Mapping of brain activity in mesencephalic and diencephalic structures of toads during presentation of visual key stimuli: a computer assisted analysis of (14C)2DG autoradiographs

Summary The (¹⁴C)2DG autoradiographic technique has been employed to quantitatively map glucose utilization in the mesencephalon, the diencephalon and the cerebellum, of toads in response to configurational moving visual stimuli: (i) a 0.4 cm × 2.8 cm worm-like stripe (W) which elicited prey catching responses, (ii) a 8.4 cm × 8.4 cm square (S) that released predator avoidance responses, and (iii) a 2.8 cm × 0.4 cm antiworm-like stripe (A) which elicited no motor activity.For various brain nuclei different relationships were obtained: The optic tectum showed statistical significant higher 2DG uptake during worm-stimulation (¯X _W) than during antiworm stimulation (¯X _A), i.e.¯X _W>¯X _A. The latter visual pattern led to a 2DG utilization that was statistically significant stronger than during stimulation with a square (¯X _S), i.e.¯X _A>¯X _S. Thus, in comparison between right and left hemisphere as well as between brains the following ratios were obtained:Optic tectum:¯X _W>¯X _A>¯X _S; nucleus isthmi:¯X _W>¯X _A-¯X _s; posterodorsal lateral thalamic nucleus:¯X _S>¯X _A>¯X _W; posteroventral lateral thalamic nucleus:¯X _S>¯X _A¯X _W; posterior thalamic nucleus:¯X _W>¯X _A¯X _S; anteripr division of the lateral thalamic nucleus:¯X _W>¯X _A¯X _S; anterior thalamic nucleus:¯X _A>¯X _S>¯X _W; nucleus of Bellonci and dorsal division of the ventrolateral thalamic nucleus:¯X _W¯X _A¯X _S; cerebellum:¯X _S¯X _W>¯X _A.Abbreviations A anterior thalamic nucleus - Cb cerebellum - Hyp hypothalamus - Ist nucleus isthmi - cl. Ist contralateral Ist - La lateral thalamic nucleus, anterior division - Lpd lateral thalamic nucleus, posterodorsal division - Lpv lateral thalamic nucleus, posteroventral division - MP medial pallium - NB/VLd nucleus of Bellonci and ventrolateral thalamic nucleus, dorsal division - P posterior thalamic nucleus - PO preoptic area - Sna snapping evoking area=ventrolateral tectum - Str striatum - Tec tectum opticum     

Increased endogenous retroviral gene expression is a consequence of lymphocyte activation

Plasma cells of line 151(5) chickens have been shown to express elevated levels of endogenous retroviral envelope glycoprotein (VEG), measured relative to levels expressed by both immature B cells and resting peripheral B lymphocytes. In this study we analyzed the relationship between peripheral blood lymphocyte (PBL) maturation and the level of VEG expression. A culture system was developed that would support maturation of pokeweed mitogen-activated peripheral B lymphocytes. As analyzed by cytofluorometry, both Ig+ and Ig- lymphoblasts present in the pokeweed mitogen-stimulated cultures expressed detectable levels of VEG in contrast to bursacytes and PBL. Similarly, Ig- blasts, which were present in concanavalin A-stimulated cultures of PBL and presumed to represent activated T cells, were also positive for the expression of VEG. Immature T cells, i.e., thymocytes, although negative by immunofluorescence analysis, expressed VEG at levels that were detectable by radioimmunochemical techniques. These results indicate that T cells as well as B cells constitutively express VEG, and that mitogenic activation of the resting lymphocyte induces an increase in VEG expression.     

Der hemmende Einfluß gleichzeitig bewegter Beuteattrappen auf das Beutefangverhalten der Erdkröte (Bufo bufo L.)

