A modified silent substitution electroretinography protocol to separate photoreceptor subclass function in lightly sedated dogs

OBJECTIVE

A previously published study successfully isolated photoreceptor responses from canine rods, long/medium-wavelength (L/M) cones, and short-wavelength (S) cones using silent substitution electroretinography (ERG) performed under general anesthesia. We hypothesized that responses would be similar in dogs under sedation and that a curtailed protocol suitable for use in clinical patients could effectively isolate responses from all three photoreceptor subtypes.

ANIMALS STUDIED

Three normal adult purpose-bred beagles (2 females and 1 male).

METHODS

Dogs were dark-adapted for 1 hour. Sine wave color stimuli were delivered using LEDs in a Ganzfeld dome. The ERG protocol under anesthesia was performed as previously published; sedated ERG protocols were performed after a 3-day washout period. Intravenous sedation (dexmedetomidine 1.25 mcg/kg, butorphanol 0.1 mg/kg) was administered for sedation. Statistical analysis was performed using two-way repeated-measures ANOVA and linear regression.

RESULTS

In both anesthetized and sedated animals, rod-derived responses peaked at low frequency (4-12 Hz), L/M-cone responses peaked at high frequency (32-38 Hz), and S-cone responses peaked at low frequency (4-12 Hz). The frequencies eliciting maximal responses were similar in sedated and anesthetized protocols, although rod amplitudes were significantly higher in the sedated protocols compared with anesthetized (P < .001).

CONCLUSION

We present a clinically applicable method to consistently isolate rod and cone subclass function in sedated dogs. This may allow detailed evaluation of photoreceptor function in clinical patients with rod or cone subclass deficits without the need for general anesthesia or protracted adaptation times.

Dectin-2 sensing of house dust mite is critical for the initiation of airway inflammation

How the immune system senses aeroallergens and triggers an aberrant inflammation is poorly understood. Dectin-2 is a house dust mite (HDM)-sensing pattern recognition receptor. In a 3-week mouse model of repeated intranasal HDM challenge, anti-Dectin-2 potently attenuated the characteristic allergic inflammation and airway hyper-responsiveness. Anti-Dectin-2 also prevented neutrophil influx following a single HDM challenge. Interestingly, cysteinyl leukotrienes, but not chemokine and cytokine levels were inhibited by anti-Dectin-2 in this acute model, and in ex vivo challenge of cultured alveolar macrophages with HDM. Furthermore in the single-challenge model, zileuton, an inhibitor of leukotriene production, produced a similar effect as Dectin-2 blockade. Together these data suggest alveolar macrophage sensing of HDM by Dectin-2 elicits the production of cysteinyl leukotrienes, and this axis is key for the initiation of airway inflammation to this aeroallergen. Finally, we found Dectin-2-positive infiltrating cells present in bronchial biopsies from asthmatic subjects.

Distinct responses to hypoxia in subpopulations of distal pulmonary artery cells contribute to pulmonary vascular remodeling in emphysema

We have shown previously that hypoxia inhibits the growth of distal human pulmonary artery smooth muscle cells (PASMC) isolated under standard normoxic conditions (PASMC(norm)). By contrast, a subpopulation of PASMC, isolated through survival selection under hypoxia was found to proliferate in response to hypoxia (PASMC(hyp)). We sought to investigate the role of hypoxia-inducible factor (HIF) in these differential responses and to assess the relationship between HIF, proliferation, apoptosis, and pulmonary vascular remodeling in emphysema. PASMC were derived from lobar resections for lung cancer. Hypoxia induced apoptosis in PASMC(norm) (as assessed by TUNEL) and mRNA expression of Bax and Bcl-2, and induced proliferation in PASMC(hyp) (as assessed by (3)H-thymidine incorporation). Both observations were mimicked by dimethyloxallyl glycine, a prolyl-hydroxylase inhibitor used to stabilize HIF under normoxia. Pulmonary vascular remodeling was graded in lung samples taken from patients undergoing lung volume reduction surgery for severe heterogenous emphysema. Carbonic anhydrase IX expression in the medial compartment was used as a surrogate of medial hypoxia and HIF stabilization and increased with increasing vascular remodeling. In addition, a mixture of proliferation, assessed by proliferating-cell nuclear antigen, and apoptosis, assessed by active caspase 3 staining, were both higher in more severely remodeled vessels. Hypoxia drives apoptosis and proliferation via HIF in distinct subpopulations of distal PASMC. These differential responses may be important in the pulmonary vascular remodeling seen in emphysema and further support the key role of HIF in hypoxic pulmonary hypertension.

