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.     

Early recognition ofStreptococcus pneumoniae in patients with community-acquired pneumonia

The objective of this study was to assess the predictive value of signs, symptoms, and rapidly available laboratory parameters for pneumococci in community-acquired pneumonia (CAP). A prospective study on patients with CAP who were admitted to hospital was conducted. Clinical and laboratory data were collected according to a protocol. Two hundred sixty-eight patients aged 18 years or older, not living in a nursing home or not admitted to hospital within one week of this admission, with a new infiltrate on the chest radiograph consistent with pneumonia were included. According to microbiological and serological tests, patients were allocated to one of two aetiological groups,Streptococcus pneumoniae or other pathogens. Seventy-three variables were examined for a correlation with one of the aetiological categories by means of univariate and multivariate analysis. The resulting discriminant function was considered a clinical test for which posttest probabilities for pneumococcal pneumonia were calculated.Streptococcus pneumoniae was demonstrated in 79 patients and other pathogens in 83; no pathogens were detectable in 106 patients. The variables cardiovascular disease, acute onset, pleuritic pain, gram-positive bacteria in the sputum Gram stain, and leucocyte count correctly predicted the cause of CAP in 80% of all cases in both groups. Depending on the prevalence ofStreptococcus pneumoniae, posttest probabilities for pneumococcal pneumonia were up to 90%. It is concluded that data on history, together with the result of the Gram stain of sputum and the leucocyte count, can help to distinguishStreptococcus pneumoniae from other pathogens causing CAP.     

Adaptation and habituation of the vestibulo-ocular reflex in intact and inferior olive-lesioned rats

Summary The gain of the vestibulo-ocular reflex (VOR) of intact pigmented rats was adaptively modified by training protocols that created a visual-vestibular conflict. For training, head restrained animals were oscillated on a turntable in front of an optokinetic pattern projected onto a cylindrical wall. The optokinetic pattern either moved the same amplitude with the animal (in-phase: 0.05 Hz ± 20°/s) or opposite in direction (out-of-phase: turntable and pattern 0.05 Hz ± 10°/s each). VOR responses were tested in darkness before and after each 8 min training period for a duration of 40 min. During out-of-phase training the gain of compensatory eye movements measured in light was close to 2 from the beginning on and the VOR tested in darkness increased in gain progressively from 0.48 (±0.12) to 0.9 (±0.3; P < 0.05) in 5 out of 7 rats. Two rats did not adapt their VOR gain. Phase values decreased slightly by about 10°. During in-phase stimulation compensatory eye movements were almost completely suppressed (gain close to 0) from the beginning on and the VOR tested in darkness decreased gradually in gain from 0.62 (±0.17) to 0.13 (±0.1; P<0.001) in all 6 trained rats. Phase values decreased in parallel from 151° to 119° (P< 0.01). The effectiveness of the in-phase training paradigm in the absence of compensatory eye movements indicates that retinal image slip is the relevant signal for adaptation. In seven rats with histologically verified almost complete inferior olive (IO) lesions (chemically induced at least 45 days prior to training), out-of-phase and in-phase stimulation evoked compensatory eye movements with gains comparable to those in intact rats. VOR parameters measured in darkness were altered with respect to those of control rats. Gain differed extremely between individuals and phase lag re acceleration was in all IO-lesioned rats larger than in intact rats. The time constant of the VOR in response to table velocity steps was significantly longer (17 s ±4) than in intact rats (11 s ± 3). Training did not alter the gain of the VOR in 5 out of 7 IO-lesioned rats. One rat increased its gain during out-of-phase training in the first, but not during a second training session (and not during in-phase training) and another rat decreased its gain during in-phase training (but not during out-of-phase training). These changes in VOR gain might have occurred by chance rather than by learning. The absence of adaptation in IO-lesioned rats can be explained either by the absence of climbing fiber mediated slip signals in the cerebellar cortex or by lesion-induced secondary changes which result in a long-term reduction of the inhibitory efficacy of Purkinje-cells. In the absence of arousing stimuli VOR responses of intact rats exhibit a strong decrement during table oscillations in darkness. Between trials, with the rat at rest, response magnitude recovered spontaneously. Six out of 8 IO-lesioned rats expressed a very similar modification of their VOR gain. These results indicate that the neural mechanisms responsible for adaptive gain decrease during in-phase training and those responsible for a gain decrease during short-term habituation are different.     

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.     

