bluuebunny/crossref_metadata_2025 huggingface dataset:
A descriptive and comparative lectin histochemical study of the vomeronasal system in pigs and sheep
Authors: SALAZAR IGNACIO , SANCHEZ‐QUINTEIRO PABLO , LOMBARDERO MATILDE , CIFUENTES JOSE MANUEL
Published: March 2003

The accessory olfactory bulb (AOB) is the primary target of the sensory epithelium of the vomeronasal organ (VNO), and thus constitutes a fundamental component of the accessory olfactory system, which is involved in responses to behaviour‐related olfactory stimuli. In this study we investigated the characteristics of the AOB, VNO, vomeronasal nerves (VNNs) and caudal nasal nerve (CdNN) in pigs and sheep, species in which olfaction plays a key behavioural role both in the neonatal period and in adulthood. The patterns of staining of the AOB by the Bandeiraea simplicifolia and Lycopersicon esculentum lectins were the same in the 2 species, whereas the Ulex europeus and Dolichos biflorus lectins gave different patterns. In both species, lectin staining of the AOB was consistent with that of the VNNs, while the CdNN did not label any of the structures studied. The entire sensory epithelium of the pig was labelled by Ulex europeus and Lycopersicum esculentum lectins, and all 4 lectins used labelled the mucomicrovillar surface of the sensory epithelium in sheep.
The relationship between accessory foramina and tumour spread on the medial mandibular surface
Authors: FANIBUNDA K. , MATTHEWS J. N. S.
Published: March 2003

The medial cortical surface of the mandible can be involved by tumour infiltration from the floor of the mouth. A detailed study of spread via accessory foramina through the edentulous alveolar crest has been previously undertaken, but no similar study has been carried out for the medial surface. In order to gain further appreciation of the mode of tumour spread, a study of the number and distribution of accessory foramina on the medial mandibular surface was performed on 89 mandibles. The number of foramina varied greatly from specimen to specimen. In the ascending ramus above the inferior dental foramen, 3 mandibles showed no foramina; the condylar section possessed the greatest proportion followed by the sigmoid and the coronoid. On the rest of the medial surface below the inferior dental foramen, all specimens showed at least 1 accessory foramen; the greatest concentration was in the middle third along the path of the inferior dental canal, followed by the upper third and the lower third section. Accessory foramina were repeatedly present at certain dedicated sites. The medial facing wall of the inferior dental foramen was found to be the commonest dedicated site (98.3%) followed by foramina on either side of the genial tubercles (71.9%), the digastric fossa (71.9%) and the median foramen above the genial tubercles (64%). The findings of this study are in keeping with the current observation that the lower border is least commonly involved in tumour spread. In view of the presence of accessory foramina along the inferior dental canal and especially on the medial facing wall of the inferior dental foramen, it is imperative to preclude tumour spread in this region prior to undertaking the conservative rim resection procedure. Medial to the symphysis the alveolar mucosa dips down almost to the level of the dedicated foramina in the vicinity of the genial tubercles. As a general rule the attached muscle forms a barrier to tumour spread except in the later stages, however, in irradiated mandibles resistance to spread has been previously reported to be diminished. Under these circumstances, it is possible that the numerous accessory foramina reported in this study could facilitate a direct pathway into the cancellous bone.
Innervation of the cavernous body of the human efferent tear ducts and function in tear outflow mechanism
Authors: PAULSEN FRIEDRICH , HALLMANN UTA , PAULSEN JENS , THALE ANDREAS
Published: March 2003

The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not previously investigated. Different S‐100 protein antisera, neuronal markers (neuron‐specific enolase, anti‐200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene‐related peptide, vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also examined by means of standard transmission electron microscopy.

The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins, and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a plexus‐like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S‐100 protein (S 100), neuron‐specific enolase (NSE), anti‐200 kDa neurofilament (RT 97), calcitonin gene‐related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands.

Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural control of the cavernous body of the human efferent tear ducts. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow. Related functions such as a role in the occurrence of epiphora related to emotional responses are relevant. Moreover, malfunction in the innervation of the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passages.
Dynamic ultrastructure of mouse pulmonary alveoli revealed by an in vivo cryotechnique in combination with freeze‐substitution
Authors: TAKAYAMA ICHIRO , TERADA NOBUO , BABA TAKESHI , UEDA HIDEHO , FUJII YASUHISA , KATO YASUKO , OHNO SHINICHI
Published: March 2003

A morphological approach to cell dynamics is usually difficult, since routine preparative techniques for electron microscopy always induce artifacts due to cessation of the blood supply into organs. An in vivo cryotechnique followed by the freeze‐substitution method probably reduces such problems. It was applied for examining the pulmonary alveoli of BALB/c mice in vivo. The following ultrastructural features were revealed. (1) A surfactant layer provided a continuous covering to the alveolar epithelium. (2) Pleural epithelial cells, alveolar cells and endothelial cells contained many small vesicles and pits. In the alveolar epithelium, they were often localised near microtubules. (3) Typical lamellar structures in large alveolar epithelial cells were rarely detected. (4) Circulating erythrocytes with various shapes were observed in branching blood capillaries. (5) A close association between erythrocytes and the endothelium was seen at the peripheral alveolar septum. Such ultrastructural arrangements may be appropriate for the physiological functions of the pulmonary alveoli, such as exchanges of gases or materials in vivo.
Parameters of calcium homeostasis in normal neuronal ageing
Authors: TOESCU EMIL C. , VERKHRATSKY ALEXEJ
Published: March 2003

