Effects of hyperoxia on nitric oxide synthase expression, nitric oxide activity, and lung injury in rat pups

Although hyperoxic exposure is an important contributor to the development of bronchopulmonary dysplasia and nitric oxide (NO) has been implicated in the pulmonary response to oxygen, the role of NO in mediating chronic neonatal lung injury is unclear. Therefore, rat pups were exposed to normoxia or hyperoxia (>95% O2) from d 21 to 29. After the rats were killed, their lungs were removed for analysis of nitric oxide synthase (NOS) expression, NO activity as measured by 3',5'-cyclic guanosine monophosphate (cGMP) assay, and lung pathology. Hyperoxia caused 5-fold and 2-fold increases in inducible (i) NOS and endothelial (e) NOS levels, respectively. NO activity was assessed by measuring cGMP levels after normoxic or hyperoxic exposure in the presence and absence of NOS blockade with either aminoguanidine (AG) or Nomega-nitro-L-arginine (L-NNA). cGMP levels were elevated in hyperoxic versus normoxic rats (287+/-15 versus 106+/-9 pmol/mg protein, respectively, p < 0.001), and this increase in cGMP was attenuated after NOS blockade with either AG or L-NNA. Hyperoxic exposure significantly increased lung/body weight ratios and induced histologic changes of interstitial and alveolar edema; however, these hyperoxia-induced histologic changes were not altered by NOS blockade with AG or L-NNA. We conclude that hyperoxic exposure of rat pups up-regulated both iNOS and eNOS and increased NO activity as measured by cGMP levels derived from both iNOS and eNOS. Blockade of NOS reduced cGMP levels in the hyperoxic rat pups; however, it did not seem to reverse the pathologic consequences of hyperoxic exposure.

Prolonged hypoxia increases vascular endothelial growth factor mRNA and protein in adult mouse brain

Brain hypoxia induces an increase in brain vascularity, presumably mediated by vascular endothelial growth factor (VEGF), but it is unclear whether VEGF is required to maintain the increase. In these studies, brain VEGF mRNA and protein levels were measured in adult mice kept in hypobaric chambers at 0.5 atm for 0, 0.5, 1, 2, 4, 7, and 21 days. Hypoxia was accompanied by a transient increase of VEGF mRNA expression: twofold by 0.5 day and a maximum of fivefold by 2 days; these were followed by a decrease at 4 days and a return to basal levels by 7-21 days. VEGF protein expression induced by hypoxia was bimodal, initially paralleling VEGF mRNA. There was an initial small increase at 12 h that reached a maximum by day 2, and, after a transient decrease on day 4, the protein expression increased again on day 7 before it returned to normoxic levels after 21 days. Thus, despite continued hypoxia, both VEGF mRNA and protein levels returned to basal after 7 days. These data suggest a metabolic negative-feedback system for VEGF expression during prolonged hypoxia in the brain.

Lymphocyte and eosinophil influx into alveolar tissue in nocturnal asthma

We have shown in nocturnal asthma that alveolar tissue eosinophils are increased at night as compared with the proximal airway, and that they correlate with the overnight decrement in lung function. As the CD4+ cell is thought to be the principal orchestrating cell in eosinophil recruitment, we evaluated its presence in the proximal and distal airways in nocturnal asthma. Eleven patients with nocturnal asthma (NA) and 10 patients with non-nocturnal asthma (NNA) underwent two bronchoscopies with proximal airway endobronchial and distal alveolar tissue transbronchial biopsy in a random order at 4:00 P.M. and at 4:00 A.M. separated by 1 wk. Immunohistochemical staining and morphometric analysis were used to determine the number of CD3+, CD4+, and CD8+ cells and EG2+ eosinophils per mm2 in the epithelium, lamina propria, and alveolar tissue. At 4:00 A.M., the NA group had a significantly greater number of CD4+ cells in the alveolar tissue than the NNA group (9.8 cells/ mm2 [5.6-30.8, interquartile (IQ)] versus 1.5 cells/mm2 [0-6. 3, IQ], p = 0.04). Within the NA group, there were significantly greater numbers of CD3+, CD4+, CD8+, and EG2+ cells in the proximal airway lamina propria than in the distal airway at both 4:00 P.M. and 4:00 A.M. There were no differences within the epithelium between the groups at either time point. Only alveolar tissue, not airway tissue, CD4+ cells correlated inversely with the percentage predicted FEV1 at 4:00 A.M. (r = -0.68, p = 0.0018) and positively with the number of alveolar tissue EG2+ cells (r = 0.66, p = 0.01). These findings suggest that the CD4+ lymphocyte is increased in the alveolar tissue at night in nocturnal asthma as compared with non-nocturnal asthma.

Mechanism for substance P-induced relaxation of precontracted airway smooth muscle during development

Release of substance P (SP) from sensory nerve endings of the tracheobronchial system modulates airway smooth muscle contraction and may cause relaxation of precontracted airways. We sought to elucidate the effect of postnatal maturation on SP-induced relaxation of precontracted airways and determine the roles of endogenously generated nitric oxide (NO) and prostaglandins (PGs). Cylindrical airway segments were isolated from the midtrachea of rats at four different ages, 1, 2, and 4 wk and 3 mo, and contracted to 50-75% of the maximum response induced by bethanechol. SP was then administered in the absence and presence of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME), the PG inhibitor indomethacin, or both. Relaxation of airways with SP decreased significantly with advancing postnatal age. SP-induced tracheal relaxation was consistently attenuated by pretreatment with L-NAME, indomethacin, or both. In a different group of animals, L-NAME significantly attenuated the relaxant response of airways to PGE2 exposure, but indomethacin had no significant effect on the relaxant response to exogenous NO. We conclude that SP induces a relaxant effect on precontracted airway smooth muscle, which decreases with advancing age and is mediated via SP-induced release of NO and/or PG.

Endocrine regulation of fetal adipose tissue metabolism in the pig: interaction of porcine growth hormone and thyroxine

OBJECTIVE

This study tested the hypothesis that combined treatment of thyroxine (T4) and growth hormone (GH) could normalize cellular and metabolic aspects of adipose tissue development of hypophysectomized fetal pigs.

RESEARCH METHODS AND PROCEDURES

On day 70 of gestation, pig fetuses were hypophysectomized by microcauterization or remained intact. Hypophysectomized fetuses remained untreated or were treated from day 90 to day 105 of gestation with T4, GH, or a combination of both hormones.

RESULTS

Body weights were unaffected by hypophysectomy or hormone treatment. De novo lipogenesis in subcutaneous adipose tissue was increased 10-fold by hypophysectomy, consistent with our previous results. This increase was abolished by GH treatment in the hypophysectomized fetuses. In contrast, T4 treatment of the hypophysectomized fetuses resulted in a 12-fold further increase in adipose tissue lipogenesis, an effect that was negated by concomitant administration of GH. Lipolytic response to isoproterenol was decreased by hypophysectomy, unaffected by GH treatment, and restored to intact values by T4 or by T4+GH treatment in the hypophysectomized fetuses.

DISCUSSION

In contrast to T4, GH does not influence serum insulin-like growth factor-I or adipose tissue lipolysis, but decreases lipogenesis in the fetal pig. However, replacing both T4 and GH normalized hypophysectomized fetuses to a greater extent than either GH or T4 alone. Thus, any influence of thyroid hormones on stimulating adipose tissue lipogenesis in the developing fetal pig may be normally counterregulated by pituitary-derived growth hormone.

