Screening for malnutrition in emergency laparotomy patients: a comparison of three tools

INTRODUCTION

Malnourished patients undergoing emergency laparotomy are at risk of significant morbidity. The optimum screening tool to identify such patients in practice and research is yet to be determined. This study aims to compare the performance of three nutrition risk tools in predicting time without enteral nutrition in this population.

METHODS

A prospective cohort study (NCT04696367) was conducted across two sites, recruiting patients undergoing National Emergency Laparotomy Audit eligible procedures. Data collected included demographics, diagnosis, procedure and outcomes. Nutrition risk was assessed using three tools: Malnutrition Universal Screening Tool (MUST) score, Nutritional Risk Index (NRI) and Nutritional Risk Score 2002 (NRS-2002). Complications were assessed with the Comprehensive Complication Index. Quality of life was measured at baseline and 5 days postsurgery using EQ-5D-5L.

RESULTS

A total of 59 patients were recruited. Median age was 69 years. Of the 59 participants, 23 were judged high risk using MUST score, 13 using NRS and 8 using NRI. Median time to restart enteral intake was 7 days (interquartile range 7-14). Time without intake was correlated with increasing score using MUST (r=0.463, p<0.001) and NRS-2002 (r=0.296, p=0.03) but not NRI (r=-0.121, p=0.38). High-risk nutritional groups also had increased length of hospital stay, but not complication scores.

CONCLUSIONS

Patients undergoing emergency laparotomy spend a prolonged time without enteral nutrition. Although all nutritional tools demonstrated some propensity to identify patients at higher risk of needing nutritional support, their performance was variable. Nevertheless, some may be useful in future clinical studies.

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.

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.

Passive smoking, allergic rhinitis and nasal obstruction in children

Allergic rhinitis is a common cause of nasal obstruction in childhood. This prospective study looked at the effect of passive smoking on nasal obstruction in children with and without allergic rhinitis. Eighty-one children took part. Each child was asked to score his or her degree of nasal obstruction on a visual analogue scale. Exposure to passive smoking was determined subjectively using a parental questionnaire, and objectively by measuring the urinary cotinine/creatinine ratio. Results were tabulated using Microsoft Excel and analysed with SPSS statistical software. Nasal obstruction was significantly worse in children with a positive history of allergic rhinitis (p < 0.05). There was also a trend towards a higher nasal obstruction score in children without allergic rhinitis exposed to passive smoking compared to those who were not so exposed. As would be expected, nasal obstruction is worse in children with allergic rhinitis than in those without. Passive smoking tends to increase the symptom of nasal obstruction in children without allergic rhinitis.

Aryepiglottoplasty for laryngomalacia: the Alder Hey experience

Laryngomalacia is the most common cause of stridor in infants. Severely affected children are at risk of feeding difficulties, apnoeic episodes and cor pulmonale secondary to upper airway obstruction. The aim of this study was to assess the outcome of aryepiglottoplasty. This is a simple surgical procedure that relieves the obstruction by dividing the aryepiglottic folds. Thirty children had an aryepiglottoplasty at the Royal Liverpool Children’s Hospital between January 1995 and June 2001. The case notes of all 30 children were reviewed for age, sex, age at operation, indications, operative technique, complications and long-term outcomes. Complete resolution of stridor was obtained in 83 per cent of patients, with an improvement in a further 7 per cent. Post-operative complications included lower respiratory tract infections (13 per cent) and vomiting (7 per cent). In conclusion, simple endoscopic aryepiglottoplasty remains an effective way of treating upper airway obstruction in children. Its high resolution and low complication rate make it a safe, first choice procedure for treatment of moderate to severe laryngomalacia.

Paediatric otolaryngology services in the UK: a postal questionnaire survey of ENT consultants

Approximately half a million children in England and Wales receive in-patient or day-case surgical treatment annually. Otolaryngology is the surgical specialty that provides the greatest number of episodes of such care. As 30-50 per cent of our total volume of work is paediatric, we feel it is important to assess current attitudes to paediatric otolaryngological practice. In its year 2000 document Children's Surgery: a First Class Service, The Royal College of Surgeons (RCS) of England sets out recommendations on how children's surgical services should be delivered in the UK. A postal questionnaire was sent to all UK-based ENT consultant members of the British Association of Otorhinolaryngologists-Head and Neck Surgeons (BAO-HNS). The questionnaire was designed to assess the current practice of paediatric otolaryngology in the UK with an emphasis on the RCS recommendations. Wide variations were found, and they are discussed with reference to the recommendations.

Otitis media in children

Otitis media is the term used for a group of conditions characterized by inflammation of the middle-ear cleft. These conditions are particularly common in children where they present important diagnostic and therapeutic dilemmas.

Advances in genetic manipulations in the treatment of hearing disorders

Gene transfer into the inner ear is an attractive technology for clinical applications. It offers the hope of preventing, arresting, reversing or curing vestibular or hearing disorders caused by hereditary diseases or environmental insults. There are currently very few treatment options for vestibular disorders and sensorineural hearing loss, and therefore, it is important to investigate and develop new technologies for inner ear disease. In utero gene transfer may indeed be an option, but this technology will have many technical and ethical issues that remain to be overcome.

