Geometrical characteristics of mitochondria and active presynaptic zones in the dorsal horn of the cat spinal cord

A morphometric electron microscope study was carried out on the ultrastructure of 140 presynaptic terminals (PT) in the dorsal horn of the cat spinal cord. Some spatial characteristics of mitochondria and active zones (AZ) for these PT were examined using statistical stereological analysis techniques. The distribution of 3-dimensional mitochondrial radii was determined, together with average mitochondrial volume, mean area of the external membrane, and average numbers of the test population falling within the PT. Distribution of diameters and estimates of mean area of AZ were obtained, as well as of mean value of synaptic clefts. The relationship between findings from morphometric research and parameters of processes underlying ionic transmembrane diffusion and accumulation is discussed.Dnepopetrovsk State University. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 741–747, November–December, 1989.     

Inhibition in the neurons of the somatosensory cortex and the possibility of intracortical propagation of excitation

Extra- and intracellular leads were used to study the reactions of neurons in the pyramidal tract (PT) of the cat brain to antidromic and afferent effects. It was shown that afferent activation of PT neurons proceeds heterogeneously. Three types of PT neurons were identified, successively involved in the impulse response to afferent stimulation. By means of paired stimuli we determined the heterogeneous changes in sensitivity of late reacting PT neurons. It was found that, under certain conditions, the different IPSP evoked by afferent stimulation or PT stimulation do not prevent the appearance of impulse responses to secondary synaptic activation. A conclusion was drawn from these experiments on the localization of the excitatory intracortical terminals on the somas of the PT neurons and on the limited effect of inhibitory processes upon intracortical propagation of the afferent signal reaching the cortex. A functional scheme of intracortical PT neuron links is presented.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 465–473, September–October, 1971.     

Statistical estimation of the membrane area and numbers of active sites at presynaptic terminals

A study was made of geometrical features of electron micrographic profiles of presynaptic terminals (PT) in the dorsal horn of the cat spinal cord. A statistical approach whereby an area of enclosed membrane may be estimated on the basis of the parameters of its flat random sections is described. An estimation of the mean area of the plasmalemma of the test PT was obtained using this approach. The probability estimate of the mean number of active sites per presynaptic bouton is considered, as well as the possible use of statistical data so obtained for determining characteristics of physical processes occurring at presynapses.Dnepropetrovsk State University. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 29–36, January–February, 1990.     

Effect of dilution rate on the release of pertussis toxin and lipopolysaccharide ofBordetella pertussis

Summary The kinetics ofBordetella pertussis growth was studied in a glutamate-limited continuous culture. Growth kinetics corresponded to Monod's model. The saturation constant and maximum specific growth rate were estimated as well as the energetic parameters, theoretical yield of cells and maintenance coefficient. Release of pertussis toxin (PT) and lipopolysaccharide (LPS) were growth-associated. In addition, they showed a linear relationship between them. Growth rate affected neither outer membrane proteins nor the cell-bound LPS pattern.Nomenclature X cell concentration (g L^–1) - specific growth rate (h^–1) - _m maximum specific growth rate (h^–1) - D dilution rate (h^–1) - S concentration of growth rate-limiting nutrient (glutamate) (mmol L^–1 or g L^–1) - Ks substrate saturation constant (mol L^–1) - m_s maintenance coefficient (g g^–1 h^–1) - Y_x/s theoretical yield of cells from glutamate (g g^–1) - Y_x/s yield of cells from glutamate (g g^–1) - Y_PT/s yield of soluble PT from glutamate (mg g^–1) - Y_KDO/s yield of cell-free KDO from glutamate (g g^–1) - Y_PT/x specific yield of soluble PT (mg g^–1) - Y_KDO/x specific yield of cell-free KDO (g g^–1) - q_PT specific soluble PT production rate (mg g^–1 h^–1) - q_KDO specific cell-free KDO production rate (g g^–1 h^–1)     

Stereometric characteristics of ultrastructure of presynaptic terminals in the dorsal horn of the cat spinal cord

Morphometric statistical techniques were used to investigate geometric aspects of 240 axodendritic presynaptic terminals (PT) located in the dorsal horn of the gray matter of the cat spinal cord. Parameters describing the configuration and average spatial radius of the three-dimensional PT (approximated by irregular ellipsoid were estimated on the basis of the morphometry of random PT sections applying aspects of the theory of probability. Lack of any correlation between location of the active zone and the configurational pattern (extent) of terminals was demonstrated. Densitometric distribution of average spatial PT radii was obtained (mean: 0.820 µm). The relatively limited scatter of this distribution would indicate extremely close similarity between parameters of the PT comprising the test group.Dnepropetrovsk University. A. A. Bogomolets Institute of Physiology, Academy of the Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 403–410, May–June, 1989.     

