The influence of isatin on guanylyl cyclase of rat heart membranes

The influence of indole-2,3 dione (isatin) on particulate guanylyl cyclase (GC) from rat heart membranes was investigated in the presence of adenylylimidodiphosphate (AMP-PNP). The latter activated GC in a concentration-dependent manner and 100 microM isatin abolished this effect. The IC(50) value, 2 microM, for the inhibition of stimulation of GC induced by 50 microM AMP-PNP, was close to the upper physiological level of isatin. These results indicate that isatin may interact with GC independently of its regulation by natriuretic peptides.

Cutting edge: functional characterization of the effect of the C3H/HeJ defect in mice that lack an Lpsn gene: in vivo evidence for a dominant negative mutation

A point mutation in the Tlr4 gene, which encodes Toll-like receptor 4, has recently been proposed to underlie LPS hyporesponsiveness in C3H/HeJ mice (Lpsd). The data presented herein demonstrate that F1 progeny from crosses between mice that carry a approximately 9-cM deletion of chromosome 4 (including deletion of LpsTlr4) and C3H/HeJ mice (i.e., Lps0 x Lpsd F1 mice) exhibit a pattern of LPS sensitivity, measured by TNF activity, that is indistinguishable from that exhibited by Lpsn x Lpsd F1 progeny and whose average response is "intermediate" to parental responses. Thus, these data provide clear functional support for the hypothesis that the C3H/HeJ defect exerts a dominant negative effect on LPS sensitivity; however, expression of a normal Toll-like receptor 4 molecule is apparently not required.

Autoregressive modeling of the EEG in systemic kainic acid-induced epileptogenesis

Background activity as well as three kinds of bilateral epileptiform discharges, recorded from the cerebral cortex and hippocampus of freely behaving rats treated with intravenous kainic acid (KA), were analysed by the directed transfer function (DTF) method within multivariate autoregressive modeling of the EEG. This method reveals statistical influence (flow of activity) between brain regions at different frequencies. There was no significant influence between rhythms in different brain regions in the background EEG. Early after KA administration, low frequency rhythms (< 10Hz) in the frontal cortex began to lead slow rhythms in other areas and high frequency rhythms (20-60 Hz), possibly gamma oscillations, intensified in the hippocampus. In spike-wave discharges, frontal cortex led both low and high frequency rhythms. Initially during generalised non-convulsive discharges, slow rhythms originated from frontal cortex and high frequency rhythms from hippocampus while later, slow rhythms as well, often arose from hippocampus. During the convulsive discharge, the flow of activity of dominant slow rhythms repeatedly changed between hippocampus and neocortex, with more frequent dominance of the hippocampus, while hippocampus continued to lead high frequency rhythms. We conclude that KA-induced epileptiform discharges are cortical and hippocampal events, specifically that the frontal cortex is early to express low frequency rhythms and the hippocampus, high frequency rhythms. More generally, the findings suggest that epileptiform discharges result from interacting rhythms of different frequencies that arise from different structures, and that gamma oscillations possibly contribute to widespread synchronisation during some forms of epileptogenesis.

Regulation of the transglutaminase I gene. Identification of DNA elements involved in its transcriptional control in tracheobronchial epithelial cells

The transglutaminase I (TGase I) gene encodes an enzyme that catalyzes the cross-linking of structural proteins involved in the formation of the cornified envelope during squamous cell differentiation. To identify DNA elements important for the transcriptional control of the TGase I gene, we analyzed the ability of a 2.9-kilobase pair (kb) upstream regulatory region to control the expression of a reporter gene in vivo and in vitro. Transgenic mice bearing the pTG(-2.9kb)CAT construct exhibited the same pattern of tissue-specific expression of CAT as reported for TGase I. Deletion analysis in transiently transfected rabbit tracheal epithelial cells indicated that two sequences from bp -490 to -470 and from -54 to -37 are involved in the activation of TGase I transcription. Point mutation analysis and mobility shift assays showed that the sequence located between -54 and -37 is a functional Sp1-like transcription element. Sp1 and Sp3, but not Sp2, are part of nuclear protein complexes from differentiated RbTE cells binding to this site. The element TGATGTCA between bp -490 and -470 is contained in a larger 22-bp palindrome and resembles the consensus cAMP response element-binding protein (CREB)/AP-1 element recognized by dimeric complexes of members of the CREB, ATF, Fos, and Jun families. Mutations in this sequence greatly reduced promoter activity. Supershift analysis identified CREB1, JunB, c-Fos, Fra-1, and c-Jun in protein complexes isolated from differentiated rabbit tracheal epithelial cells binding to this site. Our study shows that the Sp1- and CREB/AP-1-like sites act in concert to stimulate transcription of the TGase I gene. The 2.9-kb promoter region could guide expression of specific genes in the granular layer of the epidermis and could be useful in gene therapy.

