Atmospheric CO2 levels from 2.7 billion years ago inferred from micrometeorite oxidation.

Earth's atmospheric composition during the Archean eon of 4 to 2.5 billion years ago has few constraints. However, the geochemistry of recently discovered iron-rich micrometeorites from 2.7 billion-year-old limestones could serve as a proxy for ancient gas concentrations. When micrometeorites entered the atmosphere, they melted and preserved a record of atmospheric interaction. We model the motion, evaporation, and kinetic oxidation by CO2 of micrometeorites entering a CO2-rich atmosphere. We consider a CO2-rich rather than an O2-rich atmosphere, as considered previously, because this better represents likely atmospheric conditions in the anoxic Archean. Our model reproduces the observed oxidation state of micrometeorites at 2.7 Ga for an estimated atmospheric CO2 concentration of >70% by volume. Even if the early atmosphere was thinner than today, the elevated CO2 level indicated by our model result would help resolve how the Late Archean Earth remained warm when the young Sun was ~20% fainter.

Environmental niches and metabolic diversity in Neoarchean lakes.

The diversification of macro-organisms over the last 500 million years often coincided with the development of new environmental niches. Microbial diversification over the last 4 billion years likely followed similar patterns. However, linkages between environmental settings and microbial ecology have so far not been described from the ancient rock record. In this study, we investigated carbon, nitrogen, and molybdenum isotopes, and iron speciation in five non-marine stratigraphic units of the Neoarchean Fortescue Group, Western Australia, that are similar in age (2.78-2.72 Ga) but differ in their hydro-geologic setting. Our data suggest that the felsic-dominated and hydrologically open lakes of the Bellary and Hardey formations were probably dominated by methanogenesis (δ13 Corg  = -38.7 ± 4.2‰) and biologic N2 fixation (δ15 Nbulk  =-0.6 ± 1.0‰), whereas the Mt. Roe, Tumbiana and Kylena Formations, with more mafic siliciclastic sediments, preserve evidence of methanotrophy (δ13 Corg as low as -57.4‰, δ13 Ccarb as low as -9.2‰) and NH3 loss under alkaline conditions. Evidence of oxygenic photosynthesis is recorded only in the closed evaporitic Tumbiana lakes marked by abundant stromatolites, limited evidence of Fe and S cycling, fractionated Mo isotopes (δ98/95 Mo = +0.4 ± 0.4‰), and the widest range in δ13 Corg (-57‰ to -15‰), suggesting oxidative processes and multiple carbon fixation pathways. Methanotrophy in the three mafic settings was probably coupled to a combination of oxidants, including O2 and SO42- . Overall, our results may indicate that early microbial evolution on the Precambrian Earth was in part influenced by geological parameters. We speculate that expanding habitats, such as those linked to continental growth, may have been an important factor in the evolution of life.

Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures.

Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N2, but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean-presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N2 pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN2 and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN2 to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO2, and (c) atmospheric oxygenation could have initiated a stepwise pN2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N2 and O2 is a signature of an oxygen-producing biosphere. Key Words: Biosignatures-Early Earth-Planetary atmospheres. Astrobiology 16, 949-963.

Oesophageal substitution with free and pedicled jejunum: short- and long-term outcomes.

In children, the indications for oesophageal substitution are principally, long gap oesophageal atresia (OA), severe anastomotic disruption following primary repair of OA and severe caustic or peptic strictures. We present an outcome review of eight cases who underwent oesophageal substitution with jejunum at our institution between 1986 and 2001. The purpose of this study was to evaluate our experience with free/pedicled jejunal grafts and its long-term outcome as an oesophageal substitute. Operative and postoperative outcome with free and pedicled jejunal grafts in four cases of pure OA, two cases of OA and distal tracheo-oesophageal fistula (TOF), one patient with a high retrolaryngeal oesophageal web and one case of severe caustic oesophageal stricture. Six patients had an oesophagostomy and a gastrostomy fashioned previously. Eleven free jejunal grafts were performed in six patients (three intraoperative redo interpositions for immediate graft loss, three separate grafts in one patient and two free grafts in two patients). One patient's pedicled jejunal graft proximally required microvascular anastomosis while the other had a pedicled graft without microvascular anastomosis. Early postoperative complications included four upper anastomotic leaks (three free grafts, one pedicled with microvascular support), pneumothorax requiring prolonged ventilation and Horner's syndrome. Recurrent laryngeal nerve injury occurred in the patient who had a high retrolaryngeal oesophageal web. During follow up (5-18 years) late complications of upper anastomotic stricture in four patients and graft redundancy with subsequent kinking of the lower anastomosis were observed in one patient. Three patients established a complete oral diet; a further three patients relied on supplemental gastrostomy feeds and one patient is entirely gastrostomy fed. There were two late deaths, one from aspiration and the other from a severe asthmatic attack (5 and 7 months postoperatively, respectively). Our results indicate that there are significant complications related to the use of free jejunal grafts. Early recognition and treatment are of paramount importance in the ultimate achievement of a successful technical outcome.

