Effect of alcohol intake on muscle glycogen storage after prolonged exercise

We studied the effects of alcohol intake on postexercise muscle glycogen restoration with samples from vastus lateralis being collected immediately after glycogen-depleting cycling and after a set recovery period. Six well-trained cyclists undertook a study of 8-h recovery (2 meals), and another nine cyclists undertook a separate 24-h protocol (4 meals). In each study, subjects completed three trials in crossover order: control (C) diet [meals providing carbohydrate (CHO) of 1.75 g/kg]; alcohol-displacement (A) diet (1.5 g/kg alcohol displacing CHO energy from C) and alcohol + CHO (AC) diet (C + 1.5 g/kg alcohol). Alcohol intake reduced postmeal glycemia especially in A trial and 24-h study, although insulin responses were maintained. Alcohol intake increased serum triglycerides, particularly in the 24-h study and AC trial. Glycogen storage was decreased in A diets compared with C at 8 h (24.4 +/- 7 vs. 44.6 +/- 6 mmol/kg wet wt, means +/- SE, P < 0.05) and 24 h (68 +/- 5 vs. 82 +/- 5 mmol/kg wet wt, P < 0.05). There was a trend to reduced glycogen storage with AC in 8 h (36.2 +/- 8 mmol/kg wet wt, P = 0.1) but no difference in 24 h (85 +/- 9 mmol/kg wet wt). We conclude that 1). the direct effect of alcohol on postexercise glycogen synthesis is unclear, and 2). the main effect of alcohol intake is indirect, by displacing CHO intake from optimal recovery nutrition practices.

Nasal continuous positive airway pressure versus nasal intermittent positive pressure ventilation for preterm neonates: a systematic review and meta-analysis

AIM

To determine whether nasal intermittent positive pressure ventilation (NIPPV) is more effective in preterm infants than nasal continuous positive airway pressure (NCPAP) in reducing the rate of extubation failure following mechanical ventilation, and reducing the frequency of apnoea of prematurity and subsequent need for endotracheal intubation.

METHODS

Randomized trials of NIPPV versus NCPAP were sought and their data extracted and analysed independently by the authors using the methodology of the Cochrane Collaboration. The analysis used relative risk (RR), risk difference (RD) and number needed to treat (NNT) with 95% confidence intervals.

RESULTS

The three studies identified, comparing NIPPV with NCPAP in the postextubation period, all used synchronized NIPPV (SNIPPV), which was more effective than NCPAP in preventing failure of extubation [RR 0.21 (0.10, 0.45), RD -0.32 (-0.45, -0.20), NNT 3 (2, 5)]. Two studies compared NIPPV versus NCPAP for the treatment of apnoea of prematurity. Although meta-analysis was not possible one trial showed a reduction in apnoea frequency with NIPPV and the other a trend favouring NIPPV.

CONCLUSION

SNIPPV is an effective method of augmenting the beneficial effects of NCPAP in preterm infants in the postextubation period. Further research is required to delineate the role of NIPPV in the management of apnoea of prematurity.

Nasal CPAP for neonates: what do we know in 2003?

Despite the acknowledged clinical usefulness of nasal CPAP, uncertainties regarding aspects of its application remain. Clinical indications for the application of nasal CPAP vary greatly between institutions. Furthermore, defining the optimal nasal CPAP system is complicated by the multiplicity of nasal CPAP devices and techniques available to the clinician. This review aims to identify what we know about nasal CPAP and what important questions remain.

Epinephrine for the resuscitation of apparently stillborn or extremely bradycardic newborn infants

BACKGROUND

Epinephrine is a cardiac stimulant with complex effects on the heart and blood vessels. It has been used for decades in all age groups to treat cardiac arrest and bradycardia. Despite formal guidelines for the use of epinephrine in neonatal resuscitation, the evidence for these recommendations has not yet been rigorously scrutinised. While it is understood that this evidence is in large part derived from animal models and the adult human population, the contribution from work in the neonatal population remains unclear. In particular, it remains to be determined if any randomised studies in neonates have helped to establish if the administration of epinephrine in the context of apparent stillbirth or extreme bradycardia might influence mortality and morbidity.

PRIMARY OBJECTIVE

~bullet~To determine if the administration of epinephrine to apparently stillborn and extremely bradycardic newborns reduces mortality and morbidity Secondary objectives: ~bullet~To determine the effect of intravenous versus endotracheal administration on mortality and morbidity ~bullet~To determine the effect of high dose versus standard dose epinephrine on mortality and morbidity, where high dose is defined as any dose greater than the current recommended standard dose of 0.1 to 0.3ml/kg of a 1:10,000 solution of epinephrine ~bullet~To determine whether the effect of epinephrine on mortality and morbidity varies with gestational age, i.e. term (greater than or equal to 37 weeks) versus pre-term (less than 37 weeks)

SEARCH STRATEGY

Searches were made of Medline from 1966 to December 2002, CINAHL (from 1982), Current Contents (from 1988), EMBASE, and the Cochrane Controlled Trials Register (2002, issue 4). Bibliographies of conference proceedings were reviewed and unpublished studies were sought by hand searching the conference proceedings of the Society for Pediatric Research and the European Society for Pediatric Research from 1993 to 2002.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of newborns, both pre-term and term, receiving epinephrine for unexpected apparent stillbirth or extreme bradycardia.

DATA COLLECTION AND ANALYSIS

No studies were found meeting the criteria for inclusion in this review

MAIN RESULTS

No studies were found meeting the criteria for inclusion in this review.

REVIEWER'S CONCLUSIONS

We found no randomised, controlled trials evaluating the administration of epinephrine to the apparently stillborn or extremely bradycardic newborn infant. Similarly, we found no randomised, controlled trials which addressed the issues of optimum dosage and route of administration of epinephrine. Current recommendations for the use of epinephrine in newborn infants are based only on evidence derived from animal models and the human adult literature. Randomised trials in neonates are urgently required to determine the role of epinephrine in this population.

Prophylactic methylxanthines for extubation in preterm infants

BACKGROUND

When preterm infants have been given intermittent positive pressure ventilation (IPPV) for respiratory failure, weaning from support and tracheal extubation may be difficult. A significant contributing factor is thought to be the relatively poor respiratory drive and tendency to develop hypercarbia and apnea, particularly in very preterm infants. Methylxanthine treatment started before extubation might stimulate breathing and increase the chances of successful weaning from IPPV.

OBJECTIVES

In preterm infants being weaned from IPPV and in whom endotracheal extubation is planned, does treatment with methylxanthine reduce the use of intubation and IPPV, without clinically important side effects?

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal Trials, The Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3 2002), MEDLINE (1966 to October 2002).

SELECTION CRITERIA

All published trials utilising random or quasi-random patient allocation, in which treatment with methylxanthines (theophylline or caffeine) was compared with placebo or no treatment to improve the chances of successful extubation of preterm or low birth weight infants, were included.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Collaboration and its Neonatal Review Group were used. The second author assessed the quality of trials and extracted data independently. Results are expressed as relative risk (RR) and risk difference (RD) with 95% confidence intervals.

MAIN RESULTS

Overall analysis of the six published trials shows that methylxanthine treatment results in a reduction in failure of extubation within one week [summary RR 0.47 (0.32, 0.70)]. Overall there is an absolute reduction of 27 % in the incidence of failed extubation [summary RD -.27 (-.39, -.15)]. Thus, overall in these six trials the number needed to treat (NNT) with methylxanthine to prevent one case of failed extubation is 3.7 (2.7, 6.7). There is significant heterogeneity in the RD meta-analysis (p=0.007) related to the large variation in baseline rate in the control groups (range 20 - 100%). One study (Durand 1987) found that treatment was effective in reducing failed extubation in those born at less than 1000 grams and who were less than one week old. In the small prespecified subgroups in this trial, infants of less than 1 kg birth weight and older than one week and those of birth weight 1000-1250 grams who had failed extubation once, no significant benefit was found.

REVIEWER'S CONCLUSIONS

Implications for practice. Methylxanthines increase the chances of successful extubation of preterm infants within one week. One trial suggests that this benefit is principally in infants of extremely low birth weight extubated in the first week. There is insufficient information to assess side effects or longer term effects on child development. Implications for research. Further trials are required comparing methylxanthines with placebo for extubation of very preterm infants. There is a need to stratify infants by gestational age (a better indicator of immaturity) rather than birth weight in future studies. Caffeine, with its wider therapeutic margin (Blanchard 1992, Steer 2002) would be the better treatment to evaluate against placebo. Side effects and neuro-developmental status at follow up should be included as outcomes.

Nasal continuous positive airways pressure immediately after extubation for preventing morbidity in preterm infants

BACKGROUND

Preterm infants being extubated following a period of intermittent positive pressure ventilation via an endotracheal tube are at risk of developing respiratory failure as a result of apnea, respiratory acidosis and hypoxia. Nasal continuous positive airway pressure appears to stabilise the upper airway, improve lung function and reduce apnea and may therefore have a role in facilitating extubation in this population.

OBJECTIVES

In preterm infants having their endotracheal tube removed following a period of intermittent positive pressure ventilation (IPPV), does management with nasal continuous positive airways pressure (NCPAP) lead to an increased proportion remaining free of additional ventilatory support, compared to extubation directly to headbox oxygen?

