Chronic fetal hypoxia increases activin A concentrations in the late-pregnant sheep

OBJECTIVE

To determine whether activin A concentrations are altered in chronic fetal hypoxemia and intrauterine fetal growth restriction (IUGR).

DESIGN

In vivo animal experimental model.

SETTING

Department of Physiology, Monash University.

POPULATION

Chronically catherised fetal sheep in late pregnancy.

METHODS

Chronic fetal hypoxia and IUGR were experimentally induced by single umbilical artery ligation (SUAL) in catheterised fetal sheep. Maternal and fetal blood samples and amniotic fluid (AF) samples were collected during surgery and thereafter on alternate days, until the time of delivery for analyte measurement. Fetal blood gas parameters were measured daily.

MAIN OUTCOME MEASURES

Plasma and AF was used to analyse activin A, prostaglandin E2 (PGE2) and cortisol and fetal blood gas analysis was undertaken in whole blood.

RESULTS

SUAL produced asymmetric IUGR and non-acidaemic chronic fetal hypoxia and resulted in preterm labour (129 [3] days). AF activin A concentrations were 10-fold higher in the SUAL group than in controls whereas levels in the fetal and maternal circulations were similar between groups.

CONCLUSIONS

SUAL-induced IUGR and fetal hypoxaemia increases AF activin A. This may be an important adaptive or protective response to IUGR.

Effect of graded hypoxia on activin A, prostaglandin E2 and cortisol levels in the late-pregnant sheep

The aim of the present study was to determine whether activin A concentrations are dependent on feto–placental oxygen availability and to investigate the temporal relationship of activin A with prostaglandin (PG) E2 and cortisol. Nine fetal sheep (six hypoxic and three control) were instrumented and catheterised at 0.8 gestation. Reduced uterine blood flow was used to achieve three levels of hypoxia (mild = fetal SaO2 40–50%; moderate = fetal SaO2 30–40%; severe = fetal SaO2 20–30%), for 4 h on 3 consecutive days. Activin A, PGE2 and cortisol levels were determined in maternal and fetal blood and amniotic fluid. Moderate and severe hypoxia produced a significant (P < 0.05) increase in fetal plasma activin A concentrations. The amniotic fluid activin A concentrations were 15-fold higher than those in the fetal circulation, but were unchanged by hypoxia. The fetal PGE2 response reflected the degree of hypoxia over the 3 days, with moderate and severe hypoxia producing a significant (P < 0.05) increase in PGE2 concentrations. Fetal plasma cortisol concentrations were increased (P < 0.05) during all levels of hypoxia. Fetal arterial activin A was increased in response to moderate and severe hypoxia, but levels were not maintained over the hypoxic period. The increases in activin A and cortisol concentrations preceded the increase in PGE2.

Detection of optical asymmetry in amino acids by gas chromatography for extraterrestrial space exploration: results of a new soil processing scheme with breadboard instrumentation

The life-detection experiments of the Viking spacecraft are of an active biology type that will attempt to elicit metabolic responses from soil samples. Because bioresponses may be difficult to stimulate, it is desirable also to devise a purely chemical life-detection experiment. The unique chemical property of living systems on which such an experiment could be based is the optical activity of the amino acids that compose its protein. We have devised a new soil processing scheme which has been laboratory tested and for which we have built semi-automated breadboard instrumentation. The system involves the operations of heating, filtering, evaporation, conversion of the isolated amino acids to volatile diastereomers, injection onto a gas chromatographic column, and detection using a flame ionization detector. The breadboard form of the soil processing scheme and instrumentation has been successfully end-to-end tested.

Clinical rib fractures: are follow-up chest X-rays a waste of resources?

