Showing papers in "Annals of the New York Academy of Sciences in 1969"

Measurements of Subnanosecond Fluorescence Lifetimes with a Cross-Correlation Phase Fluorometer

Abstract: The methods for the direct determination of fluorescence lifetimes may be discussed by considering each single fluorescent species as a detector in which the response to an infinitely narrow pulse of light decays in time, t, according to the exponential law I ( t ) = I(0) x exp (kt) . From the relations of the exciting light with the light emitted by such exponential detector, the rate constant k or its reciprocal T, the lifetime of the excited state may be determined. FIGURE 1 shows the Fourier spectrum characteristic of an exponential detector (cf. McLachlan, 1963). The detector responds without attenuation or change of phase to all frequencies from zero to those approaching k, while frequencies of this order or exceeding k are progressively more attenuated. The phase of the emitted light lags behind that of the excitation by 4.5\" when o = k, and tends to 90\" lag towards complete attenuation. It follows that, for the determination of k, the fluorescence must be excited by light of one or more frequencies in the neighborhood of k (hatched area of FIGURE 1 ) . The former is practically realized by excitation with sinusoidally modulated light, and the latter by excitation with light pulses the frequency spectrum of which is made up of a narrow band of frequencies. Classical electrodynamics shows that, for emission in the visible and ultraviolet regions of the spectrum, k is of the order of los sec-1 (or T of order 10-8 sec). Therefore, the frequencies to be employed in the excitation must be of the order of l O s / 2 ~ or in the region of 1-50 MHz. Light modulated at a single frequency in this range may be produced by various electro-optical methods, (Gaviola, 1927; Maerks, 1938; Bauer & Rozwadowski, 1959; Miiller et al., 1965), whereas techniques for the production of approximately Gaussian pulses of half-width 0.3 to 3 nsec (D'Alessio et al. 1964, Hundley et al. 1967) have been described. Each type of method has its own advantages and disadvantages. The pulse method is particularly useful when several modes of decay are possible, although the methods employing a single frequency are undoubtedly the more accurate because of the extreme frequency selection attainable by electronic techniques. They are also better adapted to the measurement of lifetimes in the subnanosecond region, and because we had this object in mind we have chosen to employ sinusoidally modulated light of fixed frequency in our measurements. The theory of the fluorometer, so named by Gaviola who constructed the first apparatus of this kind in 1926, has been given in detail by Dushinsky (1933). If a fluorescent species is illuminated with light modulated with frequency f, describable by the expression E(t) = A + B cos 27rft * This research was supported by United States Public Health Service Grant GM 11223.

Open-Field Behavior in the Rat: what does it Mean?

Abstract: The rationale underlying the use of the open-field test is roughly as follows. Many mammals, when exposed to strange or noxious stimuli, will typically “freeze.” Freezing appears to have adaptative significance in that it is more difficult for a predator to observe a nonmoving animal. A second consequence of exposure to such stimuli is that this will often trigger off activity in the autonomic nervous system. One of the results of such activity is that the animal will defecate. Thus, an emotional animal may be defined as one which, when exposed to noxious or novel stimuli, does not move about and will defecate. To construct such a set of stimuli for the laboratory rat, which is our most common experimental subject, is relatively easy. All we have to do is place the rat into an environment that is distinctly different from any environment he has previously encountered. The open field meets these requirements since it is an apparatus in which the rat has not previously been placed and since its dimensions are vastly greater than the boundaries of his usual living quarters. These conditions should ensure that the open field is both strange and at least mildly noxious to the rat. By drawing appropriately sized squares on the floor of the open field, it is possible to quantify activity by recording the number of squares the animal enters during a given unit of time. One easily quantifies defecation by counting the number of boluses dropped during the testing interval. Given these data the operational definition of an emotional animal is one that has a low activity score and a high defecation score. I believe that the above statements fairly represent the rationale for the use of the open-field test. My statements are reasonable, they have ethological validity and they are, of course, completely circular. We can state, if we wish, that emotionality is that which the open-field test measures and feel safe, secure, and smug behind such a statement. If we do this, however, we are avoiding one quite unpleasant aspect of reality: How do we demonstrate the validity of the statement that the open-field test measures the construct of emotionality? What I should like to do today is describe two experiments that give general validity to the use of the open-field test as a measure of the construct of emotional reactivity. However, these data also indicate that the test measures a second behavioral dimension, so that there are certain difficulties in the interpretation of the open-field activity score.

The organization of the avian telencephalon and some speculations on the phylogeny of the amniote telencephalon

