bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural abnormalities do not explain the early functional abnormalities in the peripheral nerves of the streptozotocin diabetic rat
Authors: WALKER DAVID , CARRINGTON ANNE , CANNAN SUSAN A. , SAWICKI DIANE , SREDY JANET , BOULTON ANDREW J. M. , MALIK RAYAZ A.
Published: March 2003

The streptozotocin (STZ)‐diabetic rat, the most commonly employed model of experimental diabetic neuropathy, is characterised by a reduction in nerve conduction velocity, pain threshold and blood flow. Whether or not structural abnormalities underlie these functional abnormalities is unclear. 10 adult male Sprague–Dawley STZ‐diabetic rats (diabetes duration 27 d) and 10 age‐matched (23 wk) control animals were studied. Motor nerve conduction velocity (m s−1) was significantly reduced in diabetic (41.31±0.8) compared with control (46.15±1.5) animals (P<0.001). The concentration of sciatic nerve glucose (P<0.001), fructose (P<0.001) and sorbitol (P<0.001) was elevated, and myoinositol (P<0.001) was reduced in diabetic compared with control animals. Detailed morphometric studies demonstrated no significant difference in fascicular area, myelinated fibre density, fibre and axon areas as well as unmyelinated fibre density and diameter. Endoneurial capillary density, basement membrane area and endothelial cell profile number did not differ between diabetic and control animals. However, luminal area (P<0.03) was increased and endothelial cell area (P<0.08) was decreased in the diabetic rats. We conclude there is no detectable structural basis for the reduction in nerve conduction velocity, pain threshold or blood flow, observed in the streptozotocin diabetic rat.
Application of the fractionator and vertical slices to estimate total capillary length in skeletal muscle
Authors: ARTACHO‐PÉRULA EMILIO , ROLDÁN‐VILLALOBOS RAFAEL , CRUZ‐ORIVE LUIS M.
Published: March 2003

A new stereological method is proposed which combines vertical slice projections with the fractionator to estimate the total capillary length in a skeletal muscle. The method was demonstrated on the soleus muscle of a Wistar rat. The implementation required capillary highlighting, tissue sampling, and data acquisition in the form of intersection counts between capillary projections and cycloid test lines. The capillaries were demonstrated using vascular perfusion (with gelatine) of the hind leg of the rat. The sampling procedure followed the fractionator design, namely a multistage systematic sampling design with a known sampling fraction at each stage. To make the design unbiased, vertical slices were used; for efficiency, the vertical axis was chosen parallel to the main axis of the muscle. As prescribed to avoid bias, the cycloid test lines were superimposed on the slice projections, viewed under the light microscope, with their minor axes normal to the vertical axis. The estimation precision was compared for different sampling and subsampling fractions. The proposed method was globally highly efficient, unbiased, and easy to implement.
Immunohistochemical localisation of amelogenin‐like proteins and type I collagen and histochemical demonstration of sulphated glycoconjugates in developing enameloid and enamel matrices of the larval urodele (Triturus pyrrhogaster) teeth
Authors: KOGAYA YASUTOKU
Published: March 2003

The presence of collagen in enameloid distinguishes it clearly from true enamel, but little is known about the phylogenetic relationship between these 2 tissues. It has previously been reported that amelogenins are the principal proteins of the enamel matrix, that type I collagen and chondroitin sulphates are the predominant matrices in dentine, and that amphibian and reptilian aprismatic enamels contain no sulphated glycoconjugates, although certain sulphated substances are secreted into mammalian prismatic enamel during matrix formation. The larval urodele (Triturus pyrrhogaster) teeth are known to be composed of enameloid, dentine, and enamel‐like tissue. To characterise the tooth matrices, the localisation of amelogenin‐like proteins, type I collagen, and sulphated glycoconjugates was investigated. Chondroitin sulphates and fine fibrils immunoreactive for type I collagen were elaborated as the enameloid matrix inside the dental basement membrane. After the matrix had been deposited in full thickness, coarse collagen fibrils also immunoreactive for type I collagen and chondroitin sulphates were deposited below as the first dentine matrix. Further, enamel‐like matrix with no collagen fibrils or sulphated glycoconjugates but strongly immunoreactive for amelogenins was deposited on the dentine. Although no immunolabelling for amelogenins was found over the enameloid matrix, at least at the formation stage, the zone of coarse collagen fibrils of dentine was partially immunoreactive as observed in mammalian mantle dentine. From the ontogeny and matrix constituents of larval urodele teeth, it is suggested that enameloid is originally a dentine‐like tissue.
Supra and infralevator neurovascular pathways to the penile corpora cavernosa
Authors: BENOIT G. , DROUPY S. , QUILLARD J. , PARADIS V. , GIULIANO F.
Published: March 2003

