bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of pharyngeal arch arteries in early mouse embryo
Authors: Hiruma Tamiko , Nakajima Yuji , Nakamura Hiroaki 
Published: March 2003

AbstractThe formation and transformation of the pharyngeal arch arteries in the mouse embryo, from 8.5 to 13 days of gestation (DG), was observed using scanning electron microscopy of vascular casts and graphic reconstruction of 1‐µm serial epoxy‐resin sections. Late in 8.5–9DG (12 somites), the paired ventral aortae were connected to the dorsal aortae via a loop anterior to the foregut which we call the ‘primitive aortic arch’, as in the chick embryo. The primitive aortic arch extended cranio‐caudally to be transformed into the primitive internal carotid artery, which in turn gave rise to the primitive maxillary artery and the arteries supplying the brain. The second pharyngeal arch artery (PAA) appeared late in 9–9.5DG (16–17 somites), and the ventral aorta bent dorsolaterally to form the first PAA anterior to the first pharyngeal pouch by early in 9.5–10DG (21–23 somites). The third PAA appeared early in 9.5–10DG (21–23 somites), the fourth late in 9.5–10DG (27–29 somites), and the sixth at 10DG (31–34 somites). By 10.5DG (35–39 somites), the first and second PAAs had been transformed into other arteries, and the third, fourth and sixth PAAs had developed well, though the PAA system still exhibited bilateral symmetry. By 13DG, the right sixth PAA had disappeared, and the remaining PAAs formed an aortic‐arch system that was almost of the adult type.
Dopaminergic differentiation of the Nurr1‐expressing immortalized mesencephalic cell line CSM14.1in vitro
Authors: Haas Stefan Jean‐Pierre , Wree Andreas 
Published: March 2003

AbstractThe use of neural stem cells as grafts is a potential treatment for Parkinson's disease, but the potential of stem cells to differentiate into dopaminergic neurones requires investigation. The present study examined thein vitrodifferentiation of the temperature‐sensitive immortalized mesencephalic progenitor cell line CSM14.1 under defined conditions. Cells were derived from the mesencephalic region of a 14‐day‐old rat embryo, retrovirally immortalized with the Large T antigen and cultured at 33 °C in DMEM containing 10% fetal calf serum (FCS). For differentiation, the temperature was elevated at 39 °C and FCS was reduced (1%). Using histology, immunocytochemical detection of the stem cell marker Nestin and the neuronal marker MAP5 and, in addition, Western blotting to determine the presence of neurone‐specific enolase and the neurone nuclei antigen we demonstrated a differentiation of these cells into neuronal cells accompanied by a decrease in Nestin production. In Western blots, we detected the orphan nuclear receptor Nurr1 in these cells. This was followed by a time‐dependent up‐regulation of the enzymes tyrosine hydroxylase and aldehyde dehydrogenase 2 characteristic of mature dopaminergic neurones. Ourin vitromodel of dopaminergic cell differentiation corroborates recentin vivoobservations in the developing rodent brain.
Structure, function and evolution of the gas exchangers: comparative perspectives
Authors: Maina J. N. 
Published: March 2003

AbstractOver the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ‘necessity is the mother of invention’, gas exchangers have been inaugurated through stiff cost–benefit analyses that have evoked transaction of trade‐offs and compromises. Cogent structural–functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better‐refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones of the modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices – water or air – within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animals have adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water–air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter‐current, cross‐current, uniform pool and infinite pool designs have variably developed.
Coracoclavicular joint: osteologic study of 1020 human clavicles
Authors: Gumina S. , Salvatore M. , De Santis P. , Orsina L. , Postacchini F. 
Published: March 2003