Ribonuclease activity of the “myofibrillary” fraction of normal and autolyzed muscle tissue

The separation in a sucrose gradient of the myofibrillary fraction of normal and autolyzed muscle tissue gave 4 components. During post-mortem destruction of the tissue there was observed a slight decrease of the myofibrillary fraction yield and also certain changes in the distribution of protein between different components. Under the selected conditions RNase activity was found in all 4 components. During the course of autolysis enzymatic activity increased in the whole myofibrillary fraction, as well as in the lysosomal-mitochondrial components of myofibrils.Research Laboratory, Ministry of Health of the USSR, Moscow. Translated from Buylleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 5, pp. 533–537, May, 1978.     

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.     

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.     

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.     

An hypothesis regarding the cortical mechanisms of operative memory

Investigations of the neuronal activity of the cerebral cortex of monkeys during the performance of a delayed spatial choice made it possible to formulate an hypothesis regarding the neuronal systems providing for operative memory. One system functions on the principle of relay race-reverberation transmission of information. During the action of a sensory signal a population of spatially selective sensory neurons is excited. By the delay period (operative memory) this information is transmitted to a population of memory neurons. The delay period is quantized in time segments in the course of which individual populations of cells are involved in relays in the reverberation activity. Each of these populations comprises a neuronal trap in which the excitation circulates for 1.5–2 sec. At the end of the delay period switching of the excitation to a different population of cells takes place, which are associated with the preparation of a goal-directed movement (the neurons of the motor programs). Another system of neurons assures the reliability of the transitional phases of the above-named processes, specifically: 1) of the switchings of information from the sensory neurons to the memory neurons and subsequently to the neurons of the motor programs; 2) the reflection of the entire period of operative memory without relay race-reverberation; and 3) the preservation of the signal information in the activity of a unified neuronal population right up to the moment of the performance of the goal-directed movement. The above-designated systems are represented variously in the associative (frontal and parietal) zones of the neocortex.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 41, No. 6, pp. 1088–1093, November–December, 1991.     

A cyclin protein modulates mitosis in the budding yeast Saccharomyces cerevisiae

Summary For the budding yeast Saccharomyces cerevisiae the mitotic cell cycle is coordinated with cell mass at the regulatory step start. The threshold amount of cell mass (reflected as a critical size) necessary for start is proportional to nutrient quality. This relationship leads to a transient accumulation of cells at start, termed nutrient modulation, upon enrichment of nutrient conditions. Nutrient enrichment abruptly increases the critical size needed for start, causing the smaller cells, produced in the previous cell cycle, to be delayed at start while growing larger. Here we show that, in S. cerevisiae, a second cell-cycle step, at mitosis, also exhibits nutrient modulation, and is, therefore, another point of cell-cycle regulation. At both mitosis and start, nutrient modulation was found through mutation to be regulated by the activity of the cyclin-related WHI1 (CLN3) gene product.     

The static load component in muscle work

Summary By citing examples from actual work situations and discussing the concept of muscular endurance and fatigue this paper is intended to provide an account of past and current research on the static component of muscular load during work. By amplitude probability distribution analysis of electromyographic signals it is possible to estimate the static level of muscular load during work. Electromyographic studies of job rotation between different assembly tasks in electronic industries often show that there are quantitatively and qualitatively only small differences in muscular load between different tasks.     

Effect of muscular work on the motor function of the stomach and duodenum

Summary The effect of muscle work on the gastric and duodenal motor function was studied in dogs.It was observed that the static stress inhibited the hunger contractions of the stomach and duodenum; the inhibitory effect disappeared as the stress ceased. The static muscle work effect was more pronounced in hunger contractions of the stomach than in those of the duodenum. Under the influence of static stress, the periodic hunger contractions of the stomach varied more extensively than its acid and digestive contractions.Presented by Active Member Acad. Med. Sci. USSR V. N. Chernigovsky     

Particular RNA primer from growth medium differentially stimulates in vitro DNA synthesis and in vivo cell growth of Neurospora crassa and its slime mutant

Summary Purine rich small RNA-primer molecules (about 10–12 nucleotides), secreted into the growth medium of 3-h germinated conidia of N. crassa, strongly stimulated a concentration-dependent in vitro DNA synthesis of N. crassa slime mutant as well as DNAs from the human cancer cells but did not affect that from normal cells. These RNA-primer molecules stimulated also in vivo cell growth of N. crassa slime mutant, but not of the N. crassa wild type. Our studies suggest that DNAs from the slime mutant of N. crassa as well as DNAs from human cancerous cells provide increased sites for enhanced in vitro and in vivo replication of DNAs. RNA-primer molecules can be hydrolyzed by T1 RNase but not by pancreatic RNase.     

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.

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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.

