Acetylcholine metabolism in the brain of rats treated with vanadyl sulfate and certain phenylacetic acid derivatives

Summary The present work describes the effect produced by phenylacetic acid, phenylethylacetic and diphenylacetic acids (sodium salts) separated and together with vanadyl sulfate on some indices, of acetylcholine metabolism in the rat's brain. Total cholinesterase activity and the free and bound (conditionally) acetylcholine levels served as indices. As shown experimentally the use of phenylacetic acid derivatives is accompanied by reduction of the bound acetylcholine, content, whereas that of free acetylcholine and the total tissue cholinesterase activity remain unchanged. Vanadyl sulfate provokes a significant reduction of the total tissue cholinesterasic activity, but does not change the content of free and bound acetylcholine therein. In conjoint action of the above-mentioned substances, the effects of phenylacetic acid erivatives are supplemented by the anticholinesterase effect of vanadyl sulfate.(Presented by Active Member AMN SSSR S. V. Anichkov) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 2, pp. 80–83, February, 1964     

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.     

Über zwei neue anabol wirksame Steroide

Zusammenfassung 1-Methyl- ¹-androsten-17-ol-3-on-17-acetat ist unter zahlreichen von uns geprüften das zur Zeit am stärksten wirksame anabole Steroid mit der relativ geringsten androgenen Nebenwirkung. Die Beeinflussung des Cyclus bei der normalen Ratte ist gering. Eine Überlegenheit gegenüber Testosteron-17-propionat tritt am chronisch dihydrotachysterin-vergifteten Tier deutlich hervor, die sich neben der Erhaltung des Körpergewichts in der Verhütung unphysiologischer Ca-Ablagerungen manifestiert. Die anti-ulcerogene Wirkung des 1-Methyl- ¹-androsten-17-ol-3-on-17-acctat ist gleich der des Testosteron-17-propionat; hier liegt die Überlegenheit des 1-Methyl- ¹-androsten-17-ol-3-on-17-acetats in seiner schwächeren androgenen Nebenwirkung.Das 1-Methyl- ¹-androsten-17-ol-3-on-17-önanthat zeigt besonders starke und langdauernde anabole Wirkung bei sehr geringer und wesentlich kürzerer androgener Wirksamkeit.     

Modelling of electrolyte transport in renal and intestinal epithelia

Summary Epithelia can be classified as leaky and tight epithelia due to their conductive properties and their modes of solute transport. Both the proximal segment of the nephron and the intestinal tract are leaky whereas the distal nephron and the colon are tight. Consequently, inborn errors and exogenous disorders of solute transport often involve both the proximal tubule and the small intestine. In addition, effects on ion and water transport in the distal nephron closely resemble those in the large intestine. Models of solute transport in leaky and tight epithelia are presented employing porter systems known in mammalian tissues. These porter systems are discussed as possible sites of transport defects and as targets for pharmacological agents.     

Convergent inputs from articular,cutaneous and muscle receptors onto ascending tract cells in the cat spinal cord

