A clinical comparison of radiant warmer and incubator care for preterm infants from birth to 1800 grams

OBJECTIVE

The objective of this study was to compare radiant warmer and incubator care for preterm infants from birth with respect to temperature control and weight gain.

METHODS

Sixty preterm infants <33 weeks' gestation were randomized at birth to radiant warmer or incubator care. The initial goal was to maintain abdominal temperature at 36.8 degrees C in both groups and axillary temperature at 36.8 to 37.3 degrees C; air servocontrol was used for incubator infants. Infants in both groups received added humidity for 5 days if their weight was <1000 g and for 3 days if they weighed between 1000 and 1249 g. During a 3-hour period on days 1 to 7, recordings of abdominal, forehead, and foot temperatures were obtained. The percentage of the recording time during which the abdominal temperature was in the target range of between 36 degrees C and 37.5 degrees C was determined as an indicator of temperature control. Weight gain from birth to 1800 g was compared. Secondary outcomes included fluid balance and clinical events.

RESULTS

There were 30 infants in each group; 48 were <1500 g (of whom 17 were <1000 g). There were no significant differences in birth weight, gestation, gender, or illness severity scores in the 2 groups. Significant differences in temperature control were noted on day 1. Although admission temperatures were similar, lower abdominal temperatures were noted in the first 2 hours of life in the incubator group (medians were 36.6 degrees C and 35.9 degrees C in the radiant warmer and incubator groups, respectively). Similarly, mean abdominal temperatures during the 3-hour recording on day 1 were lower in the incubator group, and infants in this group spent a significantly greater percentage of the recording time with temperatures outside the target range (17.3% compared with 0.88%). Other temperature recordings from the forehead and foot were not significantly different in the groups. Fluid intakes were higher for infants under radiant warmer on days 2, 3, and 4, and the difference amounted to a mean of 12.8 mL/kg/d. Maximum sodium levels in the first week were similar in the 2 groups. Mean weight gain was 17.4 g/kg/d for the radiant warmer group and 17.1 g/kg/d for the incubator group; days to regain birth weight and length of hospital stay were not significantly different. Greater numbers of infants in the radiant warmer group required phototherapy, and adverse events (which included death, necrotizing enterocolitis, chronic lung disease, grade 3 or 4 intraventricular hemorrhage, periventricular leukomalacia, or retinopathy requiring laser treatment) were less frequent in the radiant warmer group (1 infant compared with 8 in the incubator group; relative risk 0.1; 95% confidence intervals: 0.01-0.82).

CONCLUSIONS

This study has shown differences in abdominal temperatures on day 1 and outcome, although the latter finding should be viewed with caution because of the sample size. The results indicate benefits for the initial use of the radiant warmer after birth. Although fluid requirements were higher in the radiant warmer group for days 2 through 4, the increased fluid volumes were given without apparent adverse effect.

Mutations in the gamma(2) subunit of AMP-activated protein kinase cause familial hypertrophic cardiomyopathy: evidence for the central role of energy compromise in disease pathogenesis

Familial hypertrophic cardiomyopathy (HCM) has been widely studied as a genetic model of cardiac hypertrophy and sudden cardiac death. HCM has been defined as a disease of the cardiac sarcomere, but mutations in the known contractile protein disease genes are not found in up to one-third of cases. Further, no consistent changes in contractile properties are shared by these mutant proteins, implying that an abnormality of force generation may not be the underlying mechanism of disease. Instead, all of the sarcomeric mutations appear to result in inefficient use of ATP, suggesting that an inability to maintain normal ATP levels may be the central abnormality. To test this hypothesis we have examined candidate genes involved in energy homeostasis in the heart. We now describe mutations in PRKAG2, encoding the gamma(2) subunit of AMP-activated protein kinase (AMPK), in two families with severe HCM and aberrant conduction from atria to ventricles in some affected individuals (pre-excitation or Wolff-Parkinson-White syndrome). The mutations, one missense and one in-frame single codon insertion, occur in highly conserved regions. Because AMPK provides a central sensing mechanism that protects cells from exhaustion of ATP supplies, we propose that these data substantiate energy compromise as a unifying pathogenic mechanism in all forms of HCM. This conclusion should radically redirect thinking about this disorder and also, by establishing energy depletion as a cause of myocardial dysfunction, should be relevant to the acquired forms of heart muscle disease that HCM models.

