Geographic disparities in performance of pediatric polysomnography to diagnose obstructive sleep apnea in a universal access health care system

BACKGROUND

Diagnostic polysomnography (PSG) is recommended prior to adenotonsillectomy (AT) for children with obstructive sleep apnea (OSA) and certain high-risk characteristics, but resource limitations often prevent this practice.

OBJECTIVE

We performed a population-based assessment of children across Ontario, Canada to describe and quantify disparities in PSG.

METHODS AND MATERIALS

This retrospective cohort study was performed using provincial health administrative data held at ICES. We identified children 0-10 years old who underwent PSG and AT between 2009 and 2018, and those with a PSG within 18 months prior to and/or 12 months following AT. We calculated the odds of PSG prior to/following AT after adjustment for demographics, medical comorbidities, geographic and socioeconomic characteristics. Our main predictor was driving time/distance to the nearest pediatric sleep centre ascertained using spatial analysis and geographic information systems.

RESULTS

We identified 27,837 children <10 years old who underwent AT for OSA in Ontario. Only 12.8% had a PSG within 18 months prior and 5.7% had a PSG within 12 months following AT. Shorter driving time/distance, older age, male sex and certain comorbidities were associated with increased odds of PSG.

CONCLUSION

Only a small proportion of children in our cohort underwent PSG prior to or following AT surgery despite universal access to healthcare. This study suggests a need to increase overall PSG access, particularly for those living distant from existing pediatric sleep centres. Future studies could determine if increased PSG testing in 'underserviced areas' would reduce overall surgery rates and/or improve health outcomes.

A quieting ocean: unintended consequence of a fluctuating economy

Simultaneous long-term monitoring of underwater sound and ship traffic provided an opportunity to study how low-frequency noise correlated with ocean-based commercial shipping trends. Between 2007 and 2010 changes in regional shipping off southern California occurred as a consequence of economic and regulatory events. Underwater average noise levels measured before and during these events showed a net reduction of 12 dB. Statistical models revealed that a reduction of 1 ship transit per day resulted in 1 dB decrease in average noise. This synthesis of maritime traffic statistics with ocean noise monitoring provides an important step in understanding the magnitude and potential effects of chronic noise in marine habitats.

Scale and pattern of broadnose sevengill shark Notorynchus cepedianus movement in estuarine embayments

The detailed movements of 32 acoustically tagged broadnose sevengill shark Notorynchus cepedianus were documented in and around north-east Pacific Ocean estuarine embayments from 2005 to 2007. Arrangements of passive acoustic receivers allowed analysis of movement at several spatial scales, with sex and size examined as possible factors influencing the pattern and timing of these movements. Notorynchus cepedianus exhibited a distinctly seasonal pattern of estuary use over three consecutive years, entering Willapa Bay in the spring, residing therein for extended periods of time during the summer and dispersing into nearshore coastal habitats and over the continental shelf during the autumn. Notorynchus cepedianus within Willapa Bay showed spatio-temporal patterns of segregation by size and sex, with males and small females using peripheral southern estuary channels early in the season before joining large females, who remained concentrated in central estuary channels for the entire season. Individuals displayed a high degree of fidelity not only to Willapa Bay (63% were documented returning over three consecutive seasons), but also to specific areas within the estuary, showing consistent patterns of site use from year to year. Cross-estuary movement was common during the summer, with most fish also moving into an adjacent estuarine embayment for some extent of time. Most winter and autumn coastal detections of N. cepedianus were made over the continental shelf near Oregon and Washington, U.S.A., but there were also examples of individuals moving into nearshore coastal habitats further south into California, suggesting the feasibility of broad-scale coastal movements to known birthing and nursery grounds for the species. These findings contribute to a better understanding of N. cepedianus movement ecology, which can be used to improve the holistic management of this highly mobile apex predator in regional ecosystems.

