In vivo and in vitro activities of the gp130-stimulating designer cytokine Hyper-IL-6

IL-6 is a multifactorial cytokine mediating acute inflammatory responses in the liver. When IL-6 binds to a specific receptor (IL-6R), the IL-6/IL-6R complex associates with the signal transducer gp130, initiating intracellular signaling. A soluble form of the IL-6R (sIL-6R) renders target cells sensitive to IL-6 that do not express the IL-6R on their surfaces. A designer cytokine, termed Hyper-IL-6, consisting of IL-6 covalently linked to the sIL-6R was fully active on gp130-expressing cells at 100- to 1000-fold lower concentrations than unlinked IL-6 and IL-6R. Mice were injected i.p. with Hyper-IL-6 or IL-6. Upon injection of Hyper-IL-6 into mice, the acute phase response, as measured by haptoglobin mRNA expression in the liver, was markedly increased and lasted significantly longer compared with that in mice injected with a 10-fold higher dose of IL-6 alone. On human hepatoma cells, Hyper-IL-6 caused similar effects, indicating that the longer lasting response to the fusion protein could not only be explained by the longer plasma half-life of the fusion protein. Experiments using iodinated IL-6 and Hyper-IL-6 revealed that Hyper-IL-6 bound with high affinity to gp130 and was less efficiently internalized. This effect might explain the longer lasting activity of this protein on cells. The highly active IL-6/sIL-6R designer protein might be of significant clinical importance for the stimulation of cells that are more responsive to the IL-6/sIL-6R complex than to IL-6 alone. Such cells include hemopoietic progenitor cells and hepatocytes.

Human IgA- and IgM-secreting intestinal plasma cells carry heavily mutated VH region genes

Single IgA- or IgM-secreting plasma cells were isolated from histological sections of human jejunum and terminal ileum, and Ig heavy chain variable (VH) region genes were amplified and sequenced. Taken together, 62 of 63 cells analyzed harbored somatically mutated VH region genes, indicating that the vast majority of both IgA- and IgM-secreting intestinal plasma cells derive from germinal center B cells. On average, rearranged VH genes of IgA- and IgM-secreting plasma cells showed a mutation frequency of 9.0 % and 8.5 %, respectively, which exceeds the level of somatic mutation of V region genes carried by human memory B cells. Moreover, we detected deletions or insertions in the complementarity-determining regions of 5 of the 58 functional VH region genes analyzed, suggesting that these alterations may contribute to the diversification of the human antibody repertoire in the course of an immune reaction.

A 2-year longitudinal study of swimming navigation in mice devoid of the prion protein: no evidence for neurological anomalies or spatial learning impairments

Uncontrolled accumulation of a conformationally distorted protein (PrP(Sc)) is supposed to be the pathological process leading to spongiform encephalopathy. Targeted disruptions of the Prn-P gene in the mouse have resulted in animals that did not show anomalies in spatial and avoidance learning and were resistant to experimental infections. However, another Prn-P knockout mouse was reported to show ataxia and Purkinje cell degeneration developing after 70 weeks of age. In this study the initial observations are confirmed on swimming navigation of PrP-null mutant mice using an enlarged sample of 58 mice. A representative subsample of 16 mice was then followed up for their ability of swimming navigation up to an age of two years (104 weeks). Surviving PrP-null mutants (n = 4) and controls (n = 6) did not differ in any measure, nor were there indications of ataxia and Purkinje cell degeneration. It was concluded that the PrP-knockout mice used by Büeler et al. were probably normal with respect to aging processes and that resistance to scrapie is not necessarily paid for by late neuronal degeneration. The reasons for the discrepancy between different knockout experiments require experimental clarification, however.

