Incidence and risk factors for healthcare utilisation among patients discharged on outpatient parenteral antimicrobial therapy.

Outpatient parenteral antimicrobial therapy (OPAT) programmes facilitate hospital discharge, but patients remain at risk of complications and consequent healthcare utilisation (HCU). Here we elucidated the incidence of and risk factors associated with HCU in OPAT patients. This was a retrospective, single-centre, case-control study of adult patients discharged on OPAT. Cases (n = 63) and controls (n = 126) were patients that did or did not utilise the healthcare system within 60 days. Characteristics associated with HCU in bivariate analysis (P ≤ 0.2) were included in a multivariable logistic regression model. Variables were retained in the final model if they were independently (P < 0.05) associated with 60-day HCU. Among all study patients, the mean age was 55 ± 16, 65% were men, and wound infection (22%) and cellulitis (14%) were common diagnoses. The cumulative incidence of 60-day unplanned HCU was 27% with a disproportionately higher incidence in the first 30 days (21%). A statin at discharge (adjusted odds ratios (aOR) 0.23, 95% confidence intervals (CIs) 0.09-0.57), number of prior admissions in past 12 months (aOR 1.48, 95% CIs 1.05-2.10), and a sepsis diagnosis (aOR 4.62, 95% CIs 1.23-17.3) were independently associated with HCU. HCU was most commonly due to non-infection related complications (44%) and worsening primary infection (31%). There are multiple risk factors for HCU in OPAT patients, and formal OPAT clinics may help to risk stratify and target the highest risk groups.

From Vanadis to Atropos: vanadium compounds as pharmacological tools in cell death signalling.

Vanadium compounds exert a variety of biological responses, the most notable being their effects as insulin mimetics. More recently, they have been used as pharmacological tools to investigate signalling pathways. Some peroxovanadium compounds act as powerful protein tyrosine phosphatase inhibitors, modulating both the extent and duration of phosphotyrosine signals at the level of the transmembrane growth factor receptors and targets in the cytoplasm and nucleus. A brief history of vanadium compounds, selected chemical properties of vanadium compounds and the ability of peroxovanadium complexes to modulate the activities of protein tyrosine phosphatases and tyrosine kinases are presented in this review by Anne Morinville, Dusica Maysinger and Alan Shaver. From the range of biological activities of these compounds, this review focuses on cytotoxic effects and possible roles of mitogen-activated protein kinases in mediating the effects exerted by vanadium compounds.

Hypoglycemic effects of peroxovanadium compounds in Sprague-Dawley and diabetic BB rats.

Highly purified peroxovanadium (pV) compounds, each containing an oxo ligand, one or two peroxo anions, and an ancillary ligand in the inner coordination sphere of vanadium, were shown to decrease plasma glucose markedly in both normal Sprague-Dawley and insulin-deprived diabetic BB rats. Maximal decreases in plasma glucose were at 60-100 min after intravenous, intraperitoneal, or subcutaneous administration. Synergism between these compounds and insulin was observed. Whereas parenterally administered orthovanadate or vanadyl sulfate did not induce hypoglycemia before inducing acute mortality, pV compounds effected hypoglycemia at doses much lower than those inducing acute mortality. When administered subcutaneously over a period of 3 days to insulin-deprived diabetic BB rats, pV compounds, but not vanadate, caused a significant decrease in plasma glucose concentrations and prevented the appearance of ketosis in these animals. Thus, pV compounds are the first agents other than insulin that acutely and markedly reduce plasma glucose in hypoinsulinemic diabetic BB rats.

Differential regulation of JNK activation and MKP-1 expression by peroxovanadium complexes.

