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1.
The rat and rabbit transport IgA from blood to bile by a highly efficient transcellular pathway mediated by secretory component (SC). Other mammals do not express SC on liver hepatocytes, but they do transport a small amount of IgA to bile. In the first part of this study, human polymeric IgA was radiolabeled and depleted of SC binding activity by successive affinity adsorption. Transport of this preparation intact to rat bile was 4%, but was reduced to 2% when 50 mg unlabeled asialoglycoprotein was preadministered. The 2% decline corresponds to the percent of asialo-orosomucoid diverted to bile from the lysosomal pathway. In guinea-pigs, missorting of asialo-orosomucoid intact to bile was 10% of the injected dose. Transport of normal human IgA to bile was 1-2%, even though guinea-pigs do not express SC in the liver. Excess unlabeled asialofetuin reduced the transport of asialo-orosomucoid by 10-fold and IgA by 6-fold. This demonstrates that the asialoglycoprotein receptor can mediate transport of IgA to bile in small amounts, but that this transport may be only a biological artifact resulting from limited fidelity of intracellular protein sorting. 相似文献
2.
Halasz Norbert; Nowycky Martha C.; Shepherd Gordon M.; Hofelt Tomas 《Chemical senses》1985,10(2):203-218
aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons. 相似文献
3.
Martha Macintyre 《The Australian journal of anthropology》2012,23(1):121-122
4.
5.
Martha L. Bohórquez Alonso Jorge Martínez Cotrina David Aguilar Pardo Enrique Font Miguel Molina-Borja 《Journal of Ethology》2010,28(2):305-311
Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the
predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to
both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during
transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded.
In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences
in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found
no significant differences between males and females in flight-initiation distances and height above the substratum when they
were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator
remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential
predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social
function. 相似文献
6.
Brett F BuSha Martha H Stella Harold L Manning J C Leiter 《Journal of applied physiology》2002,93(3):903-910
Imperceptible levels of proportional assist ventilation applied throughout inspiration reduced inspiratory time (TI) in awake humans. More recently, the reduction in TI was associated with flow assist, but flow assist also reaches a maximum value early during inspiration. To test the separate effects of flow assist and timing of assist, we applied a pseudorandom binary sequence of flow-assisted breaths during early, late, or throughout inspiration in eight normal subjects. We hypothesized that imperceptible flow assist would shorten TI most effectively when applied during early inspiration. Tidal volume, integrated respiratory muscle pressure per breath, TI, and TE were recorded. All stimuli (early, late, or flow assist applied throughout inspiration) resulted in a significant increase in inspiratory flow; however, only when the flow assist was applied during early inspiration was there a significant reduction in TI and the integrated respiratory muscle pressure per breath. These results provide further evidence that vagal feedback modulates breathing on a breath-by-breath basis in conscious humans within a physiological range of breath sizes. 相似文献
7.
Twenty-four-hour variations in activity,core temperature,metabolic rate,and respiratory quotient in captive chinese pangolins 总被引:1,自引:0,他引:1
Martha E. Heath 《Zoo biology》1987,6(1):1-10
The circadian rhythms in activity, core temperature (Tc), O2 consumption, CO2 production, and respiratory quotient (RQ) were monitored in four captive Chinese pangolins (Manis pentadactyla). The pangolins were strictly nocturnal, never emerging from their nest before 1600 h, and their intermittent activity continued no later than 0230. As is usual in nocturnal mammals, the highest values observed in Tc, O2 consumption, and CO2 production occurred during the night; the lowest values occurred during the day. The magnitude of the variation in Tc, O2 consumption, CO2 production, and RQ averaged 1.2°C, 1.3 ml O2 kg?1 min?1, 1.2 ml CO2 kg?1 min?1, and 0.24, respectively. The circadian pattern in RQ was independent of activity, Tc, and the metabolic parameters and was of a different character than the patterns exhibited in the other variables. RQ remained constant at either a high or low level for long periods (8–10 h) and then increased or decreased relatively rapidly (1–2h) to the other level as in a square wave, whereas the rhythms in the other variables are similar to sine waves. The sharp increase in RQ was followed by a slow decline in Tc, and the sharp decline in RQ was followed by a slow increase in Tc. 相似文献
8.
