Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system.

Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

Antibody targeting of CD24 efficiently retards growth and influences cytokine milieu in experimental carcinomas.

BACKGROUND: The targeting of cancer stem cells by monoclonal antibodies offers new options for therapy. CD24 is a glycosylphosphatidylinositol-anchored membrane protein with a small protein core and a high level of glycosylation. It is overexpressed in many human carcinomas and is correlated with poor prognosis. CD24 is a marker for pancreatic and ovarian cancer stem cells, whereas breast cancer stem cells are negative for CD24. In cancer cell lines, changes of CD24 expression can alter cellular properties in vitro and tumour growth in vivo. We have shown before that monotherapy with monoclonal antibody (mAb) SWA11 to CD24 effectively retarded tumour growth in xenotransplanted mice. METHODS: Here, we have investigated in more detail the molecular mechanisms of mAb SWA11 therapeutic effects in A549 lung and SKOV3ip ovarian carcinoma models in scid/beige and CD1 mice, respectively. We focused on anti-proliferative, pro-apoptotic, anti-angiogenic and microenvironmental effects of SWA11 mAb treatment. RESULTS: We find that CD24 targeting is associated with changes in tumour cell proliferation and angiogenesis. The treatment lead to increased infiltration of tumour tissues with immune cells suggesting involvement of ADCC. We found that SWA11 mAb treatment strongly altered the intratumoural cytokine microenvironment. The addition of SWA11 mAb to gemcitabine treatment strongly potentiated its anti-cancer efficacy in A549 lung cancer model. CONCLUSION: Our data demonstrate that targeting of CD24 could be beneficial for the anti-cancer treatment combined with standard chemotherapy regimes.

Shifts in δ15 N signature following the onset of exogenous feeding in rainbow trout Oncorhynchus mykiss: importance of combining length and age data.

The δ(15) N isotopic change of recently emerged rainbow trout Oncorhynchus mykiss due to diet shift from yolk sac to exogenous feeding was evaluated in a field study. The fit of a general model including both fish length and age in days as co-variables indicates that the specific δ(15) N of individual fish at any given time along the ontogeny is determined by its growth trajectory. The results suggest that estimations based on fish size alone could bias data interpretation and maternal origin determinations in partially migratory salmonids.

Prognostic significance of L1CAM in ovarian cancer and its role in constitutive NF-κB activation.

BACKGROUND: Overexpression of L1-cell adhesion molecule (L1CAM) has been observed for various carcinomas and correlates with poor prognosis and late-stage disease. In vitro, L1CAM enhances proliferation, cell migration, adhesion and chemoresistance. We tested L1CAM and interleukin-1 beta (IL-1ß) expression in tumor samples and ascitic fluid from ovarian carcinoma patients to examine its role as a prognostic marker. PATIENTS AND METHODS: We investigated tumor samples and ascitic fluid from 232 serous ovarian carcinoma patients for L1CAM by enzyme-linked immunosorbent assay. L1CAM expression was correlated with pathoclinical parameters and patients' outcome. IL-1ß levels were measured in tumor cell lysates. Ovarian cancer cell lines were analyzed for the contribution of L1CAM to IL-1ß production and nuclear factor 'kappa-light-chain-enhancer' of activated B-cells (NF-κB) activation. RESULTS: We observed that L1CAM-expressing tumors show a highly invasive phenotype associated with restricted tumor resectability at primary debulking surgery and increased lymphogenic spread. Soluble L1CAM proved to be a marker for poor progression-free survival and chemoresistance. In ovarian carcinoma cell lines, the specific knock-down of L1CAM reduces IL-1ß expression and NF-κB activity. CONCLUSIONS: L1CAM expression contributes to the invasive and metastatic phenotype of serous ovarian carcinoma. L1CAM expression and shedding in the tumor microenvironment could contribute to enhanced invasion and tumor progression through increased IL-1ß production and NF-κB activation.

Metastatic potential severely altered by changes in tumor cell adhesiveness and cell-surface sialylation.

