On the role of dynamic atmosphere–vegetation interactions under increasing radiative forcing

• 1 A zero‐dimensional model of local atmosphere–vegetation interaction is presented. The model includes essentials of water related two‐way feedbacks, such as the influence of vegetation on evapotranspiration, and the impact of temperature and drought on biomass growth and mortality. The simple model serves as a framework for the preliminary investigation of vegetation related feedbacks under climate change scenarios.
  • 2 Model simulations for a mid‐latitude forest area for an increasing external forcing indicate a transient growth of biomass up to a critical forcing, where drought stress begins to dominate the response. Beyond, biomass decreases, reinforced by the reduced evapotranspiration of a diminished vegetation, leading to an additional temperature increase (biomass–evapotranspiration feedback).
    • 3 The implementation of an additional feedback loop based on the hypothesis that drought stress implies not only a reduction in above‐ground biomass, but also a net reduction in roots and therefore a reduction of the amount of water accessible to the plants for transpiration, leads to the occurrence of a second stable state in the atmosphere–vegetation system. In the bistable regime, a moderate perturbation can trigger an abrupt change of state.
      • 4 The present conceptual investigations underline the importance of a dynamic vegetation subsystem in transient climate change, and stress in particular the possible role of feedbacks related to root dynamics.

     

Virus diseases of lupins

• I. INTRODUCTION
• II. APHID-TRANSMITTED VIRUSES

• (a) Potyvirus group

• (i) Bean yellow mosaic virus
• (ii) Clover yellow vein virus
• (iii) Bean common mosaic virus
• (iv) Peanut mottle virus
• (v) Bidens mottle virus

• (b) Cucumovirus group

• (i) Cucumber mosaic virus
• (ii) Peanut stunt virus

• (c) Alfalfa mosaic virus
• (d) Fabavirus group: broad bean wilt virus
• (e) Pea enation mosaic virus
• (f) Luteovirus group: soybean dwarf virus
• (g) Rhabdovirus group: lettuce necrotic yellows virus

• III. THRIPS-TRANSMITTED VIRUSES
• Tomato spotted wilt virus

• IV. NEMATODE-TRANSMITTED VIRUSES

• (a) Tobravirus group: pea early browning virus
• (b) Nepovirus group: tomato black ring virus

• V. VIRUS-LIKE DISEASES

• (a) Lupin leaf curl ‘virus’
• (b) ‘Lupin witches’ broom disease

• VI. CONTROL VII. CONCLUSIONS
• VII. CONCLUSIONS

     

Physical properties of the bovine encephalitogenic protein; molecular weight and conformation

Abstract— The highly basic encephalitogenic protein isolated from bovine spinal cord was studied by various physicochemical methods:

• 1 The molecular weight was determined by sedimentation equilibrium, by calculation from the data on sedimentation coefficients and intrinsic viscosities, by measurement of intrinsic viscosity in the presence of concentrated guanidine hydrochloride (according to the method of Tanford , Kawahara and Lapanie , 1967), and by exclusion chromatography on Sephadex G-100 columns. All values obtained were in good agreement and indicated a molecular weight of approximately 18,000–20,000.

• 2 Studies of sedimentation velocities in the presence and absence of 6 m -guanidine-HCl indicated that there was a significant difference in the values of sedimentation coefficients.

• 3 The same conditions were applied to the measurements of viscosity; the difference was small but significant. These findings and the magnitude of the intrinsic viscosity suggested that this protein was in a disordered configuration. From these data, it is concluded that the protein was apparently monodispersed, in the presence or absence of the denaturing agent. This protein behaved like a polyelectrolyte in neutral aqueous solution.

• 4 The measurements of optical rotatory dispersion also confirmed that this protein existed in a disordered configuration.

     

Temporal constancy in grasshopper assemblies (Orthoptera: Acrididae)

ABSTRACT.

• 1 Temporal constancy in the structure of grasshopper assemblies (about forty-five species each) from two types of North American grasslands was assessed; one site was followed 25 years and the other 7 years.
• 2 Densities and relative abundances varied but composition of assemblies based on ranks suggested significant structure when three or more species were included in the analysis.
• 3 Results compared favourably with other insect herbivore assemblies which have been examined; variability in population change was intermediate along the spectrum of organisms which have been studied.

