Rapid reciprocal changes in adrenergic receptors in intact isolated hepatocytes during primary cell culture

In hepatocytes freshly isolated from adult female rat livers, catecholamine-stimulated glycogenolysis is mediated predominantly by alpha 1-adrenergic receptors, and to only a minimal extent by beta 2 receptors. Primary cell culture of these hepatocytes results in a switch in the adrenergic control of glycogenolysis from an alpha 1 to a predominant beta 2 type of response. To investigate whether this switch is due to an alteration in the plasma membrane receptor composition, we characterized alpha 1 and beta 2-adrenergic receptors in both freshly isolated and cultured hepatocytes, using radioligand-binding techniques. Binding of the selective alpha 1-adrenergic antagonist [3H]prazosin and the beta-adrenergic antagonist [125I]pindolol to intact freshly isolated hepatocytes was of high affinity, saturable, and of appropriate specificity for an alpha 1- and beta 2-adrenergic receptor, respectively. Equilibrium binding studies evaluated by a computer-assisted curve-fitting procedure indicated interaction with a single class of high affinity sites for radiolabeled prazosin (KD = 126 +/- 10 pM; Bmax = 93,000 +/- 5,500 sites/cell) and pindolol (KD = 66 +/- 6 pM; Bmax = 2,000 +/- 700 sites/cell). In intact hepatocytes and in membranes prepared from these hepatocytes, competitive inhibition curves revealed the coexistence of two different sites with high and low affinities for agonists at both alpha 1- and beta 2-adrenergic receptors. When isolated hepatocytes were kept in monolayer cell culture for up to 72 hr, the switch in adrenergic control of glycogenolysis (phosphorylase a activation) from an alpha to a beta pathway was confirmed and was associated with a progressive decrease in the number of alpha 1 receptors and an increase in beta 2-adrenergic receptor density, without marked change in the affinity of agonists or antagonists. To investigate the mechanism(s) of this reciprocal change, a number of perturbations were examined including alterations in the composition of the culture medium and the influence of various hormones and inhibitors of cellular function. De novo protein synthesis is implicated in both receptor alterations as the inhibitors cycloheximide and actinomycin D prevented the increase in beta- and attenuated the decrease in alpha-adrenergic sites. The other perturbations were without effect. Thus, these studies provide evidence for a coupling of the functional alteration in glycogenolysis to changes at the receptor level per se. The mechanism underlying the reciprocal changes in hepatocyte adrenergic receptors during culture remains undefined.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cerebrospinal fluid and plasma concentrations of proinflammatory mediators in human immunodeficiency virus-infected children

BACKGROUND: The pathogenesis of HIV encephalopathy is poorly understood especially in children. Studies suggest that HIV replication and the release of proinflammatory mediators in the central nervous system contribute to the pathogenesis of HIV dementia in adults. METHODS: Cerebrospinal fluid (CSF) and plasma samples from 23 HIV-infected children were longitudinally analyzed at Weeks 0, 8, 16 and 48 for HIV RNA and concentrations of the following proinflammatory mediators: monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha, regulated upon activation, normal T cell expressed and secreted (RANTES), macrophage-inflammatory protein (MIP)-1-alpha, MIP-1-beta and matrix metalloproteinase-9 (MMP-9). RESULTS: All 23 children had detectable concentrations of MCP-1 in the CSF at all time points evaluated. However, of the remaining of proinflammatory mediators measured in CSF at baseline, only a few children had detectable concentrations: tumor necrosis factor-alpha, n = 1; RANTES, n = 5; MMP-9, n = 9; MIP-1-alpha and MIP-1-beta, n = 0. A reduction from baseline to Week 48 was observed in CSF concentrations of MCP-1 and, among children with detectable values, MMP-9, which paralleled declines in CSF HIV RNA. CONCLUSION: These results suggest that MCP-1 and MMP-9 may be involved in the pathogenesis of central nervous system disease in HIV-infected children.     

Identifying best practice through benchmarking and outcome measurement

Collecting and analyzing various types of data are essential to identifying areas for improvement. Data collection and analysis are routinely performed in hospitals and are even required by some regulatory agencies. Realization of the full benefits, which may be achieved through collection and analysis of data, should be actively pursued to prevent a meaningless exercise in paperwork. Internal historical comparison of data may be helpful but does not achieve the ultimate goal of identifying external benchmarks in order to determine best practice. External benchmarks provide a means of comparison with similar facilities, allowing the identification of processes needing improvement. The specialty of ophthalmology presents unique practice situations that are not comparable with other specialties, making it imperative to benchmark against other facilities where quick surgical case time, efficient surgical turnover times, low infection rates, and cost containment are essential and standard operations. Important data to benchmark include efficiency data, financial data, and quality or patient outcome data. After identifying facilities that excel in certain aspects of performance, it is necessary to analyze how their procedures help them achieve these favorable results. Careful data collection and analysis lead to improved practice and patient care.     

