Anaerobic ammonia oxidation with nitrogen dioxide by Nitrosomonas eutropha

Nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (NO2) was supplemented to the atmosphere. In the presence of gaseous NO2, ammonia was oxidized, nitrite and nitric oxide (NO) were formed, and hydroxylamine occurred as an intermediate. Between 40 and 60% of the produced nitrite was denitrified to dinitrogen (N2). Nitrous oxide (N2O) was shown to be an intermediate of denitrification. Under an N2 atmosphere supplemented with 25 ppm NO2 and 300 ppm CO2, the amount of cell protein increased by 0.87 mg protein per mmol ammonia oxidized, and the cell number of N. eutropha increased by 5.8 x 10(9) cells per mmol ammonia oxidized. In addition, the ATP and NADH content increased by 4.3 micromol ATP (g protein)-1 and 6.3 micromol NADH (g protein)-1 and was about the same in both anaerobically and aerobically grown cells. Without NO2, the ATP content decreased by 0.7 micromol (g protein)-1, and the NADH content decreased by 1.2 micromol (g protein)-1. NO was shown to inhibit anaerobic ammonia oxidation.

Evaluation of cell morphology by video recording and computer-assisted image analysis

The aim of this study was to evaluate the effects of various cell culture conditions on cell morphology. Cell morphology was estimated by means of video recording and computer-assisted image analysis. Cell contours from the stored images of either live cells or fixed and stained cells were determined automatically, and cellular area, form factor, and average cell brightness were calculated. Using the mouse fibroblastoid L 929 cell line (L-cells) and the rat glioma BT4C cell line, it was found that a number of methodological parameters strongly affected cell morphology. These included confluency of cells before dissociation, dissociation procedure, cell seeding density, cultivation time, and culture substratum. The substratum, particularly collagen type I and fibronectin, profoundly affected cell morphology. Using drugs affecting cytoskeletal organization or cell substratum interactions, it was shown that average cell brightness was a valuable parameter for estimation of cellular attachment. Cytochalasin D, which impairs actin filaments, caused a dramatic increase in the average cell brightness in both cell lines. Nocodazole, which depolymerizes microtubules, mainly affected the L-cells, whereas the BT4C-cells were largely unaffected, indicating that microtubules were morphological determinants for the former cell line but not for the latter. When cells were grown on fibronectin, an RGD-peptide only affected L-cell attachment, indicating that BT4C-cells only expressed low (if any) amounts of RGD recognizing integrins. The interassay precision of the employed procedure depended on culture substratum; the coefficients of variation ranged from 7-24%. Lowest variations in area determination were found for cells grown on fibronectin. The coefficient of variation of form factor determinations was generally around 20%, independent of substrata and culture time.

Prediction of teratogenic potency of valproate analogues using cerebellar aggregation cultures

The aim of this study was to develop a novel in vitro system suitable for preclinical testing for developmental toxicity of drugs. An assay system consisting of primary cultures of dissociated cerebella from 6-day-old mice was chosen, since it allowed quantification of neuronal aggregation and fasciculated neurites. A human teratogen, the antiepileptic drug valproic acid (VPA), as well as its structural analogues, ( +/- )-4-en-VPA and E-2-en-VPA, with varying teratogenic activities, were tested and found to affect aggregation and fiber formation of cerebellar neurons. Based on a dose-response study, the concentrations of compounds causing 50%, inhibition (IC50) of formation of thick and thin fibers were determined. The lowest IC50 values were found for VPA (52 +/- 7 and 86 +/- 11 microM for thick and thin fibers, respectively), which in vivo caused the highest rate of exencephaly among the three compounds tested, ( +/- )-4-en-VPA exhibited intermediate values (150 +/- 30 and 300 +/- 40 microM), whereas the highest IC50 values were found for E-2-en-VPA (260 +/- 42 and 430 +/- 40 microM). The latter compound does not induce neural tube defects, but has been shown to have neurobehavioral effects in prenatally exposed animals. Subsequently, the purified S- and R-enantiomers of 4-yn-VPA (teratogenic and non-teratogenic, respectively) were tested for their effects on aggregation and fiber formation of the cerebellar neurons. Treatment with S-4-yn-VPA resulted in pronounced changes in numbers of aggregates and fasciculated processes compared to the cultures treated with R-4-yn-VPA, indicating that the intrinsic stereoselective potency of the enantiomers may be correlated to the difference in their effects on cerebellar neurons in vitro. Thus, the teratogenic potency of VPA and its analogues correlated with their effects on aggregation of neural cells and formation of fasciculated neurites in primary cultures of dissociated cerebella, indicating that the in vitro assay system employed may be used as a pre-screening test for prediction of teratogenic potency of drugs.