Nocturnal asthma is associated with reduced glucocorticoid receptor binding affinity and decreased steroid responsiveness at night

BACKGROUND

The mechanisms for heightened nocturnal inflammation in patients with nocturnal asthma (NA) are not well understood.

OBJECTIVE

We sought to determine the glucocorticoid receptor (GR) characteristics and steroid responsiveness in subjects with NA.

METHODS

Eleven subjects with NA, 12 subjects with nonnocturnal asthma (NNA), and 16 nonasthmatic control subjects underwent blood sampling at 4 pm and 4 am in a random order separated by 1 week. GR binding affinity was measured in PBMCs by using a [3H]-dexamethasone (DX) radioligand binding assay and Scatchard analysis. The capacity of hydrocortisone (HC) and DX to suppress proliferation of PBMCs stimulated with PHA was also determined.

RESULTS

The subjects with NA exhibited a significantly lower GR binding affinity at 4 am, detected by an elevated dissociation constant (Kd) of 22.2 +/- 1.6 nmol/L compared with Kd at 4 pm (10.9 +/- 0.7 nmol/L; P =.0001). The GR Kd of the NNA and control groups did not change significantly from 4 pm to 4 am. Within the NA group, there was also a significant inverse correlation between the absolute FEV1 at 4 am and the Kd at 4 am (r = -0.65, P =.04). PBMCs from subjects with NA exhibited less suppression of PBMC proliferation with HC and DX at 4 am compared with that at 4 pm (P =.0004 and.03 for HC and DX, respectively). There were no circadian changes in suppression of PBMC proliferation in either the NNA or control groups.

CONCLUSION

GR binding affinity and steroid responsiveness exhibit a circadian variation in subjects with NA, with a reduced GR binding affinity and suppression of PBMC proliferation at 4 am that is not observed in normal subjects or asthmatic subjects without nocturnal exacerbation. These observations may contribute to nocturnal airway inflammation by inhibiting the antiinflammatory effects of glucocorticoids.

Intracerebroventricular (i.c.v.) administration of mouse leptin in rats: behavioral specificity and effects on meal patterns

Leptin is a protein that is produced primarily in fat tissue and is thought to be a lipostatic feedback signal for the regulation of body fat stores. The purpose of this study was to determine the behavioral specificity of i.c.v.-administered mouse leptin in rats and to assess the effects on meal patterns. Using a modified two-bottle paradigm we examined the putative aversive response to i.c.v. doses of 1, 5, 7, 10, and 30 microg of mouse leptin. Artificial CSF and intraperitoneal lithium chloride served as negative and positive controls, respectively. Saccharin consumption in all leptin treatments was not significantly different from the negative control. Following a recovery period, rats from the same group were used to assess the effects of a 30-microg i.c.v. dose on cumulative food intake and meal patterns using a computer-based system for acquisition of feeding data. Leptin (i.c.v.) significantly increased intermeal interval and decreased meal size. We, therefore, conclude that mouse leptin, at doses up to 30 microg i.c.v., is not aversive in the rat, and that leptin has a multiphasic effect on meal patterns.

Regulation of adipose cell development in utero

The condition of obesity is impacted by increases in fat cell number, fat cell size, or a combination of the two. It is generally believed that fat cell number is dependent on the age of onset and the degree of obesity. This review provides an update on intrauterine growth of fetal adipose tissue, the earliest period of proliferation onset, and the factors that interact to enhance or suppress development. Fetal adipose tissue development is regulated by the complex interaction of maternal, endocrine, and paracrine influences that initiate specific changes in angiogenesis, adipogenesis, and metabolism. Developmental stages and metabolic processes influenced by specific hormones and paracrine factors have been identified through examination of the offspring of obese and diabetic pregnancies, hormonal manipulation during late pregnancy in animal models, and the use of cell culture. Collectively, the results of the studies cited herein delineate the basis for imprinting or conditioning of fetal preadipocytes at the paracrine/autocrine level and a role of thyroxine, glucocorticoids, and other hormones in fetal adipose tissue development and metabolism.

Association of fat cell size and paracrine growth factors in development of hyperplastic obesity

Inguinal, epididymal, and retroperitoneal adipose tissue from lean and obese Zucker rats, 3-15 wk of age, was used to determine the association among adipocyte size distribution, the presence of paracrine growth factors in adipose tissue, and subsequent changes in adipocyte number. For each specific depot and time point, obese rats had a greater percentage of large adipocytes than did lean rats. A positive correlation (P < 0.02) was found in obese rats between the percentage of inguinal and epididymal adipocytes in the 140- to 180-micrometer size range and the ability of conditioned medium prepared from these depots to stimulate cellular proliferation in a bioassay system utilizing preadipocytes from inguinal fat pads of normal rats. Proliferative activity of the conditioned medium from all depots in obese rats was positively correlated (P < 0.01) to subsequent changes in fat cell number. The data presented here for the inguinal and epididymal depot of obese Zucker rats are consistent with the hypothesis that enlarged adipocytes secrete growth factors that induce preadipocyte proliferation.

Collagen deposition in large airways may not differentiate severe asthma from milder forms of the disease

Chronic airway inflammation and remodeling, including fibrosis, have been proposed as important contributors to asthma pathophysiology. Previous studies of airway fibrosis have been performed mainly in mild and moderate asthmatics at the subepithelial "basement membrane" (SBM) level. The current study was designed to evaluate the large airway SBM thickness and submucosal collagen deposition, as measured by three different collagen staining methods, in endobronchial biopsies from 17 severe, nine moderate, and seven mild asthmatics, as well as eight normal control subjects. Tissue eosinophils and transforming growth factor-beta (TGF-beta) immunoreactivity were also examined. There were no statistically significant differences in the SBM thickness, submucosal collagen deposition, eosinophil numbers, or TGF-beta positive cells among the three groups of asthmatics and the normal control subjects. It was only when examining all asthmatics (n = 33) together, that a modestly thickened SBM (p = 0.04), as evaluated by collagen type III immunostaining, was observed as compared with normal control subjects. Despite this difference, no significant differences were found in the amount of submucosal collagen deposition and the number of eosinophils or TGF-beta expressing cells when comparing total asthmatics and normal control subjects. Additionally, no significant correlations were found between collagen deposition and eosinophil count, TGF-beta expression level, FEV1, or duration of asthma. These results suggest that although increased collagen deposition in the SBM at the large airway level is a characteristic of asthma, it may not explain the differences in severity of asthma.

Responses of lean and obese Zucker rats to centrally administered leptin

Obese (Lepr(fa)/Lepr(fa)) Zucker rats have a missense mutation in the leptin receptor gene. One amino acid substitution in the extracellular domain common to all known leptin receptor proteins results from this mutation. Obese Zucker rats are unable to respond behaviorally to leptin which is peripherally administered. However, conflicting reports exist on whether obese Zucker rats can respond to centrally administered leptin. The purpose of this study was to determine whether obese Zucker rats responded behaviorally and metabolically to intracerebroventricularly (i.c.v.) administered leptin and to compare the responses of lean and obese Zucker rats. We found that both lean and obese Zucker rats had similar body weight and food intake responses when administered a single i.c.v. leptin injection in a range of doses (1.25, 2.5, 5, and 10 microg), as well as daily i.c.v. administered leptin for five consecutive days. Both single and daily leptin administration also decreased respiratory quotient (RQ) similarly in lean and obese Zucker rats, indicating mobilization of fat as an energy source for leptin-treated rats. After withdrawal of daily leptin treatment, lean and obese Zucker rats exhibited different recovery responses. It is concluded that obese Zucker rats can respond to exogenous leptin when leptin is delivered into the brain ventricles.