AbstractWe examined 1020 dry clavicles from cadavers of Italian origin to determine the prevalence of the coracoclavicular joint (ccj), a diarthrotic synovial joint occasionally present between the conoid tubercle of the clavicle and the superior surface of the horizontal part of the coracoid process. Five hundred and nine clavicles from individuals of different ages were submitted to X‐ray examination. Using radiography, we measured the entire length and the index of sinuosity of the anterior lateral curve, on which the distance between the conoid tubercle and the coracoid process depends. We also used radiography to record the differences in prevalence of arthritis in two neighbouring joints, the acromioclavicular and sternoclavicular joints. Of the 1020 clavicles, eight (0.8%) displayed the articular facet of the ccj. No statistical correlation was found between clavicular length and the index of sinuosity of the anterior lateral curve. The prevalence of arthritis in clavicles with ccj was higher than that revealed in clavicles without ccj. The prevalence of ccj in the studied clavicles is lower than that observed in Asian cohorts. Furthermore, ccj is not conditioned by either length or sinuosity of the anterior lateral curve of the clavicle. Finally, the assumption that ccj is a predisposing factor for degenerative changes of neighbouring joints is statistically justified.
Mouse models for human hair loss disorders
Authors: Porter Rebecca M. 
Published: March 2003

AbstractThe outer surface of the hand, limb and body is covered by the epidermis, which is elaborated into a number of specialized appendages, evolved not only to protect and reinforce the skin but also for social signalling. The most prominent of these appendages is the hair follicle. Hair follicles are remarkable because of their prolific growth characteristics and their complexity of differentiation. After initial embryonic morphogenesis, the hair follicle undergoes repeated cycles of regression and regeneration throughout the lifetime of the organism. Studies of mouse mutants with hair loss phenotypes have suggested that the mechanisms controlling the hair cycle probably involve many of the major signalling molecules used elsewhere in development, although the complete pathway of hair follicle growth control is not yet understood. Mouse studies have also led to the discovery of genes underlying several human disorders. Future studies of mouse hair‐loss mutants are likely to benefit the understanding of human hair loss as well as increasing our knowledge of mechanisms controlling morphogenesis and tumorigenesis.
High‐resolution imaging of normal anatomy, and neural and adrenal malformations in mouse embryos using magnetic resonance microscopy
Authors: Schneider Jürgen E. , Bamforth Simon D. , Farthing Cassandra R. , Clarke Kieran , Neubauer Stefan , Bhattacharya Shoumo 
Published: March 2003

AbstractAn efficient investigation of the effects of genetic or environmental manipulation on mouse development relies on the rapid and accurate screening of a substantial number of embryos for congenital malformations. Here we demonstrate that it is possible to examine normal organ development and identify malformations in mouse embryos by magnetic resonance microscopy in a substantially shorter time than by conventional histology. We imaged embryos in overnight runs of under 9 h, with an operator time of less than 1 h. In normal embryos we visualized the brain, spinal cord, ganglia, eyes, inner ear, pituitary, thyroid, thymus, trachea, bronchi, lungs, heart, kidneys, gonads, adrenals, oesophagus, stomach, intestines, spleen, liver and pancreas. Examination of the brain in embryos lacking the transcriptional coactivator Cited2 showed cerebellar and midbrain roof agenesis, in addition to exencephaly. In these embryos we were also able to detect agenesis of the adrenal gland. We confirmed all malformations by histological sectioning. Thus magnetic resonance microscopy can be used to rapidly identify developmental and organ malformations in mutant mouse embryos generated by transgenic techniques, in high‐throughput mutagenesis screens, or in screens to identify teratogenic compounds and environmental factors contributing to developmental malformations.
Variation in endophytic fungi from roots and leaves of Lepanthes (Orchidaceae)
Authors: BAYMAN PAUL , LEBRÓN LIGIA L. , TREMBLAY RAYMOND L. , LODGE D. JEAN 
Published: March 2003

