Inhaled concentrated ambient particles are associated with hematologic and bronchoalveolar lavage changes in canines

Pulmonary inflammatory and hematologic responses of canines were studied after exposure to concentrated ambient particles (CAPs) using the Harvard ambient particle concentrator (HAPC). For pulmonary inflammatory studies, normal dogs were exposed in pairs to either CAPs or filtered air (paired studies) for 6 hr/day on 3 consecutive days. For hematologic studies, dogs were exposed for 6 hr/day for 3 consecutive days with one receiving CAPs while the other was simultaneously exposed to filtered air; crossover of exposure took place the following week (crossover studies). Physicochemical characterization of CAPs exposure samples included measurements of particle mass, size distribution, and composition. No statistical differences in biologic responses were found when all CAPs and all sham exposures were compared. However, the variability in biologic response was considerably higher with CAPs exposure. Subsequent exploratory graphical analyses and mixed linear regression analyses suggested associations between CAPs constituents and biologic responses. Factor analysis was applied to the compositional data from paired and crossover experiments to determine elements consistently associated with each other in CAPs samples. In paired experiments, four factors were identified; in crossover studies, a total of six factors were observed. Bronchoalveolar lavage (BAL) and hematologic data were regressed on the factor scores. Increased BAL neutrophil percentage, total peripheral white blood cell (WBC) counts, circulating neutrophils, and circulating lymphocytes were associated with increases in the aluminum/silicon factor. Increased circulating neutrophils and increased BAL macrophages were associated with the vanadium/nickel factor. Increased BAL neutrophils were associated with the bromine/lead factor when only the compositional data from the third day of CAPs exposure were used. Significant decreases in red blood cell counts and hemoglobin levels were correlated with the sulfur factor. BAL or hematologic parameters were not associated with increases in total CAPs mass concentration. These data suggest that CAPs inhalation is associated with subtle alterations in pulmonary and systemic cell profiles, and specific components of CAPs may be responsible for these biologic responses.

Differential ability of transition metals to induce pulmonary inflammation

Transition metals are components of airborne particles and have been implicated in adverse health effects. The relative inflammatory potential of these metals is usually inferred from separate studies that focus on only one or a few individual metals. Comparisons of relative potency among several metals from these separate studies can be difficult. In one comprehensive study, we measured the pulmonary effects of equimolar doses of six metals in soluble form. Our purpose was to compare inflammatory potential and pulmonary toxicity among individual transition metals. Rats received saline, 0.1 or 1.0 micromol/kg of vanadium, nickel, iron(II), copper, manganese, or zinc as sulfates. Bronchoalveolar lavage (BAL) was performed at 0, 4, 16, or 48 h postinstillation. All treatments except V showed increased lactate dehydrogenase activity in BAL fluid; Cu- and Ni-exposed animals had the highest levels. Protein levels in BAL fluid were more than five times higher in Cu-exposed animals compared to other metal treatments at 16 and 48 h. At the 0.1 micromol/kg dose, only Cu induced significant neutrophilia at 16 and 48 h. For the 1.0 micromol/kg dose, all metals tested induced significant neutrophilia, with mean neutrophil numbers for Cu and Mn significantly higher compared to the other metals. At 48 h, neutrophil numbers were still elevated in all metal exposures. Only Mn caused substantial eosinophilia. At the 1.0 micromol/kg dose, only Cu induced macrophage inflammatory protein-2 (MIP-2) mRNA at 4 h. By 48 h, induction of MIP-2 mRNA was observed for all metal exposures except Cu, which subsequently returned to baseline levels. On an equimolar basis, Cu was the most proinflammatory metal, followed by Mn and Ni, while V, Fe(II), and Zn induced similar levels of inflammation. Overall, there were many similarities in the pulmonary responses of the metals we tested. However, we also observed divergent, metal-specific responses. These differential responses suggest that metals induce pulmonary inflammation by differing pathways or combinations of signals.