     

On the Evolutionary Relationship in the Family Brassicaceae

• 1 The study gives the evaluation of the dissepimentum and gynophore for the establishment of the evolutionary relationship in the family Brassicaceae.

• 2 The genus Macropodium R. Br. represents an organizational degree. Different, divergently going younger evolutionary lines, developed from evolutionary lines leading to both present species.

     

Interstitial cells of Cajal,macrophages and mast cells in the gut musculature: morphology,distribution, spatial and possible functional interactions

• ? Introduction
• ? Identification of the cells
  • ‐ ICC
  • ‐ Macrophages
    • ‐ Activation
    • ‐ Identification
  • ‐ Mast cells
    • ‐ Activation
    • ‐ Identification
• ? Cell distribution
  • ‐ ICC in rodent gastrointestinal tract
  • ‐ ICC in human gastrointestinal tract
  • ‐ Macrophages in rodent gastrointestinal tract
  • ‐ Macrophages in human gastrointestinal tract
  • ‐ Mast cells in rodent gastrointestinal tract
  • ‐ Mast cells in human gastrointestinal tract
• ? Inflammation
  • ‐ Models of inflammation
    • ‐ LPS administration
    • ‐ Surgical anastomosis
    • ‐ Ileal obstruction
    • ‐ Post‐operative ileus
    • ‐ Helminth infections
  • ‐ Inflammatory bowel disease
  • ‐ Achalasia
• ? Diabetes mellitus
  • ‐ NOD/LtJ mice
  • ‐ STZ‐DM rats
• ? Conclusions

Interstitial cells of Cajal (ICC) are recognized as pacemaker cells for gastrointestinal movement and are suggested to be mediators of neuromuscular transmission. Intestinal motility disturbances are often associated with a reduced number of ICC and/or ultrastructural damage, sometimes associated with immune cells. Macrophages and mast cells in the intestinal muscularis externa of rodents can be found in close spatial contact with ICC. Macrophages are a constant and regularly distributed cell population in the serosa and at the level of Auerbach’s plexus (AP). In human colon, ICC are in close contact with macrophages at the level of AP, suggesting functional interaction. It has therefore been proposed that ICC and macrophages interact. Macrophages and mast cells are considered to play important roles in the innate immune defence by producing pro‐inflammatory mediators during classical activation, which may in itself result in damage to the tissue. They also take part in alternative activation which is associated with anti‐inflammatory mediators, tissue remodelling and homeostasis, cancer, helminth infections and immunophenotype switch. ICC become damaged under various circumstances – surgical resection, possibly post‐operative ileus in rodents – where innate activation takes place, and in helminth infections – where alternative activation takes place. During alternative activation the muscularis macrophage can switch phenotype resulting in up‐regulation of F4/80 and the mannose receptor. In more chronic conditions such as Crohn’s disease and achalasia, ICC and mast cells develop close spatial contacts and piecemeal degranulation is possibly triggered.     