Agreement between measures of total motility and membrane integrity in stallion sperm

Increasing seminal plasma concentrations in extended stallion semen were utilized to model decreasing sperm motility over time. Level of agreement was determined between flow cytometric measurement of sperm membrane integrity, using a combination of SYBR-14 and propidium iodide, and computer-assisted analysis of sperm motility. Values for total sperm motility (TMOT;%) and membrane integrity (SMI;%) were similar (∼80%) at Time 0 within all sperm treatments. However, TMOT was lower than SMI after 24 and 48 h of storage in treatments with >20% seminal plasma. At Time 0, agreement (bias and absolute difference) between TMOT and SMI was high (-0.7 and 5.6%, respectively), but decreased after 24 (10.8 and 15.1%, respectively) and 48 h (23.0 and 23.8%, respectively) of cooled storage as motility declined more rapidly than SMI. We concluded that TMOT and SMI measured separate aspects of sperm quality.

Changes in Clara cell 10 kDa protein (CC10)-positive cell distribution in acute lung injury following repeated lipopolysaccharide challenge in the rat

Clara cell 10 kDa protein (CC10) is the major secretory protein of Clara cells and is thought to play a protective role in the lung owing to its anti-inflammatory properties. There is little information on the anatomical distribution of CC10-positive cells in rat lung following lipopolysaccharide (LPS) challenge. We have determined the expression of CC10 along the tracheobronchial tree in saline-treated and LPS-treated rats. Saline-treated rats showed sporadic CC10 staining in central airways and abundant staining in bronchioles. In transitional airways, most cells were positive except for squamous cells. Following LPS challenge, there was a reduction in staining in the upper airways but little change within bronchioles. Squamous epithelia within the transitional airways now showed positive staining. These cells also co-stained for pancytokeratin and appeared to co-localize with surfactant D- and Ki67-positive cells, indicating the presence of a dedifferentiated cell type with both epithelial and pneumocyte phenotypes. These data show that diffuse inflammatory injury results in generalized loss of CC10 in central airways. Conversely, the transitional airways showed evidence of a dedifferentiated population of squamous cells that now stained for CC10. We hypothesize that this is an attempt by peripheral lung to maintain alveolar sac integrity during an inflammatory episode.

New Glucocorticosteroids with an improved therapeutic ratio?

Glucocorticoids (GCs) remain the most effective therapy for inflammatory disorders. In terms of asthma, topical steroids are the mainstay for controlling the inflammatory component of the disease. However, their use is limited by the constellation of adverse effects associated with chronic, oral steroid use and the long-term adverse effects associated with inhaled steroid use. These include suppression of hypothalamic--pituitary axis, osteoporosis, reduced bone growth in the young, opportunistic infections, behavioural alterations, and disorders of lipid metabolism. Most of these effects may be attributable to the endocrine activity of steroids and are largely identical to the syndromes of endogenous corticosteroid excess (Cushing's Syndrome). Thus, the Holy Grail of steroid pharmacology is the development of agents which have a markedly improved therapeutic ratio than current steroids, especially on systemic administration. This may be achieved by the identification of molecules which elicit marked antiinflammatory effects, but have a minor impact on endocrine responses. Dissociated corticosteroids are ligands for the glucocorticoid receptor that may offer the potential for a more selective antiinflammatory profile.

RPR203494 a pyrimidine analogue of the p38 inhibitor RPR200765A with an improved in vitro potency

Following the discovery of RPR200765, a series of pyrimidine analogues have been prepared as backups. Amongst them, RPR203494 was identified with a better in vitro profile than RPR200765A.