Urban air particulate inhalation alters pulmonary function and induces pulmonary inflammation in a rodent model of chronic bronchitis

Epidemiological studies have reported increased morbidity in human populations following inhalation of elevated levels of urban particulate matter. These responses are especially prevalent in populations with chronic obstructive pulmonary diseases, including chronic bronchitis. Toxicological studies have reported altered pulmonary function and increased pulmonary inflammation following particulate inhalation in the laboratory setting. However, most of these studies have utilized artificial particles that may not accurately mimic outdoor air pollutant conditions. Few studies have utilized actual urban air particle samples in inhalation studies. In the present study, the effects of inhaled concentrated urban air particulates on pulmonary function and pulmonary inflammation are addressed. Normal rats and rats with chronic bronchitis induced by approximately 200 ppm SO(2) for 6 wk were subsequently subjected to filtered air or concentrated air particles (CAPs). Twelve rats per group in 4 groups (48 rats total) were exposed for 5 h/day for 3 consecutive days. The CAPs aerosol levels were 206, 733, and 607 microg/m(3) (MMAD = 0.18 microm, sigma(g) = 2.9) on days 1, 2, and 3, respectively. Following the final day of exposure, pulmonary function parameters, including peak expiratory flow (PEF), tidal volume (TV), respiratory frequency (RF), and minute volume (MV), were measured and compared to preexposure baseline levels. Twenty-four hours following the final day of exposure, bronchoalveolar lavage was performed for total cell counts, differential cell counts, and total lavage protein levels. Pulmonary responses to CAPs in chronic bronchitic animals indicated a significant increase in tidal volume as well as peak expiratory flow. In CAPs-exposed animals without underlying bronchitis, significantly increased tidal volume was observed. Significant pulmonary inflammation was observed in the CAPs-exposed animals, particularly those with chronic bronchitis. Significant increases in neutrophils, lymphocytes, and total lavage protein were observed. These results suggest two distinct mechanistic responses to inhaled particles: a stress-type pulmonary function response marked by increases in flow and volume, that is, deeper breathing; and acute pulmonary inflammation marked by cellular influx, particularly neutrophils. From these data it is concluded that inhaled urban air particles alter pulmonary breathing parameters and increase pulmonary inflammation.

Release and spread of immunoreactive neurokinin A in the cat spinal cord in a model of acute arthritis

Antibody microprobes were used to study the release of immunoreactive neurokinin A into the spinal cord of anaesthetised cats during and following injection of a knee joint with kaolin and carrageenan. A basal level of immunoreactive neurokinin A was detected prior to any noxious stimuli. Innocuous mechanical joint stimuli (flexion or pressure) did not alter this basal level of release. However, on injection of kaolin and carrageenan into a knee joint, evidence of release into the ipsilateral spinal cord was immediately observed. Initially, immunoreactive neurokinin A was detected in 2 regions: one at the dorsal surface of the spinal cord and the other centred on the superficial dorsal horn. Within 1 h of joint injection, however, immunoreactive neurokinin A was detected throughout the dorsal horn and the adjacent white matter. The extensive spread and persistence of immunoreactive neurokinin A in the spinal cord may underlie some of the prolonged excitability changes evoked by brief noxious stimuli and peripheral inflammation reported by other laboratories.

Recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a benign, often multi-focal neoplasm. A potentially fatal manifestation of human papilloma virus infection, the condition is characterised by multiple warty excrescences on the mucosal surface of the respiratory tract. RRP is rare--incidence is estimated at 3.5 per million person-years, with a prevalence of 4 in 100,000 children. Affected children usually require multiple interventions; the impact on patients, their families, and the healthcare system is considerable. Treatment of RRP accounts for an estimated dollar 109 million annual expenditure in the USA.

Direct lung delivery of para-aminosalicylic acid by aerosol particles

Para-aminosalicylic acid (PAS), a tuberculostatic agent, was formulated into large porous particles for direct delivery into the lungs via inhalation. These particles possess optimized physical properties for deposition throughout the respiratory tract, a drug loading of 95% by weight and physical stability over 4 weeks at elevated temperatures. Upon insufflation in rats, PAS concentrations were measured in plasma, lung lining fluid and homogenized whole lung tissue. Systemic drug concentrations peaked at 15 min, with a maximum plasma concentration of 11+/-1 microg/ml. The concentration in the lung lining fluid was 148+/-62 microg/ml at 15 min. Tissue concentrations were 65+/-20 microg/ml at 15 min and 3.2+/-0.2 microg/ml at 3h. PAS was cleared within 3 h from the lung lining fluid and plasma but was still present at therapeutic concentrations in the lung tissue. These results suggest that inhalation delivery of PAS can potentially allow for a reduction in total dose delivered while providing for higher local and similar peak systemic drug concentrations as compared to those obtained upon oral PAS dosing. Similar particles could potentially be used for the delivery of additional anti-tuberculosis agents such as rifampicin, aminoglucosides or fluoroquinolones.

