Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.

Analysis of floodplain forest sensitivity to drought

Floodplain forests are very complex, productive ecosystems, capable of storing huge amounts of soil carbon. With the increasing occurrence of extreme events, they are today among the most threatened ecosystems. Our study's main goal was to assess the productivity of a floodplain forest located at Lanžhot in the Czech Republic from two perspectives: carbon uptake (using an eddy covariance method) and stem radius variations (using dendrometers). We aimed to determine which conditions allow for high ecosystem production and what role drought plays in reducing such production potential. Additionally, we were interested to determine the relative soil water content threshold indicating the onset and duration of this event. We hypothesized that summer drought in 2018 had the most significant negative effects on the overall annual carbon and water budgets. In contrast with our original hypothesis, we found that an exceptionally warm spring in 2018 caused a positive gross primary production (GPP) and evapotranspiration (ET) anomaly that consequently led in 2018 to the highest seasonal total GPP and ET from all of the investigated years (2015–2018). The results showed ring-porous species to be the most drought resistant. Relative soil water content threshold of approximately 0.45 was determined as indicating the onset of drought stress.

This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO₂, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.

Measurement(s)	net ecosystem exchange • carbon dioxide • water • energy
Technology Type(s)	eddy covariance • measurement device
Sample Characteristic - Environment	terrestrial biome • atmosphere
Sample Characteristic - Location	Earth (planet)

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12295910

Seasonally varying relationship between stem respiration, increment and carbon allocation of Norway spruce trees

Stem respiration is an important component of an ecosystem's carbon budget. Beside environmental factors, it depends highly on tree energy demands for stem growth. Determination of the relationship between stem growth and stem respiration would help to reveal the response of stem respiration to changing climate, which is expected to substantially affect tree growth. Common measurement of stem radial increment does not record all aspects of stem growth processes, especially those connected with cell wall thickening; therefore, the relationship between stem respiration and stem radial increment may vary depending on the wood cell growth differentiation phase. This study presents results from measurements of stem respiration and increment carried out for seven growing seasons in a young Norway spruce forest. Moreover, rates of carbon allocation to stems were modeled for these years. Stem respiration was divided into maintenance (Rm) and growth respiration (Rg) based upon the mature tissue method. There was a close relationship between Rg and daily stem radial increment (dSRI), and this relationship differed before and after dSRI seasonal maximum, which was around 19 June. Before this date, Rg increased exponentially with dSRI, while after this date logarithmically. This is a result of later maxima of Rg and its slower decrease when compared with dSRI, which is connected with energy demands for cell wall thickening. Rg reached a maxima at the end of June or in July. The maximum of carbon allocation to stem peaked in late summer, when Rg mostly tended to decrease. The overall contribution of Rg to stem CO2 efflux amounted to 46.9% for the growing period from May to September and 38.2% for the year as a whole. This study shows that further deeper analysis of in situ stem growth and stem respiration dynamics is greatly needed, especially with a focus on wood formation on a cell level.

Gradient and GENERIC time evolution towards reduced dynamics

Reduction of a mesoscopic dynamical theory to equilibrium thermodynamics brings to the latter theory the fundamental thermodynamic relation (i.e. entropy as a function of the thermodynamic state variables). The reduction is made by following the mesoscopic time evolution to its conclusion, i.e. to fixed points at which the time evolution ceases to continue. The approach to fixed points is driven by entropy, that, if evaluated at the fixed points, becomes the thermodynamic entropy. Since the fixed points are parametrized by the thermodynamic state variables (by constants of motion), the thermodynamic entropy arises as a function of the thermodynamic state variables and thus the final outcome of the reduction is the fundamental thermodynamic relation. This reduction process extends also to reductions in which the reduced theory still involves the time evolution (e.g. reduction of kinetic theory to hydrodynamics). The essence of the extension is the replacement of the mesoscopic time evolution of the state variables with the corresponding mesoscopic time evolution of the vector field (i.e. of the fluxes). The fixed point in this flux time evolution is the vector field generating the reduced mesoscopic time evolution. The flux-entropy driving the flux time evolution becomes, if evaluated at the fixed point, the flux fundamental thermodynamic relation in the reduced dynamical theory. We show that the flux-entropy is a potential related to the entropy production. This article is part of the theme issue 'Fundamental aspects of nonequilibrium thermodynamics'.

Variability of stem CO2 efflux response to temperature over the diel period

This study presents results from continuous measurements of stem CO2 efflux carried out for seven growing seasons in a young Norway spruce forest. The objective of the study was to determine differences in temperature sensitivity of stem CO2 efflux (Q10) during night (when sap flow is zero or nearly zero), during early afternoon (when the maximum rate of sap flow occurs) and during two transition periods between the aforementioned periods. The highest Q10 was recorded during the period of zero sap flow, while the lowest Q10 was observed in period of the highest sap flow. Calculating Q10 using only data from the period of zero sap flow resulted in a Q10 that was higher by as much as 19% compared with Q10 calculated using 24 h data. On the other hand, basing the calculation on data from the period of the highest sap flow yielded 5.6% lower Q10 than if 24 h data were used. Considering that change in CO2 efflux lagged in time behind changing stem temperature, there was only a small effect on calculated Q10 for periods with zero and the highest sap flow. A larger effect of the time lag (by as much as 15%) was observed for the two transition periods. Stem CO2 efflux was modelled based on the night CO2 efflux response to temperature. This model had a tendency to overestimate CO2 efflux during daytime, thus indicating potential daytime depression of stem CO2 efflux compared with the values predicated on the basis of temperature caused by CO2 transport upward in the sap flow. This view was supported by our results inasmuch as the overestimation grew with sap flow that was modelled on the basis of photosynthetically active radiation and vapour pressure deficit.

Variability in temperature dependence of stem CO2 efflux from Norway spruce trees

This study presents results from continuous measurements of stem CO2 efflux carried out for seven experimental seasons (from May to October) in a young Norway spruce forest. The objectives of the study were to determine variability in the response of stem CO2 efflux to stem temperature over the season and to observe differences in the calculated relationship between stem temperature and CO2 efflux based on full growing season data or on data divided into periods according to stem growth rate. Temperature sensitivity of stem CO2 efflux (Q10) calculated for the established periods ranged between 1.61 and 3.46 and varied over the season, with the lowest values occurring in July and August. Q10 calculated using data from the full growing seasons ranged between 2.30 and 2.94 and was often significantly higher than Q10 calculated for the individual periods. Temperature-normalized stem CO2 efflux (R10) determined using Q10 from growing season data was overestimated when the temperature was below 10 °C and underestimated when the temperature was above 10 °C, compared with R10 calculated using Q10 established for the individual periods. The differences in daily mean R10 calculated by these two approaches ranged between -0.9 and 0.2 μmol CO2 m-2 s-1. The results of this study confirm that long periods for determining the temperature dependence of stem CO2 efflux encompass different statuses of the wood (especially in relation to stem growth). This may cause bias in models using this relationship for estimating stem CO2 efflux as a function of temperature.