     

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     

Category-related components in visual evoked potentials: photographs of faces,persons, flowers and tools as stimuli

Summary One hundred and sixty black-and-white photographs of faces, persons, tools and flowers constituted the four stimulus categories in the first experimental paradigm. In the second paradigm, 160 black- and-white photographs of persons in a neutral (side view), fighting, greeting and depressed postures were used. The same nine female and nine male students volunteered as subjects in both paradigms. EEG responses were recorded through the electrodes F3, F4, Cz, Oz, T5 and T6 and referenced to linked mastoid electrodes. Individually averaged EPs and grand averages of the EPs for all 18 subjects were computed as well as bipolar responses for selected pairs of electrodes. Category-related components in the evoked potentials (EPs) were found mainly in the recordings through the midline and the frontal electrodes. These category-specific differences were more prominent, however, in the bipolar recordings between these electrodes and the respective ipsilateral electrodes (T5 or T6) than in the monopolar recordings. Monopolar and bipolar EPs could be divided into those evoked by person stimuli and by non-person stimuli. Category-related differences were demonstrated by computing EP-difference curves related to pairs of stimulus categories. In addition to the statistical analysis of peak amplitudes and peak latencies of the individual curves, a 'running Wilcoxon test was applied and cross-correlation functions between the EPs evoked by different stimulus categories were computed. The face-related components of the EPs described in earlier studies could be confirmed. They were prominent in the waves peaking between 130 and 150ms and between 200 and 230ms and were stronger when faces rather than full-figure neutral persons were used as stimuli. No significant hemispheric differences could be found between any of the EPs. In the second paradigm, EEG responses evoked by person stimuli in a neutral, fighting, greeting or depressed posture exhibited only slight differences, if at all. The person-responsive components in the EPs evoked by the photographs of a neutral standing person (side view) were smaller between 120 and 200 ms than in the other three categories in which expressive persons were the stimuli.     

Enzyme-secreting function of the intestine in dogs,as influenced by adrenalectomy and injection of some steroid hormones

Summary As established in experiments on dogs with isolated intestinal sections, the amount of the solid portion and the total secretion per time unit exhibited no significant changes after unilateral adrenalectomy; however, the enterokinase and saccharase content in the secretion showed a marked drop. After bilateral adrenalectomy and administration of cortisone and desoxicorticosterone the amount of secreted solid portion of the intestinal juice becomes greater, whereas the enterokinase and saccharase content is considerably diminished. There is a tendency towards the peptidase content increase. The main features of these changes are retained if cortisone or desoxicorticosterone alone is administered for a period of 10 days, although in such conditions there occur some variations in the secretion of individual hormones. Without hormone administration the total amount of intestinal secretion and of its solid portion, as well as the quantity of enzymes secreted per time unit gradually decreases. After bilateral adrenalectomy blood is always present in the solid portion of the secretion.(Presented by V. V: Parin, Active Member, Academy of Medical Sciences, USSR) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. No. pp. 53–58     

Immunological study of HB-Ag carriers

Summary The serum immunoglobulin levels, the presence of circulating autoantibodies, the number of peripheral atypical lymphocytes and the number of DNA and RNA synthesizing mononuclear cells were studied in a group of healthy HB-Ag (australia Antigen) carriers and in a group of healthy HB-Ag negative control subjects.In the HB-Ag carriers, in spite of the persistent antigenaemia, all these immunological findings were normal (as in the control subjects).     

Oncogenic activity of the BK type of human papova virus in inbred rat strains

Summary The oncogenicity of the human polyomavirus BK (BKV) was tested in newborn inbred rats.It was found that the tumor rate was negatively correlated with the levels of T antibody 3 months after inoculation and the frequency of animals with detectable T antibodies 1.5 months after inoculation.By contrast, no influence of viral HI titers on the tumor rates was found. Thymectomy of animals resulted in most experiments in increased tumor rates. Inoculation with BKV of animals later than 24 hours after birth yielded a decrease of tumor rates.The results obtained suggest that T antibody titers present at a critical time after inoculation are associated with low oncogenicity of BKV.The oncogenicity of BKV was comparatively tested in rat strains possessing the allele l or the allele a, respectively. The oncogenicity was significantly higher in rats with the allele l than in rats with the allele a. Rats with the allele l showed lower T antibody response than rats with the allele a.These differences could be explained by the finding that cells of a origin showedin vitro a higher percentage of T antigen bearing cells than did cells of a strain possessing the allele l. In comparison to previous results obtained with BKV inoculated outbred WISTAR rats, the oncogenicity of comparable BKV doses in inbred rats was generally higher and the latency period of tumor manifestation shortened.