Obervations on the occurrence of scales and bristles of mallomonas spp. (Chrysophyceae) in the micro-laminated sediments of a small lake in finnish North Karelia

Scales and bristles ofMallomonas crassisquama (Asmund) Fott andM. elongata Reverdin are reported from the laminated sediments of Laukunlampi, a small kettlehole lake in N. Karelia, Finland. The white summer laminae in the deeper sediment are composed almost entirely ofM. crassisquama scales and bristles. The taxonomy, ecology and distribution ofM. crassisquama andM. elongata are briefly discussed and factors influencing the preservation of scales and bristles in sediments are considered. It is suggested that analysis of sedimentary associations of scales, bristles and cysts could be used to improve cyst taxonomy inMallomonas.     

The Pituitary Gland of the Roach Leuciscus rutilus

Three endocrine cell types were recognized in the proximal pars distalis (PPD) of the roach, Leuciscus rutilus, by electron microscopy. Two of these cell types are basophilic and assumed to be gonadotropic. The third cell type is acidophilic and its similarity to somatotropic (STH) cells is evident. Green fluorescent cells corresponding to cells with dense core vesicles of about 85 nm are scattered between the PPD and the proximal neurohypophysis (PNH). Their possible content of a catecholamine was demonstrated with microspectrofluorometric analyses. Four axon types with granules 65, 81, 110 and 137 nm in average diameter terminate at the basement membrane. Only fibers with granules of 81 nm enter the PPD to make synapses with the STH cells. Extensions of the basement membrane are continuous with the perivascular space and penetrate the endocrine tissue. It is postulated that axon terminals on the basement membrane are functionally equivalent to synaptic contacts on the endocrine cells. Axon type 4 has granules which in sizes correspond to those of cells in lateral and ventrolateral parts of the nucleus lateralis tuberis (NLT). A similar correlation is possible between axon type 3 and other cells in the NLT. This is in accordance with earlier conclusions of a regulation of the gonadotropic cells from the lateral (posterior) parts of the NLT.     

A method for nucleic acid hybridization to isolated chromosomes in suspension

Summary A procedure was developed to provide differential fluorescent staining of metaphase chromosomes in suspension following nucleic acid hybridization. For this purpose metaphase chromosomes were isolated from a Chinese hamster x human hybrid cell line. After hybridization with biotinylated human genomic DNA, the human chromosomes were visualized by indirect immunofluorescence using antibodies against biotin and fluoresceine-isothiocyanate-(FITC)-labeled second antibodies. This resulted in green fluorescent human chromosomes. In contrast, Chinese hamster chromosomes revealed red fluorescent staining only when counterstained with propidium iodide. Notably, interspecies chromosomal rearrangements could be easily detected. After hybridization and fluorescent staining, chromosomes still showed a well-preserved morphology under the light microscope. We suggest that this procedure may have a useful application in flow cytometry and sorting.     

Ultrastructure and adaptation in the retina of Aglais urticae (Lepidoptera)

Summary The apposition eye of Aglais urticae is composed of eucone ommatidia. Serial sectioning of blocks from the laterofrontal and lateroventral eye regions and mapping at different levels revealed that there is no torsion of whole ommatidia along their long axes.The sensory part of the ommatidium comprises nine retinula cells. The most significant features of the complicated rhabdom structure (diagrammed in Fig. 3) are as follows. The vertically aligned receptor cells V₁ and V₅, which become axonal at the level at which the ninth cell begins, have microvilli arranged in bundles. The microvilli bundles of these cells generally make an angle between 30 and 55° on one or the other side of the dorsoventral axis in the ommatidium cross section. The two orientations alternate regularly along the length of the rhabdom. The repeated sweeps of these bundles in regular intervals in combination with the curvature of the V-cell microvilli is considered to be a substitute for rhabdomere twisting. The four diagonally aligned receptor cells D_2,4,6,8 have rhabdomers that are continuous, though of variable size. These rhabdomeres, like those of the horizontally aligned cells (H₃ and H₇), extend along the entire rhabdom, though there is a small (1–2 m) interruption in the H-cell rhabdomeres; the latter have the most constant orientation. Pigment granules are most abundant in the D cells, followed by the H cells and finally the V cells. RC₉ lacks pigments.Light- and dark-adaptation experiments reveal marked horizontal migration of the retinula-cell pigment (pupil reaction) and slight vertical migration. Monochromatic adaptation experiments at wavelengths =342, 436, 522, 578, and 626 nm indicate special sensitivity of the D-cells around -520 nm. There are indications for sensitivity of V cells in the UV, and possibly of H cells in the blue. The H cells are regarded as suited for the detection of polarized light. The functional significance of these findings is discussed and compared with what is known of other butterfly eyes.This work was supported by grants from the Deutsche Forschungsgemeinschaft and the Stiftung Volkswagenwerk     

Extracellular microtubule-like structures in the retina of the rainbow trout

Summary Extracellular microtubule-like structures (MLS) are described in the retina of the rainbow trout. They appear about 30 to 40 days after hatching, when the yolk-sac is consumed and the animal begins to swim and to nourish actively. They fill a widely branched system of extracellular clefts and spaces, and connect different cells and cell types, especially outer horizontal cells and bipolar cells. The MLS are not affected by the vinca alcaloid vincristine, although this drug penetrates into the MLS-filled space, as has been shown by the formation of intracellular, vincristine-induced tubulin paracrystals. The MLS are compared with other extracellular tubular structures described in other animal tissues. Their functional significance remains unclear.     

