bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceived Versus Actual Risk for Hypertension and Diabetes in the African American Community
Authors: Graham Garth N. , Leath Brenda , Payne Kermit , Guendelman Maya , Reynolds Gladys , Kim Soo , James Barbara , Ware Donald , Hunter Mildred , Burwell Audrey , Buggs Georgia
Published: January 2006

Hypertension and diabetes mellitus are leading health concerns in the United States. Despite a disproportionate burden of both conditions among African Americans, it is estimated that 44% of diabetes cases and one quarter of hypertension cases within this population are undiagnosed. Lack of awareness of the risk of these conditions may hinder preventive efforts and the adoption of positive lifestyle changes. Based on the findings from a pilot study to develop and standardize uniform screening forms for hypertension and diabetes, this article reports on the perceived risk versus actual risk of developing these conditions among primarily African American participants using a community-based screening tool. Each form assessed both perceived and actual risk of diabetes and hypertension, respectively. A total of 265 hypertension and 225 diabetes screening forms were randomly selected from eight sites across the country. The risk perception of the overall study sample was similar to its actual risk for developing either condition. However, a significant proportion of individuals who scored at high risk for diabetes or hypertension were unaware of their risk for these conditions. These results suggest the need for developing culturally relevant interventions, public health education, and policies that address the risk misperceptions among this group.
Transfer effects in learning a second language grammatical gender system
Authors: Sabourin Laura , Stowe Laurie A. , de Haan Ger J.
Published: January 2006

In this article second language (L2) knowledge of Dutch grammatical gender is investigated. Adult speakers of German, English and a Romance language (French, Italian or Spanish) were investigated to explore the role of transfer in learning the Dutch grammatical gender system. In the first language (L1) systems, German is the most similar to Dutch coming from a historically similar system. The Romance languages have grammatical gender; however, the system is not congruent to the Dutch system. English does not have grammatical gender (although semantic gender is marked in the pronoun system). Experiment 1, a simple gender assignment task, showed that all L2 participants tested could assign the correct gender to Dutch nouns (all L2 groups performing on average above 80%), although having gender in the L1 did correlate with higher accuracy, particularly when the gender systems were very similar. Effects of noun familiarity and a default gender strategy were found for all participants. In Experiment 2 agreement between the noun and the relative pronoun was investigated. In this task a distinct performance hierarchy was found with the German group performing the best (though significantly worse than native speakers), the Romance group performing well above chance (though not as well as the German group), and the English group performing at chance. These results show that L2 acquisition of grammatical gender is affected more by the morphological similarity of gender marking in the L1 and L2 than by the presence of abstract syntactic gender features in the L1.
On the second language acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults
Authors: Tremblay Annie
Published: January 2006

This study, a partial replication of Bruhn de Garavito (1999a; 1999b), investigates the second language (L2) acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults at an advanced level of proficiency. The L2 acquisition of Spanish reflexive passives and reflexive impersonals by native French and English speakers instantiates a potential learnability problem, because (1) the constructions are superficially very similar ( se V DP) but display distinct idiosyncratic morphological and syntactic behaviour; (2) neither exists in English, and the reflexive impersonal does not exist in French; and (3) differences between the two are typically not subject to explicit instruction. Participants - 13 English, 16 French and 27 Spanish speakers (controls) - completed a 64-item grammaticality-judgement task. Results show that L2 learners could in general differentiate grammatical from ungrammatical items, but they performed significantly differently from the control group on most sentence types. A look at the participants’ accuracy rates indicates that few L2 learners performed accurately on most sentence types. Grammatical and ungrammatical test items involving [+animate] DPs preceded or not by the object-marking preposition a were particularly problematic, as L2 learners judged them both as grammatical. These results confirm that the L2 acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults instantiates a learnability problem, not yet overcome at an advanced level of proficiency.
Investigating the acquisition of the Split-IP parameter and the V2 parameter in second language Afrikaans
Authors: Conradie Simone
Published: January 2006

Researchers who assume that Universal Grammar (UG) plays a role in second language (L2) acquisition are still debating whether L2 learners have access to UG in its entirety (the Full Access hypothesis; e.g. Schwartz and Sprouse, 1994; 1996; White, 1989; 2003) or only to those aspects of UG that are instantiated in their first language (L1) grammar (the No Parameter Resetting hypothesis; e.g. Hawkins and Chan, 1997). The Full Access hypothesis predicts that parameter resetting will be possible where the L1 and L2 differ in parameter values, whereas the No Parameter Resetting hypothesis predicts that parameter resetting will not be possible. These hypotheses are tested in a study examining whether English-speaking learners of Afrikaans can reset the Split-IP parameter (SIP) (Thráinsson, 1996) and the V2 parameter from their L1 ([-SIP], [-V2]) to their L2 ([+SIP], [+V2]) values. 15 advanced English learners of Afrikaans and 10 native speakers of Afrikaans completed three tasks: a sentence manipulation task, a grammaticality judgement task and a truth-value judgement task. Results suggest that the interlanguage grammars of the L2 learners are [+SIP] and [+V2] (unlike the L1), providing evidence for the Full Access hypothesis.
Français langue seconde: from functional categories to functionalist variation
Authors: Herschensohn Julia
Published: January 2006

