Spatial distribution of seston in an artificially mixed system

Seston size distribution was determined with a Coulter Counter to investigate seston interaction and its effects on phytoplankton production. Spatial distribution patterns of the non-productive component of the seston were as complex as those commonly associated with algae. Seston might interact influencing production by changes in optical depth, abrasive actions and nutrient adsorption.     

Site of production of an oviposition-deterring pheromone component in Rhagoletis pomonella flies

Using behavioural and electrophysiological assay techniques, we identified the posterior half of the midgut as being a principal site of production of a major component of the oviposition-deterring, fruit-marking pheromone of female Rhagoletis pomonella flies. Following secretion into, and accumulation in, the gut lumen, this component is released, together with other gut contents, in the marking trail deposited during dragging of the ovipositor on the fruit surface after egg-laying, as well as in the faeces. Other components of the pheromone may be produced elsewhere.     

Nitrogenase from Rhodospirillum rubrum Relation between ‘switch-off’ effect and the membrane component. Hydrogen production and acetylene reduction with different nitrogenase component ratios

Nitrogenase activity of ‘membrane-free’ extracts, produced from nitrogenstarved Rhodospirillum rubrum to which 4 mM NH⁺₄ had been added is only about 10% of the activity in the control. The activity could be restored to 80% by including the membrane component, earlier found to activate R. rubrum nitrogenase, in the reaction mixture. The relation between this ‘switch-off/switch-on’ effect and the function of the membrane component is discussed.Hydrogen production catalyzed by R. rubrum nitrogenase is also dependent on activation by the membrane component. Hydrogen production is inhibited by acetylene but the degree of inhibition is dependent on the nitrogenase component ratio. The strongest inhibition is achieved at low MoFe protein/Fe protein ratios. The $\text{ATP}\text{2 e}{}^{\mathrm{?}}$ values are 4–5 at the component ratios giving the highest activity and increase at high MoFe protein/Fe protein ratios. CO inhibits acetylene reduction but has no effect on the hydrogen production.     

D-Amino-acid-stimulated ethylene production in seed tissues

Ethylene production by axial and cotyledonary tissues excised from Xanthium pennsylvanicum Wallr. seeds was markedly (up to 5-fold) stimulated by the D-isomers of phenylalanine, valine, leucine, threonine, methionine and eithionine while the L-isomers caused no such effect. Responsiveness of these seed tissues to D-methionine appeared soon after the beginning of imbibition, reached a maximum after 6–12 and 12–24 h for the axial and cotyledonary tissues, respectively, and then decreased sharply. D-Phenylalanine and D-methionine also stimulated ethylene production in seed tissues of X. canadense Mill. and in cotyledonary segments from seeds of Helianthus annuus L., Cucurbita moschata Duch. and Vigna radiata (L.) Wilczek. The endogeneous ethylene production and the D-amino-acid-stimulated ethylene production by the seed segments was strongly inhibited by aminoethoxyvinyl glycine, a potent inhibitor of ethylene synthesis from L-methionine.     

Angiostrongylus cantonensis: Development following pulmonary arterial transfers into permissive and nonpermissive hosts

The survival, growth, and egg-laying capacity of young adult Angiostrongylus cantonensis, surgically transferred from intracranial sites into pulmonary arteries, were studied. A variety of experimental animals (rats, guinea pigs, mice, and mastomys) were chosen as donor animals and as recipient hosts (rats, guinea pigs, and rabbits). These species were specifically chosen to span the spectrum of host permissiveness relative to worm development in an attempt to understand the mechanisms which underlie species-dependent resistance. Recipient animals were monitored not only for the development of parasites per se but also for antibody production and histopathologic changes. The results indicated that these procedures were technically feasible, with good worm development following intra-rat transfers, as early as 15 days after initial exposure. Studies were performed to analyze the constraints of development both on initial, i.e., prelung and subsequent i.e., postlung development. When worms were obtained from permissive species such as rat or mastomys, transfer into rats resulted in good growth and development; however, worms which developed initially in exposed mice or guinea pigs developed less well in the rat. Conversely, worms which developed initially in permissive host such as the rat, when transferred into a variety of less permissive hosts such as the guinea pig and rabbit, apparently did not survive and caused significant morbidity and mortality within the nonpermissive host. Histopathologic evaluation revealed a strong eosinophilic perivascular and peribronchiolar infiltration as well as granulomatous reactions surrounding the worms in the lungs of recipient guinea pigs and rabbits, changes not observed in the lungs of permissive rat recipients. As reaginic antibody responses were also more prominent in nonpermissive than in permissive animals, it is possible that IgE responses may be more directly related to the phenomenon of morbidity and/or permissiveness than are other aspects of immune response. In support of this contention was the finding of nearly equivalent hemagglutinating antibody production between permissive rats and nonpermissive guinea pigs and rabbits.     

