Free radical formation in infants: the effect of critical illness, parenteral nutrition, and enteral feeding

BACKGROUND/PURPOSE

An increase in free radical activity has been observed in patients suffering from a variety of illnesses and has been correlated with disease severity. Free radical production is increased by the administration of total parenteral nutrition (TPN) and may be linked to its adverse effects. Some of the complications of TPN can be ameliorated by partial enteral feeding. The aim of this study was to investigate free radical activity during critical illness and during the administration of parenteral nutrition.

METHODS

Three groups of surgical infants were studied: (1) control infants (n = 8) before minor surgery, (2) stable infants on the ward recovering from a major operation (n = 24), (3) critically ill infants in the neonatal intensive care unit (NICU, n = 28). Fourteen patients in the ward and 17 patients in NICU were receiving parenteral nutrition. Of the 31 patients on TPN, 9 were also receiving minimal enteral feeding (3% to 24% of total calorie intake). Plasma malondialdehyde (MDA), an index of free radical activity, was measured in all 60 infants. The Paediatric Risk of Mortality (PRISM) score was obtained on NICU patients. The cytokines tumor necrosis factor (TNF-alpha) and interleukin 6 (IL-6) were measured in 25 patients.

RESULTS

Plasma MDA was significantly higher in (1) the stable patients on the ward compared with control patients (P < .001) and (2) patients in NICU compared with stable patients in the ward (P < .001). Parenteral nutrition was associated with higher levels of plasma MDA both in stable patients in the ward and critically ill infants in NICU. There was no correlation between the PRISM score and MDA. In patients not receiving TPN there is a correlation between MDA and TNF-alpha (r = 0.54, P = .02) and between MDA and IL-6 (r = 0.74, P = .001). The level of free radical activity in patients on TPN is not changed by partial enteral feeding.

CONCLUSIONS

Critical illness causes a rise in free radical production. Parenteral nutrition causes a significant elevation in free radical activity in both stable infants in the ward and critically ill infants in NICU. The addition of minimal enteral feeding to parenteral nutrition does not reduce free radical activity. We hypothesize that the parenteral nutrition solution directly initiates free radical production.

A novel leukocyte adhesion deficiency caused by expressed but nonfunctional beta2 integrins Mac-1 and LFA-1

In the leukocyte adhesion deficiency (LAD)-1 syndrome, there is diminished expression of beta2(CD18) integrins. This is caused by lesions in the beta2-subunit gene and gives rise to recurrent bacterial infections, impaired pus formation, and poor wound healing. We describe a patient with clinical features compatible with a moderately severe phenotype of LAD-1 but who expresses the beta2 integrins lymphocyte function- associated molecule (LFA)-1 and Mac-1 at 40%-60% of normal levels. This level of expression should be adequate for normal integrin function, but both the patient's Mac-1 on neutrophils and LFA-1 on T cells failed to bind ligands such as fibrinogen and intercellular adhesion molecule (ICAM)-1, respectively, or to display a beta2-integrin activation epitope after adhesion-inducing stimuli. Unexpectedly, divalent cation treatment induced the patient's T cells to bind to ICAM-2 and ICAM-3. Sequencing of the patient's two CD18 alleles revealed the mutations S138P and G273R. Both mutations are in the beta2-subunit conserved domain, with S138P a putative divalent cation coordinating residue in the metal ion-dependent adhesion site (MIDAS) motif. After K562 cell transfection with alpha subunits, the mutated S138P beta subunit was coexpressed but did not support function, whereas the G273R mutant was not expressed. In summary, the patient described here exhibits failure of the beta2 integrins to function despite adequate levels of cell-surface expression.

Intra-amniotic inflammation in human gastroschisis: possible aetiology of postnatal bowel dysfunction

OBJECTIVE

To assess amniotic fluid for evidence of an inflammatory exudate in association with fetal gastroschisis.

SETTING

University College Hospital, London and Institute of Child Health, London.

