Identification of distinct C3b and C4b recognition sites in the human C3b/C4b receptor (CR1, CD35) by deletion mutagenesis

Complementary DNA clones encoding the NH2-terminal region of human CR1 have been isolated and sequenced. The deduced complete amino acid sequence of the F allotype of human CR1 contains 2,039 residues, including a 41-residue signal peptide, an extracellular domain of 1,930 residues, a 25-amino acid transmembrane domain, and a 43-amino acid cytoplasmic region. The extracellular domain is composed exclusively of 30 short consensus repeats (SCRs), characteristic of the family of C3/C4-binding proteins. The 28 NH2-terminal SCRs are organized as four long homologous repeats (LHRs) of seven SCRs each. The newly sequenced LHR, LHR-A, is 61% identical to LHR-B in the NH2-terminal two SCRs and greater than 99% identical in the COOH-terminal five SCRs. Eight cDNA clones were spliced to form a single construct, piABCD, that contained the entire CR1 coding sequence downstream of a cytomegalovirus promoter. COS cells transfected with piABCD transiently expressed recombinant CR1 that comigrated with the F allotype of erythrocyte CR1 on SDS-PAGE and that mediated rosette formation with sheep erythrocytes bearing C4b and C3b. Recombinant CR1 also had factor I-cofactor activity for cleavage of C3(ma). Analyses of six deletion mutants expressed in COS cells indicated that the NH2-terminal two SCRs of LHR-A contained a site determining C4 specificity and the NH2-terminal two SCRs of LHR-B and -C each had a site determining C3 specificity. The presence of these three distinct sites in CR1 may enable the receptor to interact multivalently with C4b/C3b and C3b/C3b complexes generated during activation of the classical and alternative pathways.

Serotoninergic axonal contacts on identified cat spinal dorsal horn neurons and their correlation with nucleus raphe magnus stimulation

This study examined the distribution of serotoninergic (5-HT) immunoreactive axonal contacts on spinal laminae I and II neurons by combining the intracellular horseradish peroxidase (HRP) method with immunocytochemistry. In addition, the 5-HT distribution was correlated with effects produced by electrical stimulation within the nucleus raphe magnus (NRM). Responses of lamina I neurons and lamina II stalked cells to noxious stimulation were markedly suppressed during NRM stimulation. In contrast, responses of nociceptive lamina IIa islet or non-nociceptive lamina IIb islet cells remained unchanged during nucleus raphe magnus stimulation. These inhibitory influences were positively correlated with the distribution of 5-HT immunoreactive contacts on these neurons. Nociceptive lamina I neurons and lamina II stalked cells received a significantly greater number of contacts (average of 74 and 63, respectively) than either nociceptive lamina IIa islet or non-nociceptive lamina IIb islet cells (average of 25 and eight contacts, respectively). Irrespective of cell type, most 5-HT contacts occurred on dendritic shafts rather than spines. These data reveal a differential distribution of 5-HT contacts on neurons in spinal laminae I and II, and indicate that at least a portion of the NRM modulation of dorsal horn neuronal activity is serotoninergic and concentrated on the dendritic shafts of nociceptive lamina I neurons and lamina II stalked cells.

Iontophoretic application of calcitonin gene-related peptide produces a slow and prolonged excitation of neurons in the cat lumbar dorsal horn

Calcitonin gene-related peptide (CGRP) was applied by iontophoresis onto physiologically characterized neurons. CGRP (20-100 nA) activated both wide-dynamic-range (5/8) and low-threshold mechanoreceptive units (3/12), but had no effect on nociceptive-specific neurons (0/4). The excitation was of slow onset (30 s to 3 min) and prolonged duration (up to 10 min). In none of the tested units did CGRP cause inhibition. The slow and prolonged action suggests a neuromodulatory role for CGRP in spinal cord sensory processes.

