Gene Regulation in N Mutants of Bacteriophage λ

Mutants (N(-)nin) of bacteriophage lambda in which the N gene product is not required for growth on wild-type Escherichia coli do not plate on recA bacterial mutants. Secondary mutants, selected for growth on recA, lie within the immunity region to the right of gene cI and appear identical to the cro mutants of Eisen et al. In an N(+) phage, a cro mutation causes enhanced and prolonged production of lambda exonuclease. N(-)cro phages make no detectable exonuclease, but show an increased rate of specific excision from lysogens and are excluded by P2 prophage. These properties, together with the ability to plate on recA, suggest that N(-)cro phages express genes to the left of N at a rate that is very low but higher than that for N(-)cro(+) phages. N(-)nin phages can integrate at the normal site on the bacterial chromosome, but specific excision from lysogens is immeasurably low.     

N,N,N′,N′-tetramethyl-p-phenylenediamine initiates the appearance of a well-resolved I peak in the kinetics of chlorophyll fluorescence rise in isolated thylakoids

Addition of N,N,N′,N′-tetramethyl-p-phenylendiamine (TMPD) to thylakoid membranes isolated from pea leaves initiates the appearance of peak I in the polyphasic rise of chlorophyll (Chl) fluorescence observed during strong illumination, making it similar to that observed in leaves or intact chloroplasts. This effect depends on TMPD concentration and incubation period of isolated thylakoids with TMPD. The resolution of I-peak in the presence of weak concentrations of TMPD which reduced the overlap between I- and P-peaks, resulted from a decreased reduction of both fast and slow plastoquinone (PQ) pools of the granal and stromal thylakoids, respectively, as TMPD effectively accepts electrons from reduced PQ. High concentrations of TMPD markedly decreased the J–I–P phase of fluorescence rise and greatly retarded the I–P step rise. Accumulation of oxidized TMPD in the thylakoid lumen accelerated the re-oxidation of the acceptor side of Photosystem II (PSII) as illustrated by a two-fold increase in the magnitude of the fast component and complete suppression of the middle component of the variable Chl fluorescence (F_v) decay in the dark. Evidently, exogenous addition of high concentrations of TMPD prevented the light-induced reduction of the slow PQ pool.     

Mode of action of N,N′-diphenylurea: The isolation and identification of the cytokinins in the transfer RNA from tobacco callus grown in the presence of N,N′-diphenylurea

Summary The tRNA from cytokinin-dependent tobacco callus (Nicotiana tabacum) grown on mineral medium containing N,N-diphenylurea as the source of cytokinin was found to contain 3 cytokinin-active ribonucleosides. The 2 ribonucleosides present in the largest amounts were identified conclusively by their chromatographic properties, ultra-violet and low-resolution mass spectra as the naturally-occurring cytokinins 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-9--D-ribofuranosylpurine and 6-(3-methyl-2-butenylamino)-9--ribofuranosylpurine. A third ribonucleoside, present in smaller amounts, was identified as another naturally-occurring cytokinin 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9--D-ribofuranosylpurine on the basis of its chromatographic behaviour. No evidence was found to associate the mode of action of the non-purine cytokinin, N,N-diphenylurea, with tRNA.Abbreviation DPU N,N-diphenylurea     

Synthesis of hydroxydiamines and triamines via reductive cleavage of N–N bond in substituted pyrazolidines

Aliphatic polyamines, being a versatile class of organic compounds, are widely used in many fields of medicine and organic chemistry. However, the general approach to the synthesis of chiral aliphatic polyamines has been still undeveloped. Here, we describe a new method for the synthesis of chiral trifunctional amino compounds, namely hydroxydiamines and triamines. The initial compounds, namely substituted hydroxy- or aminopyrazolidines and pyrazolines, are readily available using convenient stereoselective methods developed earlier by us. The proposed method allows synthesizing of chiral diaminoalcohols and triamines, which are the analogs of a well-known anti-TB drug, namely ethambutol, and cannot be obtained alternatively. The key step of the synthesis is N-N bond cleavage in substituted hydroxy- or aminopyrazolidines and pyrazolines with borane-tetrahydrofuran complex; other known methods for N-N bond cleavage turned out to be ineffective. The main advantage of the proposed method is the retention of a certain configuration of stereocenters in the course of the reaction. Six new chiral diasteomerically pure substituted hydroxydiamines and triamines and the enantiomerically pure triamine with four chiral centers were synthesized and characterized using NMR, IR and mass spectroscopy, as well as elemental analysis.     