A randomized clinical trial of the effectiveness of a scheduled oral analgesic dosing regimen for the management of postoperative pain in children following tonsillectomy

The purpose of this study was to determine whether around-the-clock (i.e. ATC) dosing of acetaminophen with codeine, with or without nurse coaching, compared to standard care with as needed (i.e. PRN) dosing: reduced children's reports of pain intensity with and without swallowing; increased pain relief, and increased analgesic consumption. Eighty children, 6-15 years, undergoing tonsillectomy were randomized to one of three treatment groups to receive acetaminophen with codeine (120 mg/12 mg/5 ml) for 3 days after surgery: PRN group (N = 28)-every 4 h PRN, with standard postoperative instructions, without nurse coaching; ATC group (N = 26)-every 4 h ATC, with standard postoperative instructions, without nurse coaching; and ATC+coaching group (N = 26)-every 4 h ATC, with standard postoperative instructions and nurse coaching. In all three groups, significant decreases were found over time in pain intensity scores at rest (P < 0.001) and with swallowing (P < 0.001). However, mean pain scores at rest and with swallowing were >3/10 until the fourth evening after tonsillectomy. Children in both ATC dosing groups received significantly greater amounts of acetaminophen and codeine than children in the PRN group (P < 0.003). No significant differences were found in the amount of analgesic administered between the ATC dosing groups with and without nurse coaching. No significant differences were found in the amount of nausea and vomiting among the three groups. Scheduled dosing of acetaminophen with codeine did not provide adequate pain relief for children following tonsillectomy. Nurse coaching does not increase parent's adherence with an ATC dosing schedule.     

The anti-thyroid drug methimazole induces neovascularization in the neonatal rat analogous to ROP

PURPOSE: To determine the effect of methimazole (MMI), an anti-thyroid drug known to reduce serum l-thyroxine (T4), and insulin-like growth factor (IGF)-1 concentrations, on retinal vascular development in neonatal rats. METHODS: Sprague-Dawley rats (n=175) were raised in expanded litters of 25 in room air and were exposed to MMI from birth (given as a 0.1% solution to nursing mothers for either 4 or 10 days). Experiments ended on day 4 (n=25) or 10 (n=50) of life. A third group was exposed to MMI for the initial 4 days of life and then allowed to recover for the next 6 days (n=50). Fifty control rats were analyzed on day 4 (n=25) or 10 (n=25) of life. Left eyes were fixed, and retinas were dissected and stained with adenosine diphosphatase (ADPase). Retinas were graded for presence and severity of neovascularization (NV) in a masked manner, and retinal vascular areas were quantified. In a subsequent study, serum IGF-1 and T4 levels were measured by radioimmunoassay in an additional 200 rats exposed to treatments identical to those described. RESULTS: Retinal NV occurred in 31% of rats exposed to 10 days of MMI and 4% (P=0.02) of rats exposed to 4 days of MMI, followed by 6 days of recovery. None of the rats exposed to 4 days of MMI alone and none of the control animals was graded positive for NV. Retinal vascular areas were significantly reduced in rats exposed to 4 days of MMI compared with 4-day control animals (36% +/- 6% vs. 50% +/- 6%, P=0.0001). Serum IGF-1 levels were markedly reduced in 4-day MMI rats compared with age-matched control animals (42 ng/mL vs. 133 ng/mL, P=0.0001) and in 10-day MMI rats compared with 10-day control animals (133 ng/mL vs. 206.5 ng/mL, P=0.005). Serum T4 levels were similarly suppressed in the MMI-exposed litters compared with control animals at day 10 (P=0.008). In contrast, rats exposed to 4 days of MMI followed by 6 days of recovery had normal serum IGF-1 and T4 levels by day 10. CONCLUSIONS: The anti-thyroid drug, MMI, induces NV in neonatal rats. This may be mediated by the initial suppression of serum IGF-1. Nevertheless, the lower incidence of NV when serum IGF-1 levels are initially suppressed followed by complete recovery, is contrary to a purely permissive role for serum IGF-1, as reported previously. The relationship between the temporal course of serum IGF-1 and NV in immature retinas needs further investigation.