SAMPLE

Samples of amniotic fluid in the third trimester from pregnant women with a diagnosis of fetal gastroschisis (n = 10) and from a control group (n = 10) with a normal fetus.

METHODS

Cytological analysis of the fluid was performed. Flow cytometry was performed on the amniotic fluid using antibodies for the myeloid cell antigen CD15, the leucocyte beta integrin CD11b/CD18 and CD3, CD19, CD56 and CD25. Tumour necrosis factor alpha and interleukin-8 levels were assayed in the amniotic fluid.

RESULTS

An acute inflammatory exudate, composed predominantly of neutrophil polymorphs and mononuclear cells, was found in the amniotic fluid in fetal gastroschisis but not in control cases. When amniotic fluid samples from cases of fetal gastroschisis were stained with CD15, analysis by flow cytometry showed a clear positive population. This CD15 population showed markedly elevated levels of CD11b. No distinct population of CD15 positive cells was seen in amniotic fluid samples examined from the control group. No staining was seen with antibodies to CD3, CD19, CD56 or CD25 in amniotic fluid obtained from either group. There was no significant difference between tumour necrosis factor alpha levels measured in the amniotic fluid of cases of fetal gastroschisis (median 102 pg/mL; range 20-340) and those of the control group (140 pg/mL; range 20-548) (P = 0.1). The levels of interleukin-8 were markedly elevated in the amniotic fluid of cases of fetal gastroschisis (median 6320 pg/mL; range 4732-13,800) compared with the control group (median 1738 pg/mL; range 623 2861;) (P < 0.01).

CONCLUSION

Human fetal gastroschisis is associated with an inflammatory exudate in the amniotic fluid which may have implications for postnatal bowel function.

Predictors of early school age outcomes in very low birth weight children

The purpose of this study was to examine predictors of outcome in very low birth weight (< 1500 g) children. The very low birth weight sample consisted of 68 children weighing less than 750 g at birth and 65 children weighing 750 to 1499 g at birth who had been matched to the less than 750 g birth weight children in terms of hospital of birth, age, sex, and race. Mean ages for these two groups were 6.7 and 6.9 years, respectively. Outcomes were measured in terms of tests of cognitive function, neuropsychological abilities, and academic achievement and parent and teacher ratings of child behavior and school performance. A weighted sum of the number of major neonatal medical complications (Neonatal Risk Index) provided a composite measure of biological risk. Social risks were also assessed. Results indicated that the Neonatal Risk Index was the most consistent predictor of outcomes. Even after taking social risks into account, neonatal risk predicted overall cognitive ability and other achievement, neuropsychological, and behavior outcomes. Individual neonatal complications that predicted outcomes included severe cerebral ultrasonographic abnormality, chronic lung disease, necrotizing enterocolitis, and apnea of prematurity. Research and therapy to prevent or reduce neonatal complications and amelioration of social risks are of critical importance in improving outcomes of very low birth weight.

Ageing and social rank effects on the reproductive system of free-ranging yellow baboons (Papio cynocephalus) at Mikumi National Park, Tanzania

Ageing and social status effects on reproductive condition are examined in 106 wild female baboons from 1974 to 1997. The mean duration of each reproductive state (follicular and luteal phase components, pregnancy and lactation) was examined per female, using a repeated measures analysis of variance across each of four age classes (3-6, 7-10, 11-14, and 15-20+ year olds) and dominance rank quartiles. The sex-skin swelling portion of the follicular phase increased whereas the fully swollen portion decreased in duration with advancing age and with low dominance rank. The detumescing portion of the luteal phase increased with advancing age, being most pronounced in lowest ranking females. The number of cycles to conception decreased with age, with no dominance rank effect. However, owing to variation in lactation duration, the interbirth interval was unaffected by age but was shorter in high ranking females. The miscarriage rate was unaffected by age but increased as female rank declined. Age and rank effects became significantly more pronounced in response to a crash in the study population between 1987 and 1993. In conclusion, age- and rank-related reproductive changes in baboons, like those in humans, appear to represent attempts to compensate endocrinologically for accelerated ovarian atresia and increased environmental hardship.

