Further observations on the morphogenesis of human rotavirus in MA 104 cells

Summary Human rotavirus KUN strain was cultivated in a fetal rhesus monkey kidney cell line, MA 104 cells. Four types of virus particles in cells infected with KUN strain were clearly identified: nucleoid cores, single-shelled particles, double-shelled particles, and membrane band, enveloped particles. Enveloped particles were found only in the thin sections of infected cells. When first visible, the virus precursors appeared at the ribosome free membrane of rough endoplasmic reticulum (RER), increasing in size while simultaneously being coated with nucleocapsid, inner shell. Single-shelled particles were also synthesized within bundles of filaments of viroplasm in the cytoplasma. During subsequent virus maturation two types of budding processes were observed. Double-shelled particles arising at the RER membrane entered the cisternae of the RER through an exocytosis-like process. In contrast, the enveloped particles developed in the cisternae by being completely enclosed with RER membrane, and later during cytolysis released the single-shelled particles. These enveloped virus particles appeared to be the result of inefficient virus maturation at the last stage of outer capsid formation.With 11 Figures     

Mechanism of inorganic phosphate diuresis secondary to saline infusions in the rat

Summary Clearance studies have been performed in rats undergoing saline diuresis. Saline infusion was increased from 0.15 to 0.5 ml/min during each experiment in order to examine the effect of extracellular fluid volume expansion on the excretion of sodium, inorganic phosphate, and calcium in normal and parathyroidectomized animals.In normal animals excretion of sodium, inorganic phosphate, and calcium increased significantly (P<0.001) from 13.7 to 56.6 Eq/min, from 0.69 to 1.34 M/min, and from 0.54 to 0.87 Eq/min, respectively, under these conditions. Fractional excretion of sodium rose from 3.8 to 13.3%, fractional excretion of inorganic phosphate from 13.8 to 27.2%, when infusion rate was elevated from 0.15 to 0.5 ml/min.In parathyroidectomized animals excretion rates of sodium and calcium were similar. In contrast, after parathyroidectomy inorganic phosphate excretion was almost abolished, being 0.0058 and 0.0121 M/min or 0.2 and 0.3% of filtered inorganic phosphate at the lower and the higher infusion rate, respectively.It is concluded, that the presence of intact parathyroids is a prerequisite for the mediation of the normal phosphaturic response secondary to saline infusions.This work was supported in part by a grant from the Deutsche Forschungsgemeinschaft.     

Influence of serumalbumin and dextran on sodium and water excretion by the isolated dog kidney

Summary The addition of serumalbumin or of dextran reduces sodium and water excretion by isolated kidneys submitted to a saline load. While dextran supplementation produces a considerable drop of glomerular filtration, serumalbumin supplementation induces only slight changes in filtration; a proportional increase of tubular reabsorption is observed. The difference between the response to dextran and serumalbumin may be related to differences in intrarenal blood circulation. Changes in plasma protein concentration play a role in autonomous renal response to saline loading and influence tubular sodium reabsorption. This autonomous renal response is primarily related to plasma dilution.This work has been performed with the help of the Fonds National de la Recherche Scientifique.     

Evidence for a direct relationship between mitochondrial genome organization and regeneration ability in hexaploid wheat somatic tissue cultures

Summary Embryogenic and non-embryogenic long-term callus cultures of hexaploid wheat exhibit differences in the organization of their mitochondrial genome. Embryogenic and non-embryogenic fractions of callus cultures initiated from immature embryos of the wheat cultivar Chinese Spring have been isolated and subsequently subcultured. DNA-DNA hybridization experiments using labelled cloned wheat mitochondrial DNA fragments have shown that the mitochondrial DNA organization of embryogenic subcultures derived from embryogenic parts of Chinese Spring calli is closely related to that of the initial Chinese Spring calli, while non-embryogenic subcultures derived from non-embryogenic fragments of Chinese Spring calli exhibit a mitochondrial DNA organization similar to that found in non-embryogenic calli derived from cultivar Aquila. In addition, somatic tissue cultures initiated from three other non-embryogenic wheat cultivars (Talent, Thésée and Capitole) display mitochondrial DNA arrangements similar to those found in cultivar Aquila. These results strongly suggest that, in wheat callus cultures, a particular mitochondrial genome organization is correlated with the ability of cultured cells to regenerate whole plants.Abbreviations mtDNA mitochondrial DNA - ctDNA chloroplast DNA - rRNA ribosomal RNA - kb kilobase pair - cv cultivar - 2,4-D 2,4-dichlorophenoxyacetic acid     

