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At least 19 recordsLinked to original sources
PubMed1977

Observations on the combined effect of ultrasound and certain cytoxics on the growth of the roots of Zea mays.

Seedling roots of Zea mays were used in combined treatments with ultrasonic radiation (pulsed and continuous beams) and the cytotoxic drugs vincristine and hydroxyurea respectively. It has been found that ultrasound and the above-mentioned drugs act independently of each other, a result similar to that obtained with ultrasound and X rays. This leads to the suggestion that the mechanism of damage due to the drugs is different from that due to ultrasound. An increase in drug effectiveness under the action of ultrasound has not been found.

Antibiotics, Antineoplastic↗
PubMed1979

Ultrastructural cytochemistry of the nucleus in Zea mays embryos during germination.

The ultrastructure of embryonic root cells of Zea mays was studied from the quiescent stage (dry seed) to 72 h of germination. Semithin and ultrathin sections of tissues fixed with only glutaraldehyde and embedded in Epon were observed after usual section staining and after cytochemical reactions specific for DNA or preferential for ribonucleoproteiNS. In quiescent cells, dense chromatin forms a network which fills a great part of the nucleoplasm. Following germination, gradual dispersion of chromatin occurs: total dispersion is reached at 24 h. After 48 h the chromatin appears moderately condensed again. The nucleolus is compact and predominately fibrillar in dry cells. At 48 h a typical pars granulosa is differentiated. At 8 h a pronounced vacuolation of the nucleolus is observed; nucleolar vacuoles persist until 72 h but become less numerous. During the first 8 h of germination a nucleolus organizer region (NOR) in an eccentric position is associated with the nucleolus; by 24 h and later this NOR has disappeared. No DNA can be visualized in the nucleolar matrix between 0 and 8 h of germination, whereas later, when the nucleolus is reactivated. DNA is always detected in the nucleolar matrix and vacuoles. During the first 72 h of germination, heavily contrasted areas, rich in ribonucleoproteins and appearing to be fibrillar texture, are found in the nucleoplasm, often in closed contact with the dense chromatin. In quiescent cells dense ribonucleoprotein granules, approximately 40 nm in diameter are found dispersed or clustered in the nucleoplasm; after 8 h larger (50 nm), dense ribonucleoprotein granules are found frequently clustered in granular areas in the extranucleolar space. At 8 h of germination, when the nucleolus is temporarily highly vacuolated, unusual 35-nm ribonucleoprotein granules are found both in the smallest vacuoles and on the periphery of the nucleolus.

Cell Nucleolus↗
PubMed1978

RNA synthesis and changes in template--DNA activity during the growth and differentiation of parenchyma cells of the primary cortex of roots of Zea mays and Tulipa kaufmanniana.

In this study, changes in DNA transcription activity are presented during parenchymal cell differentiation of the primary cortex of roots of a species with elevated DNA content in which endomitotic polyploidization does not occur (Tulipa kaufmanniana), as well as a species with low content levels in which an increase in endomitotic polyploidization occurs during differentiation (Zea mays). Changes in the degree of histone acetylation during the cellular differentiation of both species were also studied. An autoradiographic method was employed using the following indicators: for transcription activity--3H-uridine; for potential activity of template DNA--3H-actinomycin D (3H-AMD); for histone acetylation--the intensity of labelled nuclei after incubation with 3H-sodium acetate, as well as decrease in nuclei radioactivity after extraction of the histone fractions. It was found that during cellular growth and differentiation in both Zea mays and Tulipa daufmanniana (and therefore, irrespective of the presence or absence of endomitotic polyploidization) a progressive decrease of DNA transcription activity occurs. At the same time, the possibility that the acetylation of arginine--rich histones plays a definite, yet undecisive, role in the regulation of DNA transcription activity cannot be excluded.

DNA↗
PubMed1975

Cholinesterases from plant tissues. VI. Preliminary characterization of enzymes from Solanum melongena L. and Zea mays L.

Enzymes capable of hydrolyzing esters of thiocholine have been assayed in extracts of Solanum melongena L. (eggplant) and Zea Mays L. (corn). The enzymes from both species are inhibited by the anti-cholinesterases neostigmine, physostigmine, and 284c51 and by AMO-1618, a plant growth retardant and they both have pH optima near pH 8.0. The enzyme from eggplant is maximally active at a substrate concentration of 0.15 mM acetylthiocholine and is inhibited at higher substrate concentrations. On the basis of this last property, the magnitude of inhibition by the various inhibitors, and the substrate specificity, we conclude that the enzyme from eggplant, but not that from corn, is a cholinesterase.

Acetylthiocholine↗
PubMed1976

Relationship of nuclease activity and synthesis to senescence of corn (Zea mays L.) stalk pith, cob parenchyma and first developed leaf tissues.

An increase in total RNase activity was associated with three patterns of cell senescence in corn (Zea mays L.) (cv. WF9 X 38-11) cob parenchyma during the first two weeks following silking, stalk pith tissue after internode elongation and the first developed leaf of seedlings. Stalk pith tissue had two RNase activities, one inhibited by EDTA and one not. Both remained in approximately equal amounts in young to old pith tissue. In the first developed leaf of seedlings, the activity not inhibited by EDTA remained at a constant low level during the period studied, while the other activity varied. No inhibition by EDTA was found in cob parenchyma tissue. Incubation of sections of cob parenchyma and stalk pith tissues suggested that the total RNase activity of cob parenchyma is very stable and that of stalk pith tissue is relatively stable. An age-related increase in DNase activity was found in stalk pith tissue and in the first developed leaf of seedlings, but not in cob parenchyma tissue.

