Stable charged cosmic strings.

We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18) m. The vacuum remains stable in our model, because neutral strings are not energetically favored.

Canopy CO2 exchange of sugar beet under different CO2 concentrations and nitrogen supply: results from a free-air CO2 enrichment study.

Sugar beet (Beta vulgaris ssp. altissima Döll) was grown in the field under free-air CO(2) enrichment (FACE, 550 ppm) and different nitrogen (N) supply (2001: 126 (N100) and 63 kg.ha(-1) (N50); 2004: 156 (N100) and 75 kg.ha(-1)) during two crop rotations. Canopy CO(2) exchange rates (CCER) were measured during the main growth phase (leaf area index > or =2) using a dynamic chamber system. Canopy CO(2) exchange data were analysed with respect to treatment effects on seasonal means and light use efficiency and light response characteristics. CO(2) enrichment enhanced CCER throughout the season. However, in both years, CCER declined after the second half of August independent of radiation and [CO(2)]. Elevated [CO(2)] strongly stimulated CCER on a seasonal basis, whereas the reduction of CCER caused by low N was below 10% and not significant. There were no effects of N on daily radiation use efficiency of carbon gain calculated from CCER data, but a strong enhancement by CO(2) enrichment. CCER closely tracked diurnal variations in incident photosynthetic photon flux density (PPFD, mumol.m(-2).s(-1)). The relationship between CCER and incident PPFD was curvilinear. In both seasons, initial slopes and maximum rates (CCER(max)) were determined from two 6-day periods using these relationships. The first period was measured after canopy closure (first half of July) and the second in the second half of August. In the first period, elevated [CO(2)] increased the initial slopes. Low N supply affected neither the initial slopes nor their response to elevated [CO(2)] in either period. In contrast to initial slopes, N stress limited the [CO(2)] response of CCER(max) in the first period. In the second period, however, this interaction of [CO(2)] and N on CCER(max) was completely dominated by a general decline of CCER(max) whereas no general decline of the initial slopes occurred in the second period. This response of light response parameters to [CO(2)] and N suggests that, in sugar beet, the decline of CCER in the late season may rely on limiting mechanisms such as photosynthetic acclimation responses to elevated [CO(2)] caused by sink limitations.

Gap-junction-mediated propagation and amplification of cell injury.

Gap junctions are conductive channels that connect the interiors of coupled cells. We determined whether gap junctions propagate transcellular signals during metabolic stress and whether such signaling exacerbates cell injury. Although overexpression of the human proto-oncogene bcl2 in C6 glioma cells normally increased their resistance to injury, the relative resistance of bcl2+ cells to calcium overload, oxidative stress and metabolic inhibition was compromised when they formed gap junctions with more vulnerable cells. The likelihood of death was in direct proportion to the number and density of gap junctions with their less resistant neighbors. Thus, dying glia killed neighboring cells that would otherwise have escaped injury. This process of glial 'fratricide' may provide a basis for the secondary propagation of brain injury in cerebral ischemia.

Growth and nutritive quality of Poa pratensis as influenced by ozone and competition.

Interspecific plant competition has been hypothesized to alter effects of early-season ozone (O3) stress. A phytometer-based approach was utilized to investigate O3 effects on growth and nutritive quality of Poa pratensis grown in monoculture and in mixed cultures with four competitor-plant species (Anthoxanthum odoratum, Achillea millefolium, Rumex acetosa and Veronica chamaedrys). Mesocosms were exposed during April/May 2000-2002 to charcoal-filtered air+25 ppb O3 (control) or non-filtered air+50 ppb O3 (elevated O3). Biomass production was not affected by O3, but foliar injury symptoms were observed in May 2002. Early-season O3 exposure decreased relative food value of P. pratensis by an average of 8%, which is sufficient to have nutritional implications for its utilization by herbivores. However, forage quality response to O3 was not changed by interspecific competition. Lack of injury and nutritive quality response in P. pratensis harvested in September may reflect recovery from early-season O3 exposure.