An analysis of postsynaptic potentials of tectal neurons of the frog: correlation with impulses recorded from the terminals of retinotectal afferents

Summary The purpose of this study is to examine the synaptic action between terminals of retinal ganglion cell axons and tectal neurons. To accomplish this, an extracellular single unit identified as retinotectal fiber was first isolated from the superficial layer of the optic tectum and intracellular responses were recorded from a tectal neuron in the vicinity of the extracellular recording electrode. On-off retinal fibers and both E-E (EPSP at on and off of diffuse light) and EI-EI type (EPSP-IPSP combination at on and off of diffuse light) tectal neurons were selected for the pre- and postsynaptic pair. Postsynaptic responses to a small moving square were averaged by triggering with the isolated presynaptic impulses. The latency of the resultant EPSPs indicated that most of the E-E and EI-EI type tectal neurons were monosynaptically activated by on-off retinal fibers. One of the E-E type tectal neurons was identified as a large ganglionic neuron in layer 8.     

Three-dimensional reconstruction of transmitter-identified central neurons by “en bloc” immunofluorescence histochemistry and confocal scanning microscopy

Summary A new method for three-dimensional reconstruction of transmitter-identified neurons is presented which involves en bloc immunofluorescence histochemistry and confocal scanning microscopy. The technique was applied to different types of neurons in the rat brain and lamprey spinal cord. Thick sections or tissue blocs (50–200 m thick) were incubated with antisera against neuropeptides or monoaminergic markers, followed by fluorescent secondary antibodies. Three-dimensional reconstructions were obtained by scanning the preparations in sequential focal planes with a thin laser beam, while sampling the emitted light in each focal plane. The method is convenient and can be applied to a wide variety of neuron types. The reconstructions obtained are accurate since the optical serial sections of the specimen are perfectly aligned, and optic disturbances such as halo phenomena do not occur.     

Catecholamine excretion by the healthy adult human

Summary During the past few years much progress has been made concerning the development of accurate chemical methods for the determination of adrenaline, noradrenaline, and hydroxy-methoxy mandelic acid in urine and blood plasma. The problem of establishing standard values for the healthy average adult human of both sexes has thus become more urgent. We determined creatinine, adrenaline and noradrenaline (trihydroxyindole method) as well as hydroxy-methoxy mandelic acid (HMMA) in 16 men and 11 women. The daily excretion of creatinine remained to within 5% in 12 of the 27 subjects but varied by more than 5% to over 20% in the remaining 15 subjects. The mean values of the 24 hr urinary catecholamine excretion were: for men: noradrenaline = 24.3±6.9 g, adrenaline = 7.1±2.9 g, the NA/A ratio = 4.1±2.3, HMMA=6.9±2.1 mg; for women: noradrenaline = 23.1±7.1 g, adrenaline = 5.6±2.4 g, ratio = 5.1±3.6, HMMA=6.2±2.5 mg. A study of the diurnal variation showed that adrenaline and noradrenaline excretion was highest during the period from 7–15 hr, decreased from 15–23 hr by 20% for noradrenaline and by 30% for adrenaline, and further decreased during the time from 23–7 hr by 45% for noradrenaline and 75% for adrenaline; the excretion of HMMA was the same during the two day-time periods and was 35% lower during the night. The resting plasma levels were: for men: noradrenaline = 0.12 g/l and adrenaline = 0.23 g/l; for women: noradrenaline = 0.11 g/l and adrenaline =0.21 g/l. The values reported here agreed well with data obtained by Kärki (1956) from bioassay and were of the same order of magnitude as those collected by Brunjes (1964) using a different version of the trihydroxyidole method. The discrepancies with some other studies were critically reviewed.     