A plastic adherent variant line (ESb-M) of a highly invasive and metastatic murine T cell lymphoma (ESb) was found to have lost its metastatic potential while still being tumorigenic in normal syngeneic hosts. The variant retained most of its ESb-derived antigenic and biochemical characteristics but differed at binding sites for certain lectins with specificity for terminal N-acetylgalactosamine residues. Whereas such sites were masked by sialic acid on metastatic ESb cells, they became unmasked on the adherent variant line. Metastatic revertants of ESb-M cells did not express the respective lectin receptor sites because these were again masked by sialic acid. It is suggested that the masking of specific lectin receptors sites on the tumor cell surface is of crucial importance for metastatis. If freely exposed, these sites may change adherence characteristics of the cells possibly not only in vitro (to plastic) but also in vivo.

Ectodomain shedding of L1 adhesion molecule promotes cell migration by autocrine binding to integrins.

The L1 adhesion molecule plays an important role in axon guidance and cell migration in the nervous system. L1 is also expressed by many human carcinomas. In addition to cell surface expression, the L1 ectodomain can be released by a metalloproteinase, but the biological function of this process is unknown. Here we demonstrate that membrane-proximal cleavage of L1 can be detected in tumors and in the developing mouse brain. The shedding of L1 involved a disintegrin and metalloproteinase (ADAM)10, as transfection with dominant-negative ADAM10 completely abolishes L1 release. L1-transfected CHO cells (L1-CHO) showed enhanced haptotactic migration on fibronectin and laminin, which was blocked by antibodies to alpha v beta 5 and L1. Migration of L1-CHO cells, but not the basal migration of CHO cells, was blocked by a metalloproteinase inhibitor, indicating a role for L1 shedding in the migration process. CHO and metalloproteinase-inhibited L1-CHO cells were stimulated to migrate by soluble L1-Fc protein. The induction of migration was blocked by alpha v beta 5-specific antibodies and required Arg-Gly-Asp sites in L1. A 150-kD L1 fragment released by plasmin could also stimulate CHO cell migration. We propose that ectodomain-released L1 promotes migration by autocrine/paracrine stimulation via alpha v beta 5. This regulatory loop could be relevant for migratory processes under physiological and pathophysiological conditions.

Isotopic tracking of change in diet and habitat use in african elephants.

The carbon, nitrogen, and strontium isotope compositions of elephants in Amboseli Park, Kenya, were measured to examine changes in diet and habitat use since the 1960s. Carbon isotope ratios, which reflect the photosynthetic pathway of food plants, record a shift in diet from trees and shrubs to grass. Strontium isotope ratios, which reflect the geologic age of bedrock, document the concentration of elephants within the park. The high isotopic variability produced by behavioral and ecological shifts, if it is representative of other East African elephant populations, may complicate the use of isotopes as indicators of the source region of ivory.

L1 cell adhesion molecule (L1CAM) as a pathogenetic factor in endometriosis.

BACKGROUND: Endometriosis is a benign and progressive disease with a high prevalence. Women with endometriosis, especially with atypical endometriosis, have a higher probability for developing ovarian cancer compared with women without endometriosis. The L1 cell adhesion molecule (L1CAM) is over expressed in ovarian and endometrial carcinomas and is associated with a bad prognosis. Here, we have analysed L1CAM expression in endometriosis. METHODS AND RESULTS: In our study with the samples from 79 patients with, and 37 patients without, endometriosis, we found that endometriosis cell lines and short-term cultures of endometrium from women with endometriosis expressed L1CAM at the mRNA and protein level. Quantitative RT-PCR analysis showed that L1CAM was expressed at significantly higher level in the epithelial compartment from patients with endometriosis compared with healthy controls (P = 0.0126). By immunohistochemical staining, 15 of 31 ovarian endometriotic lesions (48%) were shown to have L1CAM-positive staining. Of these 15 L1CAM-positive samples, 13 were atypical endometriotic lesions. Soluble L1 present in the conditioned medium of epithelial endometrium cultures from women with endometriosis was able to stimulate neurite outgrowth as measured in a chicken ganglion assay. CONCLUSIONS: We propose that L1CAM could promote endometriosis development by increasing enervation and aggravation. L1CAM expression is higher in atypical endometriosis compared with normal endometriosis.

