Electronic cell counting to measure total cell numbers in bronchoalveolar lavage fluid

Cell counting of bronchoalveolar lavage (BAL) fluid is performed manually in routine practice. This has both methodological and inherent errors; however, the accuracy and suitability of automated counting devices have been questioned. In this study, a Coulter Counter D Industrial model was calibrated and then used to measure the total cell count in unprocessed bronchoalveolar lavage fluid, and compared to a standard manual method. Bronchoalveolar lavage was performed on 34 patients undergoing routine bronchoscopy. An aliquot of unprocessed bronchoalveolar lavage fluid was taken for all counting procedures. Manual counts were performed blind by two experienced independent observers using improved Neubauer chambers. Electronic counting measured 1 ml aliquots suspended in 10 and 20 ml Isoton counting 0.5 and 1 ml duplicates. The correlation coefficients between electronic and manual counts were good. The coefficients of repeatability of electronic counts, for repeat counts, both on the same dilution (Intra-Coulter: 0.1 x 10(5) cells.ml-1) and different dilutions (Interdilution-Coulter: 0.48 x 10(5) cells.ml-1), were superior compared to those for repeat manual counts by the same observer (1.03 x 10(5) cells.ml-1), and counts between observers (1.82 x 10(5) cells.ml-1). This method offers a quick, precise and simple method for counting cells in unprocessed bronchoalveolar lavage fluid, which is both less labour intensive and subjective than manual counting.

Localization and regulation of low affinity nerve growth factor receptor expression in the rat olfactory system during development and regeneration

Nerve growth factor (NGF), a classic neurotrophic factor, promotes neuronal survival, maintenance, regeneration and differentiation in the peripheral nervous system and parts of the central nervous system. NGF activity is mediated by cell surface bound receptors including the low affinity NGF receptor (LNGFr) which is expressed by some peripheral and central neurons and is present on peripheral nerve Schwann cells during development and regeneration. The olfactory system is a useful model for the study of the role of LNGFr in neuronal development and regeneration. The growth of olfactory axons into the brain begins in the embryo and continues through the first few postnatal weeks. In mature animals there is persistent turnover and generation of olfactory receptor neurons (ORNs) and continuous growth of new axons into the olfactory bulb. These new axons grow along the preexisting olfactory pathway. In the mature olfactory system, LNGFr has been observed in the glomerular layer of the olfactory bulb, the target of ORNs. However, neither the cellular localization nor the developmental expression of LNGFr has been characterized. Here, we tested the hypothesis that LNGFr expression is developmentally regulated in the olfactory nerve and is reinduced following injury to the mature olfactory nerve. LNGFr-immunoreactivity (IR) was first observed in the olfactory mucosa at embryonic day (E)13 and in the olfactory nerve at E14. LNGFr-IR increased in the nerve during embryonic development, began to decrease at around postnatal day (P)5 and was scarcely detectable in normal adults. The staining pattern suggests that LNGFr is located on the olfactory nerve Schwann cells. Streaks of LNGFr-IR were present in the adult olfactory nerve. We reasoned that these streaks might represent transient reexpression of LNGFr associated with normal olfactory neuron turnover and replacement. Consistent with this hypothesis, LNGFr was robustly reexpressed in the adult olfactory nerve following lesion of the olfactory epithelium. Starting late in development (E21) and in the adult, LNGFr-IR was also observed on fibers in deep layers of the olfactory bulb. LNGFr-IR was also observed in neurons of the nucleus of the diagonal band (NDB) in the basal forebrain. NDB is the sole source of cholinergic afferents of the olfactory bulb. Thus, we tested the hypothesis that LNGFr in the deep layers of the olfactory bulb is located on NDB axons by making lesions of NDB. Following the lesion, LNGFr-IR disappeared in the deep layers of the olfactory bulb but remained in the glomerular layer.(ABSTRACT TRUNCATED AT 400 WORDS)

Permeability of the blood-brain barrier within rat intrastriatal transplants assessed by simultaneous systemic injection of horseradish peroxidase and Evans blue dye

Both horseradish peroxidase (HRP) and Evans blue dye (EBD) have been used previously to characterize the status of the blood-brain barrier (BBB) within brain tissue transplants and host brain tissue. We investigated the possibility that a differential permeability of the vasculature to these two markers can account for discrepancies in the literature concerning the presence of an intact BBB within the grafted tissues. Intravascular injection of both HRP and EBD was used to evaluate the status of the BBB within intracerebral tissue transplants. Simultaneous injection of HRP and EBD in rats with adrenal medulla transplants or C-6 glioma tumors demonstrated a lack of a BBB within these grafts. Both markers produced consistent results within each tissue type, although HRP was generally a more sensitive marker. In contrast to the lack of a BBB in the C-6 gliomas or adrenal medulla transplants, 1-week-old fetal striatal transplants had a BBB essentially intact to both HRP and EBD. Any reported discrepancies in the characterization of the BBB are not likely due to differences between the properties of HRP or EBD. Fetal striatal transplants appear to have an intact BBB at 1 week following transplantation.

The role of mast cell activation in cholestatic pruritus

Jaundiced patients experience intense pruritus, the pathophysiology of which is unclear. In this study, blood histamine concentrations, skin mast cell counts and intracellular histamine concentrations in peritoneal mast cells were examined in an experimental model of biliary obstruction. Three weeks after bile duct ligation (BDL), total blood histamine concentrations were significantly elevated compared with those from control animals (p < 0.0001). Skin mast cell counts were increased (p < 0.05) and peritoneal mast cell histamine content decreased (p < 0.05) in jaundiced animals. These results demonstrate that mast cells degranulate in biliary obstruction with consequent release of histamine into the systemic circulation. This may contribute to cholestatic pruritus. These data may have significant pharmacological implications in patients with obstructive jaundice.

Differential reactivity of human bronchoalveolar lavage mast cells to substance P

Substance P (SP) stimulates human skin and rodent mast cells. Since neuropeptide-mediated reflexes may be important in asthma, the ability of SP to stimulate human mast cells obtained at bronchoalveolar lavage (BAL) was examined. Routine BAL (n = 22) samples were obtained and histamine release experiments performed in a standard manner. Spontaneous histamine release was bimodally distributed (Group A, high spontaneous release/Group B, normal spontaneous release). Further, Group A had significantly elevated corrected SP-induced histamine release compared to Group B but the corrected calcium ionophore A23187-induced responses were similar. No differences were found in clinical history, age, lavage return or total cell numbers between groups. However, differential cell counts revealed significantly elevated mast cell numbers in Group A providing further evidence for altered mast cell responsivity associated with mast cell hyperplasia. In asthma, BAL mast cells have increased spontaneous and stimulated secretory responses; thus, in asthma SP may also stimulate pulmonary mast cells.