Summary 1.Responses were recorded from 160 ascending tract cells in segments L4 to L6 of the spinal cord in chloralose anaesthetized, spinalized cats. The tract cells were identified by antidromic activation following stimulation of pathways in the lateral and ventral funiculi at the level of the spinal cord transection at the thoracolumbar junction. Axonal conduction velocities ranged from 9 to 114 m/s. 2. A sample of 152 of the neurones examined could be subdivided according to the distribution of their receptive fields into 49 cells activated just from receptors located in skin (s cells), 17 neurones excited by receptors in deep tissues (d cells), 15 units with a convergent input from receptors in skin and deep tissues (sd cells), and 25 neurones with a convergent input from the knee joint and either skin (sj cells), deep tissues (dj cells) or both (sdj cells). No receptive fields could be demonstrated for the remaining 46 neurones. 3. S and sj cells were found almost exclusively in the dorsal horn, whereas many d, sd, sdj and dj units were in the ventral horn. Almost all of the cells that lacked receptive fields were in the ventral horn or intermediate grey. 4. Ninety-one of 158 cells (56%) demonstrated no background activity. Of these, 43 cells (27%) lacked receptive fields. Many of the silent neurones were in the ventral horn, but some were in the dorsal horn. Of 25 cells having knee joint input, 18 (72%) had background activity. 5. All of the neurones that had a receptive field in the knee joint also had a convergent input from receptors in other tissues. In 3 cases, there was a receptive field in the skin over the foot (sj cells). For 16 cells, receptive fields included not only the knee joint but also skin and deep tissue (sdj cells). Usually, the cutaneous receptive field was near the knee joint, but sometimes it was remote, such as on the foot. The deep receptive fields were chiefly in the muscles of the thigh and/or leg. For 6 dj cells, the receptive fields included not only the knee joint but also deep fields like those of sdj cells. 6. Cutaneous receptive fields were classified as low threshold (cells excited best by innocuous intensities of mechanical stimulation), wide dynamic range (cells activated by weak mechanical stimuli, but the best responses were to noxious stimuli) or high threshold (innocuous stimuli had little effect, but noxious mechanical stimuli produced a vigorous discharge). Similarly, stimulation of the knee joint with weak mechanical stimuli could excite some neurones, while others could be activated by weak or strong articular stimuli but were excited best by noxious stimuli, and still other neurones were activated by knee joint stimuli only if the intensity was noxious. 7. In several instances, contralateral receptive fields were noted. These were generally in deep tissue or in the knee joint. 8. It was concluded that many of the responses to articular stimulation of the spinal cord ascending tract cells examined in this study could have been mediated by the fine afferent fibres that supply the knee joint. Although further work will be required to determine which particular ascending tracts transmit nociceptive information concerning the knee joint, it can be proposed that many of the responses demonstrated here were likely to play a role in either joint pain of in triggering responses associated with joint pain.     

The Involvement of Dopamine in Strengthening Cortical Signals Activating NMDA Receptors in the Striatum (a hypothetical mechanism)

A possible mechanism is proposed for the enhancement/weakening of those cortical signals in the cortex-basal ganglia-thalamus-cortex neural network which induce/do not induce opening of NMDA channels in the spiny neurons of the striatum and which can be regarded as strong/weak in terms of this measure. The mechanism is based on the modulatory influences of dopamine on changes in the efficiency of corticostriatal inputs. In the absence of dopamine, relative increases in the intensity of strong (weak) cortical signals can lead to the induction of long-term potentiation (depression) of corticostriatal synapses. In this case, because of the differently directed influences on thalamic cells of signals passing via strionigral and striopallidal cells, strong signals at the output of the thalamus are weakened, while weak signals are strengthened. Activation of dopamine D₁ (D₂) receptors on strionigral (striopallidal) neurons may facilitate increases in the extent of long-term potentiation/depression (decreases in the extent of long-term potentiation/depression or induction of long-term potentiation/depression). The consequence of this is that strong signals at the output of the thalamus can be strengthened synergistically, while weak signals cab be weakened synergistically. Background cortical signals evoking tonic release of dopamine in the striatum can decrease strengthening because of weakening of the modulatory influence of dopamine on the modification of corticostriatal synapses.     

Investigation of the “valency” of antibodies by means of azoproteins

Summary The valency of antibodies was studied by the method of exhaustion of antisera against mono-and diazoproteins, and subsequent cross reactions both with the antibodies left over in the supernatant fluid of the serum and with the precipitating and nonprecipitating antibodies isolated from the precipitate.It was proved that the antibodies interact with the antigens as multivalent compounds.The valency determined with regard to the azoproteins is dependent upon the number of groups introduced.Thus, bivalent antibodies correspond to monoazoproteins and trivalent ones to diazoproteins.The valency of antibodies is, evidently, determined by the structural similarity of the heterologous and the immunizing antigens as well as by the less complete specific conformity between the individual structural peculiarities of the antigen and its antibody.From the Tashkent Pharmaceutical Institute (Director-Docent M. A. Azizov)Presented by Active Member AMN SSSR N. N. Zhukov-Verezhnikov     

Assessment of the State of Activation of the Cortical Zones in Humans during Visual Attention and Selection

