Complete inhibition of spontaneous activity in neuronal networks in vitro by deltamethrin and permethrin.

Types I and II pyrethroid insecticides cause temporally distinct decreases in voltage-gated sodium channel (VGSC) inactivation rates that are proposed to underlie their characteristic differences in toxicity signs. How alterations in VGSC channel function give rise to the characteristic differences in signs of pyrethroid intoxication is not completely understood, particularly those changes that occur in functional networks of interconnected neurons. To characterize better pyrethroid actions at the network level, effects of the Type I pyrethroid permethrin (PM) and the Type II pyrethroid deltamethrin (DM) on spontaneous glutamate network-dependent spikes and bursts were investigated in primary cultures of frontal cortex or spinal cord neurons grown on microelectrode arrays (MEAs). Fast GABAergic transmission was blocked by BIC, and concentration-dependent effects of DM (1nM to 5microM) and PM (10nM to 50microM) were examined. Both compounds caused concentration-dependent reductions in the network spike and burst rates. DM was more potent than PM, with IC(50) values of approximately 0.13 and approximately 4microM for inhibition of spike rate in cortical and spinal cord neurons, respectively. Both compounds decreased the percentage of spikes that occurred within a burst and increased the interspike interval within bursts. Onset of effects was rapid, but recovery from total activity loss was not readily achievable. Individual neurons responded heterogeneously; activity of most declined monophasically, but activity in others exhibited biphasic responses with increases followed by decreases in activity. In spinal cord, DM caused a greater number of biphasic responses (29%) than PM (10%). These results demonstrate that both DM and PM inhibit activity of glutamatergic networks, but with different potencies.

Quantification of zinc toxicity using neuronal networks on microelectrode arrays.

Murine neuronal networks, derived from embryonic frontal cortex (FC) tissue grown on microelectrode arrays, were used to investigate zinc toxicity at concentrations ranging from 20 to 2000 microM total zinc acetate added to the culture medium. Continual multi-channel recording of spontaneous action potential generation allowed a quantitative analysis of the temporal evolution of network spike activity generation at specific zinc acetate concentrations. Cultures responded with immediate concentration-dependent excitation lasting from 5 to 50 min and consisting of increased spiking and enhanced, coordinated bursting, followed by irreversible activity decay. The time to 50% and 90% activity loss was concentration dependent, highly reproducible, and formed linear functions in log-log plots. Above 100 microM total zinc acetate, the activity loss was associated with massive cell swelling, blebbing, and even vigorous neuronal cell lysing. Glia showed stress, but did not participate in the extensive cell swelling. Network activity loss generally preceded morphological changes. Cultures pretreated with the GABA(A) receptor antagonists bicuculline (40 microM) and picrotoxin (1mM) lacked the initial excitation phase. This suggests that zinc-induced excitation may be mediated by interfering with GABA inhibition. Partial network protection was achieved by stopping spontaneous activity with either tetrodotoxin (200 nM) or lidocaine (250 microM). However, recovery was not complete and slow deterioration of network activity continued over 6-h periods. Removal of zinc by early medium changes showed irreversible, catastrophic network failure to develop in a concentration-dependent time window between 50% and 90% activity loss.

Detection of physiologically active compounds using cell-based biosensors.

Cell-based biosensors are portable devices that contain living biological cells that monitor physiological changes induced by exposure to environmental perturbations such as toxicants, pathogens or other agents. Methods of detecting physiological changes include extracellular electrical recordings, optical measurements, and, in the future, functional genomics and proteomics. Several technical developments are occurring that will increase the feasibility of cell-based biosensors for field applications; these developments include stem cell and 3D culture technologies. Possible scenarios for the use of cell-based biosensors include broad-range detectors of unknown threat agents and functional assessment of identified agents.

In vitro simulation of neural trauma by laser.

A serious lack of knowledge about central nervous system trauma is encountered on the cellular level where the inability to create precise experimental lesions of known magnitude has limited our understanding of the reactions of single cells to injury. We used a laser cell surgery technique developed in this laboratory to manipulate neurons in a controlled environment, in order to observe pathologic reactions during and immediately after the injury. This technique is especially suited for axonal and dendritic amputations close to the perikaryon. The laser provided three different physical modes of injury to neurites: direct vaporization of cytoplasm, pressure wave damage from external vaporization of substrate material, and photobiologically-induced localized cytoskeletal destruction leading to the slow pinching of processes followed by transection. Our data indicated a great similarity between laser impact damage and the cellular damage produced by physical trauma to the central nervous system.