Zusammenfassung Durch simultane visuelle Bewegungsreize, die von mehreren Beutetieren (z.B. Mehlkäferlarven) ausgehen, wird der Beutefang der Erdkröte (Bufo bufo L.) gehemmt. An diese Verhaltensheobaehtung anknüpfend, wurde die Abhängigkeit dieses inhibitorischen Umfeldeffektes von verschiedenen visuellen Reizparametern im Attrappen versuch quantitativ gemessen: Im frontalen Gesichtsfeld der Kröte rotierte vor dunklem Hintergrund eine weiße, rechteckige, 2,5 × 20° große Beuteattrappe (Zentralattrappe, z) mit dem Rechteckzentrum im Drehpunkt. Zusätzlich konnten mehrere Kreisscheiben von 5 bzw. 10° (Peripherattrappen, p) um die Zentralattrappe bewegt werden.Die Beutefangaktivität R _z [Beutefangreaktionen x min^–1] auf die allein gebotene Zentralattrappe war bei einer Sehwinkelgeschwindigkeit v _s der distalen Attrappenkanten 10v _s30 [grad x see^–1] maximal und sank für kleinere oder größere Winkelgeschwindigkeiten wieder ab. Eine mit v _s=25 [grad x sec^–1] allein bewegte Peripherattrappe löste maximale Beutefangaktivität R _p aus. Mit zunehmender Anzahl n _p simultan bewegter Peripherattrappen sank die Beutefangaktivität ab.Mehrere, um den gleichen Drehpunkt bewegte Peripherattrappen, deren Abstand untereinander =10° betrug, blieben von der Kröte unbeantwortet. Sie bildeten ein inhibitorisches Umfeld und hemmten dadurch die Reaktion auf die gleichzeitig bewegte Zentralattrappe z. — Die im Simultanreizungsversuch gemessene Beutefangaktivität R _zp war abhängig vom Abstand [grad] zwischen Zentralattrappe und Peripherattrappen ( : Kürzester Abstand zwischen z und p): Für =10° war R _zp0 und stieg für >10° an. — Kontrollversuche, die jeweils auf die Simultanreizung mit z allein folgten (R _z), ließen eine -abhängige Nachhemmung erkennen. — Die hemmende Wirkung auf die Beantwortung von z war auch von der Sehwinkelgeschwindigkeit v _s der Peripherattrappen abhängig; sie war bei derjenigen Sehwinkelgeschwindigkeit (v _s=25 [grad × sec^–1]) maximal, mit der die Zentralattrappe, allein geboten, maximale Beutefangaktivität auslöste; für v _sg25 [grad × sec^–1] nahm die Hemmung wieder ab.Die Versuchsergebnisse lassen auf inhibitorische Verknüpfungen innerhalb des zentralen visuellen Systems schließen. Es wird vermutet, daß die Reiz-Verhaltens-reaktionsbeziehungen in den visuellen Simultanreizungsversuchen durch eine Art zentrale laterale Inhibition bestimmt werden.

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Inhibitory effect of simultaneously moved prey dummies on the prey catching behaviour of the common toad (Bufo bufo L.)

Summary The prey catching behaviour of the toad (Bufo bufo L.) is generally inhibited by simultaneously visual moving stimuli caused by a group of prey animals (mealworms). According to this behavioural observation the dependence of this inhibitory effect on several visual parameters were quantitatively measured in dummy experiments: in the frontal visual field of the toad a white rectangular prey dummy of 2,5×20° (central dummy, z) was rotating in a centre against dark background. In addition several disks of 5 or 10° diameter (peripheral dummies, p) could simultaneously rotate around the central dummy (Figs. 1 and 7).The prey catching activity R _z [catching reactions x min^–1] released by rotation of only the central dummy z increased with increasing angular velocity v _s of the stimulus distal edges, reaching a maximum for 10v_s30 [degrees x sec^–1] and decreasing for v _s>30 [degrees x sec^–1] (Fig. 5).A single peripheral dummy p, moved at v _s=25 [degrees x sec^–1], released maximal catching activity R _p. The activity R _p decreased with the increasing number n _p of simultaneously offered dummies (Fig. 6).The prey catching behaviour of the toad was inhibited, when several peripheral dummies p were moved around the centre with a distance =10° from each other. They caused an inhibitory field and they also inhibited the response to a simultaneously moved central dummy z. The prey catching activity, measured in experiments in which z and p rotated simultaneously, depends on the distance [degrees] between z and p ( being the shortest distance between z and p). For =10°, R _zp was zero; R _zp increased for >10° (Figs. 9 and 10). — Control experiments carried out with z allone — after having applied the simultaneous stimulation — showed a - dependent after-inhibition (Fig. 9). — The inhibitory effect on the response to z also depended on the angular velocity v _s of p; the inhibition was at a maximum for v _s25 [degrees x sec^–1], and it decreased for v _s25 [degrees x sec^–1] (Fig. 11).The experimental results suggest inhibitory interactions within the central visual system. It is supposed that the relation between stimulus and behavioural reaction in simultaneous stimulating experiments results from some kind of central nervous lateral inhibition.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5).     

