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.     

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.     

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.     

Intraspecific variation in the structural organization and redundancy of chloroplast ribosomal DNA cistrons in Euglena gracilis

Summary Chloroplast DNAs from six different laboratory collections of Euglena gracilis strain Z and var. bacillaris were analyzed with restriction endonucleases EcoRI and Bam HI. The most variable portion of the organelle genome is the region containing the ribosomal cistrons. Intraspecific differences occur in both ribosomal DNA cistron number (one or three) and structural organization among those strains designated as strain Z and bacillaris. One culture previously designated as Z is most likely bacillaris.     

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.     

Photobehavioral differentiation in natural populations ofDrosophila pseudoobscura andDrosophila persimilis

The photoresponses of natural populations ofD. pseudoobscura andD. persimilis, occurring sympatrically, are measured in two environmental conditions (at rest and disturbed). Comparisons of the responses, intraspecifically and interspecifically, lead to the following conclusions. These must be considered within the confines of the operational nature of the measurement of laboratory photoresponses. (1) Within each species population, significant nonenvironmental differentiation has been allowed or produced by selection in the at rest photoresponse. No significant nonenvironmental differentiation is found in the photoresponse measured in a disturbed condition. (2) Within each species population, a higher mean disturbed photoresponse has been favored. The intensities or patterns of selection acting on these two photoresponses have differed such that more intrapopulation differentiation has been allowed or produced in the at rest photoresponse. (3) A higher mean photoresponse has been favored inD. persimilis for both conditions. The intensities or patterns of selection acting between these two species populations on the at rest photoresponse have differed such that more intrapopulation differentiation has been allowed or produced inD. persimilis. (4) Comparisons of this study with one on intraspecific and interspecific differentiaiton in wing length lead to the conclusion that the selective differences inferred above have acted at a level more specifically attuned to photobehavior.     

Nitrogen metabolite repression in Aspergillus nidulans: A farewell to tamA?

Summary Previous work has established that nitrogen metabolite repression in Aspergillus nidulans is mediated by the positive acting regulatory gene areA. Pateman and Kinghorn (1977) proposed that the gene tamA plays an equally important regulatory role in nitrogen metabolite repression as the result of work with tamA^r-50, an allele leading to inability to utilise nitrogen sources other than ammonium, and tamA^d-1, an allele leading to nitrogen metabolite derepression. Both tamA^r-50 and tamA^d-1 were subsequently lost. We have therefore attempted to reconstruct Pateman and Kinghorn's work with tamA. We propose that tamA^r-50 was in fact a pyroB^– tamA^– double mutation. pyroB^– mutations lead to a block in vitamin B₆ biosynthesis which can be supplemented by extremely high concentrations of ammonium. tamA^– mutations, possibly as the result of a membrane alteration, reduce the concentration of ammonium required to supplement the pyroB^– auxotrophy. There is, however, no evidence that pyroB^– or tamA- mutations, alone or in combination, affect the regulation of the levels of a number of enzymes subject to nitrogen metabolite repression. Reversion of pyroB^– strains constitutes a powerful positive selection technique for obtaining a wide variety of mutations in glnA, the probable structural gene for glutamine synthetase. We suggest that the nitrogen metabolite derepressed phenotype attributed to tamA^d-1 might have resulted from an extremely leaky glnA^– mutation.     

Lability in the responses of cells in the auditory cortex of squirrel monkeys to species-specific vocalizations

Summary The activity of 28 cells located mainly in the secondary auditory cortex (A II) of awake squirrel-monkeys, was extracellularly recorded for periods of up to 6 h. Seven different species-specific vocalizations, which were repeatedly presented to the monkey, were used as auditory stimuli. Twenty-six cells responded, at least once, to one or more vocalizations; 22 cells revealed some change in their response (pattern or strength) to at least one vocalization (change in response). Twenty-one cells exhibited a change in the number and/or type of vocalization to which they responded during the recording period (change in selectivity). At some time during the recording period all the responding cells exhibited a change in response and/or a change in selectivity (change in responsiveness). A change in response of a cell to a vocalization did not necessarily exclude a change in selectivity, associated with the same vocalization, later in time and vice-versa. A change in responsiveness to one vocalization was not necessarily correlated with changes in responsiveness to other vocalizations.     

