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.     

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.     

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     

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.     

Retrovirus and filovirus “immunosuppressive motif” and the evolution of virus pathogenicity in HIV-1, HIV-2, and ebola viruses

The immunosuppressive motif was found to be present in the glycoproteins of retroviruses and filoviruses. This sequence is also conserved in the pathogenic lentiviruses, HIV-1 and SIV, and is absent from HIV-2 gp41 and from an apathogenic simian retrovirus. The present analysis deals with the possible involvement of the immunosuppresessive motif in the pathogenicity of retroviruses and filoviruses, and the reasons for the conservation of this motif. The ancestral gene from which the immunosuppressive motif originated is not known.     

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.     

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.

     

“Dark” (compacted) neurons may not die through the necrotic pathway

Dark neurons were produced in the cortex of the rat brain by hypoglycemic convulsions. In the somatodendritic domain of each affected neuron, the ultrastructural elements, except for disturbed mitochondria, were remarkably preserved during the acute stage, but the distances between them were reduced dramatically (ultrastructural compaction). Following a 1-min convulsion period, only a few neurons were involved and their environment appeared undamaged. In contrast, 1-h convulsions affected many neurons and caused swelling of astrocytic processes and neuronal dendrites (excitotoxic neuropil). A proportion of dark neurons recovered the normal structure in 2 days. The non-recovering dark neurons were removed from the brain cortex through two entirely different pathways. In the case of 1-h convulsions, their organelles swelled, then disintegrated and finally dispersed into the neuropil through large gaps in the plasma membrane (necrotic-like removal). Following a 1-min convulsion period, the non-recovering dark neurons fell apart into membrane-bound fragments that retained the compacted interior even after being engulfed by astrocytes or microglial cells (apoptotic-like removal). Consequently, in contrast to what is generally accepted, the dark neurons produced by 1-min hypoglycemic convulsions do not die as a consequence of necrosis. As regards the case of 1-h convulsions, it is assumed that a necrotic-like removal process is imposed, by an excitotoxic environment, on dark neurons that previously died through a non-necrotic pathway. Apoptotic neurons were produced in the hippocampal dentate gyrus by intraventricularly administered colchicine. After the biochemical processes had been completed and the chromatin condensation in the nucleus had reached an advanced phase, the ultrastructural elements in the somatodendritic cytoplasm of the affected cells became compacted. If present in an apparently undamaged environment such apoptotic neurons were removed from the dentate gyrus through the apoptotic sequence of morphological changes, whereas those present in an impaired environment were removed through a necrotic-like sequence of morphological changes. This suggests that the removal pathway may depend on the environment and not on the death pathway, as also assumed in the case of the dark neurons produced by hypoglycemic convulsions.     

The distribution of lanthanum in tight junctions of the kidney tubule

Summary The penetration of either ionic or colloidal lanthanum into the tight junctions of different tubular segments of the rat kidney was studied with the electron microscope. After perfusing the tracer through the aorta it was found that ionic and colloidal lanthanum penetrated the tight junctions of both the proximal and distal convoluted tubules, while the junctions of the collecting tubules were free of tracer. An attempt to correlate junctional tightness and electrical resistance in these epithelia is presented.     

Function dependent changes in the subcellular distribution of high energy phosphates in fast and slow rat skeletal muscles

Function dependent changes in the subcellular distribution of ATP, ADP, creatine phosphate (CrP) and creatine (Cr) in rat fast-twitch gastrocnemius and slow-twitch soleus muscles were studied by fractionation of freeze-clamped and freeze-dried tissue in non-aqueous solvents.During 5 min of isotonic contraction of gastrocnemius muscles the mitochondrial content of total creatine [(CrP+Cr)] decreases by 9.5 nmol/mg total protein whereas there is an increase in extramitochondrial total creatine by 12.3 nmol/mg total protein, indicating a net transfer of 10 nmol total creatine/mg total protein/5 min across the mitochondrial inner membrane.During short-term stimulation (6 s) of gastrocnemius muscles the socalled additionally-bound ADP correlates not only with force (Hebisch et al. 1984) but also with filament overlap. This confirms the previous suggestion that additionally-bound ADP represents actomyosin-ADP-complexes.Following long-term stimulation (10 s), the rate of decay of force is at least two orders of magnitude faster than that of additionally bound ADP. This indicates a decrease of actomyosin-ADP complexes due to formation of myosin-ADP complexes.Short-term stimulation (6 s) of slow-twitch soleus muscles does not lead to any force-dependent change in the content of additionally-bound ADP, similar to the finding in long-term contracting gastrocnemius muscles. Denervation of soleus muscles leads to a decrease in additionally-bound ADP to values comparable to those found in resting fast-twitch gastrocnemius muscles.     