The membrane proximal cytokine receptor domain of the human interleukin-6 receptor is sufficient for ligand binding but not for gp130 association

Interleukin-6 (IL-6) belongs to the family of the "four-helix bundle" cytokines. The extracellular parts of their receptors consist of several Ig- and fibronectin type III-like domains. Characteristic of these receptors is a cytokine-binding module consisting of two such fibronectin domains defined by a set of four conserved cysteines and a tryptophan-serine-X-tryptophan-serine (WSXWS) sequence motif. On target cells, IL-6 binds to a specific IL-6 receptor (IL-6R), and the complex of IL-6.IL-6R associates with the signal transducing protein gp130. The IL-6R consists of three extracellular domains. The NH2-terminal Ig-like domain is not needed for ligand binding and signal initiation. Here we have investigated the properties and functional role of the third membrane proximal domain. The protein can be efficiently expressed in bacteria, and the refolded domain is shown to be sufficient for IL-6 binding. When complexed with IL-6, however, it fails to associate with the gp130 protein. Since the second and the third domain together with IL-6 can bind to gp130 and induce signaling, our data demonstrate the ligand binding function of the third domain and point to an important role of the second domain in complex formation with gp130 and signaling.

[Concentration-dependent changes in the latency and amplitude of somatosensory-evoked potentials by desflurane, isoflurane and sevoflurane]

PURPOSE

Comparison of the influence of desflurane, isoflurane, and sevoflurane on the parameters of cortical somatosensory evoked potentials (SEP).

METHODS

A total of 41 patients were randomly allocated to either the isoflurane, desflurane or sevoflurane group. Following induction with propofol and intubation, concentration of the volatile anaesthetic was kept constant at 1.3, 1.0, and 0.7 MAC for 15 minutes each in randomised sequences. No opioids or N2O were used. Cortical somatosensory evoked potentials were recorded following median nerve stimulation at the wrist with 1.5 times motor threshold current. SEP were evaluated for latencies of peak N20 and P25 as well as peak-to-peak amplitude N20P25. Measurements at the end of the 15 minute equilibration intervals were compared by analysis of variance for repeated measurements. Latencies and the logarithm of the amplitudes were assumed to be normally distributed.

RESULTS

SEP could be recorded in all patients and at all concentrations. Latency of cortical SEP increased with anaesthetic concentration in a linear manner. No differences in latency increase were found between the three anaesthetics (ANOVA). In contrast, the decrease in amplitude with increasing anaesthetic concentration was non-linear. It was large from control to 0.7 MAC, but small in the range between 0.7 and 1.3 MAC. Amplitude reduction was larger with isoflurane than with sevoflurane or desflurane.

CONCLUSION

1) Sevoflurane and desflurane are better suited for anaesthetic management during intraoperative electrophysiological monitoring than isoflurane, because SEP amplitudes are better preserved. 2) SEP amplitude is less altered by changing anaesthetic concentrations in the concentration range from 0.7 to 1.3 MAC than SEP latency.

A randomized controlled trial of early postoperative feeding in gynecologic oncology patients undergoing intra-abdominal surgery

OBJECTIVE

To evaluate the safety and efficacy of early oral feeding after intra-abdominal surgery in gynecologic oncology patients.

METHODS

During a 1-year period, 200 gynecologic oncology patients undergoing intra-abdominal surgery were enrolled in a randomized controlled trial of early compared with traditional oral postoperative feeding. Patients allocated to early postoperative oral feeding began a clear liquid diet on the first postoperative day and then advanced to a regular diet as tolerated. Patients allocated to traditional postoperative oral feeding received nothing by mouth until return of bowel function (defined as the passage of flatus in the absence of vomiting or abdominal distention), then began a clear liquid diet, and advanced to a regular diet as tolerated.

RESULTS

Age, case distribution, surgery length, blood loss, and first passage of flatus were similar in the early and traditional feeding groups. Significantly more patients in the early group developed nausea. Despite this, the incidence of vomiting, abdominal distention, incidence and duration of nasogastric tube use, and percentage of patients who tolerated clear liquid and regular diets on the first attempt were comparable in both groups. Time to development of bowel sounds, time to initiation of clear liquid and regular diets, and hospital stay were significantly longer in the traditional group. Major complications (eg, pneumonia, atelectasis, and wound complications) and febrile morbidity occurred equally in both groups. There were no known anastamotic complications or aspirations in either group. Postoperative changes in hematologic indices and electrolytes were comparable in both groups.

CONCLUSION

Early postoperative feeding in gynecologic oncology patients undergoing intra-abdominal surgery is safe and well tolerated.