Untersuchungen über die Anteile zentralnervöser Aktionen an der taxisspezifischen Ermüdung beim Beutefang der Erdkröte (Bufo bufo L.)

Zusammenfassung In der vorliegenden Arbeit wurden die neurophysiologischen Grundlagen der taxisspezifischen Ermüdung beim Beutefang der Erdkröte (Bufo bufo L.) mit Hilfe von Hirnausschaltungen näher untersucht. Die Befunde wurden mathematisch-statistisch ausgewertet.Nach wiederholter Auslösung der Richtbewegung durch Reizung eines konstanten Retinabereiches mit einer bewegten Beuteattrappe sinkt die Reaktionsbereitschaft ab. Das Maß für die Bereitschaft ist die Anzahl vergeblicher Richtbewegungen dieser Reizserie. Innerhalb einer Reizserienfolge (mehrere Reizserien, getrennt durch Erholungspausen konstanter Dauer) zeigt die Abnahme der Reaktionsanzahlen je Reizserie einen exponentiellen, periodisch gedämpften Verlauf. Dem periodischen Ausschwingen der Reaktionsbereitschaft innerhalb einer Reizserienfolge kann die Verknüpfung von zwei Vorgängen zugrunde liegen: einem stetig abklingenden, exponentiellen, und einem periodischen Vorgang (Oszillation).Der exponentielle Verlauf läßt sich durch Variation der Erholungspausen ändern. Bei kurzen Erholungspausen sinken die Reaktionsanzahlen in aufeinanderfolgenden Reizserien schneller ab als bei langen Pausen.Durch triebbestimmende Faktoren, wie Jahreszeit, Tageszeit und Sättigungsgrad, läßt sich die allgemeine Reaktionshöhe verändern. Einflüsse auf den exponentiellen Verlauf konnten meistens nicht nachgewiesen werden.Nach partiellen Vorderhirnexstirpationen sinken die Reaktionsanzahlen im Verlauf der Reizserienfolge schneller als vor der Operation. Die Amplitude der Oszillation hat sich gegenüber den Normaltieren erhöht. Vorderhirnlose Kröten versagen beim Beutefang; das Fluchtverhalten bleibt jedoch erhalten.Nach Defekten im dorsalen Bereich des Zwischen- und des Mittelhirns (tammhirndefekte) vermindern sich die Reaktionsanzahlen innerhalb einer Reizserienfolge oft sehr viel langsamer als bei intakten Tieren. Amplitude, Frequenz und Dämpfung der Oszillation haben sich häufig verringert. Stammhirndefekte Kröten zeigen gesteigerte (enthemmte) Beutefangreaktionen. Sie schnappen nach beliebig großen, bewegten Gegenständen. Das Fluchtverhalten fällt aus. Je nach der Größe und der Lage des Defektes kann das Beuteverhalten selektiv für ein Auge, für beide Augen oder auch für getrennte Retinabereiche enthemmt werden. In gleicher Weise reagieren auch stammhirndefekte vorderhirnlose Kröten.Die taxisspezifische Ermüdung der Erdkröte (Bufo bufo L.) läßt sich als Folge einer reizspezifischen Nachwirkung deuten, die während einer Reizserie laufend zunimmt und die Ausführung der zugeordneten Reaktion hemmt. Das zentrale Wirkungsgefüge wird erörtert.

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Investigations on central nervous actions to the taxis-specific fatigue in the prey-catching behaviour of the common toad (Bufo bufo L.)