Climatic and biotic controls on annual carbon storage in Amazonian ecosystems

• 1 The role of undisturbed tropical land ecosystems in the global carbon budget is not well understood. It has been suggested that interannual climate variability can affect the capacity of these ecosystems to store carbon in the short term. In this paper, we use a transient version of the Terrestrial Ecosystem Model (TEM) to estimate annual carbon storage in undisturbed Amazonian ecosystems during the period 1980–94, and to understand the underlying causes of the year‐to‐year variations in net carbon storage for this region.
  • 2 We estimate that the total carbon storage in the undisturbed ecosystems of the Amazon Basin in 1980 was 127.6 Pg C, with about 94.3 Pg C in vegetation and 33.3 Pg C in the reactive pool of soil organic carbon. About 83% of the total carbon storage occurred in tropical evergreen forests. Based on our model’s results, we estimate that, over the past 15 years, the total carbon storage has increased by 3.1 Pg C (+ 2%), with a 1.9‐Pg C (+2%) increase in vegetation carbon and a 1.2‐Pg C (+4%) increase in reactive soil organic carbon. The modelled results indicate that the largest relative changes in net carbon storage have occurred in tropical deciduous forests, but that the largest absolute changes in net carbon storage have occurred in the moist and wet forests of the Basin.
    • 3 Our results show that the strength of interannual variations in net carbon storage of undisturbed ecosystems in the Amazon Basin varies from a carbon source of 0.2 Pg C/year to a carbon sink of 0.7 Pg C/year. Precipitation, especially the amount received during the drier months, appears to be a major controller of annual net carbon storage in the Amazon Basin. Our analysis indicates further that changes in precipitation combine with changes in temperature to affect net carbon storage through influencing soil moisture and nutrient availability.
      • 4 On average, our results suggest that the undisturbed Amazonian ecosystems accumulated 0.2 Pg C/year as a result of climate variability and increasing atmospheric CO₂ over the study period. This amount is large enough to have compensated for most of the carbon losses associated with tropical deforestation in the Amazon during the same period.
        • 5 Comparisons with empirical data indicate that climate variability and CO₂ fertilization explain most of the variation in net carbon storage for the undisturbed ecosystems. Our analyses suggest that assessment of the regional carbon budget in the tropics should be made over at least one cycle of El Niño–Southern Oscillation because of interannual climate variability. Our analyses also suggest that proper scaling of the site‐specific and subannual measurements of carbon fluxes to produce Basin‐wide flux estimates must take into account seasonal and spatial variations in net carbon storage.

     

TOXIC EFFECTS OF OXYGEN ON CEREBRAL METABOLISM

Abstract— The effect of 100% O₂ at one atmosphere on carbohydrate metabolism in cell-free homogenates of rat brain was studied under different experimental conditions. The principal findings were the following:

• 1 Compared to 10% O₂-90% N₂, oxygen at one atmosphere inhibited metabolism of α-oxoglutarate and depressed the net synthesis of ATP. With glucose as substrate, accumulation of ATP was also markedly inhibited but substrate utilization was only slightly affected.

• 2 Glycolysis in brain was relatively resistant to oxygen toxicity, except in the presence of added Cu²⁺.

• 3 With α-oxoglutarate as the substrate, inhibition of the formation of ATP occurred earlier than inhibition of substrate utilization, indicating the particular sensitivity of oxidative phosphorylation to inactivation by oxygen in vitro.

• 4 Cu²⁺ and Fe²⁺ accentuated oxygen toxicity but appeared to act by different mechanisms. Co²⁺ exerted a protective effect.

• 5 The sulphydryl compounds, dithiothreitol and reduced glutathione, strongly diminished the toxic effect of oxygen.

     

A new inexpensive suction apparatus for sampling arthropods in grassland

Abstract.

• 1 We describe a new technique for sampling arthropods from grassland and other vegetation, using a modified petrol-driven suction apparatus called a‘Blow & Vac’.
• 2 The new apparatus was tested by comparing its efficiency in extracting arthropods from vegetation with that of a conventional Dietrick, or‘D-Vac’, suction sampler.
• 3 Unimpeded air velocity inside the suction tube was approximately 4 times that of the D-Vac.
• 4 In field trials on semi-natural grasslands, the Blow & Vac caught more individuals of most spider and certain beetle species compared to the D-Vac and approximately equal numbers of Auchenorrhyncha.
• 5 We conclude that the‘Blow & Vac’has considerable potential for sampling arthropod populations. Its low cost and weight make it a suitable alternative to the conventional D-Vac apparatus.

     

METABOLISM OF AMINO ACIDS IN INCUBATED SLICES OF MOUSE BRAIN1

• 1 Slices of mouse brain were incubated with [U-¹⁴C]alanine, valine, leucine, phenylalanine, proline, histidine, lysine, arginine or aspartic acid, and the extent of metabolism was estimated by analyses utilizing paper chromatography of the tissue extracts and with an amino acid analyser.

• 2 The metabolism of Ala and Asp was high; of Leu and Pro, moderate; and of Lys, Arg and Phe, low; the metabolism of Val and His was not significant. The time-course of metabolism in most cases showed varying rates, indicating heterogeneous metabolic compartments for the amino acids.

