CELLULAR DIFFERENTIATION OF TERMINAL REGIONS OF TRICHOMES OF OSCILLATORIA PRINCEPS (CYANOPHYCEAE)1

The terminal regions of Oscillatoria princeps Vaucher display cells which differ from intercalary cells of the same trichome. These end cells have an extensively thickened calyptra replacing normal crosswalls. The thylakoids are extensively disrupted in terminal cells and the cytoplasm displays general disorganization characteristic of necrotic cells. The development of terminal regions occurs within a 5 day period following breakage of the trichome and appears characteristic of O. princeps. The ecological implications of terminal region differentiation are also considered including reaction to variations in current, temperature and light intensities.     

A comparative study on vascularization and the structure of the epidermis of an amphibious mudskipper fish,Scartelaos gigas (Gobiidae,Teleostei), on different parts of the body and the appendages

Epidermal structure of the amphibious mudskipper, Scartelaos gigas (Gobiidae), was investigated in relation to their terrestrial adaptation whereby a histological study on the epidermis of 15 regions including nine body regions, five fins and the sucking disc was carried out. The structure of the epidermis consists of three layers: an outermost layer with polygonal cells or rather flattened cells, small cells and mucous cells; a thick middle layer with voluminous cells swollen by epidermal cells; and the stratum germinativum. A dermal bulge was located at each apical area of the epidermis of almost all body regions, but was not existent in the operculum and the appendages, including none of the fins or the sucking disc. In the epidermis of the body regions, the dermal bulges had numerous dermal capillaries just beneath the stratum germinativum. By contrast, the appendages never had dermal capillaries due to the absence of the dermal bulge. Based on these results, the cutaneous air uptake in S. gigas would seem to be more effective in the upper body regions that are most often exposed to air than in the lower body regions, however, cutaneous air uptake is not likely to occur in the appendages.     

DNase I sensitivity in facultative and constitutive heterochromatin

In situ nick translation allows the detection of DNase I sensitive and insensitive regions in fixed mammalian mitotic chromosomes. We have determined the difference in DNase I sensitivity between the active and inactive X chromosomes inMicrotus agrestis (rodent) cells, along both their euchromatic and constitutive heterochromatic regions. In addition, we analysed the DNase I sensitivity of the constitutive heterochromatic regions in mouse chromosomes. InMicrotus agrestis female cells the active X chromosome is sensitive to DNase I along its euchromatic region while the inactive X chromosome is insensitive except for an early replicating region at its distal end. The late replicating constitutive heterochromatic regions, however, in both the active and inactive X chromosome are sensitive to DNase I. In mouse cells on the other hand, the constitutive heterochromatin is insensitive to DNase I both in mitotic chromosomes and interphase nuclei.     

A Caulobacter MreB mutant with irregular cell shape exhibits compensatory widening to maintain a preferred surface area to volume ratio

Rod‐shaped bacteria typically elongate at a uniform width. To investigate the genetic and physiological determinants involved in this process, we studied a mutation in the morphogenetic protein MreB in Caulobacter crescentus that gives rise to cells with a variable‐width phenotype, where cells have regions that are both thinner and wider than wild‐type. During growth, individual cells develop a balance of wide and thin regions, and mutant MreB dynamically localizes to poles and thin regions. Surprisingly, the surface area to volume ratio of these irregularly shaped cells is, on average, very similar to wild‐type. We propose that, while mutant MreB localizes to thin regions and promotes rod‐like growth there, wide regions develop as a compensatory mechanism, allowing cells to maintain a wild‐type‐like surface area to volume ratio. To support this model, we have shown that cell widening is abrogated in growth conditions that promote higher surface area to volume ratios, and we have observed individual cells with high ratios return to wild‐type levels over several hours by developing wide regions, suggesting that compensation can take place at the level of individual cells.     