RX 821002 as a tool for physiological investigation of alpha(2)-adrenoceptors

RX 821002 is the 2-methoxy congener of idazoxan. In binding and tissue studies it behaves as a selective antagonist of alpha(2)-adrenoceptors, with at least 5 times greater affinity for these receptors than any other binding site. It does not select between the different types of alpha(2)-receptor. Although this drug probably has no future as a therapeutic agent, it remains a good probe for physiological activity at alpha(2)-adrenoceptors in animal experiments. A particularly useful feature of this compound is its lack of binding at I(1) and I(2) imidazoline receptors. However, it has relatively high affinity for 5-HT(1A) receptors (at which it acts as an antagonist) and a tendency to behave as an inverse agonist at alpha(2A)-adrenoceptors in some cell culture systems. These potential drawbacks may be overcome by careful design of experiments, and the greater selectivity of RX 821002 renders it much superior to yohimbine or idazoxan as a tool for probing physiological actions at alpha(2)-receptors. It can be compared favorably with other selective antagonists such as atipamezole. In physiological studies, RX 821002 augments norepinephrine release in the frontal cortex and increases drinking behavior in rat. In rabbit, intrathecal administration of this drug enhances somatic and autonomic motor outflows, showing that tonic adrenergic descending inhibition of withdrawal reflexes and sympathetic pre-ganglionic neurons is strong in this species. The potentiation of reflexes may be considered a pro-nociceptive action. In the same model, RX 821002 antagonizes the inhibitory effects of the mu opioid fentanyl, indicating that exogenous opioids synergize with endogenously released norepinephrine in the spinal cord. Thus, the careful use of RX 821002 has revealed several aspects of the physiological activity of alpha(2)-adrenoceptors in rabbit spinal cord and rat brain. We recommend that RX 821002 and/or compounds with similar selectivity for alpha(2)-adrenoceptors (atipamezole, MK-912, RS-79948) should be used in preference to yohimbine or idazoxan in all future studies of this type.

Freshly generated stainless steel welding fume induces greater lung inflammation in rats as compared to aged fume

It has been previously reported that both short- and long-lived reactive oxygen species (ROS) are present on the surface of freshly generated fumes. The objective of this study was to determine if freshly formed welding fume induces greater lung inflammation and injury in rats due to the presence of reactive oxygen species than aged welding fume. Fume was collected during gas metal arc welding using a stainless steel consumable electrode and found to be of respirable size with a mean diameter of 0.77 microm +/- 0.48. Male CD/VAF rats were dosed intratracheally with the welding fume 30 min (fresh) and 1 and 7 days (aged) after fume collection at a dose of 1.0 mg/100 g b wt. Bronchoalveolar lavage (BAL) was performed 24 h post-instillation. Lung injury and inflammation were assessed by measuring the concentration of neutrophils, albumin, lactate dehydrogenase (LDH), and glucosaminidase (GLU) in the recovered BAL fluid. More neutrophils and enhanced GLU activity were observed for the 'fresh' group as compared to both 'aged' groups (P < 0.05). Slight, but not significant, elevations were seen in albumin content and LDH activity for the 'fresh' group as compared to the 'aged' groups. No significant differences were observed for any of the parameters when fume aged for 1 and 7 days were compared. When the 'fresh' and 'aged' fumes (12.5, 25, and 50 microg/ml) were suspended in dichlorofluorescin (15 microM), a probe which becomes fluorescent when oxidized, the concentration-dependent increases in fluorescence were greater for the 'fresh' fume versus the 'aged' fumes. We have demonstrated that freshly generated stainless steel welding fume induces greater lung inflammation than 'aged' fume. This is likely due to a higher concentration of ROS on fresh fume surfaces.

