ASPECTS OF THE INTEGRATION OF THE TAXONOMY OF LICHENIZED AND NON-LICHENIZED PYRENOCARPOUS ASCOMYCETES

The integration of the taxonomy of lichenized and non-lichenized pyrenocarpous ascomycetes is still in progress. Within this group, at least 12 lichenization events, three re-lichenizations and at least 24 de-lichenization events, are supposed to have occurred during evolution. This is evident from the increasing amount of information regarding phylogeny and classification of pyrenocarpous fungi. The total number of lichenization events, including re- and de-lichenization, within all fungi is estimated to be at least 100. However, the vast majority of the pyrenocarpous lichens are concentrated in a few relatively large, presumably monophyletic, groups. In some cases, proposed integrations have proven to be untenable, for exampleMicrotheliopsisand with theHerpotrichiellaceae,Flavobatheliumwith theDimeriaceaeand most notably theNormandinathallus with the basidio-mycetes and its ascocarps withSphaerulinain theMycosphaerellaceae. The same is true for many cases where lichenized taxa were unwittingly included in otherwise non-lichenized groups, such asDidymosphaeriaandMassarina, or even described in new, presumably non-lichenized, genera likeHolstiella,StarbaeckiellaandTitanella.     

INFLUENCE OF LIGHT OF VERY LOW INTENSITY ON PHOTOTROPIC REACTIONS OF ANIMALS

1. The negative phototropism of certain land isopods was investigated over a large range of intensities, especially low ones. The responses were determined quantitatively by measuring the angle through which an animal turned away from a line perpendicular to the rays of light. 2. In the absence of light the undirected movements set up by obscure stimuli were such as to compensate each other statistically, the average path being a movement in the direction in which the animal was headed. 3. Over a large range of intensities (0.0026 m.c. up) the average turning is maximal, about 55° (Oniscus). This maximal response is due to an anatomical peculiarity, in that the carapace cuts off the light on the eye after the animal has turned 50–60°. This peculiarity probably accounts for specific differences among land isopods. Any light, therefore, which is strong enough to turn an animal through this maximal angle in a radial distance of 10 cm. will give results whose mean will be maximal. 4. Below 0.0026 m.c. the amount of angular deflection becomes less and less, in proportion to the logarithm of the intensity, until at 0.00003 m.c. the movements are the same as in darkness. 5. This proportionality between amount of turning and the logarithm of the intensity indicates the photochemical nature of phototropism on the basis of Hecht''s work with Mya. As a result, Loeb''s theory of phototropism may then be stated in the mathematical form See PDF for Equation in which I ₁ and I ₂ are the two intensities, E ₁ and E ₂, their respective effects, and R, the muscular action set up by the difference in photochemical effect on the two sides.     

EFFECTS OF POTASSIUM ON THE POTENTIAL OF HALICYSTIS

Sea water in which sodium has been replaced by potassium produces about the same degree of negativity in Halicystis and in Valonia. With increasing dilution of this sea water up to 1 ÷ 16 the degree of negativity steadily falls off in Halicystis. This differs from the situation in Valonia where Damon finds that with increasing dilution the negativity passes through a minimum after which increasing dilution produces increasing negativity. But conditions in the two organisms differ so greatly that a comparison is of rather doubtful significance.     

THYROXIN AS A DEPRESSANT OF THE DIVISION RATE OF PARAMECIUM

In concentrations of 1:10⁴, 1:10⁵, 1:10⁶, in alkaline solution with a hydrogen ion concentration approximating that characteristic of normal human blood, thyroxin acts like total thyroid in accelerating certain metabolic processes in Paramecium, notably those connected with the phenomena of excretion. Unlike total thyroid, thyroxin depresses the division rate of Paramecium, the degree of depression varying directly with its concentration. This depression of the division rate is due to the action of the thyroxin directly on Paramecium, not to a modification of the food supply.     