Four recent volumes on acquisition of French by different populations cover a range of areas, particularly the development of verbal tense/agreement and nominal gender/concord in first language (L1) acquirers, as opposed to second language (L2) learners; the generalizability of grammatical deficits (e.g. difficulty acquiring parametrized features different from the L1); and variation in acquisition between functional features from different domains: nominal and verbal, for example, are not all acquired at a comparable rate or with analogous errors across different learning populations. The detailed data on acquisition of French presented in these studies furnishes strong evidence for Universal Grammar (UG) systematicity that is not at all predictable from input frequency alone.
New technology increases perioperative haemoglobin levels for paediatric cardiopulmonary bypass: what is the benefit?
Authors: Thuys Clarke , Horton Stephen , Bennett Martin , Augustin Simon
Published: January 2006

Increasing perioperative haemoglobin level by reducing priming volume and maintaining a safe cardiopulmonary bypass (CPB) system is the aim of every perfusionist. In this study, we have compared the two membrane oxygenators and pump systems used for paediatric bypass at the Royal Children’s Hospital on a regular basis since 1988. We looked at all patients who had the Cobe VPCML (Cobe Laboratories, Denver, CO, USA) and Terumo RX-05 (Terumo Corporation, Tokyo, Japan) oxygenators used for flows from 800 mL/min up to the maximum rated flow for the respective oxygenator from January 2002 until March 2004. The VPCML refers to using only the 0.4-m2 section of the oxygenator. The pump systems used were the Stöckert CAPS (Stöckert Instrumente GmbH, Munich, Germany) and Jostra HL 30 (Jostra AB, Lund, Sweden). Changing from the VPCML to the RX-05 resulted in a 37% reduction in priming volume. The introduction of the Jostra HL 30 with a custom-designed mast system reduced the priming volume by another 15%. This change in priming volume allowed a significant increase, from 6 to 34%, in the percentage of patients who received bloodless primes, and for those patients who received blood primes, an increase in haemoglobin (Hb) on bypass from 8.2 to 9.6 g/dL, on average.
Respiratory failure of two sp gastric bypass patients and subsequent rescue with extracorporeal membrane oxygenation
Authors: Mongero L B , Beck J R , Charette K A , Stewart A
Published: January 2006

Severe obesity is a chronic condition that is difficult to treat through diet and exercise alone. Gastrointestinal surgery for obesity (bariatric surgery) alters the digestive process by either restrictive surgical alterations or malabsorptive operations. Some 10 - 20% of patients who have weight-loss surgery require follow-up operations to correct complications. Hypoxemia after gastric bypass surgery for morbid obesity, a reported complication, can occur as early as 24 h post surgery.

Two patients presented with severe hypoxia and were placed on veno-venous extracorporeal membrane oxygenation (ECMO). Patient No. 1 had an obstruction of the alimentary limb of the gastric bypass due to suture adhesions, and patient No. 2 had an incarcerated diaphragmatic hernia. While on ECMO, ventilation using a protective strategy (60% FiO2, pressure-controlled ventilation inspiratory pressure (PCV) IP 25-27, positive end-expiratory pressure (PEEP) 10-14, permissive hyper-capnia) was employed. An inflow cannula to the level of the right atrium served as arterial outflow from the circuit to the patient, while the femoral vein served as venous inflow to the ECMO circuit.

Although ECMO in adult respiratory failure is often used as the last resort due to serious associated adverse events, we report two patients with life-threatening complications from gastric bypass who were rescued, resuscitated to day 7, and uneventfully discharged from the hospital to home.
Cardiopulmonary bypass for adults with congenital heart disease: pitfalls for perfusionists
Authors: Schmitz Michael L , Faulkner Sherry C , Johnson Charles E , Tucker Juan L , Imamura Michiaki , Greenberg S Bruce , Drummond-Webb Jonathan J
Published: January 2006

The fixed incidence of congenital heart defects and improved survival have resulted in increasing numbers of adults with congenital heart disease (CHD) who have undergone complex repairs and/or palliations. Eventually, there will be more adults with CHD than children. They will require cardiac surgical interventions associated with progression of their CHD or for age-related disease, such as coronary revascularization. During bypass, anatomical shunts may exist within or without the heart. Left-to-right shunts can result in dramatically lower systemic blood flow than pump flow due to ‘steal’, while pulmonary edema ensues due to excessive pulmonary flow. Right-to-left shunts carry risks of massive air embolism and double or triple venous cannulation may be necessary. Cannulation of composite reconstructed aortas may be difficult, risking dissection or aortic obstruction, and double arterial cannulation may be indicated. Aberrant coronary arterial and venous anatomy may preclude adequate myocardial preservation with common techniques and can be complicated by aortic insufficiency. Valves and conduits may exhibit failure. Conventional monitoring, such as central venous oximetry, may be misleading. Monitoring, such as serial lactate measurement, near-infrared spectroscopy and transcranial Doppler blood velocity, offer advantages for such patients. The perfusionist needs to be aware of such conditions as much congenital aberrancy may present unexpectedly during cardiac surgery.
Perfusion Education and Training in Europe
Authors: Merkle Frank
Published: January 2006

Perfusion education and training varies considerably throughout Europe. Unlike in the US, where a common curriculum for perfusion education has been established, each European country has its own education system. This fact is further complicated by a multitude of national languages and cultures. Thus, perfusion education programmes vary, not only in content, but also in their academic levels.

