Action spectra for fruiting of the mushroom Coprinus congregatus

Spectral sensitivity for photostimulated and photoinhibited phases of the development of Coprinus congregatus Bull. ex Fr. was determined from 405–730 nm. The cultures were exposed during 12 h to a constant number of incident quanta. Spectral sensitivity for photoinduction of primordia formation, for photoinhibition of primordia development and for photomaturation of primordia was quite similar, suggesting a common photoreceptor during fruit-body morphogenesis. A defined action spectrum for the photoinhibitory effect of a light break during the inductive night was determined from 407–690 nm. The most effective wavelengths were in the blue (445 nm). Wavelengths longer than 510 nm were ineffective. The general shape of this action spectrum was similar to those obtained for many blue light responses in which a flavoprotein was postulated to be the photoreceptor.     

Genetic control of metabolism of mutagenic purine base analogs 6-hydroxylaminopurine and 2-amino-6-hydroxylaminopurine in yeast <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

We studied the effect of inactivation of genes, which control biosynthesis of inosine monophosphate (IMP) de novo and purine salvage and interconversion pathways, on sensitivity of yeast Saccharomyces cerevisiae to the mutagenic and toxic action of 6-hydroxylaminopurine (HAP) and 2-amino-6-hydroxylaminopurine (AHA). It was shown that the manifestation of HAP and AHA mutagenic properties depends on the action of enzyme adenine phosphoribosyltransferase encoded in yeast by APT1 gene. A blockade of any step of IMP biosynthesis, with the exception of the block mediated by inactivation of genes ADE16 and ADE17 leading to the accumulation of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), was shown to enhance yeast cell sensitivity to the HAP mutagenic effect; however, it does not affect the sensitivity to AHA. A block of conversion of IMP into adenosine monophosphate (AMP) causes hypersensitivity of yeast cells to the mutagenic action of HAP and to the toxic effect of HAP, AHA, and hypoxanthine. It is possible that this enhancement of sensitivity to HAP and AHA is due to changes in the pool of purines. We conclude that genes ADE12, ADE13, AAH1, and HAM1 controlling processes of purine salvage and interconversion in yeast, make the greatest contribution to the protection against the toxic and mutagenic action of the examined analogs. Possible mechanisms of HAP detoxication in bacteria, yeast, and humans are discussed.     

Anxiolytic action of beta-carbolines in rats

The decreased sensitivity to the anxiolytic action of diazepam, BC-3-KEE, IME-6MEO-TGBC, IME-6MEO-DBC was shown in rats with experimental alcoholism. The degree of the decreased sensitivity was dependent on the affinity of the compounds to benzodiazepine receptors.     

Response in tonic type neurons of the cat auditory cortex to tones of different frequencies and intensities

In experiments on immobilized cats, intra- and extracellular response in tonic type neurons to tones of differing frequencies and intensities were investigated, as well as the organizational pattern of receptive fields in these units. Tonic type neurons were encountered at different cortical layers, but mostly (93% of the total) were located at a depth of 1.0–2.2 mm. Minimum thresholds required for response in these neurons were on average 7.7 dB below that found in neurons generating a phasic reaction in response to a tone. "Tonic" differed from "phasic" neurons in their inferior frequency-discriminative ability, with a Q₁₀ value averaging 4.1±0.4 as against 9.1±0.7 in phasic neurons. Size of receptive fields in tonic neurons (as revealed by occurrence of spike response in these units) was 3.5 times that observed in phasic cells. Length of action potentials in the majority (80%) of tonic neurons was about one and a half times to twice that found in phasic units. Tonic neurons also displayed a high degree of sensitivity to changes in the duration and intensity of acoustic stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, July–August, pp. 498–506, 1969.     

Sensitivity of embryonal lungs of mice, rats and humans to exposure to nitrosomethylurea in organ cultures

With the direct action of nitrosomethylurea (NMU) in a concentration of 0.05 mg/ml on the organic cultures of the embryonic lung of mice of the A line, Wistar rats and man they developed a different degree of degenerative changes and hyperplastic epithelial proliferates. A toxic effect prevailed in the cultures at the initial experimental periods. The most sensitive to the toxic action of NMU was the lung tissue of rat embryos, and the least--of mice. The incidence of hyperplastic proliferates was, on the contrary, the greatest in the cultures of mouse lungs, and the least--of rat lungs. The sensitivity of the embryonic lungs of the man and rodents to the toxic action of NMU in repeated administration into the nutrient medium diminished during the cultivation. There was an increase of survival of the experimental cultures in comparison with the intact control.     