Naloxone enhancement of spinal reflexes in the rabbit

The effects of intravenous morphine, (-)-naloxone and (+)-naloxone have been studied on three ipsilateral cutaneo-muscular reflexes in spinal rabbits. Morphine, 3 mg/kg caused a slow-onset depression of all three reflexes. This effect was naloxone reversible. The ipsilateral extensor reflexes, sural to gastrocnemius medialis and saphenous to vastus lateralis were both enhanced to more than double control size following a 5 micrograms/kg dose of naloxone given in the absence of morphine. For the sural-gastrocnemius reflex, naloxone potentiated the reflex drive from all groups of myelinated afferent fibres. The ipsilateral flexion reflex, sural to semitendinosus, was only weakly enhanced by naloxone, the 5 micrograms dose leading to an increase in the size of the reflex to 130% of control. All observed actions of naloxone were stereospecific as the enantiomer (+)-naloxone failed to affect any of the reflexes even in a dose of 50 micrograms/kg. We conclude from these findings that opioid peptides are tonically released in rabbit spinal cord, and that they have differential effects in control of flexion and extension reflexes. It is suggested that the ipsilateral extension reflexes are held under a more powerful opioid-mediated depression than that operating upon the flexion reflexes, and that this difference may be related to the greater inhibitory inflow to extensor motoneurones from ipsilateral skin areas.

Effect of age on respiratory defense mechanisms: pulmonary bacterial clearance in Fischer 344 rats after intratracheal instillation of Listeria monocytogenes

STUDY OBJECTIVES

To examine the lung defense mechanisms of both young and aged rats before and after pulmonary challenge with a bacterial pathogen.

DESIGN

Male Fischer 344 rats, either 2.5 months or 20 months of age, were intratracheally inoculated with 5 x 10(3), 5 x 10(4), or 5 x 10(5) Listeria monocytogenes, and the effects on mortality, lung inflammation, pulmonary bacterial clearance, alveolar macrophage (AM) function, and T-lymphocyte characterization were determined.

MEASUREMENTS AND RESULTS

In noninfected control animals, the older rats had lower numbers of AMs on lavage and a lower percentage of total T, CD4+, and CD8+ cells. No difference was observed between noninfected young and old rats in AM function, assessing both chemiluminescence and nitric oxide (NO) production. After bacterial challenge, aged rats exhibited an increase in mortality, pulmonary infection, and edema, and lung lesions, which were more extensive than those observed in the younger rats. Interestingly, AM chemiluminescence was enhanced, while AM NO, a highly important antibacterial defense product, was abrogated in the aged rats as compared to the young rats.

CONCLUSIONS

This study demonstrated that advanced age is associated with alterations in lung defense mechanisms and increased susceptibility to pulmonary bacterial infection marked by elevated mortality, slowed pulmonary bacterial clearance, and altered AM function, specifically a decrease in NO production. These observations are indicative of reduced pulmonary defense function in an older population of rats.

Tracheocutaneous fistula following paediatric tracheostomy--a 14-year experience at Alder Hey Children's Hospital

OBJECTIVE

To assess the rate of tracheocutaneous fistula requiring surgical repair and the complications and outcomes following it in the ENT department of a tertiary referral university paediatric hospital.

METHODS

A retrospective review of all children requiring airway support with a tracheostomy between 1995 and 2009 and subsequently requiring closure of tracheocutaneous fistula.

RESULTS

One hundred and ninety-three children underwent 196 tracheostomies. Seventy-three children were successfully decannulated until now. Twenty-three children (11.9%) required subsequent surgical closure of their tracheocutaneous fistula. In all these children the age at tracheostomy was less than 1 year old, and the median age at decannulation was 4 years old, (range 2-9 yo). Surgical repair was undertaken 6-12 months after decannulation. There were 4 minor complications in the postoperative period (wound infection, haemorrhage and early recurrence) and no major complications. None of the patients have experienced any degree of significant airway stenosis and there was no need for a repeat tracheotomy in any of the tracheocutaneous fistula closure patients. The cosmetic results were deemed to be good.

CONCLUSIONS

Our rate of tracheocutaneous fistula compares well with the reported rates in the literature (13-43%). There appears to be a significant relation to age at tracheostomy and duration of tracheostomy.