Soluble L-selectin concentration in bronchoalveolar lavage fluid obtained from infants who develop chronic lung disease of prematurity

AIMS

To explore the changes in neutrophil adhesion molecule expression and release into bronchoalveolar lavage fluid (BAL) obtained from infants who developed chronic lung disease (CLD).

METHODS

BAL fluid was obtained from 37 infants: 18 (median gestation 26 weeks, birthweight 835 g) who developed CLD, 12 (29 weeks, 1345 g) with respiratory distress syndrome (RDS) and seven control infants (33 weeks, 2190 g).

RESULTS

Soluble L-selectin (sL-selectin) in BAL fluid from the CLD and non-CLD groups was similar immediately after birth, but in infants who subsequently developed CLD, sL-selectin remained persistently increased (at day 7: CLD 42.6 vs RDS 6.0 ng/ml, p < 0.05; CLD vs controls 1.5 ng/ml; p < 0.05). CD11b/CD18 expression on neutrophils obtained by BAL increased with time to reach a maximum at 17 days of age in infants who developed CLD.

CONCLUSIONS

These results suggest that leucocyte traffic persists in infants who develop CLD and may have an important part to play in the pathogenesis of CLD.

Small volumes of enteral feedings normalise immune function in infants receiving parenteral nutrition

BACKGROUND/PURPOSE

Parenteral nutrition (PN) is associated with a risk of septicaemia. This may be caused by impairment of immune function related to PN. The authors investigated the effects of the addition of enteral feedings to PN on the immune status of human newborn infants.

METHODS

Ten surgical infants (age less than 6 months) requiring PN were studied in two consecutive phases: (A) after 31.1+/-6.0 days (mean +/- SEM) of PN with no enteral feeding (total PN); and (B) after 4.7+/-1.1 days from the addition of small volumes of enteral feeding to PN. Full blood count and liver function tests were not significantly different between phases A and B. A control group (n = 9) of infants receiving a normal enteral diet was also studied. Host bactericidal activity against coagulase-negative staphylococci (CNS) was measured by an in vitro whole blood model. Bacterial killing was measured after a 45-minute bacterial challenge using the Miles-Misra technique. Tumour necrosis factor-alpha (TNF-alpha) was measured by enzyme-linked immunosorbent assay (ELISA) after 2 hours of bacterial challenge.

RESULTS

The lowest level of CNS killing (37.7+/-5.2%), was observed in patients receiving total PN. This increased significantly after the addition of small enteral feeds (52.0+/-4.6%, P < .005) approaching the levels measured in controls (65.1+/-3.4%). TNF-alpha production was low during total PN (1467+/-297 pg/mL) and rose significantly after the addition of minimal enteral feeds (4,661+/-1,311 pg/mL, P < .05). The increase in CNS killing after the addition of small enteral feeds in patients on PN was significantly correlated with the duration of enteral feeding (r = 0.8, P = .006).

CONCLUSIONS

These results indicate that the introduction of small volumes of enteral feed improve the impaired killing of CNS and the abnormal cytokine response observed during total PN. This implies that stimulation of the gastrointestinal tract may modulate immune function in neonates and prevent bacterial infection.

A family clinic--optimising care for HIV infected children and their families

A family clinic providing specialist paediatric and adult medical, testing, counselling, and terminal care services for families living with HIV was set up at a paediatric tertiary care hospital in London in 1991. During the first five years, until April 1996, 185 children from 149 families attended, including 119 infected children, of whom 32 have died. Only 5% of mothers were born in the UK; the rest were born in 24 different countries, the majority in sub-Saharan Africa. Less than a quarter of children were cared for by both parents, 61% by mothers alone, and 11% by guardians or foster parents. Of the adult attendees, 76% were women, and more than half were untested when they first attended the clinic. Provision of a family planning service within the family clinic was initiated as a result of women presenting with unplanned pregnancies. Shared care with local clinics is increasing, but with the complexity around the management of paediatric HIV infection, particularly with regard to antiretroviral treatments, there is need for continued specialist input. Coordination among specialist and locally based family services is required to provide flexible, accessible, and up to date care for families living with HIV infection in London.