The last decade has witnessed a significant turn in our understanding of the mechanisms responsible for the decline of cognitive functions in aged brain. As has been demonstrated by detailed morphological reassessments, the senescence‐related changes in cognition cannot be attributed to a simple decrease in the number of neurons. It is becoming clearer that a major cause of age‐induced deterioration of brain capability involves much subtler changes at the level of synapses. These changes are either morphological, i.e. reduction in the number of effective synapses and/or functional alterations, i.e. changes in the efficacy of remaining synapses. Important questions are now raised regarding the mechanisms which mediate these synaptic changes. Clearly, an important candidate is calcium, the cytotoxic role of which is already firmly established. The wealth of evidence collected so far regarding the changes of Ca2+ homeostasis in aged neurons shows that the overall duration of cytoplasmic Ca2+ signals becomes longer. This is the most consistent result, demonstrated on different preparations and using different techniques. What is not yet clear is the underlying mechanism, as this result could be explained either through an increased Ca2+ influx or because of a deficit in the Ca2+ buffering/clearance systems. It is conceivable that these prolonged Ca2+ signals may exert a local excitotoxic effect, removing preferentially the most active synapses. Uncovering of the role of Ca2+ in the synaptic function of the aged brain presents an exciting challenge for all those involved in the neurobiology of the senescent CNS.
Fos expression in the midbrain periaqueductal grey after trigeminovascular stimulation
Authors: HOSKIN KAREN L. , BULMER DAVID C. E. , LASALANDRA MICHELE , JONKMAN ANJA , GOADSBY PETER J.
Published: March 2003

There is an accumulating body of evidence suggesting that the periaqueductal grey (PAG) is involved in the pathophysiology of migraine. Positron emission tomography (PET) studies in humans have shown that the caudal ventrolateral midbrain, encompassing the ventrolateral PAG, has activations during migraine attacks. The PAG may well be involved not only through the descending modulation of nociceptive afferent information, but also by its ascending projections to the pain processing centres of the thalamus. In this study the intranuclear oncogene protein Fos was used to mark cell activation in the PAG following stimulation of the trigeminally‐innervated superior sagittal sinus (SSS) in both cats and in nonhuman primates (Macaca nemestrina). Fos expression in the PAG increased following stimulation to a median of 242 cells (interquartile range 236–272) in the cat and 155 cells (range 104–203) in the monkey, compared with control levels of 35 cells (21–50) and 26 cells (18–33), respectively. Activation was predominantly in the ventrolateral area of the caudal PAG suggesting that the PAG is involved following trigeminally‐evoked craniovascular pain.
Evidence of neuroanatomical connection between the superior cervical ganglion and hypoglossal nerve in the hamster as revealed by tract‐tracing and degeneration methods
Authors: TSENG CHI‐YU , LUE JUNE‐HORNG , LEE SHIH‐HSIUNG , WEN CHEN‐YUAN , SHIEH JENG‐YUNG
Published: March 2003

Previous studies have shown the existence of a sympathetic component in some cranial nerves including the hypoglossal nerve. In this study, the horseradish peroxidase (HRP) tract‐tracing retrograde technique and experimental degeneration method were used to elucidate the possible neuroanatomical relationship between the superior cervical ganglion (SCG) and the hypoglossal nerve of hamsters. About 10% of the SCG principal neurons were HRP positive following the tracer application to the trunk of hypoglossal nerve. Most of the HRP‐labelled neurons were multipolar and were randomly distributed in the ganglion. When HRP was injected into the medial branch of the hypoglossal nerve, some of the SCG neurons were labelled, but they were not detected when HRP was injected into the lateral branch. The present findings suggest that postganglionic sympathetic fibres from the SCG may travel along the hypoglossal nerve trunk via its medial branch to terminate in visceral targets such as the intralingual glands. By electron microscopy, the HRP reaction product was localised in the neuronal somata and numerous unmyelinated fibres in the SCG. In addition, HRP‐labelled axon profiles considered to be the collateral branches of the principal neurons contained numerous clear round and a few dense core vesicles. Besides the above, some HRP‐labelled small myelinated fibres, considered to be visceral afferents, were also present. Results of experimental degeneration following the severance of the hypoglossal nerve showed the presence of degenerating neuronal elements both in the hypoglossal nucleus and the SCG. This confirms that the hypoglossal nerve contains sympathetic component from the SCG which may be involved in regulation of the autonomic function of the tongue.
Neural crest patterning and the evolution of the jaw
Authors: KIMMEL CHARLES B. , MILLER CRAIG T. , KEYNES ROGER J.
Published: March 2003

