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1.
Jaap J. Beintema 《Journal of the history of biology》2008,41(1):159-165
Albert (von) Szent-Györgyi started his studies on biological oxidation processes – which also resulted in the discovery of vitamin C, for which he received the Nobel Price in 1937 – in the Laboratory of Physiology of the University in Groningen in 1922–1926. These studies were later continued in Cambridge (UK) and Szeged (Hungary). When he had already received the invitation as well as the financial means to come and work in Cambridge, he still did experiments in Groningen to find out whether the adrenal extract, isolated by him and later found to be a major source of vitamin C, contained the hormone essential for the survival of cats whose adrenals were removed. He was rather upset by the negative results of this experiment, judging by the recollections of a former student of his. This history constitutes an interesting example of the difference between serendipitous discovery and planned invention. 相似文献
2.
Summary To explain the decline of Hippopha? scrub in the vegetation succession in the dunes of The Netherlands, the growth and nodulation
of Hippopha? plants grown in pots, using soil from an early stage (site AH) and a post-optimum stage (site HP), were investigated.
In HP-soil nodulation, yield, and the nitrogen and phosphorus content of test plants were always lower and the number of necrotic
nodules and the dry matter content were always higher than in AH-soil, even after inoculation with crushed nodules and the
addition of a nutrient solution. Plants in HP-soil also had darker roots, less root hairs, a higher number of short lateral
roots and a higher percentage of dead roots than those in AH-soil. These characteristics of adverse growth conditions disappeared
upon ignition or gamma-irradiation of HP-soil.
Possible explanations of these results are discussed. The degeneration of Hippopha? scrub cannot be ascribed to the age of
the plants, the absence of sufficient infective endophyte particles or to abiotic factors such as unfavourable physical (particle
size) or chemical soil conditions but is caused by biotic factors. No indications were obtained that plant-pathogenic fungi
and bacteria are involved. HP-soil in contrast to AH-soil, however, contained large numbers of the nematodeLongidorus sp., a species known to cause root deformations. The conclusion was that this nematode is one of the biotic factors involved
in the degeneration of the Hippopha? scrub. This degeneration is due to a restriction of the root system resulting in a low
phosphate uptake, a low nodulation capacity and, as a consequence, a low nitrogen content. The results demonstrate that biotic
soil factors are important in influencing succession in higher plant communities. 相似文献
3.
Bromoacetaldehyde (BAA) was used to study the secondary structure of DNA in lambda-phage particles. It was determined that about 1% of the adenines in the intraphage lambda-DNA reacts readily with BAA, thus, they are placed in DNA sites with disturbed complementary interactions. These adenines are close to the tryptophan residues of the phage protein. Fluorescence emission of epsilon A in the intraphage DNA is dramatically quenched. This, apparently, indicates the interaction between epsilon A and Trp- and/or Tyr- and/or Met-residues of phage protein. 相似文献
4.
5.
Carbonic anhydrases (CA, EC 4.2.1.1.) catalyze reversible hydration of CO2 to HCO3?+H+. Bicarbonate transport proteins, which catalyze the transmembrane movement of membrane-impermeant bicarbonate, function in cooperation with CA. Since CA and bicarbonate transporters share the substrate, bicarbonate, we examined whether novel competitive inhibitors of CA also have direct inhibitory effects on bicarbonate transporters. We expressed the human erythrocyte membrane Cl?/HCO3? exchanger, AE1, in transfected HEK293 cells as a model bicarbonate transporter. AE1 activity was assessed in both Cl?/NO3? exchange assays, which were independent of CA activity, and in Cl?/HCO3? exchange assays. Transport was measured by following changes of intracellular [Cl?] and pH, using the intracellular fluorescent reporter dyes 6-methoxy-N-(3-sulfopropyl)quinolinium and 2′,7′-bis-(2-carboxyethyl)-5-(and-6)carboxyfluorescein, respectively. We examined the effect of 16 different carbonic anhydrase inhibitors on AE1 transport activity. Among these 12 were newly-reported compounds; two were clinically used non-steroidal anti-inflammatory drugs (celecoxib and valdecoxib) and two were anti-convulsant drugs (topiramate and zonisamide). Celecoxib and four of the novel compounds significantly inhibited AE1 Cl?/NO3? exchange activity with EC50 values in the range 0.22–2.8 μM. It was evident that bulkier compounds had greater AE1 inhibitory potency. Maximum inhibition using 40 μM of each compound was only 22–53% of AE1 transport activity, possibly because assays were performed in the presence of competing substrate. In Cl?/HCO3? exchange assays, which depend on functional CA to produce transport substrate, 40 μM celecoxib inhibited AE1 by 62±4%. We conclude that some carbonic anhydrase inhibitors, including clinically-used celecoxib, will inhibit bicarbonate transport at clinically-significant concentrations. 相似文献
6.
