Firing of inferior colliculus auditory neurons is phase-locked to the hippocampus theta rhythm during paradoxical sleep and waking

The activity of 52 single auditory units in the central nucleus of the inferior colliculus (IC) was recorded along with cortical and hippocampal (CA1) electrograms and neck muscle electromyograms in behaving, head-restrained guinea pigs during paradoxical sleep (PS) and wakefulness. Sixteen (30%) of the IC auditory units showed positive correlation with the hippocampal theta () rhythm: 8 (15%) were rhythmic with phase-locking (type 1), 8 (15%) showed only phase-locking with no rhythmicity (type 2), while 70% did not show any correlation to hippocampal rhythm (type 3). During wakefulness IC neurons (4 of 13) showed a higher synchrony with hippocampal when sound-stimulated at the unit's characteristic frequency. During PS all IC auditory neurons recorded presented some hippocampal correlation: 40% were rhythmic and phase-locked to the frequency and 60% were nonrhythmic maintaining the phase-locking. Shifts in the angle of phase-locking to the rhythm were observed during PS. It is suggested that the hippocampal rhythm may play the part of an internal clock, adding a temporal dimension to the processing of auditory sensory information.     

Neuronal sources of theta rhythm in the entorhinal cortex of the rat

Summary The laminar distribution of theta () field potentials in the entorhinal cortex (EC) was investigated in paralysed and locally anesthetized rats injected with physostigmine in order to induce rhythm. Electrode penetrations through the medial, intermediate and lateral subdivisions of the EC showed in all cases: 1. the presence of rhythm from layer VI to layer III approximately in phase with CA1 rhythm; 2. an amplitude minimum between the outer third of layer III and the inner half of layer I; and 3. a phase-reversed rhythm in layers II-I with an amplitude maximum in the outer half of layer I. Results indicate the existence of neuronal sources of rhythm in the EC.     

Genetic characterization of an α-specific gene responsible for sexual agglutinability in Saccharomyces cerevisiae: mapping and gene dose effect

Summary A recessive ag1 mutation leads to specific defect in sexual agglutinability specifically in cells of the yeast Saccharomyces cerevisiae. The cryptopleurine resistance gene cry^R 1, closely linked to the mating type locus, was used to select / strains which emerged from / strains by mitotic nonreciprocal recombination, to genetically analyse ag1, since ag1 is expressed only in mating type. The ag1 gene was found to be linked to the centromere tightly, to met3 at 4.4 cM, and to ilv3 at 12 cM on chromosome X. Sexual agglutinability of cells was shown to be dependent on the dose of the AG1 gene, using / isogenic strains carrying AG1/AG1, AG1/ag1 or ag1/ag1. The sst2-1 mutation did not suppress the ag1 mutation. Based on these results, function of the AG1 gene is discussed.Abbreviations cM centimorgan - FDS first division segregation - NPD nonparental ditype - PD parental ditype - SDS second division segregation - TT tetratype     

Mathematical Simulation of Slowing of Cardiac Conduction Velocity by Elevated Extracellular [K+] in a Human Atrial Strand

We have studied the dependence of conduction velocity () on extracellular potassium concentration ([K⁺]_o) in a model of one-dimensional conduction using an idealized strand of human atrial cells. Elevated [K⁺]_o in the 5–20 mM range shifts the resting potential (V _rest) in the depolarizing direction and reduces input resistance (R _in) by increasing an inwardly rectifying K⁺ conductance, I _Kl.Our results show that in this model: (1) depends on [K⁺] in a biphasic fashion. Moderate elevations of [K⁺]_o (to less than 8 mM) result in a small increase in , whereas at higher [K⁺]_o (8–16 mM) is reduced. (2) This biphasic relationship can be attributed to the competing effects of (i) the smaller depolarization needed to reach the excitation threshold (V _thresh-V _rest) and (ii) reduced availability (increased inactivation) of sodium current, I _Na, as the cell depolarizes progressively. (3) Decreasing R _in reduces due to the increased electrical load on surrounding cells. (4) The effect on of [K⁺]_o-induced changes in R _inin the atrium (as well as other high-R _in tissue, such as that of the Purkinje system or nodes) is likely to be small. This effect could be substantial, however, under conditions in which R _in is comparable in size to gap junction resistance and membrane resistance (inverse slope of the whole-cell current–voltage relationship) when sodium channels are open, which is likely to be the case in ventricular tissue. © 2000 Biomedical Engineering Society.PAC00: 8716Uv, 8719Hh, 8716Ac     

