Developmental regulation of pectic epitopes during potato tuberisation.

We show, by immunogold labelling, that potato (Solanum tuberosum L. cv Karnico) pectic epitopes are developmentally regulated within regions of the stolon, in addition to showing tissue-specific differences in abundance and localisation. The (1-->4)-beta-D-galactan and (1-->5)-alpha-arabinan epitopes demarcate two distinct zones within stolons; galactans are enriched in primary walls of elongating cells proximal to the stolon hook, whilst arabinans predominate in younger cells distal to the hook. Low-methoxyl homogalacturonan epitopes are concentrated in the middle lamella and show a proximo-distal gradient in stolons similar to that of galactans, whilst high-methoxyl homogalacturonan is uniformly abundant. Calcium pectate is restricted to the middle lamella at cell corners and pit fields. Calcium-binding sites are uniformly present in stolon cell walls, but their total density is reduced and they become localised to a few cell corners in mature tubers, as determined by image-electron energy loss spectroscopy. During the transition from elongation growth to isodiametric expansion during tuberisation of the stolon hook, there were no detectable changes in pectic epitope abundance or localisation. As tubers matured, all epitopes increased in abundance in parenchymal cell walls, except for calcium pectate. We conclude that potentially significant changes in pectic composition occur as young cells distal to the stolon hook move into the zone of cell elongation proximal to the hook.

Altered middle lamella homogalacturonan and disrupted deposition of (1-->5)-alpha-L-arabinan in the pericarp of Cnr, a ripening mutant of tomato.

Cnr (colorless non-ripening) is a pleiotropic tomato (Lycopersicon esculentum) fruit ripening mutant with altered tissue properties including weaker cell-to-cell contacts in the pericarp (A.J. Thompson, M. Tor, C.S. Barry, J. Vrebalov, C. Orfila, M.C. Jarvis, J.J. Giovannoni, D. Grierson, G.B. Seymour [1999] Plant Physiol 120: 383-390). Whereas the genetic basis of the Cnr mutation is being identified by molecular analyses, here we report the identification of cell biological factors underlying the Cnr texture phenotype. In comparison with wild type, ripe-stage Cnr fruits have stronger, non-swollen cell walls (CW) throughout the pericarp and extensive intercellular space in the inner pericarp. Using electron energy loss spectroscopy imaging of calcium-binding capacity and anti-homogalacturonan (HG) antibody probes (PAM1 and JIM5) we demonstrate that maturation processes involving middle lamella HG are altered in Cnr fruit, resulting in the absence or a low level of HG-/calcium-based cell adhesion. We also demonstrate that the deposition of (1-->5)-alpha-L-arabinan is disrupted in Cnr pericarp CW and that this disruption occurs prior to fruit ripening. The relationship between the disruption of (1-->5)-alpha-L-arabinan deposition in pericarp CW and the Cnr phenotype is discussed.

Reduced gastric mucosal vascularity in patients with chronic gastritis.

OBJECTIVES/DESIGN: Chronic inflammation is increasingly being linked to ischaemia, but the mechanism is poorly understood, and little is known about its effect on local gastric endothelial microvessels. We aimed at studying the number and surface area of gastric mucosal endothelial microstructures in the presence or absence of chronic gastritis. METHODS: Immunohistochemical assessments were carried out on gastric antral and body biopsies taken from patients with chronic gastritis and others with normal histology. The primary antibody (QB-END/10) was raised against CD34 antigen within the endothelial cell membranes. A computer attached to a microscope was used to count the number and measure the surface area of mucosal endothelial entities. RESULTS: In patients with Helicobacter pylori gastritis (n = 19), the median number of endothelial microstructures per section was 43 in the antrum and 86 in the gastric body, compared with 205 (P = 0.00004) and 165 (P = 0.002), respectively, in subjects with normal gastric histology (n = 11). The median surface area of the endothelial microstructures was also reduced in patients with gastritis. The normal gastric antrum had more endothelial entities than the normal body (median of 205 vs 165; P = 0.007). CONCLUSIONS: Within the normal stomach, the antrum is more richly vascularized than the gastric body. However, active chronic gastritis is associated with reduction in both the number and surface area of mucosal endothelial microstructures, with the reduction being more marked in the antrum. This is different from acute inflammation, and is relevant to our understanding of the natural history of mucosal defence, particularly the greater susceptibility of the gastric antrum to ulceration, compared with the gastric body.