Pilocarpine-induced convulsions in rats: evidence for muscarinic receptor-mediated activation of locus coeruleus and norepinephrine release in cholinolytic seizure development

We recently reported that systemic administration of the anticholinesterase, soman, caused rapid depletion of forebrain norepinephrine (NE) in convulsive but not in nonconvulsive rats. As neurons in nucleus locus coeruleus (LC) provide the bulk of NE innervation to most of the forebrain and the sole source of NE input to the cortex and the olfactory bulb, soman-induced NE depletion was hypothesized to result from activation of LC neurons. This activation was thought to be due to inhibition of acetylcholinesterase by soman, leading to rapid, sustained accumulation of acetylcholine in LC, causing these cells to fire at a high sustained rate. Support for this hypothesis was provided by neurophysiological findings showing that: (i) Systemic administration of soman in anesthetized rats caused a sustained, fivefold increase in the mean firing rate of LC neurons and (ii) microinjections of soman directly into LC caused a similar increase in the firing rate of LC neurons. Soman-induced activation of LC occurred prior to and even in the absence of seizures. As systemic administration of the muscarinic receptor antagonist, scopolamine, rapidly and completely reversed soman-induced activation of LC, it was further hypothesized that activation of LC neurons following soman administration is due to muscarinic receptor stimulation. The rapid release of NE by cholinolytic agents, thus, may play an important role in the initiation and/or maintenance of convulsions. To further test the hypothesis that NE release in soman-intoxicated rats is due to muscarinic activation of LC, we have investigated the effects of the muscarinic receptor agonist, pilocarpine, on NE release and LC discharge. In one set of experiments, rats were injected with a periconvulsive dose of pilocarpine (300 mg/kg, ip); both convulsive and nonconvulsive rats were sacrificed between 1 and 96 h and monoamine levels in the rostral forebrain and olfactory bulb were determined by HPLC with electrochemical detection. NE levels declined substantially only in convulsive rats; forebrain NE levels in convulsive rats rapidly decreased to 50% of control levels at 1 h and to 37% of controls level between 2 and 4 h. The time course and magnitude of these changes were similar to those observed following soman administration in our previous study. Recovery of forebrain NE began at 8 h and was complete by 96 h following pilocarpine administration. Neither dopamine (DA) nor serotonin (5-HT) levels were changed in the forebrain and olfactory bulb of either convulsive or nonconvulsive rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Delayed cutaneous fluid leak from the puncture hole after removal of an epidural catheter

A case of a delayed but persistent cutaneous fluid leak from a puncture hole following removal of an epidural catheter is presented. The fluid was subsequently found not to be cerebrospinal but interstitial oedema fluid. This case demonstrates the importance of performing simple investigations on any such fluid before ordering more complex tests.

Physiological influence of lateral proisocortex on the midbrain periaqueductal gray: evidence for a role of an excitatory amino acid in synaptic activation

Recent anatomical studies in this laboratory have demonstrated that the proisocortex cortex adjacent and dorsal to the rhinal sulcus is one of the major forebrain afferent inputs to the midbrain periaqueductal gray matter in the rat. The physiological influence(s) of this projection has not been examined. The present studies investigated the responses of periaqueductal gray neurons to chemical and electrical stimulation of proisocortex in chloral hydrate-anesthetized rats. In addition, the role of glutamate as a possible transmitter in excitatory proisocortex-periaqueductal gray synaptic responses was tested. Microinjection of D,L-homocysteate into proisocortex excited 44% (19/43), inhibited 37% (16/43) and had no effect on 19% of periaqueductal gray cells. The onset of D,L-homocystic acid-evoked responses ranged from 2 to 60 s; the duration of responses ranged from 1 to 18 min. Low-frequency, single-pulse electrical stimulation of proisocortex robustly altered neuronal discharge in 25% of periaqueductal gray neurons sampled; 10% (74/724) of neurons were excited and 15% (107/724) were inhibited. Insular cortex-evoked excitatory responses had a mean onset latency of 19.5 +/- 4.2 ms and a mean duration of 38.5 +/- 26.9 ms. Inhibitory responses had a mean onset latency of 26.2 +/- 15.6 ms and mean duration of 108.0 +/- 84.9 ms. Trains of high-frequency electrical stimulation of proisocortex excited 22% (13/59) and inhibited 25% (15/59) of periaqueductal gray cells tested. In separate experiments, stimulation electrodes were placed in periaqueductal gray to antidromically activate proisocortex neurons that project to periaqueductal gray.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of locus coeruleus neurons by nucleus paragigantocellularis or noxious sensory stimulation is mediated by intracoerulear excitatory amino acid neurotransmission

The nucleus paragigantocellularis (PGi), located in the rostral ventrolateral medulla, is one of two major afferents to the nucleus locus coeruleus (LC). Electrical stimulation of PGi exerts a robust, predominantly excitatory influence on LC neurons that is blocked by intracerebroventricular (i.c.v.) administration of the broad spectrum excitatory amino acid (EAA) antagonists kynurenic acid (KYN) or gamma-D-glutamylglycine (DGG), but not by the selective N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoate (AP7). I.c.v. injection of KYN or DGG also blocked activation of LC neurons evoked by noxious somatosensory stimuli. These results indicate that activation of LC neurons by PGi and noxious stimuli may be mediated by an EAA acting at a non-NMDA receptor in LC. In the present study, microiontophoretic techniques were used to determine the sensitivity of LC neurons in vivo to the selective EAA receptor agonists kainate (KA), NMDA and quisqualate (QUIS). Microinfusion and microiontophoresis were also used to determine whether direct application of KYN, the preferential non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3 dione (CNQX) or the selective NMDA receptor antagonist 2-amino-5-phosphonovalerate (AP5) onto LC neurons blocked excitation elicited by stimulation of PGi or the sciatic nerve. The results demonstrated that individual LC neurons were robustly activated by direct application of KA, NMDA and QUIS. Iontophoretically applied KYN reduced or completely antagonized responses evoked by all 3 agonists. In contrast, iontophoretically applied AP5 strongly attenuated NMDA-evoked excitation, while KA-and QUIS-evoked responses were not affected by this agent. Furthermore, direct application of KYN or the specific non-NMDA receptor antagonist, CNQX, onto LC neurons substantially attenuated or completely blocked synaptic activation produced by PGi or sciatic nerve stimulation in nearly every LC neuron tested. Microinfusion of the selective NMDA receptor antagonist AP5 had no effect on sciatic nerve-evoked responses. These results confirm our hypothesis that activation of LC neurons from PGi is mediated by an EAA operating primarily at a non-NMDA receptor subtype on LC neurons. Furthermore, these findings provide additional support for the hypothesis that this pathway mediates at least some sensory-evoked responses of LC neurons.

Actions of epinephrine on neurons in the rat midbrain periaqueductal gray maintained in vitro

The effect of epinephrine (EPI) on the activity of 150 periaqueductal gray (PAG) neurons was examined using extracellular recordings in an in vitro slice preparation. Drop application of EPI inhibited 45%, excited 35%, and had no effect on 20% of PAG neurons. Both the excitatory and inhibitory effects of EPI were of long duration; excitatory responses averaged 17 min and inhibitory responses averaged 11 min in duration. EPI responses could be blocked by specific alpha-1 and alpha-2 receptor antagonists. In 35% of the neurons tested, blockade of synaptic transmission by perfusion with low calcium-high magnesium physiological saline blocked responses to EPI. The effects of EPI were site specific: 77% of the cells in the caudal ventrolateral region of the PAG were inhibited by EPI; in all other regions of PAG equal numbers of cells were excited and inhibited by EPI. It is concluded that: (a) EPI has potent effects on a majority (80%) of PAG neurons; (b) EPI responses are mediated by presynaptic as well as postsynaptic mechanisms; (c) EPI preferentially inhibits neurons in the ventrolateral subdivision of caudal PAG. As this part of PAG contains many neurons that project to the ventral medulla, it is possible that EPI modulates the PAG-medullary functions such as analgesia, autonomic regulation, defense reactions, and sexual behaviors.