Causal dimensions of college students' perceptions of physical symptoms

According to attribution theory, controllability, locus, and stability are important dimensions underlying causal explanations. The extent to which these theoretical dimensions underlie lay explanations for physical symptoms is unclear. Accordingly, in this study, attributes relevant to the lay public were empirically derived using a multidimensional scaling (MDS) procedure. Undergraduates (N=194) provided similarity judgments for 18 potential causes of physical discomfort. The MDS analysis yielded a three-dimensional solution. The first dimension captured the distinction between physical and nonphysical causes. The second dimension distinguished either variable versus stable causes or those that are controllable versus uncontrollable by health care professionals. The third dimension differentiated causes under low versus high personal control. These findings empirically confirm the theoretically proposed dimensions of personal control and stability and suggest the utility of considering the physical/nonphysical and controllability by health care professional distinctions in future work on attributions in the health domain.     

Coronary blood flow in rats native to simulated high altitude and in rats exposed to it later in life

Summary In rats exposed to a simulated high altitude of 3500 m for their whole prenatal and postnatal life a severe cardiac hypertrophy develops. In rats born and first staying 5 weeks at sea level and then being exposed to simulated high altitude, only a unilateral right cardiac hypertrophy occurs. In both groups nutritional coronary blood flow was estimated in left ventricle, right ventricle, and septum and was compared with control animals of similar age. Coronary blood flow was measured at hypoxia in all groups. At first cardiac output was determined by the Fick principle, then⁸⁶Rb was applied and the animals were killed after 55 sec. Activity of⁸⁶Rb was measured in both cardiac ventricles and septum and the fractional uptake was calculated. According to Sapirstein (1956, 1958) the distribution of⁸⁶Rb follows the distribution of cardiac output and from both these data the nutritional blood flow to the parts of the heart may be estimated.Cardiac output was similar in rats exposed to simulated high altitude later in life (newcomers) and in control animals, but it was significantly lower in rats born in the low pressure chamber (natives).Fractions of cardiac output supplying cardiac ventricles and septum in rats from both hypoxic groups were significantly higher than in control animals. In the natives they were significantly higher than in the newcomers. The fractions of cardiac output in both newcomers and natives remained significantly higher than those of the control animals, also when calculated per gram of heart tissue.Nutritional coronary blood flow (in ml/min) was higher in both ventricles and septum of the newcomers and in the right ventricle of the natives, and lower in the septum of the natives, when compared with control animals. Coronary blood flow per gram of heart tissue (in ml/min·g) was significantly higher in all cardiac parts of the newcomers, but it was about the same in all cardiac parts of the natives when compared with controls.The importance of observed changes concerning myocardial tissue oxygenation is analyzed by using Krogh's cylindrical tissue model.Presented in part at the XXVIth International Congress of Physiological Sciences, New Delhi, India, October 20–26, 1974.     

Neuron Activity in the Prefrontal Cortex of the Brain in Rats with Different Typological Characteristics in Conditions of Emotional Stimulation

Male Wistar rats were separated according to the emotional resonance method (groups of animals avoiding (altruists) and not avoiding (egotists) the pain cries of partner rats) and neuron activity in the prefrontal areas of the cortex was studied in the right and left hemispheres. Assessments were made of changes in the frequency of nerve cell spike activity (in relation to the baseline activity of neurons in sated animals) in rats subjected to one day of food deprivation and after electrical stimulation of emotionally positive (lateral hypothalamus) and negative (tegmentum of the midbrain) brain structures and after exposure to the pain cries of partner rats. The results of these experiments revealed a series of differences in the cell activities of the two groups of rats. In conditions of hunger, the discharge frequency in the altruists was higher than that in egotists. Cortical neuron responses to positive stimulation were greater than those to negative stimulation in rats of both groups. Intracerebral stimulation produced significantly greater increases in discharge frequency in neurons of both prefrontal areas of the cortex in altruists than in egotists. In both groups of rats, neurons in the right hemisphere responded to emotionally negative stimulation with significantly greater activation than cells in the left hemisphere, while activity in the left hemisphere was greater in conditions of emotionally positive stimulation. Altruists showed significantly greater neuron responses during exposure to pain cries from victim rats in both the right and left hemispheres. The responses of egotists to victim cries were not significantly different from baseline activity levels.     