Apolipoprotein A-I-stimulated apolipoprotein E secretion from human macrophages is independent of cholesterol efflux

Apolipoprotein A-I (apoA-I)-mediated cholesterol efflux involves the binding of apoA-I to the plasma membrane via its C terminus and requires cellular ATP-binding cassette transporter (ABCA1) activity. ApoA-I also stimulates secretion of apolipoprotein E (apoE) from macrophage foam cells, although the mechanism of this process is not understood. In this study, we demonstrate that apoA-I stimulates secretion of apoE independently of both ABCA1-mediated cholesterol efflux and of lipid binding by its C terminus. Pulse-chase experiments using (35)S-labeled cellular apoE demonstrate that macrophage apoE exists in both relatively mobile (E(m)) and stable (E(s)) pools, that apoA-I diverts apoE from degradation to secretion, and that only a small proportion of apoA-I-mobilized apoE is derived from the cell surface. The structural requirements for induction of apoE secretion and cholesterol efflux are clearly dissociated, as C-terminal deletions in recombinant apoA-I reduce cholesterol efflux but increase apoE secretion, and deletion of central helices 5 and 6 decreases apoE secretion without perturbing cholesterol efflux. Moreover, a range of 11- and 22-mer alpha-helical peptides representing amphipathic alpha-helical segments of apoA-I stimulate apoE secretion whereas only the C-terminal alpha-helix (domains 220-241) stimulates cholesterol efflux. Other alpha-helix-containing apolipoproteins (apoA-II, apoA-IV, apoE2, apoE3, apoE4) also stimulate apoE secretion, implying a positive feedback autocrine loop for apoE secretion, although apoE4 is less effective. Finally, apoA-I stimulates apoE secretion normally from macrophages of two unrelated subjects with genetically confirmed Tangier Disease (mutations C733R and c.5220-5222delTCT; and mutations A1046D and c.4629-4630insA), despite severely inhibited cholesterol efflux. We conclude that apoA-I stimulates secretion of apoE independently of cholesterol efflux, and that this represents a novel, ABCA-1-independent, positive feedback pathway for stimulation of potentially anti-atherogenic apoE secretion by alpha-helix-containing molecules including apoA-I and apoE.

Nebulizer choice for inhaled colistin treatment in cystic fibrosis

STUDY OBJECTIVES

To develop practical ways of nebulizing colistin by determining the rate of drug output, total drug output, and particle-size distribution of two commercially available jet nebulizers, the disposable Hudson 1730 Updraft II (Hudson Respiratory Care; Temecula, CA) and the reusable Pari LC Star breath-enhanced nebulizer (Pari Respiratory Equipment; Midlothian, VA).

METHODS

The nebulizers contained colistin, 75 mg, in 4 mL of isotonic solution. Particle-size distribution was measured by helium-neon laser diffraction, allowing calculation of the respirable fraction (RF), the mass of aerosol comprised of droplets < 5 microm.

RESULTS

The mean (95% confidence interval [CI]) total rate of output of the Updraft II was 2.6 mg/min (2.0, 3.1; n = 4) with 1.3 mg/min (1.0, 1.5) mg/min within the RF. The rate of output of the LC Star increased in a quadratic relationship to the inspiratory flow, delivering 1.8 mg/min (0.7, 2.0; n = 4) with 1.4 mg/min (1.3, 1.6) within the RF, and 6.2 mg/min (5.6, 6.8) with 5.3 mg/min (4.8, 5.7) within the RF, at 0 L/min and 20 L/min inspiratory flows, respectively. Efficiency, as the rate of expected pulmonary deposition divided by rate of total output, was then calculated. The LC Star estimated 56% (51, 61) efficiency, with pulmonary delivery of 29% (26, 32) of the charge of the nebulizer, compared to the Updraft II at 22% (22, 23) efficiency and expected pulmonary deposition of 10% (10, 10) of the dose.

CONCLUSIONS

Colistin can be successfully nebulized with both nebulizers tested. This study provides an estimate of in vivo efficiency and expected pulmonary deposition that may be used in future trials.

Red muscle activation patterns in yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas during steady swimming