Gaba sensitivity of the somata and dendrites of pyramidal cells in isolated slices of rat hippocampus

During experiments on isolated slices slices of rat hippocampus the inhibitory action of -aminobutyric acid (GABA) was investigated on the excitation of field CA, pyramidal neurons, together with the effects of bicuculline, penicillin and thiopentone on this process. It was found that GABA effectively and reversibly reduced the amplitude of the antrodomic population spike in the area of both the somata and the dendrites of these cells. The sensitivity of apical dendrites to GABA exceeded that of the somata by one order, increasing in a proximal-distal direction. The somata of pyramidal neurons were marked by pronounced desensitization to GABA. Bicuculline and penicillin acted as GABA antagonists at all the levels of CA, pyramidal cells investigated. Bicuculline blocked the effects of GABA on somata and dendrites in almost equal measure. The antagonistic effects of penicillin were 10 times greater in the pyramidal layer than in the dendritic region. Thiopentone reinforced the inhibitory effects of GABA. The potentiating effects of thiopentone were exerted most strongly on the dendrites. It is postulated that the membrane of field CA, neurons contain two types of bicuculline-sensitive GABA receptors, differing in their location (mainly on the cell body or dendrite), their pharmacology, and degree of desensitization to GABA.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 737–746, November–December, 1985.     

The involvement of a rhodopsin-like photopigment in the photoperiodic response of the Japanese quail

Summary A technique has been developed for the investigation of the photopigment involved in the photoperiodic control of reproduction in Japanese quail,Coturnix coturnix. When these photoreceptors were exposed to white or monochromatic light a clear relationship was found between light intensity and the extent of photo-induced luteinizing hormone (LH) secretion. A spectroradiometric investigation of the passage of light through the skull and brain enabled us to illuminate the hypothalamic region with equal numbers of photons at a range of wavelengths. Action spectra were then conducted and showed a photopigment with a peak sensitivity at wavelengths near 500 nm. An excellent match was obtained when the standard absorption spectrum for a rhodopsin was fitted to the action spectrum, suggesting a rhodopsin maximally sensitive at 492 nm. The absolute sensitivity of the photoreceptors was calculated at a range of wavelengths: with light at 500 nm, 2.85×10^–12 E·cm^–2·s^–1 triggered the photoperiodic response. This level of sensitivity is matched only by the rhodopsin visual pigments.Abbreviations LH luteinizing hormone - T transmission     

Veratrum viride; hypotensive and cardiac effects of intravenous use

The hypotensive action of veratrum viride given intravenously was studied in 24 patients, 22 of them hypertensive and 2 normotensive. Vasodepression of considerable but variable degree was obtained in all patients. Maximum hypotension occurred 8 to 15 minutes after injection and relative hypotension usually lasted at least two hours. In four patients subnormal hypotension occurred but there were no clinical manifestations of shock. The blood pressure rose promptly when pressor drugs were administered.A dose of 0.3 to 0.5 mg. brought about a satisfactory decrease in blood pressure. The degree of decrease was affected by the speed of administration and in a few patients by idiosyncratic sensitivity to the drug. Veratrum has an extravagal action on the pulse rate, and in that and other respects resembles digitalis. Veratrum should be given with caution to digitalized patients. Atropine reduced but did not abolish the hypotensive effect of veratrum, and was more effective when given before veratrum. This indicates that the parasympathomimetic action of veratrum is important in the mechanism of blood pressure reduction.     

Diversity within a population of Shigella sonnei according to markers of medicinal preparations

As revealed in this study, S. sonnei population is represented by two clusters with respect to the sensitivity to different antibiotics. A higher degree of diversity was observed with respect to the action of streptomycin, kefzol, ampicillin, chloramphenicol and kanamycin in comparison with the action of gentamicin, nevigramon, rafampicin, tetracycline and polymyxin. The level of diversity of S. sonnei with respect to the sensitivity to antibiotics under study underwent essential changes during the calendar year. The distributions obtained study quite closely corresponded to changes in Sonne dysentery morbidity observed within the year period: the first cluster corresponded to the period of morbidity between the seasons and the second one, to the seasonal period of morbidity. The minimal coefficient of diversity fell on May while the maximum--on September. The minimal level of S. sonnei diversity, as a rule, corresponds to the minimum biosystems stability.     