Convergent inputs from articular,cutaneous and muscle receptors onto ascending tract cells in the cat spinal cord

Summary 1.Responses were recorded from 160 ascending tract cells in segments L4 to L6 of the spinal cord in chloralose anaesthetized, spinalized cats. The tract cells were identified by antidromic activation following stimulation of pathways in the lateral and ventral funiculi at the level of the spinal cord transection at the thoracolumbar junction. Axonal conduction velocities ranged from 9 to 114 m/s. 2. A sample of 152 of the neurones examined could be subdivided according to the distribution of their receptive fields into 49 cells activated just from receptors located in skin (s cells), 17 neurones excited by receptors in deep tissues (d cells), 15 units with a convergent input from receptors in skin and deep tissues (sd cells), and 25 neurones with a convergent input from the knee joint and either skin (sj cells), deep tissues (dj cells) or both (sdj cells). No receptive fields could be demonstrated for the remaining 46 neurones. 3. S and sj cells were found almost exclusively in the dorsal horn, whereas many d, sd, sdj and dj units were in the ventral horn. Almost all of the cells that lacked receptive fields were in the ventral horn or intermediate grey. 4. Ninety-one of 158 cells (56%) demonstrated no background activity. Of these, 43 cells (27%) lacked receptive fields. Many of the silent neurones were in the ventral horn, but some were in the dorsal horn. Of 25 cells having knee joint input, 18 (72%) had background activity. 5. All of the neurones that had a receptive field in the knee joint also had a convergent input from receptors in other tissues. In 3 cases, there was a receptive field in the skin over the foot (sj cells). For 16 cells, receptive fields included not only the knee joint but also skin and deep tissue (sdj cells). Usually, the cutaneous receptive field was near the knee joint, but sometimes it was remote, such as on the foot. The deep receptive fields were chiefly in the muscles of the thigh and/or leg. For 6 dj cells, the receptive fields included not only the knee joint but also deep fields like those of sdj cells. 6. Cutaneous receptive fields were classified as low threshold (cells excited best by innocuous intensities of mechanical stimulation), wide dynamic range (cells activated by weak mechanical stimuli, but the best responses were to noxious stimuli) or high threshold (innocuous stimuli had little effect, but noxious mechanical stimuli produced a vigorous discharge). Similarly, stimulation of the knee joint with weak mechanical stimuli could excite some neurones, while others could be activated by weak or strong articular stimuli but were excited best by noxious stimuli, and still other neurones were activated by knee joint stimuli only if the intensity was noxious. 7. In several instances, contralateral receptive fields were noted. These were generally in deep tissue or in the knee joint. 8. It was concluded that many of the responses to articular stimulation of the spinal cord ascending tract cells examined in this study could have been mediated by the fine afferent fibres that supply the knee joint. Although further work will be required to determine which particular ascending tracts transmit nociceptive information concerning the knee joint, it can be proposed that many of the responses demonstrated here were likely to play a role in either joint pain of in triggering responses associated with joint pain.     

Foraging strategies ofDrosophila melanogaster: A chromosomal analysis

Two larval foraging strategies inDrosophila melanogaster were identified, rover and sitter. Rovers traverse a large area while feeding whereas sitters cover a small area. The difference between rovers and sitters was analyzed genetically by chromosomal substitutions between isogenic stocks. Differences in larval locomotor behavior (crawling behavior) can be attributed to the second chromosome, the rover strategy being dominant over the sitter strategy. Differences in feeding rate (shoveling behavior) are affected additively by both the second and third chromosomes. Natural populations ofDrosophila larvae were sampled three times over a 2-month period; rovers and sitters were at constant frequencies in these populations. The two foraging strategies are discussed in the light of resource utilization in environments where food is distributed continuously or discontinuously.     