The aim of this study was to provide a comprehensive description of both penile innervation and vascularisation. Eighty‐five male cadavers were examined through gross and microscopic anatomical analysis. The pelvic nerve plexus had both parasympathetic and sympathetic roots. It was distributed to the external urethral sphincter giving rise to cavernous nerves which anastomosed in 70% of the cases with the pudendal nerve in the penile root. Accessory pudendal arteries were present in the pelvis in 70% of the cases, anastomosing in 70% of the cases with the cavernous arteries that originated from the pudendal arteries. Transalbugineal anastomoses were always seen between the cavernous artery and the spongiosal arterial network. There were 2 venous pathways, 1 in the pelvis and 1 in the perineum with a common origin from the deep dorsal penile vein. It is concluded that there are 2 neurovascular pathways destined for the penis that are topographically distinct. One is located in the pelvis and the other in the perineum. We were unable to determine the functional balance between these 2 anastomosing pathways but experimental data have shown that they are both involved in penile erection. These 2 neurovascular pathways, above and below the levator ani, together with their anastomoses, form a neurovascular loop around the levator ani.
Exposure of rats to a high but not low dose of ethanol during early postnatal life increases the rate of loss of optic nerve axons and decreases the rate of myelination
Authors: HARRIS SIMON J. , WILCE PETER , BEDI KULDIP S.
Published: March 2003

Visual system abnormalities are commonly encountered in the fetal alcohol syndrome although the level of exposure at which they become manifest is uncertain. In this study we have examined the effects of either low (ETLD) or high dose (ETHD) ethanol, given between postnatal days 4–9, on the axons of the rat optic nerve. Rats were exposed to ethanol vapour in a special chamber for a period of 3 h per day during the treatment period. The blood alcohol concentration in the ETLD animals averaged ∼ 171 mg/dl and in the ETHD animals ∼ 430 mg/dl at the end of the treatment on any given day. Groups of 10 and 30‐d‐old mother‐reared control (MRC), separation control (SC), ETLD and ETHD rats were anaesthetised with an intraperitoneal injection of ketamine and xylazine, and killed by intracardiac perfusion with phosphate‐buffered glutaraldehyde. In the 10‐d‐old rat optic nerves there was a total of ∼ 145000–165000 axons in MRC, SC and ETLD animals. About 4% of these fibres were myelinated. The differences between these groups were not statistically significant. However, the 10‐d‐old ETHD animals had only about 75000 optic nerve axons (P < 0.05) of which about 2.8% were myelinated. By 30 d of age there was a total of between 75000–90000 optic nerve axons, irrespective of the group examined. The proportion of axons which were myelinated at this age was still significantly lower (P < 0.001) in the ETHD animals (∼ 77%) than in the other groups (about 98%). It is concluded that the normal stages of development and maturation of the rat optic nerve axons, as assessed in this study, can be severely compromised by exposure to a relatively high (but not low) dose of ethanol between postnatal d 4 and 9.
The effects of growth hormone and IGF‐1 deficiency on cerebrovascular and brain ageing
Authors: SONNTAG WILLIAM E. , LYNCH COLLEEN , THORNTON PHILLIP , KHAN AMIR , BENNETT SEAN , INGRAM RHONDA
Published: March 2003

Research studies clearly indicate that age‐related changes in cellular and tissue function are linked to decreases in the anabolic hormones, growth hormone and insulin‐like growth factor (IGF)‐1. Although there has been extensive research on the effects of these hormones on bone and muscle mass, their effect on cerebrovascular and brain ageing has received little attention. We have also observed that in response to moderate calorie restriction (a treatment that increases mean and maximal lifespan by 30–40%), age‐related decreases in growth hormone secretion are ameliorated (despite a decline in plasma levels of IGF‐1) suggesting that some of the effects of calorie restriction are mediated by modifying the regulation of the growth hormone/IGF‐1 axis. Recently, we have observed that microvascular density on the surface of the brain decreases with age and that these vascular changes are ameliorated by moderate calorie restriction. Analysis of cerebral blood flow paralleled the changes in vasculature in both groups. Administration of growth hormone for 28 d was also found to increase microvascular density in aged animals and further analysis indicated that the cerebral vasculature is an important paracrine source of IGF‐1 for the brain. In subsequent studies, administration of GHRH (to increase endogenous release of growth hormone) or direct administration of IGF‐1 was shown to reverse the age‐related decline in spatial working and reference memory. Similarly, antagonism of IGF‐1 action in the brains of young animals impaired both learning and reference memory. Investigation of the mechanisms of action of IGF‐1 suggested that this hormone regulates age‐related alterations in NMDA receptor subtypes (e.g. NMDAR2A and R2B). The beneficial role of growth hormone and IGF‐1 in ameliorating vascular and brain ageing are counterbalanced by their well‐recognised roles in age‐related pathogenesis. Although research in this area is still evolving, our results suggest that decreases in growth hormone and IGF‐1 with age have both beneficial and deleterious effects. Furthermore, part of the actions of moderate calorie restriction on tissue function and lifespan may be mediated through alterations in the growth hormone/IGF‐1 axis.
The existence of the vomeronasal organ in postnatal chimpanzees and evidence for its homology with that of humans
Authors: SMITH TIMOTHY D. , SIEGEL MICHAEL I. , BONAR CHRISTOPHER J. , BHATNAGAR KUNWAR P. , MOONEY MARK P. , BURROWS ANNIE M. , SMITH MATTHEW A. , MAICO LISETTE M.
Published: March 2003