A simple and rapid anti-ligand enzyme immunoassay for visualization of low-density lipoprotein membrane receptors.

Triton X-114 was used to solubilize the membrane proteins of bovine adrenal cortex and human leukocytes. The solubilized membrane proteins were subjected to electrophoresis and transblotted to nitrocellulose paper and incubated with LDL/acetyl-LDL. The combination of peroxidase-conjugated second antibody and 4-chloronaphthol/H2O2 allowed rapid development of colored bands where LDL or acetyl-LDL bound to electroblotted proteins. The ELISA is highly sensitive and efficient for screening a large number of samples and avoids the need for a continuous supply of radiolabeled antibodies and autoradiography.

Change to abacavir-lamivudine-tenofovir combination treatment in patients with HIV-1 who had complete virological suppression.

Patients who have not received previous antiretroviral treatment (ART) have a high failure rate on the combination treatment of abacavir, lamivudine, and tenovir. We assessed the virological failure rate in eight patients with HIV-1 who switched to this combination after having complete virological suppression from their previous long-term ART (median 8.0 months, range 7.5-18.0). Five of the eight patients showed virological failure. Four of these five patients had either the K65R mutation, the M184V/I mutation, or both. This combination of drugs cannot therefore be recommended as alternative treatment in patients with HIV-1 who are fully virologically suppressed.

Complications of varicella zoster virus reactivation in HIV-infected homosexual men.

OBJECT: To study the complication rate of varicella zoster virus (VZV) reactivation and the relationship between complications, presentation and localization of zoster and immune function in HIV disease. DESIGN AND METHODS: A total of 142 episodes of VZV reactivation in 113 out of 544 HIV-1-infected participants in the Amsterdam Cohort Study of homosexual men were studied. Persistent hyperkeratotic or necrotic skin lesions, post-herpetic neuralgia, other neurological events, ocular events and pneumonitis occurring within 6 months of the onset of the last episode of VZV reactivation were defined as complications, provided that other possible diagnoses were excluded and the event had been previously described in the literature as related to VZV reactivation. RESULTS: Twenty-four complications occurred in 15 (11%) of these 142 episodes. Complications occurred exclusively in the 40 episodes with either multidermatomal or disseminated presentation, or a trigeminal localization, or both. In the group of episodes of unidermatomal zoster at a non-trigeminal localization no complications occurred. Twenty-one episodes of herpes zoster were localized in the trigeminal area. Localization was not significantly associated with the level of immune function. Compared to unidermatomal presentation (n = 120), multidermatomal (n = 15) and disseminated presentation (n = 7) occurred at lower median CD4+ cell counts (330, 240 and 50 x 10(6)/l, respectively; P = 0.003) and significantly lower levels of CD3 monoclonal antibodies or phytohaemagglutinin-induced T-cell reactivity in vitro. Complications were related to CD4+ cell counts, but in the cases of disseminated, multidermatomal or trigeminal zoster a CD4+ cell measurement provided no additional information on the risk of complications. CONCLUSION: In HIV-infected individuals the extent of the clinical presentation and the occurrence of complications of VZV reactivation are related to the degree of immunodeficiency. In episodes of VZV reactivation with either multidermatomal or disseminated presentation or a trigeminal localization, or both the complication rate was high. CD4+ cell counts provided no additional information on the complication risk. Oral acyclovir appears to be sufficient as therapy for unidermatomal zoster at a non-trigeminal localization.

Toxicity and drug exposure in a quadruple drug regimen in HIV-1 infected patients participating in the ADAM study.