Summary In the experiments described in the present paper, the author tried, by means of brain lesions to become nearer acquainted with the neurophysiological fundamentals of the taxis-specific fatigue in the prey-catching behaviour of the Common Toad (Bufo bufo L.). In statistical analyses, the results could be treated.When the release of the turning movements, by stimulating a constant part of the retina with a moving prey-dummy, is repeated, the responsiveness decreases (Fig. 4). Index of this responsiveness is the number of futile turning movements in a certain stimulus series. Within a sequence of series (several stimulus series separated by recovery intervals of constant duration), the decrease of response numbers in each series takes an exponential (Figs. 6 and 18 b normal), periodically (Figs. 6 and 18c normal) quenched course. This leads to the conclusion that an exponential process interferes with an oscillation.The exponential course can be altered by varying the recovery intervals. When the intervals are short, the response numbers decrease, in successive stimulus series, faster than when the pauses are long (Fig. 6).The general level of reaction can be changed by factors which determine the motivation, e.g. by season, temperature, and degree of satiation. Influences upon the exponential course could, mostly, not be ascertained.After the telencephalon has been partially extirpated, the response numbers diminish faster than before the operation (Figs. 10 and 11). The amplitude of the oscillation is higher than it is with normal individuals (Fig. 18a–c VH/E₂ and VH/E₃). Toads having no telencephalon fail to catch prey; the escape behaviour, however, is maintained.As a result of lesions in the dorsal regions of the diencephalon and mesencephalon (STH-lesions, Fig. 3), the response numbers often diminish, within a sequence of stimulus series, much slower than they do with intact animals (Fig. 12 STH/D₁). Amplitude, frequency and quenching of the oscillation often have decreased (Fig. 19a–c Sth/D ₁+VH). Toads operated in this way show excessive prey catching reactions. They snap at moving objects of whatever size (Fig. 15). The escape behaviour fails. According to the size and localization of the defect, the prey-catching behaviour can be intensified selectively for one eye, for both of them, or for separated parts of the retina. Toads defective in the dorsal regions of their diencephalon and mesencephalon (STH-lesion) and deprived of their telencephalon, react in the same manner (Figs. 13 and 20 STH/D_{1, 2}-VH).The taxis-specific fatigue of Bufo bufo L. can be interpreted as a consequence of a stimulus-specific after-effect (Fig. 17), which increases continuously during a series of stimuli and inhibits the realization of the coordinated reaction. Finally, the author discusses the central meachnism (Fig. 16).

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Zum Teil mit Unterstützung durch die Deutsche Forschungsgemeinschaft (Ew 7/1 a u. b und Ew 7/2).     

Subunit selectivity and epitope characterization of mAbs directed against the GABAA/benzodiazepine receptor

mAbs bd 17, bd 24, and bd 28 raised against bovine cerebral gamma-aminobutyric acid (GABAA)/benzodiazepine receptors were analyzed for their ability to detect each of 12 GABAA receptor subunits expressed in cultured mammalian cells. Results showed that mAb bd 17 recognizes epitopes on both beta 2 and beta 3 subunits while mAb bd 24 is selective for the alpha 1 subunit of human and bovine, but not of rat origin. The latter antibody reacts with the rat alpha 1 subunit carrying an engineered Leu at position four, documenting the first epitope mapping of a GABAA receptor subunit-specific mAb. In contrast to mAbs bd 17 and bd 24, mAb bd 28 reacts with all GABAA receptor subunits tested but not with a glycine receptor subunit, suggesting the presence of shared epitopes on subunits of GABA-gated chloride channels.     

Influence of tidal volume on respiratory compliance in anesthetized infants and young children

Recent studies have suggested a close association between total respiratory compliance (Crs) and tidal volume in anesthetized paralyzed infants who are being artificially ventilated. To investigate this further, the multiple occlusion technique was used to measure Crs in 20 anesthetized infants and young children (aged 1-25 mo) before elective surgery. Measurements were made after intubation 1) during spontaneous breathing (SB), 2) after administration of a non-depolarizing muscle relaxant with tidal volume and frequency mimicking that during SB, and 3) with the child still paralyzed but tidal volume approximately double that during SB. Compared with values obtained during SB, there was no significant change in Crs after paralysis when ventilation matched the child's own pattern (P greater than 0.2). When ventilated with the larger tidal volumes, the infants showed a highly significant increase in Crs (mean 62%, range 14-158%, P less than 0.0001). These results may have implications not only for studies performed during anesthesia but also when infants were monitored in the intensive care setting. Values of Crs obtained in ventilated infants may reflect both the mechanical behavior of the respiratory system and the pattern of ventilation at the time of measurement.     