Rib fractures (RFs) are estimated to be present in 10 per cent of all traumatic injuries. However, up to 50 per cent of all fractures go undetected on the screening chest X-ray (CXR). The purpose of this study was to identify the incidence of clinical (CRFs) and objective rib fractures (ORFs) as well as to examine the utility of the routine follow-up CXR with regard to patient recovery and healthcare cost. We identified patients sustaining RF in addition to other traumatic injuries with an Injury Severity Score (ISS) < or = 15 and RF as the primary pathology. Five hundred fifty-two patients sustained blunt thoracic trauma with resultant RF. Two hundred nine patients had RFs and an ISS < or = 15. The average ISS was 8. Follow-up films illustrated that 93 per cent of CRFs had resolution of any pathology, 4 per cent had persistent X-ray findings, and 4 per cent were lost to follow-up. Ultimately 93 per cent of patients with CRF were able to resume daily activities without disability and 3 per cent incurred lifestyle changes at home or work, which was significantly better than those with ORFs (P < 0.05). Follow-up films produced no change in clinical management and cost approximately $2000/year. The prognosis for CRFs is excellent if treatment consists of appropriate pain management and pulmonary rehabilitation. We do not advocate routine follow-up CXRs in addition to physical examination for the evaluation of CRFs unless clinical deterioration is evident.

Indoor pollutant levels from the use of unvented natural gas fireplaces in Boulder, Colorado

High CO and NO2 concentrations have been documented in homes with unvented combustion appliances, such as natural gas fireplaces. In addition, polycyclic aromatic hydrocarbons (PAH) are emitted from incomplete natural gas combustion. The acute health risks of CO and NO2 exposure have been well established for the general population and for certain high-risk groups, including infants, the elderly, and people with heart disease or asthma. Health effects from PAH exposure are less well known, but may include increased risk of cancer. We monitored CO emissions during the operation of unvented natural gas fireplaces in two residences in Boulder, CO, at various times between 1997 and 2000. During 1999, we expanded our tests to include measurements of NO2 and PAH. Results show significant pollutant accumulation indoors when the fireplaces were used for extended periods of time. In one case, CO concentrations greater than 100 ppm accumulated in under 2 hr of operation; a person at rest exposed for 10 hr to this environment would get a mild case of CO poisoning with an estimated 10% carboxyhemoglobin level. Appreciable NO2 concentrations were also detected, with a 4-hr time average reaching 0.36 ppm. Similar time-average total PAH concentrations reached 35 ng/m3. The results of this study provide preliminary insights to potential indoor air quality problems in homes operating unvented natural gas fireplaces in Boulder.

Prevalence of CVD risk factors and impact of a two-year education program for premenopausal women

Indicators of cardiovascular disease risk in premenopausal women before, during, and after a 2-year educational intervention measured prevalence of risk and program effectiveness. Women (n = 277) were assigned to either treatment/education (n = 174) or control (n = 103) group. Many had at least one cardiovascular disease risk factor: high BMI (n = 123); high-fat diet (n = 160); and/or high body fat percent (n = 136). The treatment group was significant for change in calories from fat (P <.01). This study shows that premenopausal women have cardiovascular disease risks that should be addressed, and that nutrition education can successfully change dietary behavior.

The origin of life--did it occur at high temperatures?

A high-temperature origin of life has been proposed, largely for the reason that the hyperthermophiles are claimed to be the last common ancestor of modern organisms. Even if they are the oldest extant organisms, which is in dispute, their existence can say nothing about the temperatures of the origin of life, the RNA world, and organisms preceding the hyperthermophiles. There is no geological evidence for the physical setting of the origin of life because there are no unmetamorphosed rocks from that period. Prebiotic chemistry points to a low-temperature origin because most biochemicals decompose rather rapidly at temperatures of 100 degrees C (e.g., half-lives are 73 min for ribose, 21 days for cytosine, and 204 days for adenine). Hyperthermophiles may appear at the base of some phylogenetic trees because they outcompeted the mesophiles when they adapted to lower temperatures, possibly due to enhanced production of heat-shock proteins.