Evaluation of a (pilot) stage-tailored brief smoking cessation intervention among hospital patients presenting to a hospital pre-admission clinic

Despite the significant benefits of advising all smokers to quit, hospital patients who smoke do not systematically receive this advice. This study sought to determine the prevalence of smoking, attitudes of patients towards not smoking while in hospital, and the feasibility and effectiveness of a brief smoking cessation intervention in a pre-admission clinic context. Over 230 smokers received a brief smoking cessation intervention, while a control group (n = 114) received only a free Quit Kit. The age-standardised smoking prevalence was 19%; a further 3% of patients were recent quitters. Most smokers do not expect or experience problems with not smoking while in hospital. Brief smoking cessation advice tailored to stage-of-change by a health worker in a hospital pre-admission clinic significantly increased the quit rates for females.

The Australian National Workplace Health Project: design and baseline findings

BACKGROUND

This paper describes the study design, recruitment, measurement, and initial recruitment outcomes of Australia's largest workplace intervention trial, the National Workplace Health Project.

METHODS

This was a cluster-randomized trial of socio-behavioral and environmental interventions focusing on key behaviors of physical activity, healthy food choices, cigarette smoking, and alcohol consumption, as well as motivational readiness for change. Twenty worksites were randomized separately for each intervention using a two-by-two factorial design. All participants underwent a health risk appraisal and measurements were made at baseline and at 1 and 2 years.

RESULTS

The overall response rate for the baseline survey was 73% with 61% attending the health risk appraisal. The sample was predominantly male, English-speaking, married, blue-collar workers. Overall, 12% reported unsafe alcohol consumption, 26% were current smokers, 44% were physically inactive, 74% ate at most one piece of fruit per day, and 26% ate at most one serving of vegetables per day. Intervention and control conditions were similar at baseline for the primary outcomes, except that a higher proportion of the sociobehavioral intervention condition was more physically active (59%) than the corresponding control condition (53%).

CONCLUSIONS

This study will permit the rigorous evaluation of the efficacy of sociobehavioral and environ mental intervention approaches to workplace health promotion. Although participants were randomized by worksite, intervention and control conditions were similar at baseline; any differences in the primary out come variables will be controlled for in the analysis.

Gene delivery to the myocardium by intrapericardial injection

Several studies have demonstrated the feasibility of gene transfer into the heart muscle. However, all the available data also indicate that the extent of transfection remains limited. As an alternative method to intravascular administration, we have developed a novel strategy which uses the pericardial sac. When a replication-deficient adenovirus containing the cDNA encoding a bacterial beta-galactosidase is injected into the pericardial sac of adult Wistar rats the staining is exclusively restricted to the pericardial cell layers. However, injecting a mixture of collagenase and hyaluronidase together with the virus, leads to a large diffusion of the transgene activity, reaching up to 40% of the myocardium. Transgene expression is predominant in the left ventricle and the interventricular septum but limited in the right ventricle. In vivo echocardiographic measurements of the left ventricular diameters at end diastolic and end systolic times show no difference between virus- and sham-injected animals, thus indicating a good clinical tolerance to this strategy of virus delivery. The same protocol has been used with the same efficiency in mice, which leads us to propose injection into the pericardial sac as an effective and harmless method for gene transfer into the heart muscle.

Prevention of stress fractures using custom biomechanical shoe orthoses

In a prospective study of stress fractures the hypothesis that training with custom made biomechanical shoe orthoses could lessen the incidence of stress fractures in infantry recruits was tested. Recruits were assigned randomly to groups and given soft biomechanical orthoses or semirigid biomechanical orthoses and compared with a control group that did not train in biomechanical orthoses. All recruits wore infantry boots with soles designed like those of basketball shoes. Recruits were examined biweekly during 14 weeks of basic training. The incidence of stress fractures was 15.7% for the recruits with the semirigid biomechanical orthoses, 10.7% for the recruits with the soft biomechanical orthoses, and 27% for the control group. The soft biomechanical orthoses were tolerated better by the recruits than were the semirigid devices. Among trainees at high risk for stress fractures, prophylactic use of custom made biomechanical orthoses may be warranted.

