Propranolol reduces IFN-γ driven PD-L1 immunosuppression and improves anti-tumour immunity in ovarian cancer

The immune system plays an important role in controlling epithelial ovarian cancer (EOC). EOC is considered to be a "cold tumour," a tumour that has not triggered a strong response by the immune system. However, tumour infiltrating lymphocytes (TILs) and the expression of programmed cell death ligand (PD-L1) are used as prognostic indicators in EOC. Immunotherapy such as PD-(L)1 inhibitors have shown limited benefit in EOC. Since the immune system is affected by behavioural stress and the beta-adrenergic signalling pathway, this study aimed to explore the impact of propranolol (PRO), a beta-blocker, on anti-tumour immunity in both in vitro and in vivo EOC models. Noradrenaline (NA), an adrenergic agonist, did not directly regulate PD-L1 expression but PD-L1 was significantly upregulated by IFN-γ in EOC cell lines. IFN-γ also increased PD-L1 on extracellular vesicles (EVs) released by ID8 cells. PRO significantly decreased IFN-γ levels in primary immune cells activated ex vivo and showed increased viability of the CD8⁺ cell population in an EV-immune cell co-incubation. In addition, PRO reverted PD-L1 upregulation and significantly decreased IL-10 levels in an immune-cancer cell co-culture. Chronic behavioural stress increased metastasis in mice while PRO monotherapy and the combo of PRO and PD-(L)1 inhibitor significantly decreased stress-induced metastasis. The combined therapy also reduced tumour weight compared to the cancer control group and induced anti-tumour T-cell responses with significant CD8 expression in tumour tissues. In conclusion, PRO showed a modulation of the cancer immune response by decreasing IFN-γ production and, in turn, IFN-γ-mediated PD-L1 overexpression. The combined therapy of PRO and PD-(L)1 inhibitor decreased metastasis and improved anti-tumour immunity offering a promising new therapy.

Learning of probabilistic punishment as a model of anxiety produces changes in action but not punisher encoding in the dmPFC and VTA

Previously, we developed a novel model for anxiety during motivated behavior by training rats to perform a task where actions executed to obtain a reward were probabilistically punished and observed that after learning, neuronal activity in the ventral tegmental area (VTA) and dorsomedial prefrontal cortex (dmPFC) represent the relationship between action and punishment risk (Park and Moghaddam, 2017). Here, we used male and female rats to expand on the previous work by focusing on neural changes in the dmPFC and VTA that were associated with the learning of probabilistic punishment, and anxiolytic treatment with diazepam after learning. We find that adaptive neural responses of dmPFC and VTA during the learning of anxiogenic contingencies are independent from the punisher experience and occur primarily during the peri-action and reward period. Our results also identify peri-action ramping of VTA neural calcium activity, and VTA-dmPFC correlated activity, as potential markers for the anxiolytic properties of diazepam.

Co-occurrence of preconception maternal childhood adversity and opioid use during pregnancy: Implications for offspring brain development

Understanding of the effects of in utero opioid exposure on neurodevelopment is a priority given the recent dramatic increase in opioid use among pregnant individuals. However, opioid abuse does not occur in isolation-pregnant individuals abusing opioids often have a significant history of adverse experiences in childhood, among other co-occurring factors. Understanding the specific pathways in which these frequently co-occurring factors may interact and cumulatively influence offspring brain development in utero represents a priority for future research in this area. We highlight maternal history of childhood adversity (CA) as one such co-occurring factor that is more prevalent among individuals using opioids during pregnancy and which is increasingly shown to affect offspring neurodevelopment through mechanisms beginning in utero. Despite the high incidence of CA history in pregnant individuals using opioids, we understand very little about the effects of comorbid prenatal opioid exposure and maternal CA history on fetal brain development. Here, we first provide an overview of current knowledge regarding effects of opioid exposure and maternal CA on offspring neurodevelopment that may occur during gestation. We then outline potential mechanistic pathways through which these factors might have interactive and cumulative influences on offspring neurodevelopment as a foundation for future research in this area.

Smooth muscle relaxation and activation of the large conductance Ca(++)-activated K+ (BK(Ca)) channel by novel oestrogens

BACKGROUND AND PURPOSE

Oestrogens can interact directly with membrane receptors and channels and can activate vascular BK(Ca) channels. We hypothesized that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BK(Ca) channel, rather than at an intracellular site.

EXPERIMENTAL APPROACH

We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable.

KEY RESULTS

Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol-induced relaxation was iberiotoxin sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol.

CONCLUSION AND IMPLICATIONS

The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on NO and BK(Ca) channel activation. The activation of BK(Ca) currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane-impermeant Quat DME-oestradiol lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.

Effects of age on feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis

This study used behavioral and electrophysiological techniques to examine age-related changes in the feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis. Increasing age was associated with a 50% decrease in long-term food consumption. Analysis of short-term sucrose-evoked feeding bouts showed an age-related increase in the number of animals that failed to respond to the stimulus. Of the animals that did respond increasing age was associated with a decrease in the number of sucrose-evoked bites and a increase in the duration of the swallow phase. These changes were observed with both 0.01 and 0.05M sucrose stimuli but were not seen when 0.1M sucrose was used as the stimulus. Electrophysiological analysis of the chemosensory pathway in semi-intact lip-CNS preparations failed to demonstrate a significant change in the neuronal information entering the cerebral ganglia from the lips via the median lip nerve, but did demonstrate an age-related deficit in the neuronal output from the cerebral ganglia. This deficit was also dependent on the sucrose concentration and mirrored the concentration-dependent changes in feeding behavior. In summary, aging appeared to affect central but not peripheral processing of chemosensory information and suggests that this deficit contributes to the age-related changes in feeding behavior.

High-density lipoprotein apolipoprotein A-I kinetics: comparison of radioactive and stable isotope studies

To compare the kinetic determinants of high-density lipoprotein (HDL) apolipoprotein A-I (apoA-I) concentration in lean normolipidaemic subjects using radioisotope and stable isotope studies. We pooled data from 16 radioisotope and 13 stable isotope studies to investigate the kinetics of apoA-I in lean normolipidemic individuals. We also examined the associations of HDL kinetic parameters with age, sex, body mass index (BMI) and concentrations of apoA-I, triglycerides, HDL cholesterol and low-density lipoprotein (LDL) cholesterol. Lean subjects from radioisotope and stable isotope studies were matched for age, gender, BMI and lipid profile. The apoA-I concentration was significantly lower in the radioisotope group than the stable isotope group (P = 0.031). There was no significant difference in HDL apoA-I fractional catabolic rate (FCR) and production rate (PR) between the groups. In the radioisotope group, HDL apoA-I FCR was significantly associated with apoA-I and HDL cholesterol concentrations (r = -0.681, P < 0.001 and r = -0.542, P < 0.001, respectively), whereas in the stable isotope group, only HDL apoA-I PR was significantly associated with apoA-I concentration (r = 0.455, P = 0.004). Our findings suggest that HDL apoA-I FCR is the primary determinant of apoA-I concentrations in lean subjects in studies using radiotracer techniques. By contrast, HDL apoA-I PR is the primary determinant of apoA-I concentration in lean subject in studies employing stable isotope methods. These discrepancies may be reconciled by differences in methodologies and/or study population characteristics.