Muscarinic receptor binding sites of the M4 subtype in porcine lung parenchyma

Muscarinic acetylcholine receptors regulate distal airway resistance and secretion. The subtype expressed in the lung in different species remains uncertain. It has recently become possible to identify the M4 subtype by careful comparison of antagonist affinities. We characterized the binding of [3H]quinuclidinyl benzilate ([3H]QNB) to muscarinic receptors in cell membranes from lung parenchyma of 2-8 week old pigs in comparison to cloned human M3 and M4 receptors expressed in COS cells, to M2 in rat atria and to M4 in bovine adrenal medulla. In porcine lung, [3H]QNB bound with high affinity (Kd = 95 +/- 9 pM) to a single homogeneous population of muscarinic receptor sites (Bmax = 340 +/- 10 fmol/mg protein). Competition studies showed that the affinity (expressed as pKi) of 3 selective blockers was in close agreement between pig lung and cloned human m4 (r = 0.996). A series of 10 blockers showed affinities closely matching reported values for M4 receptors of the adrenal medulla (r = 0.965). Conversely, affinity values in porcine lung differed significantly (P < 0.05, t-test) from those determined in parallel with either human cloned M3 or with rat atria expressing the M2 subtype. We conclude that pig lung muscarinic receptor binding sites most closely resemble the M4 subtype, in contrast to the M3 subtype typical of large airways in this species.

Pathophysiology of nocturnal asthma

LEARNING OBJECTIVES

This article will focus on the pathophysiologic changes underlying the nocturnal worsening of asthma and the therapeutic approach to this disorder.

DATA SOURCES

Selected articles appearing since 1985 dealing specifically with the underlying pathologic features and therapy of nocturnal asthma.

STUDY SELECTION

Studies that aimed to elucidate the pathologic features, mechanisms, and therapeutic strategies for the treatment of nocturnal asthma are summarized.

RESULTS

Nocturnal asthma is associated with significant decline in pulmonary function and increase of airway inflammation at night. The administration of medications must be designed to achieve the maximal effect during the night in nocturnal asthma.

CONCLUSIONS

The further elucidation of the reasons underlying nocturnal asthma should lead to more specific therapeutic interventions with maximal effect at night.

The effects of upper respiratory infection on T-cell proliferation and steroid sensitivity of asthmatics

BACKGROUND

The common cold is a potent trigger for asthma symptoms. Although the mechanisms are not completely understood, inflammatory events may play an important role.

OBJECTIVE

We tested the hypothesis that changes in steroid responsiveness are implicated in the relationship between asthma and the common cold.

METHODS

We investigated the steroid sensitivity of T cells from 10 patients with asthma (not taking steroids) and 10 control subjects, during upper respiratory infection and at recovery (6 weeks later). We stimulated peripheral blood mononuclear cells with phytohemagglutinin to measure T-cell proliferation, sensitivity to the inhibitory effects of steroids, and cytokine production.

RESULTS

During infection compared with recovery, the asthma group exhibited lower responsiveness to dexamethasone at 10(-10) and 10(-9)mol/L and to 10(-10)mol/L hydrocortisone (P <.05) and both groups had decreased T-cell proliferation (P <.05). During recovery, patients with asthma had greater T-cell proliferation than control subjects (P <.02); the values expressed as uptake of [3H]-thymidine were 60119+/-3944 cpm (asthma) and 39078+/-6459 cpm (control subjects). The asthma group had higher TNF-alpha and IFN-gamma production during infection (P <.05); changes in IL-8 and IL-10 levels were not significant, and IL-4 was not detected.

CONCLUSION

During infection, asthmatic subjects exhibit decreased T-cell responsiveness to steroids. The T-cell proliferative response to phytohemagglutinin, higher in asthma, is decreased with a common cold. These findings are associated with changes in the cytokine profile. Thus viral-induced upper respiratory infections can produce an inflammatory milieu with altered steroid function and selective increases in cytokines.

Effect of supplementary dietary biotin on hoof growth and hoof growth rate in ponies: a controlled trial

The effect of dietary biotin supplementation, at a dose rate of 0.12 mg/kg bwt, on growth and growth rate of the hooves of 8 match-paired poines was investigated in a controlled feeding trial. Treatment animals had a mean hoof growth at the midline dead centre of the hoof capsule of 35.34 mm after 5 months of biotin supplementation compared to control animals 30.69 mm (P < 0.05). Comparison of regression analysis also showed that biotin supplementation produced a significantly higher (P < 0.02) growth rate of hoof horn in this trial. Treatment animals had a 15% higher growth rate of hoof horn and 15% more hoof growth at the midline dead centre, after 5 months of biotin supplementation compared to control ponies. No differences were found between feet for growth of horn, but the older animals in the trial had significantly lower hoof growth (P < 0.05) than the remaining poines.

Expression of epithelial markers in nocturnal asthma

BACKGROUND

Although the airway epithelium participates in inflammation and repair, the circadian expression of epithelial cell markers involved in these processes has not been investigated.

OBJECTIVE

We sought to determine whether expression of CD51 (vitronectin and fibronectin receptor), CD54 (intercellular adhesion molecule-1), HLA-DR (activation marker), CD29 (beta1 integrin), CD49b (collagen receptor), and CD11b (complement receptor) exhibit a circadian rhythm in asthma.

METHODS

Eleven patients with nocturnal asthma (NA), 9 subjects with nonnocturnal asthma (NNA), and 10 control subjects underwent bronchoscopy at 4 PM and 4 AM in a random order 1 week apart, with brushing of the proximal and distal airways. The percentage of cells staining for a particular marker was determined.

RESULTS

At 4 PM, HLA-DR in the proximal airways and CD54 in the distal airways was significantly greater in control subjects as compared with asthmatic subjects (HLA-DR, control subjects: 10.0% [range, 5.0% to 21.0%]; NNA: 8.0% [range, 4.0% to 14.5%] NA: 3.5% [range, 2.0% to 6.0%], P = .01; CD54, control subjects: 17.0% [range, 8.0% to 25.0%], NNA: 8.0% [range, 5.3% to 11.5%], NA: 7.0% [range, 4.0% to 15.0%], P = .O;). At 4 AM, CD51 in the distal airways was significantly greater in patients with NA as compared with patients with NNA and control subjects (control subjects, 23.0% [range, 13.8% to 30.5%]; NNA, 32.0% [range, 13.0% to 35.0%]; NA, 40.0% [range, 23.0% to 50.0%], P = .05). Expression of CD51 in the distal airways correlated with the degree of airway obstruction (r = -0.57, P = .001). Control subjects exhibited significant circadian variation in the expression of HLA-DR in the proximal airways and CD54 in the distal airways.

