bluuebunny/crossref_metadata_2025_split huggingface dataset:
Origins of flower morphology
Authors: Endress Peter K. 
Published: August 2002

AbstractFlowers evolved in many steps, probably starting long before flowering plants (angiophytes) originated. Certain parts of flowers are conservative and have not changed much during evolution; others are evolutionarily highly plastic. Here conservative features are discussed and an attempt is made to trace them back through their evolutionary history. Microsporangia and ovules (which develop into seeds) are preangiophyte floral elements. Angiospermy, combined with postgenital fusion, was the most prominent key innovation in angiophytes. Angiospermy and thecal organization of stamens originated earlier than all clades of extant angiosperms (the crown group of angiophytes). Differentiation of a perianth into calyx and corolla and syncarpy appeared after the first branching of the basalmost clades of extant angiosperms. Sympetaly and floral tubes as well as tenuinucellar, unitegmic ovules originated as major innovations in the clade that led to asterids. An obvious trend in flower evolution is increased synorganisation of parts, which led to new structures. Fixation of floral organ number and position was a precondition for synorganization. Concomitantly, plasticity changed from number and position of organs to shape of the new structures. Character distribution mapped onto cladograms indicates that key innovations do not appear suddenly, but start with trials and only later become deeply rooted genetically in the organization. This is implied from the common occurrence of reversals in the early history of an innovation. J. Exp. Zool. (Mol. Dev. Evol.) 291:105–115, 2001. © 2001 Wiley‐Liss, Inc.
Timing of SOX9 downregulation and female sex determination in gonads of the sea turtle Lepidochelys olivacea
Authors: Torres‐Maldonado Leda , Moreno‐Mendoza Norma , Landa Abraham , Merchant‐Larios Horacio 
Published: August 2002

AbstractThe SRY‐related gene SOX9 is involved in the differentiation of Sertoli cells in male gonads of vertebrates with different kinds of sex determination. In the olive ridley Lepidochelys olivacea, a species with temperature sex determination (TSD), the SOX9 protein is expressed at stages 21–24 in medullary cells in gonads of embryos incubated at both male‐(MPT) or female‐promoting temperatures (FPT). However, at FPT the expression of SOX9 protein decreases at stage 25 and disappears at stage 26, suggesting this as the critical period for SOX9 regulation by temperature. Here, we used reverse transcriptase polymerase chain reaction (RT‐PCR) to detect SOX9 transcripts in gonads of embryos switched from MPT to FPT at stage 23 and sampled at days 6–14. Simultaneously, groups of embryos were switched back to MPT and gonadal sex was established. SOX9 transcripts were detected at days 6–12 of switching, when embryos reached stage 25 and were no longer detected at day 14, when the embryos were at stage 26. Embryos switched back to MPT at days 6 or 8 formed testes, whereas embryos switched at days 10 or 14 developed ovaries. Results suggest that at MPT the male sex‐determining pathway that maintains SOX9 expression in male gonads is established at stage 24. In contrast, at FPT, the female sex‐determining pathway involved in downregulation of SOX9 in female gonads occurs within two days at stage 25. J. Exp. Zool. 290:498–503, 2001. © 2001 Wiley‐Liss, Inc.
Sperm surface proteases in ascidian fertilization
Authors: Lambert Charles C. , Someno Tetsuya , Sawada Hitoshi 
Published: August 2002

AbstractAscidian eggs are surrounded by a noncellular layer and two cellular layers, which are penetrated by sperm. Three sperm surface proteases are essential for fertilization of eggs from the stolidobranch ascidian Halocynthia: spermosin, acrosin, and the proteasome. In the phlebobranch Ciona, a chymotrypsin‐like protease and the proteasome are essential in fertilization. Sperm from the phlebobranch ascidians Phallusia mammillata, Ascidia (=Phallusia) nigra, and Ascidia columbiana, all express spermosin, acrosin, and the proteasomal chymotrypsin activities on their surfaces. Chymostatin blocks cleavage in phlebobranchs, but inhibitors of spermosin and acrosin only delay it by several minutes. Protease inhibitors have little effect upon sperm binding in Phallusia but strongly affect the rate of sperm passage through the vitelline coat. Peptide substrates and inhibitors to spermosin and acrosin cause a significant decline in the number of eggs undergoing pre‐meiotic contractions at 3 min after fertilization. Thus while chymotrypsin activity is essential for penetration of the vitelline coat, spermosin and acrosin both function to increase the rate of fertilization. A crucial step in the divergence of the phlebobranchs and stolidobranchs may have been the conversion of spermosin and acrosin to essential proteases in the stolidobranchs, or, perhaps, their essential function was lost in the evolution of phlebobranchs. Aplousobranch ascidians are all colonial with very small zooids. Sperm from Aplidium californicum, Aplidium solidum (Polyclinidae), and Distaplia occidentalis (Holozoidae) have acrosin and chymotrypsin activities but lack spermosin activity. This enzyme is also missing from sperm of colonial phlebobranch and stolidobranch ascidians, suggesting that spermosin is not necessary for small zooids with internal fertilization. J. Exp. Zool. 292:88–95, 2002. © 2002 Wiley‐Liss, Inc.
Forbidden subgraphs that imply hamiltonian‐connectedness*
Authors: Broersma Hajo , Faudree Ralph J. , Huck Andreas , Trommel Huib , Veldman Henk Jan 
Published: August 2002