Cost-effective imaging approach to the nonbilious vomiting infant.

OBJECTIVE: To develop a cost- and time-effective algorithm for differentiating hypertrophic pyloric stenosis (HPS) from other medical causes of emesis in infants referred from community-based pediatricians and family practitioners to the imaging department of a tertiary children's care facility. METHODS: Eighty-nine vomiting infants (22 females, 67 males) between the ages of 11 and 120 days (mean, 43.5 days) had received nothing by mouth for at least 1 hour before the study. Each child was assessed for duration of vomiting, status of body weight, time and volume of last ingestion, and time of last emesis. A #8 French (Sherwood Medical, St Louis, MO) nasogastric feeding tube was placed in the child's stomach. The contents were aspirated and measured to determine likelihood of HPS. An aspirated volume >/=5 mL implicated gastric outlet obstruction, and ultrasonography (US) was performed. If this study was positive for HPS, the patient was referred for surgery. If US was negative, an upper gastrointestinal series (UGI) was performed. An aspirated stomach contents volume <5 mL suggested a medical cause for the emesis, and UGI was performed. Pediatric surgeons with no knowledge of the volume results palpated the abdomens of 73 of 89 infants (82%). RESULTS: Twenty-three of 89 patients (25%) had HPS. The aspirate criteria for HPS had a sensitivity of 91%, a specificity of 88%, and an accuracy of 89%. Of the false-positive studies (total = 8), six were related to recent significant ingestion (within 2 hours of the study), and two were attributable to antral dysmotility. The surgeons palpated the mass in 10 of 19 patients (53%). Sensitivity and specificity were 53% and 93%, respectively. Only 6 of 89 infants (7%) required both US and UGI to determine the etiology of the nonbilious vomiting. By performing the UGI in 66 patients, it was also found that 14% had slow gastric emptying and 79% had gastroesophageal reflux. Eighty-one percent of the gastroesophageal reflux was significant. CONCLUSION: The volumetric method of determining the proper imaging study is cost- and time-effective in the evaluation of the nonbilious vomiting infant for pyloric stenosis. If US was performed initially in all patients referred for imaging, two studies would have been performed in 68 of 89 patients (76%) to define the etiology of the emesis. Because we used the volumetric method, 62 fewer imaging studies were performed, representing a savings of $4464 and 30 hours of physician time. If children are given nothing by mouth for 3 to 4 hours before gastric aspiration, the specificity of the volumetric method improves to 94%, and the accuracy improves to 96%.

Neural networks in radiologic diagnosis. I. Introduction and illustration.

Artificial neural networks (NNs) process information in a manner similar to the way the human brain is thought to process information. Neural networks have potential application in radiology as an artificial intelligence technique that can provide computer-aided diagnostic assistance for the practicing radiologist. The basic characteristics of NNs and the manner in which information propagates through an NN are discussed in nontechnical language, to assist the diagnostic radiologist in understanding the basic principles of neurocomputing. Computer-aided diagnosis selection in pediatric chest radiography using NNs is discussed in a companion article.

Neural networks in radiologic diagnosis. II. Interpretation of neonatal chest radiographs.

A neural network (NN) system was trained to choose one or more diagnoses from a list of 12 possible diagnoses, based on 21 radiographic observations made on each of a series of neonatal chest radiographs. Initially, an experienced pediatric radiologist provided both the radiographic observations and ranked differential diagnoses for each of 77 neonatal chest radiographs in the preliminary phase used to train the NN. Subsequently, two pediatric radiologists (one of whom provided the initial training-phase data) independently read a series of 103 neonatal chest radiographs (different from the training set) and compiled a list of radiographic findings and differential diagnoses for each radiograph. The trained NN was then asked to provide a list of differential diagnoses for each case from the radiologists' lists of findings. Agreement between the network and each radiologist independently was greater than between the two radiologists. Both the positive and negative agreement between the network and either radiologist was greater than the inter-radiologist agreements for most of the diagnostic endpoints.

Calcium antagonists fail to protect mammalian spinal neurons after physical injury.