Characterization of microwell cultures of dissociated brain tissue for studies of cell-cell interactions

Microwell cultures of dissociated tissue from prenatal rat hippocampus and cerebral cortex as well as from early postnatal cerebellum were used for quantification of neuronal aggregation, process extension, and fasciculation. It was shown that the cells in culture from these different brain regions developed differently with regard to both architecture and rate of differentiation. The effect of a polyclonal antibody against the neural cell adhesion molecule (NCAM), the excitatory amino acid receptor agonist N-methyl-D-aspartate (NMDA), and the neurotoxin acrylamide on aggregation and fiber formation was investigated. Exposure to the NCAM antibody led to formation of fewer but larger aggregates and stimulated the morphological development of the cultures. Acrylamide affected aggregate formation, leading to smaller but more numerous aggregates, and it inhibited process extension and fasciculation. Treatment with NMDA affected process formation and led to formation of more numerous but smaller aggregates. Some of these effects were strongly tissue-dependent. Thus, large differences were seen regarding the effect of the NCAM antibody on aggregation and process extension in cultures from the different brain areas. The culture systems appear to represent convenient and reliable screening tools to study the influence of putative morphoregulatory substances on cell-cell interactions during early neuronal development.

Functional characterization of NCAM fibronectin type III domains: demonstration of modulatory effects of the proline-rich sequence encoded by alternatively spliced exons a and AAG

In order to characterize the functions of the two fibronectin type III (F3) homology domains of the neural cell adhesion molecule (NCAM), we investigated the effects of two variants, expressed as fusion proteins, of the NCAM-F3 domains on attachment and spreading of NCAM-expressing fibroblasts, cerebellar cell aggregation and fiber formation, and on growth cones. The two fusion proteins were different with regard to a short proline-rich insert of six amino acids between the two F3 domains. Immobilized NCAM-F3 fusion proteins were found to mediate attachment of both transmembrane and lipid-anchored NCAM expressing fibroblasts. Also NCAM-negative cells adhered to the NCAM-F3 substratum, although to a lesser extent, implying the possibility of a heterophilic ligand to NCAM-F3 domains on the surface of fibroblasts. Cellular spreading on NCAM-F3 substratum was selectively increased in fibroblasts expressing transmembrane NCAM, and only the NCAM-F3 fusion protein lacking the proline-rich insert was able to elicit this effect. Primary cultures of mouse cerebellum were strongly inhibited with regard to formation of cellular aggregates and fibers, when incubated in the presence of either of the two NCAM-F3 fusion proteins, the fusion protein with the proline-rich insert being the more effective one. Finally, the morphology of growth cones from rat cerebellar granule cells changed significantly when grown on NCAM-F3 substrata as revealed by computer-assisted image analysis. Thus, our data indicate that the NCAM-F3 domain are involved in cell-cell adhesion, and that insertion of the proline-rich sequence has a modulatory effect on NCAM-F3 domain functions.

