bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphometric study of the regeneration of individual rays in teleost tail fins
Authors: MARÍ‐BEFFA M. , PALMQVIST P. , MARÍN‐GIRÓN F. , MONTES G. S. , BECERRA J.
Published: March 2003

The results obtained using morphometric variables which describe fin ray regeneration patterns are reported for individual fin ray amputations in the goldfish (Carassius auratus) and zebrafish (Brachydanio rerio). Classical and updated experiments are compared to verify previous morphogenetic models of cell tractions (Oster et al. 1983) or epidermis‐mesenchyme induction (Saunders et al. 1959) applied to the limb of other vertebrates. Position‐dependent patterns within the fin of Carassius auratus are analysed under a comparative protocol using morphometric methods. Conditions in which the apical epidermis is separated from blastema may differentiate small fin rays, thus suggesting this epidermis is involved in blastemal formation. Blastemal cells differentiating as lepidotrichia forming cells (LFCs) may also be related to morphological changes in covering epidermis. Long‐range interactions from neighbouring fin ray blastemas or short‐range interactions within the blastema, may be postulated through the analysis of segmentation.
Spermiogenesis and spermiation in a monotreme mammal, the platypus, Ornithorhynchus anatinus
Authors: LIN MINJIE , JONES RUSSELL C.
Published: March 2003

Spermatogenesis in the platypus (Ornithorhynchus anatinus) is of considerable biological interest as the structure of its gametes more closely resemble that of reptiles and birds than marsupial or eutherian mammals. The ultrastructure of 16 steps of spermatid development is described and provides a basis for determining the kinetics of spermatogenesis. Steps 1–3 correspond to the Golgi phase of spermatid development, steps 4–8 correspond to the cap phase, steps 9–12 are the acrosomal phase, and steps 13–16 are the maturation phase. Acrosomal development follows the reptilian model and no acrosomal granule is formed. Most other features of spermiogenesis are similar to processes in reptiles and birds. However, some are unique to mammals. For example, a thin, lateral margin of the acrosome of platypus sperm expands over the nucleus as in other mammals, and more than in reptiles and birds. Also, a tubulobulbar complex develops around the spermatid head, a feature which appears to be unique to mammals. Further, during spermiation the residual body is released from the caudal end of the nucleus of platypus sperm leaving a cytoplasmic droplet located at the proximal end of the middle piece as in marsupial and eutherian mammals. Other features of spermiogenesis in platypus appear to be unique to monotremes. For example, nuclear condensation involves the formation of a layer of chromatin granules under the nucleolemma, and development of the fibrous sheath of the principal piece starts much later in the platypus than in birds or eutherian mammals.
X‐ray microtomographic study of mineral distribution in enamel of mandibular rat incisors
Authors: WONG F. S. L. , ELLIOTT J. C. , DAVIS G. R. , ANDERSON P.
Published: March 2003

X‐ray microtomography was used to study the mineral concentrations in sequential slices of enamel of 5 mandibular incisors which showed an increase from ∼ 1.0 to ∼ 2.7 g cm−3 from the apex towards the incisal end. For points at the same distance from the apex, there were differences up to 0.6 g cm−3 between the teeth. The change of mean concentrations in the slices with distance could be modelled as (different) saturating exponentials. Under the assumption of a uniform growth rate of a mandibular incisor of 0.6 mm per day and a common time origin for the start of maturation (taken as a mineral concentration of 1 g cm−3), the distances were transformed to a common time frame to give a pooled data set. A single saturating exponential could be fitted to this pooled transformed data; this was: Cm = 2.84−1.94exp (−0.18d) where Cm is the mean mineral concentration (g cm−3) and d the time (days) from the start of maturation. This gives an asymptotic concentration of 2.84 g cm−3 towards the incisal end, with a time constant of 7.7 days. The mineral concentration distribution functions were found to be more positively skewed closer to the apex, but more negatively skewed towards the incisal end. The difference between the higher mineral concentration in the outer enamel and the enamel near the amelodentinal junction (ADJ) was ∼ 3%. The direction of maximum increase in concentration from the outer enamel surface to the ADJ meets the boundary of the ADJ at ∼ 80°. Three dimensional surface rendering of isodensity contours showed that the previously described C‐shaped pattern of mineralisation is not solely a surface phenomenon, but extends through the depth of the enamel.
To what extent are the retinal capillaries ensheathed by Müller cells? A stereological study in the tree shrew Tupaia belangeri
Authors: OCHS MATTHIAS , MAYHEW TERRY M. , KNABE WOLFGANG
Published: March 2003