To learn about muscle function in two species of tuna (yellowfin Thunnus albacares and skipjack Katsuwonus pelamis), a series of electromyogram (EMG) electrodes was implanted down the length of the body in the internal red (aerobic) muscle. Additionally, a buckle force transducer was fitted around the deep caudal tendons on the same side of the peduncle as the electrodes. Recordings of muscle activity and caudal tendon forces were made while the fish swam over a range of steady, sustainable cruising speeds in a large water tunnel treadmill. In both species, the onset of red muscle activation proceeds sequentially in a rostro-caudal direction, while the offset (or deactivation) is nearly simultaneous at all sites, so that EMG burst duration decreases towards the tail. Muscle duty cycle at each location remains a constant proportion of the tailbeat period (T), independent of swimming speed, and peak force is registered in the tail tendons just as all ipsilateral muscle deactivates. Mean duty cycles in skipjack are longer than those in yellowfin. In yellowfin red muscle, there is complete segregation of contralateral activity, while in skipjack there is slight overlap. In both species, all internal red muscle on one side is active simultaneously for part of each cycle, lasting 0.18T in yellowfin and 0.11T in skipjack. (Across the distance encompassing the majority of the red muscle mass, 0.35-0.65L, where L is fork length, the duration is 0.25T in both species.) When red muscle activation patterns were compared across a variety of fish species, it became apparent that the EMG patterns grade in a progression that parallels the kinematic spectrum of swimming modes from anguilliform to thunniform. The tuna EMG pattern, underlying the thunniform swimming mode, culminates this progression, exhibiting an activation pattern at the extreme opposite end of the spectrum from the anguilliform mode.

Muscle dynamics in skipjack tuna: timing of red muscle shortening in relation to activation and body curvature during steady swimming

Cyclic length changes in the internal red muscle of skipjack tuna (Katsuwonus pelamis) were measured using sonomicrometry while the fish swam in a water tunnel at steady speeds of 1.1-2.3 L s(−)(1), where L is fork length. These data were coupled with simultaneous electromyographic (EMG) recordings. The onset of EMG activity occurred at virtually the same phase of the strain cycle for muscle at axial locations between approximately 0.4L and 0.74L, where the majority of the internal red muscle is located. Furthermore, EMG activity always began during muscle lengthening, 40–50 prior to peak length, suggesting that force enhancement by stretching and net positive work probably occur in red muscle all along the body. Our results support the idea that positive contractile power is derived from all the aerobic swimming muscle in tunas, while force transmission is provided primarily by connective tissue structures, such as skin and tendons, rather than by muscles performing negative work. We also compared measured muscle length changes with midline curvature (as a potential index of muscle strain) calculated from synchronised video image analysis. Unlike contraction of the superficial red muscle in other fish, the shortening of internal red muscle in skipjack tuna substantially lags behind changes in the local midline curvature. The temporal separation of red muscle shortening and local curvature is so pronounced that, in the mid-body region, muscle shortening at each location is synchronous with midline curvature at locations that are 7–8 cm (i.e. 8–10 vertebral segments) more posterior. These results suggest that contraction of the internal red muscle causes deformation of the body at more posterior locations, rather than locally. This situation represents a unique departure from the model of a homogeneous bending beam, which describes red muscle strain in other fish during steady swimming, but is consistent with the idea that tunas produce thrust by motion of the caudal fin rather than by undulation of segments along the body.

Phytoestrogens alter adrenocortical function: genistein and daidzein suppress glucocorticoid and stimulate androgen production by cultured adrenal cortical cells

Phytoestrogens influence a variety of biological processes. As 17beta-estradiol alters adrenocortical cell function, we examined whether the dietary phytoestrogens, genistein and daidzein, have related effects. In cultured human fetal and postnatal adrenal cortical cells, genistein and daidzein (both 0.4-40 micromol/L) decreased ACTH-stimulated cortisol production to basal levels (ED50, 1-4 micromol/L). In the adult adrenocortical cell line, H295, genistein, daidzein, and 17beta-estradiol (10 micromol/L) decreased cAMP-stimulated cortisol synthesis in a similar fashion. Neither genistein nor daidzein altered basal or ACTH-stimulated dehydroepiandosterone sulfate (DHEA-S) production in fetal adrenocortical cells, whereas in postnatal adrenocortical cells, DHEA and DHEA-S were markedly increased (ED50, 1-4 micromol/L). In H295 cells, basal and cAMP-stimulated DHEA production were similarly increased by the phytoestrogens and 17beta-estradiol. Genistein and daidzein did not affect the expression of steroid-metabolizing enzymes. However, genistein and daidzein specifically inhibited the activity of 21-hydroxylase (P450c21); the activities of other steroidogenic enzymes were not affected. Thus, phytoestrogens may decrease cortisol synthesis by suppressing the activity of P450c21 and, as a consequence, increase DHEA/DHEA-S synthesis by shunting metabolites away from the glucocorticoid synthetic pathway. Therefore, consumption of foods containing phytoestrogens may alter adrenocortical function by decreasing cortisol and increasing androgen production.