Bisperoxovanadium complexes have been identified as insulinomimetic agents and protein tyrosine phosphatase inhibitors. The aim of the present study was to examine the effects of the most potent bisperoxovanadium complex, potassium bisperoxo (1,10-phenanthroline) oxovanadate (V) [bpV(phen)], on expression and activation of c-jun N-terminal protein kinases (JNK) and on expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) in different cell lines. We compared the effects of bpV(phen) with the effects of tumor necrosis factor-alpha (TNF-alpha), a known regulator of JNK phosphorylation and inducer of MKP-1. Treatment with bpV(phen) causes significant and sustained down-regulation of MKP-1 expression both in PC12 and HeLa cells. In contrast, TNF-alpha induces MKP-1 expression in PC12 cells and does not alter MKP-1 expression in HeLa cells. Both bpV(phen) and TNF-alpha induce MKP-1 expression in OVCAR-3 cell line but with different dynamics: TNF-alpha causes transient and bpV(phen) sustained induction of MKP-1 expression. Temporal pattern of level of MKP-1 expression correlates with the regulation of JNK phosphorylation by bpV(phen) and TNF-alpha in PC12 cells. However, no detectable phospho-JNK signal is observed in either OVCAR-3 or HeLa cells treated with bpV(phen). In contrast, TNF-alpha causes strong and sustained JNK phosphorylation in OVCAR-3 cell line, and strong but transient JNK activation in HeLa cells. BpV(phen) and TNF-alpha does not alter JNK expression in any of the cell lines studied. We demonstrate that the effect of two stressors, bpV(phen) and TNF-alpha, on MKP-1 expression and JNK phosphorylation are strikingly different, depending on the cell type. These results suggest the possible role of MKP-1 in regulation of JNK phosphorylation in both PC12 and OVCAR-3 cell lines treated with bpV(phen).

MKP-1 as a target for pharmacological manipulations in PC12 cell survival.

Dual specificity mitogen activated protein kinase phosphatase-1 (MKP-1) inactivates extracellular signal-regulated kinase (ERK), p38 and/or c-jun N-terminal protein kinase (JNK) by dephosphorylation via a negative feed-back loop. The aim of the present study was to assess the role of expression of MKP-1 and phosphorylation status of mitogen-activated protein kinases (MAPKs) in promoting cell survival in PC12 cells. We used FK506 and three different monoperoxovanadium complexes (mpVs) as pharmacological tools for manipulation of MKP-1 expression. Peroxovanadium compounds, known to be insulinomimetic agents and protein tyrosine phosphatase inhibitors, are cytotoxic to the cells, they activate JNK and down-regulate MPK-1. On the other hand, FK 506 has transient effect on ERK activation. However, when the agents are used in combination, ERK phosphorylation is prolonged and intensified, MKP-1 expression is increased, and cell survival is enhanced. The concomitant alterations observed in intensities and duration of phospho-ERKs and phospho-JNKs signals suggest that monoperoxovanadium complexes in combination with FK 506 enhance survival of PC12 cells by an induction of MKP-1 expression.

Activation of MAPK by potassium bisperoxo(1,10-phenanthroline)oxovanadate (V).

Potassium bisperoxo(1,10-phenantroline)oxovanadate (V) [bpV(phen)] is a potent protein tyrocine phosphatase inhibitor which mediates a variety of biological effects. The aim of these studies was to examine the role(s) of mitogen activated protein kinase (MAPK) pathways in PC12 cell proliferation and toxicity by bpV(phen). BpV(phen) exerts a bimodal effect in PC12 cells: proliferation at low and cell death at higher micromolar concentrations. Activation of MAPK by bpV(phen) depends on time and concentration. The phosphorylation pattern of extracellular regulated kinases (ERK 1/2), c-jun N-terminal activated kinases (JNK) and p38 in PC12 cells is strikingly different. Activation of JNK is sustained in PC12 cells. In contrast, ERK 1/2 activation is transient and treatment with PD98059 indicates that ERK activation by bpV(phen) is partly independent from the ras-MEK pathway. Stability studies of bpV(phen) in DMEM and PBS showed linear relationship with T1/2 about 6 h and 10 days in DMEM and PBS, respectively. Comparison between the time courses of MAPK activation and kinetics of bpV(phen) decomposition as assessed by 51V-NMR analysis show that the initial and maximal phosphorylation signals are produced in the presence of the complex bpV(phen) and not caused by the decomposition products of bpV(phen).

