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Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4° C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample. 相似文献
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JOSEF PFEILSCHIFTER WOLFGANG EBERHARDT RICHARD HUMMEL DIETER KUNZ HEIKO MÜHL DOROTHEA NITSCH CHRISTOPH PLÜSS GABY WALKER 《Cell biology international》1996,20(1):51-58
In recent years, NO, a gas previously considered a potentially toxic chemical, has become established as a diffusible universal messenger mediating cell—cell communication throughout the body. In mammals, NO is a recognized mediator of blood vessel relaxation that helps to maintain blood pressure. In the central nervous system NO acts as a non-conventional neurotransmitter and participates in the establishment of long-term plasticity required for memory formation. In addition, NO is responsible for some parts of the host response to sepsis and inflammation and contributes to certain disease states. A number of strategies have emerged with regard to a pharmacological control of pathological NO overproductions. This review will discuss these novel therapeutic approaches that may provide new means for clinical medicine. 相似文献
46.
Lead is a toxic heavy metal that adversely affects nervous tissues; it often occurs as an environmental pollutant. We investigated histological changes in the cerebral cortex, hippocampus and cerebellum of adult albino mice following exposure to lead acetate. We also studied the possible ameliorative effect of the chelating agent, L-cysteine, on lead-induced neurotoxicity. We divided albino mice into six groups: 1) vehicle-only control, 2) L-cysteine control, 3 and 4) treated for 7 days with 20 and 40 mg/kg lead acetate, respectively, and 5 and 6) treated for 7 days with 20 and 40 mg/kg lead acetate, respectively, followed by 50 mg/kg L-cysteine for 7 days. Lead acetate administration caused disorganization of cell layers, neuronal loss and degeneration, and neuropil vacuolization. Brain sections from lead-intoxicated mice treated with L-cysteine showed fewer pathological changes; the neuropil showed less vacuolization and the neurons appeared less damaged. L-cysteine at the dose we used only marginally alleviated lead-induced toxicity. 相似文献
47.
A mouse genomic clone containing a lactate dehydrogenase-A (LDH-A)
processed pseudogene and a B1 repetitive element was isolated, and a
nucleotide sequence of approximately 3 kb was determined. The pseudogene
and B1 element are flanked by perfect 13-bp repeats, and the B1 sequence
starts at 14 nucleotides 3' to the presumptive polyadenylation signal of
the pseudogene. The nucleotide sequences of the LDH-A genes and processed
pseudogenes from mouse, rat, and human were compared, and a phylogenetic
tree was constructed. The rate and pattern of nucleotide substitutions in
the LDH-A pseudogenes are similar to previously reported results (Li et al.
1984). The average rate of nucleotide substitutions in the LDH-A
pseudogenes is 4.3 X 10(- 9)/site/year. The substitutions of C----T and
G----A are most frequent, and A----G substitutions are relatively high. The
rate of synonymous substitutions in the LDH-A genes is 5.3 X 10(-9), which
is not significantly higher than the average rate of 4.7 X 10(-9) for 35
mammalian genes. The rate of nonsynonymous substitutions in the LDH-A genes
is 0.20 X 10(-9), which is considerably lower than the average rate of 0.88
X 10(-9) for 35 mammalian genes. Thus, the mammalian LDH-A gene appears to
be highly conserved in evolution.
相似文献
48.
M A Sukoyan N M Matveeva N D Belyaev S D Pack A A Gradov A G Shilov N S Zhdanova O L Serov 《Molecular & general genetics : MGG》1984,196(1):97-104
Summary By means of metaphase chromosomes, the genes for mink thymidine kinase (TK) and hypoxanthine-phosphoribosyltransferase (HPRT) were transferred to mutant mouse cells, LMTK-, A9 (HPRT-) and teratocarcinoma cells, PCC4-aza 1 (HPRT-). Eighteen colonies were isolated from LMTK- (series A), 9 from A9 (series B) and none from PCC4-aza 1. The transformed clones contained mink TK or HPRT. Analysis of syntenic markers in series B demonstrated that one clone contained mink glucose-6-phosphate dehydrogenase (G6PD) and the other alpha-galactosidase; in series A, nine clones contained mink galactokinase (GALK) and six mink aldolase C (ALDC). Analysis of 12 asyntenic markers located in ten mink chromosomes showed the presence of only aconitase-1 (ACON1) (the marker of mink chromosome 12) in three clones of series A. The clones lost mink ACON1 between the fifth to tenth passages. Cytogenetic analysis established the presence of a fragment of mink chromosome 8 in eight clones of series A, but not in series B. The clones of series A lost mink TK together with mink GALK and ALDC during back-selection; in B, back-selection retained mink G6PD. No stable TK+ phenotype was detected in clones with a visible fragment of mink chromosome 8. Stability analysis demonstrated that about half of the clones of series B have stable HPRT+ phenotype whereas only three clones of series A have stable TK+ phenotype. It is suggested that the recipient cells, LMTK- and A9, differ in their competence for genetic transformation and integration of foreign genes. 相似文献
49.
Phylogenetic screening of the human genome: identification of differentially hybridizing repetitive sequence families 总被引:1,自引:0,他引:1
The phi-screen, a method of phylogenetic screening, can be employed to
detect repetitive sequence families that differentially hybridize between
closely related species. Such differences may involve sequence divergence
or variations in copy number, including total presence versus absence of a
family of repeated DNA. We present the results of a phi-screen comparing
the human genome to that of the prosimian, Galago crassicaudatus. Three
human repetitive families that are divergent or not present in galago have
been detected. One of these families is described in detail; it is similar
among the anthropoids but is present in a lower copy number and/or
divergent form in prosimians. The family is clearly related to the
transposon-like human element (THE) described by Paulson et al. (1985).
THEs have long terminal repeats reminiscent of retroviruses but are unique
in that they have no sequence similarity to known mammalian retroviruses.
The sequence of a solo long terminal repeat, found unassociated with THE
internal sequence, is presented. This family member, THE p2, is bordered by
a 5-bp target-site repeat and is interrupted by the insertion of an Alu
element. A solo THE element sequenced by Wiginton et al. (1986) contains an
insertion of Alu at precisely the same position as does THE p2.
相似文献
50.
V. A. Belyaev M. M. Dubrovin D. A. Kozlov A. A. Terent’ev A. E. Trenin G. V. Sholin 《Plasma Physics Reports》2009,35(8):698-701
Spectra of detached electrons produced in mutual collisions of D− ions in the relative energy range of 1.8−6.1 eV were investigated. In addition to electrons corresponding to conversion of
D− ions into D0 atoms, peaks corresponding to the production of D2 molecules and D2− molecular ions in the ground electronic state were revealed. The existence of D2− ions over a time longer than the period of molecular oscillations was confirmed experimentally for the first time. 相似文献