The state of cortical activation during visual symbol shape and position selection tasks was assessed in humans in terms of the magnitude of prestimulus negativity (contingent negative variation, CNV) and the amplitude of the N1–P3 complex in evoked potentials (EP). Evoked potentials in the frontal, parietal, occipital, and temporal leads were recorded in 18 young healthy subjects in two sets of experimental conditions: in a screened chamber and in an open field beside the experimenter, who communicated the results to the subjects and guided them towards quicker and more precise responses to the target stimuli. The maximum magnitudes of CNV and evoked potentials during selective attention were seen in the parietal areas, and additional increases of activation indexes were observed in the open field, where subjects' motivation was enhanced. The state of readiness (CNV) was an informative measure of cortical activation, as it determined the parameters of subsequent evoked potentials; the more marked the readiness, the more marked and stable were EP. Comparison of the situations of passive observation and selective reactions to stimuli revealed a reciprocal relationship between CNV in these conditions: the greater the magnitude of CNV in passive conditions, the smaller the difference between CNV in passive conditions and during selective attention and vice versa. We termed this additivity of involuntary and voluntary attention. The fact that activation indexes were greatest in the parietal areas suggests that the occipital-parietal system is dominant in visual selection tasks in humans.     

Metameriest?rungen und ihre Konsequenzen im S?ugetierexperiment

Zusammenfassung Störungen der Segmentierung werden bei der Hausmaus durch die Erbfaktoren Crooked tail und Rib fusions wie auch durch weitere Gene hervorgerufen. Eine Phänokopie der Mutation Rib fusions durch Sulfonylharnstoff (Rastinon) wird beschrieben. Als Ursache der beobachteten Wirbel-Rippenmißildungen ist eine Störung der Zellaggregation zu betrachten, die sich durch alle Entwicklungsphasen bis zur knöchernen Fehlbildung auswirkt.Die empfindliche Phase ist die Heraussonderung der Ursegmente aus dem undifferenzierten Mesoblasten. Ihre Beeinflussung, speziell durch hypoglykämische Agentien, wird nach Ort und Zeit analysiert und die Entwicklung der entstehenden Mißbildung untersucht.Es wird die Hypothese aufgestellt, daß in dieser Phase ein erhöhter Energiebedarf besteht, der durch eine Störung der Oxydationsprozesse blockiert werden kann.Ausgeführt mit Hilfe der Stiftung für wissenschaftliche Forschung an der Universität Zürich.     

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.

     

A1166C variant of angiotensin II type 1 receptor gene is associated with severe hypertension in pregnancy independently of T235 variant of angiotensinogen gene

Hypertension in pregnancy (HP) is a multifactorial disease manifested due to a complex combination of environmental factors and several predisposing genes including factors in the renin angiotensin system. The aim of this study was to assess the association between the A1166C variant of the angiotensin II type 1 receptor (AT1) gene and severe HP. We carried out association studies and multivariate analyses including other candidate causal factors of HP such as the M235T variant of the angiotensinogen (AGT) gene, prepregnancy body mass index (BMI), and family history of hypertension in Japanese subjects. One hundred and fourteen patients with severe HP and 291 normal pregnancy controls were genotyped. Among primiparous subjects, the frequency of AC+CC genotype of AT1 was significantly higher in severe HP than in the controls. A multivariate analysis with AC+CC genotype of AT1 and TT genotype of AGT revealed that these were independently associated with primiparous severe HP. However, when family history of hypertension and prepregnancy BMI 25 were added as factors examined in the multivariate analysis, only TT genotype of AGT and family history of hypertension were found to be independent potent factors. The present results suggest that the C1166 allele of the AT1 gene may be concerned with the predisposition to essential hypertension independently of the T235 allele of the AGT gene.     

Differentiation of extracellular matrix in the cellular cartilage ("Zellknorpel") of the mouse pinna

Summary Differentiation of cellular cartilage was studied in the mouse pinna with particular reference to matrix material. Fixation of glycosaminoglycans was performed by the use of acridine orange and elastin was identified by staining thin sections with tannic acid and uranyl acetate.Condensation of mesenchymal cells (prechondroblasts) initiates the formation of a blastema of cartilaginous tissue at postnatal day 4. The synthesis of acidic glycosaminoglycans begins at postnatal day 8 when prechondroblasts transform to chondroblasts. Glycosaminoglycans can be detected within secretory vesicles of chondroblasts at postnatal day 8, in the extracellular space at postnatal day 13. Delicate collagen fibrils and elastic fiber microfibrils are seen between prechondroblasts and chondroblasts. Deposition of elastin begins at postnatal day 11. A network of elastic fibers and lamellae is formed, which replaces both collagen fibrils and elastic fiber microfibrils. In the interstice of mature cellular cartilage only elastin and proteoglycans are present (postnatal day 21).These findings indicate that cellular cartilage represents an independent kind of supporting tissue, which may serve as a progenitor of hyaline or elastic cartilage (transitional cellular cartilage) but does not differentiate from hyalin cartilage.With financial support from the Hochschuljubiläumsstiftung der Stadt Wien. Part of this work has been presented at the 3. Arbeitstagung der Anatomischen Gesellschaft, Würzburg, 6.-8. 10. 1982     