Long-Term Posttetanic Changes of Synaptic Transmission and Synapse Morphology of the Pike <Emphasis Type="Italic">Esox lucius</Emphasis> Olfactory Bulb

In the olfactory bulb (OB) of the pike, phenomena of long posttetanic potentiation (LPTP) and long posttetanic depression (LPTD) are reproduced. Probability of induction of LPTP and level of its expression are shown to depend direct on parameters of density of axo-dendritic synapses in the glomerular neuropil and size of its active zones (AZ). In pikes with the high level of these parameters (the synapse density 5.2 per 20 µm², the mean length of AZ cross-section 293 nm), potentiation appear in 95% of cases, while in pikes with low values (the density 3.1, the AZ length 239 nm) in as low as 30%, with LPTD developing rather often instead of LPTP. The LPTP in the phase of its maximal development (60 min after tetanus) corresponds to an increase of the mean length of AZ cross-section of axodendritic synapses by 13.6%, while the LPTD—to its decrease by 16.5% as compared with control. The LPTP induction phase (5–15 min after tetanus) is not associated with any ultrastructural transformations of postsynaptic AZ of axo-dendritic synapses. By the morphometric method, it has been established that LPTP in the pike OB is of the homosynaptic nature, i.e., is due to an enhancement of synaptic efficiency of the excitatory afferent input just subjected to tetanization. On the whole, by using axo-dendritic synapses of the pike OB as an example it was shown that in simple, flat, asymmetric excitatory synapses a steady enhancement of their effectiveness was accompanied by an increase of length of AZ cross-sections, while a reduction of their efficiency—by its decrease.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 3, 2005, pp. 285–292.Original Russian Text Copyright © 2005 by Ruzhinskaya, Gdovskii.     

States of high conductance in a large-scale model of the visual cortex

This paper reports on the consequences of large, activity dependent, synaptic conductances for neurons in a large-scale neuronal network model of the input layer 4C of the Macaque primary visual cortex (Area V1). This high conductance state accounts for experimental observations about orientation selectivity, dynamics, and response magnitude (D. McLaughlin et al. (2000) Proc. Natl. Acad. Sci. USA 97: 8087–8092), and the linear dependence of Simple cells on visual stimuli (J. Wielaard et al. (2001) J. Neuroscience 21: 5203–5211). The source of large conductances in the model can be traced to inhibitory corticocortical synapses, and the model's predictions of large conductance changes are consistent with recent intracellular measurements (L. Borg-Graham et al. (1998) Nature 393: 369–373; J. Hirsch et al. (1998) J. Neuroscience 15: 9517–9528; J.S. Anderson et al. (2000) J. Neurophysiol. 84: 909–926). During visual stimulation, these conductances are large enough that their associated time-scales become the shortest in the model cortex, even below that of synaptic interactions. One consequence of this activity driven separation of time-scales is that a neuron responds very quickly to temporal changes in its synaptic drive, with its intracellular membrane potential tracking closely an effective reversal potential composed of the instantaneous synaptic inputs. From the effective potential and large synaptic conductance, the spiking activity of a cell can be expressed in an interesting and simplified manner, with the result suggesting how accurate and smoothly graded responses are achieved in the model network. Further, since neurons in this high-conductance state respond quickly, they are also good candidates as coincidence detectors and burst transmitters.     

Optimizing Exchange Transfusion for Severe Unconjugated Hyperbilirubinemia: Studies in the Gunn Rat

Background

Severe unconjugated hyperbilirubinemia carries the risk of neurotoxicity. Phototherapy (PT) and exchange transfusion (ET) are cornerstones in the treatment of unconjugated hyperbilirubinemia. Studies to improve ET efficacy have been hampered by the low application of ET in humans and by the lack of an in vivo model. The absence of an appropriate animal model has also prevented to determine the efficacy of adjunct or alternative treatment options such as albumin (Alb) administration.

Aim

To establish an in vivo model for ET and to determine the most effective treatment (combination) of ET, PT and Alb administration.

