Synchronizing, sedative and anticonvulsive effects of centrally administered somatostatin in the conscious rabbit

The effects of intracerebroventricular injection of somatostatin-14 on the cortical and deep structure electrical activity, somatic behavior and rectal temperature, were studied in 45 unanesthetized rabbits. In addition the antiepileptic action of the peptide was tested in these models: pentamethylenetetrazole-induced cortical spikes and waves, epileptic focus by topical application of strychnine and voltage-threshold for amygdala after-discharge. The results indicate that somatostatin exerts synchronizing, sedative and weak antiepileptic effects when centrally administered to rabbits.     

DNA Replication and Cell Cycle Progression Regulatedby Long Range Interaction between Protein Complexes bound to DNA

A nonstationary interaction that controlsDNA replication and the cell cycle isderived from many-body physics in achemically open T cell. The model predictsa long range force F() =– (/2) (1 – )(2 – )between thepre-replication complexes (pre-RCs) boundby the origins in DNA, = /N being the relativedisplacement of pre-RCs, the number of pre-RCs, Nthe number of replicons to be replicated,and the compressibilitymodulus in the lattice of pre-RCs whichbehaves dynamically like an elasticallybraced string. Initiation of DNAreplication is induced at the threshold = N by a switch ofsign of F'(), fromattraction (–) and assembly in the G ₁ phase (0<<N), to repulsion (+) and partialdisassembly in the S phase (N< < 2N), withrelease of licensing factors from pre-RCs,thus explaining prevention ofre-replication. Replication is terminatedby a switch of sign of force at = 2N, from repulsion inS phase back to attraction in G ₂, when all primed replicons havebeen duplicated once. F(0) = 0corresponds to a resting cell in theabsence of driving force at = 0. The model thus ensures that the DNAcontent in G ₂ cells is exactlytwice that of G ₁ cells. The switch of interaction at the R-point, at which N pre-RCs have been assembled, starts the release of Rb protein thus also explaining the shift in the Rb phosphorylation from mitogen-dependent cyclinD to mitogen-independent cyclin E.Shape,slope and scale of the response curvesderived agree well with experimental datafrom dividing T cells and polymerising MTs,the variable length of which is due to anonlinear dependence of the growthamplitude on the initial concentrations oftubulin dimers and guanosine-tri-phosphate(GTP). The model also explains the dynamic instabilityin growing MTs.     

卵黄抗体经滴鼻途径引起动物免疫反应的研究

研究鸡卵黄免疫球蛋白 (IgY)经滴鼻途径是否引起动物的粘膜免疫反应以及反应的程度。制备抗H3 N2 型流感病毒特异性IgY ,以滴鼻方式免疫实验家兔和豚鼠。实验动物在免疫后不同时期采血 ,检测特异性抗IgY抗体水平。豚鼠以相同IgY静脉攻击 ,观察动物的反应。实验结果表明 ,豚鼠和实验家兔均产生了特异性粘膜免疫反应 ,应慎重采用IgY以滴鼻方式来预防和治疗疾病。     

Structural mechanism for inactivation and activation of CAD/DFF40 in the apoptotic pathway

CAD/DFF40 is responsible for the degradation of chromosomal DNA into nucleosomal fragments and subsequent chromatin condensation during apoptosis. It exists as an inactive complex with its inhibitor ICAD/DFF45 in proliferating cells but becomes activated upon cleavage of ICAD/DFF45 into three domains by caspases in dying cells. The molecular mechanism underlying the control and activation of CAD/DFF40 was unknown. Here, the crystal structure of activated CAD/DFF40 reveals that it is a pair of molecular scissors with a deep active-site crevice that appears ideal for distinguishing internucleosomal DNA from nucleosomal DNA. Ensuing studies show that ICAD/DFF45 sequesters the nonfunctional CAD/DFF40 monomer and is also able to disassemble the functional CAD/DFF40 dimer. This capacity requires the involvement of the middle domain of ICAD/DFF45, which by itself cannot remain bound to CAD/DFF40 due to low binding affinity for the enzyme. Thus, the consequence of the caspase-cleavage of ICAD/DFF45 is a self-assembly of CAD/DFF40 into the active dimer.     