Biological activity of IL-4 and IL-13 on human endothelial cells: functional evidence that both cytokines act through the same receptor

The cytokine IL-4 has unique effects on human endothelial cells. It specifically increases expression of vascular cell adhesion molecule (VCAM)-1 promoting adhesion of lymphocytes but not neutrophils, and causes profound effects on the morphology of endothelial monolayers characterized by formation of cell clusters and the appearance of holes in the cultured monolayer. In this study we show that the effects of IL-13 on human umbilical vein endothelial cells (HUVEC) are indistinguishable from those of IL-4. Both cytokines induce the same morphological changes in cultured HUVEC monolayers which are distinct from any other cytokine. In addition, IL-13 and IL-4 stimulate comparable levels of VCAM-1 expression with similar time kinetics, but at doses 10-fold less than those required for B cell activation and proliferation. Using a combination of mutant IL-4 antagonists and mAb to the IL-4R alpha chain (CD124), we show that expression of IL-4R alpha is essential for HUVEC responses to both IL-4 and IL-13, consistent with this receptor subunit being a component of the receptors for both cytokines. In contrast, the common gamma chain (gamma c), which is a component of the classical IL-4 receptor, was not detected on endothelial cells by flow cytometry or immunogold histochemistry. In addition, RT-PCR showed extremely low or absent gamma c mRNA, consistent with the absence of detectable surface protein. These results strongly suggest that the cytokines IL-4 and IL-13 are both important in modulating endothelial cell function, and may act through a single receptor complex on human endothelial cells that includes the IL-4R alpha chain but not the gamma c chain.

Control of lymphocyte adhesion to brain and aortic endothelium: ICAM-1, VCAM-1 and negative charge

Lymphocyte adhesion to CNS endothelium is low by comparison with non-CNS endothelium. It has been proposed that this could be due to the high surface charge of brain endothelium, or a low constitutive expression of adhesion molecules. In this study we compared the influence of these factors on lymphocyte adhesion to BEC and aortic endothelium (AEC) in culture. Brain endothelium expresses very low levels of VCAM-1, and lower levels of ICAM-1 than aortic endothelium. The negative charge differed between the endothelia, but this had a minimal effect on lymphocyte adhesion. The anionic sites were, however, more stable on brain endothelium, remaining unchanged after endothelial cell activation with cytokines, while redistribution was observed on cytokine-activated aortic endothelium.

Intestinal glycosaminoglycans in neonatal necrotizing enterocolitis

Advanced necrotizing enterocolitis (NEC) is a common neonatal surgical emergency of unknown aetiology. Despite improvements in the prognosis, the aggressive form of the disease is still associated with significant rates of morbidity and mortality. Recent evidence indicates that the extracellular matrix (ECM) is important in gastrointestinal development and glycosaminoglycans, major constituents of the ECM, are attenuated in inflammatory bowel disease. The hypothesis of this study was that changes in the nature and distribution of intestinal glycosaminoglycans occur in NEC. The distribution and nature of glycosaminoglycans were determined in 31 sections of well preserved resection margins and severely diseased bowel from eight neonates affected by NEC. An established histological method of glycosaminoglycans analysis using cationic gold with silver enhancement was employed in this study. The identity of specific glycosaminoglycans was also elucidated using a combination of cationic gold staining and glycanase digestion. In well preserved tissue, staining was seen throughout the full thickness of the bowel. The epithelial basement membrane and basolateral surfaces, lamina propria and submucosa were particularly prominent. In moderate disease, patchy loss of anionic sites was frequently observed with glycosaminoglycans-deficient areas adjacent to intact sites. In severe NEC, there was extensive loss of glycosaminoglycans in most of the sections examined. Glycanase analysis revealed that the glycosaminoglycans in well preserved tissue were sensitive to chondroitinase ABC and only vascular sites were sensitive to heparinase III. The consequences of glycosaminoglycans loss in NEC as demonstrated in this study are not known but modulation of gastrointestinal glycosaminoglycans could be important in the pathogenesis of NEC and may underlie some of the clinical manifestations of this condition.