OBJECTIVE: To study the relationship between toxicity and the exposure to nelfinavir and saquinavir as part of a quadruple drug regimen. DESIGN: The ADAM study is a randomized study to investigate the feasibility of induction-maintenance therapy in HIV-1 infection. METHODS: HIV-1-infected patients with no prior use of antiretroviral treatment started induction therapy consisting of stavudine + lamivudine + nelfinavir + saquinavir for a period of 26 weeks. Data regarding toxicity of the quadruple regimen and exposure to the protease inhibitors were collected. RESULTS: Seven of the 65 patients enrolled had to switch therapy for reasons of toxicity within the first 26 weeks. Diarrhoea was frequently reported (49 of 65, one discontinuation), but could be relieved by using antidiarrhoeal agents. Laboratory monitoring revealed elevated liver enzymes (leading to four discontinuations) and mild to moderate elevations of triglycerides and cholesterol (nine and 23 of 65, respectively). The exposure to saquinavir and nelfinavir was lower than expected. Abdominal pain was associated with a higher exposure to nelfinavir or saquinavir. The association of nausea and abdominal distension with drug exposure appeared to vary over time. CONCLUSIONS: The quadruple drug regimen was quite well tolerated. Diarrhoea was frequently reported but could be relieved by the use of antidiarrhoeal agents. In comparison with other protease inhibitor combinations, lipid abnormalities in plasma were infrequent and mild. With the exception of diarrhoea, all gastrointestinal complaints observed were found to be associated with the level of exposure to nelfinavir or saquinavir. The exposure to the protease inhibitors was relatively low, although the virologic efficacy of the regimen used was satisfactory.

The effect of plasma drug concentrations on HIV-1 clearance rate during quadruple drug therapy.

OBJECTIVE: To investigate the relationship between exposure to antiretroviral drugs and the initial decline of plasma HIV-1 RNA. DESIGN: Open-label study in antiretroviral-naive HIV-1 infected patients using a quadruple drug regimen [nelfinavir (NFV), saquinavir (SQV), stavudine, and lamivudine]. METHODS: The elimination rate constant (k) for HIV-1 clearance was calculated during the first 2 weeks of treatment in 29 patients. Exposure to NFV and SQV was quantified on each study visit. Observed NFV and SQV concentrations were related to those expected in a reference population and a concentration ratio was calculated. The median concentration ratios for NFV and SQV, the baseline CD4+ lymphocyte count and baseline log10 HIV-1 RNA were correlated with k. RESULTS: A significant positive correlation was observed between k and the median NFV (P = 0.001) or SQV concentration ratio (P = 0.016) in univariate analysis. In multivariate analyses, the median NFV concentration ratio remained significantly correlated with k. CONCLUSIONS: The variation in the rate of decline of plasma HIV-1 RNA between patients after the initiation of a quadruple drug regimen could be explained by differences in exposure to NFV or SQV. Determination of k could be used to optimise further antiretroviral drug therapy and may be a first tool to assess antiretroviral activities of new or increasing doses of drugs administered in combination regimens. Furthermore, our data suggest that exposure to antiretroviral drugs should be incorporated in mathematical models to describe HIV-1 dynamics in more detail.

Immune restoration does not invariably occur following long-term HIV-1 suppression during antiretroviral therapy. INCAS Study Group.