Changes in the properties of the modulatory cerebral giant cells contribute to aging in the feeding system of Lymnaea

This study examined whether electrophysiological changes in the endogenous properties and connectivity of the modulatory serotonergic cerebral giant cells (CGCs) contributed to the age-related changes in feeding behavior of the pond snail, Lymnaea. With increasing age there was a decrease in spontaneous CGC firing rates and decreased excitability of the CGCs to both chemosensory stimulation (0.05M sucrose applied to the lips) and direct intracellular current injection. These changes could be accounted for by a decrease in the input resistance of the neuron and an increase in the amplitude and the duration of the after-hyperpolarization. Decreases were also seen in the % of CGC pairs that were electrically coupled causing asynchronous firing. Together these changes would tend to reduce the ability of the CGCs to gate and control the frequency of the feeding behavior. Part of the ability of the CGCs to gate and frequency control the feeding network is to provide a background level of excitation to the feeding motor neurons. Recordings from B1 and B4 motor neurons showed an age-related hyperpolarization of the resting membrane potential consistent with a deficit in CGC function. Increases were seen in the strength of the evoked CGC-->B1 connection, however, this increase failed to compensate for the deficits in CGC excitability. In summary, age-related changes in the properties of the CGCs were consistent with them contributing to the age-related changes in feeding behavior seen in Lymnaea.

Clostridium perfringens type A enterotoxin forms mepacrine-sensitive pores in pure phospholipid bilayers in the absence of putative receptor proteins

Clostridium perfringens enterotoxin (CPE) is an important cause of food poisoning with no significant homology to other enterotoxins and its mechanism of action remains uncertain. Although CPE has recently been shown to complex with tight junction proteins, we have previously demonstrated that CPE increases ionic permeability in single Caco-2 cells using the whole-cell patch-clamp technique, thereby excluding any paracellular permeability. In this paper we demonstrate that CPE forms pores in synthetic phospholipid membranes in the absence of receptor proteins. The properties of the pores are consistent with CPE-induced permeability changes in Caco-2 cells suggesting that CPE has innate pore-forming ability.

Volume--activated chloride currents in HeLa cells are blocked by tamoxifen but not by a membrane impermeant quaternary analogue

BACKGROUND/AIMS

Tamoxifen has been shown to inhibit volume activated chloride currents in many cell types. Tamoxifen has also been reported to inhibit a number of cation channels as well as cytosolic proteins such as calmodulin. The mechanism of channel block by tamoxifen is not known but three hypotheses can be proposed: i) a direct effect following binding to the channel protein from the aqueous environment or ii) a direct effect on the channel protein after partitioning into the lipid membrane or iii) an indirect mechanism via binding to intracellular regulatory proteins after diffusion across the lipid membrane. The aim of these experiments was to distinguish between these hypotheses using membrane permeant and impermeant antioestrogens.

METHODS

Volume activated chloride currents were recorded from single HeLa cells using whole cell patch clamp technique. The ability of tamoxifen and its membrane impermeant quaternary derivative ethyl bromide tamoxifen (EBT) to inhibit these currents was examined.

RESULTS

Extracellular tamoxifen at 3 microM inhibited volume activated chloride currents in HeLa cells whereas EBT had no effect up to 10 microM when applied either to the extracellular bathing solution or the intracellular solution via the patch pipette.

CONCLUSION

Eliminating the ability of tamoxifen to cross the plasma membrane abolishes its channel blocking activity against volume activated chloride channels in HeLa cells.

Discovery of zoniporide: a potent and selective sodium-hydrogen exchanger type 1 (NHE-1) inhibitor with high aqueous solubility

Zoniporide (CP-597,396) is a potent and selective inhibitor of NHE-1, which exhibits high aqueous solubility and acceptable pharmacokinetics for intravenous administration. The discovery, synthesis, activities, and rat and dog pharmacokinetics of this compound are presented. The potency and selectivity of zoniporide may be due to the conformation that the molecule adopts due to the presence of a cyclopropyl and a 5-quinolinyl substituent on the central pyrazole ring of the molecule.

Does MMP-2 expression and secretion change with increasing serial passage of keratocytes in culture?

The effects of ageing on matrix metalloprotease degradation of the extracellular matrix during corneal wound healing are largely unknown. The following study used an in vitro model of ageing to assess changes in MMP-2 RNA expression and protein secretion. Early passage (EP) EK1.BR keratocyte cultures from 14 to 18 cumulative population doublings (cpds) and late passage (LP) cultures from 40 to 47 cpds were used to isolate protein and mRNA samples. Total protein from EP and LP cultures was measured using the Bradford protein assay. Zymographic analysis of EP and LP samples was carried out to compare MMP-2 activity. Northern blot analysis was used to assess changes in MMP-2 mRNA expression by EP and LP cultures, using a digoxigenin (DIG) based chemiluminescent detection system. LP cultures secreted more total protein per cell. MMP-2 but not MMP-9 activity was detected in keratocyte cultures. Densitometric analysis of zymograms and calculation of MMP-2 activity indicated a significant increase in MMP-2 activity per cell (P<0.05, n=11). No difference was observed in the levels of MMP-2 mRNA expressed by EP and LP cultures. An increase in MMP-2 activity per cell by LP cultures suggests that senescent keratocytes increase their degradative capacity. Similar changes in the keratocyte phenotype within the ageing cornea may alter the balanced response necessary for adequate wound healing and may have implications for the therapeutic use of MMP inhibitors in the eye.

Membrane impermeant antioestrogens discriminate between ligand- and voltage-gated cation channels in NG108-15 cells

Native 5-HT(3) and AChR ligand-gated cation channels can be inhibited (blocked) by the non-steroidal antioestrogen tamoxifen. However, the exact site and mechanism of inhibition by tamoxifen on these channels remain unclear. We have investigated the action of the membrane impermeant quaternary derivative, ethylbromide tamoxifen (EBT), on native ligand-gated 5-HT(3) receptor channels and voltage-gated K(+) channels in NG108-15 cells using whole cell patch clamp. Extracellular EBT inhibited whole cell cationic currents of 5-HT(3) receptors with IC(50) of 0.22+/-0.4 microM (n(H)=1.05+/-0.2). The channel block was characterised by voltage independent and use independent behaviour (similar to that of tamoxifen). EBT was unable to inhibit voltage-gated K(+) currents in NG108-15 cells. This was in contrast to the inhibition by tamoxifen which, at similar concentrations, accelerated the apparent inactivation of these outward K(+) currents. The inhibition of 5-HT(3) receptors by a membrane impermeant derivative of tamoxifen supports the view that the binding site for antioestrogens is extracellular and the inhibition is not mediated through genomic/transcriptional activity.