AbstractIt is proven that if G is a 3‐connected claw‐free graph which is also H1‐free (where H1 consists of two disjoint triangles connected by an edge), then G is hamiltonian‐connected. Also, examples will be described that determine a finite family of graphs ${\cal L}$ such that if a 3‐connected graph being claw‐free and L‐free implies G is hamiltonian‐connected, then L $\in \cal L$. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 104–119, 2002
Attacking Poverty and the ‘post‐Washington consensus’
Authors: Mosley Paul 
Published: August 2002

AbstractHas the increasingly pro‐poor stance of the World Bank, as manifested in particular in its most recent World Development Report (WDR), caused it to abandon its traditionally free‐market attitudes ? The answer is ‘yes and no’. The pursuit of ‘security’ espoused by the WDR has forced the Bank to acknowledge widespread market failure in the provision of security, both social and financial; and this has caused the Bank to espouse some measures very inconsistent with the Washington consensus, such as international capital controls. On the other hand, the old agenda of rolling back the frontiers of the state remains, and is given a new twist in WDR 2000 by the revelation that the ‘voices of the poor’ are arrayed against bureaucratic abuses. Debate within the Bank has become much more open and transparent, and this has exposed long‐persisting internal differences about what markets still need to be liberalized in what environments. Copyright © 2001 John Wiley & Sons, Ltd.
From social networks to public action in urban governance: where does benefit accrue?
Authors: Beall Jo 
Published: August 2002

AbstractThe key question addressed in this paper is in what ways strategies at the community level make a difference to urban governance and for whom? The research on which it draws was concerned with two issues of relevance. The first was what poor people and communities do for themselves when city governments are unable or unwilling to extend resources to them. The second was to understand the institutional relationships, both formal and informal, between people in poverty and the organizations of city governance. In addition to local government, business and NGOs, these are understood to include associations of mutuality and community level organizations, particularly households, social networks, and political and developmental CBOs (see also Beall and Kanji, 1999). Drawing on research conducted in the nine case study cities, evidence of local level networks and associational life is examined to assess where benefits accrue when they are harnessed in the interests of city governance. These are very different cities and livelihood strategies and patterns of public action and urban governance are undoubtedly context‐specific. However, patterns emerge that are comparable and worthy of comment. Copyright © 2001 John Wiley & Sons, Ltd.
Morphology of the prometamorphic larva of the spadefoot toad, Scaphiopus intermontanus (Anura: Pelobatidae), with an emphasis on the lateral line system and mouthparts
Authors: Hall John A. , Larsen John H. , Fitzner Richard E. 
Published: August 2002

AbstractWe provide a detailed description of the larval morphology of the Great Basin spadefoot toad (Scaphiopus intermontanus), a species with documented morphological variability in larval structures associated with feeding. We based our findings on laboratory‐raised individuals fed a herbivorous diet. We characterized the morphology of the prometamorphic larva (limited to developmental stages 37 and 38) and then related our findings to the larval ecology of the species. Based on its morphology, such as slightly depressed body, dorsally positioned eyes, anteroventrally oriented oral disc, intermediate tail fin height and slightly attenuated tail tip, relative lack of ventral neuromasts (compared to Xenopus laevis), and pigmentation banding patterns, and habits, such as selection of breeding sites by adults and larval foraging behavior, S. intermontanus can be characterized best as belonging to a (lentic‐) benthic guild of anuran larvae. Nevertheless, the larvae are capable of occupying a broader array of ecological niches. Because we characterized individuals raised on a herbivorous diet, our morphological descriptions apply only to the herbivorous S. intermontanus larva (and perhaps to those larvae that are dietary generalists and may feed carnivorously only infrequently). Our findings can serve as a baseline for future morphological and developmental comparisons with the carnivorous morphological variant of this species. J. Morphol. 252:114–130, 2002. © 2002 Wiley‐Liss, Inc.
Placentation in garter snakes: Scanning EM of the placental membranes of Thamnophis ordinoides and T. sirtalis
Authors: Blackburn Daniel G. , Stewart James R. , Baxter Duane C. , Hoffman Loren H. 
Published: August 2002