This article aims to give a comprehensive overview of the situation in each of the 20 member states of the European Board of Cardiovascular Perfusion (EBCP). The EBCP delegates were polled for a description of the process of training and education of clinical perfusionists in their respective countries. Following the initial delegate poll in 2001, an update of the material was performed in spring 2005.

In summary, training of clinical perfusionists in Europe varies considerably between countries. A professional body is necessary to oversee the training process and to guarantee a minimum level of clinical competency for cardiovascular perfusionists.
Development of an instrument to indirectly monitor arterial pCO2 during cardiopulmonary bypass
Authors: Høgetveit Jan Olav , Kristiansen Frode , Pedersen Thore H
Published: January 2006

Arterial blood carbon dioxide tension (PaCO2) during cardiopulmonary bypass (CBP) is important to the conduct of perfusion with alpha-stat or pH-stat strategy. Temperature changes during CBP complicate any attempts to monitor carbon dioxide tension in the exhaust outlet of an oxygenator (PexCO2) because CO2 becomes more soluble with decreasing temperatures. Normally, this would have been the obvious and easy choice of method to indirectly measure the patient’s PaCO2.

Several tests have been performed with ordinary capnographs modified to measure pCO2 at the oxygenator exhaust gas port. These tests have shown varying degrees of precision ( Br J Anaesth 1999; 82(6): 843-46; J Extra-Corpor Technol 2003; 35(3): 218-23; Br J Anaesth 2000; 84: 536; J Extra-Corpor Technol 1994; 26: 64-67). Some of the best results have been achieved by Potger et al. ( J Extra-Corpor Technol 2003; 35(3): 218-23), who found a strong correlation between the arterial temperature-corrected PexCO2 when using a standard capnograph monitoring the PaCO2 measured from a blood gas analyser (PbCO2).

Our group has developed a new instrument, especially designed for oxygenator gas exhaust monitoring. The new instrument has automatic temperature correction, enabling it to show both original and corrected pCO2 values, simultaneously. Ordinary capnograph functions, such as zeroing, flow control and calibration routines, are included. The solution consists of a pCO2 sensor module, a temperature sensor, a water trap and a dedicated PC mounted on a heart-lung machine. Since the heart-lung machine was already equipped with a computer for data logging and a temperature sensor, only a box containing the pCO2 sensor module and the water trap had to be added.

The PC uses a specially written program designed to collect data, make the necessary calculations and display the results on the computer screen. A temperature correction was developed based on a linear regression analysis for a data-set of 15 patients, assuming that the deviation between the measured PexCO2 from the oxygenator exhaust outlet and the PbCO2 from the blood gas analyser was linearly dependent on arterial temperature alone.

Eighty-six blood gas samples were compared to the corrected PexCO2 values. The final product displayed good qualities of stability and was accurate when temperature fluctuated from 32 to 388C, even during rewarming, which has been reported to be a problem for other PexCO2 investigations ( J Extra-Corpor Technol 2003; 35(3): 218-23).
Clinical evaluation of an instrument to measure carbon dioxide tension at the oxygenator gas outlet in cardiopulmonary bypass
Authors: Kristiansen Frode , Høgetveit Jan Olav , Pedersen Thore H
Published: January 2006

This paper presents the clinical testing of a new capno-graph designed to measure the carbon dioxide tension at the oxygenator exhaust outlet in cardiopulmonary bypass (CPB). During CPB, there is a need for reliable, accurate and instant estimates of the arterial blood CO2 tension (PaCO2) in the patient. Currently, the standard practice for measuring PaCO2 involves the manual collection of intermittent blood samples, followed by a separate analysis performed by a blood gas analyser. Probes for inline blood gas measurement exist, but they are expensive and, thus, unsuitable for routine use. A well-known method is to measure PexCO2, ie, the partial pressure of CO2 in the exhaust gas output from the oxygenator and use this as an indirect estimate for PaCO2.

Based on a commercially available CO2 sensor circuit board, a laminar flow capnograph was developed. A standard sample line with integrated water trap was connected to the oxygenator exhaust port. Fifty patients were divided into six different groups with respect to oxygenator type and temperature range. Both arterial and venous blood gas samples were drawn from the CPB circuit at various temperatures.

Alfa-stat corrected pCO2 values were obtained by running a linear regression for each group based on the arterial temperature and then correcting the PexCO2 accordingly. The accuracy of the six groups was found to be (±SD): ±4.3, ±4.8, ±5.7, ±1.0, ±3.7 and ±2.1%. These results suggest that oxygenator exhaust capnography is a simple, inexpensive and reliable method of estimating the PaCO2 in both adult and pediatric patients at all relevant temperatures.
Use of a large bore syringe creates significantly fewer high intensity transient signals (HITS) into a cardiopulmonary bypass system than a small bore syringe
Authors: Rudolph James L , Tilahun Daniel , Treanor Patrick R , Pochay Val E , Mahendrakar Meetali A , Sagar Praveen , Babikian Viken L
Published: January 2006

Introduction: High intensity transient signals (HITS) have been reported to occur following perfusionist intervention during cardiac surgery. This study investigates the relationship of the syringe bore, injection rate, and HITS created.