Muscle strain histories in swimming milkfish in steady and sprinting gaits

Adult milkfish (Chanos chanos) swam in a water-tunnel flume over a wide range of speeds. Fish were instrumented with sonomicrometers to measure shortening of red and white myotomal muscle. Muscle strain was also calculated from simultaneous overhead views of the swimming fish. This allowed us to test the hypothesis that the muscle shortens in phase with local body bending. The fish swam at slow speeds [U&lt;2.6 fork lengths s-1 (=FL s-1)] where only peripheral red muscle was powering body movements, and also at higher speeds (2. 6&gt;U&gt;4.6 FL s-1) where they adopted a sprinting gait in which the white muscle is believed to power the body movements. For all combinations of speeds and body locations where we had simultaneous measurements of muscle strain and body bending (0.5 and 0.7FL), both techniques were equivalent predictors of muscle strain histories. Cross-correlation coefficients for comparisons between these techniques exceeded 0.95 in all cases and had temporal separations of less than 7 ms on average. Muscle strain measured using sonomicrometry within the speed range 0.9-2.6 FL s-1 showed that muscle strain did not increase substantially over that speed range, while tail-beat frequency increased by 140 %. While using a sprinting gait, muscle strains became bimodal, with strains within bursts being approximately double those between bursts. Muscle strain calculated from local body bending for a range of locations on the body indicated that muscle strain increases rostrally to caudally, but only by less than 4 %. These results suggest that swimming muscle, which forms a large fraction of the body volume in a fish, undergoes a history of strain that is similar to that expected for a homogeneous, continuous beam. This has been an implicit assumption for many studies of muscle function in many fish, but has not been tested explicitly until now. This result is achieved in spite of the presence of complex and inhomogeneous geometry in the folding of myotomes, collagenous myosepta and tendon, and the anatomical distinction between red and white muscle fibers.

Safety and immunogenicity of HIV recombinant envelope vaccines in HIV-infected infants and children. National Institutes of Health-sponsored Pediatric AIDS Clinical Trials Group (ACTG-218)

Study objectives were to evaluate the safety and immunogenicity of three HIV recombinant glycoproteins in HIV-infected infants and children between 1 month and 18 years of age with asymptomatic (P-1) infection. Using Chiron rgp 120 (SF-2) 15 or 50 microg; MicroGeneSys rgp 160 (IIIB) 40 or 320 microg; Genentech rgp120 (MN) 75 or 300 microg; or adjuvant control (Alum or MF-59), children were randomized to a double-blind, placebo-controlled, dose-escalating study of vaccine administered intramuscularly at entry and 1, 2, 3, 4, and 6 months later. No adverse events were attributed to study vaccines. Between 30% and 56% of volunteers exhibited a lymphoproliferative response as defined in terms of stimulation index (SI) to vaccine antigens; 65% of vaccinees but none of placebo recipients exhibited moderate or strong responses after enzyme immunoassay to HIV specific antigens. CD4 cell counts and quantitative HIV culture did not differ significantly among vaccine and control groups, nor were differences found among groups in HIV disease progression. The rgp160 and gp120 subunit vaccines were safe and immunogenic in this population.

Asymmetric bipedal locomotion--an adaptive response to incomplete spinal injury in the chick

The purpose of this study was to compare the asymmetric gait induced by unilateral spinal cord injury in chicks with asymmetric gaits of other bipeds and quadrupeds. After lateral hemisection of the left thoracic spinal cord, kinetic (ground reaction forces) and kinematic (distance and timing) data were recorded as chicks moved overground unrestrained. Ground reaction forces were analyzed to obtain the mechanical energy changes throughout the stride. Kinematic measurements were obtained over a range of speeds to determine the velocity-dependent characteristics of the gait. Hemisected chicks adopted an asymmetric hopping gait in which the animals hopped from the right leg (contralateral to the lesion) onto the left (ipsilateral) leg but then fell forward onto the right leg. Mechanical energy fluctuations throughout a single stride (i.e., two steps) approximated the oscillations that occur during a single walking step of control animals. When examined over a range of velocities, asymmetries in limb timing remained constant, but distance measurements such as step length became more symmetric as speed increased. The results show that, after spinal hemisection, adaptations of the remaining neural circuitry permitted the production of a locomotor pattern that, in addition to providing effective support and propulsion, incorporated some of the energy-conserving mechanisms of the normal walk. Adjustment of this novel locomotor pattern for different velocities further demonstrates the flexibility of locomotor circuitry. Comparisons with other studies shows that this gait shares some temporal and energetic features with asymmetric gaits of several bipedal species, including humans. In particular, hemisected chicks and some hemiplegic humans adopt an asymmetric gait in which maximum energy recovery occurs during the stance of the affected limb; these similarities probably relate to common mechanical constraints imposed on bipedal forms of terrestrial locomotion.