Two types of amyloid precursor protein (APP) mRNA in rat glioma cell lines: upregulation via a cyclic AMP-dependent pathway

APP is a multifunctional transmembrane glycoprotein and the only known natural source of beta A4 peptide-the major constituent of senile plaques in Alzheimer's disease (AD). The expression and cAMP-dependent regulation of the APP gene were investigated in primary cultures of rat astrocytes and two related glioma cell lines, BT4C and BT4Cn, which exhibit distinct invasive phenotypes. Besides the well-characterized 3.5 kb APP mRNA class, a robust expression of an unusual 2.8 kb APP mRNA class was revealed by Northern blotting in both glioma cell lines, but not in the astrocytes. Low amounts of the 2.8 kb APP mRNA species were also observed in rat liver and occasionally in aged rat brain. The 2.8 kb APP mRNA contained exons 1-18 and may thus be generated by truncation of the 3' untranslated region. For the first time, regulation of the APP gene via a cAMP-dependent mechanism was shown. Exposure to dBcAMP dramatically upregulated the 3.5 and 2.8 kb transcripts in BT4C cells, and, to a lesser extent, in BT4Cn cells where the constitutive expression of the APP gene was much higher. Elucidation of the factors involved in cAMP-dependent induction of APP mRNA in these cells may shed more light on the molecular mechanisms of APP overexpression.

Quantitative whole body scintigraphy--a simplified approach

In this paper we present investigations on a simplified method of quantitative whole body scintigraphy by using a dual head LFOV-gamma camera and a calibration algorithm without the need of additional attenuation or scatter correction. Validation of this approach to the anthropomorphic phantom as well as in patient studies showed a high accuracy concerning quantification of whole body activity (102.8% and 97.72%, resp.), by contrast organ activities were recovered with an error range up to 12%. The described method can be easily performed using commercially available software packages and is recommendable especially for quantitative whole body scintigraphy in a clinical setting.

99m-Tc-HMPAO-SPECT in diagnosis of early cerebral vasculitis

The objective of this study was to evaluate whether mild neurological symptoms suggestive of neuropsychiatric involvement may be associated with cerebral perfusion defects as detected by functional brain imaging with 99m-Tc-HMPAO-SPECT (single photon emission computed tomography). SPECT analysis for the early detection of central nervous system (CNS) involvement was evaluated in 40 consecutive patients with systemic vasculitis or with Sneddon's syndrome. Of these, 18 patients showed overt neuropsychiatric symptoms, so-called major symptoms (e.g. motoric or sensible defects); 6 had mild symptoms like headache or cognitive disorders, so-called minor symptoms: 16 patients did not present with any of these symptoms. SPECT abnormalities were detected in 16 of the 18 patients with overt neuropsychiatric symptoms (89%). Five of the 6 patients with minor symptoms (83%) and 5 of the 16 patients without neurological symptoms (31%) also had SPECT abnormalities. There was no relation to disease activity or duration. We concluded that the high sensitivity of SPECT (87.5%) in detecting perfusion abnormalities among the evaluated group of patients indicates its suitability for early diagnosis of vasculitic CNS involvement.

Quantitative Whole Body Scintigraphy – A Simplified Approach

In this paper we present investigations on a simplified method of quantitative whole body scintigraphy by using a dual head LFOV-gamma camera and a calibration algorithm without the need of additional attenuation or scatter correction. Validation of this approach to the anthropomorphic phantom as well as in patient studies showed a high accuracy concerning quantification of whole body activity (102.8% and 97.72%, resp.), by contrast organ activities were recovered with an error range up to 12%. The described method can be easily performed using commercially available software packages and is recommendable especially for quantitative whole body scintigraphy in a clinical setting.

High-resolution SPECT of the temporomandibular joint in chronic craniofacial pain disorders: a pilot study

Chronic craniofacial pain disorders commonly cause physicians diagnostic difficulties. The purpose of this study was, on one hand, to detect pathological focuses of the craniofacial skeleton using a new system of high-resolution single photon emission computertomography (SPECT), and on the other hand, to compare the results with those obtained via high-field magnetic resonance imaging (MRI) as far as temporomandibular joint affections are concerned. SPECT can be regarded as a supplementary diagnostic mean for patients displaying the symptoms of chronic craniofacial pain disorders, especially in cases where clinical and paraclinical investigations do not coïncide or which are refractory to treatment, not least to differentiate between somatic and psychogenic causes, respectively.