Intraseptal infusion of selective and competitive glutamate receptor agonist NMDA and antagonist d-2-amino-5-phosphonopentanoic acid spectral implications for the physostigmine-induced hippocampal theta rhythm in urethane-anesthetized rats

Theta () rhythm may be mediated, at least in part, by a glutamate neurotransmitter. Thus, in the present study, it was hypothesized that the septum glutamatergic NMDA receptor subtype may be involved in the modulation of physostigmine-induced rhythm. To test this hypothesis, we analyzed, in the urethane-anesthetized rat, the effects of septum application of NMDA and d-2-amino-5-phosphonopentanoic acid (AP5), selective and competitive NMDA agonist and antagonist, respectively, on the spectral characteristics of hippocampal rhythm elicited by intravenous injection of a anticholinesterase agent, physostigmine. A low dose (16 nmol) of AP5 did not significantly affect EEG recordings, whereas a high dose (50.75 nmol) resulted in significant decreases in phase (-61.8%) at frequency, peak power (-64.2%), and absolute power of the low-frequency band (-67%). These electroencephalographic alterations, which appeared at 50.75 nmol AP5, were amplified following application of massive doses of the drug (121.8 nmol, n=1, and 162 nmol, n=1). Amplification, however, was slight and the waves remained clearly detectable. On the other hand, the infusion of NMDA resulted in a significant increase in frequency (+25%) of this rhythm, but this effect was completely antagonized by prior local administration of 16 nmol AP5. Our data suggest that the septal NMDA receptors exert subtle modulatory influences on the septohippocampal cells involved in physostigmine-induced wave production, which has not been reported elsewhere: tonic with respect to both low-frequency band power and phase, and phasic with respect to frequency. Our data also indicate that the septum may be a sensitive action site for exogenously administered glutamatergic drugs.     

In vivo intracellular recordings of medial septal and diagonal band of Broca neurons: relationships with theta rhythm

Transmembrane potentials from medial septal and diagonal band of Broca (MS-DBB) neurons and hippocampal field activity were recorded in curarized and urethanized rats. MS-DBB cells were studied during large amplitude irregular activity and during hippocampal rhythm, elicited by either sensory (i.e. stroking the fur on the animal's back) or electrical stimulation of the reticularis pontis oralis nucleus (RPO). Three types of cells were described according to their firing pattern and the characteristics of their intracellular rhythm. Type A neurons displayed continuous rhythmic oscillations in the membrane potential (Vm) of approximately 17 mV. These oscillations generated rhythmic high-frequency spike trains which were phase-locked with hippocampal rhythm. Type A cells revealed intracellular rhythm even in the absence of hippocampal rhythm, suggesting that the activity of this type of cell was the most important in hippocampal genesis. Type B cells were characterized by marked postspike afterhyperpolarization and intracellular oscillations of smaller amplitude than in type A cells. Type C cells revealed a post-spike afterdepolarization and a lower amplitude, intracellular rhythm only in the presence of hippocampal rhythm. Type C neurons could fire slow spikes at depolarizing (46% of cells) or hyperpolarizing (15% of cells) Vms. Type B and C cells were intracellularly stained with Lucifer yellow. Although type B and C neurons revealed dissimilar electrophysiological properties, they had comparable morphological shapes. RPO electrical stimulation generated hippocampal rhythm and intracellular rhythm in types A and B cells but not in type C cells, and increased the spike rate in type C neurons. Electrical stimulation of the fornix only evoked synaptic responses in type B and C neurons, with antidromic responses being elicited in 12% of type C cells. These results indicate that probably most of the type A rhythmic cells did not receive direct hippocampal feedback and that at least some type C cells were projecting neurons. The present findings demonstrate that rhythm oscillations in the Vm of MS-DBB neurons elicit different rhythmic discharge patterns.     