Clavulanic acid dehydrogenase: structural and biochemical analysis of the final step in the biosynthesis of the beta-lactamase inhibitor clavulanic acid

The ultimate step in the biosynthesis of the medicinally important beta-lactamase inhibitor clavulanic acid is catalyzed by clavulanic acid dehydrogenase (CAD). CAD is responsible for the NAPDH-dependent reduction of the unstable intermediate clavulanate-9-aldehyde to yield clavulanic acid. Here, we report biochemical and structural studies on CAD. Biophysical analyses demonstrate that CAD exists as dimeric and tetrameric species in solution. The reaction performed by CAD was shown to be reversible, allowing the use of clavulanic acid for activity analyses. The crystal structure of CAD was solved using single-wavelength anomalous diffraction with a seleno-methionine derivative. The structure reveals that the individual monomers comprise a single domain possessing the Rossmann fold, characteristic of dinucleotide-binding enzymes. The monomers are arranged as tetramers, similar to other tetrameric members of the short-chain dehydrogenase/reductase family. The structure of the unreactive complex of CAD with clavulanic acid and NADPH suggests how CAD is able to catalyze the reduction of clavulanate-9-aldehyde without fragmentation of the bicyclic beta-lactam ring structure. The relative positions of NADPH and clavulanic acid, in the active site, together with the presence of the latter in an eclipsed conformation, rationalizes previous labeling studies demonstrating that the incorporation of the C5 pro-R, but not pro-S, hydrogen of ornithine/arginine into the C9 position of clavulanic acid occurs with overall inversion of configuration.     

Phase relationships of cerebral cortex potentials in the rabbit during the execution of motor responses

EEG waves phase relations in the sensorimotor and visual cortical areas were studied in 12 rabbits before and during a motor reaction in response to light stimulation. Phase relations in the background activity were characterized by a considerable dispersion (from 26 to 45 degrees). Light stimulation increased the quantity of synphasic EEG oscillations in adjacent cortical points and stabilized the phase shift between EEG waves in the sensorimotor and visual cortical areas. Motor reactions of rabbits to light occurred when theta-rhythm with the most constant phase shift was observed in the EEG of these areas.     

Enzymes of Cerebral GABA Metabolism and Synaptosomal GABA Uptake in Acute Liver Failure in the Rabbit: Evidence for Decreased Cerebral GABA-Transaminase Activity

Abstract: Measurements of the activities of the two key enzymes in cerebral GABA metabolism—glutamate decarboxylase (GAD) and GABA-transaminase (GABA-T)—were performed in normal rabbits and in rabbits with hepatic encephalopathy due to galactosamine-induced liver failure. Furthermore the uptake of GABA by synaptosomes was studied. Hepatic encephalopathy was associated with a marked decrease in the activity of GAB A-T. This decrease in activity was already apparent in galactosamine-treated rabbits before the onset of hepatic encephalopathy. Sera and serum ultrafiltrates of rabbits with hepatic encephalopathy but not of normal rabbits or of rabbits with uremic encephalopathy were shown to inhibit GABA-T activity in vitro . Cerebral GAD activity and synaptosomal GABA uptake in rabbits with hepatic encephalopathy and in untreated animals were not different. These later findings indicate that hepatic encephalopathy is not associated with alterations of presynaptic GABA nerve terminals in the central nervous system. The demonstration of a decrease in cortical GABA-T activity provides indirect evidence for decreased GABA turnover in the brains of rabbits with hepatic encephalopathy and thus is compatible with augmented GABA-ergic inhibitory neurotransmission contributing to the neural inhibition of hepatic encephalopathy.     

Effects of Fetal Treatment with Methylazoxymethanol acetate at Various Gestational Dates on the Neurochemistry of the Adult Neocortex of the Rat

The effects of gestational date (13, 14, 15, and 17 days) of administration of methylazoxymethanol acetate (20 mg/kg) on the cortical synaptic chemistry and morphology of the rat has been examined in adult offspring. Treatment at 13 days of gestation (DG) resulted in cortical hypoplasia that affected primarily the deep layers whereas treatment at 14 and 15 days gestation caused a severe hypoplasia of cortical neurons above layer V and a 66 to 77% reduction in cortical mass. The 17-DG treatment caused only a 20% reduction in cortical weight with effects apparent only in the superficial layers. At no treatment date did the specific activity of glutamate decarboxylase differ significantly from control. In contrast, presynaptic markers for noradrenergic (tyrosine hydroxylase and norepinephrine) and for serotonergic (serotonin) terminals were increased in concentration in direct proportion to the degree of cortical hypoplasia. The specific activity of choline acetyltransferase was significantly increased at all treatment dates but total activity per cortical slab was significantly reduced on treatment days 13–15.     