Interstitial pulmonary edema in children and adolescents with diabetic ketoacidosis.

The acute complications of diabetic ketoacidosis in children and adolescents are well recognized but not completely understood. Clinical studies have focused primarily on brain edema. We have investigated the prevalence and course of interstitial pulmonary edema in patients with severe diabetic ketoacidosis all of whom had uneventful clinical courses. High resolution computed tomography scans of the lungs were analyzed by determining the Hounsfield attenuation level and then converting to physical density values. All seven patients had evidence of interstitial pulmonary edema on the first scan, which was performed within 1 h of hydration and prior to receiving insulin; six of the seven patients had increased pulmonary density 6-8 h into treatment, and all had complete resolution of the interstitial changes at discharge. Our study suggests that subclinical interstitial pulmonary edema may be a frequent occurrence in children and adolescents with severe diabetic ketoacidosis and may very well be present prior to treatment. The study also supports the philosophy of cautious rehydration and the close monitoring of children and adolescents with diabetic ketoacidosis until a more complete understanding of this pathophysiologic event is achieved.

Poisoning.

Knowledge of the toxicologic nature of ingested substances provides a proper framework for general and specific therapies best suited to meet the needs of the patient. Monitoring and direct observation provided in the PICU can aid proper therapy for many intoxicants. Good supportive care coupled with specific pharmacotherapy will provide the best chance for a successful outcome.

Esophageal-aortic erosion associated with double aortic arch and tracheomalacia. Experience with 2 infants.

Patients with double aortic arch may require lengthy intubation for ventilatory support. The need for endotracheal and nasogastric intubation may be prolonged in such patients because of associated tracheomalacia. Iatrogenic tracheal or esophageal erosion with subsequent aortic fistulization is an unusual but catastrophic complication that may result from such intubation. We report the cases of 2 infants with double aortic arch and tracheomalacia who developed iatrogenic esophageal-aortic erosion. This complication was successfully managed in 1 of the infants. We conclude from our experience that the important steps in preventing this complication include 1) expediting the exclusion of upper-airway compromise in intubated infants who have a presentation characteristic of bronchospastic airway disease (hyperinflation and hypercapnia) that seems unresponsive to usual therapeutic measures; and 2) expediting the diagnosis of vascular ring in order to minimize the duration of dual tracheal and esophageal intubation. Effective management of this problem, once established, requires primary closure of the esophageal perforation, removal of the nasogastric tube, interposition of thick viable tissue between the esophagus and the aorta, and decompressive gastrostomy and feeding jejunostomy. Concomitant aortopexy may be appropriate.

Psychosocial interventions for suicidal children and adolescents.

This paper discusses the role of psychosocial intervention in the treatment of suicidal youth, summarizes the existing relevant literature, describes model programs for treating suicidal youth, and discusses efficacy-to-effectiveness issues in working with this population.

The evolution of mutation rates: separating causes from consequences.

Natural selection can adjust the rate of mutation in a population by acting on allelic variation affecting processes of DNA replication and repair. Because mutation is the ultimate source of the genetic variation required for adaptation, it can be appealing to suppose that the genomic mutation rate is adjusted to a level that best promotes adaptation. Most mutations with phenotypic effects are harmful, however, and thus there is relentless selection within populations for lower genomic mutation rates. Selection on beneficial mutations can counter this effect by favoring alleles that raise the mutation rate, but the effect of beneficial mutations on the genomic mutation rate is extremely sensitive to recombination and is unlikely to be important in sexual populations. In contrast, high genomic mutation rates can evolve in asexual populations under the influence of beneficial mutations, but this phenomenon is probably of limited adaptive significance and represents, at best, a temporary reprieve from the continual selection pressure to reduce mutation. The physiological cost of reducing mutation below the low level observed in most populations may be the most important factor in setting the genomic mutation rate in sexual and asexual systems, regardless of the benefits of mutation in producing new adaptive variation. Maintenance of mutation rates higher than the minimum set by this "cost of fidelity" is likely only under special circumstances.

