RFLP tagging of a salt tolerance gene in rice

A salt tolerant rice mutant (M-20) was obtained through selection in vitro. Its tolerance was stably inherited over eight generations and most traints between M-20 and its sensitive original 77–170 (Oryza sativa) were very similar. By deriving an F₂ population of M-20 × 77–170 and splitting every F₂ individual into two parts, with one part planted in normal conditions and another part in saline conditions, the inheritance of salt tolerance in rice was studied. Under normal conditions, there was no apparent segregation among F₂ individuals. Under saline conditions, however, the segregation of traits was obvious. According to our standards, the ratio of salt sensitive:moderately-tolerant:tolerant plants was 25:42:18, in accordance with a 1:2:1 ratio. It suggested that the improvement of salt tolerance in our materials was induced by the mutation of a major tolerant gene which showed incomplete dominance. By use of 130 RFLP probes distributed throughout the rice genome, the gene was tagged by a single copy DNA probe, RG4, which was located on chromosome 7. The genetic distance between the salt tolerant gene and RG4 was 7.0 ± 2.9 cM. Based on the split method, a method which could be currently used to evaluate the damage of salt stress in rice was proposed.     

大鼠不同脑区突触体钙水平的年龄差异

本实验使用荧光指示剂Ｆｕｒａ－２与Ｔｂ~（３＋）,检测了不同年龄组大鼠的不同脑区（海马、皮层、间脑、小脑）突触体内游离钙与膜结合钙水平。结果显示,与青年对照组相比,老年大鼠大部分脑区（海马、皮层、间脑）突触体内游离钙水平显著增高,尤其是海马突触体内游离钙增高极为显著;其突触体膜结合钙水平表现为：海马、小脑两脑区明显升高,而皮层、间脑两脑区明显下降,呈现一种全脑范围内的钙水平失衡。提示动物的衰老与其脑内钙自体平衡失调有关。     

The fragile X mental retardation syndrome protein interacts with novel homologs FXR1 and FXR2.

Fragile X Mental Retardation Syndrome is the most common form of hereditary mental retardation, and is caused by defects in the FMR1 gene. FMR1 is an RNA-binding protein and the syndrome results from lack of expression of FMR1 or expression of a mutant protein that is impaired in RNA binding. The specific function of FMR1 is not known. As a step towards understanding the function of FMR1 we searched for proteins that interact with it in vivo. We have cloned and sequenced a protein that interacts tightly with FMR1 in vivo and in vitro. This novel protein, FXR2, is very similar to FMR1 (60% identity). FXR2 encodes a 74 kDa protein which, like FMR1, contains two KH domains, has the capacity to bind RNA and is localized to the cytoplasm. The FXR2 gene is located on human chromosome 17 at 17p13.1. In addition, FMR1 and FXR2 interact tightly with the recently described autosomal homolog FXR1. Each of these three proteins is capable of forming heteromers with the others, and each can also form homomers. FXR1 and FXR2 are thus likely to play important roles in the function of FMR1 and in the pathogenesis of the Fragile X Mental Retardation Syndrome.     

Cryopreservation of leucocytes of channel catfish for subsequent cytogenetic analysis

Channel catfish leucocytes cryopreserved with glycerol or dimethyl sulphoxide (DMSO) had significantly higher ( P <0.05) viability and recovery rates than did cells cryopreserved with methanol. After 7 days of frozen storage, a 24 to 27% reduction of viability was observed for cells cryopreserved with glycerol; a 25 to 43% reduction for cells frozen with DMSO, and a 67 to 100% reduction for cells frozen with methanol. The concentration of cryoprotectants affected the viability of cryopreserved cells significantly ( p <0.05). The viability reduction was 36% for cells frozen with 5% of cryoprotectants, 30% for cells frozen with 10% of cryoprotectants, and 49% for cells frozen with 15% of cryoprotectants. The viability of cells frozen at the slower rate (-2.7°C min⁻¹) was significantly higher ( p <0.05) than that of cells frozen at the faster rate (-45°C min⁻¹). Best results were obtained for cells cryopreserved with 10% of glycerol or DMSO and frozen at the slower rate. The chromosomes prepared from cells cryopreserved using this procedure were identical to those prepared from fresh cells, and to those reported in the literature for channel Catfish.     

A Nondestructive Method of Determining Bursaphelenchus xylophilus Infestation of Monochamus spp. Vectors

Pine wilt is caused by the nematode Bursaphelenchus xylophilus, which is transported to host trees in the trachea of Monochamus spp. (Coleoptera: Cerambycidae). The study of the relationship between the nematode and its beetle vectors has been hampered by the inability to estimate nematode presence or density within live beetles. This report describes a rapid method for estimating nematode load within live M. carolinensis and M. alternatus by visual examination of the atrium of the first abdominal spiracle. Visual estimates of nematode numbers correlated highly with actual nematode numbers. This method is a timesaving technique for determining relative numbers of B. xylophilus in pine wilt research.     