Most investigations of calcium antagonists as treatments for experimental spinal cord injury (SCI) have not demonstrated significant reduction of tissue damage or improvement in neurologic outcome. Many of these studies were prompted by reports that these agents increase blood flow to ischemic tissues. However, in vitro studies of renal and neuronal tissues subjected to an anoxic stress have shown that the calcium antagonists can confer direct protection on stressed parenchymal cells. We have used a tissue culture model of nerve cell injury to investigate whether calcium antagonists increase the probability of survival of spinal cord neurons after a defined physical trauma. Preliminary toxicity studies determined the maximum nontoxic dosages of verapamil (80 microM), nifedipine (10 microM), and chlorpromazine (10 microM) for neurons in our cultures. Preselected neurons (100-200 per study) were subjected to amputation of one primary dendrite at a distance of 100 microns from the perikaryon. Erythrosine B tests of viability conducted 24 h after lesioning failed to demonstrate that neurons injured in the presence of any one of these agents had an increased probability of survival compared to operated control neurons. Viability evaluations conducted 2 h after injury with phase contrast microscopy showed no evidence of slowed deterioration. Correction for other lesion physical parameters (lesion diameter and the extent of proximal segment retraction) also failed to reveal any increased protection by these agents. We conclude that calcium antagonists alone will not be useful for treatment of the primary injury of SCI.

NMDA antagonists prevent hypothermic injury and death of mammalian spinal neurons.

Prolonged (2-6 h) cooling of monolayer cultures of dissociated murine spinal cord at temperatures below 17 degrees C caused pronounced swelling of neuronal perikarya and dendrites. The numbers of swollen neurons in a culture increased as the temperature was reduced, and at 7 degrees C-10 degrees C all of the neurons were swollen. On rewarming the cultures to 37 degrees C, the majority of the swollen neurons died (up to 74% at 10 degrees C). Glial cells were not affected. Addition of the NMDA antagonists D-2-amino-5-phosphonovalerate (DAPV, 100 microM), ketamine (100 microM), and dibenzocyclohepteneimine (MK801, 10 microM) to spinal cord cultures before lowering the temperature to 10 degrees C minimized the dendrosomatic swelling and reduced neuronal mortality from 74% to 10%. These data show a surprising sensitivity of some neurons to nonfreezing low temperatures and suggest direct involvement of the NMDA receptor in hypothermia-related neuronal death.

Neuronal survival and dynamics of ultrastructural damage after dendrotomy in low calcium.

To determine the contributions of calcium to development of ultrastructural damage and neuronal death after mechanical injury, we amputated primary dendrites from over 300 cultured mammalian spinal neurons under normal (1.8 mM) or low (less than or equal to 30 microM) calcium conditions. Two general categories of early ultrastructural change were seen in both normal and low calcium: (1) a lesion-dependent gradient of damage that moved centripetally through the proximal segment and penetrated the soma within 15 min and (2) dilation of the somal Golgi/smooth endoplasmic reticulum (SER), which preceded the wave of deterioration from the lesion. Although the somal Golgi/SER changes were similar in both normal and low calcium, the damage gradient in low calcium differed from the damage gradient in normal calcium. (1) Microtubules and neurofilaments were preserved, (2) mitochondria became more electron dense but did not develop electronlucent foci or high amplitude swelling, and (3) an extensive vesicular gradient formed consisting of rows of swollen SER vesicles. Sodium ionophores have been reported to cause similar changes. Survival studies showed that calcium reduction significantly delayed neuronal death. Survival was 63 +/- 16% vs 35 +/- 8% (p less than 0.003) at 2 h and 30 +/- 7% vs 23 +/- 8% at 6 h in low and normal calcium, respectively. Dead neurons that had been lesioned in low calcium also showed greater ultrastructural preservation than neurons that died after dendrotomy in normal calcium. We hypothesize that under low calcium conditions, the large sodium injury current plays an important role in neuronal deterioration and death after mechanical trauma.

Effects of methylprednisolone on lesioned and uninjured mammalian spinal neurons: viability, ultrastructure, and network electrophysiology.