Differentiating drought legacy effects on vegetation growth over the temperate Northern Hemisphere

In view of future changes in climate, it is important to better understand how different plant functional groups (PFGs) respond to warmer and drier conditions, particularly in temperate regions where an increase in both the frequency and severity of drought is expected. The patterns and mechanisms of immediate and delayed impacts of extreme drought on vegetation growth remain poorly quantified. Using satellite measurements of vegetation greenness, in-situ tree-ring records, eddy-covariance CO₂ and water flux measurements, and meta-analyses of source water of plant use among PFGs, we show that drought legacy effects on vegetation growth differ markedly between forests, shrubs and grass across diverse bioclimatic conditions over the temperate Northern Hemisphere. Deep-rooted forests exhibit a drought legacy response with reduced growth during up to 4 years after an extreme drought, whereas shrubs and grass have drought legacy effects of approximately 2 years and 1 year, respectively. Statistical analyses partly attribute the differences in drought legacy effects among PFGs to plant eco-hydrological properties (related to traits), including plant water use and hydraulic responses. These results can be used to improve the representation of drought response of different PFGs in land surface models, and assess their biogeochemical and biophysical feedbacks in response to a warmer and drier climate.

Extreme warm temperatures alter forest phenology and productivity in Europe

Recent climate warming has shifted the timing of spring and autumn vegetation phenological events in the temperate and boreal forest ecosystems of Europe. In many areas spring phenological events start earlier and autumn events switch between earlier and later onset. Consequently, the length of growing season in mid and high latitudes of European forest is extended. However, the lagged effects (i.e. the impact of a warm spring or autumn on the subsequent phenological events) on vegetation phenology and productivity are less explored. In this study, we have (1) characterised extreme warm spring and extreme warm autumn events in Europe during 2003-2011, and (2) investigated if direct impact on forest phenology and productivity due to a specific warm event translated to a lagged effect in subsequent phenological events. We found that warmer events in spring occurred extensively in high latitude Europe producing a significant earlier onset of greening (OG) in broadleaf deciduous forest (BLDF) and mixed forest (MF). However, this earlier OG did not show any significant lagged effects on autumnal senescence. Needleleaf evergreen forest (NLEF), BLDF and MF showed a significantly delayed end of senescence (EOS) as a result of extreme warm autumn events; and in the following year's spring phenological events, OG started significantly earlier. Extreme warm spring events directly led to significant (p=0.0189) increases in the productivity of BLDF. In order to have a complete understanding of ecosystems response to warm temperature during key phenological events, particularly autumn events, the lagged effect on the next growing season should be considered.

Basophils are not the key antigen-presenting cells in allergic patients

BACKGROUND

Recent data obtained in mouse models have initiated a controversy whether basophils are the key antigen-presenting cells (APCs) in allergy. Here, we investigate whether basophils are of importance for the presentation of allergen and the induction of T cell proliferation in allergic patients.

METHODS

T cells, basophils, and APCs depleted of basophils were purified from allergic patients. Co-culture systems based on purified major allergens were established to study allergen-specific T cell responses using proliferation assays.

RESULTS

Only co-cultures of T cells with APCs depleted of basophils but not with basophils proliferated in response to allergen. Even addition of IL-3 to T cell-basophil co-cultures failed to induce allergen-specific T cell proliferation.

CONCLUSIONS

Our data demonstrate by classical in vitro proliferation assays that basophils are not key antigen-presenting cells that promote T cell proliferation in secondary immune responses to allergen in allergic patients.

Carbon exchange between ecosystems and atmosphere in the Czech Republic is affected by climate factors

By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands.

Photooxidation technology for correlated light and electron microscopy

The combination of the capabilities of light microscopical techniques with the power of resolution of electron microscopy along with technical advances has led to a gradual decline of the gap between classical light and electron microscopy. Among the correlative techniques using the synergistic opportunities, photooxidation methods have been established as valuable tools for visualizing cell structures at both light and electron microscopic level. Fluorescent dyes are used to oxidize the substrate diaminobenzidine, which in its oxidized state forms fine granular precipitates. Stained with osmium, the diaminobenzidine precipitates are well discernible in the electron microscope, thus labelling and defining the cellular structures, which at light microscopy level are recorded by fluorescent probes. The underlying photooxidation reaction is based on the excitation of free oxygen radicals that form upon illumination of fluorochromes; this is a central step in the procedure, which mainly influences the success of the method. This article summarizes basic steps of the technology and progresses, shows efforts and elaborated pathways, and focuses on methodical solutions as to the applicability of different fluorochromes, as well as conditions for fine structural localizations of the reaction products.

New organic FET-like photoactive device, experiments and DFT modeling

We present the possible construction of an organic FET-like photoactive device in which source-drain current through a phthalocyanine ( H(2)Pc film is affected by a photo-induced dipolar field in a photoactive "gate" electrode. The influence of the dipolar electric field on charge transfer between H(2)Pc molecules is modeled by DFT quantum-chemical calculations on H(2)Pc dimers and tetramers.

Seasonal variation in CO2 efflux of stems and branches of Norway spruce trees

BACKGROUND AND AIMS

Stem and branch respiration, important components of total forest ecosystem respiration, were measured on Norway spruce (Picea abies) trees from May to October in four consecutive years in order (1) to evaluate the influence of temperature on woody tissue CO2 efflux with special focus on variation in Q10 (change in respiration rate resulting from a 10 degrees C increase in temperature) within and between seasons, and (2) to quantify the contribution of above-ground woody tissue (stem and branch) respiration to the carbon balance of the forest ecosystem.

METHODS

Stem and branch CO2 efflux were measured, using an IRGA and a closed gas exchange system, 3-4 times per month on 22-year-old trees under natural conditions. Measurements of ecosystem CO2 fluxes were also determined during the whole experiment by using the eddy covariance system. Stem and branch temperatures were monitored at 10-min intervals during the whole experiment.

KEY RESULTS

The temperature of the woody tissue of stems and branches explained up to 68% of their CO2 efflux. The mean annual Q10 values ranged from 2.20 to 2.32 for stems and from 2.03 to 2.25 for branches. The mean annual normalized respiration rate, R10, for stems and branches ranged from 1.71 to 2.12 micromol CO2 m(-2)s (-1) and from 0.24 to 0.31 micromol CO2 m(-2) s(-1), respectively. The annual contribution of stem and branch CO2 efflux to total ecosystem respiration were, respectively, 8.9 and 8.1% in 1999, 9.2 and 9.2% in 2000, 7.6 and 8.6% in 2001, and 8.6 and 7.9% in 2002. Standard deviation for both components ranged from 3 to 8% of the mean.