Glutamate and tachykinin receptors in central sensitization of withdrawal reflexes in the decerebrated rabbit

This study assessed the involvement of NMDA and group I metabotropic glutamate receptors, and tachykinin NK1 and NK3 receptors, in central sensitization of withdrawal reflexes in the decerebrated rabbit. Reflexes evoked in the ankle flexor tibialis anterior and the knee flexor semitendinosus by electrical stimulation at the base of the toes were enhanced for 29-63 min after application of 20% mustard oil to the tips of the toes. Selective antagonists of mGlu1, mGlu5, NMDA and NR2B-subunit-containing NMDA glutamate receptors, as well as NK1, and NK3 receptors, and a non-selective blocker of all tachykinin receptors, were assessed for their effects on the magnitude and duration of the increase in reflexes induced by mustard oil. Dizocilpine, an antagonist of all NMDA receptors (1 mg intrathecal) abolished facilitation of tibialis anterior reflexes and significantly reduced the magnitude and duration of increase of the semitendinosus response. The NR2B-subtype selective antagonist CP-101,606 decreased the magnitude of facilitation of both reflexes but had no effect on duration of enhancement. Selective antagonists for the mGlu1 (CPCCOEt, 1-3 mg intrathecal), mGlu5 (MPEP, 0.2-1 mg intrathecal), NK1 (L-733,060, 0.3 mg intrathecal) or NK3 (SR 142,801, 1 mg kg(-1) i.v.) receptors had no effect on the amplitude or duration of sensitization. However, the non-selective tachykinin receptor blocker ZD-6021 (0.3 mg intrathecal) reduced the amplitude but not the duration of sensitization in the flexor reflexes. Combination of ZD-6021 with CP-101,606 (doses as above) decreased both aspects of the sensitization response. Dizocilpine reduced reflexes evoked from the heel per se, and dizocilpine, CP-101,606 and ZD-6021 reduced arterial blood pressure. Otherwise the drugs used had no effects on baseline variables. The present data confirm the importance of NMDA receptors as a critical part of the process of central sensitization, provide no evidence for a role of metabotropic glutamate receptors, and show that simultaneous blockade of all tachykinin receptors is required to reveal their role in hyperalgesia. The data further indicate that a combined pharmacological approach offers a potential way forward for the development of new antihyperalgesic agents.

Endoscopy: a must in neonatal respiratory distress

Respiratory distress in a newborn presents both diagnostic and therapeutic dilemmas. Definitive treatment must be preceded by an accurate diagnosis other than in extremes. Complete tracheal rings are a very rare congenital cause of airway obstruction. Unlike other causes of upper airway obstruction, this cannot be relieved by tracheostomy, which may be counterproductive. We report the case of an 8-day-old female baby who presented with respiratory distress and was found to have complete tracheal rings and right pulmonary agenesis. The value of tracheo-bronchoscopy in this case cannot be overstressed.

Complete tracheal rings: lower airway symptoms can delay diagnosis

Bronchial asthma is a very common condition seen in children diagnosed by clinical examination. While treating these children, all the other possible causes of breathlessness including complete tracheal rings should be considered. Further investigations in the form of endoscopy may need to be carried out in doubtful cases.

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.

Tetrodotoxin block of A-fibre conduction and its effect on reflex responses evoked by electrical stimulation of the sural nerve in the decerebrated rabbit

In the present study, we have investigated the viability of using tetrodotoxin (TTX) to induce selective blockade of myelinated fibre conduction in rabbit sural nerve, and explored some aspects of reflexes evoked by non-myelinated sural nerve afferents before and after application of TTX. In rabbits decerebrated under halothane-nitrous oxide anaesthesia, application of 30 nM TTX to the desheathed sural nerve completely blocked Abeta and Adelta waves of the compound action potential evoked by electrical stimulation of the nerve at 95 times threshold. The amplitude of C-fibre volleys evoked by these stimuli was reduced to a mean of 60 % of pre-treatment values. Reflexes evoked in medial gastrocnemius motoneurones by sural nerve stimulation showed corresponding changes after TTX treatment, with activation latency increasing from 5-7 ms in the control state to > 100 ms after TTX application. Temporal summation (wind up) in long latency reflexes (> 100 ms) was significantly enhanced after application of TTX. These data show that low concentrations of TTX can selectively block conduction in rabbit sural nerve A-fibres, providing a method for studying the central actions of non-myelinated C-fibres in isolation.

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.

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.

Epistaxis in children with vascular malformations--commentary of two cases and literature review

Vascular anomalies can cause epistaxis in children. The authors present two cases of recurrent epistaxis secondary to rare causes and discuss their presentations. Both cases were managed conservatively since intervention in these vascular lesions carries a high risk of damaging adjacent structures.

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.

