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E Huebner

Publications and source records attributed to E Huebner.

6 recordsLinked to original sources
PubMed1992

Spatial and temporal transcellular current patterns during oogenesis.

We have used the two-dimensional vibrating probe to examine spatial and temporal patterns in the transcellular current flow around telotrophic ovarioles of the insect Rhodnius prolixus. We demonstrate a dynamic pattern of currents which correlates with various stages of vitellogenesis. Asymmetries exist in the radial current pattern around intact ovarioles, particularly around the terminal follicle, and may correlate with early developmental axes. The extra-cellular current pattern is largely reflected by a similar, though weaker pattern of currents over the germ cell membranes, indicating that both germ cell and somatic cell membranes are involved in current generation. Current enters previtellogenic oocytes and leaves oocytes entering vitellogenesis. We speculate that current reversal and loss of trophic cord contact may represent an electrophysiological feedback control mechanism during oogenesis.

Animals↗
PubMed1979

Studies on a morphologically distinct colchicine-resistance variant of Entamoeba sp.

Colchicine has a temperature-dependent cytotoxic effect on Entamoeba sp. (Laredo isolate) that is most apparent when the drug is applied during the initiation of cultures at a concentration of 7.5 mM or higher. Continued transfer of cultures in medium containing progressively increasing concentrations of colchicine has resulted in a variant that grows prolifically in the presence of colchicine (7.5 mM) with a generation time comparable to that of the parent stock, Comparison of a number of parameters of the 2 variants revealed that colchicine resistance was accompanied by a change in cell shape, a reduced membrane permeability, which could partially be overcome by the addition of dimethyl sulfoxide (DMSO), and a reduced tolerance to osmotic stress. However, the parent strain and resistant variant were equally susceptible to cycloheximide and puromycin suggesting that the acquired colchicine resistance may not be explained on the basis of an entirely unspecific generalized reduced ability for drug uptake. Colchicine resistance and altered structure were found to be stable over a long period of time. The possible interdependence of these 2 parameters and their relation to cell motility in Entamoeba sp. are discussed.

Animals↗
PubMed1975

Structural and functional dynamics of oogenesis in Glossina austeni: general features, previtellogenesis and nurse cells.

Glossina austeni oogenesis throughout its nine-day pregnancy cycle is described with the focus on previtellogenic stages. The ultrastructural details of the oocyte-nurse cell relationship and cyst formation is presented. The oocyte develops in a syncytial association with 15 nurse cells with the entire unit surrounded by a follicular epithelium. The nurse cells have large elaborate nucleoli. Evidence of nuclear emissions and the presence of an unusual cytoplasmic membrane association were found. A variety of nuclear inclusions are seen in the oocyte. Glycogen, lipid, ribosomes and membrane organelles accumulate in the oocyte during previtellogenesis.

Animals↗
PubMed1975

Structural and functional dynamics of oogenesis in Glossina austeni: vitellogenesis with special reference to the follicular epithelium.

Morphological changes of the oocyte, follicle cells and nurse cells of the ovaries of the viviparous fly Glossina austeni during vitellogenesis and postvitellogenesis are outlined. During vitellogenesis, material is pinocytosed and incorporated into yolk spheres by subsequent fusions. Various lines of evidence are presented that indicate much of this material is derived from the follicular epithelium. The ultrastructure of the follicular cells throughout the 9 day cycle and their role in protein synthesis is presented. Subsequent to vitellogenesis, the follicle cells synthesize the secondary envelopes.

Animals↗