THE PRESERVATION OF ULTRASTRUCTURE AND ANTIGENICITY

Protocol development for somatic embryogenesis, SSR markers and genetic modification of Stipagrostis pennata (Trin.) De Winter

BACKGROUND

Stipagrostis pennata (Trin.) De Winter is an important species for fixing sand in shifting and semi-fixed sandy lands, for grazing, and potentially as a source of lignocellulose fibres for pulp and paper industry. The seeds have low viability, which limits uses for revegetation. Somatic embryogenesis offers an alternative method for obtaining large numbers of plants from limited seed sources.

RESULTS

A protocol for plant regeneration from somatic embryos of S. pennata was developed. Somatic embryogenesis was induced on Murashige & Skoog (MS) medium supplemented with 3 mg·L-1 2,4-D subsequently shoots were induced on MS medium and supplemented with 5 mg·L-1 zeatin riboside. The highest shoots induction was obtained when embryogenic callus derived from mature embryos (96%) in combination with MS filter-sterilized medium was used from Khuzestan location. The genetic stability of regenerated plants was analysed using ten simple sequence repeats (SSR) markers from S. pennata which showed no somaclonal variation in regenerated plants from somatic embryos of S. pennata. The regenerated plants of S. pennata showed genetic stability without any somaclonal variation for the four pairs of primers that gave the expected amplicon sizes. This data seems very reliable as three of the PCR products belonged to the coding region of the genome. Furthermore, stable expression of GUS was obtained after Agrobacterium-mediated transformation using a super binary vector carried by a bacterial strain LBA4404.

CONCLUSION

To our knowledge, the current work is the first attempt to develop an in vitro protocol for somatic embryogenesis including the SSR marker analyses of regenerated plants, and Agrobacterium-mediated transformation of S. pennata that can be used for its large-scale production for commercial purposes.

Oolong tea and LR-White resin: a new method of plant sample preparation for transmission electron microscopy

Simplifying sample processing, shortening the sample preparation time, and adjusting procedures to suitable for new health and safety regulations, these issues are the current challenges which electron microscopic examinations need to face. In order to resolve these problems, new plant tissue sample processing protocols for transmission electron microscopy should be developed. In the present study, we chose the LR-White resin-assisted processing protocol for the ultrastructural observation of different types of plant tissues. Moreover, we explored Oolong tea extract (OTE) as a substitute for UA in staining ultrathin sections of plant samples. The results revealed that there was no significant difference between the OTE double staining method and the traditional double staining method. Furthermore, in some organelles, such as mitochondria in root cells of tomatoes and chloroplast in leaf cells of watermelons, the OTE double staining method achieved little better results than the traditional double staining method. Therefore, OTE demonstrated good potentials in replacing UA as a counterstain on ultrathin sections. In addition, sample preparation time was significantly shortened and simplified using LR-White resin. This novel protocol reduced the time for preparing plant samples, and hazardous reagents in traditional method (acetone and UA) were also replaced by less toxic ones (ethanol and OTE).

Out with the old and in with the new: rapid specimen preparation procedures for electron microscopy of sectioned biological material

This article presents the best current practices for preparation of biological samples for examination as thin sections in an electron microscope. The historical development of fixation, dehydration, and embedding procedures for biological materials are reviewed for both conventional and low temperature methods. Conventional procedures for processing cells and tissues are usually done over days and often produce distortions, extractions, and other artifacts that are not acceptable for today's structural biology standards. High-pressure freezing and freeze substitution can minimize some of these artifacts. New methods that reduce the times for freeze substitution and resin embedding to a few hours are discussed as well as a new rapid room temperature method for preparing cells for on-section immunolabeling without the use of aldehyde fixatives.

Immunogold for detection of avian leukosis/sarcoma virus in formalin-fixed heart and kidney

Immunoprobes are used in the qualitative and semi-quantitative demonstration of antigens in clinical samples. In the present study, an immunogold method has been used for routine and rapid detection of avian leukosis/sarcoma virus (AL/SV) in sections of formalin-fixed chicken heart and kidney. Application of this ultrastructural indirect immunogold labelling technique (IILT) will enable pathologists to obtain a definitive diagnosis of avian AL/SV infection when inclusions or putative viral particles are observed by light or electron microscopy. IILT also may be used in research on AL/SV infections.

Nodulation of Crotalaria podocarpa DC. by Methylobacterium nodulans displays very unusual features

Crotalaria are plants of the Fabaceae family whose nodulation characteristics have been little explored despite the recent discovery of their unexpected ability to be efficiently nodulated in symbiosis with bacteria of the genus Methylobacterium. It has been shown that methylotrophy plays a key role in this unusual symbiotic system, as it is expressed within the nodule and as non-methylotroph mutants had a depleting effect on plant growth response. Within the nodule, Methylobacterium is thus able to obtain carbon both from host plant photosynthesis and from methylotrophy. In this context, the aim of the present study was to show the histological and cytological impacts of both symbiotic and methylotrophic metabolism within Crotalaria podocarpa nodules. It was established that if Crotalaria nodules are multilobed, each lobe has the morphology of indeterminate nodules but with a different anatomy; that is, without root hair infection or infection threads. In the fixation zone, bacteroids display a spherical shape and there is no uninfected cell. Crotalaria nodulation by Methylobacterium displayed some very unusual characteristics such as starch storage within bacteroid-filled cells of the fixation zone and also the complete lysis of apical nodular tissues (where bacteria have a free-living shape and express methylotrophy). This lysis could possibly reflect the bacterial degradation of plant wall pectins through bacterial pectin methyl esterases, thus producing methanol as a substrate, allowing bacterial multiplication before release from the nodule.