Differences in resistance of metastatic tumor cells and cells from local tumor growth to cytotoxicity of natural killer cells.

Cells from local tumor growth (L-3LL) were compared to metastatic tumor cells (M-3LL) for their susceptibility to the cytotoxicity of natural killer (NK) cells. M-3LL cells were more resistant in vitro to NK cells from normal spleens than were L-3LL cells. A similar phenomenon of relative resistance of metastatic cells to NK activity was found when L-3LL and M-3LL cells were admixed with normal spleen cells and then inoculated into syngeneic mice. Because hybrid resistance was shown to be based on mechanisms that in principle are similar to mechanisms involved in NK activity, we tested the growth of M-3LL and L-3LL cells in semiallogeneic F1 mice. The in vitro effect of NK cells from semiallogeneic mice on M-3LL and L-3LL cells was tested in parallel. In vitro tests showed that irrespective of the haplotype of the spleen cell donors, L-3LL cells were more susceptible to NK activity than were M-3LL cells. In vivo experiments indicated that whereas M-3LL and L-3LL cells grew similarly in syngeneic recipients, M-3LL cells grew far more in F1 mice than did L-3LL cells. Thus metastatic cells are more resistant to NK activity than are cells of the local tumor growth. This relative resistance may determine, among other factors, the metastatic spread and progression of tumor cells.

Differences in cell surface antigens of tumor metastases and those of the local tumor.

Tests were made to determine whether cell surface tumor antigens of metastases differed from the tumor antigens of the cell population of the local tumor growth. C57BL/6 mouse spleen lymphocytes sensitized against monolayers of the local growth of the 3LL Lewis lung carcinoma (L-3LL) in the presence of syngeneic serum generated lymphocytes that were cytotoxic to L-3LL but significantly less cytotoxic to target cells derived from lung metastases (M-3LL). Lymphocytes sensitized against M-3LL were significantly more cytotoxic against M-3LL than against L-3LL cells. Anti-M-3LL cytotoxic lymphocytes but not anti-L-3LL, admixed with either L-3LL cells or M-3LL tumor cells, when injected into syngeneic recipients reduced lung metastasis significantly. Results indicated that cells with high metastatic capacity and distinct antigenic properties exist within the tumor cell population and that immunoselection might be involved in the production of lung metastases.

Different patterns of lectin binding and cell surface sialylation detected on related high- and low-metastatic tumor lines.

We have analyzed cell surface-bound carbohydrates in two different model systems for metastasis composed of closely related tumor cell lines with differing metastatic potential. The first system studied was that of the DBA/2-derived T-lymphoma lines (Eb/ESb) and some recently established sublines of ESb with altered metastatic behavior (ESb-M and ESb-MR). The second system consisted of the highly metastatic MDAY-D2 cells, a wheat germ agglutinin-resistant low metastatic subline MDW40, and two metastatic revertants from the latter. The cells were stained with fluorescein isothiocyanate-conjugated lectins and analyzed by flow cytofluorography. All low-metastatic tumor lines expressed receptor sites for the lectins soybean agglutinin (SBA) and Vicia villosa (VV). The metastatic lines had the respective lectin binding sites blocked by sialic acid (SA). A good correlation was found within the cell lineages Eb leads to ESb leads to ESb-M leads to ESb-MR and MDAY-D2 leads to MDW40 leads to MDW40M1 between reactivity of SBA and VV and metastatic potential. The amount of neuraminidase-accessible SA was similar for all cell types (except MDW40) indicating differences in the positioning of SA. For high-metastatic ESb cells, the sialylation of SBA and VV receptor sites was paralleled by a relative decrease of SA associated with receptor sites for peanut agglutinin. Low-metastatic Eb cells, in contrast, had their peanut agglutinin receptor sites sialylated but expressed asialylated SBA and VV receptor sites. Eb cells were also found to have 2-fold higher activities in galactose-specific sialyltransferases. It is proposed that the differences in positioning of SA on the cell surface leading to masking or unmasking of terminal sugars could influence the metastatic potential of tumor cells.

Nanoscale petrographic and geochemical insights on the origin of the Palaeoproterozoic stromatolitic phosphorites from Aravalli Supergroup, India.