Fine structure in cellulose microfibrils: NMR evidence from onion and quince.

It has been controversial for many years whether in the cellulose of higher plants, the microfibrils are aggregates of 'elementary fibrils', which have been suggested to be about 3.5 nm in diameter. Solid-state NMR spectroscopy was used to examine two celluloses whose fibril diameters had been established by electron microscopy: onion (8-10 nm, but containing 40% of xyloglucan as well as cellulose) and quince (2 nm cellulose core). Both of these forms of cellulose contained crystalline units of similar size, as estimated from the ratio of surface to interior chains, and the time required for proton magnetisation to diffuse from the surface to the interior. It is suggested that the onion microfibrils must therefore be constructed from a number of cellulose subunits 2 nm in diameter, smaller than the 'elementary fibrils' envisaged previously. The size of these subunits would permit a hexagonal arrangement resembling the cellulose synthase complex.

The novel fluorinated 2-nitroimidazole hypoxia probe SR-4554: reductive metabolism and semiquantitative localisation in human ovarian cancer multicellular spheroids as measured by electron energy loss spectroscopic analysis.

The novel fluorinated 2-nitroimidazole SR-4554 is undergoing preclinical development as a magnetic resonance spectroscopy and imaging probe for hypoxic tumour cells. We have used electron energy loss spectroscopic analysis (EELS) to show selective reduction and differential subcellular localisation of SR-4554 in human ovarian multicellular spheroids. SR-4554 was demonstrated to be metabolised by these A2780 cells under hypoxic but not under normal aerobic cell culture conditions. The EELS technique illustrated that the relative amount of drug within the cytoplasm of cells from both the inner region (150-160 microns from edge) and outer edge of the spheroid did not differ significantly after an initial 3 h incubation with drug. In contrast, an 8-fold differential between the amount of drug retained in the cytoplasm (primarily ribosomes and endoplasmic reticulum) of cells from the inner vs outer regions of the spheroids was observed following a subsequent 2 h 'chase' culture in drug-free medium. Within cells from the hypoxic region of the spheroid, SR-4554 was mainly associated with the endoplasmic reticulum, nucleus and the cytoplasmic side of intracellular vesicles and also to a lesser extent with the nuclear periphery. Interestingly, the drug was only weakly associated with the mitochondria and plasma membrane of the cells. The characteristics of cellular and subcellular distribution of SR-4554 are consistent with the hypothesis that 2-nitroimidazole compounds undergo hypoxia-mediated enzymatic reduction to reactive species. These reactive species are selectively retained in the cells in which they are metabolised through covalent association with subcellular components. These findings provide additional support for the clinical development of the drug as a non-invasive probe for tumour hypoxia and at the same time illustrate the utility of the EELS technique for examining the heterogeneity of drug distribution both between and within cells.

Differential intracellular processing of the anthracycline drug ME2303 in doxorubicin-sensitive (A2780) and -resistant (A2780AD) human ovarian cancer cells as studied with confocal laser scanning microscopy and image analysis.