Strain differences in rabbit adrenocortical structure and morphological evidence of corticomedullary communication

Interstrain differences in the structure of the mouse and rat adrenal cortex are well known, but related data on rabbits are not available. This study was planned to demonstrate possible strain differences in rabbit adrenal morphology and morphological evidence of a communication between cortex and medulla. For this purpose, the zonation of the adrenal cortex of intact mature male and female rabbits of different strains (New Zealand, Chinchilla and California) were compared using morphometry and the corticomedullary junction was evaluated for close relationship. Marked intersex and interstrain differences were found in the adrenocortical zonation. Female rabbits had larger adrenocortical zones than corresponding males. The rabbits of Chinchilla and California strains had the largest cortical sizes. This difference depended largely upon the higher thickness of the zona fasciculata. Whereas, there were no significant strain differences in the thickness of zona glomerulosa and zona reticularis. Furthermore, examination of corticomedullary junction showed that cortex and medulla were interwoven. Single and small accumulations of cortical cells were spread throughout the medulla. Our morphological data showed the presence of significant interstrain differences in the adrenocortical zonation in the rabbits and provide evidence for a possible paracrine interaction between medullary and cortical cells.     

The morphofunctional characteristics of the neurons in the sensorimotor cortex of old rabbits during the trace assimilation of rhythm]

Extracellular neuronal activity was recorded from 460 neurons from alert young (5-7 months), middle-aged (54-65 months) and old (66-85 months) rabbits. Trace rhythmic activity of sensorimotor cortical neurons was examined after long-lasting (10-20 min) rhythmic (0.5-2 Hz) electrocutaneous stimulation of the contralateral forelimb. Spectral analysis of spike activity showed age-related differences in capability of producing a rhythm of previous stimulation in spontaneous neuronal activity. In young animals propriate rhythmic fluctuations of firing rate appeared after the first or second sessions of stimulations (on the first experimental day), in middle-aged ones--after 2-4 sessions (on the second or third days); cortical neurons in old rabbits did not exhibit trace rhythmic activity. Significant morphological changes in glial and neuronal cells were observed in sensorimotor cortex of old rabbits. It is proposed that morphological deteriorations may be the reason of the impairement of trace processes during aging.     

Synchronization dynamics in the neuronal work of the neocortex and hippocampus during learning before and after the administration of nootropics and narcotics

The basal difference in action of the studied drugs was that nootropics (phenybut in a dose of 40 mg/kg and pyracetam in a dose of 200-400 mg/kg) did not change the initial action of pain reinforcement on synchronism in responses of the cortical neurones of alert nonimmobilized rabbits by inhibitory type (coincidence of the presence and absence of impulse activity) towards its decrease, while narcotics of various types (ethanol in a dose of 4-6 mg/kg, morphine-like opiate DAGO and opioid peptide DADLE in doses of 250 mkg/kg) eliminated the action of pain reinforcement on synchronism in responses of the cortical neurones both by inhibitory and activation (time of coincidence only of the presence of impulse activity) types. These and other drugs mainly weakened the initial action of both the inhibitory and reinforced light flashes of synchronism in neurones activity both by inhibitory and activation types. There was no constant parallelism between changes of synchronization and the frequency of the cortical impulses.     

Tonic component of the conditioned reflex process and its functional role

Tonic background activity of 266 neurones in the hippocampus and different neocortical areas was studied in freely moving rabbits in the process of defensive and food instrumental conditioned performance and during switching-over of instrumental and classical food and defensive reflexes. Associations of CS and reinforcement evoke background activity changes in most of recorded cortical neurones preceding the development of other conditioned manifestations. Conditioned reflex was performed only after reaching the background firing rate of almost every examined neurone optimal for its realization. The performance of different conditioned reflexes was associated with different background activity levels of cortical neurones. The above mentioned data form the experimental basis for the identification of the tonic component in conditioned process which reflects tonic character of temporary connection formation and function.     

