Contaminating viral sequences in high-throughput sequencing viromics: a linkage study of 700 sequencing libraries

OBJECTIVES

Sample preparation for high-throughput sequencing (HTS) includes treatment with various laboratory components, potentially carrying viral nucleic acids, the extent of which has not been thoroughly investigated. Our aim was to systematically examine a diverse repertoire of laboratory components used to prepare samples for HTS in order to identify contaminating viral sequences.

METHODS

A total of 322 samples of mainly human origin were analysed using eight protocols, applying a wide variety of laboratory components. Several samples (60% of human specimens) were processed using different protocols. In total, 712 sequencing libraries were investigated for viral sequence contamination.

RESULTS

Among sequences showing similarity to viruses, 493 were significantly associated with the use of laboratory components. Each of these viral sequences had sporadic appearance, only being identified in a subset of the samples treated with the linked laboratory component, and some were not identified in the non-template control samples. Remarkably, more than 65% of all viral sequences identified were within viral clusters linked to the use of laboratory components.

CONCLUSIONS

We show that high prevalence of contaminating viral sequences can be expected in HTS-based virome data and provide an extensive list of novel contaminating viral sequences that can be used for evaluation of viral findings in future virome and metagenome studies. Moreover, we show that detection can be problematic due to stochastic appearance and limited non-template controls. Although the exact origin of these viral sequences requires further research, our results support laboratory-component-linked viral sequence contamination of both biological and synthetic origin.

Autosomal SNP typing of forensic samples with the GenPlex™ HID System: results of a collaborative study

The GenPlex™ HID System (Applied Biosystems - AB) offers typing of 48 of the 52 SNPforID SNPs and amelogenin. Previous studies have shown a high reproducibility of the GenPlex™ HID System using 250-500pg DNA of good quality. An international exercise was performed by 14 laboratories (9 in Europe and 5 in the US) in order to test the robustness and reliability of the GenPlex™ HID System on forensic samples. Three samples with partly degraded DNA and 10 samples with low amounts of DNA were analyzed in duplicates using various amounts of DNA. In order to compare the performance of the GenPlex™ HID System with the most commonly used STR kits, 500pg of partly degraded DNA from three samples was typed by the laboratories using one or more STR kits. The median SNP typing success rate was 92.3% with 500pg of partly degraded DNA. Three of the fourteen laboratories counted for more than two thirds of the locus dropouts. The median percentage of discrepant results was 0.2% with 500pg degraded DNA. An increasing percentage of locus dropouts and discrepant results were observed when lower amounts of DNA were used. Different success rates were observed for the various SNPs. The rs763869 SNP was the least successful. With the exception of the MiniFiler™ kit (AB), GenPlex™ HID performed better than five other tested STR kits. When partly degraded DNA was analyzed, GenPlex™ HID showed a very low mean mach probability, while all STR kits except MiniFiler™ had very limited discriminatory power.

A task failure has no effect on the electromechanical delay of the peroneus longus

OBJECTIVE

Ankle inversion injuries represent the most common trauma sustained by athletes. Muscle fatigue from activity may contribute to a delay in the response of the ankle proprioceptors and dynamic restraints during unexpected inversion. The purpose of this investigation was to determine if the electromechanical delay (EMD) of the peroneus longus is influenced by a task failure exercise.

SUBJECTS

Sixteen subjects (age 20 +/- 1.1 y; mass 71.6 +/- 12.5 kg; height 173.0 +/- 8.7 cm; 9 male, 1 female) with no lower extremity injuries reported for data collection.

MEASUREMENTS

Data were collected from each subject's dominant leg using surface electromyography (EMG). Electrodes were applied over the peroneus longus (PL) using a standard protocol. A stimulating electrode was applied to the common peroneal nerve. Subjects were placed in a monopedal stance on a force platform. A low amplitude, short duration stimulus was applied to the common peroneal nerve. The EMG was used to determine timing of the M wave and the force platform was used to determine the onset of foot pronation. Once 6 trials were recorded, subjects completed 2 sets of an isotonic activity that isolated the peroneals. The task was completed to failure for each set. Immediately following the task failure exercise, subjects returned to the force platform for 6 additional trials recorded as before. Analysis of data was performed by determining the onset of the M wave as the beginning of positive EMG activity following the end of the imposed stimulus response. This point was superimposed on the force platform curve and the point at which a 10 N.m force change occurred was used to calculate the EMD (time difference between the force platform indicator and the M wave indicator).

RESULTS

Average EMD prior to the task failure exercise was 13.35 +/- 3.47 ms. Following the task failure exercise, the average EMD was 12.67 +/- 3.86 ms. A paired samples t test revealed no significant differences with regard to EMD between pre- and post-task failure exercise for the PL (p = 0.448).

CONCLUSION

We concluded that the task failure exercise did not affect the electromechanical delay of the PL.

Capsaicin regulates voltage-dependent sodium channels by altering lipid bilayer elasticity

At submicromolar concentrations, capsaicin specifically activates the TRPV1 receptor involved in nociception. At micro- to millimolar concentrations, commonly used in clinical and in vitro studies, capsaicin also modulates the function of a large number of seemingly unrelated membrane proteins, many of which are similarly modulated by the capsaicin antagonist capsazepine. The mechanism(s) underlying this widespread regulation of protein function are not understood. We investigated whether capsaicin could regulate membrane protein function by changing the elasticity of the host lipid bilayer. This was done by studying capsaicin's effects on lipid bilayer stiffness, measured using gramicidin A (gA) channels as molecular force-transducers, and on voltage-dependent sodium channels (VDSC) known to be regulated by bilayer elasticity. Capsaicin and capsazepine (10-100 microM) increase gA channel appearance rate and lifetime without measurably altering bilayer thickness or channel conductance, meaning that the changes in bilayer elasticity are sufficient to alter the conformation of an embedded protein. Capsaicin and capsazepine promote VDSC inactivation, similar to other amphiphiles that decrease bilayer stiffness, producing use-dependent current inhibition. For capsaicin, the quantitative relation between the decrease in bilayer stiffness and the hyperpolarizing shift in inactivation conforms to that previously found for other amphiphiles. Capsaicin's effects on gA channels and VDSC are similar to those of Triton X-100, although these amphiphiles promote opposite lipid monolayer curvature. We conclude that capsaicin can regulate VDSC function by altering bilayer elasticity. This mechanism may underlie the promiscuous regulation of membrane protein function by capsaicin and capsazepine-and by amphiphilic drugs generally.

Effects of a task failure exercise on the peroneus longus and brevis during perturbed gait

Ankle inversion injuries represent the most common trauma sustained by athletes. Muscle fatigue from activity may contribute to a delay in the response of the ankle proprioceptors and dynamic restraints during unexpected inversion. The purpose of this investigation was to determine changes in peroneal average EMG, peak EMG, and time to peak EMG following a task failure exercise. Thirty-two subjects (age 20+/-1.43 yrs; 21 male, 11 female) with no lower extremity injuries reported for data collection. Data were collected from each subject's dominant leg using surface electromyography (EMG). EMG electrodes were applied over the peroneus longus (PL) and brevis (PB) using a standard protocol Subjects walked at a fixed pace on a 6.1 m runway with one section that could be unexpectedly dropped into 30 degrees of inversion upon foot contact. Trials with perturbed and unperturbed gait were randomized to reduce prediction of the unexpected inversion. Once 3 trials of perturbed gait were recorded, subjects completed an isotonic activity that isolated the peroneals. The task was completed to failure. Immediately following the task failure exercise, subjects walked on the perturbation runway once again until 3 trials of perturbed gait were recorded. Analysis revealed no significant differences with regard to average muscle activity between pre- and post-task failure exercise for the PL (F1,31 = 0.133; p = 0.718) or for the PB (F1,31 = 0.795; p = 0.380). There was also no significant difference in peak muscle activity pre- to post-task failure for the PL (F1,31 = 0.032; p = 0.859) or the PB (F1,31 = 0.156; p = 0.695). Finally, there was no significant difference in time-to-peak muscle activity pre- to post-task failure for the PL (F1,31 = 0.830; p = 0.369) or the PB (F1,31 = 1.037; p = 0.316). We concluded that the task failure exercise did not contribute to changes in peroneal activity during perturbed gait. These results indicate that peroneal fatigue does not play a significant role in the incidence of inversion ankle sprains.