BACKGROUND: Current antiretroviral treatment can induce significant and sustained virological and immunological responses in HIV-1-infected persons over at least the short- to mid-term. OBJECTIVES: In this study, long-term immune reconstitution was investigated during highly active antiretroviral therapy. METHODS: Patients enrolled in the INCAS study in The Netherlands were treated for 102 weeks (range 52-144 weeks) with nevirapine (NVP) + zidovudine (ZDV) (n = 9), didanosine (ddl) + ZDV (n = 10), or NVP + ddl + ZDV (n = 10). Memory and naïve CD4+ and CD8+ T cells were measured using CD45RA and CD27 monoclonal antibodies (mAb), T-cell function was assayed by CD3 + CD28 mAb stimulation, and plasma HIV-1 RNA load was measured by ultra-direct assay (cut-off < 20 copies/ml). RESULTS: Compared to both double combination regimens the triple combination regimen resulted in the most sustained increase in CD4+ T cells (change in CD4+, + 253 x 10(6) cells/l; standard error, 79 x 10(6) cells/l) and reduction of plasma HIV-1 RNA. In nine patients (31%) (ddl + ZDV, n = 2; NVP + ddl + ZDV, n = 7) plasma HIV-1 RNA levels remained below cut-off for at least 2 years. On average, these long-term virological responders demonstrated a significantly higher increase of naïve and memory CD4+ T cells (P = 0.01 and 0.02, respectively) as compared with patients with a virological failure, and showed improved T-cell function and normalization of the naïve; memory CD8+ T-cell ratio. However, individual virological success or failure did not predict the degree of immunological response. T-cell patterns were independent of baseline CD4+ T-cell count, T-cell function, HIV-1 RNA load or age. Low numbers of naïve CD4+ T cells at baseline resulted in modest long-term naïve T-cell recovery. CONCLUSIONS: Patients with prolonged undetectable plasma HIV-1 RNA levels during antiretroviral therapy do not invariably show immune restoration. Naïve T-cell recovery in the setting of complete viral suppression is a gradual process, similar to that reported for immune recovery in adults after chemotherapy and bone marrow transplantation.

Glia cells of the monkey retina. I. Astrocytes.

Morphology and distribution of retinal astrocytes have been studied in macaque monkeys by immunocytochemical localization of glial fibrillary acidic protein (GFAP). With the exception of the fovea and the far periphery, astrocytes are ubiquitous in the nerve fiber layer (NFL) and the ganglion cell layer (GCL) of the monkey retina. The morphology of NFL astrocytes changes gradually, from star-shaped in the periphery to bipolar close to the optic disc. By contrast, GCL astrocytes maintain their star-shaped appearance throughout the retina. Astrocytes are unevenly distributed in the monkey retina, showing the highest concentration around the optic disc, and particularly low densities in the perifoveal region and the far periphery. The fovea proper is devoid of astrocytes. Employing high-resolution confocal microscopy, we could demonstrate that astrocytes form manifold contacts to blood vessels. In addition, bundles of NFL astrocyte processes are co-localized with axon bundles, individual astrocytes forming contacts to several axon bundles. In contrast, a similar affinity of astrocytes to ganglion cell somata was never observed. Thus, our data confirm and extend the current knowledge of morphology and putative function of astrocytes in mammalian and especially the primate retina.

Lesion-induced transient suppression of inhibitory function in rat neocortex in vitro.

The structural and functional consequences of a local thermolesion were examined in rat neocortex with electrophysiological in vitro techniques and immunocytochemistry. Age-matched untreated and sham-operated animals served as controls and were analysed in the same way. The lesions consisted of a core of coagulated tissue 2-3 mm in diameter and reached ventrally into the deep cortical layers. After two days reactive astrocytes and after nine days a dense gliosis were observed in the immediate vicinity. Modifications in the intrinsic membrane characteristics and the synaptic network properties were investigated with intra- and extracellular recording techniques after survival times of one to eight days. Neurons recorded in the surrounding of lesions in neocortical slices revealed a significantly more depolarized resting membrane potential and a higher neuronal input resistance. In comparison to cells in control slices, maximal discharge rates to injection of depolarizing current pulses of neurons close to a focal lesion were not significantly altered and intrinsic burst firing was never observed. However, between postlesion days 1 and 5, neurons in the surroundings of lesions showed a transient increase in synaptic excitability. This hyperactivity was most clearly pronounced at a distance of 2-3 mm from the centre of the lesion (i.e. about 1-1.5 mm away from the lesion border) and characterized by long-duration field potential responses and multiphasic long-lasting excitatory postsynaptic potentials to orthodromic stimulation of the afferent input. This lesion-induced hyperexcitability was associated with a significant reduction in the peak conductance of the Cl(-)-dependent fast inhibitory postsynaptic potential and the K(+)-dependent long-latency inhibitory postsynaptic potential, suggesting that the intracortical GABAergic system was functionally impaired. The decrease in synaptic inhibition was associated with prolonged N-methyl-D-aspartate receptor-mediated activity, which could be reversibly blocked by D-amino-phosphonovaleric acid. In addition, neurons recorded in the vicinity of the lesion responded to an orthodromic synaptic stimulus with a long-lasting burst. The lesion-induced disturbance in the balance between the excitatory and inhibitory system may not only have profound influences on the mechanisms of intracortical information processing, but may also lead to the expression of epileptiform activity and long-term functional deficits.

