APPLICATION OF THE MEMBRANE FILTER FOR THE QUANTITATIVE STUDY OF TRANSFORMATIONS WITH PARTICULAR REFERENCE TO PHENOTYPIC EXPRESSION OF AN ERYTHROMYCIN-RESISTANCE MUTATION.

Iyer, V. N. (University of Rochester, Rochester, N.Y.). Application of the membrane filter for the quantitative study of transformations with particular reference to phenotypic expression of an erythromycin-resistance mutation. J. Bacteriol. 84:326-330. 1962.-A technique using membrane filters for quantitative studies of transformation of pneumococci is described and some possible applications discussed. This method has been found amenable to the study of the integration and phenotypic expression of an erythromycin-resistance mutation of pneumococci which is characterized by a low frequency of transformation and delayed expression. The expression of survival occurs prior to the expression of colony-forming ability in the presence of erythromycin.     

STUDIES ON THE MECHANISM OF INSECTICIDAL ACTION OF ORGANO-PHOSPHORUS COMPOUNDS WITH PARTICULAR REFERENCE TO THEIR ANTIESTERASE ACTIVITY

The preparation of an extract of the mealworm larvae, Tenebrio molitor L. which hydrolyses ethyl butyrate and o -nitrophenyl acetate, but not acetylcholine, is described. The inhibition of this esterase by TEPP-containing materials and parathion was determined.
An enzyme that hydrolysed o -nitrophenyl acetate and was inhibited by a TEPP-containing material was demonstrated in the five other insect species used.
The relative toxicities as contact insecticides to adult Tribolium castaneum Hbst. of ten samples of TEPP-containing materials were compared with their relative activities as esterase inhibitors. There was not an exact quantitative correlation between TEPP content estimated chemically, insecticidal activity and anti-esterase activity; but the correlation was sufficient to suggest interdependence of these factors.
Eggs of Diataraxia oleracea L. and Ephestia kühniella Zell, were shown to contain an enzyme that hydrolysed o -nitrophenyl acetate and was inhibited by the TEPP-containing materials. This enzyme was present in eggs less than 24 hr. old, i.e. before there was any visible signs of development. The TEPP was shown to be toxic to these eggs and in high concentrations kills at an early stage of development before differentiation of the nervous system. This, in conjunction with the other evidence, suggests that esterases other than the choline-esterase of the nervous system are important when considering the toxic action of these compounds.
Comparison of the anti-esterase activity and toxicity of parathion and TEPP-containing materials as insecticides showed that although the TEPP materials were the more potent enzyme inhibitors, parathion was the more potent contact insecticide to five species of insects. This appears to be due to the relative instability of TEPP. The study of the rates of action of the two poisons applied at different concentrations supports this view.     

东江鲤鱼种群动态及其最大持续渔获量的研究

本文研究东江鲤鱼的种群动态并进行渔业生物学分析。用Von Bertalanffy生长方程可以表达东江鲤鱼体长、体重与年龄的关系,L=39.308R-42.611,L_t=851[1-e(-0.173(t 0.0394))]W_t=19171.5[1-e~(-0.173(t 0.0394))]~3。通过渔获物统计资料计算种群的自然死亡率D=0.27和捕捞死亡率E=0.25,并分析比较产卵力及产卵群体的结构类型。通过比较各种捕捞强度和最小捕捞规格的不同的总渔获量和群体的相对数量,提出获得持续渔获量的捕捞强度F=0.35及最小捕捞年龄t=2。     

ON THE CHEMICAL COMPOSITION OF THE AXOPLASM OF SQUID GIANT NERVE FIBERS WITH PARTICULAR REFERENCE TO ITS ION PATTERN

Investigations dealing with the determination of the major chemical constituents of the axoplasm of the giant nerve fiber of the squid are described. Particular emphasis has been placed on determining the components involved in acid-base balance. It was found that 72 per cent of the total solids of axoplasm, representing 13.5 per cent of the wet material, are of relatively low molecular weight (dialyzable) and consist mainly of charged ionic or dipolar constituents. Of the 520 micromoles per gm. of total base, 72 per cent are balanced by organic acids: aspartic acid (65 micro equivalents per gm.), glutamic acid (10 micro equivalents), fumaric and succinic acids (15 micro equivalents), a new polycarboxylic acid (35 micro equivalents), and isethionic acid, a biologically novel sulfonic acid (220 micro equivalents). Besides potassium, sodium, small amounts of calcium, and magnesium there is a considerable fraction of organic (nitrogenous) base. Other features of the chemical composition of squid axoplasm include a relatively high concentration of taurine (100 micro equivalents) and an ultraviolet absorbing substance possibly identical with N-methylpicolinic acid. The distribution of the phosphates, especially the concentration of ATP, has been investigated. Specific techniques elaborated in connection with this study have been described and the biochemical implications of the analytical results are discussed.     

EPIPHYTES ON CLADOPHORA GLOMERATA IN THE GREAT LAKES AND ST. LAWRENCE SEAWAY WITH PARTICULAR REFERENCE TO THE RED ALGA CHROODACTYLON RAMOSUM (= ASTEROCYTIS SMARGDINA)1

The range of Cladophora glomerata² along the east and north shorelines of the Great Lakes and St. Lawrence Seaway extends form just east of Montreal to Thunder Bay on Lake Superior. However, it does not occur at sites sampled in Georgian Bay, the North Channel or eastern Lake Superior. The dominant epiphytes on Cladophora throughout this range are the blue-green algae, particularly Lyngbya diguetii, L. epiphytica and Chamaesiphon incrustans, which account for 53 to 90% of the cell density. The diatoms Cocconeis pediculus and Rhoicosphenia curvata contribute to much of the remaining density. The red alga Chroodactylon ramosum is a minor component of Cladophora epiphyton but is widespread in Lakes Ontario, Erie and Huron. Filament morphology, cell diameters and lengths of Chroodactylon are quite similar to those of marine forms. In addition, this alga has been reported to be quite tolerant of a wide range of salinities. Chroodactylon has been found in 33 freshwater sites throughout North America and 30 of these are from the Great Lakes or its drainage basin. Therefore, it appears possible that Chroodactylon, like Bangia atropurpurea, has originated in the Great Lakes by a migration from the Atlantic Ocean.