Arrest at the G2/M transition of the cell cycle by protein-tyrosine phosphatase inhibition: studies on a neuronal and a glial cell line.

The addition of the peroxovanadium (pV) derivatives potassium bisperoxo(1,10-phenanthroline)oxovanadate(v) (bpV[phen]) or potassium bisperoxo(pyridine-2-carboxylato) oxovanadate(v) (bpV[pic]), both of which are potent inhibitors of protein tyrosine phosphatases (PTPs) [Posner et al. (1994): J Biol Chem 269:4596-4604], to the culture medium of neuroblastoma NB 41 and glioma C6 cells resulted in a marked decrease in their proliferation rates and a progressive accumulation at the G2/M transition of the cell cycle. The effect was dependent on dose, cell type, and a pV compound employed. Mean values of the RNA-to-DNA and RNA-to-protein ratios in NB cells treated for 48 h with increased doses of bpV[phen] showed that general synthetic functions were not altered, nor did we observe oxidative damage to DNA using a sensitive DNA-nick detection assay. No changes in the expression and localization of vimentin, a component of the intermediate filament cytoskeleton, were observed by indirect immunofluorescence, showing that treatment did not disturb the cytoskeleton network. Measurements of BrdU incorporation into newly synthesized DNA showed that cells treated were not totally arrested. Furthermore, cells arrested G2/M were able to reenter the cycle rapidly after the release of inhibition. This progressive accumulation of G2/M coincided with the detection of tyrosine-phosphorylated p34cdc2 and a dramatic reduction in its kinase activity toward histone H1 by 48 h of culture. Both compounds were equally potent in inhibiting the catalytic activity of a yeast and the structurally distant mouse cdc25B in vitro, suggesting that augmented tyrosine phosphorylation of p34cdc2 derived from the in vivo inhibition of cdc25. Their equal in vitro potency contrasted with the considerably greater potency of bpV[phen] in vivo, in vivo suggesting that factors regulating the intracellular access of these compounds to cdc25 might be critical in determining in vivo specificity. In conclusion the final consequence of long-term exposure to potent and structurally defined PTP inhibitors on two highly proliferative nerve cell lines is to restrict cell growth. The corresponding hyperphosphorylation and reduced activity of p34cdc2 likely reflects the unusual sensitivity of cdc25 as an in vivo target for peroxovanadium compounds.

Peroxovanadium compounds: biological actions and mechanism of insulin-mimesis.

When used alone, both vanadate and hydrogen peroxide (H2O2) are weakly insulin-mimetic, while in combination they are strongly synergistic due to the formation of aqueous peroxovanadium species pV(aq). Administration of these pV(aq) species leads to activation of the insulin receptor tyrosine kinase (IRK), autophosphorylation at tyrosine residues and inhibition of phosphotyrosine phosphatases (PTPs). We therefore undertook to synthesize a series of peroxovanadium (pV) compounds containing one or two peroxo anions, an oxo anion and an ancillary ligand in the inner co-ordination sphere of vanadium, whose properties and insulin-mimetic potencies could be assessed. These pV compounds were shown to be the most potent inhibitors of PTPs yet described. Their PTP inhibitory potency correlated with their capacity to stimulate IRK activity. Some pV compounds showed much greater potency as inhibitors of insulin receptor (IR) dephosphorylation than epidermal growth factor receptor (EGFR) dephosphorylation, implying relative specificity as PTP inhibitors. Replacement of vanadium with either molybdenum or tungsten resulted in equally potent inhibition of IR dephosphorylation. However IRK activation was reduced by greater than 80% suggesting that these compounds did not access intracellular PTPs. The insulin-like activity of these pV compounds were demonstrable in vivo. Intra venous (i.v.) administration of bpV(pic) and bpV(phen) resulted in the lowering of plasma glucose concentrations in normal rats in a dose dependent manner. The greater potency of bpV(pic) compared to bpV(phen) was explicable, in part, by the capacity of the former but not the latter to act on skeletal muscle as well as liver. Finally administration of bpV(phen) and insulin led to a synergism, where tyrosine phosphorylation of the IR beta-subunit increased by 20-fold and led to the appearance of four insulin-dependent in vivo substrates. The insulin-mimetic properties of the pV compounds raises the possibility for their use as insulin replacements in the management of diabetes mellitus.