Rapid diagnostic thin section electron microscopy of bacterial endospores

Emerging infectious diseases such as SARS and the bioterror attacks with anthrax spores that occurred after September 11th, 2001 have highlighted the need to be better prepared for the detection and management of infectious pathogens that threaten public health. Negative staining electron microscopy is one method used to screen environmental and clinical samples for relevant infectious pathogens. Unfortunately, bacterial endospores, like those of Bacillus anthracis, are difficult to identify using this method because of their density that prevents imaging of structural details. Thin section electron microscopy would be an alternative method but this usually requires a few days for preparation and diagnosis. In the present paper we describe the development of a rapid thin section protocol, using mainly Bacillus subtilis spores as a model, which allows an unequivocal diagnosis of endospores within 2 h. The protocol involves chemical fixation assisted by heat or microwaves, rapid dehydration, embedding in the low-viscosity resin LR White and chemically enhanced polymerization. Structural preservation of spores is comparable to preservation after standard Epon embedding. Immunolabeling experiments using B. atrophaeus spores and a specific antibody suggest that the protocol preserves significant antigenicity for on-section immunocytochemistry and therefore offers the possibility for the strain typing of spores using specific antibodies. Further experiments with vegetative bacteria, viruses and cell cultures indicate that the rapid thin section protocol not only preserves spores but also other biological structures. Because of its universality and speed the described protocol complements negative staining electron microscopy as a front line method for the morphology-based diagnosis of pathogens in environmental and clinical samples.

Identification and immuno-electron microscopy localization of p40, a protein component of immunosuppressive virus-like particles from Leptopilina heterotoma, a virulent parasitoid wasp of Drosophila

Lamellocytes are specialized larval blood cells of Drosophila that carry out encapsulation of metazoan pathogens such as parasitoid wasps. Large virus-like particles (VLPs) from two closely related virulent parasitoid wasp species, Leptopilina heterotoma and Leptopilina victoriae, suppress the host encapsulation response by promoting lysis of lamellocytes. The molecular basis of VLP-lamellocyte interaction and lamellocyte lysis is not understood. Here, it was shown that mature VLPs are composed of at least four major proteins. Polyclonal antisera against the most abundant L. heterotoma VLP protein, p40, cross-reacted with the most abundant L. victoriae VLP protein, p47.5. Immuno-electron microscopy (EM) of the long gland-reservoir complex revealed that p40 was expressed early in VLP biogenesis and was detected along with VLP precursors within the long gland cells and lumen. In the reservoir, VLPs had an angular core, resembled mature particles and p40 was detected outside the VLP cores. Immuno-EM staining of mature VLPs from both species localized the p40 and p47.5 proteins largely to the periphery of the VLPs and along the VLP spike-like projections. p40 staining was observed in VLP-treated host haemocytes. In vitro, anti-p40 antibody almost completely blocked the ability of L. heterotoma VLPs to promote lamellocyte lysis. Anti-p40 antibody blocked lysis by L. victoriae VLPs by >50%. It is proposed that the VLP surface proteins p40 and p47.5 share antigenic determinants and significantly contribute to the strong virulence of their Hymenopteran hosts.

Qualitatively distinct patterns of cytokines are released by human dendritic cells in response to different pathogens

Dendritic cells produce cytokines that regulate the class of the adaptive immune response. Microbial recognition is mediated, at least in part, by pattern recognition receptors such as Toll-like receptors, which influence dendritic cell maturation. In humans it is not yet clear how intact pathogens modulate the developing immune response. To address the effects of intact pathogens on the maturation and effector functions of human dendritic cells, we investigated their responses to a number of microbial pathogens. We studied a range of micro-organisms including Gram-negative bacteria (Escherichia coli and Salmonella enterica sv. typhimurium), Gram-positive cocci (Staphylococcus aureus) and atypical bacteria (Mycobacterium tuberculosis and Mycoplasma hominis) as well as the human protozoal parasite Trichomonas vaginalis. The micro-organisms were fixed in formaldehyde to prevent replication whilst preserving surface morphology. All the pathogens induced similar up-regulation of dendritic cell activation-associated cell surface markers but there was a profound difference in the patterns of cytokines produced by the stimulated dendritic cells. Some pathogens (E. coli, Salmonella enterica sv. typhimurium and S. aureus) induced interleukin-12 (IL-12), IL-10 and interferon-alpha whereas others (M. tuberculosis, Mycoplasma hominis and T. vaginalis) induced only IL-10. This differential effect was not altered by costimulation of the dendritic cells through CD40. These results support the notion that human dendritic cells are plastic in their response to microbial stimuli and that the nature of the pathogen dictates the response of the dendritic cell.

Detection and localization of a peptidoglycan hydrolase in Lactobacillus delbrueckii subsp. bulgaricus

Peptidoglycan hydrolase activities in Lactobacillus delbrueckii subsp. bulgaricus were detected by analysis of bacterial extracts on denaturing polyacrylamide gel electrophoresis containing lyophilized Micrococcus lysodeikticus cells as substrate. A hydrolase with an estimated molecular mass of 80 kDa was found to cross-react on Western blot with monoclonal antibodies raised against muramidase-2 of Enterococcus hirae. These antibodies were also used to demonstrate that the method of cell sample preparation affected protein detection. Slot and Western blots indicate that the peptidoglycan hydrolase from L. bulgaricus is bound to the cell wall. Immuno-labeling followed by optical and electron microscopic observations suggest that this hydrolase is intracellular and restricted mainly to the space between the membrane and the cell wall.