abstract

Here we present ideas connecting the behaviour of the cranial neural crest during development with the venerable, perhaps incorrect, view that gill‐supporting cartilages of an ancient agnathan evolved into the skeleton of an early gnathostome's jaw. We discuss the pattern of migration of the cranial neural crest ectomesenchyme in zebrafish, along with the subsequent arrangement of postmigratory crest and head mesoderm in the nascent pharyngeal segments (branchiomeres), in diverse gnathostomes and in lampreys. These characteristics provide for a plausible von Baerian explanation for the problematic inside‐outside change in topology of the gills and their supports between these 2 major groups of vertebrates. We consider it likely that the jaw supports did indeed arise from branchiomeric cartilages.
Derivation of the mammalian skull vault
Authors: MORRISS‐KAY GILLIAN M.
Published: March 2003

abstract

This review describes the evolutionary history of the mammalian skull vault as a basis for understanding its complex structure. Current information on the developmental tissue origins of the skull vault bones (mesoderm and neural crest) is assessed for mammals and other tetrapods. This information is discussed in the context of evolutionary changes in the proportions of the skull vault bones at the sarcopterygiantetrapod transition. The dual tissue origin of the skull vault is considered in relation to the molecular mechanisms underlying osteogenic cell proliferation and differentiation in the sutural growth centres and in the proportionate contributions of different sutures to skull growth.
Frequency variations of discrete cranial traits in major human populations. III. Hyperostotic variations
Authors: HANIHARA TSUNEHIKO , ISHIDA HAJIME
Published: March 2003

Seven discrete cranial traits usually categorised as hyperostotic characters, the medial palatine canal, hypoglossal canal bridging, precondylar tubercle, condylus tertius, jugular foramen bridging, auditory exostosis, and mylohyoid bridging were investigated in 81 major human population samples from around the world. Significant asymmetric occurrences of the bilateral traits were detected in the medial palatine canal and jugular foramen bridging in several samples. Significant intertrait associations were found between some pairs of the traits, but not consistently across the large geographical samples. The auditory exostosis showed a predominant occurrence in males. With the exception of the auditory exostosis and mylohyoid bridging in a few samples, significant sex differences were slight. The frequency distributions of the traits (except for the auditory exostosis) showed some interregional clinality and intraregional discontinuity, suggesting that genetic drift could have contributed to the observed pattern of variation.
Surgical anatomy of the sural and superficial fibular nerves with an emphasis on the approach to the lateral malleolus
Authors: SOLOMON L. B. , FERRIS L. , TEDMAN R. , HENNEBERG M.
Published: March 2003

The aim of this study was to investigate the risk and to analyse the significance of laceration of the sural and superficial fibular nerves during the surgical approach to the lateral malleolus. The sural and the superficial fibular nerves, and their branches were dissected under ×3 magnifying lenses in 68 embalmed leg‐ankle‐foot specimens. The specimens were measured, drawn and photographed. In 35% of specimens the superficial fibular nerve branched before piercing the crural fascia, and in all these specimens the medial dorsal cutaneous nerve of the foot was located in the anterior compartment while the intermediate dorsal cutaneous nerve of the foot was located in the lateral compartment. In 35% of specimens the intermediate dorsal cutaneous nerve of the foot was absent or did not innervate any toe. The deep part of the superficial fibular nerve was in contact with the intermuscular septum. Its superficial part was parallel with the lateral malleolus when the nerve pierced the fascia more proximally and oblique to the lateral malleolus when the nerve pierced the fascia distally. In one case the intermediate dorsal cutaneous nerve of the foot was in danger of laceration during a subcutaneous incision to the lateral malleolus. In 7 cases (10%) the sural nerve overlapped or was tangent to the tip of the malleolus. Malleolar nerve branches were identified in 76% of the cases (in 28% from both sources). The sural nerve supplies the lateral 5 dorsal digital nerves in 40% of cases. Our study indicates that during the approach to the lateral malleolus there is a high risk of laceration of malleolar branches from both the sural and the superficial fibular nerves. There is less risk of damage to the main trunk of these nerves, but the 10% chance of laceration of sural nerve at the tip of the malleolus is significant. As the sural nerve supplies the superficial innervation to the lateral half of the foot and toes in 40% of cases, the risk of its laceration is even more important than indicated by the common anatomical teaching.
Expression of VEGF121 and VEGF165 in hypertrophic chondrocytes of the human growth plate and epiphyseal cartilage
Authors: Petersen Wolf , Tsokos Michael , Pufe Thomas
Published: March 2003

Vascular endothelial growth factor (VEGF) plays an important role during endochondral bone formation in hypertrophic cartilage remodelling. We examined VEGF and VEGF receptor expression in tibiae from fetuses, newborns and children immunohistochemically. Expression of mRNA for the different VEGF splice forms and for VEGF receptors KDR and FLT‐1 was analysed by reverse transcription‐polymerase chain reaction (RT‐PCR). VEGF could be immunolocalized intracellularly in the hypertrophic chondrocytes of the growth plate and in the chondrocytes around cartilage canals of the epiphysis, respectively. The resting zone and the proliferative zone of the growth plate were VEGF‐negative. In cartilage samples of all growth plates analysed, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. RT‐PCR for VEGF mRNA of normal hyaline cartilage was negative. At vessels growing into the hypertrophic cartilage FLT‐1 (VEGFR‐1) and KDR (VGEFR‐2) could be visualized. Reverse transcription‐polymerase chain reaction (RT‐PCR) substantiated the results regarding FLT‐1 and KDR expression. The results of our study suggest that the splice forms VEGF121 and VEGF165 and the receptors KDR and FLT‐1 of the known angiogenetic peptide VEGF play a role in process of endochondral ossification.
Uptake of 109Cd by roots and hyphae of a Glomus mosseae/ Trifolium subterraneum mycorrhiza from soil amended with high and low concentrations of cadmium
Authors: JONER E. J. , LEYVAL C.
Published: March 2003