Transformation of substrate specificity of EcoRl restrictase by glycerol

In the presence of glycerol, EcoRl restriction endonuclease hydrolyzes DNA into a larger number of fragments than under ordinary conditions. On the addition of glycerol to 50% concentration, this enzyme begins to act by what is called the EcoRl' type of restriction, which was producible experimentally only by reducing the ionic strength and increasing the pH of the solution. However, under these extremal conditions, the enzyme is quickly inactivated and does not give reproducible results, especially during the hydrolysis of high-molecular-weight DNA. The conditions found for manifestation of EcoRl' activity yield reproductible results, which is essentially equivalent to the discovery of a new restriction endonuclease.The nomenclature of the restriction enzymes follows that of Smith and Nathans [6].Laboratory of Biochemistry, D. I. Inanovskii Institute of Virology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR S. S. Debov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 7, pp. 46–48, July, 1977.     

An improved apparatus for the optical recording of contraction of single heart cells

An optical system for measuring changes in cell length during unloaded contractions of cardiac myocytes is described. A one-dimensional video image of a cell is obtained every 4 ms with a linear photodiode array, which is aligned with the longitudinal axis of the cell. The circuit used to process the image from the photodiode array has a variety of features to aid in the accurate determination of the distance between the ends of the cell, i.e. the cell length. First, the video image of the cell is divided into two windows, one encompassing the front edge of the cell, the other encompassing the rear edge. Other cells or debris beyond the cell edges are excluded. Changes in the general light level, for example as a result of debris floating above the cell, have little effect because within the windows the background light level is subtracted from the signals before they are processed further. To detect the cell edges, the system determines when the signals within the windows exceed (front edge) or drop below (rear edge) chosen threscholds, which are different for the front and rear edges. The system has memory and it identifies the rear edge of the cell as the last time the signal falls below the threshold; because of this bright spots within the cell are not mistaken for the end of the cell. The system has hysteresis, which enables it to ignore small fluctuations in brightness around the threshold. The system is easy to use, accurate, readily calibrated, and it has good spatial and time resolution (about 0.25 m and 4 ms respectively).     

Acetylcholine metabolism in the brain of rats treated with vanadyl sulfate and certain phenylacetic acid derivatives

Summary The present work describes the effect produced by phenylacetic acid, phenylethylacetic and diphenylacetic acids (sodium salts) separated and together with vanadyl sulfate on some indices, of acetylcholine metabolism in the rat's brain. Total cholinesterase activity and the free and bound (conditionally) acetylcholine levels served as indices. As shown experimentally the use of phenylacetic acid derivatives is accompanied by reduction of the bound acetylcholine, content, whereas that of free acetylcholine and the total tissue cholinesterase activity remain unchanged. Vanadyl sulfate provokes a significant reduction of the total tissue cholinesterasic activity, but does not change the content of free and bound acetylcholine therein. In conjoint action of the above-mentioned substances, the effects of phenylacetic acid erivatives are supplemented by the anticholinesterase effect of vanadyl sulfate.(Presented by Active Member AMN SSSR S. V. Anichkov) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 2, pp. 80–83, February, 1964     

Carbon dioxide,extracellular pH and fibre water in frog skeletal muscle

The fibre water of frog skeletal muscle was increased by exposure of the muscle to CO₂. Exposure to acid at constant PCO₂ caused no change in fibre water although muscle weight decreased, whereas exposure to alkali increased fibre water.Supported by the Schweizerische Stiftung für Midizinisch-Biologische Stipendien     

On the existence of a lyotropic and osmotic type of collagen swelling produced by representative electrolytes and anelectrolytes

Summary The influence of NaI, NaCl, urea, glucose and sucrose on venous tissue volume were studied with regard to osmotic (electrostatic and dehydrating) and lyotropic effects. NaI leads to the highest volume increase and to the extreme irreversibility of this change. The tested anelectrolytes cause a decrease of tissue volume over the whole range of concentration with the exception that, beyond 1.0 osM, urea causes an increase. The large reversibility of this increase is pointed out. A strict discrimination between osmotic and lyotropic volume change is questioned.     