CONCLUSIONS

Stem and branch CO2 efflux varied diurnally and seasonally, and were related to the temperature of the woody tissue and to growth. The proportion of CO2 efflux from stems and branches is a significant component of the total forest ecosystem respiration, approx. 8% over the 4 years, and predictive models must take their contribution into account.

Estimation of protease activity in soils at low temperatures by casein amendment and with substitution of buffer by demineralized water

The aim of this work was to modify the method of Ladd and Buttler (1972), by substituting Tris-HCl buffer (pH 8.52) with demineralized water (DEMI H(2)O), in order to assess its suitability for measurement of casein-protease activity at pH levels close to those of real soil in H(2)O. Measurements were undertaken over a range of incubation temperatures from 3 to 49 degrees C. Testing was performed on one organic soil and two different mineral soils. The substitution of Tris-HCl buffer by DEMI H(2)O at 49 degrees C decreased casein-protease activity to 67.25% in mineral soil and to 53.76% in organic soil. With decreasing temperature casein-protease activity decreased the most in organic soil, i.e., 0.07% of original its value at 3 degrees C. The incubation period was extended to maximally 336 h at 3 degrees C to totally obtain >10.0% of L-tyrosine equivalents released at optimum or close to optimum temperature and pH conditions. The Q(10) values of casein-protease activity measured after substituting Tris-HCl buffer with DEMI H(2)O were unexpectedly high. Between the temperatures of 3 and 49 degrees C Q(10) ranged from 3.46 to 4.25, whereas between 3 and 25 degrees C Q(10) ranged from 6.78 to 11.08. Therefore, the modified method of Ladd and Buttler (1972) presented can be used for measurement of soil casein-protease activity under pH conditions close to that of real soil pH and at an averaged soil temperatures measured in the field. This modification makes possible an expression of soil casein-protease activity potential - when being combined with measurements of casein-protease activity under optimum or close to optimum temperature and pH conditions, if high concentration of casein is present.

Carotid endarterectomy after ischemic stroke--is there a justification for delayed surgery?

PURPOSE

To assess the relationship between outcome of carotid surgery and wait after ischemic stroke.

METHODS

We retrospectively analysed data from patients undergoing carotid endarterectomy after ischemic stroke. We investigated the time interval between the event and endarterectomy in relation to surgical results and complications.

RESULTS

Between January 2000 and December 2003, 104 patients were scheduled to undergo carotid endarterectomy after a recent stroke. Endarterectomy was performed within 6 h in seven patients (6.7%); within 4 weeks in 29 (27.9%); 4 weeks or more in 62 (59.6%) and six (5.8%) patients received no further therapy. Perioperative complications among patients treated within 4 weeks were 3.4% and were comparable to those treated after 4 weeks (4.8%). However, more than 12% of the patients awaiting operation experienced a new cerebrovascular event (ischemic stroke or carotid occlusion), most of them occurred in the 3rd or 4th week after the initial event.

CONCLUSION

Our data indicates, that carotid endarterectomy can be performed with a comparable risk within a short delay after stroke. In addition severe cerebrovascular events occurring within the waiting period may be avoided.

A variant of Cenani-Lenz syndactyly (CLS): review of the literature and attempt of classification

An oligodactylous variant of Cenani-Lenz syndactyly and its surgical treatment is presented. The deformity is believed to be of autosomal recessive inheritance and caused by a disordered axial and longitudinal differentiation of the upper and lower extremities. The classical form is mainly characterised by a complete syndactyly of the hands. Malformations may also affect the bones of the forearm and, to a lesser extent, the lower limbs. We analysed clinical features and compared them with those previously described. According to our research of literature and our clinical findings there seem to exist two grossly different clinical phenotypes: spoon hand type and oligodactyly type. Typical constant clinical features such as carpal, metacarpal and digital synostoses, disorganisation of carpal bones, reduction of digital rays and syndactyly of toes are found in the reported cases. Inconstant features such as radio-ulnar synostosis, brachymesomelia, metatarsal synostoses and reduction of metatarsal rays may be present. In our case, successful bilateral digital ray individualisation and tendon transfers were performed to construct a grip function of the grossly deformed hands.

Decompression without anterior transposition: an effective minimally invasive technique for cubital tunnel syndrome

Cubital tunnel syndrome represents the second most common compression neuropathy in the upper limb. There are three main surgical procedures to deal with this issue, namely simple decompression, medial epicondylectomy and anterior transposition. Nevertheless, optimal surgical treatment is still open to question. In the past three years we performed decompression of the nerve with or without external neurolysis and epineuriotomy on 52 patients (55 extremities). Preoperative diagnostic procedures included functional hand status, neurophysiological evaluation, X-ray of the elbow and neurosonography. Patients were then divided into three groups according to the staging criteria of Dellon. After an average follow-up of 13 months, the outcome was evaluated by complete examination of hand function, electrophysiological studies and interview with the patients. Postoperatively, two-point discrimination as well as strength improved significantly. Postoperative grip was 28.78 kg (79.8 % of the other hand), compared to 20.31 kg (58 % of the other hand) preoperatively (p = 0.000). Evaluation of each stage individually showed that the best functional outcome was achieved by the minimum-staged group with improvements in strength and sensory in all patients and total relief in two-thirds. In the severe-staged group, improvement could still be found in 75 % of the patients. Evaluation of conduction velocities showed highly significant improvements for both motor and sensory conduction velocities. In summary, simple decompression, if necessary modified with external neurolysis and epineuriotomy, showed high success rates in all stages. Decompression is a minimally invasive procedure, but very effective for mild as well as for severe cases and therefore the optimal treatment in cubital tunnel syndrome.

Vascular permeability and hyperpermeability in a murine adenocarcinoma after fractionated radiotherapy: an ultrastructural tracer study

Large radiation doses cause postradiation vascular hyperpermeability by disrupting endothelia. The cumulative sequences of small doses (fractionated radiotherapy) standard in clinical practice cause it too, but not by endothelial disruption: the mechanisms are unknown. In this study, correlated fluorescent and ultrastructural localisation of a tracer revealed the architecture, fine structure and function of microvessels in mouse AT17 tumours, before and after 42 Gy fractionated radiation. Before irradiation, tumour vascular permeability lay in the normophysiological range defined by the gut and cerebral cortex. A double barrier regulated permeability: vesicular transport through the endothelial wall required approximately 2 h and then the basement membrane charge barrier trapped tracer for 2 h longer. Irradiation abolished the double barrier: tracer passed instantly through both endothelial wall and underlying basement membrane, forming diffusion haloes around microvessels within 2-5 min. Structurally, irradiated tumour microvessels were lined by a continuous and vital endothelium with closed interendothelial junctions; endothelial basement membranes were intact, though loosened. Irradiated endothelia exhibited extremely active membrane motility and intracellular vesicle trafficking. Radiation treatment raised vascular permeability by enhancing transendothelial transcytosis, and by altering the passive filter properties of the subendothelial basement membrane. This type of vascular hyperpermeability should be susceptible to pharmacological modulation.