Tuberous sclerosis complex and Wolff-Parkinson-White syndrome

This report highlights the association between tuberous sclerosis and Wolff-Parkinson-White syndrome. Ten patients with concurrent diagnoses of Wolff-Parkinson-White syndrome and tuberous sclerosis were identified. Wolff-Parkinson-White syndrome presented early in life, nine cases being diagnosed in the first year. Eight of the 10 cases were male. In eight cases, the syndrome was associated with supraventricular tachycardias, and in nine with cardiac rhabdomyomata. One child died from cardiac failure secondary to obstruction of the left ventricular outflow tract by a rhabdomyoma. Five of nine survivors showed resolution of Wolff-Parkinson-White syndrome on follow up. The accessory pathway was localised in nine patients from surface electrocardiograms: six children had left sided pathways and three had right sided pathways.

Magic-angle spinning and solution 13C nuclear magnetic resonance studies of medium- and long-chain cholesteryl esters in model bilayers

The incorporation of cholesteryl esters (CE) with saturated acyl chains into the lamellar structure of phospholipids was studied by 13C nuclear magnetic resonance (NMR) spectroscopy. The CE (octanoate, palmitate, and stearate) were 13C-enriched in the carboxyl carbon to enhance the signals of the small amounts of bilayer-incorporated CE. Magic-angle spinning (MAS) NMR was used to detect signals in unsonicated multilamellar phosphatidylcholine (PC), and solution NMR was used to detect signals in PC small unilamellar vesicles (SUV). All CE showed a carbonyl peak reflecting localization of the carbonyl at the aqueous interface (Hamilton & Small, 1982). The maximal incorporation decreased with chain length, from 5 mol % for octanoate to 1.4 mol % for stearate in multilayers; the stearate ester had a solubility slightly lower than that of cholesteryl oleate (2 mol %). The maximal incorporation of a specific CE was 1.2-2.0 times higher in SUV than in multilayers. Cholesteryl oleate did not prevent solubilization of cholesteryl stearate in the PC interface. CE in excess of the solubility maximum in multilayer samples was shown to be crystalline at 35 degrees C by MAS NMR; thus, in the bilayer the CE gained considerable mobility compared to its mobility in its pure bulk phase at body temperature. Furthermore, CE with two saturated chains were not distinguishable from esters with an unsaturated chain with respect to mobility and position in the interface. These fundamental interfacial properties assure utilization of CE with common dietary fatty acyl chains.

Seizure activity causing loss of cardiac output after a Fontan operation

After a Fontan operation pulmonary blood flow is heavily dependent on respiration. Two patients with a Fontan and normal sinus rhythm developed episodes of collapse with loss of cardiac output secondary to the tonic phase of an epileptic fit. The forced expiratory effort during the tonic phase severely compromised systemic venous return and led to collapse due to loss of cardiac output.

Rotational resonance NMR determination of intra- and intermolecular distance constraints in dipalmitoylphosphatidylcholine bilayers

Rotational resonance (RR) NMR methods are explored for determining intramolecular and intermolecular distances between 13C-labeled sites in membrane bilayers. Specific 13C labels have been incorporated into dipalmitoylphosphatidylcholine (DPPC) and a hydrophobic peptide corresponding to the transmembrane domain of human glycophorin A. The exchange of magnetization between these labels in the RR NMR experiment can be related to their internuclear separation. Intramolecular magnetization exchange rates have been measured between 13C labels incorporated at the 1-position of the sn-1 acyl chain (1-[1-13C]) and the 2-position of the sn-2 acyl chain (2-[2-13C]) of DPPC. These positions are 5.3-5.5 A apart in the crystal structure of dimyristoylphosphatidylcholine (DMPC), but are estimated to be 4.5-5.0 A apart in DPPC below the subphase transition temperature. These results are consistent with a smaller axial displacement between the sn-1 and sn-2 acyl chains than the approximately 3.6-A displacement observed in the DMPC crystal structure. Intermolecular magnetization transfer rates have been measured between 1,2-[2-13C]DPPC and 2-[1,13C]DPPC and between 1,2-[1-13C]DPPC and 2-[2-13C]DPPC. In addition, intermolecular magnetization exchange rates have been measured between 1,2-[2-13C]DPPC and the 13C-OH position of Y93 in the glycophorin transmembrane domain. These intermolecular distance measurements demonstrate that the relative orientation and location of membrane lipids and peptides can be established using RR NMR methods.

