Pigment migration and spectral sensitivity in the compound eye of moths

Summary The spectral sensitivity of dark adapted eyes of the moth Manduca sexta (Lepidoptera: Sphingidae) was measured between 350 and 650 nm by determining the relative number of photons necessary to elicit a retinal potential of 50 V. The spectral sensitivity was determined in eyes with the screening pigment: a) in the extreme distal position, b) in a proximal position, and c) with the pigment removed. Sensitivity maxima were found at about 350 to 370, 450 and 530 nm, irrespective of pigment position.Pigment movement is associated with a change in light attenuation of 2 to 3 log units at all wavelengths between 350 and 650 nm. Only small variations, about 0.6 log units, in screening effect were observed throughout the measured spectrum, and therefore the effect of pigment movement on spectral sensitivity is small.There is a slightly larger decline in sensitivity of eyes with the pigment removed compared to eyes with the pigment in the distal position at wavelengths above 530 nm. This result suggests that the distally located pigments have a slight screening effect.We are grateful to Dr. Bo Lindström for advice regarding the statistical treatment of the experimental data.This work was supported partly by the Swedish Medical Research Council, Stifteisen Gustaf och Tyra Svenssons Minne, Reservationsanslaget,and partly by the Air Force Office of Scientific Research through the European Office of Aerospace Research, OAR, United States Air Force under grant number EOOAR-68-0036.     

Spectral absorption by screening pigment granules in the compound eye of butterflies (Heliconius)

Summary The spectral absorption by single granules, clusters and masses of granules of the screening pigment in the compound eye of the butterfly genusHeliconius was studied by microspectrophotometry. Most of the pigment granules were found to have an almost constant absorption in the wavelength region 300 to 700 nm. Other granules showed a maximal absorption either at about 450 or 560 nm. The maximum at 450 nm is suggested to be caused by xanthommatin and that at 560 nm by ommines. The pigment screen inHeliconius is concluded to be a neutral grey filter.This work was supported by the Swedish Medical Research Council, grant No. B71-14X-104 06B and 070, Sällskapet för Medicinsk Porskning and Reservationsanslaget, and the Deutsche Forschungsgemeinschaft.     

The physical and morphological properties of the pigment screen in the compound eye of a shrimp (Crustacea)

Summary The pigment cells of the compound eye of the shrimps (Crangon crangon andC. allmani) were studied by electron microscopy (SEM and TEM) and microspectrophotometry. The compound eyes of these species contain light-absorbing and -reflecting pigments contained in granules, located in 5 different cells. The light absorbing pigment granules (light screen) are situated in (1) the distal pigment cells, (2) the retinular cells, (3) the basal pigment cells. The reflecting pigment granules are located in (4) the distal, and (5) the proximal reflecting pigment cells. Another innominate cell type investing the ommatidia contains vacuoles without pigment content. The innominate cell type, and the basal absorbing pigment cell (3) listed above, have not earlier been reported for a crustacean species. Measurements of the spectral absorption on sliced and squashed ommatidia show that all components of the light screen have an increased absorption in the wavelength regions 400–450 nm and 530–570 nm, probably due to xanthommatin and ommin. The spectral absorbancy of the reflecting pigment cells were not determined. Similar cells in other species are known to contain pteridines.We thank Prof. Dr. Langer, Bochum, Germany, for his kind help. The work was supported by funds from the Karolinska Institutet to Doc. G. Struwe, and grant NFR No. 2760-007 to Doc. R. Elofsson.     

Electron microscopic observations on the reactional changes occurring in insect nerve fibers after transection

Summary An electron microscopic study of the interganglionic connectives of an orthopteran (Laplatacris dispar) demonstrated that a reaction starts in the sectioned fibers very soon after transection (30 minutes). This reaction is closely similar to that observed in sectioned nerves of vertebrates and consists in the appearance of microvesicles and the proliferation of mitochondria. Sectioned connectives were studied from 30 minutes to 88 hours after section. The reaction mentioned increases progressively during the indicated lapse of time.This research was supported by the United States Air Force under Contract No AF 49 (638) 585 and Grant Af 61-64, monitored by the Air Force Office of Scientific Research, Air Force Research Division of the Air Research and Development Command.     

