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This report summarizes our electron spin resonance (ESR) detection of oxygenated radical formation by freshly crushed quartz particles in a cell-free aqueous medium, and its inihibition by radical scavengers. This study was undertaken with to elucidate the primary biochemical mechanism involved in the development of silicosis (Farber, 1983; Reiser and Last, 1979; Silicosis and Silicate Disease Committee, 1988). In particular the mechanism by which the quartz particles exert their toxic action on cells and the process(es) by which these actions progress to fibrogenesis are still not well understood (Farber, 1983; Reiser and Last, 1979;). It is generally believed that the action of quartz particles on the cell membrane is the starting point of the silicotic process (Farber, 1983; Parazzi et al., 1968). Thus the surface characteristics of the quartz particles have been the subject of several recent studies (Bolis et al., 1983; Dalal et al., 1986; Fubini et al., 1987). Recently, We reported that mechanical crushing of quartz under normal atmosphere generates free radicals which decay with time, and that these free radicals are associated with a higher cytotoxicity of fresh quartz dust as compared to aged dust from the same stock (Dalal et al., 1986; Vallyathan et al., 1988). The formation of Si· and SiO·-type of radicals from quartz particles crushed under atmospheric conditions has also been reported by Fubini et al. (1987).

The central stimulant effect of cocaine is generally considered related to its potentiating effect on biogenic amines. However, the individual role and significance of the amines involved in various stimulant effects of cocaine are still a controversial topic. Cocaine is a potent inhibitor of noradrenaline uptake (Hertting, Axelrod, and Whitby, 1961; Ross and Renyi, 1967; Langer and Enero, 1974; Azzaro, Ziance, and Rutledge, 1974), dopamine uptake (Fuxe, Hamberger, and Malmfors, 1967; Ross and Renyi, 1967; Harris and Baldessarini, 1973; Heikkila, Orlansky, Mytilineou, and Cohen, 1975), and serotonin uptake (Ross and Renyi, 1969; Friedman, Gershon, and Rotrosen, 1975). High affinity uptake of tryptophan into synaptosomes is also inhibited (Knapp and Mandell, 1972). In vivo studies have shown that cocaine induces a short-lasting uptake inhibition into brain tissues of noradrenaline (Schanberg and Cook, 1972), dopamine (Fuxe, Ham-berger, and Malmfors, 1967), and serotonin (Ross and Renyi, 1969).

For several years it has been widely accepted that the membrane-bound Na,K-ATPase is the enzymatic machinery for the active transport of Na+ and K+ across the cell membrane. The recent demonstration that ouabain-inhibitable, ATP-dependent Na+ and K+ transport can be mea­ sured in vesicles reconstituted from purified Na,K-ATPase and phospholip­ ids provided direct evidence that Na,K-ATPase is, in fact, the sodium pump. Since the last review in this series, numerous papers have appeared that bear on the nature and mechanism of the pump. We still do not know, however, how the hydrolysis of ATP is coupled to the movement of Na+ and K+ across the plasma membrane, or how the inhibition of Na,K­ ATPase by cardiac glycosides leads to an increased force of myocardial contraction. One of the obstacles to unraveling this puzzle is that neither the minimum molecular constituents nor the organization of these constit­ uents in the Na,K-ATPase is known. We have therefore chosen to concen­ trate on the structure of the enzyme and on the biochemical mechanism of the fragmented enzyme. The reader is also referred to earlier reviews of the sodium pump (23, 41. 79).

The standard procedure for evaluating carcinogen risk is the rodent bioassay coupled with statistically-based risk extrapolation. Extrapolation serves to bridge the physiological differences between the experimental species and man and between the experimental exposure scenario and that occurring in the “real world”. Little of what is known, however, about carcinogen pharmacokinetics, biochemical mechanisms of action, and cancer biology in either the experimental species or in man is used in risk assessment because no paradigm has been available to guide the incorporation of this information. Moolgavkar and Venzon (1979), and Moolgavkar and Knudson (1981), have described a biologically structured model of carcinogenesis (M-V-K model) that provides quantitative insights into the relationship between cellular proliferation, mutation, and tumor development. This is not, however, (and was not intended to be) a fully integrated model of chemical carcinogenesis as it lacks a biologically-based description of carcinogen pharmacokinetics, nor does it explicitly define biochemical mechanisms linking target tissue dose with tumorigenesis.