Temporal discharge patterns of tectal and medullary neurons chronically recorded during snapping toward prey in toads Bufo bufo spinosus

In freely moving toads, the temporal discharge patterns of tectal and medullary neurons were observed during prey-catching.

1. Tectal T5.2 and T8.1 neurons displayed a premotor warming up firing that in the former was addressed specifically to prey orienting or snapping and in the latter generally to almost any kind of body movement.
2. The temporal discharge patterns of T5.2 neurons during snapping were different from those during orienting toward prey. Snapping started in the peak phase of warming up; firing was immediately terminated during the snap; thereafter some rebound activity was observed. Orienting started after the premotor warming up in the declining phase whilst the neuron kept on firing during orienting and then settled when the orienting movement was completed.
3. In toads which were not motivated to catch prey — comparabl to immobilized ones — the discharge frequency of T5.2 neurons toward a prey stimulus revealed no such warming up.
4. Because it is known that prey-selective T5.2 neurons are controlled by pretectal inhibitory influences, the following experiment was conducted: during recording a T5.2 neuron a pretectal lesion was applied ipsilaterally to the recording site. After a few seconds, the neuron showed a strong premotor wanning up in response to any kind of moving object, followed by prey-catching.
5. In the medulla oblongata, different H-type neurons of the hypoglossal nucleus displayed specific discharge patterns which resembled the tongue protractor and retractor muscle activities; a third type resembled the activity of the genio/sterno-hyoid muscle, which are suggested to stabilize the hyoid bone during snapping.
6. There were medullary M8-type neurons with properties similar to T8.1.
7. Snapping could be triggered by electrical stimulation of the optic tectum in the representation of the frontal visual field, but not by stimulation in the hypoglossal nucleus or the adjacent medial reticular formation.
8. A concept of a neuronal circuit for the coordination of tongue muscle contractions in response to prey is proposed.

     

Molecular drift of the bride of sevenless (boss) gene in Drosophila

DNA sequences were determined for three to five alleles of the bride-of- sevenless (boss) gene in each of four species of Drosophila. The product of boss is a transmembrane receptor for a ligand coded by the sevenless gene that triggers differentiation of the R7 photoreceptor cell in the compound eye. Population parameters affecting the rate and pattern of molecular evolution of boss were estimated from the multinomial configurations of nucleotide polymorphisms of synonymous codons. The time of divergence between D. melanogaster and D. simulans was estimated as approximately 1 Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and that between the two pairs of sibling species as approximately 2 Myr. (The boss genes themselves have estimated divergence times approximately 50% greater than the species divergence times.) The effective size of the species was estimated as approximately 5 x 10(6), and the average mutation rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of amino acid polymorphisms within species to fixed differences between species suggests that approximately 25% of all possible single-step amino acid replacements in the boss gene product may be selectively neutral or nearly neutral. The data also imply that random genetic drift has been responsible for virtually all of the observed differences in the portion of the boss gene analyzed among the four species.      

Visual unit,EEG and sustained potential shift responses to biologically significant stimuli in the brain of toads (Bufo bufo)

Summary Visual unit activity, EEG changes and sustained potential shifts (SPS) were recorded from the toad tectum whilst the animal was presented with a visual stimulus. Telencephalic EEGs were also recorded.On the surface of the tectum, retinal unit activity preceded a sustained negative shift in potential and an increase in the amplitude and dominant frequency of the EEG. In deeper layers of the tectum, T5 units with configurational selectivity for wormlike stimuli were found. The activity of these units followed a pronounced SPS and EEG change.Visual unit activity was most pronounced during the negative-going phase of the synchronised EEG, when there was also a small decrease in amplitude of neuronal spikes. Similarities between the latencies and durations of EEGs and SPSs, and their response decrements, on repeated stimulus presentation, implies a close relationship between them not shared by the visual units studied. The specific activity of tectal units is discussed in relation to the correlated EEG and SPS changes, which may form part of an adaptive sensitizing mechanism.Abbreviations EEG electroencephalogram - ERF excitatory receptive field - SPS sustained potential shift - T4, T5 tectal neurons