Effect of low-energy microwaves on DNA stability in solution

DNA isolated from liver of healthy and tumor-bearing (sarcoma 45) rats was irradiated in water-salt solution with weak microwaves (64.5 GHz, 50 μW/cm²). The heat stability of DNA increased with irradiation time (a raise of 1.5°C in T _m for “tumor” DNA after 90 min, without changes in ΔT), which may be associated with dehydration of the surrounding Na⁺ ions.     

Reorganization of Receptive Fields of Cortical Field 21a Neurons and Formation of Responses to Moving Visual Stimuli

Using extracellular recording of spike activity from single neurons of field 21a of the cat neocortex, we examined in detail the spatial organization of receptive fields (RFs) of such cells after conditions of presentation of an immobile blinking light spot (a static RF) and moving visual stimuli (dynamic RFs). As was shown, the excitability of different RF subfields of a group of neurons possessing homogeneous on–off organization of the static RF changes significantly depended on the contrast, shape, dimension, orientation, and direction of movement of the applied mobile visual stimulus. This is manifested in changes in the number of discharge centers and shifts of their spatial localization. A hypothesis on the possible role of synchronous activation of the neurons neighboring the cell under study in the formation of an additional neuronal mechanism providing specialization of neuronal responses is proposed.     

Responses of Neurons of the Extrastriate Area 21b of the Cat Brain Cortex to Changes in Orientation of Moving Visual Stimuli

We studied the responses of neurons of the extrastriate cortical area 21b of the cat to changes in orientation of the movements of visual stimuli within the receptive field (RF) of the neuron under study. Our experiments demonstrated that 24 of 108 cells (22%) responded differentially to a certain extent to orientation of the movements of visual stimuli. As a whole, neurons of the area 21b did not demonstrate fine tuning on the optimum angle of orientation. In many cases, neuronal responses to different orientations of the movement of visual stimulus depended significantly on specific parameters of this stimulus (its shape, dimensions, and contrast). Some directionally sensitive neurons responded to a change in orientation of the movement of visual stimuli by modification of the index of directionality. We also studied spatial organization of the RF of neurons with the presentation of stationary visual stimuli. Comparison of the neuronal responses to a change in orientation of the movements of stimuli and to presentation of stationary stimuli showed that the correlation between the orientation sensitivity of the neuron under study and the stationary functional organization of its RF was insignificant. We hypothesize that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation.     

Histamine-Mediated Regulation of Electrical Activity during the Bladder–Urethra Interaction in Rats

The effect of histamine on background spontaneous electrical activity of the interrelated bladder and urethra was studied in rats. The basic characteristics of pacemaker activity (action potential amplitude, average peak rise rate, peak rise time, peak half-width, rhythmogenicity frequency) were analyzed both in normal conditions and upon exposure to histamine (10^–4 mol/L). A comparison of the action potential parameters in the above organs demonstrated far lower values of the amplitude (by 34.19%; p ≤ 0.001), peak rise rate (by 30.39%; p ≤ 0.01) and peak rise time (by 18%; p ≤ 0.01) at a reduced rhythmogenicity frequency. Histamine evoked a considerable increase in the amplitude and its rise rate in the bladder (by 50.59 and 56.36%, respectively; p ≤ 0.001) and rhythmogenicity frequency (by 18%; p ≤ 0.01) at a constancy of the remaining two parameters. In the urethra, no obvious changes were detected in the action potential parameters. Morphohistochemical analysis also supported the involvement of histamine in the activation of rhythmogenicity only in the bladder. Thus, histamine is not implicated in the genesis of tonic contractions in the urethra, in contrast to its activating effect on the bladder.     