CONCLUSION

The increased CD51 at night in patients with NA may be related to increased airway inflammation and repair processes in response to injury. The circadian changes in CD54 and HLA-DR in control subjects require further study to determine their significance. (J Allergy Clin

Detection of Mycoplasma pneumoniae in the airways of adults with chronic asthma

Infection with Mycoplasma pneumoniae has been shown to exacerbate asthma in humans. However, the role of M. pneumoniae in the pathogenesis of chronic asthma has not been defined. Eighteen asthmatics with chronic, stable asthma and 11 nonasthmatic control subjects underwent evaluation of the upper and lower airways and serologic analysis to determine the presence of M. pneumoniae, Chlamydia pneumoniae, and seven respiratory viruses through culture, enzyme-linked immunoassay (EIA) and polymerase chain reaction (PCR). M. pneumoniae was detected by PCR in 10 of 18 asthmatics and one of 11 control subjects (p = 0.02). In nine of the 10 patients, the organism was detected in bronchoalveolar lavage or bronchial biopsies. Seven of 18 asthmatics and one of 11 control subjects were also positive for M. fermentans and M. genitalium by PCR. All patients' cultures, EIAs, and serology were negative for M. pneumoniae. All PCR and cultures were negative for C. pneumoniae, and all EIAs for respiratory viruses were negative in all subjects. Nine asthmatics and one control subject exhibited positive serology for C. pneumoniae (p = 0.05). M. pneumoniae was present in the lower airways of chronic, stable asthmatics with greater frequency than control subjects, and may play a role in the pathogenesis of chronic asthma.

Single-implant segmental osteotomy: a case report

This case report describes the use of a single-implant osteotomy in repositioning a significantly malaligned, osseointegrated endosseous implant. This technique represents a modification of the single-tooth osteotomy that has been used for many years to reposition the natural dental unit. It provides the dental practitioner with a treatment alternative that is safe, cost-effective, and predictable. The goals of the procedure, the surgical technique employed, and the clinical result are presented.

Nocturnal asthma and the use of theophylline

The nocturnal worsening of asthma is a common event in asthma patients. Some studies have shown the prevalence of nocturnal asthma to be as high as 75% of patients. It is important to understand this phenomenon as nocturnal asthma is associated with decreased daytime cognitive function and increased morbidity and mortality. The exact mechanism for decrements in overnight lung function is not known. However, there are many different processes associated with nocturnal asthma. Day-to-night change in both circulating bronchodilating and bronchoconstricting mediators occur which favour airway narrowing and increased bronchial hyperresponsiveness at night. The beta2 adrenergic receptors decrease in both number and function at night which is associated with a genetic polymorphism, a glycine 16 substitution. Neuroinfluences such as increased nocturnal cholinergic tone also contribute to nocturnal asthma, and a hallmark of nocturnal asthma is increased airway inflammation during sleep. Long-acting theophylline preparations have long been associated with improvement in overnight lung function. Some of these agents can be used in a chronotherapeutic modality, that is, higher blood levels at night when the disease is worse and lower blood levels during the day when lung function is routinely better. Theophylline works as both a bronchodilator and an anti-inflammatory agent to improve nocturnal asthma.

Human corticotropin-releasing hormone improves overnight FEV1 in nocturnal asthma

Corticotropin-releasing hormone (CRH) exhibits anti-inflammatory properties independent of its effect on adrenal function. We investigated the safety and effect of CRH in nocturnal asthma, a disease where inflammation is prominent. Five subjects underwent an overnight infusion of placebo on the first night, CRH at a 2.5 micrograms/kg/hr on the second night, and three subjects received CRH at 4.0 micrograms/kg/hr on the third night. A significant improvement occurred in overnight change in forced expiratory volume 1 sec. % (delta FEV1) with CRH (+17.4 +/- 9.1%) as opposed to placebo (-25.9 +/- 7.1%), p = 0.024, CRH was well tolerated. Further research with CRH may clarify the pathophysiology of nocturnal asthma.

Anthelmintics and ion-channels: after a puncture, use a patch

Two of three major types of anthelminitic, the avermectins and the nicotinic agonists, exert their therapeutic effect by an action on ligand-gated membrane ion-channels of nematodes. The avermectins, such as ivermectin, open glutamategated chloride channels which have so far been found only in invertebrate preparations; nicotinic anthelmintics, like levamisole, selectively gate nematode nicotinic acetylcholine receptors. We describe recent advances in the knowledge of the molecular structure of these ion-channel receptors in nematodes. Because opening of the ion-channels by these two groups of anthelmintic generates currents across cell membranes of nematodes, we can use electrophysiological methods to examine properties of the channels, the mode of action of the anthelmintics, and changes in the receptors associated with anthelmintic resistance. We illustrate some of our observations on these receptors using a two micro-electrode current-clamp technique to monitor membrane resistance (the puncture); and then some observations using The patch-clamp technique to monitor currents through individual ion-channels (the patch). The receptors for the two major groups of anthelmintics may not be homogeneous. Even in a single membrane patch from one muscle cell, nematode nicotinic acetylcholine receptors show evidence of heterogeneity and the avermectins may have multiple sites-of-action. If separate independent recessive genes are involved in production of different receptor subtypes, and if each subtype has to change to allow the development of resistance by the whole nematode, then the probability of resistance developing would be smaller than for anthelminitics with a single site-of-action. The MISER (multiple independent sites-of-action evading resistance) concept favours the development and use of anthelminitics with more than one site-of-action.

Persistence of the biphasic ventilatory response to hypoxia in preterm infants

OBJECTIVE

To characterize postnatal maturation of the biphasic ventilatory response to hypoxia in order to determine whether it persists beyond the first weeks of life in preterm infants, and the contributions of respiratory frequency and tidal volume to this response.

METHODS

Stable preterm infants were studied at two postnatal ages, 2 to 3 weeks (n = 12) and 4 to 8 weeks (n = 12), before hospital discharge at 35 weeks (range, 33 to 38 weeks) of postconceptional age. Infants were exposed to 5 minutes of 15% (or 13%) inspired oxygen; ventilation, oxygen saturation, end-tidal partial pressure of carbon dioxide, and heart rate were simultaneously recorded.

RESULTS

Minute ventilation exhibited a characteristic biphasic response to hypoxia at both postnatal ages, regardless of the development of periodic breathing. At both ages there was a transient increase in tidal volume, which peaked at 1 minute, accompanied by a sustained decrease in respiratory frequency as a result of significant prolongation of expiratory time.

CONCLUSION

The characteristic biphasic ventilatory response to hypoxia persists into the second month of postnatal life in preterm infants. We speculate that this finding is consistent with the prolonged vulnerability of such infants to neonatal apnea.