Untersuchungen An Hemiploiden Nachkommen Autotetraploider

Ohne ZusammenfassungMit 2 Textabbildungen     

Kerngesteuerte Gynodi?zie bei Salvia nemorosa

Zusammenfassung der Ergebnisse BeiSalvia nemorosa wurde eine Form der Gynodiözie festgestellt, die nicht plasmatisch bedingt ist. Ein dominanter Faktor für Weiblichkeit F bewirkt, daß in der Regel die Weibchen zur Hälfte zwittrige Nachkommen haben. Auch rein weibliche Nachkommenschaften und solche, in denen mehr Weibchen als Zwitter enthalten sind, kommen vor. Als Erklärung dafür wird angenommen, daß ein mit f gekoppelter Letalfaktor und wahrscheinlich noch weitere Letal- und Subletalfaktoren die Entstehung der Zwitter verhindern oder ihre Fertilität einschränken.Das ist der zweite bekanntgewordene Fall einer karyotisch gesteuerten Gynodiözie. Er ist deshalb besonders interessant, weil ein Teil der Genotypen, in bestimmter Zusammenstellung, demSatureja-Modell entspricht. Es wird diskutiert, wie weit bei den verschiedenen Vererbungsmechanismen die Stabilität des gynodiözischen Systems gewahrt wird.     

A p300 and SIRT1 Regulated Acetylation Switch of C/EBPα Controls Mitochondrial Function

1. Download high-res image (137KB)
2. Download full-size image

     

Micropatterns in Festuca rubra-dominated salt-marsh vegetation induced by sheep grazing

Micropatterns induced by sheep grazing, were studied in three consecutive years in a Festuca rubra-dominated salt marsh in a grazing trial with five different stocking rates (0, 1.5, 3, 4.5 and 10 sheep ha^-1). The micropatterns were formed by a mosaic of short and tall F. rubra stands on a scale of square decimeters. Permanent transects of 2 m × 10 m were used to study the stability of these patterns, and to analyze interactions between the vegetation, the marsh elevation and the sheep. Micropatterns occurred only in the lightly to moderately grazed paddocks (1.5–4.5 sheep ha^-1) with the highest spatial diversity in the 3 sheep ha^-1 transect. When grazing was excluded, micropatterns did not develop; nor did they develop in the traditionally and most intensively grazed paddock (10 sheep ha^-1). Detailed observations in one year showed that crude-protein content did not differ between green leaves from the short and tall stands, whereas in vitro digestibility was slightly higher in the short stands. In the same year, tiller density and length of full-grown leaves increased substantially in both stands from May to September. At the same time, sheep preference shifted from tall to short stands, which suggests an interplay between intake rate and digestibility in the sheep selectivity.Seven years after establishment of the grazing trial, the 10 sheep ha^-1 transect still showed a smooth relief typical of the starting point of the other transects. These transects developed a more hummocky topography, with the highest spatial diversity occurring on the 1.5 sheep ha^-1 transect. Marsh elevations were on average up to 3 cm lower in the short than in the tall stands, which indicates that the somewhat lower-elevated patches were grazed more intensively than the higher-elevated patches.In most cases, micropatterns changed from one year to the other, probably due to weather fluctuations. The incidence of tall stands was influenced by the rainfall balance. If the incidences of both the short and the tall stands were around 50%, however, the micropatterns showed a clear correlation with the marsh elevation. The rainfall balance seemed therefore a decisive factor for a possible correspondence between micropatterns in two consecutive years. Elevation differences were so subtle that greater than average sedimentation during a winter season could change the elevation pattern. Hence both rainfall balance and winter sedimentation counteracted the stability of the micropatterns. During our three-year study period, micropatterns were only stable in one out of six possible paired comparisons. This low micropattern stability contrasts with other studies in inland environments, which shows that in more dynamic environments, abiotic processes are likely to overrule summer grazing in determining vegetation patterns.     

Assimilation of gaseous ammonia and the transport of its products in barley and spinach leaves

The interactions between the assimilation and transport of nitrogenand carbon were investigated in barley and spinach leaves. Bothplants were fumigated with NH₃ (1 mg m^–3 and the contentof amino acids, sucrose and carbon intermediates of amino acidmetabolism were analysed in the leaves, apoplast and phloemsap. The following changes took place in the C- and N-metabolismof barley leaves during 5 h of fumigation with NH₃ (a) The contentsof amino acids, especially glutamine, largely increased andthe contents of sucrose, 2-oxoglutarate, phosphoenolpyruvate,and glycerate-3-phosphate declined. (b) A decrease in the phophoenolpyruvatecontent was accompanied by an increased activity of phosphoenolpyruvatecarboxylase. (c) The altered cytosolic concentrations of aminoacids and sucrose during NH₃ fumigation correlated with similarchanges in the apoplast and phloem sap. The altered percentageof each amino acid relative to the total amino acid concentrationin the cytosol, caused by NH₃ fumigation, is reflected in theapoplast and the phloem sap. The results indicate that the concentrations of amino acids in the cytosol determine their concentrationsin the phloem. Key words: Amino acids, ammonia fumigation, barley leaves, C: N partitioning, phosphoenolpyruvate carboxylase, phloem sap, spinach leaves