Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA.

The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.

Combined effects of exposure to engineered silver nanoparticles and the water-soluble fraction of crude oil in the marine copepod Calanus finmarchicus.

While it is likely that ENPs may occur together with other contaminants in nature, the combined effects of exposure to both ENPs and environmental contaminants are not studied sufficiently. In this study, we investigated the acute and sublethal toxicity of PVP coated silver nanoparticles (AgNP) and ionic silver (Ag+; administered as AgNO3) to the marine copepod Calanus finmarchicus. We further studied effects of single exposures to AgNPs (nominal concentrations: low 15 µg L-1 NPL, high 150 µg L-1 NPH) or Ag+ (60 µg L-1), and effects of co-exposure to AgNPs, Ag+ and the water-soluble fraction (WSF; 100 µg L-1) of a crude oil (AgNP + WSF; Ag++WSF). The gene expression and the activity of antioxidant defense enzymes SOD, CAT and GST, as well as the gene expression of HSP90 and CYP330A1 were determined as sublethal endpoints. Results show that Ag+ was more acutely toxic compared to AgNPs, with 96 h LC50 concentrations of 403 µg L-1 for AgNPs, and 147 µg L-1 for Ag+. Organismal uptake of Ag following exposure was similar for AgNP and Ag+, and was not significantly different when co-exposed to WSF. Exposure to AgNPs alone caused increases in gene expressions of GST and SOD, whereas WSF exposure caused an induction in SOD. Responses in enzyme activities were generally low, with significant effects observed only on SOD activity in NPL and WSF exposures and on GST activity in NPL and NPH exposures. Combined AgNP and WSF exposures caused slightly altered responses in expression of SOD, GST and CYP330A1 genes compared to the single exposures of either AgNPs or WSF. However, there was no clear pattern of cumulative effects caused by co-exposures of AgNPs and WSF. The present study indicates that the exposure to AgNPs, Ag+, and to a lesser degree WSF cause an oxidative stress response in C. finmarchicus, which was slightly, but mostly not significantly altered in combined exposures. This indicated that the combined effects between Ag and WSF are relatively limited, at least with regard to oxidative stress.

Carbon source utilization profiles as a method to identify sources of faecal pollution in water.

AIMS: Carbon source utilization profiles as a phenotypic fingerprinting methodology for determining sources of faecal pollution in water were evaluated. METHODS AND RESULTS: Three hundred and sixty-five Enterococcus isolates were collected from known faecal sources in four different geographical regions and were identified to species with the commercial Biolog system. Discriminant analysis (DA) was used to identify the substrate-containing wells that best classified the 365 isolates by source. By using 30 of the 95 wells for the analysis, the average rate of correct classification (ARCC) by source was 92.7% for a human vs non-human two-way classification when isolates from all regions were combined into one library. Corresponding ARCCs for other classification schemes were 81.9% for a four-way classification of human vs livestock vs wildlife vs domestic pets, and 85.7% for a three-way classification without human isolates. When three individual libraries were made based on classification of sources within Enterococcus species, the ARCC was 95.3% for the Ent. faecalis library, 95.8% for the Ent. gallinarum library and 94.7% for the Ent. mundtii library. Thirty Enterococcus isolates (unknown sources) were obtained from each of three stream sites where a specific source of pollution was apparent; 90.0% of the isolates from a human-suspected source were classified as human, 86.6% were classified as livestock from a livestock-suspected site, and 93.3% were classified as wildlife from a wildlife-suspected site. CONCLUSIONS: Phenotypic fingerprinting with carbon source utilization profiles provided levels of correct classification by sources from an Enterococcus library that were in the upper range of those reported in the literature. ARCCs for three Enterococcus species-specific libraries were very high and may be the best approach for further developing this concept and methodology. SIGNIFICANCE ANC IMPACT OF THE STUDY: The results, based on a modest Enterococcus library and a preliminary field validation test, demonstrated the potential for carbon source utilization profiles to be employed as a phenotypic method for determining sources of faecal pollution in water.