Duodenal duplication cyst: beware of the lesser sac collection.

A 11-month-old boy presented with a 4-month history of failure to thrive. His initial presentation was highlighted by fever, postprandial abdominal pain and lethargy. The diagnosis was elusive despite extensive investigations. A contrast enhanced abdominal computerised tomogram (CT) suggested the presence of a pancreatic pseudocyst. At laparotomy, a lesser sac collection was drained and the patient's general condition improved. Three weeks postoperatively, the symptoms recurred and a second contrast enhanced abdominal CT revealed a duodenal duplication cyst. A 6.5-cm duodenal duplication cyst communicating with the fourth part of the duodenum was resected in its entirety with resolution of the patients' symptoms and establishment of adequate growth.

Unusual complication of a central venous line in a neonate.

The placement of a central venous line in a low birthweight neonate led to a complication that highlights the need for continued vigilance after the position of the line is checked and thought satisfactory.

The primary management of testicular maldescent in gastroschisis.

Gastroschisis (GS) is the commonest abdominal-wall defect in the Western world. The conventional practice has been reduction of the viscera and closure of the abdominal wall as an emergency procedure. The testis is often a part of the prolapsed viscera along with the bowel loops, stomach, fallopian tube, etc. The primary management of prolapsed (PT) (3) and intra-abdominal (5) testes (IAT) in this condition was studied in 16 consecutive male babies with GS, each was managed by simple reposition of the testes and closure of the abdominal wall. The babies were followed up for spontaneous descent of the testes. At 18-month follow-up, all five IAT had descended into the scrotum spontaneously and were palpably normal. Of the three extra-abdominal PT, two had descended into the scrotum and were normal in size and on palpation. One was palpable in the superficial inguinal pouch. Simple reposition of the testes into the abdomen and closure of the abdominal defect is the correct approach for primary management of PT or IAT in a newborn with GS.

Central-venous access through the peripheral route in surgical neonates: an audit of 125 consecutive lines from a regional neonatal centre.

A long Percutaneous silastic IV line is frequently used in surgical neonates for infusion of hyperosmolar parenteral nutrition fluid into a central vein for several days without the need for operative insertion of a Broviac catheter or risks of direct puncture of a central vein. Our study was aimed at auditing the performance of 125 consecutive lines over a 2-year period. During this period, insertion was attempted in 125 babies; in 13 cases the line could not be inserted because of technical problems. The gestational ages varied between 25 and 41 weeks and weights between 630 g and 4.2 kg. Success did not appear to be related to the age or weight of the baby. The mean duration of complication-free performance was 22.4 days. There was a significant difference between the complication rate of lines inserted in the operating theatre versus those on the ward (P < 0.05). There was no significant increase in complications in lines used for over 4 weeks. The technique adopted by us for inserting these lines is likely to succeed in the majority of cases, including premature and small-for-dates babies. In our experience, lines inserted in the controlled theatre environment either before or after abdominal surgery performed better. The manufacturer's recommendation to electively change the line every 4 weeks needs further prospective evaluation.

Dysgerminoma associated with hypercalcemia: A case report.