Retrograde tracing of projections between the nucleus submedius, the ventrolateral orbital cortex, and the midbrain in the rat

The fluorescent tracers fluoro-gold and 1,1'-dioctadecyl-3,3,3,3-tetramethyl indocarbocyanine perchlorate were used as retrograde markers to examine reciprocal connections between the rat nucleus submedius and the ventrolateral orbital cortex. In addition, midbrain projections to each of these regions were examined. In the prefrontal cortex, we found that input from the nucleus submedius terminates rostrally within the lateral and ventral areas of the ventrolateral orbital cortex. Conversely, the cortical input to the nucleus submedius originates from the medial and dorsal parts of the ventrolateral orbital cortex. Our data also demonstrated that neurons from the ventrolateral periaqueductal gray and the raphe nuclei project to the midline nuclei of the thalamus, including a small projection to the nucleus submedius. We further determined that regions within the ventrolateral periaqueductal gray and raphe nuclei project to the ventrolateral orbital cortex, and that these regions overlap with those that project to the nucleus submedius. These findings suggest that the nucleus submedius might be part of a neural circuit involved in the activation of endogenous analgesia.

Curing characteristics of flowable and sculptable bulk-fill composites

OBJECTIVES

The aim of this study was to determine and correlate the degree of conversion (DC) with Vickers hardness (VH) and translucency parameter (TP) with the depth of cure (DoC) of five bulk-fill composites.

MATERIALS AND METHODS

Six specimens per group, consisting of Tetric EvoCeram Bulk Fill ("TEC Bulk," Ivoclar Vivadent), SonicFill (Kerr), SDR Smart Dentin Replacement ("SDR," Dentsply), Xenius base ("Xenius," StickTech; commercialized as EverX Posterior, GC), Filtek Bulk Fill flowable ("Filtek Bulk," 3M ESPE), and Tetric EvoCeram ("TEC," control), were prepared for DC and VH: two 2-mm-thick layers, each light-cured for 10 s; one 4-mm bulk-fill, light-cured for 10 or 20 s; and one 6-mm bulk-fill, cured for 20 s. DC was measured using a Fourier-transform infrared spectrometer, VH using a Vickers hardness tester. DoC and TP were measured using an acetone-shaking test and a spectrophotometer, respectively. Data were analyzed using ANOVA and Pearson's correlation (α = 0.05).

RESULTS

DC and VH ranged between 40-70 % and 30-80 VHN, respectively. TEC Bulk, Xenius, and SonicFill, bulk-filled as 4-mm-thick specimens, showed bottom-to-top hardness ratios above 80 % after 20 s curing. A positive linear correlation was found for bottom DC and VH. An average DC ratio of 0.9 corresponded to a bottom-to-top VH ratio of 0.8.

CONCLUSIONS

Sculptable bulk-fills require 20 s, whereas 10 s curing time was sufficient for flowable bulk-fills using a high-intensity LED unit.

CLINICAL RELEVANCE

Clinicians should be aware that longer curing times may be required for sculptable than flowable bulk-fill composites in order to achieve optimal curing characteristics.

Responses of neurons in the rat nucleus submedius to noxious and innocuous mechanical cutaneous stimulation

Extracellular recordings were used to characterize responses to cutaneous mechanical stimulation of 78 neurons in the rat nucleus submedius (SM). Thirty-nine of these units were activated by some type of cutaneous mechanical stimulation. Eighteen cells were activated exclusively by noxious stimuli. In 13 of these cells, responses were of swift onset and relatively rapid termination following stimulus application. In contrast, in three neurons responses were delayed both in onset and termination, and in two the response was immediate, but the markedly increased evoked activity outlasted stimulus application by 13 min. Receptive fields (RFs) of these nociceptive neurons were generally large, although none were bilateral. Four SM neurons were activated by innocuous stimuli, but their maximal response was obtained only after noxious stimulation. Responses of all of these neurons were of immediate onset and recovery, and their RFs were large (two were bilateral). Twelve SM neurons were activated maximally by innocuous stimuli. Responses of seven of these cells were immediate in onset and termination, while that of three were delayed in both onset and termination. Two of the 12 innocuous-only neurons quickly became unresponsive to repeated stimulus applications, and could be reactivated only after a rest period during which no stimuli were applied. RFs of these units were also generally large, and in three cases were bilateral. Five SM neurons responded by decreasing, or completely ceasing, their firing subsequent to noxious-only (n = 2), or innocuous-only (n = 3) stimulation. Four of these units had large RFs (two were bilateral). The remaining 39 SM neurons could not be activated by any type of mechanical cutaneous stimulation we tried. Electrical stimulation of the ventrolateral orbital cortex (VLO) was employed to examine frontal cortical projections of 21 SM neurons. Ten of these units were activated, although all of them synaptically rather than antidromically, and two were inhibited. There was no clear-cut relationship between neuronal location, physiological type, RF site, or VLO stimulation effects among the 39 SM neurons. These results provide further support for the involvement of SM neurons in nociceptive information signaling, and suggest additionally that the role of the nucleus is not limited to nociception but encompasses a wider range of cutaneous sensations.