Granulated metrial gland cells in the pregnant uterus of mice expressing the collagen mutation tight-skin (Tsk/+)

Summary Influences of the extracellular matrix (ECM) on the differentiation and distribution of granulated metrial gland (GMG) cells, a uterine natural killer (NK)-like cell subset, were studied by histological examination of implantation sites in the mouse mutant Tsk/+. Tsk/+ mice overproduce collagens I and III. GMG cell differentiation appeared to progress normally in Tsk/+ mice between days 6.5 and 12.5 of gestation. The distribution of GMG cells, however, was abnormal. Significant numbers of GMG cells were found in the antimesometrial and lateral decidual regions at day 8.5 of gestation and in the regions between implantation sites until day 10.5 of gestation. Loss of GMG cells from these regions normally occurs by day 6.5 of gestation. These data suggest that alterations to the ECM change the migration properties or life span of GMG cells.     

Confocal laser scanning light microscopy of the extra-thecal epithelia of undecalcified scleractinian corals

The extra-thecal epithelia of cryofixed undecalcified, freeze-substituted polyps of the scleractinian corals Galaxea fascicularis and Tubastrea faulkneri and axial and basal polyps of Acropora formosa have been examined, in anhydrously prepared thick slices, by confocal laser scanning light microscopy. The avoidance of chemical fixation and decalcification makes it possible to determine whether previously seen structures are real or artefactual products of swelling, shrinkage and distortion. All of the epithelia of all the corals examined are characterised by well defined intercellular spaces. Mucocytes are present in all cell layers in Galaxea and Tubastrea but are not present in any cell layers in the axial polyp of Acropora although they are abundant in the oral ectoderm of the basal polyps in this coral. Zooxanthellae are absent in Tubastrea, the epithelia of the exert septa of Galaxea and the axial polyp of Acropora. The calicoblastic ectoderm is generally composed of thin squamous cells with large intercellular spaces. At rapidly calcifying regions such as the tips of the exert septa of Galaxea, the calicoblastic cells are elongated with extensive arborisation of the basal regions of the cells. They are separated by large intercellular spaces and contain numerous fluorescent granules. The apical regions of these cells appear to be closely applied to the surface of the skeleton. There is no evidence of a space between the apical region of the calicoblastic cells and the skeleton.     

Do anthocyanins function as antioxidants in leaves? Imaging of H2O2 in red and green leaves after mechanical injury

Purified anthocyanin extracts show strong antioxidant properties in vitro, but it is not known whether they can scavenge reactive oxygen in living cells. The oxidative responses in red and green portions of Pseudowintera colorata leaf laminae were compared by the real‐time imaging of H₂O₂ in cells after mechanical injury. An oxidative burst was elicited almost immediately from chloroplasts in the palisade mesophyll, as evidenced using the fluorochromes dichlorofluorescein and scopoletin. H₂O₂ accumulated in green lamina regions for 10 min, and then decreased slowly. By contrast, red regions recovered rapidly, and maintained consistently low levels of H₂O₂. Infusion of cells with N‐acetyl‐l ‐cysteine accelerated the depletion of H₂O₂ from green regions. Wounded leaves ultimately developed a localized necrotic lesion and an intense anthocyanic band. The red regions were enriched in anthocyanins, flavonols, dihydroflavonols, and hydroxycinnamic acids. Only the anthocyanins were suitably located to account for the enhanced rates of H₂O₂ scavenging. The data support the hypothesis that red cells have elevated antioxidant capabilities in vivo.     

Physiology of the Rhizobium-legume association: I—The presence of bacterial DNA within the plant root

Summary Rhizobium deoxyribonucleic acid has been detected within Vicia faba root cells by in situ hybridization and autoradiography after exposure of root apexes to Rhizobium viable cells. Reannealed regions are localized into the cortex cells; the presence of bacterial DNA is specific for the root tissue; labelled regions were not detectable within apexes exposed to non-nodulating strains or to bacteria other than Rhizobium; Rhizobium DNA was not detectable in tissues of plants other than its leguminous host. re]19750313     

Leaf curl disease of Almond caused byTaphrina deformans (Berk.) Tul.

