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Since all biological, organic material contains carbon and hydrogen, radioactive isotopes of these two elements have proven to be very important in tracing the course of metabolites in biological systems. The simultaneous use of C14- and H3-tagged metabolites under identical experimental conditions greatly extends the usefulness of tracer methodology in various field of research. In biochemistry, double-labeled nutrients permit the study of the incorporation of a C14-labeled compound and a tritiated labeled compound in the same experiment. This can be accomplished either by labeling two parts of the same molecule, as in the case of tritiated methyl-labeled acetate and carboxyl-labeled acetate (acetate-1-C14), or by introducing two different metabolites in the same experiment as glucose-U-C14 and tritiated acetate [1]. Another type of double-label experiment is one in which the turnover of a product and the incorporation of precursors into the product can be measured in the same experimental animals [2]. In pharmacology the metabolic fate of a drug labeled with both C14 and tritium can be followed [3]. When the drug is labeled in two different positions of the molecule, changes in the C14: H3 ratio indicate that specific activity can be used for analysis where the isotope-derivative or dilution-derivative methods are employed [4]. These procedures are of particular value for the estimation of components of a mixture of related compounds for which individual chemical methods of analysis are not available. It should be noted that the accuracy of these methods of assay are independent of loss of material.

The incorporation of 1-(14)C-Acetate into tissue cholesterol of the baboon was measured. Using this indicator gray matter of the cerebrum indicated greater metabolic activity than did white matter.Other tissues besides neural tissue were examined. The peak of radioactivity occurred between 3 and 4 hr. The highest incorporation of radioactivity was measured in the adrenal gland. Liver, spleen and kidney values were of intermediate order.

The low molecular weight components of Elapidae venoms were investigated. The first separations of snake venom toxins by thin-layer chromatography (TLC) on silica gel were achieved. Sixteen Elapidae venoms were compared by starch gel electrophoresis and TLC. Almost three-quarters of the venom was dialyzable. The adsorption of toxins onto the larger protein molecules in snake venoms was demonstrated by measuring dialysis rates as well as showing that homogeneous electrophoretic bands yielded multiple spots by TLC. The feasibility of separating the low particle weight toxins of Elapidae venoms by silicic acid TLC and column chromatography was demonstrated. A low molecular weight toxic principle of Naja naja was isolated, partially characterized, and shown to be one of the most lethal materials isolated from biological sources (ld50 = 0·03 mg per kg).

Glucose-1 and glucose-6 labeled with tritium or carbon-14 were incorporated in vivo into brain and liver sterol. Differential incorporations of glucose labeled in both positions were compared. A higher than expected incorporation of C-1 from glucose was noted.

Contrary to the limited effects of alkyl amides and their corresponding N -derivatives, alkyl amines affected both gram-positive and gram-negative organisms. As with other alkyl derivatives the most sensitive gram-negative bacteria were usually more resistant than the most resistant gram-positive bacteria. Compounds with a chain-length of 11 to 15 are most active. Although some of the general properties relating the activity of fatty acids to their antimicrobial action are similar to those of amine compounds, the amines are unique in that monounsaturation does not increase compound activity. The possible modes of action of these compounds are discussed.

By the application of the isotope derivative technique with radioactive methanol, a procedure for measuring esterified and nonesterified fatty acids was devised. The present method is ideally suited to measuring large numbers of biological samples when total fatty acid content is required. The wide range of sample size, short time required for measurement, applicability to both free and esterified fatty acids, and possibility of computorized data processing make the present method a valuable supplement to gasliquid chromatography.

A new instrument is described for evaluating electrophoretograms on various media. The same densitometer can be used to evaluate spots on chromatographic strips and for colorimetric analysis of solutions. The versatility of this instrument makes it a useful adjunct to any analytical laboratory.

Clofibrate can both inhibit and stimulate the oxidation of succinate by mouse liver mitochondria, depending on whether the salt or the esterified form of the drug is used. Sodium clofibrate is a strong inhibitor whereas clofibrate ethyl ester is an active stimulator of succinate oxidation by mouse liver mitochondria.

Publisher Summary The potential of the adult brain for lipid metabolism has always been regarded as limited. Recently, the admission of newer evidence has challenged this static concept for neural metabolism. Studies with radioactive nutrients on the intact animal are difficult to interpret because of the protective mechanisms (blood-brain barrier) of the brain, which controls the movement of substances into and out of the neural tissue. Thus the unavailability of injected precursors to become incorporated into compounds of the central nervous system has been interpreted by early investigators as indicative of a limited metabolic potentiality. Through special techniques and experimental designs, recent studies have mitigated against this static metabolic picture for neural tissue, which now indicates extensive metabolic potentials. Pursuing the problems of cholesterol biosynthesis in various tissues by simultaneous use of selected 14 C- and 3 H-precursors, it has been previously reported that acetate was a poor choice for the study of the brain cholesterol formation. In this and similar studies, glucose is shown to be a better carbon source for brain cholesterol than acetate. It is of interest, therefore, to examine the contribution of a non-carbohydrate labeled substance and glucose as both became incorporated into the sterol of the developing mouse brain. Mice representing three age groups are simultaneously injected with acetate-2- 3 H and glucose-U- 14 C and the incorporation of these labeled nutrients into brain cholesterol was measured in this chapter.