Abstract: There have been numerous surveys of the morphology of the avian telencephalon and attempts to compare it to the various divisions of the telencephalon of other vertebrates. These comparisons were often tenuous, based upon apparent resemblance to structures in mammals. Time does not permit a complete survey of all structures discernible within the forebrain, and the present report is a resume of only some of the recent findings on the avian telencephalon. The major portion of the avian telencephalon consists of a mass of grey matter in the lateral wall of the hemisphere subdivided into several regions, all ending with the suffix “-striaturn,” and with a small region of clearly laminated pallium. As il consequence of the relatively small amount of pallium in birds, most suggestions concerning the nature of the avian telencephalon have derived from the striatal appearance of the cell masses in the forebrain. FIGURE 1 is a Nissl-stained section of a transverse section through the pigeon telencephalon showing the location of the paleo-, neo-, and various subdivisions of the hyperstriatum. It is worth recalling, however, the original reason for designating these areas as striatum. Striatum was simply a descriptive term indicating that these regions consisted of large masses of grey matter with bundles of myelinated axons passing through them, giving them a striated appearance. However, this simple descriptive feature provided no information about the differences between different masses of grey matter within the telencephalon, their connections, or participation in any functional system, and in no way provided any defining characteristics of the cells that would permit comparing them to cell masses in other vertebrates. There was no logical reason to expect that all striatal structures were necessarily comparable, except that they consisted of masses of neurons, glia and axons. Even more puzzling was the striking discrepancy between the relatively small amount of pallium and large volume of striatum in sauropsids, and the apparently inverse ratios of large areas of pallium and only moderate amounts of striatum in mamma1s.t

Some neurological species differences - a posteriori*

Abstract: “Human imagination is the source of the greatest triumphs of science, technology, art, and philosophy. We must be careful not to cripple its exercise by arbitrary restrictions. It gives us our preeminence over the brutes.” C. J. Herrick 1956 The Evolution of Human Nature

Conditions producing psychogenic polydipsia in animals

Abstract: A brief summary of the first report (Falk, 1961a) on schedule-induced polydipsia will suffice to introduce this phenomenon. Fourteen normal rats were maintained at 70-80 percent of their free-feeding body weight by limiting their intake of food. The animals earned most of their daily food ration by bar-pressing on a variable-interval one-minute (VI 1 min) schedule for 45-mg Noyes food pellets during 3.17-hour daily experimental sessions. On this schedule, a barpress is reinforced by a food pellet at varying times from a previous reinforcement (from a few seconds to two minutes), the average interreinforcement time being one minute. Each animal performed in a sound-attenuated box, with the automatic control and recording equipment in an adjoining room. No external environmental cue informed the animal exactly when a bar-press would yield a pellet. At the end of each daily session, the animal was returned to its home cage and given any food supplement necessary to maintain body weight at the value selected. Water was always available. During the session licks from a calibrated water reservoir were recorded electronically. In the home cage, any water drunk from a calibrated animal drinking tube between sessions was measured. On this schedule a typical behavior pattern rapidly developed. After earning a food pellet, the rat would consume it and drink about 0.5 ml of water. During the 3.17-hour session, intake averaged 92.5 ml, or 3.43 times the preexperimental, 24-hour water intake level. Between sessions, although water was available, intake averaged less than 1 ml. Such a phenomenon is strange and unprecedented, for the animals are drinking approximately one-half their body weight in a few hours. Water deprivation, heat stress, or osmotic-loading techniques do not approach comparable stimulation of water intake. Under normal laboratory maintenance conditions, daily water intake levels remain rather constant, and even strong facilitating stimuli induce only moderate increases. The evidence will be examined to determine whether this polydipsic phenomenon can be explained either on physiological grounds or with respect to simple behavioral considerations. The variables of which the polydipsia is a function will be summarized as far as these are known at present. A theoretical explanation in terms of adjunctive behavior will be given, and methodological implications and cautions for thirst research attempted.

Studies of self-associating systems by equilibrium ultracentrifugation.

Abstract: Self-associating systems, wherein n molecular subunits (monomers) associate reversibly to form discrete oligomers (n-mers), provide an excellent opportunity for thermodynamic studies of molecular interactions in solutions. These simplest of all possible associating systems should permit, a priori, more thorough and critical investigations than appear feasible with more complex systems. Thermodynamic characterization of such systems potentially provides information about enthalpies and entropies of association. Perturbations of the reactions, by alterations of solvent milieu or by modification of the associating species themselves, may be used to probe the details of the basic processes involved and facilitate interpretation of the derived parameters. A thermodynamic approach to such studies requires, first, a knowledge of the reversibility of the reactions, second, information as to the stoichiometries (and homogeneity) involved, and third, precise determinations of association constants. Equilibrium ultracentrifugation is one of the more effective tools for obtaining such information, especially at early stages of the investigation where stoichiometries, heterogeneity and extent of reversibility are relatively unknown. After a system is well defined, it is then relatively easy to pass on to other, perhaps more rapid or more convenient, techniques such as osmotic pressure, light-scattering, specific optical absorption or rotatory changes, or other individually applicable observation procedures. In this paper we reemphasize a simple method of detecting heterogeneitywithin limits-in associating systems and therefore, by implication, of noting reversibility. We also present methods of estimating stoichiometries in favorable cases, for both ideal and nonideal self-associating solutes, and for evaluating association constants of nonideal systems. Illustrations of these methods are provided from ongoing studies on the association behavior of P-lactoglobulin A. For the most part, our experiments utilize the high-speed equilibrium technique (Yphantis, 1964) but, often, with the modification discussed by Teller and COworkers (Teller, Horbett, Richards and Schachman, 1969) of using somewhat lower speeds so as to spread the usefully observable region of a concentration distribution throughout most of the solution column.

Afferent impulse discharges from glucoreceptors in the liver of the guinea pig.

Abstract: Afferent activity from vagal nerve filament of guinea pig liver was recorded. Perfusion of liver by hypertonic solution caused an increase in firing rate. There may be osmoreceptors in the liver.