Cerebrovascular adaptation in chronic hydrocephalus.

This study characterizes the regional changes in vascularity, which accompanies chronic progressive hydrocephalus. Fifteen dogs underwent surgical induction of hydrocephalus and were used for histologic studies. Animals were divided into 4 groups: surgical control, short term (< or = 5 weeks), intermediate term (8 weeks), and long term (10 to 12 weeks). Vessel diameter, density, and luminal area were calculated by imaging quantification after manual vessel identification in the cortical gray, white matter, and caudate nucleus. Capillary vessel diameter decreased 23.5% to 30.2% (P < 0.01) in the caudate, but then returned to normal at 12 weeks. Capillary vessel density decreased 53.5% (P < 0.05) in the cortical gray, but then increased to 234.8% (P < 0.01) over surgical controls at 12 weeks. There was no initial decrease in capillary density in the caudate; however, the long-term group capillary density was significantly greater (172.8% to 210.5%, P < 0.01) than surgical controls. Overall, there was a short-term decrease in lumen area, with recovery in the longer term. Glial fibrillary acidic protein (GFAP) immunohistochemistry demonstrated the pattern of GFAP staining and reactive astrocytes differed in the caudate compared with the occipital cortex. This data suggest that an increase in capillary density and diameter may be an adaptive process allowing maintenance of adequate cerebral perfusion and metabolic support in the hypoxic environment of chronic hydrocephalus.

Colon and anal sphincter contractions evoked by microstimulation of the sacral spinal cord in cats.

The colon and anal sphincter contractions induced by microstimulation of the S2 spinal cord were investigated by measuring the intraluminal pressure change via saline filled balloons in alpha-chlorolose anesthetized cats. Stimulation of sacral ventral roots (S1-S3) revealed that the S2 efferent outflow usually produces the largest colon response. Stimulation of the S2 ventral root or the spinal cord both indicated that 15 Hz stimulation was the optimal frequency for evoking colon contractions. Colon and anal sphincter contractions were also influenced by stimulation intensity and pulsewidth. Locations in S2 spinal cord, where microstimulation evoked a distal/proximal colon pressure response that was greater than the anal sphincter response, included the area of sacral parasympathetic nucleus (SPN), the area medial to the SPN extending to the dorsal commissure, and areas deep in the ventral horn. Anal sphincter relaxation was evoked by microstimulation in more restricted locations in S2 spinal cord, which appeared to overlap with those evoking anal sphincter contractions. These results suggest a possible method to evoke colon contraction and defecation by microstimulation of the S2 spinal cord with multiple microelectrodes.

Pediatric angiosarcoma of the heart: a unique presentation and metastatic pattern.

We report the seventh case of angiosarcoma of the heart in a child. The patient was a 23-month-old female who presented for lower extremity limping and underwent open surgical biopsy of the femur. Immediately postoperatively, she developed pericardial tamponade, and a bulky intracardiac mass was discovered as the underlying cause. The mass was composed of highly pleomorphic tumor cells reactive for the endothelial markers CD31, CD34, and factor VIII-related antigen (FVIII-RA). Staging evaluation revealed widespread metastases involving the brain, ovaries, and bone marrow. She died of complications of metastatic disease 8 months following initial presentation. Unusual features of this case include the young age of the patient, left-sided nature of the cardiac tumor, presentation secondary to metastatic disease, and the pattern of metastases. The literature on cardiac angiosarcoma, which is limited to six case reports in the pediatric population, is also reviewed.

Multimicroelectrode stimulation within the cat L6 spinal cord: influences of electrode combinations and stimulus interleave time on knee joint extension torque.

