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N Klein

Publications and source records attributed to N Klein.

At least 73 records · Page 4Linked to original sources
PubMed1999

A study of the variability seen in the international normalized ratio obtained using different sensitivity thromboplastin reagents on different instrument types.

We performed an extensive study to check international normalized ratio (INR) recovery using three different rabbit thromboplastin reagents of different sensitivities [international sensitivity index (ISI) circa 1.1, 1.3 and 2.0] on two different instrument types. Both instrument types used an optical end point: one nephelometric at 660 nm, one photometric at 880 nm. Each thromboplastin reagent in the study had an instrument-specific ISI value assigned to it by the reagent manufacturer. Samples obtained from stable orally anticoagulated patients were tested on four different instruments of each type with the three different sensitivity reagents. Excellent correlation between INR values was seen between all results (r values between 0.97 and 0.99). Regression analysis gave slopes between 0.92 and 1.07, and a maximum deviation of intercept from zero of 0.21. Variations in CV of less than 2% were seen within each instrument type. This study shows that if instrument-specific ISI values are used, comparable INR values can be obtained using reagents of different sensitivity on multiple instruments of the same or different types. This study demonstrates the validity of the INR/ISI system.

Adult↗
PubMed1999

Endothelial adhesion molecule expression and its inhibition by recombinant bactericidal/permeability-increasing protein are influenced by the capsulation and lipooligosaccharide structure of Neisseria meningitidis.

Vascular endothelial injury is responsible for many of the clinical manifestations of severe meningococcal disease. Binding and migration of activated host inflammatory cells is a central process in vascular damage. The expression and function of adhesion molecules regulate interactions between leukocytes and endothelial cells. Little is known about how meningococci directly influence these receptors. In this study we have explored the effect of Neisseria meningitidis on endothelial adhesion molecule expression and found this organism to be a potent inducer of the adhesion molecules CD62E, ICAM-1, and VCAM-1. Exposure of endothelium to a serogroup B strain of Neisseria meningitidis, B1940, and a range of isogenic mutants revealed that lipooligosaccharide (LOS) structure and capsulation influence the expression of adhesion molecules. Following only a brief exposure (15 min) to the bacteria, there were large differences in the capacity of the different mutants to induce vascular cell adhesion molecules, with the unencapsulated and truncated LOS strains being most potent (P < 0.05). Furthermore, the pattern of cell adhesion molecule expression was different with purified endotoxin from that with intact bacteria. Meningococci were more potent stimuli of CD62E expression than was endotoxin, whereas endotoxin was at least as effective as meningococci in inducing ICAM-1 and VCAM-1. The effect of bactericidal/permeability increasing protein (rBPI(21)), an antibacterial molecule with antiendotoxin properties, was also dependent on LOS structure. The strains which possessed a truncated or nonsialylated LOS, whether capsulated or not, were more sensitive to the inhibitory effects of rBPI(21). These findings could have important implications for the use of antiendotoxin therapy in meningococcal disease.

Anti-Bacterial Agents↗
PubMed1999

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.

Adolescent↗
PubMed1999

Calcium-induced stabilization of AU-rich short-lived mRNAs is a common default response.

The AU-rich element (AUUUA)n, found in the 3' noncoding region of many short-lived cytokine and proto-oncogene mRNAs, is sufficient to specifically target these mRNAs for rapid degradation in mammalian cells. The mechanism by which the AU-rich element promotes rapid mRNA decay is not known. Previous studies have shown that release of intracellular stored calcium by ionophore treatment of thymocytes and mast cells inhibits the rapid turnover of AU-rich interleukin mRNAs. Increased cytoplasmic half-life of interleukin mRNAs was linked to calcium-induced activation of the N-terminal c-Jun kinase. In this report we have characterized the calcium-induced stabilization of AU-rich mRNAs. We show that calcium induces stabilization of mRNAs with canonical AU-rich elements in all cell types tested. These results indicate that short-lived mRNA stabilization by calcium is not unique to immune cells nor interleukin mRNAs, but is a widespread default response that includes generic AU-rich mRNAs. Stabilization is shown to be rapid but transient, and to act without altering nuclear transcription or cytoplasmic translation rates. These data support the view that calcium release likely stabilizes short-lived mRNAs by altering trans-acting decay factors that promote AU-rich mRNA turnover.

Adenine↗
PubMed1999

Immunodeficiency and the gut: clues to the role of the immune system in gastrointestinal disease.

Gastrointestinal disease occurs in a high proportion of patients with primary immunodeficiency. While enteric infections are responsible for the gastrointestinal pathology in many individuals, it is now clear that infection alone is not sufficient to explain the gut pathology found in many immunodeficiencies. This article focuses on recent developments in this field and highlights the insights gained in understanding the complex relationship between immunodeficiency and the gut.

Carrier Proteins↗
PubMed1998

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.

Bacteremia↗
PubMed1998

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.

Achievement↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Analysis of Variance↗
PubMed1997

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.

Adolescent↗
PubMed1996

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.

Colon↗
PubMed1996

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.

Anti-Inflammatory Agents↗
PubMed1996

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.

Animals↗
PubMed1996

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.

CD11 Antigens↗
PubMed1996

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.

Antibodies, Monoclonal↗