Use of intravenous lipids in critically ill patients with sepsis without and with hepatic failure

BACKGROUND

Fat is the preferred energy fuel both in patients with sepsis and with hepatic failure. Thus lipid emulsions should serve as an ideal nutritional substrate in parenteral nutrition. However, previous studies have generated conflicting results on the utilization of artificial lipids in these disease states, and systematic studies in critically ill patients with combined organ dysfunctions and additional complications are lacking. We compared the elimination, hydrolysis, and oxidation of a 20% lipid emulsion in critically ill patients on respiratory support with sepsis and with sepsis plus hepatic failure and in healthy control subjects.

SETTING

Medical critical care unit of a university hospital.

SUBJECTS AND METHODS

Eight critically ill patients with sepsis, 8 patients with sepsis and decompensated chronic hepatic failure, and 10 healthy volunteers were investigated. Elimination and hydrolysis was evaluated during constant i.v. infusion of 4.5 mg.kg body wt-1.min-1 of triglycerides during 120 minutes. Concentrations of plasma triglycerides, free fatty acids, and glycerol were measured, and elimination parameters were analyzed from plasma curves of triglycerides by using a two-compartment model. Resting energy expenditure and substrate oxidation were measured by indirect calorimetry.

RESULTS

In patients with sepsis without and with hepatic failure the rise in plasma triglycerides was blunted and the clearance of triglycerides was enhanced by 20% and 40% (p < .05), respectively, compared with healthy controls. Basal free fatty acid concentrations were elevated, and the rise of free fatty acids and glycerol was comparable to healthy subjects. Energy expenditure was increased and lipid oxidation (as fraction of total energy expenditure) was slightly elevated in both patient groups; the rise in lipid oxidation during lipid infusion was comparable to controls. No side effects or impairment of gas exchange was seen.

CONCLUSIONS

In a clinically relevant dosage range, the utilization of an i.v. lipid emulsion, the elimination and hydrolysis of triglycerides, and the lipid oxidation is not impaired in ventilated critically ill patients with sepsis or sepsis and chronic hepatic failure. Lipid emulsions thus are efficiently metabolized in critically ill patients with combined organ dysfunctions and associated sepsis.

Inhibition of human peripheral blood mononuclear cell proliferation by Streptococcus pyogenes cell extract is associated with arginine deiminase activity

Streptococcus pyogenes (group A Streptococcus) cell extracts (CE) have a remarkably powerful and dose-dependent inhibitory effect on antigen, superantigen, or mitogen-stimulated human peripheral blood mononuclear cell (PBMC) proliferation in vitro. Purification of the inhibitory component present in S. pyogenes type M5 (Manfredo strain) CE by anion-exchange chromatography followed by gel filtration chromatography showed that the inhibitor had an approximate native molecular mass of 100 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified inhibitory fractions followed by silver staining gave a single band with an approximate molecular mass of 47 kDa, indicating that the inhibitor is composed of two identical subunits. NH2-terminal sequencing of the protein revealed that it was identical to the previously characterized streptococcal acid glycoprotein (SAGP); this protein possesses between 31.5 and 39.0% amino acid identity with arginine deiminase (AD) from Mycoplasma hominis, Mycoplasma arginini, Pseudomonas putida, and Pseudomonas aeruginosa. AD enzyme activity was present in unfractionated CE prepared from a range of streptococcal strains, and partially purified inhibitory fractions of Manfredo CE also had high levels of activity. The inhibitory effect of Manfredo CE was overcome by the addition of L-arginine to proliferation assays in which human PBMC were stimulated with phytohemagglutinin. We conclude that SAGP, or its homolog, possesses AD activity and that the potent inhibition of proliferation of human T cells by streptococcal CE is due to activity of this enzyme.