Immunocytochemical identification of serotonin axonal contacts on characterized neurons in laminae I and II of the cat dorsal horn

Serotonergic pathways from brainstem to spinal cord play an important role in the modulation of pain perception. To establish where that modulation occurs, we examined serotonin-immunoreactive axonal contacts on individually characterized laminae I and II dorsal horn neurons intracellularly filled with horseradish peroxidase. We found serotonin axonal contacts on marginal, stalked, and islet cells. Contacts preferentially occurred on dendritic shafts rather than on spines. Marginal and stalked cells received the heaviest innervation.

The effect of continuous morphine analgesia on chronic thermal hyperalgesia due to sciatic constriction injury in rats

We employed hindfoot withdrawal latencies to radiant heat to assess the analgesic effect of prolonged morphine infusion on thermal hyperalgesia induced by chronic constriction injury (CCI) of the rat sciatic nerve. All CCI rats developed thermal hyperalgesia while sham-operated animals did not. Continuous systemic infusion of morphine dose-dependently reversed the thermal hyperalgesia in the CCI rats. In contrast, thermal hyperalgesia persisted in saline-treated CCI rats. Tolerance to morphine's analgesic effect did not develop over a period of seven days of morphine infusion, which is considered long-term for animal models. These data suggest that morphine acts rapidly and effectively to reduce behavioral signs of hyperalgesia in rats with sciatic CCI, without the concomitant development of tolerance. Scheduled administration of morphine might be an appropriate treatment regimen for relief of neuropathic pain, and the infrequent use of opioids in equivalent human clinical pain syndromes due to fear of opioid unresponsiveness and tolerance might need to be re-evaluated.

Responses of neurons in the rat ventrolateral orbital cortex to phasic and tonic nociceptive stimulation

Responses of ventrolateral orbital cortex (VLO) neurons to innocuous touch and pressure, and noxious pinch and cold were examined by extracellular recordings. Eight neurons increased their firing rate in a graded fashion to all stimuli applied, 4 units decreased their discharges, and 6 neurons remained unaffected. All responsive units displayed the greatest change in firing rate during noxious cold, and all exhibited whole-body receptive fields. These data further implicate the VLO in nonciception.

Long-term changes in sciatic-evoked A-fiber dorsal horn field potentials accompany loose ligation of the sciatic nerve in rats

The goal of the present study was to examine whether loose ligation of the sciatic nerve was associated with long-term changes in neuronal excitability in the spinal dorsal horn in urethane-anesthetized rats. The sciatic nerve was stimulated with 0. 1 ms long pulses at 1 stimulus/5 min, and the evoked dorsal horn field potentials remained stable in the absence of tetanic stimulation. In one set of control and ligated animals, high-frequency tetanic stimulation was applied to the nerve at 50 Hz (one 400 ms train of twenty 0.1 ms pulses), and the field potentials were recorded again (1 stimulus/5 min) for up to 4 h post-tetanus. In control animals, this protocol produced significant increases in field potential amplitudes at 15, 30 and 60 min post-tetanus. Interestingly, after this time the evoked field potentials began to decrease, and attained less than 50% of their pre-tetanic values at 240 min post-tetanus. In contrast, in ligated rats the pattern of post-tetanic potentiation was significantly different as the increases in amplitude persisted, and at 240 min post-tetanus the field potentials were almost twice their baseline values. In another set of control and ligated animals, low-frequency tetanic stimulation was applied at 5 Hz (one 400 ms train of two 0.1 ms pulses). Again a differential pattern of post-tetanic responses between control and ligated rats was seen. In control animals, a significant decrease in amplitude was evident within 30 min, and the depression became progressively more pronounced as the field potentials attained about a quarter of their baseline values at 180 min, and remained at these low levels at 240 min post-tetanus. On the other hand, in ligated animals, the depression was not significant, and at 240 min post-tetanus the field potentials were still at about 80% of their baseline values. These data demonstrate that long-term changes in spinal dorsal horn neuronal excitability accompany sciatic ligation to perhaps contribute to the development of neuropathic pain. These changes may result from a lessening of normally strong inhibitory processes in the spinal dorsal horn to generate conditions which favor post-tetanic potentiation over depression of dorsal horn neuronal responses.