An in vitro investigation was undertaken to provide information regarding the effectiveness of methylprednisolone sodium succinate (MPSS) as a treatment for the primary mechanical injury of spinal cord (SC) trauma. Exposure of uninjured mouse SC cells to MPSS for 24 h caused neuronal stress when the concentration exceeded 150 micrograms/mL; neuronal death occurred at concentrations above 600 micrograms/mL. The concentration range for MPSS protection of SC neurons subjected to a defined physical injury (laser microbeam transection of a primary dendrite 100 microns from the perikaryon) was very narrow: survival in the 30 micrograms/mL group differed significantly from the untreated control group (68.5% +/- 14.1 vs. 47.1% +/- 14.1), treatment with 20 or 60 micrograms/mL MPSS did not increase survival, and treatment with 100 micrograms/mL MPSS accelerated ultrastructural deterioration and increased the likelihood of death. Enhanced survival of lesioned neurons was observed when 30 micrograms/mL MPSS was applied within 15 min of dendrotomy but not when MPSS was administered 2 h after lesioning. Multimicroelectrode plate (MMEP) studies of SC network electrical activity indicated that MPSS associated readily with neuronal membranes. This finding was consistent with the hypothesis that MPSS may protect lesioned neurons by stabilizing damaged membranes, enhancing lesion resealing, and limiting the spread of ion-mediated damage. However, comparisons of neurite die-back 24 h after dendrotomy found no significant difference between MPSS-treated and control neurons. Application of 30 or 100 micrograms/mL MPSS increased the spontaneous burst activity of SC networks grown on MMEPs, however, there was no evidence that the increased excitability at these concentrations was the result of specific actions of MPSS on GABA or NMDA synapses.

In vitro investigations of the effects of nonfreezing low temperatures on lesioned and uninjured mammalian spinal neurons.

This two-part investigation explored the parameters and mechanisms of: (1) injury to spinal cord (SC) neurons by nonfreezing low temperatures, and (2) hypothermic protection of SC neurons subjected to a defined, physical injury (dendrite transection). Conclusions from the studies of hypothermic injury were: (1) morphologic and ultrastructural signs of stress developed in SC neurons as the temperature was decreased below 17 degrees C; (2) most neurons showing stress during cooling died upon rewarming to 37 degrees C; (3) spontaneous SC network activity was not significantly changed by cooling to 17 degrees C for 2 hours and rewarming, but cooling to 10 degrees C for 1 hour caused a reduction of burst frequency after rewarming, and cooling to 10 degrees C for 2 hours resulted in electrical silence after rewarming; and (4) application of N-methyl-D-aspartate (NMDA) antagonists before cooling prevented neuronal death, ultrastructural damage, and loss of activity upon rewarming, but application after cooling (before rewarming) was not protective. Conclusions from the studies of hypothermic protection were: (1) cooling at 17 degrees C for 2 hours followed by rewarming to 37 degrees C significantly increased lesioned neuron survival, but protection was lost when the period at 17 degrees C was increased to 6 hours; (2) NMDA blockade under normothermic (37 degrees C) or hypothermic (17 degrees C or 10 degrees C for 2 hours) conditions was not more protective of lesioned neurons than cooling to 17 degrees C (no NMDA antagonist); and (3) 200 microM thiopental or 100 microM pentobarbital increased lesioned neuron survival to a degree comparable to cooling for 2 hours at 17 degrees C.

Biliary sludge formation during enteral nutrition: prevalence and natural history.

BACKGROUND: Total parenteral nutrition is an etiologic factor in the formation of biliary sludge. We studied whether enteral nutrition is also a risk factor for sludge. METHODS: Fifty patients with a needle catheter jejunostomy (NCJ) placed during a major abdominal operation underwent preoperative and weekly postoperative ultrasonography until NCJ feedings were discontinued (1 to 6 weeks). RESULTS: All patients were men. The mean age was 63.2 +/- 1.6 years. Fourteen asymptomatic patients (28.0%) had biliary sludge within 2 weeks of beginning enteral feedings through a NCJ. Complete ultrasonographic resolution of sludge was observed in 13 of the 14 positive patients within 1 to 2 weeks of resuming an oral diet. One patient was lost to follow-up after 14 week; a positive sonogram had persisted but the patient remained asymptomatic. During the period of observation, no other patient had signs of biliary tract disease. CONCLUSIONS: (1) Biliary sludge may form in some patients during enteral feeding with NCJ. (2) Sludge is cleared by the gallbladder once an oral diet is resumed. (3) There appears to be little risk of complications during postoperative enteral feeding.