Human keratocyte migration into collagen gels declines with in vitro ageing

Although senescence in various cell types has been shown to have detrimental effects on wound repair, the effect of this phenomenon on corneal function with increasing age has yet to be elucidated. This study investigated the effect of in vitro ageing on keratocyte migration into a collagen gel matrix. The keratocyte cell strain EK1. BR was cultured to late passage and a comparison of early passage migration with that of late passage migration was carried out. Early or late passage keratocytes were seeded onto 6 collagen gels (1.75 mg ml(-1)) for each experiment. Gels were incubated at 37 degrees C for 72 h, stained with calcein AM (0.5 mg ml(-1)) and assayed for cell migration using fluorescent microscopy. Changes in the effect of EGF on keratocyte migration with age were assessed by the addition of EGF (20 ng ml(-1)) to 3 of the 6 gels in each experiment. Proliferative lifespan was measured by immunocytochemical detection of Ki67 activity. This study shows for the first time that keratocyte migration, and migration in response to EGF stimulation, significantly declines with increasing age of keratocytes in culture (P<0.001). As keratocyte migration in response to cytokine stimulation is vital for corneal repair, the accumulation of senescent keratocytes with age may impair corneal wound healing.

Novel materials to enhance keratoprosthesis integration

BACKGROUND

The successful integration of keratoprostheses (KPros) within the cornea depends in part on peripheral host keratocyte adhesion to anchor the implant in place and prevent epithelial downgrowth. The following study incorporated different acrylate co-monomers with poly(hydroxyethyl methacrylate) (p(HEMA)) and measured the suitability of these materials as potential skirt materials in terms of their ability to enhance keratocyte adhesion to p(HEMA).

METHODS

p(HEMA) hydrogels incorporating varying amounts of the acrylate co-monomers methacrylic acid (MA), 2-(dimethylamino)ethyl methacrylate (DEM), or phenoxyethyl methacrylate (PEM) were formed by free radical polymerisation. Keratocytes were seeded onto discs of each material and incubated at 37 degrees C for 72 hours. Assays for viable cell adhesion were carried out. A viability/cytotoxicity assay using solutions of calcein-AM (0.5 mM) and ethidium homodimer-1 (EthD-1) (0.5 microM) were used to measure viable and non-viable cell adhesion, respectively. An ATP assay was also used to quantify cell adhesion in terms of the amount of ATP present following lysis of adherent cells.

RESULTS

The viability/cytotoxicity assays indicated that the incorporation of 15 mol% of the co-monomer PEM or of 20 mol% DEM increased cell adhesion to p(HEMA) by at least four times. The ATP assays confirmed the results for PEM but absorption of ATP to the DEM containing hydrogel indicated that the assay was not a suitable measure of cell adhesion to this material.

CONCLUSIONS

The properties of p(HEMA) may be moderated to enhance keratocyte adhesion by the incorporation of PEM or DEM suggesting that these may be suitable materials for use in the further development of a novel KPro skirt material.

Racial differences in temporal changes in newborn viability and survival by gestational age

This study examines trends in the rates of very preterm, moderately preterm and gestational age-specific neonatal mortality, and in the gestational age limit of viability in South Carolina (SC) from 1975 to 1994. We also investigate whether trends were similar between African-Americans and Whites. We hypothesised that disproportionate reductions in gestational age-specific mortality, rather than any major changes in the gestational age distributions of either race group, underlie any increasing racial disparity in overall mortality rates. During 1975-94, single livebirths, who were born to mothers resident in SC and were either White or African-American based on recorded maternal race, were selected for the investigation. We define the gestational age limit of viability as the gestational age at which > or = 50% of infants in the population died within 28 days of life. Although preterm percentages have not improved, there was a marked decline in neonatal mortality. Gestational age-specific neonatal mortality decreased for both race groups, although there were greater reductions for White preterm infants. By the end of the study period, the African-American neonatal mortality rate was 2.3 times that of Whites and the gestational age at which 50% of newborns died within 28 days of life was 24.5 weeks for Whites and 23.9 weeks for African-Americans. The ongoing decline in neonatal mortality continues to be mainly due to reductions in gestational age-specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in neonatal mortality rates. Preterm African-American infants no longer have a marked survival advantage over White infants, even at the gestational age limit of viability.

Developmental outcome of neonatal intensive care: what questions are we asking?

Recent neonatal intensive care outcome studies are asking more focused research questions and incorporating, at least implicitly, pathogenetic models. A few have grappled with the complex issues of health-related quality of life and functional outcomes and the many factors that affect these outcomes. The need to evaluate high-risk obstetrics is increasingly recognized. Studies of risk factors for neurodevelopmental outcomes provide valuable insights into mechanisms of and recovery from central nervous system injury. Ongoing study of the efficacy and effectiveness of interventions must continue amid concern about availability of family and developmental support for increasing numbers of survivors of high-risk obstetric and neonatal intensive care.

Design and synthesis of thrombin inhibitors: analogues of MD-805 with reduced stereogenicity and improved potency

Mitsubishi's MD-805, a potent and selective inhibitor of thrombin which contains four stereogenic centers, has been the starting point for an optimization program. A systematic synthetic study resulted in thrombin inhibitors achiral at P2 and P3 but with a 10-fold increase in potency over the original lead. A number of 4-substituted piperidines were synthesized and examined as replacements for 2-carboxy-4-methylpiperidine at P2; 4-fluoroethylpiperidine (FEP) among others provided inhibitors (e.g. 45g) of increased potency. An enantioselective route was developed to 3(R)-methyl-1,2,3,4-tetrahydroquinolinesulfonyl chloride. Inhibitors containing this enantiomerically pure P3 (42d) had similar potency to the racemic material and provided support, with modeling studies, for the preparation of the gem 3,3-disubstituted compounds. A series of inhibitors containing the novel 3, 3-dimethyl-1,2,3,4-tetrahydroquinolinesulfonyl (DMTHQS) P3 (Table 5) were synthesized and showed a similar activity profile as the monomethyl series. The combination of P3-DMTHQS, P2-FEP, and P1-arginine (45g) had a K(i) of 6 nM (MD-805 K(i) = 85 nM). In animal models of both venous and arterial thrombosis, one inhibitor (42e) was shown to produce a dose-dependent inhibition of thrombus formation that in some situations was superior to that of MD-805.