• 3 Production of CO₂ was high from Asp, moderate from Ala, and low from Leu; the other amino acids were not oxidized to CO₂ to any significant extent. A large portion of the metabolized label was trapped in the form of Glu or Asp.

• 4 Metabolism increased with increasing concentration of amino acid to some extent and was largely inhibited by omission of glucose, by anaerobic conditions, or by cyanide. Although these conditions also inhibit uptake, the time-course and extent of inhibition uptake and metabolism were different.

• 5 With Asp, Ala and Phe, metabolism was lowest in slices from pons-medulla; the brain area exhibiting the highest metabolism differed for each amino acid. The metabolism of Asp was lower in brain samples from newborn than in those from adults; the metabolism of Leu was higher in slices from newborn brain.

• 6 The results indicate that the majority of the amino acids can be metabolized in brain tissue and that the metabolic rates are influenced by a number of factors, among them the level of amino acids and the level of available energy.

     

Subcellular distribution of aromatic amino acid transaminases in rat brain

Abstract— The subcellular distributions of tyrosine transaminase, DOPA transaminase, tryptophan transaminase and 5-hydroxytryptophan (5-HTP) transaminase were studied in rat brain.

• 1 For all of these transaminases 60-81 per cent of the total activities were found in the crude mitochondrial fraction. Tyrosine transaminase was the most active enzyme.

• 2 Tyrosine transaminase and DOPA transaminase had very similar distributions in all fractions, but the distribution of tryptophan transaminase and 5-HTP transaminase differed in the microsomal (Mic) and synaptic vesicle (M₂) fractions. Only 5-HTP transaminase was highly concentrated in the M₂ fraction.

• 3 DOPA transaminase was inhibited by dopamine and 5-HT, but these compounds had no effect on 5-HTP transaminase. Both enzymes were completely inhibited by m-hydroxybenzoyloxyamine.

     

Gene therapy in Alzheimer’s disease – potential for disease modification

• ? Introduction
• ? Targets and ongoing research
  • ‐ NGF
    • ‐ Neurotrophic function of NGF
    • ‐ Levels of NGF in AD
    • ‐ Role of NGF in AD
    • ‐ NGF as a therapeutic agent
    • ‐ Development of NGF gene therapy
    • ‐ In vivo gene delivery of NGF
  • ‐ BDNF
    • ‐ Neurotrophic function of BDNF
    • ‐ BDNF levels in AD
    • ‐ BDNF function in AD
    • ? Towards BDNF gene therapy
  • ‐ Neprilysin
    • ‐ Role of neprilysin in AD
    • ‐ Neprilysin levels in AD
    • ‐ Gene delivery of neprilysin in AD animal models
• ? Potential gene therapy target candidates
  • ‐ APOE
  • ‐ ECE
  • ‐ Cathepsin B
  • ‐ Other Aβ degrading enzymes
• ? Down‐regulation of AD‐associated proteins by siRNA
  • ‐ BACE1
  • ‐ APP
• ? Concluding remarks

Alzheimer’s disease (AD) is the major cause of dementia in the elderly, leading to memory loss and cognitive decline. The mechanism underlying onset of the disease has not been fully elucidated. However, characteristic pathological manifestations include extracellular accumulation and aggregation of the amyloid β‐peptide (Aβ) into plaques and intracellular accumulation and aggregation of hyperphosphorylated tau, forming neurofibrillary tangles. Despite extensive research worldwide, no disease modifying treatment is yet available. In this review, we focus on gene therapy as a potential treatment for AD, and summarize recent work in the field, ranging from proof‐of‐concept studies in animal models to clinical trials. The multifactorial causes of AD offer a variety of possible targets for gene therapy, including two neurotrophic growth factors, nerve growth factor and brain‐derived neurotrophic factor, Aβ‐degrading enzymes, such as neprilysin, endothelin‐converting enzyme and cathepsin B, and AD associated apolipoprotein E. This review also discusses advantages and drawbacks of various rapidly developing virus‐mediated gene delivery techniques for gene therapy. Finally, approaches aiming at down‐regulating amyloid precursor protein (APP) and β‐site APP cleaving enzyme 1 levels by means of siRNA‐mediated knockdown are briefly summarized. Overall, the prospects appear hopeful that gene therapy has the potential to be a disease modifying treatment for AD.     