Methods: Syringes (10 mL) with a male luer-lock connection (Large Bore) and Abboject ‘jet syringes’ with a 20 GA needle and male luer-lock connector (Small Bore) were filled with 10 mL of 0.9 N saline. A perfusionist was randomly assigned a set of four similar syringes followed by the other syringe bore. Each of the four syringes was injected into an in vitro saline-primed cardiopulmonary bypass (CPB) system over 5, 10, 15, or 20 sec. Sixteen randomizations of small and large bore syringes were completed at the four injection times (128 injections). HITS in the CPB arterial line were detected with transcranial Doppler (TCD) probes, were recorded for the 2 min following the injection, and were counted independently off-line by two reviewers.

Results: The use of a large bore syringe compared to a small bore syringe created significantly fewer HITS (29±6 versus 145±17 [mean±SEM], p <0.001) introduced into the CPB arterial line. Injection over a longer time produced significantly fewer HITS than shorter injection times ( p <0.001).

Conclusion: Significantly fewer HITS are introduced into the CPB system by using standard syringes and slower injection time.
Comparison of ACT point-of-care measurements: repeatability and agreement
Authors: Bosch Y PJ , Ganushchak Y M , de Jong D S
Published: January 2006

Background: Accurate control of heparin anticoagulation is necessary during all stages of cardiopulmonary bypass (CPB). The activated clotting time, first described by Hattersley in 1966, is mostly used for determination of anticoagulation. Either celite or kaolin are used as activators. An ACT value of 480 sec is proposed to be the safe minimum level for anticoagulation during CPB. This study was designed to determine if the activated coagulation time (ACT) values of each analyser separately are repeatable, and to determine whether there exists a significant difference in ACT values measured by three different analysers: the GEM PCL (Instrumentation Laboratory), the Hemochron 801 (International Techni-dyne Corporation) and the ACT II Automated Coagulation Timer (Medtronic).

Methods: All patients underwent cardiovascular surgical procedures requiring heparinisation (200 - 300 IU/kg). Blood samples for the measurement of the ACT were taken from all patients before and after heparinisation, during CPB, and after protamine administration. All samples were measured in duplicate with the three different analysers. To compare the activated clotting time data, the method described by Bland and Altman was used. The Pearson correlation coefficient was used to determine whether the differences were related to the average ACTs. p-Values < 0.05 were considered statistically significant.

Results: The results showed that the three tested ACT analysers met the requirements of repeatability. The mean differences and standard deviations of the ACT values measured with the GEM PCL, the Hemochron 801, and the ACT II analyser were, respectively, -8.789 ± 37.61, -19.779±68.82, and -6.239±39.21, with p-values=0.177, 0.081 and 0.384, respectively. The Pearson correlation coefficients were too low (-0.012, -0.221 and -0.241, respectively) to show any correlation between the differences and the means. The ACT values measured with the Hemochron 801 were not significantly different from the ACT values measured with the ACT II analyser: ΔACT=-34.09 ± 146.68, with p=0.132. However, the GEM PCL did not agree with the Hemochron 801: ΔACT=-80.29 ± 143.06, with p=0.001, or the ACT II analyser: ΔACT=-119.139 ± 138.51, with p<0.001. A rather strong correlation was evident between the differences and the means measured with the GEM PCL compared with the Hemochron 801 (r=0.68) and the ACT II analyser (r=0.76).

Conclusions: All analysers used celite or kaolin as activator. However, it was evident that the ACT measurements depended also on the analyser that had been chosen. A precaution that ACT values could not always be interpreted in the same way seems to be necessary.
Influence of aspirin or heparin on platelet function and postoperative blood loss after coronary artery bypass surgery
Authors: Sirvinskas Edmundas , Veikutiene Audrone , Grybauskas Pranas , Cimbolaityte Jurate , Mongirdiene Ausra , Veikutis Vincentas , Raliene Laima
Published: January 2006

The aim of the study was to assess the effect of aspirin or heparin pretreatment on platelet function and bleeding in the early postoperative period after coronary artery bypass grafting (CABG) surgery.

Seventy-five male patients with coronary artery disease who underwent CABG with cardiopulmonary bypass (CPB) were studied. The patients were divided into three groups: Group 1 ( n = 25) included patients receiving aspirin pretreatment, Group 2 ( n = 22) received heparin pretreatment, and Group 3 ( n = 28) included patients who received no antiplatelet or anticoagulant pretreatment. Twenty-four hours after surgery, all patients were administered aspirin therapy that was continued throughout their hospitalization period. We assessed the following preoperative blood coagulation indices: activated partial thromboplastin time (aPTT), international normalized ratio (INR), and fibrinogen. We compared platelet count and platelet aggregation induced by adenosinediphosphate (ADP) before surgery, 1 h after surgery, 20 h after surgery and on the seventh postoperative day. We assessed drained blood loss within 20 postoperative hours.

