Organisms found at the Air-Water Interface (AWI) are often difficult to collect and usually show distortion upon collection and fixation by traditional methods. Furthermore, the spatial relations between the organisms and the complexity of their biofilm community is disrupted or destroyed by collection methods that involve bulk water collection, filtration, settling or rotating drums. Samples shown here were collected on the Tualatin River, Oregon, a eutrophic rural/suburban stream with welldeveloped Aquatic Surface Films (ASF or Microlayers) in quiet waters.

Here, I describe a simple method of collection for Aquatic Surface Films (Microlayers), by drawing a glass substrate slowly through the surface film, allowing both organic chemicals and small organisms to adhere to the surface of the glass. This is similar to the collection of a Langmuir-Blodgett film, and it has been proposed that chemical and biological films at the surface might allow this type of collection.

AGL15 (AGAMOUS-like 15) was originally identified as a sequence preferentially expressed in developing plant embryos by comparing PCR-generated ‘differential displays’ of embryo and non-embryo RNA populations. The sequence is expressed at low levels and encodes a member of the MADS domain family (named for the first four members to be identified: MCM1, AGAMOUS, DEFICIENS, and SERUM RESPONSE FACTOR) of regulatory factors. Members of the MADS domain family play pivotal roles in critical developmental events in a wide variety of organisms: in specification of mating type in yeast (MCM1), in responses to the environment in human cells (SRF), in control of mesoderm differentiation in Drosophila and muscle differentiation in humans (MEF2), and in determination of meristem and organ identity during flower development in plants (AGAMOUS, DEFICIENS/APETALA3, GLOBOSA/PISTILLATA, etc.). AGL15 is the only MADS domain factor identified to date that is expressed in a highly preferential manner in plant embryos.

The mechanism of cytokinesis in higher plants is distinct from that of animal and yeast cells. Dividing plant cells are separated by the de novo construction of the cell-plate across the inside of the cell. Assembly of this new organelle is directed by a specialized cytoskeletal structure called the phragmoplast, a unique macromolecular scaffold that appears late in mitosis and is composed of intermediate filaments, microfilaments, and microtubules. Secretory vesicles are guided along the phragmoplast cytoskeleton toward the equatorial region of the structure where they coalesce and fuse to form a membranous tubular-vesicular network within which cell wall biosynthesis is initiated. A smoother more plate-like structure develops and extends radially outward as additional vesicles are added to the growing margin of the cell-plate until it ultimately fuses with the parental plasma membrane yielding two daughter cells separated by a common cell wall and extracellular space.

The Ascochyta blight caused by Ascochyta rabiei ( Pass.) Labr. is a serious foliar fungal disease of chickpea (Cicer arientinum L.). The histo- and cytopathological examination of hostpathogen interactions was conducted in resistant ( ELC-195) and susceptible (Canitez-87) cultivars of chickpea at 3, 5, 7 days after inoculation with A. rabiei. Several histological studies have been made with A. Rabiei. No ultrastructural studies comparing the resistant and susceptible reactions of chickpea to A. rabiei have been reported.

The hypersensitive response (HR) is a very common reaction in resistant chickpea plants challenged with A. Rabiei. The FfR has also been associated with defence reactions which is phytoalexin synthesis. Phytoalexins are compounds, synthesised in host plant cells, after infection, which have antimicrobial properties. Fligh concentrations are often found in nearby necrotic cells which prevents further growth of the A. Rabiei in resistance chickpea.

A. rabiei produce typical appressorium formation for cuticle penetration but stomata penetration have been observed in some micrographs (Fig.l).

Leaf senescence is an orderly, active process in which nutrients in a leaf are reclaimed and mobilized to other parts of the plant. It is considered to be the final stage in leaf development. During senescence leaves undergo highly coordinated changes in cell structure, metabolism, and gene expression. For example, chloroplasts undergo obvious structural modifications during leaf senescence. Regarding gene expression, genes with steady-state mRNA levels that increase during senescence are often referred to as senescence-associated genes, or SAGs.

In order to study ultrastructural changes that occur during senescence, portions of fully expanded, mid-senescent, and fully senescent Arabidopsis thaliana leaves were chemically fixed using vacuum-accelerated microwave processing. Thin sections were observed for ultrastructural changes such as development of transfer cells that are characterized by the presence of cell wall ingrowths. Transfer cell development is correlated with an increased capacity of tissues to take up materials, related partly to an increase in plasma membrane surface area.