Time series analysis of magnetoencephalographic data during copying

We used standard time series modeling to analyze magnetoencephalographic (MEG) data acquired during three tasks. Each task lasted 45 s, for a total data acquisition period of 135 s. Ten healthy human subjects fixated their eyes on a central blue point for 45 s (fixation only, F task). Then a pentagon (visual template) appeared surrounding the fixation point which simultaneously became red (fixation + template, FT task). After 45 s, the fixation point changed to green, which was the go signal for the subjects to begin continuously copying the pentagon for 45 s using a joystick and without visual feedback of their movement trajectory (fixation + template + copying, FTC task). MEG data were acquired continuously from 248 axial gradiometers at a sampling rate of 1017.25 Hz. After removal of cardiac artifacts and rejection of records with eyeblink artifacts, a Box–Jenkins autoregressive integrative moving average (ARIMA) analysis was applied to the unsmoothed, unaveraged MEG time series for model identification and estimation within 25 time lags (~25 ms). We found that an ARIMA model of 25th order autoregressive, first order differencing, and first order moving average (p=25, d=1, q=1) adequately modeled the series and yielded residuals practically stationary with respect to their mean, variance, and autocorrelation structure. These prewhitened residuals were then used for assessing pairwise associations between series using crosscorrelation analysis with ±25 time lags (~ ±25 ms). The cross-correlograms thus obtained revealed rich and consistent patterns of interactions between series with respect to positive and/or negative correlations. The overall prevalence of these patterns was very similar in the three tasks used, and, for particular sensor pairs, they tended to be preserved across tasks.     

Cationic proteins of human granulocytes Effects on human platelet aggregation and serotonin release

Immune-aggregate and thrombin-mediated [³H]serotonin release from human platelets are shown to be enhanced when platelets are preincubated with the antibacterial chymotrypsin-like cationic protein isolated from human granulocytes. The enhancement is dose dependent and inhibited by heating of the cationic protein. Release with chymotrypsin-like cationic protein alone was not observed, although the protein was shown to micro-aggregate platelets irreversibly by an ADP-dependent reaction. Platelet macro-aggregation induced by immune-aggregate was also enhanced by chymotrypsin-like cationic protein whereas platelet macro-aggregation induced by thrombin was inhibited competitively. Platelet micro-aggregation induced by chymotrypsin-like cationic protein was inhibited when preincubated for more than 5 min with a 2-fold molar excess of-1-antitrypsin. Chymotrypsin-like cationic protein interaction with several platelet reactions suggests a close relationship between neutrophils and platelets in the inflammatory process.     

The use of electrophoretic karyotypes in the classification of yeasts: Kluyveromyces marxianus and K. lactis

Summary The relationship between varieties marxianus and lactis of Kluyveromyces marxianus was investigated. Strains of these varieties readily form hybrids, but their classification in one species has recently been contested. Enzyme patterns and the GC contents of their DNAs differed significantly. Moreover, DNA-DNA reassociation was less than 15%. Since the generally accepted definition of a species is based on gene exchange, we used two approaches for directly detecting genetic recombination in crosses between representatives of both species. First, multiple marked strains were crossed, and the offspring from the resulting hybrids analyzed. Secondly, the fate of individual chromosomes in identical crosses was followed by comparing the karyotypes of the parent strains, the hybrids formed between them, and the descendants of these hybrids. Karyotypes were obtained by orthogonal-field-altemation gel electrophoresis (OFAGE). Gene exchange was not detected with either method. We therefore concluded that the formation of hybrids, even when they produced viable offspring, was not sufficient to include var. lactis and var. marxianus in one species.     