A model for the binding of low molecular weight inhibitors to the active site of thrombin

This paper describes the construction, validation and application of an active site model of the serine protease thrombin. Initial use was made of medium resolution X-ray crystallographic structures of thrombin complexed with low molecular weight, non-specific inhibitors to create a computationally useable active site shell of the enzyme. Molecular mechanics methods were then applied to dock known ligands into the active site region in order to derive a model that would accurately predict binding conformations. Validation of the modelling process was achieved by comparison of the predicted enzyme-bound conformations with their known, crystallographic binding conformations. The resultant model was used extensively for predictive purposes prior to obtaining confirmatory crystal data relating to a ligand possessing a novel and unexpected binding component complexed to thrombin. The data served both to confirm the accuracy of the binding site model and to provide information for the further refinement of the model.

The pharmacokinetics and metabolism of CP-191,166, an angiotensin II receptor antagonist, in rats and dogs

CP-191,166 is an orally active, non-peptide angiotensin II (AII) receptor antagonist developed for the treatment of hypertension and congestive heart failure (CHF). In this study, the intravenous (iv) and oral (po) single dose pharmacokinetics (PK), oral multiple dose PK and P450-mediated metabolism of CP-191,166 were determined in rats and dogs. CP-191,166 was administered in both single and multiple (22-29 day) doses to Sprague-Dawley rats (3 mg/kg iv and 5, 10, 25 and 200 mg/kg po) and to beagle dogs (5 mg/kg iv and 5, 15 and 50 mg/kg po). Blood samples were collected between 0 and 48 h and plasma CP-191,166 concentrations were determined using high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The in vitro metabolism of CP-191,166 was also evaluated with rat and dog liver microsomes. The results of these studies suggest that in both species, there may be saturable clearance occurring with higher doses, T(max) was at or near the earliest sample time point for all doses, suggesting that the drug was rapidly absorbed, and CP-191,166 was eliminated with t(1/2) values of 8-9 h. No rat or dog microsomal metabolism was observed, suggesting that metabolites detected in vivo in dogs were non-P450-mediated.

Trends and racial differences in birth weight and related survival

OBJECTIVE

In the past two decades, infant mortality rates in the United States declined in African-American and White populations. Despite this, racial disparities in infant mortality rates have increased and rates of low birth weight deliveries have shown little change. In this study, we examine temporal changes in birth weight distributions, birth weight specific neonatal mortality, and the birth weight threshold for an adverse risk of survival within both racial groups in order to explore the mechanisms for the disparities in infant mortality rates.

METHOD

Single live births born to South Carolina resident mothers between 1975 and 1994 and considered White or African-American based on the mother's report of maternal race on the birth certificate were selected for investigation. We define the birth weight threshold for adverse survival odds as the birth weight at which 50% or more of infants in the population died within the first month of life.

RESULTS

Despite significant increases in very low birth weight percentages, neonatal mortality rates markedly declined. Birth weight specific neonatal mortality decreased for both races, although greater reductions accrued to White low birth weight infants. By the end of the study period, the birth weight at which over 50% of newborns died within the first month of life was 696 g for Whites and 673 g for African-Americans.

DISCUSSION

The ongoing decline in neonatal mortality is mainly due to reductions in birth weight specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in mortality rates. Moreover, the relatively greater and increasing mortality risk from postmaturity and macrosomia in infants of African-America mothers may further exacerbate the racial gap in infant mortality.

The control of hyperendemic glycopeptide-resistant Enterococcus spp. on a haematology unit by changing antibiotic usage

The rectal carriage of glycopeptide-resistant Enterococcus spp. (GRE) had been established at approximately 50% in a series of prevalence studies on a busy haematological malignancy unit. The aim of this study was to reduce the chance of patients acquiring GRE. A prospective three-phase sequential study was performed. In Phase 1, the acquisition rate of GRE detectable by rectal swab was measured without any intervention for a period of 4 months. For the following 8 months (Phase 2), the first-line treatment for febrile neutropenic episodes was changed from monotherapy with ceftazidime to piperacillin/tazobactam. In addition, an intense education programme was introduced to improve hygiene to reduce the risk of case-to-case spread. In the final 4 months (Phase 3), ceftazidime was again used as the first-line antimicrobial, while continuing the same level of training in relation to hygiene. The carriage of GRE was measured from rectal swabs done weekly. During the initial 4 months, at any time, 40-50% of patients in the unit were colonized with GRE, and 43 of 75 (57%) new patients initially negative for GRE acquired it within 6 weeks of their admission. In Phase 2, 25 patients out of 129 (19%) acquired GRE, with the acquisition rate falling progressively so that in the last 3 months, only one new patient acquired GRE (logrank comparison of probabilities for cohort 1 vs cohort 2b: P < 0.0001). A return to ceftazidime in Phase 3 was associated with a return of the risk of acquiring detectable GRE colonization, despite continued hygiene teaching and surveillance, with 21 out of 58 patients (36%) acquiring GRE (cohort 1 vs cohort 3: P = 0.08). Glycopeptide usage was not reduced during the period of the study. Clinical cases were seen only in Phases 1 and 3. Although the reduction in the risk of acquiring GRE may have been due in part to hygiene practices as well as to the change in antimicrobial usage, or may have occurred spontaneously for other reasons, the return of the problem with the reintroduction of ceftazidime strongly suggests that this antibiotic was responsible for encouraging the acquisition of detectable GRE.

Agonist and antagonist effects of histamine H3 receptor ligands on 5-HT3 receptor-mediated ion currents in NG108-15 cells

The ability of histamine H3 receptor ligands to interact with 5-HT3 receptors in NG108-15 cells was studied using the whole cell patch clamp recording technique. Imetit, a histamine H3 receptor agonist, generated inward currents and exhibited weak partial agonist activity at the 5-HT3 receptor (EC50 = 11.8 microM). Imetit-induced currents were slow to desensitize and at a high concentration reduced in size. The histamine H3 receptor antagonists iodophenpropit and thioperamide did not generate inward currents but were able to inhibit 5-hydroxytryptamine (5-HT) responses with an IC50 of 1.57+/-0.3 microM and 13.7+/-3.5 microM, respectively. Thioperamide is probably a non-competitive antagonist which may have more than one binding site on the receptor.

Speech intelligibility in children after cochlear implantation

OBJECTIVE

This study aimed to evaluate the long-term speech intelligibility of young deaf children after cochlear implantation.

STUDY DESIGN

The study design was a prospective study following a large group of consecutively implanted deaf children with up to 5 years' cochlear implant use.

SETTING

The study was conducted at a pediatric tertiary referral center for cochlear implantation.

PATIENTS

All children in the study were congenitally deaf or deafened before 3 years of age. They each received a Nucleus multichannel cochlear implant before the age of 7 years. Eighty-four subjects were evaluated up to 5 years after cochlear implantation.

INTERVENTION

Cochlear implantation followed by an intensive program of local and center-based assessment and rehabilitation was performed.