Hybridization of Chinese hamster cells sensitive to ultraviolet irradiation

Resistance to UV-light was studied in two UV-sensitive aneuploid Chinese hamster cell clones to different origin and degree of sensitivity, their respective polyploids and somatic cell hybrids. The karyotype of the parental clones, cell hybrids and polyploids was analyzed in parallel. A great variability of karyotypes was detected in hybrid cells. Serial cultivation of hybrids was accompanied by chromosome loss. Soon after fusion the hybrid clones proved to be more resistant to UV than the parental sensitive cells. However, their sensitivity increased with passages. The comparison of UV-sensitivity with data on karyotype analysis allowed to assume that the increase in sensitivity was correlated with the loss of particular chromosomes or chromosome regions. The results obtained indicated the existence of a polygenic control of UV-sensitivity, the multiple genes being assigned to different chromosomes. A reverse effect of ploidy was detected, i.e. a decrease in the resistance to the lethal action of UV-light in polyploids as compared to the parental clones.     

Aging of the erythrocyte--XVII. Changes in the properties of superoxide dismutase

1. An increase in the sensitivity of superoxide dismutase (SOD) to the action of diethyldithio-carbamate and cyanide was observed in red cell fractions of greater age. 2. It suggests that SOD inactivation during erythrocyte aging is not an "all or none" process but involves transition(s) between enzyme forms of different properties. 3. An increase in the ratio of less mobile to the more mobile SOD bands was observed by polyacrylamide-gel-electrophoresis in older erythrocytes.     

Trichromatic color vision in the salamander (Salamandra salamandra)

Spectral sensitivity functions were measured between 334 nm and 683 nm in Salamandra salamandra by utilizing two behavioral reactions: the negative phototactic response, and the prey catching behavior elicited by a moving worm dummy. The action spectrum of the negative phototactic response revealed 3 pronounced maxima: at 360–400 nm, at 520–540 nm, and at 600–640 nm. In the range around 450 nm, there was a reaction gap where sensitivity could not be measured. The action spectrum of the prey catching behavior was entirely different: maximal sensitivity was found at 500 nm and at 570 nm. Between 500 nm and 334 nm sensitivity decreased continuously for about 1 log unit (Fig. 6).Experiments under chromatic adaptation using the prey catching behavior indicate that the relatively high sensitivity in the ultraviolet range is not due to a separate ultraviolet photoreceptor, but is based on the responses of a photoreceptor maximally sensitive at about 500 nm.Color discrimination was tested by moving a colored worm dummy within a differently colored surround of equal subjective brightness. The salamanders were able to discriminate blue from green, and green from red (Fig. 10). The results can be explained by assuming a trichromatic color vision based on 3 photoreceptor types maximally sensitive around 450 nm, 500 nm and 570 nm (Fig. 12).     

Effect of tyramine on the spinal cord afferent link of pressor reflexes

In anesthetized cats, tyramine application on the dorsal surface of C6-TI spinal cord segments suppressed the pressor components of blood pressure reflexes evoked by radial nerve A sigma or A + C afferent stimulation. Tyramine application on L4-SI spinal cord segments suppressed pressor reflexes to tibial nerve stimulation. Both the degree and the rate of reflex suppression increased with the rise in tyramine concentration from I to 4%. Along with these local effects "distant" tyramine action was demonstrated: pressor reflexes to radial nerve stimulation increased when tyramine was applied on L4-SI segments, but after its application on C6-TI segments pressor reflexes to tibial nerve stimulation increased in some cats, decreased in the other ones, or remained practically unchanged.     

Multi-loop representation of the segmental muscle stretch reflex

Bees were trained to react to differences both in the size and in the degree of greyness of discs. To measure the differential sensitivity on these parameters, differences in size and shade of grey (-intervals) were established such as lead to a specific choice reaction (Fig. 3). The -intervals may be described for both parameters by Weber's rule (Fig. 4). The main result is the following relationship between the differential sensitivity and the equivalence curve as defined by cross modality matching. The bee treats two discs, which differ from a reference disc in diameter or in degree of greyness, as equivalent when both differ from the reference disc by an equal number of -intervals (Fig. 6). The choice reactions between the reference disc and the discs of the equivalent pair are the same for these parameters. This does not hold for another parameter (Fig. 7A and B). Problems of infering from the -intervals to the differential sensitivity are then discussed.     

Spectral Sensitivity of the Planarian Ocellus

The ocellar potential (OP) of planaria was recorded using microelectrode techniques. The action spectrum and spectral sensitivity of the OP are described. Maximum OP sensitivity was found with 508 nm light. A moderate increase in sensitivity to blue light was observed. This is typical of many invertebrate photoreceptors and was shown, by selective chromatic adaptation, not to indicate the presence of a second pigment.     