Chemical carcinogenesis is a process beginning with carcinogen absorption and ending with development of a malignant tumor. Individual elements of this process have been studied intensively but no comprehensive model has been developed. This report describes a comprehensive model which incorporates carcinogen pharmacokinetics, biochemical mechanism of action, and the resultant mutation of normal cells to malignancy. Model parameters correspond to specific physiological and biochemical structures and processes. The model was encoded in a simulation language and used to examine biochemical and cellular effects of exposure to an initiator and a promoter. With laboratory validation, the model should be useful for interpretation and design of studies on carcinogenic mechanisms and for risk assessment.

Besides curing diseases of all kinds, traditionally the old culture of China has also been committed to the idea of prevention of diseases, as reflected in the Chinese saying: “Treat a person before he has fallen ill and not only when he is already sick” [50]. Indeed, major aspects of research pursued in my laboratory group at the German Cancer Research Center are guided by the idea of contributing to the prevention of cancer by the identification of the risk factors involved, especially of cocarcinogens of the promotor type. Another important aspect is the investigation of the biochemical mechanism of action of such risk factors to provide clues for their chemical redesign to medicinally useful anticancer drugs.

Synthetic retinoids induce terata by the same molecular mechanism as that associated with elevated concentrations of their naturally occurring congeners. The evidence for definite retinoid structure-activity relationships and for specific cellular receptors in their biochemical mechanism of action illustrates the threshold basis of retinoid teratogenesis

Post-decapitative ischemic treatment imposed on the developing rat brain elicited a marked increase in its susceptibility to free fatty acid (FFA) release between 14 and 17 days, an observation similar to that reported by Bazan (Acta Physiol. Lat. Am.21, 15, 1971). Although the level of diacylglycerols (DG) also increased during this period, the extent of the increase was not as obvious as the FFA. Ischemic treatment to rats after 17 days of age elicited increases in DG and FFA enriched in stearic and arachidonic acids. The delayed response in susceptibility of brain tissue to ischemia-induced changes seems to suggest that the biochemical mechanism(s) responsible for the FFA and DG release is better correlated to events commensurating with synaptogenesis than with myelination.

It is astonishing that even in the highly sophisticated and scientific time in which we live the bulk of useful drugs derive from serendipity rather than inductive reasoning. Because of this it is not infrequent that we are presented with compounds that are therapeutically effective but whose mode of action remains mysterious. It is worthwhile bearing in mind that it is only in the past 20 or 30 years that we have understood how digitalis and morphine work despite the fact that they were in use for between one and a half to two centuries previously. We are still not clear how the corticosteroids exert their anti-inflammatory effect even with the extensive research on the subject in the 30 odd years since their development. It is especially difficult to determine which biological result of their use is the main one when the drugs in question have multiple actions and therapeutic benefits (as with the corticosteroids). This is certainly the case with the retinoids. Here are drugs that are active in psoriasis (plaque type, erythro-dermic, pustular and arthropathic), the disorders of keratinization (including the ichthyotic disorders, erythrokeratoderma variabilis and Darier’s disease), acne and cutaneous malignancies. To make matters even more difficult they possess a variety of immunomodulating effects and act as immune adjuvants as well as having a prophylactic effect on various tumours. Is it possible that all these actions can be explained by one major biochemical mechanism?

The principal topic in Chapter 7 was a treatment of aggregation of NTP subunits accompanied by fast NTPase activity at the polymer tips. Actin and microtubules were believed, at one time, to behave in this relatively simple way. As of this writing, it seems clear that, in both cases, NTP subunits actually penetrate (or survive) into the polymer ends by virtue of addition of subsequent subunits: conversion of an added NTP subunit into an NDP subunit is in fact not fast compared to on-off transitions.1 Thus there may be a collection or “cap” of surviving NTP subunits at each polymer end. Though this much seems clear, further details are in the process of being worked out and are by no means generally agreed upon. For this reason, in this chapter we bypass biochemical details (except for illustrative examples in Section 24) and devote the bulk of the chapter to a consideration of two-phase behavior at the polymer ends. The two phases referred to are a polymer end either with or without an NTP cap. This subject can be dealt with without a commitment to a particular detailed biochemical model; we merely assume that some unspecified biochemical mechanism exists that generates two-phase activity (see Section 24 for examples). Actually, so far there is evidence for two-phase activity in microtubules2–4 but not in actin.