Hypercalcemia is an extremely rare paraneoplastic manifestation of malignancy in children. The authors report a case of dysgerminoma in a 14-year-old girl associated with severe hypercalcemia that only resolved after excision of the tumor. There are only 6 previously reported cases of dysgerminoma associated with hypercalcemia. Serum calcium levels should be checked in all children with solid ovarian tumors. Hypercalcemia in such circumstances may be resistant to medical management, and surgical resection of the tumor results in the normalization of calcium levels.

The preparation, solubilisation and binding characteristics of a beta 2-adrenoceptor isolated from transfected Chinese hamster cells.

beta 2-Adrenoceptor agonists (beta-agonists) are well known for their growth promoting and repartitioning effects in many species. Although the use of these compounds to increase muscle mass in stockfarming is prohibited within the EU, under directive 96/22/EC, significant illegal use still occurs. With legal and illegal synthesis of new structurally related compounds, the detection of traditional beta-agonists and new derivatives becomes increasingly problematical. This method describes the isolation and solubilisation of a beta 2-adrenoceptor from a transfected Chinese hamster ovary cell line, using the detergent digitonin. The solubilised receptor retained its activity and was isolated from the cell membrane at a concentration of 550 +/- 100 fmol mg-1 of solubilised protein. Competition analysis using the tritiated antagonist dihydroalprenolol revealed receptor affinity for five structurally different beta-agonists, with IC50 values ranging from 2.1 +/- 0.76 x 10(-7) M for salmeterol to 1.1 +/- 0.62 x 10(-5) M for ractopamine. This study has demonstrated that transfected cell lines with a high expression of beta 2-adrenoceptors are a convenient source of active receptor material. Solubilised beta 2-adrenoceptors could form the basis of a multi-analyte screening assay for use in routine screening.

Isotopic evidence for microbial sulphate reduction in the early Archaean era.

Sulphate-reducing microbes affect the modern sulphur cycle, and may be quite ancient, though when they evolved is uncertain. These organisms produce sulphide while oxidizing organic matter or hydrogen with sulphate. At sulphate concentrations greater than 1 mM, the sulphides are isotopically fractionated (depleted in 34S) by 10-40/1000 compared to the sulphate, with fractionations decreasing to near 0/1000 at lower concentrations. The isotope record of sedimentary sulphides shows large fractionations relative to seawater sulphate by 2.7 Gyr ago, indicating microbial sulphate reduction. In older rocks, however, much smaller fractionations are of equivocal origin, possibly biogenic but also possibly volcanogenic. Here we report microscopic sulphides in approximately 3.47-Gyr-old barites from North Pole, Australia, with maximum fractionations of 21.1/1000, about a mean of 11.6/1000, clearly indicating microbial sulphate reduction. Our results extend the geological record of microbial sulphate reduction back more than 750 million years, and represent direct evidence of an early specific metabolic pathway--allowing time calibration of a deep node on the tree of life.

Pyloric atresia: five new cases, a new association, and a review of the literature with guidelines.

BACKGROUND/PURPOSE: Pyloric atresia is an uncommon condition occurring in 1 of 100,000 live births. When occurring in isolation, the clinical course usually is uncomplicated after surgical treatment. However, it may occur in association with other congenital abnormalities. The authors present 5 new cases, 3 of associated abnormalities including 1 of esophageal atresia and 2 of agenesis of the gall bladder and malrotation. Agenesis of the gall bladder has not been described previously in combination with pyloric atresia. The literature has been reviewed and guidelines are suggested for the management. METHODS: The case records of 4 neonates who presented to the author's institution between January 1998 and June 1999 and 1 who presented at another center in 1991 were reviewed. A Medline literature search was performed, and guidelines were developed for the management of this condition based on our cases and the literature review. RESULTS: Patients 1 and 5 had no associated anomalies. Patient 2 had associated esophageal atresia, tracheoesophageal fistula, atrial septal defect, crossed renal ectopia, malrotation, and absent gall bladder. Patient 3 had a rectovestibular fistula, vaginal atresia, atrial septal defect, malrotation absent gallbladder, and absent extrahepatic portal vein. Patient 4 had epidermolysis bullosa. Patients 2 and 5 had unremarkable recoveries, patients 2 and 3 had markedly delayed gastric emptying that responded to cisapride. Patient 3 has portal hypertension and remains under close follow-up. Patient 4 died at 22 days of age of pseudomonas sepsis. CONCLUSIONS: Based on our cases and literature review, we have adopted the following guidelines: (1) All children with pyloric atresia should be screened for multiple anomalies. (2) Delayed gastric emptying should be considered early and may respond to prokinetic agents. (3) Association with Epidermolysis bullosa should not preclude surgical treatment. (4) A skin biopsy specimen should be taken at the time of surgery for electron microscopy if there is a family history of epidermolysis bullosa.

