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Biomedical subjects

N Klein

Publications and source records attributed to N Klein.

At least 91 records · Page 5Linked to original sources
PubMed1995

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.

Amino Acid Sequence↗
PubMed1995

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.

Adult↗
PubMed1995

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.

Animals↗
PubMed1995

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.

Achievement↗
PubMed1994

The role of platelet-derived growth factor production by tumor-associated macrophages in tumor stroma formation in lung cancer.

Lung cancer is the most common cause of death by cancer in developed countries. Since a tumor cannot develop without the parallel expansion of a tumor stroma, a better understanding of its formation could lead to new therapeutical approaches. In this respect, since platelet-derived growth-factor (PDGF) is a chemotactic and growth factor for mesenchymal and endothelial cells, lung tumors of patients undergoing surgery for non-small cell lung cancer were evaluated for their replication rate using iododeoxyuridine incorporation, and for the expression of PDGF genes and the presence of PDGF A and B chains and of PDGF receptor alpha and beta subunits. This observation demonstrates that: (a) tumor cells and stroma mesenchymal cells, but not tumor-associated macrophages, display a high replication rate; (b) 1 of 3 tumors are characterized by cancer cells expressing the genes for PDGF A and/or B chains, while 1 of 2 tumors are composed of tumor cells presenting PDGF receptors alpha and beta subunits on their surface, and in only 1 of 6 tumors, tumor cells coexpress PDGF and its receptor; (c) in almost all tumors, tumor-associated macrophages express PDGF A and/or B chain genes; (d) mesenchymal cells, as well as endothelial cells, do not express PDGF A and B chain genes but do express PDGF receptor alpha and beta subunits; and (e) an ongoing active process was suggested in the periphery of the tumor by the simultaneous strong expression of PDGF A and B chain genes by tumor-associated macrophages and the high replication rate of mesenchymal and endothelial cells in the same area. Thus, PDGF is likely to have a limited autocrine role in tumor cell replication but is a potential player, in a paracrine fashion, in tumor stroma development.

Carcinoma, Non-Small-Cell Lung↗
PubMed1994

School-age outcomes in children with birth weights under 750 g.

BACKGROUND: Since the mid-1980s, increasing numbers of children with birth weights under 750 g have survived to school age. METHODS: We matched a regional cohort of 68 surviving children born from 1982 through 1986 with birth weights under 750 g (mean, 670 g; gestational age, 25.7 weeks) with 65 children weighting 750 to 1499 g at birth and 61 children born at term. Growth, neurosensory status, and functioning at school age in the three groups were compared. Associations of biologic and social risk factors with major developmental outcomes were examined by means of logistic-regression analyses. RESULTS: Children with birth weights under 750 g were inferior to both comparison groups in cognitive ability, psychomotor skills, and academic achievement. They had poorer social skills and adaptive behavior and more behavioral and attention problems. The mean (+/- SD) Mental Processing Composite score for the cohort was 87 +/- 15, as compared with 93 +/- 14 for children with birth weights of 750 to 1499 g and 100 +/- 13 for children born at term (P < 0.001). The rates of mental retardation (IQ < 70) in the three groups were 21, 8, and 2 percent, respectively; the rates of cerebral palsy were 9, 6, and 0 percent; and the rates of severe visual disability were 25, 5, and 2 percent. Major cerebral ultrasonographic abnormalities were associated with mental retardation (odds ratio, 5.4; 95 percent confidence interval, 1.8 to 15.8) and cerebral palsy (odds ratio, 15.2; 95 percent confidence interval, 3.0 to 77.4). Oxygen dependence at 36 weeks was associated with mental retardation (odds ratio, 4.5; 95 percent confidence interval, 1.2 to 10.7) and severe visual disability (odds ratio, 4.3; 95 percent confidence interval, 1.3 to 14.2). Social disadvantage, though associated with several neuropsychological outcomes, was not associated with major developmental impairment. CONCLUSIONS: Children with birth weights under 750 g who survive represent a subgroup of very-low-birth-weight children who are at high risk for neurobehavioral dysfunction and poor school performance.

Adaptation, Physiological↗
PubMed1994

Endotoxin-induced neutrophil adherence to endothelium: relationship to CD11b/CD18 and L-selectin expression and matrix disruption.