Cleveland Clinic continuous flow blood pump: progress in development

The Cleveland Clinic continuous flow blood pump is the central element of our innovative ventricular assist system (IVAS). Recent progress has been made in the design/fabrication of a pulsatile mock loop, journal bearing materials testing, and evaluation of a system control algorithm. These results have allowed an acceleration of our program.

Regulation of peroxisome proliferator-activated receptor alpha-induced transactivation by the nuclear orphan receptor TAK1/TR4

Recently, we reported the cloning of the nuclear orphan receptor TAK1. In this study, we characterized the sequence requirements for optimal TAK1 binding and analyzed the repression of the peroxisome proliferator-activated receptor alpha (PPARalpha) signaling pathway by TAK1. Site selection analysis showed that TAK1 has the greatest affinity for direct repeat-1 response elements (RE) containing AGGTCAAAGGTCA (TAK1-RE) to which it binds as a homodimer. TAK1 is a very weak inducer of TAK1-RE-dependent transcriptional activation. We observed that TAK1, as PPARalpha, is expressed within rat hepatocytes and is able to bind the peroxisome proliferator response elements (PPREs) present in the promoter of the PPARalpha target genes rat enoyl-CoA hydratase (HD) and peroxisomal fatty acyl-CoA oxidase (ACOX). TAK1 is unable to induce PPRE-dependent transcriptional activation and represses PPARalpha-mediated transactivation through these elements in a dose-dependent manner. Two-hybrid analysis showed that TAK1 does not form heterodimers with either PPARalpha or retinoid X receptor (RXRalpha), indicating that this repression does not involve a mechanism by which TAK1 titrates out PPARalpha or RXRalpha from PPAR.RXR complexes. Further studies demonstrated that the PPARalpha ligand 8(S)-hydroxyeicosatetraenoic acid strongly promotes the interaction of PPARalpha with the co-activator RIP-140 but decreases the interaction of PPARalpha with the co-repressor SMRT. In contrast, TAK1 interacts with RIP-140 but not with SMRT and competes with PPARalpha for RIP-140 binding. These observations indicated that the antagonistic effects of TAK1 on PPARalpha.RXRalpha transactivation act at least at two levels in the PPARalpha signaling pathway: competition of TAK1 with PPARalpha.RXR for binding to PPREs as well as to common co-activators, such as RIP-140. Our results suggest an important role for TAK1 in modulating PPARalpha-controlled gene expression in hepatocytes.

The tumor necrosis factor-inducing potency of lipopolysaccharide and uronic acid polymers is increased when they are covalently linked to particles

Lipopolysaccharide (LPS) and polymers of the uronic acid family stimulate monocytes to produce tumor necrosis factor (TNF). The TNF-inducing potency of these polysaccharides may depend on their supramolecular configuration. In this study detoxified LPS and uronic acid polymers have been covalently linked to particles which have been added to monocytes under serum-free conditions. Reducing the size of mannuronan from 350,000 to 5,500 Da (M-blocks) led to a 10- to 100-fold reduction in TNF-inducing potency. However, covalently linking the M-blocks to monodisperse suspensions of magnetic particles increased the TNF-inducing potency by up to 60,000-fold. Also, the TNF-inducing potency of glucuronic acid polymers was increased when they were linked to particles, but no potentiation was observed with guluronic acid blocks covalently attached to particles. Furthermore, O chains of LPS (detoxified LPS) became potent TNF inducers when they were presented to monocytes on a particle surface. No activation of the LPS-responsive SW480 adenocarcinoma cells was found with detoxified LPS or M-block particles, suggesting a preference for cells expressing CD14 and/or other membrane molecules. The potentiating effects were not restricted to polymers attached to aminated magnetic particles. Of particular interest, we found that short blocks of mannuronan induced TNF production also when covalently linked to biodegradable, bovine serum albumin particles.