UNDER-REPLICATION OF RIBOSOMAL CISTRONS IN POLYTENE CHROMOSOMES OF RHYNCHOSCIARA

DNA preparations obtained from several tissues of Rhynchosciara americana and two related species, R. milleri and R. papaveroi, were hybridized to R. americana rRNA. The percentage of hybridization was found to be higher in tissues with low polyteny than in tissues with high polyteny, suggesting a relationship between the amount of rDNA and the tissue polyteny. This could be explained by under-replication of ribosomal cistrons in polytene cells, such as those from the salivary gland. Only slight tissue-dependent changes in the percentages of hybridization can be observed in heterologous hybridization using Xenopus laevis rRNA. The possibility that these experiments could not detect differences in the amount of ribosomal cistrons among tissues is discussed. The female:male ratio for the percentages of hybridization in the salivary gland of R. americana agrees with the results obtained by in situ hybridization experiments (16, 17) which have shown that the rRNA cistrons are distributed among chromosomes other than chromosome X.     

THE INFLUENCE OF THE MODE OF NUTRITION ON THE DIGESTIVE SYSTEM OF OCHROMONAS MALHAMENSIS

The intracellular distribution and level of acid hydrolases in Ochromonas malhamensis were studied in cells grown osmotrophically in a defined medium, in a carbon-free starvation medium, and during phagotrophy in each of these media. By cytochemical techniques, little enzymic reaction product was observed in the vacuoles of osmotrophic cells grown in the defined medium. Starved cells, however, contained autophagic vacuoles and cannibalized other Ochromonas cells. Dense enzymic reaction product was observed in the digestive vacuoles and in the Golgi cisternae of these starved cells. Moreover, starved cells and cells grown in a nutritionally complete medium ingested Escherichia coli which appeared in digestive vacuoles containing enzymic reaction product. Biochemical assays for lysosomal acid phosphatase (E.C. 3.1.3.2 orthophosphoric monoester phosphohydrolase) and acid ribonuclease (E.C. 2.7.7.16 ribonucleate nucleotido-2'-transferase) were done on Ochromonas cultures in the same experimental treatments and under identical assay conditions as the cytochemical study. During starvation, the acid hydrolase specific activities were consistently twice those found in cells grown in an osmotrophic complete medium. Ochromonas fed E. coli showed no increase in acid hydrolase specific activity as compared to controls not fed E. coli. The latency of lysosomal acid hydrolases in cells fixed with glutaraldehyde was reduced, suggesting that this fixative increases lysosomal membrane permeability and may release enzymes or their reaction products into the cytoplasmic matrix during cytochemical analysis. This could explain the cytoplasmic staining artifact sometimes observed with glutaraldehyde-fixed cells when studied by the Gomori technique. This study confirms that Ochromonas malhamensis, a phytoflagellate, does produce digestive vacuoles and can ingest bacteria, thereby fulfilling its role as a heterotroph in an aquatic food chain. When Ochromonas is grown in a nutritionally complete osmotrophic medium, phagocytosis causes appearance of acid hydrolases in the digestive vacuoles, whereas the total activity of the enzymes remains unchanged. An organic carbon-free medium strongly stimulates acid hydrolaes activity and causes these enzymes to appear in the digestive vacuoles whether phagocytosis occurs or not.     

EFFECTS OF HYDROXYL ON NEGATIVE AND POSITIVE CELLS OF NITELLA

Remarkable changes are brought about by KOH in transforming negative cells of Nitella (showing dilute solution negative with KOH) to positive cells (showing dilute solution positive with KOH). NaOH is less effective as a transforming agent. This might be explained on the ground that the protoplasm contains an acid (possibly a fatty acid) which makes the cell negative and which is dissolved out more rapidly by KOH than by NaOH, as happens with the fatty acids in ordinary soaps. Part of a negative cell can be changed to positive by exposure to KOH while the untreated portion remains negative. After exposure to KOH the potential the protoplasm has when in contact with NaCl may increase. At the same time there may be an increase in the potassium effect; i.e., in the change of P.D. in a positive direction observed when 0.01 M KCl is replaced by 0.01 M NaCl. In some cases the order of ionic mobilities is u _K > v _OH > u _Na. This shows that the protoplasmic surface cannot be a pore system: for in such a system all cations must have greater mobilities than all anions or vice versa.     