Summary The host/parasite relationship ofTaphrina deformans (Berk.) Tul. on Almond,Prunus dulcis (Miller) D. A. Webb (=Prunus amygdalus Stokes), has been studied with the light microscope by clearing and sectioning infected leaves.A quantitative study of the host reaction shows that the presence of the fungus causes immediate cell division (hyperplasia) followed by cell enlargement (hypertrophy) and cell differentiation. The epidermal and bundle sheath cells in infected regions contain anthocyanin.The vegetative mycelium is located in intercellular spaces in three distinct leaf regions. The sub-epidermal and intercellular hyphae are morphologically similar, consisting of an irregularly branching network of cells separated by unusual septa. Sub-cuticular hyphae have a more regular shape and become short and wide during development of the disease.Infection margins illustrate changes in the healthy leaf caused byT. deformans and observations indicate that the fungus spreads in the upper leaf regions.     

Centromere organization in meiotic chromosomes of Parascaris univalens

The chromosomes of Parascaris univalens possess a continuous centromeric structure spanning their entire length in gonial cells. A cytological and ultrastructural analysis of P. univalens meiotic chromosomes was performed. The results show that during meiosis the holocentric germline chromosomes of male P. univalens undergo restriction of kinetic activity to the heterochromatic terminal regions. These regions lack kinetochore structures and interact directly with spindle microtubules.     

A novel intercellular junction between cone cells in the compound eye of Ephestia kuehniella

A previously unidentified intercellular junction between cone cells in the compound eye of the moth Ephestia is described. The junctions are characterized by deposition of granular material, in register, along portions of the membranes of adjacent cone cells during compound eye development and by a constant intercellular space of 8–10 nm. Accumulation of the cone cell material along localized regions of the cell membrane suggests an interaction between a specialized area of the membrane and a specific cytoplasmic constituent, and the exact matching of the regions of deposition between adjacent cells implies intercellular interaction. The junctional nature of these membrane regions is often obscured in the adult crystalline cone but is inferred from observations on developing cone cells.     

Binding and penetration ofRhizobium japonicum to cultured soybean cells

A cultured soybean cell line, SB-1 was used to evaluate the initial interaction between the soybean cells andRhizobium japonicum. Co-culturing ofR. japonicum with SB-1 cells in suspension resulted in strain-specific polar attachment. This attachment can be inhibited by galactose and antibodies raised against seed soybean agglutinin (SBA). A lectin was purified from SB-1 cells which shares properties with SBA in terms of immunological reactivity, sugar binding activity, polypeptide molecular weight and peptide maps. When the SB-1 cells were co-cultured withR. japonicum for three weeks in solid agar medium, histological staining revealed bacterial penetration into certain SB-1 cells. Furthermore, there were focal regions of cells with prominent nuclei representing actively proliferating regions. These observations are analogous to that ofin vivo nodule initiation in soybean roots.     

Structural differentiation in the mid-gut epithelium of the phasmid Carausius morosus Brunner

The epithelial cells of the anterior central and posterior regions of the midgut of Carausius morosus are described. Possible functions of the cells, indicated by structural differentiation, are discussed.     

SINGLE-CELL PIGMENTATION OF PORPHYRA LINEARIS ANALYZED BY FOURIER TRANSFORM MULTI-PIXEL SPECTROSCOPY AND IMAGE ANALYSIS1

The novel method of Fourier transform multi-pixel spectroscopy was used for the nondestructive analysis of and comparison of pigmentation in different regions of live thalli of the red alga Porphyra linearis. Because the thallus in this alga consists of a monolayer of nonoverlapping cells, we were able to analyze the pigmentation of single cells by combining light absorbance with natural fluorescence data. From the image of each cell in the vegetative male and female reproductive and holdfast regions, more than 4 ± 10⁴ fluorescence and absorbance spectra were obtained. Specific pigments in the different regions were localized by the use of a software program of similarity mapping followed by image construction. The reconstructed images revealed subcellular localization of each pigment according to specific spectroscopic fingerprints. The results showed that the vegetative and female reproductive cell types had a significantly higher content of phycoerythrin than of phycocyanin, and quite similar chlorophyll a levels. Most of the holdfast cells were poorly pigmented, but had more chlorophyll a than phycoerythrin or phycocyanin. The male reproductive cells contained only traces of pigments. Thus, by using Fourier transform multipixel spectroscopy, we were able to characterize the pigmentation of different regions of the thallus and follow the distribution patterns of the different pigments on the subcellular level along the differentiation gradient of the alga.     

