染色体辐射效应的微机检测 Ⅱ断片率 微核率与细胞畸变率间的相关性检测

本文继前文后,按照设计的线性回归程序在“IBM—PC/XT”微型计算机上,进一步检测了断片率、微核率与细胞畸变率之间的相关性,肯定了微核测定法,断片测定法可以替代染色体畸变分析法。     

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [³⁵S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 M KN-93, but binding is not affected by 5 M KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 M KN-93, but not by 5 M KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.Abbreviations CaM calmodulin - CaMK (II) Ca²⁺/calmodulin-dependent protein kinase (II) - CBP CaM-binding protein - CDPK Ca²⁺-dependent protein kinase - MCK1 maize homolog of mamalian CaMK This work is supported by the National Aeronautics and Space Administration grant No: NAGW 238.     

RT－cDNA克隆－PCR法获取犬瘟热病毒融合蛋白基因（F）

纯化鸡胚成纤维细胞培养的犬瘟热病毒（ＣａｎｉｎｅＤｉｓｔｅｍｐｅｒＶｉｒｕｓ,ＣＤＶ）,获得病毒基因组ＲＮＡ后,反转录合成双链病毒Ｆ基因ｃＤＮＡ。将此双链ｃＤＮＡ平端插入ＰＵＣ１９质粒ＳａｍⅠ位点构建重组质粒,进行ｃＤＮＡ克隆。以重组克隆质粒为模板ＰＣＲ扩增,获得ＣＤＶ全长Ｆ基因。将此Ｆ基因插入表达载体ＰＢＶ２２０,在大肠杆菌中表达,通过对表达产物的最终鉴定,可确认所获片段为ＣＤＶ全长Ｆ基因．     

Study on fibroin heavy chain of the silkwormBombyx mori by fluorescencein situ hybridization (FISH)

The sericulture industry plays a very important role in our national economy. Silkworm (Bombyx mori) is always regarded as a model animal and biological reactor. There have been detailed studies on the structure, expression and control and molecular evolution of silk genes. However, few, if any, reports are available on the localization of structural genes in silkworm by molecular cytogenetics. The present experiment has tentatively localized theFib-H gene at the distal end of the 25th linkage group, namely at the 25-0.0 position, and verified thatFib-H has only one locus, thus providing a temporary solution to the problem about its localization.     

Observations on the division characterization of diploid nuclear in <Emphasis Type="Italic">Porphyra</Emphasis> (Bangiales,Rhodophyta)

Nuclear divisions of carpospores, conchocelis and conchospores of Porphyra yezoensis, P. haitanensis, P. katadai var. hemiphylla and P. oligospermatangia from China were investigated. The observations showed diploid chromosome numbers of 2n = 6 for P. yezoensis and P. oligospermatangia, and 2n = 10 for P. haitanensis and P. katadai var. hemiphylla. For all four species, somatic pairing of chromosome sets was observed in late prophase. Sister chromosomes separated at anaphase as mitosis took place in carpospores, conchocelis filamentous cells, conchosporangial branch cells and sporangial cells (conchospore formation). Chromosome configurations of tetrad and ring-shaped in conchospore germination were observed, demonstrating the occurrence of meiosis. The characteristics of diploid nuclear division in 2n = 6 species are the same as those of 2n = 10 species. The influence of somatic pairing on nuclear division of diploid cells in Porphyra was discussed.     

Cytological mechanism of pollen abortion resulting from allelic interaction of F1 pollen sterility locus in rice (Oryza sativa L.)

Pollen abortion is one of the major reasons causing the inter-subspecific F₁ hybrid sterility in rice and is due to allelic interaction of F₁ pollen sterility genes. The microsporogenesis and microgametogenesis of Taichung 65 and its three F₁ hybrids were comparatively studied by using techniques of differential interference contrast microscopy, semi-thin section light microscopy, epifluorescence microscopy and TEM. The results showed that there were differences among the cytological mechanisms of pollen abortion due to allelic interaction at the three F₁ pollen sterility loci. The allelic interaction at S-a locus resulted in microspores unable to extend the protoplasm membrane with the enlargement of the microspore at the middle microspore stage and finally producing empty abortive pollen. The allelic interaction at S-b locus caused asynchronous development of microspores at the middle microspore stage producing stainable abortive pollen. The allelic interaction at S-c locus mainly led to the non-dissolution of the generative cell wall and finally caused the hybrid F₁ mainly producing stainable abortive pollen. Genotypic identification indicated that the abortive pollen were those with S ^j allele.     