Serological Studies Using Polyclonal Antisera Prepared Against the Viral Coat Protein of Four Begomoviruses Expressed in Escherichia coli

Polyclonal rabbit antisera were produced to the coat protein of Bean golden mosaic virus Brazil isolate (BGMV), Cabbage leaf curl virus (CabLCV), Tomato yellow leaf curl virus (TYLCV), and Tomato mottle virus (ToMoV), all expressed in Escherichia coli by the pETh expression vector. The expressed coat protein of each virus was purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for use as an immunogen. The antisera to BGMV, CabLCV, TYLCV, and ToMoV reacted in indirect (plate-trapping) enzyme-linked immunosorbent assay (ELISA) with extracts from begomovirus-infected tissue. The antisera to BGMV, CabLCV, TYLCV, and ToMoV also reacted specifically with the test begomovirus antigens in leaf imprint blots and Western blots. The CabLCV and TYLCV antisera were used to detect Bean golden yellow mosaic virus antigens by immunogold labeling of thin sections of infected bean tissues. In tissue blot immunoassays, the TYLCV antiserum reacted well with TYLCV antigens but not with ToMoV antigens, while CabLCV antiserum reacted well with ToMoV antigens and weakly with TYLCV antigens. The results indicate that polyclonal antisera prepared to expressed begomovirus coat proteins were useful for the detection of begomoviruses in an array of assays.

Glutamine cycle enzymes in the crayfish giant nerve fiber: implications for axon-to-glia signaling

Two of the key enzymes involved in glutamate metabolism, glutaminase and glutamine synthetase, were quantitatively localized to axons and glia of the crayfish giant nerve fiber by immunocytochemistry and electron microscopy of antibody-linked gold microspheres. In Western blots, rabbit antisera for glutamine synthetase and glutaminase specifically recognized crayfish polypeptides corresponding approximately in size to subunits of purified mammalian brain enzymes. Glutamine synthetase immunoreactivity was found to be 11 times greater in the adaxonal glial cells than in the axon. Glutaminase immunoreactivity was found in somewhat greater concentration (2.5:1) in glia as compared to axoplasm. Glutamate immunoreactivity also was evaluated and found to be present in high concentration in both glia and axons, as might be expected for an important substrate of cellular metabolism. Using radiolabeled substrates it was demonstrated that glutamine and glutamate were interconverted by the native enzymes in the intact crayfish giant nerve fiber and that the formation of glutamine from glutamate occurred in the axoplasm-free nerve fiber, the cellular component of which is primarily periaxonal glia. The results of this investigation provide immunocytochemical and metabolic evidence consistent with an intercellular glutamine cycle that modulates the concentration of periaxonal glutamate and glutamine in a manner similar to that described for perisynaptic regions of the vertebrate central nervous system. These findings further corroborate previous electrophysiological evidence that glutamate serves as the axon-to-glial cell neurochemical signal that activates glial cell mechanisms responsible for periaxonal ion homeostasis.

The biological reality of the interlacunar network in the embryonic, cartilaginous, skeleton: a thiazine dye/absolute ethanol/LR White resin protocol for visualizing the network with minimal tissue shrinkage

Third toe phalanges of chicks aged 8-13 days in ovo and 7-day post-natal rat femoral growth plate were examined to determine whether the interlacunar network (IN), a structure with no lipoprotein membrane component or cytoplasmic organelles, is a genuine component of young growth cartilage. In chick phalanges dehydrated by 70% (v/v) ethanol and LR White resin, variable metachromatic staining of the interlacunar network by toluidine blue and red staining by picro-Sirius red indicate the presence of glycosaminoglycans and collagen. The network in phalanges dehydrated by 80% (v/v) ethanol appears little different; however, the network is much less widely detectable in phalanges dehydrated by 90% (v/v) ethanol and, after dehydration by absolute ethanol, is almost completely undetectable. In contrast, when the young cartilage is permeated by a thiazine dye such as toluidine blue, using a solution of dye in the aldehyde fixative, the network is widely detectable, following dehydration by absolute ethanol, both in chick phalanges and in rat growth plate. Comparison of projected areas shows that the extent to which whole chick feet are found to have shrunk, by the time that they are photographed under LR White resin, is determined principally by the extent of dehydration, by 70% (v/v) or absolute ethanol; post-shrinkage areas are 33% or 35% of areas measured in buffer for 70% (v/v) ethanol/LR White resin and 71% or 75% for absolute ethanol/LR White resin (the higher value in each is for the toluidine blue treatment). The network is thus present in radically shrunk tissue, but, significantly, is also fully represented in tissue shrunk by only a conventional margin and is therefore not produced as an artefact by exceptional tissue shrinkage as has been suggested.