The cellular ensheathment of capillaries in the 3 outer capillary layers of the central retina of the adult tree shrew Tupaia belangeri was studied quantitatively by transmission electron microscopy. Using a stereological approach, the relative surface of capillary basal lamina ensheathed by Müller cells and by nonmacroglial cells (collectively termed non‐Müller cells) was estimated in 5 animals. The participation of Müller cells was distinctly different in the 3 capillary layers studied. In the outermost capillary layer 1, the mean (standard deviation) percentage surface coverage by non‐Müller cell processes was 46.8 (15.3)%. Much less of the capillary basal lamina was ensheathed by non‐Müller cells in capillary layers 2 and 3 (3.0 (2.1)% and 0.3 (0.3)% respectively). The observed total variation of the stereological estimates for the surface fraction of Müller cells (expressed as the between‐subject coefficient of variation) was significantly higher in capillary layer 1 (28.8%) compared with capillary layers 2 (2.2%) and 3 (0.3%). In capillary layer 1, the high observed total variation was due to a high biological variation among animals for the fractions of both Müller cell and non‐Müller cell ensheathment. The rare occurrence of direct contacts between the capillary basal lamina and the perikarya of either microglial cells (capillary layer 3) or amacrine cells (capillary layer 2) corresponded well to the low stereological values obtained for the relative capillary surface ensheathed by non‐Müller cells in these capillary layers. Previously, extensive and frequent contacts between the basal lamina of capillaries belonging to capillary layer 1 and horizontal cells had been observed in single sections. The present study quantitatively demonstrates a marked paucity of macroglial investment of capillaries located in capillary layer 1 of Tupaia. It can be concluded that horizontal cells ensheath most of the capillary surface not invested by Müller cells.
Human patellar articular proportions: recent and Pleistocene patterns
Authors: TRINKAUS ERIK
Published: March 2003

The degrees of mediolateral asymmetry of the patellar articular facet, as well as the median and lateral articular angles of the facet, were compared across samples of recent humans and of Pleistocene archaic and modern fossil humans. All samples exhibit considerable variability in these patellar proportions. The articular angles are similar across the different samples, but there is a trend towards decreasing lateral angles with decreasing robusticity. The archaic humans exhibit significantly more symmetry of the medial and lateral facets than do any of the recent human samples. However, given the variability in medial versus lateral patellofemoral contact forces documented for extant humans and the roles of the distal oblique portions of vastus medialis and vastus lateralis in patellar stabilisation, it is unclear to what extent this variation in patellar articular proportions may affect knee kinesiology. The contrasts may be related to different levels of patellar stability and/or musculoskeletal hypertrophy, but they appear unlikely to have affected primary knee function.
Differential expression of proteoglycan epitopes by ovine intervertebral disc cells
Authors: MELROSE JAMES , SMITH SUSAN , GHOSH PETER
Published: March 2003

The alginate bead culture system has been utilised by several groups to examine the in vitro proteoglycan (PG) metabolism of chondrocytes and intervertebral disc cells, but the nature of the PGs produced has not been examined in detail. This is largely due to the difficulty of separating the anionically charged sodium alginate support matrix from PGs which are similarly charged. In the present study ovine annulus fibrosus, transitional zone and nucleus pulposus cells were dissociated enzymatically from their respective matrices by sequential digestion with pronase/clostridial collagenase and DNAase and then cultured in alginate beads for 10 d. The beads were solubilised and subjected to DEAE Sepharose CL6B anion exchange chromatography to separate the sodium alginate bead support matrix material quantitatively from the disc cell PGs. The alginate free bead PGs were then subjected to composite agarose polyacrylamide gel electrophoresis to resolve PG populations and the PGs were transferred to nitrocellulose membranes by semidry electroblotting. The PGs were identified by probing the blots with a panel of antibodies to defined PG core protein and glycosaminoglycan side chain epitopes. Alginate beads of disc cells were also embedded in paraffin wax and 4μm sections cut to immunolocalise decorin, biglycan, versican, and the 7‐D‐4 PG epitope within the beads. Decorin and biglycan had similar distributions in the beads, being localised on the cell surface whereas versican and the 7‐D‐4 PG epitope were immunolocalised interterritoriarly. This study is the first to demonstrate that ovine disc cells synthesise versican in alginate bead culture. Furthermore the immunoblotting studies also showed that a proportion of the 7‐D‐4 PG epitope was colocalised with versican.
The morphometric changes in the gills of the estuarine crab Chasmagnathus granulatus under hyper‐ and hyporegulation conditions are not caused by proliferation of specialised cells
Authors: GENOVESE G. , LUQUET C. M. , PAZ D. A. , ROSA G. A. , PELLERANO G. N.
Published: March 2003

Chasmagnathus granulatus is a hyper‐hyporegulating crab that inhabits changing habitats of salinity in Brazil, Uruguay and Argentina. Since the gills are the main sites for active ion transport in crabs, the adaptive changes in the gill epithelium occurring under different conditions of salinity were studied by means of morphological and morphometric analysis, and immunohistochemical identification of cell proliferation (BrdU technique). In anterior (1–3) gills the epithelium thickness from crabs acclimatised to 12, 34 and 44 g/l ranged from 1.27 to 2.46 μm, with no significant change during acclimatisation, thus denoting a respiratory function. Medial (4–5) gill epithelium was slightly thicker in extreme salinities, but these differences were not statistically significant. In contrast, epithelial thickness of the posterior (6–8) gills increased significantly up to 8.10 μm (dorsal zone of gill 8) both in hyper‐ and hyposaline media compared with seawater. The dark areas measured in gill 8 treated with AgNO3 revealed putative ion transporting tissue, especially at 12 and 44 g/l, corresponding to the zones of higher epithelial thickness. Hence these areas seem to participate both in hyper‐ and hyporegulation. Proliferating cells labelled with BrdU almost never occurred in the gills/salinity combinations studied during the initial 48 h of transfer from seawater to hyperconcentrated or diluted media, thus suggesting an increase in cell size rather than cell proliferation.
Main trajectories of nerves that traverse and surround the tympanic cavity in the rat
Authors: WEIJNEN J. A. W. M. , SURINK S. , VERSTRALEN M. J. M. , MOERKERKEN A. , DE BREE G. J. , BLEYS R. L. A. W.
Published: March 2003