Template-directed synthesis of oligonucleotides under eutectic conditions

One of the most important sets of model prebiotic experiments consists of reactions that synthesize complementary oligonucleotides from preformed templates under nonenzymatic conditions. Most of these experiments are conducted at 4 degrees C using 0.01-0.1 M concentrations of activated nucleotide monomer and template (monomer equivalent). In an attempt to extend the conditions under which this type of reaction can occur, we have concentrated the reactants by freezing at -18 degrees C, which is close to the NaCl-H2O eutectic at -21 degrees C. The results from this set of experiments suggest that successful syntheses can occur with poly(C) concentrations as low at 5 x 10(-4) M and 2MeImpG concentrations at 10(-3) M. It was also anticipated that this mechanism might allow the previously unsuccessful poly(A)-directed synthesis of oligo(U)s to occur. However, no template effect was seen with the poly(A) and ImpU system. The failure of these conditions to allow template-directed synthesis of oligo(U)s supports the previously proposed idea that pyrimidines may not have been part of the earliest genetic material. Because of the low concentrations of monomer and template that would be expected from prebiotic syntheses, this lower temperature could be considered a more plausible geologic setting for template-directed synthesis than the standard reaction conditions.

Current status of the prebiotic synthesis of small molecules

The prebiotic synthesis of small molecules has been accomplished using various simulated atmospheres with CH4, N2, and NH3, H2O being the most effective, but H2, CO, N2, H2O and H2, CO2, N2, H2O also give good yields of organic compounds provided H2/CO > 1 and H2/CO2 > 2. The spark discharge is a very effective source of energy in such experiments, because it is a good source of HCN. Ultraviolet light would also have been important on the primitive earth. Almost all prebiotic amino acids are made by the hydrolysis of an amino nitrile formed from an aldehyde, NH3 and HCN (Strecker synthesis). There are reasonable prebiotic syntheses worked out for the twenty amino acids that occur in proteins, with the exception of lysine, arginine and histidine. The purines are derived from the polymerization of HCN, and the precursor of the pyrimidines is cyanoacetylene. The sugars (including ribose), would have been formed from the base catalyzed polymerization of formaldehyde. There is no good prebiotic synthesis of straight chain fatty acids. Of the vitamin coenzymes, only nicotinic acid has been synthesized under prebiotic conditions. Many of the molecules that are produced in these simulated primitive earth experiments are found in a group of meteorites that contain organic compounds, called the carbonaceous chondrites. Since such prebiotic syntheses took place on the parent body of the carbonaceous chondrites, generally thought to be an asteroid, it is plausible, but not proved, that such syntheses took place on the primitive earth, and that the first living organisms were formed out of these compounds.

Racemization and the origin of optically active organic compounds in living organisms

The organic compounds synthesized in prebiotic experiments are racemic mixtures. A number of proposals have been offered to explain how asymmetric organic compounds formed on the Earth before life arose, with the influence of chiral weak nuclear interactions being the most frequent proposal. This and other proposed asymmetric syntheses give only sight enantiomeric excess and any slight excess will be degraded by racemization. This applies particularly to amino acids where half-lives of 10(5)-10(6) years are to be expected at temperatures characteristic of the Earth's surface. Since the generation of chiral molecules could not have been a significant process under geological conditions, the origins of this asymmetry must have occurred at the time of the origin of life or shortly thereafter. It is possible that the compounds in the first living organisms were prochiral rather than chiral; this is unlikely for amino acids, but it is possible for the monomers of RNA-like molecules.