The favorite cigarette of the day

The choice of a favorite cigarette smoked during a given day varies considerably. Preferences are related to nicotine dependence and the lifestyles of smokers. In a sample of 5124 smokers, the after-dinner cigarette was chosen as the cigarette which they would miss most, while the next largest proportion of smokers (33%) said that they would miss the first cigarette of the morning most. The latter group scored highest on tests of nicotine dependence. In contrast, infrequent smokers (chippers) chose the after-dinner cigarette.Supported in part by NHLBI Grant HL39770 and California Tobacco-Related Disease Program Grant 1RT-87.     

Effect of injury to the medial forebrain bundle and preoptic region on activity of a strychnine-induced epileptiform focus (on the phenomenon of the hyperactive determinant dispatch station)

Experiments on cats showed that injury to the medial forebrain bundle (MFB) and to some extent of the preoptic region (PR) also on the side of application of strychnine to the cerebral cortex (middle suprasylvian gyrus) causes depression of seizure activity (spike potentials) in the strychnine focus and also in a secondary mirror focus in the symmetrical zone of the cortex of the opposite hemisphere. The same effect could be obtained in some cases after injury to MFB only. Injury to MFB and to part of PR on the side of the mirror focus causes depression of spike potentials in that focus only and does not affect activity in the primary epileptiform focus. The effects described above are examined from the standpoint of the role of the determinant dispatch station (DDS) in CNS activity: The primary epileptiform focus is a hyperactive DDS which induces the appearance of secondary foci and maintains and determines the character of their activity. It can be concluded from these experimental results that MFB participates in the modulation of cortical epileptiform activity.Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Moscow. Laboratory of Electrophysiology, V. P. Filatov Institute of Eye Diseases and Tissue Therapy, Odessa. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 10, pp. 1155–1158, October, 1976.     

The structure of a feline picornavirus and its relevance to cubic viruses in general

Summary Using the negative staining technique the pattern of subunits (capsomeres) on the surface of cubic viruses can be revealed as either white projections against a dark background (posimeres),e.g. adenoviruses, or as dark hollows surrounded by a lighter rim (negameres),e.g. reoviruses. A symmetrical pattern of 32 negameres has been demonstrated for some recently isolated feline picornaviruses and from an extension of these studies, based on radiographs of foam-rubber models, it is postulated that posimere or negamere formation may be obtained by relatively minor variation of a basic structure unit.     

Importance of the composition of the diet to the manifestation of signs of forked mutations in the offspring of Drosophila melanogaster

Summary An analysis was made of the early differences in the number of macrochaetae in the offspring ofDrosophila melanogaster (forked mutant) in the culture with yeast and raisin media. The greatest expressiveness of the mutation signs was revealed in keeping both parents on yeast nutritive medium. No difference in the results was noted in crossing the years females and raisin males. Conversely, crossing of raisin females with yeast males resulted in a marked reduction of the number of anomalousmacrochaetae. If both parents were kept on the raisin nutritive medium the offspring most closely approached the normal level. Thus, the change of the nutritive medium of the parents from yeast to raisin had a normalizing effect on the phenotype of the offspring. The shift of the manifestation of the hereditary characteristics depends mainly on the character of the mother's food. Evidently peculiarities of the female metabolism with one or another nutritive medium affect the properties of gametes developing in the ovaries.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 54, No. 9, pp. 100–103, September, 1962     

Control of locomotion in marine mollusc Clione limacina IV. Role of type 12 interneurons