Oscillations and multiple steady states in a cyclic gene model with repression

In this paper we study the cyclic gene model with repression considered by H. T. Banks and J. M. Mahaffy. Roughly, the model describes a biochemical feedback loop consisting of an integer number G of single gene reaction sequences in series. The model leads to a system of functional differential equations. We show that there is a qualitative difference in the dynamics between even and odd G if the feedback repression is sufficiently large. For even G, multiple stable steady states can coexist while for odd G, periodic orbits exist.This research was supported in part by the Air Force Office of Scientific Research under Contract #AFOSR-84-0376 and by the US Army Research Office under Contract #DAAG29-84-K-0082     

On visual adaptation: II. The electroretinogram and the bipolar cells

First a model for theb-wave of the electroretinogram is given. The essential part of the model is the diffusion into the rod-bipolar synapse of a transmitter substance, followed by the induction of an inhibitor. Making use of this model, adaptation to an illumination too weak to cause of significant decrease in the concentration of visual pigment is interpreted as due to a decreased effectiveness of the rod impulse in exciting the bipolar cell. The disparity between threshold changes for very small test spots and for relatively large spots is explained simply, without invoking any additional physiological mechanisms. This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Contract No. AF(638)-414 and in part by the United States Public Health Service Training Grant 2G-833.     

Electroencephalographic evidence of “Gestalt” in the perception of movement by the frog

Summary Some records, obtained from the surface of the optic tectum of the frog with moving visual stimuli are presented as evidence of a global oscillation of the tectal activity whose time course is specific for different patterns of stimulation.The research reported in this document has been sponsored by the 6570th Aerospace Medical Research Laboratory under grant AF EOAR 65-44 through the European Office of Aerospace Research (OAR), United States Air Force.     

A neural net model for escape learning

An escape learning situation is discussed in terms of a neural model in which a stimulus can result in a conditioned excitement and a specific conditioned response. By using the simplest relations between the strengths of conditioning and the number of reinforcements and by introducing a distribution of fluctuations occurring regularly in time, one can calculate the probabilities of various responses, as well as the various latencies, in successive trials. The results are in moderately satisfactory agreement with the data of R. L. Solomon and L. C. Wynne (Psychol. Monogr.,67, No. 4, 1953). Consequences of the model for various experimental situations are discussed. This research was supported in part by the United States Public Health Service Grant RCA GM K6 18,420 and in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Grant No. AF AFOSR 370-64.     

A mathematical interpretation of motor reactions to fixed and moving stimulation of the eye

The results of experiments performed by L.S. Stone and by R. W. Sperry on vision in salamanders are analyzed. A summary of Reichardt's theory, which originated in the researches of B. Hassenstein on insects, is given, and an application to salamanders is carried out. Introducing a simpler mathematical development based on the onefactor theory of excitation, the same formal results are obtained. A complete model, which includes those results and tries to fit the salamander behavior described by stone, is elaborated and translated into Boolean terms. As a complementary consideration, it is pointed out that the functional rigidity of the visuomotor system, deriving from a biological molecular hysteresis, could be framed in theneuro-affinity principle, the spatial expression of which would turn out to be abiological field. This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command under Contract No. AF 18(600)-1454. Reproduction in whole or in part is permitted for any purpose of the United States Government.     