Genetic linkage analysis of susceptibility to particle exposure in mice

Particle-induced increases in respiratory morbidity and mortality have been observed worldwide in industrialized cities but the toxicologic mechanisms have not been elucidated. It is hypothesized that subpopulations including the elderly and individuals with cardiopulmonary disease are particularly at risk to the effects of exposure. Genetic background is another important host factor that may contribute to interindividual responsivity to particulate exposure. This study was designed to identify susceptibility loci for alveolar macrophage (AM) immune dysfunction induced by inhalation of sulfate-associated carbon particles in susceptible C57BL/6J and resistant C3H/ HeJ inbred mice. AMs were chosen for study because they represent an important component of host defense, and compromised host defense has been hypothesized to be an important factor in particle-induced respiratory morbidity. The quantitative phenotype for these studies was Fc receptor-mediated phagocytic function, an index of AM integrity. Analyses of macrophage dysfunction phenotypes of segregant and nonsegregant populations derived from these two strains indicate that two unlinked genes control susceptibility. A genome-wide linkage analysis of an intercross (F(2)) cohort identified significant and suggestive quantitative trait loci (QTLs) on chromosomes 17 and 11, respectively. Candidate susceptibility genes were identified for mice and humans by comparative mapping. Importantly, both QTLs overlap previously identified QTLs for susceptibility to another common pollutant, ozone. This is the first demonstration that genetic background is an important determinant of responsiveness to particle-induced immune dysfunction, and it has important implications for understanding the epidemiologic associations between particulates and morbidity and mortality.

Adrenergic and opioidergic modulation of a spinal reflex in the decerebrated rabbit

1. In the decerebrated and spinalized rabbit, electrical stimulation of the sural nerve evokes a short-latency reflex in the ipsilateral ankle extensor gastrocnemius medialis (GM) which is tonically suppressed by endogenous opioids. In the present study we have investigated the inhibitory influences affecting this reflex in non-spinalized, decerebrated rabbits. 2. In non-spinalized rabbits, the thresholds and latencies of the sural-GM reflex were significantly higher than in spinalized preparations. The opioid antagonist naloxone and the alpha-adrenoceptor antagonist idazoxan potentiated the reflex in both preparations. Naloxone was significantly more effective in spinalized rabbits whereas idazoxan had a much larger effect in non-spinalized animals. 3. When the spinal cord was sectioned in the presence of naloxone alone, the GM reflex always increased in size. An ipsilateral hemisection of the cord was as effective as total section in this respect. When the section was performed in the presence of idazoxan and naloxone, the response usually decreased in size. 4. The alpha 2-adrenoceptor agonist clonidine depressed the reflex in spinalized rabbits, an action that was reversed by idazoxan but not by naloxone. 5. These data show that in the decerebrated, non-spinalized rabbit, the sural-GM reflex is tonically suppressed by endogenous opioids, presumably acting at the segmental level, and by an ipsilateral descending pathway which involves an alpha-adrenoceptor-mediated synapse. Activity in this descending pathway masks the facilitatory effects of opioid antagonists on spinal reflexes in this preparation.

Early post-operative morbidity following tonsillectomy in children: implications for day surgery

Adenotonsillectomy and tonsillectomy are amongst the most commonly performed surgical procedures. In our prospective study we looked at early post-operative morbidity (haemorrhage, vomiting and pyrexia) in 521 consecutive children following tonsillectomy, adenotonsillectomy and adenoidectomy. While the incidence of reactionary haemorrhage is low, pyrexia and vomiting are common. The implications of this high early post-operative morbidity for day surgery are discussed.