Paediatric acute mastoiditis: the Alder Hey experience

Acute mastoiditis was a common condition in the pre-antibiotic era, but has become rare now with the widespread use of antibiotics. A retrospective study was carried out of patients with acute mastoiditis who were seen at Alder Hey Children's Hospital, Liverpool over a five-year period. Their case records were identified and details of gender, age at presentation, symptoms, signs and clinical management were noted and analysed. Twenty-one patients who presented with acute mastoiditis were identified. The patients' age at presentation ranged from three months to 14 years. Five cases out of 21 (23.8 per cent) were under one year of age. Eighteen cases (85.7 per cent) presented with post-aural swelling while 12 (57.1 per cent) had aural discharge. All patients were treated with intravenous antibiotics and only five patients (23.8 per cent) required surgical intervention in the form of a cortical mastoidectomy with, or without, myringotomy. A significant number of cases can be treated conservatively with intravenous antibiotics. Surgery in the form of cortical mastoidectomy can be reserved for complicated cases and in those in whom conservative treatment has failed.

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.

The spatial organization of central sensitization of hind limb flexor reflexes in the decerebrated, spinalized rabbit

This study was designed to investigate the relationship between the location of a noxious stimulus and the magnitude and duration of the plastic effects induced by that stimulus in withdrawal reflexes acting about the knee and the ankle, in rabbits. Reflexes were evoked in the nerves to the anterior tibial and semitendinosus flexor muscles by electrical stimulation at the toes. Repetitive, high intensity electrical stimulation of nerve trunks (sural, medial gastrocnemius, superficial peroneal, tibial, 100 pulses, 20 V, 1 ms at 0.5 Hz) was generally found to be a poor method for inducing central sensitization in these flexor reflexes. 'Natural' noxious stimulation induced more reliable enhancement of both reflexes. Mechanical (clamp) or chemical (mustard oil) stimulation of the heel induced prolonged (median duration >30 min) increases in reflexes to both muscles. Mechanical (clamp and superficial pinch) or chemical (mustard oil) stimulation of the toes, and injection of bradykinin into the gastrocnemius muscles or into the soft tissues of the sole of the foot, also led to enhancement of both reflexes, with the median duration of potentiation between 7 and 30 min. The effects obtained from deep tissue stimulation were generally weaker than those obtained after stimulation of superficial structures. These data show that there were no major differences in the effects obtained from the heel vs the toes, or between the two reflexes. It appears that the spatial organization of the spinal mechanisms underlying central sensitization of flexor withdrawal reflexes is rather more crudely drawn than that pertaining to the reflexes themselves. Furthermore, the data indicate that in the present preparation, afferents from deep tissues are no more effective in generating central sensitization than those from superficial structures.

Opioid and GABA receptors involved in mediation and modulation of tonic and stimulus-evoked inhibition of a spinal reflex in the decerebrated and spinalized rabbit

The purposes of this study were to investigate: (i) the identity of the opioid peptide(s) mediating tonic and stimulus-evoked inhibition of the sural-medial gastrocnemius reflex of the decerebrated, spinalized rabbit and (ii) the modulation of these processes by endogenous GABA. The selective delta receptor antagonist naltrindole (100 nmol kg(-1) i.v.), the GABA(A) blocker bicuculline (300 nmol intrathecal, i.th.), and the GABA(B) antagonist CGP 35348 (1 micromol i.th.) increased gastrocnemius reflexes to 150-160% of pre-drug values, whereas a sub-maximal dose of naloxone (30 nmol kg(-1) i.v.) augmented reflexes to >500% of controls. Kelatorphan, an inhibitor of enkephalin metabolism (2 micromol i.th.), depressed gastrocnemius responses by 50% and potentiated the inhibitory effects of methionine enkephalin. Repetitive electrical stimulation of the superficial or common peroneal nerves inhibited reflexes for 15-20 min. This effect was significantly reduced by naltrindole and CGP 35348. It was not reduced by a low dose (30 nmol kg(-1) i.v.) of naloxone or by bicuculline. When naloxone and naltrindole were combined at 30 nmol kg(-1) each, stimulus-evoked inhibition was blocked. Given after bicuculline, naloxone at 100 nmol kg(-1) i.v. abolished peroneal-evoked inhibition, but a dose of 300 nmol kg(-1) was required to produce the same effect after CGP 35348. Kelatorphan augmented the depth and duration of inhibition evoked by peroneal nerve stimulation. These data are consistent with the involvement of enkephalin-like peptides in tonic and stimulus-evoked inhibition of the sural-gastrocnemius reflex. Tonic inhibition in rabbit spinal cord is dominated by opioids acting through mu receptors, whereas co-activation of delta, mu and GABA(B) receptors mediates stimulus-evoked inhibition. It is possible that GABA(B) receptors inhibit the release of spinal opioids while simultaneously supporting their actions at post-synaptic targets.