Suppression of relaxin gene expression by retinoids in squamous differentiated rabbit tracheal epithelial cells

Northern blot analysis of total RNA from a variety of rabbit tissues indicated that placenta is the primary site of expression of the protein hormone relaxin (previously called SQ10) in rabbits. Relaxin was not detected by this method in other rabbit tissues, including normal trachea and several squamous tissues. However, relaxin is highly induced during squamous cell differentiation in cultured rabbit tracheal epithelial (RbTE) cells. Retinoic acid and retinoids that selectively bind to the nuclear retinoid receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs), and induce RARE- or RXRE-dependent transactivation as well as repression of AP-1-dependent transactivation, were all effective in suppressing relaxin expression. In addition, the retinoid SR11302, which exhibits only anti-AP-1 activity but does not induce RARE- or RXRE-dependent transactivation, was also able to inhibit relaxin expression. These results suggest that the suppression of relaxin expression is related to the anti-AP-1 activity of retinoids. To determine whether the relaxin gene is regulated by retinoids at the level of transcription, a 4.3 kb fragment of the 5' flanking region of the rabbit relaxin gene was cloned and analyzed. This regulatory region included a classic TATA-box as well as consensus sequences for several transcription factors, including CREB, NF-kappaB and AP-1. The ability of the 4.3 kb regulatory region to control the transcription of a luciferase reporter gene was analyzed in transiently transfected, squamous-differentiated RbTE cells. The results demonstrated that this regulatory region caused strong transactivation of the reporter gene. This transactivation was inhibited by retinoic acid, suggesting retinoid control at the transcriptional level. Deletion analysis indicated that multiple regulatory elements are involved in the regulation of relaxin gene expression during squamous differentiation as well as in the suppression by retinoids.

Induction of the nuclear orphan receptor RORgamma during adipocyte differentiation of D1 and 3T3-L1 cells

Here, we analyzed the expression of the three members of the retinoid-like orphan receptor (ROR) nuclear receptor subfamily during adipocyte differentiation. RORalpha and RORgamma mRNA were upregulated during adipocyte differentiation in preadipocyte D1 and 3T3-L1 cells, whereas RORbeta mRNA could not be detected. The induction of RORalpha and RORgamma mRNA succeeded the induction of peroxisome proliferator-activated receptor gamma (PPARgamma) and CCAAT/enhancer binding protein alpha and occurred at a similar time interval as did the increase in aP2 and lipoprotein lipase mRNA. Like the expression of PPARgamma and aP2, the induction of RORgamma mRNA was repressed by tumor necrosis factor alpha and transforming growth factor beta. The induction of adipogenesis by prostaglandin D2 and two thiazolidinediones in the multipotent stem cells C3H10T1/2 was also accompanied by an induction in RORgamma mRNA. In contrast to parental cells, clofibrate induces adipogenesis and RORalpha and RORgamma mRNA in BALB/c3T3 cells that ectopically express PPARgamma. RORgamma mediates its effect on transcription through specific response elements. Cotransfection of RORalpha or RORgamma and (RORgamma response element)4-chloramphenicol acetyltransferase into preadipocyte D1 cells induced transactivation of chloramphenicol acetyltransferase about 100-fold, suggesting that ROR plays a role in the regulation of gene expression in adipocytes. The nuclear orphan receptor Rev-ErbAalpha, which did not exhibit transactivation function, was able to inhibit transactivation by RORgamma at two different levels. Our results show that RORgamma is induced during adipocyte differentiation in D1 and 3T3-L1 cells and functions as an active transcription factor, suggesting a role for RORgamma in the regulation of gene expression during this differentiation process.