On the human use of human beings

Abstract: After reading through the Conference program and considering the titles of the papers to be presented, I would like to add a new consideration to the discussion-the individual-which to me is the object of all our efforts. For the end we seek in medicine-the objective toward which our use of computers must be oriented-is the well-being and fulfillment of each and every individual. This statement of our end, or goal, I will leave for the moment as an assertion. It is, of course, open to debate, as is any statement, but I have heard no criticism of it to date which would persuade me of the necessity to amend it. On the other hand, I have encountered very strong defenses of its validity. Therefore, I will let it stand as an assumption. This brings me to the title I have given to my remarks. Most of this title, as you are well aware, is the title of a book by Norbert Weiner. I have used it because the several writings of Weiner, one of this century’s rare mathematical geniuses, emphasize for me the multiple dimensions and implications of the many issues we will discuss and deliberate on during this Conference. Throughout Weiner’s essays, there is focus on technology and science as a means to an end, and at the same time concern lest, in concentrating on our means, we lose sight of our ends. For Weiner, ends, purpose, objectives, and goals are dominant. Technology, the system, has validity and purpose only in terms of external points to which it is oriented, and it is in terms of these that its relevance must be assessed and the system justified. Thus, in considering the use of technology in m e d i c i n d a t a processing and mechanization, the use of computers, and so on-Weiner might say, as do I, that we must look at not just the “how,” but, more importantly, the “why.” And in responding to the question of “why,” we cannot be satisfied with the Everest dictum: “Because it is there.” Use of computers or of any other technology in medicine, only because we think we have arrived at the technological capacity to effect their use, can lead only to a Pyrrhic victory. I do not mean to imply that computers and other technological innovations should not be used or that the “how” is not important, too. Far from it. I am concerned that the “how” is related to the “why”-that we use our technological capacity to further our progress toward an identified and fully explicated goal, and that this goal is never forgotten.

Taste versus calories: sensory and metabolic signals in the control of food intake.

Abstract: In this paper we would like to discuss the role of sensory and metabolic signals in the control of food intake. The problem can be defined by perusing FIGURE 1, which presents a simplified version of a previously published schema outlining the control of intake in flow chart form (Jacobs, 1962). The initial conditions assume an animal already eating food. We shall not be concerned with the particular causes initiating the meal. Starting with the top of the FIGURE 1, then, we may ask classical question of physiologists analyzing intake regulation: What does the diet contain that can act as a signal to monitor subsequent intake? This signal can increase intake in a short-term positive feedback loop, as seen in the lower right side of the Figure, or decrease it in a negative feedback loop. The latter case we have called satiety. The two classes of physicochemical stimuli which interest us are labeled calories and taste. Both sets of signals are initiated in specialized receptor systems and relayed to the central nervous system (CNS) by nervous and/or humoral paths. It should be pointed out that our choice of the terms, taste and calories, is an oversimplification of the actual situation, which is at least hinted at in FIGURE 2. This diagram shows the same system, with the physicochemical stimuli expanded. What we have called calories are in fact only one of a large number of potential metabolic signals, and taste, only one of a number of potential seniory signals. The metabolic class includes all of the classical factors that physiologists have implicated in food intake. When a single factor is singled out and perhaps overemphasized, we have a “theory” of intake, as in the classical glucostatic and thermostatic hypotheses. Some would also consider a lipostatic or perhaps an “aminostatic” theory as well. Most people working in this area now accept Edward Adolph’s dictum that food intake is under multiple factor control, and that some combination of all of the metabolic signals is involved. The sensory category summarizes the classes of stimuli contained in food which have been of interest to the sensory psychologist, but which, for the most part, have been ignored by the regulatory physiologist. FIGURE 2 suggests many interesting problems, e.g. which receptor system responds to which classes of stimuli? Where are the latter located? Are they independent? For the purpose of this discussion, we can ignore these complexities. Returning to the simpler case (FIGURE 1 ) , we can now point out that the terms,

Ischemic injury of myocardium.

Abstract: The sudden onset of ischemia in myocardium is followed within a few seconds by a series of striking functional changes: The area becomes cyanotic; cooler; hydrogen accumulates; electrocardiographic changes appear; and, within 30 to 60 seconds, contraction ceases in the affected myocardium. These changes within the ischemic focus are directly related to the development of local anoxia, which causes the affected cells to shift from an aerobic to an anaerobic form of metabolism, resulting in a substantial decrease in energy production. Although injured and nonfunctional, these severely ischemic, markedly anoxic cells are viable and survive for a period of time. Early restoration of the coronary blood flow to an ischemic focus is followed by almost instantaneous restoration of aerobic metabolism and contractile function. However, if the period of ischemia is more prolonged, restoration of the blood supply is not followed by restoration of function, since the affected cells are either dying or dead. The severely ischemic viable cells are reversibly injured, whereas the severely ischemic dead cells are irreversibly injured. Our chief interest has been in determining what event or series of events within the cells dictates the onset of irreversible injury.' Our studies are predicated on the assumption that intracellular events discoverable by direct analysis of the tissue lead to the development of the irreversible state. Tissue known to be severely ischemic and fairly uniformly injured is required for analysis in direct studies of early changes in structure and/or function during ischemic injury. One must be able to identify and sample the affected tissue even though it appears normal upon gross examination. We have found that the posterior papillary muscle is an area of maximum ischemia in the large posterolateral infarct resulting from high occlusion of the circumflex branch of the left coronary artery in the dog heart.2 The posterior papillary muscle is easily identified, and the upper two-thirds of the muscle are uniformly injured in those dogs in which the cyanosis extends to the apex of the heart posteriorly. The muscle is ultimately almost completely replaced by scar tissue. The anterior superior portion of the septum of the left ventricle is not involved in this infarct; therefore it is used as a source of nonischemic control tissue.