Interactions between cutaneous afferent inputs to a withdrawal reflex in the decerebrated rabbit and their control by descending and segmental systems

Previous studies have suggested that activation of nociceptive afferents from the heel recruits a supraspinal mechanism, which is modulated by adrenergic descending inhibition, that augments withdrawal reflexes in medial gastrocnemius (MG) motoneurones. To test this idea, we have studied the temporal evolution of reflexes evoked in MG by electrical stimulation of sural nerve A(beta)-, A(delta)- and C-fibre axons at 1 Hz, in decerebrated rabbits. Reflexes were analysed in three time bands, estimated to accord to afferent drive from A(beta)- (phase 1), A(delta)- (phase 2) and C-fibre (phase 3) inputs. Stimulation of A(delta)- and C-fibres gave significant temporal summation of all reflexes. The alpha(2)-adrenoceptor antagonist RX 821002 ((2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-1-H-imidazole)-HCl) (100 microg intrathecal (i.t.)) potentiated, and the alpha(2)-agonist dexmedetomidine (1-30 microg i.t.) depressed all reflexes per se, but the effects of these drugs on temporal summation were secondary to changes in baseline excitability. When C-fibres were stimulated, the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (1 mg i.t.) reduced temporal summation of phase 2 and 3 but not phase 1 reflexes. Spinalisation at L1 in the absence of drugs increased phase 2 and 3 reflexes but had no effect on phase 1, whereas spinalisation after RX 821002 resulted in decreased phase 1 responses with no significant change in later phases. Spinalisation in the presence of dizocilpine resulted in small reductions in phase 3 reflexes only. In all cases spinalisation virtually abolished temporal summation. In spinalised animals, dizocilpine selectively reduced late reflexes, and the opioid antagonist naloxone (100 microg i.t.) augmented all reflexes but gave rise to temporal subtraction of reflexes when C-fibres were stimulated.The present experiments have revealed a number of novel and important features of the sural-MG reflex pathway: (i) activity in fine afferent axons augments the reflexogenic potential of all subsequent afferent input, thereby allowing all afferent drive from the sural field to contribute to withdrawal of the heel; (ii) endogenous adrenergic control of this reflex pathway is completely non-selective; (iii) there is a non-adrenergic element of descending inhibition that is selective for the late components of MG reflex responses, and this element is directed particularly against transmission through NMDA receptors; (iv) temporal summation in this reflex is dependent on NMDA receptor-dependent and -independent mechanisms; and (v) this temporal summation is in some way dependent on the integrity of descending pathways.

The effects of anaesthetics and remote noxious stimuli on the jaw-opening reflex evoked by tooth-pulp stimulation in the cat

Previous studies indicate that the threshold of the jaw opening reflex (JOR) evoked by tooth-pulp stimulation is much lower in cats subjected to minimal surgical trauma and a short period of anaesthesia than in animals prepared for stereotaxic recording from the brainstem. Experiments have been carried out to determine whether the higher JOR thresholds observed in the latter group of cats could be attributed to the duration of the anaesthesia or the greater surgical trauma to which they were subjected. The effects on the JOR evoked by tooth-pulp stimulation of brief episodes of noxious and high intensity electrical stimulation of other tissues have been studied in anaesthetized cats. In lightly anaesthetized, control animals, the reflex threshold was usually below 100 microA, 0.1 ms and maintained anaesthesia did not affect this. Alphaxalone/alphadolone, methohexitone and alpha-chloralose produced similar results. Noxious or high intensity electrical stimuli applied to a paw, a pinna or the scalp caused either no change or a decrease in the JOR threshold of cats lightly anaesthetized with alphaxalone/alphadolone. With deeper anaesthesia, these same conditioning stimuli caused a maintained increase in JOR threshold which could be reversed by decreasing the anaesthetic dose. The results suggest that the high threshold of the JOR observed in earlier experiments was not due to anaesthesia but may have been caused by trauma.

The thresholds of the jaw-opening reflex and trigeminal brainstem neurons to tooth-pulp stimulation in acutely and chronically prepared cats