Genomic structure and chromosomal mapping of the nuclear orphan receptor ROR gamma (RORC) gene

The nuclear orphan receptor subfamily ROR/RZR is part of the steroid and thyroid hormone/retinoid receptor superfamily and consists of three different genes, alpha, beta, and gamma. In this study, we determined the genomic structure of mouse ROR gamma and the chromosomal localization of both mouse ROR gamma and human ROR gamma (HGMW-approved symbol RORC). The genomic structure of the mouse ROR gamma gene was derived from the analysis of P1 vector clones containing large genomic fragments encoding ROR gamma. These results revealed that the mROR gamma gene has a complex structure consisting of 11 exons separated by 10 introns spanning more than 21 kb of genomic DNA. The DNA-binding domain is contained in two exons, 3 and 4, each encoding one zinc-finger. The splice site between exon 3 and exon 4 is identical to that found in RAR and TR3 receptors. ROR gamma is expressed as two mRNAs, 2.3 and 3.0 kb in size, that are derived by the use of alternative polyadenylation signals. We show by fluorescence in situ hybridization that the mouse ROR gamma gene is located on chromosome 3, in a region that corresponds to band 3F2.1-2.2. The human ROR gamma was mapped to chromosome region 1q21. The results demonstrate that the ROR gamma genes are located in chromosomal regions that are syntenic between mouse and human.

Flow analysis of the Cleveland Clinic centrifugal pump

An implantable ventricular assist blood pump is being developed by the Cleveland Clinic Foundation in cooperation with the NASA Lewis Research Center. At the nominal design condition, the pump provides blood flow at the rate of 5 L/min at a pressure rise of 100 mmHg and a rotation speed of 3000 RPM. Bench testing of the centrifugal pump in a water/glycerin mixture has provided flow and pressure data at several rotative speeds. A one-dimensional empirically based pump flow analysis computer code developed at NASA Lewis Research Center has been used in the design process to simulate the flow in the primary radial pump stage. The computer model was used to size key impeller and volute geometric parameters that influence pressure rise and flow. Input requirements to the computer model include a simple representation of the pump geometry. The model estimates the flow conditions under design and off-design operating conditions at the impeller leading and trailing edges, and the volute inlet and exit. Output from the computer model is compared to flow and pressure data obtained from bench testing.

Design of a DSP controller for an innovative ventricular assist system

The design and development of the digital signal processor controller for an innovative ventricular assist system is presented. A DSP56005 is used as the central processor, with other peripheral components. System hardware and software were developed through the advanced development system, and stand alone operation of the system was also accomplished. Two different control modes--current control mode and speed control mode--were developed and investigated. Performance of efficiency and dynamic response were examined through experimental testing.

Analysis of a new PM motor design for a rotary dynamic blood Pump

The permanent magnet (PM) motor for a rotary dynamic blood pump requires high power density to coordinate the motor size with the limited pump space and high efficiency to reduce the size and weight of the associated batteries. The motor also serves as a passive axial magnetic thrust bearing, a reacting hydraulic force, and provides a stabilizing force for the radial journal bearing. This article presents analysis of a new PM motor for the blood pump application. High power density is achieved by using the Halbach magnetic array, and high efficiency is accomplished by optimizing the rotor magnet assembly and the stator slots/windings. While both radial and axial forces are greatly enhanced, pulsating components of the torque and force are also significantly reduced.

Characterization of the response element and DNA binding properties of the nuclear orphan receptor germ cell nuclear factor/retinoid receptor-related testis-associated receptor

Recently, we have reported the cloning of the germ cell-specific, nuclear orphan receptor germ cell nuclear factor (GCNF)/RTR. In this study, we characterize the RTR response elements by an electrophoretic mobility shift assay/polymerase chain reaction-based, DNA binding site selection strategy. RTR binds with the greatest affinity to response elements containing TCA(AG(G/T)TCA)2 (consensus RTR response element; conRTRE), to which it binds as a homodimer. RTR is also able to bind as a monomer to a single core motif TCAAG(G/T)TCA, albeit with a lower affinity. Mutation analysis supports the specific requirements of the 5'-flanking sequence and the core motif of the RTRE for optimal binding of RTR. An RTR-specific antiserum (RTR-Ab2) was raised that causes supershift of the RTR-conRTRE complex in EMSA. Based on the sequence of the conRTRE, we located a putative RTRE, referred to as P2-RE, in the 5' promoter-flanking region of the mouse protamine 2 gene, which is induced during the same stage of spermatogenesis as RTR. The ability of RTR-Ab2 to cause a supershift of an RTR-RTRE complex with nuclear extracts from different tissues correlated with the tissue- and development-specific expression of RTR. Transfection of RTR in CV-1 cells was unable to cause RTRE-dependent transactivation of a CAT reporter gene; however, an RTR-VP16 fusion protein could induce transactivation through several RTREs, including P2-RE.