Plant regeneration via organogenesis from adventitious bud explants of a medicinal herb species, <Emphasis Type="Italic">Polygonatum cyrtonema</Emphasis>

Summary Explants derived from adventitious buds, rhizomes, stems, and leaves of a medicinal plant, Polygonatum cyrtonema, were studied for plantlet regeneration, and only adventitious bud explants were able to be regenerated into plantlets. Regeneration was also accompanied by the formation of rhizome-like tissue, the medicinal portion of the plant. The optimum hormone combination for plantlet regenertion was 4.44 μM benzyladenine plus 2.26 μM 2,4-dichlorophenoxyacetic acid, at which new adventitious buds were obtained from 96.6% of the adventitious bud explants, with an average of 5.2 buds per explant. The best medium for root induction was half-strength Murashige and Skoog medium with 4.57 μM α-naphthaleneacetic acid, as 92% of regenerated buds rooted. Regenerated plantlets were successfully transferred to a greenhouse with 86% survival. Histological observation indicated that new adventitious buds originated from the superficial meristematic cell cluster of the granular callus induced from adventitious bud explants via organogenesis.     

A single residue mutation of 5-enoylpyruvylshikimate-3-phosphate synthase in Pseudomonas stutzeri enhances resistance to the herbicide glyphosate

A novel class II 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) was identified from Pseudomonas stutzeri A1501 by complementation of an Escherichia coli auxotrophic aroA mutant. The single amino acid substitution of serine (Ser) for asparagine (Asn)-130 of the A1501 EPSPS enhanced resistance to 200 mM glyphosate. The mutated EPSPS had a 2.5-fold increase for IC(50) [glyphosate] value, a 2-fold increase for K (i) [glyphosate] value, but a K (m) [PEP] value similar to that of wild type. The effect of the single residue mutation on glyphosate resistance was also analyzed using a computer-based three-dimensional model.     

Developmental changes of glucocorticoid receptors in the rat pancreas

Glucocorticoids are known to play a role in the maturation of the exocrine pancreas. The exact mechanism of glucocorticoid action in pancreatic ontogeny is, however, not clear. The present study characterized and quantitated the binding of [3H]dexamethasone to cytosol fractions from pancreata of rats at various ages. Trunk blood samples from these rats were also checked for levels of free and bound corticosterone. Specific and saturable bindings for dexamethasone were found in pancreatic cytosol fractions from newborn suckling and adult rats. Competition studies showed a preference for steroids with glucocorticoid activity. Specific binding was relatively low in pancreatic cytosol from newly born and 1-day old pups. A significant rise was seen after day 15. Cytosolic binding capacities were greatest from pancreata obtained from pups at weaning (3rd to 5th weeks). Values then declined toward the adult level. Scatchard analysis revealed a single class of binding sites with a dissociation constant (Kd) of 7.3 (+/- 1.1) X 10(-8) M and number of binding sites equalled to 1.29 (+/- 0.18) X 10(-13) mole/mg of cytosolic protein in adult rat pancreas. Pancreata from 25- and 15-day old rats had Kds of 3.4 (+/- 0.8) X 10(-8) M and 2.7 (+/- 0.7) X 10(-8) M with the number of binding sites equal to 1.77 (+/- 0.21) X 10(-13) mole/mg protein and 1.31 (+/- 0.16) X 10(-13) mole/mg protein respectively. Total plasma corticosterone concentration was low before day 10. It rose significantly by day 15, peaked at day 25, and then declined after weaning. About 5-15% of corticosterone during weaning and about 20-30% before and after weaning were in the free form. The peak level of dexamethasone binding corresponded to an increase in the plasma corticosterone level during weaning. This suggests a close relationship between plasma corticosterone levels and pancreatic glucocorticoid receptors. Both may, therefore, play a role in pancreatic development in the rat.