It is currently thought that New World monkeys, prosimians, and humans are the only primates to possess vomeronasal organs (VNOs) as adults. Recent studies of the human VNO suggest that previous investigations on Old World primates may have missed the VNO. We examined nasal septa from the chimpanzee (Pan troglodytes) grossly and histologically for comparison with nasal septa from humans, Old World monkeys (Macaca fascicularis, M. nemistrina) and prosimian primates (Microcebus murinus, Otolemur garnettii). Grossly, chimpanzees had depressions on the nasal septum similar to fossae reported anterior to the VNO openings in humans. Histologically, chimpanzees and humans had bilateral epithelial tubes which were above the superior margin of the paraseptal cartilages (vomeronasal cartilage homologue). The epithelial tubes had a homogeneous ciliated epithelium. These structures were thus positionally and structurally identical to the human VNO and unlike the well‐developed prosimian VNOs which were surrounded by vomeronasal cartilage. Macaques had no structures which resembled the VNO of either the prosimians or humans. The results demonstrate that the VNO is present postnatally in the chimpanzee and is almost identical to the human VNO in its anatomical position and histological structure. This in turn suggests that the reported absence of the VNO in at least some adult Old World primates is artifactual, and that further study may provide evidence for its existence in other species.
Semiquantitative analysis of collagen types in the hypertrophied left ventricle
Authors: LINEHAN KATHERINE A. , SEYMOUR ANNE‐MARIE L. , WILLIAMS PAMELA E.
Published: March 2003

Cardiac fibrosis is a characteristic feature of left ventricular hypertrophy. The aim of this study was to develop a simple and accurate method to analyse collagen accumulation, taking into account the variation in cardiac muscle fibre orientation and nonuniform collagen distribution. This technique was used to determine the amount and types of collagen that accumulate during pressure overload cardiac hypertrophy. These data were correlated with myocyte size, and with the diastolic stress–strain relationship of the intact myocardium. Myocyte size was significantly increased in the hypertrophied hearts, compared with age and sex matched controls (control 363±25 μm2 vs experimental 244μm2; mean±S.E., P < 0.05). No overall collagen accumulation was observed in the hypertrophied hearts, but a significant increase in collagen I was found with a reduction in the amount of collagen III in experimental animals. Since no increase in diastolic stiffness of the hearts was observed, these results indicate that an increase in the overall collagen content of the heart, rather than the upregulation of a specific type, may be necessary to cause diastolic dysfunction.
Actin polymerisation during morphogenesis of the acrosome as spermatozoa undergo epididymal maturation in the tammar wallaby (Macropus eugenii)
Authors: SCARLETT CHRIS J. , LIN MINJIE , AITKEN R. JOHN
Published: March 2003

In the tammar wallaby (Macropus eugenii), post‐testicular acrosomal shaping involves a complex infolding and fusion of the anterior and lateral projections of the scoop‐shaped acrosome into a compact button‐like structure occupying the depression on the anterior end of the sperm nucleus. The present study has generated cytochemical and histological evidence to demonstrate that the occurrence of actin filaments (F‐actin, labelled by Phalloidin‐FITC) in the acrosome of tammar wallaby spermatozoa is temporally and spatially associated with the process of acrosomal shaping in the epididymis, through a pool of monomeric actin (G‐actin, labelled by Rh‐DNase I) present in the acrosome throughout all stages of epididymal maturation. F‐actin was not detected in the acrosome of testicular spermatozoa, but was found in the infolding and condensing acrosome of caput and corpus epididymal spermatozoa. When the spermatozoa completed acrosome shaping in the cauda epididymidis, F‐actin disappeared from the acrosomal area. The strong correlation between the occurrence of F‐actin and the events of acrosomal shaping suggested that the post‐testicular shaping of the acrosome might depend on a precise succession of assembly and disassembly of F‐actin within the acrosome as the spermatozoa transit the epididymis. Thus, actin filaments might play a significant role in the acrosomal transformation, as they are commonly involved in morphological changes in somatic cells.
Biometric study of the relationships between palmar neurovascular structures, the flexor retinaculum and the distal wrist crease
Authors: OLAVE E. , DEL SOL M. , GABRIELLI C. , MANDIOLA E. , RODRIGUES C. F. S.
Published: March 2003

During surgical exposure of the carpal tunnel it is possible to injure the neurovascular structures closely related to the flexor retinaculum, such as the superficial palmar arch and the communicating branch between the ulnar and median nerves. Because of the importance of these structures and with the purpose of increasing knowledge of anatomical details concerning to their location, a biometric study was performed on the retinaculum and the communicating branch, and between the communicating branch and the distal wrist crease, as well as between the retinaculum and the superficial palmar arch. We dissected 56 hands from 28 Brazilian formalin‐preserved cadavers of both sexes (24 male) at the Federal University of São Paulo–Escola Paulista de Medicina, Brazil. The communicating branch was observed in 96.4% of cases and the superficial palmar arch in 78.6%. The communicating branch was found between the common palmar digital nerve of the 4th interosseous space (from the ulnar nerve) to the homonymous nerve of the 3rd interosseous space (from the median nerve). In males, the distance between the distal wrist crease and the site where the communicating branch originates from the ulnar component had an average of 33.9±5.5 mm on the right side and 30.2±8.2 mm on the left. The distance between the distal wrist crease and the junction of the communicating branch with the common palmar digital nerve of the 3rd interosseous space was 43.6±6.9 mm on the right and 40.2±6.2 mm on the left side. Conversely, in 14.8% of cases (1 female), the communicating branch was observed to emerge from the common palmar digital nerve of the 3rd interosseous space. The distance between the retinaculum and the superficial palmar arch in the axial line of the 4th metacarpal bone was on average 7.3±4.3 mm on the right and 8.3±3.5 mm on the left side. At the same level, the distance between the retinaculum and the communicating branch was 6.2±3.7 mm on the right side and 5.1±2.8 mm on the left. These results can be used as a reference during surgical procedures in the palmar region.
The role of early neural activity in the maturation of turtle retinal function
Authors: SERNAGOR EVELYNE , MEHTA VANDANA
Published: March 2003

