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1.
2.
Most of the previous studies on the effects of iron deficiency on skeletal muscle respiratory capacity and work performance have been investigated in severe or moderate iron-deficiency anemia. We report here that even in mild iron deficiency where the hemoglobin concentration was 10 g/dl and the iron stores in livers and spleen were not completely depleted, a marked reduction in succinate dehydrogenase was observed in skeletal muscles but not in heart. Similarly, cytochrome oxidase activities were reduced. Although no significant change in glycerophosphate dehydrogenase was detected in the iron-deficient rats, exposure to cold in this group greatly reduced this enzyme activity. As cold acclimatization accelerates marrow erythropoiesis (20) which in turn, demands more iron, it seems that in the iron-insufficient state, this iron demand for marrow activity may persist at the expense of the tissue iron pool, resulting in a marked reduction in glycerophosphate dehydrogenase activities. Since succinate dehydrogenase plays a significant role in the impairment of mitochondrial function and early fatigue of iron-deficient muscle (11), the present study shows that even in mild iron deficiency, some loss of muscle functions could result as succinate dehydrogenase activities were greatly reduced. 相似文献
3.
X. M. Zhou P. H.-S. Jen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(4):389-398
This study examines the role of neural inhibition in auditory spatial selectivity of inferior collicular neurons of the big
brown bat, Eptesicus fuscus, using a two-tone inhibition paradigm. Two-tone inhibition decreases auditory spatial response areas but increases the slopes
of directional sensitivity curves of inferior collicular neurons. Inferior collicular neurons have either directionally-selective
or hemifield directional sensitivity curves. A directionally-selective curve always has a peak which is at least 50% larger
than the minimum. A hemifield directional sensitivity curve rises from an ipsilateral angle by more than 50% and either reaches
a plateau or declines by less than 50% over a range of contralateral angles. Two-tone inhibition does not change directionally-selective
curves but changes most hemifield directional sensitivity curves into directionally-selective curves. Auditory spatial selectivity
determined both with and without two-tone inhibition increases with increasing best-excitatory frequency. Sharpening of auditory
spatial selectivity by two-tone inhibition is larger for neurons with smaller differences between excitatory and inhibitory
best frequencies. The effect of two-tone inhibition on auditory spatial selectivity increases with increasing inhibitory tone
intensity but decreases with increasing intertone interval. The implications of these findings in bat echolocation are discussed.
Accepted: 18 January 2000 相似文献
4.
Phospholipid-Sensitive Ca2+ -Dependent Protein Kinase Preferentially Phosphorylates Serine-115 of Bovine Myelin Basic Protein 总被引:1,自引:0,他引:1
R. Scott Turner C.-H. Jen Chou† Gonzalo J. Mazzei Philip Dembure ‡ J. F. Kuo 《Journal of neurochemistry》1984,43(5):1257-1264
Phospholipid-sensitive Ca2+ -dependent protein kinase (PL-Ca-PK) and cyclic AMP-dependent protein kinase (A-PK) both preferentially phosphorylated serine residues of bovine myelin basic protein (MBP). Tryptic peptide maps of MBP phosphorylated by PL-Ca-PK or A-PK, however, revealed different phosphopeptides, suggesting a difference in the intramolecular substrate specificity for the two enzymes. Serine-115 of MBP, in the sequence (-Arg-Phe-Ser(115)-Trp-), was found to be a preferred and probably major phosphorylation site for PL-Ca-PK. Because serine-115 of bovine MBP corresponds to serine-113 of rabbit MBP, an in vivo phosphorylation site reported by Martenson et al. (1983), and PL-Ca-PK is present at a very high level in brain and myelin, it is suggested that the enzyme may be responsible for the in vivo phosphorylation of this and other sites in MBP. 相似文献
5.
Rolf Kleine Dr. Jenö Ponyi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1967,55(1):39-50
Zusammenfassung Es werden die Exopeptidase- und Dipeptidaseaktivitäten des Hepatopankreas und Magensaftes von Astacus astacus (L.) und Cambarus affinis (Say) quantitativ bestimmt (Durchschnittswerte von ca. 90 Tieren). Die besonders im Magensaft vorkommende Carboxypeptidase hydrolysiert Carbobenzoxyglycyl-l- phenylalanin und Carbobenzoxy-l-glutamyl-l-tyrosin ungefähr gleichstark (pH-Optimum 7,6 bzw. 7,0). Im Vergleich zur kristallisierten Pankreascarboxypeptidase wird das Magensaftenzym stärker durch Hydrozimtsäure als durch o-Phenanthrolin gehemmt. SH-Gruppen sind für die Wirkung nicht nötig. Die Leucinamid- und Leucin--naphthylamid-Hydrolyse ist nicht auf die klassische Leucinaminopeptidase, sondern auf eine metallionenunabhängige und puromycinempfindliche Arylamidase-ähnliche Wirkung (pH-Optimum 7,7–8,0) zurückzuführen. Amidase- und Dipeptidase (Substrat: Glycyl-l-lencin)-Wirkung sind besonders im Hepatopankreas aktiv.