Die Nebennierenrindenfunktion unter Applikation von 9α-Fluorcortisol

Zusammenfassung Untersuchungen über den Einfluß von 9-Fluorcortisol auf die Nebennierenrindenfunktion ergaben — in Verbindung mit in der Literatur mitgeteilten Werten — eine dosisabhängige Einschränkung der Ausscheidung von Nebennierenrindenhormonen. Die Ansprechbarkeit der Nebennierenrinde auf exogenes ACTH bleibt erhalten. Es ist daher eine Hemmung der hypophysären ACTH-Sekretion anzunehmen, die durch die Struktur des synthetischen Steroids erklärbar ist. — In geringer Dosierung, wie sie als Erhaltungsdosis bei Langzeittherapie verabfolgt wird, verursacht 9-Fluorcortisol keine wesentliche Einschränkung der Hormonausscheidung.

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Effect of 9-fluorocortisol on adrenocortical function

Summary Investigation of adrenal cortical function during administration of 9-fluorcortisol revealed—in connection with results obtained from the literature—a dose-related inhibition of the secretion of adrenocortical hormones. Adrenal cortical response to exogenous ACTH remains unaffected. An inhibition of hypophyseal ACTH-secretion is therefore assumed, caused by the structure of the synthetic steroid. At low dosage, as applied in long-term treatment, no significant alteration of steroid excretion patterns was observed.

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Astonin-H, Hersteller: Fa. E. Merck A.G., Darmstadt.

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In der Arbeit werden folgende Abkürzungen verwendet: 17-KS=17-Ketosteroide; 17-OH-CS=17-Hydroxycorticosteroide; F=Cortisol=Pregn-4-en-11,17,21-triol-3,20-dion; E=Cortison=Pregn-4-en-17,21-diol-3,11,20-trion; THF=Tetrahydrocortisol=5-Pregnan-3,11,17,21-tetrol-20-on; allo-THF=allo-Tetrahydrocortisol=5-Pregnan-3,11,17,21-tetrol-20-on; THE=Tetrahydrocortison=5-Pregnan-3,17,21-triol-11,20-dion; Andro=Androsteron=5-Androstan-3-ol-17-on; Ätio=Ätiocholanolon=5-Androstan-3-ol-17-on; DHA=Dehydroepiandrosteron=Androst-5-en-3-ol-17-on.

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Herrn Prof. Dr. med. H. Franke zum 60. Geburtstag gewidmet.     

The sloping alveolar plateau of tracer gases washed out from mixed venous blood in man

The gating current off-response of the frog node of Ranvier shows a fast and a slow phase, reflecting presumably charges moving back into the resting position and charges returning from immobilization. The paper describes measurements of the time constant of the slow component, _off2, at different potentials at 20 or 17°C. The time constant _off2 decreased markedly when the potential to which the fibre was repolarized at the end of the test pulses was decreased from –100 to –145 mV. _off2 was compared with _{off2 gat} and _{off2 Na}, the time constants of the recovery of gating current and peak sodium current from the effect of a depolarizing conditioning pulse. The three time constants were equal at –145 mV, but somewhat different at –100 to –130 mV, the sequence being516-6. The inequality _{off2 gat} < _off2 was small and statistically not significant. It does not seem to be due to contamination of the charge movement with ionic currents because a) theQ _off/Q _on ratio was near 1.0 at –100 to –120 mV, b) partial replacement of internal CsCl by KCl did not significantly alter _off2 orQ _off/Q _on, c) _off2 was independent of pulse size. The small incquality _{re gat} < _off2 suggests that charges which have returned from immobilization are not immediately available for displacement. The inequality _{re gat} < _{re Na} was larger and statistically significant at –100 and –110 mV. It confirms previous measurements of Nonner (1980). Although _{re gat} < _{re Na}, recovery of the gating current preceded recovery of the sodium current, because it started from a higher level.     