Tonic activation of locus coeruleus neurons by systemic or intracoerulear microinjection of an irreversible acetylcholinesterase inhibitor: increased discharge rate and induction of C-fos

Recent studies in this laboratory have demonstrated that intramuscular injection of the irreversible acetylcholinesterase (AChE) inhibitor, soman (pinacolylmethylphosphonofluoridate), produces a rapid (1-2 h) and profound depletion (70% of control) of norepinephrine (NE) in the olfactory bulb and forebrain. NE is decreased only in convulsing animals. As NE-containing locus coeruleus (LC) neurons provide the only NE input to the olfactory bulb and the major NE innervation of the forebrain, the reduction of NE suggests that soman may cause tonic activation of LC neurons leading to rapid depletion of NE. Activation of LC may result from: (i) facilitation of cholinergic transmission in LC; (ii) soman-induced activation of excitatory inputs to LC; or (iii) generalized activation of LC neurons due to seizures. The present experiments were designed to assess these alternatives. We examined whether LC neuronal activity, c-fos expression, and AChE staining are altered after peripheral (systemic) or direct intracoerulear injection of soman in anesthetized rats. Both modes of soman administration rapidly and potently increase the spontaneous discharge rate of LC neurons. This activation was associated with a desynchronization of the electroencephalogram, but not with seizures. The discharge of LC neurons remained elevated at all postsoman intervals examined (up to 2 h) and was rapidly and completely reversed by systemic injection of the muscarinic receptor antagonist scopolamine hydrochloride, but not by the nicotinic receptor antagonist mecamylamine. Both systemic and intracoerulear soman administration completely inhibited AChE staining in LC and rapidly induced the expression of c-fos in LC neurons. These results demonstrate that soman potently and tonically activates LC neurons. This effect appears to be mediated by direct inhibition of AChE in LC leading to a rapid accumulation of ACh. Unhydrolyzed ACh tonically activates LC neurons via muscarinic receptors. Soman-induced activation of LC neurons does not require seizures. We conclude that depletion of forebrain and olfactory bulb NE after systemic administration of soman results from tonic hypercholinergic stimulation of LC.

Brain norepinephrine reductions in soman-intoxicated rats: association with convulsions and AChE inhibition, time course, and relation to other monoamines

The organophosphate chemical nerve agent, soman, causes convulsions, neuropathology, and, ultimately, death. A major problem in treating soman intoxication is that peripherally acting pharmacological agents which prevent death do not prevent seizures. Although a primary cause of these symptoms is the excess of acetylcholine which follows acetylcholinesterase (AChE) inhibition, centrally acting muscarinic blockers, such as atropine, alleviate, but do not block, the convulsive actions of soman. Moreover, there is a relatively weak relationship between CNS reductions of AChE and the incidence of convulsions. There is evidence suggesting that soman intoxication stimulates the release of norepinephrine (NE) in the brain. Recent evidence has implicated NE in the induction and/or maintenance of seizures. Thus, in the present study the relations among soman-induced convulsions, AChE inhibition, and brain NE and other monoamine changes were examined. The time course of brain NE recovery was also determined. Rats were injected (im) with a single dose (78 micrograms/kg) of soman. At this dose 68% of the injected rats developed convulsions. Both convulsive and nonconvulsive rats were sacrificed between 1 and 96 h following soman injection and NE levels in the rostral forebrain and olfactory bulb were determined by HPLC with electrochemical detection. In all convulsive rats NE levels declined substantially. Forebrain NE levels were decreased by 50% at 1 h and 70% at 2 h following soman injection. Recovery of NE began at 8 h and was complete by 96 h following soman administration. Although nonconvulsive rats showed other signs of intoxication, NE levels in these rats were unchanged. Dopamine (DA) and serotonin (5-HT) levels were not significantly affected in either convulsive or nonconvulsive rats. However, 5-hydroxyindoleacetic acid, the major metabolite of 5-HT, and homovanillic acid and 3,4-dihydroxyphenylacetic acid, the two major metabolites of DA, were increased significantly in the forebrain of convulsive, but not nonconvulsive rats, indicating an increase in 5-HT and DA turnover. However, in contrast to the abrupt decline in NE, these increases in DA and 5-HT metabolites were slow and progressive. Taken together, the present results and other recent findings suggest that rapid, sustained NE release could play a role in the induction and/or maintenance of soman-induced convulsions, whereas increased release of 5-HT and DA may be a consequence of seizures. Further investigation of the role of NE in soman-induced convulsions may lead to improved treatment of soman intoxication and a better understanding of the role of NE in other forms of seizures, including human epilepsy.

Inhibition of noradrenergic locus coeruleus neurons by C1 adrenergic cells in the rostral ventral medulla

Recent anatomical and physiological experiments indicate that the nucleus locus coeruleus receives a predominant excitatory amino acid input, as well as a substantial inhibitory input, from the nucleus paragigantocellularis in the ventrolateral medulla. To determine whether C1 adrenergic neurons are involved in the inhibitory projection, the effects of the alpha-2 adrenoceptor antagonist, idazoxan, on inhibitory responses of locus coeruleus neurons to paragigantocellularis stimulation were characterized in the rat. Intravenous administration of idazoxan (0.2-1 mg/kg) attenuated paragigantocellularis-evoked inhibition, and often revealed an underlying weak excitation. Intraventricular administration of kynurenate, an excitatory amino acid antagonist, eliminated excitation from paragigantocellularis and disclosed an underlying inhibitory response in many locus coeruleus neurons that were previously excited by paragigantocellularis stimulation. These results revealed that about 90% of locus coeruleus neurons receive inhibition from the paragigantocellularis. Intravenous idazoxan significantly reduced such paragigantocellularis-evoked inhibition, completely blocking this response in three of eight locus coeruleus cells tested. Idazoxan was much more potent when locally infused into the locus coeruleus. Local infusion of idazoxan (0.1-2.5 ng) into locus coeruleus produced a dose-dependent decrease of paragigantocellularis-evoked inhibition and completely blocked the inhibition in 10/33 locus coeruleus neurons, indicating that the site of idazoxan action was in the locus coeruleus. These results extend our previous anatomical studies of adrenergic input to locus coeruleus, and indicate that C1 adrenergic neurons in the paragigantocellularis provide a direct inhibitory input to the great majority of locus coeruleus noradrenergic neurons. In addition, this is the first report of a neuronal response to activation of C1 adrenergic cells indicating that these neurons are strongly inhibitory when acting at alpha-2 receptors in vivo.