Coding of natural scenes in primary visual cortex

Natural scene coding in ferret visual cortex was investigated using a new technique for multi-site recording of neuronal activity from the cortical surface. Surface recordings accurately reflected radially aligned layer 2/3 activity. At individual sites, evoked activity to natural scenes was weakly correlated with the local image contrast structure falling within the cells' classical receptive field. However, a population code, derived from activity integrated across cortical sites having retinotopically overlapping receptive fields, correlated strongly with the local image contrast structure. Cell responses demonstrated high lifetime sparseness, population sparseness, and high dispersal values, implying efficient neural coding in terms of information processing. These results indicate that while cells at an individual cortical site do not provide a reliable estimate of the local contrast structure in natural scenes, cell activity integrated across distributed cortical sites is closely related to this structure in the form of a sparse and dispersed code.     

Quantitation of glucose-6-phosphate dehydrogenase activity in cortical fractions of the nephron in sodium-depleted and sodium-loaded rabbits

Summary Glucose-6-phosphate dehydrogenase activity was measured quantitatively in isolated cortical fractions of the nephron in sodium-depeleted and sodium-loaded rabbits. The samples consisted of isolated fractions of macula densa, proximal convoluted tubule, distal convoluted tubule and glomerulus. In sodium-depleted rabbits enzyme activity was identical to that of normal rabbits. In sodium-loaded rabbits a significant decrease in enzyme activity was found in the macula densa and proximal convoluted tubule. However, using conventional histochemical incubation methods semiquantitative estimation of glucose-6-phosphate dehydrogenase showed a slight decrease in enzyme activity in the macula densa and distal convoluted tubule, and a slight increase in the proximal convoluted tubule during sodiumdepletion. During sodium-load a pronounced decrease in enzyme activity was seen in the macula densa and distal convoluted tubule. These results show that semiquantitative histochemical evaluation of changes in enzyme activity is less reliable than the more precise quantitative method especially when there are only slight changes in enzyme activity. Only where there were marked changes in histochemical enzyme activity might the results of quantitative and semiquantitative methods be in accord.     

Cortical upper layer neurons derive from the subventricular zone as indicated by Svet1 gene expression

The cerebral cortex is composed of a large variety of different neuron types. All cortical neurons, except some interneurons, are born in two proliferative zones, the cortical ventricular (VZ) and subventricular (SVZ) zones. The relative contribution of both proliferative zones to the generation of the diversity of the cortical neurons is not well understood. To further dissect the underlying mechanism, molecular markers specific for the SVZ are required. Towards this end we performed a subtraction of cDNA libraries, generated from E15.5 and E18.5 mouse cerebral cortex. A novel cDNA, Svet1, was cloned which was specifically expressed in the proliferating cells of the SVZ but not the VZ. The VZ is marked by the expression of the Otx1 gene. Later in development, Svet1 and Otx1 were expressed in subsets of cells of upper (II-IV) and deep (V-VI) layers, respectively. In the reeler cortex, where the layers are inverted, Svet1 and Otx1 label precursors of the upper and deeper layers, respectively, in their new location. Interestingly, in the Pax6/small eye mutant, Svet1 activity was abolished in the SVZ and in the upper part of the cortical plate while the Otx1 expression domain remained unchanged. Therefore, using Svet1 and Otx1 as cell-type-specific molecular markers for the upper and deep cortical layers we conclude that the Sey mutation affects predominantly the differentiation of the SVZ cells that fail to migrate into the cortical plate. The abnormality of the SVZ coincides with the absence of upper layer cells in the cortex. Taken together our data suggest that while the specification of deep cortical layers occurs in the ventricular zone, the SVZ is important for the proper specification of upper layers.     