To guide surgery of nerves that traverse and surround the tympanic cavity in the rat, anatomical illustrations are required that are topographically correct. In this study, maps of this area are presented, extending from the superior cervical ganglion to the otic ganglion. They were derived from observations that were made during dissections using a ventral approach. Major blood vessels, bones, transected muscles of the tongue and neck and supra and infrahyoid muscles serve as landmarks in the illustrations. The course of the mandibular, facial, glossopharyngeal, vagus, accessory and hypoglossal nerves with their branches, and components of the sympathetic system, are shown and discussed with reference to data available in the literature. Discrepancies in this literature can be clarified and new data are presented on the trajectories of several nerves. The course of the tympanic nerve was established. This nerve originates from the glossopharyngeal nerve, enters the tympanic cavity, crosses the promontory, passes the tensor tympani muscle dorsally, and continues its route intracranially to the otic ganglion as the lesser petrosal nerve after intersecting with the greater petrosal nerve. Auricular branches of the glossopharyngeal and of the vagus nerve were noted. We also observed a pterygopalatine branch of the internal carotid nerve, that penetrates the tympanic cavity and courses across the promontory.
Patterns of age‐dependent changes in the numbers of lymph follicles and germinal centres in somatic and mesenteric lymph nodes in growing C57Bl/6 mice
Authors: HOSHI HAJIME , HORIE KAEKO , TANAKA KIYOSHI , NAGATA HIDETUGU , AIZAWA SIN , HIRAMOTO MASAKI , RYOUKE TOSHIO , AIJIMA HIROSHI
Published: March 2003

The timing of the first appearance of lymph follicles and germinal centres in various lymph nodes, and the ways in which numbers of these and IgM‐synthesising cells increase within the nodes, were investigated in male and female C57Bl/6N mice aged from 4 d to 16 wk. The lymphoid organs examined were the Peyer's patches, spleen, somatic (submandibular, deep cervical, brachial, axillary, inguinal and popliteal) and visceral (mesenteric and lumbar) lymph nodes. Primary follicles appeared in most somatic lymph nodes 6 d after birth. The number of follicles per node then increased rather sharply in larger lymph nodes and slowly in smaller nodes, up to 28 d of age, reaching a level which varied according to the location of the node. Thereafter, the number of follicles in the somatic lymph nodes increased only slightly to moderately, reaching a peak or plateau at 8–12 wk. In the mesenteric (ileocaecal) nodes, primary follicles first appeared at 12 d, then increased linearly during the suckling period and after weaning to reach a plateau at 8 wk of age. Germinal centres appeared in the submandibular and mesenteric nodes at 28 d and their numbers increased consistently in the latter, while remaining low in the former. The impact of possible ‘natural’ exogenous antigen stimulation of the various lymph nodes was estimated from the presence of IgM‐synthesising cells and germinal centres. Differences between the patterns of age‐dependent changes in the numbers of lymph follicles observed in the somatic and mesenteric lymph nodes during their ontogeny are discussed in relation to differences in the magnitude of the exogenous antigen stimulatory effect. We also found that the variations in the numbers of lymph follicles produced in somatic lymph nodes at different locations during the first 28 d after birth reflected differences in the dimensions of the body regions drained by a particular somatic lymph node at this stage of development.
Fine structure of the developing epidermis in the embryo of the American alligator (Alligator mississippiensis, Crocodilia, Reptilia)
Authors: ALIBARDI LORENZO , THOMPSON MICHAEL B.
Published: March 2003

The morphological transition from the simple epidermis that contacts the amniotic fluid of embryonic crocodilians to the adult epidermis required in a terrestrial environment has never been described. We used light and electron microscopy to study the development, differentiation and keratinisation of the epidermis of the American alligator, Alligator mississippiensis, between early and late stages of embryonic skin formation. In early embryonic development, the epidermis consists of a flat bilayer. As it develops, the bilayered epidermis comes to lie beneath the peridermis. Glycogen is almost absent from the bilayered epidermis but increases in basal and suprabasal cells when scales form. Glycogen disappears from suprabasal cells that accumulate keratin. The peridermis and 1 or 2 subperidermal layers form an embryonic epidermis that is partially or totally lost before hatching. These cells accumulate coarse filaments and form reticulate bodies. Mucous and lamellate granules are produced in the Golgi apparatus and are partly secreted extracellularly. The embryonic cells darken with the formation of larger reticulate bodies that aggregate with intermediate filaments and other cell organelles, as their nuclear chromatin condenses. Thin β‐cells resembling those of scutate scales of birds develop beneath the embryonic epidermis and form a stratified β‐layer that varies in thickness in different body regions. The epidermis differentiates first in the back, tail and belly. At the beginning of β‐cell differentiation, the cytoplasm contains sparse bundles of α‐keratin filaments, glycogen and lipid droplets or vacuoles apparently derived from the endoplasmic reticulum and Golgi apparatus. These organelles disappear rapidly as irregular bundles of electron‐dense β‐keratin filaments accumulate and form larger bundles. The larger bundles consist of 3 nm thick electron‐pale keratin microfibrils and are derived from the assemblage of β‐keratin molecules produced by ribosomes. While in mammals the epidermal barrier is formed by α‐keratinocytes, in the alligator the barrier is formed by β‐keratin cells. The β‐layer is reduced or absent from the small hinge region between scales. In the latter areas the barrier is made of a or a mixture of α/β keratinocytes. Thus alligators resemble birds where the β‐keratin molecules are deposited directly over an α‐keratin scaffold, rather than an initial production of β‐keratin packets which then merge with α‐keratin, as occurs in the Chelonia and Lepidosauria. The pigmentation of the epidermis of embryos is mostly derived from epidermal melanocytes.
The course of the buccal nerve: relationships with the temporalis muscle during the prenatal period
Authors: MÉRIDA‐VELASCO J. R. , RODRÍGUEZ‐VÁZQUEZ J. F. , DE LA CUADRA C. , MÉRIDA‐VELASCO J. A. , JIMÉNEZ‐COLLADO J.
Published: March 2003