Hand movements in laparoscopic suturing: a simple vector analysis

BACKGROUND

Laparoscopic suturing is a complex task that is vital to the performance of many advanced laparoscopic procedures. Mastery can be difficult and problematic for surgical trainees.

METHODS

We present a description of hand movements in laparoscopic suturing. Complex maneuvers are simplified into linear motions using vectors. The analysis is intended to be a tool for training in the art of laparoscopic surgery.

RESULTS

Linear hand movements in the x and y axes produce opposite motions at the instrument tip. Position along the z axis influences the extent of hand movement relative to the instrument tip. Rotational movements of the hand produce an equal rotation of the instrument tip. Revolution is a complex motion that combines movements in x and y axes. Vector analysis reveals that the arc of revolution must be reversed to produce the desired needle motion.

CONCLUSIONS

A conceptual understanding of hand-movement vectors facilitates the efficient mastery of the complex skills required for laparoscopic suturing.

EMG analysis of peroneal and tibialis anterior muscle activity prior to foot contact during functional activities

The purpose of this investigation was to determine the pre-activity of the tibialis anterior (TA), peroneus longus (PL), and peroneus brevis (PB) prior to foot contact during three conditions. Twenty-six subjects (age 22 +/- 2 yrs; 15 male, 11 female) with no lower extremity injuries reported for data collection. Data were collected from each subject's dominant leg using surface electromyography (EMG). EMG electrodes were applied over the test muscles using a standard protocol. A heel-toe strike transducer was affixed to the bottom of the subject's shoe. The subject completed two randomized trials of walking on a treadmill (5.6 kph), jogging on a treadmill (9.3 kph) and drop landing from a 38 cm box. Isometric reference positions (IRPs) were recorded for the TA, PL, and PB. Muscle data were normalized to IRPs and the average processed EMG for the 200 ms prior to heel strike during walking and jogging and prior to toe strike when dropping from the box was used for analysis. A one-way repeated measures MANOVA was used to detect differences in pre-activity of the muscles between the three conditions. Univariate tests were used to determine differences for each muscle and Tukey's was applied post hoc to determine individual effect differences. The MANOVA revealed significant differences among the three conditions (F2.50 = 10.770; P < .0005). Average TA activity was significantly higher during jogging (Tukey's; P < .0005). Significant differences existed between each condition for the TA. Average PL and PB activity was significantly higher when drop landing (Tukey's; P < .0005). There was no significant difference between walking and jogging for the PL and PB. The amount of muscle pre-activity occurring before heel or toe strike provides useful information for the examination of reaction times to unexpected inversion during dynamic activities.

Nociceptin is a potent inhibitor of N-type Ca(2+) channels in rat sympathetic ganglion neurons

Nociceptin, an endogenous agonist of the opioid receptor-like(1) (ORL(1)) receptor, is implicated in a wide range of physiological functions including cardiovascular control. However, the effect of nociceptin on peripheral sympathetic ganglion neurons has not been studied. Whole-cell voltage clamp was used to study Ca(2+) currents on freshly dissociated sympathetic superior cervical ganglion neurons from juvenile rats. Nociceptin (1 microM) caused a fast inhibition of the peak currents by 69+/-3% in all neurons. Strong positive prepulses counteracted the inhibition of the peak current by 64% and no effect of nociceptin was observed when the cells were pre-incubated with Pertussis toxin. The inhibition was reversible and dose-dependent with an EC(50) of 508+/-50 pM. Blockade of N-type channels by 1 microM omega-conotoxin GVIA reduced the peak currents by 83+/-1% and abolished the action of nociceptin. Naloxone could not prevent the inhibition by nociceptin and [D-Ala(2), N-Me-Phe(4), Gly(5)-ol] enkephalin (DAMGO) only depressed a small proportion of the current in 1/7 neurons. These data suggests that nociceptin inhibits transmitter release from sympathetic neurons by a selective blockade of N-type channels, which may be of importance for its depressive effect on the cardiovascular system.

Tissue specific differences in the regulation of the UDP glucuronosyltransferase 2B17 gene promoter

The human UDP glucuronosyltransferase UGT2B17, glucuronidates androgens and is expressed in the liver and the prostate. Although evidence suggests that variations in UGT2B17 expression between tissues may be a critical determinant of androgen response, the factors that regulate UGT2B17 expression in the liver and prostate are unknown. In this study, we have isolated a 596 bp promoter of the UGT2B17 gene and studied its regulation in the liver cell line, HepG2 and the prostate cell line, LNCaP. The transcription start site of UGT2B17 was mapped and proteins that bound to the proximal promoter were detected by DNase1 footprint analysis. A region (-40 to -52 bp) which resembled a hepatocyte nuclear factor 1 (HNF1) binding site bound proteins in nuclear extracts from HepG2 cells, but did not bind proteins from LNCaP nuclear extracts. In HepG2 cells, HNF1alpha bound to this region and activated the UGT2B17 promoter, as assessed by functional and gel shift assays. HNF1alpha activation of the promoter was prevented by mutation or deletion of the putative HNF1 site. The related transcription factor HNF1beta, which is present in HepG2 cells, did not activate the promoter. The UGT2B17 promoter could also be activated by exogenous HNF1alpha in LNCaP cells. However, because these cells do not contain HNF1alpha, other transcription factors must regulate the UGT2B17 promoter. Cotransfection experiments showed that HNF1beta, elevates promoter activity in LNCaP cells. This activation did not involve the putative HNF1 region (-40 to -52 bp) since mutation of this region did not affect promoter activation by HNF1beta. These results suggest that the UGT2B17 promoter is regulated by different factors in liver-derived HepG2 and prostate-derived LNCaP cells.

Release of calcitonin gene-related peptide (CGRP) from guinea pig dura mater in vitro is inhibited by sumatriptan but unaffected by nitric oxide

Migraine attacks can be provoked by administration of nitroglycerin, suggesting a role for nitric oxide (NO). The fact that release of the neuropeptide CGRP from trigeminal sensory nerves occurs during the pain phase of migraine and that NO can augment transmitter release prompted us to study CGRP release from the in situ dura mater in guinea pig skulls. Release of CGRP by capsaicin or by high potassium concentration was concentration-dependent and counteracted in calcium-free medium. The anti-migraine compound, sumatriptan, inhibited CGRP release via the 5-HT1-receptor. The NO donors, nitroglycerin, sodium nitroprusside and S-nitroso-N-acetylpenicillamine did not influence CGRP release, alone or together with the stimulants. We concluded that the skull preparation is well suited for scrutinizing CGRP release from dura mater. The fact that sumatriptan inhibits CGRP release as in migraine patients suggests a use for the present preparation in headache research.

