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61.
Data are presented on primary productivity, cell size distributionsand the standing stocks of living and detrital paniculate organiccarbon (POC) in the waters of the SW Tasman Sea. Primary productivitywas measured by both standard 4- and 12-h incubations as wellas time-series incubations. Data are presented for 14C uptakeand loss in 12L/12D methods. The importance of time zero anddark controls is demonstrated. The uptake of 14C in the lightwas linear and the loss of label in the following dark periodranged from zero to 39%. The loss of label in the dark was correlatedwith the particle size distribution, being greatest in oligotrophicwaters dominated by small cells (2530%) and least inspring bloom areas (020%) dominated by large diatoms.Kinetic data were strongly supportive of a major grazing impactby microphagous organisms. The data were an experimental confirmationof recent theoretical models of 14C uptake and grazing. Sizedistributions of phytoplankton and detritus were measured byHIAC and by microscopic counting. The phytoplankton consistedof a ubiquitous group of picoplankton, and variable contributionsfrom small flagellates and diatoms. The distribution of totalcell volume was dominated by large cells in spring bloom areas.Chlorophyll concentrations were strongly correlated with themean cell size of the phytoplankton. Comparison of the resultsof 14C uptake experiments with the results of experiments todetermine changes in POC, by counting particles, gave good correlation.In detail, the comparison of the methods revealed systematicerrors with the greatest discrepancy between the methods atlow apparent growth rates. The detritus showed constant sizedistributions in surface waters. The mean size of detritus particlesreduced rapidly with depth and declined in a way suggestingbiological reprocessing and removal by grazing. These resultsare discussed in the context of the patterns of carbon metabolismin the photic zone, the role of living and detrital POC andthe balance of new versus regeneratedproduction in surface waters. 相似文献
62.
Big Moose Basin: simulation of response to acidic deposition 总被引:2,自引:1,他引:1
George F. Davis John J. Whipple Steven A. Gherini Carl W. Chen Robert A. Goldstein Arland H. Johannes Peter W.H Chan Ronald K. Munson 《Biogeochemistry》1987,3(1-3):141-161
The ILWAS model has been enhanced for application to multiple-lake hydrologic basins. This version of the model has been applied to the Big Moose basin, which includes Big Moose Lake and its tributary streams, lakes, and watersheds. The basin, as defined, includes an area of 96 km2, with over 20 lakes and ponds, and 70 km of streams. Hydrologic and chemical calibrations have been made using data from seven sampling stations. When total atmospheric sulfur loading to the basin is halved, the model predicts, after four years of simulation, a decreasing sulfate concentration and to a lesser extent a rising alkalinity at Big Moose Lake outlet. At the end of four years, the results show an increase in pH of 0.1 to 0.5 pH units depending upon season. 相似文献
63.
Jill E. Schneider Joan M. Hamilton George N. Wade 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(1):39-44
Summary Mice selectively bred for either high or low levels of thermoregulatory nest building were cold-acclimated (5°C) for 3 weeks without nesting material; then body weight and food intake were measured. The mice selected for low nest building (Lows) of both sexes showed lower feed efficiencies than the high nest-building mice (Highs), although their body weights were not significantly different (Table 1). This adds to a large body of evidence which suggests that nest building and feed efficiency were influenced by a common mechanism (Lacy et al. 1978; Sulzbach and Lynch 1984; Lunch et al. 1981; Lynch and Roberts 1984).Brown adipose tissue mitochondrial GDP binding and cytochrome c oxidase activity were measured in the above mice. In females, the Lows had 100% higher levels of total GDP binding than the Highs, while no difference between the lines was seen in males (Fig. 2). Thus in the High females, lower energy expenditure through brown fat thermogenesis may account for their greater feed efficiency. In males, the genetic differences in feed efficiency must be due to differences in either thermogenesis in tissues other than brown fat, or mechanisms which reduce heat loss.Abbreviations
Highs
Mice from lines selectively bred for high levels of nest-building;Lows mice from the low nest-building selected lines 相似文献
64.