Large-scale rotating filter perfusion system for high-density growth of mammalian suspension cultures

Summary A system has been developed for growth and maintenance of mammalian cells in suspension culture at high density. In principle, the maintenance of constant levels of required nutrients coupled with the removal of toxic cell byproducts can support much higher suspension cell densities than may be obtained in conventional spinners. The system consisted of 4- or 40-liter reaction vessels equipped with a vertically supported rotating cylindrical filter. Agitation was provided by the magnetically driven, rotating filter. Fresh medium was supplied at a rate of 10 to 20 ml/h per 10⁹ cells and the expended medium free of cells was withdrawn through the rotating filter. Both pH and dissolved O₂ and CO₂ were monitored and regulated. Walker 256 carcinosarcoma cells have been grown in these reactors to densities 10-to 30-fold greater than that obtained in Bellco spinners. In addition to high cell densities, the yield of cells per liter of medium used was 2- to 3-fold that obtained in the conventional systems. Both 4-and 40-liter versions of this reactor have been operated without the use of antibiotics. The 40-liter reactor also has been modified for chemostat operation. In a single run, for example, the Walker cell density was maintained between 6 and 10×10⁶ cells/ml with a total yield of 8.7×10¹¹ cells from 360 liters of medium.     

Sertoli cells of adult rats “in vitro”

Summary A cell line obtained from isolated seminiferous tubules of adult rat testis has been studied in vitro over a period of 35 days.Light and electron microscopic studies performed from hour 2 to the end of culture have shown the presence of a monomorphic cell population. After 5–6 days of culture the cells formed a monolayer. The cytoplasm of the cells contained numerous lipid bodies and produced numerous projections. The nucleus showed several indentations and one or more nucleoli. From the 9th to the 15th day of culture the cells developed a large amount of endoplasmic reticulum, Golgi apparatus and aggregates of electron dense granules. From the 20th to 40th day the cell cultures progressively degenerated.Immunochemical analysis of the culture medium revealed the presence of estradiol-17, which reached its maximum production rate from the 8th day to the 18th day of culture. Corresponding to cell involution estradiol concentration underwent a rapid decrease.On the basis of morphological and biochemical data the cells could be considered Sertoli cells.This work was supported by Grants n. 74.00155.04 and n. 75.01224.04 from the Consiglio Nazionale delle Ricerche (C.N.R.), Rome, Italy, and by Istituto di Ricerca F. Angelini, Rome, ItalyPart of this work was presented at the 10th Italian Congress of Electron Microscopy. Ostuni 1–4 October 1975The excellent technical assistance of Miss Laura Vassallo, Daniela Venturini and Mr. Massimo Rosati and Mario Termine is deeply appreciated     

Gynandromorphs of the pycnogonid Anoplodactylus portus

A large sample of the pycriogonid Anoplodactylus portus , collected from the Pacific side of the Panama Canal Zone, contains a high percentage of gynandromorphs. The literature on aquatic arthropod gynandromorphs is outlined. The nature and variations of the sexual mosaic population are described and discussed. The several morphological differences between normal and mosaic members of the population are illustrated, and the possible origin of these gynandromorphs is discussed.     

巴山松天然林生物量和生产力的研究

 经测定分析陕西南部28—37年生巴山松天然林的生物量和净初级生产量,结果表明,林分乔木层生物量为81.28t／ha,草本下木生物量为1.45t／ha,林分凋落物量为11.16t／ha;乔木层净初级生产量为6.94t／ha·yr,约45%分配到树叶。巴山松林的消光系数平均为0.33。在地上部生产结构方面,枝重主要集中在树冠中、下部,叶龄愈大,叶重在树冠下部的比例愈高。巴山松林木的根系总长度约99.4km／ha,其中细根占58%。