Glutathione accelerates sodium channel inactivation in excised rat axonal membrane patches

The effects of glutathione were studied on the gating behaviour of sodium channels in membrane patches of rat axons. Depolarizing pulses from –120 to –40 mV elicited sodium currents of up to 500 pA, indicating the simultaneous activation of up to 250 sodium channels. Inactivation of these channels in the excised, inside-out configuration was fitted by two time constants ( _h1=0.81 ms; _h2= 5.03 ms) and open time histograms at 0 mV revealed a biexponential distribution of channel openings ( _short=0.28 ms; _long=3.68 ms). Both, the slow time constant of inactivation and the long lasting single channel openings disappeared after addition of the reducing agent glutathione (2–5 mM) to the bathing solution. Sodium channels of excised patches with glutathione present on the cytoplasmatic face of the membrane had inactivation kinetics similar to channels recorded in the cell-attached configuration. These observations indicate that redox processes may contribute to the gating of axonal sodium channels.     

Two anonymous X-specific human sequences detecting restriction fragment length polymorphisms in region Xq26→qter

Two anonymous X-specific sequences isolated from a genomic library of flow-sorted X chromosomal DNA were selected for study because they revealed restriction fragment length polymorphisms in the region Xq26 qter. One sequence, DXS10, detected a two-allele TaqI polymorphic system with allele frequencies of 0.33 and 0.67. The other, 4D-8, defined an Mspl polymorphism with allele frequencies of 0.18 and 0.82. DXS10 is tightly linked to the hypoxanthine phosphoribosyltransferase (HPRT)locus with recombination distance =0 cM at LOD=5.55 (95 % probability limit <15 cM). DXS10 maps to Xq26 but is not contained within the HPRTlocus itself. 4D-8 shows no detectable linkage to the HPRTlocus, with maximum likelihood estimate for =50 cM and a LOD score of –2.61 at = 5 cM. These two polymorphisms provide additional chromosomal loci for gene mapping by linkage at the distal end of the long arm of the human X chromosome.     

Affinity chromatography of primary human amnion interferon

Summary The chromatographic behavior of human amniotic interferon on various affinity chromatography ligands was studied. Most of this interferon bound strongly to bovine plasma albumin-agarose, cibacron blue F3 GA-agarose, concanavalin A-agarose and L-tryptophyl-L-tyrosine--carboxyl-pentyl-agarose. After binding most of the interferon activity was eluted only with 50 percent ethylene glycol, showing the high hydrophobicity of this interferon. Smaller quantities could be recovered after phosphate-buffered saline elution or with increased salt concentration. On BPA--carboxy-pentyl-agarose and -aminohexyl-agarose, the majority of the biological activity was found in the break-through fraction (eluted with phosphate buffered saline) while some interferon was displaced with high salt or ethylene glycol. Increasing the salt concentration and lowering the pH was necessary to elute interferon from zinc chelate-agarose.These patterns indicate that human amniotic interferon is similar to human fibroblast () interferon but different from human leukocyte () interferon. However, the heterogeneity displayed by amniotic interferon on bovine plasma albumin-agarose requires further investigation.Abbreviations used Am interferon human amniotic membrane interferon - BPA bovine plasma albumin - CPE cytopathic effect - BPA-CH-Sepharose 4B BPA--carboxyl-pentyl-agarose - AH-Sepharose 4B -amino-hexyl-agarose - Con-A-Sepharose-4B concanavalin A-agarose - Blue Sepharose CL-6 B Cibacron Blue F3GA-agarose - E₀ 0.02M phosphate, pH 7.4, 0.15M NaCl - E₁ 0.02M phosphate, pH 7.4, 1M NaCl - E₂ E₁ plus 50 percent ethylene glycol With 4 FiguresDeceased.     

Differential effects of interleukin-1α and β on the arachidonic acid cascade in human synovial cells and chondrocytes in culture

The effects of interleukin-1 and were tested on the [³H]-arachidonic acid release and the prostaglandin synthesis by human cultured synovial cells and chondrocytes. Both forms of interleukin-1 stimulated the arachidonic acid release but interleukin-1 was more potent than IL-1. Human synovial cells and chondrocytes synthesized three types of prostaglandins upon stimulation with interleukin-1 or : prostaglandin E₂, F₂ and 6-keto-prostaglandin F₁. Regarding the synthesis of these prostaglandins, IL-1 was again more potent than IL-1. A comparison between interleukin-1-stimulated synovial cells and chondrocytes revealed neither significant quantitative nor qualitative differences in both the arachidonic acid release and the prostaglandin synthesis.     

