Response of potatoes to N fertilizer: Quantitative relations for components of growth

Summary Quantitative relationships for key processes influencing N response were derived from measurements of inorganic N in soil, the weights and N contents of foliage and tubers made at intervals during growth of maincrop potatoes in 11 N fertilizer experiments.Apparent mineralization rates (calculated from measurements of N uptake and inorganic N in the top metre and averaged over the growth period) were remarkably similar from site to site despite wide differences in the textures, water contents and organic matter contents of the soils. They were mostly about 0.78 kg N ha^–1 m^–1 d^–1.Inorganic N in the top 50 cm of soil was rapidly removed by the crop until it fell on all sites to a low value (about 4 g N cm^–3) which was maintained for the remainder of the growth period. When N fertilizer was applied, growth rate until at least the end of July was always well defined by a single coefficient in a previously derived equation. Average values of this coefficient for each of the soil types and for each of the years in which the experiments were carried out were within 20% of each other.The minimum %N in the dry matter needed to permit maximum growth rate declined with increase in plant weight in a similar manner to that previously found for other crops.Equations were found for the partition of assimilate and of nitrogen between the foliage and tubers. The coefficients in them were little affected by whether or not N fertilizer was applied.According to these relationships the maximum potential dry weight yield of tubers is 20 t ha^–1 and requires the crop to contain at least 290 kg N ha^–1.     

The concept of a changing receptor concentration: implications for the theory of drug action

Drugs are considered to produce their effects on biological tissues either by altering some physical property of cells or by interacting with specific cellular components, called receptors. Most drugs and endogenous neurotransmitters act on highly selective receptors located on the outer surface membrane of cells. These receptors were believed, until recently, to be stationary on the cell surface and to be present in unvarying numbers. Consequently, most early theorists modeled the drug-receptor interaction on the basis of stationary and static receptor molecules. The substantial advances in our understanding of drug action based on these models have partly justified this view. However, recent electron microscopic studies have revealed the presence of structures, including "coated" pits and vesicles, that appear to provide a mechanism by which cell surface receptors might be internalized in a process of endocytosis. The precise intracellular fate of these internalized receptors is unknown, but based on present understanding, it seems reasonable to believe that some are destroyed intracellularly whereas others are recycled to the cell surface. The importance of such processes to pharmacologic theory is a new awareness of a cellular pathway that is capable of internalizing drugs, receptors, or both. The implications of such a process to the theory of drug action extends to some unexplained drug phenomena such as down regulation, drug tolerance, tachyphyllaxis, and partial agonism. We present herein the theoretical framework for a model of drug action that incorporates the possibility of receptor internalization and subsequent degradation, recycling, or replacement.     

Genetical investigations into β-glucan content in barley

Summary Random inbred lines produced by doubled haploidy (DH) and single seed descent (SSD) have been used to investigate the genetics of -glucan (gum) content in barley (Hordeum vulgare). Genetical analyses indicated that gum content is controlled by a simple additive genetic system. Significant negative genetic correlations were observed between -glucan content, thousand grain weight and height in the DH samples. These correlations were much reduced in the SSD samples and would suggest linkage of the genes controlling these characters. The presence of repulsion linkages could be exploited in a barley breeding programme by producing F1 derived DH to generate recombinants with high thousand grain weight and low -glucan content. Genetical parameters estimated from DH and F3 samples have successfully been used to predict the number of inbred lines transgressing the parental range for -glucan content and bivariate combinations involving -glucan.     

Effects of ribavirin and adenine arabinoside on tobacco mosaic virus in Nicotiana tabacum L. var Xanthi tissue cultures

Although both ribavirin (1--ribofuranosyl-1,2,4-triazole-3carboxamide) and adenine arabinoside inhibited the multiplication of tobacco mosaic virus (TMV) in mechanically inoculated leaf tissues, neither chemical inhibited virus multiplication in unorganized tobacco callus after in vitro inoculation. The adenine deaminase inhibitor, pentostatin, did not increase the activity of adenine arabinoside in cultured cells. Several different developmental conditions and media did not increase the ability of either chemical to eradicate the virus from tobacco tissue cultures. However, the virus was eradicated from TMV-infected callus when grown in the presence of combinations of ribavirin and adenine arabinoside in shoot inducing medium.     