BRIGHTNESS DISCRIMINATION AS A FUNCTION OF THE DURATION OF THE INCREMENT IN INTENSITY

1. This investigation has been concerned with an analysis of brightness discrimination as it is influenced by the duration of ΔI. The durations used extend from 0.002 second to 0.5 second. 2. ΔI/I values at constant intensity are highest for the shortest duration and decrease with an increase in duration up to the limits of a critical exposure time. At durations longer than the critical duration the ratio ΔI/I remains constant. 3. The Bunsen-Roscoe law holds for the photolysis due to ΔI. This is shown by the fact that, within the limits of a critical duration, the product of ΔI and exposure time is constant for any value of prevailing intensity, I. 4. At durations greater than the critical duration the Bunsen-Roscoe law is superseded by the relation ΔI = Constant. This change of relation is considered in the light of Hartline''s discussion (1934). 5. The critical duration is a function of intensity. As intensity increases the critical duration decreases. 6. Hecht''s theory (1935) accounts for the data of this experiment if it be assumed that brightness discrimination is determined by a constant amount of photolysis.     

THE POLYMERIZATION OF ACTIN: ITS ROLE IN THE GENERATION OF THE ACROSOMAL PROCESS OF CERTAIN ECHINODERM SPERM

When Asterias or Thyone sperm come in contact with egg jelly, a long process which in Thyone measures up to 90 µm in length is formed from the acrosomal region. This process can be generated in less than 30 s. Within this process is a bundle of microfilaments. Water extracts prepared from acetone powders of Asterias sperm contain a protein which binds rabbit skeletal muscle myosin forming a complex whose viscosity is reduced by ATP. Within this extract is a protein with the same molecular weight as muscle actin. It can be purified either by collecting the pellet produced after the addition of Mg⁺⁺ or by reextracting an acetone powder of actomyosin prepared by the addition of highly purified muscle myosin to the extract. The sperm actin can be polymerized and by electron microscopy the polymer is indistinguishable from muscle F-actin. The sperm actin was shown to be localized in the microfilaments in the acrosomal processes by: (a) heavy meromyosin binding in situ, (b) sodium dodecyl sulfate (SDS) gel electrophoresis of the isolated acrosomal processes and a comparison to gels of flagella which contain no band corresponding to the molecular weight of actin, and (c) SDS gel electrophoresis of the extract from isolated acrosomal caps. Since the precursor for the microfilaments in the unreacted sperm appears amorphous, we suspected that the force for the generation of the acrosomal process is brought about by the polymerization of the sperm actin. This supposition was confirmed, for when unreacted sperm were lysed with the detergent Triton X-100 and the state of the actin in the sperm extract was analyzed by centrifugation, we determined that at least 80% of the actin in the unreacted sperm was in the monomeric state.     

THE ORIENTATION OF ANIMALS BY OPPOSED BEAMS OF LIGHT

When orientation is attained under the influence of beams of parallel light opposed at 180° the deflection θ from a path at right angles to the beams is given by tan See PDF for Equation, where I ₁ and I ₂ are the photic intensities and H is the average angle between the photoreceptive surfaces. This expression is independent of the units in which I is measured, and holds whether the primary photosensory effect is proportional to I or to log I. When photokinetic side-to-side motions of the head occur, H decreases with increasing total acting light intensity, but increases if higher total light intensity restricts the amplitude of random movements; in each case, H is very nearly proportional to log I ₁ I ₂. For beams of light at 90°, See PDF for Equation. The application of these equations to some particular instances is discussed, and it is shown why certain simpler empirical formulæ previously found by others yield fair concordance with the experimental data. The result is thus in complete accord with the tropism theory, since the equations are based simply on the assumption that when orientation is attained photic excitation is the same on the two sides.     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. X