Immunogold localization of TGF beta 1 protein and mRNA in human skin using a colloidal gold/digoxygenin system

Tissue preservation, and immunogold cytochemical and in-situ hybridization labelling intensities vary according to the preparatory protocols used. We wished to determine which preparative protocols produce optimal preservation, protein and mRNA labelling. Nine combinations of fixative and embedding resin were therefore studied using postembedding immunoelectron microscopy and a novel immunogold digoxygenin in situ hybridization (ISH) system, to quantitate the presence of transforming growth factor beta 1 (TGF beta 1) protein and message in human skin. The best preservation was observed in tissue fixed in 1% glutaraldehyde and embedded in LR White resin or low acid glycolmethacrylate resin (LA-GMA). Preservation was poor in tissue fixed with 1% glutaraldehyde and fair in 4% paraformaldeyde, when embedded in Unicryl. Ethanediol dehydration coupled with LA-GMA embedding resulted in reasonable preservation. Based on quantitative measures of the labelling density for TGF beta 1 protein and mRNA, immunogold labelling was adequate with 1% glutaraldehyde fixation coupled with LR White or LA-GMA resins, and also with 4% paraformaldehyde and LR White resin, but was best with ethanediol dehydration and LA-GMA embedding. ISH labelling under basal conditions was best in LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde. The ISH label in tissue fixed with 1% glutaraldehyde and embedded in LA-GMA was significantly increased by treatment with proteinase K. Overall, ethanediol dehydration was associated with a good immunoelectron microscopic (IEM) label while LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde resulted in a consistently detectable ISH label. LA-GMA embedding with 1% glutaraldehyde fixation gave a good result with both IEM and ISH labelling.

Immune electron-microscopy study of the trimeric glycoprotein (CD 103) of hairy cell leukemia using the Ber-ACT8 monoclonal antibody

We describe a method which makes it possible to study the expression of the trimeric glycoprotein (TGP, CD 103) on the surface of hairy cells (HCs) by electron microscopy (e.m.). The monoclonal antibody (mAb) Ber-ACT8 was used to identify the TGP. By testing mucosa of the small intestine, we found that a prefixation incubation with Ber-ACT8 was necessary. After isolation with a density gradient, Ber-ACT8 incubation, and fixation, the peroxidase-anti-peroxidase (PAP) method was used to make the TGP visible. The HCs showed a clearly discernible stain on their surface, a fairly constant distribution of the TGP, and a very good ultrastructural preservation. This method makes it possible to demonstrate the TGP or other unfixable antigens by e.m.

Immunochemical studies on the cercarial-specific calcium binding protein of Schistosoma mansoni

Stage-specific expression of the mRNA encoding the cercarial-specific 8 kDa CaBP has been described previously. To gain information on possible function(s) of this protein we raised antibodies to the CaBP in rabbits immunized with a CaBP-TrpE fusion protein synthesized in bacteria. Western blots showed high levels of CaBP in cercariae and 3 h schistosomula, trace amounts in 24 h schistosomula, and none in miracidia sporocyst and adult worm, as found for the mRNA. The CaBP molecule has a short half-life (< or = 4 h) similar to that of the mRNA. Other experiments demonstrate that the CaBP may interact with a putative target molecule in a calcium-dependent manner to form a complex of 45 kDa. Immunogold electron microscopy showed CaBP in selected regions of cercariae and 3 h schistosomula: tegument, head gland, subtegumental cells, flame cells, intestinal wall and the body-tail junction. Other investigators have shown that the head gland and subtegumental cells synthesize and translocate granules to the tegument during transformation from cercariae (living freely in water) to schistosomula (residing in vertebrate host). These observations and the time-course of CaBP detection suggest that the CaBP synthesized in the head gland and subtegumental cells is translocated to the tegument where it plays a role in tegument modifications required for adaptation to parasite life in the host. CaBP was not found in muscles and mitochondria, suggesting that it is not involved in the rapid motility and aerobic metabolism characteristic of cercariae.

Ethanolic dehydration and its effect on membrane-bound enzymes of Chlorogloeopsis fritschii and Chlorella pyrenoidosa

Ethanolic dehydration (20% to 70%) of the thylakoid membranes of Chlorogloeopsis fritschii resulted in an 8% to 58% loss of glutamine synthetase activity. In Chlorella pyrenoidosa, hydroxypyruvate reductase and fumarase, marker enzymes of the peroxisomes and mitochondria, respectively, diffused from the organelles on dehydration.

Characterization of agarose as an encapsulation medium for particulate specimens for transmission electron microscopy

Agarose, agar, and gelatin were initially compared as encapsulation media for 3 structurally diverse particulate specimens: bacteria, yeast, and mitochondria. Agarose proved superior to both gelatin and agar for ease of handling and overall image quality (minimum background). All sample types exhibited high quality fixation and structural detail with no heat damage from the agarose medium. Based on this finding, we further characterized agarose encapsulation as affected by post-fixation, en bloc staining and resin type. Osmium tetroxide post-fixation, followed by en bloc uranyl acetate staining, could be performed without an increase in the electron density of the encapsulation medium. Agarose proved successful as an encapsulation medium regardless of the resin type or preparation protocol, thus providing flexibility in experimental design and excellent results over a range of variables.

Freeze substitution after fast-freeze fixation in preparation for immunocytochemistry

As compared to classical chemical fixation, the physical immobilization of ultrastructures by fast-freeze fixation (FFF) and the subsequent exchange of water in its solid state by freeze substitution (FS) improve the preparation procedure for immunogold labeling (IGL). FFF-FS results in a morphological preservation of unchallenged quality, as well as in a better preservation of antigenic reactivity, thus allowing remarkable precision of labeling on sections. However, FFF, particularly over a cooled metal plate, requires a heavy and expensive machine. It is not suitable for all biological specimens and in the best conditions, which remain difficult to standardize, the thickness of the well-preserved portion of the specimen does not exceed a few microns for compact tissues, and exceptionally 30-40 microns for isolated cells. The FS procedure is long and must be adjusted empirically for every new specimen and antigenic detection. The preservation of a given antigen's reactivity in the presence of fixative agents and embedding resins remains unpredictable. The action of fixative agents is different and milder in FS than when they are used classically in chemical fixation. By chance, one of the best FS procedures for the preservation of both ultrastructure and antigenicity appears to be by using acetone alone, together with a molecular sieve to improve the water exchange process. A large choice of embedding resins usually allows us to find a compromise between ultrastructural and antigenic preservation.