Electrical stimuli were applied to tooth-pulp in cats and the thresholds of the jaw-opening reflex and of neurons in the trigeminal sensory nuclei were determined. The effects of the method of preparation of the animal for stereotaxic recording were determined by making observations on animals set up in one of three ways: acutely in the usual manner; chronically, three to five days before recording; and acutely with precautions to minimize nociceptive input to the central nervous system. The threshold of the jaw-opening reflex increased progressively during the setting up of the normal, acute preparations and at the time brainstem recording began was significantly higher in these than in either the chronic or low-trauma acute preparations. Previous studies have shown that the increase in threshold is maintained for several hours and is not due to the effects of the anaesthetic. In normal acute preparations, few units (27/154) were found that had thresholds below 50 microA, 0.1 ms, whereas many units were encountered that responded to such a stimulus in chronic (147/152) and low-trauma acute (99/127) animals. In the chronic and in low-trauma acute preparations, there was no significant difference between the thresholds of the units in the main sensory trigeminal nucleus and spinal subnucleus oralis compared with those in subnucleus caudalis. Thus the preparation of an animal for stereotaxic recording can cause a severe and long-lasting depression in the excitability of neurons in the trigeminal sensory nuclei and an increase in the threshold of the jaw-opening reflex. This effect will have influenced the results of previous studies on the responses evoked in central neurons by stimulation of tooth-pulp, and may have similarly affected recordings from other regions.

The limitations of peak nasal flow measurement

The Youlten Peak Nasal Flow Meter is a convenient device for obtaining objective measurments of nasal patency and gives static values which correlate well--though inversely--with resistance measured by rhinomanometry. In this study peak nasal flow and nasal resistance are compared before and after intranasal challenge using histamine. The comparatively small change in nasal resistance induced by low-dose histamine is not reliably detected by the peak flow meter. Large changes in nasal resistance with a higher dose of histamine are reflected by significant but small changes in peak nasal inspiratory flow. It is concluded that changes in nasal patency as measured by the Youlten meter are an insensitive measure of nasal patency compared with rhinomanometrically measured resistance changes. Continued use of the latter is recommended for physiological research.

Spinal 5-HT-receptors and tonic modulation of transmission through a withdrawal reflex pathway in the decerebrated rabbit

1. In decerebrated, non-spinalized rabbits, intrathecal administration of either of the selective 5-HT1A-receptor antagonists (S)WAY-100135 or WAY-100635 resulted in dose-dependent enhancement of the reflex responses of gastrocnemius motoneurones evoked by electrical stimulation of all myelinated afferents of the sural nerve. The approximate ED50 for WAY-100635 was 0.9 nmol and that for (S)WAY-100135 13 nmol. Intrathecal doses of the antagonists which caused maximal facilitation of reflexes in non-spinalized rabbits had no effect in spinalized preparations. 2. In non-spinalized animals, intravenous administration of (S)WAY-100135 was significantly less effective in enhancing reflexes than when it was given by the intrathecal route. 3. When given intrathecally, the selective 5-HT 2A/2C-receptor antagonist, ICI 170,809, produced a bellshaped dose-effect curve, augmenting reflexes at low doses (< or = 44 nmol), but reducing them at higher doses (982 nmol). Idazoxan, the selective alpha 2-adrenoceptor antagonist, was less effective in enhancing reflex responses when given intrathecally after ICI 170,809 compared to when it was given alone. Intravenous ICI 170,809 resulted only in enhancement of reflexes and the facilitatory effects of subsequent intrathecal administration of idazoxan were not compromised. 4. The selective 5-HT3-receptor blocker ondansetron faciliated gastrocnemius medialis reflex responses in a dose-related manner when given by either intrathecal or intravenous routes. This drug was slightly more potent when given i.v. and it did not alter the efficacy of subsequent intrathecal administration of idazoxan. 5. None of the antagonists had any consistent effects on arterial blood pressure or heart rate. 6. These data are consistent with the idea that, in the decrebrated rabbit, 5-HT released from descending axons has multiple roles in controlling transmission through the sural-gastrocnemius medialis reflex pathway. Thus, it appears 5-HT tonically inhibits transmission between sural nerve afferents and gastrocnemius motoneurones by an action at spinal 5-HT1A-receptors. Spinal 5-HT2A/2C-receptors may mediate a weak inhibition of transmission in the spinal cord, but more convincing evidence was obtained for their involvement in descending facilitatory tone. Further, some of the facilitatory consequences of spinal alpha 2-adrenoceptor blockade may be mediated through 5-HT2 type receptors. Spinal 5-HT3 receptors do not appear to have a major role in tonic modulation of the sural-gastrocnemius medialis reflex.