The Involvement of Dopamine in Strengthening Cortical Signals Activating NMDA Receptors in the Striatum (a hypothetical mechanism)

A possible mechanism is proposed for the enhancement/weakening of those cortical signals in the cortex-basal ganglia-thalamus-cortex neural network which induce/do not induce opening of NMDA channels in the spiny neurons of the striatum and which can be regarded as strong/weak in terms of this measure. The mechanism is based on the modulatory influences of dopamine on changes in the efficiency of corticostriatal inputs. In the absence of dopamine, relative increases in the intensity of strong (weak) cortical signals can lead to the induction of long-term potentiation (depression) of corticostriatal synapses. In this case, because of the differently directed influences on thalamic cells of signals passing via strionigral and striopallidal cells, strong signals at the output of the thalamus are weakened, while weak signals are strengthened. Activation of dopamine D₁ (D₂) receptors on strionigral (striopallidal) neurons may facilitate increases in the extent of long-term potentiation/depression (decreases in the extent of long-term potentiation/depression or induction of long-term potentiation/depression). The consequence of this is that strong signals at the output of the thalamus can be strengthened synergistically, while weak signals cab be weakened synergistically. Background cortical signals evoking tonic release of dopamine in the striatum can decrease strengthening because of weakening of the modulatory influence of dopamine on the modification of corticostriatal synapses.     

Präzisierung der Reizwirkung mittelfrequenter Wechselströme

Zusammenfassung Bei der Mittelfrequenz-Impuls-Reizung ist streng darauf zu achten, daß keine polaritären Reizkomponenten auftreten. Die diesbezügliche Kontrolle wird am besten mit Hilfe des Konvertibilitätstestes vorgenommen, d. h., es darf beim Vertauschen der Zuführungen zu den Reizelektroden weder die Reizschwelle bzw. die Größe des kollektiven Reizerfolges noch dessen Latenzzeit eine signifikante Änderung erfahren. Auf diese Weise wird die Phasenunabhängigkeit des echten Mittelfrequenz-Reizeffektes nachgewiesen.Diesen Anforderungen entsprechen Mittelfrequenz-Impulse, deren Trägerfrequenz über einige wenige Perioden sich aufschaukelt und ebenso wieder abklingt. Demgegenüber sind Mittelfrequenz-Stromstöße mit phasenstarrem Einsatz und Ende nicht unbedingt frei von polaritären Ein- bzw. Ausschalt-effekten, indem sowohl die erste als auch die letzte Trägerperiode einen polaritären Wechselimpuls-Reizeffekt ergeben kann, je nach Phasenlage bezogen auf die wirksame Reizelektrode und Art der Ansprechbarkeit des Reizobjektes (Nerv) auf entsprechend kurze gleitspiegelsymmetrische Wechselimpulse. Für eine echte Mittelfrequenz-Stromstoß-Reizung ist demnach ebenfalls ein Aufschaukeln und Abklingen der Trägerfrequenz über einige wenige Perioden erforderlich.Es besteht ein prinzipieller Unterschied zwischen der echten Mittelfrequenz-Reizung, die phasen -bzw. periodenunabhängig ist und schon früher als apolaritär bezeichnet wurde, und der konventionellen polaritären Reizung, die als polaritäre Komplikation der Mittelfrequenz-Reizung auftreten kann.Diese Präzisierung der Reizwirkung mittelfrequenter Wechselströme wurde angeregt durch zwei im Text erwähnte Publikationen, in denen in keineswegs überzeugender Weise versucht wird, die Mittelfrequenz-Reizung letzten Endes auf das polare Gesetz der Erregung zurückzuführen.

---

Summary The particular excitatory action exerted by middle-frequency alternating current can only be revealed if care is taken to eliminate the occurrence of so-called polarity effects. Such effects are produced by the short alternating impulses represented by the first and the last period of a middle-frequency current pulse and are based on the polar law of excitation.In order to prevent such polarity intrusions, it is necessary to increase and decrease the amplitude of the middle-frequency current pulses over a few carrierperiods, or, to use amplitude-modulated middle-frequency impulses of variable shape and duration of envelope.A true middle-frequency excitatory effect is easily demonstrated by resorting to the convertibility test. It will then become evident that stimulation threshold, magnitude as well as latency of response do not change during reversal of the stimulating poles. This means, that no significant phase change of the response with regard to the carrier-frequency occurs when the leads to the stimulating electrodes are commuted, and that, as a result, true middle-frequency effects do not depend upon one particular catelectrotonic variation among the carrier-periods of a middle-frequency current pulse.It can thus be concluded that a fundamental difference exists between true middle-frequency stimulation, which is based on a non-polarity or apolarity principle, and the conventional stimulation of the polar or polarity type.This paper has been written in the hope of dispelling some errors of interpretation (discussed in the text) tending to ascribe the excitatory effects of middle-frequency impulse stimulation to the classical polar law of excitation.

