Digestion of prey in foraminifera is not anomalous: A correlation of light microscopic, cytochemical, and hvem technics to study phagotrophy in two allogromiids

Correlative light, high-voltage electron and conventional electron microscopic methods were used to investigate digestion in two allogromiid foraminiferans, Allogromia sp., strain NF, and A. laticollaris Arnold. Microscopic observations showed that bacterial prey are phagocytosed by reticulopodia and are transported to the allogromiid cell body within blister-like phagosomes. Larger prey (algae, diatoms) are transported along the reticulopodial surface and are either stored extrathalamously or phagocytosed at the oral opening (peduncle). Studies of allogromiids optimally fixed and labeled with an extracellular-space label (colloidal thorium) showed that phagocytosed prey are completely enclosed by a plasma membrane envelope; this finding was corroborated by a serial-section three-dimensional reconstruction of the oral zone of one allogromiid. Cytochemical staining for acid phosphatase showed that lysosomes are absent from reticulopods but abundant in the cell body, particularly in the oral zone cytoplasm. We conclude that digestion in allogromiid foraminiferans is accomplished by a vacuole-based digestive apparatus and not by extracellular digestion within a lacunary system, as has been suggested in earlier studies.     

Effects of starvation on growth and reproductive apparatus of two immature freshwater snails Biomphalaria pfeifferi and Biomphalaria glabrata (Gastropoda: Planorbidae)

Starvation of immature snails of Biomphalaria pfeifferi and B. glabrata results in an arrest of growth and animals remain immature. Spermatogenesis is limited to spermatogonia (B.g.) or spermatocytes 1 (B.p.). The number and the size of oocytes remain inferior to that of controls. Animals show reduced genital tracts.Once feeding is restored, growth is resumed but wet weight and shell diameter do not reach the same level as in controls. Fecundity and gametogenesis do not differ from that in controls. Genital tracts weight is proportional to body weight.     

Tannic acid characterized membranes of animal cells

Summary Tannic acid affects one face of some cytoplasmic membranes causing them to appear thin in electron micrographs.Trans vesicles of Golgi apparatus, dictyosome-like-structures, headcaps and aerosomes of germ cells, and certain lysosomes all have membranes that appear thin after tannic acid fixation and, in addition, are all characterized as being acid phosphatase positive. Thus, thin membranes appear functionally related and to be associated with cellular components that have lysosome or lysosome-like character.     

Special secretory cells in the soybean seed coat

Summary The seed coat of soybean (Glycine max L. Merr.) is of physiological interest for synthesis and transport of amino acids and photosynthates during embryo development. A transmission and scanning electron microscopic study to elucidate the structure of the seed coat disclosed a specialized convex area (antipit) appressed to a concave pit in the center of the abaxial surface of the cotyledon. The antipit, which lies on the inner surface of the seed coat at a medial point in the anterior to posterior direction of the seed, contained specialized secretory cells bounded by loose multi-layered cell walls. These cells were rectangular in the developing seed, varied in length, and contributed directly to the convex morphology of the antipit seen on the ventral surface of the seed coat. At maturity these cells assumed the shape of a cone, extending from the aleurone layer in a perpendicular array. The aleurone and cone cells contained numerous Golgi apparatus, laminated rough endoplasmic reticulum, secretory vesicles, and amyloplasts. Secretory vesicles arose directly from tubules of fenestrated trans cisternae of the Golgi apparatus. Mitochondria were clustered with the amyloplasts; stacks of lamellar cisternae of rough endoplasmic reticulum were associated with the nucleus and Golgi apparatus. The cellular contents, the interconnections by plasmodesmata, and the close physical association with the cotyledon suggested that the aleurone and cone cells may be involved in symplastic transport of nutrients for use by the developing embryo.This paper is dedicated to the memory of my parents, Joseph and Theresa Yaklich, who by their example taught me the value of work and the enjoyment of simple things.     

A cryptic cytostome is present inEuglena

Summary A short cylindrical pocket arises as an infolding from the ventral surface of the reservoir near the canal in several species ofEuglena (E. mutabilis, E. gracilis strain T,E. spec.). The structure is linked to a band of microtubules which is shown to be identical to the ventral flagellar root of the euglenoid flagellar root system. An absolute configuration analysis of the flagellar root system inE. mutabilis and a comparison with the flagellar apparatus of colourlessEuglenophyceae and the bodonids (Kinetoplastida) reveals structural and positional homology between the reservoir pocket ofEuglena and the cytostome of these organisms and strongly supports the phylogenetic derivation of theEuglenophyceae from theKinetoplastida and the evolution of greenEuglenophyceae from phagotrophic colourless taxa. The functional significance of the cryptic cytostome ofEuglena is discussed in relation to the occurrence of intracellular endosymbiotic bacteria.     