During multimicroelectrode stimulation within the cat L6 spinal cord, the number of electrodes activated, their separation distance, and the stimulus interleave time all influenced isometric knee joint extension torque. The torque evoked by stimulation with a three electrode combination could be enhanced or suppressed when compared with that evoked by single or paired electrode stimulation. A similar difference was noted when comparing two electrode combination versus single electrode stimulation. Relative fatigue was not improved significantly by interleaving the stimuli from two or three microelectrodes. Compared with the extension torque response evoked by noninterleaved stimulation, torque evoked by interleaved stimulation with the two microelectrode combination was decreased when the electrode distance was 2.0 mm or less and increased when the electrode distance was 3.0 mm. Designing an optimal stimulation strategy for multimicroelectrode spinal cord stimulation will be challenging and complex if a suppression effect among these electrodes is to be avoided. To reduce muscle fatigue, an asynchronous, interleaved strategy of stimulation may be required.

Isometric torque about the knee joint generated by microstimulation of the cat L6 spinal cord.

Isometric torque was generated about the knee joint by microstimulation of the cat L6 spinal cord using a single microelectrode. The torque responses varied with microstimulation location. Appreciable extension torque was generated by microstimulation in ventrolateral locations of the L6 spinal cord. Stimulation parameters (intensity, frequency and pulse-width) also influenced the extension torque. Specific stimulation parameters (100 microA intensity, 40 Hz frequency and 0.20 ms pulse-width) appear best suited for mapping the spinal cord based on knee joint torque responses. Low levels of cocontraction of the extensor and flexor could be achieved when extension torque was produced, but also varied with the stimulation locations. There are locations in the L6 ventral horn where microstimulation could evoke sustained extension for at least 4 min with only a slight change in torque. This study suggests the possibility of restoring lower limb function in patients with spinal cord injury above the lumbar level.

Penile erection produced by microstimulation of the sacral spinal cord of the cat.

The sacral neural pathways mediating penile erection in the cat were studied by measuring the change in cavernous sinus pressure (CSP) elicited by stimulation of the sacral ventral roots or by microstimulation of the sacral spinal cord. Ventral root stimulation revealed that the S1 segment rather than S2 and S3 spinal segments could evoke the largest CSP responses. Microstimulation in the S1 spinal cord elicited large CSP responses but small or no bladder contractions. Maximal CSP responses were evoked by microstimulation in the middle of the S1 ventral horn, 1.6-2.8 mm below the cord surface and midway between the midline and the lateral edge of the gray matter. The area was 200-400 microm wide (medial to lateral) and extended 1-2 mm in the rostrocaudal direction. Maximal CSP responses to spinal cord microstimulation were elicited by stimulus intensities of 50-150 microA, at a pulse width of 0.2 ms and at frequencies of 3040 Hz and occurred after delay of 8-40 s. This study suggests that focal microstimulation of the sacral spinal cord might be useful in eliciting penile erectile activity in patients with spinal cord injury.

Role of spinal glutamatergic transmission in the ascending limb of the micturition reflex pathway in the rat.

This study was undertaken to evaluate the role of glutamate receptors at spinal synapses on the ascending limb of the micturition reflex. In urethane-anesthetized female rats, a tungsten electrode was inserted stereotaxically into the dorsal part of the rostral pons to record field potentials which were evoked by electrical stimulation of the pelvic nerve (PLN) (1-15 V, 0.05 ms pulse duration at 100-300 Hz, 5-30 ms train duration). The effects of glutamate receptor antagonists administered intrathecally (i.t.) on the PLN-evoked field potentials in the dorsal part of the rostral brainstem were examined. PLN stimulation evoked short latency (10-22 ms) negative field potentials (85 +/- 4 microV) in a limited area of the dorsal part of the rostral pons (bregma -9.0 to -8.4, L 0.5 to 1. 5, H 4.2 to 5.4). The i.t. administration of LY215490 (0.1-30 microg), a competitive alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor antagonist, reduced the amplitude of the evoked potentials in a dose-dependent manner; 84 +/- 6%, 59 +/- 11% (P < .001), 31 +/- 10% (P < .001), 17 +/- 9% (P < .001) of control after 0.1, 1, 10, 30 microg of LY215490, respectively. The i.t. administration of MK-801 (1-100 microg), a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, also reduced the amplitude of the evoked potentials in a dose-dependent manner; 93 +/- 21%, 76 +/- 14%, 52 +/- 9% (P < .001), 39 +/- 9% (P < .001) of control after 1, 10, 30, 100 microg of MK-801, respectively. Combined administration of LY215490 (0.1 microg) and MK-801 (1 microg), in doses which individually did not elicit a significant effect, markedly reduced the amplitude of the evoked potentials (27 +/- 9% of control, P = . 0002). These results suggest that AMPA and NMDA glutamatergic synaptic mechanisms play a key role in the spinal processing of afferent input from the bladder and that these mechanisms function synergistically in the ascending limb of the spinobulbospinal micturition reflex pathway.