AbstractSurface topography and cross‐sections of the placental membranes were examined by scanning electron microscopy in two species of Thamnophis. The chorionic epithelium of the chorioallantoic placenta consists of broad, squamous cells that lack surface specializations. The apposed uterine epithelium contains ciliated cells and larger, nonciliated cells. Neither the epithelium of the chorion nor that of the uterus is eroded; thus, underlying capillaries are not exposed to the luminal surface. In both the omphaloplacenta and the omphalallantoic placenta, epithelium of the omphalopleure consists of brush‐border cells bearing prominent microvilli, interspersed with cells bearing minuscule microvilli. These surface epithelial cells are joined at their apices and their lateral surfaces are extensively sculpted by intercellular channels, presenting the appearance of an epithelium specialized for absorption. Deep to the epithelium lie the yolk spheres of the isolated yolk mass, interspersed with endodermal cells. Surface topography of the uterine epithelia of the omphaloplacenta and omphalallantoic placenta is relatively unspecialized. The acellular shell membrane separates maternal and fetal tissues in each of the three placental types. Marked differences in surface features of the chorioallantois and omphalopleure probably reflect different roles of these membranes in gas exchange and transfer of water and nutrients. J. Morphol. 252:263–275, 2002. © 2002 Wiley‐Liss, Inc.
Collateral flow in coarctation of the aorta with magnetic resonance velocity mapping: Correlation to morphological imaging of collateral vessels
Authors: Holmqvist Catarina , Ståhlberg Freddy , Hanséus Katarina , Hochbergs Peter , Sandström Staffan , Larsson Elna‐Marie , Laurin Sven 
Published: August 2002

AbstractPurposeTo correlate quantification of collateral flow in aortic coarctation with the morphological visualization of the collateral vessels and to compare different approaches to measurement of collateral flow.Materials and MethodsThirteen children with coarctation were examined with T1‐weighted spin‐echo (T1‐W SE) imaging and 3D contrast‐enhanced magnetic resonance angiography (MRA). MR velocity mapping was performed at four levels in the descending aorta.ResultsThe flow immediately above and below the coarctation did not differ significantly. Measuring within the coarctation resulted in flow overestimation. The increase of flow from proximal to distal aorta was 12 ± 21% in patients with no or uncertain collaterals and 69 ± 55% in patients with pronounced collaterals. Spin‐echo images and MRA were comparable in visualizing collateral vessels. The visual estimation of collaterals correlated reasonably well with flow quantification MR velocity mapping.ConclusionCollateral flow assessment with MR velocity mapping is an accurate technique for evaluating the hemodynamic importance of a coarctation and is recommended if abundant collaterals are not visualized with spin echo or MRA. J. Magn. Reson. Imaging 2002;15:39–46. © 2002 Wiley‐Liss, Inc.
Three‐dimensional true‐FISP imaging of the coronary arteries: Improved contrast with T2‐preparation
Authors: Shea Steven M. , Deshpande Vibhas S. , Chung Yiu‐Cho , Li Debiao 
Published: August 2002