Ferredoxin-NADP reductase from Euglena gracilis Klebs var. Bacillaris Cori purified to apparent homogeneity, yields a typical 36 kDa and an unusual 15 kDa polypeptide on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, exhibits a typical flavoprotein spectrum, contains FAD, and catalyzes NADPH-dependent iodonitrotetrazolium-violet diaphorase, NADPH-specific ferredoxin-dependent cytochrome-c-550 reductase and NADPH-NAD transhydrogenase activities. Rabbit antibody to the purified FNR blocks these activities specifically and also blocks the iodonitrotetrazolium-violet diaphorase activity of Euglena chloroplasts completely. The low iodonitrotetrazolium-violet diaphorase activity in the plastidless mutant, W10BSmL, is mitochondrial and is not specifically blocked by the ferredoxin-NADP reductase antibody. Dark-grown non-dividing (resting) wild-type Euglena cells show a 4-fold increase in ferredoxin-NADP reductase activity during greening at 970 lx. Half of the low ferredoxin-NADP reductase activity in dark-grown cells is initially soluble, but by the end of chloroplast development nearly all of the enzyme is membrane-bound. The binding of ferredoxin-NADP reductase on exposure to light correlates with the extent of thylakoid membrane formation. Immunoblots of wild-type extracts during greening indicate that the 15 kDa polypeptide increases in the same manner as the extent of reductase binding to thylakoid membranes. 相似文献
9.
Dominique Robertson Elizabeth D. Earle Martha A. Mutschler 《Plant Cell, Tissue and Organ Culture》1988,14(1):15-24
Factors affecting the division of cells derived from leaf and cotyledon protoplasts from Brassica oleracea L. var. italica (Green Comet hybrid broccoli) were examined to optimize conditions for plant regeneration and to determine whether there was a genetic basis for improved regeneration from protoplasts derived from plants previously regenerated from tissue cultures [15]. When leaf protoplasts from different plants grown from hybrid seed were isolated and cultured simultaneously, division efficiencies of 1–95% were obtained. Cells from some plants showed high division efficiencies in consecutive experiments while cells from other plants had consistently low division rates. More plants from hybrid seed gave high division efficiencies when cotyledon protoplasts were used. However, cotyledon or leaf protoplasts from selfed progeny of regenerated plants produced more vigorous calli and more shoots than protoplasts from hybrid seed. These results suggest that there may be a genetic component to the increased totipotency of Brassica oleracea protoplasts. 相似文献
10.
Walter Stöcker Uta Raeder Martha M. C. Bijlholt Trijntje Wichertjes Ernst F. J. van Bruggen Jürgen Markl 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(3):271-289
Summary Two-hexameric (2×6) hemocyanins from the brachyuran crabsCancer pagurus andCallinectes sapidus, the freshwater crayfishAstacus leptodactylus and the lobsterHomarus americanus were isolated and dissociated into native subunits.The subunits of each hemocyanin were analyzed by electrophoresis and immunology. Three immunologically distinct subunit types, which were termed, and, could be identified in each case. They were isolated preparatively, and interspecifically correlated. Subunit is subdivided into several electrophoretically distinct isoforms which are immunologically closely related (Astacus) or identical (other species). InAstacus andCancer one of these isoforms was shown to dimerize and to act as inter-hexamer bridge. It represents a fourth subunit type termed. A fifth, diffuse component, which in PAGE migrated at the position of a dimer, was identified in the crossed immunoelectrophoretic patterns as denatured hemocyanin.A common feature of the four hemocyanins is the presence of 4 copies of and 8 copies of/ within the 2×6 particles. The: ratio is 4:4 in the two Astacidea and 6:2 in the two Brachyura. exists in 2 copies inAstacus andCancer which means that a single dimer- is present in a two-hexamer. This leaves 2 monomeric copies inAstacus and 4 inCancer.Every subunit from the four species except ofAstacus
- was capable to form hexamers in reassembly experiments. If subunit combinations were tested, hetero-hexamers were formed preferentially. Two-hexamers were reconstituted only in the presence of all subunit types and the native subunit stoichiometry was required to obtain twohexamers in considerable yields. Factors limiting 2×6 reassembly are discussed.Authentic 2×6 molecules ofAstacus, Homarus andCancer hemocyanin were immunolabeled with subunit-specific antibody fragments (Fab) or IgG molecules, and the resulting immuno complexes were studied in the electron microscope. A topological model of the quaternary structure of decapod 2×6 hemocyanins is derived, showing the position of each copy of the four subunit types. In this model, the inter-hexamer bridge- is surrounded by two and two subunits forming the central core of the dodecamer. Two additional and two additional subunits form the periphery together with one subunit occupying the peripheral short edges of each hexameric half structure. The model is discussed with respect to the current literature.Abbreviations
PAGE
polyacrylamide gel electrophoresis
-
SDS
sodium dodecyl sulfate
This paper is decicated to Professor Dr. Bernt LinzenPreliminary accounts of this work have been presented in the proceedings of a symposium at Tutzing 1985. Linzen B (ed) (1986) Invertebrate oxygen carriers. Springer, Berlin Heidelberg New York. This also includes: Stöcker et al. 1986; Markl et al. 1986) and in a review article (Markl 1986) 相似文献