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81.
Personnel records kept by military units of American colonials during the French and Indian War (1755-1763) are analyzed for relationships between environmental factors and stature. A robust American economy and direct access to high-quality food were apparently critical to tallness of this white American male sample. American-born men were taller at all ages than those who had migrated from Europe. January temperatures, rural versus urban birth, and ethnicity also showed stature relationships within the American-born group; thermal effects were by far the strongest of the non-nutritional factors. 相似文献
82.
Embryo survival and alevin emergence pattern of brown trout were studied in simulated redds with different homogeneous gravel sizes and different concentrations of peat material. Optimal survival (95%) occurred in 18 mm gravel and survival decreased with decreasing gravel size. High concentrations (40%) of peat material resulted in low survival (65%). The proportion of premature emerging alevins increased in finer gravels and at high peat concentrations. Premature alevins had a large yolk sac and are probably very vulnerable to predators. 相似文献
83.
Daniel Scherman 《Journal of neurochemistry》1986,47(2):331-339
The objective of the present study was to estimate extracellular pH (pHe) and intracellular pH (pHi) during near-complete forebrain ischemia in the rat, and to evaluate the relative importance of lactic acidosis and rise in tissue Pco2 (Ptco2) in causing pHe and pHi to fall. The animals, which were ventilated, normoxic, normocapnic, and normothermic, were subjected to 15 min of ischemia, either without or with 30-60 min of recirculation. Ptco2 was measured with a tissue electrode, pHe with a double-barrel liquid ion-exchanger microelectrode, changes in extracellular fluid (ECF) volume by impedance measurements, tissue CO2 content by a microdiffusion technique, and labile tissue metabolites by enzymatic fluorometric methods. Ischemia caused Ptco2 to rise to between 95 and 190 mm Hg (mean 149 mm Hg), and pHe to fall by 0.45-1.05 units (mean 0.70 units). During recovery, Ptco2 normalized within 5 min and pHe after 15-30 min. During ischemia, high-energy phosphates were depleted and tissue lactate content increased to 15 mumol X g-1. The total CO2 content (Tco2) was minimally or moderately reduced (normal, 11.9 mumol X g-1; range of ischemic values, 7.9-12.1 mumol X g-1), this range probably reflecting variable amounts of remaining blood flow. Impedance measurements demonstrated that ECF volume during ischemia was reduced to 55% of control, with gradual normalization during the first 15-30 min of recirculation. From values for Ptco2, Tco2, [HCO3-]e, and ECF volume, [HCO3-]i and pHi could be calculated. These values pertain to an idealized homogeneous intracellular compartment, and the methods used cannot detect whether different intracellular compartments diverge in their acid-base responses.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
84.
Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic
hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the
presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction
in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in
red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies
demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy
was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage
age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms
for hemolytic protection by drugs are proposed. 相似文献
85.
Photoacoustic and fluorescence measurements of the chilling response and their relationship to carbon dioxide uptake in tomato plants 总被引:5,自引:0,他引:5
The response of tomato plants to various chilling treatments was studied using two approaches for the measurement of photosynthetic activity. One involved the use of a portable fluorometer for the measurement of in-vivo chlorophyll fluorescence, while the other employed a newly introduced photoacoustic system which allowed changes in oxygen evolution to be followed in a leaf disc. A strong correlation was found between results obtained by each system and those obtained by a conventional open gas-exchange system for the determination of CO2 uptake. Both systems of measurements could readily distinguish between the effects of chilling in the dark (at 3° C for 18 h) and chilling at high photon flux density (2000 mol m-2 s-1 for 5h at 5° C). Chilling in the dark had practically no effect on the quantum yield of oxygen evolution, chlorophyll fluorescence or CO2 uptake, while chilling at excessively high photon flux density resulted in a sharp reduction (50–70%) in the quantum yields obtained. The results support the view that photosystem II cannot be the primary site of damage by chilling in the dark, although it is significantly affected by chilling at high light intensity.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- PA
photoacoustic
- PFD
photon flux density
- PSII
photosystem II 相似文献
86.
87.