Comparative architectonics of the neocortex of mammals and their evolutionary interpretation

Abstract: Cytoarchitectonics and myeloarchitectonics of the cerebral cortex were introduced around the turn of the century as a method of outlining cortical areas with the particular scope of localizing functional units. Together with the neurophysiological approach, such functionally and architectonically determined cortical areas could be’ demonstrated throughout most of the mammalian orders. In particular, sensory receiving areas for vision, audition, and tactility and, contiguous with the latter, effector motor areas could be outlined. From the point of view of the architectonicists, particular terms were coined regarding the structure of the neocortex on the one hand and of the older cortices on the other. The neocortex, insofar as it passes through a 6-laminated period during fetal life, is referred to as isogenetic cortex, short isocortex. The older cortices-the medial archicortex (hippocampus formation of mammals) and the lateral paleocortex (olfactory cortex proper) which exhibit very peculiar characteristics in addition to limited lamination are classified as allogenetic cortex, short allocortex. However, two particular intermediate structural steps are encountered, the first going out from allocortex to isocortex, referred to as periallocortex, and the second intercalated between the latter and the mature isocortex, referred to as proisocortex. Periallocortex ( pAll) and proisocortex (Pro) mediate structurally between the extreme types of allocortex and isocortex (FIGURE 1 ) . Both the architectonic and the electrophysiological studies were first made in monkey and in man (Brodmann, 1909; Campbell, 1905; Foerster, 1936; C. & 0. Vogt, 1919) and subsequently in many other mammals. For example, the central region of higher primates comprises the precentral motor cortex, an agranular type of cortex with the largest pyramidal cells of layer V, and the postcentral somatic sensory cortex, a highly granular type of cortex with the highest degree of granularization in area 3b. For this hypergranular type, von Economo (1925) introduced the term koniocortex, which means powder cortex, since not only granular layers I1 and IV are well elaborated, but the whole outer main stratum of cell layers 11,111, and IV appears enriched with granular cells and stands out by its cell density against a light V and dense VI of the inner main stratum. It is this hypergranular type which, with specific modifications, also forms the central areas of the auditory and visual regions. The agranular motor cortex and the eugranular sensory cortex meet in the depth of the deep central sulcus of higher primates corresponding to a general rule, which we have elaborated in a series of mammals, that the majority of the bottoms of sulci and even fissurets form the limit of architectonic areas.? (Sanides, 1962; Sanides & Krishnamurti, 1967; Sanides & Hoffmann, in press.) The central sulcus of higher primates has, moreover, a decisive meaning for

Evolution of the Peroxisome

Abstract: The work reported in this monograph has clearly established the presence of peroxisome-like particles in lower and higher representatives of both major biological kingdoms. Such findings invite speculation on the phylogenetic history of these particles, especially since some of the characters of peroxisomes label them as “primitive”, in both the literal and the figurative sense of the word. Some thoughts on the origin and evolutionary fate of peroxisomes were set forth briefly in earlier publications.4,5J0 They will be developed in a more systematic fashion in the present paper, in the hope that they may contribute to our understanding of the biological significance of peroxisomes, and perhaps provide some sort of guide for fruitful experimentation.

Glyoxysomes of castor bean endosperm and their relation to gluconeogenesis

Abstract: Ripe seeds of the castor bean (Ricinus communis) are very rich in fat ( > 60% of the dry weight) that is contained in endosperm tissue surrounding the embryo. During germination there is a precipitous fall in the total fat content, and sugars, principally sucrose, are formed. These sugars are absorbed and utilized by the growing embryo, but during the fifth day of germination, at 30' C, when fat breakdown is at its height, a gram of sugar accumulates for each gram of fat consumed.l

Alpha- and beta-thalassemia in Thailand.

Abstract: In Thailand, both aand P-thalassemia are widespread and there is more than one subtype in each variety. Hemoglobin (Hb) E which is a2, p;6G'u+Lys (Hunt & Ingram, 1959) is remarkably frequent (Na-Nakorn et al . , 1956; Sundharagiati et al., 1958, 1959a, 1959b; Flatz et al., 1965; Wasi et al., 1967a), reaching 50 percent in certain areas. These abnormal genes in different combinations result in a spectrum of syndromes ranging from asymptomatic heterozygotes to lethal H b Bart's hydrops fetalis. Attempts have been made to characterize the various genotypes by clinical, hematologic, biochemical, genetic and cord blood studies. This paper summarizes the manifestations of these syndromes, with particular emphasis on the diseased forms.