MAIN OUTCOME MEASURES

A speech intelligibility rating scale evaluated the spontaneous speech of each child before and at yearly intervals for 5 years after implantation.

RESULTS

After cochlear implantation, the difference between the speech intelligibility ratings increased significantly each year for 4 years (Mann-Whitney U-test). For the first 2 years, the average rating remained "prerecognizable words" or "unintelligible speech." It was not until the 3-year interval that the average intelligibility rating became category 3 (intelligible speech if someone concentrates and lip-reads). At the 4-year interval, 85% of children had some intelligible connected speech. This improvement continued, and at the 5-year interval, the median speech intelligibility was category 4 (intelligible speech to a listener with a little experience of deaf speech) and the mode was category 5 (intelligible speech to all listeners).

CONCLUSION

Congenital and prelingually deaf children gradually develop intelligible speech that does not plateau 5 years after implantation.

Impact of the perception of viability on resource allocation in the neonatal intensive care unit

OBJECTIVE

To understand how neonatologists' perceptions of viability impact their willingness to recommend or provide medical interventions for infants born at 23 to 24 weeks' gestation.

STUDY DESIGN

A 25-question survey mailed to 3056 neonatologists in the United States in 1992 yielded 1131 responses. Seven hundred seventy-five (775 of 1131, 69%) reported they believed that the lower limit of viability was 23 to 24 weeks' gestation. These respondents were asked if they were willing to recommend or provide a series of medical interventions for infants born at 23 and 24 weeks' gestation.

RESULTS

Most respondents would provide ventilation (82% and 95%) and surfactant (62% and 78%) for infants born at 23 and 24 weeks' gestation, respectively. The respondent's prediction of <100% mortality, infant factors, and parental wishes were significant predictors of willingness to resuscitate infants born at 23 weeks' gestation.

CONCLUSION

There is considerable variation among neonatologists in their willingness to recommend or provide medical interventions for infants born at 23 to 24 weeks' gestation.

Inhibition of ligand-gated cation-selective channels by tamoxifen

The nonsteroidal antioestrogen tamoxifen has been shown to block a number of voltage-gated cation-selective channels but its effect on ligand-gated cation-selective channels has not been studied. We have investigated the action of tamoxifen and the related derivative toremifene on ligand-gated cationic nicotinic acetylcholine and 5-HT3 receptor channels. Tamoxifen and toremifene both inhibited cationic currents of adult-type human muscle nicotinic acetylcholine receptors expressed in Xenopus oocytes with similar IC50 values of 1.2 +/- 0.03 microM (nH = 0.84 +/- 0.02) and 1.2 +/- 0.1 microM (nH = 1.1 +/- 0.1), respectively. Tamoxifen could also block native 5-HT3 receptors in NG108-15 neuroblastoma/glioma hybrid cells with IC50 = 0.81 +/- 0.15 microM and nH of 1.3 +/- 0.3. The characteristics of block by tamoxifen at the 5-HT3 receptor were voltage- and use-independent. The inhibition of the 5-HT-evoked currents were not overcome by increasing concentrations of 5-HT consistent with a noncompetitive mechanism of block.

The association between adequacy of prenatal care utilization and subsequent pediatric care utilization in the United States

OBJECTIVE

To explore the association between adequacy of prenatal care utilization and subsequent pediatric care utilization.

DESIGN

A longitudinal follow-up of a nationally representative sample of infants born in 1988.

PARTICIPANTS

Nine thousand four hundred forty women who had a live birth in 1988, and whose child was alive at the time of interview, and 8285 women from the original sample who were reinterviewed in 1991.

MAIN OUTCOME MEASURE

There were four outcome measures: number of well-child visits; adequate immunization for diphtheria, tetanus, and pertussis; adequate immunization for polio; and continuity of a regular source of care, as measured by the number of sites for pediatric care.

RESULTS

Children whose mothers had less than adequate prenatal care utilization had significantly fewer well-child visits, and were significantly less likely to have adequate immunizations, even after income, health insurance coverage, content of prenatal care, wantedness of child, sites of prenatal and pediatric care, and maternal and pregnancy risk characteristics were taken into account. Less than adequate prenatal care utilization was not associated with having more than one pediatric care site.

CONCLUSIONS

Prenatal care utilization can be used to identify and target interventions to women who are at risk for not obtaining well-child care or complete immunizations for their children.

Rapid determination of oral pharmacokinetics and plasma free fraction using cocktail approaches: methods and application

PURPOSE

To apply cocktail approaches for protein binding (PB) and pharmacokinetics (PK) within a discovery program as a means of providing timely systemic exposure (AUC and Cmax) data.

METHODS

For PB data, a procedure of cocktail ultrafiltration, mixed matrix sample preparation and single quadrupole atmospheric pressure ionization LC/MS analysis was used. In vivo PK studies consisted of 4 experimental compounds and a control compound dosed orally at 1 mg/kg (5 mg/kg total dose), with plasma samples obtained at 0.5, 1, 2, 4 and 8 h post dose. For PB and in vivo PK analysis, a control compound was tested within each cocktail to ensure consistent reproducibility.

RESULTS

Approximately 2 weeks were spent comparing single and cocktail approaches to determine the feasibility of this method for this project. Comparisons of cocktail data with single compound data revealed no significant differences between the approaches. The oral AUC values ranged from 0.01 to 9.28 micrograms.hr/ml and the Cmax values ranged from 0.04 to 2.17 micrograms/ml. Free fractions of the 44 compounds studied ranged from 0.006 to 0.271. Using the free fraction values to correct for free AUC and Cmax results in ranges of 0.001 to 0.473 microgram.hr/ml, and 0.001 to 0.119 microgram/ml, respectively.

CONCLUSIONS

All 44 compounds tested had similar potencies in vivo. Thus, these results suggest that a respective 400 and 100-fold range in AUC and Cmax corrected for free fraction exist in the presence of comparable in vivo activity. The ability to generate this type of data in a timely manner allowed the selection of a candidate with low peripheral exposure relative to the effective dose. The free fraction and PK data on the 44 compounds described was collected within three work days by 2 lab scientists.