Octamer transcription factor-1 enhances hepatic nuclear factor-1alpha-mediated activation of the human UDP glucuronosyltransferase 2B7 promoter

The human UDP glucuronosyltransferase, UGT2B7, is expressed in the liver and gastrointestinal tract, where it catalyzes the glucuronidation of steroids and bile acids. In this study, the UGT2B7 gene was isolated and its proximal promoter was analyzed. The UGT2B7 gene consists of 6 exons and extends over 16 kilobases (kb). It does not contain a canonical TATA box but has a region (-2 to -40) adjacent to the transcription start site that binds nuclear proteins. This region contains a consensus hepatic nuclear factor-1alpha (HNF1alpha)-binding site and an overlapping AT-rich segment. Varying lengths of the UGT2B7 gene promoter, with and without these sites, were fused to the firefly luciferase reporter gene and transfected into HepG2 cells. UGT2B7 promoter activity with the HNF1/AT-rich element was stimulated by cotransfection with HNF1alpha. Additional activation was observed when HNF1alpha and octamer transcription factor-1 (Oct-1) were cotransfected simultaneously. However, Oct-1 alone did not stimulate promoter activity and did not bind to the promoter in the absence of HNF1alpha. Deletion of the HNF1/AT-rich region, or mutations in this region, abolished UGT2B7 gene promoter activity and prevented HNF1alpha-mediated increases in promoter activity. The presence of HNF1alpha and octamer transcription factor-1 (Oct-1) in the protein complex that bound to the HNF1/AT-rich region was demonstrated by gel shift analyses with antibodies specific to HNF1alpha and Oct-1 protein. These results strongly suggest that the liver-enriched factor HNF1alpha binds to, and activates, the UGT2B7 gene promoter and that the ubiquitous transcription factor, Oct-1, enhances this activation by directly interacting with HNF1alpha. This interaction between HNF1alpha and Oct-1 may fine-tune UGT2B7 expression.

Correlation between N-acetylaspartate levels and histopathologic changes in cortical infarcts of mice after middle cerebral artery occlusion

The aim of the present study was to evaluate the use of the endogenous neuronal compound N-acetylaspartate (NAA) as a marker of neuronal damage after focal cerebral ischemia in mice. After occlusion of the middle cerebral artery (MCAO) the ischemic cortex was sampled, guided by 2,3,5-triphenyltetrazolium chloride (TTC) staining, and the NAA concentration was measured by high-pressure liquid chromatography (HPLC). Conventional histology and immunohistological methods using antibodies against neuron-specific enolase (NSE), neurofilaments (NF), synaptophysin, glial fibrillary acidic protein (GFAP), and carbodiamide-linked NAA and N-acetylaspartylglutamate (NAAG). The level of NAA rapidly declined to 50% and 20% of control levels in infarcted tissue after 6 hours and 24 hours, respectively. No further decrease was observed during the observation period of 1 week. Within the first 6 hours the number of normal-appearing neurons in the infarcted cortical tissue decreased to 70% of control, of which the majority were eosinophilic. After 24 hours almost no normal-appearing neurons were seen. The number of eosinophilic neurons decreased steadily to virtually zero after 7 days. The number of immunopositive cells in the NSE, NF, and synaptophysin staining within the infarct was progressively reduced, and after 3 to 7 days the immunoreactions were confined to discrete granulomatous structures in the center of the infarct, which otherwise was infested with macrophages. This granulomatous material also stained positive for NAA. The number of cells with positive GFAP immunoreactions progressively increased in the circumference of the infarct. They also showed increased immunoreaction against NAA and NSE. The study shows that the level of NAA 7 days after ischemia does not decline to zero but remains at 10% to 20% of control values. The fact NAA is trapped in cell debris and NAA immunoreactivity is observed in the peri-infarct areas restricts its use as a marker of neuronal density.

Electron Microscopic Detection of Novel, Coiled Viruslike Particles Associated with Graft-Inoculation of Prunus Species

Coiled, viruslike particles (spirions) were detected by electron microscopic examination of crude extracts from flowers, leaves, and/or roots of infected Prunus avium, P. mume, and P. serrulata. The particles were observed in ultrathin sections of lower epidermis, palisade, and spongy mesophyll cells of leaves of P. avium and P. mume. Spring (March and April) appears to be optimal for detection of the particles in both screenhouse and field-grown plants. The particles were successfully graft-transmitted to P. armeniaca (cvs. Luizet and Tilton), P. avium (cvs. Bing, F12/1, Mazzard, and Sam), P. mahaleb, and P. persica (cv. Elberta). Individual spirions measured 132 × 34 nm. The particles appear to be coiled forms of a filamentous virus. Filaments extending from some coiled particles were approximately 13 nm wide, with striations at a pitch of 3.24 nm. No disease symptoms or cytopathological abnormalities were associated with the presence of the particles in the Prunus species studied. The particles were not detected in virus-free control plants.

N-substituted adenosines as novel neuroprotective A(1) agonists with diminished hypotensive effects

The synthesis and pharmacological profile of a series of neuroprotective adenosine agonists are described. Novel A(1) agonists with potent central nervous system effects and diminished influence on the cardiovascular system are reported and compared to selected reference adenosine agonists. The novel compounds featured are derived structurally from two key lead structures: 2-chloro-N-(1-phenoxy-2-propyl)adenosine (NNC 21-0041, 9) and 2-chloro-N-(1-piperidinyl)adenosine (NNC 90-1515, 4). The agonists are characterized in terms of their in vitro profiles, both binding and functional, and in vivo activity in relevant animal models. Neuroprotective properties assessed after postischemic dosing in a Mongolian gerbil severe temporary forebrain ischemia paradigm, using hippocampal CA1 damage endpoints, and the efficacy of these agonists in an A(1) functional assay show similarities to some reference adenosine agonists. However, the new compounds we describe exhibit diminished cardiovascular effects in both anesthetized and awake rats when compared to reference A(1) agonists such as (R)-phenylisopropyladenosine (R-PIA, 5), N-cyclopentyladenosine (CPA, 2), 4, N-[(1S,trans)-2-hydroxycyclopentyl]adenosine (GR 79236, 26), N-cyclohexyl-2'-O-methyladenosine (SDZ WAG 994, 27), and N-[(2-methylphenyl)methyl]adenosine (Metrifudil, 28). In mouse permanent middle cerebral artery occlusion focal ischemia, 2-chloro-N-[(R)-[(2-benzothiazolyl)thio]-2-propyl]adenosine (NNC 21-0136, 12) exhibited significant neuroprotection at the remarkably low total intraperitoneal dose of 0.1 mg/kg, a dose at which no cardiovascular effects are observed in conscious rats. The novel agonists described inhibit 6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate-induced seizures, and in mouse locomotor activity higher doses are required to reach ED(50) values than for reference A(1) agonists. We conclude that two of the novel adenosine derivatives revealed herein, 12 and 5'-deoxy-5'-chloro-N-[4-(phenylthio)-1-piperidinyl]adenosine (NNC 21-0147, 13), representatives of a new series of P(1) ligands, reinforce the fact that novel selective adenosine A(1) agonists have potential in the treatment of cerebral ischemia in humans.