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE up to November 2002, Cochrane Controlled Trials Register (The Cochrane Library, Issue 4, 2002), previous reviews including cross references, abstracts of conferences and symposia proceedings, expert informants and journal handsearching mainly in the English language.

SELECTION CRITERIA

All trials utilising random or quasi-random patient allocation, in which NCPAP (delivered by any method) was compared with headbox oxygen for post-extubation care were included. Methodological quality was assessed independently by the two authors.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by the two authors. Prespecified subgroup analysis to determine the impact of different levels of NCPAP, differences in duration of IPPV and use of aminophylline were also performed using the same package. Data were analysed using relative risk (RR), risk difference (RD) and number needed to treat (NNT).

MAIN RESULTS

Nasal CPAP, when applied to preterm infants being extubated following IPPV, reduces the incidence of adverse clinical events (apnea, respiratory acidosis and increased oxygen requirements) indicating the need for additional ventilatory support [RR 0.62 (0.49, 0.77), RD -0.17 (-0.24,-0.10), NNT 6 (4,10)].

IMPLICATIONS FOR PRACTICE

nasal CPAP is effective in preventing failure of extubation in preterm infants following a period of endotracheal intubation and IPPV. Implication for research: further definition of the gestational age and weight groups in whom these results apply is required. Optimal levels of NCPAP as well as methods of administration remain to be determined.

In vitro comparison of nasal continuous positive airway pressure devices for neonates

OBJECTIVE

To compare the resistance in vitro of different devices used for the delivery of nasal continuous positive airway pressure (NCPAP) in neonates.

DESIGN

Flows of 4-8 litres/min were passed through a selection of neonatal NCPAP devices (single prong, Duotube, Argyle prong, Hudson prong, Infant Flow Driver), and the resultant fall in pressure measured using a calibrated pressure transducer.

RESULTS

The decrease in pressure (cm H(2)O) for each device (size in parentheses) at a constant flow of 6 litres/min was: Duotube: (2.5), 21; (3.0), 6.2; (3.5), 2.3; single prong: (2.5), 4.4; (3.0), 2.1; (3.5), 1.2; Argyle prong: (XS), 3.6; (S), 1.9; (L), 1.5; Hudson prong: (0), 3.1; (1), 1.8; (2), 0.6; (3), 0.4; (4), 0.3; Infant Flow Driver: (small), 0.3; (medium), -0.3; (large), -0.5.

CONCLUSIONS

A large variation in the potential fall in pressure may occur in the clinical setting. Devices with short double prongs had the lowest resistance to flow. These results have implications in the selection of the optimal device/s for clinical application and for future comparisons in randomised trials of NCPAP in neonates.

Evaluating "old" definitions for the "new" bronchopulmonary dysplasia

OBJECTIVES

To examine the accuracy of different criteria for the diagnosis of bronchopulmonary dysplasia (BPD), based on the final age at which oxygen therapy was stopped, in predicting pulmonary and neurologic outcomes at 18-month corrected age.

STUDY DESIGN

Data were collected prospectively on infants with birth weights between 500 and 999 g enrolled in the Trial of Indomethacin Prophylaxis in Preterms (TIPP) who survived to discharge home. Differing postnatal ages and postmenstrual ages at which supplemental oxygen therapy was no longer required formed the criteria for defining BPD. Diagnostic accuracy of each criterion for defining BPD was calculated for both poor pulmonary and poor neurosensory outcomes.

RESULTS

The prevalence of poor pulmonary outcome was 54% and of poor neurosensory outcome was 34% in the 956 infants who were eligible for this analysis. Accuracy of different definitions of BPD was limited but greatest when using supplemental oxygen requirement at 36 weeks' postmenstrual age to predict long-term pulmonary outcome (63%) and 40 weeks to predict long-term neurosensory outcome (68%).

CONCLUSIONS

Poor pulmonary outcome and poor neurosensory outcome are common late adverse outcomes in this population. BPD as defined by duration of oxygen therapy is a less accurate surrogate currently than in previous eras.

Blood lipid and lipoprotein adaptations to exercise: a quantitative analysis

Dose-response relationships between exercise training volume and blood lipid changes suggest that exercise can favourably alter blood lipids at low training volumes, although the effects may not be observable until certain exercise thresholds are met. The thresholds established from cross-sectional literature occur at training volumes of 24 to 32 km (15 to 20 miles) per week of brisk walking or jogging and elicit between 1200 to 2200 kcal/wk. This range of weekly energy expenditure is associated with 2 to 3 mg/dl increases in high-density lipoprotein-cholesterol (HDL-C) and triglyceride (TG) reductions of 8 to 20 mg/dl. Evidence from cross-sectional studies indicates that greater changes in HDL-C levels can be expected with additional increases in exercise training volume. HDL-C and TG changes are often observed after training regimens requiring energy expenditures similar to those characterised from cross-sectional data. Training programmes that elicit 1200 to 2200 kcal/wk in exercise are often effective at elevating HDL-C levels from 2 to 8 mg/dl, and lowering TG levels by 5 to 38 mg/dl. Exercise training seldom alters total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C). However, this range of weekly exercise energy expenditure is also associated with TC and LDL-C reductions when they are reported. The frequency and extent to which most of these lipid changes are reported are similar in both genders, with the exception of TG. Thus, for most individuals, the positive effects of regular exercise are exerted on blood lipids at low training volumes and accrue so that noticeable differences frequently occur with weekly energy expenditures of 1200 to 2200 kcal/wk. It appears that weekly exercise caloric expenditures that meet or exceed the higher end of this range are more likely to produce the desired lipid changes. This amount of physical activity, performed at moderate intensities, is reasonable and attainable for most individuals and is within the American College of Sports Medicine's currently recommended range for healthy adults.

Devices and pressure sources for administration of nasal continuous positive airway pressure (NCPAP) in preterm neonates

BACKGROUND

Nasal continuous positive airway pressure (NCPAP) is used to support preterm infants recently extubated, those experiencing significant apnoea of prematurity and those with respiratory distress soon after birth as an alternative to intubation and ventilation. This review will focus exclusively on identifying the most effective pressure source and interface for NCPAP delivery in preterm infants.

OBJECTIVES

In preterm infants extubated to NCPAP following intermittent positive pressure ventilation (IPPV) for respiratory distress syndrome (RDS) or in those treated with NCPAP soon after birth, which technique of pressure generation and which type of nasal interface for NCPAP delivery most effectively reduces the need for additional respiratory support?

SEARCH STRATEGY

The strategy included searches of MEDLINE (1966-2002), the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002), CINAHL, abstracts from conference proceedings, cross-referencing of previous reviews and the use of expert informants.

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing different techniques of NCPAP pressure generation and/or nasal interfaces in preterm infants extubated to NCPAP following IPPV for RDS or treated with NCPAP soon after birth.

DATA COLLECTION AND ANALYSIS

Data was extracted and analysed by the first three authors. Dichotomous results were analysed using the relative risk (RR), risk difference (RD) and number needed to treat (NNT).

MAIN RESULTS

1. Preterm infants being extubated to NCPAP following a period of IPPV for RDS: Meta-analysis of the results from Davis 2001 and Roukema 1999a demonstrated that short binasal prongs are more effective at preventing re-intubation than single nasal or nasopharyngeal prongs [typical RR 0.59 (CI: 0.41, 0.85), typical RD -0.21 (CI: -0.35, -0.07), NNT 5 (CI: 3, 14)]. In the single study comparing short binasal prong devices (Sun 1999) the re-intubation rate was significantly lower with the Infant Flow Driver than with the Medicorp prong [RR 0.33 (CI: 0.17, 0.67), RD -0.32 (CI: -0.49, -0.15), NNT 3 (CI: 2, 7)]. 2. Preterm infants primarily treated with NCPAP soon after birth: The one trial identified, Mazzella 2001, found a significantly lower oxygen requirement and respiratory rate in those randomised to short binasal prongs when compared with CPAP delivered via nasopharyngeal prong. The requirement for intubation beyond 48 hours from randomisation was not assessed. No studies comparing different techniques of pressure generation were identified.

REVIEWER'S CONCLUSIONS

Short binasal prong devices are more effective than single prongs in reducing the rate of re-intubation. Although the Infant Flow Driver appears more effective than Medicorp prongs the most effective short binasal prong device remains to be determined. The improvement in respiratory parameters with short binasal prongs suggests they are more effective than nasopharyngeal CPAP in the treatment of early RDS. Further studies incorporating longer-term outcomes are required. Studies are also needed to determine the optimal pressure source for the delivery of NCPAP.

Continuous distending pressure for respiratory distress syndrome in preterm infants

BACKGROUND

Respiratory distress syndrome (RDS) is the single most important cause of morbidity and mortality in preterm infants (Greenough 1998, Bancalari 1992). Intermittent positive pressure ventilation (IPPV) with surfactant is the standard treatment for the condition. The major difficulty with IPPV is that it is invasive, resulting in airway and lung injury and contributing to the development of chronic lung disease.