Many experimental findings suggest that disturbances of noradrenergic neurons in the CNS are involved in the pathogenesis of depressive disorders. Moreover, evidence indicates that adaptive changes of central noradrenergic neurons contribute to the biochemical mechanism of action of most anti-depressive treatments (Goodwin, 1984; Johnstone, 1982). Accordingly, assessing the activity of central noradrenergic neurons in depressive patients has become important in psychiatric research.

Neuropathy is one of the most severe side effects of disulfiram therapy. We report the case of a young man who developed a neuropathy following disulfiram administration, with a virtually complete recovery in 14 months. We then discuss 37 cases of disulfiram neuropathy reported since 1971. Evidence is given that: (1) there is no numerical sex prevalence, although the incidence of the disease in women is probably disproportionately high; (2) symptom onset latency is dose-dependent, being longer at 250 mg/day or less; (3) neurological deficits are also dose-dependent, being milder at 250 mg/day or less; (4) the two previous findings and single observations suggest that disulfiram neuropathy is a dose-dependent phenomenon; (5) recovery probably follows a course which depends primarily on the initial degree of impairment; (6) the genetic mechanism probably involves carbon disulfide and a hypothesis as to the possible biochemical mechanism is proposed; (7) chloral hydrate can bear a potentiation effect on neuropathy, and the association with disulfiram is best avoided. Further, we give guidelines for the differentiation between alcoholic and disulfiram neuropathy, advise prescribing the drug at 250 mg daily or less, if possible, and stress the utmost importance of an early diagnosis.

Benzodiazepines have found wide therapeutic application in the treatment of anxiety, sleep disorders, muscle spasms and convulsions. In the present report we describe recent progress in the clarification of the mechanism of action of benzodiazepines: benzodiazepines are bound to a specific target structure in the brain, termed benzodiazepine receptor, in order to elicit their pharmacological and therapeutic central effects. The receptor is characterized by a binding site highly specific for benzodiazepines. In addition to the identification, characteristics and distribution of the benzodiazepine receptor in normal human brain, its alteration in Huntington’s disease are described. Furthermore, present views on the biochemical mechanism of action of benzodiazepine are discussed.

Gossypol does indeed prove to be a simple, safe, economical, and reversible method of male contraception, an understanding of its biochemical mechanism of action will be essential, since such elucidation may lead to the development of synthetic compounds exhibiting the desired antifertility effect without the toxicity so far noted in animals and in humans.

ALTHOUGH the inheritance of resistance1 in wheat (Triticum aestivum L.) to stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) is fairly well understood, most efforts to elucidate the biochemical mechanism involved have been unsuccessful. Biochemical studies of plant diseases involving rusts and other obligate parasites2 have contributed to knowledge of biochemical symptomatology, but no chemical changes have been correlated with the action of specific genes for resistance. Future advances it seemed, would depend on a reliable test to facilitate such correlations, and so we have developed a bioassay with the necessary specificity, which detects the presence of metabolites involved in the expression of the resistance. We have thus been able to demonstrate a gene-specific RNA that seems to be directly responsible for initiating the resistant reaction in wheat against stem rust. A preliminary report of some of these findings has been presented3.

The study of antibiotic resistance determinants is an active area of investigation that covers many aspects of plasmid biology. Thus, there is interest in, not only the biochemical mechanism by which the determinants express their resistance, but also in the distribution, origins and dissemination of resistance mechanisms. The problem of dissemination is particularly interesting since antibiotic resistance provides a convenient marker for the investigation of transposable elements. Parenthically, it should be added that plasmid-encoded resistance determinants are key components of all cloning vectors used in recombinant-DNA experimentation 1and “amp” and “tet” have become almost bywords in the field!