Cryopreparation provides new insight into the effects of brefeldin A on the structure of the HepG2 Golgi apparatus

High-pressure freezing and freeze-substitution were used to study Golgi ultrastructure and its brefeldin A-induced transformations in HepG2 human hepatoma cells. Cryoimmobilization arrested subcellular dynamics within milliseconds, thus considerably improving the temporal resolution in monitoring the very early effects of high brefeldin concentrations at the ultrastructural level (i.e., 20 microg/ml brefeldin applied for 35 s to 8 min). Moreover, this approach ruled out possible cumulative and/or synergistic effects of the drug and fixatives. Several findings differed from studies based on chemical fixation. In particular, Golgi breakdown did not proceed gradually but occurred in distinct steps. We found a conspicuous lag between the absence of nonclathrin coats on Golgi membranes after 30 s of brefeldin treatment and the disassembly of the stacks, which did not start until after 90 to 120 s. At this time, domains at the trans and cis faces separated from the stacks, starting tubulation and fragmentation. After 3-5 min the Golgi apparatus was completely replaced by loose meshworks of straight tubules of different sizes and staining properties; also frequent were bent tubules and vesicles forming glomerule-like structures. After 8 min all kinds of Golgi-derived structures had aggregated within huge clusters. The morphologically highly distinct structures found after brefeldin treatment could in part be correlated with particular Golgi domains in the control cells.

Tracing uptake of C3dg-conjugated antigen into B cells via complement receptor type 2 (CR2, CD21)

Electron microscopy was used to study the internalization and delivery of ligands for complement receptor type 2 (CR2, CD21) to endocytic compartments of B-lymphoblastoid Raji cells. Opsonized antigen was mimicked with purified C3dg conjugated to colloidal gold. C3dg-gold bound specifically to the cell surface in a time-dependent manner, and preincubation of the cells with a monoclonal antibody blocking the CR2 ligand-binding site completely inhibited any C3dg-gold binding. Notably, the binding of C3d-gold was confined to cell surface protrusions, eg, microvilli. C3dg-gold was apparently internalized through coated pits located at the bases of microvilli and could be traced to different compartments of the endocytic pathway. The morphologic characteristics and intracellular distribution of these multivesicular or multilaminar structures were compatible with those of compartments known to harbor major histocompatibility complex (MHC) class II molecules. Immunolabeling showed that the internalized C3dg-gold colocalized with MHC class II in these structures. These data provide the first ultrastructural evidence that complement-coated antigens are endocytosed by antigen-nonspecific B cells by CR2 and are delivered to the compartments in which peptide loading for antigen presentation occurs. They support the notion that CR2 may play a role in antigen presentation by B cells regardless of B-cell receptor specificity. (Blood. 2000;95:2617-2623)

Molecular characterization of an autoallergen, Hom s 1, identified by serum IgE from atopic dermatitis patients

Atopy is a genetically determined disorder that affects 10%-20% of the population. Many symptoms of patients with atopy (allergic rhinitis, conjunctivitis, asthma, and anaphylaxis) result from events occurring after crosslinking of cell-bound IgE by per se innocuous environmental antigens. The frequently raised hypothesis that autosensitization can also be a pathogenetic factor in atopy, gained support by our recent demonstration of IgE antibodies against human proteins in atopic dermatitis patients. To unravel the molecular nature of IgE-defined autoantigens, we used serum IgE from atopic dermatitis patients to screen a human epithelial cDNA expression library. One of the cDNA-encoding IgE-reactive products contained 1501 bp of a 2274 bp open-reading frame finally identified by sequence analysis of two additional cDNA clones resulting from oligonucleotide screening. The IgE-defined autoantigen, designated Hom s 1, exhibited an almost complete sequence identity with a recently described antigen recognized by cytotoxic T cells of a squamous cell carcinoma patient. Purified recombinant Hom s 1 specifically bound IgE from patients with severe atopy. When used as immunogen in rabbits, recombinant Hom s 1 gave rise to an anti-serum that reacted with a cytoplasmic protein exhibiting a broad cellular and tissue reactivity (skin, lung >> gastrointestinal tract >> muscle, brain) and identified a 55 kDa protein in blotted serum IgE preparations. The attractive possibility remains that the Hom s 1-triggered IgE response contributes to the events resulting in allergic tissue inflammation. If so, the respective recombinant molecule may serve as a paradigmatic tool for the diagnosis and treatment of patients with "intrinsic" atopy.

The possible role of the immune system in Alzheimer's disease

Currently, there is little doubt that the immune system plays a role in the neurodegenerative process in Alzheimer's disease (AD). Inflammatory proteins such as complement components, enzymes, eicosanoids, and cytokines are found in association with cerebral amyloid plaques and may exacerbate the fundamental pathology of AD, by stimulating Amyloid beta (A beta) production, supporting its aggregation and increasing its cytotoxicity. Activated microglia and astrocytes are the main source of these proteins, and A beta may trigger their release. Interestingly, there are also indications that the immune system may play a protective role against the development of AD. Microglial cells have been shown to degrade A beta, and recent evidence suggests that autoreactive A beta-specific T cells may be relevant to the elimination of the peptide. This mechanism seems, however, impaired in the majority of patients with AD. The immune system seems thus to represent a natural line of defense against the accumulation of dangerous amyloidogenic substances. Impairment of this specific immunological defense mechanism and the failure to eliminate a toxic metabolite can be the basis for a chronic nonspecific inflammatory process in the brain, as described above. AD is a good example how an immune response initially aiming at maintaining the integrity of the body may fail and consequently lead to tissue destruction and neuronal loss.