Astroglia contain a specific transport mechanism for N-acetyl-L-aspartate

N-Acetylaspartate (NAA) is the second most abundant amino acid in the adult brain. It is located and synthesized in neurons and probably degraded in the glia compartment, but the transport mechanisms are unknown. Rat primary neuron and astrocyte cell cultures were exposed to the L isomer of [3H]NAA and demonstrated concentration-dependent uptake of [3H]NAA with a Km approximately 80 microM. However, Vmax was 23+/-6.4 pmol/mg of protein/min in astrocytes but only 1.13+/-0.4 pmol/mg of protein/min in neurons. The fact that neuron cultures contain 3-5% astrocytes suggests that the uptake mechanism is expressed only in glial cells. The astrocyte uptake was temperature and sodium chloride dependent and specific for L-NAA. The affinity for structural analogues was (IC50 in mM) as follows: L-NAA (0.12) > N-acetylaspartylglutamate (0.4) > N-acetylglutamate (0.42) > L-aspartate (>1) > L-glutamate (>1) > or = DL-threo-beta-hydroxyaspartate > N-acetyl-L-histidine. The naturally occurring amino acids showed no inhibitory effect at 1 mM. The glutamate transport blocker trans-pyrrolidine-2,4-dicarboxylate exhibited an IC50 of 0.57 mM, whereas another specific glutamate transport inhibitor, DL-threo-beta-hydroxyaspartate, had an IC50 of >1 mM. The experiments suggest that NAA transport in brain parenchyma occurs by a novel type of sodium-dependent carrier that is present only in glial cells.

Diversity of Holocene life forms in fossil glacier ice

Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained and characterized 120 clones that represent at least 57 distinct taxa and reveal a diversity of fungi, plants, algae, and protists. The organisms derive from distant sources as well as from the local arctic environment. Our results suggest that additional taxa may soon be readily identified, providing a plank for future studies of deep ice cores and yielding valuable information about ancient communities and their change over time.

N-Acetylaspartate distribution in rat brain striatum during acute brain ischemia

Brain N-acetylaspartate (NAA) can be quantified by in vivo proton magnetic resonance spectroscopy (1H-MRS) and is used in clinical settings as a marker of neuronal density. It is, however, uncertain whether the change in brain NAA content in acute stroke is reliably measured by 1H-MRS and how NAA is distributed within the ischemic area. Rats were exposed to middle cerebral artery occlusion. Preischemic values of [NAA] in striatum were 11 mmol/L by 1H-MRS and 8 mmol/kg by HPLC. The methods showed a comparable reduction during the 8 hours of ischemia. The interstitial level of [NAA] ([NAA]e) was determined by microdialysis using [3H]NAA to assess in vivo recovery. After induction of ischemia, [NAA]e increased linearly from 70 micromol/L to a peak level of 2 mmol/L after 2 to 3 hours before declining to 0.7 mmol/L at 7 hours. For comparison, [NAA]e was measured in striatum during global ischemia, revealing that [NAA]e increased linearly to 4 mmol/L after 3 hours and this level was maintained for the next 4 h. From the change in in vivo recovery of the interstitial space volume marker [14C]mannitol, the relative amount of NAA distributed in the interstitial space was calculated to be 0.2% of the total brain NAA during normal conditions and only 2 to 6% during ischemia. It was concluded that the majority of brain NAA is intracellularly located during ischemia despite large increases of interstitial [NAA]. Thus, MR quantification of NAA during acute ischemia reflects primarily changes in intracellular levels of NAA.

Gap-junction-mediated propagation and amplification of cell injury

Gap junctions are conductive channels that connect the interiors of coupled cells. We determined whether gap junctions propagate transcellular signals during metabolic stress and whether such signaling exacerbates cell injury. Although overexpression of the human proto-oncogene bcl2 in C6 glioma cells normally increased their resistance to injury, the relative resistance of bcl2+ cells to calcium overload, oxidative stress and metabolic inhibition was compromised when they formed gap junctions with more vulnerable cells. The likelihood of death was in direct proportion to the number and density of gap junctions with their less resistant neighbors. Thus, dying glia killed neighboring cells that would otherwise have escaped injury. This process of glial 'fratricide' may provide a basis for the secondary propagation of brain injury in cerebral ischemia.

C/EBPalpha is a regulator of the UDP glucuronosyltransferase UGT2B1 gene

The rat UDP glucuronosyltransferase, UGT2B1, is expressed in the liver where it glucuronidates steroids, environmental toxins, and carcinogens. A region between -88 and -111 base pairs upstream from the UGT2B1 gene transcription start site contains a CCAAT enhancer binding protein (C/EBP)-like element and was previously shown by Dnase I footprint analysis to bind to proteins in both rat liver and human hepatoma (HepG2) cell nuclear extracts. In this study, the importance of this region in the regulation of the UGT2B1 gene was assessed by functional and DNA binding assays. Varying lengths of the UGT2B1 gene promoter, with and without the C/EBP-like element, were fused to the chloramphenicol acetyltransferase reporter gene and transfected into HepG2 cells. Transcriptional activity of the UGT2B1 promoter construct containing the C/EBP-like element was strongly elevated in the presence of a cotransfected C/EBPalpha expression vector. In contrast, no change was observed when an expression vector encoding C/EBPbeta was cotransfected with the UGT2B1 promoter constructs. Introduction of point mutations into the C/EBP-like element prevented any C/EBPalpha-mediated increase in chloramphenicol acetyltransferase activity. Gel shift analyses demonstrated that the C/EBP-like element binds a complex of nuclear proteins present in both HepG2 cells and rat liver. The presence of C/EBPalpha in this complex was confirmed by supershift analysis with antiserum to this factor. These data strongly suggest that the liver-enriched factor C/EBPalpha binds to, and activates, the UGT2B1 gene promoter. The importance of C/EBPalpha in the regulation of the homologous mouse UGT2B1 gene was also assessed in vivo. Transcripts homologous to UGT2B1 were detected in the livers of mice containing intact c/ebpalpha and c/ebpbeta genes and in mice containing a homozygous null mutation in the c/ebpbeta gene. In contrast, these transcripts were not detected in mice with a disrupted hepatic c/ebpalpha gene. These data extend the findings with the rat UGT2B1 gene promoter and establish that C/EBPalpha, but not C/EBPbeta, is an essential transcriptional regulator of the homologous UGT2B1 gene in the mouse.