Cell Survival↗
PubMed1979

Comparative susceptibility of starch granules of double- and triple-mutants containing amylose-extender, waxy, sugary-1, sugary-2 and dull genes of maize inbred OH43 (Zea mays L.) to amylase.

Starch granules were prepared from 14 double- and 26 triple-mutants containing amylose-extender (ae), 14 double- and 18 triple-mutants containing waxy (wx), 15 double- and 20 triple-mutants containing sugary-1 (su1), 13 double- and 23 triple-mutants containing sugary-2 (su2), and 14 double- and 19 triple-mutants containing dull (du) of maize inbred Oh43 (Zea mays L.). The relative susceptibilities of these starch granules to fungal glucoamylase were determined and the starch granules were examined by scanning electron microscopy. A commercial normal maize starch was used as a control. Starch granules of the double- and triple-mutants containing su1 and su2 were digested two to eight times faster than normal. The ae gene reduced susceptibility and seems to be epistatic to su1 and su2. Starch granules of the double- and triple-mutants containing wx were digested about two times faster than normal and those containing shrunken-2 (sh2) were digested 1.2 to eight times faster than normal. Starch granules of triple-mutant combinations with opaque-2 (o2) showed digestion properties which were comparable to those of their respective monopaque double-mutant counterpart.

Glucan 1,4-alpha-Glucosidase↗
PubMed1979

Nitrogen-metabolizing enzymes of Diplodia maydis, a Zea mays L. stalk rot causing fungus.

The nitrogen source available to Diplodia maydis in vivo is reported to affect the severity of stalk rot in maize. Nitrate and (or) ammonium salts were tested for their effect on the type of nitrogen metabolism found in Diplodia maydis in vitro. The level of glutamate dehydrogenase remained essentially constant on either nitrogen salt but nitrate reductase was induced by growth on nitrate salts and was not extractable on ammonium salts. Properties of nitrate reductase reported here are similar to those reported for the higher plant and Neurospora crassa enzymes. Thr relationship of nitrogen metabolism in Diplodia maydis to Zea mays L. stalk rot is discussed.

Ammonia↗
PubMed2025

Zea mays Meiotic Spindle Ultrastructure Reveals Kinetochore-Microtubule Interface and Embedded Membrane Components.

UNLABELLED: Introduction: Spindles are microtubules-based machines whose primary function is to accurately segregate chromosomes in both mitotic and meiotic cell division. The structure of spindles is critical for their function; errors in morphology or attachment to chromosomes lead to aneuploidy, potentially resulting in disease, infertility, and lethality. Electron microscopy studies have yielded fine-detail spindle ultrastructures in many plant and animal species, but no studies have investigated the spindle of Zea mays, a critical crop, and cytogenetic model system. METHODS: Here we use electron tomography (ET), reconstruction, and modeling to obtain three-dimensional, nanometer-resolution of the Z. mays meiotic spindle. Structures such as microtubules, kinetochores, vesicles, membrane channels, and nuclear envelope were modeled through a partial spindle reconstruction, and confirmed using immunostaining and live fluorescence microscopy. RESULTS: ET revealed that maize spindles contain 8-18 kinetochore microtubules (kMTs) per kinetochore, which are approximately 776 nm in diameter and 316 nm in depth. Small ∼37 nm vesicles were identified, as well as larger (∼5 µm long, 800 nm wide) membrane structures with channels that allow spindle microtubules to pass through. These membrane channels stain positively for the ER-marker protein disulfide isomerase. Imaging of prophase meiotic cells revealed a cross-hatch microtubule arrangement in the perinuclear ring on the external surface of the nuclear envelope, which also contained type II nuclear grooves with transnuclear microtubules passing from the nucleus to the cytoplasm. CONCLUSIONS: Z. mays meiotic spindles are similar to animal counterparts with a comparable number of kMTs and pre-spindle transnuclear microtubules but also plant-specific features such as Golgi-derived vesicles to assist cell plate formation, internal ER membrane channels, and a perinuclear microtubule ring that aids spindle assembly. Maize kinetochores have an electron-diffuse ball in cup morphology that is comparable in size to Drosophila kinetochores and larger than mammalian kinetochores. .

Zea mays↗
PubMed1976

Histochemical studies on reserve substances and enzymes in female gametophyte of Zea mays.

Cytochemical changes during the early development of maize caryopsis are reported. Changes in the localization of different reserve substances (e.g. polysaccharides, proteins, nucleic acids and lipids) and enzymes (acid phosphatase, esterase, lipase, phosphorylase, succinate dehydrogenase, cytochrome oxidase and peroxidase) have been studied in unfertilized and fertilized ovules. Before pollination very feeble enzyme activity (acid phosphatase, succinate dehydrogenase, cytochrome oxidase and peroxidase) was observed. Reserve substances were present in low amounts before pollination. Pollination stimulated the accumulation of several substances and enzymes in the tip of the nucellus, micropylar zone. Just prior to, during and after fertilization, the cells in the micropylar zone had strong reaction for several enzymes indicating temporary enhancement of metabolic activity in the micropylar zone. The role of antipodals in the storage of reserve food products and nutrition of embryo and early stages of endosperm development is discussed. The pattern of enzymatic changes within the embryo sac reflected the biochemical changes operative during quiescent and active stages. The nucellus of Zea mays contains many enzymes required for hydrolysis of reserved food substances. A role of acid phosphatase in autolysis of nucellar cells, after fertilization is suggested. Post-fertilization increase in the activity of enzymes and accumulation of reserve materials is interpreted as reflecting a presumed increase in the metabolic rate relative to growth and differentiation.

Acid Phosphatase↗