The cumulative interferon yield from cultures of poly(I)·poly(C)-induced human diploid fibroblasts (FS-4) in the first 24 hr after induction is increased (superinduced) approximately 50-fold by appropriate treatment with 5,6-dichloro-1-β- d -ribofuranosylbenzimidazole (DRB) and cycloheximide. Two components have been defined in the biochemical mechanism of this paradoxical enhancement. The content of polyadenylated interferon mRNA in induced and superinduced FS-4 cells was assayed by translation in oocytes in Xenopus laevis . First, as reported earlier (P. B. Sehgal, D. S. Lyles, and I. Tamm, Virology 89 , 186–198, 1978), interferon mRNA is approximately 14-fold more stable in the continuous presence of DRB (40 μ M ) than in inhibitor-free controls. Second, estimates of the content of interferon mRNA during the first 3 hr of induction in control cultures and in those exposed to DRB alone or cycloheximide alone are consistent with a 3- to 4-fold higher apparent rate of synthesis of interferon mRNA in treated cultures than would be expected if cycloheximide had no effect on transcription and DRB (40 AM) inhibited transcription ∼80% (P. B. Sehgal, I. Tamm, and J. Vilbek, Virology , 70 , 256–259; 542–544, 1976).

Selenite cataract is a fairly recently described, experimental animal model for cataract (1). Selenite cataract has been extensively characterized histologically (2) and biochemically (3,4). The model has been particularly useful for studies on the roles of calcium accumulation and lens proteolysis in cataract formation (4). This review describes current knowledge of the biochemical mechanism for selenite cataract and indicates how the model may be used for further understanding of cataractogenesis in general.

It has been apparent from this conference that the FUra-CF combination is of exceptional interest to investigators in all areas of cancer chemotherapy, from basic biochemistry to clinical studies. There are a number of reasons for this. First, the FUra-CF combination was proposed on the basis of rational a priori biochemical studies at the enzymological level, which revealed the role of CH2H4PteGlu in the mechanism of interaction between FdUMP and TS. Secondly, there is a multiplicity of biochemical pathways and reactions involved in the conversion of CF to the reduced folate cofactor form. This provides the opportunity for many more biochemical studies which in turn should give rise to more ideas for drug modulation. Thirdly, the basic concept seems to hold up across the board. In contrast to many modulation ideas which seem to work basically as conceived in vitro only to fizzle out when taken to in vivo systems, the effect of adding folates works in stabilizing the ternary complex in the test tube, it works to enhance the toxicity of the drugs in cell culture, and so far all indications are that the same biochemical mechanism is operative in human patients as well. This is encouraging in that it validates a concept of cancer drug pharmacology for which there was heretofore little precedent, namely, that finding out more about how drugs work will lead to more effective ways to use them.

—The injection of ethanol in mice produced a transient rise in 5-hydroxyindoleacetic acid (5-HIAA) levels in brain. However, no concomitant changes in serotonin (5-HT) levels were noted. In an attempt to explain the biochemical mechanism by which ethanol produced this effect, uptake of tryptophan by brain, serotonin turnover in brain, and transport of 5-HIAA from brain were investigated. No changes in tryptophan levels or uptake into brain of ethanol-treated mice were noted. Ethanol 3 g/kg was found to decrease serotonin turnover. Ethanol was also demonstrated to inhibit the removal of 5-HIAA from the central nervous system, and was found to be an inhibitor of 5-HIAA uptake by isolated choroid plexus. The inhibition of biogenic acid transport was noted even at sub-hypnotic levels of ethanol.

Brain free fatty acids (FFA) and diacylglycerols (DG) are maintained in a dynamic equilibrium with the membrane phospholipids. Many factors, including ischemia and drug induced convulsion, are known to disturb the equilibrium resulting in alteration of the FFA and DG level. The biochemical mechanism responsible for the disturbances is not yet fully understood. In this study, the FFA and DG in brain due to carbamylcholine and pentylenetetrazol induced convulsion and the suppressive action by scopolamine and diazepam was investigated. Carbamylcholine injected into rat brain intracerebrally gave rise to clonic and tonic seizures as well as exhibited some of the cholinergic symptoms. An increase in FFA and DG level was observed. The increase in FFA (but not DG) was blocked by pretreatment of scopolamine. Scopolamine injection (i. p.) alone could reduce the FFA level in brain but not DG. In all cases, subjecting the brain to 2 min post-decapitative ischemia resulted in a large increase in FFA and DG. Carbamylcholine stimulation potentiated the ischemia-induced increase in FFA and DG. Under this type of stimulation, arachidonic and stearic acids were preferentially released during stimulation and ischemia. Seizure was observed within two min after pentylenetetrazol administration (i. p.) to young rats. This drug also induced an increase in brain FFA but apparently was not effective in modulating the DG level. Pretreatment of rats with diazepam could effectively reduce the pentylenetetrazol-induced convulsion and FFA increase. A decrease in both FFA and DG was observed when rats were treated with diazepam (i. p.) alone. In general, FFA level in brain is increased during stimulation and decreased during depression. The differences in the FFA and DG changes as shown by convulsive and anti-convulsive agents further suggest that multiple biochemical mechanisms are present in mediating these changes.