Subterranean clover (Trifolium subterraneum L.) in symbiosis with Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe was grown in compartmented pots. Side compartments were filled with soil where recently added (1 wk) radio‐labelled cadmium (Cd) at three levels of non‐labelled Cd could be accessed by either roots or arbuscular mycorrhizal hyphae. All treatments were replicated with non‐mycorrhizal plants. After a growth period of 52 d roots and shoots were analysed for 109Cd, and lengths of roots and hyphae in respective labelled compartments determined. Cadmium uptake by roots was not significantly influenced by the mycorrhizal status of the plant. Uptake of Cd from hyphal compartments was higher in mycorrhizal than in non‐mycorrhizal plants, corresponding to 96, 127 and 131% of that in non‐mycorrhizal plants when 1, 10 and 100 mg Cd kg−1 was added, respectively. A large proportion of the increased Cd content of mycorrhizal plants was sequestered in the roots. It is concluded that extraradical hyphae of AM fungi can transport Cd from soil to plants, but that transfer from fungus to plant is restricted due to fungal immobilization. No reduction of hyphal growth into soil with up to 20 mg extractable Cd kg−1 was observed.
Interactions between plant‐growth‐promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi and Rhizobium spp. in the rhizosphere of Anthyllis cytisoides, a model legume for revegetation in mediterranean semi‐arid ecosystems
Authors: REQUENA N. , JIMENEZ I. , TORO M. , BAREA J. M.
Published: March 2003

Arbuscular mycorrhizal (AM) fungi, Rhizobium bacteria and plant‐growth‐promoting rhizobacteria (PGPR) were isolated from a representative area of a desertified semi‐arid ecosystem in the south‐east of Spain. Microbial isolates were characterized and screened for effectiveness by a single‐inoculation trial in soil microcosms. Anthyllis cytisoides L., a mycotrophic pioneer legume, dominant in the target mediterranean ecosystem, was the test plant. Several microbial cultures from existing collections were also included in the screening process. Two AM fungi (Glomus coronatum, native, and Glomus intraradices. exotic), two Rhizobium bacteria (NR4 and NR9, both native) and two PGPR (A2, native, and E, exotic) were selected. A further screening for the appropriate double and triple combinations of microbial inoculants was then performed. The parameters evaluated were biomass accumulation and allocation, N and P uptake, N2‐fixation (15N) and specific root length. Overall, G. coronatum, native in the field site was more effective than the exotic G. intraradices in co‐inoculation treatments. In general, our results support the importance of physiological and genetic adaptation of microbes to the whole environment, thus local isolates must be involved. Many microbial combinations were effective in improving either plant development, nutrient uptake, N2‐fixation or root system quality. Selective and specific functional compatibility relationships in plant response between the microbial inoculants, were observed. Despite the difficulty of selecting a multifunctional microbial inoculum, appropriate microbial combinations can be recommended for a given biotechnological input related to improvement of plant performance. This could be exploited in nursery production of target plant species endowed with optimized rhizosphere/mycorrhizosphere systems that can be tailored to help plants to establish and survive in nutrient‐deficient, degraded habitats. The relevance of this microbial‐based approach in the context of a reclamation strategy addressed to environmental sustainability purposes is discussed.
Genetic approaches in plant physiology
Authors: KOORNNEEF M. , ALONSO‐BLANCO C. , PEETERS A. J. M.
Published: March 2003

summary

The use of genetics in plant biology aims at the physiological and molecular genetical characterization of the phenotypic variation for the trait under study. Efficient mutant and gene isolation procedures have been developed for a number of plant models such as Arabidopsis thaliana. For this, the map position of the genes and insertion mutagenesis are used. The latter also allows the characterization of genes that are not easily recognized in mutant approaches, by using enhancer or gene‐trapping procedures and reverse genetics. In addition to mutants, natural variation present among wild and cultivated varieties of a species provides an important source of genetic variation. The use of molecular markers, advanced mapping populations and specific cytogenetic stocks in case of polyploids, enables a detailed characterization of such natural variation even when it is of a quantitative and polygenic nature. Examples of the various genetic approaches are given.
Repeated sequence markers in pea (Pisum sativum)
Authors: TURNER L. , ELLIS T. H. N.
Published: March 2003

summary

Multiple‐marker techniques based on PCR are highly informative in genetic analysis. The bulk of many genomes is comprised of repeated sequences, and thus anonymous markers derived from genomic DNA are likely to correspond to repeated DNA sequences. Here we show that repeated‐sequence‐derived markers can provide information similar in quality to that of other PCR‐based markers. Presumably this reflects the abundance of this repeat type in anonymous PCR markers such as RAPDs or AFLPs.
Seed/cotyledon size and nutrient content play a major role in early performance of species on nutrient‐poor soils
Authors: MILBERG PER , LAMONT BYRON B.
Published: March 2003