Reciprocal connections between the medial preoptic area and the midbrain periaqueductal gray in rat: A WGA-HRP and PHA-L study

The midbrain periaqueductal gray (PAG) participates in diverse functions such as analgesia, autonomic regulation, sexual behavior, and defense/escape responses. Anatomical studies of the circuits involved in such functions have largely focused on the connections of PAG with the medulla. Projections to PAG from forebrain structures are extensive, but their organization has received little attention. Previous anatomic studies indicate that the medial preoptic area (MPO), involved in a variety of physiological and behavioral functions, is a major source of afferent input to the periaqueductal gray. Here, we have examined the topography of reciprocal connections between these two structures in the rat by using wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) and Phaseolus vulgaris leucoagglutinin (PHA-L). Multiple WGA-HRP injections at several rostrocaudal levels of PAG retrogradely labeled large numbers of neurons in the medial preoptic area; labeled cells were primarily located in the medial preoptic nucleus, the median preoptic nucleus, and the region lateral to the medial preoptic nucleus. The distribution of labeled cells shifted medially to laterally along the rostral to caudal axis of the medial preoptic area. Rostrally, there was selective retrograde labeling in the central and lateral divisions of medial preoptic nucleus, whereas caudally, labeled cells were primarily located only in the lateral subdivision of medial preoptic nucleus. Tracer injections in PAG also produced strong anterograde labeling in MPO. WGA-HRP and PHA-L injections in the medial preoptic area resulted in dense anterograde labeling along the entire rostrocaudal axis of PAG. The terminal labeling in PAG from the medial preoptic area was not uniformly distributed throughout PAG, however. Instead, this projection formed one or two rostrocaudally oriented longitudinal columns that terminated in different subregions of PAG along the entire rostrocaudal axis of this structure. Rostrally, inputs from the medial preoptic area project heavily to dorsomedial PAG, and at mid-PAG levels, the projection becomes distinctly bipartite with two discrete longitudinal terminal columns in dorsomedial and lateral PAG; caudally, the heaviest labeling is in ventrolateral PAG. The projection also exhibited a central to peripheral (radial) gradient; labelled fibers and terminals were heaviest near the aqueduct and much lower in the peripheral parts of PAG. WGA-HRP injections in MPO also produced retrograde labeling of neurons at all rostrocaudal levels of PAG; more neurons were labeled in the rostral than the caudal half of PAG. The majority of labeled cells were located in dorsomedial and ventral/ventrolateral parts of PAG; only a few neurons in the dorsal raphe region appear to project to MPO.(ABSTRACT TRUNCATED AT 400 WORDS)

Intravascular anti-IgE challenge in perfused lungs: mediator release and vascular pressor response

Intravascular application of goat anti-rabbit immunoglobulin E (IgE) was used to stimulate parenchymal mast cells in situ in perfused rabbit lungs. Sustained pulmonary arterial pressure rise was evoked in the absence of lung vascular permeability increase and lung edema formation. Early prostaglandin (PG) D2 and histamine release into the perfusate was documented, accompanied by more sustained liberation of cysteinyl leukotrienes (LT), LTB4, and PGI2. The quantities of these inflammatory mediators displayed the following order: histamine greater than cysteinyl-LT greater than PGI2 greater than LTB4 greater than PGD2. Pressor response and inflammatory mediator release revealed corresponding bell-shaped dose dependencies. Cyclooxygenase inhibition (acetylsalicylic acid) suppressed prostanoid generation, increased LT release, and did not substantially affect pressor response and histamine liberation. BW755 C, a cyclo- and lipoxygenase inhibitor, blocked the release of cysteinyl-LT and markedly reduced the liberation of the other inflammatory mediators as well as the pressor response. The H1-antagonist clemastine caused a moderate reduction of the anti-IgE-provoked pressure rise. We conclude that intravascular anti-IgE challenge in intact lungs provokes the release of an inflammatory mediator profile compatible with in situ lung parenchymal mast cell activation. Pulmonary hypertension represents the predominant vascular response, presumably mediated by cysteinyl-LT and, to a minor extent, histamine liberation.

Change in obstetric practice in response to fear of litigation in the British Isles

The increased number of medical negligence claims against obstetricians and gynaecologists has led to concerns about a trend towards defensive medical practice in the UK. The attitudes of obstetricians in the British Isles to tests of fetal and maternal wellbeing, which may influence decisions about patient care, were investigated in 3194 Fellows and Members of the Royal College of Obstetricians and Gynaecologists. Perceived accuracy of tests ranged from 86.3% for fetal blood sampling to 25.9% for biochemical tests. Despite some tests being perceived as having poor accuracy, all were widely used even by those who deemed them inaccurate. The most frequent explanations given for this paradoxical finding were that such tests were an aid to clinical judgement and were necessary for medicolegal reasons. Our data indicate that tests deemed to be inaccurate are used in clinical practice because some obstetricians fear litigation. Our findings were not influenced by age, gender, grade of doctor, or site of practice.

Subregions of the periaqueductal gray topographically innervate the rostral ventral medulla in the rat

Previous anatomical and physiological studies have revealed a substantial projection from the periaqueductal gray (PAG) to the nucleus paragigantocellularis (PGi). In addition, physiological studies have indicated that the PAG is composed of functionally distinct subregions. However, projections from PAG subregions to PGi have not been comprehensively examined. In the present study, we sought to examine possible topographic specificity for projections from subregions of the PAG to PGi. Pressure or iontophoretic injections of wheat germ agglutinin-conjugated horseradish peroxidase, or of Fluoro-Gold, placed into the PGi of the rat retrogradely labeled a substantial number of neurons in the PAG from the level of the Edinger-Westphal nucleus to the caudal midbrain. Retrogradely labeled neurons were preferentially aggregated in distinct subregions of the PAG. Rostrally, at the level of the oculomotor nucleus, labeled neurons were i) compactly aggregated in the ventromedial portion of the PAG corresponding closely to the supraoculomotor nucleus of the central gray, ii) in the lateral and ventrolateral PAG, and iii) in medial dorsal PAG. More caudally, retrogradely labeled neurons became less numerous in the dorsomedial PAG but were more widely scattered throughout the lateral and ventrolateral parts of the PAG. Only few retrogradely labeled neurons were found in the ventromedial part of the PAG at caudal levels. Injections of retrograde tracers restricted to subregions of the PGi suggested topography for afferents from the PAG. Injections into the lateral portion of the PGi yielded the greatest number of labeled neurons within the rostral ventromedial PAG. Medially placed injections yielded numerous retrogradely labeled neurons in the lateral and ventrolateral PAG. Injections placed in the rostral pole of the PGi (medial to the facial nucleus) produced the greatest number of retrogradely labeled neurons in the dorsal PAG. To examine the pathways taken by fibers projecting from PAG neurons to the medulla, and to further specify the topography for the terminations of these afferents in the PGi, the anterograde tracer Phaseolus vulgaris-leucoagglutinin was iontophoretically deposited into subregions of the PAG that contained retrogradely labeled neurons in the above experiments. These results revealed distinct fiber pathways to the rostral medulla that arise from the dorsal, lateral/ventrolateral, and ventromedial parts of the PAG. These injections also showed that there are differential but overlapping innervation patterns within the PGi. Consistent with the retrograde tracing results, injections into the rostral ventromedial PAG near the supraoculomotor nucleus yielded anterograde labeling immediately ventral to the nucleus ambiguus in the ventrolateral medulla, within the retrofacial portion of the PGi.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of histamine release from peritoneal mast cells derived from diabetic and control rats

Clinical and experimental diabetes are associated with an increased number of mast cells and elevated tissue histamine concentrations. This study compared histamine release from peritoneal mast cells derived from diabetic and control rats. Experimental diabetes was induced by a single i.v. injection of streptozotocin (50 mg/kg body weight). Measurement of plasma glucose levels confirmed the diabetic state. Peritoneal mast cells were stimulated for 10 min with the lectin concanavalin A (0.5-100 micrograms/ml) in the presence or absence of phosphatidylserine, clinical dextran (0.6-1200 micrograms/ml) in the presence of phosphatidylserine, the calcium ionophore A23187 (0.1-1 microM) or the basic releasing agent compound 48/80 (0.1-10 micrograms/ml). Histamine release induced by these agents was similar in both populations. Further studies will compare the differences in histamine release from mast cells isolated from different tissues, e.g. heart and lung. In addition, physiological stimuli which are altered in the diabetic state (e.g. hyperosmolalar solutions and free radical generating systems) are under investigation.