Dietary fat type and level influence adiposity development in obese but not lean Zucker rats

The development of obesity is influenced by a variety of factors including genetics and dietary fat type and level. To examine the interaction between these factors, male lean and obese Zucker rats (5 weeks initial age) were fed either a low-fat (15% calories) or one of two high-fat diets (65% calories; predominant fat source of either soybean oil or palm olein) for 8 weeks. Body weight, food intake, indirect calorimetry, and body composition determinations were performed. As expected, food intake, body weight, feed efficiency, oxygen consumption, heat production and carcass lipid were all significantly higher in obese compared to lean rats. Dietary fat level and/or type influenced body weight gain, oxygen consumption, heat production, energy balance, and carcass weight and lipid content in the obese but not in the lean Zucker rats. Oxygen consumption and carcass weight were increased approximately 25% and 10% respectively in obese rats fed either of the two high-fat diets as compared to those fed the low-fat diet. The type of fat fed in the high-fat diets also influenced body weight gain, heat production, energy balance, and carcass lipid content of the obese rats. Body weight gain and carcass lipid content were increased (16%-17%; P < 0.005) in obese rats fed the high-fat palm olein diet as compared to those fed the low-fat diet. These parameters were not increased in obese rats fed the high-fat soybean oil diet. In contrast, indirect calorimetry measurements indicated a moderate increase in heat production (Kcal/effective body mass/day; 14.5%) and decrease in energy balance (44.8%) in the obese rats fed the high-fat soybean oil diet as compared to those fed the low-fat diet. Energy expenditure and lipid accumulation were negligibly influenced by dietary fat level or type in the lean Zucker rats. The differential response of the lean and obese Zucker rats to this short-term dietary manipulation demonstrate that genetic background can influence an individual's response to dietary fat type and level. The genetically obese Zucker rat appears to be a good model for further studies of high-fat diet-induced obesity.

Dietary fat type influences protein consumption in rats given 8-hydroxy-2-(Di-n-propylamino)tetralin

Our previous work indicates that type and level of dietary fat influences selection of protein and carbohydrate diets. Serotonin (5HT) appears to be involved in this feeding behavior. In the present study, we examined the effects of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on feeding behavior, and fenfluramine on in vitro 5HT and 5-hydroxyindoleacetic acid (5HIAA) release from the brain in rats fed tallow or corn oil. Male, Sprague-Dawley rats were given a diet containing corn oil or tallow for 2 days. In Experiment 1, rats received an injection of 8-OH-DPAT (a 5HT1A agonist) or saline and were then allowed to select from two diets: low protein/high carbohydrate or high protein/low carbohydrate. Prior exposure to tallow caused an increased intake of protein and 8-OH-DPAT blunted this effect. In Experiment 2, the dorsal raphe from rats fed tallow or corn oil was superfused with fenfluramine or vehicle. Superfusates were collected for analysis of 5HT and 5HIAA. Fenfluramine increased serotonin release in tallow-fed animals as compared to basal. These results suggest that serotonin may be involved in mediating tallow's effect on macronutrient selection.

Intracerebroventricular administration of antisense oligodeoxynucleotide against GLUT2 glucose transporter mRNA reduces food intake, body weight change and glucoprivic feeding response in rats

The GLUT2 glucose transporter, which may play a glucose-sensing role in hepatocyte and islet beta cells because of its low affinity and high Km for glucose, has been identified in some discrete brain areas that are related to feeding behavior and energy metabolism. We tested the hypothesis that brain GLUT2 may play a role in the control of food intake by antisense technology loss-of-function analysis. Antisense oligonucleotides directed against GLUT2 mRNA were administered intracerebroventricularly to eight rats daily for 13 days. Another eight rats were administered intracerebroventricularly with missense oligonucleotides as the control. Food intake was monitored by a computerized feeding system. Data were analyzed using a one-way general linear model or Mann-Whitney U test when appropriate. Cumulative food intake and body weight change in antisense-treated rats were significantly lower (18 and 160%, respectively) in the group treated with antisense oligonucleotides than in the group treated with missense control oligonucleotides. There was no increase in cumulative food intake in response to 2-deoxyglucose challenge in rats treated with antisense oligonucleotide, but in those treated with missense control oligonucleotide, cumulative food intake was fivefold greater in response to 2-deoxyglucose. These data suggest a possible role of brain GLUT2 in the regulation of food intake and body energy stores.

Whole body composition of rats determined by dual energy X-ray absorptiometry is correlated with chemical analysis

The use of dual energy X-ray absorptiometry (DXA) is increasing in animal research, but data comparing whole body composition by DXA and chemical analysis (CHEM) in rats are limited. Lean and obese Zucker female rats were used to compare DXA (QDR1000W, Hologic, Waltham, MA) values with CHEM data for percent fat (%FATDXA, %FATCHEM), lean body mass (%PROTDXA, %PROTCHEM) and bone mineral content (%BMCDXA, %ASHCHEM). Four groups of rats (n = 9) were tested for differences in body composition due to consumption of a 100 g guar gum supplement/kg to see if DXA was as sensitive as CHEM in detecting body composition differences induced by diet. The study was analyzed using a split-plot ANOVA where the main plot was a 2 x 2 factorial with phenotype (obese or lean) and treatment (guar gum or control) as the effects, and the subplot was method of detecting body composition (DXA and CHEM), which was treated as a repeated measure. Absolute values for percent fat differed significantly (P < 0.0001) between the two methods as %FATDXA was consistently higher than %FATCHEM. There was not a statistically significant difference due to method for %PROT (P = 0.13). Values for %BMCDXA were significantly (P < 0.0049) lower than %ASHCHEM values. The differences in body composition due to diet treatment were detected similarly by DXA and CHEM. Significant correlations were found between the methods (P < 0.0001) for %FAT (r = 0.99), %PROT (r = 0.96) and %BMC or ASH (r = 0.81). Bland-Altman plots showed good agreement between methods, and regression equations were developed to estimate CHEM values from DXA readings. DXA may provide an alternative method for assessing changes in whole body composition.

Longer-term fourth ventricular 5-thioglucose infusion increases body fat in the rat

5-Thioglucose (5-TG) has been shown to increase food intake after acute administration. To determine the longer-term effects of 5-TG on feeding and body composition, thirty-four female Sprague-Dawley rats were cannulated into the fourth ventricle and infused with artificial CSF and either 0.01 M 5-TG or 0.1 M 5-TG using osmotic pumps. Food intake and body weight were monitored daily. Rats were killed after 14 days of infusion. Carcass and fatpad weights were measured, and body compositions were determined. Food intake was not different during the first week of infusion; however, cumulative food intake was decreased in the 0.1 M 5-TG group during the second week as compared to the CSF control group. Body weight and carcass weight of this group also decreased as compared to the control. The group receiving the higher dose of 5-TG (0.1 M) had increased fatpad weights in all three depots examined (inguinal, retroperitoneal, and perimetrial depot); the group with lower dose of 5-TG infusion (0.01 M) increased the fatpad weights in the retroperitoneal and perimetrial depot, as compared to the CSF group. Data from the body composition analysis were consistent with the results of the fatpad weights. In conclusion, the present study demonstrated that chronic fourth ventricular 5-TG infusion increased body fat without increasing food intake, suggesting that energy expenditure is decreased under this condition. The results of this study indicate that glucose metabolism in the hindbrain is important in the control of energy expenditure, body fat deposition, and thus energy balance regulation.

Neuropeptide Y antibody attenuates 2-deoxy-D-glucose induced feeding in rats

2-deoxy-D-glucose (2-DG) has been shown to induce increased feeding responses in animals. Recent studies suggest the possible involvement of neuropeptide Y (NPY) in 2-DG-induced feeding. The present study examined the effect of immunoneutralization of endogenous NPY on 2-DG-induced feeding. NPY antibody injected into the paraventricular nucleus of the rats significantly attenuated 2-DG-induced feeding, suggesting that hypothalamic NPY may mediate, at least partly, the effect of 2-DG on food intake.