Possible mechanism of c-fos expression in trigeminal nucleus caudalis following cortical spreading depression

Cortical spreading depression (CSD) is characterized by a transient, reversible depression of EEG activity which advances across the cortical surface at a velocity of 2-5 mm/min. CSD was originally linked to the aura phase of migraine, but recently also to migraine headache. The theory is that CSD activates meningeal trigeminal C-fibers causing neurogenic inflammation and pain (Moskowitz, M.A., Nozaki, K. and Kraig, R.P., Neocortical spreading depression provokes the expression of c-fos protein-like immunoreactivity within trigeminal nucleus caudalis via trigeminovascular mechanisms, J. Neurosci., 13 (1993) 1167-1177). The present study is an examination of the proposed link between CSD elicited in rats and activation of trigeminal nerve fibers. Multiple CSDs were elicited unilaterally for 1 h by KCl injections (1 M, 5 microliters) into the right hemisphere, while NaCl (1 M, 5 microliters) was injected into the left as control. After an additional 1 h the animals were sacrificed and trigeminal activation assessed by the expression of c-fos in trigeminal nucleus caudalis (TNC) using immunohistochemistry. The correlation between the number of CSDs and the extent of c-fos expression was determined. In addition the effect of sumatriptan (0.3 mg/kg) and morphine (3 mg/kg) given i.v. 30 min before elicitation of CSD was evaluated. CSD caused increased c-fos expression in lamina I and II of TNC where C-fibers, end, the response being greater ipsilaterally. Morphine, but not sumatriptan, reduced c-fos expression in both the ipsilateral and contralateral TNC by 71% (P < 0.05 and P = 0.19, respectively), confirming that nociceptors have been activated. No positive correlation was seen between the number of CSDs and the extent of c-fos expression in TNC. Instead we observed a positive, linear correlation between the number of KCl injections and the extent of c-fos expression in TNC (correlation coefficient r = 0.709, P < 0.05). We suggest that the C-fiber activation observed is caused by hyperosmolar KCl/NaCl and not CSD. Hence, our results do not support the hypothesis of Moskowitz et al. (Moskowitz, M.A., Nozaki, K. and Kraig, R.P., Neocortical spreading depression provokes the expression of c-fos protein-like immunoreactivity within trigeminal nucleus caudalis via trigeminovascular mechanisms, J. Neurosci., 13 (1993) 1167-1177) which links CSD with migraine headache.

Transient elevation of interstitial N-acetylaspartate in reversible global brain ischemia

We evaluated the changes of interstitial N-acetylaspartate (NAA) concentration ([NAA]e) in rat striatum by microdialysis following transient global ischemia and depolarization. The dialysate NAA concentration ([NAA]d) values were corrected for the in vivo recovery to obtain [NAA]e, by the use of [3H]mannitol in the perfusion fluid. During global ischemia the relative loss (RL) of [3H]mannitol decreased to 40% of preischemic values, reflecting the decrease in extracellular volume fraction. During reperfusion RL of [3H]mannitol quickly normalized. The [NAA]d doubled during transient ischemia, which, after correction for in vivo recovery, corresponds to a fivefold increase in [NAA]e (p < 0.05). Reperfusion induced a > 10-fold increase of [NAA]e (p < 0.01) with subsequent normalization after 45 min. KCl at 100 microM caused a reversible 50% reduction in RL of [3H]mannitol and a three times increase in [NAA]e (p < 0.05) but no further increase when normal perfusate was reintroduced. The mechanisms of NAA release from neurons are unknown but may involve the activation of unknown channels/carriers-possibly in relation to a volume regulatory response. The present study shows that the distribution of NAA in brain is dynamically regulated in acute ischemia and suggests that changes of NAA levels could be caused by other means than neuronal loss.

HNF1 alpha activates the rat UDP glucuronosyltransferase UGT2B1 gene promoter

The rat UDP glucuronosyltransferase UGT2B1 is expressed mainly in the liver where it glucuronidates steroids and environmental toxins and carcinogens. A region between -42 and -55 bp upstream from the UGT2B1 gene transcription start site was previously identified as sharing sequence similarity with the hepatocyte nuclear factor 1 (HNF1) consensus binding site. In this study, the importance of this region in the regulation of the UGT2B1 gene was confirmed by functional and DNA binding assays. A minimal UGT2B1 gene promoter containing the putative HNF1 binding site was fused to the CAT reporter gene and transfected into HepG2 cells. Only low levels of CAT activity were detected. This activity was increased 50-fold when an HNF1 alpha expression vector was co-transfected with the UGT2B1 promoter CAT construct but was not altered when a HNF1 beta expression vector was used. A UGT2B1 promoter construct with the HNF1-like region deleted was not activated by either co-transfected HNF1 expression vector. DNase 1 footprinting and gel-shift analysis demonstrated that nuclear proteins present in both HepG2 cells and rat liver bind to the HNF1-like element. The presence of HNF1 alpha in these nuclear proteins that bind to the HNF1-like element was confirmed by supershift analysis with antisera to HNF1 alpha. Specific binding of nuclear proteins to the HNF1-like element was not seen in extracts from three cell lines derived from nonhepatic tissues. These data strongly suggest that the liver-enriched factor HNF1 alpha binds to, and activates, the UGT2B1 gene promoter

Membrane stiffness and channel function

Alterations in the stiffness of lipid bilayers are likely to constitute a general mechanism for modulation of membrane protein function. Gramicidin channels can be used as molecular force transducers to measure such changes in bilayer stiffness. As an application, we show that N-type calcium channel inactivation is shifted reversibly toward negative potentials by synthetic detergents that decrease bilayer stiffness. Cholesterol, which increases bilayer stiffness, shifts channel inactivation toward positive potentials. The voltage activation of the calcium channels is unaffected by the changes in stiffness. Changes in bilayer stiffness can be predicted from the molecular shapes of membrane-active compounds, which suggests a basis for the pharmacological effects of such compounds.

Calcium movements in traumatic brain injury: the role of glutamate receptor-operated ion channels

Ion-selective microelectrodes were used to study acute effects of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy- 5-methyl-4-isoxazole (AMPA) receptor blockade on posttraumatic calcium disturbances. An autoradiographic technique with 45 Ca2+ was used to study calcium disturbances at 8, 24, and 72 h. Compression contusion trauma of the cerebral cortex was produced by a 21-g weight dropped from a height of 35 cm onto a piston that compressed the brain 2 mm. Pre- and posttrauma interstitial [Ca2+] ([Ca2+]e) concentrations were measured in the perimeter, i.e., the shear stress zone (SSZ) and in the central region (CR) of the trauma site. For the [Ca2+]e studies the animals were divided into controls and groups pretreated with dizocilipine maleate (MK-801) or with 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[F]quinoxaline (NBQX). In all groups, [Ca2+]e decreased from pretrauma values of approximately 1 mM to posttraumatic values of 0.1 mM in both the CR and the SSZ. This was followed by a slow restitution toward pretraumatic levels during the 2-h observation period. There was no significant difference in recovery pattern between controls and pretreated animals. Accumulation of 45Ca2+ and serum proteins was seen in the entire SSZ, while neuronal necrosis was confined to a narrow band within the SSZ. The CR was unaffected apart from occasional eosinophilic neurons and showed no accumulation of 45Ca2+. Posttraumatic treatment with MK-801 or NBQX had no obvious effect on neuronal injury in the SSZ. We conclude that (a) acute [Ca2+]e disturbances in compression contusion brain trauma are not affected by blockade of NMDA or AMPA receptors, (b) 45Ca2+ accumulation in the SSZ reflects mainly protein accumulation due to blood-brain barrier breakdown rather than cell death, and (c) acute cellular Ca2+ over-load per se does not seem to be a major determinant of cell death after cerebral trauma in our model.

Is calcium accumulation post-injury an indicator of cell damage?

It is generally agreed that excessive intracellular calcium accumulation is the main culprit for nerve cell damage following brain injury. Many autoradiographic studies of the post-injury brain have demonstrated an accumulation of 45Ca2+ in regions exhibiting neuronal damage. We have recently observed, after cortical contusion trauma [10], that there was a discrepancy between the extent of cell damage and the extent of 45Ca2+ in autoradiograms; rather the distribution of 45Ca2+ followed that of serum proteins. In addition 45Ca2+ was also observed in white matter, which had no signs of damage. We tested the hypothesis that 45Ca2+ accumulation was coupled to the presence of protein by directly injecting albumin into the brain cortex. There was a highly significant correlation between the content of 45Ca2+ and of albumin as measured by ELISA. A similar pattern was found after a cortical freeze-lesion in the contralateral hemisphere. However, in the ipsilateral hemisphere where cell damage was observed, the relation broke down and calcium accumulated in excess. We conclude that calcium accumulation in the brain is not only the result of cell damage but also the presence of calcium-binding proteins, e.g. albumin.