Stromatolites composed of apatite occur in post-Lomagundi-Jatuli successions (late Palaeoproterozoic) and suggest the emergence of novel types of biomineralization at that time. The microscopic and nanoscopic petrology of organic matter in stromatolitic phosphorites might provide insights into the suite of diagenetic processes that formed these types of stromatolites. Correlated geochemical micro-analyses of the organic matter could also yield molecular, elemental and isotopic compositions and thus insights into the role of specific micro-organisms among these communities. Here, we report on the occurrence of nanoscopic disseminated organic matter in the Palaeoproterozoic stromatolitic phosphorite from the Aravalli Supergroup of north-west India. Organic petrography by micro-Raman and Transmission Electron Microscopy demonstrates syngeneity of the organic matter. Total organic carbon contents of these stromatolitic phosphorite columns are between 0.05 and 3.0 wt% and have a large range of δ(13) Corg values with an average of -18.5‰ (1σ = 4.5‰). δ(15) N values of decarbonated rock powders are between -1.2 and +2.7‰. These isotopic compositions point to the important role of biological N2 -fixation and CO2 -fixation by the pentose phosphate pathway consistent with a population of cyanobacteria. Microscopic spheroidal grains of apatite (MSGA) occur in association with calcite microspar in microbial mats from stromatolite columns and with chert in the core of diagenetic apatite rosettes. Organic matter extracted from the stromatolitic phosphorites contains a range of molecular functional group (e.g. carboxylic acid, alcohol, and aliphatic hydrocarbons) as well as nitrile and nitro groups as determined from C- and N-XANES spectra. The presence of organic nitrogen was independently confirmed by a CN(-) peak detected by ToF-SIMS. Nanoscale petrography and geochemistry allow for a refinement of the formation model for the accretion and phototrophic growth of stromatolites. The original microbial biomass is inferred to have been dominated by cyanobacteria, which might be an important contributor of organic matter in shallow-marine phosphorites.

A novel germ line p53 mutation in intron 6 in diverse childhood malignancies.

Screening for p53 mutations in exons 5 to 8 in 124 pediatric malignancies identified 18 abnormal shifts using single strand conformation polymorphism: 12 were missense mutations and in 6, no mutation was detected in the exon or in the splice donor acceptor sequences. Sequencing was then performed in the adjacent introns, revealing a G to A base substitution at 39 base pairs upstream to exon 7. This mutation was identified in the germ line of five of the patients, and also in the father of one, whose parents were available. For comparison, of the 184 normal controls similarly screened, only one had this mutation (P=0.036). Positive staining of p53 protein was observed in three of the paraffin embedded tissues that were available: brain tumor, rhabdomyosarcoma, and lymphocytes from a normal lymph node from the rhabdomyosarcoma patient. All tumors with the identified intron mutation were Li-Fraumeni syndrome tumors. Sequencing of all exons including splice sites was performed and revealed no mutation. We suggest that this mutation in intron 6 of the p53 gene stabilizes the wild type p53 protein, resulting in its abnormal accumulation. Mutations in the noncoding region of p53 should be further studied.

Diastolic biomechanics in normal infants utilizing MRI tissue tagging.

BACKGROUND: Most of what is known about diastolic function in normal infants is derived from flow and pressure measurements. Little is known about regional diastolic strain and wall motion. METHODS AND RESULTS: Magnetic resonance tissue tagging was performed in 11 normal infants to determine regional diastolic strain and wall motion. Tracking diastolic motion of the intersection points and finite strain analysis yielded regional rotation, radial displacement, and E(1) and E(2) strains at 3 short-axis levels (significance was defined as P<0.05). E(2) "circumferential lengthening" strains were significantly greater at the lateral wall, regardless of short-axis level, whereas E(1) "radial thinning" strains were similar in all wall regions at all short-axis levels. In general, no differences were noted in strain dispersion within a wall region or in endocardial/epicardial strain at all short-axis levels. At all short-axis levels, septal radial motion was significantly less than in other wall regions. No significant differences in radial wall motion between short-axis levels were noted. Rotation was significantly greater at the apical short-axis level in all wall regions than in other short-axis levels, and it was clockwise. At the atrioventricular valve, septal and anterior walls rotated slightly clockwise, whereas the lateral and inferior walls rotated counterclockwise. CONCLUSIONS: Diastolic biomechanics in infants are not homogeneous. The lateral walls are affected most by strain, and the septal walls undergo the least radial wall motion. Apical walls undergo the most rotation. These normal data may help in the understanding of diastolic dysfunction in infants with congenital heart disease.