RAPD variation in relation to population size and plant fitness in the rare Gentianella germanica (Gentianaceae)

We investigated the distribution of genetic variation and the relationship between population size and genetic variation in the rare plant Gentianella germanica using RAPD (random amplified polymorphic DNA) profiles. Plants for the analysis were grown from seeds sampled from 72 parent plants in 11 G. germanica populations of different size (40-5000 fruiting individuals). In large populations, seeds were sampled from parents in two spatially distinct subpopulations comparable in area to the total area covered by small populations. Analysis of molecular variance revealed significant genetic variation among populations (P <0.001), while genetic variation among subpopulations was marginally significant (P <0.06). Average molecular variance within subpopulations in large populations did not differ significantly from whole-population values. There was a positive correlation between genetic variation and population size (P <0.01). Genetic variation was also positively correlated with the number of seeds per plant in the field (P <0.02) and the number of flowers per planted seed in a common garden experiment (P <0.051). We conclude that gene flow among natural populations is very limited and that reduced plant fitness in small populations of G. germanica most likely has genetic causes. Management should aim to increase the size of small populations to minimize further loss of genetic variation. Because a large proportion of genetic variation is among populations, even small populations are worth preserving.

Anatomy of lipase binding sites: the scissile fatty acid binding site

Shape and physico-chemical properties of the scissile fatty acid binding sites of six lipases and two serine esterases were analyzed and compared in order to understand the molecular basis of substrate specificity. All eight serine esterases and lipases have similar architecture and catalytic mechanism of ester hydrolysis, but different substrate specificities for the acyl moiety. Lipases and esterases differ in the geometry of their binding sites, lipases have a large, hydrophobic scissile fatty acid binding site, esterases like acetylcholinesterase and bromoperoxidase have a small acyl binding pocket, which fits exactly to their favorite substrates. The lipases were subdivided into three sub-groups: (1) lipases with a hydrophobic, crevice-like binding site located near the protein surface (lipases from Rhizomucor and Rhizopus); (2) lipases with a funnel-like binding site (lipases from Candida antarctica, Pseudomonas and mammalian pancreas and cutinase); and (3) lipases with a tunnel-like binding site (lipase from Candida rugosa). The length of the scissile fatty acid binding site varies considerably among the lipases between 7.8 A in cutinase and 22 A in Candida rugosa and Rhizomucor miehei lipase. Location and properties of the scissile fatty acid binding sites of all lipases of known structure were characterized. Our model also identifies the residues which mediate chain length specificity and thus may guide protein engineering of lipases for changed chain length specificity. The model was supported by published experimental data on the chain length specificity profile of various lipases and on mutants of fungal lipases with changed fatty acid chain length specificity.

Helical superstructures from charged Poly(styrene)-Poly(isocyanodipeptide) block copolymers

Amphiphilic block copolymers containing a poly(styrene) tail and a charged helical poly(isocyanide) headgroup derived from isocyano-L-alanine-L-alanine and isocyano-L-alanine-L-histidine were prepared. Analogous to low-molecular mass surfactants, these block copolymers self-assembled in aqueous systems to form micelles, vesicles, and bilayer aggregates. The morphology of these aggregates can be controlled by variation of the length of the poly(isocyanide) block, the pH, and the anion-headgroup interactions. The chirality of the macromolecules results in the formation of helical superstructures that have a helical sense opposite to that of the constituent block copolymers. The great variety of morphologies displayed by these block copolymers and the fact that they are easily accessible from poly(styrene) and different types of peptides open new opportunities for applications in the fields of life and materials sciences.

Rapid actin-based plasticity in dendritic spines

Dendritic spines have been proposed as primary sites of synaptic plasticity in the brain. Consistent with this hypothesis, spines contain high concentrations of actin, suggesting that they might be motile. To investigate this possibility, we made video recordings from hippocampal neurons expressing actin tagged with green fluorescent protein (GFP-actin). This reagent incorporates into actin-containing structures and allows the visualization of actin dynamics in living neurons. In mature neurons, recordings of GFP fluorescence revealed large actin-dependent changes in dendritic spine shape, similar to those inferred from previous studies using fixed tissues. Visible changes occurred within seconds, suggesting that anatomical plasticity at synapses can be extremely rapid. As well as providing a molecular basis for structural plasticity, the presence of motile actin in dendritic spines implicates the postsynaptic element as a primary site of this phenomenon.