The inheritance of elements of geotropic performance in lines of rats (A and B) has been investigated by examining the orientation of young offspring produced in matings of F_1(AxB) with A: Previous studies had shown that the three recognizable groups of receptor elements concerned in geotropic orientation in each of these lines appeared to be inherited in such a way that B groups were dominant with respect to A groups, although this was to a minor extent complicated by influences affecting the variation of orientation as well as the exact form of the curve relating orientation angle (θ) to slope of surface. In the backcross F₁ x A, therefore, at least eight different types of curves were to be expected. These are in fact identifiable among the forty-one individuals carefully studied. Their classification is concordant with the behavior of the respective indices of variation of θ, for which an interpretation has been provided. The basic result is, therefore, that the three receptor groups of excitation units are inherited independently, and alternatively as regards the members of a homologous pair, and that rather simple dominance relations obtain between homologous groups from the two races, namely that a B effect is dominant over the homologous A effect. This interpretation has been tested in various ways, and is in principle completely consistent with the results of a similar experiment involving races A and K.     

INTRACELLULAR LOCALIZATION OF KYNURENINE IN THE FATBODY OF DROSOPHILA

Light blue fluorescent globules accumulate in the cells of the anterior region of the fatbody of Drosophila larvae near the time of pupation. This fluorescent material appears in the Ore-R wild type strain as well as mutant strains in which the synthesis of both the red and brown eye pigments is affected. The vermilion mutant, which is characterized by the absence of the brown pigment component in the eye, was the only strain among those examined which did not develop the light blue fluorescent globules. Utilizing chromatographic techniques together with the information gained by examination of the mutant strains, the fluorescent material has been identified as kynurenine. Of particular interest is the manner of appearance of the fluorescent material in the vicinity of the nuclear membrane of the fat cells.     

SOME ASPECTS OF THE STRUCTURAL ORGANIZATION OF THE MYOFIBRIL AS REVEALED BY ANTIBODY-STAINING METHODS

From observations of fluorescent antibody staining and antibody staining in electron microscopy, evidence is presented for the following: (a) Direct contact of the actin and myosin filaments occurs at all stages of contraction. This results in inhibition of antibody staining of the H-meromyosin portion of the myosin molecule in the region of overlap of the thin and thick filaments. (b) Small structural changes occur in the thick filaments during contraction. This leads to exposure of antigenic sites of the L-meromyosin portion of the myosin molecule. The accessibility of these antigenic sites is dependent upon the sarcomere length. (c) The M line is composed of a protein which is weakly bound to the center of the thick filament and is not actin, myosin, or tropomyosin. (d) Tropomyosin as well as actin is present in the I band. (e) If actin or tropomyosin is present in the Z line, it is masked and unavailable for staining with antibody.     

THE EFFECT OF RADIOACTIVE RADIATIONS AND X-RAYS ON ENZYMES : III. A UNIT OF MEASURE OF ACTIVITY FOR RADIUM EMANATION.

In this communication we have introduced a unit to express activity or power of a given preparation of radium emanation. We have named this unit the curie-power and defined it as the activity of 1 curie of radium emanation and its radioactive products in equilibrium with it. We suggest the introduction of this unit in order that we may make a more comprehensive statement of our experimental observation. In the radiochemical reaction effected by the radiations (beta and gamma) from radium emanation in which enzymes are inactivated the chemical change in a given system is a function of the product of two variables; namely, the average activity of the radium emanation, P_a, expressed in terms of the unit millicurie-power, and time, t, expressed in hours. This product has the dimensions of energy and is identical with W which is measured in terms of the energy unit, millicurie-power hours.     

THE PHOTOTROPIC EXCITATION OF LIMAX

The photic orientation of Limax creeping geotropically upon a vertical plate is such that the phototropic vector determining the angular deflection β from the vertical path is proportional to log I. This is proved by the fact that with horizontal illumination tan β is directly proportional to log I; with non-horizontal light rays from a small source the ratio See PDF for Equation is directly proportional to log I (where A = the angle between light rays and the path of orientation), the vector diagram of the field of excitation being in this case not a right-angled triangle.     