Neuronal localization of dopamine and 5-Hydroxytryptamine in some mollusca

Summary The localization of biogenic monoamines in ganglionic tissues from Anodonta piscinalis, Helix pomatia, and Buccinum undatum has been studied by means of the histochemical fluorescence method of Falck and Hillarp.In cerebral, visceral, and pedal ganglia (besides nonfluorescent nerve cells) neurons emitting a green or yellow fluorescence were found. No other cell systems exhibiting a specific fluorescence were observed. An abundance of monoaminergic terminals were found in the central parts of these ganglia. Spectrophotofluorimetric determinations showed that there are large quantities of dopamine and 5-hydroxytryptamine in the tissues investigated. The amounts of dopamine and 5-hydroxytryptamine agree well with the distribution of green and yellow fluorescence, respectively, in the ganglia.There are many similarities between the vertebrate and the molluscan monoaminergic neurons. The morphology of the neurons is the same, the intraneuronal distribution of the monoamines is identical, depletion experiments with reserpine and denervation experiments give the same results, and the synaptic arrangement of monoaminergic fibres on non-adrenergic neurons has the same appearance. Apparently, however, dopamine and 5-hydroxytryptamine are the only monoamines acting as neuronal transmitters in the species investigated.The research reported in this document has been sponsored by the Air Force Office of Scientific Research under Grant AF EOAR 64-5 through the European Office of Aerospace Research (OAR), United States Air Force and by the Swedish Natural Science Research Council.     

A canonical form for neural nets without circles

By “neural net” will be meant “neural net without circles.” Every neural net effects a transformation from inputs (i.e., firing patterns of the input neurons) to outputs (firing patterns of the output neurons). Two neural nets will be calledequivalent if they effect the same transformation from inputs to outputs. A canonical form is found for neural nets with respect to equivalence; i.e., a class of neural nets is defined, no two of which are equivalent, and which contains a neural net equivalent to any given neural net. This research was supported by the U.S. Air Force under Contract AF 49(638)-414 monitored by the Air Force Office of Scientific Research.     

Decision equation for binary systems. Application to neuronal behavior

Summary The exact mathematical treatment is given for a non linear equation describing the delayed yes-or-no response to a binary system to external stimulations, in some typical cases of interest. Comparison is made with neurophysiological data on the frequency rate of firings of stimulated neurons; the same equation, however, can be conceivably applied to a vast variety of phenomena. The procedures followed to solve the problems that arise in connection with this equation could be extended to more general types of non linear equations.The research reported in this document has been sponsored in part by the Air Force Office of Scientific Research under Contract no. AF EOAR 65-44 through the European Office of Aerospace Research, OAR, United States Air Force.     

Note on the fusion frequency for stimuli of alternating duration

The case of alternating stimulus patterns of moderately high intensity is considered in terms of the model previously discussed (Landahl, 1957,Bull. Math. Biophysics,19, 157–62). If both of the alternating patterns have the same light-dark ratio, then the relation between the period of the longer and the period of the shorter pattern at the critical flicker frequency is independent of the light-dark ratio and is given by a dimensionless expression which is roughly in agreement with data in which the light-dark ratio is one (C. R. Brown and D. M. Forsyth, 1959,Science,129, 390–91). This research was supported in whole or in part by the U. S. Air Force under Contract AF 49(638)-414 monitored by the Air Force Office of Scientific Research.     

The derivation of D’Arcy Thompson’s theory of transformations from the theory of optimal design

It is shown informally that Cohn’s theory of Optimal Forms can be construed as a comparative theory, and that when this is done the celebrated theory of transformations of D’Arcy Thompson follows as a consequence. The implications of this type of theoretical foundation for the Thompson theory with regard to problems of comparative morphology are discussed, and some suggestions for the further implementation of the theory are described. This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under Contract No. AF 49(638)-917.     

On visual adaptation: I. Photochemistry

Quantitative aspects of the photochemistry of visual adaptation are considered. A simplied model is given that fits data on changes of rhodopsin concentration during and following strong illumination. A variation on Wald’s compartment hypothesis is shown to fit the quasilinear dependence of log threshold upon pigment concentration. Finally, there is a brief review of pertinent data on cone pigments. This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Contract No. AF(638)-414, and in part by the United States Public Health Service Training Grant 2G-833.     