Poly-β-hydroxybuterate (PHB), a biodegradable polyester, is accumulated as a storage compound in many species of bacteria. It belongs to a class of polymers called polyhydroxyalkanoates (PHAs). PHA's were originally identified in 1923.However these polymers first came to the attention of industry in the early 1980's when they were recognized as having thermoplastic properties.Monsanto currently markets a form of PHA produced via fermentation under the trade name Biopol™. It is used to make biodegradable plastic products such as credit cards, bottles and disposable drinking cups. However fermentation is an expensive route to production. The use of crop plants genetically engineered to produce PHA's could provide a less expensive source of the plastic and therefore a more attractive alternative to traditional non-biodegradable petrochemical derived plastics. PHB production in plants was first demonstrated in 1992 in transgenic Arabidopsis thaliana by Chris Somerville and coworkers. They showed that PHB production was tolerated by the plant if it was targeted to the chloroplasts.

Potamogeton pectinatus is a submerged halophyte which occurs in waters of low salinity (5% to 10%). Its upper salinity tolerance has been reported to be 19%. Reasons why P.pectinatus is unable to tolerate salinities in excess of 19%is important to our understanding of its biology. In the present study, leaf ultrastructure of plants growing at low salinity was compared with plants growing at high salinity in order to assess the effects of different salinities on the ultrastructure. Attention was focussed on ultrastructural changes occurring in the leaf epidermis, the main photosynthetic tissue.

Plants were grown in seawater at two salinities : 5%(low salinity) and 20% (high salinity). Pieces of mature leaf blades from both treatments were harvested and prepared for Transmission Electron Microscopy (TEM) following standard procedures. The overall distribution and concentration of chlorine (CI) in the leaves was ascertained since this element is the most abundant anion in seawater and is important in considerations of salt tolerance in submerged halophytes.

Understanding the light-harvesting properties of algae and higher plants are a fundamental topic in photosynthesis research. Much oceanographic research has focused on characterizing the in vivo chlorophyll-specific absorption coefficient, a*ph (λ) in phytoplankton because it serves as an input variable for bio-optical modeling of photosynthesis using remote sensing instrumentation such as moorings, drifters, and satellites. Values of a*ph (λ) vary spectrally and the magnitude depends on accessory pigments, photo-protective pigments, and pigment packaging effects. Several studies have shown that the contribution of cellular characteristics to a*ph(λ) varies with growth conditions including temperature, light, and nutrients. It has been shown that a*ph (λ) values in Phaeocystis vary predictably at 4°C over light intensities under light limitation. Phaeocystis demonstrated significant pigment package effects that depended on single cell diameter and thylakoid membrane stacking. Using thick sections obtained from fixed and embedded cultures of colonial P. antarctica, we calculated tomographic reconstructions of individual chloroplasts under light-limiting conditions for net photosynthesis in order to gain an understanding of the continuity of thylakoid membranes and understand the spatial relationship between the pyrenoid, the starch containing organelle, and thylakoid membranes.

The ability to visualize the chromosomes, especially in three-dimensional (3D) space, has great benefits for the understanding of genes’ function. The availability of various trisomic genotype in maize provides an excellent system for the study of 3D chromosome arrangement at various developmental stages. Laser scanning confocal microscopy and digital deconvolution technique is best suited for this type of work. A preliminary database on the three-dimensional arrangement of Ohio43 inbred line has been established; this information is essential for the evaluation of the effect of additional chromosome in trisomy genotypes.

Tassel inflorescence of maize (Zea mays L.) trisomy 6 in Ohio43 background were collected from the field station at the University of Western Ontario in London, Ontario, Canada, during the summer of 1998. Tassels at the proper developmental stages were fixed in 3:1 (95% EtOH / acetic acid) solution and stored at room temperature. After dissection from the spikelet, anthers were treated with the Feulgen-method, dehydrated in ethanol series and cleared in methyl salicylate.

Visualization is interdependent with gene mapping and DNA sequencing, because spatial relationships are important to understand function. The ability to visualize the chromosomes, especially in threedimensional (3D) space, has great benefits for the better understanding of a gene's function. For these reasons, a better technique is needed to study the chromosomes in 3D. Studying the stages of meiosis I provides an excellent opportunity to evaluate the capability of 3D imaging techniques. The loosening of the chromosomes in meiosis I exemplify the advantages of 3D imaging.