Immunity in Schistosomiasis

Abstract: After some 20 years of international research in immunity to schistosomiasis, our knowledge of the mechanism of resistance to this disease remains largely unknown, and the possibility of a rational progress toward control by immunological methods is still remote. Nevertheless, it is important that work in this field be fully supported. An understanding of the immunology of schistosomiasis means an understanding of one vital aspect of the host/parasite relationship. Findings and interpretations in this field will have a strong influence on many practical aspects of controlling the disease, especially on future approaches to chemotherapy. In this paper we have attempted to summarize what is known about immunity to schistosomiasis in man and in experimental animals. Particular attention has been paid to the rhesus monkey, in which we have defined more clearly the stimulus to acquired immunity. We have speculated about the mechanism that enables the adult worms t o survive for long periods without being affected by the immune response. Finally, we have attempted, as far as we can, to relate our findings in the rhesus to man.

Dynamic asymmetries in the corticosteroid feedback path and distribution-metabolism-binding elements of the adrenocortical system.

Abstract: Effective analysis of physiological systems requires knowledge about their dynamic characteristics. In the case of the endocrine control systems, such information is difficult to obtain, and, understandably, a great part of the endocrine literature emphasizes mainly the static characteristics of components or their connectivity. In 1961, Clynes pointed out that unidirectional rate sensitivity is a dynamic characteristic that may be present in a variety of biological systems, and that its properties could establish a two-channel mode of control of a variable that he termed “rein He further suggested that hormonal systems might have such properties. His ideas prompted the present work, which has explored dynamic asymmetries within the adrenocortical system, and has led to the discovery of unidirectional rate-sensitive properties within the corticosteroid negative feedback path of that system. As a result of the present work, the adrenocortical system appears to have asymmetrical dynamic properties that could qualify it to serve as one channel, or rein, in multiple-channel chemical control arrangements.

Eeg, psychological, and neurological alterations in humans with organophosphorus exposure*

Abstract: In the early 195O’s, the University of Colorado Medical Center conducted a multidisciplinary investigation of industrial and agricultural workers acutely exposed to a variety of pesticides. The focus of this program was a special project involving the intensive study of workers engaged in the manufacture of several organophosphorus (OP) anticholinesterase compoh,. ’.,. Because of the acute confusional states induced by O P exposure and because of the need for more information regarding the central effects of OP exposure in humans, an effort was made to examine certain psychological, neurological, and clinical-neurophysiological variables; additionally, a number of biochemical parameters were investigated. Since January, 1965, a group of men from this same industrial population has been studied; many of the current subjects have been continuously employed in the same capacity since 1950. This report is concerned primarily with some of the psychological, neurological, and clinical-neurophysiological results of these studies. In the 1952 program, psychological testing involved a large battery of measures designed to search for classic evidences of brain damage. Data analysis revealed no formal evidences of organic brain damage in psychological test terms. Testing done within 72 hours of exposure almost always showed erratic and slowed functioning, interpreted as indicating the presence of clinical delirium for many individuals within three days of a symptomatic exposure. The one differentiating test in the original study was the Rotary-Pursuit task, a test of hand-eye coordination. Recently exposed men had worse performance than controls, but we have since found that this type of test is unreliable because of technical limitations. Neurological examinations revealed multiple minor signs such as generalized weakness and confusion shortly after exposure; hard neurological signs were absent after treatment and clinical recovery. In the 1952 study, electroencephalograms were done as close to time of exposure as possible and, in many cases, repeated after treatment and recovery. Typical slow-wave bursts after activation by overbreathing were observed if EEGs were done soon after untreated exposure (FIGURE 1 ). These findings were similar to those reported by Grob (1953). A t this time, it was believed that adequate treatment normalized the EEG. These old EEGs have been reevaluated in light of findings from our current investigations and modern knowledge of the neurophysiology of drowsiness and sleep. Upon reevaluation, we find an increase in medium-voltage, irregular theta activity, OCcurring in bursts of one to five seconds’ duration, most often seen during light drowsiness. Special characteristics of the drowsy EEG-there is a normal increase in slow activity-made it easy to overlook this change. In the 1952 study, psychiatric interviews were done o n 78 men: 56 with histories

Pathology of experimental neurogenic tumors chemically induced during prenatal and postnatal life

Abstract: Among the neoplasms of the human body, those of the nervous system belong in a special category, not in regard to the general characteristics of neoplastic growth but rather to the peculiarities dictated by the functional and morphological specificity and heterogeneity of the organ from which these tumors are derived. The complicated structural organization of the nervous system, compared with other organs, and its cellular and regional diversity explain the following characteristics of neurogenic tumors: wide range of morphological variability, inherent tendency toward infiltrative and destructive growth, variable growth rate without extraneural metastasis, close relationship between type of neoplasm and the site at which it generally occurs, and ageand sex-dependent incidence. One can safely state that the classical, morphology-oriented research in human neurooncology, with the attempt to describe and classify brain tumors in detail, has come to an end, although there are still some unresolved differences of opinions regarding tumor classification (Ziilch, 1948, 1956, 1965; Kernohan & Sayre, 1952; Henschen, 1955; Russell & Rubinstein, 1963; Polak, 1966; Zulch & Wechsler, 1968). Experimental neurooncology is essential, since fundamental questions regarding etiology and pathogenesis of human neurogenic tumors are still unanswered. A thorough knowledge of the characteristics of human neurogenic tumors is, however, a necessary prerequisite for the direction of experimental research and for the proper comparative evaluation of the results obtained by experimental means. This monograph is entitled “Research in the Experimental and Clinical Aspects of Brain Tumors.” Therefore, we decided to give preference in this paper to results obtained from experimental neurooncology. Special emphasis is placed on a new model dealing with resorptive carcinogens, developed in Professor Druckrey’s department,