OBJECTIVES

In spontaneously breathing preterm infants with RDS, to determine if continuous distending pressure (CDP) reduces the need for IPPV and associated morbidity without adverse effects.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002), MEDLINE (1966-January 2002), and EMBASE (1980-January 2002), previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal hand searching mainly in the English language.

SELECTION CRITERIA

All trials using random or quasi-random allocation of preterm infants with RDS were eligible. Interventions were continuous distending pressure including continuous positive airway pressure (CPAP) by mask, nasal prong, nasopharyngeal tube, or endotracheal tube, or continuous negative pressure (CNP) via a chamber enclosing the thorax and lower body, compared with standard care.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and its Neonatal Review Group were used, including independent assessment of trial quality and extraction of data by each author.

MAIN RESULTS

CDP is associated with a lower rate of failed treatment (death or use of assisted ventilation) [summary RR 0.70 (0.55, 0.88), RD -0.22 (-0.35, -0.09), NNT 5 (3, 11)], overall mortality [summary RR 0.52 (0.32, 0.87), RD -0.15 (-0.26, -0.04), NNT 7 (4, 25)], and mortality in infants with birthweights above 1500 g [summary RR 0.24 (0.07, 0.84), RD -0.281 (-0.483, -0.078), NNT 4 (2, 13)]. The use of CDP is associated with an increased rate of pneumothorax [summary RR 2.36 (1.25, 5.54), RD 0.14 (0.04, 0.23), NNH 7 (4, 24)].

REVIEWER'S CONCLUSIONS

In preterm infants with RDS the application of CDP either as CPAP or CNP is associated with benefits in terms of reduced respiratory failure and reduced mortality. CDP is associated with an increased rate of pneumothorax. The applicability of these results to current practice is difficult to assess, given the intensive care setting of the 1970s when four out of five of these trials were done. Where resources are limited, such as in developing countries, CPAP for RDS may have a clinical role. Further research is required to determine the best mode of administration and its role in modern intensive care settings

Early versus delayed initiation of continuous distending pressure for respiratory distress syndrome in preterm infants

BACKGROUND

The application of a continuous distending pressure (CDP) has been shown to have some benefits in the treatment of pre-term infants with respiratory distress syndrome (RDS). CDP has the potential to reduce lung damage, particularly if applied early before atelectasis has occurred. Early application of CDP may better conserve an infant's own surfactant stores and consequently be more effective than CDP applied later in the course of RDS.

OBJECTIVES

In pre-term infants with RDS to determine if early compared with delayed initiation of CDP results in lower mortality and reduced need for intermittent positive pressure ventilation.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register (Issue 1, 2002), MEDLINE (1966-2001), previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal hand searching mainly in the English language.

SELECTION CRITERIA

Trials among pre-term infants with respiratory distress syndrome spontaneously breathing at trial entry, which used random or quasi-random allocation to either early or delayed CDP.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and its Neonatal Review Group were used, including independent assessment of trial quality and extraction of data by two authors.

MAIN RESULTS

In six studies on a total of 165 infants, early CDP was associated with a significant reduction in subsequent use of intermittent positive pressure ventilation, typical RR 0.55, RD -0.16, NNT 6, but there was no evidence of effect on overall mortality. There was no evidence of effect on the rates of pneumothorax (five studies) or bronchopulmonary dysplasia (one study). Early CDP resulted in a reduction in duration of oxygen therapy in the single study reporting this outcome.

REVIEWER'S CONCLUSIONS

Early application of CDP has a clinical benefit in the treatment of RDS in that it reduces subsequent use of IPPV and thus may be useful in preventing the adverse effects of this treatment. However, many of the trials were done in the 1970s and 1980s and re-evaluation of the strategy of early CDP in the era of antenatal steroid use and early surfactant administration is indicated.

Nasal intermittent positive pressure ventilation (NIPPV) versus nasal continuous positive airway pressure (NCPAP) for apnea of prematurity

BACKGROUND

Apnea of prematurity is almost universal in infants who are born before 34 weeks gestation. Previous randomised trials and systematic reviews have found methylxanthines to be effective in preventing apnea of prematurity. However, recent concerns about potential long term side effects of methylxanthines on the neurodevelopment of low birth weight infants have led to an increased interest in alternate methods of treating apnea of prematurity. Nasal continuous positive airway pressure (NCPAP) is a useful method of respiratory support which reduces the incidence of obstructive or mixed apnea. However, apneic infants managed with NCPAP, with or without methylxanthines, sometimes require endotracheal intubation with its attendant morbidity and cost. Nasal intermittent positive pressure ventilation (NIPPV) is a simple, effective mode of respiratory support for older children and adults. It has been used to treat apnea in preterm infants but case reports of gastrointestinal perforations have limited its widespread use.

OBJECTIVES

In preterm infants with recurrent apnea, does treatment with NIPPV lead to a greater reduction in apnea and need for intubation and mechanical ventilation, as compared with treatment with NCPAP? Does NIPPV increase the incidence of gastrointestinal complications, i.e. gastric distension leading to cessation of feeds, or perforation?

SEARCH STRATEGY

MEDLINE was searched (1966-Oct week 2, 2001). Other sources included the Cochrane Controlled Trials Register (Cochrane Library, Disk Issue 3, 2001) and CINAHL (1982-Sept week 4, 2001). Also used were expert informants, previous reviews including cross-references, and conference and symposia proceedings.

SELECTION CRITERIA

All randomised and quasi-randomised trials were included. Participants included unventilated preterm infants experiencing apnea of prematurity. Interventions compared were intermittent positive pressure ventilation administered via the nasal route, either by short nasal prongs or nasopharyngeal tube, and nasal CPAP delivered by the same methods. Types of outcome measures: - failure of therapy as defined by apnea that is frequent or severe requiring additional ventilatory support - rates of endotracheal intubation - rates of apnea and bradycardia expressed as events per hour - gastrointestinal complications i.e. abdominal distension requiring cessation of feeds, or GI perforation

DATA COLLECTION AND ANALYSIS

Data were extracted independently by the three reviewers. The trials were analysed using relative risk (RR), risk difference (RD) and number needed to treat (NNT) for dichotomous data; means and weighted mean difference (WMD) were used for continuous data.

MAIN RESULTS

Two trials, enrolling 54 infants in total, fulfilled the inclusion criteria. Both reported only the short term results (4 to 6 hours) of the interventions. Only one infant (randomised to NCPAP) required intubation during this period. Ryan (1989), in a cross over study of 20 infants, showed no significant difference in rates of apnea (events/hr) between the 2 interventions [WMD -0.10 (-0.53,0.33)]. Lin (1998) randomised 34 infants and demonstrated a greater reduction in frequency of apneas (events/hr) with NIPPV compared to NCPAP [WMD -1.19 (-2.31,-0.07)]. Meta-analysis of both trials showed no difference in pCO2 (mmHg) at the end of the 4-6 hour study period [WMD 0.95 (-3.05,4.94)]. No data were reported on gastrointestinal complications.

IMPLICATIONS FOR PRACTICE

NIPPV may be a useful method of augmenting the beneficial effects of NCPAP in preterm infants with apnea that is frequent or severe. Its use appears to reduce the frequency of apneas more effectively than NCPAP. Additional safety and efficacy data are required before recommending NIPPV as standard therapy for apnea.

IMPLICATIONS FOR RESEARCH

Future trials with sufficient power should assess the efficacy (reduction in failure of therapy) and safety (GI complications) of NIPPV. Outcomes should be assessed throughout the entire period during which the infant requires assisted ventilation. The recent ability to synchronise NIPPV with an infant's spontaneous respirations is a promising development requiring further assessment.

Effects of short-duration and long-duration exercise on lipoprotein(a)

PURPOSE

Most studies that use either a single exercise session, exercise training, or a cross-sectional design have failed to find a relationship between exercise and plasma lipoprotein(a) [Lp(a)] concentrations. However, a few studies investigating the effects of longer and/or more strenuous exercise have shown elevated Lp(a) concentrations, possibly as an acute-phase reactant to muscle damage. Based on the assumption that greater muscle damage would occur with exercise of longer duration, the purpose of the present study was to determine whether exercise of longer duration would increase Lp(a) concentration and creatine kinase (CK) activity more than exercise of shorter duration.

METHODS

Ten endurance-trained men (mean +/- SD: age, 27 +/- 6 yr; maximal oxygen consumption [VO(2max)], 57 +/- 7 mL x kg(-1) x min(-1)) completed two separate exercise sessions at 70% VO(2max). One session required 800 kcal of energy expenditure (60 +/- 6 min), and the other required 1500 kcal (112 +/- 12 min). Fasted blood samples were taken immediately before (0-pre), immediately after (0-post), 1 d after (1-post), and 2 d after (2-post) each exercise session.

RESULTS

CK activity increased after both exercise sessions (mean +/- SE; 800 kcal: 0-pre 55 +/- 11, 1-post 168 +/- 64 U x L(-1) x min(-1); 1500 kcal: 0-pre 51 +/- 5, 1-post 187 +/- 30, 2-post 123 +/- 19 U x L(-1) x min(-1); P < 0.05). However, median Lp(a) concentrations were not altered by either exercise session (800 kcal: 0-pre 5.0 mg x dL(-1), 0-post 3.2 mg x dL(-1), 1-post 4.0 mg x dL(-1), 2-post 3.4 mg x dL(-1); 1500 kcal: 0-pre 5.8 mg x dL(-1), 0-post 4.3 mg x dL(-1), 1-post 3.2 mg x dL(-1), 2-post 5.3 mg x dL(-1)). In addition, no relationship existed between exercise-induced changes in CK activity and Lp(a) concentration (800 kcal: r = -0.26; 1500 kcal: r = -0.02).