Phase behavior of mixtures of DPPC and POPG

The phase relation of dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) has been determined by measurement of the endothermic transitions of mixtures of DPPC and POPG in 100 mM NaCl, 50 mM PIPES (pH 7.0). With the use of differential scanning calorimetry, the gel-liquid crystalline phase transitions of pure POPG and DPPC were estimated to be 274 K and 315.8 K, respectively. With mixtures, there was considerable broadening of the endotherms, but there was no evidence of immiscibility. At high and low mole fractions of DPPC, the observed transition regions are not different from that calculated assuming ideal behavior. However in the central region of the phase diagram, there were deviations from both the ideal liquidus and solidus curves. The chemical shift anisotropy of the 13C-labelled carbonyl carbon of pure DPPC was determined as a function of temperature. At 298 K, a broad peak characteristic of axially symmetric motional averaging of the shielding tensor was observed. At a temperature of 300 K, a narrow peak at 173 ppm was superimposed upon the broad peak. The magnitude of the narrow resonance increased with temperature over the range of 300 to 315 K with the spectrum obtained at the latter point almost completely devoid of any broad features. Spectra obtained with a 9:1 mole ratio of DPPC/POPG was very similar to that obtained with pure DPPC. However, with increasing amounts of POPG, both the temperature at which the narrow resonance appeared and the temperature at which only a narrow resonance was observed were reduced. Over the range of 0 to 50 mol % POPG, there was no major change in the width or shape of the spectra which contained only a broad or narrow resonance. Also for mol % of POPG of 20% and less, there was agreement between the temperature at which only the narrow component was observed and the completion of the main phase transition based on the DSC scans. However, at the two higher mol % of 33 and 50%, the temperature at which only the narrow component was observed was lower than the temperature established for the completion of the main phase transition.

Interfacial conformation of dipalmitoylglycerol and dipalmitoylphosphatidylcholine in phospholipid bilayers

Diacylglycerols are minor constituents of membrane lipids, yet are essential in the activation and membrane association of protein kinase C. Solid-state 13C NMR experiments have been used to characterize the orientation of the glycerol backbone of dipalmitoylglycerol (DPG) and dipalmitoylphosphatidylcholine (DPPC) in egg phosphatidylcholine (PC) bilayers. The 13C NMR spectra of both DPG and DPPC specifically 13C-labeled at the sn-2 chain carbonyl exhibit a single narrow resonance (approximately 2 ppm) in liquid-crystalline egg PC bilayers. In contrast, specific 13C-labeling of both the sn-1 and sn-2 chain carbonyls results in an additional broad component (24-32 ppm) with an axially symmetric line shape. These data reveal that DPG has a distinct motionally-averaged structure in PC bilayers that is similar to that of DPPC and is not significantly affected by the absence of the large polar PC headgroup. The NMR line shapes are roughly consistent with the results of previous FTIR and NMR studies that indicate the sn-1 chain extends from the C1 carbon of the glycerol backbone into the hydrophobic interior of the bilayer, while the sn-2 chain first extends parallel to the bilayer surface and incorporates a bend at the ester linkage in order to keep the sn-1 and sn-2 chains parallel. However, the data suggest that the time-averaged orientation of the glycerol backbone is tilted from the bilayer normal, in contrast to the nearly parallel orientation observed in the crystal structures of phosphatidylcholines and phosphatidylethanolamines or the perpendicular orientation observed in the crystal structures of diacylglycerols.

