Comparative histology of antelope placentomes

The histological structure of ruminant (family: Bovidae) placentomes in eight antelope species was compared to that of domestic cattle and sheep. The chorioallantoic villi differed in degree of branching, surface corrugation, and complexity of utero-placental junction. All species had the epitheliochorial type of placenta, with the epithelial lining of maternal caruncular crypts varying between cellular and syncytial types.     

Herbicide Resistance in Datura innoxia: Cross-Resistance of Sulfonylurea-Resistant Cell Lines to Imidazolinones

Cells resistant to the sulfonylurea herbicides chlorsulfuron and sulfometuron methyl were isolated from a predominantly haploid cell suspension culture of Datura innoxia P. Mill. Exponentially growing cell colonies (aggregates of about 40 cells) were mutagenized with ethyl methane sulfonate, subcultured for 10 days to allow growth recovery and plated on a medium containing either chlorsulfuron or sulfometuron methyl at a concentration (10⁻⁸ molar) which killed wild type cells. Surviving clones were picked up after 3 to 4 weeks, further proliferated as callus or cell suspension cultures, and tested for their resistance to both the sulfonylureas and imidazolinones, a chemically different class of herbicides. The variants were stable and showed high (100- to 1000-fold) resistance to the sulfonylureas. While some also exhibited cross resistance to imidazolinones, others showed no cross-resistance at all or, as in one case, greater sensitivity than wild type cells to the imidazolinones. Both classes of herbicides tested inhibited acetolactate synthase activity isolated from wild type cells. The acetolactate synthase of the resistant variants, however, was found to be resistant to the sulfonylureas and also to the imidazolinone(s) in those cells showing cross-resistance to the latter. The lack of cross-resistance observed in some cases provides evidence that the two groups of herbicides have slightly different sites on the acetolactate synthase molecule.     

First evidence for polyamine conjugation mediated by an enzymic activity in plants

An enzyme activity, found for the first time in plants, mainly located in the 22,000g supernatant of the crude extract of sprout apices of Helianthus tuberosus L. cv OB1 tubers, is able in vitro to covalently bind polyamines to endogenous substrates of different molecular weights. The major assay parameters, such as pH, dithiothreitol, and extract concentrations were optimized. The time course of the reaction, the dependence on putrescine concentration, its competition with histamine, the capacity to bind spermidine and spermine better than putrescine, the stability of the reaction product and analysis of the latter by sodium dodecyl sulfate polyacrylamide gel electrophoresis and thin-layer chromatography suggest that putrescine is linked to endogenous substrates by means of an enzyme reaction that shows some similarities with transglutaminase activities detected in animals. However, the activities of the crude extract and of a fraction eluted from a Sephadex G25 column were not affected by CaCl₂ concentrations lower or equal to 5 millimolar; 4 or 10 millimolar EGTA caused a very small reduction; higher concentrations of CaCl₂ and 15 millimolar or more of EDTA were inhibitory. N,N′-dimethylcasein was not recognized as a substrate. These data indicate that this activity also displays some characteristics which are different from those of animal transglutaminases.     

The flea ovary: ultrastructure and analysis of cell clusters

Panoistic ovarioles are found in the order of fleas (Siphonaptera). Only in some species of the Hystrichopsylloidea do polytrophic meroistic ovaries occur. No stem cells and no dividing cystocytes are found in female imagines of Hystrichopsylla talpae. However, each germ cell cluster consists of 32 cells which are generated by five mitotic cycles during the pupal stage. One of the cells containing five intercellular bridges becomes the oocyte, the others serve as nurse cells. Thus, germ cell cluster formation follows the 2(n)-rule. However, no polyfusome is found and nurse cells do not form a rosette. Furthermore, nurse cells remain small and show the same ultrastructural characters as the oocytes, which became distinguishable from nurse cells only by their enhanced growth during pre-vitellogenesis. The first phase of pre-vitellogenesis is dominated by the production of an unknown cytoplasmatic component, consisting of spherical particles, clearly distinguishable from ribosomes by diameter and contrast. The next phase is characterized by a tremendous increase in the production of ribosomes. During this second phase another cytoplasmic component consisting of ball-like structures becomes prominent. During pre-vitellogenesis, germ cell nuclei undergo a pronounced structural change in which, finally, numerous extranucleolar particles predominate. Thus, H. talpae has a polytrophic meroistic ovary, but its oocyte genomes behave panoistically.     

休克过程中内源性阿片样物质对交感-肾上腺髓质系统的影响

内源性阿片样物质(endogenous opiate substance,EOS)在中枢及外周广泛分布,对机体功能产生多方面影响。就其心血管效应而言,休克等应激状态 EOS水平明显升高,可在心血管中枢、交感神经节、交感神经末梢膨体、肾上腺髓质及心血管效应器官等多个环节程度不同地影响交感-肾上腺髓质系统的活性,参与抑制心血管功能。纳洛酮等阿片受体阻断剂可能通过上述环节程度不等地拮抗 EOS 的作用,部分改善休克个体的心血管功能而表现出一定的抗休克效应。     

山西垣曲和山东蒙阴等地始新世介形类

山西垣曲县垣曲组、山东蒙阴县官庄组和临朐县五图组中的介形类化石,计15属31种,其中1新属18新种及5未定种。这些介形类化石对我国第三纪地层,特别是对第三纪含油地层的划分对比具有重要意义。     

微体化石的处理

本文较全面地介绍一些微体化石的实验室处理方法,它包括岩样的破碎、松样、冲洗和挑选等各方面的技术问题,以及在分析处理过程中应注意的事项。