Changes in N-acetyl-aspartate content during focal and global brain ischemia of the rat

N-Acetyl-aspartate (NAA) is almost exclusively localized in neurons in the mature brain and might be used as a neuronal marker. It has been reported that the NAA content in human brain is decreased in neurodegenerative diseases and in stroke. Since the NAA content can be determined by nuclear magnetic resonance techniques, it has potential as a diagnostic and prognostic marker. The objective of this study was to examine the change of NAA content and related substances following cerebral ischemia and compare the results to the damage of the tissue. We used rats to study the changes of NAA, N-acetyl-aspartyl-glutamate (NAAG), glutamate, and aspartate contents over a time course of 24 h in brain regions affected by either permanent middle cerebral artery occlusion (focal ischemia) or decapitation (global ischemia). The decreases of NAA and NAAG contents following global brain ischemia were linear over time but significant only after 4 and 2 h, respectively. After 24 h, the levels of NAA and NAAG were 24 and 44% of control values, respectively. The concentration of glutamate did not change, whereas the aspartate content increased at a rate comparable with the rate of decrease of NAA content. This is consistent with NAA being preferentially degraded by the enzyme amidohydrolase II in global ischemia. In focal ischemia, there was a rapid decline of NAA within the first 8 h of ischemia followed by a slower rate of reduction. The reductions of NAA and NAAG contents in focal ischemia were significant after 4 and 24 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Halothane anesthesia enhances the effect of dopamine uptake inhibition on interstitial levels of striatal dopamine

The anesthetic, isoflurane, has been shown to potentiate the ability of the dopamine (DA)-uptake inhibitor, nomifensine, to increase the brain interstitial dopamine level ([DA]e). Since the effect of the more commenly used anesthetic, halothane, on this system is unknown, we determined [DA]e by microdialysis in the striatum of rats, conscious or anesthetized with halothane, in the presence of the more selective DA uptake inhibitor, vanoxerine (GBR 12909), or the DA releaser, d-amphetamine. Basal [DA]e was not changed by halothane. However, in halothane-anesthetized rats, the vanoxerine (3 mg/kg i.v.)-induced DA response increased severalfold compared to the response in conscious rats. The initial peak response to d-amphetamine (1 mg/kg i.v.) did not change, but the late response (1-3 h after injection) was augmented in anesthetized rats. Halothane is believed to increase firing of DA neurons in the substantia nigra and, hence, to release striatal DA. We hypothesize that [DA]e is maintained at a normal level during the increased firing by equally increased activity of the DA transporter. However, when the DA transporter is blocked by vanoxerine, the increased DA release is unimpaired and [DA]e rises.

Cerebrovascular permeability and brain edema after cortical photochemical infarcts in the rat

The importance of protein extravasation for the development of vasogenic brain edema is still controversial. We, therefore, assessed the cerebrovascular permeability to serum proteins in relation to the development and resolution of brain edema in a photochemical cortical lesion in the rat. Cortical infarction was induced by in situ thrombosis using an argon laser beam aimed at the exposed parietal bone in animals given rose bengal i.v. The histology and the cerebrovascular permeability to serum proteins were scrutinized from 2 h to 3 weeks after the insult. The presence of serum proteins was demonstrated by an immunoperoxidase technique. The cerebral water content was estimated by specific gravity measurements of the cortical tissue in a kerosene-monobromobenzene gradient column from 2 h to 7 days after infarction. The blood-brain barrier was permeable to proteins at 2 h following the insult and proteins spread into the medial and lateral tissue reaching a maximum at 24 h. The specific gravity did not deviate from control values at 2 h. After 8 h the specific gravity of the lesion decreased with smaller decreases in the immediately adjacent tissue. At 24 h the changes in specific gravities reached a maximum in all regions except the immediately lateral area. The edema was generally worse in tissue medial to rather than lateral to the infarct. The degradation of serum proteins and the resolution of the brain edema followed the same time course with partial resolution of 72 h. By 1 week serum proteins and edema were confined to the central necrotic core. The results suggest a relationship between cerebrovascular permeability and cerebral edema in photochemical cortical infarction.

Characterization of cortical depolarizations evoked in focal cerebral ischemia

Cortical tissue surrounding acute ischemic infarcts undergoes repetitive spontaneous depolarizations. It is unknown whether these events are episodes of spreading depression (SD) elicited by the elevated interstitial K+ ([K+]e) in the ischemic core or whether they are evoked by transient decreases of the local blood flow. Electrophysiologically, depolarization caused by SD or by ischemia (ID) can be distinguished by their characteristic patterns of [K+]e rise: During SD, [K+]e rises abruptly, while in ID, this fast rate of increase is preceded by a slow rate lasting minutes. To characterize the depolarizations, we occluded the right middle cerebral artery (MCA) in rats and inserted two K(+)-sensitive microelectrodes into the cortex surrounding the evolving infarct. Repeated increases in [K+]e arose spontaneously following MCA occlusion. [K+]e increased during these transients from a resting level of 3-6 to 60 mM. One-third of these transient increases in [K+]e were biphasic, consisting of a slow initial increase to 10-12 mM, which lasted for minutes, followed by an abrupt increase, a pattern characteristic of ID. The remaining two-thirds exhibited a steep monotonic increase in [K+]e (< 10 s), characteristic of SD. The duration of the transients was a function of the pattern of [K+]e increase: ID-like transients lasted an average 10.7 +/- 5.1 min, whereas the duration of SD-like transients was 5.7 +/- 3.4 min. Both types of K+ transients occurred in an apparently random fashion in individual animals. A K+ transient was never observed solely at one electrode.(ABSTRACT TRUNCATED AT 250 WORDS)

Lactate and postischemic recovery of energy metabolism and electrical activity in the isolated perfused rat brain

The aim of the present study was to evaluate whether lactate can maintain the energy metabolism and electrical activity of isolated perfused rat brain in the absence of glucose. To exhaust cerebral glucose stores and simultaneously raise endogenous lactate, complete ischemia was induced. After ischemia, when a glucose-free perfusate was supplied, restoration of interstitial potassium (Ke+), cortical discontinuous current (DC) potential, electroencephalogram (EEG) activity, and ATP and phosphocreatine (PCr) was not significantly different from postischemic recovery findings when a glucose-containing perfusate was used. In the group receiving glucose-free perfusate, postischemic application of 1 mM iodoacetic acid did not inhibit the recovery of electrical activity, Ke+, or DC potential. After recovery of Ke+ in glucose-free reperfusion, a 20-30-Hz EEG pattern appeared and was maintained for about 20 min followed by disappearance of spontaneous electrical activity. An abrupt increase of Ke+, a steep negative DC shift, and a substantial decrease of ATP and PCr occurred after about 22 min of reperfusion. During the first 5 min of glucose-free reperfusion, consumption of lactate was significantly higher (0.89 mumol/g wet weight/min) than during reperfusion with medium containing glucose (0.41 mumol/g ww/min). Increasing amounts of tissue lactate prolonged maintenance of electrical function in glucose-free reperfusion. This correlation could not be found for free fatty acids. In conclusion, after a few minutes of ischemia, the brain is able to recover cellular ion transport and electrical activity without a supply of glucose, preferentially by combustion of lactate accumulated in brain tissue. This mechanism is only useful during a limited time period until the lactate accumulated during ischemia is combusted.