George G. Laties 《Physiologia plantarum》1987,69(2):305-312
When treated with ethylene in O2, conditioned potato (Solanum tuberosum L. cv. Russet Burbank) tubers – that is, tubers kept at room temperature for 10 days or more – yield slices that are CN? resistant. Ten % CO2 in the gas mixture not only synergizes the effect of ethylene, but replaces the need for conditioning as well. The response to CO2 is more pronounced with increasing time from harvest. By contrast fresh slices from untreated tubers are CN? sensitive, as are slices from tubers incubated in O2 or O2 plus CO2. The suggestion is made that CN? resistance is constitutive, and that treatment with ethylene/CO2 in O2 confers on potato tuber tissue a resistance to the extensive degradation of membrane phospholipids that normally attends slicing and leads to the loss of CN? resistance. In this connection respiration inhibition by imidazole, an inhibitor of fatty acid α-oxidation, is extensive in slices of untreated tubers, and sharply diminished in slices of ethylene-treated tubers in proportion to their CN? resistance. The coextensive rise of respiration rate and CN? resistance in aged potato slices has led to the presumption that the CN?-resistant path mediates the respiration climax. Accordingly the alkaloid, lycorine, has been considered to inhibit the development of CN? resistance in aging potato slices because it curtails the wound-induced respiration. A comparison was carried out on the effect of lycorine on CN?-sensitive and CN?-resistant fresh slices – the latter obtained from ethylene/CO2-treated tubers. Lycorine suppressed the development of the wound-induced respiration without restricting the development of CN? resistance. 相似文献
65.
Jay Hinton Michel C. M. Pérombelon George P. C. Salmond 《Molecular & general genetics : MGG》1987,207(2-3):466-470
Summary The suicide vector pJB4JI was used to generate a range of Tn5-induced mutants of Erwinia carotovora subsp. carotovora (Ecc). One mutant, HC500, was a cysteine auxotroph which had a non-pectolytic, non-cellulolytic, non-proteolytic phenotype when grown under sulphate-limitation. The cysteine lesion of HC500 was shown to be analogous to the cysB mutation of Escherichia coli. The Ecc-cysB
+ gene product was identified as a protein of Mr 36000. 相似文献
66.
Environmental factors influencing the vertical migration of planktonic rotifers in a hypereutrophic tarn 总被引:4,自引:4,他引:0
The diel vertical migration of planktonic rotifers in a small, hypereutrophic tarn was investigated on four occasions in 1983. When the tarn was isothermal the rotifers were distributed throughout the water column. After stratification, the rotifers were confined to the top 1–2 m of oxygenated water. On all four dates the rotifers were aggregated at specific depths in the water column. On some occasions, the pattern of aggregation changed as the animals performed distinct diurnal migrations. Keratella cochlearis, K. quadrata and Polyarthra vulgaris usually followed the reverse migrations of the phytoplankton. In contrast, the movements of Anuraeopsis fissa were less pronounced and were associated with variations in the depth of the oxycline. 相似文献
67.
Characterization of the chicken oocyte receptor for low and very low density lipoproteins 总被引:9,自引:0,他引:9
The chicken oocyte receptor for low and very low density lipoproteins has been identified and characterized. Receptor activity present in octyl-beta-D-glucoside extracts of oocyte membranes was measured by a solid phase filtration assay, and the receptor was visualized by ligand blotting. The protein had an apparent Mr of 95,000 in sodium dodecyl sulfate-polyacrylamide gels under nonreducing conditions and exhibited high affinity for apolipoprotein B-containing lipoproteins, but not for high density lipoproteins or lipoproteins in which lysine residues had been reductively methylated. Binding of lipoproteins was sensitive to EDTA, suramin, and treatment with Pronase. In these aspects, the avian oocyte system was analogous to the mammalian low density lipoprotein receptor in somatic cells. Furthermore, a structural relationship between the mammalian and avian receptors was revealed by immunoblotting: polyclonal antibodies directed against the purified bovine low density lipoprotein receptor reacted selectively with the 95-kDa chicken receptor present in crude oocyte membrane extracts. 相似文献
68.