Tassel inflorescence from maize (Zea mays L., inbreed Ohio43) was collected from the field station at the University of Western Ontario in London, Ontario, Canada during the summer of 1998. Tassels at proper developmental stages were fixed in 3:1 (EtOH / acetic acid) solution. The anthers were stained with the Feulgen method and cleared in methyl salicylate.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that bioaccumulate in the food chain and thus pose a health risk to human beings and other animals. The exceptional dielectric and lubricating properties of the PCBs resulted in their extensive use during the mid-1950s as lubricants in electrical generators and transformers. PCBs have a long half-life and persist in the environment causing concerns related to their toxicity. The present research on congener 118 (2,3',4,4',5-pentachlorobiphenyl) involves the quantification of hepatocyte alterations using stereology techniques. Application of a quantitative technique to estimate liver pathology confers more confidence in evaluating toxicity of a xenobiotic, and in the determination of its NOAEL (No Observable Adverse Effect Level).

Alterations in the volume fraction of cellular constituents in the hepatocytes induced by congener 118 were estimated relative to the sex of, and dose fed to a laboratory population of weanling Sprague-Dawley rats. The rats were given the PCB dose in concentrations of 2, 200, and 2,000 ppb to females and 10, 1,000 and 10,000 ppb to males; three animals were used in each dose group.

Immunocytochemistry studies have established that multivesicular bodies (MVBs) in alveolar type II epithelial cells are important for processing pulmonary surfactant protein precursors (proSP; Voorhout et al., 1992 and 1993). Localization of pulmonary surfactant protein A (SP-A) gold and cationic ferritin to the MVBs demonstrated that MVBs also serve as endosomal/lysosomal compartments for recycling SPs (Williams et al., 1984, Ryan et al., 1989). However, these studies did not elucidate whether the biosynthesis of pulmonary SPs and endocytosis occur in the same MVBs. In this study, we used primary murine alveolar type II epithelial cell cultures as a model to determine if the biosynthetic and endocytic compartments colocalized in MVBs. The endocytic compartments of MVBs were identified using BSA gold conjugates, while the biosynthetic pathway was detected with antibodies directed against proSPs.

Alveolar type II epithelial cells isolated from 6 weeks old C57B/6 mice were grown on Transwell cell inserts in the presence of 6 nm BSA gold conjugates (BSAG6) adjusted to final concentration of OD520 5.0 in DMEM, 25 mM HEPES, and 10% fetal bovine serum, pH 7.3, at 37 °C for 20 hours.

Tamoxifen and taxol are two promising chemotherapeutic agents currently used in cancer treatment, but each has its own unique mechanism of action. Tamoxifen, known to inhibit the activity of estrogen on malignant mammary gland cells, was recently approved by the FDA for the treatment of breast cancer. Taxol, extracted from the Pacific Yew tree, Taxus brevifolia, is an antimitotic agent that binds specifically to the β-subunit, promoting the assembly and stabilization of tubulin polymers. Studies have shown that tamoxifen and taxol induce cytostatic and cytotoxic effects leading to the death of several cancer cell types in vitro.In this research, the surface ultrastructural effects of both tamoxifen and taxol were investigated in human cervical cancer cells (HeLa).

Exponentially growing cells were treated with 5, 10, 15, and 20 μg/ml of tamoxifen and 1 μg/ml of taxol (LC50) for 24, 48, 72, and 96 hours. For scanning electron microscopy (SEM), the cells were grown on coverslips, fixed in 2% glutaraldehyde followed by 1% osmium tetroxide.

Mitochondrial DNA (mtDNA) mutations have been found associated with several neuromuscular diseases. In order to address further mechanisms of pathogenesis of the specific mtDNA mutations in responsible for these diseases, the ρ° human cell culture system has been established and has been widely used in recent years (4)'(5). This system is based upon the repopulating of human cells, which are completely depleted of mtDNA (termed ρ° cells), with exogenous mitochondria containing the mtDNA of interest. Molecular genetic and biochemical analysis showed that transformants can be obtained with various mitochondrial donors and the respiratory competence can be restored. In this study, the ultrastructural and immunocytochemical variations of mitochondria in human cell lines cultured in this system observed by transmission electron microscopy are reported.

Cell cultures for wild-type 143B, ρ206, and transmitochondrial cell lines have been described previously. Cells were trypsinized and collected from individual culture plates, and then were fixed with 3% paraformaldehyde and 0.04% glutaradehyde in 0.1 M phosphate-buffered saline (PBS) with 4% sucrose (pH 7.6) at RT.

The gregarine Pterospora is a parasite found in the body cavities of bamboo worms (Polychaeta: Maldanidae). The gamont stage of Pterospora has a bizarre structure with a main cell body and multiple posterior cytoplasmic extensions (Fig. 1). The cells are found in pairs within the coelom of the host and move by cytoplasmic streaming as they fill and empty their posterior extensions. Reports of this parasite in the literature are few (see references 1 & 2 for a review) and no ultrastructural details have been published regarding the genus. This study examines the fine structure of the gamont stage with particular emphasis on the structure of the pellicle.