Island biogeography and landscape ecology of mammals inhabiting fragmented, temperate rain forests

• 1 We expanded the island biogeography paradigm to test whether mammalian communities of the heavily fragmented temperate rain forests of the Olympic Peninsula were influenced by local environmental conditions, biogeographic factors (fragment area and isolation) and characteristics of the surrounding landscape.
  • 2 We used live‐trapping, sign surveys and infra‐red triggered cameras to compare distributions of non‐volant mammals among fragments and between fragments and other principal landscape components (continuous old‐growth, riparian corridors, second‐growth forest and clearcuts).
    • 3 Of the 24 species of non‐volant mammals detected during our studies, 18 occurred in at least one fragment.
      • 4 Species richness of old‐growth mammals was not significantly correlated with fragment area or isolation, per se, but was significantly and positively correlated with the amount of old‐growth fragments and old second‐growth (41–159 years) in the surrounding landscape (r² = 0.95, P < 0.005).
        • 5 Distributions of three old‐growth dependent species [shrew‐mole (Neurotrichus gibbsii), Douglas squirrel (Tamiasciurus douglasii) and Trowbridge shew (Sorex trowbridgii)] were significantly associated with local environmental conditions within the fragment, with geographical isolation from continuous old‐growth and riparian corridors, and with the amount of old‐growth and old second growth in the adjacent matrix.

     

THE COMPARTMENTATION OF GLUTAMATE AND ITS METABOLITES IN FRACTIONS OF NEURON CELL BODIES AND NEUROPIL; STUDIED BY INTRAVENTRICULAR INJECTION OF [U-14C]GLUTAMATE

Abstract—

• 1 The in vivo metabolism of glutamate in rat neuron cell bodies and neuropil was studied after intraventricular injection of (U-¹⁴C)glutamic acid followed by separation of the tissue into neuronal and neuropil fractions.

• 2 The losses of amino acid and of radioactivity during the fractionation were equivalent. Recoveries were: glutamate, 32; glutamine, 15; aspartate, 25; GABA, 41; alanine, 30 per cent. In the washed cell fractions glutamine was 45 per cent and alanine 132 per cent higher in the neuronal fraction, glutamate was 62, GABA 77 and aspartate 95 per cent of neuropil levels. This contrasted with results obtained previously for in vitro incorporation. Calculation from these results indicated that 28 per cent of the original cell suspension was neuronal, 72 per cent neuropil. In the final cell preparations, 29 per cent of the neuron cell bodies and 26 per cent of the neuropil were recovered.

• 3 Specific activity of glutamate in the neuronal fraction 15 min after injection was higher than in the original suspension, but had declined to 30 per cent of its initial value by 2 h. In the neuropil, specific activity of glutamate was below that of the cell suspension at 15 min, but at later times rose above it by up to 40 per cent.

• 4 Radioactivity was detected in aspartate and glutamine 15 min after injection and GABA by 60 min after injection. In the original cell suspension the specific activity of glutamine was higher than that of glutamate at all times (the Waelsch effect) but aspartate and GABA were lower than glutamate.

• 5 In the neuronal fraction the specific activity of glutamine was below that of glutamate at all times, indicating a precursor-product relationship. In the neuropil fraction, glutamine specific activity remained above glutamate for the first hour.

• 6 These results are discussed in relation to the interpretation of the Waelsch effect in terms of metabolic compartmentation.

     

EFFECT OF THYROID HORMONE ON THE BIOCHEMICAL MATURATION OF RAT BRAIN: CONVERSION OF GLUCOSE-CARBON INTO AMINO ACIDS

• 1 The rapid and extensive conversion of glucose-carbon into amino acids is an index of the final coordination of the mechanisms underlying energy metabolism in the adult brain. This phenomenon develops in the rat during a short period extending from 10 to about 19 days after birth. The underlying factors have been analysed.

• 2 The development of the pattern of distribution of glucose-carbon characteristic of the adult brain was markedly influenced by the thyroid state of the animals. The age-curve for the conversion of glucose-carbon into brain amino acids was displaced to the left after treatment with thyroid hormone (T₃) in infancy thus indicating an accelerated maturation. Conversely, neonatal thyroidectomy resulted in a significant retardation in the conversion of glucose-carbon into amino acids.