Electroretinogram and the spectral sensitivity of the compound eyes in the firefly Photuris versicolor (Coleoptera-Lampyridae): A correspondence between green sensitivity and species bioluminescence emission

ERGs were recorded from the dorsal sector of dark- and chromatic-adapted compound eyes in the dark-active firefly Photuris versicolor ♀ and ♂ at different wavelengths across the spectrum ranging from 320 nm to 700 nm over 4.5 log units of change in the stimulus intensity. ERG elicited by white light stimulus was an on-negative monophasic wave typical of scotopic eyes. ERGs elicited by chromatic stimuli differed in their waveform characteristics in the short (near-u.v. and violet) and long (green-yellow) wavelengths. The slope of the intensity-response curves at different stimulus wavelengths were similar for phasic response and differed for the plateau component of the ERG. The spectral sensitivity curves obtained under dark- and chromatic-adapted conditions revealed peaks in the near-u.v. (λ_max, 380 nm) and in the green (λ_max 550 nm), suggesting the presence of at least two receptor types in the dorsal sector of the compound eyes of P. versicolor. The green (550 nm) peak corresponds with the species bioluminescence emission peak (552 nm).     

On the reversibility of environmentally induced alterations in abstract biological systems

The environmentally induced alterations in structure of (M, ℜ) which were described previously (R. Rosen,Bull. Math. Biophysics,23, 165–171, 1961) are examined from the standpoint of determining under what circumstances they can be reversed by further environmental interactions. For simplicity we consider only the case of (M, ℜ)-systems possessing one “metabolic” and one “genetic” component. In the case of environmentally induced alteration of the “metabolic” component alone, a necessary and sufficient condition is given for the reversibility of the alteration. In the case of alteration of the “genetic” component, the situation becomes more complex; several partial results are given, but a full analysis is not available at this time. Some possible biological implications of this analysis are discussed. This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under Contract no. AF-49(638)-917 and Grant no. AF-AFOSR-9-63.     

Excitation parameters of the repetitive firing mechanism from a statistical evaluation of nerve impulse trains

Repetitive firing of single tonic neurones is modeled to include in detail both membrane excitation kinetics and electrotonic effects due to membrane non-uniformities in the impulse encoder region. The model is evaluated dynamically and compared with similar data obtained from the crayfish stretch receptor neuron. Two dynamic techniques utilizing small amplitude sinusoidal signals are employed. One technique is used to fix the values of two parameters which relate to the electrotonic control of membrane potential in the interspike interval and to the relaxation time of the K-conductance during repetitive firing. The other technique is employed as a consistency check. The dynamics are particularly sensitive to the K-channel relaxation time in the interspike interval.Research supported by NSF grant BNS 77-22532 and Public Health Service Grant EY 00293. Computer facilities were made available by a grant from the Air Force Office of Scientific Research (AFOSR-1221) and by the University of Minnesota Computer Center     

Convergence of one-dimensional diffusion processes to a jump process related to population genetics

A conjecture on the convergence of diffusion models in population genetics to a simple Markov chain model is proved. The notion of bi-generalized diffusion processes and their limit theorems are used systematically to prove the conjecture. Three limits; strong selection-weak mutation limit, moderate selection-weak mutation limit, weak selection-weak mutation limit are considered for typical diffusion models in population genetics.Supported in part by Research Grant from the Ministry of Education, Science and Culture of JapanSupported by the Air Force Office of Scientific Research Contract No. F49620 85C 0144     

A model for conditioning and the effect of spaced trials in learning

A mechanism is suggested in which a postulated substance can enter a synaptic region only during the simultaneous action of a conditioned and an unconditioned stimulus. If this substance remains and produces a physico-chemical change, then a consequence is that the degree of learning will depend on the spacing of conditioning trials and the time constant of the process will be related to the rate of diffusion or transport of the substance along the axon. This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Contract No. AF 49(638)-414.