Comparison of the localization of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Cry1A δ-endotoxins and their binding proteins in larval midgut of tobacco hornworm, <Emphasis Type="Italic">Manduca sexta</Emphasis>

Tobacco hornworm, Manduca sexta, is a model insect for studying the action of Bacillus thuringiensis (Bt) Cry toxins on lepidopterans. The proteins, which bind Bt toxins to midgut epithelial cells, are key factors involved in the insecticidal functions of the toxins. Three Cry1A-binding proteins, viz., aminopeptidase N (APN), the cadherin-like Bt-R₁, and membrane-type alkaline phosphatase (m-ALP), were localized, by immunohistochemistry, in sections from the anterior, middle, and posterior regions of the midgut from second instar M. sexta larvae. Both APN and m-ALP were distributed predominantly along microvilli in the posterior region and to a lesser extent on the apical tip of microvilli in the anterior and middle regions. Bt-R₁ was localized at the base of microvilli in the anterior region, over the entire microvilli in the middle region, and at both the apex and base of microvilli in the posterior region. The localization of rhodamine-labeled Cry1Aa, Cry1Ab, and Cry1Ac binding was determined on sections from the same midgut regions. Cry1Aa and Cry1Ab bound to the apical tip of microvilli almost equally in all midgut regions. Binding of Cry1Ac was much stronger in the posterior region than in the anterior and middle regions. Thus, binding sites for Bt proteins and Cry1A toxins are co-localized on the microvilli of M. sexta midgut epithelial cells.     

Impact of the exodermis on infection of roots byFusarium culmorum

Patterns of infection withFusarium culmorum (W G Smith) Saccardo were observed in seedling roots of barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), maize (Zea mays L.) and asparagus (Asparagus officinalis L). Apical regions of the main roots were not infected. Since penetration into the root occurred several days after inoculation and the roots were growing during the experiment, these regions had apparently not been in existence long enough to be infected. In older regions of barley, wheat and asparagus, hyphae entered through the tips of lateral roots. In barley and wheat, which had not developed any suberin lamellae in their subepidermal layer, infection occurred randomly over the remainder of the root. In maize, the fungus penetrated the epidermis at many sites but did not breach the exodermis in which all cells possessed both Casparian bands and suberin lamellae. Maize roots, therefore, sustained only minimal infections. In asparagus, the fungus grew through the short (passage) cells but never the long cells of the exodermis. In doing so, it penetrated cells possessing Casparian bands but lacking suberin lamellae. The results support the hypothesis that suberin lamellae provide effective barriers to the growth ofF. culmorum hyphae.     

Tandem genes encode cell-surface polypeptides SspA and SspB which mediate adhesion of the oral bacterium Streptococcus gordonii to human and bacterial receptors

The highly conserved antigen I/II family of polypeptides produced by oral streptococci are believed to be colonization determinants and may mediate adhesion of bacterial cells to salivary glycoproteins adsorbed to cells and tissues in the human oral cavity. Streptococcus gordonii is shown to express, on the cell surface, two antigen I/II polypeptides designated SspA and SspB (formerly Ssp-5) that are the products of tandemly arranged chromosomal genes. The structure and arrangement of these genes is similar in two independently isolated strains, DL1 and M5, of S. gordonii. The mature polypeptide sequences of M5 SspA (1539 amino acid (aa) residues) and SspB (1462 aa residues) are almost wholly conserved (98% identical) in the C-terminal regions (from residues 796 in SspA and 719 in SspB, to the respective C-termini), well-conserved (84%) at the N-terminal regions (residues 1–429), and divergent (only 27% identical residues) within the intervening central regions. Insertional inactivation of the sspA gene in S. gordonii DL1 resulted in reduced binding of cells to salivary agglutinin glycoprotein (SAG), human erythrocytes, and to the oral bacterium Actinomyces naeslundii. Further reductions in streptococcal cell adhesion to SAG and to two strains of A. naeslundii were observed when both sspA and sspB genes were inactivated. The results suggest that both SspA and SspB polypeptides are involved in adhesion of S. gordonii cells to human and bacterial receptors.     