Recognition by peptide mapping of three different structural groups of outer membrane protein YOP-1 of Yersinia enterocolitica and Yersinia pseudotuberculosis

The structural relation of YOP-1 of european and american Yersinia enterocolitica serotypes O3, O9, O5, 27, and O8 and O20, respectively, and Y. pseudotuberculosis serotypes I, II, and III was compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping using Staphylococcus aureus protease V8. Apparent molecular weights of YOP-1 ranged from 206,000 (O3) to approx. 180,000 (O8). According to their respective peptide maps YOP-1 of the european and american Y. enterocolitica serotypes and Y. pseudotuberculosis serotypes could be assigned to three different groups. Evaluation of several isolates of Y. enterocolitica serotypes O3, O9, and O8 by peptide mapping indicated that YOP-1 is conserved within a serotype. However, one serotype O8 isolate differed from the consensus peptide pattern of the other serotype O8 and O20 isolates. The similarity of the peptide patterns of Yersinia serotypes which predominate in certain geographical locations, i. e., european and american Y. enterocolitica serotypes, suggest common evolution of YOP-1 of these serotypes independent of the evolution of the other serotypes.     

Continuity of the bulbar locomotor strip is not essential for walking

Bilateral destruction of the medulla, interrupting both locomotor strips, was carried out on mesencephalic cats. After the operation walking could still be induced by stimulation of the more rostral (and also caudal) portion of the strip, although in some experiments the threshold of walking was raised. The connection of the locomotor strip with other structures of the brain stem and spinal cord is discussed on the basis of these findings.A. N. Belozerskii Interfaculty Laboratory, M. V. Lomonosov Moscow State University. Laboratory of Physiology of Movements, Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR M. I. Kuzin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 1, pp. 3–6, January, 1980.     

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.     

Biophysical studies of teschen disease virus (Talfan strain)

Summary Studies have been made of the heterogeneity of infectivity and CFA in Teschen virus (Talfan strain) suspensions. Most of the infectivity was contained in two components of densities 1.46 gm./ml. and 1.35 gm./ml. The physical, chemical and immunological properties of these components have been compared. It was possible, however, to convert a large proportion of 1.46 component to 1.35 component by treating the 1.46 component with sodium dodecyl sulphate. This would indicate that the 1.46 component was a complex formed between the infective particles and cellular debris.Further studies on the growth characteristics and electron microscopy of the virus have been made.     

Evaluation of mouse monoclonal antibodies raised against an isolate of the variant avian paramyxovirus type 1 responsible for the current panzootic in pigeons

Summary Nine monoclonal antibodies raised against pigeon variant avian paramyxovirus type 1 isolate pigeon/England/617/83 were tested for their ability to react with classical and other pigeon variant isolates. Two of the monoclonal antibodies appeared to be specific for 617/83 reacting with no other virus. The remaining seven monoclonal antibodies bound to cells infected with all other pigeon isolates in indirect immunoperoxidase (IIP) tests but four distinct groups of other PMV-1 viruses were formed on the basis of the binding patterns. One of the monoclonal antibodies 161/617 caused haemagglutination inhibition (HI) of all the pigeon isolates tested but none of the other PMV-1 viruses and these results reflected the IIP results with this monoclonal antibody.161/617 was also shown to inhibit viruses of the avian paramyxovirus type 3 serogroup in HI tests. This reaction and the ability to bind to infected cells in IIP tests appeared to be restricted to PMV-3 viruses isolated from exotic birds and did not occur with viruses of ostensively the same serotype from turkeys.     