Expression of amino-terminally truncated PrP in the mouse leading to ataxia and specific cerebellar lesions

The physiological role of prion protein (PrP) remains unknown. Mice devoid of PrP develop normally but are resistant to scrapie; introduction of a PrP transgene restores susceptibility to the disease. To identify the regions of PrP necessary for this activity, we prepared PrP knockout mice expressing PrPs with amino-proximal deletions. Surprisingly, PrP lacking residues 32-121 or 32-134, but not with shorter deletions, caused severe ataxia and neuronal death limited to the granular layer of the cerebellum as early as 1-3 months after birth. The defect was completely abolished by introducing one copy of a wild-type PrP gene. We speculate that these truncated PrPs may be nonfunctional and compete with some other molecule with a PrP-like function for a common ligand.

The use of transgenic mice in the investigation of transmissible spongiform encephalopathies

The prion, the transmissible agent that causes spongiform encephalopathies such as scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease, is believed to be devoid of nucleic acid and to be identical to PrPSc (prion protein: scrapie form), a modified form of the normal host protein PrPC (prion protein: cellular form) which is encoded by the single copy gene Prnp. The 'protein only' hypothesis proposes that PrPSc, when introduced into a normal host, causes the conversion of PrPC into PrPSc; it therefore predicts that an animal devoid of PrPC should be resistant to prion diseases. The authors generated homozygous Prnp(o/o) ('PrP knockout') mice and showed that, after inoculation with prions, these mice remained free from scrapie for at least two years while wild-type controls all died within six months. There was no propagation of prions in the Prnp(o/o) animals. Surprisingly, heterozygous Prnp(o/+) mice, which express PrPC at about half the normal level, also showed enhanced resistance to scrapie despite high levels of infectious agent and PrPSc in the brain at an early stage. After introduction of murine PrP transgenes, Prnp(o/o) mice became highly susceptible to mouse--but not to hamster--prions, while the insertion of Syrian hamster PrP transgenes rendered the mice susceptible to hamster prions but much less susceptible to mouse prions. These complementation experiments enabled the application of reverse genetics. The authors prepared animals transgenic for genes encoding PrP with amino terminal deletions of various lengths and found that PrP that lacks 48 amino proximal amino acids (which comprise four of the five octa repeats of PrP) is still biologically active.

Oxygen-dependent regulation of the expression of the catalase gene katA of Lactobacillus sakei LTH677

The catalase gene katA of Lactobacillus sakei LTH677 was cloned and expressed in Escherichia coli UM2, Lactobacillus casei LK1, and Lactobacillus curvatus LTH1432. The last host is a catalase-deficient plasmid-cured derivative of a starter organism used in meat fermentation. The regulation of katA expression was found to be the same in L. sakei LTH677 and the recombinant strains. The addition of H2O2 to anaerobic cultures, as well as a switch to aerobic conditions, resulted in a strong increase in KatA activity. The expression was investigated in more detail with L. sakei LTH677 and L. curvatus LTH4002. The recombinant strain LTH4002 did not accumulate H2O2 under glucose-limited aerobic conditions and remained viable in the stationary phase. Under inductive conditions, the katA-specific mRNA and the apoenzyme were synthesized de novo. Deletion derivatives of the katA promoter were produced, and the regulatory response was investigated by fusion to the beta-glucuronidase reporter gene gusA and expression in L. sakei LTH677. The fact that gene expression was subject to induction was confirmed at the level of transcription and protein synthesis. A small putative regulatory sequence of at least 25 bp was identified located upstream of the -35 site. Competition experiments performed with L. sakei LTH677 harboring the fusion constructs consisting of the katA promoter and gusA revealed that an activator protein is involved in the transcriptional induction of katA.

Inotropic response of stunned hypertrophied myocardium: responsiveness of hypertrophied and normal postischemic isolated rat hearts to calcium and dopamine stimulation

OBJECTIVE

Severely hypertrophied myocardium was described to have a reduced tolerance towards ischemia. For non-hypertrophied hearts inconclusive findings on the Ca(2+)-responsiveness are reported. Information sensitivity to reversible ischemia and on postischemic Ca(2+)-responsiveness of hearts with clinically common moderate hypertrophy is lacking. Thus, the responsiveness of hypertrophied and normal postischemic myocardium to positive inotropic stimulation should be investigated in the present study.