Measurement of the apparent diffusion coefficient of N‐butane in soil

Measurements of in‐soil diffusion coefficients and the application of an appropriate diffusional model can allow for a more accurate prediction of soil gas concentrations and movement to locate subterranean contamination of volatile materials. The present study was undertaken to measure and evaluate the “apparent in‐soil diffusion coefficient”; for n‐butane through soil columns under non‐steady‐state conditions. The term “apparent in‐soil diffusion coefficient”; refers to a numerical coefficient that primarily describes the movement of the material by diffusion but also contains effects due to other mechanisms (e.g., adsorption and solubility).

Six test columns were evaluated at three soil porosity levels ranging from 0.30 to 0.43 and at two column temperature conditions, nominally 18°C and 7°C. Soil columns measured 25.4 cm in diameter by 84 cm in height and contained a moist sand/silt/clay mixture. The numerical range for the apparent in‐soil diffusion coefficients for n‐butane was 0.447 × 10^‐3cm²/s to 0.561 × 10^‐3cm²/s. The lower coefficient values were associated with lower soil porosity levels and cooler column conditions.     

Direct modulatory effect of hexasodium N,N,N′,N′-ethylenediamine-tetramethylenephosphonate on bone cell function in vitro

The phosphonate hexasodium N,N,N′,N′-ethylenediamine-tetramethylenephosphonate (EDITEMP · Na₆) reduced alkaline phosphatase (Alp) activity and cAMP response to parathyroid hormone (PTH) in primary cultures of foetal rat calvaria cells in a dose-dependent manner, while not affecting culture DNA content. EDITEMP · Na₆ also inhibited the mineralization of three-dimensional bone nodules formed in vitro, but not the number of nodules formed. Bone cell culture DNA content was also reduced by EDITEMP · Na₆ but at concentrations in excess of those needed to modulate osteoblastic cell function. Withdrawal of EDITEMP · Na₆ led to slow but complete recovery of Alp activity. At EDITEMP · Na₆ concentrations of 25 μM and higher, recovery of Alp activity appeared to be independent of protein and/or DNA synthesis. Cell culture acid phosphatase (Acp) activity was not affected by EDITEMP · Na₆. The results indicate that EDITEMP · Na₆ has a direct inhibitory effect on (mature) osteoblastic cell function. In the presence of bone tissue this inhibition also occurred, although not at a relatively low dose level.     

N,N′-carbonyldiimidazole-induced diketopiperazine formation in aqueous solution in the presence of adenosine-5′-monophosphate

Summary 3(2)-O-glycyl-adenosine-5-monophosphate is an intermediate in the conversion of N-[imidazolyl-(1)-carbonyl]-glycine to diketopiperazine in the presence of adenosine-5-monophosphate. The significance of these observations to prebiotic chemistry is discussed.Abbreviations AMP adenosine-5-monophosphate - A adenosine     

N,N′-Dinitrosopiperazine-Mediated AGR2 Is Involved in Metastasis of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) has a high metastatic character in the clinic, but its mechanism is not clear. As a carcinogen with organ specificity for the nasopharyngeal epithelium, N,N′-Dinitrosopiperazine (DNP) is involved in NPC metastasis. Herein, our data revealed that anterior gradient 2 (AGR2) was overexpressed in human NPC tissues, particularly in cervical lymph node metastatic NPC (LMNPC). High AGR2 expression was associated with NPC metastasis. Importantly, DNP induced AGR2 expression, and increased cell motility and invasion in the NPC cell line 6–10B. However, DNP-mediated cell motility and invasion was dramatically decreased when transfected with siRNA-AGR2. Further, AGR2 directly regulated cathepsin (CTS) B and D by binding them in vitro. These results indicate that DNP induces AGR2 expression, regulates CTSB and CTSD, increases cell motility and invasion, and promotes NPC tumor metastasis. Therefore, DNP-mediated AGR2 expression may be an important factor in prolific NPC metastasis.     