Flat embedding and immunolabelling of SW 1116 colon carcinoma cells in LR white: an improved technique in light and electron microscopy

Human SW 1116 colon carcinoma cells were grown on matrix-covered coverslips and flat embedded in specially prepared gelatin capsules in the hydrophylic resin LR White. Dehydration and polymerization were carried out so as to maximize preservation of antigenicity. Sections were cut perpendicular to the substratum. To visualize mucin, semithin sections of SW 1116 cells were stained with periodic acid Schiff (PAS) reagent for light microscopy, and ultrathin sections were labelled with a monoclonal mucin antibody (Mab 19-9) and immunogold for electron microscopy. Immunofluorescence was carried out on whole cultured cells using Mab 19-9. The morphological preservation of SW 1116 cells embedded in LR White was comparable to that of Epon-embedded cells. Mucin was localized on the microvillar surface of the apical plasma membrane and occasionally in intercellular spaces between adjacent cells. Mucin was also present in vesicles in the apical and lateral part, and to a lesser extent in the basal part of the cells. We conclude that this new technology significantly improves the morphological preservation of cells and tissues in LR White, while also serving to sustain the antigenicity of cellular antigens.

Electron immunocytochemical localization of Actinobacillus actinomycetemcomitans leukotoxin

The Actinobacillus actinomycetemcomitans leukotoxin was localized in A. actinomycetemcomitans bacteria using an electron immunocytochemical thin-section labeling method. An immuno-dot blot procedure was initially used to ascertain the optimal specimen fixation. This consisted of a periodate-lysine-paraformaldehyde (2%) fixative in a phosphate buffer followed by embedding in LR White. Affinity-purified toxin was used to produce a monospecific polyclonal antibody. The reaction sites were visualized with a colloidal gold-tagged reporter antibody. The leukotoxin was found to be localized either in the cell envelope and/or in membranous vesicles on the outer surface of the bacterial cell. These results support previous observations indicating the same location.

Medium temperature epoxy resin for immunocytochemistry: Quetol 651 with water

The addition of 1% water to the epoxy resin Quetol increased the labeling intensity of the sample. The significant decrease of the curing temperature of the epoxy resin may assist in preservation of antigens. Water may also reduce the cross-linkage of the resin allowing more antigen to be available to the antibodies. The modified Quetol resin is an option for use in immunocytochemistry studies.

Colloidal gold labeling of sections and cell surfaces

Colloidal gold labeling techniques can be simplified enough to become practical for diagnostic use in a hospital electron microscopy laboratory. Methods found to be practical and reproducible are presented, including production of colloidal gold reagents, polar embedding for gold labeling of thin sections, and use of silver enhancement on semithin sections. Methods for cell surface labeling are emphasized; they are technically straightforward and can be applied to investigation of multiple diagnostic problems.

Characterization of a murine monoclonal antibody, 5D-4, reacting with pancreatic cancers and islets of Langerhans

A murine monoclonal antibody (5D-4) was prepared by immunizing mice ip with human pancreatic cancer cell line (AsPC-1). The 5D-4 MAb reacted immunohistochemically with pancreatic and gastrointestinal tract tumors as well as pancreatic islets, and to a less extent with normal tissues. The 5D-4 MAb reacted not only with ca 50 KDa and 30 KDa solubilized protein from AsPC-1 cells by Western blot analysis but also with human insulin in a competition RIA. Double immunoperoxidase staining showed that the 5D-4 MAb cross-reacted with insulin but did not react with glucagon, somatostatin or pancreatic polypeptide. Immunoelectron micrograph of Langerhans island double-stained with the 5D-4 MAb and anti-insulin Ab revealed that the 5D-4 Mab recognized human insulin and ca 50 KDa and 30 KDa antigens in B-cells of islets of Langerhans. Thus, the 5D-4 Mab may be useful for the diagnosis of islet cell tumors as well as pancreatic cancers.

Effects of monomeric acrylic embedding media on the antigenicity of two epitopes of the MIC2-encoded Ewing's sarcoma cell membrane antigen