Laser scanning confocal microscopy has been used to follow the uptake and efflux of the 2-fluoroglycoside of doxorubicin, ME2303, in live cultures of the human ovarian cancer cell line A2780 and its doxorubicin-resistant variant A2780AD. Our methods combine confocal laser scanning microscopy and image analysis to examine the dynamics of anthracycline drugs in cancer cells. Cytotoxicity determined by MTT dye reduction showed that A2780AD cells were more than 400 times less sensitive to doxorubicin compared to A2780 cells but almost 9 times more sensitive to ME2303 compared to doxorubicin. The naturally fluorescent drug was tracked within live cells at 37 degrees C to provide time-course information in relation to nuclear and Golgi-associated cellular domains, as indicated by BODIPY FL ceramide-associated fluorescence. In both cell types, ME2303 was characterised by strong nuclear membrane and perinucleolar fluorescence and as a localised punctate pattern within the nucleus. A2780AD cells accumulated ME2303 in their nuclei at a much reduced rate compared to the doxorubicin-sensitive cells, and ME2303 efflux from resistant cell nuclei was approximately twice as fast as from A2780 cells. The relative uptake of ME2303 into Golgi-associated domains and the nucleus were monitored simultaneously during the initial 35 min of exposure to 10 microM ME2303 and during the first 45 min of a "chase" culture following exposure to 20 microM ME2303. ME2303 was detectable within the Golgi-associated domains of A2780 cells several minutes later and in less relative concentration than in A2780AD cells 15 min into a chase culture. Our results suggest the direct involvement of differences in drug processing via the Golgi apparatus in the expression of P-glycoprotein-related drug resistance.

The use of parallel EEL spectral imaging and elemental mapping in the rapid assessment of anti-cancer drug localization.

Both electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS) have great potential for use in several areas of cancer research. In biologically targeted radiotherapy, cytotoxic drug therapy and boron neutron capture therapy the effectiveness of many drugs is often critically dependent upon the intracellular localization of the agent employed. We describe the use of parallel EEL spectral imaging to assess the penetration and location of the iodine-containing drug meta-iodobenzyl guanidine, of potential value in targeted radiotherapy, and for the rapid detection of boron within borate-adsorbed polystyrene beads, of potential value in boron neutron capture therapy. We also describe elemental mapping of boron following low-temperature embedding. These results show how the techniques could be applied to many forms of cancer research by discussing the validity and limitations of the techniques experimentally. We also provide an outline of other areas in this field which could benefit from the future application of ESI and EELS.

Intracellular localization of metaiodobenzyl guanidine in human neuroblastoma cells by electron spectroscopic imaging.

The targeted radiotherapy of neuroblastoma with 131l-labelled metaiodobenzyl guanidine (mIBG) is now the subject of several clinical studies. The precise intracellular localization of mIBG, necessary for nuclear microdosimetry, has not previously been described. We report the use of electron-energy-loss spectroscopy and electron spectroscopic imaging to establish the intracellular distribution of mIBG in cells from the human neuroblastoma line NBI-G which had been incubated with the drug by mapping iodine in ultra-thin sections of tumours. Most of the iodine is found within the mitochondria, with lesser amounts in the vesicles and on the nuclear membrane. The use of alternative radionuclides with different physical characteristics has been suggested to optimize the efficacy of this therapeutic strategy. The lack of penetration of mIBG into the nucleoplasm means that ultra-short-range Auger electron emitters such as 125I are not likely to prove more cytotoxic than 131I.

Maternal transferrin uptake by and transfer across the visceral yolk sac of the early postimplantation rat conceptus in vitro.

Uptake and transfer of maternal transferrin by rat embryos during organogenesis in vitro was investigated using radiolabelled rat transferrin and rocket immunoelectrophoresis. Colloidal gold to which rat transferrin was adsorbed was used as an electron microscopical marker in order to follow the route taken by internalised transferrin across the visceral yolk sac. Culture of rat conceptuses from 9.5 to 11.5 days of gestation in rat or human sera resulted in the passage of rat or human transferrin from the culture medium into the extraembryonic coelom as determined by quantitative immunoelectrophoretic analysis of exo-coelomic fluid. The concentration of human transferrin which was transferred to the exo-coelomic fluid of conceptuses cultured in whole human serum at 10.5 days and 11.5 days of gestation was similar to the concentration of rat transferrin in the fluid of conceptuses cultured in rat serum which had been diluted with Hanks' saline to 50% in order to match the levels of transferrin found in human serum. Growth of rat embryos in 50% rat serum was identical to embryonic growth in 100% rat serum. Uptake of radiolabelled rat transferrin by the visceral yolk sac at 11.5 days of gestation, following culture for 60 min in radiolabelled medium, was much greater than nonspecific uptake of radiolabelled bovine serum albumin. Accumulation of radiolabelled transferrin by the embryo was reduced by the inclusion of unlabelled transferrin into the culture medium. Uptake of transferrin adsorbed 18 nm gold particles was mediated by attachment to coated pits on the apical cell surface of the extraembryonic endoderm. Transferrin-adsorbed gold colloid was internalised via coated vesicles and found in cisternal structures of the peripheral and juxtanuclear areas, as well as in smooth and coated vesicles deep within the cell. The intercellular presence of gold particles in the endodermal layer of the visceral yolk sac and their presence in the mesoderm after 60 min of incubation suggested that passage of transferrin was rapid and mediated by vesicular evagination from the extraembryonic endoderm. These findings suggest that maternal transferrin is the primary source of transferrin for the early rat embryo and its passage to the exo-coelom and embryo is mediated by specific receptors on the apical surface of the extraembryonic endoderm.