summary

We examined the importance of seed size in the early establishment of seedlings of four cotyledonous species restricted to nutrient‐impoverished soils in south‐western Australia. Experimentally removing cotyledons from seedlings increased mortality and reduced root‐penetration, growth rate and final weight of plants after 12 wk, in proportion to seed size. The impact of removal of the cotyledons was least in the smallest‐seeded, Eucalyptus loxophleba Benth., grown in the more fertile of two soils, and greatest in the largest‐seeded, Hakea psilorrhyncha R. M. Barker, whose growth was otherwise unaffected by soil type. In the smallest‐seeded species, cotyledon content of most mineral nutrients increased over time, especially in the more fertile soil, while chlorophyll content showed some decrease by the end of the experiment. In the other species, most nutrients (especially N, P, K and Cu in the less fertile soil) were translocated from the cotyledons to the growing plant, and chlorophyll content declined markedly. The translocated N, P, K, Mg and Cu in these species made up a substantial part of the total plant content by 12 wk after germination, while total Ca and Fe tended to increase in the cotyledons via substantial soil uptake. The results indicate, contrary to reports for some other species, that the cotyledons have an important nutritional function in the early establishment of seedlings in these species. The results also show that, in the larger‐seeded species, young seedlings rely to a greater extent on nutrient support from the cotyledons than from the soil. We propose that large seeds might be an adaptation for enhancing establishment in nutrient‐poor soils.
Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses
Authors: BUSSOTTI F. , GRAVANO E. , GROSSONI P. , TANI C.
Published: March 2003

Sclerophylly and synthesis of phenolic compounds are active responses of plants subjected to environmental stress (drought, low nutrient supply, u.v.‐B radiation, ozone). Here we describe the morphological and histochemical alterations occurring in field‐grown leaves of Fagus sylvatica L. from three sites located along an ecological gradient: from a site in cool and protected conditions to one located on a mountain ridge, where the trees grow on a thin layer of soil and are exposed to the wind and to intense solar radiation in summer. The morphological data show that, as the ecological conditions of the stand worsen, individual leaf surface decreases, while the thickness of the leaves and their specific d. wt (i.e. d. wt per unit leaf area) increases. Histochemical and ultrastructural tests show a marked increase of phenolics during the course of the year. These substances, present primarily in the leaves of trees growing in stress conditions, have been identified mainly as tannins. They accumulate in the vacuoles, especially those of the upper epidermal layer and the palisade mesophyll; at a later stage they appear to be solubilized in the cytoplasm and retranslocated, eventually impregnating the outer wall of the epidermal cells amidst the cellulose fibrils, where they cluster together and form an electron‐opaque layer between the wall and the cuticle. Observation of the epidermal cells also reveals that the outer cell wall is thicker. The paper discusses the roles of secondary metabolites in protection and detoxification processes; the possible ecological significance of these alterations in the ecophysiology of beech trees.
Fungal infections of the phytoplankton: seasonality, minimal host density, and specificity in a mesotrophic lake
Authors: HOLFELD HARALD
Published: March 2003

Phytoplankton infections by fungal parasites in the upper, mixed layer of a mesotrophic northern temperate lake were analysed according to the following parameters: host and parasite species, host population density and prevalence of infection, resting spore formation by the parasite, and the lowest host density at which parasites appeared. The phytoplankton taxa recorded included the Cyanobacteria, Dinomastigota, Chrysophyceae, Bacillariophyceae, Chlorophyceae, Cryptophyceae and Haptophyceae, but infection was never found in the last two classes. The parasites belonged almost exclusively to the monocentric Chytridiomycetes. Fungal epidemics occurred at all times of the year. Parasites appeared at population densities as low as about 1 cell ml−1 in some host species, with infection prevalence sometimes exceeding 80%. The proportion of the total phytoplankton biovolume infected by fungi was usually much <1%, but occasionally reached 10%. Parasitism proved to be highly species‐specific, with one parasite species usually infecting only one host species. In the case of Zygorhizidium planktonicum, which infected both Asterionella formosa and Synedra acus, there is evidence that two species‐specific formae speciales, each infecting only one of these two host species, are present in the lake.
The role of DNA methylation on nuclear and cell differentiation in the filamentous caulonema of the moss Funaria hygrometrica
Authors: KINGHAM KEITH I. , DUCKETT JEFFREY G. , GAZDOVA BLANKA , KOVARIK ALES , BEZDEK MILAN , LEITCH ANDREW R.
Published: March 2003

This paper describes the effects of hypomethylation with 5‐azacytidine (5azaC) and dihydroxypropyladenine (DHPA) on protonemata of the moss Funaria hygrometrica Hedw. Following treatment with 5azaC or DHPA, hypomethylation of the EcoR II (CCA(T)GG) and Pst I (CTGCAG) sites in ribosomal DNA (rDNA) was confirmed using restriction enzyme analysis and Southern hybridization. Hypomethylation of the genome had profound effects on protonemal differentiation. Whilst apical cell organization and cell dimensions and shape remained unchanged, there was a marked retardation in both cytoplasmic and nuclear differentiation. Developmental abnormalities included: late and erratic side branch formation, some loss of the distinction between chloronema and caulonema, formation of aberrant buds, and loss of the potential to form brood and tmema cells after 5azaC treatment which in general had more profound effects than DHPA. Cytologically, caulonema cells were less highly polarized or unpolarized, and tended to retain small round chloroplasts, whilst nuclei in the hypomethylated protonema endoreduplicated to lower levels and tended to remain more spherical. Increased nucleolar volumes and loss of intranucleolar rDNA heterochromatin following hypomethylation might be the result of increased transcriptional activity of ribosomal RNA (rRNA) genes and drug‐induced DNA decondensation, respectively. Growing hypomethylated protonema at 25°C induced extremely atypical cells and development. This temperature sensitivity and aberrations in development overall can be attributed to changes in the normal patterns of gene expression brought about by hypomethylation of gene promoter or regulator regions.
Interactions between arbuscular mycorrhizal fungi and the hemiparasitic angiosperm Rhinanthus minor during co‐infection of a host
Authors: DAVIES D. M. , GRAVES J. D.
Published: March 2003