With the identification and structural characterization of several visual pigments has come a new era of investigation. The above comparisons of amino acids sequences predict specific functional domains that may be tested to tell us how visual pigments function to absorb light and transform this "signal" to trigger a neural response. The details of how rod and cone pigments differ are now known for human pigments. The striking similarities between vertebrate and invertebrate pigments are remarkable for pigments that have been subject to divergence for over 500 million years. There are yet challenges ahead of us. The true tertiary structure of visual pigments must be obtained from a 3-dimensional crystal structure. The predictions for functional domains of interaction with the GTP binding protein must be confirmed or redefined. A rigorous definition of the chromophore environment and the properties that control the wavelength of absorption of 11-cis retinal chromophore are certainly still on the drawing boards. Specific genetic alteration through in vitro mutagenesis promises much insight, but the technology for expressing these membrane proteins in functional form has yet to be achieved. We may expect, however, these problems will be addressed and in the next few years facts should replace what are now speculations. Finally, it is a delightful observation that nature has capitalized on a general biochemical mechanism for control of second messengers in the cytoplasm of cells. Protein structural data deduced from genetic information now document the hypothesis that the structure and function of receptors for the catecholamines and that of visual pigments are similar. The receptors for serotonin, leukotrienes, prostaglandins, histamine and acetylcholine (muscarinic) are expected to belong to this same family. The lessons learned about visual pigments can be applied broadly to a general set of membrane receptors.

During amphibian metamorphosis, many tissues and organs undergo dramatic biochemical changes associated with the physiological transition from an aquatic to a terrestrial environment. Because of the dramatic nature of many of these changes, and the implication of underlying hormonal control, they have been utilized as model systems in numerous investigations of the biochemical mechanism of action of thyroid hormone (TH) (reviewed by Cohen et al., 1978, and Frieden, this volume). It is the purpose of this chapter to survey several organ systems and tissues whose changes during metamorphosis have been well characterized biochemically and to consider the experimental evidence for possible hormonal control of the changes. We will include the endodermally derived liver and intestine, the mesodermally derived kidney, and the ectodermally derived integument and eye. Biochemical changes in the blood are reviewed by Broyles (this volume). For all of these tissues, TH control has been implicated, but in many cases multiple actions of several other hormones are strongly suggested (see reviews by Dodd and Dodd, 1976, and White and Nicoll, this volume). Morphological and cytological changes accompanying the metamorphosis of these tissues have been reviewed elsewhere in this volume (see especially Fox).

The effect of various antibiotic drugs on wound-healing was investigated following parenteral administration in rats. The criterion for healing was the tensile strength of an incised and sutured healing skin wound. Therapeutic doses of gentamycin and tetracycline and sub-toxic doses of ampicillin demonstrated a significant inhibition of cicatrisation. The underlying biochemical mechanism involved in delays in the wound-healing process that are not attributable to bacterial causes is assumed to be the inhibition of protein synthesis, particularly that of connective tissue.

Publisher Summary The biochemical mechanism of resistance of the strains isolated from patients is described in the chapter. The mechanism of resistance to aminoglycosidic antibiotics was initiated by H. Umezawa and coworker. They first examined the reactions of kanamycin-neomycin acetyl transferase and of kanamycin-neomycin phosphate transferase. They described a method that gave enough of the enzyme reaction-products for structural determination, and they elucidated the structures of most of the reaction products. The chapter proves the direct relationship between the enzymes and the resistance; this was first shown by the fact that kanamycin C (which has no 6´-amino group to be acetylated) inhibits the resistant strain that produces the enzyme involved in acetylation of the 6´-amino group of kanamycins A and B. The reaction mechanism of kanamycin-neomycin phosphate transferase has been studied in detail, and the result permits prediction of the structures of derivatives active in inhibiting the growth of resistant organisms. The compounds thus synthesized are useful in the treatment of resistant infections, and are becoming more valuable as probes for further analysis of the biochemical mechanism of resistance. Determination of the structures of enzymes involved in resistance, in the future, give information useful in predicting new types of resistant organisms that may develop, and the structures of compounds active against future resistant strains.

