A METHOD FOR DETERMINING THE RENNET ACTIVITY OF CHYMO-TRYPSIN

The rennet activity of chymo-trypsin (or pepsin) is conveniently measured by allowing a standard solution of milk to which chymotrypsin has been added to flow slowly through a graduated pipette and observing the rate and distance of flow of the milk before it clots. The time required for chymo-trypsin to clot milk may be calculated from these observations. The rennet activity is expressed as the reciprocal of the time in minutes required for 1 ml. of enzyme solution to clot 10 ml. of standard milk powder solution.     

A METHOD FOR DETERMINING THE OXYGEN CONSUMPTION OF A SINGLE CELL

1. A method for measuring the O₂ consumption of a single cell is described. The cell is placed in a capillary tube adjacent to a bubble of air. KOH (5 per cent) is drawn in on the opposite side of the air and both ends of the tube are sealed with mineral oil. The decrease in the volume of the gas, representing the O₂ consumed, is followed. 2. The possible errors of the technique are appraised. 3. A single Actinosphaerium eichhornii consumes 0.00113 mm.³ of O₂ per hour. A single Paramecium caudatum consumes 0.00049 mm.³ of O₂ per hour. 4. The significance of the results and the limitations of the method are discussed.     

离体灌流心脏希氏束电图记录方法

为稳定地记录离体心脏希氏束电图,我们研制成一种新型的二合一插管电极,利用这种电极可同时完成Ｌａｎｇｅｎｄｏｒｆｆ法心脏灌流及希氏束电位记录。心脏取自成年家兔或幼狗,与Ｌａｎｇｅｎｄｏｒｆｆ法相同,首先经主动脉逆行插入这种插管电极实现心脏灌流,然后在示波器监视下小心转动插管,当电极贴近希氏束部位时,即可记录到离体灌流心脏的希氏束电位。实践证明：这种方法操作简便,组织损伤小,波型记录稳定。如配合心电等     

MODELING METHOD OF LOOP FOR PROTEIN ENGINEERING

IntroductionAfullunderstandingofproteinfunctionrequiresaknowledgeof＊thedgethree－d［men－slonalstructures．SuchstructuralInformationIsusuallyprovldedbyhlgh－resolutlonX－rayandneutrondlffractlonstudiesorsolutionnuclearmagneticresonanceexperiments．ThestudyofproteintertiarystructureshasledtoagreaterInsightIntomanyimportantbiologicalprocesses．Unfortunately,formanyprotelnssuchexperlmentallydetermlnedstructuresareIncompleteornonexistent．Forexample,nostructuralInformationmaybeavailablefort…     

A DIRECT METHOD FOR DETERMINING DOPAMINE SYNTHESIS AND OUTPUT OF DOPAMINE METABOLITES FROM BRAIN IN AWAKE ANIMALS

Abstract— A direct method for measuring the rate of dopamine (DA) synthesis and the DA metabolites by the brain of awake monkeys ( Macaca arctoides ) is described. The method utilizes a coupling of a measure of cerebral blood flow with the mass spectrometrically determined difference in the concentrations of the metabolite under study in plasma obtained from arterial and internal jugular bulb blood. For homovanillic acid (HVA) a consistent and highly significant veno-arterial (V-A) difference of 2.2 ± 0.4 ng/ml of plasma ( P < 0.0005) was found. When this V-A difference was coupled with a measure of cerebral blood flow it was determined that, in the awake monkey, the average output of HVA by brain was 113.4 ± 19.1ng/100g brain min⁻¹. There were large individual variations, however, between animals (range = 38-194 ng/100g brain min⁻¹). In contrast to HVA, no consistent V-A difference for dihydroxyphenylacetic acid (DOPAC) was found; i.e. the concentrations of DOPAC in plasma obtained from arterial and internal jugular bulb venous blood were essentially identical. These data indicate that, in contrast to the rat, in this non-human primate HVA is the major metabolic product of brain DA. Since HVA is the major metabolite of DA, production of HVA under steady state conditions gives a measure of DA synthesis by whole brain; i.e. the rate of DA synthesis by whole brain in the awake monkey is 113.4 ± 19.1ng/100g brain min⁻¹. It is suggested that this technique may be of value in both basic and applied types of studies.     