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.

     

Comparison of the estrous cycles in mice of high and low cancer lines

Summary In February and May the author studied the duration of the estrous cycle stages in female mice of high A and low C₅₇ cancer lines. It was established that the average duration of the estrus is much greater and of diestrus much shorter in the A than that of the corresponding stages in the C₅₇ line.The estrous cycles of the C₅₇ line females do not undergo any significant seasonal changes while in the A line they approach the character of the normal mice spring cycles.Desviations from the normal duration of the estrous cycle stages in the high cancer line mice denote a disturbed hypophyseal — ovarian hormonal balance.Presented by Active Member AMN SSSR V. N. Chernigovskii     

Sodium chloride preference in hypertensive (H) and normotensive (N) rats

Summary Salt consumption was compared in two strains of rats, selected for their disparate proneness (strain H) or resistance (strain N) to Doca-salt hypertension.NaCl intake was similar in H and N rats prior to an following administration of Doca, while their respective blood pressures at the end of this experiment was 178±5 mm Hgvs. 134±3 mm Hg. Thus, disparate responses of the blood pressure to Doca in the two strains cannot be ascribed to differences in salt intake.In another study, salt preference was tested in H and N rats by two-bottle self-selecting technique. Before Doca, saline preference in H rats averaged 60.3±5.8% of total daily fluid consumption,vs 18±4.2% in N rats. Following Doca treatment for 3 weeks the respective values were 96±1.7%vs. 67±6.6%. Thus Doca treatment enhanced salt appetite in both strains, but salt preference remained significantly higher in the H rats.The increased susceptibility to hypertension and the enhanced salt appetite in the H rat, corroborates similar reports in the Okamoto SH rat. In the Brookhaven S rat, however, susceptibility to hypertension is associated with salt avoidance. The conflicting data do not support a unified concept of a genetically determined link between salt appetite and proneness to hypertension.This work was supported in part by a grant from the joint research fund of the Hebrew University-Hadassah Medical School, Jerusalem, and by a grant in aid from Merck Sharpe and Dohme, Research Laboratories.     

The penetration of the salivary glands ofRhodnius prolixus byTrypanosoma rangeli

Ultrastructural studies of the mechanism of penetration of the salivary gland of the reduviid bugRhodnius prolixus byTrypanosoma rangeli showed that trypanosomes from the haemocoele penetrate the outer membranes of the gland flagellum foremost, disrupting the inner layers, to pass between the muscle cells to reach the gland cell basement membrane. This latter is also penetrated flagellum foremost, the parasite invaginating the gland cell plasmalemma beneath, to create a vacuole in which the trypanosome crosses the gland cells to reach the central lumen, often only losing its containing vacuole just before leaving the cell.The structure of the outer membranes surrounding the salivary gland appeared similar to, and often actually part of, the basement membrane of the gland cells. These outer membranes were found to enclose large numbers of multinuleate giant form trypanosomes, whose significance is as yet unknown, but could perhaps represent a stage in the life cycle of the parasite where genetic interchange could take place.     

Effect of the factors of space flight on erythropoiesis

After orbital flight for 19–22 days on the satellites Kosmos-605 and Kosmos-782 erythropoiesis of rats was inhibited and the morphology of their megakaryocytes was modified. These changes disappeared by the 25th–27th day after the flight.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 2, pp. 238–240, February, 1977.