cDNA cloning, genomic structure, and chromosome mapping of the human epithelial membrane protein CL-20 gene (EMP1), a member of the PMP22 family

CL-20 is a novel gene encoding a protein that is structurally related to but distinct from the peripheral myelin protein PMP22. Like PMP22, CL-20 is likely to play important roles in the regulation of cell proliferation, differentiation, and cell death. In this study, we describe the cloning and sequencing of a cDNA encoding the human homologue of CL-20 and characterize the genomic structure of this gene. The hCL-20 gene (HGMW-approved symbol EMP1) encodes a protein of 157 amino acids that exhibits 76% identity to the rabbit CL-20 and to the rat EMP-1, which have been described recently, and 39% identity to human PMP22. CL-20 contains four hydrophobic domains, suggesting that it is an integral membrane protein. In particular the second hydrophobic domain encoded within the fourth exon is highly conserved among CL-20, EMP-1, and PMP22, suggesting a functional role for this region. CL-20 mRNA is abundant in squamous-differentiated bronchial epithelial cells; however, low levels of CL-20 mRNA can be detected in several human tissues by Northern analysis. Retinoic acid, which inhibits squamous differentiation, represses CL-20 expression in normal human bronchial epithelial cells. The genomic structure of the hCL-20 gene was analyzed using a P1 vector containing this gene. The hCL-20 gene contains five exons about 0.2, 0.12, 0.1, 0.14, and 2.2 kb and four introns about 15, 1.9, 0.1, and 0.7 kb. We have mapped the hCL-20 gene to chromosome 12p12 by fluorescence in situ hybridization.

Fos induction following systemic kainic acid: early expression in hippocampus and later widespread expression correlated with seizure

We determined the distribution of Fos protein expression in a model of generalised epilepsy caused by excessive neuronal excitation. Fos immunoreactivity was mapped in forebrain in unrestrained rats, previously prepared with an indwelling venous catheter, after the intravenous administration of kainic acid (10 mg/kg). We determined cerebral activation following various periods of exposure to kainic acid by using intravenous administration of pentobarbitone to prevent further activation. Within a few minutes, kainic acid caused episodes of staring, sniffing, wet dog shakes, nodding and chewing. Fos induction occurred initially and simultaneously in hippocampus, subiculum, septum and entorhinal cortex as early as 9.5 min after kainate injection. After up to 40 min of staring, sniffing, wet dog shakes, nodding and chewing, Fos induction was not further increased above levels present within the first 9.5 min. After 56 +/- 6 min a motor convulsion occurred, initially affecting the jaw, head and tail and variably extending to the forelimbs, trunk or hindlimbs. Following the convulsive event, additional Fos was expressed in hippocampus, thalamus, caudate-putamen and other subcortical structures and in the cerebral cortex. Fos induction was sometimes asymmetric in entorhinal, visual, piriform, cingulum, parietal and frontal cortices and in amygdala and dorsal endopiriform area. Electroencephalographic recordings after a few minutes exposure to kainic acid revealed an increased amplitude of fast frequencies in hippocampus which appeared to correlate with Fos induction in this structure. The findings are generally consistent with the reported distribution and slow development of kainic acid-induced seizure activity using electrophysiological and deoxyglucose methods. However, the Fos distribution suggests that (i) hippocampal, possibly dentate, activation precedes significant activation elsewhere, (ii) extensive involvement of other cerebral structures and cerebral cortex occurs simultaneously and correlates with motor seizures and (iii) brain structures can be recruited asymmetrically.