THE EFFECTS OF RADIATIONS ON BIOLOGICAL SYSTEMS : II. IMMEDIATE AND SUBSEQUENT EFFECTS OF X-RAY IRRADIATION UPON RESPIRATION OF DROSOPHILA LARVAE

By means of measurement of CO₂ respiratory rates it has been possible to observe immediate and latent effects of x-ray irradiations upon Drosophila larvae. The observations were extended over a period of several days, the duration of the prepupal period being observed also. In every instance a significant decrease in the rate of CO₂ respiration was observed immediately after irradiation. This decrease was univariant with the period of irradiation within the experimental limits.     

GEOTROPIC CURVATURE OF AVENA COLEOPTILES

Applying a photographic recording method, and working on enlargements of the plates so obtained, the shape of the geotropically curving coleoptile of Avena was studied. This shape is expressed in terms of curvature of the neutral axis of the coleoptile; for the true geotropic response of the strain of Avena used, the curvature of the neutral axis is an arc of a circle. The "rate of curvature" is taken as the derivative of the curve relating time with the angle with the horizontal made by the tangent to the neutral axis at the tip. This rate increases up to a maximum and then decreases gradually. No "geogrowth" of the whole coleoptile is found. It is shown that the curvature is due to an increase in the elongation of the lower side of the horizontally placed coleoptile with a concomitant decrease of the rate of elongation of the upper side. This is correlated with a shift in distribution of "growth substance" in the tip as affected by change of position of the coleoptile.     

DIFFERENTIATION OF THE CHLOROPLAST OF ANTHOCEROS

It has been demonstrated that the following changes accompany differentiation in the plastid of the liverwort Anthoceros eckloni. The inner membrane of the plastid folds to give rise to small vesicles which grow and may fuse to form thylakoids, i.e. flat bags. The thylakoids may "pair" to produce the doublets (thick membranes) of the grana. The doublets may be produced also by the invagination of a thylakoid. In both cases, the doublets are produced only where outside-to-outside contact of thylakoid membranes occurs, which supports the thesis that the thylakoid membranes are polarized. The thylakoids also fold outwards, anastomose, and may fuse. This results in a complicated membrane system, for which an interpretation becomes very difficult. The starch is produced in the matrix, and the pyrenoid bodies are interpreted as specialized regions of the matrix. Younger plastids have grana, but the mature plastid has so many doublets that distinct grana cannot be recognized. This interpretation of the changes which occur during the differentiation of the plastid differs radically from those of Menke (1961) and Manton (1962) who studied this same genus, but is compatible with findings in algae and angiosperms.     

ELECTRON MICROSCOPIC AND HISTOCHEMICAL COMPARISON OF THE TWO TYPES OF ELECTROPLAQUES OF NARCINE BRASILIENSIS

The torpedine electric fish Narcine brasiliensis has two morphologically distinct electric organs (main and accessory) which also differ with respect to a number of electrophysiological properties. The fine structure of the electroplaques of these organs has been examined by electron microscopy and by a histochemical method for localizing esterase activity with a high degree of resolution. In both kinds of electroplaques the innervated surface (ventral in those of the main organ, dorsal in those of the accessory) is the only site of esterase activity. The latter is further confined to the regions of synaptic contact between vesicle-containing axon terminals and the electroplaque membrane. The synaptic apparatus is similar to, but less elaborate than, that of neuromuscular junctions. The axon terminals and electroplaque membranes are free of connective tissue envelopments. The membrane of the uninnervated surfaces forms a continuum with a dense canalicular network which penetrates deeply into the 7 µ thick electroplaques of the main organ. The canalicular network has about the same thickness in the 20 µ electroplaques of the accessory organ. Except for this difference, the two kinds of cells appear to have the same fine structure. This finding is discussed in relation to the electrophysiological data on functional differences.