J R Harkema C G Plopper D M Hyde J A St George 《The journal of histochemistry and cytochemistry》1987,35(3):279-286
Inhaled irritants induce secretory cell hyperplasia in nasal epithelium of animals. To characterize this response histochemically it is first important to know the histochemical character and distribution of epithelial mucosubstance in the normal nasal cavity. An automated image analyzing method was used to detect and quantitate acidic, neutral, and sulfated mucosubstances in the epithelium lining the nasal and paranasal airways of eight bonnet monkeys. Tissue sections 2 micron thick from defined regions of these airways were stained with either alcian blue/periodic acid-Schiff to demonstrate acid and neutral mucosubstances or high iron diamine to demonstrate sulfated mucins. Respiratory epithelium covering maxilloturbinates had the largest volume of stainable mucosubstance per unit surface area of basal lamina, whereas the maxillary sinus epithelium had the least. There was a general anteroposterior increase in the quantity of total epithelial mucosubstance along the septal and lateral walls of the nasal cavity, and there was more acidic than neutral mucosubstance in the posterior nasal airway than in the anterior. Epithelial mucosubstance in the maxillary sinus was predominantly neutral. Therefore, we conclude that there are substantial regional quantitative differences in stainable mucosubstances in the primate nasal epithelium which must be considered when examining nasal mucosa for irritant-induced changes in epithelial mucins. 相似文献
69.
Mitochondrial DNA of the extinct quagga: Relatedness and extent of postmortem change 总被引:4,自引:0,他引:4
Russell G. Higuchi Lisa A. Wrischnik Elizabeth Oakes Matthew George Benton Tong Allan C. Wilson 《Journal of molecular evolution》1987,25(4):283-287
Sequences are reported for portions of two mitochondrial genes from a domestic horse and a plains zebra and compared to those published for a quagga and a mountain zebra. The extinct quagga and plains zebra sequences are identical at all silent sites, whereas the horse sequence differs from both of them by 11 silent substitutions. Postmortem changes in quagga DNA may account for the two coding substitutions between the quagga and plains zebra sequences. The hypothesis that the closest relative of the quagga is the domestic horse receives no support from these data. From the extent of sequence divergence between horse and zebra mitochondrial DNAs (mtDNAs), as well as from information about the fossil record, we estimate that the mean rate of mtDNA divergence in Equus is similar to that in other mammals, i.e., roughly 2% per million years. 相似文献
70.
d-Aspartate in Human Brain 总被引:3,自引:3,他引:0
Eugene H. Man George H. Fisher Iris L. Payan Rodolfo Cadilla-Perezrios Nancy M. Garcia Radhika Chemburkar Georgine Arends William H. Frey II 《Journal of neurochemistry》1987,48(2):510-515
The presence of the biologically uncommon D-aspartic acid (D-aspartate) in human brain white matter has been previously reported. The earlier study has now been expanded to include D/L-aspartate ratios from 67 normal brains. The data show that the D-aspartate content increases rapidly from 1 year to approximately 35 years of age, levels off in middle age, and then appears to decrease somewhat. The D-aspartate content in gray matter remains at a consistently low level (half of that found in white matter) throughout the human life span. Within the limitations of current analytical methods, there was no detectable difference in D/L-aspartate ratios in white and gray matter of brains with Alzheimer's disease and several other pathologies when compared with brains of normal subjects. However, the presence of a significant D-aspartate level in white matter during the adult life span may lead to changes in protein configuration related to dysfunctions associated with the aging brain. 相似文献