The aim of this study was to describe the course of the buccal nerve and its relationships with the temporalis muscle during the prenatal period. Serial sections of 90 human fetal specimens ranging from 9 to 17 wk development were studied by light microscopy. Each fetal specimen was studied on both right and left sides, making a total of 180 cases for study. A 3‐D reconstruction of the region analysed in one of the specimens was made. In 89 cases the buccal nerve was located medial to the temporalis muscle; in 73 cases it penetrated the muscle; in 15 cases it lay in a canal formed by the muscle fibres and was covered by fascia, and finally, in 3 cases it was a branch of the inferior alveolar nerve. The study has revealed that in a large number of cases the buccal nerve maintains an intimate association with the temporalis muscle.
Frequency variations of discrete cranial traits in major human populations. II. Hypostotic variations
Authors: HANIHARA TSUNEHIKO , ISHIDA HAJIME
Published: March 2003

Five discrete hypostotic cranial traits, tympanic dehiscence, ovale‐spinosum confluence, metopism, transverse zygomatic suture vestige, and biasterionic suture, were investigated in 81 human population samples. Except for ovale‐spinosum confluence, marked asymmetric occurrences of the bilateral traits were not detected in the majority of the samples. Significant intertrait association was observed mainly between the biasterionic suture and other sutural variations including accessory ossicles. The traits showing relatively consistent sex differences across diverse populations were tympanic dehiscence, which is predominant in females, and biasterionic suture in males. On a world scale, the 5 hypostotic cranial traits showed distinctive patterns of geographical variation. Different clinal variations within and between macrogeographical areas such as western and eastern parts of the Old World were found for the frequencies of the traits. The Ainu may be the most distinct outlier in the eastern Asian region on the basis of the incidence of the traits, especially the transverse zygomatic suture vestige. The interregional variation without reasonable adaptive value and nonadaptive shift of the possible outliers presented in this study suggest that the genetic background for the occurrence of these traits cannot be excluded completely.
The evolution of the pectoral girdle
Authors: McGONNELL IMELDA M.
Published: March 2003

abstract

The pectoral girdle articulates the forelimb with the axial skeleton in all vertebrates with paired anterior appendages. The structure of the pectoral girdle and its position along the axial skeleton has changed significantly during vertebrate evolution. These morphological changes have been well described, but there is little comparative embryology to indicate how these changes may have occurred. It is equally obscure how the muscles that connect the head with the pectoral girdle have maintained appropriate attachments even though these 2 structures have become separated. Here I review the changes in the pectoral girdle across different vertebrate taxa, indicating, where known, the developmental mechanisms underlying these changes. I also suggest how the muscular connections between the head and pectoral girdle have been maintained between these once adjacent bones, displaced during vertebrate evolution.
Derivation and spontaneous differentiation of human embryonic stem cells*
Authors: Amit Michal , Itskovitz‐Eldor Joseph
Published: March 2003

Embryonic stem (ES) cells are unique cells derived from the inner cell mass of the mammalian blastocyst. These cells are immortal and pluripotent, retain their developmental potential after prolonged culture, and can be continuously cultured in an undifferentiated state. Many in vitro differentiation systems have been developed for mouse ES cells, including reproducible methods for mouse ES cell differentiation into haematopoietic and neural precursors, cardiomyocytes, insulin‐secreting cells, endothelial cells and various other cell types. The derivation of new human ES cell lines provides the opportunity to develop unique models for developmental research and for cell therapies. In this review we consider the derivation and spontaneous differentiation of human ES cells.
Calcium‐sensing receptors and parathyroid hormone‐related protein in the caudal neurosecretory system of the flounder (Platichthys flesus)
Authors: Ingleton P. M. , Bendell L. A. , Flanagan J. A. , Teitsma C. , Balment R. J.
Published: March 2003

The caudal neurosecretory system of the flounder (Platichthys flesus) has been examined by immunocytochemistry and in situ hybridization for the expression of parathyroid hormone‐related protein (PTHrP) and calcium‐sensing receptors (CaSR). The N‐terminus nucleotide and deduced amino acid sequences of flounder PTHrP were determined and used to prepare oligonucleotide probes and homologous antiserum. The Dahlgren cells of the posterior spinal cord and their axons contained PTHrP protein which was also detected around the capillaries of the urophysis. PTHrP gene expression was abundant in the Dahlgren perikarya and axons in the spinal cord, but it was absent from nerve endings in the urophysis. Calcium‐sensing receptor protein was present in the Dahlgren perikarya and axons, also with abundant gene expression, but there was neither protein nor mRNA in the urophysis. There were no apparent differences between freshwater‐ and seawater‐adapted fish in either CaSR or PTHrP expression in the caudal neurosecretory system. These observations suggest that Dahlgren cells produce PTHrP which may be released from axons abutting capillaries in the urophysis. However, the sensing of ionic calcium appears to be confined to the perikarya of the Dahlgren cells in the spinal cord neuropil, suggesting that they are responsive to calcium in the central nervous system rather than the general circulation.
Blood–brain barrier breakdown in septic encephalopathy and brain tumours*
Authors: Davies D. C.
Published: March 2003