A new obligately chemolithoautotrophic, nitrite-oxidizing bacterium, Nitrospira moscoviensis sp. nov. and its phylogenetic relationship

A gram-negative, non-motile, non-marine, nitrite-oxidizing bacterium was isolated from an enrichment culture initiated with a sample from a partially corroded area of an iron pipe of a heating system in Moscow, Russia. The cells were 0.9-2.2 microns x 0.2-0.4 microns in size. They were helical- to vibroid-shaped and often formed spirals with up to three turns 0.8-1.0 micron in width. The organism possessed an enlarged periplasmic space and lacked intracytoplasmic membranes and carboxysomes. The cells tended to excrete extracellular polymers, forming aggregates. The bacterium grew optimally at 39 degrees C and pH 7.6-8.0 in a mineral medium with nitrite as sole energy source and carbon dioxide as sole carbon source. The optimal nitrite concentration was 0.35 mM. Nitrite was oxidized to nitrate stoichiometrically. The doubling time was 12 h in a mineral medium with 7.5 mM nitrite. The cell yield was low; only 0.9 mg protein/l was formed during oxidation of 7.5 mM nitrite. Under anoxic conditions, hydrogen was used as electron donor with nitrate as electron acceptor. Organic matter (yeast extract, meat extract, peptone) supported neither mixotrophic nor heterotrophic growth. At concentrations as low as 0.75 g organic matter/l or higher, growth of nitrite-oxidizing cells was inhibited. The cells contained cytochromes of the b- and c-type. The G+C content of DNA was 56.9 +/- 0.4 mol%. The chemolithoautotrophic nitrite-oxidizer differed from the terrestrial members of the genus Nitrobacter with regard to morphology and substrate range and equaled Nitrospira marina in both characteristics. The isolated bacterium is designated as a new species of the genus Nitrospira.(ABSTRACT TRUNCATED AT 250 WORDS)

NCAM-antibodies modulate induction of long-term potentiation in rat hippocampal CA1

The neural cell adhesion molecule (NCAM) probably plays a role in neural plasticity in the adult vertebrate brain. We here present evidence that NCAM may be involved in long-term potentiation (LTP) in the CA1-region of rat hippocampal slices. It is shown that local application of antibodies against NCAM inhibits subsequent LTP-induction. Thus NCAM may be directly involved in the initial phase of LTP-induction. These results have important implications for the possible involvement of NCAM in learning and memory.

The ability to re-express polysialylated NCAM in soleus muscle after denervation is reduced in aged rats compared to young adult rats

The neural cell-adhesion molecule, NCAM, contains an unusual homopolymer of sialic acid units, polysialic acid. This carbohydrate seems to be involved in neurite outgrowth, bundling and branching, processes which are important during reinnervation. In aged rats, reinnervation of denervated muscle fibres is incomplete. In this study, age-related changes in the degree of polysialylation of NCAM re-expressed after denervation were examined using a monoclonal antibody recognizing polysialic acid and a polyclonal antibody recognizing NCAM. The results show that, after denervation, the degree of polysialylation on NCAM was clearly reduced in rat soleus muscle of aged, compared to young, adult rats. This age-related change in expression of polysialic acid probably influences the reinnervation process in aged muscle.

Localization of NCAM on NCAM-B-expressing cells with inhibited migration in collagen

The extracellular matrix is a key element in neuronal development and tumour invasion, providing a substratum which sustains the adhesion and migration of cells. In order to study interactions between the neural cell adhesion molecule (NCAM) and collagen, we transfected mouse L cells with cDNA encoding the human transmembrane NCAM isoform of 140 kDa (NCAM-B). An L-cell/collagen type I system was used to study the influence of NCAM expression on in vitro invasion. We here report that migration of NCAM-expressing cells in collagen was inhibited compared to that of NCAM-negative cells transfected with the empty vector. Immunofluorescence confocal laser scanning microscopy (CLSM) and immunogold electron microscopy using anti-human NCAM antibodies demonstrated a heterogeneous distribution of NCAM on the plasma membrane of transfected L cells grown on collagen. NCAM was preferentially located at the surface of broad cytoplasmic protrusions and slender extensions, some of which were facing the collagen. This was in contrast to the homogeneous surface distribution of NCAM on cells grown on plastic. These data suggest that NCAM and collagen type I interact, and that this might lead to the migration inhibition of NCAM-expressing cells.