Serum cortisol in asthma: marker of nocturnal worsening of symptoms and lung function?

Changes in the hormone cortisol have been implicated in the pathogenesis of nocturnal worsening of asthma, or nocturnal asthma (NA). We studied 45 patients, 15 with NA, 15 subjects with non-nocturnal asthma (NNA), and 15 controls over a 24h period, measuring forced expiratory volume in 1 second (FEV1) and serum cortisol at 08:00, 12:00, 16:00, 20:00, 23:00, 04:00, and 08:00 the following day. Evaluation of the time response curves for cortisol revealed a significant difference in the shape of the curves (p = 0.04 by mixed-effects model). Evaluation of individual time points revealed that the cortisol levels in the NNA and control groups were significantly lower than in the NA group at 20:00 (NNA: 3.5 +/- 0.8 mg/mL;

CONTROLS

3.4 +/- 0.8 mg/mL; NA: 4.9 +/- 0.8 mg/mL; p = 0.007). The percentage (%) predicted FEV1 was significantly different among the three groups over the 24h period (p < 0.001). The percentage predicted FEV1 was significantly lower in the NA group compared to the control group at all time points and significantly lower than the NNA group at 16:00, 23:00, and 04:00. The difference among the groups was most pronounced at 04:00, when the percentage predicted FEV1 was 58.9 +/- 2.2% in the NA group, 76.8 +/- 2.9% in the NNA group, and 91.6 +/- 2.8% in the control group (p = 0.001, where each group is significantly different from the others). Although the time response curves for cortisol were significantly different among the three groups, the differences in serum levels of cortisol do not appear to be clinically significant. Therefore, serum levels of cortisol may not be the appropriate measurement to assess the role of cortisol in nocturnal asthma.

Role of the medullary raphe nuclei in the respiratory response to CO2

We characterized the role of neurons within the midline of the medulla oblongata on phrenic and hypoglossal nerve responses to hypercapnia during early-development. Studies were performed on decorticate or anesthetized; vagotomized and mechanically ventilated 14-20 day old piglets. Reversible withdrawal of midline neuronal activity was induced by microinjections of lidocaine (2%, 300 nl; n = 10) and lesioning was caused by microinjections of the neurotoxic agent, ibotenic acid (n = 12), at the same sites. At any given end-tidal CO2, peak phrenic and hypoglossal activities after lidocaine were significantly lower than in the control period (P < 0.01). Similarly, 1-2 h after injections of ibotenic acid, both phrenic and hypoglossal nerve responses to CO2 were significantly lower than in the control period (P < 0.01). The results indicate for the first time that the medullary midline neurons are required for full expression of ventilatory responses to hypercapnia and raise the possibility that dysfunction of these nuclei may contribute to respiratory instability during early postnatal life.

Further studies on the chronotherapy of asthma with inhaled steroids: the effect of dosage timing on drug efficacy

BACKGROUND

Chronotherapy studies with inhaled corticosteroids have shown optimal therapeutic benefit when steroids are administered four times per day (QID) or once daily at 3 PM.

OBJECTIVE

This study evaluated whether more convenient once-daily dosage times (8 AM and 5:30 PM) produce improvement in asthma equivalent to QID.

METHODS

Efficacy outcome measures included FEV1, peak expiratory flow rates, bronchial responsiveness, use of beta2-agonists, nocturnal awakenings, and responses to a quality of life questionnaire. Systemic effects were blood eosinophil count, cortisol level, 24-hour urinary cortisol, and evaluation for oral candidiasis and dysphonia.

RESULTS

Baseline measurements for all three treatment groups were similar. For morning peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.001) and the 5:30 PM group (p = 0.003), but not the 8 AM group (p = 0.75). For evening peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.005) and the 5:30 PM group (p = 0.01), but not for the 8 AM group (p = 0.47). There were significant improvements in all other outcome variables for each group except PC20. There was a significant improvement in PC20 only in the QID group. The systemic effects of the three regimens were comparable.

CONCLUSION

Dosing of inhaled steroid at 5:30 PM had no increased systemic effects and produced efficacy similar to QID dosing. Dosing at 8 AM did not produce results consistently comparable to QID dosing. Optimal once-daily dosing of inhaled steroid is between 3 PM and 5:30 PM.

Target sites of anthelmintics

This paper reviews sites of action of anthelmintic drugs including: (1) levamisole and pyrantel, which act as agonists at nicotinic acetylcholine receptors of nematodes; (2) the avermectins, which potentiate or gate the opening of glutamategated chloride channels found only in invertebrates; (3) piperazine, which acts as an agonist at GABA gated chloride channels on nematode muscle; (4) praziquantel, which increases the permeability of trematode tegument to calcium and results in contraction of the parasite muscle; (5) the benzimidazoles, like thiabendazole, which bind selectively to parasite beta-tubulin and prevents microtubule formation; (6) the proton ionophores, like closantel, which uncouple oxidative phosphorylation; (7) diamphenethide and clorsulon, which selectively inhibit glucose metabolism of Fasciola and; (8) diethylcarbamazine, which appears to interfere with arachidonic acid metabolism of filarial parasites and host. The review concludes with brief comments on the development of anthelmintics in the future.

An evaluation of colchicine as an alternative to inhaled corticosteriods in moderate asthma. National Heart, Lung, and Blood Institute's Asthma Clinical Research Network

Colchicine demonstrates an array of anti-inflammatory properties of potential relevance to asthma. However, the efficacy of colchicine as an alternative to inhaled corticosteroid therapy for asthma is unknown. Five centers participated in a controlled trial testing the hypothesis that in patients with moderate asthma needing inhaled corticosteroids for control, colchicine provides therapeutic benefit as measured by maintenance of control when inhaled steroids are discontinued. Subjects were stabilized on triamcinolane acetonide (800 microg daily) and then enrolled in a 2-wk run-in during which all subjects took both colchicine (0.6 mg/twice a day) and triamcinolone. At the end of the run-in, all subjects discontinued triamcinolone and were randomized to continued colchicine (n = 35) or placebo (n = 36) for a 6-wk double-blind treatment period. The treatment groups were similar in terms of disease severity. After corticosteroid withdrawal, 60% of colchicine-treated and 56% of placebo-treated subjects were considered treatment failures as defined by preset criteria. No significant difference in survival curves was found between treatment groups (log rank = 0.38). Other measures, including changes in FEV1, peak expiratory flow, symptoms, rescue albuterol use, and quality of life scores, also did not differ between groups. Of note, subjects failing treatment had significantly greater methacholine responsiveness at baseline than did survivors (PC20, 0.81+/-1.38 versus 2.11+/-2.74 mg/ml; p = 0.01). An analysis of treatment failures suggested that the criteria selected for failure reflected a clinically meaningful but safe level of deterioration. We conclude that colchicine is no better than placebo as an alternative to inhaled corticosteroids in patients with moderate asthma. Additionally, we conclude that the use of treatment failure as the primary outcome variable in an asthma clinical trial where treatment is withdrawn is feasible and safe under carefully monitored conditions.