Regional changes in interstitial K+ and Ca2+ levels following cortical compression contusion trauma in rats

Brain trauma is associated with acute functional impairment and neuronal injury. At present, it is unclear to what extent disturbances in ion homeostasis are involved in these changes. We used ion-selective microelectrodes to register interstitial potassium ([K+]e) and calcium ([Ca2+]e) concentrations in the brain cortex following cerebral compression contusion in the rat. The trauma was produced by dropping a 21 g weight from a height of 35 cm onto a piston that compressed the cortex 1.5 mm. Ion measurements were made in two different locations of the contused region: in the perimeter, i.e., the shear stress zone (region A), and in the center (region B). The trauma resulted in an immediate increase in [K+]e from a control level of 3 mM to a level > 60 mM in both regions, and a concomitant negative shift in DC potential. In both regions, there was a simultaneous, dramatic decrease in [Ca2+]e from a baseline of 1.1 mM to 0.3-0.1 mM. Interstitial [K+] and the DC potential normalized within 3 min after trauma. In region B, [Ca2+]e recovered to near control levels within 5 min after ictus. In region A, however, recovery of [Ca2+]e was significantly slower, with a return to near baseline values within 50 min after trauma. The prolonged lowering of [Ca2+]e in region A was associated with an inability to propagate cortical spreading depression, suggesting a profound functional disturbance. Histologic evaluation 72 h after trauma revealed that neuronal injury was confined exclusively to region A. The results indicate that compression contusion trauma produces a transient membrane depolarization associated with a pronounced cellular release of K+ and a massive Ca2+ entry into the intracellular compartment. We suggest that the acute functional impairment and the subsequent neuronal injury in region A is caused by the prolonged disturbance of cellular calcium homeostasis mediated by leaky membranes exposed to shear stress.

Brain interstitial volume fraction and tortuosity in anoxia. Evaluation of the ion-selective micro-electrode method

The micro-electrode method for determination of interstitial volume fraction (alpha) (Nicholson & Phillips 1981), was evaluated. The extracellular marker, tetramethylammonium+, is iontophoretically ejected from a micropipette and the change in concentration measured at a distance by an ion-sensitive micro-electrode and fitted to a diffusion equation. We used suspensions of human red blood cells as a model system and found that the values of alpha determined by this method and by haematocrit measurement were linearly correlated (r = 0.94) and not significantly different. The micro-electrode method was used to characterize the interstitial space in rat brain cortex during normal conditions and during arrest of blood flow supply. Transport of solutes in interstitial space is governed by two characteristics, the interstitial volume fraction and the tortuosity factor. During control conditions, the interstitial volume fraction was 0.18 +/- 0.02 (mean +/- SEM), whereas it decreased to 0.07 +/- 0.01 in ischaemia. The tortuosity factor was 1.40 +/- 0.05 in controls and increased to 1.63 +/- 0.09 during ischaemia. Our measurements support the validity of the micro-electrode method (Nicholson & Phillips 1981) and demonstrate that arrest of blood supply changes interstitial diffusional characteristics of brain cortex mainly by diminishing the size of the interstitial diffusional space.

The effect of glutamate receptor blockade on anoxic depolarization and cortical spreading depression

We examined the effect of blockade of N-methyl-D-aspartate (NMDA) and non-NMDA subtype glutamate receptors on anoxic depolarization (AD) and cortical spreading depression (CSD). [K+]e and the direct current (DC) potential were measured with microelectrodes in the cerebral cortex of barbiturate-anesthetized rats. NMDA blockade was achieved by injection of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate [MK-801; 3 and 10 mg/kg] or amino-7-phosphonoheptanoate (APH; 4.5 and 10 mg/kg). Non-NMDA receptor blockade was achieved by injection of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)quinoxaline (NBQX; 10 and 20 mg/kg). MK-801 and APH blocked CSD, while NBQX did not. In control rats, the latency from circulatory arrest to AD was 2.1 +/- 0.1 min, while the amplitude of the DC shift was 21 +/- 1 mV, and [K+]e increased to 50 +/- 6 mM. All variables remained unchanged in animals treated with MK-801, APH, or NBQX. Finally, MK-801 (14 mg/kg) and NBQX (40 mg/kg) were given in combination to examine the effect of total glutamate receptor blockade on AD. This combination slightly accelerated the onset of AD, probably owing to circulatory failure. In conclusion, AD was unaffected by glutamate receptor blockade. In contrast, NMDA receptors play a crucial role for CSD.

Transcriptional regulation of the chicken CYP2H1 gene. Localization of a phenobarbital-responsive enhancer domain

The mechanism by which the drugs phenobarbital and 2-allyl-2-isopropylacetamide induce levels of chicken cytochrome P-450 (CYP) mRNAs has been investigated in primary hepatocyte cultures from 17-day-old chick embryos. It has been demonstrated that three CYP mRNAs of 3.5, 2.5, and 2.2 kilobases (kb) are strongly induced by phenobarbital in primary hepatocytes, as found previously in chick embryo liver in ovo (Hansen, A. J., Elferink, L. A., and May, B. K. (1989) DNA (NY) 8, 179-191), and that, at least for the 3.5-kb mRNA, this is predominantly a result of enhanced transcription of the corresponding gene, CYP2H1. Transient transfection assays were carried out in primary cultures using constructs containing different lengths of CYP2H1 gene 5'-flanking sequence fused to the reporter chloramphenicol acetyl-transferase (CAT) gene. These experiments established that cis-acting elements located in the first 0.5 kb of the CYP2H1 gene 5'-flanking region direct high basal expression of the CAT gene, but do not mediate phenobarbital inducibility. When constructs containing more than 1.1 kb of CYP2H1 gene 5'-flanking sequence were examined, phenobarbital induction of CAT expression was observed, and a drug-responsive domain between positions -5.9 and -1.1 kb was identified. This domain has the properties of an enhancer, since it is able to confer phenobarbital responsiveness to the enhancerless SV40 promoter when tested in either orientation or at different distances from the promoter. The enhancer domain also responds to 2-allyl-2-isopropylacetamide, but whether the action of the two drugs is mediated by a single nuclear receptor interacting with common DNA elements in the domain remains to be established.

Scar skin and dapple apple viroids are seed-borne and persistent in infected apple trees

The closely related apple scar skin viroid (ASSV) and dapple apple viroid (DAV) were identified in whole seeds from infected pome fruits by hybridization of extracted nucleic acids with a 32P-labelled ASSV cRNA probe. Viroid amounts were greater in seed coats and subcoats than in seed cotyledons and embryos. ASSV or DAV was also detected in nucleic acid extracts from infected seeds, cotyledons and embryos by reverse transcription/polymerase chain reaction with viroid-cDNA-specific primers followed by Southern blot hybridization analysis of the amplified products with an ASSV cRNA probe. These results indicate that ASSV and DAV are seed-borne. ASSV and DAV were also found in the anthers, petals, receptacles, leaves, bark and roots of infected trees. The results suggest that viroid-infected trees constitute potential sources of the viroid in field spread. ASSV and DAV infections have been observed sporadically in commercial orchards in the United States and Canada and the infected trees have been eliminated. The use of viroid-free sources of seeds, seedlings, rootstocks and budwood should greatly reduce the risk of the future spread of the viroid.