Alternative bases in the RNA world: the prebiotic synthesis of urazole and its ribosides

Urazole is a five-membered heterocyclic compound which is isosteric with uracil's hydrogen-bonding segment. Urazole reacts spontaneoulsy with ribose (and other aldoses) to give a mixture of four ribosides: alpha and beta pyranosides and furanosides. This reaction occurs in aqueous solution at mild temperatures. Thermodynamic and kinetic parameters for the reaction of urazole with ribose were determined. In contrast, uracil is completely unreactive with ribose under these conditions. Urazole's unusual reactivity is ascribed to the hydrazine portion of the molecule. Urazole can be synthesized from biuret and hydrazine under prebiotic conditions. The prebiotic synthesis of guanazole, which is isosteric in part to diaminopyrimidine and cytosine, is accomplished from dicyandiamide and hydrazine. Kinetic parameters for both prebiotic reactions were measured. Urazole and guanazole are transparent in the UV, which would be a favorable property in the absence of an ozone layer on the early Earth. Urazole makes hydrogen bonds with adenine in DMSO similar to those of uracil, as established by H NMR. All of these properties make urazole an attractive potential precursor to uracil and guanazole a potential precursor to cytosine in the RNA or pre-RNA world.

The spark discharge synthesis of amino acids from various hydrocarbons

The spark discharge synthesis of amino acids using an atmosphere of CH4 + N2 + H2O + NH3 has been investigated with variable pNH3. The amino acids produced using higher hydrocarbons (ethane, ethylene, acetylene, propane, butane, and isobutane) instead of CH4 were also investigated. There was considerable range in the absolute yields of amino acids, but the yields relative to glycine (or alpha-amino-n-butyric acid) were more uniform. The relative yields of the C3 to C6 aliphatic alpha-amino acids are nearly the same (with a few exceptions) with all the hydrocarbons. The glycine yields are more variable. The precursors to the C3-C6 aliphatic amino acids seem to be produced in the same process, which is separate from the synthesis of glycine precursors. It may be possible to use these relative yields as a signature for a spark discharge synthesis provided corrections can be made for subsequent decomposition events (e.g. in the Murchison meteorite).

Attempted nonenzymatic template-directed oligomerizations on a polyadenylic acid template: implications for the nature of the first genetic material

Previous attempts to produce nonenzymatic template-directed oligomerizations of activated pyrimidines on polypurine templates have been unsuccessful. The only efficient reactions are those where the template is composed primarily of pyrimidines, especially cytosine. Because molecular evolution requires that a synthesized daughter polynucleotide be capable of acting as a template for the synthesis of the original polynucleotide, the one-way replication achieved thus far is inadequate to initiate an evolving system. Several uracil analogs were used in this investigation in order to search for possible replacements for uracil. The monomers used in this investigation were the imidazolides of UMP, xanthosine 5'-monophosphate, the bis-monophosphates of the acyclic nucleosides of uracil, and 2,4-quinazolinedione. The concentrations of various salts, buffers, pH, and temperature were among the different variables investigated in attempts to find conditions that would permit template-directed oligomerizations. Although the different monomers in this study demonstrated varying abilities to form very short oligomers, we were unable to detect any enhancement of this oligomerization that could be attributed to the poly(A) template. Although special conditions might be found that would allow purine-rich templates to work, these reactions cannot be considered robust. The results of our experiments suggest that pyrimidines were not part of the original replicating system on the primitive Earth. It has already been shown that ribose is an unlikely component of the first replicating systems, and we now suggest that phosphate was absent as well. This is due to the low solubility of phosphate in the present ocean (3 x 10(-6) M), as well as the difficulty of prebiotic activation of phosphates.

Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise

The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-(2)H(5)]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by approximately 130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P < 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.

Malignant and benign bone tumors

The authors have intentionally included some confusing examples to demonstrate that the imaging findings of benign and malignant pediatric bone lesions are not always pathognomonic. The radiologist's role is to recognize malignant bone lesions and encourage the prompt referral of these patients to an appropriate institution for biopsy and treatment. The radiologist must also be able to identify benign lesions and help determine whether these lesions require biopsy and intervention or simply observation.

Tumor volume or dynamic contrast-enhanced MRI for prediction of clinical outcome of Ewing sarcoma family of tumors

BACKGROUND

The identification of risk factors that predict poor clinical outcome at the time of diagnosis could lead to intensified early therapy and improved outcome for pediatric patients with Ewing sarcoma family of tumors (ESFT).

