硒对糖尿病大鼠骨密度影响的初步研究

本试验通过给SD大鼠注射链尿佐菌素(streptozotocin,STZ)破坏其胰脏以复制糖尿病模型,通过在饲料中添加不同浓度和形态的硒研究了硒对骨密度(BMD)的影响。结论:糖尿病大鼠较易继发骨质疏松,其骨密度下降以胫骨、肱骨出现最早;低硒组患鼠骨密度下降加快;高硒组能延缓患鼠骨密度下降;硒的形态对糖尿病患鼠骨密度影响差异不显著(P>0.05)。     

调温移栽地黄脱毒试管苗探讨

采用调节空间温度的方法移栽地黄脱毒试管苗,可使移栽苗成活率达到９５ ％ 以上。     

Observed dynamics of ponderosa pine (<Emphasis Type="Italic">Pinus ponderosa</Emphasis> var. <Emphasis Type="Italic">ponderosa</Emphasis> Dougl. ex Laws.) seedling recruitment in the Cascade Range,USA

An observational study of early seedling establishment (first 1–2 summers after emergence) was conducted in four ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) stands east of the Cascade Range crest in central Oregon, USA. Newly emerged ponderosa pine seedlings were identified at the start of summer and were monitored through their second summer; a subsequent cohort of seedlings was identified and monitored for one summer. About 3% of the viable seed that was produced resulted in new seedlings. Mortality was substantial immediately following emergence. Most seedlings emerged without shading from understory vegetation, but few survived. Most seedlings alive after one year had emerged beneath live cover; by the end of two summers only shaded seedlings were alive. 63–85% of new seedlings initiated in clusters attributed to rodent caching, and seedlings originating in clusters remained a substantial proportion of the cohort (60%) after two seasons. Results suggest that understory vegetation in these types of stands facilitates the recruitment of ponderosa pine seedlings, most likely by buffering them against environmental stressors during the seedling establishment phase. They also reveal that seed caching rodents are highly active in seed redistribution and can exert a lasting influence on seedling recruitment.     

浇灌方式对白肋烟根系发育及成活率的影响

为了研究水份对白肋烟根系发育及成活率的影响,采用田间试验研究手段,设置5种不同的浇灌方式,通过对土壤含水量、土壤温度、新根数、心叶大小、成活率等进行比较研究,定量地描述了水份与根系生长之间的动态关系。结果表明:处理3土壤水份含量较高,夜间地温较高,移栽后不萎蔫,亩产值和亩产量最高,原烟外观质量颜色近红黄,身份适中,结构疏松,光泽鲜明,综合表现较好。其次是处理5。     

进城农民工生存状况与意愿的研究——以广州番禺区为例

从广州番禺区随机抽取600名农民工作为问卷调查对象,通过研究发现,当前农民工的生存状况不容乐观,住房、就业、福利等方面存在诸多问题。     

Summer planting performance of white spruce 1 + 0 container seedlings affected by nursery short-day treatment

Impacts of nursery short-day treatments on the survival, growth and needle damage of about 5,000 1 + 0 container white spruce (Picea glauca [Moench] Voss) seedlings from a single seedlot were studied for two growing seasons following planting on July 22, 1999 at four boreal reforestation sites in Northern Alberta, Canada of varying soil texture, drainage, aspect, slope, and slope position. Each site was separated into two areas that were site-prepared by either ripping or mounding. When seedlings reached a height of about 20 cm under normal greenhouse growth conditions, the seedlings from different germination dates over a 7-week period were exposed to one of five different conditioning treatments (T), mainly through varying the duration of 12-h short-day exposure to 0 (T0), 3 (T3), 7 (T7), 10 (T10), or 15 (T15) days followed by different periods of reduced N supply. N-reduction produced few differences in needle nutrient concentrations and so was not considered a likely cause of differences in field performance. The treatments progressively (from T0 to T15) increased tolerance to drought and frost, and resulted in a similar seedling size for T3, T7 and T10 (planting height of 21 cm and ground diameter of 2.9 mm) although T0 seedlings were smaller (20 cm) and T15 taller (24 cm). The weather in 1999 was dry, particularly in the weeks immediately before and after planting, but relatively moist and favorable in 2000 and 2001 apart from one major frost event (−7°C) in May 2000. Survival, growth and needle damage varied substantially among sites and short-day treatments, and the treatment differences were largely consistent across the four sites. In general the growth was better on the ripped than on the mounded areas. Seedlings in T7 (intermediate tolerance) survived and grew best in the first year but T0 (actively growing) did best during the second year. After 2 years, no differences were observed among T0, T3 and T7 in mortality (18%) and total height growth (15 cm). However, T10 and T15 had higher mortality (24 and 43%), and lower height growth (12 and 10 cm, respectively). The percentage of seedlings showing very severe needle damage after 2 years increased from T0 through T15 (14–33%). New root egress in the field also differed significantly among treatments and was positively and highly correlated with survival rate and growth. These results suggest that a longer short-day regime, as in T10 or T15, may be counterproductive and a shorter regime may be more effective in improving the performance of summer-planted white spruce seedlings.     