Striated ciliary root-golgi association in branchial crown epithelial cells ofOwenia. Visualization of Ca2+-binding sites and ATPase activities

Summary Striated Ciliary Roots (SCRs), about 3 m long, are attached to the basal bodies of branchial crown ciliated epithelial cells ofOwenia. These SCRs appear to consist of 5–7-nm diameter filaments organized in a cross-striation pattern with an apparent variable periodicity of 50 to 80 nm. The most exciting observation emerging from this study is the constant and conspicuous close spatial relationship between SCRs and fairly well developed Golgi apparatus. By enhancing contrast and preservation of cell components, the OsFeCN postfixation-staining of material prefixed in glutaraldehyde in the presence of calcium has revealed some fine-structural details within the SCR-Golgi Association. By means of the calcium precipitation method, with antimonate or oxalate in conjunction with X-ray microanalysis, we have identified calcium within SCR dark bands and SCR-associated Golgi bodies. The ability to bind calcium makes the Golgi apparatus a likely candidate for Ca²⁺ regulation of putative contraction of the SCRs and/or ciliary motility. The slight period variability measured in the SCRs and cytochemical localization of Mg²⁺, Ca²⁺-dependent ATPase activities associated with cross striations support the view that theOwenia SCRs may be contractile organelles.The striking and specific close structural association between the Golgi apparatus and the SCR showing Ca²⁺-binding capabilities suggests that some sort of Ca²⁺-mediated functional relationship between these organelles may exist.Abbreviations SCR striated ciliary root - OsFeCN method osmium tetroxide-ferricyanide method - EDTA ethylenediamine tetraacetic acid - EGTA ethyleneglycol-bis-(-aminoethyl ether) N,N-tetraacetic acid - ATP adenosine 5-triphosphoric acid - ATPase adenosine triphosphatase - ASW artificial sea-water     

Colocalization of α-lactalbumin and a major casein in secretory vesicles of rat mammary epithelial cells

Summary Whether both casein and noncasein (serum or whey) proteins of milk are contained within the same secretory vesicles of milk secreting mammary epithelial cells was explored. Antibodies to a major casein and to -lactalbumin of rat milk were localized in thin sections with colloidal gold-conjugated second antibodies. Antibodies to the casein component bound to an antigen present within lumina of Golgi apparatus cisternae and within secretory vesicles. This antigen was also recognized in structures within secretory vesicles and within alveolar lumina which were ultrastructurally identified as casein micelles. Antigens recognized by antibodies to -lactalbumin also were present in Golgi apparatus cisternae and within secretory vesicles. Both anti-casein and anti--lactalbumin antibodies recognized antigens within the same secretory vesicles. These observations show that one major noncasein protein of rat's milk is present in casein-containing secretory vesicles.     

Golgi apparatus activity and membrane flow during scale biogenesis in the green flagellateScherffelia dubia (Prasinophyceae). I: Flagellar regeneration

Summary Cells ofScherffelia dubia regenerate flagella with a complete scale covering after experimental flagellar amputation. Flagellar regeneration was used to study Golgi apparatus (GA) activity during flagellar scale production. By comparing the number of scales present on mature flagella with the flagellar regeneration kinetics, it is calculated that each cell produces ca. 260 scales per minute during flagellar regeneration. Flagellar scales are assembled exclusively in the GA and abstricted from the rims of thetrans-most GA cisternae into vesicles. Exocytosis of scales occurs at the base of the anterior flagellar groove. The central portion of thetrans-most cisterna, containing no scales, detaches from the stack of cisternae and develops a coat to become a coated polygonal vesicle. Scale biogenesis involves continuous turnover of GA cisternae, and scale production rates indicate maturation of four cisternae per minute from each of the cells two dictyosomes. A possible model of membrane flow routes during flagellar regeneration, which involves a membrane recycling loop via the coated polygonal vesicles, is presented.     

Heliobacterium chlorum: cell organization and structure

The basic cellular organization of Heliobacterium chlorum is described using the freeze-etching technique. Internal cell membranes have not been observed in most cells, leading to the conclusion that the photosynthetic apparatus of these organisms must be localized in the cell membrane of the bacterium. The two fracture faces of the cell membrane are markedly different. The cytoplasmic (PF) face is covered with densely packed particles averaging 8 nm in diameter, while the exoplasmic (EF) face contains far fewer particles, averaging approximately 10 nm in diameter. Although a few differentiated regions were noted within these fracture faces, the overall appearance of the cell membrane was remarkably uniform. The Heliobacterium chlorum cell wall is a strikingly regular structure, composed of repeating subunits arranged in a rectangular pattern at a spacing of 11 nm in either direction. We have isolated cell wall fragments by brief sonication in distilled water, and visualized the cell wall structure by negative staining as well as deep-etching.Abbreviations PF protoplasmic fracture face - EF exoplasmic fracture face     

Ultrastructural observations on the kinetosomes,and Golgi bodies during the asexual life cycle ofSaprolegnia

Summary At the onset of zoospore cleavage the centrioles ofSaprolegnia ferax reorientate, develop into kinetosomes and become associated with microtubular roots and a striate fibre. After cytoplasmic cleavage a flagellum, with a hitherto undescribed transition zone structure, develops from each kinetosome. Flagellum axonemes occur inside recently encysted primary spores. In vegetative hyphae and germinating cysts most recognizable Golgi bodies are characteristically associated with a cisternum of the endoplasmic reticulum and a mitochondrion but during sporogenesis they all lie adjacent to nuclei where they are apparently active in vesicle production. The structural details of these changes are described and their significance discussed. We wish to acknowledge the numerous helpful discussions with Dr. J. L. Gay. The senior author held a S.R.C. studentship during the course of this work, part of which was submitted in partial fulfillment of the requirements for the degree of Ph. D. at the University of London.