紫外激光消融过程的等效模型研究

本文引用等效模型,对激光消融过程进行了推导与计算,和实验结果比较表明,所得公式与实验结果能较好相符,可用于描述紫外激光消融过程。     

Evidence that 5-HT2 antagonism elicits a 5-HT3-mediated increase in dopamine transmission

Amperozide, a novel atypical antipsychotic drug with few extrapyramidal side effects, is a strong serotonin₂ (5-HT₂) antagonist but has low affinity for dopamine receptors in vitro. The effect of amperozide on the dopaminergic synapse was studied with an in vivo microdialysis technique using anesthetized male Sprague-Dawley rats. Following implantation of dialysis probes into the striatum and nucleus accumbens (NuAc), amperozide was intravenously infused as six consecutive incremental doses (0.5, 0.5, 1.0, 2.0, 4.0 and 8.0 mg/kg) at intervals of 15 min. From the beginning of drug infusion, perfusates were collected in fractions every 30 min throughout a total period of 120 min. The samples were then immediately analyzed by high-performance liquid chromatography with electrochemical detection. Amperozide induced a dose-related elevation of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindolacetic acid (5-HIAA) levels in both areas.p-Chlorophenylalanine (pCPA) pretreatment abolished the production of 5-HIAA in both areas and attenuated the amperozide-induced rise of DOPAC but not of dopamine. After pretreatment with an intravenous 5-HT₃ antagonist, MDL 72222, the amperozide-induced changes in dopamine, DOPAC and 5-HIAA in both areas were lower than in the saline control group. Preliminary data showed that afterpCPA pretreatment, incremental concentrations of the 5-HT₃ agonist 1-(m-chlorophenyl)-biguanide perfused via the probe also produced significant elevation of dopamine and DOPAC levels in these two areas. Taken together, these results suggest that amperozide may directly block 5-HT₂ receptors in the striatum and NuAc, thereby enhancing 5-HT transmission. The enhanced 5-HT transmission may activate postsynpatic 5-HT₃ receptors located on the dopaminergic terminals, leading to changes in dopamine transmission in these two areas.     

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord

Summary It is well-known that a large number of factors can influence the expression of neuropeptides in the nervous system. In the present study, the effects of unilateral and bilateral irradiation to the rat head and neck on the expression of neuropeptides in the innervation of the submandibular gland and in the ganglionic cells of the submandibular ganglion was examined ten days and six months after treatment. Antisera directed against enkephalin and bombesin and immunohistochemical methods were used. The effects of bilateral irradiation on the staining pattern of various neuropeptides in the cervical spinal cord were also studied. In the submandibular gland and in the submandibular ganglionic cells, there was a markedly increased neuropeptide expression ten days after bilateral treatment, as seen after staining with both antisera used, while no changes occurred after unilateral treatment. Six months after treatment, the pattern of neuropeptide expression in the submandibular gland/ganglion corresponded to that seen in controls. Irradiation did not lead to any changes in the staining pattern of neuropeptides in the spinal cord. The observations show that there is a great complexity in the susceptibility of nervous tissues to radiotherapy with respect to influences on the expression of neuropeptides.     

ISOLATION AND CHARACTERIZATION OF PHASE-SPECIFIC COMPLEMENTARY DNAs FROM SPOROPHYTES AND GAMETOPHYTES OF PORPHYRA PURPUREA (RHODOPHYTA) USING SUBTRACTED COMPLEMENTARY DNA LIBRARIES1

The red alga Porphyra purpurea (Roth) C. Agardh has a life cycle that alternates between shell-boring, filamentous sporophytes and free-living, foliose gametophytes. The significant morphological differences between these two phases suggest that many genes should be developmentally regulated and expressed in a phase-specific manner. In this study, we prepared and screened subtracted complementary DNA (cDNA) libraries specific for the sporophyte and gametophyte of P. purpurea. This involved the construction of cDNA libraries from each phase, followed by the removal of common clones through subtractive hybridization. Sampling of the subtracted libraries indicated that 8–10% of the recombinant colonies in each library were specific for the appropriate phase. Of 20 putative phase-specific cDNAs selected from each subtracted library, eight unique clones were obtained for the sporophyte and seven for the gametophyte. After confirming their phase-specificities by hybridization to gametophyte and sporophyte messenger RNA, these 15 phase-specific cDNAs were sequenced, and the deduced amino acid sequences were used to search protein databanks. Two proteins encoded by the sporophyte-specific cDNAs and two by the gametophyte-specific cDNAs were identified by their similarity to databank entries.     