Bronchoscopic evaluation of severe asthma. Persistent inflammation associated with high dose glucocorticoids

The role of inflammation in the pathogenesis of severe asthma chronically treated with high doses of glucocorticoids is poorly understood. Despite this, treatment has been aimed at advancing anti-inflammatory and immunomodulator therapy. This study was designed to evaluate both the presence and type of airway inflammation in patients with severe asthma. A prospective bronchoscopic study evaluated 14 severe, high-dose oral glucocorticoid dependent asthmatics. Bronchoalveolar lavage fluid was analyzed for cytology and inflammatory mediators. Endobronchial and transbronchial biopsies were performed in selected patients for morphometric evaluation of macrophage/monocytes, neutrophils, eosinophils and lymphocytes. These results were compared with lavage and endo- and transbronchial biopsy studies in normal controls and patients with moderate asthma. The concentration of eosinophils in bronchoalveolar lavage fluid was highest in the moderate asthmatics not on glucocorticoids, with very little difference between normal controls and severe asthmatics (significant difference among the groups, p = 0.007). In contrast, the severe asthmatics demonstrated a twofold higher concentration of neutrophils in lavage than either the mild-moderate asthmatics, or the normal controls (p = 0.032 among the groups, p < 0.05 between the severe asthmatics and both controls). Similar results were obtained in the endobronchial and transbronchial biopsy specimens, which consistently showed significantly higher numbers of neutrophils in the severe asthmatics than in the control groups. The eicosanoid mediators, thromboxane and leukotriene B4, were also highest in the severe asthma group (differences among the groups, p = 0.019 and p = 0.023, respectively). These findings suggest that inflammation remains in severe symptomatic asthmatics despite treatment with high dose glucocorticoids which may be due to the severity of disease, glucocorticoid treatment, or other as yet undefined factors.

Role of endogenous NO in modulating airway contraction mediated by muscarinic receptors during development

We sought to characterize the role of endogenous nitric oxide (NO) released from airway epithelium in attenuating tracheal smooth muscle (TSM) contraction induced by exposure to acetylcholine (ACh). Organ bath experiments were performed on TSM from young pigs of three ages (3-7 days, 2-3 wk, and 3 mo). Concentration-response curves to cumulative doses of ACh (10(-8) to 10(-4) M) were generated before and after addition of the NO synthase blocker N omega-nitro-L-arginine methyl ester (L-NAME). L-NAME caused a significant increase in cholinergic sensitivity (decrease in 50% effective dose) at 3-7 days and 2-3 wk but not 3 mo. Maximum responses to ACh increased after L-NAME at all three ages. Removal of tracheal epithelium caused a significant increase in sensitivity to ACh at all ages, which progressively declined with advancing age. In the absence of epithelium, L-NAME no longer influenced contractile responses to ACh. Density of M3 muscarinic receptors in tracheal epithelium was upregulated in the youngest piglets. We conclude that, under in vitro conditions, release of endogenous NO opposes cholinergically induced contraction of piglet TSM. This phenomenon diminishes with advancing postnatal age, requires an intact airway epithelium, and correlates with upregulation of M3 muscarinic receptors in airway epithelium. We speculate that NO may play a useful role in attenuating cholinergically mediated airway smooth muscle contraction in early life when pulmonary function is characterized by high airway resistance.

Eosinophil-associated TGF-beta1 mRNA expression and airways fibrosis in bronchial asthma

The histopathology of bronchial asthma is associated with structural changes within the airways, including subepithelial fibrosis, as well as chronic eosinophilic inflammation. The mechanisms responsible for this tissue remodeling, and in particular the role of inflammatory cells, remain to be established. Transforming growth factor-beta (TGF-beta) is a potent profibrotic cytokine which may contribute to the thickening of the reticular lamina by the deposition of collagen fibers. To investigate the molecular mechanisms underlying these structural changes, we have investigated the expression of TGF-beta1 mRNA and immunoreactivity within the bronchial mucosa of mild to severe asthmatic individuals and normal control subjects using the techniques of in situ hybridization and immunocytochemistry. As eosinophils are prominent within the asthmatic airway and are known to synthesize pro-inflammatory cytokines, the presence of TGF-beta1 mRNA and immunoreactive protein in eosinophils was also examined. Asthmatic individuals exhibited a greater expression of TGF-beta1 mRNA and immunoreactivity in the airways submucosa than normal control subjects (P < 0.05), and these increases were directly related to the severity of the disorder. The extent of airways fibrosis, as detected histochemically, was also increased in asthmatics compared with normal control subjects (P < 0.005). In asthmatic subjects, the presence of subepithelial fibrosis was associated with the severity of the disease and correlated with the decline in forced expiratory volume in 1 s (r2 = 0.78; P < 0.05). Within the asthmatic airways, EG2-positive eosinophils represented the major source of TGF-beta1 mRNA and immunoreactivity. These results provide evidence that TGF-beta1 may play a role in the fibrotic changes occurring within asthmatic airways and that activated eosinophils are a major source of this cytokine.

Quality control of peak flow meters for multicenter clinical trials. The Asthma Clinical Research Network (ACRN)

Although peak expiratory flow (PEF) measurements are recommended for monitoring and assessing treatment of asthmatic patients, and widely employed to assess outcome in clinical trials and epidemiologic studies, information about performance of peak flow meters (PFM) under field conditions is lacking. We describe a simple testing system consisting of a testing chamber, a spirometer, and a calibration syringe to evaluate the relative accuracy or median relative bias (MRB), precision, or inter-quartile range (IQR) of the mini-Wright PFM. The relative accuracy ranged from -4.4 to 13.2% (mean, 4.1%) and the precision from 0.06 to 11.5% (mean, 1.2%). Durability of this PFM was assessed during a 26-wk clinical trial in 255 asthmatic subjects at five centers. Seventy-one PFM (19.9%) were identified as having failed to meet acceptance criteria, predominantly because of loss of relative accuracy, by the clinics at follow-up visits (n = 36), and by the Data Coordinating Center on retrospective review of quality control measurements submitted by the clinics (n = 35). This study indicates that a simple device can be used to evaluate the relative accuracy and precision of a given PFM and to ensure the quality of PEF measurements during a clinical trial. To the extent that one can extrapolate these data to other devices, our findings indicate that the failure rate of PFM over time can be high, indicating that quality control of a PFM over time is absolutely essential in clinical trials as well as in routine clinical care.

A vesicle preparation for resolving single-channel currents in tegument of male Schistosoma mansoni

A tegumental vesicle preparation from adult male Schistosoma mansoni was developed that allows the resolution of single ion-channel currents. Adult male schistosomes were exposed to a low pH (3.75) medium for a period of approximately 30 min at 37 degrees C. During this period smooth vesicles formed from the tegument. Fluorescence microscopy following staining of the tegument with the dye, 5-N-[octadecanoyl]aminofluorescein (AF-18), transmission electron microscopy and scanning electron microscopy revealed that the vesicles were produced from the outer tegumental membrane. The fluorescence studies showed the presence of the double bilayer structure of the outer membrane in > 41% of the vesicles. These studies suggested that the preparation is suitable for single-channel recording with the patch-clamp technique. Cell-attached and isolated inside-out patch recordings of ion-channel activity were obtained with giga-ohm resistance seals. Different types of ion-channel were recorded from tegumental vesicles from male schistosomes, illustrating the potential of the technique. The channels observed included: a non-selective cation channel (360 pS); a K+ channel (with a conductance of 115 pS in high bath-K conditions); and a Cl- selective channel (20 pS). The currents of these ion-channels may cross the double bilayer of the outer tegumental membrane.

