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Odd Terje Sandlund Hilmar J. Malmquist Bror Jonsson Skúli Skúlason Sigurdur S. Snorrason Pétur M. Jónasson Rolf Gydemo Torfinn Lindem 《Environmental Biology of Fishes》1988,23(3):183-195
Synopsis Population densities of age-0 arctic chaff in the surf zone averaged 1.83 and 4.70 fish m-2 in August 1984 and June 1985, respectively. Length variation of the littoral fish was low in early summer, increasing in
late summer and autumn. Newly emerged charr, ∼ 20 mm long, appeared in the stony shallow water zone during both May and June.
From length variation and variation in mouth position of the young charr, it is concluded that at least two of the four chaff
morphs in the lake are present in the surf zone during spring and summer. In August, some of the larger age-0 charr had moved
out from the surf zone, into the pelagic and the deeper epibenthic waters. The food of young littoral charr was dominated
by large chironomid larvae (instar 3 and 4) and pupae
Contribution from the Thingvallavatn project 相似文献
64.
Peptidase activity capable of inactivating luteinizing hormone (LHRH) may have a physiological role in partially determining hypothalamic LHRH levels as well as LHRH levels at the gonadotrope. In our previous work ( Lapp and O' Conner , 1984, companion paper), use of the synthetic substrate leucine-p-nitroanilide (Leu-p-NA) to assay LHRH-degradative activity was validated by several methods. The current studies were conducted in order to monitor peptidase activity in the hypothalamus and pituitary throughout the rat 4-day estrous cycle. Activity in both tissues was significantly decreased during proestrus and diestrus I. It seems possible that the proestrous reduction in peptidase activity represents a permissive period necessary for the induction of the LHRH and LH surges. The decreased degradative activity in the pituitary on diestrus I may be involved in inducing the pituitary LHRH receptors which are reportedly synthesized prior to proestrus. The peptidase exhibits positive cooperativity with Leu-p-NA, and the degree of this cooperativity also fluctuates during the estrous cycle. Estradiol and progesterone given alone or in combination to prepubertal castrate animals increased the activity of the hypothalamic peptidase in vitro. The degree of positive cooperativity with which the enzyme functioned was also apparently altered by these gonadal steroids. 相似文献
65.
The tissues of female Ascaris suum were assayed for alpha,apha'-glucoside 1-D-glucohydrolase (trehalase) activity. A soluble from of the enzyme was isolated from muscle tissue and purified approximately 37-fold. The enzyme was specific for trehalose as substrate. The pH optimum for enzymatic activity was found to be 6.0, and the apparent Km for trehalose was estimated to be 2.1 x 10-4 M. The product of the reaction was identified as D-glucose by chemical, chromatographic and enzymatic methods. 相似文献
66.
Time-pulse generator for flow-volume curves 总被引:3,自引:0,他引:3
67.
Olav Hilmar Iversen 《Virchows Archiv. B, Cell pathology including molecular pathology》1978,28(1):93-95
The epidermal cell kinetics in nude mice is investigated by determining the mitotic rate and the mitotic count, the H3Tdr labelling index, and the proportion of basal cells in the different cell cycle phases by flow cytometry. The mitotic duration was calculated. The parameter values of the epidermal cell kinetics of the nude mouse are largely similar to those of the hairless mouse. 相似文献
68.
Soluble factors and the immune response: in vitro studies of the immunosuppression induced by the graft-versus-host reaction 总被引:3,自引:0,他引:3
In vitro experiments were carried out to investigate the cause(s) of the immunosuppression induced by the graft-versus-host (GVH) reaction in F1 hybrid mice injected with parental strain lymphoid cells. A modified Marbrook culture chamber, made up of two cell compartments separated by a cell impermeable membrane, was used in these studies. Spleen cells from either normal animals (NSC) or from animals experiencing a GVH reaction (GVH-SC) were cultured with sheep red blood cells (SRBC) and the direct plaque-forming cell (PFC) response to SRBC was measured. It was found that normal thymus, lymph node and spleen cells, separated from the GVH-SC by a cell impermeable membrane, restored partially or totally the immune response of the suppressed cells, while bone marrow cells did not. It was also found that GVH-SC inhibited the PFC response to SRBC of NSC when mixed in culture at a ratio of 1:5. Conversely the inhibitory effect of GVH-SC on the immune response of NSC was abrogated when the two cell populations were separated by a cell impermeable membrane. These observations demonstrate that GVH-induced immunosuppression is caused, at least in part, by the deficiency of a T-cell derived factor which is a necessary component of the normal immune response. It is suggested that the suppressive effect of GVH-SC on the immune response of NSC is mediated by a non-T cell which regulates the release and/or production of the T-cell derived factor. 相似文献
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70.
Hoffrogge R Beyer S Hübner R Mikkat S Mix E Scharf C Schmitz U Pauleweit S Berth M Zubrzycki IZ Christoph H Pahnke J Wolkenhauer O Uhrmacher A Völker U Rolfs A 《Proteomics》2007,7(1):33-46
Targeted differentiation of neural progenitor cells (NPCs) is a challenge for treatment of neurodegenerative diseases by cell replacement therapy and cell signalling manipulation. Here, we applied a proteome profiling approach to the rat striatal progenitor model cell line ST14A in order to elucidate cellular differentiation processes. Native cells and cells transfected with the glial cell line-derived neurotrophic factor (GDNF) gene were investigated at the proliferative state and at seven time points up to 72 h after induction of differentiation. 2-DE combined with MALDI-MS was used to create a reference 2-DE-map of 652 spots of which 164 were identified and assigned to 155 unique proteins. For identification of protein expression changes during cell differentiation, spot patterns of triplicate gels were matched to the 2-DE-map. Besides proteins that display expression changes in native cells, we also noted 43 protein-spots that were differentially regulated by GDNF overexpression in more than four time points of the experiment. The expression patterns of putative differentiation markers such as annexin 5 (ANXA5), glucosidase II beta subunit (GLU2B), phosphatidylethanolamine-binding protein 1 (PEBP1), myosin regulatory light chain 2-A (MLRA), NASCENT polypeptide-associated complex alpha (NACA), elongation factor 2 (EF2), peroxiredoxin-1 (PRDX1) and proliferating cell nuclear antigen (PCNA) were verified by Western blotting. The results reflect the large rearrangements of the proteome during the differentiation process of NPCs and their strong modification by neurotrophic factors like GDNF. 相似文献