Complex chromosomal rearrangements are very rare chromosomal abnormalities. Individuals with a complex chromosomal rearrangement can be phenotypically normal or display a clinical abnormality. It is believed that these abnormalities are due to either microdeletions or microduplications at the translocation breakpoints or as a result of disruption of the genes located in the breakpoints. In this study we describe a 2-year-old child with mental retardation and developmental delay in whom a de novo apparently balanced exceptional complex chromosomal rearrangement was found through conventional cytogenetic analysis. Using both cytogenetic and FISH analysis, the patient's karyotype was found to be: 46,XY,der(5)t(5;7)(p15.1;7q34),t(5;8)(q13.1;8q24.1)dn. A large, clinically significant deletion which encompassed 887.69 kb was detected at the 5q12.1–5q12.3 (chr5:62.886.523–63.774.210) genomic region using array-CGH. This deleted region includes the HTR1A and RNF180 genes. This is the first report of an individual with an apparently balanced complex chromosomal rearrangement in conjunction with a microdeletion at 5q12.1–5q12.3 in which there are both mental-motor retardation and dysmorphia. 相似文献
7.
Nguyen Thi Dieu Thuy Nguyen Thi Thu Nguyen Giang Son Le Thi Thu Ha Vo Khanh Hung Nguyen Thao Nguyen Do Vo Anh Khoa 《Microbiology and immunology》2013,57(7):518-526
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important swine pathogens because it is highly infectious and causes economic losses due to decreased pig productivity. In this study, the 603 bp complete major envelope protein encoding gene (ORF5) of 32 field PRRSV isolates from Vietnam collected during 2008–2012 were sequenced and analyzed. Multiple nucleotide (nt) and deduced amino acid (aa) alignments of ORF5 were performed on the 32 isolates: the representative strains (European and North American genotypes), Chinese strains available in GenBank and vaccine strains licensed for use in Vietnam. The results showed 94.8–100.0% nt identity and 94.0–100% aa similarity among the 32 isolates. These isolates shared similarities with the prototype of the North American PRRSV strain (VR‐2332; nt 87.8–89.3%, aa 87.5–90.0%), and Lelystat virus, the prototype of the European PRRSV strain (LV; nt 61.1–61.9%, aa 55.1‐57.0%). There was greater similarity with QN07 (nt 96.5‐98.5%, aa 96.0‐99.0%) from the 2007 PRRS outbreak in QuangNam Province, CH‐1a (nt 93.2–95.1%, 91.5–93.5%) isolated in China in 1995 and JXA1 (nt 96.5–98.6%, aa 95.0–98.0%), the highly pathogenic strain from China isolated in 2006. The Vietnamese isolates were more similar to JXA1‐R (nt 96.5–98.6%, aa 95.0–98.0%), the strain used in Chinese vaccines, than to Ingelvac MLV/BSL‐PS (nt 87.2–89.0%, aa 86.0–89.0%). Phylogenetic analysis showed that the 32 isolates were of the North American genotype and classified into sub‐lineage 8.7. This sub‐lineage contains highly pathogenic Chinese PRRSV strains. This study documents genetic variation in circulating PRRSV strains and could assist more effective use of PRRS vaccines in Vietnam. 相似文献
8.
Yeva B. Dalyan Samvel G. Haroutiunian Gayane V. Ananyan Volodya I. Vardanyan Dmitri Y. Lando Valeri N. Madakyan 《Journal of biomolecular structure & dynamics》2013,31(5):677-687
Abstract Interactions of meso-tetra-(4-N-oxyethylpyridyl) porphyrin (TOEPyP(4)), its 3-N analog (TOEPyP(3)) and their Co, Cu, Ni, Zn metallocomplexes with duplex DNA have been investigated by uv/visible absorbance and circular dichrosim spectroscopies. Results reveal the interactions of these complexes with duplex DNA are of two types. (1) External binding of duplex DNA by metalloporphyrins containing Zn and Co, and (2) Binding of duplex DNA both externally and internally (by intercalation) by porphyrins not containing metals, and metalloporphyrins containing Cu and Ni. Results indicate that (4N-oxyethylpyridyl) porphyrins intercalate more preferably in the structure of duplex DNA and have weaker external binding than 3N-porphyrins. 相似文献
9.
10.
Richard B. Forward Jr Elizabeth Freeman Kristen Gall Katie Saba 《Marine and Freshwater Behaviour and Physiology》2013,45(5):305-319
The supratidal amphipod Talorchestia longicornis Say has a circadian rhythm in activity, in which it is active on the substrate surface at night and inactive in burrows during the day. The present study determined: (1) the circadian rhythms in individual versus groups of amphipods; (2) the range of temperature cycles that entrain the circadian rhythm; (3) entrainment by high-temperature cycles versus light?:?dark cycles, and (4) seasonal substrate temperature cycles. The circadian rhythm was determined by monitoring temporal changes in surface activity using a video system. Individual and groups of amphipods have similar circadian rhythms. Entrainment occurred only to temperature cycles that included temperatures below 20°C (10–20, 15–20, 17–19, 15–25°C) but not to temperatures above 20°C (20–25, 20–30°C), and required only a 2°C temperature cycle (17–19°C). Diel substrate temperatures were above 20°C in the summer and below 20°C during the winter. Upon simultaneous exposure to a diel high-temperature cycle (20–30°C) and a light?:?dark cycle phased differently, amphipods entrained to the light?:?dark cycle. Past studies found that a temperature cycle below 20°C overrode the light?:?dark cycle for entrainment. The functional significance of this change in entrainment cues may be that while buried during the winter, the activity rhythm remains in phase with the day?:?night cycle by the substrate temperature cycles. During the summer, T. longicornis switches to the light?:?dark cycle for entrainment, perhaps as a mechanism to phase activity precisely to the short summer nights. 相似文献