A microtitre plate assay for the detection of antibiotics in porcine urine.

Techniques for screening porcine samples for antimicrobial residues in the EU usually involve analysis of samples taken post slaughter, and are either time consuming or expensive. Some of the positive test results at this screening stage could be avoided by allowing the animal sufficient withdrawal time following drug treatment. A method is described that can detect the presence of five major antibiotics in porcine urine at concentrations below 1 microgram ml-1 for each of the compounds. The test uses Bacillus subtilis, which is already widely employed in antimicrobial inhibition assays, and when combined with a colorimetric substrate, p-nitrophenyl-beta-D-glucopyranoside, can detect inhibitory substances within an assay time of four and a half hours. The method, which uses microtitre plate technology, could be developed into a convenient test kit for use at farm level to determine whether animals were still excreting antimicrobials in their urine prior to their submission for slaughter.

Archean molecular fossils and the early rise of eukaryotes.

Molecular fossils of biological lipids are preserved in 2700-million-year-old shales from the Pilbara Craton, Australia. Sequential extraction of adjacent samples shows that these hydrocarbon biomarkers are indigenous and syngenetic to the Archean shales, greatly extending the known geological range of such molecules. The presence of abundant 2alpha-methylhopanes, which are characteristic of cyanobacteria, indicates that oxygenic photosynthesis evolved well before the atmosphere became oxidizing. The presence of steranes, particularly cholestane and its 28- to 30-carbon analogs, provides persuasive evidence for the existence of eukaryotes 500 million to 1 billion years before the extant fossil record indicates that the lineage arose.

Regulation and expression of multidrug resistance (MDR) transcripts in the intestinal epithelium.

A paucity of information exists on the regulation of gene expression in the undifferentiated intestine. The intestinal epithelium is one of the few normal tissues expressing the multidrug resistance (MDR) genes that confer the multidrug resistant phenotype to a variety of tumours. Expression of mdr1a has been observed in the primitive rat intestinal epithelial cell line, IEC-18. It is hypothesized that characterization of MDR gene expression in IEC-18 cells will provide insight into gene regulation in undifferentiated intestinal cells. A series of hamster mdr1a promoter deletion constructs was studied in IEC-18 and a region with 12-13-fold enhancer activity was identified. This region was shown to function in an orientation- and promoter context-independent manner, specifically in IEC-18 cells. Unexpectedly, Northern probing revealed a greater expression of mdr1b than mdr1a in IEC-18 cells. A quantitative reverse transcription polymerase chain reaction assay was used to compare the relative expression of MDR genes in IEC cells, fetal intestine, and in the undifferentiated and differentiated components of adult intestinal epithelium. MDR transcript levels in IEC cells were found to resemble those of fetal intestine and small intestinal crypts, where a conversion from mixed mdr1a/mdr1b to predominantly mdr1a expression occurs as cells mature. This work describes two contributions to the field of gene regulation in the undifferentiated intestine--first, the initial characterization of a putative mdr1a enhancer region with specificity for primitive intestinal cells and secondly, the first report of mdr1b detection in the intestine and its expression in primitive cell types.

Acritarchs and microfossils from the Mesoproterozoic Bangemall Group, northwestern Australia.