CONCLUSION

These results suggest that plasma Lp(a) concentration will not increase in response to minor exercise-induced muscle damage in endurance-trained runners.

The association between physical activity, cardiorespiratory fitness, and lipoprotein(a) concentrations in a tri-ethnic sample of women: The Cross-Cultural Activity Participation Study

The purpose of this cross-sectional study was threefold: (1) to examine ethnic differences in plasma lipoprotein(a) [Lp(a)] concentrations; (2) to examine the relationship between physical activity levels (moderate, moderate-vigorous, and total MET-min/day) and Lp(a) concentrations; and (3) to determine the relationship between maximal treadmill time and Lp(a) concentrations among African-American, Native American, and Caucasian women (n=140, ages 40-70 years: 54.5+/-10.7). Physical activity records were kept for two 4-day periods, scheduled 1 month apart, a total of 8 days, and each activity was assigned a code from the 'Compendium of physical activity'. Subjects completed a graded exercise test to determine maximal treadmill time, and a fasted blood sample was collected to quantify Lp(a) concentration. Lp(a) concentrations were negatively skewed with a geometric mean of 28.3 mg/dl (25-75%: 10.4-43.1 mg/dl) in African-Americans (n=47), 2.9 mg/dl (25-75%: 1.2-7.4 mg/dl) in Native Americans (n=45), and 9.4 mg/dl (25-75%: 2.6-22.4 mg/dl) in Caucasians (n=48). African-American women had significantly higher (p<0.05) Lp(a) concentrations than either Native Americans or Caucasians. No relationships were observed among moderate, moderate-vigorous, and total MET-min/day of physical activity, maximal treadmill time, and Lp(a) concentrations. Significant ethnic differences in Lp(a) concentrations were found, with African-American women having higher Lp(a) concentrations than Native American and Caucasian women. Lp(a) concentrations were not associated with any physical activity variables. Therefore, physical activity and maximal treadmill time did not influence Lp(a) concentrations in this tri-ethnic population of women.

Nasal intermittent positive pressure ventilation (NIPPV) versus nasal continuous positive airway pressure (NCPAP) for preterm neonates after extubation

BACKGROUND

Previous randomised trials and meta-analyses have shown nasal continuous positive airway pressure (NCPAP) to be a useful method of respiratory support after extubation. However, infants managed in this way sometimes "fail" and require endotracheal reintubation with its attendant risks and expense. Nasal intermittent positive pressure ventilation (NIPPV) is a method of augmenting NCPAP by delivering ventilator breaths via the nasal prongs. Older children and adults with chronic respiratory failure have been shown to benefit from NIPPV and the technique has been applied to neonates. However severe side effects including gastric perforation have been reported and clinicians remain uncertain about the role of NIPPV in neonatology. It has recently become possible to synchronise delivery of NIPPV with the infant's own breathing efforts which may make the modality more useful in this patient group.

OBJECTIVES

To determine whether the use of NIPPV as compared to NCPAP, in the preterm infant extubated following a period of intermittent positive pressure ventilation, decreases the rate of extubation failure without adverse effects.

SEARCH STRATEGY

Medline was searched using the MeSH terms: Infant, Newborn (exp) and Positive-pressure respiration (exp). Other sources included the Cochrane Controlled Trials Register, CINAHL using search terms: Infant, newborn and intermittent positive pressure ventilation, expert informants, previous reviews including cross-references and conference and symposia proceedings were used.

SELECTION CRITERIA

Randomised trials comparing the use of NIPPV with NCPAP in preterm infants being extubated were selected for this review.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including extubation failure, endotracheal reintubation, rates of apnea, gastrointestinal perforation, feeding intolerance, chronic lung disease and duration of hospital stay were extracted independently by the three reviewers. The trials were analysed using relative risk (RR), risk difference (RD) and number needed to treat (NNT) for dichotomous outcomes and weighted mean difference (WMD) for continuous outcomes.

MAIN RESULTS

Three trials comparing extubation of infants to NIPPV or to NCPAP were identified. All trials used the synchronised form of NIPPV. Each showed a statistically significant benefit for infants extubated to NIPPV in terms of prevention of extubation failure criteria. The meta-analysis shows the effect is also clinically important [RR 0.21 (0.10, 0.45), RD -0.32 (-0.45, -0.20), NNT 3 (2, 5)]. There were no reports of gastrointestinal perforation in any of the trials. Differences in rates of chronic lung disease approached but did not achieve statistical significance favouring NIPPV [RR 0.73 (0.49, 1.07), RD -0.15 (-0.33, 0.03)].

IMPLICATIONS FOR PRACTICE

NIPPV is a useful method of augmenting the beneficial effects of NCPAP in preterm infants. Its use reduces the incidence of symptoms of extubation failure more effectively than NCPAP. Within the limits of the small numbers of infants randomised to NIPPV there is a reassuring absence of the gastrointestinal side effects that were reported in previous case series.

IMPLICATIONS FOR RESEARCH

Future trials should enrol sufficient infants to detect differences in important outcomes such as chronic lung disease and gastrointestinal perforation. The impact of synchronisation of NIPPV on the technique's safety and efficacy should be established in future trials.

The drug epidemic: effects on newborn infants and health resource consumption at a tertiary perinatal centre

OBJECTIVES

Illicit drug taking in Australia, with its attendant social and medical consequences, is increasing and the effects extend to maternity hospitals where infants born to addicted mothers have more health problems in the neonatal period. The aims of this study were to evaluate (1) the patterns of illness of such infants and (2) the burden imposed on the neonatal department of a large tertiary maternity centre.

METHODOLOGY

An audit was conducted of all Chemical Dependency Unit (CDU) mothers and babies delivered at the Royal Women's Hospital, Melbourne, Australia during 1997. Data were compared with those from a concurrent control group of mothers and babies randomly generated from the hospital's obstetric database.

RESULTS

Ninety-six infants born to CDU mothers were compared with a control group of 200 infant/mother pairs. The majority of women in the CDU clinic were treated for narcotic addiction with methadone (90%) but most continued to use heroin during pregnancy (68%). Infants born to CDU mothers were significantly less mature and lighter than control infants. Fifty-three (55%) CDU infants required admission to the Special Care Nursery either because of neonatal abstinence syndrome (n = 29) or other medical reasons (n = 24). The median length of hospital stay was significantly longer in CDU compared with control infants (8 vs 3 days, P < 0.01).

CONCLUSIONS

Infants born to drug dependent mothers have more neonatal problems requiring specialized medical and nursing expertise, compared with control infants. These infants are large consumers of scarce health resources.

Methylxanthines and sensorineural outcome at 14 years in children < 1501 g birthweight

OBJECTIVES

Methylxanthines, including theophylline, have been used extensively and successfully to treat apnoea in preterm infants. However, long-term consequences of such therapy are largely unknown. The aim of this study was to determine the relationship between theophylline therapy and outcome at 14 years of age in surviving preterm children of birthweight < 1501 g.

METHODOLOGY

The subjects of this study were 154 consecutive survivors with birthweights < 1501 g born from 1 October 1980 to 31 March 1982; 130 (84.4%) were assessed at 14 years of age. Outcomes included motor function, psychological test scores, and growth.

RESULTS

Of the 130 children assessed, 69 (53.1%) had been exposed to theophylline; 13.0% had cerebral palsy, significantly higher than 1.6% in the 61 children not exposed to theophylline (P < 0.02). This difference remained statistically significant after adjusting for potential confounding variables including the presence of cerebroventricular haemorrhage. In contrast, after adjusting for known confounding variables, children who had received theophylline achieved higher psychological test scores. There was no association between theophylline therapy and growth.

CONCLUSIONS

Theophylline therapy in the newborn period is associated with some evidence of harmful, but also helpful sensorineural effects at 14 years of age.

Continuous positive airway pressure versus theophylline for apnea in preterm infants

BACKGROUND

Recurrent apnea is common in preterm infants, particularly at very early gestational ages. These episodes of loss of effective breathing can lead to hypoxemia and bradycardia which may be severe enough to require resuscitation including use of positive pressure ventilation. Theophylline stimulation of breathing and continuous positive airways pressure have been used to prevent apnea and its consequences.

OBJECTIVES

The main objective was to determine in preterm infants with recurrent apnea, if treatment with CPAP compared with treatment with theophylline leads to a clinically important reduction in apnea or use of mechanical ventilation, without clinically important side effects.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. This includes searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conferences, symposia proceedings, expert informants and journal hand searching mainly in the English language.

SELECTION CRITERIA

All trials using random or quasi-random allocation to CPAP or theophylline in preterm infants with clinical recurrent apnea/bradycardia were eligible.

DATA COLLECTION AND ANALYSIS

Data were extracted using standard methods of the Cochrane Collaboration and its Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk.

