The analysis of planktonic rotifer populations: A plea for long-term investigations

Short-term species succession, and long-term community development, of planktonic rotifer populations of the temperate zone and factors influencing species' abundance (ie., physical and chemical limitations, food and exploitative competition, mechanical interference competition, predation, parasitism) are described and discussed. The long-term development of plankton communities in three European lakes is described and the major events are discussed in relation to ecological interactions. Frequently, the shortcomings of our knowledge about population ecology and ecophysiology of rotifers prevent explanations of short-term and, especially, of long-term developments of these plankton organisms. The need for qualitative and quantitative observations in the field and in the laboratory over long periods becomes obvious.     

Automatic bioprocess control. 1. A general concept.

Automation of bioprocesses is presented and discussed. A general concept is applied to laboratory scale reactors as well as to large scale production facilities consisting of many unit operations with a hierarchical and highly modular structure. The implementation of non-dedicated and intelligent analytical subsystems is foreseen. Hard- and software requirements are discussed in view of the functional requirements of both scientific research and production engineering. Some practical experience is reported using several different components in parallel installations.     

Ploidy effect on the radiation reaction of mammalian cells

Summary The variation of X-ray sensitivity was investigated during the cell cycle. The cells were most sensitive during the S phase and less sensitive during the G₂- and G₁ phase. Furthermore, the repair of X-ray damage was investigated in stationary (plateau phase) cells. The cells of both lines were able to repair damage to nearly the same extent.

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Zusammenfassung Die Variation der Strahlensensibilität während des Zellcyclus wurde untersucht. Die Zellen reagierten am sensibelsten in der S-Phase, weniger sensibel in der G₂-und G₁-Phase. Weiterhin wurde die Reparation von Strahlenschäden bei stationären (Plateauphase-)Zellen untersucht. Die Zellen beider Linien sind in etwa gleichem Maße reparationsfähig.

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Supported (I-IV) by the Deutsche Forschungsgemeinschaft (Mi/100, 1-7).     

Diversity in cyclic sesquiterpene production by Gossypium hirsutum

Major sesquiterpene components of oil of Texas Race Stock 810 of Gossypium hirsutum were - and β-selinene. This is the seventh cyclic terpene type found to date in this genus. Both - and β-selinene, along with aromadendrene, were found but only as minor components of extracts of several domestic cultivars of G. hirsutum.     

The vascularization of the neural stalk and the pars nervosa of the hypophysis in the toad,Bufo bufo (L.) (amphibia,anura)

The angioarchitecture of the neural stalk and the encephaloposthypophysial portal system of the hypophysis of the toad, Bufo bufo (L.), was studied using three different methods. The neural stalk is mainly supplied by branches of the arteria infundibularis superficialis which form a widemeshed vascular network. Dorsally this network continues into the plexus of the pars nervosa. The vascularization of the pars nervosa is made up of the encephalo-posthypophysial portal system. This portal system consists of a hypothalamic branch (=portion), a mesencephalic and a mesencephalicbulbar branch (=portion). The hypothalamic branch was found to drain the pars ventralis of the tuber cinereum as well as more dorsal regions of the diencephalon. The mesencephalic-bulbar trunk enters the hypothalamic branch. The resulting common stem of the encephalo-posthypophysial portal vein the curves around the retroinfundibular communicating artery, crosses its ventral side and runs caudally. The secondary capillary plexus of the pars nervosa is characterized by well defined capillary plexus of the pars nervosa is characterized by well defined capillary networks which are located at the periphery of the parenchyma of the pars nervosa, thus forming a rostral, dorsal and ventro-caudal net. The central region of the parenchyma of the pars nervosa is supplied only by main branches of the encephalo-postpophysial portal vein. The venous drainage of the pars nervosa is via the vena hypophysea transversa.     

Pulsation of nuclei in insect oocytes is reversibly inhibited by cytochalasin B

Oocyte nuclei of the dipteran insect Heteropeza pygmaea display swift pulsating movements during in vitro follicle formation in the ovaries. Low doses of cytochalasin B (CB) completely inhibit the nuclear movements within a few minutes and cause the nuclei to assume spherical shapes. If the drug is removed, nuclear pulsation is resumed within 5–10 min. Phalloidin and colchicine do not affect the nuclear movements. Actin is shown by indirect immunofluorescence microscopy to be present in considerable amounts all over the cytoplasm of the oocytes. It is concluded that microfilaments are responsible for pulsation of the oocyte nuclei, whereas microtubules are not involved.     

Formal kinetics of poly-β-hydroxybutyric acid (PHB) production in Alcaligenes eutrophus H 16 and Mycoplana rubra R 14 with respect to the dissolved oxygen tension in ammonium-limited batch cultures

Summary Under chemolithoautotrophic growth conditions with the organism Alcaligenes eutrophus H16 the exponential growth phase is characterized by two different growth rates, each associated with different specific rates of ammonium consumption. On the basis of the analytical determination of Poly--hydroxybutyric acid (PHB), it can be conclusively shown that PHB is synthesized even during the exponential growth phase at a specific rate proportional to the specific growth rates of total biomass. After complete consumption of ammonium, the increase of biomass is exclusively due to PHB synthesis, whereas protein and rest biomass (cell dry weight minus PHB) remain constant. After an extended period of fermentation, the PHB content reaches a saturation value. The transient phase between the growth and the storage phase is very short in comparison to the duration of the whole fermentation. In the case of Alcaligenes eutrophus, strain H 16, high concentrations of dissolved oxygen strongly influence growth as well as PHB synthesis.Abbrevations ^cO₂,L concentration of oxygen in the liquid phase (dissolved oxygen tension: d.o.t) - ^cH₂,L concentration of hydrogen in the liquid phase - ^cCO₂,L concentration of carbon dioxide in the liquid phase - S limiting substrate, concentration of - X total biomass, concentration of; total cell dry weight - P product; PHB, concentration of - R rest biomass: X-P, concentration of - ^rX dX/dt growth rate - ^rP dP/dt rate of PHB synthesis - ^rR dR/dt rate of rest biomass production - ^r0 ^dcO₂,L/dt rate of oxygen consumption - X dX/dt·1/X=r_X·1/X specific growth rate - P dP/dt·1/P=r_P·1/P specific rate of product formation - R dR/dt·1/R=r_R·1/R specific rate of rest biomass formation - r₀/R specific respiration rate     

cell clones and pattern formation: Studies onsevenless,a mutant ofDrosophila melanogaster

Summary sev ^LY3,the only existing allele at thesev locus (1–33,2±0,2), behaves as strongly hypomorph or even as amorph. Ommatidia in asev compound eye have only seven receptor cells, the position of the R7 pattern element being vacant. Various criteria showing that the missing cell is R7 have been verified. These include (i) anatomical characteristics ofsev ommatidia; (ii) behaviour of central R cells insev rdgB double mutants; (iii) medullary projection of central R cell axons; and (iv) mitotic pattern ofsev imaginal discs. The analysis of morphogeneticsev-sev ⁺ mosaics has shown thatsev is expressed autonomously by R7 cells, indicating that thesev phenotype is not due to asev genotype of ommatidial pattern elements other than R7. The study of third instarsev imaginal discs has not brought any direct evidence for death of clustered presumptive R7 cells; however, clonal analysis of the developingsev compound eye has given evidence of developmental parameters comparable to those ofsev ⁺, therefore favouring the hypothesis that R7 cells die insev mutants. On the other hand,sev ⁺ seems to be required for the determination of the R7 cells, since thesev phenotype cannot be uncovered during the last mitoses of heterozygous mutant cells.