Summary 1. Type 12 interneurons in pedal ganglia of Clione limacina exerted a strong influence upon the locomotor generator during intense swimming. These neurons generated plateau potentials, i.e. their membrane potential had two stable states: the upper one when a neuron was depolarized, and the down one, separated by 30–40 mV. The interneurons could remain in each state for a long time. Short depolarizing and hyperpolarizing current pulses, as well as excitatory and inhibitory postsynaptic potentials, could transfer the interneurons from one state to another. 2. When the pedal ganglia generated the locomotory rhythm, type 12 neurons received an EPSP and passed to the upper state in the V₂-phase of a locomotor cycle. They remained at this state until the beginning of the D₁-phase when they received an IPSP and passed to the down state. The EPSP in type 12 neurons was produced by type 8d neurons, and the IPSP by type 7 neurons. 3. Type 12 neurons exerted inhibitory influences upon many neurons active in the V₁ and V₂ phases, and excitatory influences upon the D-phase interneurons (type 7). 4. The functional role of type 12 neurons was to limit the activity of neurons discharging in the V-phase of a locomotory cycle. In addition, they enhanced the excitation of the D-phase neurons and promoted, thus, the transition from the V-phase to the D-phase.     

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.     

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.     

Effect of “flow anoxia” and “non flow anoxia” on the NAD/NADH redox state of the intact brain cortex of the cat

In the present study, we compared the nicotin-amide adenine dinucleotide (NAD) reducing potencies of flow anoxia and non flow anoxia in the cat brain cortex. In animals anaesthetized with alpha-D-glucochloralose flow anoxia and non flow anoxia were produced by ventilating for 2 and 25 min, respectively, with nitrogen gas. Following non flow anoxia, the brain cortices of dead animals were superfused with oxygen saturated artificial cerebrospinal fluid (mock CSF), and subsequently with CSF containing various concentrations (10^–3–10^–1 M) of potassium cyanide. NADH (reduced NAD) fluorescence of the brain cortex was measured through a cranial window with microscope fluororeflectometer. Ventilating the animals for 2 and 25 min with nitrogen gas increased cortical NADH fluorescence (NAD reduction) by 43.5±2.8% and 135.3±6.1%, respectively. Oxygen saturated CSF superfusion of the ischemic brain cortex restored the cortical NAD/NADH redox state to the preanocic level (oxidation of NADH). 10^–1 M cyanide, applied after superfusion of the brain cortex with oxygen saturated CSF resulted in comparable NAD reduction to that produced by non flow anoxia. On the basis of these findings it is suggested that non flow anoxia leads to much greater cortical NAD reduction than flow anoxia, because oxygen tension in the cortex may not fall to zero mm Hg during nitrogen anoxia lasting for 2 min. Besides this, a more pronounced substrate mobilization and acidosis may also contribute to the greater NAD reducing potency of non flow anoxia. Finally, since 10–15 min after the death of the animal the cerebral carbohydrate reserves are completely exhausted, and in our experiments non flow anoxia, reoxygenation of the ischemic brain cortex and inhibition of the cortical mitochondrial electron transport by cyanide (10^–1 M) resulted in comparable redox state changes (as far as their magnitude is concerned), it is concluded that the recorded changes in NADH fluorescence were of mitochondrial origin.     

Facts and reflections on thalamocortical reverberation of impulses

Experiments on cats, either unanesthetized or anesthetized with various doses of pentobarbital, showed that the cortical rhythmic after-discharge (slow after-activity), which has been regarded as a manifestation of reverberation of impulses in thalamocortical circuits [17], consists of a burst of spontaneous spindles evoked by stimulation. This conclusion is supported by the following facts: Spontaneous spindles and the rhythmic after-discharge respond absolutely identically (disappear) to activation of the EEG and deepening of pentobarbital anesthesia. The absence of thalamocortical reverberation is also indicated by the preservation of a rhythmic after-discharge (to clicks), synchronous with the cortex, in the thalamic relay nucleus (the medial geniculate body) after cooling or after removal of its projection zone.Translated from Neirofiziologiya, Vol. 7, No. 4, pp. 339–345, July–August, 1975.