Preoperative blood coagulation indices did not differ among the groups. Platelet count was also similar. One hour after surgery, platelet count significantly decreased in all groups ( p <0.001), after 20 postoperative hours it did not undergo any marked changes, and on the seventh postoperative day, it significantly increased in all groups ( p <0.001). Before surgery, the lowest index of ADP-induced platelet aggregation was found in Group 1 ( p <0.05). One hour after surgery, platelet aggregation significantly decreased in all groups, most markedly in Group 3 ( p <0.001), yet after 20 h, its restitution tendency and a significant increase in all groups was noted. On the seventh day, a further increase in the statistical mean platelet aggregation value was noted in Groups 2 and 3. Comparison of platelet aggregation after 20 postoperative hours and on the seventh day after surgery revealed a significantly higher than 10% increase of the index in 32% of patients in Group 1 ( p <0.05), 27.3% of patients in Group 2 ( p <0.05) and in 35.7% of patients in Group 3 ( p <0.001). The lowest statistically significant value of postoperative blood loss was noted in Group 2 ( p <0.01).

Our study has shown that aspirin or heparin pretreatment had no impact on the dynamics of platelet function in the early postoperative period after CABG. The lowest postoperative blood loss was noted in patients pretreated with heparin.
Reliability of point-of-care hematocrit, blood gas, electrolyte, lactate and glucose measurement during cardiopulmonary bypass
Authors: Steinfelder-Visscher J , Weerwind P W , Teerenstra S , Brouwer M HJ
Published: January 2006

Background: Recently, the GEM Premier blood gas analyser was upgraded to the GEM Premier 3000. In addition to pH, pCO2, pO2, Na+, K+, Ca2+, and hematocrit measurement, glucose and lactate can be measured on the GEM Premier 3000. In this prospective clinical study, the analytical performance of the GEM Premier 3000 was compared with the Ciba Corning 865 analyser for blood gas/electrolytes/metabolites, and for hematocrit with the Sysmex XE 2100 instrument.

Methods: During a 6-month period, 127 blood samples were analysed on both the GEM Premier 3000 analyser and our laboratory analysers (Ciba Corning 865/Sysmex 2100 instrument), and compared using the agreement analysis for quantitative data.

Results: With the exception of K+, the other parameters (pCO2, pO2, Na+, Ca2+, hematocrit, glucose, and lactate) can be described in terms of the mean and standard deviation of the differences. For K+ measurement, a clear linear trend (r=0.79, p<0.001) in the deviation of the GEM Premier 3000 from the Ciba Corning was noticed, ie, in the lower or upper K+ reference range, the GEM Premier 3000 measured systematically too low or too high, respectively. Furthermore, in comparison with the other parameters, a therapeutically unacceptable systematic difference (mean of difference: -2.2%, p =0.05) in hematocrit measurement on the GEM Premier 3000 was observed for hematocrit values below 30%. The variance of the readings for the GEM Premier 3000 measurements was at clinically acceptable levels.

Conclusion: The GEM Premier 3000 analyser seems to be suitable for point-of-care testing of electrolytes, metabolites, and blood gases during cardiopulmonary bypass. However, its downward bias in hematocrit values below 30% suggests that using the GEM Premier 3000 as a transfusion trigger leads to overtreatment with packed red cells.
Leucocyte-depleting arterial line filtration does not reduce myocardial injury assessed by Troponin T during routine coronary artery bypass grafting using crossclamp fibrillation
Authors: Whitaker Donald C , Stygall Jan , Harrison Michael JG , Mackie Ian J , Kemp Michael , Hooper James , Pugsley Wilfred B , Newman Stanton P
Published: January 2006

Introduction: Leucocyte filtration can reduce inflammation and end-organ damage. The aim of this study was to test the cardioprotective effect of systemic leucocyte filtration during cardiopulmonary bypass (CPB) for coronary revascularization.

Methods: Sixty patients scheduled for elective coronary artery bypass grafting were prospectively randomised to receive either a test leucocyte-depleting (LD) filter or a control standard arterial line filter in the CPB circuit. Myocardial injury was determined by serum Troponin T concentration up to 72 h postoperatively. In addition, perioperative neutrophil counts, serum elastase and electrocardiograms (ECGs) were evaluated.

Results: There was a peak of Troponin T release at 6 h in both groups. There was no difference between LD or control group Troponin T at any time point. No difference in neutrophil count was found. A greater rise in neutrophil elastase occurred in the LD group during CPB and 10 min post CPB (376 and 496 versus 108 and 228 mcg/L, p <0.001).

Conclusions: LD arterial line filters did not confer any cardioprotective effect as measured by Troponin T in elective coronary revascularization cases.
Ras-dva, a member of novel family of small GTPases, is required for the anterior ectoderm patterning in theXenopus laevisembryo
Authors: Tereshina Maria B. , Zaraisky Andrey G. , Novoselov Vladimir V.
Published: January 2006