Distribution of single-channel conductances in cultured rat hippocampal neurons

1. The nonhomogeneous spatial distribution of ionic channels in neurons has been implied from intracellular recordings at somatic and dendritic locations. These reports indicate that Na- and Ca-dependent regenerative currents are distributed differently throughout the neuron. Although a variety of K conductances and a noninactivating Na conductance have been described in intracellular studies, little is known about the spatial distribution of inward and outward currents throughout different regions of the neuron. 2. We recorded from cell-attached patches from cultured hippocampal cells from 1-day-old rats. The cells were cultured for 3-21 days. The spatial distribution of a variety of ionic channels was determined by comparing the conductances from somatic and dendritic membranes. Single-channel currents obtained from cell-attached patches were identified by the time course of ensemble (averaged) responses, voltage dependence, and the effect of channel blocking agents. 3. We consistently observed that only the rapidly inactivating inward current was localized to the soma. The other channel types that we studied, including an inward noninactivating, delayed rectifier and transient A-type currents, were observed in both the somatic and dendritic regions. 4. We suggest that the distribution of ionic conductances that we have observed may be functional in limiting excitability during development of neurons.

[Risk factors in home accidents among preschool children]

The present investigation is part of an investigation concerning preschool children's accidents at home. A total of 3,011 homes with preschool children were examined with the object of reducing the number of accidents involving preschool children. Selected risk factors were registered (falls, burns, poisoning) responsible for accidents to preschool children in their homes and this information was compared with information about the type of housing, district and the social status. The investigation revealed that 30% of the homes had "dangerous" windows, 30% had taps which could be swung out over free floor space and 42% did not have special electric safety main switches. Articles for cleaning, medicine and poisons were only stored in locked cupboards in 2.5 and 8% of the homes, respectively. These circumstances were more common in flats than in one-family homes. No significant differences were found between the physical risk factors chosen in the present investigation between the individual social status groups. Prevention of children's accidents in the home consists of increased information to families with children, to architects and manufacturers and increased attention to safety in the home by legislation and guidelines.

Hemin administration to rats reduces levels of hepatic mRNAs for phenobarbitone-inducible enzymes

The levels of hepatic mRNAs for several enzymes involved in drug metabolism were measured following administration to rats of either phenobarbitone or 2-allyl-2-isopropylacetamide. There was a substantial elevation in the mRNA levels for cytochromes P450 IIB1, IIB2, and IIIA1, epoxide hydrolase, glutathione-S-transferase Ya/Yc subunit, UDP-glucuronosyltransferase isoenzyme (UDPGTr-2), NADPH-cytochrome P450 oxidoreductase, and 5-aminolevulinate synthase. When rats were treated with hemin, together with inducing drug, there was a marked reduction in the induced levels of these mRNAs, with decreases in the range of 55-95%. Basal levels of these mRNAs in the noninduced rat liver were also lowered by hemin administration. Nuclear run-on transcriptional experiments showed that hemin administration substantially lowered both the basal and drug-induced transcriptional activities of the genes for cytochrome P450IIB1/IIB2 and 5-aminolevulinate synthase. In contrast, the mRNA for heme oxygenase was elevated by hemin treatment, whereas the mRNA levels of beta-actin, albumin, and ornithine transcarbamylase, used as controls, were not affected. Treatment of rats with clofibrate resulted in increased levels of mRNA for cytochrome IVA1 and, in addition, those for cytochromes P450IIB1 and P450IIB2. Hemin administration repressed the induction of mRNA levels for cytochromes P450IIB1 and IIB2 but not that for cytochrome P450 IVA1. Additionally, the induction of P450IAI by beta-naphthoflavone was not affected by hemin. The results suggest that heme may negatively control the induction of cytochromes P450IIB1 and IIB2 and other hepatic enzymes by phenobarbitone and phenobarbitone-like drugs and perhaps play a role in regulating drug metabolism. There is, however, no evidence at present as to whether heme has a direct role in such a mechanism or whether injected hemin promotes a secondary response.

Extracellular pH in the rat brain during hypoglycemic coma and recovery

It has previously been shown that hypoglycemic coma is accompanied by marked energy failure and by loss of cellular ionic homeostasis. The general proposal is that shortage of carbohydrate substrate prevents lactic acid formation and thereby acidosis during hypoglycemic coma. The objective of the present study was to explore whether rapid downhill ion fluxes, known to occur during coma, are accompanied by changes in extra- and/or intracellular pH (pHe and/or pHi), and how these relate to the de- and repolarization of cellular membranes. Cortical pHe was recorded by microelectrodes in insulin-injected rats subjected to 30 min of hypoglycemic coma, with cellular membrane depolarization. Some rats were allowed up to 180 min of recovery after glucose infusion and membrane repolarization. Arterial blood gases and physiological parameters were monitored to maintain normotension, normoxia, normocapnia, and normal plasma pH. Following depolarization during hypoglycemia, a prompt, rapidly reversible alkaline pHe shift of about 0.1 units was observed in 37/43 rats. Immediately thereafter, all rats showed an acid pH shift of about 0.2 units. This shift developed during the first minute, and pHe remained at that level until repolarization was induced. Following repolarization, there was an additional, rapid, further lowering of pHe by about 0.05 units, followed by a more prolonged decrease in pHe that was maximal at 90 min of recovery (delta pHe of approximately -0.4 units). The pHe then slowly normalized but was still decreased (-0.18 pH units) after 180 min when the experiment was terminated. The calculated pHi showed no major alterations during hypoglycemic coma or after membrane repolarization following glucose administration.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline: a neuroprotectant for cerebral ischemia

2,3-Dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) is an analog of the quinoxalinedione antagonists to the non-N-methyl-D-aspartate (non-NMDA) glutamate receptor. NBQX is a potent and selective inhibitor of binding to the quisqualate subtype of the glutamate receptor, with no activity at the NMDA and glycine sites. NBQX protects against global ischemia, even when administered 2 hours after an ischemic challenge.

Cortical spreading depression is associated with arachidonic acid accumulation and preservation of energy charge

The present study aimed to study the relation between the release of arachidonic acid (AA) and the energy state in cerebral cortices of rats during single episodes of cortical spreading depression (CSD). The changes in concentrations of AA, labile phosphate compounds [ATP, ADP, AMP, and phosphocreatine (PCr)], and glycolytic metabolites (lactate, pyruvate, glucose, and glycogen) were studied during and following the large change of the local direct current (DC) potential. Free AA increased markedly during the DC shift, continued to increase during the subsequent 3 min, and returned to control levels at 4-5 min after CSD. PCr decreased by 38% in the first minutes following the DC shift, while ADP increased by 38%. Both returned to normal within a few minutes. ATP, AMP, and energy charge remained constant throughout the experimental period. Glucose decreased by 47% and glycogen by 34% for a few minutes following CSD, while lactate increased by 105% at 2-3 min and by 77% at 4-5 min after CSD. The metabolites returned to control levels at 10 min after CSD. Considering the constant energy charge at all time points during CSD, it is suggested that the AA rise reflects augmented phospholipase activity due to either increased intracellular [Ca2+] or receptor stimulation or both. The possibility that N-methyl-D-aspartate receptors play a role in the release of AA, and that free AA in turn could be part of the mechanism of CSD, is discussed.