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31.
Summary The results reported in this paper substantiate Vilter's (1968) hypothesis that the absence of basophilia of acid mucosubstances after a so-called histochemical methylation with acidified methanol may be due to, among other factors, the lactonisation of carboxyl groups rather than, as is generally held, their esterification. Sections from several fixed tissues of Syrian hamster and mouse were treated at 60 ° or at room temperature with dry methanol, ethanol, butan-l-ol, benzene or cyclohexane containing 0.35% hydrogen chloride or 1% thionyl chloride. Others were treated with methanolic methyl iodide or etheral diazomethane. With most of these solutions, the azurophilia attributable to mucosubstance carboxyl and sulphate half-ester groups was eventually abolished; subsequent saponification restored only the azurophilia due to carboxyl groups. However, some variation was found for each methylating agent, and also between different mucosubstances. 相似文献
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34.
Dibutyryl cAMP, aminophylline, and beta-adrenergic agonists protect against pulmonary edema caused by phosgene 总被引:3,自引:0,他引:3
35.
Micronekton and macrozooplankton in the open waters near Antarctic ice edge zones (AMERIEZ 1983 and 1986) 总被引:4,自引:4,他引:0
Summary Micronekton and macrozooplankton assemblages (0–1000 m) were sampled from the open ocean in the vicinity of marginal ice zones in the southern Scotia and western Weddell Seas using midwater trawls. Small regional differences in species composition were found in the differing hydrographic settings with the Scotia Sea being slightly more diverse. Most species exhibited broad vertical ranges with no distinct pattern of vertical movement. Exceptions were mesopelagic fish and Salpa thompsoni which undertook diel vertical migrations. Biomass was high (2.4–3.1 g DW/m2), comparable to Pacific subarctic waters. Euphausia superba and Salpa tompsoni were the numerical and biomass dominants, representing over 50% of the total numbers and standing stocks. In terms of biomass, euphausiids were the most important group at shallow depths (0–200 m) but were surpassed by salps in the Scotia Sea and mesopelagic fish in the Weddell Sea when all depths down to 1000 m were considered. Pelagic fish biomass (3.3–4.4 g WW/m2) greatly exceeded published estimates for birds (0.025–0.070 g WW/m2), seals (0.068–0.089 g WW/m2) and whales (0.167 to 0.399 g WW/m2), making mesopelagic fish the most prevalent krill predators in the Antarctic oceanic system. 相似文献
36.
Phytoplankton dynamics and sedimentation processes during spring and summer in Balsfjord,Northern Norway 总被引:3,自引:0,他引:3
Summary Chlorophyll a, phytoplankton species composition and carbon (PPC) estimated from cell-counts, were monitored together with hydrographic parameters and nutrients in the upper 50 m of Balsfjord (ca. 70° N), northern Norway between 08 February and 29 June 1982. Sediment traps were placed at 10, 50, 100, and 170 m (10 m above bottom) for intervals of 5–20 days during the study period. Trap contents were analyzed for phytoplankton as above; dry weight, particulate organic material (POM), particulate organic nitrogen and carbon (PON and POC), ash, and particulate phosphorus were also measured. The phytoplankton community exhibited three main phases: During the first (02–15 April, chiefly surface biomass) and the second (20 April–10 May, deep biomass-maximum and spring bloom peak) periods, Phaeocystis pouchetii dominated biomass (ca. 50% of PPC) followed by vegetative cells of Chaetoceros socialis. In the third period (10 May onwards, characterized by surface estuarinecir-culation), dino- and microflagellates dominated the low post-bloom biomass. Protozooplankton comprising tintinnids, other ciliates and heterotrophic dinoflagellates increased in abundance. Vegetative cells of phytoplankton were scarce in trap collections at 50 m or below; resting cells of Chaetoceros comprised nearly all the intact sedimenting phytoplankton. Krill faeces accounted for >90% by volume of the total faecal material trapped, despite a >21 biomass dominance of copepods in the fjord. The greatest sedimentation rates of krill faeces were at > 100 m, reflecting the downward migration of krill during the day. In all, 2–3 g Cm–2 of krill faeces were collected, representing ca. twice that from intact phytoplankton cells. POC in the traps at 50 m was ca. 11 gm–2, accounting for ca. 17% of the estimated primary production during the study period. As the secondary production is high, a large proportion of the production of P. pouchetii must be grazed by herbivores. Copepod faeces are probably remineralized in the euphotic zone, while those of krill provide the major coupling between the pelagial and the benthos. The implications of such a sedimentation model for partitioning energy flow between the pelagial and the benthos is discussed. 相似文献
37.