Low-temperature 2H NMR spectroscopy of phospholipid bilayers containing docosahexaenoyl (22:6 omega 3) chains

Polyunsaturated fatty acids are widely distributed components of biological membranes and are believed to be involved in many biological functions. However, the mechanisms by which they act on a molecular level are not understood. To further investigate the unique properties of omega 3 polyunsaturated phospholipid bilayers, deuterium nuclear magnetic resonance (2H NMR) studies have been made of the liquid-crystalline (L alpha) and gel phases of a homologous series of mixed-chain phosphatidylcholines containing docosahexaenoic acid: (per-2H-n:0)(22:6)PC, where n = 12, 14, 16, and 18. The moments of the 2H NMR lineshapes have been evaluated, and from these the warming and cooling main phase transition temperatures were determined. The transition temperatures of the mixed-chain series were found to be significantly lower than those of the corresponding lipids in the disaturated series, di(per-2H-n:0)PC, with hystereses ranging from 2 to 14 degrees C. Distinct effects of the docosahexaenoyl chain on bilayer order were found, though these effects varied across the mixed-chain series. In evaluating the moment data, an empirical method for normalizing the moments with respect to differences in temperature was applied, in addition to using the reduced temperature method. For the systems studied here, the method of normalization had no significant effect on the interpretation of the moment data.

Thermotropic phase properties of the hydroxyceramide/cholesterol system

The interaction of cholesterol with ceramides containing alpha-hydroxy fatty acyl chains (hydroxyceramides) has been studied as a foundation for characterizing the lipid bilayers of the stratum corneum. A relatively large quantity of cerebrosides was obtained from bovine brain and converted to ceramides through removal of the carbohydrate side chain. The ceramides were separated based on the absence or presence of hydroxy fatty acyl chains. The lyophilized hydroxyceramides showed a broad melting region at 92 degrees C. Hydroxyceramides dispersed in water produced a relatively narrow, thermotropic transition at 75 degrees C. The effect of cholesterol on this thermotropic phase transition of hydroxyceramides was determined by differential scanning calorimetry. With respect to the main transition, cholesterol caused a broadening of the phase transition at relatively low levels as well as a decrease in the peak transition temperature. The presence of cholesterol at levels in excess of 7 wt% gave rise to an additional low-temperature transition at 55 degrees C. Upon immediate rescanning, this transition was exothermic, but with increasing incubation time the area under the excess heat capacity curve as a function of temperature became smaller. After two days or more, the transition observed was endothermic. At cholesterol levels between 40 and 50 wt%, multiple peaks were observed. From comparisons with related systems, the cooperative thermal transitions of hydroxyceramides with cholesterol are suggested to result from changes in hydrogen bonding or be due to phase separation. The composition of isolated brain ceramides is being compared with that reported for the stratum corneum.

The effect of lung surfactant apolipoproteins B/C on the chemical shift anisotropy of sn-2-[1-13C]dipalmitoylphosphatidylcholine

Nuclear magnetic resonance spectroscopy has been used to investigate the effect of the lung surfactant apolipoproteins B/C on dipalmitoylphosphatidylcholine to address the mechanism by which the adsorption rate of phospholipids from the bulk to the air/water interface is enhanced. Apolipoproteins B/C were isolated from bovine lung and separated from associated lipids by lipophilic Sephadex column chromatography. Amino acid analysis indicated the presence of both apolipoproteins B and C. The 13C chemical shift anisotropy of DPPC was determined as a function of temperature. Previous workers (Wittebort et al., Biochemistry, 20 (1981) 3487-3502) have concluded that the observed magnitude of the chemical shift anisotropy of the carbonyl group of the sn-2 acyl chain in pure DPPC is a result of rapid rotation about an axis along the length of the phospholipid both in the gel and liquid crystalline state. The orientation of the carbonyl group with respect to the axis of diffusion, however, undergoes an approximately 25-30 degrees shift in passage from the gel to liquid crystalline state, with the intermediate, rippled (P beta') state composed of an exchange between these two orientations. The presence of physiological concentrations SP-B/C reduced the width of the anisotropy of DPPC below but had no effect on lipids above the main phase transition temperature. This suggests that SP-B/C has a general effect on the entire assembly of lipids. The temperature of the onset of the orientational change is lowered indicating a portion of the lipids are affected by the lung surfactant apolipoproteins.