The chemistry of peroxovanadium compounds relevant to insulin mimesis.

The inorganic coordination chemistry of peroxovanadium compounds relevant to insulin mimesis is reviewed. The structure and kinetic reactivity of solutions of vanadate anion, vanadyl complexes and peroxovanadate complexes are briefly compared. Peroxovanadium compounds contain an oxo group, one or two peroxo ligands (O2(2-)) and an ancillary ligand which is usually bidentate. These compounds approximate a trigonal bipyramidal structure which can be divided conceptually into a polar 'oxo' half and a relatively non-polar organic half. This presents a number of interesting design variations which are discussed with respect to the development of a rudimentary structure-activity correlation of insulin mimetic ability.

Selective activation of the rat hepatic endosomal insulin receptor kinase. Role for the endosome in insulin signaling.

Insulin administration activates the insulin receptor kinase (IRK) in both plasma membrane (PM) and endosomes (ENs) raising the possibility of transmembrane signaling occurring in the endosomal compartment. Peroxovanadium compounds activate the IRK by inhibiting IR-associated phosphotyrosine phosphatase(s). Following the administration of the phosphotyrosine phosphatase inhibitor bisperoxo(1,10-phenanthroline)-oxovanadate (V) anion (bpV(phen)) activation of the hepatic IRK in ENs preceded that in PM by 5 min. When colchicine treatment preceded bpV(phen) administration IRK activation in ENs was unaffected but was totally abrogated in PM. Insulin receptor substrate-1 tyrosine phosphorylation followed the kinetics of IRK activation in ENs not PM and a hypoglycemic response similar to that achieved with a pharmacological dose of insulin ensued. These studies demonstrate that ENs constitute a site for IR-mediated signal transduction.

A stable peroxovanadium compound with insulin-like action in human fat cells.

Aqueous solutions of peroxovanadium (pV) compounds are potent insulin-mimics in various types of cell. Since chemical instability is a problem with these agents, we studied the insulin-like action in human fat cells of a stable pV complex, bpV(pic). It enhanced 14C-U-glucose uptake in a dose-dependent manner by approximately twofold which was slightly less than the effect of insulin (approximately threefold). The pV complex did not alter cell-surface insulin binding and submaximal concentrations did not influence cellular sensitivity to insulin action on glucose uptake. The bpV(pic) inhibited the lipolytic effect of isoprenaline to the same extent as insulin; however, when the cGMP-inhibitable low-K(m) phosphodiesterase (cGI-PDE) was blocked with the specific inhibitor OPC 3911, the antilipolytic effect of insulin, but not that of bpV(pic), was completely prevented. Moreover, when lipolysis was stimulated by the non-hydrolysable cAMP analogue N6-monobutyryl cAMP, bpV(pic), in contrast to insulin, maintained an antilipolytic effect. These findings indicate that bpV(pic) exerts its antilipolytic effect not only through cGI-PDE activation, similar to the effect of insulin, but also by means of other mechanisms. The tyrosine kinase activity of insulin receptors from human placenta was not altered by the pV compound itself, whereas bpV(pic) clearly enhanced insulin-stimulated activity. In contrast, in situ tyrosine phosphorylation of the insulin receptor beta-subunit as well as that of several other proteins was clearly increased in cells which were treated with bpV(pic), whereas vanadate only amplified insulin-stimulated tyrosine phosphorylation. In conclusion, bpV(pic) exerts powerful insulin-like effects in human fat cells and may be a new and potentially useful agent in the management of insulin-resistant states.