Irradiation induces G2/M cell cycle arrest and apoptosis in p53-deficient lymphoblastic leukemia cells without affecting Bcl-2 and Bax expression

The tumor suppressor p53 has been implicated in gamma irradiation-induced apoptosis. To investigate possible consequences of wild-type p53 loss in leukemia, we studied the effect of a single dose of gamma irradiation upon p53-deficient human T-ALL (acute lymphoblastic leukemia) CCRF - CEM cells. Exposure to 3 - 96 Gy caused p53-independent cell death in a dose and time-dependent fashion. By electron microscopic and other criteria, this cell death was classified as apoptosis. At low to intermediate levels of irradiation, apoptosis was preceded by accumulation of cells in the G2/M phase of the cell division cycle. Expression of Bcl-2 and Bax were not detectably altered after irradiation. Expression of the temperature sensitive mouse p53 V135 mutant induced apoptosis on its own but only slightly increased the sensitivity of CCRF - CEM cells to gamma irradiation. Thus, in these, and perhaps other leukemia cells, a p53- and Bcl-2/Bax-independent mechanism is operative that efficiently senses irradiation effects and translates this signal into arrest in the G2/M phase of the cell cycle and subsequent apoptosis.

Endocytic routes to the Golgi apparatus

The endocytic routes of labelled lectins as well as cationic ferritin were studied in cells with a regulated secretion, i.e. pancreatic beta cells, and in constitutively secreting cells, i.e. fibroblasts and HepG2 hepatoma cells, paying particular attention to routes into the Golgi apparatus. Considerable amounts of internalised molecules were taken up into the trans Golgi network (TGN) and into Golgi subcompartments in all three cell types as well as in secretory granules of the pancreatic beta cells. The internalised materials did not pass rapidly the TGN and Golgi stacks, but were still present hours after internalisation, being then particularly concentrated in TGN-elements and in the transmost Golgi cisterna. Endocytosed materials reached forming secretory granules present in the TGN. Further, direct fusion between endocytotic vesicles and mature secretory granules was observed. Golgi subcompartments as well as endocytic TGN containing endocytosed materials were in close apposition to specialised regions of the endoplasmic reticulum. The Golgi apparatus including its parts containing endocytosed materials were transformed into a tubular reticulum upon treatment with the fungal metabolite Brefeldin A. Rarely, internalised material was observed in the lumen of the endoplasmic reticulum, thus providing evidence for an endocytic plasma membrane to endoplasmic reticulum route.

Free neurovascular transfer of latissimus dorsi muscle to the bladder. I. Experimental studies

OBJECTIVES

Experimental studies were undertaken to investigate the practicability of a microneurovascular transfer of latissimus dorsi muscle to the bladder, and to look for possible techniques enhancing evacuation of a reservoir such as the bladder by striated muscle.

MATERIALS AND METHODS

Twelve dogs were used for the studies. They were divided into 3 groups. Group I: Evacuation proficiency of a re-configured latissimus dorsi under tension was hydrodynamically tested after 6 months. Group II: Microneurovascular latissimus dorsi transposition anastomosing thoracodorsal vessels and nerve to circumflexa ilium profunda vessels and a lumbar plexus motor nerve, respectively, was performed to cover the bladder devoid of up to 50% of the detrusor muscle. Group III: Microneurovascular latissimus dorsi transposition was used to reconstruct the bladder after supratrigonal cystectomy. Urodynamic and radiographic in vivo studies were done after 6 and 9 months.

RESULTS

Stimulation of the thoracodorsal nerve of geometrically reconfigurated non-transposed latissimus dorsi reservoirs after 6 months yielded average intraluminar pressures of 190 cm. H2O at maximum capacity, and 35 cm. H2O at a minimum capacity of 10 to 15 cc. Stimulation of latissimus dorsi transposed to the bladder resulted in a visible and measurable contraction of the transplanted muscle after 9 months. Mean bladder volumes in group II animals pre- and postoperatively were 267.5 and 270 cc, respectively. During cystography the bladder outline was smooth both during filling and voiding. Light and electron microscopic examination confirmed viable, re-innervated muscle.

CONCLUSIONS

The "tension-torsion" reconfiguration produced intraluminal pressures which should enable stimulated striated muscle to evacuate bladder-like reservoirs successfully. Microneurovascular free transfer of latissimus dorsi muscle resulted in reinnervated, functional muscle in the pelvis. Augmentation cystoplasty using the latissimus dorsi in conjunction with a free omental flap for substitution of an accompanying mucosal defect was unsuccessful. The concept of microneurovascular transfer of latissimus dorsi muscle to the pelvis may be used for complicated fistula of the lower urinary tract, and may be a possible solution for the therapy resistent acontractile bladder.

Interactions of the Alzheimer beta amyloid fragment (25-35) with peripheral blood dendritic cells

We have previously demonstrated that soluble amyloid beta protein (A beta) induces IL-2 receptor expression and proliferation in peripheral T cells from young and old healthy individuals, but not from patients with Alzheimer's disease (AD). It seemed of interest to examine how the immune system would react upon stimulation with A beta in its aggregated form. It was the aim of this study to define interactions between the spontaneously aggregating A beta (25-35) and antigen-presenting cells. Human dendritic cells (DC), propagated from the peripheral blood of young healthy individuals, were incubated with A beta (25-35) and its effects on DC survival, cytokine release, and surface marker expression were monitored. The question whether DC could present amyloid to T cells was also addressed. We demonstrated that A beta (25-35) does not induce DC apoptosis or necrosis. This was shown by electron microscopy as well as by nuclear staining with propidium iodide. Some peptide aggregates were found in intracellular vacuoles of DC. This process did not increase production of TNF alpha and did not change the surface expression of CD18, CD11a or CD11b. A decreased surface expression of MHC class II molecules was, however, noted. DC pulsed with A beta aggregates were unable to stimulate T cells in an autologous coculture system. The results demonstrate that amyloid may escape immune recognition by its failure to activate antigen-presenting cells and by inhibiting MHC class II surface expression.

Role of 7,8-dihydroneopterin in T-cell apoptosis and HTLV-1 transcription in vitro

Adult T-cell leukemia is associated with high levels of neopterin, released in large amounts from human macrophages upon stimulation with interferon-gamma. Recent data suggested a potential role of neopterin-derivatives in oxygen radical-mediated processes, and evidence accumulates that oxidative stress is involved in the pathogenesis of viral diseases. We now report that increased concentrations of 7,8-dihydroneopterin may lead to enhanced apoptosis and disturbance of the redox-balance of human leukemic Jurkat T cells. Additionally, we demonstrate that 7,8-dihydroneopterin and hydrogen peroxide activate the type 1 human T-cell leukemia virus (HTLV-1) long terminal repeat (LTR). Furthermore, we found that the activity of the HTLV-1 transactivator protein Tax is amplified by an elevated concentration of 7,8-dihydroneopterin. Tax did not significantly augment 7,8-dihydroneopterin mediated apoptosis. Based on our data we propose that 7,8-dihydroneopterin may be involved in the progression to higher stages of HTLV-1 associated disease.