The role of N efflux and root abscission in determining plant δ 15 N

Plant and Soil - We investigated the relationship between plant δ15N and rates of nitrate supply in wheat (Triticum aestivum; L. cv. SST015) and how this relates to N efflux and root...     

Fates of N′-Methylnicotinamide and Nicotinamide N-Oxide in Mice

This experiment was performed to investigate the possibility that N′ -methylnicotinamide (N′-methyl-3-pyridinecarboxamide) and nicotinamide N-oxide have niacin activity or not in animals. When 20 mg N′-methylnicotinamide per mouse was administered, urinary excretion of nicotinamide, N¹-methylnicotinamide (MNA), N¹-methyl-2-pyridone-5-carboxamide (2-Py), and N¹-methyl-4-pyridone-3-carboxamide (4-Py) increased 24-, 3-, 3-, and 3-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were almost the same as those when 20 mg nicotinamide was administered. Therefore, the relative activity of N′-methylnicotinamide to nicotinamide as niacin was considered to be about 1. When 20 mg nicotinamide N-oxide per mouse was administered, urinary excretion of nicotinamide, MNA, 2-Py, and 4-Py increased 6.4-, 1.8-, 1.6-, and 1.7-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were about 1/2 of those when 20 mg nicotinamide was administered, so the relative activity of nicotinamide N-oxide to nicotinamide as niacin is considered to be about 1/2. In conclusion, it was found the possibility that the reactions N′-methylnicotinamide → nicotinamide and nicotinamide N-oxide → nicotinamide occur, at least in mice, and that therefore N′-methylnicotinamide and nicotinamide N-oxide have niacin activity.     

Digestibility of extruded proteins and metabolic transit of N ε -carboxymethyllysine in rats

Milk proteins are frequently used as supplements in fortified foods. However, processing produces chemical changes which likely affect the nutritional advantage. This study was intended to explore the possible difference in digestibility between extruded and non-extruded caseins and how the dietary N ^ε -carboxymethyllysine (CML) is metabolised. Normal rats were randomized into either an extruded protein diet (EP) or the same with unextruded proteins (UEP), for two periods of 2 weeks at 7 to 9 and 11 to 13 weeks of age. However, no difference in protein digestibility was detected between the two diets, either in young or in adult animals, despite a 9.4-fold higher level of CML and an 8.5-fold higher level of lysinoalanine in the EP than in the UEP. No diet-related changes were observed in plasma CML, either protein bound or free. Amounts of 38 and 48 % of the orally absorbed CML were excreted in urine and faeces, respectively, in UEP-fed rats. Lower rates of excretion were found in the EP-fed rats (23 and 37 %, respectively). A second animal study using a single oral dose of free CML (400 μg/rat) was set up to measure the systemic concentration of CML every hour from 0 to 4 h. It revealed that protein-bound CML was not affected by the oral dose of CML, and the highest free CML level found in the circulation was 600 ng/mL. Extruded proteins, therefore, appear to be well digested, and CML rapidly eliminated. Since its elimination is, however, incomplete, the question of its biodistribution and metabolism remains open.     