Proteins of the Rpf (resuscitation promoting factor) family are peptidoglycan hydrolases

The secreted Micrococcus luteus protein, Rpf, is required for successful resuscitation of dormant "non-culturable" M. luteus cells and for growth stimulation in poor media. The biochemical mechanism of Rpf action remained unknown. Theoretical predictions of Rpf domain architecture and organization, together with a recent NMR analysis of the protein structure, indicate that the conserved Rpf domain has a lysozyme-like fold. In the present study, we found that both the secreted native protein and the recombinant protein lyse crude preparations of M. luteus cell walls. They also hydrolyze 4-methylumbelliferyl-beta-D-N,N',N'-triacetylchitotrioside, a synthetic substrate for peptidoglycan muramidases, with optimum activity at pH 6. The Rpf protein also has weak proteolytic activity against N-CBZ-Gly-Gly-Arg-beta-naphthylamide, a substrate for trypsin-like enzymes. Rpf activity towards 4-methylumbelliferyl-beta-D-N,N',N'-triacetylchitotrioside was reduced when the glutamate residue at position 54, invariant for all Rpf family proteins and presumably involved in catalysis, was altered. The same amino acid substitution resulted in impaired resuscitation activity of Rpf. The data indicate that Rpf is a peptidoglycan-hydrolyzing enzyme, and strongly suggest that this specific activity is responsible for its growth promotion and resuscitation activity. A possible mechanism of Rpf-mediated resuscitation is discussed.     

“Irregular” visual receptive fields of neurons of the cat lateral geniculate body

Using point-to-point testing, the spatial organization of receptive fields (RF) of the neurons of the lateral geniculate body (LGB) was studied in cats with pretrigeminally transected brainstcm (without general anesthesia). In 60% of studied neurons (96 units of 160 examined), configuration of their RF considerably differed from round or ellipsoid. The shape of such RF was frequently rather complex, and they were qualified as irregular receptive fields (IRF). Presentation of the stable flickering spot throughout the entire surface of 60 IRF (63%) evoked qualitatively similar responses of a neuron, i.e., these IRF were homogeneous. In 29 cells the responses were of theon-off type, 22 neurons generatedoff responses, andon responses were observed in 9 cells. In the rest of the IRF (37%), it was possible to differentiate the subfields, whose stimulation evoked generation of different types of responses, i.e., these IRF were heterogeneous. In the case of moving stimuli, the neurons with homogeneous IRF showed no directional selectivity, while such selectivity was observed in most units with heterogeneous IRF.Neirofiziologiya/Neurophysiology, Vol. 28, No. 1, pp. 7–16, January–February, 1996.     

Changes in the amino acids content of almond buds during their hibernation and development

Auto?i p?edkládají výsledky chromatografického stanovení volných aminokyselin a aminokyselin bílkovinných frakcí rozpustných v ethanolu a louhu, a nerozpustných, v květních a vegetativních pupenech dvou r?zně v??i zimě odolných odr?d mandloně Non-plus-ultra a Voch?aberdi, odebraných v r?zn?ch termínech od podzimu do jara. Chromatografické stanovení aminokyselin v pupenech ukázalo :

1. 1.
   V květních a vegetativních pupenech se projevuje béhem podzimu a zimy dosti dob?e pozorovatelný rozdíl v obsahu a poměru aminokyselin skoro v?ech frakcí. Nejvýrazněj?í rozdíl se projevuje v kvalitativním obrazci a poměru volných aminokyselin a aminokyselin frakcí rozpustnych v ethanolu, slaběji u frakcí rozpustnych v louhu a nerozpustných.     

Characterization of spontaneous electrical activity of the urinary tract: Ureter,bladder, urethra

The study aimed to characterize spontaneous electrical activity of the ureter, urinary bladder and urethra as well as their interrelationship. The basic parameters of pacemaker activity (amplitude, frequency, peak rise rate, peak rise time, peak half-width) were comparatively analyzed in each of the active areas. Out of the three areas compared, the ureteral rhythmogenic zone displayed the maximum amplitude and apex formation rate. Under conditions of urine influx from the ureter into the bladder and isolation of these organs from the urethra, the amplitude and peak rise rate in the latter decreased by almost 20%. At the same time, all the parameters of the ureter and bladder remained intact. Complete block of urine influx into the bladder by transecting the ureter at the appropriate area led to a slight decrease in the amplitude of action potentials, peak rise rate and rhythmogenicity frequency in the bladder, respectively, by 14.2, 12.5 and 16% at the constancy of other parameters of its activity. Subsequent isolation of the bladder from the urethra had no appreciable effect on the altered parameters of the former. The similar tendency towards a reduction of the parameters was observed under the same conditions in the urethra. Thus, a relationship was revealed between autonomous activities of the ureter, bladder and urethra. The regulatory role in this process is provided by the urine flow through these organs.