The appearance of methyl esters of fatty acids in lipid extracts was studied. Experimental evidence indicates that these esters are both natural components of tissues as well as products of technical manipulation. Effect of temperature on the latter process was studied. The results of these experiments show that the post-mortem increase of fatty acid methyl esters could best be explained by postulating an enzymatic rather than a chemical process.

During the past decade, our laboratory has been involved in studying the biosynthesis of brain cholesterol under various conditions. As a result of these studies, we feel that the hypothesis of metabolic stability of cholesterol in adult life is untenable. Our data suggest that there are several compartments of sterol metabolism ranging from extremely fast to metabolically very slow. It is our hypothesis that (a) brain function is more nearly associated with fast turnover compartments than with metabolically slow ones; (b) these compartments can be altered by a variety of stress conditions.

Publisher Summary This chapter discusses the effect of chemical and physical agents on brain cholesterol. The brain represents the largest repository of body cholesterol however relatively little is known about its metabolism and even less about its function and role within the central nervous system. It has been suggested that cholesterol turnover may be more rapid in some areas than in others. In view of new evidence that indicates both biosynthetic capacity and turnover ability of cholesterol in adult brain, studies dealing with the effect of chemical and physical agents on the constituent have become more rational. That the stability of brain cholesterol was so readily accepted in view of early experiments showing drug effect is difficult to comprehend. Drug stimulants and drug depressants may have their mechanism of action directly or indirectly on brain cholesterol. It is clear from the diversity of chemical structures which affect cholesterol metabolism in general and brain cholesterol in particular that further work will be necessary to relate the mechanisms of drug action on brain cholesterol and brain function.

Die Chironomiden stellen ein bevorzugtes cytologisches Untersuchungsobjekt dar. Besonders die Riesenchromosomen in den Speicheldrusen sind hochpolytan und konnen in ihrer Struktur sehr gut sichtbar gemacht werden. Wie Mechelke nachwies, bilden die Riesenchromosomen in den drei Lappen der Speicheldrusen von Acricotopus ein unterschiedliches Strukturmuster aus, das durch Anschwellen einzelner Querscheiben oder Querscheibenkomplexe entsteht. In diesen aufgeblahten Querscheiben, den sog. Puffs und BalbianiRingen wird verstarkt RNS synthetisiert. In Analogie zu dem unterschiedlichen Struktur-muster der Riesenchromosomen in den einzelnen Speicheldrusenlappen liesen sich chemische Unterschiede zwischen den Drusenlappen feststellen. In Haupt- und Nebenlappen der Speicheldrusen wurde Hydroxyprolin nachgewiesen; es wird hier wahrscheinlich synthetisiert. Dagegen konnte in dem Vorderlappen diese Aminosaure nicht gefunden werden. Hydroxyprolin kommt weder im restlichen Tierkorper noch in der Nahrung vor. Versuche mit 14C-Prolin sollten nun zeigen, ob Puffs oder Balbiani-Ringen im Haupt- und Nebenlappen der Speicheldrusen eine direkte Beteiligung bei der Hydroxyprolinsynthese zukommt. Die Autoradiographien der mit 14C-Prolin inkubierten Speicheldrusen ergaben aber keine spezifische Anreicherung der Aktivitat an irgendeiner Stelle der Riesenchromosomen. Wie bei einer Verabreichung anderer aktiver Aminosauren findet sich auch bei einer Verfutterung von 14C-Prolin die Aktivitat im Zellplasma und besonders in dem Sekret der Drusenzellen.

Publisher Summary This chapter presents a critical review of brain cholesterol metabolism. Modern aspects of brain sterol metabolism are reviewed by Davison and Kabara. Consequently, for this review, the chapter emphasizes only the more recent concepts of brain cholesterol metabolism. To form a backdrop for the discussion of brain cholesterol metabolism, the anatomical and chemical changes taking place in the central nervous system (CNS) during growth and development are outlined in the chapter. Because sex, nutrition, precursor used, diurnal variation, etc., influence biosynthetic rates as measured, their influence should be considered in any developmental analysis of metabolic capacity within the CNS. Whole brain values obtained in the past from animals injected with a radioactive precursor did not reflect metabolism or changes in metabolism of anatomical areas, individual cells or organelles. Although accurate information is not available, conclusions based on such comparisons lead to statements in the literature which are very difficult to change, even in the face of new and more conclusive data.

Conclusions1. Various resorcinol derivatives of a non-toxic nature have been shown to be active against EEE virus under in vitro conditions. 2. Some factors affecting inactivation of EEE virus by 2,7-diiodotetraiodofluorescein have been presented and their importance in an in vitro study on compound-virus interaction stressed. 3. An in vitro screening technic has been demonstrated permitting the study of the effect of compound configuration on virus activity.