Risk factors for bronchopulmonary dysplasia after extracorporeal membrane oxygenation.

OBJECTIVE: To determine risk factors for the development of bronchopulmonary dysplasia (BPD) after treatment with extracorporeal membrane oxygenation (ECMO). DESIGN: Retrospective case-control study. SETTING: Tertiary care level 3 neonatal intensive care unit. PARTICIPANTS: Seventy-three newborns treated with ECMO for severe respiratory failure during a 5-year period, who survived until day of life 28, and who did not have pulmonary hypoplasia as the initial cause for respiratory failure. INTERVENTIONS: None. MAIN OUTCOME MEASURE: The presence of BPD after treatment with ECMO, which was defined as oxygen and/or ventilatory requirements at day of life 28, with characteristic abnormalities seen on chest x-ray film. RESULTS: The age at ECMO initiation was significantly greater for patients with BPD compared with patients without BPD (mean +/- SD, 135 +/- 68 hours vs 50 +/- 37 hours; P < .001). There was an 11.5-fold increased risk for the development of BPD if ECMO was initiated at greater than 96 hours of age. The primary diagnosis of respiratory distress syndrome imparted a 5.2-fold increased risk for the development of BPD. Patients with BPD required ECMO significantly longer than patients without BPD (203 +/- 73 hours vs 122 +/- 51 hours; P < .001). CONCLUSION: These results demonstrate that delayed use of ECMO in treating neonatal respiratory failure is associated with an increased risk for the development of BPD and a longer duration of ECMO therapy.

Biliary pancreatitis: the era of laparoscopic cholecystectomy.

OBJECTIVE: To evaluate the efficacy and safety of a combined approach to the treatment of biliary pancreatitis using laparoscopic cholecystectomy and selective endoscopic retrograde cholangiopancreatography (ERCP). DESIGN: Consecutive case series. SETTING: Tertiary care center. PATIENTS: All patients undergoing primary operations for biliary pancreatitis during 2 time periods were included. In the open era (June 1982 through May 1988), there were 276 patients; in the laparoscopic era (January 1996 through June 1997), there were 114 patients. INTERVENTIONS: Open cholecystectomy with or without common bile duct exploration (CBDE); laparoscopic cholecystectomy with selective ERCP and/or laparoscopic CBDE. MAIN OUTCOME MEASURES: Two periods were compared for morbidity, mortality, the duration of preoperative and postoperative stays, and the total length of hospitalization. RESULTS: Both groups were demographically similar and had the same mortality (1.9%). Laparoscopic cholecystectomies provided a preoperative stay comparable to open cholecystectomy (6.4 vs 5.8 days), a shorter postoperative stay (1.5 vs 8.5 days), a lower incidence of CBDE (6.6% vs 26%), and a lower morbidity (8% vs 13.7%). The addition of an ERCP to laparoscopic cholecystectomy was associated with prolongation of the preoperative stay (7.4 vs 5.0 days), a comparable postoperative stay, a lower conversion rate (7.5% vs 13%), and fewer CBDEs (3% vs 13%). In 27 (42%) of the 64 ERCP cases, no stones were found. CONCLUSIONS: Treatment of biliary pancreatitis with combined laparoscopic cholecystectomy and selective ERCP is safe and effective and is associated with a shorter hospitalization and fewer CBDEs than open cholecystectomy. Unnecessary ERCPs can be reduced by improved selection criteria or greater dependence on operative CBDE.

A closed flow chamber for long-term multichannel recording and optical monitoring.

An autoclavable chamber and associated medium circulation system has been constructed to provide a stable environment for mammalian cultures for long periods of time. The chamber was specifically designed for (a) multichannel electrophysiological recording from monolayer networks with photoetched multielectrode matrices, (b) for microscope observations of networks in the living state and (c) for the manipulation of such networks with laser cell surgery. The chamber components can be assembled under sterile conditions in less than 30 s to minimize pH and osmolarity stress to the monolayer cultures. An open chamber version provides a constant medium bath for pharmacological studies. The closed chamber version, attached to a 10-ml medium reservoir and a peristaltic pump, has so far provided constant conditions for continual recording over an 8-day period. Flow characteristics within the closed chamber, optical properties, pH maintenance, and schemes for drug addition are described.