     

Hemoglobin heterogeneity under conditions of abnormal erythropoiesis

Experiments on rats showed that changes in the hemoglobin profile during hypoxia are determined by switching of erythropoiesis from the basic to emergency mode. The basic mode of erythropoiesis is typical of the mature organism under normal conditions. The reserve or emergency mode is realized in fetuses, senile animals, and during hypoxia. This mode is characterized by production of large erythrocytes with high content of fetal hemoglobin.     

“Dumping” of rebound nystagmus and optokinetic afternystagmus in humans

Rebound nystagmus (RN) is an involuntary movement of the eyes, characterized by slow-phase eye velocity in the direction of previously maintained eccentric gaze. The purpose of this study was to clarify the neural or neuromuscular events that are responsible for the generation of RN. To do so, we examined whether a briefly presented visual stimulus during RN reduces (i.e., dumps) subsequent eye velocity, compared with the velocity of slow-phase eye movements when no visual stimulus was presented. For comparison, dumping was examined also for optokinetic afternystagmus (OKAN), which is generally believed to result from eye-velocity signals stored in a central neural integrator as a consequence of optokinetic stimulation. Results obtained from ten normal observers showed that RN and OKAN both exhibit dumping: average slow-phase eye velocities were reliably slower after fixation of a 0.6 deg stationary target than on trials when no fixation target was presented. Although RN decayed faster than OKAN in darkness, the magnitude of dumping increased similarly with the duration of the visual stimulus (25 ms to 4 s) for both types of eye movement. The results imply that signals from a central velocity-storage mechanism contribute to the generation of RN.     

Zur Frage der aggregationsbedingten Aktivierungen von Pockenviren

Zusammenfassung Mit Hilfe von Gruppensynergismus-Diagrammen habenSharp und Mitarbeiter drei aggregationsbedingte Pockenvirus-Aktivierungsphänomene demonstriert: anomale Plaquebildung durch Kaninchenpockenvirus, MultiplizitätsAktivierung von Vacciniavirus und Multiplizitäts-Reaktivierung an vorher partiell inaktivierten Viruspopulationen.Die Basis sämtlicher Gruppensynergismus-Diagramme bildet die von den Autoren als allgemeingültig angenommene Proportionalität der Plaquetiter zu den Mengen kinetisch autonomer oder aktiver Viruseinheiten. Anhand eines einfachen Modelles einer aggregierenden Viruspopulation wird nachgewiesen, daß diese Annahme unhaltbar ist und zu der unrichtigen Interpretation führen muß, niedrig aktive Viruspopulationen würden durch Teilchenaggregierung Steigerungen ihrer biologischen Aktivität erfahren.Die Ursachen der Fehlschlüsse werden untersucht und durch Beispiele erläutert.

---

Concerning aggregation dependent activations of poxvirusesI. Erroneous conclusions deduced from group synergism diagrams

Summary With the aid of group synergism diagramsSharp and coworkers have demonstrated three activation phenomena of pox viruses, depending on particle aggregation: anomalous plaque production of rabbitpox virus, multiplicity activation of vaccinia virus and multiplicity reactivation of partially inactivated viruses.The authors' basis for all group synergism diagrams is supposed proportionality between the number of plaques and kinetically autonomous or active virus units. Certain shortcomings inherent in this concept can be shown by using a simple model of an aggregating virus population. It can further be shown that this hypothesis leads to the misinterpretation that an increase in virus activity were caused by particle aggregation.The sources of the errors are investigated and are illustrated by examples.