L-isoleucine and L-leucine: tumor promoters of bladder cancer in rats

A 4-week assay for screening tumor promoters of bladder cancer has been developed in which increased agglutinability of isolated rat bladder cells with concanavalin A is used as an indicator. On the basis of this assay system, L-isoleucine and L-leucine were suspected of being possible tumor promoters. Results of 40- to 60-week carcinogenesis experiments in which N-butyl-N-(4-hydroxybutyl)nitrosamine was used as an initiator demonstrate that L-isoleucine and L-leucine promote bladder cancer in rats. This finding may be relevant to the high incidence of human bladder cancer in Western countries, where the diet is rich in protein.     

Sensitive enzyme immunoassay of colistin and its application to detect residual colistin in rainbow trout tissue

An antibody against colistin (CL), an antibiotic effective for gram-negative bacteria, was produced in rabbits immunized with a colistin-protein conjugate. The conjugate was prepared by a novel and convenient procedure devised to couple an amino group of CL to thiol groups of bovine serum albumin (BSA) introduced by thiol exchange reduction of its disulfide bonds with dithiothreitol, using N-(m-maleimidobenzoyloxy)succinimide (MBS) as a cross-linker. Enzyme labeling of CL with beta-D-galactosidase was performed by utilizing another cross-linker, N-(gamma-maleimidobutyryloxy)succinimide, by means of a convenient labeling method. A double antibody enzyme immunoassay of CL, which could determine as little as 30 ng/mL of CL, was developed using labeled CL and anti-CL antiserum. With this assay, drug levels were easily determined in fish tissue after CL administration. The enzyme immunoassay should provide a useful tool for detection and quantitation of residual drugs in foods and related products.     

Importance of bringing dogs in contact with children during their socialization period for better behavior

Much attention has been given to the role that dogs play in the social, physical, and psychological development of children. Furthermore, dogs are now playing a new important role in animal-assisted education (AAE). However, some dogs have difficulty getting along with children. The aim of this study was to demonstrate how dogs' contact with children during and after their socialization period influenced their responses toward children. In total, 31 pet dogs were divided into three groups. Group 1 dogs had been in contact with children during the canine socialization period (between 3 and 12 weeks of age); Group 2 dogs had been in contact with children after this socialization period; Group 3 dogs seldom had contact with children. As soon as a child entered the room, the dog was presented three stimuli by the child over the course of several intervals. The dogs' responses were evaluated by analyzing behavior and heart rates. The dogs that had been in contact with children during their socialization period did not show aggressive behavior or excited behavior toward the child in our test. Moreover, their heart rates were significantly decreased even during the last stimulus, which involved the child running around the dog while calling its name. This study suggested that the dogs having contact with children during socialization period might not show inappropriate responses toward children and could be suitable for taking part in AAE.     

The evaluation of autonomic nervous system activation during learning in rhesus macaques with the analysis of the heart rate variability

The aims of this study were to measure the activity of the autonomic nervous system using heart rate variability (HRV) during learning tasks and to clarify the relationship between learning to overcome a difficult situation and the autonomic nervous system in monkeys. Two young male monkeys (Macaca mulatta) were given simple discrimination learning tasks (DL) and delayed matching to samples tasks (DMTS); Holter-type electrocardiography was done, and HRV was measured. We defined the frequency bands of HRV in rhesus macaques; the low frequency (LF) was 0.01-0.15 Hz, and the high frequency (HF) was 0.15-0.50 Hz. Based on these frequency bands, the LF/HF ratios during learning tasks were analyzed, and a significant increase in the ratio was found during the tasks. The variances in the HF differed between the DL and DMTS tasks; during DMTS tasks, HF variances had a tendency to increase. Our results indicate that increased sympathetic activity accompanied learning and suggest that the parasympathetic nervous system plays a key role during learning, particularly when difficult tasks are being learned.     

