Variation in ptaquiloside content in bracken (Pteridium esculentum (Forst. f) Cockayne) in New Zealand

AIM: To examine stands of bracken fern (Pteridium esculentum) from throughout New Zealand for the presence and concentration of ptaquiloside (Pta), and to compare the presence and/or concentrations of Pta in areas where bovine enzootic haematuria (BEH) and/or acute haemorrhagic syndrome (AHS) has been known to occur with those where BEH/AHS has not been recorded.

METHODS: Stands of bracken fern were sampled from 275 sites throughout New Zealand. Sixty-two stands were from a regional survey predominantly from the Waikato and Coromandel regions, 27 were from a farm in the King Country where BEH/AHS had been investigated previously, and 186 were from a national survey of the North and South Islands. Sampling sites were from a mixture of grazed paddocks, roadsides, and forest and bush areas. Samples comprised whole young fronds, the tops of unfurling young fronds, or, for the Regional Survey, mature green fronds from the previous season. Pta was extracted from the samples, and measured using high-performance liquid chromatography. Information on the occurrence of BEH/AHS at specific locations was obtained from published information and records from animal health laboratories in New Zealand.

RESULTS: The 275 samples contained widely varying concentrations of Pta. In the Farm Survey, concentrations ranged from 280–13,300 (mean 3,800) µg/g (on a dry-weight basis) in the 63% of samples that contained Pta. A high proportion of samples from the Regional and National Surveys covering large areas of the country contained no detectable levels of Pta. The majority (61%) of samples from these two surveys which contained Pta were from areas where BEH/AHS was reported to occur. Combining data from all surveys, in areas with reported BEH/AHS, 42% of samples collected contained Pta, compared with 6% where BEH/AHS was not known to occur.

CONCLUSIONS: Concentrations of Pta in bracken in New Zealand vary greatly, and in a high proportion of stands Pta is not found. A higher incidence of Pta, and some very high concentrations, are found in areas where BEH/AHS was known to occur.     

A mutant of Arabidopsis lacking a chloroplast-specific lipid

In order to investigate the functional significance of membrane lipid unsaturation, we have isolated a series of mutants of Arabidopsis thaliana which are deficient in particular membrane fatty acids. The first of these mutants completely lacks Delta3-trans-hexadecenoate, an acyl group that until now has been thought to play an important role in the structure or function of thylakoid membranes in photosynthetic eukaryotes. The apparent absence of any marked physiological effect of the mutation illustrates the potential of this approach to the analysis of membrane structure and function.     

管碟法测定生物效价影响因素的探讨及改进

《中国兽药典》（2005年版）收载的兽用抗生素药品效价的微生物检定包括两种方法,即管碟法和浊度法。目前多数使用者仍以管碟法为主。管碟法作为抗生素效价测定的经典方法,具有它的优点,但此方法操作步骤复杂,试验影响因素多,需要从每个环节严格控制,才能得到与真值更为接近的结果。笔者结合日常工作实践,对管碟法测定抗生素生物效价过程中的多种影响因素进行探讨及改进,使测定条件得到了较好的控制,有利于提高效价测定结果的精密度和准确度。     

Inactivation of the BSE agent by the heat and pressure process for manufacturing gelatine

Dietary exposure to the bovine spongiform encephalopathy (BSE) agent is the probable cause of variant Creutzfeldt-Jakob disease in people. The industrial manufacturing process for the production of gelatine and colloidal protein by the heat and pressure process was downscaled accurately and its capacity to remove or inactivate bse infectivity was investigated. Gelatine was made from bones experimentally contaminated with mouse brain infected with the 301V strain of mouse-passaged bse agent in which the infective titre was 10(8.7) ID50/g. No infectivity was detected in the extracted protein (> or =10(0.45) ID50/g), and the calculated clearance factor was 10(6.5) ID50 or more.     

Tryptophan operon of Escherichia coli: regulatory behavior in Salmonella typhimurium cytoplasm

Hybrids hemizygous for the tryptophan genes were prepared by episomal transfer of an Escherichia coli element into Salmonella typhimurium. Regulation of enzyme production by hybrids carrying wild-type E. coli genes in response to changes in the growth medium occurs in precisely the same manner as in haploid E. coli wild type. Mutant alleles of the anthranilate synhetase gene of E. coli which prevent derepression in E. coli function identically in S. typhimurium. At least one Salmonella tryptophan regulatory gene unlinked to the structural genes is known. Any dijferences which may exist between the tryptophan regulatory genes of E. coli and Salmonella have little effect on the regulation of enzyme formation in hybrids.     

The role of translocation in selectivity of herbicides with reference to MCPA and MCPB

The distribution of 2.5 mM-[¹⁴C]MCPA

1 MCPA = (2-methyl-4-chlorophenoxyacetic acid).

and [¹⁴C]MCPB

2 MCPB = (4-(2-methyI-4-chlorophenoxy) butyric acid).

formulated as sodium salts with 0.05% tergitol, have been investigated when applied to an isolated leaf/agar block sink system of Vicia faba L. Results are presented which show the effect on absorption and translocation of method of application, age of treatment leaf, treatment period, pretreatment with 5 μM ATP and removal of cuticle wax by chloroform wipe treatment. Significant negative correlations between cuticle wax fixation/translocation and leaf tissue content/translocation were recorded for both compounds, particularly MCPB, suggesting the involvement of both physicochemical and metabolic components in the process of absorption and translocation. The nature of the mechanisms involved was further investigated using isolated cuticle/epidermal systems and tightly-coupled mitochondria isolated from roots of V. faba L. The results suggest that non-movement of MCPB in this species is largely due to its enhanced retention within the cuticle and to the fact that it is a more effective uncoupler of oxidative phosphorylation than MCPA. The importance of these findings in terms of the relative efficiency of translocation of MCPA and MCPB when applied in vivo is discussed.     

Recent climate observations compared to projections

We present recent observed climate trends for carbon dioxide concentration, global mean air temperature, and global sea level, and we compare these trends to previous model projections as summarized in the 2001 assessment report of the Intergovernmental Panel on Climate Change (IPCC). The IPCC scenarios and projections start in the year 1990, which is also the base year of the Kyoto protocol, in which almost all industrialized nations accepted a binding commitment to reduce their greenhouse gas emissions. The data available for the period since 1990 raise concerns that the climate system, in particular sea level, may be responding more quickly to climate change than our current generation of models indicates.     

The Interdependence of Deformational and Thermal Processes in Mountain Belts

Crustal temperatures within collisional orogens are anomalously high compared with temperatures at comparable depths in stable continents, which is evidence of thermal processes that are fundamental to orogenesis. These temperatures can be explained by the redistribution of crust enriched in heat-producing elements through the accretion of crust from the down-going plate to the upper plate and surface erosion. With the use of geologically reasonable rates, the model results predict high temperatures (over 600°C) and inverted upper-plate geotherms (about 100°C over 20 kilometers) at shallow depths (20 to 40 kilometers) by 25 to 35 million years after collision. This study emphasizes the interdependence of deformational, surficial, and thermal processes.     

Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids

The origin of a new diploid species by means of hybridization requires the successful merger of differentiated parental species' genomes. To study this process, the genomic composition of three experimentally synthesized hybrid lineages was compared with that of an ancient hybrid species. The genomic composition of the synthesized and ancient hybrids was concordant (rs = 0.68, P < 0.0001), indicating that selection to a large extent governs hybrid species formation. Further, nonrandom rates of introgression and significant associations among unlinked markers in each of the three synthesized hybrid lineages imply that interactions between coadapted parental species' genes constrain the genomic composition of hybrid species.