Quantification of monomer elution and carbon-carbon double bonds in dental adhesive systems using HPLC and micro-Raman spectroscopy

OBJECTIVES

To quantify monomer elution from different adhesive systems using reverse-phase high-performance liquid chromatography (HPLC) and correlate this elution with the ratio of carbon-carbon double bonds from monomer to polymer (RDB) obtained using micro-Raman spectroscopy.

METHODS

Thirty dentine discs were cut from 30 human, intact, third molars and randomly allocated to five groups according to the adhesive applied: total-etch, Excite (Ivoclar Vivadent), two-bottle self-etch, Clearfil SE (Kuraray), one-bottle self-etch, Clearfil 3S (Kuraray), ormocer-based, Admira (Voco) and Filtek Silorane adhesive system (FS) (3M ESPE). Monomer elution was studied 1h, 6h, 24h, 96h and 7 days after immersion in 75% ethanol/water. The RDB was calculated immediately after light-curing and thereafter at 24h and 7 days. The data were statistically analysed using one-way ANOVA and Pearson's correlation coefficient (p<0.05).

RESULTS

More than 90% of the whole elution occurred during the first 1h, except for BisGMA in FS, with the highest absolute amount from Clearfil SE and the highest wt% from Admira. Initial RDB was in the ascending order FS<Admira<Excite<Clearfil SE<Clearfil 3S. In all groups, the RDB was significantly higher after 24h and 7 days than immediately after light-curing (p<0.05). Negative correlation was found only for the elution of HEMA and the RDB of Clearfil 3S.

CONCLUSIONS

Different adhesive systems showed different monomer elution kinetics. In all systems, the RDB increased after monomer elution. Overall, no direct correlation exists between the RDB of adhesives and the elution of unreacted monomers.

Bulbospinal serotoninergic pathways in the frog Rana pipiens

We combined retrograde fluorescent tracing with rhodamine immunofluorescence to identify the origin of serotoninergic neurons with descending projections to the spinal cord of frogs. After injections of Fluoro-gold into the spinal cord, retrogradely labeled immunoreactive serotoninergic neurons were detected in the caudal part of the brainstem from the level of the obex through the level of the VIII nerve. These doubly labeled cells were distributed along the midline throughout the rostrocaudal extent of the dorsal portion of the raphe nuclear region. Doubly labeled neurons were more numerous in the rostral than in the caudal part of the raphe area. The fluorescent tracer 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) was then placed in and around the middle and rostral raphe nuclear region. Anterogradely labeled fibers could be traced bilaterally in the lateral portion of the dorsal funiculus and the lateral and ventral funiculi. These fibers were seen terminating in the dorsal and ventral horns, as well as in the intermediate grey matter. After placement of DiI in the caudal raphe area, labeled fibers were found only in the intermediate grey and ventral horn. These findings suggest that the organization of bulbospinal serotoninergic pathways in the frog is similar to that of mammals, and that an isolated amphibian spinal cord preparation could be a useful model for pharmacological and physiological studies of the action of serotonin (5HT) in the spinal cord.

Immunoreactive enkephalin is contained within some trigeminal and spinal neurons projecting to the rat medial thalamus

In order to determine whether enkephalin is contained within rat trigeminothalamic and spinothalamic neurons, we have combined the techniques of retrograde labeling and immunocytochemistry. Injection sites were limited to medial thalamic nuclei. Retrogradely labeled neurons were most often seen contralaterally in trigeminal and spinal laminae I, V, VI and VII. After immunocytochemical processing, about 10% of the retrogradely labeled cells exhibited enkephalin immunoreactivity. These double-labeled neurons were located in laminae VI and VII.