SUMMARYLittle is known about non‐mycorrhizal endophytic fungi in tropical orchids; still less is known about how endophytes vary within and between individual orchid plants. Fungal endophytes were isolated from roots and leaves of epiphytic and lithophytic orchids in the genus Lepanthes; seven species, from rainforests in Puerto Rico, were sampled. The endophytes observed most frequently were Xylaria species and Rhizoctonia‐like fungi, found in 29% of roots and 19% of leaves, and 45 % of roots and 31 % of leaves, respectively. Five deuteromycete genera were also isolated, occurring in 19 % of roots and 43 % of leaves (combined). At least nine species of Xylaria were found, with several species sometimes occurring in a single plant. Differences between roots and leaves in frequency of Xylaria and Rhizoctonia isolates were not significant, although differences among orchid species in number and types of endophytes were. Heterogeneity of endophytes in single plants and plant organs was greater than differences between species. Many Lepanthes species are very restricted in distribution, and knowledge of their interactions with endophytes might be useful in species management.
Regulation of thiophene biosynthesis by sulphate in roots of marigolds
Authors: ARROO R. R. J. , JACOBS J. J. M. R. , VAN GESTEL J. A. M. , KENKEL H. , JANNINK W. , CROES A. F. , WULLEMS G. J. 
Published: March 2003

SUMMARYThe incorporation of [35S] sulphur in thiophenes by Tagetes patula roots was used as a model to study the regulation of secondary metabolism with a limited supply of substrate. Growth and thiophene accumulation were measured in root cultures incubated at various sulphate concentrations in the medium. A 20‐fold to 40‐fold reduction in the sulphate concentration did not affect elongation growth, branching and biomass production within 14 d but decreased the thiophene level to 25–50% of the control in the same period. The reduction in thiophene content was found to result from a decline in biosynthetic capacity of 80–95% after 8 d. This capacity was restored when roots were transferred to standard medium. The restoration took more than 24 h and was suppressed by cordycepin, an inhibitor of mRNA processing. It is concluded that the rate of thiophene synthesis is regulated by a control mechanism that reacts to the availability of sulphate to the roots.
Polyamine synthesis and accumulation in the hypersensitive response to TMV in Nicotiana tabacum
Authors: TORRIGIANI PATRIZIA , RABITI ANNA LAURA , BORTOLOTTI CRISTINA , BETTI LUCIETTA , MARANI FRANCESCA , CANOVA ANTONIO , BAGNI NELLO 
Published: March 2003

summaryThe possible involvement of polyamines in the tobacco mosaic virus (TMV)‐induced hypersensitive reaction (HR) in Nicotiana tabacum (L.) cv. Samsun NN, which bears the N resistance gene, was investigated. Concentrations of free and conjugated polyamines, as well as the activities of their biosynthetic enzymes ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), were analysed in the necrotic area (I, internal zone) and in the two concentric zones surrounding it (M, middle zone; E, external zone) during the progression of the HR (1, 3 and 5 d from TMV inoculation). Results were compared with those obtained in control plants (mock‐inoculated) and with the pattern in susceptible TMV‐infected tobacco plants.In the HR, concentration increased towards zone I for free putrescine and spermidine. Highest concentrations in zones M and I occurred on day 3. Conjugated polyamines similarly showed an increasing concentration gradient towards zone I, with maximum accumulation on day 5. ODC and ADC activities also showed an increasing gradient towards zone I that could be related to the increase in free and conjugated polyamines. By contrast, in control plants concentrations of free and conjugated polyamines decreased from day 1 to day 5, ODC activity increased slightly, whereas ADC activity did not show significant changes. In the TMV‐infected susceptible tobacco plants, polyamines tended to remain in the free state instead of being conjugated as infection progressed. These results suggest that polyamines could play a role in mechanisms of resistance to biotic stress.
Components of relative growth rate and their interrelations in 59 temperate plant species
Authors: HUNT RODERICK , CORNELISSEN J. H. C. 
Published: March 2003