Detection of HIV-1 distribution in different blood fractions by two nucleic acid amplification assays.

A new amplification procedure, NASBA (nucleic acid sequence-based amplification), was used together with the polymerase chain reaction (PCR) to detect HIV-1 sequences in different blood fractions of both HIV-infected and uninfected samples. We tested whole blood, plasma, peripheral blood mononuclear cells (PBMCs), and platelets. No HIV-1 sequences were found in blood fractions of 37 uninfected persons either by PCR, reverse transcriptase-PCR (RT-PCR), or NASBA. We found that none of the infected plasma samples contained HIV-1 DNA sequences. However, a high percentage of these plasma samples was positive for HIV-1 RNA: 86% by NASBA and 80% by RT-PCR. The concordance on a sample-to-sample basis of NASBA and RT-PCR was 91%. Only 33% of the plasma samples was HIV-1 p24-antigen positive, demonstrating the superior sensitivity of amplification procedures. We found that almost all PBMC fractions were positive for HIV-1 (pro)viral sequences (99% HIV-1 DNA positive, 91% HIV-1 RNA positive). A large proportion of the platelet fractions contained HIV-1 RNA, as demonstrated by positive RT-PCR and NASBA results. We found an inverse relation between CD4+ T cell count and T cell reactivity on the one hand and detection of HIV-1 sequences by PCR, RT-PCR, and NASBA on the other hand in all blood fractions. Quantification of the HIV-1 PCR signal in PBMCs revealed an inverse relation of proviral titers with CD4+ levels. This finding supports earlier observations that clinical disease and low CD4+ cell counts are related to an increased viral burden.

Prospective longitudinal analysis of viral load and surrogate markers in relation to clinical progression in HIV type 1-infected persons.

The temporal relationship between viral and surrogate markers and clinical status was analyzed prospectively every 8 weeks in 34 asymptomatic HIV-1-infected persons. After 3 years, 25 persons remained clinically healthy whereas 9 persons showed clinical progression. In accordance with other reports we found that at study entry HIV-RNA load was predictive of clinical progression. All markers tested evolved significantly in time in both progressors and nonprogressors. The HIV RNA load in plasma and HIV DNA load in T cells were linearly related only in nonprogressors. In addition, the RNA/DNA ratio during follow-up was significantly higher in progressors, indicating a higher replication rate in progressors. The HIV DNA load correlated inversely with CD4+ T cell counts and positively with p24 antigenemia in both nonprogressors and progressors. A significant correlation of HIV DNA load with SI phenotype occurred in progressors only. HIV RNA levels correlated with beta 2-microglobulin level and with p24 antigenemia but not with SI phenotype. These three markers can all routinely be measured in plasma; however, only the HIV RNA levels appear to be informative for clinical progression. Six to 8 months before clinical progression, an SI phenotype switch, increased HIV RNA in plasma, and decreased CD4+ T cell counts were all indicative of an impending clinical event.

Effects of sulphur dioxide and acid rain alone or in combination on growth and yield of broad bean plants.