Analysis of polynuclear aromatic and aliphatic components in soil humic acids using ruthenium tetroxide oxidation

Although condensed aromatic components are considered to be one of the major structural units of soil humic acids (HAs) and to be responsible for the dark colour of HAs, their amount and composition remain largely unknown. In ruthenium tetroxide oxidation (RTO), condensed aromatic components are detectable as their degradation products, mainly benzenepolycarboxylic acids (BPCAs). We applied this technique to soil HAs with various degrees of humification (darkening). The yields of water‐ and dichloromethane‐soluble products from HAs upon RTO after methylation ranged from 210 to 430 mg g⁻¹ and 10–40 mg g⁻¹, respectively. Eight kinds of BPCAs with two to six carboxyl groups, and seven kinds of BPCAs with additional side chains (tentative assignment) were obtained as methylated counterparts. The yield of each BPCA and the sum of the yields of BPCAs (12–85 mg g⁻¹ HAs) increased with increasing degree of humification and aromatic C content. The compositions of BPCAs indicated that the degree of condensation was greater in the HAs with greater degrees of humification. The sum of the yields of aliphatic compounds ranged from 0.1 to 6.5 mg g⁻¹, and decreased with increasing degree of humification. The C₁₂ to C₃₀ monocarboxylic acid methyl esters accounted for > 56% of the aliphatic compounds assigned, which may be present mainly as end alkyl groups in the HA molecules. We also obtained the methylated counterparts of C₁₄ to C₂₄ dicarboxylic acids; these were possibly derived from polymethylene bridges between adjacent aromatic rings.     

Effect of Anions in Simulated Precipitation on the Uptake of Heavy Metals and Aluminum by Brassica Rapa L. Grown in Heavy -Metal -Contaminated Sandy Soil

This study investigated the effect of anions on the uptake of heavy metals and aluminum by Brassica rapa L. from non-contaminated, Cd-contaminated, and sewage sludge compost (SSC)-amended sandy soil. Four types of artificial precipitation were applied: deionized water (pH 5.7) as a control, and solutions of HNO₃, H₂SO₄, and HCl prepared to pH 4.5. Precipitation was applied daily during the last 20 d of cultivation. The pH of the Cd-treated soil after harvest was not affected by any precipitation treatment. Shoot concentrations of heavy metals and Al were unaffected by any treatments on non-contaminated soil. In contrast, all acid treatments increased the Cd concentration in shoots grown on Cd-contaminated soil, but only HNO₃ precipitation increased it in SSC-amended soil. These results indicate, even without large soil pH change, there is a possibility that the Cd uptake by B. rapa L. depends on anions in precipitation and chemical form of Cd in the soil under conditions of heavy metal enrichment.     

Characterization of DAX‐8 adsorbed soil fulvic acid fractions by various types of analyses

We investigated the optical absorption properties (A ₄₀₀/C and A ₆₀₀/C values), elemental composition, weight-averaged molecular weight (Mw), and liquid-state carbon-13 (¹³C) nuclear magnetic resonance (NMR) spectroscopy of DAX-8 adsorbed fulvic acid fractions (DAX-8 FAs) in various soils (n?=?36) to establish the general trends in their chemical characteristics. We also compared our results with those of humic acids (HAs) obtained from the same soils used in this study and other published data to discuss the differences between them. Our results clearly indicate that DAX-8 FAs with high carboxyl C content have small Mw and low hydrogen to carbon (H/C) ratio. In addition, DAX-8 FAs with high carbonyl C and alkyl C content have high A ₄₀₀/C values and H/C ratios, respectively. These results strongly suggest that DAX-8 FAs with high aliphatic chemical properties have low carboxyl C content, large Mw and high H/C ratio. There are significant differences in chemical characteristics among the various soil types in almost all data; e.g., DAX-8 FAs from Podzols showed significantly higher A ₄₀₀/C values, larger Mw, higher carbonyl C and O-aryl C content than those obtained from Andosols. However, these two C functional groups are relatively low values in the total C content among all soil types, suggesting that DAX-8 FAs may exhibit only small differences in chemical properties among the various soil types. The comparison with published data regarding soil HAs shows that DAX-8 FAs are characterized by smaller Mw; lower C, H, and nitrogen (N); higher oxygen (O) content; higher O/C; lower O/H ratios; higher carboxyl C content; and lower aryl C content in total C.     

Expression analysis of defense-related genes in wild kiwifruit (Actinidia rufa) tolerant to bacterial canker

Journal of General Plant Pathology - Kiwifruit bacterial canker, which is caused by Pseudomonas syringae pv. actinidiae biovar 3 (Psa3), is found throughout kiwifruit-growing countries. Here, we...