In the developing vertebrate retina, ganglion cells fire spontaneous bursts of action potentials long before the eye becomes exposed to sensory experience at birth. These early bursts are synchronised between neighbouring retinal ganglion cells (RGCs), yielding unique spatiotemporal patterns: ‘waves’ of activity sweep across large retinal areas every few minutes. Both at retinal and extraretinal levels, these embryonic retinal waves are believed to guide the wiring of the visual system using hebbian mechanisms of synaptic strengthening.

In the first part of this review, we recapitulate the evidence for a role of these embryonic spontaneous bursts of activity in shaping developing complex receptive field properties of RGCs in the turtle embryonic retina. We also discuss the role of visual experience in establishing RGC visual functions, and how spontaneous activity and visual experience interact to bring developing receptive fields to maturation. We have hypothesised that the physiological changes associated with development reflect modifications in the dendritic arbours of RGCs, the anatomical substrate of their receptive fields. We demonstrate that there is a temporal correlation between the period of receptive field expansion and that of dendritic growth. Moreover, the immature spontaneous activity contributes to dendritic growth in developing RGCs. Intracellular staining of RGCs reveals, however, that immature receptive fields only rarely show direct correlation with the layout of the corresponding dendritic tree. To investigate the possibility that not only the presence of the spontaneous activity, but even the precise spatiotemporal patterns encoded in retinal waves might contribute to the refinement of retinal neural circuitry, first we must clarify the mechanisms mediating the generation and propagation of these waves across development. In the second part of this review, we present evidence that turtle retinal waves, visualised using calcium imaging, exhibit profound changes in their spatiotemporal patterns during development. From fast waves sweeping across large retinal areas and recruiting many cells on their trajectory at early stages, waves become slower and eventually stop propagating towards hatching, when they become stationary patches of neighbouring coactive RGCs. A developmental switch from excitatory to inhibitory GABAA responses appears to mediate the modification in spontaneous activity patterns while the retina develops. Future chronic studies using specific spatiotemporal alterations of the waves will shed a new light on how the wave dynamics help in sculpting retinal receptive fields.
Study of axillary lymph node asymmetry in a female population
Authors: CAPPELLO F. , BELLAFIORE M. , PALMA A. , MARCIANO V. , ZUMMO G. , FARINA F. , BUCCHIERI F.
Published: March 2003

We analysed a large series of axillary lymph nodes, with and without metastases following radical mastectomy for breast cancer. We found left/right asymmetry in numbers of lymph nodes, and also asymmetry of lymph node dimensions, which could have been the caused by tumoral antigenic stimulation. The distribution of hyperplastic node patterns differed significantly.
A degeneration‐based hypothesis for interpreting fibrillar changes in the osteoarthritic cartilage matrix
Authors: BROOM NEIL , CHEN MIN‐HUEY , HARDY ANTHONY
Published: March 2003

The collagen fibrillar architectures in the general matrix of cartilage slices removed from both normal and osteoarthritic femoral heads were examined by both differential interference light microscopy and scanning electron microscopy. Whereas the normal general matrix contained a finely differentiated pseudo‐random weave of fibrils developed from an interconnected array of radial elements, the osteoarthritic general matrix was characterised by the presence of structurally distinct regions consisting of strongly aligned radial bundles of fibrils and associated intense tangles or ‘knotted’ features. Simple structural models were developed to explore possible transformation structures based on two different types of interconnectivity in the three‐dimensional fibrillar network. These models support the hypothesis that the distinctive ultrastructural features of the osteoarthritic general matrix can develop as a consequence of largely passive degradative changes occurring in the fibrillar weave originally present in the normal matrix. This could, in principle, occur independently of any new structure that might develop as a consequence of any upregulation of collagen associated with the osteoarthritic process.
Composite cellular defence stratagem in the avian respiratory system: functional morphology of the free (surface) macrophages and specialized pulmonary epithelia
Authors: Nganpiep L. N. , Maina J. N.
Published: March 2003