Yields and accumulations of N and P in farmer-managed intercrops of maize–pigeonpea in semi-arid Africa

Maize (Zea mays L.) is a major staple food in Sub-Saharan Africa but low soil fertility, limited resources and droughts keep yields low. Cultivation of maize intercropped with pigeonpea (Cajanus cajan L. Millsp.) is common in some areas of eastern and southern Africa. The objectives of this study were (1) to investigate dry matter, nitrogen (N) and phosphorus (P) accumulation in different plant components of maize–pigeonpea intercropping systems and (2) to report the effects of the intercrops on soil fertility. Maize–pigeonpea intercrops were compared to sole maize grown using farmersȁ9 practices. Intercropping maize and pigeonpea increased (P < 0.05) total system yield compared to sole maize in terms of biomass, N and P accumulation. Pigeonpea planted in maize did not reduce (P < 0.05) the accumulation of dry matter, N nor P in the maize grain. The harvest indices of maize, calculated on basis dry matter, N or P did not differ either (P < 0.05). Total soil C and N contents and inorganic N content, nitrate and ammonium, were not affected by two seasons of maize–pigeonpea intercropping compared to sole maize (P > 0.11). Nitrate and ammonium levels in soil were still not affected by the treatments after the soils were incubated in anaerobic conditions for 8 days at 37°C (P > 0.11). However, pigeonpea added up to 60 kg of N ha⁻¹ to the system and accumulated up to 6 kg of P ha⁻¹ and only 25% of this N and P were exported in the grain. In conclusion, beside the added grain yield of pigeonpea in the intercropped systems, pigeonpea increased the recirculation of dry matter, N and P, which may have a long-term effect on soil fertility. Furthermore, the stems from pigeonpea contributed to household fuel wood consumption. The intercropped system thus had multiple benefits that gave significant increase in combined yield per unit area without additional labour requirements. The main requirement in order to up-scale the maize–pigeonpea intercropping approach is sufficient supply of high-quality pigeonpea seeds.     

The increase in activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in skeletal muscles of rats after subcutaneous administration of N,N′-dimethyl-para-phenylenediamine

Summary After subcutaneous administration of N,N-dimethyl-para-phenylenediamine (DPPD) in rats, a myogenic myopathy was produced in the skeletal muscles. In this communication, the results of the application of various histochemical techniques for the localization of oxidoreductases, transferases, hydrolases and isomerases and biochemical techniques for the estimation of activities of oxidoreductases in the experimental skeletal muscles are presented. The most striking result was the activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase which increased dramatically during the early phase of the muscle disease. The increase in activity of the pentose phosphate shunt enzymes was the first pathological alteration and was present as early as 8 h after a single injection of DPPD. Histochemical techniques for demonstration of activity of both enzymes are therefore highly suited for the detection of minor diseases and the early onset of major diseases of the neuromuscular system. Some glycolytic enzymes as well as some enzymes of the aerobic part of the metabolism showed an early decrease or increase in activity indicating a metabolic imbalance in the muscle fibres. There were more fibres with an intermediate pattern of the energy yielding enzymes in the experimental muscle specimens then in specimens from the control groups. The activity of the catabolic hydrolytic enzymes was strongly increased in pathological muscles. The aerobic muscles were more vulnerable to DPPD than the anaerobic muscles.     

Exploration of secondary and tertiary pharmacophores in unsymmetrical N,N′-diaryl urea inhibitors of soluble epoxide hydrolase

The impact of various secondary and tertiary pharmacophores on in vitro potency of soluble epoxide hydrolase (sEH) inhibitors based on the unsymmetrical urea scaffold 1 is discussed. N,N′-Diaryl urea inhibitors of soluble epoxide hydrolase exhibit subtle variations in inhibitory potency depending on the secondary pharmacophore but tolerate considerable structural variation in the second linker/tertiary pharmacophore fragment.     

Simultaneous acquisition of 13Cα–15N and 1H–15N–15N sequential correlations in proteins: application of dual receivers in 3D HNN

We describe here, adaptation of the HNN pulse sequence for multiple nuclei detection using two independent receivers by utilizing the detectable ¹³C^α transverse magnetization which was otherwise dephased out in the conventional HNN experiment. It enables acquisition of 2D ¹³C^α–¹⁵N sequential correlations along with the standard 3D ¹⁵N–¹⁵N–¹H correlations, which provides directionality to sequential walk in HNN, on one hand, and enhances the speed of backbone assignment, on the other. We foresee that the implementation of dual direct detection opens up new avenues for a wide variety of modifications that would further enhance the value and applications of the experiment, and enable derivation of hitherto impossible information.