The injury to vascular endothelium seen in severe bacterial infection may be mediated by neutrophil-derived enzymes. Neutrophil adhesion to endothelium, a prerequisite for this process, is mediated sequentially by the leukocyte adhesion molecules L-selectin and the beta 2 integrins, including CD11b/CD18. We have explored the relationship between expression of these molecules, neutrophil adherence, endothelial activation, and consequent endothelial injury, as assessed in vitro by changes to HS and FN matrices that colocalize. Endothelial prestimulation with LPS (endotoxin) caused an increase in adherence and an inversely proportional disruption in the HS matrix; disruption of the FN matrix only occurred on the further addition of fMLP. Although maximal changes in these matrices were associated with elevation of neutrophil CD11b/CD18 and reduction in L-selectin expression, these changes did not determine either the nature or extent of endothelial damage. CD11b/CD18 expression was similar in both adherent and nonadherent neutrophils, while L-selectin was shed in association with adherence in the absence of other stimuli. These changes in expression were thus independently regulated. This model may provide further insights into the interrelationship between neutrophil adhesion and activation and endothelial damage in infection with gram-negative bacteria.

Antigens, CD↗
PubMed1993

Biology and neurobiology of Borna disease viruses (BDV), defined by antibodies, neutralizability and their pathogenic potential.

Borna disease viruses (BDV) isolated from more than 20 naturally infected horses, 2 sheep and a possible feline isolate were included in these studies. Most of these wild-type viruses were grown in rabbit cells. Specifically rabbit-adapted viruses establish persistent infection in immortalized cell lines of various animal species. Brain-, tissue culture-, and cell-free released viruses could all be neutralized with antibodies from naturally and experimentally infected animals (horse; hamster, rat, rabbit, mouse, and chicken), with highest titres in birds. Splenectomized rabbits, which were subsequently infected with BDV, efficiently produced high titres of neutralizing antibodies. All of the neutralizing sera and cerebrospinal fluids from infected animals inhibited tissue culture spread of BDV. Experimental infection and hyperimmunization induced antibodies directed against the major components of the soluble antigen (60, 40/38, 25 and 14.5 kD proteins). Analysis of the s-antigen complex with these sera and 6 stable monoclonal antibodies revealed that it consists of 40/38 and 25 kD proteins. Although each of these antibodies detected intracellular virus-specific structures they did not recognize outer plasma membrane antigens, showed no cross-reactivity, and had no neutralizing capacity. Unifying pathogenetic concepts of this neurotropic virus and its structural elements are discussed.

Animals↗
PubMed1993

Changes in neutrophil CD11b/CD18 and L-selectin expression and release of interleukin 8 and elastase in paediatric cardiopulmonary bypass.

Children undergoing cardiopulmonary bypass (CPB) surgery for congenital heart defects develop an acute post-operative capillary leak which may be due to endothelial injury inflicted by adherent neutrophils (PMN). Direct immunofluorescence and flow cytometry were used to measure CD11a/CD18, CD11b/CD18 and L-selectin (L-s) expression on circulating PMN in CPB circuits containing human blood and in children undergoing CPB. In vitro, a general rise in CD11b/CD18 expression over 2 h contrasted with complete loss of L-s in a small but progressively increasing proportion of PMN. Marked but inconsistent changes in CD11b/CD18 and L-s were observed in vivo, in conjunction with fluctuations in circulating PMN count. Circulating IL-8 was detected starting at rewarming from hypothermia and reperfusion of the heart and lungs with a simultaneous, closely correlated rise in both PMN count and circulating elastase. IL-1 and TNF were not detected. These studies demonstrate changes in the pathways of PMN-endothelial interaction during and after CPB.

Antigens, CD↗
PubMed1993

Health of very low birth weight children during their first eight years.

To determine the impact of very low birth weight (VLBW) on medical outcomes during childhood, we compared the health of 249 VLBW children born from 1977 through 1979 with that of 363 normal birth weight (NBW) control children at 8 years of age. Measures included the rates of specific illnesses, surgical procedures and accidents, growth, and other physical findings. The number of medical conditions and surgical procedures was significantly greater in the VLBW children than in the NBW control children. Eighteen percent of VLBW versus 5% of NBW children had had respiratory conditions (p < 0.001), mainly before 3 years of age. Surgical procedures were more common both before and after 3 years of age, but accidents occurred with similar frequency. The VLBW children had significantly lower weight, height, and head circumference and more minor physical stigmata. Thus medical illness, surgical interventions, and poor growth attainment are part of the ongoing morbidity of VLBW children during childhood.