Septic encephalopathy is associated with breakdown of the blood–brain barrier and cerebral oedema. These features are also common properties of brain tumours. Perimicrovessel oedema, disruption of associated astrocyte end feet and neuronal injury occur in a porcine model of acute septic encephalopathy. The adrenergic system has been implicated in the inflammatory response to sepsis and may play a role in controlling blood–brain barrier permeability, since the β2‐adrenoceptor agonist dopexamine inhibits perimicrovessel oedema formation whereas the α1‐adrenoceptor agonist methoxamine provokes it. Electron microscopy revealed tight junction opening in high‐grade astrocytoma microvessels. Expression of the tight junction protein occludin is reduced in these microvessels and this reduction is inversely correlated with the degree of cerebral oedema. Normal astrocytes secrete factors that induce barrier properties in endothelial cells, whereas high‐grade astrocytomas secrete vascular endothelial growth factor, which stimulates angiogenesis, down regulates occludin and increases endothelial cell permeability. The water channel protein aquaporin‐4 is normally expressed in astrocyte foot processes around cerebral microvessels. Its expression is massively up‐regulated in high‐grade astrocytoma and around metastatic adenocarcinoma. There is a significant correlation between aquaporin‐4 expression and the degree of cerebral oedema, but it is not clear whether increased aquaporin‐4 expression enhances oedema formation or clearance. These results suggest that the pathophysiology of brain oedema is multifactorial, but that there may be common processes operating regardless of the aetiology.
An anatomical and electrophysiological study of the genitofemoral nerve and some of its targets in the male rat
Authors: Zempoalteca René , Martínez‐Gómez Margarita , Hudson Robyn , Cruz Yolanda , Lucio Rosa Angélica
Published: March 2003

Anatomical descriptions of the genitofemoral nerve (GFn) innervating the lower pelvic area are contradictory. Here we re‐examine its origin and innervation by its various branches of principal target organs in the male rat. Using gross dissection, electrophysiological techniques and retrograde tracing of motoneurones with horseradish peroxidase, we confirm that the GFn originates from lumbar spinal nerves 1 and 2, and that at the level of the common iliac artery it divides into a lateral femoral and a medial genital branch. In contrast to previous studies, we report that the genital and not the femoral branch innervates the abdominal–inguinal skin, and not only the genital but also the femoral branch innervates the cremaster muscle (Cm) surrounding the testes. Motoneurones innervating the Cm proper are located in the ventral nucleus of L1 and L2, and those innervating the muscular transition region of the rostral Cm are located in the ventral nucleus in L1 and the ventrolateral nucleus in L2. The GFn may contribute to male reproductive performance by transmitting cutaneous information during copulation and, via contraction of the Cm to promote ejaculation, the protective displacement of the testes into the abdominal cavity during fighting and as a sperm‐protecting thermoregulatory measure.
Characteristics of a caesium‐resistant (Cs+‐R) mutant of the N2‐fixing cyanobacterium Nostoc muscorum: dependence on Cs+ or Rb+ for normal diazotrophy and osmotolerance
Authors: SINGH S. , SINGH A. K. , CHAKRAVARTHY D. , SINGH T. P. K. , SINGH H. N.
Published: March 2003

Spontaneous mutation of the cyanobacterium Nostoc muscorum to a caesium resistant (Cs+‐R) phenotype resulted in severe impairment of its nitrogenase activity, oxygenic photosynthesis, chlorophyll a content and osmotolerance. Among alkali cations only Cs+ or Rb+ restored these physiological processes to an almost normal level. Parent and mutant were similar with respect to Cs+ or Rb+ uptake and accumulation and also to regulation by NH4+. The ions Na+ or K+, at much higher concentration, significantly influenced Cs+ uptake and accumulation in both the mutant and the parent. These findings have important implications for cyanobacteria growing in Cs+‐polluted habitats.
Xylem sap abscisic acid concentration and stomatal conductance of mycorrhizal Vigna unguiculata in drying soil
Authors: EBEL ROBERT C. , DUAN XIANGRONG , STILL DAVID W. , AUGE ROBERT M.
Published: March 2003

This study was conducted to determine whether xylem abscisic acid (ABA) concentration is altered by mycorrhizal symbiosis of cowpea plants grown in drying soil, and to determine whether stomatal sensitivity to xylem ABA is altered by the symbiosis. We allowed the entire root zone to dry and found that at high soil water contents (θ), mycorrhizal plants had higher stomatal conductance (gs) and lower xylem [ABA]than did non‐mycorrhizal plants, but the difference disappeared at low tH, probably because of stomatal closure. The altered gs and xylem [ABA] were apparently not related to plant water status since shoot water potential, xylem sap osmotic potential and shoot water content were similar for mycorrhizal and non‐mycorrhizal plants across the range of soil moisture. These differences were also not related to P nutrition or plant size. The relationship of gs to xylem [ABA] was not affected by the symbiosis, indicating that either stomatal sensitivity to xylem ABA was not affected by other xylem constituents, or that more than one xylem constituent was altered by the symbiosis but was offsetting in its effect on gs. We conclude that the symbiosis altered gs non–hydraulically, and that the factor might be xylem ABA.
Effects of long‐term atmospheric CO2 enrichment on the mineral concentration of Citrus aurantium leaves
Authors: PEÑUELAS JOSEP , IDSO SHERWOOD B. , RIBAS ANGELA , KIMBALL BRUCE A.
Published: March 2003