Comparative electron microscopic studies of pre- and postembedding immunolabeling experiments have shown that the antigenicity of some epitopes is lost during acrylic resin embedding of the respective tissues. In the present investigation we have tested the sensitivities of two embedding-labile epitopes (HBA-71 and HBA-45) of the Ewing's sarcoma-associated MIC2-encoded E2 antigen to the effects of the different treatment steps, which are necessary for the preparation of ultrathin sections. The extent of antigenic retention was quantitated using flow cytometry and enzyme-linked immunosorbent assays (ELISA) of tumor cell lines, thymocytes and cell membrane extracts. Fixation, dehydration and high temperature treatment of MIC2-positive cells showed only minor effects on the reactivity with the HBA-71 and HBA-45 antibodies. However, exposure of the cells to the monomeric acrylic resins LR White (LRW), LR Gold (LRG) and Lowicryl K4M at 4 degrees C for 2-18 h resulted in a significant reduction of the HBA-71 and HBA-45 reactivities. In contrast, the antigenicity of both epitopes was maintained during treatment with the apolar Lowicryl HM20 embedding medium under these non-polymerizing conditions. The resins have no direct effect on the HBA-71/HBA-45 antigen, since it could be extracted in intact form from membranes of native, but not of fixed, tumour cells using LRW for membrane solubilization. These data indicate that the HBA-71/HBA-45 antigen remains in the cell membrane and is indirectly influenced by the extraction/modification of adjacent membrane constituents. The adverse effects of the polymerization process, in the case of embedding at low temperature in Lowicryl HM20, destroyed MIC2-antigenicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Egg exudate-induced reduction of sperm lysin sensitivity in the vitelline coat after fertilization of Bufo japonicus and its participation in polyspermy block

The jellyless eggs of Bufo japonicus or those from which the vitelline coats (VCs) had been removed (denuded eggs) were electrically activated. The exudate that accompanied egg activation (AEX) was collected to study its role in preventing polyspermy. When dejellied (but VC intact) eggs were treated with AEX, the eggs lost not only fertilizability but also the sensitivity of their VCs to the sperm lysin. By contrast, denuded eggs treated with AEX were fertilizable; even activated eggs were highly fertilizable, provided they were deprived of their VCs and inseminated 30 min after activation. The loss of sensitivity to sperm lysin occurred in VCs 3-5 min after activation either in De Boer's or 1/20 De Boer's solution. The activity of AEX to reduce the sensitivity of VCs to sperm lysin was heat-sensitive and dependent on Ca2+, but it was not affected at all by the variety of protease inhibitors used. The activity was lost by the preincubation of AEX with fragmented VCs in the presence of Ca2+, suggesting Ca(2+)-dependent binding of AEX molecules to the VC at fertilization. Immunocytochemical studies employing anti-AEX rabbit serum showed that the pertinent antigens were localized in the cortical granules of unfertilized eggs and in both the inner surface of VCs and the perivitelline space of fertilized eggs. We conclude that the AEX-induced loss of lysin sensitivity in VCs and the deposition of cortical granule materials on the inner wall of VCs constitute a slow and permanent block to polyspermy.

Localization of nucleolar chromatin by immunocytochemistry and in situ hybridization at the electron microscopic level

Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well as the definition of nucleolar structures in which enzymes of the rDNA transcription machinery reside have been investigated in mammalian cells by various immunogold labelling approaches at the ultrastructural level. The precise intranucleolar location of rRNA genes has been further specified by electron microscopic in situ hybridization with a non-autoradiographic procedure. Our results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA topoisomerase I are located together. Taking into account the potential value and limitations of immunoelectron microscopic techniques, we propose that transcription of the rRNA genes takes place within the confines of the fibrillar centers, probably close to the boundary regions to the surrounding dense fibrillar component.

New aspects of bacterial ultrastructure as revealed by modern acrylics for electron microscopy

Modern acrylics can be used over a wide temperature range (+60 degrees C to -80 degrees C) for infiltration, embedding, and polymerization. They can be used in procedures involving chemical fixation or rapid freezing. This flexibility allows for studies to be carried out upon the effects that different parameters involved in preparing biological tissue for microscopy have upon structure and retention of immunoreactivity. With most preparative methods contributions have been made to our knowledge on bacterial structure in gram-negative and gram-positive cells. The future should lie in integrating the advantages of the various methods for the purpose of advancing our understanding of bacterial structure/function.

High resolution cytochemical study of the vesicular-arbuscular mycorrhizal association, Glomus clarum×Allium porrum

Roots of leek, colonized or not by Glomus clarum Nicolson & Schenck, were ultrastructurally examined for the presence of different sugars using lectin-gold complexes. N-acetyl-d-glucosamine (GlcNAc), N-acetyl-d-galactosamine (GalNAc), l-fucose (l-FUC), d-mannose (d-Man) and sialic acid sugar residues were localized in various cellular components of the mycorrhizal fungus. GlcNAc, GalNAc, d-Man and sialic acid residues were localized in the colonized host, particularly in the plasmalemma and cytoplasm surrounding the arbuscular hyphae. The same sugars were not present in the non-colonized host. These results indicated that the production of these sugars had been triggered during the plant-fungus association. In the interfacial matrix, GalNAc and d-Galactose (d-Gal) residues were present in moderate amounts. In cell walls and protoplasm of non-colonized and colonized hosts, mainly d-Gal was detected. Ribonucleic acid (RNA) was cytochemically localized in the fungus and host by means of a RNAse-gold complex. Of interest, was the specific localization of RNA in the granular wall layer of vesicles. The ultracytochemical results are discussed in relation to host-symbiont interaction, along with speculations on the function and significance of these macromolecules.

Immunohistochemical staining of bromodeoxyuridine-labelled cells in the mouse embryo

The aim of this study was to compare two immunohistochemical methods, avidin-biotin peroxidase and immunogold silver staining (IGSS), in the detection of 5-bromodeoxyuridine incorporation in mouse embryo tissues. In addition, two fixation schedules, formal-saline and a mixture of formaldehyde and glutaraldehyde (4FIG), and two embedding procedures, paraffin wax and the acrylic resin L.R. White, were also compared. Pregnant mice were injected with 600 mg per kilogram body weight on days 10 or 15 (plug day = day 1) of gestation and the embryos recovered 2 h after treatment and fixed in formal-saline or 4FIG. Fixed material was then processed into wax blocks or L. R. White resin. After sectioning, the antigen-antibody reaction was visualized using either the avidin-biotin peroxidase or IGSS methods. All methods tested gave a well-contrasted, highly specific reaction, but IGSS in combination with 4FIG and L. R. White gave a clearer and more sensitive signal than other combinations.