Characterization of exocoelomic fluid protein from rat conceptuses cultured in rat and human sera: a measure of yolk sac activity during organogenesis.

Fluid from the extraembryonic coelom of 11.5-day rat embryos cultured in 100% rat serum, 100% human serum and 90% human serum supplemented with 10% rat serum between days 9.5 and 11.5 postconception were compared using polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. The protein composition of the exocoelomic fluids differed considerably from one another and from each of their respective culture sera. The majority of proteins in the exocoelom were derived from macromolecular transport but some contribution was made from protein synthesis by the conceptus. Eighteen proteins normally found in rat serum were found in the exocoelom of conceptuses cultured in 100% rat serum. Eighteen proteins were found in the exocoelom of rat conceptuses cultured in 100% human serum, of which ten were derived from human serum and eight were proteins normally found in rat serum. Analysis of fluid from conceptuses cultured in 90% human serum supplemented with 10% rat serum showed eleven human serum proteins and ten rat serum proteins. Differences in the composition of both human and rat proteins between the latter two fluids were also evident.

Growth of rat embryos in the serum of alcohol drinkers.

Seven healthy male volunteers who had fasted overnight consumed Scotch whisky (70-85 g absolute alcohol) in a period of 15 minutes after venesection at 9.30 a.m. An hour later a further quantity of blood was collected. Rat embryos (9.5 days of gestation) grown for four hours in 'post-drink' serum (115 mg alcohol/100 ml serum) followed by 44 hours in 'pre-drink' serum were compared to controls cultured in normal human serum for 48 hours. All cultures contained 90% human serum and 10% rat serum. The embryos were examined morphologically and their protein content was measured to assess in vitro growth and differentiation. The results demonstrated the teratogenic and growth-retarding effects of alcohol ingestion. Addition of ethanol (120 mg/100 ml) to the culture medium produced similar results. Culture of 9.5-day rat embryos for 24 hours in 'post-drink' serum (115 mg/100 ml alcohol) containing 10 or 20 micrograms acetaldehyde/ml or in pre-drink serum containing similar amounts of acetaldehyde showed a toxic effect of acetaldehyde only at concentrations of 20 micrograms/ml, in the absence of alcohol.

Dose-dependent induction of embryonic abnormalities in vitro by tissue homogenates of placenta and decidua.

Homogenate preparations from normal rat placental and decidual tissue induced abnormalities when included in the culture medium of rat embryos between Day 9.5 and Day 11.5. Abnormal embryos were produced between doses of 2.5 and 4 mg/ml for the placental homogenate and between doses of 1.2 and 4 mg/ml for the decidual homogenate, but were not produced by a solution of bovine serum albumin or by a protein preparation of rat lung tissue at the same concentration. The degree to which the embryos were malformed depended on the dose and which of the two homogenates was used. The decidual homogenate preparation was more pathogenic than the placental homogenate, but both were able to produce neural-tube defects and a severe reduction in embryonic size. The possible association between these findings and some known proteins within such homogenates is discussed.