summaryThree groups of species (21 herbaceous monocotyledons, 22 herbaceous dicotyledons and 16 woody dicotyledons), including representatives of a wide range of natural habitats and life forms in inland Britain, were grown in the seedling phase in a resource‐rich controlled environment and assessed over a 14‐day period (21 d in the case of woody species). Mean values of relative growth rate (RGR), unit leaf rate (ULR), leaf area ratio (LAR), leaf weight fraction (LWF), specific leaf area (SLA), and the root‐shoot allometric coefficient were derived.In herbaceous species, the grand mean RGR was 0.20 d−1 comparable to values previously recorded. For woody species, the mean was 0.09 d−1. An existing assumption linking high RGR to high allocation to photosynthetic biomass was upheld by comparisons made between groups. Within groups, however, no pattern of this kind could be demonstrated.When photosynthetically active radiation was increased from 125 to 250 μmol m−2 s−1, ULR was increased almost pro rata. The parallel response in RGR was only slight, being offset by considerable reductions in LAR. The apparent mean quantum yield for photosynthesis in herbaceous species (whole‐plant d. wt basis) was 0–60 g mol−1.There was no significant dependence of RGR on ULR in any of the three groups of species, although the absolute magnitude of ULR declined in the order: herbaceous monocotyledons > herbaceous dicotyledons > woody dicotyledons. In all three groups, RGR was strongly dependent upon LAR but no differences emerged in absolute scale of LAR. The absolute scale of mean LWF decreased from herbaceous to woody species, but the dependence of LAR on LWF strengthened. Groups showed no systematic differences in magnitude of SLA, but the correlation of LAR with SLA was strong throughout.Multiple regression showed that the leading determinants of RGR were ULR and SLA in herbaceous species and LWF in woody species. Principal components analyses (PCA) on each of the three groups explained at least 77% of variation and agreed closely with an optimal (non‐hierarchical) classification. Only six cluster ‘types’ were recognized out of the 16 theoretically possible combinations of ‘high’ or ‘low’ values of the four growth parameters. Strong evidence of evolutionary trade‐offs emerged, most strikingly in that high RGR was never seen in combination with low SLA. The morphological/physiological types identified by an all‐groups PCA separated woody from the herbaceous species, but dicotyledons were almost congruent with the monocotyledons.The non‐growth‐analytical attributes most strongly correlated with mean RGR were percentage yield at a low level of mineral nutrients, leaf nitrogen concentration, and seed weight. It was concluded that mean RGR plays a central role in the identification of pathways of evolutionary specialization in herbaceous species.
Soil Mg and Ni as causal factors of plant occurrence and distribution at the Meikle Kilrannoch ultramafic site in Scotland
Authors: NAGY L. , PROCTOR J. 
Published: March 2003

summarySolution culture experiments were made using two subspecies of Cerastium fontanum and Cochlearia pyrenaica ssp. alpina (Bab.) Dalby and Festuca rubra L.of ultramafic and non‐ultramafic origin to test: (1) whether Mg and Ni toxicities are likely to exclude non‐ultramafic races of the three species; (2) whether tolerance to Mg and Ni toxicities by the ultramafic plants differed markedly among the species; and (3) to use (2) to generate a hypothesis about controlling factors of species distribution on the Meikle Kilrannoch (MK1) ultramafics. The solution cultures were based on soil solution extracts with experimentally varied concentrations of Mg, Ni and Na. The solution with high (7.5 HIM) Mg and high (0.7 mg l−1) Ni concentrations simulated the ultramafic soil solution. Care was taken to use a Fe source which did not react with Ni and microelements. Of the non‐ultramafic plants, the growth of Cerastium was reduced by high concentrations of Mg but not by Ni, whereas both the Cochlearia and the Festuca suffered severe reduction in biomass production in the presence of high Mg or Ni or both. Of the ultramafic plants, Festuca was tolerant of high Mg and Ni concentrations; Cerastium was less tolerant of high Mg; and Cochlearia had low shoot production in high Ni (although the effect was ameliorated by high Mg). The different interspecific responses of the ultramafic plants to Mg and Ni supported field observations that the three species might occupy microhabitats which differ in Mg and Ni.
Effects of elevated atmospheric CO2and soil water availability on root biomass, root length, and N, P and K uptake by wheat
Authors: VAN VUUREN MARGRET M. I. , ROBINSON DAVID , FITTER ALASTAIR H. , CHASALOW SCOTT D. , WILLIAMSON LISA , RAVEN JOHN A. 
Published: March 2003

