Effects of fibronectin on hydroxyapatite formation.

There is increasing evidence that noncollagenous matrix proteins initiate bone mineralization in vivo. Fibronectin, which is present during the early phases of mineralization, may contribute to this process in bone tissues. In this context, the mineralization potential of fibronectin was tested in an agarose gel precipitation system and a metastable calcium phosphate solution. The protein inhibited the precipitation of calcium phosphate crystals in solution but had no apparent effect in gel. Conversely, fibronectin stimulated crystal formation when apatite powder was used to seed crystal growth in gel. Although these results in vitro do not clearly indicate that fibronectin is involved in the mineralization process, they are consistent with in vivo events. Free fibronectin (e.g. in biological fluids) could inhibit crystal growth but might also activate the mineralization process when absorbed on apatite powder in a bone environment and areas of ectopic mineralization.     

Studies on the basidial formation by Sclerotium rolfsii sacc. VIII. Abortive basidial formation on media

Summary It appears from the results reported above that in some isolates abortive basidia could be obtained on inorganic nitrogen compounds containing ammonium salts, on some of the vegetable extracts particularlyS. sapindus andR. sativus and on hormones specially — alpha-N-acetic acid and trichloro-phenoxy-2-4-5 acetic acid. As suggested earlier, it is likely that if some modifications are incorporated in the basal medium or by changing the quantities of this basal medium or by changing the quantities of the compounds it might be possible to formulate a suitable medium which would induce easy basidial formation byS. rolfsii isolates.     

大麦产量构成模型

通过产量构成法构建了适用于不同地区不同品种的大麦产量模拟模型.以南京、昆明、武汉3个地区各试验处理中不同大麦品种最适条件下的产量因素为基础,建立了最适条件下每株穗数相对值、每穗粒数相对值、千粒重相对值与累积光合有效辐射的回归方程,构建了实际条件下的不同大麦品种每株穗数、每穗粒数和千粒重与这三者在最适条件下的潜在值和实际条件下的水肥丰缺因子等变量的函数关系.模型较为全面地考虑了大麦品种生长发育的内外因素,内因主要体现为品种遗传特性（潜在的每株穗数、潜在的每穗粒数、潜在的千粒重和灌浆期因子）,外因包括光合有效辐射和水肥丰缺因子.运用武汉、昆明、扬州3个地区不同品种、不同播期的田间试验资料对模型进行了测试和检验.结果表明,模型对大麦产量构成因子及理论产量的模拟效果较好,模拟值与观测值吻合度高,每株穗数、每穗粒数和千粒重相对误差（RE）绝对值的平均值分别为1.96%、1.88%和1.67%,对这三者及理论产量的模拟值和观测值进行y=x回归分析,相关系数（r）在0.9464～0.9987,相关性显著,说明模型具有较高的预测性和适用性.     

植物叶片形成露水的室内模拟

叶片在空气中形成露水是干旱、半干旱地区植物水分来源之一,具有重要的生态意义.本文借助人工智能气候室和叶片温度自控系统,对影响露水形成的环境温湿度、叶片温度和叶片倾角进行调节,研究了叶倾角、环境温湿度、露点-叶温差对叶片露水累积速率和叶片露水量的影响.结果表明: 叶片露水累积速率和叶片最大露水量均随叶倾角的增加而减小,但随着环境温度、湿度和露点-叶温差的增加而增大.叶片处于水平状态时,叶片露水在达到最大露水量前呈线性快速递增,露水达到最大露水量(0.80 mm)后处于稳定值;当叶片有倾角时,叶片露水达到一定值就会发生叶片露水滑落现象,使得叶片露水量呈现锯齿形变化,且露水累积速率明显变慢.     

The influence of micelle formation on lipoxygenase kinetics.

The effects of a series of n-alcohols and n-carboxylic acids on lipoxygenase activity was studied. It was shown that to a large extent the effects of these compounds could be ascribed to physiochemical interaction with the substrate solution rather than a direct action on the enzyme itself. The effect of better substrate analogues such as stearate and oleate could also be ascribed to this effect. A type-2 lipoxygenase was found to have a very unusual velocity-substrate relationship which could be normalized by addition of calcium chloride in amounts stoichiometric with the substrate. An excess of calcium inhibited the enzyme. By comparison of results with linoleoyl sulphate/linoleoyl alcohol mixed micelles, an explanation for this unusual velocity-substrate activity is presented.     