Isolation of the Bα and Bβ mating-type loci of Schizophyllum commune

The B mating type of the basidiomycete fungus, Schizophyllum commune is determined by two, tightly linked, multi-specificity (also called multi-allelic) loci: B and B. A plasmid library was used in DNA-mediated transformation to obtain transformants that displayed B-directed development. Plasmids that conferred B1 and B1 mating-type specificities were rescued from the transformants. Fragments of DNA from each plasmid hybridized to genomic DNA from the strain used to make the plasmid library; however, they did not hybridize, or hybridized only weakly, to genomic DNA from strains with mating-type specificities different from B1 or B1. The cloned fragments are presumed to correspond to active regions of each B mating-type locus.     

Relationships of nucleus reticularis pontis oralis neuronal discharge with sensory and carbachol evoked hippocampal theta rhythm

Summary The activity of 72 neurons recorded in the reticularis pontis oralis nucleus (RPO) was examined in anesthetized and curarized rats during hippocampal theta () rhythm elicited by either sensory stimulation or carbachol microinjections. During hippocampal rhythm evoked by sensory stimulation, 63.9% of RPO neurons increased their discharge rate while the firing rate decreased in 20.8%. In all cases, the RPO neurons maintained a non-rhythmic discharge pattern. In 44% of the neurons the discharges tended to occur on the positive wave of the rhythm. Similar firing patterns were seen in 18 RPO neurons recorded during rhythm elicited by both, sensory stimulation and a carbachol microinjection; this effect was blocked by atropine. These results indicate that the RPO region contributes to the generation of hippocampal rhythm with a tonic and nonrhythmic outflow through a cholinergic system which may be muscarinic.     

Morphometry Error Due to Non-Perpendicular Section of Microvessel Characterized by Two-Dimensional Isotropic Arrangement

Formulas for calculation of the section non-perpendicularity error in estimation of the perimeter and cross-sectional area of microvessel profiles are proposed for the two-dimensional isotropic approximation. A relationship was established between the bias and random error associated with non-perpendicularity corresponding to _min for microvessel profiles meeting the condition _minB/C1, where B and C are the minimum and maximum axes of the microvessel profile, respectively.     

Interferon (type-α and γ) production by fresh and cryopreserved human mononuclear cells

Summary A comparative study of interferon (IFN) production (type- and ) was carried out using Ficoll-hypaque purified fresh and cryopreserved mononuclear cells from eight normal healthy individuals. Newcastle disease virus-NDV (R₂B strain) was used as an inducer for type- and Staphylococcal enterotoxin-A-(SEA) for type-IFN production. There was no significant difference between the titres of type- and -IFN and lymphocyte subpopulations of fresh and cryopreserved mononuclear cells studied under identical conditions.     

Interactions of the RAD7 and RAD23 excision repair genes of Saccharomyces cerevisiae with DNA repair genes in different epistasis groups

Summary The RAD7 and RAD23 genes of S. cerevisiae affect the efficiency of excision repair of UV-damaged DNA. We have examined the UV survival of strains carrying the rad7 or rad23 deletion mutation in combination with deletion mutations in genes affecting different DNA repair pathways. As expected, the rad7 and rad23 mutations interact epistatically with the excision repair defective rad1 mutation, and synergistically with the rad6 and rad52 mutations that affect the postreplication repair and recombinational repair pathways, respectively. However, the rad7rad6 and the rad23rad6 mutants exhibit the same level of UV sensitivity as the radlrad6 mutant. This observation is of interest since, in contrast to the rad7 or the rad23 mutations, the rad1 mutant is very UV sensitive and highly excision defective. This observation suggests that RAD6 and RAD7 and RAD23 genes compete for the same substrate during DNA repair.     