Curvature of Swimming Fish Midlines as an Index of Muscle Strain Suggests Swimming Muscle Produces Net Positive Work

The axial muscle used in steady swimming by fish is geometrically complex and this has required the study of in vivo muscle swimming mechanics to be done with largely inferential techniques. Currently there is some debate concerning the variation in muscle function in different regions of the body, and the importance of negative work production by muscles in posterior locations. We have used video taped kinematics of steady swimming in mackerel and then analysed the lateral flexion of the body that is thought to reflect the cycle of length change in the axial muscles. A comparison of several of the techniques used in the past to estimate muscle length changes are shown not to be equivalent. Specifically, we find that peak values of lateral deflection of the body are not correlated in time or axial position with peaks in curvature of the body midline. This is important because the timing of the muscle strain cycle is often inferred from such information. Having documented this observation in a swimming mackerel, we use analytical geometry to show that this result is a consequence of the curves that describe swimming fish midlines. Since this observation is shown to be the geometric consequence of an amplitude envelope that is not constant, it should therefore apply to other animals that propel themselves with axial undulations of increasing amplitude. Our minor result is that care must be taken when estimating the phase of swimming muscle strain from kinematics. Our major results is that appreciation of the geometric character of the kinematics these fish adopt may resolve much of the current debate concerning the mechanical performance of swimming muscle in fish. Specifically, using our estimate of the phase of muscle shortening and data on EMG timing in the mackerel we conclude that all axial muscles are activated before peak length and in a manner that should produce net positive work within each shortening cycle.Copyright 1998 Academic Press

Evaluation of surrogate markers and clinical outcomes in two-year follow-up of eighty-six human immunodeficiency virus-infected pediatric patients

OBJECTIVES

To evaluate the prognostic value of surrogate markers (HIV RNA copy number, CD4 counts and CDC clinical and immunologic categories) in HIV-infected children through a 2-year period.

METHODS

Eighty-six HIV-infected children followed by the Duke Pediatric HIV Clinic in the fall of 1994 were evaluated for plasma HIV RNA concentration (viral load), CD4 lymphocyte percentage, age, antiretroviral treatment status and CDC clinical and immunologic categories. Follow-up evaluations were performed for approximately 2 years, and the time to progression to a new CDC category C diagnosis or death was noted.

RESULTS

Of 86 children 22 had progression to new Category C diagnosis or death. Seven children died, 17 had a new Category C diagnosis and 2 had both. Among children who progressed, the median CD4 percentage at entry was 3% (absolute count, 75 cells/mm3), whereas children who had no disease progression entered with a median of 29% (868 cells/mm3). The overall median viral load at study entry was 4.58 log10 copies/ml (38,019 copies/ml, with a range of 1.7 to 6.78 logs). Children who had no disease progression had a median log copy number of 4.43, whereas 5.18 was the median for children whose disease progressed. Log copy number declined over time in children < 3 years of age, whereas it remained fairly consistent for children 3 years or older. Progression rates were determined by entry plasma HIV RNA concentration quartiles [quartile boundaries < 4.18, 4.58, > 5.08 log RNA copy/ml (< 15,136, 38,019 and > 120,226 copies/ml, respectively)]. Progression rates by quartile were 0 of 21, 4 of 22, 5 of 21 and 13 of 22. Kaplan-Meier survival curves defined by CD4% less than or greater than 15 and log RNA less than or greater than 5.0 (100,000) revealed that patients with CD4% less than 15 and plasma HIV RNA concentration > 5 log10 copies/ml did least well: 11 of 12 (92%) had a progression event at a median of 179 days. Patients with a high CD4 percentage and high viral load, or a low CD4 percentage and low viral load did similarly; 5 of 14 (36%) and 4 of 12 (33%) had progression events, respectively. Patients with high CD4 percentage and low viral load did best: only 2 of 48 (4%) had a progression event.