Endogenous adrenergic control of reflexes evoked by mechanical stimulation of the heel in the decerebrated rabbit

In decerebrated rabbits, reflexes were evoked in medial gastrocnemius motoneurones by mechanical stimulation of the heel, using four pinch strengths from 183 (innocuous) to 4577 (noxious) mN. The alpha(2)-adrenoceptor antagonist idazoxan (1-156 microg intrathecal (i.th.) significantly increased responses to pinch strengths of 607 mN and above. Subsequent administration of the alpha(1) adrenoceptor selective antagonist prazosin (200 microg i.th.) decreased reflexes to 4577 mN pinches but had no other significant effects. The opioid antagonist (-)-quadazocine (25 microg i.th.) caused no further changes in reflexes. Spinal section at L1 in the presence of this drug combination enhanced gastrocnemius responses to 183 and 607 mN stimuli, had no effect on reflexes to 1866 mN and significantly decreased responses to 4577 mN pinches. These data confirm that reflexes evoked by 'natural' stimulation of heel mechanoreceptors are subject to powerful tonic descending inhibition mediated by alpha(2)-adrenoceptors. For the highest strength stimulus, the results of alpha(2) blockade involved enabling of descending facilitation as well as reduction of descending inhibition.

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.

Adaptive changes in withdrawal reflexes after noxious stimulation at the heel and the toes in the decerebrated rabbit

In decerebrated rabbits, reflexes evoked by electrical stimulation of the toes in the ankle flexor tibialis anterior were enhanced for > 30 min after application of 20% mustard oil to the base of the toes, whereas responses of the ankle extensor medial gastrocnemius to stimulation of the heel were depressed for > 20 min by the same stimulus. Applied to the heel, mustard oil had inconsistent effects on the flexor reflex but potentiated the extensor response for approximately 1 h. Intrathecal co-administration of naloxone (25 microg) with the selective alpha(2)-adrenoceptor antagonist RX 821002 (200 microg) enhanced both reflexes to more than twice pre-drug values and reduced or abolished all effects of mustard oil. These data confirm that the location of a noxious stimulus is an important determinant of the subsequent adaptive changes in reflexes, and indicate roles for endogenous opioids and noradrenaline in these processes.

Cannabinoidergic and opioidergic inhibition of spinal reflexes in the decerebrated, spinalized rabbit

The present experiments were designed to investigate the role(s) of cannabinoid receptors in modulating transmission in the sural-medial gastrocnemius withdrawal reflex of the decerebrated, spinalized rabbit and how, if present, cannabinoid-mediated control might interact with opioid-mediated inhibitions known to impinge on this reflex pathway. The selective CB(1) receptor antagonist SR 141716A enhanced reflexes by a factor of two after a cumulative dose of 100 nmol kg(-1) i.v., but had no effect on the endogenous opioid-mediated inhibition generated by repetitive electrical stimulation of the common peroneal nerve, or on the suppression of reflexes caused by i.v. administration of the synthetic opioid fentanyl. Given at a dose of 10 nmol kg(-1) i.v., the potent, CB(1)--CB(2) cannabinoid receptor agonist HU 210 inhibited medial gastrocnemius reflexes to approximately 30% of controls and significantly decreased both heart rate and blood pressure, but did not alter the inhibition of reflexes resulting from common peroneal nerve stimulation or i.v. fentanyl. The effects of HU 210 were reversed by SR 141716A. HU 210 was just as effective in inhibiting reflexes in the presence of the opioid antagonist naloxone (5 micromol kg(-1)) as it was in untreated animals. The data show that cannabinoids, acting through CB(1) receptors, are inhibitory in rabbit spinal cord and that there appears to be some endogenous cannabinoid tone under the conditions of the present experiments. The evidence of this study is that the inhibitory effects of opioids and cannabinoids in rabbit spinal cord are completely independent of each other, and are additive rather than synergistic.

Strain-related differences of nonspecific respiratory defense mechanisms in rats using a pulmonary infectivity model

A number of animal studies have assessed pulmonary host defense mechanisms by inoculating the lungs with the bacterial agent, Listeria monocytogenes. Most studies use only a single strain of the animal to be tested; however, strain-related differences in responsiveness to pulmonary toxicants have been well documented. It was the goal of this current investigation to measure the pulmonary defense responses of two different strains of rats in a lung infectivity model. Fischer 344 (F344) and Sprague-Dawley (SD) rats were instilled intratracheally with 5 x 10(3) or 5 x 10(5) L. monocytogenes, and the effect on mortality, lung injury and inflammation, pulmonary bacterial clearance, and alveolar macrophage (AM) function was determined at 3, 5, and 7 days after bacteria treatment. Pulmonary inoculation with the higher (5 x 10(5) L. monocytogenes) dose proved to be highly pneumotoxic to the F344 rats as evidenced by an increase in mortality and more severe lung injury and inflammation when compared with the SD rats. After intratracheal instillation with the lower (5 x 10(3) L. monocytogenes) dose, pulmonary bacterial clearance was slowed and an increase in pulmonary responsiveness was observed for the F344 rats as compared to the SD rats. Specifically, the total number of neutrophils recovered from the lungs and tumor necrosis factor-alpha secreted by AMs were elevated for the F344 group throughout the 7 days, while cellular chemiluminescence, an index of reactive oxygen species production, and lung albumin and lactate dehydrogenase, indicators of injury, were increased at 3 and 5 days after bacterial instillation. This study demonstrated that respiratory defense function was compromised in F344 rats as evidenced by elevated mortality, slowed pulmonary bacterial clearance, and altered AM function. F344 rats may then represent a sensitive model for the examination of respiratory defense mechanisms after bacterial challenge.