Histamine release induced by opioid analgesics: a comparative study using porcine mast cells

Studies in vitro have demonstrated histamine release induced by opioid analgesics from rat peritoneal mast cells and human skin mast cells. In humans, elevated plasma histamine levels have also been found following intravenous or oral administration. This study compared the reactivity of five opioid analgesics on mast cell suspensions obtained from porcine heart, kidneys, liver and lungs. The five compounds investigated were hydromorphone, levomethadone, morphine, pethidine and oxycodone. Both morphine and hydromorphone produced little histamine release from all cell types tested. The other drugs demonstrated clear differences between the different cell populations. Thus, the cardiac cells responded most strongly to oxycodone but were the least responsive to pethidine. These differences, if confirmed in vivo, could indicate which drugs may be more suitable for patients with different underlying disease states.

In vitro and in vivo studies of radiographic contrast media-induced histamine release in pigs

Routine clinical use of radiographic contrast media (RCM) causes adverse reactions in some patients. To elucidate the mechanisms of these reactions both in vitro and in vivo studies are necessary. In this study, RCM-induced histamine release from isolated mast cells was compared with the in vivo release of histamine and cardiovascular symptoms using a porcine model. The 2 non-ionic preparations examined (Solutrast and Ultravist) released little or no histamine from the 4 cell types tested (porcine pulmonary, cardiac, hepatic, and renal mast cells). The 4 ionic preparations (Angiographin, Hexabrix Rayvist, and Telebrix) caused histamine release from most of the cell suspensions. In almost all cases, the cardiac mast cells were the most sensitive followed by the hepatic mast cells. All 4 RCM tested in vivo produced elevated plasma histamine levels in some animals. The highest incidence was observed using the ionic, high osmolal Rayvist (6 of 12 animals), followed by the non-ionic RCM with the lowest osmolality Ultravist (4 of 12 animals). In vivo, mechanisms in addition to direct histamine release may also be involved in RCM-induced adverse reactions, since low osmolal, non-ionic RCM can cause elevated plasma histamine levels without in vitro release. The susceptibility of cardiac mast cells to RCM-induced histamine release suggests that patients undergoing e.g. coronary angiography may be especially at risk for an adverse reaction.

Projections from the periaqueductal gray to the rostromedial pericoerulear region and nucleus locus coeruleus: anatomic and physiologic studies

Previous studies showed that the nucleus locus coeruleus (LC) receives two major afferent inputs from 1) nucleus paragigantocellularis and 2) nucleus prepositus hypoglossi, both in the rostral medulla. Recent reports suggested that the midbrain periaqueductal gray (PAG) projects to the rostromedial pericoerulear area and LC. Since the PAG is a major site for control of central antinociception, and since descending noradrenergic fibers have been implicated in pain modulation, we have investigated in detail the functional anatomy of projections from PAG to the dorsolateral pontine tegmentum. A combined anatomical and electrophysiological approach was used to assess the organization and synaptic influence of PAG on neurons in the rostromedial pericoerulear region and in LC proper. Injections of the tracer wheatgerm agglutinin conjugated to horseradish peroxidase encompassing LC proper and the rostromedial pericoerulear area retrogradely labeled neurons in PAG located lateral and ventrolateral to the cerebral aqueduct; injections restricted to LC proper did not consistently label PAG neurons. Deposits of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin into this same region of PAG labeled axons that robustly innervated the zone rostral and medial to LC. Only sparse fibers were observed in LC proper. Consistent with these results, focal electrical stimulation of LC antidromically activated only a few PAG neurons (6 of 100); all of these driven cells were located lateral and ventrolateral to the cerebral aqueduct. The majority of neurons in the rostromedial pericoerulear area were robustly activated by single pulse stimulation of PAG. In contrast, single pulse electrical stimulation of lateral PAG produced weak to moderate synaptic activation of some LC neurons; stimulation of ventrolateral PAG produced predominant inhibition of LC discharge, perhaps through recurrent collaterals subsequent to antidromic activation of neighboring LC cells. Taken together, these results indicate that PAG strongly innervates the region rostral and medial to LC, including Barrington's nucleus, but only weakly innervates LC proper. Although recent studies indicate that the dendrites of LC neurons ramify heavily and selectively in the rostromedial pericoerulear region, the results of the present physiological studies suggest that PAG preferentially targets rostromedial pericoerulear neurons rather than LC dendrites.

Obstetric accidents: the patient's perspective

Cases from the files of Action for Victims of Medical Accidents which had resulted in stillbirth, perinatal or neonatal death and long term mental or physical handicap were reviewed. In 41 cases there was both a detailed letter from the parents and an independent review by a senior obstetrician. The reviewer's main criticisms were of inadequate fetal heart monitoring, lack of involvement of senior staff and inadequate records. The fetal heart trace was missing in 7 cases and over half of the remaining 34 traces available were misinterpreted or not acted on. In 17 cases junior doctors failed to recognize fetal distress and managed a delivery that they did not have the experience to deal with. In a further 6 cases, senior staff were called but did not come. Records were criticized for being incomplete, illegible or missing. In a few cases unjustified alterations appeared to have been made. Women reported that on some occasions staff ignored their worries, were unsympathetic and gave too little information. Some parents also experienced considerable difficulty in obtaining a clear explanation of the nature and cause of their child's condition.

Afferent regulation of locus coeruleus neurons: anatomy, physiology and pharmacology