The past five years have seen a steadily accelerating advance in our understanding of the mechanisms and scope of mammalian thermogenesis. At the physiological level the recognition that brown fat is the major thermogenic organ not only in hibernators (Smith and Horwitz, 1969) but also in non-hibernators such as the rat (Foster and Frydman, 1978, 1979), together with the implication of brown fat in diet-induced thermogenesis (Rothwell and Stock, 1979) and the evidence that grown-fat thermogenesis is defective in certain examples of genetic obesity (Himms-Hagen and Desautels, 1978) have all centred interest upon this tissue. At the subcellular level the demonstrations that the mitochondria from brown fat possess a unique regulatable proton short circuit (Nicholls, 1974a) enabling ATP synthesis to be bypassed, and that this function is performed by a specialized inner membrane protein (Heaton et al., 1978) whose amount varies in synchrony with the thermogenic capacity of the tissue, have provided a biochemical mechanism to account for the physiological findings.

From the Archean geological record, one can infer that photoautotrophy evolved early in earth history; however the nature of this photosynthesis -- whether it was predominately or cyanobacterial -- is less clearly understood. General agreement tht the earth's atmosphere did not become oxygen rich before the Early Proterozoic era places constraints on theories concerning more ancient biotas. Accommodating this limitation in various ways, different workers have hypothesized (1) that blue-green algae frist evolved in the Early Proterozoic; (2) that oxygen producing proto-cyanobacteria existed in the Archean, but had no biochemical mechanism for coping with ambient O2; and (3) that true cyanobacteria flourished in the Archean, but did not oxygenate the atmosphere because of high rates of oxygen consumption caused, in part, by the emanation of reduced gases from widespread Archean volcanoes. Inversion of hypothesis three leads to another, as yet unexplored, alternative. It is possible that physiologically modern blue-green algae existed in Archean times, but had low productivity. Increased rates of primary production in the Early Proterozoic era resulted in the atmospheric transition documented in strata of this age. An answer to the question of why productivity should have changed from the Archean to the Proterozoic may lie in the differing tectonic frameworks of the two areas. The earliest evidence of widespread, stable, shallow marine platforms is found in Lower Proterozoic sedimentary sequnces. In such environments, productivity was, and is high. In contrast, Archean shallow water environments are often characterized by rapid rates of clastic and pyroclastic influx -- conditions that reduce rates of benthonic primary production. This hypothesis suggests that the temporal correlation of major shifts in tectonic mode and atmospheric composition may not be fortuitous. It also suggests that sedimentary environments may have constituted a significant limit to the abundance and diversity of early life.

A discussion of biochemical mechanisms in this symposium is critical if one wishes to develop a concept of how O3 exposure induces alterations in a plant’s metabolism, which ultimately lower a plant’s final yield or market value. Furthermore, an understanding of what is and is not known will allow future research to be formulated. In keeping with this concept, I hope to describe several possible scenarios for the development of yield reduction due to primary and secondary biochemical responses. I will concentrate upon O3, as it was the major oxidant investigated within the NCLAN studies.

Diapause of pupae of a silkworm, Antheraea pernyi Guerin-Meneville, was invariably terminated by exposure to cycles of 16 hours of light and 8 hours of darkness. When 15 minute light breaks were introduced during each 8 hour dark period at 21 hours after the beginning of the 16 hour photophase, 33 percent of the pupae did not break diapause. Diapause was broken in 67 percent of the pupae maintained in complete darkness. A similar light break introduced during a 12 hour dark period and a light break of one hour during a 14 hour dark period were not effective. Larvae of the codling moth, Laspeyresia pomonella (L.) had a similar pattern of response, but the percentage breaking diapause was always less. A biochemical mechanism which provides a possible explanation of the results with the oak silkworm is presented.