Using the clinical linguistic and auditory milestone scale for developmental screening in high-risk preterm infants

Eighty-one preterm infants (mean gestational age 29 weeks, range 24-36 weeks) discharged from The Johns Hopkins Hospital Neonatal Intensive Care Unit were followed up sequentially from birth to 2 years of age by use of the Clinical Linguistic and Auditory Milestone Scale (CLAMS) to evaluate language development. Children were studied during three time intervals: Interval 1: 3-5 months chronologic age (CA); Interval 2: 9-14 months (CA); and Interval 3: 18-24 months (CA). Psychometric test scores were compared with CLAMS Language Quotients (LQ) by use of full, partial (75%, 50%, 25%), and no "correction" for weeks of prematurity to determine whether "correcting" for prematurity would yield a more accurate estimate of eventual cognitive outcome. CLAMS LQ at Interval 1 was highly correlated with CLAMS LQ at Interval 2 and CLAMS LQ at Interval 2 correlated well with CLAMS LQ at Interval 3 (r = 0.57 and 0.64, respectively, P = 0.0001). Correlations indicated that there was an orderly, sequential development of language in the preterm infant. CLAMS evaluations correlated significantly with psychometric test results during Interval 2 and Interval 3 (r = 0.34, P < 0.02 and r = 0.75, P = 0.0001, respectively). The CLAMS proved to be a useful instrument for monitoring preterm language development in the primary pediatric care setting.

Quantitation of 4-cyclohexyl-2-hydroxy-3-(3-methylsulfanyl-2- [2-[(morpholine-4-carbonyl)amino]-3-phenylpropionylamino]propi onylamino ) butyric acid isopropyl ester (CP-80,794), a renin inhibitor, and its hydrolytic cleavage metabolite 2-[(morpholine-4-carbonyl)amino]-3-phenylpropionic acid (CP-84,364) in dog and human plasma by high-performance liquid chromatography

Simple and precise high-performance liquid chromatographic (HPLC) assays were developed and validated for the determination of a renin inhibitor (RI), 4-cyclohexyl-2-hydroxy-3- (3-methylsulfanyl-2-[2-[(morpholine-4-carbonyl)amino]- 3-phenylpropionylamino]propionylamino)butyric acid isopropyl ester (CP-80,794, I), and its hydrolytic cleavage metabolite, 2-[(morpholine-4-carbonyl)amino]-3-phenylpropionic acid (CP-84,364, II) in dog and human plasma. The internal standard for I, CP-83,092 (III, a carbon-substituted derivative of I) and analyte were extracted by liquid-liquid extraction using n-butyl chloride, cleaved to form a fragment containing a primary amine, and subsequently fluorescently derivatized for measurement by HPLC. Samples were analyzed by reversed-phase HPLC using a Waters C18 column with fluorescence detection at 390 nm excitation/440 nm emission. The quantitation limit of I was 10 ng/ml and the calibration curve was linear over the range of 0.01-1.0 microgram/ml (r2 > 0.99). In dog and human plasma, intra- and inter-assay precision ranged from 2.3 to 16% and 3.0 to 18%, respectively. The average recoveries were similar (> or = 63%) for both I and III and the upper limit of quantification of I can be as high as 4 micrograms/ml. The internal standard for II, CP-96,452 (IV, a methoxy derivative of II) and analyte were extracted by anion-exchange solid-phase extraction and subsequent liquid-liquid extraction using methyl tert.-butyl ether. Samples were analyzed by reversed-phase HPLC using a Waters C18 column with ultraviolet detection at 214 nm. The quantitation limit of II was 20 ng/ml and the calibration curve was linear over the range of 0.02-2.0 micrograms/ml (r2 > 0.99). In dog and human plasma, intra- and inter-assay precision ranged from 2.6 to 13.0% and 1.8 to 20.0%, respectively. The average recoveries were similar (> or = 75%) for both II and IV and the upper limit of quantification of II can be as high as 20 micrograms/ml. The methods described have been successfully applied to the quantification of I and II in about 5000 dog and human plasma samples over a 2 year period.

Laser applications to chemical and environmental analysis: an introduction

This issue of Applied Optics features papers on the application of laser technology to chemical and environmental analysis. Many of the contributions to this issue, although not all, result from papers presented at the 1996 OSA Topical Meeting on Laser Applications to Chemical and Environmental Analysis, which was held in Orlando, Florida, in March 1996. This successful meeting, with nearly 100 participants, continued the tradition of earlier Laser Applications to Chemical Analysis (LACA) meetings. The title change reflects an expended scope and an even greater emphasis on environmental analysis than the previous four LACA meetings.

Cycling Werner's syndrome fibroblasts display calcium-dependent potassium currents

Werner's Syndrome (WS) fibroblasts undergo premature senescence. Two hypotheses have been proposed to explain this phenomenon: (i) the phenotype is due to the overexpression of senescence-specific proteins in every cell in the population. Such proteins are known to suppress calcium-dependent potassium currents. (ii) The WS mutation greatly increases the proportion of cells that stop cycling at each generation and become senescent. If hypothesis (i) is correct, such currents should be suppressed in all WS fibroblasts; whereas hypothesis (ii) predicts that they will be retained in the cycling fraction of the population. To distinguish between these hypotheses whole-cell patch-clamp currents were recorded from cycling cells. Slowly activating outward calcium-dependent potassium currents were detected in both cycling WS and control fibroblasts. These findings support hypothesis (ii): the premature senescence of WS fibroblasts is due to an increased rate of transition from cycling to senescence in the total cell population.

Using motor milestones as a multistep process to screen preterm infants for cerebral palsy

Pediatricians often informally use motor milestones to screen infant motor development, and one advantage is that they can be used during sequential office visits, as a multistep screening process. In this study we evaluated six motor milestones (roll prone to supine, roll supine to prone, sit with support, sit without support, crawl and cruise) as a multistep process in screening for cerebral palsy in 173 high-risk preterm infants (<33 weeks gestational age) who had been followed with sequential developmental assessments for at least 18 months. At the 18 to 24 month evaluation, 31 (18%) had cerebral palsy. We found that using the motor milestones as serial screening tests for cerebral palsy was more effective in terms of positive predictive value than any individual milestone alone. Limited community resources can be more efficiently used if preterm infants with delays in more than four motor milestones are referred for further evaluation and early intervention services.

Histamine forming capacity (HFC) and its modulation by H3 receptor ligands in a model of bronchial hyper-responsiveness

The histamine forming capacity (HFC) of acutely challenged airways from sensitised guinea pigs was investigated. After exposure to nebulised bovine serum albumin (BSA) or normal saline, animals were sacrificed, the pulmonary HFC determined and concurrent in vitro histamine log concentration response curves were constructed for parenchymal strips and tracheal muscle, the latter was field stimulated to record neurogenic responses. Exposure to BSA increased the HFC above controls for 24 hours (p < 0.001) and log concentration response curves for the parenchymal strips were shifted slightly to the left with an increased maximum response. This change appeared 3 hours after exposure and remained elevated at 24 hours. Similar changes did not occur with the trachea. Pre-treatment with thioperamide augmented (p < 0.02) HFC and this increase was inhibited by alpha-methylhistamine (p < 0.05). A possible relationship may exist between increased responsiveness of lower airways to exogenous histamine and a raised endogenous formation, regulated by the H3 receptor.

