Absence of effects of low-frequency, low-amplitude magnetic fields on the properties of gramicidin A channels.

The effects of static and low-frequency magnetic fields on gramicidin A channels have been investigated using bilayer patch clamp recording and a bridge technique capable of detecting 0.3% changes in the conductance of glyceryl monooleate membranes containing many channels. In the bridge technique the conductance was assessed using 10-ms voltage pulses applied at 10 Hz. Measurements were made for LiCl, KCl, and CsCl using magnetic fields of 50, 100, 500, and 5000 microT with the frequency scanned from 10-200 Hz. The combinations of static and low-frequency fields employed include the "cyclotron resonance" conditions at which effects had been predicted to occur. In no case was there any detectable change in conductance when the magnetic fields were applied or changed. Potassium currents through single gramicidin channels have been recorded for patches in which several channels may be open at once. Fields were applied for 2 min periods interleaved with 2 min controls. Methods have been developed to analyze the multichannel records to reveal the amplitude and duration of the channels together with the frequency, depth, and apparent period of flickers. No significant differences were observed between the control and field-exposed recording periods. The peak of the distribution of opening and closing transitions always coincided for fields on and off within the resolution, 0.4%, of the recordings. There are at least two types of flicker, one with typical period less than 0.1 ms, the other with typical period from 0.3-0.8 ms. Most of the latter were not complete closures with the conductance during a flicker 15-20% above the level for a full closure.     

Induction of glycanolytic activities by Streptomyces sp. QM-B814 growing on different glucopolymers

The actinomycete Streptomyces sp. QM-B814 is able to use polymeric glucans as sole carbon source by the induction of specific extracellular enzymatic systems. Carboxymethylcellulose and barley -glucan were the most effective inducers of endoglucanase activities towards -(1,4) and mixed -(1,3)-(1,4) linkages. Avicelase activity was induced by Avicel and carboxymethylcellulose. The higher activity towards filter paper (cellulase) was measured in cultures growing in Avicel, carboxymethylcellulose, and barley -glucan. Laminarinase activity was induced only by laminarin and lichenan failed to induce significant activity levels against any of the substrates tested.     

Inhibition of Immune Complex-Induced Inflammation by A small Molecular Weight Selectin Antagonist

The anti-inflammatory effect of a small molecular weight antagonist of P- and E-selectin-dependent cell adhesion was examined. The glycolipid sulphatide was shown to block the adherence of thrombin-activated rat platelets to HL-60 cells. This interaction is known to be dependent on P-selectin. The rat dermal reverse passive Arthus reaction was used to assess the effect of sulphatide on a neutrophil dependent inflammatory response. Sulphatide dosedependently blocked both the vascular permeability increase and cell infiltration after intraperitoneal administration. These results show that a small molecular weight compound which blocks P- and E-selectin dependent adhesion in vitro can effectively block the inflammation due to immune complex deposition. A compound with this type of profile may have therapeutic potential in the treatment of immune complex mediated diseases.     

Effect of bicarbonate and root zone temperature on uptake of Zn,Fe, Mn and Cu by different rice cultivars (Oryza sativa L.) grown in calcareous soil

Pot experiments were conducted with a calcareous soil (Inceptisol) to elucidate the effects of bicarbonate (0 and 20 mM) and root zone temperature (15° and 25°C) on the uptake of Zn, Fe, Mn and Cu by "Zn-efficient" and "Zn-inefficient" rice cultivars. Bicarbonate decreased concentrations and total uptake of Zn in shoots of "Zn-inefficient" cultivars, especially of IR 26 at 25°C, but not in Zn-efficient cultivars. Bicarbonate decreased concentrations and uptake of Fe in shoots of Zn inefficient cultivars, particularly in IR 26. Concentrations and total uptake of Mn were lower in bicarbonate treatment in the Zn-inefficient cultivars at 15°C, and in all cultivars at 25°C. However, concentration and uptake of Cu were not affected by bicarbonate in all cultivars. Compared to the 25°C root zone temperature, the concentrations and total uptake of both Zn and Cu in shoots at 15°C were lower in Zn-inefficient than in the Zn-efficient cultivars. The results indicate that Zn-efficiency in rice is causally related to high tolerance of plant to elavated bicarbonate concentrations in soil solution.     

带γδ和αβ受体的T细胞（TCR）在人胎儿组织内分布的研究

本文用细胞免疫化学方法,在冰冻切片上,检测了胎儿不同组织和器官内带γδ和αβ受体的Ｔ细胞（ＴＣＲ）的分布,结果发现ＴＣＲ细胞的分布与,般Ｔ细胞不同,有相对固定的分布区,如胸腺内ＴＣＲ细胞主要分布在皮筋质交界处和髓质部;脾脏内的γδＴ主要位于边缘区,而αβＴ主要位于动脉周围淋巴鞘,在红髓和血窦两种细胞共存;淋巴结内只有少数ＴＣＲ细胞位于滤泡间或副皮质,滤泡内则未见。消化管内的ＴＣＲ细胞主要分布在小肠的固有膜,而胃、大肠和阑尾的固有膜内很少见;肝内ＴＣＲ细胞主要集中在血管和血窦周围;皮肤切片内的少数ＴＣＲ细胞见于真皮内,表皮基底层细胞内未见。这些细胞在胎儿期的免疫皮应及其生理功能还不清楚。     

钙／钙调素依赖性蛋白激酶对17．7kD和6kD胰腺蛋白的磷酸化

本文报导了胰腺提取物中两种可被钙／钙调素依赖性蛋白激酶磷酸化的热稳定蛋白。ＳＤＳ－ＰＡＧＥ测定其表观分子量分别为１７．７ｋＤ和６ｋＤ。经钙／钙调素依赖性蛋白激酶磷酸化后,其最大磷酸参入量为８．８μｍｏｌ／ｇ蛋白。同时磷酸化作用导致１７．７ｋＤ蛋白在ＳＤＳ－ＰＡＧＥ中迁移率发生变化。本文还进一步分析了各种阳离子对磷酸化的影响,并对此两种蛋白可能具有的生理功能进行了初步探讨。     

Absence of a direct role for RNase HI in initiation of DNA replication at the oriC site on the Escherichia coli chromosome.

On the basis of the experiments carried out with rnhA224 mutants, we previously concluded that RNase HI is not essential for initiation of Escherichia coli chromosome replication at oriC (T. Kogoma, N.L. Subia, and K. von Meyenburg, Mol. Gen. Genet. 200:103-109, 1985). In light of the recent finding that rnhA224 is a UGA nonsense mutation which can be leaky in certain genetic backgrounds, we reexamined this conclusion with the use of rnhA339 (Null)::cat mutants. The possibility that recB+ is required for initiation at the alternative origins (oriKs) of replication in rnhA mutants was also tested. The results clearly indicated that RNase HI is not essential for oriC initiation and that recB+ is not required for initiation at oriK sites.