Cloning of a cDNA encoding the murine orphan receptor RZR/ROR gamma and characterization of its response element

In this study, we describe the cloning of the mouse homologue of the orphan receptor, RZR/ROR gamma, a member of the nuclear receptor superfamily, from a mouse muscle cDNA library. The amino acid sequence of mouse ROR gamma (mROR gamma) is highly homologous to that of human ROR gamma, with an overall identity of 88%. Northern blot analysis using RNA from different tissues showed that mROR gamma was found to be highly expressed in skeletal muscle, liver and kidney. Analysis of the ROR gamma-response element using in vitro synthesized ROR gamma revealed that it binds as a monomer to response elements composed of a single core motif GGTCA preceded by a 6 bp AT-rich sequence. The ROR gamma-binding specificity was further defined by mutational analysis of the consensus RORE. ROR gamma was able to activate RORE-dependent transcription of the CAT reporter gene in mouse fibroblast D1 cells. ROR alpha 1 and ROR gamma inhibit the transactivation induced by GAL4(DBD)-ROR gamma in fibroblast D1 cells suggesting that these receptors compete for binding to the same coactivators.

The geometric structure, construction, and interpretation of path-following (trail-making) tests

Diagnostic comparisons of performance on parts A and B of the Trail Making Test (TMT) assume that path structure in the two parts is equivalent but that task complexity is greater for B. The two parts are shown to differ with respect to length and angular variability. However, measures of fractal dimension show no difference in structural complexity between paths A and B. This analysis suggests a principled method for generating alternative pathways, varying in complexity, and opens the way for a systematic study of path-following. It also suggests that path-following may be interpretable within a general approach, in which perceptual, linguistic, reasoning and motor processes are seen as related through different groups of geometric transformations.

Frontal cortex leads other brain structures in generalised spike-and-wave spindles and seizure spikes induced by picrotoxin

Generaliszed spike-and-wave (SW) spindles (5-7 Hz) associated with myoclonic jerks precede the occurrence of regular spikes (2-3 Hz) associated with convulsive seizure induced by picrotoxin. SW spindles occur spontaneously in rodent and cat under some experimental conditions and are considered to be models of human generalised epilepsy. These spindles have been proposed as being led by a thalamic pacemaker. To examine this possibility in picrotoxin-induced SW spindles and seizure spikes, we recorded EEG using chronically implant unipolar electrodes during intravenous picrotoxin infusion in freely behaving rat. The 6 EEG signals were digitally sampled at 1000 Hz. Linear correlation, spectral, coherence and phase analyses were undertaken to determine time differences (TDs) between EEG channels and the brain structure leading seizure activity. One frontal cortex led all other structures during SW spindles. TD between SW spindles in the leading frontal cortex (Fr1) and the contralateral Fr1 was 3.6 + / - 0.5 msec. All ipsilateral structures (hippocampus, thalamus, amygdala, caudate nucleus and occipital cortex) were delayed by more than 3 msec from Fr1 (intralaminar thalamic nuclei - by 6.3 + / - 0.9 msec). TDs of SW spindles between subcortical regions were less than 1.5 msec. Similar relationships with slightly smaller TDs were found with spikes during convulsive seizure except TDs between frontal cortices did not significantly differ from zero. We suggest that seizure activity induced by picrotoxin is led by one Fr1 during SW spindles and by both frontal cortices working as one system during convulsive seizure.

Opioid receptor activation resets the hypothalamic clock generating growth hormone secretory bursts in the rat

Plasma growth hormone (GH) concentrations were measured serially every 20 min for 6 h in unrestrained chronically-catheterised male rats to define physiological GH pulsatile secretory patterns. Bursts of GH secretion lasted 69 +/- 5 min and occurred every 177 +/- 4 min. Intravenous administration of the opioid receptor agonist morphine (200 micrograms/kg) caused an immediate GH burst of normal duration (63 +/- 3 min) in all animals. This burst of secretion occurred whatever the phase of the background GH cycle and was followed by normal trough GH levels; a second GH burst occurred 177 +/- 6 min later, an inter-burst period not different from controls. Opioid receptor blockade with naloxone (5 mg/kg) administered i.v. every 20 min during spontaneous GH bursts significantly lengthened the interburst interval from 177 +/- 4 to 200 +/- 9 min (P = 0.015). Naloxone did not affect synchronisation of the GH rhythm induced by morphine but lengthened the duration of GH secretory bursts from 69 +/- 5 to 94 +/- 9 min (P = 0.017). The findings indicate that opioid receptor activation resets the hypothalamic mechanism generating pulsatile GH secretion and that both the period of the GH rhythm and duration of the GH burst is normally shortened by opioid mechanisms.