The outcome of dual infection of the grass Lolium perenne L. by arbuscular mycorrhizal (AM) fungi and the parasitic angiosperm Rhinanthus minor L. was investigated in a glasshouse study. Colonization of L. perenne roots by AM fungi was significantly reduced by the presence of R. minor, as was host growth which fell by 44–51%. It was concluded that these two responses were linked, with AM colonization declining in response to the reduction in availability of host carbon. Parasite growth and reproductive output rose by 58% and 47% respectively when the hosts were mycorrhizal. These trends were unrelated to the attachment success of the parasite, but were accompanied by a significant increase in the formation of secondary haustoria. The benefits afforded the parasite when the hosts were mycorrhizal were attributed to increased carbon and nutrient flux resulting from alternations in sink strength. Host responses to parasitism and mycorrhizal colonization were not affected by the interaction between the two symbionts. However, the suggestion is made that the interaction between the AM fungi and parasite might have long‐term ecological implications for the host species via its impact on parasite fecundity.
Biomass, reproductive output, and physiological responses of rapid‐cycling Brassica (Brassica rapa) to ozone and modified root temperature
Authors: KLEIER CATHERINE , FARNSWORTH BLAKE , WINNER WILLIAM
Published: March 2003

Brassica rapa L. (rapid‐cycling Brassica), was grown in environmentally controlled chambers to determine the interactive effects of ozone (O3) and increased root temperature (RT) on biomass, reproductive output, and photosynthesis. Plants were grown with or without an average treatment of 63 ppb O3. RT treatments were 13°C (LRT) and 18°C (HRT). Air temperatures were 25°C/15°C day/night for all RT treatments.

Ozone affected plant biomass more than did root temperature. Plants in O3 had significantly smaller total plant d. wt, shoot weight, leaf weight, leaf area and leaf number than plants grown without O3. LRT plants tended to have slightly smaller total plant d. wt, shoot weight, root weight, leaf weight, leaf area, and leaf number than HRT plants. For all variables, LRT plants grown in O3 had the smallest biomass, and plants grown in HRT without O3 had the largest biomass.

Ozone reduced both fruit weight and fruit number; LRT also reduced fruit weight but had no effect on fruit number. Ozone reduced photosynthesis but RT had no effect. Conductance and internal CO2 were unaffected by O3 or RT.

These studies indicate that plant growth with LRT might be more reduced in the presence of O3 than growth in plants with HRT, which might be able to compensate for O3‐caused reductions in photosynthesis to avoid decreased biomass and reproductive output.
Field evidence for the carbon cost of citrus mycorrhizas
Authors: GRAHAM JAMES H. , EISSENSTAT DAVID M.
Published: March 2003

Mycorrhizas can produce negative crop responses when phosphorus availability is sufficient in agricultural soils because the fungi are of no benefit in nutrient acquisition yet continue to colonize roots and invoke parasitic costs. Benomyl fungicide was used to test this prediction in the field by limiting mycorrhizal colonization of 2‐yr‐old Valencia orange trees (Citrus sinensis (L.) Osbeck) on four rootstocks of varying mycorrhizal dependency in P‐deficient soil fertilized with and without phosphate. No known fungal pathogens of citrus roots controlled by benomyl were present on the trees or in the field soil. Young trees with or without P fertilization and benomyl treatment remained sufficient in P (0·10% leaf P) throughout the 27‐month study. Root zone drenches of benomyl reduced mycorrhizal colonization and leaf P status of Valencia orange trees on the three slower‐growing rootstocks, trifoliate orange (Poncirus trifoliata (L. ) Raf.), Swingle citrumelo (Citrus paradisi Macf.×P. trifoliata) and sour orange (Citrus aurantium L.), for the duration of three growing seasons. Benomyl affected root colonization and P status of trees on the faster‐growing rootstock, Volkamer lemon (Citrus volkameriana Tan. and Pasq.), less than for trees on the slower‐growing rootstocks and the effects were sustained for only two seasons. The shorter duration of benomyl effect for trees on Volkamer lemon rootstock compared with the slower‐growing rootstocks was explained by the loss of inhibition of mycorrhizal activity when roots grew out of the drench zone and mycorrhizas were no longer in direct contact with the fungicide. Benomyl treatment increased growth rate of Valencia orange on the slow‐growing rootstocks from 5 to 17% after three seasons, and from 2 to 9% on Volkamer lemon rootstock after two seasons compared with the non‐benomyl treated trees. The benomyl effect was attributed to reduction of costs of root colonization over time, and consequently, a greater availability of carbon assimilate for shoot growth of trees. Since mycorrhizal fungi are ubiquitous in fertilized agricultural soils and obligate biotrophs on the roots of most crop species, these results indicate a need to further investigate whether negative growth responses of P‐sufficient plants in the field occur because mycorrhizal fungi are no longer behaving as mutualists.
Spatial distribution of chitinases and β‐1,3‐glucanase transcripts in bean arbuscular mycorrhizal roots under low and high soil phosphate conditions
Authors: LAMBAIS MARCIO R. , MEHDY MONA C.
Published: March 2003