Mechanism of action of local anesthetics on synaptic transmission in the rat.

The mechanism of action of local anesthetics on synaptic transmission and their effects on synaptic components and on electrophysiologic properties of the nerve cell body are not clear. Therefore, the effects of lidocaine and bupivacaine on pre- and postsynaptic mechanisms underlying synaptic transmission in sympathetic ganglia were studied utilizing the techniques of intracellular recording and stimulation on isolated superfused superior cervical ganglia of rats. Lidocaine and bupivacaine either depressed or completely blocked synaptic transmission in sympathetic ganglia in a dose-dependent manner. Blockade of axonal conduction in presynaptic fibers was preceded by increased latency (the latency increased from 11.2 +/- 0.9 to 16.5 +/- 1.4 ms, mean +/- SEM, P less than 0.01) when the drugs were applied to the presynaptic nerves. Application of the drugs directly to the ganglion produced alterations in postsynaptic membrane properties consisting of decreased membrane resistance (from 40 +/- 3 to 32 +/- 3 M omega, P less than 0.01), increased firing threshold (from 14 +/- 0.5 to 18 +/- 0.5 mV, P less than 0.01), and decreased action potential amplitude (P less than 0.01) and/or blockade of action potential generation. Resting postsynaptic membrane potential did not change significantly. These changes were reversible. However, even after the excitatory postsynaptic potential resulting from presynaptic nerve stimulation had fully recovered during washout of the local anesthetic, the threshold for evoking the spike potential (firing level) still remained elevated for both presynaptic and intracellular stimulation of the ganglion cell, suggesting prolonged cell depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of lidocaine on the excitability and membrane properties of the nerve cell soma.

The effects of lidocaine, an amide local anesthetic, on the electrophysiologic properties of the nerve cell soma were studied on isolated superfused superior cervical ganglia of rats. Administration of 400 nmol of lidocaine to the preparation evoked significant reversible changes in the membrane properties of the nerve cell soma. The firing threshold, the action potential duration and the intracellular current threshold for firing the cells increased significantly (p less than 0.01), while the action potential amplitude decreased significantly (p less than 0.01). The resting membrane potential change was not significant. The membrane resistance decreased by 20% (p less than 0.01). The change in membrane resistance, and the spike potential evoked by excitatory postsynaptic potential or intracellular current injection were the last to recover after application of lidocaine. The results show that the postsynaptic cell body is a major site of action of the local anesthetic lidocaine, and that it is more sensitive to the action of lidocaine than the presynaptic nerve fibers. The implication of the results is that when local anesthetics are injected to areas where cell bodies and processes (axons and dendrites) are present together, such as during stellate ganglion block, lumbar sympathetic block, celiac plexus block and intrathecal administration for spinal anesthesia, the cell bodies and the processes are all affected, and their excitability and function suppressed. Further, the duration of the block will be determined by the duration of lidocaine-induced cell block rather than the duration of lidocaine-induced nerve fiber block.

Excitatory effect of substance P in parasympathetic ganglia of cat urinary bladder.