Ras-like small GTPases are involved in the regulation of many processes essential for the specification of the vertebrate body plan. Recently, we identified the gene of novel small GTPase Ras-dva, which is specifically expressed at the anterior margin of the neural plate of the Xenopus laevis embryo. Now, we demonstrate that Ras-dva and its homologs in other species constitute a novel protein family, distinct from the previously known families of small GTPases. We show that the expression of Ras-dvabegins during gastrulation throughout the anterior ectoderm and is activated by the homeodomain transcription factor Otx2; however, later on, Ras-dva expression is inhibited in the anterior neural plate by another homeodomain factor Xanf1. Downregulation of Ras-dva functioning by the dominant-negative mutant or by the antisense morpholino oligonucleotides results in severe malformations of the forebrain and derivatives of the cranial placodes. Importantly, although the observed abnormalities can be rescued by co-injection of the Ras-dva mRNA, they cannot be rescued by the mRNA of the closest Ras-dva homolog from another family of small GTPases, Ras. This fact indicates functional specificity of the Ras-dva signaling pathway. At the molecular level, downregulation of Ras-dva inhibits the expression of several regulators of the anterior neural plate and folds patterning, such as Otx2, BF-1 (also known as Foxg1), Xag2, Pax6, Slug and Sox9, and interferes with FGF8 signaling within the anterior ectoderm. By contrast, expression of the epidermal regulator BMP4 and its target genes, Vent1, Vent2band Msx1, is upregulated. Together, the data obtained indicate that Ras-dva is an essential component of the signaling network that patterns the early anterior neural plate and the adjacent ectoderm in the Xenopus laevis embryos.
Massive loss of Cajal-Retzius cells does not disrupt neocortical layer order
Authors: Yoshida Michio , Assimacopoulos Stavroula , Jones Kevin R. , Grove Elizabeth A.
Published: January 2006

Cajal-Retzius (CR) cells, the predominant source of reelin in developing neocortex, are thought to be essential for the inside out formation of neocortical layers. Fate mapping revealed that a large population of neocortical CR cells arises from the cortical hem. To investigate the function of CR cells, we therefore genetically ablated the hem. Neocortical CR cells were distributed beneath the pial surface in control mice, but were virtually absent in hem-ablated mice from embryonic day (E) 10.5 until birth. CR cells derived from other sources did not invade the neocortical primordium to compensate for hem loss. We predicted that neocortical layers would be inverted in hem-ablated animals, as in reeler mice, deficient in reelin signaling. Against expectation, layers showed the standard order. Low levels of reelin in the cortical primordium, or diffusion of reelin from other sites, may have allowed lamination to proceed. Our findings indicate, however,that the sheet of reelin-rich CR cells that covers the neocortical primordium is not required to direct layer order.
Neurogenin 2 is required for the development of ventral midbrain dopaminergic neurons
Authors: Kele Julianna , Simplicio Nicolas , Ferri Anna L. M. , Mira Helena , Guillemot François , Arenas Ernest , Ang Siew-Lan
Published: January 2006

Proneural genes are crucial regulators of neurogenesis and subtype specification in many areas of the nervous system; however, their function in dopaminergic neuron development is unknown. We report that proneural genes have an intricate pattern of expression in the ventricular zone of the ventral midbrain, where mesencephalic dopaminergic neurons are generated. Neurogenin 2(Ngn2) and Mash1 are expressed in the ventral midline, while Ngn1, Ngn2 and Mash1 are co-localized more laterally in the ventricular zone. Ngn2 is also expressed in an intermediate zone immediately adjacent to the ventricular zone at the ventral midline. To examine the function of these genes, we analyzed mutant mice in which one or two of these genes were deleted (Ngn1, Ngn2 and Mash1) or substituted (Mash1 in the Ngn2 locus). Our results demonstrate that Ngn2 is required for the differentiation of Sox2+ ventricular zone progenitors into Nurr1+postmitotic dopaminergic neuron precursors in the intermediate zone, and that it is also likely to be required for their subsequent differentiation into tyrosine hydroxylase-positive dopaminergic neurons in the marginal zone. Although Mash1 normally has no detectable function in dopaminergic neuron development, it could partially rescue the generation of dopaminergic neuron precursors in the absence of Ngn2. These results demonstrate that Ngn2 is uniquely required for the development of midbrain dopaminergic neurons.
The Sonic hedgehog pathway independently controls the patterning,proliferation and survival of neuroepithelial cells by regulating Gli activity
Authors: Cayuso Jordi , Ulloa Fausto , Cox Barny , Briscoe James , Martí Elisa
Published: January 2006

During CNS development, the proliferation of progenitors must be coordinated with the pattern of neuronal subtype generation. In the ventral neural tube, Sonic hedgehog acts as a long range morphogen to organise the pattern of cell differentiation by controlling the activity of Gli transcription factors. Here, we provide evidence that the same pathway also acts directly at long range to promote the proliferation and survival of progenitor cells. Blockade of Shh signaling or inhibition of Gli activity results in cell autonomous decreases in progenitor proliferation and survival. Conversely, positive Gli activity promotes proliferation and rescues the effects of inhibiting Shh signaling. Analysis of neural cells indicates that Shh/Gli signaling regulates the G1 phase of cell cycle and the expression of the anti-apoptotic factor Bcl2. Furthermore, Shh signaling independently regulates patterning, proliferation and survival of neural cells, thus Shh/Gli activity couples these separate cellular responses of progenitors to coordinate neural development.
Inhibition of germline proliferation duringC. elegansdauer development requires PTEN, LKB1 and AMPK signalling
Authors: Narbonne Patrick , Roy Richard
Published: January 2006

