differentiable, specific and reproduciblewithin and across animals. Certain response features were moreoften associated with one stimulus than with another. Quinineoften produced mouth opening (gaping) and head movements, whereassucrose was associated with a quiet animal licking and makingcharacteristic mouth movements. Sour reactions often resembledthose to sweet, but other features helped distinguish thoseresponses. Reactions proved to be concentration-dependent anddifferent from those to water. Quality and hedonic value wereusually accurately judged and corresponded to adult preferencebehaviors. It was inferred that rabbits at this early age arealready equipped with a functioning taste system up to the brainstemlevel. Cross-species comparisons of stereotyped reactions werediscussed.     

Magnetic cross-relaxation among protons in protein solutions.

The magnetic spin-lattice relaxation rates of solvent water nuclei are known to increase upon addition of diamagnetic solute protein. This enhancement of the relaxation rate is a function of magnetic field, and the orientational relaxation time of the protein molecules can be deduced from analysis of the field-dependent relaxation rates. Although the nature of the interactions that convey information about the dynamics of protein motion to the solvent molecules is not established, it is known that there is a contribution to the relaxation rates of solvent protons that plays no role in the relaxation of solvent deuterons and 17O nuclei. We show here that the additional interaction arises from a cross-relaxation process between solvent and solute protons. We introduce a heuristic three-parameter model in which protein protons and solvent protons are considered as two separate thermodynamic systems that interact across the protein-solvent interface. The three parameters are the intrinsic relaxation rates of each system and a cross-relaxation term. The sign of the latter term must always be positive, for all values of magnetic field, in order for magnetization energy to flow from the hotter to the cooler system. We find that the magnetic field-dependence of the cross-relaxation contribution is much like that of the remaining solvent proton relaxation, i.e., about the same as the deuteron relaxation field dependence. This finding is not compatible with the predictions of expressions for the cross-relaxation that have been used by other authors, but not applied to data over a wide range of magnetic field strength. The model predicts that the relaxation behavior of both the protein protons and the solvent protons is the sum of two exponentials, the relative contributions of which would vary with protein concentration and solvent isotopic composition in a fashion suggestive of the presence of two classes of protein protons, when there is in reality only one. This finding has immediate implications for the interpretation of published proton relaxation rates in complex systems such as tissues; these data should be reexamined with cross-relaxation taken into account.