summary

Leaf mineral concentration of Citrus aurantium (sour orange tree) was measured at bi‐monthly intervals from 30 to 85 months of exposure in a long‐term study on the effects of a 300 μmol mol−1 enrichment of atmospheric CO2, under conditions of high nutrient and water supply. There were clear seasonal trends in the concentrations of most of the elements studied. There were initial decreases in the leaf concentrations of N and the xylem‐mobile, phloem‐immobile elements Mn, Ca and Mg, as well as a significant and sustained increase in the leaf concentration of B, and no changes in the concentrations of K, Fe, Na, P, S, Zn and Cu. Interestingly, the initial reductions in the leaf concentrations of Mn, N, Ca and Mg gradually disappeared with time.
Infection of mottled stripe disease‐susceptible and resistant sugar cane varieties by the endophytic diazotroph Herbaspirilium
Authors: OLIVARES F. L. , JAMES E. K. , BALDANI J. I. , DÖBEREINER J.
Published: March 2003

Leaves of a mottled stripe disease‐susceptible cultivar (B‐4362) and of a mottled stripe disease‐resistant cultivar (SP 70–1143) of sugar cane (interspecific hybrids of Saccharum) were inoculated with the diazotrophic endophytes, Herbaspirillum rubrisubalbicans or Herbaspirillum seropedicae, via injection into the apex of the stem. At 7 and 20 d.a.i., H. seropedicae could be isolated only from a small necrotic area around the point of inoculation, where there was considerable degradation of host cells, and was not detected in any other part of the leaves. This suggested a hypersensitive response by the host to this bacterium, and no disease symptoms formed on either cultivar. By contrast, H. rubrisubalbicans could be re‐isolated from throughout the infected leaves of both cultivars at both harvests and produced widespread disease symptoms on the leaves of cv. B‐4362.

Symptoms consisted of necrotic regions near the point of inoculation, and red stripes and red patches along the vertical axis of the leaves, where the bacteria had spread in the primary and secondary veins. The xylem–conducting elements in diseased regions of leaves were filled with bacteria and, at the edges of disease symptoms, the vessels were filled with a gum which stained blue‐green with toluidine blue. This material probably contained phenolic compounds, and was produced as a host defence response. Leaves of cv. SP 70–1143 only developed small red stripes near the point of inoculation. These symptoms did not spread along the leaves, and the infected xylem vessels were never seen to be completely full of bacteria. Instead, the vessels contained encapsulated bacterial colonies attached to secondary wall deposition; these colonies were surrounded by blue‐green material that might have been host‐defence gums. In cv. B‐4362, bacteria were abundant in the intercellular spaces of mesophyll adjacent to infected xylem, and also filled sub–stomatal cavities. Immunogold labelling using polyclonal antisera raised against H. rubrisubalbicans gave a weak signal with the bacteria in cv. SP 70–1143, showing that few binding sites were available to the antibodies. By contrast, bacteria in cv. B‐4362 reacted strongly with the antibody, suggesting that they had a denser coating of immunoreactive mucus. In the later stages of infection of cv. B–4362, lysed bacteria were seen within degraded plant cells surrounded by a matrix of plant gums and bacterial mucus. This matrix reacted strongly to the H. rubrisubalbicans antibodies. Immunogold labelling using antibodies against nitrogenase component II showed that nitrogenase was expressed by bacteria in the early stages of infection of cv. B–362, but not in later stages, or by bacteria infecting cv. SP 70–1143.
Influence of cucumber mosaic virus infection on the competitive ability and reproduction of chickweed (Stellaria media)
Authors: FRIESS N. , MAILLET J.
Published: March 2003

Chickweed plants (Stellaria media Vill.), either inoculated with cucumber mosaic virus (CMV) or not, were grown to reproductive maturity at a range of densities, both in monoculture and in mixture. CMV infection did not influence the vegetative growth of plants grown in monoculture. Similarly, the total vegetative production of a population containing infected and healthy plants was the same as that of a monoculture of healthy plants. However, infected plants were disadvantaged when in competition with healthy plants, the disadvantage increasing with density and the proportion of healthy plants. Investment in sexual reproduction was reduced in infected plants at all densities and in healthy plants at high densities. In very hard conditions, plants did not even produce seeds.
Effects of soil trenching on occurrence of ectomycorrhizas on Pseudotsuga menziesii seedlings grown in mature forests of Betula papyrifera and Pseudotsuga menziesii
Authors: SIMARD SUZANNE W. , PERRY DAVID A. , SMITH JANE E. , MOLINA RANDY
Published: March 2003

Seedlings of Pseudotsuga menziesii (Mirb.) Franco were grown for six‐16 months in untrenched and trenched treatments in three 90–120‐yr‐old mixed forests dominated by Betula papyrifera Marsh, and P. menziesii in the southern interior of British Columbia. Each forest was characterized by mesic conditions and low light intensity (PAR < 200 μmol m−2 s−1) in the understorey. The objective of the study was to evaluate the influence of overstorey tree roots on (i) ectomycorrhizal fungal composition, richness and diversity, and (ii) photosynthesis and growth of understorey P. menziesii seedlings. Seventeen ectomycorrhizal morphotypes were recognized on seedlings in the untrenched treatment, and nine in the trenched treatment over the three sites. Six types occurred in both treatments, of which on average Rhizopogon vinicolor Smith type was 20 times more abundant and Thelephora type six times less abundant in the untrenched as in the trenched treatment. Of types that formed strands or rhizomorphs, eight occurred in the untrenched treatment, where they occupied on average 23% of root tips, and only four occurred in the trenched treatment over 4% of the root tips. Mean richness, diversity, and evenness of ectomycorrhizal associates per seedling were approx. twice as great in the untrenched as in the trenched treatment.