In C. elegans, reduced insulin-like signalling induces developmental quiescence, reproductive delay and lifespan extension. We show here that the C. elegans orthologues of LKB1 and AMPK cooperate during conditions of reduced insulin-like signalling to establish cell cycle quiescence in the germline stem cell population, in addition to prolonging lifespan. The inactivation of either protein causes aberrant germline proliferation during diapause-like `dauer' development, whereas the loss of AMPK uncouples developmental arrest from lifespan extension. Reduced TGF-β activity also triggers developmental quiescence independent of the insulin-like pathway. Our data suggest that these two signalling pathways converge on the C. elegans PTEN orthologue to coordinate germline proliferation with somatic development during dauer formation, via the regulation of AMPK and its upstream activator LKB1, rather than through the canonical insulin-like signalling cascade. In humans, germline mutations in TGF-β family members, PTEN or LKB1 result in related tumour-predisposing syndromes. Our findings establish a developmental relationship that may underscore their shared, characteristic aetiology.
Motoneurons and oligodendrocytes are sequentially generated from neural stem cells but do not appear to share common lineage-restricted progenitors in vivo
Authors: Wu Sen , Wu Yuanyuan , Capecchi Mario R.
Published: January 2006

Olig gene expression is proposed to mark the common progenitors of motoneurons and oligodendrocytes. In an attempt to further dissect the in vivo lineage relationships between motoneurons and oligodendrocytes, we used a conditional cell-ablation approach to kill Olig-expressing cells. Although differentiated motoneurons and oligodendrocytes were eliminated, our ablation study revealed a continuous generation and subsequent death of their precursors. Most remarkably, a normal number of oligodendrocyte precursors are formed at day 12 of mouse development, after all motoneuron precursors have been killed. The data presented herein supports a sequential model in which motoneuron and oligodendrocyte precursors are sequentially generated in vivo from neuroepithelial stem cells, but do not share a common lineage-restricted progenitor.
Human trophoblast survival at low oxygen concentrations requires metalloproteinase-mediated shedding of heparin-binding EGF-like growth factor
Authors: Armant D. Randall , Kilburn Brian A. , Petkova Anelia , Edwin Samuel S. , Duniec-Dmuchowski Zophia M. , Edwards Holly J. , Romero Roberto , Leach Richard E.
Published: January 2006

Heparin-binding EGF-like growth factor (HBEGF), which is expressed in the placenta during normal pregnancy, is downregulated in pre-eclampsia, a human pregnancy disorder associated with poor trophoblast differentiation and survival. This growth factor protects against apoptosis during stress,suggesting a role in trophoblast survival in the relatively low O2(∼2%) environment of the first trimester conceptus. Using a well-characterized human first trimester cytotrophoblast cell line, we found that a 4-hour exposure to 2% O2 upregulates HBEGF synthesis and secretion independently of an increase in its mRNA. Five other expressed members of the EGF family are largely unaffected. At 2% O2,signaling via HER1 or HER4, known HBEGF receptors, is required for both HBEGF upregulation and protection against apoptosis. This positive-feedback loop is dependent on metalloproteinase-mediated cleavage and shedding of the HBEGF ectodomain. The restoration of trophoblast survival by the addition of soluble HBEGF in cultures exposed to low O2 and metalloproteinase inhibitor suggests that the effects of HBEGF are mediated by autocrine/paracrine, rather than juxtacrine, signaling. Our results provide evidence that a post-transcriptional mechanism induced in trophoblasts by low O2rapidly amplifies HBEGF signaling to inhibit apoptosis. These findings have a high clinical significance, as the downregulation of HBEGF in pre-eclampsia is likely to be a contributing factor leading to the demise of trophoblasts.
The interpretation of morphogen gradients
Authors: Ashe Hilary L. , Briscoe James
Published: January 2006

Morphogens act as graded positional cues that control cell fate specification in many developing tissues. This concept, in which a signalling gradient regulates differential gene expression in a concentration-dependent manner, provides a basis for understanding many patterning processes. It also raises several mechanistic issues, such as how responding cells perceive and interpret the concentration-dependent information provided by a morphogen to generate precise patterns of gene expression and cell differentiation in developing tissues. Here, we review recent work on the molecular features of morphogen signalling that facilitate the interpretation of graded signals and attempt to identify some emerging common principles.
A functional screen for sonic hedgehog regulatory elements across a 1 Mb interval identifies long-range ventral forebrain enhancers
Authors: Jeong Yongsu , El-Jaick Kenia , Roessler Erich , Muenke Maximilian , Epstein Douglas J.
Published: January 2006