Determination of 1-[5-(2-cyclopropyl-5,7-dimethyl-imidazo[4,5-b] pyridin-3-ylmethyl)thiophen-2-yl]cyclopent-3-enecarboxylic acid (CP-191,166), an angiotensin II antagonist, in dog and rat plasma by high-performance liquid chromatography

A simple and precise high-performance liquid chromatographic (HPLC) assay was developed and validated for the determination of a novel angiotensin II antagonist, 1-[5-(2-cyclopropyl-5,7-dimethyl-imidazo[4,5-b]pyridin-3-ylmethyl) thiophen-2-yl]cyclopent-3-enecarboxylic acid (CP-191,166, I), in dog and rat plasma. The internal standard (II, a saturated derivative of I) and analyte were extracted by liquid-liquid extraction using methyl tert.-butyl ether. Samples were analyzed by reversed-phase HPLC using a Zorbax C8 narrow-bore column with ultraviolet detection at 289 nm. The quantitation limit of I was 10 ng/ml and the calibration curve was linear over the range of 0.01-10.0 micrograms/ml (r2 > 0.99). In dog and rat plasma, intra- and inter-assay precision ranged from 0.00 to 3.36% and 0.00 to 4.95%, respectively. The average recoveries were similar (73%) for both I and II and the upper limit of quantification of I can be as high as 500 micrograms/ml. The method described has been successfully applied to the quantification of I in about 2000 dog and rat plasma samples over a nine-month period.

Conceptualization, measurement, and use of gestational age. I. Clinical and public health practice

Despite its importance for both clinical and public health practice and the considerable effort spent during the past three decades to develop alternative estimation methods, the measurement of gestational age on both the individual and population level continues to be problematic. The availability of alternative approaches for the estimation of gestational age has to some extent obscured the basic differences in the conceptualization of these measures and influenced our current state of thinking about gestational age. As the evidence grows that these alternative gestational age estimation measures do not precisely correspond with one another, controversies have arisen regarding which method is most accurate. In the search for a single gestational age "gold standard," the potentially valuable information that these alternative measures may provide when used in combination should not be overlooked.

Perceptions of the limit of viability: neonatologists' attitudes toward extremely preterm infants

Although recent technologic advances have dramatically improved the survival of preterm infants, little information exists regarding the attitudes of neonatologists toward their smallest patients, infants born at the "limit of viability." In this pilot study we sent a single mailing of a 25-question survey designed to provide information about the medical treatment of extremely preterm infants (< 22 to 27 weeks' gestational age) to 3056 neonatologists practicing in the United States in September 1992. The 1131 (37%) respondents were well distributed geographically and by nature of practice (i.e., academic, academic affiliate, and community hospitals). Most of the respondents counseled parents that all infants < or = 22 weeks' gestational age die and that at least 75% of infants born at 23 weeks' gestation die. Only for infants born at > or = 26 weeks' gestational age did most of the neonatologists counsel parents that mortality is < or = 50%. Nonintervention or compassionate care in the delivery room was believed to be appropriate for infants less than 23 weeks' gestational age by virtually all neonatologists, by 52% of respondents for infants 23 weeks' gestational age, and by only 1% of respondents for infants 25 weeks' gestational age. Approximately two thirds of neonatologists considered parental wishes regarding resuscitation, and one quarter considered parental parity/fertility history in their medical decision making for infants born at 23 to 24 weeks' gestation. If an infant who had been previously resuscitated decompensated in spite of maximal medical treatment, most of the neonatologists were not willing to provide full resuscitation for infants born at any gestation less than 27 weeks. However, the number of neonatologists who would actively encourage withdrawal of support in a decompensating infant decreased markedly for infants born at > or equal 25 weeks' gestation. Neonatologists who responded to this survey in 1992 considered 23 to 24 weeks of gestation the limit of viability and had great concerns regarding medical decision making for these infants.

The CAT/CLAMS assessment for early intervention services. Clinical Adaptive Test/Clinical Linguistic and Auditory Milestone Scale

The Clinical Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) is a relatively new test of language, problem-solving abilities, and visual-motor skills for children ages 0 to 36 months of age. This instrument was compared to the Bayley Mental Developmental Index (MDI), the generally accepted standard of infant developmental tests. This study evaluates 328 normal children tested in infancy and then at 18 and 30 months of age. Specificity was excellent (95% to 100%) at both 18- and 30-month levels when compared to the Bayley MDI. Sensitivity, however, was 21% at the 18-month level and 67% at the 30-month level. Predictive validity (.65) and within-test validity (.69) are good. The CAT/CLAMS compares favorably with the Bayley MDI assessment of children between 18 and 30 months of age and can be used for clinical assessment of toddlers referred for development assessment prior to admission to early intervention programs.

CAT/CLAMS. A tool for the pediatric evaluation of infants and young children with developmental delay. Clinical Adaptive Test/Clinical Linguistic and Auditory Milestone Scale

The American Academy of Pediatrics recommends regular developmental screening as a part of routine child health supervision. However, the pediatrician has a limited number of tools available to further evaluate a child who is found to be suspect or abnormal on a developmental screening test. The Clinical Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) was therefore developed to provide pediatricians with a technique to assess infants and toddlers with suspected developmental delay. The CAT/CLAMS demonstrated strong psychometric properties. Concurrent validity with the Bayley Scales of Infant Development (BSID) was demonstrated in 43 children ages 12 to 19 months who were tested on three occasions with both instruments (correlation coefficient ranging between 0.63 and 0.87; P < .001). Predictive validity 6 and 12 months later was also demonstrated in this population with correlation coefficients ranging between 0.73 and 0.77, significant at the P = .001 level. Utilizing the CAT/CLAMS as part of the pediatrician's evaluation of children with developmental concerns would allow the pediatrician to compare language and nonlanguage problem-solving abilities and, therefore, aid in diagnosis and appropriate referral.

Screening for cerebral palsy in preterm infants: delay criteria for motor milestone attainment

We evaluated the efficacy of various delay criteria (12.5%, 25%, 37.5%, 5%, 50% delay) for motor milestone attainment to screen a sample of 173 high-risk preterm infants with gestational age < 32 weeks who had been sequentially followed for 18 to 24 months. Sensitivities were best with 12.5% and 25% delays, but specificities and positive predictive values were relatively lower. Since societal resources for evaluation and treatment of cerebral palsy are limited, the excellent specificities (81% to 95%) and positive predictive values (48% to 85%) with 50% delay are more important than the somewhat lower sensitivities, especially since milestones involve a multistep screening process. Screening preterm infants by obtaining a history of motor milestone attainment with each child care visit, correcting for degree of prematurity, and using a 50% delay criteria is a practical, inexpensive method of identifying infants at highest risk of cerebral palsy.

Neurocardiogenic syncope in children with a normal heart

OBJECTIVES

The purpose of this study was to review the results of investigation and management of children with syncope and a structurally normal heart.