Characterization and Distribution of a Cloned Rat μ-Opioid Receptor

Abstract: We have cloned and expressed a rat brain cDNA, TS11, that encodes a μ-opioid receptor based on pharmacological, physiological, and anatomical criteria. Membranes were prepared from COS-7 cells transiently expressing TS11 bound [³H]diprenorphine with high affinity (K_D = 0.23 ± 0.04 nM). The rank order potency of drugs competing with [³H]diprenorphine was as follows: levorphanol (K_i = 0.6 ± 0.2 nM) ≈β-endorphin (K_i = 0.7 ± 0.5 nM) ≈ morphine (K_i = 0.8 ± 0.5 nM) ≈ [d -Ala², N-Me-Phe⁴,Gly-ol⁵]-enkephalin (DAMGO; K_i = 1.6 ± 0.5 nM) ? U50,488 (K_i = 910 ± 0.78 nM) > [d -Pen^2,5]-enkephalin (K_i = 3,170 ± 98 nM) > dextrorphan (K_i = 4,100 ± 68 nM). The rank order potencies of these ligands, the stereospecificity of levorphanol, and morphine's subnanomolar K_i are consistent with a μ-opioid binding site. Two additional experiments provided evidence that this opioid-binding site is functionally coupled to G proteins: (a) In COS-7 cells 50 µM 5′-guanylylimidodiphosphate shifted a fraction of receptors with high affinity for DAMGO (IC₅₀ = 3.4 ± 0.5 nM) to a lower-affinity state (IC₅₀ = 89.0 ± 19.0 nM), and (b) exposure of Chinese hamster ovary cells stably expressing the cloned μ-opioid receptor to DAMGO resulted in a dose-dependent, naloxone-sensitive inhibition of forskolin-stimulated cyclic AMP production. The distribution of mRNA corresponding to the μ-opioid receptor encoded by TS11 was determined by in situ hybridization to brain sections prepared from adult female rats. The highest levels of μ-receptor mRNA were detected in the thalamus, medial habenula, and the caudate putamen; however, significant hybridization was also observed in many other brain regions, including the hypothalamus.     

Poly(ADP-Ribose) Synthetase Activation: An Early Indicator of Neurotoxic DNA Damage

Abstract: DNA damage activates a nuclear enzyme poly(ADP-ribose) synthetase (PARS) that facilitates DNA repair by adding multiple ADP-ribose groups to nuclear proteins such as histones and PARS itself. N -Methyl- d -aspartate neurotoxicity may involve DNA damage excessively activating PARS to deplete its substrate NAD, as PARS inhibitors prevent this toxicity. We now show that PARS is rapidly and markedly activated in PC12 cells following treatment with neurotoxic agents, including the amyloid β-protein, hydrogen peroxide, N -methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and its active metabolite N -methyl-4-phenylpyridine (MPP⁺). With MPP⁺, PARS activity is increased fivefold in 1 h and 20-fold by 3 h. By contrast, direct measurement of DNA damage by the terminal-deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay shows no significant increase by 3 h and less than fourfold by 24 h. These findings indicate that PARS activity can provide a simple, sensitive, and early index of DNA damage following neurotoxic insults.     

Cell cycle and cell size dependence of susceptibility to hydrodynamic forces

Exposure of animal cells to intense hydrodynamic forces exerted in turbulent capillary flow, and by controiled agitation and aeration, resulted in preferential destruction of S and G(2) cells and the extent of destruction of these cells was dependent upon the intensity of the action. The loss of these cells was possibly due to their larger size. However, the appearance of large numbers of membrane-bound vesicular structures similar to apoptotic bodies as well as cells with low DNA stainability (in a sub-G(1) peak) suggested that the action of adverse hydrodynamic forces on these large cells may at least in part be to induce an apoptotic response. (c) 1995 John Wiley & Sons, Inc.     

Side-chain accessibilities in the pore of a K+ channel probed by sulfhydryl-specific reagents after cysteine-scanning mutagenesis.

To gain insight into the secondary structure of the ion conduction pathway of a voltage-gated K+ channel, we used sulfhydryl-specific reagents of different diameters to probe amino acid side-chain accessibilities in the pore of the channel after cysteine-substitution mutagenesis. We identified five positions at which modified amino acid side chains are accessible from the aqueous lumen of the external channel vestibule. Covalent coupling of the 2-trimethylammonium-thioethyl group to cysteine thiols leads to position-dependent current reduction, suggesting a gradual narrowing of the pore. The fact that the modified side chains of two adjacent amino acids are reactive is not compatible with the ion conduction pathway forming a regular beta-pleated sheet at these positions. The smaller thiol reagent Cd2+ reacts with modified side chains that are also accessible to the larger (2-trimethylammoniumethyl)methanethiosulfate (MTSET) [corrected]. Our results imply that the outer vestibule of a potassium-selective ion channel narrows over a short distance of three amino acids near a position where a regular beta-structure is unlikely.     

Restriction Fragment Length Polymorphism Mapping of Quantitative Trait Loci for Malaria Parasite Susceptibility in the Mosquito Aedes Aegypti

Susceptibility of the mosquito Aedes aegypti to the malarial parasite Plasmodium gallinaceum was investigated as a quantitative trait using restriction fragment length polymorphisms (RFLP). Two F(2) populations of mosquitoes were independently prepared from pairwise matings between a highly susceptible and a refractory strain of A. aegypti. RFLP were tested for association with oocyst development on the mosquito midgut. Two putative quantitative trait loci (QTL) were identified that significantly affect susceptibility. One QTL, pgs[2,LF98], is located on chromosome 2 and accounted for 65 and 49% of the observed phenotypic variance in the two populations, respectively. A second QTL, pgs[3,MalI], is located on chromosome 3 and accounted for 14 and 10% of the observed phenotypic variance in the two populations, respectively. Both QTL exhibit a partial dominance effect on susceptibility, wherein the dominance effect is derived from the refractory parent. No indication of epistasis between these QTL was detected. Evidence suggests that either a tightly linked cluster of independent genes or a single locus affecting susceptibility to various mosquito-borne parasites and pathogens has evolved near the LF98 locus; in addition to P. gallinaceum susceptibility, this general genome region has previously been implicated in susceptibility to the filarial nematode Brugia malayi and the yellow fever virus.