Meiotic maturation in starfish oocytes is initiated by the purine base 1-methyladenine but not the nucleoside (1-methyladenosine) of this compound. The extent to which this may be the result of inaccessibility of 1-methyladenosine to cellular sites was investigated. Oocytes were homogenized at various stages of maturation, incubated with 1-methyladenosine and the effects of these homogenates on oocyte maturation were subsequently tested. Oocyte homogenates incubated with 1-methyladenosine were active in producing oocyte maturation, whereas homogenates not incubated with the nucleoside were inactive. Thus, activation of 1-methyl-adenosine occurred in response to oocyte homogenization. Specificity studies indicated that only compounds containing 1-methyladenine were activated in response homogenization. Activation of the starfish gonadotrophin (radial nerve factor) was not observed. These studies suggest that the starfish oocytes contain biochemical mechanism(s) for rendering 1-methyl-adenosine, an effective stimulator of oocyte maturation. Under normal conditions the integrity of the cell surface makes this interaction impossible. Activation of 1-methyladenosine, therefore, provides a simple and sensitive indicator of oocyte cellular integrity or damage.

Publisher Summary The purpose of this chapter is to review the progress made in the employment of methods of inhibition analysis in the whole animal in experimental cancer chemotherapy. It discusses that the term inhibition analysis is employed to designate the field of research employing competitive metabolite-analogue inhibitions in the study of biochemical reactions. The inhibition index is defined as the ratio of antagonist to metabolite in moles, which results in a defined observable effect in a specific period of time. The chapter also reviews the carious experimental procedures and examples given of the kind of information that can be obtained, employing such methods. Such studies may help integrate biological and biochemical investigation. Presumptive evidence may be obtained employing antagonists and metabolites in the whole animal regarding biochemical mechanism. The antineoplastic effectiveness of a drug is not a fixed characteristic of the drug. It may be altered by factors pertaining to the host and the tumor, as well as by the method of employment of the drug. It is possible to increase the effectiveness of drug action against tumor, relative to the toxic action of the drug for the host.

Publisher Summary This chapter discusses the chemical physiology of Trypanosomidae; it also discusses the same aspects of the Bodonidae. The Trypanosomidae are important as causative agencies of many important diseases of man and livestock. Trypanosomes become resistant against many drugs, the speed with which the resistance develops and the tenacity with which it is retained varying with different compounds. The biochemical mechanism of drug resistance seems to consist in the development of a mechanism diminishing the drug uptake. Biologically, a genetic change of some kind, perhaps a mutation, must be assumed in those cases where higher degrees of resistance have developed. The Bodonidae are free living protozoa or parasites of lower animals without economic importance. The free-living members of the family are found in surroundings containing little or no free oxygen. They have well-developed anaerobic mechanisms, but their nature is not yet known.

Twenty-two organophosphorus compounds have been given to adult hens to test their ability to produce a delayed neurotoxic effect like that produced by triorthocresyl phosphate. Fourteen compounds falling in several structurally homologous groups were active. All of them inhibited in vitro esterases of chicken CNS. No biochemical mechanism for this toxic effect can be put forward.

A fundamental study of the chemistry of BZ was conducted to assist in problems that may arise in detection, decontamination, biochemical mechanism of action, and metabolism. BZ reacts with (1) substituted phenyl isocyanates to yield 2, 3-oxazolidinediones, (2) nitriles to produce amides (Ritter reaction), and (3) alkyl halides to give quaternary ammonium salts. Analysis of BZ can be accomplished by quaternization in acetonitrile, separation of reactants, and assaying spectrally.

Hines and Knowlton1,2 have demonstrated a decrease of muscular glycogen levels after denervation. The biochemical mechanism underlying this phenomenon, however, is not clearly understood. It does not seem to be explained by an activation of phosphorolytic processes, as phosphorylase was shown by Huls and Leonard3 to decrease in the skeletal muscle after nerve transection.