The maldanid worm Axiothella mucosa was collected by shovel in St. Andrew Bay, Florida and returned to the Troy State University campus. Pterospora spp. gamonts were pipetted from minced setigers of the worms and fixed in 3% glutaraldehyde buffered with 0.05M sodium cacodylate, pH 7.5, for 1-6 hours.

Aureobasidins are cyclic depsipeptide natural products that have been shown to be fungicidal against a wide variety of fungi. We have studied the effect of an aureobasidin-like compound, SCH 56301 on the morphology and cytology of yeast cells. For both, Candida albicans and Saccharomyces cerevisiae, the normal cell cycle is disrupted by sub-lethal concentrations of the compound. In Saccharomyces, cells accumulate at the G2/M border of the cell cycle, DNA replication is essentially complete and a short nuclear spindle is visible; however, nuclear migration and spindle elongation do not occur and consequently a small round daughter cell remains attached to the mother cell. Changes in cell wall morphology are visible at old bud scars remaining on mother cells. Under the conditions of preparation of the specimens, there may have been insufficient cross-linking during treatment with SCH 56301 so that intracellular pressure appears to be pushing on a weakened cell wall at these points.

Monilinia vaccinii-corymbosi is the cause of mummy berry disease of commercial blueberries (Vaccinium spp.) grown in the United States and Canada (1). Ovaries of blueberry flowers are infected by the conidia (asexual spores) of this pathogen. However, despite their importance in disease initiation, little is known of the ultrastructural features of these conidia. The only ultrastructural data on these spores has come from the work of Batra (2) who used scanning electron microscopy to describe the morphology of the so-called “disjunctors” which connect adjacent conidia of M. vaccinii-corymbosi. The presence or absence of disjunctors is an important taxonomic character in the genus Monilinia (1) but little is known of their development and exact nature. The objective of this study was, therefore, to elucidate details of conidium and disjunctor development in M. vaccinii-corymbosi.

The Foraminifera are an enormously successful group of predominantly marine protists. They first appeared in the rock record >500 million years ago and currently are found in most planktonic and benthic marine and marginal marine environments. Though complete life cycles are known for only ˜30 of the >10,000 described extant species, these taxa illustrate reproductive patterns that are among the most diverse of all protists. The foraminiferal life cycle typically is characterized by an alternation of sexual and asexual generations during which meiosis occurs in the early phases of schizogony in the agamont. Sexual reproduction involves the production of biflagellated, triflagellated, or amoeboid gametes, and fertilization may be gametogamous, gamontogamous, or autogamous. Of these options, most Foraminifera for which sexual reproduction has been documented (44 species) produce many thousands of small biflagellated gametes that are shed directly into the surrounding seawater where gametogamous fertilization occurs.

The average somatic nucleus is only 10 microns in diameter, yet contains 2 meters of DNA coiled within its volume. This compaction must be accomplished in such a way so that the DNA remains accessible to the machinery of transcription, replication and repair. Sperm nuclei also have compacted DNA; however, structurally and functionally the arrangement of DNA in sperm is vastly different from that of somatic DNA. Somatic DNA is initially compacted by coiling around histone octamers, while sperm DNA is bound to elongate, highly basic proteins called protamines. Protamines bind the major groove of the double helix and allow adjacent DNA strands to come in close contact by neutralizing the negative charge of the sugar-phosphate backbone. Figure 1 illustrates the two most widely accepted models of DNA compaction in both somatic and sperm nuclei.

The arrangement of DNA within sperm nuclei is difficult to study because it is so highly compressed.

Plant vascular system is the principal means to carry water and food throughout the plant body. It is composed of two types of conducting vascular tissues, xylem and phloem. Xylem carries water and minerals from the root to the shoot, whereas phloem transports photosynthates from leaves to other parts of the body. The evolution of vascular system which solved the problem of water and food transport was considered to be one of the key events for the successful emergence of vascular plants on the land from aquatic environments. Although vascular tissues in almost all vascular plants consist of xylem and phloem, diverse arrangements of vascular tissues within the bundles and of vascular bundles in the stele were evolved (1). The occurrence of diverse vascular patterns in vascular plants offers an excellent opportunity to study the evolutionary mechanisms controlling pattern formation. In this report, we present our studies on the vascular differentiation and pattern formation in the inflorescence stems of Arabidopsis thaliana.