Tract-tracing and electrophysiology studies have revealed that major inputs to the nucleus locus coeruleus (LC) are found in two structures, the nucleus paragigantocellularis (PGi) and the perifascicular area of the nucleus prepositus hypoglossi (PrH), both located in the rostral medulla. Minor afferents to LC were found in the dorsal cap of the paraventricular hypothalamus and spinal lamina X. Recent studies have also revealed limited inputs from two areas nearby the LC, the caudal midbrain periaqueductal gray (PAG) and the ventromedial pericoerulear region. The pericoeruleus may provide a local circuit interface to LC neurons. Recent electron microscopic analyses have revealed that LC dendrites extend preferentially into the rostromedial and caudal juxtaependymal pericoerulear regions. These extracoerulear LC dendrites may receive afferents in addition to those projecting to LC proper. However, single-pulse stimulation of inputs to such dendritic regions reveals little or no effect on LC neurons. Double-labeling studies have revealed that a variety of neurotransmitters impinging on LC neurons originate in its two major afferents, PGi and PrH. The LC is innervated by PGi neurons that stain for markers of adrenalin, enkephalin or corticotropin-releasing factor. Within PrH, large proportions of LC-projecting neurons stained for GABA or met-enkephalin. Finally, in contrast to previous conclusions, the dorsal raphe does not provide the robust 5-HT innervation found in the LC. We conclude that 5-HT inputs may derive from local 5-HT neurons in the pericoerulear area. Neuropharmacology experiments revealed that the PGi provides a potent excitatory amino acid (EAA) input to the LC, acting primarily at non-NMDA receptors in the LC. Other studies indicated that this pathway mediates certain sensory responses of LC neurons. NMDA-mediated sensory responses were also revealed during local infusion of magnesium-free solutions. Finally, adrenergic inhibition of LC from PGi could also be detected in nearly every LC neuron tested when the EAA-mediated excitation is first eliminated. In contrast to PGi, the PrH potently and consistently inhibited LC neurons via a GABAergic projection acting at GABAA receptors within LC. Such PrH stimulation also potently attenuated LC sensory responses. Finally, afferents to PGi areas that also contain LC-projecting neurons were identified. Major inputs were primarily autonomic in nature, and included the caudal medullary reticular formation, the parabrachial and Kölliker-Fuse nuclei, the PAG, NTS and certain hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Connections between the central nucleus of the amygdala and the midbrain periaqueductal gray: topography and reciprocity

Previous reports indicate that the midbrain periaqueductal gray and the central nucleus of the amygdala are interconnected but the organization of these projections has not been characterized. We have analyzed this reciprocal circuitry using anterograde and retrograde tracing methods and image analysis. Our findings reveal that innervation of periaqueductal gray from the central nucleus of the amygdala is extensive and discretely organized along the rostrocaudal axis of periaqueductal gray. In addition, the reciprocal projection from periaqueductal gray to the central nucleus of the amygdala is more extensive and more highly organized than previously suggested. Multiple or single discrete injections of wheatgerm agglutinin-horseradish peroxidase into several rostrocaudal levels of periaqueductal gray retrogradely labeled a substantial population of neurons, predominantly located in the medial division of the central nucleus of the amygdala. Tracer injections into the central nucleus revealed a high degree of spatial organization in the projection from this nucleus to periaqueductal gray. Two discrete longitudinally directed columns in dorsomedial and lateral/ventrolateral periaqueductal gray are heavily targeted by central amygdalar inputs throughout the rostral one-half to two-thirds of periaqueductal gray. Beginning at the level of dorsal raphe and continuing caudally, inputs from the central nucleus terminate more uniformly throughout the ventral half of periaqueductal gray. In addition, a substantial population of periaqueductal gray neurons were retrogradely labeled from the central nucleus of the amygdala; these were heterogeneously distributed along the rostrocaudal axis of periaqueductal gray, and included both raphe and non-raphe neurons. Thus, the present study demonstrates that periaqueductal gray receives heavy, highly organized projections from the central nucleus of the amygdala and, in turn, has reciprocal connections with the central nucleus. Previous studies have demonstrated that longitudinally organized columns of output neurons located in dorsomedial and lateral/ventrolateral periaqueductal gray project to the ventral medulla. Thus, there may be considerable overlap between the two longitudinally organized terminal input columns from the central nucleus of the amygdala and the two longitudinal columns of descending projection neurons from periaqueductal gray to the ventral medulla. The central nucleus of the amygdala has been implicated in a variety of emotional/cognitive functions ranging from fear and orienting responses, defensive and aversive reactions, associative conditioning, cardiovascular regulation, and antinociception. Many of these same functions are strongly represented in the periaqueductal gray. It is noteworthy that the present results demonstrate that lateral periaqueductal gray, a preeminent central trigger site for behavioral and autonomic components of the defense/aversion response, is heavily targeted by inputs from the central nucleus of the amygdala at all levels of periaqueductal gray.(ABSTRACT TRUNCATED AT 400 WORDS)

Perioperative uses of histamine antagonists

Histamine release and adverse pseudoallergic/allergic reactions during the perioperative period occur frequently. The incidence of such reactions is 20%-30% for all grades of severity, 1%-5% for systemic reactions, and 0.1%-0.5% for life-threatening reactions. They can be elicited by all commonly used anesthetic agents and by surgical interventions. Both the incidence and severity can be reduced by the use of combined prophylaxis with H1- + H2-receptor antagonists. The authors recommend that this prophylaxis be given to the following groups of patients: those with a history of adverse reactions or history of allergy, patients undergoing surgery with a high risk of histamine release, elderly patients, and those with poor physical status due to underlying systemic diseases. These indications have been developed by heuristic medical decision-making, including a decision tree.

Obstetric accidents: a review of 64 cases

OBJECTIVE

To identify the causes of obstetric accidents.

DESIGN AND SETTING

Analysis of case records at the Medical Protection Society's London office covering the five years 1982-6.

SUBJECTS

Cases that had come to litigation which had resulted in stillbirth, perinatal or neonatal death, central nervous system damage to the baby, or maternal death and in which there was an opinion from a senior obstetrician consulted by the society. Of 147 cases reviewed, 64 met the criteria for the study.

MAIN OUTCOME MEASURES

The principal findings of the expert reviewers.

RESULTS

Three major topics of concern emerged common to most of the 64 cases. These were inadequate fetal heart monitoring, mismanagement of forceps, and inadequate supervision by senior staff. In 11 of the 64 cases cardiotocography was omitted, in 19 cases the trace was missing, in six cases the trace was unreadable, and in 14 of the remaining 28 cases signs of fetal distress went unnoticed or were ignored. In 31 cases forceps were used to aid delivery or were tried and abandoned in favour of caesarean section. In 16 cases two or more attempts to use forceps were made. Five infant deaths were directly attributed to mismanaged forceps. In 20 cases senior staff were criticised by the expert reviewer for failure to come to the labour ward. In many of these cases they may have given advice over the telephone, but the inadequacy of records made it impossible to tell. In these cases the labour and birth were managed by junior staff, usually a senior house officer. In six cases when senior staff did come they suggested that no action was needed.

CONCLUSION

These few cases should not be dismissed as isolated incidents in obstetric practice in Britain. They reflect more general problems--namely, concerning the ability of junior doctors to interpret fetal heart traces accurately, their ability to use forceps, and the participation of senior staff in running a labour ward and delivery suite.

