溅射用铁电陶瓷靶的烧结与显微结构分析

探讨了溅射用铁电陶瓷靶（ＰＺＴ，ＰＬＺＴ）的烧结工艺，并对其显微结构进行了分析。结果表明，采用新的烧结工艺（含保护措施），可以有效地抑制ＰｂＯ的挥发，制备出组织结构及成分均匀、ＰｂＯ含量正常、致密度较高、不变形的符合磁控溅射要求的铁电陶瓷烧结靶。     

Analysis of the relationship between age of larvae at mutagen treatment and frequency and size of spots in the wing somatic mutation and recombination test inDrosophila melanogaster

The relationship between the induction of mutant clones and the time of mutagen treatment was studied in the somatic mutation and recombination test (SMART) in wing cells ofDrosophila melanogaster. Larvae trans-heterozygous for the recessive marker mutations multiple wing hairs (mwh) and flare (flr) were produced. Batches of these larvae were then treated with mutagen at different ages spanning all three larval instars. Methyl methanesulfonate was fed acutely for 2 h by immersing the larvae in a solution of the mutagen mixed with powdered cellulose. Wings of the surviving adult flies were mounted and scored for the presence of spots. The frequency and size of single and twin spots were recorded separately. Twin spots are produced exclusively by mitotic recombination, whereas single spots can results from various types of mutational and exchange events. There exists a clear correlation between time of induction and frequency as well as size of the single spots. In young larvae only few but very large spots are induced, whereas in older larvae the frequencies are considerably increased but the sizes are smaller. The twin spots show a different relationship. Practically no twin spots are found in very young and in very old larvae. The results demonstrate that in the wing spot test the optimal age of the larvae for mutagen treatment is 72 h.     

Mutations in a human homologue of Drosophila crumbs cause retinitis pigmentosa (RP12).

Retinitis pigmentosa (RP) comprises a clinically and genetically heterogeneous group of diseases that afflicts approximately 1.5 million people worldwide. Affected individuals suffer from a progressive degeneration of the photoreceptors, eventually resulting in severe visual impairment. To isolate candidate genes for chorioretinal diseases, we cloned cDNAs specifically or preferentially expressed in the human retina and the retinal pigment epithelium (RPE) through a novel suppression subtractive hybridization (SSH) method. One of these cDNAs (RET3C11) mapped to chromosome 1q31-q32.1, a region harbouring a gene involved in a severe form of autosomal recessive RP characterized by a typical preservation of the para-arteriolar RPE (RP12; ref. 3). The full-length cDNA encodes an extracellular protein with 19 EGF-like domains, 3 laminin A G-like domains and a C-type lectin domain. This protein is homologous to the Drosophila melanogaster protein crumbs (CRB), and denoted CRB1 (crumbs homologue 1). In ten unrelated RP patients with preserved para-arteriolar RPE, we identified a homozygous AluY insertion disrupting the ORF, five homozygous missense mutations and four compound heterozygous mutations in CRB1. The similarity to CRB suggests a role for CRB1 in cell-cell interaction and possibly in the maintenance of cell polarity in the retina. The distinct RPE abnormalities observed in RP12 patients suggest that CRB1 mutations trigger a novel mechanism of photoreceptor degeneration.     

Susceptibility to testicular germ-cell tumours in a 129.MOLF-Chr 19 chromosome substitution strain.

The identification of genes that control susceptibility to testicular germ-cell tumours (TGCTs), the most common cancer affecting young men, has been difficult. In laboratory mice, TGCTs arise from primordial germ cells in only the 129 inbred strains, and susceptibility is under multigenic control. The spontaneously arising mutation Ter (ref. 5) on mouse chromosome 18 (Refs 6,7) increases TGCT frequency on a 129/Sv background. We originally used Ter in genetic crosses to identify loci that control tumorigenesis. A genome scan of tumour-bearing progeny from backcrosses between the 129/Sv-Ter/+ and MOLF/Ei strains provided modest evidence that MOLF-derived alleles on chromosome 19 enhance development of bilateral TGCTs (ref. 9). To obtain independent evidence for linkage to the MOLF chromosome, we made an autosomal chromosome substitution strain (CSS; or 'consomic strain') in which chromosome 19 of 129/Sv+/+ was replaced by its MOLF-derived homologue. The unusually high frequency of TGCTs in this CSS (even in the absence of the Ter mutation) provides evidence confirming the genome survey results, identifies linkage for a naturally occurring strain variant allele that confers susceptibility to TGCTs and illustrates the power of CSSs in complex trait analysis.     

Trail-following responses ofLeptogenys diminuta to stereoisomers of 4-methyl-3-heptanol

Behavioral tests carried out with the four stereoisomers of 4-methyl-3-heptanol revealed thatLeptogenys diminuta ants respond specifically only to the (3R, 4S)-isomer.     

Identification of 2-deoxyecdysone from the mite,Tyrophagus putrescentiae

2-Deoxyecdysone was purified from the miteTyrophagus putrescentiae and monitored by a radioimmunoassay. The compound was identified by GC-MS and LC-MS. This is the first report of an endogenous ecdysteroid from a mite.     

Involvement of D-amino acid oxidase in elimination of D-serine in mouse brain

The physiological role of D-amino acid oxidase (EC 1. 4. 3. 3) in mouse brain is described. The presence of D-enantiomers of neutral common amino acids was surveyed in the brain. D-serine was shown to be present at high concentration only in regions where the enzyme activity was low. In normal mice whose D-amino acid oxidase activity was much higher in the cerebellum than in the cerebrum, free D-serine content was apparently lower in the cerebellum than in the cerebrum. In mice of a mutant strain lacking D-amino acid-oxidase activity, the free D-serine level was remarkably high both in the cerebrum and cerebellum. The results suggest that the enzyme is involved in the elimination of free D-serine in the cerebellum.     

A potent attractant of zoospores ofAphanomyces cochlioides isolated from its host,Spinacia oleracea

A highly potent attractant of zoospores ofAphanomyces cochlioides, a causal fungus of the root rot disease of spinach (Spinacia oleracea), was isolated from spinach roots, and its structure was determined by spectroscopic evidence and chemical synthesis as cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone,1). A chromosorb particle prepared by soaking in solution of1 showed a potent attracting activity toward the zoospores using concentrations of1 above 10^–9 or 10^–10 M.     

The presence of free D-serine,D-alanine and D-proline in human plasma

Twelve neutral free amino acids, i. e., serine, threonine, glutamine, asparagine, alanine, proline, methionine, tyrosine, valine, leucine, isoleucine and phenylalanine, were surveyed for the presence of D-enantiomers in plasma samples from patients with renal diseases and from normal subjects. D-serine, D-alanine and D-proline were found in the patient's plasma. The highest concentrations (D/L ratio) of D-serine, D-alanine and D-proline were 0.2362, 0.2087 and 0.0986, respectively. The sum of the contents of the three D-amino acids in a plasma sample correlated with the serum creatinine level of the subject. No D-amino acid was shown to be present in the plasma proteins.