The role of mucosal receptors in the nasal sensation of airflow

50 subjects were admitted into a randomized double-blind placebo controlled cross-over trial with 4% lignocaine as the active drug and normal saline as the placebo. Each subject had 2 ml of solution sprayed into each nasal cavity and all subjects had both sprays but on different occasions. The order in which the sprays were administered was randomized. The subjective sensation of nasal airflow was measured using a visual analogue scale before and after the spray. These measurements were made under conditions of the same airflow rate, which was monitored throughout the experiment using a reprogrammed NR6 rhinomanometer. Objective nasal patency was measured as peak nasal inspiratory flow rate. It was found that the nasal sensation of airflow decreased slightly after both lignocaine (difference between medians 5.0; 95% confidence interval -2.91 to 6.11) and normal saline (difference between medians 6.0; 95% confidence interval -1.02 to 7.21). Nonparametric analysis of variance showed this difference to be non-significant (P = 0.73). In addition there was no significant change in objective nasal patency. The results suggest that nerve endings in the nasal mucosa play no part in sensing nasal airflow during respiration.

A sinonasal primary Ewing's sarcoma

Nasal fractures are a common complaint familiar to all otolaryngologists. Sinonasal primary Ewing's sarcomas are extremely rare. The case of a 9-year-old boy is presented whose nasal fracture and subsequent lateral nasal wall hematoma revealed an underlying Ewing's sarcoma. There are several unusual features in the history and clinical course of this patient. Following biopsies, immunohistochemistry proved essential in distinguishing a Ewing's sarcoma from other small cell tumours. It is important that a seemingly common condition can be the first presentation of a less common, more sinister pathology.

Recurrent pleomorphic adenoma

Of 209 cases of pleomorphic adenoma treated in a 30 year period, 38 were secondary referrals with recurrent disease following surgery. Of these, 25 were women and 13 men with a mean time to recurrence of 9 years 4 months. Thirty-four recurrences were in the parotid gland, three in the submandibular gland and one in the anterior faucial pillar. Seven patients were untreated due to poor general condition or refusal of further treatment. Of the remainder, 15 had superficial parotidectomy and excision of the scar and nine a total parotidectomy. Three of these had extensive surgery with local flap repair. Of the patients with submandibular gland recurrence, two had local excision and one was treated with radiotherapy alone. One patient had a recurrence in the faucial pillar. Three patients developed malignant change in the recurrent tumour, of whom one died of disease.

Reflex actions of selective stimulation of sural nerve C fibres in the rabbit

Selective electrical stimulation of the non-myelinated C fibres of the sural nerve in the decerebrated, spinalized rabbit evoked long-latency (76-160 ms), long-lasting (greater than 100 ms) reflex responses in the ipsilateral ankle extensor gastrocnemius medialis (GM). Activation of the same fibres elicited little or no response from the ipsilateral knee flexor semitendinosus (ST). Reflex responses were evoked in both GM and ST muscle nerves by stimulation of the A beta afferents of the sural nerve. The A beta-elicited reflex in GM was enhanced, and that in ST depressed by prior activation of sural nerve C fibres. Strychnine, but not picrotoxin or mecamylamine, blocked C fibre-induced inhibition of the flexor reflex. Pinching the heel with serrated forceps produced an immediate reflex discharge in GM motoneurones, whereas ST responded upon termination of the stimulus. Pinching the second toe evoked reflex activity in ST but not in GM. After strychnine (0.5 mg kg-1), both sets of motoneurones responded simultaneously to stimulation of either the heel or the toe. These data show that sural and other afferent fibres from the heel excite ipsilateral GM motoneurones and inhibit ST reflex responses. One interpretation of these findings is that fine sural afferents activate parallel inhibitory and excitatory pathways, of which the former is sensitive to strychnine and therefore probably mediated by glycine.

The distribution of nasal airflow sensitivity in normal subjects

Nasal airflow modifies the pattern of ventilation presumably due in part to nervous signals arising in the nose and transmitted along the trigeminal nerve to the respiratory centre. Nasal receptor tissue must also be important in determining the sensation of airflow at a conscious level but little attention has been paid to the distribution and function of these receptors. An experimental model to deliver a pulse of air at different velocities to various nasal test sites is described. In this way nasal sensitivity to an air jet can be mapped out. Sensitivity of the nose to an air jet is greatest at the entrance to the nose--the region of the nasal vestibule.