AbstractPurposeTo evaluate the effectiveness of a T2‐magnetization preparation scheme for improving coronary artery imaging with true fast imaging with steady‐state precession (True‐FISP).Materials and MethodsSimulations were performed to compare the blood‐myocardium signal difference with no T2‐preparation to that with various T2‐preparation times (24, 40, and 60 msec) using an electrocardiogram (ECG)‐triggered, segmented True‐FISP acquisition. Seven volunteers were imaged to evaluate the effectiveness of T2‐preparation for coronary artery delineation using True‐ FISP and to optimize the T2‐preparation time.ResultsSimulations showed that T2‐preparation improved the signal difference between blood and myocardium over that without T2‐preparation. The optimal T2‐ preparation time was determined to be 40 msec. In volunteer studies, a T2‐ preparation time of 40 msec provided a significant improvement in contrast‐ to‐noise ratio (CNR) between the coronary arteries and myocardium over that without T2‐preparation. It also showed a significant improvement in visualizing the distal portions of the coronary arteries.ConclusionT2‐preparation improves coronary artery delineation with True‐FISP. J. Magn. Reson. Imaging 2002;15:597–602. © 2002 Wiley‐Liss, Inc.
A targeted contrast agent for magnetic resonance imaging of thrombus: Implications of spatial resolution
Authors: Johansson L.O. , Bjørnerud A. , Ahlström H.K , Ladd D.L. , Fujii D.K. 
Published: August 2002

AbstractA preparation of ultra‐small superparamagnetic iron oxide (USPIO) particles coupled to an RGD peptide (RGD‐USPIO) was investigated as an MR contrast agent, targeted to activated platelets, in both ex vivo and in vivo thrombus models. Thrombus visualization ex vivo was compared using RGD‐USPIO and a non‐targeted UPSIO. The influence of thrombus visualization on thrombus exposure time to RGD‐USPIO (ex vivo) and on the spatial resolution of the MR image (ex vivo and in vivo) was assessed. RGD‐USPIO resulted in better thrombus visualization than non‐targeted USPIO ex vivo, and maximum enhancement was achieved after approximately one hour exposure time of the thrombus to RGD‐USPIO. The ability to visualize the clots was highly dependent on the spatial resolution of the image. In vivo, an in‐plane resolution of less than 0.2 × 0.2 mm2 was required for good clot visualization after contrast enhancement. It is concluded that the achievable resolution and sensitivity is a potential limitation to the usefulness of active vascular targeting in MRI. J. Magn. Reson. Imaging 2001;13:615–618. © 2001 Wiley‐Liss, Inc.
Changes in intrarenal oxygenation as evaluated by BOLD MRI in a rat kidney model for radiocontrast nephropathy
Authors: Prasad Pottumarthi V. , Priatna Agus , Spokes Katherine , Epstein Franklin H. 
Published: August 2002

AbstractThe pathogenesis of radiocontrast nephropathy is poorly understood. In an animal model, inhibition of the synthesis of nitric oxide and prostaglandins appears to predispose rats to severe renal injury following the administration of radiocontrast. Here we have investigated whether administration of radiocontrast, as well as changes in renal medullary oxygenation following pharmacologic inhibition of nitric oxide and prostaglandin synthesis, might be evaluated by blood oxygenation level‐dependent (BOLD) MRI. Nineteen anesthetized (Inactin 100 mg/kg) rats were studied. BOLD MRI measurements were performed following administration of L‐NAME (N‐nitro‐L‐arginine methyl ester, 10 mg/kg), Indomethacin (10 mg/kg), and a radiocontrast agent (sodium iothalamate 60%, 6 mL/kg). Marked sequential changes in medullary R, presumably reflecting decline in medullary pO2, were noted after each of the pharmacological interventions employed. These results, obtained by noninvasive MRI, are consistent with prior direct recordings of pO2 and doppler flow in the rat renal medulla after administration of L‐NAME, Indomethacin and iothalamate. Medullary oxygenation in rats was reduced by inhibition of the synthesis of prostaglandins and nitric oxide, as well as by intravenous injection of radiocontrast agents. BOLD MRI can noninvasively evaluate changes in medullary oxygenation in rats that appear to predispose acute renal failure. J. Magn. Reson. Imaging 2001;13:744–747. © 2001 Wiley‐Liss, Inc.
An integrated visualization system for surgical planning and guidance using image fusion and an open MR
Authors: Gering David T. , Nabavi Arya , Kikinis Ron , Hata Noby , O'Donnell Lauren J. , Grimson W. Eric L. , Jolesz Ferenc A. , Black Peter M. , Wells William M. 
Published: August 2002