CONCLUSIONS

The two most significant prognostic indicators of disease progression were the initial CD4 percentage and the plasma HIV RNA concentration, and a combination of CD4 percentage and virus load best predicted which children had progression events. Progression was less common in children who had < 100,000 HIV RNA copies/ml initially (6 of 60 vs. 16 of 26; P < 0.001; relative risk 0.16). Therefore it seems reasonable that in a child for whom complete suppression is not possible, a threshold of 100,000 (5 log10 copies/ml) can be used to mandate a change in therapy.

Future vaccines and a global perspective

Advances in medical biotechnology mean that vaccines to prevent more than 75 infectious diseases are being or have been developed. Vaccination is unfortunately not reliant purely on biotechnology but also on politics and resources. Countries with the greatest demand for vaccines have the least ability to pay for or produce them. Health-care Infrastructure and diagnostic facilities also hamper immunisation projects in developing countries. Charitable organisations are relied on heavily to support such projects but the challenge to ensure all infants are immunised against the most common infections of childhood is still enormous. Difficulties that present themselves now should not prevent us looking into future possibilities such as immunisation during pregnancy and targeting of children for immunisation against sexually transmitted diseases. Other avenues for research are in administration of vaccines. A move to mucosal immunisation rather than use of the syringe and needle would be positive both economically and from the point of view of risk of needle contamination. Plant science may also provide a new vehicle for vaccines by engineering plants such as the banana tree to be naturally bioencapsulated vaccines. Prospects for control and eradication of infectious disease in the next century are certainly good.

Insulin-like growth factors augment steroid production and expression of steroidogenic enzymes in human fetal adrenal cortical cells: implications for adrenal androgen regulation

The fetal zone is a unique adrenal cortical compartment that exists only during fetal life in humans and higher primates and produces large amounts of the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S). Growth of the fetal zone is primarily regulated by ACTH, the actions of which are mediated in part by locally produced autocrine/paracrine growth factors. We previously demonstrated that one of these growth factors, insulin-like growth factor II (IGF-II), is mitogenic for cultured fetal zone cells and is produced in high abundance by these cells in response to ACTH. In the present study, we determined whether IGF-II also modulates the differentiated function of fetal zone cells. We examined the effects of recombinant human IGF-II and the closely related peptide, IGF-I, on 1) basal and agonist-stimulated [ACTH-(1-24), forskolin, or 8-bromo-cAMP] cortisol and DHEA-S production, 2) basal and ACTH-stimulated steady state abundance of messenger ribonucleic acids (mRNAs) encoding the steroidogenic enzymes cytochrome P450 side-chain cleavage (P450scc) and cytochrome P450 17alpha-hydroxylase/17,20-lyase (P450c17), and 3) basal and ACTH-stimulated steady state abundance of mRNA encoding the ACTH receptor. Basal cortisol (23.93 +/- 1.20 pmol/10(5) cells x 24 h) and DHEA-S (548.87 +/- 43.17 pmol/10(5) cells x 24 h) productions were significantly (P < 0.05) increased by IGF-I (2.3- and 1.8-fold, respectively) and IGF-II (2.8- and 1.8-fold, respectively). As expected, ACTH, forskolin, and cAMP markedly increased the production of cortisol by 26-, 10-, and 13-fold, respectively, and that of DHEA-S by 5.4-, 4.6-, and 5.5-fold, respectively, compared with basal levels. IGF-II (100 ng/mL) significantly (P < 0.001) increased ACTH-, forskolin-, and cAMP-stimulated production of cortisol by 2.4-, 4.3-, and 3.2-fold, respectively, and that of DHEA-S by 1.4, 1.6-, and 1.4-fold, respectively. IGF-I (100 ng/mL) had similar effects as IGF-II and significantly (P < 0.001) increased ACTH-, forskolin-, and cAMP-stimulated production of cortisol by 2.8-, 3.9-, and 3.1-fold, respectively, and that of DHEA-S by 1.3-, 1.6-, and 1.4-fold, respectively. The similar potencies of IGF-I and IGF-II suggest that the actions of these factors were mediated via a common receptor, most likely the type I IGF receptor. The effects of IGF-II on ACTH-stimulated steroid production were dose-dependent (EC50, 0.5-1.0 nmol/L), and IGF-II markedly increased the steroidogenic responsiveness of fetal zone cells to ACTH. With respect to cortisol production, IGF-II shifted the ACTH dose-response curve to the left by 1 log10 order of magnitude. IGF-II also increased ACTH-stimulated abundance of mRNA encoding P450scc (1.9-fold) and P450c17 (2.2-fold). Basal expression of P450scc was not affected by IGF-II. In contrast, basal expression of P450c17 was increased 2.2-fold by IGF-II and IGF-I in a dose-responsive fashion. Neither IGF-I nor IGF-II affected basal or ACTH-stimulated abundance of mRNA encoding the ACTH receptor, suggesting that the increase in ACTH responsiveness was not mediated by an increase in ACTH-binding capacity. Taken together, these data indicate that activation of the type I IGF receptor increases ACTH responsiveness in fetal zone cells by modulating ACTH signal transduction at some point distal to ACTH receptor activation. These data also indicate that locally produced IGF-II modulates fetal adrenal cortical cell function by increasing responsiveness to ACTH and possibly (based on its direct stimulation of P450c17 expression) augmenting the potential for adrenal androgen synthesis. Thus, activation of the type I IGF receptor on adrenal cortical cells may play a pivotal role in adrenal androgen production, both physiologically in utero and at adrenarche, and in pathophysiological conditions ofhyperandrogenemia, such as the polycystic ovary syndrome.