Effect of pluronic L-81 on intestinal lipoprotein secretion in the rat

The hydrophobic nonionic detergent Pluronic L-81 has been shown to lower plasma very-low- and low-density lipoprotein cholesterol, thus preventing diet-induced atherogenesis. The major effect of this agent is a pronounced interference with intestinal lipid metabolism. For studying mesenteric lymph lipoproteins during detergent exposure, a combined micromorphological and biochemical assessment of mucosa and lymph during steady-state lipid absorption was performed. Pluronic L-81 was infused intraduodenally at a constant rate in combination with mixed micellar solutions or saline in mesenteric lymph fistula rats. Pluronic L-81 impairs transepithelial lipid flux during fat absorption, trapping export lipids within the enterocytes and leading to a cytosolic and endoplasmic reticulum lipid accumulation sparing the Golgi region. Pluronic L-81 markedly (P < 0.001) reduces mesenteric triglyceride, phospholipid, and total cholesterol secretion almost exclusively by a reduction of chylomicron formation. Chylomicron and very-low-density lipoprotein lipid composition was only insignificantly altered, except for somewhat higher phospholipid/triglyceride ratios. The chylomicron apoprotein pattern was almost unaffected. Thus, chylomicron formation decreased dramatically without major compositional alterations. The reduction of lipid and apoprotein secretion without particle augmentation is not in favour of a selective interference of Pluronic L-81 with intestinal apoprotein B-48 secretion.

Tumour-cell-endothelial interactions: free radicals are mediators of melanoma-induced endothelial cell damage

Damage to vascular endothelium may play an important role during metastasis. We used a three-dimensional model of tumour cell extravasation to test the hypothesis that certain types of tumour cells are able to induce vascular endothelial cell injury. Multicellular tumour spheroids (MCTS) of 14 human cancer cell lines and spheroids from two benign cell lines were transferred onto confluent monolayers of human endothelial cells (EC). MCTS from 4 of 7 melanoma cell lines induced damage of the endothelium which was closely associated with tumour cell attachment. Endothelial cell injury became evident morphologically by loss of cell membrane integrity and sensitivity to shear stress. Similar results were obtained with EC derived from human umbilical veins, umbilical arteries and saphenous veins. Addition of the oxygen radical scavenger catalase showed a dose- and time-dependent inhibition (up to 48 h) of EC damage in the case of the melanoma cell lines ST-ML-11, ST-ML-14 and SK-MEL-28. The scavenging enzyme superoxide dismutase proved to be protective (up to 12 h) in ST-ML-12 MCTS. In contrast, allopurinol, deferoxamine mesylate, ibuprofen, nor-dihydroguaretic acid, soybean trypsin inhibitor or aprotinin had no protective effect. None of the non-melanoma cancer cell lines or benign cells induced endothelial cell damage. Endothelial injury has been shown to enhance the process of metastasis. Our results suggest that free-radical-mediated endothelial cell damage may be one of the mechanisms contributing to the devastating metastatic potential of melanoma.

Ultrastructural lectinocytochemistry of fowl plague virus-infected and uninfected MDCK cells

Using horseradish peroxidase (HRP)-conjugated lectins for pre-embedding labelling we have shown differences in ultrastructural localization of saccharides in cell compartments of fowl plague (FP) virus-infected and uninfected MDCK cells. Lectinochemical staining of the cell compartments in the case of FP virus-infected MDCK cells was less intensive as compared with uninfected cells. Also certain differences in the staining of subcompartments of cell organells were seen. Staining of uninfected cells with Pisum sativum agglutinin (PSA)-HRP revealed an extensive visualization of Golgi complex, mainly its cis-part, TGN vesicles and lysosomes. Staining of FP virus-infected cells with the same lectin marked very lightly rough endoplasmic reticulum and not at all the Golgi complex. Staining with Erythrina cristagalli agglutinin (ECA)-HRP revealed a picture very similar to PSA-HRP staining of uninfected and FP virus-infected cells. The differences in the lectinochemical staining of cell organelles of FP virus-infected and uninfected cells may be connected with the inhibition of cell protein synthesis during FP virus morphogenesis.

Chromatin condensation during apoptosis is accompanied by degradation of lamin A+B, without enhanced activation of cdc2 kinase

Chromatin condensation paralleled by DNA fragmentation is one of the most important criteria which are used to identify apoptotic cells. However, comparable changes are also observed in interphase nuclei which have been treated with cell extracts from mitotic cells. In this respect it is known that in mitosis, the lamina structure is broken down as a result of lamin solubilization and it is possible that a similar process is happening in apoptotic cells. The experiments described in this study have used confluent cultures of an embryonic fibroblast cell line which can be induced to undergo either apoptosis at low serum conditions or mitosis. Solubilization of lamin A+B was analyzed by immunoblotting and indirect immunofluorescence. These studies showed that in mitotic cells lamina breakdown is accompanied by lamin solubilization. In apoptotic cells, a small amount of lamin is solubilized before the onset of apoptosis, thereafter, chromatin condensation is accompanied by degradation of lamin A+B to a 46-kD fragment. Analysis of cellular lysates by probing blots with anti-PSTAIR followed by anti-phosphotyrosine showed that in contrast to mitosis, dephosphorylation on tyrosine residues did not occur in apoptotic cells. At all timepoints after the onset of apoptosis there was no significant increase in the activation of p34cdc2 as determined in the histone H1 kinase assay. Coinduction of apoptosis and mitosis after release of cells from aphidicolin block showed that apoptosis could be induced in parallel with S-phase. The sudden breakdown of chromatin structure may be the result of detachment of the chromatin loops from their anchorage at the nuclear matrix, as bands of 50 kbp and corresponding multimers were detectable by field inversion gel electrophoresis (FIGE). In apoptotic cells all of the DNA was fragmented, but only 14% of the DNA was smaller than 50 kbp. DNA strand breaks were detected at the periphery of the condensed chromatin by in situ tailing (ISTAIL). Chromatin condensation during apoptosis appears to be due to a rapid proteolysis of nuclear matrix proteins which does not involve the p34cdc2 kinase.

Rat liver endocytic coated vesicles do not exhibit ATP-dependent acidification in vitro

Coated vesicle fractions from a variety of tissues have been found to contain a vacuolar proton ATPase. Since these fractions contain both plasma membrane- and Golgi-derived coated vesicles, we sought to determine specifically whether endocytic coated vesicles from rat liver contain an active vacuolar proton ATPase. Endocytic vesicles (coated vesicles and endosomes) were selectively labeled with pH-sensitive endocytic tracers (fluorescein isothiocyanate-dextran or -asialoorsomucoid). Coated vesicles were then separated from endosomes by sucrose density gradient centrifugation. Although the endosomal fractions were found to exhibit significant ATP-dependent acidification activity, highly purified coated vesicles containing pH-sensitive endocytic tracers were unable to generate a pH gradient in response to ATP addition. The coated vesicles could be passively acidified, however, by creating potassium diffusion potentials, indicating that they were in fact capable of maintaining proton gradients. Moreover, significant ATP-dependent acidification activity was observed when the coated vesicle fractions were assayed using the nonselective externally added pH probe acridine orange. Thus, it appears that rat liver endocytic coated vesicles do not contain a functional proton pump. The active vacuolar proton ATPase found in these fractions instead reflected the presence of Golgi-derived coated vesicles or contaminating membranes.