In vivo effects of peroxovanadium compounds in BB rats.

Peroxovanadium compounds, each containing an oxo ligand, one or two peroxo anions, and an ancillary ligand in the inner coordination sphere of vanadium, were synthesized, crystallized and characterized by 51V NMR as > 95% pure. They markedly decreased plasma glucose in insulin-deprived diabetic BB rats, with a nadir occurring between 60 and 100 min after intravenous, intraperitoneal or subcutaneous administration. Plasma glucose was reduced after oral administration in insulin-treated and in insulin-deprived BB rats. When compared to sodium orthovanadate, peroxovanadium compounds exhibited a markedly greater potency on a molar basis, and in relation to their toxicity. The in vivo potency can be predicted by the degree of phosphotyrosine phosphatase inhibition observed in vitro. These are the first agents other than insulin that can acutely and markedly reduce plasma glucose in hypoinsulinemic diabetic BB rats.

In vivo insulin mimetic effects of pV compounds: role for tissue targeting in determining potency.

Peroxovanadium (pV) compounds activate the insulin receptor kinase in hepatocytes and inhibit the dephosphorylation of insulin receptors in hepatic endosomes with highly correlated potencies (Posner, B. I., R. Faure, J. W. Burgess, A. P. Bevan, D. Lachance, G. Zhang-Sun, J. B. Ng, D. A. Hall, B. S. Lum, and A. Shaver J. Biol. Chem. 269: 4596-4604, 1994). After intravenous administration, K2[VO(O2)2(picolinato)].2H2O [bpV(pic)], VO(O2) (picolinato) (H2O)2 [mpV(pic)], K[VO(O2)2(picolinato)].3H2O [bpV(phen)], and K[VO(O2)2(4,7-dimethyl-1,10-phenanthroline)].1/2H2O [bpV(Me2phen)] produced 50% of their maximal hypoglycemic effect at doses of 0.04, 0.04, 0.32, and 0.65 mumol/100 g body wt, respectively. In contrast, their potencies as inhibitors of dephosphorylation were bpV(pic) = bpV(phen) > mpV(pic) = bpV(Me2phen). bpV(pic) stimulated [14C]glucose incorporation into rat diaphragm glycogen in vivo, and its effect was dose dependent, synergistic with insulin, and evident in other skeletal muscles. In contrast, bpV(phen) displayed no effect on glycogen synthesis in skeletal muscle. mpV(pic) stimulated and bpV(Me2phen) had no effect on glycogen synthesis in the diaphragm. bpV(pic) augmented rat diaphragm insulin receptor kinase 2.2-fold with a time-integrated response 70% that of insulin. In contrast, the effect of bpV(phen) was delayed and much reduced. Thus, the in vivo potencies of pV compounds reflect differing capacities to act on skeletal muscle. The ancillary ligand within the pV complex may target one tissue in preference to another.

Oral ganciclovir in children: pharmacokinetics, safety, tolerance, and antiviral effects. The Pediatric AIDS Clinical Trials Group.

The pharmacokinetics, safety, tolerance, and antiviral effects of ganciclovir (Gcv) administered orally were evaluated in 36 children infected with cytomegalovirus (CMV) who were severely immunocompromised by infection with human immunodeficiency virus type 1. In this dose-escalation study, 30 mg/kg of Gcv administered every 8 h produced serum levels similar to the dose (1 g/8 h) effective for maintenance treatment of CMV retinitis in adults. In older children, serum Gcv concentrations were similar after the administration of capsules and suspension. All doses (10-50 mg/kg/8 h) studied were safe and, except for the volume of suspension or number of pills, were well tolerated. Oral Gcv was associated with a decrease in the detection of CMV by culture or polymerase chain reaction. CMV disease occurred in 3 children during the study: one developed Gcv resistance, another had harbored resistant virus at study entry, and a third had wild-type CMV