Potted plants of Vicia faba L. cv. 'Con Amore', grown either in soil or quartz gravel were exposed in eight open-top chambers to two levels of SO2 (charcoal-filtered air and charcoal-filtered air enriched with SO2 ) and two artificial rain treatments (pH 5.6 and pH 3.0/4.0), alone or in combination. SO2 was dosed continuously (55-90 µg m-3 for 56 days) and rain solutions were applied on three days each week for 8-9 min each day resulting in 4.45 mm rainfall per week and a total H+ deposition of 0.15 kg ha-1 and a total water deposition of 37 mm. Variables measured at different stages of plant development included fresh and dry weight of whole plants, leaves, stalks, fruits and roots; number of leaves, stalks, blossoms, pods and seeds; leaf area; plant height; sulphur content. While the sulphur content of the leaves of all plants significantly increased due to the SO2 fumigation, the effect on the growth of young plants depended on the root medium; plants grown in soil were mainly influenced in a positive manner (increase of fresh and dry weight; number of leaves, blossoms and pods), whereas plants grown in quartz gravel were negatively affected. At maturity these tendencies were only observed in marketable products like seeds (plants grown in soil) or pods (plants grown in quartz gravel). The acid-rain treatment resulted in a decrease of total fresh and dry weight and fruit production of plants grown in soil, while, particularly at the beginning of the rain treatments, dry weight of whole plants and leaves as well as the number of leaves of plants grown in quartz gravel decreased. Some interactions between the two pollutants, which were mostly negative in nature, were also observed.

The response of perennial ryegrass/white clover swards to elevated atmospheric CO2 concentrations 1. Effects on competition and species composition and interaction with N supply.

The effects of long-term carbon dioxide enrichment on competition for nutrients and light in a ryegrass/clover association were determined for simulated swards of perennial ryegrass (Lolium perenne L. cv. Parcour) and white clover (Trifolium repens L. cv. Karina), which were grown as monocultures and in three mixtures (25/75, 50/50, 75/25), according to the replacement design, at two levels of nitrogen (N) supply (no additional N and 200 kg N ha-1 ) and at season-long ambient (380 ppm) and elevated (670 ppm) CO2 concentrations, in open-top chambers. Stands were cut four times, at about monthly intervals, to a height of 5 cm. Plant material was separated into different species, fresh and dry weights were determined and the content of macroelements (N, P, K, S, Mg) in both species was measured. In addition, plant height of both species at harvest dates and during several regrowth periods was monitored. Results indicate that both species made demand on different resources and profited from growth in a mixed sward. Co2 related yield increase amounted to 16-4-2 % for white clover whereas the effect of high CO2 on ryegrass yield ranged between -33% and +9% depending on N supply, mixture and year. As a result the contribution of white clover to total yield in mixed swards was significantly enhanced by CO2 enrichment at many harvests in both N supply treatments. Without additional N supply, shoot competition for light was intensified by CO2 enrichment to the disadvantage of ryegrass, since clover petioles grew longer and ryegrass was shorter at elevated CO2 With N fertilization, no marked effect of CO2 enrichment on interspecific competition could be observed. Since clover and total yield were increased by CO2 enrichment, nutrient requirements were also increased and potassium deficiency and increased intraspecific competition of clover for K was observed in the mixtures under elevated CO2 which had the highest nutrient withdrawal. Although white clover profited much more from CO2 enrichment in both N fertilization treatments, the suppression of ryegrass in mixed swards could only be observed under low N conditions. Generally, the effect of N fertilization on competitive interference between both species was much greater than the effect of CO2 enrichment and it is suggested that the effect of elevated CO2 on the balance of species and the outcome of competition in a grass/clover sward is mainly dependent on the N status.

Response of nitrogen metabolism in beans (Phaseolus vulgaris L.) after exposure to ozone and nitrogen dioxide, alone and in sequence.