Protein synthesis is not required for the inhibitory effect of selenite on cell colony formation and RNA synthesis

Selenite has been shown to undergo intracellular metabolism that results in its conversion to other low molecular weight Secontaining species and also to its incorporation into a selenocysteine residue in selenoprotein. In order to investigate whether the incorporation into protein is required for the cytotoxic effects of selenite, we have examined whether inhibition of protein synthesis prevents the inhibitory effect of selenite on the ability of cells to form colonies or to synthesize RNA. We have found that treatment of HeLa cells with cycloheximide inhibited protein synthesis by >90% but had no effect on the inhibitory effect of selenite on cell colony formation or RNA synthesis. Since protein synthesis is not necessary for these cytotoxic effects of selenite they are unlikely to result from an increase in the synthesis of selenoproteins.     

The last 140 ka in the Afro-Asian arid/semi-arid transitional zone

During the last ten years, a great number of geological or other proxy records provided radiocarbon, U/Th or TL dated information on the past climatic oscillations in the arid/semi-arid zones extending between the Atlantic and the Pacific. Comparisons and a synthetic view of these results can now be attempted for the last 140 ka, and compared with global changes, as registered in oceanic or ice cores, and with palaeomonsson models: for this purpose, wide spatial and time scales have to be used. On the whole, arid/humid alternations roughly fit global changes, cold phases corresponding to an extension of the arid areas to the South, warm phases corresponding to the shrinking of the same to the North.

The last interglacial is associated with an increase of precipitation throughout the area considered. Isotopic stage 4 brings no evidence whatsoever of humid conditions. Two wetter episodes are registrated during stage 3. A major rainfall decrease is everywhere associated with the Last Glacial Maximum (21-15 ka in most regions), the arid or semi-arid zones extending several hundred kilometers southwards, relative to the present-day pattern. The two abrupt deglaciation steps and the Younger Dryas are recorded in all of the most sensitive regions, at the margins of the present-day monsoonal range. During the Holocene, the precipitation increases everywhere (by 100–400 mn, relative to the present-day values), the optimum being at 8.5-6.5 ka. A climatic deterioration follows with an irregular pattern of dry/wet episodes, according to the different geographic conditions. The humid phase terminates at 3.5-3 ka in the whole transitional zone.

The major southward shift of the monsoonal precipitation range since its optimum, some 8000 years ago, fits the astronomical neoglacial trend and may possibly be correlated with past stage 5d, although its rapidity and spatial importance may just reflect one of the sharp successive cold/warm variations registered by GRIP during the whole stage 5.     

植物细胞离析酶的制备和应用

用 Aspergillus sp．A-19菌经固体发酵研制成一种新的植物细胞离析酶(SeparatasezA—P)。其离析单细胞的酶活力平均为70 767u／g,有效作用的pH在3．0—7．0,温度为20—45℃。发酵培养基配方是麸皮：桔皮粉：(NH₄)₂SO₄(w／w)为100:100:O．63,料水比为1 :2．0,培养适宜条件为25℃、60小时。     

斑须蝽三代卵块的空间分布和田间抽样技术研究

通过田间调查和计算,明确了斑须蝽三代卵块呈聚集分布,且以负二项分布为主。理论抽样数当t＝1．00,D＝0．3时,n＝13．091/＋63．878,如果防治指标定为百株虫卵块12块时,则最大抽样数为173株,序贯抽样的累积虫卵块数量界限为：T0（N）＝0.12N±0．4735。田间随机取样以平行线和Z字形为最佳。