Arbuscular mycorrhizal (AM) fungi extensively colonize the root cortex under low‐soil‐phosphate (P) conditions, whereas infection is limited under high‐P conditions. Fungal growth under both P conditions might be influenced by plant defence‐related gene expression. In this study, we used in situ hybridization methods to compare the cellular localization of three defence‐related mRNAs in non‐infected bean roots and in relation to fungal infection units. In non‐infected and infected roots, mRNAs encoding acidic and basic endochitinases were generally most abundant in the vascular cylinder. High‐P‐grown mycorrhizal roots showed localized accumulation of the acidic endochitinase mRNA in cortical cells containing arbuscules and in their immediate vicinity (one to five cell layers). The pattern of accumulation of the basic endochitinase mRNA was not affected by P or AM fungal infection. At the low P concentration, the β‐1,3‐glucanase mRNA accumulated predominantly in the vascular cylinder of non‐infected roots. Suppression of β‐1,3‐glucanase mRNA accumulation in these tissues was observed in non‐infected roots at the high‐P and in mycorrhizal roots at both P concentrations. The observed suppression extends at least several mm from fungal infection units, characterizing a systemic effect. Beta‐1,3‐glucanase mRNA accumulated also around a number of cortical cells containing arbuscules only at the low P concentration. The localized accumulations of the endochitinase and β‐1,3‐glucanase mRNAs suggest that the encoded proteins might be involved in the control of intraradical fungal growth.
The development of blackcurrant fruit from flower to maturity: a comparative study by 3D nuclear magnetic resonance (NMR) micro‐imaging and conventional histology
Authors: GLIDEWELL S. M. , WILLIAMSON B. , DUNCAN G. H. , CHUDEK J. A. , HUNTER G.
Published: March 2003

The development of fruits of blackcurrant (Ribes nigrum) cv. Ben Alder from flower to maturity was studied non‐invasively by nuclear magnetic resonance (NMR) microscopy, using attached and detached fruits, and the images were compared with those from low temperature scanning electron microscopy (LTSEM) and conventional resin histology. The NMR images derived from 2‐D and 3‐D datasets showed the previously unreported growth of arillar tissues to the extent that they almost completely occlude the locular cavity, but LTSEM and resin histology revealed that no fusion occurs between the arillar tissues and the gelatinous sheath surrounding each seed, or between the arillar tissues and the endocarp. The discontinuities between these tissues cause magnetic inhomogenities which result in these structures being clearly resolved by gradient echo imaging sequences. During seed maturation the endosperm changed from high (bright) to low (dark) signal intensity as lipid reserves formed and solidified, whereas the gelatinous sheath had high signal intensity throughout maturation. The high lipid concentration in the seed was manifested by chemical shift effects in the images and the increasing viscosity of the endosperm was reflected in the decrease in spin–lattice (T1) relaxation times. The funiculi, throughout development of seeds, appeared in NMR images with low signal intensity and 3‐D surface‐rendered reconstructions illustrated the complexity of the spatial array of seeds and funiculi arising from parietal placentas within the loculus. All other vascular tissues in the pericarp and placentas were resolved as a small bright core surrounded by a dark region, within a matrix of moderate signal intensity. Conventional microscopical studies then showed that the bright core discernible by NMR imaging encompassed an entire vascular bundle whereas the darker surrounding region represented small parenchyma cells with pronounced intercellular gas spaces. Other regions of the pericarp which included extremely large parenchyma cells, however, had few intercellular spaces and consequently gave rise to brighter regions of the image.
The effects of quantity and duration of simulated pollutant nitrogen deposition on root‐surface phosphatase activities in calcareous and acid grasslands: a bioassay approach
Authors: JOHNSON D. , LEAKE J. R. , LEE J. A.
Published: March 2003

A field and laboratory based bioassay has been developed to investigate the effects of the quantity and duration of simulated pollutant nitrogen (N) deposition on root‐surface phosphomonoesterase (PME) activities in calcareous and acid grasslands. Seedlings of Plantago lanceolata were transplanted to a calcareous grassland and Agrostis capillaris seedlings were grown in microcosms containing soil from an acid grassland that had received either 7 yr (long‐term) N additions or 18 months (short‐term) N and phosphorus (P) additions. The bioassay revealed that short‐term N treatments had little effect on the enzyme activity, whereas long‐term N additions significantly increased PME activity within 7 d of transplanting into the field plots. Root‐surface PME activity of A. capillaris was significantly reduced in soil that received additions of P. In the plots receiving long‐term additions of N, a strong relationship was observed between extractable soil ammonium and root‐surface PME activity. Soil ammonium concentrations accounted for 67% of the variation in PME activity of P. lanceolata in the calcareous grassland, and 86% of the variation in PME activity of A. capillaris in the acid grassland. These results provide evidence that N deposition may have considerable effects on the demand and turnover of P in ecosystems that are approaching or have reached N saturation.
Effects of mycorrhizal colonization on biomass production and nitrogen fixation of black locust (Robinia pseudoacacia) seedlings grown under elevated atmospheric carbon dioxide
Authors: OLESNIEWICZ KIRSTEN S. , THOMAS RICHARD B.
Published: March 2003