Occurrence and properties of proteolytic enzymes in the gastric juice and hepatopancreas of the crayfishes Astacus astacus (L.) and cambarus affinis (Say)I. Exopeptidases
Summary The exopeptidase and dipeptidase activities of the hepatopanereas and gastric juice of Astacus astacus (L.) and Cambarus affinis (Say) were determined (mean values from approximately 90 exemplares). The carboxypeptidase which was highly active in the gastric juice hydrolyzes carbobenzoxyglycyl-l-phenylalanine and carbobenzoxy-l-glutamyl-l-tyrosine at about the same rate (pH-optimum at 7,6 and 7,0 respectively). Compared with the crystalline pancreas carboxypeptidase the gastric juice enzyme was stronger inhibited by hydrocinnamic acid than by o-phenanthroline. Sulfhydryl groups are not essential for the enzyme action. The observed hydrolysis of leucine amide and leucine--naphthyl amide could not be attributed to the classic leucine aminopeptidase but to an arylamidase like action (pH Optimum 7,7 to 8,0) which was independent of metal ions and puromycin-sensitive. The amidase and dipeptidase (substrate: glycyl-l-leucine) are mainly localized in hepatopanereas.相似文献
6.
Heather J. Lawlor Jen A. McComb Michael A. Borowitzka 《Journal of applied phycology》1989,1(2):105-112
The effects of light quality and irradiance, and supply of organic carbon and vitamins on the growth of two forms of Ecklonia radiata in tissue culture were examined. A callus of unpigmented cells developed over the cut surface of newly excised explants of
stipe. This growth was best in the dark but stopped after 10 weeks. Pigmented, mainly filamentous clumps of cells developed
from explants after several weeks in culture. These required light for growth, with growth being enhanced by increasing photon
flux density up to 30 μmol photon m-2 s-1, with the active spectral component being red light (> 600 nm). The addition to the medium of a range of organic carbon sources
or vitamins did not stimulate growth of either culture type in the dark.
author for correspondence 相似文献
7.
G A Conder L W Jen K S Marbury S S Johnson P M Guimond E M Thomas B L Lee 《The Journal of parasitology》1990,76(2):168-170
Currently, no in vivo laboratory model is available for evaluating anthelmintics against the important ruminant helminth Haemonchus contortus. This report outlines a novel anthelmintic assay utilizing immunosuppressed (0.02% hydrocortisone in feed) jirds, Meriones unguiculatus, infected with H. contortus. Immunosuppressed jirds were inoculated with approximately 1,000 exsheathed infective larvae of H. contortus, treated per os on day 10 postinoculation (PI), and necropsied on day 13 PI. Each stomach was removed, opened longitudinally, incubated in distilled water at 37 C for 5 hr, fixed in formaldehyde solution, and stored for subsequent examination. Stomach contents were examined using a stereomicroscope (15-45x). A variety of standard anthelmintics has been evaluated in the model; modern broad-spectrum ruminant anthelmintics (benzimidazoles, febantel, ivermectin, levamisole hydrochloride, and milbemycin D) are active uniformly and in most cases at doses (mg/kg) comparable to those required for efficacy against H. contortus in ruminants. This model provides an important new tool to assess preliminarily the activity of experimental drugs against H. contortus in vivo prior to studies in ruminants and also may provide a useful tool for studying host-parasite interactions for H. contortus. 相似文献
8.
Review: Hydrogels for cell immobilization 总被引:6,自引:0,他引:6
Hydrogels are being investigated for mammalian cell immobilization. Their material properties can be engineered for biocompatibility, selective permeability, mechanical and chemical stability, and other requirements as specified by the application including uniform cell distribution and a given membrane thickness or mechanical strength. These aqueous gels are attractive for analytical and tissue engineering applications and can be used with immobilization in therapies for various diseases as well as to generate bioartificial organs. Recent advances have broadened the use of hydrogel cell immobilization in biomedical fields. To provide an overview of available technology, this review surveys the current developments in immobilization of mammalian cells in hydrogels. Discussions cover hydrogel requirements for use in adhesion, matrix entrapment, and microencapsulation, the respective processing methods, as well as current applications. (c) 1996 John Wiley & Sons, Inc. 相似文献
9.
Jan Jeník 《Folia Geobotanica》1994,29(2):291-306
Bulkiness, longevity and solidity of the body in woody plants enable the successive development of accessory shoots and adventitious roots in (1) both proximal and distal positions on organs, (2) both the above-ground and below-ground space, (3) both the aerial and soil environments. In monocotyledons, woody rhizomes play an essential role in the basic growth habit and architectural models. In dicotyledonous and a few gymnospermous trees, attached and successively disconnected ramets play a multilateral role in the pertinent life strategies. The majority of sprouts, coppice shoots and root suckers behave as opportunistic organs (a) serving as means of vegetative reproduction, (b) securing colonization of unoccupied ground, (c) increasing competitive power of the species within the community, (d) increasing survival rate of the stressed/disturbed genet in marginal habitats, (e) forming replacement for ageing or damaged organs, and (f) enabling reiteration of the genet's entire architectural model. 相似文献
10.
Abstract. A method is described for producing outgrowths of small nephron segments (average 24 cells) in culture. The method was used to estimate an overall colony-forming efficiency of 4.6% for cells constituting the segments. Efficiency was found to be lower for thick segments (1%) than for thin segments (6%) from Henle's loop. The latter higher level indicates that precursor cells are concentrated near the middle of the nephron. For comparison, a two-dose irradiation technique was used to calculate a mean number of 5 ± 2 (SE) clonogens per segment producing outgrowths. This tended to be higher than the value of about 1 calculated from the 65% of segments producing outgrowths, as expected if the remaining segments contained no clonogens. 相似文献