Filopodia, lamellipodia and retractions at mouse neuromuscular junctions

In order to determine if mature motor nerve terminals retain structures associated with development such as filopodia and lamellipodia, we studied whole mounts of mature mouse neuromuscular junctions stained with both fluorescent-labelled tetanus toxin C-fragment and alpha-bungarotoxin, and employed electron microscopy in parallel. The rapid fluorescent stain may be of general usefulness. Both filopodia and lamellipodia were found, extending beyond the border of the established postsynaptic receptors. Filopodia often appeared in clusters, were devoid of a synaptic vesicle antigen, and many withdrew in response to cytochalasin D. Control experiments demonstrated that filopodia were not induced by the toxin treatment. The mean number of filopodia per endplate varied from about one in phasic muscle to three in tonic muscle, and was twice as great in immature mouse muscle. Postsynaptic receptor-rich regions without overlying terminals were less numerous than filopodial and lamellipodial projections without underlying receptors. Electron microscopy showed that lamellipodia contained actin-like filaments and immunoreactivity to actin, but no neurofilaments, microtubules, mitochondria or vesicles. Therefore, these structures would not be visualized by in vivo mitochondrial stains. The lamellipodia protruded into the gap between muscle and a closely overlying Schwann cell process. Lamellipodia occupied about 5% of the linear extent of the terminal arbor in whole mounts, but appeared in 16% of random electron micrographic fields. Thus, the lamellipodia and filopodia typical of developing terminals are present in adulthood and represent a distinctive specialization of the nerve terminal, which may interact with the adjacent Schwann and muscle cell. The frequency of filopodia is a function of age and of muscle or motoneuron type. We suggest that some of the factors known to regulate growth of filopodia and lamellipodia in vitro or in development may continue to act at adult presynaptic nerve terminals.

Purification and identification of two serine class proteinases from dog mast biochemically and immunologically similar to human proteinases tryptase and chymase

Serine class proteinases with trypsin-like and chymotrypsin-like specificity were purified from dog mastocytoma tissue. An antiserum was produced against the chymotrypsin-like proteinase. The antiserum reacted with mast cells in skin sections prepared from normal dogs consistent with the proteinase being a mast cell constituent. The antiserum also cross-reacted with the major chymotrypsin-like proteinase isolated from normal dog skin and partially cross-reacted with human skin chymase. No cross-reaction was detected with rat chymase. The trypsin-like proteinase from dog mastocytoma tissue was similar to tryptase isolated from human skin. It had a similar subunit structure, was not inhibited by many protein proteolytic enzyme inhibitors, bound to heparin, and reacted strongly with antiserum against human tryptase. Antiserum against human tryptase also reacted with mast cells in skin sections prepared from normal dog skin. No immunocytochemical labeling of rat skin mast cells was observed with anti-human tryptase. These studies establish the presence of a trypsin-like and chymotrypsin-like proteinase in dog skin mast cells and provide immunological evidence which suggests that both proteinases are more closely related to human than rat mast cell proteinases. These immunological and biochemical relationships are important when comparing the roles of these proteinases in different animals.

Localisation of internal antigens of Plasmodium falciparum using monoclonal antibodies and colloidal gold

By the examination of several defined malarial antigens, we have demonstrated the necessity for etching pretreatments to be used in conjunction with post-embedding immunolabelling of LR White-embedded parasite material. In general, etching procedures markedly enhanced immunolabelling of the various antigens, while in some cases etching was essential for obtaining positive immunolabelling. Of the etching pretreatments evaluated, a combination of an alcoholic solution of sodium hydroxide followed by sodium metaperiodate gave optimal labelling with minimal background. A number of fixation regimes were also compared for their applicability to immunolabelling of malaria-infected erythrocytes. Generally, fixation with low concentrations of glutaraldehyde was found to be appropriate. We have also successfully used paraformaldehyde fixation coupled with etching to localise a rhoptry-associated antigen, which is presumably sensitive to glutaraldehyde fixation. Due to the high specificity of monoclonal antibodies, however, different fixation regimes may need to be considered for various combinations of antigen and antibody.

Electron microscopic structure and oxygen evolution activity of thylakoids from Avicennia marina prepared under different osmotic and ionic conditions

Stacking of thylakoid membranes in vitro was assessed using electron microscopy. Grana stacks of spinach thylakoids formed when 5 mol m^-3 MgCl₂ was present, but no stacking of thylakoids from the mangrove Avicennia marina occurred in the presence of 10 mol m^-3 ? MgCl₂ . Isolation of mangrove thylakoids with a high osmotic strength medium did not induce grana formation if the medium consisted only of sorbitol or glycinebetaine. Addition of cations to the high osmotic strength medium did induce some loose-grana formation, with divalent cations being more effective than monovalent cations. Glycinebetaine was a better osmoticum than sorbitol for grana formation provided divalent cations had been added. Oxygen evolution activity of the preparations was influenced by the amount of membrane stacking, with the preparations with the greatest amount of stacked membrane having the highest activity. Isolation with sorbitol or glycinebetaine based media did not alter this pattern, nor did assay in sorbitol or glycinebetaine. Mangrove thylakoids have a requirement for both a high osmotic strength and divalent cations for grana formation in vitro which may be related to the low water potential of the plant environment in vivo.

