Paddle cilia and discocilia — Genuine structures?

Kinocilia of epidermal sensory cells in fixed marine Turbellaria often terminate as flattened biconcave discs. The distal part of the ciliary axoneme curves back upon itself forming a 360 degree loop which is enveloped by the plasmalemma. In living animals this structure can be induced by the addition of sodium cacodylate, monobasic sodium phosphate, dibasic sodium phosphate, sucrose, calcium chloride, or formaldehyde to the sea water. Specimens treated with sodium chloride, glutaraldehyde, or osmium tetroxide do not show modified cilia. In animals prepared for EM at low temperature and with a buffered hypotonic fixative less kinocilia are modified than in animals treated with a buffered iso- or hypertonic fixative and at a higher temperature. It is assumed that the unusually shaped cilia, described as "paddle cilia" or "discocilia" in other invertebrates, do not represent a genuine but an artificial structure.     

Biomass yields of Chlorella from iron (Y x/Fe) in iron-limited batch cultures

The maximum biomass in iron-limited photosynthetic batch cultures of chlorella increased as the logarithm of the iron concentration. The growth yield from iron (Y _x/Fe) showed a marked inverse relation to the specific growth rate. The maximum biomass yield, g dry biomass/g iron consumed, was 7.5x10³ with specific growth rate 0.108 h^-1; the minimum was 0.79×10³ with specific growth rate 0.145 h^-1. The maximum specific growth rate in the exponential phase of Fe limited cultures varied as the initial Fe concentration. Fe-limited growth made the cells adhere to a glass surface.Abbreviation O.D. optical density     

Use of immunocytochemical staining of somatostatin for correlative light and electron microscopic investigation of D cells in the pancreatic islet of Xiphophorus helleri H. (Teleostei)

Summary Somatostatin-containing cells have been demonstrated by immunocytochemistry in semithin sections of the pancreatic islet of the teleost fish, Xiphophorus helleri. These cells were shown by correlative light and electron microscopy to be identical with D cells previously defined in this species by the silver impregnation method of Hellman and Hellerström.Supported in part by grants from the British Council and from the Medical Research Council of Great Britain     

Secretion of melanophore-stimulating hormone (MSH) in long-term cultures of pituitary neurointermediate lobes

Summary Neurointermediate lobes from pituitaries of the frog, Rana berlandieri forreri (Rana pipiens, sensu lato), were maintained in organ culture in media with and without serum for up to six months. The cultured tissues were examined periodically by light microscopy and transmission electron microscopy and by bioassay of the melanophore-stimulating hormone (MSH) secreted and present in the culture media. Light-microscopic observations revealed a high degree of preservation of the pars intermedia at four weeks with isolated areas of some glands maintaining histological integrity for the entire six months. Similarly, at the ultrastructural level the cells appeared morphologically intact and to be actively synthesizing and secreting hormone. Bioassays showed the glands to be continuously secreting MSH; however, larger yields of hormone were obtained in media lacking serum. No significant ultrastructural differences between cells grown in the presence or absence of serum were detected. The difference in concentration of MSH between the two groups therefore apparently results from enzymatic degradation of the hormone by the serum. Organ culture of the vertebrate neurointermediate lobe may provide a unique method for the production of large quantities of MSH and for the study of other melanotropic and opiate peptides as they may be synthesized and secreted by the pars intermedia.     

Studies on bone marrow histogenesis: Morphometric and autoradiographic studies of regenerating marrow stroma in extramedullary autoimplants and after evacuation of marrow cavity