OBJECTIVE

To compare the effectiveness of static magnetic resonance (MR) imaging measurements of tumor volume with variables obtained by dynamic contrast-enhanced MR imaging (DEMRI) in predicting ESFT outcome.

METHODS

MR examinations that included DEMRI were retrospectively reviewed. The analyses included 45 examinations of 21 patients with ESFT (performed from 1992 to 1996). Tumor volumes were measured on the static MR images, and the regions of interest were selected for DEMRI analysis. The relationships of static MR imaging and DEMRI variables with the probability of progression-free survival (PFS) and disease-free survival (DFS) were determined.

RESULTS

Larger tumor volume at the time of diagnosis predicted poorer PFS and DFS estimates. No DEMRI variable predicted outcome.

CONCLUSION

Determination of tumor volume by static MR imaging at the time of diagnosis is a simple and reliable method of predicting the clinical outcome of patients with ESFT. DEMRI is not as reliable a technique as static MR imaging for predicting the outcome of these patients.

Source apportionment of exposure to toxic volatile organic compounds using positive matrix factorization

Data from the Total Exposure Assessment Methodology studies, conducted from 1980 to 1987 in New Jersey (NJ) and California (CA), and the 1990 California Indoor Exposure study were analyzed using positive matrix factorization, a receptor-oriented source apportionment model. Personal exposure and outdoor concentrations of 14 and 17 toxic volatile organic compounds (VOCs) were studied from the NJ and CA data, respectively. Analyzing both the personal exposure and outdoor concentrations made it possible to compare toxic VOCs in outdoor air and exposure resulting from personal activities. Regression analyses of the measured concentrations versus the factor scores were performed to determine the relative contribution of each factor to total exposure concentrations. Activity patterns of the NJ and CA participants were examined to determine whether reported exposures to specific sources correspond to higher estimated contributions from the factor identified with that source. For a subset of VOCs, a preliminary analysis to determine irritancy-based contributions of factors to exposures was carried out. Major source types of toxic VOCs in both NJ and CA appear to be aromatic sources resembling automobile exhaust, gasoline vapor, or environmental tobacco smoke for personal exposures, and automobile exhaust or gasoline vapors for outdoor concentrations.

Organ donation: a statewide survey of trauma surgeons

PURPOSE

Organ procurement organizations (OPOs) operate under the premise that Americans would donate organs and/or tissue if placed in appropriate circumstances. This study evaluated opinions of Pennsylvania trauma surgeons regarding OPOs and organ donation.

METHODS

Ninety-six Pennsylvania trauma surgeons were surveyed and descriptive results calculated.

RESULTS

Ninety percent were familiar with criteria for organ donation, and about 76% would invoke their institution's brain death policy even if families did not desire to donate organs. A small portion did not routinely pronounce patients brain dead that met criteria. One fourth indicated trauma surgeons should have no role in requesting organs. A majority believed trauma surgeons should have a role in organ donation requests, either alone or with an OPO representative, and most indicated that they could influence a family's decision.

CONCLUSION

Requestor attitude is important, and our results show an overall positive attitude toward donation and a solid level of knowledge regarding donor eligibility. Hospital development programs to improve donation consent should emphasize decoupling of brain death discussion and donation request, work to improve staff attitudes about approaching patients, and address donor eligibility criteria.

Concentration by evaporation and the prebiotic synthesis of cytosine

The efficient prebiotic synthesis of cytosine from urea and cyanoacetaldehyde (CA) has recently been claimed to be invalid on the basis of possible side reactions of the starting materials and the inapplicability of prebiotic syntheses using drying beach conditions. We therefore have investigated the synthesis of cytosine and uracil from urea and cyanoacetaldehyde at 100 degrees C under dry-down conditions, and in solution at 4 degrees C and -20 degrees C. We find that cytosine is produced from the low temperature experiments more efficiently than calculated from the Arrhenius extrapolation from higher temperatures, i.e., 60-120 degrees C. In addition, we find that CA dimer is as efficient as the monomer in cytosine synthesis. We also studied whether evaporating very dilute solutions of nonvolatile organic compounds will concentrate according to theory. Solutions as dilute as 10(-4) M concentrate from pure water approximately according to theory. Similar solutions in 0.5 M NaCl have less than theoretical concentrations due to absorption, but concentrations near dryness were very high.