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.

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.

Imidazoline I(2)-receptors and spinal reflexes in the decerebrated rabbit

Idazoxan potentiates spinal reflexes in the decerebrated rabbit, an effect that has been attributed to antagonism of tonic noradrenergic inhibition. It is now known that this drug has a higher affinity for I(2)-imidazoline receptors than alpha(2)-receptors. The roles of I(2)-receptors in modulating transmission in spinal reflex pathways have been investigated using the selective ligands RX 821029 and RS-45041-190, and, as I(2)-receptors are closely associated with monoamine oxidase (MAO), the MAO inhibitors pargyline and clorgyline. In decerebrated rabbits with an intact spinal cord, intrathecal doses of 5-365 microg (cumulative) of the I(2)-ligands augmented, to 150-180% of pre-drug levels, the reflex responses of medial gastrocnemius motoneurones to electrical stimulation of the sural nerve, and significantly increased mean arterial blood pressure by approximately 10 mmHg over pre-drug values. Neither MAO inhibitor had significant effects on reflexes, but the highest dose of the MAO-A selective agent clorgyline (365 microg cumulative) caused a significant rise in blood pressure of 6 mmHg. Neither the I(2)-ligands nor the MAO inhibitors prevented the further enhancement of reflexes or blood pressure by subsequent administration of the selective alpha(2)-adrenoceptor antagonist RX 821002. In decerebrated, spinalized rabbits, intrathecal RS-45041-190 (60 microg, single dose) increased spinal reflex responses to 109% of pre-drug values, a significantly smaller effect than that seen in non-spinal preparations, and had no effect on blood pressure. These data show that imidazoline I(2)-receptors can influence somatic and autonomic motor outflows. These effects should be taken into account when interpreting the spinal effects of imidazoline-based adrenoceptor-active drugs.

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.

The role of 5-HT(1A)-receptors in fentanyl-induced bulbospinal inhibition of a spinal withdrawal reflex in the rabbit

The sural to gastrocnemius withdrawal reflex is inhibited after injection of the OP(3) (micro)-receptor-selective opioid fentanyl into the fourth ventricle of decerebrated rabbits. This effect is abolished by complete section of the spinal cord but not by the selective alpha(2)-adrenoceptor antagonist RX 821002 (Clarke RW, Parry-Baggott C, Houghton AK, Ogilvie J. The involvement of bulbo-spinal pathways in fentanyl-induced inhibition of spinal withdrawal reflexes in the decerebrated rabbit. Pain 1998;78:197-207). We have now investigated the role of 5-HT(1A) receptors in mediating the descending inhibition activated by intraventricular fentanyl. In the control state, intraventricular fentanyl (3-30 microgram/kg) inhibited gastrocnemius reflex responses to a median of 34% of pre-drug levels. After intrathecal administration of the selective 5-HT(1A) receptor antagonist WAY-100635 (100 microgram), fentanyl reduced reflex responses to 83% of pre-fentanyl values, significantly less inhibition than in the control state. In a separate group of experiments, intravenous fentanyl (0.3-30 microgram/kg) depressed the sural-gastrocnemius reflex to 17% of pre-drug controls. This inhibition was not affected by intrathecal WAY-100635 (100 microgram), but combined administration of the 5-HT(1A) antagonist with RX 821002 (100 microgram) significantly reduced the effectiveness of i.v. fentanyl. After the highest dose reflexes were 37% of pre-fentanyl levels. These data show that the bulbospinal inhibition activated by fentanyl is mediated, at least in part, by activation of spinal 5-HT(1A) receptors. That blockade of these receptors failed to influence the inhibition induced by i.v. fentanyl might be taken to mean that the brain-stem action of fentanyl does not contribute significantly to the systemic actions of this opioid. A more probable explanation is that, in the preparation used in the present study, the bulbospinal and direct spinal actions of fentanyl occlude each other to produce an overall inhibition that is less than the sum of the two effects.