Histamine release and pseudoallergic reactions induced by radiographic contrast media: comparison of Angiographin, Hexabrix and Telebrix using an in vivo canine model

Radiographic contrast media (RCM) in clinical use cause unwanted allergic/pseudoallergic reactions of all grades of severity. They also induce histamine release from a variety of mast cell populations, the extent of the histamine release reaction depending on both the organ and species. In this study 3 RCM, which had been previously shown to be effective histamine releasing agents with canine liver cells, were investigated using an in vivo canine model based on the clinical situation. The dogs (n = 36) were randomly allocated to one of 3 treatment groups and received a bolus injection (2 ml/kg body weight) of either Angiographin, Hexabrix or Telebrix. Blood pressure was monitored continuously and blood sampling, for plasma histamine measurements, was performed before and 1, 5, 10, 20 and 30 min after RCM injection. All 3 RCM caused elevated plasma histamine levels in some animals: Angiographin 9 of 12 dogs, 0.40 ng/ml, (0-1.9 ng/ml) median (range); Hexabrix 11/12, 0.5 ng/ml (0-3.8 ng/ml); Telebrix 7/12, 0.4 ng/ml (0-2.0 ng/ml). Cardiovascular reactions were observed in most animals. The hypotensive reactions occurred with a maximum 30 sec after RCM application and recovery was normally observed after 1-1.5 min. The response after Angiographin or Telebrix was significantly greater than after Hexabrix. Hypertensive reactions occurred later (15 min (5-25 min)) and did not differ between the groups. All 3 agents tested were able to elicit histamine release and cardiovascular reactions. In comparison to histamine release occurring after intravenous administration of other agents, such as hypnotics, the degree of histamine release was small.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma histamine levels in polytraumatized patients

In a prospective clinical trial, plasma histamine levels were measured in 28 polytrauma patients on day 1, 5 and 14 after trauma. Only those subjects who died were drop-outs. All patients had severe polytrauma with at least 3 body regions involved. The median plasma histamine levels at all three time points were significantly higher than in patients with single trauma of the extremities or before selective orthopaedic surgery but still in the normal range (less than 1 ng/ml). However, all patients with plasma levels above 1 ng/ml on days 1 and 5 died, as did all patients with levels above 0.5 ng/ml on day 1. Thus the elevation of plasma histamine levels, for whatever reason, appears to be a prognostic factor for bad outcome in polytrauma patients.

Visual detection of peptidase activity using fluorogenic substrates in a microtiter plate assay

A simple, inexpensive, and sensitive assay for peptidase activity has been devised. The assay was performed in a microtiter plate and was based on fluorogenic peptide substrates, many of which are commercially available. 7-Amino-4-methyl coumarin the fluorescent product liberated during an incubation period of between 1 and 16 h, was detected by inspection of the plate under ultraviolet light of wavelength 356 nm. A fluorometer was not required. Using alpha-chymotrypsin as a model enzyme, with succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanine 4-methyl-coumaryl-7-amide as substrate, it was shown that as little as 4 fmol of enzyme could be detected. The method was non-quantitative and was particularly suited to location of enzyme activity in fractions during a purification procedure. The validity of the assay was demonstrated by detection of activity of a known enzyme, alpha-chymotrypsin, after its purification by size-exclusion high-performance liquid chromatography. The method was used to locate two forms of aminopeptidase activity, in fractions from size-exclusion chromatography of an extract from reproductive tissue of Helix aspersa, using L-leucine 4-methyl-coumaryl-7-amide as substrate.

A double-labeling method for AChE and fluorescent retrograde tracers

Staining for the degradative enzyme acetylcholinesterase (AChE) is an important tool in studying central cholinergic/cholinoceptive systems. AChE staining has also been useful in identifying the projections of AChE-containing neurons and codistribution of AChE with other neurotransmitters. The intensity and opacity of conventional AChE histochemical reaction products, however, pose problems for such double-labeling studies. Here, we have successfully combined a modified version (37) of the Koelle-Friedenwald AChE reaction with retrograde transport of the fluorescent tracer, Fluoro-Gold (FG). By omitting the final intensification steps of the Koelle-Friedenwald reaction, a translucent, light-stable reaction product is created. Viewed under darkfield illumination, this precipitate is of similar intensity and sensitivity to that produced by conventional AChE histochemical processing. Prior administration of an AChE-inhibitor yields preferential staining of AChE-positive neuronal somata. This nonintensified darkfield AChE (NIDA) histochemical method was compatible with visualization of retrogradely transported FG in AChE-positive neurons, allowing unambiguous identification of the projections of AChE-containing neurons.

Acetylcholinesterase and Nissl staining in the same histological section

Acetylcholinesterase (AChE) enzyme histochemistry and Nissl staining are commonly utilized in neural architectonic studies. However, the opaque reaction deposit produced by the most commonly used AChE histochemical methods is not compatible with satisfactory Nissl staining. As a result, precise correlation of AChE and Nissl staining necessitates time-consuming comparisons of adjacent sections which may have differential shrinkage. Here, we have modified the Koelle-Friedenwald histochemical reaction for AChE by omitting the final intensification steps. The modified reaction yields a non-opaque reaction product that is selectively visualized by darkfield illumination. This non-intensified darkfield AChE (NIDA) reaction allows clear visualization of Nissl staining in the same histological section. This combined AChE-Nissl method greatly facilitates detailed correlation of enzyme and cytoarchitectonic organization.

GABA-mediated inhibition of locus coeruleus from the dorsomedial rostral medulla

Recent anatomic studies in our laboratory (Aston-Jones et al., 1986) identified the nucleus prepositus hypoglossi (PrH) in the dorsomedial medulla as a major afferent of the locus coeruleus (LC). In the present studies, the influence of projections from PrH to LC was assessed in anesthetized rats. Focal electrical stimulation of PrH inhibited the spontaneous discharge of 42 of 47 LC neurons; the latency to onset of such inhibition was 19.8 +/- 2.5 msec and its duration was 172.4 +/- 10.4 msec. PrH-evoked inhibition of LC neurons was unaffected by administration of the opiate receptor antagonist naloxone or the alpha 2-receptor antagonist idazoxan but was substantially reduced by systemic picrotoxin, an antagonist of GABA. The GABAA receptor antagonist bicuculline methiodide blocked the inhibition from PrH, whether applied by local microinfusion or iontophoresis into the LC. These results lead us to propose that PrH provides a direct inhibitory synaptic input to LC, for which GABA is the likely transmitter.

Potent inhibitory input to locus coeruleus from the nucleus prepositus hypoglossi

Previous studies reported afferents to LC from the nucleus tractus solitarius (NTS), while more recent anatomic experiments indicate that the area of the nucleus prepositus hypoglossi (PrH), but not the NTS, provides robust innervation of LC. In the present experiments, the contribution of these two dorsomedial medullary areas to LC innervation was assessed with electrophysiologic methods in anesthetized rats. Focal electrical stimulation of LC antidromically activated a substantial number of PrH neurons; such stimulation failed to antidromically activate NTS neurons. Electrical activation of PrH evoked potent, uniform inhibition of LC discharge. In contrast, NTS activation produced only weak, long latency responses in only a few LC neurons. In agreement with these results, WGA-HRP injections into NTS did not yield consistent anterograde labeling in LC. These results confirm our previous anatomic findings that PrH, but not NTS, provides major innervation of LC. Furthermore, the input from PrH potently inhibits LC activity.

Radiographic contrast media-induced histamine release: a comparative study with mast cells from different species

Radiographic contrast media in clinical use cause unwanted allergic and pseudoallergic reactions. To investigate the mechanisms of these reactions, studies on isolated mast cells from different species and sites are necessary. In this study, the effect of six commonly used contrast media on rat (peritoneal, lung) and human (lung) mast cells was investigated. The three preparations with low osmolalities (Hexabrix, Solutrast, Ultravist) released little or no histamine from the cells examined. In contrast, the three preparations with high osmolalities (Angiographin, Telebrix, Rayvist) were potent releasing agents. However, the degree of release and the order of potency was different depending on the cells investigated. Indeed, rat peritoneal mast cells required much higher concentrations before release was observed. Since the contrast media with low osmolality also cause histamine release and reactions in vivo, other systems (e.g. complement) must be additionally involved.