Differentiated 3T3L1 adipocytes are composed of heterogenous cell populations with distinct receptor tyrosine kinase signaling properties

Various studies have demonstrated that the platelet-derived growth factor (PDGF) receptor in adipocytes can activate PI 3-kinase activity without affecting insulin-responsive glucose transporter (GLUT4) translocation. To investigate this phenomenon of receptor signaling specificity, we utilized single cell analysis to determine the cellular distribution and signaling properties of PDGF and insulin in differentiated 3T3L1 adipocytes. The insulin receptor was highly expressed in a large percentage of the cell population (>95%) that also expressed caveolin 2 and GLUT4 with very low levels of the PDGF receptor. In contrast, the PDGF receptor was only expressed in approximately 10% of the differentiated 3T3L1 cell population with relatively low levels of the insulin receptor, caveolin 2, and GLUT4. Consistent with this observation, insulin stimulated the phosphorylation of Akt in the caveolin 2- and GLUT4-positive cells, whereas PDGF primarily stimulated Akt phosphorylation in the caveolin 2- and GLUT4-negative cell population. Furthermore, transfection of the PDGF receptor in the insulin receptor-, GLUT4-, and caveolin 2-positive cells resulted in the ability of PDGF to stimulate GLUT4 translocation. These data demonstrate that differentiated 3T3L1 adipocytes are not a homogeneous population of cells, and the lack of PDGF receptor expression in the GLUT4-positive cell population accounts for the inability of the endogenous PDGF receptor to activate GLUT4 translocation.

Prone positioning and inhaled nitric oxide: synergistic therapies for acute respiratory distress syndrome

BACKGROUND

Inhaled nitric oxide (INO) and prone positioning have both been advocated as methods to improve oxygenation in patients with acute respiratory distress syndrome (ARDS). This study was designed to evaluate the relative contributions of INO and prone positioning alone and in combination on gas exchange in trauma patients with ARDS.

METHODS

Sixteen patients meeting the consensus definition of ARDS were studied. Patients received mechanical ventilation in the supine position, mechanical ventilation plus INO at 1 part per million in the supine position, mechanical ventilation in the PP, and mechanical ventilation in the prone positioning plus INO at 1 part per million. A stabilization period of 1 hour was allowed at each condition. After stabilization,hemodynamic and gas exchange variables were measured.

RESULTS

INO and prone positioning both increased PaO2/FIO2 compared with ventilation in the supine position. PaO2/FIO2 increased by 14% during use of INO, and 10 of 16 patients (62%) responded to INO in the supine position. PaO2/FIO2 increased by 33%, and 14 of 16 patients (87.5%) responded to the prone position. The combination of INO and prone positioning resulted in an improvement in PaO2/FIO2 in 15 of 16 patients(94%), with a mean increase in PaO2/FIO2 of 59%. Pulmonary vascular resistance was reduced during use of INO, with a greater reduction in pulmonary vascular resistance seen with INO plus prone positioning (175 +/- 36 dynes x s/cm5 vs. 134 +/- 28 dynes x s/cm5) compared with INO in the supine position (164 +/- 48 dynes x s/cm5 vs.138 +/- 44 dynes x s/cm5). There were no significant hemodynamic effects of INO or prone positioning and no complications were seen during this relative short duration of study.

CONCLUSIONS

INO and prone positioning can contribute to improved oxygenation in patients with ARDS. The two therapies in combination are synergistic and may be important adjuncts to mechanical ventilation in the ARDS patient with refractory hypoxemia.