Summary The marrow cavity of the rat tibia was mechanically evacuated and autoimplanted to the subcutaneous tissue. The regenerative process which restored the integrity of marrow stroma and hemopoiesis, was morphometrically evaluated in whole mount of tibia. Following evacuation, the clot filled the cavity. The granulation tissue then appeared and expanded, penetrating and replacing the clot. The fibroblasts of the granulation tissue differentiated into osteoblasts forming osteoid bone. Within its interstices, the primordial marrow consisting of loose connective tissue and vascular sinuses appeared and hemopoiesis resumed. Expansion of hemopoiesis resulted in the resorption of bone and within three weeks the tibial cavity was restored to the pre-evacuation state.Autoradiography indicated that the labeling index was initially high in fibroblasts and osteoblasts but was subsequently reduced while it increased in osteocytes, cells of Haversian canals, stromal and hemopoietic cells of marrow. The finding is in disagreement with the view that the regenerative process originates from the Haversian canal. When the label was introduced on day 4 post-operatively, it subsequently appeared in osteocytes, cells of Haversian canal, stromal elements of the marrow, but not in the hemopoietic cells. This indicates complete dissociation of marrow stroma and hemopoietic stem cell.Supported by NASA Contract NSG 9061. Mehdi Tavassoli is the recipient of a CRD Award AM-70551     

The rhombencephalic recess in the rat

Summary The rhombencephalic recess, an ependymal organ, has been studied for the first time by light- and electron microscopy. It is situated mediosagittally on the floor of the rhomboid fossa at the level of the colliculus facialis. The recess and the superimposed tissue are built up by tanycytes, their apices being connected by tight junctions. HRP, injected into the c.s.f., does not penetrate into the intercellular clefts of the recess area. The recess area reveals a certain autonomy regarding its supply with arteries and capillaries. A bloodbrain barrier exists, but shows slight leakage in circumscribed areas as a result of intense transendothelial vesicular transport. The organization of the recess area is compared with that of other ependymal organs, especially circumventricular organs.The skilful technical assistance of Miss K. Bielenberg, Mrs. H. Prien, Mrs. E. Schöngarth and Mrs. H. Schöning is thankfully acknowledgedSupported by the Deutsche Forschungsgemeinschaft (Kr 569/1 and SFB 34/D4) and Stiftung Volkswagenwerk

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Flavonoids of Plummera: Taxonomic implications at the generic level within the gaillardiinae

Four populations each of Plummera floribunda and P. ambigens were examined for flavonoid content. Six compounds were isolated and identified as flavone and flavonol aglycones and flavonol glycosides. In all cases, both taxa were found to be identical in flavonoid content. Plummera was then compared to other genera in the subtribe Gaillardiinae. At the present time, it is the opinion of the author that Plummera is very closely related to, but not congeneric with Hymenoxys.     

Flavonols and C-Glycosylflavonoids of the caryophyllales

A survey of 112 species of the Caryophyllales showed the presence of flavonols in all eleven families and of C-glycosylflavonoids in nine families, being absent from the Aizoaceae and Cactaceae. 18% of the species contained both classes of compound. C-glycosylflavonoids are reported for the first time in the Amaranthaceae, Basellaceae, Didieraceae, Nyctaginaceae, Phytolaccaceae, Portulacaceae and Molluginaceae. The Caryophyllaceae contained prodominantly C-glycosylflavonoids, suggesting they are the most advanced family in the order.     

Light and Electron Microscopic Observations of Gametogenesis in Hastigerina pelagica (Foraminifera)*

SYNOPSIS. During gametogenesis mother individuals of Hastigerina pelagica (d'Orbigny) undergo significant morphological changes. Thirty h before gamete release, the cytoplasm changes from pale orange to bright red, possibly due to transport of stored lipids from the inner region to more peripheral parts of the cytoplasm. During the next 10 to 15 h the bubble capsule which surounds the calcareous shell is discarded. After all bubbles have disappeared, the individual sheds its spines by resorbing the spine bases close to the shell surface. A single mother nucleus divides into some hundreds of thousands of gamete nuclei within a span of ～ 20 h. A bulge of cytoplasm is extruded from the aperture and increases in size during the next 5 to 10 h. This bulge consists of cytoplasmic strands in which gametes and spherical bodies are embedded. The gametes and spherical bodies mature and are released during the afternoon and early evening. The gametes have 2 unequal acronematic flagella. A previously undescribed structure in foraminiferal reproduction is the spherical body which consists of a large vacuole surrounded by a thin cytoplasmic layer in which several nuclei, various typical cell organelles and multiple flagella are present. The spherical bodies are believed to play a role as receptacles of waste material, possibly including residual digestive enzymes, thereby protecting the gametes from lysis during the reproductive process. Fusion of gametes and further development into the next generation have not been observed.