MAIN RESULTS

The use of mask CPAP is associated with a higher treatment failure rate as measured by less than a 50% reduction in apnea or use of the alternative treatment [RR 2.89 (95% CI 1.12,7.47); RD 0.42 (95% CI 0. 11, 0.74)]. For every 2.4 infants (95% CI 1.4, 9.5) treated with mask CPAP rather than theophylline, there results one treatment failure. In the mask CPAP group there is more use of IPPV [RR 3.09 (1.42,6.70; RD 0.58 (95% CI 0.30, 0.86). For every 1.7 infants (95% CI 1.2, 3.3) treated with mask CPAP rather than theophylline, one infant is intubated for IPPV. In the mask CPAP group, there are trends towards more deaths in the first year, and in death or major disability in survivors at follow up, which do not reach significance. There are no differences in rates of necrotizing enterocolitis or major disability in survivors at follow up.

REVIEWER'S CONCLUSIONS

Theophylline is more effective than mask CPAP for preterm infants with apnea. Since CPAP is no longer administered by mask, the results of this review have limited importance for current clinical practice. Further evaluation of the benefits and harms of CPAP vs theophylline for preterm infants with apnea requires further trials in which CPAP is administered by current methods.

Intravenous dexamethasone for extubation of newborn infants

BACKGROUND

Endotracheal tubes are foreign bodies that may injure the upper airway causing laryngeal edema. This in turn may result in failure of extubation in preterm infants. Corticosteroids have been used prophylactically to reduce upper airway obstruction and facilitate extubation.

OBJECTIVES

In newborn infants having their endotracheal tube removed following a period of intermittent positive pressure ventilation (IPPV), what are the effects of intravenous corticosteroids on the incidence of endotracheal reintubation, stridor, atelectasis and adverse side effects?

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH search terms "dexamethasone", "extubat*" and "exp infant, newborn"), previous reviews including cross references, abstracts of conferences and symposia proceedings, expert informants, journal handsearching mainly in the English language and expert informant searches in the Japanese language by Prof. Y. Ogawa.

SELECTION CRITERIA

Trials were included which used random or quasi-random patient allocation, and which compared intravenous steroids given immediately prior to a planned extubation with placebo.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by the two authors and analysed in Revman for all trials. Prespecified subgroup analyses were performed to examine differences in response between infants at high risk for upper airway edema and those receiving routine prophylaxis prior to extubation.

MAIN RESULTS

Administration of dexamethasone prior to extubation significantly reduced the need for reintubation of the trachea. This result applies to both the high risk group and to the total population of infants enrolled. However, the incidence of extubation failure was zero in the trial that attempted to exclude infants at high risk of airway edema. The side effects of higher blood sugar levels and glycosuria were found in the 2 trials where these were sought.

REVIEWER'S CONCLUSIONS

Implications for practice Dexamethasone reduces the need for endotracheal reintubation of neonates after a period of IPPV. In view of the lack of effect in low risk infants and the documented and potential side effects, it appears reasonable to restrict its use to infants at increased risk for airway edema and obstruction, such as those who have received repeated or prolonged intubations. Implications for research Issues of dosage and applicability to the extremely low birthweight population could be addressed in future trials. Longer term outcomes such as chronic lung disease, duration of assisted ventilation and length of hospital stay should also be examined.

Prophylactic doxapram for the prevention of morbidity and mortality in preterm infants undergoing endotracheal extubation

BACKGROUND

When preterm infants have been given intermittent positive pressure ventilation (IPPV) for respiratory failure, weaning from support and tracheal extubation may be difficult. A significant contributing factor is thought to be the relatively poor respiratory effort and tendency to develop hypoventilation and apnea, particularly in very preterm infants. Doxapram stimulates breathing and appears to act via stimulation of both the peripheral chemoreceptors and the central nervous system. This effect might increase the chance of successful tracheal extubation.

OBJECTIVES

In preterm infants being weaned from IPPV and in whom endotracheal extubation is planned, does treatment with doxapram reduce the use of intubation and IPPV, or reduce other morbidity, without clinically important side effects? In this regard, how does doxapram compare with standard treatment or with an alternative treatment such as methylxanthine or CPAP? Subgroup analyses were prespecified according to birth weight and/or gestational age, use of co-interventions (methylxanthines or nasal CPAP), and route of administration (intravenous or oral).

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE and EMBASE.

SELECTION CRITERIA

Eligible studies included published trials utilising random or quasi-random patient allocation in which preterm or low birth weight infants being weaned from IPPV were given doxapram compared with standard care or other treatments, to facilitate weaning from IPPV and endotracheal extubation. Trials were independently assessed by the authors before inclusion.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Collaboration and its Neonatal Review Group were used. Each author extracted data separately; the results were compared and any differences resolved. The data were synthesized using the standard method of Neonatal Review Group with use of relative risk and risk difference.

MAIN RESULTS

Two trials involving a total of 85 infants compared doxapram and placebo. In both the individual trials and the meta-analyses there were no significant differences between the doxapram and placebo groups in any of the outcomes (failed extubation, death before discharge, respiratory failure, duration of IPPV, side effects, oxygen at 28 days or oxygen at discharge). There was a trend towards an increase in side effects (hypertension or irritability leading to cessation of treatment) in the doxapram group [summary RR 3.21 (0.53, 19.43). In one of these two trials (Huon 1998) an 'alarming rise in blood pressure' occurred in five infants in the doxapram group and none of the controls, although in only one was treatment withdrawn. One additional trial involving only eight infants compared doxapram with aminophylline, but there were insufficient data for meaningful analysis.

REVIEWER'S CONCLUSIONS

The evidence does not support the routine use of doxapram to assist endotracheal extubation in preterm infants who are eligible for methylxanthine and/or CPAP. The results should be interpreted with caution because the small number of infants studied does not allow reliable assessment of the benefits and harms of doxapram. Further trials are required to evaluate the benefits and harms of doxapram compared with no treatment or with other treatments, such as methylxanthines or CPAP, to evaluate whether it is more effective in infants not responding to these other treatments, and to assess whether the drug is effective when given orally.

Extubation from low-rate intermittent positive airways pressure versus extubation after a trial of endotracheal continuous positive airways pressure in intubated preterm infants

BACKGROUND

Failure of extubation and subsequent reintubation may result in additional stress and trauma to the premature infant. Testing infants about to be extubated with a period of endotracheal CPAP has been suggested as a method of demonstrating readiness for extubation. However, this process has been criticized as increasing the neonate's work of breathing and perhaps increasing the likelihood of extubation failure.

OBJECTIVES

In premature infants having their endotracheal tube removed, is direct extubation from low rate intermittent positive pressure ventilation (IPPV) more successful than that following a period of endotracheal continuous positive airway pressure (CPAP)?

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conferences, symposia proceedings, expert informants and journal hand searching mainly in the English language.

SELECTION CRITERIA

All trials using random or quasi-random allocation of premature infants to endotracheal CPAP or direct extubation following a period of IPPV were included.

DATA COLLECTION AND ANALYSIS

Data were extracted using standard methods of the Cochrane Collaboration and its Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk.

MAIN RESULTS

Direct extubation from low rate ventilation is associated with a trend to increased chance of successful extubation when compared to extubation after a period of endotracheal CPAP, RR 0.45 (0.19,1.07), RD -0.103 (-0.200,-0.006), NNT 10 (5,167). When only truly randomized trials are considered, this result becomes both statistically significant and clinically important, RR 0.10 (0.01,0.78), RD -0.201 (-0.319,-0.083), NNT 5 (3, 12). Similar differences are seen for the secondary outcome, apnea.

REVIEWER'S CONCLUSIONS

Preterm infants no longer requiring endotracheal intubation and IPPV should be directly extubated without a trial of ETT CPAP.

Nebulized racemic epinephrine for extubation of newborn infants

BACKGROUND

Following a period of mechanical ventilation, post-extubation upper airway obstruction can occur in newborn infants, especially after prolonged, traumatic or multiple intubations. The subsequent increase in upper airway resistance may lead to respiratory insufficiency and failure of extubation. The vasoconstrictive properties of epinephrine, and its proven efficacy in the treatment of croup in infants, has led to the routine use of inhaled nebulised epinephrine immediately post-extubation in some neonatal units. It is also recommended for neonates with post-extubation tracheal obstruction and stridor in neonatal and respiratory textbooks and reviews.

OBJECTIVES

The primary objective was to assess whether nebulised epinephrine administered immediately after extubation in neonates weaned from IPPV decreases the need for subsequent additional respiratory support.

SEARCH STRATEGY

Searches were made of Medline (MeSH search terms 'epinephrine' and 'exp infant, newborn'), the Oxford Database of Perinatal trials, expert informants and journal hand searching mainly in the English language, expert informant searches in the Japanese language by Prof. Ogawa, previous reviews including cross references, abstracts, and conference and symposia proceedings.

SELECTION CRITERIA

All randomised and quasi-randomised control trials in which nebulised epinephrine was compared with placebo immediately post-extubation in newborn infants who have been weaned from IPPV and extubated, with regard to clinically important outcomes (i.e. need for additional respiratory support, increase in oxygen requirement, respiratory distress, stridor or the occurrence of side effects).