Protein-tyrosine phosphatases PTP1B and syp are modulators of insulin-stimulated translocation of GLUT4 in transfected rat adipose cells

The protein-tyrosine phosphatases PTP1B and Syp have both been implicated as modulators of the mitogenic actions of insulin. However, the roles of these protein-tyrosine phosphatases in the metabolic actions of insulin are not well characterized. In this study, we directly assessed the ability of PTP1B and Syp to modulate insulin-stimulated translocation of the insulin-responsive glucose transporter GLUT4 in a physiologically relevant insulin target cell. Primary cultures of rat adipose cells were transiently transfected with either wild-type PTP1B (PTP1B-WT), wild-type Syp (Syp-WT), or the catalytically inactive mutants PTP1B-C/S or Syp-C/S. The effects of overexpression of these constructs on insulin-stimulated translocation of a co-transfected epitope-tagged GLUT4 were studied. Cells overexpressing either PTP1B-C/S or Syp-WT had insulin dose-response curves similar to those obtained with control cells expressing only epitope-tagged GLUT4. In contrast, for cells overexpressing PTP1B-WT the level of GLUT4 on the cell surface at each insulin dose (ranging from 0 to 60 nM) was significantly lower than that observed in the control cells. Interestingly, cells overexpressing the dominant inhibitory mutant Syp-C/S also had a small but statistically significant impairment in insulin responsiveness. At a maximally stimulating concentration of insulin (60 nM), cell surface epitope-tagged GLUT4 was approximately 20% less than that of the control cells. It is possible that effects from high level overexpression of Syp and PTP1B constructs may not reflect what occurs under physiological conditions. Nevertheless, our data raise the possibility that PTP1B may be a negative regulator of insulin-stimulated glucose transport, while Syp may have a small role as a positive mediator of the metabolic actions of insulin.

Effect of influenza immunization on immunologic and virologic characteristics of pediatric patients infected with human immunodeficiency virus

OBJECTIVES

We evaluated the responses of HIV-infected children to a single dose of split-virus influenza vaccine and the relationship to viral load and other characteristics.

METHODS

Fifty-three HIV-infected children ages 1.8 to 13.2 years were given influenza vaccine for the 1994 to 1995 influenza season (Wyeth-Ayerst: A/Texas H1N1, A/Shangdong H3N2 and B/Panama). Immunologic and virologic factors were assessed at the time of and 2 to 10 weeks after immunization.

RESULTS

The differences between pre- and postimmunization CD4+ counts, CD4+:CD8+ ratios and viral load were not significant. Thirty-one of 53 children (58.4%) had a > 2-fold increase and 16 of 53 (30%) had a 4-fold rise in their postimmunization antibody titers for at least one component of the vaccine. Influenza immunization in the 1993 to 1994 flu season and administration of intravenous immunoglobulin around the time of immunization was not associated with immune response to the vaccine. Factors that were negatively associated with antibody response included increased time between samples (P = 0.004) and decreased preimmunization CD4+:CD8+ ratio (P = 0.02).