Zur Frage der aggregationsbedingten Aktivierungen von Pockenviren

Zusammenfassung Mit Hilfe von Gruppensynergismus-Diagrammen habenSharp und Mitarbeiter drei aggregationsbedingte Pockenvirus-Aktivierungsphänomene demonstriert: anomale Plaquebildung durch Kaninchenpockenvirus, MultiplizitätsAktivierung von Vacciniavirus und Multiplizitäts-Reaktivierung an vorher partiell inaktivierten Viruspopulationen.Die Basis sämtlicher Gruppensynergismus-Diagramme bildet die von den Autoren als allgemeingültig angenommene Proportionalität der Plaquetiter zu den Mengen kinetisch autonomer oder aktiver Viruseinheiten. Anhand eines einfachen Modelles einer aggregierenden Viruspopulation wird nachgewiesen, daß diese Annahme unhaltbar ist und zu der unrichtigen Interpretation führen muß, niedrig aktive Viruspopulationen würden durch Teilchenaggregierung Steigerungen ihrer biologischen Aktivität erfahren.Die Ursachen der Fehlschlüsse werden untersucht und durch Beispiele erläutert.

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Concerning aggregation dependent activations of poxvirusesI. Erroneous conclusions deduced from group synergism diagrams

Summary With the aid of group synergism diagramsSharp and coworkers have demonstrated three activation phenomena of pox viruses, depending on particle aggregation: anomalous plaque production of rabbitpox virus, multiplicity activation of vaccinia virus and multiplicity reactivation of partially inactivated viruses.The authors' basis for all group synergism diagrams is supposed proportionality between the number of plaques and kinetically autonomous or active virus units. Certain shortcomings inherent in this concept can be shown by using a simple model of an aggregating virus population. It can further be shown that this hypothesis leads to the misinterpretation that an increase in virus activity were caused by particle aggregation.The sources of the errors are investigated and are illustrated by examples.

     

The ultrastructure of the “excretory” system of ascaris suum larvae

Summary Electron microscope observations of the excretory cell of the infective larva reveal that it contains a large nucleus surrounded by cytoplasm containing numerous organelles, multi-granular bodies, vesicles and granules typical of glandular cells. The proximal region of the excretory duct bears a number of scattered microvilli, on its adluminal surface, and the distal region is lined with a thin multilayered cuticle.In the liver stage larva 2 days after infection, 2 lateral excretory columns are present. These arise from the excretory cell body and extend posteriorly for about half the length of the intestine. Each column contains a narrow longitudinal canal surrounded by cytoplasm rich in mitochondria, granular endoplasmic reticulum, free ribosomes and large vacuoles. Evidence was obtained of the passage of substances through the wall of the canal but their chemical nature was not determined.Further extension of the lateral columns is seen in the 8-day, lung-stage larva, the columns now extending for more than two-thirds the length of the intestine. Their diameter is also increased but their internal structure is essentially similar to that of the 2-day liver-stage larva.The excretory duct which arises immediately anterior to the nucleus has a structure similar to that of the lateral columns for the first half of its length, the microvilli described in the infective larva being absent at this stage. The distal half of the duct is lined with cuticle.     

Disinhibition of hippocampal pyramidal cells during the transition into theta rhythm

The activity of hippocampal complex-spike cells (presumed pyramidal cells) and theta cells (presumed interneurons) was examined during transitions from non-theta electroencephalogram (EEG) states to theta EEG states in freely moving and sleeping rats. Theta cell firing rates were significantly depressed in a 1-s period centered on the EEG transition relative to the surrounding 1-s periods (normalized rates±SEM): 1.05±0.02 for the non-theta period, 0.59±0.03 for the transition period, and 1.36±0.04 for the theta period (n = 26 cells). Conversely, complex-spike cell firing was significantly increased during the transition period: 0.51±0.11 for the non-theta period, 2.24±0.19 for the transition period, and 0.24±0.04 for the theta period (n = 27 cells). This diametrically altered activity indicates that theta cells must be actively inhibited during the transition. The increased activity in complex-spike cells during the transition may be simply a release from inhibitory control by interneurons. The pattern of theta cell inhibition together with increased complex-spike cell activity appears to be a general property of transitions into the theta EEG state, irrespective of behavior. It is suggested that increased activity in septal afferents (GABAergic cell activity greater than cholinergic cell activity) initially inhibits hippocampal interneurons. The inhibition is not sustained because of an activity-dependent decrease in the potency of the septointerneuronal inhibition, leaving the rhythmic excitatory (cholinergic) septointerneuronal inputs, together with principal cell inputs, to increase interneuron firing rates.