一阶导数光谱法测定猫豆中左旋多巴的含量

川一阶导数光谱法测定猫豆中主旋多巴的含量,可以排除无关杂质吸收的干扰,省去复杂的分离提取步骤。试验结果表明:相关系数达0.9999,平均回收率101.5％,重现性较好。     

高效液相色谱法测定猫豆中左旋多巴的含量

本文用高效液相色谱法测定了猫豆中主旋多巴［Ｌｅｖｏｄｏｐａ］的含量。考察了加样回收率为９８．７０％,变异系数为１．９９％。     

The effects of glacial atmospheric CO2 concentrations and climate on isoprene emissions by vascular plants

Isoprene (C₅H₈) emissions by terrestrial vegetation vary with temperature and light intensity, and play an important role in biosphere–chemistry–climate interactions. Such interactions were probably substantially modified by Pleistocene climate and CO₂ cycles. Central to understanding the nature of these modifications is assessment and analysis of how emissions changed under glacial environmental conditions. Currently, even the net direction of change is difficult to predict because a CO₂‐depleted atmosphere may have stimulated emissions compensating for the negative impacts of a cooler climate. Here, we address this issue and attempt to determine the direction of change from an experimental standpoint by investigating the interaction between isoprene emissions and plant growth of two known isoprene‐emitting herbaceous species (Mucuna pruriens and Arundo donax) grown at glacial (180 ppm) to present (366 ppm) CO₂ levels. We found a significant enhancement of isoprene emissions per unit leaf area in M. pruriens under subambient CO₂ concentrations relative to ambient controls but not for A. donax. In contrast, canopy emissions remained unaltered for both plant species because enhanced leaf emissions were offset by reductions in biomass and leaf area. Separate growth experiments with M. pruriens revealed that lowering day/night temperatures by 5°C decreased canopy isoprene emissions irrespective of the CO₂ level. Incorporation of these results into a simple canopy emissions model highlights their potential to attenuate reductions in the total isoprene flux from forests under glacial conditions predicted by standard models.     

Aluminium avoidance by Mucuna pruriens

The hypothesis was tested that the avoidance of acid subsoil by the velvet bean Mucuna pruriens is based on a mechanism acting on the whole root system rather than on individual roots. In a split-root experiment with circulating nutrient solution the growth of plants with Al-containing (+/+) or Al-free (0/0) solution on both sides of the root system was compared with that of plants which had a choice (0/+). Two levels of Al (110 and 185 μ M ) were tested at two levels of Ca (50 and 1250 μ M ). In the 185 μ M Al treatment the concentration of monomeric Al varied between 53 μ M , directly after refreshing the solution, and 5 μ M at harvest time.
An external Al concentration of 110 μ M had no effect on shoot and root dry weight, while 185 μ M Al applied to both sides of the root system (+/+) increased root dry weight and reduced shoot dry weight and shoot/root ratio, compared with the 0/0 control. Application of 185 μ M Al to half of the roots, ied to a significant shift in root growth in favour of the control side; this response is described here as Al avoidance. On the basis of total root length, root dry weight and root surface area, the ratio of 0/+ roots was 3.1, 2.8 and 2.4, respectively.
Al avoidance at 185 μ M Al was confirmed in another experiment, in which root response was measured to a local P source, supplied in a third compartment containing only KH₂PO₄. A significant increase in root length and dry weight in this compartment was observed, when other roots of the same plant were growing in the presence of Al. This result indicates that Al avoidance by Mucuna roots is related to P preference.     

Pilot study to assess the validity of the single assessment process as a screening tool for dental treatment needs in older people

Objective: To assess the feasibility of using a questionnaire‐based needs assessment tool (D‐E‐N‐T‐A‐L) to screen for dental treatment need as part of the single assessment process (SAP) for older people in Sheffield. Materials and methods: Test validation study comparing questionnaire‐assessed and normative need in two consecutive samples of older adults: 48 living at home in the transition phase of older age and 29 frail older adults living in care homes. Each answered the six D‐E‐N‐T‐A‐L questions as part of SAP and a dental examination was carried out within 2 weeks in participants’ homes. Question‐defined need was then compared to the normative need. Results: Questionnaire‐defined and normative need were high in both the transitional group (83% and 90% respectively) and the frail group (83% and 62%). These high levels of need meant that the sensitivity and positive predictive values of D‐E‐N‐T‐A‐L were high, but the specificity and negative predictive values were low. Conclusion: The high levels of need in these patient groups suggests that preliminary questionnaire‐based screening is an unnecessary step. A clinical examination of all older people undergoing SAP may be necessary. Further research may be warranted on the use of questionnaires to assess dental treatment needs among people with different attendance patterns.     

中国豆科一稀见属及一裸名

本文论述中国豆科一稀见属,镰瓣豆属及一裸名,宁油麻藤。     

Isolation of Tyrosinase From Bovine Eyes

Pigmented tissues from bovine eye were used as a source for isolation of tyrosinase from normal melanocytes. Tyrosinase is highly hydrophobic and the isolation procedure is mainly based on the use of hydrophobic interaction chromatography. The bovine enzyme is, in contrast to the human melanoma tyrosinase, mainly soluble. The predominant part of the ocular enzyme from cow has a molecular weight and isoelectric behavior similar to that of the soluble tyrosinase in the human melanoma cells. The N-terminal amino acid sequence of isolated bovine tyrosinase was determined by automated Edman degradation. The N-terminal amino acid sequence from normal bovine tyrosinase was identical to the sequence of an N-terminal region of mouse melanoma tyrosinase predicted from a c-DNA clone by Kwon et al. (1988). The amino acid sequence of bovine tyrosinase shows homology to that of human tyrosinase (Wittbjer et al., 1989), but three amino acids of the 16 residues determined by us differed. Histidine was the N-terminal amino acid.