Qualitative and quantitative attributes of the free respiratory macrophages (FRMs) of the lung – air sac systems of the domestic fowl (Gallus gallus variant domesticus) and the muscovy duck (Cairina moschata) were compared with those of the alveolar macrophages of the lung of the black rat (Rattus rattus). The birds had significantly fewer FRMs compared to the rat. In the birds, the FRMs were found both in the lungs and in the air sacs. Under similar experimental conditions, the most robust FRMs were those of the domestic fowl followed by those of the rat and the duck. Flux of macrophages onto the respiratory surface from the subepithelial compartment and probably also from the pulmonary vasculature was observed in the birds but not in the rat. In the duck and the domestic fowl, a phagocytic epithelium that constituted over 70% of the surface area of the blood–gas (tissue) barrier lines the atrial muscles, the atria and the infundibulae. The epithelial cells of the upper respiratory airways contain abundant lysosomes, suggesting a high lytic capacity. By inference, the various defence strategies in the avian lung may explain the dearth of FRMs on the respiratory surface. We counter‐propose that rather than arising directly from paucity of FRMs, an aspect that has been over‐stressed by most investigators, the purported high susceptibility of birds (particularly table birds) to respiratory ailments and afflictions may be explained by factors such as inadequate management and husbandry practices and severe genetic manipulation for fast growth and high productivity, manipulations that may have weakened cellular and immunological defences.
Bone adaptation to load: microdamage as a stimulus for bone remodelling
Authors: Lee T. C. , Staines A. , Taylor D.
Published: March 2003

Mechanical loading in the proximal radius was increased by ulnar osteotomy (Group O), altered by Steinmann pinning (Group P) or unaltered in sham operated controls (Group C) in skeletally mature female sheep, aged 2–4 years. A series of intravenous fluorochromes were given to label bone formation and fuchsin‐stained microdamage assessed at intervals of up to 24 weeks. Microcracks were present in all groups and were found in the original cortex near the periosteal surface. No microcracks were found in the new, fibrolamellar bone laid down at periosteal or endosteal surfaces. Mean microcrack length (49 µm, SD 10 µm) did not differ between groups or over time. Microcrack numerical and surface densities and resorption cavity density peaked in all groups at 6 weeks, consistent with a regional acceleratory phenomenon (RAP), but the peaks were significantly greater in Group O. The density of refilling or secondary osteons peaked at 10 weeks and the mean time required for the formation of an osteon was 7.51 ± 0.59 weeks. Fatigue‐induced microdamage is normally present in bone and is increased due to repetitive loading of the mechanically overloaded radius. The location and timing of microcracks, resorption cavities and secondary osteons are consistent with the activation‐resorption‐formation remodelling cycle and suggest that microdamage is a stimulus for bone remodelling.
Digital development and morphogenesis
Authors: Sanz‐Ezquerro J. J. , Tickle C.
Published: March 2003

Signalling interactions between the polarizing region, which produces SHH, and the apical ectodermal ridge, which produces FGFs, are essential for outgrowth and patterning of vertebrate limbs. However, mechanisms that mediate translation of early positional information of cells into anatomy remain largely unknown. In particular, the molecular and cellular basis of digit morphogenesis are not fully understood, either in terms of the formation of the different digits along the antero‐posterior axis or in the way digits stop growing once pattern formation has been completed. Here we will review recent data about digit development. Manipulation of morphogenetic signals during digit formation, including application of SHH interdigitally, has shown that digit primordia possess a certain plasticity, and that digit anatomy becomes irreversibly fixed during morphogenesis. The process of generation of joints and thus segmentation and formation of digit tips is also discussed.
Postnatal development of the fore‐ and hindlimbs in the grey short‐tailed opossum, Monodelphis domestica
Authors: Martin Katherine E. A. , Mackay Sarah
Published: March 2003

Marsupials are good experimental animals for developmental studies as their offspring are born at a stage comparable to embryonic stages of eutherian species. The South American opossum, Monodelphis domestica, is particularly useful because of its small size and easy maintenance. This study was carried out to compare development of opossum fore‐ and hindlimbs during postnatal life, using light microscopy and whole mount alizarin staining. At birth, well‐developed mobile forelimbs show cartilage models of bones and myotubular striated muscle fibres. However, hindlimbs are relatively underdeveloped paddle‐like outgrowths. Two days later mesodermal condensations form models of the future hindlimb bones and mononucleate myoblast aggregates are present; by 6 days post partum (dpp) the hindlimb has reached a stage of development similar to that of the forelimb at birth. At this stage, periosteal buds have invaded forelimb long bones and nuclei in forelimb muscle fibres have become displaced to the periphery. The 16 dpp hindlimb shows long bones invaded by periosteal buds and closely packed, striated muscle fibres. Epiphyseal plates are now seen in the forelimb long bones and forelimb muscle fibres show mature characteristics. Musculoskeletal development is well correlated with the functional demands of the limbs during postnatal development in the opossum, which provides an excellent model for investigations into the genes and molecules controlling limb development.
Changes in rice root architecture, porosity, and oxygen and proton release under phosphorus deficiency
Authors: KIRK G. J. D. , VAN DU LE
Published: March 2003