Therapeutic benefit of a dissociated glucocorticoid and the relevance of in vitro separation of transrepression from transactivation activity

Glucocorticoids (GCs) are the mainstay of asthma therapy; however, major side effects limit their therapeutic use. GCs influence the expression of genes either by transactivation or transrepression. The antiinflammatory effects of steroids are thought to be due to transrepression and the side effects, transactivation. Recently, a compound, RU 24858, has been identified that demonstrated dissociation between transactivation and transrepression in vitro. RU 24858 exerts strong AP-1 inhibition (transrepression), but little or no transactivation. We investigated whether this improved in vitro profile results in the maintenance of antiinflammatory activity (evaluated in the Sephadex model of lung edema) with reduced systemic toxicity (evaluated by loss in body weight, thymus involution, and bone turnover) compared with standard GCs. RU 24858 exhibits comparable antiinflammatory activity to the standard steroid, budesonide. However, the systemic changes observed indicate that transactivation events do occur with this GC with similar potency to the standard steroids. In addition, the GCs profiled showed no differentiation on quantitative osteopenia of the femur. These results suggest that in vitro separation of transrepression from transactivation activity does not translate to an increased therapeutic ratio for GCs in vivo or that adverse effects are a consequence of transrepression.

Potential of p38 inhibitors in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic debilitating disease estimated to afflict 13% of the world population. Although palliative treatments (nonsteroidal antiinflammatory drugs or NSAIDs) are widely prescribed, there are currently only a few treatments that can modify the insidious progression of the disease (disease-modifying antirheumatic drugs or DMARDs), which frequently leads to physical incapacitation and, on occasion, death. Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) are implicated in the disease onset and in the progression of bone and joint destruction that characterizes chronic RA. p38 is an intracellular mitogen/stress-activated protein kinase (MAPK/SAPK) that regulates both the release and the actions of TNF-alpha and IL-1 beta. Inhibition of p38 kinase is thus an important potential target for novel DMARDs. Following the pioneering work conducted at SmithKline Beecham and elucidation of the roles of p38 with potent and selective inhibitors such as SB-203580, many pharmaceutical companies have embarked upon p38 synthetic programs, as indicated by the ever-increasing number of patents in this domain. At Aventis, a rapid parallel synthesis project led to the identification of RPR-200765A, a potent and selective p38 inhibitor of the lipopolysaccharide-induced release of TNF-alpha in vitro in mononuclear phagocytes and in vivo in the rat. It also reduces disease incidence and progression in the rat streptococcal cell wall arthritis model when administered orally in either a prophylactic or a therapeutic dosing regimen. Development of p38 inhibitors has been slow, probably because of toxicological problems, which might explain why only two oral p38 inhibitors, SB-242235 and VX-745, have advanced into clinical development. In the present article, the preclinical data exemplified in studies on RPR-200765A indicating why p38 inhibitors are attracting so much attention as potential novel anti-RA drugs are reviewed. Current information on the different structural classes of p38 inhibitors is presented and possible reasons for the delays in their development are critically discussed.

Human peritoneal adhesions are highly cellular, innervated, and vascularized

Peritoneal adhesions are a major complication of healing following surgery or infection and can lead to conditions such as intestinal obstruction, infertility, and chronic pain. Mature adhesions are the result of aberrant peritoneal healing and historically have been thought to consist of non-functional scar tissue. The aim of the present study was to analyse the cellular composition, vascularity, and extracellular matrix distribution of human peritoneal adhesions, to determine whether adhesions represent redundant scar tissue or are dynamic regenerating structures. Furthermore, the histological appearance of each adhesion was correlated with the clinical history of the patient, to determine whether maturity or intraperitoneal pathology influences adhesion structure. Human peritoneal adhesions were collected from 29 patients undergoing laparotomy for various conditions and were prepared for histology, immunocytochemistry, and transmission electron microscopy. All adhesions were highly vascularized, containing well-developed arterioles, venules, and capillaries. Nerve fibres, with both myelinated and non-myelinated axons, were present in adhesions from nearly two-thirds of the patients, with increased incidence in those with a malignancy. Approximately one-third of the adhesions contained conspicuous smooth muscle cell clusters lined by collagen fibres of heterogeneous size. Adipose tissue was a consistent feature of all the adhesions, with some areas displaying fibrosis. There appeared to be no correlation between the estimated maturity or site of each adhesion and its histological appearance. However, intraperitoneal pathology at the time of surgery did influence the incidence of some histological features, such as the presence of nerve fibres, clusters of smooth muscle cells, and inflammation. This study challenges previous concepts that adhesions represent non-functional scar tissue and clearly demonstrates that established adhesions are highly cellular, vascularized, and innervated, features more consistent with dynamic, regenerating structures.