Imaging of pulmonary venous pathway obstruction in patients after the modified Fontan procedure.

To evaluate the efficacy of chest roentgenograms and echocardiograms in identifying pulmonary venous pathway obstruction in patients after the modified Fontan procedure, the records of 297 patients who underwent 307 Fontan procedures between 1984 and 1990 were reviewed. Twelve cases of pulmonary venous pathway obstruction documented by autopsy (3 cases) or cardiac catheterization (9 cases with an A wave gradient greater than or equal to 4 mm Hg) were found in 10 patients (mean age 43 +/- 28 months). The mechanisms of obstruction included narrow pulmonary vein ostia in six cases, narrow left atrial outlet in four and atrial baffle obstruction in three. Two causes of obstruction were present in one case. No patient had pulmonary venous congestion on chest roentgenograms. Pathway diameters indexed to 3 square root of body surface area with two-dimensional echocardiography were found to be 6.8 +/- 1.2 mm/3 square root of m2 in the subcostal frontal view, 7.9 +/- 0.6 mm/3 square root of m2 in the subcostal sagittal view and 6.5 +/- 1.7 mm/3 square root of m2 in the apical "four-chamber" view. These values differed significantly from those in 11 age-matched patients undergoing the Fontan procedure without pulmonary venous pathway obstruction documented by catheterization (p = 0.001). With pulsed Doppler ultrasound, there was a relatively narrow range of velocities distal to the obstruction (1.3 to 2.5 m/s). In five of the seven cases with pulsed Doppler measurements, flow was continuous and the Doppler spectral recordings were not phasic. Thus, in patients who have undergone the Fontan procedure and have pulmonary venous pathway obstruction 1) chest roentgenography cannot be used as a screening tool; 2) distal velocities as low as 1.3 m/s occur, usually with nonphasic, continuous forward flow; and 3) pathway diameters indexed to 3 square root of body surface area may be used as an output-independent parameter to cross-check Doppler data.

Late ventricular geometry and performance changes of functional single ventricle throughout staged Fontan reconstruction assessed by magnetic resonance imaging.

OBJECTIVES: We sought to test the hypothesis that late ventricular geometry and performance changes occur in functional single ventricles as they progress through staged Fontan reconstruction. BACKGROUND: Indexes of ventricular geometry and performance are important in evaluating the functional state of the heart. Magnetic resonance imaging determines these indexes in complex ventricular shapes with minimal geometric assumptions. Previous studies have shown that 1 week after hemiFontan, the mass/volume ratio markedly increases. METHODS: Multiphase, multislice, spin echo (n = 5) and cine (n = 30) magnetic resonance imaging was performed in 35 patients with a functional single ventricle (1 week to 12 years old) at various stages of Fontan reconstruction (15 in the pre hemiFontan stage, 11 after [6 to 9 months] the hemiFontan procedure and 9 after [1 to 2 years] the Fontan procedure). Volume and mass were calculated at end-systole and end-diastole. Ventricular output was then obtained. Ventricular centroid motion was also calculated. RESULTS: No difference was noted (power > 72%) from the pre hemiFontan stage to 6 to 9 months after the hemiFontan procedure in (mean +/- SD) end-diastolic volume (104 +/- 24 vs. 123 +/- 40 cc/m2), mass (171 +/- 46 vs. 202 +/- 61 g/m2), ventricular output (7.9 +/- 2.2 vs. 6.6 +/- 2.4 liters/min per m2) or centroid motion (6.9 +/- 2.8 vs. 6.7 +/- 2. mm/m2). Patients in the Fontan group demonstrated a marked decrease in all indexes, indicating significant volume unloading and decrease in mass and ventricular performance. Mass/volume ratio was not significantly different among all three groups. CONCLUSIONS: No geometric and performance changes from the volume-loaded stage are noted 6 to 9 months after the hemiFontan procedure; however, major changes occur 1 to 2 years after the Fontan procedure. The dramatic changes in the mass/volume ratio seen early after the hemiFontan procedure were not detected at 6 to 9 months. Furthermore diminution of mass, volume and ventricular performance are present at least 2 years after the Fontan procedure.