DATA COLLECTION AND ANALYSIS

No studies met our criteria for inclusion in this review.

MAIN RESULTS

No studies were identified which looked at the effect of inhaled nebulised epinephrine on clinically important outcomes in infants being extubated.

REVIEWER'S CONCLUSIONS

IMPLICATIONS FOR PRACTICE

There is no evidence either supporting or refuting the use of inhaled nebulised racemic epinephrine in newborn infants.

IMPLICATIONS FOR RESEARCH

randomised controlled trials are needed comparing inhaled nebulised racemic epinephrine with placebo in neonates post-extubation. This should be looked at both as a routine treatment post-extubation and as specific treatment for post-extubation upper airway obstruction. Study populations should include the group of infants at highest risk for upper airway obstruction from mucosal swelling because of their small glottic and sub-glottic diameters (ie those infants with birthweights less than 1000 grams).

Intravenous indomethacin for preventing mortality and morbidity in very low birth weight infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

Indomethacin is used to treat symptomatic patent ductus arteriosus and may prevent or limit intraventricular haemorrhage in the neonatal period. This review examines the effectiveness of prophylactic intravenous indomethacin in reducing the mortality and morbidity associated with these conditions in infants weighing less than 1750 grams at birth.

SEARCH STRATEGY

A literature search from January 1980 to October 1994 was made in three computerised data bases: Medline; Embase; and the Oxford Database of Perinatal Trials. The search was updated in February 1997.

SELECTION CRITERIA

Strict selection criteria were applied to clinical trials: the population had to be newborn infants of birth weight < 1751 grams; the intervention had to be prophylactic intravenous indomethacin; the trial had to be randomised and controlled; and at least one of several prespecified outcomes had to be reported in the results.

DATA COLLECTION AND ANALYSIS

The methodological quality of each study was assessed using explicit criteria. Data on relevant outcome measures were extracted on two separate occasions and, where appropriate, the results of individual trials were combined using meta-analysis techniques to provide a pooled estimate of effect.

MAIN RESULTS

There is a trend towards reduced neonatal mortality in infants receiving prophylactic indomethacin, pooled relative risk (RR) = 0. 85 [95% CI 0.66 to 1.09]. The incidence of symptomatic patent ductus arteriosus is significantly reduced in treated infants, pooled RR = 0.35 [0.26 to 0.47] but there is no evidence that treatment affects respiratory outcomes. Prophylactic indomethacin significantly reduces the incidence of Grade 3 and 4 intraventricular haemorrhage in treated infants, pooled RR = 0.60 [0.43 to 0.83]. There is no evidence to suggest prophylactic indomethacin is associated with any long term adverse effect although there is a trend in treated infants towards an increased incidence of necrotizing enterocolitis, and some evidence that treatment may transiently impair renal function. There is no evidence that haemostasis is disturbed.

REVIEWER'S CONCLUSIONS

Prophylactic treatment with indomethacin has a number of immediate benefits, in particular a reduction in symptomatic patent ductus arteriosus and severe intraventricular haemorrhage. There is no evidence at present of long-term harm. Further trials are needed to assess more precisely the effects, both beneficial and harmful, on short and long-term outcomes.

Prophylactic nasal continuous positive airways pressure for preventing morbidity and mortality in very preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To determine if prophylactic nasal continuous positive airways pressure (CPAP) commenced soon after birth regardless of respiratory status in the very preterm or very low birth weight infant reduces the use of IPPV and the incidence of chronic lung disease (CLD) without adverse effects.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conferences, symposia, proceedings, expert informants, journal hand searching mainly in the English language.

SELECTION CRITERIA

All trials using random or quasi-random patient allocation of very preterm infants < 32weeks gestation and / or < 1500 gms at birth were eligible. Comparison had to be between prophylactic nasal CPAP commencing soon after birth regardless of the respiratory status of the infant compared with "standard" methods of treatment where CPAP or IPPV is used for a defined respiratory condition.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and its Neonatal Review Group, including independent assessment of trial quality and extraction of data by each author, were used. Data were analysed using relative risk (RR).

MAIN RESULTS

There are no statistically significant differences in any of the outcomes reported in the single eligible study of 82 very low birth weight infants. More infants in the prophylactic nasal CPAP group received IPPV; however, this difference is not statistically significant. There are trends towards increases in the incidence of CLD (undefined) [RR 2.27 (0.77, 6.65)], of death [RR 3.63 (0.42, 31.08)] and of intraventricular hemorrhage [RR 2.18 (0.84, 5.62)] in the treatment group. The study also found a trend towards a reduction in the incidence of necrotizing enterocolitis in the treatment group [RR 0.40 (0.13, 1.21)].

REVIEWER'S CONCLUSIONS

There is currently insufficient information to make recommendations for clinical practice. The single study reviewed showed no strong evidence of benefit in reducing the incidence of IPPV. The tendency for some adverse outcomes to be increased is of concern and more data are needed to clarify this. A multicentre randomized controlled trial comparing prophylactic nasal CPAP with "standard" methods of treatment is needed to clarify its clinical role.

Post-extubation prophylactic nasal continuous positive airway pressure in preterm infants: Systematic review and meta-analysis

OBJECTIVES

To determine whether management with nasal continuous positive airway pressure (NCPAP) in preterm infants having their endotracheal tube removed following a period of intermittent positive pressure ventilation (IPPV), leads to an increased proportion remaining free of additional ventilatory support, compared to extubation directly to headbox oxygen.

METHODOLOGY

Search Strategy- Searches were made of the Oxford Database of Perinatal Trials, Medline, abstracts of conferences and symposia proceedings, expert informants, journal hand searching mainly in the English language and expert informant searches in the Japanese language. Selection criteria- All trials utilising random or quasi-random patient allocation, in which NCPAP (delivered by any method) was compared with headbox oxygen for postextubation care were included. Methodological quality was assessed independently by the two authors. Data collection and analysis- Data were extracted independently by the two authors. Meta-analysis using event rate ratios (ERRs) and event rate differences (ERDs) was performed using Revman 3.0 statistical software. Prespecified subgroup analysis to determine the impact of different levels of NCPAP and use of aminophylline were also performed using the same package. Similar analysis to investigate the effect of postnatal age on outcomes of interest was also undertaken.

RESULTS

Nasal CPAP, when applied to preterm infants being extubated following IPPV, reduces the incidence of adverse clinical events (apnoea, respiratory acidosis and increased oxygen requirements) indicating the need for additional ventilatory support. This result is both statistically significant and clinically important; ERR, 0.62 (0.49, 0.79) and ERD, - 0.175 (- 0.256, - 0.095). A trend towards reduction in the incidence of oxygen dependency at 28 days of age is also seen in the group extubated to NCPAP; ERR, 0.86 (0.67, 1.10) and ERD, - 0.069 (- 0.177, 0.039).

CONCLUSIONS

Nasal CPAP is effective in preventing failure of extubation in preterm infants following a period of endotracheal intubation and IPPV. Further definition of the patient gestational age and weight groups to whom these results apply is required. Optimal levels of NCPAP as well as methods of administration remain to be determined.

Transverse cerebellar diameter on cranial ultrasound scan in preterm neonates in an Australian population

OBJECTIVE

Fetal measurement of transverse cerebellar diameter (TCD) has been shown to correlate well with gestational age (GA), even in the presence of growth retardation. The aim of this study was to define the normal range of TCD in preterm neonates in an Australian population between 23 and 32 weeks GA.

METHODOLOGY

Infants admitted to the Royal Women's Hospital, Melbourne, having routine cranial ultrasound scans (< 1500 g and/or of gestational age ≤ 32 weeks at birth) had their TCD measured on a cranial scan performed during the first 3 days of life. The posterior fossa was examined through the asterion using a General Electric LOGIQ 500 scanner (GE Medical Systems, Waukesha, USA) and TCD measurement was taken in the coronal plane.

RESULTS

106 infants < 1500 g and/or of GA ≤ 32 weeks at birth had their TCD measured between 1 January 1997 and 30 November 1997. Transverse cerebellar diameter and associated 95% confidence intervals are described for infants between 23 and 32 weeks GA. The linear regression equation relating TCD and GA was: TCD (mm) = -12.9 + 1.61 × GA (weeks). R² = 0.80, P < 0.001.

CONCLUSION

This is the only study of TCD measurement using cranial ultrasound in a group of preterm newborns, and forms the basis for nomograms of TCD which can be used as a tool to assist in the assessment of GA, even in growth-retarded preterm newborns, and in the diagnosis of cerebellar hypoplasia.

Why do preterm infants die in the 1990s?

OBJECTIVES

To describe the mortality rate for preterm infants (born 23-36 completed weeks' gestational age) and to determine the causes of death, focusing on avoidable causes.

DESIGN AND SETTING

Prospective cohort study of preterm infants born at Royal Women's Hospital, Melbourne (a tertiary referral hospital with a neonatal intensive care unit and a special care nursery) from January 1994 to December 1996.

SUBJECTS

2475 consecutive liveborn infants with gestational ages from 23 to 36 weeks.

MAIN OUTCOME MEASURES

Mortality rate during the primary hospitalisation, and causes of death.