Immunohistochemical studies of the distribution of a basolateral-membrane protein in intestinal epithelial cells (GZ1-Ag) in rats using monoclonal antibodies

The monoclonal antibody (mAb), GZ1, is specific for a 42-kilodalton (kD) protein (designated GZ1-Ag) present among the plasma membrane (PM) proteins of the absorptive cells of rat intestine. This protein only occurs in the basolateral PM and is absent from the microvillus membrane. GZ2 and GZ20 are two other mAbs that are also directed against GZ1-Ag but which specify other antigenic determinants of this protein than mAb GZ1. Used together, these three mAbs allow better characterization of GZ1-Ag and more precise investigation of its distribution and localization in various rat cells. We performed immunohistochemical labelling for GZ1-Ag at both the light- and electron-microscope levels and found that GZ1-Ag is extensively distributed in rat epithelial tissues. However, the amount of this protein present in epithelial tissue shows considerable variation. GZ1-Ag is not present in the secretory cells of terminal portions of most excretory glands or in cells of the endocrine glands and liver. The cells of kidney tubules, except for collecting tubules, also lack GZ1-Ag. Only small amounts of GZ1-Ag are present in the cells of the stratified squamous epithelium and transitional epithelium, the exception being superficial cells. High concentrations of GZ1-Ag occur in the excretory duct systems of glands and in the various kinds of epithelium present in the male and female genital tract. Our results also indicated that the GZ1-Ag in all of these cells has a very similar structure.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple hormone storage by 'polycrine' cells in the pancreas (from a case of nesidioblastosis)

Pancreatic tissue from a case of neonatal hypoglycaemia with nesidioblastosis has been studied by routine light and electron microscope techniques and by highly sensitive light and electron microscope immunolocalization methods. A hyperplastic nodule within the pancreas from this case contained enlarged distorted haemorrhagic islets, with a variable rim of exocrine tissue. Islet cells in these areas were shown to contain more than one hormone in separate granules. An immunoperoxidase system using hapten-labelled primary antibodies and photochemical amplification applied to serial semithin sections suggested a consistent overlap between insulin and glucagon immunoreactive cells. Serial ultrathin sections of tissue embedded in LR White showed that some heteromorphous cells with predominantly beta-granules also contained a minority population of granules which had either glucagon or glicentin immunoreactivity. In adjacent studies, the same techniques confirmed that the majority population of granules did indeed contain insulin, and immunocolloidal gold methods were used to show that glucagon and glicentin containing granules were present in the same cells. The significance of these findings is discussed, including the possibility that cells containing more than one granule type might represent a subpopulation of facultative cells in transit from producing one hormone to producing a second. The importance of sensitive immuno-electron microscopy in the investigation of endocrine lesions is stressed.

Immunocytochemical identification of nuclear structures containing snRNPs in isolated rat liver cells

Small nuclear ribonucleoproteins (snRNPs) containing U1, U2, U4, U5, and U6 small nuclear RNAs were detected by ultrastructural immunocytochemistry in the nuclei of isolated rat hepatocytes using Fab fragments of anti-Sm and anti-RNP autoantibodies. Their localization was carried out in normal cells and in cells treated with two drugs, the adenosine analog DRB and CdCl2, which alter the number and distribution of nuclear RNP components. It was found that more precise determination of the distribution of these small RNAs could be obtained by using two complementary procedures in parallel rather than either one alone. They consisted of an indirect immunoperoxidase labeling carried out before embedment and an indirect immunogold labeling applied to thin sections of cells embedded in Lowicryl K4M. The results indicate that snRNPs are associated with all extranucleolar perichromatin fibrils and granules and interchromatin fibrils, which confirms that they occur in structures involved in the synthesis and processing of hnRNA. The snRNPs are not associated with nucleolar perichromatin granules induced by DRB, which confirms that there may be two kinds of perichromatin granules. The snRNPs are also associated with the still enigmatic interchromatin granules which apparently do not contain hnRNA but at least in DRB-treated cells, also contain ribosomal RNA.

Immunocytochemical demonstration of serine: pyruvate amino-transferase in peroxisomes and mitochondria of rat kidney

The light- and electron-microscopic localization of serine: pyruvate aminotransferase (SPT) in rat kidney was studied using immunoenzyme and protein A-gold techniques. Rat kidneys were fixed by perfusion through the abdominal aorta and small tissue slices were embedded in Epon, Lowicryl K4M, or LR Gold. The Epon was removed from the semithin sections, which were then stained using the immunoenzyme technique. Ultrathin sections of Lowicryl K4M- or LR gold-embedded materials were labeled using the protein A-gold technique. At light microscopy, discrete granular reaction deposits were exclusively present in the proximal tubule, all of whose segments were positive for SPT. A weakly positive reaction was observed in the distal tubules. At electron microscopy, gold particles indicating the antigenic sites for SPT were confined to the peroxisomes and mitochondria. The labeling intensity of both organelles was dependent on the embedding resins used. The labeling of Lowicryl K4M-embedded material was weaker than that of LR gold-embedded material; Quantitative analysis confirmed this result. Our results indicate that, in rat kidney, the main intracellular sites for SPT are peroxisomes and mitochondria of the proximal tubule.