• 3 The specific radioactivity of glutamate increased five-fold in the brain of normal rats from the 10th to the 19th day of age. The values (as a percentage of those for littermate controls) were 220 in the case of the 10 day-old thyroid treated rats and about 30 for the 19 day-old thyroid deficient animals. At the age of 10 days neither treatment affected the concentration of glutamate which was also only slightly less than the control values in the brain of 19 day-old thyroid deficient animals (–17 per cent).

• 4 Specific pool(s) of glutamate associated with the formation of GABA can be demonstrated in the brain of 19 day-old rats after administration of [U-¹⁴C]glucose as a result of anoxia post mortem. These pools did not develop in the brain of 10 day-old animals. Neonatal thyroidectomy retarded the development of these glutamate pools.

• 5 Evidence is summarized which indicates that the development of the rapid conversion of glucose-carbon into amino acids reflects the enlargement, during maturation, of the metabolic compartments which are associated with neuronal processes.

     

Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 2 – clinical implications

• ? Introduction
• ? SSTR subtype tissue distribution and its relevance to tumour imaging and treatment
• ? Conclusions

     

THE MAINTENANCE OF SPECIES-RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE

• 1 According to ‘Gause's hypothesis’ a corollary of the process of evolution by natural selection is that in a community at equilibrium every species must occupy a different niche. Many botanists have found this idea improbable because they have ignored the processes of regeneration in plant communities.
• 2 Most plant communities are longer-lived than their constituent individual plants. When an individual dies, it may or may not be replaced by an individual of the same species. It is this replacement stage which is all-important to the argument presented.
• 3 Several mechanisms not involving regeneration also contribute to the maintenance of species-richness:

• (a). differences in life-form coupled with the inability of larger plants to exhaust or cut off all resources, also the development of dependence-relationships,
• (b) differences in phenology coupled with tolerance of suppression,
• (c) fluctuations in the environment coupled with relatively small differences in competitive ability between many species,
• (d) the ability of certain species-pairs to form stable mixtures because of a balance of intraspecific competition against interspecific competition,
• (e) the production of substances more toxic to the producer-species than to the other species,
• (f) differences in the primary limiting mineral nutrients or pore-sizes in the soil for neighbouring plants of different soecies, and
• (g) differences in the competitive abilities of species dependent on their physiological age coupled with the uneven-age structure of many populations.

• 4 The mechanisms listed above do not go far to explain the indefinite persistence in mixture of the many species in the most species-rich communities known.
• 5 In contrast there seem to be almost limitless possibilities for differences between species in their requirements for regeneration, i.e. the replacement of the individual plants of one generation by those of the next. This idea is illustrated for tree species and it is emphasized that foresters were the first by a wide margin to appreciate its importance.
• 6 The processes involved in the successful invasion of a gap by a given plant species and some characters of the gap that may be important are summarized in Table 2.
• 7 The definition of a plant's niche requires recognition of four components:

• (a) the habitat niche,
• (b) the life-form niche,
• (c) the phenological niche, and
• (d) the regeneration niche.

• 8 A brief account is given of the patterns of regeneration in different kinds of plant community to provide a background for studies of differentiation in the regeneration niche.
• 9 All stages in the regeneration-cycle are potentially important and examples of differentiation between species are given for each of the following stages:

• (a) Production of viable seed (including the sub-stages of flowering, pollination and seed-set),
• (b) dispersal, in space and time,
• (c) germination,
• (d) establishment, and
• (e) further development of the immature plant.

• 10 In the concluding discussion emphasis is placed on the following themes:

• (a) the kinds of work needed in future to prove or disprove that differentiation in the regeneration niche is the major explanation of the maintenance of species-richness in plant communities,
• (b) the relation of the present thesis to published ideas on the origin of phenological spread,
• (c) the relevance of the present thesis to the discussion on the presence of continua in vegetation,
• (d) the co-incidence of the present thesis and the emerging ideas of evolutionists about differentiation of angiosperm taxa, and
• (e) the importance of regeneration-studies for conservation.