Anticardiolipin antibodies in HIV infection: association with cerebral perfusion defects as detected by 99mTc-HMPAO SPECT

Anticardiolipin antibodies (ACA) belong to a heterogeneous group of antibodies directed against negatively charged phospholipids. In patients with rheumatic disorders, their presence has been correlated to the occurrence of thromboembolic complications, thrombocytopenia, abortions and other disease manifestations. Several studies have revealed the detection of mostly high-titre ACA in a significant proportion of HIV-infected patients without any known clinical relationship. In our study, ACA were detected in 17/34 HIV-infected patients, and their presence was significantly associated with the detection of cerebral perfusion abnormalities by 99mTc-HMPAO SPECT. SPECT scans were classified as normal or as focal or diffuse defects in uptake. Most patients (13/16) with cerebral perfusion defects had elevated ACA titres in contrast to 4/18 patients with normal SPECT findings (P = 0.002). Focal uptake defects were always associated with the presence of ACA. No correlation to clinical features or other laboratory parameters was evident. Our results suggest a possible implication of autoimmune mechanisms in the pathogenesis of cerebral perfusion abnormalities detected by SPECT scanning in HIV-infected patients. However, further studies are needed to evaluate the clinical significance and to develop possible therapeutic consequences.

Characterization of N-cadherin messenger RNA and polypeptide expression in rat

The cell adhesion molecule N-cadherin is a member of the cadherin gene superfamily. The protein is involved in morphogenetic processes, including neurite extension. In this study, N-cadherin mRNA and polypeptide expression were investigated in rat brain, liver, muscle, heart, kidney and lung during postnatal development and aging. Six synthetic oligonucleotide probes covering different parts of mouse N-cadherin cDNA all hybridized to 5.2, 4.3-4.4 and 3.5 kb mRNAs in rat tissues. The mRNA pattern differed between tissues and, furthermore, the amount of N-cadherin mRNA and polypeptides in brain, liver and heart was higher than in muscle, kidney and lung. N-cadherin expression decreased slightly during early postnatal development in all tissues, whereas no changes in N-cadherin expression were observed during aging. Antibodies against a fusion protein containing the transmembrane and cytoplasmic sequence of chick N-cadherin were produced. These antibodies, termed anti-N-cad-cyt, were compared to the R-156 antibodies which recognize the 24 C-terminal amino acids of N-cadherin and which have been shown to react with a broad spectrum of cadherins. Using these two antibodies, it was shown that the 130 kDa N-cadherin polypeptide was subject to calcium-dependent cleavage of the cytoplasmic domain. Conversely, in the absence of calcium the polypeptide was cleaved extracellularly, producing two C-terminal fragments of 85 and 95 kDa. A 122 kDa polypeptide was recognized by both antibodies and may be either an alternatively spliced form of N-cadherin or a closely related cadherin.

Transfection of glioma cells with the neural-cell adhesion molecule NCAM: effect on glioma-cell invasion and growth in vivo

The tumor growth and the invasive capacity of a rat glioma cell line (BT4Cn) were studied after transfection with the human transmembrane 140-kDa isoform of the neural-cell adhesion molecule, NCAM. After s.c. injection, the NCAM-transfected cells showed a slower growth rate than the parent cell line (BT4Cn). Upon intracerebral implantation with BT4Cn cells and different clones of NCAM-transfected cells, all animals developed neurological symptoms within 13-16 days. However, the tumors showed different growth characteristics. The NCAM-transfected BT4Cn cells were localized in the region of the injection site, with a sharply demarcated border between the tumor and brain tissue. In contrast, the parental cell line showed single-cell infiltration and more pronounced destruction of normal brain tissue. Using a 51Cr-release assay, spleen cells from rats transplanted with BT4Cn tumor cells generally showed a lower cytotoxic response than the spleen cells from rats transplanted with the transfected variants of BT4Cn cells, indicating that the transfection procedure in itself mediated an activation of the immune system. The present data suggest that NCAM may influence the malignant behavior of rat glioma cells in vivo.