BACKGROUND

Syncope is a common clinical problem and has many etiologies. Autonomic testing and, in particular, the tilt/orthostatic test have helped to positively diagnose neurocardiogenic syncope in a high proportion of such patients.

METHODS

Patient case notes and autonomic test charts were reviewed in 162 children aged 1 to 20 years (mean age 12.8 years) with syncope. The autonomic test consisted of orthostatic maneuver, carotid sinus massage, diving reflex, Valsalva maneuver and dose response to intravenous boluses of isoproterenol and phenylephrine. Serum levels of epinephrine and norepinephrine were drawn during the orthostatic test. After confirmation of neurocardiogenic syncope, treatment was begun with fludrocortisone and salt, and beta-adrenergic blocking agents were used as a second line of therapy when indicated.

RESULTS

The orthostatic test was positive for neurocardiogenic syncope in 100 patients (62%) and negative in 62 (38%). Patients in the former group were older, were more often female and had a diminished response to carotid sinus massage, a higher Valsalva ratio and a higher supine epinephrine level. Both groups showed an increase in epinephrine and norepinephrine levels at 5 min of standing. In the orthostatic positive group at the time of syncope, norepinephrine levels decreased, whereas epinephrine levels increased. Patients in this group were also more sensitive to the vasodilating effect of isoproterenol but not to its chronotropic effects. Eleven patients had cardioinhibitory syncope (asystole > or = 3 s). Of these, three had pacemaker implantation. Fludrocortisone and salt used in 84 patients in the orthostatic positive group produced resolution of symptoms in 55 patients (65%) and improvement in 14 (17%). Ten patients received beta-blockers, with resolution in four and improvement in four.

CONCLUSIONS

Patients with orthostatic test-proved neurocardiogenic syncope show evidence of autonomic dysfunction. They also show beta-adrenergic hypersensitivity. Treatment initiated on the basis of the protocol was associated with amelioration of symptoms in the majority of patients.

Effect of beta-adrenergic stimulation on the QT interval of children with syncope

The effect of intravenous bolus doses (0.25, 0.5, 1.0 microgram) of isoproterenol on the QT and RR intervals was reviewed in a group of 34 children undergoing autonomic testing for syncope. Twenty-one patients had a positive orthostatic test and 13 were negative. The two groups (positive and negative) were compared. Baseline QT and RR intervals were similar. The RR interval was shortened by isoproterenol in both groups. Isoproterenol shortened the QT interval in the negative group (as seen in normal persons), but produced QT prolongation in the positive group, although neither reached statistical significance when compared to baseline within the respective group. Comparing the values for RR and QT at each dose of isoproterenol (including baseline) between the two groups showed a significant difference in the QT interval after the 1.0-microgram dose of isoproterenol. Thus children with orthostatic positive neurocardiogenic syncope showed a different QT response to beta-adrenergic stimulation. This lends support to the theory of altered beta-adrenergic sensitivity being present in children with neurocardiogenic syncope.

The limit of viability--neonatal outcome of infants born at 22 to 25 weeks' gestation

BACKGROUND

With improved survival of preterm infants, questions have been raised about the limit of viability. To provide better information and counseling for parents of infants about to be delivered after 22 to 25 weeks' gestation, we evaluated the mortality and neonatal morbidity of preterm infants born at these gestational ages.

METHODS

We studied retrospectively all 142 infants born at 22 to 25 weeks' gestation (as judged by best obstetrical estimate) from May 1988 through September 1991 in a single hospital. Mortality in the first six months, including stillbirths, and neonatal morbidity (i.e., the presence of intracranial pathologic conditions, chronic lung disease, and retinopathy of prematurity) were analyzed.

RESULTS

Fifty-six infants (39 percent) survived for six months. Survival improved with increasing gestational age; none of 29 infants born at 22 weeks' gestation survived, as compared with 6 of 40 (15 percent) born at 23 weeks, 19 of 34 (56 percent) born at 24 weeks, and 31 of 39 (79 percent) born at 25 weeks. There were seven stillbirths at 22 weeks' gestation and four stillbirths at 23 weeks. The more immature the infant, the higher the incidence of neonatal complications as determined by the number of days of mechanical ventilation, the length of the hospital stay, and the presence of retinopathy of prematurity, periventricular or intraventricular hemorrhage, or periventricular leukomalacia. Only 2 percent of infants born at 23 weeks' gestation survived without severe abnormalities on cranial ultrasonography, as compared with 21 percent of those born at 24 weeks and 69 percent of those born at 25 weeks.

CONCLUSIONS

We believe that aggressive resuscitation of infants born at 25 weeks' gestation is indicated, but not of those born at 22 weeks. Whether the occasional child who is born at 23 or 24 weeks' gestation and does well justifies the considerable mortality and morbidity of the majority is a question that should be discussed by parents, health care providers, and society.

The high-risk infant

A large number of infants are born each year with biologic or environmental risk factors that put them at increased risk for developmental disability, although most do not go on to have major disabilities. Some risk factors, for example, intraparenchymal hemorrhage, periventricular cysts, encephalomalacia, and abnormal neurodevelopmental examination, carry a much higher risk of developmental disability than others. There is much overlap among risk factors, and infants with multiple risk factors generally have a greater risk of disability than infants with just a single risk factor. All high-risk infants should receive careful pediatric follow-up that includes developmental screening, but efficient use of so far quite limited resources argues for selection of the highest risk infants for comprehensive developmental follow-up or early intervention programs. A system of tracking and monitoring high-risk infants during infancy and childhood would allow for early identification of developmental delay and appropriate referral for community resources.

Effect of hyperbaric and normobaric oxygen on pulmonary endothelial cell function

The effect of prior exposure to raised partial pressures of oxygen on pulmonary endothelial cell function was assessed in the isolated perfused rat lung preparation. Prolonged exposure to both 1 bar (48 h) and 2.5 bar (11 h) of oxygen caused pulmonary edema and dyspnea. Exposure to 1 bar oxygen for 48 h (approximately 0.66 lethal duration) caused a decrease in pulmonary 5-hydroxytryptamine (5-HT) clearance, suggesting compromised endothelial cell integrity. No change in 5-hydroxy-indole acetic acid (5-HIAA) efflux was noted. However, exposure to 2.5 bar of oxygen for up to 11 h (approximately 0.85 lethal duration) did not decrease pulmonary 5-HT clearance, implying that endothelial cell integrity was not compromised after this oxygen exposure. Exposure to 2.5 bar oxygen resulted in a reduction in 5-HIAA efflux, possibly indicating a decrease in metabolism of cleared 5-HT. The absence of a demonstrable impairment of 5-HT clearance during the development of pulmonary toxicity on exposure to 2.5 bar of oxygen suggests that there may be important differences in pathologic mechanisms in response to oxygen exposure at partial pressures 1 and 2.5 bar.