AbstractA surgical guidance and visualization system is presented, which uniquely integrates capabilities for data analysis and on‐line interventional guidance into the setting of interventional MRI. Various pre‐operative scans (T1‐ and T2‐weighted MRI, MR angiography, and functional MRI (fMRI)) are fused and automatically aligned with the operating field of the interventional MR system. Both pre‐surgical and intra‐operative data may be segmented to generate three‐dimensional surface models of key anatomical and functional structures. Models are combined in a three‐dimensional scene along with reformatted slices that are driven by a tracked surgical device. Thus, pre‐operative data augments interventional imaging to expedite tissue characterization and precise localization and targeting. As the surgery progresses, and anatomical changes subsequently reduce the relevance of pre‐operative data, interventional data is refreshed for software navigation in true real time. The system has been applied in 45 neurosurgical cases and found to have beneficial utility for planning and guidance. J. Magn. Reson. Imaging 2001;13:967–975. © 2001 Wiley‐Liss, Inc.
Extent and time course of morphological changes of bone marrow induced by granulocyte‐colony stimulating factor as assessed by magnetic resonance imaging of healthy blood stem cell donors
Authors: Altehoefer Carsten , Bertz Hartmut , Ghanem Nadir A. , Langer Mathias 
Published: August 2002

AbstractThe aim of this study was to assess the time course and extent of signal alterations of red bone marrow after short‐term stimulation by recombinant human granulocyte‐colony stimulating factor (rHuG‐CSF) in healthy peripheral blood stem cell donors using magnetic resonance imaging (MRI) at low‐field strength. Twelve healthy blood stem cell donors without evidence of bone marrow disorders were prospectively investigated and underwent four MRI studies of their lumbar spine. Sagittal T1‐ and T2‐weighted spin‐echo sequences and a gradient‐echo (GE) sequence with an echo time for out‐of‐phase imaging were performed prior to rHuG‐CSF application (baseline MRI), on the day of first stem cell harvest (after 70 μg/kg body weight rHuG‐CSF, second MRI) followed by two studies 9–18 days (median 14.5 days, third MRI) and 26–48 days (median 39.5 days, fourth MRI) after discontinuation of rHuG‐CSF application. Baseline MRI showed normal marrow signal in all patients. The second MRI revealed a decrease of quantified bone marrow signal relative to nucleus pulposus in T1‐ and T2‐weighted images and an increase of relative signal in out‐of‐phase GE sequences. The greatest changes of relative marrow signal were observed at the third MRI. Compared to baseline MRI, relative marrow signal was diminished by 12% in T1‐weighted images and increased by 59% in GE sequences, consistent with a rise in marrow cellularity simulating diffuse marrow disease. At the fourth MRI quantified relative marrow signal returned to baseline levels in all sequences. In healthy individuals rHuG‐CSF application leads to significant signal changes of bone marrow in lumbar vertebra that are maximal about 2 weeks after discontinuation of rHuG‐CSF application. In patients with underlying marrow disorders who receive hematopoietic growth factors during treatment, these changes should not be confused with disease progression. J. Magn. Reson. Imaging 2001;14:141–146. © 2001 Wiley‐Liss, Inc.
Impact of bulk cardiac motion on right coronary MR angiography and vessel wall imaging
Authors: Kim W. Yong , Stuber Matthias , Kissinger Kraig V. , Andersen Niels Trolle , Manning Warren J. , Botnar René M. 
Published: August 2002

AbstractThe purpose of this study was to investigate the impact of in‐plane coronary artery motion on coronary magnetic resonance angiography (MRA) and coronary MR vessel wall imaging. Free‐breathing, navigator‐gated, 3D‐segmented k‐space turbo field echo ((TFE)/echo‐planar imaging (EPI)) coronary MRA and 2D fast spin‐echo coronary vessel wall imaging of the right coronary artery (RCA) were performed in 15 healthy adult subjects. Images were acquired at two different diastolic time periods in each subject: 1) during a subject‐specific diastasis period (in‐plane velocity <4 cm/second) identified from analysis of in‐plane coronary artery motion, and 2) using a diastolic trigger delay based on a previously implemented heart‐rate‐dependent empirical formula. RCA vessel wall imaging was only feasible with subject‐specific middiastolic acquisition, while the coronary wall could not be identified with the heart‐rate‐dependent formula. For coronary MRA, RCA border definition was improved by 13% (P < 0.001) with the use of subject‐specific trigger delay (vs. heart‐rate‐dependent delay). Subject‐specific middiastolic image acquisition improves 3D TFE/EPI coronary MRA, and is critical for RCA vessel wall imaging. J. Magn. Reson. Imaging 2001;14:383–390. © 2001 Wiley‐Liss, Inc.