Influence of microgravity on crystal formation in biomineralization.

Biomineralized tissues are widespread in animals. They are essential elements in skeletons and in statocysts. The function of both can only be understood with respect to gravitational force, which has always been present. Therefore, it is not astonishing to identify microgravity as a factor influencing biomineralization, normally resulting in the reduction of biomineralized materials. All known biominerals are composite materials, in which the organic matrix and the inorganic materials, organized in crystals, interact. If, during remodeling and turnover processes under microgravity, a defective organization of these crystals occurs, a reduction in biomineralized materials could be the result. To understand the influence of microgravity on the formation of biocrystals, we studied the shell-building process of the snail Biomphalaria glabrata as a model system. We show that, under microgravity (space shuttle flights STS-89 and STS-90), shell material is built in a regular way in both adult snails and snail embryos during the beginning of shell development. Microgravity does not influence crystal formation. Because gravity has constantly influenced evolution, the organization of biominerals with densities near 3 must have gained independence from gravitational forces, possibly early in evolution.     

Effects of DNA looping on pyrimidine dimer formation.

We have assessed the effects of DNA curvature on pyrimidine dimer (PD) formation by examining the pattern of PD formation in DNA held in a loop by lambda repressor. The loop region was composed of diverse DNA sequences such that potential PD sites occurred throughout the loop. PD formation in the loop occurred with peaks at approximately 10 base intervals, just 3' of where the bending of the DNA was inferred to be toward the major groove. This relationship between the peaks and the DNA curvature is essentially identical to that observed in the nucleosome. This indicates that DNA curvature is the major source of the periodicity of PD formation in the nucleosome, and supports an earlier model of the conformation of nucleosomal DNA based on PD formation. DNA loops containing diverse sequences should be of general value for assessing the effects of DNA curvature on DNA modification by other agents used to probe DNA-protein interactions and DNA conformation.     

Mechanics of Rouleau formation.

The formation of rouleau of red blood cells is considered from the standpoint of adhesion theory. With the use of the elastic properties of the red blood cell membrane obtained from previous work, the strain energy of the red blood cell in rouleau formation has been computed. The surface energy of adhesion for the bonding of two red blood cells is then computed from the variation of this strain energy. Computed cell shapes agree well with experiments.     

Studies on isoamyalse formation in biological fluids.

Storage of human serum, saliva and duodenal secretion transformed amylase fractions on cellulose acetate membranes into more anionic forms. Incubation with lectins, proteases, glucosidases, neuraminidase and some effectors did not modify this conversion, which was promoted by rising temperature and pH values. Increasing concentrations of ammonium ions delayed the transformation of amylolytic fractions, thus indicating nonenzymatic deamidation as the reason for isoamylase development. A change of molecular weight could be excluded.     

Endogenous formation of dimethylamine.

Exposure of rats to heat (39 +/- 1 degree C) decreased H2O2 generation in mitochondria of the liver, but not of the kidney or the heart. The effect was obtained with three substrates, succinate, glycerol 1-phosphate and choline, with a decrease to 50% in the first 2-3 days of exposure, and a further decrease on longer exposure. The dehydrogenase activity with only glycerol 1-phosphate decreased, which is indicative of the hypothyroid condition, whereas choline dehydrogenase activity remained unchanged and that of succinate dehydrogenase decreased on long exposure. The serum concentration of thyroxine decreased in heat-exposed rats. Thyroxine treatment of rats increased H2O2 generation. Hypothyroid conditions obtained by treatment with propylthiouracil or thyroidectomy caused a decrease in H2O2 generation and changes in dehydrogenase activities similar to those with heat exposure. Treatment of heat-exposed or thyroidectomized rats with thyroxine stimulated H2O2 generation by a mechanism apparently involving fresh protein synthesis. The results indicate that H2O2 generation in mitochondria of heat-exposed animals is determined by thyroid status.