Isatin is a potent endogenous antagonist of guanylate cyclase-coupled atrial natriuretic peptide receptors

Isatin (indole-2,3-dione) is an endogenous compound with anxiogenic properties. In the brain, highest levels (0.1 microgram/g) have been found in the rat hippocampus. In the present study, we show that isatin has little effect on a wide range of neurotransmitter and hormonal receptors but that it acts as an inhibitor of atrial natriuretic peptide (ANP) binding, with an IC50 of 4x 10(-7) M. It also inhibits ANP-activated particulate guanylate cyclase from rat kidney, heart and brain membranes in dose-dependent fashion, varying also with ANP concentration. These findings suggest that isatin is a new endogenous regulator of mammalian ANP activity, with potential implications for the control of both anxiety and natriuresis.

Distribution of Fos-positive neurons in cortical and subcortical structures after picrotoxin-induced convulsions varies with seizure type

The distribution of Fos protein was mapped in rat brain following a single non-focal convulsive seizure. Single seizures were induced with intravenous picrotoxin in unhandled animals housed in isolation. Different convulsive behaviours occurred unpredictably. The least severe seizures were predominantly localised to the face, head and forelimbs, without loss of posture control (restricted seizures). The most extensive seizures affected all limbs and trunk, sometimes with falling (generalised seizures). There was a correlation between seizure behaviour and distribution of Fos induction. After restricted seizures, Fos was induced at highest levels in neocortex and piriform cortex and was prominent in entorhinal cortex, caudal-ventral caudate-putamen and amygdala. Regions of thalamus were consistently and lightly labelled, but Fos induction did not occur in hippocampus. After generalised seizures, there was Fos induction in cortex but less than after restricted seizures and, in three of four animals, also in dentate gyrus, hippocampus and subiculum. There was occasional or variable labelling of thalamus, basolateral amygdala and caudate-putamen. One animal with generalised seizures showed no hippocampal Fos induction. The findings indicate that picrotoxin induces seizures with at least two different patterns of neuronal involvement. The cortex, part of the caudate-putamen, amygdala and thalamus are involved in restricted seizures while the hippocampus, cortex and thalamus are involved in generalised seizures. The results do not support the view that generalised seizures are a progression from restricted forms. Cortical Fos involvement is entirely consistent with the participation of cortex in non-focal epilepsy. In these non-focal seizures, the dentate-hippocampus may be a source of excitation to cortex in the generalised group while the cortex appears to be the predominant site of excitation in the restricted group.

Tumor necrosis factor receptor p75 mediates cell-specific activation of nuclear factor kappa B and induction of human cytomegalovirus enhancer

The functional role of human tumor necrosis factor receptor (TNFR) p75 was studied by the use of TNFR p75-specific agonistic antibodies. Human SW480T adenocarcinoma cells, stably transfected with a reporter construct containing beta-galactosidase under the control of human cytomegalovirus immediate early enhancer, were stimulated with anti-TNFR p75 polyclonal antiserum or monoclonal antibodies followed by measurement of beta-galactosidase activity and analysis by electrophoretic mobility shift assays. It was found that cross-linking of TNFR p75 led to strong induction of the human cytomegalovirus enhancer as well as activation of nuclear factor-kappa B (NF-kappa B). Stimulation of TNFR p75 also mediated activation of NF-kappa B in human KYM-1 rhabdomyosarcoma cells but not in other cell types such as U937 and HL-60 monocytic cells or in Eahy 926 endothelial cells. NF-kappa B activation induced by TNFR p75 was delayed approximately 15 min compared with NF-kappa B activation induced by TNFR p55, indicating that the two TNFRs activate NF-kappa B through different signaling pathways. The data presented in this study identify intracellular responses mediated by TNFR p75 which have not been reported previously and suggest that TNFR p75-induced activation of NF-kappa B is strictly cell type-specific.