Inhaled particle-bound sulfate: effects on pulmonary inflammatory responses and alveolar macrophage function

Acid sulfate-coated solid particles are a significant environmental hazard produced primarily by the combustion of fossil fuels. We have previously described a system for the nascent generation of carbonaceous particles surface coated with approximately 140 microg/m(3) acid sulfate [cpSO(4)(2-); 10 mg/m(3) carbon black (CB) and 10 ppm sulfur dioxide (SO(2)) at 85% relative humidity (RH)]. The effects of inhaled cpSO(4)(2-) on pulmonary host defenses are assessed in the present work. Mice were acutely exposed (4 h) to either 10 mg/m(3) CB, 10 ppm SO(2), or their combination at 10% or 85% RH in a nose-only inhalation chamber. No evidence of an inflammatory response was found following any of the exposures as assessed by total cell counts and differential cell counts from bronchoalveolar lavage fluid. However, alveolar macrophage Fc receptor-mediated phagocytosis decreased only following exposure to 140 microg cpSO(4)(2-), significant suppression occurred after 24 h, maximal suppression occurred at 3 days postexposure, and recovery to preexposure levels required 7-14 days. Intrapulmonary bactericidal activity (IBA) was also suppressed only after exposure to 140 microg cpSO(4)(2-); suppression was maximal at 1 day postexposure and recovered by day 7. To assess the effects of lower cpSO(4)(2-) concentrations, mice were repeatedly exposed to 1 mg/m(3) CB and 1 ppm SO(2) at 85% RH ( approximately 20 microg/m(3) cpSO(4)(2-) for 4 h/day) for up to 6 days. A significant decrement in IBA was observed following 5 and 6 days of exposure. These studies indicated that acute or repeated exposure to cpSO(4)(2-) could alter pulmonary host defense mechanisms.

Interstrain variation in murine susceptibility to inhaled acid-coated particles

Epidemiologic studies have demonstrated a positive correlation between concentration of acid aerosol and increased morbidity and mortality in many urban environments. To determine whether genetic background is an important risk factor for susceptibility to the toxic effects of inhaled particles, we studied the interstrain (genetic) and intrastrain (environmental) variance of lung responses to acid-coated particle (ACP) aerosol in nine strains of inbred mice. A flow-past nose-only inhalation system was used to expose mice to ACPs produced by the cogeneration of a carbon black aerosol-sulfur dioxide (SO(2)) mixture at high humidity. Three days after a single 4-h exposure to ACPs or filtered air, mice underwent bronchoalveolar lavage, and cell differentials and total protein were determined as indexes of inflammation and epithelial permeability, respectively. To determine the effect of ACPs on alveolar macrophage (AM) function, lavaged AMs were isolated from exposed animals and Fc receptor-mediated phagocytosis was evaluated. Compared with air-exposed animals, there was a slight but significant exposure effect of ACPs on the mean number of lavageable polymorphonuclear leukocytes in C3H/HeJ and C3H/HeOuJ mice. ACP exposure also caused a significant decrease in AM phagocytosis. Relative to respective air-exposed animals, Fc receptor-mediated phagocytosis was suppressed in eight of nine strains. The order of strain-specific effect of ACPs on phagocytosis was C57BL/6J > 129/J > SJL/J > BALB/cJ > C3H/HeOuJ > A/J > SWR/J > AKR/J. There was no effect of ACP exposure on AM phagocytosis in C3H/HeJ mice. The significant interstrain variation in AM response to particle challenge indicates that genetic background has an important role in susceptibility. The effects of ACPs on AM function, inflammation, and epithelial hyperpermeability were not correlated (i.e., no cosegregation). This model may have important implications concerning interindividual variation in particle-induced compromise of host defense.

The involvement of tachykinin NK2 and NK3 receptors in central sensitization of a spinal withdrawal reflex in the decerebrated, spinalized rabbit

Repetitive electrical stimulation of the sural nerve at a strength sufficient to excite C-fibres results in prolonged (> 20 min) increases in the reflex responses of gastrocnemius motoneurones evoked by stimulation of myelinated axons in the sural nerve. We have tested the susceptibility of this effect to blockade of tachykinin NK2 and NK1 receptors. In the control state, iterative stimulation of sural nerve C fibres increased gastrocnemius reflexes to a peak of between 200 and 400% of pre-stimulus levels, an effect that recovered to baseline values over 23-30 min. Pre-treatment with selective antagonists for NK2 (SR 48968, 1 mg/kg i.v.) or NK3 (SR 142801, 0.1 and 1 mg/kg i.v.) receptors failed to alter the peak facilitation resulting from sural nerve stimulation. However, both drugs significantly reduced the duration of enhancement of reflexes, to 18 min after SR 48968 and to 5 min after SR 142801. The inactive enantiomers of these compounds (SR 48965 and SR 142806, both 1 mg/kg i.v.) did not reduce facilitation of reflexes after sural nerve stimulation. We conclude that activation of tachykinin NK3 receptors is a major factor in maintaining central sensitization of the sural-gastrocnemius reflex after electrical stimulation of sural nerve C-fibres. The effects of SR 48968 were surprisingly weak and may have resulted from an effect of this compound at NK3 receptors.