Effect of the p38 kinase inhibitor, SB 203580, on allergic airway inflammation in the rat

Tumour necrosis factor-alpha (TNF-alpha) and interleukin 1beta (IL-1beta) have been implicated in the pathogenesis of asthma. The p38 kinase inhibitor, SB 203580 inhibits TNF-alpha and IL-1beta production in vitro and in vivo. In this study the effect of SB 203580 on allergen-induced airway TNF-alpha production and inflammatory cell recruitment was investigated in sensitized Brown Norway rats. The allergen-induced increase in bronchoalveolar lavage (BAL) TNF-alpha was inhibited by SB 203580 at every dose tested (10 - 100 mg kg(-1), p.o.). In contrast, neither ovalbumin-induced eosinophilia or neutrophilia were inhibited by SB 203580 (10 - 100 mg kg(-1), p.o.). In conclusion, SB 203580 inhibits BAL TNF-alpha production by 95% without inhibiting either antigen-induced airway eosinophilia or neutrophilia. This data suggests that either the residual TNF-alpha is sufficient to drive allergen-induced inflammatory cell recruitment into the lung or that TNF-alpha is not involved in allergen-induced inflammatory cell recruitment.

Increased endothelin-1 and its localization during the development of bleomycin-induced pulmonary fibrosis in rats

Endothelin-1 (Et-1) has been implicated in the pathogenesis of pulmonary fibrosis with increased levels in the lung tissue of patients with pulmonary fibrosis and profibrotic effects in vitro. In this study we have investigated the temporal changes in lung Et-1 levels and immunohistochemical localization in relation to collagen deposition during the development of bleomycin-induced pulmonary fibrosis in rats. Lung Et-1 content doubled by 3 d following the intratracheal instillation of bleomycin, and continued to increase up to 7 d when values were about threefold greater than controls. Thereafter, the values for bleomycin-treated animals remained constant up to 21 d. There was no change in collagen content at 3 d but after 7 d there was a 25% increase and by 21 d levels were almost double those of the controls. In normal lung, Et-1 was predominantly associated with epithelial cells of conducting and nonconducting airways. Following bleomycin administration, intense staining of macrophages and conducting airway and alveolar epithelial cells was observed with marked staining of perivascular, peribronchiolar, and alveolar septal connective tissue, as well as the venular and arterial intima and media. These results demonstrate elevation of Et-1 levels prior to an increase in collagen content which, along with its localization within developing fibrotic lesions, provides further evidence of a profibrotic role for Et-1 in the pathogenesis of pulmonary fibrosis.

Rhinometry and open-mouth posture in young children

A biracial sample of 348 elementary school children who were in the first grade were assessed for open-mouth posture (OMP) in the natural environment. In addition, rhinometry was performed on 296 of the children. Means were computed for percent OMP and cross-sectional nasal airway. Results indicated that, in general, these children exhibited relatively high rates of OMP. Boys displayed significantly greater OMP than girls, and black children showed significantly larger cross-sectional nasal areas than white children. A significant correlation between OMP and nasal area only was evident for children exhibiting OMP during more than 80% of the observation intervals. The implications of the findings were discussed.

Inbreeding depression in insular and central populations of Peromyscus mice

We tested the hypothesis that small, isolated populations would show less depression in fitness when inbred than would large, central populations. Laboratory stocks of Peromyscus leucopus and P. polionotus were established from insular, peninsular, and central populations. The isolated populations had one-third to one-half the genic diversity of central populations. Responses to inbreeding were highly varied: some populations had smaller litters, others experienced higher mortality, some showed slower growth rates, and one displayed no measurable effects when inbred. These results suggest that inbreeding depression is controlled by a small number of genes and that the size of the genetic load depends on which alleles are present in the founders of a population. The severity of fitness depression in inbred litters did not correlate with initial genic diversity of the stocks nor, therefore, with the size of the wild populations. Fitness measures appeared linearly related to the inbreeding coefficient of the liters, with no diminution of deleterious effects through subsequent generations of inbreeding. Thus overdominance of fitness traits probably contributed as much to the genetic load as did deleterious recessive alleles. The inbreeding level of the dam negatively affected the size, growth, and survival of litters only in genetically diverse populations, indicating that the load of recessive alleles negatively impacting maternal care may have been reduced by selection in the more peripheral populations during past bottlenecks.