RESULTS

The total mortality rate was 4.8% (118/2475). The mortality rate declined with increasing maturity. The decrease in mortality was rapid between 23 and 28 weeks' gestational age, from 64.5% at 23 weeks to 4.0% at 28 weeks, then slower, falling to 0.4% at 36 weeks. Fifty of the 118 infants who died had lethal congenital anomalies. Lethal anomalies accounted for three-quarters of deaths in infants aged 28-36 weeks. The mortality rate in infants free of lethal anomalies was 2.8% (68/2425) and only 0.2% (4/1759) for infants aged 32-36 weeks. In the 68 infants without lethal anomalies who died, few obvious preventable causes were identified.

CONCLUSIONS

Mortality rates fell rapidly between 23 and 28 weeks' gestational age. Survival rates for preterm infants born after 31 weeks' gestational age approached the survival rates of term infants. Lethal congenital anomalies were the most common cause of death; preventable causes of death were rare.

Establishment of a normal range of penile length in preterm infants

RATIONALE

Recognition of micropenis is important because it may be the only obvious manifestation of pituitary or hypothalamic hormone deficiencies. Alternatively it may indicate the presence of dysgenetic testicular tissue with malignant potential. Previously published normal ranges for premature males are based on small sample sizes, with few infants <30 weeks and none <28 weeks.

SETTING

Intensive and Special Care Nurseries, Royal Women's Hospital, Melbourne, Victoria.

SUBJECTS

188 consecutive male infants, inborn and outborn, with gestational age <37 completed weeks were examined in the first week of life. They included multiple births (n=51) and small for gestational age infants (n=16). Infants with hypospadias (n=3) or an endocrine disorder (n=1) were excluded from the study. MANOEUVRE: Stretched penile length was determined by a single examiner (RT) using a standardized measure.

RESULTS

A mean penile length with associated 95% confidence intervals is described for infants between 24 and 36 weeks inclusive. The relationship between penile length (PL, cm) and gestational age (GA, weeks) was: PL=2.27+0.16 GA.

CONCLUSION

This study confirms the normal range for penile length of premature male infants 30-36 weeks and defines the normal range <30 weeks. This should prove useful to paediatricians, paediatric surgeons and endocrinologists dealing with the increasing number of surviving male infants <30 weeks in whom penile size is questioned.

Factors affecting fibrinolytic potential: cardiovascular fitness, body composition, and lipoprotein(a)

The purpose of the study was to determine the factors that affect basal (resting) and poststressor fibrinolytic activity or potential. Variables of interest included cardiovascular fitness (maximal oxygen consumption [Vo2max]), body fat, body mass index (BMI), and lipids/lipoproteins, including lipoprotein(a) [Lp(a)]. Blood was collected from 46 middle-aged men before and after a maximal exercise test. Pearson and Spearman correlation coefficients were calculated to determine associations between the variables of interest and tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activities in the basal state and after stimulation with maximal exercise. Multiple regression analyses were also conducted to determine independent predictors of the fibrinolytic variables. Maximal exercise produced significant increases in t-PA activity and decreases in PAI-1 activity. Postexercise t-PA activity was inversely related to basal PAI-1 activity (r = -.34). Vo2max was positively correlated with t-PA activity (basal, r = .39; postexercise, r = .67) and inversely related to PAI-1 activity (basal, r = -.41; postexercise, r = -.42). Body fat was correlated with postexercise t-PA activity (r = -.60) and both basal and postexercise PAI-1 activity (r = .42), but the correlation with basal t-PA activity was not significant (P = .058). Postexercise t-PA activity was positively correlated (r = .37) with high-density lipoprotein cholesterol (HDL-C) and negatively correlated (r = -.42) with low-density lipoprotein cholesterol (LDL-C). Basal PAI-1 activity was negatively correlated with HDL-C (r = -.37), Lp(a) was not correlated with any fibrinolytic variable or fitness. Multiple regression analyses showed that Vo2max was an independent predictor of both basal and postexercise t-PA activity (R2 = .16 and .34, respectively). Triglyceride (TG) levels and Vo2max were significant independent predictors of PAI-1 activity (R2 = .31). In conclusion, cardiovascular fitness was a strong independent predictor of fibrinolytic potential. In addition, poststressor measures of fibrinolytic potential may provide more information about the fibrinolytic system than basal values.

Effect of a single session of exercise on lipoprotein(a)

Lipoprotein(a) (Lp(a)) is bound to apolipoprotein B-100 by disulfide linkage and is associated in the upper density range of low density lipoprotein cholesterol. Persons with elevated concentrations of Lp(a) are regarded as having an increased risk for premature coronary artery disease. Although many studies exist evaluating the effects of a single session of exercise on lipids and lipoproteins, little information is available concerning the effects of exercise on Lp(a). Therefore, the purpose of this study was to determine the effects of a single exercise session on plasma Lp(a). Twelve physically active men completed two 30-min submaximal treadmill exercise sessions: low intensity (LI, 50% VO2max) and high intensity (HI, 80% VO2max). Blood samples were obtained immediately before and after exercise. Total cholesterol (LI: before 4.22 +/- 0.26, after 4.24 +/- 0.28; HI: before 4.24 +/- 0.31, after 4.11 +/- 0.28 mmol.l-1, mean +/- SE) and triglyceride (LI: before 1.14 +/- 0.16, after 1.06 +/- 0.16; HI: before 1.12 +/- 0.19, after 1.21 +/- 0.19 mmol.l-1) concentrations did not differ immediately after either exercise session, nor did Lp(a) concentrations differ immediately after either exercise session (LI: before 4.1 +/- 2.2, after 4.0 +/- 2.1: HI: before 3.9 +/- 2.2, after 3.7 +/- 2.0 mg.dl-1). These results suggest that neither a low nor a high intensity exercise session lasting 30 min in duration has an immediate effect on plasma Lp(a).

Muscle glycogen storage after prolonged exercise: effect of the frequency of carbohydrate feedings

We reported previously that intake of carbohydrate foods with a high glycemic index (GI) produced greater glycogen storage and greater postprandial glucose and insulin responses during 24 h of postexercise recovery than did intake of low-GI carbohydrate foods. In the present study we examined the importance of the greater incremental glucose and insulin concentrations on glycogen repletion by comparing intake of large carbohydrate meals ("gorging") with a pattern of frequent, small, carbohydrate snacks ("nibbling"), which simulates the flattened glucose and insulin responses after low-GI carbohydrate meals. Eight well-trained triathletes [x +/- SEM: 25.6 +/- 1.5 y of age, weighing 70.2 +/- 1.9 kg, and with a maximal oxygen uptake (VO2max) of 4.2 +/- 0.2 L/min] undertook an exercise trial (2 h at 75% VO2max followed by four 30-s sprints) to deplete muscle glycogen on two occasions, 1 wk apart For 24 h after each trial, subjects rested and consumed the same diet composed exclusively of high-GI carbohydrate foods, providing 10 g carbohydrate/kg body mass. The "gorging" trial provided the food as four large meals of equal carbohydrate content eaten at 0, 4, 8, and 20 h of recovery, whereas in the "nibbling" trial each of the meals was divided into four snacks and fed at hourly intervals (0-11, 20-23 h). However, there was no significant difference in muscle glycogen storage between the two groups over the 24 h (gorging: 74.1 +/- 8.0 mmol/kg wet wt; nibbling: 94.5 +/- 14.6 mmol/kg wet wt). The results of this study suggest that there is no difference in postexercise glycogen storage over 24 h when a high-carbohydrate diet is fed as small frequent snacks or as large meals, and that a mechanism other than lowered blood glucose and insulin concentrations needs to be sought to explain the reduced rate of glycogen storage after consumption of low-GI carbohydrate foods.

Effect of coingestion of fat and protein with carbohydrate feedings on muscle glycogen storage

Dietary guidelines for achieving optimal muscle glycogen storage after prolonged exercise have been given in terms of absolute carbohydrate (CHO) intake (8-10 g.kg-1.day-1). However, it is of further interest to determine whether the addition of fat and protein to carbohydrate feedings affects muscle glycogen storage. Eight well-trained triathletes [23.1 +/- 2.0 (SE) yr; 74.0 +/- 3.4 kg; peak O2 consumption = 4.7 +/- 0.4 l/min] undertook an exercise trial (2 h at 75% peak O2 consumption, followed by four 30-s sprints) on three occasions, each 1 wk apart. For 24 h after each trial, the subjects rested and were assigned to the following diets in randomized order: control (C) diet (high glycemic index CHO foods; CHO = 7 g.kg-1.day-1), added fat and protein (FP) diet (C diet + 1.6 g.kg-1.day-1 fat + 1.2 g.kg-1.day-1 protein), and matched-energy diet [C diet + 4.8 g.kg-1.day-1 additional CHO (Polycose) to match the additional energy in the FP diet]. Meals were eaten at t = 0, 4, 8, and 21 h of recovery. The total postprandial incremental plasma glucose area was significantly reduced after the FP diet (P < 0.05). Serum free fatty acid and plasma triglyceride responses were significantly elevated during the FP trial (P < 0.05). There were no differences between trials in muscle glycogen storage over 24 h (C, 85.8 +/- 2.7 mmol/kg wet wt; FP, 80.5 +/- 8.2 mmol/kg wet wt; matched-energy, 87.9 +/- 7.0 mmol/kg wet wt).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute exercise intensity on plasma lipids and apolipoproteins in trained runners

The purpose of this study was to determine the effects of exercise intensity on lipid and lipoprotein metabolism. Concentrations of triglyceride, cholesterol, high-density lipoprotein cholesterol (HDL-C) and its subfractions (HDL2-C and HDL3-C), low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and apolipoproteins A-I, A-II, and B were measured. Ten well-trained runners completed treadmill exercise on two different occasions: a high-intensity session at 75% maximal oxygen consumption lasting 60 min and a low-intensity session at 50% maximal oxygen consumption lasting 90 min. Energy expenditure for each session was equal. Fasted blood samples were obtained 24 h before, immediately before, immediately after, and 1, 24, 48, and 72 h after each exercise session. No significant differences were found for the blood variables across time or between treatments. However, HDL-C and HDL2-C were slightly elevated on the days after each treatment. These results suggest that acute exercise sessions lasting less than 90 min, regardless of intensity, do not elicit plasma lipid, lipoprotein, and apolipoprotein changes in men who are habitually physically active and have high initial concentrations of HDL-C.