Bush bean (Phaseolus vulgaris L.) plants were exposed to low levels of ozone (O3 ) and/or nitrogen dioxide (NO2 ) in open-top chambers during the growing seasons of 1988 and 1989. Treatments consisted of charcoal-filtered (CF) air, and CF air enriched with either O3 (50-60 nll -1 ), NO2 (30-40 nll-1 ) or both gases. A daily sequential exposure, O2 followed by NO2 , was used in each year in the combined treatment: O2 was added for 8 h d-1 from 08.00 h until 16.00 h, and NO2 for 16 h d-1 from 16.00 h until 08.00 h. Growth variables and key enzymes of N assimilation in leaves were investigated during vegetative growth and at anthesis. Pollutant effects varied between years. No significant effects were found in 1988. In 1989 NO2 , alone or in sequential exposure with O3+ , increased leaf dry weight and total biomass until anthesis. Moreover, there was a parallel increase in the extractable activity of both nitrate and nitrite reductase in the NO2 treatments during vegetative growth, while glutamine synthetase and glutamate dehydrogenase were only increased by sequential exposure to O3 + NO2 . In contrast, during anthesis the activities of nitrite reductase and glutamine synthetase were lowest in leaves sequentially exposed to O3 + NO2 . Ozone alone had very little effect on N metabolism but suppressed growth during anthesis. At pod maturity, the lowest leaf dry weight and leaf area occurred in plants exposed to the sequential combination of O3 + NO2 , but yield (pod weight) was not significantly affected by any of the pollutant treatments. It is concluded that chronic exposure especially to the sequence O3 -NO2 reduced the capacity of the plants for N assimilation. The observed shift in nitrogen metabolism during the plants' development may have contributed to the adverse effects of the sequential treatment O3 + NO2 on growth variables at the end of the exposure period.

Ozone threshold doses and exposure-response relationships for the development of ozone injury symptoms in wild plant species.

The relative ozone sensitivities of 25 German native herbaceous plant species, representative of arable field margins or disturbed habitats, were examined over three consecutive growing seasons. Plants were grown from seed, potted into natural soils and exposed in open-top chambers for the entire season to different ozone-exposure regimes covering a range of concentrations from <5 to 48 ppb (seasonal 8 h daily mean). The assessment of ozone effects was carried out by recording the first day of visible symptom appearance and the percentage of injured leaves at the end of vegetative growth. Species exhibited contrasting patterns of symptom expression under ozone stress, with either ozone-specific symptoms or ozone-enhanced foliar pigmentation and senescence. Classifications of species according to their ozone susceptibility varied depending on whether measurement was of the total extent of visible injury, ozone threshold doses for the incidence of symptoms, or modelled exposure-response relationships. The most sensitive species exhibiting ozone-specific symptoms were Cirsium arvense and Sonchus asper, which responded to accumulated ozone exposures <1500 ppb.h (AOT40). For these and three other species, an AOT40 peak of a single day was found to be responsible for the incidence of ozone-specific symptoms, i.e. injury occurred rapidly within a few days of the day with the highest AOT40, while other species responded only to longer-term ozone exposures. The relative ozone sensitivity of the species was calculated by combining the different sensitivity criteria, and possible systematic trends (taxonomic or evolutionary features) are pointed out. The results suggest it may be possible to use a particular group of native herbaceous plant species with contrasting patterns of ozone sensitivity as a biomonitoring system in the field. This allows plant responses to be related either to peak values or to prolonged ozone exposure, making it possible to distinguish between short- and long-term effects of ozone.

Visualization of axonal degeneration after optic nerve lesion in rat by immunohistochemical labelling for myelin basic protein (MBP).

Immunohistochemical staining of myelin basic protein (MBP) was followed during axonal degeneration of rat retinal fibers within the first 3 weeks after injury. Wallerian degeneration of rat retinal fibers was elicited by unilateral transection or crush injury of optic nerve. MBP-labelled fibers in central retinal pathways and visual nuclei showed sequential changes of the myelin sheath, such as swelling at 1-2 days post lesion (dpi), granular staining at 4-8 dpi, and granular debris formation at 21 dpi. Consequently, immunostaining for MBP could be used to identify early stages of degenerating myelin and persisting myelin debris which is known to contain neurite growth inhibitors.