METHODS AND RESULTS

Hearts from spontaneously hypertensive rats (SHR, 4 months old) with significant LV-hypertrophy (+ 50%) and hearts from normotensive 4 months old Wistar rats were investigated using an isovolumic beating isolated heart model (8 hearts/each of the 8 groups). Functional recovery after 30 min of no-flow ischemia was 78 +/- 1% and 77 +/- 3% of preischemic control data in hypertrophied and non-hypertrophied hearts assessed as developed left ventricular pressure (non-ischemic controls: 95 +/- 2% in hypertrophied and 93 +/- 3% in non-hypertrophied controls). Maximum short-term stimulation with Ca2+ revealed a decreased peak left ventricular pressure of 124 +/- 4% in hypertrophied and 120 +/- 5% in non-hypertrophied postischemic hearts, as compared with non-ischemic controls 138 +/- 3% and 157 +/- 5%, respectively ( p < 0.01). A maximum dose of dopamine stimulated hypertrophied and non-hypertrophied postischemic hearts comparable to Ca2+. Analysing the dose-response curve for Ca(2+)-stimulation, the sensitivity expressed as fraction of the maximum was identical in non-ischemic and postischemic myocardium of hypertrophied and non-hypertrophied ventricles in spite of the reduced peak values.

CONCLUSION

The findings demonstrate that after moderate reversible ischemia the steady-state function is similarly decreased in hypertrophied and non-hypertrophied postischemic myocardium. The maximum response to Ca2+ is significantly reduced in both types of myocardium, while the Ca2+ sensitivity is unchanged. Identical results after maximum dopamine stimulation as after Ca2+ indicate that the releasibility of Ca2+ and the beta-adrenoceptors are not the critical causes for the postischemic dysfunction in hypertrophied or non-hypertrophied myocardium.

[Normal accommodative convergence excess--long-term follow-up of conservative therapy with bifocal eyeglasses]

BACKGROUND

In patients with normaccommodative convergence excess it is possible to reduce or eliminate the excess of accommodative convergence by adding plus lenses. The resulting reduction of near deviation can lead to an improvement in the quality of binocular vision at near, and also to a better compensation of an esophoria at near. The aim of the paper was to study long term results in patients with small angle esotropia and esophoria and accommodative convergence excess treated by bifocals.

METHODS

Clinical data of 91 patients were analysed retrospectively. Among them were 13 patients with esophoria, 32 patients with microesotropia and 46 with microesotropia and a phoric component. An orthoptic status was performed every three months and at every examination it was tried to reduce the added plus lenses. The mean follow up was 5.6 +/- 2.4 years (range: 1.1-13.2).

RESULTS

The mean onset of strabismus was similar in all groups: i.e. 2.5 (+/- 1.7) years. The patients received their first bifocals on average 3.4 (+/- 1.9) years later. In 40 of the 91 patients the near addition could be stopped because of sufficient decrease of accommodative convergence excess during the follow-up period. The convergence excess decreased continuously in all patients with esophoria and microesotropia and the additional plus lenses could be stopped on average after 6.4 (3.5-8.4) years (esophoria) and 5.0 (2.6-8.1) years (microesotropia) respectively. In patients with microesotropia and an additional phoric deviation bifocals were only partly successful to reduce the convergence excess. The basic angle decompensated in more than half of the patients (27 out of 46) and was operated in 14 cases by unilateral resection/recession procedure. After the operation the convergence excess decreased rapidly and the bifocals could be stopped after 4.4 (3.4-7.4) years. In the remaining 19 cases it was possible to reduced the convergence excess with bifocals in 8 patients after about 8.1 (4.1-9.3) years and in some of the remaining 11 cases a Fadenoperation has been suggested.

CONCLUSION

While wearing bifocals the accommodative convergence excess decreased completely in patients with esophoria and microesotropia. In the condition with markedly reduced binocular vision and a large phoric component at far and near, the convergence excess decreased only in some of the patients while wearing bifocals. Conventional strabismus surgery to reduce the basic angle has a positive influence. A Fadenoperation is only necessary in a few cases.

Effect of collection and preprocessing methods on neutrophil elastase plasma concentrations

OBJECTIVES

Elevated plasma levels of the elastase alpha 1-proteinase inhibitor complex (E-alpha 1 PI) have been proposed as a marker of bacterial infection and neutrophil activation. Liberation of elastase from neutrophils after collection of blood may cause falsely elevated results. Collection methods have not been validated for critically ill neonates and children. We evaluated the influence of preanalytical methods on E-alpha 1 PI results including the recommended collection into EDTA tubes.