Earlier work has shown that rice plants growing in reduced soil are able to solubilize P and thereby increase their P uptake by inducing an acidification in the rhizosphere; the acidification is caused by H+ produced in Fe2+ oxidation by root‐released O2, and by the direct release of H+ from the roots to balance cation‐anion intake. Here, we report rates of release of O2 and H+ from P‐stressed and P‐sufficient rice plants into sand cultures continuously perfused with deoxygenated nutrient solution. The P stress was sufficient to reduce plant dry mass by roughly half, but root dry mass increased roughly twofold and root surface area 2–5‐fold. The proportion of fine roots increased from 11 to 21 % of root length under P deficiency; root porosity, averaged over the whole root system, increased from 0–25 to 0.40. Apparent rates of O2 release were 0.8–3–3 μmol per plant d−1, or 22–87 μmol g−1 (root dry mass) d−1. Assuming that the bulk of the O2 was released from medium and fine roots, the fluxes of O2 were 0.02–0.13 nmol dm−2 (root surface) s−1, which is in the range found for soil‐grown plants. The release per plant was twofold greater in the low P treatment, although rates of release per unit root mass were slightly lower. The increased release under P deficiency is consistent with the increased length of fine roots and increased porosity. Rates of H+ release were 0.7–1.2 mmol per plant−1 d−1, or 1.4–6.1 mmol g−1 (root dry mass) d−1. The H+ release per unit plant dry mass was 60% greater in the low P treatment, but the release per unit root mass was 2.5‐fold lower. The increased H+ release under P deficiency was associated with increased NH4+ intake and decreased NO3− intake, and a tenfold increase in plant NO3‐N. This suggests that P deficiency reduced NO3−assimilation, causing reduced NO3− influx and/or increased efflux.
Longevity of leaves of a tropical tree, Theobroma cacao, grown under shading, in relation to position within the canopy and time of emergence
Authors: MIYAJI KEN‐ICHI , DA SILVA WALNY S. , DE PAULO T. ALVIM
Published: March 2003

summary

To gain detailed information on the structure and dynamics of the foliage within a canopy, the longevity of leaves of cacao trees (Theobroma cacao L.) growing under normal commercial planting shade in Bahia State, Brazil, was determined relative to their position within the canopy and the time of leaf emergence.

In the experimental stand, the relative light intensity above the cacao canopy ranged between 30 and 100% of full daylight, and 4–10% at ground level. The mean leaf area index for the canopy, and the extinction coefficient of the foliage were 3–9 and 0–61, respectively.

The longevity of leaves of adult trees of cacao with closely packed crowns varied with their position within the canopy, and/or the irradiance received, and the time of emergence. In particular longevity decreased greatly with the height of the leaf from ground level. The mean longevity for the upper foliage (more than 220 cm above the ground) within the canopy was 181 d; the mean longevity of the lower leaves (0–150 cm above the ground) was about twice that of the upper leaves.

Approximately 23% of emergent leaves fell within 60 d of emergence, following infection (about 14% of loss) or as a result of wind damage (about 5 % of loss). Thereafter, in mature and senescent leaves, leaf fall followed normal physiological changes.
Irradiance and nitrate‐dependent variation in growth and biomass allocation of Mycelis muralis. An analysis of its significance for a functional categorization of ‘sun’ and ‘shade’ plants
Authors: CLABBY GERARD , OSBORNE BRUCE A.
Published: March 2003

summary

The biomass of Mycelis muralis (L.) Dumort plants increased with increases in growth irradiance and nitrate supply. Comparisons of the data from this study with published information indicate that biomass production and growth rate of M. muralis are comparable to that of a number of slow‐growing species from resource‐poor environments. Biomass allocation varied with growth irradiance and nitrate supply. At high irradiances and low nitrate supplies there was a significantly greater allocation of plant mass to roots, resulting in a lower leaf area ratio (LAR) and leaf mass ratio (LMR). In contrast to the findings of a number of other studies, light level and nitrate supply had interactive effects on leaf mass per unit area (LMA). Changes in LAR due to variations in irradiance were mainly a consequence of changes in LMR. Given the ability of M. muralis to grow in deep shade, this suggests that large changes to within‐leaf allocation (LMA) are not an essential requirement for growth at low irradiances. Conversely, because M. muralis can also grow in fully exposed situations, these traits might not exclude some shade species from high irradiance habitats. However, a low growth rate, or traits which result in a low growth rate, might be advantageous in a number of resource‐poor environments.
Fructo‐oligosaccharide content and fructosyltransferase activity during growth of onion bulbs
Authors: SHIOMI NORIO , ONODERA SHUICHI , SAKAI HIDEKI
Published: March 2003

The accumulation of fructo‐oligosaccharides and the activities of fructosyltransferase (sucrose∶sucrose 1F‐fructosyltransferase (SST), 1F‐fructosyltransferase (1F‐FT) and 6G‐fructosyltransferase (6G‐FT)) in the bulbs of three onion cultivars were investigated from June to September 1993. The total fructo‐oligosaccharide content increased from June until August, then decreased in September, except in one cultivar. The levels of neokestose and its related tetrasaccharides (1F, 6G‐di‐β‐D‐fructofuranosyl sucrose and 6G (1‐β‐D‐fructofuranosyl)2sucrose) were higher than those of 1‐kestose and nystose throughout growth. The activities of 6G‐FT, 1F ‐FT and SST were high in June and July, then decreased; SST activity was very low in September. The activity ratios of 6G‐FT to 1F‐FT varied between 1·86 and 2·65 over the growth period. Two trisaccharides, three tetrasaccharides and four pentasaccharides were identified, together with a mixture of hexa‐ and heptasaccharides, all of which were synthesized in vitro from 0·1 M sucrose by an enzyme preparation of onion bulbs harvested in August. Octa‐ and nonasaccharides other than the saccharides formed from sucrose were also synthesized from 0·1 M 1‐kestose or 0·1 M neokestose. All the saccharides produced from sucrose, 1‐kestose or neokestose by the crude enzyme prepared from onion bulbs were identical to the saccharides occurring naturally in onion bulbs.
Callose deposition during the interaction between cowpea (Vigna unguiculata) and the monokaryotic stage of the cowpea rust fungus (Uromyces vignae)
Authors: ŠKALAMERA DUBRAVKA , JIBODHAND STEFAN , Heath Michele C.
Published: March 2003