Transformation of plant protoplasts with DNA: cotransformation of non-selected calf thymus carrier DNA and meiotic segregation of transforming DNA sequences

Summary With the DNA transformation procedure developed in our laboratory (13) several transformed tobacco SR1 tissues were obtained which, apart from selected and non-selected pTi sequences (T⁺), also had acquired non-selected calf thymus carrier DNA sequences (C⁺), being integrated in their nuclear genomes. From one such tissue (cNT4), with a shooty crown gall phenotype and expressing mannopine synthesis activity (Mas⁺), shoots were grafted and mature, flowering plants (gNT4) were obtained. After cross pollination with wild type SR1 tobacco pollen 49% of the seedlings obtained, had the maternal NT4-like crown gall phenotype and 51% showed wild type (SR1) features. The mannopine locus segregated independently from the locus determining the crown gall phenotype. When screened for integrated (transforming) foreign DNA sequences 97% of the NT4-like seedlings turned out to be C⁺T⁺. Most of the SR1-like seedlings, having a wild type tobacco morphology, proved to be transformed as well: roughly a 1:1:1:1 ratio as found for C⁺T⁺:C^-T⁺: C⁺T:C T SR1-like seedlings. Based on the segregation of transforming sequences during meiosis a model is presented showing the integration of these sequences in three different host chromosomes.     

家兔中脑导水管周围灰质中甲七肽样免疫活性物质具有镇痛作用并参与电针镇痛

以辐射热照射家兔鼻嘴部皮肤,测定甩头反应潜伏期(ERL)作为痛阈。通过预先埋植的慢性套管向中脑导水管周围灰质(PAG)注射甲七肽降解酶抑制剂 Captopril,观察其镇痛作用以及加强电针镇痛的作用能否被特异的甲七肽抗血清所对抗。(1)单侧 PAG 注射 Captopril240 nmol 的镇痛作用可为同一部位注射甲七肽抗血清(1μl)所翻转,注入甲啡肽抗血清则无效。(2)单侧 PAG 注射 Captopril 60 nmol 有加强电针镇痛的作用。该作用可被1μl 甲七肽抗血清所完全取消,将抗血清量减少到0.1μl 则无效。以上结果说明 PAG 内的甲七肽样免疫活性物质在镇痛和电针镇痛中发挥重要作用。     

Thiol-stimulated secretion of riboflavin and porphyrins by Escherichia coli

Abstract Streptococcus lactis strain IL594 contains 9 plasmids, designated pIL1 to pIL9. On the basis of protoplast-induced curing experiments we showed that derivatives containing pIL7 (31 kb) were resistant to UV-irradiation while derivatives lacking pIL7 were sensitive. The pIL7-determined UV-protection was confirmed by cotransfer of the plasmid and of the character into a plasmid-free derivative of S. lactis IL594. Moreover, prophage induction required higher UV-fluence in this derivative carrying pIL7 than in the plasmid-free strain. This is the first report of a plasmid-mediated UV-protection in group N streptococci.     

Microbial transformation of a fungicide-derived amine, dimethyl-p-phenylene diamine by Alcaligenes DM4

Abstract Microbial transformation of N , N -dimethyl- p -phenylene diamine (DMPDA), a microbial product formed from the fungicide fenaminosulf ( p -dimethylaminobenzenediazo sodium sulfonate) was studied by enriching microbes in soils treated with the amine. Microorganisms isolated from DMPDA-treated soil belonged to the genera of Micrococcus, Alcaligenes , and Corynebacterium . Of the various isolates, Alcaligenes DM₄ showed maximal growth on DMPDA utilizing it as sources of carbon and nitrogen. When grown in mineral salts basal medium containing 0.05% DMPDA to serve as carbon and nitrogen sources, Alcaligenes DM₄ grew exponentially up to 18 h. Even though the characterization of the complete pathway of microbial degradation of DMPDA could not be carried out due to the auto-oxidation of the compound, the initial transformation product of DMPDA by Alcaligenes DM₄ has been identified as a dimer. The dimer is generated into the culture medium presumably by the extra-cellular oxidase of Alcaligenes DM₄. It is suggested that the risk-benefit evaluation on the use of fenaminosulf is to be made taking into consideration the microbial transformations of the fungicide.