Intra-arterial administration of substance P (0.1-50 micrograms/kg) to the urinary bladder of the cat produced slow-onset and sustained bladder contractions, asynchronous firing of bladder postganglionic nerves, and facilitation of nicotinic transmission in bladder ganglia. Intracellular recording from bladder ganglia in vitro revealed that substance P depolarized ganglion cells and initiated burst of action potentials (maximal frequency 6-7 Hz). The ganglionic excitatory effect of substance P in situ was blocked by gamma-aminobutyric acid (2-20 micrograms/kg) and the substance P antagonist [D-Arg1,D-Pro2,D-Trp7.9,Leu11]substance P (0.5-20 micrograms/kg) but was not altered by atropine (10-100 micrograms/kg), hexamethonium (0.5-2 mg/kg), norepinephrine (2-20 micrograms/kg), or leucine enkephalin (0.5-20 micrograms/kg). The bladder contractions elicited by substance P were not blocked by atropine, hexamethonium, or [D-Arg1,D-Pro2,D-Trp7.9,Leu11]substance P (0.1-10 micrograms/kg) but were blocked by another substance P antagonist, [D-Pro2,D-Phe7,D-Trp9]substance P. These data indicate that substance P has a direct postsynaptic excitatory effect on neurons in the vesical parasympathetic ganglia and on bladder smooth muscle cells. The differential effects of substance P antagonists on the excitatory responses at these two sites indicate the responses were mediated by different types of tachykinin receptors.

Effects of bupivacaine on the membrane properties of nerve cell soma.

While the effects of local anaesthetics on axonal conduction and axonal membrane have been extensively studied, there is little information about the actions of these agents on nerve cell soma. Therefore, the effects of the amide local anaesthetic bupivacaine on the electrophysiologic properties of the nerve cell soma were studied on isolated superfused superior cervical ganglia of rats. Administration of 100-200 nM of bupivacaine to the preparation produced marked changes in membrane properties of the cell soma. The resting membrane potential did not change, but the membrane resistance decreased 20% (P less than 0.01). The firing threshold, the action potential duration at 50% of maximal amplitude, and the intracellular current threshold for firing the cells increased significantly (P less than 0.01), while the action potential amplitude decreased significantly (P less than 0.01), before its complete blockade. The results show that the cell soma is a major site of action of local anaesthetics. The implication of the results is that when local anaesthetics are applied to areas where cell bodies and processes (axons and dendrites) are present together, such as during celiac plexus block, lumbar sympathetic block, stellate ganglion block, etc., they will all be effectively depressed and/or blocked.

Distribution of neurons in the major pelvic ganglion of the rat which supply the bladder, colon or penis.

In male rats a large number of the postganglionic neurons which innervate the pelvic organs are located in the major pelvic ganglion. In the present study we have identified the location within this ganglion of neurons which project to either of three pelvic organs, the penis, colon or urinary bladder. Two fluorescent retrogradely-transported dyes, Fast Blue and Fluoro-Gold, were used. For most animals one dye was injected into the cavernous space of the penis, the wall of the distal colon or the wall of the urinary bladder. In a small number of animals two organs were injected, each with a different dye. One to six weeks after injection the major pelvic ganglia were fixed in buffered formaldehyde. The distribution of fluorescent dye-labelled cells was observed in whole mounts of complete ganglia and, in most cases, also in small accessory ganglia located between the ureter and the prostate. The studies showed a unique pattern of distribution for each organ-specific group of neurons. Most of the colon neurons are located in the major pelvic ganglion near the entrance of the pelvic nerve, whereas almost all of the penis neurons are near or within the penile nerve. Bladder neurons are relatively evenly distributed throughout the ganglion. These results demonstrate a distinct topographical organization of organ-specific neurons of the major pelvic ganglion of the male rat, a phenomenon which has also been observed in other peripheral ganglia.

Morphological and electrophysiological properties of pelvic ganglion cells in the rat.