Accidents↗
PubMed1993

Comparison of acceptance of clinical versus basic studies on drugs and therapeutics in infants and children.

Many clinicians and clinician-scientists have serious concerns that clinical studies (i.e. studies with patients) are less favorably accepted than basic ('bench') projects by funding agencies and by promotion committees of university departments. However, this commonly held view has not been previously verified. To test whether bias exists against clinical studies, we compared the acceptance rate of clinical vs. basic studies dealing with drugs and therapeutics in children, which were submitted to a large scientific meeting. Of 197 abstracts reporting on drug/therapeutic studies, submitted to the Society for Pediatric Research in 1993, there were 133 clinical and 64 basic studies. Fifty-nine (44.3%) of the clinical studies were accepted, significantly less than the basic projects (n = 47 or 73.4%, p < 0.0001). A basic paper was 66% more likely to be accepted (95% CI 50.7-82.6%). This trend was consistent for different groups of drugs/therapeutics, including analgesics, surfactants, corticosteroids, vaccines, hormones, and antiasthmatics. To examine whether the lower rate of acceptance of clinical papers is the result of lower scientific standard, all papers were scored for their quality by raters who were blinded to their acceptance or rejection status. In general, rejected clinical papers scored significantly higher than rejected basic papers (16 +/- 1.8 vs. 14.8 +/- 1.0, p < 0.05). Our study supports the commonly held but previously unproven view that there is a bias against clinical research, in the context of patient-based studies, when compared to basic (bench) research.

Congresses as Topic↗
PubMed1993

Anti-TNF therapy inhibits fever in cerebral malaria.

The clinical effects of a murine monoclonal antibody (CB0006) directed against tumour necrosis factor were investigated in an open study of 41 Gambian children receiving otherwise conventional therapy for cerebral malaria. Ten children received a single i.v. dose of CB0006 at 0.1 mg/kg, 10 received 1 mg/kg, 10 received 5 mg/kg, and 11 were randomly selected as controls. CB0006 rapidly formed complexes with tumour necrosis factor, which were cleared from the circulation over several days. This was associated with a dose-dependent increase in total plasma tumour necrosis factor levels and a dose-dependent reduction of fever, implying that CB0006 inhibits tumour necrosis factor by retaining it in the circulation and reducing its availability to tissue receptors. Parasite clearance rates were not impaired. The fatality rate (29% overall) was similar in CB0006-treated patients and controls, but evaluation of possible effects on mortality requires a much larger blinded study. These data show that tumour necrosis factor is involved in the pathogenesis of malaria fever, and are the first direct evidence that inhibition of a specific endogenous pyrogen can attenuate fever in man.

Animals↗
PubMed1993

Squamous metaplasia expression of proto-oncogenes and P 53 in lung cancer patients.

BACKGROUND: The question of whether bronchial squamous metaplasia is a true preneoplasia is important and demonstrated in animal for several carcinogens. We have now approached this problem in humans and in vivo. EXPERIMENTAL DESIGN: Squamous metaplasia in the close vicinity of surgically resected lung tumors were evaluated for their mitotic index and screened for proto-oncogenes and P 53 protein expression by immunohistochemistry and/or in situ hybridization. RESULTS: Among 16 patients, 4 had squamous metaplasia positive for either myc messages and/or for P 53 protein accumulation. In the same patients (3/4), the autologous bronchial tumors were also positive for the same markers. Squamous metaplasia positivity was observed essentially in patients with advanced diseases and only in squamous cell carcinomas. In addition, when evaluated with 5 iodo-2'-deoxyuridine systemic infusion, all patients presented hyperproliferative basal squamous metaplasic cells. CONCLUSIONS: These results are reminiscent of the typical preneoplastic changes observed in familial colic adenomatosis, where genetic changes accumulate in hyperproliferative cells. They also suggest that bronchial squamous metaplasia could be an authentic preneoplasia in, at least, squamous cell carcinomas.

Gene Expression Regulation, Neoplastic↗
PubMed1993

Interleukin-8 release and neutrophil degranulation after pediatric cardiopulmonary bypass.