Photosynthetic Fractionation of the Stable Isotopes of Oxygen and Carbon.

Isotope discrimination during photosynthetic exchange of O2 and CO2 was measured using enzyme, thylakoid, and whole cell preparations. Evolved oxygen from isolated spinach thylakoids was isotopically identical (within analytical error) to its source water. Similar results were obtained with Anacystis nidulans Richter and Phaeodactylum tricornutum Bohlin cultures purged with helium. For consumptive reactions, discrimination ([delta], where 1 + [delta]/1000 equals the isotope effect, k16/k18 or k12/k13) was determined by analysis of residual substrate (O2 or CO2). The [delta] for the Mehler reaction, mediated by ferredoxin or methylviologen, was 15.3[per mille (thousand) sign]. Oxygen isotope discrimination during oxygenation of ribulose-1,5-bisphosphate (RuBP) catalyzed by RuBP carboxylase/oxygenase (Rubisco) was 21.3[per mille (thousand) sign] and independent of enzyme source, unlike carbon isotope discrimination: 30.3[per mille (thousand) sign] for spinach enzyme and 19.6 to 23[per mille (thousand) sign] for Rhodospirillum rubrum and A. nidulans enzymes, depending on reaction conditions. The [delta] for O2 consumption catalyzed by glycolate oxidase was 22.7[per mille (thousand) sign]. The expected overall [delta] for photorespiration is about 21.7[per mille (thousand) sign]. Consistent with this, when Asparagus sprengeri Regel mesophyll cells approached the compensation point within a sealed vessel, the [delta]18O of dissolved O2 came to a steady-state value of about 21.5[per mille (thousand) sign] relative to the source water. The results provide improved estimates of discrimination factors in several reactions prominent in the global O cycle and indicate that photorespiration plays a significant part in determining the isotopic composition of atmospheric oxygen.

Pigment production and isotopic fractionations in continuous culture: okenone producing purple sulfur bacteria Part II.

Okenone is a carotenoid pigment unique to certain members of Chromatiaceae, the dominant family of purple sulfur bacteria (PSB) found in euxinic photic zones. Diagenetic alteration of okenone produces okenane, the only recognized molecular fossil unique to PSB. The in vivo concentrations of okenone and bacteriochlorophyll a (Bchl a) on a per cell basis were monitored and quantified as a function of light intensity in continuous cultures of the purple sulfur bacterium Marichromatium purpuratum (Mpurp1591). We show that okenone-producing PSB have constant bacteriochlorophyll to carotenoid ratios in light-harvesting antenna complexes. The in vivo concentrations of Bchl a, 0.151 ± 0.012 fmol cell(-1), and okenone, 0.103 ± 0.012 fmol cell(-1), were not dependent on average light intensity (10-225 Lux) at both steady and non-steady states. This observation revealed that in autotrophic continuous cultures of Mpurp1591, there was a constant ratio for okenone to Bchl a of 1:1.5. Okenone was therefore constitutively produced in planktonic cultures of PSB, regardless of light intensity. This confirms the legitimacy of okenone as a signature for autotrophic planktonic PSB and by extrapolation water column euxinia. We measured the δ(13)C, δ(15)N, and δ(34)S bulk biomass values from cells collected daily and determined the isotopic fractionations of Mpurp1591. There was no statistical relationship in the bulk isotope measurements or stable isotope fractionations to light intensity or cell density under steady and non-steady-state conditions. The carbon isotope fractionation between okenone and Bchl a with respect to overall bulk biomass ((13)ε pigment - biomass) was 2.2 ± 0.4‰ and -4.1 ± 0.9‰, respectively. The carbon isotopic fractionation (13ε pigment-CO2) for the production of pigments in PSB is more variable than previously thought with our reported values for okenone at -15.5 ± 1.2‰ and -21.8 ± 1.7‰ for Bchl a.