Electrophysiology of the Fetal Spinal Cord : I. Action potentials of the motoneuron

Responses from motoneurons were recorded with microelectrodes, from the spinal cords of kitten fetuses and newborn kittens between 40 days' gestation and a few days after birth. As in the adult animal, intracellularly recorded action potentials by either ortho- or antidromic shocks have two components, "A" and "B" or IS and SD. The action potentials of the adult and immature motoneuron differ mainly in the afterpotentials which are absent in the fetal cell in "good" condition. Repeated stimulation or deterioration of the cell resulted, however, in the appearance of depolarizing and hyperpolarizing afterpotentials. No major differences were found in the mode of anti- or orthodromic invasion of the adult and fetal motoneuron, but the degree of invasion of the soma-dendritic complex may be somewhat less in the fetal cells. The ventral root discharge by dorsal root stimulation could be obtained in the fetus 3 weeks before birth. This reflex discharge was concluded to be monosynaptic. Excitatory postsynaptic potentials, probably monosynaptically activated, could be recorded from inside motoneurons by stimulation of dorsal root or peripheral nerves. The most remarkable change during prenatal development was an increase in the speed and efficacy of the excitatory synaptic potentials which showed a marked change during the last weeks of prenatal life.     

Potential-dependent interaction of chemical reagents with the gating mechanism of the nerve fiber sodium channel

The action of two water-soluble carbodiimides and of Woodward's reagent K on the properties of the gating mechanism of sodium channels of the Ranvier node membrane was investigated. Treatment with carbodiimide solution (pH 4.8–5.2) at a potential of –80 to –100 mV was shown to delay activation and inactivation of the channels considerably and to reduce the sensitivity of both gating functions to changes in membrane potential. The effective activation charge, determined relative to the limiting logarithmic slope of the activation curve (z_ef) was reduced by 1.7 times. Treatment of the membrane under the same conditions, but at zero holding potential, induced much smaller changes in properties of the gating mechanism; under these conditions z_ef remained unchanged. Woodward's reagent at high negative potential induced the same changes in the gating system as carbodiimide at 0 mV. The action of Woodward's reagent also depended on potential, but by a lesser degree than when carbodiimides were used. The results suggest that two types of carboxyl groups exist on the outer surface of the membrane: "mobile," which perform the role of gating particles and which are moved from the surface when the channel changes into the open or inactivated state, and "immobile," which face the external solution whatever the state of the channel.Institute of Cytology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 5, pp. 577–590, September–October, 1984.     

Modifying action of Saccharomyces boulardii on the biological properties of enterobacteria

The influence of the exometabolites of the fungus S. boulardii, contained in the probiotic preparation "Enterol", on the biological properties of opportunistic and pathogenic enterobacteria of fecal microflora (inactivation of lysozyme, colicin production, hemolytic activity, antibiotic resistance) was studied. The study revealed that the supernatants of S. boulardii decreased antilysozyme activity (ALA) in lactose positive (lac+) and lactose negative (lac-) Escherichia coli and Klebsiella strains, but produced no influence on ALA in Salmonella. In response to the action of S. boulardii exometabolites colicin production in E. coli (lac+) was found to increase, while in E. coli (lac-) colicin production was suppressed. An increase in the sensitivity of lactose negative E. coli to cefazolin and cefotaxime under the action of S. boulardii supenatants was noted. The results obtained in this study show the probable mechanism of the corrective action of "Enterol" on intestinal biocenosis, which should be taken into consideration in the differentiated selection of probiotics for the treatment of intestinal dysbacteriosis.     

Choice of a method for determining the sensitivity of Escherichia coli to silver

Different methods (methods of discs, of stamps and of minimal inhibitory concentration determination) aimed to determine the Escherichia coli sensitivity to the action of silver on the nutrient media are studied. It is shown possible to use the method of stamps for preliminary estimation under extensive tests. It is established that the data obtained by these methods correlate between themselves with a high degree of trustworthiness and do not correlate with those data obtained in the studies of the antimicrobic action of silver in water.     

Short communication. Abscisic acid is not necessarily required for the induction of patchy stomatal closure

Patchy stomatal closure was observed in leaves of transgenic plants of Nicotiana plumbaginifolia producing antibodies that block the action of abscisic acid. Stomatal patchiness was induced by leaf detachment and subsequent water loss. Stomatal closure was followed by an irreversible reduction of maximal chlorophyll fluorescence. The degree of deviation from the A/ci-curve is correlated with steady-state diffusion conductance before leaf detachment. It is concluded that a heterogeneous sensitivity of stomata to abscisic acid is not directly involved in the induction of patchy stomatal closure.Keywords: Abscisic acid, chlorophyll fluorescence imaging, patchy stomatal closure, Nicotiana plumbaginifolia.