CONCLUSIONS

Influenza immunization in this population is safe, and a positive antibody response to influenza immunization is not associated with significant clinical events or change in HIV-1 plasma viral burden.

Ventilatory control in a primitive fish: signal conditioning via non-linear O2 affinity

Gas exchange in the gills of the air-breathing fish Amia calva was modelled to determine how the gills modify fluctuations in venous P O2. These fluctuations form the physiological signal for aerial ventilation in these fish. This study was performed to examine the signal conditioning role that the gills may play in the control system that regulates P O2. The model incorporated a non-linear Hb-O2 affinity relationship. Fluctuations in venous P O2 were modelled as sinusoids, covering a range of frequencies and amplitudes. Mean venous P O2 ranged from normoxic to hypoxic values. Over a broad range of parameters the gills amplify fluctuations in venous P O2 during transit to the arterial side. It was also observed that aquatic hypoxia reduces the effectiveness of the gills in maximizing arterial P O2, while increases in venous P O2 increase the effectiveness of the gills in the face of similar blood-water P O2 gradients. Each of these performance features is a consequence of the sigmoid Hb-O2 affinity relationship.

Measles immunity in HIV-infected children

In a retrospective study, sera from 84 children of human immunodeficiency virus (HIV)-seropositive mothers (35 HIV-infected and 49 uninfected children) with a known date of receipt of measles, mumps, and rubella vaccine were tested for antibody to measles vaccine by an indirect enzyme immunoassay (EIA) method and/or microneutralization (NEUT). At the time of last measurement, 21/35 (60.0%) HIV-infected children remained seropositive by either EIA or NEUT. Forty seven of forty-nine (95.9%) uninfected children had evidence of measles antibody. Six HIV-infected children had a documented loss of antibody over time. The majority of HIV-infected children had antibody to measles vaccine virus, which in some cases decreased over time.

De novo methylation of an MHC class I transgene following transformation with human adenoviruses is not correlated with its altered expression

The biological importance of class I histocompatibility antigens in a large variety of immune mechanisms is widely recognized, and their role in tumor rejection has been proven in several experimental tumor systems. Reduced expression of class I antigens, which is correlated with enhanced tumorigenicity, was shown in these systems to be mainly the result of transcriptional down-regulation. Mouse embryonal fibroblasts expressing H-2 antigens and the product of a miniature swine class I transgene, transformed by adenovirus 12, exhibit low levels of all class I antigens on the cell surface. Half of the cell lines demonstrate a suppressed level of class I mRNAs. Cell lines derived from transformation with the early region of adenovirus 5 express a high level of class I antigens. DNAs from adenovirus-transformed cells are extensively hypermethylated both in the 5' and the coding regions of the transgene compared to DNAs from immortalized cell lines and primary embryonal fibroblasts. Nevertheless, hypermethylation of these sequences is not correlated with mRNA level or cell-surface expression of the transgene product. Treatment of the transformed cells with high concentration of 5-azacytidine (5 Aza-C) induced merely a minor enhancement in the expression of class I mRNAs and class I antigens. Thus, this system is a perfect example of where viral transformation is associated with induced methylation of a class I gene, but hypermethylation does not affect its expression. The role of de novo methylation of genes in this system might be associated with transformation, or generation of mutations in CpG-rich sequences.

Prospects for childhood immunization in the next decade

Prospects for vaccine research, development, and use over the next decade are extraordinarily optimistic. Innovative investigative programs promise new vaccines with reduced numbers of injections, combinations of multiple antigens, and confinement of administration to the early weeks or months of life. Enhanced attention to the infrastructure and support of immunization programs should rapidly augment coverage to more than 90% of the US infant population in the first 2 years of life with all the recommended vaccines. Programs of the WHO and CVI should extend protection from morbidity and mortality of diseases preventable with vaccine to children of all nations. Adjustments and realignments of the Vaccine Injury Compensation Program should reduce to realistic dimensions the finances of benefits for children who suffer the rare, true adverse responses to required immunizations. In order to maintain familiarity and leadership in childhood immunization, pediatricians will need to maintain careful attention to and familiarity with all these emerging developments.