Capillary leak after cardiopulmonary bypass operations for correction of congenital heart defects is universally seen in children and often causes significant morbidity and mortality. Since neutrophil-mediated endothelial injury has been implicated as a pathogenetic mechanism, a prospective controlled descriptive study was performed to investigate possible activation pathways during and after the bypass procedure. Eighteen children undergoing operations, nine with cardiopulmonary bypass and nine neurosurgical craniotomy (i.e., operations without bypass), had samples of arterial blood collected at intervals before, during, and after operations. In six of nine cardiac patients circulating interleukin-8 concentrations rose from less than 30 pg/ml to very high concentrations (> 500 pg/ml); in the remaining three patients small rises (peak 57 to 81 pg/ml) were also seen. In all nine, the rise commenced at the time of rewarming, toward the end of bypass, and peaked 1 to 3 hours thereafter. Interleukin-8 release correlated significantly with length of bypass. Interleukin-1 alpha and interleukin-1 beta were not found, and traces of tumor necrosis factor-alpha were detected in one patient only. Circulating elastase alpha 1-antitrypsin concentrations rose simultaneously and correlated significantly with interleukin-8 (p < 0.001) in patients with cardiac disease, as did absolute neutrophil counts (p < 0.001). In contrast, only one of nine patients with neurosurgical disease (undergoing an unusually long operation and exchange transfusion) had a rise in circulating interleukin-8 to levels greater than 500 pg/ml (p < 0.01). The two samples from this patient with elevated interleukin-8 were the only neurosurgical samples with elevated elastase. This study demonstrates the release of interleukin-8 into the circulation after pediatric hypothermic cardiopulmonary bypass and supports the suggestion that this cytokine plays a role in the pathophysiology of capillary leak through neutrophil degranulation.

Cardiopulmonary Bypass↗
PubMed1992

Pain perception and effectiveness of the eutectic mixture of local anesthetics in children undergoing venipuncture.

The emulsion of lidocaine and prilocaine (EMLA) is effective in preventing the pain of venipuncture in children. It is therefore important to identify children who could benefit the most from EMLA. We studied the safety and feasibility of two methods of application of EMLA (patch and cream) in a randomized, open-label trial of EMLA patch versus EMLA cream in 160 children with chronic diseases undergoing venipuncture. EMLA patch or cream was applied 60 to 120 min before puncture. Pain was assessed by the children using a visual analogue score. Children also scored the pain of their last puncture and the pain of removing the tape. EMLA patch and cream had similar efficacy (visual analogue scores for the venipuncture were 8.5 +/- 16 and 9.5 +/- 17 out of 100, respectively). Side effects occurred in similar frequencies in the two groups. Adhesiveness of the patch was less effective than that of the cream with Tegaderm. Age was a major determinant of pain perception; younger children recalled more severe pain in their previous puncture. Children recently diagnosed had higher visual analogue scores than those with a long history of chronic disease. We concluded that EMLA patch and cream have a similar efficacy in children undergoing venipuncture. Young children recently diagnosed with chronic disease are most likely to benefit from EMLA.

Adolescent↗
PubMed1992

The effect of very low birth weight and social risk on neurocognitive abilities at school age.

We tested the hypothesis that very low birth weight (VLBW < 1.5 kg) children would have significantly poorer neurocognitive abilities at school age than would normal birth weight full-term age mates, that differences would persist after control for neurologic impairment and social risk, and that VLBW would interact with social risk. Two hundred forty-nine VLBW children and a randomly selected sample of 363 normal birth weight age mates born 1977 through 1979 were tested at 8 years. A neurologic examination and tests of intelligence, language, speech, reading, mathematics, spelling, visual and fine motor abilities, and behavior were performed. Twenty-four (10%) VLBW had a major neurologic abnormality compared with none of the controls. VLBW had significantly poorer scores on all tests, with the exception of speech and the total behavior score. These differences persisted among VLBW children without major neurologic abnormality, with the exception of social competence, reading, and spelling. Even normal IQ, neurologically normal VLBW had significantly poorer scores than did controls in expressive language, memory, visuomotor, and fine motor function, and measures of hyperactivity. When social risk was controlled in multiple regression analyses, VLBW still had an adverse effect on all outcome measures with the exception of speech. Social risk was, however, the major determinant of outcome. We found an interaction between VLBW and social risk only in verbal IQ and in the opposite direction than hypothesized.

Brain Damage, Chronic↗