Pharmacology of Sodium-Dependent High-Affinity l-[3H]Glutamate Transport in Glial Cultures

Abstract: Pharmacological and molecular biological studies provide evidence for subtypes of sodium-dependent high-affinity glutamate (Glu) transport in the mammalian CNS. At least some of these transporters appear to be selectively expressed in different brain regions or by different cell types. In the present study, the properties of l -[³H]Glu transport were characterized using astrocyte-enriched cultures prepared from cerebellum and cortex. In both brain regions, the kinetic data for sodium-dependent transport were consistent with a single site with K_m values of 91 ± 17 µM in cortical glial cells and 66 ± 23 µM in cerebellar glial cells. The capacities were 6.1 ± 1.6 nmol/mg of protein/min in cortical glial cells and 8.4 ± 0.9 nmol/mg of protein/min in cerebellar glial cells. The potencies of ～40 excitatory amino acid analogues for inhibition of sodium-dependent transport into glial cells prepared from cortex and cerebellum were examined, including compounds that are selective inhibitors of transport in synaptosomes prepared from either cerebellum or cortex. Of the analogues tested, 14 inhibited transport activity by >50% at 1 mM concentrations. Unlike l -[³H]Glu transport in synaptosomes prepared from cerebellum or cortex, there were no large differences between the potencies of compounds for inhibition of transport measured in glial cells prepared from these two brain regions. With the exception of (2S,1′R,2′R)-2-(carboxycyclopropyl)glycine and l -α-aminoadipate, all of the compounds examined were ～10–200-fold less potent as inhibitors of l -[³H]Glu transport measured in glial cells than as inhibitors of transport measured in synaptosomes prepared from their respective brain regions. The pharmacology of transport measured in these glial cells differs from the reported pharmacology of the cloned Glu transporters, suggesting the existence of additional uncloned Glu transporters or Glu transporter subunits.     

N-CAM and N-Cadherin Are Specifically Expressed in Xanthophores,but not in the Other Types of Pigment Cells,Melanophores, and Iridiphores

Little is known about cell-cell communication in pigment cells, whereas a number of signalling molecules have been implicated to control their migration, differentiation, and proliferation. We set out to investigate the expression of cell adhesion molecules (CAMs) in the three different types of pigment cells in poikilotherms, Oryzias latipes and Xenopus laevis. In the present experiments, the expression of N-CAM and N-cadherin in the pigment cells in vitro was examined by immunocytochemistry. Melanophores and xanthophores were isolated and cultured from scales or skins, while iridophores were harvested from skins or peritoneum. The results showed that N-CAM and N-cadherin were specifically expressed in xanthophores, but not in melanophores or iridophores in both O.latipes and X.laevis. N-CAM and N-cadherin basically colocalized in the restricted regions of xanthophores, although the N-cadherin-expressed region was broader than the N-CAM-expressed region in the same cell. The incidence of N-cadherin expression was higher than that of N-CAM expression. N-CAM and N-cadherin were expressed at the tip or the base of dendrites, or at the edge between dendrites in dendritic xanthophores. N-CAM and N-cadherin usually localized in small and narrow regions of xanthophores. This distribution pattern was essentially similar in xanthophores with round morphology, which exhibited spot, band, or semicircular immunoreactive regions on the peripheral edge of the cells. The difference in the distribution of pigment granules within the cells, culture period, fixatives, or immunofluorescent markers used in the experiments did not alter the immunostaining pattern.