Net photosynthetic rate of P. menziesii seedlings was greater in the untrenched than in the trenched treatment in July and August, but not in September 1994. Height, diameter and biomass of seedlings did not differ between treatments, but height: diameter ratio was greater in the untrenched treatment at time of harvest. The effect of trenching on seedling performance was attributed mainly to differences in ectomycorrhizal colonization patterns because trenching had no significant effect on soil nutrient concentrations (total C, total N, NH4‐N, available N, exchangeable Ca, exchangeable Mg, exchangeable K), C:N ratio, soil pH or light availability. Nor was there a significant difference in soil water in August, when seedlings in untrenched plots had higher net photosynthetic rates than those in trenched plots. Results suggest that influence of overstorey trees and pattern of ectomycorrhizal formation are important to P. menziesii seedling performance in deeply shaded forest environments.
Responses of Lotus corniculatus to environmental change
Authors: CARTER E. B. , THEODOROU M. K. , MORRIS P.
Published: March 2003

Five clonal plants of three genotypes of Lotus corniculatus were grown in each of eight controlled environments under combinations of two temperature regimes (18/10 °C and 25/15 °C), two CO2 concentrations (ambient and 700 ppmv) and two water applications (ad libitum or 60% draughted). Plants were harvested at full flower and measurements made of plant growth and development. Of the three environmental variables studied, higher growth temperatures resulted in the largest number of significant changes to the measured variables. Reproductive capacity, growth rate, shoot biomass, water use efficiency and chlorophyll content were all enhanced by raising the growth temperature from 18 to 25 °C. Doubling the CO2 concentration enhanced the growth rate, shoot biomass and water use efficiency and ameliorated some of the effects of drought, including reproductive capacity, and biomass production, but reduced flowering time, specific leaf area, and chlorophyll content of both droughted and undroughted plants. Drought alone reduced reproductive capacity, growth rate and above ground biomass but significantly increased root biomass in all environments. The agronomic effects resulting from a combined increase in growth temperature, doubled CO2 concentration and mild drought in this experiment were a shorter vegetative period and an increase in biomass, but a fall in reproductive capacity.
Effects of elevated CO2 and soil–nitrogen supply on chlorophyll fluorescence and gas exchange in Scots pine, based on a branch–in–bag experiment
Authors: WANG KAI‐YUN , KELLOMÄKI SEPPO
Published: March 2003

Applying the branch‐in‐bag method, naturally seeded Scots pine (Finns sylvestris L.) trees, 25–30 yr old, were subjected to two CO, concentrations (350 and 700/tmol mol') and two soil‐nitrogen‐supply regimes for three growing seasons (1994–96). Gas exchange and chlorophyll a fluorescence in detached shoots were measured simultaneously in a diffuse radiation field. Elevated CO, did not lead to a significant ‘downward regulation’ in the light‐saturated rate of net photosynthesis (Pn,max), the maximum apparent quantum yield (aA,max) or the maximum photochemical efficiency (Fv/Fm) of photosyscem II (PS II). However, the elevated CO2 significantly decreased the light‐saturated stoniatal conductance and increased the sensitivity of stoniatal conductance to change in low photon‐flux densities. The high soil‐nitrogen supply significantly increased photosvnthetic capacity, as manifested by increases in Pn,mBS, £tAjMBlFJFm, and the effective photochemical efficiency (dLF/F'm) at low photon‐flux densities, did not, on the other hand, enhance the magnitude of photosynthetic response to elevated CO2concentration. In addition, the treatment‐induced modifications in fluorescence parameters are discussed in detail.
The biology of mycorrhiza in the Ericaceae
Authors: KERLEY SIMON J. , READ DAVID J.
Published: March 2003

Measurements of the chitin content of the rooting horizons of a typical mor‐humus heathland soil, indicate that chitin can contain in excess of 20% of the total nitrogen in the litter (L) horizon and 30% in the fermentation (F) horizon. Much of this chitin‐nitrogen is thought to be contained in the mycelial walls of soil fungi.

Experiments were therefore designed to test the hypothesis that such sources of N could be rendered accessible to the ericaceous plants by their fungal endophytes. Mycelium of the ericoid endophyte Hymenoscyphus ericae (Read) Korf & Kernan and of the ectomycorrhizal fungus Suillus bovinus (Fr.) O. Krantze were grown in liquid culture before being killed and added either in the intact condition, or after fractionation, as sole sources of N to sterile media upon which were grown H. ericae in pure culture, or mycorrhizal and non‐mycorrhizal plants of Vaccinium macrocarpon Ait. and Calluna vulgaris L. The abilities of the test organisms to utilize the nitrogen contained in the intact mycelial necromass, or in its fractions, were assessed by determining their yields and nitrogen concentrations of their tissues.

