Properties of [3H]Prazosin-Labeled α1Adrenergic Receptors in Rat Brain and Porcine Neurointermediate Lobe Tissue

Abstract: [³H]Prazosin binding to α₁ receptors in homogenates of rat prefrontal cortical tissue and porcine pituitary neurointermediate lobe tissue was investigated. Competition curves produced by coincubating adrenergic agonists and antagonists with 0.5 n M [³H]prazosin and tissue revealed some anomalous binding properties. In the brain and pituitary tissue, agonist competition curves produced "shallow" slopes, with Hill coefficients significantly lower than unity. The IC₅₀ of the agonists epinephrine, norepinephrine, and clonidine for inhibition of 0.5 n M [³H]prazosin binding were significantly lower in the porcine pituitary than in the rat brain. Most antagonists, such as prazosin, chlorpromazine, and piperoxan, produced "steep" competition curves with Hill coefficients close to unity, with two notable exceptions. WB-4101 and phentolamine produced competition curves with Hill coefficients significantly less than unity in the rat brain preparation. Ketanserin, an antagonist, displayed a sevenfold higher affinity for the a, sites in the pituitary tissue than in the brain tissue. These anomalies in the binding results may indicate the presence of an endogenous modulatory factor affecting agonist and antagonist affinities for the a, receptor.     

Clinical characteristics associated with adverse events in patients with exacerbation of chronic obstructive pulmonary disease: a prospective cohort study

Background:

To assist physicians with difficult decisions about hospital admission for patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) presenting in the emergency department, we sought to identify clinical characteristics associated with serious adverse events.

Methods:

We conducted this prospective cohort study in 6 large Canadian academic emergency departments. Patients were assessed for standardized clinical variables and then followed for serious adverse events, defined as death, intubation, admission to a monitored unit or new visit to the emergency department requiring admission.

Results:

We enrolled 945 patients, of whom 354 (37.5%) were admitted to hospital. Of 74 (7.8%) patients with a subsequent serious adverse event, 36 (49%) had not been admitted after the initial emergency visit. Multivariable modelling identified 5 variables that were independently associated with adverse events: prior intubation, initial heart rate ≥ 110/minute, being too ill to do a walk test, hemoglobin < 100 g/L and urea ≥ 12 mmol/L. A preliminary risk scale incorporating these and 5 other clinical variables produced risk categories ranging from 2.2% for a score of 0 to 91.4% for a score of 10. Using a risk score of 2 or higher as a threshold for admission would capture all patients with a predicted risk of adverse events of 7.2% or higher, while only slightly increasing admission rates, from 37.5% to 43.2%.

Interpretation:

In Canada, many patients with COPD suffer a serious adverse event or death after being discharged home from the emergency department. We identified high-risk characteristics and developed a preliminary risk scale that, once validated, could be used to stratify the likelihood of poor outcomes and to enable rational and safe admission decisions.Chronic obstructive pulmonary disease (COPD), a respiratory disorder caused largely by smoking and characterized by progressive, incompletely reversible airflow obstruction, is a leading cause of hospital admission among older people. Patients who experience frequent exacerbations of COPD are at higher risk of death.¹ Return to the emergency department within 30 days because of worsening respiratory symptoms was reported for 35% of COPD patients discharged from Canadian academic emergency departments.²An important challenge facing physicians when treating patients with COPD exacerbation is deciding who should be admitted. Many of these patients will have a response to therapy in the emergency department and will not benefit from admission to hospital. A small but important number of patients have serious adverse events after hospital admission, such as death, mechanical ventilation or myocardial infarction. Others are discharged after prolonged management in the emergency department, only to experience a serious adverse event or return later to be admitted. These outcomes are important because many jurisdictions have a shortage of hospital beds and many emergency departments are overcrowded. There is, however, little evidence about risk factors for adverse events in patients with COPD to aid with disposition decisions in the emergency department, and existing guidelines are consensus based and have not been validated.^3–5The overall goal of this study was to evaluate patients with acute exacerbation of COPD seen in the emergency department to determine the clinical characteristics associated with short-term serious adverse events. Once validated, this information should help in efforts to improve and standardize admission practices for patients with COPD seeen in the emergency department, diminishing both unnecessary admissions and unsafe discharge decisions.     