Uvulopalatopharyngoplasty as a treatment for snoring

Uvulopalatopharyngoplaty was performed in 18 consecutive patients (15 men and three women; mean +/- standard deviation [SD] age, 46.3 +/- 7.5 years) who presented for the treatment of heavy habitual snoring. No attempt was made to select patients who were ideal anatomically for palatal modification. The loudness of snoring was measured during sleep by integrating the output of a calibrated microphone. An assessment before operation showed that nine patients had obstructive sleep apnoea; four patients had an apnoea index of greater than or equal to 25 apnoeas per hour. The patients were overweight and consumed, on average, 38 g of alcohol per day, but these variables did not change after the operation. The postoperative assessment was performed 138 +/- 44 days after uvulopalatopharyngoplasty. Fourteen patients showed a reduction in the loudness of their snoring, although snoring was abolished in one patient only (average snoring loudness in arbitrary units/min of sleep, 2.8 +/- 2.1 before operation compared with 1.4 +/- 1.5 units/min of sleep after the operation; P less than 0.05. The loudest snore in arbitrary units measured 7.1 +/- 3.3 units compared with 4.8 +/- 3.3 units, respectively; P less than 0.05). The percentage of the sleep time that was spent at an arterial oxygen saturation of less than 90% was reduced after uvulopalatopharyngoplasty (28% +/- 32% of total sleep time compared with 17% +/- 24% of total sleep time, respectively; P less than 0.05). There was no change in the apnoea index. The diastolic blood pressure was lower at the postoperative assessment (94 +/- 11 mmHg compared with 87 +/- 8 mmHg; P less than 0.05); six of 10 subjects whose diastolic blood pressures were greater than or equal to 95 mmHg before the operation had a diastolic blood pressure of less than 95 mmHg after uvulopalatopharyngoplasty (P less than 0.02). Computed tomographic scans showed an increase in the upper airway cross-sectional area at 3 cm and 4 cm above the hyoid bone after uvulopalatopharyngoplasty (P less than 0.05). We conclude that uvulopalatopharyngoplasty is an effective treatment for habitual, heavy snoring in many patients, but it is not the treatment of choice for patients with clinically-significant obstructive sleep apnoea.

Lipid-protein interactions mediate the photochemical function of rhodopsin

We have investigated the molecular features of recombinant membranes that are necessary for the photochemical function of rhodopsin. The magnitude of the metarhodopsin I to metarhodopsin II phototransient following a 25% +/- 3% bleaching flash was used as a criterion of photochemical activity at 28 degrees C and pH 7.0. Nativelike activity of rhodopsin can be reconstituted with an extract of total lipids from rod outer segment membranes, demonstrating that the protein is minimally perturbed by the reconstitution protocol. Rhodopsin photochemical activity is enhanced by phosphatidylethanolamine head groups and docosahexaenoyl (22:6 omega 3) acyl chains. An equimolar mixture of phosphatidylethanolamine and phosphatidylcholine containing 50 mol% docosahexaenoyl chains results in optimal photochemical function. These results suggest the importance of both the head-group and acyl chain composition of the rod outer segment lipids in the visual process. The extracted rod lipids and those lipid mixtures favoring the conformational change from metarhodopsin I to II can undergo lamellar (L alpha) to inverted hexagonal (HII) phase transitions near physiological temperature. Interaction of rhodopsin with membrane lipids close to a L alpha to HII (or cubic) phase boundary may thus lead to properties which influence the energetics of conformational states of the protein linked to visual function.

Magnetic circular dichroism studies on microsomal aryl hydrocarbon hydroxylase: comparison with cytochrome b-5 and cytochrome P-450-cam

Magnetic circular dichroism spectra are reported for the visible and near ultraviolet spectral regions of liver microsomes from dimethylbenzanthracene-treated rats. The sequential addition of NADH, dithionite, and carbon monoxide enables us to determine contributions to the magnetic circular dichroism by cytochromes b-5 and P-450, which dominate the spectra. The magnetic circular dichroism of the microsomal preparation is compared with that of purified oxidized and reduced cytochrome -b-5 from pig liver and with the camphor-complexed and camphor-free oxidized, reduced, and reduced carbonmonoxy cytochrome P-450-cam from Pseudomonas putida. The magnetic circular dichroism spectra of the membrane bound cytochrome -b-5 are similar to those of the purified protein, indicating that little or no alteration in the environment of the heme occurs during the isolation procedure. The soluble bacterial cytochrome P-450 also appears to be a suitable model for microsomal P-450, although differences in the magnetic circular dichroism intensity are observed for the two enzymes. No effect of dimethylbenzanthracene on the magnetic circular dichroism spectra of induced compared to control rat microsomes could be observed.