The multifactor method of EEG separation into the cortical and deep components

A new method of separation of multichannel brain electrical activity into cortical and subcortical components with the help of multifactor analysis is proposed. The method provides a means for isolation and, consequently, more reliable localization of sources of electrical activity not only in deep brain structures (on the basis of the dipole model) but also on the cortical surface. The proposed method does not depend on the rotation and interpretation of factors, and no data losses occur. The mufasel algorithm is based on integration of all selected factors (within a particular EEG or EP time segment) in two groups using a statistical criterion, which defines general and specific factors. It is assumed that general factors loaded with highly correlated derivations predominantly describe the electrical activity of deep brain structures, whereas specific factors loaded by the dynamics of electrical activity in individual derivations, reflect the integrated activity of cortical brain structures.     

Cortico-hippocampal relation of electrical activity during a motor polarization dominant in rabbits

By the method of spectral-coherent analysis, the intercentral relations were studied of the electrical activity of the sensorimotor and premotor cortices and of CAs field of the dorsal hippocampus of both hemispheres during the motor polarization dominant, created by the action of the direct current on the rabbits sensorimotor cortical area. The formation was shown of a new structure of the intercentral relations of electrical activity of the sensorimotor cortex and CA3 of the dorsal hippocampus. It should be noted that the dominant optimum and its inhibition are characterized by different interhippocampal relations: at the optimum a low range of the theta-rhythm is highly coherent while at the activation of "the non-dominant" hemisphere--a high range.     

Formation of plastic connections of the visual system during ontogenesis of the rabbit

Analysis of evoked potentials and unit activity in the visual cortical projection area of rabbits revealed a definite succession of forming of interneuronal connections in ontogeny. In early postnatal period, the neuronal reactions were characterized by stable responses with one excitatory phase corresponding to initially negative surface evoked potential. Similarity of reactions of neurones situated in the same vertical column was observed and explained by functioning of a system of rigid connections of the thalamic relay nuclei afferents with cortical pyramidal neurones. Beginning from the third week of postnatal life of rabbits the neuronal reactions assumed a distinctly expressed phasic character, and variability of responses was seen along the vertical line. The changes revealed correlated with formation of a system of interneurones providing a possibility of plastic neuronal interaction. A study of the influence of preliminary cortical stimulation of the associative areas showed that intercentral cooperation mediated by cortical interneurones providing a systemic analysis of visual information began to form from the third week of postnatal life and reached the definitive level at later stages of development.     

The modulation of sensory transmission through the medullary dorsal horn during cortically driven mastication

During mastication, reflexes are modulated and sensory transmission is altered in interneurons and ascending pathways of the rostral trigeminal sensory complex. The current experiment examines the modulation of sensory transmission through the most caudal part of the trigeminal sensory system, the medullary dorsal horn, during fictive mastication produced by cortical stimulation. Extracellular single unit activity was recorded from the medullary dorsal horn, and multiple unit activity was recorded from the trigeminal motor nucleus in anesthetized, paralyzed rabbits. The masticatory area of sensorimotor cortex was stimulated to produce rhythmic activity in the trigeminal motor nucleus (fictive mastication). Activity in the dorsal horn was compared in the presence and absence of cortical stimulation. Fifty-two percent of neurons classified as low threshold and 83% of neurons receiving noxious inputs were influenced by cortical stimulation. The cortical effects were mainly inhibitory, but 21% of wide dynamic range and 6% of low threshold cells were excited by cortical stimulation. The modulation produced by cortical stimulation, whether inhibitory or excitatory, was not phasically related to the masticatory cycle. It is likely that, when masticatory movements are commanded by the sensorimotor cortex, the program includes tonic changes in sensory transmission through the medullary dorsal horn.     

Morphological study of organotypic cerebellar cultures

Organotypic cerebellar cultures from 8-days-old (P8) mouse pups were studied following 11 days of in vitro (I IDIV) culturing. The cerebellar cytoarchitectonic structure was maintained in most parasagittal cerebellar cortical slice cultures (also containing the deep cerebellar nuclei). The two main extrinsic excitatory inputs (the climbing and the mossy fibers) seem to be replaced by other axonal types: in the molecular layer mostly by parallel fibers (for climbing fibers) and in the granular layer by intrinsic mossy fiber collaterals of local excitatory interneurons, the unipolar brush cells. However, in a few organotypic cultures, which (although preserving the trilaminar cerebellar cortical structure) were "granuloprival" but also contained some of the deep cerebellar nuclei, the participation of extracortical axons from the deep cerebellar nuclei in the replacement of the missing afferents is suggested.