summaryWe investigated interactions between the effects of elevated atmospheric carbon dioxide concentrations ([CO2]) and soil water availability on root biomass, root length and nutrient uptake by spring wheat (Triticum aestivumcv. Tonic). We grew plants at 350 and 700 μmol mol−1CO2and with frequent and infrequent watering (‘wet’ and ‘dry’ treatments, respectively). Water use per plant was 1.25 times greater at 350 than at 700 μmol CO2mol−1, and 1.4 times greater in the ‘wet’ than in the ‘dry’ treatment. Root biomass increased with [CO2] and with watering frequency. Elevated [CO2] changed the vertical distribution of the roots, with a greater stimulation of root growth in the top layers of the soil. These data were confirmed by the video data of root lengths in the ‘dry’ treatment, which showed a delayed root development at depth under elevated [CO2]. The apparent amount of N mineralized appeared to be equal for all treatments. Nutrient uptake was affected by [CO2] and by watering frequency, and there were interactions between these treatments. These interactions were different for N, K and P, which appeared to be related to differences in nutrient availability and mobility in the soil. Moreover, these interactions changed with time as the root system became larger with [CO2] and with watering frequency, and as fluctuations in soil moisture contents increased. Elevated [CO2] affected nutrient uptake in contrasting ways. Potassium uptake appeared to be reduced by the smaller mass flow of water reaching the root surface. However, this might be countered with time by the greater root biomass at elevated [CO2], by the greater soil moisture contents at elevated [CO2], enabling faster diffusion, or both. Phosphorus uptake appeared to be increased by the greater root biomass at elevated [COJ. We conclude that plant nutrient uptake at elevated [CO2] is affected by interactions with water availability, though differences between nutrients preclude generalizations of the response.
Numerical integration of phytoplankton photosynthesis through time and depth in a water column
Authors: WALSBY ANTHONY E. 
Published: March 2003

SUMMARYThe daily integral of photosynthesis for a population of planktonic cyanobacteria in the Baltic Sea is calculated by numerical analysis based on the photosynthesis‐irradiance curve of the organism, the vertical distribution of the population and details of the underwater light field. Variations in the light field are calculated from continuous recordings of surface irradiance and measurements of vertical light attenuation, with corrections for losses by reflection at the water surface that depend on the sun's elevation and roughening by wind. Integrals calculated using models in which simplifying assumptions are made about the surface irradiance overestimate the calculated value by 21% on a cloudless day and by 75%, or more, on an overcast day. Even larger discrepancies (> 100%) result when the population, which is concentrated in near‐surface layers, is assumed to be evenly distributed with depth. Errors of up to 5% result from neglect of surface reflection, and up to 12% from neglect of changes in phytoplankton distribution over 24 h. Details are given of the method of numerical analysis, using standard computer spreadsheets. Versions of the spreadsheet are described in which effects of changes in the vertical distribution of the phytoplankton and light attenuation can be calculated and the effects of water temperature and photoinhibition can be modelled. The method will improve estimates of primary productivity in natural waters. It can also be used for calculating values of the euphotic depth integrated over 24 h. The spreadsheets are available on http://www.bio.bris.ac.uk/research/walsby/integral.htm.
Appressorium formation by AM fungi on isolated cell walls of carrot roots
Authors: NAGAHASHI G. , DOUDS D. D. 
Published: March 2003

SUMMARYCell walls were isolated and purified from Ri T‐DNA‐transformed carrot roots to determine whether arbuscular mycorrhizal (AM) fungi need a signal from the host root in order to form appressoria. Large cell‐wall pieces were generated by the Parr nitrogen bomb technique. Purified cell walls were sterilized and inoculated with single spores of Gigaspora gigantea (Nicol. & Gerd.) Gerdemann & Trappe and Gigaspora margarita Becker & Hall using an in vitro culture technique. Appressoria only formed on epidermal cell walls isolated from host roots (Daucus carota L.) but did not form on epidermal cell walls isolated from non‐host roots (Beta vulgaris L.). Although appressoria formed on host‐cell walls, penetration hyphae did not fully develop. The results of this study indicate that appressorium formation by these AM fungi is a contact recognition event that does not require a signal secreted from the host root or the presence of intact host cells.