Apoptosis is induced by transforming growth factor-beta 1 within 5 hours in regressing liver without significant fragmentation of the DNA

In previous studies we showed that transforming growth factor-beta 1 induces apoptosis in hepatocyte cultures and regressing livers, the mature form being more potent than the transforming growth factor-beta 1 latency-associated protein. In this study we addressed the question of whether apoptosis can be induced within a short time after administration of transforming growth factor-beta 1. Five hours after a single intravenous injection of 25 micrograms mature transforming growth factor-beta 1/kg body weight, apoptosis is augmented ninefold in the regressing rat liver. A second preceding application induces no further augmentation. Transforming growth factor-beta 1 latency-associated protein shows no effect with either regimen. Morphological evaluation shows that 5 hr after injection of transforming growth factor-beta 1 nearly all apoptotic bodies are already engulfed by their neighbor cells. After homogenization of the transforming growth factor-beta 1-treated livers, the condensed apoptotic bodies are not destroyed and remain in the nuclear pellet. No DNA fragmentation into oligosomes could be detected after purification of the DNA from the nuclear pellet and application to conventional gel electrophoresis. Application of in situ nick translation, which allows detection of DNA single- and double-strand breaks in individual apoptotic bodies, also revealed no substantial fragmentation of the DNA in apoptotic bodies. These studies show that transforming growth factor-beta 1 is able to induce apoptosis within a rather short time and also suggest that in vivo digestion of the DNA does not lead to chromatin condensation.

Early and late transformations occurring at organelles of the Golgi area under the influence of brefeldin A: an ultrastructural and lectin cytochemical study

We investigated the early and late changes of the Golgi region under the influence of the fungal metabolite brefeldin A (BFA) by electron microscopy and lectin cytochemistry using the beta-galactose-specific lectin from the beetle Allomyrina dichotoma (Allo A). In control cells, Allo-A reactions were confined to trans-Golgi elements, the trans-Golgi network, and to endosomes and lysosomes; the nuclear envelope and endoplasmic reticulum were consistently free of Allo A reactions. Our findings with cells from three different lines (i.e., HepG2 hepatoma cells, WI38 fibroblasts, and L132 embryonic lung cells) showed tubular-reticular transformations of the Golgi stacks as early as 30 sec after application of BFA. The transformations started at the cis side and proceeded rapidly; after only a few minutes the Golgi apparatus was no longer apparent as an individual entity. Simultaneously, giant tubules grew out of the Golgi region and traversed the cytoplasm over micrometer-long distances. In part, they were reactive for Allo A. Reactions for beta-galactose occurred in cisternae of the endoplasmic reticulum after 4-5 min of BFA treatment; after 30 min the entire endoplasmic reticulum was intensely reactive for Allo A. At 5 min and later, the tubular-reticular transformations appeared more compact, forming glomerulus-like structures (glomerulini). These were closely associated with cisternae of the endoplasmic reticulum. Initially, glomerulini were mostly Allo A negative or showed peripheral Allo A-positive segments. The number of Allo A-positive glomerulini increased with the duration of treatment. Our findings identify the glomerulini as bipolar structures forming a link between the endoplasmic reticulum and the dissociating Golgi stacks.

Condensation of the chromatin at the membrane of an apoptotic nucleus is not associated with activation of an endonuclease

A current hypothesis holds that chromatin fragmentation into oligonucleosomal patterns is an early event during apoptosis. In contrast, induction of apoptosis in cultured hepatocytes by TGF-beta 1 was not associated with DNA fragmentation into oligonucleosomes in hepatocyte monolayers and apoptotic fragments. For a more rigorous test of the hypothesis we performed a number of experiments. We compared nuclear changes resulting from TGF-beta 1 with those induced by Ca2+, a known activator of endonuclease. The morphology of apoptotic and Ca(2+)-treated nuclei was different as judged by DNA staining with Hoechst 33258. Likewise, electron microscopy of apoptotic nuclei showed characteristic condensation of the chromatin as well as dissolution of the nucleolar structure and nuclear fragmentation, changes not seen after Ca2+ treatment, after three hours of incubation. Analysis of DNA fluorescence of nuclei by FACS revealed that treatment with Ca2+ reduced the signal by 20%. In contrast, nuclei from TGF-beta 1-treated hepatocytes did not exhibit a reduced signal and after sorting by FACS, apoptotic nuclei remained in the 2N and 4N fractions. The absence of detectable DNA fragmentation in apoptotic nuclei was further verified by in situ nick translation, not only in hepatocytes but also in a mouse lymphoma cell line. From these findings we conclude that activation of an endonuclease is not an early event on the pathway to morphologically recognizable apoptosis.

Induction of apoptosis in cultured hepatocytes and in the regressing liver by transforming growth factor-beta 1 occurs without activation of an endonuclease

In previous studies in vivo apoptotic liver cells were found to be positive for transforming growth factor-beta 1 (TGF-beta 1). In hepatocyte cultures TGF-beta 1 induced rounding up and fragmentation of the cells into multiple vesicles. As revealed by the DNA specific stain H33258 the chromatin of these cells condensed and segregated into masses at the nuclear membrane, followed by nuclear fragmentation. Ultrastructurally the cytoplasm was well preserved as demonstrated by the presence of intact cell organelles. These features strongly suggest that occurrence of apoptosis. Furthermore we administered TGF-beta 1 in vivo using an experimental model in which regression of the liver was initiated by a short preceding treatment with the hepatomitogen cyproterone acetate (CPA). Two doses of 1 nM TGF-beta 1/kg each augmented the incidence of apoptotic hepatocytes 5-fold. These studies strongly suggest that TGF-beta 1 is involved in the initiation of apoptosis in the liver In TGF-beta 1 treated hepatocytes both from the liver and monolayer culture no DNA fragmentation into oligosomes could be detected. Comparison of nuclei in which endonuclease was activated by Ca2+ with apoptotic nuclei revealed no obvious similarities, as demonstrated by FACS analysis, H33258 staining and electron microscopy. Thus, apoptosis induced by a growth inhibitor obviously occurs without activation of an endonuclease.