Interactive effects of elevated atmospheric CO2 and arbuscular mycorrhizal (AM) fungi on biomass production and N2 fixation were investigated using black locust (Robinia pseudoacacia). Seedlings were grown in growth chambers maintained at either 350 μmol mol−1 or 710 μmol mol−1 CO2. Seedlings were inoculated with Rhizobium spp. and were grown with or without AM fungi. The 15N isotope dilution method was used to determine N source partitioning between N2 fixation and inorganic fertilizer uptake. Elevated atmospheric CO2 significantly increased the percentage of fine roots that were colonized by AM fungi. Mycorrhizal seedlings grown under elevated CO2 had the greatest overall plant biomass production, nodulation, N and P content, and root N absorption. Additionally, elevated CO2 levels enhanced nodule and root mass production, as well as N2 fixation rates, of non‐
mycorrhizal seedlings. However, the relative response of biomass production to CO2 enrichment was greater in non‐mycorrhizal seedlings than in mycorrhizal seedlings. This study provides strong evidence that arbuscular mycorrhizal fungi play an important role in the extent to which plant nutrition of symbiotic N2‐fixing tree species is affected by enriched atmospheric CO2.
Emissions, biogenesis and metabolic utilization of chloromethane by tubers of the potato (Solanum tuberosum)
Authors: HARPER DAVID B. , HARVEY BARBARA M. R. , JEFFERS MAURICE R. , KENNEDY JAMES T.
Published: March 2003

CH3Cl emissions by freshly harvested tubers of 61 potato cultivars ranged from less than 4 to 650 ng g−1 f. wt d−1. In experiments with Anna, the cultivar displaying the highest release rate, maximum emission of CH3Cl occurred at 20°C but the rate diminished after 48 h, a decrease due in part to inhibition of CH3Cl release by the accumulation of CH3Cl in the headspace. In 1995 and 1996, CH3Cl emission by tubers was first detectable 6 wk before the normal harvest date. If tubers were stored at 20°C immediately following harvest, release attained a maximum of 350 ng g−1 f. wt d−1 about 4 d after harvest, falling to less than 4 ng g−1 f. wt d−1 within 3 wk of harvest. On storage at 6°C post‐harvest, maximum release of CH3Cl (c. 600 ng g−1) was delayed until 5 wk after harvest and release fell below 4 ng g−1 f. wt d−1 after 200 d. Release of CH3Cl was not significantly affected by cutting or bruising tuber tissue, and CH3Cl biosynthesis occurred in both core and superficial tissues of the tuber. The S‐methyl group of either L‐ or D‐methionine acted as a precursor of CH3Cl in sliced tubers, but the methylating system was specific for Cl−. An isotope dilution technique using C2H3Cl demonstrated that the amount of CH3Cl metabolized by the intact tuber was approximately 36% of the net release. However, investigations with 14CH3Cl showed that only a small proportion (7%) of the CH3Cl metabolized was fixed in involatile form in the tuber. In both skin and core tissues, fixed 14C was located primarily (80%) in the fraction soluble in phosphate buffer, but the specific activity of skin tissue was about twice that of core tissue. Autoradiography demonstrated that 14C fixation in the tuber was greatest within the lenticels, possibly indicating a microflora adapted to use the locally high concentrations of CH3Cl. Significant 14C fixation was also associated with the periderm but was not attributable to labelling of the O‐methyl groups of the phenolic components of suberin. Within the core of the tuber, 14C fixation was located primarily in the phloem, pith and medullary rays.
Mathematical modelling of morphogenesis in fungi: a key role for curvature compensation (‘autotropism’) in the local curvature distribution model
Authors: MEŠKAUSKAS AUDRIUS , NOVAK FRAZER LILYANN , MOORE DAVID
Published: March 2003

The assumption that the mushroom stem has the ability to undergo autonomic straightening enables a mathematical model to be written that accurately mimics the gravitropic reaction of the stems of Coprinus cinereus. The straightening mechanism is called curvature compensation here, but is equivalent to the ‘autotropism’ that often accompanies the gravitropic reactions of axial organs in plants. In the consequently revised local curvature distribution model, local bending rate is determined by the difference between the ‘bending signal’ (generated by gravitropic signal perception systems) and the ‘straightening signal’ (proportional to the local curvature at the given point). The model describes gravitropic stem bending in the standard assay with great accuracy but has the virtue of operating well outside the experimental data set used in its derivation. It is shown, for example, that the mathematical model can be fitted to the gravitropic reactions of stems treated with metabolic inhibitors by a change of parameters that parallel the independently derived physiological interpretation of inhibitor action. The revised local curvature distribution model promises to be a predictive tool in the further analysis of gravitropism in mushrooms.