Summary. Mice were treated on their back Bkin with a single promoting dose of the tritium labellad phorbol ester .A1 (TP A-20- 8H) in the standard manner. Methods were investigated for determination of the fate and distribution of the radioactivity in the skin ("epidermal fraction" and "connective tissue fraction") and in intemal organs (liver, kidney, spieen) at different time intervals after administration of the phorbol ester. In mice which were kept singly and prevented from licking their back akin about 65% of the total radioactivity administered is detectable in the treated area 12 hours after appli­ cation of TPA-20-8H. The rest of the radioactivity is found in the carcass (20%) andin the cage (15%). In mice which were not prevented from licking 12 hours after administration of TP A-20- 8H only 15% of the activity administered was found in the treated skin area, 40% in the carcass and 40% in the cage. The radioactivity extractable from the "epidermal fraction" (10%) of such mice consists of unchanged TPA (8%) and of metabolic products (2%). One of the metabolites may be either phorbol-13-acetate or 12-0-tetradecanoyl-phorbol. P088ible pathways of metabolism of phorbol esters as well as the problern of the "ultimate tumor pro­ motor" are being discussed. Z'U8ammenfa88'u:ng. Die Ruckenhaut von Mausen wird mit einer tumorpromovierenden Einzeldosis des tritiummarkierten Phorbolesters .A1 (TP A-20- 1H) in der standardisierten Weise behandelt. Es werden Methoden untersucht, die es erlauben, den Verbleib und die Verteilung der Radioaktivitat in der Haut ("Epidermisfraktion" und "Bindegewebsfraktion") und in inneren Organen (Leber, Nieren, Milz) zu verschiedenen Zeiten nach der Applikation des Phorbolesters zu verfolgen. Wird bei Einzelhaltung der Tiere verhindert, das sie das behandelte Hautareal ablecken, so findet man 12 Std nach Applikation von TPA-20-1H 65% der gesamten Radioaktivitat im behandelten Areal. Der Rest wird im Kadaver der Maus (20%) sowie im Kafig gefunden (15%). Wird bei Einzelhaltung das Ablecken nicht verhindert, so findet man nach 12 Std nur 15% der applizierten Aktivitat im behandelten Hautareal und 40% in Kadaver sowie 40% im Kafig. Die Radioaktivitat, die aus der "Epidermisfraktion" (10%) extrahiert werden kann, besteht zu 8% aus unverandertem TP A und zu 2% aus Stoffwechselprodukten. Von den letzten ist eines moglicherweise Phorbol-13-acetat oder 12-0-Tetradecanoyl-phorbol. Mog­ liche Stoffwechselwege fur Phorbolester und das Problem der Wirkform der Ester werden diskutiert.

A new radioactive compound the 51Cr-β-glycerophosphate complex, which accumulates in different types of tumor, has been assayed in mice transplanted subcutaneously with brain tumor. A very high tumor to brain uptake ratio was observed throughout the experiment (72 h). The optimal interval seemed to be between 6 and 24 h. The biochemical mechanism involved in the accumulation of the compound by the Tumor appeared to be more complex than a simple phosphomonoesterase action.

The effect of aflatoxin on the activities of 5 rat liver lysosomal enzymes (acid deoxyribonuclease, arylsulfatases A and B, β-glucuronidase, β-glucosidase and β-galactosidase) has been investigated in vivo and in vitro. Three hours after the administration of aflatoxin, activities of most of the enzymes increased significantly reaching maximal levels at 48 hr. The activity of acid DNase increased the most (276 per cent of the control level). At the same period (48 hr) the activity of the soluble lysosomal enzymes greatly increased. Aflatoxin had a labilizing effect on lysosomal membranes, causing the release of lysosomal enzymes into the supernatant. The data are discussed in connection with the biochemical mechanism of aflatoxin intoxication.

Experiments designed to test the possible effects of chemicals on the physiological clock aim to elucidate the biochemical mechanism of the periodicity. Diurnal changes of respiration and (in plants) of the photosynthetic capacity had been observed quite early. This suggested that the rhythm might be explained by the accumulation of respiratory or photosynthetic products. One might imagine that an accumulation of these substances could cause an inactivation of enzymes after which the substances would then gradually decompose, etc. This interpretation proved to be incorrect, as have all the other analogous explanations based on simple metabolic processes.

THE understanding of the aetiological factors involved in the curious poisoning arising from the ingestion of Lathyrus odoratus seeds has been greatly advanced by the identification of β-amino-propionitrile as the active moiety of the toxic principle and the recognition of the even more potent lathyrogenic property of aminoacetonitrile (AAN)1,2. However, the site and nature of the primary metabolic disturbance responsible for the characteristic mesenchymal lesions produced by aminonitriles have not yet been elucidated. The present investigation was designed primarily to explore the possibility of using tissue cultures as a prospective tool for studying under in vitro conditions the biochemical mechanism underlying the toxic action of AAN.