用硝酸纤维素膜亲和法纯化抗体

介绍一种改进的纯化抗体方法。将抗原蛋白固定在硝酸纤维素膜上,然后对抗体进行亲和纯化,能快速有效获得高特异性抗体。     

A METHOD FOR DETERMINING PLASTOCHRON INDICES DURING HETEROBLASTIC SHOOT GROWTH

A plastochron is defined as the time interval between two successive recurring events during the growth of plant shoots, such as leaf initiation. The plastochron index (PI) formulated by Erickson and Michelini (1957, American Journal of Botany 44: 297–305) provides a method for determining 1) morphological equivalence in a developmentally variable sample of shoots and 2) rates of development in microscopic tissues and organs, by expressing shoot age as a function of plastochron number. The PI assumes that homologous organs at successive nodes grow exponentially, at equal rates, and the plastochron remains constant. These three conditions are not met in many shoots that exhibit heteroblasty in their plastochron and the growth rate of organs at successive nodes. An alternative computational method for the PI is presented that uses two measurements taken at different times from the same organ during its exponential growth phase. The method does not assume that the PI is a linear function of time. Results of an analysis of cyme internode growth in two races of Arenaria uniflora (Caryophyllaceae) demonstrate that the method proposed is in good agreement with Erickson and Michelini's (1957) method when shoot growth is not markedly heteroblastic. The current method is also used to determine the nonlinear relation between PI and time in a race of A. uniflora that has heteroblastic cyme growth. The results generalize the PI for use in studies of heteroblasty, and for shoots where the relative plastochron rate cannot be directly determined.     

QUANTITATIVE METHOD FOR DETERMINING A REPRESENTATIVE ALGAL SAMPLE COUNT1

A method for determining a representative count of a sample dependent on number of species is presented for application to various algal communities. Constant species curves are calculated as efficiency = (number of individuals–number of species)/number of individuals and diagrammed on a plot of efficiency versus number of individuals counted. Efficiency is defined as the probability that a new species encountered is minimal. That is, as the ratio of number of species to number of individuals approaches 1, more individuals will need to be counted in order to achieve a representative count. Data and calculations of efficiency from two algal communities are presented for illustration.     

水稻脂质转移蛋白cDNA结构及相应肽链构造特征的分析

从水稻(Oryza sativa L.ssp.indica)“广陆矮4号”黄化苗cDNA库中分离到一个与其它植物脂质转移蛋白(LTP)基因同源性很高的cDNA克隆(pFDRSC144)。完成了pFDRSC144克隆中840bp插入片段全顺序的测定。结果表明,该片段包含354个碱基的编码区,编码118个氨基酸,其中包括26个氨基酸组成的信号肽。从疏/亲水性分布曲线可看出,该肽链形成的分子具有很大范围的疏水面。按Garnier二维结构预测法显示成熟蛋白的肽链主要以β-折叠肽链的形式存在,推测可能形成一种有利于脂质传送的开放性管形构造。Southern杂交分析表明,LTP基因在水稻基因组中以基因家族的形式存在。     

A SEMI-ASCENDING PAIRED DIFFERENCE METHOD FOR DETERMINING SENSORY THRESHOLDS OF ADDED SUBSTANCES TO BACKGROUND MEDIA

A testing procedure was developed to determine the concentration range including an absolute or difference threshold for a compound added to a background medium. Samples were arranged into three groups, each containing a labeled control and three randomly arranged samples. Random samples in each group included an unlabeled control and two samples containing adjacent concentration levels from a series of six increasing concentrations of the added substance. Groups were presented in ascending order by concentration of the added substance. Within each group, panelists rated each sample on a nine-point intensity scale of difference from the labeled control. Group specific psychological errors in judgement were reduced by subtracting the unlabeled controls from the sample scores. Analysis of variance was applied to these data yielding separate estimates of variance for sample scores within groups. Sets of t-tests from paired comparisons were used to construct a confidence statement regarding a threshold interval.