A METHOD FOR THE QUANTITATIVE AND QUALITATIVE DETERMINATION OF PLANKTONIC DIATOMS

SUMMARY

A method for the quantitative and qualitative determination of planktonic diatoms was developed. The method uses the Utermöhl counting technique (in which an inverted microscope is employed) as a basis but also involves the calculation of the relative density of each species in the association (as determined with the ordinary light microscope). A combination of the results thus obtained ensures that even the smallest diatoms (2,5 μm) are accounted for. These often constitute a significant proportion of the population, but are often overlooked or may not even be resolved using Utermöhl's method.     

THE COMBINATION OF ENZYME AND SUBSTRATE : I. A METHOD FOR THE QUANTITATIVE DETERMINATION OF PEPSIN. II. THE EFFECT OF THE HYDROGEN ION CONCENTRATION.

1. A quantitative method for the determination of pepsin is described depending on the change in conductivity of a digesting egg albumin solution. 2. The combination of pepsin with an insoluble substrate has been followed by this method. 3. The amount of pepsin removed from solution by a given weight of substrate is independent of the size of the particles of the substrate. 4. There is an optimum zone of hydrogen ion concentration for the combination of enzyme and substrate corresponding to the optimum for digestion. 5. It is suggested that the pepsin combines largely or entirely with the ionized protein.     

GELATINASE AND THE GATES-GILMAN-COWGILL METHOD OF PEPSIN ESTIMATION

The Gates photographic film method for pepsin estimation as developed by Gilman and Cowgill measures an activity corresponding to that determined by the hemoglobin method of Anson and Mirsky rather than that resulting from the use of the gelatin viscosity technique. Therefore, the presence of gelatinase is not a source of great error in the gelatin film procedure.     

THE MECHANISM OF THE INFLUENCE OF ACIDS AND ALKALIES ON THE DIGESTION OF PROTEINS BY PEPSIN OR TRYPSIN

1. The effect of the addition of acid on the amount of ionized protein has been compared with the effect on the rate of digestion of gelatin, casein, and hemoglobin by pepsin. 2. A similar comparison has been made of the addition of alkali in the case of trypsin with gelatin, casein, hemoglobin, globin, and edestin. 3. In general, the rate of digestion may be predicted from the amount of ionized protein as determined by the titration curve or conductivity. The rate of digestion is a minimum at the isoelectric point of the protein and a maximum at that pH at which the protein is completely combined with acid or alkali to form a salt. 4. The physical properties of the protein solution have little or no effect on the rate of digestion.     

A METHOD FOR THE QUANTITATIVE ESTIMATION OF CYTOPLASMIC STRUCTURES

A sampling procedure and calculations are described by which electron micrographs of cytoplasmic structures may be quantitatively analyzed. The relative areas occupied by formed bodies and by the "membrane space," the remainder of the cytoplasm, are evaluated. A method for making a measurement of the quantity of endoplasmic reticulum or other membrane profiles is described. The technic and results are illustrated with normal rat liver cells.     

浮游植物叶绿素与脱镁叶绿素的测定方法

叶绿素含量的测定,早已受到生理学家的重视。在生态学范畴内,浮游藻类的叶绿素含量既是浮游藻类现存量的一个指标,又是推算浮游藻类生产量的重要参量。故生态学家、水产与环境科学工作者,均日益重视叶绿素含量的测定。本文在综合国内外有关资料的基础上,结合作者的工作经验,对浮游藻类的光合色素组成、叶绿素与脱镁叶绿素的测算原理、测算方法作了详细介绍。     

A METHOD FOR THE DETERMINATION OF DIFFUSION CONSTANTS AND THE CALCULATION OF THE RADIUS AND WEIGHT OF THE HEMOGLOBIN MOLECULE

A method is described for determining the diffusion coefficient of solutes by determining the rate of passage of the solute through a thin porous membrane between two solutions of different concentration. The method has been used to determine the diffusion coefficient of carbon monoxide hemoglobin. This was found to be 0.0420 ± 0.0005 cm.² per day at 5°C. The molecular weight of carbon monoxide hemoglobin calculated by means of Einstein''s equation from this quantity is 68,600 ± 1,000.     

A NEW METHOD FOR THE DETERMINATION OF OSMOTIC PRESSURE

Lockhart , James A. (California Inst. Tech., Pasadena.) A new method for the determination of osmotic pressure. Amer. Jour. Bot. 46(10): 704–708. Illus. 1959.—A new method for the determination of osmotic pressure in appropriate plant tissues is described. This method is based on the observation that the degree of deformability of tissue equilibrated in hypertonic solution is a linear function of the extent by which the external osmotic pressure exceeds the osmotic pressure of the cell contents. Extrapolation of the deformability vs. external osmotic pressure to zero deformation yields, then, the osmotic pressure of the tissue at limiting plasmolysis. It is shown that the osmotic pressure determinations are independent of incubation time and magnitude of applied force. A simple device is described for measuring bending throughout a wide range of angles, while keeping the applied force constant.