Methods

Gunn rats received either PT, PT+Alb, ET, ET+PT, ET+PT+Alb or sham operation (each n = 7). ET was performed via the right jugular vein in ∼20 min. PT (18 µW/cm²/nm) was started after ET or at T₀. Albumin i.p. injections (2.5 g/kg) were given after ET or before starting PT. Plasma unconjugated bilirubin (UCB), plasma free bilirubin (Bf), and brain bilirubin concentrations were determined.

Results

We performed ET in 21 Gunn rats with 100% survival. At T₁, ET was profoundly more effective in decreasing both UCB −44%, p<0.01) and Bf −81%, p<0.05) than either PT or PT+Alb. After 48 h, the combination of ET+PT+Alb showed the strongest hypobilirubinemic effect (−54% compared to ET).

Conclusions

We optimized ET for severe unconjugated hyperbilirubinemia in the Gunn rat model. Our data indicate that ET is the most effective treatment option, in the acute as well as the follow-up situation.     

Raised excitability produced in cortical neurons by reinforced stimulation of the lateral hypothalamus

Response was recorded in the pyramidal tract (PT) under three experimental situations modelling the shaping of conditioned reflex (CR) during experiments on unrestrained but unanesthetized rabbits. The first paradigm consisted of direct stimulation of two points on the sensorimotor cortex, the second of the same stimuli combine with electrical stimulation (used as additional reinforcement) of the lateral hypothalamus (LH), and the third of LH stimulation in response to a rise occurring in PT response to above control level (modelling instrumental CR). An overall increase in the monosynaptic wave indicative of altered efficacy of synaptic connections was most commonly observed under all these conditions. Increase in the component directly reflecting pyramidal neuronal excitation appeared significantly more pronounced in the second and third than in the first experimental paradigm. The data obtained would point to reinforced efficacy of excitatory synaptic connections as the principal mechanism of CR, while the changed quality of electrical excitability at the membrane of cortical neurons reflects mechanisms underlying the contribution of reinforcement triggered by LH activation in cortical reordering of the motivational/emotional component of reinforcement.Higher Nervous Activity and Neurophysiology Research Institute, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 805–811, November–December, 1989.     

Cryo–electron tomography reveals a critical role of RIM1α in synaptic vesicle tethering

Synaptic vesicles are embedded in a complex filamentous network at the presynaptic terminal. Before fusion, vesicles are linked to the active zone (AZ) by short filaments (tethers). The identity of the molecules that form and regulate tethers remains unknown, but Rab3-interacting molecule (RIM) is a prominent candidate, given its central role in AZ organization. In this paper, we analyzed presynaptic architecture of RIM1α knockout (KO) mice by cryo–electron tomography. In stark contrast to previous work on dehydrated, chemically fixed samples, our data show significant alterations in vesicle distribution and AZ tethering that could provide a structural basis for the functional deficits of RIM1α KO synapses. Proteasome inhibition reversed these structural defects, suggesting a functional recovery confirmed by electrophysiological recordings. Altogether, our results not only point to the ubiquitin–proteasome system as an important regulator of presynaptic architecture and function but also show that the tethering machinery plays a critical role in exocytosis, converging into a structural model of synaptic vesicle priming by RIM1α.     

Pre-synaptic and post-synaptic factors influencing the synchronism in the transmitter secretion and the amplitude and temporal parameters of a postsynaptic response in the neuromuscular junction: a model study

Using a model of the frog neuromuscular junction, we studied the influence of pre-synaptic and post-synaptic factors on the amplitude and temporal parameters of end-plate currents (EPC). A nerve terminal (NT) was supposed to include linearly distributed active zones (AZ) that are able to release a transmitter quantum with a definite temporal distribution of the release probability (AZ DRP) after successive activation of these zones by a spreading action potential (AP). An increase in the length of a terminal, distance between AZ, and time constant of the DRP decline, or a decrease in the AP conduction velocity along the NT determines a decrease in the EPS amplitude and prolongation of its rising phase. These effects result from an increased asynchronism in the transmitter release. An expansion of the temporal parameters of minature EPC leads to an increase in the EPC amplitude, i.e., provides minimization of its loss. Various EPC models are compared, and contributions of the examined pre-synaptic and post-synaptic factors in modifications of the amplitude and temporal EPC parameters are evaluated.Neirofiziologiya/Neurophysiology, Vol. 27, No. 3, pp. 163–179, May–June, 1995.     