Effects of inhibition of complement activation using recombinant soluble complement receptor 1 on neutrophil CD11b/CD18 and L-selectin expression and release of interleukin-8 and elastase in simulated cardiopulmonary bypass

The inflammatory response to cardiopulmonary bypass includes activation of complement and induction of several neutrophil activation pathways. A recombinant soluble form of complement receptor 1 was used as a specific inhibitor of complement activation in simulated cardiopulmonary bypass circuits. Substantial complement activation was observed in these circuits with progressive accumulation of both plasma C3a and terminal complement complex. Soluble complement receptor 1 resulted in a significant reduction in C3a levels (p < 0.01) but did not inhibit terminal complement complex generation. A marked rise in neutrophil CD11b/CD18 expression, simultaneous loss of L-selectin expression, and a progressive accumulation of plasma elastase-alpha 1-antitrypsin occurred and were not affected by soluble complement receptor. However, generation of interleukin-8 in the circuits was inhibited (p < 0.05) by pretreatment with soluble complement receptor. These data suggest that changes in neutrophil activation seen during cardiopulmonary bypass may not be induced directly by anaphylatoxin generation.

Assessment of the effect of candidate anti-inflammatory treatments on the interaction between meningococci and inflammatory cells in vitro in a whole blood model

A wide range of immunomodulating agents are now available which may be of benefit in reducing inflammatory cell activation in meningococcal sepsis. In order to facilitate selection of candidate anti-inflammatory agents for clinical trials, we have used an in vitro whole blood model to evaluate the effects on meningococcal induced neutrophil and monocyte activation, of dexamethasone, prostacyclin, pentoxifylline and a human IgM anti-lipid A monoclonal antibody (HA-1A). Known concentrations of heat and penicillin killed meningococci were added to whole blood and the time course of cellular activation was determined. Using elastase alpha 1-antitrypsin (elastase-alpha 1-AT) and TNF alpha production as markers of neutrophil and monocyte activation respectively, plasma levels of elastase-alpha 1-AT and TNF alpha were found to increase in a dose-dependent manner. Elastase-alpha 1-AT was detected early, with most release occurring between 15-30 min whereas TNF alpha was detected later, between 120-180 min. Dexamethasone, prostacyclin and pentoxifylline caused a dose-dependent inhibition of TNF alpha release but had no effect on elastase release. HA-1A had no effect on either TNF alpha or elastase release. This model may be useful in determining the sequence of inflammatory cell activation and in selecting candidate anti-inflammatory agents for evaluation in clinical trials.

Achievement in children with birth weights less than 750 grams with normal cognitive abilities: evidence for specific learning disabilities

Examined achievement, behavior, and neuropsychological outcomes at early school age in a regional population of children < 750-g birth weight who were neurologically intact and who scored in the broad average range on a test of cognitive ability. Comparison groups included children of birth weight 750-1,499 g and children born at full-term. The children < 750 g performed more poorly than the higher birth weight groups on tests of math, even after adjusting for group differences in cognitive ability. Corresponding group differences were found in language, perceptual motor, and attentional skills, but not in behavior outcomes. Findings document specific weaknesses in achievement and neuropsychological skills in children < 750 g birth weight and support the need for early identification and special education interventions.