Testicular alterations in cryptorchid/orchiopexic rats chronically exposed to acrylamide or di-butyl-phthalate

Exposure of Sprague-Dawley (SD) rats to acrylamide (AA) or di-butyl-phthalate (DBP) from the 12th gestational day to the 16th postnatal week (PNW) has been shown to reduce the effectiveness of orchiopexy in recovering the testicular alterations associated with experimental cryptorchidism established at weaning. Herein, we provide information about the long-term effects of AA or DBP on the testes of cryptorchid/orchiopexic rats. Male offspring exposed in utero to 10 mg/kg/day AA or 500 mg/kg/day DBP underwent bilateral surgical cryptorchidism at the 3rd PNW and orchiopexy at the 6th week, with continuous exposure to the chemicals through diet until the 58th week. Regardless of the test chemical, there were severe qualitative/quantitative alterations in the seminiferous tubules and increased numbers of Leydig cells. There was an increase and decrease in the number of tubules with c-Kit- and placental alkaline phosphatase-labeled germ cells, respectively, as compared to those in the control group, suggesting an imbalance between apoptosis and cell proliferation processes. The histological scores of the testicular lesions at the end of this one-year study were higher than those in the previous 16-week study, indicating that exposure of rats to the toxicants AA or DBP enhanced the testicular alterations induced by the chemicals beginning at the intra-uterine life, and impaired the effectiveness of orchiopexy in restoring the testes to normal morphology. Although the present experimental protocol does not completely replicate the natural human undescended testes, our findings may contribute to understanding the alterations occurring in cryptorchid/orchiopexic testes potentially exposed to exogenous chemicals for extended periods.     

Influence of Pesticides on UDP-glucuronosyltransferase in Rat Liver Microsomes

Fifteen pesticides, representatives of different chemical groups, were tested for their inhibitory effect on the glucuronidation of 4-nitrophenol (4-NP) and phenolphthalein (PPh) by rat liver microsomes. Three herbicides (simazine, chlorsulfuron, tribenuron-methyl), two insecticides (dioxacarb, carbaryl) and one fungicide (zineb) significantly decreased the UDP-glucuronosyltransferase (UDPGT) activity. The carbamate insecticide dioxacarb was found to be the most potent inhibitor, at 1 mM concentration suppressing 4-NP-UDPGT activity completely, and reducing by 55% the activity associated with the conjugation of PPh. One millimole simazine and carbaryl affected only 4-NP glucuronidation, while chlorsulfuron and zineb exerted a marked inhibition of both 4-NP and PPh conversion. Concentrations of 0·1 mM carbaryl, dioxacarb and zineb were still inhibitory against 4-NP-UDPGT, with zineb producing 40% inhibition of PPh glucuronidation. As a whole, UDPGT isoforms conjugating PPh were less sensitive to the agrochemicals tested. Kinetic studies with dioxacarb, chlorsulfuron and carbaryl revealed a mixed type of inhibition with respect to the acceptor substrate 4-NP, with apparentK_i values of 70 μM , 120 μM and 160 μM , respectively.     

Recruitment of ponderosa pine seedlings in the Cascade Range

Abiotic stresses on seedling regeneration in xeric ecosystems are great, hence recruitment processes can be facilitated by stand factors that ameliorate the germinant-scale microenvironment. An experiment was conducted on the eastern slope of the Cascade Range to test the effects of shrub cover, simulated seed caching, and substrate on the recruitment of Pacific ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) seedlings. Failure rates of seeds sowed in exclosures were large, with less than 30% emerging as germinants in the spring following fall sowing. Simulated seed caching improved emergence rates by more than sevenfold and was responsible for 88% of all spring germinants. Emergence rates were lowest from uncached seeds on litter. Just 16% of the crop survived the summer and fall to the month of November, or less than 5 months after emergence. Shrub cover did not affect emergence rates, but establishment rates were higher: seedlings beneath shrubs succumbed to desiccation at a slower rate than unshaded seedlings. By August there were 2.3 times more survivors at shrub-shaded sites than unshaded sites, and by the end of fall, when seedlings were considered established, more than 78% existed beneath shrubs. This study provides evidence that the natural recruitment of ponderosa pine seedlings is facilitated by the occurrence of the species’ common shrub associates.