Investigation of neuronal connections in the dorsocaudal tegmentum of the cat by a microstimulation method

Unit responses in the caudal part of the tegmentum were investigated by a microstimulation method in the mesencephalic cat. The thresholds of appearance of direct and synaptic responses with latencies of 0.8–1.4 and 1.1–2.0 msec were found to depend on the distance from the electrode to the cell recorded. Responses with a low threshold (0.2–1.1 µV) were found much more often in neurons located 6.3–7.0 mm from the surface of the inferior colliculus than in more dorsal or more ventral zones. The relationship between the threshold I, in A, of the direct response of the low-threshold cells and their distance r, in , from the stimulating electrode is approximated satisfactorily by the equation I=3.3·10^–4r^1.8+0.2. The curve of I as a function of r for synaptic responses is usually more sloping and it has minima for responses recorded not near the cell. The index of synaptic response of some cells rose with an increase in the frequency of stimulation to 20–60/sec.Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 593–601, November–December, 1973.     

Investigation of a monosynaptic excitatory connection by means of a biomathematical model of neuronal interaction

A biomathematical model of neuronal interaction, including real mollusk neurons and mathematical models of functioning of deficient synaptic connections between these neurons and synaptic endings of other neurons, was created on the basis of a computer and an experimental arrangement for investigating molluscan ganglia. The effect of the properties of a monosynaptic excitatory connection of the statistical characteristics of spike trains of interacting pacemaker neurons was investigated.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 413–420, July–August, 1980.     

Structural-Based Rational Design of an Antagonist Peptide That Inhibits the Ribosome-Inactivating Activity of Ricin A Chain

Previous studies of inhibitors of ricin A chain (RA) mainly focused on the analogues of adenine and ribosomal RNA (rRNA) substrates. In this paper, a novel antagonist peptide (named PT) was designed rationally based on the crystal structure of the complex RA–rRNA. Theoretical results had clearly revealed the blockage of PT in the RA–rRNA interaction. The competitive inhibition experiment indicated that PT could significantly inhibit the binding activity of RA with anti-RA antibody. In order to further prove the competitive effect of PT against RA, N-glycosidase antagonizing activity of PT in cell-free system was evaluated using luciferase protein synthesis inhibition assay. Consequent data demonstrated that, at a RA level (0.022 nM) giving 50% decrease of protein synthesis in the absence of the peptide, protein synthesis could be recovered by the peptide for up to 80% at a level of 0.1 microgram/ml. This study highlights the interest of computation-aided method in the design of novel peptides with the ability to block the deleterious biological effects of RA. In addition, the method of luciferase protein synthesis inhibition assay in cell-free system which should provide rapid, sensitive, selective, and quantitative assessment may be developed to evaluate the potential antagonizing activity of RA inhibitors.Shuntao Wang and Jiannan Feng Contributed Equally to This Work     

Characterization of a Small Molecule Inhibitor of Plasminogen Activator Inhibitor Type 1 That Accelerates the Transition into the Latent Conformation

A novel class of small molecule inhibitors for plasminogen activator inhibitor type 1 (PAI-1), represented by AZ3976, was identified in a high throughput screening campaign. AZ3976 displayed an IC₅₀ value of 26 μm in an enzymatic chromogenic assay. In a plasma clot lysis assay, the compound was active with an IC₅₀ of 16 μm. Surprisingly, AZ3976 did not bind to active PAI-1 but bound to latent PAI-1 with a K_D of 0.29 μm at 35 °C and a binding stoichiometry of 0.94, as measured by isothermal calorimetry. Reversible binding was confirmed by surface plasmon resonance direct binding experiments. The x-ray structure of AZ3976 in complex with latent PAI-1 was determined at 2.4 Å resolution. The inhibitor was bound in the flexible joint region with the entrance to the cavity located between α-helix D and β-strand 2A. A set of surface plasmon resonance experiments revealed that AZ3976 inhibited PAI-1 by enhancing the latency transition of active PAI-1. Because AZ3976 only had measurable affinity for latent PAI-1, we propose that its mechanism of inhibition is based on binding to a small fraction in equilibrium with active PAI-1, a latent-like prelatent form, from which latent PAI-1 is then generated more rapidly. This mode of action, with induced accelerated latency transition of active PAI-1 may, together with supporting x-ray data, provide improved opportunities for small molecule drug design in the hunt for therapeutically useful PAI-1 inhibitors.     