Methacholine challenge testing: safety of low starting FEV1. Asthma Clinical Research Network (ACRN)

STUDY OBJECTIVE

The lower limit for the baseline value to initiate methacholine bronchial hyperresponsiveness testing has not been well established. Recommendations have varied from > 1 L to above 80% of predicted. The objective was to determine if an FEV1 < 60% predicted was acceptable.

DESIGN

Retrospective analysis of challenges in 88 patients with a baseline FEV1 of < 60% predicted (mean=45.8%; range, 22 to 59%.

SETTING

Academic institutions.

RESULTS

There were only four individuals whose FEV1 did not return to > 90% of baseline following one poststudy beta2-agonist treatment. All four responded to a second treatment. There were no adverse sequelae following challenge in any individual. Neither age (up to 79 years) nor gender influenced outcome.

CONCLUSIONS

In chronic moderate to severe asthma, it appears that bronchial hyperresponsiveness testing can be safely performed even in those patients with a low baseline FEV1.

Effect of hyperoxia on substance P expression and airway reactivity in the developing lung

This study was undertaken to characterize changes in the tachykinin system induced by hyperoxic exposure and the potential effects on airway contractile responses. We exposed 7-day-old rat pups to either room air or hyperoxia (> 95% O2) for 7 days to assess pulmonary beta-preprotachykinin (beta-PPT) gene expression, substance P (SP) levels, and airway contractile responses to cholinergic stimulation before and after neurokinin-1 (NK1) receptor blockade. Lung beta-PPT mRNA expression, lung and tracheal SP levels, and contractile responses to exogenous acetylcholine and electrical field stimulation were measured in vitro in normoxia- and hyperoxia-exposed tracheal cylinders. Hyperoxia caused a 1.1- to 2.6-fold increase in steady-state lung beta-PPT mRNA and a 50 and 32% increase in SP levels of lung and trachea, respectively. In response to cholinergic stimulation, maximal contractile force (Emax) of hyperoxia exposed tracheal muscle was significantly higher than for normoxic controls. Addition of the SP (NK1) receptor blocker CP-99994 (10 microM) decreased sensitivity to electrical field stimulation in both hyperoxic and normoxic trachea without a significant decline in Emax. These data provide evidence for both increased SP production and enhanced maximal contractile responses of hyperoxia-exposed neonatal trachea to cholinergic stimulation. The tachykinin peptide SP does not, however, appear to play a major role in the enhanced airway reactivity associated with hyperoxic lung injury during early postnatal life.

Modes of action of anthelmintic drugs

Modes of action of anthelmintic drugs are described. Some anthelmintic drugs act rapidly and selectively on neuromuscular transmission of nematodes. Levamisole, pyrantel and morantel are agonists at nicotinic acetylcholine receptors of nematode muscle and cause spastic paralysis. Dichlorvos and haloxon are organophosphorus cholinesterase antagonists. Piperazine is a GABA (gamma-amino-butyric acid) agonist at receptors on nematode muscles and causes flaccid paralysis. The avermectins increase the opening of glutamate-gated chloride (GluCl) channels and produce paralysis of pharyngeal pumping. Praziquantel has a selective effect on the tegument of trematodes and increases permeability of calcium. Other anthelmintics have a biochemical mode of action. The benzimidazole drugs bind selectively to beta-tubulin of nematodes, cestodes and fluke, and inhibit microtubule formation. The salicylanilides: rafoxanide, oxyclozanide, brotianide and closantel and the substituted phenol, nitroxynil, are proton ionophores. Clorsulon is a selective antagonist of fluke phosphoglycerate kinase and mutase. Diethylcarbamazine blocks host, and possibly parasite, enzymes involved in arachidonic acid metabolism, and enhances the innate, nonspecific immune system.

Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation

Non-invasive techniques for monitoring ventilation in infants are widely used in short-term laboratory-studies but have not been evaluated in routine clinical settings. To determine whether respiratory inductance plethysmography (RIP) can provide reproducible measurements of tidal volume (VT) in premature infants over an extended period of time, we monitored respiration in eight healthy preterm infants over 4.9 +/- 1.0 hours (mean +/- SD). The algebraic sum (Sum) of rib cage (RC) and abdominal (AB) motion signals (obtained by RIP) was calculated and presented over the entire recording period as percent of an initial 5 minute calibration period. VT was simultaneously measured with a nasal mask pneumotachometer with infants in prone and supine positions during active and quiet sleep. Infants were studied in the morning (AM) and again in the afternoon (PM). Between these studies they were returned to the nursery wearing the RIP in a continuous record mode. For all patients there was a significant linear relationship between VT (in mL measured by pneumotachometer) and Sum (in % of calibration value, RIP). Neither the slope of the relationship (0.074 +/- 0.03 in AM vs. 0.071 +/- 0.02 in PM), nor its variability as measured by standard error of the estimate (SEE) (2.3 +/- 0.5 in AM vs. 2.5 +/- 0.8 in PM) changed significantly from AM to PM. The relationship between VT and Sum, as well as the variability of that relationship, was not altered by position, asynchrony of RC and AB, respiratory rate, or percent RC contribution to Sum. We conclude that RIP produces consistent measurements of respiratory effort over 5 hours in healthy preterm infants without need for recalibration and is not affected by routine care.

Effect of exogenous and endogenous nitric oxide on the airway and tissue components of lung resistance in the newborn piglet

Despite widespread reports of the vasodilatory actions of nitric oxide (NO), little is known of the relaxant effect of NO on newborn airways or lung parenchymal structures. We studied the effects of inhaled NO at 20, 40, and 80 ppm on lung (Rl), tissue (Rti), and airway (R(aw)) resistance in 13 2-5-d-old anesthetized, ventilated, open-chested piglets. Rl was measured from transpulmonary pressure and air flow. Rti was measured by alveolar capsules, and R(aw) was calculated as the difference between Rl and Rti. Any given concentration of inhaled NO (20, 40, or 80 ppm) significantly decreased Rl (p < 0.001), Rti (p < 0.001), and R(aw) (p < 0.05). In addition, blockade of endogenous NO with 30 mg/kg N omega-nitro-L-arginine methyl ester (L-NAME) given i.v. in 12 piglets significantly increased Rti and Rl with variable changes in R(aw), and caused a decrease in dynamic compliance. Readministration of NO to eight piglets induced a significant decreased in Rl and Rti at 20 and 80 ppm, whereas R(aw) significantly decreased only at 80 ppm. Pulmonary arterial pressure decreased after exposure to inhaled NO and increased after L-NAME administration. Systemic arterial pressure was unaffected by inhaled NO but increased after L-NAME administration. Our results indicate that Rl, R(aw), and Rti are reduced by exogenous NO, suggesting NO-mediated airway smooth muscle relaxation throughout the newborn lung. In contrast, blockade of endogenous NO significantly increases only Rti, suggesting a physiologic role for endogenous NO in regulation of peripheral contractile elements. We speculate that NO-mediated modulation of resistance in pulmonary parenchyma may serve to regulate the balance of ventilation and perfusion and resultant gas exchange in the lungs during early postnatal development.