THE ACCELERATING EFFECT OF MANGANOUS IONS ON PHAGE ACTION

Dilute solutions of MnCl₂ or MnSO₄ accelerate the lytic effect of phage upon susceptible staphylococci. Under the conditions of our experiments the manganese-containing mixtures lysed regularly 0.5 hour sooner than the controls. The effect is shown to be due to a lowering of the lytic threshold, i.e. the quantity of phage/bacterium requisite for lysis; Mn⁺⁺ reduces the ratio from 54 to about 12. In the presence of Mn⁺⁺ phage distribution is altered and in growing phage-bacteria mixtures the extracellular phage concentration is increased by manganese to approximately 4 times that occurring in the absence of manganese. There appears to be no enhancement of phage formation nor any affect on the rate of bacterial growth. As would be anticipated, for any given initial phage concentration the end titre after completion of lysis is less in the presence of manganese than in its absence. This is due to the reduced lytic threshold produced by Mn⁺⁺, there consequently being less phage needed to bring about lytic destruction of the bacteria.     

IODINE AND THE THYROID : III. THE SPECIFIC ACTION OF IODINE IN ACCELERATING AMPHIBIAN METAMORPHOSIS.

1. Amphibian metamorphosis depends upon the amount of iodine secured by the larvæ; the greater the quantity the more rapid the differentiation. 2. Bromine is physiologically inert when fed even in large quantities to frog larvæ, hence it cannot be substituted for iodine. Bromine feeding has no effect on the thyroid. 3. Iodine is the active constituent of the thyroid gland, in the Anura at any rate, and functions within the body by stimulating intracellular oxidations; it is apparently specific in its action. 4. The basal metabolism of patients suffering from athyreosis, whose metabolism is 40 per cent below normal, is very likely held at this figure and prevented from sinking lower to the death point by the introduction of iodine into the body through food and water. 5. The thyroid gland is an organ the function of which is the extraction from the circulation, storage, and supplying to the organism, under the pressure of its needs, the small quantities of iodine taken into the body. The chief function of this gland then is the utilization of iodine in small quantities.     

STUDIES IN THE MODE OF ACTION OF INSECTICIDES

Homogenates of the thoracic nervous system of Locusta migratoria migratoriodes are able to hydrolyse acetylcholine (ACh) and o -nitrophenylacetate (NPA), and this hydrolysis can be inhibited by tetraethylpyrophosphate (TEPP) at approximately the same molar concentration for both substrates. It is possible that one acetyl-esterase is responsible for the breakdown of the two substances, and there is no reason to assume the existence of a specific acetylcholinesterase. In normal horse serum, on the other hand, the pseudocholinesterase is quite distinct from the enzyme responsible for the breakdown of NPA.
In an attempt to correlate the inhibition of the locust nerve cord acetylesterase with toxic activity to insects and mice, four chlorinated diethyl-phenylphosphates were tested as contact poisons against a number of insects and by injection against locusts and mice, and also as in vitro inhibitors of locust nerve cord acetylesterase and horse-serum pseudocholinesterase. The chemicals were the 2-chloro-, 4-chloro, 2:4-dichloro- and 2:4:5-trichloro- analogues of diethyl-phenylphosphate.
Good correlation exists between their in vitro activity against the nerve-cord acetylesterase and their contact activity to aphids, but not between the former and injection toxicity to locusts. No correlation could be established between the inhibition of horse-serum cholinesterase and injection toxicity to mice. It is thought likely that the inhibition of nerve-cord acetylesterase is of greater importance in aphids than in other insects, where the toxic action of the phosphoric esters is at least partly concerned with other vital processes, and that a detoxication mechanism in the mammal breaks down some of the phosphoric esters, but not others.     

STUDIES IN THE MODE OF ACTION OF INSECTICIDES

Acetylcholine, choline chloride, acetyl-β-methylcholine, benzoylcholine, carbamyl choline, adrenaline and d -tubocurarine are non-toxic when injected into the locust. Prostigmine is also non-toxic, and eserine considerably less toxic to the locust than to man.
The toxic effect of tetraethyl pyrophosphate (TEPP) cannot be antagonized by injection of atropine or enhanced by d -tubocurarine.
The injection of acetylcholine chloride following injection of TEPP does not affect subsequent mortality.
These findings are discussed, and it is suggested that the physiology of the nervous system of the insect is unlike that of the mammal, neither cholinesters nor adrenaline being concerned in it. Phosphorus insecticides are thought to inhibit a general esterase not specifically connected with cholinesters.     

甲基胆蒽在青蛙中的引瘤作用

前言文献中,关于在两栖类动物,用对于哺乳类有引瘤作用的物质进行的实验不多,而成功的就更少了。在有尾两栖类,Hellmich(1928)的记载是比较早的。皮下注射苏丹三(Sudan Ⅲ)油溶液的结果,只在一只实验动物 Triturus eristatus 中,得到了所谓"瘤前期病变"。     

THE ACTION OF COPPER IN ANTIFOULING PAINTS

Experiments on the number of barnacle cyprids found on plane surfaces and on the surface of small pits coated with compositions containing different amounts of cuprous oxide show that the presence of copper does not deter the cyprids from attempting to settle. Copper-oxide paints do not inhibit settlement appreciably; their efficiency as antifouling agents is caused by the toxic action of copper on cyprids and young spat after initial attachment.
The cementing of the shell to the substratum in young barnacles which have survived metamorphosis appears to be hindered by the presence of copper paints so that they are easily dislodged.     

THE MECHANISM OF GIEBERELLIN ACTION IN THE DWARF PEA

The increase in diffusible auxin in the dwarf pea followingtreatment with gibherellin has been shown not to involve theinhibition of IAA oxidase, the rate of basipetal auxin transport,decrease in growth inhibitor, the formation of a complex betweengibberellin and auxin, or the enzymatic conversion of tryptophanto ether-soluble auxin. The tryptophan conversion system fromplants treated with gibberellin formed four times more water-solubleauxin than did the enzyme preparation from control plants. Thusthe increase in water-soluble auxin appears to be the majorcause of the higher auxin level in plants treated with gibberellin. ¹Present address: Biological Institute, College of General Education,University of Tokyo, Komaba, Meguro, Tokyo.