Intracellular recording and dye injection were used to study the morphological and electrophysiological properties of rat pelvic ganglion cells. The dye-injected cells measured on the average 37 micron by 22.5 micron and had a mean number of 1.5 primary processes (axon and dendrites). The cells received unmyelinated preganglionic inputs from either the pelvic (parasympathetic) or the hypogastric (sympathetic) nerves, but no cells received inputs from both nerves. The number of synaptic inputs to each cell varied between 1 and 5 with a mean of 2. Each cell had at least one large amplitude suprathreshold EPSP which always initiated an action potential. These properties, namely, morphological simplicity, small number of inputs, security of synaptic transmission and lack of convergence between sympathetic and parasympathetic inputs, suggest that the capacity for synaptic modulation and integration in this ganglion is minimal. Such a structure should therefore relay preganglionic information to target organs with little or no alteration.

Reflex hypotension due to regional activation of left ventricular mechanoreceptors to explain the hypotension noted in clinical myocardial ischaemia or reperfusion.

To determine if regional increases in myocardial contractility, as may occur clinically in angina pectoris, myocardial infarction, or coronary thrombolysis, can initiate the reflex hypotension that sometimes accompanies these conditions, regional injections of positive inotropic agents were made into 32(3)% of the left ventricular myocardium in seven pneumonectomised dogs on total cardiac bypass. The coronary and systemic circulations were isolated and perfused separately. The systemic circulation was perfused at a constant rate so that changes in systemic pressure reflected changes in resistance. Regional injections of doses from 0.001 to 1.0 micrograms noradrenaline in a 0.1 ml volume appreciably increased regional contractility, detected visually and by strain gauge arches, whereas global contractility (left ventricular peak dP/dt) was increased much less. This caused a fall in the systemic pressure (resistance) of 14(2)% below the control value of 78(5)mm Hg, at the largest dose. The decreases in resistance were abolished by bilateral vagotomy, proving their reflex nature. The smaller (0.0001-0.01 micrograms) doses of noradrenaline and the smallest (0.25 micrograms) dose of veratridine increased regional contractility almost without increasing global contractility, indicating that the increase in regional contractility was the major cause of the reflex decrease in systemic resistance. In one animal a decrease in contractility in a control myocardial region occurred simultaneously with the experimentally produced increase in regional left ventricular contractility. This decrease may be analogous to the increase in contractility in the non-ischaemic left ventricular myocardium that occurs simultaneously with the decrease in contractility in the ischaemic region in clinical or experimental myocardial infarction. Left ventricular mechanoreceptors in the region with increased contractility probably initiate the reflex hypotension that sometimes occurs in both circumstances. Thus in angina pectoris or acute myocardial infarction the reflex hypotension probably originates in the hyperactive non-ischaemic myocardial region, whereas in coronary arterial thrombolysis it probably originates in the newly reperfused, formerly ischaemic, region.

Regulation of urinary bladder capacity by endogenous opioid peptides.

Naloxone administered to chloralose or ketamine anesthetized cats reduced urinary bladder capacity. Successive cystometrograms revealed that naloxone in doses of 0.5 microgram./kg. to 15 micrograms./kg. i.v. reduced the volume necessary to evoke micturition by 10 to 50 per cent, respectively. The effect was maximal within a few minutes, remained constant for about 1/2 hour and returned to control values over the next 2 to 3 hours. Following return to control, subsequent doses of naloxone produced no further effect on capacity. In chloralose anesthetized animals naloxone also increased the frequency and amplitude of low amplitude pressure waves on the tonus limb of the cystometrogram. Intrathecal administration of naloxone to the sacral spinal cord did not significantly reduce the volume necessary to evoke micturition even at large doses, but did increase the amplitude of micturition contractions. These data, along with previous reports, suggest that mu receptors in the brainstem alter urinary bladder capacity, while delta receptors in the spinal cord modulate the magnitude of bladder contractions. Pharmacological manipulation of these receptor systems could provide a tool for the management of neurogenic bladder dysfunction.