A comparison of primitive forebrain organization in metatherian and eutherian mammals

Abstract: Fossil evidence suggests that both the marsupial opossum and the placental insectivore existed in the Cretaceous period about 100 million years ago (Simpson, 1945). The North American opossum (Didelphis marsupialis virginiana) is an omnivorous, nocturnal, semiarboreal animal that exists as one of the least modified mammals. Insectivores are the only known placental mammals which were present during the Cretaceous period. One existing group, the hedgehogs (our results are from the Pakistanian hedgehog, Paruechinus hypornelus) , are omnivorous, nocturnal animals that also retain some of the earliest mammalian features. A comparison of forebrain organization in the opossum and the hedgehog is of special interest because these two animals are as close, perhaps, as any living form to the archetypical mammals that first showed the multilayered cellular pattern typical of mammalian neocortex. Comparison of the detailed forebrain connections of the opossum and hedgehog with reptiles on the one hand and with more specialized mammals on the other may be one useful approach to clarifying the origin and development of neocortical structures. For the past several years, we have been studying the neocortical organization of the opossum in considerable detail with an emphasis on the connections of the thalamus, basal telencephalic nuclei, and neocortex. More recently, we have been comparing the opossum forebrain with similar connectional and cellular patterns in the hedgehog and turtle forebain in an effort to demonstrate connectional homologies among these existing forms of primitive eutherian, metatherian, and reptilian brains. The techniques employed in all of these studies have been the Nissl and GolgiCox stains for cell configurations and the Nauta-Gygax (1954) and Fink-Heimer ( 1967) modification of the Nauta technique for defining fiber connections.

The anatomy of the avian auditory system

Abstract: This paper summarizes the anatomy of the ascending avian auditory system from peripheral receptor to telencephalic levels. New observations are included, but the paper is based, in large part, on the previous findings of Boord and Rasmussen (1963), Boord (1965 & 1968), Karten (1967 & 1968), and Wallenberg ( 1898), whose experimental work on the pigeon makes it possible to give a reasonably complete account. A host of detail is unknown, however, and some information is equivocal, but an account of the organization of the pigeon auditory pathways can serve as a basis for comparison with other avian and nonavian vertebrates. Although the central connections of auditory neurons are of chief concern, an understanding of the relationships between the auditory receptor and the termination of first-order neurons within primary medullary nuclei is necessary: therefore, the anatomical organization of the fiber components of the eighth cranial nerve is included.

Spontaneous, Hereditary Myocardial Degeneration and Congestive Heart Failure in a Strain of Syrian Hamsters

Abstract: Studies on the pathogenesis, therapy, and prevention of congestive heart failure are greatly hindered by the lack of easily reproducible disease models. There is presently no standardized and generally accepted method for the induction of heart failure in laboratory animals, although a number of techniques have been devised.1-lO Pertinent literature indicates that the type of failure which develops during persistently increased stress produced by overload, when the mechanical demand is enhanced in proportion to the active mass of the heart (e.g. failure caused by aortic stenosis or by aortic valve insufficiency), has been the most intensively investigated because its primary causes are the least complicated and because it can readily be imitated by experimental procedures. Although theoretically an analogous situation prevails when, conversely, the active contractile mass of the heart is diminished (e.g. by an infarct or other degenerative myocardial lesion), this type of failure is difficult to induce experimentally. Studies on dogs, rats, and other laboratory animals suggest that, if the survival time following extreme destruction of the myocardium (by coronary artery ligature or electrocautery) is sufficient, the remaining contractile ventricular mass is able to compensate for the nonfunctioning portion of the heart over a long peri0d.*~-14 In fact, some investigators believe that as little as 15-20% of the total ventricular mass is sufficient to maintain adequate systemic circulation.15 Nevertheless, it should be noted that a single injury to the heart muscle was produced in all the afore-mentioned studies, whereas spontaneous pathological processes in man often cause intermittent and graded injuries to the myocardium. The existence in an inbred strain of Syrian hamsters of a genetically transmitted (or conditioned), degenerative cardiomyopathy that terminates in congestive heart failure offers unique opportunities to study the sequence of events leading to cardiac insufficiency and to analyze the importance of extracardiac factors in the mechanism of generalized venous congestion. This hereditary disease, which has a 100% incidence in the pedigreed BIO 14.6 strain of hamsters, is apparently a primary myopathy. The degenerative lesions that occur in all striated muscles are definitely noninflammator.y in nature.16-lQ The gross and histopathological abnormalities seen in the middle-aged or older myopathic hamsters, except those of the cardiac and skeletal muscles, are consistent with long-standing passive venous congestion, and this progressive cardiovascular insufficiency may be regarded as the ultimate cause of death.20 Although our earlier studies, briefly summarized above, largely characterized the morphogenesis and, at least in some respects, the enzyme histogenesis of the cardiacand skeletal-muscle lesions of the myopathic animals, several important questions remained unanswered. We were especially interested in estab-