A Taylor A M Zuliani R E Hopkins G E Dallal P Treglia J F Kuck K Kuck 《FASEB journal》1989,3(6):1741-1746
Eye lens senile cataract is a major cause of blindness, affecting the elderly in particular. The etiology of the disorder has been elusive, and attempts to delay the onset of senile cataracts have been unsuccessful. The need for more information is underscored by epidemiologists who estimate that the ability to delay cataract formation in humans by only 10 years would eliminate the need for 50% of the cataract extractions performed annually in the United States. The Emory mouse provides the best model for human senile cataracts. Feeding Emory mice a diet that was restricted in calories by approximately 21% delayed the onset of cataracts. This is the first study that demonstrates in vivo the delay of senile-type cataracts. In these animals, aging and cataracts are associated with diverse changes in the proportion of various proteins (particularly 21, 22, 31-34 kDa) and with transformation of proteins from a soluble to an insoluble state. In advanced cataracts, there is a loss of total protein. Within a cataract grade, there is no difference between restricted and nonrestricted animals in relative proportion of specific lens proteins or in amounts of total or soluble proteins. The transition from a clear to cataractous lens appears when the soluble-to-total protein ratio falls below about 0.58. The exclusive use of gamma-crystallin as an indicator of lens viability is questioned. To the extent that cataract formation is due to lens protein oxidation and/or an inability to proteolytically remove damaged protein, it would appear that caloric restriction results in enhanced protection against lens oxidative stress or in prolonged proteolytic function. 相似文献
38.
The formation of mor humus in an experimental grassland plot, which has been acidified by long-term fertiliser treatment,
has been studied by comparing the rates of cellulose, soil organic matter and plant litter decay with those in an adjacent
plot with near-neutral pH and mull humus. The decomposition of cellulose filter paper in litter bags of 5 mm, 1-mm and 45-μm
mesh size buried at 3 to 4 cm depth the plots was followed by measuring the weight loss and changes in glucose content over
a 6 month period. Soil pH was either 5.3 or 4.3. Decomposition of native soil organic matter and plant litter in soil from
the same plots were followed using CO2 evolution in laboratory microcosms. Cellulose weight loss at pH 5.3 was greatest from the 5-mm mesh bags and least from the
45-um mesh bags. At pH 4.3 there was little weight loss from bags and no significant differences in weight loss between bags
with different sized mesh. There was, however, a reduction in the glucose content of the hydrolysed and derivatised filter
paper with time. The decomposition rate of native soil organic matter in the low pH soil was increased to that observed in
the less acid soil when the pH of the former was increased from 4.3 to 5.3. The increase in decomposition rate of added plant
litter in the more acid soil as a result of CA(OH)2 addition was only 60% of that observed in the soil with pH 5.3. These data support the hypothesis that the absence of soil
animals and the restricted microbial decomposition in the acidic soil was responsible for mor humus formation. 相似文献
39.
A survey of infectious diseases in wild turkeys (Meleagridis gallopavo silvestris) from Arkansas 总被引:5,自引:0,他引:5
B A Hopkins J K Skeeles G E Houghten D Slagle K Gardner 《Journal of wildlife diseases》1990,26(4):468-472
Wild turkeys (Meleagridis gallopavo silvestris) trapped as part of a relocation program by the Arkansas Game and Fish Commission were tested for selected infectious diseases and parasites. The 45 birds were trapped at four locations in Pope, Scott, and Montgomery counties (Arkansas, USA). Forty-four blood samples for serology, 27 blood smears and 12 fecal samples were collected. Of the serum samples tested, 20 of 44 (45%) were positive for Pasteurella multocida by enzyme-linked immunosorbent assay (ELISA), 42 of 44 (95%) were positive for Bordetella avium by ELISA, and 15 of 44 (34%) were positive for Newcastle disease virus antibody by the hemagglutination inhibition test. All serum samples were negative for Mycoplasma gallisepticum, Mycoplasma synoviae, avian paramyxovirus 3, avian influenza, hemorrhagic enteritis, Marek's disease, avian encephalomyelitis, laryngotracheitis, Salmonella pullorum and Salmonella gallinarum. Haemoproteus meleagridis was found in eight of 27 (30%) and Leucocytozoon smithi in nine of 27 (33%) blood smears; all smears were negative for Plasmodium hermani. Enteric parasites included Ascaridia dissimilis, Heterakis gallinarum, Eimeria dispersa and Raillietina spp. This study was an attempt to document the health status and disease exposure of wild turkeys in Arkansas to aid in managing and preventing the spread of disease agents to wild turkeys and other species of birds. 相似文献
40.
Kinase activity controls the sorting of the epidermal growth factor receptor within the multivesicular body 总被引:47,自引:0,他引:47
We compared the internalization and intracellular sorting of epidermal growth factor receptor (EGF-R) and point mutant kinase-negative EGF-R separately expressed in NIH 3T3 cells lacking endogenous receptor. Both EGF-Rs internalized rapidly, but kinase-negative receptor was surface down-regulated only with monensin or at 20 degrees C. Furthermore, EGF internalized by mutant receptor alone was, in significant proportion, returned to the cell surface undegraded. Hence unlike wild-type receptor, kinase-negative EGF-R recycles. By electron microscopy the early pathways of endocytosis for the two receptors were identical; however, after 10-20 min the pathways diverged at the multivesicular body (MVB). Wild-type EGF-R, destined for degradation, localized to internal vesicles, while kinase-negative EGF-R, destined for recycling, localized to surface membranes of the MVBs and moved to small tubulovesicles. We conclude that sorting of internalized receptor for degradation or recycling can occur through spatial segregation within the MVB, and sorting of EGF-R is controlled by tyrosine kinase activity. 相似文献