It was revealed that H. ericae was able to produce significantly higher yield when grown on intact fungal necromass than when provided with equivalent concentrations of N in the form of ammonium. Its yields on mycelial fractions were lower, but still significantly greater than those obtained in the controls lacking N. Significantly greater yields and N contents were also found in the ericaceous plants grown with these nitrogenous substrates in the mycorrhizal condition. Without H. ericae they had no access to the substrates. The possible ecological implications of these results are discussed.
Plant growth and reproduction on a toxic alpine ultramafic soil: adaptation to nutrient limitation
Authors: NAGY LASZLO , PROCTOR JOHN
Published: March 2003

summary

The ultramafic sites at Meikle Kilrannoch, Scotland, have small sparsely colonized patches with soils which have highly toxic (to many non‐indigenous plants) concentrations of Mg and Ni. These toxic metals are unlikely to be the main cause of the open vegetation as the indigenous plants are at least partially tolerant of them. The hypothesis that low. soil nutrients were a likely cause of the open vegetation was tested by a fertilization experiment in which major nutrients and Ca were added in August 1991 and July 1992 to replicated quadrats which initially had 5.3‐6.6% plant cover. There was a large increase in plant cover on major nutrient addition. The increase in rosette size, flowering, seed production, and recruitment of the dominant semelparous Cochlearia pyrenaica DC. ssp. alpina (Bab.) Dalby was studied in detail. The increased growth of Cochlearia (and some other native species at the site) on nutrient addition strengthens the argument that a major nutrient deficiency rather than a metal toxicity limits plant growth at Meikle Kilrannoch and shows that at least some stress tolerators respond with rapid growth and reproduction when nutrient limitation is removed. A small‐scale experiment set up in June 1993, in which the major nutrients were added separately, suggested that P and not N, or K was the limiting element. The effects of P seem to be unrelated to any possible reduction in the availability of the toxic ions Mg2+and Ni2+.
Enhanced ozone‐tolerance in wheat grown at an elevated CO2 concentration: ozone exclusion and detoxification
Authors: MCKEE I. F. , EIBLMEIER M. , POLLE A.
Published: March 2003

summary

Elevated [CO2] has been shown to protect photosynthesis and growth of wheat against moderately elevated [O3]. To investigate the role of ozone exclusion and detoxification in this protection, spring wheat (Triticum aestivum L. ev. Wembley) was grown from seed, in controlled‐environment chambers, under reciprocal combinations of [CO2] at 350 or 700 μmol mol−1and [O3] peaking at < 5 or 60 nmol mol−1, respectively. Cumulative ozone dose to the mesophyll and antioxidant status were determined throughout flag leaf development. Catalase activity correlated with rates of photorespiration and declined in response to elevated [CO2] and/or [O3]. Superoxide dismutase activity was not significantly affected by either condition. Neither ascorbate nor glutathione content was enhanced by elevated [CO2]. In wheat, at moderately elevated [O3], our results show that stomatal exclusion plays a major role in the protective effect of elevated [CO2] against O3 damage.
Biology of the ectomycorrhizal genus, Rhizopogon
Authors: MOLINA RANDY , SMITH JANE E. , MCKAY DONARAYE , MELVILLE L.H.
Published: March 2003

summary

Seedlings of Pseudotsuga menziesii (Mirb.) Franco, Pinus ponderosa Dougl. ex Laws, Arbutus menziesii Pursh., and cuttings of Arclast apliylos uva‐ursi (L.) Spreng were grown in monoculture and in conifer‐hardwood dual‐culture combinations in the glasshouse and inoculated with spore slurries of six Rhizopogon species. The primary objectives were to assess and compare the pattern of host specificity between symbionts and to study the influence of co‐cultured plants on ecromycorrhiza development. The Rhizopogon spp. ranged from genus‐specific to multiple‐host compatible. In monoculture, four Rhisopogon sp, (R. ellenae Smith, R. occidentalis Zeller & Dodge, R. smithii Hosfnrd and R. subcaerulescens Smith) formed ectomycorrhizas with Pinus ponderosa, and two Rhizopogon sp. (R. parksii Smith and R. vinicolor Smith) formed ectomycorrhizas with Pseudotsuga menziesii. None of the fungi tested developed ectomycorrhizas on Arbutus menziesii or Arctostaphylos uvaursi in monoculture. In dual culture, three of the four Rhizopogon species (R. ellenae, R. occidentalis and R. subcaerulescens) that formed ectomycorrhizas on Pinus ponderosa, formed some ectomycorrhizas on Arbutus menziesii and Arrtastaphvlos uva‐ursi. Rhizopogon parksii and R. tinicoior only formed ectomycorrhizas on Pseudotsuga mensiesti.
Laser ablation of the cell wall and localized patch clamping of the plasma membrane in the filamentous fungus Aspergillus: characterization of an anion‐selective efflux channel
Authors: ROBERTS STEPHEN K. , DIXON GRAHAM K. , DUNBAR STUART J. , SANDERS DALE
Published: March 2003

summary

We have used a pulsed u.v. laser to ablate the cell wall of the filamentous fungus Aspergillus niger van Tiegh., and expose the plasma membrane at defined points along the hypha. Using the patch clamp technique, giga ohm seals (up to 20 GΩ) and recordings of plasma membrane ion channels were obtained. We describe, for the first time in fungi, a 43 pS plasma membrane anion efflux channel. Its potential role in cell signalling and pH homeostasis is discussed.