5-Hydroxytryptophan (5-HTP) augments spontaneous and evoked phrenic motoneuron discharge in spinalized rats

Experiments on anesthetized, spinalized rats were conducted to determine the effects of systemic 5-hydroxytryptophan (5-HTP) administration on: (1) spontaneous phrenic nerve activity and (2) evoked phrenic responses to short latency, non-serotonergic synaptic inputs elicited by electrical stimulation of lateral funiculus. 5-HTP augmented spontaneous phrenic activity and allowed expression of a second, longer latency evoked response. Both effects were antagonized by methysergide. Our results suggest that spinal serotonin increases the efficacy of synaptic inputs to phrenic motoneurons.

Loose ligation of the rat sciatic nerve is accompanied by changes in the subcellular content of protein kinase C beta II and gamma in the spinal dorsal horn

This study examined whether loose ligation of the sciatic nerve was accompanied by specific changes in protein kinase C (PKC) betaII and gamma isozymes in the spinal dorsal horn. The isozyme staining pattern was visualized with immunocytochemistry. Their content in subcellular fractions was estimated from Western immunoblots. In control animals, PKC betaII immunoreactivity extended from lamina I into lamina III, while PKC gamma immunoreactivity was concentrated within laminae II and III. In ligated animals exhibiting thermal hyperalgesia, the content of both PKC betaII and gamma in the synaptosomal membrane fraction, but not crude cytosolic fraction, was significantly greater by an average of 40% from their respective controls. These data support suggestions that peripheral nerve injury engenders plastic changes in the dorsal horn to contribute to the development of persistent pain.

Immediate and Long-Term Porosity of Calcium Silicate-Based Sealers

INTRODUCTION

Open pores between endodontic sealer and root canal walls present potential niches for bacterial growth and migration pathways. The aim was to assess the internal and external porosity of calcium silicate-based sealers and to ascertain the long-term effect of storage in simulated body fluid on sealer porosity.

METHODS

Sixteen single-rooted teeth were filled with gutta-percha and 1 of 4 root canal sealers: BioRoot RCS, EndoSequence BC, MTA Fillapex, or AH Plus. Obturated roots, stored in Hank's balanced salt solution, were scanned after 7 days and after 6 months by using micro-computed tomography at an isotropic resolution of 9.9 μm. Total, open, and closed porosity were calculated in the coronal, middle, and apical thirds. Data were statistically analyzed by using general linear model and paired t test (α = 0.05).

RESULTS

Significantly higher percentage of open than closed porosity was found in all groups. Initially, significantly greater open and total porosity were found for MTA Fillapex than for AH Plus. After 6 months, the percentage of open and total porosity increased in BioRoot RCS and MTA Fillapex and decreased in AH Plus and EndoSequence BC. Both initially and after storage, coronal region of all sealers had significantly greater total porosity than middle and apical regions, which were comparable.

CONCLUSIONS

None of the root fillings were void-free, with predominant open porosity persisting after long-term storage.

Temperature rise within the pulp chamber during composite resin polymerisation using three different light sources

The purpose of the study was to compare temperature rise during polymerisation of resin based composites (RBCs) with two LED light curing units (LCUs) compared to a halogen control light.

Prenatal and postnatal chronic exposure to low levels of inorganic lead attenuates long-term potentiation in the adult rat hippocampus in vivo

Dams were exposed to 0, 100, 500, or 1000 ppm lead acetate in their drinking water for 1 week and mated. Offspring were exposed via lactation and in their drinking water after weaning. At 13 weeks, a male and a female pup from each litter were anesthetized with urethane and prepared for recording of CA3-evoked field potentials in the hippocampal CA1 region. In control and 100 ppm lead-treated animals, high-frequency stimulation (50 Hz) induced long-term potentiation (LTP) throughout a 4 h recording period. In contrast, 1000 ppm lead-treated pups showed little LTP, while those exposed to 500 ppm exhibited LTP initially but then failed to maintain it. Chronic developmental lead exposure prevented the full expression of LTP in the CA1 region of the rat hippocampus.

Responses of neurons in the ventrolateral orbital cortex to noxious cutaneous stimulation in a rat model of peripheral mononeuropathy

The responses of ventrolateral orbital cortex neurons to noxious cold pressor were compared in rats with loose ligatures tied around their sciatic nerve with those in rats in which the sciatic nerve was exposed but not ligated. In ligated rats more cells responded to cold pressor and their average afterdischarges were longer. There were no differences in the background firing rate or the magnitude of response to the cold pressor between the two groups.