The hepatitis B virus HBx protein is a dual specificity cytoplasmic activator of Ras and nuclear activator of transcription factors

The HBx protein of hepatitis B virus (HBV) is a transcriptional activator that is required for infection and may play an important role in HBV-associated hepatocarcinogenesis. Recently, we and others have shown that HBx stimulates the Ras-Raf-MAP kinase cascade, which leads to enhanced cell proliferation and the activation of transcription factors AP-1 and NF-kappa B. Other studies have shown that HBx can activate transcription by interacting directly with nuclear components of the transcription machinery. Therefore we examined the basis for the different reported activities of HBx. Here, we show that HBx is a complex protein, displaying independent activities in different intracellular locations. The intracellular distribution of HBx protein was first investigated using scanning confocal laser immunomicroscopy and by genetic studies. Our work has established that HBx expressed in cultured cells is found authentically in both the cytoplasm and the nucleus. HBx is not strongly associated with any intracellular structures, but some preferential accumulation was observed near the cell surface. Next, HBx variants were constructed containing a functional or mutant nuclear localization sequence. We show that when HBx is engineered to relocate exclusively to the nucleus, it no longer activates the Ras-Raf-MAP kinase cascade, nor does it activate transcription factors AP-1 and NF-kappa B. Surprisingly, nuclear HBx fully retains the ability to stimulate HBV enhancer I, which is activated independently of the Ras and protein kinase C pathways. Therefore HBx protein stimulates signal transduction pathways in the cytoplasm and transactivates transcription elements in the nucleus. Furthermore, SV40 T antigen is shown to induce the nuclear sequestration of HBx protein and to block its activation of NF-kappa B, demonstrating that HBx is regulated by proteins that alter its intracellular distribution. The conflicting functions of HBx protein in viral infection and possibly carcinoma may involve the regulation of its differential distribution in the cell.

Distribution and analysis of surface charge on brain endothelium in vitro and in situ

Vascular endothelial cells are associated with a number of anionic molecules. These anions are important in endothelial function, particularly in regulating permeability, haemostasis and cellular traffic. To explore the nature and distribution of anions on the brain endothelial cell (BEC) surface, we have examined rat brain endothelium in culture, and in situ. The anionic sites were probed with cationic colloidal gold and cationised ferritin, and visualised by light microscopy. Additionally we compared the distribution of the anionic sites on BEC with that present on other endothelial cell types in culture. The predominant anion detected on BEC was heparan sulphate (HS). This was distributed throughout the cell membrane, but was most densely associated with intercellular junctions. This pattern was distinct from the anionic locations observed in endothelia from aorta and epididymal fat microvessels. The distribution of anions was dependent on the age of cultured cells, with only minimal levels of HS seen at the periphery of younger cells. The nature and distribution of negative charge was different in situ. Here, sialic acid was the major surface anion, with only a small contribution from HS. The significance of these findings are discussed in relation to endothelial function in normal tissue and in pathological conditions.

Familial disseminated atypical mycobacterial infection in childhood: a human mycobacterial susceptibility gene?

Inherited defects in specific components of the immune system have provided many clues to the immunological mechanisms underlying resistance to microbial infection. We report a familial immune defect predisposing to disseminated atypical mycobacterial infection in childhood. 6 children with disseminated atypical mycobacterial infection and no recognised form of immunodeficency were identified. Four, including two brothers, come from a village in Malta, and two are brothers of Greek Cypriot origin. They presented with fever, weight loss, lymphadenopathy, and hepatosplenomegaly. They had anaemia and an acute phase response. A range of different mycobacteria (Mycobacterium fortuitum, M chelonei, and four strains of M avium intracellulare complex) were isolated. Treatment with multiple antibiotics failed to eradicate the infection, although treatment with gamma interferon was associated with improvement. Three have died and the surviving children have chronic infection. Tumour necrosis factor-alpha production in response to endotoxin and gamma-interferon was found to be defective in affected patients and their parents. T-cell proliferative responses to mycobacterial and recall antigens were reduced in parents of affected children and gamma-interferon production was diminished in the affected patients and their parents. Clinical and immunological features suggest that these patients are phenotypically similar to Lsh/Ity/Bcg susceptible mice. Understanding of this defect may provide insights into the mechanisms responsible for susceptibility to mycobacteria.