Hypothalamic corticotropin-releasing factor immunoreactivity is reduced during induction of pituitary tumors by chronic estrogen treatment

The role that estrogen plays in the regulation of corticotropin-releasing factor (CRF) is not known. A radioimmunoassay specific for rat CRF was utilized to measure the CRF-like immunoreactivity (CRF-ir) in the hypothalamus of ovariectomized rats treated with estradiol for periods up to 12 weeks. Compared to ovariectomized controls, estradiol treatment resulted in significantly reduced CRF-ir after 3 and 12 weeks, although no significant change was seen after 8 weeks. Anterior pituitary (AP) weight was greatly increased by estradiol treatment at all time points studied. Bromocriptine treatment for the last 3 weeks of the 12-week period, or removal of estradiol for 3 weeks after 9 weeks of treatment did not reverse the changes in CRF-ir even though significant regression of tumor size was achieved. There was no correlation between AP weight and CRF-ir in individual animals. These data show that chronic treatment with estrogen reduced hypothalamic CRF-ir content. Neither a direct estrogenic effect or an indirect effect mediated through alterations in the adenohypophysis could be ruled out.     

Self-collected mid-turbinate swabs for the detection of respiratory viruses in adults with acute respiratory illnesses

Background

The gold standard for respiratory virus testing is a nasopharyngeal (NP) swab, which is collected by a healthcare worker. Midturbinate (MT) swabs are an alternative due to their ease of collection and possible self-collection by patients. The objective of this study was to compare the respiratory virus isolation of flocked MT swabs compared to flocked NP swabs.

Methods

Beginning in October 2008, healthy adults aged 18 to 69 years were recruited into a cohort and followed up for symptoms of influenza. They were asked to have NP and MT swabs taken as soon as possible after the onset of a fever or two or more respiratory symptoms with an acute onset. The swabs were tested for viral respiratory infections using Seeplex® RV12 multiplex PCR detection kit. Seventy six pairs of simultaneous NP and MT swabs were collected from 38 symptomatic subjects. Twenty nine (38%) of these pairs were positive by either NP or MT swabs or both. Sixty nine (91%) of the pair results were concordant. Two samples (3%) for hCV OC43/HKU1 and 1 sample (1%) for rhinovirus A/B were positive by NP but negative by MT. One sample each for hCV 229E/NL63, hCV OC43/HKU1, respiratory syncytial virus A, and influenza B were positive by MT but negative by NP.

Conclusions

Flocked MT swabs are sensitive for the diagnosis of multiple respiratory viruses. Given the ease of MT collection and similar results between the two swabs, it is likely that MT swabs should be the preferred method of respiratory cell collection for outpatient studies. In light of this data, larger studies should be performed to ensure that this still holds true and data should also be collected on the patient preference of collection methods.     

Dopamine inhibition of anterior pituitary adenylate cyclase is mediated through the high-affinity state of the D2 receptor

The diterpinoid forskolin stimulated adenylate cyclase activity (measured by conversion of [³H]-ATP to [³H]-cAMP) in anterior pituitary from male and female rats. Inhibition of stimulated adenylate cyclase activity by potent dopaminergic agonists was demonstrable only in female anterior pituitary. The inhibition of adenylate cyclase activity displayed a typically dopaminergic rank order of agonist potencies and could be completely reversed by a specific dopamine receptor antagonist. The IC₅₀ values of dopamine agonist inhibition of adenylate cyclase activity correlated with equal molarity with the dissociation constant of the high-affinity dopamine agonist-detected receptor binding site and with the IC₅₀ values for inhibition of prolactin secretion. These findings support the hypothesis that it is the high-affinity form of the D₂ dopamine receptor in anterior pituitary which is responsible for mediating the dopaminergic function of attenuating adenylate cyclase activity.     

pH-dependent modulation of agonist interactions with [3H]-ketanserin-labelled S2 serotonin receptors

The effects of varying the pH on the properties of S₂ serotonin receptors labelled by [³H]-ketanserin were examined. Between pH 7.0 and 8.2 the agonist affinities, as determined by competition experiments, increased dramatically. Serotonin, 5-methoxytryptamine, tryptamine, bufotenine and quipazine, demonstrated 15,16,8,6 and 5-fold increases in apparent affinity between pH 7.0 and 8.2. On the other hand the antagonists, ketanserin, cinanserin, and spiperone demonstrated little or no affinity changes between pH 7.0 and 8.2. The largest shift in affinity for an antagonist occurred with spiperone, which displayed a two-fold shift. Although changing pH is a rather non-specific manipulation, the selective affect on agonist interaction with S₂ receptors indicates further investigation of this pH effect may aid in discovering the difference in receptor interactions between serotonin agonists and antagonists.