DESIGN AND METHODS

First, we compared varying acceleration speeds and centrifugation times. Centrifugation at 1550 g for 3 min resulted in reliable preparation of leukocyte free plasma. Second, we evaluated all collection tubes under consideration for absorption of E-alpha 1 PI. Finally, 12 sets of samples from healthy adults and 42 sets obtained from critically ill neonates and children were distributed into the various sampling tubes. Samples were centrifuged within 15 min of collection and analyzed with a new turbidimetric assay adapted to routine laboratory analyzers.

RESULTS

One of the two tubes containing a plasma-cell separation gel absorbed 22.1% of the E-alpha 1 PI content. In the remaining tubes without absorption of E-alpha 1 PI no differences were observed for samples from healthy adult patients. However, in samples from critically ill neonates or children, significantly higher results were obtained for plain Li-heparin tubes (mean = 183 micrograms/L), EDTA tubes (mean = 93 micrograms/L), and citrate tubes (mean = 88.5 micrograms/L) than for the Li-hep tube with cell-plasma separation gel and no absorption of E-alpha 1 PI (mean = 62.4 micrograms/L, p < 0.01).

CONCLUSION

Contrary to healthy adults, E-alpha 1 PI results in plasma samples from critically ill neonates and children depend on the type of collection tube.

Somatic hypermutation in normal and transformed human B cells

In the human, most IgM+IgD+ as well as CD5+ peripheral blood B cells express unmutated V genes and thus can be assigned to a pre-germinal centre (GC) stage of development. The memory B-cell compartment generated in the GC reaction and characterized by cells bearing somatically mutated V-region genes consists not only of class-switched cells, but also of IgM-only B cells and perhaps a subset of IgM+IgD+B cells expressing the CD27 antigen. Comparison of the rearranged V-region genes of human B-cell lymphomas with those of the normal B-cell subsets allows the identification of the progenitor cells of these tumours in terms of their stage of maturation. On this basis, most B-cell non-Hodgkin lymphomas, and in addition Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's disease (HD), are derived from B cells at a GC or post-GC stage of development. The mutation pattern indicates that the precursors of the tumour clones have been stringently selected for expression of a functional antigen receptor with one notable exception: HRS cells in classical (but not lymphocyte-predominant) HD appear to be derived from "crippled" GC B cells. Sequence analysis of rearranged V genes amplified from single tonsillar GC B cells revealed that the somatic hypermutation process introduces deletions and/or insertions into V-region genes more frequently than indicated by previous investigations. Presumably, this feature of the hypermutation mechanism is often responsible for the generation of heavy chain disease, and also several types of chromosomal translocations of oncogenes into immunoglobulin loci in human B-cell lymphomas.

Exposure to carbon black: a cancer risk?

Lung cancer is one of the most serious health problems in the industrial nations and is therefore of great public and scientific interest. Although inhalative cigarette smoking is without doubt the main cause for the increasing frequency of lung cancer, during recent years there has been more and more public interest in other substances in the environment or at the work place that are assumed to be potentially carcinogenic especially due to experiences with fibrous particles such as asbestos and their effects. Enhanced attention is also directed to inert or nuisance dusts such as carbon black. Evaluation of the possibly increased risk for humans should first be based on exact epidemiology data. In the absence of those data--as in the case of carbon black--experimental data in animals serve as the point of orientation, especially results gained in rats in long-term inhalation studies. Pathologic anatomy investigations of human lungs under similar exposure conditions, however, render results quite different from those obtained in rats and, thus, preclude ready interpretation of animal results to human risk assessment. This is particularly true for the development of lung tumors in rats under overload conditions as well as for certain tumor types not observed in human lung tissues. It is therefore quite understandable that many researchers propose to interpret the changes observed in rat lung tissues after inhalation of carbon black as rat-specific reaction mechanisms that cannot be applied to human tissues, which in the past have led to the wrong conclusions regarding human risk assessment due, among other factors, to incorrect experimental design and inaccurate nomenclature of tumorous lesions in rats.