Mechanisms of morbidity and mortality from exposure to ambient air particles

The studies reported here assessed pathophysiologic mechanisms that result from exposure to concentrated ambient particles (CAPs) in animals with and without cardiopulmonary compromise. These studies were carried out to determine the biologic plausibility of epidemiologic observations of increases in particulate air pollution associated with increases in human morbidity and mortality. Dogs were exposed two at a time to CAPs or filtered air via tracheostomy for six hours per day on three consecutive days. The electrocardiogram (ECG) and breathing pattern were recorded continuously, and indicators of inflammation were also assessed. In one experimental design, normal dogs were exposed in pairs to CAPs and subsequently to filtered air or to filtered air and subsequently CAPs (the double CAPs/double sham design). Comparisons were made between the CAPs measurements and each dog's own sham responses. In another design, one dog was exposed to CAPs while the chambermate received a sham exposure; these experiments were followed by crossover of the protocol the subsequent week (the crossover design). Comparisons were made between the CAPs exposure and both the chambermate's sham and each dog's own sham responses. The crossover experiments were conducted in normal animals and in animals who had undergone balloon occlusion of the left anterior descending (LAD) coronary artery to induce myocardial compromise. The effects of CAPs in animals with induced chronic bronchitis were part of the original specific aims; because these studies were not fully pursued, the results are presented only in Appendix A. In normal dogs, analyses of all double CAPs and crossover studies revealed low frequency (LF) and high frequency (HF) powers for heart rate variability (HRV) that were significantly higher for CAPs exposure compared to sham exposure. Variation in day-to-day exposure concentrations, aerosol composition, and pathophysiologic responses were also found. The crossover design, continuous measures of aerosol mass, and biologic responses were incorporated in the development of a statistical model that allowed isolation of changes associated with CAPs from changes due to animal variations. Comparison of individual exposures with this model revealed a range from no response in any measured parameter to statistically significant changes in cardiac autonomic balance, pulmonary air flow, and breathing pattern. On days in which dogs showed statistically significant changes in responses, the findings were consistent in both cardiac and respiratory parameters. Days associated with significant increases in LF and HF HRV, LF/ HF HRV ratio, and heart rate standard deviation (HR SD) were also associated with decreases in average heart rate. These same days had decreases in respiratory frequency, tidal volume, minute volume, and peak flows with corresponding increases in respiratory cycle times and enhanced pause (Pauenh), a measure of bronchoconstriction. These cardiac and respiratory changes suggest an effect mediated via both the sympathetic nervous system and the vagus nerve. Alternatively, days associated with increased heart rate had decreases in the HR SD; decreases or no change in HF and LF HRV; increases in respiratory flows and volumes; and decreases in breathing cycle times, all suggesting only sympathetic nervous system mediation. When all data from the crossover design experiments were assessed with this model, the heart rate and respiratory rate were significantly decreased in relation to both cumulative and actual exposure and the LF HRV, LF/HF HRV ratio, HR SD, and all other respiratory parameters were significantly increased (p < 0.0001 for all). When cardiac data were grouped by days in which the air mass trajectory came from the north or northwest (versus west, south, east, or northeast), significant increases in HR SD and HF HRV and significant decreases in average heart rate were associated with the northwest trajectory. (ABSTRACT TRUNCATED)

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.

On the role of 5-HT1B/1D receptors in modulating transmission in a spinal reflex pathway in the decerebrated rabbit

1. In decerebrated rabbits, the selective 5-HT1B/1D receptor antagonist GR 127,935 had no significant effects on reflexes evoked in medial gastrocnemius motoneurones by electrical stimulation of the sural nerve, or on arterial blood pressure or heart rate when given by the intrathecal (up to 543 nmol cumulative) or intravenous (up to 1.8 micromol cumulative) routes. 2. In decerebrated, spinalized rabbits, intrathecal GR 127,935 in doses of up to 543 nmol, had no effect on the sural-gastrocnemius reflex. Furthermore, this drug failed to alter enhancement of the sural-gastrocnemius reflex induced by 8-hydroxy-2-(di-n-propyl)aminotetralin (8-OH-DPAT), given at 300 nmol kg-1 i.v. 3. In decerebrated, spinalized rabbits, the selective 5-HT1B/1D receptor agonists L-694,247 (cumulative doses of 2 - 243 nmol kg-1 i.v.) and L-741,604 (cumulative doses of 3 - 307 nmol kg-1 i.v.), each caused the sural-gastrocnemius reflex to increase to 140% of pre-drug levels, and arterial blood pressure to rise by about 10 mmHg. Subsequent administration of GR 127,935 at 0.9 - 1.8 micromol kg-1 reversed the pressor effect of the agonists but not the increase in reflexes. The 5-HT1A receptor antagonist WAY-100,635 (185 nmol kg-1 i.v.) also failed to reverse the increase in reflexes, but the 5-HT1B/1D/5-HT2/5-HT7 ligand ritanserin (1.6 micromol kg-1 i.v.) restored reflexes to pre-drug control values after L-741,604 (it was not tested against L-694,247). 4. These data indicate that 5-HT1B/1D receptors do not significantly modulate transmission in the sural-gastrocnemius reflex pathway, and that the enhancement of reflexes by 8-OH-DPAT and L-741,604 is probably mediated by 5-HT7 receptors.

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.