Jeffrey D. Macklis Richard L. Sidman H. David Shine 《In vitro cellular & developmental biology. Plant》1985,21(3):189-194
Summary A new type of collagen surface for use with cultures of peripheral nervous system cells is described. Collagen is derivatized
to plastic culture dishes by a cross-linking reagent, 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide-metho-p-toluenesulfonate (carbodiimide), to form a uniform and durable surface for cell attachment and growth that allows dry storage,
long-term culture, and improved microscopy. Surfaces of collagen derivatized to plastic were compared to surfaces of adsorbed
or ammonia-polymerized collagen in terms of collagen binding and detachment, growth by dorsal root ganglion cells, and electron
microscopy appearances. Derivatized collagen surfaces retained more collagen and showed much less evidence of degradation
and cellular damage over periods of many weeks than did conventional adsorbed surfaces. Long-term survival of cells on derivatized
collagen was far superior to that on the other surfaces, with almost 90% of cultures still viable after 10 wk. Transmission
electron microscopy showed an organized layer of single fibrils that supported cell growth well, and scanning electron microscopy
demonstrated an increased uniformity of derivatized collagen surfaces compared to ammoniated collagen surfaces. Applications
for this improved substrate surface are discussed.
This work was supported by the Leopold Schepp Foundation, the Dysautonomia Foundation, National Institutes of Health Grants
NS14768 and NS11237, and Institutional Core Grant HD06276. 相似文献
88.
Yohei Hashimoto Hiroyuki Ishizone Midori Moriyasu Kazuko Kawanishi Atsushi Kato Masaru Ogura 《Phytochemistry》1984,23(8):1807-1808
Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene. 相似文献
89.
Abstract: Rats were treated with reserpine, desmethylimipramine, or carrier, either alone or in combination with tropolone. Either 10 min (t1) or 1 h (t2) after intraventricular injection of [3H]noradrenaline, they were decapitated. The total 3H activity and the recovery of [3H]noradrenaline were determined in tissue extracts from various brain regions. Maximum total 3H activity was measured at t1 in all tropolone-treated rats; the mean sum of these results served as an estimate of the initial tissue concentration of [3H]noradrenaline. At t1, 40–50% of the sum of [3H]noradrenaline and its metabolites was recovered unchanged in normal rats; reserpine and DMI reduced the recovery to 18–27%. In all groups, the decline of [3H]noradrenaline was retarded after t1. Inhibition of catechol-O-methyltransferase by tropolone caused consistently elevated [3H]noradrenaline levels, but did not affect the metabolic rate after t1 when compared with similarly pretreated, but tropolone-free rats. Thus, if catechol-O-methyltransferase was inhibited during the injection of [3H]noradrenaline, a higher percentage of the amine had been taken up into spaces with a slow noradrenaline turnover. The maximum increase was seen when the neuronal uptake, was inhibited by desmethylimipramine. This supported the hypothesis that an additional extraneuronal space exists, in addition to the known intraneuronal and extraneuronal compartments, which has a slow noradrenaline turnover. The tropolone effect on the noradrenaline recovery possibly shows that there might be a saturable “methylating system,” similar to that described for the periphery, in which catechol-O-methyltransferase is linked to the extraneuronal uptake2. By affecting the access of noradrenaline to non-neuronal cells it might influence the rate of noradrenaline elimination from the intercellular space. 相似文献
90.
通过过聚乙二醇6000-磷酸钾缓冲液双相分离、Sephadex G-100凝胶过滤、DEAE-Sephadex A-50离子交换层析、羟基磷灰石层析及SephadexG-100凝胶过滤等提纯步骤,从海枣曲霉(Aspergillus phoenicis)麦麸培养物抽提液中提纯得到凝胶电泳均一的β-半乳糖苷酶。该酶的最适pH为3.5—4.0,最适温度为60℃(反应15分钟),在pH5.0—8.5之间及60℃以下稳定。在65℃和70℃保温时失活50%的时间分别为27和2分钟。用SDS凝胶电泳法和梯度凝胶电泳法分别测得该酶的分子量为115,000和118,000。薄层凝胶等电聚焦法测得其等电点为pH4.6。 相似文献