Transparent indium-tin oxide electrode patterns for extracellular, multisite recording in neuronal cultures.

Glass plates coated with transparent thin film conductors of indium-tin oxide (ITO), 100 nm thick and 10 microns wide, have been successfully used to record spike potentials from neuronal monolayer cultures. The material is non-toxic to mammalian spinal neurons and is stable under warm culture medium. Laser-deinsulated recording craters that expose 100 mu m2 of ITO yield impedances of 8-10 M omega at 1 kHz with noise levels of 40 muV. Conventional gold plating of the craters reduces these impedances to below 3 M omega. The material is easily etchable and sputtered glass plates of high quality are commercially available at relatively low cost. The high light transmittance of ITO makes the conductors essentially invisible and allows unobstructed observation of circuit components in monolayer cultures. The introduction of ITO as a thin film microelectrode material should accelerate the construction of high density recording patterns that could exceed 400 microelectrodes per mm2.

A photoetched cell relocation matrix for long-term, quantitative observations of selected individual neurons in culture.

A photoetched matrix of indium tin oxide (ITO) on glass has been developed and tested as a tool to assist in the relocation and identification of individual neuronal cells in culture. The matrix is formed by 10-15 micron wide and 300 A thick ITO lines which subdivide a 1-cm2 area into 625 smaller squares. Each of the smaller squares measures 400 micron on a side and contains a photoetched two-letter "address". The address code allows precise relocation of specific regions of a culture as well as verification of the identities of individual neurons selected for repeated observation. Marks at 50 micron intervals along the sides of the address squares permit quantitative analysis of morphological changes, cell migration, reaggregation, etc. The ITO is transparent and does not interfere with visualization of even fine details of cells with high power microscopy.

Pulsed plasma deposition of allylamine on polysiloxane: a stable surface for neuronal cell adhesion.

Allylamine was pulse-plasma polymerized onto a hydrophobic polysiloxane substrate to create cell adhesion surfaces for cell culture that would not require pretreatment with polylysine, could be sterilized via autoclaving, and could be re-used for several culture cycles. We investigated two different plasma deposition protocols at 200 W RF power: (1) a duty cycle of 3 ms on and 5 ms off; and (2) a cycle of 3 ms on and 45 ms off. Control surfaces were unmodified polysiloxane, activated polysiloxane via flaming, and flamed polysiloxane further modified with poly-D-lysine (PDL). The different surfaces were characterized with XPS analysis, water contact angle, and cell adhesion and growth using dissociated murine embryonic spinal tissue. We found that both the amine content of the 3/45 duty cycle surface and the wettability was higher than that of the 3/5 surface. Also, spinal cord cells were better dispersed 24 h after seeding on the 3/45 surface, suggesting a difference in early adhesion dynamics. However, the networks on the two types of modified surfaces revealed no obvious morphological differences after 2 weeks in vitro. The stability of allylamine-decorated surfaces after autoclaving was high with only minor changes in wettability and nitrogen content. Cell growth on such surfaces after autoclaving was comparable to that found on flamed polysiloxane, freshly modified with PDL. Allylamine surfaces were still usable as cell growth substrates after three autoclaving cycles, 4 weeks under warm culture medium, and simple cleaning procedures, indicating the achievement of a long-lasting modification that did not require the repeated use of PDL before each seeding.

Recording of spontaneous activity with photoetched microelectrode surfaces from mouse spinal neurons in culture.

A matrix of photoetched gold conductors integrated into the floor of a tissue culture chamber has been used to record from mammalian spinal cord neurons grown on the insulation layer of the multielectrode plate. Spontaneous activity has been monitored from tissue microfragments less than 150 micrometers in diameter and from thin sheets of spinal cell aggregates. Maximum spike amplitudes of 360 microV with signal-to-noise ratios of 8:1 have so far been achieved and the spontaneous activity maintained for several days. Recording electrode impedances measured between 4 and 7 M omega at 1 kHz. Conductor tips were deinsulated with laser pulses that formed shallow craters 2 micrometers deep and 12 micrometers in diameter. Addition of colloidal gold or platimum black was not necessary to achieve satisfactory recordings.