Benchmarking for the competitive marketplace

One would get little argument these days regarding the importance of performance measurement in the health care industry. The traditional approach has been the straightforward use of measurable units such as financial comparisons and clinical indicators (e.g., length of stay). Also we in the health care industry have traditionally benchmarked our performance and strategies against those most like ourselves. Today's competitive market demands a more customer-focused set of performance measures that go beyond traditional approaches such as customer service. The most important task in today's environment is to study the customers' emerging priorities and adjust our business to meet those priorities.

Tonic adrenergic and serotonergic inhibition of a withdrawal reflex in rabbits subjected to different levels of surgical preparation

The excitability of the heel-gastrocnemius withdrawal reflex pathway has been monitored in rabbits undergoing surgical preparation for electrophysiological experimentation under Saffan anaesthesia. Reflexes were evoked by percutaneous electrodes inserted at the heel and recorded as electromyograph signals from the ipsilateral medial gastrocnemius muscle. Two levels of surgery were carried out. The "full surgical" preparation was performed under deep Saffan anaesthesia. The trachea, carotid artery, jugular vein and intrathecal space (via a small laminectomy at L1) were cannulated, the animals were decerebrated by suction, and the left hindlimb was immobilized by screw clamps applied to the tibia and the femur. The sciatic nerve and its branches were exposed by bisection of the posterior biceps muscle and the anaesthetic was withdrawn. In the "reduced surgery" preparation, procedures were carried out with a lighter level of Saffan anaesthesia and operated tissues were infiltrated with local anaesthetic. Only the cannulations were performed in these animals. The excitability of the heel-gastrocnemius reflex declined throughout the full surgical preparation, with the median threshold increasing from 0.8 to 4.2 mA (n=19) and responses to suprathreshold stimuli reducing in size. Most of this effect was reversed after surgery was complete and anaesthesia withdrawn subsequent to decerebration. There were no significant changes in reflex excitability during the reduced surgery preparation (n = 15). Animals prepared by each of these protocols were given increasing intrathecal doses of either the selective alpha2-adrenoceptor antagonist RX 821002 (0.3 to 300 microg) or the serotonin/5-hydroxytryptamine (5-HT)1A-receptor antagonist WAY-100635 (0.01 to 30 microg). Both drugs caused significant, dose-dependent increases in reflex responses, to four to six times pre-drug control in both groups of animals. There were no differences in the effects on reflexes of either drug between the preparations. Thus, surgical preparation of decerebrated rabbits for electrophysiological recording results in depression of hindlimb withdrawal reflexes, although much of this effect did not persist beyond the completion of surgery. Tonic monoaminergic inhibition of reflexes was present to the same extent in both preparations investigated and is not therefore an epiphenomenon of the way in which the animals were prepared.

Differences in opioidergic inhibition of spinal reflexes and Fos expression evoked by mechanical and chemical noxious stimuli in the decerebrated rabbit

Noxious mechanical and chemical stimuli were applied to the toes of the left hind limb of decerebrated, spinalized rabbits and their effects on a hind limb spinal withdrawal reflex and expression of Fos-like immunoreactivity in the spinal cord were measured. The animals were prepared so as to minimize nociceptive inputs arising from surgery. A single crush stimulus applied with a pair of haemostatic forceps caused long-lasting (c. 20 min) inhibition of reflexes evoked in medial gastrocnemius motoneurons by electrical stimulation of the skin at the heel. Naloxone (0.25 mg/kg i.v.) increased reflexes to more than 1000% of pre-drug controls and reversed crush-evoked inhibition. Mustard oil applied to the toes had no consistent effects on the heel-gastrocnemius reflex before or after naloxone. Both crush and mustard oil stimuli gave rise to unilateral increases in the number of Fos-immunopositive profiles in the superficial dorsal horn of spinal segments L7 and S1. There were significantly more Fos-immunoreactive elements in the central and lateral parts of lamina I of both segments in animals receiving the crush stimulus than there were in animals receiving the mustard oil stimulus. Immunochemical localization of enkephalins in rabbit spinal cord showed a dense network of fibres and terminals in laminae I and II, accompanied by infrequent but distinctly stained neuronal cell bodies. The same pattern, with increased numbers of visible cell bodies, was seen after treatment with colchicine. The present data show that tonic and stimulus-evoked opioidergic inhibition of the heel-gastrocnemius reflex of the rabbit are not epiphenomena of surgical preparation of the hindlimb. Opioid-mediated inhibition of the heel-gastrocnemius withdrawal reflex of the rabbit was evoked by noxious mechanical but not by chemical stimulation of the toes. Of these stimuli, the former gave rise to greater activation of neurons in central and lateral lamina I of segments L7 and S1, the region of termination of afferent fibres from the heel and the location of some enkephalin-positive neuronal cell bodies. Thus, noxious mechanical stimulation of the toes elicits inhibition of the heel-gastrocnemius withdrawal reflex, probably via activation of enkephalinergic neurons in the lateral half of lamina I in the L7 and S1 segments.