Subdomains of the rough endoplasmic reticulum in colon goblet cells of the rat: lectin-cytochemical characterization

Using lectin binding, we characterized subdomains of the rough endoplasmic reticulum (rER) in goblet cells of the rat colon. In this cell type, special rER regions can be differentiated on the basis of their content of low electron density and dilated cisternal spaces in conventional transmission electron microscopic preparations. The fine fibrillar content of these cisternal regions demonstrated high-affinity binding with lectins from wheat germ, Helix pomatia, Griffonia simplicifolia I-A4 and -B4, and Ricinus communis I, although not with the sialic acid-specific Limax flavus lectin and the fucose-binding Ulex europaeus I lectin. Sugar-inhibitory experiments indicated that glycoconjugates packed within these regions bound the lectins with higher affinity than molecules present in the Golgi apparatus and secretory granules. Furthermore, the lectin binding patterns of the rER subdomains differed from those of the Golgi apparatus and mucin granules: the terminal sugar residues sialic acid and fucose were demonstrable in the Golgi apparatus and mucin granules and were absent from the rER, while galactose-recognizing lectins bound intensely at these rER regions, weakly to Golgi elements, and were almost absent from mucin granules.

Induction of apoptosis in cultured hepatocytes and in regressing liver by transforming growth factor beta 1

In previous studies hepatocytes undergoing cell death by apoptosis but not normal hepatocytes in rat liver showed immunostaining for transforming growth factor beta 1 (TGF-beta 1). Staining was much stronger with antibodies recognizing the pro-region of TGF-beta 1 than the mature peptide itself. Therefore we investigated the ability of both forms of TGF-beta 1 to induce apoptosis in primary cultures of rat hepatocytes. Mature TGF-beta 1 induced rounding up of the cells and fragmentation into multiple vesicles. As revealed by the DNA-specific stain H33258, the chromatin of these cells condensed and segregated into masses at the nuclear membrane; this was obviously followed by fragmentation of the nucleus. Ultrastructurally the cytoplasm was well preserved, as demonstrated by the presence of intact cell organelles. These features strongly suggest the occurrence of apoptosis. Quantification of nuclei with condensed chromatin revealed that mature TGF-beta 1 was 30-fold more effective than the TGF-beta 1 latency-associated protein complex. Finally, we administered TGF-beta 1 in vivo using an experimental model in which regression of rat liver was initiated by a short preceding treatment with the hepatomitogen cyproterone acetate. Two doses of TGF-beta 1, each 1 nM/kg, augmented the incidence of apoptotic hepatocytes 5-fold. Equimolar doses of TGF-beta 1 latency-associated protein complex were ineffective. These studies suggest that TGF-beta 1 is involved in the initiation of apoptosis in the liver and that the mature form of TGF-beta 1 is the active principle.

The differential effects of N,N-dimethylformamide and transforming growth factor-beta 1 on a human ovarian cancer cell line (HOC-7)

We have compared the effects of N,N-dimethylformamide (DMF) and transforming growth factor (TGF)-beta 1 on the growth and phenotype of HOC-7 ovarian cancer cells. Previous density gradient fractionation of untreated HOC-7 cells suggested that rapidly growing small polygonal medium density cells revert spontaneously into less malignant flattened low density cells. Here we demonstrate that DMF and TGF-beta 1 induce similar flattened cell phenotypes. Both agents induce qualitatively similar alterations in the cells. DMF, however, exerted stronger effects than TGF-beta 1. The cells become flattened, develop cytoplasmic extensions, and reduce DNA-synthesis as well as anchorage-dependent and -independent growth. These effects are reversible after removal of the inducers, indicating that the cells have not become terminally differentiated. Electron microscopy demonstrates prominent filament bundles in treated cells. Immunofluorescence further shows that these cells contain large amounts of cytokeratin. Immunocytochemistry and ELISA demonstrate 1- to 5-fold higher amounts of desmoplakin and fibronectin after DMF- or TGF-beta 1-exposure. The described differentiation-like responses of HOC-7 cells can be used for recognition of pharmacologically induced maturation of ovarian cancer cells.

The effects of dimethyl sulfoxide and retinoic acid on the cell growth and the phenotype of ovarian cancer cells

We have compared the in vitro effects of the differentiation inducers dimethyl sulfoxide (DMSO) and retinoic acid (RA) on a polyclonal human ovarian cancer cell line (HOC-7). Density gradient fractionation of untreated cells reveals that a proportion of rapidly growing, polygonal cells with medium density is capable of spontaneous reversion into a slowly growing low-density phenotype with flattened morphology similar to non-transformed human ovarian surface epithelial cells. Clonal expansion of these low-density cells proves that the observed characteristics are stable for prolonged culture periods. Exposure of HOC-7 cells to DMSO and RA or removal of the serum from the medium is effective in enhancing the proportion of these low-density cells. Application of DMSO causes the cells to become flattened and elongated, and to develop rod-like protrusions. In these cytoplasmic extensions thick filament bundles are dominant. Immunofluorescence studies demonstrate that both untreated low-density subclones and DMSO-treated polyclonal cells are much more reactive for cytokeratin than medium-density subclones or untreated parental cells. Furthermore, immunocytochemistry and fixed-cell ELISA reveal 2- to 5-fold greater amounts of desmoplakins I and II and of fibronectin in low-density subclones and in DMSO-treated cells as compared to medium-density subclones and control cultures. RA exerts weaker effects on the phenotype of the cells. Both inducers reduce DNA synthesis and inhibit the anchorage-dependent and the anchorage-independent cell growth in a dose- and time-dependent manner. The restoration of the original morphology and growth rate after removal of the differentiation-inducing agents proves that the observed changes are reversible; this indicates that the cells do not become terminally differentiated.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochemical characteristics of the Golgi apparatus

Lectinocytochemistry provides a useful tool for localizing subcompartments of the complex reticular apparatus of Golgi. The technique is based on interactions of lectins with glycoconjugates present in the limiting membranes and luminal spaces of Golgi elements. Application of a series of lectins of different sugar specificities permits a differentiation between Golgi subcompartments containing glycoconjugates with different oligosaccharide side chains. These may be a) differnet glycoconjugates or b) glycoconjugates at different stages during synthesis or repair of their glycans. The lectinocytochemical studies with mannose-, glucose-, N-acetyl-glucosamine-, N-acetyl-galactosamine-, galactose-, fucose-, and sialic acid-recognizing lectins revealed predominating patterns that labeled distinct, i.e., cis, medial, trans, and transmost, regions of the Golgi apparatus. A further refinement could be achieved by differential lectin-inhibition that enables a dissection of lectin binding reactions on the basis of their binding affinities. High-affinity binding reactions showed that subcompartments are not necessarily confined to one single Golgi subregion and may change their position from one to another subregion. Some of the patterns observed may be interpreted in relation to certain steps during synthesis and modifications of glycans.