The secreted protein sonic hedgehog (Shh) plays an integral role in forming the ventral midline of the vertebrate central nervous system (CNS). In the absence of Shh function, ventral midline development is perturbed resulting in holoprosencephaly (HPE), a structural malformation of the brain, as well as in neuronal patterning and path finding defects along the length of the anteroposterior neuraxis. Central to the understanding of ventral neural tube development is how Shh transcription is regulated in the CNS. To address this issue, we devised an enhancer trap assay to systematically screen 1 Mb of DNA surrounding the Shh locus for the ability to target reporter gene expression to sites of Shh transcription in transgenic mouse embryos. This analysis uncovered six enhancers distributed over 400 kb,the combined activity of which covered all sites of Shh expression in the mouse embryonic CNS from the ventral forebrain to the posterior extent of the spinal cord. To evaluate the relative contribution of these enhancers to the overall pattern of Shh expression, individual elements were deleted in the context of a transgenic Bac reporter assay. Redundant mechanisms were found to control Shh-like reporter activity in the ventral spinal cord, hindbrain and regions of the telencephalon, whereas unique elements regulated Shh-like expression in the ventral midbrain, the majority of the ventral diencephalon and parts of the telencephalon. Three ventral forebrain enhancers locate on the distal side of translocation breakpoints that occurred upstream of Shh in human cases of HPE, suggesting that displacement of these regulatory elements from the Shh promoter is a likely cause of HPE in these individuals.
bZIP transcription factor interactions regulate DIF responses inDictyostelium
Authors: Huang Eryong , Blagg Simone L. , Keller Thomas , Katoh Mariko , Shaulsky Gad , Thompson Christopher R. L.
Published: January 2006

The signalling molecule DIF-1 is required for normal cell fate choice and patterning in Dictyostelium. To understand how these developmental processes are regulated will require knowledge of how cells receive and respond to the DIF-1 signal. Previously, we have described a bZIP transcription factor, DimA, which is required for cells to respond to DIF-1. However, it was unknown whether DimA activity is required to activate the DIF response pathway in certain cells or is a component of the response pathway itself. In this study, we describe the identification of a DimA-related bZIP transcription factor, DimB. Rapid changes in the subcellular localisation of both DimA and DimB in response to DIF-1 suggest that they are directly downstream of the DIF-1 signal. Genetic and biochemical interactions between DimA and DimB provides evidence that their ability to regulate diverse targets in response to DIF-1 is partly due to their ability to form homo- and heterodimeric complexes. DimA and DimB are therefore direct regulators of cellular responses to DIF-1.
Granulosa cells regulate intracellular pH of the murine growing oocyte via gap junctions: development of independent homeostasis during oocyte growth
Authors: FitzHarris Greg , Baltz Jay M.
Published: January 2006

Oocytes grow within ovarian follicles in which the oocyte is coupled to the surrounding granulosa cells by gap junctions. It was previously found that small growing oocytes isolated from juvenile mice and freed of their surrounding granulosa cells (denuded) lacked the ability to regulate their intracellular pH (pHi), did not exhibit the pHi-regulatory HCO3-/Cl- and Na+/H+ exchange activities found in fully-grown oocytes,and had low pHi. However, both exchangers became active as oocytes grew near to full size, and, simultaneously, oocyte pHi increased by approximately 0.25 pH units. Here, we show that, in the more physiological setting of the intact follicle, oocyte pHi is instead maintained at∼7.2 throughout oocyte development, and the growing oocyte exhibits HCO3-/Cl- exchange, which it lacks when denuded. This activity in the oocyte requires functional gap junctions, as gap junction inhibitors eliminated HCO3-/Cl-exchange activity from follicle-enclosed growing oocytes and substantially impeded the recovery of the oocyte from an induced alkalosis, implying that oocyte pHi may be regulated by pH-regulatory exchangers in granulosa cells via gap junctions. This would require robust HCO3-/Cl- exchange activity in the granulosa cells, which was confirmed using oocytectomized (OOX) cumulus-oocyte complexes. Moreover, in cumulus-oocyte complexes with granulosa cells coupled to fully-grown oocytes, HCO3-/Cl- exchange activity was identical in both compartments and faster than in denuded oocytes. Taken together, these results indicate that growing oocyte pHi is controlled by pH-regulatory mechanisms residing in the granulosa cells until the oocyte reaches a developmental stage where it becomes capable of carrying out its own homeostasis.
Loss of myogenin in postnatal life leads to normal skeletal muscle but reduced body size
Authors: Knapp Jennifer R. , Davie Judith K. , Myer Anita , Meadows Eric , Olson Eric N. , Klein William H.
Published: January 2006

Although the mechanisms regulating the formation of embryonic skeletal muscle in vertebrates are well characterized, less is known about postnatal muscle formation even though the largest increases in skeletal muscle mass occur after birth. Adult muscle stem cells (satellite cells) appear to recapitulate the events that occur in embryonic myoblasts. In particular, the myogenic basic helix-loop-helix factors, which have crucial functions in embryonic muscle development, are assumed to have similar roles in postnatal muscle formation. Here, we test this assumption by determining the role of the myogenic regulator myogenin in postnatal life. Because Myog-null mice die at birth, we generated mice with floxed alleles of Myog and mated them to transgenic mice expressing Cre recombinase to delete Myogbefore and after embryonic muscle development. Removing myogenin before embryonic muscle development resulted in myofiber deficiencies identical to those observed in Myog-null mice. However, mice in which Myog was deleted following embryonic muscle development had normal skeletal muscle, except for modest alterations in the levels of transcripts encoding Mrf4 (Myf6) and Myod1 (MyoD). Notably, Myog-deleted mice were 30% smaller than control mice, suggesting that the absence of myogenin disrupted general body growth. Our results suggest that postnatal skeletal muscle growth is controlled by mechanisms distinct from those occurring in embryonic muscle development and uncover an unsuspected non-cell autonomous role for myogenin in the regulation of tissue growth.