Parameters of a model of transmitter depletion in synapses of identified snail neurons

Elementary EPSPs arising in two different identified neurons of the parietal ganglion ofHelix pomatia were recorded after stimulation of the identified triggering neuron. Repetitive stimulation (0.1–1.5 Hz) led to low-frequency depression of EPSPs. By the use of known and modified models of transmitter depletion parameters characterizing storage, mobilization, breakdown, and liberation of transmitter were determined. The fraction of available pool (F) released in two different synapses of the same trigger neuron did not differ significantly. The available pool of transmitter (C) and the demobilization constant ( ) in synapses on the RPa3 neuron were 2–3 times higher, and mobilization (M) was 10 times higher than on the LPa2 neuron. Predictions of the depletion model showed deviations from the experimental data. A method of calculating consistently whatever law of change of F was adopted was devised. Absence of correlation between parameters F and C of the depletion model and binomial parameters p and n, calculated on the basis of the quantal hypothesis of synaptic transmission shows that this hypothesis and the transmitter depletion model describe different synaptic mechanisms.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 88–97, January–February, 1981.     

Oviposition bioassay responses of Culex tarsalis and Culex quinquefasciatus to neem products containing azadirachtin

Neem (Azadirachta indica A. Juss) products have been shown to exert pesticidal properties against a variety of insect species. In mosquito control programs, such products may have the potential to be used successfully as larvicides. In exploring other advantages of neem products, we studied the oviposition responses of Culex tarsalis Coquillett and Cx. quinquefasciatus Say to two experimental azadirachtin (AZ) formulations, wettable powder Azad ^– WP10 (WP) and emulsifiable concentrate Azad ^– EC4.5 (EC). Gravid Cx. tarsalis exhibited a distinct preference for the neem suspension of the WP, where significantly more egg rafts were collected from the treatment than from the control. The minimum effective AZ concentration for this activity was 0.5 ppm. The aged suspensions from 1–7 days at 0.5 and 1 ppm AZ were more active in eliciting oviposition responses in Cx. tarsalis than the fresh preparations. This activity of the aged suspensions lasted up to 14 and 21 days at 0.5 and 1 ppm AZ, respectively. Negative ovipositional responses were indicated in the tests of the EC vs. Cx. tarsalis, as well as both neem formulations vs. Cx. quinquefasciatus. In the tests of the EC formulation, significantly less gravid females were trapped by oviposition cups in the treatment than in the control, and in the tests of the WP significantly less egg rafts were collected from the treatment than from the control. The minimum effective concentrations for oviposition avoidance activity were 5 ppm AZ for Cx. tarsalis and 10 ppm AZ for Cx. quinquefasciatus, which lasted up to 1 and 4 days for these two species respectively. Neem products potentially used as mosquito larvicides may have many additional benefits in mosquito control programs, the oviposition modification noted in the current studies is one such example.     

Gene recognition based on nucleotide distribution of ORFs in a hyper-thermophilic crenarchaeon, Aeropyrum pernix K1.

The 2694 ORFs originally annotated as potential genes in the genome of Aeropyrum pernix can be categorized into three clusters (A, B, C), according to their nucleotide composition at three codon positions. Coding potential was found to be responsible for the phenomenon of three clusters in a 9-dimensional space derived from the nucleotide composition of ORFs: ORFs assigned to cluster A are coding ones, while those assigned to clusters B and C are non-coding ORFs. A "codingness" index called the AZ score is defined based on a clustering method used to recognize protein-coding genes in the A. pernix genome. The criterion for a coding or non-coding ORF is based on the AZ score. ORFs with AZ > 0 or AZ < 0 are coding or non-coding, respectively. Consequently, 620 out of 632 ORFs with putative functions based on the original annotation are contained in cluster A, which have positive AZ scores. In addition, all 29 ORFs encoding putative or conserved proteins newly added in RefSeq annotation also have positive AZ scores. Accordingly, the number of re-recognized protein-coding genes in the A. pernix genome is 1610, which is significantly less than 2694 in the original annotation and also much less than 1841 in the RefSeq annotation curated by NCBI staff. Annotation information of re-recognized genes and their AZ scores are available at: http://tubic.tju.edu.cn/Aper/.