summary

The interaction between the race 1 of the cowpea rust fungus (Uromyces vignae Barclay) and the resistant cowpea (Vigna unguiculata (L.) Walp.) ev. Queen Anne is characterized by the deposition of callose around intracellular fungal structures. Ultrastructural examination of the early stages of infection by basidiospores of the fungus revealed two types of deposits induced by intracellular hyphae: a non‐callose collar at the penetration site and a callose encasement around the invasion hypha. The callose encasement was developed from the site where the fungus encountered the inside of the plant cell wall and was separated from the fungus by the extrahyphal membrane and an extension of plant plasma membrane. The incidence of encasements was reduced in plants treated with inhibitors of transcription (actinomycin D), protein synthesis (cycloheximide), protein glycosylation (tunicamycin) and microfilament polymerization (cytochalasin E). Inhibitors of Golgi‐associated vesicle transfer (monensin, brefeldin A) and anti‐microtubule agents (colchicine, oryzalin) had no effect. When the fungus was killed by heat treatment in either the resistant or the susceptible cultivar, callose was deposited at various locations along the fungus, mostly in the extrahyphal matrix. The data suggest that unlike the extrahaustorial membrane surrounding D‐haustoria of this fungus, the extrahyphal membrane is capable of generating callose. Since this process does not normally occur in the susceptible or the resistant cv. even when callose is deposited in the latter by regions of the plasma membrane not associated with the fungus, we conclude that the deposition of callose by the extrahyphal membrane is inhibited by the living fungus.
Natural 15N abundance in fruit bodies of ectomycorrhizal fungi from boreal forests
Authors: TAYLOR ANDREW F. S. , HÖGBOM LARS , HÖGBERG MONA , LYON ANTHONY J. E. , NÄSHOLM TORGNY , HÖGBERG PETER
Published: March 2003

The 15N natural abundance and N concentrations of fruit bodies from 70 species (23 genera) of ectomycorrhizal fungi found in boreal forests are presented. Large intraspecific and intrageneric differences were found, e.g. 8.3‰15N in the species Dermocybe crocea and 12.6‰ in the genus Cortinarius. In addition, significant differences in both δ15N and %N were found between different parts of fruit bodies, with cap material giving consistently higher values. Proteins and amino acids were enriched by 9.7±0.4‰ (mean ± 1 SE) relative to chitin, irrespective of the part of the fruit body examined. Chitin had δ15N values similar to that of plant hosts. The higher δ15N and %N values of the caps than of the stipes probably reflect a higher portion of proteins and amino acids in the caps. The δ15N of mycorrhizal fungi can be a function of the N species used (organic N, NH4+, NO3−), the depth of soil at which the mycelium occurs, and metabolic fractionations. The metabolic fractionations, e.g. potential transaminations during the flux of N from the soil through the fungus to the plant, make it difficult, at present, to make inferences about sources of N based on δ15N values alone. No effect of sample drying temperature on δ15values of fungal material was detected.
Abscisic acid (ABA) relations in the aquatic resurrection plant Chamaegigas intrepidus under naturally fluctuating environmental conditions
Authors: SCHILLER PETRA , HEILMEIER HERMANN , HARTUNG WOLFRAM
Published: March 2003

The resurrection plant Chamaegigas intrepidus Dinter (Scrophulariaceae) grows as a typical hydrophyte in shallow rock pools on granitic outcrops in arid areas of Namibia. During the rainy season, the rock pools are temporarily filled with water. When the pools dry up, C. intrepidus desiccates and survives in an air‐dry condition for at least 8 months. After rewatering, the plants regain their metabolic activity in under 2 h. The desiccation of the vegetative organs is accompanied by a dramatic accumulation of abscisic acid (ABA). Beyond this, desiccation of roots is accompanied by the occurrence of specific dehydration‐related proteins, whereas the leaves of C. intrepidus show high levels of dehydrins in the dehydrated as well as in the hydrated state.

Investigations in Namibia showed drastic diurnal fluctuations in the pH of the rock pools. The pH value increased from slightly acidic or neutral conditions during the morning to alkaline conditions (up to pH 12) during late afternoon. Since compartmental ABA distribution depends strongly on pH gradients across membranes, the external pH would be expected to affect the ABA relations in the plant. According to the anion trap concept, an alkaline pH in the surrounding medium should cause a release of ABA from the roots, although C. intrepidus appeared to release less ABA than the terrestrial rosettes of Valerianella locusta.
Photosynthesis and photoinhibition in a tropical alpine giant rosette plant, Lobelia rhynchopetalum
Authors: FETENE M. , NAUKE P. , LÜTTGE U. , BECK E.
Published: March 2003