[Doppler ultrasonography assessment of the inferior mesenteric artery. Feasibility study and definition of morphologic and flowmetric characteristics]

The conventional and Doppler US assessment of the inferior mesenteric artery has not been reported in the literature to date. In the present study, the feasibility of Doppler US of the inferior mesenteric artery was prospectively investigated in 112 consecutive nonselected patients; the corresponding morphological features (size and vessel course) and Doppler flowmetry (peak systolic, peak diastolic and mean velocities; pulsatility index) were defined. In 32 patients (29%) neither conventional nor color-Doppler nor duplex imaging was possible. Of the extant 80 patients, in 65 (81%) all the three methods allowed the correct assessment of the inferior mesenteric artery; in 15 patients (19%) the results were suboptimal (poor US visualization, or inadequate Doppler flowmetry). In 33/80 patients, arterial blood flow was quantitatively assessed in 1/min. As for the patients who underwent further diagnostic procedures--e.g., CT and angiography--a close correlation was demonstrated between the morphological and functional data obtained by Doppler US and the corresponding CT and angiographic features. The possibility of analyzing the inferior mesenteric artery with conventional and Doppler US, besides the celiac trunk and the superior mesenteric artery, should allow splanchnic circulation to be more completely assessed, thanks to information about normal hemodynamics (after a meal or in response to pharmacological treatments) as well as about the diseases known to affect intestinal perfusion--e.g., mesenteric ischemia.

Expression of N-CAM in fertilized pre- and periimplantation and parthenogenetically activated mouse embryos

The expression of the cell adhesion molecule of the immunoglobulin family, neural cell adhesion molecule (N-CAM), in the pre- and periimplantation embryo was examined by immunocytochemistry. N-CAM is expressed on unfertilized ovulated oocytes, fertilized preimplantation embryos at all stages of development and parthenogenetically activated eggs and embryos. In fertilized embryos, expression from the 4-cell stage can be partially inhibited by blocking embryonic transcription before 38 h post human chorionic gonadotropin (hCG). Expression of N-CAM was reduced on the trophoblast of day 6 blastocysts in culture, weak on the trophoblast of embryonic outgrowths and disappears from invading trophoblast in utero. An antibody against alpha(2-8) linked polysialic acid, mAb2-2B, reacted with embryos from the 8-cell stage, and staining was similarly reduced on the trophoblast of blastocysts at the time of implantation. These results suggest a role for N-CAM in the interactions of cells of the preimplantation mammalian embryo which requires further investigation.

Demonstration of (Ca(2+)-Mg2+)-ATPase activity of the neural cell adhesion molecule

In this study a possible association between (Ca(2+)-Mg2+)-ATPase activity and the neural cell adhesion molecule, NCAM, was investigated. The effects of various detergents on ATPase activity were evaluated, and it was found that solubilization of rat brain microsomes with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS, released a major fraction of the (Ca(2+)-Mg2+)-ATPase activity together with NCAM. Using different types of solid phase immunoadsorption it was shown that NCAM antibodies selectively isolated ATPase activity. Furthermore, agarose gel immunoelectrophoresis of solubilized brain microsomes followed by ATPase assay directly in the gel revealed ATPase activity associated with the NCAM immunoprecipitate. The NCAM-associated enzyme activity had a broad nucleoside triphosphate specificity and no strict selectivity for divalent cations, indicating that the enzyme probably is an ecto-ATPase. This raises a series of intriguing questions in relation to NCAM adhesive functions.