Obesity and weight loss alter serum polyunsaturated lipids in humans

Serum omega 6 (n-6) fatty acids were assessed in 12 obese women during an outpatient very-low-calorie diet (VLCD). Ten subjects (S10) achieved a mean weight loss of 17 kg over 3-5 mo (initial weight-for-height 157%). Serum was obtained before (baseline) and monthly during the VLCD and from five of them (S5) after 2-3 mo of weight stability (refed) at 21 kg of loss. At baseline for S10, the serum phospholipid (PL) 20:4 omega 6 was 9.16 wt% and differed from normal (12.81 wt%) by P less than 0.0001, but cholesterol ester (CE) 20:4 omega 6 did not differ from normal. During 3 mo of VLCD, the S10 serum PL and CE 18:2 omega 6 fell (P less than 0.005 and 0.0001, respectively). Serum PL 20:4 omega 6 rose to normal during VLCD months 1-3 (P less than 0.01) while the serum CE 20:4 omega 6 rose above normal (P less than 0.0002). During the VLCD, S5 results paralleled S10. However when refed, S5 PL and CE 18:2 omega 6 and 20:4 omega 6 all reverted to baseline (PL 20:4 omega 6 below normal, P less than 0.001). Serum PL 20:4 omega 6 is low in moderate obesity, corrects to normal during a VLCD, but regresses to the predict abnormality after weight loss.

Differential effects of two very low calorie diets on aerobic and anaerobic performance

To determine the effects on physical performance of two different very low calorie diets (VLCD), 10 moderately obese women (BMI 32.7) were tested before and after an outpatient weight loss of 17 kg. Diet 1 (D1, n = 5) subjects lost 17.2 kg on 450-550 kcal/d from common food regimen adjusted for stature providing protein at 1.5 g/kg IBW and less than 10 g carbohydrate (CHO). Diet 2 (D2, n = 5) subjects lost 18.1 kg on a fixed composition 420 kcal/d formula providing 70 g (1.2 g/kg IBW) protein and 30 g CHO. Aerobic performance (VO2 max) was determined on a cycle ergometer. VO2 max did not change with D1 (2.16 to 2.01 l/min), while it decreased on D2 (2.44 to 2.06 l/min, P less than 0.05). Anaerobic function was assessed as peak quadricep strength on an isokinetic dynamometer, with anaerobic endurance taken as the time and number of repetitions to fatigue (less than 50 percent peak strength). Peak strength did not change on D1 (95.8 to 86.2 ft-lb), but it declined with D2 (102.0 to 89.4 ft-lb, P less than 0.05). Anaerobic time to fatigue did not change with either diet group. In conclusion, it is possible that the higher (and individualized) protein intake of D1 allowed the better preservation of VO2 max, while the higher CHO of D2 did not benefit anaerobic function. Our data suggest that physical performance tests could be used to assess for functional tissue preservation when diets are used for major weight loss.

Plasma and urinary carnitine of obese subjects on very-low-calorie diets

We evaluated the differential effects of feeding two very-low-calorie diets upon the fractions of plasma and urinary carnitine in obese females. Ten subjects received either diet D1, a 420 kcal/day formula diet, or diet D2, a 500-600 kcal/day meat/fish/poultry diet. Plasma and urinary carnitine levels were determined at the start of the study. After 1 month, plasma carnitine levels were obtained; at 2 months, both plasma and urinary carnitine levels were obtained. Subjects receiving diet D2 showed significantly higher levels of plasma total carnitine over the course of the study (p less than 0.05). Plasma short-chain acylcarnitine esters increased and free carnitine declined significantly in both groups during the study period. Subjects receiving D1 excreted significantly less urinary carnitine than those receiving D2. We conclude that long-term ingestion of very-low-calorie diets causes alterations in plasma carnitine metabolism.

Factors responsible for the differences in cultural estimates and direct microscopical counts of populations of bacterivorous nanoflagellates

Bacterivorous nanoflagellates (microflagellates) have been routinely enumerated in marine and freshwater samples using either a Most Probable Number (MPN) culture method or by a direct microscopical counting method (DC). These two techniques typically yield highly disparate estimates of the density of nanoflagellates in natural samples. We compared these methods with seawater and marine snow (macroscopic detrital aggregate) samples collected from surface waters throughout the North Atlantic and in freshwater samples collected at three stations in Lake Ontario. Densities of nanoflagellates determined by the two methods differed by as much as four orders of magnitude; the MPN estimate rarely exceeded 10% of the microscopical count, and averaged ≈ 1% of this count. The MPN estimate constituted a higher percentage of the DC value in environments with high concentrations of nanoflagellates relative to environments with low concentrations of nanoflagellates. The ratio of the culture count to the microscopical count (MPN∶DC) increased along an environmental gradient from oligotrophy to eutrophy, and was positively correlated with the density of bacteria in the samples. In laboratory experiments with two species of bacterivorous nanoflagellates, the MPN count constituted a much greater percentage of the DC count during the exponential growth phase of the nanoflagellate than during the stationary growth phase. Differences in the estimates of nanoflagellate density obtained with these two techniques probably can be explained by the trophic mode of these protozoa, their growth stage, and the amenability of these species to laboratory culture.

Effect of sodium concentration on aldosterone secretion by isolated perfused canine adrenal glands

Small changes in sodium concentration [( Na]) are not generally considered to have a major direct effect on aldosterone secretion. However, a marked disruption in the renin-aldosterone relationship has been observed in a variety of hypernatremic and hyponatremic states. Therefore, we evaluated the hypothesis that small changes in [Na] have a potent direct effect on angiotensin II- and potassium-stimulated aldosterone secretion. The left adrenal gland, abdominal aorta, and surrounding periadrenal tissue were surgically isolated from mongrel dogs and perfused with Ringers bicarbonate solution at a pressure of approximately 57 mm Hg. Infusion of a KCl test solution at the beginning and end of most experiments produced similar increases in aldosterone secretion, thus documenting the stability of these preparations. After a stable response was established to either a low dose of angiotensin II or a small increase in perfusate [K], the [Na] was changed by adding or removing NaCl. Changing perfusate [Na] from 152 to 139 mM during the infusion of either angiotensin II or potassium caused 20- to 25-fold increases in aldosterone secretion. Increasing perfusate [Na] from 145 to 152 mM inhibited aldosterone secretion to a greater extent during stimulation by lower doses (40-50 pg/ml) than by higher doses (80-100 pg/ml) of angiotensin II. These data demonstrate that during moderate stimulation by angiotensin II or potassium, small changes in [Na] have a powerful inverse effect on aldosterone secretion by a direct action on the canine adrenal gland.

In vitro measurement of cytosol and cell nuclear androgen receptors in male rat brain and pituitary

An in vitro assay procedure is described for measuring androgen receptor binding in cytosol and cell nuclei of brain and pituitary tissue using [3H]R1881 as ligand. The cell nuclear assay uses the exchange method, which permits assessment of endogenous occupancy of androgen receptors in brain and pituitary. Competition and saturation analysis indicated that [3H]R1881 binding has the specificity and nanomolar affinity expected of an androgen receptor. Moreover, we demonstrated that androgen receptor binding predominated in cytosol from castrated rats and in cell nuclei of male rats treated in vivo with testosterone. Furthermore, as expected, testicular feminized male rats showed low levels of putative androgen receptors in both cytosol and cell nuclei.

Heterotrophic Bacteria and Bacterivorous Protozoa in Oceanic Macroaggregates

Oceanic macroaggregates (marine snow and Rhizosolenia mats) sampled from the Sargasso Sea are associated with bacterial and protozoan populations up to four orders of magnitude greater than those present in samples from the surrounding water. Filamentous, curved, and spiral bacteria constituted a higher proportion of the bacteria associated with the particles than were found among bacteria in the surrounding water. Protozoan populations were dominated numerically by heterotrophic microflagellates, but ciliates and amoebas were also observed. Macroaggregates are highly enriched heterotrophic microenvironments in the oceans and may be significant for the cycling of particulate organic matter in planktonic food chains.