Feeding and self-stimulation*

Abstract: Electrical stimulation of the lateral hypothalamus has effects that are strikingly similar to the effects of an appetizing morsel of food. Both elicit eating, and both are rewarding to a food-deprived animal. If the animal is overfed, both decrease in reward value and may cause aversion. The present paper reviews and previews work from our laboratory investigating the relationship between hypothalamic reward and feeding. Before beginning we shall briefly review some of the earlier studies that are particularly relevant. Stimulation of the lateral hypothalamus is extremely rewarding to the recipient animal (Olds, 1962). A rat will press a self-stimulation lever 3,000 times an hour for hours at a time. The same stimulus turned on continuously for a minute or two elicits voracious feeding (Margules & Olds, 1962; Hoebel & Teitelbaum, 1962; Wilkinson & Peele, 1962). FIGURE 1 illustrates that self-stimulation and feeding can be elicited interchangeably in the same experimental session (Hoebel, 1962). Such a close correspondence suggested that the reward of self-stimulation might be involved in the normal rewards of eating. It was also possible, however, that the effect was just a coincidence due to adjacent, but unrelated, neural systems. If feeding and self-stimulation are actually related, then experimental manipulations that affect feeding should also affect self-stimulation. Margules & Olds (1962) and Wilkinson & Peele (1962) reported that food deprivation augmented lateral hypothalamic self-stimulation. If, instead of being deprived, the animal was tube-fed, then self-stimulation decreased (Hoebel & Teitelbaum, 1962). Thus there was a direct interaction between feeding and hypothalamic self-stimulation. Satiety was coincident with decreased hypothalamic reward, When the satiety mechanism was experimentally damaged by ventromedial hypothalamic lesions which produced hyperphagia, self-stimulation increased to a rate as fast or faster than it was before tube-feeding. This result is depicted in the upper left-hand quadrant of FrcuRE 2 which summarizes our early findings. Stimulation of the same ventromedial region in the intact animal stopped both feeding and self-stimulation. This was consistent with the other results shown in FIGURE 2, but inconclusive in itself because medial stimulation causes aversion and might have distracted the animal. The crucial experiment was ventromedial hypothalamic depression. Ventromedial destruction by electrolysis, electrocauterization, or “reversible lesions” made by local application of procaine each augmented self-stimulation and feeding. These treatments sometimes irritate surrounding tissue (Reynolds, 1965), but their effect on behavior in our experiments was the result of ventromedial depression, not irritation to the neighboring lateral region. This conclusion follows from the observation that any of the three lesion techniques applied to the ventromedial hypothalamus increased behavior, whereas the same techniques applied to the lateral hypothalamus decreased the behavior (Epstein, 1960a; Hoebel, 1962 & 1965). Valenstein and colleagues

A comparative approach to the neocortex: localization in monotremes, marsupials and insectivores*

Abstract: Information about the environment is obtained through particular sensory capacities that developed during the course of evolution. Specialized surfaces sense the types, amounts, locations and temporal relations of various forms of energy in the surround. Although the animal or its environment may move, the sensory surface presents a fixed mosaic of receptive cells. The peripheral spatial arrangement of receptors is reproduced at successive ganglionic levels of the central nervous system. Points which are contiguous peripherally tend to remain adjacent centrally whether in a volume such as the thalamus or on a surface such as the cortex. In maintaining peripheral somatic relationships central representation conforms to the bodily form. However, a small peripheral area with dense innervation may be accorded a greater amount of central representation than a large area with sparse innervation. Thus, representation is not according to peripheral proportions, but rather presents a configuration in which more sensitive surfaces receive relatively greater amounts of central representation. Despite the differential enlargement of an area, the coherence of bodily form tends to be maintained and this may result in an elongation or apparent fragmentation of the representation of a less sensitive member. The resultant image may be illustrated by a device such as a homunculus on the cerebral cortex. Motor systems at the cortical level appear to be organized much the same as sensory systems so that cerebral representation accords with the peripheral arrangement of effectors yielding movements. Information about the environment is relayed centrally in a spatial configuration that maintains the general pattern of distribution of receptors at the periphery. At each level of representation of this pattern there occur synapses which allow the business of the nervous system to be carried out. The preservation of peripheral relationships at different central levels of both receptors and effectors suggests strongly that such an arrangement forms a necessary basis for perception and volitional acts.

The open field: some comparative data.

Abstract: This paper is primarily concerned with two attributes of the open-field test of emotionality. The first concerns the generality of the behavior patterns elicited by the open-field to animals of different species and ages. The second is concerned with how the two most commonly used indices of emotionality, activity and defecation, correspond to change in heart rate, a physiological measure sometimes proposed as an indicator of emotionality. Both attributes are important if one questions the validity and reliability of the open-field test as a general measure of emotionality in a variety of animals. It is likely that the behaviors elicited by the open-field vary according to the species tested, since species probably differ in the display of their characteristic syndromes of emotionality. This paper reports comparisons of open-field behavior elicited from several disparate species.

The biochemistry of magnesium.