The role ofγδ T cells in the normal and disordered immune system

Summary A small population of T cells does not express the conventional T cell receptor characterized by the and polypeptide chains (TCR) but instead, two polypeptides termed and (TCR). This alternative receptor is able to recognize antigen. It appears early in T cell ontogeny, but its role in the thymus prior to the availability of TCR remains unclear. In selected sites such as skin or gut TCR predominates in mice which might suggest a role of T cells in the first line of defense against infection, T cells secrete lymphokines and display cytotoxic activity. However, their activation requirements may differ from what is known for T cells since MHC-nonrestricted and also CD4 and CD8 negative T cells have been described. Preferential activation by mycobacterial antigens possibly indicates a special repertoire of the T cells. In various diseases slightly increased numbers of T cells were found, but these preliminary studies have not yet provided evidence for a major pathogenetic role of T cells.List of abbreviations C constant region (immunoglobulin or TCR gene segment) - CD4 cluster of differentiation 4 (mainly on helper cells) - CD8 cluster of differentiation 8 (mainly on cytotoxic cells) - D diversity region (immunoglobulin or TCR gene segment) - DNA desoxyribonucleic acid - IL2 interleukin 2 - J joining region (immunoglobulin or TCR gene segment) - kD kiloDalton - MHC major histocompatibility complex - NK natural killer (cells) - RA rheumatoid arthritis - TCR T cell receptor - V variable region (immunoglobulin or TCR gene segment)     

A new approach for evaluation of the in vitro haemolytic potential of a solution of a new medicine

In the process of developing an intravenously injectable drug, its haemolytic potential must be considered. There are no Regulatory Guidelines for this kind of test. Many authors have set up different models, attempting to obtain early information about the behaviour of test compounds when injected into the bloodstream.In the present work, an in vitro static model is presented, which takes into account the injection rate (R _inj.) of the drug, and the blood flow rate (Q _v) of the vein in which the drug must be injected. From the relationship between these two parameters, the C_max, expressed as mg/ml, can be calculated. This latter parameter allows us to calculate the drug concentration which, at any moment during injection, comes into contact with a known aliquot of new' blood passing through the injection site. Furthermore, a dynamic test has been developed, which simulates an injection into the blood flow using a tubing system and infusion pumps set for the same R _ini. and Q _v values used in static test. Two injectable drugs, Valium® and Lanoxin®, and a commonly used vehicle, propylene glycol, have been tested by both the methods. These compounds have also been tested with another in vitro method (Prieur et al. 1973), in which a volumetric blood-to-test solution ratio of 1:1 is adopted for every drug tested, with neither R _inj. nor Q _v being taken into account. Results of the haemolytic potential obtained with the three tests have been compared.A good correlation has been observed between the static and the dynamic tests, whereas Prieur's model, which uses a drug-to-blood ratio which is far higher than in vivo, has been shown to give false positive results.It is concluded that a test for the evaluation of the haemolytic potential of drugs must take into account the pharmacodynamic characteristics of the formulation intended to be injected, and at least the blood flow rate. The proposed static test has been demonstrated to be an easy and reliable method of obtaining a true picture of the in vivo situation.     

Regulation of glycoprotein D synthesis of herpes simplex virus 1 by α 4 protein,the major regulatory protein of the virus,in stably transformed cell lines: effect of the relative gene copy numbers

Summary Earlier studies concerning 1 gene regulation by the 4 protein, the major regulatory protein of herpes simplex virus 1 (HSV-1), in stably transformed cell lines, reported conflicting results, i.e., 4 protein positively regulated the ₁ gB gene in 4/gB cells, while it negatively regulated the ₁ gD gene in 4/BJ cells. Both cell lines were derived from a common parental cell line 4/c 113 that contains 1 copy of the 4 gene, and the only apparent difference between them was the relative copy number of the gB and gD sequences (1 and 30–50, respectively) resident in the cell genome. We investigated this disparity by constructing a cell line (BA 4) that contains one copy each of the 4 and ₁ gD sequences, by fusion of 4/c 113 and BJt cells, containing and expressing respectively 1 copy of the 4 and gD genes. BA 4 cells constitutively expressed both the 4, gD genes inherited from the parental cell lines ( 4/c 113 and BJt). In BA 4 cells the 4 protein positively regulates the gD gene as evidenced from (i) higher levels of gD expression than the parental BJt cells lacking the 4 gene, and (ii) significant decrease in gD expression under conditions that render the 4 protein produced in BA 4 cells non-functional. In addition the ₂gG gene contained within the DNA fragment encoding the gD gene, is also expressed in BA 4 cells. On the basis of these data, we propose that gene regulation by the 4 protein is affected by the relative copy number of these genes, resident in the cell genome.