summary

Carbodioxide uptake, oxygen evolution and chlorophyll fluorescence of leaves of Lobelia Lobelia rhynchopetalum Hemsl., a giant rosette plant of the tropical alpine regions of Ethiopia, were studied under field conditions at 4000 m above sea level. Our objective was to investigate the photosynthetic adaptation to the combination of wide fluctuation in diurnal temperature, high photon flux densities (PFD) and low CO2 partial pressure encountered in these regions. At an ambient CO2 partial pressure of c. 17 Pa, maximal rates of CO2 uptake were low, ranging between 4 and 6 μmol m−2 s−1. Such rates, however, required high PFDs and were observed only at levels of 1500 μmol photons m−2 s−2. Carbon dioxide uptake was significantly inhibited when PFD was ≤ 2000 μmol photons m−2 s−1. On the other hand, at saturating CO2 levels, maximal photosynthetic oxygen evolution was higher (30 μmol C2 m−2 s−1). saturating at the same PFD as CO2 uptake. Quantum efficiency of CO2 uptake (0.006 mol CO2 mol photons−1, at high altitude and a low CO, partial pressure of 17 Pa) and even of oxygen evolution under CO2‐saturating conditions in the leaf O2 electrode (0.05 mol O2 mo) photons−1) indicated reduced photosynthetic efficiency. Electron transport rate (ETR) was strongly correlated with the leaf temperature. Non‐photochemical quenching (NPQ) responded inversely to leaf temperature and stomatal conductance.

The results indicated that in the morning, when the sun irradiates the partly frozen leaves with closed stomata, NPQ is the principal mechanism by which Lobelia leaves protect their photosynthetic apparatus. However, during the day, the predominant upright inclination of the leaves significantly contributes to protecting the leaves from excess light absorption. A comparison of the chlorophyll fluorescence of young and old leaves revealed that the former had high ETR and quantum efficiency of photosynthetic electron transport but a lower capacity for NPQ. Extremely high NPQ values but low ETR and low quantum efficiency were recorded for the old leaves. Thus, in the course of maturation the leaves apparently lose photosynthetic efficiency but increase their capability for protective non‐photochemical quenching.
Anti‐transpiration and anti‐growth activities in the xylem sap from plants under different types of soil stress
Authors: ZHU XIAOHONG , ZHANG JIANHUA
Published: March 2003

summary

Anti‐transpiration and anti‐growth activities of xylem sap were studied for maize, sunflower, cotton and castor bean, which were subjected to several stress treatments: soil drying, flooding and salinity. All samples of xylem sap showed an increased concentration of proteins when plants were either soil‐dried, salt‐treated or flooded. The protein transportation flux in xylem sap, i.e. the product of protein concentration and volume flux, was also increased as a result. Electrophoresis using SDS‐PAGE analysis showed that xylem proteins were of variable size. When samples of xylem sap were used to feed detached leaves or shoots in a bioassay system for their anti‐transpiration and anti‐growth activities, such xylem proteins in their original concentrations apparently showed neither direct inhibition nor enhanced effects of ABA. All samples of xylem sap from plants subjected to different stresses showed anti‐transpiration and anti‐growth activities that could be fully accounted for by their ABA concentration. In cases where such activities were more than could be explained by the ABA concentrations, filtration with a 0–20 μm microfilter removed the discrepancies.
The long‐term epidemic of Claviceps purpurea on Spartina anglica in Poole Harbour: pattern of infection, effects on seed production and the role of Fusarium heterosporum
Authors: RAYBOULD A. F. , GRAY A. J. , CLARKE R. T.
Published: March 2003

An epidemic of the ergot fungus (Claviceps purpurea (Fr.) Tul), a non‐systemic floral pathogen, appeared in populations of Spartina anglica C. E. Hubb in Poole Harbour in the 1980s. Over 70% of inflorescences were infected between 1985 and 1995. Between 1983 and 1995, there was no consistent pattern in the rank order of sites with respect to the proportion of inflorescences infected, and variation in the amount of infection was not related to inflorescence density. Among years, there was significant variation in the total biomass of ergot per inflorescence, but no significant difference in the number of ergots per inflorescence. Log–log regressions of total weight of ergot per inflorescence against the number of ergots per inflorescence showed that in all years resources for each additional ergot were limited.

There was no statistically significant difference between the number of seed set on infected and uninfected inflorescences in 1985 or 1995. Further analysis showed that, compared with uninfected inflorescences, there was higher seed output from inflorescences with fewer than 10% of spikelets infected, which balanced reduced seed output from heavily infected inflorescences. At high levels of ergot infection, a lower proportion of uninfected spikelets set seed, compared with spikelets on uninfected inflorescences. This suggests that conditions which favour ergot growth are detrimental to seed production. Compared with uninfected inflorescences, mean and total seed weights were significantly lower in inflorescences with >10% of spikelets infected.

The fungus Fusarium heterosporum Nees ex Fr. was found in association with the ergots on Spartina. There was a significant positive correlation between the average severity of Fusarium infection and the number of ergots on an inflorescence. There was a non‐significant negative correlation between severity of Fusarium and mean ergot weight, when ergot number per inflorescence was held constant. These data suggest that any negative effect of Fusarium on Claviceps is small.

The high, and temporally and spatially uniform levels of ergot infection probably result from genetic uniformity of Spartina and the lack of zonation in the salt marshes of Poole Harbour. This situation is likely to persist for the foreseeable future.