Abstract: Magnesium is the most abundant intracellular divalent cation, varying in concentration from 5 to 30 milliequivalents (mEq) per kilogram wet weight, depending upon the organism or tissue (Wacker & Parisi, 1968; Williams & Wacker, 1967). Since the discovery by Erdtmann (1927) that magnesium is an activator of mammalian alkaline phosphatase, a host of enzymes have been shown to be activated by this cation, including most of those utilizing ATP or catalyzing the transfer of phosphate. Magnesium is also an activator of systems using thiamine pyrophosphate as a coenzyme. Since ATP is required for most of the energy-requiring biological systems, including: membrane transport, amino acid activation, acetate activation, succinate activation, protein synthesis, nucleic acid synthesis, fat synthesis, coenzyme synthesis, nerve impulse generation and transmission, muscle contraction, and oxidative phosphorylation, the function of magnesium probably extends to all of these enzymes. Considerable progress has been made in defining the role of magnesium in a number of enzymes. Many have been shown to have an absolute requirement for a divalent metal cation. However, cations other than magnesium can often satisfy this requirement. Since magnesium is the most abundant intracellular cation, it is likely that the metal requirement in vivo is fulfilled by magnesium. Owing to the large number of systems in which magnesium has been shown to play a role, it is impossible to summarize them all in this brief review. Therefore, several systems that are of particular importance in terms of their biological implications or that have been studied in the greatest detail utilizing both kinetic and physical-chemical approaches have been selected for discussion.

N‐nitroso compounds in organotropic and transplacental carcinogenesis*

Abstract: For a proper judgment of the potential role of chemical substances in human carcinogenesis, it is essential to know whether cancer can be induced in every organ of experimental animals, and whether these neoplasias are comparable to the corresponding tumors in man. The answer to these questions requires systematic studies, in which the problem of specificity is fundamental. Organotropic effects (i.e., specific effects upon a certain organ) can best be attained with compounds that are inactive as such but that become activated by metabolic changes (“indirect” carcinogens). This applies to dimethylnitrosamine (Magee & Barnes, 1956), and similarly to the carcinogenic hydrazo-, azo-, or azoxyalkanes, and to l-aryl-3,3-dialkyltriazenes. The first experiments of Dutton and Heath (1956) showed that dimethylnitrosamine becomes demethylated enzymatically mainly in the liver, and leads to diazomethane as the active alkylating carcinogen. For biochemical reasons, however, we Came to the conclusion that the first step of activation is an enzymatic hydroxylation on an (alpha) aC-atom (Druckrey et al., 1961a). This should be possible in all dialkylnitrosamines possessing at least one disposable hydrogen atom in alpha position. The ac-hydroxyalkylnitrosamine then becomes dealkylated spontaneously to the corresponding monoalkylnitrosamine, which, by protonic change, yields the isomeric diazohydroxide, as explained in the formulas of FIGURE 1. Both these intermediates are extremely unstable and yield diazoalkane, diazotate, or alkyldiazonium, depending upon conditions. The latter is highly reactive. It can lead to diazotization, or decomposes rapidly to gaseous nitrogen and the respective alkyl-cation, which most probably is the ultimate “alkylating” carcinogen (Magee & Barnes, 1967). According to this “alkylation theory” of carcinogenesis, the activation of dialkylnitrosamines passes several steps, among which the initial aC-hydroxylation is the only enzymatic process. This, however, can lead to organospecific effects, as first shown with the liver carcinogen dimethylnitrosamine by Magee and Barnes (1956). In contrast to dialkylnitrosamines, the acylalkylnitrosamides react by heterolysis. Therefore, many of them are widely used in chemistry for the production of diazoalkanes and for alkylations. After heterolysis, the further degradation pathways are the same as with dialkylnitrosamines. Both groups represent the class of N-nitroso compounds.

Brain stem afferents from the spinal cord in a sample of reptilian and amphibian species

Abstract: What the ancestral vertebrate nervous system may have been, we can never hope to know from actual observation. Fortunately, there are simple vertebrates existing today that retain many features of primitive nervous system organization. To such animals the neuroanatomist must turn for the solution of problems that trouble him about the organization and function of the more complex structures of lower primates and man. To ascertain what represents a sequence of steps in the evolution of any given structure and what represents specialized adaptations will continue to be one of the most important problems for the comparative neurologist. Our understanding of the organization of the nervous systems of nonmammalian vertebrates is based primarily on material processed according to the methods of Nissl, Weigert, Marchi, and Golgi. None of these methods is useful for the demonstration of distant connections of a given cell group when the nerve fibers are thin and poorly myelinated. These techniques also provide no help for the demonstration of terminals of such axons. Because the nonmammalian nervous system is composed of a great number of such thin fibers, our understanding of long pathways of these forms is extremely poor. This is particularly unforunnate since information about connections of a given cell group provides important clues to the identification of the interspecific homologies. The development of the method for the demonstration of degenerating axons and terminals by Nauta and Gygax (1951 & 1954) and Nauta (1957) and the more recent modifications by Fink and Heimer (1967) for the selective silver impregnation of degenerated boutons tenninuux have added new precision to the analysis of neuronal circuitry. Several approaches have been used in comparative neuroanatomical studies. The main interest in our laboratory has been to make surveys of the projections of a given fiber system in a variety of species from several classes of vertebrates, with the hope that these comparisons will reveal clues to the significance and function of the structures involved. The present study deals primarily with data from cases of spinal hemisections in the turtle, snake, and alligator as examined with the silver impregnation techniques of Nauta ( 1957) and Fink-Heimer (1967). These are discussed in relation to findings in the bullfrog (Ebbesson & Camuiias, 1968) and in the Tegu lizard (Ebbesson, 1966 & 1967).