Three microfossil assemblages occur in the Mesoproterozoic Bangemall Group (1625-1000 Ma) of northwestern Australia, each occupying a different environmental and taphonomic setting. In peritidal environments, benthic prokaryotic filaments and spheroids of matting habit and small size were permineralized by early diagenetic silicification of stromatolitic carbonates. In shallow subtidal environments, benthic filaments of large size and nonmatting habit and planktonic sphaeromorph acritarchs with thin walls and moderate dimensions were compressed in mildly kerogenous shale. In deeper subtidal environments, planktonic megasphaeromorph acritarchs with thick walls were initially entombed in concretionary nodules in highly kerogenous shale and then permineralized by silica during later diagenesis. Taxonomic diversity and numerical abundance evidently decrease offshore. The three assemblages have typical Mesoproterozoic aspects: peritidal benthic habitats were dominated by Siphonophycus-Sphaerophycus-Eosynechococcus-Myxococcoides-Palaeopleurocapsa, shallow subtidal settings were occupied by Siphonophycus-Leiosphaeridia-Pterosphermopsimorpha-Satka, and offshore plankton consisted solely of very large chuarid acritarchs. Because of its taphonomic restriction to mid-intertidal stromatolites, the peritidal assemblage can be equated in microenvironment with a similar assemblage in the Neoproterozoic Draken Conglomerate, suggesting that ecological stasis at the community level can last for intervals up to 900 million years. In the deeper subtidal assemblage, the common chuarid has an unusual mode of preservation, in three dimensions in early diagenetic concretions, revealing that it possesses a thick multilamellate wall. Because of this distinctive ultrastructure, the new genus Crassicorium is erected for these fossils, which are among the oldest indubitable eukaryotes. Very large (34-55 micrometers in diameter) filaments from shallow subtidal habitats are assigned to the emended species Siphonophycus punctatum.

Backache: a rare diagnosis and unusual complication.

We report an adolescent girl who presented with an acute exacerbation of a chronic backache of 6 months duration. She complained of dribbling micturition, constipation, and an irresistible urge to strain for 72 h. In the waiting area of the local hospital she developed sudden, severe chest pain with progressive swelling of the upper torso. This proved to be the mode of presentation of a haematocolpos due to an imperforate hymen with the unusual complication of mediastinal emphysema. Imperforate hymen is a rare diagnosis, but should be considered when dealing with an adolescent girl with lower abdominal symptoms or backache.

Syndecan-1 is up-regulated in ras-transformed intestinal epithelial cells.

The syndecans, a family of cell-surface heparan sulphate proteoglycans, have been proposed to mediate cellular interactions with extracellular effector molecules, such as growth factors and components of the extracellular matrix, during critical phases of development. Transcripts of all four syndecans are expressed at varying levels in the developing rat intestine and in a series of immature rat intestinal epithelial cell lines. In addition, we report the novel finding that, in the intestinal epithelial cell lines, expression of syndecan-1 transcript is up-regulated by transformation with activated H-ras. This is in contrast to other cell lines in which ras transformation is associated with a decrease in syndecan-1 levels. The observed increase in the syndecan-1 occurs as a result of increased transcription and can be correlated with the degree of transformation of the IEC-18 cells. Transformation is also associated with a decrease in apparent molecular weight and increased shedding of the proteoglycan into the culture medium. Increased shedding of syndecan-1 into the culture medium after transformation with H-ras may contribute to the disruption of proteoglycan interactions with the extracellular matrix, leading to alterations in cell adhesion and organization.

Determination of thyreostat residues from bovine matrices using high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) methodologies were evaluated for the detection and quantification of thyreostatic drug residues in cattle serum and thyroid tissue. The paper details a protocol, using a simple ethyl acetate extraction for the determination of thiouracil, tapazole, methyl thiouracil, propyl thiouracil and phenyl thiouracil in thyroid tissue. Using two sequential HPLC injections, and quantitative analysis, in two steps, all five thyreostats were detectable at concentrations greater than 2.45-4.52 ng/g. Modifications to a published method for detection of thyreostatic residues in serum involving the addition of mercaptoethanol and a freezing step are described. The modifications improved sensitivity and allowed detection of the five thyreostats at levels greater than 16.98-35.25 ng/ml. Young bulls were treated with thyreostats to demonstrate the validity of the methodologies described. Administered thyreostats were not absorbed equally by the test animals and the compounds were not all detected in the serum samples removed at 7 days following drug withdrawal. These experiments indicate the necessity to be able to detect thyreostat residues in a variety of matrices.