Histamine release from canine lung and liver mast cells induced by radiographic contrast media

Radiographic contrast media are commonly used diagnostic aids to improve imaging, e.g. in computerized tomography. However, the routine application of these agents may cause adverse allergic/pseudoallergic reactions. In order to understand more completely the underlying mechanisms involved in these reactions, experiments on histamine release both in vivo and in vitro are necessary. Using canine mast cell suspensions from lung and liver, we have investigated the histamine release caused by six commonly used preparations. The dog is an ideal model for both in vitro and in vivo studies not only by virtue of its size but also because of its similarity to man with respect to e.g. cardiovascular reactions after drug-induced histamine release. The two non-ionic preparations (Solutrast, Ultravist) released little histamine from both cell types (ca. 4-6%). The ionic contrast media (Angiographin, Hexabrix, Telebrix, Rayvist) dose-dependently released histamine from the liver cells and pulmonary cells (maximum release between 18-35%). The liver cells (the liver is the shock organ in the dog) reacted more strongly to these agents than the pulmonary cells, thus providing further evidence for mast cell heterogeneity and the importance of selecting the appropriate mast cell model for the investigation.

Activation of locus coeruleus from nucleus paragigantocellularis: a new excitatory amino acid pathway in brain

Recent anatomic and physiologic experiments revealed that a major afferent to the nucleus locus coeruleus (LC) is the nucleus paragigantocellularis (PGi) in the rostral ventrolateral medulla (Aston-Jones et al., 1986). In the present studies, responses of LC neurons to electrical activation of PGi were characterized in anesthetized rats. Low-intensity stimulation of PGi synaptically activated 73% of LC neurons at short latencies (mean onset, 11.3 msec), while a smaller population (16%) of LC neurons exhibited purely inhibitory responses. The excitatory transmission from PGi to LC was pharmacologically analyzed, revealing it to be resistant to cholinergic receptor antagonism, but completely abolished by the excitatory amino acid (EAA) antagonists kynurenic acid and gamma-D-glutamylglycine. The specific N-methyl-D-aspartate antagonist 2--amino-7-phosphonoheptanoic acid (AP7) and the preferential quisqualate receptor antagonist glutamate diethyl ester (GDEE) did not block LC responses to PGi stimulation, leading us to the tentative conclusion that EAAs may operate primarily at a kainate-type receptor on LC neurons to effect excitation from PGi. In addition to their blockade of PGi-evoked activity, kynurenic acid and DGG exerted a similar, simultaneous blockade of the characteristic excitation of LC neurons evoked by electrical stimulation of the hindpaw. These and other results indicate that the proposed EAA pathway from PGi may serve as a final link in a variety of sensory inputs to LC.

Prediction of risk for pseudoallergic reactions and histamine release in patients undergoing anaesthesia and surgery: a computer-aided model using independence-Bayes

A computer-aided model for the prediction of pseudoallergic reactions was developed using prospective data collected from 581 patients in a controlled clinical trial examining pseudoallergic reactions to the plasma substitute Haemaccel (outdated formulation). The multivariate analysis of 22 proposed risk factors was performed using Bayes theorem. This enabled the accurate prediction of 86% of the patients who had a systemic reaction. The clinical use of such system would enable a selection of patients to receive the effective prophylactic measure of pretreatment with H1 plus H2-receptor antagonists.

The effect of serine esterase inhibitors on ionophore-induced histamine release from human pulmonary mast cells

The serine proteases tryptase and chymase are present in human pulmonary mast cells. About 10-100 times more tryptase than chymase is found in these cells. However, a clear physiological role for both enzymes remains to be elucidated; angiotensin processing has been proposed as one possible function of chymase. A dose-dependent inhibition of A23187-induced histamine release from dispersed human lung mast cells was observed after pretreatment with the serine protease inhibitor diisopropylfluorophosphate (DFP) or the chymotrypsin-like enzyme inhibitor N-tosyl-L-phenylalanine chloromethylketone (TPCK) but not with the trypsin-like enzyme inhibitor N-tosyl-L-lysine chloromethylketone (TLCK). These results indicate that a chymase is probably an important factor in a late phase of human lung mast cell activation.

The role of chymase in ionophore-induced histamine release from human pulmonary mast cells

Human pulmonary mast cells contain the serine proteases tryptase and chymase. Chymase is present in much smaller quantities than tryptase. The definite physiological role of both enzymes remains to be elucidated, angiotensin processing has been proposed as one possible function of chymase. A dose-dependent inhibition of A 23187-induced histamine release from dispersed human lung mast cells was observed after pretreatment with diisopropylfluorophosphate (DFP) or 1-1-tosyamide-2-phenylethyl chloromethyl ketone (TPCK) but not with N-2-p-tosyl-1-lysine chloromethyl ketone (TLCK). In contrast, no inhibition was observed under the same conditions with isolated rat peritoneal mast cells. These results indicate that a chymase is probably an important factor in a late phase of human lung mast cell activation. Current work focuses on the isolation of human lung chymase to further investigate this topic.

Two physiologically distinct populations of neurons in the ventrolateral medulla innervate the locus coeruleus

Recent anatomic studies indicate that the nucleus paragigantocellularis (PGi), located in the rostral ventrolateral medulla, strongly innervates the locus coeruleus (LC) while no such input derives from the more caudally located lateral reticular nucleus (LRN). In the present study, focal electrical stimulation of the LC was used to antidromically activate neurons in the ventrolateral medulla. A substantial number of PGi neurons were antidromically driven from the ipsilateral LC, while antidromic activation was virtually absent in LRN. Furthermore, several physiologic properties of antidromically driven cells in PGi define two populations within this group of neurons afferent to LC. These findings provide physiologic confirmation of an anatomically identified input to LC.

Isolation of mast cells from rabbit lung and liver: comparison of histamine release induced by the hypnotics Althesin and propanidid

The enzyme collagenase was used to disperse rabbit lung and liver into their component cells. The resulting cell suspensions contained ca. 6.9% (lung) or 6.5% (liver) mast cells and were used in studies of histamine release without further purification. Both cell suspensions exhibited a low spontaneous release of histamine (ca. 6.6% lung, ca. 7.2% liver). Both cell types responded to challenge with anti-rabbit serum with a maximum release of the amine of ca. 22% (lung) and ca. 45% (liver). Concanavalin A challenge generally resulted in bell-shaped dose response curves, however some lung preparations did not respond. The rabbit cells were refractory to stimulation by Compound 48/80 and dextran. However a dose-dependent release of histamine was elicited after challenge with the detergents cremophor El, TN (12-hydroxystearic acid polymerized with ethylene oxide, degree of polymerization 15) and the hypnotics Althesin and propanidid. The maximum release observed depended on which cell preparation had been used. These results further emphasize the functional heterogeneity of mast cells from both different species and from different organs within the same species.

A potent excitatory input to the nucleus locus coeruleus from the ventrolateral medulla

Our recent anatomic experiments reveal major innervation of the nucleus locus coeruleus (LC) from the nucleus paragigantocellularis (PGi), located in the rostral ventrolateral medulla. In the present studies, low intensity, single pulse electrical stimulation of the PGi synaptically activated most LC neurons examined (69%), while a smaller percentage of LC cells (20%) exhibited pure inhibitory responses. Pharmacologic experiments suggest that the excitatory response may be mediated by an amino acid transmitter.