Ecologically and geologically relevant isotope signatures of C, N, and S: okenone producing purple sulfur bacteria Part I.

Purple sulfur bacteria (PSB) are known to couple the carbon, nitrogen, and sulfur cycling in euxinic environments. This is the first study with multiple strains and species of okenone-producing PSB to examine the carbon (C), nitrogen (N), and sulfur (S) metabolisms and isotopic signatures in controlled laboratory conditions, investigating what isotopic fractionations might be recorded in modern environments and the geologic record. PSB play an integral role in the ecology of euxinic environments and produce the unique molecular fossil okenane, derived from the diagenetic alteration of the carotenoid pigment okenone. Cultures of Marichromatium purpuratum 1591 (Mpurp1591) were observed to have carbon isotope fractionations ((13)ε biomass - CO2), via RuBisCO, ranging from -16.1 to -23.2‰ during exponential and stationary phases of growth. Cultures of Thiocapsa marina 5653 (Tmar5653) and Mpurp1591 had a nitrogen isotope fractionation ((15)ε biomass - NH 4) of -15‰, via glutamate dehydrogenase, measured and recorded for the first time in PSB. The δ(34) SVCDT values and amount of stored elemental sulfur for Mpurp1591 cells grown autotrophically and photoheterotrophically were dependent upon their carbon metabolic pathways. We show that PSB may contribute to the isotopic enrichments observed in modern and ancient anoxic basins. In a photoheterotrophic culture of Mpurp1591 that switched to autotrophy once the organic substrate was consumed, there were bulk biomass δ(13)C values that span a broader range than recorded across the Late Devonian, Permian-Triassic, Triassic-Jurassic, and OAE2 mass extinction boundaries. This finding stresses the complexities in interpreting and assigning δ(13)C values to bulk organic matter preserved in the geologic record.

A simplified approach for assessment of intracardiac baffles and extracardiac conduits in congenital heart surgery with two- and three-dimensional magnetic resonance imaging.

BACKGROUND: Intracardiac baffles and extracardiac conduits have been used in the reconstructive surgery of a broad spectrum of congenital cardiac malformations. Periodic evaluation of these structures may not lend itself readily to echocardiographic and angiographic imaging. The purpose of the study was to describe the experience of our institution with the use of magnetic resonance imaging (MRI) in evaluating conduits and baffles and to describe the simplified approach we developed to image these structures, which allows for grouping individual lesions into broad categories. METHODS AND RESULTS: We retrospectively reviewed our MRI experience in visualizing these structures from 1989-1996. One hundred thirty-nine patients underwent MRI to visualize 144 structures (116 baffles, 28 conduits). The 116 baffles included 86 Fontan, 16 Mustard, 6 Senning, 6 left ventricle to aorta, 1 right ventricle to aorta, and 1 pulmonary vein to left atrium baffle. The 28 conduits included 15 right ventricle to pulmonary artery, 4 left ventricular apical to aorta, 2 left ventricle to pulmonary artery, 3 aorta to aorta, 2 inferior vena cava to left atrium conduits, and 2 aortic root replacements. Of the 3 aortic-aortic conduits, 1 was in conjoined twins. Both inferior vena cava-left atrial conduits were in a Baffes procedure. An infectious mass missed by echocardiography in a right ventricle to pulmonary artery conduit was visualized by MRI. With multiplanar reconstruction, contiguous images were stacked atop each other and resliced to define the salient points of the anatomy. Three-dimensional reconstruction further added to this delineation. All structures were visualized successfully, and an assessment of obstruction was made. Multiple examples of conduit and baffle narrowing were diagnosed by spin echo and cine MRI and were subsequently confirmed by catheterization and surgical inspection. CONCLUSION: MRI, with multiplanar and 3-dimensional reconstruction, is useful in examining the variety of baffles and conduits used in congenital heart surgery. MRI can add to the care of patients whose echocardiographic windows or whose angiographically overlapping structures do not allow adequate delineation of conduits and baffles.